bluuebunny/crossref_metadata_2025 huggingface dataset:
Body Composition in an Adult Population in Southern Spain: Influence of lifestyle Factors
Authors: Sotillo  , López-Jurado  , Aranda  , López-Frías  , Sánchez  , Llopis
Published: June 2008

The aim of the present study was to assess the body composition in an adult Mediterranean population by two methods, to identify groups at risk for obesity and lifestyle factors that might influence this risk. A cross-sectional study was carried out in Andalusia, a western Mediterranean region in southern Spain. Body composition was studied with anthropometric methods and bioelectric impedance analysis (BIA) in a random sample of 394 subjects (169 men, 225 women) between 20 and 60 years of age. When anthropometric methods were used, we found that 19.4% of the individuals had a body mass index (BMI) ≥ 30 kg/m2. In 46.2% of the men, more than 25% of the body weight consisted of fat, and in 74.1% of the women, more than 30% of the body weight consisted of fat. When BIA data were used, these values rose to 34.7% and 60.6% for men and women respectively. After controlling for sex, age correlated directly with percentage of body fat when skinfold thickness (r = 0.58) or BIA (r = 0.40) was used. In smokers, the number of cigarettes/day correlated directly with waist circumference (r = 0.76), after controlling for both age and sex. We found high percentages of obesity regardless of the indicator or method used, particularly in women. Factors such as sex, age, leisure-time physical exercise, educational level, and smoking appeared to influence obesity. The factors that made the greatest contribution to the rates of obesity and high waist-hip ratio were the age, time spent exercising, and educational level. In contrast, the risk of high body fat (as determined with both methods) was associated only with sex and age.
Dose–response effects of sotalol on cardiovascular function in conscious, freely moving cynomolgus monkeys
Authors: Lynch J J , Wilson A W , Hernandez L E , Nelson R A , Marsh K C , Cox B F , Mittelstadt S W
Published: June 2008

Background and purpose:

The non‐selective β‐adrenoceptor antagonist, D,L‐sotalol (sotalol) is commonly employed as a positive control during preclinical cardiovascular safety pharmacology testing, mainly because of its ability to prolong QT interval duration. However, no information appears in the literature, except in abstract form, regarding the dose–response effects of sotalol in unanesthetized monkeys. The current study was conducted to determine the dose– and plasma–response effects of orally administered sotalol on cardiovascular function in conscious non‐human primates.

Experimental approach:

Male cynomolgus monkeys were implanted with telemetry devices and the effects of sotalol hydrochloride (5, 10 and 30 mg kg−1 of body weight, p.o.) on arterial blood pressure, heart rate, body temperature and electrocardiogram waveform were continuously monitored for 6 h after dosing. Blood was sampled for the measurement of plasma concentrations of sotalol.

Key results:

Sotalol dose dependently decreased heart rate and prolonged RR, PR, QT and corrected QT intervals, while having little or no effects on the QRS complex, arterial pressure or body temperature, over the dose range tested. When the data were related to plasma concentrations of sotalol, it was clear that the cardiovascular effects occurred in a similar pattern and to a comparable degree as those reported in human studies.

Conclusions and implications:

The current study helps demonstrate the validity of utilizing telemetry‐instrumented non‐human primates for the cardiovascular safety pharmacology assessment of drugs prior to first‐in‐human testing, and its findings may serve as a reference source for the dose– and plasma–response effects of orally administered sotalol in conscious monkeys.

British Journal of Pharmacology (2008) 154, 1439–1445; doi:10.1038/bjp.2008.206; published online 2 June 2008
Gaddum and LSD: the birth and growth of experimental and clinical neuropharmacology research on 5‐HT in the UK
Authors: Green A R
Published: June 2008

The vasoconstrictor substance named serotonin was identified as 5‐hydroxytryptamine (5‐HT) by Maurice Rapport in 1949. In 1951, Rapport gave Gaddum samples of 5‐HT substance allowing him to develop a bioassay to both detect and measure the amine. Gaddum and colleagues rapidly identified 5‐HT in brain and showed that lysergic acid diethylamide (LSD) antagonized its action in peripheral tissues. Gaddum accordingly postulated that 5‐HT might have a role in mood regulation. This review examines the role of UK scientists in the first 20 years following these major discoveries, discussing their role in developing assays for 5‐HT in the CNS, identifying the enzymes involved in the synthesis and metabolism of 5‐HT and investigating the effect of drugs on brain 5‐HT. It reviews studies on the effects of LSD in humans, including Gaddum's self‐administration experiments. It outlines investigations on the role of 5‐HT in psychiatric disorders, including studies on the effect of antidepressant drugs on the 5‐HT concentration in rodent and human brain, and the attempts to examine 5‐HT biochemistry in the brains of patients with depressive illness. It is clear that a rather small group of both preclinical scientists and psychiatrists in the UK made major advances in our understanding of the role of 5‐HT in the brain, paving the way for much of the knowledge now taken for granted when discussing ways that 5‐HT might be involved in the control of mood and the idea that therapeutic drugs used to alleviate psychiatric illness might alter the function of cerebral 5‐HT.

