bluuebunny/crossref_metadata_2025 huggingface dataset:
A new interpretation of Mars aerobraking variability: Planetary wave‐tide interactions
Authors: Moudden Y. , Forbes J. M.
Published: September 2010

This study presents a new interpretation of Mars aerobraking density observations in terms of planetary wave‐tide interactions. Mars Global Surveyor and Mars Reconnaissance Orbiter provide invaluable information about tidal activity in the lower thermosphere of Mars through the longitude structure that they reveal in near‐Sun‐synchronous frame of reference. However, this same perspective does not permit one to uncover the origins of day‐to‐day variability of these structures. Herein, by employing a new arrangement of the data and understanding the relationship between spectral features in longitude space versus UT space, we are able to attribute a significant amount of density variability in the aerobraking region to the effect of tidal modulation by planetary waves in the 5–20 day period range.
Explosive lava‐water interactions in Elysium Planitia, Mars: Geologic and thermodynamic constraints on the formation of the Tartarus Colles cone groups
Authors: Hamilton Christopher W. , Fagents Sarah A. , Wilson Lionel
Published: September 2010

Volcanic rootless constructs (VRCs) are the products of explosive lava‐water interactions. VRCs are significant because they imply the presence of active lava and an underlying aqueous phase (e.g., groundwater or ice) at the time of their formation. Combined mapping of VRC locations, age‐dating of their host lava surfaces, and thermodynamic modeling of lava‐substrate interactions can therefore constrain where and when water has been present in volcanic regions. This information is valuable for identifying fossil hydrothermal systems and determining relationships between climate, near‐surface water abundance, and the potential development of habitable niches on Mars. We examined the western Tartarus Colles region (25–27°N, 170–171°E) in northeastern Elysium Planitia, Mars, and identified 167 VRC groups with a total area of ∼2000 km2. These VRCs preferentially occur where lava is ∼60 m thick. Crater size‐frequency relationships suggest the VRCs formed during the late to middle Amazonian. Modeling results suggest that at the time of VRC formation, near‐surface substrate was partially desiccated, but that the depth to the midlatitude ice table was ≲42 m. This ground ice stability zone is consistent with climate models that predict intermediate obliquity (∼35°) between 75 and 250 Ma, with obliquity excursions descending to ∼25–32°. For lava thicknesses ranging from 30 to 60 m and ground ice fractions ranging from 0.1 to 0.3, an ice volume of ∼4–23 km3could have been melted and/or vaporized by the time the lava solidified, and the associated hydrothermal systems could have retained temperatures >273 K for up to ∼1300 years.
Large‐scale responses of complex‐shaped coastlines to local shoreline stabilization and climate change
Authors: Slott Jordan M. , Murray A. Brad , Ashton Andrew D.
Published: September 2010

When modeling the large‐scale (> km) evolution of coastline morphology, the influence of natural forces is not the only consideration; ongoing direct human manipulations can substantially drive geomorphic change. In this paper, we couple a human component to a numerical model of large‐scale coastline evolution, incorporating beach “nourishment” (periodically placing sand on the beach, also called “beach replenishment” or “beach fill”). Beach nourishment is the most prevalent means humans employ to alter the natural shoreline system in our case study, the Carolina coastline. Beach nourishment can cause shorelines adjacent to those that are nourished to shift both seaward and landward. When we further consider how changes to storm behaviors could change wave climates, the magnitude of morphological change induced by beach nourishment can rival that expected from sea level rise and affect the coast as far as tens of kilometers away from the nourishment site. In some instances, nonlocal processes governing large‐scale cuspate‐cape coastline evolution may transmit the human morphological “signal” over surprisingly large (hundreds of kilometer) distances.
Preparing to Replace the Official Horizontal and Vertical Datums in the United States: Federal Geospatial Summit on Improving the National Spatial Reference System; Silver Spring, Maryland, 11–12 May 2010
Authors: Smith Dru , Shields Renee
Published: September 2010

The National Spatial Reference System (NSRS) contains both the official “horizontal” and “vertical” datums of the United States: the North American Datum of 1983 (NAD83) and the North American Vertical Datum of 1988 (NAVD88). Horizontal datums provide reference latitude and longitude on Earth's surface; vertical datums are used for describing elevation. The responsibility for defining, maintaining, and providing access to these datums falls to the National Geodetic Survey (NGS), an office within the National Oceanic and Atmospheric Administration (NOAA).

These datums were created to correct deficiencies in the previous (1920's era) datums. Still, they relied almost exclusively on terrestrial surveying and the use of passive marks for their realization. Once the Global Positioning System (GPS) and other space geodetic techniques were widely operational, some significant issues became apparent. First, NAD83 has a nongeocentricity (i.e., its origin differs from the known center of Earth's mass) of approximately 2.2 meters. Second, the use of NAVD88's unmonitored passive control benchmarks to determine elevations lacks critical vertical velocity information. Additionally, the zero‐elevation surface of NAVD88 is now known to be biased (50 centimeters) and tilted (2 meters from Florida to Alaska) relative to the geoid.
Framingham Cardiovascular Risk Profile Correlates with Impaired Hippocampal and Cortical Vasoreactivity to Hypercapnia
Authors: Glodzik Lidia , Rusinek Henry , Brys Miroslaw , Tsui Wai H , Switalski Remigiusz , Mosconi Lisa , Mistur Rachel , Pirraglia Elizabeth , de Santi Susan , Li Yi , Goldowsky Alexander , de Leon Mony J
Published: September 2010

