bluuebunny/crossref_metadata_2025 huggingface dataset:
Using wavelet analysis to detect changes in water temperature regimes at multiple scales: effects of multi‐purpose dams in the Willamette River basin
Authors: Steel E. Ashley , Lange Ian A.
Published: February 2007

Maintaining the natural complexity of water temperature regimes is a key to maintaining diverse biological communities. Insect communities, food webs, and fish respond to the magnitude and duration of water temperature fluctuations. Disruption of these natural patterns has the potential to alter physiological processes, behavioural adaptations, and community structure and dynamics. We analysed multiple >300‐day time series of water temperature from the Willamette River basin, Oregon, to assess the impact of large multi‐purpose dams on water temperature variability at temporal scales ranging from 1 to 32 days, short temporal scales that are commonly ignored. We applied wavelet analysis to quantify the variability of water temperature at multiple temporal scales simultaneously. We compared water temperature regimes above and below dams and before and after dam construction. The advantages of wavelet analysis are the ability to examine all temporal scales simultaneously and independently as well as the ability to preserve the temporal context of the wavelet coefficients. We were able to detect significant (p < 0.0001) reductions in water temperature variability, defined as the variability of the wavelet coefficients, as a result of dams at the 1‐, 2‐, 4‐, and 8‐day scales. There were no significant differences in water temperature variability between managed and natural flows at the 16‐ and 32‐day scale (p = 0.80). In addition to the well‐documented effects of dams on seasonal patterns in water temperature or on water temperature extremes, our results demonstrate that dams have significantly muted the small temporal scale variance in water temperature patterns to which many organisms may have been adapted. Conserving or restoring natural temperature patterns in rivers will require attention to these small‐scale complexities. Published in 2007 by John Wiley & Sons, Ltd.
Chemical etching of hot‐pressed p‐type polycrystalline SiC surfaces by HF/K2S2O8 solutions
Authors: Bourenane K. , Keffous A. , Nezzal G. , Boukezzata A. , Naama S.
Published: February 2007

In this work, an experimental study on the etching of p‐type hot‐pressed silicon carbide (SiC) was carried out in HF/K2S2O8 solutions. The SiC wafers used in this work were p‐type polycrystalline materials, supplied by Goodfellow, with an acceptor concentration of 2.31 × 1012 cm−3. The SiC substrate was a hot‐pressed material, the latter realized from a mixture of 1 part of SiO2 with 3 parts of C (carbon) ‘1SiO2 + 3C’ heated in an oven at 2500 °C. In order to facilitate the chemical etching of the SiC substrate, a thin aluminium film was deposited on the SiC substrate. The morphology of the etched surface was examined with varying K2S2O8 concentration. The surfaces of the etched samples were analysed using secondary ions mass spectrometry (SIMS), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT‐IR) and photoluminescence (PL). The surface morphology of the samples etched in HF/K2S2O8 is shown to depend on the solution composition. The investigation of the effect of the HF/K2S2O8 solution on SiC samples shows that as K2S2O8 concentration increases, the chemical etching reveals defects with random geometry. Finally, chemical etching of p‐type SiC induces a decrease in the PL intensity, which indicates clearly the defects on the polycrystalline SiC surface. In addition, the result is very interesting, as to date no chemical etching solution at low temperature (<100 °C) has been developed for SiC. Finally, we have proposed a dissolution mechanism of SiC in 2HF/1K2S2O8 solutions. Copyright © 2007 John Wiley & Sons, Ltd.
Does immune function influence population fluctuations and level of parasitism in the cyclic geometrid moth?
Authors: Klemola Tero , Klemola Netta , Andersson Tommi , Ruohomäki Kai
Published: February 2007

Populations of the autumnal moth, Epirrita autumnata, exhibit cycles with high amplitudes in northernmost Europe, culminating in devastating outbreak densities at favourable sites. Parasitism by hymenopteran parasitoids has been hypothesised to operate with a delayed density dependence capable of producing the observed dynamics. It has also been hypothesised that insects in crowded conditions invest greatly in their immunity as a counter‐measure to increased risk of parasitism and pathogen infections. Furthermore, inducible plant defences consequent to grazing by herbivorous insects may be linked to the performance of parasitoids and pathogens through increased immunocompetence of the herbivore feeding on the foliage, in which the defence induction has taken place. At ten sampling sites, we quantified larval abundance, outbreak status and percentage larval parasitism during an extended peak phase of a population cycle. These population level covariates, together with an individual pupal mass, were used to explain differences in the immune defence, measured as an encapsulation reaction to artificial antigen. We also conducted a field study for an investigation of the susceptibility of autumnal moth pupae to naturally occurring pupal parasitoids. We did not find obvious differences between the encapsulation rate of autumnal moths originating from the sites with different past and current larval densities and risks for parasitism. The best ranked statistical models included pupal mass and outbreak status as explanatory variables, although both showed only slight effects on the encapsulation rate. The host resistance test revealed positive relationships between the encapsulation rate, body size and percentage parasitism of the exposed pupae, indicating that pupal parasitoids chose, and/or survived better, in large host individuals irrespective of their encapsulation ability. Thus, our results do not provide support for the hypothesis that variation in the immune function drives or modulates population cycles of autumnal moths.
Teaching Pediatric Hand Surgery in Vietnam
Authors: Chung Kevin C. , Kotsis Sandra V.
Published: February 2007

Background

International volunteering missions are becoming an important focus of plastic surgeons in the United States. The purpose of this paper is to describe the teaching of pediatric hand surgery in Vietnam to share the lessons learned from this project.

