bluuebunny/crossref_metadata_2025 huggingface dataset:
Livelihood activities in a Namibian wildlife conservancy: a case study of variation within a CBNRM programme
Authors: Kanapaux William , Child Brian
Published: June 2011

Approaches to community-based natural resource management tend to vary among programmes based on the needs and characteristics of the communities in which the programmes operate. Variation also exists within individual programmes, creating the potential for conflict if management does not recognize that these differences can indicate competing interests and needs. In this study we examine livelihood activities at the household level in a wildlife conservancy along the Kwando River in the Caprivi region of Namibia. We ask how people in the conservancy make their livelihoods and what differences exist between the conservancy’s riverside and inland populations. The study finds that the inland population, c. 20 km from the river on slightly heavier soils, engages in fewer livelihood activities and has greater food security than does the riverside population. We further establish that differences between the two populations are significant enough to indicate two distinct combinations of livelihood activities with different environmental interactions. These findings suggest that any management action taken by the conservancy will affect household livelihoods differently based on location and that these differences must be considered if the conservancy is to make a successful transition from a subsistence-based agricultural system to a wildlife-based economy.
Phase transformation under beam-target interactions during high-intensity pulsed ion beam irradiation at low pressure
Authors: Zhu X.P. , Zhang F.G. , Tang Y. , Lei M.K.
Published: June 2011

Nitrides and/or carbonitrides formation of high efficiency was found on titanium target under irradiation of high-intensity pulsed ion beam (HIPIB) with a few shots at a low pressure of 10−2 Pa order, which is extraordinary in comparison with conventional thermo-chemical diffusion process such as gas nitriding and/or carbonitriding of metals necessarily heated at high temperatures during a processing time of hours. The underlying mechanism of the nitrides and carbonitrides formation on titanium targets was explored by a comparative study on three typical HIPIB sources, i.e., TEMP-6, TEMP-4M, and ETIGO-II, varying the irradiation intensity within several J/cm2 per shot of a 60–70 ns pulse duration and the shot number of similar ion species. It is revealed that ambient gases and ion source material are the main sources providing the nitrogen and carbon species for the phase transformation on titanium target at the low pressures, whereas the ion species of HIPIB composition is negligible at a low implantation dose of 1013–1014 ions/cm2. The adsorbed gaseous species, the deposited layer of the ion source material, and in-situ formed compound top layer from reactions between ablation plasma and the ambient species during HIPIB irradiation, can be effectively incorporated into the irradiated target surfaces under a controlled HIPIB-target interaction.
Is prosodic development correlated with grammatical and lexical development? Evidence from emerging intonation in Catalan and Spanish
Authors: PRIETO PILAR , ESTRELLA ANA , THORSON JILL , VANRELL MARIA DEL MAR
Published: June 2011

This investigation focuses on the development of intonation patterns in four Catalan-speaking children and two Spanish-speaking children between 0 ; 11 and 2 ; 4. Pitch contours were prosodically analyzed within the Autosegmental Metrical framework in all meaningful utterances, for a total of 6558 utterances. The pragmatic meaning and communicative function were also assessed. Three main conclusions arise from the results. First, the study shows that the Autosegmental Metrical model can be successfully used to transcribe early intonation contours. Second, results reveal that children's emerging intonation is largely independent of grammatical development, and generally it develops well before the appearance of two-word combinations. As for the relationship between lexical and intonational development, the data show that the emergence of intonational grammar is related to the onset of speech and the presence of a small lexicon. Finally, we discuss the implications of these results for the biological hypothesis of intonational production.
Risk factors for mortality in non-pregnancy-related listeriosis
Authors: MOOK P. , PATEL B. , GILLESPIE I. A.
Published: June 2011

We examined non-pregnancy-related listeriosis cases in England and Wales reported to the Health Protection Agency between 1990 and 2009 (n=1864) using unconditional multivariate logistic regression analysis to identify factors independently associated with mortality. A subset analysis of cases between 2005 and 2009 (n=694) investigated the additional effect of antibiotic therapy on survival. In these cases particular malignancies, alcoholism, cardiovascular disease, increasing age, and treatment to reduce gastric acid secretion were positively associated with mortality. The absence of a concurrent condition and presence of autoimmune disease had a protective effect. The subset analysis identified illness in winter or spring as a risk factor and antibiotic therapy as a protective factor for mortality. The impact of antibiotic therapy, seasonality and reduced gastric acid status on survival should be further investigated. Policy-makers and clinicians need to more broadly advise those at risk of contracting this disease and dying as a consequence.
Epidemiological and clinical aspects of human Brucella suis infection in Polynesia
Authors: GUERRIER G. , DARONAT J. M. , MORISSE L. , YVON J. F. , PAPPAS G.
Published: June 2011

