bluuebunny/crossref_metadata_2025 huggingface dataset:
ARFI‐prepared MRgHIFU in liver: Simultaneous mapping of ARFI‐displacement and temperature elevation, using a fast GRE‐EPI sequence
Authors: Auboiroux Vincent , Viallon Magalie , Roland Joerg , Hyacinthe Jean‐Noël , Petrusca Lorena , Morel Denis R. , Goget Thomas , Terraz Sylvain , Gross Patrick , Becker Christoph D. , Salomir Rares
Published: January 2012

MR acoustic radiation force imaging (ARFI) is an elegant adjunct to MR‐guided high intensity focused ultrasound for treatment planning and optimization, permitting in situ assessment of the focusing and targeting quality. The thermal effect of high intensity focused ultrasound pulses associated with ARFI measurements is recommended to be monitored on line, in particular when the beam crosses highly absorbent structures or interfaces (e.g., bones or air‐filled cavities). A dedicated MR sequence is proposed here, derived from a segmented gradient echo‐echo planar imaging kernel by adding a bipolar motion encoding gradient with interleaved alternating polarities. Temporal resolution was reduced to 2.1 s, with in‐plane spatial resolution of 1 mm. MR‐ARFI measurements were executed during controlled animal breathing, with trans‐costal successively steered foci, to investigate the spatial modulation of the focus intensity and the targeting offset. ARFI‐induced tissue displacement measurements enabled the accurate localization, in vivo, of the high intensity focused ultrasound focal point in sheep liver, with simultaneous monitoring of the temperature elevation. ARFI‐based precalibration of the focal point position was immediately followed by trans‐costal MR‐guided high intensity focused ultrasound ablation, monitored with a conventional proton resonance frequency shift MR thermometry sequence. The latter MR thermometry sequence had spatial resolution and geometrical distortion identical with the ARFI maps, hence no coregistration was required. Magn Reson Med, 2012. © 2012 Wiley Periodicals, Inc.
A kinetic model for vessel‐encoded dynamic angiography with arterial spin labeling
Authors: Okell Thomas W. , Chappell Michael A. , Schulz Ursula G. , Jezzard Peter
Published: January 2012

The ability to visualize blood flow in a vessel‐selective manner is of importance in a range of cerebrovascular diseases. Conventional X‐ray methods are invasive and carry risks to the patient. Recently, a noninvasive dynamic angiographic MRI‐based technique has been proposed using vessel‐encoded pseudocontinuous arterial spin labeling, yielding vessel‐selective angiograms of the four main brain‐feeding arteries. In this study, a novel kinetic model for the signal evolution in such acquisitions is derived and applied to healthy volunteers and to a patient with Moya‐Moya disease. The model incorporates bolus dispersion, T1 decay and radio frequency effects and is applicable to other angiographic methods based on continuous or pseudocontinuous arterial spin labeling. The model fits the data well in all subjects and yields parametric maps relating to blood volume, arrival time, and dispersion, changes to which may indicate disease. These maps are also used to generate synthesized images of blood inflow without bias from T1 decay and radio frequency effects, greatly improving collateral vessel visibility in the patient with Moya‐Moya disease. Relative volume flow rates in downstream vessels are also quantified, showing the relative importance of each feeding artery. This framework is likely to be of use in assessing collateral blood flow in patient groups. Magn Reson Med, 2012. © 2012 Wiley Periodicals, Inc.
DANTE‐prepared pulse trains: A novel approach to motion‐sensitized and motion‐suppressed quantitative magnetic resonance imaging
Authors: Li Linqing , Miller Karla L. , Jezzard Peter
Published: January 2012

Delay alternating with nutation for tailored excitation (DANTE) pulse trains are well appreciated as frequency‐selective excitation methods in Fourier transform NMR and for spatial tagging in MRI. In this study, nonselective DANTE pulse trains are used in combination with gradient pulses and short repetition times as motion‐sensitive preparation modules. We show that while the longitudinal magnetization of static tissue is mostly preserved, flowing spins are largely (or fully) attenuated as they fail to establish transverse steady state due to a spoiling effect caused by flow along the applied gradient. The attenuation of flowing spins is effectively insensitive to spin velocity (above a low threshold) and can be approximately quantified with a simple T1 longitudinal magnetization decay model. The relevant analytical equations for moving spins and static spins during DANTE module application are derived for both transient and steady state epochs. The equations are validated by comparing analytical solutions and numerical Bloch equation simulations against experimental observations in phantoms and in vivo. Based on this contrast mechanism, the application of the DANTE preparation to black blood vessel imaging is proposed. A simple demonstration of DANTE black blood imaging modules shows that it provides excellent blood signal suppression and static tissue signal preservation. Magn Reson Med, 2012. © 2012 Wiley Periodicals, Inc.
Fibrillation potential onset in peripheral nerve injury
Authors: Willmott Andrew D. , White Chris , Dukelow Sean P.
Published: January 2012

Introduction:

