bluuebunny/crossref_metadata_2025 huggingface dataset:
Phase transition temperature of SrTiO3 ultrathin films: An annealing study by ultraviolet Raman spectroscopy
Authors: Shi A. B. , Shen W. Z. , Wu H.
Published: September 2007

The authors present a detailed investigation of paraferroelectric phase transition temperature (TC) of SrTiO3 ultrathin films grown by molecular beam epitaxy on Si substrate under various annealing temperatures on the basis of recent understanding of the interfacial layer formation in constant oxygen atmosphere. They show that TC determined by the ultraviolet Raman spectroscopy is found to enhance linearly with the increasing compressive thermal strain. The present work demonstrates that the “strain engineering” room-temperature ferroelectricity in SrTiO3 films can also be realized through the rapid controlled annealing, in addition to the substitution of substrates in the literature.
Band structure controlled by chiral imprinting
Authors: Castro-Garay P. , Adrian Reyes J. , Ramos-Garcia R.
Published: September 2007

Using the configuration of an imprinted cholesteric elastomer immersed in a racemic solvent, the authors find the solution of the boundary-value problem for the reflection and transmission of incident optical waves due to the elastomer. They show a significant width reduction of the reflection band for certain values of nematic penetration depth, which depends on the volume fraction of molecules from the solvent, whose handedness is preferably absorbed. The appearance of nested band gaps of both handednesses during the sorting mixed chiral process is also obtained. This suggests the design of chemically controlled optical filters and optically monitored chiral pumps.
Magnetic field induced phase transition in multiferroic BiFe1−xTixO3 ceramics prepared by rapid liquid phase sintering
Authors: Kumar Manoj , Yadav K. L.
Published: September 2007

Single phase BiFe1−xTixO3 (BFTO) ceramics with varying x up to 0.35 were prepared by a rapid liquid phase sintering method to study the influence of Ti doping on their crystal structure, morphology, and magnetic behavior. Rhombohedral to orthorhombic phase was observed above x⩾0.33. The BFTO ceramics were highly resistive and with uniform morphology. Magnetic measurements revealed an increase in magnetization with the increase in Ti content and was maximum for x=0.2 ceramic. Surprisingly, a magnetic field induced phase transition from weak ferromagnetic to diamagnetic above 50kOe was observed for x=0.30 and 0.315 ceramics.
Acoustic and optical phonon assisted formation of biexcitons
Authors: Pan Ching-Ju , Lin Kuo-Feng , Hsieh Wen-Feng
Published: September 2007

Efficient exciton relaxation is required for bounding two cooled excitons to form biexciton. Acoustic and optical phonon scatterings playing key roles in exciton relaxation are responsible for formation of biexcitons at various temperatures. Using ZnO powders, the authors observed a sublinear dependence on excitation power at low temperature, in which the relaxation process involves only emission of acoustic phonons due to the excitons having kinetic energy lower than those of the optical phonons. However, the exponent comes near theoretical value of 2 for participation of optical phonons when the exciton kinetic energy approaches to the energy of the lowest optical phonon.
Plasma-assisted self-sharpening of platelet-structured single-crystalline carbon nanocones
Authors: Levchenko I. , Ostrikov K. , Long J. D. , Xu S.
Published: September 2007

A mechanism and model for the vertical growth of platelet-structured vertically aligned single-crystalline carbon nanostructures by the formation of graphene layers on a flat top surface are proposed and verified experimentally. It is demonstrated that plasma-related effects lead to self-sharpening of tapered nanocones to form needlelike nanostructures, in a good agreement with the predicted dependence of the radius of a nanocone’s flat top on the incoming ion flux and surface temperature. The growth mechanism is relevant to a broad class of nanostructures including nanotips, nanoneedles, and nanowires and can be used to improve the predictability of nanofabrication processes.
Reduced leakage current in La and Ni codoped BiFeO3 thin films
Authors: Singh S. K. , Maruyama K. , Ishiwara H.
Published: September 2007

La (2.5%) and Ni (2.5%) codoped BiFeO3 (BLFNO) thin films were formed by chemical solution deposition on Pt∕Ti∕SiO2∕Si(100) structures. BiFeO3 (BFO), La(5%)-doped BFO, and Ni(5%)-doped BFO films were studied for comparison. X-ray diffraction analysis showed that the crystal structure of all films was single perovskite phase, however, structural modifications were observed in La-doped films. The leakage current density at 500kV∕cm was reduced by approximately three orders of magnitude by codoping La and Ni atoms, compared with BFO films. In BLFNO films, well saturated remanent polarization of 70μC∕cm2 was obtained at room temperature at 10kHz with the reduced coercive field by approximately 30%.
Experimental and theoretical studies of lattice dynamics of Mg-doped InN
Authors: Davydov V. Yu. , Klochikhin A. A. , Smirnov M. B. , Smirnov A. N. , Goncharuk I. N. , Kurdyukov D. A. , Lu Hai , Schaff William J. , Lee H.-M. , Lin H.-W. , Gwo S.
Published: September 2007

