bluuebunny/crossref_metadata_2025 huggingface dataset:
Crystalline oxides on semiconductors: a future for the nanotransistor
Authors: Buongiorno Nardelli M. , Walker F. J. , McKee R. A.
Published: July 2004

This issue's Editor's Choice [1] is a brief review on promises and advantages of crystalline oxides on semiconductors, especially the role of interfaces, for semiconductor technology.

The cover picture shows at the top a Z‐contrast image of the Si:SrSi2:SrO interface, where on the left side the positions of the atoms are highlighted, and on the right side a theoretical simulation of the image is overlayed, using the theoretical equilibrium geometry of the interface as obtained from first principles (bottom, green: Si, blue: O, orange: Sr). Purple isosurfaces show the electron density of the Si–O bonding state, and the arrows give the direction of the microscopic dipoles at the interface.

The first author Marco Buongiorno Nardelli is Professor at the Department of Physics of North Carolina State University, where he heads a research group focusing on the application of ab‐initio electronic structure calculation techniques for the study of important aspects of the physics of materials (ERMES).

This paper is a presentation from the 5th Motorola Workshop on Computational Materials and Electronics (MWCME 2003), held in Austin, Texas, 13–14 November 2003. The proceedings were guest‐edited, for the fourth time in this journal, by Alex Demkov (now Freescale Semiconductor).

This issue of physica status solidi (b) also contains Original Papers presented at the XI Latin American Congress of Surface Science and Its Applications (XI CLACSA), Pucón, Chile, 7–12 December 2003. The Proceedings of this conference are to be continued in phys. stat. sol. (a) 201, No. 10 (2004) and in an online issue of phys. stat. sol. (c) 1, No. S1 (2004). (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Preface: phys. stat. sol. (b) 241/10
Authors: Demkov Alex , Gilmer David , Liang Yong , Fonseca Leonardo , Liu Chun‐Li
Published: July 2004

The following 15 papers were presented at the 5th Motorola Workshop on Computational Materials and Electronics held 13–14 November 2003 in Austin, Texas, USA . Not every talk given at the workshop is represented with a paper in this selection; however, the reader should be able to come up with a general picture and the scope of the workshop.

Traditionally, the Motorola Workshop on Computational Materials and Electronics has covered materials theory, nano‐device physics and semiconductor processing. The main focus of the 2003 Workshop was Alternative Gate Dielectrics for CMOS Technology. This year we again expanded the scope of the Workshop to include experiment, in addition to the computational materials, quantum transport, and molecular electronics. The participants came from fifteen US and one European university, four National Laboratories, International SEMATECH, and Motorola's Semiconductor and Corporate research organizations. The Workshop illustrates our continuing commitment to longer‐term research, and to the research community. We hope you will enjoy the reading.
Trimethylsilyl transfer during electron ionization mass spectral fragmentation of some ω‐hydroxycarboxylic and ω‐dicarboxylic acid trimethylsilyl derivatives and the effect of chain length
Authors: Rontani J.‐F. , Aubert C.
Published: July 2004

The electron ionization (EI) mass spectral fragmentation of ω‐hydroxycarboxylic and ω‐dicarboxylic acid trimethylsilyl derivatives was investigated. The mass spectra of these compounds exhibited fragment ions resulting from classical fragmentation of the trimethylsilyl ether and ester groups, and others resulting from the interactions between the two functionalities (m/z 147, 204, 217, [M–31]+ and [M–105]+ in the case of ω‐hydroxycarboxylic acid derivatives and m/z 147, 204, 217 and [M–131]+ in the case of ω‐dicarboxylic acid derivatives). Several fragmentation pathways were proposed to explain the formation of these different fragment ions. It is proposed that the ions at m/z 204 and 217 are formed via an initial trimethylsilyl transfer between the ether and the ester group or between the two ester groups. This transfer appeared to be more favoured in the case of ω‐dicarboxylic acid derivatives and to be dependent on the chain length. A more efficient transfer was in fact observed for compounds with a relatively long alkyl chain. In the case of shorter ω‐hydroxycarboxylic and ω‐dicarboxylic acid trimethylsilyl derivatives the formation of the ions at m/z 204 and 217 suffers strongly from competition from production of the ion at m/z 147. Copyright © 2004 John Wiley & Sons, Ltd.
Matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry as a tool for fast identification of protein binders in color layers of paintings
Authors: Hynek Radovan , Kuckova Stepanka , Hradilova Janka , Kodicek Milan
Published: July 2004

Identification of materials in color layers of paintings is necessary for correct decisions concerning restoration procedures as well as proving the authenticity of the painting. The proteins are usually important components of the painting layers. In this paper it has been demonstrated that matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOFMS) can be used for fast and reliable identification of proteins in color layers even in old, highly aged matrices. The digestion can be easily performed directly on silica wafers which are routinely used for infrared analysis. The amount of material necessary for such an analysis is extremely small. Peptide mass mapping using digestion with trypsin followed by MALDI‐TOFMS and identification of the protein was successfully used for determination of the binder from a painting of the 19th century. Copyright © 2004 John Wiley & Sons, Ltd.
MMPI‐2 assessed post‐traumatic stress disorder related to job stress, coping, and personality in police agencies
Authors: Haisch Deanne C. , Meyers Lawrence S.
Published: July 2004

