bluuebunny/crossref_metadata_2025 huggingface dataset:
GaN‐based nanocolumn LEDs: Impact of strain engineering on the electro‐optical performance
Authors: Veprek Ratko G. , Steiger Sebastian , Witzigmann Bernd
Published: March 2009

A computation of the electronic properties of GaN nanocolumn LEDs with optically active InGaN quantum disks is presented. Using the simulation framework AQUA/tdkp, the relaxation of intrinsic strains in the selected 3D structure and its effects on the built‐in piezoelectric potential and strain dependent bandedge shifts are computed.

The results show a strong relaxation of the compressive strains in the InGaN quantum disk compared to usual broad area grown structures suggesting that lower wavelength emission can be achieved at considerable lower indium contents (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Asymmetric external field effects on photoluminescence efficiency in a blue (In,Ga)N quantum‐well diode with an additional n ‐type electron reservoir layer
Authors: Fujiwara Kenzo , Katou Hirofumi , Inoue Takao , Sheu Jin‐Kong
Published: March 2009

External field effects on photoluminescence (PL) spectra of a blue In0.3Ga0.7N multiple‐quantum‐well (MQW) diode with an additional n+‐doped In0.18Ga0.82N electron reservoir layer (ERL) have been investigated at 20 K as a function of bias voltage under direct excitation conditions, where only the MQW and ERL regions are photoexcited. When the reverse bias is increased, the PL emission of MQW is strongly quenched, accompanying a blue‐shift due to compensation of the internal piezo‐fields, while the ERL emission is stable. However, the PL intensity of ERL is significantly decreased with increasing the forward field, showing asymmetric behaviors on the PL efficiency with respect to the field direction. These results indicate that field‐induced escape processes of photogenerated electrons and holes from the excited regions play an important role for determination of the PL efficiency. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effect of temperature on cryogenic characteristics of AlGaN/GaN MIS‐HEMTs
Authors: Endoh Akira , Watanabe Issei , Yamashita Yoshimi , Mimura Takashi , Matsui Toshiaki
Published: March 2009

We measured the DC and RF characteristics at 300, 220, 150, 77, and 16 K of AlGaN/GaN metal‐insulator‐semiconductor (MIS) high electron mobility transistors (HEMTs) with SiN/SiO2/SiN triple‐layer insulators. The values of the cutoff frequency fT and the maximum transconductance gm_max increased with a decrease in temperature at relatively high temperatures, i.e. between 150 and 300 K. At temperatures below 100 K, the values of fT and gm_max increased slightly. We also carried out Monte Carlo simulations of electron transport in bulk GaN at various temperatures and electric fields. The steady‐state drift velocity of electrons showed a trend similar to those of the values of fT and gm_max. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Anisotropic polarization of non‐polar GaN quantum dot emission
Authors: Mata R. , Garro N. , Cros A. , Budagosky J. A. , García‐Cristóbal A. , Vinattieri A. , Gurioli M. , Founta S. , Bellet‐Amalric E. , Daudin B.
Published: March 2009

We report on experimental and theoretical studies of the polarization selection rules of the emission of non‐polar GaN/AlN self‐assembled quantum dots. Time‐integrated and time‐resolved photoluminescence measurements have been performed to determine the degree of polarization. It is found that the emission of some samples can be predominantly polarized parallel to the wurtzite c axis, in striking difference with the previously reported results for bulk GaN and its heterostructures, in which the emission was preferentially polarized perpendicular to the c axis. Theoretical calculations based on an 8‐band k·p model are used to analyze the relative importance of strain, confinement and quantum dot shape on the polarization selection rules. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
UV/VUV photodetectors using group III‐nitride semiconductors
Authors: Saito Terubumi , Hitora Toshimi , Hitora Hisako , Kawai Hiroji , Saito Ichiro , Yamaguchi Eiichi
Published: March 2009

Schottky barrier photodiodes based on AlN, AlxGa1–xN, GaN, and InyGa1–yN were fabricated with different compositions. In addition, novel types of UV detectors with narrow spectral bandwidths were developed by combining AlxGa1–xN Schottky barrier photodiodes and optical entrance windows made of AlyGa1–yN having exactly or nearly the same composition (y ≥ x). Their spectral responsivities were measured in the spectral range including the vacuum ultraviolet region. The results showed that the devices having a wide variety of cut‐off wavelengths and narrow spectral bandwidths were successfully fabricated and achieved a high out‐of‐band rejection ratio. In addition, satisfactory performances of low noise current, low temperature coefficient, and high stability to UV photons were confirmed. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical properties of InN nanocolumns: Electron accumulation at InN non‐polar surfaces and dependence on the growth conditions
Authors: Segura‐Ruiz J. , Garro N. , Cantarero A. , Iikawa F. , Denker C. , Malindretos J. , Rizzi A.
Published: March 2009

InN nanocolumns grown by plasma‐assisted molecular beam epitaxy have been studied by photoluminescence (PL) and photoluminescence excitation (PLE). The PL peak energy was red‐shifted with respect to the PLE onset and both energies were higher than the low temperature band‐gap reported for InN. PL and PLE experiments for different excitation and detection energies indicated that the PL peaks were homogeneously broadened. This overall phenomenology has been attributed to the effects of an electron accumulation layer present atthe non‐polar surfaces of the InN nanocolumns. Variations in the growth conditions modify the edge of the PLE spectra and the PL peak energies evidencing that the density of free electrons can be somehow controlled by the growth parameters. It was observed that In‐BEP and substrate temperature leading to shorter In diffusion lengths diminished the effects of the electron accumulation layer on the optical properties. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Processing approaches of AlGaN/GaN Metal Insulator Semiconductor Hetero Field Effect Transistors (MISHFET) on Si (111) substrates
Authors: Eickelkamp Martin , Ketteniß Nico , Lautensack Christian , Noculak Achim , Kalisch Holger , Jansen Rolf H. , Vescan Andrei
Published: March 2009