British Journal of Pharmacology(2008)154, 1583–1599; doi:10.1038/bjp.2008.207; published online 26 May 2008
Isolated porcine bronchi provide a reliable model for development of bronchodilator anti‐muscarinic agents for human use
Authors: D'Agostino G , Condino A M , Gioglio L , Zonta F , Tonini M , Barbieri A
Published: June 2008

Background and purpose: In human airways, muscarinic acetylcholine receptors (mAChRs) exert a predominant role in the control of airways resistance and anti‐muscarinic agents are currently included in the pharmacological treatment of chronic obstructive pulmonary disease (COPD). However, the development of more effective mAChR antagonists is hampered by considerable species variability in the ultrastrucural and functional control of airway smooth muscle, making extrapolation of any particular animal model questionable. This study was designed to characterize the mAChRs in a bronchial preparation from pigs, animals considered to provide close models of human biology.

Experimental approach: Smooth muscle bronchial strips were examined by electron microscopy in order to compare their neuromuscular structure with that of human bronchi and used to study the affinity of a series of selective mAChR antagonists, estimated as pKis in competition binding assays with NMS and pA2, by Schild analysis, in contractile experiments.

Key results: Pharmacodynamic binding parameters and affinity profiles of a series of antagonists were consistent with the presence of a majority of M2 mAChRs along with a minor population of M3 mAChRs. Functionally, the highly significant correlation between postjunctional pA2 affinities and corresponding affinity constants at human recombinant M1–M5 subtypes indicated that smooth muscle contraction in porcine bronchi, as in human bronchi, was dependent on the M3 subtype.

Conclusion and implications: Based on the characterization of mAChRs, isolated porcine bronchi provide an additional experimental model for development of mAChR antagonists for the treatment of human airway dysfunctions.

British Journal of Pharmacology (2008) 154, 1611–1618; doi:10.1038/bjp.2008.208; published online 2 June 2008
Pharmacodynamic interaction of warfarin with cranberry but not with garlic in healthy subjects
Authors: Mohammed Abdul M I , Jiang X , Williams K M , Day R O , Roufogalis B D , Liauw W S , Xu H , McLachlan A J
Published: June 2008

Background and purpose:

Patients commonly take complementary medicines in conjunction with warfarin yet evidence supporting the safety or the risk of a herb–drug interaction is lacking. The aim of this study was to investigate the possible impact of two commonly used herbal medicines, garlic and cranberry, on the pharmacokinetics and pharmacodynamics of warfarin in healthy male subjects.

Experimental approach:

An open‐label, three‐treatment, randomized crossover clinical trial was undertaken and involved 12 healthy male subjects of known CYP2C9 and VKORC1 genotype. A single dose of 25 mg warfarin was administered alone or after 2 weeks of pretreatment with either garlic or cranberry. Warfarin enantiomer concentrations, INR, platelet aggregation and clotting factor activity were measured to assess pharmacokinetic and pharmacodynamic interactions between warfarin and herbal medicines.

Key results:

Cranberry significantly increased the area under the INR–time curve by 30% when administered with warfarin compared with treatment with warfarin alone. Cranberry did not alter S‐ or R‐warfarin pharmacokinetics or plasma protein binding. Co‐administration of garlic did not significantly alter warfarin pharmacokinetics or pharmacodynamics. Both herbal medicines showed some evidence of VKORC1 (not CYP2C9) genotype‐dependent interactions with warfarin, which is worthy of further investigation.

Conclusions and implications:

Cranberry alters the pharmacodynamics of warfarin with the potential to increase its effects significantly. Co‐administration of warfarin and cranberry requires careful monitoring.

British Journal of Pharmacology (2008) 154, 1691–1700; doi:10.1038/bjp.2008.210; published online 2 June 2008
Characterization of the α1‐adrenoceptor subtype mediating contractions of the pig internal anal sphincter
Authors: Mills K A , Hausman N , Chess‐Williams R
Published: June 2008

Background and purpose:

The internal anal sphincter has been shown to contract in response to α1‐adrenoceptor stimulation and therefore α1‐adrenoceptor agonists may be useful in treating faecal incontinence. This study characterizes the α1‐adrenoceptor subtype responsible for mediating contraction of the internal anal sphincter of the pig.

Experimental approach:

The potency of agonists and the affinities of several receptor subtype selective antagonists were determined on smooth muscle strips for the pig internal anal sphincter. Cumulative concentration–response curves were performed using phenylephrine and noradrenaline.

Key results:

The potency of the α1A‐adrenoceptor selective agonist A61603 (pEC50=7.79±0.04) was 158‐fold greater than that for noradrenaline (pEC50=5.59±0.02). Phenylephrine (pEC50=5.99±0.05) was 2.5‐fold more potent than noradrenaline. The α1D‐adrenoceptor selective antagonist BMY7378 caused rightward shifts of the concentration–response curves to phenylephrine and noradrenaline, yielding low affinity estimates of 6.59±0.15 and 6.33±0.13, respectively. Relatively high affinity estimates were obtained for the α1A‐adrenoceptor selective antagonists, RS100329 (9.01±0.14 and 9.06±0.22 with phenylephrine and noradrenaline, respectively) and 5‐methylurapidil (8.51±0.10 and 8.31±0.10, respectively). Prazosin antagonized responses of the sphincter to phenylephrine and noradrenaline, yielding mean affinity estimates of 8.58±0.10 and 8.15±0.08, respectively. The Schild slope for prazosin with phenylephrine was equal to unity (1.01±0.24), however the Schild slope using noradrenaline was significantly less than unity (0.50±0.11,P<0.05).

