bluuebunny/crossref_metadata_2025 huggingface dataset:
Variable Interference Azimuth Angle in Double-Biprism Electron Interferometry
Authors: Harada Ken , Akashi Tetsuya , Togawa Yoshihiko , Matsuda Tsuyoshi , Tonomura Akira
Published: July 2005

Double-biprism electron interferometry has been extended by enabling the control of azimuth rotation between the two filament electrodes of the biprisms. Varying the azimuth angle between the filaments induces two parameters not found in conventional electron interferometry: the azimuth angle of the interference fringes and the vertical length of the interference region. This extended interferometry enables us to obtain the phase profile of one-dimensionally structured materials widely along their elongated direction without reconstruction. Evaluation of the overall performance of the interferometry theoretically and experimentally demonstrated that it provides additional flexibility for interferometry.
Current Injection Laser Operation of GaAs/InAs Short-Period Superlattice/InP(411) Quantum Dot Laser Diodes with InAlAs Current Blocking Layer
Authors: Shimada Takashi , Hasegawa Shigehiko , Asahi Hajime
Published: July 2005

High lateral density (∼1011 cm-2) and well-aligned quantum dot (QD) structures are self-formed in (GaAs)2(InAs)
n
short period superlattices grown on InP(411) substrates by gas source molecular beam epitaxy. Light emitting diodes with these QDs as an active layer were fabricated. However, the light output power showed saturation for the driving current of over 100 mA. To overcome this problem, an InAlAs layer was inserted between QD active layer and p-type cladding layer as a current blocking layer. As a result, no saturation of output power was obtained up to 200 mA. Furthermore, pulsed current injection laser operation was realized for these layer structures.
Property Change of LiNbO3 Fabricated by Vapor Transport Equilibration Process
Authors: Kang Bonghoon , Joo Gi-Tae , Rhee Bum Ku
Published: July 2005

Congruent LiNbO3 crystal wafers were fabricated to be Li-compensated LiNbO3 by vapor transport equilibration process. The wavelength of absorption edge for Li-compensated LiNbO3 crystals is shift to shorter wavelength as the processing time increases. Through the P–E hysteresis loop, the coercive field of Li-compensated LiNbO3 was around 6–8 kV/mm. In non-critical phase matched second-harmonic generation, the phase matching temperature change as well as the birefringence change for temperature was measured. The phase matching temperature of Li-compensated LiNbO3 was observed around 230°C and the birefringence change for temperature was smaller than that of congruent LiNbO3.
High-Bandwidth Si-Based Metal Oxide Semiconductor/Silicon-on-Insulator Photodetectors for Optical Communications
Authors: Chang Shu-Tong , Liang Chi-Yuan , Hsu Buo-Chin
Published: July 2005

Novel Si-on-insulator metal oxide semiconductor (SOI MOS) photodetectors can reach a high bandwidth (22 GHz) and are fully compatible with ultralarge-scale integration (ULSI) technology. Using a the thick buried oxide in the substrate, the diffusion current can be eliminated and the device speed is determined by drift current. The device structure can be optimized by tuning the doping concentration of the buffer layer and the thickness of the epilayers. The analytical model for detector bandwidth are also proposed, and the results fit the simulation well.
Orientation of Microphase-Segregated Cylinders in Liquid Crystalline Diblock Copolymer by Magnetic Field
Authors: Tomikawa Naoki , Lu Zhibao , Itoh Tomomichi , Imrie Corrie T. , Adachi Mitsu-aki , Tokita Masatoshi , Watanabe Junji
Published: July 2005

This paper reports the first successful preparation of perfectly aligned cylindrical microdomains in liquid crystal (LC) diblock copolymer, polystyrene-block-poly-LC with a poly-LC composition of 84%, by application of a magnetic field. The prerequisite for their alignment is the exhibition of order-disorder transition of the microdomain structure. When the poly-LC segments transform from the isotropic phase to the nematic, well-defined microcylinders are concurrently formed from the weakly segregating state, and their alignment along the magnetic field is realized through the magnetic alignment of LC mesogens.
Observing Enhanced Phosphorescence and Electroluminescence from Triplet Emitter by Quantum Dot Doping
Authors: Laskar Inamur R. , Liu Hong-Wei , Huang Chin-Ping , Cheng Jung-An , Chen Teng-Ming
Published: July 2005

Luminescent CdSe/ZnS core-shell-type quantum dots (QDs) were synthesized by chemical colloidal methods. The photoluminescence (PL) intensity of a triplet emitter [bis(4-trifluoromethyl)-2-phenylbenzothiazolatoacetylacetonate–iridium(III) (Ir complex 1) and bis(4-methyl)-2-phenylbenzothiazolatoacetylacetonate–iridium(III) (Ir-complex 2)] was dramatically enhanced when bluish-green emitting CdSe/ZnS QDs were incorporated into these compounds. Experimental results indicate that the emissive region of QDs substantially overlaps with the low-energy absorption bands of Ir-complexes, indicating that the photons were absorbed by both the QDs and the Ir-complexes and that the energy absorbed by the QDs was transferred efficiently to the Ir-complex triplet emitter, resulting in the observed enhancement of PL intensity. A slow quenching of QDs emission was observed in a prepared set of solutions with gradual increasing of Ir complex concentration at a fixed QDs concentration in thin film PMMA matrix, which supports the energy transfer from Ir complex to QDs. In the fabricated double-layer electroluminescent (EL) devices, the emitting layer contained either only Ir-complex or a mixture of Ir-complex and CdSe/ZnS QDs with a specific molar ratio [Ir-complex/QDs = 1/0 (D-I); 1/0.5 (D-II), ..., 1/10 (D-V)]. The EL intensity and the luminance efficiency for D-II were higher (luminescence yield = 19.3 cd A-1) than those of the other devices. The PL and EL enhancement of the triplet emitter were also strongly supported by using ZnSe QDs rather than CdSe/ZnS QDs.
Improvement of Crystalline Quality of BeZnSe Using Buffer Layer by Migration Enhanced Epitaxy on GaP(001) Substrate
Authors: Yokoyama Takeshi , Niiyama Yuuki , Murata Tomoyuki , Watanabe Masahiro
Published: July 2005

