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Low Energy (low + energy)
Terms modified by Low Energy Selected AbstractsNitrosyl Ruthenium Diolato ComplexesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 7 2005Michael Barth Abstract [mer -(dien)(NO)Ru(AnErytH,2)]BPh4·2,H2O (1), [mer -(dien)(NO)Ru(R,R -ChxdH,2)]BPh4 (2), [mer -(dien)(NO)Ru(EthdH,2)]BPh4 (3), and [mer -(dien)(NO)Ru(Me-,- D -Ribf2,3H,2)]BPh4·5.5,H2O (4) have been synthesized in the form of light pink crystals by the reaction of [mer -(dien)(NO)RuCl2]X with the respective diol in aqueous sodium hydroxide solution (dien = diethylenetriamine, AnEryt = anhydroerythritol, Chxd = cyclohexane-1,2-diol, Ethd = ethanediol, Rib = ribose; X = BPh4 or PF6). The nitrosyl ligand exhibits a strong trans influence which causes the trans -bonded oxygen atom of the diolato ligand to form a shorter bond with the Ru centre. Mean values are 2.038 for cis and 1.946 Ĺ for transO -binding. Back donation is strongly supported by the diolato ligand resulting in low energies for the N,O stretch which can be observed as low as 1805 cm,1. trans -Oxygen atoms do not act as hydrogen-bond acceptors in any of the cases. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Generalizations of the AdS/CFT correspondence,FORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 8 2004I. Kirsch Abstract We consider generalizations of the AdS/CFT correspondence in which probe branes are embedded in gravity backgrounds dual to either conformal or confining gauge theories. These correspond to defect conformal field theories (dCFT) or QCD-like theories with fundamental matter, respectively. Moreover, starting from the dCFT we discuss the deconstruction of intersecting M5-branes and M-theory. We obtain the following results: i) Holography of defect conformal field theories. We consider holography for a general D3-Dp brane intersection in type IIB string theory (p , {3,5,7}). The corresponding near-horizon geometry is given by a probe AdS-brane in AdS5 × S5. The dual defect conformal field theory describes ,, = 4 super Yang-Mills degrees of freedom coupled to fundamental matter on a lower-dimensional space-time defect. We derive the spectrum of fluctuations about the brane embedding and determine the behaviour of correlation functions involving defect operators. We also study the dual conformal field theory in the case of intersecting D3-branes. To this end, we develop a convenient superspace approach in which both two- and four-dimensional fields are described in a two-dimensional (2,2) superspace. We show that quantum corrections vanish to all orders in perturbation theory, such that the theory remains a (defect) conformal field theory when quantized. ii) Flavour in generalized AdS/CFT dualities. We present a holographic non-perturbative description of QCD-like theories with a large number of colours by embedding D7-brane probes into two non-supersymmetric gravity backgrounds. Both backgrounds exhibit confinement of fundamental matter and a discrete glueball and meson spectrum. We numerically compute the quark condensate and meson spectrum associated with these backgrounds. In the first background, we find some numerical evidence for a first order phase transition at a critical quark mass where the D7 embedding undergoes a geometric transition. In the second, we find a chiral symmetry breaking condensate as well as the associated Goldstone boson. iii) Deconstruction of extra dimensions. We apply the deconstruction method to the dCFT of intersecting D3-branes to obtain a field theory description for intersecting M5-branes. The resulting theory corresponds to two six-dimensional (2,0) superconformal field theories which we show to have tensionless strings on their four-dimensional intersection. Moreover, we argue that the SU(2)L R-symmetry of the dCFT matches the manifest SU(2) R-symmetry of the M5-M5 intersection. We finally explore the fascinating idea of deconstructing M-theory itself. We give arguments for an equivalence of M-theory on a certain background with the Higgs branch of a four-dimensional non-supersymmetric (quiver) gauge theory: in addition to a string theoretical motivation, we find wrapped M2-branes in the mass spectrum of the quiver theory at low energies. [source] Energy transfer in master equation simulations: A new approachINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 12 2009John R. BarkerArticle first published online: 8 OCT 200 Collisional energy transfer plays a key role in recombination, unimolecular, and chemical activation reactions. For master equation simulations of such reaction systems, it is conventionally assumed that the rate constant for inelastic energy transfer collisions is independent of the excitation energy. However, numerical instabilities and nonphysical results are encountered when normalizing the collision step-size distribution in the sparse density of states regime at low energies. It is argued here that the conventional assumption is not correct, and it is shown that the numerical problems and nonphysical results are eliminated by making a plausible assumption about the energy dependence of the rate coefficient for inelastic collisions. The new assumption produces a model that is more physically realistic for any reasonable choice of collision step-size distribution, but more work remains to be done. The resulting numerical algorithm is stable and noniterative. Testing shows that overall accuracy in master equation simulations is better with this new approach than with the conventional one. This new approach is appropriate for all energy-grained master equation formulations. