bluuebunny/crossref_metadata_2025 huggingface dataset:
A Confocal Raman-AFM Study of Graphene
Authors: Schmidt U. , Dieing T. , Ibach W. , Hollricher O.
Published: October 2011

The discovery by Novoselov and Geim of a simple method to transfer a single atomic layer of carbon from the c-face of graphite to a substrate suitable for measurements of its electrical and optical properties has led to an increased interest in studying and employing two-dimensional model systems. An overview of electron and phonon properties of graphene and their relationship to the one-dimensional form of carbon known as nanotubes can be found in. The unique chemical, mechanical, electrical, and optical properties of graphene lead to its many application possibilities such as: single molecule detectors, high-strength low-weight new materials, design of new semiconductor devices, etc.
Pioneers in Optics: Sir David Brewster
Authors: Davidson Michael W.
Published: October 2011

Sir David Brewster was a Scottish physicist who invented the kaleidoscope, made major improvements to the stereoscope, and discovered the polarization phenomenon of light reflected at specific angles. Brewster was born in Jedburgh, Scotland, in 1781 and grew to become a brilliant student who entered the University of Edinburgh at the age of 12 to study the ministry. He was a prolific writer and became editor of theEdinburgh Magazinein 1802 and theEdinburgh Encyclopediain 1808. In 1799 as a teenager, Brewster's interests turned to physics with a keen focus on optics, and he constructed several telescopes while dabbling in the physics of light. Brewster was a licensed minister of the Church of Scotland but never practiced this career, instead pursuing the finer aspects of optics and light.
NetNotes
Authors: Phillips Thomas E.
Published: October 2011

Selected postings from the Microscopy Listserver from July 1, 2011 to August 31, 2011. Complete listings and subscription information can be obtained at http://www.microscopy.com. Postings may have been edited to conserve space or for clarity.
The Anglican Covenant and the ‘Puritan’ Temptation
Authors: Sedgwick Timothy F.
Published: October 2011

As ecumenical understanding of the formation and development ofepiskopéhas emphasized, there are different ways of structuringepiskopécollegially, synodically and personally, each with its own theological basis, strength and weakness. This article argues that the proposed Anglican Covenant assumes a normative understanding of the nature and role of the bishop which carries the danger of a kind of ‘puritanism’ in which the focus and energy of the churches in the Anglican Communion are narrowly focused, creating a bureaucratic form of governance that vitiates the mission of the church.
Overt and Covert Aggression in College Women with Bulimia Nervosa
Authors: Huemer Julia , Sagar Ashwini , Alquero Kathleen , Denny Katie , Shaw Richard J. , Steiner Hans
Published: October 2011

Objective: This study examines the prevalence of overt and covert aggression in women with bulimia nervosa (BN) as well as the relationship between the severity of BN and the frequency of aggressive acts. Patients and methods: 20 female college students with BN and 20 control subjects completed self-report measures of aggressive behavior and eating disorder pathology. They also completed the Juvenile Health and Wellness Survey-76 to assess general risk taking and indices of sexual behavior and mental health. Results: BN subjects reported higher levels of both overt and covert aggression (p < .001). Overt aggression tended to be more premeditated, while the self-report of covert aggression behavior was more impulsive. Levels of aggressive behavior were significantly correlated with severity of BN (p < .01). Subjects with BN reported higher levels of risk-taking and sexual behaviors. Conclusions: Aggression is an important clinical issue in BN. Subtypes of aggression suggest different pathways for overt and covert aggressive acts with impulsive covert aggression being more closely related to the binge-purge cycle. Awareness of subtypes of aggression in BN may have important clinical and treatment implications.
A volcanotectonic survey of Ascraeus Mons, Mars
Authors: Byrne Paul K. , van Wyk de Vries Benjamin , Murray John B. , Troll Valentin R.
Published: October 2011

Ascraeus Mons is one of the largest volcanoes on Mars. It is replete with well‐preserved features that can be used to understand its volcanotectonic evolution. Previous studies of this volcano focused on specific features, and were limited by the quality and coverage of contemporary data. Our objective is to review and enhance the existing developmental model for Ascraeus by considering all endogenic surface features on the volcano. We surveyed the volcano's caldera complex, flank terraces, pit structures, sinuous rilles, arcuate grabens, and small vents. We report the spatial and temporal distributions of these features, appraise their proposed formation mechanisms in light of our mapping results, and propose a detailed geological history for Ascraeus Mons. An initial shield‐building phase was followed by the formation of a summit caldera complex and small parasitic cones, while compression due to flexure of the supporting basement led to extensive terracing of the shield flanks. An eruptive hiatus followed, ending with the construction of expansive rift aprons to the northeast and southwest. Against later, extensive flank resurfacing in the late Amazonian, continued flexure formed arcuate grabens concentric to the edifice. Localized eruption and surface flow of a fluid agent (lava and/or water) from within the volcano then produced a population of rilles on the lower flanks. Finally, in a change of flank tectonic regime from compression to extension, pit crater chains and troughs developed on the main shield and rift aprons, eventually coalescing to form large embayments at the northeast and southwest base of the volcano.
Assessment of BTEX‐induced health risk under multiple uncertainties at a petroleum‐contaminated site: An integrated fuzzy stochastic approach
Authors: Zhang Xiaodong , Huang Guo H.
Published: October 2011

