bluuebunny/crossref_metadata_2025 huggingface dataset:
Single mode, high power GaAlAs/GaAs lasers
Authors: Fu R. J. , Hwang C. J. , Wang C. S. , LaLevic B.
Published: February 2003

A new channeled-substrate narrow stripe laser with double current confinement and large optical cavity has been developed. This laser incorporates symmetrical waveguiding layers to form the large cavity and additional reverse biased p-n junction to confine the current. Light output up to 60 mW with stable single longitudinal and spatial modes is obtained in cw operation at room temperature. Threshold current as low as 15 mA and differential quantum efficiency as high as 70% are achieved. Furthermore, high quality beam with far-field angle of 32°×10° (full width at half-maximum) is maintained throughout the whole power range.
Planar InP/GaInAsP/GaInAs buried-structure avalanche photodiode
Authors: Kobayashi Masahiro , Yamazaki Susumu , Kaneda Takao
Published: February 2003

A new planar InP/GaInAsP/GaInAs buried-structure avalanche photodiode, which has a buried active region and an n−-InP guardring region, has been developed. A useful guardring effect and a uniform multiplication are obtained in the multiplication range of up to 30. The diode shows a dark current of 10 nA at a bias of 90% of the breakdown voltage, a maximum avalanche gain of 50 under 1.3-μm light irradiation, and a gain-bandwidth product of about 16 GHz.
Electronic states at the hydrogenated amorphous silicon/silcon nitride interface
Authors: Street R. A. , Thompson M. J.
Published: February 2003

Electronic states at the hydrogenated amorphous silicon (a-Si:H)/silicon nitride interface are observed to depend strongly on the order of deposition. When the nitride is on top of the a-Si:H, there is an interface charge of ∼5×1011 electrons/cm2 and the interface Fermi energy is 0.25 eV from the conduction band. The bottom nitride is also in electron accumulation but with a much smaller space charge. Our results are in marked disagreement with recent data.
Tunneling spectroscopy of In0.53Ga0.47As thin films
Authors: Lu Pong-Fei , Tsui D. C. , Cox H. M.
Published: February 2003

A surface accumulation layer of electrons is observed at the oxide-In0.53Ga0.47As interface of Pb-oxide-In0.53Ga0.47As tunnel junctions, supporting the notion that metal-semiconductor contacts with low work function metals form ideal ohmic contacts to n-type In0.53Ga0.47As. The derivatives of the junction I-V characteristics give directly the band edge energy of the surface electrons, their longitudinal optical phonon emission threshold, and, in a perpendicular magnetic field, their Landau levels with m*=(0.042±0.001)m0.
Deep levels in zinc phosphide
Authors: Suda Toshikazu , Bube Richard H.
Published: February 2003

Deep majority-carrier traps have been studied by means of deep level transient spectroscopy (DLTS) in as-grown Zn3P2 polycrystals (p-type) grown either by sublimation or by iodine chemical transport using an automated digital DLTS system. Three main deep hole traps are present in both kinds of Zn3P2: hole traps with activation energy of 0.20±0.01 eV 0.36±0.005 eV, and 0.73±0.01 eV from the top of the valence band. In a few sublimation-grown samples a 0.48±0.02 eV hole trap is detected. The concentration of these levels, however, exhibits a very strong dependence on the thermal history of the samples, since Mg from the Schottky contact easily diffuses into the bulk above 50 °C and affects the concentration of the levels.
Grain growth during transient annealing of As-implanted polycrystalline silicon films
Authors: Krause S. J. , Wilson S. R. , Paulson W. M. , Gregory R. B.
Published: February 2003

Polycrystalline silicon films deposited on oxidized wafer surfaces were implanted with As and annealed on a Varian IA-200 rapid thermal annealer. The effects of annealing conditions on resultant grain size of original as-deposited columnar grains are presented with a modified model for interfacially driven grain growth. During an initial temperature rise to 910 °C the original grain size (39 nm) and dopant profile are not significantly altered. At 1145 °C the grains have grown to 90 nm and the As is uniformly distributed throughout the film. Additional annealing to 1300 °C in 20 s causes grains to grow to 260 nm. Further grain growth is retarded due to the 300-nm film thickness. During annealing of unencapsulated films a substantial loss of As results in a lower rate of grain growth. When grain size increases, Hall mobility increases and resistivity decreases.
High performance inverted and large current double interface modulation-doped field-effect transistors with the bulk (Al,Ga)As replaced by superlattice at the inverted interface
Authors: Arnold D. , Henderson T. , Klem J. , Fischer R. , Kopp W. , Ketterson A. , Masselink W. T. , Morkoç H.
Published: February 2003

Inverted modulation-doped field-effect transistors (MODFET’s) with 1-μm-long by 145-μm-wide gates and transconductances as high as 170 mS/mm have been demonstrated by replacing the troublesome doped bulk (Al,Ga)As with (Al,Ga)As/GaAs and AlAs/GaAs superlattices in which the dopants are incorporated only in the center of the GaAs wells. Mobilities of 4100 and 29 000 cm2/Vs and sheet carrier concentrations of 3.2×1012 and 1.3×1012 cm−2 at 300 and 77 K respectively were measured for superlattice inverted structures. In addition, double interface MODFET structures containing both normal and inverted heterointerfaces have been fabricated which demonstrate transconductances of 200 mS/mm and a saturation current as high as 340 mA/mm. This structure exhibited mobilities of 7200 and 54 000 cm2/Vs and sheet carrier concentrations 2.0×1012 and 1.6×1012 cm−2 at 300 and 77 K.
Fundamental mode oscillation of a buried ridge waveguide laser array
Authors: Mukai S. , Lindsey C. , Katz J. , Kapon E. , Rav-Noy Z. , Margalit S. , Yariv A.
Published: February 2003