The PK and PS scales of the MMPI‐2 were developed to index the degree of post‐traumatic stress disorder (PTSD). These scales were applied to a sample of 254 mostly male sworn and civilian law enforcement employees from four police agencies. Participants also completed surveys measuring their perceived levels of job stress, their use of a set of coping strategies, and their performance on measures of five global personality domains. The two PTSD scales appeared to have good internal structures and relatively high reliabilities. Employees at greater risk for PTSD reported higher levels of work‐related stress, seemed to use more maladaptive coping strategies, were more neurotic, and tended to be less extraverted, agreeable, and conscientious. Copyright © 2004 John Wiley & Sons, Ltd.
Achieving standards in urban systemic reform: An example of a sixth grade project‐based science curriculum
Authors: Rivet Ann E. , Krajcik Joseph S.
Published: July 2004

A challenge for urban systemic reform initiatives in science education has been to achieve local, state, and national standards for teaching and learning. We have collaborated with teachers in the Detroit Public School System to design project‐based curriculum materials that contextualize the learning of science in meaningful real‐world problems, engage students in science inquiry, and use learning technologies. We present a sixth grade project‐based science unit in which students explored the driving question “How Do Machines Help Me Build Big Things?” and address the science learning goals of balanced and unbalanced forces, simple and complex machines, and mechanical advantage. Twenty‐four teachers and over 2500 students in Detroit participated in enactments of this project over 4 years. Student learning outcomes were determined for the three learning goals and inquiry process skills using pre‐ and postachievement tests. Achievement outcomes as measured by the pre/posttest show significant and consistently high learning gains, even as participation in the project increased to include greater numbers of teachers and students in successive enactments, and leadership of the professional development support for this project transitioned from university researchers to district teacher leaders. These results illustrate that materials which contextualize learning and support student inquiry as part of an urban systemic reform effort can promote learning of important and meaningful science content aligned with standards. © 2004 Wiley Periodicals, Inc. J Res Sci Teach 41: 669–692, 2004
HXT5 expression is under control of STRE and HAP elements in the HXT5 promoter
Authors: Verwaal René , Arako Megumi , Kapur Rick , Verkleij Arie J. , Theo Verrips C. , Boonstra Johannes
Published: July 2004

Hexose transporter (Hxt) proteins transport glucose across the plasma membrane in the yeast Saccharomyces cerevisiae. Recently, we have shown that expression of HXT5 is regulated by the growth rate of the cells. Because gene expression is regulated by binding of specific transcription factors to regulatory elements in the promoters of genes, the presence of putative regulatory elements in the promoter of HXT5 was determined by computer‐assisted analysis. This revealed the presence of two putative stress‐responsive elements (STREs), one putative post‐diauxic shift (PDS) element and two putative Hap2/3/4/5p (HAP) complex binding elements. The involvement of these elements was studied by using mutations in a HXT5 promoter–LacZ fusion construct. Growth during various conditions that result in low growth rates of yeast cells revealed that the STRE most proximal to the translation initiation site seemed to be involved in particular in regulation of HXT5 expression during growth at decreased growth rates. In addition, the HAP elements seemed to be required during growth on non‐fermentable carbon sources. The PDS element and, to a lesser extent, the other STRE showed particular involvement in regulation of HXT5 expression during growth on ethanol. Finally, it was shown that the PKA pathway, which is known to be involved in expression of STRE‐regulated genes, was also involved in regulation of HXT5 expression. A possible mechanism by which expression of HXT5 could be regulated by the transcriptional regulatory elements in the promoter is discussed. Copyright © 2004 John Wiley & Sons, Ltd.
Actin distribution is disrupted upon expression of Yersinia YopO/YpkA in yeast
Authors: Nejedlik L. , Pierfelice T. , Geiser J. R.
Published: July 2004

Pathogenic Yersinia spp. use a Type III secretion system to inject effector proteins directly into host cells. The effector proteins interfere with normal cellular signalling and disrupt cytoskeletal structures that are required for phagocytosis of the invader. Here we show that Saccharomyces cerevisiae responds to one of these effector proteins, YopO/YpkA, essentially as has been observed in mammalian model systems. Expression of YopO in yeast results in inhibition of growth on solid medium. YopO expression confers a cytotoxic effect upon yeast with only 6% of cells remaining viable after 3 h of expression. Moreover, there is no obvious cell cycle arrest associated with cytotoxicity. YopO expression disrupts the normal distribution of actin in yeast. Actin is no longer observed exclusively at sites of cell growth. Concurrent with disruption of actin, we find YopO localizes to the cell periphery, where it may disrupt actin localization. Inactivation of the YopO kinase has no apparent effect upon the deleterious effects of YopO. Collectively, our results show that the yeast model system that has been constructed meets all requirements to serve as an excellent genetic model to exploit examination of YopO and its intracellular targets. Copyright © 2004 John Wiley & Sons, Ltd.
A global radio frequency noise survey as observed by the FORTE satellite at 800 km altitude
Authors: Burr Tom , Jacobson Abram , Mielke Angela
Published: July 2004

