bluuebunny/crossref_metadata_2025 huggingface dataset:
Psychiatric Diagnoses and Suicide: Revisiting the Evidence
Authors: Bertolote José Manoel , Fleischmann Alexandra , De Leo Diego , Wasserman Danuta
Published: November 2004

Abstract: Background: The key role of prevention and treatment of mental disorders in the prevention of suicide is widely acknowledged. Which specific disorders need to be targeted remains to be conclusively demonstrated. Aims: To re-examine the presence of psychiatric diagnosis in cases of completed suicide from a global perspective. Method: A review of studies reporting diagnoses of mental disorders in cases of completed suicide with or without history of admission to mental hospitals. Results: Most cases were from Europe and North America (82.2%). The majority (98%) of these had a diagnosis of at least one mental disorder. Among all diagnoses, mood disorders accounted for 30.2%, followed by substance-use related disorders (17.6%), schizophrenia (14.1%), and personality disorders (13.0%). Conclusions: The mental health paradigm in suicide prevention covers just a part of the problem. Antisuicide strategies focusing exclusively on the identification and treatment of depression need to be reconsidered. In addition to this, other mental disorders should be targeted, in particular alcohol-use disorders and schizophrenia. More emphasis should also be placed on psychosocial and environmental interventions diminishing and counteracting stress.
Newspaper Reporting of Suicide Cases in Hong Kong
Authors: Au Jade S. K. , Yip Paul S. F. , Chan Cecilia L. W. , Law Y. W.
Published: November 2004

This study addresses the concerns over newspapers' reporting of suicide cases in Hong Kong, SAR (Special Administrative Region), using the WHO guidelines on the reporting of suicide news as a reference for comparison. We compared the official suicide information extracted from the Coroner's Court for the year 2000 with newspaper reports on suicides taken from five major Chinese local newspapers, which accounted for about 80% of the total circulation in Hong Kong. The type of newspaper reporting on suicides was also examined. Newspapers tended to report on those suicide victims who suffered relationship problems, whereas those who had family problems were significantly underreported. Among the suicides reported in the newspapers, 6.2% were found on the front page and the majority of the reports were presented pictorially. The reporting of suicides was selective and the coverage was incomplete, with student suicides reported excessively. The method of reporting for Hong Kong newspapers was not in line with the recommendations of the WHO or international best practices on presenting suicide news. For this reason we recommend a partnership approach with active participation from the media on suicide prevention so that communication professionals can proactively participate in suicide prevention work more effectively.
Recollections of Bullying at School and Their Long-Term Implications for Lesbians, Gay Men, and Bisexuals
Authors: Rivers Ian
Published: November 2004

Abstract: This study explores the relationship between experiences of bullying at school, adult mental health status, and symptoms of posttraumatic stress among a sample of 119 UK residents who identified as lesbian, gay, or bisexual. Participants completed a series of questionnaires that focused upon school experiences, suicide ideation at school, sexual history, relationship status and negative affect, recent positive and negative life-events, internalized homophobia, and symptoms associated with posttraumatic stress. The results suggested that posttraumatic stress was a potential issue for 17% of participants who also scored significantly higher for depression, and reported having had more casual sexual partners than their peers. However, those who were found to exhibit symptoms of posttraumatic stress were also more accepting of their sexual orientation. A small number of participants used prescription or nonprescription drugs, or alcohol to help them cope with memories of bullying. It is suggested that posttraumatic stress may be a feature of the adult lives of men and women who experienced frequent and prolonged bullying at school as a result of their actual or perceived sexual orientation.
Deliberate Self-Harm Patients Who Discharge Themselves from the General Hospital Without Adequate Psychosocial Assessment
Authors: Crowder Rachel , Van Der Putt Rohan , Ashby Ceri-Anne , Blewett Andrew
Published: November 2004

Abstract: Deliberate self-harm patients who leave the acute hospital environment before the completion of psychiatric assessment have an increased risk of subsequent self-harm. We considered the available data on 50 premature self-discharges identified prospectively in a general hospital with a well-developed integrated-care pathway for self-harm patients, and compared them to a control group. The self-discharge group was found to be more likely to have attempted self-poisoning without alcohol intoxication or other forms or combinations of self-harm, and an absence of identifiable previous self-harm or prior contact with local specialist psychiatric services. The two groups showed no difference in age, sex, or area of residence based on community mental health team sectors. It is proposed that these findings indicate hypotheses for further studies of why people leave the hospital without adequate assessment, and how service design could be improved in order to help them.
Input to Verbal Working Memory
Authors: Jacobsen Thomas , Schröger Erich
Published: November 2004

Abstract. Working memory uses central sound representations as an informational basis. The central sound representation is the temporally and feature-integrated mental representation that corresponds to phenomenal perception. It is used in (higher-order) mental operations and stored in long-term memory. In the bottom-up processing path, the central sound representation can be probed at the level of auditory sensory memory with the mismatch negativity (MMN) of the event-related potential. The present paper reviews a newly developed MMN paradigm to tap into the processing of speech sound representations. Preattentive vowel categorization based on F1-F2 formant information occurs in speech sounds and complex tones even under conditions of high variability of the auditory input. However, an additional experiment demonstrated the limits of the preattentive categorization of language-relevant information. It tested whether the system categorizes complex tones containing the F1 and F2 formant components of the vowel /a/ differently than six sounds with nonlanguage-like F1-F2 combinations. From the absence of an MMN in this experiment, it is concluded that no adequate vowel representation was constructed. This shows limitations of the capability of preattentive vowel categorization.
“Capacity” Reconsidered:
Authors: Bornkessel Ina D. , Fiebach Christian J. , Friederici Angela D. , Schlesewsky Matthias
Published: November 2004

