bluuebunny/crossref_metadata_2025 huggingface dataset:
Absorption by static traps: Initial-value and steady-state problems
Authors: Fixman Marshall
Published: February 2003

The absorption of diffusing impurity particles by static, spherical sinks in a three-dimensional continuum has been studied with simulations and effective medium theories. The simplest effective medium theories, such as the coherent potential approximation, show significant quantitative errors at high sink volume fraction vf. However, an approximate account of pair interactions between sinks brings the theory into excellent agreement with steady-state simulations, performed for vf≤0.4, and with initial-value simulations, performed for vf≤0.3. The initial-value problem was followed to a fraction C(t)/C(0)≂10−5 remaining of the initial impurity concentration. Estimates of the value of C(tx)/C(0) at the time tx when the effective medium rate of absorption crosses below the lower bound provided by asumptotic theory range downward from 10−67 for the continuum model. Values of C(tx)/C(0) at the crossover point for lattice models can probably be much larger, if the fraction of sites occupied by traps is much larger than 0.1. The difference results from the greater ease of void formation in a lattice distribution of traps, in comparison to a continuum distribution of hard spheres, at high trap densities.
Molecular dynamics with coupling to an external bath
Authors: Berendsen H. J. C. , Postma J. P. M. , van Gunsteren W. F. , DiNola A. , Haak J. R.
Published: February 2003

In molecular dynamics (MD) simulations the need often arises to maintain such parameters as temperature or pressure rather than energy and volume, or to impose gradients for studying transport properties in nonequilibrium MD. A method is described to realize coupling to an external bath with constant temperature or pressure with adjustable time constants for the coupling. The method is easily extendable to other variables and to gradients, and can be applied also to polyatomic molecules involving internal constraints. The influence of coupling time constants on dynamical variables is evaluated. A leap-frog algorithm is presented for the general case involving constraints with coupling to both a constant temperature and a constant pressure bath.
An exactly solvable two-component solution having a ‘‘closed-loop’’ phase diagram
Authors: Huckaby Dale A. , Bellemans André
Published: February 2003

A two-component lattice model is considered in which each portion of a type A (type B) molecule which faces a neighboring site can be in any one of qA (qB) different states, only one of which can form a bond with a neighboring unlike molecule. A neighboring pair of like molecules does not interact, but a neighboring pair of unlike molecules forms a hydrogen bond if both see each other as being in bonding states, and repel if either sees the other as being in a nonbonding state. Here it is explicitly assumed that the bonding state of a molecule seen by one neighbor is independent of its bonding state seen by other neighbors. The model can be written as a ferromagnetic Ising model with a temperature dependent coupling constant, and it exhibits both an upper and a lower critical solution temperature.
A simple model for associated fluids
Authors: Smith William R. , Nezbeda Ivo
Published: February 2003

A simple site–site interaction type of model fluid is proposed to describe, on a primitive level, fluids which exhibit association (H bonding). Computer simulations have been performed on the model to obtain the site–site correlation functions, equation of state, average internal energy, specific heat, g1 and g2 factors, and concentration of polymeric species. The results show that the model is able to capture the basic qualitative properties of real associated liquids.
The ideally polarizable interface: A solvable model and general sum rules
Authors: Rosinberg M. L. , Blum L.
Published: February 2003

A model for an ideally polarizable interface is proposed where the two sides of the interface are described by two interacting classical one component plasmas of different neutralizing background densities separated by an impermeable membrane. The statistical mechanics of this system is solved exactly in two dimensions at the reduced temperature 2. The one and two body distribution functions, the potential drop, the differential capacity, and the interfacial tension are computed. The main feature of this model is that the potential drop and not the surface charge appears as the natural external variable. Several sum rules are discussed, such as the screening theorems for multipoles, the contact theorem, and the Lippmann equation. A general thermodynamic argument shows that these sum rules remain valid in three dimensions and for any value of the coupling parameter.
Orientational rainbows in atom–molecule collisions
Authors: Vervaat M. G. M. , Spalburg M. R. , Los J. , Kleyn A. W.
Published: February 2003

The experimental and calculated differential cross sections for ion pair formation in K (27 to 50 eV LAB) O2 collisions show an orientational rainbow at small scattering angle. This rainbow is found to be due to the anisotropy of the K–O2 interaction potential. Using the position of the orientational rainbow, the anisotropy in the repulsive part of the interaction potential is determined as G=[1+1.3(±)*P2(cos α)], where P2 is a Legendre polynomial and α the angle between the molecular axis and the radius vector of the atom. The interaction potential has the form V(R)=102.9 exp(−0.571R)+[Δ−1/R], where Δ is the ionization potential of K minus the vertical electron affinity of O2, the latter depending on the vibrational phase only; the term placed between the square brackets does not act during the complete collision, but only onward from that point during the collision where the ion-pair formation occurs.
Solute–solute radial distribution function, solvent effects, and caging
Authors: Ramírez S. , Bose S.
Published: February 2003

A numerical calculation of the solute–solute radial distribution function which takes into account the solute–solvent and solvent–solvent interactions is presented. The calculated potential of mean force shows maxima and minima, indicating caging effects.
Potential energy surface and rate constants for an intramolecular hydrogen–deuterium exchange on a benzene ring
Authors: Debuda P. G. , Kostin M. D.
Published: February 2003

