bluuebunny/crossref_metadata_2025 huggingface dataset:
Train‐borne measurements of tropical methane enhancements from ephemeral wetlands in Australia
Authors: Deutscher Nicholas M. , Griffith David W. T. , Paton‐Walsh Clare , Borah Rittick
Published: August 2010

We report greenhouse gas concentrations measured on a train covering a north‐south transect through central Australia from north to south coast. During the monsoonal wet season we found significant enhancements in methane that correlate well with changing area of wetland inundation in Australian tropical savanna regions. We used a meteorological and air pollution model to quantify the ephemeral wetland fluxes necessary to cause the observed enhancements and estimate the constant Australian tropical wetland emissions. Annual Australian tropical ephemeral wetland fluxes are estimated at 0.4 ± 0.2 Tg CH4, with permanent wetlands contributing a similar amount, 0.5 ± 0.2 Tg CH4.
Transport properties of the Callovo‐Oxfordian clay rock under partially saturated conditions
Authors: Jougnot D. , Revil A. , Lu N. , Wayllace A.
Published: August 2010

A series of experiments were performed to characterize the permeability, the specific storage, the capillary pressure, the streaming potential coupling coefficient, and the electrical conductivity of a very low permeability Callovo‐Oxfordian clay rock at different water saturations. The Callovo‐Oxfordian formation is presently investigated as a potential host to store nuclear wastes because of its very low permeability (typically 10 nd at saturation) and high specific surface area. We first present the constitutive transport equations including an electrokinetic cross‐coupling term in the generalized Darcy and Ohm constitutive equations. Then we present new experimental results using measurements of transient weight losses of samples submitted to a change in the relative humidity imposed by an automated humidity system in a hermetic chamber. These experiments are interpreted with a 1‐D analytical model of the coupled hydromechanical and transport equations. The hydromechanical transport properties (relative permeability and specific storage) of this clay rock are investigated in the relative saturation range from 0.23 to 0.70. We demonstrate that below 30% in relative humidity, the flux of the vapor phase with respect to the flux of the liquid water phase cannot be neglected. The relative apparent permeability can be described by a simple power law relationship with the saturation. In addition, we measure the electrical conductivity and the streaming potential coupling coefficient at various saturations. The electrical conductivity is described by a model accounting for electrical double‐layer contributions to surface conductivity. The measurement of the streaming potential coupling coefficient agrees with a power law model for the coupling coefficient versus the relative water saturation. A relationship between the exponent used to characterize the relative permeability and the second Archie's exponent used to describe the dependence of the electrical conductivity of the material with respect to the saturation is discussed.
Intensification of hot extremes in the United States
Authors: Diffenbaugh Noah S. , Ashfaq Moetasim
Published: August 2010

Governments are currently considering policies that will limit greenhouse gas concentrations, including negotiation of an international treaty to replace the expiring Kyoto Protocol. Existing mitigation targets have arisen primarily from political negotiations, and the ability of such policies to avoid dangerous impacts is still uncertain. Using a large suite of climate model experiments, we find that substantial intensification of hot extremes could occur within the next 3 decades, below the 2°C global warming target currently being considered by policy makers. We also find that the intensification of hot extremes is associated with a shift towards more anticyclonic atmospheric circulation during the warm season, along with warm‐season drying over much of the U.S. The possibility that intensification of hot extremes could result from relatively small increases in greenhouse gas concentrations suggests that constraining global warming to 2°C may not be sufficient to avoid dangerous climate change.
Rain use efficiency across a precipitation gradient on the Tibetan Plateau
Authors: Yang Yuanhe , Fang Jingyun , Fay Philip A. , Bell Jesse E. , Ji Chengjun
Published: August 2010

Our knowledge of the relationship between vegetation rain use efficiency (RUE) and precipitation is critical for predicting potential responses of grassland ecosystems to changing precipitation regimes. However, a generalized pattern of RUE along the precipitation gradient is still unavailable. Here we examined RUE variations in both Tibetan and global grasslands across precipitation gradients, using actual measurements obtained from a regional survey and a global dataset. RUE in Tibetan grasslands exhibited a unimodal pattern across the precipitation gradient, with an increasing trend in dry alpine steppe and a decreasing trend in mesic alpine meadow. RUE in alpine steppe was lower than in alpine meadow, largely due to their differences in species richness, soil texture and soil carbon content. The RUE of Tibetan grasslands was lower than global grasslands but displayed a similar trend with precipitation, suggesting the generality of a unimodal RUE pattern across diverse grassland types across broad precipitation gradients.
Dominant and diet-responsive groups of bacteria within the human colonic microbiota
Authors: Walker Alan W , Ince Jennifer , Duncan Sylvia H , Webster Lucy M , Holtrop Grietje , Ze Xiaolei , Brown David , Stares Mark D , Scott Paul , Bergerat Aurore , Louis Petra , McIntosh Freda , Johnstone Alexandra M , Lobley Gerald E , Parkhill Julian , Flint Harry J
Published: August 2010