High brucellosis seroprevalence rates in domestic swine herds have been reported in Wallis and Futuna Islands and are associated with a significant burden of human infection by Brucella suis, a species that is rarely incriminated in human disease. Between 2003 and 2010, seven patients had a positive blood culture for B. suis biovar 1, 11 symptomatic patients had a positive Rose Bengal test (RBT) and a positive serum agglutination test (SAT) and three asymptomatic cases were found to be positive for RBT, SAT or ELISA IgM (after systematic screening of 52 family members of 15 index cases). Overall, Brucella infection was diagnosed in 21 people, corresponding to a mean annual incidence of 19 cases/100 000 inhabitants. Compared to series of patients infected with other more commonly encountered Brucella spp. such as B. melitensis and B. abortus, clinical presentation and percentage and distribution of complications were similar, apart from a marked observation of significantly increased median alanine aminotransferase levels, 20 times greater than upper normal rates, but not accompanied by any particular hepatic pathology. Wallis and Futuna, where people live in close proximity to animals and where the cultural significance of pig-raising precludes the implementation of adequate veterinary preventive measures, thus represents one of the few known B. suis foci worldwide and allows for evaluation of the peculiarities of this infection.
THYROID FUNCTION IN PREGNANCY: MATERNAL AND FETAL OUTCOMES WITH HYPOTHYROIDISM AND SUBCLINICAL THYROID DYSFUNCTION
Authors: VANES NEIL K , LAZARUS JOHN H , CHAN SHIAO-Y
Published: June 2011

Thyroid hormones are important in the development of the fetus and the placenta as well as in maintaining maternal wellbeing. Thyroid disorders are common in the population as a whole, particularly in women, and therefore are common during pregnancy and the puerperium. Biochemical derangement of thyroid function tests are present in approximately 2.5–5% of pregnant women.
Linguistic validation of a disease-specific quality of life measure for children and teenagers with cardiac disease
Authors: Wray Jo , Franklin Rodney , Brown Kate , Blyth Jacqueline , Marino Bradley S.
Published: June 2011

Introduction

To anglicise an American – that is, English language – disease-specific health-related quality of life measure, using the Paediatric Cardiac Quality of Life Inventory, for children in the age group of 8–12 years and adolescents in the age group of 13–18 years with cardiac disease, and to assess conceptual equivalence of the American and British versions.

Methods

A process of forward and backward translation of the measure was undertaken before focus groups and individual interviews with 40 participants – that is, 20 children/adolescents with cardiac disease and 20 parents of children/adolescents with cardiac disease – to determine their understanding of the meaning of the questions.

Results

Interviews established that participants understood the meaning of the questions, although some found it difficult to explain the meaning of questions in which the language was explicit and wanted instead to answer the individual questions as they applied to them/their child. There was agreement that all versions of the questionnaire were relevant and comprehensive, and that the length of the questionnaires was acceptable and practical.

Conclusions

The anglicised version of the Paediatric Cardiac Quality of Life Inventory appears to be a linguistically valid measure of health-related quality of life for children and adolescents with cardiac disease. The psychometric properties of the anglicised Paediatric Cardiac Quality of Life Inventory are now being tested in a multi-centre study in the United Kingdom.
Bergman metrics and geodesics in the space of Kähler metrics on principally polarized abelian varieties
Authors: Feng Renjie
Published: June 2011

It is well known in Kähler geometry that the infinite-dimensional symmetric space $\mathcal{H}$ of smooth Kähler metrics in a fixed Kähler class on a polarized Kähler manifold is well approximated by finite-dimensional submanifolds $\mathcal{B}_k\subset\mathcal{H}$ of Bergman metrics of height k. Then it is natural to ask whether geodesics in $\mathcal{H}$ can be approximated by Bergman geodesics in $\mathcal{B}_k$. For any polarized Kähler manifold, the approximation is in the C0 topology. For some special varieties, one expects better convergence: Song and Zelditch proved the C2 convergence for the torus-invariant metrics over toric varieties. In this article, we show that some C∞ approximation exists as well as a complete asymptotic expansion for principally polarized abelian varieties.
COMMUNAL RELIGION IN JIANGNAN DELTA RURAL VILLAGES IN LATE IMPERIAL CHINA
Authors: Atsutoshi Hamashima
Published: June 2011

This article addresses the broad question of the sense of community in traditional Chinese villages, through consideration of popular cults found throughout the most highly developed region in Late Imperial China: the Jiangnan Delta. A key clue is a large-scale tenant-farmer revolt in Zhaowen County in 1846. When the uprising was suppressed, not only were twenty human ringleaders executed, but images of four local gods from village temples, who were believed to have sanctioned the rebellion, were also seized by the authorities and exposed for one year at the gates of the Zhaowen County City God temple. All four had three characteristics in common: (1) they were anthropomorphic, with human names; (2) they had living descendants of the same surname; (3) all were associated with stories involving miraculous protection of tax grain transport to the North. The descendants of these gods, all possession-type spirit mediums, or shamans, based in the villages, created the gods in response to the needs of their clients, large-scale landlords who bore responsibility for sea transport of tax grain to the North. In the mid-sixteenth century, fundamental socio-economic changes took place in the Jiangnan Delta. The landlords disappeared from the villages, leaving only the farmers, who were turning to cottage industries for cash to supplement inadequate food crop yields. The spirit mediums responded to the changes and modified their gods for a new set of clients, resulting in the survival of these cults down to the present day.
CONVECTIVE IONOSPHERIC STORMS: A REVIEW
Authors: Kelley Michael C. , Makela Jonathan J. , de La Beaujardière Odile , Retterer John
Published: June 2011