We report on the fabrication of AlGaN/GaN MISHFETs using SiO2 and SiN as gate dielectrics. In particular, two different passivation procedures are investigated with respect to the resulting electrical properties. A fluorine based ICP etch step, as used here to remove the gate dielectric prior to passivation layer deposition, is shown to deteriorate the sheet carrier concentration and mobility. Depositing the passivation layer upon the gate dielectric, on the other hand, slightly decreases the sheet resistance as compared to a conventional HFET. Gate diode characteristics reveal significant reduction of gate leakage currents in both, reverse and forward biasing regions, of 1‐2 and up to 6 orders of magnitude, respectively. All devices exhibit more pronounced current collapse compared to a conventional passivated HFET. In addition, a clear depencency on the processing scheme is observed. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
222 nm single‐peaked deep‐UV LED with thin AlGaN quantum well layers
Authors: Norimichi Noguchi , Hirayama Hideki , Yatabe Tohru , Kamata Norihiko
Published: March 2009

We fabricated 222 nm AlGaN multi‐quantum well (MQW) deep‐ultraviolet (DUV) light emitting diode (LED) on high quality AlN buffers grown by ammonia (NH3) pulse‐flow multilayer growth method on sapphire substrate. We obtained remarkable enhancement of emission intensity of 220 nm‐band DUV LED by introducing thin (<1.6 nm) quantum well. We realized a single peaked operation of a 222 nm DUV AlGaN MQW LED under pulsed current injection, which is the shortest wavelength of AlGaN LED on sapphire substrate. The maximum output power and external quantum efficiency of 222 nm AlGaN MQW LED were 14 μW and 0.003%, respectively. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Improvement of device characteristics in MIS AlGaN/GaN heterostructure field‐effect transistors by designing insulator/AlGaN structures
Authors: Maeda Narihiko , Hiroki Masanobu , Makimoto Toshiki , Enoki Takatomo , Kobayashi Takashi
Published: March 2009

To obtain a guideline for improving the device performance of GaN‐based Metal‐Insulator‐Semiconductor (MIS) heterostructure field‐effect transistors (HFETs), both HFET and MIS HFETs were fabricated and compared, whose gate capacitances are designed to be equal. With an increased insulator thickness and decreased AlGaN thickness, a high transconductance was successfully obtained that was equivalent to that of HFET, in addition to the reduced gate leakage current in MIS HFETs. Moreover, Al2O3‐based MIS HFETs were revealed to exhibit superior DC characteristics over Si3N4 MIS HFETs. Since deposition of insulators changes the electrical properties of heterostructures, considering the insulator/AlGaN structures as the total barrier layers is effective and indispensable in designing the MIS AlGaN/GaN HFETs. On the basis of the device design, MIS HFETs can be fabricated that exhibit superior device characteristics over those in conventional HFETs. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Energy levels of Nd3+ ions in GaN
Authors: Metcalfe Grace D. , Readinger Eric D. , Shen Hongen , Woodward Nathaniel T. , Dierolf Volkmar , Wraback Michael
Published: March 2009

We report the Stark energy sublevels of Nd3+ ions in GaN grown by plasma‐assisted molecular beam epitaxy as determined by luminescence spectra. The photoluminescence spectra is correlated with transitions from the 4F3/2 doublet state to the 4I9/2, 4I11/2, and 4I13/2 multiplets of the Nd3+ ion for above and below bandgap excitation, with the strongest emission occurring at 1.12 eV (1106 nm). A splitting of the 4F3/2 excited state is determined to be 4.1 meV. From photoluminescence excitation spectra, we also identify the Stark sub‐levels of the excited states 4F5/2, 2H9/2, 4F7/2, 4S3/2, 2G7/2, and 4G5/2. Photoluminescence excitation spectra exhibit an optimal excitation energy of 1.48 eV (836 nm). Site‐selective spectroscopy studies using combined excitation‐emission spectroscopy with confocal microscopy imply enhanced substantial doping at the Ga site. In addition, optical loss and gain measurements of a GaN:Nd waveguide excited above bandgap indicate an internal loss coefficient of ∼6.5 +/– 2 cm–1 and a net gain of ∼ –2 +/– 2 cm–1. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical properties of ion beam synthesized nitrogen‐rich GaN1‐xAsx
Authors: Chen C.‐H. , Yu K. M. , Walukiewicz W.
Published: March 2009

We have synthesized GaN1‐xAsx alloys using implantation of As into GaN followed by rapid thermal annealing. Appearance of a new As‐derived band at about 2.5 eV below the conduction band edge is confirmed by photomodulated transmission (PT) and photoluminescence (PL). Photoluminescence peaks at about 2.37 eV observed at low temperature in As and Ar implanted Mg doped GaN samples are attributed to emission associated with complexes of damage produced donors and Mg acceptors. The results demonstrate a feasibility of using ion beam synthesis to produce N‐rich group III nitride based highly mismatched alloys. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Stacking faults and phase changes in Mg‐doped InGaN grown on Si
Authors: Hawkridge Michael E. , Liliental‐Weber Zuzanna , Yu Kin M. , Reichertz Lothar A. , Schaff William J. , Ager Joel W. , Walukiewicz Wladek
Published: March 2009

