bluuebunny/crossref_metadata_2025 huggingface dataset:
Making Heritage in Hong Kong: A Case Study of the Central Police Station Compound
Authors: Ku Agnes Shuk-mei
Published: June 2010

This article is a case study of state–society–capital conflicts over the preservation of the Central Police Station (CPS) compound in Hong Kong during 2003–08. The conflict was between two fundamentally different approaches to urban space: a cultural economy approach that took culture and space as a source of economic profit, and an opposition discourse of preservation that emphasized cultural, historical and humanistic values as an end. The struggle turned out to be a moderate success for anti-commercialism. Drawing on and extending the notions of collective memory and spatial politics, this article examines how the various civil society actors, in their struggle against commercialism, sought to define and enhance the cultural value of the site through a variety of discourses and practices relating to history and space. It addresses the specific question of why and how certain constructions of collective memory succeed (or fail) to work with certain places in particular instances. The study shows that memories of the CPS compound contained both state-associated and people-associated accounts, between which the former prevailed. The state-associated account was embedded in a familiar, hegemonic story about Hong Kong, which, via an abstract process of symbolization around the notion of the rule of law, successfully turned the compound into an iconic symbol of identification for the city. Beyond this, the civil society actors sought also to generate a sense of lived space associated with the people, and the outcome was mixed.
Increased weed diversity, density and above-ground biomass in long-term organic crop rotations
Authors: Wortman Sam E. , Lindquist John L. , Haar Milton J. , Francis Charles A.
Published: June 2010

While weed management is consistently a top priority among farmers, there is also growing concern for the conservation of biodiversity. Maintaining diverse weed communities below bioeconomic thresholds may provide ecosystem services for the crop and the surrounding ecosystem. This study was conducted to determine if weed diversity, density and biomass differ within and among organic and conventional crop rotations. In 2007 and 2008, we sampled weed communities in four long-term crop rotations near Mead, Nebraska using seedbank analyses (elutriation and greenhouse emergence) and above-ground biomass sampling. Two conventional crop rotations consisted of a corn (Zea mays) or sorghum (Sorghum bicolor)–soybean (Glycine max)–sorghum or corn–soybean sequence and a diversified corn or sorghum–sorghum or corn–soybean–wheat (Triticum aestivum) sequence. Two organic rotations consisted of an animal manure-based soybean–corn or sorghum–soybean–wheat sequence and a green manure-based alfalfa (Medicago sativa)–alfalfa–corn or sorghum–wheat sequence. Species diversity of the weed seedbank and the above-ground weed community, as determined by the Shannon diversity index, were greatest in the organic green manure rotation. Averaged across all sampling methods and years, the weed diversity index of the organic green manure rotation was 1.07, followed by the organic animal manure (0.78), diversified conventional (0.76) and conventional (0.66) rotations. The broadleaf weed seedbank density in the tillage layer of the organic animal manure rotation was 1.4×, 3.1× and 5.1× greater than the organic green manure, diversified conventional and conventional rotations, respectively. The grass weed seedbank density in the tillage layer of the organic green manure rotation was 2.0×, 6.1× and 6.4× greater than the organic animal manure, diversified conventional and conventional rotations, respectively. The above-ground weed biomass was generally greatest in the organic rotations. The broadleaf weed biomass in sorghum and wheat did not differ between organic and conventional rotations (CRs), but grass weed biomass was greater in organic compared to CRs for all crops. The above-ground weed biomass did not differ within CRs, and within organic rotations the grass weed biomass was generally greatest in the organic green manure rotation. The weed seedbank and above-ground weed communities that have accumulated in these rotations throughout the experiment suggest a need for greater management in long-term organic rotations that primarily include annual crops. However, results suggest that including a perennial forage crop in organic rotations may reduce broadleaf weed seedbank populations and increase weed diversity.
Seasonal and QBO variations in the OH nightglow emission observed by TIMED/SABER
Authors: Gao Hong , Xu Jiyao , Wu Qian
Published: June 2010

Using TIMED/SABER observations, we present global distribution of the semiannual oscillation (SAO), annual oscillation (AO), and quasi‐biennial oscillation (QBO) in the OH nightglow peak emission rate and height as well as the intensity. The latitudinal variations of the SAO, AO, and QBO in the peak emission rate are similar to those in the intensity. For the peak emission rate and the intensity, the SAO and QBO amplitudes have three peaks (one at the equator and others at about 35°S and 35°N). The AO amplitude peaks at about 20°S and 20°N, respectively. The SAO phase is delayed poleward from the equinoxes at the equator to the solstices at 50°S/N; in addition, the phases of the AO are delayed poleward from 30°S. For the peak height, the SAO and QBO amplitudes have three peaks (around the equator, 40°S, and 40°N). Its AO amplitudes at 50°S and 50°N are larger than those at other latitudes; the phase of the SAO shifts from the solstice at the equator to near the equinoxes at 50°S/N. The airglow QBO is stronger in tropics than midlatitude and is likely the real QBO oscillation at the equator. In addition, the emission in the Southern Hemisphere is weaker than that in the Northern Hemisphere. The SAO and QBO are hemispherically symmetrical, and the AO is hemispherically antisymmetrical at some latitudes. The peak emission rate and peak height SAOs are generally in antiphase. The peak emission rate and intensity SAOs are generally in phase.
Evolution of plasma sheet particle content under different interplanetary magnetic field conditions
Authors: Wang Chih‐Ping , Lyons Larry R. , Nagai Tsugunobu , Weygand James M. , Lui A. T. Y.
Published: June 2010

