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Federal CIO Survey Report Release Webinar
Attend the virtual release of the PSC Federal CIO Survey Report, in partnership with Maximus, for a summary of the 20+ interviews conducted with federal CIOs. Gain an understanding of federal IT leaders' top challenges and priorities, the forces that are driving change in government IT, and trends that reflect shifts in how agencies are developing and delivering tools. This timely discussion will highlight successes and challenges in federal IT modernization over the last year, and also explore factors impacting both federal IT executives and federal contractors in support of agency missions, including:
Workforce challenges
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Modernization and innovation efforts
This webinar is exclusively for PSC members and includes a Q&A session with the speakers at the end.
Stephanie Sanok Kostro
Executive Vice President, Policy, PSC
Stephanie Kostro is Executive Vice President for Policy at the Professional Services Council, where she leads a strong policy team that is committed to advocating for and supporting productive collaboration between the federal government and services industry. As a recognized executive, on-air commentator, and policy expert with more than 20 years of experience in the U.S. Government and industry, she brings a wealth of knowledge in federal procurement policy and acquisition regulations, government processes and programs, and public-private partnerships.
Prior to joining PSC in 2021, Kostro was a Principal at a government relations and consulting firm where she developed and implemented policy, funding, and business development strategies for a global client base. She worked extensively with civilian, defense, diplomatic, and intelligence officials, as well as with federal departments' oversight committees in Congress.
Simon Szykman
Senior Vice President for Client Growth, Maximus
Simon Szykman serves as the Senior Vice President for Client Growth, leading sales and business development and enabling the go-to- market strategy for the Maximus U.S. Federal Services Segment. In his prior role at Attain, he was a Partner and served as Chief Technology Officer. Simon brings more than 20+ years of experience in various fields related to government information technology. His previous roles include serving as Chief Information Officer (CIO) of the U.S. Department of Commerce, CIO of Commerce's National Institute of Standards and Technology (NIST), Senior Policy Analyst in the White House Office of Science and Technology Policy, and the first Director of Cyber Security R&D at the Department of Homeland Security.
PSC POLICY LEAD
Christian Larsen
Senior Associate, Public Policy, PSC
Christian Larsen joins the Professional Services Council (PSC) as Senior Associate, Public Policy. In this role, Christian will support PSC's polices and priorities in the defense and technology sectors.
Prior to joining PSC, Christian served as a legislative research associate and most recently as manager of strategic programs at the National Defense Industrial Association (NDIA). In both these roles, Christian assisted NDIA's Policy Department on small business issues and defense issues relating to foreign military sales (FMS), export control reform, and the international political landscape surrounding these issues. Christian has also served as an intern with Aerospace Industries Association (AIA), the German Marshall Fund of the United States (GMF), and in the United States Senate.
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Judge: Sen. Stevens' trial to stay in Washington
Brendan Sullivan Jr., attorney for Sen. Ted Stevens, R-Alaska, leaves the federal court in Washington on Wednesday after a motions hearing. Stevens lost a bid Wednesday to move his corruption trial from Washington to his home state of Alaska. Manuel Balce Ceneta / AP
Aug. 20, 2008, 11:48 PM UTC / Source: The Associated Press
Sen. Ted Stevens cannot move his corruption trial from Washington to his home state of Alaska, a federal judge ruled Wednesday in a decision that could hamstring the powerful Republican's re-election bid.
The patriarch of Alaska politics, Stevens could normally expect to coast to his seventh full term in the Senate. But Democrats want to capitalize on the lengthy FBI investigation and trial to capture the once-safe Republican seat.
Stevens, 84, had hoped to stand trial by day and campaign on nights and weekends. In a state where he is known as "Uncle Ted," he could have faced a more sympathetic jury. Stevens was named the Alaskan of the Century in 2000, the Anchorage airport bears his name, and he has brought billions in federal aid to the frontier state.
Wednesday's ruling puts a damper on his campaign plans. Stevens asked for, and received, an unusually speedy trial that he hopes will clear his name before voters go to the polls. But with the trial in Washington, Democrats will have the state largely to themselves while Stevens is tethered to a defense table in the weeks leading up to the November election.
"He must have decided it's more important to get a speedy trial than to have all those days free to campaign," said Julie Hasquet, a spokeswoman for Anchorage Mayor Mark Begich, the front-runner for the Democratic nomination in the race.
Judge to consider shortened trial week
U.S. District Judge Emmet Sullivan said he would consider holding court only four days each week to make it easier for Stevens to fit in campaign trips to Alaska. But that could delay a verdict.
"We want the verdict as far on this side of Election Day as possible," defense attorney Brendan Sullivan, no relation.
Stevens did not attend the court hearing. He remained in Alaska, campaigning for next week's Republican primary.
He is charged with lying on Senate financial disclosure forms about hundreds of thousands of dollars in home renovations and other gifts he received from VECO Corp., an influential oil services contractor. Two VECO executives have pleaded guilty and admitted they bribed Alaska lawmakers, using gifts, jobs and cash to curry favor with allies and undermine their enemies.
His attorney indicated for the first time Wednesday that Stevens has known for years that he has been under FBI investigation. Brendan Sullivan said he agreed five times to extend the statute of limitations. Such deals allow FBI agents more time to investigate and give defense attorneys time to negotiate deals or persuade prosecutors not bring charges.
The cost of the lengthy investigation has apparently added up. Stevens announced Wednesday that he planned to open a legal defense fund to cover his costs. At $1,000-an-hour, Sullivan is among the nation's top lawyers and was accompanied in court Wednesday by several associates.
Sullivan is rare among Washington's legal elite because he rarely defends his clients in public, even those whose reputations are on the line. He believes winning at trial is all that matters.
Stevens is not normally so reserved. Never one to back down from a fight, he has had to change his style while campaigning under indictment. He has been reluctant to talk about the investigation or the charges against him, even last week when prosecutors previewed some of the evidence they planned to use against him at trial.
"I've trained him well," Sullivan said Wednesday. "It's not easy with public figures."
But he said Wednesday that Stevens would not be so reserved at trial.
"A defendant is only a punching bag at this stage," Sullivan said. "We cannot even begin to fight back until they begin their case."

redpajama_set_name: RedPajamaCommonCrawl


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Do High Doses of B Vitamins Increase Your Lung Cancer Risk?
New research suggests that high doses of vitamins B6 and B12 may increase the risk of lung cancer in men.
Howard Wolinsky
Medically Reviewed by Thomas Marron, MD, PhD
Excessive intake of B vitamins might not be a good idea--especially if you're male. Shutterstock (2)
Vitamin B12 is best known for helping to build blood cells and maintaining healthy nerve cells. And B6 aids adrenal function, helps calm and maintain a healthy nervous system, and plays a key role in metabolic processes.
But a study of 77,118 participants published in August 2017 in the Journal of Clinical Oncology indicates that these essential nutrients may have a dark side, especially for men.
The research suggests long-term, high-dose supplementation with vitamins B6 and B12 —which are often promoted as energy and metabolism boosters — is associated with a two- to fourfold increase in lung cancer risk in men who took these supplements compared with non-users.
Risk was highest in male smokers who took more than 20 mg of B6 or 55 micrograms of B12 a day for 10 years. Male smokers taking B6 at this dose were about three times more likely to develop lung cancer. Male smokers taking B12 at such doses were almost four times more likely to develop the disease compared with non-users.
"Our data shows that taking high doses of B6 and B12 over a very long period of time could contribute to lung cancer incidence rates in male smokers," says the epidemiologist Theodore Brasky, PhD, a member of the Cancer Control team at the Ohio State University in Columbus.
The association between lung cancer and B vitamins was not found in women.
How Much B Do You Really Need?
The Vitamins and Lifestyle (VITAL) study is long-term study designed to evaluate vitamins and other mineral supplements in relation to cancer risk in participants. Participants live in Washington state and were between the ages 50 and 76. Researchers followed them for an average of 10 years. Eight hundred eight of them had lung cancer. The association between B vitamin consumption and lung cancer showed up in several (but not all) types of lung cancer.
Cancer Research News: A Weekly Roundup of New Developments in Cancer Research and Treatment
7 Apps That Make Managing Lung Cancer Easier
Young-in Kim, MD, a University of Toronto professor of medicine and nutritional sciences who has studied the vitamin B–lung cancer link, said the study is well-designed and has significant implications.
Dr. Kim has a more moderate recommendation for consuming B vitamins: Stick with natural sources rather than relying on supplements. "A healthy and balanced diet should provide a sufficient amount of these vitamins (the recommended dietary allowance). Try to avoid supplements unless you have certain medical conditions that interfere with absorption and metabolism of these vitamins," he says.
American adults obtain most of their dietary vitamin B6 from fortified cereals, beef, poultry, starchy vegetables and some noncitrus fruit. Vitamin B12 is naturally found in animal products, including fish, meat, poultry, eggs, milk, and milk products. Vitamin B12 is generally not present in plant foods.
Kim said he wasn't surprised that the study showed the effect in men, but not women. "Several nutrition and cancer studies have shown a sex-specific effect of certain nutrients, vitamins, and minerals on cancer risk," he said.
How B Vitamins Might Influence Risk
No one knows for sure why high doses of these B vitamins might increase risk for lung cancer. "I would love to see some mechanism of these drugs in high doses causing cancer before I condemned them," says Otis Brawley, MD, the chief medical and scientific officer of the American Cancer Society in Atlanta.
It's possible, he says, that vitamins B6 and B12 are integrally involved in reactions critical for DNA synthesis and DNA methylation. In methylation, a single carbon and three hydrogens, known as a methyl group, act together to repair DNA, turn genes on and off, fight infections, and remove environmental toxins.
The Top 8 Natural Hangover Remedies
Although there's no foolproof way to prevent a hangover, there are ways to mitigate some of the most common hangover symptoms. From headache and nausea, to dehydration and fatigue, here's what doctors and dietitians recommend. Learn More
"High intake of vitamins B6 and B12 may adversely affect DNA methylation, thereby leading to aberrant DNA methylation and consequent dysregulation of gene expression involved in cancer development and progression," he says.
Room for Doubt?
Dr. Brawley says that studies like VITAL can only establish correlations and do not show causes. That doesn't necessarily mean you should continue to take high doses of the vitamins, however. "I would not have suggested high doses of these vitamins even before this study," he says. His recommendation? "A multivitamin once a day is safe. High doses of unproven drugs is not."
Most multivitamins provide the required dose of most vitamins.
The Council for Responsible Nutrition (CRN), the Washington, DC–based trade association for the dietary supplement and functional food industry, disputed the VITAL study.
Duffy MacKay, a naturopathic doctor and a senior vice president of CRN for scientific and regulatory affairs, said in a statement: "We urge consumers to resist the temptation to allow sensational headlines from this new study to alter their use of B vitamins, especially without further understanding of the nature of this study and a conversation with their healthcare practitioners."
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Please join Carey and all our accomplished readers for Line Break #1, Saturday, March 5, 5:30 pm at Q.E.D. in Astoria!
Please join Sarah and all our accomplished readers for Line Break #1, Saturday, March 5, 5:30 pm at Q.E.D. in Astoria!
Malcolm Chang reports: "I currently reside in Jackson Heights, but I have also lived in Johannesburg, Toronto, Chicago, and Los Angeles, amongst others. I was born during the apartheid era and as a third generation Chinese-South African, have been regarded at various times in my life as more Black than White, as well as more White than Black, on that odd spectrum of racial classification that existed in South Africa. I have written essays for Elle Magazine (South Africa), and a chapter of my memoirs appeared in Newtown Literary. You can also check out my blogs at Senile Delinquent and Mal and Di's Excellent Adventure. I am currently working on my memoirs and my first novel."
Please join Malcolm and all our accomplished readers for Line Break #1, Saturday, March 5, 5:30 pm at Q.E.D. in Astoria!
Sherese Francis is a Queens-based published poet, writer and blogger. Currently she runs the blog Futuristically Ancient, where she writes about the arts and cultures of the African Diaspora through an afrofuturist lens. Additionally she is the literary director of the upcoming Queens Book Festival. Besides her blog and the festival, Sherese is working on a few other projects, including a fantasy novel based in Queens called The E, a self-published chapbook called Lucy's Scroll-Bones, and a longer poetry manuscript.
Please join Sherese and all our accomplished readers for Line Break #1, Saturday, March 5, 5:30 pm at Q.E.D. in Astoria!
Line Break is here! It's the eclectic live literary magazine where poetry meets prose, fact meets fiction, and high-brow meets low-brow, at fabulous Q.E.D. in Astoria, Queens.
Saturday, March 5, 5:30-7:00 p.m.
Admission $5. Beer, wine and snacks available.
Q.E.D. is a short trip from Manhattan on the N train. Just stay on to Ditmars Boulevard at the end of the line. The Q train does not run to Queens on weekends.
Announcing the new Line Break reading series!
Greetings, New York! We're very pleased to announce the new Line Break reading series, a showcase for the vibrant literary scene of Astoria, Queens, and beyond!
In prose writing, a line break indicates the start of a new thought or scene, and that's what we hope each new episode of Line Break will bring you—new thoughts, new perspectives. A new scene.
Our thanks to Q.E.D.: A Place to Show & Tell for giving Line Break a home. Our producer and host will be author and poet William Shunn, a veteran of the "live-lit" scene in Chicago, where he hosted the acclaimed Tuesday Funk reading series for three years.
Line Break is, for now, a quarterly series. Join us for our first show at Q.E.D. on Saturday, March 5, at 5:30 pm. Watch this space for more updates, including how you can participate. We hope to see you there!


