bluuebunny/crossref_metadata_2025 huggingface dataset:
A neural-network approach to high-precision docking of autonomous vehicles/platforms
Authors: Wong Joseph , Nejat Goldie , Fenton Robert , Benhabib Beno
Published: February 2007

In this paper, a Neural-Network- (NN) based guidance methodology is proposed for the high-precision docking of autonomous vehicles/platforms. The novelty of the overall online motion-planning methodology is its applicability to cases that do not allow for the direct proximity measurement of the vehicle's pose (position and orientation). In such instances, a guidance technique that utilizes Line-of-Sight- (LOS) based task-space sensory feedback is needed to minimize the detrimental impact of accumulated systematic motion errors. Herein, the proposed NN-based guidance methodology is implemented during the final stage of the vehicle's motion (i.e., docking). Systematic motion errors, which are accumulated after a long-range motion are reduced iteratively by executing corrective motion commands generated by the NN until the vehicle achieves its desired pose within random noise limits. The proposed guidance methodology was successfully tested via simulations for a 6-dof (degree-of-freedom) vehicle and via experiments for a 3-dof high-precision planar platform.
Cross-linguistic patterns of vowel intrusion
Authors: Hall Nancy
Published: February 2007

Vowel sounds may be inserted into a word by two mechanisms: insertion of a vocalic articulatory gesture (epenthesis), or retiming of existing gestures to produce a vowel-like transition between consonants (intrusion). I argue that epenthetic vowels are phonological units but intrusive vowels are not. A representation using abstract gestures as well as segments can capture facts about the typology of vowel intrusion.
Minimality and onsetless syllables in Zinza
Authors: Odden David
Published: February 2007

A dispreference for onsetless syllables is often manifested by processes of consonant insertion or vowel deletion which eliminate onsetless syllables, and it is sometimes manifested by disallowing prosodic distinctions which onsetful syllables make, e.g. onsetless syllables may resist bearing tone or stress. This paper investigates the interaction between minimality and the structure of onsetless syllables in the Bantu language Zinza, documenting a previously unobserved onsetless effect which is partially conditioned by minimality. In Zinza, word-initial vowels of disyllables are lengthened, so /o-ljá/ becomes [óó-lja] ‘you eat’ (compare [o-líma] ‘you cultivate’ and [bá-lja] ‘they eat’, with no lengthening). These facts test previous theories of onsetless effects (Downing 1993, 1998, Odden 1995, Orie 2000). I argue that a special representation of onsetless syllables is not warranted, and does not explain this pattern of lengthening. A constraint against word-initial short onsetless syllables interacting with word minimality suffices to explain this lengthening.
Diagnostik der Körperdysmorphen Störung
Authors: Brunhoeber Stefan , Maes Jürgen
Published: February 2007

Zusammenfassung. Die diagnostische Erfassung der Körperdysmorphen Störung (KDS) wird bislang durch unscharfe Diagnosekriterien und wenig ökonomische Messinstrumente erschwert. Ziel dieser Arbeit war es daher, ein anwendungsfreundliches Instrument zu entwickeln, das sich durch eine ökonomische und einfache Handhabung auszeichnet, gleichzeitig aber auch reliable und valide Ergebnisse liefert. Der entwickelte Fragebogen wurde 68 Personen mit diagnostizierter KDS, 50 Personen einer dermatologischen Klinik, 50 Personen einer plastischen Chirurgie, 49 Studenten, 49 Personen mit Sozialer Phobie, 44 Personen mit Zwängen, 28 Personen mit Depressionen und 33 Personen mit einer realen Aussehensbeeinträchtigung vorgelegt. Um die Güte der Unterscheidung zwischen der KDS-Gruppe und den sieben Vergleichsgruppen festzustellen, wurden die Trefferquoten für eine richtige Zuordnung mit einer univariaten Diskriminanzanalyse mit Kreuzvalidierung für jeden Gruppenvergleich bestimmt. Die Trefferquoten lagen im Durchschnitt über 90 %. Die Fragebogenskalen weisen eine sehr gute interne Konsistenz (.96 bzw. .90), gute Split-Half-Reliabilitäten (.95 bzw. .80) und Retest-Reliabilitäten (.88 bzw. .80) auf. Der Körperdysmorphe Störungs-Fragebogen (KDS-F) ist dementsprechend gut geeignet, zwischen verschiedenen klinischen und nicht-klinischen Gruppen zu unterscheiden. Neben der ausführlichen Version des KDS-F wurde zusätzlich ein Kurzscreening (KDS-K) entwickelt, das noch bessere diskriminante Eigenschaften aufweist als die Langversion.
Entwicklung und Validierung von Skalen zur Erfassung von Vermeidung und Angst in Partnerschaften
Authors: Neumann Eva , Rohmann Elke , Bierhoff Hans-Werner
Published: February 2007

