bluuebunny/crossref_metadata_2025 huggingface dataset:
HOLE VELOCITY IN p-GaAs
Authors: Dalal Vikram L.
Published: February 2004

The drift velocity-electric field curve for holes in p-GaAs has been experimentally determined at 300 °K on <111> oriented samples. The velocity becomes a sublinear function of field around E=1.5×104 V/cm, but no saturation was observed up to the highest fields reached (Emax=6×104 V/cm, vmax=7.8×106 cm/sec). This result is in disagreement with the recent predictions of Kim based on analysis of GaAs avalanche diode oscillators.
HOLOGRAM WAVELENGTH SELECTOR FOR DYE LASERS
Authors: Kogelnik H. , Shank C. V. , Sosnowski T. P. , Dienes A.
Published: February 2004

A new type of wavelength selector for dye lasers is proposed. It consists of a holographically produced dielectric grating which is backed by a reflecting layer. Gratings of 2300, 3300, and 3700 lines/mm were recorded in dichromated gelatine and tested in an exciplex umbelliferone laser tuning from 3910 to 5670 Å.
LONGITUDINAL PHOTON FLUX DISTRIBUTION IN LOW-Q SEMICONDUCTOR LASERS
Authors: Ulbrich R. , Pilkuhn M. H.
Published: February 2004

A nonuniform photon flux distribution over the length of the active region in semiconductor injection lasers has been found by investigating the scattered light perpendicular to the direction of the stimulated light wave. This effect is present only in low-Q lasers.
STUDY OF FLUORESCENT LIFETIME OF THE ν3 VIBRATIONAL MODE IN SF6
Authors: Wood O. R. , Schwarz S. E.
Published: February 2004

Spontaneous emission from the ν3 fundamental vibration in SF6 gas after excitation by a pulse from a Q-switched CO2 laser is observed. The pressure dependence of the flourescence decay time indicates that, at low pressure, diffusion of excited molecules followed by deactivation at vessel walls is the dominant relaxation mechanism. At higher pressures, the time for collisional deactivation within the bulk of the gas is measured. Evidence which suggests that a longitudinal-acoustic-shock wave was present in the gas at higher pressures is given.
NEW HIGH-POWER SOURCE OF COHERENT MICROWAVE PHONONS
Authors: Auth D. C.
Published: February 2004

A new scheme for optically exciting intense microsound is proposed. The intense acoustic waves are generated by the enormous spatially periodic pressure gradients that arise under certain conditions from the interference of two high-power optical beams of short time duration. The technique provides a tuneable source of bulk and surface micro-acoustic waves.
OBSERVATION OF SPIN-WAVE SPECTRUM IN AN INSTABILITY AND MODE-LOCKING EXPERIMENT
Authors: Wang S. , Hsu Ta-lin
Published: February 2004

Spin-wave spectrum in an instability and mode-locking experiment was observed by using a spectrum analyzer. The experiment confirms that spin-wave side bands exist. The beating of the side bands with the central band is shown to be the cause for low-frequency modulation of the reflected microwave power. When a low-frequency acoustic wave was sent into the sample, the amplitude of the side bands increased at the expense of the central band. Therefore, the effect of magnetoelastic coupling can be used not only to lock the phases of the various spin-wave modes but also to regulate their amplitudes.
NANOSECOND GATING OF AN IMAGE INTENSIFIER CAPABLE OF TRIGGERED PICOSECOND PHOTOGRAPHY
Authors: Bradley D. J. , Higgins J. F. , Key M. H.
Published: February 2004

A high-gain image intensifier tube has been gated with a laser-triggered spark gap to produce single-shot nanosecond exposure, with spatial resolution of 10 1p/mm. The exposure has been directly calibrated employing a mode-locked laser pulse train and spatial resolution of 8 1p/mm has been obtained with picosecond illumination from a single mode-locked pulse.
DOUBLE INJECTION IN Au-DOPED Si p-π-n DIODES
Authors: Zwicker H. R. , Streetman B. G. , Andrews A. M. , Deuling H. J.
Published: February 2004

Calculations of the J-V characteristics of Au-doped Si p-π-n devices are presented, using a computer-aided solution of the general conduction and recombination equations. The three charge states of the Au impurity are included in the computations. The predicted characteristics for a Au density of 5×1016 cm−3 exhibit good agreement with experiment. The calculations reveal the spatial distributions of carriers and space charge within the π region for various injection levels.
MINORITY CARRIER TRAPPING BY DEFECT CLUSTERS
Authors: Gregory B. L.
Published: February 2004

A theoretical study of the trapping behavior of defect clusters in semiconductors indicates that many of the unusual trapping effects observed in neutron-irradiated materials are a natural result of placing a large density of otherwise normal deep defects within a defect cluster. The space charge which results from majority carriers trapped on such defects within the cluster produces a potential barrier for majority carriers, or a potential well for minority carriers, which greatly influences the capture kinetics of defects within the cluster. Approximate calculations have been performed for the build-up of charge within the cluster following a large pulse of injected minority carriers. The calculations predict that the excess conductivity produced by this pulse should decay at an extremely slow nonexponential rate, especially at low temperatures. The predictions are in good agreement with experimental results for photoconductive decay in neutron-irradiated silicon.
CHOPPING OF MODE-LOCKED LASER PULSES BY INTERFEROMETRIC COMBINATION OF FREQUENCY-SHIFTED PULSES
Authors: Hargrove L. E. , Rosenberg Robert L.
Published: February 2004