An eight-element phase-locked array of index-guided separate confinement ridge AlGaAs diode lasers is fabricated. In this array the absorption of light in the region between lasers is negligible and the gain profile across the array is nearly uniform. Unlike most other arrays, this array oscillates in its fundamental mode. Stable radiation patterns of near diffraction-limited single narrow beam with 1.6° width are obtained. The beam width approaches the theoretical limit for the present array structure.
Strong 〈100〉 texture formation of polycrystalline silicon films on amorphous insulator by laser recrystallization
Authors: Egami Koji , Kimura Masakazu
Published: February 2003

This letter demonstrates the optimization for the strong 〈100〉 texture formation of low pressure chemical vapor deposited (700 °C) polycrystalline silicon films on SiO2/backing substrates such as quartz glass, sapphire, and silicon by cw Ar ion laser recrystallization. We have examined the correlation of 〈100〉 texture formed with both the dwell time and the grain size. It has been found that the long dwell time (∼30 ms) and rather low laser power density are favorable for the formation of the strong 〈100〉 texture with lamellalike grains.
Efficient multiple visible light generation in a polarization-preserving optical fiber pumped by a 1.064-μm yttrium aluminum garnet laser
Authors: Nakazawa Masataka , Nakashima Takashi , Seikai Shigeyuki
Published: February 2003

Visible light generation by sum-frequency mixings in a polarization-preserving fiber has been observed with pumping by a 1.064-μm Q-switched, and mode-locked neodymium:yttrium aluminum garnet laser. The visible light has been efficiently generated when the fast axis of the test fiber was excited. The total conversion efficiency from the pump to all visible wavelengths amounts to 1% with a mode-locked pump peak power of 18 kW. By fusion splicing two fibers with different visible emission lines, we have succeeded in combining those two visible spectra into one spectrum.
Near-surface defects formed during rapid thermal annealing of preamorphized and BF+2-implanted silicon
Authors: Sands T. , Washburn J. , Gronsky R. , Maszara W. , Sadana D. K. , Rozgonyi G. A.
Published: February 2003

Near-surface defects formed during rapid thermal annealing (950–1150 °C, 10 s) of preamorphized and BF+2-implanted (100) Si have been studied by a combination of cross-sectional transmission electron microscopy and secondary-ion mass spectrometry. Two types of defects are identified: fine clusters (1.5–4 nm in diameter) are shown to be related to fluorine, and stacking faults are correlated with the presence of both excess boron above the solid solubility limit and fluorine. In addition, the peak fluorine concentration is found to be lower in samples which contain a high density (∼108 cm−2) of ‘‘hairpin’’ dislocations, indicating that a pipe diffusion mechanism for the rapid out-diffusion of fluorine may be operative.
Frequency modulation in the cleaved-coupled-cavity laser
Authors: Streifer William , Yevick David , Burnham Robert D. , Paoli Thomas L.
Published: February 2003

Enhanced frequency modulation in cleaved-coupled-cavity lasers is analyzed and results for frequency deviation per unit modulator current and lasing spectra are presented. Strong sensitivity to gap spacing and bias point are reported and nonlinearities are shown to limit distortionless analog frequency modulation. In a typical case, a 40-μA peak modulation current produces a 200-MHz maximum frequency deviation with 2% distortion.
Electroluminescence in thin-film CaS:Ce
Authors: Shanker Virendra , Tanaka Shosaku , Shiiki Masatoshi , Deguchi Hiroshi , Kobayashi Hiroshi , Sasakura Hiroshi
Published: February 2003

We report a double insulated CaS:Ce thin-film electroluminescent (EL) device which emits a bright green EL due to Ce3+ luminescent centers, being characteristic of parity allowed 5d–4f transitions. A brightness level of 500 cd/m2 and emission efficiency of 0.11 lm/W have been obtained under 5-kHz sinusoidal voltage excitation. The CaS:Ce thin film has been fabricated by coevaporation of CaS and sulfur.
Donor identification in liquid phase epitaxial indium phosphide
Authors: Skolnick M. S. , Dean P. J. , Groves S. H. , Kuphal E.
Published: February 2003

High resolution photoluminescence spectroscopy at 4.2 K and at a magnetic field of 9.7 T is employed to resolve and identify residual shallow donors in liquid phase epitaxial InP. Sulphur is found to be the dominant inadvertent contaminant in high purity material prepared from growth solutions which have undergone long baking treatments. Silicon is also observed in most samples, but at significantly lower levels than sulphur.
Yellow-emitting AlGaInP double heterostructure laser diode at 77 K grown by atmospheric metalorganic chemical vapor deposition
Authors: Ikeda M. , Honda M. , Mori Y. , Kaneko K. , Watanabe N.
Published: February 2003

Yellow-emitting pulsed laser operation of an Al0.37Ga0.15In0.48P/Al0.16Ga0.36In0.48P/ Al0.37Ga0.15In0.48P double heterostructure laser diode was obtained at 77 K. The emission wavelength was 579 nm. The threshold current density was 5.6 kA/cm2 for a diode with a Si3N4 insulated 8-μm-wide and 250-μm-long stripe geometry. The device was made from a DH wafer grown by conventional metalorganic chemical vapor deposition using triethyl metals and phosphine as source materials.
Mode locking of excimer laser pumped dye lasers
Authors: Watanabe Masayoshi , Watanabe Shuntaro , Endoh Akira
Published: February 2003

