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Sample records for znse starting materials

  1. Etch Pit Studies of II-VI-Wide Bandgap Semiconductor Materials ZnSe, ZnCdSe, and ZnCdMgSe Grown on InP

    National Research Council Canada - National Science Library

    Semendy, Fred

    1999-01-01

    Etch pit density (EPD) determination studies have been conducted on II-VI semiconductor materials ZnSe, ZnCdSe, and ZnCdMgSe grown on InP surfaces for the first time by using various etching solutions under different...

  2. Development of conductive nanotemplates on ZnSe

    International Nuclear Information System (INIS)

    Monaico, Eduard; Tiginyanu, Ion; Colibaba, Gleb; Nedeoglo, D.D.; Cojocaru, Ala; Foell, Helmut

    2011-01-01

    We demonstrate the possibility to fabricate arrays of pores oriented perpendicular and parallel to the top surface of the ZnSe nanotemplate. The control of material conductivity allows one to produce porous ZnSe samples with the mean pore diameter and characteristic skeleton wall thickness from several hundreds of nanometers to about 15 nm. In addition, electrochemical treatment of ZnSe single crystals using photoresist masks allows one to prepare buried porous structures with pores directed parallel to the top template surface, which is especially important for photonic applications.

  3. Microwave-assisted synthesis of ZnSe of various morphologies using alkylamines as ligating solvent

    International Nuclear Information System (INIS)

    Han Dongmei; Song Chunfeng; Li Xiaoyu

    2009-01-01

    ZnSe nanoparticles were prepared using alkylamines as ligating solvent by microwave-irradiation method. The high-crystalline ZnSe nanomaterials were obtained within 20 min through a simple process. The differences of morphologies in the effect of alkylamines and microwave variables were investigated. The results show that there is an inverse relationship between the size of nanoparticles and the length of the alkylamine. The average sizes were increased with the duration of irradiation time. Microwave-irradiation power affects the sizes and shapes of ZnSe materials because of the movement and polarization of amine molecules under the rapidly changing electric field of the microwave reactor. A further characterization of binding condition on surface of ZnSe nanoparticles by the FTIR absorbance measurements indicates the presence of alkylamine molecules on the surface of ZnSe nanoparticles.

  4. Characterization study of industrial waste glass as starting material ...

    African Journals Online (AJOL)

    In present study, an industrial waste glass was characterized and the potential to assess as starting material in development of bioactive materials was investigated. A waste glass collected from the two different glass industry was grounded to fine powder. The samples were characterized using X-ray fluorescence (XRF), ...

  5. Room temperature, ppb-level NO2 gas sensing of multiple-networked ZnSe nanowire sensors under UV illumination

    Directory of Open Access Journals (Sweden)

    Sunghoon Park

    2014-10-01

    Full Text Available Reports of the gas sensing properties of ZnSe are few, presumably because of the decomposition and oxidation of ZnSe at high temperatures. In this study, ZnSe nanowires were synthesized by the thermal evaporation of ZnSe powders and the sensing performance of multiple-networked ZnSe nanowire sensors toward NO2 gas was examined. The results showed that ZnSe might be a promising gas sensor material if it is used at room temperature. The response of the ZnSe nanowires to 50 ppb–5 ppm NO2 at room temperature under dark and UV illumination conditions were 101–102% and 113–234%, respectively. The responses of the ZnSe nanowires to 5 ppm NO2 increased from 102 to 234% with increasing UV illumination intensity from 0 to 1.2 mW/cm2. The response of the ZnSe nanowires was stronger than or comparable to that of typical metal oxide semiconductors reported in the literature, which require higher NO2 concentrations and operate at higher temperatures. The origin of the enhanced response of the ZnSe nanowires towards NO2 under UV illumination is also discussed.

  6. Disposition scenarios and safeguardability of fissile materials under START Treaty

    International Nuclear Information System (INIS)

    Pillay, K.K.S.

    1993-01-01

    Under the Strategic Arms Reduction Treaty (START-I) signed in 1991 and the Lisbon Protocol of 1992, a large inventory of fissile materials will be removed from the weapons fuel cycles of the United States and the Former Soviet Union (FSU). The Lisbon Protocol calls for Ukraine, Kazakstan, and Byelarus to become nonnuclear members of the treaty and for Russia to assume the responsibility of the treaty as a nuclear weapons state. In addition, the START-II Treaty, which was signed in 1993 by the United States and Russia, further reduces deployed nuclear warheads and adds to the inventory of excess special nuclear materials (SNM). Because storage of in-tact warheads has the potential for a open-quotes breakout,close quotes it would be desirable to dismantle the warheads and properly dispose of the SNMs under appropriate safeguards to prevent their reentry into the weapons fuel cycle. The SNM recovered from dismantled warheads can be disposed of in several ways, and the final choices may be up to the country having the title to the SNM. Current plans are to store them indefinitely, leaving serious safeguards concerns. Recognizing that the underlying objective of these treaties is to prevent the fissile materials from reentering the weapons fuel cycle, it is necessary to establish a verifiable disposal scheme that includes safeguards requirements. This paper identifies some realistic scenarios for the disposal of SNM from the weapons fuel cycle and examines the safeguardability of those scenarios

  7. Low levels of extraneous agents in vaccine starting materials.

    Science.gov (United States)

    Rouby, Jean-Claude

    2010-05-01

    There are different ways to define the concept of 'low levels' of extraneous agents in vaccines and vaccine starting materials, based on the amount of extraneous agents as such, the sensitivity of the detection method and the probability approach linked to the sampling method. None of these approaches, however, is entirely satisfactory--a general definition of a 'low level' cannot be provided. Since the main point is the safety of medicinal products, the risk analysis approach to 'low level' contaminations can be considered as a way to overcome the above mentioned deadlock. But as too many variables impact the risk analysis, it cannot be properly performed either. In practice, seeds are tested to show freedom from extraneous agents, the other raw materials are inactivated through a validated method. However, there are technical and regulatory limits in both cases, and neither testing nor inactivation entirely guarantees freedom from extraneous agents. Despite this unsatisfactory situation, it should be acknowledged that no truly significant disease outbreak linked to an extraneous agent has been identified until today. Regulatory actions are mainly undertaken when a sanitary problem occurs. In the end, companies remain responsible for their products. 2010 The International Association for Biologicals. Published by Elsevier Ltd. All rights reserved.

  8. Starting Point: Linking Methods and Materials for Introductory Geoscience Courses

    Science.gov (United States)

    Manduca, C. A.; MacDonald, R. H.; Merritts, D.; Savina, M.

    2004-12-01

    Introductory courses are one of the most challenging teaching environments for geoscience faculty. Courses are often large, students have a wide variety of background and skills, and student motivation can include completing a geoscience major, preparing for a career as teacher, fulfilling a distribution requirement, and general interest. The Starting Point site (http://serc.carleton.edu/introgeo/index.html) provides help for faculty teaching introductory courses by linking together examples of different teaching methods that have been used in entry-level courses with information about how to use the methods and relevant references from the geoscience and education literature. Examples span the content of geoscience courses including the atmosphere, biosphere, climate, Earth surface, energy/material cycles, human dimensions/resources, hydrosphere/cryosphere, ocean, solar system, solid earth and geologic time/earth history. Methods include interactive lecture (e.g think-pair-share, concepTests, and in-class activities and problems), investigative cases, peer review, role playing, Socratic questioning, games, and field labs. A special section of the site devoted to using an Earth System approach provides resources with content information about the various aspects of the Earth system linked to examples of teaching this content. Examples of courses incorporating Earth systems content, and strategies for designing an Earth system course are also included. A similar section on Teaching with an Earth History approach explores geologic history as a vehicle for teaching geoscience concepts and as a framework for course design. The Starting Point site has been authored and reviewed by faculty around the country. Evaluation indicates that faculty find the examples particularly helpful both for direct implementation in their classes and for sparking ideas. The help provided for using different teaching methods makes the examples particularly useful. Examples are chosen from

  9. Metal contacts on ZnSe and GaN

    Energy Technology Data Exchange (ETDEWEB)

    Duxstad, Kristin Joy [Univ. of California, Berkeley, CA (United States). Materials Science and Mineral Engineering

    1997-05-01

    Recently, considerable interest has been focused on the development of blue light emitting materials and devices. The focus has been on GaN and ZnSe, direct band gap semiconductors with bands gaps of 3.4 and 2.6 eV, respectively. To have efficient, reliable devices it is necessary to have thermally and electrically stable Ohmic contacts. This requires knowledge of the metal-semiconductor reaction behavior. To date few studies have investigated this behavior. Much information has accumulated over the years on the behavior of metals on Si and GaAs. This thesis provides new knowledge for the more ionic wide band gap semiconductors. The initial reaction temperatures, first phases formed, and phase stability of Pt, Pd, and Ni on both semiconductors were investigated. The reactions of these metals on ZnSe and GaN are discussed in detail and correlated with predicted behavior. In addition, comparisons are made between these highly ionic semiconductors and Si and GaAs. The trends observed here should also be applicable to other II-VI and III-Nitride semiconductor systems, while the information on phase formation and stability should be useful in the development of contacts for ZnSe and GaN devices.

  10. Growth of ZnSe nano-needles by pulsed laser deposition and their application in polymer/inorganic hybrid solar cells

    International Nuclear Information System (INIS)

    Chen, L.; Lai, J.S.; Fu, X.N.; Sun, J.; Ying, Z.F.; Wu, J.D.; Lu, H.; Xu, N.

    2013-01-01

    Using pulsed-laser deposition method, crystalline ZnSe nano-needles have been grown on catalyst-coated silicon (100) substrates. The crystalline ZnSe nano-needles with the middle diameters of about 20–80 nm, and the lengths ranging from 100 to 600 nm can be grown densely on 300–400 °C substrates. The as-grown ZnSe nano-needles were well crystalline and base-grown. They are potential electron-capturing materials in polymer/inorganic hybrid solar cells for their properties of good electron-conductance and high ratio surface area. Based on the ZnSe nano-needle cathode, a five-layer composite structure of polymer/inorganic hybrid solar cell has been designed and fabricated. The absorption spectra of the blend of regioregular poly(3-hexylthiophene-2,5-diyl) and phenyl-C61-butyric acid methyl ester (P3HT:PCBM), ZnSe nano-needles and the combination of P3HT:PCBM and ZnSe nano-needles were examined by ultraviolet–visible-infrared spectrophotometer, respectively. The absorption bands of the combination of P3HT:PCBM and ZnSe nano-needles fit well with the solar spectral distribution. - Highlights: ► Crystalline ZnSe nano-needles grown by pulsed laser deposition. ► A five-layer polymer/inorganic hybrid solar cell based on ZnSe nano-needles cathode. ► ZnSe nano-needles improve light absorption. ► Employment of ZnSe nano-needles increase the open-circuit voltage and fill factor

  11. Structural and optical properties of Ni doped ZnSe nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Yadav, Kanta; Dwivedi, Y.; Jaggi, Neena, E-mail: neena_jaggi@rediffmail.com

    2015-02-15

    In the present work synthesis of ZnSe:Ni nanoparticles using a simple solvothermal method has been discussed. The structural characterizations of as synthesized materials were done by powder X-ray diffraction (XRD), Transmission electron microscope (TEM) and High resolution transmission microscope (HRTEM) imaging techniques, which revealed formation of core–shell nanoparticles with crystallite size 2–4 nm. The structural parameters such as lattice constants, internal strain, dislocation density etc. of ZnSe and Ni doped ZnSe nanocrystals were estimated. Nickel doping in ZnSe host is verified by the Raman spectroscopy. Optical properties were diagnosed by UV–vis absorption and photoluminescence (PL) techniques. The observed blue-shift in UV–vis absorption edge of the prepared sample of ZnSe as compared to its value for the bulk counterpart indicates formation of nanosized particles. PL spectra of Ni{sup 2+} doped samples indicate red-shift and improved emission intensity. - Highlights: • Synthesis of core shell structures of the ZnSe by simple approach. • Enhancement of the photoluminescence emission with the increase in the concentration of Ni a transition metal into the host material. • Increase in the dislocation density and strain with decrease in grain size.

  12. Development of a hydrothermal method to synthesize spherical ZnSe nanoparticles: Appropriate templates for hollow nanostructures

    Directory of Open Access Journals (Sweden)

    S. Gharibe

    2014-01-01

    Full Text Available Hydrothermal method was used to synthesize pure ZnSe nanosphere materials. The effects of the reducing agent amount, the reaction time and temperature were investigated on the purity of ZnSe. Also, the effects of surfactants such as sodium dodecyl sulfate (SDS (anionic and cetyl trimethylammonium bromide (CTAB (cationic were studied on the morphology of ZnSe. The prepared nanospheres were characterized using XRD, SEM, TEM and UV-Vis spectroscopy. Through these techniques, it was found that the pure ZnSe nanoparticles have a zinc blend structure and in a spherical form with average diameter of 30 nm. DOI: http://dx.doi.org/10.4314/bcse.v28i1.5

  13. Characterization of single crystalline ZnTe and ZnSe grown by vapor phase transport

    Energy Technology Data Exchange (ETDEWEB)

    Trigubo, A B; Di Stefano, M C [FRBA-UTN, (1179) Buenos Aires (Argentina); Aguirre, M H [Dpto de Quim Inorg, Fac de Cs Quim, Univ Complutense, (28040) Madrid (Spain); Martinez, A M; D' Elia, R; Canepa, H; Heredia, E, E-mail: atrigubo@citefa.gov.a [CINSO-CITEFA: (1603) Villa Martelli, Pcia de Buenos Aires (Argentina)

    2009-05-01

    Tubular furnaces were designed and built to obtain single crystalline ZnTe and ZnSe ingots using respectively physical and chemical transport methods. Different temperature profiles and growth rates were analyzed in order to optimize the necessary crystalline quality for device development. Optical and scanning electron micrographs of the corrosion figures produced by chemical etching were used to obtain the dislocation density and the misorientation between adjacent subgrains in ZnTe and ZnSe wafers. Structural quality of the single crystalline material was determined by transmission electronic microscopy. Optical transmittance was measured by infrared transmission spectrometry and the resulting values were compared to commercial samples.

  14. IFR starts to burn up weapons-grade material

    International Nuclear Information System (INIS)

    Anon.

    1994-01-01

    With funding from different parts of the federal government, the Integral Fast Reactor (IFR) project has survived into fiscal year 1994 and is now embarking on a demonstration of how this type of liquid-metal-cooled reactor (LMR) can be used to burn fuel derived from weapons-grade plutonium. This month, an assembly made from weapons-grade material is to be loaded into Experimental Breeder Reactor-II in Idaho, which is serving as the prototype for the IFR concept. Although FY 1994 work is being funded by the DOE, this particular examination of plutonium burnup is backed by the Department of Defense

  15. Metal alkoxides as starting materials for hydrolysis processes

    International Nuclear Information System (INIS)

    Mukhtar, Omaima Awad

    1999-12-01

    In this thesis the preparation of some metal alkoxides and their hydrolysis products were studied. The characteristic of each prepared alkoxides and their hydrolyzates were determined. Tetra ethoxysilane was prepared by the elemental route (the reaction of silicon powder with liquid ethanol) in the presence of tin ethoxide as a catalyst. The use of tin alkoxide is considered one of the most developed ways used recently in chemistry, compared to the usage of acids and bases as catalyst previously. It had been confirmed by the usage of (infrared) IR spectroscopy, the structure of the prepared material. Also tin isopropoxide had been prepared and hydrolyzed. Ethoxides of aluminium, magnesium and tin had been prepared by the elemental route. The gelation product had been analyzed. tetraethoxysilane had been also prepared by the halosilane route. Isopropoxide of each aluminium, magnesium and tin had been synthesized, hydrolyzed, allowed to gel and analyzed by IR (infrared) spectroscopy and gas-liquid chromatography. However, results obtained indicated that tin ethoxide is an effective catalyst in the direct synthesis of tetraethoxysilane from silicon powder and liquid ethanol. Gas-liquid chromatography, infra-red (IR) analysis showed that the final reaction product was tetraethoxysilane. (Author)

  16. Methanol market slowly tightens as Brazil starts soaking up material

    International Nuclear Information System (INIS)

    Young, I.

    1992-01-01

    Although the US methanol market's response to mandated oxygen requirements in reformulated gasoline has been disappointing, the European market has surprisingly been tightening in recent weeks and looks set for a price rise in first-quarter 1993. The tightness is being felt mainly in the Mediterranean market, where the Libyan methanol plant is running at only 70% because of problems with gas feedstock supplies. More significantly, the Brazilian government has now given the go-ahead for a yearlong extension on imports of methanol for use as an ethanol replacement in fuel blending. The new authorization sets a monthly import limit of 48,000 m.t. during that period. Libya is an important supplier of methanol to the Brazilian market and has already shipped about 20,000 m.t. since the authorization was given. Another major supplier to Brazil is Russia, from its two giant 750,000-m.t./year plants at Gubakha and Tomsk. The material is shipped from the terminal at Yuzhnyy on the Black Sea, in Ukrainian territory since the collapse of the Soviet Union

  17. Simple synthesis of ZnSe nanoparticles by thermal treatment and their characterization

    Directory of Open Access Journals (Sweden)

    Aeshah Salem

    Full Text Available A simple thermal treatment was used to synthesize ZnSe nanoparticles at different calcination temperatures in a nitrogen flowing. The samples of ZnSe nanoparticles were prepared by reacting zinc nitrate (source of zinc and selenium powder with Polyvinylpyrrolidone (capping agent. Analysis of their X-ray diffraction patterns suggested the formation of an amorphous phase of the unheated material before calcination, which then transformed into a cubic crystalline structure of ZnSe nanoparticles after calcination. The phase analyses using energy-dispersive X-ray spectroscopy and Fourier-transform infrared spectroscopy confirmed the presence of Zn and Se as the original compounds of prepared ZnSe nanoparticle samples. The average particle size of the samples increased from 7 ± 5 to 18 ± 3 nm as the calcination temperature was increased from 450 to 700 °C, which is also supported by the transmission electron microscopy results. Diffuse UV–visible reflectance spectra were used to determine the optical band gap through the Kubelka–Munk equation; the energy band gap was found to decrease from 4.24 to 3.95 eV with increasing calcination temperature. Keywords: Metals, Calcination, Differential thermal analysis (DTA, Fourier transform infrared spectroscopy (FTIR

  18. Effects of chemical kinetics and starting material regeneration on the efficiency of an iodine laser amplifier

    International Nuclear Information System (INIS)

    Fisk, G.A.

    1977-05-01

    A model of the chemical kinetics occurring in an iodine laser amplifier is presented and used to calculate the degree to which the starting material is consumed as a result of laser operation. The cost of purchasing new starting material is estimated and shown to be prohibitive. A scheme for regenerating the starting material from the species present in the amplifier after lasing is proposed. It is shown that the estimated efficiency of this chemical regeneration process is appreciably higher than the projected optimum efficiency of the pumping process

  19. ZnSe MSM photodetectors prepared on GaAs and ZnSe substrates

    International Nuclear Information System (INIS)

    Lin, T.K.; Chang, S.J.; Su, Y.K.; Chiou, Y.Z.; Wang, C.K.; Chang, S.P.; Chang, C.M.; Tang, J.J.; Huang, B.R.

    2005-01-01

    Homoepitaxial and heteroepitaxial ZnSe metal-semiconductor-metal (MSM) photodetectors were both fabricated and characterized. It was found that homoepitaxial ZnSe MSM photodetector could provide us smaller dark current and large photocurrent. With an incident wavelength of 448 nm, it was found that the maximum responsivities for the homoepitaxial and heteroepitaxial ZnSe photodetectors were 0.128 and 0.045 A/W, which corresponds to a quantum efficiency of 36 and 12%, respectively. Furthermore, it was found that we achieved the minimum noise equivalent power (NEP) of 7.6 x 10 -13 W and the maximum normalized detectivity (D *) of 9.3 x 10 11 cm Hz 0.5 W -1 from our homoepitaxial ZnSe photodetector. In contrast, NEP and D * of the heteroepitaxial ZnSe photodetector were 2.9 x 10 -12 W and 2.44 x 10 11 cm Hz 0.5 W -1 , respectively

  20. The synthesis and photocatalytic activity of ZnSe microspheres

    International Nuclear Information System (INIS)

    Cao Huaqiang; Xiao Yujiang; Zhang Sichun

    2011-01-01

    This paper reports the synthesis of semiconductor ZnSe microspheres composed of nanoparticles via a solvothermal route between the organic molecule selenophene (C 4 H 4 Se) and ZnCl 2 without adding any surfactant. The ZnSe microspheres were characterized by x-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), specific surface area measurement, and photoluminescence (PL) spectra. A strong and broad blue PL emission at 443 nm in wavelength (∼2.79 eV in photon energy) is attributed to the near-band-edge (NBE) emission of ZnSe, while the 530 nm peak is a defect-related (DL) emission. The photocatalytic activity of the as-prepared ZnSe microspheres was evaluated by photodegradation of methyl orange (MO) dye under ultraviolet (UV) light and visible light irradiation. The degradations of MO reach 94% or 95.1%, close to 100%, in the presence of the as-synthesized ZnSe microspheres or commercial ZnSe powder after 7 or 10 h under UV irradiation, respectively. Meanwhile the degradations of MO reach 94.3% or 60.6% in the presence of the as-synthesized ZnSe microspheres or commercial ZnSe powder after 12 h, respectively. The degradation rate of ZnSe microspheres is twice that of ZnSe commercial powder under UV light irradiation, and three times under visible light irradiation. The degradation process of MO dye on ZnSe microspheres under UV or visible light is also discussed.

  1. Structural characterization of vacuum evaporated ZnSe thin films

    Indian Academy of Sciences (India)

    The lattice parameter, grain size, average internal stress, microstrain, dislocation density and degree of pre- ferred orientation in the film are calculated and correlated with Ts. Keywords. ZnSe thin films; X-ray diffraction; average internal stress; microstrain; dislocation density. 1. Introduction. Thin films of ZnSe has attracted ...

  2. Donor bound excitons in ZnSe nanoresonators - Applications in quantum information science

    Energy Technology Data Exchange (ETDEWEB)

    Pawlis, A. [Department of Physics, University of Paderborn, Warburger Str. 100, 33098 Paderborn, Germany and Edward L. Ginzton Laboratory, Stanford University, Stanford, California 94305-4088 (United States); Lischka, K. [Department of Physics, University of Paderborn, Warburger Str. 100, 33098 Paderborn (Germany); Sanaka, K.; Yamamoto, Y. [Edward L. Ginzton Laboratory, Stanford University, Stanford, California 94305-4088, USA and National Institute of Informatics, 2-1-2 Hitotsubashi, Chiyoda-ku, Tokyo 101-8430 (Japan); Sleiter, D. [Edward L. Ginzton Laboratory, Stanford University, Stanford, California 94305-4088 (United States)

    2014-05-15

    Here we summarize the advantages of excitons bound to isolated fluorine donor in ZnSe/ZnMgSe quantum well nano-structures. Devices based on these semiconductors, are particularly suited to implement concepts of the optical manipulation of quantum states in solid-state material. The fluorine donor in ZnSe provides a physical qubit with potential advantages over previously researched qubits. In this context we show several initial demonstrations of devices, such as a low-threshold microdisk laser and an indistinguishable single photon source. Additionally we demonstrate the realization of a controllable three-level-system qubit consisting of a single Fluorine donor in a ZnSe nano-pillar, which provides an optical accessible single electon spin qubit.

  3. Effect of crystallochemistry of starting materials on the rate of smectite to illite reaction

    International Nuclear Information System (INIS)

    Sato, Tsutomu; Isobe, Hiroshi; Ohnuki, Toshihiko; Murakami, Takashi

    1995-01-01

    A series of hydrothermal experiments was performed to determine the effect of layer charge of starting materials on the smectite to illite reaction rate that might be applied to nuclear-waste repository design. The experiments were conducted on K-saturated fractions of Wyoming smectite (SWy-1) and Tsukinuno smectite (SKu-F) in a closed system at temperatures of 95, 150, 200, 250, 300 C for run durations of up to 477 days with a 1:20 mass ratio of solid to deionized water. The mean layer charge and tetrahedral charge of SKu-F are larger than those of SWy-1. The proportion of smectite layers in illite/smectite interstratified minerals rapidly decreases, and then slowly decreases with increase in reaction time; a plot of ln (100/% smectite) vs. time produces two distinct straight lines in all experiments. These lines are suggestive of two first-order kinetic processes with different rates for this reaction; the first process has a greater rate than the second one. An Arrhenius plot of the reaction rates for each process produces a folding and straight lines for the first and second processes, respectively, suggesting that there are at least two parallel processes in the first process, and a dominant process is different between high- and low-temperature reactions. The activation energies of the first and second processes determined from the plots are the same for the two starting materials, meaning that the reaction mechanisms for the two starting materials are the same. However, the rate of the first process is different between the two starting materials, although that of the second process is similar. The difference in the rate of the first process results possibly from the difference in the amount of layer charge between the two starting smectites

  4. Characterization of a ZnSe scintillating bolometer prototype for neutrinoless double beta decay search

    Directory of Open Access Journals (Sweden)

    Tenconi M.