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 41: 748,763, 2009 [source] Structure of charge-transfer reaction complexes in anionic polymerization of isoprene: Quantum chemical calculationsINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 2 2005K. K. Kalninsh Abstract A new mechanism of isoprene anionic polymerization is proposed. Its central moment is thermal electronic excitation of a living polyisoprene,isoprene complex into the quasi-degenerate electronically excited state (S · T)1, which is of the charge (electron) transfer character. It is asserted that the probability of chemical bond formation is determined by the free valence index on carbon atoms and by the geometry of reacting complex in the excited state (S · T)1. Semi-empirical AM1 and ab initio 6-31G* quantum chemical calculations revealed low energies of triplet excited levels (<10 kcal/mole). Comparison of isoprene polymerization on free anions and on solvated ion pairs shows that both types of active centers produce vinyl 1,2 (4,3)-units. Free anions generate predominantly 1,2-units, whereas solvated ion pairs tend to form units with the 4,3-structure. Analysis of energies of excited isoprenyl lithium + isoprene complexes shows that the formation of 1,4 (4,1)- cis -polyisoprene in an inert media is most preferable. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005 [source] Magnetic impurity transition in a (d,+,s)-wave superconductorPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 3 2010L. S. BorkowskiArticle first published online: 8 FEB 2010 Abstract We consider the superconducting state of symmetry with finite concentration of Anderson impurities in the limit . The model consists of a BCS-like term in the Hamiltonian and the Anderson impurity treated in the self-consistent large- N mean field approximation. Increasing impurity concentration or lowering the ratio drives the system through a transition from a state with two sharp peaks at low energies and exponentially small density of states at the Fermi level to one with . This transition is discontinuous if the energy of the impurity resonance is the smallest energy scale in the problem. [source] Time-resolved spectroscopy in an undoped GaN (1-101)PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2008Eunhee Kim Abstract Time-resolved photoluminescence spectroscopy was performed at 77 K in a GaN (1-101) grown on a 7 degree off-axis (001) Si substrate. The sample was grown by metal-organic-vapour-phase-epitaxy (MOVPE) and was un-intentionally doped with O, C and Si. By using photoluminescence intensity correlation method, the energy relaxation process of the photogenerated carriers near the band edge was investigated in pico-second regime. The correlation signal was represented by a single exponential decay curve and the energy relaxation time was determined, which depended strongly on the kinetic energy of the excess carriers. At low energies, the relaxation time was around 700 ps, while it was as short as a few ps at the highest energy under study. The correlation signals obtained for carriers of which kinetic energy was less than 80 meV showed an anti-correlation behaviour suggesting the occurrence of carrier accumulation. The time constants for the accumulation were of several picoseconds depending on the kinetic energy, which was nearly equal to the decay time constants determined at high energies. This fact shows that the energy relaxation at high energies is controlled by the emission of an LO phonon. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Ion Energy Distributions in Magnetron Sputtering of Zinc Aluminium OxidePLASMA PROCESSES AND POLYMERS, Issue S1 2009Thomas Welzel Abstract Ion energy distributions have been measured with an energy-dispersive mass spectrometer during magnetron sputtering of Al doped ZnO. A d.c. and a pulsed d.c. discharge have been investigated. Different positive ions from the target material have been observed with low energies in d.c. and a second energy peak of about 30 eV in pulsed d.c. with only weak additional energy due to the sputter process. Negative ions are mainly O, with energies corresponding to the target voltage of several 100 eV. They originate from the target and barely from the (O2) gas and hit the substrate