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Error Statistics Philosophy
A Perfect Time to Binge Read the (Strong) Likelihood Principle
Posted on December 30, 2019 by Mayo
An essential component of inference based on familiar frequentist notions: p-values, significance and confidence levels, is the relevant sampling distribution (hence the term sampling theory, or my preferred error statistics, as we get error probabilities from the sampling distribution). This feature results in violations of a principle known as the strong likelihood principle (SLP). To state the SLP roughly, it asserts that all the evidential import in the data (for parametric inference within a model) resides in the likelihoods. If accepted, it would render error probabilities irrelevant post data.
SLP (We often drop the "strong" and just call it the LP. The "weak" LP just boils down to sufficiency)
For any two experiments E1 and E2 with different probability models f1, f2, but with the same unknown parameter θ, if outcomes x* and y* (from E1 and E2 respectively) determine the same (i.e., proportional) likelihood function (f1(x*; θ) = cf2(y*; θ) for all θ), then x* and y* are inferentially equivalent (for an inference about θ).
(What differentiates the weak and the strong LP is that the weak refers to a single experiment.)
Violation of SLP:
Whenever outcomes x* and y* from experiments E1 and E2 with different probability models f1, f2, but with the same unknown parameter θ, and f1(x*; θ) = cf2(y*; θ) for all θ, and yet outcomes x* and y* have different implications for an inference about θ.
For an example of a SLP violation, E1 might be sampling from a Normal distribution with a fixed sample size n, and E2 the corresponding experiment that uses an optional stopping rule: keep sampling until you obtain a result 2 standard deviations away from a null hypothesis that θ = 0 (and for simplicity, a known standard deviation). When you do, stop and reject the point null (in 2-sided testing).
The SLP tells us (in relation to the optional stopping rule) that once you have observed a 2-standard deviation result, there should be no evidential difference between its having arisen from experiment E1 , where n was fixed, say, at 100, and experiment E2 where the stopping rule happens to stop at n = 100. For the error statistician, by contrast, there is a difference, and this constitutes a violation of the SLP.
Now for the surprising part: Remember the 61-year old chestnut from my last post where a coin is flipped to decide which of two experiments to perform? David Cox (1958) proposes something called the Weak Conditionality Principle (WCP) to restrict the space of relevant repetitions for frequentist inference. The WCP says that once it is known which Ei produced the measurement, the assessment should be in terms of the properties of the particular Ei. Nothing could be more obvious.
The surprising upshot of Allan Birnbaum's (1962) argument is that the SLP appears to follow from applying the WCP in the case of mixtures, and so uncontroversial a principle as sufficiency (SP)–although even that has been shown to be optional, strictly speaking. But this would preclude the use of sampling distributions. J. Savage calls Birnbaum's argument "a landmark in statistics" (see [i]).
Although his argument purports that [(WCP and SP) entails SLP], I show how data may violate the SLP while holding both the WCP and SP. Such cases directly refute [WCP entails SLP].
In Birnbaum's argument, he introduces an informal, and rather vague, notion of the "evidence (or evidential meaning) of an outcome z from experiment E". He writes it: Ev(E,z).
In my formulation of the argument, I introduce a new symbol to represent a function from a given experiment-outcome pair, (E,z) to a generic inference implication. It (hopefully) lets us be clearer than does Ev.
(E,z) InfrE(z) is to be read "the inference implication from outcome z in experiment E" (according to whatever inference type/school is being discussed).
An outline of my argument is in the slides for a talk below:
Binge reading the Likelihood Principle.
If you're keen to binge read the SLP–a way to break holiday/winter break doldrums– I've pasted most of the early historical sources before the slides. The argument is simple; showing what's wrong with it took a long time. My earliest treatment, via counterexample, is in Mayo (2010). A deeper argument is in Mayo (2014) in Statistical Science.[ii] An intermediate paper Mayo (2013) corresponds to the slides below–they were presented at the JSM. Interested readers may search this blog for quite a lot of discussion of the SLP including "U-Phils" (discussions by readers) (e.g., here, and here), and amusing notes (e.g., Don't Birnbaumize that experiment my friend, and Midnight with Birnbaum).
Why this issue is bound to resurface in 2020.
I had blogged this "binge read" post a year ago, but the issue has scarcely been put to rest. I expect it to resurface in 2020 for a few reasons. Firstly, I'd promised myself that once my book (SIST) was out that I'd try to collect central textbooks that are still calling it a theorem, and write to the authors. Hence, my offer in my last post to send you a free signed copy of SIST in exchange for texts you find (1 book per textbook, and the page/pages themselves need to be sent or attached). The argument barely takes a page.
Secondly, I've already been asked to review some new attempts to declare an improvement on the original attempt. There's no mention of my disproof, nor that of Mike Evans'.
Third, it ought to come up as a crucial battle about the very notion of "evidence", blithely taken for granted in such "best practice guides" as the 2016 ASA statement on P-values and significance (ASA I). It is the interpretation of evidence (left intuitive by Birnbaum) underlying the SLP that is being presupposed.
You may not wish to engage in what looks to be (and is) a rather convoluted logical argument. That's fine, but just remember that when someone says "it's been proved mathematically" that error probabilities are irrelevant to evidence post data, you can say, "I read somewhere that this has been disproved".
[i] Savage on Birnbaum: "This paper is a landmark in statistics. . . . I, myself, like other Bayesian statisticians, have been convinced of the truth of the likelihood principle for a long time. Its consequences for statistics are very great. . . . [T]his paper is really momentous in the history of statistics. It would be hard to point to even a handful of comparable events. …once the likelihood principle is widely recognized, people will not long stop at that halfway house but will go forward and accept the implications of personalistic probability for statistics" (Savage 1962, 307-308).
The argument purports to follow from principles frequentist error statisticians accept.
[ii] The link includes comments on my paper by Bjornstad, Dawid, Evans, Fraser, Hannig, and Martin and Liu, and my rejoinder.
Classic Birnbaum Papers:
Birnbaum, A. (1962), "On the Foundations of Statistical Inference", Journal of the American Statistical Association 57(298), 269-306.
Savage, L. J., Barnard, G., Cornfield, J., Bross, I, Box, G., Good, I., Lindley, D., Clunies-Ross, C., Pratt, J., Levene, H., Goldman, T., Dempster, A., Kempthorne, O, and Birnbaum, A. (1962). "Discussion on Birnbaum's On the Foundations of Statistical Inference", Journal of the American Statistical Association 57(298), 307-326.
Birnbaum, A (1970). Statistical Methods in Scientific Inference (letter to the editor). Nature 225, 1033.
Birnbaum, A (1972), "More on Concepts of Statistical Evidence", Journal of the American Statistical Association, 67(340), 858-861.
Note to Reader: If you look at the "discussion", you can already see Birnbaum backtracking a bit, in response to Pratt's comments.
Some additional early discussion papers:
Durbin:
Durbin, J. (1970), "On Birnbaum's Theorem on the Relation Between Sufficiency, Conditionality and Likelihood", Journal of the American Statistical Association, Vol. 65, No. 329 (Mar., 1970), pp. 395-398.
Savage, L. J., (1970), "Comments on a Weakened Principle of Conditionality", Journal of the American Statistical Association, Vol. 65, No. 329 (Mar., 1970), pp. 399-401.
Birnbaum, A. (1970), "On Durbin's Modified Principle of Conditionality", Journal of the American Statistical Association, Vol. 65, No. 329 (Mar., 1970), pp. 402-403.
There's also a good discussion in Cox and Hinkley 1974.
Evans, Fraser, and Monette:
Evans, M., Fraser, D.A., and Monette, G., (1986), "On Principles and Arguments to Likelihood." The Canadian Journal of Statistics 14: 181-199.
Kalbfleisch:
Kalbfleisch, J. D. (1975), "Sufficiency and Conditionality", Biometrika, Vol. 62, No. 2 (Aug., 1975), pp. 251-259.
Barnard, G. A., (1975), "Comments on Paper by J. D. Kalbfleisch", Biometrika, Vol. 62, No. 2 (Aug., 1975), pp. 260-261.
Barndorff-Nielsen, O. (1975), "Comments on Paper by J. D. Kalbfleisch", Biometrika, Vol. 62, No. 2 (Aug., 1975), pp. 261-262.
Birnbaum, A. (1975), "Comments on Paper by J. D. Kalbfleisch", Biometrika, Vol. 62, No. 2 (Aug., 1975), pp. 262-264.
Kalbfleisch, J. D. (1975), "Reply to Comments", Biometrika, Vol. 62, No. 2 (Aug., 1975), p. 268.
Mayo, D. G. (2010). "An Error in the Argument from Conditionality and Sufficiency to the Likelihood Principle" in Error and Inference: Recent Exchanges on Experimental Reasoning, Reliability and the Objectivity and Rationality of Science (D Mayo and A. Spanos eds.), Cambridge: Cambridge University Press: 305-14.
Mayo, D. G. (2013) "Presented Version: On the Birnbaum Argument for the Strong Likelihood Principle", in JSM Proceedings, Section on Bayesian Statistical Science. Alexandria, VA: American Statistical Association: 440-453.
Mayo, D. G. (2014). Mayo paper: "On the Birnbaum Argument for the Strong Likelihood Principle," Paper with discussion and Mayo rejoinder: Statistical Science 29(2) pp. 227-239, 261-266.
Categories: Birnbaum, Birnbaum Brakes, law of likelihood	| 6 Comments
6 thoughts on "A Perfect Time to Binge Read the (Strong) Likelihood Principle"
Pingback: Midnight With Birnbaum (Happy New Year 2019)! | Error Statistics Philosophy
rkenett
Tx to this blog I went to the original 1962 JASA paper and follow up discussion. In the response of Irwin Bross is says: "A number of statisticians, Donald Mainland just to name one, have been working toward developing more realistic models or interpretations of statistical methods. But this work is almost unpublishable in JASA or other statistical journals."
I never heard of Donald Mainland but can feel empathy to his initiative. It the "more realistic models or interpretations of statistical methods" are not considered, statististics will become an academic department like the Sumerian studies department in the faculty of oriental studies.
In view of the forthcoming 2020 I posed 10 questions that I believe are in line with Mainland's initiative.
https://www.linkedin.com/pulse/ten-questions-statistics-data-science-2020-beyond-ron-s-kenett
Will be glad to get (some) answers from SIST….
Ron: I'd not heard of him either, thanks for pointing this out.
Senn new about Mainland: http://www.senns.demon.co.uk/MainlandGartPrescott.htm
Besides the Bross discussion, it was interesting to read the pragmatic Box state a precursor to "all models are wrong, but some are useful". In any case, Box seemed less impressed than Savage.
Ron: I certainly agree with #8 that professional societies should "provide an opportunity for contrarian views to be expressed". That's largely missing from the ASA at present, we'll see what happens in 2020.
OK – this is 1/10. What about the other 9?
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In a previous article, I discussed the need to close the implementation gap between evidence and action. To solve this problem, Glasziou, Ogrinc and Goodman1 propose an integration of two different approaches—Evidence-Based Medicine (EBM) and Quality Improvement (QI).
QI—a focus on "doing things right".
Together, EBM and QI will result in "doing the right things right"!
Incorporating EBM and QI in clinical training at all levels.
Click here to read the full article for free.