Groundwater pollution has gathered more and more attention in the past decades. Conducting an assessment of groundwater contamination risk is desired to provide sound bases for supporting risk‐based management decisions. Therefore, the objective of this study is to develop an integrated fuzzy stochastic approach to evaluate risks of BTEX‐contaminated groundwater under multiple uncertainties. It consists of an integrated interval fuzzy subsurface modeling system (IIFMS) and an integrated fuzzy second‐order stochastic risk assessment (IFSOSRA) model. The IIFMS is developed based on factorial design, interval analysis, and fuzzy sets approach to predict contaminant concentrations under hybrid uncertainties. Two input parameters (longitudinal dispersivity and porosity) are considered to be uncertain with known fuzzy membership functions, and intrinsic permeability is considered to be an interval number with unknown distribution information. A factorial design is conducted to evaluate interactive effects of the three uncertain factors on the modeling outputs through the developed IIFMS. The IFSOSRA model can systematically quantify variability and uncertainty, as well as their hybrids, presented as fuzzy, stochastic and second‐order stochastic parameters in health risk assessment. The developed approach haw been applied to the management of a real‐world petroleum‐contaminated site within a western Canada context. The results indicate that multiple uncertainties, under a combination of information with various data‐quality levels, can be effectively addressed to provide supports in identifying proper remedial efforts. A unique contribution of this research is the development of an integrated fuzzy stochastic approach for handling various forms of uncertainties associated with simulation and risk assessment efforts.
Hydrological minimal model for fire regime assessment in a Mediterranean ecosystem
Authors: Ursino Nadia , Rulli Maria Cristina
Published: October 2011

A new model for Mediterranean forest fire regime assessment is presented and discussed. The model is based on the experimental evidence that fire is due to both hydrological and ecological processes and the relative role of fuel load versus fuel moisture is an important driver in fire ecology. Diverse scenarios are analyzed where either the hydrological forcing or the feedback between fire and hydrological characterization of the site is changed. The model outcome demonstrates that the two‐way interaction between hydrological processes, biology, and fire regime drives the ecosystem toward a typical fire regime that may be altered either by an evolution of the biological characterization of the site or by a change of the hydrological forcing. This tenet implies that not every fire regime is compatible with the ecohydrological characterization of the site under study. This means that natural (nonantropogenic) fire cannot be modeled as an arbitrary external forcing because the coupled hydrological and biological processes determines its statistical characterization, and conversely, the fire regime affects the soil moisture availability and the outcome of different species competition under possible water stress. The new modeling approach presented here, when provided by a proper model parameterization, can advance the capability in predicting and managing fires in ecosystems influenced by climate and land use changes.
A Draft Sequence of the Puerto Rican Parrot Genome (Amazona vittata) – a Genome Project funded by a Local Community Effort
Authors: Oleksyk Taras
Published: October 2011

The genome of the Puerto Rican parrot (Amazona vittata) has been sequenced and assembled in an international collaboration supported by many individual donations from the people of Puerto Rico. This is a critically endangered endemic bird, the only surviving native parrot species in the territory of the United States, and the first parrot belonging to the large genus Amazona to have its genome sequenced and assembled. A genome of one A. vittata female was sequenced resulting in a total of almost 42.5 billion nucleotide bases equivalent to 26.89X average coverage depth. After filtering out the short fragments (<500bp), the assembly resulted in 259,423 short fragment library contigs, half of them (N50) of at least 6,983 bp in length, with a longest contig at 75,003, and 148,255 long fragment library of scaffolds with N50=19,470 with the longest at 206,462 bp length. Further sequencing is needed to generate enough coverage of the genome and close the assembly gaps. To our knowledge, this is the first genome project to be initiated and supported by local community fundraising efforts, and represents a model for the future of de novo genome projects for conservation genetics of nonhuman species.
Antimalarial Agents Targeting Nucleotide Synthesis and Electron Transport: Insight from Structural Biology
Authors: Phillips Margaret A.
Published: October 2011

Malaria remains a significant global health challenge due to wide-spread drug resistance and the lack of a vaccine. Target-based drug discovery provides an opportunity for the development of new chemical entities to combat the disease. Of the existing antimalarials, those with known targets primarily interfere with pyrimidine biosynthesis and significant effort is ongoing to identify new compounds that target this pathway. Structure-based approaches are being utilized for the design of new inhibitors that circumvent resistance to well-established targets in the pathway such as dihydrofolate reducase and the cytochrome bc1 complex and they are being applied to lead optimization programs for new targets in the pathway, particularly dihydroorotate dehydrogenase. In an effort to expand the number of targets that interfere with the synthesis of DNA and RNA precursors, computational transition state approaches have been used to identify potent inhibitors of purine biosynthesis. This chapter will evaluate the feasibility of redesigning new molecules for old targets, and the likelihood that new targets will be identified in these pathways.
Human Targets Repositioning and Cell-based Approaches for Antimalarial Discovery
Authors: Chatterjee Arnab K. , Winzeler Elizabeth A.
Published: October 2011

