bluuebunny/crossref_metadata_2025 huggingface dataset:
Research Productivity of Business Administration and Accountancy Faculty, University of Northern Philippines, Vigan City
Authors: DUMBRIQUE JEAN S. , ALON TERESITA D.
Published: September 2013

Faculty members of State Universities and Colleges (SUCs) perform research function in addition to instruction, extension and production. This study was conducted to look into the profile of the published research from year of entry up to year 2008 of the regular faculty members of the First Semester of SY 2008-2009 at the College of Business Administration and Accountancy (CBAA) of the University of Northern Philippines (UNP) as affected by some personal and professional factors. It utilized the correlational design of descriptive method of research. Findings showed that the CBAA faculty is characterized by dominance of members of the female sex, of married status, of middle to senior age, with master’s degree, with academic rank of associate professor, and with official designations. Almost half of them have received monthly salary ranging from P10, 001 – P20, 000. Very few are members of scientific/research organizations. The CBAA faculty have published research since 2000. From 2000 to 2008, a total of 43 researches have been published. These were done by nearly half (19) of the 39 regular CBAA faculty members. More researches were done with co-authors than researches by single authors. Most of these researches are of college and curricular program levels, and over four-fifths were financed personally by the faculty researchers. All the researches were published in research journals and some of them were also disseminated in lecture fora and research dissemination and utilization seminars. One research was disseminated through poster exhibit. Majority of the regular CBAA faculty members have never participated in any research activity since their year of entry to the University up to year 2008. Educational attainment and membership in scientific/research organizations came out as good indicators of faculty research productivity.Keywords: Research, higher education, research productivity, correlational descriptive method,Philippines
Characterization of El Niño, La Niña, and normal conditions through planktonic foraminifera (2006–2007) in the southeastern Pacific
Authors: Gajardo Nathalie , González Humberto E , Marchant Margarita
Published: September 2013

We conducted a study to characterize the foraminiferal association off south-central Chile under positive (January to December 2006), neutral (January to June 2007), and negative (July to September 2007) thermal anomalies, which coincided approximately with El Niño (EN), normal (NC), and La Niña (LN) conditions, respectively, using samples collected in a sediment trap located off Concepción at 2300 m depth. During the three environmental conditions, total species richness was 19, with 18 species present during EN, 14 during NC, and 14 during LN. Moreover, a typical association of subantarctic waters was observed during NC and LN, but not during EN, when we found a mixture of cold and warm water species as well as higher foraminiferal and calcium carbonate fluxes. However, diversity was very similar under the three conditions. We observed significant differences in foraminiferal and calcium carbonate fluxes between NC and EN, with higher values during the warm phase.
Estimating illegal catch of abalone and lobster along the coast of the Baja California Peninsula
Authors: Ponce-Díaz Germán , Arreguín-Sánchez Francisco , Hernández-Llamas Alfredo , Del Monte-Luna Pablo , Ramade-Villanueva Mario
Published: September 2013

Illegal catch of abalone and lobster along the west coast of the Baja California Peninsula (Mexico) was estimated from surveys conducted among fishers and data of custom duties on live lobster exported to the USA. We estimated that illegal catch of abalone amounts to 62 t yr–1 (27% of the commercial catch) and illegal catch of lobster amounts to 64 t yr–1 (5% of the commercial catch). The two methods used in this study to estimate the illegal lobster catch yielded similar and consistent results (4.7% of the legal catch when using survey data and 4.5% when using data on custom duties for 1989–2002). We conclude that the methods of estimation are useful and reliable because they are based on direct sources of information. The methods could be used for a bottom-up approach to estimate illegal catch.
Grazing of the dinoflagellate Noctiluca scintillans on the paralytic toxin-producing dinoflagellate Gymnodinium catenatum: Does grazing eliminate cells during a bloom?
Authors: Bustillos-Guzmán José J , Band-Schmidt Christine J , López-Cortés David J , Hernández-Sandoval Francisco E , Núñez-Vázquez Erick , Gárate-Lizárraga Ismael
Published: September 2013

Temperature and nutrient concentrations were measured during a mixed bloom of Noctiluca scintillans and Gymnodinium catenatum in La Paz Bay, Gulf of California. Under laboratory conditions, we offered three concentrations of G. catenatum (312, 625, or 1015 cells mL–1) to 0.53 N. scintillans cells mL–1 to study predation rates. Experiments were carried out with 750 mL of culture during a fiveday period. Sea surface temperature clearly showed a transitional period from colder to warmer water during the bloom. Field and laboratory data showed that N. scintillans fed on G. catenatum. During the trial, more than 70% of N. scintillans cells contained G. catenatum cells in their vacuoles. Ingestion rates varied; the highest ranged from 30 to 40 G. catenatum cells h–1 in each N. scintillans cell. A clear relation to the concentration of the diet was not evident. Low values of 1 to 3 G. catenatum cells h–1 in each N. scintillans cell were typical at the end of the trial. Noctiluca scintillans doubled in concentration about every 48 h; however, numerous trophonts were observed leaving the cytoplasmic membrane, suggesting cell damage. These data indicate that N. scintillans ingests G. catenatum cells but the prey appears to damage predator cells in a relatively short time.
Benthic community structure in kelp forests from the Southern California Bight
Authors: Torres-Moye Guillermo , Edwards Matthew S , Montaño-Moctezuma Cira Gabriela
Published: September 2013