Equatorial spread F (ESF) was discovered almost a century ago using the first radio wave instrument designed to study the upper atmosphere: the ionosonde. The name came from the appearance of reflections from the normally smooth ionosphere, which were spread over the altitude frequency coordinates used by the instrument. Attempts to understand this phenomenon in any depth activated such tools as radars and in situ probes such as rockets and satellites in the 1960s. Over the next 15 years, these tools expanded our experimental understanding enormously, and new nonlinear theoretical methods developed in the late 1970s, which led to proposing a name revision from ESF to convective ionospheric storms. Interest in these phenomena continues, but a new, practical aspect has developed from the associated turbulence effects on communications (transionosphere) and navigation (GPS). The first satellite to specifically investigate this problem and the associated goal of predicting occurrences is under the umbrella of the Communications/Navigation Outage Forecast System (C/NOFS). In contemplating the successful first years of the C/NOFS program, reviewing the state of the art in our knowledge of convective ionospheric storms seems appropriate. We also present some initial results of this satellite program. A major goal of the National Space Weather Program, and of C/NOFS, is predicting these storms, analogous to thunderstorms in the lower atmosphere due to their adverse effects on communication and navigation signals. Although ambitious, predictive capability is a noble and important goal in the current technological age and is potentially within our reach during the coming decade.
Nearshore human interventions reverse patterns of decline in lake calcium budgets in central Ontario as demonstrated by mass‐balance analyses
Authors: Yao Huaxia , McConnell Christopher , Somers Keith M. , Yan Norman D. , Watmough Shaun , Scheider Wolfgang
Published: June 2011

Calcium (Ca) has declined to levels threatening aquatic biota in lakes on the eastern Canadian Shield. Predictive models for future changes in lake Ca are generally based on catchment‐scale studies, but these models rarely account for unmeasured sources of Ca supply that are common in the nearshore areas of developed lakes. In this study we utilize up to 29 years of hydrological and water chemistry data for three lakes in central Ontario that differ in degree of human intervention to demonstrate that shoreline development may exert large effects on Ca mass balances. In the relative absence of shoreline development, Red Chalk Lake exhibited what we consider to be the normal response, a reduction in Ca load from the catchment over the last three decades, leading to a reduction in lake export and lake Ca concentration. Calcium load, export, and lake water Ca concentration also fell in Harp Lake, but less than in Red Chalk Lake, because Ca loads were elevated by human activities in Harp Lake's moderately developed shoreline area. By contrast, Dickie Lake experienced an exceptional change in Ca dynamics: both export and lake concentrations rose because of elevated load from the shoreline area linked to the use of dust suppressants on gravel roads. Reductions in both stream Ca concentration and flow volume have led to calcium decline in streams and lakes. Long‐term soil acidification processes and climatic variability with its link to hydrology can explain the general pattern of Ca decline in lakes on the south‐central Canadian Shield. However, given the widespread lakeshore development and use of dust suppressants on gravel roads, predictions of lake Ca levels need to take into account nearshore activities, especially those that augment rates of Ca supply.
Hepatocytic differentiation of rhesus monkey embryonic stem cells promoted by collagen gels and growth factors
Authors: Wang Xihong , Jin Lifang , Ji Shaohui , Guo Xiangyu , Chen Hongwei , Ji Weizhi
Published: June 2011

rES (rhesus monkey embryonic stem) cells have similar characteristics to human ES (embryonic stem) cells, and might be useful as a substitute model for preclinical research. Before their clinical application, it is critical to understand the roles of factors that control the differentiation of ES cells into hepatocytes. Here, we analysed the effect of collagen gels on rES cells differentiation into hepatocytes by stepwise protocols. About 80% of DE (definitive endoderm) cells were generated from rES cells after being treated with activin A. The DE cells were then plated on to collagen gels or type I collagen‐coated wells with growth factors to induce hepatocyte differentiation. In type I collagen systems, characteristics of immature hepatocytes were observed, including the expression of immature hepatic genes and the generation of 15±3% AFP (alpha fetoprotein)/CK (cytokeratin)18 double‐positive cells. In collagen gel culture, differentiated cells exhibited typical hepatocyte morphology and expressed adult liver‐specific genes. The mRNA expression of AFP (immature hepatic gene) was detected at day 11 but decreased at day 18. In contrast, mRNA expression of albumin (mature hepatic gene) was detected at day 11 and increased at day 18. Compared with type I collagen systems, significantly higher AFP/CK18 double‐positive cells (68±7%) were produced in collagen gel culture. Furthermore, some differentiated cells acquired the hepatocytic function of glycogen storage. However, only immature hepatic genes were observed in collagen gel systems if growth factors were absent. Thus, collagen gels combined with hepatocyte‐inducing growth factors efficiently promoted differentiation of hepatocytes from rES.
Effect of Fe substitution on the magnetic, transport, thermal and magnetocaloric properties in Ni50Mn38−xFexSb12 Heusler alloys
Authors: Sahoo Roshnee , Nayak Ajaya K. , Suresh K. G. , Nigam A. K.
Published: June 2011

The structural, magnetic, transport, thermal, and magnetothermal properties of quaternary Heusler alloys Ni50Mn38−xFexSb12 have been studied. Powder x-ray diffraction and temperature dependence of magnetization studies reveal that with the addition of Fe in the Mn site, the martensitic transition shifts to low temperatures. It is also found that the martensitic transition becomes broader with the increase of Fe concentration. The metamagnetic transition in M(H) isotherms becomes very prominent in x = 2 and vanishes for x = 3 and 4. A maximum positive magnetic entropy change of 14.2 J/kg K is observed for x = 2 at 288 K for 50 kOe. Electrical resistivity data show an abrupt decrease across the martensitic transition in all the alloys, except x = 6, which does not have a martensitic transition. A maximum negative magnetoresistance of 21% has been obtained for x = 2 at 50 kOe. The same alloy also shows an exchange bias field of 288 Oe.
Preferred orientation relationships with large misfit interfaces between Ni3Sn4 and Ni in reactive wetting of eutectic SnPb on Ni
Authors: Suh J. O. , Tu K. N. , Wu Albert T. , Tamura N.
Published: June 2011

