bluuebunny/crossref_metadata_2025 huggingface dataset:
Withdrawing interferon-α from psychiatric patients: clinical care or unjustifiable stigma?
Authors: Spennati A. , Pariante C. M.
Published: September 2012

IFN-α is an effective therapy for chronic viral hepatitis C and today still represents an effective first-line treatment. Unfortunately, its use is associated with a number of side-effects, including psychiatric problems like depression, mania, psychosis, delirium and other cognitive disturbances. Clinicians have been concerned about the risks of worsening of pre-existent psychiatric disorders and of precipitating suicidal attempts in psychiatric patients. The presence of a mental illness is, therefore, often deemed to be a contraindication to the use of antiviral treatment. However, this amounts to stigmatization and discrimination, as it basically implies withholding a life-saving medical treatment because of a psychiatric diagnosis. Is this clinically and socially acceptable? With novel treatments now entering clinical practice as adjuvant to IFN-α, it is particularly important to make a statement now, to ensure that psychiatric patients are not left behind. The aim of this editorial is to critically discuss this notion, by reviewing the few studies (n = 14) that have indeed administered IFN-α to patients with a pre-existing psychiatric disorder. We find evidence that these patients have rates of treatment adherence and sustained virological response similar to those of non-psychiatric patients, and that their IFN-α-induced psychiatric symptoms respond successfully to clinical management. We conclude that there is no support to withdrawing IFN-α therapy from psychiatric patients.
Early motor developmental milestones and level of neuroticism in young adulthood: a 23-year follow-up study of the Copenhagen Perinatal Cohort
Authors: Flensborg-Madsen T. , Sørensen H. J. , Revsbech R. , Mortensen E. L.
Published: September 2012

Background

Studies investigating early developmental factors in relation to psychopathology have mainly focused on schizophrenia. The personality dimension of neuroticism seems to be a general risk factor for psychopathology, but evidence on associations between early developmental precursors and personality traits is almost non-existent. This study is therefore the first to investigate associations between early motor developmental milestones and neuroticism in adulthood.

Method

Mothers of 9125 children of the Copenhagen Perinatal Cohort recorded 12 developmental milestones during the child's first year of life. A subsample of the cohort comprising 1182 individuals participated in a follow-up when they were aged 20–34 years and were administered the Eysenck Personality Questionnaire (EPQ). Associations between motor developmental milestones and level of neuroticism, extraversion and psychoticism were analysed by multiple linear regression adjusting for for sex, single-mother status, parity, mother's age, father's age, parental social status and birth weight.

Results

Among the 1182 participants with information on the EPQ, information on milestones was available for 968 participants. Infants who developed high levels of neuroticism as adults tended to sit without support, crawl, and walk with and without support significantly later than individuals with low levels of neuroticism (pvalues <0.05). These results remained significant after adjustment for the included covariates and for adult intelligence.

Conclusions

The findings are the first of their kind and suggest that delays in early motor development may not only characterize psychopathological disorders such as schizophrenia, but may also be associated with the personality dimension of neuroticism in adulthood.
COST-EFFECTIVENESS OF EXERCISE PROGRAMS IN TYPE 2 DIABETES
Authors: Coyle Doug , Coyle Kathryn , Kenny Glen P. , Boulé Normand G. , Wells George A. , Fortier Michelle , Reid Robert D. , Phillips Penny , Sigal Ronald J.
Published: September 2012

Background: A randomized controlled trial has shown that supervised, facility-based exercise training is effective in improving glycemic control in type 2 diabetes. However, these programs are associated with additional costs. This analysis assessed the cost-effectiveness of such programs.

Methods: Analysis used data from the Diabetes Aerobic and Resistance Exercise (DARE) clinical trial which compared three different exercise programs (resistance, aerobic or a combination of both) of 6 months duration with a control group (no exercise program). Clinical outcomes at 6 months were entered for individual patients into the UKPDS economic model for type 2 diabetes adapted for the Canadian context. From this, expected life-years, quality-adjusted life-years (QALYs) and costs were estimated for all patients within the trial.

Results: The combined exercise program was the most expensive ($40,050) followed by the aerobic program ($39,250), the resistance program ($38,300) and no program ($31,075). QALYs were highest for combined (8.94), followed by aerobic (8.77), resistance (8.73) and no program (8.70). The incremental cost per QALY gained for the combined exercise program was $4,792 compared with aerobic alone, $8,570 compared with resistance alone, and $37,872 compared with no program. The combined exercise program remained cost-effective for all scenarios considered within sensitivity analysis.

Conclusions: A program providing training in both resistance and aerobic exercise was the most cost-effective of the alternatives compared. Based on previous funding decisions, exercise training for individuals with diabetes can be considered an efficient use of resources.
EARLY AWARENESS AND ALERT SYSTEMS FOR MEDICAL TECHNOLOGIES IN ISRAEL
Authors: Tal Orna , Hakak Nina
Published: September 2012

Background: Throughout the world, decision makers face the need to plan on the basis of uncertainty. Prospective updates on future trends of medical technology usage are tools to improve national health status. In Israel, this challenge is met by several steps taken to promote insight into the realm of emerging technologies. Israel's unique horizon strategy refers to three time spans: the immediate to short-term (for the coming year) updating the National List of Health Services (NLHS) and quarterly scanning; the medium-term (3 years to a decade) revitalizing hospital devices and infrastructure; and long-term planning (over a decade), such as the “Health Israel 2020 Project”.

