bluuebunny/crossref_metadata_2025 huggingface dataset:
Kinetics of styrene emulsion polymerization above the critical micelle concentration: Effect of the initial monomer concentration on the molecular weight
Authors: Herrera‐Ordonez Jorge , Rivera Oscar , Maldonado‐Textle Hortensia , Ramirez Jorge C.
Published: March 2005

The emulsion polymerization of styrene above the critical micelle concentration has been experimentally studied from a low final polymer content up to a high polymer content (∼50%). A maximum in the molecular weight (M) evolution has been observed in all cases. The presence or absence of such a maximum depends on the relative values of the rate of free‐radical entry (ρ) and the rate of chain transfer to the monomer (KtrCMp, where Ktr is the chain transfer to monomer rate coefficient and CMp is the monomer concentration in particles). If ρ ≪ KtrCMp, M is constant and equal to Kp/Ktr (where Kp is the propagation rate coefficient), except at very low particles sizes typical of the early stages of the reaction, in which the chain length is limited by the particle size. On the other hand, if ρ ≫ KtrCMp, M is determined by both CMp and ρ. It is proposed that ρ is determined by the sum of the entry of the oligomeric radicals formed in the aqueous phase and those contained in particles that undergo limited coagulation. This coagulative entry can become very significant; therefore, reactor hydrodynamics can play a major role in the kinetic behavior observed. Disagreement between Clay and Gilbert's model and molecular weight distribution data can be ascribed, to a lesser or greater extent, to the degree of correctness of the quasi‐steady‐state and instantaneous‐termination approaches. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1963–1972, 2005
The CFTR gene and regulation of its expression
Authors: McCarthy Victoria A. , Harris Ann
Published: April 2005

The cystic fibrosis transmembrane conductance regulator gene (CFTR) shows clear temporal and developmental regulation of its expression. However, there are few well‐defined regulatory elements that control this pattern of expression, and their mechanism of action is poorly understood. We review the structure and organization of the CFTR gene and what is known about its regulation. The CFTR gene promoter is clearly important for maintaining levels of CFTR gene expression, but apparently it does not contain any tissue‐specific elements. Thus tissue‐specificity is probably controlled by sequences lying elsewhere in this large gene. We discuss data from our group and others implicating additional regions of CFTR in regulatory functions, and evaluate candidate transcription factors that may be involved. Further, we summarize aspects of the regulation of the developmental expression of CFTR. Definition of CFTR gene regulatory elements could be of considerable therapeutic significance, since only a small increase in CFTR expression in the correct cell type could alleviate the disease phenotype. Pediatr Pulmonol © 2005 Wiley‐Liss, Inc.
Selection of quantum chemical descriptors by chemometric methods in the study of antioxidant activity of flavonoid compounds
Authors: Weber K. C. , Honório K. M. , Da Silva S. L. , Mercadante R. , da Silva A. B. F.
Published: April 2005

In the present study, the aim was to select electronic properties responsible for free radical scavenging ability of a set of 25 flavonoid compounds employing chemometric methods. Electronic parameters were calculated using the AM1 semiempirical method, and chemometric methods (principal component analysis, hierarchical cluster analysis, and k‐nearest neighbor) were used with the aim to build models able to find relationships between electronic features and the antioxidant activity presented by the compounds studied. According to these models, four electronic variables can be considered important to discriminate more and less antioxidant flavonoid compounds: polarizability (α), charge at carbon 3 (QC3), total charge at substituent 5 (QS5), and total charge at substituent 3′ (QS3′). The features found as being responsible for the antioxidant activity of the flavonoid compounds studied are consistent with previous results found in the literature. The results obtained can also bring improvements in the search for better antioxidant flavonoid compounds. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005
Theoretical investigation of optical properties in oligo(trans‐1,2‐di(2‐thienyl) ethylene)
Authors: Marçal Nei , Laks Bernardo
Published: March 2005

The electronic structures of poly(trans‐1,2‐di(2‐thienyl)ethylene) (PTE) oligomers were theoretically analyzed following models based on neutral and charged oligomers for 1 < n < 7. Geometrical optimizations were carried out at the semiempirical level using parametric method 3 (PM3). For singly oxidized oligomer, the positive charge is concentrated around two central monomers. For doubly oxidized oligomer, the positive charge is concentrated around four central monomers. The energy of the electronic transitions and their associated oscillator strength values were also calculated for neutral and charged oligomers, so the UV‐vis absorption spectra is presented. The calculations were done using the intermediate neglect of differential overlap Hamiltonian in combination with the single configuration‐interaction technique in order to include correlations effects. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005
Energy lowering of current‐carrying single‐particle states in open‐shell atoms due to an exchange‐correlation vector potential
Authors: Orestes E. , da Silva A. B. F. , Capelle K.
Published: April 2005

