bluuebunny/crossref_metadata_2025 huggingface dataset:
How do Older Masters Athletes Account for their Performance Preservation? A Qualitative Analysis
Authors: DIONIGI RYLEE A. , HORTON SEAN , BAKER JOSEPH
Published: January 2012

The purpose of this study was to examine how older people make sense of their capacity to maintain sports performance. Performance maintenance is predominantly examined from a quantitative perspective, with little attention given to how people themselves account for it. We interviewed 44 competitors (23 females, 21 males) from the 2009 Sydney World Masters Games (aged 56–90 years; mean = 72 years). The major themes were: ‘Use it or lose it’ (performance preservation required specific ‘training’ and the continuation of general physical activity); ‘Adapt’/‘modify’ (participants compensated for their decline in speed, strength and endurance so they could continue competing in sport); ‘It's in my genes’ (participants attributed their ‘family history’ and/or innate ‘determination’ to performance maintenance); and ‘I like to push myself’ (participants valued improved performance, pushing their bodies and winning which motivated them to continually train and compete). The findings are discussed within a framework of three key performance maintenance theories: (a) preserved differentiation, (b) selective maintenance and (c) compensation. Although compensation and continued training are effective ways to counter decline in later life, this study extends past research by showing how older athletes tend to combine and/or generalise stable and unstable attributes of performance preservation. In particular, this research highlights the importance individuals and Western society place on self-responsibility for health, competition and performance maintenance, which act as key motivating factors.
How do older people describe others with cognitive impairment? A multiethnic study in the United States
Authors: LADITKA SARAH B. , LADITKA JAMES N. , LIU RUI , PRICE ANNA E. , FRIEDMAN DANIELA B. , WU BEI , BRYANT LUCINDA L. , CORWIN SARA J. , IVEY SUSAN L.
Published: January 2012

We studied how older people describe others with cognitive impairment. Forty-two focus groups represented African Americans, American Indians, Chinese Americans, Latinos, Vietnamese Americans, and Whites other than Latinos (Whites) (N = 396, ages 50+), in nine locations in the United States of America. Axial coding connected categories and identified themes. The constant comparison method compared themes across ethnic groups. African Americans, American Indians and Whites emphasised memory loss. African Americans, American Indians, Latinos and Whites stressed withdrawal, isolation and repetitive speech. African Americans, American Indians, Vietnamese Americans and Whites emphasised ‘slow thinking’. Only Whites described mood swings and personality changes. Many participants attributed dementia to stress. Terms describing others with dementia included ‘Alzheimer's’, ‘dementia’, ‘senile’ and ‘crazy’. Euphemisms were common (‘senior moment’, ‘old timer's disease’). Responses focused on memory, with limited mention of other cognitive functions. Differences among ethnic groups in descriptions of cognitive health and cognitive impairment underscore the need to tailor public health messages about cognitive health to ways that people construe its loss, and to their interest in maintaining it, so that messages and terms used are familiar, understandable and relevant to the groups for which they are designed. Health promotion efforts should develop ethnically sensitive ways to address the widely held misperception that even serious cognitive impairment is a normal characteristic of ageing and also to address stigma associated with cognitive impairment.
Source attribution of human campylobacteriosis using a meta-analysis of case-control studies of sporadic infections
Authors: DOMINGUES A. R. , PIRES S. M. , HALASA T. , HALD T.
Published: January 2012

Campylobacterspp. is a widespread and important cause of human illness worldwide. Disease is frequently associated with foodborne transmission, but other routes of exposure, such as direct contact with live animals and person-to-person transmission, are also recognized. Identifying the most important sources of human disease is essential for prioritizing food safety interventions and setting public health goals. Numerous case-control studies of sporadic infections of campylobacteriosis have been published. These studies investigated a variety of potential risk factors for disease, often using different methodologies and settings. Systematic reviews (SRs) consist of a formal process for literature review focused on a specific research question, and include the identification of relevant literature, quality assessment of relevant studies, summarization or statistical analysis of data, and conclusions. With the objective of identifying the most important risk factors for human sporadic campylobacteriosis, we performed a SR of case-control studies of human sporadic cases and a meta-analysis of the obtained results. A combined SR focusing onSalmonellaandCampylobacterstudies was performed and the results analysed separately. From 1295 identified references, 131 passed the relevance screening, 73 passed the quality assessment stage, and data was extracted from 72 studies. Of these, 38 focused on campylobacteriosis. Information on exposures of cases and controls, and estimated odds ratios for investigated risk factors were collected and analysed. In the meta-analysis, heterogeneity between the studies and possible sources of bias were investigated, and pooled odds ratios for identified risk factors were estimated. Results suggest that travelling abroad, eating undercooked chicken, environmental sources, and direct contact with farm animals were significant risk factors for campylobacteriosis. Sub-analyses by geographical region, age group, and study period were performed, and differences were discussed.
Spatial and temporal patterns in antimicrobial resistance ofSalmonellaTyphimurium in cattle in England and Wales
Authors: COX R. , SU T. , CLOUGH H. , WOODWARD M. J. , SHERLOCK C.
Published: January 2012

