bluuebunny/crossref_metadata_2025 huggingface dataset:
Preparation of Cu2ZnSnSe4 thin films by selenization of precursor evaporated from Cu2ZnSnSe4 compound
Authors: Yamaguchi T. , Kawamoto K. , Oura S. , Niiyama S. , Imanishi T.
Published: May 2013

Cu2ZnSnSe4 ingot was synthesized and then used as a precursor for selenization process in order to fabricate Cu2ZnSnSe4 thin films. The thin films were prepared at each point A‐F in our selenization process and their properties were investigated. Cu2ZnSnSe4 ingot and thin films had a kesterite Cu2ZnSnSe4 structure. From EPMA analysis and XRD studies, the mechanism of Cu2ZnSnSe4 formation was discussed. Cu‐Se phases were related to Cu2ZnSnSe4 formation. Cu2ZnSnSe4 may decompose to Sn‐Se compound during the annealing process at 550 oC. Cu2ZnSnSe4 thin film solar cells demonstrated Voc=300 mV, Isc=7.25 mA/cm2. The band gap energy of Cu2ZnSnSe4 thin film determined from the QE spectra estimated to be approximately 1.04 eV. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Hard X‐ray photoemission study of the covalent‐chain antiferromagnets TlFeS2 and TlFeSe2
Authors: Mimura Kojiro , Motonami Satoru , Shim YongGu , Wakita Kazuki , Jahangirli Zakir , Alekperov Oktay , Mamedov Nazim , Sato Hitoshi , Utsumi Yuki , Ueda Shigenori , Shimada Kenya , Taguchi Yukihiro , Kobayashi Keisuke , Bihlmayer Gustav , Namatame Hirofumi , Taniguchi Masaki
Published: May 2013

Bulk electronic structures of covalent‐chain antiferromagnets TlFeS2 and TlFeSe2 have been investigated by hard X‐ray photoemission spectroscopy (HAXPES) and band calculations based on the full‐potential linearized augmented plane wave method. Competition between localized and delocalized characters of Fe 3d electrons has been suggested by the slight discrepancies between valence‐band HAXPES spectra and calculated density of states, as well as Fe 2p spectra with a broad charge‐transfer satellite. It is assumed that this competition closely related to the crystallographic onedimensionality of these materials. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Super high sensitive low‐dimensional IR‐detector
Authors: Emil Huseynov , Namiq Ismayilov
Published: May 2013

The original design of the infrared detector providing ultrahigh parameters of responsivity is proposed. The idea lies in separation of the areas between charge carrier optical generation and formation of electrical signal. The calculations performed for CdxHg1–xTe photodetectors with x ∼ 0.21 and x ∼ 0.28 at electric bias 200 mV yield values such as Su = 108–1010 V/W for voltage response. That is several orders of magnitude more than experimentally reached values for CdxHg1–xTe‐based IR‐detectors (Su =106V/W for λ c = 11 µm, T = 77 K [Singh and Mittal, Def. Sci. J. 53(31), 281 (2003)]). Offered detector is different with very large resistance and small power consumption and dimensions of active area. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Synthesis of porous CuInS2 crystals using a stirrer
Authors: Akaki Yoji , Ohno Yuki , Momiki Takanori
Published: May 2013

Porous CuInS2 crystals were grown from starting materials CuCl2·2H2O, InCl3·4H2O and thiorea with ethylene glycol solution, that were placed into a flask, heated, and refluxed for 1 hour. The diffraction peaks only from CuInS2 phase appear for all the samples. The morphology of CuInS2 crystal was porous, and the porous crystals exist in two kinds. One kind was flower‐like crystals which complexly lack the flakes, another one was sphere‐like crystals existed with a number of the poles. The specific surface area of the samples grown by stirring starting materials with In to Cu ratio of 4.3 for 30 minutes was found approximately to be 55 m2/g. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
From SnS and PbS towards complex sulfosalts: thin film growth and properties
Authors: Lobe Sandra , Wagner Gerald , Bente Klaus
Published: May 2013

Polycrystalline thin films of Sn1−xPbxS (0 ≤ x ≤ 0.5) were grown by multi‐beam hot‐wall deposition using SnS and PbS as source materials. Employing evaporation temperatures of TPbS ≈ 680 °C and TSnS ≈ 600 °C dendritic thin film growth appears due to high supersaturation at the substrate surface (TSubstrate ≈ 240…375 °C). Therefore, both evaporation temperatures were lowered to TPbS ≈ 600 °C and TSnS ≈ 540 °C. Calculated and measured thin film compositions agree very well. The variation of the deposition time exhibits linear thin film growth. At the very beginning of film growth a well‐distinct texture can be observed. If the growth proceeds (t > 5 min) this texture disappears. As determined by transmission UV‐Vis spectroscopy all Sn1−xPbxS films show a direct allowed transition which bandgap energy increases with increasing x and an indirect allowed transition which bandgap energy decreases with increasing lead content. Decreasing film thickness leads to an increase of both bandgap energies. The obtained results were discussed with respect to a possible application as absorber material in solar cells. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Excitonic emission of CuInS2 crystals using confocal microscopy system
Authors: Horikawa Yusuke , Matsuo Shingo , Shim YongGu , Wakita Kazuki
Published: May 2013