Methods

Two medical education trips were conducted to the no. 1 Children's Hospital in Ho Chi Minh city (Saigon) to teach pediatric hand and burn reconstructive surgery to the surgeons and therapists. This is the main referral children's hospital for the country, and pediatric hand surgery expertise is not available.

Results

Structured education programs were conducted over two trips to introduce congenital hand surgery and burn reconstructive procedures using flap techniques. The education programs included lectures and surgical demonstrations of selected procedures. Their proficiency was verified by supervised conduct of these operations.

Conclusions

A well-conceived medical education program can introduce complex surgical discipline to a country. Through two trips, the surgeons at this referral center will have the capability to take care of many children requiring reconstructive hand surgery.
One‐pot synthesis of fatty acid epoxides from triacylglycerols using enzymes present in oat seeds
Authors: Piazza George J. , Foglia Thomas A.
Published: February 2007

In our previous work we used ground oat (Avena sativa) seeds as an inexpensive source of enzymes for the modification of FA or their chemical derivatives. We have extended this work by observing the products derived from an intact fat and three vegetable oils through the concerted action of oat seed enzymes. A modified reversed‐phase HPLC protocol was devised that allowed the quantification of FFA, epoxy FA, and acylglycerols without derivatization. It was found that the addition of the surfactant deoxycholate or calcium chloride was needed to observe best hydrolysis of TAG to FA. Without an added oxidant, lipase action produced up to 80% by weight of FA at pH 7–9 with small amounts of DAG and MAG. When the oxidant t‐butyl hydroperoxide was added in the presence of deoxycholate, the FA were partially converted to epoxide derivatives (up to 35% by weight). When calcium chloride replaced deoxycholate, only 4% by weight of the product was epoxide derivatives. The highest levels of FA epoxides were generated at pH7, and up to 15% by weight of the product at this pH was epoxymonostearin (monoepoxyoctadecanoylglycerol). The optimal molar amount of t‐butyl hydroperoxide to add with deoxycholate for high epoxide formation was 1.4 to 2.8 times the amount of fatty esters in soybean oil. In no instance were oxidized DAG or TAG detected, demonstrating that a highly specific enzymatic process was responsible for epoxide formation. The epoxide products may be used to produce polyols with high viscosity for grease preparations.
Phase distributions of alcohol, glycerol, and catalyst in the transesterification of soybean oil
Authors: Zhou Weiyang , Boocock D. G. B.
Published: February 2007

Two‐phase base‐catalyzed transesterification of vegetable oils is the most common method for making biodiesel. The reaction starts as separate oil and alcohol phases. At the end of the reaction, the mixture, if allowed to settle, consists of an upper ester‐rich layer and a lower glycerol‐rich layer. The compositions of these layers from the methanolysis and ethanolysis of soybean oil were measured. Synthetic mixtures and actual reaction mixtures were used either to represent or generate steadystate reaction mixtures resulting from the initial condition of 6∶1 alcohol/oil molar ratio and catalyst concentration (1.0 wt% sodium methoxide or 1.26 wt% sodium ethoxide). At 23°C, for methanolysis, 42.0% of the alcohol, 2.3% of the glycerol, and 5.9% of the catalyst were in the ester‐rich phase at steady state. In ethanolysis, 75.4% of the ethanol, 19.3% of the glycerol, and 7.5% of the catalyst were in the ester‐rich phase. The volume of the glycerol‐rich phase decreased from methanolysis to ethanolysis to propanolysis; butanolysis remained monophasic throughout. The results explain some of the general kinetic behavior observed in transesterifications and provide useful information for alcohol recovery and product purification.
Comparison of two palladium catalysts on different supports during hydrogenation
Authors: Cizmeci Melih , Musavi Anar , Tekin Aziz , Kayahan Muammer
Published: February 2007

Soybean oil was hydrogenated using two different palladium‐based catalysts, 5% palladium on carbon (Pd/C) and 10% palladium on alumina (Pd/A), at various ratios in a 4‐L reactor under constant conditions (165°C, 2 bar H2, and 500 rpm stirring rate). Reaction rate, trans isomer formation, selectivity ratios, and melting behaviors of the samples were monitored. Activity of Pd/C was about 10 times higher than that of Pd/A, and the reaction rate showed a strong dependency on the support material. Increases in the concentrations of both Pd catalysts did not have considerable effect on trans formation, which is slightly dependent on support material. Oleate selectivity (S21) for all runs varied between 2.48 and 30.34, and type of support material did not have an effect on selectivity. Melting behaviors of the samples were mainly dependent on reaction rates.
Trans-septate species of Acanthothecis and Fissurina from India
Authors: MAKHIJA Urmila , ADAWADKAR Bharati
Published: February 2007

