bluuebunny/crossref_metadata_2025 huggingface dataset:
GabiPD: GABI primary database - a plant integrative 'omics' database
Authors: Riaño-Pachón Diego Mauricio , Nagel Axel , Wagner Robert , Neigenfind Jost , Weber Elke , Diehl Svenja , Kersten Birgit
Published: August 2008

The GABI Primary Database, GabiPD, was established eight years ago in the frame of the German initiative for Genome Analysis of the Plant Biological System (Genomanalyse im biologischen System Pflanze, GABI), funded by the German Federal Ministry of Education, Research and Technology (BMBF) as well as a number of private enterprise companies. The main goal of GabiPD is to collect, integrate, visualize and link primary information from GABI projects. GabiPD, in contrast to other plant databases constitutes a repository and analysis platform for a wide array of heterogeneous data arising from high-throughput experiments in several plant species. Currently, data from different 'omics' fronts are incorporated in GabiPD (i.e., genomics, transcriptomics, metabolomics, proteomics), originating from 14 different model or crop species. We have developed the concept of GreenCards for text based retrieval of all data types in GabiPD (e.g., clones, genes, mutant plant lines, markers). All data types are pointing to the central Gene’s GreenCard, where gene information is integrated from genome annotation projects. Within the Gene’s GreenCards links to all GabiPD data related to the corresponding genes as well as cross references to large UniGene sets from NCBI and to useful gene-based external data bases are displayed. A collection of ~400000 ESTs from different species, generated in different GABI projects, is made publicly available though GabiPD. These ESTs have been cross referenced to UniGene sets from NCBI and to sequences from different plant genome projects, in an effort to ease the transfer of functional information. The centralized Gene's GreenCard also allows visualizing ESTs aligned to annotated transcripts as well as identified protein domains and gene structure. Moreover GabiPD makes available interactive genetic maps from Solanum tuberosum (potato) and Hordeum vulgare (barley). Gene expression data in GabiPD can be visualized through MapManWeb, the web interface of MapMan. Access to the data in GabiPD is provided via either the web interface (http://www.gabipd.org) or webservices that are currently available for Arabidopsis-related information. GabiPD was accessed by more than 30000 unique visitors last year from around the world.
Ion distribution in multilayers of weak polyelectrolytes: A neutron reflectometry study
Authors: Tanchak Oleh M. , Yager Kevin G. , Fritzsche Helmut , Harroun Thad , Katsaras John , Barrett Christopher J.
Published: August 2008

Neutron reflectometry was used to determine the distribution of salt ions and water in thin poly(acrylic acid) and poly(allylamine hydrochloride) polyelectrolyte multilayers assembled with and without salt. Increasing salt concentration reverses the exclusion of water from the substrate region, eventually leading to an asymmetric segregation of water near the substrate at high salt concentration. The counterions were found to localize near the substrate in films that were either assembled with salt or were exposed to salt solutions. In addition, the capping layer of the film was found to greatly influence the counterion distribution in the multilayer.
Optical response of a metal-semiconductor field effect transistor in the presence of interface states and interfacial layer at the gate contact
Authors: Chattopadhyay P. , Pal J. , Das K.
Published: August 2008

A simple analytical model on the electrical characteristics of a metal-semiconductor field effect transistor under optical illumination has been proposed by considering the inherent effects of interface states and interfacial layer at the gate-channel interface. The drain current of the device under optical illumination has been studied by treating optically generated carriers within the framework of a model that concerns arbitrary charge distribution in the channel region. It has been found that for a metal of relatively higher work function acting as the gate contact of the device, the drain current increases with increasing interface state density. An expression for the threshold voltage of the device has been derived and its dependence on the interface state density has been studied. It has been found that both the channel current and threshold voltage of the device increase appreciably under illuminated condition.
Infrared photodissociation spectroscopy and density-functional calculations of protonated methanol cluster ions: Solvation structures of an excess proton
Authors: Tono Kensuke , Kuo Jer-Lai , Tada Masanori , Fukazawa Koudai , Fukushima Naoya , Kasai Chiharu , Tsukiyama Koichi
Published: August 2008

Solvation structures of an excess proton in protonated methanol cluster ions, H+(CH3OH)n (n=5–8), were investigated by photodissociation spectroscopy in the middle infrared region (900–2300 cm–1) and by using density-functional theory. This work indicates that the excess proton is delocalized between two methanol molecules. Spectral features observed in the range 1400–1800 cm–1 are attributed to vibrational modes involving collective motion of the shared proton and the two ligand molecules. At n=6–8, broad spectral features in the region above 1800 cm–1 suggest coexistence of isomers in which the excess proton and a methanol molecule are tightly bound to form an ion core, CH3OH2+.
Colloids dragged through a polymer solution: Experiment, theory, and simulation
Authors: Gutsche Christof , Kremer Friedrich , Krüger Matthias , Rauscher Markus , Weeber Rudolf , Harting Jens
Published: August 2008

We present microrheological measurements of the drag force on colloids pulled through a solution of λ-DNA (used here as a monodisperse model polymer) with an optical tweezer. The experiments show a drag force that is larger than expected from the Stokes formula and the independently measured viscosity of the DNA solution. We attribute this to the accumulation of DNA in front of the colloid and the reduced DNA density behind the colloid. This hypothesis is corroborated by a simple drift-diffusion model for the DNA molecules, which reproduces the experimental data surprisingly well, as well as by corresponding Brownian dynamics simulations.
Effect of limiting the cathode surface on direct current microhollow cathode discharge in helium
Authors: Dufour T. , Dussart R. , Lefaucheux P. , Ranson P. , Overzet L. J. , Mandra M. , Lee J.-B. , Goeckner M.
Published: August 2008