Ni3Sn4 grains were formed on Ni by reactive wetting between molten eutectic SnPb and thermally annealed Ni foil. Using synchrotron white beam micro x-ray diffraction analysis, two kinds of preferred orientation relationships between Ni3Sn4 and Ni were found. The existence of preferred orientation with large interfacial misfit is suggested as a general mechanism of intermetallic compound formation in reactive solder wetting on metals.
Room temperature long range ferromagnetic ordering in (BiFeO3)1−x (PbTiO3)x nanocrystallites
Authors: Singh K. , Gautam Ashish , Sen K. , Kotnala R. K. , Kumar Mahesh , Gautam P. , Singh M.
Published: June 2011

Room temperature Mössbauer spectra of (BiFeO3)1−x (PbTiO3)x (x = 0, 0.1, 0.2, 0.3) nano multiferroic systems prepared by solution combustion technique reveal the long range ferromagnetic ordering, supported by M-H loop measurements. Magnetic hyperfine interaction field and isomer shift for these nanocrystallite indicate the presence of Fe3 +  ion only, likewise confirmed by from X-ray photoelectron spectroscopy study, which is essential for enhancement of multiferroic properties. A small residual magnetic moment is observed for these nanoparticles, which may be attributed to size confinement at nanoscale and to spin canting. These nanomaterials are of great importance in basic as well as applied research.
Band alignment studies in InN/p-Si(100) heterojunctions by x-ray photoelectron spectroscopy
Authors: Bhat Thirumaleshwara N. , Kumar Mahesh , Rajpalke Mohana K. , Roul Basanta , Krupanidhi S. B. , Sinha Neeraj
Published: June 2011

The band offsets in InN/p-Si heterojunctions are determined by high resolution x-ray photoemission spectroscopy. The valence band of InN is found to be 1.39 eV below that of Si. Given the bandgap of 0.7 eV for InN, a type-III heterojunction with a conduction band offset of 1.81 eV was found. Agreement between the simulated and experimental data obtained from the heterojunction spectra was found to be excellent, establishing that the method of determination was accurate. The charge neutrality level (CNL) model provided a reasonable description of the band alignment of the InN/p-Si interface and a change in the interface dipole by 0.06 eV was observed for InN/p-Si interface.
A quantitative model for stabilization effect induced by ferroelectric aging
Authors: Bao Huixin , Xue Dezhen , Wang Yu , Gao Jinghui , Zhang Lixue , Yang Sen , Yadav K. L. , Ren Xiaobing
Published: June 2011

The stabilization effect, an increase of the reverse transition temperature TC with ferroelectric aging time, was recently found in acceptor doped ferroelectrics. Such an effect has found a microscopic explanation in the symmetry-conforming principle of point defects, which also accounts for a similar stabilization effect in ferroelastic/martensite materials. However, such a microscopic model is difficult to use to make a quantitative/semiquantitative evaluation of the aging process. In the present work, we propose a single-domain thermodynamic model that provides a semiquantitative fit to the experimentally observed stabilization kinetics. Furthermore, it predicts a new aspect of ferroelectric aging: the decrease of latent heat ΔH of the reverse transition with aging time. Such a prediction was confirmed via experimental differential scanning calorimetry results.
Investigation of tribocharges and their migration in layered model toners by electron holography
Authors: Seok Jeong Jong , Murakami Yasukazu , Shindo Daisuke , Kawase Hiromitsu
Published: June 2011

The distribution of tribocharges in toner samples is studied by electron holography, a powerful tool for direct observations of the electric field. We carry out both in situ and ex situ observations on triboelectricity using model toner specimens, which are laminated with thin films, and a transmission electron microscopy specimen holder with two piezo-driving microprobes. We investigate specimens with stacking layer-patterns of “minus and weak minus” and “plus and minus.” The observed equipotential lines show a simple semi-ellipsoidal shape, regardless of the combination of toner films having different charging characteristics. Computer simulations for quantitative analyses of the electron hologram results with a modulated reference wave by a long-range electric field from the tribocharges are performed. Both the experimental results and the simulations indicate that the tribocharges are not localized at the positions where they are formed; rather they migrate to achieve a gradient charge density in the specimen. The charge quantity of the model toner is also evaluated by the simulation.
Micromagnetic study on microwave-assisted magnetic recording in perpendicular medium with intergrain exchange coupling
Authors: Nozaki Yukio , Kato Ayumu , Noda Kenji , Kanai Yasushi , Tanaka Terumitsu , Matsuyama Kimihide
Published: June 2011