Current density functional theory is used to calculate perturbatively the single‐particle energies of open‐shell atoms prepared in a current‐carrying state. We focus on the highest occupied such energy, because its negative is, in principle, the exact ionization energy. A variety of different density functionals and calculational schemes are compared with each other and with experiment. When the atom is prepared in a current‐carrying state, a current‐dependent exchange‐correlation functional is found to slightly lower the single‐particle energy of the current‐carrying orbital, as compared with a calculation using standard (current independent) density functionals for the same system. The current‐dependent terms in the exchange‐correlation functional thus provide additional stabilization of the current‐carrying state. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005
Erratum: Titanium oxides and silicates as high‐κ dielectrics: A first‐principles investigation by G.‐M. Rignanese, X. Rocquefelte, X. Gonze, Alfredo Pasquarello
Authors: Rignanese G.‐M. , Rocquefelte X. , Gonze X. , Pasquarello Alfredo
Published: March 2005

The original article to which this Erratum refers was published in International Journal of Quantum Chemistry (2005) 101(6) 793– 801
In vivo specificity of Ure2 protection from heavy metal ion and oxidative cellular damage in Saccharomyces cerevisiae
Authors: Rai Rajendra , Cooper Terrance G.
Published: April 2005

The S. cerevisiae Ure2 protein is a prion precursor able to form large homopolymers with the characteristics of amyloid particles, a function largely restricted to its 90 N‐terminal amino acids. The remaining C‐terminal domain of Ure2 plays two important roles in cellular metabolism. First, it regulates nitrogen catabolic gene expression by forming a complex with the GATA transcription factor Gln3. This complex formation correlates with Gln3 being sequestered in the cytoplasm under conditions of excess nitrogen, where Gln3/Gat1‐mediated transcription is minimal. Second, Ure2, which possesses structural homology with glutathione S‐transferases and binds to xenobiotics and glutathione, has been recently shown to be required for Cd(II) and hydrogen peroxide detoxification. Present experiments demonstrate that Ure2 possesses a far broader protection specificity, being required to avoid the toxic effects of As(III), As(V), Cr(III), Cr(VI), Se(IV), as well as Cd(II) and Ni(II), and to varying lesser degrees Co(II), Cu(II), Fe(II), Ag(I), Hg(II), cumene and t‐butyl hydroperoxides. In contrast, deletion of URE2 greatly enhances a cell's ability to withstand toxic concentrations of Zn(II) and Mo(VI). In the case of Cd(II), Ure2 does not function to decrease intracellular Cd(II) levels or influence glutathione availability for glutathionation. In fact, ure2 hypersensitivity to Cd(II) remains the same, even when glutathione is used as sole source of nitrogen for cell growth. These data suggest that Ure2 possesses a central role in metal ion detoxification, a role not demonstrably shared by either of the two known S. cerevisiae glutathione S‐transferases, Gtt1 and Gtt2, or the two glutaredoxins, Grx1 and Grx2, that also possess glutathione S‐transferase activity. Copyright © 2005 John Wiley & Sons, Ltd.
SFP1 is involved in cell size modulation in respiro‐fermentative growth conditions
Authors: Cipollina Chiara , Alberghina Lilia , Porro Danilo , Vai Marina
Published: April 2005

Saccharomyces cerevisiae grows fast on glucose, while growth slows down on ethanol as cells move from glucose fermentation to oxidative metabolism. The type of carbon source influences both the specific growth rate and cell cycle progression, as well as cell size. Yeast cells grown on glucose have a larger size than cells grown on ethanol. Here, we analysed the behaviour of a sfp1 null mutant during balanced and transitory states of growth in batch in response to changes in the growth medium carbon sources. In a screening for mutants affected in cell size at Start, SFP1 has been identified as a gene whose deletion caused one of the smallest whi phenotype. Findings presented in this work indicate that in the sfp1 null mutant the reduction in cell size is not only a consequence of the reduced growth rate but it is tightly linked to the cellular metabolism. The SFP1 gene product is required to sustain the increase of both rRNA and protein content that in wild‐type cells takes place in respiro‐fermentative growth conditions, while it seems dispensable for growth on non‐fermentable carbon sources. It follows that sfp1 cells growing on ethanol have a larger size than cells growing on glucose and, noticeably, the former enter the S phase with a critical cell size higher than the latter. These features, combined with the role of Sfp1p as a transcriptional factor, suggest that Sfp1p could be an important element in the control of the cell size modulated by nutrients. Copyright © 2005 John Wiley & Sons, Ltd.
Warmer tropics during the mid‐Pliocene? Evidence from alkenone paleothermometry and a fully coupled ocean‐atmosphere GCM
Authors: Haywood Alan M. , Dekens Petra , Ravelo Ana Christina , Williams Mark
Published: March 2005