Salmonellais the second most commonly reported human foodborne pathogen in England and Wales, and antimicrobial-resistant strains ofSalmonellaare an increasing problem in both human and veterinary medicine. In this work we used a generalized linear spatial model to estimate the spatial and temporal patterns of antimicrobial resistance inSalmonellaTyphimurium in England and Wales. Of the antimicrobials considered we found a common peak in the probability that anS. Typhimurium incident will show resistance to a given antimicrobial in late spring and in mid to late autumn; however, for one of the antimicrobials (streptomycin) there was a sharp drop, over the last 18 months of the period of investigation, in the probability of resistance. We also found a higher probability of resistance in North Wales which is consistent across the antimicrobials considered. This information contributes to our understanding of the epidemiology of antimicrobial resistance inSalmonella.
Lung and pleural fibrosis in asbestos-exposed workers: a risk factor for pneumonia mortality
Authors: VEHMAS T. , PALLASAHO P. , OKSA P.
Published: January 2012

Lungs exposed to occupational dust may be especially vulnerable to fatal infections. We followed up asbestos-exposed workers (n=590) originally screened for lung cancer with computed tomography and scored for pleuropulmonary fibrosis. We checked these workers' influenza and pneumonia mortality data (ICD-10 codes J10–J18) in the national register. In total, 191 deaths, including 43 deaths from infectious pneumonia, occurred in 6158 person-years of follow-up (mean follow-up time 10·44 years). ‘Some interstitial fibrosis’ [hazard ratio (HR) 2·26, 95% confidence interval (CI) 0·98–5·19, P=0·06] and ‘definite interstitial fibrosis’ (HR 3·70, 95% CI 1·22–11·23, P=0·02) were associated with an increased risk of death from pneumonia compared to no fibrosis. Asbestosis patients, i.e. those with both asbestos exposure and lung fibrosis, therefore appear to be particularly at risk for death from pneumonia. These patients should be vaccinated against influenza and Pneumococcus.
Myeloproliferative disorders in older people
Authors: Osborne Wendy , Jones Gail L , Jackson Graham H , Marr Helen
Published: January 2012

The term myeloproliferative disorders (MPDs) describes a group of conditions in which an intrinsic stem cell defect is present in the bone marrow. This leads to hypercellularity in one or more of the myeloid cell lines (red blood cells, platelets, granulocytes and their precursors), or increased bone marrow fibrosis. MPDs are rare; combined annual incidence is 6 per 100,000.

MPDs may present in asymptomatic patients as an incidental finding, or may be associated with constitutional features such as weight loss, sweats or lethargy. Splenomegaly is common but lymphadenopathy is not a feature. The most significant complications are: arterial thrombosis, venous thrombosis, secondary marrow fibrosis and transformation to acute myeloblastic leukaemia (AML). Treatment aims to reduce the risk of such complications.

Recent advances in the understanding of the pathogenesis of these disorders have radically changed the approach to the diagnosis of MPD and are the focus of new treatment developments.
Generalized affine Springer fibres
Authors: Kottwitz Robert , Viehmann Eva
Published: January 2012

This paper studies two new kinds of affine Springer fibres that are adapted to the root valuation strata of Goresky–Kottwitz–MacPherson. In addition it develops various linear versions of Katz's Hodge–Newton decomposition.
The Natural Patterns of Self-Cleaning Surfaces: RIMAPS Analysis of Superhydrophobic Leaves
Authors: Favret Eduardo A. , Molina Ana M.
Published: January 2012

In the last decades, a new interdisciplinary science called biomimetics has emerged that has significantly influenced the design of certain new materials. Nature, as a source of inspiration, can give us ideas and concepts to implement new functional properties. One example is the self-cleaning property (superhydrophobicity) of certain plant leaves, better known as the Lotus Effect. This term comes from the lotus leaf (Nelumbo nucifera), the best-known self-cleaning surface in nature. On this kind of leaf, water droplets roll over the leaf surface and collect dirt and other particles from the surfaces. The superhydrophobicity of these leaves is caused, in general, by a hierarchical surface structure, built by a randomly oriented small hydrophobic wax structure on the top of convex cell papillae. The wetting condition of the solid surface is a particular property of materials and depends on both surface energy and surface topography. Many papers have been written to show how superhydrophic surfaces with periodic and random patterns can be made, but few describe and characterize biological self-cleaning surfaces. These papers usually analyze them by using optical profilers and scanning electron microscopy with specific sample preparation (for example, fixation) and in some cases atomic force microscopy. The main conclusion of those works is that binary structures (hierarchical microstructures and nanostructures) and unitary structures (basically nanostructures) are found in superhydrophobic plant leaves. However, no information regarding the general micro-nano structural pattern of biological surfaces on the x-y plane has been reported. These surfaces seem to have a random pattern in most of the cases or at least a vague arrangement of its constitutive elements whose morphologies can be represented by geometrical figures (for example, hexagonal/pentagonal polygons, circles, and straight lines).
Workflow-Centric Cryo-SEM for Biological Research
Authors: Lich Ben
Published: January 2012