Zusammenfassung. Die deutsche Adaptation der “Experiences in Close Relationships“ (ECR) wird vorgestellt, der Bochumer Bindungsfragebogen (BoBi), ein Messinstrument zur Selbsteinschätzung der partnerschaftlichen Bindung entlang der beiden Dimensionen Vermeidung und Angst. Der BoBi wurde 435 Studierenden und 178 ambulanten Patienten einer psychosomatischen Klinik vorgegeben. Die zweifaktorielle Struktur des ECR konnte für den BoBi bestätigt werden. Vergleiche der BoBi-Skalen mit weiteren Partnerschafts- und Persönlichkeitsvariablen erbrachten, dass Vermeidung vor allem mit dem Fehlen von romantischer Liebe und geringerem Partnerschaftserfolg einhergeht, Angst ist durch besitzergreifende Liebe, ein Gefühl der Verbundenheit mit dem Partner und geringes Selbstwertgefühl gekennzeichnet. Dieses Ergebnismuster belegt die Konstruktvalidität des BoBi. Der BoBi kann gleichermaßen in Stichproben aus der Normalbevölkerung wie im klinischen Bereich eingesetzt werden. Studien mit dem BoBi können mit internationalen Studien mit dem ECR verglichen werden.
Suppression of δPKC Activation after Focal Cerebral Ischemia Contributes to the Protective Effect of Hypothermia
Authors: Shimohata Takayoshi , Zhao Heng , Sung Jae Hoon , Sun Guohua , Mochly-Rosen Daria , Steinberg Gary K
Published: February 2007

Mild hypothermia is a robust neuroprotective treatment for stroke. Understanding the mechanisms underlying hypothermia's benefits will lead to more effective treatments to prevent stroke damage. Delta protein kinase C ( δPKC) is a kinase that has been strongly implicated in executing ischemic damage. We investigated the effects of hypothermia on δPKC activation, as determined by its subcellular translocation, proteolytic cleavage, and phosphorylation in a focal cerebral ischemia model. The amount of constitutively activated C-terminal catalytic fragment of δPKC (CF- δPKC) increased after stroke. Both hypothermia (30 C) and the caspase-3-specific inhibitor, Z-DQMD-FMK, blocked the accumulation of activated δPKC in the penumbra. Other hallmarks of δPKC activation, its translocation to the mitochondria, and nucleus were observed in the penumbra as early as 10 mins after reperfusion. These events were blocked by hypothermia. Hypothermia also blocked CF- δPKC increases in the mitochondria and nuclei. Conversely, a specific δPKC activator, ψδRACK, decreased the neuroprotective effect of hypothermia. Finally, δPKC activity may lead to mitochondrial injury and cytochrome c release, as the timing of cytochrome c release corresponded to the time course of δPKC translocation. Both cytochrome c release and δPKC translocation were blocked by hypothermia. In conclusion, hypothermia protects against ischemic damage in part by suppressing δPKC activation after stroke.
Expression Profiling Identifies the CRH/CRH-R1 System as a Modulator of Neurovascular Gene Activity
Authors: Deussing Jan M , Kühne Claudia , Pütz Benno , Panhuysen Markus , Breu Johannes , Stenzel-Poore Mary P , Holsboer Florian , Wurst Wolfgang
Published: February 2007

Corticotropin-releasing hormone receptor type 1 (CRH-R1)-deficient mice display reduced anxiety-like behavior, a chronic corticosterone deficit, and an impaired neuroendocrine stress response caused by disruption of the hypothalamic–pituitary–adrenocortical (HPA) axis. The molecular substrates and pathways of CRH/CRH-R1-dependent signaling mechanisms underlying the behavioral phenotype as well as the consequences of lifelong glucocorticoid deficit remain largely obscure. To dissect involved neuronal circuitries, we performed comparative expression profiling of brains of CRH-R1 mutant and wild-type mice using our custom made MPIP (Max Planck Institute of Psychiatry) 17k cDNA microarray. Microarray analysis yielded 107 genes showing altered expression levels when comparing CRH-R1 knockout mice with wild-type littermates. A significant proportion of differentially expressed genes was related to control of HPA and hypothalamic–pituitary–thyroid (HPT) axes reflecting not only the disturbance of the HPA axis in CRH-R1 mutant mice but also the interplay of both neuroendocrine systems. The spatial analysis of regulated genes revealed a prevalence for genes expressed in the cerebral microvasculature. This phenotype was confirmed by the successful cross-validation of regulated genes in CRH overexpressing mice. Analysis of the cerebral vasculature of CRH-R1 mutant and CRH overexpressing mice revealed alterations of functional rather than structural properties. A direct role of the CRH/CRH-R1 system was supported by demonstrating Crhr1 expression in the adult murine cerebral vasculature. In conclusion, these data suggest a novel, previously unknown role of the CRH/CRH-R1 system in modulating neurovascular gene expression and function.
Potential Contribution of Nuclear Factor-κB to Cerebral Vasospasm after Experimental Subarachnoid Hemorrhage in Rabbits
Authors: Zhou Meng-Liang , Shi Ji-Xin , Hang Chun-Hua , Cheng Hui-Lin , Qi Xiao-Ping , Mao Lei , Chen Ke-Fei , Yin Hong-Xia
Published: February 2007

Nuclear factor-κB (NF-κB) plays a key role in inflammation, which is involved in the development of cerebral vasospasm after subarachnoid hemorrhage (SAH). In the present study, we assessed the potential role of NF-κB in regulation of cerebral vasospasm. Nuclear factor-κB DNA-binding activity was measured in cultured vascular smooth muscle cells (VSMCs) treated with hemolysate and pyrrolidine dithiocarbamate (PDTC, 80 μmol/L), an inhibitor of NF-κB. Forty-two rabbits were divided into three groups: control, SAH, and PDTC groups ( n = 14 for each group). The caliber of the basilar artery was evaluated. Nuclear factor-κB DNA-binding activity and the gene expression levels of cytokines and adhesion molecules in the basilar artery were measured. Immunohistochemical study was performed to assess the expression and localization of tumor necrosis factor (TNF)-α, intercellular adhesion molecule (ICAM)-1, and myeloperoxidase (MPO). It was observed that NF-κB DNA-binding activity was significantly increased by treatment with hemolysate in cultured VSCMs, but this increase was suppressed by pretreatment with PDTC. Severe vasospasm was observed in the SAH group, which was attenuated in the PDTC group. Subarachnoid hemorrhage could induce increases of NF-κB DNA-binding activity and the gene expression levels of TNF-α, interleukin (IL)-1β, ICAM-1, and vascular cell adhesion molecule (VCAM)-1, which were reduced in the PDTC group. Immunohistochemical study demonstrated that the expression levels of TNF-α, ICAM-1, and MPO were all increased in the SAH group, but these increases were attenuated in the PDTC group. Our results suggest that NF-κB is activated in the arterial wall after SAH, which potentially leads to vasospasm development through induction of inflammatory response.
Increased Pentose Phosphate Pathway Flux after Clinical Traumatic Brain Injury: A [1,2-13C2]glucose Labeling Study in Humans
Authors: Dusick Joshua R , Glenn Thomas C , Lee WN Paul , Vespa Paul M , Kelly Daniel F , Lee Stefan M , Hovda David A , Martin Neil A
Published: February 2007

