bluuebunny/crossref_metadata_2025 huggingface dataset:
Duloxetine in the treatment of major depressive disorder: a placebo- and paroxetine-controlled trial
Authors: Perahia D.G.S. , Wang F. , Mallinckrodt C.H. , Walker D.J. , Detke M.J.
Published: May 2006

Objective:

Duloxetine doses of 80 and 120 mg/day were assessed for efficacy and safety in the treatment of major depressive disorder (MDD).

Methods:

In this randomized, double-blind trial, patients age ≥ 18 meeting DSM-IV criteria for MDD were randomized to placebo (N = 99), duloxetine 80 mg/day (N = 93), duloxetine 120 mg/day (N = 103), or paroxetine 20 mg/day (N = 97). The primary outcome measure was mean change from baseline in the 17-item Hamilton rating scale for depression (HAMD17) total score after 8 weeks of treatment; a number of secondary efficacy measures also were assessed. Safety and tolerability were assessed via collection and analysis of treatment–emergent adverse events (TEAEs), vital signs, and weight. The Arizona sexual experiences scale was used to assess sexual functioning. Patients who had a ≥ 30% reduction from baseline in the HAMD17 total score at the end of the acute phase entered a 6-month continuation phase where they remained on the same treatment as they had taken during the acute phase; efficacy and safety/tolerability outcomes were assessed during continuation treatment.

Results:

More than 87% of patients completed the acute phase in each treatment group. Duloxetine-treated patients (both doses) showed significantly greater improvement (P < 0.05) in the HAMD17 total score at week 8 compared with placebo. Paroxetine was not significantly different from placebo (P = 0.089) on mean change on the HAMD17. Duloxetine 120 mg/day also showed significant improvement on most secondary efficacy measures (six of nine) compared with placebo while duloxetine 80 mg/day (three of nine) and paroxetine (three of nine) were significantly superior to placebo on fewer secondary measures. HAMD17 mean change data from this study and an identical sister study were pooled as defined a priori for the purposes of performing a non-inferiority test versus paroxetine. Both duloxetine doses met statistical criteria for non-inferiority to paroxetine. TEAE reporting rates were low in all treatment groups and no deaths occurred in the acute or continuation phases.

Conclusions:

The efficacy of duloxetine at doses of 80 and 120 mg/day in the treatment of MDD was demonstrated. Tolerability, as measured by TEAEs, and safety were similar to paroxetine 20 mg/day and consistent with previous published data on duloxetine in the treatment of MDD.
A naturalistic multicenter study of intramuscular olanzapine in the treatment of acutely agitated manic or schizophrenic patients
Authors: San L. , Arranz B. , Querejeta I. , Barrio S. , De la Gándara J. , Pérez V.
Published: May 2006

Background

We conducted a naturalistic, multicenter, 24-hour, nonrandomized, observational study describing for the first time the effectiveness and safety of intramuscular (IM) olanzapine to control agitation and aggression in “real world” patients with psychosis. The data thus obtained was compared with that reported from randomized double-blind clinical trials.

Method

92 patients attending psychiatric emergency settings were enrolled. The study subjects were 44 male and 48 female patients with a mean age of 36.5 ± 12 years and DSM-IV-TR diagnoses of schizophrenia (48.9%), psychotic disorder not specified (23.9%) or bipolar disorder (27.2%). 10 mg IM olanzapine was administered to all patients. An optional second injection was permitted ≥ 2 hours later in line with hospital policy. Evaluations (PANSS-EC and CGI-S) were performed at baseline and 2 and 24 hours following the IM injection.

Results

Two hours after IM olanzapine was administered, a mean decrease of –9.6 in the PANSS-EC from a baseline score of 26.5 was recorded. At the 24-hour endpoint a statistically and clinically significant reduction in the PANSS-EC scores (11.6 ± 5.3) was observed as compared with values at study entry (26.5 ± 5.9) and at 2 hours endpoint (16.9 ± 9.3), which represent a mean decrease of –14.9 and –5.3, respectively.

Conclusion

The present naturalistic study provides naturalistic data on the effectiveness of IM olanzapine in the treatment of acute agitation in patients with schizophrenia or bipolar mania that is in line the data obtained in randomized double-blind clinical trials.
Brain α‐dystroglycan displays unique glycoepitopes and preferential binding to laminin‐10/11
Authors: McDearmon Erin L. , Combs Ariana C. , Sekiguchi Kiyotoshi , Fujiwara Hironobu , Ervasti James M.
Published: May 2006

α‐Dystroglycan was quantitatively enriched from mammalian brain based on its uniform reactivity with Vicia villosa agglutinin and resolved into sub‐populations possessing or lacking the sulfated glucuronic acid epitope recognized by monoclonal antibody HNK‐1. We generated a new monoclonal antibody specific for a glycoepitope on brain α‐dystroglycan but absent from α‐dystroglycan expressed in all other tissues examined. Finally, we found that laminin‐10/11 preferentially bound to brain α‐dystroglycan compared to skeletal muscle α‐dystroglycan. Our results suggest that tissue‐specific glycosylation modifies the laminin binding specificity of α‐dystroglycan.
Folding free‐energy landscape of a 10‐residue mini‐protein, chignolin
Authors: Satoh Daisuke , Shimizu Kentaro , Nakamura Shugo , Terada Tohru
Published: May 2006

