bluuebunny/crossref_metadata_2025 huggingface dataset:
What Infants Know and What They have to Learn about Language
Authors: Mehler Jacques , Nespor Marina , Peña Marcela
Published: November 2008

The study of language acquisition during the first year of life is reviewed. We identified three areas that have contributed to our understanding of how the infant copes with linguistic signals to attain the most basic properties of its native language. Distributional properties present in the incoming utterances may allow infants to extract word candidates in the speech stream as shown in the impoverished conditions of artificial grammar studies. This procedure is important because it would work well for most natural languages. We also highlight another important mechanism that allows infants to induce structure from very scarce data. In fact, humans tend to project structural conjectures after being presented with only a few utterances. Finally, we illustrate constraints on processing that derive from perceptual and memory functions that arose much earlier during the evolutionary history of the species. We conclude that all of these machanisms are important for the infants to gain access to its native language.
Fuster’s Cherries and Linguistic Trees
Authors: Schnelle Helmut
Published: November 2008

Bridging the gap between linguistic structure representations and neurocognitive representations is a difficult challenge. This article presents an outline of how a formally specified system of constituent structure grammar could be translated into a distributed hierarchy network of associated modules. A set of syntactic constituent rule units could be reinterpreted as complex neuronal modules, which interactively generate momentary binding associations. The iterating binding activity in the network corresponds to the syntactic structure representation of a given sentence.
Immigration and Society
Authors: Hartog Joop
Published: November 2008

Presentation summary by Monika Ewa Kaminska

I believe that Europe can do without immigration. We do not need it to solve our problems. It does not help our national income. We should not push for immigration.
MHC class II‐expressing thymocytes suppress invariant NKT cell development
Authors: Li Wei , Sofi M Hanief , Wei Datsen G , Du Wenjun , Gervay‐Hague Jacquelyn , Renukaradhya Gourapura J , Brutkiewicz Randy R , Chang Cheong‐Hee
Published: November 2008

Natural killer T (NKT) cells are positively selected on cortical thymocytes expressing the non‐classical major histocompatibility complex (MHC) class I CD1d molecules. However, it is less clear how NKT cells are negatively selected in the thymus. In this study, we investigated the role of MHC class II expression in NKT cell development. Transgenic mice expressing MHC class II on thymocytes and peripheral T cells had a marked reduction in invariant NKT (iNKT) cells. Reduced numbers of iNKT cells correlated with the absence of in vivo production of cytokines in response to the iNKT cell agonist α‐galactosylceramide. Using mixed bone marrow chimeras, we found that MHC class II‐expressing thymocytes suppressed the development of iNKT cells in trans in a CD4‐dependent manner. Our observations have significant implications for human iNKT cell development as human thymocytes express MHC class II, which can lead to an inefficient selection of iNKT cells.
Extracellular HspBP1 and Hsp72 synergistically activate epidermal growth factor receptor
Authors: Evdonin Anton , Kinev Alexander , Tsupkina Natalia , Guerriero Vince , Raynes Deborah A. , Medvedeva Natalia
Published: November 2008

Background information. Heat‐inducible Hsp72 is the founding member of the Hsp70 (heat shock proteins of 70 kDa) family of molecular chaperones. It is localized primarily in cytoplasm and nucleus but is also found extracellularly. The source of e‐Hsp72 (extracellular Hsp72) is not precisely identified and may not be the same in every situation. A number of studies demonstrated that e‐Hsp72 plays an important role in cell survival, tumour rejection and immune response. However, currently little is known about regulation of e‐Hsp72 function. In cells, Hsp72 is controlled by co‐chaperones. An abundant co‐chaperone, HspBP1 (Hsp72‐binding protein 1) was found extracellularly in the serum. In the present study we analysed the secretion and function of e‐HspBP1 (extracellular HspBP1).

Results. A431 human squamous carcinoma cells accumulated Hsp72 and HspBP1 in chromogranin A‐positive granules following heat stress or in the presence of U73122, an inhibitor of phospholipase C. Following these treatments, A431 cells also increased the secretion of both proteins into the culture medium. The secreted e‐Hsp72 and e‐HspBP1 were co‐immunoprecipitated from the conditioned medium. Purified recombinant HspBP1 augmented e‐Hsp72‐mediated phosphorylation of EGFR (epidermal growth factor receptor) and its down‐stream targets, ERK1 (extracellular signal‐regulated kinase 1) and ERK2 in a concentration‐dependent manner. Finally, a HspBP1 N‐terminal domain deletion mutant and boiled recombinant HspBP1 did not affect the e‐Hsp72‐mediated activity.

Conclusions. Heat stress and PLC (phospholipase C) inhibition result in the enhanced secretion of both Hsp72 and HspBP1. In an extracellular environment, the two chaperones interact both physically and functionally, leading to the activation of th EGFR—ERK1/2 signalling pathway. However, the magnitude of EGFR activation depends on the e‐HspBP1/e‐Hsp72 ratio in the medium. Extracellular chaperone‐mediated activation of EGFR can provide a survival advantage to cells under heat shock and other stresses.
Multicultural Considerations in Assessing and Treating Hispanic Americans who Stutter
Authors: Tellis Glen
Published: November 2008

The purpose of this paper is to provide speech-language pathologists with information that addresses multicultural perceptions about stuttering and suggestions for the assessment and treatment of stuttering in Hispanic Americans. The psychometric properties of the Stuttering Inventory for Hispanic Americans are discussed. Results indicate that this scale is reliable and valid. Overall, Hispanic Americans had positive perceptions about stuttering. Suggestions for evaluation and treatment of stuttering are provided.
Client Variables Related to Relapse: A Case Study
Authors: Montgomery Catherine
Published: November 2008

