bluuebunny/crossref_metadata_2025 huggingface dataset:
Electromagnetic and absorption properties of urchinlike Ni composites at microwave frequencies
Authors: Liu T. , Zhou P. H. , Xie J. L. , Deng L. J.
Published: May 2012

In this paper, nearly monodispersed urchinlike Ni powders were synthesized by a simple hydrogen-thermal reduction method. Electromagnetic and absorption characteristics were then investigated at 0.5–18 GHz. The permeability spectra present four resonance peaks over the whole frequency range. The resonance absorption property was discussed by fitting the permeability spectrum using the well-known Landau-Lifshitz-Gilbert equation and Maxwell-Garnett mixing rule. Correspondingly, the magnetic loss of the first band observed is attributed to the natural resonance, while the other three bands are considered to originate from non-uniform exchange resonance in the permeability spectra. The maximum reflection loss can reach −43 dB at about 10 GHz with 2 mm in absorber thickness.
Effects of hydrogen, oxygen, and argon annealing on the electrical properties of ZnO and ZnO devices studied by current-voltage, deep level transient spectroscopy, and Laplace DLTS
Authors: Mtangi W. , Auret F. D. , Meyer W. E. , Legodi M. J. , Janse van Rensburg P. J. , Coelho S. M. M. , Diale M. , Nel J. M.
Published: May 2012

Effects of annealing ZnO in hydrogen, oxygen, and argon have been investigated using deep level transient spectroscopy (DLTS) and Laplace-DLTS (LDLTS) measurements. Current-voltage (IV) measurements indicate a decrease in zero–bias barrier height for all the annealed samples. Conventional DLTS measurements reveal the presence of three prominent peaks in the un-annealed and annealed samples. A new peak with an activation enthalpy of 0.60 eV has been observed in the H2 annealed samples, while an estimated energy level of 0.67 eV has been observed in Ar annealed samples. O2 annealing does not introduce new peaks but causes a decrease in the concentration of the E3 peak and an increase in concentration of the E1 peak. The concentrations of all the intrinsic defects have decreased after H2 and Ar annealing; with Ar annealing giving peaks with the lowest concentrations. The E2 peak anneals out after annealing ZnO in Ar and H2 at 300 °C. From the annealing behaviour of E3, we have attributed to transition metal ion related defects, while E4 has been explained as a defect, whose formation favours oxygen deficient conditions. Laplace DLTS has successfully been employed to resolve the closely spaced energy levels in the E4 peak, splitting it into three peaks with energy levels, 0.68 eV, 0.58 eV, and 0.50 eV below the minimum of the conduction band for the Ar annealed sample.
Effect of Si-induced defects on 1 µm absorption losses in laser-grade YAG ceramics
Authors: Gaume R. , He Y. , Markosyan A. , Byer R. L.
Published: May 2012

High sensitivity optical absorption at 1 µm was measured in 40 undoped and Nd-doped Y3Al5O12 (YAG) transparent ceramics and single crystals using photothermal common-path interferometry. Concurrently, chemical trace analysis was performed on those samples by glow discharge mass-spectroscopy. Silicon and calcium were found to be the major impurities with concentrations up to 250 wt. ppm. A univocal linear correlation between the Si content and the absorption loss at 1 µm is revealed and a possible mechanism for the formation of Si-induced color centers based on a bound polaron model is discussed. Solutions to reduce this optical absorption in ceramics are also proposed.
Direct hole and delayed electron capture on a picosecond timescale by Eu2+ centers in CaGa2S4 monitored by synchroscan with horizontal blanking
Authors: Louwers D. J. , Takizawa T. , Hidaka C. , van der Kolk E.
Published: May 2012

A Eu2+ concentration and temperature dependent energy transfer study from the host lattice to Eu2+ luminescence centers in Ca(1–x)EuxGa2S4 (x = 0.001 to 0.05) was performed with a special streak camera that combines the high timing resolution of a conventional synchroscan operation (<2 ps) with the ability to study long lived states (10 ns − 1 ms) typical for rare earth and transition metal ions. Two transfer mechanisms from the CaGa2S4 host lattice to the Eu2+ ions were identified. A fast transfer process (<4 ps) is interpreted as sequential hole-electron capture by the Eu2+ ions, and slower process (>1 ns) is interpreted as the sequential capture of a hole and an electron by Eu2+ but with the electron first entering an intermediate state trapped near Eu3+. Energy transfer via a self-trapped excitonic (STE) state is unlikely because of the absence of an anti-correlation between the STE decay-time and the Eu2+ rise-time as well as between the STE emission intensity and the Eu2+ intensity. All rise-time spectra were successfully fitted with a model representing the above transfer mechanisms.
Intrinsic stress in ZrN thin films: Evaluation of grain boundary contribution from in situ wafer curvature and ex situ x-ray diffraction techniques
Authors: Koutsokeras L. E. , Abadias G.
Published: May 2012

