bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structural variation manipulates the differential oxidative susceptibility and conformational stability of apolipoprotein E isoforms
Authors: Su Kuo‐Liang , Wen Ta‐Hsiang , Chou Chi‐Yuan , Chang Gu‐Gang , Liu Guang‐Yaw , Hung Hui‐Chih 
Published: April 2007

AbstractA growing amount of evidence implicates the involvement of apolipoprotein E (apoE) in the development of late‐onset and sporadic forms of Alzheimer's disease (AD). It is now generally believed that the ε4 allele is associated with AD and the oxidative stress is more pronounced in AD. However, only limited data are available on apoE isoform‐specificity and its relationship to both the oxidative susceptibility and conformational stability of apoE. In this article, we use site‐directed mutagenesis to investigate the structural role of amino acid residue 112, which is the only differing residue between apoE3 and E4. We examine the structural variation manipulating the oxidative susceptibility and conformational stability of apolipoprotein E isoforms. Arg112 in apoE4 was changed to Ala and Glu. Previous research has reported that apoE4 is more susceptible to free radicals than apoE3. In protein oxidation experiments, apoE4‐R112A becomes more resistant to free radicals to the same extent as apoE3. In contrast, apoE4‐R112E becomes the most susceptible protein to free radicals among all the apoE proteins. We also examine the conformational stability and the quaternary structural change by fluorescence spectroscopy and analytical ultracentrifugation, respectively. ApoE3 and E4 show apparent three‐ and two‐state unfolding patterns, respectively. ApoE4‐R112A, similar to apoE3, demonstrates a biphasic denaturation with an intermediate that appears. The denaturation curve for apoE4‐R112E, however, also displays a biphasic profile but with a slight shoulder at ∼1.5M GdmCl, implying that an unstable intermediate existed in the denaturation equilibrium. The size distribution of apoE isoforms display similar patterns. ApoE4‐R112E, however, has a greater tendency to dissociate from high‐molecular‐weight species to tetramers. These experimental data suggest that the amino acid residue 112 governs the differences in salt‐bridges between these two isoforms and thus has a significant impact on the free radical susceptibility and structural variation of the apoE isoforms. Proteins 2007. © 2007 Wiley‐Liss, Inc.
Simulation and measurement of the self‐heating in GaN HFETs
Authors: McAlister S. P. 
Published: April 2007

AbstractSelf‐heating in a GaN HFET has been simulated and used to deduce different average or effective temperatures, which are representative of the device performance. This suggests how simple electrical measurements, coupled with simulation may help reveal the maximum temperatures in a device. Some experimental data is shown indicating how electrical measurements by themselves can be used to do this. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dynamic drift‐diffusion simulation of InP/InGaAs SAGCM APD
Authors: Xiao Y. G. , Li Z. Q. , Li Z. M. Simon 
Published: April 2007

AbstractIn this work, based on the advanced drift and diffusion model with commercial software, the Crosslight APSYS, InP/InGaAs separate absorption, grading, charge and multiplication APDs for high bit‐rate operation have been modeled. Basic physical quantities such as band diagram, optical absorption and generation are calculated. Performance characteristics such as dark‐ and photo‐current, photoresponsivity, multiplication gain, breakdown voltage, excess noise, frequency response and bandwidth etc., are simulated. The modeling results are selectively presented, analyzed, and some results are compared with experiments. Device design optimization issues are further discussed with respect to the applicable features of the Crosslight APSYS within the framework of the drift‐diffusion theory. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Improved InP‐based double heterojunction bipolar transistors
Authors: Lin Y. S. , Huang J. H. , Ho C. H. 
Published: April 2007

