bluuebunny/crossref_metadata_2025 huggingface dataset:
Diffusion‐weighted PROPELLER MRI for quantitative assessment of liver tumor necrotic fraction and viable tumor volume in VX2 rabbits
Authors: Deng Jie , Virmani Sumeet , Young Joseph , Harris Kathleen , Yang Guang‐Yu , Rademaker Alfred , Woloschak Gayle , Omary Reed A. , Larson Andrew C.
Published: April 2008

Purpose

To test the hypothesis that diffusion‐weighted (DW)‐PROPELLER (periodically rotated overlapping parallel lines with enhanced reconstruction) MRI provides more accurate liver tumor necrotic fraction (NF) and viable tumor volume (VTV) measurements than conventional DW‐SE‐EPI (spin echo echo‐planar imaging) methods.

Materials and Methods

Our institutional Animal Care and Use Committee approved all experiments. In six rabbits implanted with 10 VX2 liver tumors, DW‐PROPELLER and DW‐SE‐EPI scans were performed at contiguous axial slice positions covering each tumor volume. Apparent diffusion coefficient maps of each tumor were used to generate spatially resolved tumor viability maps for NF and VTV measurements. We compared NF, whole tumor volume (WTV), and VTV measurements to corresponding reference standard histological measurements based on correlation and concordance coefficients and the Bland–Altman analysis.

Results

DW‐PROPELLER generally improved image quality with less distortion compared to DW‐SE‐EPI. DW‐PROPELLER NF, WTV, and VTV measurements were strongly correlated and satisfactorily concordant with histological measurements. DW‐SE‐EPI NF measurements were weakly correlated and poorly concordant with histological measurements. Bland–Altman analysis demonstrated that DW‐PROPELLER WTV and VTV measurements were less biased from histological measurements than the corresponding DW‐SE‐EPI measurements.

Conclusion

DW‐PROPELLER MRI can provide spatially resolved liver tumor viability maps for accurate NF and VTV measurements, superior to DW‐SE‐EPI approaches. DW‐PROPELLER measurements may serve as a noninvasive surrogate for pathology, offering the potential for more accurate assessments of therapy response than conventional anatomic size measurements. J. Magn. Reson. Imaging 2008. © 2008 Wiley‐Liss, Inc.
A clinical comparison of rigid and inflatable endorectal‐coil probes for MRI and 3D MR spectroscopic imaging (MRSI) of the prostate
Authors: Noworolski Susan M. , Crane Jason C. , Vigneron Daniel B. , Kurhanewicz John
Published: April 2008

Purpose

To compare the data quality and ease of use of four endorectal‐coil probe setups for prostate MRI.

Materials and Methods

Four endorectal‐coil probe setups were compared: 1) air‐inflated probe; 2) perfluorocarbon (PFC)‐inflated probe; 3) rigid, smaller prototype coil; and 4) rigid, smaller coil designed for biopsying the prostate. Signal‐to‐noise ratio (SNR), positioning, shimming, MRI motion artifact, and MR spectroscopic imaging (MRSI) spectral quality were assessed.

Results

Rigid coils provided approximately 2.5‐fold higher SNR than inflatable coils near the peripheral zone midline. The biopsy probe sensitivity decreased dramatically by the apex. The rigid probes, as compared to the inflatable probes, took longer to place (10 ± 2 vs. 7 ± 2 minutes, P < 0.0002), tended to be placed too superiorly, required repositioning more often (73% vs. 20%, P < 0.003), and had higher motion artifacts (P < 0.001). Shimming time was least for the PFC‐inflated probe (2 ± 0.5 minutes, P < 0.05). The air‐inflated probe produced larger linewidths (P < 0.01) and tended to have longer shim times (7 ± 4 minutes) and poorer spectral quality.

Conclusion

The inflatable coil is a good clinical choice due to ease of use, good coverage, and low motion artifacts. PFC‐inflation is recommended as it provided higher quality data than air‐inflation. The rigid, smaller probes have higher SNR and produce less tissue distortion and may be preferred for certain applications. J. Magn. Reson. Imaging 2008. © 2008 Wiley‐Liss, Inc.
Semi‐implicit schemes for transient Navier–Stokes equations and eddy viscosity models
Authors: Davis Lisa G. , Pahlevani Faranak
Published: April 2008

This study presents two computational schemes for the numerical approximation of solutions to eddy viscosity models as well as transient Navier–Stokes equations. The eddy viscosity model is one example of a class of Large Eddy Simulation models, which are used to simulate turbulent flow. The first approximation scheme is a first order single step method that treats the nonlinear term using a semi‐implicit discretization. The second scheme employs a two step approach that applies a Crank–Nicolson method for the nonlinear term while also retaining the semi‐implicit treatment used in the first scheme. A finite element approximation is used in the spatial discretization of the partial differential equations. The convergence analysis for both schemes is discussed in detail, and numerical results are given for two test problems one of which is the two dimensional flow around a cylinder. © 2008 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2009
Well‐controlled 3D skeletal epoxy‐based monoliths obtained by polymerization induced phase separation
Authors: Tsujioka Norio , Ishizuka Norio , Tanaka Nobuo , Kubo Takuya , Hosoya Ken
Published: April 2008

