bluuebunny/crossref_metadata_2025 huggingface dataset:
Sensitivity of shortwave radiative flux density, forcing, and heating rate to the aerosol vertical profile
Authors: Guan Hong , Schmid Beat , Bucholtz Anthony , Bergstrom Robert
Published: March 2010

The effect of the aerosol vertical distribution on the solar radiation profiles for idealized and measured profiles of extinction and single‐scattering albedo (SSA) during the May 2003 Atmospheric Radiation Measurement Aerosol Intensive Observation Period (AIOP) is investigated using the rapid radiative transfer model shortwave code. Calculated profiles of downwelling and upwelling solar flux density during the AIOP are compared with the measurements from solar broadband radiometers aboard a profiling research aircraft. The profiles of aerosol extinction, SSA, and water vapor obtained from the aircraft that carried the radiometers serve as the model inputs. The uplooking radiometers were mounted on a stabilized platform that kept the radiometers parallel with respect to Earth's horizontal plane. The results indicate that the vertical shape of the aerosol extinction profiles has very little impact on the clear‐sky direct radiative forcing at the top of atmosphere and surface but is important for forcing profiles of partially absorbing aerosol. The vertical distributions of absorption profiles drastically influence the forcing and heating rate profiles. Using aircraft data from 19 AIOP profiles over the southern Great Plains, we are able to achieve broadband downwelling solar flux density closure within 0.8% (bias difference) or 1.8% (RMS difference), well within the expected measurement uncertainty of 1%–3%. The poorer agreement in upwelling flux density (bias −3.7%, RMS 10%) is attributed to the use of inaccurate surface albedo data. The accurate, vertically resolved aerosol extinction data play an important role in tightening solar radiative flux density closure. This study also suggests that aircraft solar radiative flux density measurements from a stabilized platform have the potential to determine solar heating rate profiles. These measurement‐based heating rate profiles provide useful data for heating rate closure studies and indirect estimates of single‐scattering albedo assumed in radiative transfer calculations.
Long‐range transport of ozone from the Los Angeles Basin: A case study
Authors: Langford A. O. , Senff C. J. , Alvarez R. J. , Banta R. M. , Hardesty R. M.
Published: March 2010

Airborne lidar measurements of ozone above the Los Angeles Basin on 17 July 2009 show orographic lifting of ozone from the surface to the free troposphere by the San Gabriel Mountains. Mixing ratios in excess of 100 parts‐per‐billion‐by‐volume (ppbv) were measured ∼4 km above mean sea level (ASL). These observations are in excellent agreement with published model studies, confirming that topographic venting by the so called “mountain chimney effect” is a potentially important pathway for removal of pollutants from the Los Angeles Basin. The lofting of ozone and other pollutants into the free troposphere also greatly increases the potential for long‐range transport from the Basin, and trajectory calculations suggest that some of this ozone may have been transported ∼1000 km to eastern Utah and western Colorado.
Very broadband analysis of a swarm of very low frequency earthquakes and tremors beneath Kii Peninsula, SW Japan
Authors: Takeo Akiko , Idehara Koki , Iritani Ryohei , Tonegawa Takashi , Nagaoka Yutaka , Nishida Kiwamu , Kawakatsu Hitoshi , Tanaka Satoru , Miyakawa Koji , Iidaka Takashi , Obayashi Masayuki , Tsuruoka Hiroshi , Shiomi Katsuhiko , Obara Kazushige
Published: March 2010

We have conducted a temporal broadband seismic observation in Kii Peninsula, southwest Japan, and detected a swarm of 110 very low frequency earthquakes (VLFs) and deep low frequency tremors. During three days of the swarm activity, VLFs and tremors occur concurrently in two localized regions separated by ∼10 km. Stacking analyses are also employed to detect VLF signals of a period longer than 50 s, whose focal mechanisms are determined for the first time from data and shown to be consistent with the subducting plate motion. Evaluation of the VLF seismic moment implies that a substantial portion of the SSE seismic moment is released as a VLF swarm.
Can bacteria save the planet?
Authors: Hunter Philip
Published: March 2010

Bacteria might just hold the key to preserving the environment for our great grandchildren. Philip Hunter explores some of the novel ways in which systems biology and biotechnology are harnessing bacteria to produce renewable energy and clean up pollution.
Atopic dermatitis: the role of Langerhans cells in disease pathogenesis
Authors: Dubrac Sandrine , Schmuth Matthias , Ebner Susanne
Published: March 2010

The manifestation of atopic dermatitis (AD) results from a complex interaction of environmental factors, skin barrier defects and immunological phenomena. The initial events in AD remain unclear while much progress has been made in identifying the mechanisms leading to the manifestation and maintenance of allergic inflammation. AD pathogenesis can be approached from many different points of view. In this review, we describe findings in mouse models and in humans separately. We focus on recent findings that underscore the importance of Langerhans cells in initial mechanisms of skin inflammation in AD.
MRI and MRSI Application in Neurodegeneration
Authors: Sharma Rakesh
Published: March 2010

