bluuebunny/crossref_metadata_2025 huggingface dataset:
Room-temperature midinfrared two-photon photodetector
Authors: Schneider H. , Liu H. C. , Winnerl S. , Drachenko O. , Helm M. , Faist J.
Published: September 2008

We report on a two-photon detector based on resonantly enhanced nonlinear absorption between subbands in InGaAs/InAlAs quantum wells and demonstrate its use as a quadratic autocorrelator for midinfrared pulses. Modified device design allows for device operation at room temperature, which is crucial for applications in practical systems.
Mode control in an oversized backward wave oscillator
Authors: Li Zheng-Hong , Qi Yu
Published: September 2008

Internal field emission breakdown in the electrodynamic structures of high-power microwave devices can seriously limit the devices’ output power and pulse duration. Increasing the diameter of the electrodynamic structure beyond the cutoff radius can reduce these internal fields to levels, which are below critical breakdown levels, but may introduce mode competition as unwanted side effects. An oversized backward wave oscillator with rectangular profile corrugations is designed to produce TM01 high power microwave radiation without mode competition. The slow wave structure and the reflector are matched to achieve mode selection and enhance interaction efficiency. The physical mechanism for mode selection is explored both in theoretical investigation and particle in cell simulation.
Plastic deformation and optical behavior of high-purity synthetic diamond crystal subjected to high stress load at room temperature
Authors: Sumiya H. , Nakamoto Y. , Shimizu K. , Kanda H.
Published: September 2008

The optical behavior around the culet of a diamond anvil made of high-purity and defect-free synthetic diamond crystal, which was plastically deformed at room temperature, was investigated by cathodoluminescence spectroscopy. It was found that the free exciton peaks weaken while the A-band and 2BD bands appear at the culet center where plastic deformation occurred. It was demonstrated that the free exciton peaks near the edge of the culet shift to the long wavelength side, indicating that the band structure of the peripheral areas of the culet changes because of residual strain caused by the plastic deformation in the culet center.
On the Debye and transient sheaths in a discharge plasma
Authors: Lonngren Karl E. , Alexeff Igor
Published: September 2008

Using just the mathematical properties of Poisson’s equation, we obtain a general solution for the spatial variation of the electric potential surrounding an electrode that is inserted in a laboratory discharge plasma. The Debye sheath and the transient or ion matrix sheath in front of an electrode are obtained as special limiting cases.
Ion cyclotron instabilities of parallel shear flow of collisional plasma
Authors: Mikhailenko V. S. , Mikhailenko V. V. , Stepanov K. N.
Published: September 2008

The effect of transverse velocity shear of plasma flow parallel to the embedded magnetic field on the generation of electrostatic ion cyclotron waves is studied analytically by using kinetic formalism. It is found that electron-neutral collisions are destabilizing, as it is in shearless plasma flows. However, flow shear not only modifies the frequency and growth rate of a known ion cyclotron current driven (ICCD) collisional electrostatic instability, but is the source of the development of specific shear-flow-driven ion cyclotron collisional instabilities at the levels of current along the ambient magnetic field which is subcritical for the development of the ICCD instability.
Investigation of spectral gain narrowing in quantum cascade lasers using terahertz time domain spectroscopy
Authors: Jukam N. , Dhillon S. S. , Oustinov D. , Zhao Z.-Y. , Hameau S. , Tignon J. , Barbieri S. , Vasanelli A. , Filloux P. , Sirtori C. , Marcadet X.
Published: September 2008

The spectral gain of bound-to-continuum terahertz quantum cascade lasers (QCLs) is measured as a function of current density using terahertz time-domain spectroscopy. During lasing action the full width at half maximum (FWHM) of the gain is found to monotonically decrease with increasing current density until lasing action stops at which point the FWHM reaches a minimum (0.22 THz for a laser operating at 2.1 THz). Band structure calculations show that the spectral gain narrowing is due to the alignment and misalignment of the injector with the active region as a function of the applied bias field.
Size-dependent mechanical properties of molybdenum nanopillars
Authors: Kim Ju-Young , Greer Julia R.
Published: September 2008

We report the deformation behavior of single crystalline molybdenum nanopillars in uniaxial compression, which exhibits a strong size effect called the “smaller is stronger” phenomenon. We show that higher strengths arise from the increase in the yield strength rather than through postyield strain hardening. We find the yield strength at nanoscale to depend strongly on sample size and not on the initial dislocation density, a finding strikingly different from that of the bulk metal.
Rapid multidimensional data acquisition in scanning probe microscopy applied to local polarization dynamics and voltage dependent contact mechanics
Authors: Jesse Stephen , Maksymovych Peter , Kalinin Sergei V.
Published: September 2008

A rapid multidimensional spectroscopic imaging approach in scanning probe microscopy is developed and applied to piezoresponse force spectroscopy. Evolution of resonance frequency, dissipation, and piezoresponse signal at each point during acquisition of local hysteresis loops provides information on polarization dynamics and voltage dependent contact mechanics of ferroelectric surfaces. The measurements illustrate significant frequency shifts during piezoresponse force spectroscopy, necessitating the use of frequency-tracking methods. The method is universal and can be extended to other scanning probe microscopy techniques.
On the linear and nonlinear development of Görtler vortices
Authors: Tandiono  , Winoto S. H. , Shah D. A.
Published: September 2008