Conclusion and implications:

The results suggest that contraction of circular smooth muscle from the pig internal anal sphincter is mediated via a population of adrenoceptors with the pharmacological characteristics of the α1A/L‐adrenoceptor, most probably the α1L‐adrenoceptor form of this receptor.

British Journal of Pharmacology(2008)155, 110–117; doi:10.1038/bjp.2008.217; published online 2 June 2008
Atypical ubiquitin chains: new molecular signals
Authors: Ikeda Fumiyo , Dikic Ivan
Published: June 2008

Ubiquitin (Ub) is a small protein modifier that regulates many biological processes, including gene transcription, cell‐cycle progression, DNA repair, apoptosis, virus budding and receptor endocytosis. Ub can be conjugated to target proteins either as a monomer or as Ub chains that vary in length and linkage type. The various types of Ub modification are linked to distinct physiological functions in cells. MonoUb, for example, regulates DNA repair and receptor endocytosis, whereas lysine 48‐linked Ub chains label proteins for proteasomal degradation. More recently, the importance of chains conjugated through the other six lysines in Ub, known as atypical Ub chains, has been revealed. Atypical chains can be homotypic, sequentially using the same lysine residue in Ub for conjugation; mixed‐linkage, utilizing several distinct lysines to connect consecutive Ub moieties; or heterologous, connecting Ub with other Ub‐like modifiers. Here, we describe recent progress in the understanding of atypical Ub chain assembly and their recognition by Ub‐binding domains, and we discuss further their functional roles in vivo.
An Electroacoustic Analysis of Over-the-Counter Hearing Aids
Authors: Callaway Susanna Løve , Punch Jerry L.
Published: June 2008

Purpose

To determine whether 11 over-the-counter (OTC) hearing devices have the flexibility to provide adequate gain and output for 3 common hearing loss configurations.

Method

The 11 OTC hearing devices were separated into 2 price groups: a low-range group (<$100) consisting of 8 hearing devices and a midrange group ($100–$500) consisting of 3 hearing devices. Gain and output were prescribed for 3 hearing loss configurations using National Acoustic Laboratories prescriptive procedures. Low-range hearing devices were measured electroacoustically, and technical specifications were used as the source of electroacoustic information for the midrange hearing devices.

Results

Overall, midrange hearing devices met gain and output targets to a greater extent than did low-range devices. All low-range devices could be classified as special-purpose hearing aids with low-frequency emphasis. The low-range group had high equivalent input noise levels and potentially posed a residual hearing safety hazard.

Conclusions

The low-range OTC devices were found to be electroacoustically inadequate to meet the needs of the hearing impaired. Midrange OTC hearing devices are arguably a good solution for the cost-conscious consumer who cannot afford professional audiologic rehabilitation, especially if considered an interim step in the rehabilitation process.
Measures of Follow-Up in Early Hearing Detection and Intervention Programs: A Need for Standardization
Authors: Mason Craig A. , Gaffney Marcus , Green Denise R. , Grosse Scott D.
Published: June 2008

Purpose

To demonstrate the need for standardized data definitions and reporting for early hearing detection and intervention (EHDI) programs collecting information on newborn hearing screening and follow-up, and types of information best collected in a standardized manner.

Method

A hypothetical birth cohort was used to show the potential effects of nonstandardized definitions and data classifications on rates of hearing screening, audiologic follow-up, and hearing loss.

Results

The true screening rate in this cohort was 92.4%. The calculated rate was between 90.0% and 96.5%, depending on the measure used. Among children documented as screened and referred for follow-up, 61.0% received this testing. Only 49.0% were documented to have been tested. Despite a true prevalence of 3.7 per 1,000 births, only 1.5 per 1,000 children were documented with a hearing loss.

Conclusion

Ensuring that children receive recommended follow-up is challenging. Without complete reporting by audiologists to EHDI programs, accurate calculation of performance measures is impossible. Lack of documentation can lead to the overstatement of “loss to follow-up.” Also, standardization of measures is essential for programs to evaluate how many children receive recommended services and assess progress toward national goals. A new survey has been implemented to collect more detailed and standardized information about recommended services.
Word Recognition Materials for Native Speakers of Taiwan Mandarin
Authors: Nissen Shawn L. , Harris Richard W. , Dukes Alycia
Published: June 2008

Purpose

To select, digitally record, evaluate, and psychometrically equate word recognition materials that can be used to measure the speech perception abilities of native speakers of Taiwan Mandarin in quiet.

Method

Frequently used bisyllabic words produced by male and female talkers of Taiwan Mandarin were digitally recorded and subsequently evaluated using 20 native listeners with normal hearing at 10 intensity levels (−5 to 40 dB HL) in increments of 5 dB.

Results

Using logistic regression, 200 words with the steepest psychometric slopes were divided into 4 lists and 8 half-lists that were relatively equivalent in psychometric function slope. To increase auditory homogeneity of the lists, the intensity of words in each list was digitally adjusted so that the threshold of each list was equal to the midpoint between the mean thresholds of the male and female half-lists.

Conclusions

Digital recordings of the word recognition lists and the associated clinical instructions are available on CD upon request.
Can Auditory and Visual Speech Perception Be Trained Within a Group Setting?
Authors: Preminger Jill E. , Ziegler Craig H.
Published: June 2008

Purpose

This study attempted to determine whether auditory-only and auditory-visual speech perception could be trained in a group format.