This paper describes how to light several microdischarges in parallel without having to individually ballast each one. The V-I curve of a microhollow cathode discharge is characterized by a constant voltage in the normal glow regime because the plasma is able to spread over the cathode surface area to provide the additional secondary electrons needed. If one limits the cathode surface area, the V-I characteristic can be forced into an abnormal glow regime in which the operating voltage must increase with the current. It is then possible to light several microdischarges mounted in parallel without ballasting them individually.
Effects of fluorine incorporation and forming gas annealing on high-k gated germanium metal-oxide-semiconductor with GeO2 surface passivation
Authors: Xie Ruilong , He Wei , Yu Mingbin , Zhu Chunxiang
Published: August 2008

Effective pregate surface passivation and postgate treatments are very important to optimize the germanium metal-oxide-semiconductor (MOS) interface quality. In this work, pregate GeO2 surface passivation and postgate treatments including CF4-plasma treatment and forming gas annealing are employed to make high quality HfO2 gated germanium MOS capacitors. Excellent electrical characteristics with negligible capacitance-voltage stretch-out and frequency dispersion are achieved. The interface trap density of TaN∕HfO2∕GeOx∕Ge MOS structure is as low as 2.02×1011cm−2eV−1 at the minimum. Comparing to the forming gas annealing, it is found that CF4-plasma treatment is more effective to passivate interface states located in the upper half of Ge bandgap.
Symmetry-adapted perturbation theory utilizing density functional description of monomers for high-spin open-shell complexes
Authors: Żuchowski Piotr S. , Podeszwa Rafał , Moszyński Robert , Jeziorski Bogumił , Szalewicz Krzysztof
Published: August 2008

We present an implementation of symmetry-adapted perturbation theory (SAPT) to interactions of high-spin open-shell monomers forming high-spin dimers. The monomer spin-orbitals used in the expressions for the electrostatic and exchange contributions to the interaction energy are obtained from density functional theory using a spin-restricted formulation of the open-shell Kohn–Sham (ROKS) method. The dispersion and induction energies are expressed through the density-density response functions predicted by the time-dependent ROKS theory. The method was applied to several systems: NH⋯He, CN⋯Ne, H2O⋯HO2, and NH⋯NH. It provides accuracy comparable to that of the best previously available methods such as the open-shell coupled-cluster method with single, double, and noniterative triple excitations, RCCSD(T), with a significantly reduced computational cost.
Room temperature tunable blue-green luminescence in nanocrystalline (Pb1−xSrx)TiO3 thin film grown on yttrium-doped zirconia substrate
Authors: Luo L. , Ren H. Z. , Tang X. G. , Ding C. R. , Wang H. Z. , Chen X. M. , Jia J. K. , Hu Z. F.
Published: August 2008

Room temperature tunable blue-green photoluminescence was observed in nanocrystalline (Pb1−xSrx)TiO3 thin film under UV excitation. Its emission energy increases from 2.42 (at x=0.6) to 2.76 eV (at x=0.4), while the band gap decreases from 3.6 to 3.3 eV. Thin films of (Pb1−xSrx)TiO3 were prepared on yttrium-doped zirconia substrate by a simple sol-gel technique with spinning-coating process. Atom force microscope micrographs and crystallographic studies revealed the polycrystalline perovskite-type structure of the thin films. The observed optical properties are attributed to distorted octahedral due to different cation substitutions. The work shows that this kind of wide band gap and low cost nanocrystalline thin films is a very promising material for flat panel display applications and integrated light emission devices.
High speed piezoresponse force microscopy: <1 frame per second nanoscale imaging
Authors: Nath Ramesh , Chu Ying-Hao , Polomoff Nicholas A. , Ramesh Ramamoorthy , Huey Bryan D.
Published: August 2008

An atomic force microscopy (AFM) based technique is described for mapping piezoactuation with nanoscale resolution in less than a second per complete image frame. “High speed piezo force microscopy” (HSPFM) achieves this >100× increase in acquisition rates by coupling a commercial AFM with concepts of acoustics. This allows previously inaccessible dynamic studies, including measuring ferroelectric domain nucleation and growth during in situ poling. Hundreds of consecutive images are analyzed with 49 μs temporal resolution per pixel per frame, revealing 32 nucleation sites/μm2 with 36 μm/s average domain velocities. HSPFM images acquired in as fast as 1/10th s are also presented.
Investigation of plasma distribution in electron-focused electric field enhanced glow discharge plasma immersion ion implantation
Authors: Lu Qiu Yuan , Li Liu He , Fu Ricky K. Y. , Chu Paul K.
Published: August 2008

In enhanced glow discharge plasma immersion ion implantation (EGDPIII) that involves a small pointed anode and large area tabular cathode, the high negative substrate bias not only acts as the plasma producer but also supplies the implantation voltage. Consequently, an electric field is created to focus the electrons and the electron-focusing field enhances the glow discharge process. In this work, the plasma distribution is measured using a Langmuir probe to obtain the plasma density. Numerical interpolation is performed to obtain the plasma density distribution throughout the entire discharge region. The effects of different distances between the anode and cathode on the glow discharge characteristics and the influence of the plasma electron density are also evaluated. Our results experimentally verify the electron-focusing phenomenon and suggest optimal processing windows for enhanced ionization rates and efficiency in EGDPIII.
Enhanced photoluminescence and photonic bandgap modification from composite photonic crystals of macroporous silicon and nanocrystalline PbS thin films
Authors: Gutman N. , Armon A. , Sa’ar A. , Osherov A. , Golan Y.
Published: August 2008