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Cheryl Georg
WorldGroup Advisory

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Home | Career sectors | Arts and creative | Careers in theatre
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Use our handy list of jobs in theatre to find out about careers you might enjoy, whether you're creative, business-like, practical or a great people person.
If you love drama there are lots of careers to consider that connect to the theatre. Creative types might enjoy roles such as directing, playwriting or theatre design, while practical people are needed for jobs such as lighting technician or stage crew member. Good people skills are needed in most roles, but particularly if you're helping audience members day in, day out as part of the front-of-house team. And showbusiness is just that – a business, which requires producers and marketing staff to make sure that tickets sell.
Just a word of warning – theatre careers are extremely popular, so they're very competitive to get into and not particularly well paid. Once you're in, quite a lot of the jobs involve working freelance – that is, working for different employers on different shows, rather than having a permanent job. So you'll need to carry on competing for work even once you've established a career. Make sure it's definitely what you want to do before you commit by finding work experience placements and getting involved in as many shows as possible at school or in your local community.
Careers as an actor
Want to be the one on stage? Read up on how to become an actor and whether the lifestyle would suit you.
Careers as a director
Directors head up the creative side of a production, working closely with designers as well as actors to bring their vision to life. Read about how to become a theatre director.
Careers as a producer
Producers take charge behind the scenes to make sure that a show is a commercial success, delivering a quality performance on time, to budget and with lots of seats sold. Some producers also have the initial idea for a show and set all the wheels in motion. Find out more in our article on careers as a theatre producer.
Careers as a playwright
Could you write an original script for a play or musical? If you see yourself as a future writer, take a look at our advice on careers as a playwright.
Stage managers oversee the practicalities that are needed to make a play happen. They ensure the rehearsal process is well ordered, communicate between teams to make sure everyone is up to date and take charge backstage during shows. Sounds like you? Find out how to get a career in stage management.
Careers as a set designer
Set designers work closely with directors to design a set that has visual impact and ties in with the director's vision for the production. Set designers often set the overall tone for costume and lighting design too, so all these elements work together. Discover more about set design and how to get into it.
Careers as a theatre lighting designer, sound designer, lighting technician or sound technician
Theatre lighting designers and sound designers help create the world of the play to draw audience members in – their work is both artistic and technical. Lighting and sound technicians support this, doing much of the practical work needed to set up for a show. Read more about careers as a theatre lighting designer, sound designer or technician and how to get into them.
Careers as a stage crew member
Stage crew are responsible for preparing the stage for actors to perform on, making any necessary adjustments such as set changes during performances and clearing everything away once the show is over. On touring productions, this includes loading the set and any other equipment into and out of vans.
Sometimes stage crew are involved in actually constructing the set, for example using carpentry or metalwork skills; other times they just need to get it safely and securely in place on the stage. In some instances the stage crew will help set up sound and lighting equipment, under instruction from the sound and lighting teams.
Duties during the performance vary depending on the show. On a very traditional production the stage crew might fly in backcloths from above, open and close stage curtains between acts and perform set changes. More modern productions may use minimal set and have any set changes made by the cast in full view of the audience, but could have automated elements of the set or stage (such as a revolve, which turns part of the stage floor round in circles), which need operating. You're unlikely to be let loose on complicated machinery as a junior stage crew member, but could be trained up over time.
You don't tend to need any specific qualifications to get into a career as a stage crew member. However, a qualification such as a BTEC in carpentry could be useful. You can also take short courses with the Association of British Theatre Technicians to learn the basic skills and safety knowledge you need to work backstage. The Bronze Award covers topics such as manual handling, health and safety, basic knowledge for working with electrical systems, handling counterweights, handling ropes and working at height. And experience working on school, youth theatre or amateur shows will help.
Look out for entry-level opportunities with local theatres or with agencies that supply stage crew members for live events – to start with you may need to work on a casual basis as and when there is work. There's also a creative venue technician apprenticeship available, which covers a range of roles connected to stage crew and sound and lighting duties.
Careers as a fight director, aka fight choreographer
Fight directors, also known as fight choreographers, work with actors and directors to create and teach the stage combat sequences you see on stage. This can involve unarmed combat (eg kicks and punches) or armed combat (eg sword fighting). The aim is to create dramatic, realistic-looking violence while making sure the cast stay safe. Fight directors often work freelance (that is, they are employed by different theatre companies on different plays) and often teach stage combat too – for example to acting students or on courses for amateur or professional actors.
The first step towards becoming a fight director is to train and take qualifications to an advanced level with an organisation such as the British Association of Dramatic Combat, the British Association of Stage and Screen Combat or the Academy of Performance Combat. Alternatively, you could take East 15 drama school's degree in acting and stage combat. There's then a couple of further stages of training and assessment to go through to get onto the register of fight directors approved by Equity (the theatre union).
Fight directors need a good understanding of theatre and storytelling so that their fights work in context and don't just look like people randomly attacking each other. You'll probably find that studying drama or acting at school, college or university will help you. Acting degrees will typically include some stage combat, and might lead to qualifications with the above organisations, though check the details and the level of qualification carefully. Some drama degrees also include an element of stage combat, though it's less common.
Front-of-house theatre careers
Front-of-house staff look after audience members when they visit the theatre or get in touch by phone. Front of house covers box office staff (who sell tickets), ushers (who check tickets, direct people to their seats and sell programmes and ice creams), bar staff, cloakroom attendants and anyone else who interacts with the audience – for example, customer-facing staff in a shop or café if the theatre is big enough to have these. Often front-of-house jobs are part time rather than full time.
To get a front-of-house job in a theatre, it helps to have had a similar job elsewhere, for example serving customers in a pub, restaurant, shop, hotel or visitor attraction. It's also good to have had some involvement in theatre or drama to show you are interested. Some theatres now fill quite a few of their front-of-house roles with volunteers – at these organisations, you may find it easier to get paid work if you volunteer first.
Working front of house can be a useful first job in theatre if you want a career in an off-stage, business-focused role.
Careers as a theatre marketing assistant, marketing officer or marketing manager
Theatres need to attract audiences and it's the marketing department's job to do so. They need to decide who to target (which might differ from one show to another), decide how best to get their attention, put plans in action and then assess their success. Activities can include:
communicating with the creative team to decide what to say about a show
liaising with the media and organising press nights (some of this activity may be carried out by a colleague in PR or a PR agency)
writing content for publicity materials and programmes
updating the theatre's website
promoting shows and the theatre itself via social media
writing and sending emails, such as weekly newsletters, to potential audience members on the theatre's database
liaising with graphic designers and printers about printed materials (eg posters, brochures, flyers and programmes)
organising promotions such as discounts and making sure the box office staff are aware of these.
Your first marketing job in a theatre is likely to be as a marketing assistant. You'll need some relevant experience to get this job, so you could:
get a marketing job outside the theatre world before applying (beware – you're likely to earn less in a theatre)
get an office admin job that will help you develop useful skills such as using databases
find a marketing internship in a theatre
participate in extracurricular activities that will help you develop relevant skills, such as writing and proofreading (for example working on a student newspaper or community magazine), and your knowledge of theatre (for example getting involved with a student or amateur theatre group).
Sometimes theatres like their marketing assistants to have a degree, but not always. If you want to study a relevant subject you could consider English, business studies, marketing or anything related to theatre, though it's not essential to do so.
Careers as a dramatherapist
Dramatherapists don't tend to work in theatres, but their work is closely connected. They use drama as a way to help people explore and understand their feelings and behaviours, and find ways to bring about improvements in their lives. For example, they can work with people who are facing mental or physical health problems or behavioural issues, or who have autism, dementia or a learning difficulty. Dramatherapists can work in settings such as the NHS, schools, prisons, young offenders' institutions and charities.
To become a dramatherapist, you could take a degree in a subject related to theatre or psychology, or train and work as a teacher, nurse or social worker.
You'll need to work for at least a year (either paid or voluntary) in a job that involves helping people who have the types of needs you might encounter as a dramatherapist – for example you could work in a mental health role. It's also important to get involved in drama.
You'll then need to take a masters degree (a higher level degree) in dramatherapy.
How I got into movie production
Design degrees and beyond
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This Spring we'd like to help us all answer questions like: What is the Bible? How do you read it, study it? How does it apply to life? Tying in a systematic theology of the bible with a practical approach to reading it, this series will encourage a habit of Bible reading to challenge us beyond setting for information and to pursue spiritual formation.