Methods: A description of the Israeli setup of different time spans and tiers.

Results: The matrix of players, loci, interests, population groups, and incentives creates a complex situation and the Ministry of Health has to regulate the different suppliers and tiers of insurance (obligatory, supplementary, and private), balancing need, equity, and cost containment in preparing for future health care. However, preparedness is not a sterile laboratory and is pervaded by numerous dilemmas and the search for adequate evidence for new less mature technologies is an on-going challenge.

Conclusion: Bridging the forecasting chasm for the future requires analyzing needs, reinforcing evidence and seeing “around the corner” when synergizing between all the “actors” in the national arena. Expert consultation and international cooperation with similar horizon organizations can assist in paving the way for more successful planning efforts for future medical technology implementation.
HEALTH TECHNOLOGY REASSESSMENT OF NON-DRUG TECHNOLOGIES: CURRENT PRACTICES
Authors: Leggett Laura , Noseworthy Tom W. , Zarrabi Mahmood , Lorenzetti Diane , Sutherland Lloyd R. , Clement Fiona M.
Published: September 2012

Objectives: Obsolescence is a natural phase of the lifecycle of health technologies. Given increasing cost of health expenditures worldwide, health organizations have little choice but to engage in health technology reassessment (HTR); a structured, evidence-based assessment of the medical, social, ethical, and economic effects of a technology, currently used within the healthcare system, to inform optimal use of that technology in comparison to its alternatives. This research was completed to identify and summarize international HTR initiatives for non-drug technologies.

Methods: A systematic review was performed using the terms disinvestment, obsolescence, obsolete technology, ineffective, reassessment, reinvestment, reallocation, program budgeting, and marginal analysis to search PubMED, MEDLINE, EMBASE, and CINAHL until November 2011. Websites of organizations listed as members of INAHTA and HTAi were hand-searched for gray literature. Documents were excluded if they were unavailable in English, if the title/abstract was irrelevant to HTR, and/or if the document made no mention of current practices. All citations were screened in duplicate with disagreements resolved by consensus.

Results: Sixty full-text documents were reviewed and forty were included. One model for reassessment was identified; however, it has never been put into practice. Eight countries have some evidence of past or current work related to reassessment; seven have shown evidence of continued work in HTR. There is negligible focus on monitoring and implementation.

Conclusions: HTR is in its infancy. Although health technology reassessments are being conducted, there is no standardized approach. Future work should focus on developing and piloting a comprehensive methodology for completing HTR.
Mindfulness for Paranoid Beliefs: Evidence from Two Case Studies
Authors: Ellett Lyn
Published: September 2012

Background: Emerging evidence suggests that mindfulness can be beneficial for people with distressing psychosis. This study examined the hypothesis that for people with persecutory delusions in the absence of voices, mindfulness training would lead to reductions in conviction, distress, preoccupation and impact of paranoid beliefs, as well as anxiety and depression. Method: Two case studies are presented. Participants completed measures of mindfulness, anxiety and depression at baseline, end of therapy and 1 month follow-up, and bi-weekly ratings of their paranoid belief on the dimensions of conviction, preoccupation, distress and impact. Results: Ratings of conviction, distress, impact and preoccupation, and measures of anxiety and depression, reduced for both participants from baseline to end of intervention. Improvements in mindfulness of distressing thoughts and images occurred for both participants. These gains were maintained at 1 month follow-up. Conclusions: Findings suggest that mindfulness training can impact on cognition and affect specifically associated with paranoid beliefs, and is potentially relevant to both Poor Me and Bad Me paranoia.
QUADRATIC LABOR ADJUSTMENT COSTS, BUSINESS CYCLE DYNAMICS, AND OPTIMAL MONETARY POLICY
Authors: Lechthaler Wolfgang , Snower Dennis J.
Published: September 2012

We build quadratic labor adjustment costs into an otherwise standard New Keynesian model of the business cycle and show that this increases output persistence in a vein similar to that of other models of labor market frictions. Furthermore, we demonstrate the implication of quadratic labor adjustment costs for monetary policy. We show that there is a simple rule determining whether quadratic labor adjustment costs imply a trade-off between stabilizing inflation and output.
SOCIAL CAPITAL, TRUST, AND MULTIPLE EQUILIBRIA IN ECONOMIC PERFORMANCE
Authors: Growiec Katarzyna , Growiec Jakub
Published: September 2012

We propose a novel mechanism giving rise to poverty traps and multiple equilibria in economic performance. It is a potentially important source of persistent underdevelopment across countries and regions. At the core of this mechanism, bridging social capital and social trust feed back on each other, interdependently affecting individuals' earnings and subjective well-being. High trust and abundant bridging social capital reinforce each other, leading to a “high” equilibrium where both these variables take persistently high values, and earnings and well-being are high as well, whereas low trust and lack of bridging social capital create a vicious circle, leading to a “low trust trap” where all these variables are persistently low. The workings of our theoretical model are in agreement with a wide range of findings from the contemporary literature in sociology and social psychology.
Blickbewegungen beim Lesen, Leseentwicklung und Legasthenie
Authors: Radach Ralph , Günther Thomas , Huestegge Lynn
Published: September 2012