Raman studies of Mg-doped InN films with a Mg content from NMg=3.3×1019to5.5×1021cm−3 are reported. Raman and secondary ion mass spectroscopy data on the Mg content have been found to correlate well. Lattice dynamics of hexagonal InN with substitutional impurities and vacancies has been investigated in the framework of the cluster approach. Energy positions of local vibrational modes in InN have been calculated and compared with experimental findings. It is concluded that Raman spectroscopy is a good tool for quantitative characterization of Mg-doped InN.
γccytokines condition the progressive differentiation of CD4+T cells
Authors: Masse Guillemette X. , Corcuff Erwan , Strick-Marchand Hélène , Guy-Grand Delphine , Tafuri-Bladt Anna , Albert Matthew L. , Lantz Olivier , Di Santo James P.
Published: September 2007

After their initial antigen encounter in the secondary lymphoid organs, activated T cells must receive additional signals in the peripheral tissues to fully differentiate. Here, we provide evidence that γccytokines are critical during this process. Using the Marilyn (Ml) T cell antigen receptor (TCR) transgenic model, we show that male skin grafts are tolerated in the absence of γc, but that Ml CD4+T cells proliferate normally in response to antigen, traffic to the graft site and recruit an inflammatory response [including natural killer (NK) cells, neutrophils, and macrophages] that is independent of T cell γcexpression. Whereas wild-type T cells demonstrate a progressive differentiation phenotype from the spleen to the tissues, skin-infiltrating effector T cells (CD44hiCD62Llo) from γc−mice were phenotypically abnormal with reduced ICOS, NKG2D, granzyme B, and IFN-γ expression. These defects could be mapped to deficiencies in IL-2 and, surprisingly, IL-15. These results define a late checkpoint in T cell differentiation in the tissues where γccytokines, including IL-15, authenticate CD4+T cell effector functions.
Insulin gene mutations as a cause of permanent neonatal diabetes
Authors: Støy Julie , Edghill Emma L. , Flanagan Sarah E. , Ye Honggang , Paz Veronica P. , Pluzhnikov Anna , Below Jennifer E. , Hayes M. Geoffrey , Cox Nancy J. , Lipkind Gregory M. , Lipton Rebecca B. , Greeley Siri Atma W. , Patch Ann-Marie , Ellard Sian , Steiner Donald F. , Hattersley Andrew T. , Philipson Louis H. , Bell Graeme I. ,   Neonatal Diabetes International Collaborative Group**
Published: September 2007

We report 10 heterozygous mutations in the human insulin gene in 16 probands with neonatal diabetes. A combination of linkage and a candidate gene approach in a family with four diabetic members led to the identification of the initial
INS
gene mutation. The mutations are inherited in an autosomal dominant manner in this and two other small families whereas the mutations in the other 13 patients are
de novo
. Diabetes presented in probands at a median age of 9 weeks, usually with diabetic ketoacidosis or marked hyperglycemia, was not associated with β cell autoantibodies, and was treated from diagnosis with insulin. The mutations are in critical regions of the preproinsulin molecule, and we predict that they prevent normal folding and progression of proinsulin in the insulin secretory pathway. The abnormally folded proinsulin molecule may induce the unfolded protein response and undergo degradation in the endoplasmic reticulum, leading to severe endoplasmic reticulum stress and potentially β cell death by apoptosis. This process has been described in both the Akita and Munich mouse models that have dominant-acting missense mutations in the
Ins2
gene, leading to loss of β cell function and mass. One of the human mutations we report here is identical to that in the Akita mouse. The identification of insulin mutations as a cause of neonatal diabetes will facilitate the diagnosis and possibly, in time, treatment of this disorder.
New teacher learning: substantive knowledge and contextual factors
Authors: Wilson Elaine , Demetriou Helen
Published: September 2007

This article brings together an overview of ideas about teacher learning from both teacher education and workplace learning literature, and examines what and how newly qualified secondary school teachers learn in the early years of their career. We discuss the types of knowledge new teachers encounter and present a typology of teacher learning. The article also draws on a three‐year longitudinal study, presenting findings from surveys of new and more experienced teachers together with analysis of interviews with ten new teachers during the first two years of their teaching career. We present findings about how these new teachers have learned in their first two years of teaching and explore the importance of the school context and other learning factors. Suggestions for future research are also included.
A network biography: reflecting on a journey from birth to maturity of a networked learning community1
Authors: Fox Alison , Haddock June , Smith Tracy
Published: September 2007

This article charts the development of a networked learning community (NLC). NLCs were established by the National College for School Leadership in 2002 connecting groups of schools to further both pupil and teacher learning. This study examines one sub‐network in a London borough, focused on developing Assessment for Learning practices. The co‐leaders of this network also acted as project coordinators to the Teaching and Learning Research Programme funded ‘Learning How to Learn’ project (2001–2005) through which data were collected for this study. A biographical approach reflects how the co‐leaders expressed their network as having a life cycle. A model representing the cyclical nature of networking opportunities in phases of birth, youth and maturity is applied at macro and micro scales. The co‐leaders' developing understanding of their roles presents how they ‘learnt how to network’ in parallel to those in the network developing ‘learning how to learn’ practices. While framing past experiences, a biographical approach raises questions about the future of such networks. In the case of NLCs, the nationally funded initiative has ended. What will succeed this history of successful teacher–teacher and pupil–pupil networking? Does the metaphor continue to hold beyond maturity to old age and death?
Initial teacher education as a driver for professional learning and school improvement in the primary phase
Authors: Hurd Steve , Jones Marion , McNamara Olwen , Craig Barbara
Published: September 2007