Low-mobility materials, like transition metal nitrides, usually undergo large residual stress when sputter-deposited as thin films. While the origin of stress development has been an active area of research for high-mobility materials, atomistic processes are less understood for low-mobility systems. In the present work, the contribution of grain boundary to intrinsic stress in reactively magnetron-sputtered ZrN films is evaluated by combining in situ wafer curvature measurements, providing information on the overall biaxial stress, and ex situ x-ray diffraction, giving information on elastic strain (and related stress) inside crystallites. The thermal stress contribution was also determined from the in situ stress evolution during cooling down, after deposition was stopped. The stress data are correlated with variations in film microstructure and growth energetics, in the 0.13–0.42 Pa working pressure range investigated, and discussed based on existing stress models. At low pressure (high energetic bombardment conditions), a large compressive stress is observed due to atomic peening, which induces defects inside crystallites but also promotes incorporation of excess atoms in the grain boundary. Above 0.3–0.4 Pa, the adatom surface mobility is reduced, leading to the build-up of tensile stress resulting from attractive forces between under-dense neighbouring column boundary and possible void formation, while crystallites can still remain under compressive stress.
Determination of the singlet state lifetime of dissolved nitrous oxide from high field relaxation measurements
Authors: Ghosh Rajat K. , Kadlecek Stephen J. , Kuzma Nicholas N. , Rizi Rahim R.
Published: May 2012

Longitudinal spin relaxation due to modulation of dipolar interactions often limits the development of hyperpolarized magnetic tracers. Recently, it has been demonstrated that transferring spin order to a singlet state significantly increases the polarization lifetimes in systems where nitrous oxide is dissolved in a liquid solvent. Additionally, previous studies have suggested that the longitudinal relaxation of nitrous oxide is largely dominated by the spin-rotation interaction. Models of spin-relaxation under Brownian motion naïvely predict the angular momentum reorienting correlation time of the spin rotation interaction to be inversely proportional to the viscosity of the solution. This dependence implies the singlet lifetime can be lengthened by increasing the dissolving solvent's viscosity—an extension which is not observed. Our work formulates a model which describes the relaxation of nitrous oxide dissolved in various solvents. We investigate the effect of altering the temperature of the solvent, as well as the effect of varying solute-solvent interactions on the singlet state as well as the longitudinal polarization lifetime. We predict the singlet lifetime for nitrous oxide dissolved in several solvents by fitting rotational and angular momentum correlation times measured at high magnetic field, and relate singlet relaxation to translational diffusion constants.
Optical properties of armchair graphene nanoribbons embedded in hexagonal boron nitride lattices
Authors: Nematian Hamed , Moradinasab Mahdi , Pourfath Mahdi , Fathipour Morteza , Kosina Hans
Published: May 2012

Transition rules and optical properties of armchair graphene nanoribbons embedded in hexagonal boron nitride lattices are studied for the first time. Based on tight binding calculations considering first and second nearest neighbors, we show that the optical transition rules of such structures are completely different from that of conventional graphene nanoribbons. These rules are explained by the symmetry properties of the subband wave functions. The optical spectrum, the quantum efficiency, and the photoresponsivity of different nanoribbons are evaluated and their application in photodetector devices is investigated. The results are verified with first principles calculations.
Thermoelectric properties of tungsten-substituted Heusler Fe2VAl alloy
Authors: Mikami M. , Kinemuchi Y. , Ozaki K. , Terazawa Y. , Takeuchi T.
Published: May 2012

A Heusler Fe2V1-xWxAl sintered alloy was synthesized to evaluate the effect of W substitution on thermoelectric properties of the Heusler alloy. The Seebeck coefficient and the electrical conductivity are simultaneously enhanced through electron injection resulting from the W substitution. Comparison with the Si-substituted Fe2VAl alloy reveals that the additional electronic states derived from W 5d orbital in the vicinity of pseudogap are likely to degrade the Seebeck coefficient. Thermal conductivity is effectively reduced by the W substitution because of the large atomic mass and volume of W compared to the constituent elements of Fe2VAl alloy. The appreciable reduction of thermal conductivity, without a serious deterioration in electrical conduction, enhances the thermoelectric figure of merit in the Heusler alloy.
Light-induced off-diagonal thermoelectric effect via indirect optical heating of incline-oriented CaxCoO2 thin film
Authors: Takahashi Kouhei , Kanno Tsutomu , Sakai Akihiro , Adachi Hideaki , Yamada Yuka
Published: May 2012

Light-induced off-diagonal thermoelectric (ODTE) effect has been investigated in CaxCoO2 thin film coupled with a gold black light absorption layer. Increased light absorption at the gold black layer resulted in considerable enhancement of the steady-state thermoelectric voltage from the CaxCoO2 film upon continuous light heating. However, we found that the indirect optical heating process highly deteriorates the input thermal energy pulse in time-domain, and leads to significant reduction in the transient voltage generated upon pulsed light heating. The result manifests the importance of adequate thermal design of absorption layers for fabrication of light detection devices based on the ODTE effect.
Identification of device degradation positions in multi-layered phosphorescent organic light emitting devices using water probes
Authors: Yamamoto Hitoshi , Adachi Chihaya , Weaver Michael S. , Brown Julie J.
Published: May 2012

We exposed regions of green phosphorescent organic light emitting devices (PHOLEDTMs) consisting of a fac-tris(2-phenylpyridine)iridium (Ir(ppy)3) as the phosphorescent emitter to a partial pressure of water of 3 × 10−4 Pa during device fabrication to induce degradation in a specific region of the multi-layered devices. We identified the interface between the hole transport layer and the emissive layer as the most susceptive region to degradation. We discuss the luminance loss mechanism and estimate an operational lifetime of 10 000 h, after 20% loss of the initial luminance from 1000 cd/m2, is attainable from an Ir(ppy)3 PHOLED fabricated under ultra-high vacuum conditions.
Reduced longitudinal optical phonon-exciton interaction in InGaN/GaN nanorod structures
Authors: Renwick P. , Tang H. , Bai J. , Wang T.
Published: May 2012