Abstract. The influence of interindividual differences in cognitive mechanisms on language comprehension remains controversial not only due to conflicting experimental findings, but also in view of the difficulty associated with determining which measure should be used in participant classification. Here, we address the latter problem by proposing that an electrophysiological measure, individual alpha frequency (IAF), may be a suitable means of classifying interindividual differences in sentence processing. Interindividual differences in IAF have been shown to correlate with performance on memory tasks and speed of information processing. In two experiments using event-related brain potentials (ERPs), IAF-based participant groups differed systematically with regard to the processing of ambiguous sentences such that the low-IAF group showed a sustained positivity in the ambiguous region, while the high-IAF group did not. These interindividual differences were independent of whether the ambiguity was syntactic (Experiment 1) or sentence-level semantic (Experiment 2). Moreover, they were reliable only when participants were classified according to IAF, but not in classifications based on reading span, speed of processing (reaction time), or accuracy of processing (error rate).
Uppermost mantle velocities beneath China and surrounding regions
Authors: Hearn Thomas M. , Wang Suyun , Ni James F. , Xu Zhonghuai , Yu Yanxiang , Zhang Xiaodong
Published: November 2004

Seismic P wave velocity variations in the uppermost mantle beneath China are tomographically imaged using Pn wave travel time data. The average velocity of the mantle lid beneath China is 8.05 km/s, with a range from −0.30 km/s to 0.35 km/s. Eastern China has slower mantle velocities and a thinner crust than western China. Different inversions performed for shorter ray path and longer ray path data sets separated the shallow and deep structure within the mantle lid. Velocities in the lower lid are no more than 0.2 km/s faster than at the top. The fastest velocities are beneath cratons, which remained relatively undeformed despite orogenic events around their margins. The Pn velocity beneath southern Tibet is faster than that beneath northern Tibet, suggesting that this contrast delineates the northern edge of the Indian lithosphere. On the southeastern margin of the Tibetan plateau, the Panxi rift, slow Pn velocity exists in the lithosphere due to the transextensional tectonic environment. In eastern China, extension of the North China Block produced a series of NNE‐SSW trending rifts that cause slow mantle lid velocities. These slow velocities extend to the base of the mantle lid, suggesting that late Cenozoic Pacific subduction drove the rifting. Both high temperature and hydration may contribute to these low uppermost mantle velocities. The Shanxi rift, along the east margin of the Ordos platform, is characterized by a slow mantle velocity; in contrast, the Yinchuan rift, on the west margin, does not show any uppermost mantle velocity anomaly.
Three‐dimensional modeling of the Gulf of Lion's hydrodynamics (northwest Mediterranean) during January 1999 (MOOGLI3 Experiment) and late winter 1999: Western Mediterranean Intermediate Water's (WIW's) formation and its cascading over the shelf break
Authors: Dufau‐Julliand Claire , Marsaleix Patrick , Petrenko Anne , Dekeyser Ivan
Published: November 2004

The Gulf of Lion's hydrodynamics are investigated with a numerical simulation of the 1998–1999 winter, performed with a three‐dimensional (3‐D) free‐surface model and real forcings. The model initial state derives from the large‐scale outputs of the MOM (1/8°) using a specific initialization method. The model results are validated with an oceanographic data set collected in the gulf during the MOOGLI3 cruise (11–21 January 1999). The modeled outputs agree well with the main hydrological and circulation patterns observed during MOOGLI3. The study focuses on a strong and peculiar event of dense water (Western Mediterranean Intermediate Water (WIW)) formation on the continental shelf and its cascading over the shelf break. This latter was detected by a steep temperature decrease in the time series of a mooring line in the nearby Lacaze‐Duthiers canyon which is well reproduced in the simulation. Modeled dense plumes appear during the MOOGLI3 period but more especially during late winter. Shapiro's theory of dense plume propagating on a sloping bottom is applied and provides information of the plume driving mechanisms. In both cases of plume studied, friction effects and Ekman drainage by the ambient current explain only a part of the plume motion. The complementary forcing is probably the steep local bathymetry irregularities. This 3‐D simulation permits also to evaluate the total amount of WIW formed during the 1998–1999 winter over the Gulf of Lion's shelf to 500 km3.
Isotopic composition of Yb and the determination of Lu concentrations and Lu/Hf ratios by isotope dilution using MC‐ICPMS
Authors: Vervoort Jeff D. , Patchett P. Jonathan , Söderlund Ulf , Baker Mark
Published: November 2004