Photoluminescence (PL) spectra in the band‐edge region on bulk single‐crystals of CuInS2 grown by the traveling heater method have been investigated using a confocal microscopy system. The observed PL spectra are separated into two Lorentzian peaks which are assigned to be A and B free excitons, by the analysis of the excitation intensity dependence of the emissions. Consequently, we present the behaviour of B free exciton within a wide range of temperatures. The time‐resolved emissions of A free exciton have also been examined. The decay of the emissions is analyzed using a double exponential curve. Fast and slow components are attributed to nonradiative relaxation and radiative recombination, respectively. The decay‐time constant of the slow component corresponds to the radiative lifetime of A free exciton and is obtained over the wide temperature region until 300 K. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Synthesis and properties of Yb:LuAG transparent ceramics
Authors: Jiang Benxue , Lu Xiao , Zeng Yanping , Liu Shuping , Li Jiang , Liu Wenbin , Shi Yun , Pan Yubai
Published: May 2013

Yb3+‐doped Lu3Al5O12 (Yb:LuAG) transparent ceramics were fabricated by vacuum sintering and hot isostatic pressing(HIP) method. TEOS and Sc2O3 were added as sintering aids by a high energy ball milling. Transparent nearly‐fully dense samples with grain size of about tens of micrometers were obtained after 1820 °C sintering, while the grain size of HIP sample was only about several micrometers. The absorption spectra, emission spectra, and fluorescence life time of these transparent Yb:LuAG ceramics at room temperature have were measuredd. The absorption and emission cross‐section of Yb:LuAG Ceramics at 937 nm and 1030 nm were 7.6×10–21 and 23×10–21cm2 which are much higher than those of Yb:YAG crystal. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The sensitivity of backscattering coefficients to elastic scattering cross‐sections and electron stopping powers
Authors: Walker C. G. H. , Matthew J. A. D. , El‐Gomati M. M.
Published: May 2013

The sensitivity of Monte Carlo estimates of backscattering coefficients η to the accuracy of their input data is examined by studying the percentage change in η due to changes of 10% and 20% in the differential elastic scattering cross‐section dσ/dΩ and corresponding changes in the stopping power S(E) in the primary energy range 200–10,000 eV. To a good approximation equivalent elastic and inelastic scattering changes produce equal and opposite shifts in η, a result consistent with predictions of transport theory. For medium to high atomic numbers an x% error in the specification of either S(E) or dσ/dΩ produces a percentage change in η significantly less than x%, while at low atomic number Δη/η increases approximately linearly with ln E so that Monte Carlo predictions are then more sensitive to parameter precision at high energy. SCANNING 36:241–245, 2014. © 2013 Wiley Periodicals, Inc.
Experimental and computational analysis of stall cells on rectangular wings
Authors: Manolesos Marinos , Papadakis Georgios , Voutsinas Spyros G.
Published: May 2013

The present paper is the second part of a combined (experimental and computational) study on stall cells (SCs) on a rectangular wing. In the first part, tuft data were used in order to geometrically characterize a stabilized SC resulting from a localized spanwise disturbance introduced by a zigzag tape. Here, pressure measurements on the model and in the wake and aerodynamic polars at midspan are reported. The wing model had an aspect ratio value of 2, the Reynolds number was 106 and the range of angles of attack (α) was from −6° to 16°. Experimental results confirm previous findings. Furthermore, two‐dimensional and three‐dimensional Reynolds Averaged Navier‐Stokes RANS simulations are used in order to better understand the structure of SCs. 3D simulations reproduce the experimental data with a 3° delay in α and permit a qualitative analysis. It is found that the SC vortices start normal to the wing surface and extend downstream in the wake; the evolution of the SC vortices in the wake is in strong interaction with the separation line vortex and the trailing edge line vortex; as the SC vortex develops downstream in the wake, its centreline is contracted towards the SC centre; the wing wake is pushed upstream at the centre of the SC and downstream at the sides by the SC vortices; spanwise lift and drag distributions always attain their minimum at the SC centre. Copyright © 2013 John Wiley & Sons, Ltd.
Scaling and predicting solute transport processes in streams
Authors: González‐Pinzón Ricardo , Haggerty Roy , Dentz Marco
Published: May 2013

We investigated scaling of conservative solute transport using temporal moment analysis of 98 tracer experiments (384 breakthrough curves) conducted in 44 streams located on five continents. The experiments span 7 orders of magnitude in discharge (10−3 to 103 m3/s), span 5 orders of magnitude in longitudinal scale (101 to 105 m), and sample different lotic environments—forested headwater streams, hyporheic zones, desert streams, major rivers, and an urban manmade channel. Our meta‐analysis of these data reveals that the coefficient of skewness is constant over time (
,
). In contrast, the
of all commonly used solute transport models decreases over time. This shows that current theory is inconsistent with experimental data and suggests that a revised theory of solute transport is needed. Our meta‐analysis also shows that the variance (second normalized central moment) is correlated with the mean travel time (
), and the third normalized central moment and the product of the first two are very strongly correlated (
). These correlations were applied in four different streams to predict transport based on the transient storage and the aggregated dead zone models, and two probability distributions (Gumbel and log normal).
Managing brown‐headed cowbirds to sustain abundance of black‐capped vireos
Authors: Smith Kathryn N. , Campomizzi Andrew J. , Morrison Michael L. , Wilkins R. Neal
Published: May 2013