The influence of intergrain exchange coupling on the properties of microwave-assisted magnetization reversal has been investigated. The results of micromagnetic simulation suggest that the microwave frequency realizing the magnetization reversal is increased as the exchange stiffness constant among the magnetic grains becomes larger than 1 × 10−7 erg/cm if an inhomogeneous magnetization reversal occurred. The numerically expected increase in the microwave frequency was observed experimentally in perpendicularly magnetized Co/Pd multilayer with an exchange stiffness constant of ∼1 × 10−6 erg/cm. The simulations of signal recording and reproducing processes in a granular medium with assistance of a microwave field also suggest that an adequate intergrain exchange coupling is required to inhibit the nucleation of small island domains that will suppress the amplitude of the signal-noise ratio of the readback signal.
Quantum transient currents in molecular systems weakly coupled with electrodes
Authors: Liu Wei , Sasaoka Kenji , Yamamoto Takahiro , Watanabe Satoshi
Published: June 2011

The transient current dynamics of multilevel nanoscale systems weakly coupled with two electrodes has been theoretically investigated by the nonequilibrium Green’s function method. We have proposed a technique for decomposing the total time-dependent current into almost independent current components. This is a powerful technique for gaining insight into transient current behavior because the decomposed currents exhibit simple behaviors similar to those of single-level systems. We have clarified the transient current behaviors of a hydrogen molecule (two-level system) and an octatetraene molecule (eight-level system) connected to two electrodes as typical examples of multilevel systems. The transient current of the molecular hydrogen system is characterized by two current components with the same relaxation time and different oscillation periods, whereas the current of the octatetraene molecular system is decomposed into eight components, a few of which dominate the total current behavior during the initial stage.
An elastic metamaterial with simultaneously negative mass density and bulk modulus
Authors: Liu X. N. , Hu G. K. , Huang G. L. , Sun C. T.
Published: June 2011

In this letter, an elastic metamaterial which exhibits simultaneously negative effective mass density and bulk modulus is presented with a single unit structure made of solid materials. The double-negative properties are achieved through a chiral microstructure that is capable of producing simultaneous translational and rotational resonances. The negative effective mass density and effective bulk modulus are numerically determined and confirmed by the analysis of wave propagation. The left-handed wave propagation property of this metamaterial is demonstrated by the negative refraction of acoustic waves.
Elimination of the coherent effect in the optical Kerr measurement of bismuth glass using supercontinuum
Authors: Tong Junyi , Tan Wenjiang , Si Jinhai , Yang Yi , Yi Wenhui , Chen Feng , Hou Xun
Published: June 2011

A strong coherent effect was observed in the monochromatic optical Kerr effect (OKE) experiment of a Bi2O3-B2O3-SiO2 oxide glass (BI glass). To eliminate the influence of the coherent effect, we proposed a simple femtosecond two-color OKE measurement method with wavelength tunability using a supercontinuum. In the two-color OKE measurement the third order nonlinear susceptibility of the BI glass was measured to be 1.64 × 10−13 electrostatic units (esu), in which the influence of the coherent effect was eliminated. The result is smaller than that obtained in a previous monochromatic OKE experiment. In addition, we discuss the discrepancies between the result obtained in this paper and those reported in other studies.
Material strength determination in the shock compressed state using x-ray diffraction measurements
Authors: Turneaure Stefan J. , Gupta Y. M.
Published: June 2011

Analytic developments are presented to determine the strength of shock compressed single crystals from real-time x-ray diffraction (XRD) measurements. Both linear elastic and nonlinear elastic analysis methods are considered. Material strength in the shocked (constant) state may be determined using one of two approaches: from measurements of longitudinal and lateral lattice strains; or from measurements of longitudinal lattice strains and longitudinal wave profiles. The second approach is demonstrated for aluminum single crystals following shock compression along [100] to peak impact stresses of 5.5–12.7 GPa and partial release (reflection from the window material) to final stresses of 3.5–7.1 GPa. The material strength of the Al(100) in the final state was found to increase with peak stress or plastic strain. The material strength at the Hugoniot elastic limit was 0.025 GPa and the material strength in the final state was 0.52 GPa for the highest stress experiment. Because of the large final stresses, incorporating nonlinear elasticity into the analysis was necessary to obtain accurate values of the material strength; for the highest stress experiment, the material strength in the final state determined using the linear elastic analysis overestimated the strength by approximately 80%. The use of XRD measurements and the nonlinear elastic analysis method for strength determination in the shocked state is expected to be particularly useful for extreme pressures and temperatures where continuum methods for strength determination may face experimental limitations.
Magnetic nanoparticle heating efficiency reveals magneto-structural differences when characterized with wide ranging and high amplitude alternating magnetic fields
Authors: Bordelon David E. , Cornejo Christine , Grüttner Cordula , Westphal Fritz , DeWeese Theodore L. , Ivkov Robert
Published: June 2011

Magnetic nanoparticles can create heat that can be exploited to treat cancer when they are exposed to alternating magnetic fields (AMF). At a fixed frequency, the particle heating efficiency or specific power loss (SPL) depends upon the magnitude of the AMF. We characterized the amplitude-dependent SPL of three commercial dextran-iron oxide nanoparticle suspensions through saturation to 94 kA/m with a calorimeter comprising a solenoid coil that generates a uniform field to 100 kA/m at ∼150 kHz. We also describe a novel method to empirically determine the appropriate range of the heating curve from which the SPL is then calculated. These results agree with SPL values calculated from the phenomenological Box-Lucas equation. We note that the amplitude-dependent SPL among the samples was markedly different, indicating significant magneto-structural variation not anticipated by current models.
Role of dopants on the electro-optic effect in nematic liquid crystals aligned with doped polypyrrole
Authors: Raicopol Matei , Dascalu Constanta , Atasiei Ruxandra , Ionescu Andrei Th
Published: June 2011