Fibrillation potentials are an accepted electrical marker of muscle denervation that occur in axonal nerve injury. Clinically, they are used to determine the type of, and prognosis for nerve injuries. The time of occurrence after nerve injury plays a critical role in clinical decision making. This study explores the evolution of the generally accepted guideline that fibrillation potentials occur 1 to 4 weeks after axonal nerve injury. Methods: Pubmed, Ovid, and EMBASE, and current textbooks were reviewed. References were recursively followed back to the initial description of fibrillation potentials. Results: The majority of our understanding regarding the timing of onset of fibrillation potentials appears to arise from animal experiments in the mid‐20th century. Conclusions: Despite frequent use in human clinical care, published evidence for the 1 to 4 week guideline comes almost entirely from animal studies. An appreciation of this background and resulting limitations aids clinical application of this guideline. Muscle Nerve 46: 332–340, 2012
Altered mitogen‐activated protein kinase signaling in dystrophic (mdx) muscle
Authors: Smythe Gayle M. , Forwood Jade K.
Published: January 2012

Introduction:

Duchenne muscular dystrophy (DMD) results from a deficiency in the protein, dystrophin. Dystrophic myotubes are susceptible to stressful stimuli. This may be partly due to altered regulation of pro‐survival signaling pathways, but a role for mitogen‐activated protein (MAP) kinases has not been investigated.

Methods:

We examined patterns of phosphorylation of key MAP kinase proteins in cultured myotubes responding to oxidative stress, and in muscle tissue in vivo.

Results:

Dystrophic (mdx) myotubes have an increased susceptibility to oxidant‐induced death compared with wild‐type (C57Bl/10ScSn) myotubes. This correlates with late phosphorylation of c‐Jun N‐terminal kinase (JNK), and persistently high p38 MAP kinase phosphorylation in mdx myotubes. JNK and extracellular signal‐regulated kinase 1/2 (ERK1/2) also showed altered phosphorylation levels in mdx muscle tissue.

Conclusions:

We show altered patterns of MAP kinase protein phosphorylation in dystrophic muscle in vitro and in vivo. These pathways may be novel pharmacological targets for treating DMD. Muscle Nerve 46: 374–383, 2012
Spatially resolved photocurrent mapping of efficient organic solar cells fabricated on a woven mesh electrode
Authors: Kylberg William , de Castro Fernando Araujo , Chabrecek Peter , Geiger Thomas , Heier Jakob , Nicholson Patrick G. , Nüesch Frank , Theocharous Evangelos , Sonderegger Uriel , Hany Roland
Published: January 2012

Flexible organic photovoltaic devices may soon find applications in various fields, such as portable electronics or building‐integrated photovoltaics, occupying market niches that are currently not covered by the prevailing photovoltaic technology based on silicon and other inorganic materials. For these applications, there is an urgent need to replace the commonly used indium tin oxide by transparent and electrically conductive materials that can be processed cost‐effectively by large‐area compatible printing and coating processes. Here, we fabricated P3HT/PCBM organic solar cells with a power conversion efficiency of 3.1% on a flexible, transparent and conductive woven fabric electrode. The electrode is produced by a roll‐to‐roll process and consists of a polymer‐embedded fibre/metal wire grid. Metal wires protrude as little as 5 µm from the electrode plane, providing electrical contact points on a smooth surface suitable for thin film deposition. The use of spatially resolved photocurrent mapping experiments showed a high level of detailed information, with the unexpected indication that there probably exists a maximum in the cell performance versus mesh size opening and that woven fabric electrodes with largest geometrical open area do not necessarily perform better. Copyright © 2012 John Wiley & Sons, Ltd.
Proteomics and plant disease: Advances in combating a major threat to the global food supply
Authors: Rampitsch Christof , Bykova Natalia V.
Published: January 2012

The study of plant disease and immunity is benefiting tremendously from proteomics. Parallel streams of research from model systems, from pathogens in vitro and from the relevant pathogen‐crop interactions themselves have begun to reveal a model of how plants succumb to invading pathogens and how they defend themselves without the benefit of a circulating immune system. In this review, we discuss the contribution of proteomics to these advances, drawing mainly on examples from crop‐fungus interactions, from Arabidopsis‐bacteria interactions, from elicitor‐based model systems and from pathogen studies, to highlight also the important contribution of non‐crop systems to advancing crop protection.
The current state of microbial proteomics: Where we are and where we want to go
Authors: Chao Tzu‐Chiao , Hansmeier Nicole
Published: January 2012

Proteomics allows the assessment of cellular processes in an unprecedented scale by providing a comprehensive quantitative and qualitative overview of the protein content of a cell. Consequently, proteomics has been employed to investigate a multitude of bacterial processes ranging from the analysis of environmental communities, identification of virulence factors to the proteome‐guided optimization of production strains. Proteomics has, in short, become an indispensable tool for the global analysis of bacterial physiology. Nonetheless, challenges exist, especially in the accurate prediction of phenotypic consequences based on any given proteome composition. In this review, we will give an overview of current highlights in the area of microbial proteomics, discuss some current challenges and present new developments that may help in overcoming them.
Profiling protease activities by dynamic proteomics workflows
Authors: Klingler Diana , Hardt Markus
Published: January 2012