The United States and Mexico share the Southern California Bight (SCB) ecosystem in the Northeast Pacific Ocean where marine wildlife and habitats historically have been disturbed by human activities. Within this ecosystem, forests of the giant kelp Macrocystis pyrifera are critical habitats that sustain diverse biological assemblages and important fishery species. We studied patterns of temporal and spatial variability within the benthic communities of five transboundary kelp forests in California (USA) and Baja California (Mexico) over a fouryear period that included a moderate El Niño event. While the benthic marine communities shared some species, they varied significantly in community structure from each other, and the degree of dissimilarity was not related to the geographic distances among the studied habitats. Rather, species richness was significantly related to local substratum rugosity, suggesting it could be used as a proxy of relative benthic biological diversity. Temporal changes in the benthic assemblages were not consistent across all forests, and contrary to observations made during previous El Niño events in the SCB, the benthic communities did not change significantly following the 2009–2010 El Niño. Such an unexpected community response may be explained by the fact that the 2009–2010 El Niño was linked to the Modoki phenomenon, where warm sea surface temperature is focused in the central equatorial Pacific and not in the eastern Pacific Ocean. We propose that long-term conservation efforts should incorporate this ecological knowledge to support science-based decisions, binational coordination of policies, and coherent management practices including the design of transboundary conservation networks as spatial management tools for the protection, conservation, and/or restoration of the SCB ecosystem.
The constancy of ζ in single-clock Inflation at all loops
Authors: Senatore Leonardo , Zaldarriaga Matias
Published: September 2013

Abstract

Studying loop corrections to inflationary perturbations, with particular emphasis on infrared factors, is important to understand the consistency of the inflationary theory, its predictivity and to establish the existence of the slow-roll eternal inflation phenomena and its recently found volume bound. In this paper we show that ζ-correlators are time-independent at large distances at all-loop level in single clock inflation. We write the n-th order correlators of ζ as the time-integral of Green’s functions times the correlators of local sources that are function of the lower order fluctuations. The Green’s functions are such that only non-vanishing correlators of the sources at late times can lead to non- vanishing correlators for ζ at long distances. When the sources are connected by high wavenumber modes, the correlator is peaked at short distances, and these diagrams cannot lead to a time-dependence by simple diff. invariance arguments. When the sources are connected by long wavenumber modes one can use similar arguments once the constancy of ζ at lower orders was established. Therefore the conservation of ζ at a given order follows from the conservation of ζ at the lower orders. Since at tree-level ζ is constant, this implies constancy at all-loops by induction.
The Effect of Extension Constraint Knee Bracing on Dynamic Balance, Gait Mechanics, and Joint Alignment
Authors: Butler Robert J. , Queen Robin M. , Wilson Becky , Stephenson John , Barnes C. Lowry
Published: September 2013

Objective

To examine how an extension constraint knee brace affects active and passive standing knee joint alignment, dynamic balance, and gait mechanics.

Design

Repeated‐measures, within‐subjects design.

Setting

Research laboratory.

Participants

Persons (N = 24) with no current diagnosed gait dysfunction or neuromuscular limitations that limit activities of daily living.

Methods

All subjects were tested with use of dynamic balance and gait analysis. Dynamic balance was examined with the Lower Quarter Y Balance Test. Gait analysis was conducted at a freely chosen walking speed for 2 conditions: (1) use of a brace with free range of motion (FROM) and (2) use of a brace with 30‐degree extension constraint (ECON). In a subset of subjects, radiographs were used to examine standing knee alignment for 3 conditions: (1) FROM, (2) use of a knee ECON brace in a relaxed position; and (3) use of a knee ECON brace with maximal volitional quadriceps contraction.

Main Outcome Measures

Peak knee flexion, knee flexion range of motion, peak vertical ground reaction force during weight acceptance and propulsion, and maximum reach distance in the anterior, posteromedial, and posterolateral directions were measured.

Results

Differences in dynamic balance were observed between ECON and FROM for the anterior reach. Peak knee flexion increased 3.2° and peak knee extension decreased 7.4° in the ECON condition. Vertical GRF values were found to increase bilaterally during ECON at midstance but decreased bilaterally during propulsion. Radiographic images revealed that the ECON elicited a 22.2° flexion contracture with minimal quadriceps activation but only reduced motion by 4.8° with maximal volitional quadriceps activation.