Photoluminescence measurements have been performed on a series of InGaN/GaN multiple quantum well (MQW) nanorod array structures in order to investigate the influence of a nanorod structure on longitudinal optical (LO) phonon-exciton interaction. The nanorod array structures were fabricated on InGaN/GaN MQW epi-wafers using a self-organised Ni nano-mask technique. Compared with their corresponding as-grown samples, all the nanorod structures exhibit a significant reduction in Huang-Rhys factor, indicating a reduced coupling between LO-phonon and exciton. This is attributed to strain relaxation as a result of being fabricated into nanorod structures. Our excitation power dependent measurements have demonstrated that the nanorod structures exhibit a clear reduction in efficiency droop at a high excitation power. This proves a theoretical prediction previously reported, namely, LO-phonon-exciton coupling contributes to an indirect Auger recombination, leading to the efficiency droop of InGaN/GaN based emitters. The nanorod structures offering a reduced phonon-exciton coupling can pave the way for reducing or eliminating efficiency droop, one of the major challenges in the field of III-nitride optoelectronics.
Critical-current reduction in thin superconducting wires due to current crowding
Authors: Hortensius H. L. , Driessen E. F. C. , Klapwijk T. M. , Berggren K. K. , Clem J. R.
Published: May 2012

We demonstrate experimentally that the critical current in superconducting NbTiN wires is dependent on their geometrical shape, due to current-crowding effects. Geometric patterns such as 90∘ corners and sudden expansions of wire width are shown to result in the reduction of critical currents. The results are relevant for single-photon detectors as well as parametric amplifiers.
The transformations between N = 2 supersymmetric Korteweg-de Vries and Harry Dym equations
Authors: Tian Kai , Liu Q. P.
Published: May 2012

The N = 2 supercomformal transformations are employed to study supersymmetric integrable systems. It is proved that two known N = 2 supersymmetric Harry Dym equations are transformed into two N = 2 supersymmetric modified Korteweg-de Vries equations, thus are connected with two N = 2 supersymmetric Korteweg-de Vries equations.
Influence of laser lift-off on optical and structural properties of InGaN/GaN vertical blue light emitting diodes
Authors: Doan M. H. , Kim S. , Lee J. J. , Lim H. , Rotermund F. , Kim Kihong
Published: May 2012

The influences of the laser lift-off (LLO) process on the InGaN/GaN blue light emitting diode (LED) structures, grown on sapphire substrates by low-pressure metalorganic chemical vapor deposition, have been comprehensively investigated. The vertical LED structures on Cu carriers are fabricated using electroplating, LLO, and inductively coupled plasma etching processes sequentially. A detailed study is performed on the variation of defect concentration and optical properties, before and after the LLO process, employing high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM) observations, cathodoluminescence (CL), photoluminescence (PL), and high-resolution X-ray diffraction (HRXRD) measurements. The SEM observations on the distribution of dislocations after the LLO show well that even the GaN layer near to the multiple quantum wells (MQWs) is damaged. The CL measurements reveal that the peak energy of the InGaN/GaN MQW emission exhibits a blue-shift after the LLO process in addition to a reduced intensity. These behaviors are attributed to a diffusion of indium through the defects created by the LLO and creation of non-radiative recombination centers. The observed phenomena thus suggest that the MQWs, the active region of the InGaN/GaN light emitting diodes, may be damaged by the LLO process when thickness of the GaN layer below the MQW is made to be 5 μm, a conventional thickness. The CL images on the boundary between the KrF irradiated and non-irradiated regions suggest that the propagation of the KrF laser beam and an accompanied recombination enhanced defect reaction, rather than the propagation of a thermal shock wave, are the main origin of the damage effects of the LLO process on the InGaN/GaN MQWs and the n-GaN layer as well.
Arsenic speciation in food chains from mid-Atlantic hydrothermal vents
Authors: Taylor Vivien F. , Jackson Brian P. , Siegfried Matthew R. , Navratilova Jana , Francesconi Kevin A. , Kirshtein Julie , Voytek Mary
Published: May 2012