A potential energy surface for an intramolecular hydrogen–deuterium exchange is calculated with a mindo/3 program. The results are presented in tabular form and in terms of special functions which satisfy symmetry and which improve the fit in the important regions around the saddle point and minimum potential path. It is shown that the reaction is of a cooperative type in that the hydrogen and deuterium atoms move in a particular coordinated way in the region of the activated complex when the reaction occurs. The locations of the saddle points are calculated for the activated complexes of the four reaction paths of this exchange reaction. The potential energy surface is used to calculate the rate constants as a function of temperature for intramolecular hydrogen–deuterium exchange on an aromatic ring.
SCF study of the lowest 2Σ+u resonance of H−2
Authors: Sabelli Nora H. , Gislason Eric A.
Published: February 2003

A novel technique for computing properties of negative ion resonances is reported. The system is initially embedded in a spherical cage of charge +1. This lowers the energy of the resonance below the energies of the neutral molecule–free electron states, so the ground state SCF wave function corresponds to the pure resonance. The energy of the resonance is then determined by removing the cage, freezing the wave function, and computing the expectation value of the correct Hamiltonian. The negative ion basis set can be optimized at each value of R if desired. Results of SCF and projected (localized) SCF computations are reported for the 2Σ+u state of H−2. Satisfactory agreement with the complex SCF calculations of McCurdy and Mowrey is obtained. The projected SCF wave functions form a useful basis for a configuration–interaction computation.
Angular distributions of photoelectrons from resonant two-photon ionization: A graphical approach
Authors: Chien Ring-Ling
Published: February 2003

The Liouville representation is a formalism that describes quantum mechanical problems by using the space of density operators as kets and the space of observable operators as bras. It is useful for problems with complicated angular momentum coupling because it gives directly the probabilities and expectation values rather than probability amplitudes, so that some of the extended and tedious steps of the angular momentum algebra are eliminated. The graphical representation of angular momentum coupling has proved itself as another way to simplify and clarify calculations; graphical representation helps one to visualize the physics and simplifies and organizes the computations. By combining the graphical method and Liouville representation, we introduce a simple, transparent method to deal with problems of many coupled angular momenta. We use this formalism to derive the analytic expression for the angular distributions of photoelectrons. The angular distributions are represented by diagrams of density matrix and detector operators and a diagram of the transition matrix. The analytic expressions are then obtained from the diagrams by following simple general rules for the graphical reduction. A specific example, angular distributions of photoelectrons from resonant two-photon ionization of alkali atoms with hyperfine interaction, is also given.
Sedimentation of a porous sphere through fixed obstacles: Hydrodynamic interaction
Authors: Lumpkin O.
Published: February 2003

An approximate calculation of the hydrodynamic drag force on a porous spherical particle sedimenting through a random suspension of fixed obstacles is described. The method, which ignores particle-obstacle collisions, predicts that the leading correction to the retardation is proportional to the square root of the obstacle concentration. Furthermore, sedimentation velocities through a suspension of long rod obstacles, a possible model for a rigid polymer solution or a gel, and also through a suspension of spherical obstacles, are derived. Comparison of these results with sedimentation experiments in concentrated polymer solutions indicate that often neglected hydrodynamic effects may be large enough to complicate data interpretations.
Nuclear magnetic relaxation rate dispersion in supercooled heavy water under high pressure
Authors: Lang E. W. , Lüdemann H.-D. , Piculell L.
Published: February 2003

Spin-lattice (T1) and spin–spin (T2) relaxation times of the deuterons in supercooled D2O at 225 MPa, measured at two frequencies: 55.54 and 39.14 MHz down to 188 K are reported. The results show that T1 and T2 become frequency dependent in supercooled liquid water under high hydrostatic pressure at temperatures below ∼220 K. Theoretical expressions for the relaxation rates are deduced under the assumption that the orientational fluctuations of the water molecules are composed of fast librational oscillations and slower diffusional motions. The effect of the librations is to reduce the size of the deuterium quadrupole coupling constant. The diffusional motions are nearly isotropic and dominate the T dependence of the relaxation times. The autocorrelation function of the slow orientational fluctuations was assumed to be exponential at long times with a single time constant, the orientational correlation time τ2. The T dependence of the latter is well described by the VTF equation. The parameters obtained by least squares fitting the experimental spin-lattice relaxation times to an isotropic motional model correctly predict the temperature and frequency dependence of the spin–spin relaxation times.
Angle-resolved photoelectron cross section of CF4
Authors: Carlson Thomas A. , Fahlman Anders , Svensson W. Agneta , Krause M. O. , Whitley Timothy A. , Grimm Frederick A. , Piancastelli M. N. , Taylor James W.
Published: February 2003

