bluuebunny/crossref_metadata_2025_split huggingface dataset:
Intrasubband transitions in cubic AlN/GaN superlattices for detectors from near to far infrared
Authors: Mietze Christian , DeCuir E. A. , Manasreh M. O. , Lischka K. , As D. J. 
Published: February 2011

AbstractWe report the growth of cubic GaN/AlN superlattices by plasma‐assisted molecular beam epitaxy on 3C‐SiC substrates. The samples consist of 100 nm thick unintentionally doped GaN buffer and 20‐40 period superlattices of silicon doped GaN quantum wells embedded in undoped AlN barriers. The thickness of the AlN barriers is varied between 1.5 nm‐3.2 nm, while the thickness of the GaN well varies between 1.5 nm‐12.5 nm. The growth was controlled by in situ reflection high energy electron diffraction. The structural properties of our samples were studied by high resolution x‐ray diffraction. Two superlattice satellite peaks in the x‐ray spectra reveal a high structural perfection of the active region. Clear evidence for inter‐ and intrasubband transitions was observed in photoluminescence, absorbance and photoconductivity spectra measured at room temperature. Model calculations show the possibility to fabricate devices for the near‐ and far infrared region. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Influence of intersubband scattering on shift currents in GaAs quantum wells
Authors: Priyadarshi Shekhar , Pierz Klaus , Siegner Uwe , Dawson Philip , Bieler Mark 
Published: February 2011

AbstractWe have optically induced ultrafast shift currents in GaAs quantum wells and studied their dependence on excitation photon energy. We observed a current reversal between excitation of the n=1 and the n=2 light‐hole exciton transitions. A simple theoretical model allows for the explanation of the current reversal and suggests that it is due to intersubband scattering of the holes (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical properties of wide‐bandgap monolithic pillar microcavities with different geometries
Authors: Seyfried M. , Kalden J. , Sebald K. , Kruse C. , Figge S. , Gust A. , Tessarek C. , Dartsch H. , Hommel D. , Florian M. , Jahnke F. , Gutowski J. 
Published: February 2011

AbstractA customization of the optical properties of pillar microcavities on the desired applications is essential for their future use as quantum‐optical devices. Therefore, all‐epitaxial cavities with CdSe or InGaN quantum dots embedded in pillar structures with different geometries have been realized by focused‐ion‐beam etching. The high temperature stability of the emission and the large oscillator strength of quantum dots made of these material systems are combined with small mode volume pillar microcavities to utilize the light‐matter interaction. The quality factors of circularly shaped pillar microcavities have been measured and compared to theoretical calculations. As a possibility to achieve polarized light emission, asymmetrically shaped microcavities are presented. Examples of an elliptically shaped pillar as well as of photonic molecules are investigated with respect to their photoluminescence characteristics and polarization. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
2d Fourier spectroscopy of disordered quantum wells
Authors: Erementchouk Mikhail , Leuenberger Michael N. , Li Xiaoqin 
Published: February 2011

AbstractWe consider the problem of coherent coupling between spatially separated exciton states in disordered quantum wells (QW) from the perspective of two‐dimensional (2d) Fourier spectroscopy, which is sensitive to interaction between excitations. We present the basic theory of spectroscopy of QW that demonstrate split exciton resonances in linear spectra, which is characteristic for long interfacial inhomogeneities.We find that the coherent coupling is governed by the relation between the disorder correlation length rc and the characteristic length of Coulomb correlations RI. If rc ≫ RI the coherent coupling is absent and 2d spectra are simply elongated along the diagonal (inhomogeneously broadened). In the opposite limit coupling exists and manifests itself in the form of respective off‐diagonal peaks in 2d spectra (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effects of the Au(I)–Au(I) closed‐shell attraction on the electronic and phosphorescent properties in a series of coordination compounds: A theoretical study
Authors: Muñiz Jesús , Sansores Enrique , Reyes‐nava J. A. , Ramos‐sanchez V.‐H. , Olea Alfredo 
Published: February 2011