Chignolin is an artificial mini‐protein composed of 10 residues (GYDPETGTWG) that has been shown to cooperatively fold into a β‐hairpin structure in water. We extensively explored the conformational space of chignolin using a 180‐ns multicanonical molecular dynamics (MD) simulation and analyzed its folding free‐energy landscape. In the MD trajectory, we found structures that satisfy 99% of the experimental restraints and are quite close to the experimentally determined structures with Cα root‐mean‐square‐deviations of less than 0.5 Å. These structures formed a large cluster in the conformational space with the largest probability of existence, agreeing well with the experiment.
Summer transport estimates of the Kamchatka Current derived as a variational inverse of hydrophysical and surface drifter data
Authors: Panteleev G. G. , Stabeno P. , Luchin V. A. , Nechaev D. A. , Ikeda M.
Published: May 2006

The quasistationary summer Bering Sea circulation is reconstructed as a variational inverse of the hydrographic and atmospheric climatologies, transport estimates through the Bering Strait, and surface drifter data. Our results indicate the splitting of the Kamchatka Current in the vicinity of the Shirshov Ridge. This branching is in agreement with independent ARGO drifter observations. It was also found, that transport of the Kamchatka Current gradually increases downstream from 14 Sv in the Olyutorsky Gulf to 24 Sv in the Kamchatka Strait, which is twice higher than previous estimates.
A statistical investigation of preearthquake ionospheric anomaly
Authors: Liu J. Y. , Chen Y. I. , Chuo Y. J. , Chen C. S.
Published: May 2006

Empirical evidence of the preearthquake ionospheric anomalies (PEIAs) is reported by statistically investigating the relationship between variations of the plasma frequency at the ionospheric F2 peak foF2 and 184 earthquakes with magnitude M ≥ 5.0 during 1994–1999 in the Taiwan area. The PEIA, defined as the abnormal decrease more than about 25% in the ionospheric foF2 during the afternoon period, 1200–1800 LT, significantly occurs within 5 days before the earthquakes. Moreover, the odds of earthquakes with PEIA increase with the earthquake magnitude but decrease with the distance from the epicenter to the ionosonde station. These results indicate that the PEIA is energy related.
Orientation and motion of a plasma discontinuity from single‐spacecraft measurements: Generic residue analysis of Cluster data
Authors: Sonnerup B. U. Ö. , Haaland S. , Paschmann G. , Dunlop M. W. , Rème H. , Balogh A.
Published: May 2006

A unified minimum‐residue approach is presented to the use of classical conservation laws for determination of the orientation and motion of a plasma discontinuity, using data from a single spacecraft that traverses the discontinuity and makes measurements, not only on its two sides but also within it. The method is a generalization of the minimum Faraday residue (MFR) analysis technique described by Khrabrov and Sonnerup (1998a). It includes not only the standard MHD conservation laws for mass, momentum, total energy, and (where applicable) entropy, but also magnetic flux conservation from Faraday's law, absence of magnetic poles from ∇ · B = 0, and electric charge conservation from Ampère's law. A method, denoted by COM, for combining the results from more than one conservation law into a single optimal determination of the orientation and motion is presented, along with a general approach to the application of a certain class of constraints that can be placed on the vector normal to the discontinuity. The methodology, which is applicable to many types of discontinuity, including shocks, is illustrated by analysis of one magnetopause encounter by two of the four Cluster spacecraft (C1 and C3). The results from the various individual methods have considerable spread. However, in favorable circumstances and by exercising considerable care, the vector normal to the magnetopause from COM can be accurate to within a couple of degrees. For the C1 crossing, believed to be nearly a tangential discontinuity, albeit with signatures of incipient reconnection, the magnetopause speed (−56 km s−1) from COM appears accurate to within a few km s−1. The plasma flow across the magnetopause and the normal field component are both very nearly zero, and the results are consistent with those obtained from timing of the layer as it crosses the four Cluster spacecraft (assuming a constant thickness of the layer). The results for the velocity of the magnetopause and for the plasma flow across the layer are less consistent for the C3 crossing, believed to be a rotational discontinuity. For this crossing the presence of a component of the magnetic field along the normal direction could not be established with certitude. It is likely that the lower quality of the results for this crossing is caused by local multidimensional structure of the magnetopause.
Transatlantic Saharan dust transport: Model simulation and results
Authors: Kallos George , Papadopoulos Anastasios , Katsafados Petros , Nickovic Slobodan
Published: May 2006

Long‐range transport of desert dust from the Sahara across the northern Atlantic has been recorded many times by satellite imagery and ground‐based measurements. However, this evidence cannot fully describe all the phases of the atmospheric dust lifecycle. To partly compensate for the lack of such knowledge, an atmospheric model with incorporated dust uptake‐transport‐deposition module has been used in this study. The goal was to assess qualitatively and quantitatively the ability of the model to predict the dust cycle in the atmosphere for a long period. For this purpose, the complicated dust episode of June–July 1993 (almost one month) was simulated with the SKIRON weather forecasting system. This dust intrusion was associated with long‐range transport of Saharan dust across the Atlantic Ocean and simultaneous regional transport towards the Mediterranean Sea. Comparison of the forecasts with the available observations (in a qualitative and quantitatively way) indicated that the model was able to simulate the long‐range dust transport patterns and in particular to estimate the spatiotemporal distribution of the dust concentration on a satisfactory way.
An adhesion molecule in free‐living Dictyostelium amoebae with integrin β features
Authors: Cornillon Sophie , Gebbie Leigh , Benghezal Mohammed , Nair Prashant , Keller Sebastien , Wehrle‐Haller Bernhard , Charette Steve J , Brückert Franz , Letourneur François , Cosson Pierre
Published: May 2006

