bluuebunny/crossref_metadata_2025 huggingface dataset:
A Cross-Sectional Study of the Prevalence, Correlates, and Costs of Falls in Older Home Care Clients ‘At Risk’ for Falling
Authors: Markle-Reid Maureen , Browne Gina , Gafni Amiram , Roberts Jacqueline , Weir Robin , Thabane Lehana , Miles Melody , Vaitonis Vida , Hecimovich Catherine , Baxter Pamela , Henderson Sandra
Published: March 2010

Cette étude a examiné la prévalence pendant 6 mois, à l’aide des services de soutien à domicile, des facteurs de risque et des coûts de chutes de personnes âgées qui sont à risque de chute. Des 109 participants, 70,6 pour cent ont indiqué une chute dans les six mois précédents et 27,5 pour cent ont éprouvé plusieurs chutes. Bien qu’il n’y avait aucune différence statistiquement significative dans n’importe quel facteur de risque lié à la chute parmi ceux qui sont tombés (1+ chutes) et ceux qui ne sont pas tombés (0 chutes), ceux qui sont tombés ont montrés des tendances de plus en plus évidentes de fonctionnement réduit sur le plan physique, social et psychologique. Dans le coût total par personne d’utilisation des services de santé au cours des 6 derniers mois, il n’y avait aucune différence statistiquement significative entre ceux qui sont tombés et ceux qui ne sont pas tombés; toutefois, il y avait des différences significatives entre les groupes dans certains types de services de santé. L’analyse multivariable a révélé la présence de cinq facteurs de risques de chutes: troubles neurologiques (p. ex., diminution cognitive, maladie de Parkinson), l’âge ≥85 ans, risques environnementaux, glissade ou trébuchant précédente et déficience visuelle.
Does Geography Matter? The Health Service Use and Unmet Health Care Needs of Older Canadians
Authors: McDonald James Ted , Conde Heather
Published: March 2010

Le coût croissant de soins de santé et le changement des profils démographiques ont entraîné le déplacement et la redistribution du financement et des services entre les zones rurales et urbaines. La plupart des analyses économétriques de l’utilisation de services de santé au Canada incluent des contrôles larges selon la province et l’état rural/urbain; mais relativement peu du travail économétrique a porté sur la variation géographique dans l’utilisation de services de santé. À l’aide de l’Enquête sur la santé dans les collectivités canadiennes (ESCC 2.1), nous avons examiné les déterminants de diverses mesures d’utilisation des services de santé par les Canadiens âgés de 55 ou plus d’une gamme de zones urbaines et rurales de résidence. Notre analyse de régression a montré que les anciens résidents dans les zones rurales font moins visites chez un omnipraticien, chez un spécialiste et chez un dentiste par rapport aux résidents urbains. Tout étant égal, il n’existe aucune différence significative parmi nuits passées à l’hôpital ou dans les besoins de soins de santé non satisfaits. Cependant, apres contrôle pour les caractéristiques démographiques, le statut socioéconomique, l’assurance santé privée et l’état de santé, ces différences sont importantes.
Chronic Health Conditions: Changing Prevalence in an Aging Population and Some Implications for the Delivery of Health Care Services
Authors: Denton Frank T. , Spencer Byron G.
Published: March 2010

Parce que la prévalence de nombreuses conditions de santé chroniques augmente avec l’âge, nous pourrions anticiper que la proportion montrant une ou plusieurs de ces conditions, ainsi que les frais de traitement, augmenterait comme le vieillissement de la population. Combien la prévalence globale des affections chroniques augmenteraient en un quart de siècle si l’âge spécifiques des taux de prévalence n’ont pas changé? Les taux de prévalence globaux pour presque toutes les conditions qui découlent principalement de la vieillesse augmenteraient de plus de 25 pour cent, et les exigences en matière de santé auraient cru plus rapidement que la population – plus de deux fois plus rapidement dans le cas des séjours hospitaliers – si les taux pour chaque groupe d’âge sont restés constants. Combien serait requise pour l’augmentation des ressources de santé? Quelle différence rendrait-il à ces exigences si les gens avaient moins de maladies chroniques? Même de réductions modestes dans le nombre moyen de conditions à chaque âge pourraient entraîner des économies importantes.
The Canadian Elder Standard – Pricing the Cost of Basic Needs for the Canadian Elderly
Authors: MacDonald Bonnie-Jeanne , Andrews Doug , Brown Robert L.
Published: March 2010

Nous déterminons le revenu après impôt nécessaire pour financer les besoins fondamentaux des Canadiens aînés dans des circonstances différentes en ce qui concerne l’âge, le sexe, ville de résidence, ménage statut de taille, propriétaire ou locataire, moyens de transport et l’état de santé. À l’aide de notre base de l’année 2001, nous estimons les dépenses typiques pour nourriture, abri, soins à domicile à long terme, transport et divers éléments de base à la vie pour personnes âgées résidant dans cinq villes canadiennes. Il s’agit de la première étude canadienne des frais de subsistance de base adaptée aux aînés, plutôt qu’aux adultes en général, et établis sur une base absolue plutôt que relative. Nous avons également compté uniquement pour les conditions de vie de l’individu et ont établi l’effets divers que les conditions de vie des aînés exigent sur le coût des dépenses de base, en particulier pour les soins à domicile.
Quantitative risk assessment model of canine rabies introduction: application to the risk to the European Union from Morocco
Authors: NAPP S. , CASAS M. , MOSET S. , PARAMIO J. L. , CASAL J.
Published: March 2010