    2014-01-01

    Full Text Available As proposed in the LUCIFER project, ZnSe crystals are attractive materials to realize scintillating bolometers aiming at the search for neutrinoless double beta decay of the promising isotope 82Se. However, the optimization of the ZnSe-based detectors is rather complex and requires a wide-range investigation of the crystal features: optical properties, crystalline quality, scintillation yields and bolometric behaviour. Samples tested up to now show problems in the reproducibility of crucial aspects of the detector performance. In this work, we present the results obtained with a scintillating bolometer operated aboveground at about 25 mK. The detector energy absorber was a single 1 cm3 ZnSe crystal. The good energy resolution of the heat channel (about 14 keV at 1460 keV and the excellent alpha/beta discrimination capability are very encouraging for a successful realization of the LUCIFER program. The bolometric measurements were completed by optical tests on the crystal (optical transmission and luminescence measurements down to 10 K and investigation of the crystalline structure. The work here described provides a set of parameters and procedures useful for a complete pre-characterization of ZnSe crystals in view of the realization of highly performing scintillating bolometers.

  5. ZnSe thin films by chemical bath deposition method

    Energy Technology Data Exchange (ETDEWEB)

    Lokhande, C.D.; Patil, P.S.; Tributsch, H. [Hahn-Meitner-Institute, Bereich Physikalische Chemie, Abt. CS, Glienicker Strasse-100, D-14109 Berlin (Germany); Ennaoui, A. [Hahn-Meitner-Institute, Bereich Physikalische Chemie, Abt. CG, Glienicker Strasse-100, D-14109 Berlin (Germany)

    1998-09-04

    The ZnSe thin films have been deposited onto glass substrates by the simple chemical bath deposition method using selenourea as a selenide ion source from an aqueous alkaline medium. The effect of Zn ion concentration, bath temperature and deposition time period on the quality and thickness of ZnSe films has been studied. The ZnSe films have been characterized by XRD, TEM, EDAX, TRMC (time-resolved microwave conductivity), optical absorbance and RBS techniques for their structural, compositional, electronic and optical properties. The as-deposited ZnSe films are found to be amorphous, Zn rich with optical band gap, Eg, equal to 2.9 eV

  6. Fabrication and Photocatalytic Properties of ZnSe Nanorod Films

    Directory of Open Access Journals (Sweden)

    Jiajia Yin

    2016-01-01

    Full Text Available ZnSe nanorod films grown on fused quartz glass substrates via a simple two-step synthesis protocol were demonstrated to be environmentally safe and effective recyclable photocatalysts. These films showed greatly enhanced photocatalytic activity compared to pulsed laser deposition ZnSe films in the degradation of methyl orange dye solutions. The well-crystalized ZnSe nanorods had a length of 15 µm and a diameter of 200 nm and were densely grown on the substrate. The morphology, crystal structure, crystal phase, and photophysical properties of the ZnSe nanorod films were investigated using field-emission scanning electron microscopy (FE-SEM, UV-Vis spectroscopy, X-ray diffraction (XRD, transmission electron microscopy (TEM, and high resolution transmission electron microscopy (HRTEM.

  7. Fine defective structure of silicon carbide powders obtained from different starting materials

    Directory of Open Access Journals (Sweden)

    Tomila T.V.

    2006-01-01

    Full Text Available The fine defective structure of silicon carbide powders obtained from silicic acid-saccharose, aerosil-saccharose, aerosil-carbon black, and hydrated cellulose-silicic acid gel systems was investigated. The relation between IR absorption characteristics and the microstructure of SiC particles obtained from different starting materials was established. The numerical relationship between the lattice parameter a and the frequency νTO is presented.

  8. Evolution of sourdough microbiota in spontaneous sourdoughs started with different plant materials.

    Science.gov (United States)

    Ripari, Valery; Gänzle, Michael G; Berardi, Enrico

    2016-09-02

    The preparation of sourdough in bakeries may include the use of inocula, e.g. fruits, flowers or rumen cuts to accelerate the process of selection of suitable microorganisms. The aim of this work was to investigate the effect of these inocula on the microbial evolution in sourdoughs. First, the microbiota of nineteen traditional sourdoughs that were initially started with diverse inocula was identified. Second, de novo sourdoughs were started with plant materials and the evolution of sourdough microbiota was investigated by culture, and by high-resolution melting curve quantitative PCR (HRM-qPCR). This study developed a new protocol for HRM-qPCR analysis of yeast microbiota in sourdough, and indicates this independent culture method suitable for characterization of yeasts. Microbiota of traditional sourdoughs were largely independent from the use of inoculum, however, Acetobacter spp. were identified only in sourdoughs started with apple flowers or apple pulp. In de novo sourdoughs started with plant materials, microbiota rapidly stabilized, and were characterized by Lactobacillus sanfranciscensis, Lactobacillus plantarum, Lactobacillus graminis, or Lactobacillus rossiae, and Saccharomyces cerevisiae as dominant species. Competition experiments revealed that the ecological fitness of L. plantarum, L. graminis, and L. rossiae in wheat or rye malt sourdoughs was lower when compared to L. sanfranciscensis, demonstrating that their presence in de novo sourdoughs reflects dispersal limitation. In conclusion, establishment of microbiota in de novo sourdoughs is dispersal limited. This study provides scientific support for the artisanal practice to inoculate de novo sourdoughs with flowers, berries, or related plant material. Copyright © 2016. Published by Elsevier B.V.

  9. Effect of Start-Up Strategies and Electrode Materials on Carbon Dioxide Reduction on Biocathodes.

    Science.gov (United States)

    Saheb-Alam, Soroush; Singh, Abhijeet; Hermansson, Malte; Persson, Frank; Schnürer, Anna; Wilén, Britt-Marie; Modin, Oskar

    2018-02-15

    The enrichment of CO 2 -reducing microbial biocathodes is challenging. Previous research has shown that a promising approach could be to first enrich bioanodes and then lower the potential so the electrodes are converted into biocathodes. However, the effect of such a transition on the microbial community on the electrode has not been studied. The goal of this study was thus to compare the start-up of biocathodes from preenriched anodes with direct start-up from bare electrodes and to investigate changes in microbial community composition. The effect of three electrode materials on the long-term performance of the biocathodes was also investigated. In this study, preenrichment of acetate-oxidizing bioanodes did not facilitate the start-up of biocathodes. It took about 170 days for the preenriched electrodes to generate substantial cathodic current, compared to 83 days for the bare electrodes. Graphite foil and carbon felt cathodes produced higher current at the beginning of the experiment than did graphite rods. However, all electrodes produced similar current densities at the end of the over 1-year-long study (2.5 A/m 2 ). Methane was the only product detected during operation of the biocathodes. Acetate was the only product detected after inhibition of the methanogens. Microbial community analysis showed that Geobacter sp. dominated the bioanodes. On the biocathodes, the Geobacter sp. was succeeded by Methanobacterium spp., which made up more than 80% of the population. After inhibition of the methanogens, Acetobacterium sp. became dominant on the electrodes (40% relative abundance). The results suggested that bioelectrochemically generated H 2 acted as an electron donor for CO 2 reduction. IMPORTANCE In microbial electrochemical systems, living microorganisms function as catalysts for reactions on the anode and/or the cathode. There is a variety of potential applications, ranging from wastewater treatment and biogas generation to production of chemicals. Systems

  10. Ultra-thin ZnSe: Anisotropic and flexible crystal structure

    Energy Technology Data Exchange (ETDEWEB)

    Bacaksiz, C., E-mail: cihanbacaksiz@iyte.edu.tr [Department of Physics, Izmir Institute of Technology, 35430 Izmir (Turkey); Senger, R.T. [Department of Physics, Izmir Institute of Technology, 35430 Izmir (Turkey); Sahin, H. [Department of Photonics, Izmir Institute of Technology, 35430 Izmir (Turkey)

    2017-07-01

    Highlights: • Ultra-thin ZnSe is dynamically stable. • Ultra-thin ZnSe is electronically direct-gap semiconductor. • Ultra-thin ZnSe is ultra-flexible. • Ultra-thin ZnSe is mechanically in-plane anisotropic. - Abstract: By performing density functional theory-based calculations, we investigate the structural, electronic, and mechanical properties of the thinnest ever ZnSe crystal . The vibrational spectrum analysis reveals that the monolayer ZnSe is dynamically stable and has flexible nature with its soft phonon modes. In addition, a direct electronic band gap is found at the gamma point for the monolayer structure of ZnSe. We also elucidate that the monolayer ZnSe has angle dependent in-plane elastic parameters. In particular, the in-plane stiffness values are found to be 2.07 and 6.89 N/m for the arm-chair and zig-zag directions, respectively. The angle dependency is also valid for the Poisson ratio of the monolayer ZnSe. More significantly, the in-plane stiffness of the monolayer ZnSe is the one-tenth of Young modulus of bulk zb-ZnSe which indicates that the monolayer ZnSe is a quite flexible single layer crystal. With its flexible nature and in-plane anisotropic mechanical properties, the monolayer ZnSe is a good candidate for nanoscale mechanical applications.

  11. Ultra-thin ZnSe: Anisotropic and flexible crystal structure

    International Nuclear Information System (INIS)

    Bacaksiz, C.; Senger, R.T.; Sahin, H.

    2017-01-01

    Highlights: • Ultra-thin ZnSe is dynamically stable. • Ultra-thin ZnSe is electronically direct-gap semiconductor. • Ultra-thin ZnSe is ultra-flexible. • Ultra-thin ZnSe is mechanically in-plane anisotropic. - Abstract: By performing density functional theory-based calculations, we investigate the structural, electronic, and mechanical properties of the thinnest ever ZnSe crystal . The vibrational spectrum analysis reveals that the monolayer ZnSe is dynamically stable and has flexible nature with its soft phonon modes. In addition, a direct electronic band gap is found at the gamma point for the monolayer structure of ZnSe. We also elucidate that the monolayer ZnSe has angle dependent in-plane elastic parameters. In particular, the in-plane stiffness values are found to be 2.07 and 6.89 N/m for the arm-chair and zig-zag directions, respectively. The angle dependency is also valid for the Poisson ratio of the monolayer ZnSe. More significantly, the in-plane stiffness of the monolayer ZnSe is the one-tenth of Young modulus of bulk zb-ZnSe which indicates that the monolayer ZnSe is a quite flexible single layer crystal. With its flexible nature and in-plane anisotropic mechanical properties, the monolayer ZnSe is a good candidate for nanoscale mechanical applications.

  12. Electroluminescence of colloidal ZnSe quantum dots

    International Nuclear Information System (INIS)

    Dey, S.C.; Nath, S.S.

    2011-01-01

    The article reports a green chemical synthesis of colloidal ZnSe quantum dots at a moderate temperature. The prepared colloid sample is characterised by UV-vis absorption spectroscopy and transmission electron microscopy. UV-vis spectroscopy reveals as-expected blue-shift with strong absorption edge at 400 nm and micrographs show a non-uniform size distribution of ZnSe quantum dots in the range 1-4 nm. Further, photoluminescence and electroluminescence spectroscopies are carried out to study optical emission. Each of the spectroscopies reveals two emission peaks, indicating band-to-band transition and defect related transition. From the luminescence studies, it can be inferred that the recombination of electrons and holes resulting from interband transition causes violet emission and the recombination of a photon generated hole with a charged state of Zn-vacancy gives blue emission. Meanwhile electroluminescence study suggests the application of ZnSe quantum dots as an efficient light emitting device with the advantage of colour tuning (violet-blue-violet). - Highlights: → Synthesis of ZnSe quantum dots by a green chemical route. → Characterisation: UV-vis absorption spectroscopy and transmission electron microscopy. → Analysis of UV-vis absorption spectrum and transmission electron micrographs. → Study of electro-optical properties by photoluminescence and electroluminescence. → Conclusion: ZnSe quantum dots can be used as LED with dual colour emission.

  13. Magnetic and luminescent properties of vanadium-doped ZnSe crystals

    Energy Technology Data Exchange (ETDEWEB)

    Radevici, Ivan, E-mail: ivarad@utu.fi [Wihuri Physical Laboratory, Department of Physics and Astronomy, University of Turku, FI-20014 Turku (Finland); Faculty of Physics and Engineering, Moldova State University, 60 A. Mateevici str., MD-2009 Chisinau (Moldova, Republic of); Nedeoglo, Natalia; Sushkevich, Konstantin [Faculty of Physics and Engineering, Moldova State University, 60 A. Mateevici str., MD-2009 Chisinau (Moldova, Republic of); Huhtinen, Hannu [Wihuri Physical Laboratory, Department of Physics and Astronomy, University of Turku, FI-20014 Turku (Finland); Nedeoglo, Dmitrii [Faculty of Physics and Engineering, Moldova State University, 60 A. Mateevici str., MD-2009 Chisinau (Moldova, Republic of); Paturi, Petriina [Wihuri Physical Laboratory, Department of Physics and Astronomy, University of Turku, FI-20014 Turku (Finland)

    2016-12-15

    Magnetic and photoluminescence properties of vanadium-doped ZnSe crystals with impurity concentrations varied by changing the V amount in the source material from 0.03 to 0.30 at% are studied in 5–300 K temperature range. Investigation of magnetic properties shows that the studied concentrations of vanadium impurity that should not disturb crystal lattice are insignificant for observing ferromagnetic behaviour even at low temperatures. The contribution of V impurity to edge emission and its influence on infra-red emission are discussed. Similarities of magnetic and luminescent properties induced by vanadium and other transition metal impurities are discussed.

  14. Chemical bath ZnSe thin films: deposition and characterisation

    Science.gov (United States)

    Lokhande, C. D.; Patil, P. S.; Ennaoui, A.; Tributsch, H.

    1998-01-01

    The zinc selenide (ZnSe) thin films have been deposited by a simple and inexpensive chemical bath deposition (CBD) method. The selenourea was used as a selenide ion source. The ZnSe films have been characterised by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDAX), Rutherford back scattering (RBS), and optical absorption. The as-deposited ZnSe films on various substrates are found to be amorphous and contain O2 and N2 in addition to Zn and Se. The optical band gap of the film is estimated to be 2.9 eV. The films are photoactive as evidenced by time resolved microwave conductivity (TRMC).

  15. Dynamics of the line-start reluctance motor with rotor made of SMC material

    Directory of Open Access Journals (Sweden)

    Smółka Krzysztof

    2017-12-01

    Full Text Available Design and control of electric motors in such a way as to ensure the expected motor dynamics, are the problems studied for many years. Many researchers tried to solve this problem, for example by the design optimization or by the use of special control algorithms in electronic systems. In the case of low-power and fractional power motors, the manufacture cost of the final product is many times less than cost of electronic system powering them. The authors of this paper attempt to improve the dynamic of 120 W line-start synchronous reluctance motor, energized by 50 Hz mains (without any electronic systems. The authors seek a road enabling improvement of dynamics of the analyzed motor, by changing the shape and material of the rotor, in such a way to minimize the modification cost of the tools necessary for the motor production. After the initial selection, the analysis of four rotors having different tooth shapes, was conducted.

  16. In-situ high temperature XRD of calcium phosphate biomaterial using DEHPA as the starting material

    International Nuclear Information System (INIS)

    Meor Yusoff Meor Sulaiman; Masliana Muslim

    2009-01-01

    A process to produce calcium phosphate biomaterial was done using an organic based phosphoric acid (DEHPA) as its starting material. The gel obtained from this reaction was used to study calcium phosphate transformation using in-situ XRD with temperature ranges from room temperature to 1300 degree C. The results obtained from this analysis show the following phase transformation: Gel β-Ca 2 P 2 O 7 β-TCP + HA α-TCP + HA, β-Ca 2 P 2 O 7 forms at 400 degree C and as we heat the sample at 1000 degree C peaks belonging to β- TCP and HA appears showing the transformation of the β-Ca 2 P 2 O 7 phase. When the sample is heated up further to 1200 degree C, β-TCP is transform into α-TCP. In the cold in-situ study, XRD analysis was performed on the sample from room temperature to -140 degree C. At room the XRD diffractogram shows the sample as an amorphous material and as the temperature was further lowered sharp peaks begins to form indicating that the material had becomes crystalline. The peaks were identified to be that calcium hydrogen phosphate (Ca(H 2 PO 4 ) 2 ) and this indicates that there is no hydroxyl group removal during the cooling process. The relative crystallinity values obtained for the different cooling temperatures show a slow exponential increase on the initial cooling of 0 to -100 degree C and at further cooling temperatures resulted fast and linear process. Also unlike the in-situ XRD analysis performs at high temperature no phase transformation occurred at this low temperature. (Author)

  17. development of a hydrothermal method to synthesize spherical znse

    African Journals Online (AJOL)

    Preferred Customer

    nanoparticles have a zinc blend structure and in a spherical form with ... optoelectronic devices such as blue-green laser diodes and turnable mid-IR ... Solvothermal methods have also been developed for the synthesis of ZnSe and CdSe. The.

  18. Exciton dephasing in ZnSe quantum wires

    DEFF Research Database (Denmark)

    Wagner, Hans Peter; Langbein, Wolfgang Werner; Hvam, Jørn Märcher

    1998-01-01

    The homogeneous linewidths of excitons in wet-etched ZnSe quantum wires of lateral sizes down to 23 nm are studied by transient four-wave mixing. The low-density dephasing time is found to increase with decreasing wire width. This is attributed mainly to a reduction of electron-exciton scattering...

  19. On the symmetry of phosphorous doped ZnSe

    Indian Academy of Sciences (India)

    The site symmetry of P doped ZnSe is analysed in detail here, as the recent experiments suggest two possible symmetries T d and C 3 V . The reduction to C 3 V is attributed to the presence of natural impurity, Ga. Our calculations based on molecular model and Green's functions suggest that the symmetry C 3 V is possible ...

  20. On the symmetry of phosphorous doped ZnSe

    Indian Academy of Sciences (India)

    Unknown

    Abstract. The site symmetry of P doped ZnSe is analysed in detail here, as the recent experiments suggest two possible symmetries Td and C3V. The reduction to C3V is attributed to the presence of natural impurity,. Ga. Our calculations based on molecular model and Green's functions suggest that the symmetry C3V is.

  1. Low temperature scintillation in ZnSe crystals

    Czech Academy of Sciences Publication Activity Database

    Dafinei, I.; Fasoli, M.; Ferroni, F.; Mihóková, Eva; Orio, F.; Pirro, S.; Vedda, A.

    2010-01-01

    Roč. 57, č. 3 (2010), 1470-1474 ISSN 0018-9499 Institutional research plan: CEZ:AV0Z10100521 Keywords : bolometers * double beta decay * scintillation detectors * ZnSe Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.519, year: 2010

  2. Exploration of the Infrared Sensitivity for a ZnSe Electrode of an IR Image Converter

    Science.gov (United States)

    Kurt, H. Hilal

    2018-05-01

    Significant improvement has been carried out in the field of the II-VI group semiconductor device technology. Semiconductors based on the II-VI group are attractive due to their alternative uses for thermal imaging systems and photonic applications. This study focuses on experimental work on the optical, electrical and structural characterization of an infrared (IR) photodetector zinc selenide (ZnSe). In addition, the IR sensitivity of the ZnSe has primarily been investigated by exploiting the IR responses of the material for various gas pressures, p, and interelectrode distances, d, in the IR converter. The experimental findings include the results of plasma current and plasma discharge emission under various illumination conditions in the IR region. The electron density distributions inside the gas discharge gap have also been simulated in two-dimensional media. Experimentally, the current-voltage, current-time, and discharge light emission plots are produced for a wide experimental parameter range. Consequently, the structural and optical properties have been studied through atomic force microscopy and Fourier-transform infrared spectroscopy techniques to obtain a comprehensive knowledge of the material.

  3. Formation of a Colloidal CdSe and ZnSe Quantum Dots via a Gamma Radiolytic Technique

    Directory of Open Access Journals (Sweden)

    Aeshah Salem

    2016-09-01

    Full Text Available Colloidal cadmium selenide (CdSe and zinc selenide (ZnSe quantum dots with a hexagonal structure were synthesized by irradiating an aqueous solution containing metal precursors, poly (vinyl pyrrolidone, isopropyl alcohol, and organic solvents with 1.25-MeV gamma rays at a dose of 120 kGy. The radiolytic processes occurring in water result in the nucleation of particles, which leads to the growth of the quantum dots. The physical properties of the CdSe and ZnSe nanoparticles were measured by various characterization techniques. X-ray diffraction (XRD was used to confirm the nanocrystalline structure, energy-dispersive X-ray spectroscopy (EDX was used to estimate the material composition of the samples, transmission electron microscopy (TEM was used to determine the morphologies and average particle size distribution, and UV-visible spectroscopy was used to measure the optical absorption spectra, from which the band gap of the CdSe and ZnSe nanoparticles could be deduced.

  4. Vapor-phase synthesis and characterization of ZnSe nanoparticles

    Science.gov (United States)

    Sarigiannis, D.; Pawlowski, R. P.; Peck, J. D.; Mountziaris, T. J.; Kioseoglou, G.; Petrou, A.

    2002-06-01

    Compound semiconductor nanoparticles are an exciting class of materials whose unique optical and electronic properties can be exploited in a variety of applications, including optoelectronics, photovoltaics, and biophotonics. The most common route for synthesizing such nanoparticles has been via liquid-phase chemistry in reverse micelles. This paper discusses a flexible vapor-phase technique for synthesis of crystalline compound semiconductor nanoparticles using gas-phase condensation reactions near the stagnation point of a counterflow jet reactor. ZnSe nanoparticles were formed by reacting vapors of dimethylzinc: triethylamine adduct and hydrogen selenide at 120Torr and room temperature (28°C). No attempt was made to passivate the surface of the particles, which were collected as random aggregates on silicon wafers or TEM grids placed downstream of the reaction zone. Particle characterization using TEM, electron diffraction, Raman and EDAX revealed that the aggregates consisted of polycrystalline ZnSe nanoparticles, almost monodisperse in size (with diameters of ~40nm). The polycrystalline nanoparticles appear to have been formed by coagulation of smaller single-crystalline nanoparticles with characteristic size of 3-5 run.

  5. Impact of starting material (fresh versus cryopreserved marrow) on mesenchymal stem cell culture.

    Science.gov (United States)

    Kaplan, Alesia; Sackett, Katie; Sumstad, Darin; Kadidlo, Dianne; McKenna, David H

    2017-09-01

    Mesenchymal stem cells (MSCs) continue to be investigated in multiple clinical trials as potential therapy for different disorders. There is ongoing controversy surrounding the clinical use of cryopreserved versus fresh MSCs. However, little is known about how cryopreservation affects marrow as starting material. The growth kinetics of MSC cultures derived from fresh versus cryopreserved marrow were compared. Data were reviewed on the growth kinetics of MSCs derived from fresh versus cryopreserved marrow of nine donors. Marrow harvested from each donor was separated into four aliquots (one fresh and three cryopreserved for culture). Data on the date of mononuclear cell cryopreservation/thaw, MSC counts at Passages 1 and 2, MSC doubling, MSC fold expansion, viability (of mononuclear cells and final MSCs), and on flow cytometry markers of mononuclear cells and final MSCs were analyzed for the fresh and cryopreserved marrow groups. In total, 21 MSC lots (seven fresh and 14 cryopreserved) were obtained. The average age of cryopreserved mononuclear cell product was 295 days (range, 18-1241 days). There were no significant differences between MSC numbers at Passage 1 (p = 0.1), final MSC numbers (p = 0.5), MSC doubling (p = 0.7), or MSC fold expansion (p = 0.7). A significant difference was observed in viability by flow cytometry for both mononuclear cells (p = 0.002) and final MSCs (p = 0.009), with higher viability in the fresh marrow group. This study demonstrates that MSCs derived from cryopreserved marrow have the same growth characteristics as fresh marrow-derived MSCs. Further studies are needed to explore potential differences in clinical efficacy. © 2017 AABB.

