bluuebunny/crossref_metadata_2025 huggingface dataset:
Prevalence of herpes simplex virus type 1 glycoprotein G (gG) and gI genotypes in patients with different herpetic diseases during the last four decades
Authors: Sauerbrei Andreas , Pfaff Florian , Zell Roland , Wutzler Peter
Published: February 2012

The objective of this study was to genotype 375 clinical herpes simplex virus type 1 (HSV‐1) isolates collected from the German Reference Laboratory of HSV and VZV between 1973 and 2010. The method is based on the amplification and the restriction fragment length polymorphism analysis of the glycoprotein G (gG) and gI. 45.1% of isolates were classified as genotype A, 28.5% as B, and 4.3% as C. 22.1% presented different cleavage patterns for gG and gI suggesting intergenic recombinants A/B in 7.7%, A/C in 0.5%, B/A in 9.3%, B/C in 1.9%, C/A in 1.6%, and C/B in 0.5% of isolates. Two isolates from 1982 and 2010 presented atypical gI cleavage pattern consistent with novel intragenic recombination between genotypes A and C. There were no significant differences of the prevalence of genotypes A, B as well as the recombinants A/B, B/A dependent on the age/gender of patients and the time period in which the strains were isolated. Likewise, there were no significant differences in the distribution of the genotypes A and B as etiological agents of eczema herpeticum, herpes labialis, herpes genitalis, and herpetic gingivostomatitis. The number of recombinants was not different significantly in the groups of the distinct herpetic diseases. In conclusion, the study confirms the high prevalence of recombinants in clinical HSV‐1 strains. HSV‐1 infections result in clinical manifestations which are independent of the gG/gI genotype and recombinants are not associated with special herpetic diseases. J. Med. Virol. 84:651–656, 2012. © 2011 Wiley Periodicals, Inc.
Molecular characterization of OP354‐like P[8] (P[8]b subtype) human rotaviruses a species isolated in Japan
Authors: Kuzuya Mitsutaka , Fujii Ritsushi , Hamano Masako , Kida Kouji , Kanadani Tomohisa , Nishimura Keiko , Kishimoto Toshio
Published: February 2012

OP354‐like P[8] (P[8]b subtype) species A rotaviruses (RVAs) were isolated first time in Japan during a RVA survey in Okayama Prefecture between 2006 and 2009. Two of 236 RVA‐positive samples were identified as G1P[8]b by reverse transcription polymerase chain reaction. P[8]b strains (RVA/human‐wt/JPN/OH1998/2008/G1P[8]b and RVA/human‐wt/JPN/OH2024/2008/G1P[8]b) were isolated only in May, 2008 and both patients infected with P[8]b viruses lived in the same city, suggesting that the prevalence of P[8]b RVAs is limited considerably in Okayama Prefecture. Molecular analysis of four genes (VP4, VP6, VP7, and NSP4 genes) of Japanese P[8]b strains revealed that the VP4 genes of these strains were related closely to those of Southeast Asian and Indian P[8]b strains. In contrast, the VP6, VP7, and NSP4 genes of Japanese P[8]b strains were highly homologous to G1P[8]a strains prevalent in the same area. These results suggest that the Japanese P[8]b strain may be a result of reassortment events between Japanese G1P[8]a viruses and unidentified Asian viruses possessing the P[8]b VP4 gene. J. Med. Virol. 84:697–704, 2012. © 2011 Wiley Periodicals, Inc.
Human herpesvirus 6A infects human embryonic fibroblasts and induces G2/M arrest and cell death
Authors: Li Lingyun , Gu Bin , Zhou Feng , Chi Jing , Wang Fang , Liu Genyan , Ding Chuanlin , Xie Fangyi , Qing Jian , Guo Yidi , Yao Kun
Published: February 2012

Human herpesvirus 6 (HHV‐6) is a beta‐herpesvirus capable of infecting cells from different origin. In this study, infection with HHV‐6A of human embryonic fibroblasts (HEFs) was performed. Infected cells showed obvious cytopathic effects (CPE). PCR and immunohistochemical tests also confirmed that HEFs are susceptible to HHV‐6A infection. The biological effects of HHV‐6A infection on HEFs were studied. Infected cells showed decreased proliferation as measured by [3H] thymidine incorporation and cell counting. Further analysis demonstrated that infection with HHV‐6A leads to cell cycle arrest at G2/M phase and increasing cell death. This is the first demonstration that infection of HEFs with HHV‐6A causes profound alterations of cell properties. J. Med. Virol. 84:657–663, 2012. © 2011 Wiley Periodicals, Inc.
A survey for neutralizing antibodies to the three types of poliovirus among children in maiduguri, Nigeria
Authors: Baba M.M. , Haruna B.A. , Ogunmola O. , Ambe J.P. , Shidali N.N. , Oderinde B. , Marcello A. , Talle M.
Published: February 2012

