bluuebunny/crossref_metadata_2025 huggingface dataset:
Crustal structure of the NE Rockall Trough from wide‐angle seismic data modeling
Authors: Klingelhöfer F. , Edwards R. A. , Hobbs R. W. , England R. W.
Published: November 2005

Two wide‐angle seismic lines located in the northern Rockall Trough were acquired in May 2000. One line (line E) crosses the trough from the continental shelf off Lewis to normal oceanic crust west of Lousy Bank in NW‐SE direction. The other line (line D) intersects with line E, crosses the Wyville‐Thomson Ridge in a SW‐NE direction and ends in the Faeroe‐Shetland Basin. Sonobuoy data and expanding spread profiles acquired in the same area have been remodeled. Analysis of the seismic data using travel times and amplitudes reveals an up to 5 km thick sedimentary basin including an up to 1.5 km thick basaltic layer which is present in most of the trough. Further conclusions of this study are that the Rockall Trough is underlain by highly stretched continental crust of ∼13 km thickness. The crust thickens to ∼24 km beneath Lousy Bank, which is interpreted to be of continental nature. Beneath the Hebrides continental shelf a three‐layer continental crust of 26 km is modeled. An up to 12 km thick high‐velocity layer is observed underneath the ocean‐continent boundary and is interpreted as magmatic underplating resulting from excess volcanism during rifting. No evidence for an underplate layer could be distinguished beneath the trough area. Modeling of the structure of the Wyville‐Thomson Ridge revealed no existing igneous core of the ridge confirming existing theories, that it is a compressional structure.
Interaction of mineral dust with gas phase nitric acid and sulfur dioxide during the MINATROC II field campaign: First estimate of the uptake coefficient from atmospheric data
Authors: Umann B. , Arnold F. , Schaal C. , Hanke M. , Uecker J. , Aufmhoff H. , Balkanski Y. , Van Dingenen R.
Published: November 2005

Mineral dust, one of the most abundant aerosols by mass in the atmosphere, may have a lasting but to date almost unexplored effect on the trace gases nitric acid (HNO3) and sulfur dioxide (SO2). These gases have an important influence on, for example, the tropospheric ozone cycle, aerosol formation or acid rain. Within the second part of the MINATROC project (Mineral Dust and Tropospheric Chemistry) we investigated the interaction of mineral dust with gaseous HNO3 and SO2. The measurements were performed on a high mountain plateau (Izaña, Tenerife, 2367 m asl) using the highly sensitive CIMS (Chemical Ionization Mass Spectrometry) technique. During five periods of medium and one period of high atmospheric dust load, the HNO3 concentration decreased with increasing dust concentrations, and in all cases the HNO3 detection limit was reached. From the HNO3 decrease the uptake coefficient was calculated for the first time on the basis of in situ measurements. For the observed events, varied between 0.017 and 0.054. Moreover, during the dust events a significant decrease of ozone (O3) of the order of 30% was detected. The measurements and the analyses made in this paper show that the direct uptake of O3 on dust is a minor pathway for O3 depletion compared to the indirect effect, i.e., HNO3 depletion on dust which takes away a source of the O3 precursors nitrogen oxides. In contrast, a general interaction between SO2 and mineral dust was not observed. Positive as well as negative and no correlations between SO2 and mineral dust were detected.
Influence of mountain venting in the Alps on the ozone chemistry of the lower free troposphere and the European pollution export
Authors: Henne S. , Dommen J. , Neininger B. , Reimann S. , Staehelin J. , Prévôt A. S. H.
Published: November 2005

The influence of mountain venting over the Alps on ozone (O3) mixing ratios in the lower free troposphere (FT) and on export of European emissions was investigated with a Lagrangian chemical box‐model system. During summertime fair‐weather conditions mountain venting is an efficient tropospheric lifting mechanism that carries atmospheric boundary layer (ABL) pollutants to the FT. Little is known about the effect of mountain venting on net O3 production in the FT. Chemistry in a FT and an ABL air parcel was initialized with typical European summertime background FT and Alpine ABL mixing ratios, respectively, which were derived from measurements. A parameterization was developed based on previous quantification of mountain venting in the Swiss Alps, describing the injection of air from the ABL into the FT. For simulations at constant altitude (3500 m above mean sea level (MSL)), net O3 production was generally positive for day 0 of the simulation, when mountain venting occurred. Whether O3 was produced or destroyed from day 1 onward critically depended on initial nitrogen oxides (NOx) plus peroxy acetyl nitrates (PANs) mixing ratios in the ABL, and to a smaller extent on initial H2O and O3 mixing ratios, photolysis rates, and PANs chemistry. For a simulation period of 8 days O3 mixing ratios remained higher in the simulations with venting than in simulations for the FT background without venting. Simulations on cluster average forward trajectories initialized over the Alps showed that European emissions vented in the Alps have a strong influence on the Mediterranean region. O3 production on these trajectories was enhanced by the release of NOx from PANs that acted as a reservoir species while the air parcel was descending over the Mediterranean. The O3 production efficiency with regard to NOx was about 20 molecules O3 produced per molecule NOx consumed at 3500 m MSL on day 0 of the venting simulation. On the southward moving trajectories O3 production efficiency was in the range of 6–11 until day 3 of the simulation when all injected NOy was consumed.
Links between the mountain torque and the Arctic Oscillation in the Laboratoire de Météorologie Dynamique (LMDz), general circulation model
Authors: Lott F. , Goudard L. , Martin A.
Published: November 2005