We recently presented a short communication on the preparation of epoxy‐based monoliths possessing highly ordered structures by polymerization induced phase separation based on the spinodal decomposition. In this article, we describe in detail on reaction mechanisms and structural properties of the epoxy‐based monoliths with well‐controlled macropores in the micrometer range. We prepared epoxy‐based monoliths based on diglycidyl ether of bisphenol A, bis(4‐aminocyclohexyl)methane, and polyethylene glycol with a bicontinuous structure by in situ step‐growth polymerization. Different morphology of epoxy‐based monoliths could be obtained by changing formulation of monomers and porogenic solvents. Characterizations of their morphologies were performed using scanning electron microscopy, mercury intrusion porosimetry, small angle X‐ray scattering, and gas adsorption measurement (BET method). © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3272–3281, 2008
Controlled polymerization of 2‐(diethylamino)ethyl methacrylate and its block copolymer with N‐isopropylacrylamide by RAFT polymerization
Authors: Liu Li , Wu Chenglin , Zhang Jiechun , Zhang Mingming , Liu Yuwei , Wang Xiaojuan , Fu Guoqi
Published: April 2008

Poly(2‐(diethylamino)ethyl methacrylate) (PDEAEMA) homopolymers with low polydispersities were synthesized by reversible addition fragmentation chain transfer (RAFT) radical polymerization. The performances of two chain transfer agents, 2‐cyanoprop‐2‐yl dithiobenzoate and 4‐cyanopentanic acid dithiobenzoate (CPADB), were compared. It was found that the polymerization of 2‐(diethylamino) ethyl methylacrylate was under good control in the presence of CPADB with 4,4′‐azobis(4‐cyanopentanoic acid) (ACPA) as initiator in 1,4‐dioxane at 70 °C. The kinetic behaviors were investigated under different CPADB/ACPA molar ratios. A long polymerization inhibition period was observed at high [CPADB]/[ACPA] ratio. The influences of [CPADB]/[ACPA] ratio, monomer/[CPADB] ratio, and temperature were studied with respect to monomer conversion, molecular weight control, and polydispersity index (PDI). The PDI decreased from 1.21 to 1.12, as the CPADB/ACPA molar ratio changed from 2 to 10. The molecular weight of PDEAEMA could be controlled by monomer/CPADB molar ratio. The control over MW and PDI was improved as the temperature increased from 60 to 70 °C; however, an additional increase to 80 °C led to a loss of control. Using PDEAEMA macroRAFT agent, pH/thermo double‐responsive block copolymers of PDEAEMA and poly(N‐isopropylacrylamide) (PDEAEMA‐b‐PNIPAM) with narrow polydispersity (PDI, 1.24) were synthesized. The lower critical solution temperature of PDEAEMA‐b‐PNIPAM block copolymer depended on the environmental pH. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3294–3305, 2008
Q‐Space Analysis Applied to Polydisperse, Dense Random Aggregates
Authors: Hubbard J. A. , Eckels S. J. , Sorensen C. M.
Published: April 2008

Polydisperse powders of spherical shell particles and nonspherical, three dimensionally dense aggregates were dispersed as turbulent jets through an abrupt orifice nozzle and in‐situ small angle light scattering measurements were made. In contrast to traditional studies, the light scattering data were plotted versus the scattering wave vector rather than the scattering angle; we call this q‐space analysis. For dense aggregates distinct power law trends emerged, similar to those discovered previously for spherical Mie scatterers. Moreover, when the system was very polydisperse, either with a broad bimodal or monotonic with extreme range, the q‐space analysis provided particle size distribution information about these aerosol systems which was unapparent when plotted as a function of the scattering angle.
Altered expression of 12S/MT‐RNR1, MT‐CO2/COX2, and MT‐ATP6 mitochondrial genes in prostate cancer
Authors: Abril Jesús , de Heredia Miguel López , González Laura , Clèries Ramon , Nadal Marga , Condom Enric , Aguiló Fernando , Gómez‐Zaera Montserrat , Nunes Virginia
Published: April 2008

BACKGROUND

Prostate cancer is one of the commonest cancers worldwide and is responsible for nearly 6% of all male cancer deaths. Despite this relevance, the mechanisms involved in the development and progression of this malignancy remain unknown. The involvement of polypeptides of the mitochondrial respiratory chain, the Krebs cycle and the glutathione antioxidant system in this type of cancer has been previously described, although no publication has focused on the expression of mitochondrial genes in the prostate of PCa patients.

METHODS

We have determined by reverse transcription‐quantitative PCR (RT‐qPCR) the relative amount of the transcripts of eight mitochondrial genes (MT‐ND2, MT‐ND4, MT‐ND6, MT‐CYB, 12S/MT‐RNR1, 16S/MT‐RNR2, MT‐CO2/COX2, MT‐ATP6), and four nuclear genes (COX11, GSR, CS, ACO2), all of them key players in the normal metabolism of mitochondria. Additionally we analyzed the expression of Cyclophilin A (PPIA).

RESULTS

We observed differential expression of mitochondrial 12S/MT‐RNR1, MT‐CO2/COX2, and MT‐ATP6 transcripts in tumor samples when compared to their paired normal samples.