The populations of dominant species within the human colonic microbiota can potentially be modified by dietary intake with consequences for health. Here we examined the influence of precisely controlled diets in 14 overweight men. Volunteers were provided successively with a control diet, diets high in resistant starch (RS) or non-starch polysaccharides (NSPs) and a reduced carbohydrate weight loss (WL) diet, over 10 weeks. Analysis of 16S rRNA sequences in stool samples of six volunteers detected 320 phylotypes (defined at >98% identity) of which 26, including 19 cultured species, each accounted for >1% of sequences. Although samples clustered more strongly by individual than by diet, time courses obtained by targeted qPCR revealed that ‘blooms’ in specific bacterial groups occurred rapidly after a dietary change. These were rapidly reversed by the subsequent diet. Relatives of Ruminococcus bromii (R-ruminococci) increased in most volunteers on the RS diet, accounting for a mean of 17% of total bacteria compared with 3.8% on the NSP diet, whereas the uncultured Oscillibacter group increased on the RS and WL diets. Relatives of Eubacterium rectale increased on RS (to mean 10.1%) but decreased, along with Collinsella aerofaciens, on WL. Inter-individual variation was marked, however, with >60% of RS remaining unfermented in two volunteers on the RS diet, compared to <4% in the other 12 volunteers; these two individuals also showed low numbers of R-ruminococci (<1%). Dietary non-digestible carbohydrate can produce marked changes in the gut microbiota, but these depend on the initial composition of an individual's gut microbiota.
Multiple syntrophic interactions in a terephthalate-degrading methanogenic consortium
Authors: Lykidis Athanasios , Chen Chia-Lung , Tringe Susannah G , McHardy Alice C , Copeland Alex , Kyrpides Nikos C , Hugenholtz Philip , Macarie Hervé , Olmos Alejandro , Monroy Oscar , Liu Wen-Tso
Published: August 2010

Terephthalate (TA) is one of the top 50 chemicals produced worldwide. Its production results in a TA-containing wastewater that is treated by anaerobic processes through a poorly understood methanogenic syntrophy. Using metagenomics, we characterized the methanogenic consortium inside a hyper-mesophilic (that is, between mesophilic and thermophilic), TA-degrading bioreactor. We identified genes belonging to dominant Pelotomaculum species presumably involved in TA degradation through decarboxylation, dearomatization, and modified β-oxidation to H2/CO2 and acetate. These intermediates are converted to CH4/CO2 by three novel hyper-mesophilic methanogens. Additional secondary syntrophic interactions were predicted in Thermotogae, Syntrophus and candidate phyla OP5 and WWE1 populations. The OP5 encodes genes capable of anaerobic autotrophic butyrate production and Thermotogae, Syntrophus and WWE1 have the genetic potential to oxidize butyrate to CO2/H2 and acetate. These observations suggest that the TA-degrading consortium consists of additional syntrophic interactions beyond the standard H2-producing syntroph–methanogen partnership that may serve to improve community stability.
The vascular contribution to Alzheimer's disease
Authors: Altman Robin , Rutledge John C.
Published: August 2010

AD (Alzheimer's disease) is a progressive neurodegenerative disease of unknown origin. Despite questions as to the underlying cause(s) of this disease, shared risk factors for both AD and atherosclerotic cardiovascular disease indicate that vascular mechanisms may critically contribute to the development and progression of both AD and atherosclerosis. An increased risk of developing AD is linked to the presence of the apoE4 (apolipoprotein E4) allele, which is also strongly associated with increased risk of developing atherosclerotic cardiovascular disease. Recent studies also indicate that cardiovascular risk factors, including elevated blood cholesterol and triacylglycerol (triglyceride), increase the likelihood of AD and vascular dementia. Lipids and lipoproteins in the circulation interact intimately with the cerebrovasculature, and may have important effects on its constituent brain microvascular endothelial cells and the adjoining astrocytes, which are components of the neurovascular unit. The present review will examine the potential mechanisms for understanding the contributions of vascular factors, including lipids, lipoproteins and cerebrovascular Aβ (amyloid β), to AD, and suggest therapeutic strategies for the attenuation of this devastating disease process. Specifically, we will focus on the actions of apoE, TGRLs (triacylglycerol-rich lipoproteins) and TGRL lipolysis products on injury of the neurovascular unit and increases in blood–brain barrier permeability.
Effects of Dining on Tongue Endurance and Swallowing-Related Outcomes
Authors: Kays Stephanie A. , Hind Jacqueline A. , Gangnon Ronald E. , Robbins JoAnne
Published: August 2010

Purpose

The purpose of this study was to test the hypothesis that eating a meal reduces tongue strength and endurance in healthy old and young adults. It was predicted that older adults would show greater declines in tongue endurance while demonstrating higher perceived effort, longer meal durations, and clinical signs of swallowing difficulty.

Method

Twenty-two healthy adults were enrolled into 2 groups (ages 20–35 years and ages 65–82 years; 5 males and 6 females each). Maximum tongue strength (P
max
) and endurance (duration 50% of P
max
could be maintained) were measured twice at baseline and once postmeal. Subjects consumed half of a bagel with peanut butter, carrot sticks, and milk between measures.

Results

All subjects demonstrated reduced tongue strength and endurance postmeal. Young adults showed a greater decline in anterior tongue endurance compared with older adults (
p
= .05). There was no evidence that changes in tongue strength, perceived effort, or meal duration varied by age or gender. The 3 oldest subjects reported the highest effort and displayed signs of difficulty swallowing while dining.