The linear and nonlinear developments of Görtler vortices were experimentally investigated by means of hot-wire anemometer measurement. The wavelengths of the vortices were preset to be the most amplified using thin perturbation wires. Three different vortex wavelengths of 12, 15, and 20 mm were considered. These wavelengths were preserved downstream which confirm the prediction of the most amplified wavelength of Görtler vortices. The onset of the nonlinear region occurs at about the same Görtler number of 5.0 for all the wavelengths considered. In this nonlinear region, the secondary instability is initiated near the boundary layer edge, and it develops further downstream. The maximum turbulent intensity increases as the secondary instability becomes dominant in the flow. In the transition region, however, it slightly decreases before drastically increasing due to the onset of turbulence. Three maxima of intense turbulence are found in the turbulent intensity contours in the nonlinear region, which indicate the occurrence of the so-called varicose and sinuous modes of the secondary instability. Comparison with the previous available results shows that all data of maximum disturbance amplitude obtained from the same experimental setup seem to lie on a single line when they are plotted against Görtler number, regardless of the values of free-stream velocity and concave surface radius of curvature. Smaller radius of curvature results in higher vortex growth rate in the linear region due to stronger centrifugal effect. However, the vortex growth rate seems to be unaffected by free-stream velocity. The normal position of maximum disturbance amplitude reaches the maximum point exactly at the onset of nonlinear region before it drastically drops as the secondary instability is overtaking the primary instability.
Elastic molecular collision models for quantum mechanical scattering in the Monte Carlo simulation of rarefied gas flow at low temperatures
Authors: Matsumoto Hiroaki
Published: September 2008

Elastic molecular collision models for Monte Carlo simulation of rarefied gas flow, such as the variable hard sphere (VHS), variable soft sphere (VSS), and variable sphere (VS) molecular models, were extended to quantum mechanical scattering, and then applied to the simulation of spherical expansion of He4. The profiles of number density, flow velocity, and parallel and perpendicular kinetic temperatures obtained with the VHS, VSS, and VS models were in good agreement with those yielded by direct calculation of quantum mechanical scattering by Koura [Phys. Fluids 11, 3174 (1999)].
Electron dominated impact ionization and avalanche gain characteristics in InAs photodiodes
Authors: Marshall A. R. J. , Tan C. H. , Steer M. J. , David J. P. R.
Published: September 2008

An experimental investigation into impact ionization in InAs photodiodes is presented. Photomultiplication measurements on p-i-n and n-i-p diodes show that while high avalanche gains can be obtained for electron initiated multiplication, there is virtually no gain with hole initiated multiplication. This indicates that the electron ionization coefficient is significantly greater than the hole ionization coefficient raising the possibility of extremely low noise InAs avalanche photodiodes when gain is initiated by electrons. The onset of electron initiated impact ionization was detectable at electric fields below 10kVcm−1 with useful gain observed at biases below 10V.
Structural and electronic properties of crystalline InGaO3(ZnO)m
Authors: Lee W.-J. , Choi E.-A. , Bang J. , Ryu B. , Chang K. J.
Published: September 2008

Based on theoretical calculations, we find that the crystal structure of InGaO3(ZnO)m consists of an alternating stack of a wurtzite (Ga∕Zn)–O block and an In–O octahedral layer. In the (Ga∕Zn)–O block, the Ga atoms favor a modulated boundary structure against a flat boundary structure. The band spectrum shows that hole carriers are spatially confined whereas electrons move more freely through the whole crystal. The characteristics of a superlattice structure appears especially in the flat boundary structure. The band gap decreases with m due to the reduction in the quantum confinement effect.
Hydrothermally fabricated epitaxial PbTiO3 patterns patterned lithographically by etching in hydrothermal KOH solution
Authors: Ahn S. H. , Choi S. K.
Published: September 2008

We investigated the chemical etching behavior of heteroepitaxial PbTiO3 films on Nb-doped SrTiO3 substrate with mono-+c-domain fabricated by using hydrothermal epitaxy. The as-fabricated films were patterned lithographically into submicron-sized patterns with various lateral sizes using KOH solution and the etching mechanism is suggested. Our study reveals the feasibility of fabricating patterned nanodomains in PbTiO3 films by scanning probe microscopy domain engineering and a chemical etching process. Further, our study shows that an analysis of the distribution and morphology of polarized ferroelectric nanodomains in PbTiO3 is possible through a precise control over the applied bias voltage, pulse width, and time.
Valley splitting in Si quantum dots embedded in SiGe
Authors: Srinivasan S. , Klimeck G. , Rokhinson L. P.
Published: September 2008

We examine energy spectra of Si quantum dots embedded in Si0.75Ge0.25 buffers using atomistic numerical calculations for dimensions relevant to qubit implementations. The valley degeneracy of the lowest orbital state is lifted and valley splitting fluctuates with monolayer frequency as a function of the dot thickness. For dot thicknesses ≤6 nm, valley splitting is found to be >150 μeV. Using the unique advantage of atomistic calculations, we analyze the effect of buffer disorder on valley splitting. Disorder in the buffer leads to the suppression of valley splitting by a factor of 2.5; the splitting fluctuates with ≈20 μeV for different disorder realizations. Through these simulations we can guide future experiments into regions of low device-to-device fluctuations.
The effect of the last quantum barrier on the internal quantum efficiency of InGaN-light emitting diode
Authors: Park Eun-Hyun , Jang Jin , Gupta Shalini , Ferguson Ian , Jeon Soo-Kun , Lim Jae-Gu , Lee Jun-Serk , Kim Cheol-Hoi , Park Joong-Seo
Published: September 2008