Mode-locked laser pulses can be ``chopped'' into many pulses by interferometrically combining electro-optically frequency-shifted pulses. This letter presents analysis of one such scheme and confirming experimental results. Expressions are derived for the output intensity in the form of an envelope function times the input pulse intensity. Criteria are presented for obtaining significant chopping rather than just pulse narrowing and/or distortion. Calculated examples are in excellent qualitative agreement with the experiments.
AUGER ELECTRON SPECTROSCOPY IN SCANNING ELECTRON MICROSCOPY: POTENTIAL MEASUREMENTS
Authors: MacDonald N. C.
Published: February 2004

The Auger electron spectrum was measured, using an electron spectrometer mounted in a scanning electron microscope (SEM). The shift in the energy of a differentiated carbon and oxygen Auger electron peak was measured as a function of an applied potential on the surface of a specimen. The accuracy of the potential measurements is shown to be quite insensitive to transverse electric fields, and the peak shift as a function of the applied voltage is shown to be linear over a voltage range of greater than −40 to 40V for a carbon peak (E ∼270 eV). Potential differences of less than 2V were measured with a spatial resolution of less than 5μm, for a primary beam current of 1μA, and a primary beam energy of 10 keV. Auger electron peaks for carbon and oxygen together with a normal SEM micrograph are presented to demonstrate, for the first time, Auger electron chemical analysis with high spatial resolution.
EFFECTS OF COBALT ON THE SPIN REORIENTATION TEMPERATURE OF RARE-EARTH ORTHOFERRITES
Authors: Van Uitert L. G. , Sherwood R. C. , Gyorgy E. M. , Grodkiewicz W. H.
Published: February 2004

Small substitutions of Co for Fe in the orthorhombic yttrium and rare-earth orthoferrites greatly reduce uniaxial anisotropy. A percent of Co generally suffices to reorient the net moment from the c axis to the a axis at room temperature. The effect is at least two orders of magnitude greater than that for Sm substitution for other rare-earth ions.
LASER-GENERATED STRESS WAVES
Authors: Anderholm N. C.
Published: February 2004

A method of generating stress waves with a laser is demonstrated using a transparent material to impede the expansion of the vaporized absorber. A stress wave whose magnitude is 34 kbar and whose width at half-maximum is equal to the width of the laser pulse is reported.
CHANNELING STUDY OF BORON-IMPLANTED SILICON
Authors: North J. C. , Gibson W. M.
Published: February 2004

The channeling technique has been used to determine the lattice location of boron implanted into silicon by using the B11 (p,α) nuclear reaction. Approximately 30% of the boron lies on substitutional sites after a room-temperature implantation of 3×1015/cm2. The substitutional content decreases with annealing temperature up to 700 °C and then increases at higher annealing temperature. This explains a reverse annealing behavior observed in the carrier concentration. Nearly all of the boron lies on substitutional sites after annealing at 1100 °C. The nonsubstitutional boron atoms do not occupy the normal tetrahedral interstitial sites. For annealing temperatures up to 500 °C they appear to lie along <110> atomic rows, but they do not lie midway between <110> row lattice sites. After higher-temperature annealing their location appears less well-defined.
ABSORPTION PROFILES AND INVERTED LAMB DIPS OF I2 VAPOR AT 633 nm AS STUDIED WITH A He–Ne LASER
Authors: Knox J. D. , Pao Yoh-Han
Published: February 2004

The rotational-vibrational structure of the B3Πog+← X′Σou+ electronic transitions in I2127 and I2129 vapors have been examined in detail over a spectral range of 2000 MHz in the 633-nm region using He3–Ne20 and He3–Ne22 lasers. In addition, the hyperfine components of the Lamb dips in these two vapors have been observed. Due to the increased absorption, the inverted Lamb dips are easily observed in I2129.
SPIN-LONGITUDINAL AND SPIN-SHEAR ELASTIC WAVE CONVERSION IN AN AXIALLY MAGNETIZED YIG ROD
Authors: Morgenthaler F. R. , Rezende S. M. , Hu H. L. , Platzker A.
Published: February 2004

We report the first successful conversion of z-directed spin waves to longitudinal elastic waves (and vice versa) in an axially magnetized (z axis) single-crystal YIG rod. The conversions — carried out at L-band frequencies and room temperature — were possible because the symmetry axis of the rod was not along a principal crystallographic direction; the axis was chosen to be in a {100} plane at an angle of 22.5° with respect to a <100> direction in order to provide nearly maximum spin-longitudinal elastic wave coupling.
TRANSITIONS BETWEEN MODE-LOCKED STATES IN INTRACAVITY PHASE-MODULATED LASERS
Authors: Lyon D. L. , Kinsel T. S.
Published: February 2004

The transition between the two possible pulse train outputs of a mode-locked laser was studied. The experimental results are in close agreement with a simple, phenomenological model of the transition.
NEW CONTRAST MECHANISM FOR SCANNING ELECTRON MICROSCOPE
Authors: Wells Oliver C.
Published: February 2004

With normal electron incidence, the resolution of the backscattered electron image in the scanning electron microscope (SEM) is approximately equal to the classical electron pentration depth. With oblique electron incidence, a significant number of plurally scattered electrons leave the specimen in an apparently specular direction after penetrating for a distance that is an order of magnitude smaller than this. Thus with 15-keV electrons incident onto Al at 45°, a significant number of backscattered electrons leave the specimen after penetrating to less than 500-a.u. depth. These electrons can be collected over an angle that is close to the plane of the specimen surface. Other electrons leave the specimen more nearly at right angles to the surface, and these have been scattered from a greater depth. The image in the SEM can change completely if the position of the collector is changed.
CURRENT OSCILLATIONS IN CADMIUM SULPHIDE WITH OPTICALLY POLISHED PARALLEL SURFACES
Authors: Das P. , Steckl A. J.
Published: February 2004