Eighteen species in the lichen genera Acanthothecis Clem. and Fissurina Fée (Graphidaceae) with colourless, trans-septate ascospores are recorded from India. Eight new species, namely Acanthothecis collateralis, Fissurina capsulata, F. coarctata, F. karnatakensis, F. khasiana, F. longiramea, F. taeniocarpoides and F. verrucosa, and a new variety, F. dumastioides var. salazinica, are described. Fissurina saxicola ad int., clearly distinguished from the other species is recorded, but is not formally described as new to science as the material is scanty. Acanthothecis consocians, F. globulifica, F. insidiosa and F. rugosa are reported for the first time from India. A key for the trans-septate species of Acanthothecis and Fissurina in India is provided.
Phylloblastia inexpectata (Verrucariaceae), a new species of foliicolous lichen from Western Europe and Madeira
Authors: SÉRUSIAUX Emmanuël , COPPINS Brian J. , LÚCKING Robert
Published: February 2007

Phylloblastia inexpectata Sérus., Coppins & Lücking is a newly described foliicolous lichen, known from England, Scotland, Southern Italy and Madeira. It is distinguished from similar and related species by the absence of isidia and the smaller size of its ascospores. Phylloblastia pocsii is reported from Papua New Guinea for the first time.
A multipurpose tool to evaluate the nutritional quality of individual foods: Nutrimap®
Authors: Labouze E , Goffi C , Moulay L , Azaïs-Braesco V
Published: February 2007

Background/objectives

With obesity and nutrition-related diseases rising, public health authorities have recently insisted nutritional quality be included when advertising and labelling food. The concept of nutritional quality is, however, difficult to define. In this paper we present an innovative, science-based nutrient profiling system, Nutrimap®, which quantifies nutritional assets and weaknesses of foods.

Methods

The position of a food is defined according to its nutritional composition, food category, the consumer's nutritional needs, consumption data and major public health objectives for nutrition. Amounts of each of 15 relevant nutrients (in 100 kcal) are scored according to their ability to ‘rebalance’ or ‘unbalance’ the supply in the whole diet, compared with current recommendations and intakes. These scores are weighted differently in different food categories according to the measured relevance of the category to a nutrient's supply. Positive (assets) and negative (weaknesses) scores are totalled separately.

Results

Nutrimap®provides an overall estimate of the nutritional quality of same-category foods, enabling easy comparisons as exemplified for cereals and fruit/vegetables. Results are consistent with major nutritional recommendations and match classifications provided by other systems. Simulations for breakfasts show that Nutrimap®can help design meals of controlled nutritional value.

Conclusions

Combining objective scientific bases with pragmatic concerns, Nutrimap®appears to be effective in comparing food items. Decision-makers can set their own limits within the Nutrimap®-defined assets and weaknesses of foods and reach categorisations consistent with their objectives – from regulatory purposes to consumer information or support for designing meals (catering) or new products (food industry).
Who's keeping the code? Compliance with the international code for the marketing of breast-milk substitutes in Greater Glasgow
Authors: McInnes Rhona J , Wright Charlotte , Haq Shogufta , McGranachan Margaret
Published: February 2007

Objective

To evaluate compliance with the World Health Organization's International Code of Marketing of Breast-milk Substitutes in primary care, after the introduction of strict local infant feeding guidelines.

Design

An audit form was sent to all community-based health professionals with an infant feeding remit. Walking tours were conducted in a random sample of community care facilities.

Setting

Greater Glasgow Primary Care Division.

Subjects

(1) Primary-care staff with an infant feeding remit; (2) community health-care facilities.

Main outcome measures

Contact with manufacturers of breast-milk substitutes (BMS) and BMS company personnel, free samples or incentives, and advertising of BMS.

Results

Contact with company personnel was minimal, usually unsolicited and was mainly to provide product information. Free samples of BMS or feeding equipment were rare but childcare or parenting literature was more prevalent. Staff voiced concerns about the lack of relevant information for bottle-feeding mothers and the need to support the mother's feeding choice. One-third of facilities were still displaying materials non-compliant with the Code, with the most common materials being weight conversion charts and posters.

Conclusions

Contact between personnel from primary care and BMS companies was minimal and generally unsolicited. The presence of materials from BMS companies in health-care premises was more common. Due to the high level of bottle-feeding in Glasgow, primary-care staff stated a need for information about BMS.
Associations of psychosocial factors with fruit and vegetable intake
among African-Americans
Authors: Watters Joanne L , Satia Jessie A , Galanko Joseph A
Published: February 2007

Objective

To examine associations of various psychosocial factors with fruit and
vegetable intake in African-American adults.

Methods

A cross-sectional survey of a population-based sample of 658
African-Americans, aged 18–70 years, in North Carolina.
Information was collected on diet-related psychosocial (predisposing,
reinforcing and enabling) factors based on the PRECEDE (Predisposing,
Reinforcing, and Enabling Constructs in Educational Diagnosis and
Evaluation) planning framework; demographic, lifestyle and behavioural
characteristics, and fruit and vegetable intake.

Results

The mean participant age was 43.9 years (standard deviation 11.6), 57% were
female and 76% were overweight/obese. Participants expressed healthy beliefs
regarding many of, but not all, the psychosocial factors. For example,
although half of the respondents believed it is important to eat a diet high
in fruits/vegetables, only 26% knew that ≥ 5 daily
servings are recommended. The strongest associations of the psychosocial
factors with fruit/vegetable intake were for predisposing factors (e.g.
belief in the importance of a high fruit/vegetable diet and knowledge of
fruit/vegetable recommendations) and one reinforcing factor (social
support), with differences between the healthiest and least healthy
responses of 0.5–1.0 servings per day. There was evidence of
effect modification by gender in associations between psychosocial factors
and fruit/vegetable consumption (e.g. self-efficacy was only significant in
women), with higher intakes and generally healthier responses to the
psychosocial variables in women than men.

