bluuebunny/crossref_metadata_2025 huggingface dataset:
Acidic fibroblast growth factor reduces renal morphologic and functional indicators of injury caused by ischemia and reperfusion
Authors: Fu Xiaobing , Cuevas Pedro , Gimenez‐Gallego Guillermo , Tian Huiming , Sheng Zhiyong
Published: September 2002

Therapeutic effects of acidic fibroblast growth factor on postischemic renal injury were evaluated in a rat model of bilateral renal ischemia (60 minutes) and reperfusion (7 days). Twenty‐four rats were randomly divided into two groups (12 rats each). After 60 minutes of ischemia and at the onset of reperfusion, rats in the acidic fibroblast growth factor‐treated group received 2.6 µg of acidic fibroblast growth factor/rat in 50 µl of phosphate‐buffered saline solution containing 0.1% heparin (w/v) through the jugular vein, whereas the rats in the phosphate‐buffered saline solution‐treated group received the same vehicle without acidic fibroblast growth factor. Compared with the phosphate‐buffered saline solution‐treated group, rats in the acidic fibroblast growth factor‐treated group had significantly lower blood urea nitrogen (83.13 ± 26.07 versus 176.36 ± 62.36, p < 0.05) and serum creatinine (0.73 ± 0.14 versus 1.14 ± 0.36, p < 0.05) levels 1 day after occlusion. Histopathologic scores showed much less renal damage on day 1 in the acidic fibroblast growth factor‐treated rats compared with the phosphate‐buffered saline solution controls. We conclude that intravenous administration of acidic fibroblast growth factor offers significant protection against postischemic renal injury and these protective effects may come from its nonmitogenic effects such as the regulation of vessel tone and calcium concentration in the body.
Ischemia and reperfusion reduce the endogenous basic fibroblast growth factor in rat skeletal muscles: An immunohistochemical study
Authors: Fu Xiaobing , Cuevas Pedro , Gimenez‐Gallego Guillermo , Martinez‐Murillo Ricardo , Tian Huiming , Sheng Zhiyong
Published: September 2002

Polyclonal antibodies directed against human recombinant basic fibroblast growth factor were used in immunohistochemical studies to localize this growth factor in normal and wounded rat skeletal muscles. According to the intensity of the stain, three main classes of fibers could be identified: the strongly, moderately, and weakly stained fibers. Basic fibroblast growth factor immunoreactivity was found mainly in the extracellular matrix, primarily in the endomysium, which includes the heparin‐containing basal lamina, and also in the capillary basal membrane of both normal and wounded muscles; however, the signal intensity was much stronger in normal muscles. The distribution of basic fibroblast growth factor in wounded muscles became markedly heterogeneous and sparse. After 4 hours of ischemia, about 40% of skeletal muscle fibers lost their basic fibroblast growth factor immuno‐reactivity. Muscles which underwent 4 hours of ischemia and 24 hours of reperfusion had only a diminished basic fibroblast growth factor immunoreactivity. The pathologic results supported the concept of destroyed cell connection and fiber necrosis in ischemic and reperfused muscles. Potential mechanisms involved in this reduced concentration of basic fibroblast growth factor in wounded muscles may include oxygen free radical activation, a generalized effect of the inflammatory response, and reduced secretion of endogenous basic fibroblast growth factor. These results are only partially compatible with the established mitogenic role of this growth factor and suggest that a reduction of endogenous fibroblast growth factor may partly contribute to a delay in wound healing.
Effect of growth hormone replacement on wound healing in healthy older men
Authors: Papadakis Maxine A. , Hamon Greg , Stotts Nancy , Tierney Mary Jo , Martin Spencer E. , Scheuenstuhl Heinz , Hunt Thomas K
Published: September 2002

The secretion of growth hormone, an important anabolic agent, declines with aging. We hypothesize that growth hormone levels (measured as insulin‐like growth factor‐1) correlate with postoperative tissue repair in otherwise healthy, elderly persons. The goal was to determine whether growth hormone supplementation can improve wound healing in this circumstance. We conducted a randomized controlled double‐blind trial of 6 months of growth hormone replacement or placebo in 28 healthy older men (>69 years of age) with low baseline plasma insulin‐like growth factor‐1. Growth hormone doses were adjusted to elevate insulin‐like growth factor‐1 to levels expected in younger adults. Wound healing was tested by implanting 10 cm expanded polytetrafluoroethylene porous tubes for 10 days, then measuring the content of collagen (as hydroxyproline), DNA, and total protein. Hydroxyproline content was 15% greater in the wounds of the growth hormone group (n = 13) compared with the placebo group (n = 15), (4.52 ± 0.94 versus 3.92 ± 0.78 µg/cm; p = 0.04). Therefore, healthy older men who took growth hormone had enhanced reparative collagen deposition during the wound healing process. This action may be clinically useful after selected surgery or trauma in the elderly.
Comparative Study of the Ploidy Series Bromus sterilis, B. diandrus and B. rigidus (Poaceae) Based on Chromosome Numbers, Morphology and Isozymes
Authors: Oja T. , Laarmann H.
Published: September 2002