Patients with traumatic brain injury (TBI) routinely exhibit cerebral glucose uptake in excess of that expected by the low levels of oxygen consumption and lactate production. This brings into question the metabolic fate of glucose. Prior studies have shown increased flux through the pentose phosphate cycle (PPC) during cellular stress. This study assessed the PPC after TBI in humans. [1,2-13C2]glucose was infused for 60 mins in six consented, severe-TBI patients (GCS < 9) and six control subjects. Arterial and jugular bulb blood sampled during infusion was analyzed for 13C-labeled isotopomers of lactate by gas chromatography/mass spectroscopy. The product of lactate concentration and fractional abundance of isotopomers was used to determine blood concentration of each isotopomer. The difference of jugular and arterial concentrations determined cerebral contribution. The formula PPC = ( m1/ m2)/(3 + ( m1/ m2)) was used to calculate PPC flux relative to glycolysis. There was enrichment of [1,2-13C2]glucose in arterial-venous blood (enrichment averaged 16.6% in TBI subjects and 28.2% in controls) and incorporation of 13C-label into lactate, showing metabolism of labeled substrate. The PPC was increased in TBI patients relative to controls (19.6 versus 6.9%, respectively; P = 0.002) and was excellent for distinguishing the groups (AUC = 0.944, P < 0.0001). No correlations were found between PPC and other clinical parameters, although PPC was highest in patients studied within 48 h of injury (averaging 33% versus 13% in others; P = 0.0006). This elevation in the PPC in the acute period after severe TBI likely represents a shunting of substrate into alternative biochemical pathways that may be critical for preventing secondary injury and initiating recovery.
Experimental transmission of Kaposi's sarcoma‐associated herpesvirus (KSHV/HHV‐8) to SIV‐positive and SIV‐negative rhesus macaques
Authors: Renne R. , Dittmer D. , Kedes D. , Schmidt K. , Desrosiers R.C. , Luciw P.A. , Ganem D.
Published: February 2007

Abstract:  Kaposi's sarcoma‐associated herpesvirus (KSHV) is a γ‐herpesvirus associated with Kaposi's sarcoma (KS) and two lymphoproliferative diseases, primary effusion lymphoma (PEL) and multicentric Castleman's disease. Studies on the biology and pathogenesis of KSHV have been limited by lack of efficient cell culture systems and lack of a suitable animal model for KS. Here we report on the experimental inoculation of SIV‐positive and SIV‐negative rhesus macaques with KSHV‐infected PEL cells or KSHV preparations derived from PEL cells. Low levels of viral DNA could be detected in cultivated peripheral blood mononuclear cell of all animals, as well as in the bone marrow of one monkey that died from SAIDS. However, we were not able to detect KSHV‐specific antibodies or transcripts, nor did we observe any symptoms clearly related to KSHV infection (e.g. KS or lympho‐proliferative disease). Hence, although KSHV replicates in rhesus macaques at very low levels, this non‐human primate host is unlikely to provide a useful animal model for disease.
Magnetostrictive bimagnetic trilayer ribbons for temperature sensing
Authors: Mendoza Zélis P. , Sánchez F. , Vázquez M.
Published: February 2007

A magnetic biphase trilayer ribbon, consisting of a melt-spun FeSiB inner amorphous ribbon with positive magnetostriction coated by two electroplated nickel layers with negative magnetostriction, is here proposed as an element to be incorporated in temperature sensor devices. The inductance of a small coil wounded around the trilayer is characterized as the sensitive parameter. The dependence of coil’s inductance on the thickness of electroplated Ni has been evaluated in the range of measuring temperatures of 0–70°C, and optimum electroplating parameters were determined. Magnetic characteristics are determined through the study of hysteresis loops, which denote the presence of the two magnetic phases. The experimental results are interpreted considering a simple magnetoelastic model taking into account the mechanical stresses arising from the different thermal expansion coefficients of each magnetic phase.
Use of two-photon polymerization for continuous gray-level encoding of diffractive optical elements
Authors: Jia Baohua , Serbin Jesper , Kim Hwi , Lee Byoungho , Li Jiafang , Gu Min
Published: February 2007

Generation of continuous gray levels in three-dimensional diffractive optical elements has remained a challenge with the current semiconductor microfabrication method. In this letter, the authors propose and demonstrate the use of the two-photon polymerization method for fabricating three-dimensional diffractive optical elements of continuous gray levels. This method is a mask-free and low-cost single-step process. It is shown that the multilevel-phase-encoded diffractive optical element fabricated in inorganic-organic hybrid polymer material facilitates the intensity distribution synthesis with a high diffraction efficiency approaching the theoretical limit.
Ion and electron bombardment-related ion emission during the analysis of diamond using secondary ion mass spectrometry
Authors: Guzmán de la Mata Berta , Dowsett Mark G.
Published: February 2007