Current oscillations in CdS samples with optically polished parallel surfaces have been observed as a result of motion of high-field domains formed by the large acousto-electric effect due to reflection of ultrasound which builds up to large amplitude provided by net round-trip gain. The experimental results also point to different kinds of oscillations.
NONMAGNETOSTATIC VOLUME AND SURFACE WAVE MODES ON GYROMAGNETIC YIG ROD WAVEGUIDES
Authors: Tao T. F. , Tully J. W.
Published: February 2004

Electromagnetic surface waves on a gyromagnetic single crystalline YIG rod waveguide were measured by a disturbing body technique in a surface wave resonator. Both the volume and surface-mode surface waves were measured under conditions when magnetostatic analysis is not valid. Experimental results are presented to show that important nonmagnetostatic characteristics of surface wave propagation revealed in the dispersion plot have all been verified.
OBSERVATIONS OF CURRENT FILAMENTS IN CHROMIUM-DOPED GaAs
Authors: Ferro A. P. , Ghandhi S. K.
Published: February 2004

Multiple current filaments are observed during the low-impedance post-breakdown state of double injection diodes fabricated from chromium-doped, semi-insulating gallium arsenide.
OPTICAL ACTIVITY AND FARADAY ROTATION IN BISMUTH OXIDE COMPOUNDS
Authors: Feldman Albert , Brower William S. , Horowitz Deane
Published: February 2004

The optical rotatory power and Faraday rotation were measured in crystals of 17Bi2O3: Ga2O3, 7Bi2O3: ZnO, Bi12TiO20, Bi12GeO20, and Bi12SiO20 in the wavelength range 400 to 700 nm at room temperature. Our crystals were enantiomorphs of those reported previously. The large Verdet coefficients indicate that these crystals are potentially useful as magneto-optic modulator materials.
ESR AND OPTICAL ABSORPTION STUDIES OF ION-IMPLANTED SILICON
Authors: Crowder B. L. , Title R. S. , Brodsky M. H. , Pettit G. D.
Published: February 2004

The g value, line shape, and linewidth of an ESR signal in Si layers which have been damaged by ion implantation of Si, P, or As at room temperature are found to be identical to those of the electron states observed in amorphous Si films prepared by rf sputtering. Interference phenomena observed in the optical absorption spectra allow a determination of the depth to which the Si has been damaged by the energetic heavy ions. These two techniques together provide a new tool for investigating lattice disorder in ion-implanted Si layers.
TRANSIENT STIMULATED ROTATIONAL AND VIBRATIONAL RAMAN SCATTERING IN GASES
Authors: Mack M. E. , Carman R. L. , Reintjes J. , Bloembergen N.
Published: February 2004

Using a mode-locked ruby laser, stimulated rotational and vibrational Raman scattering has been observed in a variety of high-pressure gases, where previously no stimulated scattering has been reported. Pulse energy conversion efficiencies as high as 70% have been obtained. Evidence for a strong optical Stark effect is seen in the gases producing rotational scattering. Self-focusing in a collimated beam is observed in N2O and CO2.
INSTABILITIES IN SEMICONDUCTING GLASS DIODES
Authors: Shanefield D. , Lighty P. E.
Published: February 2004

A predominantly amorphous mixture of Te, As, and Ge exhibits electrical memory effects, but continued cycling of the memory leads to unstable behavior. An explanation is based on the presence of varying amounts of crystalline material, and a quantitative relationship is presented.
DEFLECTING OF LIGHT BEAMS USING A GRADIENT OF THE INDEX OF REFRACTION IN SEMICONDUCTING GLASSES
Authors: Böer K. W.
Published: February 2004

A method is described for deflecting narrow light beams, using the gradient of the index of refraction due to a temperature gradient in a current channel, in a semiconducting glass, or near a heated wire in a glass or liquid. Independent xy laser beam deflections of more than 10° have been achieved with this method.
NARROW CURIE-POINT SWITCHING TRANSFER CHARACTERISTICS IN Mn–Bi FILMS
Authors: Lewicki G. , Guisinger J. E.
Published: February 2004

Mn–Bi films can be prepared such that the magnetic field controlling Curie-point switching is on the order of 30 Oe.
InAsP–Cs2O, A HIGH-EFFICIENCY INFRARED-PHOTOCATHODE
Authors: Sonnenberg H.
Published: February 2004

The response of an InAs0.15P0.85–Cs2O photoemitter in the spectral range from 0.4 to 1.1μ is experimentally investigated. The 0.8% quantum efficiency obtained at 1.06μ represents more than an order of magnitude improvement in yield over existing S-1 photosurfaces. The physical principle upon which this photoemitter is based is discussed in terms of a simple energy-level diagram.
EPITAXY OF GOLD EVAPORATED ONTO POLAR SURFACES OF ZnO AT 20°K
Authors: Wassermann E. F. , Polacek K.
Published: February 2004

Gold films (200–500 Å) have been evaporated onto air- and vacuum-cleaved polar surfaces of ZnO. While the films grown on the air-cleaved surfaces are polycrystalline in a temperature range from 20 to about 450°K, the films grown on the vacuum-cleaved surfaces are perfect (111) single crystals in the investigated temperature range from 20 to 700°K. The low-temperature epitaxy can be explained by the strong binding energy between overgrowth and substrate, caused by the polarity of the substrate.
EFFECT OF ARSENIC PRESSURE ON HEAT TREATMENT OF LIQUID EPITAXIAL GaAs
Authors: Mũnoz E. , Snyder W. L. , Moll J. L.
Published: February 2004

