bluuebunny/crossref_metadata_2025 huggingface dataset:
Resveratrol attenuates steatosis in obese Zucker rats by decreasing fatty acid availability and reducing oxidative stress
Authors: Gómez-Zorita S. , Fernández-Quintela A. , Macarulla M. T. , Aguirre L. , Hijona E. , Bujanda L. , Milagro F. , Martínez J. A. , Portillo M. P.
Published: June 2011

Non-alcoholic fatty liver disease (NAFLD) is one of the most common manifestations of chronic liver disease worldwide. The aim of the present study was to assess the effect of resveratrol on liver fat accumulation, as well as on the activity of those enzymes involved in lipogenesis and fatty acid oxidation infa/faZucker rats. A total of thirty rats were assigned to three experimental groups and orally treated with resveratrol for 6 weeks, or without resveratrol (C: control group; RSV15 group: 15 mg/kg body weight per d; RSV45 group: 45 mg/kg body weight per d). Liver histological analysis was performed by microscopy. Levels of hepatic carnitine palmitoyltransferase-Ia (CPT-Ia), acyl-coenzyme A oxidase (ACO), fatty acid synthase, glucose-6-phosphate dehydrogenase and malic enzyme were assessed by spectrophotometry, and acetyl-CoA carboxylase was assessed by radiometry. Commercial kits were used to determine serum TAG, NEFA, total HDL and non-HDL-cholesterol, glycerol, ketonic bodies, glucose, insulin, adiponectin, aspartate aminotransferase (AST), alanine aminotransferase (ALT) and alkaline phosphatase (ALP), hepatic TAG, thiobarbituric acid reactive substrates, GSH (GSSG) and superoxide dismutase. Resveratrol reduced liver weight and TAG content. It did not modify the activity of lipogenic enzymes but it did increase CPT-Ia and ACO activities. NEFA and ALP were reduced in both resveratrol-treated groups. AST/GOT was reduced only by the lowest dose. ALT/GPT, TAG and adiponectin remained unchanged. Resveratrol reduced liver oxidative stress. This study demonstrates that resveratrol can protect the liver from NAFLD by reducing fatty acid availability. Moreover, resveratrol also protects liver from oxidative stress.
William Morris, Cultural Leadership, and the Dynamics of Taste
Authors: Harvey Charles , Press Jon , Maclean Mairi
Published: June 2011

This examination of the social processes that inform cultural production asks how tastes are formed, transmitted, embedded, and reproduced across generations. These questions are explored through a study of William Morris, his working methods and products, and their impact on the decorative arts in Victorian Britain and beyond. Through the exercise of cultural leadership, Morris gave physical expression to the ideals and sentiments of Romanticism, and this in turn gave rise to a community of taste reaching across class boundaries and generations. Morrisian products and designs, through the agency of his disciples, became institutionally embedded, emblematic of refinement and good taste. A process model of taste formation is deployed to explore the economic and social dynamics at work in the Morris case and more generally.
Twisted crossed products of C*-algebras
Authors: Packer Judith A. , Raeburn Iain
Published: June 2011

Group algebras and crossed products have always played an important role in the theory of C*-algebras, and there has also been considerable interest in various twisted analogues, where the multiplication is twisted by a two-cocycle. Here we shall discuss a very general family of twisted actions of locally compact groups on C*-algebras, and the corresponding twisted crossed product C*-algebras. We shall then establish some of the basic properties of these algebras, motivated by the requirements of some applications we have in mind [2, 9, 10]. Some of our results will be known to others, at least in principle, but we feel that a coherent account might be useful.
Lifting the ‘Violence Veil’: Examining Working Conditions in Long-term Care Facilities Using Iterative Mixed Methods
Authors: Daly Tamara , Banerjee Albert , Armstrong Pat , Armstrong Hugh , Szebehely Marta
Published: June 2011

Le présent document se concentre sur les méthodes mixtes nous avons utilisé pour comprendre conditions de travail de leur travailleurs dans les établissements de soins de longue durée. Nous avons mené une enquête auprès des syndiqués travailleurs de santé en Ontario (n= 917), et une autre enquête dans trois provinces (n= 948) et quatre pays Scandinaves (n= 1625). Neuf groupes de discussion avec les Canadiens ont eu lieu; les répondants ont été présentés avec des questions du sondage et aussi descriptive des résultats statistiques et ont été demandé: “Est-ce le reflet de votre expérience?” Les contraintes de temps pour les travailleurs et la fréquence des expériences des travailleurs de la violence physique et attentions sexuelles non désirées sont signalés. Nous discutons comment de le façon dont nous utilisé des méthodes qualitatives et quantitatives étè itératif. Nous avons trouvé pas seulement la cohérence des données mais aussi la divergence des données qui montrent comment une culture de la violence dans les établissements de soins de longue durée est acceptée par les travailleurs comme d’habitude. Comment le constat de la violence structurelle vu le jour et la signification profonde, le contexte et les idées qui proviennent de la combinaison de nos méthodes itératives sont discutées.
Revisiting Public Opinion in the 1930s and
1940s
Authors: Berinsky Adam J. , Powell Eleanor Neff , Schickler Eric , Yohai Ian Brett
Published: June 2011

