bluuebunny/crossref_metadata_2025 huggingface dataset:
Differentiation Plasticity of Human Fetal Articular Chondrocytes
Authors: Cui Ying , Wang Hong , Yu Minjun , Xu Tianri , Li Xuepei , Li Lingsong
Published: July 2006

OBJECTIVE

To test chondrogenic differentiation potential, we examined the differentiation plasticity of isolated human fetal articular chondrocytes (HFACs).

STUDY AND DESIGN SETTING

Culture‐expanded human fetal articular chondrocytes (HFACs) were analyzed for chondrogenic, adipogenic, osteogenic capacity and neural differentiation ability in defined in vitro culture systems.

RESULTS

The different assays demonstrated that culture‐expanded HFACs have potential to form cartilage in pellet mass culture, to form adipose cells, osteogenic cells, and neural cells in monolayer culture.

CONCLUSIONS

These results suggest that within human fetal articular cartilages there are MSC‐like cells that exhibit differentiation plasticity that is comparable with that of BM‐MSCs and they may be a new kind of seeding cells for head and neck cartilage reconstruction.
Vagal Nerve Stimulator Implantation: An Otolaryngologist's Perspective
Authors: Ghanem Tamer , Early Stephen V.
Published: July 2006

OBJECTIVE

This study was conducted to compare an otolaryngologist's experience with a cohort of epilepsy patients implanted with a vagal nerve stimulator (VNS) to previously published data.

METHODS

Demographics, preoperative seizure frequency, medications, and complications were retrospectively collected from patients implanted by the senior author. Postoperative medications and seizure frequency were obtained from referring neurologists.

RESULTS

Seventeen patients were implanted over a 24‐month period. Average age was 28.3 years. Patients presented with petit mal (n = 3), tonic‐clonic (n = 6), complex partial (n = 5), and grand mal (n = 8) seizures. Mean follow‐up postimplantation was 13.5 months. Most patients had at least a 50% reduction of seizure frequency, with 3 patients being seizure free. There were no postoperative infections. One patient had left vocal cord immobility. The most common side effect was voice disturbance during device activation.

CONCLUSION

Otolaryngologists are well equipped to perform VNS implantation and to diagnose and treat possible laryngeal side effects.

EBM rating: C‐4
Postoperative Radiation Therapy for T1 and T2 Primary Parotid Carcinoma: Is it Useful?
Authors: Peter Zbären , Michel Nuyens , Marco Caversaccio , Richard Greiner , Edouard Stauffer
Published: July 2006

OBJECTIVE

The benefit of postoperative radiation for advanced primary parotid carcinoma has been reported previously, whereas studies to evaluate the usefulness of postoperative radiation for T1 and T2 parotid carcinomas have never been performed.

STUDY DESIGN AND SETTING

Retrospective analysis on 58 previously untreated patients with T1 and T2 parotid carcinomas. In 34 patients, postoperative radiation was included in the treatment protocol and in 24 patients, no postoperative radiation was applied.

RESULTS

A local recurrence was observed in 8 of 24 (33%) patients withoht and in 1 of 34 (3%) patients with postoperative radiation (P < 0.5). The 5‐year actuarial and disease‐free survival rate was 83% and 70% for patients without postoperative radiation and 93% and 92% for patients with postoperative radiation.

CONCLUSION AND SIGNIFICANCE

Local recurrence was less often observed in patients with postoperative radiation. Nevertheless, prospective randomized studies are needed to confirm the usefulness of postoperative radiation in early carcinomas.

EBM rating: B‐3b
Sing, soothe and sleep: A lullaby education programme for first-time mothers
Authors: Baker Felicity , Mackinlay Elizabeth
Published: June 2006

This paper reports on an education programme conducted with first-time mothers. The study aimed to establish whether mothers found an education session on lullaby singing beneficial for them and their babies as well as reporting what lullabies were sung and why. Twenty first-time mothers were provided with examples of lullabies and asked to sing lullabies to their babies at bedtime at least four times per week over a six-week period. Data contained in interviews and in diaries kept by the mothers were used to evaluate the value of the education session, the range of lullabies sung and their frequency of use, and to gain insight into mothers' thinking when choosing lullabies. Results indicate that mothers sing a broad range of lullabies utilising a repertoire of between five and seven lullabies. Reasons for selecting lullabies varied between the different mothers and for different lullabies but most frequently, selections were based on the perception that they were quietening, calming or relaxing for their babies. Selections were also based on whether mothers knew the lullabies and were confident to sing them. The education session was evaluated with mothers reporting on how singing lullabies facilitated a deeper understanding of their babies' responses, and enhanced their own feelings associated with motherhood. Recommendations are made as to the type and context of future education sessions.
The music curriculum as ‘received’ by children: Evidence from Cyprus primary schools
Authors: Stavrou Natassa Economidou
Published: June 2006

This article reports on research investigating the ‘received’ music curriculum as experienced by children and how this corresponds with the expectations of the official music curriculum. The research was conducted in Cyprus and the sample consisted of 1196 children in their final year in primary school. Results verify a huge gap between curriculum theory and implementation, revealing that knowledge accumulated during the six years of primary education is far distant from the over-optimistic intentions of the official music curriculum. Additionally, music was found to be one of children's least favourite school subjects, suggesting the need for a more learner-centred and process-orientated music curriculum.
The influence of governmental control and early Christian missionaries on music education of Aborigines in Taiwan
Authors: Lee Angela Hao-Chun
Published: June 2006