  6. Femtosecond Laser-Induced Formation of Wurtzite Phase ZnSe Nanoparticles in Air

    Directory of Open Access Journals (Sweden)

    Hsuan I Wang

    2012-01-01

    Full Text Available We demonstrate an effective method to prepare wurtzite phase ZnSe nanoparticles from zincblende ZnSe single crystal using femtosecond pulse laser ablation. The fabricated ZnSe nanoparticles are in spherical shape and uncontaminated while synthesized under ambient environment. By controlling the laser fluences, the average size of ZnSe nanoparticles can be varied from ~16 nm to ~22 nm in diameter. In Raman spectra, the surface phonon mode becomes dominant in the smaller average particle size with uniform size distribution. The interesting phase transition from the zinc blende structure of ZnSe single crystal to wurtzite structure of ZnSe nanoparticles may have been induced by the ultrahigh ablation pressure at the local area due to the sudden injection of high energy leading to solid-solid transition.

  7. How to Start Your Own Business. Women Entrepreneurs Project. Instructional Materials.

    Science.gov (United States)

    McCaslin, Barbara S.; McNamara, Patricia P.

    This text consisting of eight learning activities packages (LAP's) was developed during the California Women Entrepreneurs Project for use in a course designed to help women entrepreneurs learn how to start their own small business. The LAP's included here are self-paced, student-centered modules which take the learner step by step through the…

  8. Synthesis, field emission properties and optical properties of ZnSe nanoflowers

    Energy Technology Data Exchange (ETDEWEB)

    Xue, S.L., E-mail: slxue@dhu.edu.cn [Department of Applied Physics, College of Science, Donghua University, Shanghai 201620 (China); Wu, S.X.; Zeng, Q.Z.; Xie, P.; Gan, K.X.; Wei, J.; Bu, S.Y.; Ye, X.N.; Xie, L. [Department of Applied Physics, College of Science, Donghua University, Shanghai 201620 (China); Zou, R.J. [State Key Laboratory for Modification and Chemical Fibers and Polymer Materials, Donghua University, Shanghai 201620 (China); Zhang, C.M.; Zhu, P.F. [Department of Physics, School of Fundamental Studies, Shanghai University of Engineering Science, Shanghai 201620 (China)

    2016-03-01

    Graphical abstract: Unique ZnSe nanoflowers have been successfully synthesized by reaction of Se powder with Zn substrates. They are characterized by XRD, SEM, TEM, XPS, EDS and Raman spectroscopy and were single crystals with cubic zinc blende (ZB) structure. They also have excellent field emission properties and optical properties. - Highlights: • Novel ZnSe nanoflowers are grown on Zn foils. • ZnSe nanoflowers are characterized by XRD, SEM, TEM, XPS and Raman spectra. • ZnSe nanoflowers on Zn foils as cathodes possess good FE properties. - Abstract: ZnSe nanoflowers have been synthesized by reaction of Se powder with Zn substrates at low temperature. The as-prepared ZnSe nanoflowers were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), X-ray energy dispersive spectroscope (EDS) and Raman spectroscopy measurements. It was found that the morphologies of the as-prepared samples highly depended on reaction time. ZnSe nanoclusters and nanoflowers formed at 573 K when the reaction time was 20 and 60 min, respectively. The as-prepared ZnSe nanoflowers were composed of radically aligned ZnSe nanorods with smooth surfaces. The results of XRD, XPS, EDS, TEM and Raman showed that the as-prepared ZnSe nanocrystals were single crystals with cubic zinc blende (ZB) structure. The formation mechanism of the as-prepared ZnSe nanoflowers was also discussed. In addition, the as-prepared ZnSe nanoflowers had excellent electron emission properties. The turn-on field of the as-prepared ZnSe nanoflowers was 3.5 V/μm and the enhancement factor was 3499. The optical properties of the as-prepared ZnSe nanoflowers were also investigated. The results demonstrated that the as-prepared ZnSe nanoflowers were potential candidates for optoelectronic devices.

  9. Synthesis, structural, optical and Raman studies of pure and lanthanum doped ZnSe nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Pushpendra, E-mail: push.nac@gmail.com [Department of Physics, Faculty of Science, Banaras Hindu University, Varanasi 221005 (India); Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 11529, Taiwan (China); Singh, Jai [Department of Physics, Faculty of Science, Banaras Hindu University, Varanasi 221005 (India); Department of Materials Science and Engineering, Pusan National University, 30 Jangjeon-dong, Geumjeong-gu, Busan 609-735 (Korea, Republic of); Pandey, Mukesh Kumar [Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 11529, Taiwan (China); Jeyanthi, C.E. [Research and Development Centre, Bharathiar University, Coimbatore 641 046 (India); Siddheswaran, R. [Department of Materials Science and Engineering, University of Concepcion, Concepcion (Chile); Paulraj, M. [Department of Physics, Faculty of Physical sciences and Mathematics, University of Concepcion, Casilla 160, Concepcion (Chile); Hui, K.N. [Department of Materials Science and Engineering, Pusan National University, 30 Jangjeon-dong, Geumjeong-gu, Busan 609-735 (Korea, Republic of); Hui, K.S., E-mail: kshui@hanyang.ac.kr [Department of Mechanical Engineering, Hanyang University, 17 Haengdang-dong, Seongdong-gu, Seoul 133-791 (Korea, Republic of)

    2014-01-01

    Graphical abstract: - Highlights: • Template-free synthesis of ZnSe and ZnSe:La nanoparticles was developed at low temperature 100 °C. • Cubic ZnSe and ZnSe:La nanoparticles were obtained by chemical route. • As-synthesized ZnSe:La nanoparticles showed higher emission intensity than ZnSe nanoparticles. • Band gap (E{sub g}) of ZnSe nanoparticles was bigger than ZnSe nanoparticles due to nanosized effect. - Abstract: In this work, a simple, effective and reproducible chemical synthetic route for the production of high-quality, pure ZnSe nanoparticles (NPs), and lanthanum-doped ZnSe (ZnSe:La) NPs is presented. The wide bandgap, luminescent pure ZnSe and ZnSe:La NPs has been synthesized at a low temperature (100 °C) in a single template-free step. The size and optical bandgap of the NPs was analyzed from powder X-ray diffraction (XRD), UV–visible (UV–vis) spectroscopy, transmission electron microscopy (TEM), and high resolution transmission electron microscopy (HRTEM). A broad photoluminescence (PL) emission across the visible spectrum has been demonstrated by a systematic blue-shift in emission due to the formation of small nanoparticles. Here, contribution to emission intensity from surface states of NPs increases with La doping. TEM data revealed that the average size of ZnSe and ZnSe:La NPs is 14 and 8 nm, respectively. On the other hand, band gap energy E{sub g} of ZnSe and ZnSe:La NPs were found to be 3.59 eV and 3.65 eV, respectively. Results showed that hydrazine hydrate played multiple roles in the formation of ZnSe and ZnSe:La NPs. A possible reaction mechanism for the growth of NPs is also discussed.

  10. Influence of the material used to build the blades of a wind turbine on their starting conditions

    Directory of Open Access Journals (Sweden)

    Năstase Eugen-Vlad

    2017-01-01

    Full Text Available Wind energy has been shown to be one of the most viable sources of renewable energy. Hydraulic machines that convert the energy of a fluid into mechanical energy are called turbines. A wind turbine is a device which extracts kinetic energy from the wind. With increasing energy demands is necessary to increase the size of wind turbines. Under these conditions the turbine will start only at high wind speeds. On the other hand, the control of high speed is more difficult and the reduction of the inertial forces becomes mandatory. This study presents an analysis of the material influence on the wind turbine starting conditions.

  11. Photoluminescence characteristics of Pb-doped, molecular-beam-epitaxy grown ZnSe crystal layers

    International Nuclear Information System (INIS)

    Mita, Yoh; Kuronuma, Ryoichi; Inoue, Masanori; Sasaki, Shoichiro; Miyamoto, Yoshinobu

    2004-01-01

    The characteristic green photoluminescence emission and related phenomena in Pb-doped, molecular-beam-epitaxy (MBE)-grown ZnSe crystal layers were investigated to explore the nature of the center responsible for the green emission. The intensity of the green emission showed a distinct nonlinear dependence on excitation intensity. Pb-diffused polycrystalline ZnSe was similarly examined for comparison. The characteristic green emission has been observed only in MBE-grown ZnSe crystal layers with moderate Pb doping. The results of the investigations on the growth conditions, luminescence, and related properties of the ZnSe crystal layers suggest that the green emission is due to isolated Pb replacing Zn and surrounded with regular ZnSe lattice with a high perfection

  12. Substrate-Dependent Differences in the Crystal Structures and Optical Properties of ZnSe Nanowires

    Directory of Open Access Journals (Sweden)

    Keumyoung Seo

    2015-01-01

    Full Text Available The optical and structural properties of ZnSe nanowires directly grown on three different substrates, SiO2, ITO, and graphene, were investigated. ZnSe nanowires grown on graphene and SiO2 were found to have cubic structures, while ZnSe nanowires grown on ITO had a mixed cubic and hexagonal structure. The main peaks in the photoluminescence spectra of ZnSe nanowires grown on SiO2, ITO, and graphene were located at 459, 627, and 627/460 nm, respectively. In addition, a field-emission light-emitting device was fabricated using ZnSe nanowires as a phosphor and graphene as an electrode. The device showed a red emission peak with Commission Internationale de L’Eclairage coordinates of (0.621, 0.315.

  13. Let's start learning radiation. Supplementary material on radiation for secondary school students

    International Nuclear Information System (INIS)

    Watanabe, Yoko; Yamashita, Kiyonobu; Shimada, Mayuka

    2015-01-01

    The Japan Atomic Energy Agency has been organizing training programs for engineers in Asian countries introducing nuclear technology. In 2012, we launched a course ‘Basic Radiation Knowledge for School Education’ as we thought disseminating accurate knowledge on radiation to school students and public would also be important in those countries after Fukushima-Daiichi nuclear power station accident. Ministry of Education, Culture, Sports, Science and Technology - Japan published supplemental learning material on radiation for secondary school students and teachers in Japanese in October 2011. Since the learning material is designed to give a clear explanation of radiation and covers various topics, we thought it would also be beneficial for young students in the world if a learning material in English was available. Therefore, we made a new learning material in English using the topics covered in supplemental learning material on radiation in Japanese as a reference. This learning material has been favourably evaluated by the International Atomic Energy Agency (IAEA) and will be widely used as a practical educational tool in many countries around the world through the IAEA. (author)

  14. Build/Couple/Pair and Multifunctional Catalysis Strategies for the Synthesis of Heterocycles from Simple Starting Materials

    DEFF Research Database (Denmark)

    Ascic, Erhad

    . Multifunctional Catalysis: Synthesis of Heterocycles from Simple Starting Materials A multifunctional catalysis approach, involving a ruthenium-catalyzed tandem ringclosing metathesis/isomerization/N-acyliminium cyclization sequence, is described. Double bonds created during ring-closing metathesis isomerize......, a series of interesting indolizidinones are formed in good yields with excellent diastereoselectivities, including a formal total synthesis of the antiparasitic natural product harmicine and the first total synthesis of mescalotam. Furthermore, preliminary asymmetric variants of the tandem process have...

  15. The effect of carbon chain length of starting materials on the formation of carbon dots and their optical properties

    Science.gov (United States)

    Pan, Xiaohua; Zhang, Yan; Sun, Xiaobo; Pan, Wei; Yu, Guifeng; Si, Shuxin; Wang, Jinping

    2018-04-01

    Carbon dots (CDs) have attracted increasing attention due to their high performances and potential applications in wide range of areas. However, their emission mechanism is not clear so far. In order to reveal more factors contributing to the emission of CDs, the effect of carbon chain length of starting materials on the formation of CDs and their optical properties was experimentally investigated in this work. In order to focus on the effect of carbon chain length, the starting materials with C, O, N in fully identical forms and only carbon chain lengths being different were selected for synthesizing CDs, including citric acid (CA) and adipic acid (AA) as carbon sources, and diamines with different carbon chain lengths (H2N(CH2)nNH2, n = 2, 4, 6) as nitrogen sources, as well as ethylenediamine (EDA) as nitrogen source and diacids with different carbon chain lengths (HOOC(CH2)nCOOH, n = 0, 2, 4, 6) as carbon sources. Therefore, the effect of carbon chain length of starting materials on the formation and optical properties of CDs can be systematically investigated by characterizing and comparing the structures and optical properties of as-prepared nine types of CDs. Moreover, the density of –NH2 on the surface of the CDs was quantitatively detected by a spectrophotometry so as to elucidate the relationship between the –NH2 related surface state and the optical properties.

  16. Transport Properties of ZnSe- ITO Hetero Junction

    Science.gov (United States)

    Ichibakase, Tsuyoshi

    In this report, ITO(Indium Tin Oxide) was used on the glass substrates as the transparent electrode, and ZnSe layer was prepared by the vacuum deposition on this ITO. Then, the electrical characteristics of this sample were investigated by mans of the electric current transport analysis. The sample that ZnSe was prepared as 3.4 μm in case of ITO-ZnSe sample, has high density level at the junction surface. The ITO-ZnSe junction has two type of diffusion current. However, the ITO-ZnSe sample that ZnSe layer was prepared as 0.1 μm can be assumed as the ohmic contact, and ITO-ZnSe(0.1μm) -CdTe sample shows the avalanche breakdown, and it is considered that the avalanche breakdown occurs in CdTe layer. It is difficult to occur the avalanche breakdown, if ZnSe-CdTe junction has high-density level and CdTe layer has high-density defect. Hence, the ZnSe-CdTe sample that CdTe layer was prepared on ITO-ZnSe(0.1μm) substrate has not high-density level at the junction surface, and the CdTe layer with little lattice imperfection can be prepared. It found that ITO-ZnSe(0.1μm) substrate is available for the II-VI compounds semiconductor device through above analysis result.

  17. Exploiting epoxidized natural rubber latex (ENRL) as a starting raw material for latex-based products

    Science.gov (United States)

    Siti Nor Qamarina, M.; Fatimah Rubaizah, M. R.; Nurul Suhaira, A.; Norhanifah, M. Y.

    2017-12-01

    Epoxidized natural rubber latex (ENRL) is a chemically modified natural rubber latex produced from epoxidation process that involves usage of organic peracids. Conversion of the ENRL into dry rubber products has been known to exhibit many beneficial properties, however limited published works were found on diversifiying the ENRL latex-based products applications. In this preliminary work, different source of raw materials and neutralization systems were investigated. The objective was to explore possibilities in producing distinctive ENRL. Findings have demonstrated that different source of raw materials and neutralization systems influenced the typical ENRL specifications, stability behavior and particle size distribution. Morphological observations performed on these ENRL systems appeared to agree with the ENRL characteristics achieved. Since experimenting these two main factors resulted in encouraging ENRL findings, detailed work shall be further scrutinized to search for an optimum condition in producing marketable ENRL specifically for latex-based products applications.

  18. Influence of the starting materials on performance of high temperature oxide fuel cells devices

    Directory of Open Access Journals (Sweden)

    Emília Satoshi Miyamaru Seo

    2004-03-01

    Full Text Available High temperature solid oxide fuel cells (SOFCs offer an environmentally friendly technology to convert gaseous fuels such as hydrogen, natural gas or gasified coal into electricity at high efficiencies. Besides the efficiency, higher than those obtained from the traditional energy conversion systems, a fuel cell provides many other advantages like reliability, modularity, fuel flexibility and very low levels of NOx and SOx emissions. The high operating temperature (950-1000 °C used by the current generation of the solid oxide fuel cells imposes severe constraints on materials selection in order to improve the lifetime of the cell. Besides the good electrical, electrochemical, mechanical and thermal properties, the individual cell components must be stable under the fuel cell operating atmospheres. Each material has to perform not only in its own right but also in conjunction with other system components. For this reason, each cell component must fulfill several different criteria. This paper reviews the materials and the methods used to fabricate the different cell components, such as the cathode, the electrolyte, the anode and the interconnect. Some remarkable results, obtained at IPEN (Nuclear Energy Research Institute in São Paulo, have been presented.

  19. Unprecedented Integral-Free Debye Temperature Formulas: Sample Applications to Heat Capacities of ZnSe and ZnTe

    Directory of Open Access Journals (Sweden)

    R. Pässler

    2017-01-01

    Full Text Available Detailed analytical and numerical analyses are performed for combinations of several complementary sets of measured heat capacities, for ZnSe and ZnTe, from the liquid-helium region up to 600 K. The isochoric (harmonic parts of heat capacities, CVh(T, are described within the frame of a properly devised four-oscillator hybrid model. Additional anharmonicity-related terms are included for comprehensive numerical fittings of the isobaric heat capacities, Cp(T. The contributions of Debye and non-Debye type due to the low-energy acoustical phonon sections are represented here for the first time by unprecedented, integral-free formulas. Indications for weak electronic contributions to the cryogenic heat capacities are found for both materials. A novel analytical framework has been constructed for high-accuracy evaluations of Debye function integrals via a couple of integral-free formulas, consisting of Debye’s conventional low-temperature series expansion in combination with an unprecedented high-temperature series representation for reciprocal values of the Debye function. The zero-temperature limits of Debye temperatures have been detected from published low-temperature Cp(T data sets to be significantly lower than previously estimated, namely, 270 (±3 K for ZnSe and 220 (±2 K for ZnTe. The high-temperature limits of the “true” (harmonic lattice Debye temperatures are found to be 317 K for ZnSe and 262 K for ZnTe.

  20. Spectral structure of the X-ray stimulated phosphorescence of monocrystalline ZnSe

    Energy Technology Data Exchange (ETDEWEB)

    Degoda, V. Ya., E-mail: degoda@univ.kiev.ua [Taras Shevchenko Kyiv National University, Physics Department, 03680 Kyiv (Ukraine); Pavlova, N. Yu., E-mail: pavlovan7@gmail.com [The National Pedagogical Dragomanov University, Pyrogova 9, 01601 Kyiv (Ukraine); Podust, G.P., E-mail: vasylenkog379@gmail.com [Taras Shevchenko Kyiv National University, Physics Department, 03680 Kyiv (Ukraine); Sofiienko, A.O., E-mail: asofienko@gmail.com [University of Bergen, Allegaten 55, PO Box 7803, 5020 Bergen (Norway)

    2015-05-15

    This work presents the extensive experimental studies of the X-ray stimulated luminescence, conductivity, phosphorescence and electric current relaxation, and the thermally stimulated luminescence and conductivity of monocrystalline ZnSe. It was found that the luminescence emission band with a maximum at 635 nm is a combination of at least three emission bands and that the appropriate recombination centres implement both electronic and hole recombination mechanisms. We propose an energy model of the traps and recombination centres in monocrystalline ZnSe and show that the majority of the generated free electrons and holes recombine in the luminescence centres with an estimated probability of 94.3% and that only a small fraction (5.7%) of generated charge carriers are accumulated in traps during the X-ray excitation of the ZnSe sample. - Highlights: • ZnSe has intensive X-ray luminescence and phosphorescence in the spectral range from 600 nm to 1000 nm. • We measured the phosphorescence of ZnSe for different wavelengths of 591 nm, 635 nm and 679 nm. • The dominant emission band of ZnSe with a maximum at 635 nm is a combination of at least three emission bands. • We propose and verify an energy model of the traps and recombination centres in monocrystalline ZnSe.

  1. Spectroscopic studies on the interaction between ZnSe nanoparticles with bovine serum albumin

    International Nuclear Information System (INIS)

    Chen, Zhi; Wu, Dudu

    2012-01-01

    The interaction between ZnSe nanoparticles (NPs) and bovine serum albumin (BSA) was studied by UV–vis, fluorescence spectroscopic techniques. The results showed that the fluorescence of BSA was strongly quenched by ZnSe NPs and the quenching mechanism was discussed to be a static quenching procedure, which was proved by quenching constant (K q ). The recorded UV–vis data and the fluorescence data quenching by the ZnSe NPs showed that the interaction between them leads to the formation of ZnSe–BSA complex. Based on the synchronous fluorescence spectra, it was established that the conformational change of BSA was induced by the interaction of ZnSe with the tyrosine micro-region of the BSA molecules. Furthermore, the temperature effects on the structural and spectroscopic properties of individual ZnSe NPs and protein and their bioconjugates (ZnSe–BSA) were also researched. It was found that, compared to the monotonic decrease of the individual ZnSe NPs fluorescence intensity, the temperature dependence of the ZnSe–BSA emission had a much more complex behavior, which was highly sensitive to the conformational changes of the protein. - Highlights: ►Interaction between bovine serum albumin (BSA) and ZnSe nanoparticles was studied. ► UV–vis data and fluorescence data demonstrated the formation of ZnSe–BSA complex. ► Temperature dependence of ZnSe–BSA emission was sensitive to the conformational changes of protein.

  2. The first principles study of elastic and thermodynamic properties of ZnSe

    Science.gov (United States)

    Khatta, Swati; Kaur, Veerpal; Tripathi, S. K.; Prakash, Satya

    2018-05-01

    The elastic and thermodynamic properties of ZnSe are investigated using thermo_pw package implemented in Quantum espresso code within the framework of density functional theory. The pseudopotential method within the local density approximation is used for the exchange-correlation potential. The physical parameters of ZnSe bulk modulus and shear modulus, anisotropy factor, Young's modulus, Poisson's ratio, Pugh's ratio and Frantsevich's ratio are calculated. The sound velocity and Debye temperature are obtained from elastic constant calculations. The Helmholtz free energy and internal energy of ZnSe are also calculated. The results are compared with available theoretical calculations and experimental data.

  3. Effects of tellurium concentration on the structure of melt-grown ZnSe crystals

    International Nuclear Information System (INIS)

    Atroshchenko, Lyubov V.; Galkin, Sergey N.; Rybalka, Irina A.; Voronkin, Evgeniy F.; Lalayants, Alexandr I.; Ryzhikov, Vladimir D.; Fedorov, Alexandr G.

    2005-01-01

    It has been shown that isovalent doping by tellurium positively affects the structural perfection of ZnSe crystals related to the completeness of the wurtzite-sphalerite phase transition. The optimum concentration range of tellurium in ZnSe crystals is 0.3-0.6 mass %. X-ray diffraction studies have shown that in ZnSe 1-x Te x crystals at tellurium concentrations below 0.3 mass % twinning and packing defects occur, while tellurium concentrations above 0.6 mass % lead to formation of tetragonal crystal lattice

  4. Aspergillus Associated with Meju, a Fermented Soybean Starting Material for Traditional Soy Sauce and Soybean Paste in Korea

    OpenAIRE

    Hong, Seung-Beom; Kim, Dae-Ho; Samson, Robert A.

    2015-01-01

    Aspergillus is an important fungal genus used for the fermentation of Asian foods; this genus is referred to as koji mold in Japan and China. A. oryzae, A. sojae, and A. tamari are used in the production of miso and shoyu in Japan, but a comprehensive taxonomic study of Aspergillus isolated from Meju, a fermented soybean starting material for traditional soy sauce and soybean paste in Korea, has not been conducted. In this study, various Aspergillus species were isolated during a study of the...

  5. Crystal Growth of ZnSe and Related Ternary Compound Semiconductors by Vapor Transport in Low Gravity

    Science.gov (United States)

    Su, Ching-Hua; Ramachandran, N.

    2013-01-01

    Crystals of ZnSe and related ternary compounds, such as ZnSeS and ZnSeTe, will be grown by physical vapor transport in the Material Science Research Rack (MSRR) on International Space Station (ISS). The objective of the project is to determine the relative contributions of gravity-driven fluid flows to the compositional distribution, incorporation of impurities and defects, and deviation from stoichiometry observed in the crystals grown by vapor transport as results of buoyance-driven convection and growth interface fluctuations caused by irregular fluid-flows on Earth. The investigation consists of extensive ground-based experimental and theoretical research efforts and concurrent flight experimentation. The objectives of the ground-based studies are (1) obtain the experimental data and conduct the analyses required to define the optimum growth parameters for the flight experiments, (2) perfect various characterization techniques to establish the standard procedure for material characterization, (3) quantitatively establish the characteristics of the crystals grown on Earth as a basis for subsequent comparative evaluations of the crystals grown in a low-gravity environment and (4) develop theoretical and analytical methods required for such evaluations. ZnSe and related ternary compounds have been grown by vapor transport technique with real time in-situ non-invasive monitoring techniques. The grown crystals have been characterized extensively by various techniques to correlate the grown crystal properties with the growth conditions.