In order to estimate electro-optical response times, measurements of the transmitted light intensity through positive uniaxial nematic thin films in planar alignment have been performed. Very fast relaxation times were experimentally found for nematic samples aligned with conductive polymers, namely, polypyrrole doped with 5 types of anions having different molecular sizes and geometries. Using undoped polypyrrole alignment layers, slower electro-optical responses were obtained. Given that the improvement in the relaxation times is induced by the presence of the anions in the polypyrrole films, the increasing of the total restoring torque of the nematic molecules to the confining surfaces—responsible for the short relaxation times—is related to the charges accumulated at the nematic-conductive polymer interface.
Progressive changes in surface structure and electronic properties on Si(001) surface by CaF2 adsorption
Authors: Alzahrani A. Z. , Usanmaz D.
Published: June 2011

Ab initio calculations, based on pseudopotentials and density functional theory, have been performed to investigate the atomic geometry and electronic structures of calcium fluoride (CaF2) on the Si(001) surface. We have considered the experimentally observed (2×1) and (3×1) reconstructions with different bonding configurations of the CaF2 molecule on the Si(001) surface. Our total energy calculations suggest that the (3×1) structure is slightly more preferable than the (2×1). The key structural parameters and electronic surface properties of their most stable structures have been discussed. In contrast to the experimental results, the most stable structures contain an appreciable bonding nature between the surface Si and F atoms, however, no real bonding between Si and Ca atoms is indicated.
Effects of synthesis conditions on the structural features and methane adsorption properties of single-walled carbon nanohorns prepared by a gas-injected arc-in-water method
Authors: Sano Noriaki , Akita Yoshihiro , Tamon Hajime
Published: June 2011

Single-walled carbon nanohorns (SWCNHs) can be easily synthesized via a gas-injected arc-in-water method that is considered to be a cost-effective technique. The electrode configuration and duration of arc discharge were modified in order to enhance the yield and methane-adsorption properties of SWCNHs. As a result, the yield of the SWCNHs was significantly increased by increasing the discharge time and the size of the cathode. Using these modified conditions, the horn units in the SWCNH aggregates increased in size, and the thermal stability of SWCNHs in an oxidative environment increased accordingly. Ab initio molecular orbital calculations were used to explain the trend in the thermal stability. When the conventional conditions were applied, a burn-off of about 40% was necessary in order to achieve the maximum specific surface area and micropore volume. Remarkably, by enlarging the cathode size, the burn-off can be reduced by almost half to achieve the enhanced micropore volume. As a result, SWCNHs obtained using the modified conditions adsorbed a larger amount of methane than did SWCNHs obtained from the conventional synthetic conditions. The effect of a mild oxidation treatment on SWCNHs on their methane adsorption suggested that SWCNHs with micropores would be more flexible than pristine SWCNHs. This tendency was elucidated using a molecular mechanics calculation.
Local raster scanning for high-speed imaging of biopolymers in atomic force microscopy
Authors: Chang Peter I. , Huang Peng , Maeng Jungyeoul , Andersson Sean B.
Published: June 2011

A novel algorithm is described and illustrated for high speed imaging of biopolymers and other stringlike samples using atomic force microscopy. The method uses the measurements in real-time to steer the tip of the instrument to localize the scanning area over the sample of interest. Depending on the sample, the scan time can be reduced by an order of magnitude or more while maintaining image resolution. Images are generated by interpolating the non-raster data using a modified Kriging algorithm. The method is demonstrated using physical simulations that include actuator and cantilever dynamics, nonlinear tip-sample interactions, and measurement noise as well as through scanning experiments in which a two-axis nanopositioning stage is steered by the algorithm using simulated height data.
Electric field induced bacterial flocculation of enteroaggregative Escherichia coli 042
Authors: Kumar Aloke , Mortensen Ninell P. , Mukherjee Partha P. , Retterer Scott T. , Doktycz Mitchel J.
Published: June 2011

A response of the aggregation dynamics of enteroaggregative Escherichia coli under low magnitude steady and oscillating electric fields is presented. The presence of uniform electric fields hampered microbial adhesion and biofilm formation on a transverse glass surface, but instead promoted the formation of flocs. Extremely heterogenous distribution of live and dead cells was observed among the flocs. Moreover, floc formation was largely observed to be independent of the frequency of alternating electric fields.
Automated probe microscopy via evolutionary optimization at the atomic scale
Authors: Woolley Richard A. J. , Stirling Julian , Radocea Adrian , Krasnogor Natalio , Moriarty Philip
Published: June 2011

We describe the development and application of an imaging protocol, which evolves a scanning probe’s atomic structure in parallel with automated optimization of the scan parameters. Our protocol coerces the system into a state that produces a specific atomic resolution image type without human involvement.
A comparison of microwave irradiation, electric, and hybrid heating for medical plastic-waste treatment
Authors: Ohtsu Yasunori , Onoda Kaneto , Kawashita Hideki , Urasaki Hiroshi
Published: June 2011