We present a global radio frequency noise survey observed from the Fast on‐Orbit Recording of Transient Events (FORTE) satellite at 800 km altitude. This is a survey of squared amplitudes (R2) in 44 frequency subbands spaced by 0.5 MHz centered at 38 MHz (“low band”) and 44 subbands spaced by 0.5 MHz centered at 130 MHz (“high band”). We define 13 geographic regions and analyze signal‐free regions of event data, generated from November 1997 to December 1999, that we assume are representative of the noise of interest (discussion provided). Because this noise distribution is nonstationary, we use cross validation to sample the distribution across time. Summary statistics presented for R2 include the mean, median, percentiles, and fractions exceeding thresholds in each of the 44 subbands for the low‐ and high‐frequency bands in each of the geographic regions. Fractions exceeding thresholds are particularly relevant to multiband signal detection. In the low band the R2 versus frequency plot for each of the 13 regions has peaks in the mean and median at approximately 35 MHz; many regions have peaks at approximately 28 and 45 MHz. The high‐band spectral plots are generally slightly smoother with less dramatic peaks than in the low band. The values of 10 × log10(R2) range from approximately −110 to −70 for both the low band and high band and are generally slightly larger in the low band. The continental United States (CONUS) region low band is notably higher, with values ranging from −105 to −62. Several future satellite projects involving triggered radio frequency broadband signal recordings can benefit from a realistic trigger‐noise survey such as done here.
Estimates of electromagnetic and turbulent energy dissipation rates under the existence of strong wind shears in the polar lower thermosphere from the European Incoherent Scatter (EISCAT) Svalbard radar observations
Authors: Fujiwara Hitoshi , Maeda Sawako , Suzuki Miyo , Nozawa Satonori , Fukunishi Hiroshi
Published: July 2004

Turbulent and electromagnetic energy dissipation rates in the altitude range of ∼98–116 km have been estimated using data obtained from the European Incoherent Scatter Svalbard radar (ESR) observations on 22 September 1998 and 12 March 1999. Solar and geomagnetic activities were moderate and quiet during the observational periods, respectively. The horizontal neutral wind fields derived from the ESR observations show strong vertical shears and temporal variations. The Richardson numbers for the wind fields sometimes show values less than 0.25. The turbulent energy dissipation rates estimated from the wind shears have wavy structures depending on the shear distributions and decrease with height rapidly from ∼110 km. The turbulent energy dissipation rates also have maxima, which sometimes exceed 1 W/kg, in the region ∼102–108 km. The electromagnetic energy dissipation rates are strongly controlled by the neutral wind in the region below ∼110 km, while the Pedersen conductivity affects the energy dissipation above ∼110 km. On average, the two energy dissipation rates change their relative importance at ∼109 km on 22 September 1998 and at ∼112 km on 12 March 1999, depending on the wind shear, the electric field, and the Pedersen conductivity. When the electromagnetic energy fluxes are small, the contribution of the neutral wind to the electromagnetic and turbulent energy dissipation becomes large and the region, where turbulent energy dissipation is dominant, also expands upward. The magnitude and the dissipation height of the energy poured from the upper and lower regions seem to be strongly dependent on the neutral wind particularly below ∼110 km. The variations of the two energy dissipation rates may have significant effects on energetics in the polar lower thermosphere.
Isotope fractionation at the soil‐atmosphere interface and the 18O budget of atmospheric oxygen
Authors: Aggarwal Pradeep K. , Dillon Michael A. , Tanweer Ahmad
Published: July 2004

The stable isotope composition of atmospheric oxygen links the carbon and water cycles of the earth and allows the estimation of changes in terrestrial and marine productivities under different climate regimes. Calculated isotope composition of atmospheric oxygen, however, is nearly three per mil lower than that observed, with the lower value attributed mostly to uncertainties in the isotopic composition of leaf moisture. Here we present an experimental model to show that a previously neglected process accompanying oxygen transport in the terrestrial subsurface may induce a large fractionation at the soil‐atmosphere interface. This additional fractionation is sufficient to reconcile the differences between observed and calculated values of the isotopic composition of atmospheric oxygen and provides self‐consistent 18O budgets for atmospheric O2 and CO2. Our results contribute to a better understanding of processes controlling the isotope composition of atmospheric oxygen under present and past climates.
A 3D discrete numerical elastic lattice method for seismic wave propagation in heterogeneous media with topography
Authors: O'Brien Gareth S. , Bean Christopher J.
Published: July 2004

A three‐dimensional elastic lattice method for the simulation of seismic waves is presented. The model consists of particles arranged on a cubic lattice which interact through a central force term and a bond‐bending force. Particle disturbances are followed through space by numerically solving their equations of motion. A vacuum free‐surface boundary condition is implicit in the method. We demonstrate that a numerical implementation of the method is capable of modelling seismic wave propagation with complex topography. This is achieved by comparing the scheme against a finite‐difference solution to the elastodynamic wave equation. The results indicate that the scheme offers an alternative 3D method for modelling wave propagation in the presence of strong topography and subsurface heterogeneity. We apply the method to seismic wave propagation on Mount Etna to illustrate its applicability in modelling a physical system.
Internal variability of the tropical Pacific ocean
Authors: Jochum M. , Murtugudde R.
Published: July 2004

