bluuebunny/crossref_metadata_2025 huggingface dataset:
Aseismic slip transients emerge spontaneously in three‐dimensional rate and state modeling of subduction earthquake sequences
Authors: Liu Yajing , Rice James R.
Published: August 2005

To investigate the possible physical mechanisms of recently observed aseismic slip events in the Cascadia, Japan and Mexico subduction zones, we apply a Dieterich‐Ruina rate and state friction law to a three dimensional model of a shallow subduction fault. That is loaded by imposed steady plate slip rate far downdip along the thrust interface. Friction properties are temperature and hence depth‐dependent, such that sliding is stable at depths below about 30 km. The system is perturbed into a significantly nonuniform slip mode along strike by introducing small along‐strike variations in the constitutive parameters a and (a − b). In addition to large heterogeneous earthquake slip at seismogenic depths, and associated postseismic transients, we found that slip events which have clearly aseismic slip rates emerge spontaneously around the downdip end of the seismogenic zone. Both transients which start well after a seismic event, and those which are triggered by other transients, are observed from the simulations. The slip velocity, depth range, and, sometimes, along‐strike migration speed of simulated transients are similar to the observations from natural subduction zones. Unstable‐stable transitional friction properties near the downdip end of the seismogenic zone are suggested to be an ingredient allowing such transients. Simulated transients can weaken the locking intensity of the updip seismogenic zone, while enhancing that of the transition zone. Spatial‐temporal correlation of aseismic transients and nearby seismicity in the Guerrero, Mexico, area suggests that transients may signal a period of increased probability for nucleating their high‐frequency counterparts, as damaging subduction thrust events.
Carbon dioxide diffuse degassing and estimation of heat release from volcanic and hydrothermal systems
Authors: Chiodini G. , Granieri D. , Avino R. , Caliro S. , Costa A. , Werner C.
Published: August 2005

We present a reliable methodology to estimate the energy associated with the subaerial diffuse degassing of volcanic‐hydrothermal fluids. The fumaroles of 15 diffuse degassing structures (DDSs) located in eight volcanic systems in the world were sampled and analyzed. Furthermore, each area was measured for soil temperature gradients and for soil CO2 fluxes. The results show that each hydrothermal or volcanic system is characterized by a typical source fluid which feeds both the fumaroles and diffuse degassing through the soil. Experimental data and the results of physical numerical modeling of the process demonstrate that the heat released by condensation of steam at depth is almost totally transferred by conduction in the uppermost part of the soil. A linear relationship is observed between the log of the steam/gas ratio measured in the fumaroles and the log of the ratio between soil thermal gradient and soil‐gas flux. The main parameter controlling this relation is the thermal conductivity of the soil (Kc). For each area, we computed the values of Kc which range from 0.4 to 2.3 W m−1 °C−1. Using the CO2 soil fluxes as a tracer of the deep fluids, we estimated that the total heat released by steam condensation in the systems considered varies from 1 to 100 MW.
Impact of dams on Yangtze River sediment supply to the sea and delta intertidal wetland response
Authors: Yang S. L. , Zhang J. , Zhu J. , Smith J. P. , Dai S. B. , Gao A. , Li P.
Published: August 2005

On the basis of estimates of sediment accumulation in reservoirs, the impact of 50,000 dams on sediment supply and intertidal wetland response in the Yangtze River catchment is examined. The total storage capacity of reservoirs is 200 × 109m3, or 22% of the Yangtze annual runoff. The sediment accumulation rate in reservoirs has increased from ∼0 in 1950 to >850 × 106t/yr in 2003. Although sediment yield has increased with broader soil erosion in the river basin, the total riverine sediment discharge rate shows a strong decreasing trend from the late 1960s to 2003, likely due to dam construction. Consequently, the total growth rate of intertidal wetlands at the delta front has decreased dramatically. A significant relationship exists between intertidal wetland growth rate and riverine sediment supply that suggests riverine sediment supply is a governing factor in the interannual to interdecadal evolution of delta wetlands. Regression analysis of intertidal wetland growth rate and sediment supply shows that intertidal wetlands at the delta front degrades when the riverine sediment discharge rate reaches a threshold level of <263 × 106t/yr. Owing to the construction of the Three Gorges Dam and other new dams, the sediment discharge rate of the Yangtze River will most likely decrease to below 150 × 106t/yr in the coming decades. Therefore unless current management policies are adjusted, drastic recession of Yangtze River delta intertidal wetlands can be expected to occur.
A double Kirchhoff approximation for very rough surface scattering using the stochastic functional approach
Authors: Wang Zhi Liang , Xu Feng , Jin Ya Qiu , Ogura Hisanao
Published: August 2005

On the basis of the stochastic functional approach, an analytical derivation for the incoherent scattering angular distribution contributed from the double Kirchhoff solution is presented for very rough surface, that is, with both the surface roughness and the correlation length comparable to the wavelength. By the second‐order Kirchhoff approximation and using the propagation shadowing function, the incoherent scattering distribution can be numerically calculated by only the two‐dimensional integrals. The numerical calculations are made for the normalized roughness σ/λ = 1.0, 1.5, and 3.5 and the normalized correlation length ℓ/λ = 1.8 and 5.0. The results show that the backscattering enhancement comes from the cross terms in the second‐order Kirchhoff approximation. However, in order to obtain the calculations agreement well with the Monte Carlo simulation, the angular shadowing effect should also be included, in addition to the propagation shadowing effect.
Structure of magnetic fields in NOAA active regions 0486 and 0501 and in the associated interplanetary ejecta
Authors: Yurchyshyn Vasyl , Hu Qiang , Abramenko Valentyna
Published: August 2005