Method

A randomized controlled trial with at least 16 participants per group was completed. A training-only group completed at least 5 hr of group speech perception training; a training plus psychosocial group completed at least 5 hr of group speech perception training and psychosocial exercises; and a control group did not receive training. Evaluations were conducted before and after training and included analytic and synthetic measures of speech perception, hearing loss–related and generic quality of life scales, and a class evaluation form.

Results

No significant group changes were measured on any of the analytic auditory-only or auditory-visual measures of speech perception, yet the majority of training participants (regardless of training group) reported improvement in auditory and auditory-visual speech perception. The training participants demonstrated a significant reduction on the emotional subscale of the hearing loss–related quality of life scale, while the control participants did not demonstrate a change on this subscale.

Conclusions

Benefits of group audiologic rehabilitation classes may not result from an actual improvement in auditory or visual speech perception abilities, but participants still perceive training in these areas as useful.
Checking Concordance between Findings and Diagnoses in Sonographic Reports by a Knowledge-Based Documentation System
Authors: Huettig M , Buscher G , Puppe F , Buscher H.-P
Published: June 2008

Purpose: Sonographic reports are examiner-dependent and may not always be reliable. We investigated concordance between documented findings and diagnostic conclusions - not the objective correctness of both - with the help of a knowledge-based documentation system. Materials and Methods: The knowledge-based documentation system SonoConsult (SC) is routinely used in the ultrasound unit of a gastroenterological clinic for more than four years. Physicians documented findings with goal directed questionnaires, and diagnostic conclusions with free text. The consistency of documented findings and diagnoses was checked with the help of SC in a two-step process: 1. the diagnoses inferred by SC based on the documented findings were compared to the diagnoses of the physicians stated as free text. 2. In case of discrepancies, a more thorough comparison was performed manually by the medical authors of this study. For judging the practical relevance of discrepancies, diagnostic codes were pre-classified as a) being presumably of higher and lower relevance for the clinician and b) requiring simple or complex inference rules from the findings. Results: In a first series of 250 consecutive cases with 934 diagnoses (3.7 diagnoses per case), 71.1 % showed agreement between diagnoses of the physicians and of SC and were judged as consistent compared to the documented findings. 24.4 % of the diagnoses suggested by the documented findings, however, were not mentioned by the physicians (false negative) and 4.5 % were mentioned by the physicians but not suggested by the documented findings (false positive). From the 24.4 % missing diagnoses, 40 % were pre-classified as being of higher relevance for the clinician. In a second series of 161 consecutive cases with 501 diagnoses (3.1 diagnoses per case), 61.1 % were judged as consistent compared to the documented findings, 36.1 % false negative and 2.8 % false positive. In this study, we differentiated the missing diagnoses due to their inferential complexity: From the 152 complex diagnoses, 44 % were missing, while from the 349 simple diagnoses, 32.7 % were missing. Conclusion: As shown for a sonographic department of a clinic of internal medicine, in sonographic reports, one has to be aware of discrepancies between question-set-based documentations of findings and diagnostic conclusions of the examiners. While a detailed documentation of findings is the basis of quality control, consistency checks between documented findings and diagnostic conclusions, which might be done automatically in an electronic patient record, would considerably improve the quality of the reports.
Low-Dose Gamma Knife Radiosurgery for Cavernous Sinus Hemangioma: Report of 3 Cases and Literature Review
Authors: Ivanov P. , Chernov M. , Hayashi M. , Nakaya K. , Izawa M. , Murata N. , Kubo O. , Ujiie H. , Muragaki Y. , Nakamura R. , Iseki H. , Hori T. , Takakura K.
Published: June 2008

Optimal management of cavernous sinus hemangiomas remains unclear. Total microsurgical removal of these neoplasms may be extremely difficult due to their rich vascularization. Three cases of cavernous sinus hemangioma treated with low-dose Gamma Knife radiosurgery are presented. Marginal dose varied from 10 to 13 Gy. Treatment planning and radiation dosimetry were done with a goal of conformal and selective coverage of the lesion with 50% prescription isodose line using multiisocenter technique. In all cases significant shrinkage of the neoplasm was marked at 3 months after treatment. Mean volume reduction at 12 months after radiosurgery was 60% (range: 45-75%). In all patients the shrinkage of the neoplasm was accompanied by notable improvement of the preexistent oculomotor nerve palsy. No radiosurgery-related complications were met during follow-up. In conclusion, low-dose Gamma Knife radiosurgery seems to be very effective for management of cavernous sinus hemangiomas, and can be considered as a treatment modality of choice for these lesions.
Plasma physics and radiation hydrodynamics in developing an extreme ultraviolet light source for lithography
Authors: Nishihara Katsunobu , Sunahara Atsushi , Sasaki Akira , Nunami Masanori , Tanuma Hajime , Fujioka Shinsuke , Shimada Yoshinori , Fujima Kazumi , Furukawa Hiroyuki , Kato Takako , Koike Fumihiro , More Richard , Murakami Masakatsu , Nishikawa Takeshi , Zhakhovskii Vasilii , Gamata Kouhei , Takata Akira , Ueda Hirofumi , Nishimura Hiroaki , Izawa Yasukazu , Miyanaga Noriaki , Mima Kunoki
Published: June 2008