Recent papers suggest that in the National Center for Environmental Prediction (NCEP) reanalysis data there is a dynamical link between the mountain torque and the Arctic Oscillation (AO) at periodicities near and below 30 days. This link essentially occurs because the AO is associated with a redistribution of mass from the polar regions to the midlatitudes, hence giving a substantial contribution to the mass term of the atmospheric angular momentum (AAM). These results are confirmed here by using a 30‐year simulation done with the Laboratoire de Météorologie Dynamique, zoom (LMDz), general circulation model. In particular, we verify that the changes in mass AAM occurring during intraseasonal variations of the AO are in good part driven by the mountain torque in the model also. In this respect, the LMDz model has the great advantage of closing the AAM budget nearly exactly, which is not the case with the NCEP reanalysis data. As the Antarctic Oscillation (AAO) is also associated with a redistribution of mass from the polar regions to the midlatitudes, its contribution to the AAM budget is also presented. As there are many fewer mountains in the Southern Hemisphere, we show that in the model as well as in the reanalysis the changes in mass AAM during intraseasonal variations of the AAO are in good part equilibrated by changes of opposite sign in wind AAM. The main interest of these results is that the mountain torque drives the changes in AAM, so it can sometimes participate actively in changes of the AO. It has a predictive value that is significant but small, around 10–15% for periodicities near and below one month, while a good fraction of the AO variability occurs at longer timescales.
Moisture variability over the South American Altiplano during the South American Low Level Jet Experiment (SALLJEX) observing season
Authors: Falvey Mark , Garreaud René D.
Published: November 2005

During the austral summer, precipitation over the high‐altitude plateau of the South American Altiplano exhibits a marked intraseasonal variability which has been associated with alternating moist and dry conditions observed at surface stations near the Altiplano western cordillera. In this study the characteristics of humid (wet) and dry (dry) episodes observed at a station on the western rim of the Altiplano during the summer of 2002–2003 are examined using observational data from the South American Low Level Jet Experiment (SALLJEX) and satellite‐based estimates of precipitable water (PW) from Global Positioning System, Moderate Resolution Imaging Spectrometer, and Passive Microwave Radiometer instruments. We find that on wet days, mean moist conditions (PW greater than 10 mm) prevail across the entire plateau. This moisture is apparently brought to the Altiplano by sustained westward advection of air at similar altitude above the continental basin and propagates across the Altiplano to moisten the atmosphere over the Pacific Ocean a considerable distance (>1000 km) west of the plateau. In contrast, during dry events, significant drying of the boundary layer is observed mainly along the western mountain range and over the southern Altiplano. There is no evidence of strong midlevel advection of dry air across the northern Altiplano, and moisture remains constant and high over the northern basin and along the Altiplano eastern ridge. Consequently, precipitation and convective cloudiness show the strongest relation to moisture along the western cordillera of the Altiplano. Significant diurnal variability of moisture is found to occur most strongly on the outer slopes of the Altiplano. There is little indication that daytime upslope flow on the eastern slope of the Altiplano plays a major role in the transport of moisture to the Altiplano during wet episodes.
Comparison of function approximation, heuristic, and derivative‐based methods for automatic calibration of computationally expensive groundwater bioremediation models
Authors: Mugunthan Pradeep , Shoemaker Christine A. , Regis Rommel G.
Published: November 2005

The performance of function approximation (FA) methods is compared to heuristic and derivative‐based nonlinear optimization methods for automatic calibration of biokinetic parameters of a groundwater bioremediation model of chlorinated ethenes on a hypothetical and a real field case. For the hypothetical case, on the basis of 10 trials on two different objective functions, the FA methods had the lowest mean and smaller deviation of the objective function among all algorithms for a combined Nash‐Sutcliffe objective and among all but the derivative‐based algorithm for a total squared error objective. The best algorithms in the hypothetical case were applied to calibrate eight parameters to data obtained from a site in California. In three trials the FA methods outperformed heuristic and derivative‐based methods for both objective functions. This study indicates that function approximation methods could be a more efficient alternative to heuristic and derivative‐based methods for automatic calibration of computationally expensive bioremediation models.
Neuroprotection associated with alternative splicing of NMDA receptors in rat cortical neurons
Authors: Jaekel Beate , Mühlberg Katja , Garcia de Arriba Susana , Reichenbach Andreas , Verdaguer Ester , Pallas Mercè , Camins Antoni , Nörenberg Wolfgang , Allgaier Clemens
Published: November 2005

Exposure of cultured cortical neurons to elevated extracellular K+concentrations (25 mM) induces membrane depolarization and an increase in action‐potential firing.

Long‐term high K+treatment was associated with an increased neuronal cell death.

In surviving neurons, multiple changes occurred in the proportion of individual NMDA receptor subunit 1 (NR1) splice variant mRNA expression, whereas the overall expression of NR1, NR2A and NR2B transcripts remained unaffected. The high K+‐induced changes in NR1 splice variant expression were virtually abolished upon a concurrent administration of tetrodotoxin (TTX; 3 μM).

In voltage‐clamp recordings performed on neurons resistant to high K+treatment, inward currents induced by NMDA (1–1000 μM) were reduced.

In K+‐resistant cells, the activity of calpain but not of caspase‐3 was diminished compared with controls kept in regular medium.

NR function as well as calpain activity was not affected in cultures concomitantly treated with high K+and either TTX or a NR antagonist (CGS19755 (selfotel) or memantine).

