bluuebunny/crossref_metadata_2025 huggingface dataset:
Cannabis use and childhood trauma interact additively to increase the risk of psychotic symptoms in adolescence
Authors: Harley M. , Kelleher I. , Clarke M. , Lynch F. , Arseneault L. , Connor D. , Fitzpatrick C. , Cannon M.
Published: December 2009

Background

Adolescent cannabis use has been shown in many studies to increase the risk of later psychosis. Childhood trauma is associated with both substance misuse and risk for psychosis. In this study our aim was to investigate whether there is a significant interaction between cannabis use and childhood trauma in increasing the risk for experiencing psychotic symptoms during adolescence.

Method

Psychiatric interviews using the Schedule for Affective Disorders and Schizophrenia for School-Age Children (K-SADS) semi-structured instrument were carried out with 211 adolescents aged between 12 and 15 years and their parents as part of a population-based study. The interview enquired about early traumatic events, cannabis use and psychiatric symptoms in adolescence.

Results

In separate analyses both cannabis use and childhood trauma were significantly associated with risk of experiencing psychotic symptoms. However, the presence of both childhood trauma and early cannabis use significantly increased the risk for psychotic symptoms beyond the risk posed by either risk factor alone, indicating that there was a greater than additive interaction between childhood trauma and cannabis use.

Conclusion

Our finding of a greater than additive interaction between childhood trauma and cannabis use may have implications for the identification of individuals at high risk of experiencing psychotic symptoms. For example, measures to actively discourage or intensively treat cannabis use in children and adolescents who have experienced abuse may help to prevent the development of psychosis in this vulnerable group. Our findings require replication in larger samples to confirm this interaction effect.
Parental practices predict psychological well-being in midlife: life-course associations among women in the 1946 British birth cohort
Authors: Huppert F. A. , Abbott R. A. , Ploubidis G. B. , Richards M. , Kuh D.
Published: December 2009

Background

Certain parenting styles are influential in the emergence of later mental health problems, but less is known about the relationship between parenting style and later psychological well-being. Our aim was to examine the association between well-being in midlife and parental behaviour during childhood and adolescence, and the role of personality as a possible mediator of this relationship.

Method

Data from 984 women in the 1946 British birth cohort study were analysed using structural equation modelling. Psychological well-being was assessed at age 52 years using Ryff's scales of psychological well-being. Parenting practices were recollected at age 43 years using the Parental Bonding Instrument. Extraversion and neuroticism were assessed at age 26 years using the Maudsley Personality Inventory.

Results

In this sample, three parenting style factors were identified: care; non-engagement; control. Higher levels of parental care were associated with higher psychological well-being, while higher parental non-engagement or control were associated with lower levels of psychological well-being. The effects of care and non-engagement were largely mediated by the offspring's personality, whereas control had direct effects on psychological well-being. The psychological well-being of adult women was at least as strongly linked to the parenting style of their fathers as to that of their mothers, particularly in relation to the adverse effects of non-engagement and control.

Conclusions

This study used a prospective longitudinal design to examine the effects of parenting practices on psychological well-being in midlife. The effects of parenting, both positive and negative, persisted well into mid-adulthood.
Neural correlates of error-related learning deficits in individuals with psychopathy
Authors: von Borries A. K. L. , Brazil I. A. , Bulten B. H. , Buitelaar J. K. , Verkes R. J. , de Bruijn E. R. A.
Published: December 2009

Background

Psychopathy (PP) is associated with a performance deficit in a variety of stimulus–response and stimulus–reinforcement learning paradigms. We tested the hypothesis that failures in error monitoring underlie these learning deficits.

Method

We measured electrophysiological correlates of error monitoring [error-related negativity (ERN)] during a probabilistic learning task in individuals with PP (n=13) and healthy matched control subjects (n=18). The task consisted of three graded learning conditions in which the amount of learning was manipulated by varying the degree to which the response was predictive of the value of the feedback (50, 80 and 100%).

Results

Behaviourally, we found impaired learning and diminished accuracy in the group of individuals with PP. Amplitudes of the response ERN (rERN) were reduced. No differences in the feedback ERN (fERN) were found.

Conclusions

The results are interpreted in terms of a deficit in initial rule learning and subsequent generalization of these rules to new stimuli. Negative feedback is adequately processed at a neural level but this information is not used to improve behaviour on subsequent trials. As learning is degraded, the process of error detection at the moment of the actual response is diminished. Therefore, the current study demonstrates that disturbed error-monitoring processes play a central role in the often reported learning deficits in individuals with PP.
Sources of Public International Law
Authors: Dingle Lesley
Published: December 2009

This paper by Lesley Dingle, Squire Law Library, University of Cambridge was presented at the BIALL Seminar held on 3 March 2009. It covers the major sources, both paper and electronic, of international law.
The Journey from Law Librarian to Managing Director: the Pros and Cons
Authors: Bailey Penny
Published: December 2009

Penny Bailey recounts the challenges she has met and dealt with in her unusual progression from a law librarian to running her own software company, Bailey Solutions.
Occurrence and orientation of anorbital ripples in near‐shore sands
Authors: Maier Irene , Hay Alex E.
Published: December 2009