We report Yb isotopic data for the purpose of accurately correcting measurements of Lu and Lu/Hf ratios during Multicollector Inductively Coupled Plasma Mass Spectrometer (MC‐ICPMS) analysis. The Yb isotopic ratios agree with recent results of Chu et al. [2002] and Amelin and Davis [2004], when corrected for mass fractionation to the same reference values. Protocols for Lu measurement involving simultaneous subtraction of Yb interference and application of a fractionation correction based on Yb are described. It is shown that Lu concentrations and Lu/Hf ratios determined by MC‐ICPMS using this methodology are more precise and potentially more accurate than results based on analysis of Lu by Thermal Ionization Mass Spectrometry (TIMS). A number of MC‐ICPMS Lu‐Hf isotopic analyses of standard rocks and other geological samples, previously analyzed by TIMS, are presented. These document reproducibility of Lu/Hf within 0.2%, where most discrepancies can be assigned to the unknown Lu mass fractionation during TIMS analysis.
Mantle heterogeneity during the formation of the North Atlantic Igneous Province: Constraints from trace element and Sr‐Nd‐Os‐O isotope systematics of Baffin Island picrites
Authors: Kent A. J. R. , Stolper E. M. , Francis D. , Woodhead J. , Frei R. , Eiler J.
Published: November 2004

Sr‐Nd‐Os‐O isotope and major and trace element data from ∼62 Ma picrites from Baffin Island constrain the composition of mantle sources sampled at the inception of North Atlantic Igneous Province (NAIP) magmatism. We recognize two compositional types. Depleted (N‐type) lavas have low 87Sr/86Sri (0.702990–0.703060) and 187Os/188Osi (0.1220–0.1247) and high 143Nd/144Ndi (0.512989–0.512999) and are depleted in incompatible elements relative to primitive mantle. Enriched (E‐type) lavas have higher 87Sr/86Sri (0.703306–0.703851) and 187Os/188Osi (0.1261–0.1303), lower 143Nd/144Ndi (0.512825–0.512906), and incompatible element concentrations similar to, or more enriched than, primitive mantle. There is also a subtle difference in oxygen isotope composition; E‐type lavas are marginally lower in δ18Oolivine value (5.16–4.84‰) than N‐type lavas (5.15–5.22‰). Chemical and isotopic variations between E‐ and N‐type lavas are inconsistent with assimilation of crust and/or subcontinental lithospheric mantle and appear to instead reflect mixing between melts derived from two distinct mantle sources. Strontium‐Nd‐O isotope compositions and incompatible trace element abundances of N‐type lavas suggest these are largely derived from the depleted upper mantle. The 187Os/188Osi ratios of N‐type lavas can also be explained by such a model but require that the depleted upper mantle had γOs of approximately −5 to −7 at 62 Ma. This range overlaps the lowest γOs values measured in abyssal peridotites. Baffin Island lava compositions are also permissive of a model involving recharging of depleted upper mantle with 3He‐rich material from the lower mantle (Stuart et al., Nature, 424, 57–59, 2003), with the proviso that recharge had no recognizable effect on the lithophile trace element and Sr‐Nd‐Os‐O isotope composition. The origin of the enriched mantle component sampled by Baffin Island lavas is less clear but may be metasomatized and high‐temperature‐altered recycled oceanic lithosphere transported within the proto Iceland plume. Differences between Baffin Island lavas and modern Icelandic basalts suggest that a range of enriched and depleted mantle sources have been tapped since the inception of magmatism in the province. Similarities between Baffin Island lavas erupted and those of similar age from East and West Greenland also suggest that the enriched component in Baffin Island lavas may have been sampled by lavas erupted over a wide geographic range.
Nonlinear complex principal component analysis of the tropical Pacific interannual wind variability
Authors: Rattan Sanjay S. P. , Hsieh William W.
Published: November 2004

Complex principal component analysis (CPCA) is a linear multivariate technique commonly applied to complex variables or 2‐dimensional vector fields such as winds or currents. A new nonlinear CPCA (NLCPCA) method has been developed via complex‐valued neural networks. NLCPCA is applied to the tropical Pacific wind field to study the interannual variability. Compared to the CPCA mode 1, the NLCPCA mode 1 is found to explain more variance and reveal the asymmetry in the wind anomalies between El Niño and La Niña states.
Effects of spatial distribution of fault slip on calculating co‐seismic displacement: Case studies of the Chi‐Chi earthquake (Mw7.6) and the Kunlun earthquake (Mw7.8)
Authors: Fu Guangyu , Sun Wenke
Published: November 2004

This study presents a segment‐summation scheme for calculating co‐seismic deformations caused by a seismic model with spatial distribution of fault slip. The basic idea is to divide such a fault plane into limited sub‐faults, so that the co‐seismic deformations caused by each sub‐fault can be evaluated by applying Okada's formulation [Okada, 1985] and summing up the individual contributions from the whole sub‐faults. Two case studies of the Chi‐Chi earthquake (Mw7.6, 1999) and the Kunlun earthquake (Mw7.8, 2001) show that there exists a big discrepancy between the results calculated for the two dislocation models. It implies that the mean dislocation model remarkably affect the calculating results. The results of RMS errors show that the co‐seismic displacements calculated by the fault with spatial distribution of fault slip improve the results by over 50% compared to the mean dislocation results.
Temporally integrated estimate of the Indonesian throughflow using tritium
Authors: Jean‐Baptiste P. , Jenkins W. J. , Dutay J. C. , Fourré E. , Leboucher V. , Fieux M.
Published: November 2004

