bluuebunny/crossref_metadata_2025 huggingface dataset:
Aperiodic recurrence of geologically recorded tsunamis during the past 5500 years in eastern Hokkaido, Japan
Authors: Sawai Yuki , Kamataki Takanobu , Shishikura Masanobu , Nasu Hiroo , Okamura Yukinobu , Satake Kenji , Thomson Katie H. , Matsumoto Dan , Fujii Yushiro , Komatsubara Junko , Aung Than Tin
Published: January 2009

Along Hokkaido's Pacific coast near the town of Kiritappu, sandy deposits in a muddy lagoon and on a nearby beach‐ridge plain provide evidence for 15 tsunamis between 200 and 6000 years ago. Additional sand beds at the lagoon probably represent the historical tsunamis of A.D. 1843 and 1894. We observed the sequences of sandy deposits in continuous slices 2 to 4 m deep. Some of the deposits consist of just a single sand bed, whereas others contain multiple units of sand, muddy sand (or sandy mud), and mud caps including plant detritus. We also found at the lagoon a 17th century tsunami deposit that thickens and thins regardless of elevation or distance inland. We bracketed the ages of most of the inferred tsunamis by radiocarbon dating of detritus, mainly seeds and leaves at the lagoon and charcoal at the beach‐ridge plain, from pretsunami and posttsunami beds. Tsunami dates computed from the bracketing ages commonly have uncertainties spanning 2 to 4 centuries. Within these uncertainties, the inferred sequence of 15 prehistoric tsunamis at the lagoon, beginning almost 6000 years ago, can be matched tsunami by tsunami with the inferred history at the beach‐ridge plain, 15 km away. The sand sheet extents suggest that most of these tsunamis were larger than any generated at Hokkaido in the last 200 years. The intervals between these inferred outsized tsunamis average nearly 400 years but range widely from about 100 to about 800 years.
Geochronology of granulitized eclogite from the Ama Drime Massif: Implications for the tectonic evolution of the South Tibetan Himalaya
Authors: Cottle John M. , Jessup Micah J. , Newell Dennis L. , Horstwood Matthew S. A. , Noble Stephen R. , Parrish Randall R. , Waters David J. , Searle Michael P.
Published: January 2009

The Ama Drime Massif (ADM) is an elongate north‐south trending antiformal feature that extends ∼70 km north across the crest of the South Tibetan Himalaya and offsets the position of the South Tibetan Detachment system. A detailed U(‐Th)‐Pb geochronologic study of granulitized mafic eclogites and associated rocks from the footwall of the ADM yields important insights into the middle to late Miocene tectonic evolution of the Himalayan orogen. The mafic igneous precursor to the granulitized eclogites is 986.6 ± 1.8 Ma and was intruded into the paleoproterozoic (1799 ± 9 Ma) Ama Drime orthogneiss, the latter being similar in age to rocks previously assigned to the Lesser Himalayan Series in the Himalayan foreland. The original eclogite‐facies mineral assemblage in the mafic rocks has been strongly overprinted by granulite facies metamorphism at 750°C and 0.7–0.8 GPa. In the host Ama Drime orthogneiss, the granulite event is correlated with synkinematic sillimanite‐grade metamorphism and muscovite dehydration melting. Monazite and xenotime ages indicate that the granulite metamorphism and associated anatexis occurred at <13.2 ± 1.4 Ma. High‐grade metamorphism was followed by postkinematic leucogranite dyke emplacement at 11.6 ± 0.4 Ma. This integrated data set indicates that high‐temperature metamorphism, decompression, and exhumation of the ADM postdates mid‐Miocene south directed midcrustal extrusion and is kinematically linked to orogen‐parallel extension.
Hydrogeologic controls on disconnection between surface water and groundwater
Authors: Brunner Philip , Cook Peter G. , Simmons Craig T.
Published: January 2009

Understanding how changes in the groundwater table affect surface water resources is of fundamental importance in quantitative hydrology. If the groundwater table below a stream is sufficiently deep, changes in the groundwater table position effectively do not alter the infiltration rate. This is referred to as a disconnected system. Previous authors noted that a low‐conductivity layer below the surface water body is a necessary but not sufficient criterion for disconnection to occur. We develop a precise criterion that allows an assessment of whether surface water–groundwater systems can disconnect or not. We further demonstrate that a disconnected system can be conceptualized by a saturated groundwater mound and the development of a capillary zone above this mound. This conceptualization is used to determine the critical water table position at the point where full disconnection is reached. A comparison of this calculated critical water table position with a measurement of the water table depth in a borehole allows the assessment of the disconnection status. A sensitivity analysis of this critical water table showed that for a given aquifer thickness and river width, the depth to groundwater where the system disconnects is approximately proportional to the stream depth and the hydraulic conductivity of the streambed sediments and inversely proportional to the thickness of these sediments and the hydraulic conductivity of the aquifer. The conceptualization also allows the disconnection problem to be analyzed using both variably saturated and fully saturated groundwater models and provides guidance for numerical and analytical approaches.
Effects of hydraulic conductivity variability on hillslope‐scale shallow subsurface flow response and storage‐discharge relations
Authors: Harman Ciaran , Sivapalan Murugesu
Published: January 2009