The effect of the last quantum barrier (LQB) on the internal quantum efficiency of GaN-light emitting diode (LED) was systematically investigated using a dual-wavelength GaN-LED design. Compared with a conventional GaN-LQB, a high indium contained In0.03Ga0.97N-LQB efficiently reduced the unintentional Mg impurity in the last quantum well and improved its photoluminescence and electroluminescence intensity up to 72% and 15%, respectively.
Multiplexed single-molecule measurements with magnetic tweezers
Authors: Ribeck Noah , Saleh Omar A.
Published: September 2008

We present a method for performing multiple single-molecule manipulation experiments in parallel with magnetic tweezers. We use a microscope with a low magnification, and thus a wide field of view, to visualize multiple DNA-tethered paramagnetic beads and apply an optimized image analysis routine to track the three-dimensional position of each bead simultaneously in real time. Force is applied to each bead using an externally applied magnetic field. Since variations in the field parameters are negligible across the field of view, nearly identical manipulations of all visible beads is possible. However, we find that the error in the position measurement is inversely proportional to the microscope’s magnification. To mitigate the increased error caused by demagnification, we have developed a strategy based on tracking multiple fixed beads. Our system is capable of simultaneously manipulating and tracking up to 34 DNA-tethered beads at 60 Hz with ∼1.5 nm resolution and with ∼10% variation in applied force.
In-plane band gap modulation investigated by secondary electron imaging of GaAsN/GaAsN:H heterostructures
Authors: Felisari L. , Grillo V. , Martelli F. , Trotta R. , Polimeni A. , Capizzi M. , Jabeen F. , Mariucci L.
Published: September 2008

GaAsN/GaAsN:H in-plane heterostructures have been investigated by secondary electron (SE) imaging in a field-emission scanning electron microscope. Adjacent GaAsN and GaAsN:H regions show a quite different SE image brightness due to the band gap energy difference between H-free and H-irradiated GaAsN. These findings provide a useful means to characterize the lateral diffusion of H and well support secondary ion mass spectroscopy results regarding the importance of a low hydrogenation temperature in order to obtain sharply defined in-plane heterostructures.
Monolithic white light emitting diodes using a (Ga,In)N/GaN multiple quantum well light converter
Authors: Damilano B. , Dussaigne A. , Brault J. , Huault T. , Natali F. , Demolon P. , De Mierry P. , Chenot S. , Massies J.
Published: September 2008

A monolithic white light emitting diode using a (Ga,In)N/GaN multiple quantum well (MQW) light converter is demonstrated. Blue photons emitted under electrical injection by (Ga,In)N/GaN QWs located inside a GaN p-n junction are partly absorbed by another (Ga,In)N/GaN MQW situated outside the junction which emits yellow-green light. The combination of the blue and yellow-green components results in white light emission.
Two dimensionally patterned GaNxAs1−x/GaAs nanostructures using N+ implantation followed by pulsed laser melting
Authors: Kim Taeseok , Aziz Michael J. , Narayanamurti Venkatesh
Published: September 2008

We present measurements on two dimensionally patterned GaNxAs1−x dots fabricated in a GaAs matrix using ion implantation followed by pulsed laser melting and rapid thermal annealing. The lithographically patterned GaNxAs1−x regions are imaged by ballistic electron emission microscopy (BEEM). By analyzing the BEEM spectra of the locally confined dots, we observe the decrease in the Schottky barrier height with nitrogen incorporation. The second derivatives of BEEM currents from unpatterned GaNxAs1−x films exhibit a decrease in Γ-like thresholds as the nitrogen concentration increases. The composition dependence of the thresholds agrees well with that of previously studied low temperature molecular beam epitaxy grown alloys.
Contrasting characteristics of linear-field and cross-field atmospheric plasma jets
Authors: Walsh J. L. , Kong M. G.
Published: September 2008

This letter reports an experimental study of two types of atmospheric pressure plasma jets in terms of their fundamental properties and their efficiency in etching polymeric materials. The first plasma jet has a cross-field configuration with its electric field perpendicular to its gas flow field, whereas the second is a linear-field device having parallel electric and flow fields. The linear-field jet is shown to drive electron transportation to the downstream application region, thus facilitating more active plasma chemistry there. This is responsible for its etching rate of polyamide films being 13-fold that of its cross-field counterpart.
High-resolution ultrasonic imaging using an etalon detector array
Authors: Huang Sheng-Wen , Hou Yang , Ashkenazi Shai , O’Donnell Matthew
Published: September 2008

A photoacoustic imaging system was built and tested to demonstrate the feasibility of high-resolution low-noise ultrasonic imaging based on parallel detection using polymer etalons. Its capability of detecting ultrasound at different elements simultaneously in the optical end was verified by imaging three 49 μm beads. An average noise-equivalent pressure of 3.6 kPa over 50 MHz for 50 μm diameter detection elements in a two-dimensional array with a diameter of 1.35 mm and a detection bandwidth of 75 MHz at –3 dB was measured. These results demonstrate the potential of polymer etalons for high-frame-rate high-resolution three-dimensional photoacoustic and ultrasound pulse-echo imaging.
Tailoring the gas sensing properties of ZnO thin films through oxygen nonstoichiometry
Authors: Kobrinsky V. , Rothschild A. , Lumelsky V. , Komem Y. , Lifshitz Y.
Published: September 2008