AbstractThis article develops two double heterostructure bipolar transistors (DHBTs) made by low‐pressure metamorphic organic chemical vapor deposition (LP‐MOCVD). One is a control DHBT with an abrupt base‐collector heterojunction (abrupt DHBT) and the other is an improved DHBT with a composite‐collector design (composite DHBT). Of the devices with no ledge passivation, the composite DHBT has a high common‐emitter current gain, a low offset voltage and voltage‐independent collector current characteristics, unlike the abrupt DHBT. The favorable performance of the composite DHBT follows mainly from the optimal collector design, which effectively lowers the potential spike at the base‐collector heterojunction. Furthermore, measurements of the composite DHBT with and without n‐InP emitter ledges are made. The composite DHBT with emitter ledges has a current gain of 180, which is 44% higher than that of the device with no emitter ledge. The higher current gain is attributable to the lower base surface recombination current in the composite DHBT with a ledge. The effectiveness of the composite‐collector design and the emitter ledge process of the presented DHBT is proven. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
GaN films deposited on (111)Si by CS‐MBD with re‐evaporation enhancement technique for UV light‐emitting devices
Authors: Arai Masatoshi , Sugimoto Koichi , Egawa Shinichi , Baba Taichi , Honda Tohru 
Published: April 2007

AbstractGaN films were deposited at low temperature by compound‐source molecular beam deposition (CS‐MBD) with re‐evaporation enhancement (REE) technique. As the interval time of the pulsed‐source feeding during the GaN deposition was increased, the amount of the excess Ga in the deposited films was decreased. Cathodoluminescence (CL) intensity was improved with the decrease in the amount of excess Ga in the deposited films. The amount of excess Ga in the deposited films decreased after using REE technique. Using REE technique, GaN‐based thin‐film electroluminescent devices (TF‐ELDs) were fabricated. Near‐ultraviolet (UV) light emission, whose peak wavelength was located at 390 nm, was observed from the devices. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
High frequency modulation effects on the relative intensity noise properties of 405 nm InAlGaN laser diodes
Authors: Yi Jong Chang , Cho Hyung Uk 
Published: April 2007

AbstractThe high frequency modulation effects on the relative intensity noise (RIN) characteristics of 405 nm InAlGaN laser diodes have been investigated taking into account the strain and thermal effects on the laser diode itself as well as external optical feedback effects. The simulation results indicate that the critical external optical feedback for –125 dB/Hz RIN is around 0.1%, a typical order found in practical DVD operating environments.By optimizing the injection current levels and its frequency, one can reduce the RIN with 0.1∼1% external feedback effect by more than 15 dB/Hz. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Investigations of InSb‐based quantum dots grown by molecular‐beam epitaxy
Authors: Deguffroy N. , Tasco V. , Baranov A. N. , Satpati B. , Trampert A. , Dunaevski M. , Titkov A. , Genty F. , Tournié E. 
Published: April 2007

AbstractInSb quantum dots (QDs) have been grown by molecular‐beam epitaxy (MBE) on GaSb substrates. Typical MBE growth conditions lead to a low density (∼109 cm–2) of large islands which are dislocated. Insertion of a thin InAs nucleation layer increases the QDs density by one order of magnitude which is interpreted in terms of differing In‐to‐group‐V binding energies. Finally, we show that a high density (∼7 x 1010 cm–2) of small coherent QDs can be grown by using a two‐steps procedure. Photoluminescence near 3.5 µm is demonstrated. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Barrier‐ and in‐well pumped GaSb‐based 2.3 µm VECSELs
Authors: Wagner J. , Schulz N. , Rattunde M. , Ritzenthaler C. , Manz C. , Wild C. , Köhler K. 
Published: April 2007

AbstractWe report on recent advances in the performance of GaSb‐based optically‐pumped vertical‐external‐cavity surface‐emitting lasers (VECSELs) emitting at wavelengths around 2.3 µm. Both barrier and in‐well pumped VECSELs have been fabricated and analysed. Both variants incorporate a diamond intra‐cavity heat spreader as an efficient means for heat extraction from the active region. For barrier‐pumping, a maximum output power of 1.5 W with a beam propagation factor of M2 ≤ 3 has been achieved at a heat sink temperature of –20°C. Using in‐well pumping at 1.96 µm, the efficiency could be more than doubled, compared to barrier pumping, due to the significantly reduced quantum deficit, yielding a slope efficiency of 31% at a heat sink temperature of 10°C. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Structural characterization of MgO/c‐Al2O3 interfaces
Authors: Minegishi T. , Hanada T. , Suzuki H. , Vashaei Z. , Oh D. C. , Sumitani K. , Sakata O. , Cho M. W. , Yao T. 
Published: April 2007