Proteases play prominent roles in many physiological processes and the pathogenesis of various diseases, which makes them interesting drug targets. To fully understand the functional role of proteases in these processes, it is necessary to characterize the target specificity of the enzymes, identify endogenous substrates and cleavage products as well as protease activators and inhibitors. The complexity of these proteolytic networks presents a considerable analytic challenge. To comprehensively characterize these systems, quantitative methods that capture the spatial and temporal distributions of the network members are needed. Recently, activity‐based workflows have come to the forefront to tackle the dynamic aspects of proteolytic processing networks in vitro, ex vivo and in vivo. In this review, we will discuss how mass spectrometry‐based approaches can be used to gain new insights into protease biology by determining substrate specificities, profiling the activity‐states of proteases, monitoring proteolysis in vivo, measuring reaction kinetics and defining in vitro and in vivo proteolytic events. In addition, examples of future aspects of protease research that go beyond mass spectrometry‐based applications are given.
Electron transfer dissociation mass spectrometry in proteomics
Authors: Kim Min‐Sik , Pandey Akhilesh
Published: January 2012

Mass spectrometry has rapidly evolved to become the platform of choice for proteomic analysis. While CID remains the major fragmentation method for peptide sequencing, electron transfer dissociation (ETD) is emerging as a complementary method for the characterization of peptides and post‐translational modifications (PTMs). Here, we review the evolution of ETD and some of its newer applications including characterization of PTMs, non‐tryptic peptides and intact proteins. We will also discuss some of the unique features of ETD such as its complementarity with CID and the use of alternating CID/ETD along with issues pertaining to analysis of ETD data. The potential of ETD for applications such as multiple reaction monitoring and proteogenomics in the future will also be discussed.
Sensitivity to silthiofam, tebuconazole and difenoconazole of Gaeumannomyces graminis var. tritici isolates from China
Authors: Yun Yingzi , Yu Fangwei , Wang Ning , Chen Huaigu , Yin Yanni , Ma Zhonghua
Published: January 2012

BACKGROUND: Wheat take‐all caused by Gaeumannomyces graminis var. tritici (Ggt) has become an emerging threat to wheat production in the last few years. Silthiofam is very effective against Ggt, and recently it has been widely used for the control of take‐all in China. However, farmers have noted a decline in control efficacy with this compound in some wheat fields, suggesting that the pathogen may have developed resistance to silthiofam.

RESULTS: Of the 66 Ggt isolates collected from different locations in China, 27 were resistant to silthiofam. There was no cross‐resistance between silthiofam and tecuconazole or difenoconazole. The effectiveness of silthiofam in controlling take‐all was compromised on wheat inoculated with silthiofam‐resistant isolates. Based on the DNA fingerprinting generated by microsatellite PCR, two predominant genetic clusters were found among these isolates and were clearly associated with the sensitivity to silthiofam.

CONCLUSION: Silthiofam has a high risk in the development of resistance in Ggt. Tebuconazole and difenoconazole show great potential for control of take‐all on wheat. Results from this study provide useful information for take‐all control and the management of fungicide resistance. Copyright © 2012 Society of Chemical Industry
Impact of buffer growth on crystalline quality of GaN grown on Si(111) substrates
Authors: Drechsel Philipp , Stauss Peter , Bergbauer Werner , Rode Patrick , Fritze Stephanie , Krost Alois , Markurt Toni , Schulz Tobias , Albrecht Martin , Riechert Henning , Steegmüller Ulrich
Published: January 2012

In this work we focus on the impact of different buffer and nucleation layers on the corresponding crystalline quality of gallium nitride (GaN), grown by metal‐organic chemical vapour deposition (MOCVD). In situ curvature measurements, X‐ray diffraction (XRD) and transmission electron microscopy (TEM) are used for advanced characterization. The influence of various growth modes on meltback etching and cracking is analyzed. Also the effect of a silicon nitride (SiN) mask on the growth of GaN and its coalescence is investigated. Furthermore, associated potential consequences for the growth of aluminium nitride (AlN) interlayers are examined to obtain a homogeneous surface without cracks and with good crystalline quality. Our studies indicate that an incomplete coalesced GaN surface located underneath the AlN interlayer leads to an increased defect density. Additionally we studied the influence of growth temperature at nucleation on the material quality and the process stability. Finally we demonstrate interlayer induced compressive strain during GaN growth with an XRD rocking‐curve full width half maximum (FWHM) as low as 450 arc seconds for the $10{\bar {1}}2$ reflection.
Comparison study of N‐ and In‐polar {0001} InN layers grown by MOVPE
Authors: Dinh Duc V. , Pristovsek M. , Solopow S. , Skuridina D. , Kneissl M.
Published: January 2012

We compare InN layers grown directly on c ‐plane (0001) sapphire and on (0001) GaN templates using metal‐organic vapor phase epitaxy. InN grown on nitridated c ‐plane sapphire showed N‐polarity, while InN grown on c ‐plane GaN templates showed In‐polarity. N‐polar and In‐polar InN layers showed different surface morphology and crystallinity. N‐polar InN was smoothest when grown at higher growth temperatures, while In‐polar InN was smoothest at intermediate growth temperatures. Growth mode of the N‐polar InN on sapphire is Frank‐Van der Merwe, while growth mode of the In‐polar InN on GaN templates is Volmer‐Weber. Electrical properties were similar for both layers. Lowtemperature photoluminescence of In‐polar InN layers is shifted to higher energies most likely due to biaxial compressive stresses. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Current‐voltage measurement of AlxIn1‐xN/AlN/GaN heterostructures
Authors: Pandey Saurabh , Fraboni Beatrice , Cavalcoli Daniela , Minj Albert , Cavallini Anna
Published: January 2012