We report evidence for the role of Mg in the formation of basal stacking faults and a phase transition in InxGa1‐xN layers doped with Mg grown by molecular beam epitaxy on Si (111) substrates with AlN buffer layers. Several samples with varying In content between x ∼ 0.1 and x ∼ 0.3 are examined by transmission electron microscopy and other techniques. High densities of basal stacking faults are observed in the central region of the InGaN layer away from the substrate or layer surface, but at varying depths within this region. Selected area diffraction patterns show that while the InGaN layer is initially in the wurtzite phase (and of good quality) AlN buffer layer, there is a change to the zinc blende phase in the upper part of the InGaN layer. SIMS measurements show that the Mg concentration drops from a maximum to a steady concentration coinciding with the presence of the basal stacking faults. There is little change in In or Ga concentrations in the same area. High‐resolution electron microscopy from the area of the stacking faults confirms that the change to the cubic phase is abrupt across one such fault. These results indicate that Mg plays a role in the formation of stacking faults and the phase change observed in InxGa1‐xN alloys. We also consider the role of In in the formation of these defects. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Low‐temperature growth of InGaN/GaN nano‐islands investigated by grazing‐incidence X‐ray diffraction
Authors: Schmidt Th. , Flege J. I. , Siebert M. , Figge S. , Yamaguchi T. , Hommel D. , Falta J.
Published: March 2009

Grazing‐incidence X‐ray diffraction (GIXRD) has been used to study the structural properties of nanoscale In‐GaN/GaN(0001) islands, and especially the influence of GaN low‐temperature overgrowth of such structures on their strain state, chemical composition and defect structure. Prior to overgrowth, the presence of almost completely relaxed islands with a very high In content is deduced from the diffraction data. After cap layer growth, the In content is found to be significantly reduced and a broad distribution of composition and strain observed. In case of multiple InGaN island layers separated by GaN spacer layers, additional diffraction spots appear, allowing to identify the formation of cubic nitride material due to the low growth temperature (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Spontaneous stratification of InGaN layers and its influence on optical properties
Authors: Liliental‐Weber Z. , Yu K.M. , Hawkridge M. , Bedair S. , Berman A.E. , Emara A. , Domagala J. , Bak‐Misiuk J.
Published: March 2009

Transmission Electron Microscopy, high resolution X‐ray diffraction and reciprocal space maps, Rutherford Back Scattering and photoluminescence were applied to study InGaN layers grown by MOCVD with increasing layer thickness (100 nm to 1000 nm) and nominally constant In concentration of 10%. Spontaneous stratification of the layer has been found. A strained layer with lower than nominal In content was found in direct contact with the underlying GaN followed by relaxed layers with a nominal or higher In concentration. A high density of randomly distributed stacking faults as well as domains with cubic structure and closely distributed stacking faults (polytype‐like) were present in the thicker layers. Strong corrugation of the thicker sample surface was observed. The appearance of multiple photoluminescence line positions was related not only to the spontaneously formed layers with different In content, but also to the structural planar defects formed in the thicker layers. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Studies of electrical resistance in Ni75Cr7Si7.5Mn10.5 and Ni80.5Cr4.2Si6.5Mn5B3.8 glass‐coated wires
Authors: García C. , Zhukova V. , Val J. J. del , Blanco J. M. , Zhukov A.
Published: March 2009

In this paper we studied thermal stability of Ni75Cr7Si7.5Mn10.5 and Ni80.5Cr4.2Si6.5Mn5B3.8 glass coated microwires with metallic nucleus diameters ranging between 10 μm and 20 μm using electrical resistance measurements, X‐ray diffraction and DSC methods. Electrical resistance was measured during Joule heating of the sample i.e. flowing the DC current. X‐ray diffraction was used to determine the crystalline structure in as‐prepared microwires.

It was found that electrical resistance per length, ρ, depends on the sample geometry. Besides this dependence is opposite for Ni75Cr7Si7.5Mn10.5 and Ni80.5Cr4.2Si6.5Mn5B3.8 glass coated microwires. Such dependences have been related with effect of rapid solidification conditions on the grain sizes and consequently on grain growth process during annealing. Temperature coefficient of resistivity in the case of Ni75Cr7Si7.5Mn10.5 microwires is much smaller (about 5 times smaller). Considerable dependence of the current density for beginning of phase transition on metallic nucleus diameter has been attributed to the thermal transfer conditions. Efficiently of joule heating for the case of thinner microwires is smaller and the current density for achieving the phase transition‐higher. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Lipophilicity Studies on Pyrrolyl‐Acetic Acid Derivatives. Experimental Versus Predicted logP Values in Relationship with Aldose Reductase Inhibitory Activity
Authors: Chrysanthakopoulos Marios , Koletsou Antigoni , Nicolaou Ioannis , Demopoulos Vassilis J. , Tsantili‐Kakoulidou Anna
Published: March 2009

The lipophilicity of a series of pyrrolyl‐acetic acid derivatives, inhibitors of the aldose reductase enzyme, was assessed by direct partitioning experiments in the n‐octanol–water system. Distribution coefficients concerning both the neutral and the anionic species were compared to calculated values generated by commonly used software. The reliability of the predictions was evaluated considering the absolute differences, as well as the correlation between experimental and predicted logP or logD values. The inferior performance of the different algorithms for logD7.4 prediction should be attributed to additional sources of errors and in particular to the nonsystematic interference of ion pairing in partitioning. Although the traditional fragmental system of Rekker as modified in PrologP (logPCDR) was quite successful in logP estimation of the pyrrolyl‐acetic acid derivatives, the nonlinear artificial neural network module ANN2005, implemented in the same software was found to be more consistent in reflecting the features involved in partitioning process. Plot of experimental logP versus aldose reductase inhibitory activity values revealed a definite trend in biological activity and adequate quantitative relationships were further established if, besides logP, Hammett electronic constant σ or Abraham's hydrogen bond acceptor term was included in the regression equation. Among the calculated logP, logPANN05 and ABlogP showed an analogous trend with biological activity, although leading to equations of inferior quality, whereas the other calculated logP values failed to show any regular pattern.
Range separation combined with the Overhauser model: Application to the H2 molecule along the dissociation curve
Authors: Gori‐Giorgi Paola , Savin Andreas
Published: March 2009