The study of free‐living amoebae has proven valuable to explain the molecular mechanisms controlling phagocytosis, cell adhesion and motility. In this study, we identified a new adhesion molecule in Dictyostelium amoebae. The SibA (Similar to Integrin Beta) protein is a type I transmembrane protein, and its cytosolic, transmembrane and extracellular domains contain features also found in integrin β chains. In addition, the conserved cytosolic domain of SibA interacts with talin, a well‐characterized partner of mammalian integrins. Finally, genetic inactivation of SIBA affects adhesion to phagocytic particles, as well as cell adhesion and spreading on its substrate. It does not visibly alter the organization of the actin cytoskeleton, cellular migration or multicellular development. Our results indicate that the SibA protein is a Dictyostelium cell adhesion molecule presenting structural and functional similarities to metazoan integrin β chains. This study sheds light on the molecular mechanisms controlling cell adhesion and their establishment during evolution.
Active control for stabilization of neoclassical tearing modes
Authors: Humphreys D. A. , Ferron J. R. , La Haye R. J. , Luce T. C. , Petty C. C. , Prater R. , Welander A. S.
Published: May 2006

This work describes active control algorithms used by DIII-D [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] to stabilize and maintain suppression of 3/2 or 2/1 neoclassical tearing modes (NTMs) by application of electron cyclotron current drive (ECCD) at the rational q surface. The DIII-D NTM control system can determine the correct q-surface/ECCD alignment and stabilize existing modes within 100–500ms of activation, or prevent mode growth with preemptive application of ECCD, in both cases enabling stable operation at normalized beta values above 3.5. Because NTMs can limit performance or cause plasma-terminating disruptions in tokamaks, their stabilization is essential to the high performance operation of ITER [R. Aymar et al., ITER Joint Central Team, ITER Home Teams, Nucl. Fusion 41, 1301 (2001)]. The DIII-D NTM control system has demonstrated many elements of an eventual ITER solution, including general algorithms for robust detection of q-surface/ECCD alignment and for real-time maintenance of alignment following the disappearance of the mode. This latter capability, unique to DIII-D, is based on real-time reconstruction of q-surface geometry by a Grad-Shafranov solver using external magnetics and internal motional Stark effect measurements. Alignment is achieved by varying either the plasma major radius (and the rational q surface) or the toroidal field (and the deposition location). The requirement to achieve and maintain q-surface/ECCD alignment with accuracy on the order of 1cm is routinely met by the DIII-D Plasma Control System and these algorithms. We discuss the integrated plasma control design process used for developing these and other general control algorithms, which includes physics-based modeling and testing of the algorithm implementation against simulations of actuator and plasma responses. This systematic design/test method and modeling environment enabled successful mode suppression by the NTM control system upon first-time use in an experimental discharge.
Structure and motion of edge turbulence in the National Spherical Torus Experiment and Alcator C-Mod
Authors: Zweben S. J. , Maqueda R. J. , Terry J. L. , Munsat T. , Myra J. R. , D’Ippolito D. , Russell D. A. , Krommes J. A. , LeBlanc B. , Stoltzfus-Dueck T. , Stotler D. P. , Williams K. M. , Bush C. E. , Maingi R. , Grulke O. , Sabbagh S. A. , White A. E.
Published: May 2006

In this paper we compare the structure and motion of edge turbulence observed in L-mode vs. H-mode plasmas in the National Spherical Torus Experiment (NSTX) [M. Ono, M. G. Bell, R. E. Bell et al., Plasma Phys. Controlled Fusion 45, A335 (2003)]. The radial and poloidal correlation lengths are not significantly different between the L-mode and the H-mode in the cases examined. The poloidal velocity fluctuations are lower and the radial profiles of the poloidal turbulence velocity are somewhat flatter in the H-mode compared with the L-mode plasmas. These results are compared with similar measurements Alcator C-Mod [E. Marmar, B. Bai, R. L. Boivin et al., Nucl. Fusion 43, 1610 (2003)], and with theoretical models.
Alfvén wave excitation and single-pass ion cyclotron heating in a fast-flowing plasma
Authors: Ando Akira , Inutake Masaaki , Hatanaka Motoi , Hattori Kunihiko , Tobari Hiroyuki , Yagai Tsuyoshi
Published: May 2006

Alfvén wave excitation and ion heating experiments were performed in a fast flowing plasma. When rf waves in the ion cyclotron range of frequency were excited by right- and left-handed helically wound antennas, shear and compressional Alfvén waves with azimuthal mode number m=−1 and m=+1, respectively were excited. The dispersion relations of the propagating waves were obtained experimentally and compared with the theoretical ones, including the Doppler effect of the plasma flow. Strong ion heating was observed in the fast-flowing plasma when rf waves were launched by the right-handed helically wound antenna in a magnetic beach configuration. The plasma thermal energy W⊥ and the ion temperature Ti drastically increased during the rf pulse. This large increase was observed under lower-density conditions, where the ratio of the ion cyclotron frequency to the ion-ion collision frequency becomes high. The resonance magnetic field was affected by the Doppler shift due to the fast-flowing plasma.
Ultrashort laser pulses and ultrashort electron bunches generated in relativistic laser-plasma interaction
Authors: Faure J. , Glinec Y. , Gallot G. , Malka V.
Published: May 2006