CONCLUSIONS

The amount of mitochondrial 12S/MT‐RNR1, MT‐CO2/COX2, and MT‐ATP6 transcripts is significantly decreased in tumor samples when compared to their paired normal sample, suggesting that mitochondrial gene expression is altered in PCa. Prostate 68:1086–1096, 2008. © 2008 Wiley‐Liss, Inc.
Three‐dimensional model of the human urotensin‐II receptor: Docking of human urotensin‐II and nonpeptide antagonists in the binding site and comparison with an antagonist pharmacophore model
Authors: Lescot Elodie , Sopkova‐de Oliveira Santos Jana , Colloc'h Nathalie , Rodrigo Jordi , Milazzo‐Segalas Isabelle , Bureau Ronan , Rault Sylvain
Published: April 2008

Human urotensin‐II (hU‐II) is a cyclic peptide that plays a central role in cardiovascular homeostasis and is considered to be the most potent mammalian vasoconstrictor identified to date. It is a natural ligand of the human urotensin‐II (hUT‐II) receptor, a member of the family of rhodopsin‐like G‐protein‐coupled receptors. To understand the molecular interactions of hU‐II and certain antagonists with the hUT‐II receptor, a model of the hUT‐II receptor in an active conformation with all its connecting loops was constructed by homology modeling. The initial model was placed in a pre‐equilibrated lipid bilayer and re‐equilibrated by several procedures of energy minimization and molecular dynamics simulations. Docking studies were performed for hU‐II and for a series of nonpeptide hUT‐II receptor antagonists in the active site of the modeled receptor structure. Results of the hU‐II docking study are in agreement with our previous work and with experimental data showing the contribution of the extracellular loops II and III to ligand recognition. The docking of hU‐II nonpeptide antagonists allows identification of key molecular interactions and confirms a previously reported hU‐II antagonist pharmacophore model. The results of the present studies will be used in structure‐based drug design for developing novel antagonists for the hUT‐II receptor. Proteins 2008. © 2008 Wiley‐Liss, Inc.
Theory of the surface plasmon polariton–exciton interaction in multi‐layer systems
Authors: Schwieger S. , Vasa P. , Runge E.
Published: April 2008

A thorough theoretical understanding of the interaction of excitons and surface plasmon polaritons (SPP) in metal–semiconductor hybrid structures is of fundamental importance for the design of SPP‐based devices. A theory to describe SPP–exciton interaction in a periodic multilayer film system is presented and demonstrated. In a hybrid system of gold nanowires on top of a GaAs/AlGaAs quantum well (QW), our calculations show the formation of coupled SPP–exciton modes. These are predicted to be observable in reflection spectra and by near‐field scanning optical microscopy. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Mg‐doped InN and InGaN – Photoluminescence, capacitance–voltage and thermopower measurements
Authors: Ager J. W. , Miller N. , Jones R. E. , Yu K. M. , Wu J. , Schaff W. J. , Walukiewicz W.
Published: April 2008

The bandgap range of InGaN extends from the near‐IR (InN, 0.65 eV) to the ultraviolet. To exploit this wide tuning range in light generation and conversion applications, pn junctions are required. The large electron affinity of InN (5.8 eV) leads to preferential formation of native donor defects, resulting in excess electron concentration in the bulk and at surfaces and interfaces. This creates difficulties for p‐type doping and/or measuring of the bulk p‐type activity. Capacitance–voltage measurements, which deplete the n‐type surface inversion layer, have been used to show that Mg is an active acceptor in InN and Inx Ga1–x N for 0.2 < x < 1.0, i.e. over the entire composition range. Mg acceptors can be compensated by irradiation‐induced native donors. Thermopower measurements were used to provide definitive evidence that Mg‐doped InN has mobile holes between 200 K and 300 K. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effect of electrode pattern on light emission distribution in InGaN/GaN light emitting diode
Authors: Hwang Sungmin , Yoon Joosun , Shim Jongin , Yoo Kyungyul
Published: April 2008

The effect of geometrical electrode pattern on the blue InGaN/GaN multi‐quantum well (MQW) light emitting diode (LED) devices is investigated both theoretically and experimentally. A 3‐dimensional circuit model of an LED is constructed and then the corresponding circuit parameters are extracted. Circuit parameters of an LED consist of the resistances of the metallic film and epitaxial layer, and intrinsic diodes representing the light‐emitting active region. Both the transmission line model (TLM) and current‐voltage (I‐V) characteristics of LED are employed to extract circuit parameters experimentally. These circuit parameters are then applied to the circuit model to generate light emission patterns in a top‐surface emitting‐type LED. Experiment results verify that the emitting light distribution from fabricated LED coincides reasonably well with the theoretical results. This makes it possible to design an LED theoretically and predict its actual properties. The LED structure proposed using the model is shown to exhibit not only good light uniformity, but also higher light output power and lower voltage drop. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Voltage tunable wavelength LEDs
Authors: Soh C. B. , Chua S. J. , Hartono H.
Published: April 2008

We report on the growth and fabrication of a LED which emits light, tunable in color, as the injection current is increased from I = 1.0 mA to 40 mA. Two multiple quantum well (MQWs) structures, designated as A and B, are grown in the LEDs, with quantum dots embedded in MQWs B while MQWs A are conventional blue emitting quantum well layers. A broad photoluminescence spectrum ranging from 430 nm to 750 nm is measured, which is the result of spectral broadening attributed to the incorporation of quantum dots in the well layer of MQWs B coupled with the grading of Indium composition in the well of MQW B. This leads to a gradual change in the emission wavelength as the electron‐hole (e‐h) pairs recombine at the different stacked layers to give a transition from red, yellow, green and cyan as injection current increases. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Non‐lithographic nanopatterning of InGaN/GaN multiple quantum well nanopillars by focused ion beams
Authors: Wu S. E. , Hsueh T. H. , Liu C. P. , Sheu J. K. , Lai W. C. , Chang S. J.
Published: April 2008