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Our facilities have segregated de-humidified areas for manufacturing moisture-sensitive products. Stainless steel panels are used for in-sterile facility core areas. The maintenance and servicing are done from the top of a false ceiling without entering the manufacturing areas.


Colleen has actually been with UCMP for the past year on a part-time basis; however, her responsibilities were limited to the coordination of two outreach projects: the Science Coalition (SC) and Integrating Science, Teaching, and Technology (ISTAT). The SC is a campuswide organization funded by the Berkeley Pledge with the task of identifying, registering, and coordinating all K-12 science outreach efforts on the Berkeley campus. ISTAT is a digital curriculum project of the Interactive University involving a collaboration between four campus units (the Berkeley Seismological Laboratory, the Center for Particle Astrophysics, the Space Sciences Laboratory, and UCMP) and the San Francisco Unified School District. Prior to her work with the SC and ISTAT, Colleen was working at the Chabot Science Center. Now fully on board at UCMP, Colleen will continue her work on the ISTAT project, but the main focus of her job will be as webmaster. Colleen will assume responsibility for the content of the UCMP web site, forming and implementing strategies for better use of the web as a vehicle for public information and outreach. She will also work as part of a team to develop plans for fundraising initiatives.
Ann is also no stranger to UC Berkeley. As a Cal student in political science and working in upper management of private student housing, Ann is quite familiar with University life. Additionally, her uncles are both in academia and she grew up enthusiastically roaming the halls of museums. She comes to us from the School of Optometry, where she was working on a temporary basis. Ann assumes the position of Administrative Assistant for the museum and thus hers will be the first smiley face as you enter our museum. An eager learner, Ann is now training on the Berkeley Financial System and will handle all payroll and accounting tasks for the museum. She is also working with Dave Lindberg to develop new protocols and integrate new uses of technology in order to add efficiency to the daily routines of UCMP.
Karen L. Grycewicz has joined her husband on the East Coast and we wish her all the best. For the last ten years, Karen was the Museum Scientist responsible for the microfossil and invertebrate collections. She also supervised the use of and training on our Environmental Scanning Electron Microscope. Karen made important additions to the UCMP data base model during its early development, incorporated the donation of major museum collections into the UCMP holdings, prepared annual exhibits for local gem and mineral shows, and prepared an impressive exhibit on paleontology for the Doe and Bancroft Libraries in the spring of 1991. We thank her for all of these contributions and much more.
We would also like to send a special thank you to DeeDee Sprouse who came to our rescue following the retirement of Yvonne Norpchen. DeeDee literally jumped right in, grasped what needed doing, and cleaned house, leaving the files and accounts in good shape to hand over to Ann Shen.


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text:
Las Elecciones estatales de Mecklemburgo-Pomerania Occidental de 2016 se celebraron el 4 de septiembre de 2016, con el objetivo de elegir a los 71 miembros del Parlamento Regional de Mecklemburgo-Pomerania Occidental.

Antecedentes
Al momento de la elección, el gobierno del estado consistía en una gran coalición entre el Partido Socialdemócrata (SPD) y la Unión Demócrata Cristiana (CDU), bajo el ministro-presidente Erwin Sellering.

Partidos participantes
Los siguientes partidos participaron en la elección:

Campaña

La gran coalición entre el SPD y la CDU  hizo campaña para defender su mayoría. Por otra parte, el resultado del partido ultraderechista Alternativa para Alemania (AfD) era esperado con impaciencia. Durante la campaña, su candidato Leif-Erik Holm colocó como uno de los temas más importantes (en el contexto de la crisis migratoria en Europa) la expansión de la religión islámica, poniendo así en práctica el pensamiento islamófobo adoptado recientemente por su partido. AfD esperaba ser la primera fuerza política en las elecciones.

Durante los últimos días de la campaña, la canciller Angela Merkel, que participó de ella y tiene su circunscripción para las elecciones federales en Mecklenburg-Vorpommern, endureció su discurso contra los inmigrantes y habló a favor de deportar a más de ellos, utilizando la palabra "Rückführung" (repatriación) en lugar de "Abschiebung" (expulsión). El 1 de septiembre, Merkel por primera vez admitió errores en sus políticas de refugiados.

Pero, en general, durante la campaña, Merkel defendió sus políticas de refugiados y la máxima de "Wir schaffen das" ("Nosotros lo conseguiremos"), diciendo que habría hecho todo de nuevo como lo hizo el año pasado. El candidato de la CDU Lorenz Caffier exigió la prohibición del burka, más policías y más desarrollo de las zonas rurales. Al mismo tiempo, el candidato del SPD y Ministro Presidente Erwin Sellering se distanció de las políticas de refugiados de Merkel y exigió un mayor respeto por las personas de Alemania del Este. Sellering por ejemplo, declaró: "No debe ser, que nuestra gente esté sufriendo, porque los refugiados están ahí".
El 2 de septiembre, Sellering dijo en el canal nacional ZDF que Merkel era el responsable de la popularidad de la AfD en el estado: "La gente que puede imaginar elegir a la AfD, está claramente preocupada por las políticas de refugiados de la canciller."