An experimental study of the interaction of ultrashort laser pulses with underdense plasmas in the relativistic regime is presented. A parameter regime of particular interest was found: the so-called bubble regime. In this regime, the laser pulse is focused to relativistic intensities and its pulse duration is comparable to or shorter than the plasma period. A wealth of physical phenomena occurs for such physical parameters. These phenomena have multiple signatures which have been investigated experimentally: (i) the generation of a high quality electron beam (high energy, very collimated, quasimonoenergetic energy distribution); (ii) the laser pulse temporal shortening in nonlinear plasma waves. In addition, experimental results suggest that the electron beam produced in this way has temporal structures shorter than 50fs.
Computational modeling of fully ionized magnetized plasmas using the fluid approximation
Authors: Schnack D. D. , Barnes D. C. , Brennan D. P. , Hegna C. C. , Held E. , Kim C. C. , Kruger S. E. , Pankin A. Y. , Sovinec C. R.
Published: May 2006

Strongly magnetized plasmas are rich in spatial and temporal scales, making a computational approach useful for studying these systems. The most accurate model of a magnetized plasma is based on a kinetic equation that describes the evolution of the distribution function for each species in six-dimensional phase space. High dimensionality renders this approach impractical for computations for long time scales. Fluid models are an approximation to the kinetic model. The reduced dimensionality allows a wider range of spatial and∕or temporal scales to be explored. Computational modeling requires understanding the ordering and closure approximations, the fundamental waves supported by the equations, and the numerical properties of the discretization scheme. Several ordering and closure schemes are reviewed and discussed, as are their normal modes, and algorithms that can be applied to obtain a numerical solution.
A new method to realize cluster synchronization in connected chaotic networks
Authors: Ma Zhongjun , Liu Zengrong , Zhang Gang
Published: May 2006

In this article, a new method, which constructs a coupling scheme with cooperative and competitive weight-couplings, is used to stabilize arbitrarily selected cluster synchronization patterns with several clusters for connected chaotic networks. By the coupling scheme, a sufficient condition about the global stability of the selected cluster synchronization patterns is derived. That is to say, when the sufficient condition is satisfied, arbitrarily selected cluster synchronization patterns in connected chaotic networks can be achieved via an appropriate coupled scheme. The effectiveness of the method is illustrated by an example.
Access to sustained high-beta with internal transport barrier and negative central magnetic shear in DIII-D
Authors: Garofalo A. M. , Doyle E. J. , Ferron J. R. , Greenfield C. M. , Groebner R. J. , Hyatt A. W. , Jackson G. L. , Jayakumar R. J. , Kinsey J. E. , La Haye R. J. , McKee G. R. , Murakami M. , Okabayashi M. , Osborne T. H. , Petty C. C. , Politzer P. A. , Reimerdes H. , Scoville J. T. , Solomon W. M. , St. John H. E. , Strait E. J. , Turnbull A. D. , Wade M. R. , VanZeeland M. A.
Published: May 2006

High values of normalized β (βN∼4) and safety factor (qmin∼2) have been sustained simultaneously for ∼2s in DIII-D [J.L. Luxon, Nucl. Fusion 42, 64 (2002)], suggesting a possible path to high fusion performance, steady-state tokamak scenarios with a large fraction of bootstrap current. The combination of internal transport barrier and negative central magnetic shear at high β results in high confinement (H89P>2.5) and large bootstrap current fraction (fBS>60%) with good alignment. Previously, stability limits in plasmas with core transport barriers have been observed at moderate values of βN (<3) because of the pressure peaking which normally develops from improved core confinement. In recent DIII-D experiments, the internal transport barrier is clearly observed in the electron density and in the ion temperature and rotation profiles at ρ∼0.5 but not in the electron temperature profile, which is very broad. The misalignment of Ti and Te gradients may help to avoid a large local pressure gradient. Furthermore, at low internal inductance ∼0.6, the current density gradients are close to the vessel and the ideal kink modes are strongly wall-coupled. Simultaneous feedback control of both external and internal sets of n=1 magnetic coils was used to maintain optimal error field correction and resistive wall mode stabilization, allowing operation above the free-boundary β limit. Large particle orbits at high safety factor in the core help to broaden both the pressure and the beam-driven current profiles, favorable for steady-state operation. At plasma current flat top and β∼5%, a noninductive current fraction of ∼100% has been observed. Stability modeling shows the possibility for operation up to the ideal-wall limit at β∼6%.
Thermal desorption of hydrogen from carbon nanosheets
Authors: Zhao X. , Outlaw R. A. , Wang J. J. , Zhu M. Y. , Smith G. D. , Holloway B. C.
Published: May 2006

Carbon nanosheets are a unique nanostructure that, at their thinnest configuration, approach a single freestanding graphene sheet. Temperature desorption spectroscopy (TDS) has shown that the hydrogen adsorption and incorporation during growth of the nanosheets by radio frequency plasma-enhanced chemical vapor deposition are significant. A numerical peak fitting to the desorption spectra (300–1273K) via the Polanyi-Wigner equation showed that desorption followed a second order process, presumably by the Langmuir-Hinshelwood mechanism. Six peaks provide the best fit to the TDS spectra. Surface desorption activation energies were determined to be 0.59, 0.63, and 0.65eV for the external graphite surface layers and 0.85, 1.15, and 1.73eV for desorption and diffusion from the bulk. In contrast to TDS data from previously studied a-C:H films [Schenk et al. J. Appl. Phys. 77, 2462 (1995)], a greater amount of hydrogen bound as sp2 hybridized carbon was observed. A previous x-ray diffraction study of these films has shown a significant graphitic character with a crystallite dimension of La=10.7nm. This result is consistent with experimental results by Raman spectroscopy that show as-grown carbon nanosheets to be crystalline as commercial graphite with a crystallite size of La=11nm. Following TDS, Raman data indicate that the average crystallite increased in size to La=15nm.
Reducing or enhancing chaos using periodic orbits
Authors: Bachelard R. , Chandre C. , Leoncini X.
Published: May 2006