In recent years, the ability to grow single crystal layers of both doped and pure diamonds has improved, and devices for applications in high power electronics and microelectronics are being developed, most of them based on boron doped diamond. In this work, convoluted angular and energy spectra (so-called secondary ion mass spectrometry energy spectra) have been measured for B+11, C+12, O+16, CO+ and CO2+ ions ejected from a single crystal boron doped diamond layer under ultralow energy oxygen and electron beam bombardment. A low energy tail was observed in the C+12, CO+, and CO2+ signals, corresponding to ions produced in the gas phase. Changing the bombardment conditions, we have identified interaction with the electron beam as the main ionization mechanism. In the case of C+12 it appears that the gas phase ions are produced by electron stimulated desorption and postionization of surface species created by the oxygen beam. We have detected high signals for CO+ and CO2+ ionized in the gas phase, which supports a mechanism previously suggested to explain the anomalously fast diamond erosion under oxygen ion beam bombardment. We also observe that some species appearing in the mass spectrum are produced by electron stimulated desorption and this needs to be remembered when analyzing these on insulating diamond with charge compensation.
Revealing direction of coupling between neuronal oscillators from time series: Phase dynamics modeling versus partial directed coherence
Authors: Smirnov Dmitry , Schelter Bjoern , Winterhalder Matthias , Timmer Jens
Published: February 2007

The problem of determining directional coupling between neuronal oscillators from their time series is addressed. We compare performance of the two well-established approaches: partial directed coherence and phase dynamics modeling. They represent linear and nonlinear time series analysis techniques, respectively. In numerical experiments, we found each of them to be applicable and superior under appropriate conditions: The latter technique is superior if the observed behavior is “closer” to limit-cycle dynamics, the former is better in cases that are closer to linear stochastic processes.
Electrophoretic properties of highly charged colloids: A hybrid molecular dynamics∕lattice Boltzmann simulation study
Authors: Chatterji Apratim , Horbach Jürgen
Published: February 2007

Using computer simulations, the electrophoretic motion of a positively charged colloid (macroion) in an electrolyte solution is studied in the framework of the primitive model. In this model, the electrolyte is considered as a system of negatively and positively charged microions (counterions and coions, respectively) that are immersed into a structureless medium. Hydrodynamic interactions are fully taken into account by applying a hybrid simulation scheme, where the charged ions (i.e., macroion and electrolyte), propagated via molecular dynamics, are coupled to a lattice Boltzmann (LB) fluid. In a recent electrophoretic experiment by Martin-Molina et al. [J. Phys. Chem. B 106, 6881 (2002)], it was shown that, for multivalent salt ions, the mobility μ initially increases with charge density σ, reaches a maximum, and then decreases with further increase of σ. The aim of the present work is to elucidate the behavior of μ at high values of σ. Even for the case of monovalent microions, a decrease of μ with σ is found. A dynamic Stern layer is defined that includes all the counterions that move with the macroion while subjected to an external electrical field. The number of counterions in the Stern layer, q0, is a crucial parameter for the behavior of μ at high values of σ. In this case, the mobility μ depends primarily on the ratio q0∕Q (with Q the valency of the macroion). The previous contention that the increase in the distortion of the electric double layer (EDL) with increasing σ leads to the lowering of μ does not hold for high σ. In fact, it is shown that the deformation of the EDL decreases with the increase of σ. The role of hydrodynamic interactions is inferred from direct comparisons to Langevin simulations where the coupling to the LB fluid is switched off. Moreover, systems with divalent counterions are considered. In this case, at high values of σ the phenomenon of charge inversion is found.
Microscopic electroabsorption line shape analysis for Ga(AsSb)∕GaAs heterostructures
Authors: Bückers C. , Blume G. , Thränhardt A. , Schlichenmaier C. , Klar P. J. , Weiser G. , Koch S. W. , Hader J. , Moloney J. V. , Hosea T. J. C. , Sweeney S. J. , Wang J.-B. , Johnson S. R. , Zhang Y.-H.
Published: February 2007

A series of Ga(AsSb)∕GaAs∕(AlGa)As samples with varying GaAs spacer width are studied by electric-field modulated absorption (EA) and reflectance spectroscopy and modeled using a microscopic theory. The analysis of the Franz–Keldysh oscillations of GaAs capping layer and of the quantum-confined Stark shift of the lowest quantum well (QW) transitions shows the strong inhomogeneity of the built-in electric field indicating that the field modulation due to an external bias voltage differs significantly for the various regions of the structures. The calculations demonstrate that the line shape of the EA spectra of these samples is extremely sensitive to the value of the small conduction band offset between GaAs and Ga(AsSb) as well as to the magnitude of the internal electric field changes caused by the external voltage modulation in the QW region. The EA spectra of the entire series of samples are modeled by the microscopic theory. The good agreement between experiment and theory allows us to extract the strength of the modulation of the built-in electric field in the QW region and to show that the band alignment between GaAs and Ga(AsSb) is of type II with a conduction band offset of approximately 40 meV.
Selective surface crystallization of nonstoichiometric 30BaO-15TiO2-55GeO2 glass
Authors: Masai Hirokazu , Fujiwara Takumi , Benino Yasuhiko , Komatsu Takayuki , Mori Hiroshi
Published: February 2007