Traditional reconstructions of sea‐surface temperatures (SSTs) produced by the Pliocene Research Interpretations and Synoptic Mapping (PRISM) Group indicate that mid‐Pliocene surface ocean temperatures were unchanged or slightly cooler than modern at the tropics and low latitudes and significantly warmer at higher latitudes, particularly in the North Atlantic. This change in the latitudinal pattern of SSTs has been attributed to enhanced meridional ocean heat transport generated by more vigorous surface ocean gyres and/or thermohaline circulation (THC). This study derives new SST estimates using the alkenone paleothermometer in the Pacific Ocean. These estimates, combined with published alkenone SST data from two Atlantic sites, are located in tropical and subtropical regions where the distribution of PRISM sites is sparse. A fully coupled ocean‐atmosphere general circulation model (OAGCM) running for the mid‐Pliocene was also used to predict SST. Significant differences are noted between absolute PRISM SSTs interpolated to our core locations and alkenone‐derived SSTs. These differences may be related to errors in the PRISM and alkenone paleothermometry estimates or to regional differences between localities where data was collected. However, the available alkenone and model‐based SST estimates are consistent in the sign of temperature change they predict and provide the first indication of warmer SSTs during the mid‐Pliocene in the tropics and subtropics. This contrasts with PRISM's estimates of unchanged or slightly cooler SSTs for the same geographical regions. The pattern of SSTs, produced by alkenone estimates and modeling, is not characteristic of that produced by enhanced meridional ocean heat transport or THC. Instead, the pattern is similar to that which might be expected as a result of higher concentrations of atmospheric CO2, which would act to warm the oceans at the tropics and other latitudes. Furthermore, model diagnostics indicate that reduced sea ice and terrestrial ice sheet extents and a strong ice‐albedo feedback played a major role in forcing mid‐Pliocene warmth. Further work aimed at validating these conclusions should concentrate on expanding the mid‐Pliocene SST data set, particularly at low latitudes, as well as undertaking model/model comparisons to assess model dependency of the results.
The spectrum of waves and turbulence at the tropopause
Authors: Duck Thomas J. , Whiteway James A.
Published: April 2005

Aircraft measurements of winds, temperatures, and composition were conducted with a high‐altitude aircraft in the tropopause region above Northern Wales during May and June 2000. Observations on 6 June 2000 along three vertically stacked horizontal flight legs show fluctuations due to both gravity waves and turbulence. Horizontal kinetic energy spectra determined from the measurements extend to 3 m in wavelength, the smallest scales yet available at these heights. The vertical wind spectrum for strong turbulence is considerably different in both shape and intensity from the non‐turbulent spectrum. A sharp knee in the turbulent spectrum at 100 m wavelength is associated with the equipartition of kinetic energy in three dimensions. At other scales the vertical motions are relatively suppressed. A wave with 500 m wavelength was found, and provides a transition between the turbulent and non‐turbulent cases.
Drifting field‐aligned density structures in the night‐side polar cap
Authors: Santolík O. , Persoon A. M. , Gurnett D. A. , Décréau P. M. E. , Pickett J. S. , Maršálek O. , Maksimovic M. , Cornilleau‐Wehrlin N.
Published: March 2005

Spatio‐temporal properties of density irregularities in the night‐side polar cap are inferred from multi‐point observations of auroral hiss at a radial distance of 5 Earth radii. In this case study, we use high resolution data of the wave instruments onboard the four Cluster spacecraft to estimate the local plasma density, obtaining values close to 1 cm−3 with density depletions decreasing down to 0.15 cm−3. Combined analysis in different points in space conclusively shows for the first time that these density structures are field‐aligned and that they predominantly drift in the anti‐sunward direction at speeds of a few km/s. This corresponds to a dawn‐to‐dusk convection electric field of approximately 1 mV/m. The transverse dimension of the observed density depletions, mapped down to the ionospheric heights, is of the order of a few tens of km. Their lifetime is probably longer than tens of seconds.
Seasonal cycle and intraseasonal oscillations in the interannual variability over the monsoon region
Authors: Goswami P. , Sijikumar S. , Mandal A.
Published: March 2005

A characteristic seasonal cycle in the interannual variability (IAV) of dynamical fields over the Indian summer monsoon (ISM) region is revealed by an investigation of daily fields from a 40‐year global data set from NCEP. The IAV, measured in terms of standard deviation, is remarkably suppressed over the monsoon region during June to September. Time‐latitude distribution of IAV shows that a suppression of IAV in the summer months is a general feature, if not as pronounced as over ISM, of the northern hemisphere. Other new features revealed by our analysis are (a) a differential, nearly out of phase behaviour between zonal and meridional wind components north of 30N, and (b) strong intraseasonal oscillations in IAV, which are once again suppressed during the monsoon months. The low IAV implies a weaker contrast in these fields for different years; implications of this feature for long range forecasting of monsoon are discussed.
Wave activity above the ionosphere of Titan: Predictions for the Cassini mission
Authors: Dóbé Zoltán , Szegő Károly
Published: March 2005

In this paper we present a study of the beam‐driven wave generation mechanisms in linear approximation which are viable in the flowside plasma mantle of Saturn's moon, Titan. The flowside plasma mantle is defined, by analogy with the dayside plasma mantle of the planet Venus and Mars, as being the interaction region between the “cold” ionospheric plasma and “hot” streaming plasma of magnetospheric or solar wind origin, with both types of plasma being present in comparable densities. Since no in situ plasma and field measurements are currently available in Titan's flowside mantle, we performed our model calculations in a broad plasma parameter space encompassing the plasma characteristics determined by Voyager 1 in Titan's wake. Two types of beam instability modes were found to be dominant: a fluid‐like (nonresonant) modified two‐stream instability (MTSI) and the kinetic (beam resonant) ion‐ion acoustic instability (IIAI). The two instability modes are characterized by distinct frequency ranges (an order or below the lower hybrid frequency for the MTSI and a few times the lower hybrid frequency for the IIAI) and are found to be dominant in well‐separated spatial regions determined by the presence/absence of cold ionospheric electrons. Giving a global rather than a specific description of the instability types expected to be the most important growing modes within Titan's flowside mantle, we intend to make predictions concerning the wave characteristics of the dominant wave modes measurable by the plasma wave instrument on board the Cassini spacecraft.
Multipoint observations of transient reconnection signatures in the cusp precipitation: A Cluster‐IMAGE detailed case study
Authors: Bosqued J. M. , Escoubet C. P. , Frey H. U. , Dunlop M. , Berchem J. , Marchaudon A. , Cerisier J. C. , Fazakerley A. , Budnik E. , Lavraud B. , Rème H. , Laakso H. , Balogh A.
Published: March 2005