Abstract: Chromosome numbers, morphological characters and isozymes of seven enzymes were studied to assess relationships between species of the Bromus diandrus‐rigidus polyploid complex and the closely related species, B. sterilis. The four different cytotypes detected, 2n = 14, 28, 42 and 56, could be divided into two species: B. sterilis (2n = 14, 28) and B. diandrus (2n = 42, 56) by morphological features and isozymes. The shape of the scar of rachilla segments in the floret proved to be a suitable character for distinguishing the two species, but not the chromosomal races within species. The tetraploid shared homozygous isozyme phenotypes with diploid B. sterilis at all loci, except one, suggesting that it is autopolyploid. No diagnostic isozymes could be found to distinguish between hexa‐ and octoploid cytotypes in the B. diandrus‐rigidus complex.
Taylor dispersion of gyrotactic swimming micro-organisms in a linear flow
Authors: Hill N. A. , Bees M. A.
Published: September 2002

The theory of generalized Taylor dispersion for suspensions of Brownian particles is developed to study the dispersion of gyrotactic swimming micro-organisms in a linear shear flow. Such creatures are bottom-heavy and experience a gravitational torque which acts to right them when they are tipped away from the vertical. They also suffer a net viscous torque in the presence of a local vorticity field. The orientation of the cells is intrinsically random but the balance of the two torques results in a bias toward a preferred swimming direction. The micro-organisms are sufficiently large that Brownian motion is negligible but their random swimming across streamlines results in a mean velocity together with diffusion. As an example, we consider the case of vertical shear flow and calculate the diffusion coefficients for a suspension of the alga Chlamydomonas nivalis. This rational derivation is compared with earlier approximations for the diffusivity.
High-resolution spectroscopy of the ν3 band of WF6 and ReF6 in a supersonic jet
Authors: Boudon V. , Rotger M. , He Y. , Hollenstein H. , Quack M. , Schmitt U.
Published: September 2002

We have recorded the Fourier-transform infrared (FTIR) spectrum of the ν3 fundamental band of WF6 in a continuous supersonic jet expansion with an instrumental bandwidth of 0.0024 cm−1 (FWHM, full width at half maximum, unapodized), using a Bomem DA.002 spectrometer. Some parts of this band have also been recorded with 0.0007 cm−1 bandwidth using a diode laser spectrometer combined with a pulsed slit jet expansion. A multiple-pass arrangement has been used for the slit jet to observe low-intensity lines. In each case, we have used a WF6:He mixture with a seeding ratio 1:3 leading to a rotational temperature of ca. 50 K. This work extends the previous investigation of Takami and Kuze [J. Chem. Phys. 80, 5994 (1984)] to much higher J transitions. In both P and R branches, rotational lines have been recorded for J up to 46–48. We have used a tensorial Hamiltonian adapted to the group chain O(3)⊃Oh and developed to the third order for the analysis of the spectra. A least-squares fit for each of the four main isotopic species: 182WF6, 183WF6, 184WF6, and 186WF6 results in band centers (in this order) 714.538 19, 714.214 06, 713.895 44, and 713.266 21 cm−1. We report furthermore first results on the high-resolution spectra of ν3 of ReF6, which exhibits a fourfold degenerate electronic ground state of Gg′ species in the OhS group. Supersonic jet-FTIR spectra show a moderately structured relatively broad band, whereas the diode laser spectroscopy of the seeded jet in the range 708–733 cm−1 results in line resolved spectra of high complexity. A preliminary analysis is discussed, while a complete analysis still represents an appreciable challenge.
Effect of viscosity on destabilization of the Rayleigh–Taylor instability by thermal conductivity in a fluid
Authors: Horikoshi Masashi , Kato Susumu , Nakamura Tatsufumi , Kato Tomokazu , Nishihara Katsunobu
Published: September 2002

The effect of viscosity on the destabilization of the Rayleigh–Taylor (RT) instability by thermal conductivity has been investigated as an extension of the Ryutov analysis [D. D. Ryutov, Phys. Plasmas 7, 4797 (2000)]. The viscosity stabilizes the RT instability for short wavelength perturbations when gradients of a molecular weight and a gravitational acceleration are in the same direction. It only reduces the growth rate for short wavelength perturbations when they are in the opposite directions. The growth rates have been quantitatively evaluated as functions of a normalized wavelength for various Prandtl numbers in the case when adiabatic perturbations are neutrally stable.
A combined scanning probe microscope
Authors: Lányi Štefan , Hruškovic Miloslav
Published: September 2002

A scanning probe microscope, combining a scanning capacitance microscope with a scanning tunneling microscope (STM) using the same probe and input electronics, has been built. The probe is shielded and its stray capacitance is less than 0.5 fF. As an input stage, a wide-bandwidth current-to-voltage converter has been applied. In the capacitance microscope mode, its phase sensitively measures the current flowing through the probe/sample capacitance. The optimum operating frequency is from 1 to 10 MHz. The achieved signal-to-noise ratio is comparable with microscopes using a videodisk pickup as the capacitance sensor. The same amplifier at reduced bandwidth serves in STM mode. Its sensitivity corresponds to standard microscopes, albeit the input bias current is larger than at good STM input stages. It can be used with tunneling currents larger than 100 pA.
Nuclear magnetic resonance method for determining the magnetic easy direction in anisotropic paramagnetic powders
Authors: Young Ben-Li , Rose M. S. , MacLaughlin D. E. , Ishida K. , Bernal O. O. , Lukefahr H. G. , Heuser K. , Freeman E. J. , Maple M. B.
Published: September 2002