We report on the fabrication of composite photonic crystals (PCs) of macroporous silicon and PbS thin films and about their passive and active optical properties. We have measured a redshift in the composite PC photonic stopbands relative to those of the PC substrate. In addition, we have measured a high extraction efficiency of the photoluminescence from the embedded PbS films due to band-edge singularities and slow-light modes of a defect-free two-dimensional composite PC. The peak extraction efficiency has been found to be six times larger than that of planar unpatterned PbS films.
A dedicated powder diffraction beamline at the Advanced Photon Source: Commissioning and early operational results
Authors: Wang Jun , Toby Brian H. , Lee Peter L. , Ribaud Lynn , Antao Sytle M. , Kurtz Charles , Ramanathan Mohan , Von Dreele Robert B. , Beno Mark A.
Published: August 2008

A new dedicated high-resolution high-throughput powder diffraction beamline has been built, fully commissioned, and opened to general users at the Advanced Photon Source. The optical design and commissioning results are presented. Beamline performance was examined using a mixture of the NIST Si and Al2O3 standard reference materials, as well as the LaB6 line-shape standard. Instrumental resolution as high as 1.7×10−4 (ΔQ∕Q) was observed.
Thermal noise cancellation in symmetric magnetoelectric bimorph laminates
Authors: Zhai Junyi , Xing Zengping , Dong Shuxiang , Li Jiefang , Viehland D.
Published: August 2008

We have found a symmetric Terfenol-D/Pb(Zr,Ti)03 (PZT) bimorph magnetoelectric (ME) laminate, which operates in a bending mode under an unsymmetrical (U-shaped) magnetic bias. It has a giant ME voltage coefficient of about 70V∕cmOe at resonance. Unlike other symmetric ME laminate structures, the symmetric bimorph structure has the capability to reject thermal noise from a magnetic signal, due to its back-to-back structure. The mechanism for the thermal noise cancellation capability is that the laminate operates in a bending mode (out charges of reverse sign), whereas the thermal noise is contained in a longitudinal mode (out charges have the same sign, allowing cancellation by differential detection).
Electron spin resonance study of spin correlations in charge-ordered La2−2xSr1+2xMn2O7(x=0.6)
Authors: Ning Wei , Yang Ren-Fu , Zhang Xiang-Qun , Cheng Zhao-hua , Sun Young
Published: August 2008

Electron spin resonance (ESR) studies have been performed on a bilayered manganite La2−2xSr1+2xMn2O7(x=0.6) single crystal. The charge ordering (CO) and antiferromagnetic (AFM) transitions can be well identified from the ESR spectra in both the ab plane and c axis directions. A coexistence of paramagnetic resonance signal and low-field AFM resonance signal was observed below the CO temperature TCO. The analysis of the ESR parameters as a function of temperature suggests the existence of weak ferromagnetic (FM) correlations in the paramagnetic state and AFM correlations below TCO. The competition of FM and AFM correlations results in a broad peak in ESR intensity. Our results also show that the intensity of AFM correlations increases with decreasing temperature as the system enters from the CO state into the A-type AFM ground state. Therefore, the evolution and anisotropy of spin correlations can be fully mapped by ESR study.
State-resolved studies of biexcitons and surface trapping dynamics in semiconductor quantum dots
Authors: Sewall Samuel L. , Cooney Ryan R. , Anderson Kevin E. H. , Dias Eva A. , Sagar D. M. , Kambhampati Patanjali
Published: August 2008

Biexcitons in strongly confined, colloidal CdSe quantum dots were investigated with excitonic state selectivity combined with 10 fs temporal precision. Within the first 50 fs, the first excited state of the biexciton was observed. By 100 ps, mixed character biexcitons were observed, comprised of a core exciton and a surface trapped exciton. The size dependence of the biexciton binding energies is reported for these specific biexcitons. Analysis of the spectral signatures of each biexcitonic state yields a quantitative measure of enhanced excited state trapping rates at the surface of the quantum dots. By comparing the biexcitonic signals to the state-filling signals, we show that it is primarily the holes which are trapped at the interface on the 100 ps time scale.
An eight-degree-of-freedom quantum dynamics study of the isotopic effect on the reaction: HD+C2H
Authors: Wang Dunyou , Huo Winifred M.
Published: August 2008

An eight-dimensional time-dependent quantum dynamics calculation is reported to study the isotopic reaction, HD+C2H, on a new modified potential energy surface. Initial-state-selected reaction probability, integral cross section, and rate constants are presented in this isotopic reaction study. Initial-state-selected reaction probability is obtained by summing over all the possible product’s arrangements in this isotopic reaction study. This study shows that vibrational excitations of HD enhance the reactivity, whereas stretching excitations of C2H only have a small effect on the reactivity. Furthermore, the bending excitations of C2H, compared to the ground-state reaction probability, hinder the reactivity. The present results are consistent with those obtained for the H2+C2H reaction. The comparison of these two reactions also shows the isotopic effect in the initial-state-selected reaction probability, integral cross section, and rate constants. The rate constant comparison shows that the HD+C2H reaction has a smaller reactivity than the H2+C2H reaction.
Single-particle placement via self-limiting electrostatic gating
Authors: Huang Hong-Wen , Bhadrachalam Pradeep , Ray Vishva , Koh Seong Jin
Published: August 2008