Brood parasites can appreciably decrease fecundity of susceptible songbird hosts, which can often cause a decrease in host abundance. Wildlife managers use brown‐headed cowbird (Molothrus ater) management to reduce parasitism frequency and benefit the conservation of the endangered black‐capped vireo (Vireo atricapilla); however, intensity of management needed to increase vireo abundance is not well‐understood. We used sensitivity analyses of population models for black‐capped vireos to assess effects on abundance of particular changes in parasitism frequency. Our models suggest that the parasitism frequency vireos can tolerate while maintaining abundance in a particular location is ≤30%. If parasitism frequency is high, trapping cowbirds during ≥1 of every 3 years may be sufficient for reducing parasitism enough to maintain abundance at managed locations. Cowbird management programs may need to be intensive in initial years to increase abundance of vireos being managed if the initial abundance is low. Rotating locations of traps each year among managed locations may be effective for maintaining vireo abundance while decreasing overall trapping effort and making more efficient use of management funds. Increasing and restoring habitat concurrent with cowbird management would likely further increase the likelihood of establishing and maintaining vireo abundance in managed locations. © The Wildlife Society, 2013
Comparison of Cis‐ and Oxaliplatin‐induced Destabilization of 15‐mer DNA‐ and RNA Duplexes by Binding to Centrally Located GG‐ and GNG Sequences
Authors: Polonyi Christopher , Albertsson Ingrid , Damian Mariana S. , Elmroth Sofi K. C.
Published: May 2013

Thermodynamic parameters are presented here illustrating the effects caused by the two anticancer active metal complexes cisplatin and oxaliplatin after introduction into four closely related RNA and DNA duplexes. The duplexes used are blunt end, fully complementary 15‐mer duplexes with a centrally located either GG‐ or GNG (here: N = T or U) binding site. For all duplexes, a common trend of reduced melting temperature was observed after platination. Analysis of the thermodynamic parameters for the duplex dissociation reactions showed good correlation between variations in melting temperatures (Tm) and ground state enthalpies (ΔH) in both DNA‐ and RNA duplexes. The melting temperatures of the native duplexes were found to be determined by their chemical nature, i.e. with observed Tm ‐values of ca. 50 °C for DNA and ca. 61 °C for RNA (CT = 2 μM and CNa+ = 129 mM, pH 6.3). Of the two types of nucleic acids, RNA is the one that exhibits the most pronounced sensitivity towards introduction of the platinum complexes, and with oxaliplatin as the more influential metalation reagent. Of note is that the thermal destabilization caused by oxaliplatin interacting with a centrally located GUG‐sequence results in a duplex stability below native DNA.
Fast Ion Conducting Nanocrystalline Alkaline Earth Fluorides Simply Prepared by Mixing or Manual Shaking
Authors: Scholz Gudrun , Meyer Klas , Düvel Andre , Heitjans Paul , Kemnitz Erhard
Published: May 2013

Simple mixing or shaking of alkaline earth hydroxides with ammonium fluoride results in nanocrystalline phase pure metal fluorides MF2 (M: Ca, Sr, Ba). The formation of the alkaline earth fluorides was investigated by varying the reaction conditions. Evidence was found that just the contact between the starting materials is sufficient for the reaction to take place. X‐ray diffraction, elemental analysis, 19F MAS NMR spectroscopy, and measurements of DC conductivities were used to characterize the fluorides regarding properties like crystal structure, crystallite sizes, local fluorine coordination, and fluorine ion conductivity. The 19F MAS NMR spectra of the phase pure fluorides prepared showed several signals, which were assigned to defects, impurities, or geometric distortions. The fluorides prepared by mixing or shaking revealed fluorine ion conductivities several orders of magnitude higher than observed for the respective microcrystalline alkaline earth fluorides. Therefore, the synthesis routine presented in this study may open a path to a very quick and simple synthesis of nanocrystalline fast fluorine ion conductors.
Synthesis and Characterization of Iron(III) Complexes of 5‐(8‐Carboxy‐1‐naphthyl)‐10, 15, 20‐tritolyl Porphyrin
Authors: Zhang Yu , Jiang Jiaxun , Hu Chuanjiang
Published: May 2013

5‐(8‐Carboxy‐1‐naphthyl)‐10, 5, 20‐tritolyl porphyrin (H3CNTTP) and its iron(III) complexes, [Fe(CNTTP)]2 and [Fe(CNTTP)(N‐MeIm)2], were synthesized and characterized. X‐ray crystallography revealed that the carboxylate group is “hanging” over the porphyrin plane. The rigid framework makes the distance between the carboxylate oxygen and iron in the same porphyrin too long to form a coordination bond. On the other hand, the carboxylate group is not bulky enough to block the axial binding site. In the presence of OH–, the carboxylate oxygen is coordinated to iron in the symmetry‐related unit, which led to the dimeric structure, [Fe(CNTTP)]2. In the presence of excess N‐methylimidazole, a six‐coordinate species, [Fe(CNTTP)(N‐MeIm)2], was obtained. In such a structure, CH···O interactions between the carboxylate group and imidazole probably play an important role to determine the orientation of imidazole plane. Two imidazole planes have relative parallel orientation. For [Fe(CNTTP)(N‐MeIm)2], 1H NMR shows pyrrole protons at the region –10 to –25 ppm. EPR shows rhombic spectrum. Those suggest [Fe(CNTTP)(N‐MeIm)2] is a type II low‐spin iron(III) porphyrinate.
Extended Lymphadenectomy in Gastric Cancer Is Debatable
Authors: Strong Vivian E. , Yoon Sam S.
Published: May 2013