The correlation between heat-treatment temperature for crystallization and orientation of surface crystalline phase, which should correspond to the intensity of second-order optical nonlinear susceptibility, in 30BaO-15TiO2-55GeO2 (BTG55) crystallized glass was examined by measurements of x-ray diffraction (XRD) and second harmonic generation. A highly oriented fresnoite (Ba2TiGe2O8) or benitoite (BaTiGe3O9) phase was found to nucleate from the same mother BTG55 glass depending on the heat-treatment temperature, and both the fresnoite and benitoite phases showed XRD patterns of surface crystallization. It was found that the crystallization behavior of the two phases was strongly affected by the heat-treatment temperature. Based on this finding, the nonlinear optical property has also been tailored using the heat-treatment procedures.
An intermolecular coupling between guest and host in the doped liquid crystal system
Authors: Xiang Ying , Li Tao , Zi-Yang Lin , Jie Lin
Published: February 2007

The magnetic-field-Induced reorientation of a planar alignment nematic liquid crystal (5CB) doped with different paramagnetic dopants has been studied in this paper. It was observed that compared with the pure 5CB, 5CB doped with five-coordinated [Cu(o-xyTQ)H2O](NO3)2 dramatically decreased the critical magnetic field strength for the reorientation, while 5CB doped with six-coordinated [Cu(DETQ)](ClO4)2 revealed no such effect. Although the two paramagnetic dopants possess the same magnetic property, they have different intermolecular couplings with host 5CB, which produce the different results. This phenomenon is very useful to study the magneto-optical component of liquid crystal.
Intermolecular interaction potentials for the Ar–C2H2, Kr–C2H2, and Xe–C2H2 weakly bound complexes: Information from molecular beam scattering, pressure broadening coefficients, and rovibrational spectroscopy
Authors: Cappelletti David , Bartolomei Massimiliano , Carmona-Novillo Estela , Pirani Fernando , Blanquet Ghislain , Thibault Franck
Published: February 2007

Integral cross sections and pressure broadening coefficients have been measured for the acetylene-krypton complex, by molecular beam scattering and by high resolution IR spectroscopy, respectively. A new potential energy surface (PES) is proposed to describe structure and dynamical properties of this prototypical weakly bound complex. The PES has been parametrized exploiting a novel atom-bond pairwise additive scheme and has been fitted to the experimental data. A similar PES has been obtained for the acetylene-xenon system by a proper scaling of the interaction parameters of the krypton case, based on empirical considerations. These PESs together with that recently proposed by the same authors [J. Phys. Chem. 109, 8471 (2005)] for the acetylene-argon case have been employed for close coupling calculations of the pressure broadening cross sections and for a characterization of the rovibrational structure of the complexes.
Energy scaling of monoenergetic electron beams generated by the laser-driven plasma based accelerator
Authors: Masuda S. , Miura E. , Koyama K. , Kato S. , Adachi M. , Watanabe T. , Torii K. , Tanimoto M.
Published: February 2007

Monoenergetic electron beams were generated in the self-modulated laser wakefield acceleration regime using a 2–6TW, 50fs Ti:sapphire laser system. The monoenergetic electron beams of energies up to 15MeV and 30MeV, with a plasma density around 1.5×1020cm−3 and 3.5×1019cm−3, respectively, were observed. The monoenergetic energy was found to be inversely proportional to the plasma density. The monoenergetic electron beam was generated at only specific plasma densities for each experimental condition. The plasma density dependence of the electron energy spectrum, the forward scattered light spectrum, and the side scattered light image of the laser pulse was studied in detail. The conditions for monoenergetic electron beam generation are discussed based on the results of the plasma diagnostics.
Effect of sheared flow on magnetic islands
Authors: Waelbroeck F. L. , Fitzpatrick R. , Grasso Daniela
Published: February 2007

The effect of sheared flow on a magnetic island is examined. In contrast to the density and temperature gradients which are flattened for sufficiently wide islands, it is found that the velocity gradient persists inside the separatrix whenever the constant-ψ approximation is satisfied. It follows that velocity shear has a negligible effect on island amplitude in that approximation. The effect of the violation of the constant-ψ approximation is explored by using the Kelvin-Stuart family of islands, and it is found that flattening is modest even when the separatrix encloses virtually all the current.
Optical and magneto-optical properties of gadolinium
Authors: Saini Sapan Mohan , Singh Nirpendra , Nautiyal Tashi , Auluck Sushil
Published: February 2007

We report calculations of the optical and magneto-optical properties of elemental rare earth gadolinium using the full potential linear augmented plane wave method and including spin-orbit coupling. Calculations are performed within the local spin density approximation (LSDA) and Coulomb corrected local spin density approximation (LSDA+U). While LSDA+U gives better agreement for density of states and magnetic moments, a comparison with the experimental data shows that both LSDA and LSDA+U are at par in representing the diagonal components of the optical conductivity. For the much smaller off-diagonal components, interestingly, the LSDA results have an edge over the LSDA+U results.
Linearly polarized lasing in one-dimensional hybrid photonic crystal containing cholesteric liquid crystal
Authors: Matsuhisa Yuko , Ozaki Ryotaro , Takao Yuuki , Ozaki Masanori
Published: February 2007

We have achieved single-mode laser action in a one-dimensional hybrid photonic crystal (HPC) containing cholesteric liquid crystal (CLC) as a defect and experimentally investigated the polarization characteristics of the laser light. The laser light emitted from the HPC containing the CLC was linearly polarized, which was different from that of the simple CLC, despite the CLC being contained in this structure. We have theoretically calculated the optical propagation to justify the experimental result. The calculated result was in good agreement with the experimental result and showed the difference in optical characteristics between the simple CLC and the HPC containing the CLC.
Numerical investigation of transient capacitances of Ge∕Si heteronanocrystal memories in retention mode
Authors: Zhu Yan , Zhao Dengtao , Liu Jianlin
Published: February 2007