This article examines the professional learning accruing from school‐based initial teacher education (ITE) within the wider policy debate on school performance. It contrasts the very positive perceptions reported by teachers on the contribution of involvement in ITE to their professional learning with the less than fulsome attitude of school inspectors. Evidence is drawn from questionnaire responses from primary school ITE coordinators and mentor‐teachers in the north‐west of England, text searches of primary school inspection reports and quantitative data collected by Ofsted. It concludes that a more explicit emphasis on initial teacher education in school inspections would give due recognition to the important role played by ITE and make it easier to promote the professional learning and school improvement outcomes which derive from school‐based initial teacher education.
School–university partnerships for educational research—distinctions, dilemmas and challenges
Authors: McLaughlin Colleen , Black-Hawkins Kristine
Published: September 2007

This article examines partnerships between universities and schools that focus on the generation of educational knowledge through practitioner research and enquiry. It draws on a seven‐year study of a partnership between the Faculty of Education, University of Cambridge and a group of eight secondary schools. The article explores what has been learned about such partnerships, including the benefits and challenges arising from some fundamental differences between the nature of schools and universities as organizations and the roles and perspectives of teachers and academics within them. It considers different understandings of the notion of knowledge generation, including which forms of knowledge are valued and found to be useful. Conditions, structures and organizational arrangements that are necessary to support such research within school–university partnerships are discussed.
Teacher development and pupil voice
Authors: Flutter Julia
Published: September 2007

The principle of ‘pupil voice’ has attained a high profile over the past decade and its key principles of encouraging pupil consultation and participation are evident in official policy and guidance in many countries around the world. While there has been official endorsement of the notions that pupils have a right to voice their opinions and should have some involvement in decision‐making affecting their lives, the implications of these arguments for day‐to‐day practice are less clear and sometimes contentious. Since the early 1990s Jean Rudduck and I have been looking at the role of pupil voice strategies in developing more effective teaching and learning in the classroom. We have examined how these strategies are used in a range of different settings—from small, rural primary schools to large, inner city comprehensive schools facing challenging circumstances. Evidence from our research, and in studies in the UK and internationally, suggests that pupil voice strategies can be transformational experiences for teachers and for pupils. This article examines the relationship between pupil voice and teacher development and, drawing on evidence from research, it will demonstrate how pupil voice strategies have enabled teachers to gain a deeper understanding of the teaching and learning processes and have helped them to change the way they think about pupils and their learning.
Hearing Facial Identities
Authors: Schweinberger Stefan R. , Robertson David , Kaufmann Jürgen M.
Published: September 2007

While audiovisual integration is well known in speech perception, faces and speech are also informative with respect to speaker recognition. To date, audiovisual integration in the recognition of familiar people has never been demonstrated. Here we show systematic benefits and costs for the recognition of familiar voices when these are combined with time-synchronized articulating faces, of corresponding or noncorresponding speaker identity, respectively. While these effects were strong for familiar voices, they were smaller or nonsignificant for unfamiliar voices, suggesting that the effects depend on the previous creation of a multimodal representation of a person's identity. Moreover, the effects were reduced or eliminated when voices were combined with the same faces presented as static pictures, demonstrating that the effects do not simply reflect the use of facial identity as a “cue” for voice recognition. This is the first direct evidence for audiovisual integration in person recognition.
Colours Sometimes Count: Awareness and Bidirectionality in Grapheme–Colour Synaesthesia
Authors: Johnson Addie , Jepma Marieke , De Jong Ritske
Published: September 2007

Three experiments were conducted with 10 grapheme–colour synaesthetes and 10 matched controls to investigate (a) whether awareness of the inducer grapheme is necessary for synaesthetic colour induction and (b) whether grapheme–colour synaesthesia may be bidirectional in the sense that not only do graphemes induce colours, but that colours influence the processing of graphemes. Using attentional blink and Stroop paradigms with digit targets, we found that some synaesthetes did report “seeing” synaesthetic colours even when they were not able to report the inducing digit. Moreover, congruency effects (effects of matching the colour of digit presentation with the synaesthetic colour associated with that digit) suggested that grapheme–colour synaesthesia can be bidirectional, at least for some synaesthetes.
Dissimilarity is used as Evidence of Category Membership in Multidimensional Perceptual Categorization: A Test of the Similarity–Dissimilarity Generalized Context Model
Authors: Stewart Neil , Morin Caroline
Published: September 2007

In exemplar models of categorization, the similarity between an exemplar and category members constitutes evidence that the exemplar belongs to the category. We test the possibility that the dissimilarity to members of competing categories also contributes to this evidence. Data were collected from two 2-dimensional perceptual categorization experiments, one with lines varying in orientation and length and the other with coloured patches varying in saturation and brightness. Model fits of the similarity–dissimilarity generalized context model were used to compare a model where only similarity was used with a model where both similarity and dissimilarity were used. For the majority of participants the similarity–dissimilarity model provided both a significantly better fit and better generalization, suggesting that people do also use dissimilarity as evidence.
A Little Learning is a Dangerous Thing: An Experimental Demonstration of Ignorance-Driven Inference
Authors: Frosch Caren A. , Philip Beaman C. , Mccloy Rachel
Published: September 2007