There has been little research conducted on Taiwanese Aboriginal music education in comparison to Aboriginal education. C. Hsu's Taiwanese Music History (1996) presents information on Aboriginal music including instruments, dance, ritual music, songs and singing, but information on music education practices is lacking. The examination of historical documentation shows that music education was used by both the Japanese government and Christian missionaries to advance their political and religious agendas. This paper will examine the development of the music education of Aborigines in Taiwan from the mid nineteenth century, when Christian missionaries first came to Taiwan, until the end of the Japanese protectorate (1945). I shall discuss how the missionaries from Britain and Canada successfully introduced Western religious music to Aboriginal communities by promoting various activities such as hymn singing and religious services. The paper will then look at the influence of government policy on Aboriginal music education during the colonial periods. These policies affected both the music taught in elementary schools and the teaching materials.
THE “WASHINGTON SYSTEM” AND ITS AFTERMATH: REEVALUATING AFTER IMPERIALISM FROM THE PERSPECTIVE OF THE JAPANESE HISTORIOGRAPHY
Authors: Mori Shigeki
Published: June 2006

Iriye, Akira. After Imperialism. Cambridge: Harvard University Press, 1965, and New
York: Atheneum, 1973, paperback; “Preface to the New Edition.” In the republished
edition. Chicago: Imprint Publications, Inc, 1990.
Chronischer Stress, Persönlichkeit und selbstberichtete körperliche Gesundheit
Authors: Becker Peter , Jansen Lars J.
Published: July 2006

Zusammenfassung. Die Untersuchung dient der pfadanalytischen Überprüfung von Hypothesen, die aus unterschiedlichen theoretischen Modellen über den Zusammenhang von chronischen Stressbelastungen, bewältigungsrelevanten Persönlichkeitseigenschaften und der selbstberichteten Gesundheit abgeleitet wurden. Ausgewertet wurden die Daten von 194 Erwachsenen. 109 Frauen und Männer nahmen an einem Stress-Resistenz-Training teil und wurden ebenso wie eine Kontrollgruppe von 85 Personen zweimal im Abstand von sechs Monaten mit dem Trierer Inventar zum chronischen Stress, dem Fragebogen zum Umgang mit Problemen, der Skala zur optimistischen Kompetenzerwartung, der Stress-Reaktivität-Skala und zwei Skalen des Fragebogens zur habituellen körperlichen Gesundheit untersucht. Am besten bewährten sich Annahmen aus einem systemischen Anforderungs-Ressourcen-Modell der Gesundheit. Eine zentrale gesundheitliche Bedeutung scheint chronischem Stress auf Grund eines Mangels an Bedürfnisbefriedigung zuzukommen. Die theoretischen Implikationen und die praktischen Konsequenzen für die Gesundheitsförderung und Prävention werden ebenso diskutiert wie die Begrenzungen der Untersuchung.
Psychosoziale Unterstützung von älteren Menschen mit einer chronischen Sehbeeinträchtigung
Authors: Kämmerer Annette , Wahl Hans-Werner , Becker Stefanie , Kaspar Roman , Himmelsbach Ines , Holz Frank , Miller Daniel
Published: July 2006

Zusammenfassung. Ziel der vorliegenden Arbeit war die empirische Prüfung einer psychosozialen Kurzintervention bei Menschen mit altersabhängiger Makuladegeneration, der primären Ursache von Sehverlust im höheren Alter. Gegenüber den bisher in der Literatur vorgelegten Interventionsansätzen war die Intervention der vorliegenden Studie in stärkerem Maße gesundheitspsychologisch fundiert. Sie umfasste insgesamt drei Sitzungen auf der Basis eines Gruppenansatzes mit je 4 bis 6 Patienten. Unterschieden wurde ferner zwischen einem emotions-orientierten und problemlöse-orientierten Vorgehen. In die Studie einbezogen wurden n = 23 Personen mit emotions-orientiertem, n = 22 Personen mit problemlöse-orientiertem Vorgehen und n = 22 Personen ohne Behandlung (Altersmittelwerte zwischen 76.1 und 77.3 Jahren). Die Behandlungsgruppen wurden vor und nach der Intervention mit eingeführten Skalen zur Depressivität, zu problemorientiertem Coping und Anpassung an den Sehverlust untersucht. Die Vergleichsgruppe wurde entsprechend nach einem vergleichbaren Zeitintervall ohne Intervention ein zweites Mal befragt. Die Befunde zeigen leicht verbesserte Depressivitätswerte speziell in der emotions-orientierten Gruppe, während sich in der problemlöse-orientierten Gruppe vor allem Verbesserungen hinsichtlich des problemorientierten Copings und der Anpassung an den Sehverlust ergaben. Die Ergebnisse unterstreichen insgesamt die Notwendigkeit einer stärkeren gesundheitspsychologischen Beachtung von chronischen Erkrankungen im Alter.
Effects of Maxwell‐Wagner polarization on soil complex dielectric permittivity under variable temperature and electrical conductivity
Authors: Chen Yongping , Or Dani
Published: June 2006