In conclusion, the present data indicate adaptive changes in NR1 splice variant expression and a decrease in NR function upon a sustained increase in neurotransmission. Accordingly, alternative splicing could be an endogenous mechanism to counteract cellular damage due to overactivation of excitatory NRs and may be associated with an impairment of necrotic mechanisms.

British Journal of Pharmacology(2006)147, 622–633. doi:10.1038/sj.bjp.0706471
Long‐term bradycardia caused by atrioventricular block can remodel the canine heart to detect the histamine H1 blocker terfenadine‐induced torsades de pointes arrhythmias
Authors: Takahara Akira , Sugiyama Atsushi , Ishida Yuko , Satoh Yoshioki , Wang Kai , Nakamura Yuji , Hashimoto Keitaro
Published: November 2005

Although a second‐generation histamine H1 blocker terfenadine induced torsades de pointes (TdP) arrhythmias in patients via the blockade of a rapid component of delayed rectifier K+ current (IKr), such action of terfenadine has not been detected in previous animal models.

We analysed the potential of the canine persistent atrioventricular block heart, a new in vivo proarrhythmia model, to detect a torsadogenic effect of terfenadine of an oral dose of 3 or 30 mg kg−1. The doses can provide therapeutic to supra‐therapeutic plasma concentrations as an anti‐histamine.

In 2 weeks of bradycardiac heart model, there were no significant changes in any of the electrocardiogram parameters after the administration of both doses of terfenadine.

In 4–6 weeks of bradycardiac heart model, the low dose of terfenadine hardly affected any of the electrocardiogram parameters except that it induced TdP in one out of six animals. The high dose significantly decreased the atrial rate and ventricular rate, prolonged the QT interval, and induced TdP in five out of six animals. Moreover, temporal variability of repolarization increased after the high‐dose administration.

These results suggest that long‐term bradycardia caused by atrioventricular block can remodel the canine heart to detect terfenadine‐induced TdP.

British Journal of Pharmacology (2006) 147, 634–641. doi:10.1038/sj.bjp.0706493
Regional heterogeneity in the haemodynamic responses to urotensin II infusion in relation to UT receptor localisation
Authors: Gardiner Sheila M , March Julie E , Kemp Philip A , Maguire Janet J , Kuc Rhoda E , Davenport Anthony P , Bennett Terence
Published: November 2005

The aim of the study was to measure regional haemodynamic responses to 6 h infusions of human urotensin II (hUII), to identify possible mediators of the effects observed, and to relate the findings to the distribution of urotensin II receptors (UT receptors).

Male, Sprague–Dawley rats had pulsed Doppler flow probes and intravascular catheters implanted for measurement of regional haemodynamics in the conscious, freely moving state. Infusions of saline (0.4 ml h−1) or hUII (30, 300 and 3000 pmol kg−1 h−1) were given i.v. for 6 h, and the effects of pretreatment with indomethacin (5 mg kg−1 h−1), NG‐nitro‐L‐arginine methyl ester (L‐NAME, 3 mg kg−1 h−1) or propranolol (1 mg kg−1; 0.5 mg kg−1 h−1) on responses to hUII (300 pmol kg−1 h−1 for 6 h) were assessed. Cellular localisation of UT receptor‐like immunoreactivity was determined in relevant tissues.

hUII caused dose‐dependent tachycardia and hindquarters vasodilatation, accompanied by a slowly developing rise in blood pressure. Haemodynamic effects of hUII were attenuated by propranolol or L‐NAME and abolished by indomethacin. UT receptor‐like immunoreactivity was detected in skeletal and vascular smooth muscle.

The findings indicate that in conscious rats, infusions of hUII cause vasodilatation, which, of the vascular beds monitored, is selective for the hindquarters and dependent on cyclooxygenase products and nitric oxide. The pressor effect of hUII under these conditions is likely to be due to an increase in cardiac output, possibly due to a positive inotropic effect. UT receptor‐like immunoreactivity present in skeletal muscle is consistent with the haemodynamic pattern.

British Journal of Pharmacology (2006) 147, 612–621. doi:10.1038/sj.bjp.0706503
Reduction of experimental colitis in the rat by inhibitors of glycogen synthase kinase‐3β
Authors: Whittle Brendan J R , Varga Csaba , Pósa Anikó , Molnár Andor , Collin Marika , Thiemermann Christoph
Published: November 2005

The effects of the inhibitors of glycogen synthase kinase‐3β (GSK‐3β), TDZD‐8 and SB 415286, which can substantially reduce the systemic inflammation associated with endotoxic shock in vivo, have now been investigated on the acute colitis provoked by trinitrobenzene sulphonic acid (TNBS) in the rat.

Administration of the GSK‐3β inhibitor TDZD‐8 (0.1, 0.33 or 1.0 mg kg−1, s.c., b.i.d., for 3 days) caused a dose‐dependent reduction in the colonic inflammation induced by intracolonic TNBS assessed after 3 days, both as the area of macroscopic involvement and as a score using 0–10 scale.

Likewise, following administration of the GSK‐3β inhibitor SB 415286 (0.1, 0.33 or 1.0 mg kg−1, s.c., b.i.d., for 3 days), the extent and degree of the TNBS‐provoked colonic inflammation was reduced.

Administration of either TDZD‐8 or SB 415286 reduced the fall in body weight following challenge with TNBS at each dose level studied.

The increase in myeloperoxidase activity, an index of neutrophil infiltration into the TNBS‐induced inflamed colon, was significantly inhibited by both TDZD‐8 and SB 415286 at each dose level.