Although rabies incidence in humans in Western Europe is low, the repeated importation of rabid animals from enzootic areas threatens the rabies-free status of terrestrial animals and challenges the public health systems in this area. Most rabid animals imported into the European Union (EU) in recent years came from Morocco. The aim of this study was to develop a probabilistic risk assessment model to estimate the probability of rabies introduction, which was applied to the risk to the EU from dogs coming from Morocco. The mean annual probability of rabies introduction was 0·21 (90% CI 0·02–0·65). The pathways that contributed the most to this probability were: (a) EU citizens who adopted a dog in Morocco (59% of the total probability) and (b) EU citizens who travelled with their dog to Morocco by ferry (34% of the total probability). The model showed a marked seasonality in the risk of rabies with almost 40% of the annual probability occurring during the months of July and August. The application of stricter border controls (assuming 100% compliance) would result in a >270-fold reduction in the likelihood of rabies introduction into the EU from Morocco.
Do neonates, infants and young children need a higher dose of enoxaparin in the cardiac intensive care unit?
Authors: Sanchez de Toledo Joan , Gunawardena Sriya , Munoz Ricardo , Orr Richard , Berry Donald , Sonderman Sara , Krallman Sara , Shiderly Dana , Wang Li , Wearden Peter , Morell Victor O. , Chrysostomou Constantinos
Published: March 2010

Background

Thromboembolic events are a serious complication occurring in critically ill children admitted to the cardiac intensive care unit. Although enoxaparin is one of the current anticoagulants of choice, dosages in children are extrapolated from adult guidelines. Recent data suggest that this population may need a higher dose than what is currently recommended to achieve target anti-factor Xa levels. The purpose of this study was to evaluate whether children less than 2 years old admitted to the cardiac intensive care unit require a higher enoxaparin dose than that currently recommended to achieve target anti-factor Xa levels.

Methods

Retrospective chart review including patients who received enoxaparin for the treatment or prophylaxis of venous thrombosis between January, 2005 and October, 2007. Patients were classified as younger and older as well as prophylactic and therapeutic on the basis of age and enoxaparin dose, respectively. Younger patients were those 2 month old or less and older patients were those older than 2 months of age.

Results

A total of 31 patients were identified; 13 (42%) were 2 months or younger and 25 (81%) were postoperative patients. Ten (32%) received prophylactic and 21 (68%) received therapeutic enoxaparin doses. To achieve optimal anti-factor Xa levels, enoxaparin dose was increased in all groups and reached statistical significance in all patients except those older than 2 months who received prophylactic enoxaparin. An average of 2.8 dosage adjustments was needed. No bleeding complications were reported.

Conclusions

Young children, infants, and neonates admitted to the cardiac intensive care unit required a significantly higher enoxaparin dose than that currently recommended to achieve target anti-factor Xa levels.
Visualization of Morphological and Molecular Features Associated with Chronic Ischemia in Bioengineered Human Skin
Authors: Gill Erin M. , Straseski Joely A. , Rasmussen Cathy A. , Liliensiek Sara J. , Eliceiri Kevin W. , Ramanujam Nirmala , White John G. , Allen-Hoffmann B. Lynn
Published: March 2010

We present an in vitro model of human skin that, together with nonlinear optical microscopy, provides a useful system for characterizing morphological and structural changes in a living skin tissue microenvironment due to changes in oxygen status and proteolytic balance. We describe for the first time the effects of chronic oxygen deprivation on a bioengineered model of human interfollicular epidermis. Histological analysis and multiphoton imaging revealed a progressively degenerating ballooning phenotype of the keratinocytes that manifested after 48 h of hypoxic exposure. Multiphoton images of the dermal compartment revealed a decrease in collagen structural order. Immunofluorescence analysis showed changes in matrix metalloproteinase (MMP)-2 protein spatial localization in the epidermis with a shift to the basal layer, and loss of Ki67 expression in proliferative basal cells after 192 h of hypoxic exposure. Upon reoxygenation MMP-2 mRNA levels showed a biphasic response, with restoration of MMP-2 levels and localization. These results indicate that chronic oxygen deprivation causes an overall degeneration in tissue architecture, combined with an imbalance in proteolytic expression and a decrease in proliferative capacity. We propose that these tissue changes are representative of the ischemic condition and that our experimental model system is appropriate for addressing mechanisms of susceptibility to chronic wounds.
Evolution of Taiwan’s health care system
Authors: Rachel Lu Jui-Fen , Chiang Tung-Liang
Published: March 2010

This study aims to present an overview of the evolutionary policy process in reforming the health care system in Taiwan, through dissecting the forces of knowledge, social-cultural context, economic resources and political system. We further identify factors, which had a significant impact on health care reform policies in Taiwan through illustrative policy examples. One of the most illuminating examples highlighted is the design and implementation of a single-payer National Health Insurance (NHI) program in 1995, after nearly five years of planning efforts (1988–1993) and a two-year legislative marathon. The NHI is one of the most popular social programs ever undertaken in the history of Taiwan, which greatly enhances financial protection against unexpected medical expenses and assures access to health services. Nonetheless, health care reform still has an unfinished agenda. Despite high satisfaction ratings, Taiwan’s health care system today is encountering mounting pressure for new reforms as a result of its rapidly aging population, economic stagnation, and imbalanced NHI checkbook. Although there may exist some heterogeneous system characteristics and challenges among different health care systems around the world, Taiwan’s experiences in reforming its health care system for the past few decades may provide valuable lessons for countries going through rapid economic and political transition.
Coincident reflection images of the Gulf Stream from seismic and hydrographic data
Authors: Mirshak R. , Nedimović M. R. , Greenan B. J. W. , Ruddick B. R. , Louden K. E.
Published: March 2010