opposite the race track. In pulsed d.c., due to the varying target voltage, energies of up to 500 eV have been observed. With increasing pressure, negative ions at the substrate are reduced exponentially in their density but not in their energy. [source] Clinical Trial of Dual Treatment with an Ablative Fractional Laser and a Nonablative Laser for the Treatment of Acne Scars in Asian PatientsDERMATOLOGIC SURGERY, Issue 7 2009SANGEUN KIM MD BACKGROUND Many methods have been proposed for the treatment of acne scars, with variable cosmetic results. Nonablative skin resurfacing is one method that has been proposed. Because of a need for more noticeable clinical improvements, the ablative fractional laser was recently introduced. OBJECTIVE To reduce complications and improve the results of ablative fractional laser resurfacing by combining this treatment of acne scars with nonablative lasers. METHODS A series of 20 patients (skin phototypes IV,V) with atrophic facial acne scars were randomly divided into two groups that received three successive monthly treatments with an ablative fractional laser using high (group A) and low (group B) energy on one facial half and an ablative fractional laser with low energy plus a nonablative resurfacing laser on the other facial half. Patients were evaluated using digital photography at each treatment visit and at 3 months postoperatively. Clinical assessment scores were determined at each treatment session and follow-up visit. RESULTS Although the use of the ablative fractional laser with high energy resulted in an improvement in patients' acne scars, the combination of ablative fractional laser resurfacing and nonablative laser resurfacing yielded the best results, as assessed in photographs as well as by the overall appearance of the acne scars. With the combination method, fewer complications were observed. [source] Engineering the properties of a cold active enzyme through rational redesign of the active siteFEBS JOURNAL, Issue 19 2001Iason Tsigos ,In an effort to explore the effects of local flexibility on the cold adaptation of enzymes, we designed point mutations aiming to modify side-chain flexibility at the active site of the psychrophilic alkaline phosphatase from the Antarctic strain TAB5. The mutagenesis targets were residues Trp260 and Ala219 of the catalytic site and His135 of the Mg2+ binding site. The replacement of Trp260 by Lys in mutant W260K, resulted in an enzyme less active than the wild-type in the temperature range 5,25 °C. The additional replacement of Ala219 by Asn in the double mutant W260K/A219N, resulted in a drastic increase in the energy of activation, which was reflected in a considerably decreased activity at temperatures of 5,15 °C and a significantly increased activity at 20,25 °C. Further substitution of His135 by Asp in the triple mutant W260K/A219N/H135D restored a low energy of activation. In addition, the His135,Asp replacement in mutants H135D and W260K/A219N/H135D resulted in considerable stabilization. These results suggest that the psychrophilic character of mutants can be established or masked by very slight variations of the wild-type sequence, which may affect active site flexibility through changes in various conformational constraints. [source] Combating deceptive advertisements and labelling on food products , an exploratory study on the perceptions of teachersINTERNATIONAL JOURNAL OF CONSUMER STUDIES, Issue 3 2003Wai-ling Theresa Lai Yeung People are becoming more health conscious nowadays, but most of them are not able to adopt a lifestyle with adequate physical exercise and a healthier eating pattern. Many attempt to compensate by taking ,health foods'. Despite the recent economic recession, the functional food market expands rapidly in Asian countries. Recent statistics indicate a huge increase in weight loss and functional food product advertising expenditure in Hong Kong and other Asian countries. In a massive survey conducted by the Hong Kong Consumer Council, it was found that 85% of the medicines, health food and therapies sampled contain questionable claims and misleading messages (Consumer Council, 1999). In fact, young people do not understand much about modern food processing, in particular those present in low energy and functional foods, and they know very little about the modern food marketing strategies. The situation is detrimental to consumer welfare especially to the younger generation. This study attempts to reflect critically on the implications of these issues for the health and well-being of young people in Hong Kong. It explores directions for designing relevant and effective education programmes to empower young people in understanding food advertising strategies and making informed decisions on food choice. The paper will begin with a critical review on the current situation in Hong Kong. An interview survey on preservice and in-service teachers' perception towards misleading