Conclusions

Extension constraint knee braces alter joint alignment, dynamic balance, knee mechanics during gait, and vertical loading during gait. However, the changes in motion observed were lower than those induced by the constraining mechanism.
Neurobiologische Grundlagen der Emotionsregulation
Authors: Steinfurth Elisa , Wendt Julia , Hamm Alfons
Published: September 2013

Es gehört zu den zentralen menschlichen Fertigkeiten, Emotionen, welche durch externale oder internale Ereignisse ausgelöst werden gemäß der kurz- und langfristigen Handlungsziele zu regulieren. Diese Fertigkeiten werden über neuronale Netzwerke im präfrontalen Kortex vermittelt. Der dorsolaterale und ventromediale präfrontale Kortex ist entscheidend beteiligt, wenn Menschen über Neubewertung der Situation versuchen ihre Emotionen kognitiv zu modulieren. Die neuronalen Netzwerke dieser präfrontalen Kortexareale hemmen dabei die Aktivität der Amygdala und reduzieren somit die Signifikanz des emotionsauslösenden Ereignisses. Emotionsregulation wird daher als Zusammenspiel von emotionsgenerierenden Regionen (z. B. Amygdala, Insel etc.) und regulierenden Kontrollregionen (z. B. dorsolateraler und ventromedialer präfrontaler Kortex) betrachtet.
Modification of polymer velvet cathode via metallic Mo coating for enhancement of high-current electron emission performances
Authors: Xiong Ying , Wang Bing , Xia Liansheng , Zhang Huang , Yi Yong
Published: September 2013

The effect of surface Mo coating on the high-current electron emission performances for polymer velvet cathode has been investigated in a diode with A-K gap of 11.5 cm by the combination of time-resolved electrical diagnostic and temporal pressure variation. Compared with uncoated polymer velvet cathode under the single-pulsed emission mode, the Mo-coated one shows lower outgassing levels (∼0.40 Pa L), slower cathode plasma expansion velocity (∼2.30 cm/μs), and higher emission stability as evidences by the change in cathode current, temporal pressure variation, and diode perveance. Moreover, after Mo coating, the emission consistency of the polymer velvet cathode between two adjacent pulses is significantly improved in double-pulsed emission mode with ∼500 ns interval between two pulses, which further confirms the effectiveness of Mo coating for enhancement of electron emission performance of polymer velvet cathodes. These results should be of interest to the high-repetitive high-power microwave systems with cold cathodes.
Photoelectron imaging of XUV photoionization of CO2 by 13–40 eV synchrotron radiation
Authors: Furch Federico J. , Birkner Sascha , Jungmann Julia H. , Kelkensberg Freek , Schulz Claus Peter , Rouzée Arnaud , Vrakking Marc J. J.
Published: September 2013

Valence band photoionization of CO2 has been studied by photoelectron spectroscopy using a velocity map imaging spectrometer and synchrotron radiation. The measured data allow retrieving electronic and vibrational branching ratios, vibrationally resolved asymmetry parameters, and the total electron yield which includes multiple strong resonances. Additionally, the spectrum of low kinetic energy electrons has been studied in the resonant region, and the evolution with photon energy of one of the forbidden transitions present in the slow photoelectrons spectrum has been carefully analyzed, indicating that in the presence of auto-ionizing resonances the vibrational populations of the ion are significantly redistributed.
Kapitza resistance between superfluid helium and solid: Role of the boundary
Authors: Amrit J. , Ramiere A.
Published: September 2013

Kapitza resistance measurements conducted at T > 1 K on silicon and niobium single crystals in contact with helium demonstrate respectively the importance of atomic scale surface roughness and dislocations due to surface damage at the boundary. Two different experimental configurations were used.
Excitation spectrum in two-dimensional superfluid 4He
Authors: Arrigoni F. , Vitali E. , Galli D. E. , Reatto L.
Published: September 2013

In this work we perform an ab-initio study of an ideal two-dimensional sample of 4He atoms, a model for 4He films adsorbed on several kinds of substrates. Starting from a realistic Hamiltonian we face the microscopic study of the excitation phonon–roton spectrum of the system at zero temperature. Our approach relies on path integral ground state Monte Carlo projection methods, allowing to evaluate exactly the dynamic density correlation functions in imaginary time, and this gives access to the dynamic structure factor of the system S(q, ω), containing information about the excitation spectrum E(q), resulting in sharp peaks in S(q, ω). The actual evaluation of S(q, ω) requires the inversion of the Laplace transform in ill-posed conditions, which we face via the genetic inversion via falsification of theories technique. We explore the full density range from the region of spinodal decomposition to the freezing density, i.e., 0.0321 Å−2–0.0658 Å−2. In particular we follow the density dependence of the excitation spectrum, focusing on the low-wave vector behavior of E(q), the roton dispersion, the strength of single quasi-particle peak, Z(q), and the static density response function, χ(q). As the density increases, the dispersion E(q) at low-wave vector changes from a superlinear (anomalous dispersion) trend to a sublinear (normal dispersion) one, anticipating the crystallization of the system; at the same time the maxon–roton structure, which is barely visible at low density, becomes well developed at high densities, and the roton wave vector has a strong density dependence. Connection is made with recent inelastic neutron scattering results from highly ordered silica nanopores partially filled with 4He.
Optimization of SiGe selective epitaxy for source/drain engineering in 22 nm node complementary metal-oxide semiconductor (CMOS)
Authors: Wang G. L. , Moeen M. , Abedin A. , Kolahdouz M. , Luo J. , Qin C. L. , Zhu H. L. , Yan J. , Yin H. Z. , Li J. F. , Zhao C. , Radamson H. H.
Published: September 2013