Because of the high interannual and seasonal variability, transports from the various methods used to estimate the Indonesian throughflow encompass a large range of values. Here, we estimate a temporally integrated transport for the throughflow from comparison of the tritium water column inventory on both sides of the throughflow. Our approach is based on the simple idea that tritium, with a radioactive decay half‐life of 12.32 yr, is well suited to infer the transit time (and consequently the mass flow) of the waters through the Indonesian archipelago. We show that the tritium budget implies a flow of 8.6 ± 4 Sv, corresponding to a transit time of 10.5 yr. This result, which represents an average over seasons and several ENSO and non‐ENSO periods, shows that repeated tritium measurements on both sides of the Indonesian Seas could provide a useful method for monitoring the long‐term evolution of the throughflow.
Exploring parameter sensitivities of the land surface using a locally coupled land‐atmosphere model
Authors: Liu Yuqiong , Gupta Hoshin V. , Sorooshian Soroosh , Bastidas Luis A. , Shuttleworth William J.
Published: November 2004

This paper presents a multicriteria analysis that explores the sensitivity of the land surface to changes in both land and atmospheric parameters, in terms of reproducing surface heat fluxes and ground temperature; for the land parameters, offline sensitivity analyses were also conducted for comparison to infer the influence of land‐atmosphere interactions. A simple “one‐at‐a‐time” sensitivity analysis was conducted first to filter out some insensitive parameters, followed by a multicriteria sensitivity analysis using the multiobjective generalized sensitivity analysis algorithm. The models used were the locally coupled National Center for Atmospheric Research (NCAR) single‐column community climate model and the offline NCAR land surface model, driven and evaluated by a summer intensive operational periods (IOP) data set from the southern Great Plains. As expected, the results show that land‐atmosphere interactions (with or without land‐atmosphere parameter interactions) can have significant influences on the sensitivity of the land surface to changes in the land parameters, and the single‐criterion sensitivities can be significantly different from the multicriteria sensitivity. These findings are mostly model and data independent and can be generally useful, regardless of the model/data dependence of the sensitivities of individual parameters. The exceptionally high sensitivities of the selected atmospheric parameters in a multicriteria sense (and in particular for latent heat) appeal for adequate attention to the specification of effective values of these parameters in an atmospheric model. Overall, this study proposes an effective framework of multicriteria sensitivity analysis beneficial to future studies in the development and parameter estimation of other complex (offline or coupled) land surface models.
Electronic Structures of Polyatomic Molecules and Valence. V. Molecules RXn
Authors: Mulliken Robert S.
Published: November 2004

Theory. The approximate construction, for shared electrons in molecules RXn, of molecular orbitals (``orbital'' means one-electron orbital wave function) as linear combinations of atomic orbitals is discussed and illustrated by equations for RX2, RX3, RX4 types. Properties of bonding, nonbonding, antibonding, also excited, molecular orbitals are described. Valence orbitals include both bonding and nonbonding types. RH3 and H3 orbitals are given as examples. Molecular orbitals constructed from atomic orbitals contain undetermined coefficients and implicit parameters (effective Z's of the atomic orbitals) which make them very flexible. They are useful for a qualitative theory which can be compared with empirical, especially chemical and spectroscopic, data. They also have value in semi-quantitative calculations (Van Vleck). Applications. Electronic structures, ionization potentials, form and stability (at least some of these properties in each case) of the molecules CH4, NH3, H2O, NH4, CH3, NH2, BeH2, RXn are described and interpreted in terms of molecular orbitals. It is shown that an electronic structure 1s22[s]22[p]6, closely related to that of the Ne atom, can be assigned to CH4 without the least necessity or justification for departing from the idea of the equivalence of the four C–H bonding directions. This seems in some respects more natural than the Pauling-Slater method in which four equivalent bonds are obtainable only with mixtures of 2s and 2p carbon orbitals. The structures assigned for NH3 and H2O are also related to that of Ne, and that for NH4 to that of Na. The ionization potential of NH4 is estimated as 4.5 volts, slightly greater than for the K atom. The proton affinity of NH3 (energy change for NH3+H+→NH4+) is estimated to be 9 volts. The ionization potential of CH3 is roughly estimated as 8.5 volts, and the energy of formation of CH4 from CH3+H is discussed. Whether molecules RX3 are plane or pyramidal can be considered to depend on the quantitative outcome of a conflict of different factors; three such factors are noted. The first of these gives an explanation of Zachariasen's rule. Empirical evidence is cited showing that the geometrical possibilities of forms RX4 tend to produce stabler electron configurations than are permitted by the possible geometry of RX3. The ultraviolet absorption spectra of CH4, NH3, and H2O are discussed in relation to the ionization potentials of these molecules.
The Infrared Absorption Spectra of NO2 and N2O4
Authors: Schaffert Roland
Published: November 2004