Studies of ignorance-driven decision making have been employed to analyse when ignorance should prove advantageous on theoretical grounds or else they have been employed to examine whether human behaviour is consistent with an ignorance-driven inference strategy (e.g., the recognition heuristic). In the current study we examine whether—under conditions where such inferences might be expected—the advantages that theoretical analyses predict are evident in human performance data. A single experiment shows that, when asked to make relative wealth judgements, participants reliably use recognition as a basis for their judgements. Their wealth judgements under these conditions are reliably more accurate when some of the target names are unknown than when participants recognize all of the names (a “less-is-more effect”). These results are consistent across a number of variations: the number of options given to participants and the nature of the wealth judgement. A basic model of recognition-based inference predicts these effects.
Serial Position Functions for Recognition of Olfactory Stimuli
Authors: Johnson Andrew J. , Miles Christopher
Published: September 2007

Two experiments examined item recognition memory for sequentially presented odours. Following a sequence of six odours participants were immediately presented with a series of two-alternative forced-choice (2AFC) test odours. The test pairs were presented in either the same order as learning or the reverse order of learning. Method of testing was either blocked (Experiment 1) or mixed (Experiment 2). Both experiments demonstrated extended recency, with an absence of primacy, for the reverse testing procedure. In contrast, the forward testing procedure revealed a null effect of serial position. The finding of extended recency is inconsistent with the single-item recency predicted by the two-component duplex theory (Phillips & Christie, 1977). We offer an alternative account of the data in which recognition accuracy is better accommodated by the cumulative number of items presented between item learning and item test.
Roles forDrosophila melanogasterMyosin IB in Maintenance of Enterocyte Brush-Border Structure and Resistance to the Bacterial PathogenPseudomonas entomophila
Authors: Hegan Peter S. , Mermall Valerie , Tilney Lewis G. , Mooseker Mark S.
Published: September 2007

Drosophila myosin IB (Myo1B) is one of two class I myosins in the Drosophila genome. In the larval and adult midgut enterocyte, Myo1B is present within the microvillus (MV) of the apical brush border (BB) where it forms lateral tethers between the MV membrane and underlying actin filament core. Expression of green fluorescent protein-Myo1B tail domain in the larval gut showed that the tail domain is sufficient for localization of Myo1B to the BB. A Myo1B deletion mutation exhibited normal larval gut physiology with respect to food uptake, clearance, and pH regulation. However, there is a threefold increase in terminal deoxynucleotidyl transferase dUTP nick-end labeling-positive enterocyte nuclei in the Myo1B mutant. Ultrastructural analysis of mutant midgut revealed many perturbations in the BB, including membrane tethering defects, MV vesiculation, and membrane shedding. The apical localization of both singed (fascin) and Dmoesin is impaired. BBs isolated from mutant and control midgut revealed that the loss of Myo1B causes the BB membrane and underlying cytoskeleton to become destabilized. Myo1B mutant larvae also exhibit enhanced sensitivity to oral infection by the bacterial pathogen Pseudomonas entomophila, and severe cytoskeletal defects are observed in the BB of proximal midgut epithelial cells soon after infection. Resistance to P. entomophila infection is restored in Myo1B mutant larvae expressing a Myo1B transgene. These results indicate that Myo1B may play a role in the local midgut response pathway of the Imd innate immune response to Gram-negative bacterial infection.
Amphiphysin 1 Is Important for Actin Polymerization during Phagocytosis
Authors: Yamada Hiroshi , Ohashi Emiko , Abe Tadashi , Kusumi Norihiro , Li Shun-AI , Yoshida Yumi , Watanabe Masami , Tomizawa Kazuhito , Kashiwakura Yuji , Kumon Hiromi , Matsui Hideki , Takei Kohji
Published: September 2007

Amphiphysin 1 is involved in clathrin-mediated endocytosis. In this study, we demonstrate that amphiphysin 1 is essential for cellular phagocytosis and that it is critical for actin polymerization. Phagocytosis in Sertoli cells was induced by stimulating phosphatidylserine receptors. This stimulation led to the formation of actin-rich structures, including ruffles, phagocytic cups, and phagosomes, all of which showed an accumulation of amphiphysin 1. Knocking out amphiphysin 1 by RNA interference in the cells resulted in the reduction of ruffle formation, actin polymerization, and phagocytosis. Phagocytosis was also drastically decreased in amph 1 (−/−) Sertoli cells. In addition, phosphatidylinositol-4,5-bisphosphate–induced actin polymerization was decreased in the knockout testis cytosol. The addition of recombinant amphiphysin 1 to the cytosol restored the polymerization process. Ruffle formation in small interfering RNA-treated cells was recovered by the expression of constitutively active Rac1, suggesting that amphiphysin 1 functions upstream of the protein. These findings support that amphiphysin 1 is important in the regulation of actin dynamics and that it is required for phagocytosis.
Analysis of Cluster-Randomized Experiments: A Comparison of Alternative Estimation Approaches
Authors: Green Donald P. , Vavreck Lynn
Published: September 2007