This chapter consists of two major areas highlighting successes and opportunities for improvement: first, the use of targeted human therapeutics against malaria parasite proliferation and second, the use of cell-based assays to find novel antimalarials. The first part of the chapter will describe the use of compounds from major human therapeutic targets, namely farnasyltranferase, histone deacetylase, protein kinase, and protease inhibitors. Compounds from the highly successful human target classes have been investigated as treatment methods for plasmodium infections and some interesting leads from medicinal chemistry optimization will be described. As a complimentary approach, the second part of this chapter describes cell-based screening as a method to generate novel antimalarial drugs. Traditionally demonstrated as a highly successful approach to anti-infectives, this part of the chapter outline new methods for high-throughput screening, hit triaging and subsequent methods available to determine mechanism of action, including recent examples in the literature.
Drug Discovery for Lower Respiratory Tract Infections
Authors: Carl Craft J
Published: October 2011

Lower respiratory tract infections are the leading cause of death due to infectious diseases in both the developing world and developed world. The clinical problem is more complicated than the high profile killers, HIV, tuberculosis and malaria, since the infections are caused by a wide variety of infectious agents, including bacteria and viruses, and covers a variety of clinical conditions. For some of the infectious agents, effective vaccines are available, but in all cases there is a need for new medicines, especially in antibacterial therapy. Over the last fifty years many new classes of antibiotics have been discovered, and antimicrobial therapy created the era of modern medicine. However, this trend has slowed down in recent years. The existing progress is being eroded by emergence of resistance against most of the classes of antibiotics. The challenge is that there is now very little research and development of new antibiotics within the pharmaceutical industry: it has become a neglected disease. The majority of drugs under development are improvements on existing classes of medicines. There are two major reasons for this lack of investment. First, the difficulty of achieving a return on investment, given the costs of drug development and the short period of therapy. Second, in recent years, there have been many uncertainties around the regulatory pathway. On top of all this, the promised fruit of the pathogen sequencing and target-based high-throughput screens has not added much to our armamentarium. However, given the mortality and morbidity, the identification of new antibiotics is still a fertile area for research, and a major commitment is needed to keep us from falling behind in the fight against these infections. Without new classes of drugs to fight infection, the long term consequence will be dramatic: a return to the pre-antibiotic era.
Children With Williams Syndrome: Language, Cognitive, and Behavioral Characteristics and Their Implications for Intervention
Authors: Mervis Carolyn B. , Velleman Shelley L.
Published: October 2011

Williams syndrome (WS) is a rare genetic disorder characterized by heart disease, failure to thrive, hearing loss, intellectual or learning disability, speech and language delay, gregariousness, and nonsocial anxiety. The WS psycholinguistic profile is complex, including relative strengths in concrete vocabulary, phonological processing, and verbal short-term memory; and relative weaknesses in relational/conceptual language, reading comprehension, and pragmatics. Many children evidence difficulties with finiteness marking and complex grammatical constructions. Speech-language intervention, support, and advocacy are crucial.
Reaction between graphene and hydrogen under oblique injection
Authors: Saito Seiki , Ito Atsushi M. , Nakamura Hiroaki
Published: October 2011

The reaction between a graphene sheet and an incident hydrogen atom was clarified through a classical molecular dynamics simulation based on the modified Brenner’s reactive empirical bond order potential under the NVE condition, in which the number of particles (N), volume (V), and total energy (E) are conserved. The energy dependence of three types of reaction (i.e., adsorption, reflection, and penetration) for the oblique injection of a hydrogen atom into a graphene sheet was investigated. The reaction depends on the energy and two angular parameters, namely, the polar angle θ and the azimuthal angle φ of the incident hydrogen atom. The reflection and adsorption rates were found to strongly depend on θ. This dependence is caused by the three-dimensional structure of small potential barriers that cover adsorption sites (i.e., a local minimum point of the potential energy). The θ dependence of the penetration rates was observed. The penetration rates are proportional to cos2θ. The φ dependence of the penetration rates was also observed when θ is large.
A coarse-grain three-site-per-nucleotide model for DNA with explicit ions
Authors: Freeman Gordon S. , Hinckley Daniel M. , de Pablo Juan J.
Published: October 2011

The “three sites per nucleotide” (3SPN) model provides a coarse-grained representation of nucleic acids for simulation of molecular processes. Previously, this model has relied on an implicit representation of the surrounding ionic environment at the level of Debye-Hückel theory. In this work, we eliminate this limitation and present an explicit representation of ions, both monovalent and divalent. The coarse-grain ion-ion and ion-phosphate potential energy functions are inferred from all-atom simulations and parameterized to reproduce key features of the local structure and organization of ions in bulk water and in the presence of DNA. The resulting model, 3SPN.1-I, is capable of reproducing the local structure observed in detailed atomistic simulations, as well as the experimental melting temperature of DNA for a range of DNA oligonucleotide lengths, CG-content, Na+ concentration, and Mg2 + concentration.
High-speed phosphor thermometry
Authors: Fuhrmann N. , Baum E. , Brübach J. , Dreizler A.
Published: October 2011