Picosecond pulses have been generated over a broad spectral range with passive mode locking of dye lasers pumped by a long-pulse XeCl laser. The rapid reduction of pulse duration to less than 10 ps was confirmed to occur within a few tens of round trips. The characteristics of mode locking were intensively investigated at the multiple wavelengths of rare-gas halide lasers such as KrF, ArF, and XeCl lasers, resulting in pulse durations of 5.5 ps at 497 nm and 7 ps at 580 nm, respectively.
Excimer laser enhanced nitridation of silicon substrates
Authors: Sugii Toshihiro , Ito Takashi , Ishikawa Hajime
Published: February 2003

Silicon direct nitridation has been successfully done using purified ammonia gas and an ArF excimer laser (λ=193 nm). Direct nitride films were grown at a substrate temperature of 400 °C and a laser pulse energy of 15 mJ/pulse cm2. As far as Auger signal intensities are concerned, there is little difference between the excimer laser enhanced nitrided films grown at 400 °C and thermally nitrided films grown at 1000 °C. The maximum film thickness grown is limited to 2.5 nm at 400 °C by diffusion of nitridation species across the grown film. The temperature rise on the substrate surface irradiated by the laser was calculated and found to be around 50 °C. Therefore, the thermal effect of the laser irradiation is of little significance in this experiment. The photochemically dissociated products of ammonia molecules were investigated by a quadrupole mass analyzer. The photochemically generated NH2 radicals seem to enhance the nitridation.
Genomic and Proteomic Analysis of Mitochondrial Carrier Proteins in Arabidopsis
Authors: Millar A. Harvey , Heazlewood Joshua L.
Published: February 2003

Plant mitochondria maintain metabolic communication with the cytosol through a family of carrier proteins. In Arabidopsis, a subset of 45 putative genes encoding members of this family have been identified based on generalized mitochondrial carrier features. No gene clusters are apparent and few of the predicted protein products have mitochondrial targeting sequences recognized by bioinformatic predictors. Only nine genes are currently represented by more than 10 expressed sequence tags at The Institute for Genomic Research. Analyses of public microarray experiments reveal differential expression profiles of the more highly expressed members of this gene family in different plant organs and in response to plant hormone application and environmental stresses. A comparison of this Arabidopsis carrier subset (45) to the yeast gene family (35) reveals 10 orthologous groups between the two species. Recent surveys of the Arabidopsis mitochondrial proteome by two-dimensional gel separations have not identified any of these carrier proteins, presumably because of their hydrophobicity and basicity. Isolating integral membrane proteins from Arabidopsis mitochondria, using one-dimensional electrophoresis for protein separation and tandem mass spectrometry-based sequencing of doubly charged peptides, we have unequivocally identified specific carrier gene products located in mitochondria. This approach has identified six of the nine carriers represented highly in expressed sequence tag databases: adenine nucleotide translocator (At3g8580 and At5g13490), dicarboxylate/tricarboxylate carrier (At5g19760), phosphate carrier (At5g14040), uncoupling protein (At3g54110), and a carrier gene of unknown function (At4g01100). Overall, the combined transcript and protein expression data indicates that only a small subset of the carrier family of genes provide the majority of carrier proteins of Arabidopsis mitochondria.
Polyamine Oxidase, a Hydrogen Peroxide-Producing Enzyme, Is Up-Regulated by Light and Down-Regulated by Auxin in the Outer Tissues of the Maize Mesocotyl
Authors: Cona Alessandra , Cenci Francesco , Cervelli Manuela , Federico Rodolfo , Mariottini Paolo , Moreno Sandra , Angelini Riccardo
Published: February 2003

Exogenously supplied auxin (1-naphthaleneacetic acid) inhibited light-induced activity increase of polyamine oxidase (PAO), a hydrogen peroxide-producing enzyme, in the outer tissues of maize (Zea mays) mesocotyl. The same phenomenon operates at PAO protein and mRNA accumulation levels. The wall-bound to extractable PAO activity ratio was unaffected by auxin treatment, either in the dark or after light exposure. Ethylene treatment did not affect PAO activity, thus excluding an effect of auxin via increased ethylene biosynthesis. The auxin polar transport inhibitorsN  1-naphthylphthalamic acid or 2,3,5-triiodobenzoic acid caused a further increase of PAO expression in outer tissues after light treatment. The small increase of PAO expression, normally occurring in the mesocotyl epidermis during plant development in the dark, was also inhibited by auxin, although to a lesser extent with respect to light-exposed tissue, and was stimulated by N  1-naphthylphthalamic acid or 2,3,5-triiodobenzoic acid, thus suggesting a complex regulation of PAO expression. Immunogold ultrastructural analysis in epidermal cells revealed the association of PAO with the secretory pathway and the cell walls. The presence of the enzyme in the cell walls of this tissue greatly increased in response to light treatment. Consistent with auxin effects on light-induced PAO expression, the hormone treatment inhibited the increase in immunogold staining both intraprotoplasmically and in the cell wall. These results suggest that both light and auxin finely tune PAO expression during the light-induced differentiation of the cell wall in the maize mesocotyl epidermal tissues.
Winter at the Alpine Timberline. Why Does Embolism Occur in Norway Spruce But Not in Stone Pine?
Authors: Mayr Stefan , Schwienbacher Franziska , Bauer Helmut
Published: February 2003

