bluuebunny/crossref_metadata_2025 huggingface dataset:
A Novel Role for an RNA Polymerase III Subunit POLR3G in Regulating Pluripotency in Human Embryonic Stem Cells
Authors: Wong Raymond Ching-Bong , Pollan Sara , Fong Helen , Ibrahim Abel , Smith Ellen L. , Ho Mirabelle , Laslett Andrew L. , Donovan Peter J.
Published: September 2011

The pluripotency of human embryonic stem cells (hESC) could have great potential for the development of cell replacement therapies. Previous studies have converged on the finding that OCT4, SOX2, and NANOG serve as key regulators in the maintenance of hESC. However, other signals that regulate hESC maintenance remain poorly studied. Here we describe a novel role of an RNA polymerase III (Pol III) subunit, POLR3G, in the maintenance of pluripotency in hESC. We demonstrate the presence of POLR3G in undifferentiated hESC, human induced pluripotent stem cells (hiPSC), and early mouse blastocysts. Downregulation of POLR3G is observed on differentiation of hESC and hiPSC, suggesting that POLR3G can be used as a molecular marker to readily identify undifferentiated pluripotent stem cells from their differentiated derivatives. Using an inducible shRNA lentiviral system, we found evidence that decreased levels of POLR3G result in loss of pluripotency and promote differentiation of hESC to all three germ layers but have no effect on cell apoptosis. On the other hand, overexpression of POLR3G has no effect on pluripotency and apoptosis in undifferentiated hESC. Interestingly, hESC expressing elevated levels of POLR3G are more resistant to differentiation. Furthermore, our experimental results show that POLR3G is a downstream target of OCT4 and NANOG, and our pharmacological study indicated that POLR3G expression can be readily regulated by the Erk1/2 signaling pathway. This study is the first to show an important role of POLR3G in the maintenance of hESC, suggesting a potential role of Pol III transcription in regulating hESC pluripotency.
Effects on Proliferation and Differentiation of Multipotent Bone Marrow Stromal Cells Engineered to Express Growth Factors for Combined Cell and Gene Therapy
Authors: Fierro Fernando A. , Kalomoiris Stefanos , Sondergaard Claus S. , Nolta Jan A.
Published: September 2011

A key mechanism for mesenchymal stem cells/bone marrow stromal cells (MSCs) to promote tissue repair is by secretion of soluble growth factors (GFs). Therefore, clinical application could be optimized by a combination of cell and gene therapies, where MSCs are genetically modified to express higher levels of a specific factor. However, it remains unknown how this overexpression may alter the fate of the MSCs. Here, we show effects of overexpressing the growth factors, such as basic fibroblast growth factor (bFGF), platelet derived growth factor B (PDGF-BB), transforming growth factor β1 (TGF-β1), and vascular endothelial growth factor (VEGF), in human bone marrow-derived MSCs. Ectopic expression of bFGF or PDGF-B lead to highly proliferating MSCs and lead to a robust increase in osteogenesis. In contrast, adipogenesis was strongly inhibited in MSCs overexpressing PDGF-B and only mildly affected in MSCs overexpressing bFGF. Overexpression of TGF-β1 blocked both osteogenic and adipogenic differentiation while inducing the formation of stress fibers and increasing the expression of the smooth muscle marker calponin-1 and the chondrogenic marker collagen type II. In contrast, MSCs overexpressing VEGF did not vary from control MSCs in any parameters, likely due to the lack of VEGF receptor expression on MSCs. MSCs engineered to overexpress VEGF strongly induced the migration of endothelial cells and enhanced blood flow restoration in a xenograft model of hind limb ischemia. These data support the rationale for genetically modifying MSCs to enhance their therapeutically relevant trophic signals, when safety and efficacy can be demonstrated, and when it can be shown that there are no unwanted effects on their proliferation and differentiation.
Hydroarylation of alkynes catalyzed by nickel
Authors: Nakao Yoshiaki
Published: September 2011

Nickel catalysts derived from bis(1,5‐cyclooctadiene)nickel [Ni(cod)2] and trialkylphosphines effect hydroarylation of alkynes through functionalization of C–H bonds of arenes including benzo‐fused five‐membered heteroarenes, pyridine‐N‐oxides, pyridines, 2‐pyridones, and perfluoroarenes. The reactions proceed with excellent stereo‐ and regioselectivity to give disubstituted arylethenes in good yields. Use of Lewis acid (LA) co‐catalysts is crucial for success in reactions of imidazoles, pyridines, and 2‐pyridones; it is possible that coordination of the LA to the nitrogen or oxygen functionalities of such substrates increases the reactivity of their C–H bonds towards nickel(0) species. DOI 10.1002/tcr.201100023
Facilitating change in undergraduate STEM instructional practices: An analytic review of the literature
Authors: Henderson Charles , Beach Andrea , Finkelstein Noah
Published: September 2011