Phosphor thermometry is a semi-invasive surface temperature measurement technique utilising the luminescence properties of doped ceramic materials. Typically, these phosphor materials are coated onto the object of interest and are excited by a short UV laser pulse. Up to now, primarily Q-switched laser systems with repetition rates of 10 Hz were employed for excitation. Accordingly, this diagnostic tool was not applicable to resolve correlated temperature transients at time scales shorter than 100 ms. This contribution reports on the first realisation of a high-speed phosphor thermometry system employing a highly repetitive laser in the kHz regime and a fast decaying phosphor. A suitable material was characterised regarding its temperature lifetime characteristic and its measurement precision. Additionally, the influence of laser power on the phosphor coating was investigated in terms of heating effects. A demonstration of this high-speed technique has been conducted inside the thermally highly transient system of an optically accessible internal combustion engine. Temperatures have been measured with a repetition rate of 6 kHz corresponding to one sample per crank angle degree at 1000 rpm.
The response of CR-39 nuclear track detector to 1–9 MeV protons
Authors: Sinenian N. , Rosenberg M. J. , Manuel M. , McDuffee S. C. , Casey D. T. , Zylstra A. B. , Rinderknecht H. G. , Gatu Johnson M. , Séguin F. H. , Frenje J. A. , Li C. K. , Petrasso R. D.
Published: October 2011

The response of CR-39 nuclear track detector (TasTrak®) to protons in the energy range of 0.92–9.28 MeV has been studied. Previous studies of the CR-39 response to protons have been extended by examining the piece-to-piece variability in addition to the effects of etch time and etchant temperature; it is shown that the shape of the CR-39 response curve to protons can vary from piece-to-piece. Effects due to the age of CR-39 have also been studied using 5.5 MeV alpha particles over a 5-year period. Track diameters were found to degrade with the age of the CR-39 itself rather than the age of the tracks, consistent with previous studies utilizing different CR-39 over shorter time periods.
Comprehensive surface analysis of GaN-capped AlGaN/GaN high electron mobility transistors: Influence of growth method
Authors: Gutt R. , Himmerlich M. , Fenske M. , Müller S. , Lim T. , Kirste L. , Waltereit P. , Köhler K. , Krischok S. , Fladung T.
Published: October 2011

AlGaN/GaN-based high electron mobility transistor heterostructures with different GaN cap layer thicknesses were grown by metalorganic vapor phase epitaxy (MOVPE) and molecular beam epitaxy. The influence of the different growth methods on the structure of the GaN caps was examined by x-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry (TOF-SIMS). Due to the high surface sensitivity of these methods, several effects, such as residual Al incorporation into the GaN cap during growth, etching of the GaN cap during cool-down, and preferential etching of Ga out of the AlGaN barrier could be evaluated. It is demonstrated that these effects play a major role for MOVPE-grown structures.
Wave propagation in embedded double-layer graphene nanoribbons as electromechanical oscillators
Authors: Shi Jin-Xing , Ni Qing-Qing , Lei Xiao-Wen , Natsuki Toshiaki
Published: October 2011

Graphene nanoribbons (GNRs) are potential nanomaterial electromechanical oscillators because of their outstanding mechanical and electronic properties. Double-layer GNRs (DLGNRs), which are two-layer finite-wide counterparts of crystalline graphene sheets coupled to each other via van der Waals interaction forces, present two kinds of vibrational modes in flexural wave propagation. These two modes are defined as the in-phase mode and anti-phase mode. In this study, based on the nonlocal Timoshenko beam theory and Winkler spring model, the wave propagation characteristics of DLGNRs embedded in an elastic matrix are investigated by dividing the vibrational mode into the in-phase mode and anti-phase mode. This will provide more accurate guidance for the application of DLGNRs. When the nonlocal effects and elastic matrix are considered, three critical frequencies are found. These are defined as the cutoff, escape, and low-cutoff frequencies. Moreover, the results show that the wave propagation characteristics of embedded DLGNRs are significantly influenced by nonlocal parameters and the Winkler foundation modulus.
Short-time self-diffusion coefficient of a particle in a colloidal suspension bounded by a microchannel: Virial expansions and simulation
Authors: Kȩdzierski Marcin , Wajnryb Eligiusz
Published: October 2011

Self-diffusion of colloidal particles confined to a cylindrical microchannel is considered theoretically and numerically. Virial expansion of the self-diffusion coefficient is performed. Two-body and three-body hydrodynamic interactions are evaluated with high precision using the multipole method. The multipole expansion algorithm is also used to perform numerical simulations of the self-diffusion coefficient, valid for all possible particle packing fractions. Comparison with earlier results shows that the widely used method of reflections is insufficient for calculations of hydrodynamic interactions even for small packing fractions and small particles radii, contrary to the prevalent opinion.
Pair force distributions in simple fluids
Authors: Brańka A. C. , Heyes D. M. , Rickayzen G.
Published: October 2011