This letter reports single-particle placement in which exactly one nanoparticle is electrostatically guided and placed onto a target location. Using an ∼20 nm Au nanoparticle colloid as a model system, we demonstrate that self-limiting interactions between a charged nanoparticle and a charged substrate surface are extremely effective in positioning a single Au nanoparticle on each target location. Detailed theoretical calculations revealed that the self-limiting capability in the nanoparticle positioning is due to an increase in the free energy barrier after the first nanoparticle lands on a target position, effectively blocking the approach of other nanoparticles.
Field-driven migration of bipolar metal particles on solid electrolytes
Authors: Peppler Klaus , Reitz Christian , Janek Jürgen
Published: August 2008

A metal particle, which is not electronically contacted but is electrically contacted by a purely cation conducting solid electrolyte, is driven into the direction of the anode when an external electric field is applied. The particle behaves as a bipolar electrode. During the field-driven movement, the metal particle changes its morphology and spreads across the surface. This process is studied in situ with an optical microscope and ex situ with a scanning electron microscope. It is discussed as an example of morphological instabilities in solid state transport.
Selective disordering of InAs/InGaAs dots-in-a-well structure patterned with sol-gel derived SiO2 strips imprinted by soft mold technique
Authors: Chia C. K. , Suryana M. , Zhao W. , Low H. Y. , Hopkinson M.
Published: August 2008

Selective impurity free vacancy disordering of InAs/InGaAs quantum dot (QD) structures imprinted with sol-gel derived SiO2 strips via a polyethylene terepthalate soft mold has been investigated. Wavelength blueshift of up to 220 nm for areas capped with the sol-gel derived SiO2 is demonstrated. The imprinted SiO2 strips were used as hard mask for plasma etching of GaAs ridge waveguide structures and were found to have similar hardness as the SiO2 prepared by plasma-enhanced chemical vapor deposition. QD intermixing using sol-gel derived SiO2 with step-thickness profile was demonstrated, and a one-step SiO2 imprinting technique for multiple band gap QD intermixing is proposed.
Improved carrier injection in gate-all-around Schottky barrier silicon nanowire field-effect transistors
Authors: Peng J. W. , Lee S. J. , Liang G. C. Albert , Singh N. , Zhu S. Y. , Lo G. Q. , Kwong D. L.
Published: August 2008

This letter presents the performance improvement of Schottky barrier metal-oxide-semiconductor field-effect transistor by employing gate-all-around (GAA) Si-nanowire (SiNW) structure. Without employing any barrier lowering technique, the mid-band-gap Ni-silicide Schottky barrier transistors demonstrated excellent performance and achieved subthreshold slope of ∼86 mV/decade and on-current of 19 μA/μm on a 12.5 nm SiNW, and subthreshold slope of ∼79 mV/decade and on-current of 207 μA/μm on a 4 nm diameter SiNW. Assisted with simulation, we show that this improvement can be attributed to the strong reduction in the Schottky barrier thickness as a result of the better gate control of GAA SiNW structure.
Thickness dependence of space charge limited current and injection limited current in organic molecular semiconductors
Authors: Agrawal Ruchi , Kumar Pramod , Ghosh Subhasis , Mahapatro Ajit Kumar
Published: August 2008

We report the experimental investigations on space charge limited current (SCLC) and injection limited current (ILC) in copper phthalocyanine (CuPc), sandwiched between two metal electrodes. Thickness dependence of current-voltage characteristics of SCLC and ILC is accurately reproduced by the electric field and temperature dependent charge carrier mobility, without invoking charge density dependent mobility. These results are interpreted using a consistent description of SCLC and ILC, based on a unified model of hopping transport within Gaussian density of states in CuPc.
Efficient all-polymer solar cells based on blend of tris(thienylenevinylene)-substituted polythiophene and poly[perylene diimide-alt-bis(dithienothiophene)]
Authors: Tan Zhan’ao , Zhou Erjun , Zhan Xiaowei , Wang Xiang , Li Yongfang , Barlow Stephen , Marder Seth R.
Published: August 2008

A narrow band-gap alternating copolymer of perylene diimide and bis(dithienothiophene) (2) and a polythiophene derivative substituted by a tris(thienylenevinylene) conjugated side chain (4) are used as acceptor and donor, respectively, in all-polymer solar cells (SCs). The optimized device based on the blend of 4 and 2 in the ratio 3:1 (w/w) gives a short circuit current (Jsc) of 5.02 mA cm−2 and a power conversion efficiency of 1.48%, under simulated AM 1.5 illumination at 100 mW cm−2. These values are among the highest values reported for all-polymer SCs.
Properties of dilute InAsN layers grown by liquid phase epitaxy
Authors: Dhar S. , Das T. D. , de la Mare M. , Krier A.
Published: August 2008

We report on the liquid phase epitaxial growth of InAsN from indium rich solution. The spectral properties of dilute bulk alloys containing N∼0.5% and which exhibit photoluminescence in the midinfrared spectral range without any postgrowth annealing are described. The blueshift in the emission spectrum is attributed to a combination of tensile strain and band filling effects.
Valence band offset of MgO/4H-SiC heterojunction measured by x-ray photoelectron spectroscopy
Authors: Zhang B. L. , Cai F. F. , Sun G. S. , Fan H. B. , Zhang P. F. , Wei H. Y. , Liu X. L. , Yang S. Y. , Zhu Q. S. , Wang Z. G.
Published: August 2008