This article reviews current scholarship about how to promote change in instructional practices used in undergraduate science, technology, engineering, and mathematics (STEM) courses. The review is based on 191 conceptual and empirical journal articles published between 1995 and 2008. Four broad categories of change strategies were developed to capture core differences within this body of literature: disseminating curriculum and pedagogy, developing reflective teachers, enacting policy, and developing shared vision. STEM education researchers largely write about change in terms of disseminating curriculum and pedagogy. Faculty development researchers largely write about change in terms of developing reflective teachers. Higher education researchers largely write about change in terms of enacting policy. New work often does not build on prior empirical or theoretical work. Although most articles claim success of the change strategy studied, evidence presented to support these claims is typically not strong. For example, only 21% of articles that studied implementation of a change strategy were categorized as presenting strong evidence to support claims of success or failure of the strategy. These analyses suggest that the state of change strategies and the study of change strategies are weak, and that research communities that study and enact change are largely isolated from one‐another. In spite of the weak state of the literature, some conclusions related to the design of change strategies can be drawn from this review. Two commonly used change strategies are clearly not effective: developing and testing “best practice” curricular materials and then making these materials available to other faculty and “top‐down” policy‐making meant to influence instructional practices. Effective change strategies: are aligned with or seek to change the beliefs of the individuals involved; involve long‐term interventions, lasting at least one semester; require understanding a college or university as a complex system and designing a strategy that is compatible with this system. © 2011 Wiley Periodicals, Inc. J Res Sci Teach 48: 952–984, 2011
Normal morphogenesis of epithelial tissues and progression of epithelial tumors
Authors: Wang Chun‐Chao , Jamal Leen , Janes Kevin A.
Published: September 2011

Epithelial cells organize into various tissue architectures that largely maintain their structure throughout the life of an organism. For decades, the morphogenesis of epithelial tissues has fascinated scientists at the interface of cell, developmental, and molecular biology. Systems biology offers ways to combine knowledge from these disciplines by building integrative models that are quantitative and predictive. Can such models be useful for gaining a deeper understanding of epithelial morphogenesis? Here, we take inventory of some recurring themes in epithelial morphogenesis that systems approaches could strive to capture. Predictive understanding of morphogenesis at the systems level would prove especially valuable for diseases such as cancer, where epithelial tissue architecture is profoundly disrupted. WIREs Syst Biol Med 2012, 4:51–78. doi: 10.1002/wsbm.159

This article is categorized under:

Physiology > Mammalian Physiology in Health and Disease
Tolerance to thermal and reductive stress in Saccharomyces cerevisiae is amenable to regulation by phosphorylation–dephosphorylation of ubiquitin conjugating enzyme 1 (Ubc1) S97 and S115
Authors: Meena Ramesh C. , Thakur Suresh , Nath Surendra , Chakrabarti Amitabha
Published: September 2011

Ubiquitin conjugating enzyme 1 (Ubc1) is a member of the E2 family of enzymes that conjugates ubiquitin to damaged proteins destined for degradation by the ubiquitin proteasomal system. It is necessary for stress tolerance and is essential for cell survival in Saccharomyces cerevisiae. Ubc1 has five serine residues that are potential substrates for phosphorylation by kinases. However, no data are available to indicate that Ubc1 function or stress tolerance in S. cerevisiae is regulated by serine phosphorylation of Ubc1. We demonstrate that Ubc1 is phosphorylated in serine residue(s). Furthermore, expression of Ubc1 mutants that are ‘constitutively phosphorylated’ or ‘dephosphorylated’ in mitogen‐activated protein (MAP) kinase serine residues (S97 and S115) affected tolerance to thermal and reductive stress in S. cerevisiae. Specifically, expression of Ubc1S97A and S115D increased thermo‐tolerance in both BY4741 and TetO7‐UBC1ura3Δ cells. Serine phosphorylation of Ubc1 was decreased in BY4741 cells following exposure at 40 °C. Tolerance to reductive stress in the same strains correlated with the expression of Ubc1S97A. Ubc1 phosphorylation did not show significant alteration under similar conditions. Both hog1Δ and slt2Δ cells expressing Ubc1S115D and Ubc1S115A were rendered tolerant to thermal and reductive stress respectively. Ubc1 phosphorylation was higher in BY4741 cells compared to hog1Δ cells at 30 °C and was significantly reduced in BY4741 cells upon exposure at 40 °C. Taken together, the cell survival assays and Ubc1 phosphorylation status in strains and under conditions as described above suggest that tolerance to thermal and reductive stress in S. cerevisiae may be regulated by MAP kinase‐mediated phosphorylation of Ubc1S97 and S115. Copyright © 2011 John Wiley & Sons, Ltd.
Glucose signalling pathway controls the programmed ribosomal frameshift efficiency in retroviral‐like element Ty3 in Saccharomyces cerevisiae
Authors: Türkel Sezai , Kaplan Güliz , Farabaugh Philip J.
Published: September 2011