Analytic expressions are derived for the frequency distribution, P(f), of pair forces, f, and those of their α-Cartesian component, fα, or P(fα), for some typical model simple fluids, expressed in terms of the radial distribution function and known constants. For strongly repulsive inverse power (IP), exponential and Yukawa purely repulsive potentials, P(f) diverges at the origin approximately as ∼f−1, but with different limiting analytic forms. P(fα) is also shown to diverge as ∼f−1 as f → 0 for the IP fluid. For the Lennard-Jones potential fluid, P(f) is finite for all f ≥ 0 but has two singularities for negative f, corresponding to the zero force limit (i.e., f → 0−) and the point of inflection in the potential. The corresponding component force distribution is singular as fα → 0 from both positive and negative force sides. The large force limit of P(f), which originates from the close neighbor interactions, is nearly exponential for the IP and LJ fluids, as is also found for granular materials. A more complete picture of force distributions in off-lattice particulate systems as a function of force law and state point (particularly the extent of “thermalization” of the particles) is provided.
Limit of validity of Ostwald's rule of stages in a statistical mechanical model of crystallization
Authors: Hedges Lester O. , Whitelam Stephen
Published: October 2011

We have only rules of thumb with which to predict how a material will crystallize, chief among which is Ostwald's rule of stages. It states that the first phase to appear upon transformation of a parent phase is the one closest to it in free energy. Although sometimes upheld, the rule is without theoretical foundation and is not universally obeyed, highlighting the need for microscopic understanding of crystallization controls. Here we study in detail the crystallization pathways of a prototypical model of patchy particles. The range of crystallization pathways it exhibits is richer than can be predicted by Ostwald's rule, but a combination of simulation and analytic theory reveals clearly how these pathways are selected by microscopic parameters. Our results suggest strategies for controlling self-assembly pathways in simulation and experiment.
Simulated pressure response of crystalline indole
Authors: Schatschneider Bohdan , Liang Jian Jie
Published: October 2011

The isostatic pressure response of crystalline indole up to 25 GPa was investigated through static geometry optimization using Tkatchenko-Scheffler dispersion-corrected density functional theory method. Different symmetries were identified in the structural evolution with increased pressure, but no motif transition was observed, owing to the stability of the herringbone (HB) motif for small polycyclic aromatic hydrocarbons. Hirshfeld surface analysis determined that there was an increase in the fraction of H···π and π···π contacts within the high pressure structures, while the fraction of H···H contacts was lowered via geometric rearrangements. It was found that isostatic pressure alone, up to 25 GPa, was not sufficient to induce a chemical reaction due to the poor π-orbital overlap existing within the HB motif. However, the applied pressure sets the stage for an activated chemical reaction when the molecules approach each other along the long molecular axis, with a reaction energy and reaction barrier of 1.05 eV and 1.80 eV per molecular unit, respectively.
X-ray Raman scattering provides evidence for interfacial acetonitrile-water dipole interactions in aqueous solutions
Authors: Huang Ningdong , Nordlund Dennis , Huang Congcong , Bergmann Uwe , Weiss Thomas M. , Pettersson Lars G. M. , Nilsson Anders
Published: October 2011

Aqueous solutions of acetonitrile (MeCN) have been studied with oxygen K-edge x-ray Raman scattering (XRS) which is found to be sensitive to the interaction between water and MeCN. The changes in the XRS spectra can be attributed to water directly interacting with MeCN and are reproduced by density functional theory calculations on small clusters of water and MeCN. The dominant structural arrangement features dipole interaction instead of H-bonds between the two species as revealed by the XRS spectra combined with spectrum calculations. Small-angle x-ray scattering shows the largest heterogeneity for a MeCN to water ratio of 0.4 in agreement with earlier small-angle neutron scattering data.
Vibrational spectroscopy of water in hydrated lipid multi-bilayers. II. Two-dimensional infrared and peak shift observables within different theoretical approximations
Authors: Gruenbaum Scott M. , Pieniazek Piotr A. , Skinner J. L.
Published: October 2011

In a previous report, we calculated the infrared absorption spectrum and both the isotropic and anisotropic pump-probe signals for the OD stretch of isotopically dilute water in dilauroylphosphatidylcholine (DLPC) multi-bilayers as a function of the lipid hydration level. These results were then compared to recent experimental measurements and are in generally good agreement. In this paper, we will further investigate the structure and dynamics of hydration water using molecular dynamics simulations and calculations of the two-dimensional infrared and vibrational echo peak shift observables for hydration water in DLPC membranes. These observables have not yet been measured experimentally, but future comparisons may provide insight into spectral diffusion processes and hydration water heterogeneity. We find that at low hydration levels the motion of water molecules inside the lipid membrane is significantly arrested, resulting in very slow spectral diffusion. At higher hydration levels, spectral diffusion is more rapid, but still slower than in bulk water. We also investigate the effects of several common approximations on the calculation of spectroscopic observables by computing these observables within multiple levels of theory. The impact of these approximations on the resulting spectra affects our interpretation of these measurements and reveals that, for example, the cumulant approximation, which may be valid for certain systems, is not a good approximation for a highly heterogeneous environment such as hydration water in lipid multi-bilayers.
Opportunities of deoxyribonucleic acid complexes composites for nonlinear optical applications
Authors: Sahraoui B. , Pranaitis M. , Gindre D. , Niziol J. , Kažukauskas V.
Published: October 2011