The orientation of linear transition ripples (LTRs) relative to incident wave direction is studied using rotary fan beam sonar images and wave and current data from electromagnetic flowmeters in ∼3 m water during SandyDuck97. LTR occurrence is determined objectively with an automatic recognition algorithm. LTRs occurred for RMS wave orbital velocities between 0.15 and 0.35 m s−1. The ripples were highly two dimensional, and of the anorbital type (λ0/D50 = 524 to 535, d0/D50 = 4300 to 25,000) with 7.6 cm mean wavelength in 150 μm median diameter sand. The ripple crests were typically aligned perpendicular to the incident sea‐and‐swell direction: specifically, about 60% of the normals to the crests differ from wave direction by less than 5° and more than 90% by less than 10°. During rapid changes in wave direction, however, ripple orientation adjustment lagged the wave direction by O(1 h). Ripple reorientation occurred piecewise along the crests, with new crest segments sometimes bridging two or more old segments. The 1 h reorientation time scale is longer by several orders of magnitude than the adjustment time based on theoretical bed load transport rate and the ripple volume. As a possible explanation, we suggest that a significant fraction of the transport, more than 90%, bypasses the ripples during orientation adjustment through large angles.
Validation of community models: 2. Development of a baseline using the Wang‐Sheeley‐Arge model
Authors: MacNeice Peter
Published: December 2009

This paper is the second in a series providing independent validation of community models of the outer corona and inner heliosphere. Here I present a comprehensive validation of the Wang‐Sheeley‐Arge (WSA) model. These results will serve as a baseline against which to compare the next generation of comparable forecasting models. The WSA model is used by a number of agencies to predict Solar wind conditions at Earth up to 4 days into the future. Given its importance to both the research and forecasting communities, it is essential that its performance be measured systematically and independently. I offer just such an independent and systematic validation. I report skill scores for the model's predictions of wind speed and interplanetary magnetic field (IMF) polarity for a large set of Carrington rotations. The model was run in all its routinely used configurations. It ingests synoptic line of sight magnetograms. For this study I generated model results for monthly magnetograms from multiple observatories, spanning the Carrington rotation range from 1650 to 2074. I compare the influence of the different magnetogram sources and performance at quiet and active times. I also consider the ability of the WSA model to forecast both sharp transitions in wind speed from slow to fast wind and reversals in the polarity of the radial component of the IMF. These results will serve as a baseline against which to compare future versions of the model as well as the current and future generation of magnetohydrodynamic models under development for forecasting use.
Current integration force and displacement self-sensing method for cantilevered piezoelectric actuators
Authors: Ivan Ioan Alexandru , Rakotondrabe Micky , Lutz Philippe , Chaillet Nicolas
Published: December 2009

This paper presents a new method of self-sensing both of the displacement and the external applied force at the tip of piezoelectric cantilevers. Integrated electric current across piezoelectric actuators is compensated against material nonlinearities (creep, hysteresis) to provide reliable information. We propose to compensate the hysteresis by using the Prandtl–Ishlinskii static approach while an auto regressive and moving average exogenous (ARMAX) model is used to minimize the creep influence. The quasistatic estimation, electronic circuit, and aspects related to long-term charge preservations are described or referenced. As an experiment, we tested the actuator entering in contact with a fixed force sensor. An input signal of 20 V peak-to-peak (10% of maximum range) led to force self-sensing errors inferior to ±8%. A final discussion about method accuracy and its limitations is made.
For nanowire growth, vapor-solid-solid (vapor-solid) mechanism is actually vapor-quasisolid-solid (vapor-quasiliquid-solid) mechanism
Authors: Noor Mohammad S.
Published: December 2009

Vapor-phase mechanisms [e.g., vapor-liquid-solid (VLS), vapor-solid-solid, oxide-assisted growth, and the self-catalytic growth mechanisms] for the unidirectional nanowire (NW) growth are not yet well understood. For this understanding, growths of GaN and InN NWs in our laboratory, without and with the assistance of foreign element catalytic agents (FECAs), such as Au and In, were performed. GaN NW growth, in the presence of FECA≡Ni, was possible at temperatures below the Ni/Ga eutectic temperature. InN NWs were grown, in the presence of Au, and at temperatures in the vicinity of Au/In eutectic temperature. They were found to have Au at the NW tip, NW base, and NW sidewalls. Extensive investigation of the fundamentals underlying these anomalies has been carried out. The temperature dependence of the VLS mechanism has also been elucidated. A large number of available elemental and compound semiconductor NWs exhibiting similar characteristics have been considered for the investigation. Based on this investigation, a chemicophysical mechanism called the vapor-quasisolid-solid (VQS) (or vapor-semisolid-solid, or vapor-quasiliquid-solid, or vapor-semiliquid-solid) mechanism has been proposed. The cause of temperature dependence of the VLS growth under different growth conditions and growth environments, and the possible relationship between the VLS and the VQS mechanisms has been presented. To better describe the vapor-phase mechanisms, including the VQS mechanism, a unified definition of droplets has been proposed. A series of experimental evidences has been set forth to substantiate the validity of the proposed mechanism, and to justify the definition of the unified droplet model. They together appear to explain the fundamental basis of the NW growth by various mechanisms, including the VQS mechanisms. They also provide solutions of many known problems, conflicts, confusions, and controversies involving NW growth.
Modeling the trajectory of a microparticle in a dielectrophoresis device
Authors: Kharboutly Mohamed , Gauthier Michaël , Chaillet Nicolas
Published: December 2009