Biologists using electron microscopy to understand the form and function of biological systems at the nanometer scale have long been confronted by a number of difficulties related to fundamental characteristics shared by most biological samples. First is the complexity and range of scales at which significant information is present, from the mesoscopic level in tissues, through the microscopic level of cells and organelles, to the nanoscopic level of macromolecules. Next is the hydrated state of most biological materials, in which water is essential to maintaining functional structure, but, at the same time, is incompatible with the vacuum environment of the scanning electron microscope (SEM). Finally, because of their fragile nature, biological structures are vulnerable to damage, by the electron beam itself or by procedures used to prepare them for SEM analysis. A new cryogenic scanning electron microscope (the Magellan cryo-SEM) workflow solution from FEI addresses all of these issues. It is an integrated workflow from sample preparation to sub-nanometer imaging that addresses the specific needs of biological research.
A New Basaltic Glass Microanalytical Reference Material for Multiple Techniques
Authors: Wilson Steve , Koenig Alan , Lowers Heather
Published: January 2012

The U.S. Geological Survey (USGS) has been producing reference materials since the 1950s. Over 50 materials have been developed to cover bulk rock, sediment, and soils for the geological community. These materials are used globally in geochemistry, environmental, and analytical laboratories that perform bulk chemistry and/or microanalysis for instrument calibration and quality assurance testing. To answer the growing demand for higher spatial resolution and sensitivity, there is a need to create a new generation of microanalytical reference materials suitable for a variety of techniques, such as scanning electron microscopy/X-ray spectrometry (SEM/EDS), electron probe microanalysis (EPMA), laser ablation inductively coupled mass spectrometry (LA-ICP-MS), and secondary ion mass spectrometry (SIMS). As such, the microanalytical reference material (MRM) needs to be stable under the beam, be homogeneous at scales of better than 10–25 micrometers for the major to ultra-trace element level, and contain all of the analytes (elements or isotopes) of interest. Previous development of basaltic glasses intended for LA-ICP-MS has resulted in a synthetic basaltic matrix series of glasses (USGS GS-series) and a natural basalt series of glasses (BCR-1G, BHVO-2G, and NKT-1G). These materials have been useful for the LA-ICP-MS community but were not originally intended for use by the electron or ion beam community. A material developed from start to finish with intended use in multiple microanalytical instruments would be useful for inter-laboratory and inter-instrument platform comparisons.

This article summarizes the experiments undertaken to produce a basalt glass reference material suitable for distribution as a multiple-technique round robin material. The goal of the analytical work presented here is to demonstrate that the elemental homogeneity of the new glass is acceptable for its use as a reference material. Because the round robin exercise is still underway, only nominal compositional ranges for each element are given in the article.
Calendar
Authors: Webster Paul
Published: January 2012

Following is a list of microscopy related meetings and courses. The editors would greatly appreciate input to this list via the electronic submission form under “events/other microscopy events” at the MSA webpage: www.microscopy.org. We will gladly add hypertext links to the notice on the web and insert a listing of the meeting in the next issue.
Meetings Large and Small
Authors: Lyman Charles
Published: January 2012

This issue highlights the large annual M&M meeting attracting over thousands of attendees and the Topical Conference attracting about 100 attendees. Both types of conferences are popular among microscopists and microanalysts.
Progress towards no-till organic weed control in western Canada
Authors: Shirtliffe Steven J. , Johnson Eric N.
Published: January 2012

Organic farmers in western Canada rely on tillage to control weeds and incorporate crop residues that could plug mechanical weed-control implements. However, tillage significantly increases the risk of soil erosion. For farmers seeking to reduce or eliminate tillage, potential alternatives include mowing or using a roller crimper for terminating green manure crops (cover crops) or using a minimum tillage (min-till) rotary hoe for mechanically controlling weeds. Although many researchers have studied organic crop production in western Canada, few have studied no-till organic production practices. Two studies were recently conducted in Saskatchewan to determine the efficacy of the following alternatives to tillage: mowing and roller crimping for weed control, and min-till rotary hoeing weed control in field pea (Pisum sativum L.). The first study compared mowing and roller crimping with tillage when terminating faba bean (Vicia faba L.) and field pea green manure crops. Early termination of annual green manure crops with roller crimping or mowing resulted in less weed regrowth compared with tillage. When compared with faba bean, field pea produced greater crop biomass, suppressed weeds better and had less regrowth. Wheat yields following pea were not affected by the method of termination. Thus, this first study indicated that roller crimping and mowing are viable alternatives to tillage to terminate field pea green manure crops. The second study evaluated the tolerance and efficacy of a min-till rotary harrow in no-till field pea production. The min-till rotary hoe was able to operate in no-till cereal residues and multiple passes did not affect the level of residue cover. Field pea exhibited excellent tolerance to the min-till rotary hoe. Good weed control occurred with multiple rotary hoe passes, and pea seed yield was 87% of the yield obtained in the herbicide-treated check. Therefore, this second study demonstrated that min-till rotary hoeing effectively controls many small seeded annual weeds in the presence of crop residue and thus can reduce the need for tillage in organic-cropping systems.
The role of riparian buffer management in reducing off-site impacts from grazed dairy systems
Authors: Aarons Sharon R. , Gourley Cameron J. P.
Published: January 2012