Short-time heat treatments in a H2 flow, and under an As vapor, have been performed on n-type and p-type GaAs crystals. Acceptors are created at the surface and proceed to the interior. The changes in carrier concentration as function of As vapor pressure showed the acceptors to be associated with As vacancies.
DIRECT OBSERVATION OF THE ASHLEY-MILNES THREE-HALVES POWER LAW POTENTIAL VERSUS DISTANCE IN THE PREBREAKDOWN SQUARE LAW REGION OF GOLD-DOPED GERMANIUM DOUBLE-INJECTION DIODES
Authors: Ham W. E. , Ashley K. L.
Published: February 2004

Measurement of potential distributions versus distance in gold-doped germanium double-injection diodes have been made and compared to the Ashley-Milnes theory. Estimates of capture cross sections of the gold centers based on these measurements have been calculated to be σn0=10−16 cm2 and σn− = 3 × 10−17 cm2 at 77.2°K.
TIME-AVERAGED DENSITY PROFILE IN THE PRESENCE OF A FINITE-AMPLITUDE HELICAL INSTABILITY
Authors: Ventrice Carl A.
Published: February 2004

Time-averaged density measurements are made in an argon plasma in the presence of a longitudinal magnetic field of strength equal to eight times the critical field for a helical instability. Under certain conditions, the positive column is found to be dominated by a finite-amplitude helical instability; and the functional form of the time-averaged density profile is in agreement with the theory of Holter and Johnson.
ACOUSTIC PARAMETRIC OSCILLATIONS IN LiNbO3
Authors: Thompson R. B. , Quate C. F.
Published: February 2004

We report on the observation of backward wave acoustic oscillations in LiNbO3. We have confined our study to fast shear waves propagating along the x axis, and we have been successful in generating these waves at a frequency of 1.43 GHz with a spatially uniform electric field at 2.86 GHz applied along the z axis. In addition, it has been possible to observe 60 dB of gain for an injected acoustic signal. Maximum peak strains are estimated to be in excess of 5 × 10−4.
CAST PERMANENT MAGNETS OF THE CO5 RE TYPE WITH A (BH)M EXCEEDING 12 MILLION G-Oe
Authors: Nesbitt E. A. , Chin G. Y. , Sherwood R. C. , Wernick J. H.
Published: February 2004

An energy product of 12.3 × 106 G-Oe has been obtained on cast samples of a cobalt rare-earth permanent magnet having the composition Co3.3Fe0.5Cu1.2Ce0.25Sm0.75. This exceeds the former high value of 9.8 × 106 G-Oe obtained in an alloy of Co3.8Fe0.5Cu0.9Ce.
COHERENCE LENGTH CURVE FOR RUBY OSCILLATOR-AMPLIFIER
Authors: Siebert L. D.
Published: February 2004

The observation of maximum holographic brightness at a pathlength difference of 1.25m is reported for a ruby oscillator-amplifier system in which the reference beam was split off the oscillator output, and the amplifier was used only in the object illumination beam. The method of obtaining the holographic coherence length curve and the explanation for the offset are discussed.
DOUBLE-HETEROSTRUCTURE INJECTION LASERS WITH ROOM-TEMPERATURE THRESHOLDS AS LOW AS 2300 A/cm2
Authors: Panish M. B. , Hayashi I. , Sumski S.
Published: February 2004

Double-heterostructure AlxGa1−xAs–GaAs– AlxGa1−xAs injection lasers with room-temperature thresholds as low as 2300 A/cm2 have been prepared by solution epitaxy. These lasers have high gain and a low temperature coefficient of the threshold up to the highest temperatures measured, 380 °K.
Sperm penetration of immature and maturing oocytes does not affect phosphorylation of mitogen-activated protein kinase in pigs
Authors: Quan H. M. , Meng X. Q. , Hou Y. , Sun Q. Y.
Published: February 2004

Pig oocytes cultured in vitro for 0, 25, 33 and 44 h were inseminated by frozen–thawed ejaculated sperm. At specified times after insemination, sperm penetration, cell cycle progression and mitogen-activated protein kinase (MAPK) phosphorylation were evaluated. It was shown that: (1) oocytes at various maturational stages could be penetrated by sperm; (2) sperm penetration did not affect meiotic cell cycle progression; (3) sperm penetration of germinal vesicle (GV) oocytes and maturing oocytes did not alter MAPK phosphorylation; and (4) when premetaphase I (pre-MI) and metaphase I (MI) oocytes, in which MAPK was activated, were fertilised, no evident MAPK dephosphorylation was detected as in metaphase II oocytes. The data suggest that sperm penetration before oocyte maturation does not affect MAPK phosphorylation and that the machinery inactivating MAPK upon fertilisation is not developed in maturing (pre-MI to MI) oocytes.
Antiinflammatory activity of soluble guanylate cyclase: cGMP-dependent down-regulation of P-selectin expression and leukocyte recruitment
Authors: Ahluwalia Amrita , Foster Paul , Scotland Ramona S. , McLean Peter G. , Mathur Anthony , Perretti Mauro , Moncada Salvador , Hobbs Adrian J.
Published: February 2004