Extreme ultraviolet (EUV) radiation from laser-produced plasma (LPP) has been thoroughly studied for application in mass production of next-generation semiconductor devices. One critical issue for the realization of an LPP-EUV light source for lithography is the conversion efficiency (CE) from incident laser power to EUV radiation of 13.5-nm wavelength (within 2% bandwidth). Another issue is solving the problem of damage caused when debris reaches an EUV collecting mirror. Here, we present an improved power balance model, which can be used for the optimization of laser and target conditions to obtain high CE. An integrated numerical simulation code has been developed for the target design. The code agrees well with experimental results not only for CE but also for detailed EUV spectral structure. We propose a two-pulse irradiation scheme for high CE, and reduced ion debris using a carbon dioxide laser and a droplet or a punch-out target. Using our benchmarked numerical simulation code, we find a possibility to obtain CE up to 6–7%, which is more than twice that achieved to date. We discuss the reduction of ion energy within the two-pulse irradiation scheme. The mitigation of energetic ions by a magnetic field is also discussed, and we conclude that no serious instability occurs due to large ion gyroradius.
Modeling of radiation and nitric oxide formation in turbulent nonpremixed flames using a flamelet/progress variable formulation
Authors: Ihme Matthias , Pitsch Heinz
Published: June 2008

A model for the prediction of the nitric oxide (NO) formation in turbulent nonpremixed flames is proposed. Since the NO formation has a strong temperature sensitivity, the accurate prediction of the flame temperature under the consideration of radiative heat losses is required. The first part of the paper addresses the extension of a flamelet-based combustion model to account for radiative heat loss effects by introducing enthalpy as an additional parameter. A transport equation for enthalpy is solved, and the radiative sink term in this equation is obtained from unsteady flamelet solutions. The model is applied to a large-eddy simulation (LES) of Sandia flame D, and the importance of the interaction between turbulence and radiation on temperature and mixture fraction is investigated. Based on the radiative flamelet formulation, a consistent model for the prediction of NO formation is developed in the second part of the paper. In this model, an additional transport equation for the NO mass fraction is solved, and the chemical source term is obtained from a flamelet library. Since the consumption rate is dependent on the NO mass fraction, this term requires modeling, which is discussed in this paper. By employing a scale similarity argument, a closure model for application in LES is presented. After the analysis of the proposed model for the thermal, nitrous oxide, and prompt pathways for NO formation, the NO model is integrated into the extended flamelet/progress variable model and applied in LES of Sandia flame D and a Pratt & Whitney aircraft engine combustor configuration.
Tunneling study of cavity grade Nb: Possible magnetic scattering at the surface
Authors: Proslier T. , Zasadzinski J. F. , Cooley L. , Antoine C. , Moore J. , Norem J. , Pellin M. , Gray K. E.
Published: June 2008

Tunneling spectroscopy was performed on Nb pieces prepared by the same processes used to etch and clean superconducting radio frequency (SRF) cavities. Air exposed, electropolished Nb exhibited a surface superconducting gap Δ=1.55meV, which is characteristic of a clean, bulk Nb. However, the tunneling density of states (DOS) was significantly broadened. The Nb pieces, which were treated with the same mild baking used to improve the Q slope in SRF cavities, reveal a sharper DOS. Good fits to the DOS were obtained by using the Shiba theory, suggesting that magnetic scattering of quasiparticles is the origin of the gapless surface superconductivity and a heretofore unrecognized contributor to the Q-slope problem of Nb SRF cavities.
Generalized binomial τ-leap method for biochemical kinetics incorporating both delay and intrinsic noise
Authors: Leier André , Marquez-Lago Tatiana T. , Burrage Kevin
Published: June 2008

The delay stochastic simulation algorithm (DSSA) by Barrio et al. [Plos Comput. Biol. 2, 117–E (2006)] was developed to simulate delayed processes in cell biology in the presence of intrinsic noise, that is, when there are small-to-moderate numbers of certain key molecules present in a chemical reaction system. These delayed processes can faithfully represent complex interactions and mechanisms that imply a number of spatiotemporal processes often not explicitly modeled such as transcription and translation, basic in the modeling of cell signaling pathways. However, for systems with widely varying reaction rate constants or large numbers of molecules, the simulation time steps of both the stochastic simulation algorithm (SSA) and the DSSA can become very small causing considerable computational overheads. In order to overcome the limit of small step sizes, various τ-leap strategies have been suggested for improving computational performance of the SSA. In this paper, we present a binomial τ-DSSA method that extends the τ-leap idea to the delay setting and avoids drawing insufficient numbers of reactions, a common shortcoming of existing binomial τ-leap methods that becomes evident when dealing with complex chemical interactions. The resulting inaccuracies are most evident in the delayed case, even when considering reaction products as potential reactants within the same time step in which they are produced. Moreover, we extend the framework to account for multicellular systems with different degrees of intercellular communication. We apply these ideas to two important genetic regulatory models, namely, the hes1 gene, implicated as a molecular clock, and a Her1/Her 7 model for coupled oscillating cells.
The restricted active space followed by second-order perturbation theory method: Theory and application to the study of CuO2 and Cu2O2 systems
Authors: Malmqvist Per Åke , Pierloot Kristine , Shahi Abdul Rehaman Moughal , Cramer Christopher J. , Gagliardi Laura
Published: June 2008