Spectacular burst of solar activity in October–November 2003, when large solar spots and intense solar flares dominated the solar surface for many consecutive days, caused intense geomagnetic storms. In this paper we analyze solar and interplanetary magnetic fields associated with the storms in October–November 2003. We used space‐ and ground‐based data in order to compare the orientations of the magnetic fields on the solar surface and at 1 AU as well as to estimate parameters of geomagnetic storms during this violent period of geomagnetic activity. Our study further supports earlier reports on the correlation between the coronal mass ejection speed and the strength of the magnetic field in an interplanetary ejecta. A good correspondence was also found between directions of the helical magnetic fields in interplanetary ejecta and in the source active regions. These findings are quite significant in terms of their potential to predict the severity of geomagnetic activity 1–2 days in advance, immediately after an Earth directed solar eruption.
Effect of the thermal tidal oscillation of the atmosphere on tropical cyclones
Authors: Yoshioka M. K. , Kurihara Y. , Ohfuchi W.
Published: August 2005

The thermal tidal oscillation was simulated together with tropical cyclones in an atmospheric general circulation model capable of realistically representing mesoscale phenomena with very high resolution. These two systems differ from each other considerably in both scale and dynamical behavior. Analyzing the numerical data produced by the model, we investigated the regional influence of tropical cyclones on the tidal oscillation, and the effect of the latter on tropical cyclones. It was observed that the tidal oscillation of the surface pressure is not locally disturbed by passing tropical cyclones. It was also revealed that the signal of the tidal oscillation is detectable in the time variations of minimum sea‐level pressure, wind field and rainfall intensity in the central areas of tropical cyclones.
Simulated change of the east Asian circulation under global warming scenario
Authors: Kimoto Masahide
Published: August 2005

Changes in east Asian circulation pattern are investigated by the most recent versions of coupled climate models, one a high resolution version of the CCSR/NIES/FRCGC model and the other an ensemble of 17 state‐of‐the‐art models made available by the international modeling community. These recent model results appear to give more credence to the following aspects: weakened winter monsoon associated with the shallower and northeastward shifted planetary wave trough over the east coast of the Eurasian Continent and increased activity of east Asian monsoonal rain band in summer associated with the strengthening of anticyclonic cells to its south and north.
Interior channels in Martian valleys: Constraints on fluvial erosion by measurements of the Mars Express High Resolution Stereo Camera
Authors: Jaumann R. , Reiss D. , Frei S. , Neukum G. , Scholten F. , Gwinner K. , Roatsch T. , Matz K.‐D. , Mertens V. , Hauber E. , Hoffmann H. , Köhler U. , Head J. W. , Hiesinger H. , Carr M. H.
Published: August 2005

In High Resolution Stereo Camera (HRSC) images of the Mars Express Mission a 130 km long interior channel is identified within a 400 km long valley network system located in the Lybia Montes. Ages of the valley floor and the surroundings as derived from crater counts define a period of ∼350 Myrs during which the valley might have been formed. Based on HRSC stereo measurements the discharge of the interior channel is estimated at ∼4800 m3/s, corresponding to a runoff production rate of ∼1 cm/day. Mass balances indicate erosion rates of a few cm/year implying the erosion activity in the valley to a few thousand years for continuous flow, or one or more orders of magnitude longer time spans for more intermittent flows. Therefore, during the Hesperian, relatively brief but recurring episodes of erosion intervals are more likely than sustained flow.
Elasticity of San Carlos olivine to 8 GPa and 1073 K
Authors: Liu Wei , Kung Jennifer , Li Baosheng
Published: August 2005

Elasticity of San Carlos olivine, (Mg0.9, Fe0.1)2SiO4, has been measured at simultaneous high pressure and high temperature to 8.2 GPa and 1073 K using ultrasonic interferometry in conjunction with synchrotron X‐radiation. The elastic moduli and their pressure and temperature derivatives are precisely determined using a pressure standard free fit using third‐order finite strain equations to the velocity and unit cell volume data in the entire pressure and temperature range, yielding KS0 = 130.3(4) GPa, G0 = 77.4(2) GPa, K′S0 = 4.61(11), G′0 = 1.61(4), ∂KS/∂T = −0.0164(5) GPa/K, and ∂G/∂T = −0.0130(3) GPa/K. Combined with previous thermoelastic data on wadsleyite, the velocity contrasts between α‐ and β‐(Mg, Fe)2SiO4 at 410‐km depth are calculated along a 1673 K adiabatic geotherm with plausible iron partition between the two phases. The fraction of olivine consistent with a ∼5% seismic discontinuity in an anhydrous mantle is constrained to be less than ∼50% with the possibility that a hydrous or a cooler mantle increases the olivine content towards pyrolitic composition.
Filling the South Atlantic anomaly by energetic electrons during a great magnetic storm
Authors: Asikainen T. , Mursula K.
Published: August 2005

