bluuebunny/crossref_metadata_2025 huggingface dataset:
Histologic changes in transplanted expanded polytetrafluoroethylene in an animal model
Authors: Kim Ji Heui , Park Chan Hum , Lee Ok Joo , Lee Jun Ho , Hong Seok Min
Published: November 2011

Objectives/Hypothesis:

Several materials have been used for nasal augmentation surgery. Expanded polytetrafluoroethylene (e‐PTFE) (Gore‐Tex; W. L. Gore & Associates, Flagstaff, AZ) has proven to be an ideal synthetic material for nasal augmentation. Gore‐Tex contains numerous pores that stabilize an implant, but this advantage has been tempered by unpredictable outcomes. The purpose of this study was to evaluate morphologic and histologic changes in nonreinforced Gore‐Tex in a rabbit model.

Study Design:

In vivo study using a rabbit model.

Methods:

To analyze histologic changes, we used 20 New Zealand white rabbits. Gore‐Tex was implanted into the nasal dorsum of the rabbits. Then, en bloc specimens containing the implant and surrounding soft tissues were sampled 1, 3, 6, and 12 months after implantation. We evaluated the three‐dimensional size of the implants over time using light and electron microscopy to investigate histologic and morphologic changes.

Results:

Following gross analysis, none of the implants were lost or extruded, and there was no evidence of wound infection. Diminution rates of thickness, width, and height in the implants were 22%, 2%, and 5%, respectively. Histologically, connective tissue growth was observed in all specimens, and the internodal space decreased owing to connective tissue ingrowth over time. Neovascularization was observed 3 months after implantation, and degenerative changes were also observed after 6 months.

Conclusions:

Gore‐Tex should be carefully trimmed for use in augmentation because of its potential to decrease in size over time. Additional studies are necessary before these results can be applied in clinical practice.
Further insights into perceived value and consumer loyalty: A “Green” perspective
Authors: Koller Monika , Floh Arne , Zauner Alexander
Published: November 2011

“Green consumption” is an increasingly important topic in today's society. The effect of the ecological value provided by traditionally non‐green products, such as automobiles, on their consumer's post‐purchase behavior, such as brand or model loyalty, requires further clarification. The present study provides qualitative and quantitative insights from car users on how the ecological aspect of consumption integrates into the link between perceived value and consumer loyalty intentions (value–loyalty link). In general, car usage is accompanied by perceived functional, economic, emotional, and social value. Perceived ecological value is shown to have a significant impact on these four value dimensions. The relevance of “green to have quality,” “green to save money,” “green to feel good,” and “green to be seen” in relation to loyalty intention is discussed. Results of a structural equation model and multigroup analysis provide the opportunity to derive both theoretical and applied implications. © 2011 Wiley Periodicals, Inc.
Exercise training mitigates anthracycline‐induced chronic cardiotoxicity in a juvenile rat model
Authors: Hayward Reid , Lien Chia‐Ying , Jensen Brock T. , Hydock David S. , Schneider Carole M.
Published: November 2011

Background

Childhood cancer survivors are at greater risk of cardiovascular complications once they reach adulthood. Anthracyclines may be a major contributor to these delayed‐onset complications, yet their use continues because of favorable clinical outcomes. Exercise has been shown to protect against anthracycline cardiotoxicity, yet it is unclear whether exercise can protect against delayed‐onset cardiotoxicity when treatment is initiated in childhood. The aim of the present study was to determine if exercise training provides cardioprotection in a juvenile rat model of delayed‐onset anthracycline cardiotoxicity.

Procedure

At 25 days of age, male Sprague–Dawley rat pups were subjected to a treatment regimen with the anthracycline doxorubicin (DOX). Pups received DOX at 2 mg/kg on 7 consecutive days (cumulative dose 14 mg/kg) or saline as a control. At the time DOX treatment began, pups remained sedentary or were allowed to voluntarily exercise. Ten weeks after the initiation of exercise, cardiac function was assessed both in vivo and ex vivo.

Results

DOX treatment stunted normal growth and significantly impaired cardiac function. While voluntary exercise did not offset changes in the growth curve, it did provide significant cardioprotection against DOX‐induced cardiotoxicity.

Conclusions

Exercise training, initiated at the time treatment begins, can protect against delayed‐onset anthracycline‐induced cardiotoxicity in adult rats that were treated with anthracyclines as juveniles. Pediatr Blood Cancer 2012; 59: 149–154. © 2011 Wiley Periodicals, Inc.
Impact of CdTe surface composition on doping and device performance in close Space sublimation deposited CdTe solar cells
Authors: Major J. D. , Proskuryakov Y. Y. , Durose K.
Published: November 2011

Cool‐down after close‐space sublimation growth of cadmium telluride films has been shown to lead to the formation of a Cd‐rich surface that can block the subsequent in‐diffusion of cadmium chloride that is used in post‐growth doping of solar cell devices. Pre‐etching of the as‐grown surfaces using a nitric–phosphoric acid etch prior to doping leads to increase in chlorine and oxygen in‐diffusion, and an associated improvement in device efficiency from <3% to 12% in controlled trials. Capacitance‐voltage analysis of such devices revealed an increase in the acceptor concentration from 3.76 × 1013 cm−3 to 5.6 × 1014 cm−3, whereas thermal admittance spectroscopy revealed fewer deep states at energies >0.4 eV for etched devices. Impedance analysis showed the improved cadmium chloride treatment—resulting from the additional etching step—removed the grain boundary component from the equivalent circuit, indicating a grain boundary passivation effect. Copyright © 2011 John Wiley & Sons, Ltd.
Psychometric properties of the Add Health School Connectedness Scale for 18 sociocultural groups
Authors: Furlong Michael J. , O'brennan Lindsey M. , You Sukkyung
Published: November 2011