We have statistically analyzed Geotail data to investigate the processes that result in a plasma sheet that is denser under a prolonged northward than southward interplanetary magnetic field (IMF) period. The observations show that the change of number density with the IMF conditions is mainly due to the changes of particle number per unit magnetic flux (particle content N), with N increasing (decreasing) as the period of northward (southward) IMF extends. The changes are quicker in the first ∼2 to 4 h then substantially slow down. The Y profiles show that N is always lowest around midnight and becomes higher toward the flanks. The observed plasma velocities suggest that plasma sheet particles undergo earthward and flankward drift transport, as well as diffusive transport resulting from drift fluctuations. The diffusion coefficients associated with fluctuating drift are estimated to be ∼105 to 106 km2/s. We have simulated evolution of N resulting from drift and diffusive transport with particle sources along the flanks. The simulation results show that the observed temporal and Y variations of N under different IMF conditions can be accounted for by the competition between the particle increase owing to particles diffusing toward midnight from the flank sources and the particle decrease owing to particles drifting away from midnight. As the IMF turns northward (southward), it is mainly the strengthening (weakening) of diffusive transport owing to the increase (decrease) of the flank source that results in the increase (decrease) of N.
Tectonic evolution of the Northeastern South China Sea from seismic interpretation
Authors: Yeh Yi‐Ching , Sibuet Jean‐Claude , Hsu Shu‐Kun , Liu Char‐Shine
Published: June 2010

We interpret a grid of 2‐D seismic reflection profiles to resolve the tectonic evolution of the northeastern South China Sea (SCS), identifying two significant postbreakup events, T1 and T2, which occurred before the end of the SCS opening. In the absence of the drilling data in the deep basin, we date these two events using the identification of the magnetic anomalies, the age of major unconformities at Ocean Drilling Program Site 1148 drilled on the northeastern SCS margin, and the age of basalt samples in the deep SCS. The tectonic phase T1 is a slight tensional tectonic event which occurred in the deep SCS, south of the Luzon‐Ryukyu Transform Plate Boundary (LRTPB). It is characterized by oceanic tilted blocks and fan‐shaped deposits, which developed 8–10 Myr after the onset of SCS seafloor spreading (37.8 Ma). It corresponds to the first ENE–WSW to E–W change in spreading direction, which occurred around chron C10 (∼28.7 Ma). Event T2 is a magmatic phase observed in the deep SCS, south of the LRTPB. It is characterized by the uplift of former spreading features caused by an early Miocene (∼22 Ma) magmatic phase, which is also recorded in north and south‐central Taiwan.
Tide‐surge Interaction Intensified by the Taiwan Strait
Authors: Zhang Wen‐Zhou , Shi Fengyan , Hong Hua‐Sheng , Shang Shao‐Ping , Kirby James T.
Published: June 2010

The Taiwan Strait is a long and wide shelf‐channel where the hydrodynamics is extremely complex, being characterized by strong tides, and where storm surges frequently occur during the typhoon season. Obvious oscillations due to tide‐surge interaction were observed by tide gauges along the northern Fujian coast, the west bank of the Taiwan Strait, during Typhoon Dan (1999). Numerical experiments indicate that nonlinear bottom friction (described by the quadratic formula) is a major factor to predict these oscillations while the nonlinear advective terms and the shallow water effect have little contribution. It is found that the tide‐surge interaction in the northern portion of the Taiwan Strait is intensified by the strait. Simulations based on simplified topographies with and without the island of Taiwan show that, in the presence of the island, the channel effect strengthens tidal currents and tends to align the major axes of tidal ellipses along the channel direction. Storm‐induced currents are also strengthened by the channel. The pattern of strong tidal currents and storm‐induced currents along the channel direction enhances tide‐surge interaction via the nonlinear bottom friction, resulting in the obvious oscillations along the northern Fujian coast.
Interannual variability of surface water extent at the global scale, 1993–2004
Authors: Papa F. , Prigent C. , Aires F. , Jimenez C. , Rossow W. B. , Matthews E.
Published: June 2010

Land surface waters play a primary role in the global water cycle and climate. As a consequence, there is a widespread demand for accurate and long‐term quantitative observations of their distribution over the whole globe. This study presents the first global data set that quantifies the monthly distribution of surface water extent at ∼25 km sampling intervals over 12 years (1993–2004). These estimates, generated from complementary multiple‐satellite observations, including passive (Special Sensor Microwave Imager) and active (ERS scatterometer) microwaves along with visible and near‐infrared imagery (advanced very high‐resolution radiometer; AVHRR), were first developed over 1993–2000. The ERS encountered technical problems in 2001 and the processing scheme had to be adapted to extend the time series. Here we investigate and discuss the adjustments of the methodology, compare the various options, and show that the data set can be extended with good confidence beyond 2000, using ERS and AVHRR mean monthly climatologies. In addition to a large seasonal and interannual variability, the new results show a slight overall decrease in global inundated area between 1993 and 2004, representing an ∼5.7% reduction of the mean annual maximum in 12 years. The decrease is mainly observed in the tropics during the 1990s. Over inland water bodies and large river basins, we assess the variability of the surface water extent against related variables such as in situ river discharges, altimeter‐derived and in situ river/floodplain water level heights, and precipitation estimates. This new 12 year data set of global surface water extent represents an unprecedented source of information for future hydrological or methane modeling.
On water vapor Jacobian in fast radiative transfer model
Authors: Chen Yong , Han Yong , Van Delst Paul , Weng Fuzhong
Published: June 2010