Conclusions

Interventions to increase fruit/vegetable intake in African-Americans may be
more effective if they focus primarily on predisposing factors, such as
knowledge, self-efficacy and attitudes, but not to the exclusion of
reinforcing and enabling factors. The psychosocial factors that are targeted
may also need to be somewhat different for African-American men and
women.
Decadal variation of the North Atlantic meridional heat transport and its relation to atmospheric processes
Authors: Martin T. , Ruprecht E.
Published: February 2007

The effects of the meridional heat transport in the North Atlantic Ocean (HTR) on the north hemispheric climate are studied using the results of the coupled model ECHAM5/MPI‐OM. Significant correlations exist between HTR and atmospheric processes over the Nordic Seas and the Eurasian continent only for low (periods longer than 40 years) and intermediate frequency variations (periods between 25 and 40 years). A positive HTR anomaly at 30°N is highly correlated with turbulent heat fluxes around 50°N. The transport through 70°N is directly related to the fluxes over the Nordic seas. From the correlation pattern with the atmospheric surface temperature and pressure one can conclude that the heat anomalies propagate along the cyclone tracks towards northeast over the Eurasian continent. The HRT anomalies are negatively correlated with the pressure over the Nordic seas and with the winter time anticyclone intensity over Siberia.
End of subduction in northern Apennines confirmed by observations of quasi‐Love waves from the great 2004 Sumatra‐Andaman earthquake
Authors: Levin V. , Park J. , Lucente F. P. , Margheriti L. , Pondrelli S.
Published: February 2007

Surface waves from the great Sumatra‐Andaman earthquakes of 2004 and 2005 that cross Italy south of ∼44°N display Love‐to‐Rayleigh scattered waves (quasi‐Love phases) diagnostic of sharp lateral gradients in the anisotropic properties of Earth's upper mantle. Surface waves that traverse Italy further north lack this distinctive phase, documenting a change in the upper mantle fabric that is corroborated by a shift in the fast polarization of shear wave birefringence. These observations suggest that orogen‐parallel asthenospheric extension behind the retreating Apennines slab has limited geographical expression. We hypothesize that subduction rollback currently terminates at 44°N, while the upper mantle flow pattern further to the north has been recently rearranged.
Development of objective‐oriented groundwater models: 2. Robust experimental design
Authors: Sun Ne‐Zheng , Yeh William W.‐G.
Published: February 2007

This paper continues the discussion in part 1 by considering the data collection strategy problem when the existing data are judged to be insufficient for constructing a reliable model. Designing an experiment for identifying a distributed parameter is very difficult because the identification of a more complex parameter structure requires more data. Moreover, without knowing the sufficiency of a design, finding an optimal design becomes meaningless. These difficulties can be avoided if we turn to the construction of objective‐oriented models. The identifiability of a distributed parameter, as defined in this paper, contains the reducibility of parameter structure. Sufficient conditions for this kind of identifiability are given. When the structure error associated with a structure reduction is too large, these conditions may not be satisfied no matter how much data are collected. In this paper we formulate a new experimental design problem that consists of two objectives: minimizing the cost and maximizing the information content, with robustness and feasibility as constraints. We develop an algorithm that can find a cost‐effective robust design for objective‐oriented parameter identification. We also present a heuristic algorithm that can find a suboptimal design with less computational effort for real case studies. The proposed methodology is used to design a pumping test for identifying a distributed hydraulic conductivity. We verify the robustness of the obtained design by assuming that the true parameter may have continuous, discrete, random, and fractured structures. Finally, the presented procedure of constructing objective‐oriented models is described step by step.
Atomistic simulations of shock induced microstructural evolution and spallation in single crystal nickel
Authors: Srinivasan S. G. , Baskes M. I. , Wagner G. J.
Published: February 2007

Spallation in single crystalline nickel was studied using molecular dynamics simulations. The shock waves—incident waves, the waves reflected from sample free surfaces, and interference between reflected waves—create and destroy many microstructural features. These features, though unimportant in determining the spall strength, control the spall nucleation site. Spall occurs by cavitation at a grain boundary junction in cold, defective, tensile regions of the sample. Atomistic calculations and experiments, though separated by six orders of magnitude in strain rates, follow a universal strain rate behavior.
Discontinuous molecular dynamics for semiflexible and rigid bodies
Authors: Hernández de la Peña Lisandro , van Zon Ramses , Schofield Jeremy , Opps Sheldon B.
Published: February 2007

A general framework for performing event-driven simulations of systems with semiflexible or rigid bodies interacting under impulsive forces is outlined. The method consists of specifying a means of computing the free evolution of constrained motion, evaluating the times at which interactions occur, and determining the consequences of interactions on subsequent motion. Algorithms for computing the times of interaction events and carrying out efficient event-driven simulations are discussed. The semiflexible case and the rigid case differ qualitatively in that the free motion of a rigid body can be computed analytically and need not be integrated numerically.
Discontinuous molecular dynamics for rigid bodies: Applications
Authors: Hernández de la Peña Lisandro , van Zon Ramses , Schofield Jeremy , Opps Sheldon B.
Published: February 2007