Studies of mass political attitudes and behavior before the 1950s
have been limited by a lack of high-quality, individual-level data.
Fortunately, data from public opinion polls conducted during the
late New Deal and World War II periods are available, although the
many difficulties of working with these data have left them largely
untouched for over 60 years. We compiled and produced readily usable
computer files for over 400 public opinion polls undertaken between
1936 and 1945 by the four major survey organizations active during
that period. We also developed a series of weights to ameliorate the
problems introduced by the quota-sampling procedures employed at the
time. The corrected data files and weights were released in May
2011. In this article, we briefly discuss the data and weighting
procedures and then present selected time series determined using
questions that were repeated on 10 or more surveys. The time series
provide considerable leverage for understanding the dynamics of
public opinion in one of the most volatile—and pivotal—eras in
American history.
War and Momentum: The 2008 Presidential
Nominations
Authors: Norpoth Helmut , Perkins David F.
Published: June 2011

In the 2008 presidential nomination campaigns, both Obama and McCain
staked out clear positions on the Iraq war. Exit polls conducted in
primary and caucus contests show that the war in Iraq was indeed the
key issue of support for the winning contenders. However, it was not
agreement with the candidates' positions that drove primary voters
into the arms of Obama and McCain; rather, it was concern with the
Iraq war. Primary voters treated the war as a valence issue, not as
a position issue. Each candidate also won an early contest (the Iowa
caucuses for Obama and the New Hampshire primary for McCain) in
which concern over the Iraq war was especially strong. Those
victories sparked a momentum for both candidates in subsequent
contests. As a result, both Obama and McCain owed their respective
nominations for president to the combination of war and
momentum.
Political Theory within Political Science
Authors: Corbett Ross J.
Published: June 2011

This article addresses Andrew Rehfeld's attempt to ensure a place for
political theory within political science, which he does partly by
showing how political theory fits into a defensible definition of
political science and partly by excluding much political theory from
the discipline in order to safeguard the rest. His account of what
the discipline should comprehend is overly narrow, however, and does
not serve the interests of the sorts of political theory he strongly
believes are worth doing. I argue instead that political science
must be defined by its subject matter alone, and that political
theory's contribution to this subject matter must be defended.
Abstract Teaching for a Concrete World: A Lesson from
Plato
Authors: Lindsay Peter
Published: June 2011

This article argues that instructors should introduce students to
abstract concepts only after they have provided concrete
illustrations of them. The advantages of working from the concrete
to the abstract are twofold: (1) students have an easier time
conceptualizing abstractions from within a particular context, and
(2) such a context provides them with a greater motivation to do so.
In an effort to mirror the pedagogical approach I defend, I begin by
reviewing the manner in which Plato introduces the concept of
justice to his readers in Book I of the Republic. I
then examine the common model of teaching abstract concepts,
demonstrate how an effective alternative differs from this model,
and review the education theories that support the alternative
model.
When Great Minds Don't Think Alike: Using Mock Trials in
Teaching Political Thought
Authors: Ahmadov Anar
Published: June 2011

This article examines a mock trial I have developed and used in
teaching the history of political thought. Mock trials have been
underused but have great potential to become an effective and
exciting tool for student learning in this area. In this mock trial,
the plaintiff, defendant, attorneys, and witnesses are eminent
political or economic thinkers or political leaders of the past.
Active engagement in this mock trial helped my students immensely in
gaining deeper insight into and a more nuanced understanding of the
ideas of the thinker they represented, as well as enhancing their
critical and analytical abilities and improving their research
skills. As a teaching tool that is amenable to creative adaptation,
a mock trial can be an engaging and effective exercise for delving
into the history of political thought and making it more
relevant.
Of Publishable Quality: Ideas for Political Science Seminar Papers
Authors: Zigerell L. J.
Published: June 2011

Many political science publications advance knowledge using previously collected data and an innovation or two in theory or methods. To encourage students embarking on a seminar paper project, I review some of these publications to illustrate that the understanding of political phenomena often advances in incremental steps.
Response to Symposium: “Pracademics”: Mixing an Academic
Career with Practical Politics
Authors: Arrington Theodore S.
Published: June 2011

As a pracademic for my entire career and a department chair for
almost 20 years, I found the wonderful symposium on pracademics to
be right on target. The examples and the advice for faculty and
administrators are invaluable to our profession. Thank you for
publishing it.
RICHARD PIERRE CLAUDE
Authors: Lockwood Bert
Published: June 2011

Richard Pierre Claude epitomized the scholar/activist. As a student
at Florida State in 1960, he sat down with friends at a lunch
counter in Tallahassee in violation of municipal law. He had a
distinguished career at the University of Maryland. One of his
proudest achievements was the founding of the Human Rights
Quarterly, which he edited for four years. The impetus
for founding HRQ was that the human rights field
was dominated by lawyers, and while a number of social scientists
were interested in doing scholarly work on human rights, the
traditional journals were not receptive to this subject matter.
Claude's vision for HRQ may be evidenced by the
results from Project Muse, an electronic website administered by
Johns Hopkins University Press. Of the 436 journals on Project Muse,
Human Rights Quarterly ranked third in terms of
downloads of articles in 2010, with 207,440.
A Response to Ugarte
Authors: Weyland Kurt
Published: June 2011

I thank Professor Ugarte for his comments and reflections and am glad
that my essay, published in a political science journal, has
elicited scholarly interest far beyond the confines of our
discipline, in a department of Spanish literature. While it would
take too much space to respond to all comments (for instance,
concerning a “turf battle”), I want to clarify a few important
points.
2011 APSA Teaching and Learning Conference Track
Summaries
Authors: Mealy Kimberly A.
Published: June 2011