This paper uses 90 min of Cluster multipoint data at ∼5 RE altitude together with global dayside imaging data provided by the IMAGE‐SI‐12 instrument to analyze the northern cusp crossed on 14 July 2001, during a period of high solar wind pressure Psw and strongly duskward interplanetary magnetic field (IMF). Simultaneous observations reveal intense cusp activity in the postnoon sector, characterized by multiple, impulsive energy‐dispersed ion injections, with a recurrence time of ∼8–10 min or less. Most of these transient signatures correspond one to one with repeated Psw enhancements. A multipoint analysis reveals that field‐aligned current sheets associated with ion steps are moving predominantly westward with a velocity, up to ∼20 km/s, in agreement with a flux tube motion controlled by magnetic tension forces when IMF By ≫ 0. These data are used to infer a source region located at ∼7–13 RE from Cluster, that is, on the dusk flank of the compressed magnetosphere, around 17–18 magnetic local time. We interpret these very dynamic and transient features as probable signatures of pulsed magnetic reconnection that is operating in a localized region of the magnetopause centered in the preferential antiparallel merging site. Our results suggest that the reconnection rate is not spontaneously self‐varying but may be directly modulated by either upstream dynamic pressure Psw or changes in the IMF polarity.
Study of ionospheric response to the 4B flare on 28 October 2003 using International GPS Service network data
Authors: Zhang D. H. , Xiao Z.
Published: March 2005

Using the GPS data from as many as 114 GPS stations of the International GPS Service for Geodynamics (IGS), the morphological features of the ionospheric total electron content (TEC) variations on the sunlit hemisphere during the 4B solar flare on 28 October 2003 is studied. It is found that the strongest sudden increase of TEC (SITEC) happened during the flare, and the magnitudes of SITEC vary at regions with different local solar zenith angle (SZA). In the northern hemisphere, the TEC enhancement is approximately symmetrical to the local noon, and its value is usually greater than 14 TECU (1 TECU = 1016/m2) if the SZA is less than 60°. On the whole, as the SZA increases, the value of TEC enhancement in the northern hemisphere decreases. It is worth mentioning that even in the regions of SZA between 90° and 100°, the SITEC was still seen from the temporal TEC curves. Using a photochemical model, the electron production rate over the sunlit boundary region is calculated and some obvious features of SITEC over this region are analyzed. In the polar region, the effect of this flare on the ionosphere exceeds the effect of the ionospheric scintillations and it seems that the ionosphere in the northern polar region responses more sensitively to this flare. In the end, superimposed on the curves of the rate of TEC change, there are some small disturbances (spikes) synchronously appearing on all curves and thus indicating an existence of similar structures in the EUV band of the flare.
Generation mechanism of electrostatic solitary structures in the Earth's auroral region
Authors: Lu Q. M. , Wang D. Y. , Wang S.
Published: March 2005

Satellite observations have revealed electrostatic solitary structures in the Earth's auroral region. These structures have positive electrostatic potentials and move along the ambient magnetic field. In this paper we performed one‐dimensional electrostatic particle simulations of electrostatic solitary waves (ESW) in plasma composed of three electron components: cold, hot, and beam electrons. First, the nearly monochromatic electrostatic acoustic waves are excited. When the amplitude of the electron acoustic (EA) waves is sufficiently large, part of hot and beam electrons are trapped by the electron acoustic waves. These waves coalesce each other during their nonlinear evolution, and at last the solitary structures with travel speed related to the beam velocity are formed at the quasi‐equilibrium stage. These structures have positive potential signatures, and they seem to be stable. Electron density cavities for cold electron component are always accompanied with these structures. In addition, the corresponding electric fields have a bipolar structure, which has also been observed in the Earth's auroral region recently. The conditions for existence of such solitary structures are investigated through our simulations, and the comparisons between our simulated results and satellite observations in the Earth's auroral regions are also discussed.
Factors controlling ionospheric outflows as observed at intermediate altitudes
Authors: Strangeway R. J. , Ergun R. E. , Su Y.‐J. , Carlson C. W. , Elphic R. C.
Published: March 2005