Vascular risk factors affect cerebral blood flow ( CBF) and cerebral vascular reactivity, contributing to cognitive decline. Hippocampus is vulnerable to both Alzheimer's disease (AD) pathology and ischemia; nonetheless, the information about the impact of vascular risk on hippocampal perfusion is minimal. Cognitively, healthy elderly (NL = 18, 69.9 ± 6.7 years) and subjects with mild cognitive impairment (MCI = 15, 74.9 ± 8.1 years) were evaluated for the Framingham cardiovascular risk profile ( FCRP). All underwent structural imaging and resting CBF assessment with arterial spin labeling (ASL) at 3T magnetic resonance imaging (MRI). In 24 subjects (NL = 17, MCI = 7), CBF was measured after a carbon dioxide rebreathing challenge. Across all subjects, FCRP negatively correlated with hippocampal (ρ = −0.41, P = 0.049) and global cortical (ρ = −0.46, P = 0.02) vasoreactivity to hypercapnia ( VRh). The FCRP– VRh relationships were most pronounced in the MCI group: hippocampus (ρ = 0.77, P = 0.04); global cortex (ρ = 0.83, P = 0.02). The FCRP did not correlate with either volume or resting CBF. The hippocampal VRh was lower in MCI than in NL subjects ( Z = −2.0, P = 0.047). This difference persisted after age and FCRP correction (F[3,20] = 4.6, P = 0.05). An elevated risk for vascular pathology is associated with a reduced response to hypercapnia in both hippocampal and cortical tissue. The VRh is more sensitive to vascular burden than either resting CBF or brain volume.
The Influence of Carbon Dioxide on Brain Activity and Metabolism in Conscious Humans
Authors: Xu Feng , Uh Jinsoo , Brier Matthew R , Hart John , Yezhuvath Uma S , Gu Hong , Yang Yihong , Lu Hanzhang
Published: September 2010

A better understanding of carbon dioxide (CO2) effect on brain activity may have a profound impact on clinical studies using CO2 manipulation to assess cerebrovascular reserve and on the use of hypercapnia as a means to calibrate functional magnetic resonance imaging (fMRI) signal. This study investigates how an increase in blood CO2, via inhalation of 5% CO2, may alter brain activity in humans. Dynamic measurement of brain metabolism revealed that mild hypercapnia resulted in a suppression of cerebral metabolic rate of oxygen ( CMRO 2) by 13.4%±2.3% ( N=14) and, furthermore, the CMRO 2 change was proportional to the subject's end-tidal CO2 (Et-CO2) change. When using functional connectivity MRI (fcMRI) to assess the changes in resting-state neural activity, it was found that hypercapnia resulted in a reduction in all fcMRI indices assessed including cluster volume, cross-correlation coefficient, and amplitude of the fcMRI signal in the default-mode network (DMN). The extent of the reduction was more pronounced than similar indices obtained in visual-evoked fMRI, suggesting a selective suppression effect on resting-state neural activity. Scalp electroencephalogram (EEG) studies comparing hypercapnia with normocapnia conditions showed a relative increase in low frequency power in the EEG spectra, suggesting that the brain is entering a low arousal state on CO2 inhalation.
Arachidonic acid actions on functional integrity and attenuation of the negative effects of palmitic acid in a clonal pancreatic β-cell line
Authors: Keane Deirdre C. , Takahashi Hilton K. , Dhayal Shalinee , Morgan Noel G. , Curi Rui , Newsholme Philip
Published: September 2010

Chronic exposure of pancreatic β-cells to saturated non-esterified fatty acids can lead to inhibition of insulin secretion and apoptosis. Several previous studies have demonstrated that saturated fatty acids such as PA (palmitic acid) are detrimental to β-cell function compared with unsaturated fatty acids. In the present study, we describe the effect of the polyunsaturated AA (arachidonic acid) on the function of the clonal pancreatic β-cell line BRIN-BD11 and demonstrate AA-dependent attenuation of PA effects. When added to β-cell incubations at 100 μM, AA can stimulate cell proliferation and chronic (24 h) basal insulin secretion. Microarray analysis and/or real-time PCR indicated significant AA-dependent up-regulation of genes involved in proliferation and fatty acid metabolism [e.g. Angptl (angiopoietin-like protein 4), Ech1 (peroxisomal Δ3,5,Δ2,4-dienoyl-CoA isomerase), Cox-1 (cyclo-oxygenase-1) and Cox-2, P<0.05]. Experiments using specific COX and LOX (lipoxygenase) inhibitors demonstrated the importance of COX-1 activity for acute (20 min) stimulation of insulin secretion, suggesting that AA metabolites may be responsible for the insulinotropic effects. Moreover, concomitant incubation of AA with PA dose-dependently attenuated the detrimental effects of the saturated fatty acid, so reducing apoptosis and decreasing parameters of oxidative stress [ROS (reactive oxygen species) and NO levels] while improving the GSH/GSSG ratio. AA decreased the protein expression of iNOS (inducible NO synthase), the p65 subunit of NF-κB (nuclear factor κB) and the p47 subunit of NADPH oxidase in PA-treated cells. These findings indicate that AA has an important regulatory and protective β-cell action, which may be beneficial to function and survival in the ‘lipotoxic’ environment commonly associated with Type 2 diabetes mellitus.
Generation of high-order rotational Raman sidebands in the deep-ultraviolet region using molecular phase modulation induced by an intensity-modulated optical pulse
Authors: Yasaka Norifumi , Kida Yuichiro , Zaitsu Shin-ichi , Imasaka Totaro
Published: September 2010