The infrared absorption spectrum of nitrogen peroxide has been investigated in the gaseous and liquid states, by using a prism spectrometer. Absorption bands were observed at 3.3μ, 3.89μ, 5.7μ, 6.14μ, 7.28μ, 7.85μ, 13.3μ and 15.6μ in the gaseous state, and at 3.65μ and 5.7μ in the liquid state. By heating the gas to a temperature of 150°C, it was found that the bands at 3.89μ, 5.7μ, 7.85μ and 13.3μ were due to N2O4, while those at 3.3μ, 6.14μ, 7.28μ and 15.6μ were due to NO2.
Wave-Mechanical Treatment of the Li2 Molecule
Authors: James Hubert M.
Published: November 2004

A treatment of the Li2 molecule by the Heitler-London method, with Slater wave functions for the atoms, has been carried out both with and without the customary approximations. In the absence of these approximations the binding computed is only a small fraction of that observed. It is found that the inner shells of the atoms may have an important effect on the magnitude of molecular binding, and may either increase or decrease it. Since their effect is associated with electron exchange it appears that they cannot be replaced by an equivalent potential field without serious error. Triple exchanges of electrons are found to be important, while polar binding is quite negligible in Li2. A criterion for the applicability of the ``interaction operator'' is developed; the error involved in its use with Li2 is small. A variational treatment has also been applied to this molecule. It yielded a binding energy less than that observed by about 0.5 e.v. The elimination of the residual error apparently requires the introduction of the interelectronic distances as coordinates. Convenient methods for the numerical treatment of multiple electron exchanges in complicated molecules are described.
Acoustical Studies. III. The Rates of Excitation of Vibrational Energy in Carbon Dioxide, Carbon Disulfide and Sulfur Dioxide
Authors: Richards William T. , Reid James A.
Published: November 2004

Measurements on these three gases at various pressures, temperatures and frequencies are reported. In all cases double collisions provide the predominant mechanism of excitation. The van der Waals or capillary forces follow the acoustical cycle without lag under the conditions of the experiments. The velocity of sound at 9 kc in carbon dioxide shows that a part of the heat capacity has already disappeared from the adiabatic elasticity at this frequency, and comparison with the measurements of other investigators leads to the belief that this term is missing even at considerably lower frequencies at ordinary temperatures. The remaining vibrational energy terms disappear together from the acoustical cycle, their rates of excitation being sensibly equal. There is a considerable activation energy necessary to excite the deformation vibration. The velocity of sound at 9 kc in carbon disulfide agrees well with that obtained by calculation from the results of band spectral analysis and hence no important energy terms appear to be lacking at this frequency. The symmetrical linear (S←C→S) and the deformation (S↓C↑S↓) vibrations leave the acoustical cycle together at high frequencies or at low pressures. A study of the dispersive region caused by this disappearance shows that the rates of excitation of the various energy states are identical within limit of error, and consequently that the activation energy of collision is uniform throughout the dispersive region. The velocity of sound at 9 kc in sulfur dioxide conforms reasonably well to the somewhat conflicting band-spectral data for the equilibrium heat capacity. There is a serious discrepancy between the results of the velocity measurements in the dispersive region here reported and the current interpretation of the few existing absorption measurements. A tentative argument is given whereby this discrepancy may be removed. Several theoretical questions which require further elucidation are discussed.
The Dipole Moments of Certain Monosubstituted Benzenes in the Vapor State
Authors: McAlpine K. B. , Smyth C. P.
Published: November 2004

The dielectric constants of the vapors of three monosubstituted benzenes have been determined over a range of temperature and used to calculate dipole moments as follows: fluorobenzene, 1.57×10-18; chlorobenzene, 1.70×10-18; nitrobenzene, 4.19×10-18. These values are considerably higher than those found from previous measurements in solution and agree well with values calculated for the vapor state by the application of an empirical equation developed by Müller to measurements in solution.
Energy Levels of a Symmetrical Double Minima Problem with Applications to the NH3 and ND3 Molecules
Authors: Manning Millard F.
Published: November 2004

The energy levels for a potential energy V = — C sech2 r/2ρ+D sech4 r/2ρ have been obtained by numerical solution of continued fractions. Values of the constants have been found such that the computed energy levels agree satisfactorily with the experimental values for the NH3 and ND3 molecules. The height of the ammonia pyramid is found to be 0.37A, the height of the potential hill is found to be 2076 cm—1, and the dissociation energy is about five volts.
The Calculation of the Free Energy of Polyatomic Molecules from Spectroscopic Data. II
Authors: Gordon A. R.
Published: November 2004

The methods already developed for computing the free energy from spectroscopic data for diatomic molecules and for triatomic unsymmetrical rotators are extended to handle the case where one or more of the fundamental frequencies is degenerate. New tables, necessary for such calculations, have been computed and the procedure is illustrated by sample calculations for nitrous oxide, hydrogen cyanide and acetylene.
Simple ideas on mixing and fragmentation
Authors: Villermaux Emmanuel
Published: November 2004

The mechanisms building the overall concentration distribution in a scalar mixture, and the drops in a spray, are examined successively. In both cases, the distributions belong to a unique family of distributions stable by self-convolution, the signature of the aggregation process from which they originate.
Paramagnetic defects in annealed ultrathin layers of SiOx, Al2O3, and ZrO2 on (100)Si
Authors: Stesmans A. , Afanas’ev V. V.
Published: November 2004