The eighth annual APSA Teaching and Learning Conference (TLC) was
held in Albuquerque, New Mexico, February 11–13, 2011, with 226
attendees onsite. The theme for the meeting was “Making Sense of
Politics and Political Science.” Using the working-group model, the
TLC track format encourages in-depth discussion and debate on
research dealing with the scholarship of teaching and learning.
2011 APSA Teaching and Learning Conference Track
Summaries
Authors: Harkness S. Suzan J. , Kuchinsky Michael , Pappas Christine
Published: June 2011

In 2004, 40 political scientists gathered in Washington, DC, to
inaugurate the APSA Teaching and Learning Conference (TLC), which
aimed to explore how we teach and how students learn best within the
discipline. A common theme linking the active-based curriculum to
political science over the past eight years has been the theory of
experiential education. Over time, the vibrant conversation within
this track has included community-based learning, service learning,
civic engagement, community-based research, simulations, case
studies, problem-based learning, and internships. The discourse has
also shifted away from asking what civic engagement is and how we
can integrate it into the curriculum toward questions such as:
2011 APSA Teaching and Learning Conference Track
Summaries
Authors: Bennion Elizabeth A. , Van Vechten Renée Bukovchik
Published: June 2011

This year's participants in the Civic Engagement II track agreed with
last year's participants that civic engagement is both a means and
an end. Active learning through community or political engagement
can provide students with a deeper understanding of political
science concepts while also helping them develop the skills they
need to become engaged citizens. Participants in this year's track
focused on how to assess the knowledge, skills, and dispositions
that students develop through coursework, internships, and
extracurricular programs.
2011 APSA Teaching and Learning Conference Track
Summaries
Authors: Gentry Bobbi , Miller William J. , Richards Erin E.
Published: June 2011

Issues addressed in the Core Curriculum and General Education track
at this year's conference are more important than ever. With the
release of Academically Adrift (Arum and Roksa
2011), increasing budget shortfalls as a result of the economic
recession, and calls for assessment and accountability, higher
education and its usefulness have come under scrutiny. While this
increasing scrutiny is a concern that others besides those in
political science should address, our field's expertise within the
political arena would suggest that we have insight into political
decision-making and can act as experts that translate information
from the classroom to the real world in a variety of ways.
2011 APSA Teaching and Learning Conference Track
Summaries
Authors: Ricks Boris E. , Okura Masako Rachel , Whitt Christopher M.
Published: June 2011

The eighth annual meeting of the Diversity, Inclusiveness, and
Equality (DIE) track at the 2011 APSA Teaching and Learning
Conference focused on issues of difference, diversity, and equality
as they relate to political science classrooms, departments, and
institutions. This year, DIE included 22 participants and seven
research papers on a broad range of issues. Subject matter included
the incorporation of diversity topics into political science
curriculum, the impact of campus demographics and diversity, and
challenges faced by faculty in teaching diversity in politics.
2011 APSA Teaching and Learning Conference Track
Summaries
Authors: Listokin Siona , McKeever Robert
Published: June 2011

Given the unique challenges of graduate education, the need for
dynamic and up-to-date research is paramount. Changes in the
delivery of postgraduate education and the postgraduate job market
necessitate that faculty continuously develop and improve graduate
programs and professional development. While much of the scholarship
concerning undergraduate education and curriculum is relevant to
graduate studies, dedicated research on graduate education in
political science is also necessary.
2011 APSA Teaching and Learning Conference Track
Summaries
Authors: Lantis Jeffrey S.
Published: June 2011

Track participants engaged in rich discussions about
“internationalization” in college and university curricula. We began
by considering contending definitions of central concepts and
educational objectives associated with internationalization.
Participants discussed different possible avenues of
internationalization, including the development of new classes, an
infusion of subjects linked to global affairs in existing classes
across the curriculum, cultural programming, and the creation of new
interdisciplinary classes. We also addressed study abroad programs,
language and cross-cultural training, and partnerships and
exchanges.
2011 APSA Teaching and Learning Conference Track
Summaries
Authors: Kollars Nina , Raymond Chad
Published: June 2011

In a weekend of pedagogical fury, members of the Simulations and Role
Play II track queried their peers to refine their ideas, presented
data on the effectiveness of simulations as pedagogical tools, and
shared methods of using simulations in the classroom. Paper
presentations and discussions examined simulations from a variety of
paradigmatic perspectives, including the use of simulations as
summative assessment instruments, the role of competition in
generating targeted learning outcomes, and the difficulty in
balancing pedagogical objectives with design constraints.
2011 APSA Teaching and Learning Conference Track
Summaries
Authors: Grigsby Ellen , Bessette Murray S. Y. , Ralston Shane
Published: June 2011

The 2011 Teaching Political Theory and Theories track drew scholars
from Europe and the United States and featured work from political
scientists representing the four major subfields. While analyzing
the nine papers presented, participants articulated a range of
perspectives on questions of pedagogy and the relationship between
political theory and political science; indeed, the variety of
perspectives confirmed the ongoing contestability of many central
concepts in both the scholarship of teaching and learning (SOTAL)
and the discipline of political science. Whether discussing ways to
develop assignments for undergraduate research projects on the Tea
Party or how to employ insights from deliberative democratic theory
to assess the role of education in addressing racial violence in the
United States, participants confronted important questions regarding
the role of theory in the discipline, the broadening of
undergraduate and graduate teaching strategies, and assessment of
the effectiveness of alternative teaching strategies.
Welfare Politics in Congress
Authors: Mead Lawrence M.
Published: June 2011