The presence of free charges and numerous discontinuities separating liquid, gas, and solid phases in partially saturated soils give rise to Maxwell‐Wagner polarization that may significantly affect bulk dielectric permittivity measurements. Evidence suggests a complex interplay shaping the response of low‐frequency (<100 MHz) dielectric permittivity to changes in ambient temperature and amount of ionic charges present in a wet soil. Model calculations based on the Maxwell‐Wagner‐Brugermann‐Hanai (MWBH) theory are supported by direct measurements using a network analyzer, showing an increase in soil bulk dielectric permittivity with increasing temperature and with higher bulk electrical conductivity at low frequency range (<100 MHz). Beyond a certain frequency the decrease in permittivity of free water becomes dominant and results in a decrease in soil bulk dielectric permittivity with increasing temperature. The value of this crossover frequency can be predicted as a function of solution electrical conductivity (EC) as confirmed in limited tests. The dielectric permittivity inferred from TDR waveform travel time analysis is not significantly influenced by the low frequency range of the dielectric spectrum. In contrast, dielectric permittivity sensors operating at frequencies lower than 100 MHz are likely to show significant sensitivity to factors affecting the Maxwell‐Wagner effect (temperature and electrical conductivity), hence requiring special care in measurement interpretation.
Application of dynamic subgrid‐scale concepts from large‐eddy simulation to modeling landscape evolution
Authors: Passalacqua Paola , Porté‐Agel Fernando , Foufoula‐Georgiou Efi , Paola Chris
Published: June 2006

Landscapes share important similarities with turbulence: both systems exhibit scale invariance (self‐similarity) over a wide range of scales, and their behavior can be described using comparable dynamic equations. In particular, modified versions of the Kardar‐Parisi‐Zhang (KPZ) equation (a low‐dimensional analog to the Navier‐Stokes equations) have been shown to capture important features of landscape evolution. This suggests that modeling techniques developed for turbulence may also be adapted to landscape simulations. Using a “toy” landscape evolution model based on a modified 2‐D KPZ equation, we find that the simulated landscape evolution shows a clear dependence on grid resolution. In particular, mean longitudinal profiles of elevation at steady state and bulk erosion rates both have an undesirable dependence on grid resolution because the erosion rate increases with resolution as increasingly small channels are resolved. We propose a new subgrid‐scale parameterization to account for the scale dependence of the sediment fluxes. Our approach is inspired by the dynamic procedure used in large‐eddy simulation of turbulent flows. The erosion coefficient, assumed exactly known at the finest resolution, is multiplied by a scale dependence coefficient, which is computed dynamically at different time steps on the basis of the dynamics of the resolved scales. This is achieved by taking advantage of the self‐similarity that characterizes landscapes over a wide range of scales. The simulated landscapes obtained with the new model show very little dependence on grid resolution.
Simplifying Second‐order Belief Attribution: What Facilitates Children’s Performance on Measures of Conceptual Understanding?
Authors: Coull Greig J. , Leekam Susan R. , Bennett Mark
Published: July 2006

This study investigated how 4‐ to 7‐year‐old children’s second‐order belief attribution might be facilitated by either reducing information processing or varying the sequence of task questions. In Experiment 1, compared withPerner and Wimmer’s (1985) original second‐order false‐belief task, a new task with reduced information‐processing demands promoted better second‐order reasoning. In Experiment 2, half the stories included a second‐order ignorance question before a second‐order belief question. The ignorance question promoted second‐order belief understanding, superseding the improvement induced by lowered processing demands. Together, the findings suggest that second‐order belief performance can be facilitated if children focus on the concept of ignorance during the sequence of questioning.
Re-entrant melting and freezing in a model system of charged colloids
Authors: Royall C. Patrick , Leunissen Mirjam E. , Hynninen Antti-Pekka , Dijkstra Marjolein , van Blaaderen Alfons
Published: July 2006

We studied the phase behavior of charged and sterically stabilized colloids using confocal microscopy in a low polarity solvent (dielectric constant 5.4). Upon increasing the colloid volume fraction we found a transition from a fluid to a body centered cubic crystal at 0.04150.0005, followed by reentrant melting at 0.11650.0015. A second crystal of different symmetry, random hexagonal close packed, was formed at a volume fraction around 0.5, similar to that of hard spheres. We attribute the intriguing phase behavior to the particle interactions that depend strongly on volume fraction, mainly due to the changes in the colloid charge. In this low polarity system the colloids acquire charge through ion adsorption. The low ionic strength leads to fewer ions per colloid at elevated volume fractions and consequently a density-dependent colloid charge.
Classification of infinitesimal symmetries in covariant classical mechanics
Authors: Modugno Marco , Saller Dirk , Tolksdorf Jürgen
Published: July 2006

In the framework of general relativistic classical mechanics on a spacetime with absolute time, we classify the infinitesimal symmetries of the classical structure by means of distinguished Lie subalgebras of the Lie algebra of “special phase function.” These subalgebras are crucial also for the classification of infinitesimal quantum symmetries, which will be analyzed in a forthcoming paper.
Experimental control of excitation flow produced by delayed pulses in a ladder of molecular levels
Authors: Garcia-Fernandez Ruth , Shore Bruce W. , Bergmann Klaas , Ekers Aigars , Yatsenko Leonid P.
Published: July 2006