Conifers growing at the alpine timberline are exposed to frost drought and freeze-thaw cycles during winter—stress factors known to induce embolism in tree xylem. The two dominant species of the European Central Alps timberline were studied: Norway spruce (Picea abies [L.] Karst) and stone pine (Pinus cembra), which usually reaches higher altitudes. We hypothesized to find embolism only at the timberline and to observe less embolism in stone pine than in Norway spruce due to avoidance mechanisms. Seasonal courses of embolism and water potential were studied at 1,700 and 2,100 m during two winter seasons and correlated to vulnerability (to drought-induced embolism), leaf conductance, and micrometeorological data. Embolism was observed only at the timberline and only in Norway spruce (up to 49.2% loss of conductivity). Conductivity losses corresponded to low water potentials (down to −3.5 MPa) but also to the number of freeze-thaw events indicating both stress factors to contribute to embolism induction. Decreasing embolism rates—probably due to refilling—were observed already in winter. Stone pine did not exhibit an adapted vulnerability (50% loss of conductivity at −3.5 MPa) but avoided critical potentials (minimum −2.3 MPa): Cuticulare conductance was 3.5-fold lower than in Norway spruce, and angles between needles and axes were found to decrease in dehydrating branches. The extent of conductivity losses in Norway spruce and the spectrum of avoidance and recovery mechanisms in both species indicates winter embolism to be relevant for tree line formation.
Comparative Analyses of Potato Expressed Sequence Tag Libraries
Authors: Ronning Catherine M. , Stegalkina Svetlana S. , Ascenzi Robert A. , Bougri Oleg , Hart Amy L. , Utterbach Teresa R. , Vanaken Susan E. , Riedmuller Steve B. , White Joseph A. , Cho Jennifer , Pertea Geo M. , Lee Yuandan , Karamycheva Svetlana , Sultana Razvan , Tsai Jennifer , Quackenbush John , Griffiths Helen M. , Restrepo Silvia , Smart Christine D. , Fry William E. , van der Hoeven Rutger , Tanksley Steve , Zhang Peifen , Jin Hailing , Yamamoto Miki L. , Baker Barbara J. , Buell C. Robin
Published: February 2003

The cultivated potato (Solanum tuberosum) shares similar biology with other members of the Solanaceae, yet has features unique within the family, such as modified stems (stolons) that develop into edible tubers. To better understand potato biology, we have undertaken a survey of the potato transcriptome using expressed sequence tags (ESTs) from diverse tissues. A total of 61,940 ESTs were generated from aerial tissues, below-ground tissues, and tissues challenged with the late-blight pathogen (Phytophthora infestans). Clustering and assembly of these ESTs resulted in a total of 19,892 unique sequences with 8,741 tentative consensus sequences and 11,151 singleton ESTs. We were able to identify a putative function for 43.7% of these sequences. A number of sequences (48) were expressed throughout the libraries sampled, representing constitutively expressed sequences. Other sequences (13,068, 21%) were uniquely expressed and were detected only in a single library. Using hierarchal and k means clustering of the EST sequences, we were able to correlate changes in gene expression with major physiological events in potato biology. Using pair-wise comparisons of tuber-related tissues, we were able to associate genes with tuber initiation, dormancy, and sprouting. We also were able to identify a number of characterized as well as novel sequences that were unique to the incompatible interaction of late-blight pathogen, thereby providing a foundation for further understanding the mechanism of resistance.
Homogentisate Phytyltransferase Activity Is Limiting for Tocopherol Biosynthesis in Arabidopsis
Authors: Collakova Eva , DellaPenna Dean
Published: February 2003

Tocopherols are essential components of the human diet and are synthesized exclusively by photosynthetic organisms. These lipophilic antioxidants consist of a chromanol ring and a 15-carbon tail derived from homogentisate (HGA) and phytyl diphosphate, respectively. Condensation of HGA and phytyl diphosphate, the committed step in tocopherol biosynthesis, is catalyzed by HGA phytyltransferase (HPT). To investigate whether HPT activity is limiting for tocopherol synthesis in plants, the gene encoding Arabidopsis HPT,HPT1, was constitutively overexpressed in Arabidopsis. In leaves, HPT1 overexpression resulted in a 10-fold increase in HPT specific activity and a 4.4-fold increase in total tocopherol content relative to wild type. In seeds, HPT1overexpression resulted in a 4-fold increase in HPT specific activity and a total seed tocopherol content that was 40% higher than wild type, primarily because of an increase in γ-tocopherol content. This enlarged pool of γ-tocopherol was almost entirely converted to α-tocopherol by crossing HPT1 overexpressing plants with lines constitutively overexpressing γ-tocopherol methyltransferase. Seed of the resulting double overexpressing lines had a 12-fold increase in vitamin E activity relative to wild type. These results indicate that HPT activity is limiting in various Arabidopsis tissues and that total tocopherol levels and vitamin E activity can be elevated in leaves and seeds by combined overexpression of the HPT1 and γ-tocopherol methyltransferase genes.
Osmotic Stress Tolerance of Transgenic Tobacco Expressing a Gene Encoding a Membrane-Located Receptor-Like Protein from Tobacco Plants
Authors: Tamura Takashi , Hara Kojiro , Yamaguchi Yube , Koizumi Nozomu , Sano Hiroshi
Published: February 2003