This study proposes a new approach to fabrication of a high‐aspect‐ratio InGaN/GaN multiple quantum well nanopillar array. This fabrication technique utilizes focused ion beam milling with modified beam‐shape tuning technology. The samples used in this work have a light‐emitting diode (LED) structure grown by metal‐organic chemical‐vapour deposition. The modified beam‐shape tuning was performed by simultaneously stigmating and defocusing the ion beam. The structural and optical properties of the ion‐beam‐milled areas were examined by high resolution transmission electron microscopy and cathodoluminescence (CL). Typical nanopillars have diameters of about 100–150 nm and heights of about 600–1000 nm. The corresponding CL spectrum at room temperature revealed the main emission to be approximately 2.98 eV, and it showed a blue shift of about 35 meV compared to as‐grown samples. A maskless, site‐controlled approach to the fabrication of nano‐LEDs was demonstrated in this work. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Nanopatterning GaN with microspheres
Authors: Ng W. N. , Wang X. H. , Leung C. H. , Lai P. T. , Choi H. W.
Published: April 2008

In this work, the fabrication and characterization of nano‐pillar arrays on GaN substrates using the technique of microsphere lithography have been demonstrated. Self‐assembled hexagonally‐packed silica microsphere array were formed on GaN wafers by the methods of spin coating and tilting. By precisely controlling the process parameters, a monolayer of microsphere array can be formed over a wide region, acting as a hard‐mask for pattern transfer of the nanostructures. After dry etching, arrays of nano‐pillars were formed on the surface of the wafer. The structure properties of the ordered nanostructures were characterized by SEM images, while photoluminescence (PL) measurements revealed a twofold enhancement of light emission intensity. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Polychromatic emission from fluorescent‐microsphere‐coated LEDs
Authors: Hui K. N. , Ng W. N. , Leung C. H. , Lai P. T. , Choi H. W.
Published: April 2008

White light LEDs using fluorescent microspheres as color conversion agents are demonstrated. The hexagonal ordered arrays of green and red fluorescence microspheres were coated on the blue micro‐hexLED centered at 480 nm by microspheres coating technique. At optimal mixed portion of green and red microspheres, white light emission is generated by a combination of blue light from LED and down conversion of fluorescence emission of green and red microspheres by blue excitation light. An overall efficiency of more than 70% is obtained by this new approach. The enhanced efficiency is attributed to two main properties of ordered micropsheres arrays: (1) efficient color conversion and (2) efficient light out‐coupling via volumetric light scattering. The resultant LED has lumnious efficiency of 31.8 lm/W with CIE coordinates of (0.30, 0.31). We have demonstrated an alternative solution of producing white light emission, apart from existing down conversion of yellow phosphor with blue or UV LED and multichip LEDs. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Epitaxial lateral overgrowth of GaN on 4 inch Si(111) by MOVPE
Authors: Cheng Kai , Motsnyi V. , Leys M. , Degroote S. , Sijmus B. , Germain M. , Borghs G.
Published: April 2008

Epitaxial Lateral Overgrowth (ELOG) of GaN on 4 inch silicon(111) substrates by MOVPE was investigated in this study. ELOG was performed on a GaN template with a couple of AlGaN intermediate layers (IL) on an AlN nucleation layer. The AlGaN ILs supply compressive stress to the top GaN template and thereafter to the ELOG layer. Consequently, layer cracking is minimized. Two masks were used in this work: a 2 inch wagon wheel mask and a 4 inch mask with parallel stripes of various filling factors and periods. The filling factor is varied from 0.33 to 0.7. The periodic spacing is in the range of 6 μm to 10 μm. Temperature, V/III ratio, pressure and stripe orientation were optimized to achieve fastest lateral growth rate. The highest lateral to vertical ratio can be more than 4. A fully coalesced layer within the critical thickness for a crack‐free layer was achieved on 4 inch silicon substrates. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Improvement of surface roughness and reduction of threading dislocation density in AlN/AlGaN templates on sapphire by employing trimethylaluminum pulsed supply growth
Authors: Noguchi Norimichi , Ohashi Tomoaki , Kamata Norihiko , Hirayama Hideki
Published: April 2008

We fabricated high‐quality AlN/AlGaN templates, which are applicable to ultraviolet (UV) emitters on sapphire, by using a trimethylaluminum (TMAl) pulsed‐supply growth method. We succeeded in achieving a dramatic improvement in the surface roughness of AlN/AlGaN layer by introducing a short‐period pulsed supply of TMAl during the growth intervals of a ‘standard’ AlGaN growth regime. We speculate that the improvement in surface roughness is due to the realization of stable group III (+c) polarity by the growth of an Al‐rich surface. In addition, we have found that this method is effective for reducing threading dislocation densities (TDD). The TDD was reduced from 2.9×109 to 1.1×109 cm–2 by introducing the TMAl pulsed supply growth. We fabricated a 350 nm‐band InAlGaN multi‐quantum well (MQW) UV light‐emitting diode (LED) on an AlN/AlGaN template formed by the TMAl pulsed supply method, and obtained an output power of 1.95 mW under room temperature (RT) CW operation. The output power of the LED was increased by a factor of 1.7 by introducing the TMAl pulsed supply method. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dislocation related defect states in GaN irradiated with 1 MeV electron‐beam
Authors: Lee Dong Uk , Ha Lim‐Kyoung , Kim Jin Soak , Kim Eun Kyu , Koh Eui Kwan , Han Il Ki
Published: April 2008