A method to reduce or enhance chaos in Hamiltonian flows with two degrees of freedom is discussed. This method is based on finding a suitable perturbation of the system such that the stability of a set of periodic orbits changes (local bifurcations). Depending on the values of the residues, reflecting their linear stability properties, a set of invariant tori is destroyed or created in the neighborhood of the chosen periodic orbits. An application on a paradigmatic system, a forced pendulum, illustrates the method.
The midpoint method for parallelization of particle simulations
Authors: Bowers Kevin J. , Dror Ron O. , Shaw David E.
Published: May 2006

The evaluation of interactions between nearby particles constitutes the majority of the computational workload involved in classical molecular dynamics (MD) simulations. In this paper, we introduce a new method for the parallelization of range-limited particle interactions that proves particularly suitable to MD applications. Because it applies not only to pairwise interactions but also to interactions involving three or more particles, the method can be used for evaluation of both nonbonded and bonded forces in a MD simulation. It requires less interprocessor data transfer than traditional spatial decomposition methods at all but the lowest levels of parallelism. It gains an additional practical advantage in certain commonly used interprocessor communication networks by distributing the communication burden more evenly across network links and by decreasing the associated latency. When used to parallelize MD, it further reduces communication requirements by allowing the computations associated with short-range nonbonded interactions, long-range electrostatics, bonded interactions, and particle migration to use much of the same communicated data. We also introduce certain variants of this method that can significantly improve the balance of computational load across processors.
Analyzing atomic liquids and solids by means of two-dimensional Raman spectra in frequency domain
Authors: Nagata Yuki , Hasegawa Taisuke , Tanimura Yoshitaka
Published: May 2006

A practical method to evaluate the contributions of the nonlinear polarizability and anharmonicity of potentials from the experimental and simulation data by using double Fourier transformation is presented. In a Lennard-Jones potential system, an approximated expression of the fifth-order response function using the ratio between nonlinear polarizability and anharmonicity exhibits a good agreement with the results of the molecular dynamics simulation. In a soft-core case, the fifth-order Raman signal indicates that the system consists of the delocalized and localized modes, and only the delocalized mode affects the dramatic change of the fifth-order Raman response functions between solid and liquid phases through nonlinear polarizability.
Frequency-selective homonuclear dipolar recoupling in solid state NMR
Authors: Paravastu Anant K. , Tycko Robert
Published: May 2006

We introduce a new approach to frequency-selective homonuclear dipolar recoupling in solid state nuclear magnetic resonance (NMR) with magic-angle spinning (MAS). This approach, to which we give the acronym SEASHORE, employs alternating periods of double-quantum recoupling and chemical shift evolution to produce phase modulations of the recoupled dipole-dipole interactions that average out undesired couplings, leaving only dipole-dipole couplings between nuclear spins with a selected pair of NMR frequencies. In principle, SEASHORE is applicable to systems with arbitrary coupling strengths and arbitrary sets of NMR frequencies. Arbitrary MAS frequencies are also possible, subject only to restrictions imposed by the pulse sequence chosen for double-quantum recoupling. We demonstrate the efficacy of SEASHORE in experimental C13 NMR measurements of frequency-selective polarization transfer in uniformly N15, C13-labeled L-valine powder and frequency-selective intermolecular polarization transfer in amyloid fibrils formed by a synthetic decapeptide containing uniformly N15, C13-labeled residues.
Broad shape resonance effects in CaF Rydberg states
Authors: Altunata Serhan N. , Coy Stephen L. , Field Robert W.
Published: May 2006

Results of ab initio R-matrix calculations [S. N. Altunata et al., J. Chem. Phys. 123, 084319 (2005)] indicate the presence of a broad shape resonance in electron-CaF+ scattering for the Σ+2 electronic symmetry near the ionization threshold. The properties of this shape resonance are analyzed using the adiabatic partial-wave expansion of the scattered electron wave function introduced by Le Dourneuf et al. [J. Phys. B 15, L685 (1982)]. The qualitative aspects of the shape resonance are explained by an adiabatic approximation on the electronic motion. Mulliken’s rule for the structure of the Rydberg state wave functions [R. S. Mulliken, J. Am. Chem. Soc. 86, 3183 (1964)] specifies that, except for an (n*)−3∕2 amplitude scale factor, every excited state wave function within one Rydberg series is built on an innermost lobe that remains invariant in shape and nodal position as a function of the excitation energy. Mulliken’s rule implies a weak energy dependence of the quantum defects for an unperturbed molecular Rydberg series, which is given by the Rydberg-Ritz formula. This zero-order picture is violated by a single Σ+2 CaF Rydberg series at all Rydberg state energies (n*=5→∞, more so with increasing n*) below the ionization threshold, under the broad width of the shape resonance. Such a violation is diagnostic of a global “scarring” of the Rydberg spectrum, which is distinct from the more familiar local level perturbations.
Experimental simulations of beam propagation over large distances in a compact linear Paul trap
Authors: Gilson Erik P. , Chung Moses , Davidson Ronald C. , Dorf Mikhail , Efthimion Philip C. , Majeski Richard
Published: May 2006