Zusammenfassung: In den letzten Jahrzehnten hat sich die Messung und Analyse von Blickbewegungen mehr und mehr zur einer Standardmethode für die Untersuchung des Lesens und der Leseentwicklung im Kindesalter entwickelt. Im vorliegenden Artikel werden zunächst einige grundlegende Erkenntnisse zur Dynamik des Lesens aus der Sicht der Blickbewegungsforschung skizziert. Auf dieser Grundlage erfolgt eine Darstellung wichtiger Aspekte der normalen und gestörten Leseentwicklung. Dabei wird vertiefend auf Befunde zu Blickbewegungen von Kindern mit Legasthenie eingegangen, die zum Teil widersprüchlich sind und in der Literatur kontrovers diskutiert werden. Hieraus ergeben sich Empfehlungen für die weitere Forschung bezüglich der Identifikation visuomotorischer Defizite, der Informationsaufnahme innerhalb der Blickspanne sowie die Verarbeitung phonologischer und räumlicher Information. Abschließend wird eine leseähnliche Scanningaufgabe vorgestellt, mit der die nichtsprachlichen Anforderungen des Lesens gut approximiert werden können. Damit kann die Frage untersucht werden, ob abweichende Blickbewegungen bei Legasthenie auch durch Faktoren wie visuelle Informationsverarbeitung und Aufmerksamkeit, Blicksteuerung oder räumliche Navigation mitverursacht sein können.
Zweite Wahl oder Selbstverwirklichung?
Authors: Dütschke Elisabeth , Boerner Sabine
Published: September 2012

Flexible Beschäftigungsverhältnisse wie Zeitarbeit und freie Mitarbeit weisen hohe Zuwachsraten auf. Bisher ist aber noch wenig darüber bekannt, wie die Betroffenen diese Beschäftigungsformen bewerten. Der vorliegende Aufsatz definiert zunächst das Konstrukt der Präferenz für flexible Beschäftigung, um die Bewertung dieser Beschäftigungsform operationalisierbar zu machen. Dann werden das Konstrukt der Präferenz sowie mögliche Korrelate zunächst im Rahmen einer Interviewstudie (n = 26) analysiert. Im Anschluss daran werden Hypothesen entwickelt und anhand einer quantitativen Befragung von n = 197 flexibel Beschäftigten geprüft. Hierbei zeigt sich, dass die Persönlichkeitseigenschaft Offenheit für Erfahrung sowie die Einstellungen Arbeitszufriedenheit und Identifikation mit dem Beruf in signifikantem Zusammenhang mit der Präferenz für flexible Beschäftigung stehen.
FEMIA–Fragebogen zur Erfassung von Merkmalen interaktiver Arbeitstätigkeiten im Einzelhandel
Authors: Pietrzyk Ulrike , Rodehacke Sarah , Hacker Winfried
Published: September 2012

Der Fragebogen zur Erfassung von Merkmalen interaktiver Arbeitstätigkeiten (FEMIA, Melzer, 2007 , 2011 ) wurde speziell zur bedingungsbezogenen Analyse, Bewertung und Gestaltung von Einzelhandelstätigkeiten entwickelt. Ziel der vorliegenden Untersuchung ist es, die Gütekriterien des Instrumentes zu überprüfen. Die Ergebnisse weisen auf eine insgesamt zufriedenstellende Reliabilität und Validität sowie gegebene Objektivität hin. Das Verfahren erfasst Anforderungen von waren- und interaktionsbezogenen Teiltätigkeiten und kann somit kundenferne monologische Arbeit im Falle der Selbstbedienung sowie bedienungs- und beratungsintensive Arbeit am Kunden abbilden. Durch die Anknüpfung an die in den internationalen Normen geforderten Merkmale gut gestalteter Aufgaben ( DIN EN ISO 6385 ) kann das Instrument künftig auch zur gesetzlich geforderten ganzheitlichen Gefährdungsbeurteilung eingesetzt werden. Der FEMIA kann im Sinne der Gefährdungsbeurteilung Hinweise auf Gestaltungserfordernisse geben.
Small molecules aimed at type III secretion systems to inhibit bacterial virulence
Authors: Tsou Lun K. , Dossa Paul D. , Hang Howard C.
Published: September 2012

The development of new anti-bacterial compounds presents a major challenge to modern medicine as bacterial strains resistant to traditional antibiotics are constantly emerging.
Osteopontin alters the functional profile of porcine microgliain vitro
Authors: Tambuyzer Bart R. , Casteleyn Christophe , Vergauwen Hans , Van Cruchten Steven , Van Ginneken Chris
Published: September 2012

OPN (osteopontin) is a secreted glycoprotein predominantly expressed in bone matrix and kidney tissue. More recently, a neuroprotective role has been attributed to this cytokine since it can be up‐regulated by microglia in neurodegeneration and inflammation. We demonstrate the expression of OPN within primary cultured microglia. Microglia incubatedin vitrowith different concentrations (0.1 fM–1 nM) of recombinant OPN showed increased proliferation at 10 fM. Moreover, conditioned medium of LLC‐PK1 cells, a pig renal epithelial cell line and a known source of secreted OPN, more than doubled the rate of proliferation of microglia. Addition of an anti‐OPN polyclonal antibody completely reversed this effect. Treatment with OPN dose‐dependently also inhibited microglial superoxide production. In contrast, phagocytosis of fluorescent‐labelled beads was enhanced by OPN. In conclusion, OPN shifts microglia, at leastin vitro, to an alternative functional profile more fit to the immune‐balanced microenvironment of the CNS (central nervous system).
Calculation of the melting point of alkali halides by means of computer simulations
Authors: Aragones J. L. , Sanz E. , Valeriani C. , Vega C.
Published: September 2012