Environmental contextArsenic occurs in marine organisms at high levels and in many chemical forms. A common explanation of this phenomenon is that algae play the central role in accumulating arsenic by producing arsenic-containing sugars that are then converted into simpler organic arsenic compounds found in fish and other marine animals. We show that animals in deep-sea vent ecosystems, which are uninhabited by algae, contain the same organic arsenic compounds as do pelagic animals, indicating that algae are not the only source of these compounds.
AbstractArsenic concentration and speciation were determined in benthic fauna collected from the Mid-Atlantic Ridge hydrothermal vents. The shrimp species, Rimicaris exoculata, the vent chimney-dwelling mussel, Bathymodiolus azoricus, Branchipolynoe seepensis, a commensal worm of B. azoricus and the gastropod Peltospira smaragdina showed variations in As concentration and in stable isotope (δ13C and δ15N) signature between species, suggesting different sources of As uptake. Arsenic speciation showed arsenobetaine to be the dominant species in R. exoculata, whereas in B. azoricus and B. seepensis arsenosugars were most abundant, although arsenobetaine, dimethylarsinate and inorganic arsenic were also observed, along with several unidentified species. Scrape samples from outside the vent chimneys covered with microbial mat, which is a presumed food source for many vent organisms, contained high levels of total As, but organic species were not detectable. The formation of arsenosugars in pelagic environments is typically attributed to marine algae, and the pathway to arsenobetaine is still unknown. The occurrence of arsenosugars and arsenobetaine in these deep sea organisms, where primary production is chemolithoautotrophic and stable isotope analyses indicate food sources are of vent origin, suggests that organic arsenicals can occur in a foodweb without algae or other photosynthetic life.
Climate-change induced tropicalisation of marine communities in Western Australia
Authors: Cheung William W. L. , Meeuwig Jessica J. , Feng Ming , Harvey Euan , Lam Vicky W. Y. , Langlois Tim , Slawinski Dirk , Sun Chaojiao , Pauly Daniel
Published: May 2012

A major observed and predicted impact of climate change on marine species is the poleward shift in their distributions and the resulting changes in community structure. Here, we used a Dynamic Bioclimate Envelope Model to project range shift of exploited marine fishes and invertebrates in Western Australia. We combined published data and expert knowledge to predict current species distributions for 30 tropical, sub-tropical and temperate species that occur along the coast of Western Australia. Using outputs from both a Regional Oceanographic Model and a Global Circulation Model, we simulated change in the distribution of each species. Our study shows that under the SRES (Special Report for Emission Scenarios) A1B scenario, the median rate of distribution shift is around 19 km decade–1 towards higher latitudes and 9 m deeper decade–1 by 2055 relative to 2005. As a result, species gains and losses are expected along the south coast and north coast of Western Australia, respectively. Also, the coast of Western Australia is expected to experience a ‘tropicalisation’ of the marine community in the future, with increasing dominance of warmer-water species. Such changes in species assemblages may have large ecological and socio-economic implications through shifts in fishing grounds and unexpected trophic effects.
Morphometry and population structure of non-harvested and harvested populations of the Japanese red coral (Paracorallium japonicum) off Amami Island, southern Japan
Authors: Iwasaki Nozomu , Fujita Toshihiko , Bavestrello Giorgio , Cattaneo-Vietti Riccardo
Published: May 2012

Precious coral harvested in the Mediterranean Sea and the northern Pacific Ocean is of commercial value yet excessive fishing has led to a serious decline in its abundance. Consequently, there is now international discussion about controlling the world trade of precious coral. To explore the possibility of a sustainable fishery of Japanese red coral (Paracorallium japonicum), the morphometry and the population structure of populations in a non-harvested area and in a harvested area were investigated using a remotely operated vehicle (ROV) off Amami Island, Southern Japan, in 2009. In the harvested population, the estimated modal ages are 10 to 20 years. In contrast, the main mode in the non-harvested population extends widely from 20 to 40 years, with a small but distinct secondary mode between 50 and 60 years. Commercially collected specimens are mainly 30–40 years old. The difference in the modes of non-harvested and harvested populations suggests that harvested populations return to the pre-fishing level after at least 10–20 years of a biological rest period. This study indicates a rotational harvest is useful for sustainable management.
A
Sleeping Beauty
mutagenesis screen reveals a tumor suppressor role for
Ncoa2/Src-2
in liver cancer
Authors: O’Donnell Kathryn A. , Keng Vincent W. , York Brian , Reineke Erin L. , Seo Daekwan , Fan Danhua , Silverstein Kevin A. T. , Schrum Christina T. , Xie Wei Rose , Mularoni Loris , Wheelan Sarah J. , Torbenson Michael S. , O’Malley Bert W. , Largaespada David A. , Boeke Jef D.
Published: May 2012

The
Sleeping Beauty
(
SB
) transposon mutagenesis system is a powerful tool that facilitates the discovery of mutations that accelerate tumorigenesis. In this study, we sought to identify mutations that cooperate with
MYC
, one of the most commonly dysregulated genes in human malignancy. We performed a forward genetic screen with a mouse model of MYC-induced liver cancer using SB-mediated mutagenesis. We sequenced insertions in 63 liver tumor nodules and identified at least 16 genes/loci that contribute to accelerated tumor development. RNAi-mediated knockdown in a liver progenitor cell line further validate three of these genes,
Ncoa2/Src-2, Zfx,
and
Dtnb
, as tumor suppressors in liver cancer. Moreover, deletion of
Ncoa2/Src-2
in mice predisposes to diethylnitrosamine-induced liver tumorigenesis. These findings reveal genes and pathways that functionally restrain MYC-mediated liver tumorigenesis and therefore may provide targets for cancer therapy.
Molecular architecture of chemoreceptor arrays revealed by cryoelectron tomography of
Escherichia coli
minicells
Authors: Liu Jun , Hu Bo , Morado Dustin R. , Jani Sneha , Manson Michael D. , Margolin William
Published: May 2012