The development of seismic oceanography requires direct comparison of seismic data to high‐resolution oceanographic measurements over long horizontal scales. Here, we compare multichannel seismic (MCS) reflection images to 300 km of spatially‐coincident, high‐resolution (<1 km) expendable bathythermograph (XBT) surveys that were collected near a frontal region of the Gulf Stream. Fronts, eddies, tendrils, and interleaving were among the features identified in both data sets. In some cases, identification of features would be difficult if only hydrographic data were collected at conventional spatial scales. Comparing MCS reflection images with others derived purely from hydrographic data reveal many similarities and show that interleaving can be clearly identified with seismic methods. Varied time lags between MCS and hydrographic data collection identified the need for the separation between collecting both data sets to be short (i.e. hours to days), with advective processes and decorerlation time scales of desired features affecting acceptable sampling strategies.
A review of snow and ice albedo and the development of a new physically based broadband albedo parameterization
Authors: Gardner Alex S. , Sharp Martin J.
Published: March 2010

We present a computationally simple, theoretically based parameterization for the broadband albedo of snow and ice that can accurately reproduce the theoretical broadband albedo under a wide range of snow, ice, and atmospheric conditions. Depending on its application, this parameterization requires between one and five input parameters. These parameters are specific surface area of snow/ice, concentration of light‐absorbing carbon, solar zenith angle, cloud optical thickness, and snow depth. The parameterization is derived by fitting equations to albedo estimates generated with a 16‐stream plane‐parallel, discrete ordinates radiative transfer model of snow and ice that is coupled to a similar model of the atmosphere. Output from this model is also used to establish the physical determinants of the spectral albedo of snow and ice and evaluate the characteristics of spectral irradiance over snow‐covered surfaces. Broadband albedo estimates determined from the radiative transfer model are compared with results from a selection of previously proposed parameterizations. Compared to these parameterizations, the newly proposed parameterization produces accurate results for a much wider range of snow, ice, and atmospheric conditions.
Significance of fracture rim zone heterogeneity for tracer transport in crystalline rock
Authors: Cvetkovic V.
Published: March 2010

Conducting fractures of crystalline rock are typically altered over long periods of time. The fracture rim zone, a result of these alterations, will as a rule have different physical and chemical properties from the unaltered (“fresh”) rock, depending on various microscopic and macroscopic factors of the alterations. In this paper, we study the impact of rim zone heterogeneity, exemplified by a decreasing porosity trend as inferred from the Äspö Hard Rock Laboratory site (Sweden), on short‐ and long‐term tracer transport. Our main finding is that this particular rim zone structure will have a dominant effect on transport of moderately to strongly sorbing tracers on experimental time scales and a notable effect on application time scales. The findings of this work lend further support to the interpretation of the relatively strong retention reported by Cvetkovic et al. The fracture rim zone porosity structure may provide an additional safety margin for sorbing radionuclides in crystalline rock at sites where fracture alteration is prevalent.
Simultaneous rejuvenation and aging of groundwater in basins due to depth‐decaying hydraulic conductivity and porosity
Authors: Jiang Xiao‐Wei , Wan Li , Cardenas M. Bayani , Ge Shemin , Wang Xu‐Sheng
Published: March 2010

The age of groundwater is a manifestation of the temporal scale of groundwater flow in basins, whose pattern was recently found to be influenced by depth‐dependent hydraulic conductivity (K). In this paper, we show through numerical simulations how well‐documented depth‐decaying K and porosity (θ) influence groundwater age. In the unit basin, depth‐decaying K and θ cause aging in deeper parts and rejuvenation near the discharge zones, and the size of rejuvenated zones decreases with the decay exponent (A). In the Tóth basin, the geometry and size of rejuvenated zones, which are generally located at the interfaces between flow systems in the mid to lower reaches of the basin, are sensitive to A. In both basins, the maximum relative age and the relative age of groundwater at the lowest discharge point are dependent on A. Therefore, the depth‐decaying K and θ cannot be ignored when interpreting groundwater age distribution.
Selective SUMO modification of cAMP-specific phosphodiesterase-4D5 (PDE4D5) regulates the functional consequences of phosphorylation by PKA and ERK
Authors: Li Xiang , Vadrevu Suryakiran , Dunlop Allan , Day Jon , Advant Noopur , Troeger Jessica , Klussmann Enno , Jaffrey Ellis , Hay Ron T. , Adams David R. , Houslay Miles D. , Baillie George S.
Published: March 2010