We study a method for controlling the flow of excitation through decaying levels in a three-level ladder excitation scheme in Na2 molecules. Like the stimulated Raman adiabatic passage (STIRAP), this method is based on the control of the evolution of adiabatic states by a suitable delayed interaction of the molecules with two radiation fields. However, unlike STIRAP, which transfers a population between two stable levels g and f via a decaying intermediate level e through the interaction of partially overlapping pulses (usually in a Λ linkage), here the final level f is not long lived. Therefore, the population reaching level f decays to other levels during the transfer process. Thus, rather than controlling the transfer into level f, we control the flow of the population through this level. In the present implementation a laser P couples a degenerate rovibrational level in the ground electronic state XΣg+1, v″=0, j″=7 to the intermediate level AΣu+1, v′=10, J′=8, which in turn is linked to the final level 5Σg+1, v=10, J=9 by a laser S, from which decay occurs to vibrational levels in the electronic A and X states. As in STIRAP, the maximum excitation flow through level f is observed when the P laser precedes the S laser. We study the influence of the laser parameters and discuss the consequences of the detection geometry on the measured signals. In addition to verifying the control of the flow of population through level f we present a procedure for the quantitative determination of the fraction κf of molecules initially in the ground level which is driven through the final level f. This calibration method is applicable for any stepwise excitation.
The effects of geometry on the hyperpolarizability
Authors: Kuzyk Mark G. , Watkins David S.
Published: July 2006

Extensive studies in the past have focused on precise calculations of the nonlinear-optical susceptibility of thousands of molecules. In this work, we use the broader approach of considering how geometry and symmetry alone play a role, irrespective of molecular constraints. We investigate the nonlinear optical response of potential energy functions that are given by a superposition of force centers (representing the nuclear charges) that lie in various planar geometrical arrangements. We find that for certain specific geometries, such as an octupolarlike molecule with donors and acceptors of varying strengths at the branches, the hyperpolarizability is near the fundamental limit. In these cases, the molecule is observed to be well approximated by a three-level model, consistent with the three-level ansatz previously used to calculate the fundamental limits. However, when the hyperpolarizability is below the apparent limit (about a factor of 30 below the fundamental limit), the system is no longer representable by a three-level model, where both two-level and many-state models are found to be appropriate, depending on the symmetry.
Identifying reactive trajectories using a moving transition state
Authors: Bartsch Thomas , Uzer T. , Moix Jeremy M. , Hernandez Rigoberto
Published: July 2006

A time-dependent no-recrossing dividing surface is shown to lead to a new criterion for identifying reactive trajectories well before they are evolved to infinite time. Numerical dynamics simulations of a dissipative anharmonic two-dimensional system confirm the efficiency of this approach. The results are compared to the standard fixed transition state dividing surface that is well-known to suffer from recrossings and therefore requires trajectories to be evolved over a long time interval before they can reliably be classified as reactive or nonreactive. The moving dividing surface can be used to identify reactive trajectories in harmonic or moderately anharmonic systems with considerably lower numerical effort or even without any simulation at all.
Perfect wetting along a three-phase line: Theory and molecular dynamics simulations
Authors: Mejía Andrés , Vega Lourdes F.
Published: July 2006

Wetting behavior along a three-phase equilibrium has been obtained by density gradient theory (DGT) and molecular dynamics simulations for a type-II equal size Lennard-Jones mixture. In order to perform a consistent comparison between both methodologies, the molecular parameters of this type of mixture were defined from the global phase diagram of equal size Lennard-Jones mixtures. We have found excellent agreement between predictions from the DGT (coupled to a Lennard-Jones equation for the bulk phases) and simulations results for both the phase and interface behavior, in the whole temperature, pressure, and concentration ranges. For all conditions explored in this work, this type-II mixture shows a three-phase equilibrium composed by a bulk immiscible liquid phase (L1) and a bulk gas phase (G) separated by a second immiscible liquid phase (L2). A similar phase distribution is obtained from the interfacial concentration profile in the whole range of conditions used in this work. This type of structure is a clear evidence that L2 completely wets the GL1 interface. The wetting behavior is also confirmed by the values and evolution of the interfacial tensions. In summary, this kind of type-II mixture does not show wetting transitions and exhibits a permanent perfect wetting in all the thermodynamic conditions explored here.
Evaluation of phenomenological one-phase criteria for the melting and freezing of softly repulsive particles
Authors: Saija Franz , Prestipino Santi , Giaquinta Paolo V.
Published: July 2006

We test the validity of some widely used phenomenological criteria for the localization of the fluid-solid transition thresholds against the phase diagrams of particles interacting through the exp-6, inverse-power-law, and Gaussian potentials. We find that one-phase rules give, on the whole, reliable estimates of freezing/melting points. The agreement is ordinarily better for a face-centered-cubic solid than for a body-centered-cubic crystal, even more so in the presence of a pressure-driven reentrant transition of the solid into a denser fluid phase, as found in the Gaussian-core model.
Femtosecond laser pulse control of multidimensional vibrational dynamics: Computational studies on the pyrazine molecule
Authors: Wang Luxia , Meyer Hans-Dieter , May Volkhard
Published: July 2006

The multiconfiguration time-dependent Hartree (MCTDH) method is combined with the optimal control theory (OCT) to study femtosecond laser pulse control of multidimensional vibrational dynamics. Simulations are presented for the widely discussed three-electronic-level vibronic coupling model of pyrazine either in a three or four vibrational coordinate version. Thus, for the first time OCT is applied to a four-coordinate system. Different control tasks are investigated and also some general aspects of the OCT-MCTDH method combination are analyzed.
Semiclassical nonadiabatic dynamics based on quantum trajectories for the O(P3,D1)+H2 system
Authors: Garashchuk Sophya , Rassolov Vitaly A. , Schatz George C.
Published: July 2006