The Community Radiative Transfer Model (CRTM) is a powerful numerical software used for satellite data assimilation and remote sensing applications. Its accuracies in simulating satellite radiances and their gradients relative to water vapor (or Jacobians) are improved through this study when the CRTM includes additional gaseous absorbers. Three water vapor transmittance regression methods (labeled with A–C, respectively) are discussed that differ primarily in vertical coordinates and the application of constraints to smooth vertical structures of the regression coefficients. Method A computes optical depth profiles at fixed pressure levels, whereas method B computes the profiles at fixed levels of the integrated absorber amount. Method C is a derived version of method B with an addition that a polynomial function is applied to the regression coefficients to improve the water vapor Jacobians. The intercomparison focuses on the modeling of 22 sounding channels routinely used at numerical weather prediction (NWP) centers: 9 Atmospheric Infrared Radiance Sounder channels, 4 High‐Resolution Infrared Sounder channels, 4 Advanced Microwave Sounding Unit‐A channels, and 5 Microwave Humidity Sounder channels. An ensemble of 48 diverse atmosphere profiles at the University of Maryland at Baltimore County was used to test the results. The results were compiled for methods A and C for water vapor line absorption only while keeping the other components the same under the CRTM framework. The comparison quantities include the water vapor Jacobians, temperature Jacobians, and the forward top‐of‐the‐atmosphere brightness temperature (BT). In the infrared, the forward models mean errors are very small (less than 0.03 K) compared to the line‐by‐line model. Temperature and water vapor Jacobian goodness‐of‐fit measure values are very small and sufficient for NWP application, except for some dry atmospheric profiles. For the cold and dry atmospheric profiles, method C can significantly improve the water vapor Jacobian profile and remove the unphysical kinks (oscillations) that appear in method A. The improved water vapor Jacobian profile results in the improved temperature Jacobian. For the microwave channels, the forward BTs show very small biases less than 0.1 K for all the channels, and the overall water vapor Jacobian using method A is better than those using method C, especially for warm and wet atmospheric profiles.
On the relationships between lightning frequency and thundercloud parameters of regional precipitation systems
Authors: Xu Weixin , Zipser Edward J. , Liu Chuntao , Jiang Haiyan
Published: June 2010

Seasonal variations on lightning activity of precipitation systems over south China and Taiwan before and after the onset of Mei‐Yu have been observed by the lightning imager sensor (LIS) on board the Tropical Rainfall Measuring Mission (TRMM) satellite. Lightning storms before Mei‐Yu onset show higher probability of lightning, higher flash rate, and larger radar reflectivity in the mixed‐phase region than the Mei‐Yu regime. However, the probability of lightning occurrence with the same threshold of maximum radar reflectivity or ice scattering signature is similar for land systems before and during Mei‐Yu season. Oceanic systems show slightly lower probability of lightning even with the same thresholds. Relationships between a set of TRMM‐observed parameters and LIS lightning frequency are further examined. For lightning systems over land, the total area of radar echo above 35 dBZ has a closer relationship with lightning flash rate at the temperature between −5°C and −15°C than other parameters. Area of lower radar reflectivity at colder temperature, e.g., area of 20 dBZ at −40°C, is also highly correlated with lightning frequency. The highest correlation between area of specific radar reflectivity and lightning frequency is found at lower temperatures when the oceanic lightning systems are examined.
Identification and characterization of a strict and a promiscuous N-acetylglucosamine-1-P uridylyltransferase in Arabidopsis
Authors: Yang Ting , Echols Merritt , Martin Andy , Bar-Peled Maor
Published: June 2010

UDP-GlcNAc is an essential precursor for glycoprotein and glycolipid synthesis. In the present study, a functional nucleotidyltransferase gene from Arabidopsis encoding a 58.3 kDa GlcNAc1pUT-1 (N-acetylglucosamine-1-phosphate uridylyltransferase) was identified. In the forward reaction the enzyme catalyses the formation of UDP-N-acetylglucosamine and PPi from the respective monosaccharide 1-phosphate and UTP. The enzyme can utilize the 4-epimer UDP-GalNAc as a substrate as well. The enzyme requires divalent ions (Mg2+ or Mn2+) for activity and is highly active between pH 6.5 and 8.0, and at 30–37 °C. The apparent Km values for the forward reaction were 337 μM (GlcNAc-1-P) and 295 μM (UTP) respectively. Another GlcNAc1pUT-2, which shares 86% amino acid sequence identity with GlcNAc1pUT-1, was found to convert, in addition to GlcNAc-1-P and GalNAc-1-P, Glc-1-P into corresponding UDP-sugars, suggesting that subtle changes in the UT family cause different substrate specificities. A three-dimensional protein structure model using the human AGX1 as template showed a conserved catalytic fold and helped identify key conserved motifs, despite the high sequence divergence. The identification of these strict and promiscuous gene products open a window to indentify new roles of amino sugar metabolism in plants and specifically their role as signalling molecules. The ability of GlcNAc1pUT-2 to utilize three different substrates may provide further understanding as to why biological systems have plasticity.
A method for reducing pressure-induced deformation in silicone microfluidics
Authors: Inglis David W.
Published: June 2010