Agriculture in general and intensive animal production in particular can degrade the environment, especially as a consequence of the overuse of nutrients. Intensively grazed dairy systems, defined by the presence of foraging animals in the landscape, are often considered a more benign approach to dairy production with perceived smaller impacts due to the reduced requirement for manure disposal. However, grazing dairy cows contribute nutrients and pathogens in excreta, and sediment through landscape deformation. These impacts can dramatically increase in parts of the farm such as feeding, watering and sacrifice areas, laneways and night paddocks where animals are concentrated and spend a disproportionate amount of time. Other practices such as the disposal of dairy shed or dairy factory effluent and cultivation of fodder crops can also pollute the environment. A common approach to reduce nutrient, pathogen and sediment losses from dairy farms is to establish buffer zones in riparian areas that act as an interface between upland land use and waterways. This is generally done by fencing riparian areas to exclude stock and revegetating with understory and overstory species, with the aim of increasing infiltration, trapping sediment and decreasing contaminant losses from upland pastures. However, poorly designed and managed riparian areas may themselves contribute to further environmental degradation. Rarely is an integrated approach, including factors such as animal behavior and dairy farm management practices, as well as an analysis of landscape and riparian hydrology used in developing riparian management recommendations for individual farms. This paper reviews the threats posed by intensively grazed dairy systems, approaches to improve riparian zone management and recommends future research needs.
The influence of organic transition strategy on chemical and biological soil tests
Authors: Ugarte Carmen M. , Wander Michelle M.
Published: January 2012

Soil testing strategies that include biologically based indicators in organic and alternative farming systems are needed in order to improve recommendations that balance production and environmental goals. In this study, soil samples were collected before and after soils were transitioned from conventional row crop production to organic management using rotations that varied in both their inputs and tillage intensity. Ley-, row crop- and vegetable-based farming systems were implemented using locally specific production practices. Subplots were imposed within each system to allow comparison of farming systems without amendment and with dairy manure- and compost-amendment. Soil analyses included standard chemical tests (0–15 cm) for available phosphorus, exchangeable potassium, calcium, magnesium, pH, total organic carbon (SOC) and total nitrogen (TN). Biological assays (0–15 and 15–30 cm) included particulate organic matter-C and -N (POM-C, POM-N), soil and POM C:N ratios, fluorescein diacetate (FDA) hydrolysis, potentially mineralizable N (PMN) and hydrolysable amino-N + NH4(IL-N). Even though cropping and tillage intensity varied among systems (ley < row crop < vegetable), organic matter and nutrient reserves were not statistically different. Nutrient concentrations tested medium to high, even without compost or manure application. Labile fractions of soil organic matter were more enriched in the deeper sampling depth; whereby, POM stocks within the 15–30 cm depth increased by 20% on average compared to roughly 6% in the surface depth. This and observed changes in other properties demonstrate the multiple benefits derived from use of winter annual or perennial crops. Results from our analyses suggested PMN and POM have particular promise as metrics of change in commercial soil testing facilities to assist recommendations for amendments to balance production and environmental goals.
Calorific values and ash contents of different organs of Masson pine (Pinus massoniana) in southern China
Authors: Zeng Wei Sheng , Tang Shou Zheng , Xiao Qian Hui
Published: January 2012

Calorific values of plants are important indices for evaluating and reflecting material cycle and energy conversion in forest ecosystems. Based on the data of Masson Pine (Pinus massoniana) in southern China, the calorific values (CVs) and ash contents (ACs) of different plant organs were analyzed systematically using hypothesis test and regression analysis in this paper. The results show: (i) the CVs and ACs of different plant organs are almost significantly different, and the order by AFCV (ash-free calorific value) from the largest to the smallest is foliage (23.55 kJ/g), branches (22.25 kJ/g), stem bark (21.71 kJ/g), root (21.52 kJ/g) and stem wood (21.35 kJ/g); and the order by AC is foliage (2.35%), stem bark (1.44%), root (1.42%), branches (1.08%) and stem wood (0.33%); (ii) the CVs and ACs of stem woods on top, middle and lower sections are significantly different, and the CVs are increasing from top to lower sections of trunk while the ACs are decreasing; (iii) the mean GCV (gross calorific value) and AFCV of aboveground part are larger than those of belowground part (roots), and the differences are also statistically significant; (iv) the CVs and ACs of different organs are related, to some extent, to diameter, height and origin of the tree, but the influence degrees of the factors on CVs and ACs are not the same.
Overlap in Speech-Language and Reading Services for Kindergartners and First Graders
Authors: Gosse Carolyn S. , Hoffman LaVae M. , Invernizzi Marcia A.
Published: January 2012

Purpose

Speech-language pathologists (SLPs) and reading professionals provide educational services to children who are at risk for reading difficulties, although these professions do not necessarily coordinate efforts. To date, there is limited evidence regarding the proportion of children who receive services from both professionals. The current study reports the prevalence and overlap of speech-language and reading services provided to kindergartners and first graders in Virginia.