The Paul Trap Simulator Experiment (PTSX) is a compact laboratory experiment that places the physicist in the frame of reference of a long, charged-particle bunch coasting through a kilometers-long magnetic alternating-gradient (AG) transport system. The transverse dynamics of particles in both systems are described by similar equations, including nonlinear space-charge effects. The time-dependent voltages applied to the PTSX quadrupole electrodes are equivalent to the axially oscillating magnetic fields applied in the AG system. Experiments concerning the quiescent propagation of intense beams over large distances can then be performed in a compact and flexible facility. An understanding and characterization of the conditions required for quiescent beam transport, minimum halo particle generation, and precise beam compression and manipulation techniques, are essential, as accelerators and transport systems demand that ever-increasing amounts of space charge be transported. Application areas include ion-beam-driven high energy density physics, high energy and nuclear physics accelerator systems, etc. One-component cesium plasmas have been trapped in PTSX that correspond to normalized beam intensities, ŝ=ωp2(0)∕2ωq2, up to 80% of the space-charge limit where self-electric forces balance the applied focusing force. Here, ωp(0)=[nb(0)eb2∕mbϵ0]1∕2 is the on-axis plasma frequency, and ωq is the smooth-focusing frequency associated with the applied focusing field. Plasmas in PTSX with values of ŝ that are 20% of the limit have been trapped for times corresponding to equivalent beam propagation over 10km. Results are presented for experiments in which the amplitude of the quadrupole focusing lattice is modified as a function of time. It is found that instantaneous changes in lattice amplitude can be detrimental to transverse confinement of the charge bunch.
The two-loop massless (λ∕4!)φ4 model in nontranslational invariant domain
Authors: Alcalde M. Aparicio , Hidalgo G. Flores , Svaiter N. F.
Published: May 2006

We study the (λ∕4!)φ4 massless scalar field theory in a four-dimensional Euclidean space, where all but one of the coordinates are unbounded. We are considering Dirichlet boundary conditions in two hyperplanes, breaking the translation invariance of the system. We show how to implement the perturbative renormalization up to two-loop level of the theory. First, analyzing the full two and four-point functions at the one-loop level, we show that the bulk counterterms are sufficient to render the theory finite. Meanwhile, at the two-loop level, we must also introduce surface counterterms in the bare Lagrangian in order to make finite the full two and also four-point Schwinger functions.
Numerical study of the steady state fluctuation relations far from equilibrium
Authors: Williams Stephen R. , Searles Debra J. , Evans Denis J.
Published: May 2006

A thermostatted dynamical model with five degrees of freedom is used to test the fluctuation relation of Evans and Searles (Ω-FR) and that of Gallavotti and Cohen (Λ-FR). In the absence of an external driving field, the model generates a time-independent ergodic equilibrium state with two conjugate pairs of Lyapunov exponents. Each conjugate pair sums to zero. The fluctuation relations are tested numerically both near and far from equilibrium. As expected from previous work, near equilibrium the Ω-FR is verified by the simulation data while the Λ-FR is not confirmed by the data. Far from equilibrium where a positive exponent in one of these conjugate pairs becomes negative, we test a conjecture regarding the Λ-FR [Bonetto et al., Physica D 105, 226 (1997); Giuliani et al., J. Stat. Phys. 119, 909 (2005)]. It was conjectured that when the number of nontrivial Lyapunov exponents that are positive becomes less than the number of such negative exponents, then the form of the Λ-FR needs to be corrected. We show that there is no evidence for this conjecture in the empirical data. In fact, when the correction factor differs from unity, the corrected form of Λ-FR is less accurate than the uncorrected Λ-FR. Also as the field increases the uncorrected Λ-FR appears to be satisfied with increasing accuracy. The reason for this observation is likely to be that as the field increases, the argument of the Λ-FR more and more accurately approximates the argument of the Ω-FR. Since the Ω-FR works for arbitrary field strengths, the uncorrected Λ-FR appears to become ever more accurate as the field increases. The final piece of evidence against the conjecture is that when the smallest positive exponent changes sign, the conjecture predicts a discontinuous change in the “correction factor” for Λ-FR. We see no evidence for a discontinuity at this field strength.
Experimental evidence of anomalous phase synchronization in two diffusively coupled Chua oscillators
Authors: Dana Syamal Kumar , Blasius Bernd , Kurths Jürgen
Published: May 2006

We study the transition to phase synchronization in two diffusively coupled, nonidentical Chua oscillators. In the experiments, depending on the used parameterization, we observe several distinct routes to phase synchronization, including states of either in-phase, out-of-phase, or antiphase synchronization, which may be intersected by an intermediate desynchronization regime with large fluctuations of the frequency difference. Furthermore, we report the first experimental evidence of an anomalous transition to phase synchronization, which is characterized by an initial enlargement of the natural frequency difference with coupling strength. This results in a maximal frequency disorder at intermediate coupling levels, whereas usual phase synchronization via monotonic decrease in frequency difference sets in only for larger coupling values. All experimental results are supported by numerical simulations of two coupled Chua models.
Mutual focusing/defocusing of Gaussian electromagnetic beams in collisional plasmas
Authors: Sodha Mahendra Singh , Sharma Ashutosh
Published: May 2006