The increase in the levels of the proinflammatory cytokine, TNF‐α, in the inflamed colon was also significantly inhibited by either compound at the highest doses evaluated.

The elevated levels of the transcription factor NF‐κB subunit p65, as determined by Western blot in the nuclear extracts from the TNBS‐provoked inflamed colonic tissue, were dose‐dependently reduced by TDZD‐8 or SB 415286 treatment.

These findings demonstrate that two chemically distinct selective inhibitors of the activity of GSK‐3β reduce the inflammation and tissue injury in a rat model of acute colitis. The mechanisms underlying this anti‐inflammatory action may be related to downregulation of NF‐κB activity, involved in the generation of proinflammatory mediators.

British Journal of Pharmacology (2006) 147, 575–582. doi:10.1038/sj.bjp.0706509
Phase diagram of complex fluids using an efficient integral equation method
Authors: Charpentier I. , Jakse N.
Published: November 2005

We present an adaptive technique for the determination of the phase diagram of fluids within the integral equation theory. It enables an efficient and accurate systematic mapping of the thermodynamic space in order to construct the binodal and spinodal lines. Results are obtained with the thermodynamically consistent integral equation proposed by Sarkisov [J. Chem. Phys. 114, 9496 (2001)] within the tangent linear technique that yields an exact differentiation of correlation functions. The generality of the numerical approach is assessed by determining both the liquid-vapor coexistence and the critical parameters of the generalized Lennard-Jones (n,6) potentials with varying repulsive part, including the hard-sphere limit.
On the role of collective and local molecular fluctuations in the relaxation of proton intrapair dipolar order in nematic 5CB
Authors: Mensio O. , Zamar R. C. , Anoardo E. , Acosta R. H. , Dong R. Y.
Published: November 2005

We investigate the role that local motions and slow cooperative fluctuations have on the relaxation of the intrapair dipolar order in the nematic 5CB. With this purpose we present a theoretical and experimental systematic study which allow us to quantify the contribution from each type of molecular fluctuation to the intrapair dipolar order relaxation time, T1D. The experimental work includes measurements of Zeeman and intrapair dipolar order relaxation times (T1Z and T1D) as a function of temperature at conventional NMR frequencies, in three complementary samples: normal and chain deuterated 4-n-pentyl-4′-cyanobiphenyl (5CB and 5CBd11) and a mixture of normal 5CB and fully deuterated 4-n-pentyl-4′-cyanobiphenyl (5CBd19), 50% in weight. Additionally we perform T1Z field-cycling Larmor frequency-dependent measurements to obtain the spectral density of the cooperative fluctuations. The obtained results are as follows. (a) The cooperative molecular fluctuations have a strong relative weight in the relaxation of the intrapair dipolar order state, even at Larmor frequencies in the range of conventional NMR. (b) Alkyl chain rotations are an important relaxation mechanism of the intrapair dipolar order at megahertz frequencies. (c) Intermolecular fluctuations mediated by translational self-diffusion of the molecules is not an efficient mechanism of relaxation of the intrapair dipolar order.
Coverage and nearest-neighbor dependence of adsorbate diffusion
Authors: Wong Kin L. , Rao Bommisetty V. , Pawin Greg , Ulin-Avila Erick , Bartels Ludwig
Published: November 2005

We present data on the coverage and nearest-neighbor dependences of the diffusion of CO on Cu(111) by time-lapsed scanning tunneling microscope (STM) imaging. Most notable is a maximum in diffusivity of CO at a local coverage of one molecule per 20 substrate atoms and a repulsion between CO molecules upon approach closer than three adsites, which in combination with a less pronounced increase in potential energy at the diffusion transition state, leads to rapid diffusion of CO molecules around one another. We propose a new method of evaluating STM-based diffusion data that provides all parameters necessary for the modeling of the dynamics of an adsorbate population.
Ab initio potential-energy surfaces of O2(XΣg−3,aΔg1,bΣg+1)+O2(XΣg−3,aΔg1,bΣg+1): Mechanism of quenching of O2(aΔg1)
Authors: Liu Jianjun , Morokuma Keiji
Published: November 2005

Ab initio computational studies were carried out in order to explore the possible mechanisms of quenching of O2(aΔg1) by O2(XΣg−3): the self-quenching of O2(aΔg1) and other energy-transfer processes involving two O2 molecules. All eighteen states arising from two O2 molecules in the XΣg−3, aΔg1, and bΣg+1 states are considered. After scans at the state-averaged complete active space self-consistent field method to identify possible regions of crossing between states belonging to different asymptotes, complete active state second-order perturbation theory high-symmetry optimization and low-symmetry scans established that four different minima on the seams of crossing (MSXs), arising between the a+a manifold and the X+b manifold and responsible for self-quenching: O2(aΔg1)+O2(aΔg1)→O2(XΣg−3)+O2(bΣg+1), have coplanar C2h or C2v symmetries and are only 0.45eV barrier relative to the a+a asymptote and energetically easily accessible. The rate constant for this process was estimated based on the Landau-Zener formalism. The MSXs for quenching of O2(aΔg1) by the ground state O2(XΣg−3):O2(aΔg1)+O2(XΣg−3)→O2(XΣg−3)+O2(XΣg−3) require higher energies and the process is not likely to be important.
Local control of molecular fragmentation: The role of orientation
Authors: Marquetand Philipp , Meier Christoph , Engel Volker
Published: November 2005