Ty3 elements of S. cerevisiae contain two overlapping coding regions, GAG3 and POL3, which are functional homologues of retroviral gag and pol genes, respectively. Pol3 is translated as a Gag3‐Pol3 fusion protein dependent on a +1 programmed frameshift at a site with the overlap between the two genes. We show that the Ty3 frameshift frequency varies up to 10‐fold in S. cerevisiae cells depending on carbon source. Frameshift efficiency is significantly lower in cells growing on glucose as carbon source than in cells growing on poor alternative carbon sources (glycerol/lactate or galactose). Our results indicate that Ty3 programmed ribosomal frameshift efficiency in response to glucose signalling requires two protein kinases: Snf1p and cAMP‐dependent protein kinase A (PKA). Increased frameshifting on alternative carbon sources also appears to require cytoplasmic localization of Snf1p, mediated by the Sip2p protein. In addition to the two required protein kinases, our results implicate that Stm1p, a ribosome‐associated protein involved in nutrient sensing, is essential for the carbon source‐dependent regulation of Ty3 frameshifting. These data indicate that Ty3 programmed ribosomal frameshift is not a constitutive process but that it is regulated in response to the glucose‐signalling pathway. Copyright © 2011 John Wiley & Sons, Ltd.
Interleukin‐15 Affects Differentiation and Apoptosis in Adipocytes: Implications in Obesity
Authors: Fuster Gemma , Almendro Vanessa , Fontes‐Oliveira Cibely Cristine , Toledo Míriam , Costelli Paola , Busquets Sílvia , López‐Soriano Francisco J. , Argilés Josep M.
Published: September 2011

Interleukin‐15 (IL‐15) is an anabolic factor for skeletal muscle and several reports have described its important role as a regulator of energy homeostasis. In this study, we analyzed the effects of IL‐15 on adipocyte differentiation using the 3T3‐L1 preadipose cell line. The data show that IL‐15 tends to reduce the rate of adipocyte proliferation, induces apoptosis, and partially stops differentiation. The signaling molecules behind these actions of the cytokine on adipose cells are: p42/p44 MAPK (which seem to be associated with the reduced rate of proliferation induced by the cytokine), STAT5 (which is related to the actions of IL‐15 on differentiation), and SAPK/JNK (which are related to the increased apoptosis induced by IL‐15). In conclusion, using the 3T3‐L1 adipocyte cell line, the results presented here show that IL‐15 exerts important effects on differentiation, proliferation and apoptosis. Altogether, the results presented here reinforce the idea that IL‐15 is an important mediator that regulates adipose size and, therefore, the role of the cytokine in affecting body weight and obesity deserves additional studies.
Application of a Novel, Heated, Nine‐Reflection ATR Crystal and a Portable FTIR Spectrometer to the Rapid Determination of Total Trans Fat
Authors: Mossoba Magdi M. , Kramer John K. G. , Azizian Hormoz , Kraft Jana , Delmonte Pierluigi , Kia Ali‐Reza Fardin , Bueso Francisco J. , Rader Jeanne I. , Lee Jung K.
Published: September 2011

Since trans fat labeling requirements became mandatory in the US and many other countries, there has been a need for rapid and accurate analytical methodologies that can facilitate compliance with the various regulations. The determination of total trans fatty acids by mid‐infrared (IR) spectroscopy is a widely used procedure that was standardized and validated as AOCS Official Method Cd 14e‐09 (negative second derivative infrared spectroscopic method for the rapid (5 min) determination of total isolated trans fat) in 2009. The C–H out‐of‐plane deformation mid‐IR band observed at 966 cm−1 is uniquely characteristic of isolated (non‐conjugated) double bonds with trans configuration. AOCS Official Method Cd 14e‐09, the most recent attenuated total reflection‐Fourier transform IR (ATR‐FTIR) official method, entails the measurement of the height of the negative second derivative of the trans absorption band. In the present study, the performance of a novel, portable FTIR system equipped with a heated 9‐bounce diamond ATR crystal was evaluated and compared to that of a conventional benchtop single‐bounce ATR‐FTIR spectrometer. The introduction of the 9‐bounce diamond ATR crystal resulted in the lowering of the limit of quantification of trans fat, as a percentage of the total fat, from approximately 2 to 0.34%. The data collected from accurately weighed gravimetric standards and 28 unknown test samples ranging in trans fat content from about 0.5 to 54%, as a percentage of the total fat, indicated that this IR official method and the use of the new 9‐bounce portable ATR‐FTIR instrumentation could lead to a five‐fold enhancement in sensitivity relative to single‐bounce systems. Implementing these changes would facilitate regulatory compliance and verification of fat and oil samples for trans fat content in the US and other countries, since all of the published regulations (e.g., “0 g trans fat per serving”) have levels of trans fat, as percentage of total fat, that exceed 0.34%.
Successful development of microsatellite markers in a challenging species: the horizontal borerAustroplatypus incompertus(Coleoptera: Curculionidae)
Authors: Smith S. , Joss T. , Stow A.
Published: September 2011

The analysis of microsatellite loci has allowed significant advances in evolutionary biology and pest management. However, until very recently, the potential benefits have been compromised by the high costs of developing these neutral markers. High-throughput sequencing provides a solution to this problem. We describe the development of 13 microsatellite markers for the eusocial ambrosia beetle,Austroplatypus incompertus, a significant pest of forests in southeast Australia. The frequency of microsatellite repeats in the genome ofA. incompertuswas determined to be low, and previous attempts at microsatellite isolation using a traditional genomic library were problematic. Here, we utilised two protocols, microsatellite-enriched genomic library construction and high-throughput 454 sequencing and characterised 13 loci which were polymorphic among 32 individuals. Numbers of alleles per locus ranged from 2 to 17, and observed and expected heterozygosities from 0.344 to 0.767 and from 0.507 to 0.860, respectively. These microsatellites have the resolution required to analyse fine-scale colony and population genetic structure. Our work demonstrates the utility of next-generation 454 sequencing as a method for rapid and cost-effective acquisition of microsatellites where other techniques have failed, or for taxa where marker development has historically been both complicated and expensive.
Development and use of EST-SSR markers for assessing genetic diversity in the brown planthopper (Nilaparvata lugensStål)
Authors: Jing S. , Liu B. , Peng L. , Peng X. , Zhu L. , Fu Q. , He G.
Published: September 2011