A 40 year integration of an eddy resolving numerical model of the tropical Pacific ocean is analyzed to quantify the interannual variability caused by internal variability of ocean dynamics. It is found that along the Pacific cold tongue internal variability contributes a significant amount to the observed interannual variability. This suggests that in this location the predictability of SST is limited to the persistence time of SST anomalies which is approximately 100 days. Furthermore, a comparison with other sources of variability suggests that internal variability may play an important role in modifying or setting up El Niño.
Tharsis recharge: A source of groundwater for Martian outflow channels
Authors: Harrison K. P. , Grimm R. E.
Published: July 2004

The large martian outflow channels terminating in Chryse Planitia are remnants of flooding events involving the localized discharge of millions of cubic kilometers of subsurface water, more than can be regionally stored in the crust. We use a dynamic groundwater model to demonstrate that snowpack or glaciers on the Tharsis rise, formed during periods of high obliquity when ice was stable at low latitudes, may have provided an efficient source of recharge and hydraulic head for the circum‐Chryse outflow channels. Water is discharged through the outflow channels several times faster in Tharsis recharge models than in comparable South Pole recharge models.
A statistical study of ionospheric profile parameters derived from Millstone Hill incoherent scatter radar measurements
Authors: Lei Jiuhou , Liu Libo , Wan Weixing , Zhang Shun‐Rong , Holt John M.
Published: July 2004

Diurnal, seasonal, and solar activity variations of the bottomside electron density profile parameters B0 and B1, representing the F2 layer thickness and shape, are studied using a large incoherent scatter radar dataset for Millstone Hill covering the period 1976–2002. These results are compared with the latest IRI model. Our statistical study is characterized by morning and afternoon falls in the diurnal variation of B0 for seasons other than summer and a ∼15% change in B1 over a solar cycle, features not fully well represented by the standard IRI model. The standard IRI B1, however, is very close to observations in terms of the diurnal variation.
A simple model of the flux content of the distant magnetotail
Authors: Milan S. E.
Published: July 2004

A simple model is presented which allows the profile of open flux within the magnetotail lobes to be determined from a knowledge of the present size of the polar cap and the past history of low‐latitude and high‐latitude dayside reconnection. The model shows that the nominal length of the tail is dependent on the elapsed time since reconnection of the oldest open field lines and that a much longer disconnected tail and wake can exist beyond this. The model is applied to two 8‐hour intervals of observations, which indicate that the length of the tail can vary by almost a factor of 10, between ∼400 and 4000 RE, in just a few hours. In addition, differing rates of lobe reconnection in the Northern and Southern Hemispheres are shown to lead to considerable differences in the lengths of the two magnetotail lobes.
Thermodynamic derivations of conditions for chemical equilibrium and of Onsager reciprocal relations for chemical reactors
Authors: Beretta Gian Paolo , Gyftopoulos Elias P.
Published: July 2004

For an isolated chemical reactor, we derive the conditions for chemical equilibrium in terms of either energy, volume, and amounts of constituents or temperature, pressure, and composition, with special emphasis on what is meant by temperature and chemical potentials as the system proceeds through nonequilibrium states towards stable chemical equilibrium. For nonequilibrium states, we give both analytical expressions and pictorial representations of the assumptions and implications underlying chemical dynamics models. In the vicinity of the chemical equilibrium state, we express the affinities of the chemical reactions, the reaction rates, and the rate of entropy generation as functions of the reaction coordinates and derive Onsager reciprocal relations without recourse to statistical fluctuations, time reversal, and the principle of microscopic reversibility.
A laboratory study of two-dimensional and three-dimensional instabilities in a quasi-two-dimensional flow driven by differential rotation of a cylindrical tank and a disc on the free surface
Authors: Kanda Isao
Published: July 2004

By laboratory experiments, we investigate instability behaviors in a differential rotation system derived from the Czochralski silicon crystal growth. The experimental apparatus consists of a rotating disc (radius a, rotation rate ω) on the surface of homogeneous salt water contained in a rotating cylindrical tank (radius R>a, rotation rate Ω<ω). The differential rotation induces the vertical Stewartson layer at the disc radius, and various flow patterns appear as the rotation rate difference ω−Ω is increased. At relatively small ω−Ω, the well-known barotropic, or circular shear, instability generates multiple vertically coherent vortices along the Stewartson layer. The number of vortices decreases with increasing ω−Ω. When there are two vortices, irregular vertical motion is observed near the axis beyond certain critical values of ω−Ω. The streamlines near the axis are elliptical and the flow behavior has properties similar to those of the elliptic instability. As ω−Ω is further increased, the irregular motion ceases and the rotation center of the flow below the disc deviates from the machine axis. The rotation center itself orbits around the machine axis. This flow behavior resembles the single-vortex mode of the circular shear instability. We focus on these two instability behaviors: The vertical irregular motion and the off-axis rotation, and examine the instability onset conditions in the light of the elliptic instability and the circular shear instability, respectively.
One-photon mass-analyzed threshold ionization spectroscopy of 1,3,5-trifluorobenzene: The Jahn-Teller effect and vibrational analysis for the molecular cation in the ground electronic state
Authors: Kwon Chan Ho , Kim Myung Soo
Published: July 2004