The treatment of the medical plastic waste, like syringes, without oxygen injection, has been achieved with hybrid heating by a combination of microwave irradiation and electric heating. Five plastic-syringes with a volume of 20 mL were used as waste samples. Three types of treatments, i.e., microwave irradiation, electric heat, and a combination of both were investigated for medical waste treatment. Two shaped stainless steel containers, like tureen and flat dish, were also examined to compare the treatment efficiency. The plastic syringes were completely treated only with the combined heating, whereas the electric heating alone made the waste melt without a reduction of the weight. It was also found that the introduction of the evaporated water in the reactor plays an important role for the complete treatment of the plastic waste.
Mn induced ferromagnetism and modulated topological surface states in Bi2Te3
Authors: Niu Chengwang , Dai Ying , Guo Meng , Wei Wei , Ma Yandong , Huang Baibiao
Published: June 2011

The ferromagnetism and topological surface states manipulated by manganese in topological insulator Bi2Te3 are investigated by means of first-principles calculations. Our results indicate that substitution Mn for Bi can induce spin-polarized hole states with a total magnetic moments of 4.0 μB, and sufficient hole carrier density is required to obtain sustained magnetization. The obvious gap at the Dirac point coinciding with sharp surface state appears as Mn doped into Bi2Te3 because the magnetic interactions break the time reversal symmetry. The study paves a way to explore topological magnetoelectric effect and spintronic device applications.
Epitaxial growth of Ni(Al)Si0.7Ge0.3 on Si0.7Ge0.3/Si(100) by Al interlayer mediated epitaxy
Authors: Zhang B. , Yu W. , Zhao Q. T. , Mussler G. , Jin L. , Buca D. , Holländer B. , Hartmann J. M. , Zhang M. , Wang X. , Mantl S.
Published: June 2011

Epitaxial growth of Ni(Al)Si0.7Ge0.3 on relaxed Si0.7Ge0.3/Si(100) substrates was achieved via an Al interlayer mediated epitaxy. After annealing, most of the Al atoms from the original 3 nm interlayer diffused toward the surface but the remaining Al atoms in the epitaxial monogermanosilicide distributed uniformly, independent of the annealing temperatures. The incorporation of Al increases the transition temperature from the Ni-rich germanosilicide phase to the monogermanosilicide phase. The reduced Ni diffusion, the increased lattice constant due to substitutional Al, and the increased thermal expansion of monogermanosilicide are assumed to be the main mechanisms enabling the epitaxial growth of the quaternary silicide.
Kinetic simulation of a nanosecond-pulsed hydrogen microdischarge
Authors: Donkó Z. , Schulze J. , Müller S. , Czarnetzki U.
Published: June 2011

The electron dynamics in a nanosecond-pulsed microdischarge in high pressure hydrogen gas is investigated space and time resolved by particle-in-cell simulations. The discharge is driven by a 10 ns voltage pulse with a peak of 1.3 kV followed by an approximately constant voltage of 300 V during 150 ns. The time resolved current, electric field, electron density, and spatio-temporal excitation rates are compared to experimental and modeling results under identical discharge conditions. Via this synergistic approach, the development of the discharge and the different phases of distinct electron dynamics are identified and understood.
Room temperature GaN/AlGaN self-mixing terahertz detector enhanced by resonant antennas
Authors: Sun Y. F. , Sun J. D. , Zhou Y. , Tan R. B. , Zeng C. H. , Xue W. , Qin H. , Zhang B. S. , Wu D. M.
Published: June 2011

This letter focuses on the fabrication and characterization of a terahertz detector integrated with a group of low pass filters and resonant antennas. The detector operates as a self-mixer on GaN/AlGaN high electron mobility transistor (HEMT). At room temperature, a strong dc photocurrent is produced with the aid of the antennas and filters. The responsivity of our HEMT device is estimated to be 53 mA/W and a noise equivalent power of 1 nW/Hz can be achieved at 300 K. In addition, the sensor properties of a similar HEMT detector without filter are tested as a comparison.
Surface dispersion engineering of planar plasmonic chirped grating for complete visible rainbow trapping
Authors: Gan Qiaoqiang , Bartoli Filbert J.
Published: June 2011

Planar chirped plasmonic nanogratings were designed, fabricated, and experimentally characterized, and “rainbow trapping” in nanoplasmonic systems is unambiguously demonstrated across the entire visible spectrum. This planar approach has significant processing advantages when compared to other approaches that require precise nanofabrication control in the vertical direction, and is compatible with large-area nanofabrication technologies. This planar chirped nanograting opens the door to develop exciting chip-scale applications based on the “rainbow” trapping effect.
Inertial blood plasma separation in a contraction–expansion array microchannel
Authors: Lee Myung Gwon , Choi Sungyoung , Kim Hee-Je , Lim Hee Kyun , Kim Joon-Ho , Huh Nam , Park Je-Kyun
Published: June 2011

Continuous inertial blood plasma separation is demonstrated in a contraction–expansion array microchannel with a low aspect ratio (AR). The separation cutoff value of the particle size can be controlled by modulation of the force balance between inertial lift and Dean drag forces. The modulation is achieved by changing the channel AR at contraction region, which causes the change in magnitudes of the inertial lift forces on the particles. The presented blood plasma separator provides a level of yield and throughput of 62.2% and 1.2 ml/h(∼1.0×108 cells/min), respectively.
Robust one-dimensional wires in lattice mismatched bilayer graphene
Authors: Wright Anthony R. , Hyart Timo
Published: June 2011