Conclusions

Young and old adults demonstrated reduced tongue strength and endurance after dining, but younger subjects showed greater declines in anterior tongue endurance, whereas older adults exhibited signs of swallowing difficulty.
Electrical and kinetic model of an atmospheric rf device for plasma aerodynamics applications
Authors: Pinheiro Mario J. , Martins Alexandre A.
Published: August 2010

The asymmetrically mounted flat plasma actuator is investigated using a self-consistent two-dimensional fluid model at atmospheric pressure. The computational model assumes the drift-diffusion approximation and uses a simple plasma kinetic model. It investigated the electrical and kinetic properties of the plasma, calculated the charged species concentrations, surface charge density, electrohydrodynamic forces, and gas speed. The present computational model contributes to understand the main physical mechanisms, and suggests ways to improve its performance.
Observation on asymmetric magnetization reversal in exchange-biased egg-shaped nanoparticles
Authors: Hu Yong , Liu Yan , Du An
Published: August 2010

For an egg-shaped nanoparticle model consisting of an antiferromagnetic (AFM) core and a ferromagnetic shell, Monte Carlo methods with a modified Metropolis algorithm are performed. We unambiguously demonstrate the dependence of exchange bias (EB) and magnetization reversal mechanism on cooling field, radius, and position of AFM core by observing the microscopic spin configurations and the microscopic spin energy distributions. The results show that the influence factors for EB and magnetization reversal mechanism are different. The effects of cooling field and radius of AFM core on EB are strong. However, the magnetization reversal mechanism is influenced strongly by the radius and position of AFM core. This work will stimulate further theoretical and experimental investigations of the relation between EB and magnetization reversal mechanism.
Reduction of deep levels generated by ion implantation into n- and p-type 4H–SiC
Authors: Kawahara Koutarou , Suda Jun , Pensl Gerhard , Kimoto Tsunenobu
Published: August 2010

The authors have investigated effects of thermal oxidation on deep levels in the whole energy range of the band gap of 4H–SiC by deep level transient spectroscopy. The deep levels are generated by ion implantation. The dominant defects in n-type samples after ion implantation and high-temperature annealing at 1700 °C are IN3 (Z1/2: EC−0.63 eV) and IN9 (EH6/7: EC−1.5 eV) in low-dose-implanted samples, and IN8 (EC−1.2 eV) in high-dose-implanted samples. These defects can remarkably be reduced by thermal oxidation at 1150 °C. In p-type samples, however, IP8 (HK4: EV+1.4 eV) survives and additional defects such as IP4 (HK0: EV+0.72 eV) appear after thermal oxidation in low-dose-implanted samples. In high-dose-implanted p-type samples, three dominant levels, IP5 (HK2: EV+0.85 eV), IP6 (EV+1.0 eV), and IP7 (HK3: EV+1.3 eV), are remarkably reduced by oxidation at 1150 °C. The dominant defect IP4 observed in p-type 4H–SiC after thermal oxidation can be reduced by subsequent annealing in Ar at 1400 °C. These phenomena are explained by a model that excess interstitials are generated at the oxidizing interface, which diffuse into the bulk region.
Pulse number dependence of laser-induced periodic surface structures for femtosecond laser irradiation of silicon
Authors: Bonse Jörn , Krüger Jörg
Published: August 2010

The formation of nearly wavelength-sized laser-induced periodic surface structures (LIPSS) on single-crystalline silicon upon irradiation with single (N=1) and multiple (N≤1000) linearly polarized femtosecond (fs) laser pulses (pulse duration τ=130 fs, central wavelength λ=800 nm) in air is studied experimentally. Scanning electron microscopy (SEM) and optical microscopy are used for imaging of the ablated surface morphologies, both revealing LIPSS with periodicities close to the laser wavelength and an orientation always perpendicular to the polarization of the fs-laser beam. It is experimentally demonstrated that these LIPSS can be formed in silicon upon irradiation by single fs-laser pulses—a result that is additionally supported by a recent theoretical model. Two-dimensional Fourier transforms of the SEM images allow the detailed analysis of the distribution of the spatial frequencies of the LIPSS and indicate, at a fixed peak fluence, a monotonous decrease in their mean spatial period between ∼770 nm (N=1) and 560 nm (N=1000). The characteristic decrease in the LIPSS period is caused by a feedback-mechanism acting upon excitation of surface plasmon polaritons at the rough silicon surface which is developing under the action of multiple pulses into a periodically corrugated surface.
Hydrodynamic interactions suppress deformation of suspension drops in Poiseuille flow
Authors: Sadlej Krzysztof , Wajnryb Eligiusz , Ekiel-Jeżewska Maria L.
Published: August 2010

Evolution of a suspension drop entrained by Poiseuille flow is studied numerically at a low Reynolds number. A suspension drop is modeled by a cloud of many nontouching particles, initially randomly distributed inside a spherical volume of a viscous fluid which is identical to the host fluid outside the drop. Evolution of particle positions and velocities is evaluated by the accurate multipole method corrected for lubrication, implemented in the HYDROMULTIPOLE numerical code. Deformation of the drop is shown to be smaller for a larger volume fraction. At high concentrations, hydrodynamic interactions between close particles significantly decrease elongation of the suspension drop along the flow in comparison to the corresponding elongation of the pure-fluid drop. Owing to hydrodynamic interactions, the particles inside a dense-suspension drop tend to stay for a long time together in the central part of the drop; later on, small clusters occasionally separate out from the drop, and are stabilized by quasiperiodic orbits of the constituent nontouching particles. Both effects significantly reduce the drop spreading along the flow. At large volume fractions, suspension drops destabilize by fragmentation, and at low volume fractions, by dispersing into single particles.
Frequency and temperature dependent impedance spectroscopy of cobalt ferrite composite thick films
Authors: Chen W. , Zhu W. , Tan O. K. , Chen X. F.
Published: August 2010