Data acquired by the Fast Auroral Snapshot (FAST) Small Explorer during the 24–25 September 1998 geomagnetic storm have been used to determine the controlling parameters for ionospheric outflows. The data were restricted to dayside magnetic local times. Two primary sources of ion outflows are considered: ion heating through dissipation of downward Poynting flux and electron heating through soft electron precipitation. Ion outflows are shown to be correlated with both, although ion outflows have a higher correlation with soft electrons, measured by the density of precipitating electrons. At 4000 km altitude it is found that fi = 1.022 × 109±0.341nep2.200±0.489, where fi is the ion flux in cm−2 s−1 and nep is precipitating electron density, with a correlation coefficient r = 0.855, based on log‐log regression. This scaling law can be mapped to other altitudes by scaling the flux and density with the magnetic field magnitude. The ion flux is also correlated with the Poynting flux, fi = 2.142 × 107±0.242S1.265±0.445, where S is the Poynting flux at 4000 km altitude in mW m−2 and r = 0.721. Either of these two scaling laws can be used specify ion outflow fluxes, since there is a strong intercorrelation between the various parameters. In particular the present study cannot completely eliminate either of the two candidate processes (ion versus electron heating in the ionosphere, corresponding to Poynting flux versus soft electron precipitation). Soft electron precipitation does have a higher correlation coefficient, however, and if possible the precipitating electron density scaling law should be used. Since Poynting flux may be more easily specified in global simulations, for example, this scaling law is a useful alternate. For the interval under study the ion outflows were dominated by oxygen ions, predominantly in the form of ion conics, with a characteristic energy of order 10–30 eV.
Nonlinear Alfvén, magnetosonic, sound, and electron inertial waves in fluid formalism
Authors: Stasiewicz K.
Published: March 2005

A fluid model of nonlinear electron and ion inertial waves in anisotropic plasmas is presented. The model has been verified for plasma beta (ratio of kinetic/magnetic pressures) in a range between 0.1 and 15. It is shown that warm plasmas support four types of nonlinear waves, which correspond to four linear modes, Alfvénic, magnetosonic, sound, and electron inertial waves. Each of these nonlinear modes has slow and fast versions. Modes slower than the sound speed have left‐handed polarization for the transverse magnetic field, while the faster modes have right‐handed polarization. It is shown by direct integration that the exponential growth rate of nonlinear modes is balanced by the ion and electron dispersion leading to solutions in the form of trains of solitons or cnoidal waves. By using a novel technique of phase portraits, it is shown how the dispersive properties of electron and ion inertial waves change at the transition between warm and hot plasmas (β ≈ 1) and how trains of solitons (“mirror modes”) are produced in a hot, anisotropic plasma. The applicability of the model is illustrated by showing that the electric currents carried by nonlinear waves measured on Cluster spacecraft in the magnetosheath at β ≈ 15 are well reproduced by currents derived from the theoretical model.
Collisional removal of O2(b1Σg+, υ = 1) by O2 at thermospheric temperatures
Authors: Pejaković Dušan A. , Wouters Eloy R. , Phillips Kristin E. , Slanger Tom G. , Copeland Richard A. , Kalogerakis Konstantinos S.
Published: March 2005

Collisional removal of O2(b1Σg+, υ = 1) by O2 is investigated at temperatures relevant to the lower thermosphere. A two‐laser technique is used, in which the visible output of the first laser directly excites ground‐state oxygen molecules to the υ = 1 level of the b1Σg+ state and the ultraviolet output of the second laser probes the O2(b1Σg+, υ = 1) population by resonantly enhanced multiphoton ionization via the υ = 4 level of the d1Πg Rydberg state. The collisional removal rate coefficient increases with temperature by a factor of five in the range 300–1000 K, with a value of about 8 × 10−11 cm3 s−1 near 1000 K. Given the magnitude of the rate coefficient, the removal by O2 plays a dominant role in controlling the population of O2(b1Σg+, υ = 1) in the mesosphere and lower thermosphere at altitudes below 150 km and likely continues to be an important removal pathway at altitudes up to about 200 km.
Wind‐induced Kuroshio warm water intrusion into Sagami Bay
Authors: Hinata H. , Yanagi T. , Takao T. , Kawamura H.
Published: March 2005

The mechanisms of the periodic Kuroshio warm water intrusion (KWWI) into Sagami Bay through the Oshima West Channel (OWC) and the fluctuation of the current field in the bay were investigated using high‐frequency oceanic radar observation data, satellite imagery, and meteorological data. During the period from 15 December 2000 to 16 January 2001 the Kuroshio took a nonlarge meander path, looping south around the Kii Peninsula and then turning sharply north toward the Izu Peninsula (IP). Kuroshio warm water (KWW) then flowed into Sagami Bay periodically through the OWC on a synoptic timescale of 8–11 days. Statistical analysis of the data indicated that the occurrence of the KWWI and the variability in the Kuroshio front were highly coherent with wind velocity field fluctuations corresponding to the passage of cyclones across northern Japan. When southward to southwestward winds dominated in and around Sagami Bay, the Kuroshio front approached the southern coast of the IP, and then the KWW strongly intruded into the bay through the OWC. When eastward to northeastward winds prevailed, the front moved offshore about 10–20 km, ending the KWWI. The distances of the Kuroshio front movements were consistent with the internal radius of the deformation estimated from conductivity‐temperature‐depth data collected off the IP, suggesting that the Kuroshio front movement was induced by the onshore‐offshore surface Ekman transport associated with the wind velocity field regime shift corresponding to the passage of cyclones. In addition, examination of the vorticity dynamics in the northern part of the bay based on radar‐derived surface current data indicated that the cyclonic circulation generated in the bay was enhanced due to the transport of the positive relative vorticity by the KWWI plus the horizontal convergence accompanied by the stretching of the vorticity.
Diurnal variability in currents and temperature on the continental shelf between central and southern California
Authors: Pidgeon Emily J. , Winant Clinton D.
Published: March 2005