A comparative study of the gas sensing properties of n- and p-type ZnO films was performed. The carrier type and concentration tailored by varying the sputtering Ar/O2 mixture were examined by Hall effect measurements. The gas sensing properties were studied by monitoring changes in the dc resistance upon exposure to hydrogen or oxygen. The selectivity of ZnO sensors to these gases was tailored by the carrier type. The origin of the doping and the defect chemistry are evaluated in view of the films’ growth process. The doping effect on the electrical conduction mechanism and sensor performance is discussed.
Effects of laser pulse duration on extreme ultraviolet spectra from double optical gating
Authors: Gilbertson Steve , Mashiko Hiroki , Li Chengquan , Moon Eric , Chang Zenghu
Published: September 2008

Previously a two-color field was combined with a polarization gating to allow for the generation of single isolated attosecond pulses from multicycle lasers. Here, the scaling of energy for the extreme ultraviolet pulses corresponding to single attosecond pulses as a function of input laser pulse duration was investigated for argon, neon, and helium gas. Laser pulses as long as 12 fs were able to generate extreme ultraviolet supercontinua with high photon flux. The spectra profile depended strongly on the carrier envelope phase of the pump laser.
Highly efficient and color stable phosphorescent white light-emitting diodes by using a charge confining emitting layer structure
Authors: Yook Kyoung Soo , Jeon Soon Ok , Joo Chul Woong , Lee Jun Yeob
Published: September 2008

Quantum efficiency of white phosphorescent organic light-emitting diodes was improved by using a device architecture to confine charges inside an emitting layer. The charge confinement was achieved by stacking two emitting layers with different charge transport properties. An emitting layer with electron transport type host was stacked on an emitting layer with hole transport type host. A maximum quantum efficiency of 18.3% and a current efficiency of 31.5 cd/A were achieved with a color coordinate of (0.38,0.36). In addition, there was little change in the emission spectra from 200 to 10,000 cd/m2.
Electrical transport properties of wafer-fused p-GaAs/n-GaN heterojunctions
Authors: Lian Chuanxin , Xing Huili Grace , Chang Yu-Chia , Fichtenbaum Nick
Published: September 2008

GaAs/GaN pn heterojunction diodes have been fabricated by direct wafer fusion and characterized by capacitance-voltage (C-V) measurements and temperature dependent current-voltage (I-V) measurements. The wafer-fused pn diode showed a good rectifying behavior, but a small turn-on voltage was observed, which was attributed to defect-assisted tunneling-recombination. The flat-band voltage extracted from C-V is around 0.46 V, much smaller than the built-in voltage calculated for an ideal GaAs/GaN pn heterojunction. A band diagram including interface charge effects together with a possible energy barrier, stemming from a layer of disordered material at the fused GaAs/GaN interface, has been proposed to explain the experimental observations.
Effects of external field on the dynamic magnetization switching of a nanostructured exchange-coupled trilayer
Authors: Kim K. S. , Lee K. J. , Lim S. H.
Published: September 2008

The dynamic magnetization switching of a nanostructured exchange-coupled trilayer with a small thickness asymmetry is investigated by micromagnetic simulation. The magnetization switching initially occurs by coherent rotation, followed by magnetization oscillation. The switching time, which is about 9 ns at an applied field just above the switching field, is a factor of two longer than that observed for a single-layered thin film. A Fourier analysis of the magnetization oscillation shows multiple oscillation frequencies, the main frequency of which decreases as the applied magnetic field increases.
Giant magnetoelectric coupling and E-field tunability in a laminated Ni2MnGa/lead-magnesium-niobate-lead titanate multiferroic heterostructure
Authors: Chen Yajie , Wang Jingmin , Liu Ming , Lou Jing , Sun Nian X. , Vittoria Carmine , Harris Vincent G.
Published: September 2008

The multiferroic properties of a laminated heterostructure consisting of magnetostrictive Ni2MnGa ribbon and piezoelectric lead-magnesium-niobate-lead titanate crystal are reported. A tunability of the electric field-induced magnetic field was measured by a shift in the ferromagnetic resonance (FMR) field by 230 Oe at X-band while applying an electric field of 6 kV/cm. Concomitantly, a frequency shift in the FMR of 370 MHz was observed. The sensitive tunability stems from a large linear magnetoelectric coupling coefficient, A=41 Oe cm/kV, measured in the heterostructure. This represents a new class of metallic multiferroic heterostructures that operate at microwave frequencies.
Alteration in testicular cell components following transiently induced ischaemia in prepubertal bulls
Authors: Schuenemann G. M. , Mendis-Handagama S. M. L. C. , Prado T. M. , Schrick F. N.
Published: September 2008