Tobacco (Nicotiana tabacum) genes regulated during the early stage of responses to wounding were screened by a modified fluorescence differential display method. Among 28 genes initially identified, a particular clone designatedNtC7 was subjected to further analysis. Its transcripts were found to accumulate rapidly and transiently within 1 h upon treatments with not only wounding but also salt and osmotic stresses. However, jasmonic and abscisic acids and ethylene did not effectively induce NtC7 transcripts. Amino acid sequence analysis suggested NtC7 to be a new type of transmembrane protein that belongs to the receptor-like protein family, and a membrane location was confirmed in onion (Allium cepa) epidermis cells transiently expressing an NtC7-green fluorescent protein fusion protein. Seeds of transgenic tobacco overexpressing NtC7normally germinated and grew in the presence of 500 mmmannitol, but not in the presence of 220 mm sodium chloride or 60 mm lithium chloride. Cuttings of mature transgenic leaf exhibited a marked tolerance upon treatment with 500 mm mannitol for 12 h, at which concentration wild-type counterparts were seriously damaged. These results suggested that NtC7 predominantly functions in maintenance of osmotic adjustment independently of ion homeostasis.
Changing the deafening silence of indigenous women's voices in educational leadership
Authors: Fitzgerald Tanya
Published: February 2003

The critique of western ethnocentric notions of leadership presented in this paper is informed by debates on issues such as gender and educational leadership that have produced meta‐narratives that explore and explain women and men's ways of leading. One of the troubling aspects of western leadership theories is the claim that the functions and features of leadership can be transported and legitimated across homogenous educational systems. Despite changes that have been made in definitions and descriptions of educational leadership to provide a focus on gender, there is the implicit assumption that while educational leadership might be practised differently according to gender, there is a failure to consider the values and practices of indigenous educational leaders. Thus, the construct of educational leadership needs to be more broadly theorised in order for knowledge of indigenous ways of leading to emerge.
The ethics of zero tolerance
Authors: Gorman Kevin , Pauken Patrick
Published: February 2003

“Zero tolerance” has become the international “buzz word” of the secondary building administrator. As school violence has increased so have the legislative and regulatory policy‐making mandates calling for increased disciplinary consequences for inappropriate student behavior. Ethical problem‐solving and decision‐making have taken a back seat to reactive discipline by school officials. Media publicity has forced proactive principals to become reactive impulsive decision‐makers. In this article, Starratt's three‐part model for ethical school administration – encompassing the ethics of critique, justice, and care – is applied to a fictional scenario and the ethical dilemma that evolves. Recommendations for practice are offered in a proposed resolution of the dilemma within the context of a central conclusion: if the school administrator of the twenty‐first century is to build and maintain an ethical educational setting where all students can learn, zero tolerance cannot dictate the only outcomes for inappropriate student behavior.
Contrast Tuning in Auditory Cortex
Authors: Barbour Dennis L. , Wang Xiaoqin
Published: February 2003

The acoustic features useful for converting auditory information into perceived objects are poorly understood. Although auditory cortex neurons have been described as being narrowly tuned and preferentially responsive to narrowband signals, naturally occurring sounds are generally wideband with unique spectral energy profiles. Through the use of parametric wideband acoustic stimuli, we found that such neurons in awake marmoset monkeys respond vigorously to wideband sounds having complex spectral shapes, preferring stimuli of either high or low spectral contrast. Low contrast–preferring neurons cannot be studied thoroughly with narrowband stimuli and have not been previously described. These findings indicate that spectral contrast reflects an important stimulus decomposition in auditory cortex and may contribute to the recognition of acoustic objects.
DNA Damage-Induced Replication Fork Regression and Processing in
Escherichia coli
Authors: Courcelle Justin , Donaldson Janet R. , Chow Kin-Hoe , Courcelle Charmain T.
Published: February 2003

DNA lesions that block replication are a primary cause of rearrangements, mutations, and lethality in all cells. After ultraviolet (UV)-induced DNA damage in
Escherichia coli
, replication recovery requires RecA and several other
recF
pathway proteins. To characterize the mechanism by which lesion-blocked replication forks recover, we used two-dimensional agarose gel electrophoresis to show that replication-blocking DNA lesions induce a transient reversal of the replication fork in vivo. The reversed replication fork intermediate is stabilized by RecA and RecF and is degraded by the RecQ-RecJ helicase-nuclease when these proteins are absent. We propose that fork regression allows repair enzymes to gain access to the replication-blocking lesion, allowing processive replication to resume once the blocking lesion is removed.
Low-Noise Current Amplifier Based on Mesoscopic Josephson Junction
Authors: Delahaye J. , Hassel J. , Lindell R. , Sillanpää M. , Paalanen M. , Seppä H. , Hakonen P.
Published: February 2003

We used the band structure of a mesoscopic Josephson junction to construct low-noise amplifiers. By taking advantage of the quantum dynamics of a Josephson junction, i.e., the interplay of interlevel transitions and the Coulomb blockade of Cooper pairs, we created transistor-like devices, Bloch oscillating transistors, with considerable current gain and high-input impedance. In these transistors, the correlated supercurrent of Cooper pairs is controlled by a small base current made up of single electrons. Our devices reached current and power gains on the order of 30 and 5, respectively. The noise temperature was estimated to be around 1 kelvin, but noise temperatures of less than 0.1 kelvin can be realistically achieved. These devices provide quantum-electronic building blocks that will be useful at low temperatures in low-noise circuit applications with an intermediate impedance level.
MAXIMAL ACCELERATION OR MAXIMAL ACCELERATIONS?
Authors: FEOLI ANTONIO
Published: February 2003

We review the arguments supporting the existence of a maximal acceleration for a massive particle and show that different values of this upper limit can be predicted in different physical situations.
A QUINTESSENCE PROBLEM IN BRANS–DICKE THEORY WITH VARYING SPEED OF LIGHT
Authors: CHAKRABORTY SUBENOY , CHAKRABORTY NARAYAN CHANDRA , DEBNATH UJJAL
Published: February 2003