The milestone in polio eradication program is to protect effectively children aged 0–5 years against the three serotypes of poliovirus. It became necessary to measure the level of neutralizing antibodies to the three poliovirus types in an endemic State in Nigeria. Neutralizing antibodies to the poliovirus types among children aged 0–5 years was estimated using micro neutralization assay. Of 129 children, 99 (76.8%), 95 (73.6%), and 95 (73.6%) had neutralizing antibodies with the geometric mean titer of 42.7, 31.3, and 33.2 for the poliovirus type 1, 2, and 3, respectively. Fifty‐three percent of the children were protected against the three types of poliovirus. Combination of poliovirus types 1 and 2, 1 and 3, and 2 and 3 were neutralized by 62.8, 58.9, and 61.2% of the children studied, respectively. Only poliovirus type 1 induced antibody titres ≥1:1,024. The number of children with neutralizing antibodies after receiving three doses was significantly higher than those who received one or two doses of oral polio vaccine (P ≤ 0.05). However, those who received more than three doses of oral polio vaccine showed no significant difference in their antibody response. The existence of immunity gap poses a risk of re‐emergence of the paralytic poliovirus. The existence of unimmunized and unprotected children along with high birth rate could impede the success of polio vaccination in Nigeria. Elimination of non‐compliance to polio vaccine, promotion of health education and documented evidence of vaccination of each child with the parents may facilitate the success of polio eradication program in Nigeria. J. Med. Virol. 84:691–696, 2012. © 2011 Wiley Periodicals, Inc.
Prevalence of etravirine resistance associated mutations in HIV‐1 strains isolated from infected individuals failing efavirenz: Comparison between subtype B and non‐B genetic variants
Authors: Pereira‐Vaz João , Duque Vitor , Pereira Branca , Mota Vanda , Morais Célia , Saraiva‐da‐Cunha José , Meliço‐Silvestre António
Published: February 2012

Etravirine (ETR) is a non‐nucleoside analogue reverse transcriptase inhibitor (NNRTI) with a high genetic barrier to the development of resistance and with potential activity against Human immunodeficiency virus type 1 (HIV‐1) strains resistant to first‐generation NNRTIs. The objective of this study was to investigate the prevalence of ETR resistance associated mutations (RAMs) in HIV‐1 strains isolated from infected individuals failing efavirenz (EFV), as well as to evaluate possible differences in the distribution of ETR RAMs between subtype B and non‐B genetic variants. Nucleotide sequences of the protease and partial reverse transcriptase (RT) coding regions of the pol gene of 55 HIV‐1 strains isolated from infected individuals failing EFV on regular follow‐up at a reference center in Portugal, were retrospectively analyzed. The most prevalent ETR RAMs observed were L100I, V90I, and K101E, with a prevalence of 16.4% (n = 9), 9.1% (n = 5), and 5.5% (n = 3), respectively. Overall, 47.3% (n = 26) of the nucleotide sequences had at least one ETR RAM: 38.2% (n = 21) had one ETR RAM, 7.3% (n = 4) had two ETR RAMs and 1.8% (n = 1) had three ETR RAMs. No statistically significant differences were found in the distribution of ETR RAMs between subtype B and non‐B genetic variants. The results demonstrate that ETR rescue therapy is a viable option in treatment‐experienced individuals failing EFV and suggests that ETR may be equally useful in HIV‐1 infections caused by different genetic variants. J. Med. Virol. 84:551–554, 2012. © 2011 Wiley Periodicals, Inc.
Modeling of doubly lossy and dispersive media with the time‐domain finite‐element dual‐field domain‐decomposition algorithm
Authors: Li Xiaolei , Jin Jian‐Ming
Published: February 2012

A numerical scheme is presented for the time‐domain finite‐element modeling of an electrically and magnetically lossy and dispersive medium in the dual‐field domain‐decomposition method. Existing approaches for modeling doubly lossy and dispersive media are extended to the dual‐field case, yielding a general dual‐field domain‐decomposition scheme for modeling large‐scale electromagnetic problems involving such media. A quantitative analysis is performed to estimate the error induced by the modeling of medium dispersion. Copyright © 2012 John Wiley & Sons, Ltd.
Fermentation, degradation and microbial nitrogen partitioning for three forage colour phenotypes within anthocyanidin‐accumulating Lc‐alfalfa progeny
Authors: Jonker Arjan , Gruber Margaret Y , Wang Yuxi , Narvaez Nelmy , Coulman Bruce , McKinnon John J , Christensen David A , Azarfar Arash , Yu Peiqiang
Published: February 2012

BACKGROUND: Alfalfa has the disadvantage of having a rapid initial rate of protein degradation, which results in pasture bloat, low efficiency of protein utilisation and excessive nitrogen (N) pollution into the environment for cattle. Introducing a gene that stimulates the accumulation of monomeric/polymeric anthocyanidins might reduce the ruminal protein degradation rate (by fixing protein and/or direct interaction with microbes) and additionally reduce methane emission. The objectives of this study were to evaluate in vitro fermentation, degradation and microbial N partitioning of three forage colour phenotypes (green, light purple‐green (LPG) and purple‐green (PG)) within newly developed Lc‐progeny and to compare them with those of parental green non‐transgenic (NT) alfalfa.

RESULTS: PG‐Lc accumulated more anthocyanidin compared with Green‐Lc (P < 0.05), with LPG‐Lc intermediate. Volatile fatty acids and potentially degradable dry matter (DM) and N were similar among the four phenotypes. Gas, methane and ammonia accumulation rates were slower for the two purple‐Lc phenotypes compared with NT‐alfalfa (P < 0.05), while Green‐Lc was intermediate. Effective degradable DM and N were lower in the three Lc‐phenotypes (P < 0.05) compared with NT‐alfalfa. Anthocyanidin concentration was negatively correlated (P < 0.05) with gas and methane production rates and effective degradability of DM and N.