The combination of density‐functional theory with other approaches to the many‐electron problem through the separation of the electron–electron interaction into a short‐range and a long‐range contribution (range separation) is a successful strategy, which is raising more and more interest in recent years. We focus here on a range‐separated method in which only the short‐range correlation energy needs to be approximated, and we model it within the “extended Overhauser approach.” We consider the paradigmatic case of the H2 molecule along the dissociation curve, finding encouraging results. By means of very accurate variational wavefunctions, we also study how the effective electron–electron interaction appearing in the Overhauser model should be to yield the exact correlation energy for standard Kohn‐Sham density functional theory. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009
Structural and interaction analysis of helical heparin oligosaccharides with the fragment molecular orbital method
Authors: Sawada Toshihiko , Fedorov Dmitri G. , Kitaura Kazuo
Published: March 2009

The fragment molecular orbital method (FMO) was applied to the geometry optimization of several heparin oligosaccharides at the RHF/6‐31(+)G(d) level combined with the polarizable continuum model (PCM). For comparison, GLYCAM force field optimization in explicit solvent was also conducted. Good accuracy of FMO was demonstrated in comparison to ab initio at the MP2/PCM level. The interaction analysis was conducted using the pair interaction energy decomposition analysis (PIEDA), and the role of hydrogen bonding and solvent was elucidated in the helix formation of heparin in solution. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009
Recent topics in numerical integration
Authors: Cools Ronald , Huybrechs Daan , Nuyens Dirk
Published: March 2009

In this article, we describe some recent topics in the approximation of univariate and multivariate integrals. We especially pay attention to progress in the area of oscillatory integrals and in quasi‐Monte Carlo methods using lattice rules. Many pointers to the relevant literature are provided. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009
New aspects in fragmentation of peptide nucleic acids: comparison of positive and negative ions by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry
Authors: Ziehe Matthias , Grossmann Tom N. , Seitz Oliver , Linscheid Michael W.
Published: March 2009

The use of peptide nucleic acids (PNAs) is steadily increasing in biochemistry and diagnostics. So far, PNAs have mostly been investigated using cationic conditions in mass spectrometry. Furthermore, the use of fragmentation techniques developed for peptides and proteins like infrared multiphoton dissociation (IRMPD) and electron capture dissociation (ECD) has barely been examined. However, especially the fragmentation behavior of PNA oligomers in negative ion mode is of high importance, due to the ability to interact with nucleic acids which are almost exclusively analyzed in the negatively charged state. In the current study PNA fragmentations under cationic and anionic conditions were investigated and different fragmentation techniques like collision‐induced dissociation (CID), IRMPD and ECD were applied. Especially when using CID and IRMPD, amide bonds were broken, whereas ECD resulted in the elimination of nucleobases. Differences were also observed between positive and negative ionization, while the sequence coverage for the negative ions was superior to positive ions. The fragmentation behavior using IRMPD led to almost complete sequence coverage. Additionally, in anions the interesting effect of multiple eliminations of HNCO was found. Copyright © 2009 John Wiley & Sons, Ltd.
Doping control analysis of emerging drugs in human plasma – identification of GW501516, S‐107, JTV‐519, and S‐40503
Authors: Thevis Mario , Beuck Simon , Thomas Andreas , Kortner Birthe , Kohler Maxie , Rodchenkov Grigory , Schänzer Wilhelm
Published: March 2009

An important aspect of preventive doping research is the rapid implementation of tests for emerging drugs with potential for misuse into routine doping control assays. New therapeutics of different classes such as PPARδ‐agonists (e.g. GW501516), ryanodine‐calstabin‐complex stabilizers (e.g. S‐107 and JTV‐519), and selective androgen receptor modulators (SARMs, e.g. S‐40503) are currently used for the treatment of particular medical conditions such as metabolic syndrome, cardiac arrhythmia, debilitating diseases and osteoporosis, respectively. Due to their being at an early stage of clinical trials and the limited availability of data on the metabolism and possible renal elimination of the active drugs, the development of protocols for doping control analyses of plasma specimens could be an option for the detection of the circulating agents. The mass spectrometric fragmentation of four emerging drug candidates (GW501516, S‐107, JTV‐519, and S‐40503) was elucidated by positive electrospray ionization and collision‐induced dissociation using a high resolution/high accuracy mass spectrometer. A screening and confirmation procedure was established based on liquid chromatography/tandem mass spectrometry requiring a volume of 100 µL of plasma. Proteins were precipitated using acetonitrile, the specimens were centrifuged and the supernatant analyzed using a triple‐quadrupole mass spectrometer employing multiple reaction monitoring of diagnostic ion transitions. The method was validated with regard to specificity, limits of detection (0.4–8.3 ng/mL), recoveries (72–98%), intraday and interday precisions (12–21%), and ion suppression/enhancement effects. Copyright © 2009 John Wiley & Sons, Ltd.
Critical assessment of the applicability of gas chromatography‐combustion‐isotope ratio mass spectrometry to determine amino sugar dynamics in soil
Authors: Decock Charlotte , Denef Karolien , Bodé Samuel , Six Johan , Boeckx Pascal
Published: March 2009