Partial photoelectron cross sections σ and angular distribution parameters β were obtained for the first five valence orbitals in CF4: 1t1, 4t2, 1e, 3t2, and 4a1, as a function of photon energy from 17 to 70 eV. These data were taken with the aid of angle-resolved photoelectron spectroscopy and synchrotron radiation. The results were compared with earlier data on CCl4. Substantial differences were found. These are explained partly in terms of the absence of a Cooper minimum with a fluorine compound as opposed to the presence of a Cooper minimum with chlorine compounds and partly in terms of the position of shape resonances. Data on CF4 were also compared with recent calculations of Stephens et al., who used the multiple-scattering Xα method. Structure in the photoelectron spectrum of CF4 lying on the low energy side of the third band was identified as due to autoionization and evidence is given as to its specific nature.
Water–hydrocarbon interactions: Rotational spectroscopy and structure of the water–acetylene complex
Authors: Peterson K. I. , Klemperer W.
Published: February 2003

The radiofrequency and microwave spectra of C2H2–H2O, C2H2–D2O, C2D2–H2O, and C2D2–D2O have been measured by molecular beam electric resonance spectroscopy. Rotational constants and dipole moments are reported. The structure is effectively planar with the acetylene hydrogen bonded to the oxygen of the water. The hydrogen-bond length and stretching force constant are calculated to be. 2.229 Å and 0.065 mdyn/Å, respectively. Considering the lone pair orbital structure of the water molecule, an equilibrium structure having the water plane tilted away from the a axis of the complex is expected. Even so, a comparison of the dipole moments for the different isotopically substituted species shows that the height of the barrier hindering an inversion motion is low enough that no vibrational levels lie below the top of the barrier in the double-minimum potential well.
Photoionization spectra and electronic structure of small iron clusters
Authors: Rohlfing Eric A. , Cox D. M. , Kaldor A. , Johnson K. H.
Published: February 2003

Laser photoionization spectra over the range 4.5–6.5 eV have been taken for iron clusters of from 2 to 25 atoms. From the observed ionization thresholds, the cluster ionization potentials are determined and trends in I.P. vs cluster size are examined. In the case of the iron dimer, a sharp, vertical threshold is seen which places the I.P. of Fe2 at 6.30±0.01 eV. Finally, SCF Xα scattered wave molecular orbital calculations have been carried out on the iron dimer and iron trimer. These results show the importance of ferromagnetic spin polarization in the electronic structure of Fe2 and Fe3.
The interdependence of small linewidth and frequency changes of a vibration in liquid mixtures of CDCl3 and CCl4
Authors: Asthana B. P. , Kiefer W. , Knapp E. W.
Published: February 2003

The isotropic Raman linewidths and frequency shifts of the ν1 (C–D) vibration of CDCl3 in CCl4 have been measured precisely as a function of the concentration of CDCl3 using the recently developed technique of four-channel Raman difference spectroscopy. The results obtained reveal that even the small variation of the linewidths and frequency shifts with concentration have a strong interdependence. A rigorous analysis of the results with the analytical model [E. W. Knapp and S. F. Fischer, J. Chem. Phys. 76, 4730 (1982)] which takes into account simultaneously, the static and dynamic aspects of the concentration fluctuations at the reference molecule, yields that a reasonable agreement with the experimental data is obtained only if the dynamics is included (R>0).
Electron diffraction studies of hot molecules. IV. Asymmetries of nonbonded distribution functions of SF6, SiF4, and CF4
Authors: Bartell Lawrence S. , Stanton John F.
Published: February 2003

Highly significant improvements in the agreement between observed and calculated intensities of electrons diffracted by hot molecules were obtained by optimizing the skew parameter â for the nonbonded distributions. Derived â values (±2σ) were 2.75(11), 0.72(13), and 2.0(4) Å−1 for SF6, SiF4, and CF4, respectively. These measured skew parameters are approximately 2 Å−1 higher in each case than values previously proposed on the basis of Morse asymmetry factors and the nonlinear transformation between curvilinear and normal coordinates of molecules. The principal factor responsible for the increase is the previously unknown intrinsic anharmonicity in bending deformations. Silicon tetrafluoride has a lower â value than the other molecules studied primarily because its bending force constant is lower, relative to stretching. Practical as well as theoretical implications of present findings are discussed.
Diode laser spectroscopy of the ν3 band of carbon tetrachloride (C35Cl4): Stark modulation and cold jet infrared absorption spectrum
Authors: Yamamoto Satoshi , Takami Michio , Kuchitsu Kozo
Published: February 2003

The infrared vibration-rotation spectrum of the ν3 band of C35Cl4 was measured by using a tunable diode laser. Heavily congested Q-branch spectrum was analyzed on the basis of the Stark effect, which extract transitions of tetrahedral species among various isotopic species. Low-J lines were measured in a supercooled molecular jet, which supressed hot bands and high-J rotational lines. The following constants of the ν3 band were determined: ν0=798.7489(4) cm−1, B3−B0=−0.39(5) MHz, α220=−3.33(6) MHz, and α224=−0.185(9) MHz. The Fermi resonance between the ν3 and ν1+ν4 states was analyzed with the aid of an empirical anharmonic force field.
Reaction surface Hamiltonian for the dynamics of reactions in polyatomic systems
Authors: Carrington Tucker , Miller William H.
Published: February 2003