SiGe has been widely used for source/drain (S/D) engineering in pMOSFETs to enhance channel mobility. In this study, selective Si1−xGex growth (0.25 ≤ x ≤ 0.35) with boron concentration of 1–3 × 1020 cm−3 in the process for 22 nm node complementary metal-oxide semiconductor (CMOS) has been investigated and optimized. The growth parameters were carefully tuned to achieve deposition of high quality and highly strained material. The thermal budget was decreased to 800 °C to suppress dopant diffusion, to minimize Si loss in S/D recesses, and to preserve the S/D recess shape. Two layers of Si1−xGex were deposited: a bottom layer with high Ge content (x = 0.35) which filled the recess and a cap layer with low Ge content (x = 0.25) which was elevated in the S/D regions. The elevated SiGe cap layer was intended to be consumed during the Ni-silicidation process in order to avoid strain reduction in the channel region arising from strain relaxation in SiGe S/D. In this study, a kinetic gas model was also applied to predict the pattern dependency of the growth and to determine the epi-profile in different transistor arrays. The input parameters include growth temperature, partial pressures of reactant gases, and chip layout. By using this model, the number of test wafers for epitaxy experiments can be decreased significantly. When the epitaxy process parameters can be readily predicted by the model for epi-profile control in an advanced chip design, fast and cost-effective process development can be achieved.
Temperature dependence of magnetoresistive output of pseudo spin valves with Co2Fe(Al1−xSix) Heusler alloys and a Ag spacer
Authors: Furubayashi T. , Nakatani T. M. , Goripati H. S. , Sukegawa H. , Takahashi Y. K. , Inomata K. , Hono K.
Published: September 2013

We investigated the temperature dependence of magnetoresistive (MR) outputs of current-perpendicular-to-plane pseudo spin valves with Co2FeAl1−xSix (0 ≤ x ≤ 1) Heusler alloy ferromagnetic layers and a Ag spacer layer to optimize x. The MR ratios at room temperature do not show x dependence, while the MR ratios measured at 5 K showed strong x dependence; the largest resistance change-area product ΔRA = 21 mΩ·μm2 was obtained for x = 1 and ΔRA decreased with decreasing x. The results apparently contradicts with the theoretical prediction that the highest spin polarization is attained for x = 0.5. The discrepancy is due to the structural origin that the L21 order is obtained only in the Co2FeSi alloy film.
The contact line behaviour of solid-liquid-gas diffuse-interface models
Authors: Sibley David N. , Nold Andreas , Savva Nikos , Kalliadasis Serafim
Published: September 2013

A solid-liquid-gas moving contact line is considered through a diffuse-interface model with the classical boundary condition of no-slip at the solid surface. Examination of the asymptotic behaviour as the contact line is approached shows that the relaxation of the classical model of a sharp liquid-gas interface, whilst retaining the no-slip condition, resolves the stress, and pressure singularities associated with the moving contact line problem while the fluid velocity is well defined (not multi-valued). The moving contact line behaviour is analysed for a general problem relevant for any density dependent dynamic viscosity and volume viscosity, and for general microscopic contact angle and double well free-energy forms. Away from the contact line, analysis of the diffuse-interface model shows that the Navier–Stokes equations and classical interfacial boundary conditions are obtained at leading order in the sharp-interface limit, justifying the creeping flow problem imposed in an intermediate region in the seminal work of Seppecher [Int. J. Eng. Sci. 34, 977–992 (1996)]. Corrections to Seppecher's work are given, as an incorrect solution form was originally used.
Simulation and modeling of turbulence subjected to a period of uniform plane strain
Authors: Zusi Christopher J. , Perot J. Blair
Published: September 2013

Direct numerical simulation is used to evaluate the effect of plane strain on isotropic homogeneous turbulence. The subsequent return to isotropy after the removal of the strain is also investigated. Large, moderate, and small strain rates are computed at moderate turbulence Reynolds numbers. The initial turbulence is generated via mechanical mixing so that the large scale turbulence develops relatively naturally. Turbulence length scales, Reynolds numbers, decay rates, and anisotropy are computed over the range of the simulations, with the goal of quantifying how anisotropic decay behaves. The simulations indicate that large scale anisotropy may not decay to zero at very large times. In agreement with experimental data, the presence of a recovery region is discerned before the return process is observed. Trajectory crossing is observed on the anisotropy invariant map indicating that anisotropy itself is not sufficient to determine its time evolution. Model constants for classic return-to-isotropy models are determined from the data and shown to vary with time. The oriented-eddy collision model [M. B. Martell and J. B. Perot, “The oriented-eddy collision turbulence model,” Flow, Turbul. Combust. 89(3), 335 (2012)], which includes turbulent structure information, is shown to predict the salient structure of the straining and return process.
Low background high efficiency radiocesium detection system based on positron emission tomography technology
Authors: Yamamoto Seiichi , Ogata Yoshimune
Published: September 2013