Much debate still exists regarding the appropriate extent of lymphadenectomy for gastric adenocarcinoma. In high incidence countries in Eastern Asia, more extensive (e.g. D2) lymphadenectomies are standard, and these surgeries are generally done by experienced surgeons with low morbidity (<20 %) and mortality (<1 %). In United States and Western Europe, where the incidence of gastric adenocarcinoma is much lower, the majority of patients are treated at non‐referral centers with less extensive (e.g. D1 or D0) lymphadenectomy. This symposium article first reviews early studies that led to recommendations for less extensive lymphadenectomy. Two large prospective, randomized trials performed in the United Kingdom and the Netherlands in the 1990s failed to demonstrate a survival benefit of D2 over D1 lymphadenectomy, but these trials have been criticized for inadequate surgical training and high surgical morbidity (43–46 %) and high mortality rates (10–13 %) in the D2 group. We then discuss more contemporary studies that support more extensive lymphadenectomy with a minimum of 16 lymph nodes for adequate staging. The 15‐year follow‐up of the Netherlands trial now demonstrates an improved disease‐specific survival and locoregional recurrence in the D2 group. A prospective, randomized trial from Taiwan found a survival benefit of more extensive lymphadenectomies, and another randomized trial from Japan found adding dissection of para‐aortic nodes to a D2 lymphadenectomy did not improve survival. Western surgeons have increasingly accepted the importance of performing more than a D1 node dissection, and Eastern surgeons are accepting that more than a D2 node dissection does not improve survival and increases morbidity. Thus both Eastern and Western approaches are favoring D2 lymphadenectomy as a standard, and on this topic we appear to be harmonizing.
Undergraduate Surgery Clerkship and the Choice of Surgery as a Career: Perspective from a Developing Country
Authors: Ekenze S. O. , Ugwumba F. O. , Obi U. M. , Ekenze O. S.
Published: May 2013

Background

There are concerns regarding a possible decline in the proportion of students choosing surgery as a career in some countries in sub‐Saharan Africa. Published works indicate that most students choose their ultimate career during undergraduate training. The present study was undertaken to assess the medical student’s perception of the surgery clerkship and determine its influence in the choice of surgery as a career.

Methods

The study involved a cross‐sectional survey of 2009 and 2010 graduating medical classes of the University of Nigeria based on self‐administered questionnaires. The clerkship evaluation was assessed on a 3‐point Likert scale (1 = poor; 3 = excellent).

Results

The response rate was 70.3 % (275/391); 179 (65.1 %) of the students were males and 96 (34.9 %), females. Sixty‐one (22.2 %) rated the overall quality of their surgery clerkship as excellent (mean rating = 2). Compared with the other three major clerkships, surgery has the lowest rating for overall quality (mean rating: surgery = 2; others = 2.2). Aspects of the clerkship experience that contributed to the overall lower rating of surgery include quality of opportunity to participate in direct patient care; clarity of posting goals and objectives; experience in learning history taking skills, basic physical examination skills, and interpretation of laboratory data; accessibility of faculty; and students’ perception that they were treated in a respectful manner. The major suggestions to improve clerkship quality were these: (1) more involvement in direct patient care (n = 154; 56 %), and (2) improvement in student–faculty interaction (n = 9 1; 33.1 %). Overall, 96 (34.9 %) students selected surgery as a specialty, and 39.3 % (108/275) selected the other three major specialties. Surgery was selected by 17/48 (35.4 %), 59/166 (35.5 %), and 20/61 (32.8 %) students who rated the surgery clerkship as “poor,” “just right,” and “excellent,” respectively (p = 0.876). Factors indicated as major influences in the choice of surgical specialty included personal satisfaction 41.7 % (40/96), clerkship experience 36.4 % (35/96), and diligence of faculty 13.5 % (13/96).

Conclusions

Periodic assessment of the satisfaction of medical students regarding their surgical clerkship experience is important. In our setting, we have identified aspects of the surgical clerkship that could be improved to enhance the quality of the experience, ensure the attractiveness of the field to the most qualified candidates, and boost interest in surgery as a career.
Transnationales ethnisches Unternehmertum. Das Fallbeispiel türkischstämmiger Unternehmer in Duisburg-Marxloh
Authors: Fürst Ariana , Balke Jan
Published: May 2013

Within the debate of transnational migration the phenomenon of transnational ethnic entrepreneurship is gaining in importance. Transnational ethnic entrepreneurship—in comparison to the already widely-discussed “traditional” ethnic economy—exhibits special features, i.e. its integration into cross-border production and distribution networks as well as modes of transnational living and working. On basis of an explorative study of Turkish entrepreneurs in Duisburg-Marxloh (Germany), the paper discusses different forms of intensity of transnational ethnic entrepreneurship concerning actor-specific and structural characteristics. It also illustrates the importance of transnational ethnic entrepreneurship for the local economy and the general development of the city quarter. Three “generations” of transnational ethnic entrepreneurship as well as three intensity-forms of transnational economic activities have been identified. Furthermore, the findings ascertain the entrepreneurs’ importance for the stabilization of the city quarter, regarding in particular its structural development as well as its image upgrading. At the same time the results show that the interconnection between transnational ethnic entrepreneurs as well as their integration into urban development strategies and institutional measures is on a low level. Transnational ethnic entrepreneurship as a strategic potential for urban development has yet not been fully explored, further research on this subject and planning action are required.
Solvent isotope and viscosity effects on the steady‐state kinetics of the flavoprotein nitroalkane oxidase
Authors: Gadda Giovanni , Fitzpatrick Paul F.
Published: May 2013