A multireference second-order perturbation theory using a restricted active space self-consistent field wave function as reference (RASPT2/RASSCF) is described. This model is particularly effective for cases where a chemical system requires a balanced orbital active space that is too large to be addressed by the complete active space self-consistent field model with or without second-order perturbation theory (CASPT2 or CASSCF, respectively). Rather than permitting all possible electronic configurations of the electrons in the active space to appear in the reference wave function, certain orbitals are sequestered into two subspaces that permit a maximum number of occupations or holes, respectively, in any given configuration, thereby reducing the total number of possible configurations. Subsequent second-order perturbation theory captures additional dynamical correlation effects. Applications of the theory to the electronic structure of complexes involved in the activation of molecular oxygen by mono- and binuclear copper complexes are presented. In the mononuclear case, RASPT2 and CASPT2 provide very similar results. In the binuclear cases, however, only RASPT2 proves quantitatively useful, owing to the very large size of the necessary active space.
Existence of non-Landau solutions for Langmuir waves
Authors: Belmont G. , Mottez F. , Chust T. , Hess S.
Published: June 2008

The propagation of linear one dimensional (1D) Langmuir waves is reinvestigated using numerical simulations of a new type with very low noise. The dependence of the result on the initial conditions is shown. New solutions are exhibited, with properties different from Landau’s, even in the asymptotic behavior, in particular with regard to the damping rate. These solutions are shown to demand a special preparation of the initial plasma perturbation, but in a way which is quite physical, without any singularity in the electron distribution function, contrary to the classical van Kampen’s solutions. Using an original theoretical calculation, a simple analytical form is derived for the perturbed distribution function, which allows interpreting both the Landau and non-Landau solutions observed numerically. The numerical results presented and their interpretations are potentially important in several respects: 1) They outline that Landau solutions, for the 1D electrostatic problem in collisionless plasmas, are only a few among an infinite amount of others; even if the non-Landau solutions are much less probable, their existence provides a different view on the concept of kinetic damping and may suggest interpretations different from usual for the subsequent nonlinear effects; 2) they show that the shape of the initial perturbation δf(v), and not only its amplitude, is important for the long time wave properties, both linear and nonlinear; 3) the existence of non-Landau solutions makes clear that the classical energy arguments cannot be fully universal as long as they allow deriving the Landau damping rate independently of the initial conditions; 4) the particle signature of Landau damping, different from the usual guess, should imply a change in our understanding of the role of the resonant particles.
Behavior of aluminum shear modulus in solid-liquid mixed phase: Estimation with percolation theory
Authors: Ran Xianwen , Yu Yuying , Tan Hua , Tang Wenhui
Published: June 2008

The variation of aluminum shear modulus with the melting-mass fraction in the solid-liquid mixed phase has been estimated by the percolation theory. With the total number of calculated sites from 0.125×106 to 8.0×106, it is shown that there are two critical points corresponding to the melting-mass fraction 0.313 and 0.687, respectively. At the critical point 0.313, the longitudinal sound velocity begins to attenuate to bulk sound velocity and completely attenuates to bulk sound velocity at the critical point 0.687. This is in accord with previous independent and our sound velocity data of aluminum in the solid-liquid phase, and suggests a different interpretation of shock sound speed data for melt mass fraction.
Study of the temporal current stability of field-emitted electrons from ultrananocrystalline diamond films
Authors: Uppireddi Kishore , Weiner Brad R. , Morell Gerardo
Published: June 2008

The temporal current stability and the current fluctuations of the field emission current obtained from ultrananocrystalline diamond (UNCD) films were investigated. The films were synthesized by Ar-rich dc plasma assisted hot filament chemical vapor deposition. The field emission properties were correlated to the films’ composition (sp2 and sp3 bonded carbon volume fractions) and nanostructure. The compositional analysis was done by modeling the films’ spectroscopic ellipsometry [Ψ (E), Δ (E)] data by using a two layer structure and the Bruggeman effective medium approximation. The results indicate that the local field enhancement in UNCD films is related to their intrinsic morphology at the diamond-grain boundary-vacuum interface, and the sp3∕sp2 carbon volume fraction plays a significant function on the short- and long-term current stabilities of field emitted electrons.
An experimental study on Rosensweig instability of a ferrofluid droplet
Authors: Chen Ching-Yao , Cheng Z.-Y.
Published: June 2008

We experimentally investigate the interfacial morphologies of Rosensweig instability on an extremely thin layer of ferrofluid droplets under a constant perpendicular magnetic field. Striking patterns consisting of numerous subscale droplets that developed from Rosensweig instability are observed. For a dry plate, on which surface tension dominates, the breaking pattern of subscale droplets can be characterized by a dimensionless magnetic Bond number Bom. In general, a more pronounced instability, which is evident by a greater number of breaking subscale droplets N, arises with a higher Bom. For a magnetic Bond number that is larger than a critical value, we identify a new mode of interfacial breakup pattern, where the central droplet is torn apart with major mass loss. In addition, we found that the volume fractions of breaking subscale droplets are strongly affected by the height variation of the initial fluid surface and appear unevenly distributed with dominance of a central droplet. On the other hand, for a prewetted plate, a nearly flat fluid surface is achieved due to a smaller contact angle, which then leads to virtually evenly distributed subscale droplets. A global size for all breaking subscale droplets is observed regardless of their initial diameters. The number of breaking subscale droplets (N) and the diameter of the initial droplet (D) can be approximated by a quadratic proportionality of N∼D2.
Lifetime measurements of SO2 below the Clement’s A-band
Authors: Biswal Himansu S. , Kumar S. V. K. , Wategaonkar Sanjay J.
Published: June 2008