Current‐voltage measurements with Schottky contacts in a planar back‐to‐back configuration have been performed for InAlN/AlN/GaN heterostructures with different AlN interlayer thicknesses. We have identified the onset of a 2‐dimensional electron gas (2DEG) controlled conduction from current‐voltage curves analyses. A model has been proposed to determine the 2DEG electrical properties and the effects of the AlN thickness on the measured current‐voltage curves have been discussed. The 2DEG properties extracted from current‐voltage analyses have been compared with Hall measurements which shows excellent agreement in values. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Structural, chemical, and electrical characterization of indium nitride produced by pulsed laser ablation
Authors: Orlando Stefano , Santagata Antonio , Parisi Giovanni Pompeo , Medici Luca , Kaciulis Saulius , Mezzi Alessio , Bellucci Alessandro , Cappelli Emilia , Trucchi Daniele Maria
Published: January 2012

The peculiar electronic characteristics of indium nitride offers great technological potential for novel device applications in several areas such as: multi‐junction solar cells, terahertz emitters, chemical sensors, and light emitting diodes. Reactive pulsed laser ablation has been used to deposit indium nitride thin films for its versatility. The laser source employed has been a Nd:YAG (∼8 ns, 532 nm, 10 Hz) performing the ablation in a RF‐generated nitrogen plasma. Thin films have been deposited varying some parameters such as the substrate temperature, the nitrogen gas pressure, and the RF power. Structural (XRD) and chemical (XPS) characterizations have been performed. Electrical resistivity of the films has been evaluated to correlate structural and chemical properties to the electrical ones. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Low loss EEL spectroscopy performed on InxAl1‐xN layers grown by MOVPE: comparison between experiment and ab‐initio calculations
Authors: Letrouit A. , Kret S. , Ivaldi F. , Carlin J. F. , Kaufman N. A. K. , Grandjean N. , Górecka J.
Published: January 2012

We present Electron Energy‐Loss Spectroscopy (EELS) studies of InxAl1‐xN MOVPE epilayers containing 16‐28 at% of indium. EELS investigations show a significant change of the plasmon energy (Ep) with the indium concentration. In the case of these compounds, the results have been compared for the first time with ab‐initio calculations performed with Wien2k and present a good agreement. Ep follows a linear relation with respect to composition allowing the correct identification of the spectra features. The acquisitions of the low‐loss EELS spectra have been performed in the homogeneous area for all the InxAl1‐xN samples. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
InGaN/GaN quantum wells grown on freestanding HfO2 photonic crystals
Authors: Wang Yongjin , Wu Tong , Hu Fangren , Zhu Hongbo , Hane Kazuhiro
Published: January 2012

We report here epitaxial growth of InGaN/GaN quantum wells (QWs) on suspended HfO2 photonic crystal structures by molecular beam epitaxy (MBE). Suspended HfO2 photonic crystals are achieved on silicon substrate by combining film evaporation, electron beam lithography, fast atom beam etching of HfO2 film with dry etching of silicon substrate. InGaN/GaN QWs are subsequently grown on suspended HfO2 photonic crystal structures by MBE technique, and freestanding HfO2 photonic crystal slab can sustain complicated stress change during MBE growth. The reflectance and photoluminescence measurements are performed for epitaxial III‐nitride structures (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical studies of GaN nanocolumns containing InGaN quantum disks and the effect of strain relaxation on the carrier distribution
Authors: Holmes Mark J. , Park Young S. , Wang Xu , Chan Christopher C. S. , Reid Benjamin P. L. , Kim HeeDae , Luo Jun , Warner Jamie H. , Taylor Robert A.
Published: January 2012

The optical properties of GaN nanocolumns containing pairs of InxGa1–xN (x ∼ 0.1) quantum disks (QDisks) have been experimentally measured. Strain simulations reveal an inhomogeneous distribution of strain, and furthermore, a relaxation between successive QDisks along the growth direction of the column. Although this inhomogeneous distribution of strain may indicate a lateral separation of carriers in the QDisk, the decay lifetime of the emission suggests far less carrier separation. The quantum confined stark effect is found to create an inhomogeneous distribution of charge within the QDisks along the growth direction of the rod. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effect of hole injection in AlGaN/GaN HEMT with GIT structure by numerical simulation
Authors: Chonan Hiroshi , Ide Toshihide , Shen Xu‐Qiang , Shimizu Mitsuaki
Published: January 2012

The numerical simulation of the AlGaN/GaN HEMT with GIT structure is performed while varying the radiative recombination lifetime of electron and hole, and the conductivity modulation in the channel by the hole injection from the gate electrode is investigated. When the radiative recombination lifetime is long, two peaks in the transconductance curve, gm vs. VG is found, and the hole injection from the gate electrode is enhanced. The accumulation of hole is found in the GaN layer under the channel around the source electrode, and the conductivity modulation is significant at the source‐gate region and at the drain side of the gate electrode. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Reduction of peak electric field strength in GaN‐HEMT with carbon doping layer
Authors: Narita Tetsuo , Kikuta Daigo , Iguchi Hiroko , Ito Kenji , Tomita Kazuyoshi , Uesugi Tsutomu , Kachi Tetsu
Published: January 2012