The aim of the present study was to evaluate transient testicular ischaemia (induced using elastrator bands) in Jersey calves on testicular morphology and development. Treatments (at 27 ± 5 days of age) consisted of control (0 h banding) and banding for 2, 4 or 8 h (n = 4 in each group). After castration (at 60 ± 5 days of age), the right testis was used for calculation of cell components per testis according to the point-counting method. Bodyweight (59.8 ± 6.2 kg) and scrotal circumference (SC) at banding (9.1 ± 0.2 cm) did not differ between groups. Fresh testis weight, scrotal temperature immediately before band removal and daily SC growth were decreased in ischaemic (4 and 8 h) testes compared with controls (P < 0.05). In addition, the number of Sertoli and Leydig cells was significantly reduced in the 8 h ischaemic treatment group (P < 0.05). Transiently induced ischaemia significantly decreased the number of germ cells in the 8 h ischaemic treatment group (13 ± 5 × 106 cells) compared with the 0, 2 and 4 h ischaemic treatment groups (38 ± 6, 32 ± 6 and 33 ± 5 × 106 cells, respectively; P < 0.05). These results suggest that transiently induced ischaemia for 8 h significantly decreases the number of germ, Sertoli and Leydig cells in prepubertal testis.
Effect of impaired glucose tolerance during pregnancy on the expression of VEGF receptors in human placenta
Authors: Marini M. , Vichi D. , Toscano A. , Thyrion G. D. Zappoli , Bonaccini L. , Parretti E. , Gheri G. , Pacini A. , Sgambati E.
Published: September 2008

The aim of the present study was to determine the expression of vascular endothelial growth factor (VEGF) receptors VEGFR-1, VEGFR-2 and VEGFR-3 in placentas from pregnancies complicated by altered glycaemia. Placentas from women with physiological pregnancies (Group 1), pregnancies complicated by minor degree of glucose intolerance (MDGI, Group 2) and by gestational diabetes mellitus (GDM) treated with insulin (Group 3) were collected. Immunohistochemistry, RT–PCR and western blot were employed to evaluate receptor expression. In the three study groups, VEGFR-1 immunoreactivity was detected in all the placental components. VEGFR-2 immunoreactivity was observed in the vessels of all the placentas from Groups 1 and 2, but only in some placentas of Group 3. VEGFR-3 reactivity was observed in all the components of Group 1; in Groups 2 and 3 reactivity was observed in some portions of the trophoblast or the whole trophoblast, and in the stroma. VEGFR-1 and VEGFR-2 mRNA levels in Groups 2 and 3 were significantly higher compared with Group 1, whereas those of VEGFR-3 were significantly lower. Receptor protein levels were significantly lower in Groups 2 and 3 compared with Group 1. These findings demonstrated dysregulation of expression of the three placental receptors, both in GDM and in MDGI.
The FLYWCH transcription factors FLH-1, FLH-2, and FLH-3 repress embryonic expression of microRNA genes in C. elegans
Authors: Ow Maria C. , Martinez Natalia J. , Olsen Philip H. , Silverman Howard S. , Barrasa M. Inmaculada , Conradt Barbara , Walhout Albertha J.M. , Ambros Victor
Published: September 2008

MicroRNAs (miRNAs) are small noncoding RNAs that regulate gene expression post-transcriptionally via antisense base-pairing. Although miRNAs are involved in a variety of important biological functions, little is known about their transcriptional regulation. Using yeast one-hybrid assays, we identified transcription factors with a FLYWCH Zn-finger DNA-binding domain that bind to the promoters of several Caenorhabditis elegans miRNA genes. The products of the flh-1 and flh-2 genes function redundantly to repress embryonic expression of lin-4, mir-48, and mir-241, miRNA genes that are normally expressed only post-embryonically. Although single mutations in either flh-1 or flh-2 genes result in a viable phenotype, double mutation of flh-1 and flh-2 results in early larval lethality and an enhanced derepression of their target miRNAs in embryos. Double mutations in flh-2 and a third FLYWCH Zn-finger-containing transcription factor, flh-3, also result in enhanced precocious expression of target miRNAs. Mutations of lin-4 or mir-48&mir-241 do not rescue the lethal flh-1; flh-2 double-mutant phenotype, suggesting that the inviability is not solely the result of precocious expression of these miRNAs. Therefore, the FLH-1 and FLH-2 proteins likely play a more general role in regulating gene expression in embryos.
Defining the regulatory network of the tissue-specific splicing factors Fox-1 and Fox-2
Authors: Zhang Chaolin , Zhang Zuo , Castle John , Sun Shuying , Johnson Jason , Krainer Adrian R. , Zhang Michael Q.
Published: September 2008

The precise regulation of many alternative splicing (AS) events by specific splicing factors is essential to determine tissue types and developmental stages. However, the molecular basis of tissue-specific AS regulation and the properties of splicing regulatory networks (SRNs) are poorly understood. Here we comprehensively predict the targets of the brain- and muscle-specific splicing factor Fox-1 (A2BP1) and its paralog Fox-2 (RBM9) and systematically define the corresponding SRNs genome-wide. Fox-1/2 are conserved from worm to human, and specifically recognize the RNA element UGCAUG. We integrate Fox-1/2-binding specificity with phylogenetic conservation, splicing microarray data, and additional computational and experimental characterization. We predict thousands of Fox-1/2 targets with conserved binding sites, at a false discovery rate (FDR) of ∼24%, including many validated experimentally, suggesting a surprisingly extensive SRN. The preferred position of the binding sites differs according to AS pattern, and determines either activation or repression of exon recognition by Fox-1/2. Many predicted targets are important for neuromuscular functions, and have been implicated in several genetic diseases. We also identified instances of binding site creation or loss in different vertebrate lineages and human populations, which likely reflect fine-tuning of gene expression regulation during evolution.
The T-box transcription factor Eomes/Tbr2 regulates neurogenesis in the cortical subventricular zone
Authors: Arnold Sebastian J. , Huang Guo-Jen , Cheung Amanda F.P. , Era Takumi , Nishikawa Shin-Ichi , Bikoff Elizabeth K. , Molnár Zoltán , Robertson Elizabeth J. , Groszer Matthias
Published: September 2008

