Only show content I have access to (230)
Only show open access (33)
Chapters (497)
Last 3 years (190)
Over 3 years (1552)
Physics And Astronomy (428)
Materials Research (307)
Chemistry (304)
Psychiatry (122)
Area Studies (116)
Earth and Environmental Sciences (113)
Politics and International Relations (81)
Classical Studies (65)
MRS Online Proceedings Library Archive (277)
ASA News (92)
Journal of Fluid Mechanics (48)
British Journal of Nutrition (37)
Infection Control & Hospital Epidemiology (36)
Antiquity (32)
The British Journal of Psychiatry (32)
Weed Science (27)
Cambridge Quarterly of Healthcare Ethics (26)
Cardiology in the Young (22)
CNS Spectrums (21)
Proceedings of the International Astronomical Union (21)
Weed Technology (21)
Journal of Materials Research (19)
Quaternary Research (19)
Prehospital and Disaster Medicine (18)
Microscopy and Microanalysis (15)
The Journal of Economic History (15)
Journal of the International Neuropsychological Society (14)
Behavioral and Brain Sciences (13)
Epidemiology & Infection (13)
Boydell & Brewer (17)
Anthem Press (1)
ISEAS–Yusof Ishak Institute (1)
Materials Research Society (304)
African Studies Association (95)
Weed Science Society of America (56)
Nutrition Society (46)
The Royal College of Psychiatrists (37)
Society for Healthcare Epidemiology of America (SHEA) (36)
International Astronomical Union (33)
Ryan Test (30)
HTAi Organizational Members (26)
AEPC Association of European Paediatric Cardiology (22)
Neuroscience Education Institute (21)
Royal College of Speech and Language Therapists (21)
test society (19)
World Association for Disaster and Emergency Medicine (18)
The Roman Society - JRS and BRI (17)
The Association for Asian Studies (16)
Brazilian Society for Microscopy and Microanalysis (SBMM) (15)
Economic History Association EHA JEH (15)
International Neuropsychological Society INS (14)
The Australian Society of Otolaryngology Head and Neck Surgery (13)
Women and Politics Section-APSA (12)
Cambridge Library Collection - Classics (28)
Studies in the Social and Cultural Foundations of Language (25)
Cambridge Studies in Probability, Induction and Decision Theory (22)
Cambridge Texts in the History of Political Thought (20)
Cambridge Studies in Medieval Literature (19)
Anglo-Saxon Studies (17)
Cambridge Surveys of Economic Literature (17)
Political Economy of Institutions and Decisions (16)
Society for New Testament Studies Monograph Series (16)
Cambridge Aerospace Series (15)
The Cambridge Edition of the Works of Joseph Conrad (14)
Case Studies in Neurology (5)
The Cambridge History of the Second World War (4)
Ecological Reviews (3)
Cambridge Companions to the Ancient World (2)
Cambridge Handbooks in Language and Linguistics (2)
Cambridge Companions to Literature (1)
Law in Context (1)
New Cambridge History of the Bible (1)
The American Law Institute Reporters Studies on WTO Law (1)
Cambridge Library Collection (28)
Cambridge Histories (6)
Cambridge Histories - American History (4)
Cambridge Histories - Asian History (4)
Cambridge Histories - British & European History (4)
Cambridge Histories - Global History (4)
Cambridge Histories - Middle East & African Studies (4)
Cambridge Companions (3)
Cambridge Companions to Literature and Classics (3)
Cambridge Handbooks of Linguistics (2)
Cambridge Histories - Literature (1)
Cambridge Histories - Religion (1)
Gridded and direct Epoch of Reionisation bispectrum estimates using the Murchison Widefield Array
Cathryn M. Trott, Catherine A. Watkinson, Christopher H. Jordan, Shintaro Yoshiura, Suman Majumdar, N. Barry, R. Byrne, B. J. Hazelton, K. Hasegawa, R. Joseph, T. Kaneuji, K. Kubota, W. Li, J. Line, C. Lynch, B. McKinley, D. A. Mitchell, M. F. Morales, S. Murray, B. Pindor, J. C. Pober, M. Rahimi, J. Riding, K. Takahashi, S. J. Tingay, R. B. Wayth, R. L. Webster, M. Wilensky, J. S. B. Wyithe, Q. Zheng, David Emrich, A. P. Beardsley, T. Booler, B. Crosse, T. M. O. Franzen, L. Horsley, M. Johnston-Hollitt, D. L. Kaplan, D. Kenney, D. Pallot, G. Sleap, K. Steele, M. Walker, A. Williams, C. Wu
Published online by Cambridge University Press: 18 July 2019, e023