Enzymes from the PDE (phosphodiesterase) 4 cAMP-specific PDE family are crucial for the maintenance of compartmentalized cAMP responses in many cell types. Regulation of PDE activity can be achieved via post-translational modification such as phosphorylation by ERK (extracellular-signal-regulated kinase) MAPKs (mitogen-activated protein kinases) and PKA (protein kinase A). In the present paper, we report for the first time that PDE4 isoforms from the PDE4A and PDE4D subfamilies can be selectively modified by SUMO (small ubiquitin-related modifier). We have identified a single SUMO site within a consensus tetrapeptide motif, ΨKXE (where Ψ represents a hydrophobic residue), which lies in the catalytic unit of these enzymes. SUMO modification of PDE4 at this site was observed upon overexpression of the SUMO E3 ligase PIASy [protein inhibitor of activated STAT (signal transducer and activator of transcription) Y] in HEK (human embryonic kidney)-293 cells and we identify PIASy as a novel binding partner for long PDE4 isoforms. Site-directed mutagenesis of the acceptor lysine residue ablated conjugation of PDE4 with SUMO, suggesting the presence of a single SUMO site in the first subdomain of the conserved PDE4 catalytic unit. This observation was supported by both cell-free in vitro SUMOylation assays and analysis of SUMOylated spot-immobilized peptide arrays. SUMO modification of long PDE4 isoforms serves to augment their activation by PKA phosphorylation and repress their inhibition by ERK phosphorylation. Following ligation of β-adrenergic receptors, SUMOylation of PDE4 isoforms sufficiently amplified PKA-stimulated PDE4 activity to reduce markedly the PKA phosphorylation status of the β2-adrenergic receptor. These results highlight a new means whereby cells might achieve the selective regulation of the activity of cAMP-specific PDE4 enyzmes.
Structural contributions of Delta class glutathione transferase active-site residues to catalysis
Authors: Wongsantichon Jantana , Robinson Robert C. , Ketterman  Albert J.
Published: March 2010

GST (glutathione transferase) is a dimeric enzyme recognized for biotransformation of xenobiotics and endogenous toxic compounds. In the present study, residues forming the hydrophobic substrate-binding site (H-site) of a Delta class enzyme were investigated in detail for the first time by site-directed mutagenesis and crystallographic studies. Enzyme kinetics reveal that Tyr111 indirectly stabilizes GSH binding, Tyr119 modulates hydrophobic substrate binding and Phe123 indirectly modulates catalysis. Mutations at Tyr111 and Phe123 also showed evidence for positive co-operativity for GSH and 1-chloro-2,4-dinitrobenzene respectively, strongly suggesting a role for these residues in manipulating subunit–subunit communication. In the present paper we report crystal structures of the wild-type enzyme, and two mutants, in complex with S-hexylglutathione. This study has identified an aromatic ‘zipper’ in the H-site contributing a network of aromatic π–π interactions. Several residues of the cluster directly interact with the hydrophobic substrate, whereas others indirectly maintain conformational stability of the dimeric structure through the C-terminal domain (domain II). The Y119E mutant structure shows major main-chain rearrangement of domain II. This reorganization is moderated through the ‘zipper’ that contributes to the H-site remodelling, thus illustrating a role in co-substrate binding modulation. The F123A structure shows molecular rearrangement of the H-site in one subunit, but not the other, explaining weakened hydrophobic substrate binding and kinetic co-operativity effects of Phe123 mutations. The three crystal structures provide comprehensive evidence of the aromatic ‘zipper’ residues having an impact upon protein stability, catalysis and specificity. Consequently, ‘zipper’ residues appear to modulate and co-ordinate substrate processing through permissive flexing.
Four probe architecture using high spatial resolution single multi-walled carbon nanotube electrodes for electrophysiology and bioimpedance monitoring of whole tissue
Authors: de Asis Edward D. , Leung Joseph , Wood Sally , Nguyen Cattien V.
Published: March 2010

We report the application of a sensor with a multielectrode architecture consisting of four single multiwalled carbon nanotube electrodes (sMWNT electrodes) with nanotube tip diameters of approximately 30 nm to stimulation, recording, and bioimpedance characterization of whole muscle. Parallel pairs of sMWNT electrodes achieve improved stimulation efficiency from a reduction in electrode impedance and enhanced signal-to-noise ratio by detecting endogenic signals from a larger population of electrically active cells. The sensor with a four sMWNT electrode configuration can monitor changes in whole tissue bioimpedance.
Generalization of symmetric α-stable Lévy distributions for q>1
Authors: Umarov Sabir , Tsallis Constantino , Gell-Mann Murray , Steinberg Stanly
Published: March 2010

The α-stable distributions introduced by Lévy play an important role in probabilistic theoretical studies and their various applications, e.g., in statistical physics, life sciences, and economics. In the present paper we study sequences of long-range dependent random variables whose distributions have asymptotic power-law decay, and which are called (q,α)-stable distributions. These sequences are generalizations of independent and identically distributed α-stable distributions and have not been previously studied. Long-range dependent (q,α)-stable distributions might arise in the description of anomalous processes in nonextensive statistical mechanics, cell biology, finance. The parameter q controls dependence. If q=1 then they are classical independent and identically distributed with α-stable Lévy distributions. In the present paper we establish basic properties of (q,α)-stable distributions and generalize the result of Umarov et al. [Milan J. Math. 76, 307 (2008)], where the particular case α=2,q∊[1,3) was considered, to the whole range of stability and nonextensivity parameters α∊(0,2] and q∊[1,3), respectively. We also discuss possible further extensions of the results that we obtain and formulate some conjectures.
Solid fraction in dendritic solidification of a liquid
Authors: Makkonen Lasse
Published: March 2010

When a liquid is cooled below its equilibrium solidification temperature the solidification takes place as growing dendrites of microscopic scale. An essential feature of the material formed this way is its solid fraction f, which is less than unity due to liquid entrapped between the solid dendrites. In this letter, f in directional solidification of a pure liquid is solved analytically showing that f is independent of the growth conditions. In this sense, this solidification process is self-regulating and f is a material parameter. For water, as an example, the ice fraction is 70% in agreement with experimental data.
Marshmallowing of nanopillar arrays by field emission
Authors: Qin Hua , Kim Hyun-Seok , Blick Robert H.
Published: March 2010