Event-driven molecular dynamics simulations are carried out on two rigid-body systems which differ in the symmetry of their molecular mass distributions. First, simulations of methane in which the molecules interact via discontinuous potentials are compared with simulations in which the molecules interact through standard continuous Lennard-Jones potentials. It is shown that under similar conditions of temperature and pressure, the rigid discontinuous molecular dynamics method reproduces the essential dynamical and structural features found in continuous-potential simulations at both gas and liquid densities. Moreover, the discontinuous molecular dynamics approach is demonstrated to be between 3 and 100 times more efficient than the standard molecular dynamics method depending on the specific conditions of the simulation. The rigid discontinuous molecular dynamics method is also applied to a discontinuous-potential model of a liquid composed of rigid benzene molecules, and equilibrium and dynamical properties are shown to be in qualitative agreement with more detailed continuous-potential models of benzene. The few qualitative differences in the angular dynamics of the two models are related to the relatively crude treatment of variations in the discontinuous repulsive interactions as one benzene molecule rotates by another.
Methodological aspects in the calculation of parity-violating effects in nuclear magnetic resonance parameters
Authors: Weijo Ville , Bast Radovan , Manninen Pekka , Saue Trond , Vaara Juha
Published: February 2007

We examine the quantum chemical calculation of parity-violating (PV) electroweak contributions to the spectral parameters of nuclear magnetic resonance (NMR) from a methodological point of view. Nuclear magnetic shielding and indirect spin-spin coupling constants are considered and evaluated for three chiral molecules, H2O2, H2S2, and H2Se2. The effects of the choice of a one-particle basis set and the treatment of electron correlation, as well as the effects of special relativity, are studied. All of them are found to be relevant. The basis-set dependence is very pronounced, especially at the electron correlated ab initio levels of theory. Coupled-cluster and density-functional theory (DFT) results for PV contributions differ significantly from the Hartree-Fock data. DFT overestimates the PV effects, particularly with nonhybrid exchange-correlation functionals. Beginning from third-row elements, special relativity is of importance for the PV NMR properties, shown here by comparing perturbational one-component and various four-component calculations. In contrast to what is found for nuclear magnetic shielding, the choice of the model for nuclear charge distribution—point charge or extended (Gaussian)—has a significant impact on the PV contribution to the spin-spin coupling constants.
Measurements of threshold photoemission magnetic dichroism using ultraviolet lasers and a photoelastic modulator
Authors: Nakagawa Takeshi , Yokoyama Toshihiko , Hosaka Masahito , Katoh Masahiro
Published: February 2007

A magneto-optical method based on valence band photoemission by laser excitation is described. Total photoexcited electron dichroism is detected using wave plates or a photoelastic modulator. Compared to the direct current method using wave plates, a modulation technique assisted by a photoelastic modulator has an advantage to improve the signal-to-noise ratio of magnetic dichroism by a factor of 10. The magnetic circular and linear dichroism can be investigated with this technique. An application to magnetic domain imaging using photoemission electron microscope is also demonstrated.
Ab initio study of interaction-induced NMR shielding constants in mixed rare gas dimers
Authors: Antušek Andrej , Jaszuński Michał , Rizzo Antonio
Published: February 2007

The interaction-induced contribution to the NMR shielding constants in homonuclear A2 and heteronuclear AB (A,B=He,Ne,Ar) dimers is obtained ab initio by employing a coupled cluster singles and doubles with perturbative treatment of triples wave function model and extended correlation-consistent basis sets. The second virial coefficients entering the expansion of the property with the density are then computed in a fully quantum mechanical approach, for temperatures ranging from the limit of dissociation of the dimer to well above standard conditions. The results can be used to describe the density and temperature dependence of the shielding constants in binary mixtures of helium, neon, and argon. The predicted effects should be observable for the interaction of Ne21 with other rare gases.
Noncontact-mode scanning capacitance force microscopy towards quantitative two-dimensional carrier profiling on semiconductor devices
Authors: Kimura Kenjiro , Kobayashi Kei , Matsushige Kazumi , Usuda Koji , Yamada Hirofumi
Published: February 2007

Scanning capacitance force microscopy (SCFM) is a promising tool for investigation of two-dimensional carrier density distribution on semiconducting devices. Its sensitivity is strongly dependent on the Q factor of the mechanical resonance mode of the cantilever. Therefore, measurement in vacuum is more appropriate for increasing the sensitivity. In this letter, the authors describe noncontact-mode (NC) SCFM which is combined with the frequency modulation detection method and its signal characteristics. The authors derived a quasiquantitative calibration curve which correlates to the amplitude signal in NC-SCFM to the dopant density. Using the calibration curve, the authors obtained a quasiquantitative two-dimensional dopant density distribution map on a cross-sectional transistor device.
Strength-improved Zr-based metallic glass/porous tungsten phase composite by hydrostatic extrusion
Authors: Xue Y. F. , Cai H. N. , Wang L. , Wang F. C. , Zhang H. F.
Published: February 2007