  6. Preparation and photocatalytic activity of hollow ZnSe microspheres via Ostwald ripening

    International Nuclear Information System (INIS)

    Zhang Lihui; Yang Heqing; Xie Xiaoli; Zhang Fenghua; Li Li

    2009-01-01

    Hollow ZnSe microspheres were prepared via a facile hydrothermal reaction of Zn(AC) 2 .2H 2 O with Na 2 SeO 3 and ethylene glycol in NaOH solution at 180 deg. C for 12 h. The products were characterized by means of X-ray diffraction, scanning electron microscopy, transmission electron microscopy and Raman spectrum. The hollow microspheres with the diameters of about 2 μm are constructed from ZnSe nanoparticles with the cubic zinc blende structure, the size of hollow interiors and constituent ZnSe nanodots can be tuned by changing the reaction time. The hollow microspheres are formed via an Ostwald ripening process. Photoluminescence and photocatalytic activity of the hollow ZnSe microspheres were studied at room temperature. The results indicate that the hollow microspheres constructed from ZnSe nanoparticles display a strong near-band edge emission at 479 nm and a very weak deep defect (DD) related emission at 556 nm and a high photocatalytic activity in the photodegradation of methyl orange. The photodegradation of methyl orange catalyzed by the ZnSe microspheres is a pseudo first-order reaction

  7. Controllable synthesis, growth mechanism and optical properties of the ZnSe quantum dots and nanoparticles with different crystalline phases

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Bo [Key Laboratory of Excited State Physics, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, 3888 Eastern Nan-Hu Road, Changchun 130033 (China); Graduate School of the Chinese Academy of Sciences, Beijing 100049 (China); Institute of Condensed State Physics, Jilin Normal University, Siping 136000 (China); Yang, Jinghai, E-mail: jhyang1@jlnu.edu.cn [Institute of Condensed State Physics, Jilin Normal University, Siping 136000 (China); Cao, Jian; Yang, Lili; Gao, Ming; Wei, Maobin; Liu, Yang [Institute of Condensed State Physics, Jilin Normal University, Siping 136000 (China); Song, Hang [Key Laboratory of Excited State Physics, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, 3888 Eastern Nan-Hu Road, Changchun 130033 (China)

    2013-03-15

    Graphical abstract: The ZnSe quantum dots (3.5 nm) with the wurtzite structure exhibited a strong near band-edge emission (NBE) peak centered at 422 nm. The zinc blende ZnSe nanoparticles (21 nm) exhibited near-band-edge luminescence peak centered at 472 nm. Highlights: ► The results of TEM showed that the ZnSe quantum dots were about 3.5 nm. ► The ZnSe quantum dots exhibited a near band-edge emission peak centered at 422 nm. ► The ZnSe nanoparticles exhibited near-band-edge luminescence peak centered at 472 nm. - Abstract: ZnSe precursors were prepared by a solvothermal method at 180 °C without any surface-active agents. ZnSe quantum dots and nanoparticles were obtained by annealing the precursors at 300 °C for 2 h in argon atmosphere. The ZnSe quantum dots were about 3.5 nm, while the ZnSe nanoparticles were about 21 nm, as observed using TEM. The growth mechanisms for the two samples were discussed; this proved that the high coordination ability of ethylenediamine to zinc played an important role in the final phase of the products. The ZnSe quantum dots with the wurtzite structure exhibited a strong near band-edge emission (NBE) peak centered at 422 nm, which was blue-shifted in comparison to that of the bulk ZnSe, which was mainly caused by the quantum confinement effect. However, the zinc blende ZnSe nanoparticles exhibited a near-band-edge luminescence peak centered at 472 nm.

  8. Two Stages of Impact Fracture of Polycrystalline ZnS and ZnSe Compounds

    Science.gov (United States)

    Shcherbakov, I. P.; Dunaev, A. A.; Chmel', A. E.

    2018-04-01

    Mechanoluminescence (ML) in ductile solids is caused by the motion of charged dislocations in the deformable material. Interatomic bond ruptures followed by electronic structure reconfiguration are the main source of ML in brittle bodies. We studied ML in ceramics composed of mixed ionic/covalent ZnS and ZnSe compounds, which are generated during impact loading higher than the limit deformation. Depending on synthesis method and thermal treatment, the resulting ceramics had different size and geometry of grains and intergrain boundary structure, which presumably may have a significant effect on the dislocation glide. In both materials, the time sweeps of ML pulses have two well-resolved peaks. The position of the peaks along the time axis is substantially dependent on the size of ceramic-forming grains and, to a smaller extent, on the barrier properties of intergrain boundaries. The first peak is associated with plastic deformation preceding disintegration of the crystal structure. The second peak emerges upon crack nucleation as interatomic bonds are ruptured and the material is undergoing local deformation in tips of propagating cracks. The distributions of ML pulse amplitudes (the dependences between the number of pulses and their amplitude) calculated for both peaks individually follow the power law, which demonstrates that the electronic processes having different excitation mechanisms (dislocation motion vs bond rupture) are correlated.

  9. Effect of starting materials and processing variables for the production of discontinuous filament Nb3Sn wire

    International Nuclear Information System (INIS)

    Upadhyay, P.L.; Dew-Hughes, D.

    1986-01-01

    Discontinuous multifilamentary wires of Nb 3 Sn have been prepared from compacted mixtures of 30 wt. %Nb in Cu, extruded, drawn, annealed, tin plated and reacted. Processing variables include starting materials, extrusion ratio and extrusion temperature. Continuous lengths of wire could be satisfactorily produced from compacts of either ultra-pure Nb (VPN about 95 kg mm -2 ) and Cu powder or from centrifugal arc-cast Nb spheroids (VPN about 120 kg mm -2 ) and tough pitch Cu powder. After a total area reduction of 10 4 : 1, the latter materials resulted in long, unbroken, highly regular filaments of Nb about 6μm in diameter. The high degree of perfection of these filaments is due in part to the uniformity of the initial spheroids, compared to the highly irregular hydride-dehydride Nb powder. However their greater hardness requires that the spheroids be coprocessed in a less-pure Cu matrix. Critical currents were measured on helical specimens involving more than 1m length of wire, in fields up to 15T at 4.2 K, after reaction for various times at different temperatures. Overall current densities of 3 X 10 8 Am -2 were obtained at 12T in the best samples. Further reductions are expected to produce material with improved current densities

  10. Starting electronics

    CERN Document Server

    Brindley, Keith

    2005-01-01

    Starting Electronics is unrivalled as a highly practical introduction for hobbyists, students and technicians. Keith Brindley introduces readers to the functions of the main component types, their uses, and the basic principles of building and designing electronic circuits. Breadboard layouts make this very much a ready-to-run book for the experimenter; and the use of multimeter, but not oscilloscopes, puts this practical exploration of electronics within reach of every home enthusiast's pocket. The third edition has kept the simplicity and clarity of the original. New material

  11. Optoelectronic study and annealing stability of room temperature pulsed laser ablated ZnSe polycrystalline thin films

    Energy Technology Data Exchange (ETDEWEB)

    Khan, Taj Muhammad, E-mail: tajakashne@gmail.com; Zakria, M.; Ahmad, Mushtaq; Shakoor, Rana I.

    2014-03-15

    increased from 2.65 eV to 2.7 eV for the annealed crystalline film at 350 °C which was further decreased to 2.56 eV for the annealed amorphous film at 400 °C. The observed results manifested that room temperature pulsed laser ablated ZnSe thin film showed excellent structural, optical and morphological stability up 350 °C for optoelectronic applications. -- Highlights: • Room temperature synthesis of ZnSe thin film by PLD. • Annealing effect on Raman scattering of the deposited material. • Optical properties. • Structural properties. • Semiconductor nanostructures.

  12. Press Start

    Science.gov (United States)

    Harteveld, Casper

    This level sets the stage for the design philosophy called “Triadic Game Design” (TGD). This design philosophy can be summarized with the following sentence: it takes two to tango, but it takes three to design a meaningful game or a game with a purpose. Before the philosophy is further explained, this level will first delve into what is meant by a meaningful game or a game with a purpose. Many terms and definitions have seen the light and in this book I will specifically orient at digital games that aim to have an effect beyond the context of the game itself. Subsequently, a historical overview is given of the usage of games with a serious purpose which starts from the moment we human beings started to walk on our feet till our contemporary society. It turns out that we have been using games for all kinds of non-entertainment purposes for already quite a long time. With this introductory material in the back of our minds, I will explain the concept of TGD by means of a puzzle. After that, the protagonist of this book, the game Levee Patroller, is introduced. Based on the development of this game, the idea of TGD, which stresses to balance three different worlds, the worlds of Reality, Meaning, and Play, came into being. Interested? Then I suggest to quickly “press start!”

  13. Synthesis and photoluminescence of Cr-, Ni-, Co-, and Ti-doped ZnSe nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Huy, Bui The [Anastro Laboratory, Department of Chemistry, Changwon National University, Changwon 641-773 (Korea, Republic of); Nhatrang Institute of Technology and Research Application, 2 Hungvuong, Nhatrang (Viet Nam); Seo, Min-Ho; Kumar, Avvaru Praveen [Anastro Laboratory, Department of Chemistry, Changwon National University, Changwon 641-773 (Korea, Republic of); Jeong, Hyuk [Department of Chemistry, Sookmyung Women’s University, Seoul 140-742 (Korea, Republic of); Lee, Yong-Ill, E-mail: yilee@changwon.ac.kr [Anastro Laboratory, Department of Chemistry, Changwon National University, Changwon 641-773 (Korea, Republic of)

    2014-03-05

    Highlights: • The chain length, structure of surfactants operated the size nanoparticles. • Ni{sup 2+}, Co{sup 2+}, Cr{sup 3+}, and Ti{sup 3+} did not create any new centers in the structure of ZnSe. • Doping may have influenced the nanoparticles size because of the Zn replacement. • The TM ions change in ligand field caused the influence on fluorescence intensity. -- Abstract: We developed a facile strategy to synthesize transition metal (TM; Ni, Cr, Co, and Ti)-doped ZnSe nanoparticles (NPs) in aqueous media using a chemical co-precipitation method. Co-precipitation was performed in the presence of one of four different surfactants, namely mercaptoacetic acid (MAA), 3-mercaptopropionic acid (MPA), thioglycerol (TGC), or (3-mercaptopropyl) trimethoxysilane (MPTMS). Surface morphology, chemical, and crystalline properties of the TM-doped ZnSe NPs were studied by transmission electron microscopy (TEM) and X-ray diffraction (XRD). Optical features were characterized by UV–visible and photoluminescence spectroscopies. The influence of various experimental parameters, including the amount of TM and the ratio of precursors, as well as different types of surfactants on the photoluminescence properties of TM-doped ZnSe NPs was investigated systematically. TM-doped ZnSe NPs were excited in the UV region and exhibited photoluminescence in the visible region. Intensity was affected by the concentration of the TM. The results showed that MPA had a stronger influence on photoluminescence than MAA, TGC, and MPTMS. The photoluminescence intensity of TM-doped ZnSe NPs was 30% higher than that of undoped ZnSe NPs.

  14. Systematic studies using 2-(1-adamantylethynyl)pyrimidine-5-carbaldehyde as a starting material in Soai's asymmetric autocatalysis.

    Science.gov (United States)

    Busch, Mark; Schlageter, Martin; Weingand, Daniel; Gehring, Timo

    2009-08-17

    Herein, we present a new substrate for the Soai reaction, which has an adamantylethynyl residue (1 g) and exhibits asymmetric autocatalysis, yielding products with enantiomeric excesses above 99%. For the first time, all reactions were performed on a parallel synthesizer system to ensure identical reaction conditions. A detailed systematic study of reaction parameters was performed and we report the highest enhancements of enantiomeric excess reported so far in the Soai reaction in one reaction cycle (7.2-->94.1% ee or 3.1-->92.1% ee). Our results led to a set of reaction parameters that yield reproducible results. Therefore, our new starting material 1 g is suitable for systematic and mechanistic studies on this remarkable reaction. A series of experiments designed to quantify the amplification of enantiomeric excess demonstrated that the reaction can be used in principle as a tool for the detection of low enantiomeric excesses: under definite conditions, an unknown low enantiomeric excess (0.1-7%) was amplified to a detectable one. A back calculation to the original value offers a new method for the determination of small enantiomeric excesses.

  15. Aspergillus Associated with Meju, a Fermented Soybean Starting Material for Traditional Soy Sauce and Soybean Paste in Korea.

    Science.gov (United States)

    Hong, Seung-Beom; Kim, Dae-Ho; Samson, Robert A

    2015-09-01

    Aspergillus is an important fungal genus used for the fermentation of Asian foods; this genus is referred to as koji mold in Japan and China. A. oryzae, A. sojae, and A. tamari are used in the production of miso and shoyu in Japan, but a comprehensive taxonomic study of Aspergillus isolated from Meju, a fermented soybean starting material for traditional soy sauce and soybean paste in Korea, has not been conducted. In this study, various Aspergillus species were isolated during a study of the mycobiota of Meju, and the aspergilli were identified based on phenotypic characteristics and sequencing of the β-tubulin gene. Most strains of Aspergillus were found to belong to the following sections: Aspergillus (n = 220), Flavi (n = 213), and Nigri (n = 54). The most commonly identified species were A. oryzae (n = 183), A. pseudoglaucus (Eurotium repens) (n = 81), A. chevalieri (E. chevalieri) (n = 62), A. montevidensis (E. amstelodami) (n = 34), A. niger (n = 21), A. tamari (n = 15), A. ruber (E. rubrum) (n = 15), A. proliferans (n = 14), and A. luchuensis (n = 14); 25 species were identified from 533 Aspergillus strains. Aspergillus strains were mainly found during the high temperature fermentation period in the later steps of Meju fermentation.

  16. Controlled Growth of ZnSe Nanocrystals by Tuning Reactivity and Amount of Zinc Precursor

    Directory of Open Access Journals (Sweden)

    Lai-Jun Zhang

    2013-01-01

    Full Text Available Zinc selenide (ZnSe nanocrystals were synthesized via a phosphine-free route using the highly reactive alkylamine-H2Se complex as selenium precursor and zinc precursors with different reactivity. The reactivity of zinc precursor was tuned by using three kinds of zinc carboxylates with different alkyl chain lengths, including zinc acetate, zinc nonanoate, and zinc stearate. The effect of the reactivity and the amount of zinc precursor on nucleation and growth of ZnSe nanocrystals were investigated by ultraviolet-visible absorption and photoluminescence spectra. Result indicates that the growth and optical property of the resulting ZnSe nanocrystals are strongly dependent on the alkyl chain length and the amount of the zinc carboxylates and both shorter alkyl chain length, and more amount of zinc carboxylate will lead to faster growth of ZnSe nanocrystals. This allows that the controlled growth and excellent optical property of high-quality ZnSe nanocrystals can be achieved by combining the different reactivity and the used amount of zinc precursor, such as by using stoichiometric and reactive Zn precursor and Se precursor or by using larger amount of more unreactive Zn precursor relative to the highly reactive alkylamine-H2Se complex precursor.

  17. ZnSe passivation layer for the efficiency enhancement of CuInS2 quantum dots sensitized solar cells

    International Nuclear Information System (INIS)

    Peng, Zhuoyin; Liu, Yueli; Zhao, Yinghan; Chen, Keqiang; Cheng, Yuqing; Kovalev, Valery; Chen, Wen

    2014-01-01

    Highlights: • ZnSe is employed as passivation layer in CuInS 2 quantum dots sensitized solar cells. • Slight red-shift has been occurred in UV–vis absorption spectra with ZnSe coating. • CuInS 2 based solar cells coated by ZnSe have better efficiency than that of ZnS. • Higher rate of charge transport can be produced after coating with ZnSe. -- Abstract: The effect of ZnSe passivation layer is investigated in the CuInS 2 quantum dot sensitized solar cells, which is used to improve the photovoltaic performance. The CuInS 2 quantum dot sensitized TiO 2 photo-anodes are prepared by assembly linking technique, and then deposited by the ZnSe passivation layer using the successive ionic layer absorption and reaction technique. The optical absorption edge and photoluminescence peak have slightly red-shifted after the passivation layer coating. Under solar light illumination, the ZnSe passivation layer based CuInS 2 quantum dot sensitized solar cells have the higher photovoltaic efficiency of 0.95% and incident photon conversion efficiency response than that of pure CuInS 2 based solar cells and ZnS passivation layer based solar cells, as the electron injection rate becomes faster after coating with ZnSe passivation layer

  18. Formation and properties of epitaxial CdSe, ZnSe quantum dots. Conventional molecular beam epitaxy and related techniques

    International Nuclear Information System (INIS)

    Mahapatra, Suddhasatta

    2008-01-01

    This thesis systematically investigates three such alternative approaches, along with conventional MBE, with emphasis on the formation-mechanism of QDs, and optimization of their morphological and optical attributes. it is shown here that no distinct 3D islands are formed in MBE growth of CdSe on ZnSe. While CdSe heteroepitaxy occurs in the multilayer-mode at T G =300 C, a reentrant recovery of the layer-by-layer mode is reported in this thesis, for growth at T G D =230 C). The process steps of the third variant technique, developed in course of this work, are very similar to those of the previous one-the only alteration being the substitution of selenium with tellurium as the cap-forming-material. (orig.)

  19. Optical properties of single wurtzite/zinc-blende ZnSe nanowires grown at low temperature

    Energy Technology Data Exchange (ETDEWEB)

    Zannier, V. [IOM-CNR Laboratorio TASC, S. S. 14, Km. 163.5, I-34149 Trieste (Italy); Department of Physics, University of Trieste, Via Valerio 2, I-34127 Trieste (Italy); Cremel, T.; Kheng, K. [Univ. Grenoble Alpes, F-38000 Grenoble (France); CEA, INAC-SP2M, « Nanophysique et Semiconducteurs » Group, F-38000 Grenoble (France); Artioli, A.; Ferrand, D. [Univ. Grenoble Alpes, F-38000 Grenoble (France); CNRS, Institut Néel, « Nanophysique et Semiconducteurs » Group, F-38000 Grenoble (France); Grillo, V. [IMEM-CNR, Parco Area delle Scienze 37/A, I-43010 Parma (Italy); S3 NANO-CNR, Via Campi 213/A, I-41125 Modena (Italy); Rubini, S. [IOM-CNR Laboratorio TASC, S. S. 14, Km. 163.5, I-34149 Trieste (Italy)

    2015-09-07

    ZnSe nanowires with a dominant wurtzite structure have been grown at low temperature (300 °C) by molecular beam epitaxy assisted by solid Au nanoparticles. The nanowires emission is polarized perpendicularly to their axis in agreement with the wurtzite selection rules. Alternations of wurtzite and zinc-blende regions have been observed by transmission electron microscopy, and their impact on the nanowires optical properties has been studied by microphotoluminescence. The nanowires show a dominant intense near-band-edge emission as well as the ZnSe wurtzite free exciton line. A type II band alignment between zinc-blende and wurtzite ZnSe is evidenced by time-resolved photoluminescence. From this measurement, we deduce values for the conduction and valence band offsets of 98 and 50 meV, respectively.

  20. Synthesis and Fluorescence Property of Mn-Doped ZnSe Nanowires

    Directory of Open Access Journals (Sweden)

    Dongmei Han

    2010-01-01

    Full Text Available Water-soluble Mn-doped ZnSe luminescent nanowires were successfully prepared by hydrothermal method without any heavy metal ions and toxic reagents. The morphology, composition, and property of the products were investigated. The experimental results showed that the Mn-doped ZnSe nanowires were single well crystallized and had a zinc blende structure. The average length of the nanowires was about 2-3 μm, and the diameter was 80 nm. With the increase of Mn2+-doped concentration, the absorbance peak showed large difference. The UV-vis absorbance spectrum showed that the Mn-doped ZnSe nanowires had a sharp absorption band appearing at 360 nm. The PL spectrum revealed that the nanowires had two distinct emission bands centered at 432 and 580 nm.

  1. The photodiode of UV-range on the basis of ZnSe

    Directory of Open Access Journals (Sweden)

    Perevertailo V. L.

    2010-03-01

    Full Text Available The construction and technology of Shottky photodiode on the basis of ZnSe, sensible in the ultraviolet region of spectrum are considered. Researches of electrophysical and photo-electric descriptions of photodiodes of Shottky Nі–ZnSe(Te,O–Іn are conducted and it is shown, that they can be applied in devices for radiometry and dissymmetry UV radiations in the ranges UVA, UVB and UVC. Comparison of parameters of developed UV photodiodes based on ZnSe with analogues showed that small capacitance and low value of dark current is their substantial difference of other ones.

  2. Effect of Indium nano-sandwiching on the structural and optical performance of ZnSe films

    Directory of Open Access Journals (Sweden)

    S.E. Al Garni

    Full Text Available In the current study, we attempted to explore the effects of the Indium nanosandwiching on the mechanical and optical properties of the physically evaporated ZnSe thin films by means of X-ray diffractions and ultraviolet spectrophotometry techniques. While the thickness of each layer of ZnSe was fixed at 1.0 μm, the thickness of the nanosandwiched Indium thin films was varied in the range of 25–100 nm. It was observed that the as grown ZnSe films exhibits cubic and hexagonal nature of crystallization as those of the ZnSe powders before the film deposition. The cubic phases weighs ∼70% of the structure. The analysis of this phases revealed that there is a systematic variation process presented by the decreasing of; the lattice constant, compressing strain, stress, stacking faults and dislocation intensity and increasing grain size resulted from increasing the Indium layer thickness in the range of 50–100 nm. In addition, the nanosandwiching of Indium between two layers of ZnSe is observed to enhance the absorbability of the ZnSe. Particularly, at incident photon energy of 2.38 eV the absorbability of the ZnSe films which are sandwiched with 100 nm Indium is increased by 13.8 times. Moreover, increasing the thickness of the Indium layer shrinks the optical energy band gap. These systematic variations in mechanical and optical properties are assigned to the better recrystallization process that is associated with Indium insertion which in turn allows total internal energy redistribution in the ZnSe films through the enlargement of grains. Keywords: ZnSe, Nanosandwiching, Mechanical, Optical gap

  3. Random lasing of microporous surface of Cr2+:ZnSe crystal induced by femtosecond laser

    International Nuclear Information System (INIS)

    Yang, Xianheng; Feng, Guoying; Yao, Ke; Yi, Jiayu; Zhang, Hong; Zhou, Shouhuan

    2015-01-01

    We demonstrate a random lasing emission based on microporous surface of Cr 2+ :ZnSe crystal prepared by femtosecond pulsed laser ablation in high vacuum (below 5 × 10 −4 Pa). The scanning electron microscope results show that there are a mass of micropores with an average size of ∼13 μm and smaller ones with ∼1.2 μm on the surface of Cr 2+ :ZnSe crystal. The adjacent micropore spacing of the smaller micropores ranges from 1 μm to 5 μm. Under 1750 nm excitation of Nd:YAG (355 nm) pumped optical parametric oscillator, a random lasing emission with center wavelength of 2350 nm and laser-like threshold of 0.3 mJ/pulse is observed. The emission lifetime of 2350 nm laser reduces from 800 ns to 30 ns as the pump energy increases above threshold. The emission spectra and decay time of smooth surface, groove and microporous surface of Cr 2+ :ZnSe crystal are contrasted. The optional pump wavelength range is from 1500 nm to 1950 nm, which in accordance with the optical absorption property of Cr 2+ :ZnSe crystal. The peak position of excitation spectra is almost identical to the strongest absorption wavelength

  4. Relaxation of nonthermal hh and lh excitons in ZnSe quantum wells

    DEFF Research Database (Denmark)

    Kalt, H.; Hoffmann, J.; Umlauff, M.

    1998-01-01

    The strong exciton-LO phonon coupling in ZnSe QWs gives a direct access to the relaxation dynamics of nonthermal, free heavy-hole and light-hole excitons. Narrow hot-exciton distributions can be generated by LO-phonon assisted exciton formation. The thermalization of these excitons is monitored b...

  5. High resistivity ZnSe coated substrates for microstrip gas chambers

    International Nuclear Information System (INIS)

    Sudharsanan, R.; Greenwald, A.C.; Vakerlis, G.; Yoganathan, M.; Cho, H.S.; Kadyk, J.; Dubeau, J.; Dixit, M.