The valence band offset (VBO) of MgO(111)/4H-SiC heterojunction has been directly measured by x-ray photoelectron spectroscopy. The VBO is determined to be 3.65±0.23 eV and the conduction band offset is deduced to be 0.92±0.23 eV, indicating that the heterojunction has a type-I band alignment. The accurate determination of the valence and conduction band offsets is important for the applications of MgO/SiC optoelectronic devices.
Complete thin film mechanical characterization using picosecond ultrasonics and nanostructured transducers: experimental demonstration on SiO2
Authors: Mante P. A. , Robillard J. F. , Devos A.
Published: August 2008

Complete mechanical measurements are performed in submicron films using the picosecond ultrasonic technique. The Al layer deposited on the top of the sample acting as a transducer is replaced with a nanostructured Al film. Using an usual picosecond ultrasonic setup we can excite and detect high-frequency longitudinal and surface acoustic waves. From this we can deduce Young’s modulus and Poisson’s ratio of any isotropic thin film. Experimental results obtained for a thin silica layer on silicon are in very good agreement with literature.
Coplanar waveguide radio frequency ferromagnetic parametric amplifier
Authors: Bao Mingqiang , Khitun Alexander , Wu Yina , Lee Joo-Young , Wang Kang L. , Jacob Ajey P.
Published: August 2008

In this letter, we report a coplanar waveguide ferromagnetic parametric amplifier fabricated on a ferromagnetic Permalloy thin film. It shows a power gain of 4 dB at 1.15 GHz when the pump power is 11.1 dBm at the pump frequency of 2.30 GHz under the bias field of 13 Oe. This prototype ferromagnetic device can be integrated with the complementary metal-oxide semiconductor process technology and has potential applications as a spin-wave amplifier, a low noise amplifier, or an active bandpass filter.
Indium-free transparent organic light emitting diodes with Al doped ZnO electrodes grown by atomic layer and pulsed laser deposition
Authors: Meyer J. , Görrn P. , Hamwi S. , Johannes H.-H. , Riedl T. , Kowalsky W.
Published: August 2008

We present highly efficient transparent organic light emitting diodes (OLEDs) with Al doped ZnO (AZO) electrodes prepared by atomic layer deposition and pulsed laser deposition (PLD). The power and current efficiencies exceed 27 lm/W and 44 cd/A at a brightness level of 100 cd/m2, respectively. At the same time, the transmissivity of the devices is above 73% in the visible part of the spectrum. Owing to an efficient WO3 buffer layer and an optimized PLD process for the deposition of the top AZO electrode, the OLEDs show leakage current densities as low as 3×10−5 mA/cm2 at a reverse bias of 6 V. Therefore, our study paves the way for indium-free, see-through OLED displays.
Defect-induced negative differential resistance in single-walled carbon nanotubes
Authors: Buchs G. , Ruffieux P. , Gröning P. , Gröning O.
Published: August 2008

The authors report on the observation of a negative differential resistance (NDR) behavior in tunneling spectra recorded on hydrogen and nitrogen plasma-induced atomic defects on semiconducting single-walled carbon nanotubes (SWNTs). The NDR is observed only in the positive bias range of the spectra. This bias asymmetry and the spectral shape in the NDR region can be explained on the basis of a bias-dependent tunneling barrier height model. Within this model the NDR behavior can be directly related to defect-induced sharp electronic states in the SWNT band gap created at the defect sites.
Direct observation and control of the Walker breakdown process during a field driven domain wall motion
Authors: Glathe S. , Mattheis R. , Berkov D. V.
Published: August 2008

We report the real-time study of a domain wall motion in giant magnetoresistance nanostrips. We have visualized the Walker breakdown process (WBP) [N. L. Schryer and L. R. Walker, J. Appl. Phys. 45, 5406 (1974)] in single shot experiments. The domain wall motion above the Walker breakdown is highly nonperiodic. Surprisingly, the time intervals of movement are equal or larger than those where the domain wall nearly stops. When an additional transversal magnetic field is applied, domain wall motion becomes more regular, enabling the study of the WBP in more detail. A sufficiently large transverse field can suppress the WBP completely.
Diverse Economies and the Negotiations and Practices of Ethical Finance: The Case of Charity Bank
Authors: Buttle Martin
Published: August 2008

This paper draws on the emerging literature on diverse economies to analyse the everyday practices in a new type of finance organisation. Social finance organisations (SFOs), on the one hand, provide a mechanism for ‘ethical’ investors to invest money in line with their values and, on the other, provide loan finance sensitive to the needs of a variety of charities, and social enterprise and civil society organisations which have traditionally found access to finance difficult. They work through a mode of operation which emphasises partnership, reconnection, and association between stakeholders. Furthermore, social finance practitioners have developed a series of negotiation strategies for balancing social concerns with financial ones. The paper argues that there remain few analyses from inside organisations trying to practise economic relations differently. It demonstrates how theoretical debates on economic–social relationships are expressed on a day-to-day basis. The paper develops the concept of a sociofinancial narrative to highlight how social and financial organisational logics are hybridised within SFOs. This leads to a discussion on the integration of ethics into economic practice, in the context of neoliberalism as well as the entanglement of analysing alternatives through an ethnographic lens.
Arthropod 'rain' into tropical streams: the importance of intact riparian forest and influences on fish diets
Authors: Chan Eric K. W. , Zhang Yixin , Dudgeon David
Published: August 2008