The reaction path description of chemical reactions has difficulty if there are regions where the reaction path is sharply curved, as is typically the case, e.g., in light atom (e.g., H,D) transfer reactions. It is shown here how this can be overcome by introducing two reaction coordinate-like degrees of freedom, i.e., two coordinates, r1 and r2, that are allowed to undergo arbitrarily large amplitude motion (LAM). Rather than a reaction path and a reaction coordinate measuring distance along it, the picture is now that of a reaction surface with two reaction-like coordinates (r1,r2) which specify position on the surface. The reaction surface is defined by minimizing the potential energy of the polyatomic system for fixed values of r1 and r2, and an algorithm for using ab initio quantum chemistry methods to do this is described. The remaining (3N−8) internal degrees of freedom are characterized as local harmonic motion orthogonal to the reaction surface; these local normal modes are defined by diagonalizing an appropriately projected force constant matrix. The classical (and quantum) reaction surface Hamiltonian is then derived, i.e., the Hamiltonian for which the dynamical variables are the two reaction-like coordinates (r1,r2) and the (3N−8) local normal mode coordinates (plus the usual three Euler angles for overall rotation), and their conjugate momenta. A zeroth order dynamical model is also described which has the form of a collinear-like atom–diatom reaction, i.e., a system with two degrees of freedom—in an effective 2D potential. This effective potential consists of the actual potential energy on the 2D reaction surface, the vibrationally adiabatic energy of the (3N−8) local normal modes, and the rotational energy of the complete polyatomic system, the latter two quantities being functions of the coordinates (r1,r2) on the reaction surface.
The systems biology markup language (SBML): a medium for
representation and exchange of biochemical network models
Authors: Hucka M. , Finney A. , Sauro H. M. , Bolouri H. , Doyle J. C. , Kitano H. , Arkin A. P. , Bornstein B. J. , Bray D. , Cornish-Bowden A. , Cuellar A. A. , Dronov S. , Gilles E. D. , Ginkel M. , Gor V. , Goryanin I. I. , Hedley W. J. , Hodgman T. C. , Hofmeyr J.-H. , Hunter P. J. , Juty N. S. , Kasberger J. L. , Kremling A. , Kummer U. , Le Novère N. , Loew L. M. , Lucio D. , Mendes P. , Minch E. , Mjolsness E. D. , Nakayama Y. , Nelson M. R. , Nielsen P. F. , Sakurada T. , Schaff J. C. , Shapiro B. E. , Shimizu T. S. , Spence H. D. , Stelling J. , Takahashi K. , Tomita M. , Wagner J. , Wang J.
Published: February 2003

Motivation: Molecular biotechnology now makes it possible to build elaborate systems models, but the systems biology community needs information standards if models are to be shared, evaluated and developed cooperatively.

Results: We summarize the Systems Biology Markup Language (SBML) Level 1, a free, open, XML-based format for representing biochemical reaction networks. SBML is a software-independent language for describing models common to research in many areas of computational biology, including cell signaling pathways, metabolic pathways, gene regulation, and others.

Availability: The specification of SBML Level 1 is freely available from http://www.sbml.org/

Contact: sysbio-team@caltech.edu

* To whom correspondence should be addressed.
Detection of unrelated proteins in sequences multiple alignments by using
predicted secondary structures
Authors: Errami Mounir , Geourjon Christophe , Deléage Gilbert
Published: February 2003

Motivation: Multiple sequence alignments are essential tools for establishing the homology relations between proteins. Essential amino acids for the function and/or the structure are generally conserved, thus providing key arguments to help in protein characterization. However for distant proteins, it is more difficult to establish, in a reliable way, the homology relations that may exist between them. In this article, we show that secondary structure prediction is a valuable way to validate protein families at low identity rate.

Results: We show that the analysis of the secondary structures compatibility is a reliable way to discard non-related proteins in low identity multiple alignment.

Availability: This validation is possible through our NPS@ server (http://npsa-pbil.ibcp.fr)

Contact: g.deleage@ibcp.fr

* To whom correspondence should be addressed.
Statistical alignment based on fragment insertion and deletion models
Authors: Metzler Dirk
Published: February 2003

Motivation: The topic of this paper is the estimation of alignments and mutation rates based on stochastic sequence–evolution models that allow insertions and deletions of subsequences (‘fragments’) and not just single bases. The model we propose is a variant of a model introduced by Thorne et al., (J. Mol. Evol., 34, 3–16, 1992). The computational tractability of the model depends on certain restrictions in the insertion/deletion process; possible effects we discuss.

Results: The process of fragment insertion and deletion in the sequence–evolution model induces a hidden Markov structure at the level of alignments and thus makes possible efficient statistical alignment algorithms. As an example we apply a sampling procedure to assess the variability in alignment and mutation parameter estimates for HVR1 sequences of human and orangutan, improving results of previous work. Simulation studies give evidence that estimation methods based on the proposed model also give satisfactory results when applied to data for which the restrictions in the insertion/deletion process do not hold.

Availability: The source code of the software for sampling alignments and mutation rates for a pair of DNA sequences according to the fragment insertion and deletion model is freely available from http://www.math.uni-frankfurt.de/~stoch/software/mcmcsalut under the terms of the GNU public license (GPL, 2000).