A Lao Airlines ATR 72-600 crashed on the 16th of October, 2013, at around 4:10pm local (0910Z) near Pakse, Laos.
The aircraft, registered under RDPL-34233, was MSN (Manufacturer Serial Number) 1071, delivered from the production line in March 2013. The brand new airplane was operating as domestic flight QV301 between Vientiane(IATA: VTE, ICAO: VLVT) and Pakse (IATA: PKZ, ICAO: VLPS) with 44 passengers and 5 crew members on board. All 49 on board are feared no-more.
The great circle distance between between Vientiane and Pakse is 250NM. Part of the flight occurs over neighboring Thailand. The crash seems to have happened when approaching runway 15 of VLPS. The aircraft crashed about 5NM from touchdown. Weather is a suspect, considering cyclone Nari's effect on the region.
The runway at Pakse is 5332 feet long. The airport has a VOR, and NDB, but no ILS. The airport is co-operated by military and civilian authorities.
Lao Airlines was founded in 1976. In 1995, the airline received its first ATR 72. According to the airline, the ATR 72s (4 ATR 72-500 + 2 ATR 72-600 including one that crashed) form the backbone of the carrier's fleet for international and major domestic services. Its fleet also comprises 4 Airbus A320 and 4 Xian MA60. The Chinese aircraft fleet is due to the country's closer links with its Eastern neighbor. Laos was a French colony between 1893 and 1949.
"At this time, the circumstances of the accident are still to be determined. Official sources of Lao Airlines declared that "the aircraft ran into extreme bad weather conditions and was reportedly crashed into the Mekong river. There were no news of survivors at this time".


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Alberto Emilio Nadra (Buenos Aires, Argentina, 15 April 1952) is an Argentinean politician, writer and journalist of Marxist formation. He stood out as a human rights activist and also in the constitution of the Argentinean Youth Political Coordination (Coordinadora de Juventudes Políticas Argentinas) between 1970 and 1980.

Childhood and youth
Nadra was born in Buenos Aires on April 12 of 1952, the youngest of the three children of Fernando Nadra and Zulma Beltramone. However, his family was able to sign him in the local civil registry on April 15, due to complications associated to political pursuits and his father's imprisonment.
He made his elementary studies in different schools of Buenos Aires, sometimes with false identities and documents. This period of his life was determining for his posterior social and political commitment, and he has named it as "The lost childhood" ("La infancia extraviada") in his books Secrets in Red (Secretos en Rojo).

Nadra made his first year of high school in an institution situated in Haedo, Buenos Aires, but after completing the academic year, the authorities forced him to abandon the place due to his student activism. He finished his studies in the baccalaureate of National School Mariano Moreno and later he began to study Sociology and Law in the University of Buenos Aires (UBA), but he did not complete any of the two careers.

On March 26 of 1982 he married Leonor Canelles, the eldest daughter of the leader of the trade-union of construction, Jorge Canelles, one of the primary promoters of the popular rebellion called the Cordobazo, along with the Secretary of the Trade-union "Luz y Fuerza", Agustín Tosco.

Student militancy
In 1965 he was chosen by his classmates as a student delegate in a high school of commercial orientation situated in Haedo, Buenos Aires. During that period he took part in a wall newspaper, in which the invasion that 42.000 American marines had made in Dominic Republic to prevent the reinstatement of the legitimate government of Juan Bosch was reported and condemned. As a result of the manifestation, the authorities expelled him from the school. After his classmates' mobilization, Nadra was reincorporated, but the school directors imposed a disciplinary sanction and asked him to change of establishment the following year.

In 1966 Nadra entered to the Mariano Moreno National School, where he collaborated in the reorganization of the Student Center between 1966 and 1967, meanwhile the dictatorship of Juan Carlos Onganía prohibited any type of student activism. In 1968, Nadra was one of the delegates that promoted the first high school strike, against the imposition of curriculums considered by the students as anti-pedagogical and restrictive.
In 1969 his school's Student Center repudiated the assassinations of students in popular manifestations in some Argentinean provinces, like Corrientes, Rosario and Córdoba. The students began to use black badges in their jackets and dusts covers. This measure was generalized in several public establishments of the country.

During his years as a college student, Nadra was member of the Delegate Council and the Student Center of the Faculty of Philosophy and Literature of the Buenos Aires University. He also participated in the occupation of establishments and in some confrontations with the local police and the Guard of Infantry, as a part of the national movement against the admission exams in 1970 and 1971. Many times, Nadra was imprisoned and illegally deprived of his freedom by the police and para-police groups.

Political Militancy
Nadra began his political activity as a member of the Federación Juvenil Comunista. He was involved in its student's organisms and in its press union. In 1970 and 1982 he was elected to be a member of the Political Relations Commission and of the Central Committee of that organization. Nadra also directed the biweekly "Aquí y Ahora" during a period of the military dictatorship and until 1984, when he began to collaborate in the direction of the Communist Party of Argentina.

In this period he was part of the Editorial Council of the magazine Nueva Era and he directed the seminary Propuesta (with a distribution of 150,000 copies). He also participated in the redactions of the documents Tesis and Informe Central, the theoretical axes of the so-called "turn" process, in the XVI Congress of the organization, in November 1986. In spite of having been elected as member of the Central Committee in that ceremony, the denaturalization of the "turn" made more evident the differences between Nadra and the hegemonic sector of the Direction. As a result, he gave up the PC on October 8 of 1990, after 26 years of militancy activity.

In the first years of the decade of 1970, Nadra was one of the founders of Political Youth of Argentina and he collaborated in his reconstruction, between the military coup and 1982. That same year, the JPA were relaunched as Movement of Political Youth.

Generally omitted in the testimonial and academic works about the resistance to the National Reorganization Progress (Proceso de Reorganizacion Nacional), the action of the JPA –with the common efforts of young peronists, communists, radical, intransigent, Christian democrats and socialists, among others- motorized the reappearance of the juvenile action in the labor and student movement, the agricultural youth and the cultural spaces of actors, plastic artists and writers.
Among his most important initiatives we can find the call for peace in the Beagle Conflict, the mobilization for the visit of de Inter-American Commission on Human Rights in 1979, the march of the Commission of the 25 and of the CGT Brazil to the San Cayetano church, and on March 30 of 1982, the Day of debate and mobilization in the surrounding area of Plaza de Mayo.

In parallel with his cooperation works with other political organizations, Nadra was involved in strong controversies. Many of them from his biweekly column "Temas de Debate" (Topics on Debate), in the newspaper Aquí y Ahora. In 1997, stands out his rough reply to the article of Juan Gelman in Página/12, although the newspaper published it partially.
More recently, Nadra replied to the critics of Manuel Gaggero to the communists, in an article about the assault of the People's Revolutionary Army to the Monte Chingolo's headquarters.

In December 1997 he integrated the Confluence Forum, with a hundred of political, social and artistic personalities that claimed strong changes to the programmatic document "Carta a los Argentinos" (approved for the Alliance for Work, Justice and Education in 1998, as an electoral platform) y questioned the election of Fernando de la Rúa as a presidential candidate in 1999.

He was part of the UNITE party, and, as a part of his direction, he accorded with Néstor Kirchner  a programmatical approach to support his candidature at the end of 2002, afterwards led by the Front for Victory.

Between 2004 and December 2015 he was delegated of Sedronar in the National Congress.

Human Rights
Across his militancy in the JPA, Nadra was intimately committed with APDH, LADH, the relatives of missing and imprisoned by political reasons, the Grandmothers of the Plaza de Mayo and the Mothers of the Plaza de Mayo. In 1977 he participated, along with other youthful leaders to the first march of the Mothers of Plaza de Mayo and he was also one of the organizers of the youth seminars of the Permanent Assembly for Human Rights in 1979 and 1980.