Transient capacitances were numerically investigated for Ge∕Si heteronanocrystal memories. Flatband voltage shifts (ΔVfb) were obtained. The results suggest that the Ge∕Si heteronanocrystal memories have significantly longer data retention compared with the memories embedding Si nanocrystals only. It is also found that larger heteronanocrystal leads to longer retention, larger device capacitance, and smaller ΔVfb.
Quantitative comparison between dynamic structure factors obtained experimentally and those calculated with Doi-Onuki theory
Authors: Takenaka Mikihito , Nishitsuji Shotaro , Hasegawa Hirokazu
Published: February 2007

This paper reports results of quantitative comparison between dynamic structure factors obtained experimentally and those calculated by using the Doi and Onuki (DO) theory for semidilute polymer solutions. The authors obtained the dynamic structure factors with dynamic light scattering (DLS) experiment while the dynamic structure factors were calculated by using DO theory with osmotic compressibility, viscoelastic relaxation function, and friction coefficient which are obtained independently of DLS experiment. Calculated dynamic structure factors agree with experimental ones well and can express the q-dependent fast modes and the q-insensitive slow mode which experimental ones show. The authors estimated the characteristic parameters, interdiffusion coefficient and cooperative diffusion coefficient, from experimental and calculated results by using the procedure proposed by Einaga and Fujita [Polymer 40, 565 (1999)]. The estimated parameters for the DLS experiment agree with those for the calculation. These agreements in dynamic structure factors and the parameters indicate that DO theory can describe well the relaxation processes of semidilute polymer solutions.
Nonlinear optical phenomena in nanowires
Authors: Ruda H. E. , Shik A.
Published: February 2007

The theory of second harmonic generation (SHG) in nanowires with different dielectric constants from their environment is developed. A nonuniform distribution of the optical electric field created by image forces results in strong SHG even in materials with inversion symmetry. Integral intensity, spatial distribution, and the polarization of the SHG depend dramatically on the light polarization, as well as on the mutual orientation of the light wave vector and nanowire axis. In semiconducting or dielectric nanowires, the SHG is maximal when the light polarization is parallel to the nanowire axis. In metallic nanowires, the SHG is a function of the light frequency ω being maximal when ω or 2ω coincide with the surface plasmon frequency. At the first resonant frequency, the SHG is caused mostly by light polarized perpendicularly and at the second frequency—parallel to the nanowire axis.
Conformations in dioctyl substituted polyfluorene: A combined theoretical and experimental Raman scattering study
Authors: Volz C. , Arif M. , Guha S.
Published: February 2007

The structural properties of polyfluorenes (PF) are extremely sensitive to the choice of functionalizing side chains. Dioctyl substituted PF (PF8) adopts metastable structures that depend upon the thermal history and choice of solvents used in film forming conditions. We present a detailed study of the changes in the backbone and side chain morphology in PF8, induced by the various crystallographic phases, using Raman scattering techniques. The vibrational frequencies and intensities of fluorene oligomers are calculated using hybrid density-functional theory with a 3-21G* basis set. The alkyl side chains are modeled as limiting conformations: all anti, anti-gauche-gauche, and end gauche representations. The calculated vibrational spectra of single chain oligomers in conjunction with our experimental results demonstrate the β phase, which is known to originate in regions of enhanced chain planarity as a direct consequence of the alkyl side chain conformation.
Chemical interface analysis of as grown HfO2 ultrathin films on SiO2
Authors: Maunoury C. , Dabertrand K. , Martinez E. , Saadoune M. , Lafond D. , Pierre F. , Renault O. , Lhostis S. , Bailey P. , Noakes T. C. Q. , Jalabert D.
Published: February 2007

The quality of the interface between a HfO2 high-k gate dielectric and the Si substrate directly influences its electrical properties. The chemical composition of the interfacial region of HfO2 deposited on a SiO2∕Si(100) substrate by pulsed liquid injection metal organic chemical vapor deposition at 430 and 550°C was investigated by medium energy ion scattering, angular resolved x-ray photoemission spectroscopy analysis, and high resolution transmission electron microscopy. It is shown that the HfO2∕SiO2 interface is abrupt with low roughness and no silicate. The interface roughness with SiO2 is found to be close to that generally measured in silicon technology (silicon oxide above silicon substrates) [E. A. Irene, Solid-State Electron., 45, 1207 (2001)]. The analysis of the experimental results indicates that the deposition technique does not lead to the formation of an extended silicate layer at the HfO2∕SiO2 interface.
Variational techniques in general relativity: A metric-affine approach to Kaluza’s theory
Authors: Massa Enrico , Vignolo Stefano
Published: February 2007

A new variational principle for general relativity based on an action functional I(Φ,∇) involving both the metric Φ and the connection ∇ as independent, unconstrained degrees of freedom is presented. The extremals of I are seen to be pairs (Φ,∇) in which Φ is a Ricci flat metric and ∇ is the associated Riemannian connection. An application to Kaluza’s theory [Sitz. Preuss. Akad. Wiss., 966 (1921)] of interacting gravitational and electromagnetic fields is discussed.
Bogoliubov Hamiltonians and one-parameter groups of Bogoliubov transformations
Authors: Bruneau Laurent , Dereziński Jan
Published: February 2007