One-photon mass-analyzed threshold ionization spectrum of 1,3,5-trifluorobenzene was obtained by using vacuum ultraviolet radiation generated by four-wave difference frequency mixing in Kr. The Jahn-Teller parameters for the e′ modes (ν8−ν14) of 1,3,5-C6H3F3+ in the ground electronic state needed for spectral analysis were taken from the density functional theory results initially and were upgraded through fits to the experimental results. Excellent agreement was achieved between the experimental and calculated Jahn-Teller energy levels. Assignments of the Jahn-Teller inactive modes were accomplished by referring to the calculated frequencies and the selection rule. The ionization energy of 1,3,5-trifluorobenzene determined from the position of the 0-0 band was 9.6359±0.0006 eV.
Does chlorine peroxide absorb below 250 nm?
Authors: Peterson Kirk A. , Francisco Joseph S.
Published: July 2004

Low-lying singlet and triplet electronic excited states of ClOOCl are presented. Calculations of the excitation energies and oscillator strengths are reported using excited state coupled cluster response methods, as well as the complete active space self-consistent field method with the full Breit-Pauli spin-orbit operator. These calculations predict that for ClOOCl there should be a weakly absorbing triplet state lying below the lowest absorbing singlet excited state. This state is predicted to have an absorption maximum at about 385±25 nm. This lowest triplet state is calculated to be dissociative and leads to ClOO+Cl.
Replica-exchange extensions of simulated tempering method
Authors: Mitsutake Ayori , Okamoto Yuko
Published: July 2004

In this paper we consider combinations of two well-known generalized-ensemble algorithms, namely, simulated tempering and replica-exchange method. We discuss two examples of such combinations. One is the replica-exchange simulated tempering and the other is the simulated tempering replica-exchange method. In the former method, a short replica-exchange simulation is first performed and the simulated tempering weight factor is obtained by the multiple-histogram reweighting techniques. This process of simulated tempering weight factor determination is faster and simpler than that in the usual iterative process. A long simulated tempering production run is then performed with this weight factor. The latter method is a further extension of the former in which a simulated tempering replica-exchange simulation is performed with a small number of replicas. These algorithms are particularly useful for studying frustrated systems with rough energy landscape. We give the formulations of these two methods in detail and demonstrate their effectiveness taking the example of the system of a 17-residue helical peptide.
Far-infrared absorption by collisionally interacting nitrogen and methane molecules
Authors: Buser Michael , Frommhold Lothar , Gustafsson Magnus , Moraldi Massimo , Champagne Mark H. , Hunt K. L. C.
Published: July 2004

Quantum line shape calculations of the rototranslational enhancement spectra of nitrogen-methane gaseous mixtures are reported. The calculations are based on a recent theoretical dipole function for interacting N2 and CH4 molecules, which accounts for the long-range induction mechanisms: multipolar inductions and dispersion force-induced dipoles. Multipolar induction alone was often found to approximate the actual dipole surfaces of pairs of interacting linear molecules reasonably well. However, in the case of the N2-CH4 pair, the absorption spectra calculated with such a dipole function still show a substantial intensity defect at the high frequencies (>250 cm−1) when compared to existing measurements at temperatures from 126 to 297 K, much as was previously reported.
Geometry change of simple aromatics upon electronic excitation obtained from Franck-Condon fits of dispersed fluorescence spectra
Authors: Imhof Petra , Krügler Daniel , Brause Robert , Kleinermanns Karl
Published: July 2004

The S1 state geometries of benzonitrile, p-cyanophenol, o-cyanophenol, chlorobenzene, and p-chlorophenol were determined by Franck-Condon simulations and a fit of the geometry to the vibronic intensities and effective rotational constants in the harmonic limit based on ab initio force constants.
Raman H-bond pair volume for water
Authors: Walrafen George E.
Published: July 2004

The dispersion of the H-bond pair volume ΔV over the decoupled OD and coupled OH-stretching contours from HDO in H2O was determined from Raman intensities at pressures to 9700 bar at 301 K. The dispersion of ΔV was determined from −RT[∂ ln(Ii/IREF)/∂P]T versus ω (in cm−1), where i refers to ω’s over the stretching contours and IREF refers to the reference intensity at the isosbestic frequency. The maximum H-bond pair volume (defined for breakage) is 1.4±0.1 cm3/mol H-bond, which corresponds to the volume difference between a large dispersion maximum at 2675 cm−1 (near the OD stretch ω of HDO in dense supercritical water) and a large, broad minimum centered near 2375 cm−1 (just below the OD stretch ω of HDO in lda ice). The average 〈ΔV〉 is 0.71±0.10 cm3/mol H-bond. Other minima near 2625 cm−1 (OD) and 3550 cm−1 (OH) refers to bent H-bonds whose angles are ≈150 deg. Isothermal pressurization of water lowers the molal volume by decreasing the concentration of long, weak H-bonds, and increasing the concentrations of bent H-bonds and short, strong, linear H-bonds. Such bending, shortening, and strengthening produces freezing to ice VI near 10 kbar at 301 K. The isobaric temperature derivative of the maximum H-bond volume is (∂ΔV/∂T)P⩽(2–5)×10−3 cm3/deg mol H-bond. The OH enthalpy dispersion curve for saturated NaBF4 in water, yields a large maximum at 3530–3540 cm−1 indicating that BF4− interacts preferentially with the dangling or “free” OH groups of water thus producing weak, strongly bent H-bonds having angles similar to those of the 3550 cm−1 high-pressure H-bond bending feature.
On the ground state of titanium phosphide, TiP: A theoretical investigation
Authors: Tzeli Demeter , Mavridis Aristides
Published: July 2004