The O(P3,D1)+H2→OH+H reaction is studied using trajectory dynamics within the approximate quantum potential approach. Calculations of the wave-packet reaction probabilities are performed for four coupled electronic states for total angular momentum J=0 using a mixed coordinate/polar representation of the wave function. Semiclassical dynamics is based on a single set of trajectories evolving on an effective potential-energy surface and in the presence of the approximate quantum potential. Population functions associated with each trajectory are computed for each electronic state. The effective surface is a linear combination of the electronic states with the contributions of individual components defined by their time-dependent average populations. The wave-packet reaction probabilities are in good agreement with the quantum-mechanical results. Intersystem crossing is found to have negligible effect on reaction probabilities summed over final electronic states.
Orientational ordering in hard rectangles: The role of three-body correlations
Authors: Martínez-Ratón Yuri , Velasco Enrique , Mederos Luis
Published: July 2006

We investigate the effect of three-body correlations on the phase behavior of hard rectangle two-dimensional fluids. The third virial coefficient B3 is incorporated via an equation of state that recovers scaled particle theory for parallel hard rectangles. This coefficient, a functional of the orientational distribution function, is calculated by Monte Carlo integration, using an accurate parametrized distribution function, for various particle aspect ratios in the range of 1–25. A bifurcation analysis of the free energy calculated from the obtained equation of state is applied to find the isotropic (I)-uniaxial nematic (Nu) and isotropic-tetratic nematic (Nt) spinodals and to study the order of these phase transitions. We find that the relative stability of the Nt phase with respect to the isotropic phase is enhanced by the introduction of B3. Finally, we have calculated the complete phase diagram using a variational procedure and compared the results with those obtained from scaled particle theory and with Monte Carlo simulations carried out for hard rectangles with various aspect ratios. The predictions of our proposed equation of state as regards the transition densities between the isotropic and orientationally ordered phases for small aspect ratios are in fair agreement with simulations. Also, the critical aspect ratio below which the Nt phase becomes stable is predicted to increase due to three-body correlations, although the corresponding value is underestimated with respect to simulation.
Two-component cosmological fluids with gravitational instabilities
Authors: Gailis R. M. , Frankel N. E.
Published: July 2006

A survey of linearized cosmological fluid equations with a number of different matter components is made. To begin with, the one-component case is reconsidered to illustrate some important mathematical and physical points rarely discussed in the literature. The work of some previous studies of two-component systems are examined and reanalyzed to point out some deficiencies of solutions, and further solutions and physical interpretation are then presented. This leads into a general two-component model with variable velocity dispersion parameters and mass density fractions of each component. The equations, applicable to both hot dark matter (HDM) and cold dark matter (CDM) universes are solved in the long wavelength limit. This region is of interest, because some modes in this range of wave numbers are Jeans unstable. The mixture Jeans wave number of the two-component system is introduced and interpreted, and the solutions are discussed, particularly in comparison to analogous solutions previously derived for plasma modes. This work is applicable to that region in the early Universe (20<z<140), where large scale structure formation is thought to have occurred.
Preferential site occupancy of krypton atoms on free argon-cluster surfaces
Authors: Lundwall M. , Lindblad A. , Bergersen H. , Rander T. , Öhrwall G. , Tchaplyguine M. , Svensson S. , Björneholm O.
Published: July 2006

Argon clusters have been doped with krypton atoms in a pick-up setup and investigated by means of ultraviolet and x-ray photoelectron spectroscopy (UPS and XPS). The width of the krypton surface feature in the XPS spectra from mixed krypton/argon clusters has been studied and found to be narrower than in the case of homogeneous krypton clusters. By considering known spectral broadening mechanisms of the cluster features and the electron binding energy shift of the cluster surface feature relative to the atomic signal, we conclude that krypton ad-atoms preferentially occupy high-coordination surface sites on the argon host-cluster.
The influence of correlation on the interpretation of Hund’s multiplicity rule: A quantum Monte Carlo study
Authors: Oyamada Takayuki , Hongo Kenta , Kawazoe Yoshiyuki , Yasuhara Hiroshi
Published: July 2006

A systematic quantum Monte Carlo study of 2p atoms (C, N, O) and 3p atoms (Si, P, S) is performed to investigate the influence of correlation on the interpretation of Hund’s multiplicity rule, which is an extension of our previous study of the carbon atom [J. Chem. Phys. 121, 7144 (2004)] to heavier atoms. The accuracy in the present study is significantly improved as compared with the previous study. A detailed analysis of the correlation contribution to individual energy components of the total energy is given beyond the self-consistent Hartree-Fock calculation. The stability of the highest spin-multiplicity state of all the atoms is ascribed to the greater electron-nucleus attraction energy that is gained at the cost of increasing the electron-electron repulsion energy as well as the kinetic energy. The present study demonstrates that correlation does not change the above conclusion due to the Hartree-Fock theory to support Boyd’s less screening mechanism.
Analytic calculation of energies and wave functions of the quartic and pure quartic oscillators
Authors: Liverts E. Z. , Mandelzweig V. B. , Tabakin F.
Published: July 2006