Local control theory, where the instantaneous response of a system to an external field determines the control field, is employed for the purpose of inducing molecular fragmentation processes via infrared excitation. In particular, the effects of the orientational motion are investigated and compared with the idealized case of a frozen rotation. It is shown that the rotational degree of freedom is crucial for the applicability of the employed local control algorithm. The addition of an additional static electric field which induces a molecular preorientation offers an efficient way for the local control. In particular, with increasing static field strength, the fragmentation yield approaches unity so that the idealized rotationless case is recovered. Numerical results are presented for the NaI molecule.
Simplified modeling of 13.5 nm unresolved transition array emission of a Sn plasma and comparison with experiment
Authors: White J. , Hayden P. , Dunne P. , Cummings A. , Murphy N. , Sheridan P. , O’Sullivan G.
Published: November 2005

One key aspect in the drive to optimize the radiative output of a laser-produced plasma for extreme ultraviolet lithography is the radiation transport through the plasma. In tin-based plasmas, the radiation in the 2% bandwidth at 13.5 nm is predominantly due to 4d-4f and 4p-4d transitions from a range of tin ions (Sn7+ to Sn12+). The complexity of the configurations involved in these transitions is such that a line-by-line analysis is, computationally, extremely intensive. This work seeks to model the emission profiles of each ion by treating the transition arrays statistically, thus greatly simplifying radiation transport modeling. The results of the model are compared with experimental spectra from tin-based laser-produced plasmas.
Aging in a free-energy landscape model for glassy relaxation
Authors: Diezemann Gregor
Published: November 2005

The aging properties of a simple free-energy landscape model for the primary relaxation in supercooled liquids are investigated. The intermediate scattering function and the rotational correlation functions are calculated for the generic situation of a quench from a high temperature to below the glass transition temperature. It is found that the reequilibration of molecular orientations takes longer than for translational degrees of freedom. The time scale for reequilibration is determined by that of the primary relaxation as an intrinsic property of the model.
Structure, stability, and diffusion of arsenic-silicon interstitial pairs
Authors: Harrison Scott A. , Edgar Thomas F. , Hwang Gyeong S.
Published: November 2005

Recent experimental studies [A. Ural, P. B. Griffin, and J. D. Plummer, J. Appl. Phys. 85, 6440 (1999); R. Kim, T. Hirose, T. Shano, H. Tsuji, and K. Taniguchi, Jpn. J. Appl. Phys. 41, 227 (2002); S. Solmi, M. Ferri, M. Bersani, D. Giubertoni, and V. Soncini, J. Appl. Phys. 94, 4950 (2003)] have suggested the importance of Si interstitials in As transient enhanced diffusion during pn junction formation in silicon. Using density functional theory calculations within the generalized gradient approximation, we have examined the structure, stability and diffusion of As–Sii pairs. For the negatively charged As–Sii pair, we find a minimum energy structure in which the As atom bridges two approximate lattice Si atoms, while for the neutral and positively charged As–Sii we find the lowest energy structure is comprised of an As and Sii pair that is aligned in the [110] direction while sharing a lattice site. Our results suggest that in n-type extrinsic regions the diffusion of −1 charged As–Sii pairs will be prevailing with an overall activation energy of 3.1–3.4eV, while under intrinsic conditions the neutral and −1 charged pairs will both contribute to arsenic diffusion. The predicted activation energies are similar to experimental observations for As diffusion and previous calculations for As-vacancy complex diffusion. These results clearly support that interstitials can contribute significantly to As transient enhanced diffusion, particularly in the region where interstitials exist in excess.
Vibrational energy relaxation of the OH(D) stretch fundamental of methanol in carbon tetrachloride
Authors: Gulmen Tolga S. , Sibert Edwin L.
Published: November 2005

The lifetimes of the hydroxyl stretch fundamentals of two methanol isotopomers, MeOH and MeOD, in carbon tetrachloride solvent are calculated through the use of the perturbative Landau-Teller and fluctuating Landau-Teller methods. Examination of these systems allows for insight into the nature of the vibrational couplings that lead to intramolecular vibrational energy transfer. While both systems display energy transfer to nearly degenerate modes, MeOD also displays strong coupling to an off-resonant vibration. The relaxation of MeOH and MeOD occurs through transitions involving a total change in the vibrational quanta of 4 and 3, respectively. We calculate vibrational energy relaxation lifetimes of 4–5 ps for MeOH and 2–3 ps for MeOD that agree well with the experimentally determined values.
Strain dependent facet stabilization in selective-area heteroepitaxial growth of GaN nanostructures
Authors: Shahedipour-Sandvik F. , Grandusky J. , Alizadeh A. , Keimel C. , Ganti S. P. , Taylor S. T. , LeBoeuf S. F. , Sharma P.
Published: November 2005

We report on the selective-area heteroepitaxy and facet evolution of submicron GaN islands on GaN-sapphire, AlN-sapphire, and bare sapphire substrates. It is shown that strain due to the lattice mismatch between GaN and the underlying substrate has a significant influence on the final morphology and faceting of submicron islands. Under identical metalorganic chemical vapor deposition growth parameters, islands with low or no mismatch strain exhibit pyramidal morphologies, while highly strained islands evolve into prismatic shapes. Furthermore, islands grown with relatively low compressive mismatch strain yield more uniform arrays of pyramids as compared to the nonstrained, homoepitaxially grown crystals. It is proposed that the strain dependency of Ehrlich-Schwoebel barriers across different crystallographic planes could potentially account for the observed morphologies during selective area growth of GaN islands.
Theory of damped quantum rotation in NMR spectra. I. Fundamental aspects
Authors: Ratajczyk T. , Szymański S.
Published: November 2005