We show that lattice mismatched bilayer graphene can realize robust one-dimensional wires. By considering a single domain wall, where the masses of the Dirac electrons change their sign, we establish a general projection principle. This determines how the existence of topological zero-energy domain wall states depends on the direction of the domain wall and locations of the massive Dirac cones inside the bulk Brillouin zone. We generalize this idea for arbitrary patterns of domain walls, showing that the topologically protected states exist only in the presence of an odd number of topological domain walls.
Enhanced performance in polymer photovoltaic cells with chloroform treated indium tin oxide anode modification
Authors: Xu Z. Q. , Li J. , Yang J. P. , Cheng P. P. , Zhao J. , Lee S. T. , Li Y. Q. , Tang J. X.
Published: June 2011

Enhanced performance of a poly(3-hexylthiophene):(6,6)-phenyl C61 butyric acid methyl ester bulk heterojunction polymer photovoltaic cell is reported by modifying the indium tin oxide (ITO) anode with chloroform solution. Instead of the traditional UV-ozone treatment, the optimized chloroform modification on ITO anode can result in an enhancement in the power conversion efficiency of an identical device, originating from an increase in the photocurrent with negligible change in the open-circuit voltage. The performance enhancement is attributed to the work function modification of the ITO substrate through the surface incorporation of the chlorine, and thus improved charge collection efficiency.
Volume charge carrier number fluctuations probed by low frequency noise measurements in InN layers
Authors: Mutta Geeta Rani , Routoure Jean Marc , Guillet Bruno , Méchin Laurence , Grandal Javier , Martin-Horcajo Sara , Brazzini Tommaso , Calle Fernando , Sánchez-García Miguel A. , Marie Philippe , Ruterana Pierre
Published: June 2011

Bulk conduction in molecular beam epitaxial InN layers has been confirmed using low frequency noise measurements versus temperature. A generation-recombination process has been identified at low temperatures ≤100 K and attributed to a trap with a discrete energy level in the band gap. The energy position of this trap has been determined to be around 52 meV below the conduction band minimum.
Engineering conduction and valence band states in site-controlled pyramidal quantum dots
Authors: Mohan A. , Gallo P. , Felici M. , Dwir B. , Rudra A. , Faist J. , Kapon E.
Published: June 2011

We demonstrate engineering of carrier states in the conduction band (CB) and valence band (VB) of site-controlled InGaAs/GaAs quantum dots (QDs) grown into pyramidal recesses, by controlling their shape, size, and composition. QDs with CB level separation ranging from ∼15 to 70 meV are obtained, useful in applications based on intraband transitions, e.g., QD photodetectors and QD cascade lasers. Moreover, by varying the aspect ratio and composition of the QDs we are able to switch the polarization of the dominant interband transition, a feature of interest for producing single photon emitters and QD amplifiers with prescribed polarization states
Ultrafast electron dynamics of intersubband excitation concerning cross-phase modulation in an InGaAs/AlAs/AlAsSb coupled double quantum well
Authors: Ogasawara Takeshi , Gozu Shinichiro , Mozume Teruo , Akita Kazumichi , Akimoto Ryoichi , Kuwatsuka Haruhiko , Hasama Toshifumi , Ishikawa Hiroshi
Published: June 2011

The ultrafast electron dynamics accompanying intersubband excitation in an InGaAs/AlAs/AlAsSb double quantum well has been investigated by femtosecond pump-probe spectroscopy. The photoinduced changes in the refractive index that causes cross-phase modulation is dominated by a decreased number as well as increased temperature of the electrons in the lower conduction subbands. The change in the number of conduction electrons decays monotonically, whereas the change in the electron temperature exhibits a maximum at around 0.9 ps after the photoexcitation. Heating of the conduction electrons is caused by their excess energy after intersubband longitudinal-optical phonon scattering.
Transmission-electron diffraction by MeV electron pulses
Authors: Murooka Y. , Naruse N. , Sakakihara S. , Ishimaru M. , Yang J. , Tanimura K.
Published: June 2011

We have developed a compact ultrafast electron diffractometer, consisting of a laser-driven rf photocathode that generates 3.0 MeV probe electron pulses, three-stage lens optics, and a custom-built detector for relativistic electrons. High-quality single-shot transmission electron diffraction has been detected from 180-nm-thick Si single crystals, with an excellent special resolution for diffracted beams; the spot width of 0.02 A−1 is obtained. The pulse width is estimated to be 100 fs in duration. Characteristics of the electron beam and other diffractometer features are discussed.
Interlayer magnetic coupling in perpendicular anisotropy L1-FePt based pseudo spin valve
Authors: Ho P. , Han G. C. , Chow G. M. , Chen J. S.
Published: June 2011

The interlayer coupling effects in L10-FePt based pseudo spin valve were investigated through the reversal behavior and exchange bias properties of the soft L10-FePt layer. The magnitude and sign of the exchange bias field were highly dependent on the magnetization state of the hard L10-FePt layer. In the presence of a fully saturated hard L10-FePt layer, the exchange bias effect stemmed from interlayer interactions due to possible pinholes, Ruderman–Kittel–Kasuya–Yosida or Néel coupling. With a partially saturated hard L10-FePt layer, stray fields emanated from the domain walls of the nonuniformly magnetized hard L10-FePt layer also contributed to the overall coupling strength.