In this paper, we illustrate new functionalities for nonlinear optical applications of bio-molecular systems. This study presents DNA complex with new ionic surfactants. These surfactants enabled DNA solubility in solvents other than alcohols, like aromatic and chlorinated ones. Composites with two nonlinear optical (NLO) active dyes are subjects of the second and third harmonic generation experiments. The found effective nonlinear susceptibilities values are much higher than that for standard fused silica. We also demonstrate any influence of the surfactant on NLO properties.
Concurrent electromigration and creep in lead-free solder
Authors: Pharr Matt , Zhao Kejie , Suo Zhigang , Ouyang Fan-Yi , Liu Pilin
Published: October 2011

When electric current flows in a solder bump, electromigration generates stress, but creep relaxes it. After some time, the bump develops a steady-state stress field. We present a theory to show that the two processes — electromigration and creep — set an intrinsic length. When the intrinsic length is large compared to the height of the bump, electromigration is fast relative to creep and the steady-state stress field is linearly distributed in the bump. When the intrinsic length is small compared to the height of the bump, electromigration is slow relative to creep and the steady-state stress field nearly vanishes in the bump, except in a thin layer along the boundary of the bump. We further show that a critical electric current exists, below which the bump can sustain the steady-state stress field without forming voids. Theoretical predictions are compared with existing experimental observations.
Aligned and exchange-coupled FePt-based films
Authors: Liu Y. , George T. A. , Skomski Ralph , Sellmyer D. J.
Published: October 2011

Two-phase nanostructures of hard L10-ordered FePt and soft iron-rich fcc Fe-Pt are investigated experimentally and by model calculations. The Fe-Pt thin films were produced by epitaxial co-sputtering onto MgO and have a thickness of about 10 nm. They form two-phase dots that cover a large fraction of the surface but are separated from each other. X-ray diffraction and TEM show that the c-axis of the phase FePt is aligned in the direction normal to the film plane. The experimental and theoretical hysteresis loops indicate archetypical exchange coupling, and excellent magnetic properties are obtained. The largest values of coercivity, saturation magnetization, and nominal energy product obtained in the samples studied are 51 kOe, 1287 emu/cc, and 54 MGOe, respectively.
Microwave evaluation of Pb0.4Sr0.6TiO3 thin films prepared by magnetron sputtering on silicon: Performance comparison with Ba0.3Sr0.7TiO3 thin films
Authors: Ponchel F. , Lei X. , Rémiens D. , Wang G. , Dong X.
Published: October 2011

Pb0.4Sr0.6TiO3 (PST) thin films were deposited on high resistivity silicon substrate by radio frequency magnetron sputtering. A pure perovskite phase was obtained at a low post annealing temperature of 650 °C. The relative dielectric constant, loss factor, tenability, and figure of merit were determined over a large frequency range of 1 GHz to 60 GHz. A large tunability about 60% and a relatively low loss of 16% at 60 GHz were obtained. PST is an alternative material for microwave agile devices integrated with silicon and this is discussed from the standpoint of monolithic integration with a low thermal budget.
Miniaturized concentration cells for small-scale energy harvesting based on reverse electrodialysis
Authors: Banan Sadeghian Ramin , Pantchenko Oxana , Tate Daniel , Shakouri Ali
Published: October 2011

We describe experimental and theoretical results that demonstrate the feasibility of power generation using concentration cells based on ionic concentration gradients and reverse electrodialysis. A peak power density of 0.2 (0.7) μW cm−2 and a maximum energy density of 0.4 (0.4) mJ cm−3 delivered in 3 h to a 2 (5) kΩ resistor were recorded using a microfiltration (anion exchange) membrane, respectively. A comprehensive model is developed to predict the evolution of the output voltage with time in relation to the solute concentration in each cell and derive the power density and efficiency limits.
Influence of high temperature AlN buffer on optical gain in AlGaN/AlGaN multiple quantum well structures
Authors: Gong Y. P. , Xing K. , Wang T.
Published: October 2011

Standard stripe-length dependent optical-pumping measurements have been performed on AlGaN/AlGaN multiple quantum wells (MQWs) on an AlN buffer grown using two different kinds of technologies, i.e., “GaN interlayer” and “porous AlN buffer.” The net modal gains of the two samples along both m- and a-axis have been obtained, showing that the net modal gain of the MQWs on the AlN grown using “GaN interlayer” is higher than that on the AlN grown using “porous AlN buffer.” Reciprocal space mapping measurements have indicated that the MQW structure on the AlN structure grown using “GaN interlayer” is fully strained while that on the AlN grown using “porous AlN buffer” is partially strain-relaxed. The net modal gain along the m-axis is higher than that along the a-axis in both samples, highly reasonably indicating that the most favourable orientation for forming the cavity facets is not 〈11-20〉 direction of c-plane sapphire, along which III-nitride on c-plane sapphire is normally cleaved.
Temperature dependance of the tunneling density of states in sub-micron planar metal/oxide/graphene junctions
Authors: Hacohen-Gourgy S. , Diamant I. , Almog B. , Dubi Y. , Deutscher G.
Published: October 2011