We have developed a method for determining the magnetic easy direction (crystalline direction of maximum magnetic susceptibility) in powdered samples of paramagnetic crystals using nuclear magnetic resonance (NMR) spectroscopy. Single-crystal powder grains are aligned using a magnetic field both with and without rotation of the sample about an axis perpendicular to the alignment field. Depending on the magnetic easy direction of the material, only one method produces a good crystalline alignment. By qualitatively comparing the direction-dependent powder-pattern NMR spectra of samples aligned using the two alignment methods, we have successfully determined the magnetic easy directions in CePtSi and Y0.85U0.15Pd2Al3 compounds.
A hybrid quantum mechanical molecular mechanical method: Application to hydration free energy calculations
Authors: Shoeib Tamer , Ruggiero Giuseppe D. , Siu K. W. Michael , Hopkinson Alan C. , Williams Ian H.
Published: September 2002

A hybrid quantum mechanical molecular mechanical (QMMM) approach is used to study H3O+, H2O, NH4+, NH3, Cl−, HCl, F−, HF, CH3COO−, CH3COOH, Ag+ and glycine in both zwitterionic and nonzwitterionic forms in water. The free energies of hydration of these species are presented and are shown to compare favorably with experimental values. The difference in water–glycine interaction energy between the zwitterionic and nonzwitterionic forms is calculated as a lower limit and is in line with previous findings. The first theoretical examination of the Ag+–glycine complex in solution is presented.
Simulation of cylindrical ion temperature gradient modes in the Columbia Linear Machine experiment
Authors: Parker S. E. , Sen A. K.
Published: September 2002

A comparison of the Columbia Linear Machine experiment [A. K. Sen, J. Chen, and M. Mauel, Phys. Rev. Lett. 66, 429 (1991)] with three-dimensional nonlinear electrostatic gyrokinetic simulation results is given, as well as comparisons with linear theory and simple theoretical predictions of nonlinear saturation. Linear theory is in reasonable agreement with the both experimental and simulation results. An analysis of the radial mode width which is localized by variation in the ion temperature gradient is given and compares well with both experiment and simulation. The theoretical estimate of the nonlinear saturation level is within a factor of 2 of what is observed in experiment and in simulation. In addition, both experiment and simulation show excitation of longer wavelength modes with poloidal mode numbers smaller than the linearly most unstable mode.
Precision auto-alignment for the specimen stage of an ellipsometer
Authors: Park Sunglim , Jung Jaewha , Gweon DaeGab , Kim Young Dong
Published: September 2002

We present a new three-step auto-alignment algorithm for the specimen stage of an ellipsometer with adjustable angle of incidence. Correction of errors in tilt angle and position of the specimen stage can be performed by locating the reflected light spot at the center of the detector at two different angles of incidence. The current method does not need auxiliary focusing equipment. The alignment algorithm works to high precision in both model simulation and practical experiments with a rotating analyzer ellipsometer.
Effects of stress annealing in nitrogen on the effective contact-potential difference, charges, and traps at the Si/SiO2 interface of metal–oxide–semiconductor devices
Authors: Przewlocki Henryk M. , Massoud Hisham Z.
Published: September 2002

In this article, we report the results of a study of the effects of high-temperature stress annealing in nitrogen on the electrical properties of metal/oxide/semiconductor devices. In this study, we have experimentally characterized the dependence of the reduced effective contact-potential difference, the effective oxide charge (Neff), and the midgap interface trap density (Dit) on the annealing conditions in nitrogen. We have correlated such properties with the dependence of the index of refraction and oxide stress on the annealing conditions and oxide thickness in a companion article. We consider the contributions of the thermal-relaxation and nitrogen-incorporation processes in determining changes in the electrical properties with annealing time. This model description is consistent with other annealing studies carried out in argon where only the thermal-relaxation process is present.
Effect of Landau damping on kinetic Alfvén and ion-acoustic solitary waves in a magnetized nonthermal plasma with warm ions
Authors: Bandyopadhyay Anup , Das K. P.
Published: September 2002

The evolution equations describing both kinetic Alfvén wave and ion-acoustic wave in a nonthermal magnetized plasma with warm ions including weak nonlinearity and weak dispersion with the effect of Landau damping have been derived. These equations reduce to two coupled equations constituting the KdV–ZK (Korteweg–de Vries–Zakharov–Kuznetsov) equation for both kinetic Alfvén wave and ion-acoustic wave, including an extra term accounting for the effect of Landau damping. When the coefficient of the nonlinear term of the evolution equation for ion-acoustic wave vanishes, the nonlinear behavior of ion-acoustic wave, including the effect of Landau damping, is described by two coupled equations constituting the modified KdV–ZK (MKdV–ZK) equation, including an extra term accounting for the effect of Landau damping. It is found that there is no effect of Landau damping on the solitary structures of the kinetic Alfvén wave. Both the macroscopic evolution equations for the ion-acoustic wave admits solitary wave solutions, the former having a sech2 profile and the latter having a sech profile. In either case, it is found that the amplitude of the ion-acoustic solitary wave decreases slowly with time.
Ion-acoustic filamentation of a current-driven plasma
Authors: Shokri B. , Khorashadi S. M. , Dastmalchi M.
Published: September 2002