food advertising and labelling will then be reported. The situations at schools will be defined and problems faced by teachers in providing relevant consumer education programmes to students will be identified. Finally, the study will look to the future, with a view to developing students' critical skills in evaluating claims offered in food advertisements. [source] Quality of life in chronic disease: a comparison between patients with heart failure and patients with aphasia after strokeJOURNAL OF CLINICAL NURSING, Issue 13-14 2010Ĺsa Franzén-Dahlin Objectives., This study aimed to describe the impact of heart failure and of stroke with aphasia on quality of life (QoL) and to compare the different domains of QoL in these groups. Background., The prevalence of chronic conditions has increased during the last decades, and chronic diseases such as stroke and heart failure may have a great impact on QoL. Design., Comparative study of patients from two randomised controlled studies. Method., Seventy-nine patients with heart failure and 70 patients with aphasia after stroke were evaluated concerning the severity of their disease and by QoL, as measured with the Nottingham Health Profile, in the acute phase and after six months. Results., The severity of the disease improved between baseline and six month for both groups. Correlations between New York Heart Association (NYHA) class and all QoL domains were seen in patients with heart failure after six months. The degree of aphasia correlated to mobility, social, emotional and total score after six month. QoL in patients with heart failure was more affected in the domains of sleep and energy in the acute phase and in the energy domain at six months. Conclusion., Although low energy is more frequent among patients with heart failure, both groups report poor QoL. Improvement in severity of the disease is not necessarily accompanied by improvement in QoL. Relevance to clinical practice., Nottingham Health Profile can easily be used as a screening instrument, aiming to identify patients at risk for adverse effects on QoL. A better understanding of the subjective QoL of patients with chronic disease is fundamental for health care professionals to be able to identify and support vulnerable patients. [source] Quality of life and symptom attribution in long-term colon cancer survivorsJOURNAL OF EVALUATION IN CLINICAL PRACTICE, Issue 2 2008Etienne Phipps PhD Aims and objectives, This study investigates how long-term colon cancer survivors evaluate their health, functional status and quality of life, and whether there are differences based on age, gender or ethnicity. Methods, Thirty long-term survivors of at least stage I colon cancer were interviewed in person between December 2004 and May 2005. The interview protocol included the Medical Outcomes Study 36-Item Short Form, Quality of Life , Cancer Survivor, and study-specific questions that asked about physical and non-physical problems they attributed to colon cancer. Results, Substantial percentages of survivors attributed their problems with lack of energy (83%), sexual functioning (67%), bowel problems (63%), poor body image (47%) and emotional problems (40%) to having had colon cancer. Of those problems attributed to colon cancer, sexual functioning and pain were given the highest severity rankings by survivors. The majority of long-term colon cancer survivors reported distress regarding future diagnostic tests, a second cancer, and spread of cancer. Women reported greater problems completing daily activities as a result of physical problems (P = 0.003) and more pain (P = 0.07) than men. African Americans appear to report marginally better overall quality of life (P = 0.07) and psychological well-being than whites (P = 0.07). Conclusion, The majority of long-term colon cancer survivors with resected colon cancer and disease-free for 5 years reported problems with low energy, sexual functioning and bowel problems. [source] Bone mass is preserved in a critical-sized osteotomy by low energy pulsed electromagnetic fields as quantitated by in vivo micro-computed tomographyJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 5 2004Michael O. Ibiwoye Abstract The effectiveness of non-invasive pulsed electromagnetic fields (PEMF) on stimulating bone formation in vivo to augment fracture healing is still controversial, largely because of technical ambiguities in data interpretation within several previous studies. To address this uncertainty, we implemented a rigorously controlled, blinded protocol using a bilateral, mid-diaphyseal fibular osteotomy model in aged rats that achieved a non-union status within 3,4 weeks post-surgery. Bilateral osteotomies allowed delivery of a PEMF treatment protocol on one hind limb, with the contralateral limb representing a within-animal sham-treatment. Bone volumes in both PEMF-treated and sham-treated fibulae were assessed simultaneously in vivo using highly