In this paper the authors have considered the mutual focusing/defocusing of a number of coaxial Gaussian electromagnetic beams in a singly ionized collisional plasma (initially in thermal equilibrium) and the ionosphere (with singly charged ions). Starting from the expression of the electron temperature in terms of the irradiance of the waves, expressions for the electron density and the dielectric function in the form ∊o(z,E∙E*)−r2∊2(z,E∙E*) have been derived; the power loss by electrons to heavy particles is assumed to be much larger than that due to thermal conduction. The dominant nonlinearity considered herein is the radial redistribution of the electron density on account of the radial dependence of the electric field of the waves and consequently of the electron temperature. Using this expression for the dielectric function, the coupled wave equations corresponding to different beams have been solved in the paraxial approximation, yielding a system of coupled second-order differential equations for the beamwidths. The coupled equations for the widths of two beams have been solved numerically for some typical cases; the critical curves for the two beams have also been obtained. The effect of one beam on the critical curve and the dependence of the beamwidth on the distance of propagation of the other beam have been specifically considered. The results have been presented in the form of graphs for plasmas in thermal equilibrium and also for daytime midlatitude ionosphere at a height of 150km. A discussion of the results is also presented.
A dual-level approach to density-functional theory
Authors: Nakajima Takahito , Hirao Kimihiko
Published: May 2006

An efficient approximate scheme for density-functional theory (DFT) calculations, which eliminates the time-consuming self-consistent-field (SCF) procedure, is proposed using a dual-level DFT approach. In this approach, dual levels of basis sets and exchange-correlation functionals are adopted. The dual-level DFT approach is based on the idea that the total electron density in the ground state can be represented in terms of the density evaluated using the low-quality basis set and the low-cost exchange-correlation functional. Since the SCF procedure is avoided in the total energy evaluation, the dual-level DFT approach drastically reduces the computational cost. The applications of several dual-level DFT calculations to molecular systems show that our approach is more efficient than the self-consistent DFT approach with a moderate accuracy.
Experimental and theoretical (e,2e) ionization cross sections for a hydrogen target at 75.3eV incident energy in a coplanar asymmetric geometry
Authors: Gao Junfang , Madison D. H. , Peacher J. L. , Murray Andrew James , Hussey Martyn J.
Published: May 2006

Very recently it was shown that the molecular three-body distorted wave (M3DW) approach gives good agreement with the shape of the experimental data for electron-impact ionization of H2 in a coplanar symmetric geometry, providing the incident electrons have an energy of 35eV or greater. One of the weaknesses of these studies was that only the shape of the cross section could be compared to experiment, since there was no absolute or relative normalization of the data. Here we report a joint experimental/theoretical study of electron-impact ionization of H2 in a coplanar asymmetric geometry where the energy of the incident electron was fixed, and different pairs of final state electron energies were used. In this case, the experimental data can be normalized such that only one renormalization factor is required. It is shown that the M3DW is pretty good in agreement with experiment. However, a better treatment of polarization and exchange between the continuum and bound state electrons is required before quantitative agreement between experiment and theory is achieved.
Thermal decomposition of alkyl monolayers covalently grafted on (111) silicon
Authors: Faucheux A. , Yang F. , Allongue P. , Henry de Villeneuve C. , Ozanam F. , Chazalviel J.-N.
Published: May 2006

Alkyl monolayers have been covalently grafted onto atomically flat (111) hydrogenated silicon surfaces through hydrosilylation of 1-alkenes. The thermal stability of the layers under oxidizing or reducing atmospheres has been investigated by quantitative in situ infrared spectroscopy, using a specially designed variable-temperature cell. The layers are thermally stable up to 250°C. In the range of 250–300°C, the main reaction is alkene desorption accompanied with silicon oxidation. The characteristic desorption temperature is not significantly affected by changing the atmosphere, the initial packing density of the layers, or the chain length from C18 to C6, but very short chains appear more stable.
Biaxial strain and lattice constants of InN (0001) films grown by plasma-assisted molecular beam epitaxy
Authors: Dimakis E. , Iliopoulos E. , Tsagaraki K. , Adikimenakis A. , Georgakilas A.
Published: May 2006

We present a systematic study, using high resolution x-ray diffraction, of the in-plane a and out-of-plane c lattice parameters of high quality InN films grown by molecular beam epitaxy on GaN∕Al2O3 (0001) substrates. It is found that their values are dependent on the nucleation and growth conditions. Films nucleated in a two- or three-dimensional growth mode exhibit biaxial compressive or tensile strain, respectively. The linear dependence of c on a is consistent with biaxial strain being present in the films. A biaxial strain relaxation coefficient of 0.43±0.04 is deduced. The values of the lattice constants for the case of strain-free InN are estimated to be in the ranges c=5.699±0.004Å and a=3.535±0.005Å.
Role of elastic anisotropy in the vertical alignment of In(Ga)As quantum dot superlattices
Authors: Gutiérrez M. , Herrera M. , González D. , García R. , Hopkinson M.
Published: May 2006

This letter shows the effect of the elastic anisotropic strain field in the vertical stacking for multilayer In(Ga)As∕GaAs quantum dot (QD) structures grown by molecular beam epitaxy. This effect explains the QD enlargement in vertical correlated stacking and the possibility to obtain QD vertical anticorrelated stacking. The anticorrelation configuration in these structures is dependent not only on the QD size and on the interlayer spacing but also on the QD density. With appropriate choice of these structural parameters, a QD body centered cubic arrangement can be produced with a narrower size distribution which is in marked contrast to commonly observed vertically correlated QDs.
The impact of the π-electron conjugation length on the three-photon absorption cross section of fluorene derivatives
Authors: Cohanoschi Ion , Belfield Kevin D. , Toro Carlos , Yao Sheng , Hernández Florencio E.
Published: May 2006