High resolution laser induced fluorescence spectrum of jet-cooled SO2 is recorded toward the blue side of the Clement’s A-Band in the region of 314–319nm. Time resolved fluorescence measurements have been carried out for all the prominent peaks in this region. Most of the peaks exhibited double exponential decay profiles. Some of the rovibronic bands exhibited quantum beats with strong quantum beats observed at 315.261 and 315.271nm. This is the first observation of quantum beats in SO2 in the absence of any external magnetic or electric fields. The decay profiles of the beating rovibronic bands were fitted using a four-level model by least-squares fitting method. The fitting shows that all the measured bands were double exponential with a similar first lifetime of ∼3μs and a varying second lifetime of the order of 1μs–100ns with a beating frequency of ∼1MHz. These quantum beats, in the absence of any external field, indicate rotational level mixing between the ÃA21 and the B̃B11 vibronic states which are near resonant due to the high density of states of these two states.
Surface depletion effects in semiconducting nanowires
Authors: Simpkins B. S. , Mastro M. A. , Eddy C. R. , Pehrsson P. E.
Published: June 2008

The impact of surface depletion on the electronic properties of semiconductor nanowires (NWs) is explored both theoretically and experimentally. The impact of dopant concentration, surface barrier height, and NW radius on surface depletion and extracted material properties are determined by solving Poisson’s equation for the cylindrical system. The theoretical results reveal a size-dependent systematic error in carrier concentration extraction, which is verified through experiment. Interrogation of GaN NWs with radii from 15 to 70 nm exposed an error that reaches over an order of magnitude for the samples studied. These data compared favorably to an analytical treatment assuming physically reasonable material properties. While this manuscript focuses on GaN, the systematic error discussed will be present for any semiconducting NW, which exhibits surface band bending and therefore influences the behavior and characterization of a wide range of semiconducting nanoelements.
Plasmon-enhanced midinfrared generation from difference frequency in semiconductor quantum dots
Authors: Yan Jie-Yun , Zhang Wei , Duan Suqing , Zhao Xian-Geng
Published: June 2008

We investigate the midinfrared generation from difference frequency in self-assembled quantum dots near metal nanoparticles with two-color interband excitations. The generated signal strength is enhanced by several orders of magnitude due to the plasmon-exciton resonance in the nanosuperstructures. The signal enhancement is found to be the result of competition between local electric field enhancement and excitonic lifetime shortening. Therefore, there exists an optimal interparticle distance for the difference-frequency generation. This nanomolecule is proposed to be an excellent candidate for the midinfrared quantum dot laser.
Photoluminescence enhancement and quenching of single CdSe∕ZnS nanocrystals on metal surfaces dominated by plasmon resonant energy transfer
Authors: Matsuda Kazunari , Ito Yuichi , Kanemitsu Yoshihiko
Published: June 2008

We studied the mechanism of the photoluminescence (PL) enhancement and quenching of single CdSe∕ZnS nanocrystals on rough Au surfaces. Single nanocrystal spectroscopy revealed that the PL enhancement depends strongly on the excitation wavelength and liner-polarization angle due to the localized plasmon excitation and is also sensitive to the nanocrystal size. The polarization- and size-dependent PL enhancement and quenching are determined by the balance between the resonant energy transfer from the nanocrystal to the Au surface and the electric field enhancement.
Mixed phases in p-type CuInSe2 thin films detected by using micro-Raman scattering spectroscopy
Authors: Wang D. , Wan L. , Bai Z. , Cao Y.
Published: June 2008

In order to detect some subtle differences concerning different atomic orderings presented in the CuInSe2 compound, low-temperature Raman scattering was carried out on CuInSe2 thin films. By considering the phonon dispersion curves and using the Ridley model, it shows that the chalcopyrite A1 mode decayed asymmetrically into phonons with frequencies of ∼123 and ∼50cm−1, which are attributed to a TO and a LA phonon along the Γ-X and Γ-N directions of the Brillouin zone. However, the A1 mode of the CuAu-ordered CuInSe2 showed almost no frequency change upon increasing the temperature up to 400K.
Evaluation of B∕A nonlinear parameter using an acoustic self-calibrated pulse-echo method
Authors: Vander Meulen F. , Haumesser L.
Published: June 2008

The objective of this work is to develop an easy-to-build and robust setup for measuring the nonlinearity parameter B∕A in fluids using ultrasound. The method is based on the pulse-echo technique, using a single element broadband acoustic transducer, and requires electrical signal measurements. Results obtained in water and denatured alcohol validate the proposed procedure. The choice of a suitable primary wave frequency is discussed with regard to the transducer sensitivity. Further, the influence of the perturbations introduced by the experimental device nonlinearities, and the role of the reflector on the measured second harmonic field amplitude are investigated.
Temperature dependent conduction and UV induced metal-to-insulator transition in ZnO nanowires
Authors: Chang Pai-Chun , Lu Jia Grace
Published: June 2008