AbstractWe have found that MgO deposited on c‐Al2O3 substrates at high temperatures formed MgAl2O4 by interdiffusion during MgO layer growth. The formation of spinel MgAl2O4 has been confirmed by in‐situ reflection high energy electron diffraction (RHEED) and grazing incident X‐ray diffracition (GIXD). The critical temperature (TC) for the formation of MgAl2O4 was found to be around 700 °C above which MgAl2O4 is formed at the MgO/c‐Al2O3 interface. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ultrafast nonlinear optical response of weakly confined excitons in GaAs thin films
Authors: Kojima O. , Isu T. , Ishi‐Hayase J. , Sasaki M. , Tsuchiya M. 
Published: April 2007

AbstractWe report on an ultrafast nonlinear optical response of weakly confined excitons in GaAs thin films observed by a two‐beam degenerate four‐wave‐mixing (DFWM) technique. An ultrafast optical response comparable to the pulse width appears under ultrashort‐pulse‐laser excitation condition. We clarified from the DFWM spectra that the plural exciton states contribute to the ultrafast response. The results imply a possibility of ultrafast switching devices using weakly confined excitons. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electroabsorption modulators on waveguide micro‐ring cavity resonators with self‐aligned total internal reflectors
Authors: Yi Jong Chang , Kim Doo Gun , Chung Youngchul , Dagli Nadir 
Published: April 2007

AbstractThe switching characteristics of an electroabsorption modulator fabricated on a waveguide‐coupled micro‐ring‐cavity resonator were investigated. The ring cavity resonator consists of ridge waveguide regions, total internal reflector mirrors, and a coupling region. The coupling region is implemented with a multimode interferometer (MMI) waveguide to enhance the coupling coefficient. The total internal reflection mirrors were fabricated by self‐aligned RIBE process resulting in minimal insertion losses of around 0.7 dB/mirror. The gain medium was a 1.55 μm InGaAsP MQW ridge waveguide, and the passive waveguide was a re‐grown 1.4 μm InGaAsP ridge structure. The sharp variation of the optical transmission through the micro‐ring‐cavity resonator near the resonance wavelength was utilized to realize efficient semiconductor optical modulators with a high extinction ratio. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Enhancement mode high mobility n‐MOSFET on gallium arsenide substrate
Authors: Rajagopalan K. , Abrokwah J. , Droopad R. , Passlack M. 
Published: April 2007

AbstractMOS heterostructures grown by molecular beam epitaxy on III‐V substrates, employing a high‐κ dielectric stack (κ ≈ 20) comprising of gallium oxide and gadolinium gallium oxide have been fabricated. Mobilities exceeding 12,000 and 6,000 cm2/Vs, for sheet carrier concentration ns of about 2.5x1012 cm–2 were measured from InP and GaAs based MOSFET structures, respectively. These structures were designed for enhancement mode operation and include a 10 nm thick strained InxGa1–xAs channel layer with In mole fraction x of 0.3 and 0.75 on GaAs and InP substrates, respectively. NMOSFETs with a gate length of 1 μm and a source‐drain spacing of 3 μm were fabricated. These devices show a threshold voltage of 0.11 V. The saturation current, transconductance and on‐resistance were measured to be 380 mA/mm, 250 mS/mm, 4.5 Ω‐mm. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Determination of ruthenium originating from the investigational anti‐cancer drug NAMI‐A in human plasma ultrafiltrate, plasma, and urine by inductively coupled plasma mass spectrometry
Authors: Brouwers Elke E. M. , Tibben Matthijs M. , Rosing Hilde , Schellens Jan H. M. , Beijnen Jos H. 
Published: April 2007