Cobalt ferrite (CoFe2O4) composite thick films consisting of two different sized CoFe2O4 particles were deposited on Pt/Ti/SiO2/Si substrate by a hybridized sol-gel processing and spin coating technique. X-ray diffraction analysis showed a pure spinel phase of CoFe2O4, which was also confirmed by micro-Raman spectra. Scanning electronic microscope indicated a dense microstructure with a thickness above 8 μm. The detailed electrical investigations were conducted in the frequency range of 100 Hz–1 MHz and temperature range between 25 and 200 °C. Real and imaginary parts of impedance (Z′ and Z″) in the above frequency and temperature domain suggested the coexistence of two relaxation regimes: one was induced by electrode polarization; while the other was attributed to the coeffect of grains and grain boundaries, which was totally different from its counterpart of bulks and also not reported in other ferrites. Electrical modulus (M′ and M″) further showed the crossover from grains effect to grain boundaries effect with increasing measured temperature under the suppression of electrode polarization. A non-Debye relaxation behavior and two segments of frequency independent conductivity were observed in dielectric spectra, which was also consistent with the results of ac conductivity spectra. In the conductivity spectra, double power law and single power law were separately applied to the coeffect from grains and grain boundaries and electrode polarization effect. Moreover, the dc conductivity from both effects well obeyed the Arrhenius law and their activation energies were matching to the ones calculated from imaginary impedance peaks, the detailed physical mechanisms on them were finally discussed.
Background carrier concentration in midwave and longwave InAs/GaSb type II superlattices on GaAs substrate
Authors: Khoshakhlagh A. , Jaeckel F. , Hains C. , Rodriguez J. B. , Dawson L. R. , Malloy K. , Krishna S.
Published: August 2010

We report on the measurement of the background carrier concentration of midwave and long-wave infrared (MWIR and LWIR) type-II InAs/GaSb superlattices (SLs) on GaAs substrates. The transport properties of SLs are characterized using temperature dependent Hall measurements. It is found that the conduction in the MWIR SLs is dominated by holes at low temperatures and by electrons at high temperatures. However, the transport in LWIR SL is dominated by electrons at all temperatures. In-plane transport characteristics of LW SLs grown at different temperatures shows that interface roughness scattering is the dominant scattering mechanism at high temperatures.
ZnO as a buffer layer for growth of BiFeO3 thin films
Authors: Wu Jiagang , Wang John
Published: August 2010

Multiferroic BiFeO3 thin film was grown on the ZnO-buffered Pt/TiO2/SiO2/Si(100) substrate by off-axis radio frequency magnetron sputtering, where the ZnO buffer layer gave rise to a strong (110) texture for the BiFeO3 thin film. The resulting BiFeO3/ZnO thin film exhibits diode-like and resistive hysteresis behavior, in which the resistive hysteresis and rectifying ratio are dependent on the applied voltage and temperature. The resistive switching behavior of the BiFeO3/ZnO thin film is shown to relate to the trap-controlled space charge limited conduction and interface-limited Fowler–Nordheim tunneling, while the polarization reversal takes place in the BiFeO3 layer of the heterostructure. The BiFeO3/ZnO thin film is also demonstrated with a higher remanent polarization (2Pr∼153.6 μC/cm2), a much lower dielectric loss (tan δ∼0.012), and a better fatigue endurance as compared to those of the BiFeO3 thin film without a ZnO buffer layer, where the much reduced leakage is largely responsible for the enhanced ferroelectric behavior. The ZnO as a buffer layer for BiFeO3 significantly changes the dielectric relaxation and conduction mechanisms, when the dielectric relaxation and electrical conduction are governed by the thermal excitation of carriers from the second-ionization and short-range motion of oxygen vacancies, respectively, while the relaxation process remains the same over the entire temperature range of 20 to 200 °C investigated in the present study.
Theoretical analysis of spectral linewidth of terahertz oscillators using resonant tunneling diodes and their coupled arrays
Authors: Asada Masahiro
Published: August 2010

The spectral linewidth of terahertz oscillators using resonant tunneling diodes and their coupled arrays is theoretically analyzed. The theoretical linewidths of single oscillators are consistent with the measured results. The linewidth of resonant tunneling diodes is considerably broader than that of terahertz quantum cascade lasers because of lower output power and the existence of shot noise. The theoretical analysis for a single oscillator is extended to a coupled array, and it is shown that the linewidth of a coupled N-element array reduces to 1/N that of a single oscillator, if the frequency deviation among the elements is small. With an increasing frequency deviation, the linewidth increases and exceeds that of a single oscillator. The linewidth also increases with the imaginary part of the coupling admittance between the elements.
Polarization Raman spectroscopy of GaN nanorod bundles
Authors: Tite T. , Lee C. J. , Chang Y.-M.
Published: August 2010