The effect of thermal motion of charged particles in the filamentation of a nonrelativistic current-driven plasma in the ion-acoustic frequency region is investigated. The period and the establishment time of the filamentation structure and the threshold for instability development are obtained.
Molecular dynamics simulations of Mach cones in two-dimensional Yukawa crystals
Authors: Ma Z. W. , Bhattacharjee A.
Published: September 2002

Molecular dynamics simulations of Mach cones in a two-dimensional, hexagonal dusty plasma crystal are presented. The initial conditions and physical parameters (such as the dust charge, interparticle spacing, the Debye length, and externally imposed laser force) are chosen to correspond to typical laboratory experimental conditions. The interparticle potential is assumed to be Yukawa. Conditions under which compressional and shear wave Mach cones are excited in laboratory experiments are discussed.
Bogoliubov transformations and exact isolated solutions for simple nonadiabatic Hamiltonians
Authors: Emary C. , Bishop R. F.
Published: September 2002

We present a new method for finding isolated exact solutions of a class of nonadiabatic Hamiltonians of relevance to quantum optics and allied areas. Central to our approach is the use of Bogoliubov transformations of the bosonic fields in the models. We demonstrate the simplicity and efficiency of this method by applying it to the Rabi Hamiltonian.
A laser ablation electron impact ionization time-of-flight mass spectrometer for analysis of condensed materials
Authors: Drewnick F. , Wieser P. H.
Published: September 2002

Laser desorption/ionization (LDI) mass spectrometry suffers from poor reproducibility and a strong bias in representing the chemical composition of the sample in the mass spectra. In regard to develop laser mass spectrometry towards a quantitative analysis technique desorption and ionization processes should be separated. Here we describe a time-of-flight mass spectrometer (TOF-MS) with laser ablation and subsequent electron impact ionization (LA-EI-MS). Sample material is ablated by an Nd-YAG laser pulse (λ=355 nm, E=0.5–35 mJ, τ=9 ns), which produces ions and neutrals in the ablation plume. After expansion, parts of the plume enter the EI ion source where neutrals are ionized by electron impact (Eel=70 eV). Ions are extracted from the ion source into the flight tube of the TOF-MS by applying a pulsed repeller potential. Depending on delay times between laser pulse and repeller pulse either neutrals or ions emitted from the sample were analyzed. Different mass spectra of the same sample are obtained in these two analyzing modes under the same irradiation conditions. With a relative standard deviation of 10% to 15%, reproducibility of mass spectra is significantly better in LA-EI-MS than in LDI-MS.
A cryogenic scanning near-field optical microscope with shear-force gapwidth control
Authors: Kramer A. , Segura J.-M. , Hunkeler A. , Renn A. , Hecht B.
Published: September 2002

We present a scanning near-field optical microscope designed for nanoscale optical imaging and spectroscopy as well as simultaneous tuning fork shear-force topographic imaging at cryogenic temperatures. The whole setup is immersed in superfluid helium (T=1.8 K). In this medium we observe resonance frequency fluctuations of the tuning fork sensor with an amplitude of Δν≈5%–10% of the full width at half-maximum of the resonance. Possible reasons for the occurrence of the frequency fluctuations are discussed. A stable gapwidth feedback can still be achieved if the set value of the frequency shift is chosen slightly larger than the fluctuation amplitude. As an example we demonstrate shear-force topographic imaging of a silicon grating in superfluid helium.
Cavities with axially uniform fields for use in electron paramagnetic resonance. II. Free space generalization
Authors: Anderson James R. , Mett Richard R. , Hyde James S.
Published: September 2002

The radio frequency (rf) magnetic field in a microwave cavity ought to be uniform along a line sample in electron paramagnetic resonance (EPR) spectroscopy so that all portions respond uniformly. Mett, Froncisz, and Hyde discovered a way to achieve this objective [Rev. Sci. Instrum. 72, 4188 (2001)]. Their resonators consisted of three regions, a central section for the sample with dimensions at the cutoff condition, and two end sections that had the same cross section as the central section but were made electrically larger by filling them with a low-loss dielectric. The end sections were each one-quarter wavelength long. We have found that the dielectric in the end sections can be omitted and the dimensions made correspondingly larger. Effects of the resulting discontinuities in cavity cross sections perpendicular to the cavity axis have been analyzed using finite element high frequency structure simulator calculations. Closed form expressions for Q values and relative rf field values have been obtained. The length of the uniform field region is decreased somewhat by the discontinuities (∼1 cm at X band). This disadvantage is outweighed by the benefits of higher Q values and elimination of impurity EPR signals from the dielectric materials. End sections may be cylindrical or hemispherical for cylindrical modes and rectangular or hemicircular for rectangular modes.
A simplified model for the Briggs–Rauscher reaction mechanism
Authors: Kim Kyoung-Ran , Lee Dong J. , Shin Kook Joe
Published: September 2002

A model for the Briggs–Rauscher reaction mechanism with four intermediates and seven steps is proposed by simplifying the model of De Kepper and Epstein [J. Am. Chem. Soc. 104, 49 (1982)]. Assigning suitable rate constants for the steps of the simplified model, we obtain numerical results for the nonlinear dynamic behaviors such as oscillations, limit cycle, multistability, and inverse regulation of the iodine concentration. The results are compared with experiments and other previous models. The comparison shows that the present simplified model expresses the nonlinear dynamic behaviors better than the previous models.
Equilibrium correlations in interfaces between two immiscible liquids
Authors: Stecki J. , Toxvaerd S.
Published: September 2002