Using multireference variational and coupled cluster methods in conjunction with very large core-correlation-consistent basis sets, we have confirmed that the ground state of TiP is of 2Σ+ symmetry with the first excited state A 2Δ no more than 3.5 kcal/mol higher. We also report full potential energy curves, dissociation energies, bond lengths, dipole moments, and the usual spectroscopic constants.
The effective fragment potential: Small clusters and radial distribution functions
Authors: Netzloff Heather M. , Gordon Mark S.
Published: July 2004

The effective fragment potential (EFP) method for treating solvent effects provides relative energies and structures that are in excellent agreement with the analogous fully quantum [i.e., Hartree-Fock (HF), density functional theory (DFT), and second order perturbation theory (MP2)] results for small water clusters. The ability of the method to predict bulk water properties with a comparable accuracy is assessed by performing EFP molecular dynamics simulations. The resulting radial distribution functions (RDF) suggest that as the underlying quantum method is improved from HF to DFT to MP2, the agreement with the experimental RDF also improves. The MP2-based EFP method yields a RDF that is in excellent agreement with experiment.
Quantum hydrodynamics: Application to N-dimensional reactive scattering
Authors: Kendrick Brian K.
Published: July 2004

The quantum hydrodynamic equations associated with the de Broglie-Bohm formulation of quantum mechanics are solved using a new methodology which gives an accurate, unitary, and stable propagation of a time dependent quantum wave packet [B. K. Kendrick, J. Chem. Phys. 119, 5805 (2003)]. The methodology is applied to an N-dimensional model chemical reaction with an activation barrier. A parallel version of the methodology is presented which is designed to run on massively parallel supercomputers. The computational scaling properties of the parallel code are investigated both as a function of the number of processors and the dimension N. A decoupling scheme is introduced which decouples the multidimensional quantum hydrodynamic equations into a set of uncoupled one-dimensional problems. The decoupling scheme dramatically reduces the computation time and is highly parallelizable. Furthermore, the computation time is shown to scale linearly with respect to the dimension N=2,…,100.
Characterization of polyethylene crystallization from an oriented melt by molecular dynamics simulation
Authors: Ko Min Jae , Waheed Numan , Lavine Marc S. , Rutledge Gregory C.
Published: July 2004

Molecular dynamics is used to characterize the process of crystallization for a united atom model of polyethylene. An oriented melt is produced by uniaxial deformation under constant load, followed by quenching below the melting temperature at zero load. The development of crystallinity is monitored simultaneously using molecular-based order parameters for density, energy, and orientation. For crystallization temperatures ranging from 325 to 375 K, these simulations clearly show the hallmarks of crystal nucleation and growth. We can identify multiple nucleation events, lamellar growth up to the limit imposed by periodic boundaries of the simulation cell, and lamellar thickening. We observe a competition between the rate of nucleation, which results in multiple crystallites, the rate of chain extension, which results in thicker lamellae, and the rate of chain conformational relaxation, which is manifested in lower degrees of residual order in the noncrystalline portion of the simulation. The temperature dependence of lamellar thickness is in accord with experimental data. At the higher temperatures, tilted chain lamellae are observed to form with lamellar interfaces corresponding approximately to the [201] facet, indicative of the influence of interfacial energy.
Memory effect in friction on a particle caused by a system of fixed or moving scatterers with power law potential
Authors: Felderhof B. U. , Vehns Thin
Published: July 2004

The memory function for friction on a particle caused by a system of fixed or moving scatterers is evaluated for power law interaction. For a dilute system the study extends the steady-state calculation based on the Boltzmann equation to the case of frequency dependence due to the dynamics of the scattering process. For a dense gas an Enskog approximation can be used. The power law potential leads to scaling behavior of the dynamical friction coefficient as a function of reduced mass, coupling coefficient, and energy.
Microphase separation of weakly charged block polyelectrolyte solutions: Donnan theory for dynamic polymer morphologies
Authors: Kyrylyuk A. V. , Fraaije J. G. E. M.
Published: July 2004

A mean-field dynamic density functional theory for the phase behavior of concentrated weakly charged block polyelectrolyte solutions is developed, using the Donnan membrane equilibrium approach to account for electrostatic interactions. In this limit all long-range electrostatic interactions are canceled and the net charge density in any region on a coarse-grained scale is zero. The phase diagram of a model triblock polyelectrolyte in solution as a function of the charge of the solvophilic block and the solvent concentration is established. Different mesoscopic structures (lamellar, bicontinuous, hexagonal, micellar, and dispersed coexisting phases) are formed depending on the copolymer charge asymmetry. It is found that upon changing the charge of the solvophilic copolymer block the polyelectrolyte solution does not follow the lyotropic sequence of phases of this polymer. Upon increase in the charge of the solvophilic blocks, changes in copolymer morphology take place by means of change in curvature of polymeric domains.
Non-Markovian theory of open systems in classical limit
Authors: Neufeld A. A.
Published: July 2004