We propose a reduction in the peak electric field strength at the drain side of the gate electrode in a high‐electron mobility transistor using a carbon‐doped GaN layer. Simulation results indicated that the peak electric field strength decreased with decrease in the spacing between the 2‐dimensional electron gas (2DEG) channel and the carbon doped GaN layer due to the acceptor‐like states of carbon. Experimental results supported the simulation results by the higher breakdown voltages obtained with smaller spacing layers. Current collapse phenomena were relatively suppressed with a 0.5 µm thick spacing layer compared to 2 or 3 µm thick spacing layers, due to reduction of the electric field strength. From these results, we could conclude that the carbon doped GaN layer enables the combination of high breakdown voltage and low current collapse by improved design of the spacing between the channel and the carbon containing layer in a GaN‐based device (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Faceting in AlN bulk crystal growth and its impact on optical properties of the crystals
Authors: Bickermann Matthias , Epelbaum Boris M. , Filip Octavian , Tautz Barbara , Heimann Paul , Winnacker Albrecht
Published: January 2012

The surface of bulk AlN single crystals grown by PVT on Al‐polar (0001) seeds is typically constructed from prismatic, pyramidal, and basal plane facets. Simultaneous growth on different facets with different surface kinetics leads to formation of a zonar structure which is visible due to local differences in coloration in the wafers. Four zones on an AlN wafer representing (1) growth on {1013} pyramidal facets, (2) growth adjacent to ridges and (0001) basal plane facets, and (3) + (4) outer and centre areas corresponding to surface depressions are investigated. They show striking differences in optical absorption (OA) spectra, cathodoluminescence (CL) spectra and chemical analysis (SIMS). In areas near ridges and (0001) facets and in centres of depressions, deep‐UV absorption as well as luminescence is significantly increased. We assign OA and CL bands observed in these zones to the presence of carbon and/or the lack of oxygen due to local segregation effects caused by faceting. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Higher output power of near‐ultraviolet LED grown on GaN substrate with back‐side etching
Authors: Fang Yen‐Hsiang , Fu Yi‐Keng , Xuan Rong , Jiang Ren‐Hao , Lin Chia‐Feng
Published: January 2012

The 405 nm near‐ultra violet (NUV) InGaN/GaN multiple‐quantum‐well light‐emitting diodes (LEDs) grown on GaN substrate with a roughened backside on the N‐face surface of GaN substrate were fabricated through a chemical wet‐etching process to increase light‐extraction efficiency. The stable crystallographic etching planes were formed as the GaN {1011} planes. The back‐side etching NUV LEDs had larger output power than that of conventional NUV‐LEDs, NUV‐LEDs with wider wells, and NUV‐LEDs grown on pattern sapphire substrate.

When the NUV LED were operated as a forward current of 20 mA, the increasing output power of back‐side etching NUV LEDs was about 70%, 106%, and 8% than that of conventional NUV‐LEDs, NUV‐LEDs with wider wells, and NUV‐LEDs grown on pattern sapphire substrate (PSS), respectively. This larger enhancement result from the improved light extraction attributed to the different transmittance as hexagonal pyramid on N‐face GaN was etched (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Valence band offsets at oxide/InN interfaces determined by X‐ray photoelectron spectroscopy
Authors: Eisenhardt Anja , Eichapfel Georg , Himmerlich Marcel , Knübel Andreas , Passow Thorsten , Wang Chunyu , Benkhelifa Fouad , Aidam Rolf , Krischok Stefan
Published: January 2012

The valence band offset (VBO) at the interface between indium nitride (InN) and selected oxide materials (Al2O3, TiO2, In2O3 and HfO2) is determined using X‐ray photoelectron spectroscopy (XPS). For exact VBO determination, InN samples with oxide cap layers of varying thickness are investigated. The VBO values are extrapolated by linear regression of the thickness dependent energetic distances ΔE between the valence band maxima (VBM) at the oxide and InN surface and their corresponding heterointerface. The determined VBO values are (2.7 ± 0.2) eV for Al2O3/InN, (1.8 ± 0.2) eV for TiO2/InN, (1.5 ± 0.2) eV for In2O3/InN, (1.3 ± 0.2) eV for e‐beam evaporated HfO2 on InN, and (2.0 ± 0.2) eV for atomic layer deposited HfO2 on InN. In some cases the oxide deposition process leads to an oxidation of the InN film at the oxide/InN interface (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Responsivity and photocurrent dynamics in single GaN nanowires
Authors: González‐Posada F. , Songmuang R. , Den Hertog M. , Monroy E.
Published: January 2012

We report on the photocurrent behaviour of single GaN n+‐n ‐n+ nanowires (NWs) grown by plasma‐assisted molecular‐beam epitaxy on Si(111). The ultraviolet (350 nm) to visible (450 nm) responsivity ratio is larger than three orders of magnitude. A relevant feature is that the photocurrent scales sublinearly with optical power, following a I ∼ Pα (α < 1) law in all the measured range, with α increasing with the measuring frequency. The photocurrent time response remains in the tens/hundreds of millisecond range, in contrast to the persistent (hours) photoconductivity effects observed in two‐dimensional photoconductors. The NW performance is independent of the measuring atmosphere, either in the air or in vacuum. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Integrated high reflectivity silicon substrates for GaN LEDs
Authors: Arkun F. Erdem , Dargis Rytis , Smith Robin , Williams David , Clark Andrew , Lebby Michael
Published: January 2012