Static density and concentration correlations in momentum space are determined quantitatively in molecular dynamics computer experiments on the interface between two liquid phases of a binary mixture. The interaction between spherical particles of equal sizes is modeled by 6–12 Lennard-Jones potentials. The resulting four density-density correlations are inverted to four direct correlation functions. Transformation to density-concentration variables inspired by the Bhatia–Thornton transformation and the hitherto unknown characteristic shapes of their projections, including the generalization of the Yvon–Zwanzig–Triezenberg projection, are discussed in detail; it is demonstrated that the q4 coefficient again is negative. This precludes its interpretation as a rigidity coefficient. The interfacial contributions decay rather quickly with the momentum q, becoming totally submerged by short-range bulk and bulklike fluctuations at q-values of the order of 1/5 of the q-value of the nearest-neighbor (first) peak in the scattering factor.
The effect of intermolecular interactions on the electric properties of helium and argon. III. Quantum statistical calculations of the dielectric second virial coefficients
Authors: Rizzo Antonio , Hättig Christof , Fernández Berta , Koch Henrik
Published: September 2002

The second dielectric virial coefficients of helium and argon are investigated using a fully quantum statistical approach and recent accurate ab initio results for the interatomic potentials and the interaction-induced polarizabilities. We thereby extend a preceding investigation based on a semiclassical approach to include quantum effects. For helium the results support the findings of a previous study by Moszynski et al. [J. Chem. Phys. 247, 440 (1995)] that quantum effects are substantial for temperatures below 10 K, while they are practically negligible above 70 K. For argon special care is needed in the numerical integrations carried out in the quantum statistical calculation of the virial coefficients, due to the presence of quasibound states in the continuum and a slow convergence of the summation over the angular momentum. Here quantum effects are practically negligible in the range of temperatures experimentally investigated, i.e., between 243 and 408 K. As far as comparison with experimental data is concerned, large discrepancies are found for some of the low-temperature experimental measurements of helium. Agreement is also unsatisfactory for high temperatures for argon and experimental redetermination is suggested.
Ab initio simulations of the KrO− anion photoelectron spectra
Authors: Buchachenko A. A. , Szczȩśniak M. M. , Kłos Jacek , Chałasiński Grzegorz
Published: September 2002

The photoelectron spectra of the weakly bound KrO− anion are simulated using a theory which combines the atoms-in-molecule model for molecular electronic wave functions and the Rau–Fano model for photodetachment intensities [J. Chem. Phys. 112, 5852 (2000)]. The nonrelativistic potential energy curves of the anion are obtained from ab initio calculations. The calculated spectra and their temperature variation agree with the experimental data presented in the preceding article. The strong selectivity of the photodetachment process with respect to the symmetry of fine-structure components is rationalized and quantified.
Nonequilibrium molecular dynamics simulations of a simple dipolar fluid under shear flow
Authors: McWhirter J. Liam , Patey G. N.
Published: September 2002

Nonequilibrium molecular dynamics (NEMD) simulations are used to investigate the behavior of a fluid of dipolar Lennard-Jones (LJ) particles under planar Couette flow. Such systems can be viewed as simple models for magnetic ferrofluids. Various issues that arise in such simulations are discussed. These include the importance of the long-range dipolar forces, the influence of different thermostats, and the induction of orientational order. The shear viscosity is found to be somewhat sensitive to the treatment of the dipolar interactions with spherical truncation giving lower values than Ewald sums. The system considered is characterized by a moderate dipole moment, and strong orientational order does not develop at low shear rates. However, the direction of the weak polarization correlates with the shear-induced distortion of the fluid structure. At very high shear rates the fluid behavior depends on the thermostat applied. While the results are not strongly sensitive to details of the rotational thermostat, this is not the case for translational motion. A translationally biased thermostat leads to a string phase, although string formation requires significantly higher shear rates for the dipolar fluid than for the corresponding LJ system. For the dipolar fluid, the string phase is accompanied by strong orientational ordering perpendicular to the flow for Ewald sums and with the flow for the spherically truncated case. In the Ewald systems the order was ferroelectric for conducting boundary conditions, and an antiferroelectric domain structure formed in the vacuum case. For the truncated potential individually polarized chains are randomly oriented with or against the flow. The string phase and the orientational ordering disappears when the translationally unbiased thermostat of Evans and co-workers is employed. Some NEMD simulations with oscillating shear were also performed. These yielded layer structures and again strong orientational order in the dipolar case.
Ultraviolet photodissociation of bromoform at 234 and 267 nm by means of ion velocity imaging
Authors: Xu Dadong , Francisco Joseph S. , Huang Jianhua , Jackson William M.
Published: September 2002