The process of changing an aspect on one’s self that has been such an integral part of life is challenging, to say the least. Even though we believe we want this change, we sometimes unknowingly create obstacles for ourselves, generally due to fears of what life changes are to come as a result. What follows is a story of one client, his honest self exploration of his fears about becoming more fluent and the ultimate outcome.
Working with People Who Stutter of Diverse Cultural Backgrounds: Some Ideas to Consider
Authors: Daniels Derek E.
Published: November 2008

As the United States continues to undergo changing demographics, speech-language pathologists will find themselves working more with clients who stutter of diverse cultural backgrounds. The purpose of this article is to outline key principles for addressing cultural issues with clients who stutter. Sociocultural theory is introduced as a conceptual framework to guide assessment and therapeutic decision-making processes. Next, key principles are presented to assist clinicians in understanding a client’s cultural context, and using this as a frame of reference for treatment. Finally, a case example is presented to illustrate the ways in which a clinician can approach treatment in the specific cultural context of the client.
Microwave absorption properties and the isotropic antenna mechanism of ZnO nanotrees
Authors: Zhuo R. F. , Qiao L. , Feng H. T. , Chen J. T. , Yan D. , Wu Z. G. , Yan P. X.
Published: November 2008

In this paper, ZnO nanowires and ZnO nanotrees have been prepared and their microwave absorption properties have been investigated in detail. Complex permittivity and permeability of the ZnO nanostructures and paraffin composites have been measured in a frequency of 0.1–18 GHz. Excellent microwave absorption performances have been observed in ZnO nanotree composite compared to ZnO nanowire composite, and the maximum absorption is enhanced as the concentration of the nanotrees increases in the composite. The value of minimum reflection loss for the composites with 60 vol % ZnO nanotrees is −58 dB at 4.2 GHz with a thickness of 4.0 mm. Such strong absorption is attributed to the unique isotropic antenna morphology of the ZnO nanotrees in the composite.
Probing the mechanisms of fibril formation using lattice models
Authors: Li Mai Suan , Klimov D. K. , Straub J. E. , Thirumalai D.
Published: November 2008

Using exhaustive Monte Carlo simulations we study the kinetics and mechanism of fibril formation using lattice models as a function of temperature (T) and the number of chains (M). While these models are, at best, caricatures of peptides, we show that a number of generic features thought to govern fibril assembly are captured by the toy model. The monomer, which contains eight beads made from three letters (hydrophobic, polar, and charged), adopts a compact conformation in the native state. In both the single-layered protofilament (seen for M⩽10) and the two-layer fibril (M>10) structures, the monomers are arranged in an antiparallel fashion with the “strandlike” conformation that is perpendicular to the fibril axis. Partial unfolding of the folded monomer that populates an aggregation prone conformation (N*) is required for ordered assembly. The contacts in the N* conformation, which is one of the four structures in the first “excited” state of the monomer, are also present in the native conformation. The time scale for fibril formation is a minimum in the T-range when the conformation N* is substantially populated. The kinetics of fibril assembly occurs in three distinct stages. In each stage there is a cascade of events that transforms the monomers and oligomers to ordered structures. In the first “burst” stage, highly mobile oligomers of varying sizes form. The conversion to the N* conformation occurs within the oligomers during the second stage in which a vast number of interchain contacts are established. As time progresses, a dominant cluster emerges that contains a majority of the chains. In the final stage, the aggregation of N* particles serve as a template onto which smaller oligomers or monomers can dock and undergo conversion to fibril structures. The overall time for growth in the latter stages is well described by the Lifshitz–Slyazov growth kinetics for crystallization from supersaturated solutions. The detailed analysis shows that elements of the three popular models, namely, nucleation and growth, templated assembly, and nucleated conformational conversion are present at various stages of fibril assembly.
Density-functional theory study of vibrational relaxation of CO stretching excitation on Si(100)
Authors: Sakong Sung , Kratzer Peter , Han Xu , Laß Kristian , Weingart Oliver , Hasselbrink Eckart
Published: November 2008

A first-principles theory is presented for calculating the lifetime of adsorbate vibrations on semiconductor or insulator surfaces, where dissipation of the vibrational energy to substrate phonons is the dominant relaxation mechanism. As an example, we study the stretching vibration of CO/Si(100), where a lifetime of 2.3 ns has been measured recently [K. Laß, X. Han, and E. Hasselbrink, J. Chem. Phys. 123, 051102 (2005)]. Density-functional theory (DFT) calculations for the local modes of the adsorbate, including their anharmonic coupling, are combined with force field calculations for the substrate phonons. Using the DFT–Perdew–Burke–Ernzerhof functional, we have determined the most stable adsorption site for CO on top of the lower Si atom of the Si surface dimer, the local normal modes of CO, and the multidimensional potential energy surface for the CO vibrations. The anharmonic stretching frequency of adsorbed CO obtained in DFT-PBE is 5% lower than the experimental value, while the B3LYP functional reproduces the CO stretching frequency with only 1.4% error. The coupling between the anharmonic vibrational modes and the phonon continuum is evaluated within first-order perturbation theory, and transition rates for the CO vibrational relaxation are calculated using Fermi’s golden rule. The lifetime of 0.5 ns obtained with DFT-PBE is in qualitative agreement with experiment, while using vibrational frequencies from the B3LYP functional gives a much too long lifetime as compared to experiment. We find that the numerical value of the lifetime is very sensitive to the harmonic frequencies used as input to the calculation of the transition rate. An empirical adjustment of these frequencies yields excellent agreement between our theory and experiment. From these calculations we conclude that the most probable microscopic decay channel of the CO stretching mode is into four lateral shift/bending quanta and one phonon.
Dynamics of reactions O(D1)+C6H6 and C6D6
Authors: Chen Hui-Fen , Liang Chi-Wei , Lin Jim J. , Lee Yuan-Pern , Ogilvie J. F. , Xu Z. F. , Lin M. C.
Published: November 2008