Between September 6 and 20 of 1979, Nadra integrated the youthful delegation that made the speech in the Inter-American Commission on Human Rights, CIDH.

Plan Cóndor
Recently it was revealed that Nadra was an important part of the network of counterintelligence and solidarity that saved lives, denounced atrocities and even promoted actions during the so-called Operation Condor. This plan of the dictatorships of the Latin American South Cone was based on the extermination of the left-wing movement and the revolutionary nationalism, with the logistic help and under the direction of the CIA.
The network in which Nadra took part, connected the graphic and radio media from Moscow, Prague and Berlin, as well as others from Occidental Europe, with the activities that were being done inside the affected countries and had the logistic and intelligence support of the communist parties of the continent and the "Social Field", as it was called in that time.
Other links in this informative and logistic network were the journalists and communist militants Isidoro Gilbert, Arturo Lozza, Rodolfo Nadra y Adolfo Coronato (de la Argentina), José Miguel Varas, Luis Córdova, Enrique Martini and José Maldavsky (from Chile), Elvio Romero (from Paraguay); Niko Scwartz and Ricardo Saxlund (from Uruguay), among others.

Journalistic work
Alberto Nadra began his work as a journalist in the weekly publication Propósitos, created by Leónidas Barletta. After that, Nadra was correspondent for local and foreign media, and he also worked as chief of redaction and directed several newspapers. His press investigations took him to Rome, Moscow, Habana, Algeria, Paris, Prague, Samarkanda, Irkutsk. Between 1973 and 1989 he visited Chile, Brazil, Bolivia, Paraguay and Uruguay.

In 1973 he participated in an operation of rescue and diffusion of the last poem of Víctor Jara, written little before his murder in the National Stadium of Santiago de Chile, after the military coup led by Augusto Pinochet. His commitment with the denunciations of the violations of human rights in Argentina continued while he was working as chief of redaction and editor of the South Cone area reporting from Buenos Aires for the Prensa Latina (PL-Cuba) Agency, between 1976 and 1983.
In 1977 Nadra received and published one copy of the letter that Rodolfo Walsh sent to the military junta, just before his kidnap and disappearance. From that moment on, PL was the first agency which spread the document in all the world media, even before it was known in Argentina.
Nadra was threatened with death and in some partially declassified documents from the CIA he appears as "agent of intelligence" ". In 1979, the Journalists International Organization distinguished his work with the Journalist Merit Award.

In the press syndicalism area, Nadra took part in the Electoral Meeting of the Association Journalists of Buenos Aires (known as APBA in that moment, and then UTPBA), for the elections of July 27 to July 31 of 1972. In those elections participated Jorge Luis Bernetti, Carlos Borro, María Victoria "Vicky" Walsh, Eduardo Molina, Vedia, María Cristina Suárez (Brown List); y Sergio Peralta, Enrique Tortosa, Julio Orione, Walter Fumarola, Ricardo Mainardi, Jorge Marrone (Blue and White List). In 1975 the union was intervened by Isabel Perón government. This situation continued during the following military government.

In 1983, some days after the democratic recovery, Nadra travelled to Moscow as delegate of the Youthful Communist Federation to make a speech in the International Journalists Congress in Moscow.
Between 1995 and 1999 he was producer and host of the TV show "Política en Acción", that was broadcast by the Politics and Economic Channel, of the cable TV operator Cablevision.

In 2004 he cofounded "Los 100" (The hundred), collective of journalists and communication workers that encouraged the Audiovisual Communication Services Law. Currently, Alberto Nadra works as organization secretary.

Teaching
During his Sociology and Law studies, he worked as assistant professor in the classes of Carlos Santiago Nino and Enrique Bacigalupo. However, after this period, Nadra moved away of the academic life in order to concentrate his efforts in the political activity.
Between 1982 and 1987 he taught journalism and discourse analysis in the Foundation of Economic and Social Studies (Fundación de Estudios Económicos y Sociales) in Argentina, Chile and Bolivia. A few years later he taught Informative Analysis in the Institute of Specialized Journalism (IPE), located in Mercedes, Buenos Aires province. In 1999 he was the director of the course "Ethics, Journalism and Society", in the University of Palermo (Buenos Aires).

Awards and Distinctions
Award for "Professional Merit" of the Journalists International Organization, 1979, for his work on human rights in Argentina.

Award Héctor Oesterheld 2003, for his journalistic work.

Published books
SECRETOS EN ROJO. Un militante entre dos siglos/Alberto Nadra. Buenos Aires, Ediciones Corregidor, 2012.
In June 2015 a corrected and extended version was published and was declared of "Cultural Interest and for the Human Rights Promotion and Defense", by the unanimous vote of the Legislature of the City of Buenos Aires, on November 26 of 2015.

DE KIRCHNER A MACRI. Crónicas de una derrota/Alberto Nadra. Buenos Aires, Ediciones Corregidor, 2016.

References

Bibliography

  Fondo Fernando Nadra, Biblioteca Nacional.

External links
 Brigada Santiago Pampillón; Una Historia Olvidada, por Alberto Nadra
 Opinión: La Militancia Juvenil: de Lanusee a Cámpora; de Videla a Alfonsín
 A 30 años de la visita de la CIDH, una mirada al papel del movimiento juvenil
 Alberto Nadra: Adiós, Raúl
 Alberto Nadra: Cámara de Diputados de la Nación
 Apogeo y caída del Partido Comunista- Perfil.com
 El Partido Comunista bajo la mirada setentista - Primera Fuente
 Hasta Siempre, Néstor, por Alberto Nadra
 Alberto Nadra: Transversalidad, Concertación y Pejotización
 ALBERTO NADRA 05 12 13 - YouTube
 Julio, Rocco y la eterna presencia de Silvio Frondizi, por Alberto Nadra
 Secretos en Rojo. Reportaje a Alberto Nadra- La Barraca
 Carta Abierta al compañero Mariano Recalde
 Fraude, manipulación y militancia
 Sepan
 Bibloteca Nacional de la República Argentina: https://web.archive.org/web/20170928044946/http://trapalanda.bn.gov.ar/jspui/handle/123456789/17165
 Biblioteca Nacional de la República Argentina: https://web.archive.org/web/20161220214715/http://trapalanda.bn.gov.ar/jspui/handle/123456789/17164
 Facebook de Alberto Nadra

1952 births
Argentine journalists
Male journalists
Argentine male writers
Argentine people of Italian descent
Argentine people of Syrian descent
People from Buenos Aires
Argentine human rights activists
Living people
Academic staff of the University of Palermo (Buenos Aires)

redpajama_set_name: RedPajamaWikipedia


text:
\section{Introduction}
One of the characteristic features of a dusty plasma is the strong Coulomb interaction among the nearby negatively charged dust particles. The interaction strength determines its dynamical behavior to the external forces. Therefore, the investigation of the response of the dust grain medium to the external forces such as electrostatic force, neutral drag force, radiation pressure force, thermophoretic force, Lorentz force is of great interest \cite{shukladustybook}. The external forces either affect the motion of dust grains directly or through the dynamics of the plasma species. External magnetic fields play a double role to control the dynamics of the dust grains, namely first through the Lorentz force acting on the plasma species (electrons and ions) and secondly through the Lorentz force acting on the dust particles. The motion of electrons and ions in the external magnetic field (B) affects the dust particles via the Coulomb collisions among them, which has been proven theoretically as well as experimentally \cite{kawrotation,magnetirotationecrplasma,dzlievarotationstrongb}. However, the Lorentz force acting on the dust grains in the presence of a magnetic field needs to be explored in more detail. In laboratory magnetized plasma, there are big challenges to keep the plasma homogeneity and to create a stable dust cluster in an electrostatic potential well with a negligible role of $\vec{E} \times  \vec{B}$  ion drift on the dust grains at strong B (B $>$ 3 T), where one can realize the role of B-field to rotate the charged grains due to the Lorentz force. There are challenges to choose an appropriate potential well, selection of an appropriate particle size and types of materials, and discharge conditions to realize the hypothesis of the Lorentz force on the dust grains in a magnetized plasma.
\par
In recent years, a lot of effort has been made to study the dust dynamics in the magnetized plasma background. Maemura {\textit {et al.}} \cite{dusttransportinb} reported the transport of negatively charged particles in a DC discharge plasma when the applied magnetic field is perpendicular to the ambipolar electric field (E), which is a result of the $\vec{E} \times  \vec{B}$  drift of the magnetized electrons. The role of the longitudinal magnetic field (along the discharge axis) to the dust cluster confined in the electrostatic trap of the strata in a DC glow discharge has been studied in detail \cite{vasilievdcrotationinb,vasilmagneticrotation,karasevlongitudinalbrotation,
dustrotationindcwithb,dustrotationindcwithb1,dzlievarotationstratamagnetic,
dzlievarotationstrongb,karasevstrongb}. In these studies, they observed the rotation of dust clusters about the discharge axis due to the $\vec{E} \times  \vec{B}$  drift motion of ions. In a different DC discharge configuration, Sato {\textit {et al.}} \cite{satorotation} studied a volumetric or 3D dusty plasma in the presence of a magnetic field. They demonstrated the role of the coupling among the charged particles to establish the rotational motion in the magnetized plasma. Apart from DC discharges, a set of experiments have been performed in the magnetized rf discharges, where the rf sheath provides an electrostatic trap to the charged particles. The experiments of Konopka {\textit{et al.}} \cite{knopkamagneticrotation} and Huang {\textit{ et al.}} \cite{huangdustrotationrf} have demonstrated the role of the magnetic field on a 2D strongly coupled dust cluster, which exhibits a rigid and sheared rotation due to the $\vec{E} \times  \vec{B}$  drift of ions in the azimuthal direction. The dynamics of a pair of grains in a planar 2D structure containing maximum 12 particles in the presence of a magnetic field has been studied by Cheung {\textit{ et al.}} \cite{cheung2to12planarrotation} and Ishihara {\textit{ et al.}} \cite{2dclusterrotation}. The dust cluster rotation is supposed to be based on the  $\vec{E} \times  \vec{B}$  drift of the ions in the azimuthal direction of a cylindrical geometry. The azimuthal motion of ions transfers their momentum to the dust grains \cite{kawrotation,rotationinionflow}. The azimuthal motion of the neutral gas due to the drifted ions may also cause the dust rotation in the presence of a magnetic field \cite{nedospasovrotationtheory1,gasinduceddustroataion}. Instead of rotation, dust grains can also settle in the current filaments and show various kinds of patterns or ordered structures \cite{mirkpatterninb,thomasorderinb} in strong magnetic fields. All these studies were performed for a 2D dust cluster or 2D dusty plasma in the presence of an external magnetic field. Only limited work on the 3D dusty plasma is performed in magnetized DC and rf discharges \cite{satorotation,dynamiccirculation}. Saitou {\textit {et al.}} \cite{satoprl} have observed the dynamic circulation of charged particles in a 3D dusty plasma in the presence of a magnetic field (B $\sim$ 0.2 T). However, there are still many unanswered questions, e.g.,  about the evaluation of vortices with magnetic field. Do such vortices exist even at strong B-field?. What are the possible sources to drive such vortices?. Does a dusty plasma exist at central region at higher B-field (B $>$ 0.2 T)?. Is such motion common in other 3D dusty plasma system in presence of a B-field?. To get the answer of some of these questions, 3D dusty plasma studies in strong magnetic field are required. The aim of the present investigation is to explore the dynamics of 3D dusty plasma in strongly magnetized rf discharge.\par
Section~\ref{sec:exp_setup} deals with the detailed description of the experimental set-up and the plasma and dusty plasma production. The dynamics of a 3D dusty plasma confined by conducting and non-conducting rings is discussed in Section~\ref{sec:dynamics}.  The origin of the observed vortex flow on the basis of available theoretical models is discussed in Section~\ref{sec:discussion}. A brief summary of the work along with concluding remarks is provided in Section~\ref{sec:summary}.