It is shown that minimally coupled scalar field in Brans–Dicke theory with varying speed of light can solve the quintessence problem and it is possible to have a non-decelerated expansion of the present universe with Brans–Dicke-theory for anisotropic models without any matter.
ENERGY-EFFICIENT BROADCASTING IN WIRELESS AD HOC NETWORKS LOWER BOUNDS AND ALGORITHMS
Authors: BIAN FANG , GOEL ASHISH , RAGHAVENDRA C. S. , LI XIN
Published: February 2003

Energy-efficient communication is critical for increasing life of power limited wireless ad hoc networks. There has been considerable interest in minimum energy broadcast operations. In this paper, we develop bounds and an algorithm for minimizing energy cost for broadcasting from any source to all other nodes in the network. Most prior work have used simpler model for energy cost for wireless communications by accounting only the analog radiation cost for transmission and ignored the fixed cost for electronics in transmission and reception circuitry in nodes. Furthermore, in a network it is possible for some node pairs not be able to communicate directly even though they are in their radio ranges due to obstacles present in the terrain of the network.
Developmental Constraints Aid the Acquisition of Binocular Disparity Sensitivities
Authors: Dominguez Melissa , Jacobs Robert A.
Published: February 2003

This article considers the hypothesis that systems learning aspects of visual perception may benefit from the use of suitably designed developmental progressions during training. We report the results of simulations in which four models were trained to detect binocular disparities in pairs of visual images. Three of the models were developmental models in the sense that the nature of their visual input changed during the course of training. These models received a relatively impoverished visual input early in training, and the quality of this input improved as training progressed. One model used a coarse-scale-to-multiscale developmental progression, another used a fine-scale-to-multiscale progression, and the third used a random progression. The final model was nondevelopmental in the sense that the nature of its input remained the same throughout the training period. The simulation results show that the two developmental models whose progressions were organized by spatial frequency content consistently outperformed the nondevelopmental and random developmental models. We speculate that the superior performance of these two models is due to two important features of their developmental progressions: (1) these models were exposed to visual inputs at a single scale early in training, and (2) the spatial scale of their inputs progressed in an orderly fashion from one scale to a neighboring scale during training. Simulation results consistent with these speculations are presented. We conclude that suitably designed developmental sequences can be useful to systems learning to detect binocular disparities. The idea that visual development can aid visual learning is a viable hypothesis in need of study.
Travis and Arms revisited: a second look at a widely used bioconcentration algorithm
Authors: Birak Pamela , Yurk Jeffrey , Adeshina Femi , Lorber Matthew , Pollard Karen , Choudhury Harlal , Kroner Stephen
Published: February 2003

In 1988, Travis and Arms reviewed the literature and collected data to develop a relationship between the octanol-water partition coefficient ( Kow) and the uptake of organic compounds into milk and beef (Travis and Arms, 1988). These equations have been utilized for predicting biotransfer factors for organic chemicals when empirical data are lacking. During the external peer review of the draft US Environmental Protection Agency (EPA) guidance entitled Human Health Risk Assessment Protocol for Hazardous Waste Combustion Facilities (US EPA, 1998) and the development of Superfund’s Ecological Soil Screening Levels (US EPA, 2000b), questions challenging the derivation and use of these equations were raised. The primary questions raised were: 1) Are the equations presented in Travis and Arms (1988) for the estimation of transfer of organic compounds from contaminated feed to beef and milk technically valid and reproducible? If so, (2) are the equations appropriate across the entire log Kow range? For these reasons, this study was undertaken to validate the original Travis and Arms equations, to review more recent literature, and, if appropriate, to add to the original Travis and Arms data set to obtain updated equations. This paper presents an evaluation of the original Travis and Arms equations, limitations to their use, and steps to reduce uncertainties associated with their use by updating with more current literature.
Minidose Warfarin Prophylaxis for Catheter-Associated Thrombosis in Cancer Patients: Can It Be Safely Associated With Fluorouracil-Based Chemotherapy?
Authors: Masci Giovanna , Magagnoli Massimo , Zucali Paolo Andrea , Castagna Luca , Carnaghi Carlo , Sarina Barbara , Pedicini Vittorio , Fallini Monica , Santoro Armando
Published: February 2003

Purpose: The use of prophylactic low-dose oral warfarin in cancer patients with a central venous catheter (CVC) in place has an established role in the prevention of thrombotic complications and is associated with a low hemorrhagic risk. Despite the literature indicating an adverse interaction between warfarin and fluorouracil (FU), the frequency of this interaction and whether it occurs when minidose warfarin is used is unknown. We analyzed the incidence of alterations in the International Normalized Ratio (INR) and bleeding in cancer patients given minidose warfarin during treatment with continuous-infusion FU-based regimens.

Patients and Methods: Between July 1999 and August 2001, 95 cancer patients were evaluated. Forty-one patients (43%) had liver metastases. Seventy-nine patients (83%) had a Groshong CVC (Bard Access System, Salt Lake City, UT), and 16 (17%) had a Port-a-Cath device (Bard Access System). All patients received oral warfarin at a dose of 1 mg/daily as prophylaxis beginning the day after the catheter was positioned. An INR of more than 1.5 was considered significantly elevated.

Results: INR elevation occurred in 31 patients (33%), with 18 patients (19%) having an INR more than 3.0. Twelve (39%) of the 31 patients had liver metastases. Bleeding was observed in eight patients (8%); seven of these patients had elevated INR levels. We observed INR elevations in 12 of 21 patients treated with a FU, folinic acid, and oxaliplatin (FOLFOX) regimen, 11 of 40 treated with a de Gramont regimen (FU and folinic acid), and five of 19 treated with a FU, folinic acid, and irinotecan (FOLFIRI) regimen.