MRI combined with MR spectroscopy generates better information of both brain tissue composition and mesurement of metabolites or neurochemicals in multiple sclerosis(MS), Alzheimer's disease and epilepsy. New fast imaging techniques are technical advance in visualizing accurate anatomy and measurement of absolute neurochemicals in brain. Gray metter seated MS lesions is a new form of disease and lesion may appear normal on MRI but show spectroscopy peaks. High magnetic field scanners are available for fast imaging.
Structural basis for the efficient phosphorylation of AZT-MP (3′-azido-3′-deoxythymidine monophosphate) and dGMP by Plasmodium falciparum type I thymidylate kinase
Authors: Whittingham Jean L. , Carrero-Lerida Juana , Brannigan James A. , Ruiz-Perez Luis M. , Silva Ana P. G. , Fogg Mark J. , Wilkinson Anthony J. , Gilbert Ian H. , Wilson Keith S. , González-Pacanowska Dolores
Published: March 2010

Plasmodium falciparum is the causative agent of malaria, a disease where new drug targets are required due to increasing resistance to current anti-malarials. TMPK (thymidylate kinase) is a good candidate as it is essential for the synthesis of dTTP, a critical precursor of DNA and has been much studied due to its role in prodrug activation and as a drug target. Type I TMPKs, such as the human enzyme, phosphorylate the substrate AZT (3′-azido-3′-deoxythymidine)-MP (monophosphate) inefficiently compared with type II TMPKs (e.g. Escherichia coli TMPK). In the present paper we report that eukaryotic PfTMPK (P. falciparum TMPK) presents sequence features of a type I enzyme yet the kinetic parameters for AZT-MP phosphorylation are similar to those of the highly efficient E. coli enzyme. Structural information shows that this is explained by a different juxtaposition of the P-loop and the azide of AZT-MP. Subsequent formation of the transition state requires no further movement of the PfTMPK P-loop, with no steric conflicts for the azide moiety, allowing efficient phosphate transfer. Likewise, we present results that confirm the ability of the enzyme to uniquely accept dGMP as a substrate and shed light on the basis for its wider substrate specificity. Information resulting from two ternary complexes (dTMP–ADP and AZT-MP–ADP) and a binary complex with the transition state analogue AP5dT [P1-(5′-adenosyl)-P5-(5′-thymidyl) pentaphosphate] all reveal significant differences with the human enzyme, notably in the lid region and in the P-loop which may be exploited in the rational design of Plasmodium-specific TMPK inhibitors with therapeutic potential.
Determination in oocytes of the reproductive modes for the brine shrimp Artemia parthenogenetica
Authors: Dai Zhong-Min , Li Ran , Dai Li , Yang Jin-Shu , Chen Su , Zeng Qing-Guo , Yang Fan , Yang Wei-Jun
Published: March 2010

The brine shrimp, Artemia, reproduces either oviparously, producing encysted embryos (diapause cysts), or ovoviviparously, producing free-swimming nauplii. Environmental factors, such as photoperiod, have been applied to control the reproduction mode of Artemia, but when the determination of a reproductive mode occurs remains unknown. We analysed the differential gene expression between oocytes from oviparous and ovoviviparous Artemia reared under different photoperiods. A total of 692 qualified cDNA clones were obtained by subtractive hybridization, 327 of which matched GenBank® Nucleotide Sequence Database entries. Gene expressions of 44 cDNAs (representing 56 clones) were analysed in oocytes using real-time PCR. Among these genes, 11 (21 clones) were significantly (P<0.05) up-regulated and 7 (9 clones) down-regulated in Artemia oocytes that subsequently enter diapause. Remarkably, known diapause-related proteins such as ArHsp22 (Artemia heat-shock protein 22) and chitin-binding proteins are found to be already differentially expressed. Furthermore, RNAi (RNA interference) knockdown of a differentially expressed gene, polo-like kinase 1, in oocyte of ovoviviparous Artemia led to the production of white embryos rather than free-swimming nauplii. In summary, our results provide evidence at the molecular level that the reproductive mode of Artemia is already determined at the oocyte stage of their life cycle.
Role of nuclear factor κB in liver health and disease
Authors: Robinson Stuart M. , Mann Derek A.
Published: March 2010

NF-κB (nuclear factor κB) is a heterodimeric transcription factor that is constitutively expressed in all cell types and has a central role as a transcriptional regulator in response to cellular stress. In the present review, we discuss the role of NF-κB signalling in the maintenance of liver homoeostasis as well as in the pathogenesis of a wide variety of conditions affecting the liver, including viral hepatitis, steatohepatitis, cirrhosis and hepatocellular carcinoma. Much of the current knowledge of NF-κB signalling in the liver relates to the canonical pathway, the IKK [IκB (inhibitor of κB) kinase] complex and the RelA subunit. We explore the weaknesses of the experimental approaches to date and suggest that further work is needed to investigate in detail the discreet functions of each of the Rel subunits in liver physiology and disease.
T-cell-directed therapies in inflammatory bowel diseases
Authors: Monteleone Giovanni , Caprioli Flavio
Published: March 2010

Gut inflammation occurring in patients with IBDs (inflammatory bowel diseases) is associated with exaggerated and poorly controlled T-cell-mediated immune responses, which are directed against normal components of the gut flora. T-cells accumulate in the inflamed gut of IBD patients as a result of multiple mechanisms, including enhanced recruitment of cells from the bloodstream, sustained cell cycling and diminished susceptibility of cells to undergo apoptosis. Activated T-cells produce huge amounts of cytokines, which contribute to amplify and sustain the ongoing mucosal inflammation. Strategies aimed at interfering with T-cell accumulation and/or function in the gut have been employed with clinical success in patients with IBDs. In the present article, we review the available results showing that T-cell-directed therapies are useful to dampen the tissue-damaging immune response in IBDs.
Theory of “Selectivity” of label-free nanobiosensors: A geometro-physical perspective
Authors: Nair Pradeep R. , Alam Muhammad A.
Published: March 2010