Undoped GaN layers with thickness of 278 µm were grown by hydride vapor phase epitaxy method. The samples with different threading dislocation densities of 9.0x106 cm–2 and 7.2x106 cm–2 were irradiated by electron‐beam with the energy of 1 MeV and dose of 1x1015 cm–2. The defect states of the samples after electron beam irradiation were characterized by deep level transient spectroscopy measurement. After the electron‐beam irradiation, the the defects appeared to states with the activation energies of 0.61 eV, 0.30 eV, and 0.57 eV. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The CL emission observation of the InGaN/GaN MQWs V shaped pits with different superlattices underlayers
Authors: Lai W. C. , Huang Y. S. , Yen Y. W. , Sheu J. K. , Hsueh T. H , Kuo C. H. , Chang S. J.
Published: April 2008

We prepared InGaN/GaN multiquantum wells (MQWs) with InGaN/GaN strained layer superlattice (SLS) underlayer and with GaN/AlGaN SLS underlayer to create different V‐shaped pits. It was found that pit density became smaller while pit depth and pit diameter both became larger, as compared to the sample without SLS. It was also found that sample surface became rougher with the SLS. Furthermore, it was found that light output intensities observed from the samples with SLS were stronger. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Surface and boundary‐layer modelling for the Mars Exploration Rover sites
Authors: Savijärvi Hannu , Kauhanen Janne
Published: April 2008

The boundary layer and surface temperatures at the two Mars Exploration Rover sites (Spirit at Gusev Crater; Opportunity at Meridiani plains) were simulated with a soil–atmosphere column model and compared with the observations retrieved from scans through the thin and dusty CO2 atmosphere by the miniature thermal emission spectrometers (mini‐TES) onboard the two rovers.

The quite repetitive diurnal temperature cycle is reproduced fairly well by the model. In particular the surface temperatures appear to be well simulated. They are strongly controlled by the downwelling solar and thermal radiation from the atmosphere. Turbulent heat fluxes are small compared with net radiation, so they are relatively unimportant in the surface heat budget. Turbulence is nevertheless important in transferring heat convectively up from the radiatively heated and strongly superadiabatic daytime atmospheric surface layer. A strong surface inversion develops during each night.

The annual cycle is also well simulated, except that during the warm and dusty perihelion/summer period the temperatures appear overestimated by the model. This may be due to inaccurate handling of dust in the model, or to dust accumulation on the instrument optics, or perhaps both. The annual temperature cycle demonstrates the large eccentricity of Mars' orbit, the seasonal effects and the variable dustiness of the atmosphere. Copyright © 2008 Royal Meteorological Society
MP2, DFT‐D, and PCM study of the HMB–TCNE complex: Thermodynamics, electric properties, and solvent effects
Authors: Kysel Ondrej , Budzák Šimon , Medveď Miroslav , Mach Pavel
Published: April 2008

Geometry, thermodynamic, and electric properties of the π‐EDA complex between hexamethylbenzene (HMB) and tetracyanoethylene (TCNE) are investigated at the MP2/6‐31G* and, partly, DFT‐D/6‐31G* levels. Solvent effects on the properties are evaluated using the PCM model. Fully optimized HMB–TCNE geometry in gas phase is a stacking complex with an interplanar distance 2.87 × 10−10 m and the corresponding BSSE corrected interaction energy is −51.3 kJ mol−1. As expected, the interplanar distance is much shorter in comparison with HF and DFT results. However the crystal structures of both (HMB)2–TCNE and HMB–TCNE complexes have interplanar distances somewhat larger (3.18 and 3.28 × 10−10 m, respectively) than our MP2 gas phase value. Our estimate of the distance in CCl4 on the basis of PCM solvent effect study is also larger (3.06–3.16 × 10−10 m). The calculated enthalpy, entropy, Gibbs energy, and equilibrium constant of HMB–TCNE complex formation in gas phase are: ΔH0 = −61.59 kJ mol−1, ΔS = −143 J mol−1 K−1, ΔG0 = −18.97 kJ mol−1, and K = 2,100 dm3 mol−1. Experimental data, however, measured in CCl4 are significantly lower: ΔH0 = −34 kJ mol−1, ΔS = −70.4 J mol−1 K−1, ΔG0 = −13.01 kJ mol−1, and K = 190 dm3 mol−1. The differences are caused by solvation effects which stabilize more the isolated components than the complex. The total solvent destabilization of Gibbs energy of the complex relatively to that of components is equal to 5.9 kJ mol−1 which is very close to our PCM value 6.5 kJ mol−1. MP2/6‐31G* dipole moment and polarizabilities are in reasonable agreement with experiment (3.56 D versus 2.8 D for dipole moment). The difference here is due to solvent effect which enlarges interplanar distance and thus decreases dipole moment value. The MP2/6‐31G* study supplemented by DFT‐D parameterization for enthalpy calculation, and by the PCM approach to include solvent effect seems to be proper tools to elucidate the properties of π‐EDA complexes. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008
Initial formation of contact layers on Ni/SiC samples studied by XPS
Authors: Pérez‐García S. A. , Cao Y. , Nyborg L.
Published: April 2008