Analysts of cluster-randomized field experiments have an array of estimation techniques to choose from. Using Monte Carlo simulation, we evaluate the properties of point estimates and standard errors (SEs) generated by ordinary least squares (OLS) as applied to both individual-level and cluster-level data. We also compare OLS to alternative random effects estimators, such as generalized least squares (GLS). Our simulations assess efficiency across a variety of scenarios involving varying sample sizes and numbers of clusters. Our results confirm that conventional OLS SEs are severely biased downward and that, for all estimators, gains in efficiency come mainly from increasing the number of clusters, not increasing the number of individuals within clusters. We find relatively minor differences across alternative estimation approaches, but GLS seems to enjoy a slight edge in terms of the efficiency of its point estimates and the accuracy of its SEs. We illustrate the application of alternative estimation approaches using a clustered experiment in which Rock the Vote TV advertisements were used to encourage young voters in 85 cable TV markets to vote in the 2004 presidential election.
Increasing Concerns about Corn Earworm Susceptibility to Pyrethroids in the Midwestern USA
Authors: Hutchison W. D. , Weinzierl R. A.
Published: September 2007

Because of growing concern about inconsistent corn earworm (CEW control, particularly in Midwest sweet corn, and the documented migratory behavior of CEW adults, a symposium was organized for the Annual Meeting of the North Central Branch of the Entomological Society of America in 2006. The purpose of the symposium was to provide a comprehensive overview of the status and impact of H. zea resistance to synthetic pyrethroids, with a focus on the midwestern, northeastern, and southern US.

Accepted for publication 4 June 2007. Published 19 July 2007.
The Aerobiology and Population Genetic Structure of Gibberella zeae
Authors: Schmale David G. , Bergstrom Gary C.
Published: September 2007

Gibberella zeae causes Fusarium head blight (FHB) of wheat and barley and Gibberella ear rot (GER) of corn. Ascospores of G. zeae rely on atmospheric motion systems for transport to susceptible host plants. A long term objective of our research is to determine where inoculum for FHB and GER comes from and how far it travels. We measured the distance that ascospores of G. zeae were forcibly discharged in still air, and determined that long-range transport is favored by day-time ascospore release. We used remote-piloted aircraft to collect viable spores of G. zeae in the lower atmosphere. Viable spores of G. zeae were abundant in the lower atmosphere during all times of the day and night under a broad range of environmental conditions. Viable spores of G. zeae were deposited over wheat and corn fields mainly at random and predominantly at night. We used amplified fragment length polymorphisms (AFLPs) to characterize the genetic structure of atmospheric populations of G. zeae over multiple years. Genotypic diversity was high in the atmospheric populations of G. zeae, and nearly all of the isolates in each of the populations represented unique AFLP haplotypes. Diverse atmospheric populations of G. zeae are indicative of wellmixed sources of aerial inoculum, potentially originating from local and more distant sources. Introduced strains of G. zeae with altered virulence or mycotoxin profiles, moving over long distances, have the potential to spread rapidly into previously unexposed wheat and corn production regions.

Accepted for publication 14 February 2007. Published 26 July 2007.
Biomimetics for next generation materials
Authors: Barthelat Francois
Published: September 2007

Billions of years of evolution have produced extremely efficient natural materials, which are increasingly becoming a source of inspiration for engineers. Biomimetics—the science of imitating nature—is a growing multidisciplinary field which is now leading to the fabrication of novel materials with remarkable mechanical properties. This article discusses the mechanics of hard biological materials, and more specifically of nacre and bone. These high-performance natural composites are made up of relatively weak components (brittle minerals and soft proteins) arranged in intricate ways to achieve specific combinations of stiffness, strength and toughness (resistance to cracking). Determining which features control the performance of these materials is the first step in biomimetics. These ‘key features’ can then be implemented into artificial bio-inspired synthetic materials, using innovative techniques such as layer-by-layer assembly or ice-templated crystallization. The most promising approaches, however, are self-assembly and biomineralization because they will enable tight control of structures at the nanoscale. In this ‘bottom-up’ fabrication, also inspired from nature, molecular structures and crystals are assembled with a little or no external intervention. The resulting materials will offer new combinations of low weight, stiffness and toughness, with added functionalities such as self-healing. Only tight collaborations between engineers, chemists, materials scientists and biologists will make these ‘next-generation’ materials a reality.
Soil mechanics: breaking ground
Authors: Einav Itai
Published: September 2007

In soil mechanics, student's models are classified as simple models that teach us unexplained elements of behaviour; an example is the Cam clay constitutive models of critical state soil mechanics (CSSM). ‘Engineer's models’ are models that elaborate the theory to fit more behavioural trends; this is usually done by adding fitting parameters to the student's models. Can currently unexplained behavioural trends of soil be explained without adding fitting parameters to CSSM models, by developing alternative student's models based on modern theories?