Micro- and nanoparticles can be trapped by a nonuniform electric field through the effect of the dielectrophoretic principle. Dielectrophoresis (DEP) is used to separate, manipulate, and detect microparticles in several domains, such as in biological or carbon nanotube manipulations. Current methods to simulate the trajectory of microparticles under a DEP force field are based on finite element model (FEM), which requires new simulations when electrode potential is changed, or on analytic equations limited to very simple geometries. In this paper, we propose a hybrid method, between analytic and numeric calculations and able to simulate complex geometries and to easily change the electrode potential along the trajectory. A small number of FEM simulations are used to create a database, which enables online calculation of the object trajectory as a function of electrode potentials.
Calculations of nonlinear wave-packet interferometry signals in the pump-probe limit as tests for vibrational control over electronic excitation transfer
Authors: Biggs Jason D. , Cina Jeffrey A.
Published: December 2009

The preceding paper [J. D. Biggs and J. A. Cina, J. Chem. Phys. 131, 224101 (2009)] (referred to here as Paper 1), describes a strategy for externally influencing the course of short-time electronic excitation transfer (EET) in molecular dimers and observing the process by nonlinear wave-packet interferometry (nl-WPI). External influence can, for example, be exerted by inducing coherent intramolecular vibration in one of the chromophores prior to short-pulse electronic excitation of the other. Within a sample of isotropically oriented dimers having a specified internal geometry, a vibrational mode internal to the acceptor chromophore can be preferentially driven by electronically nonresonant impulsive stimulated Raman (or resonant infrared) excitation with a short polarized “control” pulse. A subsequent electronically resonant polarized pump then preferentially excites the donor, and EET ensues. Paper 1 investigates control-pulse-influenced nl-WPI as a tool for the spectroscopic evaluation of the effect of coherent molecular vibration on excitation transfer, presenting general expressions for the nl-WPI difference signal from a dimer following the action of a control pulse of arbitrary polarization and shape. Electronic excitation is to be effected and its interchromophore transfer monitored by resonant pump and probe “pulses,” respectively, each consisting of an optical-phase-controlled ultrashort pulse-pair having arbitrary polarization, duration, center frequency, and other characteristics. Here we test both the control strategy and its spectroscopic investigation—with some sacrifice of amplitude-level detail—by calculating the pump-probe difference signal. That signal is the limiting case of the control-influenced nl-WPI signal in which the two pulses in the pump pulse-pair coincide, as do the two pulses in the probe pulse-pair. We present calculated pump-probe difference signals for (1) a model excitation-transfer complex in which two equal-energy monomers each support one moderately Franck–Condon active intramolecular vibration; (2) a simplified model of the covalent dimer dithia-anthracenophane, representing its EET dynamics following selective impulsive excitation of the weakly Franck–Condon active ν12 anthracene vibration at 385 cm−1; and (3) a model complex featuring moderate electronic-vibrational coupling in which the site energy of the acceptor chromophore is lower than that of the donor.
Quantification of metal oxide semiconductor field effect transistor device reliability with low-Vt lanthanum-incorporated high permittivity dielectrics
Authors: O’Sullivan B. J. , Aoulaiche M. , Cho M. J. , Kauerauf T. , Degraeve R. , Okawa H. , Schram T. , Hoffmann T. Y. , Groeseneken G. , Biesemans S. , Nakabayashi T. , Ikeda A. , Niwa M.
Published: December 2009

Results from an extensive reliability characterization of HfLaSiO(N) devices, with TaN gate electrodes, are reported. It is shown that the effect of the lanthanum, initially deposited as La2O3, on a SiO2/HfSiO(N) stack, permeates the Si/SiO2 interface. A lower midgap interface state density is observed at this interface, but increased densities are seen towards the band edges. The presence of lanthanum in the dielectric results in defects in the interface layer and in the high-κ dielectric. A profile of defects in the gate stack is suggested, inferred from a combination of electrical measurements. From the location of the defects, it is argued that the reliability of lanthanum-incorporated devices is not compromised by its presence, thus enabling a reliable route to Vt tuning of n-type metal oxide semiconductor devices.
Piezoresponse through a ferroelectric nanotube wall
Authors: Nonnenmann Stephen S. , Gallo Eric M. , Coster Michael T. , Soja Gregory R. , Johnson Craig L. , Joseph Rahul S. , Spanier Jonathan E.
Published: December 2009

We report on the controlled local switching and imaging of local ferroelectric polarizations oriented perpendicular to the long axis of a lead zirconate titanate (PZT) nanotube. Piezoresponse force microscopy and ferroelectric piezoelectric hysteresis data indicate stable polarizations oriented along the radial, finite-thickness direction can be formed in a nanoshell geometry. The results of infrared spectroscopy and of the character of as-found polarizations are consistent with recent findings linking surface chemical environment to ferroelectric stability and to orientation of ferroelectric polarizations.
Pyroelectric effect enhancement in laminate composites under short circuit condition
Authors: Chang H. H. S. , Whatmore R. W. , Huang Z.
Published: December 2009