Poly(dimethylsiloxane) or PDMS is an excellent material for replica molding, widely used in microfluidics research. Its low elastic modulus, or high deformability, assists its release from challenging molds, such as those with high feature density, high aspect ratios, and even negative sidewalls. However, owing to the same properties, PDMS-based microfluidic devices stretch and change shape when fluid is pushed or pulled through them. This paper shows how severe this change can be and gives a simple method for limiting this change that sacrifices few of the desirable characteristics of PDMS. A thin layer of PDMS between two rigid glass substrates is shown to drastically reduce pressure-induced shape changes while preserving deformability during mold separation and gas permeability.
Effects of time-varying E×B flow on slab ion-temperature-gradient turbulence
Authors: Maeyama S. , Ishizawa A. , Watanabe T.-H. , Škorić M. M. , Nakajima N. , Tsuji-Iio S. , Tsutsui H.
Published: June 2010

Effects of time-varying sheared E×B flow on turbulence driven by slab ion temperature gradient instabilities are investigated by means of Landau fluid simulation. Here, the E×B flow, which consists of stationary and time-periodic oscillatory parts, is externally imposed to the turbulence. The dependence on the amplitude and frequency of E×B flow is examined in the case that the amplitude of oscillatory part is the same or less than that of stationary part. The ion heat transport caused by turbulence oscillates with the same period as the E×B flow and the time-averaged transport coefficient is larger than the coefficient which is evaluated without the oscillatory part. The time-averaged coefficient is maximized when the amplitude of oscillatory part is equal to that of stationary part. As the frequency of E×B flow increases, the time-averaged coefficient decreases and is close to the coefficient which is evaluated without the oscillatory part. This mechanism is explained by introducing a kind of the logistic equation which describes the time evolution of transport coefficient as a response of turbulence to the amplitude of E×B flow.
Flexible sheets falling in an inviscid fluid
Authors: Alben Silas
Published: June 2010

We use inviscid simulations to study falling flexible sheets in the two-parameter space of sheet density and bending rigidity. The basic behavior is a repeated series of accelerations to a critical speed at which the sheet flexes and rapidly decelerates, shedding large vortices. The maximum and average speeds of the sheet are closely related to the critical flutter speed. The sheet trajectories also show persistent circling, quasiperiodic flapping, and more complex repeated patterns. For small bending rigidity, the motion becomes less regular. At intermediate bending rigidity, trajectories show a well-defined falling angle relative to the vertical. For larger sheet density and bending rigidity, the overall motion is more horizontal.
A matched filter for chaos
Authors: Corron Ned J. , Blakely Jonathan N. , Stahl Mark T.
Published: June 2010

A novel chaotic oscillator is shown to admit an exact analytic solution and a simple matched filter. The oscillator is a hybrid dynamical system including both a differential equation and a discrete switching condition. The analytic solution is written as a linear convolution of a symbol sequence and a fixed basis function, similar to that of conventional communication waveforms. Waveform returns at switching times are shown to be conjugate to a chaotic shift map, effectively proving the existence of chaos in the system. A matched filter in the form of a delay differential equation is derived for the basis function. Applying the matched filter to a received waveform, the bit error rate for detecting symbols is derived, and explicit closed-form expressions are presented for special cases. The oscillator and matched filter are realized in a low-frequency electronic circuit. Remarkable agreement between the analytic solution and the measured chaotic waveform is observed.
Global stabilization of fixed points using predictive control
Authors: Liz Eduardo , Franco Daniel
Published: June 2010

We analyze the global stability properties of some methods of predictive control. We particularly focus on the optimal control function introduced by de Sousa Vieira and Lichtenberg [Phys. Rev. E 54, 1200 (1996)]. We rigorously prove that it is possible to use this method for the global stabilization of a discrete system xn+1=f(xn) into a positive equilibrium for a class of maps commonly used in population dynamics. Moreover, the controlled system is globally stable for all values of the control parameter for which it is locally asymptotically stable. Our study highlights the difficulty of obtaining global stability results for other methods of predictive control, where higher iterations of f are used in the control scheme.
Ionization of doped helium nanodroplets: Complexes of C60 with water clusters
Authors: Denifl S. , Zappa F. , Mähr I. , Mauracher A. , Probst M. , Urban J. , Mach P. , Bacher A. , Bohme D. K. , Echt O. , Märk T. D. , Scheier P.
Published: June 2010

Water clusters are known to undergo an autoprotonation reaction upon ionization by photons or electron impact, resulting in the formation of (H2O)nH3O+. Ejection of OH cannot be quenched by near-threshold ionization; it is only partly quenched when clusters are complexed with inert gas atoms. Mass spectra recorded by electron ionization of water-doped helium droplets show that the helium matrix also fails to quench OH loss. The situation changes drastically when helium droplets are codoped with C60. Charged C60-water complexes are predominantly unprotonated; C60(H2O)4+ and (C60)2(H2O)4+ appear with enhanced abundance. Another intense ion series is due to C60(H2O)nOH+; dehydrogenation is proposed to be initiated by charge transfer between the primary He+ ion and C60. The resulting electronically excited C60+∗ leads to the formation of a doubly charged C60-water complex either via emission of an Auger electron from C60+∗, or internal Penning ionization of the attached water complex, followed by charge separation within {C60(H2O)n}2+. This mechanism would also explain previous observations of dehydrogenation reactions in doped helium droplets. Mass-analyzed ion kinetic energy scans reveal spontaneous (unimolecular) dissociation of C60(H2O)n+. In addition to the loss of single water molecules, a prominent reaction channel yields bare C60+ for sizes n=3, 4, or 6. Ab initio Hartree–Fock calculations for C60-water complexes reveal negligible charge transfer within neutral complexes. Cationic complexes are well described as water clusters weakly bound to C60+. For n=3, 4, or 6, fissionlike desorption of the entire water complex from C60(H2O)n+ energetically competes with the evaporation of a single water molecule.
Plasma tubes becoming collimated as a result of magnetohydrodynamic pumping
Authors: Yun Gunsu S. , Bellan Paul M.
Published: June 2010