Figures 3–5 were printed incorrectly on pp. 351–52 of the above
publication. The correct figures, titles, and captions, are
presented below.
APSA 2011 Africa Workshop: “Representation
Reconsidered”
Authors: LeVan Carl
Published: June 2011

The American Political Science Association's 2011 Africa Workshop
will be led by Todd Eisenstadt and Carl LeVan, both of American
University in Washington, DC, along with Josephine Ahikire from
Makerere University in Uganda and Karuti Kanyinga from the
University of Nairobi. The Institute for Development Studies at the
University of Nairobi will be hosting the workshop in July. The
workshop will be the fourth in a multi-year effort supported by the
Andrew W. Mellon Foundation to encourage collaboration between
political scientists in United States and Africa.
2011 APSA Teaching and Learning Conference Track
Summaries
Authors: Mulcare Dan , Hanka Matt
Published: June 2011

The Teaching Research Methods track at the 2011 APSA Teaching and
Learning Conference built upon many of the themes from past years
and brought to fruition some of the recommendations made at previous
meetings. The group touched on numerous topics, but there were a few
main themes that informed each conversation. First, the papers and
commentary focused on determining the best way to give our students,
especially our majors, a solid research methods background. Because
faculty from many types of colleges and universities were present
and offered varying accounts of the particular needs and career
goals of their school's students, the group did not reach a
consensus as to a uniform course of study that would be appropriate
for every institution. Although participants had different ideas
about how to implement a methods course of study, many presentations
highlighted the necessity to forefront methods training and further
integrate it into the political science curriculum.
Strategien zur Untersuchung des Wissenschafts-Praxis-Transfers
Authors: Kanning Uwe P. , Thielsch Meinald T. , Brandenburg Torsten
Published: June 2011

Fragen der Praxisrelevanz psychologischer Forschung sind zunehmend Gegenstand empirischer Analysen. Dabei lassen sich drei Forschungsstrategien unterscheiden: Input-Analysen untersuchen den Praxisbezug wissenschaftlicher Publikationen. Prozess-Analysen fragen danach, wie sich Berufspraktiker über wissenschaftliche Erkenntnisse informieren. Output-Analysen schauen, inwieweit wissenschaftliche Erkenntnisse praktisch umgesetzt werden. Neben einer Reflexion dieser Strategien werden Ergebnisse einer Umfrage vorgestellt. Sie zeigen, dass wissenschaftliche Erkenntnisse vor allem dann in der Praxis wahrgenommen werden, wenn sie in Büchern, Praxiszeitschriften oder über das Internet publiziert wurden.
The Answer-Until-Correct Item Format Revisited
Authors: Muñiz José , Menéndez Fernando
Published: June 2011

Current availability of computers has led to the use of a new series of response formats that are an alternative to the classical dichotomic format, and to the recovery of other formats, like the case of the answer-until-correct (AUC) format, whose efficient administration requires this kind of technology. The goal of the present study is to determine whether the use of the AUC format improves test reliability and validity in comparison to the classical dichotomic format. Three samples of 174, 431, and 1,446 Spanish students from secondary education, professional training, and high school, ages between 13 and 20 years, were used. A 100-item test and a 25-item test that assessed knowledge of Universal History were used, both tests administered by Internet with the AUC format. There were 56 experimental conditions, resulting from the manipulation of eight scoring models and seven test lengths. The data were analyzed from the perspective of the Classical Test Theory and also with Item Response Theory (IRT) models. Reliability and construct validity, analyzed from the classic perspective, did not seem to improve significantly when using the AUC format; however, when assessing reliability with the Information Function obtained by means of IRT models, the advantages of the AUC format versus the dichotomic format become clear. For low levels of the trait assessed, scores obtained with the AUC format provide more information than scores obtained with the dichotomic format. Lastly, these results are commented on, and the possibilities and limits of the AUC format in highly computerized psychological and educational contexts are analyzed.
Performance evaluation of selected ionospheric delay models during geomagnetic storm conditions in low‐latitude region
Authors: Venkata Ratnam D. , Sarma A. D. , Satya Srinivas V. , Sreelatha P.
Published: June 2011

Investigation of space weather effects on GPS satellite navigation systems is very crucial in high‐precision positional applications such as aircraft landings and missile guidance, etc. The geomagnetic storms can drastically affect the total electron content (TEC) of the ionosphere even in low latitudes, especially for Indian region as it comes under low‐latitude region. Hence, the performance of three prominent ionospheric models is investigated for adverse ionospheric conditions using 17 GPS TEC stations data. The models characterized the ionospheric disturbances due to two magnetic storms well.
Using terrigenic 4He to identify and quantify regional groundwater discharge to streams
Authors: Gardner W. Payton , Harrington Glenn A. , Solomon D. Kip , Cook Peter G.
Published: June 2011