A fully classical limit of the recently published quantum-classical approximation [A. A. Neufeld, J. Chem. Phys. 119, 2488 (2003)] is obtained and analyzed. The resulting kinetic equations are capable of describing the evolution of an open system on the entire time axis, including the short-time non-Markovian stage, and are valid beyond linear response regime. We have shown, that proceeding to the classical mechanics limit we restrict the class of allowed correlations between an open system and a canonical bath, so that the initial conditions and the relaxation operator has to be appropriately modified (projected). Disregard of the projection may lead to unphysical behavior, since mechanism of the decay of some correlations is essentially of quantum-mechanical nature, and is not correctly described by classical mechanics. The projection (quantum correction to the kinetics) is particularly important for the non-Markovian regime of relaxation towards canonical equilibrium. The conformity of the developed method to the conventional approaches is demonstrated using a model of Brownian motion (heavy particle in the bath of light ones), for which the obtained non-Markovian equations are reduced to the standard Fokker-Planck equation in phase space.
Laplace-transformed diagonal Dyson correction to quasiparticle energies in periodic systems
Authors: Pino Ramiro , Scuseria Gustavo E.
Published: July 2004

We present a method to self-consistently evaluate quasiparticle energies of periodic systems within the diagonal approximation for solving Dyson’s equation. Our method is based on the Laplace transform of the second-order Møller-Plesset perturbation (MP2) theory kernel in the atomic basis formulation. The overhead computational cost of evaluating the fully self-consistent diagonal correction over the MP2 band energy calculation is negligible. We present numerical benchmark results for the band structure of trans-polyacetylene and compare it with MP2 and other approaches.
Second order Møller-Plesset perturbation theory based upon the fragment molecular orbital method
Authors: Fedorov Dmitri G. , Kitaura Kazuo
Published: July 2004

The fragment molecular orbital (FMO) method was combined with the second order Møller–Plesset (MP2) perturbation theory. The accuracy of the method using the 6-31G* basis set was tested on (H2O)n, n=16,32,64; α-helices and β-strands of alanine n-mers, n=10,20,40; as well as on (H2O)n, n=16,32,64 using the 6-31++G** basis set. Relative to the regular MP2 results that could be afforded, the FMO2-MP2 error in the correlation energy did not exceed 0.003 a.u., the error in the correlation energy gradient did not exceed 0.000 05 a.u./bohr and the error in the correlation contribution to dipole moment did not exceed 0.03 debye. An approximation reducing computational load based on fragment separation was introduced and tested. The FMO2-MP2 method demonstrated nearly linear scaling and drastically reduced the memory requirements of the regular MP2, making possible calculations with several thousands basis functions using small Pentium clusters. As an example, (H2O)64 with the 6-31++G** basis set (1920 basis functions) can be run in 1 Gbyte RAM and it took 136 s on a 40-node Pentium4 cluster.
Ab initio potential energy surface and rovibrational spectrum of Ar−HCCCN
Authors: Zhou Yanzi , Xie Daiqian
Published: July 2004

We report an ab initio intermolecular potential energy surface of the Ar−HCCCN complex using a supermolecular method. The calculations were performed using the fourth-order Møller–Plesset theory with the full counterpoise correction for the basis set superposition error and a large basis set including bond functions. The complex was found to have a planar T-shaped structure minimum and a linear minimum with the Ar atom facing the H atom. The T-shaped minimum is the global minimum with the well depth of 236.81 cm−1. A potential barrier separating the two minima is located at R=5.57 Å and θ=20.39° with the height of 151.59 cm−1. The two-dimensional discrete variable representation was employed to calculate the rovibrational energy levels for Ar−HCCCN. The rovibrational spectra including intensities for the ground state and the first excited intermolecular vibrational state are also presented. The results show that the spectra are mostly b-type (ΔKa=±1) transitions with weak a-type (ΔKa=0) transitions in structure, which are in good agreement with the recent experimental results [A. Huckauf, W. Jager, P. Botschwina, and R. Oswald, J. Chem. Phys. 119, 7749 (2003)].
Quasiclassical trajectory study of the collision-induced dissociation of CH3SH++Ar
Authors: Martı́nez-Núñez Emilio , Vázquez Saulo A. , Marques Jorge M. C.
Published: July 2004

Quasiclassical trajectory calculations were carried out to study the dynamics of energy transfer and collision-induced dissociation (CID) of CH3SH++Ar at collision energies ranging from 4.34 to 34.7 eV. The relative abundances calculated for the most relevant product ions are found to be in good agreement with experiment, except for the lowest energies investigated. In general, the dissociation to form CH3++SH is the dominant channel, even though it is not among the energetically favored reaction pathways. The results corroborate that this selective dissociation observed upon collisional activation arises from a more efficient translational to vibrational energy transfer for the low-frequency C–S stretching mode than for the high-frequency C–H stretching modes, together with weak couplings between the low- and high-frequency modes of vibration. The calculations suggest that CID takes place preferentially by a direct CH3++SH detachment, and more efficiently when the Ar atom collides with the methyl group-side of CH3SH+.
Optimal control theory for a target state distributed in time: Optimizing the probe-pulse signal of a pump-probe-scheme
Authors: Kaiser Andreas , May Volkhard
Published: July 2004