The pyroelectric coefficients of laminate composites under short circuit condition have been investigated by analytical modeling and numerical simulations. Indicators for various pyroelectric/non-pyroelectric material pairs that can be utilized to determine their pyroelectric coefficient enhancement credentials have been identified. Six pyroelectric materials were paired with six non-pyroelectric/elastic materials and their pyroelectric coefficient enhancement potential and figure of merit for efficiency were investigated. The best performing partnership out of the 36 pairs was lead zirconate titanate (PZT5H)-chlorinated polyvinyl chloride thermoplastic (CPVC) for thickness ratios (R) below 0.09 and PZT5H-zinc for R larger than 0.09 with both demonstrating total pyroelectric coefficient of approximately −20×10−4 C m−2 K−1 at R=0.09, which corresponds to approximately 300% increase in the coefficient. PZT5H-CPVC also showed maximum of 800% rise in the pyroelectric coefficient while figure of merit for efficiency indicated up to twentyfold increase in its electrical response output per given thermal stimuli when compared to that of PZT5H by itself.
Thermal anomalies in ternary Ge42−xPbxSe58 glasses near the charge carrier reversal threshold
Authors: Ramesh K. , Prashantha M. , Gopal E. S. R. , Reddy N. Koteeswara
Published: December 2009

The carrier type reversal (CTR) from p- to n-type in semiconducting chalcogenide glasses is an important and a long standing problem in glass science. Ge–Se glasses exhibit CTR when the metallic elements Bi and Pb are added. For example, bulk Ge42−xSe58Pbx glasses exhibit CTR around 8–9at.% of Pb. These glasses have been prepared by melt quenching method. Glass transition temperature (Tg), Specific heat change between the liquid and the glassy states (ΔCp) at Tg and the nonreversing heat flow (ΔHnr) measured by modulated differential scanning calorimetry exhibit anomalies at 9at.% of Pb. These observed anomalies are interpreted on the basis of the nano scale phase separation occurring in these glasses.
A molecular dynamics simulation study of crystalline 1,3,5-triamino-2,4,6-trinitrobenzene as a function of pressure and temperature
Authors: Bedrov Dmitry , Borodin Oleg , Smith Grant D. , Sewell Thomas D. , Dattelbaum Dana M. , Stevens Lewis L.
Published: December 2009

Quantum chemistry-based dipole polarizable and nonpolarizable force fields have been developed for 1,3,5-triamino-2,4,6-trinitrobenzene (TATB). Molecular dynamics simulations of TATB crystals were performed for hydrostatic pressures up to 10 GPa at 300 K and for temperatures between 200 and 400 K at atmospheric pressure. The predicted heat of sublimation and room-temperature volumetric hydrostatic compression curve were found to be in good agreement with available experimental data. The hydrostatic compression curves for individual unit cell parameters were found to be in reasonable agreement with those data. The pressure- and temperature-dependent second-order isothermal elastic tensor was determined for temperatures between 200 and 400 K at normal pressure and for pressures up to 10 GPa on the 300 K isotherm. Simulations indicate considerable anisotropy in the mechanical response, with modest softening and significant stiffening of the crystal with increased temperature and pressure, respectively. For most properties the polarizable potential was found to yield better agreement with available experimental properties.
Contactless electroreflectance of InGaN layers with indium content ≤36%: The surface band bending, band gap bowing, and Stokes shift issues
Authors: Kudrawiec R. , Siekacz M. , Kryśko M. , Cywiński G. , Misiewicz J. , Skierbiszewski C.
Published: December 2009

Contactless electroreflectance (CER) supported by photoluminescence (PL) has been applied to study (i) the surface band bending, (ii) the band gap bowing, and (iii) the Stokes shift for InGaN layers grown by molecular beam epitaxy with 0.14≤In≤0.36. The type of surface band bending has been investigated on the basis of the shape of CER resonance. It has been found that the surface band bending changes from n-type for layers with low indium content (In<27%) to flatband (or weak p-type band) for layers with In∼35%. The band gap bowing has been determined to be 1.4±0.2 and 2.1±0.3 eV for CER data with and without strain corrections, respectively. From this analysis it has been concluded that the reliable value of the bowing parameter for unstrained InGaN should be between 1.4 and 2.1 eV. Comparing CER with PL data it has been found that the Stokes shift rises from 20 to 120 meV when the indium concentration increased from 14% to 36%. In addition, it has been observed that the intensity of PL from InGaN layers decreased exponentially with the increase in the indium content. The last two findings are attributed to an easier formation of native point defects and stronger indium segregation in InGaN alloys with higher indium concentrations.
Magnetic properties and spin-glass-like behavior in stoichiometric Mn3In compound
Authors: Zhang Q. , Li D. , Cui W. B. , Li J. , Zhang Z. D.
Published: December 2009