This study deals with the quantitative assessment of the coverage and thickness of Ni silicide films formed during annealing of SiC substrates with sputtered thin films of Ni. The analytical approach involves the use of XPS and depth profiling by means of successive ion etchings and XPS analyses. For either 3 or 6 nm initial Ni film thickness, a 10 nm Ni2Si product is formed. On top of this product, the C released is accumulated in a very thin (1–2 nm) film. In neither case, the Ni2Si covers the whole surface, although the coverage is almost complete (∼90%) in the latter case. For the greater initial Ni‐film thickness of 17 nm, the thickness of the Ni2Si product corresponds well to the value of 25 nm expected from the Ni/Ni2Si stoichiometric relationship. This thickness is significantly greater than a critical level and the film covers the whole surface. Carbon is similarly accumulated in a very thin layer on the top surface, although the major part of C (∼70%) is found inside the main reaction product layer. Copyright © 2008 John Wiley & Sons, Ltd.
Structuring interorganizational cooperation: the role of economic integration in strategic alliances
Authors: Luo Yadong
Published: April 2008

This study addresses a new dimension that describes interdependence between alliance members, namely, economic integration–the extent to which resources contributed by different alliance members and subsequent operations using these resources are effectively blended into an alliance's value chain to the point where if one member withdraws, the remaining member(s) suffer great loss. We posit that economic integration has a linear positive effect on alliance stability but a curvilinear (diminished) effect on alliance profitability. Moreover, when economic integration is stronger, other dyadic variables such as interparty trust, joint governance and procedural justice will have a greater effect on alliance performance. Analysis of 198 cross‐cultural strategic alliances in an emerging market generally supports these propositions. Copyright © 2008 John Wiley & Sons, Ltd.
The accentuated CEO career horizon problem: evidence from international acquisitions
Authors: Matta Elie , Beamish Paul W.
Published: April 2008

We develop a conceptual model of the career horizon problem of CEOs approaching retirement and discuss its implications on firm risk taking, specifically in engagement in international acquisitions. Based on prospect theory and agency theory, we emphasize the legacy conservation and wealth preservation concerns of CEOs and investigate how their holdings of in‐the‐money unexercised options and firm equity accentuate or mitigate the career horizon problem. The model is tested in the context of international acquisitions with a sample of 293 U.S. firms over a five‐year period (1995–1999). We find that a longer CEO career horizon is associated with a higher likelihood of international acquisitions. We also find that CEOs nearing retirement with high levels of in‐the‐money unexercised options and equity holdings are less likely to engage in international acquisitions than CEOs with low levels of in‐the‐money options and equity holdings. The study raises important considerations about the implications of CEOs' equity and in‐the‐money option holdings on firm risk taking at various stages of their career horizon. Copyright © 2008 John Wiley & Sons, Ltd.
Asymmetric interactions between foreign and domestic banks: effects on market entry
Authors: Li Jiatao
Published: April 2008

An inverted U‐shaped relationship is thought to exist between the number of firms entrenched in a market and the rate of new entrants. This study examined early and late entry by foreign and U.S. banks into the California market following a deregulation in the banking industry in the early 1980s. The study was designed to elucidate the competitive interactions between foreign and domestic banks. Specifically, what response did the entry of foreign banks elicit from domestic banks and what influence did the entry of domestic banks exert on the evolution of the foreign banks in the market. Data covering the period from 1979 to 1988 demonstrate that the density of foreign banks operating in the market had a U‐shaped relationship with the rate of entry of U.S. banks, supporting the argument that foreign investment can encourage the expansion of domestic banks. Although foreign banks were not an obstacle to domestic bank entries, the presence of domestic banks deterred the entry of foreign banks. Copyright © 2008 John Wiley & Sons, Ltd.
A bargaining perspective on strategic outsourcing and supply competition
Authors: De Fontenay Catherine C. , Gans Joshua S.
Published: April 2008

This article considers the outsourcing choice of a downstream firm with its own upstream production resources or assets. The novelty of the approach is to consider the outsourced function as involving resources consistent with the resource‐based view of the firm. From a bargaining perspective, we characterize a downstream firm's decision whether to outsource to an independent or to an established upstream firm. In so doing, the downstream firm faces a trade‐off between lower input costs afforded by independent competition, and higher resource value associated with those who can consolidate upstream capabilities. We show that this trade‐off is resolved in favor of outsourcing to an established firm. Copyright © 2008 John Wiley & Sons, Ltd.
Design of A Soft X‐ray Source with Periodic Microstructure Using Resonance Transition Radiation for Tabletop Synchrotron
Authors: Sugano Koji , Sun Weiyu , Tsuchiya Toshiyuki , Tabata Osamu
Published: April 2008

A soft X‐ray source with a periodic aluminum multilayer structure with vacuum layers in between for tabletop synchrotrons with low‐energy electrons was designed, and the dependence of radiation performance on structural parameters was clarified using a theoretical calculation of the resonance transition radiation. A photon density of 1 keV pr incident electron was calculated by optimizing the thickness of the aluminum and vacuum layers. Furthermore, the designed structure was fabricated by a microfabrication technique. The effects of dimensional error on the photon density are discussed on the basis of the calculated results and the prototype structure of a 6‐MeV synchrotron. It is clarified that dimensional errors of 1.5% in Al layers and of plus or minus a few dozen nanometers in the vacuum layers are negligible in obtaining a photon density of more than 90% of the maximum value. © 2008 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.
Low‐Noise Fully Differential Amplifiers Using JFET‐CMOS Integration Technology for Smart Sensors
Authors: Takao Hidekuni , Vatedka Radhakrishna , Ito Yoshiaki , Komakine Fumihito , Serge Kolelas , Sawada Kazuaki , Ishida Makoto
Published: April 2008