Contact: dmetzler@math.uni-frankfurt.de
Unusual diffusion enhancement of Ti in ion prebombarded MgO(100) during postbombardment annealing
Authors: Lu M. , Lupu C. , Rabalais J. W.
Published: February 2003

An unusual diffusion enhancement of Ti in Ar+ prebombarded MgO(100) was observed during postbombardment annealing at 1100 °C. Ti diffusion in the postannealed sample is enhanced with respect to the sample without postannealing. Thermal dissociation of small cationic vacancy clusters is known to be responsible for this type of radiation enhanced diffusion (RED), or nonsteady state RED. It is inferred from previous work that the small vacancy clusters are mainly divacancies. The unusual diffusion enhancement is attributed to thermal dissociation of large vacancy clusters during postannealing, leading to a divacancy creation mechanism. A model is proposed which qualitatively explains the observed diffusion enhancement.
Characterization of hydrogen etched 6H–SiC(0001) substrates and subsequently grown AlN films
Authors: Hartman J. D. , Roskowski A. M. , Reitmeier Z. J. , Tracy K. M. , Davis R. F. , Nemanich R. J.
Published: February 2003

Wafers of n-type, 6H–SiC(0001) with (ND–NA)=(5.1–7.5)×1017 and 2.5×1018 were etched in a flowing 25%H2/75%He mixture within the range of 1500–1640 °C at 1 atm. Equilibrium thermodynamic calculations indicated that the presence of atomic hydrogen is necessary to achieve etching of SiC. Atomic force microscopy, optical microscopy, and low energy electron diffraction of the etched surface revealed a faceted surface morphology with unit cell and half unit cell high steps and a 1×1 reconstruction. The latter sample also exhibited a much larger number of hexagonal pits on the surface. Annealing the etched samples under ultrahigh vacuum (UHV) at 1030 °C for 15 min resulted in (1) a reduction of the surface oxygen and adventitious hydrocarbons below the detection limit of Auger electron spectroscopy, (2) a (√3×√3)R30° reconstructed surface and (3) a Si-to-C peak-to-peak height ratio of 1.2. By contrast, using a chemical vapor cleaning (CVC) process consisting of an exposure to 3000 Langmuir (L) of silane at 1030 °C for 10 min under UHV conditions resulted in a (3×3) surface reconstruction, a Si-to-C ratio of 3.9, and islands of excess silicon. Continued annealing of the latter material for an additional 10 min at 1030 °C resulted in a (1×1) LEED pattern with a diffuse ring. Films of AlN grown via MOCVD at a sample platter temperature of 1274 °C for 15 min on hydrogen etched wafers having a doping concentration of 8.7×1017 cm−3 and cleaned via annealing had a rms roughness value of ≈0.4 nm.
Construction and performance of a low energy ion gun
Authors: Popova I. , Muha R. , Chen Z. , Yates J. T.
Published: February 2003

We report the conversion of a conventional high energy ion gun into a low energy ion gun. The conversion procedure described here maintains the ion current capability of the high energy gun along with its good spatial and ion energy distribution characteristics. Several low energy ion guns have been described previously in the literature [J. T. Yates, Jr., Experimental Innovations in Surface Science (Springer-Verlag-AIP, New York, 1998), pp. 307–329] but all require the construction of new ion optics, whereas this approach utilizes existing ion optics and electronic control capabilities of a commercial ion gun. This ion gun may be employed for studies where it is desired to use ions as reactive species without significant sputter damage of the target.
Transition from E to H mode discharge in pulse-modulated inductively coupled plasmas
Authors: Edamura Manabu , Benck Eric C.
Published: February 2003

Time-resolved measurements of pulse-modulated inductively coupled plasmas were carried out by using a Langmuir probe. It was found that under a certain set of conditions (a mixture of 20% O2 and 80% Ar, a pressure of 2.67 Pa, an rf power of 200 W, a pulse frequency of 500 Hz, and an rf-off time of 100 μs), a plasma transits from E mode (capacitive coupling mode) to H mode (inductive coupling mode) after the rf-off time. With a shorter rf-off time of 50 μs, the plasma returned to H mode without passing through E mode. Whether H mode or E mode appears after the rf-off time depends on the electron density at the end of the afterglow. Namely, the restoration to H mode after the rf-off time occurs if the plasma has an adequate electron density, and E mode occurs if electron density is not enough to sustain H mode. It was also found that electron temperature decreases and plasma potential increases gradually during E mode because of the change of the electron-energy distribution. The change of the plasma reduces the impedance mismatching gradually and increases the electron density until the transition to H mode occurs. Such mode transition behavior strongly depends on the basic characteristics of the plasma processing apparatus during continuous discharge and also on the condition of the chamber wall.
Structure and growth of basal and random oriented MoSx coatings deposited by magnetron sputtering
Authors: Zhang Xiaoling , Lauwerens W. , He Jiawen , Celis J.-P.
Published: February 2003