The reaction between O(D1) and C6H6 (or C6D6) was investigated with crossed-molecular-beam reactive scattering and time-resolved Fourier-transform infrared spectroscopy. From the crossed-molecular-beam experiments, four product channels were identified. The major channel is the formation of three fragments CO+C5H5+H; the channels for formation of C5H6+CO and C6H5O+H from O(D1)+C6H6 and OD+C6D5 from O(D1)+C6D6 are minor. The angular distributions for the formation of CO and H indicate a mechanism involving a long-lived collision complex. Rotationally resolved infrared emission spectra of CO (1≤υ≤6) and OH (1≤υ≤3) were recorded with a step-scan Fourier-transform spectrometer. At the earliest applicable period (0–5 μs), CO shows a rotational distribution corresponding to a temperature of ∼1480 K for υ=1 and 920–700 K for υ=2–6, indicating possible involvement of two reaction channels; the vibrational distribution of CO corresponds to a temperature of ∼5800 K. OH shows a rotational distribution corresponding to a temperature of ∼650 K for υ=1–3 and a vibrational temperature of ∼4830 K. The branching ratio of [CO]/[OH]=2.1±0.4 for O(D1)+C6H6 and [CO]/[OD]>2.9 for O(D1)+C6D6 is consistent with the expectation for an abstraction reaction. The mechanism of the reaction may be understood from considering the energetics of the intermediate species and transition states calculated at the G2M(CC5) level of theory for the O(D1)+C6H6 reaction. The experimentally observed branching ratios and deuterium isotope effect are consistent with those predicted from calculations.
Determination of the elastic modulus of mesoporous silica thin films by x-ray reflectivity via the capillary condensation of water
Authors: Dourdain S. , Britton D. T. , Reichert H. , Gibaud A.
Published: November 2008

The mechanical properties of mesoporous silica films were characterized by x-ray reflectivity measurements. The measurements provide information on the deformation of the pores and the walls induced by the adsorption of water in the pores. The analysis of the nanoscaled deformations supplies a method to determine the elastic modulus E of thin porous films. The nanodeformation of the porous network during its filling with water is interpreted in three regimes of isotherm sorptions.
On designing dielectric elastomer actuators
Authors: Moscardo Mickael , Zhao Xuanhe , Suo Zhigang , Lapusta Yuri
Published: November 2008

Subject to a voltage, a dielectric elastomer can deform substantially, making it a desirable material for actuators. Designing such an actuator, however, has been challenging due to nonlinear equations of state, as well as multiple modes of failure, parameters of design, and measures of performance. This paper explores these issues, using a spring-roll actuator as an example. We formulate the equations of state with two degrees of freedom and describe the constraints due to several modes of failure of the elastomer, including electrical breakdown, electromechanical instability, loss of tension, and tensile rupture. Also included is the compressive limit of the spring. We show that, for the spring-roll actuator, loss of tension in the axial direction will always precede electromechanical instability. We then describe a procedure to maximize the range of actuation by choosing the parameters of design, such as the prestretch of the elastomer and the stiffness of the spring.
Regulating self-organizing nanostructures via external mechanism
Authors: Li J. Y. , Du Q. G. , Ducharme Stephen
Published: November 2008

Self-organizing nanostructures are ubiquitous in both natural and synthetic materials. They are not only appealing scientifically, by revealing the intrinsic atomic and molecular interactions that might be difficult to detect otherwise, but may also hold the key for the development of novel functional structures and devices. For their technological potential to be fully realized, the size, morphology, and distribution of the self-organizing nanostructures must be regulated. In this paper, we investigate the principles under which the self-organizing nanostructures can be regulated via external mechanisms. Using nanomesa and nanowell formation in polyvinylidene fluoride trifluoroethylene copolymer film as an example, we demonstrate that the external mechanism, if appropriately applied, can not only change the structure stability and trigger pattern formation in the otherwise stable films where self-organizing nanostructure is impossible to form, but can also regulate the size, morphology, and distribution of self-organizing nanostructures in a very effective manner. While the analysis is carried out for a particular system, the principles should be applicable for a wide range of self-organizing materials and structures.
Core/shell structures of oxygen-rich nanofeatures in oxide-dispersion strengthened Fe–Cr alloys
Authors: Marquis Emmanuelle A.
Published: November 2008

With the significant improvement in high temperature creep properties and resistance to radiation damage by addition of nanoscale oxide features, oxide-dispersion strengthened (ODS) ferritic/martensitic alloys are potential candidates for structural applications in nuclear fusion reactors. The structure of the oxygen-rich nanofeatures was analyzed by atom-probe tomography in three ODS alloys: MA957, ODS Fe–12wt%Cr, and ODS Eurofer-97. Although field evaporation and reconstruction of the precipitates suffer from artefacts, a core/shell structure is found even for very small precipitates. Precipitate cores are Y rich while shell regions are enriched in Ti, Cr, or V depending on alloy composition.
GaN/AlN short-period superlattices for intersubband optoelectronics: A systematic study of their epitaxial growth, design, and performance
Authors: Kandaswamy P. K. , Guillot F. , Bellet-Amalric E. , Monroy E. , Nevou L. , Tchernycheva M. , Michon A. , Julien F. H. , Baumann E. , Giorgetta F. R. , Hofstetter D. , Remmele T. , Albrecht M. , Birner S. , Dang Le Si
Published: November 2008