We study energetic particles in the inner magnetosphere during the great storm of March 31, 2001, using low‐altitude NOAA‐15 and 16 satellites. The NOAA/SEM‐2 instruments can monitor energetic particles above 30 keV from the equator to nearly polar latitudes. The South Atlantic anomaly (SAA) is seen by NOAA/SEM‐2 as a region of an increased flux of precipitating energetic protons in a limited MLT sector at low latitudes. At 0945 UT the NOAA‐16 satellite observed a strong increase of trapped 100–300 keV electrons at a very low invariant latitude of L = 1.14 in the 02 MLT sector, i.e., a few MLT hours behind SAA. The injected electrons drifted eastwards and joined SAA, as first observed by the NOAA‐15 satellite at 1030 UT in the 07 MLT sector. Thereafter the electrons were permanently trapped within the SAA and drifted around the Earth together with SAA. The lower‐energy (30–100 keV) part of the injected electrons was first detected by NOAA‐16 at 1125 UT in the same MLT, and L region. These electrons drifted longer behind the SAA region at a drift speed which agrees well with the theoretical estimate. Later, they also joined SAA and were thereafter trapped in it. Inside the SAA region the electron fluxes decreased exponentially with an e‐folding decay time of about 8.6 h. The results show that a great storm can effectively fill the SAA region by trapped energetic electrons. We present the observations and discuss the generation of energetic electrons at very low latitudes, as well as the mechanism of trapping them inside the SAA.
Application of modern radiative transfer tools to model laboratory quartz emissivity
Authors: Pitman Karly M. , Wolff Michael J. , Clayton Geoffrey C.
Published: August 2005

Planetary remote sensing of regolith surfaces requires use of theoretical models for interpretation of constituent grain physical properties. In this work, we review and critically evaluate past efforts to strengthen numerical radiative transfer (RT) models with comparison to a trusted set of nadir incidence laboratory quartz emissivity spectra. By first establishing a baseline statistical metric to rate successful model‐laboratory emissivity spectral fits, we assess the efficacy of hybrid computational solutions (Mie theory + numerically exact RT algorithm) to calculate theoretical emissivity values for micron‐sized α‐quartz particles in the thermal infrared (2000–200 cm−1) wave number range. We show that Mie theory, a widely used but poor approximation to irregular grain shape, fails to produce the single scattering albedo and asymmetry parameter needed to arrive at the desired laboratory emissivity values. Through simple numerical experiments, we show that corrections to single scattering albedo and asymmetry parameter values generated via Mie theory become more necessary with increasing grain size. We directly compare the performance of diffraction subtraction and static structure factor corrections to the single scattering albedo, asymmetry parameter, and emissivity for dense packing of grains. Through these sensitivity studies, we provide evidence that, assuming RT methods work well given sufficiently well‐quantified inputs, assumptions about the scatterer itself constitute the most crucial aspect of modeling emissivity values.
Neutrophils and the kallikrein–kinin system in proteinase‐activated receptor 4‐mediated inflammation in rodents
Authors: Houle Steeve , Papez Martin D , Ferazzini Mara , Hollenberg Morley D , Vergnolle Nathalie
Published: August 2005

We evaluated a potential role for proteinase‐activated receptor 4 (PAR4) in a rodent paw inflammation model, with a focus on two main features of inflammation: (1) oedema and (2) granulocyte recruitment.

A PAR4 antagonist (Pepducin P4pal‐10; palmitoyl‐SGRRYGHALR‐NH2) reduced both the oedema and granulocyte recruitment induced by a localized administration of carrageenan in the rat hind paw, pointing to a key role for PAR4 in this inflammation model.

Further, intraplantar injection in the mouse hind paw of a PAR4 agonist (AYPGKF‐NH2), but not its standard PAR4‐inactive peptide control (YAPGKF‐NH2), caused an inflammatory reaction characterized by oedema (increased paw thickness) and granulocyte recruitment (increased paw myeloperoxidase activity). The PAR4 agonist‐induced effects were inhibited in mice pretreated with pepducin P4pal10.

These PAR4 agonist‐mediated effects were not affected by pretreatment with inhibitors of either NO production or prostaglandin release (L‐NAME and indomethacin, respectively).

However, selective immuno‐depletion of neutrophils significantly reduced PAR4 agonist‐induced oedema formation.

Moreover, AYPGKF‐NH2‐induced oedema was also reduced by pretreatment with either a kinin B2 receptor antagonist (icatibant) or a tissue or plasma kallikrein inhibitor (FE999024 and FE999026, respectively), but not with a kinin B1 receptor antagonist (SSR240612).

We conclude: (1) that PAR4 plays an important role in the inflammatory response as it mediates some of the hallmarks of inflammation and (2) that PAR4‐mediated oedema is dependent on the recruitment of neutrophils and components of the kallikrein–kinin system.

British Journal of Pharmacology (2005) 146, 670–678. doi:10.1038/sj.bjp.0706371
The inhibitory effect of alendronate, a nitrogen‐containing bisphosphonate on the PI3K–Akt–NFκB pathway in osteosarcoma cells
Authors: Inoue Ryosuke , Matsuki Nori‐aki , Jing Gao , Kanematsu Takashi , Abe Kihachiro , Hirata Masato
Published: August 2005

Bisphosphonates are inhibitors of tumor cell growth as well as of bone resorption by inducing cell apoptosis. However, little is known regarding the mechanisms by which the drug induces cell apoptosis. The aim of the present study was to determine the effect of alendronate, one of the nitrogen‐containing bisphosphonates on the phoshoinositide 3‐kinase (PI3K)–Akt–NFκB pathway, the major cell survival pathway.