Nitric oxide (NO) production by the vascular endothelium maintains an essential antiinflammatory, cytoprotective influence on the blood vessel wall. A key component of this activity is attributed to prevention of leukocyte–endothelial cell interactions, yet the underlying mechanisms remain unclear. The NO receptor, soluble guanylate cyclase (sGC), is expressed in endothelial cells but fulfils an unknown function. Therefore, we used intravital microscopy in mesenteric postcapillary venules from WT and endothelial nitric oxide synthase (eNOS) knockout (eNOS–/–) mice, and an sGC activator (BAY 41–2272), to investigate a potential role for sGC in the regulation of adhesion molecule expression and leukocyte recruitment. Leukocyte rolling and adhesion was 6-fold greater in eNOS–/–than WT animals. BAY 41–2272 and the NO-donor, diethylamine-NONOate, reduced leukocyte rolling and adhesion in eNOS–/–mice to levels observed in WT animals. These effects were blocked by the sGC inhibitor ODQ [1H-(1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one], which itself caused a 6-fold increase in leukocyte rolling and adhesion in WT mice. Increased leukocyte rolling and adhesion in IL-1β-treated mice was also inhibited by BAY 41–2272. Fluorescence-activated cell sorting analysisin vitroand a specific P-selectin neutralizing antibodyin vivorevealed that selective down-regulation of P-selectin expression accounted for the antiadhesive effects of sGC activation. These data demonstrate that sGC plays a key antiinflammatory role by inhibiting P-selectin expression and leukocyte recruitment.
Diffusion at finite speed and random walks
Authors: Keller Joseph B.
Published: February 2004

Diffusion, which occurs with infinite speed, results from a random walk with steps of finite speed. We resolve this paradox and derive a modified diffusion equation with finite speed.
Kv1.3 potassium channels are localized in the immunological synapse formed between cytotoxic and target cells
Authors: Panyi G. , Vámosi G. , Bacsó Z. , Bagdány M. , Bodnár A. , Varga Z. , Gáspár R. , Mátyus L. , Damjanovich S.
Published: February 2004

Membrane proteins of cytotoxic T cells specifically reorganize to form an immunological synapse (IS) on interaction with their specific target. In this paper, we investigated the redistribution of Kv1.3 channels, which are the dominant voltage-gated potassium channels, in the plasma membrane of allogen-activated human cytotoxic T lymphocytes (CTLs) on interacting with their specific target cells. Kv1.3 channels bearing a FLAG epitope were expressed in the CTLs and the cell-surface distribution of fluorescently labeled ion channels was determined from confocal laser-scanning microscopy images. FLAG epitope-tagged Kv1.3 channels showed a patchy distribution in CTLs not engaged with target cells, whereas the channels were accumulated in the IS formed between CTLs and specific target lymphocytes. Localization of Kv1.3 channels in the IS might open an unrevealed possibility in the regulation of ion channel activity by signaling molecules accumulated in the IS.
Caspase cleavage of Bim
EL
triggers a positive feedback amplification of apoptotic signaling
Authors: Chen Dan , Zhou Qiang
Published: February 2004

Members of the Bcl-2 protein family that share only the Bcl-2 homology 3 (BH3) domain are known mostly as sentinels for apoptotic stimuli and initiators of apoptosis. One BH3-only protein, Bim, is the major physiological antagonist of the prosurvival proteins in B and T lymphocytes. It is required for hematopoietic homeostasis and to preclude autoimmunity. Here, we show that the Bim
EL
isoform, which was predominant in T cells, existed in both phosphorylated and unphosphorylated forms. Whereas the unphosphorylated Bim
EL
was sequestered to microtubules by means of a direct interaction with tubulin, the phosphorylated protein was released from microtubules. The freed Bim
EL
was subjected to caspase cleavage at an early stage of apoptosis induced by stimuli that activate either the mitochondria- or death receptor-dependent apoptosis pathway. The N-terminally cleaved Bim
EL
became hyperactive in inducing apoptosis because of its more efficient targeting of Bcl-2. Thus, unlike many other BH3-only proteins, Bim
EL
can be activated downstream of the caspase cascade, leading to a positive feedback amplification of apoptotic signals.
Multiple evidence for nucleotide metabolism in the chloroplast thylakoid lumen
Authors: Spetea Cornelia , Hundal Torill , Lundin Björn , Heddad Mounia , Adamska Iwona , Andersson Bertil
Published: February 2004

The apparatus of photosynthetic energy conversion in chloroplasts is quite well characterized with respect to structure and function. Light-driven electron transport in the thylakoid membrane is coupled to synthesis of ATP, used to drive energy-dependent metabolic processes in the stroma and the outer surface of the thylakoid membrane. The role of the inner (luminal) compartment of the thylakoids has, however, remained largely unknown although recent proteomic analyses have revealed the presence of up to 80 different proteins. Further, there are no reports concerning the presence of nucleotides in the thylakoid lumen. Here, we bring three lines of experimental evidence for nucleotide-dependent processes in this chloroplast compartment. (
i
) The thylakoid lumen contains a protein of 17.2 kDa, catalyzing the transfer of the γ-phosphate group from ATP to GDP, proposed to correspond to the nucleoside diphosphate kinase III. (
ii
) The 33-kDa subunit of photosystem II, bound to the luminal side of the thylakoid membrane and associated with the water-splitting process, can bind GTP. (
iii
) The thylakoid membrane contains a nucleotide transport system that is suggested to be associated with a 36.5-kDa nucleotide-binding protein. Our results imply, against current dogmas, that the thylakoid lumen contains nucleotides, thereby providing unexpected aspects on this chloroplast compartment from a metabolic and regulatory perspective and expanding its functional significance beyond a pure bioenergetic function.
Mammalian Overlapping Genes: The Comparative Perspective
Authors: Veeramachaneni Vamsi , Makalowski Wojciech , Galdzicki Michal , Sood Raman , Makalowska Izabela
Published: February 2004

It is believed that 3.2 billion bp of the human genome harbor ∼35,000 protein-coding genes. On average, one could expect one gene per 300,000 nucleotides (nt). Although the distribution of the genes in the human genome is not random,it is rather surprising that a large number of genes overlap in the mammalian genomes. Thousands of overlapping genes were recently identified in the human and mouse genomes. However,the origin and evolution of overlapping genes are still unknown. We identified 1316 pairs of overlapping genes in humans and mice and studied their evolutionary patterns. It appears that these genes do not demonstrate greater than usual conservation. Studies of the gene structure and overlap pattern showed that only a small fraction of analyzed genes preserved exactly the same pattern in both organisms.
High-Resolution Analysis of DNA Copy Number Using Oligonucleotide Microarrays
Authors: Bignell Graham R. , Huang Jing , Greshock Joel , Watt Stephen , Butler Adam , West Sofie , Grigorova Mira , Jones Keith W. , Wei Wen , Stratton Michael R. , Futreal P. Andrew , Weber Barbara , Shapero Michael H. , Wooster Richard
Published: February 2004