We fabricated nanoscale field electron emitters formed by highly-doped silicon nanopillars on a silicon membrane. Electron-beam induced deposition of carbon-based contaminants is employed as a probe of the spatial activity of electron emission from the nanopillars. In stark contrast to the general assumption that field emission only occurs at the tips of nanoscale emitters, we found strong emission from the sidewalls of the nanopillars. This is revealed by the deposition of carbon contaminants on these sidewalls, so that the nanopillars finally resemble marshmallows. We conclude that field emission from nanostructured surfaces is more intricate than previously expected.
Ab initio study of intrinsic, H, and He point defects in hcp-Er
Authors: Yang L. , Peng S. M. , Long X. G. , Gao F. , Heinisch H. L. , Kurtz R. J. , Zu X. T.
Published: March 2010

Ab initio calculations based on density functional theory have been performed to determine the properties of self-interstitial atoms (SIAs), vacancies, and single H and He atoms in hcp-Er. The results show that the most stable configuration for a SIA is a basal octahedral configuration, while the octahedral (O), basal split, and crowdion (C) interstitial configurations are less stable, followed by the split ⟨0001⟩ dumbbell and tetrahedral configurations. For both H and He defects, the formation energy of an interstitial atom is less than that of a substitutional atom in hcp-Er. Furthermore, the tetrahedral interstitial position is more stable than an octahedral position for both He and H interstitials. The hybridization of the He and H defects with Er atoms has been used to explain the relative stabilities of these defects in hcp-Er.
Heavily Ga-doped germanium layers produced by ion implantation and flash lamp annealing: Structure and electrical activation
Authors: Heera V. , Mücklich A. , Posselt M. , Voelskow M. , Wündisch C. , Schmidt B. , Skrotzki R. , Heinig K. H. , Herrmannsdörfer T. , Skorupa W.
Published: March 2010

Heavily p-type doped Ge layers were fabricated by 100 keV Ga implantation and subsequent flash lamp annealing for 3 ms in the temperature range between 700 and 900 °C. For comparison, some samples were annealed in a rapid thermal processor for 60 s. Ga fluences of 2×1015, 6×1015, and 2×1016 cm−2 were chosen in order to achieve Ga peak concentrations ranging from values slightly below the equilibrium solid solubility limit of 4.9×1020 cm−3 up to 3.5×1021 cm−3 which corresponds to a maximum Ga content of about 8 at. %. The structure of the doped layer and the Ga distribution were investigated by Rutherford backscattering spectrometry in combination with ion channeling, cross-sectional electron microscopy, and secondary ion mass spectrometry. Temperature dependent Hall effect measurements were carried out in order to determine the electrical properties of the Ga-doped Ge layers. It is shown that by flash lamp annealing Ga diffusion into the bulk can be completely avoided and the Ga loss by outdiffusion from the surface is reduced. The lowest sheet resistance of 36 Ω/sq. was achieved for the medium Ga concentration annealed at 900 °C. The best Ga activation values are 73%, 60%, and 24% for the three Ga fluences under investigation. The Ga activation is correlated with the layer regrowth. Incomplete epitaxial regrowth as observed in some samples leads to lower activation.
UV-visible-near infrared photoabsorption and photodetection using close-packed metallic gold nanoparticle network
Authors: Xie Xian Ning , Zhong Yu Lin , Dhoni Mohan S. , Xie Yilin , Loh Kian Ping , Sow Chorng Haur , Ji Wei , Wee Andrew Thye Shen
Published: March 2010

Photocurrent generation and photodetection are usually based on semiconductor crystals including Si, CdS, and PbS. This work reports the enhanced photoabsorption and photodetection of close-packed metallic Au nanoparticles (NPs) in the UV-VIS (visible)-NIR (near infrared) region. Photoabsorption in the UV-VIS regions is associated with the interband transition and surface plasmon resonance of AuNPs, while the enhanced NIR absorption is due to the collective effect of interacting AuNPs in the close-packed network. Consequently, the AuNPs exhibits photodetection behavior in the wavelength range of 300–1500 nm. It is proposed that the inter-AuNP photoejection and delocalization of electron-hole pairs changes the carrier lifetime and transit dynamics in favor of photocarrier conduction, thus significantly facilitating photocurrent generation in the metallic AuNP close-pack. Moreover, due to the power-law conduction mechanism in AuNP networks, the quantum yield of AuNPs can be tuned from 10−6 to 10−1 photoelectron/photon by increasing the bias voltage from 0 to 5 V. The AuNP quantum yield of 10−1 at 5 V is as high as that of commercial Si photodetectors at 0 V, and this demonstrates the immediate applicability of AuNPs in photodetection. In view of the compatibility of AuNPs with wet-chemistry and inkjet printing processes at low temperatures, metallic AuNPs may provide a convenient alternative to semiconductor crystals in photodetection and perhaps photovoltaic applications.
Modeling metallic nanoparticle synthesis in a magnetron-based nanocluster source by gas condensation of a sputtered vapor
Authors: Quesnel E , Pauliac-Vaujour E , Muffato V
Published: March 2010