We apply two methods to estimate the 21-cm bispectrum from data taken within the Epoch of Reionisation (EoR) project of the Murchison Widefield Array (MWA). Using data acquired with the Phase II compact array allows a direct bispectrum estimate to be undertaken on the multiple redundantly spaced triangles of antenna tiles, as well as an estimate based on data gridded to the uv-plane. The direct and gridded bispectrum estimators are applied to 21 h of high-band (167–197 MHz; z = 6.2–7.5) data from the 2016 and 2017 observing seasons. Analytic predictions for the bispectrum bias and variance for point-source foregrounds are derived. We compare the output of these approaches, the foreground contribution to the signal, and future prospects for measuring the bispectra with redundant and non-redundant arrays. We find that some triangle configurations yield bispectrum estimates that are consistent with the expected noise level after 10 h, while equilateral configurations are strongly foreground-dominated. Careful choice of triangle configurations may be made to reduce foreground bias that hinders power spectrum estimators, and the 21-cm bispectrum may be accessible in less time than the 21-cm power spectrum for some wave modes, with detections in hundreds of hours.
Radical Arab Nationalism and Political Islam. By Lahouari Addi. Translated by Anthony Roberts. Washington, DC: Georgetown University Press, 2017. xi + 276 pp. $104.95 hardcover, $34.95 paper
Joseph J. Kaminski
Journal: Politics and Religion / Volume 12 / Issue 3 / September 2019
Correlation between white blood cell count and mood-stabilising treatment response in two bipolar disorder trials
Ole Köhler-Forsberg, Louisa G. Sylvia, Charles L. Bowden, Joseph R. Calabrese, Michael E. Thase, Richard C. Shelton, Melvin McInnis, Mauricio Tohen, James H. Kocsis, Terence A. Ketter, Edward S. Friedman, Thilo Deckersbach, Michael J. Ostacher, Dan V. Iosifescu, Susan McElroy, Andrew A. Nierenberg
Journal: Acta Neuropsychiatrica / Volume 31 / Issue 4 / August 2019
Immune system markers may predict affective disorder treatment response, but whether an overall immune system marker predicts bipolar disorder treatment effect is unclear.
Bipolar CHOICE (N = 482) and LiTMUS (N = 283) were similar comparative effectiveness trials treating patients with bipolar disorder for 24 weeks with four different treatment arms (standard-dose lithium, quetiapine, moderate-dose lithium plus optimised personalised treatment (OPT) and OPT without lithium). We performed secondary mixed effects linear regression analyses adjusted for age, gender, smoking and body mass index to investigate relationships between pre-treatment white blood cell (WBC) levels and clinical global impression scale (CGI) response.
Compared to participants with WBC counts of 4.5–10 × 109/l, participants with WBC < 4.5 or WBC ≥ 10 showed similar improvement within each specific treatment arm and in gender-stratified analyses.
An overall immune system marker did not predict differential treatment response to four different treatment approaches for bipolar disorder all lasting 24 weeks.
Roderick Lemonde MacFarquhar, 1930–2019
Roderick MacFarquhar Article Collection
Joseph Fewsmith, Alastair Iain Johnston, Elizabeth J. Perry, Ezra F. Vogel
Journal: The China Quarterly / Volume 238 / June 2019
Lifetime bipolar disorder comorbidity and related clinical characteristics in patients with primary obsessive compulsive disorder: a report from the International College of Obsessive–Compulsive Spectrum Disorders (ICOCS)
Bernardo Dell'Osso, Matteo Vismara, Beatrice Benatti, Giovanna Cirnigliaro, Benedetta Grancini, Naomi A. Fineberg, Michael Van Ameringen, Eric Hollander, Dan J. Stein, Josè M. Menchon, Carolyn I. Rodriguez, Humberto Nicolini, Nuria Lanzagorta, Stefano Pallanti, Giacomo Grassi, Christine Lochner, Donatella Marazziti, Georgi Hranov, Oguz Karamustafalioglu, Luchezar Hranov, Joseph Zohar
Journal: CNS Spectrums , First View
Published online by Cambridge University Press: 27 May 2019, pp. 1-7
Bipolar disorder (BD) and obsessive compulsive disorder (OCD) are prevalent, comorbid, and disabling conditions, often characterized by early onset and chronic course. When comorbid, OCD and BD can determine a more pernicious course of illness, posing therapeutic challenges for clinicians. Available reports on prevalence and clinical characteristics of comorbidity between BD and OCD showed mixed results, likely depending on the primary diagnosis of analyzed samples.