Method

This study analyzed a population-level database of reading screening scores from 74,730 kindergartners and 75,088 first graders. Information regarding the speech-language services received by these children was obtained. Prevalence rates of speech-language impairment, reading risk, and comorbidity were calculated. The distribution of children receiving speech-language services across categories of reading competence was examined.

Results

Findings indicated that ∼6% of the children received speech-language services and 11.1% of the kindergartners and 13.7% of the first graders received reading services. One-quarter of the children receiving speech-language services also received reading services. Furthermore, children receiving speech-language services received reading services at twice the rate of children who were not receiving speech-language services in both kindergarten (23.1% vs. 9.1%) and first grade (25.2% vs. 11.3%).

Clinical Implications

This study provides empirical support for improving coordination between SLPs and reading professionals.
Preliteracy Speech Sound Production Skill and Later Literacy Outcomes: A Study Using the Templin Archive
Authors: Overby Megan S. , Trainin Guy , Smit Ann Bosma , Bernthal John E. , Nelson Ron
Published: January 2012

Purpose

This archival study examined the relationship between the speech sound production skill of kindergarten children and literacy outcomes in Grades 1–3 in a data set where most children’s vocabulary skills were within normal limits, speech therapy was not provided until 2nd grade, and phonological awareness instruction was discouraged at the time data were collected.

Method

Data were accessed from the Templin Archive (2004), and the speech sound production skill of 272 kindergartners were examined relative to literacy outcomes in 1st and 2nd grade (reading) and 3rd grade (spelling).

Results

Kindergartners in the 7th percentile for speech sound production skill scored more poorly in 1st- and 2nd-grade reading and 3rd-grade spelling than did kindergartners with average speech sound production skill; kindergartners in the 98th percentile achieved superior literacy skills compared to the mean. Phonological awareness mediated the effects of speech sound production skill on reading and spelling; vocabulary did not account for any unique variance.

Conclusion

Speech sound disorders appear to be an overt manifestation of a complex interaction among variables influencing literacy skills, including nonlanguage cognition, vocabulary, letter knowledge, and phonological awareness. These interrelationships hold across the range of speech sound production skill, as children with superior speech sound production skill experience superior literacy outcomes.
How Grammatical Are 3-Year-Olds?
Authors: Eisenberg Sarita L. , Guo Ling-Yu , Ghermezi Mor
Published: January 2012

Purpose

This study investigated the level of grammatical accuracy in typically developing 3-year-olds and the types of errors they produce.

Method

Twenty-two 3-year-olds participated in a picture description task. The percentage of grammatical utterances was computed and error types were analyzed.

Results

The mean level of grammatical accuracy in typical 3-year-olds was ∼71%, with a wide range of variability. The current study revealed a variety of error types produced by 3-year-olds, most of which were produced by fewer than 5 children. The pattern observed for most of the children was to produce a scattering of errors with no more than a few of any 1 error type.

Conclusion

The level of grammatical accuracy in 3-year-olds was skewed toward the high end. Although tense marking errors were the most frequent error type, they accounted for only 1/3 of the errors produced by 3-year-olds. A more general measure of grammaticality that considers additional aspects of language might, therefore, be useful in assessing language at this age.
Narrative Writing in Children and Adolescents: Examining the Literate Lexicon
Authors: Sun Lei , Nippold Marilyn A.
Published: January 2012

Purpose

This study was designed primarily to examine the use of abstract nouns and metacognitive verbs in the narrative writing of school-age children and adolescents.

Method

Three groups of typically developing students ages 11, 14, and 17 years (
n
= 40 per group) were asked to write a story about something funny, sad, or scary that had happened to them and a friend. Each student’s narrative essay was examined for the use of abstract nouns (e.g.,
accomplishment, loneliness, mystery
) and metacognitive verbs (e.g.,
assume, discover, realize
) and for the production of complex syntax as measured by mean length of T-unit (MLTU) and clausal density (CD).

Results

Age-related growth in narrative writing was documented for both types of words. Additionally, the use of abstract nouns and metacognitive verbs was associated with the production of complex syntax, reflecting the lexicon–syntax interface.