An important problem in scientific hydrology is accounting for the effect of small‐scale heterogeneity in lumped representations of flow through landscapes. In this work we investigate the effect of lateral variations in hydraulic conductivity on saturated subsurface lateral flow through hillslopes using an idealized model based on the Boussinesq equation. The model simulates flow over an impervious planar base through heterogeneous conductivity fields in response to simple recharge inputs and periodic recharge events. The results indicate that the hillslope‐scale response depends on the relative importance of topographic and water table potential gradients driving flow. The relative magnitude of these drivers is related to a dimensionless variable . Where water table gradients dominate, a network of flow paths channel flow through the hillslope toward high‐conductivity areas, and the response is primarily dependent on the boundary condition at the toe of the hillslope. Where the topographic gradients dominate, the flow is delayed by low‐conductivity areas, producing a power law–like response, suggesting that high exponents in observed storage‐discharge relations may be traced to the presence of heterogeneity in the landscape. These observations suggest that the nature of the lumped hillslope‐scale hydrologic models depends on the emergent behaviors that arise at that scale as a result of the interactions between hillslope properties (including their variability in space), the relationship between the hillslopes and their surrounding landscape elements (through the boundary conditions), and the temporal variability of the recharge that enters the system.
Structural and functional characterization of SplA, an exclusively specific protease of Staphylococcus aureus
Authors: Stec-Niemczyk Justyna , Pustelny Katarzyna , Kisielewska Magdalena , Bista Michal , Boulware Kevin T. , Stennicke Henning R. , Thogersen Ida B. , Daugherty Patrick S. , Enghild Jan J. , Baczynski Krzysztof , Popowicz Grzegorz M. , Dubin Adam , Potempa Jan , Dubin Grzegorz
Published: January 2009

Staphylococcus aureus is a dangerous human pathogen whose antibiotic resistance is steadily increasing and no efficient vaccine is as yet available. This serious threat drives extensive studies on staphylococcal physiology and pathogenicity pathways, especially virulence factors. Spl (serine protease-like) proteins encoded by an operon containing up to six genes are a good example of poorly characterized secreted proteins probably involved in virulence. In the present study, we describe an efficient heterologous expression system for SplA and detailed biochemical and structural characterization of the recombinant SplA protease. The enzyme shares a significant sequence homology to V8 protease and epidermolytic toxins which are well documented staphylococcal virulence factors. SplA has a very narrow substrate specificity apparently imposed by the precise recognition of three amino acid residues positioned N-terminal to the hydrolysed peptide bond. To explain determinants of this extended specificity we resolve the crystal structure of SplA and define the consensus model of substrate binding. Furthermore we demonstrate that artificial N-terminal elongation of mature SplA mimicking a naturally present signal peptide abolishes enzymatic activity. The probable physiological role of the process is discussed. Of interest, even though precise N-terminal trimming is a common regulatory mechanism among S1 family enzymes, the crystal structure of SplA reveals novel significantly different mechanistic details.
Transient limb ischaemia remotely preconditions through a humoral mechanism acting directly on the myocardium: evidence suggesting cross-species protection
Authors: Shimizu Mikiko , Tropak Michael , Diaz Roberto J. , Suto Fumiaki , Surendra Harinee , Kuzmin Elena , Li Jing , Gross Gil , Wilson Gregory J. , Callahan John , Redington Andrew N.
Published: January 2009

rIPC (remote ischaemic preconditioning) is a phenomenon whereby short periods of ischaemia and reperfusion of a tissue or organ (e.g. mesentery, kidney) can protect a distant tissue or organ (e.g. heart) against subsequent, potentially lethal, ischaemia. We, and others, have shown that transient limb ischaemia can provide potent myocardial protection experimentally and clinically during cardiac surgery. Nonetheless, our understanding of the signal transduction from remote stimulus to local effect remains incomplete. The aim of the present study was to define the humoral nature of rIPC effector(s) from limb ischaemia and to study their local effects in isolated heart and cardiomyocyte models. Using a Langendorff preparation, we show that infarct size after coronary artery ligation and reperfusion was substantially reduced by rIPC in vivo, this stimulus up-regulating the MAPKs (mitogen-activating protein kinases) p42/p44, and inducing PKCε (protein kinase Cε) subcellular redistribution. Pre-treatment with the plasma and dialysate of plasma (obtained using 15 kDa cut-off dialysis membrane) from donor rabbits subjected to rIPC similarly protected against infarction. The effectiveness of the rIPC dialysate was abrogated by passage through a C18 hydrophobic column, but eluate from this column provided the same level of protection. The dialysate of rIPC plasma from rabbits and humans was also tested in an isolated fresh cardiomyocyte model of simulated ischaemia and reperfusion. Necrosis in cardiomyocytes treated with rIPC dialysate was substantially reduced compared with control, and was similar to cells pre-treated by ‘classical’ preconditioning. This effect, by rabbit rIPC dialysate, was blocked by pre-treatment with the opiate receptor blocker naloxone. In conclusion, in vivo transient limb ischaemia releases a low-molecular-mass (<15 kDa) hydrophobic circulating factor(s) which induce(s) a potent protection against myocardial ischaemia/reperfusion injury in Langendorff-perfused hearts and isolated cardiomyocytes in the same species. This cardioprotection is transferable across species, independent of local neurogenic activity, and requires opioid receptor activation.
Magnetic properties and transport of epitaxial La0.47Ce0.20Ca0.33MnO3−δ films
Authors: Ren W. J. , Yang J. L. , Zhang Y. Q. , Li D. , Wang Z. H. , Zhao X. G. , Zhang Z. D.
Published: January 2009