Hydrostatic extrusion, as a quite rarely applied technique, is used for the deformation of the Zr-based metallic glass/porous tungsten phase composite prepared by pressure infiltration. The fracture strength increases from 1852MPa for the as-cast composite to 2112MPa for the as-extruded composite. An apparent work hardening behavior was also observed in the as-extruded composite. The improved mechanical properties of the as-extruded composite are proposed to contribute to the stable interface between the metallic glass phase and the tungsten phase and the high dislocation density of the tungsten phase.
Enhanced near-infrared photoluminescence from isoelectronic luminescent centers in sulfur-implanted silicon with copper or silver coimplantation
Authors: Zhang J. G. , Wang X. X. , Cheng B. W. , Yu J. Z. , Wang Q. M. , Hau J. , Ding L. , Ge W. K.
Published: February 2007

Enhanced near-infrared photoluminescence (PL) from sulfur-related isoelectronic luminescent centers in silicon was observed from thermally quenched sulfur-implanted silicon in which additional copper or silver ions had been coimplanted. The PL from the sulfur and copper coimplanted silicon peaked between 70 and 100K and persisted to 260K. This result strongly supports the original conjecture from the optical detection of magnetic resonance studies that the strong PL from sulfur-doped silicon comes from S–Cu isoelectronic complexes [Frens et al., Phys. Rev. B 46, 12316 (1992); Mason et al., ibid. 58, 7007 (1998).].
Broadband quantum cascade laser emitting from 7.7to8.4μm operating up to 340K
Authors: Ng W. H. , Zibik E. A. , Soulby M. R. , Wilson L. R. , Cockburn J. W. , Liu H. Y. , Steer M. J. , Hopkinson M.
Published: February 2007

A broadband midinfrared laser operating up to 340K in pulsed mode is presented. It was realized by incorporating seven different quantum cascade active regions with 0.2μm increments to emit at different wavelengths. Despite the relatively large wavelength increments, a continuous lasing spectrum is obtained from 7.7to8.4μm, with significant improvements in threshold current and temperature performance compared with previously reported broadband quantum cascade lasers. A full temperature dependent characterization was performed, and the threshold current density at 300K was 6.5kA∕cm2, with peak output power of over 100mW. A characteristic temperature of T0=192K was obtained.
Experimental and theoretical study of heterogeneous iron precipitation in silicon
Authors: Haarahiltunen A. , Väinölä H. , Anttila O. , Yli-Koski M. , Sinkkonen J.
Published: February 2007

Heterogeneous iron precipitation in silicon was studied experimentally by measuring the gettering efficiency of oxide precipitate density of 1×1010cm−3. The wafers were contaminated with varying iron concentrations, and the gettering efficiency was studied using isothermal annealing in the temperature range from 300to780°C. It was found that iron precipitation obeys the so-called s-curve behavior: if iron precipitation occurs, nearly all iron is gettered. For example, after 30min annealing at 700°C, the highest initial iron concentration of 8×1013cm−3 drops to 3×1012cm−3, where as two lower initial iron concentrations of 5×1012 and 2×1013cm−3 remain nearly constant. This means that the level of supersaturation plays a significant role in the final gettering efficiency, and a rather high level of supersaturation is required before iron precipitation occurs at all. In addition, a model is presented for the growth and dissolution of iron precipitates at oxygen-related defects in silicon during thermal processing. The heterogeneous nucleation of iron is taken into account by special growth and dissolution rates, which are inserted into the Fokker-Planck equation. Comparison of simulated results to experimental ones proves that this model can be used to estimate internal gettering efficiency of iron under a variety of processing conditions.
Interface between platinum(111) and liquid isopropanol (2-propanol): A model for molecular dynamics studies
Authors: Tarmyshov Konstantin B. , Müller-Plathe Florian
Published: February 2007

A molecular dynamics model and its parametrization procedure are devised and used to study adsorption of isopropanol on platinum(111) (Pt(111)) surface in unsaturated and oversaturated coverages regimes. Static and dynamic properties of the interface between Pt(111) and liquid isopropanol are also investigated. The magnitude of the adsorption energy at unsaturated level increases at higher coverages. At the oversaturated coverage (multilayer adsorption) the adsorption energy reduces, which coincides with findings by Panja et al. in their temperature-programed desorption experiment [Surf. Sci. 395, 248 (1998)]. The density analysis showed a strong packing of molecules at the interface followed by a depletion layer and then by an oscillating density profile up to 3nm. The distribution of individual atom types showed that the first adsorbed layer forms a hydrophobic methyl “brush.” This brush then determines the distributions further from the surface. In the second layer methyl and methine groups are closer to the surface and followed by the hydroxyl groups; the third layer has exactly the inverted distribution. The alternating pattern extends up to about 2nm from the surface. The orientational structure of molecules as a function of distance of molecules is determined by the atom distribution and surprisingly does not depend on the electrostatic or chemical interactions of isopropanol with the metal surface. However, possible formation of hydrogen bonds in the first layer is notably influenced by these interactions. The surface-adsorbate interactions influence the mobility of isopropanol molecules only in the first layer. Mobility in the higher layers is independent of these interactions.
Leukocyte margination in a model microvessel
Authors: Freund Jonathan B.
Published: February 2007