Detailed information on the topography and microstructure of sulfur deficient MoSx coatings deposited by magnetron sputtering at a different argon pressure, is presented. Hereto, a transmission electron microscopy investigation was done on cross sections from the interface between substrate and coating up to the outer part of 1.6 to 3 μm thick coatings. The evolution in structure and crystallographic orientation across these coatings is presented. In this way, the growth modes of MoSx coatings with different crystallographic orientation are clarified, and the reasons why different crystallographic orientations are obtained, are explained. This clarifies also the wear dependence of some of these coatings on relative humidity.
Sputter deposition of a spongelike morphology in metal coatings
Authors: Jankowski A. F. , Hayes J. P.
Published: February 2003

Metallic films are grown with a “spongelike” morphology in the as-deposited condition using planar magnetron sputtering. The morphology of the deposit is characterized by metallic continuity in three dimensions with continuous and open porosity on the submicron scale. The stabilization of the spongelike morphology is found over a limited range of the sputter deposition parameters, that is, of working gas pressure and substrate temperature. This spongelike morphology is an extension of the features as generally represented in the classic zone models of growth for physical vapor deposits. Nickel coatings are deposited with working gas pressures up to 4 Pa and for substrate temperatures up to 1100 K. The morphology of the deposits is examined in plan and in cross section views with scanning electron microscopy. The parametric range of gas pressure and substrate temperature (relative to absolute melt point) under which the spongelike metal deposits are produced appear universal for other metals including gold, silver, and aluminum.
Morphology of GaN(0001) and GaN(0001̄) surfaces: Persistence of surface clusters
Authors: Manske Westley T. , Ratkovich Anthony S. , Lemke Chris J. , McEllistrem Marcus T.
Published: February 2003

We report a scanning tunneling microscopy and low energy electron diffraction study of GaN(0001) and GaN(0001̄) surfaces. Surface preparation methods included anneal, N2+ sputter/anneal, and chemical etching with Br2. The onset of surface facet formation by thermal anneal is 1050 K, determined by electron diffraction, whereas the onset of facet formation by Br2 etching at elevated sample temperatures is 765 K. For all surfaces studied, facetted and unfacetted, nanosize clusters are observed in scanning tunneling microscopy images regardless of treatment. The presence and persistence of these clusters is discussed, as well as their potential impact on studies of GaN surface chemistry and surface electronic structure.
Molecular dynamics simulation of ion bombardment on hydrogen terminated Si(001)2×1 surface
Authors: Satake Koji , Graves David B.
Published: February 2003

Molecular dynamics simulations were performed to investigate H2+ and SiH3+ ion bombardment of hydrogen terminated Si(001)2×1 surfaces. Normal incidence ion bombardment effects on dangling bond generation, adatom diffusion, and nucleation were studied as a function of incident energy between 10 and 40 eV. The dangling bond generation rate due to H2+ impacts at 20 and 40 eV was about twice that of SiH3+. However these effects appeared to be insignificant compared to probable neutral radical effects under typical plasma-enhanced chemical vapor deposition conditions. The enhanced diffusion of Si adatoms due to ion bombardment was observed to be minor in comparison with thermal diffusion and the disruption of ledge sites due to SiH3+ ion bombardment is not significant, with ion incident energies up to 40 eV. Ion bombardment in the incident energy range between 10 and 20 eV can contribute the modification of surface kinetics without bulk damage.
Atomic structure analysis of SiO2/Si and Si3N4/Si interfaces by high-resolution transmission electron microscopy
Authors: Ikarashi Nobuyuki , Watanabe Koji , Miyamoto Yoshiyuki
Published: February 2003

We used cross-sectional high-resolution transmission electron microscopy to directly observe the atomic structures at SiO2/Si and Si3N4/Si interfaces. These observations provided the first direct evidence that cristobalite-like crystalline SiO2 exists at the interface. Our observations also show that in one of the observed N-induced interfacial geometries, a N atom replaces a Si atom at the second interfacial layer, and a dangling bond was produced on a Si atom adjacent to the N atom. We thus argue that a large elastic strain at a crystalline SiO2/Si interface probably plays an important role in preserving the initial atomic-scale flatness of the interface; that is, the strain results in layer-by-layer oxidation. Furthermore, we infer that the difference in interfacial flatness between Si3N4/Si and SiO2/Si can be explained in terms of the difference in their interfacial strain.
Enhanced chemical vapor deposition of tantalum oxide thin films from in-situ reduction of PtOx electrode
Authors: Liu Tzu-Ping , Huang Wei-Pang , Wu Tai-Bor
Published: February 2003

Amorphous TaOx thin films were deposited on a PtOx electrode by low pressure chemical vapor deposition (LPCVD) in Ar atmosphere with the use of Ta(OC2H5)5 as a precursor. An in situ reduction of PtOx electrode was found during the LPCVD process, and the active oxygen released from the reduction of the PtOx electrode enhanced the deposition of TaOx films with an activation energy of 0.43±0.03 eV lower than the value, 0.57±0.01 eV, obtained from deposition on the Pt electrode. The growth of TaOx was controlled by the reduction reaction of PtOx, which had an activation energy of 0.32±0.04 eV, and the activated oxidation/decomposition reaction of Ta(OC2H5)5, which had a low activation energy of 0.11±0.05 eV. It was also found that the reduction of PtOx roughed the surface of the PtOx electrode, and the rough structure significantly enhanced the capacitance of Pt/TaOx/PtOx although an increase of the leakage current also accompanied it.
Injuries among older adults: the challenge of optimizing safety and minimizing unintended consequences
Authors: Binder S
Published: February 2003

Objectives:To describe the problem of falls, motor vehicle related injuries, and suicide among older adults, and issues related to their prevention.