Single-phase epitaxial La0.47Ce0.20Ca0.33MnO3−δ films on (001) SrTiO3 were prepared by pulsed laser deposition and by reducing the oxygen pressure for deposition. The decrease in the magnitude of oxygen drives the transformation of Ce4+ to Ce3+ ion, restraining the appearance of CeO2 that usually exists as impurity in bulk La0.47Ce0.20Ca0.33MnO3. The magnetic transition temperature of the films increases with increasing the deposition oxygen pressure. The temperature dependence of the electrical resistance (R) of the single-phase films obeys the thermally activated behavior. A postannealing procedure was carried out on a film deposited in 0.4Pa. The magnetic transition temperature is markedly increased and R is dramatically decreased by annealing. A metal-insulator transition occurs at 217K with a magnetoresistance of −73% for the annealed film. This metal-insulator transition temperature is much higher than that of the bulk La0.47Ce0.20Ca0.33MnO3.
Exchange bias behavior of nanocrystalline FeCuNbSiB ribbons
Authors: He J. , Zhao D. L. , Wang X. L. , Yao Q. , Qiang Y.
Published: January 2009

Exchange bias phenomena of nanocrystalline FeCuNbSiB ribbons have been investigated at room temperature. It was found that the rougher surface of ribbons annealed in longitudinal field played a main role in bringing the bias behavior in our ribbons. The topography of ribbon surfaces and the configuration of magnetic domains were specially observed in order to make clear the dependence of bias behavior on the induced magnetic anisotropy. A simple phenomenological explanation was also put forward to promote the comprehension of loop shift in ribbons and its possibility of potential applications.
Stability of ferromagnetic state of epitaxially grown ordered FeRh thin films
Authors: Suzuki Ippei , Koike Takayoshi , Itoh Mitsuru , Taniyama Tomoyasu , Sato Tetsuya
Published: January 2009

We report on the magnetic properties of B2-type ordered FeRh epitaxial thin films deposited on MgO(001) substarates as a function of film thickness. All the films show a clear magnetic phase transition from the antiferromagnetic state to the ferromagnetic state with increasing temperature while the transition temperature of a 10-nm-thick film decreases down to 300K. The 10-nm-thick film also shows a large magnetization even in the antiferromagnetic state compared with other thicker films. These magnetization data indicate that the ferromagnetic state is becoming more stable than the antiferromagnetic state with decreasing film thickness. Such thickness dependent magnetic properties are qualitatively compatible with a theoretical prediction for FeRh(001) thin layers.
Comment on “New statistical mechanical model for calculating Kirkwood factors in self-associating liquid systems and its application to alkanol+cyclohexane mixtures” [J. Chem. Phys. 127, 114501 (2007)]
Authors: Durov Vladimir A.
Published: January 2009

A brief overview of the current state of the research on calculation of Kirkwood factor of liquid alcohols and their mixtures is presented. On the basis of the accurate solution for the correlation factor, obtained in the author’s published papers, it was stated that the formulas for Kirkwood factor of alcohols gK and their mixtures with inert solvents (hydrocarbons) obtained in the paper by Vasiltsova and Heintz [J. Chem. Phys. 127, 114501 (2007)], in the opinion of the present author, are erroneous and contradict all preceding results obtained in this area of research. On the basis of the rigorous solution for Kirkwood factor of liquids with predominant chainlike aggregation it has been shown that the generally accepted opinion based on the famous Kirkwood formula gK=1+z⟨cosγ⟩, where z is coordination number, ⟨cosγ⟩ is average cosine of angle between adjacent dipoles in liquids ([J. G. Kirkwood, J. Chem. Phys. 7, 911 (1939)], Eq. (19)) that Kirkwood factor as determined by the mean cosine of the angle between adjacent dipoles should be modified for the liquids consisting of nonlinear molecules with the complex type of the supramolecular organization. Alcohols are examples of such liquids, in which long-range intermolecular correlations beyond the nearest coordination shells are essential for their structural organization.
Implosion dynamics and radiation characteristics of wire-array Z pinches on the Cornell Beam Research Accelerator
Authors: McBride R. D. , Shelkovenko T. A. , Pikuz S. A. , Hammer D. A. , Greenly J. B. , Kusse B. R. , Douglass J. D. , Knapp P. F. , Bell K. S. , Blesener I. C. , Chalenski D. A.
Published: January 2009

Experimental results are presented that characterize the implosion dynamics and radiation output of wire-array Z pinches on the 1-MA, 100-ns rise-time Cornell Beam Research Accelerator (COBRA) [J. B. Greenly et al., Rev. Sci. Instrum. 79, 073501 (2008)]. The load geometries investigated include 20-mm-tall cylindrical arrays ranging from 4to16mm in diameter, and consisting of 8, 16, or 32 wires of either tungsten, aluminum, or Invar (64% iron, 36% nickel). Diagnostics fielded include an optical streak camera, a time-gated extreme-ultraviolet framing camera, a laser shadowgraph system, time-integrated pinhole cameras, an x-ray wide-band focusing spectrograph with spatial resolution, an x-ray streak camera, a load voltage monitor, a Faraday cup, a bolometer, silicon diodes, and diamond photoconducting detectors. The data produced by the entire suite of diagnostics are analyzed and presented to provide a detailed picture of the overall implosion process and resulting radiation output on COBRA. The highest x-ray peak powers (300–500GW) and total energy yields (6–10kJ) were obtained using 4-mm-diameter arrays that stagnated before peak current. Additional findings include a decrease in soft x-ray radiation prior to stagnation as the initial wire spacing was changed from 1.6mmto785μm, and a timing correlation between the onset of energetic electrons, hard x-ray generation, and the arrival of trailing current on axis—a correlation that is likely due to the formation of micropinches. The details of these and other findings are presented and discussed.
Critical behavior of the magnetization in the spin-gapped system NiCl2–4SC(NH2)2
Authors: Paduan-Filho A. , Al-Hassanieh K. A. , Sengupta P. , Zapf V. S. , Jaime M. , Lacerda A. , Kenzelmann M.
Published: January 2009