The epitaxial growth of BeZnSe on a GaP(001) substrate has been demonstrated using migration enhanced epitaxy (MEE), in which the group-II materials (Be, Zn) and Se were irradiated on a substrate by turns, in order to improve the crystalline quality of the epilayer. As a result, in the photoluminescence (PL) measurements, the full-width at half-maximum (FWHM) value of the BeZnSe epilayer grown by molecular beam epitaxy (MBE) with a buffer layer (BL) grown by MEE was 56 meV at 13 K, and 82 meV at room temperature. The etch pit density (EPD) of the oval-type pits was 3.0 ×107 cm-2, and no small-type pits were observed. These results were obtained by reducing the number of stacking faults and/or perfect dislocations in the initial growth stage of MEE.
Polymer Stabilized Liquid Crystal Grating Consisting of Periodic Reverse Twist Domains
Authors: Honma Michinori , Takeishi Michitoshi , Nose Toshiaki
Published: July 2005

We attempt to form periodic reverse twist domains using a microscale rubbing pattern. Conditions for the injection of a liquid crystal (LC) material into an empty cell are discussed. The fabricated LC cells with periodic reverse twist domains are applied to electrically controllable LC gratings. The stability of the periodic reverse twist domains, when a high voltage is applied and the LC cell is heated, is discussed. To stabilize the periodic reverse twist domains, a polymer stabilization technique using a UV-curable LC material is employed. The influence of the density of the UV-curable LC material on the diffraction properties of LC gratings is investigated, experimentally.
The Effect of N2 Flow Rate in He/O2/N2 on the Characteristics of Large Area Pin-to-Plate Dielectric Barrier Discharge
Authors: Lee Yong-Hyuk , Kyung Se-Jin , Jeong Chang-Hyun , Yeom Geun-Young
Published: July 2005

In this study, the effects of N2 flow rate in the He/O2/N2 gas mixture on the characteristics of a pin-to-plate dielectric barrier discharge (DBD) having the size of 100 mm ×1000 mm have been investigated for the application to flat panel display processing such as photoresist ashing. The pin-to-plate DBD showed about 70–120% higher photoresist ashing rate at the same applied voltage compared to the conventional DBD. The addition of 3 slm of N2 to He(10 slm)/O2(3 slm) showed the highest photoresist ashing rate of about 580 nm/min for the pin-to-plate DBD at 12 kV of AC voltage. The increase of N2 flow rate in He/O2 gas mixture up to 3 slm appeared to increase the density of N2
+ ions and N2 metastables while the oxygen atomic density appeared to decrease continuously. The increase of photoresist ashing rate with the increase of N2 flow rate up to 3 slm was related to the increase of the substrate surface temperature by the increased collision of N2
+ ions and N2 metastables with the substrate.
Hydrogen Evolution from p-GaN Cathode in Water under UV Light Irradiation
Authors: Kobayashi Naoki , Narumi Toru , Morita Ryusuke
Published: July 2005

Hydrogen is evolved at a zero bias when a p-type GaN cathode in an electrolyte solution is irradiated with UV light, although both hydrogen evolution rate and photocurrent decrease during the irradiation. Spontaneous hydrogen evolution indicates that the conduction bandedge of p-GaN is above the reduction potential of H+(aq). From the relationship between the volume of generated hydrogen and the number of electrons traveling from the Pt anode to the p-GaN cathode, the reaction efficiency of electrons injected from the conduction band of the p-GaN cathode with H+(aq) in a neutral Na2SO4 electrolyte solution is larger than 70%. As a result, the overall quantum efficiency for the hydrogen generation before degradation is estimated to be 4–6% at a wavelength of 340 nm by considering the incident photon-to-current efficiency of p-GaN.
A 37% Efficiency, Kilohertz Repetition Rate Cryogenically Cooled Ti:Sapphire Regenerative Amplifier
Authors: Matsushima Isao , Yashiro Hidehiko , Tomie Toshihisa
Published: July 2005

We present a high-efficiency Ti:sapphire regenerative amplifier being developed as a pumping laser for a high-brilliance laser-plasma X-ray source operating at a multi-kHz repetition rate. A ring resonator is adopted for stable single transverse mode operation and a laser rod is cryogenically cooled to suppress the strong thermal lens effect. By reducing losses in the resonator and by matching the pumping mode volume with the resonator mode, the conversion efficiency is increased to 37%. The output power is 7.4 W when pumped by a 1 kHz 20 W green laser.
Raman Spectroscopic Characterization of Tetragonal PbZrxTi1-xO3 Thin Films: A Rapid Evaluation Method for c-Domain Volume
Authors: Nishida Ken , Osada Minoru , Wada Syunshuke , Okamoto Shoji , Ueno Risako , Funakubo Hiroshi , Katoda Takashi
Published: July 2005