The embryonic subventricular zone (SVZ) is a critical site for generating cortical projection neurons; however, molecular mechanisms regulating neurogenesis specifically in the SVZ are largely unknown. The transcription factor Eomes/Tbr2 is transiently expressed in cortical SVZ progenitor cells. Here we demonstrate that conditional inactivation of Tbr2 during early brain development causes microcephaly and severe behavioral deficits. In Tbr2 mutants the number of SVZ progenitor cells is reduced and the differentiation of upper cortical layer neurons is disturbed. Neurogenesis in the adult dentate gyrus but not the subependymal zone is abolished. These studies establish Tbr2 as a key regulator of neurogenesis in the SVZ.
The nuclear receptor tailless is required for neurogenesis in the adult subventricular zone
Authors: Liu Hai-Kun , Belz Thorsten , Bock Dagmar , Takacs Andrea , Wu Hui , Lichter Peter , Chai Minqiang , Schütz Günther
Published: September 2008

The tailless (Tlx) gene encodes an orphan nuclear receptor that is expressed by neural stem/progenitor cells in the adult brain of the subventricular zone (SVZ) and the dentate gyrus (DG). The function of Tlx in neural stem cells of the adult SVZ remains largely unknown. We show here that in the SVZ of the adult brain Tlx is exclusively expressed in astrocyte-like B cells. An inducible mutation of the Tlx gene in the adult brain leads to complete loss of SVZ neurogenesis. Furthermore, analysis indicates that Tlx is required for the transition from radial glial cells to astrocyte-like neural stem cells. These findings demonstrate the crucial role of Tlx in the generation and maintenance of NSCs in the adult SVZ in vivo.
Organizational Learning in Multinationals: R&D Networks of Japanese and US MNEs in the UK*
Authors: Lam Alice
Published: September 2008

ABSTRACTThe institutional approach treats organizational forms and behaviour as contingent upon institutions that are durable and socially embedded and so several authors have argued that the nature and modes of operation of multinational enterprises (MNEs) vary according to their national origins. This paper examines the ways in which national patterns of organization and innovation affect Japanese and US MNEs’ global R&D networks and transnational learning, based on case studies of their R&D laboratories in the UK. In particular, it focuses on how these MNEs tap into foreign academic knowledge base and scientific labour through collaborative links with higher education institutions.

Relative to many Japanese MNEs, US firms have developed a greater organizational capacity for coordinating globally dispersed learning and embedding themselves in local innovation networks because the liberal institutional environment within which US MNEs have developed enables them to extend their organizational and human resource systems across institutional and geographical boundaries. By contrast, Japanese MNEs appear to be more limited in their transnational learning because of the much more tightly integrated organizational and business system within which they are embedded. The paper also illustrates how the contrasting logics of the US ‘professional community’ and the Japanese ‘organizational community’ model of learning are manifested in MNEs.
Two Dimensions of the Internationalization of Firms*
Authors: Hassel A. , Höpner M. , Kurdelbusch A. , Rehder B. , Zugehör R.
Published: September 2008

ABSTRACTThe paper argues that there are two dimensions of internationalization: one which refers to the production activities of firms abroad and one which focuses on the corporate governance dimension of firms. While the first one is well known in the literature on internationalization, the financial dimension has not yet been addressed empirically. At the same time there are indicators that financial internationalization is gaining importance. Using a sample of the 100 largest German companies it shows that both dimensions, the real and the financial dimension, do not co‐vary and therefore cannot be combined into one index.
Institutional Conditioning of Foreign Expansion: Some Evidence from Finnish‐Based Paper Industry Firms, 1994–2000*
Authors: Laurila Juha , Ropponen Minna
Published: September 2008

ABSTRACTAnalyses of the foreign expansion of firms based on economics have recently been supplemented with institutionally‐oriented studies demonstrating that foreign expansion is partly conditioned by the institutional environment in which the expanding firms are embedded. In this paper, we join this emerging stream of research with an empirical study on three Finnish‐based paper industry firms from 1994 to 2000. By showing how changes in the patterns and forms of foreign expansion coincide with changes in the forms of corporate ownership and the cognitive constructions of organizational actors, our study confirms that foreign expansion cannot be adequately understood without reference to the institutional environment in which it originated. In particular, we show that foreign expansion can turn into an institutional requirement that directs the development of firms in part irrespective of the economic aspects involved.
Investigating trophic‐level variability in Celtic Sea fish predators
Authors: Chassot E. , Rouyer T. , Trenkel V. M. , Gascuel D.
Published: September 2008

The trophic level (TL) mean and variance, and the degree of omnivory for five Celtic Sea fish predators were estimated using a database of stomach content records characterized by a high level of taxonomic resolution. The predators occupied a high position in the food web,i.e.4·75 for Atlantic codGadus morhua, 4·44 for haddockMelanogrammus aeglefinus, 4·88 for European hakeMerluccius merluccius, 5·00 for megrimLepidorhombus whiffiagonisand 5·27 for whitingMerlangius merlangus. The level of taxonomic resolution of the prey did not greatly affect meanTLpredator values; an effect on variance was evident, low resolution masking intra‐population variability inTL. Generalized additive models (GAM) were used to explain the variability of predatorTLcaused by environmental variables (International Council for the Exploration of the Sea, ICES, division and season) and predator characteristics (total length,LT). Significant year, location season and interaction effects were found for some species and withLTat the scale of ICES subdivision. The species‐specific variability ofTLcould be due to spatio‐temporal variations in prey availability and in predator selectivity following ontogenetic changes. Omnivorous fishTLwas less affected by spatio‐temporal variations. In addition, results showed that the omnivory index andTLvariability provide dissimilar information on predator feeding strategy. Combining information onTLvariability and omnivory allowed between within‐individual and between‐individual components contributing to trophic niche width to be separated and the type of generalization of fish predators to be identified.
Diel variation in food intake and diet composition of three native fish species in floodplain lagoons of the Macintyre River, Australia
Authors: Medeiros E. S. F. , Arthington A. H.
Published: September 2008