CONCLUSION: The Lc‐alfalfa phenotypes accumulated anthocyanidin. Fermentation and degradation parameters indicated a reduced rate of fermentation and effective degradability for both purple anthocyanidin‐accumulating Lc‐alfalfa phenotypes compared with NT‐alfalfa. Copyright © 2012 Society of Chemical Industry
Population genetic structure and diversity of the endangered Cantabrian capercaillie
Authors: Vázquez José F. , Pérez Trinidad , Quirós Francisco , Obeso José R. , Albornoz Jesús , Domínguez Ana
Published: February 2012

The Cantabrian capercaillie (Tetrao urogallus cantabricus) occupies the southwestern edge of the grouse family distribution range in Eurasia. It is endemic to the Cantabrian Mountains in northwestern Spain and is geographically isolated and separated from the neighboring population in the Pyrenees by a distance of 300 km. Over the last decades, the population has undergone a dramatic decline and is now threatened with extinction. This study presents the genetic analysis of the Cantabrian capercaillie population using non‐invasive samples. We performed genotyping of 45 individuals using 20 microsatellites and a sex marker. The data highlight the need for using a large number of markers when considering fragmented small populations. Genetic diversity (HE = 0.50) and average number of alleles (3.40) in the population were low. The population is fragmented into 2 clusters (FST = 0.113) that fit with areas on both sides of the transportation ways that divide its range. Both clusters exhibited additional heterozygote deficits. Geographical distance was negatively correlated with genetic relatedness (r = −0.44,P ≤ 0.001). The data show a recent decline in effective population size that can be related to an ongoing process of population reduction and fragmentation. Conservation actions should focus on the protection of local demes by maintaining a dense network of suitable patches to maximize reproductive output and the number of potential dispersers to reconnect the 2 subpopulations. © 2012 The Wildlife Society.
Lithium niobate on insulator (LNOI) for micro‐photonic devices
Authors: Poberaj G. , Hu H. , Sohler W. , Günter P.
Published: February 2012

The state‐of‐the‐art of high‐refractive‐index‐contrast single‐crystalline thin lithium niobate (LiNbO3) films as a new platform for high‐density integrated optics is reviewed. Sub‐micrometer thin LiNbO3 films are obtained by “ion‐slicing”. They can be bonded by two different techniques to a low‐index substrate to obtain “lithium niobate on insulator” (LNOI) even as wafer of 3” diameter. Different micro‐ and nano‐structuring techniques have been used to successfully develop micro‐photonic devices. To be specific, the fabrication and characterization of LNOI photonic wires with cross‐section < 1 µm2, periodically poled LNOI photonic wires for second harmonic generation, electro‐optically tunable microring resonators, free standing microrings for hybrid integration, and photonic crystal structures are described.
On the Viscoelastic Properties of Collagen‐Gel‐Based Lattices under Cyclic Loading: Applications for Vascular Tissue Engineering
Authors: Achilli Matteo , Meghezi Sébastien , Mantovani Diego
Published: February 2012

Reconstituted collagen gels are widely used as scaffolds even though their low strength and poor elasticity limit their applications in VTE. Here, two approaches are adopted to modify their mechanical behavior: in the first, gels prepared under physiologic conditions are remodeled by cell‐mediated contraction; in the second, gels prepared in non‐physiologic conditions are chemically crosslinked. Samples are tested under cyclic loading and their viscoelastic behavior is assessed. The results show that both approaches result in lattices with adequate strength, and crosslinking significantly reduces hysteresis and permanent deformation. SEM shows that SMCs are capable of contracting and remodeling all the lattices, confirming that these are suitable supports for tissue regeneration.

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Uses of proton pump inhibitors and hypomagnesemia
Authors: Gau Jen‐Tzer , Yang Yu‐Xiao , Chen Roger , Kao Tzu‐Cheg
Published: February 2012

Purpose

Hypomagnesemia associated with proton pump inhibitor (PPI) therapy has been documented in case reports. We performed a cross‐sectional study to examine the association between PPI use and serum magnesium (Mg) levels or hypomagnesemia.

Methods

Data were extracted from hospitalized adults with basic metabolic panels and/or serum magnesium levels available during the hospital stays. The first Mg value was used for data analysis. Hypomagnesemia is defined as levels less than 1.7 mg/dL (or 0.70 mmol/L). Multiple linear and logistic regression analyses were used to assess the association between PPI use and Mg levels or hypomagnesemia, respectively.

Results

Among study patients, PPI users (n = 207) had a mean Mg level of 1.91[SD = 0.34] mg/dL, and non‐users (n = 280) 2.00 (0.30) mg/dL, p = 0.004. PPI use was associated with lower serum Mg levels (adjusted coefficient β = −0.10, 95%CI = [−0.16, −0.04]) after adjusting for confounders. PPI use was associated with risk of hypomagnesemia after adjusting for confounders (adjusted OR = 2.50, 95%CI = [1.43, 4.36]). Both standard (1) and high (2 or higher) defined daily dose units of PPI therapy were associated with hypomagnesemia.

Conclusions

PPI use was associated with lower serum Mg levels and hypomagnesemia in a population of hospitalized adult patients. Our study supports the general notion that long‐term PPI use could be associated with sub‐clinical Mg insufficiency or deficiency status. Copyright © 2012 John Wiley & Sons, Ltd.
Adverse drug reaction reporting by nurses: analysis of Italian pharmacovigilance database
Authors: Conforti Anita , Opri Sibilla , D'Incau Paola , Sottosanti Laura , Moretti Ugo , Ferrazin Fernanda , Leone Roberto
Published: February 2012

Purpose

The aim of this study was to describe the pattern of adverse drug reaction (ADR) reports sent by Italian nurses after the enactment of the law involving them in the pharmacovigilance system. We also compared the quantity and quality of reports by nurses with those of reports by hospital physicians sent in the same period.

Methods

We analysed the reports sent to the Italian pharmacovigilance database by nurses from January 2004 to December 2010. Only reports with ADRs causality assessment defined as definite, probable or possible were included in the analysis. The nurses' reports were compared with those sent by hospital physicians in the same period. We excluded from this analysis reports associated with vaccines.