In this paper, we study the liquid-solid coexistence of NaCl-type alkali halides, described by interaction potentials such as Tosi-Fumi (TF), Smith-Dang (SD), and Joung-Cheatham (JC), and compute their melting temperature (Tm) at 1 bar via three independent routes: (1) liquid/solid direct coexistence, (2) free-energy calculations, and (3) Hamiltonian Gibbs-Duhem integration. The melting points obtained by the three routes are consistent with each other. The calculated Tm of the Tosi-Fumi model of NaCl is in good agreement with the experimental value as well as with other numerical calculations. However, the other two models considered for NaCl, SD and JC, overestimate the melting temperature of NaCl by more than 200 K. We have also computed the melting temperature of other alkali halides using the Tosi-Fumi interaction potential and observed that the predictions are not always as close to the experimental values as they are for NaCl. It seems that there is still room for improvement in the area of force-fields for alkaline halides, given that so far most models are still unable to describe a simple yet important property such as the melting point.
The interplay of the polyelectrolyte-surface electrostatic and non-electrostatic interactions in the polyelectrolytes adsorption onto two charged objects – A self-consistent field study
Authors: Tong Chaohui
Published: September 2012

The continuum self-consistent field (SCF) theory is applied to the study of the adsorption of flexible polyelectrolytes (PEs) onto the surfaces of two parallel and infinitely long charged columns, taking into account the short-range monomer-surface non-Coulombic interaction. Due to the complex interplay between the electrostatic and surface interactions, very interesting PE adsorption behaviors in terms of the degree of charge compensation and the bridging chain conformation are found from the numerical solution of the SCF equations. The screening-enhanced salt effect and the permanent adsorption of PEs, irrespectively of the salt concentration, emerge in the presence of the monomer-surface non-electrostatic interaction. The numerical results reveal that, for relatively weak monomer-surface interactions, the degree of charge compensation decreases with increasing monomer-surface interaction. Numerical result shows that, for the strength of monomer-surface interaction above the desorption-adsorption critical value and in a salt-free solution, the total amount of the adsorbed PE chains is linearly proportional to the surface charge density in the high PE charge fraction regime.
Giant magneto-resistance estimated from direct observation of nanoscale ferromagnetic domain evolution in La0.325Pr0.3Ca0.375MnO3
Authors: Schofield Marvin A. , He Jiaqing , Volkov Vyacheslav V. , Zhu Yimei
Published: September 2012

Using transmission electron microscopy techniques, we directly imaged the magnetic microstructure of La0.325Pr0.3Ca0.375MnO3 samples as a function of applied field. We measured the domain wall width of two types of domain walls present in the sample, the average domain size, and critical field values for onset and completion of domain wall annihilation. Within an intuitive resistor model, we describe the possible magneto-resistance as a function of applied field at constant temperature and show how local spin inhomogeneities contribute directly to the macroscopic GMR properties.
Dynamic mechanisms of generation of oscillatory cluster patterns in a globally coupled chemical system
Authors: Rotstein Horacio G. , Wu Hui
Published: September 2012

We use simulations and dynamical systems tools to investigate the mechanisms of generation of phase-locked and localized oscillatory cluster patterns in a globally coupled Oregonator model where the activator receives global feedback from the inhibitor, mimicking experimental results observed in the photosensitive Belousov-Zhabotinsky reaction. A homogeneous two-cluster system (two clusters with equal cluster size) displays antiphase patterns. Heterogenous two-cluster systems (two clusters with different sizes) display both phase-locked and localized patterns depending on the parameter values. In a localized pattern the oscillation amplitude of the largest cluster is roughly an order of magnitude smaller than the oscillation amplitude of the smaller cluster, reflecting the effect of self-inhibition exerted by the global feedback term. The transition from phase-locked to localized cluster patterns occurs as the intensity of global feedback increases. Three qualitatively different basic mechanisms, described previously for a globally coupled FitzHugh-Nagumo model, are involved in the generation of the observed patterns. The swing-and-release mechanism is related to the canard phenomenon (canard explosion of limit cycles) in relaxation oscillators. The hold-and-release and hold-and-escape mechanisms are related to the release and escape mechanisms in synaptically connected neural models. The methods we use can be extended to the investigation of oscillatory chemical reactions with other types of non-local coupling.
Design principles for plasmonic thin film GaAs solar cells with high absorption enhancement
Authors: Hong Lei , Rusli  , Wang Xincai , Zheng Hongyu , He Lining , Xu Xiaoyan , Wang Hao , Yu HongYu
Published: September 2012

In this paper, a systematic design and analysis of gallium arsenide thin film solar cells incorporated with a periodic silver nanoparticles (NPs) structure to enhance light absorption is presented using the finite element method. The influence of the silver nanoparticles diameter and structure periodicity on light absorption has been examined. It is found that the absorption is significantly enhanced due to the surface plasmon induced by the silver nanoparticles. The optimal structural parameters are achieved when the diameter of the nanoparticles is 200 nm and the periodicity is 444 nm. This gives rise to a maximum ultimate photocurrent of 26.32 mA/cm2 under AM1.5G solar irradiation. In addition, the underlying physics that accounts for the enhancement is discussed.
Polymer microfabrication by scanning based microstereolithography: Optical design and material functionality
Authors: Goswami Ankur , Phani Arindam , Umarji A. M. , Madras Giridhar
Published: September 2012