Here I apply an alternative theory to CSSM, called ‘breakage mechanics’, and develop a simple student's model for sand. Its unique and distinctive feature is the use of an energy balance equation that connects grain size reduction to consumption of energy, which enables us to predict how grain size distribution (gsd) evolves—an unprecedented capability in constitutive modelling. With only four parameters, the model is physically clarifying what CSSM cannot for sand: the dependency of yielding and critical state on the initial gsd and void ratio.
Adaptive optics in microscopy
Authors: Booth Martin J
Published: September 2007

The imaging properties of optical microscopes are often compromised by aberrations that reduce image resolution and contrast. Adaptive optics technology has been employed in various systems to correct these aberrations and restore performance. This has required various departures from the traditional adaptive optics schemes that are used in astronomy. This review discusses the sources of aberrations, their effects and their correction with adaptive optics, particularly in confocal and two-photon microscopes. Different methods of wavefront sensing, indirect aberration measurement and aberration correction devices are discussed. Applications of adaptive optics in the related areas of optical data storage, optical tweezers and micro/nanofabrication are also reviewed.
Probing the localized-to-delocalized transition
Authors: Concepcion Javier J , Dattelbaum Dana M , Meyer Thomas J , Rocha Reginaldo C
Published: September 2007

Detailed understanding of the transition between localized and delocalized behaviour in mixed valence compounds has been elusive as evidenced by many interpretations of the Creutz–Taube ion, [(NH3)5Ru(pz)Ru(NH3)5]5+. In a review in 2001, experimental protocols and a systematic model to probe this region were proposed and applied to examples in the literature. The model included: (i) multiple orbital interactions in ligand-bridged transition metal complexes, (ii) inclusion of spin-orbit coupling which, for dπ5–dπ6complexes, leads to five low-energy bands, two from interconfigurational (dπ→dπ) transitions at the dπ5site and three from intervalence transfer transitions, (iii) differences in time scale between coupled vibrations and solvent modes which can result in solvent averaging with continued electronic asymmetry defining ‘class II–III’, an addition to the Robin–Day classification scheme, and (iv) delineation of coupled vibrations into barrier vibrations and ‘spectator’ vibrations. The latter provide direct insight into localization or delocalization and time scales for electron transfer. In this paper, the earlier model is applied to a series of mixed-valence molecules.
Urinary excretion and blood level of prions in scrapie-infected hamsters
Authors: Murayama Yuichi , Yoshioka Miyako , Okada Hiroyuki , Takata Masuhiro , Yokoyama Takashi , Mohri Shirou
Published: September 2007

Prions, infectious agents causing transmissible spongiform encephalopathy (TSE), are composed primarily of the pathogenic form (PrPSc) of the host-encoded prion protein. Although very low levels of infectivity have been detected in urine from scrapie-infected rodents, no reports of urinary PrPSc have been substantiated. Studies on the dynamics of urinary PrPSc during infection are needed to ensure the safety of urine-derived biopharmaceuticals and to assess the possible horizontal transmission of prion diseases. Using the protein misfolding cyclic amplification technique, a time-course study of urinary excretion and blood levels of PrPSc was performed in Sc237-infected hamsters and a high rate of PrPSc excretion was found during the terminal stage of the disease. Following oral administration, PrPSc was present in all buffy coat samples examined; it was also present in most of the plasma samples obtained from hamsters in the symptomatic stage. PrPSc was excreted in urine for a few days after oral administration; subsequently, urinary PrPSc was not detected until the terminal disease stage. These results represent the first biochemical detection of PrPSc in urine from TSE-infected animals.
Adaptation of plum pox virus to a herbaceous host (Pisum sativum) following serial passages
Authors: Wallis Christopher M. , Stone Andrew L. , Sherman Diana J. , Damsteegt Vernon D. , Gildow Fred E. , Schneider William L.
Published: September 2007

Plum pox virus (PPV) populations from peaches are able to adapt consistently to herbaceous hosts, characterized by a reduction in time to symptom development, increases in inoculation efficiency and increased titres. PPV adaptation was studied by using pea (Pisum sativum) as an alternative host. Two isolates of PPV from peaches were inoculated and passaged in peas ten times using either aphid or mechanical inoculation, generating four independent passage lines. Mechanical-transmission efficiency from peach to pea improved from 3 % at passage 1 to 100 % by serial passage 4 on peas. Inoculation using aphid vectors required six to ten serial passages in pea to reach a peak of 50–60 % transmission efficiency. Sequence analyses of all four PPV population lines inoculated sequentially to pea identified a specific mutation occurring consistently in the NIb gene when compared with the same PPV isolates passaged in parallel in peach. The mutation allowed PPV to replicate up to 20 times faster in the new host. Pea-adapted strains of PPV at every passage were also tested for their ability to infect the original host, peach. Regardless of the number of previous passages, all pea-adapted PPV strains consistently infected peach at low levels using aphid inoculation.
Persistent memory CD4+ and CD8+ T-cell responses in recovered severe acute respiratory syndrome (SARS) patients to SARS coronavirus M antigen
Authors: Yang Litao , Peng Hui , Zhu Zhaoling , Li Gang , Huang Zitong , Zhao Zhixin , Koup Richard A. , Bailer Robert T. , Wu Changyou
Published: September 2007