We assessed prevalence and clinical characteristics of BD comorbidity in a large international sample of patients with primary OCD (n = 401), through the International College of Obsessive–Compulsive Spectrum Disorders (ICOCS) snapshot database, by comparing OCD subjects with vs without BD comorbidity.
Among primary OCD patients, 6.2% showed comorbidity with BD. OCD patients with vs without BD comorbidity more frequently had a previous hospitalization (p < 0.001) and current augmentation therapies (p < 0.001). They also showed greater severity of OCD (p < 0.001), as measured by the Yale–Brown Obsessive Compulsive Scale (Y-BOCS).
These findings from a large international sample indicate that approximately 1 out of 16 patients with primary OCD may additionally have BD comorbidity along with other specific clinical characteristics, including more frequent previous hospitalizations, more complex therapeutic regimens, and a greater severity of OCD. Prospective international studies are needed to confirm our findings.
Identification of proteins for controlled nucleation of metal-organic crystals for nanoenergetics
Zachary E. Reinert, Chia-Suei Hung, Andrea R. Poole, Joseph M. Slocik, Marquise G. Crosby, Srikanth Singamaneni, Rajesh R. Naik, Patrick B. Dennis, Wendy J. Crookes-Goodson, Maneesh K. Gupta
Journal: MRS Communications / Volume 9 / Issue 2 / June 2019
Here, we report that a marine sandworm Nereis virens jaw protein, Nvjp1, nucleates hemozoin with similar activity as the native parasite hemozoin protein, HisRPII. X-ray diffraction and scanning electron microscopy confirm the identity of the hemozoin produced from Nvjp1-containing reactions. Finally, we observed that nAl assembled with hemozoin from Nvjp1 reactions has a substantially higher energetic output when compared to analogous thermite from the synthetic standard or HisRPII-nucleated hemozoin. Our results demonstrate that a marine sandworm protein can nucleate malaria pigment and set the stage for engineering recombinant hemozoin production for nanoenergetic applications.
Beryllium-10 dating of the Foothills Erratics Train in Alberta, Canada, indicates detachment of the Laurentide Ice Sheet from the Rocky Mountains at ~15 ka
Martin Margold, John C. Gosse, Alan J. Hidy, Robin J. Woywitka, Joseph M. Young, Duane Froese
Journal: Quaternary Research , First View
Published online by Cambridge University Press: 17 April 2019, pp. 1-14
The Foothills Erratics Train consists of large quartzite blocks of Rocky Mountains origin deposited on the eastern slopes of the Rocky Mountain Foothills in Alberta between ~53.5°N and 49°N. The blocks were deposited in their present locations when the western margin of the Laurentide Ice Sheet (LIS) detached from the local ice masses of the Rocky Mountains, which initiated the opening of the southern end of the ice-free corridor between the Cordilleran Ice Sheet and the LIS. We use 10Be exposure dating to constrain the beginning of this decoupling. Based on a group of 12 samples well-clustered in time, we date the detachment of the western LIS margin from the Rocky Mountain front to ~14.9 ± 0.9 ka. This is ~1000 years later than previously assumed, but a lack of a latitudinal trend in the ages over a distance of ~500 km is consistent with the rapid opening of a long wedge of unglaciated terrain portrayed in existing ice-retreat reconstructions. A later separation of the western LIS margin from the mountain front implies higher ice margin–retreat rates in order to meet the Younger Dryas ice margin position near the boundary of the Canadian Shield ~2000 years later.