AbstractThe Au(I)–Au(I) closed‐shell or aurophilic attraction has been the subject of interest in the experimental and theoretical chemistry fields, due to the intriguing properties associated to it. The presence of phosphorescence in “aurophilic” compounds has been addressed to a wide range of applications, but it has not yet been fully understood. A theoretical study on the electronic and phosphorescent properties of the following series of dinuclear gold complexes has been performed: [Au2(dmpm) (i‐mnt)] (1), [Au2(μ‐Me‐TU) (μ‐dppm)] (2), and [Au2(μ‐G)(μ‐dmpe)] (3). Full geometry optimizations at the second‐order Møller–Plesset perturbation theory (MP2) were carried out for each of the species. These calculations made evident that, at the ground‐state geometry, the Au(I) cations allocated at the center of the ring show a short Au–Au distance below the sum of the van der Waals radii, at the range of the aurophilic attraction. An intermolecular Au(I)–Au(I) closed‐shell attraction for a pair of the systems under study is found. This attraction is comparable to that of the hydrogen bonds. The phosphorescent properties experimentally observed for this series were also characterized through ab initio techniques. The obtained results allow to fit reasonably the excitation energies with the experimental data and to identify a correlation between the strength of the Au(I)–Au(I) interaction and the phosphorescent behavior. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011
A DFT/TDDFT study of porphyrazines and phthalocyanine oxo‐titanium derivatives as potential dyes in solar cells
Authors: Zarate Ximena , Schott Eduardo , Arratia‐Pérez Ramiro 
Published: February 2011

AbstractDensity functional theory and time dependent density functional theory calculations at the level of LDA/BP86/TZ2P were performed systematically on several Ti(IV) complexes of porphyrazines and one phthalocyanine. We performed an analysis of the frontier molecular orbitals of the ground state electronic structures and also discuss in particular the good concordance of our results with the experimental data, which affords to predict the geometrical and optical properties of new complexes (3, 4, and 7). We also emphasize the characterization of the UV–vis absorption spectra and propose transitions that contribute to the Q and B bands. Some useful calculated properties in complexes 2, 3, and 7, like: high light absorption in the visible region of the spectra, transitions involved in these bands with a determined direction, charge separation, bigger highest occupied molecular orbital–lowest unoccupied molecular orbital (HOMO‐LUMO) gaps than complexes 4 and 5, and the energy of their LUMO orbitals (that are higher than the lowest energy level of the conduction band of the TiO2) indicate that system complexes 2, 3, and 7 could act as light‐harvesting sensitizers for dye‐sensitized solar cells (DSCs). These proposals were made using a model of the previously experimentally known phthalocyanine, which was used as sensitizer in DSCs devices, comparing its electronic properties with the herein proposed sensitizers. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011
Potential energy curves and interpretation of electronic spectrum of the yttrium nitride
Authors: Dou Xiaotong , Han Huixian , Zhai Gaohong , Suo Bingbing 
Published: February 2011

AbstractPotential energy curves of 14 electronic states of yttrium nitride (YN) are calculated by using multistate complete active space second order perturbation theory. The ground state is predicted as X1Σ+ and has the equilibrium bond length of 1.809 Å and vibrational frequency of 658 cm−1. Two low‐lying excited states, a3Σ+ and A1Σ+, locate at 2,360 and 3,670 cm−1 higher than the ground state, which are in agreement with experimental excitation energies of 2,423 and 3,700 cm−1, respectively. The high‐order singlet, the D1Π state, lies at 19,232 cm−1 above the ground state with the equilibrium bond length of 2.057 Å and vibrational frequency of 562 cm−1. The D1Π → X1Σ transition is dipole allowed and may contribute to spectra of YN in visible region. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem 111:3378–3384, 2011
Effective reproduction numbers are commonly overestimated early in a disease outbreak
Authors: Mercer G. N. , Glass K. , Becker N. G. 
Published: February 2011

AbstractReproduction numbers estimated from disease incidence data can give public health authorities valuable information about the progression and likely size of a disease outbreak. Here, we show that methods for estimating effective reproduction numbers commonly give overestimates early in an outbreak. This is due to many factors including the nature of outbreaks that are used for estimation, incorrectly accounting for imported cases and outbreaks arising in subpopulations with higher transmission rates. Awareness of this bias is necessary to correctly interpret estimates from early disease outbreak data. Copyright © 2011 John Wiley & Sons, Ltd.
Gamma irradiation of treated waste rubber powder and its composites with waste polyethylene
Authors: El‐Nemr Khaled F. , Khalil Ahmed M. 
Published: February 2011