Collimated magnetized plasma structures are commonly observed on galactic, stellar, and laboratory scales. The Caltech plasma gun produces magnetically driven plasma jets bearing a striking resemblance to astrophysical jets and solar coronal loops by imposing boundary conditions analogous to those plasmas. This paper presents experimental observations of gun-produced plasma jets that support a previously proposed magnetohydrodynamic (MHD) pumping model [P. M. Bellan, Phys. Plasmas 10, 1999 (2003)] as a universal collimation mechanism. For any initially flared, magnetized plasma tube with a finite axial current, the model predicts (i) magnetic pumping of plasma particles from a constricted region into a bulged region and (ii) tube collimation if the flow slows down at the bulged region leading to accumulation of mass and thus concentrating the azimuthal magnetic flux frozen in the mass flow (i.e., increasing the pinch force). Time- and space-resolved spectroscopic measurements of gun-produced plasmas have confirmed the highly dynamic nature of the process leading to a collimated state, namely, (i) suprathermal Alfvénic flow (30–50 km/s), (ii) large density amplification from ∼1017 to ∼1022 m−3 in an Alfvénic time scale (5–10 μs), and (iii) flow slowing down and mass accumulation at the flow front, the place where the tube collimation occurs according to high-speed camera imaging. These observations are consistent with the predictions of the MHD pumping model, and offer valuable insight into the formation mechanism of laboratory, solar, and astrophysical plasma structures.
Tetrahedral order, pair correlation entropy, and waterlike liquid state anomalies: Comparison of GeO2 with BeF2, SiO2, and H2O
Authors: Jabes B. Shadrack , Agarwal Manish , Chakravarty Charusita
Published: June 2010

Molecular dynamics simulations of the Oeffner–Elliot model of germania (GeO2) are performed to identify nested regions of anomalous behavior in structural order, diffusivity, and pair entropy in the density-temperature plane, analogous to that seen in BeF2, SiO2, and H2O. The decreasing constraint of local tetrahedrality in GeO2, compared to SiO2 and BeF2, substantially lowers the onset temperatures for anomalous behavior relative to the experimental melting temperatures (Tm). Germania resembles water, more strongly than the ionic melts, in terms of temperatures for onset of anomalous behavior as well as in the order maps; for example, the structural anomaly sets in at 3.42Tm in BeF2, 3.09Tm in SiO2, 1.43Tm in GeO2, and 1.21Tm in H2O. The detailed shapes of the anomalous regimes vary for different systems but the relative temperatures of onset for different anomalies are very similar in the different systems. The pair correlation entropy is shown to be a crucial and experimentally accessible quantity for relating structure, entropy, and diffusivity that could be potentially useful for a large class of inorganic ionic liquids.
Nonlinear Langmuir structures: Soliton and shock in a rotating weakly relativistic electron-positron magnetoplasma with stationary positive ions
Authors: El-Labany S. K. , Moslem W. M. , El-Awady E. I.
Published: June 2010

Theoretical and numerical studies are performed for nonlinear Langmuir structures (soliton and shock) in a rotating weakly relativistic electron-positron magnetoplasma with background stationary positive ions. For this purpose, the reductive perturbation technique is employed to the weakly relativistic hydrodynamical electrons/positrons fluid equations and Poisson equation, obtaining extended Zakharov–Kuznetsov equation. The latter has been solved analytically. The features of the nonlinear excitations and their propagation conditions are investigated numerically. Our finding could elucidate the nonlinear electrostatic structures that propagate in astrophysical plasma situations where rotating, magnetized plasma can exist; such as polar cups region of pulsars, around active galactic nuclei, neutron stars, and white dwarfs.
Coulomb explosion in dicationic noble gas clusters: A genetic algorithm-based approach to critical size estimation for the suppression of Coulomb explosion and prediction of dissociation channels
Authors: Nandy Subhajit , Chaudhury Pinaki , Bhattacharyya S. P.
Published: June 2010

We present a genetic algorithm based investigation of structural fragmentation in dicationic noble gas clusters, Arn+2, Krn+2, and Xen+2, where n denotes the size of the cluster. Dications are predicted to be stable above a threshold size of the cluster when positive charges are assumed to remain localized on two noble gas atoms and the Lennard-Jones potential along with bare Coulomb and ion-induced dipole interactions are taken into account for describing the potential energy surface. Our cutoff values are close to those obtained experimentally [P. Scheier and T. D. Mark, J. Chem. Phys. 11, 3056 (1987)] and theoretically [J. G. Gay and B. J. Berne, Phys. Rev. Lett. 49, 194 (1982)]. When the charges are allowed to be equally distributed over four noble gas atoms in the cluster and the nonpolarization interaction terms are allowed to remain unchanged, our method successfully identifies the size threshold for stability as well as the nature of the channels of dissociation as function of cluster size. In Arn2+, for example, fissionlike fragmentation is predicted for n=55 while for n=43, the predicted outcome is nonfission fragmentation in complete agreement with earlier work [Golberg et al., J. Chem. Phys. 100, 8277 (1994)].
Double conical crystal x-ray spectrometer for high resolution ultrafast x-ray absorption near-edge spectroscopy of Al K edge
Authors: Levy A. , Dorchies F. , Fourment C. , Harmand M. , Hulin S. , Santos J. J. , Descamps D. , Petit S. , Bouillaud R.
Published: June 2010