The photochemistry of bromoform is of considerable importance to understanding the impact of short-lived halogen species on bromine chemistry in the atmosphere. In the present work, the products of the ultraviolet photodissociation of bromoform at 234 and 267 nm are determined by time-of-flight mass spectrometry and velocity ion imaging. Both ground Br (2P3/2) and spin–orbit excited Br (2P1/2) atoms are found to be formed via resonance-enhanced multiphoton ionization detection. Radical products are detected via vacuum ultraviolet photoionization at 118 nm. The results indicate that there is a primary molecule bromine elimination channel consisting of CHBr+Br2. The quantum yields for atomic Br and molecular Br2 elimination channels are determined from the time-of-flight spectra to be 0.74 and 0.26 at 234 nm, respectively. At 267 nm, they are 0.84 and 0.16, respectively. Energy and angular distributions are deduced from the 2D images of Br, CHBr, and CHBr2. The direct studies described in this paper on the photodissociation of bromoform suggest that the current atmospheric photochemical models that do not anticipate the formation of Br2 need to be reinvestigated to determine their implications for atmospheric bromine chemistry.
Comment on “The effect of the charge density of microemulsion droplets on the bending elasticity of their amphiphilic film” [J. Chem. Phys. 114, 10105 (2001)]
Authors: Lisy V.
Published: September 2002

It is shown that the work by Farago and Gradzielski [J. Chem. Phys. 114, 10105 (2001)] is based on incorrect expressions for the scattering functions, contains a number of other serious defects, and should be revised.
Debye shielding distortion of dust grains in dusty plasmas
Authors: Yaqoob Faisal , Ali Shahid , Murtaza G. , Nasim M. H.
Published: September 2002

The shielded potential and the energy loss of N2 projectiles propagating through a multicomponent dusty plasma are studied. Analytically general expressions have been obtained for the potential and for the energy loss, taking into account the two-body correlation effects. However, numerical calculations have been performed for one, three, and six projectiles, incorporating interference between two consecutive projectiles. It is found that the correlation effect causes distortion in the potential profile depending upon the separation between the two projectiles. The distortion becomes pronounced for separation smaller than the Debye length.
Characteristics of chromium doped spinel crystals for a fiber-optic thermometer application
Authors: Aizawa H. , Ohishi N. , Ogawa S. , Watanabe E. , Katsumata T. , Komuro S. , Morikawa T. , Toba E.
Published: September 2002

The chromium doped spinel crystals, MgAl2O4:Cr3+, have been grown using floating zone technique and its application for the fiber-optic thermometer is discussed on the basis of the temperature dependence of the fluorescence lifetime. Lifetimes of the spinel crystals (τ=10 ms), which decrease with temperature, were about 3 times larger than that of the ruby crystals (τ=4 ms) at room temperature. Temperature coefficients of the photoluminescence (PL) lifetimes for spinel crystals (37 μs/K) are also 3 times longer than that for the ruby crystals (10 μs/K). The spinel crystals are potentially useful sensor probes for the fiber-optic thermometer, which have an advantage of high sensitivity due to long PL lifetime and large temperature coefficient.
Two-dimensional approximation of rotating flows for a fluid layer of arbitrary depth
Authors: Suh Y. K.
Published: September 2002

This paper presents a two-dimensional approximation method for rotating flows, which can be applied to a fluid layer of arbitrary depth. The three-dimensional Navier–Stokes equations are first evaluated at the mid plane between the two rotating horizontal planar walls to obtain two-dimensional equations. To treat the vertical derivatives, the linear equations are constructed and solved under the assumption of small Rossby numbers. Application to the spin-up flows in a circular cylinder shows that the present method is superior to the classical model, the latter being based on the assumption that the thickness of the Ekman boundary layer is very small compared with the depth of the fluid layer.
Influence of the thermodynamic equilibrium state in the excitation of samples by a plasma at atmospheric pressure
Authors: Calzada M. D. , Garcı́a M. C. , Luque J. M. , Santiago I.
Published: September 2002

The microwave induced plasmas have been successfully used as an excitation source in atomic emission and mass spectrometry for the analytical determination of substances. In this work a study of the influence of the thermodynamic equilibrium state over the capacity of sample excitation of an argon plasma flame sustained by a surface wave at atmospheric pressure is presented. The state of the thermodynamic equilibrium in the discharge is determined by the relation between its temperatures and densities. The values of these parameters depend on the energy available in the discharge, which is also responsible for the excitation of the samples introduced into the plasma. We have compared the behavior of two characteristic parameters of plasma (electron density and temperature) and of the ArI level population with the microwave power. The results have shown that the values of these parameters and populations had a tendency to remain constant for microwave powers above a certain value. Thus, from 100 W only a part of the energy injected into the discharge is absorbed in the plasma and the plasma equilibrium state is not consequently modified. This behavior is the same as that found for atomic lines of both halogens and iron introduced as samples into the plasma and seems to show that if the plasma is close to thermodynamic equilibrium the excitation of the samples is favored.
Forces between chemically patterned plates immersed in binary liquid mixtures
Authors: Overduin S. D. , Patey G. N.
Published: September 2002

Grand canonical Monte Carlo calculations are used to investigate the phase behavior of a binary mixture of Lennard-Jones particles confined between planar, parallel, chemically patterned plates. Attention is focused on the influence of surface-induced transitions on the net force acting between the plates. In addition to the stable and metastable bulk states that play a crucial role for homogeneous surfaces, for certain patterns and surface separations a bridge phase analogous to that recently reported for one-component systems is observed. It is found that bridge phase formation leads to strongly attractive plate–plate forces that are equal in magnitude to those observed for homogeneous surfaces. The significance of our results for the interaction and behavior of nonuniform macroparticles in solution is discussed.
Saturation and entropic trapping of monodisperse polymers in porous media
Authors: Nixon Grant I. , Slater Gary W.
Published: September 2002