We present the use of Raman spectroscopy as a rapid and convenient evaluation tool for domain distribution of tetragonal PbZr
x
Ti1-x
O3 (PZT) thin films. From polarized Raman analyses of epitaxial PZT thin films with various c-domain volumes, we found that the intensity of the A
1(TO) modes linearly scales with the c-domain volume. These observations, as well as the quick and nondestructive characteristics of this technique, clearly imply that Raman spectroscopy has enormous potential to quantify the fraction of c-domain volumes in a wide range of PZT devices.
Reaction Mechanisms of Brominated Chemically Amplified Resists
Authors: Yamamoto Hiroki , Kozawa Takahiro , Nakano Atsuro , Okamoto Kazumasa , Tagawa Seiichi , Ando Tomoyuki , Sato Mitsuru , Komano Hiroji
Published: July 2005

Poly(4-hydroxystyrene) (PHS) and its derivatives are widely-used base polymers for chemically amplified resists. Halogenation of polymers is a popular strategy to improve resist performance. However, the reaction mechanisms for halogenated PHS have not been investigated. We investigated the reaction mechanisms for brominated PHS from the viewpoint of acid generation. We found that brominated PHS without acid generators can produce acids with 55% efficiency compared with PHS with 3.1 mol % (10 wt %) triphenylsulfonium triflate. The acid yield of brominated PHS was twice that of poly(4-bromostyrene).
Transcranial Optical Imaging of Cold-Injured Brain in Rat
Authors: Ueda Yoshinori , Sato Shunichi , Ooigawa Hidetoshi , Nawashiro Hiroshi , Saitoh Daizoh , Shima Katsuji , Ashida Hiroshi , Obara Minoru
Published: July 2005

We performed a transcranial optical imaging of a cold-injured brain in a rat. The rat skull was illuminated with a 633 nm HeNe laser, and the distribution of reflected light intensity was imaged with a cooled charge-coupled device (CCD) camera. An increase in reflected light intensity was observed in the injured area. The analysis of brain tissues perfused with India ink suggested that a reduced blood flow rate in the area of injury enhances reflection.
Fabrication of DNA Nanofibers on a Planar Surface by Electrospinning
Authors: Takahashi Takuya , Taniguchi Masateru , Kawai Tomoji
Published: July 2005

The electrospinning method was employed for preparing DNA nanofibers on a mica substrate using a high electrostatic field. The DNA nanofibers were examined using atomic force microscopy. It was found that the amount, shape, average height and average length of the nanofibers depended on the experimental conditions. By controlling the applied voltage and the concentration of DNA, we obtained stretched DNA nanofibers at 20 kV and 1.5 wt % with an average height and length of 1.8 nm and 1 µm, respectively.
Rapid Preparation of CuInS2 Bulk Polycrystals by Two-Step Microwave Heating Process Using a Domestic Microwave Oven
Authors: Susaki Masami
Published: July 2005

CuInS2 bulk polycrystals have been prepared from stoichiometric mixtures of the elements in rapid time scales using a domestic microwave oven. The growth procedure involves a direct synthetic reaction and a succeeding melt solidification with the assistance of a CuO microwave heater. This leads to the successful preparation of homogeneous and densified CuInS2 crystals having n-type conductivity. The photoluminescence spectra of these crystals at 9 K exhibit sharp emission lines corresponding to free-exciton, bound-exciton and donor-to-valence-band emissions.
Etching Characteristics of Ge2Sb2Te5 Using High-Density Helicon Plasma for the Nonvolatile Phase-Change Memory Applications
Authors: Yoon Sung-Min , Lee Nam-Yeal , Ryu Sang-Ouk , Park Young-Sam , Lee Seung-Yun , Choi Kyu-Jeong , Yu Byoung-Gon
Published: July 2005

We investigated the etching behaviors of GST, which has been mainly employed for the realization of phase-change type nonvolatile memory devices, using high-density helicon plasma etching system under the various etching gas conditions. Our results provide the etch rates of GST thin films as a function of gas mixing ratio when the gas mixtures of Ar/Cl2 and Ar/CHF3 were applied. It was found that the etch selectivities of GST to SiO2 and to TiN were optimized at Ar/Cl2 = 90/10 and Ar/CHF3 = 80/20, respectively. It was also confirmed that there is no significant change in composition of GST after the etching process. Using the obtained results, we can design the etching process in a systematic way for the fabrication of GST-loaded phase-change type memory devices.
Heteroepitaxial Structure of F16VOPc/VOPc Fabricated on a KBr Substrate
Authors: Kambayashi Takuya , Ofuji Masato , Uno Souichiro , Hoshi Hajime , Takezoe Hideo , Ishikawa Ken
Published: July 2005

A hexadecafluorovanadylphthalocyanine (F16VOPc)/vanadylphthalocyanine (VOPc) heterostructure was fabricated by organic molecular beam epitaxy (OMBE) at 100°C on KBr. The structure was analyzed by transmission electron diffraction (TED) analysis and atomic force microscopy (AFM). It was revealed that the F16VOPc layer grows orientationally on the VOPc layer epitaxially grown on KBr. The lattice structures of F16VOPc are different on KBr and on VOPc; the former has two equivalent square lattices, while the latter has a unidirectional lattice. The F16VOPc layer is composed of pyramidal domains, and their size is smaller than that of F16VOPc domains grown on KBr. In this heterostructure, all the molecular planes of F16VOPc and VOPc are parallel to the KBr surface, which is possibly favorable for charge transfer between the F16VOPc and VOPc layers.
A Ferromagnetic Oxide Semiconductor as Spin Injection Electrode in Magnetic Tunnel Junction
Authors: Toyosaki Hidemi , Fukumura Tomoteru , Ueno Kazunori , Nakano Masaki , Kawasaki Masashi
Published: July 2005