Modern label-free biosensors are generally far more sensitive and require orders of magnitude less incubation time compared to their classical counterparts. However, a more important characteristic regarding the viability of this technology for applications in genomics/proteomics is defined by the “Selectivity,” i.e., the ability to concurrently and uniquely detect multiple target biomolecules in the presence of interfering species. Currently, there is no theory of Selectivity that allows optimization of competing factors and there are few experiments to probe this problem systematically. In this article, we use the elementary considerations of surface exclusion, diffusion limited transport, and void distribution function to provide guidance for optimum incubation time required for effective surface functionalization, and to identify the dominant components of unspecific adsorption. We conclude that optimally designed label-free schemes can compete favorably with other assay techniques, both in sensitivity as well as in selectivity.
Measurement of the photostability of silicon nanoparticles under UVA and near infrared irradiation
Authors: Mantey Kevin , Kwit Matthew , Nayfeh M. H. , Kumar Ashok , Stephenson Larry D. , Nelson Andrew J.
Published: March 2010

We examine the photostability of silicon nanoparticles when they are dispersed in liquid or immobilized in gels or on surfaces. We show that the photoluminescence in static solution develops, under UV irradiation, a long-term stability at the 50% level. Under the same conditions, common dye molecules such as coumarin and stilbene quench with time at rates 8 and 50 fold faster, and exhibit no long-term stability. For the case of immobilized particles in agarose gel as well as on a quartz substrate we used two-photon near infrared femtosecond excitation at 780 nm to induce the blue luminescence. “Parking” the excitation beam, focused on such stationery particles shows that they, unlike similarly immobilized dye molecules, are highly photostable at more than 80%–90% level and do not bleach. The photostability is discussed in terms of excited state interactions and structuring of the silicon outer shell.
Mechanisms for generating toroidal rotation in tokamaks without external momentum input
Authors: Solomon W. M. , Burrell K. H. , Garofalo A. M. , Kaye S. M. , Bell R. E. , Cole A. J. , deGrassie J. S. , Diamond P. H. , Hahm T. S. , Jackson G. L. , Lanctot M. J. , Petty C. C. , Reimerdes H. , Sabbagh S. A. , Strait E. J. , Tala T. , Waltz R. E.
Published: March 2010

Recent experiments on DIII-D [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] and National Spherical Torus Experiment (NSTX) [M. Ono et al., Nucl. Fusion 40, 557 (2000)] have focused on investigating mechanisms of driving rotation in fusion plasmas. The so-called intrinsic rotation is generated by an effective torque, driven by residual stresses in the plasma, which appears to originate in the plasma edge. A clear scaling of this intrinsic drive with the H-mode pressure gradient is observed. Coupled with the experimentally inferred pinch of angular momentum, such an edge source is capable of producing sheared rotation profiles. Intrinsic drive is also possible directly in the core, although the physics mechanisms are much more complex. Another option which is being explored is the use of nonresonant magnetic fields for spinning the plasma. It is found beneficially that the torque from these fields can be enhanced at low rotation, which assists in spinning the plasma from rest, and offers increased resistance against plasma slowing.
Formation of viscoplastic drops by capillary breakup
Authors: German G. , Bertola V.
Published: March 2010

The process of growth and detachment of drops from a capillary nozzle is studied experimentally by high-speed imaging. Newtonian drops are compared to shear-thinning and viscoplastic drops. Both Newtonian and shear-thinning fluid drops grow on the end of the capillary until a maximum supportable tensile stress is reached in the drop neck, after which they become unstable and detach. The critical stress is not influenced by variations in viscosity or in the degree of shear thinning. Viscoplastic fluids show a different behavior: at low values of the yield stress, the critical stability behavior is similar to that of Newtonian and shear-thinning drops. Above a threshold value, characterized in terms of the drop size, surface tension and tensile yield-stress magnitude, yield-stress forces are larger than surface forces, and the maximum tensile stress achievable in the drop neck at the point of critical stability is governed by the von Mises criterion.
Numerical simulation and modeling of GaAs quantum-well solar cells
Authors: Kailuweit P. , Kellenbenz R. , Philipps S. P. , Guter W. , Bett A. W. , Dimroth F.
Published: March 2010

This paper presents results of numerical simulations of GaAs solar cells with quantum wells (QWs) included in the intrinsic region between the emitter and base layer. These QWs extend the absorption edge beyond that of the GaAs bandgap. The modeling of the solar cell characteristics was carried out within a commercially available semiconductor simulation environment. In order to consider the absorption properties of the wells a numerical model using a finite rectangular QW was established. The model is successfully validated through a comparison of the simulated external quantum efficiency (EQE)with measurement results of two different QW solar cell structures. As a first application of our model the variation in the EQE with the QW thickness is studied.
Predissociation and dissociative ionization of Rydberg states of Xe2 and the photodissociation of Xe2+
Authors: Shubert V. Alvin , Rednic Maria , Pratt Stephen T.
Published: March 2010