Magnetic and transport properties of stoichiometric Mn3In compound are extensively studied by means of dc magnetization, ac susceptibility, magnetic relaxation, and electrical resistivity measurements. It is found that Mn3In is a ferrimagnet with Curie temperature of 80 K and that a metallic spin-glass-like (SGL) state exists below 45 K, which is indicated by the difference between zero-field-cooled (ZFC) and field-cooled (FC) magnetization curves, invariable FC moments, large remanence effect, magnetic relaxation, and electrical resistivity abnormality. Moreover, the SGL state in Mn3In exhibits some anomalous behaviors, such as no cusp in the ZFC curve at the frozen temperature Tf, a remarkable high-field irreversibility, and a high-field relaxation process. The presence of the SGL state in the Mn3In compound without doping or substitution is discussed in terms of magnetic cluster mode.
Improving surface acousto-optical interaction by high aspect ratio electrodes
Authors: Dühring Maria B. , Laude Vincent , Khelif Abdelkrim
Published: December 2009

The acousto-optical interaction of an optical wave confined inside a waveguide and a surface acoustic wave launched by an interdigital transducer (IDT) at the surface of a piezoelectric material is considered. The IDT with high aspect ratio electrodes supports several acoustic modes that are strongly confined to the surface, causing a significant increase in the strain underneath the surface. A finite element method is employed to model the surface acoustic waves generated by a finite length IDT with 12 electrode pairs and subsequently to study their interaction with an optical wave propagating in a waveguide buried in the lithium niobate substrate supporting the electrodes. The interaction can be increased up to 600 times using these new types of surface acoustic waves as compared to using a conventional IDT with thin electrodes. This result could find applications in improved acousto-optical integrated modulators.
Calculations of rovibrational energies and dipole transition intensities for polyatomic molecules using MULTIMODE
Authors: Carter Stuart , Sharma Amit R. , Bowman Joel M. , Rosmus Pavel , Tarroni Riccardo
Published: December 2009

We report rigorous calculations of rovibrational energies and dipole transition intensities for three molecules using a new version of the code MULTIMODE. The key features of this code which permit, for the first time, such calculations for moderately sized but otherwise general polyatomic molecules are briefly described. Calculations for the triatomic molecule BF2 are done to validate the code. New calculations for H2CO and H2CS are reported; these make use of semiempirical potentials but ab initio dipole moment surfaces. The new dipole surface for H2CO is a full-dimensional fit to the dipole moment obtained with the coupled-cluster with single and double excitations and a perturbative treatment of triple excitations method with the augmented correlation consistent triple zeta basis set. Detailed comparisons are made with experimental results from a fit to relative data for H2CS and absolute intensities from the HITRAN database for H2CO.
Electron bunch length monitors using spatially encoded electro-optical technique in an orthogonal configuration
Authors: Yang X. , Tsang T. , Rao T. , Murphy J. B. , Shen Y. , Wang X. J.
Published: December 2009

A single-shot, nondestructive, electro-optical, electron bunch length monitor is experimentally verified by encoding the Coulomb field of the bunch profile on the spatial intensity distribution of an unchirped femtosecond laser pulse in an orthogonal geometry, hence a temporal-to-spatial transformation. This electron bunch measurement scheme can simultaneously measure large timing jitter (approximately in picoseconds) with a wide measurement time span covering picosecond to subpicosecond ranges.
Nanotube nucleation versus carbon-catalyst adhesion–Probed by molecular dynamics simulations
Authors: Ribas Morgana A. , Ding Feng , Balbuena Perla B. , Yakobson Boris I.
Published: December 2009

Catalytic nucleation of carbon nanotubes (CNTs) remains a challenge for the theory: Which factors and forces decide if the gathering sp2-network of atoms will adhere to the catalyst particle and fully cover it or the graphitic cap will liberate itself to extend into a hollow filament? This intimate mechanism cannot be seen in experiment, yet it can be investigated through comprehensive molecular dynamics. We systematically vary the adhesion strength (Wad) of the graphitic cap to the catalyst and temperature T (and C diffusion rate). Observations allow us to build a statistically representative map of CNT nucleation and define the conditions for growth or metal encapsulation in a fullerene-shell (catalyst poisoning). It shows clearly that weak Wad, sufficient thermal kinetic energy (high T) or fast C diffusion favor the CNT nucleation. In particular, below 600 K carbon-diffusion on the catalyst surface limits the growth, but at higher T it fully depends on cap lift-off. Informed choice of parameters allowed us to obtain the longest simulated nanotube structures. The study reveals a means of designing the catalyst for better CNT synthesis, potentially at desirably low temperatures.
A review on photovoltaic thermal collectors
Authors: Singh Baljit , Othman M. Y.
Published: December 2009

The content of this review consists of the types and the parameters influencing the performance (electrical and thermal) and also covers the numerical, analytical, and experimental models of photovoltaic thermal (PVT) collectors. The PVT systems using air and water as heat extraction agents were discussed. The parameters affecting the PVT performance such as the glazing, mass flow rate, and influence of absorber and design types were discussed in details. From the exergy analysis, it was found that the unglazed collector gives better total (electrical+thermal) exergy, whereas the energy analysis favors the glazed collectors. From the literature review, it is obvious that the PVT systems are very useful in the future. There are no substantial initiatives taken in order to reduce the cost and to make PVT collectors favorable. Increasing the competitiveness of PVT collectors will enhance the utilization of renewable energy devices. This communication was done to ease future studies to be conducted by researchers.
Plasma-assisted atomic layer deposition of TiN/Al2O3 stacks for metal-oxide-semiconductor capacitor applications
Authors: Hoogeland D. , Jinesh K. B. , Roozeboom F. , Besling W. F. A. , van de Sanden M. C. M. , Kessels W. M. M.
Published: December 2009