To assess genetic diversity in populations of the brown planthopper (Nilaparvata lugensStål) (Homoptera: Delphacidae), we have developed and applied microsatellite, or simple sequence repeat (SSR), markers from expressed sequence tags (ESTs). We found that the brown planthopper clusters of ESTs were rich in SSRs with unique frequencies and distributions of SSR motifs. Three hundred and fifty-one EST-SSR markers were developed and yielded clear bands from samples of four brown planthopper populations. High cross-species transferability of these markers was detected in the closely related planthopperN. muiri. The newly developed EST-SSR markers provided sufficient resolution to distinguish within and among biotypes. Analyses based on SSR data revealed host resistance-based genetic differentiation among different brown planthopper populations; the genetic diversity of populations feeding on susceptible rice varieties was lower than that of populations feeding on resistant rice varieties. This is the first large-scale development of brown planthopper SSR markers, which will be useful for future molecular genetics and genomics studies of this serious agricultural pest.
A Bayesian approach for correcting for partial plating in fluctuation experiments
Authors: ZHENG QI
Published: September 2011

The fluctuation experiment is the preferred method for estimating microbial mutation rates. A difficult task facing the data analyst is to infer the mean number of mutations from the number of mutant cells that only indirectly reflects the number of mutations. Partial plating, commonly practised in the laboratory, renders this task even more challenging by allowing only a portion of the mutant cells to be counted. In this paper, we propose a Bayesian approach to correcting for partial plating in the analysis of fluctuation experiments.
Strong renewal theorems and Lyapunov spectra forα-Farey andα-Lüroth systems
Authors: KESSEBÖHMER MARC , MUNDAY SARA , STRATMANN BERND O.
Published: September 2011

In this paper, we introduce and study theα-Farey map and its associated jump transformation, theα-Lüroth map, for an arbitrary countable partitionαof the unit interval with atoms which accumulate only at the origin. These maps represent linearized generalizations of the Farey map and the Gauss map from elementary number theory. First, a thorough analysis of some of their topological and ergodic theoretical properties is given, including establishing exactness for both types of these maps. The first main result then is to establish weak and strong renewal laws for what we have calledα-sum-level sets for theα-Lüroth map. Similar results have previously been obtained for the Farey map and the Gauss map by using infinite ergodic theory. In this respect, a side product of the paper is to allow for greater transparency of some of the core ideas of infinite ergodic theory. The second remaining result is to obtain a complete description of the Lyapunov spectra of theα-Farey map and theα-Lüroth map in terms of the thermodynamical formalism. We show how to derive these spectra and then give various examples which demonstrate the diversity of their behaviours in dependence on the chosen partitionα.
Teaching Pragmatics: Trends and Issues
Authors: Taguchi Naoko
Published: September 2011

Theoretical, empirical, and practical interest in pragmatic competence and development for second language (L2) learners has resulted in a large body of literature on teaching L2 pragmatics. This body of literature has diverged into two major domains: (a) a group of experimental studies directly testing the efficacy of various instructional methods in pragmatics learning and (b) research that explores optimal instructional practice and resources for pragmatic development in formal classroom settings. This article reviews literature in these two domains and aims at providing a collective view of the available options for pragmatics teaching and the ways that pragmatic development can best be promoted in the classroom. In the area of instructional intervention, this article reviews studies under the common theoretical second language acquisition paradigms of explicit versus implicit instruction, input processing instruction, and skill acquisition and practice. In the area of classroom practice and resources, three domains of research and pedagogical practices are reviewed: material development and teacher education, learner strategies and autonomous learning, and incidental pragmatics learning in the classroom. Finally, this article discusses unique challenges and opportunities that have been embraced by pragmatics teaching in the current era of poststructuralism and multiculturalism.
Research in Language-Literature Instruction: Meeting the Call for Change?
Authors: Paesani Kate
Published: September 2011

The purpose of this review is to assess whether recent scholarship on language-literature instruction—the deliberate integration of language development and literary study at all levels of the foreign language curriculum—within the context of U.S. institutions of higher education reflects shifts in thinking regarding the role of literature in foreign language curricula. These shifts have come in response to the 2007 Report of the Modern Language Association Ad Hoc Committee on Foreign Languages, which recommended replacing the traditional two-tiered program structure with more coherent curricula that merge language and content, and to the general questioning of communicative language teaching as a viable method for language instruction and adequate preparation for advanced-level work in a foreign language. Current approaches to language-literature instruction and foreign language curriculum design favor multimodal language development that places equal importance on oral and written language and interpretative interaction with literature to construct textual meaning and establish form-meaning connections. This review surveys empirical and classroom practice research on literature in language courses and language in literature courses and concludes with a consideration of larger curricular issues and areas for future research.
Teaching Second Languages for the Workplace
Authors: Newton Jonathan , Kusmierczyk Ewa
Published: September 2011