The PI3K–Akt–NFκB pathway was activated in the osteosarcoma cell line MG‐63 treated with tumor necrosis factor‐αor insulin. Saos‐2 was also used in some experiments. This was assessed by the production of phosphatidylinositol 3,4,5‐trisphosphate (PtdIns(3,4,5)P3), increased PI3K activity, phosphorylation of Akt at serine 473 and threonine 308, increase in activity of the inhibitor of nuclear factorκB (IκB) kinase (IKK) and finally phosphorylation of IκB and its subsequent degradation.

Pretreatment with alendronate at 100 μMfor 24 h prior to the stimulation with tumor necrosis factor‐αor insulin partially inhibited the IκB phosphorylation and degradation. These events were more clearly observed in the presence of inhibitors of proteasomes, which are responsible for the degradation of IκB. The drug also partially inhibited the activity of IKK, but almost fully inhibited the phosphorylation of Akt and the production of PtdIns(3,4,5)P3.

The inhibitory effect of alendronate on IκB phosphorylation and degradation was not attenuated by the exogenous addition of geranylgeraniol to replenish the cytosolic isoprenyl lipid substrate.

The present findings demonstrate that alendronate inhibited the PI3K–Akt–NFκB cell survival pathway at the point of PI3K activation, thus indicating the presence of new targets of alendronate.

British Journal of Pharmacology(2005)146, 633–641. doi:10.1038/sj.bjp.0706373
Away from generalized gradient approximation: Orbital-dependent exchange-correlation functionals
Authors: Baerends E. J. , Gritsenko O. V.
Published: August 2005

The local-density approximation of density functional theory (DFT) is remarkably accurate, for instance, for geometries and frequencies, and the generalized gradient approximations have also made bond energies quite reliable. Sometimes, however, one meets with failure in individual cases. One of the possible routes towards better functionals would be the incorporation of orbital dependence (which is an implicit density dependency) in the functionals. We discuss this approach both for energies and for response properties. One possibility is the use of the Hartree–Fock-type exchange energy expression as orbital-dependent functional. We will argue that in spite of the increasing popularity of this approach, it does not offer any advantage over Hartree–Fock for energies. We will advocate not to apply the separation of exchange and correlation, which is so ingrained in quantum chemistry, but to model both simultaneously. For response properties the energies and shapes of the virtual orbitals are crucial. We will discuss the benefits that Kohn–Sham potentials can offer which are derived from either an orbital-dependent energy functional, including the exact-exchange functional, or which can be obtained directly as orbital-dependent functional. We highlight the similarity of the Hartree–Fock and Kohn–Sham occupied orbitals and orbital energies, and the essentially different meanings the virtual orbitals and orbital energies have in these two models. We will show that these differences are beneficial for DFT in the case of localized excitations (in a small molecule or in a fragment), but are detrimental for charge-transfer excitations. Again, orbital dependency, in this case in the exchange-correlation kernel, offers a solution.
Orbital- and state-dependent functionals in density-functional theory
Authors: Görling Andreas
Published: August 2005

Shortcomings of present density-functional methods are considered. Kohn–Sham and time-dependent density-functional methods using orbital- and state-dependent functionals for exchange-correlation energies, potentials, and kernels are discussed as possible remedy for some of these shortcomings. A view on the Kohn–Sham formalism is presented which differs somewhat from the one conventionally taken. The crucial step of constructing local multiplicative exchange-correlation potentials in Kohn–Sham methods based on orbital- and state-dependent functionals is discussed. The description of open-shell systems via a symmetrized Kohn–Sham formalism employing state-dependent exchange-correlation functionals is elucidated. The generalized adiabatic connection Kohn–Sham approach for the self-consistent treatment of excited states within a density-functional framework is considered. In the latter approach orbital- and state-dependent exchange-correlation functionals occur in a density-functional framework which is no longer based on the Hohenberg–Kohn theorem but on a more general relation between electron densities and local multiplicative potentials.
Ab initio density functional theory: The best of both worlds?
Authors: Bartlett Rodney J. , Lotrich Victor F. , Schweigert Igor V.
Published: August 2005

Density functional theory (DFT), in its current local, gradient corrected, and hybrid implementations and their extensions, is approaching an impasse. To continue to progress toward the quality of results demanded by today’s ab initio quantum chemistry encourages a new direction. We believe ab initio DFT is a promising route to pursue. Whereas conventional DFT cannot describe weak interactions, photoelectron spectra, or many potential energy surfaces, ab initio DFT, even in its initial, optimized effective potential, second-order many-body perturbation theory form [OEP (2)-semi canonical], is shown to do all well. In fact, we obtain accuracy that frequently exceeds MP2, being competitive with coupled-cluster theory in some cases. Furthermore, this is accomplished within a relatively fast computational procedure that scales like iterative second order. We illustrate our results with several molecular examples including Ne2,Be2,F2, and benzene.
Time-dependent density functional theory: Past, present, and future
Authors: Burke Kieron , Werschnik Jan , Gross E. K. U.
Published: August 2005