We performed polarization Raman spectroscopy on single wurtzite GaN nanorod bundles grown by plasma-assisted molecular beam epitaxy. The obtained Raman spectra were compared with those of GaN epilayer. The spectral difference between the GaN nanorod bundles and epilayer reveals the relaxation of Raman selection rules in these GaN nanorod bundles. The deviation of polarization-dependent Raman spectroscopy from the prediction of Raman selection rules is attributed to both the orientation of the crystal axis with respect to the polarization vectors of incident and scattered light and the structural defects in the merging boundary of GaN nanorods. The presence of high defect density induced by local strain at the merging boundary was further confirmed by transmission electron microscopy. The averaged defect interspacing was estimated to be around 3 nm based on the spatial correlation model.
Random laser action in dye solutions containing Stöber silica nanoparticles
Authors: Brito-Silva A. M. , Galembeck André , Gomes Anderson S. L. , Jesus-Silva Alcenisio J. , de Araújo Cid B.
Published: August 2010

Random laser action is obtained in a diffusive weakly scattering regime using an alcohol solution of rhodamine 640 with silica nanoparticles prepared by the Stöber method, with different average diameters of 49, 90, 219, and 490 nm. Particle size and concentration has proven to affect the random laser performance. It is also shown that silica nanoparticles contributes for a much slower photodegradation of the dye molecules than titania nanoparticles that has been used in the majority of the dye random lasers. This fact makes it advantageous to use silica nanoparticles for the fundamental studies of random laser, due to its increase in lifetime under pumping conditions.
Giant electrorheological effect in Fe2O3 nanofluids under low dc electric fields
Authors: Raykar Vijay S. , Sahoo S. K. , Singh Ashok K.
Published: August 2010

In this paper, we report the electrorheological (ER) properties of low concentration Fe2O3 nanofluids prepared in ethylene glycol (EG). Spherical Fe2O3 nanoparticles (NPs) were obtained by emulsion method in powder form. The obtained NPs were stabilized in time by acetylacetone in EG. The prepared Fe2O3 NPs were characterized using X-ray diffraction and transmission electron microscopy. Fe2O3 nanofluids were tested for ER behavior at low dc electric fields. Giant ER (GER) effect was observed in Fe2O3 nanofluid of higher concentration at electric field of 10 V/mm. The current passing through suspensions and electrohydrodynamic (EHD) convection was reflected in ring like structure formation of Fe2O3 NPs. Relation between suspension viscosity and Mason number revealed that the analysis has to be revised for GER fluids.
Enhanced thermoelectricity in composites by electronic structure modifications and nanostructuring
Authors: Popescu A. , Woods L. M.
Published: August 2010

The thermoelectric performance of nanocomposites with locally distorted density of states is investigated. The analytical expressions we have derived allow us to explore the effects of localized states modeled as Lorentzians on the materials transport properties in terms of their sharpness and locations relative to the Fermi level. Further optimization of the transport through nanostructuring design is also explored. We show that composites with both locally distorted density of states and nanostructure integration open the possibility for significant enhancement of the thermoelectric performance at room temperature.
Dynamics of highly excited barium atoms deposited on large argon clusters. I. General trends
Authors: Masson A. , Poisson L. , Gaveau M.-A. , Soep B. , Mestdagh J.-M. , Mazet V. , Spiegelman F.
Published: August 2010

Ba ( Ar ) ≈ 750 clusters were generated by associating the supersonic expansion and the pick-up techniques. A femtosecond pump (266.3 nm)-probe (792 or 399.2 nm) experiment was performed to document the dynamics of electronically excited barium within the very multidimensional environment of the argon cluster. Barium was excited in the vicinity of the 6s9p P1 state and probed by ionization. The velocity imaging technique was used to monitor the energy distribution of photoelectrons and photoions as a function of the delay time between the pump and the probe pulses. A complex dynamics was revealed, which can be interpreted as a sequence/superposition of elementary processes, one of which is the ejection of barium out of the cluster. The latter has an efficiency, which starts increasing 5 ps after the pump pulse, the largest ejection probability being at 10 ps. The ejection process lasts at a very long time, up to 60 ps. A competing process is the partial solvation of barium in low lying electronic states. Both processes are preceded by a complex electronic relaxation, which is not fully unraveled here, the present paper being the first one in a series.
The wave energy resource along Australia’s Southern margin
Authors: Hemer M. A. , Griffin D. A.
Published: August 2010

The Southern Australian margin is one of the most energetic regions in the world suitable for the extraction of wave energy for electricity generation. We have produced a data set in which the deep-water wave energy resource for the region is described by three representative deep-water wave states, equivalent to the 10th, 50th, and 90th percentiles of the deep-water wave energy flux, derived from archives of the USA National Oceanic and Atmospheric Administration (NOAA) WaveWatch III (NWW3) operational wave model. The Simulating WAves Nearshore (SWAN) wave model is then applied along the full Southern Australian margin to propagate these representative wave states into the near-shore region to quantify the effects of shallow water processes such as refraction, shoaling, and bottom friction. The wave energy incident on the 25-m isobath (∼30–50 kW/m) is approximately 35%–50% less than the World Energy Council estimates of offshore wave energy but is approximately 20% greater than the energy observed from long-term buoy deployments on the midshelf. The latter discrepancy is attributed to an overestimation of significant wave height along the Southern Australian margin by the NWW3 model. The near-shore model applied in this study adequately simulates the attenuation of wave heights across the continental shelf when compared with estimates of wave height attenuation obtained from the Topex satellite altimeter. The attenuation of wave energy across the continental shelf reduces the estimates of offshore wave energy as given by the World Energy Council; however the wave energy resource incident on the Southern Australian margin remains considerable. We estimate that if 10% of the incident near-shore energy in this region, which is an ambitious target when conversion efficiency is considered, were converted to electricity, approximately 130 TW h/yr (one-half of Australia’s total present-day electricity consumption) would be produced.
Quantitative evaluation of contact stiffness between pressed solid surfaces using dual-frequency ultrasound
Authors: Guo Xiasheng , Zhang Dong , Wu Junru
Published: August 2010