Electron spin resonance (ESR) measurements on (100)Si∕SiOx∕ZrO2 and (100)Si∕Al2O3∕ZrO2 stacks with nm-thick dielectric layers reveal, upon postdeposition oxidation (PDO) in the range of 650–800°C, the appearance of various SiO2-characteristic defects, including E′ and EX centers and a 95-G doublet. These defects generally grow during PDO treatment, attesting to significant modification of the SiOx interlayer, and∕or additional SiOx interlayer growth. The ESR results on E′ indicate that the SiOx interlayer formed in (100)Si∕SiOx∕ZrO2 is drastically inferior to standard thermal (100)Si∕SiO2, exhibiting over one order of magnitude more O-deficiency centers. The (100)Si∕Al2O3 system appears more robust in terms of SiOx interlayer growth, and has better interlayer properties.
Photoelectron kinetic energy dependence in near threshold ionization of NO from A state studied by time-resolved photoelectron imaging
Authors: Tsubouchi Masaaki , Suzuki Toshinori
Published: November 2004

Photoelectron angular distributions in the laboratory frame (LF-PADs) from the A(2Σ+) state of NO molecule were measured by femtosecond time-resolved photoelectron imaging with (1+1′) resonance enhanced multiphoton ionization via the A state. High-precision measurements of the anisotropy parameters of LF-PADs were performed for the photoelectron kinetic energy from 0.03 to 1.05 eV as a function of the pump-probe delay time. The revival feature of the rotational wave packet on the A state was clearly observed in the time dependence of the photoelectron anisotropy parameters. By approximating the phase shifts of the photoelectron partial waves by the quantum defects in the high-lying Rydberg states using the multichannel quantum defect theory, the energy-dependent photoionization transition dipole moments were determined, for the first time, from time-dependent LF-PADs measured by time-resolved photoelectron spectroscopy.
Constant-volume heat capacity in a near-critical fluid from Monte Carlo simulations
Authors: Daub Christopher D. , Camp Philip J. , Patey G. N.
Published: November 2004

We consider a near-critical fluid of hard spheres with short-range interactions (∼r−6) and obtain its constant-volume heat capacity CV by means of Monte Carlo calculations in the canonical ensemble. The question addressed is whether or not the heat capacities of the finite-size systems studied in simulations can provide a reliable indication of nonclassical criticality. For the model fluid considered here this is found to be the case. The heat capacity along the critical isochore shows a peak near the critical temperature, with a system size dependence that is consistent with the known Ising universality class of the model. The relevance of our results to recent attempts to determine the universality class of ionic fluids through calculations of CV is briefly discussed.
Well-balanced basis sets for second-order Møller–Plesset treatment of argon-aromatic molecule complexes
Authors: Makarewicz Jan
Published: November 2004

Efficient ab initio method for studies of van der Waals complexes of argon and aromatic molecules is presented. It is based on the supermolecular second-order Møller–Plesset (MP2) perturbation theory combined with well-balanced basis sets. The error resulting from incompleteness of such basis sets is almost exactly canceled by the correlation error inherent in the MP2 method. Two basis sets adapted to the MP2 method are selected from various medium-sized basis sets. The standard augmented correlation consistent polarized valence double-ζ basis set and a smaller reduced version derived from it are shown to perform exceptionally well. They are employed in a large scale computation of the potential energy surfaces of argon-benzene and argon-fluorobenzene complexes. The results are critically compared with ab initio high level coupled-cluster calculations and experimental data available. The calculated MP2 equilibrium geometry, dissociation energy, and the vibrational states of the stretching mode are proved to be in excellent agreement with the experiment. However, the bending fundamentals are systematically overestimated by about 1 cm−1. This deficiency is removed by introducing a simple correction function which improves the MP2 potential energy surface. This function can be easily determined and applied to arbitrary argon-aromatic molecule complexes. The MP2 method is compared to the density-functional theory. Local, semilocal, and hybrid models are tested and the results obtained clearly show that none of these models is capable of accurate description of the van der Waals interaction.
Ab initio direct dynamics trajectory simulation of C2H5F→C2H4+HF product energy partitioning
Authors: Sun Lipeng , Hase William L.
Published: November 2004

Direct dynamics classical trajectory simulations were performed to study product energy partitioning in C2H5F→C2H4+HF dissociation. The intrinsic reaction coordinate potential energy curve, reaction energetics, and transition state (TS) properties were calculated for this reaction at different levels of electronic structure theory, and MP2/6-31G* was chosen as a meaningful and practical method for performing the direct dynamics. The trajectories show that the HF bond, uncoupled from the other degrees of freedom, is formed within the first 10 fs as the system moves from the TS towards products. The populations of the HF vibration states, determined from the simulations, decrease monotonically as found from experiments. However, the simulation’s populations for the low and high energy vibration states are larger and smaller, respectively, than the experimental results. The HF rotational temperature found from the simulations is in agreement with experiment. Increasing the TS’s excess energy gives higher rotational temperatures for both C2H4 and HF. Energy is partitioned to the products from both the excess energy in the TS and the potential energy release in the exit channel. Partitioning from these two energy sources is distinguished by varying the TS’s excess energy. An analysis of the simulation’s energy disposal shows that the fractions of the excess energy partitioned to relative translation, C2H4 vibration, C2H4 rotation, HF vibration, and HF rotation, are 0.17, 0.64, 0.076, 0.067, and 0.046, respectively, and are in good agreement with previous simulations on empirical potentials and experiments. The partitioning found for the potential energy release is 81%, <0.05%, 5%, 11%, and 3% to relative translation, C2H4 vibration, C2H4 rotation, HF vibration, and HF rotation. This result is substantially different than the deduction from experiments, which summarizes the partitioning as 20%, 45%, 24%, and <12% to relative translation, C2H4 vibration+rotation, HF vibration, and HF rotation. Possible origins of the difference between the simulations and experiments in the release of the potential energy is discussed.
Collision photography: Polarization imaging of atom-molecule collisions
Authors: Goldstein R. , Figl C. , Grosser J. , Hoffmann O. , Jungen M. , Stalder J. , Rebentrost F.
Published: November 2004