The flavoprotein nitroalkane oxidase catalyzes the oxidative denitrification of a broad range of primary and secondary nitroalkanes to yield the respective aldehydes or ketones, hydrogen peroxide and nitrite. With nitroethane as substrate the D2O(k
cat/K
M) value is 0.6 and the D2O
k
cat value is 2.4. The k
cat proton inventory is consistent with a single exchangeable proton in flight, while the k
cat/K
M is consistent with either a single proton in flight in the transition state or a medium effect. Increasing the solvent viscosity did not affect the k
cat or k
cat/K
M value significantly, establishing that nitroethane binding is at equilibrium and that product release does not limit k
cat.
Density dependence of dynamical heterogeneity in fluid methanol
Authors: Loubeyre Louis , Ahart Muhtar , Gramsch Stephen A. , Hemley Russell J.
Published: May 2013

Brillouin and Raman scattering experiments on methanol through its glass transition under pressure are reported. The Brillouin scattering data were analyzed using viscoelastic theory and a fit to the Vinet equation of state. The variation in the linewidth of the longitudinal acoustic mode with pressure shows a broad maximum centered around 3 GPa. The pressure evolution of the relaxation time in the GHz range is obtained, and the Raman data are analyzed in terms of the Boson peak and its associated relaxation time in the THz range. The pressure evolution of these two relaxation processes extends previous determinations of relaxations at lower frequency based on dielectric measurements in supercooled methanol. The relaxation processes in glass-forming methanol have now been investigated over a wide frequency range and their evolution followed over a large variation of density.
Kinetics of loop formation in worm-like chain polymers
Authors: Afra Reza , Todd Brian A.
Published: May 2013

A common theoretical approach to calculating reaction kinetics is to approximate a high-dimensional conformational search with a one-dimensional diffusion along an effective reaction coordinate. We employed Brownian dynamics simulations to test the validity of this approximation for loop formation kinetics in the worm-like chain polymer model. This model is often used to describe polymers that exhibit backbone stiffness beyond the monomer length scale. We find that one-dimensional diffusion models overestimate the looping time and do not predict the quantitatively correct dependence of looping time on chain length or capture radius. Our findings highlight the difficulty of describing high-dimensional polymers with simple kinetic theories.
The nature of chemical reaction-driven tip-streaming
Authors: Mayer H. C. , Krechetnikov R.
Published: May 2013

The discovery of chemical reaction-driven tip-streaming (also known as “an amazing drop”) was made about a decade ago during measurements of the dynamic interfacial tension of a water-alkali pendant droplet immersed in oil-linoleic acid. A plausible explanation for this self-sustained ejection of micron sized droplets from the tip of the macroscopic pendant drop was offered at that time and attributed to Marangoni stresses driving the reaction-produced surfactant along the interface. Later, asymptotic theory based on the analysis of a complete fluid dynamical formulation supported this hypothesis. As this discovery promised a way of microdroplet generation without the need for complex microchannel geometries or externally imposed flow or electric fields, we were recently motivated to study the influence of the reagent concentrations and reaction rate on the droplet generation. However, in an attempt to recreate the original experiments, we revealed that the cause for tip-streaming is not what it originally seemed to be. This led to a series of experiments clarifying the role of the Marangoni stresses and the crucial differences from similar phenomena. As the mechanism by which the phenomenon was originally thought to operate was supported by recent theoretical studies, the present work leads to new intriguing questions of existence and conditions under which a chemical reaction alone can drive Marangoni stresses capable of self-sustaining the process of tip-streaming.
Temperature dependence of charge carrier mobility in single-crystal chemical vapour deposition diamond
Authors: Jansen Hendrik , Dobos Daniel , Eisel Thomas , Pernegger Heinz , Eremin Vladimir , Wermes Norbert
Published: May 2013

Measurements of the temperature dependence of the charge carrier mobility in single-crystal chemical vapour deposition diamond using the transient current technique are presented in a temperature range from 2 K to room temperature. An α-source is used to create free charge carriers in the diamond bulk. The evolution of the current signal induced by their drift under the influence of an externally applied field is studied as a function of the temperature and the electric field strength. The electric field strength is varied by a factor of 30. The measurements are used to extract the transit time, the drift velocity, the saturation velocity, and the low-field mobility in terms of which the results are interpreted. Three samples have been studied which show the same behaviour. For holes, the mobility increases with decreasing temperature due to the acoustic phonon scattering, but it saturates for ultra-cold temperatures. The low-field mobility for holes at room temperature is measured as μ0h(295K)=(2534±20) cm2/Vs saturating against μ0h(→2K)=(11130±120) cm2/Vs. For electrons, only a lower limit on the low-field mobility can be given. It is measured as μ¯0e(295K)=(1802±14) cm2/Vs saturating against μ¯0e(→2K)=(3058±27) cm2/Vs. The electron transit time at low fields shows a different behaviour than the hole transit time and is not following the expected behaviour. This is likely to be caused by a high temperature valley re-population effect.
Monte Carlo simulation strategies to compute interfacial and bulk properties of binary fluid mixtures
Authors: Kumar Vaibhaw , Errington Jeffrey R.
Published: May 2013