The chemoreceptors of
Escherichia coli
localize to the cell poles and form a highly ordered array in concert with the CheA kinase and the CheW coupling factor. However, a high-resolution structure of the array has been lacking, and the molecular basis of array assembly has thus remained elusive. Here, we use cryoelectron tomography of flagellated
E. coli
minicells to derive a 3D map of the intact array. Docking of high-resolution structures into the 3D map provides a model of the core signaling complex, in which a CheA/CheW dimer bridges two adjacent receptor trimers via multiple hydrophobic interactions. A further, hitherto unknown, hydrophobic interaction between CheW and the homologous P5 domain of CheA in an adjacent core complex connects the complexes into an extended array. This architecture provides a structural basis for array formation and could explain the high sensitivity and cooperativity of chemotaxis signaling in
E. coli
.
Lysine
63
-linked ubiquitylation of PIN2 auxin carrier protein governs hormonally controlled adaptation of
Arabidopsis
root growth
Authors: Leitner Johannes , Petrášek Jan , Tomanov Konstantin , Retzer Katarzyna , Pařezová Markéta , Korbei Barbara , Bachmair Andreas , Zažímalová Eva , Luschnig Christian
Published: May 2012

Cross-talk between plant cells and their surroundings requires tight regulation of information exchange at the plasma membrane (PM), which involves dynamic adjustments of PM protein localization and turnover to modulate signal perception and solute transport at the interface between cells and their surroundings. In animals and fungi, turnover of PM proteins is controlled by reversible ubiquitylation, which signals endocytosis and delivery to the cell’s lytic compartment, and there is emerging evidence for related mechanisms in plants. Here, we describe the fate of
Arabidopsis
PIN2 protein, required for directional cellular efflux of the phytohormone auxin, and identify
cis
- and
trans
-acting mediators of PIN2 ubiquitylation. We demonstrate that ubiquitin acts as a principal signal for PM protein endocytosis in plants and reveal dynamic adjustments in PIN2 ubiquitylation coinciding with variations in vacuolar targeting and proteolytic turnover. We show that control of PIN2 proteolytic turnover via its ubiquitylation status is of significant importance for auxin distribution in root meristems and for environmentally controlled adaptations of root growth. Moreover, we provide experimental evidence indicating that PIN2 vacuolar sorting depends on modification specifically by lysine
63
-linked ubiquitin chains. Collectively, our results establish lysine
63
-linked PM cargo ubiquitylation as a regulator of polar auxin transport and adaptive growth responses in higher plants.
The Role of Streamflow and Land Use in Limiting Oversummer Survival of Juvenile Steelhead in California Streams
Authors: Grantham Theodore E. , Newburn David A. , McCarthy Michael A. , Merenlender Adina M.
Published: May 2012

Increasing human pressures on freshwater resources have led to global declines in fish populations and have made the protection of instream flows critical to the conservation of riverine ecosystems. However, uncertainty in predicting ecological responses to flow variability has hindered implementation of successful environmental flow management. An improved understanding of the relationships between streamflows and Pacific salmon Oncorhynchus spp. population persistence is particularly needed in semiarid regions such as California, where streamflows during the dry season are highly variable and increasingly threatened by withdrawals to meet human water demands. To examine the effects of summer low flows on a threatened salmonid species, we analyzed 9 years of count data for juvenile steelhead O. mykiss from nine stream reaches in four coastal California watersheds. We used a Bayesian modeling framework to examine the relative influences of streamflow, land use, and habitat quality on juvenile steelhead oversummer survival. An estimated mean survival of 30% suggested that the dry season is a significant period of stress for juvenile steelhead rearing in tributary streams. The models indicated that the magnitude of summer flow and the duration of low‐flow conditions were both important in explaining interannual variation in juvenile survival rates, which showed a consistent increasing trend with higher early and late‐summer flows among all sites. The results also suggested an adverse effect of intensive agricultural land use on juvenile steelhead populations, while local habitat suitability had a positive effect. Although additional research is needed to identify the mechanisms by which flow influences fish survival in the dry season, these findings indicate that water quantity is a potential limiting factor to juvenile steelhead survival in coastal California watersheds and suggest that protection of summer streamflows is important for the conservation of threatened salmonid populations.
Effects of Entrainment and Bypass at Screened Irrigation Canals on Juvenile Steelhead
Authors: Simpson William G. , Ostrand Kenneth G.
Published: May 2012

Expensive bypass screens have been installed throughout the western United States to prevent the entrainment of valuable anadromous salmonids into irrigation canals. However, few studies have quantified the annual extent and variability of entrainment and bypass success for anadromous salmonids emigrating through screened irrigation diversion networks in a basinwide context. By monitoring the movement of hatchery steelhead Oncorhynchus mykiss surrogates marked with passive integrated transponder tags through three irrigation canals, we estimated canal entrainment, bypass success, and survival for threatened juvenile steelhead emigrating from the Umatilla River in northeast Oregon. Annual entrainment of steelhead was positively related to the days of canal operation and negatively related to mean seasonal river flow. The relationship between flow and entrainment differed by canal; as a result, steelhead entrainment was not always greatest at canals with the largest water diversion rates. Binary models (steelhead entrainment or no entrainment) that best described daily entrainment depicted the influence of annual differences in river flows on canal entrainment and indicated that this relationship can change under different values of thermal experience (sum of daily mean temperatures). Most of the entrained hatchery steelhead (range = 97–100%) were returned to the river by screened bypasses, even when large percentages of the steelhead population were entrained. Based on similarities in movement, hatchery steelhead were good surrogates for the entrainment of naturally reared steelhead. We estimated that the three fish screens in the Umatilla River basin prevented losses of up to 25% of the steelhead population to irrigation canals over 5 years. Interannual variability in fish entrainment should be considered when monitoring irrigation canals, and managers should not necessarily limit entrainment monitoring or screening projects to canals that divert the most water.
Prey Density and Nonvisual Feeding by Larval Striped Bass
Authors: Duston J. , Astatkie T.
Published: May 2012