Optimal control theory (OCT) is formulated for the case of a two-color pump-probe experiment. The approach allows to calculate the pump-pulse shape in such a way that the probe-pulse absorption signal is maximized. Since the latter quantity is given by the time-averaged expectation value of a time dependent operator (the probe-pulse field-strength times the dipole operator) a version of OCT has to be used where the target state is distributed in time. The method is applied to a molecular three-level system with the pump-pulse driving the transition from the electronic ground state into the first-excited electronic state and the probe-pulse connecting the first-excited state with a higher lying electronic state. Depending on the probe-pulse duration, the vibrational wave packet becomes localized or at least highly concentrated in the Franck-Condon window for the transition into the higher-excited state. The dependence on the probe-pulse duration and on the delay time between the optimized pump-pulse and the probe-pulse is discussed in detail. The whole study demonstrates the feasibility of laser pulse induced temporal wave packet localization and the use of spectroscopic quantities as target states in experiments on femtosecond laser pulse control.
Experimental demonstration of split side-gated resonant interband tunneling devices
Authors: Moon J. S. , Chow D. H. , Schulman J. N. , Deelman P. , Zinck J. J. , Ting D. Z.- Y.
Published: July 2004

We report a prototype side-gated asymmetric resonant interband tunneling device (RITD) fabricated with an AlSb∕InAs∕GaSb∕AlSb heterostructure for Rashba spin filter applications. This device features independent control gates along the sides of an RITD mesa structure that can be used to provide an electric field orthogonal to the resonant tunneling current. The distribution of lateral wave vectors for electrons approaching the RITD active layers obtains a nonzero average through the application of the orthogonal electric field, a requirement for Rashba spin filter operation. Measured current–voltage curves show a modulation of the tunneling current with a side gate bias, demonstrating lateral electric-field projection into the resonant tunneling mesa structure. The prototype device was fabricated to submicron dimensions utilizing a conformal and scalable processing scheme.
Vertical diffusion of water molecules near the surface of ice
Authors: Jung Kwang-Hwan , Park Seong-Chan , Kim Jung-Hwan , Kang Heon
Published: July 2004

We studied diffusion of water molecules in the direction perpendicular to the surface of an ice film. Amorphous ice films of H2O were deposited on Ru(0001) at temperature of 100–140 K for thickness of 1–5 bilayer (BL) in vacuum, and a fractional coverage of D2O was added onto the surface. Vertical migration of surface D2O molecules to the underlying H2O multilayer and the reverse migration of H2O resulted in change of their surface concentrations. Temporal variation of the H2O and D2O surface concentrations was monitored by the technique of Cs+ reactive ion scattering to reveal kinetics of the vertical diffusion in depth resolution of 1 BL. The first-order rate coefficient for the migration of surface water molecules ranged from k1=5.7(±0.6)×10−4 s−1 at T=100 K to k1=6.7(±2.0)×10−2 s−1 at 140 K, with an activation energy of 13.7±1.7 kJ mol−1. The equivalent surface diffusion coefficients were Ds=7×10−19 cm2 s−1 at 100 K and Ds=8×10−17 cm2 s−1 at 140 K. The measured activation energy was close to interstitial migration energy (15 kJ mol−1) and was much lower than diffusion activation energy in bulk ice (52–70 kJ mol−1). The result suggested that water molecules diffused via the interstitial mechanism near the surface where defect concentrations were very high.
H/D isotopic exchange between water molecules at ice surfaces
Authors: Park Seong-Chan , Jung Kwang-Hwan , Kang Heon
Published: July 2004

H/D isotopic exchange between H2O and D2O molecules was studied at the surface of ice films at 90–140 K by the technique of Cs+ reactive ion scattering. Ice films were deposited on a Ru(0001) substrate in different compositions of H2O and D2O and in various structures to study the kinetics of isotopic exchange. H/D exchange was very slow on an ice film at 95–100 K, even when H2O and D2O were uniformly mixed in the film. At 140 K, H/D exchange occurred in a time scale of several minutes on the uniform mixture film. Kinetic measurement gave the rate coefficient for the exchange reaction, k(140 K)=1.6(±0.3)×10−19 cm2 molecule−1 s−1 and k(100 K)⩽5.7(±0.5)×10−21 cm2 molecule−1 s−1 and the Arrhenius activation energy, Ea⩾9.8 kJ mol−1. Addition of HCl on the film to provide excess protons greatly accelerated the isotopic exchange reaction such that it went to completion very quickly at the surface. The rapid reaction, however, was confined within the first bilayer (BL) of the surface and did not readily propagate to the underlying sublayer. The isotopic exchange in the vertical direction was almost completely blocked at 95 K, and it slowly occurred only to a depth of 3 BLs from the surface at 140 K. Thus, the proton transfer was highly directional. The lateral proton transfer at the surface was attributed to the increased mobility of protonic defects at the molecularly disordered and activated surface. The slow, vertical proton transfer was probably assisted by self-diffusion of water molecules.