Copper nanoparticles (NPs) were synthesized by inert-gas condensation of a sputtered metallic vapor using a dedicated commercial reactor. By controlling the time of residence of NPs in the carrier gas phase via the tuning of the collision path length, Cu NPs were produced. They exhibit various and well controlled diameters (3–10 nm) and a relatively narrow size dispersion. On the basis of these experimental results, a detailed modeling of NP nucleation and growth based on the classical nucleation theory was developed. It takes into account the peculiar geometry and thermal profile of the NP reactor. The simulated curves, calculated by a MATLAB® program developed for that purpose, exhibit a good qualitative agreement with experiment. Moreover, they highlight the role of process parameters and the strong influence of the reactor temperature profile on the NP size distribution. In the future, such calculations could be used for the optimization of the NP source design in order to increase its efficiency and reproducibility.
Characteristics of a magnetohydrodynamic electrical power generator using convexly divergent channel
Authors: Murakami Tomoyuki , Okuno Yoshihiro
Published: March 2010

We describe a magnetohydrodynamic (MHD) electrical power generator equipped with a convexly divergent channel, as determined through shock-tunnel-based experiments. The slight enhancement in a MHD channel divergence upstream provides boundary layer relief in a MHD flow decelerated by a retarding Lorentz force. Despite the present approach being simple and requiring a relatively minor modification of the MHD channel profile, the quality of MHD power-generating plasma and the energy conversion efficiency are improved compared to those from a previous linearly divergent channel; an excessive increase in static pressure is suppressed and a Hall field is enhanced, whereby notably high isentropic efficiency is achieved.
Mechanism of carbon nanostructure synthesis in arc plasma
Authors: Keidar M. , Shashurin A. , Volotskova O. , Raitses Y. , Beilis I. I.
Published: March 2010

Plasma enhanced techniques are widely used for synthesis of carbon nanostructures. The primary focus of this paper is to summarize recent experimental and theoretical advances in understanding of single-wall carbon nanotube (SWNT) synthesis mechanism in arcs, and to describe methods of controlling arc plasma parameters. Fundamental issues related to synthesis of SWNTs, which is a relationship between plasma parameters and SWNT characteristics are considered. It is shown that characteristics of synthesized SWNTs can be altered by varying plasma parameters. Effects of electrical and magnetic fields applied during SWNT synthesis in arc plasma are explored. Magnetic field has a profound effect on the diameter, chirality, and length of a SWNT synthesized in the arc plasma. An average length of SWNT increases by a factor of 2 in discharge with magnetic field and an amount of long nanotubes with the length above 5 μm also increases in comparison with that observed in the discharge without a magnetic field. In addition, synthesis of a few-layer graphene in a magnetic field presence is discovered. A coupled model of plasma-electrode phenomena in atmospheric-pressure anodic arc in helium is described. Calculations indicate that substantial fraction of the current at the cathode is conducted by ions (0.7–0.9 of the total current). It is shown that nonmonotonic behavior of the arc current-voltage characteristic can be reproduced taking into account the experimentally observed dependence of the arc radius on arc current.
Instrument for near infrared emission spectroscopic probing of human fingertips in vivo
Authors: Chaiken J. , Deng Bin , Bussjager Rebecca J. , Shaheen George , Rice David , Stehlik Dave , Fayos John
Published: March 2010

We present instrumentation for probing of volar side fingertip capillary beds with free space coupled near infrared light while collecting Raman, Rayleigh, and Mie scattered light as well as fluorescence. Fingertip skin capillary beds are highly vascularized relative to other tissues and present a desirable target for noninvasive probing of blood. But human hands and fingers in particular are also highly idiosyncratic body parts requiring specific apparatus to allow careful and methodical spectoscopic probing. The apparatus includes means for precise and reproducible placement of the tissues relative to the optical aperture. Appropriate means are provided for applying and maintaining pressure to keep surface tissues immobile during experiments while obtaining the desired blood content and flow. Soft matter, e.g., skin, extrudes into the aperture in response to any applied pressure, e.g., to keep the tissue in registration with the optical system, so the position, contact area, pressure, and force are continuously measured and recorded to produce feedback for an actuator applying force and to discern the compliance of the test subject. The compliance strongly affects the reliability of the measurement and human factors must be adequately managed in the case of in vivo probing. The apparatus produces reproducible observations and measurements that allow consistent probing of the tissues of a wide range of skin types.
Effect of ion bombardment on the field emission property of tetrapod ZnO
Authors: Cui Yunkang , Zhang Xiaobing , Lei Wei , Di Yunsong , Wang Jinchan , Yang Xiaxi
Published: March 2010

The influences of ion bombardment on the field emission performance of tetrapod ZnO nanostructures are reported. As the scanning electron microscopy images and photoluminescence spectrum show, the tips of the field emitters are destroyed and the surface state of the field emitters is also changed after the ion bombardment. The ion bombardment has a considerable effect on the field emission properties of the tetrapod ZnO field emitters. After Ar+ ion bombardment with the energy of 3 keV and the ion current of 0.05 μA for 30 min, the turn-on field increases about 63% and the threshold field increases about 77%, respectively. There are two main reasons for the variation in field-emission property: (1) the decrement of the field enhancement factor β, which is caused by the variation in morphology of field emitter; (2) the increment of work function φ, which is caused by the changed concentration of the surface oxygen vacancy.
Dissociative electron attachment in nonplanar chlorocarbons with π∗/σ∗-coupled molecular orbitals
Authors: Aflatooni K. , Gallup G. A. , Burrow P. D.
Published: March 2010