In this paper, CMOS‐based low‐noise amplifiers with JFET‐CMOS technology for high‐resolution sensor interface circuits are presented. A differential difference amplifier (DDA) configuration is employed to realize differential signal amplification with very high input impedance, which is required for the front‐end circuit in many sensor applications. Low‐noise JFET devices are used as input pair of the input differential stages or source‐grounded output load devices, which are dominant in the total noise floor of DDA circuits. A fully differential amplifier circuit with pure CMOS DDA and three types of JFET‐CMOS DDAs were fabricated and their noise performances were compared. The results show that the total noise floor of the JFET‐CMOS amplifier was much lower compared to that of the pure CMOS configuration. The noise‐reduction effect of JFET replacement depends on the circuit configuration. The noise reduction effect by JFET device was maximum of about − 18 dB at 2.5 Hz. JFET‐CMOS technology is very effective in improving the signal‐to‐noise ratio (SNR) of a sensor interface circuit with CMOS‐based sensing systems. © 2008 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.
A Superhydrophobic Microvalve for Manipulating Microliquids Containing Biological Molecules
Authors: Yasuda Takashi , Ishizuka Katsutoshi , Ezoe Mika
Published: April 2008

This paper presents a novel microvalve including a superhydrophobic surface that inhibits adsorption of a liquid that contains biological molecules. This microvalve was fabricated by anodizing the Si surface of a microchannel wall and making the channel surface partially superhydrophobic. The superhydrophobicity could be modified by changing the anodization time and current density during the anodization process. Experiments using a cell‐culture medium showed that the fabricated microvalve successfully opened/closed repeatedly by applying a positive/negative pressure from the inlet, and that it could be opened within 0.5 s by an inlet pressure of more than 9 kPa. Also, we could continue switching the microvalve at 1 Hz for about 3 h (10 800 switching) while adjusting the required inlet pressures, which increased with time. © 2008 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.
MEMS‐based Air Turbine with Radial‐inflow Type Journal Bearing
Authors: Tanaka Shuji , Miura Yuichi , Kang Piljoong , Hikichi Kousuke , Esashi Masayoshi
Published: April 2008

A microelectromechanical‐systems (MEMS)‐based air turbine with a new bearing system was designed, fabricated, and evaluated. The bearing system uses a radial‐inflow type journal bearing and a single‐sided hydroinertia thrust bearing. To fabricate the radial‐inflow type journal bearing, cavity‐through deep reactive ion etching (DRIE) in conjunction with silicon‐to‐silicon direct bonding was used. Two etched silicon substrates were directly bonded, and then the bonded silicon substrates were etched by DRIE through the inside cavities. A maximum rotation speed of 95 000 rpm was achieved. The measured and calculated frequency responses of the rotor‐bearing system suggest that the maximum rotation speed was probably limited by the pitching mode resonance. © 2008 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.
Electrostatically Controlled, Pneumatically Actuated Microvalve with Low Pressure Loss
Authors: Satoh Daisuke , Tanaka Shuji , Esashi Masayoshi
Published: April 2008

This paper describes a microvalve to control liquefied gas in a micro fuel reforming system. To realize both high pressure leak tolerance and low pressure loss, a main valve is pneumatically actuated by the pressure of the liquefied gas itself, and its pneumatic actuation is controlled by two electrostatic sub‐valves. The fabricated microvalve was tested in terms of pressure loss in the open state, leakage in the closed state, driving voltage, and response time. The pressure loss was close to the theoretical value, which was sufficiently low for the application. The apparent leakage was not detected until the input pressure reached 150 kPa (gage). The driving voltage of the sub‐valve was 30‐40 V. The response time from the closed to the open state is expected to be less than 200 ms. The experimental results suggest that all the required functions such as low pressure loss, electrostatic actuation and leak proof operation can be realized. © 2008 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.
Quantitative Evaluation of Corrosive Sulfur in Electrical Insulating Oil
Authors: Ito Takashi , Morishima Yoshiyuki
Published: April 2008

This paper presents quantitative evaluation method of corrosive sulfur in insulating oil. The level of corrosion on copper strip which was aged in insulating oil is expressed numerically by the amount of sulfur on it. Since X‐ray strength by wave length dispersive X‐ray (WDX) and measurement value of sulfur on copper strip by titration show good correlation, the amount of sulfur can be obtained rapidly only by WDX. The performance of passivator such as BTA or Irgamet39 was quantitatively evaluated by WDX. The evaluation of life of passivator was also achieved. Copyright © 2008 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.
Analyzing Method of Temporal Brain Activation in fMRI Measurements
Authors: Fukami Tadanori , Nakajima Natsuki , Shimada Takamasa , Ishikawa Fumito , Ishikawa Bunnoshin , Saito Yoichi
Published: April 2008

In this paper, we propose a method to acquire the temporal changes of activations by combining a slide of the analysis time window and t‐value. An advantage of this method is that it can acquire rough changes of the activated areas even with data having low time resolution. Nine normal subjects participated in the study of the visual oddball paradigm, which consisted of a random series of 30 targets and 30 control stimuli. Here, the subjects were instructed to push a button as the go‐task when a target stimulus occurred. We investigated the activated area in three types of analysis time sections: from stimulus onset to 5 s after the stimulus (time section A; TS‐A); from 5 to 10 s (TS‐B); and from 10 to 15 s (TS‐C). We also investigated the temporal change of the t‐value between go and no‐go responses in blood oxygenation level dependent (BOLD) signals. In this study, we picked up the following eight representative areas corresponding with previous reports: left primary motor area and left somatosensory motor area, supramarginal gyri (SMG), right superior parietal lobule, right inferior frontal gyrus, cerebellum (cerebellar tonsil), and right medial frontal gyrus. Among them, the left primary motor area and left somatosensory motor area showed prominent activation (t > 10) in TS‐A and TS‐B, respectively. Activity at the left supramarginal gyrus decreased gradually with time, and right insula showed constant activation through all time sections.