By employing plasma-assisted atomic layer deposition, thin films of Al2O3 and TiN are subsequently deposited in a single reactor at a single substrate temperature with the objective of fabricating high-quality TiN/Al2O3/p-Si metal-oxide-semiconductor capacitors. Transmission electron microscopy and Rutherford backscattering spectroscopy analyses show well-defined interfaces and good Al2O3 stoichiometry, respectively. Electrical investigation of as-deposited test structures demonstrates leakage current densities as low as ∼1 nA/cm2. Current-voltage (I-V) measurements demonstrate clear Fowler–Nordheim tunneling with an average TiN/Al2O3 barrier height of 3.3 eV. Steep Weibull distributions of the breakdown electric field around 7.5 MV/cm indicate good reliability of these devices. Time-dependent dielectric breakdown measurements demonstrate that the devices can sustain high operating electric fields of 3–4 MV/cm for the 10 year lifetime criterion. From capacitance-voltage (C-V) measurements, a dielectric constant (k) of 8.7±0.1 was extracted for the Al2O3. No direct dependence on the deposition temperature was found in the range 350–400 °C, although the stack deposited at 400 °C demonstrates significantly lower C-V hysteresis of ∼50 mV. A negative fixed oxide charge density of (9.6±0.2)×1012 cm−2 was found to be present at the Al2O3/p-Si interface.
Depolarization blueshift in intersubband transitions of triangular quantum wires
Authors: Zhang B. , Lu Y. W. , Song H. P. , Liu X. L. , Yang S. Y. , Zhu Q. S. , Wang Z. G.
Published: December 2009

The depolarization effect (DE) in the intersubband transitions (ISBTs) of triangular cross-section quantum wires has been calculated in the framework of the effective-mass envelope-function theory and the self-consistent field approximation (Hartree approximation). Similar to quantum wells, the DE can bring an upward shift in ISBT. The shift quantities are affected significantly by apex angle but are insensitive to triangle size.
Characterization of multifunctional structural capacitors for embedded energy storage
Authors: Lin Yirong , Sodano Henry A.
Published: December 2009

Multifunctional composites are a class of materials that combine structural and other functionalities such as sensing, actuation, energy harvesting, and vibration control in order to maximize structural performance while minimizing weight and complexity. Among all the multifunctional composites developed so far, piezoelectric composites have been widely studied due to the high coupling of energy between the electrical and mechanical domains and the inherently high dielectric constant. Several piezoelectric fiber composites have been developed for sensing and actuation applications; however, none of the previously studied composites fully embed all components of an energy storage device as load bearing members of the structure. A multifunctional fiber that can be embedded in a composite material to perform sensing and actuation has been recently developed [Y. Lin and H. A. Sodano, Adv. Funct. Mater. 18, 592 (2008)], in addition to providing load bearing functionality. The design was achieved by coating a common structural fiber, silicon carbide, with a barium titanate piezoelectric shell, and poling the active material radically by employing the structural fiber as one of the electrodes. The silicon carbide core fiber also carries external mechanical loading to protect the brittle barium titanate shell from fracture. The excellent piezoelectric and dielectric properties of the barium titanate material make the active structural fiber an outstanding candidate for converting and storing ambient mechanical energy into electrical energy to power other electric devices in the system. This paper focuses on the characterization of energy storage capability of the multifunctional fiber provided by the dielectric properties of the barium titanate shell. The capacitances of the multifunctional fibers with four different aspect ratios are tested and compared with the theoretical expressions for the cylindrical capacitor, while the breakdown voltages of the multifunctional fibers are tested according to American Society for Testing and Materials standards (ASTM D 149–97a). The stored energy is calculated from the testing results and the best aspect ratio for energy storage application can be determined. The resulting capacitive fiber is shown to have an energy density approximately two orders of magnitude higher than structural capacitors in the literature.
Modeling the anisotropic self-assembly of spherical polymer-grafted nanoparticles
Authors: Pryamtisyn Victor , Ganesan Venkat , Panagiotopoulos Athanassios Z. , Liu Hongjun , Kumar Sanat K.
Published: December 2009

Recent experimental results demonstrated that polymer grafted nanoparticles in solvents display self-assembly behavior similar to the microphase separation of block copolymers and other amphiphiles. We present a mean-field theory and complementary computer simulations to shed light on the parametric underpinnings of the experimental observations. Our theory suggests that such self-assembled structures occur most readily when the nanoparticle size is comparable to the radius of gyration of the polymer brush chains. Much smaller particle sizes are predicted to yield uniform particle dispersions, while larger particles are expected to agglomerate due to phase separation from the solvent. Selected aspects of our theoretical predictions are corroborated by computer simulations.
Phase transition of Zn2SnO4 nanowires under high pressure
Authors: Shen X. , Shen J. , You S. J. , Yang L. X. , Tang L. Y. , Li Y. C. , Liu J. , Yang H. , Zhu K. , Liu Y. L. , Zhou W. Y. , Jin C. Q. , Yu R. C. , Xie S. S.
Published: December 2009