A magnetic tunnel junctions composed of room temperature ferromagnetic semiconductor rutile Ti1-xCoxO2-δand ferromagnetic metal Fe0.1Co0.9separated by AlOxbarrier showed positive tunneling magnetoresistance (TMR) with a ratio of ∼11% at 15 K, indicating that Ti1-xCoxO2-δcan be used as a spin injection electrode. The TMR decreased with increasing temperature and vanished above 180 K. TMR action at high temperature is likely prohibited by the inelastic tunneling conduction due to the low quality of the amorphous barrier layer and/or the junction interface.
High Temperature Stability 850-nm In0.15Al0.08Ga0.77As/Al0.3Ga0.7As Vertical-Cavity Surface-Emitting Laser with Single Al0.75Ga0.25As Current Blocking Layer
Authors: Chang Yi-An , Lai Fang-I , Yu Hsin-Chieh , Kuo Hao-Chung , Laih Li-Wen , Yu Chun-Lung , Wang Shing-Chung
Published: July 2005

In this paper, we employed a high bandgap Al0.75Ga0.25As layer acting as an electronic blocking layer in the upper In0.15Al0.08Ga0.77As/Al0.3Ga0.7As active region before the growth of p-type layers of 850-nm vertical-cavity surface-emitting lasers (VCSELs). A threshold current of 1.33 mA and slope efficiency of 0.53 W/A at 25°C were obtained, and the temperature dependent light output and voltage versus current (L–I–V) characteristics showed that the VCSELs with a high bandgap Al0.75Ga0.25As layer were more stable when the substrate temperature was in a range of 25–95°C. The threshold current increased with temperature up to 95°C was less than 21% and the slope efficiency dropped only 24.5%.
Enhancement of Photoluminescence in CaTiO3:Pr3+ by Ba and Sr Substitution for Ca
Authors: Wang Xusheng , Xu Chao-Nan , Yamada Hiroshi
Published: July 2005

Photoluminescence properties were improved in CaTiO3:Pr3+ phosphor by substitution of Ba and Sr for Ca to a large extent of Ba (0–20%) and Sr (0–45%) fractions. Red emission intensity at 612 nm was greatly enhanced. It achieved its largest value in Ca0.7Sr0.3TiO3:Pr3+ sample, higher by 192% than CaTiO3:Pr3+. Enhancement of red emission in Ba and Sr added CaTiO3:Pr3+ is inferred to originate from improvement of Pr3+ 4f5d capture probability to electrons in the host conduction band and charge transfer state, which are lowered by Ba and Sr addition.
Emission Gain Narrowing in Dye-Doped Polymer Dispersed Liquid Crystals
Authors: Harada Haruo , Nakatsu Masaomi , Naito Hiroyoshi
Published: July 2005

Photoluminescence in dye-doped polymer-dispersed liquid crystals (PDLCs) has been studied. Gain narrowing in the photoluminescence spectra of dye-doped PDLC is observed. From the pumped area and temperature dependence of the peak intensity and the full width at half maximum of the emission band, it is found that multiple light scattering plays an essential role in the gain narrowing in dye-doped PDLC.
High-Velocity White Dwarfs and Galactic Structure
Authors: Reid I. Neill
Published: July 2005

▪ Abstract  A number of recent investigations suggest that cool white dwarfs are more numerous than predicted by conventional Galactic models and that those stars make a significant contribution to the mass budget of the Milky Way. In particular, there is speculation that cool white dwarfs are linked with the dark-matter halos. This review examines those recent results and matches them against current understanding of the properties of the stellar populations that make up the Milky Way, taking due account of the relative star formation histories of the disk and the thick disk. The new white dwarf observations do not require any additions to the conventional stellar populations of the Milky Way. There is no credible evidence of either an underlying population of ancient white dwarfs or a link between high-velocity degenerates and dark matter. Nonetheless, placed in the proper context, these high-velocity white dwarfs provide interesting insight on the likely history of the Milky Way. We show that the thick disk is likely to contribute ∼20% of Solar Neighborhood white dwarfs. If the thick disk is an old, single-burst population, as favored by most investigations, then those white dwarfs dominate at faint absolute magnitudes. As a result, analyses of the low-luminosity cutoff in the local white dwarf–luminosity function actually set limits on the age of the thick disk, rather than the thin disk. In absolute terms, these results imply that the thick disk is no older than 10 Gyrs, whereas major star formation in the thin disk may not have started until 7 to 8 Gyrs ago. Moreover, the enhanced [α/Fe] ratios in thick-disk and halo main-sequence stars suggest that those two populations have similar ages, implying a relatively young age for the field halo.
Increase in tension-dependent ATP consumption induced by cardiac troponin T mutation
Authors: Chandra Murali , Tschirgi Matthew L. , Tardiff Jil C.
Published: July 2005