Investigation of healthcare infection risks from water-related organisms: Summary of CDC consultations, 2014—2017
Kiran M. Perkins, Sujan C. Reddy, Ryan Fagan, Matthew J. Arduino, Joseph F. Perz
Journal: Infection Control & Hospital Epidemiology / Volume 40 / Issue 6 / June 2019
Water exposures in healthcare settings and during healthcare delivery can place patients at risk for infection with water-related organisms and can potentially lead to outbreaks. We aimed to describe Centers for Disease Control and Prevention (CDC) consultations involving water-related organisms leading to healthcare-associated infections (HAIs).
Retrospective observational study.
We reviewed internal CDC records from January 1, 2014, through December 31, 2017, using water-related terms and organisms, excluding Legionella, to identify consultations that involved potential or confirmed transmission of water-related organisms in healthcare. We determined plausible exposure pathways and routes of transmission when possible.
Of 620 consultations during the study period, we identified 134 consultations (21.6%), with 1,380 patients, that involved the investigation of potential water-related HAIs or infection control lapses with the potential for water-related HAIs. Nontuberculous mycobacteria were involved in the greatest number of investigations (n = 40, 29.9%). Most frequently, investigations involved medical products (n = 48, 35.8%), and most of these products were medical devices (n = 40, 83.3%). We identified a variety of plausible water-exposure pathways, including medication preparation near water splash zones and water contamination at the manufacturing sites of medications and medical devices.
Water-related investigations represent a substantial proportion of CDC HAI consultations and likely represent only a fraction of all water-related HAI investigations and outbreaks occurring in US healthcare facilities. Water-related HAI investigations should consider all potential pathways of water exposure. Finally, healthcare facilities should develop and implement water management programs to limit the growth and spread of water-related organisms.
21 - Vervet Monkeys (Chlorocebus pygerthrus), Chimpanzees (Pan troglodytes), and Humans (Homo sapiens): Studying Interactions Using Stable Isotope Analysis
from Part VI - Ethnoprimatology
By Matt Sponheimer, James E. Loudon, J. Paul Grobler, Kimberly Moyer, Joseph G. Lorenz
Trudy R. Turner, University of Wisconsin, Milwaukee, Christopher A. Schmitt, Boston University, Jennifer Danzy Cramer
Book: Savanna Monkeys
Print publication: 21 March 2019, pp 255-262
8 - Population Genetic Structure of Vervet Monkeys in South Africa
from Part III - Population Genetics
By Willem G. Coetzer, Joseph G. Lorenz, Nelson B. Freimer, J. Paul Grobler
Influences of forested and grassland vegetation on late Quaternary ecosystem development as recorded in lacustrine sediments
Kendra K. McLauchlan, Ioan Lascu, Emily Mellicant, Robert J. Scharping, Joseph J. Williams
Journal: Quaternary Research / Volume 92 / Issue 1 / July 2019
Geosphere-biosphere interactions are ubiquitous features of the Earth surface, yet the development of interactions between newly exposed lithologic surfaces and colonizing plants during primary succession after glaciation are lacking temporal detail. To assess the nature, rate, and magnitude of vegetation influence on parent material and sediment delivery, we analyzed ecosystem and geochemical proxies from lacustrine sediment cores at a grassland site and a forested site in the northern United States. Over time, terrigenous inputs declined at both sites, with increasing amounts of organic inputs toward present. The similarities between sites were striking given that the grassland sequence began in the Early Holocene, and the forested sequence began after the last glacial maximum. Multiple mechanisms of chemical weathering, hydrologic transport, and changes in source material potentially contribute to this pattern. Although there were strong links between vegetation composition and nitrogen cycling at each site, it appears that changes in forest type, or from oak woodland to grassland, did not exert a large influence on elemental (K, Ti, Si, Ca, Fe, Mn, and S) abundance in the sedimentary sequences. Rather, other factors in the catchment-lake system determined the temporal sequence of elemental abundance.