\section{Experimental setup}  \label{sec:exp_setup}
Experiments are performed in an aluminium vacuum chamber, which is placed at the center of a
superconducting electromagnet ($B_{max}$ $\sim$ 4 T) to introduce a homogeneous magnetic field in the plasma (or dusty plasma). The magnetized dusty plasma device which has been used in the present study is shown in Fig.~\ref{fig:fig1}(a). The orientation of the electromagnet from the horizontal (Fig.~\ref{fig:fig1}(a)) to the vertical (Fig.\ref{fig:fig1}(b)) can be changed. The present experiments are performed in the vertical orientation of the electromagnet. A schematic diagram of the experimental setup is presented in Fig.\ref{fig:fig1}(b). More details about the superconducting electromagnet can be found in ref\cite{mangilalpsst}. At first, the vacuum chamber is evacuated to base pressure p $<$ $10^{-2}$ Pa using a pumping system consisting of a rotary and turbo molecular pump. The experiments are performed with argon gas and the pressure inside the chamber is controlled by using a mass flow controller (MFC) and gate valve controller. For a given argon pressure, the plasma is ignited between an aluminium electrode of 65 mm diameter (lower electrode) and an indium tin oxide (ITO) coated electrode of 65 mm diameter (upper electrode) using a 13.56 MHz rf generator with a matching network. Both electrodes are separated by 30 mm and the upper transparent electrode is grounded along with the vacuum chamber. The special design of the lower electrode, having a ring-shaped periphery with a height of 2 mm and width of 5 mm, provides a radial confinement to the negatively charged dust particles which are levitated above the lower electrode. An additional conducting (aluminium) or non-conducting (Teflon) ring is used to create a 3D dusty plasma in a strong magnetic field. The motivation behind the use of different materials (aluminium and Teflon) for the confinement rings is to observe the role of the depth of the electrostatic potential well  on the dynamics of dust grain medium in an magnetized plasma. It has been observed that dust grains without an additional confining ring or a larger diameter ring are lost from central region to the edge of lower electrode  in the case of strong magnetic field (B $>$ 0.2 T).
Many rings of different inner diameter (30 mm, 40 mm, and 8 mm) and height (2 mm, 3 mm and 4 mm) are tested for the present study. We have found an appropriate ring of inner diameter 10 mm, outer diameter 20 mm, and height 4 mm to create a deep electrostatic potential well to study the 3D dusty plasma in a strong B. Moreover, particle selection is also necessary to create a 3D dusty plasma at ground level experiments. Our primary measurements with different sized Melamine Formaldehyde (MF) particles suggest to use particles of radius, $r_d$ $\simeq$ 1.7 $\mu$m to create an appropriate volume of dusty plasma at low power (P = 3.5 W). The vacuum chamber has 8 sides (or radial) ports.  A dust dispenser, which is installed at one of the side ports of the vacuum chamber, is used for injecting the dust particles into the plasma. Two opposite side ports are used to observe the dusty plasma using a red laser and a CCD camera in the vertical plane. The CCD camera records images in the vertical plane (Y--Z plane) at 20 fps with a resolution of 1024 $\times$ 768 pixels. A CMOS camera is also installed to observe the dust dynamics through the transparent upper electrode in the horizontal plane (X--Y plane) at a frame rate of 90 fps and with a resolution of 2048$\times$2048 pixels. A full view of the dusty plasma in the vertical (Y--Z) plane at X = 0 cm is shown in Fig.\ref{fig:fig2}(a). Fig.~\ref{fig:fig2}(b) represents the dusty plasma view in the horizontal (X--Y) plane at Z $\sim$ 0.8 cm. The stored images are analyzed with the help of ImageJ \cite{imagejsoftware} software and MATLAB based open-access software, called openPIV \cite{piv}.\par
\begin{figure*}
 \centering
\subfloat{{\includegraphics[scale=0.48]{Fig1a}}}%
\qquad
\subfloat{{\includegraphics[scale=0.480]{Fig1b}}
 \caption{\label{fig:fig1} (a) Magnetized Dusty Plasma Device at JLU. (b) Schematic diagram of the experimental setup for the dusty plasma study in a strong magnetic field (1) superconducting electromagnet, (2) magnet coils, (3) vacuum chamber, (4) upper ITO coated transparent electrode, (5) lower aluminium electrode, (6) rf power generator, (7) aluminium or Teflon ring, (8) levitated dust particles, (9) CCD camera for vertical view, (10) CMOS camera for the horizontal view, (11) mirror, and  (12) red laser with a cylindrical lens. The blue arrow indicates the direction of magnetic field (B).}
 \end{figure*}