    1998-01-01

    Microstrip gas chambers (MSGCs) require substrates with sheet resistance in the range of 10 13 --10 16 ohms/square to eliminate polarization and surface charging effects between the electrodes. Thin films of II-VI semiconductors deposited on glass or plastic substrates are attractive for this application since bulk resistivity of these semiconductors vary in the range 10 9 --10 12 ohm-cm and films with good uniformity can be deposited over large-areas using inexpensive deposition techniques. In this paper, deposition, characterization, and fabrication of MSGCs using ZnSe thin films are reported for the first time. ZnSe thin films were deposited on glass and plastic substrates by thermal evaporation. Sheet resistance of ZnSe varied in the range of 10 15 to 10 16 ohms/square depending on the deposition conditions. A MSGC detector fabricated using a 0.5 microm thick ZnSe layer on glass substrate exhibited best values; gas gain of 25,000 and an energy resolution of about 16.7% FWHM at a gain of 1,080 for a 55 Fe source

  6. Structural investigation of the ZnSe(001)-c(2×2) surface

    DEFF Research Database (Denmark)

    Weigand, W.; Müller, A.; Kilian, L.

    2003-01-01

    Zinc selenide is a model system for II-VI compound semiconductors. The geometric structure of the clean (001)-c(2x2) surface has recently been the subject of intense debate. We report here a surface x-ray-diffraction study on the ZnSe(001)-c(2x2) surface performed under ultrahigh vacuum using...

  7. Unravelling the size and temperature dependence of exciton lifetimes in colloidal ZnSe quantum dots

    NARCIS (Netherlands)

    Eilers, Joren; Van Hest, Jacobine; Meijerink, A; Donega, Celso De Mello

    2014-01-01

    We report on the temperature dependence of the band-edge photoluminescence decay of organically capped colloidal ZnSe quantum dots (QDs) in the size range from 4.0 to 7.5 nm. A similar trend is observed for all investigated sizes: the decay time is short (∼5 ns) above 20 K and increases sharply

  8. Passive Fe2+ : ZnSe single-crystal Q switch for 3-mu m lasers

    NARCIS (Netherlands)

    Voronov, AA; Kozlovskii, [No Value; Korostelin, YV; Podmar'kov, YP; Polushkin, VG; Frolov, MP

    Passive Q-switching of 3-mu m lasers with the help of a Fe2+ : ZnSe single crystal is demonstrated. The 6-mJ, 50-ns giant pulses are obtained from a 2.9364-mu m Er : YAG laser by using this passive Q switch.

  9. Interaction and Dephasing of Excitons in ZnSe Quantum Wires

    DEFF Research Database (Denmark)

    Wagner, Hans Peter; Langbein, Wolfgang; Hvam, Jørn Märcher

    1999-01-01

    We study the coherent formation of biexcitons in wet-etched ZnSe quantum wires of lateral sizes down to 23 nm by transient degenerate four-wave mixing. We observe an increase of the biexciton binding energy with decreasing wire width reaching 30% energy enhancement in the smallest wire structure...

  10. Room-temperature 1.2-J Fe{sup 2+}:ZnSe laser

    Energy Technology Data Exchange (ETDEWEB)

    Velikanov, S D; Zaretsky, N A; Zotov, E A; Maneshkin, A A; Yutkin, I M [Russian Federal Nuclear Center ' All-Russian Research Institute of Experimental Physics' , Sarov, Nizhnii Novgorod region (Russian Federation); Kazantsev, S Yu; Kononov, I G; Firsov, K N [A M Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation); Korostelin, Yu V; Frolov, M P [P N Lebedev Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation)

    2016-01-31

    The characteristics of a laser based on a Fe{sup 2+}:ZnSe single crystal pumped by an electric-discharge HF laser at room temperature are studied. The HF laser beam diameter on the crystal surface was 17 mm. The achieved laser energy was 1.2 J with an efficiency of ∼ 25% with respect to the pump energy. (letters)

  11. The influence of production conditions, starting material and deposition environment on charcoal alteration in a tropical biome.

    Science.gov (United States)

    Ascough, Philippa; Bird, Michael; Meredith, Will; Large, David; Snape, Colin; Manion, Corinne

    2014-05-01

    Natural and anthropogenic burning events are a key link in the global carbon cycle, substantially influencing atmospheric CO2 levels, and consuming c.8700 teragrams yr-1 of dry biomass [1,2,3]. An important result of this process is charcoal, when lignocellulosic structures in biomass (e.g. wood) are converted to aromatic domains with high chemical stability. Charcoal is therefore not readily re-oxidized to CO2, with estimates of 5-7 ky for the half-life of charcoal carbon in soils [3,4]. Charcoal's high carbon content coupled with high environmental resistance has led to the concept of biochar as a valuable means of global carbon sequestration, capable of carbon offsets comparable to annual anthropogenic fuel emissions [5,6,7]. Charcoal is not, however, an environmentally inert substance, and at least some components of charcoal are susceptible to alteration in depositional environments. Despite the importance of charcoal in global carbon cycling, the mechanisms by which charcoal is altered in the environment remain, as yet, poorly understood. This fact limits our ability to properly incorporate both natural environmental charcoal and biochar into global carbon budgets. This study aimed to improve understanding of charcoal alteration in the environment by examining the influence of production conditions, starting material and deposition environment on the physical and chemical characteristics of charcoal at a field site in the Daintree rainforest. These factors have been identified as critical in determining the dynamics of charcoal in depositional environments [8,9] and climatic conditions at the field site (in Tropical Queensland, Australia) are likely to result in extensive alteration of charcoal. Charcoal from wood (Nothofagus spp.), algae (Enteromorpha spp.), and sugarcane (Saccharum spp.) biomass was produced at temperatures over 300-500°C and exposed to conditions of varying pH and vegetation cover. The effect of these variables on charcoal chemistry

  12. Fabrication and testing of diamond-machined gratings in ZnSe, GaP, and bismuth germanate for the near infrared and visible

    Energy Technology Data Exchange (ETDEWEB)

    Kuzmenko, P J; Little, S L; Ikeda, Y; Kobayashi, N

    2008-06-22

    High quality immersion gratings for infrared applications have been demonstrated in silicon and germanium. To extend this technology to shorter wavelengths other materials must be investigated. We selected three materials, zinc selenide, gallium phosphide and bismuth germanate (Bi{sub 4}Ge{sub 3}O{sub 12}), based on high refractive index, good visible transmission and commercial availability in useful sizes. Crystal samples were diamond turned on an ultra-precision lathe to identify preferred cutting directions. Using this information we diamond-flycut test gratings over a range of feed rates to determine the optimal cutting conditions. For both ZnSe and GaP good surface quality was achieved at feed rates up to 1.0 cm/minute using a special compound angle diamond tool with negative rake angles on both cutting surfaces. The surface roughness of the groove facets was about 4 nm. A Zygo interferometer measured grating wavefront errors in reflection. For the ZnSe the RMS error was < {lambda}/20 at 633nm. More extensive testing was performed with a HeNe laser source and a cooled CCD camera. These measurements demonstrated high relative diffraction efficiency (> 80%), low random groove error (2.0 nm rms), and Rowland ghost intensities at < 0.1%. Preliminary tests on bismuth germanate show high tool wear.

  13. Study of de-aggregation of mechanochemically synthesized ZnSe nanoparticles by re-milling in the presence of ZnCl2 solution

    Directory of Open Access Journals (Sweden)

    Marcela Achimovičová

    2013-12-01

    Full Text Available Conventional mechanochemical synthesis of zinc selenide, ZnSe nanoparticles was performed in a planetary ball mill by high-energy milling of zinc (Zn and selenium (Se powders. Mechanochemically synthesized ZnSe was subsequently re-milled in circulation mill in ZnCl2 solution in order to study de-aggregation, physical-chemical and optical properties of ZnSe nanoparticles. The mechanochemically synthesized and re-milled samples were characterized by X-ray diffraction analysis (XRD that confirmed the presence of cubic and hexagonal ZnSe phases. Size of crystallites calculated from XRD patterns has decreased from 50 to 19 nm for cubic ZnSe phase and from 145 to 2.5 nm for hexagonal ZnSe phase after re-milling for 110 min in ZnCl2 solution. Size, phase composition, morphology, and crystallinity of ZnSe nanoparticles were studied by transmission electron microscopy (TEM and selected area electron diffraction (SAED. UV-Vis optical spectroscopy has provided an evidence of blue shift of the re-milled nanocrystalline ZnSe particles from the direct band gap of 2.67 eV characteristic of bulk ZnSe crystals. Colloidal stability of ZnSe nanoparticles dispersions was studied by ? �potential measurements.

  14. Commercial-scale recycling of NdFeB-type magnets with grain boundary modification yields products with 'designer properties' that exceed those of starting materials.

    Science.gov (United States)

    Zakotnik, M; Tudor, C O

    2015-10-01

    NdFeB-type magnets dominate the market for high performance magnetic materials, yet production of 'virgin' magnets via mining is environmentally, financially and energetically costly. Hence, interest is growing in 'magnet to magnet' recycling schemes that offer the potential for cheaper, more environmentally-friendly solutions to the world's growing appetite for rare-earth based magnetic materials. Unfortunately, previously described recycling processes only partially capitalise on this potential, because the methods described to date are limited to 'laboratory scale' or operate only under ideal conditions and result in products that fail to recapture the coercivity of the starting, scrap materials. Herein, we report a commercial scale process (120 kg batches) that completely recovers the properties of the starting scrap magnets. Indeed, 'grain boundary modification', via careful addition of a proprietary mix of blended elements, produces magnets with 'designer properties' that can exceed those of the starting materials and can be closely tailored to meet a wide variety of end-user applications, including high-coercivity (>2000 kA/m), sintered magnets suitable for motor applications. Copyright © 2015 Elsevier Ltd. All rights reserved.

  15. Evolvement of soft templates in surfactant/cosurfactant system for shape control of ZnSe nanocrystals

    International Nuclear Information System (INIS)

    Hou Bo; Liu Yongjun; Li Yanjuan; Yuan Bo; Jia Mingfen; Jiang Fengzhi

    2012-01-01

    Highlights: ► Soft templates were found in the shape control synthesis of ZnSe nanocrystals. ► Micelle formation model in the soft templates system was proposed and proved. ► Different shapes of ZnSe nanocrystals were prepared and explained by proposed model. - Abstract: The evolution of soft templates in the synthesis of ZnSe nanocrystals realized through a surfactant/cosurfactant system was investigated and a micelle formation process model was proposed. Through freeze-fracture electron microscopy, it was proven that template micelles were formed in the zinc precursors. Furthermore, it was found that a long stirring period was essential for achieving the lowest energy state of the soft templates which were used for synthesizing monodisperse ZnSe quantum dots.

  16. Evolvement of soft templates in surfactant/cosurfactant system for shape control of ZnSe nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Hou Bo [Key Laboratory of Medicinal Chemistry for Natural Resource, Ministry of Education, School of Chemical Science and Technology, Yunnan University, Kunming 650091 (China); Liu Yongjun [Advanced Analysis and Measurement Center, Yunnan University, Kunming 650091 (China); Li Yanjuan [Key Laboratory of Medicinal Chemistry for Natural Resource, Ministry of Education, School of Chemical Science and Technology, Yunnan University, Kunming 650091 (China); Yuan Bo [Advanced Analysis and Measurement Center, Yunnan University, Kunming 650091 (China); Jia Mingfen [Key Laboratory of Medicinal Chemistry for Natural Resource, Ministry of Education, School of Chemical Science and Technology, Yunnan University, Kunming 650091 (China); Jiang Fengzhi, E-mail: fengzhij@ynu.edu.cn [Key Laboratory of Medicinal Chemistry for Natural Resource, Ministry of Education, School of Chemical Science and Technology, Yunnan University, Kunming 650091 (China); Advanced Analysis and Measurement Center, Yunnan University, Kunming 650091 (China)

    2012-03-25

    Highlights: Black-Right-Pointing-Pointer Soft templates were found in the shape control synthesis of ZnSe nanocrystals. Black-Right-Pointing-Pointer Micelle formation model in the soft templates system was proposed and proved. Black-Right-Pointing-Pointer Different shapes of ZnSe nanocrystals were prepared and explained by proposed model. - Abstract: The evolution of soft templates in the synthesis of ZnSe nanocrystals realized through a surfactant/cosurfactant system was investigated and a micelle formation process model was proposed. Through freeze-fracture electron microscopy, it was proven that template micelles were formed in the zinc precursors. Furthermore, it was found that a long stirring period was essential for achieving the lowest energy state of the soft templates which were used for synthesizing monodisperse ZnSe quantum dots.

  17. Enhanced photocatalytic reduction of CO2 to methanol by ZnO nanoparticles deposited on ZnSe nanosheet

    Science.gov (United States)

    Zhang, Shuangfang; Yin, Xiaohong; Zheng, Yinan

    2018-02-01

    In this work ZnO/ZnSe composites were successfully synthesized via solvothermal method and characterized by a series of experiments for investigating into their compositions, morphologies, microstructures and the activities of photocatalytic reduction of CO2. The methanol rates of bare ZnO and ZnSe respectively were 763.9 μmol/gcat/h and 503.88 μmol/gcat/h. However, the sample of 3 wt% ZnO/ZnSe performed better photocatalytic activity up 1581.82 μmol/gcat/h compared to bare ZnO and ZnSe. In the as-prepared photocatalyst the nanosheet of ZnSe benefited the light harvest; suitable deposition of ZnO on the ZnSe nanosheet constructed a type II heterojunction for transferring the photo-generated electron to reduce CO2.

  18. Bias polarity-sensitive electrical failure characteristics of ZnSe nanowire in metal–semiconductor–metal nanostructure

    Directory of Open Access Journals (Sweden)

    Yu Tan

    2014-04-01

    Full Text Available The effect of bias polarity on the electrical breakdown behavior of the single ZnSe nanowire (NW in the metal–semiconductor–metal (M–S–M nanostructure under high current density and high bias conditions has been studied in the present paper. The experimental results show that the failure of the ZnSe NW in M–S–M nanostructure was sensitive to bias polarity since the NW commonly collapsed at the negatively biased Au metal electrode due to high Joule heat produced in NW at the reversely biased Schottky barrier. Thus, the electrical breakdown behavior of the ZnSe NW was highly dominated by the cathode-controlled mode due to the high resistance of the depletion region of ZnSe NW at the reversely biased Schottky contact.

  19. Development of a Pump-Probe System using a Non-Coated ZnSe Beam Splitter Cube for an MIR-FEL

    CERN Document Server

    Heya, Manabu; Horiike, Hiroshi; Ishii, Katsonuri; Suzuki, Sachiko

    2004-01-01

    A pump-probe technique is essential for a proper understanding of laser interaction with tissue and material. Our pump-probe system divides the incident mid-infrared Free Electron Laser (MIR-FEL) into two beams with equal intensity, and crosses simultaneously the two incoming beams at the same position. One is for a pump beam, another is for a probe beam. Time-resolved absorption spectroscopy involving this technique gives us information on the vibrational dynamics of molecules. We have developed this system for an MIR-FEL using a non-coating ZnSe beam splitter cube. The beam splitter cube is composed of two ZnSe prisms in the shape like a trapezoid. The two pulses with equal intensity are generated due to Fresnel reflection and transmission at the boundary between two prisms, then are reflected due to total reflection at other side boundaries between each prism and air, and illuminate simultaneously the same spot. We have conducted a proof-of-concept of experiment of this system using an MIR-FEL. We showed t...

  20. Why START?

    International Nuclear Information System (INIS)

    Mendelsohn, J.

    1991-01-01

    Barring some major unexpected downturn in US-Soviet relations, it seems likely that the long-awaited Strategic Arms Reduction Talks (START) treaty will be signed sometime in 1991. Under negotiation for the past nine years, public acceptance and Senate approval of a START treaty will be facilitated by the generally less confrontational East-West relationship which has evolved over that time, by the growing constraints on the US defense budget, and by the obvious merits of the treaty itself. Not only will the nearly complete START treaty be an extremely useful and powerful arms control agreement, it is also decidedly advantageous to US security interests. First and foremost, a START treaty will cap and reduce the steady buildup of nuclear weapons that has characterized the last 30 years of the US-Soviet strategic relationship. As a result of the basic outline originally agreed to at the Reykjavik summit, START will take a 25 to 35 percent bite out of existing nuclear arsenals, impose approximately a 50 percent cut in overall Soviet ballistic missile warheads and throw-weight (lifting power or payload capacity), and produce an exact 50 percent cut in Soviet SS-18 missiles

  1. Starting out

    NARCIS (Netherlands)

    Ans Merens; Freek Bucx

    2018-01-01

    Original title: Werken aan de start Women in the Netherlands have been outperforming men in education for many years now. However, this superior educational achievement does not translate into a better position on the labour market. More women work today than in the past, but still fewer than men.

  2. Spectral memory of photoconduction of high-resistance ZnSe

    International Nuclear Information System (INIS)

    Gorya, O.S.; Kovalev, L.E.; Korotkov, V.A.; Malikova, L.V.; Simashkevich, A.V.

    1989-01-01

    Relaxation of photoconductivity of ZnSr crystal in case of a photoconductivity burst when exposing a sample to light with quantum energy E=1.305 eV after preliminary excitation by light with quantum energy 2.61 eV. The phenomenon of nonequilibrium photoconductivity considered permitted to suggest a new method for determination of the energy position of local levels in the forbidden band of semiconductors. Investigations carried out permitted to detect in ZnSe acceptors, lying in the forbidden band, as well as deep centers. It is supposed that the effect of spectral memory of photoconductivity of high-ohmic crystals (ZnSe, ZnS, CdS) relates to the existence of defects with metastable states in them

  3. Ultrafast carrier dynamics in band edge and broad deep defect emission ZnSe nanowires

    Science.gov (United States)

    Othonos, Andreas; Lioudakis, Emmanouil; Philipose, U.; Ruda, Harry E.

    2007-12-01

    Ultrafast carrier dynamics of ZnSe nanowires grown under different growth conditions have been studied. Transient absorption measurements reveal the dependence of the competing effects of state filling and photoinduced absorption on the probed energy states. The relaxation of the photogenerated carriers occupying defect states in the stoichiometric and Se-rich samples are single exponentials with time constants of 3-4ps. State filling is the main contribution for probe energies below 1.85eV in the Zn-rich grown sample. This ultrafast carrier dynamics study provides an important insight into the role that intrinsic point defects play in the observed photoluminescence from ZnSe nanowires.

  4. Defect complexes formed with Ag atoms in CDTE, ZnTe, and ZnSe

    CERN Document Server

    Wolf, H; Ostheimer, V; Hamann, J; Lany, S; Wichert, T

    2000-01-01

    Using the radioactive acceptor $^{111}\\!$Ag for perturbed $\\gamma$-$\\gamma$-angular correlation (PAC) spectroscopy for the first time, defect complexes formed with Ag are investigated in the II-VI semiconductors CdTe, ZnTe and ZnSe. The donors In, Br and the Te-vacancy were found to passivate Ag acceptors in CdTe via pair formation, which was also observed in In-doped ZnTe. In undoped or Sb-doped CdTe and in undoped ZnSe, the PAC experiments indicate the compensation of Ag acceptors by the formation of double broken bond centres, which are characterised by an electric field gradient with an asymmetry parameter close to h = 1. Additionally, a very large electric field gradient was observed in CdTe, which is possibly connected with residual impurities.

  5. Temperature dependence of the infrared luminescence of ZnSe grown

    International Nuclear Information System (INIS)

    Vakulenko, O.V.; Kravchenko, V.M.

    2000-01-01

    Photoluminescence (PL) spectra of undoped ZnSe crystals grown by the sublimation method are studied within the spectral range 500-1030 nm at T 100/330 K. PL was excited with N 2 , He - Cd, and Ar + lasers. Under Ar + laser excitation (h ν e xc g ), the IP 1.3 eV band is observed in addition to the red 1.9 eV band. The temperature dependences of the peak intensities (TD) of both bands are measured. The TD of IR band has a peak at 260 K and flattens out at T < 180. To interpret such a TD, two models are considered the model of multi charge donor as a luminescence center and the model of simple donor. It is suggested that the IR PL band may be due to intracentor transitions between some levels of multi charge donor-like defects of the ZnSe lattice

  6. ZnSe nanotrenches: formation mechanism and its role as a 1D template

    Directory of Open Access Journals (Sweden)

    Lok Shu Kin

    2011-01-01

    Full Text Available Abstract High-resolution transmission electron microscopy was used to characterize the microstructures of ZnSe nanotrenches induced by mobile Au-alloy droplets. The contact side interfaces between the AuZnδ alloy droplets and the ZnSe as well as the four side walls of the resulting <011>-oriented nanotrenches were found all belong to the {111} plane family, with the front and back walls being the {111}A planes while the other two side walls being the {111}B planes. These findings offer a deeper understanding on the formation mechanism of the nanotrenches. Pure Au nanodashes were formed upon further deposition of Au on the nanotrenches. PACS: 61.46.Df, Structure of nanocrystals and nanoparticles. 81.16.Rf, Micro and nanoscale pattern formation. 68.37.Og, High resolution transmission electron microscopy.

  7. Clustering and percolation threshold in diphase systems of random centered quantum dots of ZnSe

    International Nuclear Information System (INIS)

    Bondar', N.V.

    2009-01-01

    A characteristic feature due to the formation of a percolation phase transition of carriers has been observed in a two-phase system consisting of borosilicate glass with ZnSe quantum dots. For near-threshold quantum-dot concentrations, changes due to microscopic fluctuations of the quantum-dot density have been observed in the intensities of radiation emission bands. This phenomenon is reminiscent of critical opalescence, where similar fluctuations of the density of a pure substance arise near a phase transition. It is proposed that the dielectric mismatch between the matrix and ZnSe plays a large role in the carrier (exciton) delocalization, resulting in the appearance of a 'dielectric trap' on the interface and the formation there of surface states of excitons. The spatial overlapping of states which occurs at the critical concentration of quantum dots results in carrier tunneling and the appearance of a percolation transition in such a system

  8. Luminescence from ZnSe excited by picosecond mid-infrared FEL pulses

    International Nuclear Information System (INIS)

    Mitsuyu, T.; Suzuki, T.; Tomimasu, T.

    1998-01-01

    We have observed blue band-edge emission from a ZnSe crystal under irradiation of mid-infrared picosecond free electron laser (FEL) pulses. The emission characteristics including spectrum, excitation power dependence, excitation wavelength dependence, and decay time have been investigated. The experimental results have indicated that it is difficult to understand the excitation process by multiphoton excitation, thermal excitation, or excitation through mid-gap levels. (Copyright (c) 1998 Elsevier Science B.V., Amsterdam. All rights reserved.)

  9. Positron annihilation study of mechanochemical reaction between Zn+Se and Zn+S

    International Nuclear Information System (INIS)

    Kajcsos, Zs.; Horvath, D.; Tshakarov, C.G.; Gospodinov, G.G.; Vertes, A.

    1981-01-01

    Positron lifetime spectra were recorded and evaluated in mixtures of Zn+S and Zn+Se powders for various periods. The intensity of the long-lived positron lifetime component is shown to increase with grinding time until an abrupt decrease takes place at a specific grinding time, indicating the onset of the effective chemical reaction. The suitability of positron annihilation for investigating mechanochemical reactions is clearly demonstrated. (author)

  10. ZnSe quantum dots based fluorescence quenching method for determination of paeoniflorin

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Zhi [Center of Analysis, Guangdong Medical College, Dongguan 523808 (China); School of Chinese Herbal Medicine, Guangzhou University of Chinese Medicine, Guangzhou 510006 (China); Chen, Jiayi; Liang, Qiaowen [School of Chinese Herbal Medicine, Guangzhou University of Chinese Medicine, Guangzhou 510006 (China); Wu, Dudu [Center of Analysis, Guangdong Medical College, Dongguan 523808 (China); Zeng, Yuaner, E-mail: zengyuaner@126.com [School of Chinese Herbal Medicine, Guangzhou University of Chinese Medicine, Guangzhou 510006 (China); Jiang, Bin, E-mail: gzjiangbin@hotmail.com [School of Chinese Herbal Medicine, Guangzhou University of Chinese Medicine, Guangzhou 510006 (China)

    2014-01-15

    Water soluble ZnSe quantum dots (QDs) modified by mercaptoacetic acid (MAA) were used to determinate paeoniflorin in aqueous solutions by the fluorescence spectroscopic technique. The results showed that the fluorescence of the modified ZnSe QDs could be quenched by paeoniflorin effectively in physiological buffer solution. The optimum fluorescence intensity was found to be at incubation time 10 min, pH 7.0 and temperature 25 °C. Under the optimal conditions, the detection limit of paeoniflorin was 7.30×10{sup −7} mol L{sup −1}. Moreover, the quenching mechanism was discussed to be a static quenching procedure, which was proved by quenching rate constant K{sub q} (1.02×10{sup 13} L mol{sup −1} s{sup −1}). -- Highlights: • The fluorescence intensity of ZnSe QDs could be quenched by paeoniflorin. • Foreign substance showed insignificant effect for determination of paeoniflorin. • The quenching mechanism was discussed to be a static quenching procedure.