Long time series are used to describe the diurnal variability in the meteorological and astronomical tidal forcing and the temperature and current response on the continental shelf of California between Port San Luis and Port Hueneme. Spectral characteristics are used to attribute the response to each of the forcing mechanisms. The diurnal temperature field is decomposed into two dominant vertical modes. A surface‐enhanced mode is coherent with the meteorological forcing, suggesting that it is a direct response to local heating and wind forcing. The amplitude of the second mode is maximum at middepth. Spectra of this mode exhibit multiple peaks at frequencies corresponding to the astronomical tidal forcing. The phase difference between the middepth mode and the tidally dominated sea level is not consistent across the region. We conclude that this mode is a localized baroclinic response to the astronomical tidal forcing. The diurnal velocity field is dominated by a clockwise component. At the surface this component is coherent across the study region, and it is also coherent with the diurnal wind stress, suggesting that it is a direct response to the diurnal heating and wind forcing. Coherence with the surface‐enhanced temperature mode further confirms this. A weaker, barotropic counterclockwise component is also present in the diurnal velocity field. Spectra of this component exhibit multiple peaks at periods corresponding to the astronomical tidal forcing. The phase difference between this component and the surface elevation varies little between the observational sites. We conclude that this velocity component represents a barotropic response to astronomical forcing that is coherent over the study area.
Effect of tidal flat on the thermal effluent dispersion from a power plant
Authors: Yanagi Tetsuo , Sugimatsu Koichi , Shibaki Hidenori , Shin Hong‐Ryeol , Kim Hong‐Sun
Published: March 2005

The effect of a tidal flat on the dispersion of thermal effluent from the nuclear power plant at YongGwang (5.8 × 106 kW) along the west coast of Korea was investigated using intensive field observations and three‐dimensional numerical simulations. The calculated sea surface temperature distribution reproduces well the observed one with a root mean square error of 0.53°C. A water column on the tidal flat area received a heat influx of 168 W m−2 on 17 April 2003 and transported the received heat to the adjacent coastal water at low water. The total heat supply from the tidal flat area to the coastal water was 6.6 × 1010 W, and was larger by about 1 order of magnitude than that from the power plant of 7.0 × 109 W on 17 April 2003, which was a fine day at spring tide. This fact shows that the effect of the tidal flat on the thermal effluent from the power plant is very large.
Near‐bottom shear stresses in a small, highly stratified estuary
Authors: Fugate David C. , Chant Robert J.
Published: March 2005

This paper examines near‐bottom shear stresses at two locations in a small, highly stratified estuary: the Navesink River, New Jersey, USA. The shear stresses obtained from acoustic Doppler current profilers (ADCPs) operating in the recently developed mode 11 at a high spatial resolution are examined in detail. Measurement noise of the ADCP is estimated using autocorrelation analyses and is found to be small but correlated with velocity. Measurement noise in estimates of Reynolds stress is found to be somewhat smaller than that obtained in earlier studies for the ADCP operating in mode 4. Internal waves may have produced observed correlated oscillatory motions. The effect of these motions on Reynolds stress estimates is quantified and shown to be at least an order of magnitude less than the total measured stress and probably much less. The high‐spatial‐resolution profiles from the ADCP operating in mode 11 allow excellent measurements of near‐bed vertical velocity gradients. Log profile estimates of stress are poorly related to Reynolds estimates, even when stability measures based on near‐bed density gradients are taken into account. We show that upper layer pycnoclines likely inhibit turbulence and bias log profile estimates even at a half meter above the bed, where the water column is well mixed.
Construction of the dual family of Gazeau–Klauder coherent states via temporally stable nonlinear coherent states
Authors: Roknizadeh R. , Tavassoly M. K.
Published: March 2005

Using the analytic representation of the so-called Gazeau–Klauder coherent states (CSs), we shall demonstrate that how a new class of generalized CSs, namely the family of dual states associated with theses states, can be constructed through viewing these states as temporally stable nonlinear CSs. Also we find that the ladder operators, as well as the displacement type operator corresponding to these two pairs of generalized CSs, may be easily obtained using our formalism, without employing the supersymmetric quantum mechanics (SUSYQM) techniques. Then, we have applied this method to some physical systems with known spectrum, such as Pöschl–Teller, infinite well, Morse potential and hydrogenlike spectrum as some quantum mechanical systems. Finally, we propose the generalized form of the Gazeau–Klauder CS and the corresponding dual family.
A theoretical study for mechanical contact between carbon nanotubes
Authors: Takagi Yoshiteru , Uda Tsuyoshi , Ohno Takahisa
Published: March 2005

We have theoretically investigated motions of single-walled carbon nanotubes (SWNTs) which are mounted on a flat substrate layer of SWNTs by tight-binding molecular dynamics simulations. One of the most interesting motions is the conversion of force and torque, where the force and torque acting initially on the mounted tube finally results in the lateral motion and rolling of the supporting tubes in the substrate. This motion is well understood in terms of the total energy surface of the SWNT/SWNT system. It is suggested that an undulation of the total energy surface plays a role as an atomic-scale gear tooth in the field of nanomechanics, in spite of the atomically smooth surface of SWNT.
Effect of chemical structure on the isobaric and isochoric fragility in polychlorinated biphenyls
Authors: Roland C. M. , Casalini R.
Published: April 2005