Amino sugars in soils have been used as markers of microbial necromass and to determine the relative contribution of bacterial and fungal residues to soil organic matter. However, little is known about the dynamics of amino sugars in soil. This is partly because of a lack of adequate techniques to determine ‘turnover rates’ of amino sugars in soil. We conducted an incubation experiment where 13C‐labeled organic substrates of different quality were added to a sandy soil. The objectives were to evaluate the applicability of compound‐specific stable isotope analysis via gas chromatography‐combustion‐isotope ratio mass spectrometry (GC‐C‐IRMS) for the determination of 13C amino sugars and to demonstrate amino sugar dynamics in soil. We found total analytical errors between 0.8 and 2.6‰ for the δ13C‐values of the soil amino sugars as a result of the required δ13C‐corrections for isotopic alterations due to derivatization, isotopic fractionation and analytical conditions. Furthermore, the δ13C‐values of internal standards in samples determined via GC‐C‐IRMS deviated considerably from the δ13C‐values of the pure compounds determined via elemental analyzer IRMS (with a variation of 9 to 10‰ between the first and third quartile among all samples). This questions the applicability of GC‐C‐IRMS for soil amino sugar analysis. Liquid chromatography‐combustion‐IRMS (LC‐C‐IRMS) might be a promising alternative since derivatization, one of the main sources of error when using GC‐C‐IRMS, is eliminated from the procedure. The high 13C‐enrichment of the substrate allowed for the detection of very high 13C‐labels in soil amino sugars after 1 week of incubation, while no significant differences in amino sugar concentrations over time and across treatments were observed. This suggests steady‐state conditions upon substrate addition, i.e. amino sugar formation equalled amino sugar decomposition. Furthermore, higher quality substrates seemed to favor the production of fungal‐derived amino sugars. Copyright © 2009 John Wiley & Sons, Ltd.
Electrospray ionization mass spectrometry as a critical tool for revealing new properties of snake venom phospholipase A2
Authors: Liu Shuqing , Zhang Cuili , Xu Yue‐Fei , Yang Fan , Sun Ming‐Zhong
Published: March 2009

Results from high‐performance liquid chromatography/nano‐electrospray ionization tandem mass spectrometry (HPLC/nESI‐MS/MS) coupled to two‐dimensional sodium dodecyl sulfate‐polyacrylamide gel electrophoresis (2D SDS‐PAGE) indicated that the monomer and dimer of phospholipase A2 (PLA2) coexisted in crude Chinese Agkistrodon blomhoffii Ussurensis snake venom (ABUSV). Then, an acidic PLA2 with the accurate molecular mass of 13979.6 Da was purified from ABUSV (mo‐ABUSV‐aPLA2). MS/MS‐derived peptides from ABUSV‐aPLA2 were compared with other homologous snake venom PLA2s, which in turn showed that ABUSV‐aPLA2 is a novel snake venom PLA2. Meanwhile, the ABUSV‐aPLA2 dimer (di‐ABUSV‐aPLA2) was also obtained. MS/MS analysis identified the same peptides from di‐ABUSV‐aPLA2 as from mo‐ABUSV‐aPLA2, which indicates that di‐ABUSV‐aPLA2 is a homodimer. One Ca2+ ion is contained per ABUSV‐aPLA2. The Ca2+ ion is critical for both the hydrolytic activity and the structure of ABUSV‐aPLA2. Pro‐Q Emerald and Pro‐Q Diamond specific glycoprotein and phosphoprotein staining combined with MS/MS analysis indicated that the ABUSV‐aPLA2 is both a glycoprotein and a phosphoprotein, which to our knowledge is the first such report for a snake venom PLA2 and thus provides new threads for the study of the functions and structures of snake venom PLA2s. One phosphorylation site and the size of the glycan chain are determined by using HPLC/nESI‐MS/MS and matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI‐TOF) MS. The delicate utilization of ESI‐MS can exert tremendous impact on protein sciences. Copyright © 2009 John Wiley & Sons, Ltd.
The impact of outsourcing new technologies on integrative capabilities and performance
Authors: Weigelt Carmen
Published: March 2009

Outsourcing plays an important role for firms adopting new technologies. Although outsourcing provides access to a new technology, it does not guarantee that a firm can subsequently integrate the technology with existing business processes and leverage it in the marketplace. This distinction, however, has rarely been made in the literature. In the context of business process enhancing technologies, this study builds on the resource‐based and knowledge‐based views to study the impact of outsourcing on firms' subsequent performance in the market and their integrative capabilities, that is, a firm's capacity to use and assimilate a new technology with its business processes and build upon it. The study argues that greater reliance on outsourcing may reduce a firm's learning by doing, internal investment, and tacit knowledge applications, thereby impeding a firm's integrative capabilities and performance in the market. The study uses survey and archival data on banks' outsourcing strategies for Internet adoption to test for the performance consequences of outsourcing, which are found to be negative. However, the findings also show that outsourcing is less detrimental for firms with experience in prior related technology. Copyright © 2009 John Wiley & Sons, Ltd.
Why top management team characteristics matter when employing a chief operating officer: a strategic contingency perspective
Authors: Marcel Jeremy J.
Published: March 2009