The feeding periodicity of three species of fishes in floodplain lagoons of the Macintyre River varied during 24 h cycles, however, peak feeding activity (around midday and late afternoon) was similar among the species studied, despite differences in their trophic position. In contrast, sampling season and site seemed to have a stronger effect on the composition of the diet than time of day. These findings have implications for studies of trophic dynamics and food web structure in floodplain lagoons.
Relationship between body shape and trophic niche segregation in two closely related sympatric fishes
Authors: Russo T. , Pulcini D. , O’Leary Á. , Cataudella S. , Mariani S.
Published: September 2008

Diet, shape and their covariation were analysed in juvenile flounder Platichthys flesus and plaice Pleuronectes platessa specimens from a tidal inshore habitat (Dublin Bay) in the Irish Sea. Stomach content analysis revealed differences in the diet, suggesting a substantial degree of resource partitioning between the species. Geometric morphometrics detected significant and discriminating differences in body shape, particularly in the head region. Most interestingly, a high degree of correlation was detected between diet and shape. The ontogenetic and ecological implications of the diet and shape covariation pattern were discussed, suggesting that morphological differences, in particular in the head region, may represent the functional platform which allows for the existence of ecologically significant differences in prey search and capture between P. platessa and P. flesus.
Divergent life histories among smallmouth bass Micropterus dolomieu inhabiting a connected river–lake system
Authors: Barthel B. L. , Cooke S. J. , Svec J. H. , Suski C. D. , Bunt C. M. , Phelan F. J. S. , Philipp D. P.
Published: September 2008

Annual reproductive surveys monitored nesting location, reproductive success and the age and size of individually tagged male smallmouth bass Micropterus dolomieu that reproduced in Millers Lake, a 45 ha widening of the Mississippi River, Ontario, and in a 1·5 km pool and riffle section of the river directly upstream. The vast majority of males displayed fidelity to either the river or the lake as reproductive habitat throughout their lifetimes. Nearly, half of the males that reproduced in successive years exhibited strong nest‐site fidelity by nesting within 20 m of their previous year’s nest site. In most years, when compared to those in the lake, reproductive males in the river differed significantly in reproductive characteristics including age and size at maturation and nesting success rates. A 3 year telemetry project identified two distinct habitat use patterns: lake‐resident fish remained in the lake throughout the year and potamodromous individuals migrated from the lake to upriver spawning habitat in the spring and then returned to the lake prior to the onset of winter. Integration of habitat use and reproductive data suggests that there are significant differences in the life‐history strategies of fish that reproduce in the river v. the lake.
Interaction between hatchery and wild juvenile white‐spotted charr Salvelinus leucomaenis in a stream enclosure experiment
Authors: Yamamoto S. , Nakamura H. , Koga K.
Published: September 2008

The competitive interactions between hatchery and wild juvenile white‐spotted charr Salvelinus leucomaenis were examined in enclosure experiments in a natural stream. A total of 24 enclosures (1·0 × 1·0 × 0·7 m height) were arranged in stream in an array for randomized block design with replicates of three treatments (wild fish only, hatchery fish only, wild plus hatchery fish). Three experiments were conducted in 2006, using different densities and sizes for each experimental trial. When densities in enclosures were controlled to be equal among treatments (4 individuals m−2: substitutive design), wild fish in the presence of hatchery fish had significantly higher growth rates than the wild fish alone treatment. When densities in enclosures were controlled to be 4 individuals m−2 hatchery fish only treatment, 4 individuals m−2 wild fish only treatment and 8 individuals m−2 in the hatchery plus wild fish treatment (additive design), wild fish in the presence of hatchery fish had significantly lower growth rate than the wild fish alone treatment. Hatchery fish in the presence of wild fish also grew significantly slower than the hatchery fish alone treatment. When densities in enclosures were controlled to be equal among treatments (4 individuals m−2) but hatchery fish were 1·1 times longer than wild fish, growth of wild fish in the presence of the larger hatchery fish did not differ significantly from growth of the wild fish alone treatment. These results suggested that relative size of hatchery fish in relation to wild fish and increased fish density are two important factors influencing the growth of wild juvenile S. leucomaenis.
Different ocean and climate factors control the marine survival of wild and hatchery Atlantic salmon Salmo salar in the north‐east Atlantic Ocean
Authors: Peyronnet A. , Friedland K. D. , Ó Maoileidigh N.
Published: September 2008