  11. ZnSe quantum dots based fluorescence quenching method for determination of paeoniflorin

    International Nuclear Information System (INIS)

    Chen, Zhi; Chen, Jiayi; Liang, Qiaowen; Wu, Dudu; Zeng, Yuaner; Jiang, Bin

    2014-01-01

    Water soluble ZnSe quantum dots (QDs) modified by mercaptoacetic acid (MAA) were used to determinate paeoniflorin in aqueous solutions by the fluorescence spectroscopic technique. The results showed that the fluorescence of the modified ZnSe QDs could be quenched by paeoniflorin effectively in physiological buffer solution. The optimum fluorescence intensity was found to be at incubation time 10 min, pH 7.0 and temperature 25 °C. Under the optimal conditions, the detection limit of paeoniflorin was 7.30×10 −7 mol L −1 . Moreover, the quenching mechanism was discussed to be a static quenching procedure, which was proved by quenching rate constant K q (1.02×10 13 L mol −1 s −1 ). -- Highlights: • The fluorescence intensity of ZnSe QDs could be quenched by paeoniflorin. • Foreign substance showed insignificant effect for determination of paeoniflorin. • The quenching mechanism was discussed to be a static quenching procedure

  12. Bound magnetic polaron in Zn-rich cobalt-doped ZnSe nanowires

    Science.gov (United States)

    Hou, Lipeng; Pan, Longfei; Liang, Bianbian; Liu, Yuting; Zhang, Li; Bukhtiar, Arfan; Shi, Lijie; Liu, Ruibin; Zou, Bingsuo

    2018-02-01

    The micro-luminescence spectra of the diluted magnetic semiconductor (DMS) can reflect the spin-exciton interaction and related relaxation process. Here the micro-photoluminescence (micro-PL) spectra and PL lifetime measurements have been done on an individual ferromagnetic (FM)-coupled cobalt (Co) doped zinc selenide (ZnSe) nanowire. There occurs a double-peak profile in its near bandedge emission spectrum: the first peak is from free exciton (FX) and the second comes from magnetic polaron (MP). In their temperature dependent PL spectra, the MP emission peak demonstrates obviously temperature-independent behavior, in contrast to the behaviors of FX and reported exciton MP in nanobelt. It is found that in this Co(II) doped ZnSe nanowires, this MP’s temperature-independent emission is related to the coupling between exciton and a FM nanocluster (↑↑↓). The nanocluster is likely due to the interaction of Se vacancies of the wide bandgap semiconductors with the antiferromagnetic (AFM) arrangement transition metal (TM) ions in these Se-deficient Co doped ZnSe nanowires. These results reflect that the AFM coupling TM ions pair can give rise to FM behavior with the involvement of positive charge defect, also indicating that the micro-luminescence detection can be used to study the magnetic coupling in DMS.

  13. EFFECTS OF USING PHASE CHANGE MATERIALS ON THE COLD START EXHAUST EMİSSİONS CHARACTERİSTİCS OF DIESEL ENGINES

    Directory of Open Access Journals (Sweden)

    Ferhat Kaya

    2016-05-01

    Full Text Available During the last two decades, the diesel engine performance and drivability have significantly improved with the latest technologic developments. Nevertheless, one of the disadvantageous of diesel engines is related to the difficulties for starting at cold conditions, particularly in the conditions where the ambient temperature is near or below 0ºC. Additionally, the harmful exhaust emissions are also at significantly important levels during the cold start conditions. Most of carbon monoxide (CO emissions from diesel engines are produced during the engine warm-up period.  In order to improve cold start characteristics of diesel engines, many measures have been proposed, such as glow plugs and air heaters in air intake lines.In this study, in order to increase the cold start performance and improve the exhaust emission characteristics of a direct injection diesel engine, phase change materials (PCMs have been used.PCMs have high heats of fusion and they can absorb latent energy before melting. During the phase change, temperature of PCMs remains nearly constant. In this study, a PCMs was used with the 45-51ºC melting temperature band in a heat exchanger. Hot water from an external source was circulated in the exchanger to carry out the experiments in the same conditions and was used as heat source in order to melt the PCMs.Engine intake air has been passed through the exchanger before engine intake manifold.  During the engine cooling period, the PCM in the produced heat exchanger have increased the cooling time period of engine intake air.An experimental setup has been established to observe the cold start characteristics of the two cylinder diesel engine with and without using the produced exchanger. Temperature measurements from different points, CO exhaust emissions, engine speed and in cylinder pressure measurements have been used to evaluate the contribution of exchanger and increasing the intake air temperature by using the PCMs. The

  14. A straightforward and efficient method for the synthesis of diversely substituted {beta}-aminoketones and {gamma}-aminoalcohols from 3-(N,N-dimethylamino)propiophenones as starting materials

    Energy Technology Data Exchange (ETDEWEB)

    Abonia, Rodrigo; Arteaga, Danny; Castillo, Juan; Insuasty, Braulio; Quiroga, Jairo; Ortiz, Alejandro, E-mail: rodrigo.abonia@correounivalle.edu.co [Universidad del Valle, Cali (Colombia). Department of Chemistry. Research Group of Heterocyclic Compounds

    2013-09-15

    Libraries of novel {beta}-aminoketones and {gamma}-aminoalcohols showing a wide structural diversity were easily obtained from a simple approach, using 3-(N,N-dimethylamino)propiophenone derivatives as key starting material. The procedure involved initially an N-alkylation of secondary benzylamines with propiophenone salts yielding the desired {beta}-aminoketones. Chemical or catalytic reduction of their carbonyl groups provided the final {gamma}-aminoalcohols in good yields. This protocol proved to be convenient as an alternative route for the synthesis of the local anesthetic Falicain Registered-Sign and for the topic antifungal drug Naftifine Registered-Sign . (author)

  15. Microbial behavior and changes in food constituents during fermentation of Japanese sourdoughs with different rye and wheat starting materials.

    Science.gov (United States)

    Fujimoto, Akihito; Ito, Keisuke; Itou, Madoka; Narushima, Noriko; Ito, Takayuki; Yamamoto, Akihisa; Hirayama, Satoru; Furukawa, Soichi; Morinaga, Yasushi; Miyamoto, Takahisa

    2018-01-01

    Sourdough is a food item made by kneading grain flour and water together and allowing fermentation through the action of lactic acid bacteria (Lactobacillales) and yeast. Typically, Japanese bakeries make sourdough with rye flour, wheat flour, malt extract, and water and allow spontaneous fermentation for 6 days. We compared the microbial behavior and food components, such as organic acids, sugars, and free amino acids, of sourdoughs made using two different rye and wheat flours during the 6-day fermentation period. Comparisons were made for two types of rye and wheat flours, using different production sites and different milling, distribution, and storage conditions. The microbial count was evaluated using different culture media. All sourdough types showed a significant increase in lactic acid levels on fermentation day 2 and a decrease in free amino acid levels on day 4. Low overall lactic acid production and little fluctuation in sugar levels occurred in sourdough made from French ingredients. For sourdough made from Japanese ingredients, sugar levels (chiefly glucose, sucrose, and maltose) declined on fermentation day 1, increased on day 2, and declined by day 5. With the French ingredients, no yeast cells were detected until day 3, and many acid precursors of sourdough flavor components were detected. Yet with the Japanese ingredients, 10 6 /g yeast cells were detected on days 3-5, as well as sourdough-flavor esters and alcohols. Differences in raw material quality affected the microbial behavior and changes in food constituents during the fermentation process and, consequently, the sourdough flavor. Copyright © 2017 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

  16. to start

    Indian Academy of Sciences (India)

    Click here to start. Table of contents. Slide 1 · Slide 2 · Slide 3 · Slide 4 · Slide 5 · Slide 6 · Slide 7 · Slide 8 · Slide 9 · Slide 10 · Slide 11 · Slide 12 · Slide 13 · Slide 14 · Slide 15 · Slide 16 · Slide 17 · Slide 18 · Slide 19 · Slide 20 · Slide 21 · Slide 22 · Slide 23 · Slide 24 · Slide 25 · Slide 26 · Slide 27 · Slide 28 · Slide 29 · Slide 30.

  17. Formation and properties of epitaxial CdSe, ZnSe quantum dots. Conventional molecular beam epitaxy and related techniques

    Energy Technology Data Exchange (ETDEWEB)

    Mahapatra, Suddhasatta

    2008-01-16

    This thesis systematically investigates three such alternative approaches, along with conventional MBE, with emphasis on the formation-mechanism of QDs, and optimization of their morphological and optical attributes. it is shown here that no distinct 3D islands are formed in MBE growth of CdSe on ZnSe. While CdSe heteroepitaxy occurs in the multilayer-mode at T{sub G}=300 C, a reentrant recovery of the layer-by-layer mode is reported in this thesis, for growth at T{sub G}<{proportional_to}240 C. In the second variant technique, formation of large and distinct islands is demonstrated by deposition of amorphous selenium (a-Se) onto a 2D CdSe epilayer at room temperature and its subsequent desorption at a higher temperature (T{sub D}=230 C). The process steps of the third variant technique, developed in course of this work, are very similar to those of the previous one-the only alteration being the substitution of selenium with tellurium as the cap-forming-material. (orig.)

  18. Manifestation of Crystal Lattice Distortions in the IR Reflection Spectra of Abrasion-Treated ZnSe Ceramics

    Science.gov (United States)

    Sitnikova, V. E.; Dunaev, A. A.; Mamalimov, R. I.; Pakhomov, P. M.; Khizhnyak, S. D.; Chmel, A. E.

    2017-07-01

    The Fourier IR reflection spectra of ZnSe ceramics prepared by hot pressing (HP), physical vapor deposition (PVD), and PVD combined with hot isostatic pressing (HIP) are presented. The optical constants of polished and dry-ground specimens were used for comparison. The grinding treatment simulated the erosion of the outer surface of optical elements made of zinc selenide under the influence of solid dust particles and deposits. In the polished specimens residual stresses showed up in the IR reflection spectra of the ZnSePVD and ZnSeHIP ceramics, which had well-defined orientation of grains, but were not present in the spectra of the ZnSeHIP ceramics as a result of mutual compensation of the stresses in the randomly oriented grains of the material. The stresses, which appeared as a shift of the absorption bands calculated by the Kramers-Kronig method, increased significantly after abrasive treatment of the specimens. For all the treated ceramics the intensity of the absorption bands resulting from the anharmonicity of the vibrations in the distorted crystal lattice increased by several times. The last effect also depends on the production prehistory of the ceramics.

  19. Comparative study of porosification in InAs, InP, ZnSe and ZnCdS

    International Nuclear Information System (INIS)

    Monaico, Eduard; Tiginyanu, Ion; Nielsch, Kornelius; Ursaki, Veaceslav; Colibaba, Gleb; Nedeoglo, Dmitrii; Cojocaru, Ala; Foell Helmut

    2013-01-01

    We report on a comparative study of the pore growth during anodization of a narrow-bandgap III-V compound (InAs), a medium-bandgap III-V one (InP) and wide-bandgap II-VI semiconductors (ZnSe and Zn 0,4 Cd 0,6 S). According to the obtained results, the morphology of the porous layers can be controlled by the composition of the electrolyte and the applied electrochemical parameters. It was evidenced that in the narrow bandgap semiconductor InAs it is difficult to control the mechanism of pore growth. Both current line oriented pores and crystallographically oriented pores were produced in the medium-bandgap material InP. The electrochemical nanostructuring of wide-bandgap semiconductors realized in single crystalline high conductivity samples evidenced only current-line oriented pores. This behavior is explained in terms of difference in the values of electronegativity of the constituent atoms and the degree of ionicity. (authors)

  20. Aqueous based synthesis of N-acetyl-L-cysteine capped ZnSe nanocrystals with intense blue emission

    Science.gov (United States)

    Soheyli, Ehsan; Sahraei, Reza; Nabiyouni, Gholamreza

    2016-10-01

    In this work a very simple reflux route for preparation of ZnSe nanocrystals with minor modification and faster preparation over conventional ones is introduced. X-ray diffraction analysis indicated that the ZnSe nanocrystals have a cubic structure. The complete disappearance of the S-H band in FT-IR spectrum of N-acetyl-L-cysteine capped ZnSe nanocrystals was an indication over formation of Zn-thiol covalent bonds at the surface of the nanocrystals which results in passivation of small nanocrystals. The strong size-quantization regime was responsible of significant blue shift in absorption/emission spectra. Using the well-known calculations, band gap and Urbach energy of the ZnSe nanocrystals were measured and their average size was estimated optically to be around 4.6 nm along with the TEM image. A dark blue emission with higher relative intensity of excitonic to trap emissions (compared to conventional method), very narrow excitonic emission peak of about 16 nm and remarkable stability was obtained from the ZnSe nanocrystals.

  1. Single-step in-situ synthesis and optical properties of ZnSe nanostructured dielectric nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Dey, Chirantan; Rahaman Molla, Atiar; Tarafder, Anal; Karmakar, Basudeb, E-mail: basudebk@cgcri.res.in [CSIR-Central Glass and Ceramic Research Institute, Glass Science and Technology Section, Glass Division, 196, Raja S. C. Mullick Road, 700032 Kolkata (India); Kr Mishra, Manish; De, Goutam [CSIR-Central Glass and Ceramic Research Institute, Nano-Structured Materials Division, 196, Raja S. C. Mullick Road, 700032 Kolkata (India); Goswami, Madhumita; Kothiyal, G. P. [Glass and Advanced Ceramics Division, Bhaba Atomic Research Centre, Trombay, 400085 Mumbai (India)

    2014-04-07

    This work provides the evidence of visible red photoluminescent light emission from ZnSe nanocrystals (NCs) grown within a dielectric (borosilicate glass) matrix synthesized by a single step in-situ technique for the first time and the NC sizes were controlled by varying only the concentration of ZnSe in glass matrix. The ZnSe NCs were investigated by UV-Vis optical absorption spectroscopy, Raman spectroscopy, and transmission electron microscopy (TEM). The sizes of the ZnSe NCs estimated from the TEM images are found to alter in the range of 2–53 nm. Their smaller sizes of the NCs were also calculated by using the optical absorption spectra and the effective mass approximation model. The band gap enlargements both for carrier and exciton confinements were evaluated and found to be changed in the range of 0–1.0 eV. The Raman spectroscopic studies showed blue shifted Raman peaks of ZnSe at 295 and 315 cm{sup −1} indicating phonon confinement effect as well as compressive stress effect on the surface atoms of the NCs. Red photoluminescence in ZnSe-glass nanocomposite reveals a broad multiple-peak structure due to overlapping of emission from NC size related electron-hole recombination (∼707 nm) and emissions from defects to traps, which were formed due to Se and Zn vacancies signifying potential application in photonics.

  2. ZnSe passivation layer for the efficiency enhancement of CuInS{sub 2} quantum dots sensitized solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Peng, Zhuoyin; Liu, Yueli; Zhao, Yinghan; Chen, Keqiang; Cheng, Yuqing [State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, School of Materials Science and Engineering, Wuhan University of Technology, Wuhan 430070 (China); Kovalev, Valery [Department of Mechanics and Mathematics, Moscow State University named after M.V. Lomonosov, Leninskie Gory 1, 119992 Moscow (Russian Federation); Chen, Wen, E-mail: chenw@whut.edu.cn [State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, School of Materials Science and Engineering, Wuhan University of Technology, Wuhan 430070 (China)

    2014-02-25

    Highlights: • ZnSe is employed as passivation layer in CuInS{sub 2} quantum dots sensitized solar cells. • Slight red-shift has been occurred in UV–vis absorption spectra with ZnSe coating. • CuInS{sub 2} based solar cells coated by ZnSe have better efficiency than that of ZnS. • Higher rate of charge transport can be produced after coating with ZnSe. -- Abstract: The effect of ZnSe passivation layer is investigated in the CuInS{sub 2} quantum dot sensitized solar cells, which is used to improve the photovoltaic performance. The CuInS{sub 2} quantum dot sensitized TiO{sub 2} photo-anodes are prepared by assembly linking technique, and then deposited by the ZnSe passivation layer using the successive ionic layer absorption and reaction technique. The optical absorption edge and photoluminescence peak have slightly red-shifted after the passivation layer coating. Under solar light illumination, the ZnSe passivation layer based CuInS{sub 2} quantum dot sensitized solar cells have the higher photovoltaic efficiency of 0.95% and incident photon conversion efficiency response than that of pure CuInS{sub 2} based solar cells and ZnS passivation layer based solar cells, as the electron injection rate becomes faster after coating with ZnSe passivation layer.

  3. Influence of CdTe sub-monolayer stressor on CdSe quantum dot self-assembling in ZnSe

    International Nuclear Information System (INIS)

    Sedova, I.V.; Lyublinskaya, O.G.; Sorokin, S.V.; Sitnikova, A.A.; Solnyshkov, D.D.; Rykhova, O.V.; Toropov, A.A.; Ivanov, S.V.

    2006-01-01

    This paper reports on the attempt to apply the stressor-controlled quantum dot (QD) fabrication technique to the conventional CdSe/ZnSe nanostructures. Super-strained CdTe fractional monolayer (Δa/a∝14% for CdTe/ZnSe) grown on top of the Te-stabilized ZnSe surface prior to deposition of the QD material (CdSe) has been used as a stressor which is expected to affect size, composition and density of CdSe QDs. The grown structures are studied by X-ray diffraction, transmission-electron microscopy, photoluminescence (PL) and PL excitation in comparison with conventional CdSe/ZnSe QDs obtained by a modified migration enhanced epitaxy technique. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  4. Polytypism and band alignment in ZnSe nanowires revealed by photoluminescence spectroscopy of embedded (Zn,Cd)Se quantum dots

    Science.gov (United States)

    Bieker, S.; Pfeuffer, R.; Kiessling, T.; Tarakina, N.; Schumacher, C.; Ossau, W.; Molenkamp, L. W.; Karczewski, G.

    2015-03-01

    We report on the optical characterization of single (Zn,Cd)Se quantum dots (QDs) embedded in vapor-liquid-solid-grown ZnSe nanowires (NWs). The temperature dependent quenching of the QD luminescence demonstrates that their electronic structure is comparable to that of self-assembled (Zn,Cd)Se QDs in ZnSe matrices. The photoluminescence excitation (PLE) spectrum of single nanowire QDs reveals the presence of both zinc blende (ZB) and wurtzite (WZ) crystal modifications of ZnSe in the NW shafts. PLE provides, therefore, a complementary technique to transmission electron microscopy imaging to reveal polytypism in ZnSe NWs. A transient quenching of the PL emission suggests a type II staggered band alignment at the ZB/WZ interface in our ZnSe NWs.

  5. Effect of process conditions and chemical composition on the microstructure and properties of chemically vapor deposited SiC, Si, ZnSe, ZnS and ZnS(x)Se(1-x)

    Science.gov (United States)

    Pickering, Michael A.; Taylor, Raymond L.; Goela, Jitendra S.; Desai, Hemant D.

    1992-01-01

    Subatmospheric pressure CVD processes have been developed to produce theoretically dense, highly pure, void-free and large area bulk materials, SiC, Si, ZnSe, ZnS and ZnS(x)Se(1-x). These materials are used for optical elements, such as mirrors, lenses and windows, over a wide spectral range from the VUV to the IR. We discuss the effect of CVD process conditions on the microstructure and properties of these materials, with emphasis on optical performance. In addition, we discuss the effect of chemical composition on the properties of the composite material ZnS(x)Se(1-x). We first present a general overview of the bulk CVD process and the relationship between process conditions, such as temperature, pressure, reactant gas concentration and growth rate, and the microstructure, morphology and properties of CVD-grown materials. Then we discuss specific results for CVD-grown SiC, Si, ZnSe, ZnS and ZnS(x)Se(1-x).

  6. Room temperature deposition of ZnSe thin films by successive ionic layer adsorption and reaction (SILAR) method

    International Nuclear Information System (INIS)

    Kale, R.B.; Lokhande, C.D.

    2004-01-01

    The zinc selenide (ZnSe) thin films are deposited onto glass substrate using relatively simple and inexpensive successive ionic layer adsorption and reaction (SILAR) method. The films are deposited using zinc acetate sodium selenosulphate precursors. The concentration, pH, immersion and rinsing times and number of immersion cycles have been optimized to obtain good quality ZnSe thin films. The X-ray diffraction (XRD) study and scanning electron microscopy (SEM) studies reveals nanocrystalline nature alongwith some amorphous phase present in ZnSe thin films. Energy dispersive X-ray (EDAX) analysis shows that the films are Se deficient. From optical absorption data, the optical band gap 'E g ' for as-deposited thin film was found to be 2.8 eV and electrical resistivity in the order of 10 7 Ω cm

  7. IDENTIFICACIÓN DE UNA NUEVA FASE EN LA ESTRUCTURA CRISTALINA DEL COMPUESTO CUATERNARIO Cu2ZnSnSe4 DURANTE LA ETAPA INCORPORACIÓN DEL ZnSe

    Directory of Open Access Journals (Sweden)

    Anderon Dussán Cuenca

    Full Text Available En este trabajo se presenta un estudio de las propiedades estructurales de películas delgadas del compuesto Cu2ZnSnSe4 variando tanto la masa (M X como la temperatura del sustrato al cual fue evaporado (Ts el compuesto binario ZnSe. Todas las muestras fueron depositadas por el método de co-evaporación en tres etapas y manteniendo constante los demás parámetros. A partir de las medidas de difracción de Rayos x fue posible establecer con el incremento de la Ts la presencia de fases binarias asociadas al compuesto cuaternario durante el proceso de crecimiento del material. Se encontró que alrededor del pico principal, 2θ = 27,1°, predominan las fases binarias y la presencia del ZnSe que se forma durante la subsecuente etapa de selenización del material. Una especie de bifurcación en el pico principal (2θ = 27,1° fue observado para la transición entre M ZnSe = 0,153 g a 0,171 g. Medidas de difracción de rayos x fueron realizadas al compuesto binarios puro, observándose una correspondencia con los picos encontrados alrededor del pico principal del compuesto. Un estudio a través de espectroscopia Raman evidenció corrimientos raman asociados a los compuestos binarios observados por XRD. A partir de la ecuación de Scherrer se encontró que los tamaños de los cristalitos variaban entre 80 y 90 nm.

  8. Naturally Abundance Vanillin as Starting Material to Synthesizing 4-(4-Hydroxy-3-methoxyphenyl-6-methyl-3,4-dihydropyrimidin-2(1H-one

    Directory of Open Access Journals (Sweden)

    Masruri MASRURI

    2015-12-01

    Full Text Available Indonesia is the second biggest producer of natural vanillin. Traditionally it was isolated from the bean of vanilla (Vanilla planifolia Andrews. This paper reports on applying vanillin as starting material for synthesizing a biologically important chemical structure 3,4-dihydropyrimidinone. The reaction was undertaken in one step following multi component reaction (MCR. Products determination was undergone using FTIR and UV-Vis spectrophotometry, and also liquid chromatography-mass spectrometry (LCMS. After purification under flash column chromatography in ethyl acetate-hexane, it was found a white solid of 4-(4-hydroxy-3-methoxyphenyl-6-methyl-3,4-dihydropyrimidin-2(1H-one in 67% yield with a few amount of an unreacted vanillin.

  9. Defect reactions of implanted Li in ZnSe observed by $\\beta$-NMR

    CERN Document Server

    Kroll, F; Füllgrabe, M; Mai, F; Marbach, K; Peters, D; Geithner, W; Kappertz, S; Keim, M; Kloos, S; Wilbert, S; Neugart, R; Lievens, P; Georg, U

    2001-01-01

    Using $\\beta$-radiation-detected nuclear magnetic resonance ($\\beta$-NMR), we investigated the microscopic behavior of implanted $^{8}$Li in nominally undoped ZnSe crystals. From the temperature-dependent amplitudes of high-resolution NMR spectra we conclude a gradual interstitial-to-substitutional site change between 200 and 350 K. This is in accordance with earlier emission channeling results. We argue that this conversion proceeds via Li$_{i}^+$ + V$_{\\textrm{Zn}}^{2-}$ to ${\\textrm{Li}}_{\\textrm{Zn}}^{-}$ and involves implantation-related Zn vacancies. (13 refs).