We investigate the effect of polymer concentration on the diffusion and localization (entropic trapping) of linear polymer chains in a two-dimensional model system of small obstacles and large pores. Three distinct regimes are identified: the entropic trapping regime, a reptation regime where the larger pores are polymer saturated and the untrapped polymers reptate, and finally a crowding regime where intermolecular interactions dominate. In this model system, the entropic trapping, reptation, and crowding mechanisms compete and lead to a characteristic maximum in the diffusion coefficient for intermediate polymer concentrations.
Gibbs ensemble Monte Carlo simulations of coexistence properties of a polarizable potential model of water
Authors: Dang Liem X. , Chang Tsun-Mei , Panagiotopoulos Athanassios Z.
Published: September 2002

The vapor pressure, heat of vaporization, and liquid/vapor densities along the coexistence curve of the polarizable water model of Dang and Chang [J. Chem. Phys. 106, 8149 (1997)] were calculated by using Gibbs ensemble Monte Carlo simulation techniques. Long-range interactions such as charge–charge, charge–dipole, and dipole–dipole were evaluated by using Ewald summation techniques. The model yields good agreement with the corresponding experimental data in the lower temperature region, but only moderate agreement in the higher temperature region. The critical temperature and density were estimated to be 565 K and 0.28 g/cm3, compared to experimental Tc=647 K and ρc=0.32 g/cm3.
State-resolved radiative lifetimes of the NH(A 3Π,v=0) radical and rate constants for the quenching by NH3
Authors: Hake A. , Stuhl F.
Published: September 2002

A reinvestigation of the radiative lifetimes and the quenching rate constants of single excited rotational states (N,Fj,e/f ) (j=1–3) of the NH(A 3Π,v=0) radical has been performed. The quenching species was the parent molecule NH3. The electronically excited NH(A 3Π) radicals are generated by first forming ground state NH(X 3Σ−) in the ArF laser photolysis of NH3; after a delay, NH(X 3Σ−) is pumped by a dye laser to selected fine structure levels of the A 3Π state. Both the radiative lifetimes and quenching rate constants were found to be dependent on the rotational level but not on the spin and Λ-doublet component. The formation of a blast wave was observed under certain conditions leading to time dependent changes of the number density and temperature in the system. In case of a blast wave, kinetic measurements have to be evaluated with great care.
Soft x-ray output from a pinch plasma using laser-induced Au plasma
Authors: Ohzu Akira , Ito Kazunori
Published: September 2002

An experimental investigation of the characteristics of soft x-ray output emitted from a pinch plasma using a laser-induced Au plasma has been performed. The Au plasma is produced by focusing a laser pulse with a focal spot diameter of 100 μm on the tip of an Au pin anode electrode. A pulsed pinch discharge driven by a Marx generator utilizes the plasma as a discharge medium. Soft x-ray output with a pulse duration of ∼120 ns, an energy of ∼1 μJ mm−2, and an effective photon energy of ∼1 keV, has been obtained with the discharge. It is shown that the output characteristics depend strongly on the Marx charging voltage, laser pulse energy, and delay time of the discharge from the laser irradiation.
Dynamic magnetic behavior of Fe3O4 colloidal nanoparticles
Authors: Hrianca I. , Caizer C. , Schlett Z.
Published: September 2002

This article studies the dynamic magnetic behavior of a system of colloidal Fe3O4 nanoparticles dispersed in kerosene. By increasing the frequency of the magnetizing field from 50 to 640 Hz, and by reducing the temperature from 300 to 77 K, the measuring time is getting closer to the magnetic relaxation time. Under these conditions, it was possible to observe how the dynamic behavior is modified by the parallel arrangement of the easy magnetization axes of the particles from the frozen ferrofluid, as opposed to the situation when the axes are randomly oriented. Unlike the superparamagnetic behavior at room temperature, at low temperatures the magnetization has a hysteresis loop. This behavior is due to Néel relaxation processes. It has been shown that the relaxation time resulting from the Néel theory is determined by an effective anisotropy constant that takes into account the magnetocrystalline anisotropy, as well as the shape and surface anisotropy. The relaxation time becomes greater when the easy magnetization axes of the nanoparticles are aligned in the direction of the magnetization field, as opposed to the case when the axes are oriented in all directions. The results show that the remanence increases both with the decrease of the temperature and with the increase of the frequency of the magnetization field. At the temperature of 77 K, the saturation magnetization Msat of the colloidal suspension increases by 57.1% compared to the value at the temperature of 300 K, whereas the saturation (spontaneous) magnetization Ms of bulk Fe3O4 increases by only 6.6% in the same temperature range. Using the core-shell model, we assumed that the surfactant decreases the superexchange interaction in the shell, as opposed to the core of the particle; this leads to an increase of the magnetic diameter when the temperature is decreasing.
Instantaneous normal mode analysis of correlated cluster motions in hydrogen bonded liquids
Authors: Garberoglio G. , Vallauri R. , Sutmann G.
Published: September 2002