We have studied the effect of growth and design parameters on the performance of Si-doped GaN/AlN multiquantum-well (MQW) structures for intersubband optoelectronics in the near infrared. The samples under study display infrared absorption in the 1.3–1.9 μm wavelength range, originating from the photoexcitation of electrons from the first to the second electronic level in the QWs. A commonly observed feature is the presence of multiple peaks in both intersubband absorption and interband emission spectra, which are attributed to monolayer thickness fluctuations in the quantum wells. These thickness fluctuations are induced by dislocations and eventually by cracks or metal accumulation during growth. The best optical performance is attained in samples synthesized with a moderate Ga excess during the growth of both the GaN QWs and the AlN barriers without growth interruptions. The optical properties are degraded at high growth temperatures (>720 °C) due to the thermal activation of the AlN etching of GaN. From the point of view of strain, GaN/AlN MQWs evolve rapidly to an equilibrium average lattice parameter, which is independent of the substrate. As a result, we do not observe any significant effect of the underlayers on the optical performance of the MQW structure. The average lattice parameter is different from the expected value from elastic energy minimization, which points out the presence of periodic misfit dislocations in the structure. The structural quality of the samples is independent of Si doping up to 1020 cm−3. By contrast, the intersubband absorption spectrum broadens and blueshifts with doping as a result of electron-electron interactions. This behavior is independent of the Si doping location in the structure, either in the QWs or in the barriers. It is found that the magnitude of the intersubband absorption is not directly determined by the Si concentration in the wells. Instead, depending on the Al mole fraction of the cap layer, the internal electric field due to piezoelectric and spontaneous polarization can deplete or induce charge accumulation in the QWs. In fact, this polarization-induced doping can result in a significant and even dominant contribution to the infrared absorption in GaN/AlN MQW structures.
Carbon nanotube dispersed liquid crystal: A nano electromechanical system
Authors: Basu Rajratan , Iannacchione Germano S.
Published: November 2008

Electric field induced director orientation of a nematic liquid crystal (LC)+carbon nanotube (CNT) system reveals insights on switching behavior for this anisotropic composite. Once the field goes off, the LC+CNT system relaxes back to the original orientation through a mechanical rotation, revealing the intrinsic dynamics. LC molecules and CNTs cooperatively form local pseudonematic domains in the isotropic phase due to strong LC-CNT interactions. These field-responsive anisotropic domains do not relax back to the original orientation on switching of the field off, which could find potential applications in memory devices.
Exploring the dynamics of reaction N+SiH4 with crossed molecular-beam experiments and quantum-chemical calculations
Authors: Lu I-Chung , Chen Wei-Kan , Chaudhuri Chanchal , Huang Wen-Jian , Lin Jim J. , Lee Shih-Huang
Published: November 2008

We investigated the reaction N(S4,D2,P2)+SiH4 in crossed molecular beams at a collision energy of 4.7 kcal mol−1 with a time-of-flight mass spectrometer and selective photoionization. Ion signals were observed at m/z=42–45, associated with two product channels, HSiNH/SiNH2+H+H and HSiN/HNSi+H2+H. The species producing the signal at m/z=43 is assigned to product HSiN/HNSi and that at m/z=44 to product HSiNH/SiNH2. The signal observed at m/z=42 is attributed to daughter ions of those two products and that at m/z=45 to S29i and S30i isotopic variants. We report time-of-flight spectra as a function of laboratory angle and simulations for the two products, from which both kinetic-energy and angular distributions of products in the center-of-mass (c.m.) frame were derived. The dependence of release of kinetic energy on the c.m. scattering angle is weak. The average translational energy released is 7.7 kcal mol−1 for product channel HSiNH/SiNH2+H+H and 30.3 kcal mol−1 for product channel HSiN/HNSi+H2+H. Through consecutive triple fragmentation, the angular distribution is slightly anisotropic for product HSiNH/SiNH2 but isotropic for product HSiN/HNSi. Assuming equal efficiencies of detection, we estimate the branching ratios of products HSiNH/SiNH2 and HSiN/HNSi to be roughly 15:85. To facilitate an understanding of the reaction mechanisms, we calculated the potential-energy surface for reaction N(D2)+SiH4 with quantum-chemical methods. Reactions N(D2)+SiH4→SiNH2+H+H and N(D2)+SiH4→HNSi+H2+H account satisfactorily for the present experimental results. Isomeric products HSiNH and HSiN are minor in this work.
Magnetic characterization of iron nanocubes
Authors: Trunova Anastasia V. , Meckenstock R. , Barsukov I. , Hassel C. , Margeat O. , Spasova M. , Lindner J. , Farle M.
Published: November 2008

Nearly perfect single crystalline Fe core-shell nanocubes with (100) facets and 13.6 nm edge length were prepared by wet-chemical methods. While the core is metallic, the shell is composed of either Fe3O4 or γ-Fe2O3. The cubes were deposited onto GaAs substrates with monolayer coverage as proved by scanning electron microscopy. Oxygen and hydrogen plasmas were used to remove the ligand system and the oxide shell. Both types of samples were investigated by ferromagnetic resonance. While the g-factor (g=2.09) and crystalline anisotropy (K4=4.8×104 J/m3) of the pure iron cubes show up with bulk values, the saturation magnetization is reduced to (M(5K)=(1.2±0.12)×106 A/m) 70% of bulk value and the effective damping parameter (α=0.03) is increased by one order of magnitude with respect to bulk Fe.
Phase contrast imaging simulation and measurements using polychromatic sources with small source-object distances
Authors: Golosio Bruno , Delogu Pasquale , Zanette Irene , Carpinelli Massimo , Masala Giovanni Luca , Oliva Piernicola , Stefanini Arnaldo , Stumbo Simone
Published: November 2008