A dual-frequency ultrasonic technique is proposed for the quantitative evaluation of contact stiffness between pressed solid surfaces. Analytical solutions are obtained using a perturbation method, predicting the generation of difference-frequency and sum-frequency components, together with second harmonics of two primary waves. Experiments are performed for three types of interfaces, i.e., the interfaces of two aluminum alloy blocks with and without couplant and two glass blocks without couplant. The linear and nonlinear interfacial stiffness are measured quantitatively with the aid of a laser interferometer. The results of simulations are used to compare with experimental results. Nonlinearity parameters are defined to describe the nonlinearity generation efficiencies, while their pressure dependences are examined both theoretically and experimentally. Results show that couplant between interfaces affects the contact stiffness evaluations in an enhanced manner. The contacts between the transducer–sample interfaces are found to be the main source of errors.
Side-polished fiber Bragg grating refractive index sensor with TbFeCo magnetoptic thin film
Authors: Yang Minghong , Dai Jixiang , Li Xiaobin , Wang Junjie
Published: August 2010

Fiber Bragg grating (FBG) is side-polished to enable interaction with sensitive materials around FBG fiber core. Using TbFeCo magneto-optic thin film deposited onto FBG fiber core as transducer, a FBG refractive index senor for magnetic field/current characterization is first proposed and demonstrated in this paper. Magnetic field sensing experiments show 19 pm of wavelength shift at a magnetic field intensity of 50 mT, the average linearity of magnetic field response is 0.9877.
Laser-induced damage threshold of silicon in millisecond, nanosecond, and picosecond regimes
Authors: Wang X. , Shen Z. H. , Lu J. , Ni X. W.
Published: August 2010

Millisecond, nanosecond, and picosecond laser pulse induced damage thresholds on single-crystal are investigated in this study. The thresholds of laser-induced damage on silicon are calculated theoretically for three pulse widths based on the thermal damage model. An axisymmetric mathematical model is established for the transient temperature field of the silicon. Experiments are performed to test the damage thresholds of silicon at various pulse widths. The results indicate that the damage thresholds obviously increase with the increasing of laser pulse width. Additionally, the experimental results agree well with theoretical calculations and numerical simulation results.
Investigation of the roles of gas-phase CF2 molecules and F atoms during fluorocarbon plasma processing of Si and ZrO2 substrates
Authors: Cuddy Michael F. , Fisher Ellen R.
Published: August 2010

The molecular-level chemistry involved in the processing of silicon and zirconia substrates by inductively coupled fluorocarbon (FC) plasmas produced from CF4 and C2F6 precursors has been explored. The roles of gas-phase excited, neutral, and ionic species, especially CF2 and F, were examined as they contribute to FC film formation and substrate etching. The surface reactivity of CF2 radicals in C2F6 plasmas has a dependence on substrate material and plasma system, as measured by our imaging of radicals interacting with surfaces (IRIS) technique. Relative concentrations of excited state species are also dependent upon substrate type. Moreover, differences in the nature and concentrations of gas-phase species in CF4 and C2F6 plasmas contribute to markedly different surface compositions for FC films deposited on substrates as revealed from x-ray photoelectron spectroscopic analysis. These data have led to the development of a scheme that illustrates the mechanisms of film formation and destruction in these FC/substrate systems with respect to CF2 and F gas-phase species and also Si and ZrO2 substrates.
Solubilization of aromatic and hydrophobic moieties by arginine in aqueous solutions
Authors: Li Jianguo , Garg Manju , Shah Dhawal , Rajagopalan Raj
Published: August 2010

Experiments hold intriguing, circumstantial clues to the mechanisms behind arginine-mediated solubilization of small organic drugs and suppression of protein aggregation driven by hydrophobic or aromatic associations, but how exactly arginine’s molecular structure and interactions contribute to its function remains unclear since attention has focused so far on the thermodynamics of the preferential exclusion or binding of arginine. Here, we examine, through molecular dynamics simulations, how arginine solubilizes nanoscale particles with hydrophobic surfaces or aromatic-ring-type surface interactions. We show that preferential, hydrophobic, and dispersion interactions of arginine’s guanidinium group with the particles lead to a surfactant-like behavior of arginine around the particles and to a solvation layer with a protective polar mask creating a hydrophilic shell. Additionally, arginine-arginine association around the solvation layer further prevents aggregative contacts. The results shed some light on the mechanistic basis of arginine’s function as a suppressant of protein aggregation, although the complex energy landscapes and kinetic pathways of aggregation are protein-dependent and pose formidable challenges to developing comprehensive mechanistic pictures. Our results suggest arginine’s mode of interaction with hydrophobic patches and aromatic residues could reduce aggregation-prone intermediate states of proteins and shield protein-protein aggregative contacts. The approach used here offers a systematic way of exploring implications of other amino acid/excipient interactions by studying interactions of the excipient with particles grafted with amino acids.
Link atom bond length effect in ONIOM excited state calculations
Authors: Caricato Marco , Vreven Thom , Trucks Gary W. , Frisch Michael J.
Published: August 2010