In situ high-pressure angle dispersive x-ray diffraction experiments using synchrotron radiation on inverse spinel structure Zn2SnO4 nanowires were carried out with a diamond anvil cell at room temperature. The crystal symmetry becomes lower at around 12.9 GPa and an intermediate phase with an orthorhombic structure occurs. At about 32.7 GPa, a phase transition occurs accompanying a high-pressure phase. In situ Raman scattering investigation was also performed to explore the phase transition. In the pressure range 15.5–32.8 GPa, the intermediate phase is also detected and a high-pressure phase is observed above 32.8 GPa. The high-pressure phase is considered to possess the ambient pressure structure of CaFe2O4.
Dynamic pathways to mediate reactions buried in thermal fluctuations. I. Time-dependent normal form theory for multidimensional Langevin equation
Authors: Kawai Shinnosuke , Komatsuzaki Tamiki
Published: December 2009

We present a novel theory which enables us to explore the mechanism of reaction selectivity and robust functions in complex systems persisting under thermal fluctuation. The theory constructs a nonlinear coordinate transformation so that the equation of motion for the new reaction coordinate is independent of the other nonreactive coordinates in the presence of thermal fluctuation. In this article we suppose that reacting systems subject to thermal noise are described by a multidimensional Langevin equation without a priori assumption for the form of potential. The reaction coordinate is composed not only of all the coordinates and velocities associated with the system (solute) but also of the random force exerted by the environment (solvent) with friction constants. The sign of the reaction coordinate at any instantaneous moment in the region of a saddle determines the fate of the reaction, i.e., whether the reaction will proceed through to the products or go back to the reactants. By assuming the statistical properties of the random force, one can know a priori a well-defined boundary of the reaction which separates the full position-velocity space in the saddle region into mainly reactive and mainly nonreactive regions even under thermal fluctuation. The analytical expression of the reaction coordinate provides the firm foundation on the mechanism of how and why reaction proceeds in thermal fluctuating environments.
Atomic structure of the Ag/Ge(111)-(3×3) surface: From scanning tunneling microscopy observation to theoretical study
Authors: Chou L.-W. , Wu H. C. , Lee Y.-R. , Jiang J.-C. , Su C. , Lin J.-C.
Published: December 2009

The atomic structure of the Ag/Ge(111)-(3×3)R30° surface is studied by scanning tunneling microscopy (STM) and the density functional theory (DFT) calculations. Our STM images have shown a structure which is different from the widely accepted honeycomb-chained-triangle (HCT) model before. The structure is similar to the inequivalent triangle (IET) model found for the Ag/Si(111)-(3×3)R30° surface. This model proposed two types of silver triangles with different sizes in the unit cell, corresponding to the bright spots and the dark spots in the STM image. A distinguishable hexagonal pattern of the IET structure was well disclosed in the temperature range from 100 to 473 K in our STM studies for Ag/Ge(111)-(3×3)R30°. Furthermore, the result of the DFT calculations showed that the IET structure is 0.20 eV energetically more stable than the HCT model. Besides, the Ge triangles, which were not disclosed in earlier STM research, are found in this study.
Surface chemical potential in multilayered Stranski–Krastanow systems: An analytic study and anticipated applications
Authors: Li X. L.
Published: December 2009

An analytic thermodynamic model has been established to quantitatively calculate the surface chemical potential in multilayered Stranski–Krastanow (SK) systems. It was found that we cannot only control the array of quantum dots (QDs) through changing the depth of buried inclusion but also fabricate nanostructures with other shapes such as quantum rings through selecting proper inclusion. The theoretical results are in good agreement with the experimental observations and reveal physical mechanisms involved in the vertical alignment of stacked QDs, which implies that the established thermodynamic theory could be expected to be applicable to address the self-assembly of QDs in multilayered SK systems.
Control of spatiotemporal patterns in the Gray–Scott model
Authors: Kyrychko Y. N. , Blyuss K. B. , Hogan S. J. , Schöll E.
Published: December 2009

This paper studies the effects of a time-delayed feedback control on the appearance and development of spatiotemporal patterns in a reaction-diffusion system. Different types of control schemes are investigated, including single-species, diagonal, and mixed control. This approach helps to unveil different dynamical regimes, which arise from chaotic state or from traveling waves. In the case of spatiotemporal chaos, the control can either stabilize uniform steady states or lead to bistability between a trivial steady state and a propagating traveling wave. Furthermore, when the basic state is a stable traveling pulse, the control is able to advance stationary Turing patterns or yield the above-mentioned bistability regime. In each case, the stability boundary is found in the parameter space of the control strength and the time delay, and numerical simulations suggest that diagonal control fails to control the spatiotemporal chaos.
First-principles investigation of organic semiconductors for thermoelectric applications
Authors: Wang Dong , Tang Ling , Long Mengqiu , Shuai Zhigang
Published: December 2009