We demonstrated the efficient excitation of coherent molecular motion for the generation of high-order rotational Stokes and anti-Stokes Raman emissions using a femtosecond laser. Molecular phase modulation of a probe beam was efficiently induced by an optical beat of the pump beam emitting at two different frequencies, the separation of which corresponded to the multiplicative inverse of the period of molecular rotation. The spectral width of the probe pulse was expanded to 10 nm in the deep-ultraviolet region, suggesting the generation of a 10 fs pulse by Fourier synthesis of the emission lines.
Effects influencing electron and hole retention times in Ge nanocrystal memory structures operating in the direct tunneling regime
Authors: Peibst R. , Erenburg M. , Bugiel E. , Hofmann K. R.
Published: September 2010

We present an experimental study of the electron and hole charging and discharging processes in the direct tunneling regime of Ge nanocrystals (NCs) embedded in the SiO2 of metal/oxide/semiconductor transistors. A specific aim was to verify theoretical predictions of very long hole retention times for Ge NCs embedded in SiO2 with thin (direct) tunneling barriers which could be harnessed for fast nonvolatile memories. While we observed longer electron retention times than theoretically predicted, we did not find experimentally the expected long hole retention times. To explain the discrepancies between our results and the theoretical predictions, several nonideal properties of the real Ge–NC:SiO2/Si system were investigated. In particular, a Ge NC preparation-induced increase in the volume trap density in the tunnel oxide and an increase in the trap density at the interface between the tunnel oxide and the Si substrate were detected. However, this moderate increase in the trap densities by about one order of magnitude (as compared to reference samples without any Ge NCs) does not provide a plausible explanation for the short hole retention times observed. Rather, an electron current into the NCs during hole retention seems to limit the retention times. This effect should already occur in the ideal Ge–NC:SiO2/Si system, thus preventing the non-volatile memory applications of Ge NC based devices operating in the direct tunneling regime.
Effect of Au contamination on the electrical characteristics of a “model” small-angle grain boundary in n-type direct silicon bonded wafer
Authors: Yu X. , Li X. , Fan R. , Yang D. , Kittler M. , Reiche M. , Seibt M. , Rozgonyi G.
Published: September 2010

We have investigated the electrical characteristics of a “model” small-angle grain boundary (GB) in n-type direct silicon bonded wafers with intentional Au contamination. It is found that the Au aggregated at the GB can cause new acceptorlike states, developing a potential barrier. The density of Au-related GB states is about 1–2×1012 cm−2 eV−1 in the energy range of Ec-0.65–Ec-0.33 eV. With the energy level becoming deeper, the corresponding electron capture cross-section becomes larger, in the order of magnitude 10−16–10−15 cm2. It is believed that Au contamination has strong influence on the electrical properties of GB. These results are interesting for the GB engineering of n-type multicrystalline silicon solar cells for terrestrial application.
Rashba electron’s ballistic transport in two-dimensional quantum waveguide
Authors: Liu Duan-Yang , Xia Jian-Bai
Published: September 2010

The ballistic transport of Rashba electrons in a straight structure in two-dimensional electron gas is studied. It is found that there is no mixing between the wave functions of spin up and spin down states, and the transfer matrix is independent for the spin in every interface. The influence of the structure and Rashba coefficient on the electron transport is investigated. Our results indicate that the transmission probabilities are independent of the sign and magnitude of the Rashba coefficient and it depends on the shape of the structure, especially the stub width. The antiresonance is found, where the quasiconfined state is formed in the center part of the structure.
A general figure of merit for thick and thin transparent conductive carbon nanotube coatings
Authors: Pekker Á. , Kamarás K.
Published: September 2010

We suggest a wavelength-dependent figure of merit for transparent conducting nanotube networks, composed of the sheet resistance and the optical density. We argue that this would be more useful than other suggestions prevailing in the literature because it relies on more realistic assumptions regarding the optical parameters of real nanotubes: it takes into account the fact that the dc resistivity depends on the concentration of free carriers, while the visible absorption is caused by bound carriers. Based on sheet resistance measurements and wide-range transmission spectra, we compare several commercial nanotube types and find correlation between metal enrichment and figure of merit. A simple graphical approach is suggested to determine if the required optical and transport properties can be achieved by varying the thickness of the nanotube layer or a more aggressive treatment is needed. The procedure can be extended to oxide coatings as well.
Excess entropy scaling of dynamic quantities for fluids of dumbbell-shaped particles
Authors: Chopra Ravi , Truskett Thomas M. , Errington Jeffrey R.
Published: September 2010