How different mutations in cardiac troponin T (cTnT) lead to distinct secondary downstream cellular remodeling in familial hypertrophic cardiomyopathy (FHC) remains elusive. To explore the molecular basis for the distinct impact of different mutations in cTnT on cardiac myocytes, we studied mechanical activity of detergent-skinned muscle fiber bundles from different lines of transgenic (TG) mouse hearts that express wild-type cTnT (WTTG), R92W cTnT, R92L cTnT, and Delta-160 cTnT (deletion of amino acid 160). The amount of mutant cTnT is ∼50% of the total myocellular cTnT in both R92W and R92L TG mouse hearts and ∼35% in Delta-160 TG mouse hearts. Myofilament Ca2+sensitivity was enhanced in all mutant cTnT TG cardiac muscle fibers. Compared with the WTTG fibers, Ca2+sensitivity increased significantly at short sarcomere length (SL) of 1.9 μm ( P < 0.001) in R92W TG fibers by 2.2-fold, in R92L by 2.0-fold, and in Delta-160 by 1.3-fold. At long SL of 2.3 μm, Ca2+sensitivity increased significantly ( P < 0.01) in a similar manner (R92W, 2.5-fold; R92L, 1.9-fold; Delta-160, 1.3-fold). Ca2+-activated maximal tension remained unaltered in all TG muscle fibers. However, tension-dependent ATP consumption increased significantly in Delta-160 TG muscle fibers at both short SL (23%, P < 0.005) and long SL (37%, P < 0.0001), suggesting a mutation-induced change in cross-bridge detachment rate constant. Chronic stresses on relative cellular ATP level in cardiac myocytes may cause a strain on energy-dependent Ca2+homeostatic mechanisms. This may result in pathological remodeling that we observed in Delta-160 TG cardiac myocytes where the ratio of sarco(endo)plasmic reticulum Ca2+-ATPase 2/phospholamban decreased significantly. Our results suggest that different types of stresses imposed on cardiac myocytes would trigger distinct cellular signaling, which leads to remodeling that may be unique to some mutants.
Na+-K+ pump activation inhibits endothelium-dependent relaxation by activating the forward mode of Na+/Ca2+ exchanger in mouse aorta
Authors: Kim Moon Young , Seol Geun Hee , Liang Guo Hua , Kim Ji Aee , Suh Suk Hyo
Published: July 2005

The effect of Na+-K+ pump activation on endothelium-dependent relaxation (EDR) and on intracellular Ca2+ concentration ([Ca2+]i) was examined in mouse aorta and mouse aortic endothelial cells (MAECs). The Na+-K+ pump was activated by increasing extracellular K+ concentration ([K+]o) from 6 to 12 mM. In aortic rings, the Na+ ionophore monensin evoked EDR, and this EDR was inhibited by the Na+/Ca2+ exchanger (NCX; reverse mode) inhibitor KB-R7943. Monensin-induced Na+ loading or extracellular Na+ depletion (Na+ replaced by Li+) increased [Ca2+]i in MAECs, and this increase was inhibited by KB-R7943. Na+-K+ pump activation inhibited EDR and [Ca2+]i increase (K+-induced inhibition of EDR and [Ca2+]i increase). The Na+-K+ pump inhibitor ouabain inhibited K+-induced inhibition of EDR. Monensin (>0.1 μM) and the NCX (forward and reverse mode) inhibitors 2′4′-dichlorobenzamil (>10 μM) or Ni2+ (>100 μM) inhibited K+-induced inhibition of EDR and [Ca2+]i increase. KB-R7943 did not inhibit K+-induced inhibition at up to 10 μM but did at 30 μM. In current-clamped MAECs, an increase in [K+]o from 6 to 12 mM depolarized the membrane potential, which was inhibited by ouabain, Ni2+, or KB-R7943. In aortic rings, the concentration of cGMP was significantly increased by acetylcholine and decreased on increasing [K+]o from 6 to 12 mM. This decrease in cGMP was significantly inhibited by pretreating with ouabain (100 μM), Ni2+ (300 μM), or KB-R7943 (30 μM). These results suggest that activation of the forward mode of NCX after Na+-K+ pump activation inhibits Ca2+ mobilization in endothelial cells, thereby modulating vasomotor tone.
Gene expression profiling of the long-term adaptive response to hypoxia in the gills of adult zebrafish
Authors: van der Meer David L. M. , van den Thillart Guido E. E. J. M. , Witte Frans , de Bakker Merijn A. G. , Besser Jaya , Richardson Michael K. , Spaink Herman P. , Leito Jelani T. D. , Bagowski Christoph P.
Published: July 2005

Low oxygen levels (hypoxia) play a role in clinical conditions such as stroke, chronic ischemia, and cancer. To better understand these diseases, it is crucial to study the responses of vertebrates to hypoxia. Among vertebrates, some teleosts have developed the ability to adapt to extremely low oxygen levels. We have studied long-term adaptive responses to hypoxia in adult zebrafish. We used zebrafish that survived severe hypoxic conditions for 3 wk and showed adaptive behavioral and phenotypic changes. We used cDNA microarrays to investigate hypoxia-induced changes in expression of 15,532 genes in the respiratory organs (the gills). We have identified 367 differentially expressed genes of which 117 showed hypoxia-induced and 250 hypoxia-reduced expressions. Metabolic depression was indicated by repression of genes in the TCA cycle in the electron transport chain and of genes involved in protein biosynthesis. We observed enhanced expression of the monocarboxylate transporter and of the oxygen transporter myoglobin. The hypoxia-induced group further included the genes for Niemann-Pick C disease and for Wolman disease [lysosomal acid lipase (LAL)]. Both diseases lead to a similar intra- and extracellular accumulation of cholesterol and glycolipids. The Niemann-Pick C protein binds to cholesterol from internal lysosomal membranes and is involved in cholesterol trafficking. LAL is responsible for lysosomal cholesterol degradation. Our data suggest a novel adaptive mechanism to hypoxia, the induction of genes for lysosomal lipid trafficking and degradation. Studying physiological responses to hypoxia in species tolerant for extremely low oxygen levels can help identify novel regulatory genes, which may have important clinical implications.
Smooth muscle dynamics and maximal expiratory flow in asthma
Authors: Lambert Rodney K. , Wilson Theodore A.
Published: July 2005