AbstractThis investigation was undertaken to prepare composites of waste polyethylene (WPE) with concentrations of 5, 15, and 25 wt% of waste rubber powder (WRP) and to determine the changes in properties of these composites before and after treatment of the WRP with acrylic acid. Mechanical, physical, thermal, FTIR, and SEM investigations showed that treated and gamma‐irradiated WRPs gave better properties than untreated ones. Hence, a simple method to prepare composites based on recycled polyethylene and waste rubber powder could be achieved without using expensive treatment of the polymeric wastes. J. VINYL ADDIT. TECHNOL., 2011. © 2011 Society of Plastics Engineers
One step forward to a sustainable green solution for extruded foam PVC building products
Authors: Chang Hong , Abu‐Zahra Nidal 
Published: February 2011

AbstractThis paper is dedicated to the development of a robust and cost‐effective formulation to maximize the use of recycled poly(vinyl chloride) (PVC) back into its virgin compounds. This study concludes that a balanced stabilizer and lubricant formulation will overcome the detrimental effects of repeated heat history on the recycled/regrind PVC. The developed formulation using up to 70% of recycled/regrind PVC has been successfully implemented in the extrusion process for manufacturing high‐quality foam PVC profiles for the building industry. As a result, this study takes a huge step forward toward a green and sustainable solution for PVC applications. J. VINYL ADDIT. TECHNOL., 2011. © 2011 Society of Plastics Engineers
Devulcanization of waste tires using a twin‐screw extruder: The effects of processing conditions
Authors: Yazdani Hamid , Karrabi Mohammad , Ghasmi Ismaeil , Azizi Hamed , Bakhshandeh Gholam Reza 
Published: February 2011

AbstractDuring recent decades, for both economic and environmental reasons, recycling of waste tires that are based on SBR/NR has been widely considered. In this study the devulcanization process of the tread section of waste tires was carried out by using a twin‐screw extruder. The effects of barrel temperature and screw speed were investigated. Percent of devulcanization, sol fraction, and curing behavior of devulcanized samples were studied. After the addition of curing agents into the devulcanizates, the general behavior of the rheometry test for rubber compounds was observed. Percent of devulcanization and sol fraction depended on the screw speed and barrel temperature, respectively. The devulcanized samples were formulated with virgin rubber (15/85 wt% ratio) and re‐cured successfully. Tensile strength, elongation at break, compression set, hardness, and resilience were evaluated. It was found that the mechanical properties of the compound containing devulcanizates were slightly inferior to those of the virgin compound. J. VINYL ADDIT. TECHNOL., 2011. © 2011 Society of Plastics Engineers
Use of and satisfaction with support received among survivors from three Scandinavian countries after the 2004 Southeast Asian tsunami
Authors: Michel P.O. , Rosendal S. , Weisaeth L. , Heir T. 
Published: February 2011

AbstractIntroductionThere is limited guidance regarding effective preventions for post-disaster mental health problems and what kind of support is preferred by disaster survivors.AimTo describe the use of and satisfaction with support in three Scandinavian countries after the tsunami and analyzing the association between support and posttraumatic stress reactions.MethodThe sample comprises 6772 responders who returned to Scandinavia from the tsunami-struck countries of Southeast Asia in 2004.ResultsMost were satisfied with informal support on site. Support from embassies/consulates was not received well, leaving about 64% of the Danes/Norwegians and 73% of the Swedes dissatisfied. After returning home, support from close relatives rendered highest degree of satisfaction. Consultation with general practitioner (GP) was reported by 63% of Norwegians, 40% of Danes, and 16% of Swedes. Most responders (60–77%) were satisfied with their GP, although Norwegians were least satisfied. Using support was associated with higher levels of posttraumatic stress symptoms.ConclusionsInformal support was used to a high degree and rendered considerable satisfaction in all three countries, while the use of and satisfaction with formal support varied more. Lack of satisfaction with embassies and consulates may indicate deficiencies in the authorities’ preparedness in assisting disaster stricken citizens abroad.
Tree-ring reconstructions of May–June precipitation for western Anatolia
Authors: Köse Nesibe , Akkemik Ünal , Dalfes H. Nüzhet , Özeren M. Sinan 
Published: February 2011