Genomic copy number alterations are a feature of many human diseases including cancer. We have evaluated the effectiveness of an oligonucleotide array, originally designed to detect single-nucleotide polymorphisms, to assess DNA copy number. We first showed that fluorescent signal from the oligonucleotide array varies in proportion to both decreases and increases in copy number. Subsequently we applied the system to a series of 20 cancer cell lines. All of the putative homozygous deletions (10) and high-level amplifications (12; putative copy number >4) tested were confirmed by PCR (either qPCR or normal PCR) analysis. Low-level copy number changes for two of the lines under analysis were compared with BAC array CGH; 77% (n = 44) of the autosomal chromosomes used in the comparison showed consistent patterns of LOH (loss of heterozygosity) and low-level amplification. Of the remaining 10 comparisons that were discordant, eight were caused by low SNP densities and failed in both lines. The studies demonstrate that combining the genotype and copy number analyses gives greater insight into the underlying genetic alterations in cancer cells with identification of complex events including loss and reduplication of loci.
Expression of Sonic hedgehog (SHH) signaling molecules in ameloblastomas
Authors: Kumamoto Hiroyuki , Ohki Kousuke , Ooya Kiyoshi
Published: February 2004

Background:  To clarify the roles of Sonic hedgehog (SHH) signal transduction in oncogenesis and cytodifferentiation of odontogenic tumors, expression of SHH, Patched (PTC), Smoothened (SMO), and GLI1 was analyzed in ameloblastomas as well as in tooth germs.

Methods:  Tissue specimens of 9 tooth germs, 36 benign ameloblastomas, and 1 malignant ameloblastoma were examined by reverse transcriptase‐polymerase chain reaction (RT‐PCR) and immunohistochemistry for the expression of SHH, PTC, SMO, and GLI1.

Results:  Expression of SHH, PTC, SMO, and GLI1 mRNA was detected in all tooth germ and ameloblastoma samples. Immunohistochemical reactivity for SHH, PTC, SMO, and GLI1 was detected in both normal and neoplastic odontogenic tissues. Expression of SHH, PTC, and GLI1 was more evident in epithelial cells than in mesenchymal cells, whereas SMO reactivity was marked in both epithelial and mesenchymal components in tooth germs and ameloblastomas. In ameloblastomas, these SHH signaling molecules were expressed more intensely in peripheral columnar or cuboidal cells than in central polyhedral cells; keratinizing cells and granular cells showed no or little reactivity.

Conclusion:  Expression of SHH, PTC, SMO, and GLI1 in tooth germs and ameloblastomas suggests that these SHH signaling molecules might play a role in epithelial–mesenchymal interactions and cell proliferation in tooth development as well as in growth of these epithelial odontogenic tumors.
Internet project‐based learning environment: the effects of thinking styles on learning transfer
Authors: Lee C.‐I. , Tsai F.‐Y.
Published: February 2004

The purpose of this study, in an environment of Internet project‐based learning, is to undertake research on the effects of thinking styles on learning transfer. In this study, we establish an environment that incorporates project‐based learning and Internet. Within this environment, we divide our sample of elementary school students into four groups: Executive Group, Legislative Group, Judicial Group, and Mixed Group. Taking the learning of ‘Natural Science’ as an example, we investigate the effects of different thinking styles on learning transfer. The results of this study are:

significant differences between the near transfer of the Executive Group and the Legislative Group,

no significant differences in far transfer are found among groups of different thinking styles,

the near transfer of the Mixed Group is superior to that of the Legislative Group and the Judicial Group, and

the far transfer of the Mixed Group is superior to that of the Legislative Group.
Popularity functions, partisan effects, and support in Parliament
Authors: Veiga Francisco José , Veiga Linda Gonçalves
Published: February 2004

This paper analyzes the popularity of the main political entities in Portugal. Estimation results of popularity functions validate the responsibility hypothesis, with unemployment, and to a lesser extent inflation, affecting popularity levels. There is also evidence of personality effects, of popularity erosion over consecutive terms and of honeymoon effects. Finally, we found that voters' evaluations of incumbents' performance regarding unemployment is affected by their support in Parliament – when an incumbent faces more opposition in Parliament, voters are less likely to hold him responsible for unemployment increases.
Segmentation induced by intraluminal fatty acid in isolated guinea‐pig duodenum and jejunum
Authors: Gwynne Rachel M. , Thomas E. A. , Goh S. M. , Sjövall H. , Bornstein J. C.
Published: February 2004