We use molecular simulation to study the ability of entropy scaling relationships to describe the kinetic properties of two Lennard-Jones dumbbell models. We begin by examining the excess entropy, the key quantity used to correlate dynamic properties within entropy scaling strategies. We compute the thermodynamic excess entropy as well as contributions to the two-body excess entropy stemming from translational and orientational intermolecular correlations. Our results indicate that the total two-body contribution accounts for more than 70% of the thermodynamic excess entropy at all state conditions explored. For the two dumbbell models studied here, the orientational component of the two-body excess entropy dominates at moderate and high fluid densities. We next investigate the relationships between kinetic properties and various contributions to the excess entropy. Four dynamic properties are considered: translational and rotational diffusivities, a characteristic relaxation time for rotational motion, and a collective relaxation time stemming from analysis of the coherent intermediate-scattering function. We find that the thermodynamic excess entropy provides the best metric for describing kinetic properties. For each of the dynamic properties considered, reduced data collapse onto a common curve when expressed as a function of the thermodynamic excess entropy. The likelihood of a two-body contribution to the excess entropy serving as a reliable scaling variable is linked to the extent to which it correlates with the thermodynamic excess entropy. The total two-body term contributes significantly to the excess entropy, and therefore this quantity generally serves as a suitable scaling variable.
Quantum effects in the radial thermal expansion of bundles of single-walled carbon nanotubes doped with He4
Authors: Dolbin A. V. , Esel’son V. B. , Gavrilko V. G. , Manzhelii V. G. , Vinnikov N. A. , Popov S. N. , Sundqvist B.
Published: September 2010

The radial thermal expansion αr of bundles of single-walled carbon nanotubes saturated with He4 impurities to the molar concentration 9.4% has been investigated in the interval 2.5–9.5K using the dilatometric method. In the interval 2.1–3.7K αr is negative and is several times higher than the negative αr for pure nanotube bundles. Most likely this points to He4 atom tunneling between different positions in the nanotube bundle system. The excess expansion was reduced with decreasing He4 concentration.
The energy minimization problem for two-level dissipative quantum systems
Authors: Bonnard B. , Cots O. , Shcherbakova N. , Sugny D.
Published: September 2010

In this article, we study the energy minimization problem of dissipative two-level quantum systems whose dynamics is governed by the Kossakowski–Lindblad equations. In the first part, we classify the extremal curve solutions of the Pontryagin maximum principle. The optimality properties are analyzed using the concept of conjugate points and the Hamilton–Jacobi–Bellman equation. This analysis completed by numerical simulations based on adapted algorithms allows a computation of the optimal control law whose robustness with respect to the initial conditions and dissipative parameters is also detailed. In the final section, an application in nuclear magnetic resonance is presented.
Integrated Lax formalism for principal chiral model
Authors: Yılmaz Nejat T.
Published: September 2010

By solving the first-order algebraic field equations which arise in the dual formulation of the D=2 principal chiral model (PCM), we construct an integrated Lax formalism built explicitly on the dual fields of the model rather than the currents. The Lagrangian of the dual scalar field theory is also constructed. Furthermore, we present the first-order partial differential equation (PDE) system for an exponential parametrization of the solutions and discuss the integrability of this system.
Twin-variant reorientation-induced large magnetoresistance effect in Ni50Mn29Ga21 single crystal
Authors: Zeng Min , Or Siu Wing , Zhu Zhiyong , Ho S. L.
Published: September 2010

We report a significant magnetoresistance (MR) effect arisen from magnetic field-induced reorientation of martensitic twin variants in a ferromagnetic shape memory Ni50Mn29Ga21 single crystal. The measured electrical resistivity shows large anisotropy and the measured MR value is as large as 25% over the wide temperature range of 230-315 K at a moderate magnetic field of 1.2 T. It is found that a proper combination of the initial state of martensitic twin variants and the direction and magnitude of applied magnetic field can give rise to either positive or negative MR value of ∼25%, thus allowing a periodic modulation of the MR effect in response to varying the spatial angle between the directions of applied magnetic field and electric current for every 180°.
Microbending losses in double-coated optical fibers caused by axial strain-induced creep deformation of polymeric coatings
Authors: Hsueh Yu-Chun , Lai Liang-Hsun , Tseng Tzu-Fan , Wu Jeng-Yue , Shiue Sham-Tsong
Published: September 2010

The viscoelastic behavior of commercial UV-cured polymeric coatings of optical fibers is evaluated using dynamic mechanic analysis. The results indicate that relaxation of stresses and/or strains in these coatings occurs by creep deformation. The axial strain-induced viscoelastic stresses in optical fibers are derived from the exact viscoelastic behavior of the polymeric coatings. Compressive radial stress on the glass fiber produces microbending losses, and therefore, microbending losses in double-coated optical fibers that are caused by axial strain-induced creep deformation of polymeric coatings are investigated. These microbending losses can be minimized by suitably selecting the thickness and physical properties of the polymeric coatings, as follows. The radius, Poisson’s ratio, and strain ratio of the primary coating should be increased, but the Young’s modulus and relaxation time of the primary coating should be decreased. The radius, Young’s modulus, Poisson’s ratio, and strain ratio of the secondary coating should be decreased, but the relaxation time of the secondary coating should be increased. When the thickness and physical properties of the polymeric coating are chosen to minimize the microbending loss, the thickness and Young’s modulus of the secondary coatings should be large enough to withstand an external mechanical force.
Deep levels affecting the resistivity in semi-insulating 6H–SiC
Authors: Kato M. , Kito K. , Ichimura M.
Published: September 2010