We present a new technique for identifying and quantifying the discharge of long residence time, regional groundwater to rivers using naturally occurring tracers measured within the river. Terrigenic 4He and 222Rn, synoptically sampled along a 100 km reach in the Fitzroy River in northern Western Australia, are used to identify areas of groundwater inflow to the river and to distinguish shallow, local and deep, regional groundwater. Models of tracer transport in the river can be numerically optimized to calculate total groundwater discharge and to separate regional and local discharge fractions. Discharge of regional groundwater composes close to 15% of the total groundwater discharge along the entire reach, varying spatially along the reach from 0% to 100% of total groundwater discharge. This method should be applicable in river systems where groundwater with elevated terrigenic helium could be discharging to the river. The ability to separate locally from regionally derived groundwater discharge has significant implications for calculating catchment water budgets, for predicting catchment response to changes in precipitation, and for sustainable management of the catchment.
Annotated Manhattan plots and QQ plots for GWAS using R, Revisited
Authors: Turner Stephen
Published: June 2011

This manuscript provides software and a tutorial for creating manhattan plots and QQ plots for genome-wide association studies using the R statistical computing environment.
An elementary model of torus canards
Authors: Benes G. Nicholas , Barry Anna M. , Kaper Tasso J. , Kramer Mark A. , Burke John
Published: June 2011

We study the recently observed phenomena of torus canards. These are a higher-dimensional generalization of the classical canard orbits familiar from planar systems and arise in fast-slow systems of ordinary differential equations in which the fast subsystem contains a saddle-node bifurcation of limit cycles. Torus canards are trajectories that pass near the saddle-node and subsequently spend long times near a repelling branch of slowly varying limit cycles. In this article, we carry out a study of torus canards in an elementary third-order system that consists of a rotated planar system of van der Pol type in which the rotational symmetry is broken by including a phase-dependent term in the slow component of the vector field. In the regime of fast rotation, the torus canards behave much like their planar counterparts. In the regime of slow rotation, the phase dependence creates rich torus canard dynamics and dynamics of mixed mode type. The results of this elementary model provide insight into the torus canards observed in a higher-dimensional neuroscience model.
AlGaN based III-nitride tunnel barrier hyperspectral detector: Effect of internal polarization
Authors: Tripathi N. , Bell L. D. , Shahedipour-Sandvik F.
Published: June 2011

We report on the recent progress made toward development of a III-nitride based tunable hyperspectral detector pixel with the potential advantages of reduced hardware complexity and increased dynamic control on the detection parameters in the context of existing hyperspectral detection systems. We discuss the concept, experiments, and simulation of devices along with the different obstacles to be overcome before this technology can mature into a commercial application.
Confocal Raman depth-scanning spectroscopic study of phonon−plasmon modes in GaN epilayers
Authors: Strelchuk V. V. , Bryksa V. P. , Avramenko K. A. , Valakh M. Ya. , Belyaev A. E. , Mazur Yu. I. , Ware M. E. , DeCuir E. A. , Salamo G. J.
Published: June 2011

Coupled longitudinal-optical (LO)-phonon-plasmon excitations were studied using confocal micro-Raman spectroscopy. The high-quality Si-doped GaN epilayers were grown in a Gunn diode structure on (0001) sapphire substrates by plasma assisted molecular beam epitaxy. Depth-profiled Raman spectra exhibit a spatial variation of both low, ω-, and high, ω+, frequency coupled phonon−plasmon modes (CPPMs) in the n-GaN layers. To describe the features of the CPPMs in the Raman spectra a self-consistent model that includes both the electro-optic and deformation-potential as well as charge-density fluctuation mechanisms as important processes for light scattering in n-GaN has been proposed. An agreement between the theoretical and experimental line shapes of the Raman spectra is obtained. From the best line-shape fitting of the CPPMs the depth profiles of the plasmon and phonon damping, plasmon frequency, free carrier concentrations, and electron mobility as well as the contributions of the electron−phonon interaction and charge density fluctuations to the Raman cross section in the GaN layers are determined. It is found that these depth profiles exhibit considerable nonuniformity and change at different laser pump-power excitations. Despite the high electron concentration in the n+-GaN layers, a strong peak of the unscreened A1(LO) phonon is also observed. A possible origin for the appearance of this mode is discussed.
Gadolinium gallium oxide/gallium oxide insulators on GaAs and In0.53Ga0.47As n+ MOS capacitors: The interface state model and beyond
Authors: Paterson G. W. , Holland M. C. , Bentley S. J. , Thayne I. G. , Long A. R.
Published: June 2011

The electrical characteristics of n+ GaAs and In0.53Ga0.47As MOS capacitors with a dielectric stack of Ga2O3/Gd0.25Ga0.15O0.6 have been examined in detail and compared to the interface state model. The deviations from the model are assessed and the limitations of different interface state density extraction techniques are highlighted. The results of a model which accounts for many of the electrical characteristics of the InGaAs material by including states within the oxide and at the interface are reported. A hypothesis that may explain the difference between the GaAs and InGaAs characteristics and the similarities between the properties of many different oxides on InGaAs is discussed, leading to suggestions on how the oxide quality may be improved.
Internal rotation: Single diagonalization approach versus standard approaches, application to the methyl peroxy radical $\widetilde{\hspace*{-4pt}A}\leftarrow \widetilde{\hspace*{-2pt}X}$Ã←X̃ transition
Authors: Dupré Patrick
Published: June 2011