The Rydberg states of Xe2 in the region between 76 000 and 84 000 cm−1 were studied by using a combination of two-photon excitation and velocity map ion imaging. The electronic states in this region are based on the Xe(S10)+Xe 6p and 5d dissociation limits, and the large number of states leads to numerous curve crossings and distorted potentials. These Rydberg states can decay by predissociation or fluorescence or can be photoionized, dissociatively photoionized, or photodissociated by the absorption of a single additional photon. Furthermore, the molecular ion can be photodissociated as well. While numerous other techniques have been applied to this problem, velocity map ion imaging provides a high resolution approach to determine the operative processes. When combined with existing data obtained by other methods, the present experiments allow a more complete understanding of the assignment and behavior of these states.
Variable-range-hopping conduction processes in oxygen deficient polycrystalline ZnO films
Authors: Huang Yung-Lung , Chiu Shao-Pin , Zhu Zhi-Xin , Li Zhi-Qing , Lin Juhn-Jong
Published: March 2010

We have fabricated oxygen deficient polycrystalline ZnO films by the rf sputtering deposition method. To systematically investigate the charge transport mechanisms in these samples, the electrical resistivities have been measured over a wide range of temperature from 300 K down to liquid-helium temperatures. We found that below about 100 K, the variable-range-hopping (VRH) conduction processes govern the charge transport properties. In particular, the Mott VRH conduction process dominates at higher temperatures, while crossing over to the Efros–Shklovskii (ES) VRH conduction process at lower temperatures. The crossover occurred at temperatures as high as a few tens degrees kelvin. Moreover, the temperature behavior of resistivity over the entire VRH conduction regime from the Mott-type to the ES-type process can be well described by a universal scaling law.
Dual-doped thermographic phosphor particles as surrogates for green fluorescent protein-labeled cells in tests of cytometric neurocatheters
Authors: Allison S. W. , Gillies G. T.
Published: March 2010

We investigated the laser-induced fluorescence of particles of a compound thermographic phosphor La2O2S:Eu(1%) and Gd2O2S:Eu(1%) to see if they can serve as a surrogate for cells transfected with the green fluorescent protein, in tests of neurocatheters used for intraparenchymal cell delivery. At an excitation wavelength of 337 nm and a concentration of ≈2×106 particles ml−1, the resulting slurries produced fluorescence intensities at 625 nm that were within a factor of 2 of those produced by similar number densities of relevant cells, thus suggesting the utility of this approach.
Systematic investigation of sustained laser-induced incandescence in carbon nanotubes
Authors: Lim Zhi Han , Lee Andrielle , Lim Kassandra Yu Yan , Zhu Yanwu , Sow Chorng-Haur
Published: March 2010

A focused laser beam irradiating on aligned carbon nanotubes (CNTs) in moderate vacuum results in bright and sustained laser-induced incandescence (LII) in CNTs. The incandescence corresponds to blackbody radiation from laser-heated CNTs at ∼2400 K. Post-LII craters with well-defined ring boundaries in the CNT array were observed and examined with scanning electron microscopy and Raman spectroscopy. The enhanced purity of CNTs after LII as indicated by Raman spectroscopy studies was attributed to the removal of amorphous carbons on the as-grown CNTs during LII. A dynamic study of the crater formation further elucidates the nature of such craters. Through a systematic study of the effect of vacuum level and gaseous environment on LII, we discovered the process of thermal runaway during LII in CNTs. Thermal runaway is a threat to a sustained LII and can be prevented in nitrogen and argon environments. Oxygen was found to be responsible for thermal runaway reactions.
Analysis of photoconductive gain as it applies to single-photon detection
Authors: Rowe M. A. , Salley G. M. , Gansen E. J. , Etzel S. M. , Nam S. W. , Mirin R. P.
Published: March 2010

We detail a mathematical framework for photoconductive gain applied to the detection of single photons. Because photoconductive gain is derived from the ability to measure current change for an extended period, its magnitude is reduced as detection speed is increased. We theoretically show that high-speed detection is still possible as long as the noise spectrum of the device is 1/f in nature. Using signal analysis techniques, we develop tools to apply to device noise spectra to determine the performance of single-photon detectors that utilize photoconductive gain. We show that there is no speed penalty when one considers the signal-to-noise ratio for the fundamental 1/f noise typical of high electron mobility transistors. We outline a technique for quickly characterizing a detector’s sensitivity and speed through purely electrical measurements of the device’s noise spectra. Consequently, the performance of the detector can be determined and optimized without conducting optical measurements. Finally, we employ this analysis to a quantum dot, optically gated field-effect transistor and verify our results with optical measurements.
An experimental procedure for precise evaluation of electron density distribution of a nanostructured material by coherent x-ray diffraction microscopy
Authors: Takahashi Yukio , Kubo Hideto , Nishino Yoshinori , Furukawa Hayato , Tsutsumi Ryosuke , Yamauchi Kazuto , Ishikawa Tetsuya , Matsubara Eiichiro
Published: March 2010

We developed a coherent x-ray diffraction microscopy (CXDM) system that enables us to precisely evaluate the electron density of an isolated sample. This system enables us to determine the dose per surface unit of x rays illuminated onto an isolated sample by combining incident x-ray intensity monitoring and the CXDM of a reference sample. By using this system, we determined the dose of x rays illuminated onto a nanostructured island fabricated by focused-ion-beam chemical vapor deposition and derived the electron density distribution of such a nanostructured island. A projection image of the nanostructured island with a spatial resolution of 24.1 nm and a contrast resolution higher than 2.3×107 electrons/pixel was successfully reconstructed.
Length and end group dependence of the electronic transport properties in carbon atomic molecular wires
Authors: Deng Xiaoqing , Zhang Zhenhua , Zhou Jicheng , Qiu Ming , Tang Guiping
Published: March 2010