An x-ray spectrometer devoted to dynamical studies of transient systems using the x-ray absorption fine spectroscopy technique is presented in this article. Using an ultrafast laser-induced x-ray source, this optical device based on a set of two potassium acid phthalate conical crystals allows the extraction of x-ray absorption near-edge spectroscopy structures following the Al absorption K edge. The proposed experimental protocol leads to a measurement of the absorption spectra free from any crystal reflectivity defaults and shot-to-shot x-ray spectral fluctuation. According to the detailed analysis of the experimental results, a spectral resolution of 0.7 eV rms and relative fluctuation lower than 1% rms are achieved, demonstrated to be limited by the statistics of photon counting on the x-ray detector.
Communications: Accurate and efficient approximations to explicitly correlated coupled-cluster singles and doubles, CCSD-F12
Authors: Hättig Christof , Tew David P. , Köhn Andreas
Published: June 2010

We propose a novel explicitly correlated coupled-cluster singles and doubles method CCSD(F12∗), which retains the accuracy of CCSD-F12 while the computational costs are only insignificantly larger than those for a conventional CCSD calculation.
Ab initio calculations on the X̃ B21 and Ã A21 states of AsH2, and Franck–Condon simulation, including anharmonicity, of the Ã(,,)-X̃ single vibronic level emission spectrum of AsH2
Authors: Lee Edmond P. F. , Mok Daniel K. W. , Chau Foo-tim , Dyke John M.
Published: June 2010

Restricted-spin coupled-cluster single-double plus perturbative triple excitation {RCCSD(T)} calculations were carried out on the X̃ B21 and Ã A21 states of AsH2 employing the fully relativistic small-core effective core potential (ECP10MDF) for As and basis sets of up to the augmented correlation-consistent polarized valence quintuple-zeta (aug-cc-pV5Z) quality. Minimum-energy geometrical parameters and relative electronic energies were evaluated, including contributions from extrapolation to the complete basis set limit and from outer core correlation of the As 3d10 electrons employing additional tight 4d3f2g2h functions designed for As. In addition, simplified, explicitly correlated CCSD(T)-F12 calculations were also performed employing different atomic orbital basis sets of up to aug-cc-pVQZ quality, and associated complementary auxiliary and density-fitting basis sets. The best theoretical estimate of the relative electronic energy of the Ã A21 state of AsH2 relative to the X̃ B21 state including zero-point energy correction (T0) is 19 954(32) cm−1, which agrees very well with available experimental T0 values of 19 909.4531(18) and 19 909.4910(17) cm−1 obtained from recent laser induced fluorescence and cavity ringdown absorption spectroscopic studies. In addition, potential energy functions (PEFs) of the X̃ B21 and Ã A21 states of AsH2 were computed at different RCCSD(T) and CCSD(T)-F12 levels. These PEFs were used in variational calculations of anharmonic vibrational wave functions, which were then utilized to calculate Franck–Condon factors (FCFs) between these two states, using a method which includes allowance for anharmonicity and Duschinsky rotation. The Ã(0,0,0)-X̃ single vibronic level (SVL) emission spectrum of AsH2 was simulated using these computed FCFs. Comparison between simulated and available experimental vibrationally resolved spectra of the Ã(0,0,0)-X̃ SVL emission of AsH2, which consist essentially of the bending (2n) series, suggests that there is a significant loss in intensity in the low emission energy region of the experimental spectrum.
Nonlinear acoustic resonances to probe a threaded interface
Authors: Rivière Jacques , Renaud Guillaume , Haupert Sylvain , Talmant Maryline , Laugier Pascal , Johnson Paul A.
Published: June 2010

We evaluate the sensitivity of multimodal nonlinear resonance spectroscopy to torque changes in a threaded interface. Our system is comprised of a bolt progressively tightened in an aluminum plate. Different modes of the system are studied in the range 1–25 kHz, which correspond primarily to bending modes of the plate. Nonlinear parameters expressing the importance of resonance frequency and damping variations are extracted and compared to linear ones. The influence of each mode shape on the sensitivity of nonlinear parameters is discussed. Results suggest that a multimodal measurement is an appropriate and sensitive method for monitoring bolt tightening. Further, we show that the nonlinear components provide new information regarding the interface, which can be linked to different friction theories. This work has import to study of friction and to nondestructive evaluation of interfaces for widespread application and basic research.
Light induced solid-phase crystallization of Si nanolayers in Si/SiO2 multiple quantum wells
Authors: Mchedlidze T. , Arguirov T. , Kouteva-Arguirova S. , Kittler M.
Published: June 2010