A new approach avoiding double (two-step) diagonalization is proposed to deal with internal rotation. The development of this method was stimulated by the jet-cooled high resolution spectrum of the vibrationless \documentclass[12pt]{minimal}\begin{document}$\widetilde{A}\leftarrow \widetilde{X}$\end{document}Ã←X̃ transition of the deuterated species of the methyl peroxy radical. This spectrum, originally analyzed with a rigid rotor Hamiltonian including spin-rotation but neglecting internal rotation, has been revisited in the previous paper (P. Dupré, J. Chem. Phys. 134, 244308 (2011)10.1063/1.3599953) and a determinable yaw of the molecular principal axes of inertia about the c-axis (axis-switching) during the electronic transition was established. The spectral resolution of the jet-cooled data of the vibrationless transition (∼7355 − 7390 cm−1) does not allow the observation of splitting due to internal rotation of the methyl top, but when these data are combined with the low resolution room temperature data (∼7200 − 8000 cm−1) accurate fits or simulations of the two sets of data are possible. A recent study of the room temperature data has been reported in this journal (G. M. P. Just et al., J. Chem. Phys. 127, 044310 (2007)) showing evidence of the internal rotation coupling by analyzing the intensity of the torsional mode energy progression. That investigation combined ab initio quantum chemistry calculations and the rho-axis-method (RAM) to model the internal rotation. Here, a comparison of full spectral intensity analyses based on both the usual RAM and on the new approach requiring a single-diagonalization principal-axis-method is presented. The comparison favors the single-diagonalization approach. Axis-switching and spin-rotation coupling are incorporated in the analysis, in which the use of the principal axes of inertia is maintained. Symmetries, energy levels, and advantages are carefully discussed for all methods.
Evolutionary determination of experimental parameters for ptychographical imaging
Authors: Shenfield Alex , Rodenburg John M.
Published: June 2011

The Ptychographical Iterative Engine (PIE) algorithm is a recently developed novel method of Coherent Diffractive Imaging (CDI) that uses multiple overlapping diffraction patterns to reconstruct an image. This method has successfully produced high quality reconstructions at both optical and X-ray wavelengths but the need for accurate knowledge of the probe positions is currently a limiting factor in the production of high resolution reconstructions at electron wavelengths. This paper examines the shape of the search landscape for producing optimal image reconstructions in the specific case of electron microscopy and then shows how evolutionary search methods can be used to reliably determine experimental parameters in the electron microscopy case (such as the spherical aberration in the probe and the probe positions).
Scanning tunneling microscopy image modeling for zigzag-edge graphene nanoribbons
Authors: Chen Xiongwen , Wan Haiqing , Song Kehui , Tang Dongsheng , Zhou Guanghui
Published: June 2011

Based on the nonequilibrium Green’s function with tight-binding approximation scheme, we study the scanning tunneling microscopy (STM) current from a semi-infinite quantum wire to carbon sites of a zigzag-edge graphene nanoribbon (ZGNR) via an adatom on it. We find that although the existence of local edge states, only the even order number carbon chains near the edge provide good conducting channels, and the STM image should be alternative with dark-bright fringes. This effect has not been shown in previous studies by treating a ZGNR in its entirety, and it may be useful for the STM experimental characterization on graphene samples.
Comparative study of n-MgZnO/p-Si ultraviolet-B photodetector performance with different device structures
Authors: Hou Y. N. , Mei Z. X. , Liang H. L. , Ye D. Q. , Liang S. , Gu C. Z. , Du X. L.
Published: June 2011

A comparative study of n-MgZnO/p-Si UV-B photodetector performance was carried out with different device structures. The experimental results demonstrate superior photoresponse characteristics of the p-n heterojunction detector against the Schottky type metal-semiconductor-metal counterpart, including a sharper cutoff wavelength at 300 nm, a larger peak photoresponsivity of 1 A/W, and a faster response speed. The role of built-in field and low interface scattering in p-n heterojunction is explored, and the energy band diagram of n-MgZnO/p-Si is employed to interpret the efficient suppression of visible light photoresponse from Si substrate, revealing the applicability of this heterostructure in fabrication of deep ultraviolet detectors.
Growth and orientation dependence of electrical properties of 0.92Na0.5Bi0.5TiO3-0.08 K0.5Bi0.5TiO3 lead-free piezoelectric single crystal
Authors: Sun Renbing , Zhao Xiangyong , Zhang Qinhui , Fang Bijun , Zhang Haiwu , Li Xiaobing , Lin Di , Wang Sheng , Luo Haosu
Published: June 2011