A computational model for maximal expiratory flow in constricted lungs is presented. The model was constructed by combining a previous computational model for maximal expiratory flow in normal lungs and a previous mathematical model for smooth muscle dynamics. Maximal expiratory flow-volume curves were computed for different levels of smooth muscle activation. The computed maximal expiratory flow-volume curves agree with data in the literature on flow in constricted nonasthmatic subjects. In the model, muscle force during expiration depends on the balance between the decrease in force that accompanies muscle shortening and the recovery of force that occurs during the time course of expiration, and the computed increase in residual volume (RV) depends on the magnitude of force recovery. The model was also used to calculate RV for a vital capacity maneuver with a slow rate of expiration, and RV was found to be further increased for this maneuver. We propose that the measurement of RV for a vital capacity maneuver with a slow rate of expiration would provide a more sensitive test of smooth muscle activation than the measurement of maximal expiratory flow.
Molecular Classification and Pathogenesis of Eosinophilic Disorders: 2005 Update
Authors: Gotlib Jason
Published: July 2005

Use of the term ‘idiopathic hypereosinophilic syndrome (HES)’ has highlighted our basic lack of understanding of the molecular pathophysiology of eosinophilic disorders. However, over the last 10 years, the study of hypereosinophilia has enjoyed a revival. This interest has been rekindled by two factors: (1) the development of increasingly sophisticated molecular biology techniques that have unmasked recurrent genetic abnormalities linked to eosinophilia, and (2) the successful application of targeted therapy with agents such as imatinib to treat eosinophilic diseases. To date, most of these recurrent molecular abnormalities have resulted in constitutively activated fusion tyrosine kinases whose phenotypic consequence is an eosinophilia-associated myeloid disorder. Most notable among these are rearrangements of platelet-derived growth factor receptors α and β (PDGFRα, PDGFRβ), which define a small subset of patients with eosinophilic chronic myeloproliferative disorders (MPDs) and/or overlap myelodysplastic syndrome/MPD syndromes, including chronic myelomonocytic leukemia. Discovery of the cryptic FIP1L1-PDGFRA gene fusion in cytogenetically normal patients with systemic mast cell disease with eosinophilia or idiopathic HES has redefined these diseases as clonal eosinophilias. A growing list of fibroblast growth factor receptor 1 fusion partners has similarly emerged in the 8p11 myeloproliferative syndromes, which are often characterized by elevated eosinophil counts. Herein the focus is on the molecular gains made in these MPD-type eosinophilias, and the classification and clinicopathological issues related to hypereosinophilic syndromes, including the lymphocyte variant. Success in establishing the molecular basis of a group of once seemingly heterogeneous diseases has now the laid the foundation for establishing a semi-molecular classification scheme of eosinophilic disorders.
Clonality and Molecular Pathogenesis of Mastocytosis
Authors: Akin Cem
Published: July 2005

Mast cell is a hematopoietic lineage dependent on Kit signaling for growth, differentiation, and survival. Mast cells are found in excessive numbers in tissues in a heterogeneous group of disorders collectively known as mastocytosis. Last decade has witnessed important advancements in our understanding of the molecular pathology of mastocytosis. First, systemic mastocytosis has been found to be associated with activating codon 816 mutations of the c-kit gene. Second, this mutation was used as a tracking marker to elucidate the clonal nature of mastocytosis. These findings have resulted in consideration of systemic mastocytosis as a clonal neoplastic disorder of a hematopoietic progenitor cell. Improved knowledge of the mechanisms causing pathological mast cell growth will lead to the discovery of novel treatment options including drugs targeting the mutated Kit protein.
The Molecular Basis of Lecithin:Cholesterol Acyltransferase Deficiency Syndromes
Authors: Calabresi Laura , Pisciotta Livia , Costantin Anna , Frigerio Ilaria , Eberini Ivano , Alessandrini Paola , Arca Marcello , Bittolo Bon Gabriele , Boscutti Giuliano , Busnach Ghil , Frascà Giovanni , Gesualdo Loreto , Gigante Maddalena , Lupattelli Graziana , Montali Anna , Pizzolitto Stefano , Rabbone Ivana , Rolleri Marina , Ruotolo Giacomo , Sampietro Tiziana , Sessa Adalberto , Vaudo Gaetano , Cantafora Alfredo , Veglia Fabrizio , Calandra Sebastiano , Bertolini Stefano , Franceschini Guido
Published: July 2005

Objective—

To better understand the role of lecithin:cholesterol acyltransferase (LCAT) in lipoprotein metabolism through the genetic and biochemical characterization of families carrying mutations in the
LCAT
gene.

Methods and Results—

Thirteen families carrying 17 different mutations in the
LCAT
gene were identified by Lipid Clinics and Departments of Nephrology throughout Italy. DNA analysis of 82 family members identified 15 carriers of 2 mutant
LCAT
alleles, 11 with familial LCAT deficiency (FLD) and 4 with fish-eye disease (FED). Forty-four individuals carried 1 mutant
LCAT
allele, and 23 had a normal genotype. Plasma unesterified cholesterol, unesterified/total cholesterol ratio, triglycerides, very-low-density lipoprotein cholesterol, and pre-β high-density lipoprotein (LDL) were elevated, and high-density lipoprotein (HDL) cholesterol, apolipoprotein A-I, apolipoprotein A-II, apolipoprotein B, LpA-I, LpA-I:A-II, cholesterol esterification rate, LCAT activity and concentration, and LDL and HDL
3
particle size were reduced in a gene–dose-dependent manner in carriers of mutant
LCAT
alleles. No differences were found in the lipid/lipoprotein profile of FLD and FED cases, except for higher plasma unesterified cholesterol and unesterified/total cholesterol ratio in the former.