Phase contrast imaging is a technique widely used in synchrotron facilities for nondestructive analysis. Such technique can also be implemented through microfocus x-ray tube systems. Recently, a relatively new type of compact, quasimonochromatic x-ray sources based on Compton backscattering has been proposed for phase contrast imaging applications. In order to plan a phase contrast imaging system setup, to evaluate the system performance and to choose the experimental parameters that optimize the image quality, it is important to have reliable software for phase contrast imaging simulation. Several software tools have been developed and tested against experimental measurements at synchrotron facilities devoted to phase contrast imaging. However, many approximations that are valid in such conditions (e.g., large source-object distance, small transverse size of the object, plane wave approximation, monochromatic beam, and Gaussian-shaped source focal spot) are not generally suitable for x-ray tubes and other compact systems. In this work we describe a general method for the simulation of phase contrast imaging using polychromatic sources based on a spherical wave description of the beam and on a double-Gaussian model of the source focal spot, we discuss the validity of some possible approximations, and we test the simulations against experimental measurements using a microfocus x-ray tube on three types of polymers (nylon, poly-ethylene-terephthalate, and poly-methyl-methacrylate) at varying source-object distance. It will be shown that, as long as all experimental conditions are described accurately in the simulations, the described method yields results that are in good agreement with experimental measurements.
Multiwalled carbon nanotube sheets as transparent electrodes in high brightness organic light-emitting diodes
Authors: Williams Christopher D. , Robles Raquel Ovalle , Zhang Mei , Li Sergey , Baughman Ray H. , Zakhidov Anvar A.
Published: November 2008

We have fabricated efficient organic light emitting diodes using strong, transparent carbon nanotube (CNT) sheets as the hole-injecting anode. These devices show a brightness of 4500 cd/m2 and current efficiency near 2.5 cd/A, which is close to the efficiency we achieve with a similar device, which uses indium tin oxide (ITO) as the anode. We demonstrate that proper planarization of the electrode using the water-soluble polymer poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) is necessary for achieving high efficiency and can be accomplished by spin casting multiple layers. We believe that increased conductivity of the sheets could lead to CNT-based devices with efficiencies exceeding those on ITO.
Theoretical modeling on hydrogen evolution in ultraviolet light-treated hydrogenated silicon nitride
Authors: Sun Rong , Wang Lei , Cheng Jing , Michel Jurgen , Kimerling Lionel , Balseanu Mihaela , Xia Li-Qun , M’saad Hichem
Published: November 2008

Ultraviolet light illumination is shown experimentally to be able to induce hydrogen evolution in hydrogenated amorphous silicon nitride (a-SixNyHz) film and the total hydrogen (H) removal percentage depends strongly on the composition with a maximum with balanced silicon-hydrogen and nitride-hydrogen single bonds (Si–H/N–H ratio equals to 1). We developed a general model for analyzing H removal in such alloyed glass system. Our statistical Monte Carlo models reveal that H2 evolution is the result of highly selective chemical reactions among nearest neighbor SiH and NH bonds in a-SiNxHy, which leads to formation of Si–N bonds. This process is sensitive to its local chemical environment. The nearest neighbor coordination number and the presence of SiH2 and NH2 groups in a-SixNyHz network have impact on the total H removal. Our model gives quantitative measures for all the corresponding reaction constants, consistent with experimental observations.
Fermi edge singularity in II–VI semiconductor resonant tunneling structures
Authors: Rüth M. , Slobodskyy T. , Gould C. , Schmidt G. , Molenkamp L. W.
Published: November 2008

We report on the observation of Fermi edge enhanced resonant tunneling transport in a II–VI semiconductor heterostructure. The resonant transport through a self-assembled CdSe quantum dot survives up to 45 K and probes a disordered two-dimensional-like emitter, which dominates the magnetic field dependence of the transport. An enhancement of the tunnel current through many particle effects is clearly observable, even without an applied magnetic field. Additional fine structure in the tunneling current suggests that while conventional Fermi edge singularity theory successfully reproduces the general features of the increased transmission, it is not adequate to describe all details of the current enhancement.
Electrically pumped ultraviolet ZnO diode lasers on Si
Authors: Chu Sheng , Olmedo Mario , Yang Zheng , Kong Jieying , Liu Jianlin
Published: November 2008

Electrically pumped ZnO quantum well diode lasers are reported. Sb-doped p-type ZnO/Ga-doped n-type ZnO with an MgZnO/ZnO/MgZnO quantum well embedded in the junction was grown on Si by molecular beam epitaxy. The diodes emit lasing at room temperature with a very low threshold injection current density of 10 A/cm2. The lasing mechanism is exciton-related recombination and the feedback is provided by close-loop scattering from closely packed nanocolumnar ZnO grains formed on Si.
Laser generation and detection of longitudinal and shear acoustic waves in a diamond anvil cell
Authors: Chigarev Nikolay , Zinin Pavel , Ming Li-Chung , Amulele George , Bulou Alain , Gusev Vitalyi
Published: November 2008