We introduce Monte Carlo simulation methods for determining interfacial properties of binary fluid mixtures. The interface potential approach, in which the interfacial properties of a system are related to the surface excess free energy of a thin fluid film in contact with a surface, is utilized to deduce the wetting characteristics of a fluid mixture. The strategy described here provides an effective means to obtain the evolution of interfacial properties with the chemical composition of the fluid. This task is accomplished by implementing an activity fraction expanded ensemble technique, which allows one to obtain elements of the interface potential as a function of composition. We also show how this technique can be utilized to calculate bulk coexistence properties of fluid mixtures in an efficient manner. The computational strategies introduced here are applied to three model systems. One includes an argon-methane fluid mixture that is known to display simple behavior in the bulk. The second fluid model contains a size asymmetric mixture that exhibits azeotropy. The third model fluid is the well-studied size symmetric mixture that displays liquid-liquid-vapor phase coexistence. The techniques outlined here are used to compile the composition dependence of spreading and drying coefficients, liquid-vapor surface tension, and contact angle for these systems. We also compare our surface tension results with values estimated from predictive-style models that provide the surface tension of a fluid mixture in terms of pure component properties. Overall, we find that the general approach pursued here provides an efficient and precise means to calculate the bulk and wetting properties of fluid mixtures.
Electron collisions with the HCOOH⋯(H2O)n complexes (n = 1, 2) in liquid phase: The influence of microsolvation on the π* resonance of formic acid
Authors: Freitas T. C. , Coutinho K. , Varella M. T. do N. , Lima M. A. P. , Canuto S. , Bettega M. H. F.
Published: May 2013

We report momentum transfer cross sections for elastic collisions of low-energy electrons with the HCOOH⋯(H2O)n complexes, with n = 1, 2, in liquid phase. The scattering cross sections were computed using the Schwinger multichannel method with pseudopotentials in the static-exchange and static-exchange plus polarization approximations, for energies ranging from 0.5 eV to 6 eV. We considered ten different structures of HCOOH⋯H2O and six structures of HCOOH⋯(H2O)2 which were generated using classical Monte Carlo simulations of formic acid in aqueous solution at normal conditions of temperature and pressure. The aim of this work is to investigate the influence of microsolvation on the π* shape resonance of formic acid. Previous theoretical and experimental studies reported a π* shape resonance for HCOOH at around 1.9 eV. This resonance can be either more stable or less stable in comparison to the isolated molecule depending on the complex structure and the water role played in the hydrogen bond interaction. This behavior is explained in terms of (i) the polarization of the formic acid molecule due to the water molecules and (ii) the net charge of the solute. The proton donor or acceptor character of the water molecules in the hydrogen bond is important for understanding the stabilization versus destabilization of the π* resonances in the complexes. Our results indicate that the surrounding water molecules may affect the lifetime of the π* resonance and hence the processes driven by this anion state, such as the dissociative electron attachment.
Temperature measurements and an improved equation of state for shocked liquid benzene
Authors: Lacina D. , Gupta Y. M.
Published: May 2013

Time-resolved, Raman spectroscopy measurements were used to determine temperatures in multiply shocked liquid benzene to peak pressures of ∼19 GPa. The previously reported equation of state (EOS) for benzene provides temperatures that are lower than the experimental measurements. To achieve improved temperature calculations, key thermodynamic parameters in the existing EOS were varied to examine and understand the sensitivity of temperatures to those parameters. Using the sensitivity studies, the benzene EOS parameters were refined to provide a good agreement between the calculated temperatures and the measured temperatures in multiply shocked benzene. Use of the improved EOS also leads to an increase in the decomposition temperature from 1315 K to 1485 K, for singly shocked liquid benzene. The present work underscores the importance of temperature measurements for developing accurate EOS for shocked liquids.
New developments for the investigation of hard X-rays emitted by peeling adhesive tapes
Authors: Krämer D. , Lützenkirchen-Hecht D. , Lühmann B. , Keite-Telgenbüscher K. , Frahm R.
Published: May 2013

We realized an advanced apparatus for the investigation of emitted X-rays produced by peeling adhesive tape rolls under vacuum conditions. Two stepper motors can unwind and rewind a tape roll, and an additional roller with an optical encoder provides measurement and control of the tape speed. This way reproducible and consecutive experiments are feasible without having to change the tape or break the vacuum. The dependence of the X-ray emission on tape speed, gas pressure, type of adhesive tape, and detector angle has been investigated. The resulting spectra are continuous and span an X-ray energy range of typically 2–60 keV with high intensity. Furthermore, the new apparatus allows the in situ metalization of adhesive tape rolls by a gold sputter source. A significantly increased X-ray emission was observed for adhesive tapes with a metal coating. Thin metal foils have been placed between the tape and the detector, different K- and L-absorption edges could be measured. A considerable enhancement of the emission was achieved under the influence of the magnetic field of an NdFeB permanent magnet.
Dynamics of exciton transfer in coupled polymer chains
Authors: Zhang Y. L. , Liu X. J. , Sun Z. , An Z.
Published: May 2013