Workplace culture and organization are evolving as they adapt to globalization and rapid technological development. Likewise, the nature and role of workplace language and the literacy demands of work are changing in the face of increasingly multicultural workplaces and global communication networks. Among these changes, recent research has highlighted the role that informal modes of interpersonal communication play in the functioning of the modern workplace. Successful participation in such interactions is seen as not just a question of fitting in socially, but of doing work through talk. Ethnographic research in the workplace has stressed the importance of understanding language by viewing it within its social setting and understanding the interactional norms of particular communities of practice. Research into language programs for the workplace reflects this shift in emphasis. In contrast to research in the field of language for specific purposes on the specialized vocabulary and formal registers of particular professions, a growing body of research focuses on teaching and learning the language of routine workplace interactions. This article reviews current research into the nature of workplace language, noting in particular the contributions from ethnographic and language socialization research. It then discusses research into four aspects of the content of language programs for the workplace: employability skills, interpersonal communication, intercultural and critical language awareness, and teaching focused on the employment interview.
Content-and-Language Integrated Learning: From Practice to Principles?
Authors: Dalton-Puffer Christiane
Published: September 2011

This article surveys recent work oncontent-and-language integrated learning(CLIL). Related to both content-based instruction and immersion education by virtue of its dual focus on language and content, CLIL is here understood as an educational model for contexts where the classroom provides the only site for learners’ interaction in the target language. That is, CLIL is about either foreign languages or lingua francas. The discussion foregrounds a prototypical CLIL context (Europe) but also refers to work done elsewhere. The first part of the discussion focuses on policy issues, describing how CLIL practice operates in a tension between grassroots decisions and higher order policymaking, an area where European multi- and plurilingual policies and the strong impact of English as a lingua franca play a particularly interesting role. The latter is, of course, of definite relevance also in other parts of the world. The second part of the article synthesizes research on learning outcomes in CLIL. Here, the absence of standardized content testing means that the main focus is on language-learning outcomes. The third section deals with classroom-based CLIL research and participants’ use of their language resources for learning and teaching, including such diverse perspectives as discourse pragmatics, speech acts, academic language functions, and genre. The final part of the article discusses theoretical underpinnings of CLIL, delineating their current state of elaboration as applied linguistic research in the area is gaining momentum.
Teaching Multimodal and Digital Literacy in L2 Settings: New Literacies, New Basics, New Pedagogies
Authors: Lotherington Heather , Jenson Jennifer
Published: September 2011

Globalization and digitization have reshaped the communication landscape, affecting how and with whom we communicate, and deeply altering the terrain of language and literacy education. As children in urban contexts become socialized into communities of increasing cultural and communicational connectivity, complexity, and convergence (Jenkins, 2004), and funding for specialist second language (L2) support declines, classrooms have become linguistically heterogeneous spaces where every teacher is a teacher of L2 learners.

This article has two purposes: The first is to give an overview of the concept of multimodal literacies, which utilize diverse media to represent visual, audio, gestural, spatial, and tactile dimensions of communication in addition to traditional written and oral forms (Cope & Kalantzis, 2009a). Since the New London Group's manifesto on multiliteracies in 1996, which merged language and literacy education agendas in L2 teaching, language arts, media literacy, and cultural studies, new basics have developed that apply to all classrooms and all learners. Second, this article reviews and reports on innovative pedagogical approaches to multimodal literacies involving L2 learners. These are grounded theoretically (Cope & Kalantzis, 2009a, 2009b; Kress, 2003, 2010; New London Group, 1996) and epistemologically (de Castell & Jenson, 2003; Gee, 2009, 2010; Kellner, 2004; Lankshear & Knobel, 2003, 2006).
Editor's Introduction
Authors: Polio Charlene
Published: September 2011

With this volume of the Annual Review of Applied Linguistics (ARAL), I continue the tradition of my predecessors of producing a volume on the topic second language pedagogy about every five years. Although applied linguistics encompasses more than the teaching and learning of second languages, articles on these topics tend to be among the most downloaded from the ARAL web site. I decided, however, to break with the tradition of focusing mostly on specific skill areas. Because language teaching is a situated activity that cannot be separated from its contexts and learners, the first section is devoted to language learning in or for specific contexts (secondary school settings, online, the workplace, the Asia-Pacific region, and study abroad), and the second section focuses on specific learners (young learners, adult emergent readers, and hearing learners of sign language). These are followed by a section on integrated approaches and includes articles on language-literature instruction, content and language integrated learning, the application of corpus research to language teaching, and multimodal literacy. The final section includes articles on more specific skill areas including teaching non-Roman writing systems, collaborative writing, and pragmatics.
Serological evidence ofCoxiella burnetiiexposure in native marsupials and introduced animals in Queensland, Australia
Authors: COOPER A. , GOULLET M. , MITCHELL J. , KETHEESAN N. , GOVAN B.
Published: September 2011