The process of light-induced crystallization (LIC) of nanometer-thick amorphous silicon (a-Si) layers in Si/SiO2 multiquantum wells (MQW) was investigated using Raman spectroscopy. In the present investigations, a laser was employed as the light source. An analysis of obtained and previously published results suggests strong influence of radiation wavelength on the outcome of the process. Namely, for certain ranges of wavelengths and radiation fluxes the crystallization proceeds through the light-induced solid phase crystallization (LISPC) process. An optimal set of radiation wavelength and flux values allows formation of fully crystallized and almost strain-free layers of nanocrystalline silicon (Si-nc). The difference in the absorption coefficients between a-Si and Si-nc was considered responsible for the obtained results. A mechanism explaining the wavelength and the radiation flux dependence was proposed. Understanding of the mechanism of LISPC in MQW structures would allow improving the LIC processes for thin silicon films.
Computing the conformational entropy for RNA folds
Authors: Liu Liang , Chen Shi-Jie
Published: June 2010

We develop a polymer physics-based method to compute the conformational entropy for RNA tertiary folds, namely, conformations consisting of multiple helices connected through (cross-linked) loops. The theory is based on a virtual bond conformational model for the nucleotide chain. A key issue in the calculation of the entropy is how to treat the excluded volume interactions. The weak excluded volume interference between the different loops leads to the decomposition of the whole structure into a number of three-body building blocks, each consisting of a loop and two helices connected to the two ends of the loop. The simple construct of the three-body system allows an accurate computation for the conformational entropy for each building block. The assembly of the building blocks gives the entropy of the whole structure. This approach enables treatment of molten globule-like folds (partially unfolded tertiary structures) for RNAs. Extensive tests against experiments and exact computer enumerations indicate that the method can give accurate results for the entropy. The method developed here provides a solid first step toward a systematic development of a theory for the entropy and free energy landscape for complex tertiary folds for RNAs and proteins.
Valence band effective mass of non-c-plane nitride heterostructures
Authors: Kojima K. , Funato M. , Kawakami Y. , Noda S.
Published: June 2010

Valence band (VB) effective masses of nonpolar and semipolar nitride heterostructures were studied using k⋅p perturbation theory, with a particular focus on band mixing. When the absolute value of the energy separation of the topmost two VBs (|ΔE|) is sufficiently larger than the spin-orbit interaction (Δso), the mixing between these two VBs was negligible. This enabled us to calculate an analytical expression for VB mass expression. Under this condition, the effective mass of the top VB was reduced less than 10% along a certain direction, and less than 25% for an in-plane (x′y′-plane) average, compared to the c-plane case. When ΔE was comparable with Δso, however, the VB structure became isotropic due to band mixing. Consequently, the VB band structure approached that of the c-plane and optical polarization was suppressed. On the other hand, VB mass along the growth direction (z′) was always heavy, similar to that of the c-plane. However, the topmost two VBs had slightly different mass values along z′, which affected radiative properties of non-c-plane nitride quantum wells (less than 2 nm wide) through the difference in quantum confinement strengths.
Two-state conductance in single Zn porphyrin molecular junctions
Authors: Qian Guoguang , Saha Swatilekha , Lewis K. M.
Published: June 2010

Conductance measurements were taken by forming single molecule junctions between a scanning tunneling microscope tip and a gold substrate. We observed the existence of a two-state conductance in porphyrin molecules ligating a zinc atom. Peaks in the conductance histograms showed molecules changed from a high conductance state to a low conductance state. This effect was not observed for porphyrin molecules without a ligating atom. We discuss how this phenomenon may be attributed to conformational changes in the molecule.
Diode lasers with asymmetric waveguide and improved beam properties
Authors: Chen Jianfeng , Kipshidze Gela , Shterengas Leon
Published: June 2010

Fast axis beam divergence of 1.95 μm GaSb-based diode lasers was reduced to 42° of full-width-at-half-maximum. The beam properties were improved thanks to development of efficient laser heterostructure with asymmetric waveguide. Near field was expanded almost exclusively into n-cladding by reduction in the refractive index step at the corresponding heterointeraface. The related reduction in the band offset between waveguide core and n-cladding was balanced by introduction of the thin carrier stopper layer. Multimode 100 μm wide ridge waveguide lasers demonstrated continuous wave output power of about 1.5 W at 8 A at 20 °C.
The dependence of the oxidation enhancement of InP(100) surface on the coverage of the adsorbed Cs
Authors: Sun Yun , Liu Zhi , Pianetta Piero
Published: June 2010

We report the oxidation of the InP(100) surface promoted by adsorbed Cs by synchrotron radiation photoemission. Oxygen exposure causes reduction in the charge transferred to the InP substrate from Cs and the growth of indium oxide and phosphorous oxide. The oxide growth displays a clear dependence on the Cs coverage. The oxidation of phosphorous is negligible up to 1000 L of O2 exposure when the Cs coverage is less than half a monolayer (ML) but the formation of the second half-ML of Cs greatly accelerates the oxidation. This different enhancement of the InP oxidation by the first and the second half-ML of Cs is due to the double layer structure of the adsorbed Cs atoms, and consequently the higher 6s electron density in the Cs atoms when Cs coverage is larger than 0.5 ML.
Resistive switching behaviors of ZnO nanorod layers
Authors: Chang Wen-Yuan , Lin Chin-An , He Jr-Hau , Wu Tai-Bor
Published: June 2010