The dynamics of singlet and triplet exciton transfer in coupled polymer chains are investigated within the Su-Schrieffer-Heeger+Pariser-Parr-Pople model including both electron-phonon (e-p) coupling and electron-electron (e-e) interactions, using a multi-configurational time-dependent Hartree-Fock dynamic method. In order to explain the processes involved, the effects of on-site and long-range e-e interactions on the locality of the singlet and triplet excitons are first investigated on an isolated chain. It is found that the locality of the singlet exciton decreases, while the locality of the triplet exciton increases with an increase in the on-site e-e interactions. On the other hand, an increase in the long-range e-e interaction results in a more localized singlet exciton and triplet exciton. In coupled polymer chains, we then quantitatively show the yields of singlet and triplet exciton transfer products under the same interchain coupling. It is found that the yield of singlet interchain excitons is much higher than that of triplet interchain excitons, that is to say, singlet exciton transfer is significantly easier than that for triplet excitons. This results from the fact that the singlet exciton is more delocalized than the triplet exciton. In addition, hopping of electrons with opposite spins between the coupled chains can facilitate the transfer of singlet excitons. The results are of great significance for understanding the photoelectric conversion process and developing high-power organic optoelectronic applications.
Coulomb problem in non-commutative quantum mechanics
Authors: Gáliková Veronika , Prešnajder Peter
Published: May 2013

The aim of this paper is to find out how it would be possible for space non-commutativity (NC) to alter the quantum mechanics (QM) solution of the Coulomb problem. The NC parameter λ is to be regarded as a measure of the non-commutativity – setting λ = 0 which means a return to the standard quantum mechanics. As the very first step a rotationally invariant NC space ${\bf R}^3_\lambda$Rλ3, an analog of the Coulomb problem configuration space (R3 with the origin excluded) is introduced. ${\bf R}^3_\lambda$Rλ3 is generated by NC coordinates realized as operators acting in an auxiliary (Fock) space ${\cal F}$F. The properly weighted Hilbert-Schmidt operators in ${\cal F}$F form ${\cal H}_\lambda$Hλ, a NC analog of the Hilbert space of the wave functions. We will refer to them as “wave functions”   also in the NC case. The definition of a NC analog of the hamiltonian as a hermitian operator in ${\cal H}_\lambda$Hλ is one of the key parts of this paper. The resulting problem is exactly solvable. The full solution is provided, including formulas for the bound states for E < 0 and low-energy scattering for E > 0 (both containing NC corrections analytic in λ) and also formulas for high-energy scattering and unexpected bound states at ultra-high energy (both containing NC corrections singular in λ). All the NC contributions to the known QM solutions either vanish or disappear in the limit λ → 0.
Effective complex permittivity tensor of a periodic array of cylinders
Authors: Godin Yuri A.
Published: May 2013

We determine the effective complex permittivity of a two-dimensional composite, consisting of an arbitrary doubly periodic array of identical circular cylinders in a homogeneous matrix, and whose dielectric properties are complex-valued. Efficient formulas are provided to determine the effective complex permittivity tensor which are in excellent agreement with numerical calculations. We also show that in contrast to the real-valued case, the real and imaginary parts of the effective complex-valued tensor can exhibit non-monotonic behavior as functions of volume fraction of cylinders, and can be either greater or less than that of the constituents.
Electron beam driven lower hybrid waves in a dusty plasma
Authors: Prakash Ved , Vijayshri  , Sharma Suresh C. , Gupta Ruby
Published: May 2013

An electron beam propagating through a magnetized dusty plasma drives electrostatic lower hybrid waves to instability via Cerenkov interaction. A dispersion relation and the growth rate of the instability for this process have been derived taking into account the dust charge fluctuations. The frequency and the growth rate of the unstable wave increase with the relative density of negatively charged dust grains. Moreover, the growth rate of the instability increases with beam density and scales as the one-third power of the beam density. In addition, the dependence of the growth rate on the beam velocity is also discussed.
Graded bandgap structure for PbS/CdS/ZnS quantum-dot-sensitized solar cells with a PbxCd1−xS interlayer
Authors: Kim Jongmin , Choi Hongsik , Nahm Changwoo , Kim Chohui , Ik Kim Jae , Lee Woojin , Kang Suji , Lee Byungho , Hwang Taehyun , Hejin Park Helen , Park Byungwoo
Published: May 2013

To suppress the electron-hole recombination in the multishell sensitizer for quantum-dot-sensitized solar cells (QDSCs), the PbxCd1−xS interlayer is incorporated between the PbS core and CdS shell. The PbS/PbxCd1−xS/CdS structure enhances the cell efficiency by ∼60% compared to PbS/CdS QDSCs, and consequently shows a power-conversion efficiency of 1.37% with ZnS coating. Open-circuit voltage decay confirmed that the PbxCd1−xS interlayer effectively reduces the recombination at the PbS/CdS interface. Furthermore, with respect to the peak shift of incident photon-to-current conversion efficiency, the interlayer also increases the light-harvesting efficiency in the higher-wavelength region by reducing the exciton confinement within the PbS sensitizer.
Microstructural phase separation related in-plane fourfold symmetric superconductivity in K0.8Fe1.65Se2 crystals
Authors: Xie L. , Yin Y. W. , Teng M. L. , Su T. S. , Li X. G. , Li J. Q.
Published: May 2013

Through angle-resolved out-of-plane electrical transport measurements on K0.8Fe1.65Se2 crystals, it is found that the upper critical field Hc2, the out-of-plane resistivity ρc, and the activation energy U for flux motion all show a distinct fourfold symmetry which is probably related to the fourfold symmetric superconducting stripes arising from the special phase separation nature. A scaling approach was proposed to analyze the fourfold symmetry of Hc2, which fits the experimental data very well, and the fourfold symmetric behaviors of ρc in flux flow region were described by a modified Bardeen-Stephen equation after considering the phase separated stripes.
In situ doped phosphorus diffusion behavior in germanium epilayer on silicon substrate by ultra-high vacuum chemical vapor deposition
Authors: Huang Shihao , Li Cheng , Chen Chengzhao , Wang Chen , Yan Guangming , Lai Hongkai , Chen Songyan
Published: May 2013