Shiva Mahadeva. Dagar Brothers. Dhrupad, Classical Vocal Music of North India. Recordings uncredited. Annotated by Felix van Lamsweerde. PAN Records PAN 4001-02KCD. 2 CDs with 11 pages of notes in English, 4 b/w photographs of performers and instruments, 1 b/w photograph of folk art. Region: South Asia-North India. 14 tracks recorded at a live performance (6 tracks on CD 1; 8 tracks on CD 2). Tracks 1-6 on CD 1: Malkauns; Tracks 1-3 on CD 2: Darbari Kanada; 4: Adana; 5: Bhatiyar; 6-8: Demonstration. CD 1:71'30; CD 2:67'35. 1996.
Joseph J. Palackal
Journal: Yearbook for Traditional Music / Volume 31 / 1999
Lotus Signatures: Dr. N. Ramani, flute, and Trichy Sankaran, mrdangam. Annotations by David Nelson. Music of the World CDT-141. CD with 4 pages of notes in English and 2 photographs of performers. No bibliography. 5 tracks recorded in the studio. 58'56. 1997.
Published online by Cambridge University Press: 07 March 2019, p. 207
Muslim Fula Business Elites and Politics in Sierra Leone. ByAlusine Jalloh. Rochester, N.Y.: University of Rochester Press, 2018. xvi + 320 pp. Photographs, maps, bibliography, notes, index. Cloth, $120.00. ISBN: 978-1-58046-917-3.
Joseph J. Bangura
Journal: Business History Review / Volume 92 / Issue 4 / Winter 2018
Further Application of the Intermediate X-Ray Probe
Isidore Adler, Joseph Axelrod, Jaime J. R. Branco
Journal: Advances in X-ray Analysis / Volume 2 / 1958
The electron probe is an extremely valuable tool for chemical analysis on a microscopic scale. There are many situations, however, that require analyses in the millimeter rather than micron range, where in fact, the use of the electron probe causes concern about sample homogeneity. The X-ray probe consisting of a small X-ray beam and focusing monochromator is very useful for this intermediate region. This X-ray probe is equally useful for electrically non-conducting as well as conducting specimens. Analysis need not be performed in vacuum and can be done with great rapidity.
For example by traversing a polished section of a combination of opaque minerals, it was possible to determine the distribution of copper, silver, arsenic, iron, and mercury and to show that an unidentified mineral was a copper arsenic mineral rather than an arsenoargentite as had been supposed.
3503 Restrictive feeding and excessive hunger in young children with obesity: A case series
Sally Grace Eagleton, Callie L. Brown, Melissa J. Moses, Joseph A. Skelton
Journal: Journal of Clinical and Translational Science / Volume 3 / Issue s1 / March 2019
OBJECTIVES/SPECIFIC AIMS: The purpose of this case series is to show how helping parents instill a non-restrictive, structure-based (i.e., authoritative) approach to feeding is useful in addressing family food conflicts in a clinical child obesity treatment program. METHODS/STUDY POPULATION: Case reports are presented for 3 young children (two 8-year-old males and one 7-year-old female) with obesity (BMI ≥ 95th percentile for age and sex). Patients underwent family-based treatment at Brenner FIT® (Families In Training), an interdisciplinary tertiary weight management clinic. RESULTS/ANTICIPATED RESULTS: All patients experienced a period of rapid weight gain and/or severe onset obesity. Parents reported a combination of problematic eating behaviors (e.g., sneaking food, frequent complaints of hunger, vomiting from rapid consumption). Families implemented structure-based feeding with a meal-snack schedule and allowed children to eat until they were full from the food provided at meal-snack times. BMI z-score decreased from 2.19 to 2.07 in patient 1 and from 2.43 to 2.09 in patient 2 (follow-up weight was not available for patient 3). DISCUSSION/SIGNIFICANCE OF IMPACT: The improvements observed by our clinical program after families lifted restriction and instituted authoritative feeding is anecdotal evidence for the ecological validity of existing empirical work. Randomized controlled trials are needed to examine causality.