A 0.92Na0.5Bi0.5TiO3-0.08 K0.5Bi0.5TiO3 (0.92NBT-0.08KBT) lead-free piezoelectric single crystal with dimensions of Φ 35 × 10 mm was successfully grown by the top-seeded solution growth method. The effective segregation coefficient for K was calculated to be 0.27. An x-ray powder diffraction measurement showed that the as-grown crystal possesses a rhombohedral perovskite structure at room temperature. The room-temperature dielectric constants for poled 〈001〉, 〈110〉, and 〈111〉 oriented crystal samples are found to be 683, 567, and 435 at 1 kHz, respectively. The (Tm, ɛm) values for 〈001〉, 〈110〉, and 〈111〉 oriented crystals are (316 °C, 4318), (317 °C, 4160), and (318 °C, 4348) at 1 kHz, which indicate that the dielectric parameters of the as-grown crystals show weaker anisotropy. The curves, ɛ(T), for the three crystallographic orientations show two anomalies at about 170 and 320 °C, respectively, relating to the ferroelectric-antiferroelectric phase and the antiferroelectric-paraelectric phase. There is a thermal hysteresis, ΔT ≈ 35 °C for the ferroelectric-antiferroelectric phase transformation between heating and cooling. The antiferroelectric phase, the thermal hysteresis, and the dielectric relaxor behavior around 170 °C can be attributed to the formation of an intermediate orthorhombic modulated phase at 170–320 °C. For the 〈001〉, 〈110〉, and 〈111〉 crystal samples, the room-temperature piezoelectric constants, d33, reach 175, 130, and 70 pC/N, respectively. The remanent polarization for the 〈001〉, 〈110〉, and 〈111〉 crystal samples are 8.1, 10.8, and 13.5 μC/cm2, respectively, and the ratio is 1:1.33:1.67, close to 1:2:3. The diffusive factors, α, are found to be 1.94, 1.91, and 1.50 for the 〈001〉, 〈110〉, and 〈111〉 oriented crystal samples, which indicate that the antiferroelectric-paraelectric phase transition of the as-grown 0.92NBT-0.08KBT crystal is a strong diffuse one. The electromechanical coupling coefficients for the 〈001〉, 〈110〉, and 〈111〉 oriented 0.92NBT-0.08KBT crystals at room temperature are 52, 50, and 48%, respectively. The values of kt for the three main crystallographic orientations change slightly with the increase of temperature from 15 to 140 °C, demonstrating a relatively stable thermal electromechanical coupling property.
Ab initio study of excited state electronic circular dichroism. Two prototype cases: Methyl oxirane and R-(+)-1,1′-bi(2-naphthol)
Authors: Rizzo Antonio , Vahtras Olav
Published: June 2011

A computational approach to the calculation of excited state electronic circular dichroism (ESECD) spectra of chiral molecules is discussed. Frequency dependent quadratic response theory is employed to compute the rotatory strength for transitions between excited electronic states, by employing both a magnetic gauge dependent and a (velocity-based) magnetic gauge independent approach. Application is made to the lowest excited states of two prototypical chiral molecules, propylene oxide, also known as 1,2-epoxypropane or methyl oxirane, and R-(+)-1,1′-bi(2-naphthol), or BINOL. The dependence of the rotatory strength for transitions between the lowest three excited states of methyl oxirane upon the quality and extension of the basis set is analyzed, by employing a hierarchy of correlation consistent basis sets. Once established that basis sets of at least triple zeta quality, and at least doubly augmented, are sufficient to ensure sufficiently converged results, at least at the Hartree-Fock self-consistent field (HF-SCF) level, the rotatory strengths for all transitions between the lowest excited electronic states of methyl oxirane are computed and analyzed, employing HF-SCF, and density functional theory (DFT) electronic structure models. For DFT, both the popular B3LYP and its recently highly successful CAM-B3LYP extension are exploited. The strong dependence of the spectra upon electron correlation is highlighted. A HF-SCF and DFT study is carried out also for BINOL, a system where excited states show the typical pairing structure arising from the interaction of the two monomeric moieties, and whose conformational changes following photoexcitation were studied recently with via time-resolved CD.
Gas phase solvatochromic effects of phenol and naphthol photoacids
Authors: Melnichuk Anna , Bartlett Rodney J.
Published: June 2011

A quantum chemical study of spectral shifts by single molecule solvation of phenol, α-naphthol, and β-naphthol is presented. The methods employed include the equation-of-motion coupled cluster, the similarity transformed equation-of-motion coupled cluster, single excitation configuration-interaction, and time-dependent density functional theory. Based on the calculations, there is no evidence that there is significant charge-transfer between the solute and the solvent. Instead, it appears that the observed solvation redshift is due to the nature of the excited state on the solute molecule.
Vibrational resonance in feedforward network
Authors: Qin Ying-mei , Wang Jiang , Men Cong , Deng Bin , Wei Xi-le
Published: June 2011

This paper investigates vibrational resonance in multi-layer feedforward network (FFN) based on FitzHugh-Nagumo (FHN) neuron model. High-frequency stimuli can improve the input-output linearity of firing rates, especially for the inputs with low firing rate. For FFN network, it is found that high-frequency disturbances play important roles in enhancing the propagation of weak signal through layers. Synfire-enhanced phenomenon of signal propagation is also observed in multi-layers network, when the signal transmission is affected by high-frequency disturbances. Network connections are found to be important for the propagation of weak signal. Besides that, the characteristics of high-frequency stimuli such as heterogeneity and frequency can also modulate the propagation of neural code through layers.
Low-temperature spatially resolved micro-photoluminescence mapping in CdZnTe single crystals
Authors: Yang G. , Bolotnikov A. E. , Cui Y. , Camarda G. S. , Hossain A. , Kim K. H. , Gul R. , James R. B.
Published: June 2011

We utilized a low-temperature spatially resolved micro-photoluminescence mapping technique to investigate the spatial variation of photoluminescence- and electronic-defect states in areas of CdZnTe (CZT) single crystals containing structural-imperfections. Photoluminescence mapping of the donor-bound-exciton emission reveals an unexpected blue-shift of the CZT bandgap at Te inclusions, which indicates that for optical measurements the localized strain field needs to be considered for accurate calculation of Zn composition and energy levels near micro-scale defects. We observed that the line widths of the donor-bound-exciton peak and defect-related D band are broadened in regions with a high density of dislocations; in contrast, the donor-acceptor-pair peak is narrowed.
Structural and optical properties of single crystalline columbite tin oxide film
Authors: Kong Lingyi , Ma Jin , Luan Caina , Zhu Zhen
Published: June 2011