Results

A total number of 1403 reports by nurses have been evaluated. The percentage of nurses' reports of ADRs, which were serious, were 22.9% lower than the 44.9% of reports by physicians, whereas the proportion of probable ADR reports were higher among nurses than hospital physicians (76% vs 67%). Nurses put more emphasis than physicians on application site disorders (log OR = 0.91, 95%CI = 0.55–1.27), skin reactions (log OR = 0.81, 95%CI = 0.70–0.92) and nervous system reactions (log OR = 0.28, 95%CI = 0.11–0.44), whereas physicians more frequently report blood, platelet and liver disorders. Six drugs are present in both the top 10 drugs reported by nurses and hospital doctors.

Conclusion

This study gives evidence for the potential capacity of nurses to improve the detection of ADRs. Copyright © 2012 John Wiley & Sons, Ltd.
Open questions after 20 years of CuInS2 research
Authors: Scheer Roland
Published: February 2012

In the early 1990s, CuInS2 thin film solar cells with >10% efficiency had been developed. Since then, they are limited by an open‐circuit voltage which is too low for the band gap of CuInS2. Recombination at the CdS/CuInS2 interface was made responsible for this shortcoming. This was concluded from two experimental results: a conduction band cliff found at the buffer/absorber interface and activation energy of the saturation current being smaller than the absorber band gap energy. However, replacing the CdS buffer layer in the Mo/CuInS2/buffer/ZnO heterostructure solar cell with wide gap buffers did not lead to substantially higher Voc. Also the activation energy was unaltered. In this paper, we discuss interface and bulk aspects of CuInS2 and Cu(In,Ga)S2 cells, try to give a consistent picture and make suggestions for novel experiments. Copyright © 2012 John Wiley & Sons, Ltd.
Al/Ni : V/Ag metal stacks as rear‐side metallization for crystalline silicon solar cells
Authors: Jung Verena , Köntges Marc
Published: February 2012

Rear sides of crystalline silicon solar cells are usually covered with aluminum on which it is difficult to solder. To ease soldering, we present a durability study for a Ni : V/Ag stack on evaporated Al as rear‐side metallization. We adapt this cost‐effective metallization stack from the microelectronic industry and investigate it as metallization for silicon solar cells. Here, a long‐term stability of the metallization and of the solder joint must be guaranteed for 25 years and is therefore evaluated in detail by thermal aging experiments. During this experiment, the mechanical stability of the solder joints is measured. The chemical stability and the intermetallic compound (IMC) growth within the solder joints are examined by secondary electron microscopy, backscattered electron imaging, and energy dispersive X‐ray analysis. Experiments with either a Sn–Ag‐coated copper tab or pure Sn–Ag solder show two different sorts of IMCs at the Ni : V/Solder interface. With the copper tab, a Cu–Ni–Sn compound, presumably (Cu1 ‐ xNix)6Sn5, grows at the Ni/solder interface, whereas in case of a pure Sn–Ag solder, a Ni–Sn compound grows, which is likely to be Ni3Sn4. Analysis of the reaction kinetics leads to activation energies of 77 and 42 kJ/mol, respectively, for a diffusion‐controlled IMC growth. By using temperature histograms of PV modules in the field, the necessary minimum Ni : V layer thickness is estimated: without a copper tab up to 1.6 µm Ni and with a copper tab less than 0.2 µm may be consumed by IMC formation during 25 years of lifetime. Copyright © 2012 John Wiley & Sons, Ltd.
Inclinable Shear Box Simulations of Deepening Active Layers on Perennially Frozen Scree Slopes
Authors: Rist A. , Phillips M. , Springman S. M.
Published: February 2012

A series of systematic shear tests were performed using an inclinable shear box containing a coarse‐grained active layer overlying a fine‐grained permafrost layer, a stratigraphy observed in the field. The angle of mobilised interface friction Φmob was determined as depending on the grain size of the active layer and the permafrost, the water content of the active layer and the ice content of the permafrost. Φmob was found to be 8° lower for ice‐free permafrost compared to permafrost containing ice. This result implies a possible long‐term decrease of active‐layer slope stability on scree slopes in Alpine permafrost terrain under warming conditions. Copyright © 2012 John Wiley & Sons, Ltd.
Influence of permafrost on water storage in West Siberian peatlands revealed from a new database of soil properties
Authors: Smith Laurence C. , Beilman David. W. , Kremenetski Konstantin V. , Sheng Yongwei , MacDonald Glen M. , Lammers Richard B. , Shiklomanov Alexander I. , Lapshina Elena D.
Published: February 2012

Russia's West Siberian Lowland (WSL) contains the most extensive peatlands on Earth with many underlain by permafrost. We present a new database of 12 705 measurements of vertical water content and bulk soil properties from 98 permafrost and non‐permafrost cores collected in raised bogs and peat plateaus across the region, together with in‐situ measurements of surface moisture and thaw depth, botanical descriptions of dominant surface vegetation species assemblage, and field notes. Data analyses reveal significant contrasts (p < 0.01 to p < 0.0001) between permafrost and non‐permafrost sites. On average, permafrost WSL peatlands exhibit drier surfaces, shallower depth, lower organic matter content and higher bulk density than do non‐permafrost sites. Peat bulk density and ash‐free density increase with depth for non‐permafrost but not for permafrost sites. Gravimetric water content averages 92.0% near the surface and 89.3% at depth in non‐permafrost, but 81.6% and 85.4%, respectively, in permafrost, suggesting that the disappearance of permafrost could produce moister surfaces across the WSL. GIS extrapolation of these results suggests that WSL peatlands may contain ~1200 km3 of water and ice, a large storage equivalent to ~2‐m average liquid water depth and approximately three times the total annual flow in the Ob' River. A global estimate of ~6900‐km3 subsurface water storage for all northern peatlands suggests a volume comparable to or greater than the total water storage in northern lakes. The database is freely available as supplementary material for scientific use at http://onlinelibrary.wiley.com/doi/10.1002/ppp.735/suppinfo. Copyright © 2012 John Wiley & Sons, Ltd.
Characterization and Analysis of Tetranitrate Esters
Authors: Oxley Jimmie C. , Smith James L. , Brady Joseph E. , Brown Austin C.
Published: February 2012