3280 Mycobacterium bovis Bacille-Calmette-Guérin infection aggravates atherosclerosis
Moises Huaman, Joseph E. Qualls, David Kuhel, Shinsmon Jose, Eddy Konaniah, Ravi Komaravolu, Carl J. Fichtenbaum, George S. Deepe, David Y. Hui
OBJECTIVES/SPECIFIC AIMS: The study aimed at assessing whether M. bovis BCG infection and inflammation exacerbates the development of atherosclerosis in Ldlr-/- mice. METHODS/STUDY POPULATION: Twelve-week old male Ldlr-/- mice (n=10) were infected with M. bovis BCG (0.3–3.0x10^6 colony-forming units (CFUs)) via the intranasal route, to simulate a natural respiratory route of infection. Mice were subsequently fed a western-type diet (WD) containing 21% fat and 0.2% cholesterol for 16 weeks. Age-matched uninfected Ldlr-/- mice (n=10) fed with an identical WD served as controls. Mice were euthanized after 16 weeks of WD to examine atherosclerotic lesions in aortic root sections and en face aorta using Oil Red O staining. Plasma cholesterol and triglyceride levels were measured by enzymatic assays and lipoprotein distribution was assessed using fast protein liquid chromatography. Because of the important role of T cells and monocytes in atherosclerosis development, we assessed these cell subsets in blood using flow cytometry at 8 and 16 weeks. Experiments were conducted in duplicate. We used unpaired Student's t-test for group comparisons of numeric variables and flow cytometry data. RESULTS/ANTICIPATED RESULTS: M. bovis BCG infection significantly increased atherosclerotic lesions in en face aorta (plaque size per aorta area ratio; 0.15±0.13 vs. 0.06±0.02; P<0.01), but not in the aortic root. There were no significant differences in plasma cholesterol (1,160 mg/dL vs. 1,278 mg/dL; P = 0.36), triglycerides (340 mg/dL vs. 413 mg/dL; P = 0.28), or lipoprotein profiles between infected vs. uninfected mice at 16 weeks. M. bovis BCG increased circulating T lymphocytes (1,490 cells/uL vs. 1,227 cells/uL; P = 0.03) and monocytes (901 cells/uL vs. 414 cells/uL; P<0.01) within 8 weeks post-infection. When we assessed T lymphocyte subsets, M. bovis BCG infection increased total CD4+ T cell counts (556 cells/uL vs. 416 cells/uL; P<0.01) but not CD8+ T cells. No differences in the proportion of CD44+CD25+ activated T lymphocytes were noted between groups. When we assessed monocyte subsets, M. bovis BCG infection increased the numbers of Ly6Chigh (709 cells/uL vs. 362 cells/uL; P<0.01) and Ly6Clow (145 cells/uL vs. 35 cells/uL; P<0.01) monocytes. Infection was associated with an increased proportion of Ly6Clow monocytes at week 8 (17% vs. 8%; P<0.01) and week 16 (19% vs. 5%; P<0.01), compared to uninfected mice. DISCUSSION/SIGNIFICANCE OF IMPACT: M. bovis BCG infection increased the extent of atherosclerosis formation in the aortas of WD-fed hyperlipidemic Ldlr-/- mice after 16 weeks. Lipid profiles were similar between infected and uninfected mice, and therefore do not explain the observed differences in atherosclerosis. Compared to uninfected controls, M. bovis BCG-infected mice exhibited increased CD4+ T cell and monocyte driven inflammation. Interestingly, M. bovis BCG-infected mice had a higher proportion of non-classical Ly6Clow monocytes, suggesting a pro-atherogenic contribution of these cells in our model. Overall, our results support a pathogenic role of mycobacterial infection in atherosclerosis development and ASCVD.
Treatment-resistant and Multi-therapy resistant criteria for bipolar depression: A consensus definition – CORRIGENDUM
Diego Hidalgo-Mazzei, Michael Berk, Andrea Cipriani, Anthony J. Cleare, Arianna Di Florio, Daniel Dietch, John R. Geddes, Guy M. Goodwin, Heinz Grunze, Joseph F. Hayes, Ian Jones, Siegfried Kasper, Karine Macritchie, R. Hamish McAllister-Williams, Richard Morriss, Sam Nayrouz, Sofia Pappa, Jair C. Soares, Daniel J. Smith, Trisha Suppes, Peter Talbot, Eduard Vieta, Stuart Watson, Lakshmi N. Yatham, Allan H. Young, Paul R. A. Stokes
Journal: The British Journal of Psychiatry / Volume 214 / Issue 5 / May 2019
Published online by Cambridge University Press: 28 February 2019, p. 309
3 - A Framework for Secure Learning
from Part I - Overview of Adversarial Machine Learning
Anthony D. Joseph, University of California, Berkeley, Blaine Nelson, Benjamin I. P. Rubinstein, University of Melbourne, J. D. Tygar, University of California, Berkeley
Book: Adversarial Machine Learning
Print publication: 21 February 2019, pp 29-66
In this chapter we introduce a framework for qualitatively assessing the security of machine learning systems that captures a broad set of security characteristics common to a number of related adversarial learning settings. There has been a rich set of work that examines the security of machine learning systems; here we survey prior studies of learning in adversarial environments, attacks against learning systems, and proposals for making systems secure against attacks. We identify different classes of attacks on machine learning systems (Section 3.3), categorizing a threat in terms of three crucial properties.