Larvae of striped bass Morone saxatilis from the Shubenacadie River, Nova Scotia, exhibited a good nonvisual feeding mechanism that may be valuable for survival in their turbid estuarine nursery habitat. Their capture of brine shrimp Artemia salina nauplii during 60‐min feeding trials in darkness was significantly affected by the interaction between prey density and larval age. Mean capture rate among larvae that were offered 50, 200, and 800 prey/L at 9 d posthatch (dph) was 3, 7, and 15 prey·larva−1·h−1, respectively, and increased progressively with age to 26, 92, and 220 prey·larva−1·h−1 at 22 dph. By comparison, prey capture rate in the light (20 lx) among 8–13‐dph larvae that were offered 50 prey/L was about fourfold higher than the capture rate for nonvisual feeding; however, at 800 prey/L, capture rates in lighted conditions and in darkness were similar. Among larvae with noninflated swim bladders, prey capture in the dark was severely inhibited.
THE BENEFITS OF MIGRATION
Authors: Damelang Andreas , Haas Anette
Published: May 2012

Assuming that migration and integration have lasting effects on economic and social processes, this paper analyses if a diverse cultural environment has a positive impact on labour market success. We expect that culturally diverse labour markets provide new opportunities through an open and tolerant climate, thus contributing to overall economic growth. We test this assumption by analysing the successful transition from education to work depending on the regional distribution and ethnic mix of the foreign population in Germany (cultural diversity). To account for variation within Germany, cultural diversity is observed at small administrative units. We analyse a cohort of young adults at the time of the successful completion of their apprenticeship in Germany and follow them through the beginning of their career. The concentration on a homogenous group regarding occupational certificates enables us to focus on the effects of the local and social environment as well as individual characteristics such as their national background on finding a job (or not). We apply an instrumental variable design to disentangle the effects of cultural diversity and share of foreigners. The results show that both young foreigners and Germans face significantly lower barriers for employment entry in culturally more diverse German regions.
Musicians outperform nonmusicians in magnitude estimation: Evidence of a common processing mechanism for time, space and numbers
Authors: Agrillo Christian , Piffer Laura
Published: May 2012

It has been proposed that time, space, and numbers may be computed by a common magnitude system. Even though several behavioural and neuroanatomical studies have focused on this topic, the debate is still open. To date, nobody has used the individual differences for one of these domains to investigate the existence of a shared cognitive system. Musicians are known to outperform nonmusicians in temporal discrimination tasks. We therefore observed professional musicians and nonmusicians undertaking three different tasks: temporal (participants were required to estimate which of two tones lasted longer), spatial (which line was longer), and numerical discrimination (which group of dots was more numerous). If time, space, and numbers are processed by the same mechanism, it is expected that musicians will have a greater ability, even in nontemporal dimensions. As expected, musicians were more accurate with regard to temporal discrimination. They also gave better performances in both the spatial and the numerical tasks, but only outside the subitizing range. Our data are in accordance with the existence of a common magnitude system. We suggest, however, that this mechanism may not involve the whole numerical range.
A New Metric of Antibiotic Class Resistance in Gram-Negative Bacilli Isolated from Hospitalized Children
Authors: Patel Sameer J. , O'Toole Dana , Larson Elaine
Published: May 2012

Objective.

The purpose of this study was to describe patterns of infection or colonization with antibiotic-resistant gram-negative bacilli (GNB) in hospitalized children utilizing an electronic health record.

Setting.

Tertiary care facility.

Participants.

Pediatric patients 18 years of age or younger hospitalized from January 1, 2006, to December 31, 2008.

Methods.

Children were identified who had (1) at least 1 positive culture for a multidrug-resistant (MDR) GNB, defined as a GNB with resistance to 3 or more antibiotic classes; or (2) additive drug resistance, defined as isolation of more than 1 GNB that collectively as a group demonstrated resistance to 3 or more antibiotic classes over the study period. Differences in clinical characteristics between the 2 groups were ascertained, including history of admissions and transfers, comorbid conditions, receipt of procedures, and antibiotic exposure.

Results.

Of 56,235 pediatric patients, 46 children were infected or colonized with an MDR GNB, of which 16 were resistant to 3 classes and 30 were resistant to 4 classes. Another 39 patients had positive cultures for GNB that exhibited additive drug resistance. Patients with additive drug resistance were more likely than patients with MDR GNB to have had previous admissions to a long-term facility (8 vs 2; P = .04) and had more mean admissions (7 vs 3; P <.01) and more mean antibiotic-days (P < .01 to P = .02). Six patients with additive drug resistance later had a positive culture with an MDR GNB.

Conclusions.

An electronic health record can be used to track antibiotic class resistance in GNB isolated from hospitalized children over multiple cultures and hospitalizations.
Preoperative Skin Antiseptic Preparations for Preventing Surgical Site Infections: A Systematic Review
Authors: Kamel Chris , McGahan Lynda , Polisena Julie , Mierzwinski-Urban Monika , Embil John M.
Published: May 2012

Objective.