Total absolute cross sections for the dissociative electron attachment (DEA) process are reported for a series of nonplanar ethylenic and phenylic compounds monosubstituted with (CH2)nCl groups, where n=1–4. Coupling between the local π∗ molecular orbitals provided by the unsaturated moieties and the σ∗ (C–Cl) orbital is thus examined as a function of the separation of these groups. In particular, the coupling is viewed from the perspective of the interacting temporary negative ions formed by short lived occupation of these orbitals and their decay into the DEA channel. A theoretical treatment of “remote” bond breaking, presented elsewhere, satisfactorily accounts for DEA in the chloroethylenic compounds presented here and emphasizes not only the delocalization of the coupled anionic wave functions but the importance of their relative phases. The dependence of the cross sections on the vertical attachment energies, measured by electron transmission spectroscopy, is also explored and compared to that found previously in chlorinated alkanes.
Transient thermoreflectance imaging of active photonic crystals
Authors: Moreau Virginie , Tessier Gilles , Raineri Fabrice , Brunstein Maia , Yacomotti Alejandro , Raj Rama , Sagnes Isabelle , Levenson Ariel , De Wilde Yannick
Published: March 2010

Transient thermoreflectance imaging is used to study the dynamics of the temperature inside active two-dimensional photonic crystals (PhCs). We developed a pump-probe setup suited for optically pumped devices that presents submicrosecond time resolution and submicrometer spatial resolution. Characteristic thermal dissipation times of 429 ns in a PhC Bloch mode cavity and of 999 ns in a PhC membrane are measured. This technique gives also access to the diffusivity of the suspended PhC.
Position-dependent coupling between a channel waveguide and a distorted microsphere resonator
Authors: Senthil Murugan Ganapathy , Panitchob Yuwapat , Tull Elizabeth J. , Bartlett Philip N. , Hewak Daniel W. , Zervas Michalis N. , Wilkinson James S.
Published: March 2010

Glass microsphere resonators have the potential to add significant functionality to planar lightwave circuits when coupled to waveguides where they can provide wavelength filtering, delay and low-power switching, and laser functions. Design of such photonic circuits requires precise coupling between spheres and waveguides to allow control of Q-factor and hence of stored energy and resonator bandwidth. In this paper an erbium-doped silicate glass microsphere is coupled to an ion-exchanged glass waveguide, and excitation spectra for the sphere whispering-gallery modes are determined as a function of spatial separation. Modal assignment allows extraction of the physical parameters of the microsphere and the dependence of Q-factor with separation is compared with theory. All practical microspheres exhibit a small degree of ellipticity and the effects of this upon whispering-gallery mode excitation and wavelength splitting are explored. It has been shown that appropriate displacement and orientation of slightly deformed microspheres with respect to the waveguide can be used to control the effective Q-factor and optimize the spectral shape of the optical devices. This can result in either single high-Q peaks or substantially broadened and spectrally flattened resonances.
Dynamics and spectroscopy of vibrational overtone excited glyoxylic acid and 2,2-dihydroxyacetic acid in the gas-phase
Authors: Takahashi Kaito , Plath Kathryn L. , Axson Jessica L. , Nelson Galen C. , Skodje Rex T. , Vaida Veronica
Published: March 2010

The early time dynamics of vibrationally excited glyoxylic acid and of its monohydrate 2,2-dihydroxyacetic acid are investigated by theoretical and spectroscopic methods. A combination of “on-the-fly” dynamical simulations and cavity ring-down spectroscopy on the excited O–H stretching vibrational levels of these molecules observed that conformers that possess the correct structure and orientation react upon excitation of ΔυOH=4,5, while the structurally different but near isoenergetic conformers do not undergo unimolecular decay by the same direct and fast process. Experiment and theory give a femtosecond time scale for hydrogen atom chattering in the vibrationally excited glyoxylic acid. This process is the precursor for the concerted decarboxylation of the ketoacid. We extrapolate the results obtained here to suggest a rapid subpicosecond overall reaction. In these light-initiated reactions, relatively cold hydroxycarbenes, stable against further unimolecular decay, are expected products since most of the excitation energy is consumed by the endothermicity of the reaction. Glyoxylic acid and its monohydrate are atmospherically relevant ketoacids. The vibrational overtone initiated reactions of glyoxylic acid leading to di- and monohydroxycarbenes on subpicosecond time scales are potentially of importance in atmospheric chemistry since the reaction is sufficiently rapid to avoid collisional dissipation.
Directed transport driven by Lévy flights coexisting with subdiffusion
Authors: Ai Bao-quan , He Ya-feng
Published: March 2010

Transport of the Brownian particles driven by Lévy flights coexisting with subdiffusion in asymmetric periodic potentials is investigated in the absence of any external driving forces. Using the Langevin-type dynamics with subordination techniques, we obtain the group velocity which can measure the transport. It is found that the group velocity increases monotonically with the subdiffusive index and there exists an optimal value of the Lévy index at which the group velocity takes its maximal value. There is a threshold value of the subdiffusive index below which the ratchet effects will disappear. The nonthermal character of the Lévy flights and the asymmetry of the potential are necessary to obtain the directed transport. Some peculiar phenomena induced by the competition between Lévy flights and subdiffusion are also observed. The pseudonormal diffusion will appear on the level of the median.
Ab initio approach to the electronic properties of sodium-ammonia clusters: Comparison with ammonia clusters
Authors: Almeida T. S. , Cabral B. J. Costa
Published: March 2010