\begin{figure*}
 \centering
\subfloat{{\includegraphics[scale=0.505]{Fig2a.pdf}}}%
\qquad
\subfloat{{\includegraphics[scale=0.3850]{Fig2b.pdf}}
 \caption{\label{fig:fig2} (a) Full view of dusty plasma in a vertical plane (Y--Z) at the centre of the ring (X = 0 cm). A vertical yellow dashed line passes through the centre of Y-axis. The lower electrode surface represents Z = 0 cm. (b) The horizontal view of the dusty plasma at the yellow dashed line (at Z $\sim$ 0.8 cm) in Fig.\ref{fig:fig2}(a)}.
 \end{figure*}
\section{Dust dynamics in the presence of magnetic field}  \label{sec:dynamics}
The role of an external magnetic field on the dusty plasma has been explored by performing experiments using a conducting (aluminium) and non-conducting (Teflon) ring, which creates a deep and shallow potential well to confine the negatively charged dust particles. There is a stereoscopy technique to track the 3-dimensional motion of particles in the confining potential well \cite{3dvorticesrfplasma}. However, there are limitations in our experiments to diagnose the 3-dimensional dusty plasma using this technique. Therefore, the dynamics of the dust grains in the vertical and horizontal planes are studied to understand the dynamics of 3-dimensional dusty plasma in a strong magnetic field. The detailed results are discussed in the following subsections.
\subsection{Dynamics of the dusty plasma confined by a conducting ring}
An aluminium ring modifies the potential distribution in the sheath region of the lower electrode \cite{rfsheathpotentialdistributation}. It is known that charged particles follow the equipotential contour to achieve an equilibrium position. Therefore, particles are confined in a bowl shaped potential well created by the aluminium ring. Experiments are carried out at an argon pressure of p = 35 Pa and input rf power of P = 3.5 W. It should be noted that gas pressure and input rf power are major discharge parameters causing the plasma current filaments in a strong B-field. In our device, current filaments appear at threshold magnetic field (B $>$ 1) T in the low pressure (p $<$ 10 Pa) and high power (P $>$ 5 W)  discharge. The threshold value of B-field shifts to the higher value with increasing the gas pressure at given rf power. Since the experiments are performed at high pressure (p = 35 Pa) and low rf power (P = 3.5 W),  plasma filaments start to appear above B $>$ 2.2 T. Thus, dust grains are confined in the potential well of the homogeneous plasma in the given magnetic field regime (B $>$ 1 T).
Fig.~\ref{fig:fig3} shows the collective dynamics of 3D dusty plasma in the vertical (Y--Z) plane (at X = 0 cm) at various strengths of the external magnetic field. In this figure, all the images are reconstructed by the superimposition of five consecutive still images. The directed motion of dust grains forms elongated tracks, whereas the thermal motion of grains leaves white dots. In the absence of an external magnetic field, particles exhibit a thermal motion about their equilibrium position. As the magnetic field is increased up to 0.03 T (B $>$ 0.02 T), the edge particles start to rotate in the vertical plane and form a vortex structure (V-I) on either side of the ring edge. Due to the symmetry of dusty plasma about the axis passing through Y = 0 cm in this plane (see Fig.~\ref{fig:fig1}(a)), only the left side of the vortex structure is considered for the further analysis. At low B, the central region particles exhibit either thermal motion or  $\vec{E} \times  \vec{B}$  drift motion in the X--Y plane (or in the azimuthal direction of the cylindrical coordinate), which will be discussed later. Further increase of the magnetic field B $>$ 0.15 T leads to a reduction in the size of the edge vortex (V--I) (see Fig.~\ref{fig:fig4}) and a rotation of the central region particles in the opposite direction, forming a pair of counter-rotating vortices. Since the edge vortices seem nearly circular, the diameter of vortex in the radial (or along Y-axis) direction is considered the size of vortex. At B = 0.2 T, particles in the edge vortex (V--I) and central region vortex (V--II) are observed to rotate in opposite directions and form a counter-rotating vortex pair in this plane. The characteristics (shape, size, angular velocity etc.) of the counter-rotating vortices changes with further increase of the magnetic field up to 0.8 T. At strong magnetic field, B $>$ 0.8 T, the volume of dusty plasma or dust layers in vertical direction decreases. Hence, the size of the central vortex (V--II) reduces and the particles also exhibit a complex vortex motion which is difficult to diagnose with the existing optical diagnostics. It is noticed that the levitation height of the dust cloud shifts from Z $\sim$ 0.6 mm to 0.4 mm (see Fig.~\ref{fig:fig5}), which indicates the reduction of the sheath thickness at strong magnetic field.\par
\begin{figure*}
\centering
 \includegraphics[scale=0.86]{Fig3.pdf}
\caption{\label{fig:fig3} Video images of the dust cloud (aluminium ring) in the vertical (Y--Z) plane at X = 0 cm. Images at different magnetic fields are obtained by a superposition of five consecutive images at a time interval of 65 ms. The edge vortex and central region vortex are represented by V-I and V-II, respectively. The vortex structures at different strengths of the magnetic field are observed at fixed input rf power, P = 3.5 W and argon pressure, p = 35 Pa. The dotted yellow line represents the axis of symmetry. The yellow solid line with an arrow indicates the direction of the vortex flow in the vertical plane of the 3D dusty plasma. The red dash line represents the size (or diameter) of edge vortex.}\par
\end{figure*}
\begin{figure}
\centering
 \includegraphics[scale=0.37]{Fig4}
\caption{\label{fig:fig4} Variation of the size of the edge vortex (V-I) depending on the external magnetic field strength.}
\end{figure}
To investigate the details of the velocity distribution and angular frequency ($\omega$) of rotating particles in a vortex structure the still images are analyzed using a MATLAB based open-access software, called openPIV \cite{piv} software. The PIV images of the dusty plasma in the vertical plane at different strengths of the magnetic field (Fig.~\ref{fig:fig3}) are depicted in Fig.~\ref{fig:fig5}. These PIV images are constructed using an adaptive 2-pass algorithm (a 64$\times$ 64, 50\% overlap followed by a 32 $\times$ 32, 50\% overlap analysis). The contour maps of the average magnitude of the velocities are constructed after averaging the velocity vectors of consecutive 50 frames. In the color map of the PIV images, the direction of the velocity vector represents the rotational direction of the dust grain medium \cite{williamspivanalysis}. Colour bars show the magnitude of the velocity distribution of rotating particles in the vortex structure. It is clear from Fig.~\ref{fig:fig5} that the rotating particles have inhomogeneous velocity distribution in the vortex structure and the velocity of the rotating particles in either the edge vortex (V--I) or the central vortex (V--II) increases as the magnetic field is increased from 0.05 T to 0.8 T. The error over the averaged value of velocity at a given location of vortices (V--I and V--II) at different values of B-field varies between 10 to 20\%, which is estimated by analysing two consecutive PIV images for a set of 50 frames. It is noticed that rotating particles in the vertical plane moves to the next plane. Therefore, dust grain motion can not be considered as an ideal 2D motion in this plane. It clearly indicates the presence of a third velocity component.  It is observed that density of edge particles decreases toward higher B-field. These both factors, presence of third velocity component and less dust density in interrogation area, are mainly possible error sources in PIV analysis \cite{williamspivanalysis}.\par
To get the angular frequency, $\omega = v_t/\rho$, of the rotating particles in the edge vortex and central region vortex, circular paths or arcs about the center of the vortex ($\rho$ = 0 mm) are analysed for different values of B-field. Here $v_t$ is the tangential  (or azimuthal) velocity and $\rho$ is the radial distance from the center of a vortex. It is evident that central vortices as well as some of the edge vortices are not circular. Therefore, the tangential velocity is estimated along the circular paths (arcs) at different values of $\rho$. Since $v_t$ is not homogeneous along the circular path, different values of $\omega$ are obtained at given $\rho$. For the comparative study, an average value of $\omega$ is calculated from different values of $\omega$ at given $\rho$. An average angular frequency of the rotating particles in the edge vortex (V--I) and  central region vortex (V-II) is presented in Fig.~\ref{fig:fig6}(a) and Fig.~\ref{fig:fig6}(b), respectively. It is clearly from fig.~\ref{fig:fig6} that the angular frequency of the rotating particles decreases as the radial distance of the particles increases from the center of the vortex, $\rho$ = 0 mm, for a given magnetic field. This is a signature of a differential or sheared rotation of the particles in the vortex. The angular frequency of the rotation increases with increasing external magnetic field at a given radial location from the center of the vortex, as shown in Fig.~\ref{fig:fig6}. It is also clear from figure~\ref{fig:fig6} that the dust particles of the edge vortex (V--I) always have higher values of $\omega$ as compared to the central vortex (V--II) at a given value of the magnetic field.\par
\begin{figure*}
\centering
 \includegraphics[scale=0.53]{Fig5}
\caption{\label{fig:fig5} PIV images of the corresponding video images of Fig.~\ref{fig:fig3} at different magnetic field strengths in the vertical (Y--Z) plane. These images are constructed after averaging the velocity vectors over 50 frames. Arrows indicate the direction of rotation in a vortex and color bars represent the magnitude of the velocity of the rotating particles.}
\end{figure*}
\begin{figure*}
 \centering
\subfloat{{\includegraphics[scale=0.35]{Fig6a}}}%
\qquad
\subfloat{{\includegraphics[scale=0.35]{Fig6b}}
\caption{\label{fig:fig6} The variation of the averaged angular frequency of dust particles in the (a)  edge vortex (V--I)  and (b) central region vortex (V--II) at various strengths of the magnetic field.}
 \end{figure*}
For getting more information on the vortex flow in a 3D dusty plasma, images of the horizontal (or X--Y) plane of another experiment at similar discharge conditions are analyzed at different Z-positions. In Fig.~\ref{fig:fig7}, two PIV color map images of the dusty plasma at Z $\sim$ 1.1 cm and Z $\sim$ 0.7 cm in the presence of a magnetic field of B = 0.4 T are displayed. The direction of velocity vectors is outwards in Fig.~\ref{fig:fig7}(a) and inwards in Fig.~\ref{fig:fig7}(b), which corresponds to the edge vortex (V--I) and central region vortex (V--II), respectively. Now it is clear from figure~\ref{fig:fig7} that the edge vortex and central region vortex in the Y--Z plane are cross sections of the rotating dust torus. A single vortex corresponds to a rotating dust torus. At higher magnetic fields, a pair of counter-rotating vortices in the Y-Z plane is nothing but a cross-section of a pair of counter-rotating tori in a dusty plasma. The characteristics of the central region vortex (V--II) (dust torus) is found to be similar to that reported in unmagnetized rf discharge by Mulsow \textit{et al.}\cite{3dvorticesrfplasma}. It is also observed that the velocity vectors have some angle to the radial direction (in the cylindrical coordinate) which suggest an $\vec{E} \times  \vec{B}$ drift motion of the dust particles in the azimuthal direction along with rotational motion in the Y--Z plane. There may also be the possibility to have such kind of motion due to the dust-neutral collisions during the motion in the vertical plane. Therefore, the rotating dust particles in Y--Z plane always have a drift in the azimuthal direction. It clearly indicates that particles do not rotate in a single Y--Z plane or a cross section of the dust torus but they shift to the next plane during the rotation. After a certain value of the magnetic field (B $>$ 0.5 T), the rotating particles have a higher drift velocity (or azimuthal component) which is a signature of the helical type of motion in a dust torus.\par
 It is well known that the dust-dust interaction strength, which is termed as Coulomb coupling, is required  for the vortex flow. In the case of weak coupling, dust grains do not show a collective response to external or internal forces. In our case, the particles levitated in the strong electric field of the sheath or the deep potential well (see Fig.~\ref{fig:fig2}(b)) seem to be weakly coupled because they do not participate in the vortex flow. These particles are acted upon by the ion drag force in the azimuthal or $\vec{E_r} \times  \vec{B}$  direction and rotate in the horizontal plane, as shown in Fig.~\ref{fig:fig8}. Details about such a 2D dust cluster rotation due to the $\vec{E} \times  \vec{B}$  ion drift have been explained in earlier studies\cite{knopkamagneticrotation,vasilmagneticrotation,satorotation,kawrotation}.