Time-dependent density functional theory (TDDFT) is presently enjoying enormous popularity in quantum chemistry, as a useful tool for extracting electronic excited state energies. This article discusses how TDDFT is much broader in scope, and yields predictions for many more properties. We discuss some of the challenges involved in making accurate predictions for these properties.
Time-resolved coherent anti-Stokes Raman-scattering measurements of I2 in solid Kr: Vibrational dephasing on the ground electronic state at 2.6–32 K
Authors: Kiviniemi Tiina , Aumanen Jukka , Myllyperkiö Pasi , Apkarian V. A. , Pettersson Mika
Published: August 2005

Time-resolved coherent anti-Stokes Raman-scattering (CARS) measurements are carried out for iodine (I2) in solid krypton matrices. The dependence of vibrational dephasing time on temperature and vibrational quantum number v is studied. The v dependence is approximately quadratic, while the temperature dependence of both vibrational dephasing and spectral shift, although weak, fits the exponential form characteristic of dephasing by pseudolocal phonons. The analysis of the data indicates that the frequency of the pseudolocal phonons is ∼30cm−1. The longest dephasing times are observed for v=2 being ∼300ps and limited by inhomogeneous broadening. An increase in the dephasing rate of v=2 as the temperature is lowered to T=2.6K is taken as a clear indication of lattice-strain-induced inhomogeneity of the ensemble coherence.
Anisotropic thermal expansion of monoclinic potassium lutetium tungstate single crystals
Authors: Wang Kunpeng , Zhang Jianxiu , Wang Jiyang , Zhang Huaijin , Wang Zhengping , Yu Wentao , Wang Xuping , Lu Qingming , Ba Mingfang , Boughton Robert I.
Published: August 2005

The anisotropic thermal expansion of a single crystal of KLu(WO4)2(KLuW), obtained by the top-seeded solution growth method, has been investigated over a wide temperature range (50–600 °C). The linear thermal-expansion tensor has been determined and its principal X, Y, and Z axes are in the [705], [010], and [107] crystallographic directions, respectively. The principal thermal-expansion coefficients αI, αII, and αIII are 12.8×10−6, 7.8×10−6, and 22.2×10−6K−1, respectively. The principal axis with maximum thermal expansion (Z with αIII=22.2×10−6) is located at 10.37° from the c axis. In comparison with KGd(WO4)2 and KYb(WO4)2, the thermal-expansion anisotropy of KLuW is weaker and therefore optical-quality crystals are easier to obtain than with KGdW and KYbW from a thermal-expansion standpoint.
State-to-state scattering of D2 from Cu(100) and Pd(111)
Authors: Shackman Leah C. , Sitz Greg O.
Published: August 2005

Results from state resolved experiments are presented for the interaction of D2(v=1,J=2) with Cu(100) and Pd(111). The reflected molecules were probed using quantum state specific spectroscopy. For D2 scattered from Cu(100) the vibrational survival probability and some transition inelastic probabilities were measured for incident energies from 70–200meV. The survival probability was found to be larger then that found previously for H2(v=1) scattered from the same surface; these differences are discussed in terms of the lower zero point energy and smaller vibrational energy spacings of D2. D2 translational energy exchange was studied for several different scattering channels and interpreted using simple classical calculations. The survival probability was also measured for D2(v=1) scattered from Pd(111) at one incident energy. Pd is reactive for D2 dissociation and this survival probability was measured to be small and also to be much smaller than that for H2(v=1) under similar conditions. Vibrational relaxation channels were studied for D2 scattering from both Cu(100) and Pd(111). The vibrational relaxation probability on both surfaces was also found to be smaller than that measured for comparable channels for H2. The smaller survival probability and vibrational relaxation probability for D2 on Pd(111) cannot be easily accounted for by the difference in zero point energy and vibrational energy spacings.
Adsorption of comb copolymers on weakly attractive solid surfaces
Authors: Striolo A. , Jayaraman A. , Genzer J. , Hall C. K.
Published: August 2005

In this work continuum and lattice Monte Carlo simulation methods are used to study the adsorption of linear and comb polymers on flat surfaces. Selected polymer segments, located at the tips of the side chains in comb polymers or equally spaced along the linear polymers, are attracted to each other and to the surface via square-well potentials. The rest of the polymer segments are modeled as tangent hard spheres in the continuum model and as self-avoiding random walks in the lattice model. Results are presented in terms of segment-density profiles, distribution functions, and radii of gyration of the adsorbed polymers. At infinite dilution the presence of short side chains promotes the adsorption of polymers favoring both a decrease in the depletion-layer thickness and a spreading of the polymer molecule on the surface. The presence of long side chains favors the adsorption of polymers on the surface, but does not permit the spreading of the polymers. At finite concentration linear polymers and comb polymers with long side chains readily adsorb on the solid surface, while comb polymers with short side chains are unlikely to adsorb. The simple models of comb copolymers with short side chains used here show properties similar to those of associating polymers and of globular proteins in aqueous solutions, and can be used as a first approximation to investigate the mechanism of adsorption of proteins onto hydrophobic surfaces.
The structure of the mixed OH+H2O overlayer on Pt{111}
Authors: Held G. , Clay C. , Barrett S. D. , Haq S. , Hodgson A.
Published: August 2005