Tin oxide (SnO2) films were deposited on Y-stabilized ZrO2 (YSZ) (120) substrates at 500–750 °C by metalorganic chemical vapor deposition. The film deposited at 700 °C exhibited the best crystallinity, especially with a single crystalline columbite structure (C-SnO2). The structural and optical properties of this film were investigated in detail. A schematic diagram was proposed to clarify the growth mechanism, in which an epitaxial relationship of C-SnO2(120)||YSZ(120) with C-SnO2[001]||YSZ[001] was illustrated. The C-SnO2 film showed excellent transparency and the optical band gap was about 3.74 eV.
Improved tunneling magnetoresistance in (Ga,Mn)As/AlOx/CoFeB magnetic tunnel junctions
Authors: Yu G. Q. , Chen L. , Rizwan Syed , Zhao J. H. , XU K. , Han X. F.
Published: June 2011

We fabricated (Ga,Mn)As/AlOx/Co40Fe40B20 magnetic tunnel junctions with ferromagnetic semiconductor/insulator/ferromagnetic metal (S/I/F) structure. The treatments of pre-annealing and post-plasma cleaning on the (Ga,Mn)As film were introduced before the growth of the subsequent layers. A high tunneling magnetoresistance (TMR) ratio of 101% is achieved at 2 K, and the spin polarization of (Ga,Mn)As, P = 56.8%, is deduced from Jullière’s formula. The improved TMR ratio is primarily due to the improved magnetism of (Ga,Mn)As layer by low-temperature annealing and cleaned interface between (Ga,Mn)As and AlOx attained by subsequent plasma cleaning process.
Ultrafast internal conversion in ethylene. I. The excited state lifetime
Authors: Tao H. , Allison T. K. , Wright T. W. , Stooke A. M. , Khurmi C. , van Tilborg J. , Liu Y. , Falcone R. W. , Belkacem A. , Martinez T. J.
Published: June 2011

Using a combined theoretical and experimental approach, we investigate the non-adiabatic dynamics of the prototypical ethylene (C2H4) molecule upon π → π* excitation. In this first part of a two part series, we focus on the lifetime of the excited electronic state. The femtosecond time-resolved photoelectron spectrum (TRPES) of ethylene is simulated based on our recent molecular dynamics simulation using the ab initio multiple spawning method with multi-state second order perturbation theory [H. Tao, B. G. Levine, and T. J. Martinez, J. Phys. Chem. A 113, 13656 (2009)]10.1021/jp9063565. We find excellent agreement between the TRPES calculation and the photoion signal observed in a pump-probe experiment using femtosecond vacuum ultraviolet (hν = 7.7 eV) pulses for both pump and probe. These results explain the apparent discrepancy over the excited state lifetime between theory and experiment that has existed for ten years, with experiments [e.g., P. Farmanara, V. Stert, and W. Radloff, Chem. Phys. Lett. 288, 518 (1998)10.1016/S0009-2614(98)00312-1 and K. Kosma, S. A. Trushin, W. Fuss, and W. E. Schmid, J. Phys. Chem. A 112, 7514 (2008)]10.1021/jp803548c reporting much shorter lifetimes than predicted by theory. Investigation of the TRPES indicates that the fast decay of the photoion yield originates from both energetic and electronic factors, with the energetic factor playing a larger role in shaping the signal.
Vertical field switching for blue-phase liquid crystal devices
Authors: Cheng Hui-Chuan , Yan Jin , Ishinabe Takahiro , Wu Shin-Tson
Published: June 2011

A low-voltage (< 10 V), high-transmittance (> 80%), submillisecond-response, and hysteresis-free polymer-stabilized blue-phase liquid crystal (BPLC) device with vertical field switching (VFS) and oblique incident light are demonstrated experimentally. Unlike the commonly employed in-plane switching in which the electric field is primarily in lateral direction and not uniform spatially, the VFS mode has uniform longitudinal field. As a result, the operating voltage is reduced by ∼ 3.2 × which in turn helps to eliminate hysteresis. The VFS mode is a promising candidate for the emerging BPLC display and photonic devices.
Compact and high-quality gamma-ray source applied to 10 μm-range resolution radiography
Authors: Ben-Ismaïl A. , Lundh O. , Rechatin C. , Lim J. K. , Faure J. , Corde S. , Malka V.
Published: June 2011

Gamma-ray beams with optimal and tuneable size, temperature, and dose are of great interest for a large variety of applications. These photons can be produced by the conversion of energetic electrons through the bremsstrahlung process in a dense material. This work presents the experimental demonstration of 30 μm resolution radiography of dense objects using an optimized gamma-ray source, produced with a high-quality electron beam delivered by a compact laser-plasma accelerator.
Microscale solar cells for high concentration on polycrystalline Cu(In,Ga)Se2 thin films
Authors: Paire Myriam , Lombez Laurent , Péré-Laperne Nicolas , Collin Stephane , Pelouard Jean-Luc , Lincot Daniel , Guillemoles Jean-François
Published: June 2011

We report high concentration experiments on polycrystalline thin film solar cells. High level regime is reached, thanks to the micrometric scale of the Cu(In,Ga)Se2 cells, which strongly decreases resistive losses. A 4% absolute efficiency increase is obtained at a concentration of ×120, and current densities as high as 100 A/cm2 can be measured. These results show that the use of polycrystalline thin films under high concentration is possible, with important technological consequences.