Ab initio results for the electronic properties of sodium-ammonia [Na(NH3)n;n=1–8] and the corresponding ionized structures [Na+(NH3)n] are reported and compared with those for neutral ammonia clusters [(NH3)n]. Emphasis was placed on the analysis of polarization effects and calculation of vertical and adiabatic ionization potentials. The theoretical discussion is based on second order Møller–Plesset perturbation theory and Green’s function or electron propagator theory calculations. Our results for the ionization energies (IEs) of Na(NH3)n clusters are in very good agreement with experimental information. The relationship between the dependence of the IEs on the number of ammonia molecules (n), polarization effects, and hydrogen bond formation is investigated. The presence of a hydrogen bond acceptor-only ammonia molecule that binds a delocalized excess electron in Na(NH3)6–7 clusters is discussed.
Co-concentration dependence of half-metallic properties in Co–Mn–Si epitaxial films
Authors: Sakuraba Y. , Hirose N. , Oogane M. , Nakamura T. , Ando Y. , Takanashi K.
Published: March 2010

Co-enriched Co2MnSi epitaxial films, i.e., Co2(1+x)Mn1−xSi1−x (CCMS) were fabricated to investigate the Co-concentration dependence of half-metallicity in a Co–Mn–Si Heusler alloy. The tunnel magnetoresistance ratio in the magnetic tunnel junctions with a CCMS electrode slightly reduces with x from −0.02 to 0.13, then suddenly drops at x=0.20. The half-metallic gap in the G-V curve also disappears when x becomes 0.20. The multiplet structure in x-ray magnetic circular dichroism spectra around Co L-edges, implying half-metallicity of CCMS, also vanishes at x=0.20. These results consistently indicate the half-metallic nature of CCMS is destroyed when the Co atomic concentration is over 57 at. %.
Large enhancement of anisotropic magnetoresistance and thermal stability in Ta/NiFe/Ta trilayers with interfacial Pt addition
Authors: Liu Y. F. , Cai J. W. , Sun L.
Published: March 2010

Ta/NiFe/Ta trilayers, extensively used for anisotropic magnetoresistance (AMR) sensors, exhibit severely reduced MR ratio at small NiFe thickness and appreciable moment loss, especially after annealing. By inserting ultrathin Pt layers at the interfaces of the trilayers, AMR can be significantly enhanced for thin NiFe films due to the strong electron spin-orbit scattering at Pt/NiFe interfaces along with suppression of interfacial magnetic dead layers. Furthermore, the Pt layers also reduce Ta and NiFe interdiffusion and result in negligible moment loss and AMR degradation after annealing at 350 °C.
Communications: Classical trajectory study of the postquenching dynamics of OH A ∑2+ by H2 initiated at conical intersections
Authors: Kamarchik Eugene , Fu Bina , Bowman Joel M.
Published: March 2010

We report results of a classical trajectory calculation of the postquenching dynamics of OH A ∑2+ by H2. This is done by performing roughly 100 000 trajectories at previously identified conical intersections (CoIs) [B. C. Hoffman and D. R. Yarkony, J. Chem. Phys. 113, 10091 (2000)]. The initial momenta are sampled fully and partially microcanonically, corresponding to “adiabatic” and “diabatic” model of the dynamics, respectively. The trajectories are propagated on a new ground state ab initio-based potential energy surface. This surface is a permutationally invariant fit to roughly 23 000 electronic energies (multireference configuration interaction/correlation-consistent-augmented-triple-zeta basis) at configurations obtained mostly from direct-dynamics calculations (complete active space second order perturbation theory with correlation-consistent-augment double-zeta basis), also initiated at the CoIs. Final rovibrational state distributions of the ground electronic state OH product and the H-atom translational energy distributions for abstraction and insertion mechanisms are calculated and compared to experimental ones. Agreement for these observable quantities is good. The branching between reactive and nonreactive quenching is sensitive to the momenta sampling; very good agreement with experiment is obtained using the diabatic sampling but not with the adiabatic sampling. The calculated H2 rovibrational distributions (not measured experimentally) are also presented.
Influence of 4f electronic states on the surface states of rare-earth hexaborides
Authors: Patil Swapnil , Adhikary Ganesh , Balakrishnan Geetha , Maiti Kalobaran
Published: March 2010

We study the surface electronic structure of a series of rare-earth hexaborides using state-of-the-art high resolution photoemission spectroscopy. Experimental results reveal a surface state around 1.8 eV binding energy in all the hexaborides indicating its generic nature in this class of compounds. The surface and bulk electronic structures near the Fermi level, ϵF are almost similar in each of the compounds. This suggests an interesting possibility of fabricating new materials possessing low work function like LaB6 where the behavior of mobile electrons can be tuned by rare-earth substitutions.
A level set based approach for modeling oxidation processes of ligand stabilized metallic nanoparticles
Authors: Auge A. , Weddemann A. , Vogel B. , Wittbracht F. , Hütten A.
Published: March 2010

The oxidation behavior of metallic nanoparticles is investigated in respect to ligand influences. The nanoparticle oxidation is modeled in a shell-core approach. The shell represents oxidation of surface atoms modeled by Johnson–Mehl–Avrami–Kolmogorov equations for isothermal growth. The oxidation of the nanoparticle core is described by a model introduced by Cabrera and Mott [Rep. Prog. Phys. 12, 163 (1949)]. In order to investigate the ligand influence one single parameter is introduced for both surface and bulk oxidation. The growth of the oxide layer is simulated in a level set framework via finite element methods. The theoretical results are compared to experimental findings of Kanninen et al. [J. Coll. Interf. Sci. 318, 88 (2008)].