To evaluate the clinical effectiveness of preoperative skin antiseptic preparations and application techniques for the prevention of surgical site infections (SSIs).

Design.

Systematic review of the literature using Medline, EMBASE, and other databases, for the period January 2001 to June 2011.

Methods.

Comparative studies (including randomized and nonrandomized trials) of preoperative skin antisepsis preparations and application techniques were included. Two researchers reviewed each study and extracted data using standardized tables developed before the study. Studies were reviewed for their methodological quality and clinical findings.

Results.

Twenty studies (n = 9,520 patients) were included in the review. The results indicated that presurgical antiseptic showering is effective for reducing skin flora and may reduce SSI rates. Given the heterogeneity of the studies and the results, conclusions about which antiseptic is more effective at reducing SSIs cannot be drawn.

Conclusions.

The evidence suggests that preoperative antiseptic showers reduce bacterial colonization and may be effective at preventing SSIs. The antiseptic application method is inconsequential, and data are lacking to suggest which antiseptic solution is the most effective. Disinfectant products are often mixed with alcohol or water, which makes it difficult to form overall conclusions regarding an active ingredient. Large, well-conducted randomized controlled trials with consistent protocols comparing agents in the same bases are needed to provide unequivocal evidence on the effectiveness of one antiseptic preparation over another for the prevention of SSIs.
Outbreak of Methicillin-Resistant Staphylococcus aureus ST398 in a Dutch Nursing Home
Authors: Verkade Erwin , Bosch Thijs , Hendriks Yvonne , Kluytmans Jan
Published: May 2012

We describe an outbreak of methicillin-resistant Staphybcoccus aureus (MRSA) ST398 in a nursing home in the Netherlands. Seven residents and 4 healthcare workers were identified with MRSA ST398, but 2 of the healthcare workers carried other strains. This study demonstrates that MRSA ST398 can spread in nursing homes.
Outbreak of Carbapenem-Resistant Providencia stuartii in an Intensive Care Unit
Authors: Zavascki Alexandre P. , Carvalhaes Cecília G. , da Silva Geórgia L. , Soares Sílvia Pedroso Tavares , de Alcåntara Luciana R. , Elias Laura S. , Sandri Ana M. , Gales Ana C.
Published: May 2012

Outbreaks by carbapenem-resistant Providencia stuartii (CRPS) are rarely described. Clinical characteristics of patients with CRPS in an intensive care unit and resistance mechanisms were investigated. Carbapenemase production and/or outer membrane alterations were not detected; only CTX-M-2 and AmpC hyperproduction were noted. The outbreak was ultimately controlled in a 3-month period.
Integration of perovskite PZT thin films on diamond substrate without buffer layer
Authors: Chandran Maneesh , Tiwari Brajesh , Kumaran C R , Samji Sunil K , Bhattacharya S S , Rao M S Ramachandra
Published: May 2012

Integration of lead zirconate titanate (PZT) thin film on diamond substrate offers a great deal of potential for the application of multifunctional devices under extreme conditions. However, fabrication of perovskite PZT thin films on diamond substrate without a buffer layer has not been realized to date. We report for the first time on the successful deposition of PZT thin film directly on a diamond substrate without any buffer layer using the pulsed-laser deposition technique. The perovskite phase was realized only under specific growth conditions. X-ray diffraction and Raman studies confirmed the perovskite phase. The ferroelectric behaviour of the deposited PZT thin film was confirmed using piezo response microscope phase image and ferroelectric hysteresis loop.
Magnetization reversal analysis of a thin B2-type ordered Co50Fe50 film by magnetooptic Kerr effect
Authors: Kuschel T , Hamrle J , Pištora J , Saito K , Bosu S , Sakuraba Y , Takanashi K , Wollschläger J
Published: May 2012

The magnetic structure of a thin B2 ordered Co50Fe50 film is determined by vectorial magnetometry using magnetooptic Kerr effect including different polarizations of the incident light and varied directions of the external magnetic field. Both the magnetic reversal process and the magnetic remanence reveal two in-plane magnetic easy axes of different strengths which are not orthogonal. Atypical magnetization curves including multidomain states in magnetic remanence with some magnetic moments providing antiparallel alignment to the direction of the previously applied external field (if projected to the direction of the external field) confirm the appearance of different strong magnetic easy axes. This magnetic structure can be explained by a cubic magnetic anisotropy (CMA) induced by the crystalline film structure superimposed by an additional uniaxial magnetic anisotropy (UMA) which is not parallel to one of the magnetic easy axes of the CMA. The results are compared with the regular magnetic behaviour of a thin A2 ordered Co50Fe50 film with UMA parallel to one of the magnetic easy axes of the CMA.
Investigations on a nano-scale periodical waveguide structure taking surface plasmon polaritons into consideration
Authors: Liu Weihao , Zhong Renbin , Zhou Jun , Zhang Yaxin , Hu Min , Liu Shenggang
Published: May 2012