We characterized the temperature dependence of electrical resistivities and deep levels in semi-insulating 6H–SiC bulk wafers. Two of the three wafers characterized showed n-type conductivity while the third showed p-type conductivity. We measured the temperature dependence of the resistivity (ρ) and estimated its activation energy for all the samples. On the basis of the deep level parameters obtained from current deep level transient spectroscopy and photoinduced current level transient spectroscopy, we were able to reproduce ρ for n-type samples but not for the p-type sample. These results suggest that although the deep levels observed in this study have significant effects on ρ for semi-insulating n-type 6H–SiC, there are unobserved deep levels compensating acceptors.
Point-defect study from low-temperature photoluminescence of CdGa2Se4 layers through the postannealing in various ambient
Authors: You S. H. , Hong K. J. , Jeong T. S. , Youn C. J.
Published: September 2010

The CdGa2Se4 layers were grown by the hot-wall epitaxy method. From the absorption measurement, the band-gap variation in CdGa2Se4 was well interpreted using Varshni’s equation. After the postannealing in various ambient, the behavior of point defects in CdGa2Se4 was investigated by measuring photoluminescence (PL). Point defects originating from VCd, VSe, Cdint, and/or Seint were classified as donor or acceptor types. Thus, the Ga in CdGa2Se4 did not form native defects because the Ga existed in the form of stable bonds in CdGa2Se4. Based on these PL results, we schemed out a band diagram of the recombination process in CdGa2Se4.
Orbital ordering-driven ferromagnetism in LaCoO3 nanowires
Authors: Wang Yang , Fan Hong Jin
Published: September 2010

The structure and magnetic properties of LaCoO3 nanowires are investigated as a function of the diameter in the temperature range of 5–300 K. Ferromagnetism below 85 K is observed in these nanowires, in agreement with the recent observations in LaCoO3 epitaxial thin films and nanoparticles. With the diameter of nanowires decreasing, the unit-cell volume increases, while both the global and local structural distortions lessen, accompanied by the gradual enhancement of ferromagnetism. The structure analysis reveals that LaCoO3 nanowires exhibit a monoclinic distorted structure with I2/a space group in the entire investigated temperature range. Different from bulks, there is no clear spin-state transition occurring with temperature in LaCoO3 nanowires. There exists a noticeable Jahn–Teller (JT) distortion in the nanowires even at the lowest temperature, namely, orbital-ordered JT active Co3+ ions with intermediate-spin (IS) state persist at low temperatures, which is not observed in bulk LaCoO3. These results indicate that the ferromagnetism in the nanowires is driven by the orbital ordering of IS Co3+.
Experimental results on microwave pulse compression using helically corrugated waveguide
Authors: McStravick M. , Samsonov S. V. , Ronald K. , Mishakin S. V. , He W. , Denisov G. G. , Whyte C. G. , Bratman V. L. , Cross A. W. , Young A. R. , MacInnes P. , Robertson C. W. , Phelps A. D. R.
Published: September 2010

The paper presents new results on the development of a method to generate ultrahigh-power short-microwave pulses by using a known principle of compression (reduction in pulse duration accompanying with increase in pulse amplitude) of a frequency-swept wave packet propagating through a dispersive medium. An oversized circular waveguide with helical-corrugations of its inner surface ensures an eigenwave with strongly frequency dependent group velocity far from cutoff. These dispersive properties in conjunction with high rf breakdown strength and low Ohmic losses make a helically corrugated waveguide attractive for increasing microwave peak power. The experiments performed at kilowatt power levels, demonstrate that an X-band microwave pulse of 80 ns duration with a 5% frequency sweep can be compressed into a 1.5 ns pulse having 25 times higher peak power by optimizing the frequency modulation of the input wave packet.
Aqueous solvation of As(OH)3: A Monte Carlo study with flexible polarizable classical interaction potentials
Authors: Hernández-Cobos J. , Vargas M. Cristina , Ramírez-Solís A. , Ortega-Blake I.
Published: September 2010

A theoretical study of the hydration of arsenious acid is presented. This study included ab initio calculations and Monte Carlo simulations. The model potentials used for the simulations were ab initio derived and they include polarizability, nonadditivity, and molecular relaxation. It is shown that with these refined potentials it is possible to reproduce the available experimental evidence and therefore permit the study of clusters, as well as of the hydration process in solution. From the study of stepwise hydration and the Monte Carlo simulation of the condensed phase it is concluded that As(OH)3 presents a hydration scheme similar to an amphipathic molecule. This phenomenon is explained as due to the existence of both a positive electrostatic potential and a localized lone pair in the vicinity of As. These results are used to rationalize the known passage of As(OH)3 through aqua-glyceroporines.
Test of a new heat-flow equation for dense-fluid shock waves
Authors: Holian Brad Lee , Mareschal Michel , Ravelo Ramon
Published: September 2010

Using a recently proposed equation for the heat-flux vector that goes beyond Fourier’s Law of heat conduction, we model shockwave propagation in the dense Lennard-Jones fluid. Disequilibrium among the three components of temperature, namely, the difference between the kinetic temperature in the direction of a planar shock wave and those in the transverse directions, particularly in the region near the shock front, gives rise to a new transport (equilibration) mechanism not seen in usual one-dimensional heat-flow situations. The modification of the heat-flow equation was tested earlier for the case of strong shock waves in the ideal gas, which had been studied in the past and compared to Navier–Stokes–Fourier solutions. Now, the Lennard-Jones fluid, whose equation of state and transport properties have been determined from independent calculations, allows us to study the case where potential, as well as kinetic contributions are important. The new heat-flow treatment improves the agreement with nonequilibrium molecular-dynamics simulations under strong shock wave conditions, compared to Navier–Stokes.
Comparative and quantitative study of neutral debris emanated from tin plasmas produced by neodymium-doped yttrium-aluminum-garnet and carbon dioxide laser pulses
Authors: Matsuoka Yuji , Nakai Yuki , Fujioka Shinsuke , Maeda Shinsuke , Shimomura Masashi , Shimada Yoshinori , Sunahara Atsushi , Nishimura Hiroaki , Yoshida Minoru
Published: September 2010