Several research groups have attempted to optimize photopolymerization parameters to increase the throughput of scanning based microstereolithography (MSL) systems through modified beam scanning techniques. Efforts in reducing the curing line width have been implemented through high numerical aperture (NA) optical setups. However, the intensity contour symmetry and the depth of field of focus have led to grossly non-vertical and non-uniform curing profiles. This work tries to review the photopolymerization process in a scanning based MSL system from the aspect of material functionality and optical design. The focus has been to exploit the rich potential of photoreactor scanning system in achieving desired fabrication modalities (minimum curing width, uniform depth profile, and vertical curing profile) even with a reduced NA optical setup and a single movable stage. The present study tries to manipulate to its advantage the effect of optimized lower [c] (photoinitiator (PI) concentration) in reducing the minimum curing width to ∼10–20 μm even with a higher spot size (∼21.36 μm) through a judiciously chosen “monomer–PI” system. Optimization on grounds of increasing Emax (maximum laser exposure energy at surface) by optimizing the scan rate provides enough time for the monomer or resin to get cured across the entire resist thickness (surface to substrate ∼10–100 μm), leading to uniform depth profiles along the entire scan lengths.
Quantitative evaluation of hidden defects in cast iron components using ultrasound activated lock-in vibrothermography
Authors: Montanini R. , Freni F. , Rossi G. L.
Published: September 2012

This paper reports one of the first experimental results on the application of ultrasound activated lock-in vibrothermography for quantitative assessment of buried flaws in complex cast parts. The use of amplitude modulated ultrasonic heat generation allowed selective response of defective areas within the part, as the defect itself is turned into a local thermal wave emitter. Quantitative evaluation of hidden damages was accomplished by estimating independently both the area and the depth extension of the buried flaws, while x-ray 3D computed tomography was used as reference for sizing accuracy assessment. To retrieve flaw's area, a simple yet effective histogram-based phase image segmentation algorithm with automatic pixels classification has been developed. A clear correlation was found between the thermal (phase) signature measured by the infrared camera on the target surface and the actual mean cross-section area of the flaw. Due to the very fast cycle time (<30 s/part), the method could potentially be applied for 100% quality control of casting components.
Femtosecond pump/supercontinuum-probe setup with 20 kHz repetition rate
Authors: Auböck Gerald , Consani Cristina , Monni Roberto , Cannizzo Andrea , van Mourik Frank , Chergui Majed
Published: September 2012

We developed a fast multichannel detection system for pump-probe spectroscopy, capable of detecting single shot super-continuum spectra at the repetition rate (10–50 kHz) of an amplified femtosecond laser system. By tandem pumping the amplifier with three pump lasers we obtain very low noise operation, with less than 0.1% rms intensity fluctuations at the output of the amplifier. We also propose an alternative way of chopping the pump beam. With a synchronized scanning mirror two spots in the sample are illuminated by the train of pump pulses in an alternating fashion, such that when both spots are interrogated by the probe pulse, the duty cycle of the experiment is doubled.
Cluster formation restricts dynamic nuclear polarization of xenon in solid mixtures
Authors: Kuzma N. N. , Pourfathi M. , Kara H. , Manasseh P. , Ghosh R. K. , Ardenkjaer-Larsen J. H. , Kadlecek S. J. , Rizi R. R.
Published: September 2012

During dynamic nuclear polarization (DNP) at 1.5 K and 5 T, 129Xe nuclear magnetic resonance (NMR) spectra of a homogeneous xenon/1-propanol/trityl-radical solid mixture exhibit a single peak, broadened by 1H neighbors. A second peak appears upon annealing for several hours at 125 K. Its characteristic width and chemical shift indicate the presence of spontaneously formed pure Xe clusters. Microwave irradiation at the appropriate frequencies can bring both peaks to either positive or negative polarization. The peculiar time evolution of 129Xe polarization in pure Xe clusters during DNP can be modelled as an interplay of spin diffusion and T1 relaxation. Our simple spherical-cluster model offers a sensitive tool to evaluate major DNP parameters in situ, revealing a severe spin-diffusion bottleneck at the cluster boundaries and a significant sample overheating due to microwave irradiation. Subsequent DNP system modifications designed to reduce the overheating resulted in four-fold increase of 129Xe polarization, from 5.3% to 21%.
Implicit ligand theory: Rigorous binding free energies and thermodynamic expectations from molecular docking
Authors: Minh David D. L.
Published: September 2012

A rigorous formalism for estimating noncovalent binding free energies and thermodynamic expectations from calculations in which receptor configurations are sampled independently from the ligand is derived. Due to this separation, receptor configurations only need to be sampled once, facilitating the use of binding free energy calculations in virtual screening. Demonstrative calculations on a host-guest system yield good agreement with previous free energy calculations and isothermal titration calorimetry measurements. Implicit ligand theory provides guidance on how to improve existing molecular docking algorithms and insight into the concepts of induced fit and conformational selection in noncovalent macromolecular recognition.
High-power high-efficiency optically pumped semiconductor disk lasers in the green spectral region with a broad tuning range
Authors: Hein A. , Menzel S. , Unger P.
Published: September 2012