After the 2011 nuclear power plant accident at Fukushima, radiocesium contamination in food became a serious concern in Japan. However, low background and high efficiency radiocesium detectors are expensive and huge, including semiconductor germanium detectors. To solve this problem, we developed a radiocesium detector by employing positron emission tomography (PET) technology. Because 134Cs emits two gamma photons (795 and 605 keV) within 5 ps, they can selectively be measured with coincidence. Such major environmental gamma photons as 40K (1.46 MeV) are single photon emitters and a coincidence measurement reduces the detection limit of radiocesium detectors. We arranged eight sets of Bi4Ge3O12 (BGO) scintillation detectors in double rings (four for each ring) and measured the coincidence between these detectors using PET data acquisition system. A 50 × 50 × 30 mm BGO was optically coupled to a 2 in. square photomultiplier tube (PMT). By measuring the coincidence, we eliminated most single gamma photons from the energy distribution and only detected those from 134Cs at an average efficiency of 12%. The minimum detectable concentration of the system for the 100 s acquisition time is less than half of the food monitor requirements in Japan (25 Bq/kg). These results show that the developed radiocesium detector based on PET technology is promising to detect low level radiocesium.
A comparison of reduced coordinate sets for describing protein structure
Authors: Hinsen Konrad , Hu Shuangwei , Kneller Gerald R. , Niemi Antti J.
Published: September 2013

In all-atom molecular simulation studies of proteins, each atom in the protein is represented by a point mass and interactions are defined in terms of the atomic positions. In recent years, various simplified approaches have been proposed. These approaches aim to improve computational efficiency and to provide a better physical insight. The simplified models can differ widely in their description of the geometry and the interactions inside the protein. This study explores the most fundamental choice in the simplified protein models: the choice of a coordinate set defining the protein structure. A simplified model can use fewer point masses than the all-atom model and/or eliminate some of the internal coordinates of the molecule by setting them to an average or ideal value. We look at the implications of such choices for the overall protein structure. We find that care must be taken for angular coordinates, where even very small variations can lead to significant changes in the positions of far away atoms. In particular, we show that the ϕ/ψ torsion angles are not a sufficient coordinate set, whereas another coordinate set with two degrees of freedom per residue, virtual Cα backbone bond, and torsion angles performs satisfactorily.
Pyrolysis of furan in a microreactor
Authors: Urness Kimberly N. , Guan Qi , Golan Amir , Daily John W. , Nimlos Mark R. , Stanton John F. , Ahmed Musahid , Ellison G. Barney
Published: September 2013

A silicon carbide microtubular reactor has been used to measure branching ratios in the thermal decomposition of furan, C4H4O. The pyrolysis experiments are carried out by passing a dilute mixture of furan (approximately 0.01%) entrained in a stream of helium through the heated reactor. The SiC reactor (0.66 mm i.d., 2 mm o.d., 2.5 cm long) operates with continuous flow. Experiments were performed with a reactor inlet pressure of 100–300 Torr and a wall temperature between 1200 and 1600 K; characteristic residence times in the reactor are 60–150 μs. The unimolecular decomposition pathway of furan is confirmed to be: furan (+ M) $\rightleftharpoons$⇌ α-carbene or β-carbene. The α-carbene fragments to CH2=C=O + HC≡CH while the β-carbene isomerizes to CH2=C=CHCHO. The formyl allene can isomerize to CO + CH3C≡CH or it can fragment to H + CO + HCCCH2. Tunable synchrotron radiation photoionization mass spectrometry is used to monitor the products and to measure the branching ratio of the two carbenes as well as the ratio of [HCCCH2]/[CH3C≡CH]. The results of these pyrolysis experiments demonstrate a preference for 80%–90% of furan decomposition to occur via the β-carbene. For reactor temperatures of 1200–1400 K, no propargyl radicals are formed. As the temperature rises to 1500–1600 K, at most 10% of the decomposition of CH2=C=CHCHO produces H + CO + HCCCH2 radicals. Thermodynamic conditions in the reactor have been modeled by computational fluid dynamics and the experimental results are compared to the predictions of three furan pyrolysis mechanisms. Uncertainty in the pressure-dependency of the initiation reaction rates is a possible a source of discrepancy between experimental results and theoretical predictions.
Numerical investigation of pulsatile flow in endovascular stents
Authors: Rouhi A. , Piomelli U. , Vlachos P.
Published: September 2013

The flow in a plane channel with two idealized stents (one Λ-shaped, the other X-shaped) is studied numerically. A periodic pressure gradient corresponding to one measured in the left anterior descending coronary artery was used to drive the flow. Two Reynolds numbers were examined, one (Re = 80) corresponding to resting conditions, the other (Re = 200) to exercise. The stents were implemented by an immersed boundary method. The formation and migration of vortices that had been observed experimentally was also seen here. In the previous studies, the compliance mismatch between stent and vessel was conjectured to be the reason for this phenomenon. However, in the present study we demonstrate that the vortices form despite the fact that the walls were rigid. Flow visualization and quantitative analysis lead us to conclude that this process is due to the stent wires that generate small localized recirculation regions that, when they interact with the near-wall flow reversal, result in the formation of these vortical structures. The recirculation regions grow and merge when the imposed waveform produces near-wall flow reversal, forming coherent quasi-spanwise vortices, that migrate away from the wall. The flow behavior due to the stents was compared with an unstented channel. The geometric characteristics of the Λ-stent caused less deviation of the flow from an unstented channel than the X-stent. Investigating the role of advection and diffusion indicated that at Re = 80 advection has negligible contribution in the transport mechanism. Advection plays a role in the generation of streamwise vortices created for both stents at both Reynolds numbers. The effect of these vortices on the near-wall flow behavior is more significant for the Λ-stent compared to the X-stent and at Re = 200 with respect to Re = 80. Finally, it was observed that increasing the Reynolds number leads to early vortex formation and the creation of the vortex in a stented channel is coincident with the near wall flow reversal in an unstented one.
A reference-beam autocollimator with nanoradian sensitivity from mHz to kHz and dynamic range of 107
Authors: Arp T. B. , Hagedorn C. A. , Schlamminger S. , Gundlach J. H.
Published: September 2013