The damped quantum rotation (DQR) theory, formulated originally for methyl-like atomic groupings, is now extended to hindered (N>3)-fold molecular rotors, such as the cyclopentadienyl, benzene, and cycloheptatrienyl rings in solid phase environments. It heightens the significance of the Pauli principle in shaping up the stochastic dynamics of such objects, reflected in NMR line shapes. The corresponding NMR line-shape equation is derived; its stochastic part is shown for the first time to have the double commutator form for any values of the quantum-mechanical (coherence-damping) rate constants entering it. Constraints on the relative magnitudes of such constants are determined under which the DQR line-shape equation is converted into the phenomenological Alexander-Binsch equation describing classical jumps of the rotor. When all the quantum rate constants happen to be equal, the phenomenological model of equal jump rates between any two of the N (equivalent) orientations of the rotor is reproduced. On the other hand, the seemingly most plausible (for N>3) nearest-neighbor hopping model does not have any peculiar grounds in the DQR approach. For the special instances of stochastic molecular motions addressed in this work, the extended DQR formalism affords a quantification of the “degree of classicality” represented by a complete set of the relevant quantum rate constants. In view of our earlier experimental findings for the methyl rotors, the very occurrence of the nonclassical DQR effects seems unquestionable even for the objects of the size of benzene. The question of under what circumstances such effects can be big enough to be detected experimentally will be addressed in Part II of this work.
Hole-injecting conducting-polymer compositions for highly efficient and stable organic light-emitting diodes
Authors: Lee Tae-Woo , Kwon Ohyun , Kim Mu-Gyeom , Park Sang Hun , Chung Jaegwan , Kim Sang Yeol , Chung Youngsu , Park Joon-Yong , Han Eunsil , Huh Dal Ho , Park Jong-Jin , Pu Lyongsun
Published: November 2005

This letter introduces conducting polymer compositions which can be used for hole-injection layer in organic light-emitting diodes. The compositions are composed of poly (3,4-ethylenedioxythiophene) (PEDOT), polystyrene sulfonic acid (PSS) and a perfluorinated ionomer. The films based on these compositions showed much higher workfunction (∼5.3–5.7eV) than conventional PEDOT/PSS (∼5.0–5.2eV). When we fabricated blue polymer light-emitting diodes by using these compositions as a hole-injection layer, the luminescent efficiency was improved and the device lifetime was also enhanced relative to the device using the commercially available PEDOT/PSS. These compositions including perfluorinated ionomers can be one of the promising candidates for a hole-injection layer in organic light-emitting devices.
Calculating initial-state-selected reaction probabilities from thermal flux eigenstates: A transition-state-based approach
Authors: Huarte-Larrañaga Fermín , Manthe Uwe
Published: November 2005

An approach for the calculation of initial-state-selected reaction probabilities utilizing a transition-state view and the multiconfigurational time-dependent Hartree approach is presented. Using flux correlation functions, wave packets located in the transition-state region are constructed and propagated into the asymptotic region to obtain initial-state-selected reaction probabilities. A complete set of reaction probabilities is obtained from a single set of thermal flux eigenstates. Concepts previously applied with success to the calculation of k(T) or N(E) are transferred to the calculation of state-selected probabilities. The benchmark H+H2 (J=0) reaction on the LSTH potential-energy surface is used to test the reliability of this approach.
Quantum dynamics driven by continuous laser fields under measurements: Towards measurement-assisted quantum dynamics control
Authors: Sugawara M.
Published: November 2005

We study quantum system dynamics driven by continuous laser fields under the measurement process. In order to take into account the system transition due to the measurement, we define the superoperator which eliminates the coherence relevant to the measured quantum states. We clarify that the dynamics of the measured states is frozen in the frequent measurement limit, while the space spanned by unmeasured states is isolated from the original system. We also derive the effective Liouvillian which governs incoherent population dynamics under the condition, in which measurements are frequently applied. We apply the formulation to two-level and Λ-type three-level systems and clarify how the quantum measurements hinder the coherent population dynamics driven by the continuous laser fields in practical examples. Analysis on the laser field amplitude dependency of the final distribution in the t→∞ limit suggests the possibility of the measurement-assisted quantum control.
Relativistic calculation of indirect NMR spin-spin couplings using the Douglas-Kroll-Hess approximation
Authors: Melo Juan I. , Ruiz de Azúa Martín C. , Peralta Juan E. , Scuseria Gustavo E.
Published: November 2005

We have employed the Douglas-Kroll-Hess approximation to derive the perturbative Hamiltonians involved in the calculation of NMR spin-spin couplings in molecules containing heavy elements. We have applied this two-component quasirelativistic approach using finite perturbation theory in combination with a generalized Kohn-Sham code that includes the spin-orbit interaction self-consistently and works with Hartree-Fock and both pure and hybrid density functionals. We present numerical results for one-bond spin-spin couplings in the series of tetrahydrides CH4, SiH4, GeH4, and SnH4. Our two-component Hartree-Fock results are in good agreement with four-component Dirac-Hartree-Fock calculations, although a density-functional treatment better reproduces the available experimental data.
Accurate and efficient treatment of two-electron contributions in quasirelativistic high-order Douglas-Kroll density-functional calculations
Authors: van Wüllen Christoph , Michauk Christine
Published: November 2005