Thermal behaviors, vapor pressures, densities, and drop weight impact results, as well as analytical protocols, are reported for three tetranitrate esters: erythritol tetranitrate (ETN), 1,4‐dinitrato‐2,3‐dinitro‐2,3bis(nitratomethylene) butane (DNTN), and pentaerythritol tetranitrate (PETN). ETN and DNTN both melt below 100 °C and have ambient vapor pressures comparable to TNT. While LC/MS was shown to be a viable technique for analysis of all three tetranitrate esters, only ETN was successfully analyzed by GC/MS. Performance of these nitrate esters as evaluated in lab using the small‐scale explosivity device (SSED) suggested RDX≫DNTN>PETN>ETN. Detonation velocities were calculated using Cheetah 6.0. Since the starting material is now widely available, it is likely that law enforcement will find ETN in future improvised explosive devices. This paper with its analytical schemes should prove useful in identification of this homemade explosive.
The complex symbiotic relationships of bark beetles with microorganisms: a potential practical approach for biological control in forestry
Authors: Popa Valentin , Déziel Eric , Lavallée Robert , Bauce Eric , Guertin Claude
Published: February 2012

Bark beetles, especiallyDendroctonusspecies, are considered to be serious pests of the coniferous forests in North America. Bark beetle forest pests undergo population eruptions, causing regionwide economic losses. In order to save forests, finding new and innovative environmentally friendly approaches in wood‐boring insect pest management is more important than ever. Several biological control methods have been attempted over time to limit the damage and spreading of bark beetle epidemics. The use of entomopathogenic microorganisms against bark beetle populations is an attractive alternative tool for many biological control programmes in forestry. However, the effectiveness of these biological control agents is strongly affected by environmental factors, as well as by the susceptibility of the insect host. Bark beetle susceptibility to entomopathogens varies greatly between species. According to recent literature, bark beetles are engaged in symbiotic relationships with fungi and bacteria. These types of relationship are very complex and apparently involved in bark beetle defensive mechanisms against pathogens. The latest scientific discoveries in multipartite symbiosis have unravelled unexpected opportunities in bark beetle pest management, which are discussed in this article. Copyright © 2012 Society of Chemical Industry
Electrical characterisation of GaN and AlGaN layers grown by plasma‐assisted MBE
Authors: Kolkovsky V. , Scheffler L. , Sobanska M. , Klosek K. , Zytkiewicz Z. R. , Weber J.
Published: February 2012

In the present study GaN and Alx Ga1‐x N layers (with x below 5%) grown by plasma‐assisted MBE (PAMBE) were investigated by deep level transient spectroscopy (DLTS) and high‐resolution Laplace DLTS. In GaN a dominant DLTS peak was observed at about 120 K. Using the high‐resolution Laplace DLTS technique we demonstrate that this peak consists of two close components. Defects related to the nitrogen vacancy are the most probable candidates for the origin of these levels. Two other dominant peaks were observed in the DLTS spectra in AlxGa1‐xN layers with x = 1.4% and x = 3%, respectively. The position of the peaks depends on the Al content and shifts towards higher temperatures with Al concentration. The electrical properties of the peaks and their origin will be discussed. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Zn doped GaN for single‐photon emission
Authors: Behrends Arne , Ledig Johannes , Al‐Suleiman Mohamed Aid Mansur , Peters Silke , Racu Ana Maria , Schmunk Waldemar , Hofer Helmut , Kück Stefan , Bakin Andrey , Waag Andreas
Published: February 2012

In this work we report on the optical investigation of Zn doped GaN films fabricated by metal organic chemical vapor deposition. The samples show bright emission in the blue spectral range around 2.9 eV when Si codoping is provided. This emission is suggested to be used for single‐photon emission, thus the density of the Zn‐Si pairs was drastically reduced leading to a decrease of the blue luminescence. For electrically excited single‐photon sources these Zn‐Si pairs have to be incorporated into LEDs, therefore we fabricated GaN‐based nano‐LEDs which show electroluminescence at 430 nm (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Development of ZnO:Al‐based transparent contacts deposited at low‐temperature by RF‐sputtering on InN layers
Authors: Fernández S. , Naranjo F. B. , de Abril O. , Valdueza‐Felip S.
Published: February 2012

Nitride semiconductors (Al,Ga,In)N attain material properties that make them suitable for photovoltaic and optoelectronics devices to be used in hard environments. These properties include an energy gap continuously tuneable within the energy range of the solar spectrum, a high radiation resistance and thermal stability. The developing of efficient devices requires contacts with low resistivity and high transmittance in visible region. ZnO:Al (AZO) emerges as a feasible candidate for transparent contact to nitride semiconductors, taking advantage of its low resistivity, high transparency in visible wavelengths and a very low lattice mismatch with respect to nitride semiconductors. This work presents a study of the applications of AZO films deposited at low‐temperature by RF magnetron sputtering as transparent contact for InN layers. The optimization of AZO conditions deposition lead to the obtaining of contacts which shows an ohmic behaviour for the as‐deposited layer, regardless the thickness of the ZnO:Al contact layer. Specific contact resistances of 1.6 Ω·cm2 were achieved for the contact with 90 nm thick ZnO:Al layer without any post‐deposition treatment (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electromodulation spectroscopy of optical transitions and electric field distribution in GaN/AlGaN/GaN transistor heterostructures with various AlGaN layer thicknesses
Authors: Kudrawiec R. , Gladysiewicz M. , Misiewicz J. , Siekacz M. , Cywinski G. , Wolny P. , Skierbiszewski C.
Published: February 2012