The state of Queensland has the highest incidence of Q fever in Australia. In recent years, there has been an increase in human cases where no contacts with the typical reservoir animals or occupations were reported. The aim of this study was to determine the seroprevalence ofCoxiella burnetiiin Australian native animals and introduced animals in northern and southeastern Queensland. Australian native marsupials sampled included the brushtail possum (Trichosurus vulpecula) and common northern bandicoot (Isoodon macrourus). Introduced species sampled included dingoes (Canis lupus dingo), cats (Felis catus), foxes (Vulpes vulpes) and pigs (Sus scrofa). Serum samples were tested by ELISA for both phase II and phase I antigens of the organism using an Australian isolate. The serological evidence ofC. burnetiiinfection demonstrated in these species has public health implications due to their increasing movement into residential areas in regional Queensland. This study is the first known investigation ofC. burnetiiseroprevalence in these species in northern Queensland.
Late recurrence of infra-Hisian complete atrioventricular block
Authors: Chang Hok-Keong , Wang Jieh-Neng , Wu Jing-Ming
Published: September 2011

Acquired complete atrioventricular block that is caused by infectious myocarditis is usually transient and has a favourable outcome. We report the case of a 15-year-old girl who had complete infra-Hisian atrioventricular block due to adeno viral myocarditis and received a permanent pacemaker at the age of 10 months. The pacemaker lost its function at the age of 7 years. However, she experienced a late recurrence of complete atrioventricular block 10 years later. Complete atrioventricular block is rarely recovered if it persisted for 2 weeks. Even in the patients with late recovery, long-term follow-up and pacemaker therapy are still needed.
Effect of serum concentration on the cytotoxicity of clay particles
Authors: Lordan Sinéad , Higginbotham Clement L.
Published: September 2011

Nanoparticle cytotoxicity testing based on in vitro methods frequently lack consistency. Even the inclusion of the commonly employed growth supplement, FCS (fetal calf serum), generates variable results. Thus, our object was to investigate the effect of FCS concentration on the cytotoxic behaviour of the unmodified nanoclay, Cloisite® Na+. Human monocytic U937 cells in medium supplemented with 5% FCS, 2.5% FCS or serum‐free medium were treated with 1 mg/ml Cloisite Na+. Cell growth in 2.5% FCS was significantly inhibited by Cloisite Na+ within 48 h, whereas little effect was seen with a supplement of 5% FCS. Without serum, cell growth was inhibited and Cloisite Na+ had a detrimental effect on these cells. In media supplemented with FCS, the nanoclays agglomerated together to form large bundles, whereas they were evenly dispersed throughout the medium in the absence of serum. Clay particles, therefore, have cytotoxic properties that may be linked to their dispersion pattern. These adverse effects seem to be masked by 5% FCS. Serum supplementation is an important consideration in the toxicological assessments of nanomaterials on cells, which needs to be addressed in the standardization of in vitro testing methods.
Hydrodynamic simulation of converging shock waves in porous conical samples enclosed within solid targets
Authors: Khishchenko K. V. , Charakhch’yan A. A. , Fortov V. E. , Frolova A. A. , Milyavskiy V. V. , Shurshalov L. V.
Published: September 2011

Axially symmetric flows with converging shock waves in conical solid targets of steel or lead filled by porous aluminum, graphite, or polytetrafluoroethylene under impact of an aluminum plate with the velocity from 2.5 to 9 km/s have been simulated numerically in the framework of the model of the hypoelastic ideal-plastic solid. Equations of state for all materials in question are used to describe thermodynamic properties of the impactor and target over a wide range of pressures and temperatures, taking into account phase transitions. The graphite-to-diamond transformation is taken into consideration based on a kinetic model. Three different convergent cone configurations of the targets either with a closed cavity or with an outlet hole are analyzed. An appreciable increase of the pressure and temperature within the target cavity as well as of the ejected material velocity on decreasing the initial density of a sample is demonstrated in the simulations. Numerical results that can be compared with possible further experiments for verification of the predictions are presented and discussed.
Formation mechanisms of embedded wurtzite and zincblende indium nitride nanocrystals
Authors: Wood A. W. , Weng X. , Wang Y. Q. , Goldman R. S.
Published: September 2011

We have examined the formation of InN nanocrystals embedded in InAs. Low temperature (77K) N ion implantation into InAs leads to the formation of an amorphous layer with crystalline InAs remnants. Rapid thermal annealing up to 550 °C leads to the nucleation of zincblende InN nanocrystals with a maximum likelihood radius of 1.3 ± 0.2 nm. Rapid thermal annealing at 600 °C leads to nucleation of zincblende and wurtzite InN, with an increase in maximum likelihood radius to 2.6 ± 0.4 nm. These results are consistent with the predictions of a thermodynamic model for the nanoscale-size-dependence of zincblende and wurtzite InN nucleation.
Landau-Ginzburg-Devonshire theory for electromechanical hysteresis loop formation in piezoresponse force microscopy of thin films
Authors: Morozovska A. N. , Eliseev E. A. , Bravina S. L. , Kalinin S. V.
Published: September 2011