Amount of neutral debris emanated from extreme ultraviolet light source must be minimized to maximize its lifetime. Emanation of neutral atomic debris was experimentally investigated using laser-induced-fluorescence technique for carbon dioxide (CO2, 10.6 μm in wavelength) and Nd-doped yttrium-aluminum-garnet (Nd:YAG, 1.064 μm) lasers irradiated tin foils. Total number of neutral atomic debris from CO2 laser-irradiated tin foils was 1/100 times smaller than that from Nd:YAG irradiated ones. Competitiveness of CO2 laser was revealed in terms of debris mitigation.
Correlation-bound anions of NaCl clusters
Authors: Sommerfeld Thomas , Bhattarai Bijay , Vysotskiy Victor P. , Cederbaum Lorenz S.
Published: September 2010

In the past a variety of electron binding motifs has been identified for sodium chloride cluster anions. As for all of these clusters the excess electron is predicted to be bound in self-consistent-field calculations, the different binding mechanisms can be understood in terms of a one-electron potential largely due to the permanent multipole moments of the neutral cluster. Here we investigate a new class of (NaCl)N− anion that is predicted to be bound only after electron correlation has been taken into account. Correlation-bound states of the trimer, (NaCl)3−, and tetramer, (NaCl)4−, are characterized using Green’s function and an equation-of-motion coupled-cluster method, and the computed electron binding energies as well as the distributions of the excess electrons as inferred from natural orbitals of the coupled-cluster calculations are compared with that of dipole-bound, quadrupole-bound, and defectlike (NaCl)N− anions. For the (NaCl)4− tetramer anion the correlation-bound state is predicted to represent the most stable isomer. Our results provide a sensitive test case for the development of improved one-electron model potentials for excess electrons bound to alkali halide clusters, and suggest that cluster abundance as inferred from peak intensities of photoelectron spectra is not directly related to the relative stability of the clusters.
Enhanced magnetoresistance in lateral spin-valves
Authors: Adari R. , Patil T. , Murthy M. , Maheshwari R. , Vaidya G. , Ganguly S. , Saha D.
Published: September 2010

The effect of feature sizes on the characteristics of lateral spintronic devices have been investigated experimentally and theoretically. It is demonstrated that confining spin-transport in the active region of a device enhances magnitude of the spin-dependent response substantially. Numerical simulation of spin-transport corroborates the experimental observations. Device characteristics are found to be a strong function of spin-polarizer and analyzer dimensions. The response is observed to attain a peak value for an optimum device feature size, and this is seen to be a function of temperature. Spin dependent effects become weaker for very small and very large devices.
Two-dimensional electron gas in Zn-polar ZnMgO/ZnO heterostructure grown by metal-organic vapor phase epitaxy
Authors: Ye J. D. , Pannirselvam S. , Lim S. T. , Bi J. F. , Sun X. W. , Lo G. Q. , Teo K. L.
Published: September 2010

We report the formation of two-dimensional electron gas (2DEG) at the Zn1−xMgxO/ZnO interface grown by metal-organic vapor phase epitaxy on sapphire substrates. The existence of the 2DEG is confirmed by the observation of Shubnikov–de Haas oscillations and the integer quantum Hall effect. In particular, the Zn0.8Mg0.2O/ZnO heterostructure shows a high Hall mobility of 2138 cm2/V s with a carrier sheet density of 3.51×1012 cm−2 at 1.4 K. We attribute the origin of 2DEG to be the donor states on ZnMgO surface. The dependence of carrier sheet density of 2DEG on ZnMgO layer thickness and Mg composition (x) are also investigated.
Nanopore-array-dispersed semiconductor quantum dots as nanosensors for gas detection
Authors: Zhao Zhouying , Dansereau Teresa M. , Petrukhina Marina A. , Carpenter Michael A.
Published: September 2010

CdSe quantum dots (QDs) and anodic aluminum oxide (AAO) nanopore arrays were integrated to form an optically active element for chemical vapor detection. The introduction of porous AAO as a platform for QD dispersion is found to have twofolds of merit for QD based chemical sensing. First, AAO intensifies QD photoluminescence (PL), thus increasing the measurable responses, due both to redistributing high intensity near-fields for efficient excitation of QDs and introducing strong scattering effects for enhanced extraction of the resulting QD emission. Second, the nanopores of AAO retard film-wetting effects which occur at higher target chemical exposures and result in an inverted PL response as seen from QDs or QD-polymer films cast on nonporous substrates. The PL and response sensitivity of QDs on AAO is further increased through the use of an Au coated silicon support which increases the overall reflectivity of the composite material stack. These strategies enable QD-based materials to be used for sensitive detection of chemical vapors with monotonic trends across large concentration ranges, for example, 10–9400 ppm xylenes. This method is readily extendable to other systems and opens the door to the development of QD-based optical or optoelectronic devices.
Sonic gradient index lens for aqueous applications
Authors: Martin Theodore P. , Nicholas Michael , Orris Gregory J. , Cai Liang-Wu , Torrent Daniel , Sánchez-Dehesa José
Published: September 2010