Optically pumped semiconductor disk lasers with an infra-red fundamental emission at around 1050 nm are presented. Design and characteristics of the devices are discussed and evaluated. A maximum output power of infra-red radiation of 18 W close to room temperature and rather high slope and differential quantum efficiencies are demonstrated. Utilizing intra-cavity second-harmonic generation in a folded resonator, green optical output powers exceeding 8 W are generated. A maximum total conversion efficiency of 22% and a relatively broad tuning range of 22 nm in the second-harmonic regime are achieved.
Full-zone k.p model for the electronic structure of unstrained GaAs1−xPx and strained AlxIn1−xAs alloys
Authors: Neffati R. , Saïdi I. , Boujdaria K.
Published: September 2012

We analyze the electronic energy band structure of strained and unstrained III-V semiconductors alloys within full-zone k.p approach in order to reach a realistic and minimal k.p model, parametrized to provide an accurate description of both valence and conduction bands. We show that a 40-band k.p model is fairly sufficient to reproduce accurately the overall band structure, obviating the use of any fictitious s* orbital. As an application, the 40-level k.p model is used to describe the band offsets as well as the band parameters in the strained AlxIn1−xAs/AlyGa1−yAs system.
Structure and properties of La-modified Na0.5Bi0.5TiO3 at ambient and elevated temperatures
Authors: Aksel Elena , Forrester Jennifer S. , Foronda Humberto M. , Dittmer Robert , Damjanovic Dragan , Jones Jacob L.
Published: September 2012

The crystal structure and property changes of sodium bismuth titanate (Na0.5Bi0.5TiO3, NBT) piezoelectric ceramics are reported as a function of La modification (0.5–2.0 at. %) and increasing temperature using high resolution x-ray diffraction, permittivity, depolarization, and polarization and strain hysteresis measurements. La substitution is found to decrease the depolarization temperature of NBT (e.g., 1.5 at. % La substitution lowers the depolarization temperature by 60 °C relative to the unmodified composition) with little impact on the room temperature polarization and strain hysteresis. The room temperature structures of the various NBT compositions were modeled using a mixture of the monoclinic Cc space group and the cubic Pm3¯m phase, where the Pm3¯m phase is used to model local regions in the material which do not obey the long range Cc space group. With increasing La substitution, the lattice parameter distortions associated with the Cc phase approached that of the prototypical cubic unit cell and the fraction of the Pm3¯m phase increased. The relationship between these crystallographic changes and the depolarization behavior of La-modified NBT is discussed.
Control of a hybrid wind turbine/battery energy storage power generation system considering statistical wind characteristics
Authors: Shahirinia A. H. , Hajizadeh A. , Yu D. C. , Feliachi A.
Published: September 2012

This paper presents controller design and simulation studies of a hybrid wind turbine/battery energy storage power generation interface to control active and reactive power in distribution systems. First, the modeling of grid-connected hybrid power system was illustrated. A known Weibull distribution presented the wind speed. Further analysis has been considered based on the law of large number and the wind power generated from a closed-form. Power electronic converters used to connect hybrid power system to the AC system. Fuzzy sliding mode controller for the voltage source converter has been presented to control reactive and active powers in the utility grid. In order to verify the proper operation of the proposed controller, a known load profile has been considered. Finally, simulation results have been illustrated to show power flow control capability of the developed control strategy in distribution systems.
Element-specific study of local segmental dynamics of polyethylene terephthalate upon physical aging
Authors: Sato K. , Sprengel W.
Published: September 2012

Time-dependent relaxation processes upon physical aging below the glass transition temperature have been studied in polyethylene terephthalate by high-precision dilatometry (DLT), differential scanning calorimetry (DSC), and element-specific positron and positronium (Ps) annihilation spectroscopy. The macroscopic volume change observed by DLT can be described by the Kohlrausch-Williams-Watts decay function, whereas changes in the relaxation enthalpies evaluated by DSC and free volumes probed by positron and Ps annihilation spectroscopy are reproduced by two superimposed exponentials. The multi-method approach reveals three kinds of relaxation processes with characteristic relaxation times: (a) fast Arrhenius-type β relaxation involving the instantaneous local segmental densification along with the exclusion of oxygen atoms from free volumes, (b) macroscopically observable non-Arrhenius-type α relaxation originated from a distribution of relaxation times due to the heterogeneous dynamics of solid-state- and liquid-state-like local segments, and (c) extremely slow Arrhenius-type α relaxation as the consequence of a uniform relaxation time solely due to the thermal dependence of nanometer-scale solid-state-like local segments.
Spectrally resolved fluorescence lifetime imaging microscope using tunable bandpass filters
Authors: Jeong Hyeong-Jun , Ahn Jin-Woo , Do Dukho , Gweon Dae-Gab
Published: September 2012

A simple structure of spectral fluorescence lifetime imaging microscope (SLIM) is designed with the use of tunable bandpass filter, a kind of Fabry-perot filter that transmission wavelength is varying according to incident angle of light. Feasibility tests of this angle-tuned bandpass filter (ATBF) are performed and it shows high transmission and constant spectral bandwidth (20 nm) with respect to angle of incidence. Furthermore, using two ATBFs in series, spectral bandwidth can be adjustable down to 4 nm. In this paper, dual ATBFs are implemented to the detection part of fluorescence lifetime imaging microscope (FLIM) system so that we obtained spectrally resolved FLIM images. We compare these SLIM images with an original FLIM image and confirm that the former case provides high accuracy to analyze lifetime distribution as well as high contrast of images. The proposed SLIM microscope with good wavelength selectivity has many opportunities to utilize to other applications such as FLIM-Föster resonant energy transfer and autofluorescence imaging.
Fast microtomography using bright monochromatic x-rays
Authors: Jung J. W. , Lee J. S. , Kwon N. , Park S. J. , Chang S. , Kim J. , Pyo J. , Kohmura Y. , Nishino Y. , Yamamoto M. , Ishikawa T. , Je J. H.
Published: September 2012