We report accurate magnetization measurements on the spin-gap compound NiCl2–4SC(NH2)2 around the low portion of the magnetic induced phase ordering. The critical density of the magnetization at the phase boundary is analyzed in terms of a Bose–Einstein condensation (BEC) of bosonic particles, and the boson interaction strength is obtained as v0=0.61meV. The detailed analysis of the magnetization data across the transition leads to the conclusion for the preservation of the U(1) symmetry, as required for BEC.
Electrically driven spin polarization in Pr0.7Ca0.3MnO3∕YBa2Cu3O7 heterostructures
Authors: Lin J. G. , Hsu Daniel , Chiang C. H. , Chan W. C.
Published: January 2009

The current and temperature dependent electrical transport is investigated in Pr0.7Ca0.3MnO3∕YBa2Cu3O7 (PCMO/YBCO) heterostructures which are fabricated by pulsed laser deposition. Two PCMO/YBCO heterostructures are made with the thicknesses of PCMO varied. It is shown that the superconducting transition temperature significantly decreases with increasing thickness of PCMO and with increasing applied current, which are related to the pair breaking via the polarized electrons. However, the current-dependent normal-state resistivity shows two crossing points, indicating the competition of various phases. According to our analysis, the melting of charge ordering state by the electrical current may be the major cause for the electrically driven enhancement of spin polarization in PCMO/YBCO.
S
33
NMR measurements in S33-enriched ferromagnetic EuS and the question of power-law behaviors
Authors: Bykovetz N. , Klein J. , Lin C. L.
Published: January 2009

In order to resolve two previous conflicting reports on detectable but weak nuclear magnetic resonance (NMR) S33 signals in unenriched EuS, a sample of S33-enriched EuS was prepared and the NMR and its temperature dependence were measured in the range from 1.3to4.2K. It was verified that the T=0 extrapolated NMR signal has a value of 12.73MHz (≈39kG), not 5.4MHz, as one group had reported. The temperature dependence of the NMR was used to assess the applicability of two proposed spin-wave-region power-law schemes. The schemes attempted to systematize and explain the simple power-law behaviors measured by NMR and other techniques that have been reported (or have been present in measured data, but not reported) for more than five decades. The scheme proposed by Koebler et al. [Physica B 364, 55 (2005)] contends that the low-temperature magnetization of EuS follows a simple T2 behavior all the way up to 0.75Tc. The S33 spin-echo measurements are consistent with a power law, but cast doubt on a T2 dependence. Possible reasons for discrepancies between various EuS NMR measurements are discussed in the paper as well as means of resolving such issues by future experiments.
Size dependence of magnetic parameters and surface disorder in magnetite nanoparticles
Authors: Dutta P. , Pal S. , Seehra M. S. , Shah N. , Huffman G. P.
Published: January 2009

Magnetic properties of oleic acid/oleylamine coated magnetite nanoparticles of average diameter D=4, 6, 8, 10, and 12nm are reported. The samples were characterized by transmission electron microscopy and x-ray diffraction (XRD) with XRD showing increasing disorder with decreasing D. Magnetization M vs temperature T data show the blocking temperature TB decreasing with decreasing D from TB=38K for 12nm to TB=6.5K for D=4nm. The saturation magnetization Ms at 2K also decreases from Ms=62emu∕g for 12nm to Ms=17emu∕g for 4nm but the coercivity at 2K increases with a decrease in D. It is shown that Ms fits Ms=92(1−2d∕D)3 with d=0.68nm for D>4nm and d=0.86 for D=4nm. This equation is derived assuming a core-shell model with shell of thickness d consisting of disordered spins not contributing to Ms.
Grain-size-dependent magnetic susceptibility of nanocrystalline terbium
Authors: Philippi Stefan , Markmann Jürgen , Birringer Rainer , Michels Andreas
Published: January 2009

This paper reports grain-size-dependent magnetic susceptibility data on nanocrystalline bulk Tb. We find that at small grain size Curie–Weiss behavior is not present for temperatures up to about 80K above the transition temperature and that the helical antiferromagnetic phase is absent. Possible origins for the suppression of the helix phase in nanoscaled Tb are discussed in terms of internal magnetostatic fields and competing length scales (grain size versus wavelength of the helix phase).
Antivortex dynamics in magnetic nanostripes
Authors: Kunz Andrew , Breitbach Eric C. , Smith Andy J.
Published: January 2009