The structure of the mixed p(3×3)-(3OH+3H2O) phase on Pt{111} has been investigated by low-energy electron diffraction-IV structure analysis. The OH+H2O overlayer consists of hexagonal rings of coplanar oxygen atoms interlinked by hydrogen bonds. Lateral shifts of the O atoms away from atop sites result in different O–O separations and hexagons with only large separations (2.81 and 3.02 Å) linked by hexagons with alternating separations of 2.49 and 2.81∕3.02Å. This unusual pattern is consistent with a hydrogen-bonded network in which water is adsorbed in cyclic rings separated by OH in a p(3×3) structure. The topmost two layers of the Pt atoms relax inwards with respect to the clean surface and both show vertical buckling of up to 0.06 Å. In addition, significant shifts away from the lateral bulk positions have been found for the second layer of Pt atoms.
The influence of the growth rate on the preferred orientation of magnetron-sputtered Ti–Al–N thin films studied by in situ x-ray diffraction
Authors: Beckers M. , Schell N. , Martins R. M. S. , Mücklich A. , Möller W.
Published: August 2005

In situ x-ray diffraction has been used to characterize the growth and microstructure of wear protective Ti1−xAlxN thin films. The films were deposited onto oxidized Si(100) wafers in a sputter chamber mounted onto a six-circle goniometer located at a synchrotron-radiation beam line. Off-plane and in-plane x-ray diffraction data were recorded in situ during growth, in order to follow the development of microstructure and preferred orientation as a function of film thickness. The measurements were supplemented by ex situ cross-sectional transmission electron microscopy analyses. The films were deposited by reactive cosputtering from metallic Ti and Al targets in Ar∕N2 gas mixtures at substrate temperatures of 150 and 300°C, substrate bias voltages of −30 and +10V, and deposition rates between 0.9 and 0.3Å∕s. The film composition was changed between pure TiN and Ti0.91Al0.09N. Films deposited at higher deposition rates show columnar structure with competitive growth between (001) and (111) crystalline orientation, which slowly evolves into a (111) preferred orientation containing inter- and intracolumn porosities. Reducing the deposition rate to 0.3Å∕s leads to an almost complete (001) preferred orientation with reduced surface roughness, practically independent of the deposition temperature. As the stress state of the films remains low for both deposition rates, it is suggested that the ion-to-neutral arrival rate (JI∕JTi+Al) determines the texture development rather than the stress. This is corroborated by applying a positive substrate bias, which, by suppressing ion impingement, leads back to an evolving (111) preferred orientation.
Overlapping resonances in the coherent control of radiationless transitions: Internal conversion in pyrazine
Authors: Christopher P. S. , Shapiro Moshe , Brumer Paul
Published: August 2005

Coherent control of radiationless transitions is developed and applied to internal conversion. Conditions for active versus passive control are described and overlapping resonances are shown necessary for the phase control of radiationless transitions in molecular systems. Applications to pyrazine show the possibility of extensive control via optimized state preparation, as well as the significant role of overlapping resonances, even in the evolution of single vibrational states in S2.
Decay behavior of least-squares coefficients in auxiliary basis expansions
Authors: Gill P. M. W. , Gilbert A. T. B. , Taylor S. W. , Friesecke G. , Head-Gordon M.
Published: August 2005

Many quantum chemical methods, both wave function and density based, rely on an expansion of elements of the electron density in an auxiliary basis. However, little is known about the analytical behavior of the expansion coefficients and, in particular, about their rate of decay with distance. We discuss an exactly solvable model system and characterize the expansion coefficients for various fitting metrics and various dimensionalities of the auxiliary basis. In the case of Coulomb fitting, we find that the decay rate depends critically on the effective dimensionality D of the auxiliary basis, varying from O(r−1) to O(r−3) to O(e−ζr) for D=1, 2, or 3.
Infrared absorption and electron paramagnetic resonance studies of vinyl radical in noble-gas matrices
Authors: Tanskanen Hanna , Khriachtchev Leonid , Räsänen Markku , Feldman Vladimir I. , Sukhov Fedor F. , Orlov Aleksei Yu. , Tyurin Daniil A.
Published: August 2005

Vinyl radicals produced by annealing-induced reaction of mobilized hydrogen atoms with acetylene molecules in solid noble-gas matrices (Ar, Kr, and Xe) were characterized by Fourier transform infrared and electron paramagnetic resonance (EPR) spectroscopies. The hydrogen atoms were generated from acetylene by UV photolysis or fast electron irradiation. Two vibrational modes of the vinyl radical (ν7 and ν5) were assigned in IR absorption studies. The assignment is based on data for various isotopic substitutions (D and C13) and confirmed by comparison with the EPR measurements and density-functional theory calculations. The data on the ν7 mode is in agreement with previous experimental and theoretical results whereas the ν5 frequency agrees well with the computational data but conflicts with the gas-phase IR emission results.
A heat-transfer and fluid-flow-based model to obtain a specific weld geometry using various combinations of welding variables
Authors: Mishra S. , DebRoy T.
Published: August 2005