Carrying out theoretical calculations using the nonequilibrium Green’s function method combined with the density functional theory, the transport properties of functionalized atomic chains of carbon atoms with different lengths are investigated. The results show that the I-V evolution and rectifying performance can be affected by the length of wire when both ends of it is capped with the benzene-thiol attached with an amino group and the pyridine attached with nitro group. But when capped with the benzene-thiol attached with an amino group and the nitro group, we can observe a surprised result that different systems show similar I-V characteristics and their transport properties are almost independent of molecular length, which suggests that this is a favorable way to design more ideal molecular interconnecting wires with a high length-independent conductance behavior.
Ferroelectric phase transition in Sn2+ ions doped (Ba,Ca)TiO3 ceramics
Authors: Suzuki Shoichiro , Takeda Toshikazu , Ando Akira , Takagi Hiroshi
Published: March 2010

Solid solutions of BaTiO3 ferroelectric ceramics containing Sn2+ ions have been synthesized by solid state reaction with Ca2+ codoping. The crystal structures of Sn2+ ions doped (Ba,Ca)TiO3 were identified as tetragonal perovskite type BaTiO3 based on x-ray diffraction profiles analysis. (Ba1−xCax)TiO3 (x=0.13) tetragonality increased with Sn ions doping. Temperature dependence of the dielectric properties for Sn2+ ions doped (Ba1−xCax)TiO3 ceramic sample showed a tetragonal-to-cubic phase transition temperature of 155 °C, which is higher than that of undoped (Ba1−xCax)TiO3 (135 °C). By using synchrotron x-ray absorption near-edge structure spectroscopy the valence state of Sn ions in the (Ba1−x−yCaxSny)TiO3 (x=0.13, y=0.05) ferroelectric ceramics was identified to be Sn2+.
Comparison of three current sources for single-electrode capacitance measurement
Authors: Chen D. X. , Deng X. , Yang W. Q.
Published: March 2010

The capacitance of a single electrode is usually measured by injecting a current to the electrode and measuring the resultant voltage on the electrode. In this case, a voltage-controlled current source with a high bandwidth is needed because the impedance is inversely proportional to the excitation frequency. In this design note, three different current sources are discussed: (1) the Howland current source, (2) a modified Howland current source, and (3) a dual op-amp current source. The principle and dynamic performances are presented and compared. Simulation and experimental results show that although the Howland current source has the lowest (i.e., worst) output impedance, its output is the most stable among the three current sources when the frequency changes. Therefore, it is suitable for single-electrode capacitance measurement. Initial tests have proven the feasibility of single-electrode capacitance sensor with the Howland current source.
Gain analysis of blue nitride-based lasers by small signal modulation
Authors: Müller J. , Scheubeck M. , Sabathil M. , Brüderl G. , Dini D. , Tautz S. , Lermer T. , Breidenassel A. , Lutgen S.
Published: March 2010

With a small signal frequency-modulation of the driving current, the resonance frequency and the damping factor of the optical output power response of blue nitride-based ridge lasers grown on [0001]-plane gallium-nitride substrates were investigated with a network analyzer setup. From the linear dependence of the squared resonance frequency on the driving current, the gain coefficients of the logarithmic gain model could be extracted being 7680 cm−1 for blue nitride-based lasers. For this purpose, additional parameters such as the carrier density and the confinement factor were assigned by carrier lifetime and quantum efficiency measurements and one dimensional transfer matrix simulations, respectively.
Self-assembly method of linearly aligning ZnO quantum dots for a nanophotonic signal transmission device
Authors: Yatsui T. , Ryu Y. , Morishima T. , Nomura W. , Kawazoe T. , Yonezawa T. , Washizu M. , Fujita H. , Ohtsu M.
Published: March 2010

We report a self-assembly method that aligns nanometer-sized quantum dots (QDs) into a straight line along which photonic signals can be transmitted by optically near-field effects. ZnO QDs were bound electrostatically to DNA to form a one-dimensional QD chain. The photoluminescence intensity under parallel polarization excitation along the QDs chain was much greater than under perpendicular polarization excitation, indicating an efficient signal transmission along the QD chain. As optical near-field energy can transmit through the resonant energy level, nanophotonic signal transmission devices have a number of potential applications, such as wavelength division multiplexing using QDs of different sizes.
Rapid detection of melamine in whole milk mediated by unmodified gold nanoparticles
Authors: Wei Fang , Lam Robert , Cheng Stacy , Lu Steven , Ho Dean , Li Na
Published: March 2010

A strategy for rapid and facile detection of melamine in food and other substances is described. Unmodified gold nanoparticles enable a colorimetric signal output that is amplified through integration by precipitation formation via a chemical component specific to melamine. The sensitivity was determined to be ∼40 ppb with a two standard deviation cutoff.
X-ray nanodiffraction at individual SiGe/Si(001) dot molecules and its numerical description based on kinematical scattering theory
Authors: Dubslaff M. , Hanke M. , Schöder S. , Burghammer M. , Boeck T. , Patommel J.
Published: March 2010

Individual self-assembled SiGe/Si(001) dot molecules were investigated by scanning x-ray nanodiffraction with a beam size of 250 nm in diameter (full width at half maximum). The samples contain dot molecules with either one, two, three, or four dots. Different azimuthal configurations were measured and compared with simulated diffraction patterns. We have combined finite element calculations, kinematic scattering simulations, and experimental measurements to obtain information about lateral positional correlation as well as strain and germanium content within individual dot molecules.
Mg doping of GaN grown by plasma-assisted molecular beam epitaxy under nitrogen-rich conditions
Authors: Zhang Meng , Bhattacharya Pallab , Guo Wei , Banerjee Animesh
Published: March 2010