Phosphorus diffusion behaviors in in situ doped germanium epilayers on Si substrate grown in an ultra high vacuum chemical vapor deposition system at 500 °C are investigated. The phosphorus diffusion mechanism during the growth process is dominated by the extrinsic diffusion process, which can be well described with a model including a cubic dependence of diffusivity on the doping concentration. The phosphorus diffusivity into the boron-doped Ge is lower than that into the intrinsic Ge layer by about one order of magnitude. An in situ doped Ge n/p junction with rectification ratio of 1.84 × 102 is achieved by inserting an intrinsic Ge layer to avoid impurity compensation.
In situ atomic force microscope study of high-temperature untwinning surface relief in Mn-Fe-Cu antiferromagnetic shape memory alloy
Authors: Wang L. , Cui Y. G. , Wan J. F. , Rong Y. H. , Zhang J. H. , Jin X. , Cai M. M.
Published: May 2013

The N-type untwinning surface relief associated with the fcc ↔ fct martensitic transformation (MT) was observed in the Mn81.5Fe14.0Cu4.5 antiferromagnetic high-temperature shape memory alloy (SMA) by in situ atomic force microscopy. The measured untwinning relief angles (θα|θβ) at the ridge and at the valley were different, and both angles were less than the conventional values. The surface relief exhibited good reversibility during heating and cooling because of the crystallographic reversibility of thermal-elastic SMAs. Untwinning shear was proposed as the main mechanism of the N-type surface relief. The order of the reverse MT was discussed based on the experimental measurements.
Single-mode tapered quantum cascade lasers
Authors: Rauter Patrick , Menzel Stefan , Gokden B. , K. Goyal Anish , Wang Christine A. , Sanchez Antonio , Turner George , Capasso Federico
Published: May 2013

We demonstrate tapered quantum cascade lasers monolithically integrated with a distributed Bragg reflector acting as both a wavelength-selective back mirror and a transverse mode filter. Each of the 14 devices operates at a different wavelength between 9.2 and 9.7 μm, where nine devices feature single-mode operation at peak powers between 0.3 and 1.6 W at room temperature. High output power and excellent beam quality with peak brightness values up to 1.6 MW cm−2 sr−1 render these two-terminal devices highly suitable for stand-off spectroscopy applications.
Attitudes of primary health care physician managers toward research: a pre-experimental study
Authors: Jahan Saulat , Henary Basem
Published: May 2013

Research in primary health care (PHC) is underdeveloped and scarce, especially in developing countries. It is important to understand the attitudes and aspirations of PHC physicians for the promotion of research. The aim of this study was to determine the attitudes of PHC physician managers toward research in Qassim province and to identify barriers that impede performing research in the PHC system. The study was based on social cognitive theory framework, and was pre-experimental with a ‘one-group pre-test–post-test’ design. The study participants were physician managers in PHC administration, Qassim. The participants’ attitudes were measured by adapting statements from the Attitude Towards Research scale. The intervention was the 1-day training program ‘Introduction to Research in Primary Health Care’. A total of 23 PHC physicians participated in the study. The mean age of the participants was 45.4 (±1.6) years, and the mean years of work experience was 16.2 (±2.2) years. Only one participant had an article published in a peer-reviewed journal. The results of the study showed that PHC physicians had a baseline positive attitude toward research that was further enhanced after participating in an introductory research-training program. During the pre-test, out of the total score of 63, the mean score on attitude toward research was 48.35 (±6.8) while the mean total attitude score in the post-test was 49.7 (±6.6). However, the difference was not statistically significant at P < 0.05. The item with the highest score regarded the role of research in the improvement of health care services, while the lowest-scoring item was about support from administration to conduct research. The participants recognised lack of skills, lack of training and inadequate resources as major barriers in conducting research. Our study results suggest that the PHC physicians’ positive attitudes toward research can be further improved through in-service training. To promote research in PHC in Qassim, regular research-training programs and incentives for conducting research should be provided to the PHC physicians.
Outcomes and opportunities: a nurse-led model of chronic disease management in Australian general practice
Authors: Eley Diann S. , Patterson Elizabeth , Young Jacqui , Fahey Paul P. , Del Mar Chris B. , Hegney Desley G. , Synnott Robyn L. , Mahomed Rosemary , Baker Peter G. , Scuffham Paul A.
Published: May 2013

The Australian government’s commitment to health service reform has placed general practice at the centre of its agenda to manage chronic disease. Concerns about the capacity of GPs to meet the growing chronic disease burden has stimulated the implementation and testing of new models of care that better utilise practice nurses (PN). This paper reports on a mixed-methods study nested within a larger study that trialled the feasibility and acceptability of a new model of nurse-led chronic disease management in three general practices. Patients over 18 years of age with type 2 diabetes, hypertension or stable ischaemic heart disease were randomised into PN-led or usual GP-led care. Primary outcomes were self-reported quality of life and perceptions of the model’s feasibility and acceptability from the perspective of patients and GPs. Over the 12-month study quality of life decreased but the trend between groups was not statistically different. Qualitative data indicate that the PN-led model was acceptable and feasible to GPs and patients. It is possible to extend the scope of PN care to lead the routine clinical management of patients’ stable chronic diseases. All GPs identified significant advantages to the model and elected to continue with the PN-led care after our study concluded.