Electromechanical hysteresis loop formation in piezoresponse force microscopy of thin ferroelectric films is studied with special emphasis on the effects of tip size and film thickness, as well as dependence on the tip voltage frequency. Here, we use a combination of Landau-Ginzburg-Devonshire (LGD) theory for the description of the local polarization reversal, with decoupling approximation for the calculation of the local piezoresponse loops shape, coercive voltages, and amplitude. LGD approach enables addressing both thermodynamics and kinetics of hysteresis loop formation. In contrast to the “rigid” ferroelectric approximation, this approach allows for the piezoelectric tensor component’s dependence on the ferroelectric polarization and dielectric permittivity. This model rationalizes the non-classical shape of the dynamic piezoelectric force microscopy loops.
Electrical properties of ZnO nanorods studied by conductive atomic force microscopy
Authors: Beinik I. , Kratzer M. , Wachauer A. , Wang L. , Lechner R. T. , Teichert C. , Motz C. , Anwand W. , Brauer G. , Chen X. Y. , Hsu X. Y. , Djurišić A. B.
Published: September 2011

ZnO nanostructures are promising candidates for the development of novel electronic devices due to their unique electrical and optical properties. Here, we present a complementary electrical characterization of individual upright standing and lying ZnO nanorods using conductive atomic force microscopy (C-AFM). Initially, the electrical properties of the arrays of upright standing ZnO NRs were characterized using two-dimensional current maps. The current maps were recorded simultaneously with the topography acquired by contact mode AFM. Further, C-AFM was utilized to determine the local current-voltage (I-V) characteristics of the top and side facets of individual upright standing NRs. Current-voltage characterization revealed a characteristic similar to that of a Schottky diode. Detailed discussion of the electrical properties is based on local I-V curves, as well as on the 2D current maps recorded from specific areas.
Bubble polarization domain patterns in periodically ordered epitaxial ferroelectric nanodot arrays
Authors: Gao X. S. , Xue F. , Qin M. H. , Liu J. M. , Rodriguez B. J. , Liu L. F. , Alexe M. , Hesse D.
Published: September 2011

In this work, bubble polarization domains in periodically ordered ferroelectric Pb(Zr0.4Ti0.6)O3 nanodot arrays and their formation mechanisms have been investigated by piezoresponse force microscopy (PFM) and Monte-Carlo simulations. The PFM observations reveal the coexistence of single domain and apparent bubble domain patterns within the same nanodot array, which also exhibit dissimilar polarization reversal processes. The formation of various polarization configurations can be accounted for by the interplay of various factors, such as polarization anisotropy and depolarization field. Using Monte-Carlo simulation, we are able to reproduce bubble and single domains and further predict that these patterns can be tailored by varying the nanodot parameters, including dot height, aspect ratio, etc.
Watching domains grow: In-situ studies of polarization switching by combined scanning probe and scanning transmission electron microscopy
Authors: Chang Hyejung , Kalinin Sergei V. , Yang Seungyeul , Yu Pu , Bhattacharya Saswata , Wu Ping P. , Balke Nina , Jesse Stephen , Chen Long Q. , Ramesh Ramamoorthy , Pennycook Stephen J. , Borisevich Albina Y.
Published: September 2011

Ferroelectric domain nucleation and growth in multiferroic BiFeO3 films is observed directly by applying a local electric field with a conductive tip inside a scanning transmission electron microscope. The nucleation and growth of a ferroelastic domain and its interaction with pre-existing 71° domain walls are observed and compared with the results of phase-field modeling. In particular, a preferential nucleation site and direction-dependent pinning of domain walls are observed due to slow kinetics of metastable switching in the sample without a bottom electrode. These in situ spatially resolved observations of a first-order bias-induced phase transition reveal the mesoscopic mechanisms underpinning functionality of a wide range of multiferroic materials.
The complex spectrum of a “simple” free radical: The ${\rm \tilde A}$Ã-${\rm \tilde X}$X̃ band system of the jet-cooled boron difluoride free radical
Authors: Yang Jie , Ellis Blaine , Clouthier Dennis J.
Published: September 2011

The near-ultraviolet band system of the jet-cooled boron difluoride free radical has been studied by a combination of laser-induced fluorescence and single vibronic level wavelength resolved emission spectroscopies. The radical was produced in a supersonic discharge jet using a precursor mixture of 1%–3% of BF3 or 10BF3 in high pressure argon. A large number of bands were found in the 340–286 nm region and assigned as transitions from the ${\tilde X}^2A_1$X̃2A1 ground state to the lower Renner-Teller component of the ${\tilde A}$Ã2Π excited state, based on our previous ab initio potential energy surface predictions, matching the emission spectra Franck-Condon profiles of 11BF2 and 10BF2, and comparison of observed and calculated boron isotope effects. Several bands have been rotationally analyzed providing ground state structural parameters of $r^{\prime\prime}_{0}$r0′′ (BF) = 1.3102(9) Å and $\theta^{\prime\prime}_0$θ0′′ (FBF) = 119.7(6)°. The ground state totally symmetric vibrational energy levels of both boron isotopologues have also been measured and assigned up to energies of more than 8000 cm−1. Although BF2 might be considered to be a “simple” free radical, understanding the details of its electronic spectrum remains a major challenge for both theory and experiment.
Point force and generalized point source on the surface of semi-infinite transversely isotropic material
Authors: Karapetian Edgar , Kalinin Sergei V.
Published: September 2011