We study the acoustic scattering properties of a phononic crystal designed to behave as a gradient index lens in water, both experimentally and theoretically. The gradient index lens is designed using a square lattice of stainless-steel cylinders based on a multiple scattering approach in the homogenization limit. We experimentally demonstrate that the lens follows the graded index equations derived for optics by mapping the pressure intensity generated from a spherical source at 20 kHz. We find good agreement between the experimental result and theoretical modeling based on multiple scattering theory.
Can silicon behave like graphene? A first-principles study
Authors: Houssa M. , Pourtois G. , Afanas’ev V. V. , Stesmans A.
Published: September 2010

The electronic properties of two-dimensional hexagonal silicon (silicene) are investigated using first-principles simulations. Though silicene is predicted to be a gapless semiconductor, due to the sp2-hybridization of its atomic orbitals, the weak overlapping between 3pz orbitals of neighbor Si atoms leads to a very reactive surface, resulting in a more energetically stable semiconducting surface upon the adsorption of foreign chemical species. It is predicted that silicene inserted into a graphitelike lattice, like ultrathin AlN stacks, preserves its sp2-hydridization, and hence its graphenelike electronic properties.
Cooling rate and energy dependence of pulsed laser fabricated graphene on nickel at reduced temperature
Authors: Koh A. T. T. , Foong Y. M. , Chua Daniel H. C.
Published: September 2010

Few-layer graphene was fabricated on nickel substrates using pulsed laser deposition at a relatively low temperature of 750 °C. The effects of cooling rate and laser energy on the ability to produce crystalline graphene layers were studied. It was observed that using a cooling rate of 1 and 50 °C/min produced few-layer graphene while the latter gave less defects. Laser energy was a less critical factor as long as the laser energy was below 100 mJ, however a higher laser energy was detrimental to the precipitation process. The mechanisms behind the observation of such phenomena are explained.
Rare-earth plasma extreme ultraviolet sources at 6.5–6.7 nm
Authors: Otsuka Takamitsu , Kilbane Deirdre , White John , Higashiguchi Takeshi , Yugami Noboru , Yatagai Toyohiko , Jiang Weihua , Endo Akira , Dunne Padraig , O’Sullivan Gerry
Published: September 2010

We have demonstrated a laser-produced plasma extreme ultraviolet source operating in the 6.5–6.7 nm region based on rare-earth targets of Gd and Tb coupled with a Mo/B4C multilayer mirror. Multiply charged ions produce strong resonance emission lines, which combine to yield an intense unresolved transition array. The spectra of these resonant lines around 6.7 nm (in-band: 6.7 nm ±1%) suggest that the in-band emission increases with increased plasma volume by suppressing the plasma hydrodynamic expansion loss at an electron temperature of about 50 eV, resulting in maximized emission.
Modeling surface segregation phenomena in the (111) surface of ordered Pt3Ti crystal
Authors: Duan Zhiyao , Zhong Jun , Wang Guofeng
Published: September 2010

We investigated the surface segregation phenomena in the (111) surface of ordered Pt3Ti crystal using density functional theory (DFT) calculation (with no configuration sampling) and Monte Carlo (MC) simulation method (employing modified embedded atom method potentials and with extensive configuration sampling). Our DFT study suggested that the off-stoichiometric effect (specifically, a Pt concentration higher than 75 at. %) accounted for the experimentally observed Pt segregation to the outermost layer of the Pt3Ti (111). Our MC simulations predicted that in a Pt3Ti (111) sample with a Pt concentration slightly above 75 at. %, Pt atoms would segregate to the surface to form a pure Pt outermost layer, while the ordered Pt3Ti crystal structure would be maintained in the second layer and below. Moreover, our DFT calculations revealed that the d-band center of the Pt-segregated Pt3Ti (111) surface would downshift by 0.21 eV as compared to that of a pure Pt (111) surface. As a result, O adsorption energy on the Pt-segregated Pt3Ti (111) surface was found to be at least 0.16 eV weaker than that on the pure Pt (111) surface. Thus, we theoretically modeled the geometric and electronic structures of the Pt-segregated Pt3Ti (111) surface and further suggested that the Pt surface segregation could lead to enhanced catalytic activity for oxygen reduction reactions on Pt3Ti alloy catalysts.
Natural Resource Management implications of the pre-European non-volant mammal fauna of the southern tip of Eyre Peninsula, South Australia
Authors: McDowell Matthew C. , Medlin Graham C.
Published: September 2010

Sinkholes and coastal caves located in, around and between the Coffin Bay and Lincoln National Parks were surveyed for pre-European fossils, which were collected from or just below the sediment surface. Twenty-four pre-European fossil samples, including eight already in the collections of the South Australian Museum, were analysed and 25 native and five introduced species of non-volant mammal were identified. Native and introduced species were often found together, indicating that the sites have accumulated mammal remains in both pre- and post-European times. Only four of the non-volant native mammals recovered are known to be extant in the study area today: Lasiorhinus latifrons, Macropus fuliginosus, Cercartetus concinnus and Rattus fuscipes. In contrast, 20 native species recorded have been extirpated and one (Potorous platyops) is now extinct. C. concinnus was recorded from only one of the fossil assemblages but is known to be widespread in the study area today. This may indicate recent vegetation change related to European land management practices and have implications for natural resource management in the area.
A novel observation of dingoes (Canis lupus dingo) attacking a swimming eastern grey kangaroo (Macropus giganteus)
Authors: Purcell Brad V.
Published: September 2010