Conclusion: A high incidence of INR abnormalities was observed in our cohort of patients, especially those treated with FOLFOX regimen. Clinicians should be aware of this interaction and should regularly monitor the prothrombin time in patients receiving warfarin and FU.
Interleukin-2 After Autologous Stem-Cell Transplantation for Adult Patients With Acute Myeloid Leukemia in First Complete Remission
Authors: Stein Anthony S. , O’Donnell Margaret R. , Slovak Marilyn L. , Snyder David S. , Nademanee Auayporn P. , Parker Pablo , Molina Arturo , Somlo George , Fung Henry C. , Krishnan Amrita , Rodriguez Roberto , Spielberger Ricardo T. , Wang Shirong , Dagis Andrew , Vora Nayana , Arber Daniel A. , Niland Joyce C. , Forman Stephen J.
Published: February 2003

Purpose: To determine the disease-free survival (DFS) and toxicity of administering interleukin-2 (IL-2) immunotherapy early after autologous stem-cell transplantation (ASCT) to simulate a graft versus leukemia effect observed in allogeneic transplantation.

Patients and Methods: Fifty-six patients with acute myeloid leukemia in first remission received a single consolidation of high-dose cytarabine-idarubicin at a median of 1.1 month postremission with the intent to proceed to ASCT and IL-2 9 × 106 U/m2/24 h for 4 days, followed by 10 days of IL-2 1.6 × 106 U/m2/24 h on hematologic recovery.

Results: Eighty-four percent of patients received the intended ASCT, and 68% of patients received IL-2 treatment. With a median follow-up of 39.4 months (range, 1.2 to 76.3 months), the 2-year cumulative probability of DFS for all 56 patients is 68% (95% confidence interval [CI], 55% to 80%) and 74% (95% CI, 57% to 85%) for the 39 patients undergoing IL-2 treatment after ASCT. The 2-year cumulative probability of DFS for favorable, intermediate, and unfavorable cytogenetics is 88% (95% CI, 59% to 97%), 48% (95% CI, 26% to 67%), and 70% (95% CI, 23% to 93%), respectively. Toxicities from IL-2 were mainly thrombocytopenia, leukopenia, fever, and fluid retention. Two septic deaths occurred during neutropenia, which includes one during consolidation and one during transplant, for an overall 4% mortality rate.

Conclusion: These results suggest that a moderate dose of IL-2 after high-dose cytarabine-idarubicin–mobilized ASCT is associated with a low regimen-related toxicity and may improve DFS. A phase III study of IL-2 is now warranted.
Inhibition of F-Box Protein p45SKP2 Expression and Stabilization of Cyclin-Dependent Kinase Inhibitor p27KIP1 in Vitamin D Analog-Treated Cancer Cells
Authors: Lin Roberto , Wang Tian Tian , Miller Wilson H. , White John H.
Published: February 2003

Treatment of cancer cells with 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] or its analogs induces growth arrest and expression of the cyclin-dependent kinase inhibitor p27KIP1. Although 1,25(OH)2D3 transiently enhances p27kip1 gene transcription in some cells, its effects on p27KIP1 protein levels are generally more gradual and sustained. This suggests that 1,25(OH)2D3 treatment may be stabilizing p27KIP1 protein, which is sensitive to modification by the SCFSKP2 protein ubiquitin ligase and proteosomal degradation. Here, we show that treatment of AT-84 head and neck squamous carcinoma cells with the 1,25(OH)2D3 analog EB1089 increases p27KIP1 protein levels without significantly affecting expression of its mRNA. EB1089 treatment repressed expression of mRNAs encoding the F-box protein p45SKP2, a marker of poor head and neck cancer prognosis, and the cyclin kinase subunit CKS1, which is essential for targeting p45SKP2 to p27KIP1. This coincided with a reduction of total p45SKP2 protein, and p45SKP2 associated with p27KIP1. Consistent with these findings, turnover of p27KIP1 protein was strongly inhibited in the presence of EB1089. A similar reduction in p45SKP2 expression and stabilization of p27KIP1 protein was observed in 1,25(OH)2D3-sensitive UF-1 promyelocytic leukemia cells, which also respond by transiently increasing p27kip1 gene transcription. Our results reveal that 1,25(OH)2D3 analogs increase levels of p27KIP1 in different cell types by inhibiting expression of SCFSKP2 subunits and reducing turnover of p27KIP1 protein.
Decreased Expression of Tumor Necrosis Factor-α-Stimulated Gene 6 in Cumulus Cells of the Cyclooxygenase-2 and EP2 Null Mice
Authors: Ochsner Scott A. , Russell Darryl L. , Day Anthony J. , Breyer Richard M. , Richards Joanne S.
Published: February 2003

Ovulation, the release of fertilizable oocytes from mature follicles, involves tissue remodeling and increased prostaglandin (PG) signaling. Cyclooxygenase (COX)-2 is the rate-limiting enzyme during PG synthesis. Female mice null for either COX-2 or the PGE2 receptor EP2 are infertile, show decreased ovulation, and exhibit abnormal cumulus expansion. Cumulus expansion is the production of a complex extracellular matrix surrounding the cumulus-oocyte complex (COC). Matrix components consist of hyaluronan, proteoglycans, and proteins with hyaluronan binding domains. One such hyaluronan binding protein is TNFα-stimulated gene 6 (TSG-6). By various methods, we show induction of TSG-6 and hyaluronan synthase-2 mRNA in ovaries of mice treated with pregnant mare serum gonadotropin and human chorionic gonadotropin. By in situ hybridization, we show that both genes are expressed in periantral mural granulosa cells and cumulus cells of the mouse ovary. Notably, RT-PCR and in situ hybridization show that TSG-6 mRNA but not hyaluronan synthase-2 mRNA expression is selectively reduced in cumulus cells of COX-2 and EP2 null mice. Western analysis further confirms that TSG-6 protein is reduced in isolated COCs but remains covalently associated with interα-trypsin inhibitor in COX-2 null mice. These observations identify TSG-6 as a target of PG action and show that its production in ovulatory follicles is associated with proper formation of the cumulus-derived extracellular matrix.
The 5′-Flanking Region of the Murine Epididymal Protein of 17 Kilodaltons Gene Targets Transgene Expression in the Epididymis
Authors: Suzuki Kichiya , Araki Yoshihiko , Zhu Mei-Ying , Lareyre Jean-Jacques , Matusik Robert J. , Orgebin-Crist Marie-Claire
Published: February 2003