Terrestrial arthropods might represent an important energy source for stream predators, but these trophic linkages have seldom been studied in the tropics. Terrestrial arthropod inputs (essentially, arthropod ‘rain’) into four streams with different riparian vegetation (two draining shrublands and two draining forests) were measured over three consecutive seasons (dry, wet, dry) from 2005 to 2007 in monsoonal Hong Kong. Predatory minnows, Parazacco spilurus (Cyprinidae), were collected and their consumption of terrestrial arthropods was estimated. Inputs of arthropods were dominated by Diptera, Collembola, Formicidae and aerial Hymenoptera, accounting for ≥73% of the arthropod abundance. Seasonal variation was marked: numbers in the dry seasons were approximately half (47–57%) those in the wet season, and biomass fell to one-third (33–37%) of the wet-season value. Shrubland streams received 19–43% fewer individuals and 6–34% less biomass than shaded forest streams. An analysis of fish diets in three of the four streams showed that terrestrial insects and spiders were more important prey in the two forest streams, accounting for 35–43% of prey abundance (39–43% by volume) v. 28% (27%) in the shrubland stream. Because riparian vegetation is the source of terrestrial arthropod inputs to streams, degradation of streamside forests that reduce these inputs will have consequences for the diets of stream fishes.
Molecular basis of the interaction between the antiapoptotic Bcl-2 family proteins and the proapoptotic protein ASPP2
Authors: Katz Chen , Benyamini Hadar , Rotem Shahar , Lebendiker Mario , Danieli Tsafi , Iosub Anat , Refaely Hadar , Dines Monica , Bronner Vered , Bravman Tsafrir , Shalev Deborah E. , Rüdiger Stefan , Friedler Assaf
Published: August 2008

We have characterized the molecular basis of the interaction between ASPP2 and Bcl-2, which are key proteins in the apoptotic pathway. The C-terminal ankyrin repeats and SH3 domain of ASPP2 (ASPP2
Ank-SH3
) mediate its interactions with the antiapoptotic protein Bcl-2. We used biophysical and computational methods to identify the interaction sites of Bcl-2 and its homologues with ASPP2. Using peptide array screening, we found that ASPP2
Ank-SH3
binds two homologous sites in all three Bcl proteins tested: (
i
) the conserved BH4 motif, and (
ii
) a binding site for proapoptotic regulators. Quantitative binding studies revealed that binding of ASPP2
Ank-SH3
to the Bcl-2 family members is selective at two levels: (
i
) interaction with Bcl-2-derived peptides is the tightest compared to peptides from the other family members, and (
ii
) within Bcl-2, binding of ASPP2
Ank-SH3
to the BH4 domain is tightest. Sequence alignment of the ASPP2-binding peptides combined with binding studies of mutated peptides revealed that two nonconserved positions where only Bcl-2 contains positively charged residues account for its tighter binding. The experimental binding results served as a basis for docking analysis, by which we modeled the complexes of ASPP2
Ank-SH3
with the full-length Bcl proteins. Using peptide arrays and quantitative binding studies, we found that Bcl-2 binds three loops in ASPP2
Ank-SH3
with similar affinity, in agreement with our predicted model. Based on our results, we propose a mechanism in which ASPP2 induces apoptosis by inhibiting functional sites of the antiapoptotic Bcl-2 proteins.
Interleukin-6 regulates pancreatic α-cell mass expansion
Authors: Ellingsgaard Helga , Ehses Jan A. , Hammar Eva B. , Van Lommel Leentje , Quintens Roel , Martens Geert , Kerr-Conte Julie , Pattou Francois , Berney Thierry , Pipeleers Daniel , Halban Philippe A. , Schuit Frans C. , Donath Marc Y.
Published: August 2008

Interleukin-6 (IL-6) is systemically elevated in obesity and is a predictive factor to develop type 2 diabetes. Pancreatic islet pathology in type 2 diabetes is characterized by reduced β-cell function and mass, an increased proportion of α-cells relative to β-cells, and α-cell dysfunction. Here we show that the α cell is a primary target of IL-6 actions. Beginning with investigating the tissue-specific expression pattern of the IL-6 receptor (IL-6R) in both mice and rats, we find the highest expression of the IL-6R in the endocrine pancreas, with highest expression on the α-cell. The islet IL-6R is functional, and IL-6 acutely regulates both pro-glucagon mRNA and glucagon secretion in mouse and human islets, with no acute effect on insulin secretion. Furthermore, IL-6 stimulates α-cell proliferation, prevents apoptosis due to metabolic stress, and regulates α-cell massin vivo. Using IL-6 KO mice fed a high-fat diet, we find that IL-6 is necessary for high-fat diet-induced increased α-cell mass, an effect that occurs early in response to diet change. Further, after high-fat diet feeding, IL-6 KO mice without expansion of α-cell mass display decreased fasting glucagon levels. However, despite these α-cell effects, high-fat feeding of IL-6 KO mice results in increased fed glycemia due to impaired insulin secretion, with unchanged insulin sensitivity and similar body weights. Thus, we conclude that IL-6 is necessary for the expansion of pancreatic α-cell mass in response to high-fat diet feeding, and we suggest that this expansion may be needed for functional β-cell compensation to increased metabolic demand.
Late-surviving megafauna in Tasmania, Australia, implicate human involvement in their extinction
Authors: Turney Chris S. M. , Flannery Timothy F. , Roberts Richard G. , Reid Craig , Fifield L. Keith , Higham Tom F. G. , Jacobs Zenobia , Kemp Noel , Colhoun Eric A. , Kalin Robert M. , Ogle Neil
Published: August 2008