Numerical heat transfer and fluid flow models have provided significant insight into welding processes and welded materials that could not have been achieved otherwise. However, the use of these models has been limited by two major problems. First, the model predictions do not always agree with the experimental results because some input parameters such as the arc efficiency cannot be accurately prescribed. Second, and more important, these models cannot determine multiple pathways or sets of welding variables that can lead to a particular weld attribute such as the weld pool geometry, which is defined by an equilibrium temperature surface. Here we show that the computational heat transfer and fluid flow models of fusion welding can overcome the aforementioned difficulties by combining with a genetic algorithm. The reliability of the convective heat transfer model can be significantly improved by optimizing the values of the uncertain input parameters from a limited volume of the experimental data. Furthermore, the procedure can calculate multiple sets of welding variables, each leading to the same weld geometry. These multiple paths were obtained via a global search using a genetic algorithm within the phenomenological framework of the equations of conservation of mass, momentum, and energy. This computational procedure was applied to the gas tungsten arc welding of Ti–6Al–4V alloy to calculate various sets of welding variables to achieve a specified weld geometry. The calculated sets of welding parameters showed wide variations of values. However, each set of welding parameters resulted in a specified geometry showing the effectiveness of the computational procedure.
Ion- and dust-acoustic solitons in dusty plasmas: Existence conditions for positive and negative potential solutions
Authors: Verheest Frank , Cattaert Tom , Hellberg Manfred A.
Published: August 2005

The usual description of dust-modified ion-acoustic and dust-acoustic solitons in plasmas containing negative dust is in terms of Boltzmann distributions for the hotter species. In the dust-modified ion-acoustic regime, besides positive potential solitons, negative structures can also be generated, for electrons with a polytropic index γe≠1, as well as for Boltzmann electrons, subject to conditions that are not too stringent. These general conditions were previously either ignored or given for weakly nonlinear solutions only. In the dust-acoustic domain in plasmas with negatively charged dust, however, only negative potential solitons can occur, even when the lighter species have non-Boltzmann distributions. For Boltzmann electrons only an infinite dust compression limits the soliton amplitudes and corresponding Mach numbers, whereas for γe≠1, the electron density, too, can be a limiting factor for the existence domain of such solitons.
High room-temperature figure of merit of thin layers prepared by laser ablation from Bi2Te3 target
Authors: Walachová J. , Zeipl R. , Zelinka J. , Malina V. , Pavelka M. , Jelínek M. , Studnička V. , Lošt’ák P.
Published: August 2005

The figure of merit ZT is measured by a Harman method on simple devices prepared on single thermoelectric layers of different thicknesses. The thermoelectric layers are prepared at different conditions by laser ablation from Bi2Te3 target. The best measured figure of merit ZT is for our devices ZT=2.65. This result is comparable with the results obtained on superlattices. ZT oscillated with the thickness of the layers. On some devices the Seebeck coefficient is measured and using conductivity measurements along the thermoelectric layers the thermal conductivity is estimated from ZT. The low thermal conductivity of samples is explained by the quantum size effect and by existence of few phases of type Bi2(m+n)Te3n in the thermoelectric layers.
Single-molecule mobility and spectral measurements in submicrometer fluidic channels
Authors: Stavis Samuel M. , Edel Joshua B. , Li Yougen , Samiee Kevan T. , Luo Dan , Craighead Harold G.
Published: August 2005

Electrophoretic mobility differences of biological molecules are frequently exploited to physically separate and subsequently identify the components of a mixture. We present a method to rapidly identify single molecules by measuring both their mobility and fluorescence emission under continuous flow without separation. Submicrometer fluidic channels were used to detect individual nucleic-acid-engineered fluorescent labels driven electrokinetically in free solution. Two separate focal volumes along the length of the fluidic channel collected spectral, spatial, and temporal information from the passage of fluorescent labels through the channel. One focal volume was defined by a focused 488-nm-wavelength laser and the other by a focused 568-nm laser. The subfemtoliter focal volumes resulted in signal-to-noise ratios sufficient for single-fluorophore detection, and the two excitation wavelengths enabled detection of multicolor fluorescent labels and discrimination of single-color detection events. Each fluorescent label was uniformly excited and analyzed as it passed through the channel. Flow control facilitated high throughput at low concentrations, as well as a balance of several experimental parameters. Two fluorescent labels were considered for identification by single-molecule mobility measurements. Approximately 81% of fluorescent labels of one variety and 77% of the other were found to be identifiable based on their mobility alone. As implemented, this method could be used in conjunction with spectral analysis of fluorescent labels to enhance the resolution of single-molecule identification. Ultimately, this technique could be used autonomously to detect biomolecules bound to fluorescent labels and to identify similarly labeled biomolecules by their mobility.
Multiscale modeling, simulations, and experiments of coating growth on nanofibers. Part I. Sputtering
Authors: Buldum A. , Busuladzic I. , Clemons C. B. , Dill L. H. , Kreider K. L. , Young G. W. , Evans E. A. , Zhang G. , Hariharan S. I. , Kiefer W.
Published: August 2005

This paper is Part I of an integrated experimental/modeling investigation of a procedure to coat nanofibers and core-clad nanostructures with thin-film materials using plasma-enhanced physical vapor deposition. In the experimental effort, electrospun polymer nanofibers are coated with aluminum under varying operating conditions to observe changes in the coating morphology. This procedure begins with the sputtering of the coating material from a target. This paper focuses on the sputtering process and transport of the sputtered material through the reactor. The interrelationships among the processing factors for the sputtering and transport are investigated from a detailed modeling approach that describes the salient physical and chemical phenomena. Solution strategies that couple continuum and atomistic models are used. At the continuum scale, the sheath region and the reactor dynamics near the target surface are described. At the atomic level, molecular-dynamics (MD) simulations are used to study the sputtering and deposition mechanisms. Ion kinetic energies and fluxes are passed from the continuum sheath model to the MD simulations. These simulations calculate sputtering and sticking probabilities that in turn are used to calculate parameters for the continuum reactor model. The reactor model determines the concentration field of the coating material.
Virgin domain structures in mesoscopic Co patterns: Comparison between simulation and experiment
Authors: Cherifi S. , Hertel R. , Kirschner J. , Wang H. , Belkhou R. , Locatelli A. , Heun S. , Pavlovska A. , Bauer E.
Published: August 2005