 \begin{figure*}
\centering
 \includegraphics[scale=0.55]{Fig7}
\caption{\label{fig:fig7} (a) PIV velocity maps, constructed after averaging the velocity vectors over 50 frames in the horizontal (X--Y) plane at (a) Z $\sim$ 1.1 cm and (b) Z $\sim$ 0.7 cm in the presence of an external magnetic field of B = 0.4 T. The potential well is created by using the aluminium ring at argon pressure, p = 35 Pa and input rf power, P = 3.5 W.}
\end{figure*}
\begin{figure}
\centering
 \includegraphics[scale=0.45]{Fig8}
\caption{\label{fig:fig8} PIV velocity maps, constructed after averaging the velocity vectors over 40 frames in the horizontal (X--Y) plane at Z $\sim$ 0.6 cm in the presence of external magnetic field of B = 0.2 T. The potential well is created by using the aluminium ring at argon pressure, p = 35 Pa and input rf power, P = 3.5 W.}
\end{figure}
 \subsection{Dynamics of the dusty plasma confined by an insulating ring}
 In the previous subsection, dust grains were confined in a deep potential well of an aluminium ring, which has the same potential as the lower electrode. In the deep potential well, we have seen mixed motions of weakly and strongly coupled dust grains. Does the dusty plasma show a similar kind of motion when they are confined in a shallow potential well? Is it possible to get both phases of dusty plasma in shallow potential well? To answer these questions, a set of experiments is carried out in a dusty plasma which is confined by a non-conducting (Teflon) ring. Fig.~\ref{fig:fig9} shows the dynamics of a 3D dusty plasma created at argon pressure of p = 35 Pa and input rf power of P = 3.5 W in the presence of an external magnetic field. This figure is obtained after superimposing five consecutive images for tracking the motion of the dust particles. It is observed that the dust grains do not show any directed motion and exhibit only a thermal motion in the shallow potential in the absence of an external magnetic field (B = 0 T). The dust grains also exhibit only a thermal motion at low magnetic field (B $<$ 0.03 T) and after that they start to rotate in this plane and form a pair of counter-rotating vortex structures at B $\sim$ 0.05 T. With increasing magnetic field up to 0.1 T, we observe two well separated vortex structures at the edge of the potential well in this plane. Since the dusty plasma is symmetric about the X-axis in the Y--Z plane, we focus only on the left side region of the dust grain medium. The central region particles have a thermal as well as  $\vec{E_r} \times  \vec{B}$  motion in the X--Y plane at low B. With increasing the magnetic field strength (B $>$ 0.15 T), the dust grains in the central region start to rotate along with the edge vortex in opposite direction,  resulting in a pair of counter-rotating vortex structures. Further increase in the magnetic field from 0.2 T to 0.7 T modifies the characteristics of this pair of counter-rotating vortices. At B $\sim$ 0.7 T, the central region vortex is shifted to the edge of the potential well and a well-separated pair of vortices is observed. At strong magnetic field (B $>$ 0.7 T), the dusty plasma volume reduces and only a few edge particles exhibit a vortex motion. As discussed before, the vortex structure in the vertical plane is a cross-section of the rotating dust torus. Hence at lower magnetic field a single rotating dust torus and a pair of counter-rotating dust tori at higher B is observed.\\
 \begin{figure*}
\centering
 \includegraphics[scale=0.86]{Fig9}
\caption{\label{fig:fig9} Video images of the dust cloud in the vertical (Y--Z) plane at X = 0 cm. The images at different magnetic fields are obtained by a superposition of five consecutive images at a time interval of 65 ms. A Teflon ring is used to create a potential well at fixed input rf power, P = 3.5 W and argon pressure, p = 35 Pa. The yellow solid line with an arrow indicates the direction of vortex flow in the vertical plane of the 3D dusty plasma.  V--I and V--II represent the edge vortex and central region vortex, respectively.}
\end{figure*}
The PIV images of the dusty plasma in the vertical plane at different strengths of the magnetic field (of Fig.~\ref{fig:fig9}) are depicted in Fig.~\ref{fig:fig10}. The earlier discussed PIV analysis technique is used to obtain the angular frequency distribution of rotating particles in a vortex structure at different B-field. The average angular frequency of dust grains in the edge vortex (V--I) and central region vortex (V--II) is presented in Fig.~\ref{fig:fig11}(a) and Fig.~\ref{fig:fig11}(b), respectively. It is clear from Fig.~\ref{fig:fig11} that the angular frequency $\omega$ decreases from the center to the outer edge of the vortices, which is a signature of the differential rotation. At given location of the vortex structure, the value of $\omega$ is observed to be higher at high magnetic field, showing the increase of $\omega$ with increasing external magnetic field. It is also clear from Fig.~\ref{fig:fig11} that particles in the edge vortex always have a higher value of $\omega$ as compared to the central vortex at  given B-field.. Moreover, the particles confined in the potential well of the conducting ring have a higher angular frequency than in the case of the non-conducting ring.
\begin{figure*}
\centering
 \includegraphics[scale=0.52]{Fig10}
\caption{\label{fig:fig10} PIV images of the corresponding video images of Fig.~\ref{fig:fig9} at different magnetic field strengths in the vertical (Y--Z) plane. These images are constructed after averaging the velocity vectors over 50 frames. Arrows indicate the direction of rotation in a vortex and color bars represent the magnitude of the velocity of the rotating particles.}
\end{figure*}
\begin{figure*}
 \centering
\subfloat{{\includegraphics[scale=0.35]{Fig11a}}}%
\qquad
\subfloat{{\includegraphics[scale=0.35]{Fig11b}}
 \caption{\label{fig:fig11} The average angular frequency variation of particles in (a) edge vortex (V--I) and (b) central region vortex (V--II) when the potential well is created by a non-conducting (Teflon) ring at pressure, p = 35 Pa and rf power, P = 3.5 W. }
 \end{figure*}
\section{Discussion} \label{sec:discussion}
The rotating dust grain medium in the external magnetic field can be described by the Navier-Stokes equation with the continuity equation of an in-compressible fluid of constant mass density \cite{vortexmicrogravity, satoprl}
\begin{equation}
 \frac{d \vec{v_d}}{dt} =  -\frac{1}{\rho_d} \nabla p_e+
 \eta\nabla^2 \vec{v_d} + \frac{ q_d}{m_d} (\vec{v_d}  \times  \vec{B}) +
\frac{1}{m_d} (\vec{F}),
\end{equation} where
\begin{equation}
\vec{F} = \vec{F_E} + \vec{F_g} + \vec{F_i} + \vec{F_n} + \vec{F_{th}}
\end{equation}
where $\rho_d = m_d  n_d$ is dust mass density, $n_d$ is the dust density, $p_e$ is an electrostatic pressure of the dust grain medium, $m_d$ is mass of the dust grain, $\eta$ is the kinetic viscosity of the dust grain medium, and $\vec{v_d}$ is the dust velocity. In the second equation, $\vec{F_E}$, $\vec{F_g}$, $\vec{F_i}$ , $\vec{F_n}$, $\vec{F_{th}}$ are the electrostatic force, gravitational force, ion-drag force, neutral drag force and thermophoretic force, respectively. The present set of experiments are carried out at an argon pressure of 35 Pa and the dust density $n_d$ varies between $10^4$ to $10^5$ $cm^{-3}$ for given range of B-field (B $<$ 0.8 T). Since dust density or dusty plasma volume at given B-field does not change during the vortex motion, dust grain medium is considered as an in-compressible fluid. Moreover, the rotational velocity of dust grains increases linearly ($>$ 10 \%) with reducing the neutral pressure to 30 Pa at given discharge conditions. It is known that the viscous force depends on the Coulomb interaction (or $Q_d$) among the flowing dust grains \cite{fortovviscosity2}. We observe a slight change ($<$ 3\%) in the ion current during the reduction of pressure  (p = 35 to 30 Pa) at B = 0.05 T (measured with probe), which indicates a negligible change of $Q_d$ or viscosity during the reduction of pressure from 35 to 30 Pa. In PIV images, we see a a slight  velocity gradient, which also favors a less viscous force compared to neutral drag force. Therefore, dust viscous force ($\eta\nabla^2 \vec{v_d}$) is neglected in comparison to neutral drag force ($F_n$) causing dissipation losses during the steady vortex motion. For given discharge conditions, the Lorentz force on the dust grain is of the order of $10^{-18}$ to $10^{-20}$ N which is negligible compared to the external force $F$ of the order of  $10^{-12}$ to $10^{-13}$ N. It shows that the magnetic field does not directly exert a force (or Lorentz force) on charged dust grains to rotate in this plane. The vortex motion in the dust grain medium can be described by the vorticity equation, which can be deduced from equation (1) after taking the curl of both sides \cite{vortexmicrogravity}
\begin{equation}
\frac{d \vec{\omega}}{dt} =  \nabla \times \Big[-\frac{1}{\rho_d} \nabla p_e + \frac{1}{m_d} (\vec{F_E} + \vec{F_g} + \vec{F_i} + \vec{F_n} + \vec{F_{th}})\Big],
\end{equation}
 where $\omega = \nabla \times \vec{v_d}$ is the vorticity of the rotating dust grain medium.
Since the input power is low (P = 3.5 W), the role of thremophoretic force to the rotational motion is considered to be negligible.  $\nabla \times \nabla$$p_e$  and  $\nabla \times \vec{F_g}$  are zero, hence, equation (3) reduces to the form
\begin{equation}
\frac{d \vec{\omega}}{dt} = \frac{1}{m_d} \Big (\nabla \times \vec{F_E} +  \nabla \times \vec{F_i} +  \nabla \times \vec{F_n} \Big)
\end{equation}
For the stationary two-dimensional (2D) vortices in an incompressible dusty plasma, equation (4) can be expressed as \cite{vortexmicrogravity}
\begin{equation}
\nabla \times \vec{F_E} +  \nabla \times \vec{F_i} +  \nabla \times \vec{F_n} = 0
\end{equation}