Ground state energies and wave functions of quartic and pure quartic oscillators are calculated by first casting the Schrödinger equation into a nonlinear Riccati form and then solving that nonlinear equation analytically in the first iteration of the quasilinearization method (QLM). In the QLM the nonlinear differential equation is solved by approximating the nonlinear terms by a sequence of linear expressions. The QLM is iterative but not perturbative and gives stable solutions to nonlinear problems without depending on the existence of a smallness parameter. Our explicit analytic results are then compared with exact numerical and also with WKB solutions and it is found that our ground state wave functions, using a range of small to large coupling constants, yield a precision of between 0.1 and 1 percent and are more accurate than WKB solutions by two to three orders of magnitude. In addition, our QLM wave functions are devoid of unphysical turning point singularities and thus allow one to make analytical estimates of how variation of the oscillator parameters affects physical systems that can be described by the quartic and pure quartic oscillators.
Jacobi ϑ-functions and discrete Fourier transforms
Authors: Ruzzi M.
Published: July 2006

Properties of the Jacobi ϑ3-function and its derivatives under discrete Fourier transforms are investigated, and several interesting results are obtained. The role of modulo N equivalence classes in the theory of ϑ-functions is stressed. An important conjecture is studied.
The weak Hopf algebras related to generalized Kac-Moody algebra
Authors: Zhixiang Wu
Published: July 2006

We define a kind of quantized enveloping algebra of a generalized Kac-Moody algebra G by adding a generator J satisfying Jm=Jm−1 for some integer m. We denote this algebra by wUqτ(G). This algebra is a weak Hopf algebra if and only if m=2. In general, it is a bialgebra, and contains a Hopf subalgebra. This Hopf subalgebra is isomorphic to the usually quantum envelope algebra Uq(G) of a generalized Kac-Moody algebra G.
Single-electron tunneling force spectroscopy of an individual electronic state in a nonconducting surface
Authors: Bussmann E. , Williams C. C.
Published: July 2006

A tunneling spectroscopy technique to measure the energy level of an electronic state in a completely nonconducting surface is demonstrated. Spectroscopy is performed by electrostatic force detection of single-electron tunneling between a scanning probe and the state as a function of an applied voltage. An electronic state near the surface of a SiO2 film is found 5.5±0.2eV below the conduction band edge. A random telegraph signal, caused by sporadic back-and-forth single-electron tunneling, is observed as the probe Fermi level passes through the state energy.
Crystal structure prediction using ab initio evolutionary techniques: Principles and applications
Authors: Oganov Artem R. , Glass Colin W.
Published: July 2006

We have developed an efficient and reliable methodology for crystal structure prediction, merging ab initio total-energy calculations and a specifically devised evolutionary algorithm. This method allows one to predict the most stable crystal structure and a number of low-energy metastable structures for a given compound at any P-T conditions without requiring any experimental input. Extremely high (nearly 100%) success rate has been observed in a few tens of tests done so far, including ionic, covalent, metallic, and molecular structures with up to 40 atoms in the unit cell. We have been able to resolve some important problems in high-pressure crystallography and report a number of new high-pressure crystal structures (stable phases: ε-oxygen, new phase of sulphur, new metastable phases of carbon, sulphur and nitrogen, stable and metastable phases of CaCO3). Physical reasons for the success of this methodology are discussed.
State-to-state correlated study of CD3I photodissociation at 266 and 304nm
Authors: Li Guosheng , Hwang Hyun Jin
Published: July 2006

High-resolution photofragment translational spectroscopy is used in this work to measure the translational and internal energy distributions in the CD3 and iodine fragments produced from the photodissociation of CD3I at 266 and 304nm. Channel selected detection, via resonantly enhanced multiphoton ionization, combined with one-dimensional core sampling provides detailed information about vibrational state distributions of the CD3 fragments. The vibrational state distributions of CD3 fragments in the I*(P1∕22) channel have a propensity of ν2′ umbrella bending mode with a maximum at ν2′=1 for 266nm photodissociation. For I*(P1∕22) channel at 304nm photodissociation, vibrational state distributions of CD3 fragment have a maximum in the vibrational ground state. For the I(P3∕22) channel (Q11←Q0+3), ν2′ umbrella bending vibrational distribution is measured as the predominant vibrational mode but has a much broader distribution when compared to that of the I* channel. The vibrational state distributions of the CD3 fragment produced from the perpendicular transition, i.e., Q13, which was determined at 304nm photodissociation, has a maximum at ν2′=1. The curve crossing possibility between the Q11 and Q0+3 adiabatic potentials is determined as 0.19 for 266 and 0.85 for 304nm. The trend in reaction dynamics in 266 and 304nm photodissociation of CD3I is compared with theoretical calculations. A bond dissociation energy D0(C–I)=56.60±0.5kcal∕mol was derived by applying laws of energy conservation.
Single-particle levitation system for automated study of homogeneous solute nucleation
Authors: Olsen Adam P. , Flagan Richard C. , Kornfield Julia A.
Published: July 2006

We present an instrument that addresses two critical requirements for quantitative measurements of the homogeneous crystal nucleation rate in supersaturated aqueous solution. First, the need to perform repeated measurements of nucleation incubation times is met by automating experiments to enable programmable cycling of thermodynamic conditions. Second, the need for precise and robust control of the chemical potential in supersaturated aqueous solution is met by implementing a novel technique for regulating relative humidity. The apparatus levitates and weighs micron-sized samples in an electric field, providing access to highly supersaturated states. We report repeated observations of the crystal nucleation incubation time in a supersaturated aqueous sodium chloride droplet, from which we infer the nucleation rate.
Precise localization and correlation of single nanoparticle optical responses and morphology
Authors: Jin Rongchao , Jureller Justin E. , Scherer Norbert F.
Published: July 2006