The magnetization states of 20-nm-thick rectangular Co thin-film elements are studied with micromagnetic modeling and x-ray magnetic circular dichroism photoemission electron microscopy. The energies of ten domain configurations obtained in the modeling are compared with the frequency of occurrence of the corresponding virgin domain structures as a function of aspect ratio from 1:1 to 1:3 and of width from 200to600nm. The results show that the abundance of the virgin states is largely determined by the magnetic energy densities of the elements.
A low loss, dielectric substrate in ZnAl2O4–TiO2 system for microelectronic applications
Authors: Surendran K. P. , Sebastian M. T. , Manjusha M. V. , Philip Jacob
Published: August 2005

A temperature stable low loss substrate based on 0.83ZnAl2O4–0.17TiO2 (ZAT) was developed as a substitute to Al2O3 for possible applications in microelectronic industry as substrates and packaging materials. The thermal conductivity of ZAT is 59Wm−1K−1 which is more than twice as that of Al2O3. The thermal-expansion coefficient of this dielectric is 6.3ppm∕°C which is comparable to that of silicon used in microelectronic circuitry. Furthermore, 0.83ZnAl2O4–0.17TiO2 dielectric is chemically inert with silicon, which increases its applicability in microelectronic packages.
Thomson scattering from laser-produced gold plasmas in radiation conversion layer
Authors: Wang Zhebin , Zheng Jian , Zhao Bin , Yu C. X. , Jiang Xiaohua , Li Wenhong , Liu Shenye , Ding Yongkun , Zheng Zhijian
Published: August 2005

With a 263.3 nm probe laser beam, the Thomson scattering (TS) spectra are measured at the distance from the surface of gold disc targets as close as 50μm. All of the TS spectra become narrower with time, which indicates the overall drop of plasma temperature as the high-Z plasmas blow off. The experimental data show that there are distinct characteristics between the inner region (i.e., 50 and 100μm away from target surface) and the outer region. The gradient of the electron temperature in outer region is toward the target and becomes opposite to that in the inner region. The asymmetries of the TS spectra in the inner region are in good agreement with calculation based on the Spitzer–Härm theory. In the outer region, however, the discrepancies between the experiments and calculations are significant, which may be a hint that the electron energy transport becomes flux limited or nonlocal in this region.
Redshift of the light emission from highly strained In0.3Ga0.7As∕GaAs quantum wells by dipole δ doping
Authors: Fu Y. , Wang S.-M. , Wang X.-D. , Larsson A.
Published: August 2005

We have studied theoretically the energy band structures and optical properties of highly strained dipole δ-doped In0.3Ga0.7As∕GaAs single quantum wells. Including dopant diffusion effect, strain in the quantum well, spin-orbital interactions, and many-body effects, the self-consistent calculations of the eight-band k∙p model and the Poisson equation show that the dipole δ doping induces an electric field across the In0.3Ga0.7As quantum well by the Stark effect so that both the interband transition energy and the wave-function overlap between the ground-state electrons and holes are reduced. Applying an external bias across the quantum well partially cancels the built-in electric field and reduces the wavelength redshift. The calculated material gain peak is close to the experimental lasing wavelength.
Numerical simulation of binary liquid droplet collision
Authors: Pan Yu , Suga Kazuhiko
Published: August 2005

A numerical investigation of binary droplet collision has been conducted. The complete process of the collision of two liquid droplets is dynamically simulated by solving the incompressible Navier-Stokes equations coupled with the convective equation of the level set function that captures the interface between the liquid and the gas phases. The simulations cover four major regimes of binary collision: bouncing, coalescence, reflexive separation, and stretching separation. For water droplets in air, the numerical results are compared with the experiments by and Ashgriz and Poo [J. Fluid Mech. 221, 183 (1990)] on collision consequences. For hydrocarbon (C14H30) droplets in nitrogen gas, the simulated results are compared in detail with the time-resolved photographic images of the collision processes obtained by Qian and Law [J. Fluid Mech. 331, 59 (1997)] in every collision regime. The present numerical results suggest that the mechanism of a bouncing collision is governed by the macroscopic dynamics. However, the fact that the present macroscopic numerical model is unable to capture the collision regime of coalescence after minor deformation supports the speculation that its mechanism is related to the microscopic dynamics. Furthermore, the transition from bouncing to coalescence collisions has been predicted and agrees well with the analytical model. The mechanism of satellite droplet formation for head-on collision and stretching separation collision is also studied based on the detailed time-resolved dynamic simulation results. It is then confirmed that end pinching is the main cause of satellite formation in head-on collisions whereas the capillary-wave instability becomes dominant in large impact parameter cases. In the case of an intermediate impact parameter, the effects of twisting and stretching due to the angular momentum and the inertia of the colliding droplets are significant for the satellite formation.