We could see various patterns on temporal activation at different positions in the brain. Copyright © 2008 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.
Fine‐Needle Aspiration Biopsy of Benign Thyroid Nodules: An Evidence‐Based Review
Authors: Lundgren Catharina Ihre , Zedenius Jan , Skoog Lambert
Published: April 2008

Background

Since the development of fine‐needle aspiration biopsy (FNAB) techniques, preoperative diagnosis and subsequent strategies for patient treatment have changed and evolved greatly. This is true also for thyroid FNAB: the vast majority of thyroid nodules are benign, and hence do not necessarily require surgical treatment.

Methods

A comprehensive Medline and Cochrane Library search was performed evaluating FNAB in the thyroid. In the last decade more than 400 articles on the subject have been published. Data in relation to the experience with FNAB at the Karolinska University Hospital since its introduction were also reviewed.

Results

The development of FNAB since the 1960s at the Karolinska University Hospital is described. During the period 1992–1996 the accuracy of the clinical routine was evaluated by studying the outcomes of almost 4,000 FNAs of the thyroid. The results were good, with only a few false‐negative and false‐positive results, but the problem of differentiating follicular adenoma from follicular carcinoma remained a significant problem. The use of immunological analysis has greatly increased the possibility of obtaining valuable information on cellular characteristics.

Conclusion

A successful FNAB service rests on several factors, and the importance of clinical conferences between all specialists involved in the diagnosis and treatment of patients with thyroid disorders cannot be overemphasized. At the Karolinska University Hospital there are weekly conferences where patients are discussed both pre‐ and postoperatively. These conferences lead to optimal interaction between the different specialists and, most important, substantial improvement in the clinical management of patients with thyroid disorders.
Choledochal Cysts in Children: Epidemiology and Outcomes
Authors: Singhavejsakul Jesda , Ukarapol Nuthapong
Published: April 2008

Background

The purpose of the present study was to evaluate the epidemiology and outcomes of choledochal cysts in children.

Methods

We performed a retrospective review of the records of all cases of choledochal cyst in children 0–14 years of age presenting at Chiang Mai University Hospital from May 2000 to February 2007. Demographic and clinical data, including laboratory and radiographic studies, as well as surgical and nonsurgical treatments and outcomes, were recorded.

Results

There were 32 patients (25 female) with a mean age at diagnosis of 4.1 years (range: 1 month to 14.8 years). The most common clinical presentation was jaundice (n = 17), followed by abdominal pain (n = 16), nausea/vomiting (n = 10), and abdominal mass (n = 8). Based on the Tondani modification of the Alonso‐Lej classification, 20 cases were type I, whereas 9, 2, and 1 of the patients had types IV, V, and II, respectively. Biliary tract infections, including cholecystitis (n = 5) and cholangitis (n = 3), were the most common preoperative complications. Twenty‐six patients had definitive surgery consisting of cystectomy with Roux‐en‐Y hepaticojejunostomy. Postoperative complications were noted in 3 patients and included intestinal obstruction, bleeding, and cholangitis. Three patients died, all younger than 2 years of age (p = 0.022).

Conclusion

The epidemiology of choledochal cysts in Thai children was similar to cases reported from other regions. Early diagnosis and treatment, particularly in children under 2 years of age, should be emphasized, because these patients are at a higher risk for development of chronic liver disease and poor outcome.
Diagnostic Accuracy of CT and Ultrasonography for Evaluating Metastatic Cervical Lymph Nodes in Patients with Thyroid Cancer
Authors: Ahn Ji Eun , Lee Jeong Hyun , Yi Jong Sook , Shong Young Ki , Hong Seok Joon , Lee Deok Hee , Choi Choong Gon , Kim Sang Joon
Published: April 2008

Background

The present study was designed to investigate the diagnostic ability of computed tomography (CT) and ultrasonography (USG) in the preoperative evaluation of the cervical nodal status of patients with thyroid cancer.

Methods

The study population consisted of 37 consecutive patients (female:male = 30:7, age range: 20–68 years) who subsequently underwent total thyroidectomy and neck dissection for thyroid cancer. The results of the review of the preoperative CT and those of the original USG reports were compared with the histopathologic results. The accuracy was evaluated by “per level” and “per patient” analyses of whether the CT or USG results had or had not altered the choice of surgical method.

Results

By “per level” analysis, the sensitivities, specificities, and diagnostic accuracies were 77%, 70%, 74% for CT and 62%, 79%, 68% for USG, respectively, with a significant difference in the sensitivities (p = 0.002). When the lymph node levels were grouped into central and lateral compartments, all of the values for the lateral compartment tended to be higher than those for the central compartment for both CT (78%, 78%, 78% versus 74%, 44%, 64%) and USG (65%, 82%, 71 versus 55%, 69%, 60%). By per patient analysis, the sensitivities, specificities, and diagnostic accuracies of CT and USG were 100%, 90%, 97% and 100%, 80%, 95%, respectively.

Conclusion

Despite of very high accuracy of USG by per patient analysis, the superior sensitivity of CT on the per level analysis may enable CT to play a complementary role for determining the surgical extent in selected patients with thyroid cancer.