Methods:Summary and synthesis of selected literature.

Results:About 39 000 adults aged 65 and older die each year in the United States from injuries; worldwide this annual toll is about 946 000 persons. The top three causes of injury related death in this age goup in the United State are falls, those related to motor vehicle crashes, and suicide. Effective strategies exist for preventing fall related injuries and deaths. Preventing injuries and deaths from motor vehicles and suicide may be more difficult because of the nature of these problems.

Conclusions:As the number and percentage of older adults continues to rise in the United States and globally, new approaches to preventing injuries will be critical. Interventions will need to operate at multiple levels—directed at the individual, at interpersonal relationships, and at the community level.
Injury prevention in sport: not yet part of the game?
Authors: Chalmers D J
Published: February 2003

Background:There is a saying in sport that “injury is just part of the game”. In other words, injury in sport is seen as inevitable.

Objective:To examine progress toward reaching the contrary position that “injury prevention is just part of the game”.

Methods:The four steps of van Mechelen’s “sequence of prevention” model provide a structure for examining progress.

Results:What is known about the size of the problem (step 1)? Most is known about more serious injuries and about injuries in élite and professional sport. Least is known about less serious injuries, injury in community level and amateur sport, and injury occurring in recreational activities. What is known about risk factors (step 2)? Despite calls for analytic studies since the early 1980s, few such studies have been reported in the literature. What is known about the effectiveness of preventive measures (step 3)? Few randomized controlled trials have been reported in the literature. Are there systems in place to monitor sports injury (step 4)? Examples are given of systems in North America, Europe, and Australasia.

Conclusions:With a few exceptions, progress has not gone beyond step 1 in van Mechelen’s model. Challenges for the future include: deciding where research efforts should be placed, standardization of definitions and methods of data collection and reporting, identification of risk factors and mechanisms of injury, and the evaluation of interventions. Finally, if the field of sports injury prevention is to advance, multidisciplinary collaboration will be required, along with the involvement of the sports community.
Occupational injury prevention research: progress and priorities
Authors: Stout N A , Linn H I
Published: February 2003

The twentieth century witnessed remarkable reductions in the number and rate of occupational fatalities and injuries. However, many preventable injuries and deaths still occur. Barriers to progress in occupational injury prevention are discussed, along with strategies for overcoming them. In mining, the frequency of death has dramatically declined over the century. The latest figures from the BLS indicate that less than 6000 worker deaths from injury occurred in 2000. Catastrophic events have prompted increased attention, resources, and action on workplace hazards and risks, resulting in sweeping changes, including new protective laws. Science based approaches to prevention have contributed to progress. Multidisciplinary collaboration among injury prevention researchers, and collaboration and cooperation among multiple sectors, have improved the relevance and application of injury prevention research and development. Barriers to further progress include lack of evaluation of the effectiveness of prevention strategies and technologies, including cost effectiveness; lack of widespread implementation of known, effective prevention; and lack of efficient transfer and implementation of prevention knowledge and products to the workplace. Evaluation and implementation of prevention efforts are most successfully achieved in partnership between researchers and the industry at risk, which requires outreach efforts on the part of the occupational research community.
A meta-analysis of the efficacy of over-the-counter nicotine replacement
Authors: Hughes J R , Shiffman S , Callas P , Zhang J
Published: February 2003

Objective:To determine whether over-the-counter (OTC) nicotine replacement therapy (NRT) is pharmacologically efficacious, whether it produces abstinence rates similar to those in prescription settings, and to estimate the long term (that is, greater than six month) abstinence rate with OTC NRT.

Method:Systematic literature review.

Data sources:Medline, Psych Abstracts, bibliographies, requests of scientists.

Study selection:Studies comparing OTC NRT versus OTC placebo or studies comparing OTC NRT versus prescription NRT that reported abstinence rates and for which a full study report was available.

Data extraction:Two of the authors independently reviewed studies and compared results.

Data synthesis:Meta-analysis was performed by first testing for homogeneity across studies, then combining odds ratios (ORs) weighting by inverse variance and proportions weighting by study sample size.

Results:One OTC NRT versus OTC placebo nicotine gum study was excluded due to small sample size and different setting. The four remaining studies were randomised trials of nicotine versus placebo patch with ORs of 2.1–3.2. These outcomes were homogenous and when combined resulted in an OR favouring NRT of 2.5 (95% confidence interval (CI) 1.8 to 3.6). Among the two randomised and two non-randomised trials of OTC NRT versus prescription NRT, one small study had an OR of 0.3, two others had ORs of 1.0 and 1.4, and a fourth study had an OR of 3.6. These results were not homogenous; however, when combined via a random effects model the estimated OR was not less than 1.0—that is, OR 1.4 (95% CI 0.6 to 3.3). The long term (that is, greater than six months) quit rates for OTC NRT was 1% and 6% in two studies and 8–11% in five other studies. These results were not homogenous; however, when combined the estimated OR was 7% (95% CI 4% to 11%).