The physiological inflammation response depends upon the multibody interactions of blood cells in the microcirculation that bring leukocytes (white blood cells) to the vessel walls. We investigate the fluid mechanics of this using numerical simulations of 29 red blood cells and one leukocyte flowing in a two-dimensional microvessel, with the cells modeled as linearly elastic shell membranes. Despite its obvious simplifications, this model successfully reproduces the increasingly blunted velocity profiles and increased leukocyte margination observed at lower shear rates in actual microvessels. Red cell aggregation is shown to be unnecessary for margination. The relative stiffness of the red cells in our simulations is varied by over a factor of 10, but the margination is found to be much less correlated with this than it is to changes associated with the blunting of the mean velocity profile at lower shear rates. While velocity around the leukocyte when it is near the wall depends upon the red cell properties, it changes little for strongly versus weakly marginating cases. In the more strongly marginating cases, however, a red cell is frequently observed to be leaning on the upstream side of the leukocyte and appears to stabilize it, preventing other red cells from coming between it and the wall. A well-known feature of the microcirculation is a near-wall cell-free layer. In our simulations, it is observed that the leukocyte’s most probable position is at the edge of this layer. This wall stand-off distance increases with velocity following a scaling that would be expected for a lubrication mechanism, assuming that there were a nearly constant force pushing the cells toward the wall. The leukocyte’s near-wall position is observed to be less stable with increasing mean stand-off distance, but this distance would have potentially greater effect on adhesion since the range of the molecular binding is so short.
Laboratory experiments on the generation of internal tidal beams over steep slopes
Authors: Gostiaux Louis , Dauxois Thierry
Published: February 2007

We designed a simple laboratory experiment to study internal tides generation. We consider a steep continental shelf, for which the internal tide is shown to be emitted from the critical point, which is clearly amphidromic. We also discuss the dependence of the width of the emitted beam on the local curvature of topography and on viscosity. Finally, we derive the form of the resulting internal tidal beam by drawing an analogy with an oscillating cylinder in a static fluid.
Characterization of a derivative photoacoustic spectrometer
Authors: Guo Lina , Tang Zhilie , He Yongheng , Zhang Hanchao
Published: February 2007

A design of derivative photoacoustic spectrometer is presented in this article. It mainly includes a wavelength-intensity splitter and a complementary chopper. In our design, a dual wavelength derivative method is introduced to implement a derivative operation. Through the wavelength-intensity splitter, two beams are obtained and then complementarily modulated by the complementary chopper to satisfy the first derivative requirements as well as to achieve the differential of photoacoustic signals. As examples, the first derivative photoacoustic spectra of He–Ne laser and xenon lamp are also presented in this article. The results show that the first derivative photoacoustic spectrum can provide a superior fine spectral structure and spectral resolution compared to the photoacoustic absorption spectrum.
Time-resolved intervalley transitions in GaN single crystals
Authors: Wu S. , Geiser P. , Jun J. , Karpinski J. , Wang D. , Sobolewski Roman
Published: February 2007

We present a direct observation of time-resolved intervalley transitions of electrons between the conduction band Γ and L valleys in GaN single crystals using a two-color (ultraviolet and near-infrared), femtosecond, pump-probe spectroscopic technique. We have found that the threshold for the Γ↔L transition appears at the energy of 4.51±0.05eV and the electron scattering time from the Γ to L valley is comparable to the 170fs width of our pump pulses, while the return process of electrons from L to Γ is measurably slower. The L to Γ scattering time is 1.02ps, while the total depopulation time of the L valley is estimated to be ∼20ps. Our physical model, based on the three-state rate equations, fitted our experimental data very well and allowed us to calculate the optical phonon emission time of 290fs. The deformation potential between the two valleys was also obtained from the intervalley scattering modeling and the value was 0.92×109eV∕cm.
Theoretical determination of lasing resonances in a microring
Authors: Baktur Reyhan , Pearson L. W. , Ballato J.
Published: February 2007

We present a theoretical development for the lasing frequencies of a microring laser. Such a microring is typically made from an optically active polymer, which is fabricated on a metallic wire or glass optical fiber in order to provide a substrate of well-defined geometry. Lasing resonances of the microring are computed as zeros of characteristic equations, which can be arranged such that a whispering gallery term appears explicitly together with a residual term associated with waveguide modes. It is found that the residual term recedes as the thickness of the microring increases, leaving a characteristic equation associated with a pure whispering gallery mode (WGM). The resonant condition is examined to compute the lasing frequencies and the thickness of the microring that supports WGM. Computed data are compared with published experimental data on polymer microring lasers, and computed results match well with experiments.
Low-temperature-induced swelling of a hydrophobic polymer: A lattice approach
Authors: Buzano C. , De Stefanis E. , Pretti M.
Published: February 2007

The authors investigate equilibrium properties of a simple model of hydrophobic polymer in aqueous solution by means of dynamic Monte Carlo simulations. The solvent is described by a simplified two-dimensional model, defined on a triangular lattice, which has been previously shown to account for most thermodynamic anomalies of pure water and of hydrophobic solvation for monomeric solutes. The polymer is modeled as a self-avoiding walk on the same lattice. In this framework, the degrees of freedom of water are taken into account explicitly, and in principle there is no need to introduce effective self-contact interactions for the polymer in order to mimic the hydrophobic effect. In certain conditions, the authors observe low-temperature-induced swelling, i.e., expansion of the polymer globule upon decreasing temperature. The authors discuss the relationship between this phenomenon and the anomalous properties of the solvent.
Ferroelectriclike and pyroelectric behavior of CaCu3Ti4O12 ceramics
Authors: Shri Prakash B. , Varma K. B. R.
Published: February 2007