Conclusion—

In a large series of subjects carrying mutations in the
LCAT
gene, the inheritance of a mutated LCAT genotype causes a gene–dose-dependent alteration in the plasma lipid/lipoprotein profile, which is remarkably similar between subjects classified as FLD or FED.
PPARα, but not PPARγ, Activators Decrease Macrophage-Laden Atherosclerotic Lesions in a Nondiabetic Mouse Model of Mixed Dyslipidemia
Authors: Hennuyer Nathalie , Tailleux Anne , Torpier Gérard , Mezdour Hafid , Fruchart Jean-Charles , Staels Bart , Fiévet Catherine
Published: July 2005

Objective—

Peroxisome proliferator-activated receptor (PPAR) α and γ are nuclear receptors that may modulate atherogenesis, not only by correcting metabolic disorders predisposing to atherosclerosis but also by directly acting at the level of the vascular wall. The accumulation of lipid-laden macrophages in the arterial wall is an early pivotal event participating in the initiation and promotion of atherosclerotic lesion formation. Because PPARα and γ modulate macrophage gene expression and cellular function, it has been suggested that their ligands may modulate atherosclerosis development via direct effects on macrophages. In this report, we investigated the effect of a PPARα ligand (fenofibrate) and 2 PPARγ ligands (rosiglitazone and pioglitazone) on atherogenesis in a dyslipidemic nondiabetic murine model that develops essentially macrophage-laden lesions.

Methods and Results—

Mice were fed a Western diet supplemented or not with fenofibrate (100 mpk), rosiglitazone (10 mpk), or pioglitazone (40 mpk) for 10 weeks. Atherosclerotic lesions together with metabolic parameters were measured after treatment. Fenofibrate treatment significantly improved lipoprotein metabolism toward a less atherogenic phenotype but did not affect insulin sensitivity. Contrarily, rosiglitazone and pioglitazone improved glucose homeostasis, whereas they did not improve lipoprotein metabolism. Fenofibrate treatment significantly decreased the accumulation of lipids and macrophages in the aortic sinus. However, surprisingly, neither rosiglitazone nor pioglitazone had an effect on lesion lipid accumulation or macrophage content.

Conclusion—

These results indicate that in a dyslipidemic nondiabetic murine model, PPARα, but not PPARγ, activators protect against macrophage foam cell formation.
Signaling Pathways Involved in Adenosine Triphosphate-Induced Endothelial Cell Barrier Enhancement
Authors: Kolosova Irina A. , Mirzapoiazova Tamara , Adyshev Djanybek , Usatyuk Peter , Romer Lewis H. , Jacobson Jeffrey R. , Natarajan Viswanathan , Pearse David B. , Garcia Joe G.N. , Verin Alexander D.
Published: July 2005

Endothelial barrier dysfunction caused by inflammatory agonists is a frequent underlying cause of vascular leak and edema. Novel strategies to preserve barrier integrity could have profound clinical impact. Adenosine triphosphate (ATP) released from endothelial cells by shear stress and injury has been shown to protect the endothelial barrier in some settings. We have demonstrated that ATP and its nonhydrolyzed analogues enhanced barrier properties of cultured endothelial cell monolayers and caused remodeling of cell–cell junctions. Increases in cytosolic Ca
2+
and Erk activation caused by ATP were irrelevant to barrier enhancement. Experiments using biochemical inhibitors or siRNA indicated that G proteins (specifically G
αq
and G
αi2
), protein kinase A (PKA), and the PKA substrate vasodilator-stimulated phosphoprotein were involved in ATP-induced barrier enhancement. ATP treatment decreased phosphorylation of myosin light chain and specifically activated myosin-associated phosphatase. Depletion of G
αq
with siRNA prevented ATP-induced activation of myosin phosphatase. We conclude that the mechanisms of ATP-induced barrier enhancement are independent of intracellular Ca
2+
, but involve activation of myosin phosphatase via a novel G-protein–coupled mechanism and PKA.
Optical Action Potential Upstroke Morphology Reveals Near-Surface Transmural Propagation Direction
Authors: Hyatt Christopher J. , Mironov Sergey F. , Vetter Frederick J. , Zemlin Christian W. , Pertsov Arkady M.
Published: July 2005

The analysis of surface-activation patterns and measurements of conduction velocity in ventricular myocardium is complicated by the fact that the electrical wavefront has a complex 3D shape and can approach the heart surface at various angles. Recent theoretical studies suggest that the optical upstroke is sensitive to the subsurface orientation of the wavefront. Our goal here was to (1) establish the quantitative relationship between optical upstroke morphology and subsurface wavefront orientation using computer modeling and (2) test theoretical predictions experimentally in isolated coronary-perfused swine right ventricular preparations. We show in numerical simulations that by suitable placement of linear epicardial stimulating electrodes, the angle φ of wavefronts with respect to the heart surface can be controlled. Using this method, we developed theoretical predictions of the optical upstroke shape dependence on φ. We determined that the level
V
F
* at which the rate of rise of the optical upstroke reaches the maximum linearly depends on φ. A similar relationship was found in simulations with epicardial point stimulation. The optical mapping data were in good agreement with theory. Plane waves propagating parallel to myocardial fibers produced upstrokes with
V
F
*<0.5, consistent with theoretical predictions for φ>0. Similarly, we obtained good agreement with theory for plane waves propagating in a direction perpendicular to fibers (
V
F
*>0.5 when φ<0). Finally, during epicardial point stimulation, we discovered characteristic saddle-shaped
V
F
* maps that were in excellent agreement with theoretically predicted changes in φ during wavefront expansion. Our findings should allow for improved interpretation of the results of optical mapping of intact heart preparations.
Data-Robust Tight Lower Bounds to the Information Carried by Spike Times of a Neuronal Population
Authors: Pola G. , Petersen R. S. , Thiele A. , Young M. P. , Panzeri S.
Published: July 2005