Laser ultrasonics in a point-source-point-receiver configuration is applied for the evaluation of elastic properties of nontransparent materials in a diamond anvil cell at high pressures. Measurement of both longitudinal and shear acoustic wave velocities in an iron foil at pressures up to 23 GPa does not require any information in addition to the one obtained by all-optical pump-probe technique.
Origin of highly spatially selective etching in deeply implanted complex oxides
Authors: Ofan Avishai , Gaathon Ophir , Vanamurthy Lakshmanan , Bakhru Sasha , Bakhru Hassaram , Evans-Lutterodt Kenneth , Osgood Richard M.
Published: November 2008

The origin of the rate of anomalously high spatially selective etching of a buried heavily implanted region in complex oxides is studied. Single-crystal LiNbO3 samples are prepared with a 0.4μm wide implanted region at depth of 10μm, using 5×1016cm−2 fluence of 3.8MeV He+, and wet etched after a low-temperature anneal. An etch-rate enhancement of 104 is found after implantation and low-temperature 175–275°C post-implantation annealing. Experiments using time-resolved optical microscopy, x-ray diffraction, and proximal-probe microscopy show that this enhancement arises from the more rapid etch-solution transport in the microdomain network formed in the implanted region after annealing.
Plasma-assisted molecular beam epitaxy growth of GaN nanowires using indium-enhanced diffusion
Authors: Landré O. , Songmuang R. , Renard J. , Bellet-Amalric E. , Renevier H. , Daudin B.
Published: November 2008

It is shown that catalyst-free growth of well-separated GaN nanowires by plasma-assisted molecular beam epitaxy can be achieved at moderate temperature using an additional indium flux. The results are consistently interpreted by considering that thermally assisted or indium-assisted in-plane Ga adatom diffusion play an equivalent role, i.e., prevent growth of a two-dimensional GaN layer between nanowires, a necessary condition to their growth.
Synchrotron radiation photoemission spectroscopic study of band offsets and interface self-cleaning by atomic layer deposited HfO2 on In0.53Ga0.47As and In0.52Al0.48As
Authors: Kobayashi M. , Chen P. T. , Sun Y. , Goel N. , Majhi P. , Garner M. , Tsai W. , Pianetta P. , Nishi Y.
Published: November 2008

The synchrotron radiation photoemission spectroscopic study was conducted to (a) investigate the surface chemistry of In0.53Ga0.47As and In0.52Al0.48As postchemical and thermal treatments, (b) construct band diagram, and (c) investigate the interface property of HfO2∕In0.53Ga0.47As and HfO2∕In0.52Al0.48As. Dilute HCl and HF etch remove native oxides on In0.53Ga0.47As and In0.52Al0.47As, whereas in situ vacuum annealing removes surface arsenic pileup. After the atomic layer deposition of HfO2, native oxides were considerably reduced compared to that in as-received epilayers, strongly suggesting the self-clean mechanism. Valence and conduction band offsets are measured to be 3.37±0.1 and 1.80±0.3eV for In0.53Ga0.47As and 3.00±0.1 and 1.47±0.3eV for In0.52Al0.47As, respectively.
Composition effects on quantum dot-based resonance energy transfer
Authors: Sadhu Suparna , Patra Amitava
Published: November 2008

The effect of composition on resonance energy transfer between CdxZn1−xS quantum dot (donor) and Nile red dye (acceptor) is studied by steady state and time-resolved spectroscopy. The energy transfer efficiency varies from 14% to 47% with change in the composition from Cd0.31Zn0.69S to Cd0.62Zn0.38S nanocrystals which follows the Förster resonance energy transfer process. Considering single donor and multiple acceptors interactions, the calculated average distances (rn) between donor and acceptor are 25.8, 31.6, and 39.9Å for Cd0.62Zn0.38S, Cd0.52Zn0.48S, and Cd0.31Zn0.69S nanocrystals, respectively.
Large tunnel magnetoresistance in Co2FeAl0.5Si0.5∕MgO∕Co2FeAl0.5Si0.5 magnetic tunnel junctions prepared on thermally oxidized Si substrates with MgO buffer
Authors: Wang Wenhong , Sukegawa Hiroaki , Shan Rong , Inomata Koichiro
Published: November 2008

Magnetic tunnel junctions (MTJs) using polycrystalline Co2FeAl0.5Si0.5 (CFAS) electrodes with a MgO tunnel barrier were fabricated onto thermally oxidized Si substrates. Highly (001)-oriented and B2-ordered CFAS electrodes were obtained by optimizing growth conditions and postannealing temperature. The microfabricated MTJs exhibited relatively high tunnel magnetoresistance (TMR) ratios of 125% at room temperature and 196% at 7K. The large TMR obtained using oxidized Si substrates indicates that CFAS is promising for the practical applications.
Chaotic dynamics in semiconductor lasers subjected to polarization-rotated optical feedback
Authors: Takeuchi Yasutoshi , Shogenji Rui , Ohtsubo Junji
Published: November 2008

In-phase or synchronized oscillations between transverse electric (TE) and transverse magnetic (TM) modes with a loop delay are common phenomena in the numerical studies of semiconductor lasers subjected to polarization-rotated optical feedback. However, we experimentally find antiphase oscillations of laser output powers with zero time lag under appropriate conditions of orthogonal polarization optical feedback. Antiphase oscillations are well reproduced by the numerical simulations for the experimental model taking into account the frequency detuning between the two modes.
Geographic Dialectics?
Authors: Sheppard Eric
Published: November 2008