  10. Microsized structures assisted nanostructure formation on ZnSe wafer by femtosecond laser irradiation

    International Nuclear Information System (INIS)

    Wang, Shutong; Feng, Guoying; Zhou, Shouhuan

    2014-01-01

    Micro/nano patterning of ZnSe wafer is demonstrated by femtosecond laser irradiation through a diffracting pinhole. The irradiation results obtained at fluences above the ablation threshold are characterized by scanning electron microscopy. The microsized structure with low spatial frequency has a good agreement with Fresnel diffraction theory. Laser induced periodic surface structures and laser-induced periodic curvelet surface structures with high spatial frequency have been found on the surfaces of microsized structures, such as spikes and valleys. We interpret its formation in terms of the interference between the reflected laser field on the surface of the valley and the incident laser pulse

  11. On Some Physical Properties of GeSe3-Sb2Se3-ZnSe Thin Films and Their Radiation Response

    International Nuclear Information System (INIS)

    Hosni, H.M.M.A.

    2010-01-01

    Thin films of the chalcogenides GeSe 3 , Sb 2 Se 3 , ZnSe, (GeSe 3 )80(Sb 2 Se 3 )20 and (GeSe 3 )70(Sb 2 Se 3 )10(ZnSe)20, are prepared by thermal evaporation onto glass substrates. The effect of ZnSe incorporation with both GeSe 3 , Sb 2 Se 3 results in amorphous (GeSe 3 )70(Sb 2 Se 3 )10(ZnSe)20 composition as obtained from the X-ray analysis. Electrical measurements reveal a decrease in dc activation energy, ΔEdc, and an increase in ac activation energy, ΔEac, for (GeSe 3 )70(Sb 2 Se 3 )10(ZnSe)20 as compared with (GeSe 3 )80(Sb 2 Se 3 )20. Optical energy gap, Eg, and band tail width, Ee, are estimated in UV/VIS spectral region for fresh and γ-irradiated films, revealing a decrease in Eg and an increase in Ee for ZnSe and (GeSe 3 )70(Sb 2 Se 3 )10(ZnSe)20 compositions, with irradiation dose.

  12. Laser properties of Fe2+:ZnSe fabricated by solid-state diffusion bonding

    Science.gov (United States)

    Balabanov, S. S.; Firsov, K. N.; Gavrishchuk, E. M.; Ikonnikov, V. B.; Kazantsev, S. Yu; Kononov, I. G.; Kotereva, T. V.; Savin, D. V.; Timofeeva, N. A.

    2018-04-01

    The characteristics of an Fe2+:ZnSe laser at room temperature and its active elements with undoped faces were studied. Polycrystalline elements with one or two diffusion-doped internal layers were obtained by the solid-state diffusion bonding technique applied to chemical vapor deposition grown ZnSe plates preliminary doped with Fe2+ ions in the process of hot isostatic pressing. A non-chain electric-discharge HF laser was used to pump the crystals. It was demonstrated that increasing the number of doped layers allows increasing the maximum diameter of the pump radiation spot and the pump energy without the appearance of transversal parasitic oscillation. For the two-layer-doped active element with a diameter of 20 mm an output energy of 480 mJ was achieved with 37% total efficiency with respect to the absorbed energy. The obtained results demonstrate the potential of the developed technology for fabrication of active elements by the solid-state diffusion bonding technique combined with the hot isostatic pressing treatment for efficient IR lasers based on chalcogenides doped with transition metal ions.

  13. Band structure and optical properties of sinusoidal superlattices: ZnSe1-xTex

    International Nuclear Information System (INIS)

    Yang, G.; Lee, S.; Furdyna, J. K.

    2000-01-01

    This paper examines the band structure and optical selection rules in superlattices with a sinusoidal potential profile. The analysis is motivated by the recent successful fabrication of high quality ZnSe 1-x Te x superlattices in which the composition x varies sinusoidally along the growth direction. Although the band alignment in the ZnSe 1-x Te x sinusoidal superlattices is staggered (type II), they exhibit unexpectedly strong photoluminescence, thus suggesting interesting optical behavior. The band structure of such sinusoidal superlattices is formulated in terms of the nearly-free-electron (NFE) approximation, in which the superlattice potential is treated as a perturbation. The resulting band structure is unique, characterized by a single minigap separating two wide, free-electron-like subbands for both electrons and holes. Interband selection rules are derived for optical transitions involving conduction and valence-band states at the superlattice Brillouin-zone center, and at the zone edge. A number of transitions are predicted due to wave-function mixing of different subband states. It should be noted that the zone-center and zone-edge transitions are especially easy to distinguish in these superlattices because of the large width of the respective subbands. The results of the NFE approximation are shown to hold surprisingly well over a wide range of parameters, particularly when the period of the superlattice is short. (c) 2000 The American Physical Society

  14. Blue-green ZnSe lasers with a new type of active region

    International Nuclear Information System (INIS)

    Ivanov, S.V.; Toropov, A.A.; Sorokin, S.V.; Shubina, T.V.; Sedova, I.V.; Kop'ev, P.S.; Alferov, Zh.I.; Waag, A.; Lugauer, H.J.; Reuscher, G.; Keim, M.; Fischer, F.F.; Landwehr, G.

    1999-01-01

    We report the results of an experimental study of molecular-beam epitaxy of ZnSe-based laser heterostructures with a new structure of the active region, which contains a fractional-monolayer CdSe recombination region in an expanded ZnSe quantum well and a waveguide based on a variably-strained, short-period superlattice are reported. Growth of a fractional-monolayer CdSe region with a nominal thickness of 2-3 ML, i.e., less than the critical thickness, on a ZnSe surface (Δa/a∼7%) leads to the formation of self-organized, pseudomorphic, CdSe-enriched islands with lateral dimensions ∼10-30 nm and density ∼2x10 10 cm -2 , which serve as efficient centers of carrier localization, giving rise to effective spatial separation of defective regions and regions of radiative recombination and, as a result, a higher quantum efficiency. Laser structures for optical pumping in the (Zn, Mg) (S, Se) system with a record-low threshold power density (less than 4 kW/cm 2 at 300 K) and continuous-wave laser diodes in the system (Be, Mg, Zn) Se with a 2.5 to 2.8-ML-thick, fractional-monolayer CdSe active region have been obtained. The laser structures and diodes have an improved degradation resistance

  15. Biomimetic nanostructures in ZnS and ZnSe provide broadband anti-reflectivity

    Science.gov (United States)

    Chan, L.; DeCuir, E. A., Jr.; Fu, R.; Morse, D. E.; Gordon, M. J.

    2017-11-01

    Graded-index, moth eye-inspired anti-reflective features were fabricated in ZnS and ZnSe via nanosphere lithography using a Langmuir-Blodgett dip-coating method with plasma-based mask reduction and pattern transfer. Arrays of hexagonally close-packed conical frusta (top diameter = 300 nm, pitch = 690 nm, height = 2800 nm) were realized by isotropic etching (size-reduction) of the colloidal mask with CF4/Ar, followed by pattern transfer into the substrate using CH4/H2 plasma etching. Substantial increases in broadband transmission were achieved across the 2-20 μm range, yielding 23% and 26% single-side transmission improvement, and 92% and 88% absolute double-side transmission for ZnS and ZnSe, respectively, in excellent agreement with finite difference time domain (FDTD) optical simulations. Experimental differences in direct versus total transmission, and the general fall off of transmission at short wavelengths, were attributed to diffuse forward scattering and diffractive effects, as predicted by far-field scattering patterns using FDTD. The fabrication method presented can be used to enhance efficiency for multiple IR applications by minimizing reflective losses, while offering the further advantages of scalability and low cost.

  16. Spin-Related Micro-Photoluminescence in Fe3+ Doped ZnSe Nanoribbons

    Directory of Open Access Journals (Sweden)

    Lipeng Hou

    2016-12-01

    Full Text Available Spin-related emission properties have important applications in the future information technology; however, they involve microscopic ferromagnetic coupling, antiferromagnetic or ferrimagnetic coupling between transition metal ions and excitons, or d state coupling with phonons is not well understood in these diluted magnetic semiconductors (DMS. Fe3+ doped ZnSe nanoribbons, as a DMS example, have been successfully prepared by a thermal evaporation method. Their power-dependent micro-photoluminescence (PL spectra and temperature-dependent PL spectra of a single ZnSe:Fe nanoribbon have been obtained and demonstrated that alio-valence ion doping diminishes the exciton magnetic polaron (EMP effect by introducing exceeded charges. The d-d transition emission peaks of Fe3+ assigned to the 4T2 (G → 6A1 (S transition at 553 nm and 4T1 (G → 6A1 (S transition at 630 nm in the ZnSe lattice have been observed. The emission lifetimes and their temperature dependences have been obtained, which reflected different spin–phonon interactions. There exists a sharp decrease of PL lifetime at about 60 K, which hints at a magnetic phase transition. These spin–spin and spin–phonon interaction related PL phenomena are applicable in the future spin-related photonic nanodevices.

  17. ZnSe Light Emitting Diode Quantum Efficiency and Emission Characterization

    Directory of Open Access Journals (Sweden)

    Sahbudin U.K.

    2016-01-01

    Full Text Available ZnSe has demonstrated as a potential candidate in realizing advance LED in some appications for current and future works that utilize a cheaper preparation technique. Blue and white LEDs have been shown to spread across compound semiconductors. This II-VI compound semiconductor with a direct and wide band gap is used in the study which focused on a preparation and its characterization. The device is developed using a circular chip of ZnSe but only part of the active region is designed to allow shorter computation time. Analyses of the proposed LED are performed in an environment that allows optical transition and nonradiative recombination mechanisms. Voltage variation from 0 V to 1.5 V is maintained throughout the observation. The curent-voltage plot shows the p-n junction or diode behavior with central emissive layer. The two dimensions surface emission rate obtained indicates that voltage increment causes the emission concentration to become higher near the central pcontact. The LED efficiency is assessed in terms of internal quantum efficiency and emitting rate.

  18. Random lasing of microporous surface of Cr{sup 2+}:ZnSe crystal induced by femtosecond laser

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Xianheng; Feng, Guoying, E-mail: guoing-feng@scu.edu.cn, E-mail: zhoush@scu.edu.cn; Yao, Ke; Yi, Jiayu; Zhang, Hong [College of Electronics and Information Engineering, Sichuan University, Chengdu 610065 (China); Zhou, Shouhuan, E-mail: guoing-feng@scu.edu.cn, E-mail: zhoush@scu.edu.cn [College of Electronics and Information Engineering, Sichuan University, Chengdu 610065 (China); North China Research Institute of Electro-Optics, Beijing 100015 (China)

    2015-06-15

    We demonstrate a random lasing emission based on microporous surface of Cr{sup 2+}:ZnSe crystal prepared by femtosecond pulsed laser ablation in high vacuum (below 5 × 10{sup −4} Pa). The scanning electron microscope results show that there are a mass of micropores with an average size of ∼13 μm and smaller ones with ∼1.2 μm on the surface of Cr{sup 2+}:ZnSe crystal. The adjacent micropore spacing of the smaller micropores ranges from 1 μm to 5 μm. Under 1750 nm excitation of Nd:YAG (355 nm) pumped optical parametric oscillator, a random lasing emission with center wavelength of 2350 nm and laser-like threshold of 0.3 mJ/pulse is observed. The emission lifetime of 2350 nm laser reduces from 800 ns to 30 ns as the pump energy increases above threshold. The emission spectra and decay time of smooth surface, groove and microporous surface of Cr{sup 2+}:ZnSe crystal are contrasted. The optional pump wavelength range is from 1500 nm to 1950 nm, which in accordance with the optical absorption property of Cr{sup 2+}:ZnSe crystal. The peak position of excitation spectra is almost identical to the strongest absorption wavelength.

  19. Dispersion of the second-order nonlinear susceptibility in ZnTe, ZnSe, and ZnS

    DEFF Research Database (Denmark)

    Wagner, Hans Peter; Kühnelt, M.; Langbein, Wolfgang Werner

    1998-01-01

    We have measured the absolute values of the second-harmonic generation (SHG) coefficient \\d\\ for the zinc-blende II-VI semiconductors ZnTe, ZnSe, and ZnS at room temperature. The investigated spectral region of the fundamental radiation lambda(F) ranges from 520 to 1321 nm using various pulsed...

  20. Bulletin of Materials Science | Indian Academy of Sciences

    Indian Academy of Sciences (India)

    Electron density distribution and bonding in ZnSe and PbSe using maximum entropy method (MEM) · K S Syed Ali R Saravanan S Israel R K Rajaram · More Details Abstract Fulltext PDF. The study of electronic structure of materials and bonding is an important part of material characterization. The maximum entropy method ...

  1. Multi-wall carbon nanotubes/epoxy resin composites characterization of the starting materials and evaluation of thermal and electrical conductivity

    International Nuclear Information System (INIS)

    Silva, Wellington Marcos da

    2009-01-01

    In this study we investigate the electrical and thermal properties of I) composite materials fabricated with O, I, 0,5 and I wt% of concentric multi-wall carbon nanotubes/epoxy resin (MWNT) dispersed randomly in the resin; 2) MWNT buckypaper/resin composite materials; 3) and neat MWNT buckypaper. Initially, we use the techniques of thermogravimetry, infrared spectroscopy, nuclear magnetic resonance, energy dispersive spectroscopy, x-ray fluorescence, scanning and transmission electron microscopy for a broadening characterization of the starting materials, to evaluate its morphology, purity, chemical composition and structure, in order to optimize the properties of crosslinked resin and, consequently, of the composite systems. Important parameters such as the average molecular mass and the equivalent weight of epoxy resin (DGEBA) were determined by 1 H-NMR analysis and, after that, resin/curing agent relations with Phr 10, 15, 20 and 53,2 were elaborated and investigated by thermogravimetry, the resin/curing agent relation with Phr 10 showed to be the most thermally stable. This stoichiometric relation was used to elaborate the composites. We have evaluated that the effect of adding 10 wt% of the solvent acetone to the epoxy resin preparation does not alter its properties so we have adopted two routes to fabricate the composites. In the first route we used 10 wt% of acetone and, in the second the MWNT were dispersed in the matrix without using the solvent. However, no significant difference was observed for the dispersion of the bundle tubes in both systems. The electrical conductivity of the composites and buckypapers was evaluated by impedance spectroscopy and the thermal conductivity by the flash laser flash method. Only the buckypapers presented high values for electrical conductivity (10 3 S.m -1 ). The composite systems presented values of 10 -3 S.m -1 , only a bit different from the value of the crosslinked resin. For thermal conductivity, the values for the

  2. Comparative study of ZnSe thin films deposited from modified chemical bath solutions with ammonia-containing and ammonia-free precursors

    International Nuclear Information System (INIS)

    Chen Liangyan; Zhang Daoli; Zhai Guangmei; Zhang Jianbing

    2010-01-01

    Ammonia is one of the complexing agents which are the most commonly used in the precursors of ZnSe thin films by chemical bath deposition, but its high volatility may be harmful to human beings and environments. In our experiments, ZnSe films were obtained from modified chemical solutions with ammonia-containing and ammonia-free precursors. X-ray diffraction, field-emission scanning electron microscope (FSEM), and absorption spectrum were applied to investigate the microstructure, morphology and optical properties of the samples obtained from both growth conditions, which were investigated in this work. The ammonia-free chemical bath deposited ZnSe films showed comparable properties with the ammonia-containing ones, indicating that ZnSe films from ammonia-free chemical solution may be preferred buffer layer in thin film solar cells with less environmental contamination.

  3. Synthesis of ZnSe nanocrystals (NCs) using a rapid microwave irradiation method and investigation of the effect of copper (Cu) doping on the optical properties

    Energy Technology Data Exchange (ETDEWEB)

    Molaei, M., E-mail: m.molaei@vru.ac.ir; Khezripour, A.R.; Karimipour, M.

    2014-10-30

    Highlights: • ZnSe nanocrystals were synthesized using a rapid microwave method. • Synthesized ZnSe NCs indicated an emission with two peaks. • For ZnSe:Cu NCs band edge emission of the ZnSe was completely disappeared. • Synthesized NCs can be dispersed in water therefore they are proper for biological applications. - Abstract: ZnSe nanocrystals (NCs) were synthesized using a microwave activated method. Synthesized NCs were characterized by means of X-ray diffraction (XRD), UV–visible (UV–vis) optical spectroscopy and photoluminescence (PL). XRD analysis demonstrated cubic zinc blende NCs. TEM image indicated round shape NCs and most of the particles had diameters of about 3 nm. Band gap of the NCs was obtained about 3.15 eV and PL spectra indicates a broad emission with two peaks located about 415 and 500 nm related to band edge and trap state respectively. For ZnSe:Cu NCs, PL intensity of band gap emission of ZnSe NCs at 415 nm decreased gradually with the increase in the concentration of Cu dopant ions and for precursor ratio of Cu:Zn 1% band gap emission at 415 nm disappeared completely. At the same conditions, PL QY was obtained about 2% and 8% for ZnSe and ZnSe:Cu (1%) NCs, respectively.

  4. Polytypism in ZnS, ZnSe, and ZnTe: First-principles study

    KAUST Repository

    Boutaiba, F.; Belabbes, Abderrezak; Ferhat, M.; Bechstedt, F.

    2014-01-01

    We report results of first-principles calculations based on the projector augmented wave (PAW) method to explore the structural, thermodynamic, and electronic properties of cubic (3C) and hexagonal (6H, 4H, and 2H) polytypes of II-VI compounds: ZnS, ZnSe, and ZnTe. We find that the different bond stacking in II-VI polytypes remarkably influences the resulting physical properties. Furthermore, the degree of hexagonality is found to be useful to understand both the ground-state properties and the electronic structure of these compounds. The resulting lattice parameters, energetic stability, and characteristic band energies are in good agreement with available experimental data. Trends with hexagonality of the polytype are investigated.

  5. Polytypism in ZnS, ZnSe, and ZnTe: First-principles study

    KAUST Repository

    Boutaiba, F.

    2014-06-23

    We report results of first-principles calculations based on the projector augmented wave (PAW) method to explore the structural, thermodynamic, and electronic properties of cubic (3C) and hexagonal (6H, 4H, and 2H) polytypes of II-VI compounds: ZnS, ZnSe, and ZnTe. We find that the different bond stacking in II-VI polytypes remarkably influences the resulting physical properties. Furthermore, the degree of hexagonality is found to be useful to understand both the ground-state properties and the electronic structure of these compounds. The resulting lattice parameters, energetic stability, and characteristic band energies are in good agreement with available experimental data. Trends with hexagonality of the polytype are investigated.

  6. Femtosecond pulsed laser ablation in microfluidics for synthesis of photoluminescent ZnSe quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Chao, E-mail: chaoyangscu@gmail.com [College of Electronics and Information Engineering, Sichuan University, No. 24 South Section 1, 1st Ring Road, Chengdu 610064 (China); Feng, Guoying, E-mail: guoing_feng@scu.edu.cn [College of Electronics and Information Engineering, Sichuan University, No. 24 South Section 1, 1st Ring Road, Chengdu 610064 (China); Dai, Shenyu, E-mail: 232127079@qq.com [College of Electronics and Information Engineering, Sichuan University, No. 24 South Section 1, 1st Ring Road, Chengdu 610064 (China); Wang, Shutong, E-mail: wangshutong.scu@gmail.com [College of Electronics and Information Engineering, Sichuan University, No. 24 South Section 1, 1st Ring Road, Chengdu 610064 (China); Li, Guang, E-mail: 632524844@qq.com [College of Electronics and Information Engineering, Sichuan University, No. 24 South Section 1, 1st Ring Road, Chengdu 610064 (China); Zhang, Hua [College of Electronics and Information Engineering, Sichuan University, No. 24 South Section 1, 1st Ring Road, Chengdu 610064 (China); Zhou, Shouhuan, E-mail: zhoush@scu.edu.cn [College of Electronics and Information Engineering, Sichuan University, No. 24 South Section 1, 1st Ring Road, Chengdu 610064 (China); North China Research Institute of Electro-Optics, 4 Jiuxianqiao Street, Chaoyang District, Beijing 100015 (China)

    2017-08-31

    Highlights: • A novel method for synthesis and coating of quantum dots by ultrafast laser pulses. • Mild and “green” synthesis method without toxic chemicals. • Enhanced bright green light emission without doped transition metal ions. • Ultrafast laser and coating layer enhanced the emission originated from defects. - Abstract: A simple but new toxic chemical free method, Femtosecond Laser Ablation in Microfluidics (FLAM) was proposed for the first time. ZnSe quantum dots of 4–6 nm were synthesized and with the use of hyperbranched Polyethyleneimine (PEI) as both structural and functional coated layer. These aqueous nanosized micelles consisting of quantum dots exhibit deep defect states emission of bright green light centered at 500 nm. A possible mechanism for the enhanced board band emission was discussed. The properties of toxic matters free and enhanced photoluminescence without doped transition metal ions demonstrate an application potential for biomedical imaging.

  7. Nitrogen doping of ZnSe by OMVPE using a novel organometallic precursor

    International Nuclear Information System (INIS)

    Akram, S.; Bhat, I.B.; Melas, A.A.

    1994-01-01

    We have investigated phenylhydrazine (PhHz) as a potential nitrogen dopant source in organometallic vapor phase epitaxial growth of ZnSe. Dimethylzinc and dimethylselenide were the zinc and selenium precursors, respectively. Photoluminescence and secondary ion mass spectroscopy measurements indicate that high incorporation efficiency compared to ammonia can be achieved using this dopant source. For example, nitrogen incorporation in the 2.5 x 10 18 /cm -3 level was achieved at 350 degrees C under ultraviolet excitation when the PhHz partial pressure was 1 x 10 -8 atm. These layers had 1-2 x 10 15 /cm -3 electrically active acceptors. Films grown at higher partial pressures of PhHz were highly compensated. 9 refs., 5 figs

  8. Femtosecond pulsed laser ablation in microfluidics for synthesis of photoluminescent ZnSe quantum dots

    International Nuclear Information System (INIS)

    Yang, Chao; Feng, Guoying; Dai, Shenyu; Wang, Shutong; Li, Guang; Zhang, Hua; Zhou, Shouhuan

    2017-01-01

    Highlights: • A novel method for synthesis and coating of quantum dots by ultrafast laser pulses. • Mild and “green” synthesis method without toxic chemicals. • Enhanced bright green light emission without doped transition metal ions. • Ultrafast laser and coating layer enhanced the emission originated from defects. - Abstract: A simple but new toxic chemical free method, Femtosecond Laser Ablation in Microfluidics (FLAM) was proposed for the first time. ZnSe quantum dots of 4–6 nm were synthesized and with the use of hyperbranched Polyethyleneimine (PEI) as both structural and functional coated layer. These aqueous nanosized micelles consisting of quantum dots exhibit deep defect states emission of bright green light centered at 500 nm. A possible mechanism for the enhanced board band emission was discussed. The properties of toxic matters free and enhanced photoluminescence without doped transition metal ions demonstrate an application potential for biomedical imaging.

  9. Ab Initio factorized LCAO calculations of the electronic band structure of ZnSe, ZnS, and the (ZnSe)1(ZnS)1 strained-layer superlattice

    International Nuclear Information System (INIS)

    Marshall, T.S.; Wilson, T.M.

    1992-01-01

    The authors report on the results of electronic band structure calculations of bulk ZnSe, bulk ZnS and the (ZnSe) 1 (ZnS) 1 , strained-layer superlattice (SLS) using the ab initio factorized linear combination of atomic orbitals method. The bulk calculations were done using the standard primitive nonrectangular 2-atom zinc blende unit cell, while the SLS calculation was done using a primitive tetragonal 4-atom unit cell modeled from the CuAu I structure. The analytic fit to the SLS crystalline potential was determined by using the nonlinear coefficients from the bulk fits. The CPU time saved by factorizing the energy matrix integrals and using a rectangular unit cell is discussed

  10. Guided Growth of Horizontal ZnSe Nanowires and their Integration into High-Performance Blue-UV Photodetectors.

    Science.gov (United States)

    Oksenberg, Eitan; Popovitz-Biro, Ronit; Rechav, Katya; Joselevich, Ernesto

    2015-07-15

    Perfectly aligned horizontal ZnSe nano-wires are obtained by guided growth, and easily integrated into high-performance blue-UV photodetectors. Their crystal phase and crystallographic orientation are controlled by the epitaxial relations with six different sapphire planes. Guided growth paves the way for the large-scale integration of nanowires into optoelectronic devices. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Thickness-dependent dispersion parameters, energy gap and nonlinear refractive index of ZnSe thin films

    International Nuclear Information System (INIS)

    Prakash, Deo; Shaaban, E.R.; Shapaan, M.; Mohamed, S.H.; Othman, A.A.; Verma, K.D.