AbstractIn this study, we aim to examine past dry and wet events for the western Anatolia, performing local and spatial reconstructions. 17 new black pine site chronologies were developed, May–June precipitation time series were reconstructed for four localities, and the first spatial May–June precipitation reconstruction was achieved for western Anatolia. The long-term local May–June precipitation reconstructions contain mostly one-year and less commonly, two-year drought events. The longest consecutive dry period (AD 1925–1928) in the reconstructed time series for Kütahya lasted four years. Spatial reconstructions revealed that between AD 1786 and 1930 the extreme dry years for all of western Anatolia were AD 1887, 1893, 1794 and 1740. The driest year during the 215-year-long period under consideration was 1887. The wettest years for the entire western Anatolia were determined to be AD 1835, 1876, 1881 and 1901. There is a big overlap between agricultural famine years and dry years as determined from reconstructions. In this context, our study provides a basis for understanding agricultural drought and better management of regional water resources.
Eutrophication threatens the biochemical diversity in lichens
Authors: HAUCK Markus 
Published: February 2011

AbstractLichens respond sensitively to ambient nitrogen levels. Global change, which includes the increase of nitrogen-polluted environments, causes the decline of species sensitive to eutrophication, whereas some species tolerant of high nitrogen levels increase. Lichens produce hundreds of carbon-based secondary substances (so-called lichen substances), most of which are unique to the lichen symbiosis. In the present paper, correlative patterns between the eutrophication tolerance of lichen species and their secondary chemistry are analyzed using two data sets, one classifying the eutrophication tolerance of more than 500 Central European lichen species, and another of epiphytic lichens from more than 1200 plots from the Netherlands. Analyses show that, in general, the diversity of lichen secondary metabolites decreases along with increasing tolerance to eutrophication. Most notable is the reduced diversity of depsides and depsidones, the two largest groups of lichen substances, but dibenzofurans and fatty acids are also generally found in lichens sensitive to eutrophication. Conversely, anthraquinones and pulvinic acids are found most frequently in lichens from nitrogen-rich environments that can result from eutrophication. A family-wide analysis of the datasets indicates that loss of chemical diversity is not due to a single species-rich lichen family, but a characteristic of many lichen families.
Lecanora sorediomarginata, a new epiphytic lichen species discovered along the Portuguese coast
Authors: RODRIGUES Sandrina Azevedo , TERRÓN-ALFONSO Arsenio , ELIX John A. , PÉREZ-ORTEGA Sergio , TØNSBERG Tor , FERNÁNDEZ-SALEGUI Ana Belén , SOARES Amadeu M. V. M. 
Published: February 2011

AbstractLecanora sorediomarginataRodrigues, Terrón & Elix sp. nov., described as new to science from Portugal, is characterized morphologically by a crustose whitish-grey to greenish thallus developing soralia from small, marginal warts and chemically by the presence of 3,5-dichloro-2′-O-methylnorstenosporic acid [major], 3,5-dichloro-2′-O-methylanziaic acid [minor], 3,5-dichloro-2′-O-methylnordivaricatic acid [minor], 5-chloro-2′-O-methylanziaic acid [trace], atranorin [minor], chloroatranorin [minor], and usnic acid [trace]. It is chemically similar toL. lividocinerea, to which it shows phylogenetic affinities based on ITS rDNA sequence analysis, and toL. sulphurella.Lecanora sorediomarginatais epiphytic onPinus pinasterandP. pinea, in pine forests on sand dunes along the Portuguese coast.
Copper localization, elemental content, and thallus colour in the copper hyperaccumulator lichenLecanora sierraefrom California
Authors: PURVIS O. W. , BENNETT J. P. , SPRATT J. 
Published: February 2011