A murine epididymal retinoic-acid-binding protein (mE-RABP) is specifically expressed in the mid/distal caput epididymidis and is androgen regulated. The murine epididymal protein of 17 kDa (mEP17) gene, a novel gene homologous to mE-RABP, is located within 5 kb of the 5′-flanking region of the mE-RABP gene. In contrast, expression of the mEP17 gene is restricted to the initial segment and regulated by factor(s) contained in testicular fluid. To identify cis-DNA regulatory element(s) involved in the tissue- and region-specific expression of the mEP17 gene in transgenic mice, we have studied the expression of a transgene containing 5.3 kb of the 5′-flanking region of the mEP17 gene (5.3mEP17) linked to chloramphenicol acetyltransferase (CAT) reporter gene. Significant caput epididymidis-specific CAT activity was detected in transgenic mouse lines; and CAT gene expression is restricted to the initial segment, as is the expression of the endogenous mEP17 gene. Ontogenic expression and testicular factor dependency also mimic that of endogenous mEP17 gene. These results suggest that the 5.3mEP17 fragment contains all the information required for spatial and temporal expression in the mouse epididymis. The 5.3mEP17 fragment will be useful to express a foreign gene of interest in the epididymis in an initial segment-specific manner.
Divergent Expression of Type 2 Deiodinase and the Putative Thyroxine-Binding Protein p29, in Rat Brain, Suggests that They Are Functionally Unrelated Proteins
Authors: Montero-Pedrazuela Ana , Bernal Juan , Guadaño-Ferraz Ana
Published: February 2003

Deiodinases (D1, D2, and D3) are selenoproteins involved in thyroid hormone metabolism. Generation of the active hormone T3, from T4, is carried out by D1 and D2, whereas D3 degrades both hormones. The identity of the cloned D2 as a selenoprotein is well supported by biochemical and physiological data. However, an alternative view has proposed that type 2 deiodinase is a nonselenoprotein complex containing a putative T4 binding subunit called p29, with an almost identity in sequence with the Dickkopf protein Dkk3.

To explore a possible functional relationship between p29 and D2, we have compared their mRNA expression patterns in the rat brain. In brain, parenchyma p29 was expressed in neurons. High expression levels were found in all the regions of the blood-cerebrospinal fluid (CSF) barrier. p29 was present in different types of cells than D2, with the exception of the tanycytes. Our data do not support that p29 has a functional relationship with D2. On the other hand, expression of p29 in the blood-CSF barrier suggests that it might be involved in T4 transport to and from the CSF, but further studies are needed to substantiate this hypothesis.
Defective Activation of Atypical Protein Kinase C ζ and λ by Insulin and Phosphatidylinositol-3,4,5-(PO4)3 in Skeletal Muscle of Rats Following High-Fat Feeding and Streptozotocin-Induced Diabetes
Authors: Kanoh Yoshinori , Sajan Mini P. , Bandyopadhyay Gautam , Miura Atsushi , Standaert Mary L. , Farese Robert V.
Published: February 2003

Insulin-stimulated glucose transport in skeletal muscle is thought to be effected at least partly through atypical protein kinase C isoforms (aPKCs) operating downstream of phosphatidylinositol (PI) 3-kinase and 3-phosphoinositide-dependent protein kinase-1 (PDK-1). However, relatively little is known about the activation of aPKCs in physiological conditions or insulin-resistant states. Presently, we studied aPKC activation in vastus lateralis muscles of normal chow-fed and high-fat-fed rats and after streptozotocin (STZ)-induced diabetes. In normal chow-fed rats, dose-dependent increases in aPKC activity approached maximal levels after 15–30 min of stimulation by relatively high and lower, presumably more physiological, insulin concentrations, achieved by im insulin or ip glucose administration. Insulin-induced activation of aPKCs was impaired in both high-fat-fed and STZ-diabetic rats, but, surprisingly, IRS-1-dependent and IRS-2-dependent PI 3-kinase activation was not appreciably compromised. Most interestingly, direct in vitro activation of aPKCs by PI-3,4,5-(PO4)3, the lipid product of PI 3-kinase, was impaired in both high-fat-fed and STZ-diabetic rats. Defects in activation of aPKCs by insulin and PI-3,4,5-(PO4)3 could not be explained by diminished PDK-1-dependent phosphorylation of threonine-410 in the PKC-ζ activation loop, as this phosphorylation was increased even in the absence of insulin treatment in high-fat-fed rats. Conclusions: 1) muscle aPKCs are activated at relatively low, presumably physiological, as well as higher supraphysiological, insulin concentrations; 2) aPKC activation is defective in muscles of high-fat-fed and STZ-diabetic rats; and 3) defective aPKC activation in these states is at least partly due to impaired responsiveness to PI-3,4,5-(PO4)3, apparently at activation steps distal to PDK-1-dependent loop phosphorylation.