Small intestinal movements depend on the composition of the chyme with mixing predominating at high nutrient levels and propulsion being prevalent at low nutrient levels. The mechanisms coupling nutrients to motility are unknown. We used computer analysis of video recordings of isolated guinea‐pig duodenum, jejunum and ileum to examine movements induced by a fatty acid, decanoic acid. Increasing intraluminal pressure past a threshold using control saline consistently evoked propulsive reflexes: lumen‐occluding constrictions appeared at the oral end propagating at 20.4 ± 2.4 mm s−1 (mean ±s.d., jejunum) to the anal end before being repeated until the intraluminal pressure was returned to control. Subthreshold pressure increases sometimes evoked a transient series of constrictions appearing at the oral end and propagating anally at 18.4 ± 4.7 mm s−1 (jejunum). At basal pressures, decanoic acid dose‐dependently induced motor activity consisting of 40–60 s episodes of constrictions separated by 40–200 s periods of quiescence and lasting up to 2 h. Five contraction patterns were identified within episodes including localized stationary constrictions; constrictions that propagated slowly (5–8 mm s−1) for short distances orally or anally; and constrictions that propagated orally or anally for the length of the preparation at 14–20 mm s−1. Decanoic acid induced motor activity was reversibly abolished by tetrodotoxin (3 μm), hyoscine (1 μm) and hexamethonium (100 μm), but was insensitive to blockade of P2 purinoceptors by PPADS (60 μm). Thus, decanoic acid induces motor activity equivalent to segmentation in guinea‐pig small intestine in vitro and this depends on intrinsic neural pathways.
Propagation of pacemaker activity in the guinea‐pig antrum
Authors: Hennig G. W. , Hirst G. D. S. , Park K. J. , Smith C. B. , Sanders K. M. , Ward S. M. , Smith T. K.
Published: February 2004

Cyclical periods of depolarization (slow waves) underlie peristaltic contractions involved in mixing and emptying of contents in the gastric antrum. Slow waves originate from a myenteric network of interstitial cells of Cajal (ICC‐MY). In this study we have visualized the sequence and propagation of Ca2+ transients associated with pacemaker potentials in the ICC network and longitudinal (LM) and circular muscle (CM) layers of the isolated guinea‐pig gastric antrum. Gastric antrum was dissected to reveal the ICC‐MY network, loaded with Fluo‐4 AM and activity was monitored at 37°C. Ca2+ waves propagated throughout the ICC‐MY network at an average velocity of 3.24 ± 0.12 mm s−1 at a frequency of 4.87 ± 0.16 cycles min−1 (n= 4). The propagation of the Ca2+ wave often appeared ‘step‐like’, with separate regions of the network being activated after variable delays. The direction of propagation was highly variable (Δ angle of propagation 44.3 ± 10.9 deg per cycle) and was not confined to the axes of the longitudinal or circular muscle. Ca2+ waves appeared to spread out radially from the site of initiation. The initiating Ca2+ wave in ICC‐MY was correlated to secondary Ca2+ waves in intramuscular interstial cells of Cajal, ICC‐IM, and smooth muscle cells, and the local distortion (contraction) in a field of view. TTX (1 μm) had little effect on slow wave or pacemaker potential activity, but 2‐APB (50 μm) blocked all Ca2+ waves, indicating a pivotal role for intracellular Ca2+ stores. Nicardipine (2 μm) eliminated the Ca2+ transient generated by smooth muscle, but did not affect the fast upstroke associated with ICC‐MY. These results indicate that slow waves follow a sequence of activation, beginning with the ICC‐MY and ICC‐IM network, followed later by a sustained Ca2+ transient in the muscle layers that is responsible for contraction.
Interlaboratory comparison of microphone calibration
Authors: Wong George S. K. , Wu Lixue
Published: February 2004

The results of an interlaboratory comparison on microphone calibration involving five National Metrology Institutes (NMIs) are presented. The Institute for National Measurement Standards (INMS—Canada), was the pilot laboratory that provided the data analysis for this investigation. The final results presented here were discussed and agreed upon by all participants. The maximum rms deviation for the two LS1P laboratory standard microphones measured by the above participants is 0.037 dB, which may be considered as the key comparison reference value.
Matched-field depth estimation for active sonar
Authors: Hickman Granger , Krolik Jeffrey L.
Published: February 2004

This work concerns the problem of estimating the depth of a submerged scatterer in a shallow-water ocean by using an active sonar and a horizontal receiver array. As in passive matched-field processing (MFP) techniques, numerical modeling of multipath propagation is used to facilitate localization. However, unlike passive MFP methods where estimation of source range is critically dependent on relative modal phase modeling, in active sonar source range is approximately known from travel-time measurements. Thus the proposed matched-field depth estimation (MFDE) method does not require knowledge of the complex relative multipath amplitudes which also depend on the unknown scatterer characteristics. Depth localization is achieved by modeling depth-dependent relative delays and elevation angle spreads between multipaths. A maximum likelihood depth estimate is derived under the assumption that returns from a sequence of pings are uncorrelated and the scatterer is at constant depth. The Cramér–Rao lower bound on depth estimation mean-square-error is computed and compared with Monte Carlo simulation results for a typical range-dependent, shallow-water Mediterranean environment. Depth estimation performance to within 10% of the water column depth is predicted at signal-to-noise ratios of greater than 10 dB. Real data results are reported for depth estimation of an echo repeater to within 10-m accuracy in this same shallow water environment.
Acoustic field induced in spheres with inhomogeneous density by external sources
Authors: Kokkorakis Gerassimos C. , Fikioris John G.
Published: February 2004

Acoustic or electromagnetic fields induced in the interior of inhomogeneous penetrable bodies by external sources can be evaluated via well-known volume integral equations. For bodies of arbitrary shape and/or composition, for which separation of variables fails, a direct attack for the solution of these integral equations is the only available approach. In a previous paper by the same authors the scalar (acoustic) field in inhomogeneous spheres of arbitrary compressibility, but with constant density, was considered. In the present one the direct hybrid (analytical-numerical) method applied to the much simpler integral equation for spheres with constant density is generalized to densities that vary with r, θ, or even φ. This extension is by no means trivial, owing to the appearance of the derivatives of both the density and the unknown function in the volume integral, a fact necessitating a more subtle and accuracy-sensitive approach. Again, the spherical shape allows use of the orthogonal spherical harmonics and of Dini’s expansions of a general type for the radial functions. The convergence of the latter, shown to be superior to other possible sets of orthogonal expansions, can be further optimized by the proper selection of a crucial parameter in their eigenvalue equation.
On Rayleigh waves in incompressible orthotropic elastic solids
Authors: Ogden Ray W. , Vinh Pham Chi
Published: February 2004