Establishing the cause of past extinctions is critical if we are to understand better what might trigger future occurrences and how to prevent them. The mechanisms of continental late Pleistocene megafaunal extinction, however, are still fiercely contested. Potential factors contributing to their demise include climatic change, human impact, or some combination. On the Australian mainland, 90% of the megafauna became extinct by ≈46 thousand years (ka) ago, soon after the first archaeological evidence for human colonization of the continent. Yet, on the neighboring island of Tasmania (which was connected to the mainland when sea levels were lower), megafaunal extinction appears to have taken place before the initial human arrival between 43 and 40 ka, which would seem to exonerate people as a contributing factor in the extirpation of the island megafauna. Age estimates for the last megafauna, however, are poorly constrained. Here, we show, by direct dating of fossil remains and their associated sediments, that some Tasmanian megafauna survived until at least 41 ka (i.e., after their extinction on the Australian mainland) and thus overlapped with humans. Furthermore, a vegetation record for Tasmania spanning the last 130 ka shows that no significant regional climatic or environmental change occurred between 43 and 37 ka, when a land bridge existed between Tasmania and the mainland. Our results are consistent with a model of human-induced extinction for the Tasmanian megafauna, most probably driven by hunting, and they reaffirm the value of islands adjacent to continental landmasses as tests of competing hypotheses for late Quaternary megafaunal extinctions.
Endogenous oxidative stress produces diversity and adaptability in biofilm communities
Authors: Boles Blaise R. , Singh Pradeep K.
Published: August 2008

Many bacterial species are capable of biofilm growth, in which cells live and replicate within multicellular community groups. Recent work shows that biofilm growth by a wide variety of bacterial species can generate genetic diversity in microbial populations. This finding is significant because the presence of diverse subpopulations can extend the range of conditions in which communities can thrive. Here, we used biofilms formed by the pathogen
Pseudomonas aeruginosa
to investigate how this population diversity is produced. We found that some cells within biofilms incur double-stranded DNA breaks caused by endogenous oxidative stress. Genetic variants then result when breaks are repaired by a mutagenic mechanism involving recombinatorial DNA repair genes. We hypothesized that the mutations produced could promote the adaptation of biofilm communities to changing conditions in addition to generating diversity. To test this idea, we exposed biofilms to an antibiotic and found that the oxidative stress-break repair mechanism increased the emergence of antibiotic-resistant bacteria. The diversity and adaptability produced by this mechanism could help biofilm communities survive in harsh environments.
Methionine oxidation impairs reverse cholesterol transport by apolipoprotein A-I
Authors: Shao Baohai , Cavigiolio Giorgio , Brot Nathan , Oda Michael N. , Heinecke Jay W.
Published: August 2008

HDL protects against vascular disease by accepting free cholesterol from macrophage foam cells in the artery wall. This pathway is critically dependent on lecithin:cholesterol acyltransferase (LCAT), which rapidly converts cholesterol to cholesteryl ester. The physiological activator of LCAT is apolipoprotein A-I (apoA-I), the major HDL protein. However, cholesterol removal is compromised if apoA-I is exposed to reactive intermediates. In humans with established cardiovascular disease, myeloperoxidase (MPO) oxidizes HDL, and oxidation by MPO impairs apoA-I's ability to activate LCAT
in vitro
. Because a single methionine residue in apoA-I, Met-148, resides near the center of the protein's LCAT activation domain, we determined whether its oxidation by MPO could account for the loss of LCAT activity. Mass spectrometric analysis demonstrated that oxidation of Met-148 to methionine sulfoxide associated quantitatively with loss of LCAT activity in both discoidal HDL and HDL
3
, the enzyme's physiological substrates. Reversing oxidation with methionine sulfoxide reductase restored HDL's ability to activate LCAT. Discoidal HDL prepared with apoA-I containing a Met-148→Leu mutation was significantly resistant to inactivation by MPO. Based on structural data in the literature, we propose that oxidation of Met-148 disrupts apoA-I's central loop, which overlaps the LCAT activation domain. These observations implicate oxidation of a single Met in apoA-I in impaired LCAT activation, a critical early step in reverse cholesterol transport.
Alfalfa benefits fromMedicago truncatula: TheRCT1gene fromM. truncatulaconfers broad-spectrum resistance to anthracnose in alfalfa
Authors: Yang Shengming , Gao Muqiang , Xu Chenwu , Gao Jianchang , Deshpande Shweta , Lin Shaoping , Roe Bruce A. , Zhu Hongyan
Published: August 2008

Alfalfa is economically the most important forage legume worldwide. A recurrent challenge to alfalfa production is the significant yield loss caused by disease. Although knowledge of molecular mechanisms underlying host resistance should facilitate the genetic improvement of alfalfa, the acquisition of such knowledge is hampered by alfalfa's tetrasomic inheritance and outcrossing nature. However, alfalfa is congeneric with the reference legumeMedicago truncatula, providing an opportunity to useM. truncatulaas a surrogate to clone the counterparts of many agronomically important genes in alfalfa. In particular, the high degree of sequence identity and remarkably conserved genome structure and function between the two species enablesM. truncatulagenes to be used directly in alfalfa improvement. Here we report the map-based cloning ofRCT1, a host resistance (R) gene inM. truncatulathat confers resistance to multiple races ofColletotrichum trifolii, a hemibiotrophic fungal pathogen that causes anthracnose disease of alfalfa.RCT1is a member of the Toll-interleukin-1 receptor/nucleotide-binding site/leucine-rich repeat (TIR-NBS-LRR) class of plantRgenes and confers broad-spectrum anthracnose resistance when transferred into susceptible alfalfa plants. Thus,RCT1provides a novel resource to develop anthracnose-resistant alfalfa cultivars and contributes to our understanding of host resistance against the fungal genusColletotrichum. This work demonstrates the potential of usingM. truncatulagenes for genetic improvement of alfalfa.
Localizing organomercury uptake and accumulation in zebrafish larvae at the tissue and cellular level
Authors: Korbas Malgorzata , Blechinger Scott R. , Krone Patrick H. , Pickering Ingrid J. , George Graham N.
Published: August 2008