GaN/AlGaN/GaN field effect transistor (FET) heterostructures with various thicknesses of AlGaN layer (10, 20, and 30nm) were investigated by electromodulation spectroscopy [i.e. contactless electroreflectance (CER) and photoreflectance (PR)]. In PR spectra optical transitions in GaN cap, AlGaN and GaN buffer layers were clearly observed whereas in CER spectra the optical transition in GaN buffer layer was not observed due to the screening of band bending modulation in CER spectroscopy by the two dimensional electron gas at the AlGaN/GaN interface. The transition related to GaN‐cap was observed ∼0.1 eV above the energy gap of GaN due to the quantum confinement in the surface GaN quantum well. The built‐in electric field in AlGaN layer was determined from the analysis of AlGaN‐related Franz‐Keldysh oscillation. For the sample with 10, 20, and 30nm thick AlGaN layer the electric field has been determined from CER(PR) measurements to be 0.30(0.27), 0.46(0.39) and 0.78(0.63) MV/cm, respectively. The smaller electric field, which is obtained from PR measurements, results from the photovoltaic effect which is eliminated in CER spectroscopy. The electric field distribution in the full heterostructure (GaN(cap) layer, AlGaN layer, and near the AlGaN/GaN interface in GaN(buffer) layer) has been found comparing theoretical calculations for the full heterostructure with the electric field for AlGaN layer obtained from CER measurements. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dynamics of the transition from weak to strong exciton‐photon coupling regime in a GaAs microcavity: angle resolved measurements
Authors: Belykh V. V. , Mylnikov D. A. , Sibeldin N. N.
Published: February 2012

The emission dynamics of a GaAs microcavity with embedded quantum wells at different angles of observation with respect to the sample normal under conditions of nonresonant picosecond‐pulse excitation is studied. At considerably high excitation densities, above a certain threshold, a very intense, fast, and spectrally narrow (at small angles of observation) component in the PL dynamics appears at short times, with the spectral position corresponding to the bare cavity mode, indicating the onset of lasing in the weak coupling regime. At longer times lasing ceases and the transition from weak to strong coupling regime is observed, as it follows from the spectral positions of the peaks in time‐resolved spectra at different angles of observation.

At moderate excitation densities, kinetic dependences of the spectral shift and width of the lower polariton emission line (these parameters are often used to distinguish between strong and weak coupling regimes) as a function of angle of observation (polariton energy) are analyzed. In particular, it is shown that the decay time of the spectral shift is almost independent of the polariton energy and could be used as the characteristic time of the transition from weak to strong coupling regime. On the other hand, the decay time of the emission line broadening strongly depends on the polariton energy, indicating that the linewidth kinetics is essentially determined by the cooling of the electron‐hole system. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Synthesis and characterization of CdxMn1‐xS magnetic nanoparticles stabilized with poly(vinyl alcohol) for biomedical applications
Authors: Schatkoski Vanessa , Mansur Alexandra , González Juan , Mansur Herman
Published: February 2012

In this work we report the synthesis and characterization of CdxMn1‐xS nanoparticles using poly(vinyl alcohol) as stabilizing agent aiming at the production of quantum dots nanocrystals with photoluminescence properties. UV‐visible spectroscopy (UV‐vis), photoluminescence (PL) spectroscopy and transmission electron microscopy (TEM) were used to characterize the formation and the relative stability of CdS nanoparticles. The results have clearly shown the influence of the Mn2+ partially replacing Cd2+ in the optical behavior of the semiconductor QDs produced. Moreover, the TEM images have not indicated any detectable segregation or phase separation caused by the amount of Mn+2 added to the CdS system (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Carbon diffusion and reactivity in Mn5Ge3 thin films
Authors: Petit Matthieu , Dau Minh Tuan , Monier Guillaume , Michez Lisa , Barre Xavier , Spiesser Aurelie , Thanh Vinh Le , Glachant Alain , Coudreau Cyril , Bideux Luc , Robert‐Goumet Christine
Published: February 2012

The Curie temperature of Mn5Ge3 has been successfully enhanced by carbon doping. In this context the diffusion of a carbon thin film in Mn5Ge3 has been studied at room temperature. A value of the diffusivity of about D = 2.4 × 10‐23 ± 0.5 × 10‐23 m2 s‐1 is reported. This value is in the typical range of interstitial diffusion coefficients. Moreover Auger Ge and Mn peaks shifts and Ge3d core level have been investigated to get some details on the reactivity of carbon atoms in Mn5Ge3.