Encuestas

Partidos

Preferencia de Ministro-Presidente

Resultados

La AfD obtuvo casi el 21 por ciento de los votos, convirtiéndose en la segunda fuerza política. Todos los partidos "establecidos" sufrieron pérdidas significativas. El SPD se situó en torno al 30 por ciento siendo la primera fuerza, pero perdió alrededor de cinco puntos porcentuales. La CDU disminuyó del 23 por ciento al 19, descendiendo al tercer lugar. La Izquierda disminuyó del 18 al 13 por ciento y los Verdes de un 8,7 por ciento a un 4,8%, perdiendo su representación al igual que el NPD.  Tampoco el FDP pudo entrar en el Parlamento.

De los 36 mandatos directos, el SPD obtuvo 26 (dos más que en 2011), la CDU 7 (cinco menos que en 2011) y la AfD 3.

De los 1.328.320 electores inscritos, votaron 821.581 (61,9%). 806.419 votos fueron válidos y 15.162 nulos.

Los resultados finales oficiales son:

Formación de gobierno
El nuevo Parlamento Regional se constituyó el 4 de octubre de 2016.

El 1 de noviembre, Sellering fue reelegido por el Parlamento para un tercer mandato, habiendo formado una coalición con la CDU.

Referencias

Elecciones de Mecklemburgo-Pomerania Occidental
Elecciones en Europa de 2016
Alemania en 2016