We describe an autocollimating optical angle sensor with a dynamic range of 9 mrad and nrad/\documentclass[12pt]{minimal}\begin{document}$\sqrt{\textrm {Hz}}$\end{document} Hz sensitivity at frequencies from 5 mHz to 3 kHz. This work improves the standard multi-slit autocollimator design by adding two optical components, a reference mirror and a condensing lens. This autocollimator makes a differential measurement between a reference mirror and a target mirror, suppressing common-mode noise sources. The condensing lens reduces optical aberrations, increases intensity, and improves image quality. To further improve the stability of the device at low frequencies the body of the autocollimator is designed to reduce temperature variations and their effects. A new data processing technique was developed in order to suppress the effects of imperfections in the CCD.
The spin-lattice relaxation in superfluid inclusions formed in the solid helium matrix
Authors: Birchenko A. P. , Vekhov Ye. O. , Mikhin N. P. , Rudavskii E. Ya.
Published: September 2013

Processes of spin-lattice relaxation in superfluid inclusions, formed during growth and rapid cooling of helium crystals, are studied by the pulse nuclear magnetic resonance method. Measurements of spin-lattice relaxation times were carried out using the two spin-echoes method. This allows to obtain reliable data for each of the coexisting phases of a two-phase system HCP matrix—superfluid inclusions. The samples of the solid solution 1% 3He in 4He with molar volume 20.2 cm3/mol are investigated in the temperature range 1.4–1.9 K. It is found that the time of spin-lattice relaxation in superfluid drops differs significantly from that in bulk superfluid. It is shown that in both cases the dominant relaxation mechanism is the wall relaxation, which is a few orders of magnitude faster than the bulk relaxation. However, in the bulk fluid, the velocity of wall relaxation is determined by the time of diffusion of atoms to the walls, while the spin relaxation processes directly on the wall play a major role in the superfluid inclusions. In the case of superfluid droplets, 3He atoms are the only magnetic impurities on the walls of the inclusions. They are much less efficient magnetic centers than the strong magnetic particles on the walls of the cell. Moreover, a spontaneous dramatic change is observed in the amplitude of one of the echo-signals, which is associated with the solidification of superfluid droplets and the formation of long-lived metastable disordered (glass) state.
Phonon transformation at a superfluid helium-solid interface
Authors: Adamenko I. N. , Nemchenko E. K.
Published: September 2013

The hamiltonian for the interaction of phonons in superfluid helium with an oscillating solid surface is derived. It can be used to calculate the probabilities of elastic, and all the possible inelastic, processes for phonon transformation at superfluid helium-solid interfaces. The contributions of all these processes to the heat flux and to the difference in the heat fluxes between the superfluid helium and the solid are calculated. These results are compared with experimental data and with the results obtained by others.
On the possibility of two phase transitions in liquid helium
Authors: Poluektov Yu. M. , Rybalko A. S.
Published: September 2013

An explanation is proposed for the maxima in the dielectric constant and density observed in liquid helium slightly above the superfluid transition temperature. It is shown that they may be caused by a phase transition that results in spontaneous polarization of the helium. This kind of transition is possible in the liquid because when an atom is polarized its energy levels are lowered, so that the polarization is energetically favorable, especially for light atoms. In addition, the development of a dipole moment in an atom leads to the appearance of an additional electric field and, therefore, to an increase in the energy. The possible spontaneous polarization of the system of atoms is determined by the competition among these factors. In accordance with this concept, as the temperature of liquid helium is lowered there is an initial phase transition into a polarized normal phase, followed by one from this nonzero polarization state into the superfluid state. The transition of the normal fluid into the polarized phase is described in terms of a phenomenological theory of phase transitions. The transition can be of first or second order.
Photodissociation dynamics of C4H2 at 164.41 nm: Competitive dissociation pathways
Authors: Yu Shengrui , Su Shu , Zhang Yongwei , Dai Dongxu , Yuan Kaijun , Yang Xueming
Published: September 2013

Photodissociation dynamics of C4H2 at 164.41 nm through the Rydberg state R(1Σu) have been studied using the high-resolution H atom Rydberg tagging technique. Experimental evidences show that two different predissociation pathways exist to form the ground C4H (X2Σ+) and electronically excited C4H (A2Π) products: the former has statistical and isotropic translational energy distribution through internal conversion (IC) to the ground state, while the latter has non-statistical and anisotropic translational energy distribution through IC to the excited repulsive state. The vibrational progressions of C4H (A2Π) products have also been observed and assigned.
On the stick-slip flow from slit and cylindrical dies of a Phan-Thien and Tanner fluid model. II. Linear stability analysis
Authors: Karapetsas George , Tsamopoulos John
Published: September 2013