Conclusions:OTC NRT is pharmacologically efficacious and produces modest quit rates similar to that seen in real world prescription practice.
Smoking and financial stress
Authors: Siahpush M , Borland R , Scollo M
Published: February 2003

Aim:Stress relief is commonly provided as a reason for smoking. However, it is plausible that the cost of smoking may create financial stress, particularly among the poor. The aim of the study was to examine the relationship between smoking and financial stress.

Design:Cross sectional survey of households from private dwellings conducted by the Australian Bureau of Statistics (ABS), using a stratified multistage area sample design.

Setting:Australia, 1998–99.

Participants:Nationally representative sample of households (n = 6892).

Main outcome measures:The outcome measures of objective financial stress were two dichotomous variables indicating whether the household had experienced any financial stress or severe financial stress in the past 12 months.

Results:The odds of experiencing any financial stress were 1.5 (95% confidence interval (CI) 1.3 to 1.7) times greater, and the odds of severe financial stress were twice (95% CI 1.6 to 2.5) as large for smoking households than non-smoking households. The effect of smoking on financial stress did not vary significantly across categories of income. Among smoking households, higher percentage of total household expenditure on tobacco was significantly related to financial stress.

Conclusions:Given data were cross sectional, firm conclusions cannot be drawn about the causal relationship between smoking and financial stress. It is likely that they both affect each other. Undoubtedly, expenditure on tobacco will reduce available funds that could otherwise be used to ameliorate financial stress.
Measuring the accumulated hazards of smoking: global and regional estimates for 2000
Authors: Ezzati M , Lopez A D
Published: February 2003

Objective:Current prevalence of smoking, even where data are available, is a poor proxy for cumulative hazards of smoking, which depend on several factors including the age at which smoking began, duration of smoking, number of cigarettes smoked per day, degree of inhalation, and cigarette characteristics such as tar and nicotine content or filter type.

Methods:We extended the Peto-Lopez smoking impact ratio method to estimate accumulated hazards of smoking for different regions of the world. Lung cancer mortality data were obtained from the Global Burden of Disease mortality database. The American Cancer Society Cancer Prevention Study, phase II (CPS-II) with follow up for the years 1982 to 1988 was the reference population. For the global application of the method, never-smoker lung cancer mortality rates were chosen based on the estimated use of coal for household energy in each region.

Results:Men in industrialised countries of Europe, North America, and the Western Pacific had the largest accumulated hazards of smoking. Young and middle age males in many regions of the developing world also had large smoking risks. The accumulated hazards of smoking for women were highest in North America followed by Europe.

Conclusions:In the absence of detailed data on smoking prevalence and history, lung cancer mortality provides a robust indicator of the accumulated hazards of smoking. These hazards in developing countries are currently more concentrated among young and middle aged males.
A molecular marker map in 'Kanota' × 'Ogle' hexaploid oat (Avenaspp.) enhanced by additional markers and a robust framework
Authors: Wight Charlene P , Tinker Nicholas A , Kianian Shahryar F , Sorrells Mark E , O'Donoughue Louise S , Hoffman David L , Groh Susanne , Scoles Graham J , Li Cheng Dao , Webster Francis H , Phillips Ronald L , Rines Howard W , Livingston Suzanne M , Armstrong Kenneth C , Fedak George , Molnar Stephen J
Published: February 2003

Molecular mapping of cultivated oats was conducted to update the previous reference map constructed using a recombinant inbred (RI) population derived from Avena byzantina C. Koch cv. Kanota × Avena sativa L. cv. Ogle. In the current work, 607 new markers were scored, many on a larger set of RI lines (133 vs. 71) than previously reported. A robust, updated framework map was developed to resolve linkage associations among 286 markers. The remaining 880 markers were placed individually within the most likely framework interval using χ2tests. This molecular framework incorporates and builds on previous studies, including physical mapping and linkage mapping in additional oat populations. The resulting map provides a common tool for use by oat researchers concerned with structural genomics, functional genomics, and molecular breeding.Key words: molecular marker, RFLP, linkage map, oat, Avena.
The conversion of wheat RFLP probes into STS markers via the single-stranded conformation polymorphism technique
Authors: Forsström Per-Olov , Koebner Robert , Merker Arnulf
Published: February 2003

We describe a flexible and general strategy for converting a wheat RFLP-based assay into a PCR-based sequence-tagged site (STS), and have applied it to derive markers for a powdery mildew resistance gene present in a wheatrye translocation. The concept is based on deriving PCR primers that amplify all of the homoeoloci defined by a single-copy cDNA sequence, and separating the resulting mixture of homoeoamplicons via single-stranded conformation polymorphism (SSCP) gels, which are able to detect minor differences between related DNA sequences. After their separation, the individual homoeoamplicons were sequenced and these were used to define nucleotide polymorphisms that could be exploited to design locus-specific PCR primers. In one case, we were able to demonstrate that the assay was allele specific.Key words: wheatrye introgression, powdery mildew, RFLP, SSCP, STS.