The National Longitudinal Study of Adolescent Health's School Connectedness Scale (SCS) has been widely used in psychological, public health, and education research, but has undergone limited psychometric analysis. This study used the responses of 500,800 junior and senior high school students who completed the biennial California Healthy Kids Survey, which includes the SCS. The results supported the use of the SCS as a unidimensional measure and showed that it has acceptable reliability (α = .82 to .88) and concurrent validity (r = .44 to .55) across 18 sociocultural groups. A series of multiple group analyses confirmed configural, metric, and scalar equivalence across groups. The SCS shows promise as measurement instrument for school psychologists; however, further research is needed to examine its underlying latent school connectedness construct. © 2011 Wiley Periodicals, Inc.
Organizing by Projects: A Strategy for Local Development—The Case of NGOs in a Developing Country
Authors: Navarro-Flores Olga
Published: November 2011

North and South nongovernmental organizations (NGOs) have been “partners” in international development for more than a decade. Studies have documented their approaches and strategies, yet little is still known about how they organize and how their projects help them to achieve their mission. The authors propose a contextualized and historical perspective to better understand how and why NGOs organize by projects, and how this strengthens their strategy and commitment to local development.
Adsorption, transport and degradation of fipronil termiticide in three Hawaii soils
Authors: Shuai Xiufu , Chen Jingyu , Ray Chittaranjan
Published: November 2011

BACKGROUND: The behavior of the termiticide fipronil in soils was studied to assess its potential to contaminate ground and surface water. This study characterizes (1) adsorption of fipronil in three different soils, (2) transport of fipronil through leaching and runoff under simulated rainfall in these soils and (3) degradation of fipronil to fipronil sulfide and fipronil sulfone in these soils.

RESULTS: The adsorption experiments showed a Freundlich isotherm for fipronil with Koc equal to 1184 L kg−1. In the leaching experiments, the concentration of fipronil and its metabolites in leachate and runoff decreased asymptotically with time. The concentration of fipronil in the leachate from the three soils correlated inversely with soil organic carbon content. The degradation experiment showed that the half‐life of fipronil in the soils ranged from 28 to 34 days when soil moisture content was 75% of field capacities, and that 10.7–23.5% of the degraded fipronil was transformed into the two metabolites (fipronil sulfide and fipronil sulfone).

CONCLUSION: Fipronil showed large losses through leaching but small losses via runoff owing to low volumes of runoff water generated and/or negligible particle‐facilitated transport of fipronil. The half‐life values of fipronil in all three soils were similar. Copyright © 2011 Society of Chemical Industry
Local internal quantum efficiency of a green light emitting InGaN/GaN quantum well
Authors: Danhof J. , Schwarz U. T. , Meyer T. , Vierheilig C. , Peter M.
Published: November 2011

Excitation density‐dependent microphotoluminescence measurements were performed on a green light (515 nm) emitting InGaN/GaN multiquantum well sample of low threading dislocation density (5 × 107 cm−2). For the observed structure we find a different shape of the local internal quantum efficiency (IQE) curve at spots of different efficiency. Evaluation of the measured local IQE curves in terms of the standard model including Shockley–Read–Hall (SRH), radiative recombination, and a third order loss term (droop) leads to the conclusion that SRH nonradiative recombination varies spatially on a sub‐micrometer length scale while both other terms remain constant.
Biaxial stress‐induced giant bandgap shift in BiFeO3 epitaxial films
Authors: Fu Z. , Yin Z. G. , Chen N. F. , Zhang X. W. , Zhang H. , Bai Y. M. , Wu J. L.
Published: November 2011

Thickness‐dependent stress relaxation and its influence on the bandgap of BiFeO3 have been investigated. BiFeO3 films with 15 at% Bi excess allow the control of lattice mismatch‐induced biaxial stress up to 10.8 GPa on SrTiO3(001) substrates. Heteroepitaxy of such films follows the Stranski–Krastanov growth mode, as suggested by island formation on the wetting layer accompanied with stress relaxation. The bandgap is linearly decreased with the in‐plane compressive stress, and a large stress coefficient of 67 meV/GPa was extracted. A 0.7 eV red‐shift of the bandgap was observed in the fully epitaxially strained film. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Recombinatorial biosynthesis of polyketides
Authors: Starcevic Antonio , Wolf Kerstin , Diminic Janko , Zucko Jurica , Ruzic Ida Trninic , Long Paul F , Hranueli Daslav , Cullum John
Published: November 2011