Mn Auger transitions display a shift of 4 eV whereas Ge transitions do not. Similarly Ge3d core level does not contain C related contribution but presents a Mn one. These observations confirmed the fact that carbon atoms are not inert species for Mn. It suggests that a ternary Ge‐Mn‐C alloy could occur and should be taken into account when doping the Mn5Ge3 with carbon. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Adsorption of OH and H at the LiNbO3(0001) surface
Authors: Hölscher R. , Sanna S. , Schmidt W. G.
Published: February 2012

The adsorption of single hydrogen atoms and hydroxyl radicals (OH) at the polar (0001) surface is simulated by means of first‐principles total energy calculations, in order to investigate the influence of ferroelectric poling on the surface physics and chemistry of LiNbO3. H and OH are found to adsorb at a similar site both at the positive and at the negative (0001) surface. Despite this, the adsorption energy is for both adsorbates strongly polarization dependent, with adsorption energy differences as high as 2 eV. This striking contrast is traced back to electrostatic effects, which lead to a different bonding scenario at the two LN(0001) sides. The polar radical OH lies relatively flat on the positive surface, with the adsorbate oxygen forming a covalent bond with the surface oxygen. At the negative face, OH adsorbs roughly perpendicular and the adsorbate oxygen forms a bond of covalent nature with the surface cations. The adsorbate dipole moment is directed against the spontaneous polarization of the substrate. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Formation of ultra‐thin nitridation layer on Si(100) by hot‐wire method
Authors: Inao Haruki , Izumi Akira
Published: February 2012

In this work we study the deposition of indium oxynitride prepared by reactive RF magnetron sputtering. This material shows multi‐functionality in electrical and photonic applications. It shows transparence in visible range, wide band gap, high resistivity, low linkage current and response for light. The deposition processes were performed in a home build magnetron sputtering system, using a four‐inch pure In (99.999%) target, nitrogen and oxygen as process gases. The pressure was kept constant in 1.33 Pa and the RF power (13.56 MHz) was constant 250 W. The optical band gap was estimated for samples deposited with 0%, 10%, 20%, 50%, 80% and 85% of oxygen concentration in the gas mixture and the band gap values obtained were 1.32 eV, 2.47 eV, 2.65 eV, 2.50 eV, 3.04 eV and 3.00 eV, respectively. The IxV analysis shows a low leakage current (∼10–8 A). The increase in the oxygen concentration in the plasma promotes change in the character of these thin films from conductor to semiconductor material (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Adsorption of 5,10,15,20‐tetrakis (4‐bromophenyl)porphyrin on germanium(001)
Authors: Berner N. C. , Sergeeva Y. N. , Sergeeva N. N. , Senge M. O. , Cafolla A. A. , McGovern I. T.
Published: February 2012

A comparative study of 5,10,15,20‐tetrakis(4‐bromophenyl)porphyrin and 5,10,15,20‐tetraphenylporphyrin molecules adsorbed on the Ge(001) surface, using scanning tunnelling microscopy and photoemission spectroscopy, reveals that the bromine substituents influence the adsorption mechanism significantly. A strong bromine‐germanium interaction is observed, affecting the adsorption geometry of the entire molecule. Neither molecule appears to be mobile on the surface, which indicates additional interaction between the macromolecule and the surface. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Interface state characterization of ALD‐Al2O3/GaN and ALD‐Al2O3/AlGaN/GaN structures
Authors: Hori Yujin , Mizue Chihoko , Hashizume Tamotsu
Published: February 2012

We have characterized the interface states of Al2O3/GaN and Al2O3/AlGaN/GaN structures prepared by atomic layer deposition using the conventional and photo‐assisted capacitance‐voltage (C–V) measurements. In order to control the interface states, an N2O‐radical treatment was applied to the GaN and AlGaN surfaces prior to the deposition of the Al2O3 layer. We observed good C–V behavior and a relatively low density of interface states for the N2O‐radical treated Al2O3/GaN structure. To estimate the state density distributions at the Al2O3/AlGaN interface, we applied the photo‐assisted C–V measurement to the Al2O3/AlGaN/GaN heterostructures. The present Al2O3/AlGaN structre showed higher interface state densities than the Al2O3/GaN structure. However, we found that the N2O‐radical treatment is effective in reducing the density of interface states at the Al2O3/GaN and Al2O3/AlGaN systems (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Formation of boron‐nitride ultra‐thin films on Si(111)
Authors: Shimoyama Iwao , Baba Yuji , Sekiguchi Tetsuhiro , Nath Krishna G.
Published: February 2012

Chemical vapor deposition is employed to form hexagonal boron nitride (h ‐BN) monolayer films on Si(111) with a borazine precursor. The electronic structure and orientation of the films are analyzed by near edge X‐ray absorption fine structure (NEXAFS) spectroscopy and X‐ray photoelectron spectroscopy (XPS). XPS analysis shows that monolayer‐level stoichiometric BN films were formed. The B K‐edge NEXAFS spectra show two discrete peaks that have graphite‐like polarization dependence in the low‐energy region. Polarization dependence analysis of the NEXAFS indicates that the BN films had two‐dimensional orientation on the Si(111) substrate. Based on the density functional theory calculations, these discrete peaks are assigned to π* peaks at an intact h ‐BN site and edge B‐H site. Comparison with the electronic structures of bulk h ‐BN and h ‐BN/Ni(111) clarifies that the interaction between the BN layer and Si substrate was very small. This indicates that the h ‐BN monolayer was physisorbed on Si(111), making a steep interface and conserving the intrinsic electronic structure (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Heterojunction characteristics of ZnO and CuO substrates formed by direct bonding
Authors: Abe Hiroshi , Fujishima Masahide , Komiyama Takao , Chonan Yasunori , Yamaguchi Hiroyuki , Aoyama Takashi
Published: February 2012