Acceptor doping of GaN with Mg during plasma-assisted molecular beam epitaxy, under N-rich conditions and a relatively high growth temperature of 740 °C, was investigated. The p-doping level steadily increases with increasing Mg flux. The highest doping level achieved, determined from Hall measurements, is 2.1×1018 cm−3. The corresponding doping efficiency and hole mobility are ∼4.9% and 3.7 cm2/V s at room temperature. Cross-sectional transmission electron microscopy and photoluminescence measurements confirm good crystalline and optical quality of the Mg-doped layers. An InGaN/GaN quantum dot light emitting diode (λpeak=529 nm) with p-GaN contact layers grown under N-rich condition exhibits a low series resistance of 9.8 Ω.
Electrical-stress-induced degradation in AlGaN/GaN high electron mobility transistors grown under gallium-rich, nitrogen-rich, and ammonia-rich conditions
Authors: Roy T. , Puzyrev Y. S. , Tuttle B. R. , Fleetwood D. M. , Schrimpf R. D. , Brown D. F. , Mishra U. K. , Pantelides S. T.
Published: March 2010

We have evaluated the long-term electrical reliability of GaN/AlGaN high-electron-mobility transistors grown under Ga-rich, N-rich, and NH3-rich conditions. Vpinch-off shifts positively after stress for devices grown under Ga-rich and N-rich conditions, while it shifts negatively for NH3-rich devices. Density functional theory calculations suggest that the hot-electron-induced release of hydrogen from hydrogenated Ga-vacancies is primarily responsible for the degradation of devices grown in Ga-rich and N-rich conditions, while hydrogenated N-antisites are the dominant defects causing degradation in devices grown under NH3-rich conditions.
Monte Carlo simulation of magnetic properties of irregular Fe islands on Pb/Si(111) substrate based on the scanning tunneling microscopy image
Authors: Du Hai-Feng , He Wei , Sun Da-Li , Fang Ya-Peng , Liu Hao-Liang , Zhang Xiang-Qun , Cheng Zhao-Hua
Published: March 2010

Magnetic properties of irregular Fe islands grown on Si(111) substrate with Pb buffer layer by molecular beam epitaxy have been investigated by means of Monte Carlo simulation. During the simulation, the dipolar interaction energy among islands and the demagnetization energy of each island were accurately calculated in the Fourier space with the aid of cluster multiple labeling technique. The simulated results, i.e., the magnetic hysteresis loops and the temperature dependence of remanent magnetization, are in good agreement with the experimental ones measured by in situ surface magneto-optical Kerr effect (SMOKE).
Impact of top electrode on electrical stress reliability of metal-insulator-metal capacitor with amorphous ZrTiO4 film
Authors: Wu Yung-Hsien , Lin Chia-Chun , Chen Lun-Lun , Chen Bo-Yu , Wu Min-Lin , Wu Jia-Rong
Published: March 2010

For metal-insulator-metal (MIM) capacitors with an amorphous ZrTiO4 film as the dielectric, the impact of top electrode including Ni and Al on electrical stress reliability was studied and the mechanisms to explain the electrode-dependent reliability were also proposed in this work. It has been found that the Ni-electrode MIM capacitors reveal good reliability in terms of 0.91% capacitance change after ten-year operation under −2 V constant voltage stress while that for those with Al electrode degrades to 1.92%. This undesirable higher capacitance change can be mainly ascribed to a larger permittivity modulation in the dielectric that is due to higher leakage current and consequently more trapped charges and dipoles caused by a lower electrode work function. In addition, a parasitic Al2O3 film in the Al-electrode MIM capacitors also worsens the integrity of the dielectric because of the existence of additional traps.
Xenografting restores spermatogenesis to cryptorchid testicular tissue but does not rescue the phenotype of idiopathic testicular degeneration in the horse (Equus caballus)
Authors: Turner Regina M. , Rathi Rahul , Honaramooz Ali , Zeng Wenxian , Dobrinski Ina
Published: March 2010

Spermatogenesis from many mammalian species occurs in fragments of normal testis tissue xenografted to mice. Here we apply xenografting to the study of testicular pathology. Using the horse model, we investigated whether exposure to a permissive extratesticular environment in the mouse host would rescue spermatogenesis in cryptorchid testicular tissue or in tissue affected by idiopathic testicular degeneration (ITD). In cryptorchid tissue, where the extratesticular environment is abnormal, xenografting induced spermatogenesis up to meiosis in a subpopulation of seminiferous tubules. Thus, spermatogonia survive and partially retain their potential to differentiate in cryptorchid horse testes. In contrast, the primary defect in equine ITD is hypothesised to be tissue autologous. In support of this, xenografting did not restore spermatogenesis to tissue affected by ITD, thus confirming that the testis itself is primarily diseased. This outcome was not affected by supplementation of exogenous gonadotropins to the mouse host or by reconstitution of a normal reproductive regulatory axis supplied by functional porcine testicular xenografts. These studies demonstrate the usefulness of xenografting for the study of testicular pathology.
Evaluation of the function of fresh and frozen - thawed sex-sorted and non-sorted stallion spermatozoa using a heterologous oocyte binding assay
Authors: Clulow J. R. , Evans G. , Maxwell W. M. C. , Morris L. H. A.
Published: March 2010