A ferroelectriclike hysteresis loop was obtained at room temperature for CaCu3Ti4O12 (CCTO) ceramic. The remnant polarization and coercive field for 1100°C∕5h sintered CaCu3Ti4O12 ceramics were 0.063μC∕cm2 and 195V∕cm, respectively. Remnant polarization increased while the coercive field decreased with increase in sintering temperature/duration, implying that these were microstructural dependent. The observation of the hysteresis loop for CCTO ceramic was corroborated by its pyroelectric behavior, and the pyroelectric current at room temperature was −0.0028nA. These findings were attributed to the presence of mixed-valent Ti ions, apart from off center displacement of Ti ions in TiO6 octahedra.
Structural properties of Bi-stabilized reconstructions of GaInAs(100) surface
Authors: Laukkanen P. , Ahola-Tuomi M. , Kuzmin M. , Perälä R. E. , Väyrynen I. J. , Tukiainen A. , Pakarinen J. , Saarinen M. , Pessa M.
Published: February 2007

Bismuth (Bi) is a surfactant which controls the electronic and structural properties of epitaxially grown GaInAs and GaInP alloys. The authors have studied Bi-terminated surfaces of GaInAs(100) layers, deposited onto InP(100) substrates, by means of scanning tunneling microscopy and spectroscopy and x-ray photoelectron spectroscopy. It appears that Bi stabilizes an interesting (2×1) surface reconstruction on GaInAs(100). Under certain conditions, this reconstruction undergoes a phase transition to (2×4), which has about one-half of the Bi content of the (2×1) surface. Based on the experimental findings, they discuss mechanisms leading to this phase transition.
Electric fatigue in poly(vinylidene fluoride-trifluoroethylene) 68∕32 copolymer films under cyclic electric field
Authors: Fang F. , Yang W. , Zhang M. Z.
Published: February 2007

Electric fatigue under cyclic loading was characterized for poly(vinylidene fluoride-trifluoroethylene) 68∕32 copolymer films prepared under two processing conditions. For the copolymer films prepared by solution casting and then annealing (termed as unstretched films), the remanent polarization (Pr) decreases while the coercive field (Ec) increases as the field cycles. For the copolymer films prepared by stretching the solution-cast films and then annealing (termed as stretched films), both Pr and Ec decrease as the cycle number increases. Scanning electron microscopy observation and x-ray diffraction analysis were carried out to examine the morphology and microstructure changes during the electric field cycling. The differences in the polarization and electric fatigue behavior between the unstretched and the stretched copolymer films can be mainly attributed to the change of the crystallinity, the orientation degree of the polymer chains and electric dipoles, as well as the interfacial layer effects.
Low temperature growth of ZnMnO: A way to avoid inclusions of foreign phases and spinodal decomposition
Authors: Wójcik A. , Godlewski M. , Guziewicz E. , Kopalko K. , Jakieła R. , Kiecana M. , Sawicki M. , Guziewicz M. , Putkonen M. , Niinistö L. , Dumont Y. , Keller N.
Published: February 2007

The authors demonstrate herein that by lowering of a growth temperature they can obtain ZnMnO layers with homogeneous Mn distribution, which are free of Mn accumulations and inclusions of foreign phases due to other Mn oxides. These layers (with low Mn content fractions) show paramagnetic phase in room temperature magnetization measurements. Contribution of a high temperature ferromagnetic phase is missing, which the authors relate to blocking of spinodal decomposition of ZnMnO under controlled growth conditions of atomic layer deposition.
Spin-cast composite gate insulation for low driving voltages and memory effect in organic field-effect transistors
Authors: Yildirim F. A. , Ucurum C. , Schliewe R. R. , Bauhofer W. , Meixner R. M. , Goebel H. , Krautschneider W.
Published: February 2007

The authors report on a solution-processed composite film based on poly(vinylidene fluoride/trifluoroethylene) copolymer and barium titanate (BT) nanopowder, to be used as ferroelectric high-κ gate insulation in organic field-effect transistors (OFETs). Flexible films of up to 50vol% BT powder content are produced by preparing homogeneous dispersion of the powder in the polymer solutions. The films exhibited high specific volume resistivities combined with dielectric constants of up to 51.5 at 1kHz. Low-voltage OFETs with ferroelectric hysteresis and good memory retention properties were demonstrated by using the composite films.
Scale-length optimizing of short pulse CuKα laser-plasma sources
Authors: Khattak F. Y. , Garcia Saiz E. , Dzelzainis T. , Riley D. , Zhai Z.
Published: February 2007

The authors present experimental results showing how the use of a high contrast femtosecond laser system allows better optimization of Kα emission from a Cu target. The shorter scale-length preformed plasma is better optimized for resonance absorption of the laser light when the laser is moved away from best focus. The experimental data show a central peak of Kα emission at tight focus with strong secondary peaks at large offset. The use of these secondary peaks results in a much reduced hard x-ray background and should lead to shorter Kα pulses than at tight focus.