The n‐ZnO/p‐CuO heterojunction characteristics have been investigated by direct bonding of ZnO and CuO substrates at room temperatures, and by post‐annealing at 800ºC. The ZnO substrate was fabricated by mixing of ZnO and Al2O3 (2%) powders, pressing at 50 MPa, and sintering at 1400 °C while the CuO substrate was fabricated by mixing of CuO and Li2CO3 (1%) powders, pressing at 300 MPa, and sintering at 700 °C. Rectifying behaviour with an ideality factor of 126 was observed after bonding of these substrates. Post‐annealing of the heterojunction, however, significantly increased both the forward and the reverse currents, and the rectifying behaviour was lost. Symmetrical I‐V curves with threshold voltages of about ± 1 V were observed and this degradation could be explained by impurity (Al and Li) segregation at the junction interface. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The structural and material properties of Cu(In,Ga)Se2 thin films
Authors: Wu Ya‐Fen , Hsu Hung‐Pin , Wang Jen‐Cheng , Chen Hui‐Ying
Published: February 2012

We report on the structural and material properties of Cu‐poor CuIn1‐xGax Se2 (CIGS) thin films with different gallium contents grown using the co‐evaporation technique. Temperature‐dependent photoluminescence (PL) and high‐resolution X‐ray diffraction measurements were performed. The PL emission peaks observed around 1.0‐1.2 eV are attributed to donor‐acceptor pair luminescence. These donor‐acceptor pair emissions are considered to originate from relatively shallow acceptor and donor energy levels. In addition, the X‐ray diffraction spectra of the samples are simulated using a theoretical model. From the analysis, it is found that the sample with higher gallium content exhibits smaller grain size and the microstructure size uniformity is reduced. The theoretical calculation result is consistent with the experimental results derived from the PL spectra. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Diurnal equilibrium convection and land surface–atmosphere interactions in an idealized cloud‐resolving model
Authors: Schlemmer Linda , Hohenegger Cathy , Schmidli Juerg , Schär Christoph
Published: February 2012

The influence of soil moisture and atmospheric stability on mid‐latitude diurnal convection and land–atmosphere exchange is investigated in an idealized cloud‐resolving modelling framework using a full set of parametrization schemes. In each member of a series of month‐long experiments, the model attains a state where deep, precipitating convection is triggered every day. This state is referred to as equilibrium diurnal convection. The triggering occurs via different mechanisms depending on the atmosphere–soil setting. In our framework latent heat fluxes comprise the primary control over the precipitation amounts. We find that evaporation is regulated by the availability of energy on the one hand and the availability of soil moisture and the near‐surface saturation deficit of the atmosphere on the other. Increased cloud cover over wet soils reduces net short‐wave radiation but increases net long‐wave radiation, leading to a near‐compensation of the two effects on available energy. Increased boundary layer moisture is removed by deep convection, thus increasing the near‐surface saturation deficit and preventing a negative feedback of boundary layer moisture content on the latent heat fluxes. We also find that there is a spatial correlation between soil moisture and precipitation anomalies, suggesting that the soil moisture precipitation feedback acts on a scale of 10–50 km. Copyright © 2012 Royal Meteorological Society
Electrochemical reduction of aryl diazonium salts: a versatile way for carbon nanotubes functionalisation
Authors: Raicopol Matei , Necula Luiza , Ionita Mariana , Pilan Luisa
Published: February 2012

Single‐walled carbon nanotubes (SWCNTs) possess a wealth of exceptional structural, mechanical and electronic properties. An interesting challenge is their functionalisation without altering their electronic properties by a route that ensures a stable and a strong grafting of the desired molecules. Aryl diazonium salts are promising candidates for introducing molecular tools by surface modifications. We report here the functionalisation of SWCNTs through the electrochemical reduction of aryl diazonium salts. Experiments were carried out first on a glassy carbon electrode, taking into account its low porosity and structural similarity with SWCNTs. The surface modification of both substrates is checked by electrochemical signals related to the different immobilised moieties obtained by voltammetric methods and the blocking action of the modified electrodes for Fe(CN)63−/4− redox probe in cyclic voltammetry measurements. This procedure allowed the use of a variety of diazonium salts, including those that provide moieties favourable to further elaboration after attachment to the SWCNTs. Copyright © 2012 John Wiley & Sons, Ltd.
Spectroscopy of carbon: from diamond to nitride films
Authors: Kaciulis S.
Published: February 2012

Every surface scientist knows about the importance of carbon spectroscopy: the signals of C 1 s and C KLL usually are indicating the surface cleanness, whereas C 1 s peak is often used as a reference for the calibration of energy scale. Carbon spectroscopy becomes even more important in the case of the studies dedicated to new carbon‐based materials, such as nanotubes, graphene, diamond‐like carbon (DLC), carbon nitride, carbides, etc. It is well‐known that the carbon atoms can be arranged in a great variety of crystalline and disordered structures, because their electrons can hybridize in sp3, sp2and even in linear sp configurations. Namely, the hybridization of carbon electrons defines the mechanical, electrical and optical properties of these materials. Indeed, between the pure diamond (sp3) and graphite (sp2), there are many phases of amorphous material characterized by different sp2/sp3ratios and generally named DLC. Electron spectroscopies (X‐ray photoelectron spectroscopy, Auger electron spectroscopy and electron energy loss spectroscopy) are widely recognized as analytical techniques, able to identify the bonds of diamond, graphite and amorphous phases of carbon. The binding energy of C 1 s spectrum together with its plasmon losses, the shape of Auger peak and valence band spectra can be used to characterize the structure of carbon‐based materials. In this study, an overview is reported on carbon spectroscopy, comparing different experimental methods. Their application for the characterization of DLC and carbon nitride films, including the determination of carbon's sp2/sp3ratio is discussed and illustrated by experimental results obtained for a series of thin films of these materials. Copyright © 2012 John Wiley & Sons, Ltd.