We develop new data-robust lower-bound methods to quantify the information carried by the timing of spikes emitted by neuronal populations. These methods have better sampling properties and are tighter than previous bounds based on neglecting correlation in the noise entropy. Our new lower bounds are precise also in the presence of strongly correlated firing. They are not precise only if correlations are strongly stimulus modulated over a long time range. Under conditions typical of many neurophysiological experiments, these techniques permit precise information estimates to be made even with data samples that are three orders of magnitude smaller than the size of the response space.
The Cocktail Party Problem
Authors: Haykin Simon , Chen Zhe
Published: July 2005

This review presents an overview of a challenging problem in auditory perception, the cocktail party phenomenon, the delineation of which goes back to a classic paper by Cherry in 1953. In this review, we address the following issues: (1) human auditory scene analysis, which is a general process carried out by the auditory system of a human listener; (2) insight into auditory perception, which is derived from Marr's vision theory; (3) computational auditory scene analysis, which focuses on specific approaches aimed at solving the machine cocktail party problem; (4) active audition, the proposal for which is motivated by analogy with active vision, and (5) discussion of brain theory and independent component analysis, on the one hand, and correlative neural firing, on the other.
Learning Bounds for Kernel Regression Using Effective Data Dimensionality
Authors: Zhang Tong
Published: July 2005

Kernel methods can embed finite-dimensional data into infinite-dimensional feature spaces. In spite of the large underlying feature dimensionality, kernel methods can achieve good generalization ability. This observation is often wrongly interpreted, and it has been used to argue that kernel learning can magically avoid the “curse-of-dimensionality” phenomenon encountered in statistical estimation problems. This letter shows that although using kernel representation, one can embed data into an infinite-dimensional feature space; the effective dimensionality of this embedding, which determines the learning complexity of the underlying kernel machine, is usually small. In particular, we introduce an algebraic definition of a scale-sensitive effective dimension associated with a kernel representation. Based on this quantity, we derive upper bounds on the generalization performance of some kernel regression methods. Moreover, we show that the resulting convergent rates are optimal under various circumstances.
The Anti-Terrorist Legislation in the US: Inter Arma Silent Leges?
Authors: Vervaele John
Published: July 2005

The greatest danger posed by terrorism to our democracy and to our constitutional republic may be our executive branch’s overreaction to terrorism and its use of terrorism to erode the constitutionally mandated checks and balances and sharing of powers in foreign affairs, war powers and combating international crime. (Blakesley, 1992)
Advanced Methods for Characterizing the Immersion Factor of Irradiance Sensors
Authors: Hooker Stanford B. , Zibordi Giuseppe
Published: July 2005

Two new immersion factor methods are evaluated by comparing them with the so-called traditional (or incremental) method. For the first method, the optical measurements taken at discrete water depths are substituted by continuous profiles created by removing the water from the tank used in the experimental procedure at a constant flow rate with a pump. In the second method, the commonly used large tank is replaced by a small water vessel with sidewall baffles, which permits the use of a quality-assured volume of water. The summary of the validation results produced for the different methods shows a significant convergence of the two new methods with the traditional method with differences generally well below 1%. The average repeatabilities for single-sensor characterizations (across seven wavelengths) of the three methods are very similar and approximately 0.5%. The evaluation of the continuous method demonstrates its full applicability in the determination of immersion factors with a significant time savings. The results obtained with the small water vessel demonstrate the possibility of significantly reducing the size of the tank (along with decreasing the execution time) and permitting a completely reproducible methodology (based on the use of pure water). The small tank approach readily permits the isolation and quantification of individual sources of uncertainty, the results of which confirm the following aspects of the general experimental methodology: (a) pure water is preferred over tap water, (b) the water should not be recycled (so it does not age), (c) bubbles should be removed from all wetted surfaces, (d) the water surface should be kept as clean as possible, (e) sidewall reflections can be properly minimized with internal baffles, and (f) a pure water characterization can be easily corrected to produce an appropriate seawater characterization. Within the context of experimental efficiency and reproducibility, this study suggests that the combination of a properly baffled small tank with a constant-flow pump would be an optimal system.
Impact of Radar Tilt and Ground Clutter on Wind Measurements in Clear Air
Authors: Martin William J. , Shapiro Alan
Published: July 2005

From geometrical considerations, the optimum tilt angle for a meteorological radar at which the best possible vertical resolution results is derived. This optimum angle is a compromise between the effects of beam divergence and range gate spacing. For typical S-band radar parameters, this optimum tilt angle is found to be about 7°. However, wind analyses at this tilt angle were found not to be accurate in practice because of ground clutter contamination, and suboptimal angles need to be used. Most of the ground clutter was found to be sensed in the radar beam sidelobes. The data presented here imply that ground clutter is a serious contaminant at tilt angles as high as 45°. For clear-air wind profiling in the boundary layer, the impact of ground clutter contamination increased as the tilt angle was increased.

Data presented from four radars [the Goodland, Kansas, Weather Surveillance Radar-1988 Doppler (WSR-88D); the University of Oklahoma’s Doppler on Wheels; NCAR’s S-band dual-polarization Doppler radar (S-Pol); and NSSL’s Cimarron] suggest that a fairly narrow range of tilt angles from 1° to 2° is generally acceptable for wind profiling of the boundary layer in clear-air conditions. Tilt angles outside this range lead to significant systematic errors, primarily from ground clutter contamination.