redpajama_set_name: RedPajamaWikipedia


text:
Evaluation of ammonia fibre expansion (AFEX) pretreatment for enzymatic hydrolysis of switchgrass harvested in different seasons and locations
Bryan Bals1,
Chad Rogers1,
Mingjie Jin1,
Venkatesh Balan1 &
Bruce Dale1
When producing biofuels from dedicated feedstock, agronomic factors such as harvest time and location can impact the downstream production. Thus, this paper studies the effectiveness of ammonia fibre expansion (AFEX) pretreatment on two harvest times (July and October) and ecotypes/locations (Cave-in-Rock (CIR) harvested in Michigan and Alamo harvested in Alabama) for switchgrass (Panicum virgatum).
Both harvest date and ecotype/location determine the pretreatment conditions that produce maximum sugar yields. There was a high degree of correlation between glucose and xylose released regardless of the harvest, pretreatment conditions, or enzyme formulation. Enzyme formulation that produced maximum sugar yields was the same across all harvests except for the CIR October harvest. The least mature sample, the July harvest of CIR switchgrass, released the most sugars (520 g/kg biomass) during enzymatic hydrolysis while requiring the least severe pretreatment conditions. In contrast, the most mature harvest released the least amount of sugars (410 g/kg biomass). All hydrolysates were highly fermentable, although xylose utilisation in the July CIR hydrolysate was poor.
Each harvest type and location responded differently to AFEX pretreatment, although all harvests successfully produced fermentable sugars. Thus, it is necessary to consider an integrated approach between agricultural production and biochemical processing in order to insure optimal productivity.
The conversion of lignocellulosic biomass to ethanol is a renewable, environmentally friendly alternative to oil for transportation fuel. Although agricultural residues such as corn stover and wheat straw will most likely play a significant role, dedicated energy crops must also be grown in order to make enough biofuels. Gallagher et al., for example, estimate 7.9 billion gallons of ethanol per year can be produced from corn stover (assuming 80 gallons per dry ton) [1]. However, the US Energy Security and Investment Act of 2007 mandates 16 billion gallons of cellulosic ethanol by 2022.
Switchgrass (Panicum virgatum) is a native North American perennial grass, commonly cited as a potential dedicated bioenergy feedstock. Intensive research on switchgrass production has been successful in increasing yields [2], and a recent on-farm study suggests that it can be produced for as little as US$46 per metric tonne [3]. The Oak Ridge National Laboratory predicts that 171 million tons of switchgrass can be produced economically within the US [4].
Despite the potential for ethanol from switchgrass, several questions remain regarding best production and harvesting practices. Several cultivars have been developed from both switchgrass ecotypes, upland and lowland. In general, lowland cultivars provide the highest yields at lower latitudes, but upland varieties are more suited for a cooler climate [5]. In addition, several papers have proposed multiple harvests per year. Fike et al. reported 36% increase in biomass yield for upland and 8% increase for lowland cultivars of switchgrass when harvesting in both June and October compared to one harvest in October [6]. Monti et al. observed similar trends for the first 2 years of harvests, yet in later years the multiple-harvest scenario had lower yields than a single harvest [7]. Despite the possibility of lower yields, there may be other advantages to performing multiple harvests. An earlier harvest will likely contain more digestible carbohydrates, thus potentially leading to greater sugar recovery. In addition, immature switchgrass may provide other valuable coproducts such as protein that could improve the overall economics of a biorefinery [8, 9].
As with production and harvesting, several options are available for pretreatment and conversion of switchgrass to ethanol [10]. In general, switchgrass responds favourably to pretreatment and hydrolysis, with several studies reporting greater than 90% conversion of cell wall carbohydrates to sugars [11, 12]. These studies vary considerably in the type of pretreatment used as well as hydrolysis and fermentation conditions, and thus are not directly comparable. In addition, some studies did not specify the type and harvest date of the switchgrass used, thus making it difficult to assess these results. Dien et al. observed declining sugar yields in late maturity switchgrass relative to earlier maturities when subjected to dilute acid pretreatment and enzymatic hydrolysis [13]. To date, we do not know of any study that compares the response of different cultivars or harvest locations of switchgrass to pretreatment and hydrolysis.
Ammonia fibre expansion (AFEX) is a promising method for pretreating agricultural material for bioenergy production. During this process, liquid ammonia is added to the biomass under moderate pressure (100 to 400 psi) and temperature (70 to 200°C) before rapidly releasing the pressure. Major process parameters are the temperature of the reaction, residence time, ammonia loading, and water loading. This process decrystallises the cellulose, hydrolyses hemicellulose, removes and depolymerises lignin, and increases the size and number of micropores in the cell wall, thereby significantly increasing the rate of enzymatic hydrolysis [14]. In previous studies, AFEX treatment resulted in near theoretical yields of glucose on different types of agricultural residues [15] and energy crops [16, 17]. In particular, previous work has shown conversions of over 90% of the glucan and 70% xylose on switchgrass, although again the cultivar/ecotype and harvest date was not specified [18].
Thus, the goal of this paper is to determine the effectiveness of AFEX pretreatment on two harvest times (July and October) and ecotypes/locations (upland switchgrass in Michigan and lowland switchgrass in Alabama) for switchgrass. In particular, the response of each switchgrass sample to variations in the four pretreatment parameters, different enzyme loadings, and fermentation is considered for this work. These responses are compared across harvest dates and locations in order to assess the potential for multiple harvest systems and the variability in switchgrass yields, respectively.
Two varieties of switchgrass were used for this study. Alamo (a lowland variety) switchgrass, grown at Auburn University (Auburn, AL, USA), was harvested in mid July and mid October 2005. Cave-in-Rock (CIR) switchgrass (an upland variety) was grown at Michigan State University (East Lansing, MI, USA) and harvested in early July and mid October 2008. All varieties were milled using a Fitzpatrick JT-6 Homoloid hammer mill (Continental Process Systems, Westmont, IL, USA) to a mesh size of 2 mm. Samples were dried to less than 10% moisture and stored at 2°C until use.
AFEX conditions experiment
For screening AFEX conditions, pretreatment was performed in a 22 ml reactor. Switchgrass was premixed with water at the desired loading and 3 g dry weight was added to the reactor before being sealed shut. Air was removed from the reactor using a vacuum. Anhydrous ammonia was preheated to a desired pressure in the ammonia loading vessel, and the biomass preheated to the desired temperature. Both the ammonia pressure and biomass temperature were chosen in order to reach a specified temperature once the ammonia was added to the biomass. The heat of mixing between ammonia and water raises the temperature beyond the preheated values, and a precise final temperature is therefore difficult to obtain. Instead, a range of preheated values was used to obtain a range of temperatures, and the final temperature of the biomass was recorded and used. Pressure was released at the end of the desired residence time by turning a ball valve. After the reaction, the biomass was removed and allowed to dry in a fume hood overnight. Based on previous studies [15], it was assumed that no net change in the biomass weight occurred during pretreatment.
AFEX conditions ranged from 0.4 to 2 g ammonia/g dry biomass, 0.4 to 2 g water/g dry biomass, and 5 to 30 min residence time. In addition, the temperature range was generally between 80 to 200°C. At least 45 total AFEX conditions were chosen for each type of switchgrass tested. The 'corner points' of ammonia and water were specifically chosen at a moderate temperature and pressure. In addition, a near centre point (1 g ammonia/g dry biomass, 1 g water/g dry biomass, 15 min residence time, moderate temperature) was replicated multiple times. The remaining conditions were assigned randomly.
Enzymatic hydrolysis was performed at 3% dry biomass loading and 15 ml total volume. A 0.05 M citrate buffer was used to keep the pH constant at approximately 5.0. Tetracycline and cycloheximide were added to prevent microbial and fungal growth. Accelerase (Genencor, Rochester, NY, batch no. 1600844643) was used as the cellulase and loaded at 5 mg Accelerase/g dry biomass (3.2 filter paper units (FPU)/g dry biomass). Hydrolysates were incubated at 50°C and rotated at 200 rpm for 72 h. After the incubation period, enzymes were deactivated by heating samples to 99°C. Monomeric glucose and xylose concentration was determined through high performance liquid chromatography (HPLC) using a BioRad (Richmond, CA, USA) Aminex HPX-87P carbohydrate analysis column. Degassed HPLC water with a flow rate of 0.6 ml/min was used as the mobile phase, while the temperature in the column was kept constant at 85°C.
Sugars are reported as the total monomeric glucose and xylose released from the biomass during enzyme hydrolysis. This includes sugars produced from hydrolysis of polymeric sugars as well as soluble sugars that were not degraded during pretreatment. No attempt was made to determine the degradation of soluble sugars during pretreatment or the conversion of polysaccharides to monomeric sugars.
A reduced linear model based on the total monomeric glucose and xylose released during enzymatic hydrolysis was used to analyse the results using Minitab 15 (Minitab, State College, PA, USA) as the statistical software package. Ammonia loading, water loading, residence time, and the final reaction temperature were used as parameters as well as all interaction effects. Any parameter or interaction term that did not have a significant effect (P < 0.05) was eliminated. The final model was used to analyse the response of total sugar yield to each pretreatment parameter as well as to estimate the optimal AFEX conditions for each switchgrass sample.
Enzyme addition experiment
For all subsequent experiments described in this paper, AFEX was performed at the estimated optimal conditions determined from the above experiments. The same treatment method was used except that AFEX was performed in a 1.5 l reactor rather than a 22 ml reactor. Between 80 to 150 g dry switchgrass was used for each batch. The amount of switchgrass depended on the ammonia loading, as a practical limitation of the ammonia loading vessel was 160 g. Multiple batches of AFEX treatment were performed, and no significant differences (P < 0.05) were seen in sugar released through enzymatic hydrolysis between batches. All batches were then combined before proceeding with further experiments.
Four commercial enzymatic mixtures were used in these experiments: Accelerase, the b-glucosidase Novozyme 188 (Novozymes, Cambridge, MA, batch no. 058K1144), Multifect Xylanase (Genencor, batch no. 4900805391), and Multifect Pectinase (Genencor, batch no. 4010833580). Enzyme concentrations were determined by nitrogen analysis using a Skalar Primacs SN Total Nitrogen Analyser (Breda, The Netherlands), which uses the Dumas method of combusting all nitrogen to NOx. Enzyme loading varied between 5 to 20 mg/g biomass for Accelerase and 0 to 10 mg/g biomass for the other enzyme mixtures. A total of 48 hydrolysis experiments were run for each type of switchgrass, representing 25 different enzyme combinations determined using the Box-Behnken method [19]. Hydrolysis was performed in the manner stated above. Results were analysed with Minitab 15 using response surface methodology to determine the importance of each type of enzyme in releasing sugars.
Rate determination
For the rate experiments, the estimated optimal enzyme loading for each biomass was used as determined from the previous experiment. Hydrolysis was performed in 250 ml flasks with a working volume of 100 ml. All other conditions were as stated previously. Samples of 1 ml were taken at 0, 3, 6, 10, 24, 72, and 168 h. Cut pipette tips were used in order to sample both solids and liquid from the flasks, thereby preventing bias in later hydrolysis time periods due to changing the solid loading.