During extrusion of viscoelastic fluids various flow instabilities may arise resulting in a distorted free surface. In order to investigate the factors generating these instabilities we performed a linear stability analysis at zero Reynolds number around the steady solution of the cylindrical or planar stick-slip flow for a viscoelastic fluid following the affine exponential Phan-Thien Tanner (PTT) model. Stick-slip flow is an important special case of the extrudate swell problem, since the latter reduces to it in the limit of infinite surface tension but avoids the complications of a free-boundary flow. The linear stability analysis is performed for various values of the rheological parameters of the PTT model in order to determine the effects of all material properties. It is found that the flow becomes unstable as the Weissenberg number increases above a critical value, due to a Hopf bifurcation suggesting that the flow will become periodic in time. Both the critical value of the Weissenberg number and the frequency of the instability depend strongly on the rheological parameters of the viscoelastic model. The corresponding eigenvectors indicate that the perturbed flow field has a spatially periodic structure, initiated at the rim of the die, extending for up to 5–7 die gaps downstream, but confined close to the surface of the extrudate, in qualitative agreement with existing experiments. This suggests that instability is generated by the combination of the singularity in the velocity and stress fields at the die lip and the strong extension that the extruded polymer undergoes near its surface. The elasticity alone can be responsible for the appearance of instabilities in the extrusion process of viscoelastic fluids and the often used assumptions of wall slip or compressibility, although they might be present, are not required. Finally, the mechanisms that produce these instabilities are examined through energy analysis of the disturbance flow.
An experimental study on annoyance scale for assessment of wind turbine noise
Authors: Seong Yeolwan , Lee Seunghoon , Young Gwak Doo , Cho Yoonho , Hong Jiyoung , Lee Soogab
Published: September 2013

Wind turbine noise referred to as “swishing sound” causes annoyance due to the amplitude modulation of the noise aerodynamically generated from blades. For the propagation characteristic of sound emitted from blade, the noise can be heard differently from place to place. For that reason, many studies on numerical index evaluating annoyance caused by wind turbine noise have been examined. The results, however, showed little correlation with change of equivalent continuous sound pressure level. In the present study, twenty-eight stimuli created by numerical simulation for the test were provided and thirty-two subjects assessed noise-induced annoyance. Additionally, a correlation analysis between sound descriptors and subjective annoyance was performed by using regression analysis with SAS software. This study shows that the maximum sound pressure level with fast time A-weighting (LAFmax) explains well the annoyance characteristics compared to the other descriptors considered.
Investigation of the effect of bilayer membrane structures and fluctuation amplitudes on SANS/SAXS profile for short membrane wavelength
Authors: Lee Victor , Hawa Takumi
Published: September 2013

The effect of bilayer membrane structures and fluctuation amplitudes on small angle neutron scattering (SANS) and small angle X-ray scattering (SAXS) profile is investigated based on harmonic motions of the surfactant bilayers with bending as well as thickness fluctuation motions. In this study we consider the case in which the wavelength of the bilayer membrane is shorter than the thickness of the membrane. We find that the thickness of the surfactant bilayer membrane, dm, affects both qdip and qpeak of I(q,0) profile, and that the fluctuation amplitude, a, of the membrane changes the peak of I(q,0). A simple formula is derived to estimate the thickness of the bilayer based on the qdip of the profile obtained from the simulation. The resulting estimates of the thickness of the bilayer with harmonic motion showed accuracy within 1%. Moreover, the bilayer thicknesses estimated from the proposed formula show an excellent agreement with the SANS and SAXS experimental results available in the literatures. We also propose a curve fit model, which describes the relationship between the fluctuation amplitude and the normalized qpeak ratio. The present results show the feasibility of the simple formula to estimate the fluctuation amplitude based on the SANS and SAXS profiles.
Schrödinger operator with a strong varying interaction on a curve in $\mathbb {R}^2$R2
Authors: Kondej Sylwia
Published: September 2013

In this paper, we study a two-dimensional quantum system governed by the Hamiltonian corresponding to the formal expression −Δ−(α+ω(·))δ(·−Γ), where α > 0, ω(·) is a continuous compactly supported function and Γ is a curve in \documentclass[12pt]{minimal}\begin{document}$\mathbb {R}^2$\end{document}R2. We derive the asymptotics of eigenvalues for α → ∞ and analyze consequences of introducing varying delta potential.
A resonant biaxial Helmholtz coil employing a fractal capacitor bank
Authors: Martin James E.
Published: September 2013

The design and construction of a series resonant biaxial Helmholtz coil for the production of magnetic fields as large as 500 G in the range of 100–2500 Hz is described. Important aspects of ac coil design are discussed, including: minimizing power losses due to the expected Joule heating, self-induced eddy currents, and skin resistance; controlling the stray capacitance; maximizing field homogeneity; and keeping peak voltages at acceptable levels. The design and construction of a computer-controlled, optically isolated fractal capacitor bank is then treated, and various aspects of capacitor selection and characterization were discussed. The system performance is demonstrated, including stability and the possibility of field component dephasing with typical magnetic samples.
An innovative experimental setup for the measurement of sputtering yield induced by keV energy ions
Authors: Salou P. , Lebius H. , Benyagoub A. , Langlinay T. , Lelièvre D. , Ban-d’Etat B.
Published: September 2013