AbstractWe present a highly sensitive, rapid method for the determination of ruthenium originating from the investigational anti‐cancer drug NAMI‐A in human plasma ultrafiltrate, plasma, and urine. The method is based on the quantification of ruthenium by inductively coupled plasma mass spectrometry and allows quantification of 30 ng L−1 ruthenium in plasma ultrafiltrate and urine, and 75 ng L−1 ruthenium in human plasma, in 150 µL of matrix. The sample pretreatment procedure is straightforward and only involves dilution with appropriate diluents. The performance of the method, in terms of accuracy and precision, fulfilled the most recent FDA guidelines for bioanalytical method validation. Validated ranges of quantification were 30.0 to 1 × 104 ng L−1 for ruthenium in plasma ultrafiltrate and urine and 75.0 to 1 × 104 ng L−1 for ruthenium in plasma. The applicability of the method and its superiority to atomic‐absorption spectrometry were demonstrated in two patients who were treated with intravenous NAMI‐A in a phase I trial. The assay is now successfully used to support pharmacokinetic studies in cancer patients treated with NAMI‐A. Copyright © 2007 John Wiley & Sons, Ltd.
Mutual antagonism of SoxB1 and canonical Wnt signaling in sea urchin embryos
Authors: Angerer Lynne M. , Kenny Alan P. , Newman Laurel A. , Angerer Robert C. 
Published: April 2007

AbstractEarly development of animal embryos involves establishing axial polarities that specify the anlage of major tissues in a 3‐dimensional pattern. Cell fates are specified on this coordinate system through a combination of differential inheritance of maternal regulatory molecules and signaling interactions among cells. Correct patterning of cell fates along the primary axis of the sea urchin embryo depends on tightly regulating the ratio of activities of two nuclear regulatory proteins, SoxB1 and nuclear β–catenin. The latter acts at the top of the gene regulatory network that specifies mesoderm and endoderm and activates, directly or indirectly, signaling by Delta, Wnt8 and Nodal. In contrast, SoxB1 initially accumulates in all nuclei but is progressively eliminated from presumptive mesoderm and endoderm by β‐catenin‐dependent transcriptional repression and by localized protein turnover, a novel pathway acting downstream of canonical Wnt signaling. A precise temporal program for SoxB1 down regulation is crucial for endomesoderm development because SoxB1 interferes with β–catenin's transcriptional regulatory function. The mechanisms we are beginning to understand that govern the β–catenin‐SoxB1 antagonism in sea urchin embryos are likely to have broad significance, since Sox factors are involved in regulating many developmental processes in many deuterostome embryos.
Secondary axis specification in sea urchin embryos
Authors: Bradham Cynthia A. , McClay David R. 
Published: April 2007

AbstractSecondary axis specification is a process that relies on asymmetric nuclearization of transcription factors in flies and vertebrates, such that the crucial factor is nuclear and therefore functional only in cells along one side of the embryo. In vertebrates, this transcription factor is β‐catenin, which is canonically activated downstream from Wnt signals. However, the sea urchin uses asymmetric β‐catenin nuclearization during specification of the primary animal‐vegetal axis, rather than the secondary oral‐aboral (OA) axis. OA specification relies instead on the asymmetric localization of p38 MAPK, a signaling kinase that directly modulates transcription factor activity. A number of genes are expressed in the oral territory downstream from p38, including Nodal and Goosecoid, both of which are associated with secondary axis specification in vertebrate embryos. Because the p38 asymmetry is the earliest known event in the specification of the OA axis, an outstanding question concerns identifying the apparatus upstream from p38 that regulates its asymmetrical activity. Intriguingly, this may be controlled by reactive oxygen species released from the mitochondria, which are asymmetrically distributed about the OA axis.
The many faces of egg activation at fertilization
Authors: Leguia Mariana , Wessel Gary M. 
Published: April 2007

AbstractThe signaling networks controlling calcium release and cortical granule exocytosis at fertilization are complex and multilayered, providing various points for regulatory input and quality control. Though it is clear that many of the mechanisms leading to both calcium release and cortical granule exocytosis are conserved, a great deal of variability exists between homologous signaling pathways in different species. The signaling pathways responsible for the release of calcium seen at fertilization vary from species to species, yet they center around the importance of IP3‐mediated signaling. Similarly, while there are differences in the mechanisms of regulated secretion between species and between intracellular membrane trafficking events, particularly with respect to time and space, all seem to be dependent on the SNARE proteins and their regulator and effector proteins. What has been most helpful in these studies is the convergence of studies from many different species of eggs. With the amazing divergence of reproductive processes and mechanisms that exists throughout phylogeny, it is comforting to see such strong overlapping roles of key players in widely disparate eggs.
Recent structural applications of active control technology
Authors: Soong T. T. , Reinhorn A. M. , Aizawa S. , Higashino M. 
Published: April 2007