We also present secure learning as a game between an attacker and a defender— the taxonomy determines the structure of the game and its cost model. Further, this taxonomy provides a basis for evaluating the resilience of the systems described by analyzing threats against them to construct defenses. The development of defensive learning techniques is more tentative, but we also discuss a variety of techniques that show promise for defending against different types of attacks.
The work we present not only provides a common language for thinking and writing about secure learning, but goes beyond that to show how the framework applies to both algorithm design and the evaluation of real-world systems. Not only does the framework elicit common themes in otherwise disparate domains but it has also motivated our study of practical machine learning systems as presented in Chapters 5, 6, and 8. These foundational principles for characterizing attacks against learning systems are an essential first step if secure machine learning is to reach its potential as a tool for use in real systems in security-sensitive domains.
This chapter builds on earlier research (Barreno, Nelson, Sears, Joseph, & Tygar 2006; Barreno, Nelson, Joseph, & Tygar 2010; Barreno 2008).
Analyzing the Phases of Learning
Attacks can occur at each of the phases of the learning process that were outlined in Section 2.2. Figure 2.1(a) depicts how data flows through each phase of learning. We briefly outline how attacks against these phases differ.
The Measuring Phase
With knowledge of the measurement process, an adversary can design malicious instances to mimic the measurements of innocuous data. After a successful attack against the measurement mechanism, the system may require expensive reinstrumentation or redesign to accomplish its task.
5 - Availability Attack Case Study: SpamBayes
from Part II - Causative Attacks on Machine Learning
Adversaries can also execute attacks designed to degrade the classifier's ability to distinguish between allowed and disallowed events. These Causative Availability attacks against learning algorithms cause the resulting classifiers to have unacceptably high false-positive rates; i.e., a successfully poisoned classifier will misclassify benign input as potential attacks, creating an unacceptable level of interruption in legitimate activity. This chapter provides a case study of one such attack on the SpamBayes spam detection system. We show that cleverly crafted attack messages—pernicious spam email that an uninformed human user would likely identify and label as spam—can exploit Spam- Bayes' learning algorithm, causing the learned classifier to have an unreasonably high false-positive rate. (Chapter 6 demonstrates Causative attacks that instead result in classifiers with an unreasonably high false-negative rate—these are Integrity attacks.) We also show effective defenses against these attacks and discuss the tradeoffs required to defend against them.
We examine several attacks against the SpamBayes spam filter, each of which embodies a particular insight into the vulnerability of the underlying learning technique. In doing so, we more broadly demonstrate attacks that could affect any system that uses a similar learning algorithm. The attacks we present target the learning algorithm used by the spam filter SpamBayes (spambayes.sourceforge.net), but several other filters also use the same underlying learning algorithm, including BogoFilter (bogofilter.sourceforge. net), the spam filter in Mozilla's Thunderbird email client (mozilla.org), and the machine learning component of SpamAssassin (spamassassin.apache.org). The primary difference between the learning elements of these three filters is in their tokenization methods; i.e., the learning algorithm is fundamentally identical, but each filter uses a different set of features. We demonstrate the vulnerability of the underlying algorithm for SpamBayes because it uses a pure machine learning method, it is familiar to the academic community (Meyer & Whateley 2004), and it is popular with over 700,000 downloads. Although here we only analyze SpamBayes, the fact that these other systems use the same learning algorithm suggests that other filters are also vulnerable to similar attacks. However, the overall effectiveness of the attacks would depend on how each of the other filters incorporates the learned classifier into the final filtering decision.