In a thin magnetic nanostripe, an antivortex nucleates inside a moving domain wall when driven by an in-plane magnetic field greater than the so-called Walker field. The nucleated antivortex must cross the width of the nanostripe before the domain wall can propagate again, leading to low average domain wall speeds. A large out-of-plane magnetic field, applied perpendicularly to the plane of the nanostripe, inhibits the nucleation of the antivortex leading to fast domain wall speeds for all in-plane driving fields. We present micromagnetic simulation results relating the antivortex dynamics to the strength of the out-of-plane field. An asymmetry in the motion is observed which depends on the alignment of the antivortex core magnetic moments to the direction of the out-of-plane field. The size of the core is directly related to its crossing speed, both depending on the strength of the perpendicular field and the alignment of the core moments and direction of the out-of-plane field.
Determination of the strain energy release rate for C/a-Si composite film produced in nanoindentation tests
Authors: Han Chang-Fu , Wu Bo-Hsiung , Huang Chao-Yu , Lin Jen-Fin
Published: January 2009

A general mechanical model that describes the contact behavior and deformations arising at all layers (including the substrate) is developed in the present study for multilayer specimens to evaluate the theoretical contact parameters. The governing differential equations for the depth solutions of the indenter tip formed at all layers of the specimen under their contact force and depth are developed individually. These two contact parameters allow the evaluation of the internal stress and strain using the membrane theory. The strain energy release rate can thus be determined if the internal stress is available. The mean value of these pop-in depths is almost constant when operating at various loading rates. The present model is precisely if it has good agreement with experiments. The pop-in internal stress was found to be strongly dependent on the C-film thickness (thus the material properties) but independent of the applied indentation system (thus indentation conditions). The pop-in internal stress and strain energy release rate can be significantly lowered by increasing the C-film thickness. Furthermore, pop-in always formed at a depth near the interface of the C/a-Si composite film and Si substrate.
Different effects of a laser prepulse on the proton generation between plastic and metal targets irradiated by an ultraintense laser pulse
Authors: Lee K. , Lee J. Y. , Cha Y.-H. , Lee Y. W. , Park S. H. , Jeong Y. U.
Published: January 2009

The effect of a laser prepulse on the generation of proton beams is compared between plastic and metal targets by irradiating a 30fs, 2.4×1018W∕cm2 Ti:sapphire laser pulse. Proton energies generated from both target materials increase as the pulse duration of the laser prepulse decreases. However, it was found that there are distinct differences with respect to target materials. In the case of aluminum targets, as target thickness decreases, proton energy gets higher, which is well described by an isothermal expansion model. However, in the case of Mylar® targets, no such dependence on target thickness could be observed, and the highest maximum proton energies are higher by factors of 1.5 to 3 than those from aluminum targets or those predicted by the isothermal expansion model. Such characteristics of the proton beams from Mylar® targets can be accounted for by a bulk acceleration model, or acceleration by a resistively induced electric field.
Light-emission mechanism of thermally annealed silicon-rich silicon oxide revisited: What is the role of silicon nanocrystals?
Authors: Khriachtchev Leonid , Nikitin Timur , Velagapudi Rama , Lahtinen Jouko , Novikov Sergei
Published: January 2009

The experimental data obtained with Raman, x-ray photoelectron, and continuous-wave and time-resolved photoluminescence spectroscopies on silicon-rich silicon oxide samples with different O/Si ratios and annealing temperatures are analyzed. It is shown that Si grains, with atoms bound as in bulk Si, are not the direct emitting phase, which is in agreement with the model of localized light-emitting centers. These oxygen-defect centers probably locate in suboxide structures and the excitation migrates to them from the absorbing Si grains. The photoluminescence quantum yield strongly increases for samples with larger O/Si ratios, suggesting a nonradiative capture of migrating excitons in Si grains.
Thermal conductivity of molten alkali halides: Temperature and density dependence
Authors: Ohtori Norikazu , Oono Takuya , Takase Keiichi
Published: January 2009

The thermal conductivities of a series of molten alkali halides have been evaluated by using molecular dynamics simulation within the framework of Fumi–Tosi potential models. Although the calculated results showed 0%–50% larger values than experimental results depending on system, they are in agreement with each other in showing both negative temperature and ionic mass dependence. In order to clarify the cause of the negative temperature dependence in more detail, the thermal conductivity under constant temperature or constant density was evaluated for all alkali chlorides and all sodium halides. The calculations reveal that the thermal conductivity depends strongly on density but only weakly on temperature. While the integrated value of the autocorrelation function for energy current increases with temperature, this is canceled out by the reciprocal temperature factor in relation to the thermal conductivity. With increasing density the integrated value increases, and this dominates the behavior of the thermal conductivity. By repeating the calculations with different ionic masses, we have concluded that the thermal conductivity is a function of m−1/2(N/V)2/3, where m is the geometric mean of ionic mass between anion and cation and N/V is the number density.
Accuracy and efficiency of the sophisticated direct simulation Monte Carlo algorithm for simulating noncontinuum gas flows
Authors: Bird G. A. , Gallis M. A. , Torczynski J. R. , Rader D. J.
Published: January 2009