We analyze the correlated motions of hydrogen bonded clusters in liquid hydrogen fluoride, methanol, and water using the Instantaneous Normal Mode approach. In the case of hydrogen fluoride and methanol, which form a topologically linear hydrogen bond network, the relevant cluster is a triplet formed by a molecule and its two neighbors. In the case of water, whose hydrogen bond structure has a local tetrahedral symmetry, the basic unit considered is the pentamer formed by a molecule and its four neighbors. For each of these clusters we identify, using symmetry arguments, the a priori modes describing the relative motions of the cluster molecules and introduce suitable projections in order to evaluate how much these modes contribute to the actual motions at different frequencies. In the case of hydrogen fluoride we confirm the assignment of a 50 rad/ps peak observed in the single and collective correlation function spectra to the stretching of the hydrogen bonded network. In the case of methanol the analysis of the correlated motions of the triplets shows that in the intermediate frequency range (around 25 rad/ps) a picture similar to what is observed in hydrogen fluoride applies, whereas the high frequency properties of the liquid (beyond 50 rad/ps) are mostly due to the asymmetric stretching motion. In the case of water we demonstrate that the a priori modes, based on the full tetrahedral symmetry of the water pentamer, do indeed mix strongly under the effect of the interaction with the neighbors. The results are related to the spectroscopic measurement.
Enhanced fundamental and self-frequency-doubling laser emission efficiency in F43/2 directly pumped Nd-activated nonlinear crystals: The case of GdCa4O(BO3)3
Authors: Lupei V. , Aka G. , Vivien D.
Published: September 2002

The possibilities of improvement of laser emission characteristics and reduction of heat generation by direct pumping at 887 nm into the emitting level F43/2 of Nd3+ in the self-frequency-doubling crystal Nd–GdCOB [GdCa4O(BO3)3] are discussed. Enhanced laser emission performances at fundamental 1060 nm, and especially at the self-frequency-doubled 530 nm wavelengths as compared to the traditional 811 nm pumping into the F45/2 level, are demonstrated.
Phase behavior of films adsorbed on model crystal surfaces
Authors: Patrykiejew A. , Sokołowski S. , Binder K.
Published: September 2002

The paper discusses the structure and phase behavior of films adsorbed on the (100) plane of model face-centered cubic crystals characterized by different strength of the surface potential studied by means of Monte Carlo simulation. Melting and disordering of incommensurate and commensurate monolayer and bilayer films formed on strongly attractive surfaces as well as the behavior of small droplets deposited on weakly attractive surfaces are discussed. Besides, the nature of the commensurate–incommensurate transition in monolayer films is considered and shown to exhibit different mechanism depending on the strength of the adsorbing potential. It is also shown that the formation of higher layers, on top of the dense incommensurate solid monolayer, may lead to the restructuring of the first layer and to a partial recovery of epitaxial structure in the film. The crossover from the regime of complete to incomplete wetting is studied with the help of the Monte Carlo simulation method in both canonical and grand canonical ensembles. In particular, discussion focusses on melting and spreading of microdrops deposited on weakly attractive surfaces.
Nonlinear dust Alfvén waves in plasmas with shear flow
Authors: Haque Q. , Saleem H.
Published: September 2002

In the presence of a nonuniform magnetic field and shear flow, two coupled nonlinear equations for perturbed electromagnetic fields are derived in a dusty plasma. A linear instability of dust Alfvén waves is discussed and the analytical solution of the nonlinear equations is found in the form of tripolar vortices.
Structure and speciation of liquid 2HF/KF: A molecular dynamics study
Authors: Simon Christian , Cartailler Thierry , Turq Pierre
Published: September 2002

Industrial generation of fluorine relies on electrolysis of liquid 2HF/KF solutions. Whereas pure HF has been widely studied experimentally [see, for example, T. Pffeiderer et al., J. Chem. Phys. 113, 3690 (2000)] as well as theoretically [U. Röthlisberger and M. Parrinello, J. Chem. Phys. 106, 4658 (1997)], there is an important lack of description and information at the atomic level for KF solutions in HF. To our knowledge this work is the first attempt to model 2HF/KF at atomic scale by classical molecular dynamics. The model we present here is based on well-tried classical models for pure HF and pure KF. This simple model allows simulation of a system that undergoes a glass-like transition at the experimental transition temperature of 2HF/KF. Furthermore, the clusters spontaneously formed in the liquid give an image of the microscopic structure consistent with previous ab initio studies [T. von Rosenvinge, M. L. Klein, and M. Parrinello, J. Chem. Phys. 107, 8012, 1997)]. Equilibrium proportions between the clusters are computed. Finally, exchange process of molecules between clusters is highlighted, giving deeper insight of the dynamical equilibrium between the clusters. The results presented here are consistent with ab initio simulations cited above and with the sketchy experimental data available on the liquid structure.
Renormalized coupled-cluster calculations of reactive potential energy surfaces: A comparison of the CCSD(T), renormalized CCSD(T), and full configuration interaction results for the collinear BeFH system
Authors: McGuire Michael J. , Kowalski Karol , Piecuch Piotr
Published: September 2002

The recently proposed renormalized (R) and completely renormalized (CR) coupled-cluster singles, doubles, and noniterative triples (CCSD(T)) methods have been used to calculate the ground-state potential energy surface (PES) for the collinear BeFH system corresponding to the Be+HF→BeF+H reaction. It has been demonstrated that the ground-state PES obtained in the CR-CCSD(T) calculations is in perfect agreement with the exact PES obtained in the full configuration interaction calculations, whereas the PES resulting from the standard CCSD(T) calculations is qualitatively incorrect.