The membrane (M) protein of severe acute respiratory syndrome coronavirus (SARS-CoV) is a major glycoprotein with multiple biological functions. In this study, we found that memory T cells against M protein were persistent in recovered SARS patients by detecting gamma interferon (IFN-γ) production using ELISA and ELISpot assays. Flow cytometric analysis showed that both CD4+and CD8+T cells were involved in cellular responses to SARS-CoV M antigen. Furthermore, memory CD8+T cells displayed an effector memory cell phenotype expressing CD45RO−CCR7−CD62L−. In contrast, the majority of IFN-γ+CD4+T cells were central memory cells with the expression of CD45RO+CCR7+CD62L−. The epitope screening from 30 synthetic overlapping peptides that cover the entire SARS-CoV M protein identified four human T-cell immunodominant peptides, p21-44, p65-91, p117-140 and p200-220. All four immunodominant peptides could elicit cellular immunity with a predominance of CD8+T-cell response. This data may have important implication for developing SARS vaccines.
Evidence for functional significance of the permuted C motif in Co2+-stimulated RNA-dependent RNA polymerase of infectious bursal disease virus
Authors: Letzel Tobias , Mundt Egbert , Gorbalenya Alexander E.
Published: September 2007

Segment B of bisegmented infectious bursal disease virus (IBDV) encodes virus protein 1 (VP1), possessing RNA-dependent RNA polymerase (RdRp) activity. This multidomain protein includes an RdRp domain with a non-canonical order of three sequence motifs forming the active site: C–A–B. The A–B–C order of the motifs, as found in RdRps of the majority of viruses, was converted by relocation (permutation) of motif C to a C–A–B order. Due to the unusual location and unproven significance, the motif was named ‘C?’. This motif includes an Ala–Asp–Asn tripeptide that replaces the C motif Gly–Asp–Asp sequence, widely considered a hallmark of RdRps. In this study, functional significance of the C? motif was investigated by using purified His-tagged VP1 mutants with either a double replacement (ADN to GDD) or two single-site mutants (ADD or GDN). All mutants showed a significant reduction of RdRp activity in vitro, in comparison to that of VP1. Only the least-affected GDN mutant gave rise to viable, albeit partially impaired, progeny using a reverse-genetics system. Experiments performed to investigate whether the C motif was implicated in the control of metal dependence revealed that, compared with Mn2+ and Mg2+, Co2+ stimulated RdRp unconventionally. No activity was observed in the presence of several divalent cations. Of two Co2+ salts with Cl− and anions, the former was a stronger stimulant for RdRp. When cell-culture medium was supplemented with 50 μM Co2+, an increase in IBDV progeny yield was observed. The obtained results provide evidence that the unusual Co2+ dependence of the IBDV RdRp might be linked to the permuted organization of the motif.
Enteroglial and neuronal involvement without apparent neuron loss in ileal enteric nervous system plexuses from scrapie-affected sheep
Authors: Marruchella Giuseppe , Ligios Ciriaco , Albanese Valeria , Cancedda Maria Giovanna , Madau Laura , Lalatta-Costerbosa Giovanna , Mazzoni Maurizio , Clavenzani Paolo , Chiocchetti Roberto , Sarli Giuseppe , De Grossi Luigi , Agrimi Umberto , Aguzzi Adriano , Di Guardo Giovanni
Published: September 2007

The enteric nervous system (ENS) probably plays a dominant role in sheep scrapie pathogenesis, but little is known about the cell types involved. We investigated the ileal myenteric and submucosal plexuses of four naturally and four orally experimentally scrapie-affected ARQ/ARQ Sarda sheep, as well as those of 12 healthy-control Sarda sheep carrying different PrP genotypes. All scrapie-affected animals, euthanized at clinical-disease end stage, showed PrPd deposition within enteric glial cells (EGCs) and calbindin-immunoreactive (CALB-IR) and neuronal nitric oxide synthase (nNOS)-IR neurons. Whole-mount investigations revealed no significant differences between the densities of total, CALB-IR and nNOS-IR neurons in scrapie-affected versus healthy sheep, irrespective of PrP genotype. Our results suggest that EGCs and CALB-IR and nNOS-IR neurons are probably involved in the pathogenesis of natural and oral experimental sheep scrapie. Furthermore, the infectious agent may be less pathogenic towards ENS neurons than it is towards central nervous system neurons.
Molecular epidemiological analyses of Japanese encephalitis virus isolates from swine in Japan from 2002 to 2004
Authors: Nerome Reiko , Tajima Shigeru , Takasaki Tomohiko , Yoshida Takashi , Kotaki Akira , Lim Chang-Kweng , Ito Mikako , Sugiyama Akira , Yamauchi Akinori , Yano Takuya , Kameyama Taeko , Morishita Ichiko , Kuwayama Masaru , Ogawa Tomoko , Sahara Keiji , Ikegaya Asaka , Kanda Masahiro , Hosoya Yoshiyuki , Itokazu Kiyomasa , Onishi Hajime , Chiya Seizou , Yoshida Yasuko , Tabei Yukiko , Katsuki Kazuko , Tabata Koji , Harada Seiya , Kurane Ichiro
Published: September 2007