The influence of climate and ocean conditions on the marine survival of 1SW Irish Atlantic salmon Salmo salar was explored. Generalized additive models (GAM) explained c. 85% of the observed variations in survival and provided an insight into the mechanisms involved. A positive phase of the North Atlantic oscillation (NAO) and increasing sea surface temperatures (SST) were linked to a decrease in S. salar survival. The NAO in the winter before the smolts migration contributed to c. 70% of the deviance in marine survival of wild fish. The abundance of the copepod Calanus finmarchicus in the north‐east Atlantic Ocean explained a further 25% of these variations in wild S. salar survival. By contrast, hatchery populations seem to be controlled by additional processes involving coastal SST. The marine recruitment of hatchery S. salar was largely explained (70% of the deviance) by SST close to the Irish coast in the spring before the year of the smolts migration. This study constitutes the first description of the processes controlling marine recruitment for these populations.
Habitat fragmentation and body‐shape variation of African hindCephalopholis taeniops(Valenciennes) in an archipelago system (Cape Verde, eastern Atlantic Ocean)
Authors: Medina A. , Brêthes J.‐C. , Sévigny J.‐M.
Published: September 2008

Morphological variations of the serranid fishCephalopholis taeniopswere studied in relation to habitat fragmentation in the Cape Verde Archipelago. While a significant allometric effect existed (11·5% of total body‐shape variation), differences in morphology associated with sex and ontogeny were not significant. MANOVA followed by CVA showed that each island presented a particular allometric pattern. Average body shape for all islands was well discriminated with CVA models. Pair‐wise comparisons of the ontogeny of morphological change between islands revealed that northern islands (Santo Antão, São Vicente and Santa Luzia) along with Boavista Island showed a similar direction in shape ontogeny, while all other paired comparisons indicated different ontogenetic patterns. When comparing directions of inter‐population shape changes, individuals from Fogo Island, the southernmost locality, departed far from the orthogonal relation, suggesting that they were undergoing independent body‐shape trajectories. Physical isolation by geographic distance and depth was positively correlated with morphological divergence among populations from different islands. This finding supports the hypothesis that habitat fragmentation in the Cape Verde Archipelago can be interpreted in terms of marine population structure.
Can seasonal home‐range size in pikeEsox luciuspredict excursion distance?
Authors: Knight C. M. , Gozlan R. E. , Lucas M. C.
Published: September 2008

The hypothesis that vagility, or tendency to move, in pikeEsox luciuscan be predicted from individual home range was tested using telemetry. Independently of fish size, mean annual excursion distance was positively correlated to winter (0·02–0·95 ha) and spring (0·02–0·59 ha) home ranges but not summer and autumn home ranges.
Habitat selection and the colonization of new territories by Chromis viridis
Authors: Ben‐Tzvi O. , Abelson A. , Polak O. , Kiflawi M.
Published: September 2008

The settlement and recruitment patterns of Chromis viridis were followed during three consecutive seasons along the reefs of Eilat, Red Sea. The findings, based on intensive field surveys and a translocation experiment, indicated a strong and repeatable preference for some, but not other, colonies of the branching coral Acropora eurystoma; with significantly more larvae settling onto preferred colonies that house conspecific adults and juveniles. Furthermore, these findings showed that, given high recruitment rates, settlement‐site selection could drive migration by adults and older juveniles. As only some C. viridis schools received direct settlement, it was suggested that settlement‐driven migration is responsible for the replenishment of those schools that do not receive settlement and to the colonization of previously unoccupied coral colonies.
Every Child Matters outcomes: What Do They Mean for Disabled Children and Young People?
Authors: Sloper Patricia , Beresford Bryony , Rabiee Parvaneh
Published: September 2008

To date, little attention has been paid to the appropriateness of the Every Child Matters (ECM) outcomes framework to disabled children.1 This article reports findings from a research project which sought the views of disabled children and their parents about their desired outcomes. Twenty‐nine children and 90 parents were interviewed. The findings indicate that ECM outcomes are appropriate to disabled children but can have different meanings. In addition, the need to recognise the importance of maintaining outcomes, as well as progress, is highlighted.
Age‐specific interval breast cancers in Japan: estimation of the proper sensitivity of screening using a population‐based cancer registry
Authors: Suzuki Akihiko , Kuriyama Shinichi , Kawai Masaaki , Amari Masakazu , Takeda Motohiro , Ishida Takanori , Ohnuki Koji , Nishino Yoshikazu , Tsuji Ichiro , Shibuya Daisuke , Ohuchi Noriaki
Published: September 2008

The age‐specific sensitivity of a screening program was investigated using a population‐based cancer registry as a source of false‐negative cancer cases. A population‐based screening program for breast cancer was run using either clinical breast examinations (CBE) alone or mammography combined with CBE in the Miyagi Prefecture from 1997 to 2002. Interval cancers were newly identified by linking the screening records to the population‐based cancer registry to estimate the number of false‐negative cases of screening program. Among 112 071 women screened by mammography combined with CBE, the number of detected cancers, false‐negative cases and the sensitivity were 289, 22 and 92.9%, respectively, based on the reports from participating municipalities. The number of newly found false‐negative cases and corrected sensitivity when using the registry were 34 and 83.8%, respectively. In detected cancers, the sensitivity of screening by mammography combined with CBE in women ranging from 40 to 49 years of age based on a population‐based cancer registry was much lower than that in women 50–59 and 60–69 years of age (40–49: 18, 71.4%, 50–59: 19, 85.8%, 60–69: 19, 87.2%). These data suggest that the accurate outcome of an evaluation of breast cancer screening must include the use of a population‐based cancer registry for detecting false‐negative cases. Screening by mammography combined with CBE may therefore not be sufficiently sensitive for women ranging from 40 to 49 years of age. (Cancer Sci 2008; 99: 2264–2267)