The accuracy of a recently proposed direct simulation Monte Carlo (DSMC) algorithm, termed “sophisticated DSMC,” is investigated by comparing simulation results to analytical solutions of the Boltzmann equation for one-dimensional Fourier–Couette flow. An argon-like hard-sphere gas at 273.15 K and 266.644 Pa is confined between two parallel, fully accommodating walls 1 mm apart that have unequal temperatures and unequal tangential velocities. The simulations are performed using a one-dimensional implementation. In harmony with previous work, the accuracy metrics studied are the ratios of the DSMC-calculated transport properties and Sonine polynomial coefficients to their corresponding infinite-approximation Chapman–Enskog theoretical values. The sophisticated DSMC algorithm is shown to reproduce the theoretical results to high precision. The efficiency of the sophisticated DSMC algorithm relative to the original algorithm is demonstrated for a two-dimensional “real-world” application.
Analytic expressions for electrical energy and electrical force of two spheres
Authors: Liu Bo-Tau , Hsu Jyh-Ping
Published: January 2009

Analytical expressions for the electrical force and the electrical energy of two spheres immersed in a symmetric electrolyte solution are derived under conditions of constant surface potential and constant surface charge. Previous analysis under Debye–Huckel condition (linear case) is extended to the corresponding nonlinear case; because the level of the surface potential is arbitrary the results obtained have much wider applications. In general, the performance of the analytical formulas derived is satisfactory, and better than that of the available results in literature. For the case of constant surface potential, the analytic formulas obtained are most accurate for large particles, and for the case of constant surface charge, they are most accurate for small particles.
A systematic understanding of orbital energy shift in polar solvent
Authors: Iida Kenji , Yokogawa Daisuke , Sato Hirofumi , Sakaki Shigeyoshi
Published: January 2009

The orbital energy of molecule is significantly shifted upon going from gas phase to solution phase. Based on Koopmans’ theorem, the shift should be related to the change of ionization potential. However, the computed shift looks usually random and clear understanding has not been attained yet. Furthermore it is obtained only after solving complicated equations. In this study, we report a systematic framework for understanding the orbital energy shift by solvation effect and simple approximate formulae are presented.
Twisted absolute instability in lifted flames
Authors: Nichols Joseph W. , Chomaz Jean-Marc , Schmid Peter J.
Published: January 2009

The theory of resonant modes is extended to finite length systems containing pinch points of complex axial wavenumber k0 and frequency ω0 with arbitrary ωkk0=∂2ω/∂k2. The quantity ωkk0 is shown to be an important indicator of how streamwise boundary conditions modify the local absolute mode at (k0,ω0). In particular, when Im(ωkk0)>0, the pinch point is twisted, and resonant modes owing to streamwise boundary conditions may then have growth rates greater than that of the unbounded absolute mode. In this case, global instability may occur while the flow is only convectively unstable. The premixing zone between the nozzle and a lifted flame on a variable-density jet is an example of a streamwise-confined system containing a twisted pinch point. For this system, linear stability analysis is employed to locate resonant modes along a solution curve in the complex k and ω planes. The orientation of the solution curve predicts destabilization owing to streamwise confinement as well as increasing global frequency with decreasing lift-off height as observed in previous direct numerical simulations. The theory also suggests that low-frequency fluctuations observed in the simulations may be explained by beating between two resonant modes of slightly differing frequencies.
Switching spectroscopy piezoresponse force microscopy of polycrystalline capacitor structures
Authors: Bintachitt Patamas , Trolier-McKinstry Susan , Seal Katyayani , Jesse Stephen , Kalinin Sergei V.
Published: January 2009

Polarization switching in polycrystalline PbZr0.52Ti0.48O3 films on Pt-coated Si substrates was studied by switching spectroscopy piezoresponse force microscopy (SSPFM). Acquisition of multiple hysteresis loops allows polarization switching parameters, including nucleation, coercive biases, and switchable response to be mapped in real space. In contrast to measurements made on the free surface, those on the metal-ferroelectric-metal capacitor structures show the evolution of correlated switching of 102–103 grain clusters with well-defined imprint and nucleation biases. The role of substrate bending on clustering and SSPFM detection mechanisms are discussed. These studies demonstrate real-space imaging of mesoscopic polarization reversal in real-world devices.
Transport and sedimentation of suspended particles in inertial pressure-driven flow
Authors: Yan Yiguang , Koplik Joel
Published: January 2009

The dynamics of flowing suspensions of spherical particles in a channel, including their sedimentation under gravity, is studied using lattice Boltzmann simulations. Spherical particles confined to a three-dimensional periodic channel of constant width are driven through it by an applied pressure gradient while gravity acts to deposit the particles on the bottom wall. The particle diameter is 1/10 the channel width and bulk concentrations varying from 0.13 to 0.34 are considered. The simulations cover a range of buoyancy and Reynolds numbers and include the effects of inertia. In the neutral buoyancy case, we observe concentration profiles peaked at the center of the channel, plus secondary peaks near the walls due to layering effects, and velocity profiles which become increasingly blunted as particle concentration rises. Gravity produces a three-layer system with clear fluid, flowing suspension, and dense sediment regions having parabolic, pluglike, and nearly stagnant velocity profiles, respectively. In most cases, the fluid and particle fluxes decrease and the clear fluid region width increase with gravitational forcing, although nonmonotonic behavior is observed in some cases.
Electrodeposition of single-crystalline silver pearl chains
Authors: Wu Zhe , Li Hong-Min , Xiong Xiang , Ma Guo-Bin , Wang Mu , Peng Ru-Wen , Ming Nai-Ben
Published: January 2009