AbstractA number of active control systems have been developed, fabricated and installed in full‐scale structures and they have been subjected to actual wind forces and ground motions. The focus of this paper is on the observed response of several of these systems. They include an active bracing system and an active mass damper system installed in a six‐story experimental building, and two hybrid mass damper systems installed in two actual buildings. The configurations of these systems are summarized together with their performance characteristics. Observed performance of these systems during actual wind storms and moderate earthquakes shows that they meet their basic design objectives. Furthermore, their performance can be adequately predicted through simplified analytical and simulation procedures.
An optimal design procedure for delayed control of linear structures
Authors: Baratta A. , Papa F , Zuccaro G. 
Published: April 2007

AbstractThe purpose of the paper is to investigate the problem of the delayed active control of a linear system controlled by a closed‐loop linear law under the action of external dynamic forces. The choice of the optimal parameters, for each assigned delay, is pursued through the optimization of the controlled response with the constraint of limiting the control force under a prefixed threshold. The behaviour of the response, varying the control parameters, is investigated through the mapping of the “solution in the norm” of the response rather than the definition of the punctual response of the system.Numerical applications for different values of the delay are performed for a SDOF structure showing the range of the feasibility of the closed‐loop linear approach on one side, and proving the critical role of the delay on the other side.
Active modal control with piezo‐electric layers optimization
Authors: Collet M. , Jezequel L. 
Published: April 2007

AbstractModal filter concept is introduced for structural vibration analysis and control. The modal filter is a means to extract the modal coordinates of each mode from the system outputs by mapping the response vector from the physical space to the modal space. This concept was used originally to deal with the spill‐over problem in the control of a continuous system. We have chosen to optimize some semi‐distributed piezo‐electric layers by minimizing the influence of unwanted modes on the sensors and actuators. Confirmation of our computation was obtained by an experimental set‐up of optimal active modal control on a thin composite plate. Thus, experimental optimal control in the independent modal space of this plate has been possible without any effect of spill‐over. The efficiency and the robustness of this procedure was demonstrated by our experimental analysis.
Active structural control by neural networks
Authors: Faravelli L. , Venini P. 
Published: April 2007

AbstractThe present paper develops some alternative schemes to apply back‐propagation neural networks in the area of active structural control. The structural systems referred to are plane hysteretic structures, the restoring forces of which are idealized by an endochronic model. The control algorithms herein developed call for two different neural networks in order to approximate the forward and backward dynamics of the system. The latter network is the actual controller whereas the former one is needed to determine the response of a virtual system upon which no control forces are applied. Results from successful numerical examples are proposed with the objective of computing a quantitative measure of the effectiveness of the system.
Acceleration feedback method applied to active‐passive composite tuned mass damper
Authors: Nishimura Isao , Sakamoto Mitsuo , Yamada Toshikazu , Koshika Norihide , Kobori Takuji 
Published: April 2007

AbstractThis paper discusses the optimization of the active‐passive composite tuned mass damper which was recently proposed by the authors for the purpose of reducing response vibrations of building structures subjected to disturbance excitations such as wind pressures or earthquakes. The parameter optimization, control force reduction, control energy minimization are discussed under several different types of excitations. A harmonic excitation, a stationary white noise and a non‐stationary random excitation such as earthquake are all considered for the derivation of formulae.
Seismic performance of buildings with a class of adaptive nonlinear hybrid systems
Authors: Barbat A. H. , Rodellar J. , Molinares N. , Ryan E. P. 
Published: April 2007

AbstractA class of hybrid control system which combines a passive nonlinear base isolator with an active controller is analyzed. The passive component of the system has a hysteretic behaviour. A single control force is applied on the structural base by means of a new adaptive control strategy, not requiring knowledge of the system parameters and the excitation and able to handle the typical nonlinearities associated with base isolators. A numerical study is performed to assess the improvement of the behaviour of buildings equipped with this control system.