We demonstrate nanometer scale localization of the nonlinear optical response of single nanoparticles and aggregates and correlate this with their morphology. The essence of our approach is to create position markers on an optical and electron-transparent substrate (Si3N4 thin film) that allows optical measurements and transmission electron microscopy (TEM) imaging of the identical nanoparticles or aggregates. The second harmonic activity optical image of individual Ag nanostructures is registered with the TEM image. Centroid localization of the optical signals allows correlation with better than 25nm precision. This is sufficient to determine the origin of optical “hot spots” within multiparticle aggregates.
Lensless focusing with subwavelength resolution by direct synthesis of the angular spectrum
Authors: Hong Stanley S. , Horn Berthold K. P. , Freeman Dennis M. , Mermelstein Michael S.
Published: July 2006

We consider the coherent superposition of unfocused wave fronts for lensless focusing of electromagnetic waves with subwavelength resolution. Near the focal point, intensity distributions generated using the approach approximate those generated using lenses. Far from the focal point, discretization of spatial frequencies results in a trade-off between the number of wave fronts and the accuracy of the approximation. We experimentally demonstrate the feasibility of the approach by generating an approximation of an azimuthally polarized Bessel beam with a focal spot diameter (full width at half maximum intensity) of 0.37λ.
Detection of 0.5THz radiation from intrinsic Bi2Sr2CaCu2O8 Josephson junctions
Authors: Batov I. E. , Jin X. Y. , Shitov S. V. , Koval Y. , Müller P. , Ustinov A. V.
Published: July 2006

We report the detection of electromagnetic radiation at about 500GHz from current-biased intrinsic Bi2Sr2CaCu2O8 single crystal Josephson junctions. We used two silicon lenses to quasioptically couple radiation from our samples to an integrated superconducting heterodyne receiver. The estimated maximum Josephson radiation power which reached the receiver antenna was about 1pW. We attribute the observed radiation to individual Josephson junctions of the stack and discuss a possibility of the phase locking of a larger number of junctions.
Model-based dynamic resistive wall mode identification and feedback control in the DIII-D tokamak
Authors: In Y. , Kim J. S. , Edgell D. H. , Strait E. J. , Humphreys D. A. , Walker M. L. , Jackson G. L. , Chu M. S. , Johnson R. , La Haye R. J. , Okabayashi M. , Garofalo A. M. , Reimerdes H.
Published: July 2006

A new model-based dynamic resistive wall mode (RWM) identification and feedback control algorithm has been developed. While the overall RWM structure can be detected by a model-based matched filter in a similar manner to a conventional sensor-based scheme, it is significantly influenced by edge-localized-modes (ELMs). A recent study suggested that such ELM noise might cause the RWM control system to respond in an undesirable way. Thus, an advanced algorithm to discriminate ELMs from RWM has been incorporated into this model-based control scheme, dynamic Kalman filter. Specifically, the DIII-D [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] resistive vessel wall was modeled in two ways: picture frame model or eigenmode treatment. Based on the picture frame model, the first real-time, closed-loop test results of the Kalman filter algorithms during DIII-D experimental operation are presented. The Kalman filtering scheme was experimentally confirmed to be effective in discriminating ELMs from RWM. As a result, the actuator coils (I-coils) were rarely excited during ELMs, while retaining the sensitivity to RWM. However, finding an optimized set of operating parameters for the control algorithm requires further analysis and design. Meanwhile, a more advanced Kalman filter based on a more accurate eigenmode model has been developed. According to this eigenmode approach, significant improvement in terms of control performance has been predicted, while maintaining good ELM discrimination.
Low-noise electromagnetic δf particle-in-cell simulation of electron Bernstein waves
Authors: Xiang Nong , Cary John R. , Barnes Daniel C. , Carlsson John
Published: July 2006

The conversion of the extraordinary (X) mode to an electron Bernstein wave (EBW) is one way to get rf energy into an overdense plasma. Analysis of this is complex, as the EBW is a fully kinetic wave, and so its linear propagation is described by an intractable integro-differential equation. Nonlinear effects cannot be calculated within this rubric at all. Full particle-in-cell (PIC) simulations cannot be used for these analyses, as the noise levels for reasonable simulation parameters are much greater than the typical rf amplitudes. It is shown that the delta-f computations are effective for this analysis. In particular, the accuracy of those computations has been verified by comparison with full PIC, cold plasma theory, and small gyroradius theory. This computational method is then used to analyze mode conversion in different frequency regimes. In particular, reasonable agreement with the theoretical predictions of Ram and Schultz [Phys. Plasmas 7, 4084 (2000)] in the linear regime is found, where 100% X−B mode conversion has been obtained when the driving frequency is less than twice the electron gyrofrequency. The results show that cold-plasma theory well predicts the mode conversion efficiency, as is consistent with the phase-space picture of mode conversion. From this it can be shown that nearly 100% X−B mode conversion cannot be obtained when the frequency is higher than the electron second harmonic cyclotron frequency.
Multiple-gap spark gap switch
Authors: Liu Z. , Yan K. , Winands G. J. J. , Pemen A. J. M. , Van Heesch E. J. M. , Pawelek D. B.
Published: July 2006