Modular polyketide synthases (PKSs) from Streptomyces and related genera of bacteria produce many important pharmaceuticals. A program called CompGen was developed to carry out in silico homologous recombination between gene clusters encoding PKSs and determine whether recombinants have cluster architectures compatible with the production of polyketides. The chemical structure of recombinant polyketides was also predicted. In silico recombination was carried out for 47 well-characterised clusters. The predicted recombinants would produce 11,796 different polyketide structures. The molecular weights and average degree of reduction of the chemical structures are dispersed around the parental structures indicating that they are likely to include pharmaceutically interesting compounds. The details of the recombinants and the chemical structures were entered in a database called r-CSDB. The virtual compound library is a useful resource for computer-aided drug design and chemoinformatics strategies for finding pharmaceutically relevant chemical entities. A strategy to construct recombinant Streptomyces strains to produce these polyketides is described and the critical steps of mobilizing large biosynthetic clusters and producing new linear cloning vectors are illustrated by experimental data.
Interfacial Properties of Polyethylene Glycol/Vinyltriethoxysilane (PEG/VTES) Copolymers and their Application to Stain Resistance
Authors: Chao Yin‐Chun , Su Shuenn‐Kung , Lin Ya‐Wun , Hsu Wan‐Ting , Huang Kuo‐Shien
Published: November 2011

In this study, polyethylene glycol (PEG) and vinyltriethoxysilane (VTES) were used in different proportions to produce a series of PEG–VTES copolymers. The copolymer molecular structures were confirmed by FTIR spectroscopy. In addition, their surface activities were evaluated by evaluating the surface tension, contact angle, and foaming properties. The results showed that these surfactants exhibited excellent surface activities and wetting power, as well as low foaming. Consequently, the application of a series of PEG/VTES copolymers can make cotton fabrics stain resistant.
Optimization of Enzymatic Synthesis of Phytosteryl Caprylates Using Response Surface Methodology
Authors: Tan Zhuliang , Shahidi Fereidoon
Published: November 2011

Phytosterols are known to lower total blood cholesterol and low‐density lipoprotein (LDL) cholesterol. However, low solubility of phytosterols in edible oils and their high melting point limit their use in food products. Esterification of phytosterols with fatty acids will render them higher solubility in oils and lowers their melting points. In this work, caprylic acid (C8:0) was selected for the esterification process because it serves as a rapid energy source with little or no deposition in the body and is often recommended by nutritionists for the treatment of candidiasis due to its antimicrobial properties. Here optimization of enzymatic synthesis of phytosteryl caprylates using response surface methodology (RSM) was investigated. The optimization process used a face‐centred central composite design (CCD) and under optimized conditions (9.25 h, 2.15 substrate mole ratio, and 7.93% enzyme load) the resultant conversion yield was 98%.
Nanoencapsulation of Alpha‐linolenic Acid with Modified Emulsion Diffusion Method
Authors: Habib Salam M. , Amr Ayed S. , Hamadneh Imad M.
Published: November 2011

Nanocapsules of alpha‐linolenic acid (α‐LA) were prepared by a modified emulsion diffusion technique with encapsulation efficiency of 93%. Polylactic acid (PLA) was used as the encapsulating polymer with acetone and ethyl acetate as organic solvents, and Tween 20, gelatin and Pluronic‐F68 in water as stabilizers. Two ratios of organic to aqueous phases were used with each solvent and stabilizer. Nanocapsule dispersions with a particle size less than 100 nm and a zeta potential as high as 33 mV were obtained as verified by scanning electron microscopy and the dynamic light scattering technique respectively. Both particle size and zeta potential were influenced by such preparation conditions as the type of stabilizer, type of organic solvent and the organic to aqueous phase ratio. Acetone was superior to ethyl acetate, and Tween 20 was superior to each of Pluronic‐F68 and gelatin in obtaining smaller, less aggregated nanocapsules. An organic to aqueous phase ratio of 1:5 was shown to be more suitable for the formation of smaller nanocapsules, particularly when acetone was used as the organic solvent.
Multimodale Rehabilitation bei chronischen Rückenschmerzen: Konzepte, Wirksamkeit und Umsetzung
Authors: Dibbelt Susanne , Greitemann Bernhard
Published: November 2011

Einleitung

Die multikausale Verursachung von unspezifischen chronischen Rückenschmerzen ist gut belegt und bestätigt das bio-psycho-sozialen Modell chronischer Schmerzen, wonach ungünstige Strategien in der Bewältigung von Schmerz, aber auch anhaltende psychosoziale berufliche Belastungen zur Entstehung und Chronifizierung von Rückenschmerzen beitragen. Entsprechend haben sich multimodale Behandlungsansätze auch in deutschen Reha–Einrichtungen als effektiv erwiesen.
Democracy and Quality of Life in Asian Societies
Authors: SASAOKA SHINYA , SEKI KATSUNORI
Published: November 2011

This article examines whether democracy affects quality of life. Scholars have conducted surveys to investigate whether democracy is likely to lead to good quality of life. There are two contested views to the relationship: some suggest that democracy has a positive causal effect on quality of life, whereas others contend that democracy does not play such a role. Previous findings are supported by cross-national statistical analysis with aggregated survey data. However, aggregated survey data may cause ecological fallacy. Also, in order to ascertain the extant research, it would be beneficial to test the hypothesis by incorporating both individual- and country-level variables. Therefore, this paper applied hierarchical modeling to investigate the regularity. Both individual-level perception of democracy and country-level political regime data were incorporated in our empirical model. Our findings suggest that individual-level satisfaction with democracy has positive causal effect on one's quality of life, whereas the country-level characteristic of the political regime has no effect.
Space-Time Compatibility Effects in the Auditory Modality
Authors: Kong Feng , You Xuqun
Published: November 2011