Pressure-volume-temperature data, along with dielectric relaxation measurements, are reported for a series of polychlorinated biphenyls (PCB), differing in the number of chlorine atoms on their phenyl rings. Analysis of the results reveals that with increasing chlorine content, the relaxation times of the PCB become governed to a greater degree by density ρ relative to the effect of temperature T. This result is consistent with the respective magnitudes of the scaling exponent γ yielding superpositioning of the relaxation times measured at various temperatures and pressures, when plotted versus ργ∕T. While at constant (atmospheric) pressure, fragilities for the various PCB are equivalent, the fragility at constant volume varies inversely with chlorine content. Evidently, the presence of bulkier chlorine atoms on the phenyl rings magnifies the effect which the density has on the relaxation dynamics.
Structural, electronic, and dielectric properties of ultrathin zirconia films on silicon
Authors: Sayan S. , Nguyen N. V. , Ehrstein J. , Emge T. , Garfunkel E. , Croft M. , Zhao Xinyuan , Vanderbilt David , Levin I. , Gusev E. P. , Kim Hyoungsub , McIntyre P. J.
Published: April 2005

As high-permittivity dielectrics approach use in metal-oxide-semiconductor field-effect transistor production, an atomic level understanding of their dielectric properties and the capacitance of structures made from them is being rigorously pursued. We and others have shown that crystal structure of ZrO2 films have considerable effects on permittivity as well as band gap. The as-deposited films reported here appear amorphous below a critical thickness (∼5.4nm) and transform to a predominantly tetragonal phase upon annealing. At much higher thickness the stable monoclinic phase will be favored. These phase changes may have a significant effect on channel mobility.
Quantum averaging and resonances: Two-level atom in a one-mode quantized field
Authors: Amniat-Talab M. , Guérin S. , Jauslin H. R.
Published: March 2005

We construct a nonperturbative approach based on quantum averaging combined with resonant transformations to detect the resonances of a given Hamiltonian and to treat them. This approach, which generalizes the rotating-wave approximation, takes into account the resonances at low field and also at high field (nonlinear resonances). This allows us to derive effective Hamiltonians that contain the qualitative features of the spectrum, i.e., crossings and avoided crossings, as a function of the coupling constant. At a second stage the precision of the spectrum can be improved quantitatively by standard perturbative methods like contact transformations. We illustrate this method by determining the spectrum of a two-level atom interacting with a single-mode quantized field.
Dipole moments of HDO in highly excited vibrational states measured by Stark induced photofragment quantum beat spectroscopy
Authors: Theulé Patrice , Callegari Andrea , Rizzo Thomas R. , Muenter John S.
Published: March 2005

We report here a measurement of electric dipole moments in highly vibrationally excited HDO molecules. We use photofragment yield detected quantum beat spectroscopy to determine electric field induced splittings of the J=1 rotational levels of HDO excited with 4, 5, and 8 quanta of vibration in the OH stretching mode. The splittings allow us to deduce μa and μb, the projections of dipole moment onto the molecular rotation inertial axes. We compare the measured HDO dipole moment components with the results of quantitative calculations based on Morse oscillator wave functions and an ab initio dipole moment surface. The vibrational dependence of the dipole moment components reflect both structural and electronic changes in HDO upon vibrational excitation; principally the vibrational dependence of the O–H bond length and bond angle, and the resulting change in orientation of the principal inertial coordinate system. The dipole moment data also provide a sensitive test of theoretical dipole moment and potential energy surfaces, particularly for molecular configurations far from equilibrium.
Geometry optimization of periodic systems using internal coordinates
Authors: Bučko Tomáš , Hafner Jürgen , Ángyán János G.
Published: March 2005

An algorithm is proposed for the structural optimization of periodic systems in internal (chemical) coordinates. Internal coordinates may include in addition to the usual bond lengths, bond angles, out-of-plane and dihedral angles, various “lattice internal coordinates” such as cell edge lengths, cell angles, cell volume, etc. The coordinate transformations between Cartesian (or fractional) and internal coordinates are performed by a generalized Wilson B-matrix, which in contrast to the previous formulation by Kudin et al. [J. Chem. Phys. 114, 2919 (2001)] includes the explicit dependence of the lattice parameters on the positions of all unit cell atoms. The performance of the method, including constrained optimizations, is demonstrated on several examples, such as layered and microporous materials (gibbsite and chabazite) as well as the urea molecular crystal. The calculations used energies and forces from the ab initio density functional theory plane wave method in the projector-augmented wave formalism.
Scattering amplitude and scattering phase for the Schrödinger equation with strong magnetic field
Authors: Michel Laurent
Published: March 2005

In this paper we consider the Schrödinger equation with constant magnetic field of strength b>0 in all dimension. We study the behavior of the scattering amplitude and the scattering phase when the parameter b goes to infinity and the energy is far from the Landau levels.
An in situ study of the t-butyllithium initiated polymerization of butadiene in d-heptane via small angle neutron scattering and H1-NMR
Authors: Niu A. Z. , Stellbrink J. , Allgaier J. , Willner L. , Radulescu A. , Richter D. , Koenig B. W. , May R. P. , Fetters L. J.
Published: April 2005