The dingo (Canis lupus dingo) is a keystone species in Australian ecosystems. The current study reports four dingoes observed attacking a swimming eastern grey kangaroo (Macropus giganteus) in the Wollondilly River, New South Wales. It is proposed that kangaroos need to stand at a certain depth of water to escape an attack by dingoes. If dingoes can continue attacking from opposing directions without threat of injury from the kangaroo, such as in shallow water where dingoes can stand or deep water where kangaroos cannot stand, then the attack may continue until the predator(s) kill the prey or the prey escapes. Further research on such behaviours is needed to understand the functional role of dingoes and the importance of pack structure in development of hunting strategies.
Variation in the home-range size of the squirrel glider (Petaurus norfolcensis)
Authors: Goldingay Ross L. , Sharpe David J. , Dobson Matt D. J.
Published: September 2010

The home-range area of animals may vary geographically and in response to habitat quality. We investigated the size of squirrel glider (Petaurus norfolcensis) home ranges near Brisbane, Queensland, and at Tea Gardens on the central coast of New South Wales. Habitat at both sites had been partially cleared and had been subjected to grazing for several decades. Twelve gliders were tracked over an average of 3.5 months in Brisbane. The fixed kernel (FK95%) home-range estimate averaged 4.6 ± 0.7 (s.e.) ha while the minimum convex polygon (MCP100%) averaged 6.7 ± 1.5 ha. Six gliders were tracked over 1 month at Tea Gardens. The FK95% home-range estimate averaged 14.8 ± 2.4 ha while the MCP100% averaged 13.3 ± 3.1 ha. The Tea Gardens values are derived from relatively short periods and are likely to underestimate the areas used. This study demonstrates that home-range size can vary substantially in the squirrel glider. This has implications for understanding how this species responds to variation in habitat quality and highlights the need for site-specific studies to inform aspects of management.
Observations of a large colony of bats roosting in a church
Authors: Sanderson Ken J. , Napier Gillian , Johnston Greg R.
Published: September 2010

The nightly and seasonal activity patterns of a large colony of bats roosting in a country church are described. In summer 400–700 bats from two species – southern freetail bat (Mormopterus sp. 4) and chocolate wattled bat (Chalinolobus morio) – left the roost beginning around civil twilight. Bats emerged at a rate of up to 40–50 min–1, and took 30 min or longer to clear the roost.
Direct male parental care observed in wild sugar gliders
Authors: Goldingay Ross L.
Published: September 2010

Observations were made of a pair of wild sugar gliders (Petaurus breviceps) occupying a nest box. When the two young of this pair were ~65 days old, the adult male remained with them within the nest box for at least the first three hours of the night on consecutive nights. This is consistent with the hypothesis that, whilst the mother forages, care from other family members is required to prevent the young becoming hypothermic. This provides the first field evidence of direct male parental care in this species.
Skin and bone: observations of dingo scavenging during a chronic food shortage
Authors: Allen Benjamin L.
Published: September 2010

Dingo (Canis lupus dingo and hybrids) diet studies primarily rely on analyses of prey remains found in stomachs or scats (i.e. faeces). However, dingoes are also scavengers, and doubt may remain as to whether or not a given item found in a stomach/scat was killed or scavenged. This paper briefly reports some incidental observations of dingoes scavenging cattle (Bos taurus), red kangaroos (Macropus rufus), wedge-tailed eagles (Aquila audax), and other dingo carcasses during a chronic food shortage. This confirms that diet studies may not be evidence for predation, and that dietary items collected during a discrete period may not actually reflect the period when the item died.
High koala mortality associated with low browse moisture in tropical environments
Authors: Clifton Irene Delma
Published: September 2010

At St Bees Island, central Queensland, during drought conditions from July 2001 to April 2003, 85% of koala deaths occurred when browse moisture fell below 51% fresh weight. Drought-induced mortality (and changing frequencies or intensities of drought due to climate change) may have a considerable effect upon this population.
The Radio-FIR Correlation in the Milky Way
Authors: Zhang J. , Hopkins A. , Barnes P. J. , Cagnes M. , Yonekura Y. , Fukui Y.
Published: September 2010

We investigate the scale on which the correlation arises between the 843 MHz radio and the 60 μm far-infrared (FIR) emission from star forming regions in the Milky way. The correlation, which exists on the smallest scales investigated (down to ≈ 4 pc), becomes noticeably tight on fields of size 30′, corresponding to physical scales of ≈ 20–50 pc. The FIR to radio flux ratio on this scale is consi stent with the radio emission being dominated by thermal emission. We also investigate the location dependence of qmean, a parameter measuring the mean FIR to radio flux ratio, of a sample of star forming regions. We show that qmean displays a modest dependence on galactic latitude. If this is interpreted as a dependence on the intensity of star formation activity, the result is consistent with studies of the Large Magellanic Cloud (LMC) and other near by galaxies that show elevated values for q in regions of enhanced star formation.