Previous research suggests that past and future temporal concepts are spatially represented from left to right along a mental line. And these concepts can both prime motor responses to left or right space and direct visual spatial attention. The present study aimed at investigating the nature of this space-time conceptual metaphor in different auditory tasks. In the first experiment, subjects categorized time-related words (past or future) that were presented binaurally. In the second experiment, subjects detected left-ear or right-ear targets following time-related words. The similar space-time compatibility effects were found in these two experiments. Our results demonstrate that the activation of temporal concepts can both prime motor responses to left or right space and influence the orientation of auditory spatial attention, suggesting that the modality of the stimulus input is unimportant for the left-right mapping of time. These results are explained by the “intermediate coding” account.
The Use of Virtual Reality for Episodic Memory Assessment
Authors: Sauzéon Hélène , Arvind Pala Prashant , Larrue Florian , Wallet Gregory , Déjos Marie , Zheng Xia , Guitton Pascal , N’Kaoua Bernard
Published: November 2011

Episodic memory was assessed using Virtual Reality (VR). Forty-four (44) subjects visualized a target virtual apartment containing specific objects in each room. Then they visualized a second virtual apartment comprised of specific objects and objects shared by the two apartments. Subjects navigated in the virtual apartments in one of the following two conditions: active and passive. Four main episodic memory components were scored from the VR exposures: (1) learning effect; (2) active forgetting effect; (3) strategies at encoding and at retrieval; and (4) false recognitions (FRs). The effect of navigation mode (active vs. passive) on each memory component was examined. Active subjects had better learning and retrieval (recognition hits) performances compared to passive subjects. A beneficial effect of active navigation was also observed on the source-based FR rates. Active subjects made fewer source-based FRs compared to passive subjects. These overall results for the effect of active navigation are discussed in terms of the distinction between item-specific and relational processing.
Hydrologic response of catchments to precipitation: Quantification of mechanical carriers and origins of water
Authors: Park Y.‐J. , Sudicky E. A. , Brookfield A. E. , Jones J. P.
Published: November 2011

Precipitation‐induced overland and groundwater flow and mixing processes are quantified to analyze the temporal (event and pre‐event water) and spatial (groundwater discharge and overland runoff) origins of water entering a stream. Using a distributed‐parameter control volume finite‐element simulator that can simultaneously solve the fully coupled partial differential equations describing 2‐D Manning and 3‐D Darcian flow and advective‐dispersive transport, mechanical flow (driven by hydraulic potential) and tracer‐based hydrograph separation (driven by dispersive mixing as well as mechanical flow) are simulated in response to precipitation events in two cross sections oriented parallel and perpendicular to a stream. The results indicate that as precipitation becomes more intense, the subsurface mechanical flow contributions tend to become less significant relative to the total pre‐event stream discharge. Hydrodynamic mixing can play an important role in enhancing pre‐event tracer signals in the stream. This implies that temporally tagged chemical signals introduced into surface‐subsurface flow systems from precipitation may not be strong enough to detect the changes in the subsurface flow system. It is concluded that diffusive/dispersive mixing, capillary fringe groundwater ridging, and macropore flow can influence the temporal sources of water in the stream, but any sole mechanism may not fully explain the strong pre‐event water discharge. Further investigations of the influence of heterogeneity, residence time, geomorphology, and root zone processes are required to confirm the conclusions of this study.
Meteorin is a Chemokinetic Factor in Neuroblast Migration and Promotes Stroke-Induced Striatal Neurogenesis
Authors: Wang Zhaolu , Andrade Nuno , Torp Malene , Wattananit Somsak , Arvidsson Andreas , Kokaia Zaal , Jørgensen Jesper Roland , Lindvall Olle
Published: November 2011

Ischemic stroke affecting the adult brain causes increased progenitor proliferation in the subventricular zone (SVZ) and generation of neuroblasts, which migrate into the damaged striatum and differentiate to mature neurons. Meteorin (METRN), a newly discovered neurotrophic factor, is highly expressed in neural progenitor cells and immature neurons during development, suggesting that it may be involved in neurogenesis. Here, we show that METRN promotes migration of neuroblasts from SVZ explants of postnatal rats and stroke-subjected adult rats via a chemokinetic mechanism, and reduces N-methyl-d-asparate-induced apoptotic cell death in SVZ cells in vitro. Stroke induced by middle cerebral artery occlusion upregulates the expression of endogenous METRN in cells with neuronal phenotype in striatum. Recombinant METRN infused into the stroke-damaged brain stimulates cell proliferation in SVZ, promotes neuroblast migration, and increases the number of immature and mature neurons in the ischemic striatum. Our findings identify METRN as a new factor promoting neurogenesis both in vitro and in vivo by multiple mechanisms. Further work will be needed to translate METRN's actions on endogenous neurogenesis into improved recovery after stroke.
Coexistence of reentrant-spin-glass and ferromagnetic martensitic phases in the Mn2Ni1.6Sn0.4 Heusler alloy
Authors: Ma L. , Wang W. H. , Lu J. B. , Li J. Q. , Zhen C. M. , Hou D. L. , Wu G. H.
Published: November 2011

A giant exchange bias field of up to 1170 Oe was observed in the Mn2Ni1.6Sn0.4 Heusler alloy. A reentrant spin glass phase and a ferromagnetic martensitic phase coexist below the blocking temperature as confirmed by dc magnetization and ac susceptibility measurements. Exchange bias in Mn2Ni1.6Sn0.4 is thought to originate from the interface exchange interaction between the reentrant spin glass phase and the ferromagnetic martensitic phase. X-ray diffraction and selected area electron diffraction results demonstrate that excess Mn atoms occupy Ni and Sn sites randomly. In this way, Mn-Mn clusters are formed and constitute the reentrant-spin-glass phase.
Ab-initio aprroach to the electronic, structural, elastic, and finite-temperature thermodynamic properties of Ti2AX (A = Al or Ga and X = C or N)
Authors: Duong Thien , Gibbons Sean , Kinra Rajeev , Arróyave Raymundo
Published: November 2011