In this paper the secular equation for the Rayleigh wave speed in an incompressible orthotropic elastic solid is obtained in a form that does not admit spurious solutions. It is then shown that inequalities on the material constants that ensure positive definiteness of the strain–energy function guarantee existence and uniqueness of the Rayleigh wave speed. Finally, an explicit formula for the Rayleigh wave speed is obtained.
Old World frog and bird vocalizations contain prominent ultrasonic harmonics
Authors: Narins Peter M. , Feng Albert S. , Lin Wenyu , Schnitzler Hans-Ulrich , Denzinger Annette , Suthers Roderick A. , Xu Chunhe
Published: February 2004

Several groups of mammals such as bats, dolphins and whales are known to produce ultrasonic signals which are used for navigation and hunting by means of echolocation, as well as for communication. In contrast, frogs and birds produce sounds during night- and day-time hours that are audible to humans; their sounds are so pervasive that together with those of insects, they are considered the primary sounds of nature. Here we show that an Old World frog (Amolops tormotus) and an oscine songbird (Abroscopus albogularis) living near noisy streams reliably produce acoustic signals that contain prominent ultrasonic harmonics. Our findings provide the first evidence that anurans and passerines are capable of generating tonal ultrasonic call components and should stimulate the quest for additional ultrasonic species.
On the calculation of the transmission line parameters for long tubes using the method of multiple scales
Authors: Scheichl Stefan
Published: February 2004

The present paper deals with the classical problem of linear sound propagation in tubes with isothermal walls. The perturbation technique of the method of multiple scales in combination with matched asymptotic expansions is applied to derive the first-order solutions and, in addition, the second-order solutions representing the correction due to boundary layer attenuation. The propagation length is assumed to be so large that in order to obtain asymptotic solutions which extend over the whole spatial range the first-order corrections to the classical attenuation rates of the different modes come into play as well. Starting with the case of the characteristic wavelength being large compared to the characteristic dimension of the duct, the analysis is then extended to the case where both of these quantities are of the same order of magnitude. Furthermore, the transmission line parameters and the transfer functions relating the sound pressures at the ends of the duct to the axial velocities are calculated.
A positron emission tomography study of the neural basis of informational and energetic masking effects in speech perception
Authors: Scott Sophie K. , Rosen Stuart , Wickham Lindsay , Wise Richard J. S.
Published: February 2004

Positron emission tomography (PET) was used to investigate the neural basis of the comprehension of speech in unmodulated noise (“energetic” masking, dominated by effects at the auditory periphery), and when presented with another speaker (“informational” masking, dominated by more central effects). Each type of signal was presented at four different signal-to-noise ratios (SNRs) (+3, 0, −3, −6 dB for the speech-in-speech, +6, +3, 0, −3 dB for the speech-in-noise), with listeners instructed to listen for meaning to the target speaker. Consistent with behavioral studies, there was SNR-dependent activation associated with the comprehension of speech in noise, with no SNR-dependent activity for the comprehension of speech-in-speech (at low or negative SNRs). There was, in addition, activation in bilateral superior temporal gyri which was associated with the informational masking condition. The extent to which this activation of classical “speech” areas of the temporal lobes might delineate the neural basis of the informational masking is considered, as is the relationship of these findings to the interfering effects of unattended speech and sound on more explicit working memory tasks. This study is a novel demonstration of candidate neural systems involved in the perception of speech in noisy environments, and of the processing of multiple speakers in the dorso-lateral temporal lobes.
Scattering of sound from axisymetric sources by multiple circular cylinders
Authors: Sherer Scott E.
Published: February 2004

A general analytic method for calculating the scattering of sound by multiple rigid circular cylinders arranged in an arbitrary parallel configuration is presented. The sound scattered by this collection of cylinders is generated by a time-periodic, spatially distributed, axisymmetric source located within the domain of interest. A Hankel transform method is used to calculate the incident field, while separation of variables is used to obtain the scattered fields from each cylinder in the collection. The unknown scattering coefficients are determined through the use of general addition theorems that allows the various fields to be readily transformed between coordinate systems. The method is validated using various two-, three-, and four-cylinder configurations, and the number of coefficients that must be retained in the truncated series is examined. Benchmark configurations consisting of two- and three-cylinder systems with cylinders of varying radii are also presented. These solutions have been used to validate computational aeroacoustic solvers developed for complex geometries.
Development of [ɹ] in young, Midwestern, American children
Authors: McGowan Richard S. , Nittrouer Susan , Manning Carol J.
Published: February 2004

Beginning at the age of about 14 months, eight children who lived in a rhotic dialect region of the United States were recorded approximately every 2 months interacting with their parents. All were recorded until at least the age of 26 months, and some until the age of 31 months. Acoustic analyses of speech samples indicated that these young children acquired [ɹ] production ability at different ages for [ɹ]’s in different syllable positions. The children, as a group, had started to produce postvocalic and syllabic [ɹ] in an adult-like manner by the end of the recording sessions, but were not yet showing evidence of having acquired prevocalic [ɹ]. Articulatory limitations of young children are posited as a cause for the difference in development of [ɹ] according to syllable position. Specifically, it is speculated that adult-like prevocalic [ɹ] production requires two lingual constrictions: one in the mouth, and the other in the pharynx, while postvocalic and syllabic [ɹ] requires only one oral constriction. Two lingual constrictions could be difficult for young children to produce.