A fast microtomography system for high-resolution high-speed imaging has been developed using bright monochromatic x-rays at the BL29XU beamline of SPring-8. The shortest scan time for microtomography we attained was 0.25 s in 1.25 μm effective pixel size by combining the bright monochromatic x-rays, a fast rotating sample stage, and a high performance x-ray imaging detector. The feasibility of the tomography system was successfully demonstrated by visualization of rising bubbles in a viscous liquid, an interesting issue in multiphase flow physics. This system also provides a high spatial (a measurable feature size of 300 nm) or a very high temporal (9.8 μs) resolution in radiographs.
Electrothermal instability growth in magnetically driven pulsed power liners
Authors: Peterson Kyle J. , Sinars Daniel B. , Yu Edmund P. , Herrmann Mark C. , Cuneo Michael E. , Slutz Stephen A. , Smith Ian C. , Atherton Briggs W. , Knudson Marcus D. , Nakhleh Charles
Published: September 2012

This paper explores the role of electro-thermal instabilities on the dynamics of magnetically accelerated implosion systems. Electro-thermal instabilities result from non-uniform heating due to temperature dependence in the conductivity of a material. Comparatively little is known about these types of instabilities compared to the well known Magneto-Rayleigh-Taylor (MRT) instability. We present simulations that show electrothermal instabilities form immediately after the surface material of a conductor melts and can act as a significant seed to subsequent MRT instability growth. We also present the results of several experiments performed on Sandia National Laboratories Z accelerator to investigate signatures of electrothermal instability growth on well characterized initially solid aluminum and copper rods driven with a 20 MA, 100 ns risetime current pulse. These experiments show excellent agreement with electrothermal instability simulations and exhibit larger instability growth than can be explained by MRT theory alone.
Controlled axial and radial Te-doping of GaAs nanowires
Authors: Salehzadeh O. , Kavanagh K. L. , Watkins S. P.
Published: September 2012

Tellurium (Te)-doping of Au-catalyzed GaAs nanowires (NWs) grown by metalorganic vapor phase epitaxy (MOVPE) via the vapor-liquid-solid (VLS) mechanism is presented. Electrical measurements were performed inside a scanning electron microscope by contacting a tungsten nanoprobe to the Au end of individual NWs grown on a heavily n-type GaAs substrate. Rectifying current-voltage (I-V) characteristics are observed due to the formation of a junction at the Au nanoparticle (NP)/NW interface. The electron concentration ne and contact barrier heights, φ0b, were determined from the analyses of these characteristics. As expected, φ0b increased (from 0.63 ± 0.03 eV to 0.71 ± 0.02 eV) with decreasing Te-precursor flow rate, corresponding to a decrease in ne from (9 ± 1) × 1017 cm−3 to (1.5 ± 0.5) × 1017 cm−3. Meanwhile, undoped NWs had space-charge-limited characteristics. There was a large influence of the residual gallium (Ga) in the NP, on barrier properties, controlled by the group V precursor flow (on or off) during the cooling of the NW sample at the end of the growth process. With the group V flow off during cooling, a decrease in φ0b from 0.79 ± 0.04 eV to 0.63 ± 0.03 eV is observed consistent with a higher Ga alloy concentration in the NP, confirmed by energy dispersive spectroscopy measurements. We also demonstrate the fabrication of core/shell, undoped/Te-doped, GaAs NWs with very high Te doping (∼1019 cm−3).
Orientational interactions in block copolymer melts: Self-consistent field theory
Authors: Zhao Wei , Russell Thomas P. , Grason Gregory M.
Published: September 2012

We study the phase behavior of diblock copolymer melts with one block possessing orientation-dependent segmental interactions using self-consistent field theory. A generalized coarse-grained description is introduced based on the local (polar) orientational order parameter and K, an effective Frank elastic constant for orientational gradients. To explore the role played by orientational interactions in assembly thermodynamics, we apply the theory to two-dimensional melt morphologies for a range of K. As microphase segregation necessarily introduces splay deformations of the segment orientation, we find that increasing the stiffness K raises the critical χN at the onset of microphase separation. Furthermore, we find that strong orientational interactions in one block give rise to highly asymmetric phase diagrams due to the large penalty for high-splay morphologies, such as the cylindrical phase. Finally, we analyze the costs of inter-segmental splay as well as the size dependence of domain spacing on K based on a strong-segregation picture of morphologies.
Optimized laser pulse profile for efficient radiation pressure acceleration of ions
Authors: Bulanov S. S. , Schroeder C. B. , Esarey E. , Leemans W. P.
Published: September 2012

The radiation pressure acceleration regime of laser ion acceleration requires high intensity laser pulses to function efficiently. Moreover, the foil should be opaque for incident radiation during the interaction to ensure maximum momentum transfer from the pulse to the foil, which requires proper matching of the target to the laser pulse. However, in the ultrarelativistic regime, this leads to large acceleration distances, over which the high laser intensity for a Gaussian laser pulse must be maintained. It is shown that proper tailoring of the laser pulse profile can significantly reduce the acceleration distance, leading to a compact laser ion accelerator, requiring less energy to operate.
Symmetry breaking in linearly coupled Korteweg-de Vries systems
Authors: Espinosa-Cerón A. , Malomed B. A. , Fujioka J. , Rodríguez R. F.
Published: September 2012