Two-component quasirelativistic approaches are in principle capable of reproducing results from fully relativistic calculations based on the four-component Dirac equation (with fixed particle number). For one-electron systems, this also holds in practice, but in many-electron systems one has to transform the two-electron interaction, which is necessary because a picture change occurs when going from the Dirac equation to a two-component method. For one-electron properties, one can take full account of picture change in a manageable way, but for the electron interaction, this would spoil the computational advantages which are the main reason to perform quasirelativistic calculations. Exploiting those picture change effects are largest in the atomic cores, which in molecular applications do not differ too much from the cores of isolated neutral atoms, we propose an elegant, efficient, and accurate approximation to the two-electron picture change problem. The new approach, called the “model potential” approach because it makes use of atomic (four- and two-component) data to estimate picture change effects in molecules, shares with the nuclear-only approach that the Douglas-Kroll operator needs to be constructed only once (not in each self-consistent-field iteration) and that no time-consuming multicenter relativistic two-electron integrals need to be calculated. The new approach correctly describes the screening of both the nearest nucleus and distant nuclei, for the scalar-relativistic as well as the spin-orbit parts of the Hamiltonian. The approach is tested on atomic and molecular-orbital energies as well as spectroscopic constants of the lead dimer.
Effect of thin iridium oxide on the formation of interface dipole in organic light-emitting diodes
Authors: Kim Soo Young , Lee Jong-Lam
Published: November 2005

The 4,4′-bis[N-(1-naphtyl)-N-phenyl-amino]biphenyl was in situ deposited on both iridium-oxide-coated indium-tin-oxide (IrOx–ITO) and O2-plasma-treated ITO (O2–ITO), and their interface dipole energies were quantitatively determined using synchrotron radiation photoemission spectroscopy. The dipole energies of both O2–ITO and IrOx–ITO were same with each other, −0.3eV, meaning the formation of same amount of interface dipole. The secondary electron emission spectra revealed that the work function of IrOx–ITO is higher by 0.5eV than that of O2–ITO, resulting in the decrease of the turn-on voltage via reduction of hole injection barrier.
The Gauss-Landau-Hall problem on Riemannian surfaces
Authors: Barros Manuel , Romero Alfonso , Cabrerizo José L. , Fernández Manuel
Published: November 2005

We introduce the notion of Gauss-Landau-Hall magnetic field on a Riemannian surface. The corresponding Landau-Hall problem is shown to be equivalent to the dynamics of a massive boson. This allows one to view that problem as a globally stated, variational one. In this framework, flowlines appear as critical points of an action with density depending on the proper acceleration. Moreover, we can study global stability of flowlines. In this equivalence, the massless particle model corresponds with a limit case obtained when the force of the Gauss-Landau-Hall magnetic field increases arbitrarily. We also obtain properties related with the completeness of flowlines for general magnetic fields. The paper also contains results relative to the Landau-Hall problem associated with a uniform magnetic field. For example, we characterize those revolution surfaces whose parallels are all normal flowlines of a uniform magnetic field.
Investigation of annealing effects on the adsorption of Ni on 4H–SiC (0001) surfaces using scanning tunneling microscopy and spectroscopy
Authors: Blackwood I. P. , Teng K. S. , Maffeïs T. G. G. , Franks J. R. , Wilks S. P.
Published: November 2005

The adsorption of Ni on 4H-SiC surfaces as a function of temperature has been investigated using scanning tunneling microscopy (STM) and variable tip-sample separation scanning tunneling spectroscopy (VTSS-STS). A submonolayer of Ni was deposited on an atomically clean (√3×√3) 4H-SiC sample, which was then annealed sequentially from 400to1000°C. VTSS-STS showed a reduction in the apparent surface band gap after Ni deposition, attributed to metal induced gap states. The size of the Ni clusters changed after annealing, due to the formation of Ni-silicides and diffusion. The surface band bending on Ni clusters increased upon annealing to 500°C, in good agreement with Schottky contact formation models. After annealing at 1000°C for 3min, various surface reconstructions were observed with STM, which are typical of graphite. Ni-silicide clusters also diffused into the SiC and some could still be observed below the graphite surface. VTSS-STS measurements of the graphite surface above diffused clusters displayed Ohmic behavior.
Dielectric constant dispersion of yttrium-doped (Ba,Sr)TiO3 films in the high-frequency (10kHz–67GHz) domain
Authors: Jeong Doo Seok , Hwang Cheol Seong , Baniecki J. D. , Shioga T. , Kurihara K. , Kamehara N. , Ishii M.
Published: November 2005

The frequency dispersion of the dielectric constant of yttrium (Y)-doped (Ba,Sr)TiO3 thin films (Y-BST) in the high-frequency domain (10kHz–67GHz) was investigated. In order to remove the substantial parasitic capacitances, inductances, and resistances from the measured impedance data, test samples, short-circuit standard, and open-circuit standard structures were fabricated and their frequency response was measured. Before removing parasitic components, the measured dielectric response showed a rolloff at approximately 4GHz. However, after circuit calibration, the dielectric constant was almost constant up to 40GHz where another rolloff was observed. However, this rolloff was due to the uncompensated small parasitic components. Therefore, the dielectric constant of the Y-BST films (170 with a film thickness of 30nm) showed small frequency dispersion corresponding to the Curie–von Schweidler dispersion, of which the exponent is −0.0131, up to 40GHz. Furthermore, the decrease of the capacitance was 17% in the frequency range from 10kHzto40GHz.
Reconstruction of atomic images from multiple-energy x-ray holograms of FePt films by the scattering pattern matrix method
Authors: Takahashi Yukio , Matsubara Eiichiro , Kawazoe Yoshiyuki , Takanashi Koki , Shima Toshiyuki
Published: November 2005