sensitive, high-resolution micro-computed tomography (,CT) over the course of treatment. We found a significant reduction in the amount of time-dependent bone volume loss in PEMF-treated, distal fibular segments as compared to their contralateral sham-treated bones. Osteotomy gap size was significantly smaller in hind limbs exposed to PEMF over sham-treatment. Therefore, our data demonstrate measurable biological consequences of PEMF exposure on in vivo bone tissue. © 2004 Orthopaedic Research Society. Published y Elsevier Ltd. All rights reserved. [source] SEAWEED ABUNDANCE AND DIVERSITY IN HIGH ENERGY AND LOW ENERGY AREAS AT PORT ARANSAS, TEXAS JETTIESJOURNAL OF PHYCOLOGY, Issue 3 2001Article first published online: 24 SEP 200 Agan, J. C. & Lehman, R. L. Department of Physical and Life Sciences, Texas A&M University-Corpus Christi 6300 Ocean Dr., Corpus Christi, TX 78412 USA Benthic algal sampling from high and low energy zones at a selected site on the south jetty at Port Aransas, Texas was completed between April 1999 and February 2000. Species composition and seasonal periodicity in relation to temperature and salinity fluctuations were determined. Dominant plants throughout the year included Bryocladia cuspidata, Bryocladia thyrsigera, Gelidium pusillum, Centroceras clavulatum, Ulva fasciata, and Padina gymnospora. The Rhodophyta dominated species coverage, along with biomass accumulation, although Chlorophyta species accrued the greatest biomass on the high energy side in April and June sampling. Chlorophyta are important to benthic coverage and biomass in the shallowest of waters, despite being fewer in species richness. Phaeophyta species including Petalonia fascia, Hincksia mitchelliae, and Ectocarpus siliculosus were found only during the cooler months. Padina gymnospora was the one exception as it was collected year-round. Results indicate that a greater Rhodophyta abundance was found on the channel side (low energy), where as, the surf side (high energy) contained a greater Chlorophyta abundance. Phaeophyta abundance for both high and low energy sites were comparable possibly due to the greater depth of water in which they are located. Little variance occurred in average biomass accumulation throughout the year. Highest biomass was in August (216.613g dry weight) with lowest occurring in April (107.4205g dry weight). [source] SEAWEED ABUNDANCE AND DIVERSITY IN HIGH ENERGY AND LOW ENERGY AREAS AT PORT ARANSAS, TEXAS JETTIESJOURNAL OF PHYCOLOGY, Issue 2001Article first published online: 9 OCT 200 Agan, J. C. & Lehman, R. L. Department of Physical and Life Sciences, Texas A&M University-Corpus Christi 6300 Ocean Dr., Corpus Christi, TX 78412 USA Benthic algal sampling from high and low energy zones at a selected site on the south jetty at Port Aransas, Texas was completed between April 1999 and February 2000. Species composition and seasonal periodicity in relation to temperature and salinity fluctuations were determined. Dominant plants throughout the year included Bryocladia cuspidata, Bryocladia thyrsigera, Gelidium pusillum, Centroceras clavulatum, Ulva fasciata, and Padina gymnospora. The Rhodophyta dominated species coverage, along with biomass accumulation, although Chlorophyta species accrued the greatest biomass on the high energy side in April and June sampling. Chlorophyta are important to benthic coverage and biomass in the shallowest of waters, despite being fewer in species richness. Phaeophyta species including Petalonia fascia, Hincksia mitchelliae, and Ectocarpus siliculosus were found only during the cooler months. Padina gymnospora was the one exception as it was collected year-round. Results indicate that a greater Rhodophyta abundance was found on the channel side (low energy), where as, the surf side (high energy) contained a greater Chlorophyta abundance. Phaeophyta abundance for both high and low energy sites were comparable possibly due to the greater depth of water in which they are located. Little variance occurred in average biomass accumulation throughout the year. Highest biomass was in August (216.613g dry weight) with lowest occurring in April (107.4205g dry weight). [source] Linear polarization scans for resonant X-ray diffraction with a double-phase-plate configurationJOURNAL OF SYNCHROTRON RADIATION, Issue 6 2009Valerio Scagnoli An in-vacuum double-phase-plate diffractometer for performing polarization scans combined with resonant X-ray diffraction experiments is presented. The use of two phase plates enables the correction of some of the aberration effects owing to the divergence of the beam and its energy spread. A higher rate of rotated polarization is thus obtained in comparison with a system with only a single retarder. Consequently, thinner phase plates can be used to obtain the required rotated polarization rate. These results are particularly interesting for applications at low energy (e.g. 4,keV) where the absorption owing to the phase plate(s) plays