We consider solitons in a system of linearly coupled Korteweg-de Vries (KdV) equations, which model two-layer settings in various physical media. We demonstrate that traveling symmetric solitons with identical components are stable at velocities lower than a certain threshold value. Above the threshold, which is found exactly, the symmetric modes are unstable against spontaneous symmetry breaking, which gives rise to stable asymmetric solitons. The shape of the asymmetric solitons is found by means of a variational approximation and in the numerical form. Simulations of the evolution of an unstable symmetric soliton sometimes produce its breakup into two different asymmetric modes. Collisions between moving stable solitons, symmetric and asymmetric ones, are studied numerically, featuring noteworthy features. In particular, collisions between asymmetric solitons with identical polarities are always elastic, while in the case of opposite polarities the collision leads to a switch of the polarities of both solitons. Three-soliton collisions are studied too, featuring quite complex interaction scenarios.
Influence of AlGaN barrier thickness on electrical and device properties in Al0.14Ga0.86N/GaN high electron mobility transistor structures
Authors: Waltereit P. , Bronner W. , Musser M. , Raay F. van , Dammann M. , Cäsar M. , Müller S. , Kirste L. , Köhler K. , Quay R. , Mikulla M. , Ambacher O.
Published: September 2012

We investigate the influence of the AlGaN barrier thickness in Al0.14Ga0.86N/GaN heterostructures on both the electrical properties of the heterostructure itself as well as on high electron mobility transistors fabricated on these structures. With increasing barrier thickness, we observe decreasing sheet resistances, transconductances, and threshold voltages. The observed changes are well-described by modelling. We demonstrate that an increase in the barrier thickness in AlGaN/GaN heterostructures results in an increase in available high-frequency input power swing before turn-on of the Schottky gate. The device long-term stability under direct current stress is not affected by the increase in barrier thickness as shown by on-wafer reliability tests at 150 °C base plate temperature. These results pave the way towards AlGaN/GaN transistors offering high robustness under extreme mismatch conditions as well as excellent high-frequency power performance.
Optical absorption in graphene integrated on silicon waveguides
Authors: Li Huan , Anugrah Yoska , Koester Steven J. , Li Mo
Published: September 2012

To fully utilize graphene's remarkable optical properties for optoelectronic applications, it needs to be integrated in planar photonic systems. Here, we demonstrate integration of graphene on silicon photonic circuits and precise measurement of the optical absorption coefficient in a graphene/waveguide hybrid structure. A method based on Mach-Zehnder interferometry is employed to achieve high measurement precision and consistency, yielding a maximal value of absorption coefficient of 0.2 dB/μm when graphene is located directly on top of the waveguide. The averaged results obtained from a large number of samples agree with theoretical model utilizing the universal ac conductivity in graphene. Our work provides an important guide for the design and optimization of integrated graphene optoelectronic devices.
Electroluminescence and electric current response spectroscopy applied to the characterization of polymer light-emitting electrochemical cells
Authors: Gozzi Giovani , Mendonça Faria Roberto , Fugikawa Santos Lucas
Published: September 2012

Frequency-dependent electroluminescence and electric current response spectroscopy were applied to polymeric light-emitting electrochemical cells in order to obtain information about the operation mechanism regimes of such devices. Three clearly distinct frequency regimes could be identified: a dielectric regime at high frequencies; an ionic transport regime, characterized by ionic drift and electronic diffusion; and an electrolytic regime, characterized by electronic injection from the electrodes and electrochemical doping of the conjugated polymer. From the analysis of the results, it was possible to evaluate parameters like the diffusion speed of electronic charge carriers in the active layer and the voltage drop necessary for operation.
Fabricating high-density magnetic storage elements by low-dose ion beam irradiation
Authors: Neb R. , Sebastian T. , Pirro P. , Hillebrands B. , Pofahl S. , Schäfer R. , Reuscher B.
Published: September 2012

We fabricate magnetic storage elements by irradiating an antiferromagnetically coupled ferromagnetic/nonmagnetic/ferromagnetic trilayer by a low-dose ion beam. The irradiated areas become ferromagnetically coupled and are capable of storing information if their size is small enough. We employ Fe/Cr/Fe trilayers and a 30 keV focused Ga+-ion beam to demonstrate the working principle for a storage array with a bit density of 7  Gbit/in.2. Micromagnetic simulations suggest that bit densities of at least two magnitudes of order larger should be possible.
Optical polarization properties of a nanowire quantum dot probed along perpendicular orientations
Authors: Bulgarini Gabriele , Reimer Michael E. , Zwiller Val
Published: September 2012

We report on the optical properties of single quantum dots in nanowires probed along orthogonal directions. We address the same quantum dot from either the nanowire side or along the nanowire axis via reflection on a micro-prism. The collected photoluminescence intensity from nanowires lying on a substrate is improved 3-fold using the prism as compared to usual collection from the top. More importantly, we circumvent the polarizing effect of the nanowire and access the intrinsic polarization properties of the quantum emitter. Our technique is compatible with the design of complex nanowire devices for the development of quantum opto-electronics.