We report differential scattering experiments on the laser excitation of Na+M collision pairs with M=N2, CO, C2H2, and CO2. The collision event is probed by the laser polarization revealing geometric and electronic properties of the collision pair. The experimental data are compared to the results of a Monte Carlo trajectory simulation using ab initio quantum chemical data.
Potential energy surface for H2O(3A″) from accurate ab initio data with inclusion of long-range interactions
Authors: Brandão João , Mogo César , Silva Bruno C.
Published: November 2004

A new potential energy surface for the O(3P)+H2 system in the lowest A″3 state is built using ab initio data calculated by Rogers et al. [J. Phys. Chem. A 104, 2308 (2000)] and the double many-body expansion formalism. It incorporates a semiempirical model of long-range interactions, which should play an important role at low collision energies. Preliminary quasiclassical trajectory results at 12.6 kcal/mol collision energy, show that the deeper van der Waals region described in this new surface translates into a four times higher cross section than that of Rogers’ A″3 surface. To confirm this hypothesis, a second surface was calibrated. The two surfaces are fitted with rmsd<0.5 kcal/mol and differ mainly on the depth of the van der Waals region. That difference in the van der Waals region corresponds to a 22% lower cross section of the less deep surface, which is still three times higher than the equivalent results from Rogers’ A″3 surface. This study reflects the importance of a correct description of van der Waals forces on potential energy surfaces.
Molecular elimination in photolysis of fluorobenzene at 193 nm: Internal energy of HF determined with time-resolved Fourier-transform spectroscopy
Authors: Wu Chia-Yan , Wu Yu-Jong , Lee Yuan-Pern
Published: November 2004

Following photodissociation of fluorobenzene (C6H5F) at 193 nm, rotationally resolved emission spectra of HF(1⩽v⩽4) in the spectral region 2800–4000 cm−1 are detected with a step-scan Fourier-transform spectrometer. In the period 0.1–1.1 μs after photolysis, HF(v⩽4) shows similar Boltzmann-type rotational distributions corresponding to a temperature ∼1830 K; a short extrapolation from data in the period 0.1–4.1 μs leads to a nascent rotational temperature of 1920±140 K with an average rotational energy of 15±3 kJ mol−1. The observed vibrational distribution of (v=1):(v=2):(v=3):(v=4)=(60±7):(24±3):(10.5±1.2):(5.3±0.5) corresponds to a vibrational temperature of 6400±180 K. An average vibrational energy of 33±9/3 kJ mol−1 is derived based on the observed population of HF(1⩽v⩽4) and an estimate of the population of HF(v=0) by extrapolation. The observed internal energy distribution of HF is consistent with that expected for the four-center (α,β) elimination channel. A modified impulse model taking into account geometries and displacement vectors of transition states during bond breaking predicts satisfactorily the rotational excitation of HF. We also compare internal energies of HF observed in this work with those from photolysis of vinyl fluoride (CH2CHF) and 2-chloro-1,1-difluoroethene (CF2CHCl) at 193 nm.
The impact of the actual geometrical structure of a thermoelectric material on its electronic transport properties: The case of doped skutterudite systems
Authors: Bertini Luca , Gatti Carlo
Published: November 2004

By doping CoSb3 with Sn, Ba, and La, several structural outcomes are possible. The effect these different structures have on the electronic transport properties of the resulting materials is evaluated by means of an ab initio electronic structure approach and by using the semiclassical Boltzmann theory to derive the electronic transport properties from the band structure. It is shown that the calculated Seebeck coefficient is a very useful indicator of both the actual content of the dopant element and of where it mainly locates into the CoSb3 structure. The use of such an indicator, along with geometrical considerations, demonstrates that the Sn atom occupies both the interstitial and the pnicogen ring positions with relative occupancies and ensuing thermoelectric properties, which heavily depend on the synthesis’ conditions. The same indicator also suggests that the La atom, which occupies only interstitial positions, has a far lower maximal solubility in CoSb3 than that claimed experimentally.
Polarization quantum beat spectroscopy of HCF(Ã1A″). I. F19 and H1 hyperfine structure and Zeeman effect
Authors: Fan Haiyan , Ionescu Ionela , Xin Ju , Reid Scott A.
Published: November 2004