A triggered multiple-gap spark gap switch has been developed and tested under atmosphere. By means of an LCR trigger circuit, the multiple-gap switch can be used very reliably. For the same switching voltage (35.5kV), with increasing the number of gaps from 2 to 6, the switching current rise time is reduced from 13.5to6ns, and the energy efficiency is increased from 87% to 92%. An eight-gap switch was also tested, and the switching current rise time is much smaller than the usable rise time of the current probe (3.5ns). One interesting application of the multiple-gap switch is to improve the switching performance in the multiple-switch and transmission lines based pulsed power circuit. To verify this application, a six-gap switch was tested. In contrast to a single-gap switch, the output current rise time was improved from 21to11ns by the six-gap switch.
Double-side superconducting MgB2 films for microwave and electronic applications
Authors: Chen Li-ping , Ding Li-li , Feng Qing-rong , Xiong Guang-cheng , Wang Yun-fei , Luo Sheng , Zhang Xue-qiang , He Yu-sheng
Published: July 2006

Double-side superconducting MgB2 films have been grown on double-side polished sapphire substrates by using hybrid physical-chemical vapor deposition method. The zero resistance temperatures TC(0)>37K and the critical current densities JC(5K,0T)>3×106A∕cm2 have been achieved for both sides. In the first 8.73G MgB2 microstrip resonator fabricated by a double-side film, an unloaded Q value of 3400 at 11K was obtained corresponding to surface resistance of 1.2mΩ for the MgB2∕Al2O3 interface. By simply using a sapphire substrate with two polished holes, superconducting connection has been achieved for the double-side MgB2 film. The results show potential applications for the superconducting MgB2 films in microwave and electronic devices.
Hybrid apparatus for Bose-Einstein condensation and cavity quantum electrodynamics: Single atom detection in quantum degenerate gases
Authors: Öttl Anton , Ritter Stephan , Köhl Michael , Esslinger Tilman
Published: July 2006

We present and characterize an experimental system in which we achieve the integration of an ultrahigh finesse optical cavity with a Bose-Einstein condensate (BEC). The conceptually novel design of the apparatus for the production of BECs features nested vacuum chambers and an in vacuo magnetic transport configuration. It grants large scale spatial access to the BEC for samples and probes via a modular and exchangeable “science platform.” We are able to produce Rb87 condensates of 5×106 atoms and to output couple continuous atom lasers. The cavity is mounted on the science platform on top of a vibration isolation system. The optical cavity works in the strong coupling regime of cavity quantum electrodynamics and serves as a quantum optical detector for single atoms. This system enables us to study atom optics on a single particle level and to further develop the field of quantum atom optics. We describe the technological modules and the operation of the combined BEC cavity apparatus. Its performance is characterized by single atom detection measurements for thermal and quantum degenerate atomic beams. The atom laser provides a fast and controllable supply of atoms coupling with the cavity mode and allows for an efficient study of atom field interactions in the strong coupling regime. Moreover, the high detection efficiency for quantum degenerate atoms distinguishes the cavity as a sensitive and weakly invasive probe for cold atomic clouds.
Observation of optical gain in solutions of CdS quantum dots at room temperature in the blue region
Authors: Darugar Qusai , Qian Wei , El-Sayed Mostafa A.
Published: July 2006

The optical gain dynamics has been studied for two CdS quantum dot samples dispersed in toluene at room temperature. This was carried out by using femtosecond transient absorption technique with an excitation at 400nm and gain measurement was studied at the fluorescence maxima (440 and 460nm). The optical gain lifetime was found to be as long as 20ps under pump fluence as low as 0.77mJ∕cm2. The low threshold is the result of long lifetime of electrons and holes and narrow emission bandwidth. These results suggest that CdS quantum dots in solution are excellent gain media for optically pumped high power blue lasers.
Cantilever based mass sensor with hard contact readout
Authors: Dohn S. , Hansen O. , Boisen A.
Published: July 2006

We present a method for microcantilever resonant frequency detection. We measure the direct current from an intermittent contact once every vibration cycle between the conducting cantilever and a counterelectrode at a low bias voltage with respect to the cantilever, while the excitation frequency and amplitude are varied. The result is an almost “digital” detection of the resonant frequency. A relative frequency resolution Δf∕f of 1∕80000 with high signal to noise ratio in ambient conditions is demonstrated. The detection method can be applied to portable sensor systems with very high frequency nanoelectromechanical cantilevers using simple off-chip electronics.
Local structure and medium-range ordering in relaxor ferroelectric Pb(Zn1∕3Nb2∕3)O3 studied using neutron pair distribution function analysis
Authors: Jeong I.-K. , Lee J. K.
Published: July 2006

We studied an evolution of local structure and medium-range ordering in relaxor ferroelectric Pb(Zn1∕3Nb2∕3)O3 (PZN) from 550 to 15K using neutron pair distribution function analysis. We show that the local structure of PZN is distorted at all temperatures studied. With decreasing temperature, a medium-range ordering of local polarizations develops with no global rhombohedral phase transition below TM. Instead, the crystal structure can be described as a mixture of polar nanoregions in a disordered lattice, similar to the case of Pb(Mg1∕3Nb2∕3)O3.