We report in this letter the fabrication of unique single-crystalline silver filaments with periodic, pearl-chain-like structures by electrodeposition without using any templates, surfactants, and additives. Fourier transform infrared spectroscopy, infrared focus-plane-array imaging, and numerical simulations demonstrate that the excited surface waves may sustain on the silver “pearl chains” in midinfrared range. Based on the propagation features of surface waves on the silver filaments, we suggest that such a structure can be applied for light transmission in midinfrared range.
Defect states in carbon nanotubes and related band structure engineering: A first-principles study
Authors: Kahaly Mousumi Upadhyay
Published: January 2009

Electronic structures of faulted nanosystems are of particular technological relevance because realistic large scale synthesis of nanostructures inevitably leads to defects of one form or the other. In this work, we determine the atomic and electronic structures of carbon nanotubes (CNTs) with two of the major types of defects using first-principles pseudopotential-based density functional theory calculations: (i) substitution with other atoms, and (ii) defects formed by removal of C atoms in the otherwise perfect honeycomb graphene network. We find that doping with B or N atom at different carbon sites of a CNT gives a simple shift in the Fermi energy and a nonmagnetic state. We evaluate the energy cost associated with the formation of nanotube interconnects by introducing a pair of heptagon and pentagon at the junction of two nanotubes and discuss how different defects can lead to band structure control. Further, a line defect for faulted CNTs is discussed for CNTs, which exhibit stronger one-dimensional character of the charge densities and electronic structure in comparison to defect-free CNTs.
Three-level dendritic structure with simultaneously negative permeability and permittivity under normal incidence of electromagnetic wave
Authors: Yao Y. , Fu Q. H. , Zhao X. P.
Published: January 2009

We present the model of three-level dendritic structure for left-handed metamaterials under normal incidence of electromagnetic radiation and investigate the electromagnetic responses in microwave band by simulation. The influence of branch lengths a, b, and c on the electric and magnetic resonance frequencies is studied by the transmission spectrum of single three-level dendritic structure. Moreover, the transmission of multiple three-level dendritic structures exhibits the interaction between the elements. To confirm the left-handed behaviors of three-level dendritic structures, the permittivity ε and permeability μ are calculated by S-parameter retrieval method. The results show that the ε and μ are indeed simultaneously negative around 9.2 GHz.
Fabrication and characterization of three-dimensional all metallic photonic crystals for near infrared applications
Authors: Yang Yu-Lin , Hou Fu-Ju , Wu Shich-Chuan , Huang Wen-Hsien , Lai Ming-Chih , Huang Yang-Tung
Published: January 2009

Three-dimensional all metallic photonic crystals with a feature size of 0.20 μm were fabricated using electron-beam lithography with the photoresist of hydrogen silesquioxane. This process method has high compatibility with the fabrication of damascene copper interconnections and also simplifies the whole process flow. The dependence of the complete photonic band gaps on polarization was experimentally observed and compared with the simulation results. The band edge for the four-layer lattice was found at a wavelength of around 0.80 μm in normal incidence.
ZnO
/
Mg
0.2
Zn
0.8
O
coaxial nanorod heterostructures for high-performance electronic nanodevice applications
Authors: Lee Chul-Ho , Yoo Jinkyoung , Doh Yong-Joo , Yi Gyu-Chul
Published: January 2009

We report on fabrication and electrical characteristics of field effect transistors (FETs) based on ZnO/Mg0.2Zn0.8O coaxial nanorod heterostructures. As compared to bare ZnO nanorod FETs, coaxial nanorod heterostructure FETs exhibited the enhanced mobility (∼110 cm2/V s), superior subthreshold swing (∼200 mV/decade), and negligibly small hysteresis to demonstrate very stable operation of high-performance nanorod FETs. In situ surface passivation and carrier confinement effects provided by heteroepitaxially grown Mg0.2Zn0.8O shell layer are presumably responsible for the highly enhanced device performance.
Morphotropic phase boundary and electrical properties of K1−xNaxNbO3 lead-free ceramics
Authors: Dai Ye-Jing , Zhang Xiao-Wen , Chen Ke-Pi
Published: January 2009

Lead-free K1−xNaxNbO3 ceramics with x=0.48–0.54 were prepared by a conventional solid-state reaction method to investigate the influence of the K/Na ratio on phase structures and electrical properties. The results suggest that a typical morphotropic phase boundary exists at x=0.52–0.525, separating the monoclinic and orthorhombic phases. The sample with the composition near x=0.52 shows the maximum values of the piezoelectric constant (d33=160 pC/N) and the electromechanical coupling coefficient (kt=47%). The results provide a helpful guidance to consider the optimal ratio of K to Na for designing and developing new (K,Na)NbO3-based ceramics.
Trap states and transport characteristics in picene thin film field-effect transistor
Authors: Kawasaki Naoko , Kubozono Yoshihiro , Okamoto Hideki , Fujiwara Akihiko , Yamaji Minoru
Published: January 2009

Transport characteristics and trap states are investigated in picene thin film field-effect transistor under O2 atmosphere on the basis of multiple shallow trap and release (MTR) model. The channel transport is dominated by MTR below 300 K. It has been clarified on the basis of MTR model that the O2-exposure induces a drastic reduction in shallow trap density to increase both the field-effect mobility μ and on-off ratio. We also found that the O2-exposure never caused an increase in hole carrier density. Actually, a very high μ value of 3.2 cm2 V−1 s−1 is realized under 500 Torr of O2.
Temperature and electric field dependence of the carrier emission processes in a quantum dot-based memory structure
Authors: Nowozin T. , Marent A. , Geller M. , Bimberg D. , Akçay N. , Öncan N.
Published: January 2009