We present the tunneling measurements of sub-micron metal/insulator/graphene planar tunnel junctions up to room temperature. We observe a gate independent gap, as previously observed only by low temperature STM [Y. Zhang et al., Nat. Phys. 4, 627 (2008)]. No gap appears at temperatures above 150 K, which is four times smaller than the theoretically expected Tc, from the accepted mean field model [T. O. Wehling et al., Phys. Rev. Lett. 101, 216803 (2008)]. We show that taking into account an additional vibrational effect of out-of-plane phonon soft modes the gap may disappear from the measurements at temperatures much lower than the calculated Tc.
Amplitude and phase of shaped nonlinear excitation fields in a four-wave mixing microscope
Authors: Raghunathan Varun , Nikolaenko Alexei , Chung Chao-Yu , Potma Eric O.
Published: October 2011

We describe precise measurements of the amplitude and phase profiles of tightly focused nonlinear excitation fields in a four-wave mixing (FWM) microscope. By combining spatial light modulator based beam shaping with interferometric detection, we present the focal FWM excitation fields of various Hermite-Gaussian and Laguerre-Gaussian LG01 beam modes. We observe well-defined spatial phase patterns for the focal fields associated with these beam modes. Such precise measurements of shaped nonlinear excitation fields have implications for the development of resolution enhancement schemes and tip-enhanced imaging methods in FWM microscopy.
Time-frequency analysis for microwave reflectometry data processing in the HL-2A tokamak
Authors: Zhong W. L. , Shi Z. B. , Zou X. L. , Ding X. T. , Huang X. L. , Dong Y. B. , Liu Z. T. , Xiao W. W. , Ji X. Q. , Cui Z. Y. , Liu Yi , Yan L. W. , Yang Q. W. , Duan X. R.
Published: October 2011

The Choi-Williams distribution (CWD) technique is introduced as a time-frequency tool for processing data measured from the new developed homodyne and the fixed frequency reflectometry in the HL-2A tokamak. The comparison between spectrogram and CWD for the simulated signal is presented. It indicates that the CWD can greatly improve the representation of the time-frequency content of the multi-components signal. Its effectiveness is demonstrated through two applications in HL-2A, which are the extraction of beat frequencies from the frequency modulated-continuous wave reflectometry (FM-CW) and the characterizing of the fluctuations. The density profile inversed from the group delay of the FM-CW and the density fluctuations deduced from the fixed-frequency reflectometry would be more reliable and accurate by using the CWD technique.
Note: Continuing improvements on the novel flat-response x-ray detector
Authors: Li Zhichao , Zhu Xiaoli , Jiang Xiaohua , Liu Shenye , Zheng Jian , Li Sanwei , Wang Zhebin , Yang Dong , Zhang Huan , Guo Liang , Xin Jiang , Song Tianming , Ding Yongkun
Published: October 2011

This note describes multi-updates of the novel flat-response x-ray detector in fabrication technology, experimental application, and data uncertainty evaluation. Unlike the previous design, the compound filter is combined into one piece through an improved fabrication process that greatly enhanced its self-supporting capability. A method of pinhole-array imaging is introduced into the experimental application process to stop any debris from the hohlraum and to uniformly reduce the radiation flux. The experimental results show that this method works well. Furthermore, a method of uncertainty evaluation of the radiation flux measurement by the novel flat-response x-ray detector has been developed. The influence of the radiation spectrum to the flux measurement is analyzed. The evaluation shows that the relative uncertainty of the radiation flux is about 10% in higher radiation temperature condition (Tr > 150 eV) and 16% in lower radiation temperature condition (Tr < 100 eV).
2-Chloro-2,2-difluoracetamide (ClF2CC(O)NH2). Thermal Decomposition, Vapour Infrared, Mass Spectrometry, Low-temperature NMR, and Theoretical Studies. Solvent Effects on Conformational Preferences
Authors: Iriarte Ana G. , Cutin Edgardo H. , Argüello Gustavo A.
Published: October 2011

Gas-phase thermal decomposition of 2-chloro-2,2-difluoracetamide (CDFA) was studied at temperatures between 270 and 290°C. The rate constant for the decomposition follows the Arrhenius equation. Mass spectrometry was used to analyze the decomposition pattern of the title compound. The FT-IR spectrum of the vapour phase and the infrared spectra of CDFA in protic and aprotic solvents were recorded. Potential energy surfaces were studied by theoretical calculations performed at the density functional theory level (PBEPBE and B3LYP methods) using the 6-31G*, 6-31+G*, 6-311+G**, aug-cc-pVDZ, and aug-cc-pVTZ basis sets.
Synthesis and Evaluation of Potentially Transdermal Morphine Derivatives
Authors: Young Jacqui F. , Thienthong Neeranat , Hearn Milton T. W. , Robinson Andrea J. , Jackson W. Roy
Published: October 2011