Detailed theoretical analysis and computer simulations on the electromagnetic characteristics of a nano-scale periodical waveguide structure, taking surface plasmon polaritons (SPPs) into consideration, are carried out in this paper. The results show that SPPs will significantly influence the electromagnetic characteristics of the structure. When the operation frequency is in a certain band—the ‘radial confinement band’, neither radial surface plasmon waves nor guided waves, which both will lead to radial energy loss, can be excited in the structure. And the electromagnetic waves are completely confined within the longitudinal waveguide and propagate along it with little attenuation. The radial energy loss is then significantly reduced. These results are of great significance not only for increasing the efficiency of the radiation sources based on the nano-scale periodical waveguide structure but also for the development of high-efficiency waveguides and wide-band filters in the infrared and visible light regimes.
Measurement of the densities of Cu and Ag vapours in a low-voltage switch using the hook method
Authors: Lins Günter
Published: May 2012

In a research model of a low-voltage circuit breaker with fixed contacts and windows for optical access, arcs powered by either a high-current transformer or a capacitor bank were initiated by the explosion of tungsten wires. Air at atmospheric pressure was the switching medium. The number densities of neutral silver and copper vapours from contacts and arc runners were measured simultaneously by the hook method using a Mach–Zehnder interferometer combined with a 1 m spectrograph and a gated intensified CCD camera. When an arc current was flowing, a substantial fraction of the metal vapour was ionized, and thus not amenable to a density measurement with the technique chosen. To nevertheless obtain approximate density values, the arc current was forced to zero within 8 to 10 µs at a preset time and measurements were carried out 100 µs after extinction of the arc. At that time the metal vapour was expected to have recombined to a large extent but not yet diffused to the walls in significant amounts. Depending on the current amplitude reached within the arc duration the arc remained anchored to the silver contacts or commutated to the copper arc runners. At a maximum current amplitude of 650 A Ag vapour densities of the order of 1022 m−3 were observed near the anode outweighing the Cu vapour density by a factor of 20. When at 1600 A the arc commutated to the arc runners a Cu vapour density of 8 × 1021 m−3 was reached while the Ag density remained limited to 2 × 1021 m−3.
On the choice of electromagnetic model for short high-intensity arcs, applied to welding
Authors: Choquet Isabelle , Shirvan Alireza Javidi , Nilsson Håkan
Published: May 2012

We have considered four different approaches for modelling the electromagnetic fields of high-intensity electric arcs: (i) three-dimensional, (ii) two-dimensional axi-symmetric, (iii) the electric potential formulation and (iv) the magnetic field formulation. The underlying assumptions and the differences between these models are described in detail. Models (i) to (iii) reduce to the same limit for an axi-symmetric configuration with negligible radial current density, contrary to model (iv). Models (i) to (iii) were retained and implemented in the open source CFD software OpenFOAM. The simulation results were first validated against the analytic solution of an infinite electric rod. Perfect agreement was obtained for all the models tested. The electromagnetic models (i) to (iii) were then coupled with thermal fluid mechanics, and applied to axi-symmetric gas tungsten arc welding test cases with short arc (2, 3 and 5 mm) and truncated conical electrode tip. Models (i) and (ii) lead to the same simulation results, but not model (iii). Model (iii) is suited in the specific limit of long axi-symmetric arc with negligible electrode tip effect, i.e. negligible radial current density. For short axi-symmetric arc with significant electrode tip effect, the more general axi-symmetric formulation of model (ii) should instead be used.
Modulation of the operational characteristics of amorphous In–Ga–Zn–O thin-film transistors by In2O3 nanoparticles
Authors: Lee Min-Jung , Lee Tae Il , Park Jee Ho , Kim Jung Han , Chae Gee Sung , Jun Myung Chul , Hwang Yong Kee , Baik Hong Koo , Lee Woong , Myoung Jae-Min
Published: May 2012

The structure of thin-film transistors (TFTs) based on amorphous In–Ga–Zn–O (a-IGZO) was modified by spin coating a suspension of In2O3 nanoparticles on a SiO2/p++ Si layered wafer surface prior to the deposition of IGZO layer by room-temperature sputtering. The number of particles per unit area (surface density) of the In2O3 nanoparticles could be controlled by applying multiple spin coatings of the nanoparticle suspension. During the deposition of IGZO, the In2O3 nanoparticles initially located on the substrate surface migrated to the top of the IGZO layer indicating that they were not embedded within the IGZO layer, but they supplied In to the IGZO layer to increase the In concentration in the channel layer. As a result, the channel characteristics of the a-IGZO TFT were modulated so that the device showed an enhanced performance as compared with the reference device prepared without the nanoparticle treatment. Such an improved device performance is attributed to the nano-scale changes in the structure of (InO)
n
ordering assisted by increased In concentration in the amorphous channel layer.
Diffusion of Ag ions under random potential barriers in silver-containing chalcogenide glasses
Authors: Stehlik S , Shimakawa K , Wagner T , Frumar M
Published: May 2012

We show that a random walk model of diffused ions interprets well the experimentally deduced Nyquist plots in ionic chalcogenide glasses. Fitting of the model to the experimental data in the Nyquist plots of Ag–As–S(Se) glasses taken as case examples yields important physical parameters such as number of mobile Ag+ ions, hopping relaxation time and diffusion coefficient. It was found that the number of freely moving Ag+ ions is almost independent of Ag content in Ag
x
(As0.33S(Se)0.67)100−x
glasses, while the maximum hopping relaxation time is highly dependent on Ag concentration.