The electrostatic force on a dust grain of charge $Q_d$ in the electric field of the sheath is given as $\vec{F_E} = Q_d \vec{E}$. Since ions are streaming in the direction of electric field, the ion drag force can be written as $\vec{F_i} = F_i \hat{E}$. Here $F_i$ represents the magnitude of the ion drag force on the dust grain. In the present set of experiments, there is no directed gas flow inside the chamber. Thus, neutrals provide a frictional background to resist the motion of the dust grains. According to Epstein friction \cite{neutraldragepstein}, the neutral friction experienced by the dust grains is $\vec{F}_n = -m_d \nu_{dn} \vec{v}_d$. Here, $\nu_{dn}$ is the dust--neutral friction frequency. After substituting the values of these forces in equation (5), we get the following expression
\begin{equation}
\nabla Q_d \times \vec{E} +  \nabla F_i(E) \times \hat{E} =  m_d \nu_{dn} \nabla \times \vec{v_d}
\end{equation}
In this equation, the L.H.S terms are the energy source for driving the vortex motion and the R.H.S term corresponds to the energy loss during the vortex motion. Thus, for maintaining a stationary vortex flow in the dusty plasma, the energy gain by particles must be balanced by the energy loss. It is clear from equation (5) that the charge gradient and ion drag gradient along with the electric field are possible energy sources to drive the vortex motion. The charge gradient arises due to the inhomogeneity in the background plasma of the dust grain medium \cite{mangirotationpop,vaulinaselfoscillation}. For the ion drag force on the dust grain we take \cite{kharpakiondragforce}
\begin{equation}
\vec{F_i} = \frac{8}{3} \sqrt{2 \pi k_B T_i M_i} r_d^2 n_i  \Big [ 1 + \frac{z \tau}{2} + \frac{z^2 \tau^2 \Lambda}{4} \Big]  (\vec{v_i}-\vec{v_d})
\end{equation}
where $M_i$, $T_i$, and $n_i$ denote the mass, temperature and density of ions, respectively. $\vec{v_i} >> \vec{v_d}$ is the average ion velocity (ion drift velocity), $k_B$ is the Boltzmann constant, $z = Z_d e^2 /r_d T_e$ is the dimensionless charge of the dust particle, where $Z_d$ is the dimensionless grain potential in units of $T_e/e$, $\tau = T_e/T_i$ is the electron-to-ion temperature ratio, and $\Lambda$ is the modified Coulomb logarithm integrated over the ion velocity distribution function \cite{kharpakiondragforce}.
It is clear from equation (7) that the ion density and velocity are two major variables to determine the magnitude of ion drag force ($F_i$), hence, the ion drag gradient ($ \nabla F_i(E)$) depends on $n_i$ and $v_i$ in the sheath region of the ring electrode. \par
For the quantitative descriptions of dust dynamics in an external magnetic field, it is required to estimate both driving force terms of Eq. 6. In the present case, a single Langmuir probe exerts an electrostatic force to the confined dust grain medium and expels the particles from the confined potential well, which does not allow us to measure the background plasma parameters of the dust grain medium. Another issue to use the single Langmuir probe in moderately collisional magnetized plasma (B $>$ 0.1 T) is the reduction of ion current and formation of secondary plasma near the tip of probe when bias voltage crosses the plasma potential. Therefore, erroneous plasma parameters are expected at higher B-field. It is possible to use the single Langmuir probe in weakly magnetized plasma (B $<$ 0.1 T). However, the spatial variation of plasma parameters (from Y $\sim$ 8 mm to Y = 0 mm) is $<$ 10 \%. The Langmuir probe method which estimates the plasma parameters ($n$, $T_e$ and $V_p$) with an error of $>$ 10 \% in a low density plasma does not give the true values of the plasma parameters at different spatial locations (Y-values). It is known that plasma potential and plasma density can be estimated using the known values of floating potential ($V_f$) and ion saturation current  ($I_i$), respectively  for a given $T_e$ \cite{probemerlino}.
Since $V_f$ and $I_i$ are direct measurable plasma parameters \cite{mangilalpsst}, they are measured along the Y-axis (or radial direction) to understand the dynamics of the dust grain medium qualitatively in presence of the external magnetic field. A cylindrical probe of length $\sim$ 2 mm and radius of 0.125 mm  is used to measure $I_i$ and $V_f$ along the Y-axis (see Fig.~~\ref{fig:fig2} (b)). Fig.\ref{fig:fig12} shows the spatial variation (along Y-axis) of  $V_f$  and $I_i$ at Z $\sim$ 1 cm for a given discharge conditions (P = 3.5 W, p = 35 Pa) at different strengths of B-field. The errors in the measured values of $V_f$ and $I_i$ are within $\pm$ 5\% for the given B-field. The spatial measurement error (along Y-axis) in $V_f$ and $I_i$ is $\pm$ 0.2 mm.\par
It should be noted that dust grains absorb free electrons and reduce the density in dusty plasma. The Havnes parameter \cite{havnes}, $P_h$ = $Z_d n_d/n_i$, decides the density of free electrons in a dusty plasma. It has been assumed that plasma parameters are not strongly affected by the dust grains if $P_h < 1$ and plasma parameters without dust can be used to understand the dynamics of dusty plasma. In the present work, $P_h$ has the value $<$ 0.5 for $n_d$ $\sim$ 3$\times 10^{4}$ to 5 $\times 10^{4}$ $cm^{-3}$, $n_i$ $\sim$ 6$\times 10^{8}$ $cm^{-3}$, and $Z_d \sim$ 5$\times$ $10^3$ in the absence of B-field. The earlier experimental work also suggest that the spatial dependence of the plasma parameters remains nearly same with and without dust grains with a slightly higher or lower value at given location. Therefore, we have measured the ion saturation current and floating potential without dust particles and expect a similar spatial trend in the dusty plasma.\par
\begin{figure*}
 \centering
\subfloat{{\includegraphics[scale=0.315]{Fig12a}}}%
\subfloat{{\includegraphics[scale=0.3150]{Fig12b}}
 \caption{\label{fig:fig12}(a) Floating potential measured by a cylindrical probe with respect to ground along the Y-axis (or radial direction) from the center of aluminium ring (Y = 0 mm) to the ring surface (Y = 10 mm) at Z $\sim$ 1.0 cm for various strengths of magnetic fields. (b) Ion saturation current variation at same probe location for different values of B-field. The probe is kept at a fixed bias voltage of -30 V and the ion current is measured for power of P = 3.5 W at a pressure, p = 35 Pa.}
 \end{figure*}
In the absence of magnetic field, the dust grains exhibit a thermal motion in the potential well (Fig.~\ref{fig:fig2}). The ion density and velocity gradient, which determine the magnitude of the ion drag gradient ($\nabla F_i(E)$) near the edge of the ring (or edge of the potential well) are not sufficient to drive the vortex flow. With the application of a magnetic field, the confinement of electrons increases the plasma density as well as $T_e$ at low B (B $<$ 0.05 T) \cite{mangilalpsst}. Therefore, the variation in ion current at given location in the plasma is maximum in this range of B-field. In the present set of experiments, the expected variation of $T_e$ along the Y-axis (Y = 0 to 8 mm) is negligible because of the small spatial variation of the plasma density. In our previous study, it has been confirmed that $T_e$ remains almost constant while the plasma density is increased \cite{mangilalpsst}. Therefore, spatial variation of plasma density and plasma potential is considered to be equivalent to the variation of $I_i$ and $V_f$ \cite{probemerlino} as shown in Fig.~\ref{fig:fig12}.\par
In the presence of magnetic field, the time-averaged electric potential distribution in the sheath region of the ring is modified which increases the radial electric field ($E_r$) in the sheath region of the ring \cite{2drotationmagneticfield2}. It is clear from Fig.~\ref{fig:fig12}(a) that the gradient of $V_f$ (or $V_p$) in the edge region increases with increasing B-field, which indicates the increase of radial E-field. The velocity of drifting ions ($\vec{v_i} = \mu_i \vec{E_r}$) increases with increasing the strength of B-field. However, the ion density is less in the edge region than in the central region (see Fig.~\ref{fig:fig12}(b)) which points the ion density gradient in the opposite direction than the radial E-field. But the $V_f$ gradient is higher than the ion density gradient in edge region, which indicates that the role of velocity gradient (or radial E-field) is stronger than ion density to drive the vortex flow through radial ion shear flow or gradient (Eq. 6 and 7) in the presence of the electric field ($E_z$) against the dissipation losses by neutrals\cite{vortexmicrogravity,icedustyvortex,laishramshearflow}. Hence the rotating edge particles form a vortex structure (V--I) in the Y--Z plane or a single rotating dust torus in 3D dusty plasma. The gradient of $V_f$ in the edge region continuously increases as the strength of B-field is increased, which shows higher radial E-field at strong B. In our observations, we see a reduction in size of the edge vortex (see Fig.~\ref{fig:fig4}) which also confirms the role of radial E-field in the formation of edge vortex (V--I). A schematic diagram of the direction of rotation due to the shear in the ion drag force along with electric field is shown in Fig.~\ref{fig:fig13}(a). In our experiments, the direction of the edge vortex flow (see Fig.~\ref{fig:fig3} and Fig.~\ref{fig:fig9}) is found to be similar to that predicted by theoretical model which confirms the role of the ion drag gradient or ion shear flow along with electric field for creating the edge vortex (V--I) in a vertical plane or a rotating dust torus in 3D dusty plasma. The magnitude of the driving force ($\vert\nabla F_i(E) \times \vec{E_z} \vert$) determines the angular frequency of the rotating particles in the dust torus, which strongly depends on the potential distribution in the edge region (or radial electric field). Since a B-field increases the gradient of potential in the edge region (see Fig.~\ref{fig:fig12}(a)), $\omega$ increases with increasing the strength of the external magnetic field. \\
\begin{figure}
\centering
 \includegraphics[scale = 0.9]{Fig13}
\caption{\label{fig:fig13}Schematic representation of the rotational direction of particles caused by driving forces (a)  ion shear flow and  (b) dust charge gradient.}
\end{figure}
The radial component of  the electric field ($E_r$) in the presence of the magnetic field also drives an azimuthal flow of the ions through the $\vec{E_r} \times  \vec{B}$ drift. These drifted ions in the azimuthal direction transfer their momentum to the dust particles and set them into rotational motion \cite{2dclusterrotation,knopkamagneticrotation,satorotation}. Due to the  $\vec{E_r} \times  \vec{B}$ drift motion of ions, the rotating dust grain in a vortex can move to the next vertical plane. This is one of possible causes to have the azimuthal velocity component along with the radial velocity component in the X--Y plane of a rotating dust torus (see Fig.~\ref{fig:fig7}). In the case of the conducting ring electrode, particles which are confined in the deep sheath region or bottom of the potential well are assumed to be less strongly coupled. We assume that these particles are either a result of agglomeration of particles or the presence of some massive impurity particles in the sample of mono-dispersive MF particles. They do not participate in the vortex motion leading to a dust torus. These particles rotate in the azimuthal direction in the X--Y plane, which can be seen in Fig.~\ref{fig:fig8}.\par
At the higher magnetic field, B $>$ 0.15 T, dust grains in the central region rotate in opposite direction to the edge vortex flow and form a pair of counter-rotating dust vortices (or dust tori). It is seen in Fig.~\ref{fig:fig12}(a) that the gradient of $V_f$ is stronger in the edge region than in the central region of plasma at higher B-field. Fig.~\ref{fig:fig12}(b) shows that the ion density gradient increases in central region of plasma at higher strength of B-field. However, the role of $v_i$  ($\vec{v_i} = \mu_i \vec{E_r}$) determining the magnitude of ion drag gradient dominates over ion density $n_i$ in the central region dust grains medium. The $\vec{E_r} \times  \vec{B}$  ion drift induced motion of dust grains  (Fig.~\ref{fig:fig8}) at given B-field also indicates the radial outward flow of ions. Both results are in favour of a negligible role of ion density gradient to drive the vortex flow in opposite direction (V--II). Thus, the second driving force (Eq. 6) which arises due to the dust charge gradient may excite the central region vortex motion  (V--II)  in the presence of E-field or gravity \cite{vaulinajetp,vaulinaselfoscillation, selfexcitedmotion,mangirotationpop,mangilalvortexseries,horizontalrotation}. The spatial plasma inhomogeneity is one of the possible causes for the dust charge gradient \cite{mangilalvortexseries}. Figure~\ref{fig:fig12}(b) confirms the inhomogeneity in the plasma density in the central region at higher B. It has been proven by a theoretical model that even 1 \% of dust charge gradient can initiate the vortex motion through an instability \cite{vaulinaselfoscillation,vaulinasripta2004}. The direction of rotation due to the dust charge gradient along with E-field or gravity is shown in Fig.~\ref{fig:fig13}(b). At B $>$ 0.15 T, ions start to be magnetized and electrons are fully magnetized. The magnetic field reduces the plasma loss to the ring electrode, hence, the density of the plasma confined in the ring electrode increases. In spite of the ion current, the plasma glow intensity around and in the ring electrode (without dust particles) noticed with naked eyes also confirms the plasma density enhancement at higher B (B $>$ 0.15 T). It is fact that plasma density increases with increasing the glow intensity in rf discharge.  Therefore, we expect the plasma density gradient towards the center of ring at strong B-field.
\par
In our recent study, the role of the B-field on the surface potential (or charge) on the spherical probe (or large dust grain) has been studied \cite{mangilalpsst}. The grain charge is determined by the balance of electrons and ions flux to its surface \cite{Charging}. It has been observed in experiments that the dust charge strongly depends on the plasma density \cite{mangilalpsst} in the magnetized plasma.  It collects more electrons in the higher density region than that in low density region in the presence of B-field. A higher electron current makes its surface more negative. A reduction of the electron flux to dust surface in the low plasma density region makes its surface less negative \cite{floatingpotential,mangilalpsst}. Since the plasma is quasi-neutral in the central region, the electron density is almost equal to the ion density. In the present set of experiments, the plasma density (or electron density) gradient in the central region (expected $>$ 10 \%) creates a dust charge gradient in the same direction. This dust charge gradient $\nabla Q_d = e\nabla Z_d$, orthogonal to the gravitational force ($\vec{F}_g$), or ion drag force ($\vec{F}_I$) acting on the dust particles drives the vortex flow \cite{vaulinajetp,vaulinaselfoscillation, selfexcitedmotion,mangirotationpop,mangilalvortexseries,horizontalrotation}. With increasing magnetic field from 0.2 T to 0.8 T, the angular frequency of the rotating particles in the central region vortex (V--II) increases. This increase in $\omega$ is due to the increase in the magnitude of the dust charge gradient which depends on the gradient of the plasma density. Hence the angular frequency of the central vortex flow (V--II) increases with increasing the strength of the external B-field. The direction of the vortex flow is in the direction of the charge gradient, which is in accordance with the available theoretical model \cite{vaulinaselfoscillation}.\\
\section{Summary} \label{sec:summary}
The present work highlights the collective dynamics of a 3D dusty plasma in the presence of an external strong magnetic field. The 3D dusty plasma is created in a capacitively coupled discharge by placing an additional conducting or non-conducting ring of a specific diameter and width on the lower powered electrode. The observed results of the reported work are summarized as:
\begin{enumerate}
\item A 3D dusty plasma in a strong magnetic field can be created using an additional conducting or non-conducting ring of a particular inner diameter and width (or thickness) in an rf discharge.
\item The magnetic field modifies the potential distribution of the edge region or sheath region and a potential gradient is develop near the edge region of ring, which gives rise to a radial electric field, hence, increases the ion shear flow. The ion drag gradient along with the E-field drives the vortex flow near the edge of potential well and an edge vortex (V--I) is formed.
\item At higher magnetic fields (B $>$ 0.15 T), electrons are fully magnetized and ions start to get magnetized, which increases the plasma density in the central region of the dusty plasma with increasing B-field. Thus, the magnetic field creates an inhomogeneous plasma in the confining potential well for B $>$ 0.15 T. The plasma inhomogeneity is responsible for the dust charge gradient, which along with the electric field or gravity drives the central vortex motion.
\item The angular frequency has a radial dependence which suggests a differential or sheared rotational motion in the vortices.
\item The magnetic field enhances the angular frequency of the rotating particles in the vortex. Particles in the potential well of the conducting ring have a higher angular frequency than that of the non-conducting ring.
\end{enumerate}