On the bosonic Fock space, a family of Bogoliubov automorphisms corresponding to a strongly continuous one-parameter group of symplectic maps (R(t))t∊R is considered. We give conditions that guarantee it to be implemented by a strongly continuous one-parameter group U(t) of unitary operators. The generator of such U(t) will be called a Bogoliubov Hamiltonian. Given (R(t))t∊R, a Bogoliubov Hamiltonian is defined up to an additive constant. We introduce two kinds of Bogoliubov Hamiltonians: type I, characterized by vanishing of the expectation value at the vacuum, and type II, characterized by the fact that its infimum equals zero. We give conditions so that they are well defined. We show that there exist cases when only HI is well defined, even though the classical Hamiltonian is positive (which may be interpreted as a kind of an infrared catastrophe), and when only HII is well defined (which means that one needs to introduce an infinite counterterm in the formula for the Hamiltonian).
Manipulation of strain relaxation in metamorphic heterostructures
Authors: Tångring I. , Wang S. M. , Zhu X. R. , Larsson A. , Lai Z. H. , Sadeghi M.
Published: February 2007

The authors have discovered that high doping densities in an alloy graded InGaAs buffer have dramatic effects on strain relaxation dynamics and consequently surface and optical qualities in metamorphic heterostructures. Compared with undoped graded buffers, the use of Be doping significantly improves structural, surface, and optical qualities while the use of Si doping deteriorates all these properties. This discovery is significant for the realization of metamorphic optoelectronic devices.
Interface between a polar perovskite oxide and silicon from monoatomic lines
Authors: Devos I. , Boulenc P.
Published: February 2007

The authors report a study on the interface between polar high-κ materials and the Si(001)-(2×1) reconstructed surface with LaAlO3 taken as a prototype material. The construction of the interface is based on the prior growth of metal lines followed by oxidation, whose stability against oxygen coverage is studied. Electronic structure calculations within the density functional theory framework help in building the interface and understanding its bonding structure. Moreover, the authors computed a conduction band offset of 1.9eV, in agreement with the electronic application requirement. The results may provide a guidance for interface processing.
Surface diffusion effects on growth of nanowires by chemical beam epitaxy
Authors: Persson A. I. , Fröberg L. E. , Jeppesen S. , Björk M. T. , Samuelson L.
Published: February 2007

Surface processes play a large role in the growth of semiconductor nanowires by chemical beam epitaxy. In particular, for III-V nanowires the surface diffusion of group-III species is important to understand in order to control the nanowire growth. In this paper, we have grown InAs-based nanowires positioned by electron beam lithography and have investigated the dependence of the diffusion of In species on temperature, group-III and -V source pressure and group-V source combinations by measuring nanowire growth rate for different nanowire spacings. We present a model which relates the nanowire growth rate to the migration length of In species. The model is fitted to the experimental data for different growth conditions, using the migration length as fitting parameter. The results show that the migration length increases with decreasing temperature and increasing group-V/group-III source pressure ratio. This will most often lead to an increase in growth rate, but deviations will occur due to incomplete decomposition and changes in sticking coefficient for group-III species. The results also show that the introduction of phosphorous precursor for growth of InAs1−xPx nanowires decreases the migration length of the In species followed by a decrease in nanowire growth rate.
Dielectric and ac conduction properties of zinc phthalocyanine (ZnPc) thin films
Authors: Senthilarasu S. , Sathyamoorthy R. , Ascencio J. A. , Lee Soo-Hyoung , Hahn Y. B.
Published: February 2007

The dielectric responses of zinc phthalocyanine (ZnPc) thin films, deposited using the vacuum evaporation technique, were studied as functions of frequency and temperature. The conductivity of the deposited films decreases with increase in temperature. The dielectric studies clearly indicated that the Debye type of polarization exists in these films. The relaxation phenomena have been confirmed from the Cole-Cole plot. The relaxation times have been evaluated from the plot and were found to be (τa) 0.0137 and 0.0106s at 303 and 403K, respectively. The prevailing conduction mechanism in ZnPc films, under an ac field, was found to be electronic hopping. The activation energy was evaluated from the Arrhenius plot and was found to be 1.28eV. Based on the structure, and with the help of quantum mechanics calculations, the electronic structure and behavior that upheld our experimental results were identified.
Electromagnetic eigenmodes of collisional and collisionless plasmas and their stability to stimulated Brillouin scattering
Authors: Pathak Vishwa Bandhu , Tripathi V. K.
Published: February 2007

Nonlinear electromagnetic eigenmodes of collisional and collisionless plasmas, when the temporal extent of the modes is longer than the ambipolar diffusion time, have been investigated. The nonlinearity in a collisionless plasma arises through ponderomotive force, whereas in collisional plasmas Ohmic nonlinearity prevails. The mode structure in both cases, representing a balance between the nonlinearity-induced self-convergence and diffraction-induced divergence, closely resembles Gaussian form. The spot size of the mode decreases with the increasing axial amplitude of the laser, attains a minimum, and then rises very gradually. The modes are susceptible to stimulated Brillouin backscattering. The growth rate of the Brillouin process initially increases with mode amplitude, attains a maximum, and then decreases. The reduction in the growth rate is caused by strong electron evacuation from the axial region by the ponderomotive force and thermal pressure gradient force created by nonuniform Ohmic heating.
Intrinsic gettering Based on rapid thermal annealing in germanium-doped Czochralski silicon
Authors: Chen Jiahe , Yang Deren , Ma Xiangyang , Li Hong , Que Duanlin
Published: February 2007