In this work, the electronic, structural, elastic, and thermodynamic properties of Ti2AX MAX phases (A = Al or Ga, X = C or N) were investigated using density functional theory (DFT). It is shown that the calculations of the electronic, structural, and elastic properties of these structures, using local density approximation (LDA) and generalized gradient approximation (GGA) coupled with projected augmented-wave (PAW) pseudopotentials, agree well with experiments. A thermodynamic model, which considers the vibrational and electronic contributions to the total free energy of the system, was used to investigate the finite-temperature thermodynamic properties of Ti2AX. The vibrational contribution was calculated using the supercell method, whereas the electronic contribution resulted from one-dimensional integration of electronic density of states (DOSs). To verify the model, the specific heats of pure elements were calculated and compared to experimental data. The DFT-D2 technique was used to calculate the heat capacity of graphite, taking into account the van der Waals (vdW) effect. Good agreement between the calculations and experiments for the specific heats of graphite and other pure elements lends validity to the approach used. The calculated results for the specific heats of Ti2AlC and Ti2AlN match well with experimental data. These strengthen the results of specific heats of Ti2GaC and Ti2GaN as well as other calculated thermodynamic properties, including the energies of formation and thermal expansion coefficient.
Ab initio properties of Li-group-II molecules for ultracold matter studies
Authors: Kotochigova Svetlana , Petrov Alexander , Linnik Maria , Kłos Jacek , Julienne Paul S.
Published: November 2011

We perform a systematic investigation of the electronic properties of the 2Σ+ ground state of Li-alkaline-earth dimers. These molecules are proposed as possible candidates for quantum simulation of lattice-spin models. We apply powerful quantum chemistry coupled-cluster method and large basis sets to calculate potential energies and permanent dipole moments for the LiBe, LiMg, LiCa, LiSr, and LiYb molecules. Agreement of calculated molecular constants with existing experimental data is better than or equal to 8%. Our results reveal a surprising irregularity in the dissociation energy and bond length with an increase in the reduced mass of the molecule. At the same time, the permanent dipole moment at the equilibrium separation has the smallest value between 0.01 a.u. and 0.1 a.u. for the heaviest (LiSr and LiYb) molecules and increases to 1.4 a.u. for the lightest (LiBe), where 1 a.u. is one atomic unit of dipole moment. We consider our study of the 2Σ+ molecules a first step towards a comprehensive analysis of their interactions in an optical trap.
Reactions between chlorine atom and acetylene in solid para-hydrogen: Infrared spectrum of the 1-chloroethyl radical
Authors: Golec Barbara , Lee Yuan-Pern
Published: November 2011

We applied infrared matrix isolation spectroscopy to investigate the reactions between Cl atom and acetylene (C2H2) in a para-hydrogen (p-H2) matrix at 3.2 K; Cl was produced via photodissociation at 365 nm of matrix-isolated Cl2 in situ. The 1-chloroethyl radical (·CHClCH3) and chloroethene (C2H3Cl) are identified as the main products of the reaction Cl + C2H2 in solid p-H2. IR absorption lines at 738.2, 1027.6, 1283.4, 1377.1, 1426.6, 1442.6, and 2861.2 cm−1 are assigned to the 1-chloroethyl radical. For the reaction of Cl + C2D2, lines due to the ·CDClCH2D radical and trans-CHDCDCl are observed; the former likely has a syn-conformation. These assignments are based on comparison of observed vibrational wavenumbers and 13C- and D-isotopic shifts with those predicted with the B3LYP/aug-cc-pVDZ and MP2/aug-cc-pVDZ methods. Our observation indicates that the primary addition product of Cl + C2H2, 2-chlorovinyl (·CHCHCl) reacts readily with a neighboring p-H2 molecule to form ·CHClCH3 and C2H3Cl. Observation of ·CDClCH2D and trans-CHDCDCl from Cl + C2D2 further supports this conclusion. Although the reactivity of p-H2 appears to be a disadvantage for making highly reactive free radicals in solid p-H2, the formation of 1-chloroethyl radical indicates that this secondary reaction might be advantageous in producing radicals that are difficult to prepare from simple photolysis or bimolecular reactions in situ.
Hydrophobic interactions in presence of osmolytes urea and trimethylamine-N-oxide
Authors: Sarma Rahul , Paul Sandip
Published: November 2011

Molecular dynamics simulations were carried out to study the influences of two naturally occurring osmolytes, urea, and trimethylamine-N-oxide (TMAO) on the hydrophobic interactions between neopentane molecules. In this study, we used two different models of neopentane: One is of single united site (UA) and another contains five-sites. We observe that, these two neopentane models behave differently in pure water as well as solutions containing osmolytes. Presence of urea molecules increases the stability of solvent-separated state for five-site model, whereas osmolytes have negligible effect in regard to clustering of UA model of neopentane. For both models, dehydration of neopentane and preferential solvation of it by urea and TMAO over water molecules are also observed. We also find the collapse of the second-shell of water by urea and water structure enhancement by TMAO. The orientational distributions of water molecules around different layers of neopentane were also calculated and we find that orientation of water molecules near to hydrophobic moiety is anisotropic and osmolytes have negligible effect on it. We also observe osmolyte-induced water-water hydrogen bond life time increase in the hydration shell of neopentane as well as in the subsequent water layers.
Comment on “The effects of Si doping on dislocation movement and tensile stress in GaN films” [J. Appl. Phys. 109, 073509 (2011)]
Authors: Dadgar A. , Krost A.
Published: November 2011