As radical geography, inflected by Marx, has transformed into critical geography, influenced by poststructuralism and feminism, dialectical reasoning has come under attack from some poststructural geographers. Their construction of dialectics as inconsistent with poststructural thinking, difference, and assemblages is based, however, on a Hegelian conception of the dialectic. This Hegelian imaginary reflects the intellectual history of radical and/or critical anglophone geography. Yet, dialectics can be read in a non-Hegelian, much less totalizing and ideological, and more geographical way. This broader reading opens up space for considering parallels between dialectics, the assemblages of Deleuze and Guattari, and aspects of complexity theory.
Novel 5-(3-(Substituted)-4,5-dihydroisoxazol-5-yl)-2-methoxyphenyl Derivatives: Synthesis and Anticancer Activity
Authors: Liu Xin-Hua , Song Bao-An , Bhadury Pinaki S. , Zhu Hai-Liang , Cui Ping , Hou Ke-Ke , Xu Hong-Li
Published: November 2008

Thirty novel 5-(3-(substituted phenyl)-4,5-dihydroisoxazol-5-yl)-2-methoxyphenyl derivatives were synthesized and evaluated for their antitumour activity. The bioassays showed that the 2-fluorobenzoyl derivative 6ai, the 4-trifluoromethylbenzoyl derivative 6ah, and the 3-trifluoromethyl isoxazole derivatives (6ch and 6ci) were highly effective against PC-3 cells. The IC50 values of 6ah and 6ai against PC-3 cells were 1.5 and 1.8 μg mL–1, respectively.
Synthesis of 2,5-Diazabicyclo[2.2.2]octanes by Dieckmann Analogous Cyclization
Authors: Holl Ralph , Dykstra Mareike , Schneiders Martin , Fröhlich Roland , Kitamura Masato , Würthwein Ernst-Ulrich , Wünsch Bernhard
Published: November 2008

Starting with (S)-aspartate, methyl (S)-2-[1-allyl-4-(4-methoxybenzyl)-3,6-dioxopiperazin-2-yl]acetate 10 was synthesized in a four-step synthesis. Deprotonation of 10 and subsequent trapping of the first cyclization product led to the bicyclic mixed acetal 13 in 15% yield. The low yield of 13, compared with the yield of the corresponding glutamate derivatives, is explained by the higher energy (strain) of the bicyclo[2.2.2]octane system and the lower conformational flexibility of the shorter acetate side chain. The formation of a six-membered Na+-chelate 12 as intermediate is responsible for the high diastereoselectivity of the cyclization step.
The Scholarships of Teaching and Pedagogy: Time to Abandon the Distinction?
Authors: Irons Jessica G. , Buskist William
Published: November 2008

We surveyed the editorial board of Teaching of Psychology regarding their perspectives on the distinction between the scholarships of teaching and pedagogy. Respondents provided wide-ranging and divergent answers to our queries, suggesting that scholarship, its attendant activities, and distinctions among related terms are complex issues in need of further clarification. We suggest that the distinction between the scholarships of teaching and pedagogy is unclear and unnecessary.
Perceived Usefulness of Learning Outcomes Predicts Ratings of Departmental Helpfulness
Authors: Marsh Patricia A. , Poepsel Dennis L.
Published: November 2008

Psychology seniors at a Midwest university reflected on the student learning outcomes (SLOs) for the major. This study examined the relations among students' perceived usefulness of the SLOs, measures of learning, ratings of self-confidence in their knowledge of psychology, and evaluations of the department's helpfulness in students' skill development. Correlations showed few significant relations between usefulness of the SLOs and measures of learning and no relations with ratings of self-confidence. Perceived usefulness of the outcomes was a significant predictor of the department's perceived helpfulness in students' skill development. However, students' perceptions of the department dropped significantly by the end of the capstone course. We discuss implications related to activities teachers might use to enhance learning.
Use of Virtual Reality Technology to Enhance Undergraduate Learning in Abnormal Psychology
Authors: Stark-Wroblewski Kim , Kreiner David S. , Boeding Christopher M. , Lopata Ashley N. , Ryan Joseph J. , Church Tina M.
Published: November 2008

We examined whether using virtual reality (VR) technology to provide students with direct exposure to evidence-based psychological treatment approaches would enhance their understanding of and appreciation for such treatments. Students enrolled in an abnormal psychology course participated in a VR session designed to help clients overcome the fear of flying. We assessed students' understanding of how cognitive behavioral, exposure-based therapies work, as well as their attitudes toward various forms of intervention, prior to and after their participation in the VR session. We found that incorporating firsthand experience with evidence-based psychological treatments, such as VR exposure for overcoming the fear of flying, can be useful in enhancing students' understanding of such treatments.
Faculty Perceptions of SoTL at a Research Institution: A Preliminary Study
Authors: Buch Kim
Published: November 2008

Boyer (1990) and others have challenged the traditional boundaries of scholarship, calling for a broader view that includes the scholarship of integration, application, and teaching. The discipline of psychology has been productively involved in the debate, resulting in both contributions to the literature and changes in reward policies in some departments (e.g., Mathie et al., 2004). I examined psychology faculty's perceptions of how their department evaluates the scholarship of pedagogy and what they believe are the true boundaries of scholarship in psychology. I found a significant gap in what is “counted” as scholarship and what faculty believe should be counted.
Mixed ligand Ni(II) complexes: DNA binding, oxidative and photo-cleavage studies
Authors: Prabhakara M.C. , Bhojya Naik H.S.
Published: November 2008