We present a combined H1-NMR and small angle neutron scattering in situ study of the anionic polymerization of butadiene using t-butyllithium as the initiator. Both initiation and propagation phases were explored. This combined approach allows the structural and kinetic characteristics to be accessed and cross compared. The use of the D22 instrument (ILL Grenoble) permits the attainment of Q≈2×10−3Å. This, in turn, led to the identification of coexisting large-scale and smaller aggregates during all stages of the polymerization. The smaller aggregates contain most of the reacted monomers. Their structure changes from high functionality wormlike chains at early stages of the reaction to starlike aggregates where the crossover occurs at a degree of polymerization of ≈40. The initiation event involved these small, high functionality (≈120) aggregates that apparently consisted of cross-associated t-butyllithium with the newly formed allylic-lithium head groups. As the initiation event progressed the initiation rate increased while the functionality of these small aggregates decreased and their size increased. Propagation, in the absence of initiation, was found to have a rate constant that was molecular weight dependent. At ∼11kg∕mol the measured polymerization rate was found to increase while no further structural changes were seen.
The multicomponent generalized Kaup–Newell hierarchy and its multicomponent integrable couplings system with two arbitrary functions
Authors: Xia Tiecheng , Fan Engui
Published: March 2005

We devise a new simple loop algebra G̃M and an isospectral problem. By making use of the Tu scheme, the multicomponent generalized Kaup–Newell hierarchy is obtained. Furthermore, an expanding loop algebra F̃M of the loop algebra G̃M is presented. Based on F̃M, the multicomponent integrable couplings system with two arbitrary functions of the multicomponent generalized Kaup–Newell hierarchy are worked out. The method can be applied to other nonlinear evolution equations hierarchy.
Two-color resonant four-wave mixing spectroscopy of highly predissociated levels in the ÃA12 state of CH3S
Authors: Liu Ching-Ping , Reid Scott A. , Lee Yuan-Pern
Published: March 2005

We report results of two-color resonant four-wave mixing experiments on highly predissociated levels of the methylthio (or thiomethoxy) radical CH3S in its first excited electronic state ÃA12. Following photolysis of jet-cooled dimethyl disulfide at 248nm, the spectra were measured with a hole-burning scheme in which the probe laser excited specific rotational transitions in band 33. The spectral simplification afforded by the two-color method allows accurate determination of line positions and homogeneous linewidths, which are reported for the C–S stretching states 3v(v=3–7) and combination states 113v(v=0–2), 213v(v=3–6), and 11213v(v=0,1) involving the symmetric CH3 stretching (ν1) mode and the CH3 umbrella (ν2) mode. The spectra show pronounced mode specificity, as the homogeneous linewidth of levels with similar energies varies up to two orders of magnitude; ν3 is clearly a promoting mode for dissociation. Derived vibrational wave numbers ω1′, ω2′, and ω3′ of the Ã state agree satisfactorily with ab initio predictions.
Phase coexistence in heterogeneous porous media: A new extension to Gibbs ensemble Monte Carlo simulation method
Authors: Puibasset Joël
Published: April 2005

The effect of confinement on phase behavior of simple fluids is still an area of intensive research. In between experiment and theory, molecular simulation is a powerful tool to study the effect of confinement in realistic porous materials, containing some disorder. Previous simulation works aiming at establishing the phase diagram of a confined Lennard-Jones-type fluid, concentrated on simple pore geometries (slits or cylinders). The development of the Gibbs ensemble Monte Carlo technique by Panagiotopoulos [Mol. Phys. 61, 813 (1987)], greatly favored the study of such simple geometries for two reasons. First, the technique is very efficient to calculate the phase diagram, since each run (at a given temperature) converges directly to an equilibrium between a gaslike and a liquidlike phase. Second, due to volume exchange procedure between the two phases, at least one invariant direction of space is required for applicability of this method, which is the case for slits or cylinders. Generally, the introduction of some disorder in such simple pores breaks the initial invariance in one of the space directions and prevents to work in the Gibbs ensemble. The simulation techniques for such disordered systems are numerous (grand canonical Monte Carlo, molecular dynamics, histogram reweighting, N-P-T+test method, Gibbs–Duhem integration procedure, etc.). However, the Gibbs ensemble technique, which gives directly the coexistence between phases, was never generalized to such systems. In this work, we focus on two weakly disordered pores for which a modified Gibbs ensemble Monte Carlo technique can be applied. One of the pores is geometrically undulated, whereas the second is cylindrical but presents a chemical variation which gives rise to a modulation of the wall potential. In the first case almost no change in the phase diagram is observed, whereas in the second strong modifications are reported.
Spherical functions on homogeneous superspaces
Authors: Zhang R. B. , Zou Y. M.
Published: March 2005

Homogeneous superspaces arising from the general linear supergroup are studied within a Hopf algebraic framework. Spherical functions on homogeneous superspaces are introduced, and the structures of the superalgebras of the spherical functions on classes of homogeneous superspaces are described explicitly.