Conclusion

The narrative writing task employed in this study was effective in eliciting literate words and complex syntax in school-age children and adolescents.
The propagator of the attractive delta-Bose gas in one dimension
Authors: Prolhac Sylvain , Spohn Herbert
Published: January 2012

We consider the quantum δ-Bose gas on the infinite line. For repulsive interactions, Tracy and Widom have obtained an exact formula for the quantum propagator. In our contribution we explicitly perform its analytic continuation to attractive interactions. We also study the connection to the expansion of the propagator in terms of the Bethe ansatz eigenfunctions. Thereby we provide an independent proof of their completeness.
Different forms of the Kadanoff–Baym equations in quantum statistical mechanics
Authors: Kondratyev A. S. , Shahid N.
Published: January 2012

A new form of the Kadanoff–Baym equations for a system of interacting particles is offered on the basis of the retarded and advanced quantum Green’s functions. The comparison of the traditional and the offered forms of the equations allows to analyze the question to what extent Landau–Silin kinetic equations for the neutral Fermi-liquid and for the electron liquid of normal metals take into account quickly varying in space and time disturbances.
Non-relativistic quantum theory of induced Cherenkov radiation and Compton scattering in plasma
Authors: Kuzelev M. V. , Rukhadze A. A.
Published: January 2012

The role of quantum effects in the theory of Langmuir waves in collisionless plasma is discussed. It is shown that quantum effects do can be significant at resonant interactions between flows of quantum particles and plasma eigenmodes.
Negative ions at an interface between liquid helium mixtures
Authors: Dyugaev A. M. , Grigoriev P. D. , Lebedeva E. V.
Published: January 2012

The properties of electron bubbles electrostatically forced against an interface between liquid 3He and saturated 4He–3He mixture were determined at low temperatures. The equilibrium state of such objects is characterized by the binding energy of 6.5 K and oscillatory spectrum of first excitations with a frequency of 0.6·1010 s–1. The shifting electric field E = 100 V/cm at the temperature T = 0.2 K leads to decaying the bound bubble state with the lifetime τ ≈ 1 s. The experimental study of bubble electron states can appear to be useful for determining properties of an interface between liquid helium mixtures.
On chemical bonding and helium distribution in hcp beryllium
Authors: Bakai A. S. , Timoshevskii A. N. , Yanchitsky B. Z.
Published: January 2012

The electron densities of states and spatial distribution of electron density in the system hcp beryllium-helium were investigated by means of ab-initio methods of simulation. It was found that contrary to predictions of the “jelly” model, the energetically more favorable configuration is that where a helium atom is located at the most restricted position, on a triangular face of two adjacent tetrahedrons, and where the charge density of electrons is maximal. It is established that this occurs due to hybridization of electron states of helium and nearest beryllium atom. The helium binding energy is about 5.6 eV. The spatial distribution of the charge density is investigated in details. Calculation of solution energy of helium in hcp beryllium was performed. The helium location at lattice sites in different interstitial positions and in divacancy complexes were considered. It is found that helium implemented into hcp beryllium favors formation of divacancies.
Heat capacity of an electron gas at the surface of a nanotube with its superlattice in a magnetic field
Authors: Ermolaev A. M. , Rashba G. I. , Solyanik M. A.
Published: January 2012

The effect of modulating potential at the surface of a nanotube in a longitudinal magnetic field on heat capacity of a degenerate and nondegenerate electron gas is considered. The heat capacity is represented by monotonic and oscillating terms. Heat capacity of a degenerate electron gas exhibits de Haas-van Alphen type oscillations, dependent on density of electrons, and Aharonov-Bohm type oscillation dependent on the intensity of the magnetic field going through the nanotube cross section.
Angular magnetostriction oscillations in layered conductors with multisheet Fermi surfaces
Authors: Kirichenko O. V. , Peschansky V. G.
Published: January 2012

The dependence of the electrical conductivity of layered conductors with a quasi-two dimensional electron energy spectrum on the orientation of an external magnetic field is studied. The oscillatory dependence of the magnetostriction of conductors with a multisheet Fermi surface (FS) on the angle of inclination of a strong magnetic field to the layers is found to contain valuable information on the shape of the FS. In particular, the period of the oscillations can be used to determine the magnitude of the corrugation in a plane sheet of the Fermi surface.
New features of magnetoresistance in highly anisotropic layered metals
Authors: Grigoriev P. D.
Published: January 2012

The angular and magnetic-field variations of the interlayer magnetoresistance calculated in the limits of high magnetic field and very high anisotropy manifest several unusual properties. The monotonic part of the interlayer magnetoresistance increases with rising magnetic field along the current, which contradicts the standard theory and changes the angular dependence of the magnetoresistance. The Dingle temperature increases with magnetic field, dampens the magnetic quantum oscillations, and changes the field dependence of their amplitudes.
Spontaneous spin polarization of systems with impurity hybridized electron states in conduction band of crystals
Authors: Okulov V. I. , Pamyatnykh E. A. , Silin V. P.
Published: January 2012

A theoretical description of spontaneous spin polarization in systems of hybridized electron states on donor impurities with low concentration in a conduction band of a crystal is developed. On the base of general equations for the energy of spin splitting of the electron spectrum, formulated within the framework of the Fermi-liquid approach, it is shown that in systems of such a type the spin ordering mechanism of conduction electrons, which is more efficient than the usually considered mechanism of an exchange interaction with magnetic impurities, takes place. The possible realization of spontaneous spin ordering of electrons in hybridized states is substantiated for the case of total polarization of the system within the model of Fermi-liquid constants. Possibilities of finding manifestations of spontaneous spin polarization of an electron impurity system in thermodynamic properties (heat capacity and elastic moduli) are discussed. Evidences of such manifestations are presented from an analysis of available experimental data.
Oscillations of kinks on dislocation lines in crystals and low-temperature transport anomalies as a “passport” of newly-induced defects
Authors: Mezhov-Deglin L. P. , Mukhin S. I.
Published: January 2012