We investigate how the choice of the link atom bond length affects an electronic transition energy calculation with the so-called our own N-layer integrated molecular orbital molecular mechanics (ONIOM) hybrid method. This follows our previous paper [M. Caricato et al., J. Chem. Phys. 131, 134105 (2009)], where we showed that ONIOM is able to accurately approximate electronic transition energies computed at a high level of theory such as the equation of motion coupled cluster singles and doubles (EOM-CCSD) method. In this study we show that the same guidelines used in ONIOM ground state calculations can also be followed in excited state calculations, and that the link atom bond length has little effect on the ONIOM energy when a sensible model system is chosen. We also suggest further guidelines for excited state calculations which can help in checking the effectiveness of the definition of the model system and controlling the noise in the calculation.
Terahertz photonic band gap for the transverse-magnetic modes formed by using a planar waveguide structure with a photonic crystal electrode
Authors: Sakasegawa Y. , Ihara T. , Hirakawa K.
Published: August 2010

We have investigated the terahertz (THz) emission from a semiconductor superlattice placed in a waveguide structure with a photonic crystal surface electrode of a honeycomb lattice pattern. For uniformly applying bias voltages, we inserted a semitransparent Ti film between the superlattice layer and the photonic crystal electrode. It is found that optimization of the sheet resistivity of the Ti layer is crucial to suppress the coupling between the waveguide mode and the surface leaky mode and obtain a clear photonic band gap. When the Ti layer was 40 nm, a large extinction ratio of ∼120 in the THz emission intensity was obtained at the midgap frequency around 1.7 THz.
Patterning nanowire and micro-/nanoparticle array on micropillar-structured surface: Experiment and modeling
Authors: Lin Chung Hsun , Guan Jingjiao , Chau Shiu Wu , Chen Shia Chung , Lee L. James
Published: August 2010

DNA molecules in a solution can be immobilized and stretched into a highly ordered array on a solid surface containing micropillars by molecular combing technique. However, the mechanism of this process is not well understood. In this study, we demonstrated the generation of DNA nanostrand array with linear, zigzag, and fork-zigzag patterns and the microfluidic processes are modeled based on a deforming body-fitted grid approach. The simulation results provide insights for explaining the stretching, immobilizing, and patterning of DNA molecules observed in the experiments.
Effects of active layer thickness and thermal annealing on polythiophene: Fullerene bulk heterojunction photovoltaic devices
Authors: Zeng Lichang , Tang Ching W. , Chen Shaw H.
Published: August 2010

The effect of thermal annealing on photovoltaic devices comprising poly(3-hexylthiophene):[6,6]-phenyl C61 butyric acid methyl ester (P3HT:PCBM) with thicknesses up to 1200 nm was investigated. Without thermal annealing, the efficiency of the as-prepared devices decreased with increasing active layer thickness, reflecting largely a reduction in the short-circuit current density and an inverse photocurrent spectral response. Thermal annealing of the full devices was found to substantially recover thick-film device efficiencies while reducing the thin-film device efficiencies. The profound variations in photovoltaic characteristics were interpreted in terms of vertical phase separation in the P3HT:PCBM blend film and Li+ diffusion from the LiF/Al contact.
Metal-organic chemical vapor deposition of quasi-normally-off AlGaN/GaN field-effect transistors on silicon substrates using low-temperature grown AlN cap layers
Authors: Tan S. , Selvaraj S. L. , Egawa T.
Published: August 2010

Low-temperature AlN grown on AlGaN/GaN heterostructure in situ by metal-organic chemical vapor deposition is used as gate insulator and passivation layer to form quasi-normally-off field-effect transistors on 4 in. silicon substrate. The AlN layer not only increases the sheet carrier density and mobility, which results in the increase of the maximum drain current and transconductance, but also decreases gate leakage and current collapse. Simulated band diagrams indicate that only a small potential difference exists between the AlN surface barrier height and the AlN/AlGaN interface. We show that low-temperature grown AlN is effective in suppressing trapping effects and in improving device performance.
Investigation of the intermediate phase and magnetocaloric properties in high-pressure annealing Ni–Mn–Co–Sn alloy
Authors: Ma S. C. , Xuan H. C. , Zhang C. L. , Wang L. Y. , Cao Q. Q. , Wang D. H. , Du Y. W.
Published: August 2010

The Ni–Mn–Co–Sn alloy is prepared by high-pressure annealing method. Besides the enhanced martensitic transformation temperature and the Curie temperature of austenite, an intermediate phase above the martensitic transformation is observed in this alloy. As a result, two successive magnetic entropy changes with the same sign are obtained around room-temperature, corresponding to the martensitic transformation and intermediate phase transition, respectively. The origin of the intermediate phase for high-pressure annealing Ni–Mn–Co–Sn alloy is discussed.
Effect of polarization-memory in SrTiO3/La0.9Sr0.1MnO3 multilayer on Si substrate
Authors: Zhang Yingtang , Zhang Yiming , Li Shengtao
Published: August 2010