Fermentation studies were carried out using Saccharomyces cerevisiae 424A (LNH-ST), a yeast strain genetically modified at Purdue University, West Lafayette, IN, USA, to coferment xylose into ethanol. The yeast was grown on yeast extract phosphate (YEP) media before transferring to switchgrass hydrolysate at an initial cell density of 2.0 OD at 600 nm (approximately 0.95 g/l). The hydrolysates used were at 20% solid loading, with the exception of the October Alamo harvest which was grown at 10% solid loading due to lack of available sample material. All hydrolysates were prepared as mentioned above with the exception that 50 mg/l chloramphenicol was used as the antibiotic. Because a 20% solid loading mixture has no standing water and is thus unable to be mixed properly in a shake flask, the biomass and enzyme was added in a fed-batch manner to allow the fibre structure to break down. It was found that adding half of the enzyme and biomass immediately and half after 3 h residence time was sufficient to insure flowability. After hydrolysis, the solids and liquids were separated and fermentation was performed on the liquid portion only. Duplicate hydrolysates were combined together prior to fermentation, and fermentation was carried out in duplicates. No detoxification of the hydrolysate or nutrient supplementation of the fermentation media was performed [20]. Fermentation was carried out at 30°C, 150 rpm in unbaffled Erlenmeyer flasks.
Switchgrass cell wall composition was determined based upon the standard method described by the National Renewable Energy Laboratory (NREL) [21]. Total extractives were determined using an accelerated solvent extractor with water followed by ethanol as the solvent at 1, 500 psi. A portion of the water extract was analysed via HPLC for soluble sugars. For total carbohydrate analysis, extracted switchgrass was hydrolysed in 72% sulfuric acid at 30°C for 1 h, followed by 1 h hydrolysis in 4% sulfuric acid at 121°C. The resulting hydrolysate was filtered, and the remaining solids were gravimetrically analysed to determine acid-insoluble lignin. Total sugars released within the hydrolysate were analysed using a BioRad Aminex 87 H column with a constant flow rate of 0.6 ml/min using 5 mM sulfuric acid and a temperature of 65°C. Ash content was gravimetrically determined by combusting at 575°C for 16 h. All composition experiments were performed in triplicate. Significant differences between harvests were determined using a single-factor analysis of variance at a 95% confidence interval.
Table 1 shows the composition of the four harvests of switchgrass. There were significant differences in glucan and xylan content in CIR switchgrass, but not Alamo switchgrass. Of particular importance is the lignin, which increases from 10.4% to 16.7% between the July and October harvest of CIR switchgrass. The amount of lignin present has been linked to poor hydrolysis yields, particularly as AFEX does not remove lignin. However, increased glucan and xylan content shows the potential for the later harvest to achieve higher overall sugar yields. Both xylan and lignin showed a general trend of increasing with increasing maturity, as the July harvest of the northern CIR switchgrass contained the least amount of both compounds between all harvests, while the October harvest of CIR contained the most xylan, and the two October harvests both contained high lignin. The CIR switchgrass, grown in Michigan, experienced a shorter growing season than the Alamo harvests, and thus the July harvest of CIR is less mature than Alamo, while the October harvest of CIR is more mature than Alamo, as the northern variety tends to senesce earlier in the year.
Table 1 Composition analysis (as percentage of total dry weight) for the July and October harvests of Cave-in-Rock (CIR) and Alamo switchgrass.
As expected, solubles and ash decreased for later harvests, as the grass senesces at the end of the growing season and mobilises those compounds for storage in the root system. CIR switchgrass also tended to contain more solubles and ash than the Alamo switchgrass. Overall mass closure ranged from 92% to 97%. Remaining material may include acid-soluble lignin, galactan and other minor sugars, and insoluble protein. Acid soluble lignin in particular can range from 2% to 6% of the total composition [22, 23]. AFEX does not remove any material from the biomass, and so this acid soluble lignin may still impact hydrolysis yields.
AFEX conditions
The range of glucose and xylose yields is shown in Figure 1. In general, the release of glucose and xylose was similar across AFEX conditions; that is, AFEX conditions that produced high glucose yields also produced high xylose yields. This correlation was higher for the October harvests for both plantings of switchgrass than the July harvests. Xylose yields are within the same range for all harvests of switchgrass, with most samples between 50 to 100 g xylose/kg switchgrass depending upon the conditions used. Maximum xylose yields were similar across all harvests. The amount of glucose released tended to be higher for CIR switchgrass harvested in July relative to all other harvests. In contrast, the October harvest of CIR switchgrass tended to have the lowest glucose yields, with a maximum glucose yield of 172 g/kg switchgrass.
Box and whisker plot for sugar yields at varying pretreatment conditions. Minimum and maximum values, as well as the interquartile range, are shown. Median values are represented by the + sign. Pretreatment conditions were varied as stated in the text. For all data points, hydrolysis was performed at 3% solid loading, 50°C, 200 rpm rotation, and 5 mg Accelerase/g dry biomass, with samples collected after 72 h.
Furthermore, different AFEX conditions did not greatly affect glucose yields for the October harvest of CIR switchgrass, with an inner quartile range of only 135 to 156 g/kg switchgrass. In comparison, Alamo October harvest had a broader range, with an inner quartile range of 162 to 197 g/kg switchgrass and a maximum yield of 247 g/kg. The July harvest of Alamo switchgrass had similar yields for its inner quartile range, but the maximum sugar yield (209 g/kg) was well below the October harvest. Thus, while most pretreatment conditions show a similar digestibility for both harvests of Alamo switchgrass, the best AFEX conditions tended to produce greater glucose release for the October harvest.
For the CIR switchgrass, the October harvest required more severe pretreatment conditions (higher temperature, more ammonia, and/or longer residence times) than the July harvest, as seen in Table 2. In contrast, both harvests of Alamo switchgrass had similar pretreatment conditions, although the October harvest required a greater ammonia loading. In all cases, the models gave a reasonable approximation of the results, with R2 values at or above 80%. AFEX is a complex physiochemical pretreatment, resulting in multiple changes to the cell wall structure. One primary effect is to solubilise and remove lignin and hemicellulose from the cellulose. Because the CIR July switchgrass has less lignin and hemicellulose than the other harvests, it may require less extreme conditions to properly solubilise and remove this material.
Table 2 Optimal ammonia fibre expansion (AFEX) conditions within the parameters tested in this study.
Although most pretreatment conditions affected the glucose and xylose yields in a similar manner, xylose yields tended to be lower than expected at high temperatures. Currently unpublished research in our laboratory suggests that xylan is degraded at high temperatures. Likewise, soluble sugars also degrade at high temperatures. These issues may partially explain why both CIR harvests require low temperatures relative to the Alamo harvests. The CIR July switchgrass is high in sucrose, and thus requires low temperatures to preserve these sugars, whereas the CIR October harvest had highly indigestible cellulose. Because the glucose released was low and did not greatly vary across all pretreatment conditions, a lower temperature was required to obtain high overall sugar release.
The differences in water requirements for the two types of switchgrass used is pronounced. Alamo switchgrass required high water to biomass ratios while CIR switchgrass required low water to biomass ratio. Water has a complex role in AFEX pretreatment, as it acts as a competing catalyst for breaking acetyl bonds, moderates the pH, and aids in solubilising ammonia. In addition, high ammonia concentrations (relative to water) act to convert crystalline cellulose to the more digestible cellulose III [24]. This may be the reason for the high ammonia/low water requirement for CIR October switchgrass. If so, a more anhydrous AFEX pretreatment may improve glucose yields for this harvest. For the CIR July harvest, the water loading is highly dependent upon the temperature of the process. At high temperatures, high water loadings must be used, while low loadings are required for high yields at low temperatures. The high water loadings at high temperatures may act as a moderating influence on sugar degradation by ammonia reactions, as it reduces the ammonia concentration and pH of the reaction.
Enzyme conditions
The response of glucose and xylose yields using different enzyme loadings is seen in Figure 2. In general, higher enzyme loadings led to greater sugar production, as expected. However, due to the high costs of enzymes, high enzyme loadings are unlikely to provide maximum economic benefit. As the material cost of enzymes is unknown, the economic optimal enzyme loading is currently unknown and will likely change with future research into enzyme combinations and production. Instead, the maximum sugar yields produced using at most 15 mg enzyme/kg biomass was used to determine optimal enzyme loadings. Using this constraint, optimal enzyme loadings and sugar yields are shown in Table 3.
Table 3 Optimal enzyme loadings for enzymatic hydrolysis of four harvests of switchgrass.
Box and whisker plot for sugar yields at varying enzyme loadings. Ammonia fibre expansion (AFEX) pretreatment was kept constant for each harvest (conditions listed in Table 2), and enzyme loadings were varied as stated in the text. Hydrolysis was performed at 3% solid loading, 50°C, and 200 rpm rotation, with samples collected after 72 h.
The model gave a strong approximation of the data for three harvests, although the correlation coefficient for the October Alamo harvest was fairly low (65%). In this instance, the model did not accurately predict experimental results, overpredicting the true value. Despite this, individual enzyme conditions suggest that the optimal enzyme loading at 15 mg/g total loading is similar to the value predicted by the model. Increasing the Accelerase loading beyond 5 mg/g biomass did not greatly improve sugar yields, while including both pectinase and xylanase were necessary for high yields.
Despite different conditions providing varying amounts of cellulase and hemicellulase, there was also a reasonably strong correlation between glucose and xylose yields for all harvests studied (data not shown). This suggests a degree of synergy between glucan and xylan hydrolysis regardless of the enzyme used. Given how closely glucan and xylan polymers are intertwined with each other in the cell wall, this is not an unexpected result. Furthermore, it should be noted that each of the enzyme complexes contain activities on several different compounds [25], and so the cellulase mixtures also contain hemicellulase activity and vice versa. Increased breakdown of cellulose in cellulase-rich enzyme conditions may be increasing accessibility to the xylan, and vice versa in hemicellulase-rich enzyme conditions, thus explaining the strong correlation.
The CIR switchgrass harvested in July produced significantly more glucose than the other three harvests, yet released similar amounts of xylose. In contrast, the Alamo October switchgrass produced substantially more xylose than either the CIR October or Alamo July switchgrass, despite a similar range of glucose released. Sugar yields at or exceeding 500 g/kg biomass were seen at relatively low (<20 g/kg biomass) enzyme dosage for the Alamo October and CIR July harvests, suggesting strong potential as cellulosic feedstocks. While yields increased for the CIR October harvest compared to no additional enzymes, the overall conversion remains low. Overall sugar yield was high only in the case of CIR switchgrass harvested in July (90% total yield), while the other three yields ranged from 60% to 70%.