AbstractAn unusual dark blue-green lichen,Lecanora sierrae, was discovered over 30 years ago by Czehura near copper mines in the Lights Creek District, Plumas County, Northern California. Using atomic absorption spectroscopy, Czehura found that dark green lichen samples from Warren Canyon contained 4% Cu in ash and suggested that its colour was due to copper accumulation in the cortex. The present study addressed the hypothesis that the green colour in similar material we sampled from Warren Canyon in 2008, is caused by copper localization in the thallus. Optical microscopy and electron microprobe analysis of specimens ofL. sierraeconfirmed that copper localization took place in the cortex. Elemental analyses ofL. sierraeand three other species from the same localities showed high enrichments of copper and selenium, suggesting that copper selenates or selenites might occur in these lichens and be responsible for the unusual colour.
New polymorphic mitochondrial markers for sponge phylogeography
Authors: Rua Cintia P.J. , Zilberberg Carla , Solé-Cava Antonio M. 
Published: February 2011

Phylogeography and population genetic studies in the Porifera have been limited by the lack of available polymorphic DNA markers. In this paper, we tested four new mitochondrial markers in nine demosponge species from a wide taxonomic range: partial sequences of the ATP synthase 6 (ATP6) and the cytochrome oxidase 2 (CO2) genes and two spacers: one located between ATP6 and CO2 and the other between the NADH dehydrogenase subunit 5 (ND5) and the small subunit ribosomal RNA (rns) genes. The new markers presented levels of nucleotide diversity up to 2.4 times higher (π = 0.015 for CO2) than those observed for the most commonly used mitochondrial marker in sponges, the cytochrome oxidase 1 gene (π = 0.006), making them suitable for alpha-level systematics, phylogeography and population genetics studies.
The wildcatFelis silvestrisin northern Turkey: assessment of status using camera trapping
Authors: Can Özgün Emre , Kandemi̇r İrfan , Togan İnci̇ 
Published: February 2011

AbstractThe wildcatFelis silvestrisis a protected species in Turkey but the lack of information on its status is an obstacle to conservation initiatives. To assess the status of the species we interviewed local forestry and wildlife personnel and conducted field surveys in selected sites in northern, eastern and western Turkey during 2000–2007. In January–May 2006 we surveyed for the wildcat using 16 passive infrared-trigged camera traps in Yaylacı k Research Forest, a 50-km2forest patch in Yenice Forest in northern Turkey. A total sampling effort of 1,200 camera trap days over 40 km2yielded photo-captures of eight individual wildcats over five sampling occasions. Using the softwareMARKto estimate population size the closed capture–recapture modelM0, which assumes a constant capture probability among all occasions and individuals, best fitted the capture history data. The wildcat population size in Yaylacı k Research Forest was estimated to be 11 (confidence interval 9–23). Yenice Forest is probably one of the most important areas for the long-term conservation of the wildcat as it is the largest intact forest habitat in Turkey with little human presence, and without human settlements, and with a high diversity of prey species. However, it has been a major logging area and is not protected. The future of Yenice Forest and its wildcat population could be secured by granting this region a protection status and enforcing environmental legislation.
Sprouting, succession and tree species diversity in a South African coastal dune forest
Authors: Nzunda Emmanuel Fred 
Published: February 2011

Abstract:Sprouting may play a significant role in maintenance of plant diversity where prevailing disturbance frequency and severity allows. When disturbance frequency and severity decrease, strong sprouters may be outcompeted. As a result, species composition and diversity may change. This study was carried out to investigate the relationship between sprouting, succession and species diversity in a coastal dune forest that currently suffers from low-severity, chronic disturbance due to sea winds and loose sand substrate. Historically, the site was occupied by shifting cultivators who left the site about 80 y ago. Data on trees that were at least 1.3 m tall from 42 sample plots measuring 20 × 20 m were used. The plots were ranked in order of advancement of succession using the first axis of Principal Components Analysis of forest structural variables. Regeneration pattern was examined using analysis of stem diameter frequency distribution. Abundance and regeneration of strong basal sprouters, incidence of basal sprouting and species diversity decreased with advancement of succession. Only a few species could regenerate under the canopy of late-successional sites. Basal sprouts decreased with advancement of succession whereas trunk sprouts increased. These results suggest that maintenance of high species diversity may need a level of disturbance that allows regeneration and maintenance of strong basal sprouters.