In the publication by Moram et al. [J. Appl. Phys. 109, 073509 (2011)], some statements were made which disagree with the measurements presented by the authors of the article. In particular, silicon doping is claimed to suppress dislocation movement in GaN epitaxy hampering stress reduction during growth. We show that the data indeed prove the opposite, in agreement with prior publications.
Electron interaction with nitromethane embedded in helium droplets: Attachment and ionization measurements
Authors: da Silva F. Ferreira , Ptasińska S. , Denifl S. , Gschliesser D. , Postler J. , Matias C. , Märk T. D. , Limão-Vieira P. , Scheier P.
Published: November 2011

Results of a detailed study on electron interactions with nitromethane (CH3NO2) embedded in helium nanodroplets are reported. Anionic and cationic products formed are analysed by mass spectrometry. When the doped helium droplets are irradiated with low-energy electrons of about 2 eV kinetic energy, exclusively parent cluster anions (CH3NO2)n− are formed. At 8.5 eV, three anion cluster series are observed, i.e., (CH3NO2)n−, [(CH3NO2)n–H]−, and (CH3NO2)nNO2−, the latter being the most abundant. The results obtained for anions are compared with previous electron attachment studies with bare nitromethane and nitromethane condensed on a surface. The cation chemistry (induced by electron ionization of the helium matrix at 70 eV and subsequent charge transfer from He+ to the dopant cluster) is dominated by production of methylated and protonated nitromethane clusters, (CH3NO2)nCH3+ and (CH3NO2)nH+.
Effect of indirect interband absorption in Ge/SiGe quantum wells
Authors: Kim Jungho , Ahn Doyeol
Published: November 2011

The effect of the indirect interband absorption both below and above the direct gap in Ge/SiGe quantum-well (QW) structures is theoretically investigated in comparison to the direct interband absorption. The theoretical formula for the indirect interband absorption is derived based on the second-order time-dependent perturbation theory. The direct interband absorption is calculated by summing the bound-state exciton contribution based on the variational method and the QW continuum-state contribution in the consideration of the valence band mixing effect and a Sommerfeld excitonic enhancement factor. The calculated indirect interband absorption parabolically increases below the direct bandgap and shows a stair-step-like gradual increase above the direct bandgap. The calculated optical absorption spectra at room temperature are compared with the experimental results measured by Kuo et al. [Nature 437, 1334 (2005)]. Although the indirect interband absorption is very small below the direct bandgap, the contribution of the gradually increasing indirect interband absorption is significant at the high transition energy above the direct bandgap.
Comparison of chemical and thermal protein denaturation by combination of computational and experimental approaches. II
Authors: Wang Qian , Christiansen Alexander , Samiotakis Antonios , Wittung-Stafshede Pernilla , Cheung Margaret S.
Published: November 2011

Chemical and thermal denaturation methods have been widely used to investigate folding processes of proteins in vitro. However, a molecular understanding of the relationship between these two perturbation methods is lacking. Here, we combined computational and experimental approaches to investigate denaturing effects on three structurally different proteins. We derived a linear relationship between thermal denaturation at temperature Tb and chemical denaturation at another temperature Tu using the stability change of a protein (ΔG). For this, we related the dependence of ΔG on temperature, in the Gibbs-Helmholtz equation, to that of ΔG on urea concentration in the linear extrapolation method, assuming that there is a temperature pair from the urea (Tu) and the aqueous (Tb) ensembles that produces the same protein structures. We tested this relationship on apoazurin, cytochrome c, and apoflavodoxin using coarse-grained molecular simulations. We found a linear correlation between the temperature for a particular structural ensemble in the absence of urea, Tb, and the temperature of the same structural ensemble at a specific urea concentration, Tu. The in silico results agreed with in vitro far-UV circular dichroism data on apoazurin and cytochrome c. We conclude that chemical and thermal unfolding processes correlate in terms of thermodynamics and structural ensembles at most conditions; however, deviations were found at high concentrations of denaturant.
Tunneling through stacked InAs/InGaAs/InP self-assembled quantum dots in a magnetic field
Authors: Silva A. G. , Lopez F. E. , Guimarães P. S. S. , Pires M. P. , Souza P. L. , Landi S. M. , Villas-Bôas J. M. , Vieira G. S. , Vinck-Posada H. , Rodriguez B. A.
Published: November 2011

We report results of an investigation of vertical transport in stacked InAs/InGaAs/InP self-assembled quantum dot multi-layers and show evidence of tunneling between quantum dot states in adjacent layers. In the presence of magnetic fields up to 12 T applied parallel to the current, tunneling through Zeeman-split quasi-zero dimensional states is observed. The difference in the g factor of two quantum dots in adjacent layers, which is due to the difference in confinement, is estimated from the data. The experimental value obtained for the difference in g factor is in good agreement with that obtained from a calculation of the quantum dots’ energy levels in the presence of the magnetic field.
Effect of surface charge density and electro-osmotic flow on ionic current in a bipolar nanopore fluidic diode
Authors: Pal Singh Kunwar , Kumar Manoj
Published: November 2011