a key role in the feasibility of these experiments. Measurements by means of polarization scans at the uranium M4 edge on UO2 enable the contributions of the magnetic and quadrupole ordering in the material to be disentangled. [source] CHARACTERIZATION OF AGGLOMERATION PROCESS AS A FUNCTION OF MOISTURE CONTENT USING A MODEL FOOD POWDERJOURNAL OF TEXTURE STUDIES, Issue 1 2006S. MUKHERJEE ABSTRACT A model food-powder system using rice flour of different moisture contents (11 to 22%) was used to study rheological behavior by employing a powder rheometer to obtain maximum force, energy for compression and decompression. The latter parameters were sensitive at moisture contents of ,18%. The compacted mass, obtained using a rotary punch-tableting machine, was subjected to compression testing to determine the maximum force and firmness of the compressed tablets. These two parameters increased markedly above the 17% moisture content. A significant (P , 0.01) relationship between energy for compression for powder and firmness of compacted mass indicated that an adequate integrity of the product could be achieved when a powder requires high energy for compression but low energy for decompression. A modified version of the Hausner ratio, often used to characterize the extent of compactness, was proposed that included a correction factor for loss of moisture during compaction. [source] Subthreshold Test Pulses Versus Low Energy Shock Delivery to Estimate High Energy Lead Impedance in Implanted Cardioverter Defibrillator PatientsPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 1p2 2003DIRK VOLLMANN VOLLMANN, D., et al.: Subthreshold Test Pulses Versus Low Energy Shock Delivery to Estimate High Energy Lead Impedance in Implanted Cardioverter Defibrillator Patients. The high energy lead impedance is valuable for detecting lead failure in ICDs, but until recently shock delivery was necessary for high energy impedance measurement. This study compared the use of subthreshold test pulses and low energy test shocks to estimate the high energy impedance. Immediately after implantation of Ventak Prizm ICDs in 29 patients, the lead impedance was measured with five subthreshold (0.4 ,J) test pulses, 5 low energy (1.1 J) shocks, and two to three high energy(16 ± 4.5 J)shocks. The mean impedances measured using high energy shocks, low energy shocks, and subthreshold pulses were42.0 ± 7.3 ,, 46.5 ± 8.1 ,, and42.4 ± 7.1 ,, respectively. The impedances measured using high and low energy shocks differed significantly(P <0.0001), while those obtained by high energy shocks and low energy pulses did not(P = 0.63). According to the Pearson correlation coefficient, the impedance measurements with subthreshold pulses and low energy shocks were both closely correlated(P < 0.0001)with impedance values determined with high energy shocks. However, while the impedance values tended to be higher when measured with low energy shocks, the concordance correlation coefficient (c) was higher for subthreshold test pulse versus high energy shock(c = 0.92)than for low versus high energy shock(c = 0.73). Furthermore, the intraindividual variability of impedance measurements was lower with subthreshold pulse measurements than with low energy shocks. Compared with low energy shocks, impedance measurement with subthreshold pulses has higher reproducibility and a higher correlation with the impedance obtained by high energy shock delivery. Safe and painless high energy impedance estimation with subthreshold pulses might, therefore, help to detect ICD lead failure during routine follow-up. (PACE 2003; 26:[Pt. II]:457,460) [source] Predicting the low energy landscape of nanoscale silica using interatomic potentialsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 6 2006S. T. BromleyArticle first published online: 18 APR 200 Abstract The energies of 52 of the lowest lying structural isomers of the (SiO2)12 nanocluster are accurately calculated via energy minimisations employing density functional theory (DFT) and also with two silica interatomic potentials (IPs). Of the tested IPs, one was specifically parameterised with respect to small silica nanoclusters, and the other was biased to accurately recover bulk silica properties, although having been applied numerous times to silica nanosystems. The predicted energetic ordering of the nanocluster isomers resulting from the IP optimisations are compared with respect to their deviance from benchmark nanocluster energies from DFT calculations. Although both IPs predict the DFT ground state isomer to be a very low energy cluster and thus are of use in global optimisation studies, large fluctuations in the IP energies of other low lying isomers (relative to the respective DFT energies) shed doubt on their wider applicability to nanoscale silica systems. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] A mini linac based positron sourcePHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 11 2009Patrice Pérez Abstract We have installed in Saclay a demonstration setup for an intense positron source in November 2008. It is based on a compact 6 MeV electron linac to produce positrons via pair production on a tungsten target. A relatively high current of 0.15 mA compensates the low energy, which is below the neutron activation threshold. The expected production rate is 4x1011 fast positrons per second. A set of coils is arranged to select the fast positrons from the diffracted electron beam in order to study the possibility to use a rare gas cryogenic moderator away from the main flux of particles. A first part of the commissioning of the linac has been performed. First attempts at measuring the fast positron flux are underway. This setup is part of a project to demonstrate the feasibility of an experiment to produce the H+ ion for a free fall measurement of neutral antihydrogen (H). Its small size and cost could be of interest for a university laboratory or industry for materials science applications. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Characteristics of amplified spontaneous emission of high indium content InGaN/GaN quantum wells with various silicon doping conditionsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2003Yung-Chen Cheng Abstract We compared the temperature dependent spectral variations of the amplified spontaneous emission (ASE) between InGaN/GaN quantum well samples of no doping, well doping, and barrier doping of silicon. The comparisons were particularly made between two series of samples with a low and a high indium content. The results show that a multi-peak ASE spectral feature and a low energy stimulated emission peak, existing at the photoluminescence shoulder, could be observed only in the high-indium-content, barrier-doped sample. Such results are supposed to originate from the formation of quantum dots of various sizes, concentrations, and shapes under the condition of barrier doping in the sample. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Effect of sodium chloride on the formation and stability of n-dodecane nanoemulsions by the PIT methodASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 4 2010Jeffery Chin Long Liew Abstract This paper provides a fundamental study of the effect of sodium chloride on the formation and stability of n-dodecane/nonionic surfactant (Brij30)/NaCl nanoemulsions produced by the phase inversion temperature (PIT) method. Nanoemulsions are an emulsion system containing droplets from 20 to 200 nm and widely used in cosmetics and pharmaceutical industries. The PIT method was chosen due to its low energy and surfactant usage to produce the nanoemulsions by heating and quenching an emulsion system. The changes of conductivity with temperatures were continuously monitored to determine phase inversion, and are found to be the same in low surfactant concentrations. PIT point was found to decrease with NaCl concentration especially from 5 to 7 wt% Brij30. At the storage temperature (20 °C), the initial droplet size decreases with NaCl concentration; however, the decrement only occurs from 4 to 7 wt% Brij30 while no nanoemulsions can be produced at 8 wt%. By adding salt, the surfactant concentration needed for the most stable nanoemulsions is reduced to 6 wt% from 7 wt%. Therefore, similar stable nanoemulsions can be produced with less surfactant in a brine system. Furthermore, most of the ageing brine-continuous nanoemulsions could be reproduced to their freshly prepared state by heating process but not for the most stable nanoemulsions. Copyright © 2010 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Quinoidal Oligothiophenes: Towards Biradical Ground-State SpeciesCHEMISTRY - A EUROPEAN JOURNAL, Issue 2 2010Ortiz Dr., Rocío Ponce Abstract A family of quinoidal oligothiophenes, from the dimer to the hexamer, with fused bis(butoxymethyl)cyclopentane groups has been extensively investigated by means of electronic and vibrational spectroscopy, electrochemical measurements, and density functional calculations. The latter predict that the electronic ground state always corresponds to a singlet state and that, for the longest oligomers, this state has biradical character that increases with increasing oligomer length. The shortest oligomers display closed-shell quinoidal structures. Calculations also predict the existence of very low energy excited triplet states that can be populated at room temperature. Aromatization of the conjugated carbon backbone is the driving force that determines the increasing biradical character of the ground state and the appearance of low-lying triplet states. UV/Vis, Raman, IR, and electrochemical experiments support the aromatic biradical structures predicted for the ground state of the longest oligomers and reveal that population of the low-lying triplet state accounts for the magnetic activity displayed by these compounds. [source] | ||||||||||||||||||||||