An innovative experimental equipment allowing to study the sputtering induced by ion beam irradiation is presented. The sputtered particles are collected on a catcher which is analyzed in situ by Auger electron spectroscopy without breaking the ultra high vacuum (less than 10−9 mbar), avoiding thus any problem linked to possible contamination. This method allows to measure the angular distribution of sputtering yield. It is now possible to study the sputtering of many elements such as carbon based materials. Preliminary results are presented in the case of highly oriented pyrolytic graphite and tungsten irradiated by an Ar+ beam at 2.8 keV and 7 keV, respectively.
Excitation of a Si/SiGe quantum dot using an on-chip microwave antenna
Authors: Kawakami E. , Scarlino P. , Schreiber L. R. , Prance J. R. , Savage D. E. , Lagally M. G. , Eriksson M. A. , Vandersypen L. M. K.
Published: September 2013

We report transport measurements on a Si/SiGe quantum dot subject to microwave excitation via an on-chip antenna. The response shows signatures of photon-assisted tunneling and only a small effect on charge stability. We also explore the use of a d.c. current applied to the antenna for generating tunable, local magnetic field gradients and put bounds on the achievable field gradients, limited by heating of the reservoirs.
Mathematical methods for restricted domain ternary liquid mixture free energy determination using light scattering
Authors: Wahle Chris W. , Ross David S. , Thurston George M.
Published: September 2013

We extend methods of solution of a light scattering partial differential equation for the free energy of mixing to apply to connected, isotropic ternary liquid composition domains that do not touch all three binary axes. To do so we mathematically analyze the problem of inferring needed Dirichlet boundary data, and solving for the free energy, with use of hypothetical static light scattering measurements that correspond to dielectric composition gradient vectors that have distinct directions. The physical idea behind the technique is that contrasting absorption properties of mixture components can result in such distinctly directed dielectric composition gradient vectors, due to their differing wavelength dependences of dielectric response. At suitably chosen wavelengths, contrasting light scattering efficiency patterns in the ternary composition triangle can then correspond to the same underlying free energy, and enlarge the scope of available information about the free energy, as shown here. We show how to use distinctly directed dielectric gradients to measure the free energy on both straight lines and curves within the ternary composition triangle, so as to provide needed Dirichlet conditions for light scattering partial differential equation solution. With use of Monte Carlo simulations of noisy light scattering data, we provide estimates of the overall system measurement time and sample spacing needed to determine the free energy to a desired degree of accuracy, for various angles between the assumed dielectric gradient vectors, and indicate how the measurement time depends on instrumental throughput parameters. The present analysis methods provide a way to use static light scattering to measure, directly, mixing free energies of many systems that contain such restricted liquid domains, including aqueous solutions of biological macromolecules, micellar mixtures and microemulsions, and many small molecule systems that are important in separation technology.
Bearing currents in wind turbine generators
Authors: Whittle M. , Trevelyan J. , Tavner P. J.
Published: September 2013

Increasing the availability of multi-megawatt wind turbines (WT) is necessary if the cost of energy generated by wind is to be reduced. It has been found that WT generator bearings have a surprisingly high failure rate, with failures happening too early to be due to classical rolling contact fatigue. One potentially important root cause of bearings failures, bearing currents, has been investigated in this paper. The use of pulse-width modulated power electronic converters in variable speed WTs results in the presence of a common-mode voltage which may drive stray currents through a parasitic circuit in the generator structure. In this paper it is shown that if appropriate mitigation strategies are not employed, the bearing lubricant may experience electric stress in excess of its dielectric strength resulting in electrostatic discharge machining (EDM) of the bearing. Moreover it is shown that rotor-fed machines are more susceptible than stator-fed machines due to the presence of a larger coupling capacitance in the stray circuit. This is significant due to the prevalence of doubly fed induction generator WTs. The need for further research in this area, particularly in order to quantify the damage caused by EDM and develop diagnostic and prognostic techniques for the application of condition monitoring to this phenomenon, has been demonstrated.
Super-Lambertian photocurrent-generation in solar cells with periodically textured interfaces
Authors: Haug F.-J. , Söderström K. , Naqavi A. , Li J. , Ballif C.
Published: September 2013

We studied solar cells with periodic interface texture. For periods of 550 and 833 nm, we found that the measured photocurrent increases under oblique incidence and assumes a maximum between 20° and 30°. For the geometries used in our experiments, the initial increase occurred for conditions close to those of photonic band gaps. In addition to a forbidden band of energies where waveguide modes cannot propagate, we found that the coupling to the high-energy branches was suppressed under conditions of high symmetry such as sinusoidal interface geometry and perpendicular incidence.
Photoluminescence properties of Tb-Eu-Mn-codoped fluoroborate glasses under γ-irradiation
Authors: Hari Babu B. , Ravi Kanth Kumar V. V.
Published: September 2013

We report here an energy transfer from Tb3+ to Eu3+, Mn2+ and Eu2+ to Tb3+ and Mn2+ for an un-irradiated and γ-irradiated B2O3-Al2O3-Na2O-SrF2 glass samples, respectively. The blue emission from Eu2+ ions as well as green and red emission from Tb3+, Eu3+, and Mn2+ ions will contribute to the generation of white light while excited at 339 nm using a xenon lamp. Furthermore, the chromaticity color coordinates, correlated color temperature, and quantum efficiency parameters are calculated for all the glass samples, and their relative variations with respect to γ-irradiation dose are presented.