To further investigate the F19 and H1 nuclear hyperfine structure and Zeeman effect in the simplest singlet carbene, HCF, we recorded polarization quantum beat spectra (QBS) of the pure bending levels 20n with n=0–7 and combination bands 10120n with n=1–6 and 20n301 with n=0–3 in the HCF Ã1A″←X̃1A′ system. The spectra were measured under jet-cooled conditions using a pulsed discharge source, both at zero field and under application of a weak magnetic field (<30 G). Analysis yielded the nuclear spin-rotation constants Caa and weak field Lande gaa factors. Consistent with a two-state model, the majority of observed vibrational levels exhibit a linear correlation of Caa and gaa, and our analysis yielded effective (ã) hyperfine constants for the F19 and H1 nuclei (in MHz) of 728(23) and 55(2), respectively. The latter was determined here owing to the high resolving power of QBS. The vibrational state selectivity of the F19 hyperfine constants is discussed, and we suggest that the underlying Renner-Teller interaction may play an important role.
Phase transition dynamics of liquid phase precipitation from a supersaturated gas mixture
Authors: Pines V. , Zlatkowski M. , Chait A.
Published: November 2004

This work presents a self-consistent description of phase transition dynamics of disperse liquid phase precipitating from a supersaturated gas mixture. The unified approach integrates the macroscale transport phenomena of cloud dynamics with the essential microphysical kinetic processes of droplet condensation, evaporation, and droplet collisions simultaneously taking place in stochastic population of liquid droplets. A complete set of governing equations with well-defined dissipative fluxes and kinetic rates is derived for phase transition dynamics from nucleation to postnucleation to coarsening stages. The local thermodynamics of precipitating system, which is considered as ternary mixture of disperse liquid phase and water vapor with dry air, is redefined to explicitly include on equal basis both the vapor content and liquid content into the fundamental thermodynamic relations and equation of state. The molecular kinetic flux regularization method for growth of submicron droplets is reexamined to include, among others, significant contribution of vapor molecular energy flux into total heat flux, resulting in new expressions for the droplet temperature, growth rate, and effective diffusion coefficients. The local kinetic rates are determined on the basis of microscale kinetic equation for the droplet distribution function. This is in contrast to commonly used semiempirical parametrization schemes for kinetic rates with adjustable parameters, wherein the probabilistic aspects of microphysical processes are not rigorously addressed. Stochastic diffusion interactions among droplets competing for the available water vapor and modifications in the kinetic equation for droplets growing in stochastic population with direct long-range diffusion interactions amongst them are discussed and formulated as well.
Dynamic light scattering by optically anisotropic colloidal particles in polyacrylamide gels
Authors: Dı́az-Leyva Pedro , Pérez Elı́as , Arauz-Lara José Luis
Published: November 2004

The translational and rotational motions of optically anisotropic spherical particles embedded in cross-linked polyacrylamide gels is studied by dynamic light scattering. The particles are liquid crystal droplets solidified in the nematic phase. The amount of cross linkers is varied to cross the sol-gel transition where the system becomes nonergodic for both translational and rotational diffusion modes of the probes. The translational and rotational dynamic correlation functions are obtained by measuring the intensity correlation function between crossed polarizers in the parallel and perpendicular geometries. Data from nonergodic systems is analyzed using an extension, to include rotations, of the method of Pusey and van Megen [Physica A 157, 705 (1989)]. Both diffusion modes are observed to be arrested as the rigidity of the gel increases.
Feature activated molecular dynamics: An efficient approach for atomistic simulation of solid-state aggregation phenomena
Authors: Prasad Manish , Sinno Talid
Published: November 2004

An efficient approach is presented for performing efficient molecular dynamics simulations of solute aggregation in crystalline solids. The method dynamically divides the total simulation space into “active” regions centered about each minority species, in which regular molecular dynamics is performed. The number, size, and shape of these regions is updated periodically based on the distribution of solute atoms within the overall simulation cell. The remainder of the system is essentially static except for periodic rescaling of the entire simulation cell in order to balance the pressure between the isolated molecular dynamics regions. The method is shown to be accurate and robust for the Environment-Dependant Interatomic Potential (EDIP) for silicon and an Embedded Atom Method potential (EAM) for copper. Several tests are performed beginning with the diffusion of a single vacancy all the way to large-scale simulations of vacancy clustering. In both material systems, the predicted evolutions agree closely with the results of standard molecular dynamics simulations. Computationally, the method is demonstrated to scale almost linearly with the concentration of solute atoms, but is essentially independent of the total system size. This scaling behavior allows for the full dynamical simulation of aggregation under conditions that are more experimentally realizable than would be possible with standard molecular dynamics.
Modified quantum trajectory dynamics using a mixed wave function representation
Authors: Garashchuk Sophya , Rassolov Vitaly A.
Published: November 2004

Dynamics of quantum trajectories provides an efficient framework for description of various quantum effects in large systems, but it is unstable near the wave function density nodes where the quantum potential becomes singular. A mixed coordinate space/polar representation of the wave function is used to circumvent this problem. The resulting modified trajectory dynamics associated with the polar representation is nonsingular and smooth. The interference structure and the nodes of the wave function density are described, in principle, exactly in the coordinate representation. The approximate version of this approach is consistent with the semiclassical linearized quantum force method [S. Garashchuk and V. A. Rassolov, J. Chem. Phys. 120, 1181 (2004)]. This approach is exact for general wave functions with the density nodes in a locally quadratic potential.