We have fabricated vertically aligned ZnO nanorod layers (NRLs) on indium tin oxide (ITO) electrodes using a hydrothermal process. The Pt/ZnO NRL/ITO capacitor exhibits bipolar resistive switching behavior. The resistive switching behavior may be related to the oxygen vacancies and/or zinc interstitials confined on the surface of the ZnO NRs, giving rise to the formation of straight and extensible conducting filaments along each vertically aligned ZnO NR. Superior stability in resistive switching characteristics was also observed, demonstrating that ZnO NRLs have the potential for next-generation nonvolatile memory applications.
Characterization of poly(vinylidenefluoride-co-hexafluoroprolylene) membranes containing nanoscopic AlO(OH)n filler with Li/LiFePO4 cell
Authors: Aravindan V. , Senthilkumar V. , Nithiananthi P. , Vickraman P.
Published: June 2010

This paper describes the nanoscopic AlO(OH)n filled in porous poly(vinylidenefluoride-co-hexafluoroprolylene) membranes by phase inversion technique. The membranes were gelled with 0.5M LiPF6 in ethylene carbonate and diethyl carbonate mixture for characterization studies. The inclusion of AlO(OH)n nanoparticles substantially enhances the ionic conductivity and mechanical and thermal stabilities, which were observed through ac impedance, tensile strength, and differential scanning calorimetry. For example, the ionic conductivity has been increased from 2.1×10−3 to 3.9×10−3 S cm−1 after the inclusion of nanoparticles. Similarly, the elongation break value is improved from 277% to 464% for the incorporation of nanoparticles. A morphological feature of the membrane was analyzed by scanning electron microscopy. Further, physicochemical properties, such as liquid uptake, porosity measurements, activation energy, and percentage of crystallinity, have also been presented. Finally, Li/polymer membrane/LiFePO4 cell was fabricated, and cycling performance of the cell was evaluated at C/10 rate. The cell delivers the initial discharge capacity 149 mAh/g at ambient temperature conditions.
High-performance, homogeneous broad-gain quantum cascade lasers based on dual-upper-state design
Authors: Fujita Kazuue , Edamura Tadataka , Furuta Shinichi , Yamanishi Masamichi
Published: June 2010

A broad-gain quantum cascade laser design with dual-upper-state is proposed to clarify its own feasibility. Devices employing the proposed active region design exhibit homogeneously wide (>330 cm−1) electroluminescence spectra of which shapes are insensitive to voltage changes. A buried heterostructure laser, emitting at λ∼8.4 μm, demonstrates a high continuous-wave output power of 152 mW together with a high constant slope efficiency of 518 W/A at room temperature. In addition, the device performance is observed to be very insensitive to temperature change; T0-values of ∼306 K and constant slope efficiency over the wide temperature range, 280–400 K.
The origin of low water vapor transmission rates through Al2O3/ZrO2 nanolaminate gas-diffusion barriers grown by atomic layer deposition
Authors: Meyer J. , Schmidt H. , Kowalsky W. , Riedl T. , Kahn A.
Published: June 2010

This paper reports on thin film gas-diffusion barriers consisting of Al2O3/ZrO2 nanolaminates (NL) grown by low-temperature (80 °C) atomic layer deposition. We show that reliable barriers with water vapor transmission rates of 3.2×10−4 g/(m2 day), measured at 80 °C and 80% relative humidity, can be realized with very thin layers down to 40 nm. We determine that ZrO2 acts as anticorrosion element in our NL. Furthermore, we demonstrate by x-ray photoemission spectroscopy that an aluminate phase is formed at the interfaces between Al2O3 and ZrO2 sublayers, which additionally improves the gas-diffusion barrier due to a densification of the layer system. These Al2O3/ZrO2 NLs prepared at low temperatures hold considerable promises for application in organic electronics and beyond.
Noise-driven signal transmission using nonlinearity of VO2 thin films
Authors: Kanki Teruo , Hotta Yasushi , Asakawa Naoki , Kawai Tomoji , Tanaka Hidekazu
Published: June 2010

We demonstrated signal transmission using the nonlinearity of VO2 in the manner of stochastic resonance (SR). A correlated insulator state of VO2 changes nonlinearly to a metallic state when an applied bias voltage increases beyond a threshold. The transition of the states between insulator and metal is adaptable to the SR theory. In this study, the response to a weak pulse signal was optimized by a particular level of noise via SR. Numerical SR simulations suggests the existence of multiple threshold channels in the insulating state, spontaneously enhancing the reliability of signal transmission.
Correlation energy of two electrons in a ball
Authors: Loos Pierre-François , Gill Peter M. W.
Published: June 2010

We study the ground-state correlation energy Ec of two electrons of opposite spin confined within a D-dimensional ball (D≥2) of radius R. In the high-density regime, we report accurate results for the exact and restricted Hartree–Fock energy, using a Hylleraas-type expansion for the former and a simple polynomial basis set for the latter. By investigating the exact limiting correlation energy Ec(0)=limR→0Ec for various values of D, we test our recent conjecture [P.-F. Loos and P. M. W. Gill, J. Chem. Phys. 131, 241101 (2009)] that in the large-D limit, Ec(0)∼−δ2/8 for any spherically symmetric confining external potential, where δ=1/(D−1).
Potential energy surface for spin-polarized rubidium trimer
Authors: Soldán Pavel
Published: June 2010

Potential energy surface for the lowest quartet state of the rubidium trimer is constructed, making use of the many-body decomposition. Interaction energies are calculated using the coupled-clusters method and interpolated using the reciprocal-power reproducing kernel Hilbert space interpolation method. Both the two-body and three-body nonadditive parts are extrapolated to exhibit the correct long-range behavior. Consequences for the low-energy scattering are briefly discussed.