Critics of the CEO/COO duo have stressed that this arrangement burdens the firm with increased costs and decreases the CEO's effectiveness. This study adopts an upper echelon perspective to argue that the presence of a COO may also create TMT‐level information‐processing benefits that can improve firm performance in certain conditions. Data from a sample of 153 firms in five industries highlight a strong positive relationship between the presence of a COO and two established measures of firm performance: return on assets and market‐to‐book ratio. The data also suggest that those relationships are contingent on the broader characteristics of the TMT. Copyright © 2009 John Wiley & Sons, Ltd.
Electrospun Nanoparticle–Nanofiber Composites via a One‐Step Synthesis
Authors: Saquing Carl D. , Manasco Joshua L. , Khan Saad A.
Published: March 2009

A facile approach to synthesize and incorporate metal nanoparticles (NPs) into electrospun polymer nanofibers (NFs) wherein the electrospinning polymer acts as both a reducing agent for the metal salt precursor, as well as a protecting and templating agent for the ensuing NPs, is reported. Such a true one‐step process at ambient conditions and free of organic solvents is demonstrated using a system comprising AgNO3 and poly(ethylene oxide) (PEO) at electrospinnable molecular weights of 600, 1000, or 2000 kDa. The PEO transforms Ag+ into AgNPs, a phenomenon that has not been previously possible at PEO molecular weights less than 20 kDa without the addition of a separate reducing agent and stabilizer or the application of heat. Results from X‐ray photoelectron spectroscopy and UV–Vis absorption spectrophotometry analyses support the formation of pseudo‐crown ethers in high molecular weight PEO as the mechanism in the development of NPs. The AgNPs reduce fiber diameter and enhance fiber quality (reduced beading) due to increased electrical conductivity. Interestingly, several of the NFs exhibit AgNP‐localized nanochain formation and protrusion from the NF surface that can be attributed to the combined effect of applied electrical field on the polymer and the differences between the electrical conductivity and polarizability of the polymer and metal NPs.
Epigenetic Reprogramming by Somatic Cell Nuclear Transfer in Primates
Authors: Sparman Michelle , Dighe Vikas , Sritanaudomchai Hathaitip , Ma Hong , Ramsey Cathy , Pedersen Darlene , Clepper Lisa , Nighot Prashant , Wolf Don , Hennebold Jon , Mitalipov Shoukhrat
Published: March 2009

We recently demonstrated that somatic cells from adult primates could be reprogrammed into a pluripotent state by somatic cell nuclear transfer. However, the low efficiency with donor cells from one monkey necessitated the need for large oocyte numbers. Here, we demonstrate nearly threefold higher blastocyst development and embryonic stem (ES) cell derivation rates with different nuclear donor cells. Two ES cell lines were isolated using adult female rhesus macaque skin fibroblasts as nuclear donors and oocytes retrieved from one female, following a single controlled ovarian stimulation. In addition to routine pluripotency tests involving in vitro and in vivo differentiation into various somatic cell types, primate ES cells derived from reprogrammed somatic cells were also capable of contributing to cells expressing markers of germ cells. Moreover, imprinted gene expression, methylation, telomere length, and X-inactivation analyses were consistent with accurate and extensive epigenetic reprogramming of somatic cells by oocyte-specific factors.

Disclosure of potential conflicts of interest is found at the end of this article.
Stepwise Differentiation of Human Embryonic Stem Cells Promotes Tendon Regeneration by Secreting Fetal Tendon Matrix and Differentiation Factors
Authors: Chen Xiao , Song Xing-Hui , Yin Zi , Zou Xiao-Hui , Wang Lin-Lin , Hu Hu , Cao Tong , Zheng Minghao , Ouyang Hong Wei
Published: March 2009

Human embryonic stem cells (hESCs) are ideal seed cells for tissue regeneration, but no research has yet been reported concerning their potential for tendon regeneration. This study investigated the strategy and efficacy of using hESCs for tendon regeneration as well as the mechanism involved. hESCs were first induced to differentiate into mesenchymal stem cells (MSCs), which had the potential to differentiate into the three mesenchymal lineages and were positive for MSC surface markers. hESC-derived MSCs (hESC–MSCs) regenerated tendon tissues in both an in vitro tissue engineering model and an in vivo ectopic tendon regeneration model, as confirmed by the expression of tendon-specific genes and structure. In in-situ rat patellar tendon repair, tendon treated with hESC–MSCs had much better structural and mechanical properties than did controls. Furthermore, hESC–MSCs remained viable at the tendon wound site for at least 4 weeks and secreted human fetal tendon-specific matrix components and differentiation factors, which then activated the endogenous regeneration process in tendon. Moreover, no teratoma was found in any samples. These findings demonstrate a safe and practical strategy of applying ESCs for tendon regeneration and may assist in future strategies to treat tendon diseases.

Disclosure of potential conflicts of interest is found at the end of this article.
Toxicology evaluation of Atlantic Canadian seafood processing plant effluent
Authors: Jamieson Bryan Lee , Gonçalves Alex Augusto , Gagnon Graham A.
Published: March 2009

The purpose of this study was to carry out an acute aquatic toxicity assessment on select effluent samples from Atlantic Canadian seafood processing plants. Raw effluent acute aquatic toxicity for the flatfish and salmon effluents was assessed using the acute lethality test and Microtox™ test. The effectiveness of dissolved air flotation treatment (DAF) in removing acute toxicity from these effluents was evaluated using the Microtox™ test. The salmon effluent failed the acute lethality test using rainbow trout while the flatfish effluent showed acute toxicity in the Microtox™ test with a 50% inhibiting concentration (IC50) of 38.84%. Subsequent treatment by DAF of the flatfish and salmon effluents increased IC50 values by 20% and 26% respectively. The findings of this study indicate that all of the processing effluents sampled showed characteristics that could potentially degrade effluent receiving waters and acute toxicity was demonstrated in the two raw finfish effluents. Application of DAF treatment was successful in significantly increasing Microtox™ IC50 values, thereby reducing acute toxicity, but failed to entirely remove acute toxicity. © 2009 Wiley Periodicals, Inc. Environ Toxicol, 2010.
Hydrothermal Synthesis and Characterization of a Novel Lead(II) Framework Containing Infinite Pb–O–Pb Linkage Extended by Novel Pb–μ1,1‐(N)CS–Pb Bridges
Authors: Ding Bin , Liu Yuan‐Yuan , Zhao Xiao‐Jun , Yang En‐Cui , Du Gui‐Xiang , Wang Xiu Guang
Published: March 2009