Thin ZnO nanowires with diameters of less than 50nm are configured as field effect transistors and studied for their transport mechanisms at different temperatures under UV illumination and gate modulation. The conductivity exhibits two regimes: at T>50K, thermally activated transport dominates with activation energy around 30–60meV attributed to the shallow donor states and at T<50K, three dimensional variable range hopping reveals in the conduction. In addition, UV irradiation leads to a metal-to-insulator transition at ∼210K. Furthermore, electrostatic gating results in a band bending giving rise to a change in the activation energy.
Investigation of electronic structure of amorphous, metastable, and stable phases of Ge1Sb2Te4 film by high-resolution x-ray photoemission spectroscopy
Authors: Lee Y. M. , Jung M.-C. , Shin H. J. , Kim K. , Song S. A.
Published: June 2008

The electronic structures of amorphous, metastable, and stable phases of Ge1Sb2Te4 film were investigated by high-resolution x-ray photoelectron spectroscopy. The Te 4d core level showed a negligible change in binding energy (BE). In the stable phase, the Ge 3d and Sb 4d core levels were, respectively, dominated by a spin-orbit-split feature at 0.1eV-lower BE and a well-defined component at 0.4eV-higher BE than those in the amorphous phase. The analysis suggests that the amorphous phase and the stable phase is respectively represented by a broad and a well-defined electronic structure and that the metastable phase is represented by two different kinds of local electronic structures. The valence-band structures showed a trend similar to that reported by Klein et al. [Phys. Rev. Lett. 100, 016402 (2008)] between the amorphous and metastable phases.
Optical bistability and multistability in one-dimensional periodic metal-dielectric photonic crystal
Authors: Wang F. Y. , Li G. X. , Tam H. L. , Cheah K. W. , Zhu S. N.
Published: June 2008

The optical bistability and multistability in one-dimensional photonic crystal with the periodic metal-dielectric structure is investigated theoretically. In linear transmission, a structure with N periods will support N−1 resonant modes which correspond to the transmission peaks. Strong localized effect in these resonant modes is obtained. Optical bistability and multistability can be achieved when the incident wavelength is close to a resonance, which can be seen as an effect of the dynamic shifting of the wavelength of the resonant modes. It is found that the threshold for optical bistability in the periodic resonant structure is lower than the nonresonant metal-dielectric structure.
Stable conductance plateaus from ridge wires grown on a patterned substrate
Authors: Pfaendler Sieglinde M.-L. , Atkinson Paola , Ritchie David A.
Published: June 2008

A (100)-GaAs substrate was prepatterned with Hall-bar mesas incorporating a constriction, subsequent molecular beam epitaxial overgrowth of a GaAs∕AlGaAs quantum well resulted in narrowed constrictions and creation of conducting wires. Constrictions parallel, perpendicular, and diagonal to [01¯1], of up to 30μm in length, were investigated. Cross-sectional scanning electron microscopy images were correlated with the electrical conductance characteristics. Quantized conductance plateaus were only observed in the [01¯1] oriented wires, where the growth process formed an apex. Measurement stability was achieved by returning to a large negative top gate voltage, thus, plateaus reproducibly retraced themselves as a function of top gate voltage, and were flat and well resolved.
Reduction of debris of a CO2 laser-produced Sn plasma extreme ultraviolet source using a magnetic field
Authors: Ueno Yoshifumi , Soumagne Georg , Sumitani Akira , Endo Akira , Higashiguchi Takeshi , Yugami Noboru
Published: June 2008

We demonstrated a fivefold reduction in Sn debris deposited on small Mo∕Si multilayer mirrors from a Sn planar target by applying a static magnetic field of 1T. The debris reduction is attributed to the decrease of more than three orders in the number of ions that reach the sample mirror due to their interaction with the applied magnetic field that guides the ions away from the mirror. The remaining deposition is due to neutral Sn atoms that do not interact with the applied magnetic field.
Influence of oxygen passivation on optical properties of PbSe thin films
Authors: Zhao F. , Mukherjee S. , Ma J. , Li D. , Elizondo S. L. , Shi Z.
Published: June 2008

A series of PbSe thin films grown on a (111)-oriented Si substrate by molecular beam epitaxy were passivated by high-purity oxygen at different annealing temperatures. The photoluminescence intensity increased by more than two orders of magnitude at 4.5μm after annealing the samples in an O2 atmosphere at 350°C. X-ray photoelectron spectroscopy revealed that PbO and SeO2 were formed during the oxidation process of PbSe, thus confirming the formation of the surface passivation layer which resulted in the observed significant increase in PL intensity.
Electrical switching in Fe∕Cr∕MgO∕Fe magnetic tunnel junctions
Authors: Halley D. , Majjad H. , Bowen M. , Najjari N. , Henry Y. , Ulhaq-Bouillet C. , Weber W. , Bertoni G. , Verbeeck J. , Van Tendeloo G.
Published: June 2008

Hysteretic resistance switching is observed in epitaxial Fe∕Cr∕MgO∕Fe magnetic tunnel junctions under bias voltage cycling between negative and positive values of about 1V. The junctions switch back and forth between high- and low-resistance states, both of which depend on the device bias history. A linear dependence is found between the magnitude of the tunnel magnetoresistance and the crafted resistance of the junctions. To explain these results, a model is proposed that considers electron transport both by elastic tunneling and by defect-assisted transmission.