The intrinsic gettering (IG) effects under different thermal processes involved with rapid thermal annealing (RTA) in Czochralski (CZ) silicon wafers with germanium doping have been investigated. It has been shown that both good quality denuded zones and high-density bulk microdefect regions could be generated in germanium-doped CZ (GCZ) silicon wafers through thermal cycles of RTA treatments plus either low-high temperature two-step annealing or high temperature single-step annealing. Moreover, more oxygen precipitation was formed in GCZ silicon wafers in comparison with conventional CZ silicon wafers, indicating the enhancement of IG capability for CZ silicon wafers by the germanium doping. The phenomena have been considered to be ascribed to the increase of vacancy concentration associated with the presence of germanium, which results in the generation of Ge-V-related complexes in GCZ silicon wafers during RTA treatments.
Herman-Kluk semiclassical dynamics of molecular rotations in laser fields
Authors: Saha Rajdeep , Ovchinnikov M.
Published: February 2007

The action-angle mapping algorithm [R. Saha and M. Ovchinnikov, J. Chem. Phys. 124, 204112 (2006)] is utilized to provide a Herman-Kluk semiclassical initial value representation (SC-IVR) treatment of quantum dynamics of systems with non-Cartesian degrees of freedom. The non-Cartesian system under investigation is a linear rotor molecule in static electric and pulsed laser field. The results demonstrate that the SC-IVR procedure described in this work provides an accurate representation of quantum rotational dynamics of the system.
An infinite-order two-component relativistic Hamiltonian by a simple one-step transformation
Authors: Iliaš Miroslav , Saue Trond
Published: February 2007

The authors report the implementation of a simple one-step method for obtaining an infinite-order two-component (IOTC) relativistic Hamiltonian using matrix algebra. They apply the IOTC Hamiltonian to calculations of excitation and ionization energies as well as electric and magnetic properties of the radon atom. The results are compared to corresponding calculations using identical basis sets and based on the four-component Dirac-Coulomb Hamiltonian as well as Douglas-Kroll-Hess and zeroth-order regular approximation Hamiltonians, all implemented in the DIRAC program package, thus allowing a comprehensive comparison of relativistic Hamiltonians within the finite basis approximation.
Delay time modulation induced oscillating synchronization and intermittent anticipatory/lag and complete synchronizations in time-delay nonlinear dynamical systems
Authors: Senthilkumar D. V. , Lakshmanan M.
Published: February 2007

Existence of a new type of oscillating synchronization that oscillates between three different types of synchronizations (anticipatory, complete, and lag synchronizations) is identified in unidirectionally coupled nonlinear time-delay systems having two different time-delays, that is feedback delay with a periodic delay time modulation and a constant coupling delay. Intermittent anticipatory, intermittent lag, and complete synchronizations are shown to exist in the same system with identical delay time modulations in both the delays. The transition from anticipatory to complete synchronization and from complete to lag synchronization as a function of coupling delay with suitable stability condition is discussed. The intermittent anticipatory and lag synchronizations are characterized by the minimum of the similarity functions and the intermittent behavior is characterized by a universal asymptotic −32 power law distribution. It is also shown that the delay time carved out of the trajectories of the time-delay system with periodic delay time modulation cannot be estimated using conventional methods, thereby reducing the possibility of decoding the message by phase space reconstruction.
Stacking fault generation during relaxation of silicon germanium on insulator layers obtained by the Ge condensation technique
Authors: Vincent B. , Damlencourt J.-F. , Delaye V. , Gassilloud R. , Clavelier L. , Morand Y.
Published: February 2007

Stacking fault generation within silicon germanium on insulator substrates fabricated by the Ge condensation technique has been evidenced by transmission electronic microscopy analyses for high Ge content enrichments (80%). This phenomenon is explained as a typical strain relaxation mechanism assisted by creation of partial dislocations of Burgers vectors equal to 1∕6⟨2−1−1⟩ and 1∕6⟨11−2⟩. Experimental results and calculations show the existence of a critical Ge enrichment during the Ge condensation process where this creation occurs. This critical Ge enrichment is dependent on the initial parameters such as the initial Ge content and the initial SiGe layer thickness.
Efficient photonic crystal cavity-waveguide couplers
Authors: Faraon Andrei , Waks Edo , Englund Dirk , Fushman Ilya , Vučković Jelena
Published: February 2007

Coupling of photonic crystal (PC) linear three-hole defect cavities to PC waveguides is theoretically and experimentally investigated. The systems are designed to increase the overlap between the evanescent cavity field and the waveguide mode and to operate in the linear dispersion region of the waveguide. The simulations indicate increased coupling when the cavity is tilted by 60° with respect to the waveguide axis, which was also confirmed by experiments. Up to 90% coupling efficiency into the waveguide was obtained.
Electric tunable behavior of sputtered lead barium zirconate thin films
Authors: Wu Lin-Jung , Wu Jenn-Ming , Huang Hsin-Erh , Bor Hui-Yun
Published: February 2007

Lead barium zirconate (PBZ) films were grown on Pt∕Ti∕SiO2∕Si substrates by rf-magnetron sputtering. The sputtered PBZ films possess pure perovskite phase, uniform microstructure, and excellent tunable behaviors. The tunability and loss tangent of sputtered PBZ films depend greatly on the oxygen mixing ratio (OMR). The optimal dielectric tunable behavior occurs in the PBZ films sputtered at 10% OMR. The sputtered PBZ film (10% OMR) possesses a value of figure of merit of 60, promising for frequency-agile applications. Bulk acoustic waves induced by electromechanical coupling occur at 2.72GHz, which is useful in fabricating filters and related devices in the microwave range.