SrTiO 3 / La 0.9 Sr 0.1 MnO 3 (STO/LSMO) multilayer was fabricated on n-Si (100) substrate by using a computer-controlled laser molecular-beam epitaxy technique. A rectifying behavior was observed in the multilayer. Meanwhile, the capancitance-voltage (C-V) characteristics were investigated, which reveals a hysteresis memory effect in forward and backward bias regions. A detail study suggests that the hysteresis behaviors originate from the cooperation and competition between the interfacial polarization and trapping/detrapping mechanisms. Our results are expected to meet the high desire of the optimization and device design of random access memory.
Global phosphorylation analysis of β-arrestin–mediated signaling downstream of a seven transmembrane receptor (7TMR)
Authors: Xiao Kunhong , Sun Jinpeng , Kim Jihee , Rajagopal Sudarshan , Zhai Bo , Villén Judit , Haas Wilhelm , Kovacs Jeffrey J. , Shukla Arun K. , Hara Makoto R. , Hernandez Marylens , Lachmann Alexander , Zhao Shan , Lin Yuan , Cheng Yishan , Mizuno Kensaku , Ma'ayan Avi , Gygi Steven P. , Lefkowitz Robert J.
Published: August 2010

β-Arrestin–mediated signaling downstream of seven transmembrane receptors (7TMRs) is a relatively new paradigm for signaling by these receptors. We examined changes in protein phosphorylation occurring when HEK293 cells expressing the angiotensin II type 1A receptor (AT1aR) were stimulated with the β-arrestin–biased ligand Sar
1
, Ile
4
, Ile
8
-angiotensin (SII), a ligand previously found to signal through β-arrestin–dependent, G protein-independent mechanisms. Using a phospho-antibody array containing 46 antibodies against signaling molecules, we found that phosphorylation of 35 proteins increased upon SII stimulation. These SII-mediated phosphorylation events were abrogated after depletion of β-arrestin 2 through siRNA-mediated knockdown. We also performed an MS-based quantitative phosphoproteome analysis after SII stimulation using a strategy of stable isotope labeling of amino acids in cell culture (SILAC). We identified 1,555 phosphoproteins (4,552 unique phosphopeptides), of which 171 proteins (222 phosphopeptides) showed increased phosphorylation, and 53 (66 phosphopeptides) showed decreased phosphorylation upon SII stimulation of the AT1aR. This study identified 38 protein kinases and three phosphatases whose phosphorylation status changed upon SII treatment. Using computational approaches, we performed system-based analyses examining the β-arrestin–mediated phosphoproteome including construction of a kinase-substrate network for β-arrestin–mediated AT1aR signaling. Our analysis demonstrates that β-arrestin–dependent signaling processes are more diverse than previously appreciated. Notably, our analysis identifies an AT1aR-mediated cytoskeletal reorganization network whereby β-arrestin regulates phosphorylation of several key proteins, including cofilin and slingshot. This study provides a system-based view of β-arrestin–mediated phosphorylation events downstream of a 7TMR and opens avenues for research in a rapidly evolving area of 7TMR signaling.
Gene targeting by homologous recombination in mouse zygotes mediated by zinc-finger nucleases
Authors: Meyer Melanie , de Angelis Martin Hrabé , Wurst Wolfgang , Kühn Ralf
Published: August 2010

Gene targeting by homologous recombination in embryonic stem cells is extensively used to generate specific mouse mutants. However, most mammalian species lack tools for targeted gene manipulation. Since double-strand breaks strongly increase the rate of homologous recombination at genomic loci, we explored whether gene targeting can be directly performed in zygotes by the use of zinc-finger nucleases. Here we report that gene targeting is achieved in 1.7–4.5% of murine one-cell embryos upon the coinjection of targeting vectors with zinc-finger nucleases, without preselection. These findings enable the manipulation of the mammalian germ line in a single step in zygotes, independent of ES cells.
Different Localizations and Cellular Behaviors of Leiomodin and Tropomodulin in Mature Cardiomyocyte Sarcomeres
Authors: Skwarek-Maruszewska Aneta , Boczkowska Malgorzata , Zajac Allison L. , Kremneva Elena , Svitkina Tatyana , Dominguez Roberto , Lappalainen Pekka
Published: August 2010

Leiomodin (Lmod) is a muscle-specific F-actin–nucleating protein that is related to the F-actin pointed-end–capping protein tropomodulin (Tmod). However, Lmod contains a unique ∼150-residue C-terminal extension that is required for its strong nucleating activity. Overexpression or depletion of Lmod compromises sarcomere organization, but the mechanism by which Lmod contributes to myofibril assembly is not well understood. We show that Tmod and Lmod localize through fundamentally different mechanisms to the pointed ends of two distinct subsets of actin filaments in myofibrils. Tmod localizes to two narrow bands immediately adjacent to M-lines, whereas Lmod displays dynamic localization to two broader bands, which are generally more separated from M-lines. Lmod's localization and F-actin nucleation activity are enhanced by interaction with tropomyosin. Unlike Tmod, the myofibril localization of Lmod depends on sustained muscle contraction and actin polymerization. We further show that Lmod expression correlates with the maturation of myofibrils in cultured cardiomyocytes and that it associates with sarcomeres only in differentiated myofibrils. Collectively, the data suggest that Lmod contributes to the final organization and maintenance of sarcomere architecture by promoting tropomyosin-dependent actin filament nucleation.