The aim of the present study was to evaluate the potential oocyte binding ability and functional integrity of fresh or frozen–thawed, sex-sorted or non-sorted stallion spermatozoa. In the absence of effective IVF procedures in the horse, a heterologous sperm-binding assay was used as an indicator of fertilising capacity to assess differences in the ability of stallion spermatozoa to bind to bovine oocytes. The functional integrity of four treatment groups was assessed: (1) fresh non-sorted spermatozoa; (2) fresh sex-sorted spermatozoa; (3) frozen–thawed non-sorted spermatozoa; and (4) frozen–thawed sex-sorted spermatozoa. Spermatozoa found in association with the zona pellucida of the bovine oocytes were deemed ‘attached’ or ‘bound’ depending on their characterisation as either acrosome intact or acrosome reacted, respectively. Significantly less frozen–thawed spermatozoa were found attached to the oocytes compared with fresh spermatozoa. No significant differences were identified between the number of attached sex-sorted and non-sorted frozen–thawed spermatozoa. However, significantly more sex-sorted than non-sorted fresh spermatozoa were found attached to the oocytes after 1 h coincubation, although after 3 h coincubation this difference was no longer apparent. In conclusion, sex-sorted fresh and frozen–thawed stallion spermatozoa are functionally capable of attaching and binding to bovine oocytes in vitro. Furthermore, fresh sex-sorted spermatozoa attach better than non-sorted spermatozoa, suggesting that they have a more advanced capacitation-like status.
Effects of changes in the concentration of systemic progesterone on ions, amino acids and energy substrates in cattle oviduct and uterine fluid and blood
Authors: Hugentobler S. A. , Sreenan J. M. , Humpherson P. G. , Leese H. J. , Diskin M. G. , Morris D. G.
Published: March 2010

Early embryo loss is a major factor affecting the conception rate in cattle. Up to 40% of cattle embryos die within 3 weeks of fertilisation while they are nutritionally dependent on oviduct and uterine fluids for their survival. Inadequate systemic progesterone is one of the factors contributing to this loss. We have characterised the effects of changes in systemic progesterone on amino acid, ion and energy substrate composition of oviduct and uterine fluids on Days 3 and 6, respectively, of the oestrus cycle in cattle. Oviduct and uterine fluids were collected in situ following infusion of progesterone. There was no effect of progesterone on oviduct fluid secretion rate; however, uterine fluid secretion rate was lowered. Progesterone increased uterine glucose, decreased oviduct sulfate and, to a lesser degree, oviduct sodium, but had no effect on any of the ions in the uterus. The most marked effect of progesterone was on oviducal amino acid concentrations, with a twofold increase in glycine, whereas in the uterus only valine was increased. These results provide novel information on the maternal environment of the early cattle embryo and provide further evidence of progesterone regulation of oviduct amino acid concentrations in cattle.
Developmental potential of bovine oocytes following IVM in the presence of glutathione ethyl ester
Authors: Curnow E. C. , Ryan J. P. , Saunders D. M. , Hayes E. S.
Published: March 2010

Glutathione (GSH) is synthesised during oocyte maturation and represents the oocyte’s main non-enzymatic defence against oxidative stress. Inadequate defence against oxidative stress may be related to poor embryo quality and viability. In the present study, bovine oocytes were matured in vitro in the presence of GSH ethyl ester (GSH-OEt), a cell permeable GSH donor, and its effects on subsequent fertilisation and embryo development were assessed. GSH-OEt significantly increased the GSH content of IVM oocytes without affecting fertilisation or Day 3 cleavage rates. Maturation in the presence of GSH-OEt did not significantly increase the blastocyst rate compared with control oocytes. However, 5 mM GSH-OEt treatment resulted in significantly higher blastocyst total cell number. The GSH level of IVM oocytes was significantly decreased in the absence of cumulus cells and when cumulus–oocyte complexes were cultured in the presence of buthionine sulfoximine (BSO), an inhibitor of GSH synthesis. The addition of GSH-OEt to cumulus-denuded or BSO-treated oocytes increased the GSH content of bovine oocytes and restored the rate of normal fertilisation, but not embryo development, to levels seen in control oocytes. Thus, GSH-OEt represents a novel approach for effective in vitro elevation of bovine oocyte GSH and improvement in blastocyst cell number.
An examination of flame shape related to convection heat transfer in deep-fuel beds
Authors: Yedinak Kara M. , Cohen Jack D. , Forthofer Jason M. , Finney Mark A.
Published: March 2010

Fire spread through a fuel bed produces an observable curved combustion interface. This shape has been schematically represented largely without consideration for fire spread processes. The shape and dynamics of the flame profile within the fuel bed likely reflect the mechanisms of heat transfer necessary for the pre-heating and ignition of the fuel during fire spread. We developed a simple laminar flame model for examining convection heat transfer as a potentially significant fire spread process. The flame model produced a flame profile qualitatively comparable to experimental flames and similar to the combustion interface of spreading fires. The model comparison to flame experiments revealed that at increasing fuel depths (>0.7 m), lateral flame extension was increased through transition and turbulent flame behaviour. Given previous research indicating that radiation is not sufficient for fire spread, this research suggests that flame turbulence can produce the convection heat transfer (i.e. flame contact) necessary for fire spread particularly in vertically arranged, discontinuous fuels such as shrub and tree canopies.
Evaluating the Farming/Language Dispersal Hypothesis with genetic variation exhibited by populations in the Southwest and Mesoamerica
Authors: Kemp Brian M. , González-Oliver Angélica , Malhi Ripan S. , Monroe Cara , Schroeder Kari Britt , McDonough John , Rhett Gillian , Resendéz Andres , Peñaloza-Espinosa Rosenda I. , Buentello-Malo Leonor , Gorodesky Clara , Smith David Glenn
Published: March 2010