Growth of GaN on epitaxial distributed Bragg reflectors (DBR) capable of 80% reflectivity at typical III‐N based LED operating wavelengths is presented. Such structures are formed by growing single crystal multilayers of gadolinium oxide‐silicon stacks on silicon (111) substrates. The large refractive index difference between gadolinium oxide and silicon (Δn = 2.2) allows highly reflective DBR mirrors to be achieved at as little as three periods. Growth of GaN is demonstrated on the DBR mirrors making these structures suitable for GaN based LED growth. DBR mirrors embedded in this engineered substrate act as a reflecting mirror for incident light from a LED grown on top of this substrate. This potentially allows increased light extraction and higher output power from these LEDs compared to that of similar LEDs grown on silicon substrates. Performance of DBR mirrors with GaN top layers as a function of the incident angle of a 488 nm laser is investigated. X‐ray diffraction and TEM are used for structural characterization of these grown structures. This engineered substrate, Mirrored SiliconTM, is suitable for high volume manufacturing at 150 and 200 mm wafers sizes. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A contextual theory of organizational learning from failures and successes: A study of acquisition completion in the global newspaper industry, 1981–2008
Authors: Muehlfeld Katrin , Rao Sahib Padma , Van Witteloostuijn Arjen
Published: January 2012

This study develops and tests theory about the context‐specificity and outcome‐dependence of experiential learning in acquisition processes. First, we investigate whether learning from experience gained in different acquisition contexts is limited to influencing subsequent outcomes of same‐context transactions. Second, we analyze whether learning patterns in response to prior successes and failures differ across acquisition contexts, depending on two properties of these contexts—the degree of structural variance and the level of stimulation of deliberate learning. Learning is assessed with respect to an underexplored organizational goal variable in acquisitions: completion of a publicly announced transaction. An analysis of 4,973 acquisition attempts in the newspaper industry in 1981–2008 largely supports our theory. Copyright © 2012 John Wiley & Sons, Ltd.
Multiscale models of thrombogenesis
Authors: Xu Zhiliang , Kim Oleg , Kamocka Malgorzata , Rosen Elliot D. , Alber Mark
Published: January 2012

To restrict the loss of blood follow from the rupture of blood vessels, the human body rapidly forms a clot consisting of platelets and fibrin. However, to prevent pathological clotting within vessels as a result of vessel damage, the response must be regulated. Clots forming within vessels (thrombi) can restrict the flow of blood causing damage to tissues in the flow field. Additionally, fragments dissociating from the primary thrombus (emboli) may lodge and clog vessels in the brain (causing ischemic stroke) or lungs (resulting in pulmonary embolism). Pathologies related to the obstruction of blood flow through the vasculature are the major cause of mortality in the United States. Venous thromboembolic disease alone accounts for 900,000 hospitalizations and 300,000 deaths per year and the incidence will increase as the population ages (Wakefield et al. J Vasc Surg 2009, 49:1620–1623). Thus, understanding the interplay between the many processes involved in thrombus development is of significant biomedical value. In this article, we first review computational models of important subprocesses of hemostasis/thrombosis including coagulation reactions, platelet activation, and fibrin assembly, respectively. We then describe several multiscale models integrating these subprocesses to simulate temporal and spatial development of thrombi. The development of validated computational models and predictive simulations will enable one to explore how the variation of multiple hemostatic factors affects thrombotic risk providing an important new tool for thrombosis research. WIREs Syst Biol Med 2012 doi: 10.1002/wsbm.1160

This article is categorized under:

Models of Systems Properties and Processes > Cellular Models

Developmental Biology > Developmental Processes in Health and Disease

Physiology > Mammalian Physiology in Health and Disease

Biological Mechanisms > Regulatory Biology
Translating India
Authors: Kothari Rita
Published: January 2012

Post nineteen eighties, what made English translation from Indian languages a culturally desirable activity? This question leads Kothari to examine the changing cultural universe of urban, English-speaking middle class in India. She examines in detail readership patterns, attitudes to English, and the course of translation studies in general. The comfort with which English is used with an Indian language as in "Yeh Dil Maange More" or "Hungry Kya" reflects a sense of familiarity that has been made with English. From this broader context of bilingualism in the first part of the book, Kothari moves on to the state of Gujarat. Taking up the case of Gujarati, she demonstartes the micro issues involved in translations and politics of language. Kothari asks new questions in translation studies and makes the production, reception and marketability of English translation her chief concern. Translating India brings amultidisciplinary perspective to literature and translation, authenticity and representation.
Changing Strategies for Child Welfare, Enduring Beliefs about Childhood: The Fresh Air Fund, 1877–1926
Authors: Guarneri Julia
Published: January 2012

In 1877, a Congregational pastor started a modest effort to send New York City tenement children on two-week summer vacations in country homes. The pastor's Fresh Air Fund grew, in the following decades, into a hugely popular program and a celebrated cause. The charity thrived in part because its simple project adapted well to several different reform environments. The fund made a place for itself in the evangelical child-saving efforts of the Gilded Age, the civic-minded reforms of the Progressive Era, and the more individualistic pursuits of the 1920s. In each era, fund leaders cast country vacations as simple means to address middle-class New Yorkers' fears about their changing city, from the influx of immigrants to the spread of disease to rising class tensions.