Mixed ligand complexes of the type [Ni(phen)2(bnp)](PF6)2 · 2H2O (1) and [Ni(bpy)2(bnp)](PF6)2 · 2H2O (2) (where phen, 1,10,Phenanathroline; bpy, 2,2 bipyridine; bnp, benzo[1.8]naphthyridinone-2-ol) have been synthesized and characterized by employing analytical and spectral methods. The DNA binding properties of the complexes with calf thymus-DNA were studied by using absorption spectra, viscosity measurements as well as thermal denaturation experiments. The absorption spectra indicated that the Ni(II) complexes intercalate tightly between the base pairs of the DNA with intrinsic DNA binding constants of 1.9 × 104 M−1 for (1) and 2.5 × 104M−1 for (2) in 5 mM Tris-HCl/50 mM NaCl buffer at pH 7.2, respectively. The large enhancement in the relative viscosity of DNA on binding to the bnp supports the proposed DNA binding modes. The oxidative cleavage and photo-cleavage activity of complexes (1) and (2) were studied. The photo-induced DNA cleavage activities of the complexes in the presence and absence of different additives were studied by using UV light at 365 nm. The results show significant nuclease activity even in the absence of additives at 60 μM concentration.
Oxidation of atenolol by diperiodatoargentate(III) in aqueous alkaline medium – a multimechanistic reaction
Authors: Jose Timy P. , Angadi Mahantesh A. , Salunke Manjalee S. , Tuwar Suresh M.
Published: November 2008

The kinetics of oxidation of antihypertensive drug, atenolol by diperiodatoargentate(III) (DPA) in a wide range of alkali has been studied spectrophotometrically. In a lower range of [OH−], the periodate had a retarding effect whereas at higher range of [OH−] the rate of reaction was accelerated. In the higher range of [OH−], the periodate had no effect whereas at lower range of [OH−], periodate and product, [Ag(I)] retarded the rate of the reaction. In the entire range of [OH−], the reaction was unit order in [DPA] and fractional order in [ATN]. Mechanisms consistent with the observed kinetic data for both lower and higher ranges of [OH−] were proposed and discussed. The active species of [Ag(III)] was found to be mono periodatoargentate(III) in lower range of [OH−] and dihydroxymonodiperiodatoargentate(III) in the higher range of [OH−]. The hydrolyzed species of atenolol was found to be the active form of atenolol. Mechanisms for both higher and lower range of [OH−] have been proposed. A composite rate law has been derived and verified for different experimental conditions.
1H NMR and spectroscopic studies of biologically active yttrium (III)-flavonoid complexes
Authors: Ansari Anees A.
Published: November 2008

The compounds, Y(L1–5)3, [where L1–5 = quercetin (L1), morin (L2), naringenin (L3), catechin (L4) and chrysin (L5)] were prepared and characterized by elemental analysis, molar conductance, UV–Vis, thermogravimetric analysis (TGA), Fourier transform infrared (FTIR), and proton nuclear magnetic resonance ( 1H NMR) spectroscopic studies. Molar conductance showed that the complexes are non-electrolytic in nature. The complexes were anhydrous as revealed by the TGA analyses. The 1H NMR spectra in DMSO-d6 revealed a diamagnetic shift. The small chemical shift of the proton resonances suggested that the complexes are dissociated in DMSO solvent and the solvent is coordinated to the Y atoms.
Group 6 metal carbonyl complexes of a family of bulky phosphines: spectroscopic and structural studies of chromium(0)-, molybdenum(0)- and tungsten(0)-pentacarbonylsilylphosphines
Authors: Rooney Colin P. , Wade John L. , Hinkle Alexander C. , Stolley Ryan M. , Miller Susie M. , Helm Monte L.
Published: November 2008

The synthesis and spectroscopic data of six Group 6 metal complexes with the silylphosphine ligands, P(C6H5){Si(CH3)3}2 and P(H){Si(CH3)3}2 are reported. The crystal structures of M(P{R}{TMS}2)(CO)5, M = Cr, Mo, W; R = C6H5 and M = Cr; R = H, are reported. All the compounds exhibit the expected structures consisting of an octahedral geometry of five carbonyl ligands and one silylphosphine ligand around the metal center. Analysis of the spectroscopic and structural data, including the previously reported P{Si(CH3)3}3 ligand, indicate the steric bulk of the ligands decreases and the sigma-donating ability increases in the series P{Si(CH3)3}3 < P(C6H5){Si(CH3)3}2 < P(H){Si(CH3)3}2.
PCAF Acetylates β-Catenin and Improves Its Stability
Authors: Ge Xinjian , Jin Qihuang , Zhang Fang , Yan Tingting , Zhai Qiwei
Published: November 2008

β-Catenin plays an important role in development and tumorigenesis. However, the effect of a key acetyltransferase p300/CBP-associated factor (PCAF) on β-catenin signaling is largely unknown. In this study, we found PCAF could increase the β-catenin transcriptional activity, induce its nuclear translocation, and up-regulate its protein level by inhibiting its ubiquitination and improving its stability. Further studies showed that PCAF directly binds to and acetylates β-catenin. The key ubiquitination sites Lys-19 and Lys-49 of β-catenin were shown as the critical residues for PCAF-induced acetylation and stabilization. Knockdown of PCAF in colon cancer cells markedly reduced the protein level, transcriptional activity, and acetylation level of β-catenin; promoted cell differentiation; inhibited cell migration; and repressed xenografted tumorigenesis and tumor growth in nude mice. All these data demonstrate that PCAF acetylates β-catenin and regulates its stability, and they raise the prospect that therapies targeting PCAF may be of clinical use in β-catenin–driven diseases, such as colon cancer.