First-principles band structure calculations coupled with the Boltzmann transport theory are used to study the thermoelectric properties in pentacene and rubrene crystals. In the constant relaxation time and rigid band approximations, the electronic contribution to the Seebeck coefficient is obtained. The absolute value of Seebeck coefficient and its temperature and carrier density dependences are in quantitative agreement with the recent field-effect-modulated measurement. The dimensionless thermoelectric figure of merit is further evaluated based on the calculated transport coefficients and experimental parameters. The peak values of figure of merit in pentacene fall in the range of 0.8–1.1, which are close to those of the best bulk thermoelectric materials. Our investigations show that organic semiconductors can be potentially good thermoelectric materials for near-room-temperature applications.
Dispersion phenomena in helical flow in a concentric annulus
Authors: Song Young Seok , Brenner Howard
Published: December 2009

We examined dispersion phenomena of solutes in helical flow in a concentric annulus through a multiscale approach. The helical flow was developed by the combination of the Poiseuille flow and Couette flow. Here, we present an analytic model that can address the multidimensional Taylor dispersion in the helical flow under a lateral field of thermophoresis (or thermal diffusion) in the gapwise direction. Macroscopic parameters including the average solute velocity and dispersivity were analyzed using relevant microscopic physicochemical properties. The mathematically obtained results were validated by the numerical simulation carried out in this study. The findings show that macrotransport processes are robust and straightforward to handle multidimensional dispersion phenomena of solutes in helical flow. This study is expected to provide a theoretical platform for applications of helical flow such as tube exchangers, oil drilling, and multidimensional field flow fractionations (e.g., helical flow field flow fractionation).
Nonradiative recombination in 1.56 μm GaInNAsSb/GaNAs quantum-well lasers
Authors: Ferguson J. W. , Smowton P. M. , Blood P. , Bae H. , Sarmiento T. , Harris J. S.
Published: December 2009

We have shown experimentally that in GaInNAsSb/GaAs quantum-well lasers there are significant nonradiative contributions to threshold current from the barriers and the well. By matching a simulation to the experiment we find that Auger recombination in the barriers is very weak, due to the low carrier density. Shockley–Read–Hall recombination is the dominant source of nonradiative current, with the barriers making the major contribution, possibly due to their higher defect density than the wells. This suggests that significant improvements could be made by optimizing growth conditions and layer design, with particular attention to the barrier.
Accurate yet feasible post-Hartree–Fock computation of magnetic interactions in large biradicals through a combined variational/perturbative approach: Setup and validation
Authors: Barone Vincenzo , Cacelli Ivo , Ferretti Alessandro , Prampolini Giacomo
Published: December 2009

We present a scheme for the calculation of the spin-spin coupling term J in diradicals which is quantitatively accurate and computationally cheap. The method exploits the use of modified virtual orbitals and perturbation theory, incorporated in a multireference configuration interaction approach. The results obtained for model diradical species which exhibit ferromagnetic and antiferromagnetic coupling are fully satisfactory and very promising for future applications of the method to larger molecular systems of technological interest in magnetic-based devices.
Terahertz Kerr effect
Authors: Hoffmann Matthias C. , Brandt Nathaniel C. , Hwang Harold Y. , Yeh Ka-Lo , Nelson Keith A.
Published: December 2009

We have observed optical birefringence in liquids induced by single-cycle terahertz pulses with field strengths exceeding 100 kV/cm. The induced change in polarization is proportional to the square of the terahertz electric field. The time-dependent terahertz Kerr signal is composed of a fast electronic response that follows the individual cycles of the electric field and a slow exponential response associated with molecular orientation.
Diffusion-gradient-induced length instabilities in the catalytic growth of carbon nanotubes
Authors: Gamalski A. , Moore E. S. , Treacy M. M. J. , Sharma R. , Rez P.
Published: December 2009

We report in situ transmission electron microscopy observations of length instabilities in the growth of straight-wall carbon nanotubes. The nanotubes are grown at: T<725 °C, P<80 mTorr by chemical vapor decomposition of acetylene on Fe nanoparticles formed in situ prior to tube growth. The growing nanotubes detach episodically from the catalyst particles, which then nucleate a fresh nanotube. Detachment is induced by the shedding of carbon-starved inner walls during diffusion-limited growth.
Probing nanoantenna-directed photothermal destruction of tumors using noninvasive laser irradiation
Authors: DasGupta Debabrata , von Maltzahn Geoffrey , Ghosh Soham , Bhatia Sangeeta N. , Das Sarit K. , Chakraborty Suman
Published: December 2009

Plasmonic nanomaterials have tremendous potential to improve the tumor specificity of traditional cancer ablation practices, yet little effort has been directed toward quantitatively understanding their photothermal energy conversion in tumor tissues. In the present work, we develop a predictive model for plasmonic nanomaterial assisted tumor destruction under extracorporeal laser irradiation. Instead of appealing to heuristically based laser intensification models with tunable, tissue absorption and scattering coefficients, we consider fundamental characteristics of optoelectrothermal energy conversion and heat dissipation for plasmonic nanomaterials within living tumor tissues to construct a simulation tool that accurately reproduces our experimental findings, including aspects of delayed time-temperature characteristics. We believe the comprehensive modeling strategy outlined here provides a groundwork for the development of anticipatory therapeutic planning tools with individually tailored treatment plans, resulting in an ultimate benefit to ailing cancer patients.