Using synchrotron x-ray fluorescence mapping, we have examined the uptake and localization of organic mercury in zebrafish larvae. Strikingly, the greatest accumulation of methyl and ethyl mercury compounds was highly localized in the rapidly dividing lens epithelium, with lower levels going to brain, optic nerve, and various other organs. The data suggest that the reported impairment of visual processes by mercury may arise not only from previously reported neurological effects, but also from direct effects on the ocular tissue. This novel approach is a powerful tool for directly investigating the molecular toxicology of heavy metals, and should be equally applicable to the study of a wide range of elements in developing embryos.
Object continuity enhances selective auditory attention
Authors: Best Virginia , Ozmeral Erol J. , Kopčo Norbert , Shinn-Cunningham Barbara G.
Published: August 2008

In complex scenes, the identity of an auditory object can build up across seconds. Given that attention operates on perceptual objects, this perceptual buildup may alter the efficacy of selective auditory attention over time. Here, we measured identification of a sequence of spoken target digits presented with distracter digits from other directions to investigate the dynamics of selective attention. Performance was better when the target location was fixed rather than changing between digits, even when listeners were cued as much as 1 s in advance about the position of each subsequent digit. Spatial continuity not only avoided well known costs associated with switching the focus of spatial attention, but also produced refinements in the spatial selectivity of attention across time. Continuity of target voice further enhanced this buildup of selective attention. Results suggest that when attention is sustained on one auditory object within a complex scene, attentional selectivity improves over time. Similar effects may come into play when attention is sustained on an object in a complex visual scene, especially in cases where visual object formation requires sustained attention.
Netrin-4 inhibits angiogenesis via binding to neogenin and recruitment of Unc5B
Authors: Lejmi Esma , Leconte Laurence , Pédron-Mazoyer Sandrine , Ropert Stanislas , Raoul William , Lavalette Sophie , Bouras Ilyes , Feron Jean-Guillaume , Maitre-Boube Martine , Assayag Franck , Feumi Charles , Alemany Monica , Jie Tan Xian , Merkulova Tatyana , Poupon Marie-France , Ruchoux Marie-Magdeleine , Tobelem Gérard , Sennlaub Florian , Plouët Jean
Published: August 2008

Netrins are secreted molecules with roles in axon guidance and angiogenesis. We identified Netrin-4 as a gene specifically overexpressed in VEGF-stimulated endothelial cells (EC)
in vitro
as well as
in vivo
. Knockdown of Netrin-4 expression in EC increased their ability to form tubular structures on Matrigel. To identify which receptor is involved, we showed by quantitative RT-PCR that EC express three of the six Netrin-1 cognate receptors: neogenin, Unc5B, and Unc5C. In contrast to Netrin-1, Netrin-4 bound only to neogenin but not to Unc5B or Unc5C receptors. Neutralization of Netrin-4 binding to neogenin by blocking antibodies abolished the chemotactic effect of Netrin-4. Furthermore, the silencing of either neogenin or Unc5B abolished Netrin-4 inhibitory effect on EC migration, suggesting that both receptors are essential for its function
in vitro
. Coimmunoprecipitation experiments demonstrated that Netrin-4 increased the association between Unc5B and neogenin on VEGF- or FGF-2-stimulated EC. Finally, we showed that Netrin-4 significantly reduced pathological angiogenesis in Matrigel and laser-induced choroidal neovascularization models. Interestingly, Netrin-4, neogenin, and Unc5B receptor expression was up-regulated in choroidal neovessel EC after laser injury. Moreover, Netrin-4 overexpression delayed tumor angiogenesis in a model of s.c. xenograft. We propose that Netrin-4 acts as an antiangiogenic factor through binding to neogenin and recruitment of Unc5B.
Mass spectrometry-based discovery of circadian peptides
Authors: Hatcher Nathan G. , Atkins Norman , Annangudi Suresh P. , Forbes Andrew J. , Kelleher Neil L. , Gillette Martha U. , Sweedler Jonathan V.
Published: August 2008

A significant challenge to understanding dynamic and heterogeneous brain systems lies in the chemical complexity of secreted intercellular messengers that change rapidly with space and time. Two solid-phase extraction collection strategies are presented that relate time and location of peptide release with mass spectrometric characterization. Here, complex suites of peptide-based cell-to-cell signaling molecules are characterized from the mammalian suprachiasmatic nucleus (SCN), site of the master circadian clock. Observed SCN releasates are peptide rich and demonstrate the co-release of established circadian neuropeptides and peptides with unknown roles in circadian rhythms. Additionally, the content of SCN releasate is stimulation specific. Stimulation paradigms reported to alter clock timing, including electrical stimulation of the retinohypothalamic tract, produce releasate mass spectra that are notably different from the spectra of compounds secreted endogenously over the course of the 24-h cycle. In addition to established SCN peptides, we report the presence of proSAAS peptides in releasates. One of these peptides, little SAAS, exhibits robust retinohypothalamic tract–stimulated release from the SCN, and exogenous application of little SAAS induces a phase delay consistent with light-mediated cues regulating circadian timing. These mass spectrometry-based analyses provide a new perspective on peptidergic signaling within the SCN and demonstrate that the integration of secreted compounds with information relating time and location of release generates new insights into intercellular signaling in the brain.