The possible interpretation of experimental data on low-temperature anomalies in weakly deformed metallic crystals prepared form ultra-pure lead, copper, and silver, as well as in crystals of 4He is discussed within the previously proposed theoretical picture of dislocations with dynamical kinks. In the case of pure metals the theoretical predictions give a general picture of interaction of conduction electrons in a sample with newly-introduced dislocations, containing dynamic kinks in the Peierls potential relief. In the field of random stresses appearing due to plastic deformation of a sample, kinks on the dislocation line form a set of one-dimensional oscillators in potential wells of different shapes. In the low temperature region at low enough density of defects pinning kinks the inelastic scattering of electrons on kinks should lead to deviations from the Wiedemann-Franz law. In particular, the inelastic scattering on kinks should result in a quadratic temperature dependence of the thermal conductivity in a metallic sample along preferential directions of dislocation axes. In the plane normal to the dislocation axis the elastic large-angle scattering of electrons is prevalent. The kink pinning by a point defect or by additional dislocations as well as the sample annealing leading to the disappearance of kinks should induce suppression of transport anomalies. Thus, the energy interval for the spectrum of kink oscillations restricted by characteristic amplitude of the Peierls relief is a “passport of deformation history” for each specific sample. For instance, in copper the temperature/energy region of the order of 1 K corresponds to it. It is also planned to discuss in the other publication applicability of mechanism of phonon scattering on mobile dislocation kinks and pinning of kinks by impurities in order to explain anomalies of phonon thermal conductivity of 4He crystals and deformed crystals of pure lead in a superconducting state.
Rosensweig instability in ferrofluids
Authors: Kats E. I.
Published: January 2012

We propose a simple model to analyze stability of the free surface of horizontally unbound ferrofluid in a vertical magnetic field. With respect to the well known Rosensweig instability (see e.g., R. E. Rosensweig, Ferrohydrodynamics, Cambridge University Press, Cambridge (1993) and references therein) we go one step further to include into consideration coupling of surface displacements to non-magnetic degree of freedoms. We show that the coupling can lead to a considerable reduction of the critical magnetic field and as well yields to nontrivial depletion layering near the surface.
Quantum oscillations in a tunable graphene bilayer
Authors: Falkovsky L. A.
Published: January 2012

The oscillations of forbidden gap, chemical potential and carrier concentration on a graphene bilayer in the quasiclassical magnetic field and in the transverse electric field created by the gate voltage are considered.
Two-dimensional Pauli operator in a magnetic field
Authors: Grinevich P. G. , Mironov A. E. , Novikov S. P.
Published: January 2012

The two-dimensional purely magnetic Schrödinger operator for the nonrelativistic particle with a spin of ½ in a magnetic field has some remarkable properties, that were discovered in the late 70s: its strongly degenerate in the ground state and it admits supersymmetry. In the present work we investigate the special case where the magnetic flux of the periodic field through the elementary cell equals zero. This case has not been covered in the previous publications. An interesting connection with the theory of solitons, in particular with Burgers-like systems and their two-dimensional analogues, is revealed. Their linearizability properties are simpler than some famous systems, such as KdV and KP. Members of the Aharonov-Bohm-type system with quantized magnetic flux play a special role in the investigation of this case.
Manifestation of the upper Hubbard band in the 2D Hubbard model at low electron density
Authors: Kagan M. Yu. , Val’kov V. V. , Woelfle P.
Published: January 2012

We consider the 2D Hubbard model in the strong-coupling case (U ≫ W) and at low electron density (nd2 ≪ 1). We find an antibound state as a pole in the two-particle T-matrix. The contribution of this pole in the self-energy reproduces a two-pole structure in the dressed one-particle Green-function similar to the Hubbard-I approximation. We also discuss briefly the Engelbrecht-Randeria mode which corresponds to the pairing of two holes below the bottom of the band for U ≫ W and low electron density. Both poles produce nontrivial corrections to Landau Fermi-liquid picture already at low electron density but do not destroy it in 2D.
Low temperature magnetically-inhomogeneous states of Sr2FeMoO6–δ compounds
Authors: Kalanda N. A. , Demyanov S. E. , Kovalev L. V.
Published: January 2012

The present paper shows that inhomogeneity in magnetic structure of Sr2FeMoO6–δ metal oxide compounds, that essentially depends on synthesis conditions, leads to different degrees of superstructural ordering of Fe3+ and Mo5+ cations. According to the temperature dependence of magnetization measured in the absence of a magnetic field, the sharp jump in the low temperature region (2.3–23 K) indicates the existence of magnetic fields with low coercivity, where the superparamagnetic state is realized. It has been established that magnetic inhomogeneity of antiferromagnetic-ferromagnetic materials promotes a frustration of the exchange coupling and facilitates a realization of the spin glass state in the material. A decrease of magnetic inhomogeneity and the corresponding increase in the degree of superstructural ordering of cations cause the negative magnetoresistivity effect to increase up to 14%, and to be unchanged at temperatures below 15 K.
Field-induced charge-density-wave transitions in the organic metal α-(BEDT-TTF)2KHg(SCN)4 under pressure
Authors: Andres D. , Kartsovnik M. V. , Biberacher W. , Neumaier K. , Sheikin I. , Müller H. , Kushch N. D.
Published: January 2012