A novel lead(II) framework [Pb2(μ1,1‐NCS)(NCS)(ADA)]n (1) can be isolated under hydrothermal conditions, by using N‐(2‐carbamoylmethyl)iminodiacetic acid (H2ADA), lead(II) oxide, and NH4NCS. Compound 1 contains the subunits of infinite Pb–O–Pb double chains. Further NCS– anions adopt two different coordination modes: for one thing a μ1,1‐(N) bridging and for another thing a terminal N‐coordination mode. These μ1,1‐NCS– ligands join adjacent PbII atoms forming novel Pb–μ1,1‐(N)CS–Pb bridges, which further extend these Pb–O–Pb double chains into a layered structure. Additionally, an emission band is observed at 481 nm in the solid‐state fluorescence spectrum of 1.
Measurement of d‐2‐hydroxyglutarate dehydrogenase activity in cell homogenates derived from d‐2‐hydroxyglutaric aciduria patients
Authors: Wickenhagen W. V. , Salomons G. S. , Gibson K. M. , Jakobs C. , Struys E. A.
Published: March 2009

d‐2‐Hydroxyglutaric aciduria (d‐2‐HGA) is a neurometabolic disorder characterized by elevated levels of d‐2‐hydroxyglutarate (d‐2‐HG) in physiological fluids. Recent findings revealed that mutations in the D2HGDH gene, encoding d‐2‐hydroxyglutarate dehydrogenase, cause d‐2‐HGA. So far, a functionalenzyme assay to determine d‐2‐hydroxyglutarate dehydrogenase activity, converting d‐2‐HG into 2‐ketoglutarate (2‐KG), has been unavailable. We have now developed a unique enzyme assay for the determination of d‐2‐hydroxyglutarate dehydrogenase activity in cells derived from d‐2‐HGA patients and controls. The enzyme assay was performed using enantiomerically pure stable‐isotope‐labelled d‐2‐hydroxy[3,3,4,4‐2H4]glutarate. This substrate is convertedby d‐2‐hydroxyglutarate dehydrogenase into 2‐[3,3,4,4‐2H4]ketoglutarate, which is subsequently converted into l‐[3,3,4,4‐2H4]glutamate by l‐glutamate dehydrogenase, present in saturating amounts in cell homogenates. Enzyme activities were quantified using LC‐MS/MS. The mean activities in control fibroblast and lymphoblast homogenates were 298 ± 207 and 1670 ± 940 pmol/h per mg protein, respectively. In fibroblast and lymphoblast cell lines derived from patients with pathogenic mutations in the D2HGDH gene, considerably decreased enzyme activities (e.g. <41 pmol/h per mg protein) were found compared with controls. This enzyme assay will have additional utility in further differentiating patients with d‐2‐HGA and l‐2‐HGA and in assessing the residual activities linked to pathogenic mutations in the D2HGDH gene.
Functional magnetic resonance imaging outcomes from a comprehensive magnetic resonance study of children with fetal alcohol spectrum disorders
Authors: Astley Susan J. , Aylward Elizabeth H. , Olson Heather Carmichael , Kerns Kimberly , Brooks Allison , Coggins Truman E. , Davies Julian , Dorn Susan , Gendler Beth , Jirikowic Tracy , Kraegel Paul , Maravilla Kenneth , Richards Todd
Published: March 2009

A comprehensive neuropsychological/psychiatric, MR imaging, (MRI), MR spectroscopy (MRS), and functional MRI (fMRI) assessment was administered to children with fetal alcohol spectrum disorders (FASD) to determine if global and/or focal abnormalities could be identified, and distinguish diagnostic subclassifications across the spectrum. The four study groups included: 1. FAS/Partial FAS; 2. Static Encephalopathy/Alcohol Exposed (SE/AE); 3. Neurobehavioral Disorder/Alcohol Exposed (ND/AE); and 4. healthy peers with no prenatal alcohol exposure. fMRI outcomes are reported here. The neuropsychological/psychiatric, MRI, and MRS outcomes are reported separately. fMRI was used to assess activation in seven brain regions during performance of N-back working memory tasks. Children across the full spectrum of FASD exhibited significant working memory deficits and altered activation patterns in brain regions that are known to be involved in working memory. These results demonstrate the potential research and diagnostic value of this non-invasive MR tool in the field of FASD.
Surgical treatment of traumatic pediatric humeral diaphyseal fractures with titanium elastic nails
Authors: Garg Sumeet , Dobbs Matthew B. , Schoenecker Perry L. , Luhmann Scott J. , Gordon J. Eric
Published: March 2009

Background

Nearly all pediatric humeral shaft fractures can be successfully treated with closed methods. Some patients, however, require internal fixation either because of an inability to maintain an adequate reduction, significant soft tissue injury, or concomitant fractures.