Three new morphine-based compounds bearing arginyl moieties, compounds 7, 9a, and 9b, have been synthesized using solid phase and solution phase techniques with the aim of obtaining new transdermal analgesics. Preliminary biological assays have shown that these compounds have a relatively high affinity for opioid receptors, achieving ≥94 % inhibition of radioligand binding at a concentration of 10 µM in non-selective opioid binding assays. Further testing on two of the analogues, 9a and 9b, demonstrated that these compounds were acting as agonists, rather than antagonists, at the opioid receptors and 9b achieved the significant result of 73 % inhibition of contractile responses in the electrically stimulated guinea pig ileum assay at a concentration of 30 µM. Unfortunately, none of the molecules showed evidence of transdermal activity.
Oxygen Exchange During the Reaction of POCl3 and Water
Authors: Thomas Andrew O. , Milham Paul J. , Morrison R. John , Clark Robert G. , Alvarez Rebeca
Published: October 2011

To investigate O exchange during the reaction of POCl3 and water, natural abundance POCl3 was reacted with water highly enriched in 18O, and the resulting H3PO4 was isolated as KH2PO4. This reaction was conducted with and without tetrahydrofuran (THF) as a solvent, and was controlled in THF and violent in its absence. Approximately 5 × 10–4 M aqueous solutions of the KH2PO4 were analyzed using electrospray ionization mass spectrometry, to estimate the proportions of the mass-clumped 16,17,18O isotope analogues of [H2PO4]–. During analysis, ~29 % of [H2PO4]– dehydrated to [PO3]–, for which the proportions of the O isotope analogues were also measured. These proportions were compared with those predicted for O exchange at either four or three positions on the P atom of POCl3. The data strongly support O exchange at all four positions, whether or not THF was used to moderate conditions during the reaction. This result clears the way for safe, predictable synthesis of heavy-O labelled orthophosphate from POCl3 and 18O enriched water for evaluation as an environmental and biochemical tracer.
Recent Highlights in the use of Lanthanide-directed Synthesis of Novel Supramolecular (Luminescent) Self-assembly Structures such as Coordination Bundles, Helicates and Sensors
Authors: Lincheneau Christophe , Stomeo Floriana , Comby Steve , Gunnlaugsson Thorfinnur
Published: October 2011

In this short review, we focus on the recent developments within the field of coordination chemistry where mono- or multimetallic supramolecular self-assemblies are formed by employing structurally defined organic ligands, taking advantage of the high coordination requirements of the lanthanides. Such synthesis results in the formation of both structurally complex and beautiful self-assemblies. Moreover, as the lanthanide ions possess both unique magnetic (e.g. GdIII and DyIII) and luminescent properties, either in the visible (EuIII, SmIII and TbIII) or near-infrared regions (YbIII, NdIII, ErIII), these physical features are usually transferred to the self-assemblies themselves, allowing the formation of highly functional structures, such as coordination networks, as well as molecular bundles and helicates. Hence, examples of the use of lanthanide-directed synthesis of luminescent sensors, some of which are formed on solid surfaces such as gold (flat surface or nanoparticles), and imaging agents are presented. Moreover, we demonstrate that by using chiral organic ligands, lanthanide-directed synthesis can also give rise to the formation of enantiomerically pure self-assemblies, the structure of which can be probed using circularly polarized luminescence.
Effect of surface roughness on adhesion of graphene membranes
Authors: Gao Wei , Huang Rui
Published: October 2011

To integrate graphene in functional devices, it is essential to understand interfacial adhesion between graphene and surrounding materials for mechanical support and encapsulation. In complement with recent efforts aiming to measure the adhesion energy experimentally, we present a theoretical model to predict how the surface roughness may affect the adhesion between graphene membranes and their substrates. It is found that the bending modulus, which increases drastically from monolayer to multilayered graphene, plays an important role in the transition from conformal to non-conformal morphology of the graphene membranes on a corrugated surface. As such, the work of adhesion drops considerably from monolayer to bilayer graphene, in good agreement with recent measurements. Moreover, the theoretical results suggest that tunable adhesion of graphene can be achieved by controlling the surface roughness of the substrate.
Magnetic orientation in advanced recording media
Authors: Chureemart J , Chureemart P , Evans R , Chantrell R W , Grady K O'
Published: October 2011

The purpose of this work is to determine the distribution of easy axis orientation in advanced perpendicular recording media capable of supporting a high areal density of 400–500 Gbits inch−2. The distribution of easy axis orientation has been investigated via the measurement of the variation of coercivity H
C with angle to the perpendicular to the film plane. At H
C there is no effect from the strong demagnetizing field. Simulations based on the assumption that each grain reverses coherently are compared with the experimental results. We find that the value of coercivity is reduced approximately 10–13% with a variation of angle to the perpendicular of 10°. The standard deviation of the distribution of the easy axis directions is between 5° and 7°.
Transient CHI start-up simulations with the TSC
Authors: Raman R. , Jardin S.C. , Menard J. , Jarboe T.R. , Bell M. , Mueller D. , Nelson B.A. , Ono M.
Published: October 2011

Transient coaxial helicity injection (CHI) has been successfully used in the helicity injected torus-II and the National Spherical Torus Experiment (NSTX) for a demonstration of closed-flux current generation without the use of the central solenoid. The Tokamak Simulation Code (TSC) has now been used to understand the scaling of CHI generated toroidal current with variations in the external toroidal field and injector flux. These simulations show favourable scaling of the CHI start-up process with increasing machine size. Closed flux in TSC is achieved as a result of the decaying CHI discharge that induces a positive loop voltage generating the initial closed-flux current.