The formation of the edge vortex is discussed on the basis of a radial ion shear flow or ion drag gradient together with the electric field in the presence of an external magnetic field. Weakly coupled particles rotate in the azimuthal direction due to the $\vec{E_r} \times  \vec{B}$ drift of the ions in this plane. The onset of the vortex motion of the central region particles at higher magnetic field is understood by the presence of a dust charge gradient along with the gravity or electric field. The direction of the vortex motion based on a theoretical model also supports our qualitatively discussed sources of driving force.\par
The present work confirms that dynamics of 3-dimensional dusty plasma is determined by the magnitude of radial ions shear flow near the confining boundary, resulting in a vortex motion in the vertical (Y--Z) plane. In a strong B-field, the dust charge gradient due to plasma inhomogeneity also induces the vortex motion in the 3D strongly coupled dusty plasma. However, a 2-dimensional dust cluster in a similar confining potential well always rotates in the azimuthal or  $\vec{E_r} \times  \vec{B}$ direction even at strong B-field. There are many challenges to diagnose the dusty plasma in the presence of strong magnetic field using the electrostatic probes as well as spectroscopy. For getting a better understanding of the collective dynamics of strongly magnetized 3D dusty plasma, computer simulation for such plasma systems are necessary. In the future, we plan to perform numerical simulations to understand the presented experimental results in more details.
\section{Data Availability Statement} The data that support the findings of this study are available from the corresponding author upon reasonable request.

redpajama_set_name: RedPajamaArXiv


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Tyronn Lue Speaks On The Burden On LeBron James' Shoulders This Season
By Tomer Azarly · 2 min read
In almost every postseason for LeBron James, he's the guy doing all the work for his team. Whether he was in Cleveland or Miami, James was the number one option for his team. However, that seems to have changed this postseason.
James has career playoff averages of 28 points, 8.8 rebounds, 6.7 assists, 1.7 steals, and 1.0 block per game on 47% shooting and had to do the most for the Cavs in the 2008-09 postseason, when he averaged 35.3 points, 9.1 rebounds, 7.3 assists and 1.6 steals. While his rebounds and assists have always been high, his lowest points-per-game average has come in this 2015-16 postseason.
Coach Tyronn Lue spoke about LeBron's play through eight games, per Dave McMenamin of ESPN.
"LeBron is letting the game come to him," Lue said after practice Saturday. "When he wants to be aggressive and he sees fit to be aggressive when the teams have a good run or whatever they may have, then he just takes over the game … And with Kyrie (Irving) and Kevin (Love) playing at a high level, he can take a lot of mileage off of his body, reduce his (usage) rate and just kind of seeing and figuring out the flow of the game."
James has averaged just 23.5 points per game this season, which is a far-cry from his 28 points per game average for his career, and the extra help that LeBron has had will be welcome sight to everyone except their next two opponents.
Evan Mobley hits milestone not seen since LeBron James 18 years ago
Reese Nasser · 3 hours ago
"I don't think he's been in this position before where he can just sit back and see the flow of the game, see where he has to take over the game and it's been great for him," said Lue. "I mean, to average 23 points or 24 points and sweep both series is big for us because now our other guys are stepping up, they're playing well and we know LeBron always can play well."
James and the Cavs will find out their Eastern Conference opponents tday when the Raptors and Heat face off in the decisive Game 7.
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Managers In Focus
How Chelsea will change forever under Frank Lampard
Anmol Singla
Frank Lampard's appointment as Head Coach to the West London football club set the fans on a path they had forgotten after the frequent dismals of their club managers over the past two decades. The Abramovich-Era has certainly taken a turn for permanence and diligence, but more importantly for patience.
The Blues have witnessed more than twelve managers over the last twenty years and while that had kept the dressing room in a constant state of conflict, it has also been a boon for the likes of Frank Lampard who have played under a dozen of different managers and were granted front row seats to witness their individual managerial styles.
The positioning of his arrival could not be at a better time as the club takes a turn leaving its old guard behind and making way for young and driven players to make their place in the club. The Chelsea Youth Academy is one of the frontiers in youth training and as an organisation; it has proved that young players can safely be given the opportunity to prove themselves at Stamford Bridge in top tier football.
Frank was not just one of my best players ever, but also one of the best professionals!
-Jose Mourinho
The club fanbase has been revived from the polarisation and expectation of low standards it suffered due to the frequent changes at the club. Fans now have risen to be more committed and motivated to support the club through the wins and defeats, whether the reason being the Head Coach or to cheer on the players that have risen through Chelsea youth ranks to make it to the first team and represent them. The likes of Tammy Abraham, Mason Mount, Billy Gilmour, Reece James, Fikayo Tomori are the future of the club and Lampard has given them all chances to prove themselves with Abraham and Mount heading the attack.
Lampard's behind-the-scenes team including Jody Morris, Peter Cech, Chris Jones and Claude Makelele are nothing short of legends at what they have achieved and they know what it is like to win. But more importantly, they know what it takes to win as a team and the sacrifice behind it. All of them together working as a well-oiled machinery may do wonders for the club.
Frank & the Future…
The only thing that Lampard needs to keep an eye on is his ability to make transfers. Transfers will play a key role in the success of the club. Inspite of being banned initially due to few unfortunate internal discrepancies, the club now has a full money chest to spend freely on available players. The mid season transfer of American player Christian Pulisic did not go in vain and the young player has proved himself worthy of instrumenting play and making sure the ball reaches the back of the net. However, the league's most expensive goalkeeper transfer met with skepticism after Kepa Arrizabalaga could not prove his prices worth in competitive games and is hanging on a loose end with Lampard looking for an out with the goalkeeper. The new season signing of Ajax winger Hakim Ziyech will come as a strong addition to the elite group of Kovacic, Jorginho and Kante. The need for a striker was also extinguished with the signing of Timo Werner from RB Leipzig who has shown promise in his ability to coordinate with the midfield. The transfers are still open and the defence sector still needs strengthening. Many options are being considered and it is up to Lampard to deal with who he sees as a valuable addition to the team.
Lampard is the right person to begin an extended prime project with the club. With his historical and emotional attachment to the club, the fans and players are bound to be patient and work harder to achieve silverware and glory. The inspirational value of Frank Lampard should not be taken for granted. It is very rare that debatably the most victorious player of a club comes back to lead and mentor that club. Banners of 'Super Frank' and 'Frankie Lampard' are hung across the Bridge and chants from the fans do not go unheard. This plays a huge factor in driving the players to do better. Same was the case when Zinedine Zidane returned to his former club Real Madrid as Manager and went on to win three consecutive titles at the UEFA Champions League.
The atmosphere among Chelsea fans has never been so positive and it is the need of the hour. It cannot be denied that it will be a challenging journey of change, but that is why Lampard has been placed in the middle of the process. He is capable of holding all of it together while big changes are made in the club. Frank Lampard will keep the fan base and the players united.
His appointment has been compared with Sir Alex Ferguson's time with Manchester United and one can only hope it is as glorious and committed.
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Former television journalist Anne Sinclair, also known as the wife of former IMF chief Dominique Strauss-Kahn, has been giving more details of a memoir she is preparing.
L'Express magazine reported on Thursday that the book will be called 21, rue la Boétie.
The address in Paris' wealthy 8th arrondissement was the location of an art gallery belonging to her grandfather, Paul Rosenberg.
Rosenberg was a gallery owner who also represented artists including Picasso, Braque and Matisse. He left Paris for the United States in 1940 to escape the Nazis and opened a gallery in New York.
The book will not be a "classic" biography, according to the magazine but, in Sinclair's words, "research into my family archives, childhood memories, portraits and stories from Bordeaux, Paris and New York."
Reports also circulated in December that Sinclair would be resuming her journalistic career by taking a top spot with the Huffington Post, which is set to launch in France.
The reports were neither confirmed nor denied by Arianna Huffington, the site's founder, or Louis Dreyfus, president at Le Monde newspaper which is partnering with Huffington in the venture.
Sinclair has remained popular throughout her husband's legal problems, ending the year by being named Woman of the Year in a poll by French women's magazine Terrafemina.