To characterize Japanese encephalitis virus (JEV) strains recently prevalent in Japan, JEV surveillance was performed in pigs from 2002 to 2004. Eleven new JEV isolates were obtained and compared with previous isolates from Japan and other Asian countries. All of the isolates were classified into genotype 1 by nucleotide sequence analysis of the E gene. Two new isolates with different levels of neurovirulence and neuroinvasiveness, but with only one nucleotide difference in the E gene, Sw/Mie/34/2004 and Sw/Mie/40/2004, were isolated at the same farm on the same day. Sw/Mie/40/2004 displayed higher neurovirulence and neuroinvasiveness in mice than the other four new isolates. Another new isolate, Sw/Hiroshima/25/2002, was neutralized by antiserum to Beijing-1 at a level similar to the homologous Beijing-1 strain, whilst seven other new isolates were neutralized at 10-fold-lower titres. However, there were no amino acid differences in the E protein among these eight isolates. The present study indicated that the 11 new JEV isolates were genetically similar, but biologically and serologically heterogeneous.
Persistence of Mastomys natalensis papillomavirus in multiple organs identifies novel targets for infection
Authors: Nafz Julia , Köhler Anja , Ohnesorge Myriam , Nindl Ingo , Stockfleth Eggert , Rösl Frank
Published: September 2007

The high incidence of multiple wart formation and skin cancer in organ-transplant recipients, as well as the question of an involvement of papillomaviruses in a variety of human cancers, require a model system for papillomavirus infections in immunocompetent animals. Such an in vivo model is represented by the multimammate rat Mastomys coucha, which is infected with Mastomys natalensis papillomavirus (MnPV). MnPV primarily induces benign skin tumours, such as papillomas and keratoacanthomas. Here, the incidence of MnPV infections in different skin areas and various organs is described. In situ hybridization showed that hair follicle cells were positive for viral DNA and that the amount of MnPV in normal skin may be considered a predictor for the development of skin tumours. MnPV infection is not restricted to the skin, but can also be detected in inner organs. As the blood and the lymphatic system were temporarily also found to be virus-positive, a haematogenic propagation of MnPV can be assumed. However, MnPV is apparently not transmitted through the germ line, as fetuses and newborns lack viral DNA, despite infection of their mothers. In conclusion, M. coucha is not only useful to study papillomavirus-induced skin carcinogenesis, but may also serve as a model to identify additional, still unknown target cells of papillomavirus infections and the potential pathological impact.
Enzymatic detergent treatment protocol that reduces protease-resistant prion protein load and infectivity from surgical-steel monofilaments contaminated with a human-derived prion strain
Authors: Lawson Victoria A. , Stewart James D. , Masters Colin L.
Published: September 2007

The unconventional nature of the infectious agent of prion diseases poses a challenge to conventional infection control methodologies. The extraneural tissue distribution of variant and sporadic Creutzfeldt–Jakob disease has increased concern regarding the risk of prion disease transmission via general surgical procedures and highlighted the need for decontamination procedures that can be incorporated into routine processing. In this study, the ability of preparations of enzymatic medical instrument cleaners to reduce the infectivity associated with a rodent-adapted strain of human prion disease, previously reported to be resistant to decontamination, was tested. Efficient degradation of the disease-associated prion protein by enzymatic cleaning preparations required high treatment temperatures (50–60 °C). Standard decontamination methods (1 M NaOH for 1 h or autoclaving at 134 °C for 18 min) reduced infectivity associated with the human-derived prion strain by less than 3 log10 LD50. In contrast, a 30 min treatment with the optimized enzymatic cleaning preparation protocols reduced infectivity by more than 3 log10 LD50 and when used in conjunction with autoclave cycles eliminated detectable levels of infectivity. The development of prion decontamination procedures that are compatible with routine cleaning and sterilization of medical and surgical instruments may reduce the risk of the transmission of prion disease in general surgery.
Complete-genome analysis of hepatitis B virus from wild-born chimpanzees in central Africa demonstrates a strain-specific geographical cluster
Authors: Makuwa Maria , Souquière Sandrine , Bourry Olivier , Rouquet Pierre , Telfer Paul , Mauclère Philippe , Kazanji Mirdad , Roques Pierre , Simon François
Published: September 2007

In order to determine whether geographical or species clustering accounts for the distribution of hepatitis B virus (HBV) in subspecies of chimpanzees in Africa, four complete chimpanzee HBV (ChHBV) genome sequences were obtained from eight hepatitis B surface antigen-positive wild-born chimpanzees from Cameroon, Republic of Congo and Gabon. The serological profiles of these chimpanzees corresponded to the acute or chronic highly replicative phase of HBV infection, as confirmed by high plasma HBV loads. Analysis of the sequence alignment of 256 aa (S region) from the eight HBV-infected chimpanzees allowed us to determine the HBV amino acid patterns specific to each chimpanzee subspecies and to their geographical origin. Phylogenetic analysis of both the S region and the complete genome confirmed this distinctive clustering of eight novel ChHBV strains within Pan troglodytes. The strong phylogenetic associations of ChHBV sequences with both chimpanzee subspecies and their geographical origin were therefore confirmed.