Tracking the Fresh Air Fund over fifty years reveals the sea changes in child-welfare work between 1877 and 1927, but it also calls attention to continuities often overlooked in the history of child welfare. Throughout the Gilded Age and Progressive Era, the fund tapped supporters' constant and deep-seated beliefs in children's potential, the restorative power of the outdoors, and a child's right to play.
Carbon dioxide emissions from Indian monsoonal estuaries
Authors: Sarma V. V. S. S. , Viswanadham R. , Rao G. D. , Prasad V. R. , Kumar B. S. K. , Naidu S. A. , Kumar N. A. , Rao D. B. , Sridevi T. , Krishna M. S. , Reddy N. P. C. , Sadhuram Y. , Murty T. V. R.
Published: January 2012

Estuaries are known to be strong source for atmospheric CO2, however, little information is available from Indian estuaries. In order to quantify CO2 emissions from the Indian estuaries, samples were collected at 27 estuaries all along the Indian coast during discharge (wet) period. The emissions of CO2 to the atmosphere from Indian estuaries were 4–5 times higher during wet than dry period. The pCO2 ranged between ∼300 and 18492 μatm which are within the range of world estuaries. The mean pCO2 and particulate organic carbon (POC) showed positive relation with rate of discharge suggesting availability of high quantities of organic matter that led to enhanced microbial decomposition. The annual CO2 fluxes from the Indian estuaries, together with dry period data available in the literature, amounts to 1.92 TgC which is >10 times less than that from the European estuaries. The low CO2 fluxes from the Indian estuaries are attributed to low flushing rates and less human settlements along the banks of the Indian estuaries.
Application of a data‐assimilation model to variability of Pacific sardine spawning and survivor habitats with ENSO in the California Current System
Authors: Song Hajoon , Miller Arthur J. , McClatchie Sam , Weber Edward D. , Nieto Karen M. , Checkley David M.
Published: January 2012

The Pacific sardine (Sardinops sagax) showed significant differences in spawning habitat area, spawning habitat quality and availability of survivor habitat as the Pacific Ocean went through the La Niña state in April 2002 to a weak El Niño in April 2003. During another El Niño/Southern Oscillation transition period in 2006–2007 when the El Niño state retreated and the La Niña returned, a similar pattern in spawning habitat quality was seen. The coupling between the atmospheric forcing, the physical ocean states and the properties of the sardine egg spawning are investigated using dynamically consistent data‐assimilation fits of the available physical oceanographic observations during these months. Fits were executed using the Regional Ocean Modeling System four‐dimensional variational assimilation platform along with adjoint model runs using a passive tracer to deduce source waters for the areas of interest. Analysis using the data‐assimilation model runs reveals that unusually strong equatorward wind‐forcing drives offshore transport during the La Niña conditions, which extends the spawning habitat for sardine further offshore. A statistical model of sardine spawning habitat shows better habitat quality during the El Niño conditions, which is associated with higher egg densities and corresponded to higher daily egg production. Concentration of eggs is also increased by convergence of water. The results of the source waters analysis using the adjoint data assimilation model support the idea that offshore transport extends the spawning habitat, and show that higher levels of nutrient are brought into the spawning habitat with high concentration of sardine eggs.
Large‐scale circulation features in the tropical western Pacific and their representation in climate models
Authors: Smith Ian N. , Moise Aurel F. , Colman Robert A.
Published: January 2012

Within the Western Pacific Monsoon (WPM) region the zonal component of the low‐level winds tends to weaken and reverse from east to west during the peak monsoon season, which also marks a peak in rainfall. This study examines how well climate models can simulate these phenomena prior to evaluating their projections for later this century. While a seasonal wind reversal or weakening appears to be reasonably well simulated by most models over much of the WPM, the relationships between large‐scale average winds and rainfall are not always well simulated. This allows us to discriminate among the models in order to see if this affects the projections. However, it so happens that this has relatively little effect, and the predominant signal is for an increase in rainfall with a weakening or negligible change to the low‐level monsoon winds. These results indicate that the WPM climate will respond more to global scale drivers such as an increase in atmospheric water vapor content and a weakening of the global circulation, rather than to more regional changes such as an increase in the land/ocean temperature contrast.
Characteristics of upward positive lightning flashes initiated from the Gaisberg Tower
Authors: Zhou Helin , Diendorfer Gerhard , Thottappillil Rajeev , Pichler Hannes , Mair Martin
Published: January 2012