The three-photon absorption cross sections of three different fluorene derivatives, with extended π-electron conjugation lengths was experimentally measured and compared with shorter π-electron conjugation length analogs. The effect of the conjugation length on the three-photon absorption cross section σ3′ of this family of molecules has been elucidated. It is demonstrated that σ3′ of the asymmetric compound D-π-π-π-A is 6.6 times larger than its shorter configuration D-π-A, while for the symmetric compounds D-π-π-π-D and A-π-π-π-A a two-fold enhancement was found relative to their shorter conjugation length analogs. Measurements of the three-photon excitation of these compounds in THF solution (10−3M) were accomplished with a tunable optical pulse generation pumped by a 25ps Nd-YAG laser.
Cavity enhanced Faraday rotation of semiconductor quantum dots
Authors: Li Y. Q. , Steuerman D. W. , Berezovsky J. , Seferos D. S. , Bazan G. C. , Awschalom D. D.
Published: May 2006

Dielectric vertical cavities are used to study the spin dynamics of molecularly self-assembled colloidal CdSe quantum dots (QDs). A quality factor dependent enhancement of Faraday rotation (∼25×) is observed and attributed to optically excited spins interacting with multiple passes of the cavity photons. This enables dynamical measurements at extremely low powers on relatively small numbers of quantum confined spins. In CdSe QDs, measurements reveal that spectroscopic contributions from exciton and electron spin precession depend on the power of excitation. We demonstrate that this scheme is amenable to chemically synthesized systems as a means to increase detection sensitivity.
Antiferromagnetic coupling and enhanced magnetization in all-ferromagnetic superlattices
Authors: Padhan P. , Prellier W. , Budhani R. C.
Published: May 2006

The structural and magnetic properties of a series of superlattices consisting of two ferromagnetic metals La0.7Sr0.3MnO3 (LSMO) and SrRuO3 (SRO) grown on (001) oriented SrTiO3 are studied. Superlattices with a fixed LSMO layer thickness of 20unit cells and varying SRO layer thickness show a sudden drop in magnetization on cooling through a temperature where both LSMO and SRO layers are ferromagnetic. This behavior suggests an antiferromagnetic coupling between the layers. In addition, the samples having thinner SRO layers (n<6) exhibit enhanced saturation magnetization at 10K. These observations are attributed to the possible modification in the stereochemistry of the Ru and Mn ions in the interfacial region.
Optoelectronic properties of transparent and conducting single-wall carbon nanotube thin films
Authors: Fanchini Giovanni , Unalan Husnu Emrah , Chhowalla Manish
Published: May 2006

Optoelectronic characterization of transparent and conducting single-wall carbon nanotube thin films is reported. By eliminating the influence of voids and bundle-bundle interactions within the effective medium theory, we show that the complex dielectric response of the individual nanotube varies with its density in the film. Specifically, the absorption peak assigned to the maximum intensity of π-π* transitions was found to decrease from Eπ=5.0eV at low nanotube density to Eπ=4.2eV at intermediate densities and increased again at higher densities to Eπ=4.5eV. Furthermore, the Drude background was found only above a critical density (Φo) of nanotubes. These results unequivocally demonstrate that the optical processes are not confined only to in-tube transitions and that the absence of confinement in nanotube networks profoundly affects the electronic behavior of the individual tube.
Alkali-halogen plasma generation by dc magnetron discharge
Authors: Oohara W. , Nakahata M. , Hatakeyama R.
Published: May 2006

An alkali-halogen plasma is generated by a dc magnetron discharge using thermal cathodes under a uniform magnetic field. Alkali-salt vapor is dissociated and ionized by E×B-drift electron impact, and alkali positive ions and halogen negative ions are produced. A magnetic-filter region is situated at an exit of the discharge region and electrons are removed from the plasma. The electron emission and E∕B fields are optimized, resulting in the alkali-halogen plasma with the ion density of 3×108cm−3 at B=0.2T.
Reduction of crystal resonator second-order normal acceleration sensitivity by overhang plates
Authors: Yang Jiashi , Guo Shaohua
Published: May 2006

We propose to use overhang plates for reducing the second-order normal acceleration sensitivity of crystal resonators. A theoretical analysis is performed. Results show that the second-order normal acceleration sensitivity of a thickness-shear resonator can be reduced by two orders of magnitude.
Multiple wavelength anisotropically polarized mid-infrared emission from InAs quantum dots
Authors: Wasserman D. , Gmachl C. , Lyon S. A. , Shaner E. A.
Published: May 2006

Multiple wavelength, anisotropically polarized midinfrared electroluminescence from self-assembled InAs quantum dots grown in AlGaAs∕GaAs heterostructures has been observed at 77K. Electrons are injected into excited quantum dot states using a graded AlGaAs injector. Direct tunneling out of the quantum dot excited states is prevented by means of a superlattice electron filter. Two midinfrared peaks are seen in the electrically pumped surface emission spectra of the device. The emission peaks are orthogonally polarized within the growth plane, indicating photon emission from intersublevel electron transitions within anisotropically shaped quantum dots.