Methods

This is a retrospective review of all traumatic humeral shaft fractures treated at our hospitals between 1999 and 2006. Thirteen pediatric patients ranging in age from 4.8 to 16.7 years (mean age 12.0 years) were treated surgically with titanium elastic nails (TENs). Relative surgical indications included open fractures, inability to maintain an acceptable reduction, the presence of ipsilateral forearm fractures (floating elbow), concomitant lower extremity fractures, and closed head injury. Two patients had associated radial nerve injury at presentation.

Results

The patients were followed for a mean of 29 months. All fractures healed in good alignment. There were no intraoperative complications, including neurologic or vascular injury, and no patient developed an infection postoperatively. Two patients had nail migration, one of whom developed nail protrusion through the skin. One patient with preoperative radial nerve injury ultimately underwent tendon transfer to restore wrist extension. Of the 13 patients, 12 reported a full return to sports and other activities with no limitations or discomfort.

Conclusions

When surgical stabilization of pediatric humeral shaft fractures is indicated, TEN fixation is effective and has a high rate of union and a low rate of complications. This technique is familiar to most orthopaedic surgeons treating pediatric fractures.

Level of evidence

Level of evidence: IV (case series)
Plant Rho‐type (Rop) GTPase‐dependent activation of receptor‐like cytoplasmic kinases in vitro
Authors: Dorjgotov Dulguun , Jurca Manuela E. , Fodor-Dunai Csilla , Szűcs Attila , Ötvös Krisztina , Klement Éva , Bíró Judit , Fehér Attila
Published: March 2009

Plants have evolved distinct mechanisms to link Rho‐type (Rop) GTPases to downstream signaling pathways as compared to other eukaryotes. Here, experimental data are provided that members of the Medicago, as well as Arabidopsis, receptor‐like cytoplasmic kinase family (RLCK Class VI) were strongly and specifically activated by GTP‐bound Rop GTPases in vitro. Deletion analysis indicated that the residues implicated in the interaction might be distributed on various parts of the kinases. Using a chimaeric Rop GTPase protein, the importance of the Rho‐insert region in kinase activation could also be verified. These data strengthen the possibility that RLCKs may serve as Rop GTPase effectors in planta.
Crystal structure of a soluble decoy receptor IL‐22BP bound to interleukin‐22
Authors: de Moura Patricia Ribeiro , Watanabe Leandra , Bleicher Lucas , Colau Didier , Dumoutier Laure , Lemaire Muriel M. , Renauld Jean-Christophe , Polikarpov Igor
Published: March 2009

MINT‐7010533: IL‐22 BP (uniprotkb:Q969J5) and IL‐22 (uniprotkb:Q9GZX6) bind (MI:0407) by X‐ray crystallography (MI:0114)
X‐ray structure of a two‐domain type laccase: A missing link in the evolution of multi‐copper proteins
Authors: Komori Hirofumi , Miyazaki Kentaro , Higuchi Yoshiki
Published: March 2009

A multi‐copper protein with two cupredoxin‐like domains was identified from our in‐house metagenomic database. The recombinant protein, mgLAC, contained four copper ions/subunits, oxidized various phenolic and non‐phenolic substrates, and had spectroscopic properties similar to common laccases. X‐ray structure analysis revealed a homotrimeric architecture for this enzyme, which resembles nitrite reductase (NIR). However, a difference in copper coordination was found at the domain interface. mgLAC contains a T2/T3 tri‐nuclear copper cluster at this site, whereas a mononuclear T2 copper occupies this position in NIR. The trimer is thus an essential part of the architecture of two‐domain multi‐copper proteins, and mgLAC may be an evolutionary precursor of NIR.
The influence of carbohydrate on cognitive performance: a critical evaluation from the perspective of glycaemic load
Authors: Gilsenan Mary B. , de Bruin Eveline A. , Dye Louise
Published: March 2009

Links between nutrition and cognition are widely acknowledged. Within the context of short-term cognitive performance, carbohydrate has been the dietary component most commonly investigated. The majority of studies investigating the influence of carbohydrate on cognitive performance have employed oral glucose drink interventions followed by measures of performance on cognitive tests. More recently, studies have investigated the effect of different carbohydrates on cognitive performance rather than just pure glucose drinks. To date, studies have not been evaluated based on a standardised measure of glycaemic response, such as glycaemic load. The present review provides a critical evaluation of eight studies that have explored the relationships between food carbohydrate and cognitive performance and allow glycaemic load to be used as a basis for comparison. The key finding is that these provide insufficient evidence to support a consistent effect of glycaemic load on short-term cognitive performance. Future studies should employ consistent test methodologies and describe food interventions in more detail to facilitate meaningful comparisons and interpretations of results.
The Morse–Bott inequalities via a dynamical systems approach
Authors: BANYAGA AUGUSTIN , HURTUBISE DAVID E.
Published: March 2009

Let f:M→ℝ be a Morse–Bott function on a compact smooth finite-dimensional manifold M. The polynomial Morse inequalities and an explicit perturbation of f defined using Morse functions fj on the critical submanifolds Cj of f show immediately that MBt(f)=Pt(M)+(1+t)R(t), where MBt(f) is the Morse–Bott polynomial of f and Pt(M) is the Poincaré polynomial of M. We prove that R(t) is a polynomial with non-negative integer coefficients by showing that the number of gradient flow lines of the perturbation of f between two critical points p,q∈Cj of relative index one coincides with the number of gradient flow lines between p and q of the Morse function fj. This leads to a relationship between the kernels of the Morse–Smale–Witten boundary operators associated to the Morse functions fj and the perturbation of f. This method works when M and all the critical submanifolds are oriented or when ℤ2 coefficients are used.