These values are comparable to previous research, although due to the variety of harvest locations and times as well as switchgrass ecotypes, exact comparisons cannot be made. Previous research on AFEX-treated switchgrass produced 73% sugar yield after 72 h, although the harvest date and location were unknown for this sample [18]. Dien et al. obtained approximately 75% sugar yield using dilute acid pretreatment on a late harvest CIR switchgrass grown in Nebraska [13], while Hu et al. obtained 59% to 90% yield from an unknown harvest in Virginia using alkali/microwave pretreatment [11].
Harvest date and cultivar/location do not appear to affect the composition of the enzyme complex required to break down the biomass, despite the different compositions of the biomass. With the exception of the October harvest of CIR switchgrass, all switchgrass harvests obtained optimal yields using an equal blend of Accelerase, Multifect Pectinase, and Multifect Xylanase. For the CIR October harvest, slightly more pectinase is needed than xylanase. Strong responses to the hemicellulases suggest that the AFEX pretreatment is not completely separating the cellulose from the surrounding cell wall material in any substrate. Although small amounts of cellobiose were seen in hydrolysates without Novozyme 188, its presence did not have a positive impact on sugar yields. Multifect Pectinase also contains strong b-glucosidase activity [25], likely eliminating the need for Novozyme 188. Increasing Accelerase beyond 5 g/kg produced only modest increases in sugar yields, which are unlikely to be economically competitive.
Rate of hydrolysis
All harvests of switchgrass showed a rapid response to enzyme addition, as seen in Figure 3. As expected, both glucose and xylose released during hydrolysis rose rapidly within the first 24 h, with a slow release afterwards. Interestingly, xylose was released faster than glucose for all samples except the July harvest of CIR switchgrass. The initial rate (defined as sugar release within the first 3 h) for xylose was between 35 to 45 g/kg/h for xylose compared to 25 to 30 g/kg/h for glucose. In addition, glucose released after 168 h was 25% higher than 24 h for all harvests except for the CIR July harvest (which was 16% higher). Xylose at 168 h compared to 24 h was only 8% to 14% higher for all harvests. The xylan appears to be readily accessible to enzymes after AFEX pretreatment relative to cellulose and responds rapidly to enzymatic attack with high xylanase addition.
Rate of hydrolysis. Glucose (right) and xylose (left) released during enzymatic hydrolysis between 3 and 168 h of residence time. Pretreatments were performed at the conditions listed in Table 2 and enzyme addition as listed in Table 3. Hydrolysis was performed at 3% solid loading, 50°C, and 200 rpm rotation.
With the exception of the CIR July harvest, the trends for glucose released were similar in all harvests tested. These three harvests saw a similar initial rate, with the primary differences appearing between 3 to 24 h of hydrolysis. In comparison, the CIR July harvest showed a very rapid initial release of glucose, with nearly all glucose released within 24 h. It is clear that AFEX pretreatment is very effective in opening up cellulose to enzymatic attack in this harvest relative to the other three harvests, likely due to being the most immature sample. Further research is needed to determine specifically what factors influence this immediate glucose release.
The harvest location or type appears to have a greater effect on xylose released than harvest date. The Alamo harvests showed a significantly higher initial rate (42 to 45 g/kg/h) of xylose release than the CIR harvests (34 to 35 g/kg/h). In addition, a greater proportion of the total xylose release was seen within the first 24 h for the Alamo harvests compared to CIR harvests.
Glucose, xylose, and ethanol concentrations for fermentations of the four switchgrass harvests are shown in Figure 4. Metabolic yield (defined as a percentage of the theoretical amount of ethanol produced from the consumption of sugars) was high in all cases, ranging from 87% for the Alamo July harvest to 97% for the CIR July harvest. Glucose fermentation was also complete, with virtually all glucose consumed within 48 h. However, a lengthy lag phase that lasted approximately 10 to 24 h was present in all switchgrass harvests. This may be due to the strain being prepared on YEP media rather than hydrolysate, and may be eliminated if the strain were adapted to AFEX hydrolysate prior to inoculation [26]. The three hydrolysates at 20% solid loading all achieved final ethanol concentrations in excess of 30 g/l. While this value is lower than the 40 g/l threshold generally accepted for ethanol production [27], this indicates the fermentability of AFEX-treated switchgrass, and further optimisation and technology improvements will likely improve these results.
Fermentation profiles. Glucose (blue), xylose (red), and ethanol (green) concentrations achieved during fermentation of switchgrass. All fermentations were performed using Saccharomyces cerevisiae at 30°C and shaken at 150 rpm. Switchgrass hydrolysate after 72 h of enzymatic hydrolysis at 20% solid loading was used except for the October harvest of Alamo switchgrass, where the solid loading was 10%. Data points are the average of duplicate fermentations.
Xylose utilisation was much slower relative to glucose and was not completely consumed within 96 h. This trend has also been seen with corn stover using the same micro-organism [20]. Over two-thirds of the xylose was consumed within 96 h for three of the harvests, a satisfactory result. However, only approximately one-third of the xylose in the CIR July harvest was consumed. This is due primarily to a longer lag phase than the other harvests. After 24 h, the cell density in the CIR July harvest was 40% of the value of the Alamo July harvest and 23% of the value of CIR October. This harvest has much higher amounts of solubles present relative to the other harvests, and the ammonia may be reacting with these molecules to produce fermentation inhibitors. Further research is needed to determine why this harvest is unable to ferment as well as other harvests. Acetate levels were fairly constant throughout fermentation, ranging from 1.3 to 1.9 g/l at 20% solid loading.
The different responses to harvest date and location/ecotype have large implications for biomass refining. Harvesting early in the season provides lower costs for pretreatment and higher potential ethanol yields, which may help offset the costs of a second harvest. With the potential additional revenue from coproducts such as proteins, the benefit for early harvests appears strong. However, any pretreatment facility will likely be designed to satisfy both harvests, and so reductions in capital costs may not actually occur. In addition, if yields from the stand decrease over time due to multiple harvests [7], a multiple harvest scenario may not be an economically viable for agronomic reasons.
Also of concern is the fact that different harvest locations or different types vary in response to pretreatment and hydrolysis. The CIR switchgrass, grown in Michigan, begins growing later in the season and senesces earlier than the Alamo switchgrass grown in Alabama. As such, while the harvest dates were similar, the relative maturities of the two varieties were different. As the CIR switchgrass was more digestible in July and less digestible in October than the Alamo material, the different relative maturities appear to have more effect on digestibility than the types of cultivars. It remains to be seen if different cultivars harvested in the same region and same season react differently to pretreatment and hydrolysis parameters. Thus, harvest practices in the northern latitudes may be adjusted to avoid the highly recalcitrant late harvest material.
Fermentable sugars are effectively released from switchgrass using AFEX pretreatment and enzymatic hydrolysis. Relatively mild pretreatment results in high ethanol yields for early harvest material, while more severe conditions are necessary for later harvests. A mixture of enzymes, including xylanase and pectinase, are required to release the greatest amounts of sugar. Xylan was digested faster than glucan for all types of biomass, with an initial rate of 35 to 45 g/kg/h xylose released compared to 25 to 30 g/kg/h glucose. The upland CIR switchgrass from Michigan harvested in July showed the greatest response to pretreatment and hydrolysis, producing 520 g monomeric sugar per kg biomass, while harvesting in October showed the least response, producing 410 g/kg biomass. All hydrolysates were fermentable, although the July CIR harvested material showed poor xylose utilisation.
Harvest date and location/ecotype have a substantial impact on AFEX pretreatment conditions and sugar released, although not a major factor in enzyme requirements. For the northern CIR switchgrass used in this study, large differences were seen in pretreatment conditions and response between the two harvests, while this difference was muted in the southern Alamo switchgrass. Although this suggests that the harvest location is the dominant response, as the northern climate has a shorter growing season than the southern climate, further research is required to separate the effects of harvest location and ecotype. Thus, harvesting strategies must be tailored to local needs in order to maximise ethanol production. An integrated approach, considering long-term viability of stands, biomass yield on the farm, pretreatment processing conditions and cost, and resulting ethanol yields simultaneously, is necessary to determine the optimal solution in satisfying both farmers' and ethanol producers' needs. In addition, these factors would affect the possibility of producing coproducts switchgrass along with bioenergy.
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Casler MD, Vogel KP, Taliaferro CM, Wynia RL: Latitudinal adaptation of switchgrass populations. Crop Sci. 2004, 44: 293-303.
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Bradshaw TC, Alizadeh H, Teymouri F, Balan V, Dale BE: Ammonia fiber expansion pretreatment and enzymatic hydrolysis on two different growth stages of reed canarygrass. Appl Biochem Biotechnol. 2007, 136: 395-405. 10.1007/s12010-007-9067-x.
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Dien BS, Ximenes EA, O'Bryan PJ, Moniruzzaman M, Li X, Balan V, Dale B, Cotta MA: Enzyme characterization for hydrolysis of AFEX and liquid hot-water pretreated distillers' grains and their conversion to ethanol. Bioresource Technol. 2008, 99: 5216-5225. 10.1016/j.biortech.2007.09.030.
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Funding for this project was provided by the Department of Energy through the Great Lakes Bioenergy Research Center (GLBRC) grant DE-FC02-07ER64494 and the Michigan State University Research Foundation. Genencor International generously donated the Accelerase 1000, Multifect Pectinase, and Multifect Xylanase to this project. Dr David Bransby at Auburn University donated the Alamo switchgrass, and the MSU Department of Crop and Soil Science donated the CIR switchgrass. Access to strain 424A(LNH-ST) was granted by Purdue University. We would like to thank Christa Gunawan and Charles Donald Jr for providing HPLC analysis and AFEX pretreatments, respectively. We would also like to thank Rebecca Garlock for providing critical comments on the manuscript.
Biomass Conversion Research Laboratory, Department of Chemical Engineering and Material Science, Michigan State University, Lansing, MI, USA
Bryan Bals
, Chad Rogers
, Mingjie Jin
, Venkatesh Balan
& Bruce Dale
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Correspondence to Bruce Dale.
BB designed the hydrolysis experiments, performed the statistical analysis, and drafted the manuscript. CR carried out the enzymatic hydrolysis experiments. MJ designed and carried out the fermentation experiment. VB participated in the design of the study and analysis. BD participated in the design and coordination of the study. All authors provided critical input to the manuscript, and read and approved the final manuscript.
Bals, B., Rogers, C., Jin, M. et al. Evaluation of ammonia fibre expansion (AFEX) pretreatment for enzymatic hydrolysis of switchgrass harvested in different seasons and locations. Biotechnol Biofuels 3, 1 (2010) doi:10.1186/1754-6834-3-1
Xylose
Sugar Yield