We report the measured current characteristics of positive lightning discharges to the Gaisberg Tower (GBT) in Austria from 2000 to 2009. On the basis of the recorded current waveforms, a total of 26 flashes consisting of initial stage only were identified as upward positive discharges initiated by an upward negative leader from GBT. They accounted for 4% (26/652) of the total flashes recorded at the GBT. Nineteen (73%) out of the 26 positive flashes occurred during nonconvective season (September–March). Median values of flash peak current, flash duration, charge transfer, and action integral were determined as 5.2 kA, 82 ms, 58 C, and 0.16 × 103 A2 s, respectively. Current pulses of high repetition rate superimposed on the initial portion of initial continuous current are inferred to be associated with the upward negative stepped leader process. The weighted arithmetic means of leader pulse peak current, leader pulse duration, leader interpulse interval, and leader pulse charge are 3 kA, 31 μs, 32 μs, and 42 mC, respectively. On the basis of an assumed stepped leader speed in the range of 8 × 104 to 4.5 × 105 m/s an upward negative stepped leader channel charge density of 15–87 mC/m, a leader length of 168–945 m, and an average leader step length of 2.4–13.3 m were estimated. The upward negative stepped leader channel charge density and length are significantly larger and smaller than their counterparts in downward negative stepped leaders, respectively, while the upward leader step length is consistent with previous studies. Possible reasons for this are discussed.
Revisiting the role of magnetic field fluctuations in nonadiabatic acceleration of ions during dipolarization
Authors: Nosé M. , Ono Y. , Christon S. P. , Lui A. T. Y.
Published: January 2012

Using energetic (9–212 keV/e) ion flux data obtained by the Geotail spacecraft, Ono et al. (2009) statistically examined changes in the energy density of H+ and O+ ions in the near‐Earth plasma sheet during substorm‐associated dipolarization. They found that ions are nonadiabatically accelerated by the electric field induced by the magnetic field fluctuations whose frequencies are close to their gyrofrequencies. The present paper revisits this result and finds it still holds.
Emerging journals
Authors: Meneghini Rogerio
Published: January 2012

Emerging countries have established national scientific journals as an alternative publication route for their researchers. However, these journals eventually need to catch up to international standards.
Research and practice coming together
Authors: Hunter Philip
Published: January 2012

Clinical research and clinical practice have been separated for too long. They need to be brought together again to improve health care and better benefit patients.
In situ proteo-metabolomics reveals metabolite secretion by the acid mine drainage bio-indicator, Euglena mutabilis
Authors: Halter David , Goulhen-Chollet Florence , Gallien Sébastien , Casiot Corinne , Hamelin Jérôme , Gilard Françoise , Heintz Dimitri , Schaeffer Christine , Carapito Christine , Van Dorsselaer Alain , Tcherkez Guillaume , Arsène-Ploetze Florence , Bertin Philippe N
Published: January 2012

Euglena mutabilis is a photosynthetic protist found in acidic aquatic environments such as peat bogs, volcanic lakes and acid mine drainages (AMDs). Through its photosynthetic metabolism, this protist is supposed to have an important role in primary production in such oligotrophic ecosystems. Nevertheless, the exact contribution of E. mutabilis in organic matter synthesis remains unclear and no evidence of metabolite secretion by this protist has been established so far. Here we combined in situ proteo-metabolomic approaches to determine the nature of the metabolites accumulated by this protist or potentially secreted into an AMD. Our results revealed that the secreted metabolites are represented by a large number of amino acids, polyamine compounds, urea and some sugars but no fatty acids, suggesting a selective organic matter contribution in this ecosystem. Such a production may have a crucial impact on the bacterial community present on the study site, as it has been suggested previously that prokaryotes transport and recycle in situ most of the metabolites secreted by E. mutabilis. Consequently, this protist may have an indirect but important role in AMD ecosystems but also in other ecological niches often described as nitrogen-limited.
Identification of a novel cyanobacterial group as active diazotrophs in a coastal microbial mat using NanoSIMS analysis
Authors: Woebken Dagmar , Burow Luke C , Prufert-Bebout Leslie , Bebout Brad M , Hoehler Tori M , Pett-Ridge Jennifer , Spormann Alfred M , Weber Peter K , Singer Steven W
Published: January 2012

N2 fixation is a key process in photosynthetic microbial mats to support the nitrogen demands associated with primary production. Despite its importance, groups that actively fix N2 and contribute to the input of organic N in these ecosystems still remain largely unclear. To investigate the active diazotrophic community in microbial mats from the Elkhorn Slough estuary, Monterey Bay, CA, USA, we conducted an extensive combined approach, including biogeochemical, molecular and high-resolution secondary ion mass spectrometry (NanoSIMS) analyses. Detailed analysis of dinitrogenase reductase (nifH) transcript clone libraries from mat samples that fixed N2 at night indicated that cyanobacterial nifH transcripts were abundant and formed a novel monophyletic lineage. Independent NanoSIMS analysis of 15N2-incubated samples revealed significant incorporation of 15N into small, non-heterocystous cyanobacterial filaments. Mat-derived enrichment cultures yielded a unicyanobacterial culture with similar filaments (named Elkhorn Slough Filamentous Cyanobacterium-1 (ESFC-1)) that contained nifH gene sequences grouping with the novel cyanobacterial lineage identified in the transcript clone libraries, displaying up to 100% amino-acid sequence identity. The 16S rRNA gene sequence recovered from this enrichment allowed for the identification of related sequences from Elkhorn Slough mats and revealed great sequence diversity in this cluster. Furthermore, by combining 15N2 tracer experiments, fluorescence in situ hybridization and NanoSIMS, in situ N2 fixation activity by the novel ESFC-1 group was demonstrated, suggesting that this group may be the most active cyanobacterial diazotroph in the Elkhorn Slough mat. Pyrotag sequences affiliated with ESFC-1 were recovered from mat samples throughout 2009, demonstrating the prevalence of this group. This work illustrates that combining standard and single-cell analyses can link phylogeny and function to identify previously unknown key functional groups in complex ecosystems.