Hole emission processes from self-organized GaAs0.4Sb0.6/GaAs quantum dots embedded in a p-n diode are studied by capacitance-voltage spectroscopy. The method introduced allows the investigation of the temperature and electric field dependence of carrier emission with time constants from below nanoseconds up to thousands of seconds. Different emission processes are clearly distinguished, such as tunneling, phonon-assisted tunneling, and thermal activation, each important for quantum-dot-based memory structures. The erase time was determined to 1.5 ms for an electric field of about 200 kV/cm. At 500 kV/cm, 10 ns are predicted sufficient for fast erasing.
Rapid efficiency roll-off in high-quality green light-emitting diodes on freestanding GaN substrates
Authors: Yang Y. , Cao X. A. , Yan C. H.
Published: January 2009

InGaN/GaN multiple-quantum-well green light-emitting diodes (LEDs) were grown on freestanding GaN and sapphire substrates. The density of microstructural defects in the LED on GaN was substantially reduced, leading to a significant reduction in defect-assisted tunneling currents and an improved injection efficiency under low bias. The LED on GaN outperformed the LED on sapphire at low injection currents and exhibited a ∼65% peak internal quantum efficiency. However, it suffered from even more dramatic efficiency roll-off, which occurs at a current density as low as 0.3 A/cm2. This behavior is explained as the combined result of efficient current injection and significant carrier overflow in a high-quality LED.
Tunnel junction transistor laser
Authors: Feng M. , Holonyak N. , Then H. W. , Wu C. H. , Walter G.
Published: January 2009

A transistor laser with a tunnel junction collector is demonstrated. Its optical output is sensitive to third terminal voltage control owing to the electron tunneling (photon-assisted or not assisted) from the base to collector, which acts in further support of resupply of holes for recombination in addition to the usual base Ohmic current, IB. Collector tunneling enhances laser operation even under a weak collector junction field and quenches it under a strong reverse-biased field. The sensitivity of the tunnel junction transistor laser to voltage control enables the tunnel junction transistor laser to be directly modulated by both current and voltage control.
Low-voltage flexible organic complementary inverters with high noise margin and high dc gain
Authors: Zhang Xiao-Hong , Potscavage William J. , Choi Seungkeun , Kippelen Bernard
Published: January 2009

We report on flexible organic complementary inverters using pentacene and C60 as active semiconductors fabricated on a plastic substrate. Individual transistors as well as inverters show good operational stability with negligible hysteresis. The threshold voltages are comparable for p-channel pentacene and n-channel C60 organic field-effect transistors, and noise margins larger than 80% of the maximum theoretical values were obtained at a supply voltage VDD as low as 3 V. A high dc gain of 180 was achieved at VDD=5 V. The inverters demonstrated good mechanical stability when tested after bending under both tensile and compressive stress.
Silicon-on-insulator photoconductors for ultrasonic vibration detection with laser speckle
Authors: Bessette Jonathan , Gogo Ashifi , Garmire Elsa
Published: January 2009

Speckle-sized photoconductive silicon-on-insulator mesas have been designed to optically detect surface vibrations at frequencies extending into the megahertz range. When a single diode laser beam reflects off a vibrating surface as a moving speckle pattern, the photoconductive mesas can detect lateral speckle motion. The capability of noncontact, nondestructive testing via laser-induced ultrasonic vibrations was demonstrated using these photoconductive silicon mesas in a simple and rugged single-monitoring-beam configuration.
Gene-centric metagenomics of the fiber-adherent bovine rumen microbiome reveals forage specific glycoside hydrolases
Authors: Brulc Jennifer M. , Antonopoulos Dionysios A. , Berg Miller Margret E. , Wilson Melissa K. , Yannarell Anthony C. , Dinsdale Elizabeth A. , Edwards Robert E. , Frank Edward D. , Emerson Joanne B. , Wacklin Pirjo , Coutinho Pedro M. , Henrissat Bernard , Nelson Karen E. , White Bryan A.
Published: January 2009

The complex microbiome of the rumen functions as an effective system for the conversion of plant cell wall biomass to microbial protein, short chain fatty acids, and gases. As such, it provides a unique genetic resource for plant cell wall degrading microbial enzymes that could be used in the production of biofuels. The rumen and gastrointestinal tract harbor a dense and complex microbiome. To gain a greater understanding of the ecology and metabolic potential of this microbiome, we used comparative metagenomics (phylotype analysis and SEED subsystems-based annotations) to examine randomly sampled pyrosequence data from 3 fiber-adherent microbiomes and 1 pooled liquid sample (a mixture of the liquid microbiome fractions from the same bovine rumens). Even though the 3 animals were fed the same diet, the community structure, predicted phylotype, and metabolic potentials in the rumen were markedly different with respect to nutrient utilization. A comparison of the glycoside hydrolase and cellulosome functional genes revealed that in the rumen microbiome, initial colonization of fiber appears to be by organisms possessing enzymes that attack the easily available side chains of complex plant polysaccharides and not the more recalcitrant main chains, especially cellulose. Furthermore, when compared with the termite hindgut microbiome, there are fundamental differences in the glycoside hydrolase content that appear to be diet driven for either the bovine rumen (forages and legumes) or the termite hindgut (wood).