Successive magnetic-field-induced charge-density-wave transitions in the layered molecular conductor α-(BEDT-TTF)2KHg(SCN)4 are studied in a hydrostatic pressure regime in which the zero field charge-density- wave (CDW) state is completely suppressed. It is shown that the orbital effect of the magnetic field restores the density wave, while orbital quantization induces transitions between different CDW states as the field strength is varied. The latter show up as distinct anomalies in the magnetoresistance as a function of field. The interplay between the orbital and Pauli paramagnetic effects, which act, respectively, to enhance and to suppress the CDW instability, is particularly manifest in the angular dependence of the field-induced anomalies.
Magnetoresistance oscillations up to 32 K in the organic metal β″-(ET)4(H3O)[Fe(C2O4)3] · C6H4Cl2
Authors: Laukhin Vladimir N. , Audouard Alain , Vignolles David , Canadell Enric , Prokhorova Tatyana G. , Yagubskii Eduard B.
Published: January 2012

The magnetic torque and magnetoresistance of the quasi-two-dimensional charge transfer salt β″-(ET)4(H3O)[Fe(C2O4)3] · C6H4Cl2 have been investigated in pulsed magnetic fields of up to 55 T. As opposed to de Haas–van Alphen oscillations, Shubnikov–de Haas oscillations are observed up to temperatures as high as 32 K at ambient pressure despite significant thermal damping in the low-temperature range. This feature, which is also observed under applied pressure, is interpreted in terms of the coexistence of a closed orbit and a quantum interference path with the same cross section.
Angle dependent magnetothermopower of α-(ET)2KHg(SCN)4
Authors: Krstovska D. , Steven E. , Choi E. S. , Brooks J. S.
Published: January 2012

The magnetic field and angle dependences of the thermopower and Nernst effect for the quasi-two dimensional (q2D) organic conductor α-(ET)2KHg(SCN)4 are measured at temperatures below (4 K) and above (9 K) the transition temperature in fields of up to 31 T. In addition, a theoretical model involving a magnetic breakdown effect between the q1D and q2D bands is proposed in order to simulate the data. Analysis of the background components of the thermopower and Nernst effect imply that at low temperatures, in the CDW state, the properties of α-(ET)2KHg(SCN)4 are determined mostly by the orbits on new, open Fermi sheets. The quantum oscillations observed in both thermoelectric effects at fields above 8 T are caused only by the α orbit.
Suppressed blinking behavior of thioglycolic acid capped CdTe quantum dot by amine functionalization
Authors: Mandal Abhijit , Tamai Naoto
Published: January 2012

Prepared water soluble thioglycolic acid capped CdTe quantum dots (QDs) were further surface functionalized by ethylene diamine (EDA). Amine functionalized CdTe QDs demonstrate enhanced luminescence intensity at ensemble measurements and suppressed luminescence intermittency behavior at the single molecule level. A clear decrease in the power law exponent for “on” time behavior is observed in amine modified CdTe QDs. Our results show that surface of CdTe QDs modified by EDA can lead to an important physical mechanism to enhance fluorescence intensity, reduce blinking, and increase photostability.
Electron mobility limited by scattering from screened positively charged dislocation lines within indium nitride
Authors: Baghani Erfan , O’Leary Stephen K.
Published: January 2012

In the present work, we address the open question of the contribution from threading dislocations to the problem of unintentional n-type conductivity exhibited by indium nitride through an examination of the effect that positively charged dislocation lines have on the transverse electron mobility within this material. Assuming that the threading dislocation lines within indium nitride act as a source for free electrons, the screening associated with the positively charged threading dislocation lines is evaluated. The impact this screening has on the dislocation limited electron mobility within this material is then considered. Our results indicate that one of the implications of attributing a donor character to the threading dislocation lines within indium nitride would be a strong non-uniformity in the free electron concentration in the plane of growth of this semiconductor. This contrasts dramatically with the case of gallium nitride.
An algebraic operator approach to electronic structure
Authors: Shenvi Neil , Yang Weitao
Published: January 2012

In this paper, we introduce an algebraic approach to electronic structure calculations. Our approach constructs a Jordan algebra based on the second-quantized electronic Hamiltonian. From the structure factor of this algebra, we show that we can calculate the energy of the ground electronic state of the Hamiltonian operator. We apply our method to several generalized Hubbard models and show that we can usually obtain a significant fraction of the correlation energy for low-to-moderate values of the electronic repulsion parameter while still retaining the O(L3) scaling of the Hartree-Fock algorithm. This surprising result, along with several other observations, suggests that our algebraic approach represents a new paradigm for electronic structure calculations which opens up many new directions for research.