The scattering pattern matrix (SPM) method, in combination with multiple-energy holographic patterns, can be used to successfully reconstruct Pt atomic images in FePt epitaxial films, that are almost free from the artifacts that often appear in the images reconstructed using the Barton algorithm. The difference in the chemical short-range-order structure in two FePt films grown at different temperatures was clearly observed. The present method provides us a concrete breakthrough for a quantitative analysis of a three-dimensional local atom arrangement around a certain element in a single crystal without any preliminary knowledge of its structure.
High-sensitivity optical chemosensor based on coated long-period gratings for sub-ppm chemical detection in water
Authors: Cusano A. , Pilla P. , Contessa L. , Iadicicco A. , Campopiano S. , Cutolo A. , Giordano M. , Guerra G.
Published: November 2005

In this work, the use of fiber long-period gratings (LPGs)—coated with nanoscale overlays of Syndiotactic Polystyrene (sPS) in the nanoporous crystalline δ form as specific and highly sensitive chemical sensors for in water monitoring—is proposed. The approach presented here, combines the excellent sorption properties of δ form sPS as a chemosensitive layer with the excellent refractive index sensitivity of LPG-based sensors as ideal transducers. In particular, when overlays with a high refractive index compared with the cladding one are deposited along the grating region, as in this case, the refraction-reflection regime at the cladding-overlay interface occurs. As result of this mechanism, the attenuation bands of coated LPGs would respond to the optical changes induced in the sensitive overlay due to chemical sorption by a significant modification of the peak central wavelength and intensity. The sensitivity depends strongly on the overlay thickness and the grating coupled cladding mode. Here, sensor probes were prepared by using a dip coating technique and a proprietary procedure to obtain the δ form sPS. An experimental demonstration of the sensor capability to perform sub-ppm detection of chloroform in water at room temperature is reported here. Also, the effects of the overlay thickness and the cladding mode order on sensor sensitivity and response time have been numerically and experimentally investigated.
Effects of collective excitations on the quantum well intersubband absorption
Authors: Mi X. W. , Cao J. C. , Zhang C. , Meng F. B.
Published: November 2005

The dependence of the intersubband absorption spectra on the Coulomb interaction and quantum well (QW) width is studied. Rather than following the Fermi–Dirac distribution, we have solved the intersubband equations of motion to determine the subband population self-consistently. We have gone beyond the linear absorption theory to show the effect of various many-body interactions on the absorption spectra. It is found that the redistribution of electrons in excited states reduces the absorption. Our results indicate that the line shape and peak position are determined by the interplay of different collective excitations, such as the Fermi edge singularity and the intersubband plasmon. The dependence of the absorption spectrum on the QW width and the subband effective masses is also discussed.
Oxygen behavior in aluminum nitride
Authors: Kazan M. , Rufflé B. , Zgheib Ch. , Masri P.
Published: November 2005

The infrared lattice-vibration spectra of three polycrystalline samples of wurtzite AlN differing in their oxygen contamination have been studied by measuring the room-temperature reflectivity at near-normal incidence in the 400-3000cm−1 frequency range using unpolarized light. A type of highly-contaminated-material reflectivity spectrum has been observed. Two-mode behavior has been observed at low oxygen concentration, one-mode behavior tends to be dominant when the oxygen concentration increases and only one-mode behavior has been observed at high oxygen concentration. Otherwise, a careful analysis of the data using the Kramers-Kronig technique and classical dispersion theory gives, in addition to the transverse and longitudinal mode frequencies, two in-band resonance modes attributed to oxygen point defects in AlN. Changes in the frequencies of these modes with oxygen concentration are interpreted as a transition in the oxygen accommodation defect as the concentration of oxygen increases. A model for the behavior of oxygen in AlN is proposed.
Atomistic simulations of grain boundary pinning in CuFe alloys
Authors: Zepeda-Ruiz Luis A. , Gilmer George H. , Sadigh Babak , Caro Alfredo , Oppelstrup Tomas , Hamza Alex V.
Published: November 2005

We apply a hybrid Monte Carlo-molecular dynamics code to the study of grain boundary motion upon annealing of pure Cu and Cu with low concentrations of Fe. The hybrid simulations account for segregation and precipitation of the low solubility Fe, together with curvature-driven grain boundary motion. Grain boundaries in two different systems, a Σ7+U-shaped half-loop grain and a nanocrystalline sample, were found to be pinned in the presence of Fe concentrations exceeding 3%.
Structural characteristics of carbon nanofibers for on-chip interconnect applications
Authors: Ominami Yusuke , Ngo Quoc , Austin Alexander J. , Yoong Hans , Yang Cary Y. , Cassell Alan M. , Cruden Brett A. , Li Jun , Meyyappan M.
Published: November 2005

In this letter, we compare the structures of plasma-enhanced chemical vapor deposition of Ni-catalyzed and Pd-catalyzed carbon nanofibers (CNFs) synthesized for on-chip interconnect applications with scanning transmission electron microscopy (STEM). The Ni-catalyzed CNF has a conventional fiberlike structure and many graphitic layers that are almost parallel to the substrate at the CNF base. In contrast, the Pd-catalyzed CNF has a multiwall nanotubelike structure on the sidewall spanning the entire CNF. The microstructure observed in the Pd-catalyzed fibers at the CNF-metal interface has the potential to lower contact resistance significantly, as our electrical measurements using current-sensing atomic force microscopy indicate. A structural model is presented based on STEM image analysis.