We have simulated bipolar nanopore fluidic diodes for different values of surface charge densities, electrolyte concentrations, and thickness of transition zone. Nanopore enrichment leads to increased nanopore conductivity with the surface charge density at low electrolyte concentrations. Potential drop across the nanopore and electric field inside the nanopore decreases. Forward current and ionic current rectification peaks for a specific value of surface charge density. Even though the electro-osmotic current component remains small as compared to other components, its non-inclusion in the modeling leads to serious errors in the solutions. Significant ion current rectification can be obtained even if transition zone between oppositely charged zones is not narrow. The effect of the surface charge is screened by counterions at higher electrolyte concentrations, which leads to reduced electrolyte polarization and a decrease in the ion current rectification.
Ferrimagnetism corresponding spin state transition in Nd3Fe5O12 garnet
Authors: Guo Li , Yuan Lin , Huang Keke , Shang Mingyu , Peng Wen , Yuan Hongming , Feng Shouhua
Published: November 2011

The irreversible transition for octahedral Fe3+ ion in Nd3Fe5O12 garnet from low-spin (LS) (S = 1/2) state to high-spin (HS) state (S = 5/2) was induced by increasing temperature. The experimental value of entropy change of LS–HS transition is in good agreement with theoretical estimations. The crystal structure is stable below 873 K. The spin state transition corresponds to the changes of the observed magnetization and Curie temperature of Nd3Fe5O12, in which saturated magnetization is consistent with calculating value. The increase of the Curie point indicates that the change of spin state results in strength in energy of superexchange interaction between two kinds of iron ions.
Phase diagram of polypeptide chains
Authors: Auer Stefan
Published: November 2011

We use a coarse grained protein model that enables us to determine the equilibrium phase diagram of natively folded α-helical and unfolded β-sheet forming peptides. The phase diagram shows that there are only two thermodynamically stable peptide phases, the peptide solution and the bulk fibrillar phase. In addition, it reveals the existence of various metastable peptide phases. The liquidlike oligomeric phases are metastable with respect to the fibrillar phases, and there is a hierarchy of metastability. The presented phase diagram provides a solid basis for understanding the assembly of polypeptide chains into the phases formed in their natively folded and unfolded conformations.
Computer simulation study of thermodynamic scaling of dynamics of 2Ca(NO3)2·3KNO3
Authors: Ribeiro Mauro C. C. , Scopigno Tullio , Ruocco Giancarlo
Published: November 2011

Molecular dynamics (MD) simulations of the glass-former 2Ca(NO3)2·3KNO3, CKN, were performed as a function of temperature at pressures 0.1 MPa, 0.5 GPa, 1.0 GPa, and 2.0 GPa. Diffusion coefficient, relaxation time of the intermediate scattering function, and anion reorientational time were obtained as a function of temperature and densitiy ρ. These dynamical properties of CKN scale as ργ/T with a common value γ = 1.8 ± 0.1. The scaling parameter γ is consistent with the exponent of the repulsive part of an effective intermolecular potential for the repulsion between the atoms at shortest distance in the equilibrium structure of liquid CKN, Ca2+, and oxygen atoms of NO3−. Correlation between potential energy and virial is obeyed for the short-range terms of the potential function, but not for the whole potential including coulombic interactions. Decoupling of diffusion coefficient and reorientational relaxation time from relaxation time take place at a given ργ/T value, i.e., breakdown of Stokes-Einstein and Debye-Stokes-Einstein equations result from combined thermal and volume effects. The MD results agree with correlations proposed between long-time relaxation and short-time dynamics, lnτ ∝ 1/〈u2〉, where the mean square displacement 〈u2〉 concerns a time window of 10.0 ps. It has been found that 〈u2〉 scales as ργ/T above and below the glass transition temperature, so that thermodynamic scaling of liquid dynamics can be thought as a consequence of theories relating short- and long-time dynamics, and the more fundamental scaling concerns short-time dynamical properties.
Grating formation by a high power radio wave in near-equator ionosphere
Authors: Singh Rohtash , Sharma A. K. , Tripathi V. K.
Published: November 2011

The formation of a volume grating in the near-equator regions of ionosphere due to a high power radio wave is investigated. The radio wave, launched from a ground based transmitter, forms a standing wave pattern below the critical layer, heating the electrons in a space periodic manner. The thermal conduction along the magnetic lines of force inhibits the rise in electron temperature, limiting the efficacy of heating to within a latitude of few degrees around the equator. The space periodic electron partial pressure leads to ambipolar diffusion creating a space periodic density ripple with wave vector along the vertical. Such a volume grating is effective to cause strong reflection of radio waves at a frequency one order of magnitude higher than the maximum plasma frequency in the ionosphere. Linearly mode converted plasma wave could scatter even higher frequency radio waves.
Gyrokinetic simulations of magnetic reconnection
Authors: Pueschel M. J. , Jenko F. , Told D. , Büchner J.
Published: November 2011