The Farming/Language Dispersal Hypothesis posits that prehistoric population expansions, precipitated by the innovation or early adop-tion of agriculture, played an important role in the uneven distribution of language families recorded across the world. In this case, the most widely spread language families today came to be distributed at the expense of those that have more restricted distributions. In the Americas, Uto-Aztecan is one such language family that may have been spread across Mesoamerica and the American Southwest by ancient farmers. We evaluated this hypothesis with a large-scale study of mitochondrial DNA (mtDNA) and Y-chromosomal DNA vari-ation in indigenous populations from these regions. Partial correlation coefficients, determined with Mantel tests, show that Y-chromosome variation in indigenous populations from the American Southwest and Mesoamerica correlates significantly with linguistic distances (r= 0.33–0.384;P< 0.02), whereas mtDNA diversity correlates significantly with only geographic distance (r= 0.619;P= 0.002). The lack of correlation between mtDNA and Y-chromosome diversity is consistent with differing population histories of males and females in these regions. Although unlikely, if groups of Uto-Aztecan speakers were responsible for the northward spread of agriculture and their languages from Mesoamerica to the Southwest, this migration was possibly biased to males. However, a recent in situ population expansion within the American Southwest (2,105 years before present; 99.5% confidence interval = 1,273–3,773 YBP), one that probably followed the introduction and intensification of maize agriculture in the region, may have blurred ancient mtDNA patterns, which might otherwise have revealed a closer genetic relationship between females in the Southwest and Mesoamerica.
Blocking the Wnt pathway, a unifying mechanism for an angiogenic inhibitor in the serine proteinase inhibitor family
Authors: Zhang Bin , Abreu Jose G. , Zhou Kevin , Chen Ying , Hu Yang , Zhou Ti , He Xi , Ma Jian-xing
Published: March 2010

The Wnt pathway regulates multiple biological and pathological processes including angiogenesis and inflammation. Here we identified a unique inhibitor of the Wnt pathway, SERPINA3K, a serine proteinase inhibitor with anti-inflammatory and angiogenic activities. SERPINA3K blocked the Wnt pathway activation induced by a Wnt ligand and by diabetes. Coprecipitation and ligand binding assay showed that SERPINA3K binds to low-density lipoprotein receptor-like protein 6 (LRP6) with a
K
d
of 10 nM, in the range of its physiological concentration in the retina. Under the same conditions, SERPINA3K did not bind to the frizzled (Fz) receptor or low-density lipoprotein receptor. Further, SERPINA3K bound to LRP6 at the extracellular domain and blocked its dimerization with the Fz receptor induced by a Wnt ligand. The antagonizing activity of SERPINA3K to LRP6 was further confirmed by
Xenopus
axis duplication assay. These results suggest that SERPINA3K is a high-affinity, endogenous antagonist of LRP6. The blockade of Wnt signaling may represent a unifying mechanism for the anti-inflammatory and anti-angiogenic effects of SERPINA3K.
Myosin complexed with ADP and blebbistatin reversibly adopts a conformation resembling the start point of the working stroke
Authors: Takács Balázs , Billington Neil , Gyimesi Máté , Kintses Bálint , Málnási-Csizmadia András , Knight Peter J. , Kovács Mihály
Published: March 2010

The powerstroke of the myosin motor is the basis of cell division and bodily movement, but has eluded empirical description due to the short lifetime and low abundance of intermediates during force generation. To gain insight into this process, we used well-established single-tryptophan and pyrene fluorescent sensors and electron microscopy to characterize the structural and kinetic properties of myosin complexed with ADP and blebbistatin, a widely used inhibitor. We found that blebbistatin does not weaken the tight actin binding of myosin.ADP, but unexpectedly it induces lever priming, a process for which the gamma-phosphate of ATP (or its analog) had been thought necessary. The results indicate that a significant fraction of the myosin.ADP.blebbistatin complex populates a previously inaccessible conformation of myosin resembling the start of the powerstroke.
Endoplasmic reticulum chaperone gp96 is essential for infection with vesicular stomatitis virus
Authors: Bloor Stuart , Maelfait Jonathan , Krumbach Rebekka , Beyaert Rudi , Randow Felix
Published: March 2010

The envelope glycoprotein of vesicular stomatitis virus (VSV-G) enables viral entry into hosts as distant as insects and vertebrates. Because of its ability to support infection of most, if not all, human cell types VSV-G is used in viral vectors for gene therapy. However, neither the receptor nor any specific host factor for VSV-G has been identified. Here we demonstrate that infection with VSV and innate immunity via Toll-like receptors (TLRs) require a shared component, the endoplasmic reticulum chaperone gp96. Cells without gp96 or with catalytically inactive gp96 do not bind VSV-G. The ubiquitous expression of gp96 is therefore essential for the remarkably broad tropism of VSV-G. Cells deficient in gp96 also lack functional TLRs, which suggests that pathogen-driven pressure for TLR-mediated immunity maintains the broad host range of VSV-G by positively selecting for the ubiquitous expression of gp96.