For a three-dimensional semi-infinite transversely isotropic material, Green’s functions (that give the full set of coupled fields due to the arbitrarily oriented point force and concentrated generalized point source, that represents either the diffusive chemical substance concentration or heat applied at the boundary of the half-space) are derived in elementary functions in a simple way, using methods of the potential theory. In the course of the analysis we derived the general solution of the field equations, represented in terms of four harmonic potential functions, which may also be relevant to other problems of chemical concentration or heat diffusion. These solutions constitute generalization of Boussinesq’s and Cerruti’s problems of elasticity for the chemically diffusive and/or thermoelastic materials.
Determination of the effective coercive field of ferroelectrics by piezoresponse force microscopy
Authors: Lilienblum M. , Soergel E.
Published: September 2011

The effective coercive field Ec for ferroelectric domain reversal is usually determined in a capacitor-like geometry by increasing an applied electric field until poling occurs. Here we present a different method based on local poling with the tip of a scanning force microscope and analyzing the dependence of the domain size on the poling parameters. This method for determining Ec is of importance because for many samples the standard technique fails, either because they are too small in size, or because they are slightly conductive. Results obtained on lithium niobate crystals of different composition conform to literature values.
Synchronization in counter-rotating oscillators
Authors: Bhowmick Sourav K. , Ghosh Dibakar , Dana Syamal K.
Published: September 2011

An oscillatory system can have opposite senses of rotation, clockwise or anticlockwise. We present a general mathematical description of how to obtain counter-rotating oscillators from the definition of a dynamical system. A type of mixed synchronization emerges in counter-rotating oscillators under diffusive scalar coupling when complete synchronization and antisynchronization coexist in different state variables. We present numerical examples of limit cycle van der Pol oscillator and chaotic Rössler and Lorenz systems. Stability conditions of mixed synchronization are analytically obtained for both Rössler and Lorenz systems. Experimental evidences of counter-rotating limit cycle and chaotic oscillators and mixed synchronization are given in electronic circuits.
Decay rate estimates for the quasi-linear Timoshenko system with nonlinear control and damping terms
Authors: Wu Yuhu , Xue Xiaoping
Published: September 2011

In this work, we consider a class of quasi-linear Timoshenko systems with nonlinear control and damping terms. We investigate the stabilization of weak solutions to the initial boundary value problem and obtain explicit decay rate estimation depending on control and damping terms.
Voltage polarity effects in Ge2Sb2Te5-based phase change memory devices
Authors: Padilla Alvaro , Burr Geoffrey W. , Rettner Charles T. , Topuria Teya , Rice Philip M. , Jackson Bryan , Virwani Kumar , Kellock Andrew J. , Dupouy Diego , Debunne Anthony , Shelby Robert M. , Gopalakrishnan Kailash , Shenoy Rohit S. , Kurdi Bülent N.
Published: September 2011

We assess voltage polarity effects in phase-change memory (PCM) devices that contain Ge2Sb2Te5 (GST) as the active material through the study of vertically asymmetric pore-cell and laterally symmetric bridge-cell structures. We show that bias polarity can greatly accelerate device failure in such GST-based PCM devices and, through extensive transmission electron microscopy-based failure analysis, trace these effects to a two-stage elemental segregation process. Segregation is initially driven by bias across the molten region of the cell and is then greatly enhanced during the crystallization process at lower temperatures. These results have implications for the design of pulses and PCM cells for maximum endurance, the use of reverse polarity for extending endurance, the requirements for uni- or bi-polar access devices, the need for materials science on active rather than initial stoichiometries, and the need to evaluate new PCM materials under both bias polarities.
Local conductance measurement of graphene layer using conductive atomic force microscopy
Authors: Ahmad Muneer , Han Sang A. , Tien D. Hoang , Jung Jongwan , Seo Yongho
Published: September 2011

This paper reports the local conductivity mapping of graphene films prepared by chemical vapor deposition and mechanical exfoliation with the help of atomic force microscope where a conducting tip scanned the graphene surface with bias voltage. The surface morphology measured by field emission scanning electron microscopy confirmed that domains and wrinkles were formed on graphene samples grown by chemical vapor deposition, and the difference in the amount of current is observed on these domain boundaries and wrinkles. The percolation current path observed in current map explains that graphene grown by the chemical vapor deposition has low conductivity compared with one mechanically exfoliated. On the other hand, exfoliated graphene layer showed sign of conductivity differences on step edges and wrinkles in comparison to flat region. The resulting observations can be explained with the help of existing theories regarding graphene and by considering the effect of sample preparation conditions.
Adhesion selectivity by electrostatic complementarity. II. Two-dimensional analysis
Authors: Jin Congrui , Bai Ying , Jagota Anand , Hui Chung-Yuen
Published: September 2011

In Part I of this work, using a one-dimensional (1D) representation of the two-dimensional (2D) electrostatic and ion concentration fields, we showed that highly selective adhesion can be achieved between two charged surfaces separated by an electrolyte. In Part II of this work, we provide a detailed theoretical justification of our 1D model by solving the electrostatic problem in a 2D configuration. We establish the conditions under which a 1D approximation is accurate in terms of material and geometrical parameters. We provide the full 2D solution that can be used to analyze other physical phenomena involving migration and separation of particles under the influence of fixed surface charges.