Fast magnetic reconnection, believed to be a mechanism for rearranging the magnetic topology and creating energetic particles in many astrophysical and laboratory plasmas, is investigated with the nonlinear gyrokinetic code Gene. After some code-code benchmarking, extensive linear studies are presented, covering all relevant parameter dependencies of two-dimensional slab reconnection. The results are used to ascertain the validity of a fluid model and understand for which parameters it fails to describe the physics correctly. The nonlinear phase is studied for two scenarios: decaying and driven turbulence. In the former case, the initially injected energy is cascading towards the largest scales of the system, whereas a fully turbulent, quasi-stationary state develops if the system is driven through a Krook-type term in the gyrokinetic Vlasov equation.
Extended Lagrangian free energy molecular dynamics
Authors: Niklasson Anders M. N. , Steneteg Peter , Bock Nicolas
Published: November 2011

Extended free energy Lagrangians are proposed for first principles molecular dynamics simulations at finite electronic temperatures for plane-wave pseudopotential and local orbital density matrix-based calculations. Thanks to the extended Lagrangian description, the electronic degrees of freedom can be integrated by stable geometric schemes that conserve the free energy. For the local orbital representations both the nuclear and electronic forces have simple and numerically efficient expressions that are well suited for reduced complexity calculations. A rapidly converging recursive Fermi operator expansion method that does not require the calculation of eigenvalues and eigenfunctions for the construction of the fractionally occupied density matrix is discussed. An efficient expression for the Pulay force that is valid also for density matrices with fractional occupation occurring at finite electronic temperatures is also demonstrated.
Temperature dependent photoluminescence of lateral polarity junctions of metal organic chemical vapor deposition grown GaN
Authors: Kirste Ronny , Collazo Ramón , Callsen Gordon , Wagner Markus R. , Kure Thomas , Sebastian Reparaz Juan , Mita Seji , Xie Jinqiao , Rice Anthony , Tweedie James , Sitar Zlatko , Hoffmann Axel
Published: November 2011

We report on fundamental structural and optical properties of lateral polarity junctions in GaN. GaN with Ga- to N-polar junctions was grown on sapphire using an AlN buffer layer. Results from scanning electron microscopy and Raman spectroscopy measurements indicate a superior quality of the Ga-polar GaN. An extremely strong luminescence signal is observed at the inversion domain boundary (IDB). Temperature dependent micro photoluminescence measurements are used to reveal the recombination processes underlying this strong emission. At 5 K the emission mainly arises from a stripe along the inversion domain boundary with a thickness of 4-5 μm. An increase of the temperature initially leads to a narrowing to below 2 μm emission area width followed by a broadening at temperatures above 70 K. The relatively broad emission area at low temperatures is explained by a diagonal IDB. It is shown that all further changes in the emission area width are related to thermalization effects of carriers and defects attracted to the IDB. The results are successfully used to confirm a theoretical model for GaN based lateral polarity junctions. Due to the strong and pronounced emission of IDBs even at elevated temperatures, it is demonstrated that lateral polarity junctions exhibit a strong potential for future high efficiency devices.
Irradiance-based emissivity correction in infrared thermography for electronic applications
Authors: Vellvehi M. , Perpiñà X. , Lauro G. L. , Perillo F. , Jordà X.
Published: November 2011

This work analyzes, discusses, and proposes a solution to the problem of the emissivity correction present in infrared thermography when coatings with known emissivity cannot be deposited on the inspected surface. It is shown that the conventional technique based on two reference thermal images and the linearization of the blackbody radiation dependence on temperature is not a reliable and accurate solution when compared with the coating procedure. In this scenario, a new approach based on the direct processing of the output signal of the infrared camera (which is proportional to the detected irradiance) is proposed to obtain an accurate emissivity and surrounding reflections map, perfectly compensating the thermal maps. The results obtained have been validated using a module as a test vehicle containing two thermal test chips which incorporate embedded temperature sensors.
A light emitting diode based photoelectrochemical screener for distributed combinatorial materials discovery
Authors: Winkler Gates R. , Winkler Jay R.
Published: November 2011

Combinatorial approaches for targeted discovery of new materials require rapid screening systems to evaluate large numbers of new material compositions. High-throughput combinatorial materials discovery is a capital-intensive undertaking requiring sophisticated robotic sample preparation and rapid screening assays. A distributed approach to combinatorial materials discovery can achieve similar goals by increasing the breadth of participation and reducing the size of the capital investment. The discovery of new photoactive materials for solar fuels production demands a screening device to probe materials for electrochemical current production upon irradiation with visible light. We have developed a system that uses an array of pulsed light-emitting diodes (LEDs) synchronized with a two-electrode potentiostat that can measure the photoelectrochemical responses of combinatorial sample arrays deposited on conducting glass plates. Compared to raster scanning methods, this LED system trades spatial resolution for a substantial reduction in scan time.
Waveguide superconducting single-photon detectors for integrated quantum photonic circuits
Authors: Sprengers J. P. , Gaggero A. , Sahin D. , Jahanmirinejad S. , Frucci G. , Mattioli F. , Leoni R. , Beetz J. , Lermer M. , Kamp M. , Höfling S. , Sanjines R. , Fiore A.
Published: November 2011

The monolithic integration of single-photon sources, passive optical circuits, and single-photon detectors enables complex and scalable quantum photonic integrated circuits, for application in linear-optics quantum computing and quantum communications. Here, we demonstrate a key component of such a circuit, a waveguide single-photon detector. Our detectors, based on superconducting nanowires on GaAs ridge waveguides, provide high efficiency (∼20%) at telecom wavelengths, high timing accuracy (∼60 ps), and response time in the ns range and are fully compatible with the integration of single-photon sources, passive networks, and modulators.