Matt and Kim Bring DIY Style to the Bedroom for "It's Alright"
Matt & Kim know how to catch our eyes with their DIY styled videos. In 2009, they stripped in Times Square, leading to police tackling them, in their "Lessons Learned" visual. And just last week, their arena-sized take on the "Harlem Shake" has earned almost 10 million views.
They're at it again with new single "It's Alright." But this time, taking us in the bedroom. The indie-pop couple act out a sexually-charged, synchronized dance routine eyes closed, all while appearing asleep.
It's another win for Matt & Kim who are always killing it on the video scene. With its quirky combination of trumpets and synthesizers, the song's a win too.


Most games are all about getting the highest score and waving the flag of victory. Golf, on the other hand, has the best players striving to brag about their low scores. The game may be different, but the competitive spirit is just as strong.Lowering your golf score can require more than a little hard work. First, you need to have the drive and desire to become a better golfer, and be willing to practice to achieve the perfect swing. You'll find that once you've begun a solid plan of action, and increased your desire to play better golf, you will become a better golfer. You will improve your golf score and you will earn more respect on the golf course.
A really good golfer will be able to effectively combine mental skill with athletic ability. After all, golf truly is a game of wits. When you are able to improve your feelings and perceptions of the sport, your personal game will improve and you'll be able to lower the scores on your card. Evolving into a better player starts with having a positive attitude.
Whenever you have a spare moment, take the time to practice putting. Practice at home and at the office. Pick up a portable putting green that you can take with you. Repeated practice will help you to gain control over the putter, and will in turn give you better control over the ball. The extra efforts today will result in skills that you'll appreciate over time. Practice as much as you can.
Be aware of the terrain on which you are playing. When you're familiar with the green, you'll be able to make your putts count and improve your golf score. Know which clubs are best for the course, and have them on hand. Be prepared to meet and overcome any challenges that may come up during your game.
You can be a great golfer but, sooner or later, you'll play with someone that's a little better. Consider this a golden opportunity. Experienced golfers are often happy to share their skills and knowledge, so don't be afraid to ask for tips. If he or she offers a little constructive criticism, don't be afraid to acknowledge your shortcomings. A willingness to improve your weak areas is the only way to strengthen your personal game. Welcome the advice of more seasoned athletes. Use it to solve your problems and you'll get the edge you need to be a better golfer.
No one likes a showoff; so don't let yourself get too cocky. It's OK to celebrate your own victories, but don't come across as arrogant if you are playing a great game. You can be proud of your efforts and your success, just be sure to keep your ego in check. The potential to earn a great golf score is little consolation if no one wants to play with you.
There are many ways to lower your golf score. Remember, however, that if you don't take the time to practice, all the tips, tricks, hints and advice won't amount to anything. Relax, take your time and apply all of those bits of knowledge to your game. Don't forget to have fun. It is just a game, after all.


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Home » MAA Publications » MAA Reviews » Origami Tessellations: Awe-Inspiring Geometric Designs
Origami Tessellations: Awe-Inspiring Geometric Designs
Sarah Boslaugh
If Eric Gjerde's new book Origami Tessellations: Awe-Inspiring Geometric Designs needed an alternative title, it might be: Origami: It's not just for kids any more! Of course origami has never been just for kids, but this book should convince you that you can create some great art using origami techniques (and it's a great outlet for the artistically-inclined who don't have skill in drawing or painting, as Mr. Gjerde says he does not). This book may also capture the interest of artistic but math-phobic students by showing them a creative use for all that geometry they had to do in school.
Origami Tessellations begins by explaining what tessellation figures are, some common tilings, and the naming convention to describe them. Gjerde then describes different types of papers suitable for origami and basic techniques, including precreasing, making pleat intersections, and making twists. This section is well-illustrated with diagrams demonstrating the different techniques and by many photographs of Islamic architecture illustrating the use of tessellation figures.
This section is followed by descriptions of 25 origami projects, each including a diagram of the folds required, step-by-step instructions, and photographs of the final product as well as intermediate stages. The projects are graded as beginner, intermediate and advanced, but "beginner" should be interpreted as someone who has previous experience with origami or a strong interest in learning about it, because even the simplest projects include a lot of steps and demand precise folding. But for someone who enjoys doing origami and wants to try some complex projects, the directions are very clear and the photographs of the finished work should serve as an inspiration.
The final section of Origami Tessellations presents a gallery of original art by various artists, demonstrating that there are no limits to what you can do with these techniques. The works on display include a Jasper Johns-like American flag, a mask which looks almost like it was carved from wood, and an in-the-round fish, as well as many variations on squares, rectangles, and hexagons.
Eric Gjerde is a technology professional and paper artist in Minneapolis. You can see more of his work at http://www.origamitessellations.com/.
Sarah Boslaugh, (seb5632@bjc.org) is a Performance Review Analyst for BJC HealthCare and an Adjunct Instructor in the Washington University School of Medicine, both in St. Louis, MO. Her books include An Intermediate Guide to SPSS Programming: Using Syntax for Data Management (Sage, 2004), Secondary Data Sources for Public Health: A Practical Guide (Cambridge, 2007), and Statistics in a Nutshell (with Paul Watters; O'Reilly, 2008), and she served as Editor-in-Chief for The Encyclopedia of Epidemiology (Sage, 2008).


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Susana Martinez-Conde
Director of the Laboratory of Visual Neuroscience
Barrow Neurological Institute
Susana is Director of the Laboratory of Visual Neuroscience at BNI. She received a B.S. in Experimental Psychology from Universidad Complutense de Madrid and a Ph.D in Medicine and Surgery from the Universidade de Santiago de Compostela. She was a postdoctoral fellow with Nobel Laureate David Hubel at Harvard Medical School, and then an Instructor in Neurobiology at the same institution. She was a Lecturer at University College London from 2001 to 2003 before assuming her directorship at BNI the following year.
Susana and Stephen are laboratory directors at the Barrow Neurological Institute (BNI) in Phoenix, Arizona, where they study various aspects of visual, sensory and cognitive neuroscience. Their research and outreach activities have been written up in hundreds of media stories including many that have appeared in The New York Times, The Wall Street Journal, The Chicago Tribune, The Boston Globe, National Public Radio, Der Spiegel, New Scientist and Wired magazine. Both are monthly columnists for ScientificAmerican.com. Their shared column on the neuroscience of illusions gets hundreds of thousands of hits every month. One of their recent column contributions is the most downloaded article in sciam.com history.
Susana and Stephen are founding board members of the Neural Correlate Society, and Susana serves as its Executive Chair. NCS hosts the annual "Best Visual Illusion of the Year Contest." The contest's website maintains an archive of visual illusions and their explanations for a broad audience, and receives almost three million hits per year. They both serve on the board of advisors for Scientific American: Mind and in addition to their column have published several feature articles in Scientific American (circulation > 1,000,000 readers) and several of its family of journals. Their academic publication credits include contributions to Nature, Nature Neuroscience, Neuron, Nature Reviews Neuroscience, and the Proceedings of the National Academy of Science, and they have each authored over 75 academic publications.


The Institute of Instrumentation, Control & Automation Australia Technology Expo features 30+ companies who showcase their products related to the Instrumentation, Control and Automation Industry.
This is an Australia-wide event held in capital cities and regional areas, providing a one stop shop for suppliers and customers to come together in a friendly, informative environment.
This free event welcomes all managers, engineers, apprentices and students.
Upcoming IICA expos this year will be held in the following locations and dates.


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Jméno a příjmení Jaroslav Pecháček se může vztahovat k následujícím osobnostem:

 Jaroslav Pecháček (politik) (1911–1997) – český politik a novinář, poúnorový emigrant a spolupracovník Svobodné Evropy
 Jaroslav Pecháček (spisovatel) (1909–1984) – český prozaik, výtvarník a publicista