    2016-01-01

    Highlights: • Combined experimental and theoretical researches on ZnSe Thin Films. • The film thickness and refractive index were determined using envelope method. • The absorption coefficient and the energy gap were calculated. • Dispersion parameters were determined using Wemple-DiDomenico relation. • The third order susceptibility and nonlinear refractive index were calculated. - Abstract: Zinc selenide (ZnSe) thin films with different thicknesses were evaporated onto glass substrates using the thermal evaporation technique. X-ray diffraction analysis confirmed that both the film and powder have cubic zinc-blende structure. The fundamental optical parameters like absorption coefficient, extinction coefficient and band gap were evaluated in transparent region of transmittance and reflectance spectrum. The optical transition of the films was found to be allowed, where the energy gap increased from 2.576 to 2.702 eV with increasing film thickness. Also, the refractive index value increase with increasing film thickness. The refractive indices evaluated through envelope method were extrapolated by Cauchy dispersion relationship over the whole spectra range. Additionally, the dispersion of refractive index was determined in terms of Wemple-DiDomenico single oscillator model. Third order susceptibility and nonlinear refractive index were determined for different thickness of ZnSe thin films.

  12. Photogenerated carriers transport behaviors in L-cysteine capped ZnSe core-shell quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Shan, Qingsong; Li, Kuiying, E-mail: kuiyingli@ysu.edu.cn; Lin, Yingying; Yin, Hua; Zhu, Ruiping [State Key Laboratory of Metastable Materials Manufacture Technology and Science, Yanshan University, Qinhuangdao 066004 (China); Xue, Zhenjie [Beijing National Laboratory for Molecular Sciences, Key Laboratory of Analytical Chemistry for Living Biosystems, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190 (China)

    2016-02-07

    The photoexcited carrier transport behavior of zinc selenide (ZnSe) quantum dots (QDs) with core–shell structure is studied because of their unique photoelectronic characteristics. The surface photovoltaic (SPV) properties of self-assembled ZnSe/ZnS/L-Cys core–shell QDs were probed via electric field induced surface photovoltage and transient photovoltage (TPV) measurements supplemented by Fourier transform infrared, laser Raman, absorption, and photoluminescence spectroscopies. The ZnSe QDs displayed p-type SPV characteristics with a broader stronger SPV response over the whole ultraviolet-to-near-infrared range compared with those of other core–shell QDs in the same group. The relationship between the SPV phase value of the QDs and external bias was revealed in their SPV phase spectrum. The wide transient photovoltage response region from 3.3 × 10{sup −8} to 2 × 10{sup −3} s was closely related to the long diffusion distance of photoexcited free charge carriers in the interfacial space–charge region of the QDs. The strong SPV response corresponding to the ZnSe core mainly originated from an obvious quantum tunneling effect in the QDs.

  13. Photogenerated carriers transport behaviors in L-cysteine capped ZnSe core-shell quantum dots

    Science.gov (United States)

    Shan, Qingsong; Li, Kuiying; Xue, Zhenjie; Lin, Yingying; Yin, Hua; Zhu, Ruiping

    2016-02-01

    The photoexcited carrier transport behavior of zinc selenide (ZnSe) quantum dots (QDs) with core-shell structure is studied because of their unique photoelectronic characteristics. The surface photovoltaic (SPV) properties of self-assembled ZnSe/ZnS/L-Cys core-shell QDs were probed via electric field induced surface photovoltage and transient photovoltage (TPV) measurements supplemented by Fourier transform infrared, laser Raman, absorption, and photoluminescence spectroscopies. The ZnSe QDs displayed p-type SPV characteristics with a broader stronger SPV response over the whole ultraviolet-to-near-infrared range compared with those of other core-shell QDs in the same group. The relationship between the SPV phase value of the QDs and external bias was revealed in their SPV phase spectrum. The wide transient photovoltage response region from 3.3 × 10-8 to 2 × 10-3 s was closely related to the long diffusion distance of photoexcited free charge carriers in the interfacial space-charge region of the QDs. The strong SPV response corresponding to the ZnSe core mainly originated from an obvious quantum tunneling effect in the QDs.

  14. Thickness-dependent dispersion parameters, energy gap and nonlinear refractive index of ZnSe thin films

    Energy Technology Data Exchange (ETDEWEB)

    Prakash, Deo [School of Computer Science & Engineering, Faculty of Engineering, SMVD University, Kakryal, Katra 182320, J& K (India); Shaaban, E.R., E-mail: esam_ramadan2008@yahoo.com [Physics Department, Faculty of Science, Al-Azhar University, Assiut 71542 (Egypt); Shapaan, M. [Department of Physics, Faculty of Science, Al-Azahar University, Cairo (Egypt); Mohamed, S.H. [Physics Department, Faculty of Science, Sohag University, 82524 Sohag (Egypt); Othman, A.A. [Physics Department, Faculty of Science, Assiut University, Assiut 71516 (Egypt); Verma, K.D., E-mail: kdverma1215868@gmail.com [Material Science Research Laboratory, Department of Physics, S. V. College, Aligarh 202001, U.P. (India)

    2016-08-15

    Highlights: • Combined experimental and theoretical researches on ZnSe Thin Films. • The film thickness and refractive index were determined using envelope method. • The absorption coefficient and the energy gap were calculated. • Dispersion parameters were determined using Wemple-DiDomenico relation. • The third order susceptibility and nonlinear refractive index were calculated. - Abstract: Zinc selenide (ZnSe) thin films with different thicknesses were evaporated onto glass substrates using the thermal evaporation technique. X-ray diffraction analysis confirmed that both the film and powder have cubic zinc-blende structure. The fundamental optical parameters like absorption coefficient, extinction coefficient and band gap were evaluated in transparent region of transmittance and reflectance spectrum. The optical transition of the films was found to be allowed, where the energy gap increased from 2.576 to 2.702 eV with increasing film thickness. Also, the refractive index value increase with increasing film thickness. The refractive indices evaluated through envelope method were extrapolated by Cauchy dispersion relationship over the whole spectra range. Additionally, the dispersion of refractive index was determined in terms of Wemple-DiDomenico single oscillator model. Third order susceptibility and nonlinear refractive index were determined for different thickness of ZnSe thin films.

  15. Microwave-assisted synthesis of L-glutathione capped ZnSe QDs and its interaction with BSA by spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Ding, Ling, E-mail: linda0911@163.com [College of Chemical Engineering and Technology, Wuhan University of Science and Technology, Wuhan 430081 (China); College of Resource and Environmental Sciences, Hubei Biomass-Resource Chemistry and Environmental Biotechnology Key Laboratory, Wuhan University, Wuhan 430079 (China); Zhou, Pei-Jiang, E-mail: zhoupj@whu.edu.cn [College of Resource and Environmental Sciences, Hubei Biomass-Resource Chemistry and Environmental Biotechnology Key Laboratory, Wuhan University, Wuhan 430079 (China); Zhan, Hong-Ju [College of Resource and Environmental Sciences, Hubei Biomass-Resource Chemistry and Environmental Biotechnology Key Laboratory, Wuhan University, Wuhan 430079 (China); Jingchu University of Technology, Jingmen 448000 (China); Chen, Chi [College of Resource and Environmental Sciences, Hubei Biomass-Resource Chemistry and Environmental Biotechnology Key Laboratory, Wuhan University, Wuhan 430079 (China); Hu, Wei [Wuhan Humanwell Pharmaceutical Co. Ltd, Wuhan 430064 (China); Zhou, Teng-Fei; Lin, Chao-Wang [College of Resource and Environmental Sciences, Hubei Biomass-Resource Chemistry and Environmental Biotechnology Key Laboratory, Wuhan University, Wuhan 430079 (China)

    2013-10-15

    Stable, water-soluble and biologically compatible ZnSe quantum dots (QDs) with L-glutathione (GSH) as a capping agent were synthesized in aqueous medium by microwave irradiation. The GSH/Zn/Se molar ratios, reaction temperature, time and pH are the crucial factors for properties of QDs. Fluorescence (FL) spectra, absorption spectra, transmission electron microscopy (TEM), X-ray powder diffraction (XRD) and Fourier transform infrared (FTIR) spectra studies showed that the optical properties of QDs were strong, shape of QDs was similar to spherical and the particle size was about 2–3 nm. The 42% quantum yield (QY) of QDs can be achieved without any post-preparative treatment. The interaction of QDs bioconjugated to bovine serum albumin (BSA) was also studied by absorption and FL spectra experiments. With addition of QDs, the FL intensity of BSA was largely quenched, which can be explained by static mechanism. The results suggested the QDs-BSA binding reaction was a static quenching. -- Highlights: • L-glutathione-capped ZnSe quantum dots were synthesized by microwave assisted in aqueous. • The facile synthesis of ZnSe QDs presented is simple and cost-effective. • Findings suggest the QDs possess highly quantum yield and narrow FWHM without any post-treatment. • The interaction mechanism between QDs and BSA is a static quenching.

  16. The influence of CdSe and ZnSe nanoparticles on the optical properties of Sm"3"+ ions in lead borate glasses

    International Nuclear Information System (INIS)

    Mallur, Saisudha B.; Heidorn, William D.; Fatokun, Stephen O.; Joshi, Krishna D.; Bista, Sandip S.; Babu, Panakkattu K.

    2017-01-01

    The effect of glass composition and the presence of CdSe/ZnSe nanoparticles (NPs) on the optical absorption and fluorescence of Sm-doped lead borate glasses are studied. Three sets of glass samples xPbO:(99.5-x) B_2O_3:0.5Sm_2O_3, x = 29.5–69.5 mol%, xPbO:(96.5-x) B_2O_3:0.5Sm_2O_3: 3CdSe/ZnSe, x = 36.5, and 56.5 mol% are prepared. NPs are grown by annealing these glasses just below the glass transition temperature. Average size of both types of NPs increases with annealing time; however, CdSe NPs grew to a larger size range (2 to 20 nm) compared to ZnSe NPs (1 to 16 nm). We analyzed the hypersensitive transition, intensity parameters, radiative transition probability, stimulated emission cross section (σ_p), and the area ratio of the electric dipole/magnetic dipole transitions of Sm"3"+. The intensity parameters show a minimum at 11 h annealing for 36.5 mol% and a maximum for the same annealing duration in 56.5 mol% PbO containing CdSe NPs. The σ_p for 56.5 mol% of PbO with CdSe NPs is found to be a maximum when the average NP size is around 14 nm. ZnSe NPs containing glasses also show significant changes in σ_p when the average particle size is ~16 nm, for 36.5 mol% PbO. Our results suggest that the optical properties of Sm"3"+ in lead borate glasses are sensitive to its electronic environment which can be modified by varying the base glass composition and/or incorporating large NPs of CdSe/ZnSe. The large σ_p values that we observe for some of the glass compositions make them attractive materials for photonic devices and photovoltaic applications.

  17. The influence of CdSe and ZnSe nanoparticles on the optical properties of Sm{sup 3+} ions in lead borate glasses

    Energy Technology Data Exchange (ETDEWEB)

    Mallur, Saisudha B.; Heidorn, William D.; Fatokun, Stephen O.; Joshi, Krishna D.; Bista, Sandip S.; Babu, Panakkattu K., E-mail: PK-Babu@wiu.edu [Western Illinois University, Department of Physics (United States)

    2017-03-15

    The effect of glass composition and the presence of CdSe/ZnSe nanoparticles (NPs) on the optical absorption and fluorescence of Sm-doped lead borate glasses are studied. Three sets of glass samples xPbO:(99.5-x) B{sub 2}O{sub 3}:0.5Sm{sub 2}O{sub 3}, x = 29.5–69.5 mol%, xPbO:(96.5-x) B{sub 2}O{sub 3}:0.5Sm{sub 2}O{sub 3}: 3CdSe/ZnSe, x = 36.5, and 56.5 mol% are prepared. NPs are grown by annealing these glasses just below the glass transition temperature. Average size of both types of NPs increases with annealing time; however, CdSe NPs grew to a larger size range (2 to 20 nm) compared to ZnSe NPs (1 to 16 nm). We analyzed the hypersensitive transition, intensity parameters, radiative transition probability, stimulated emission cross section (σ{sub p}), and the area ratio of the electric dipole/magnetic dipole transitions of Sm{sup 3+}. The intensity parameters show a minimum at 11 h annealing for 36.5 mol% and a maximum for the same annealing duration in 56.5 mol% PbO containing CdSe NPs. The σ{sub p} for 56.5 mol% of PbO with CdSe NPs is found to be a maximum when the average NP size is around 14 nm. ZnSe NPs containing glasses also show significant changes in σ{sub p} when the average particle size is ~16 nm, for 36.5 mol% PbO. Our results suggest that the optical properties of Sm{sup 3+} in lead borate glasses are sensitive to its electronic environment which can be modified by varying the base glass composition and/or incorporating large NPs of CdSe/ZnSe. The large σ{sub p} values that we observe for some of the glass compositions make them attractive materials for photonic devices and photovoltaic applications.

  18. Green synthesis of ZnSe and core–shell ZnSe@ZnS nanocrystals (NCs) using a new, rapid and room temperature photochemical approach

    Energy Technology Data Exchange (ETDEWEB)

    Molaei, M., E-mail: m.molaei@vru.ac.ir; Bahador, A.R.; Karimipour, M.

    2015-10-15

    In this work, ZnSe and core–shell ZnSe@ZnS nanocrystals (NCs) were synthesized using a one-pot, rapid and room temperature photochemical method. UV illumination provided the required energy for the chemical reactions. Synthesized NCs were characterized using X-ray diffraction spectroscopy (XRD), transmission electron microscopy (TEM), UV–vis and photoluminescence (PL) spectroscopy. XRD pattern indicated cubic zinc blende structure for ZnSe NCs and the TEM image indicated round-shaped particles, most of which had a diameter of about 3 nm. Band gap of ZnSe NCs was obtained as about 3.6 eV, which was decreased by increasing the illumination time. Synthesized NCs indicated intensive and narrow emission in the UV-blue area (370 nm) related to the excitonic recombination and a broad band emission with a peak located at about 490 nm originated from the DAP (donor–acceptor pairs) recombination. ZnS shell was grown on ZnSe cores using a reaction based on the photo-sensitivity of Na{sub 2}S{sub 2}O{sub 3}. For ZnSe@ZnS core–shell NCs, XRD diffraction peaks shifted to higher angles. TEM image indicated a shell around cores and most of the ZnSe@ZnS NCs have a diameter of about 5 nm. After the ZnS growth, ZnSe excitonic emission shifted to the longer wavelength and PL intensity was increased considerably. PL QY was obtained about 11% and 17% for ZnSe and ZnSe@ZnS core–shell QDs respectively. - Highlights: • A green photochemical approach was reported for synthesis of ZnSe NCs. • ZnS shell was grown around ZnSe using a new method. • Synthesis method was rapid, simple and at room temperature. • ZnSe NCs indicated a narrow UV-blue and a broad DAP emissions. • PL intensity was increased considerably by ZnS shell growth.

  19. Green synthesis of ZnSe and core–shell ZnSe@ZnS nanocrystals (NCs) using a new, rapid and room temperature photochemical approach

    International Nuclear Information System (INIS)

    Molaei, M.; Bahador, A.R.; Karimipour, M.

    2015-01-01

    In this work, ZnSe and core–shell ZnSe@ZnS nanocrystals (NCs) were synthesized using a one-pot, rapid and room temperature photochemical method. UV illumination provided the required energy for the chemical reactions. Synthesized NCs were characterized using X-ray diffraction spectroscopy (XRD), transmission electron microscopy (TEM), UV–vis and photoluminescence (PL) spectroscopy. XRD pattern indicated cubic zinc blende structure for ZnSe NCs and the TEM image indicated round-shaped particles, most of which had a diameter of about 3 nm. Band gap of ZnSe NCs was obtained as about 3.6 eV, which was decreased by increasing the illumination time. Synthesized NCs indicated intensive and narrow emission in the UV-blue area (370 nm) related to the excitonic recombination and a broad band emission with a peak located at about 490 nm originated from the DAP (donor–acceptor pairs) recombination. ZnS shell was grown on ZnSe cores using a reaction based on the photo-sensitivity of Na 2 S 2 O 3 . For ZnSe@ZnS core–shell NCs, XRD diffraction peaks shifted to higher angles. TEM image indicated a shell around cores and most of the ZnSe@ZnS NCs have a diameter of about 5 nm. After the ZnS growth, ZnSe excitonic emission shifted to the longer wavelength and PL intensity was increased considerably. PL QY was obtained about 11% and 17% for ZnSe and ZnSe@ZnS core–shell QDs respectively. - Highlights: • A green photochemical approach was reported for synthesis of ZnSe NCs. • ZnS shell was grown around ZnSe using a new method. • Synthesis method was rapid, simple and at room temperature. • ZnSe NCs indicated a narrow UV-blue and a broad DAP emissions. • PL intensity was increased considerably by ZnS shell growth

  20. Irradiation route to aqueous synthesis of highly luminescent ZnSe quantum dots and its function as a copper ion fluorescence sensor

    Energy Technology Data Exchange (ETDEWEB)

    Rao, Yeluri Narayana; Datta, Aparna [UGC-DAE Consortium for Scientific Research, Kolkata Centre, III/LB-8 Bidhannagar, Kolkata 700 098 (India); Das, Satyendra K. [Radiochemistry Division, Variable Energy Cyclotron Centre, 1/AF Bidhannagar, Kolkata 700 064 (India); Saha, Abhijit, E-mail: abhijit@alpha.iuc.res.in [UGC-DAE Consortium for Scientific Research, Kolkata Centre, III/LB-8 Bidhannagar, Kolkata 700 098 (India)

    2016-08-15

    Highlights: • Radiation chemical technique can provide a useful route for synthesis of ZnSe QDs. • Chelating nature of ethylene diamine is exploited for capping nanoparticles. • ZnSe QDs can be a suitable sensitive alternative to toxic cadmium-based system. • Cu(II) ion is probed by QDs in the presence of other physiologically relevant ions. - Abstract: Size-controlled synthesis of stable ZnSe QDs with narrow distribution in aqueous environment through conventional soft chemical method still poses a challenge. The proposed radiation assisted strategy demonstrates aqueous synthesis of stable, monodisperse and luminescent ZnSe QDs capped with chelating ethylene diamine under ambient conditions and at room temperature. Radiation chemical method facilitates in slow and in-situ release of selenium ion from sodium selenosulfate. The concentrations of precursors, such as zinc salt, selenium source, ethylene diamine and absorbed radiation (7–90 kGy) dose were optimized for obtaining good quality particles. Selective quenching of luminescence of as-synthesized quantum dots (QDs) by Cu{sup 2+} ions vis-à-vis other physiologically important cations provide evidence for use of ZnSe quantum dots as alternative to toxic Cd-based quantum dots to probe Cu{sup 2+} ions. The linear relation of ratio of loss in emission intensity as a function of concentration of Cu(II) indicates detection limit in nano-molar range.

  1. Mid-infrared Fe2+:ZnSe semiconductor saturable absorber mirror for passively Q-switched Er3+-doped ZBLAN fiber laser

    Directory of Open Access Journals (Sweden)

    Shougui Ning

    2018-02-01

    Full Text Available A mid-infrared (mid-IR semiconductor saturable absorber mirror (SESAM based on Fe2+:ZnSe for passively Q-switched Er3+-doped ZBLAN fiber laser has been demonstrated. Fe2+:ZnSe SESAM was fabricated by electron beam evaporation method. Fe2+ was innovatively doped into the reflective Bragg stack, in which ZnSe layer served as both doped matrix and high refractive layer during the fabricating process. By using the Fe2+:ZnSe SESAM, stable passively Q-switched pulses with the minimum pulse width of 0.43 μs under a repetition rate of 160.82 kHz were obtained. The recorded maximum average output power of 873 mW with a peak power of 12.59 W and pulse energy of 5.43 μJ were achieved. The results demonstrated a new method for fabricating Fe2+:ZnSe SESAM, which can be used in compact mid-IR Q-switched fiber laser.

  2. Study of the mobility activation in ZnSe thin films deposited using inert gas condensation

    Directory of Open Access Journals (Sweden)

    Jeewan Sharma

    2017-12-01

    Full Text Available ZnSe thin films were synthesized on glass substrates using the inert gas condensation technique at substrate temperature ranging from 25 °C to 100 °C. The hexagonal structure and average crystallite size (6.1–8.4 nm were determined from X-ray diffraction data. The transient photoconductivity was investigated using white light of intensity 8450 lx to deduce the effective density of states (Neff in the order of 1.02 × 1010–13.90 × 1010 cm−3, the frequency factor (S in the range 2.5 × 105–24.6 × 105 s−1 and the trap depth (E ranging between 0.37–0.64 eV of these films. The trap depth study revealed three different types of levels with quasi-continuous distribution below the conduction band. An increase in the photoconductivity was observed as a result of the formation of potential barriers (Vb and of the increase of carrier mobility at the crystallite boundaries. The study of the dependence of various mobility activation parameters on the deposition temperature and the crystallite size has provided better understanding of the mobility activation mechanism.

  3. Luminescence and electrophysical characteristics of ZnSe implanted with acceptor impurities

    CERN Document Server

    Georgobiani, A N; Dravin, V A; Lepnev, L S; Mullabaev, I D; Ursaki, V V; Iljukhina, Z P

    1999-01-01

    The investigation of traps and recombination centres in structures based on ZnSe single crystals by means of the deep level transient spectroscopy, photoluminescence and electroluminescence methods are presented. The implantation of Ag sup + , Au sup + and N sup + ions was used for the creation of these centres. The activation energies equal to 0.26, 0.35 and 0.86 eV were determined from the temperature dependencies of the carriers emission rate from DLTS spectra for majority carriers (electrons). The levels 0.42 and 0.26 eV were observed only in the samples implanted with Ag and Au, respectively. In the case of minority carriers (holes), in all the diodes produced by Ag sup + ions implantation, the depth of the trap was 0.30 eV. Traps with a depth of about 0.72 eV were observed independently on various kind of impurities. In all the cases when these impurities are used together with nitrogen a hole trap with a depth of 0.47 eV is observed. The concentrations and capture cross-sections of the centres were cal...

  4. Position-based dynamic of a particle system: a configurable algorithm to describe complex behaviour of continuum material starting from swarm robotics

    Science.gov (United States)

    dell'Erba, Ramiro

    2018-04-01

    In a previous work, we considered a two-dimensional lattice of particles and calculated its time evolution by using an interaction law based on the spatial position of the particles themselves. The model reproduced the behaviour of deformable bodies both according to the standard Cauchy model and second gradient theory; this success led us to use this method in more complex cases. This work is intended as the natural evolution of the previous one in which we shall consider both energy aspects, coherence with the principle of Saint Venant and we start to manage a more general tool that can be adapted to different physical phenomena, supporting complex effects like lateral contraction, anisotropy or elastoplasticity.

  5. Improving stability of photoluminescence of ZnSe thin films grown by molecular beam epitaxy by incorporating Cl dopant

    International Nuclear Information System (INIS)

    Wang, J. S.; Shen, J. L.; Chen, W. J.; Tsai, Y. H.; Wang, H. H.; Yang, C. S.; Chen, R. H.; Tsai, C. D.

    2011-01-01

    This investigation studies the effect of chlorine (Cl) dopant in ZnSe thin films that were grown by molecular beam epitaxy on their photoluminescence (PL) and the stability thereof. Free excitonic emission was observed at room-temperature in the Cl-doped sample. Photon irradiation with a wavelength of 404 nm and a power density of 9.1 W/cm 2 has a much stronger effect on PL degradation than does thermal heating to a temperature of 150 deg. C. Additionally, this study shows that the generation of nonradiative centers by both photon irradiation and thermal heating can be greatly inhibited by incorporating Cl dopant.

  6. Determination of shift in energy of band edges and band gap of ZnSe spherical quantum dot

    Science.gov (United States)

    Siboh, Dutem; Kalita, Pradip Kumar; Sarma, Jayanta Kumar; Nath, Nayan Mani

    2018-04-01

    We have determined the quantum confinement induced shifts in energy of band edges and band gap with respect to size of ZnSe spherical quantum dot employing an effective confinement potential model developed in our earlier communication "arXiv:1705.10343". We have also performed phenomenological analysis of our theoretical results in comparison with available experimental data and observe a very good agreement in this regard. Phenomenological success achieved in this regard confirms validity of the confining potential model as well as signifies the capability and applicability of the ansatz for the effective confining potential to have reasonable information in the study of real nano-structured spherical systems.

  7. A sensitive electrochemical chlorophenols sensor based on nanocomposite of ZnSe quantum dots and cetyltrimethylammonium bromide

    International Nuclear Information System (INIS)

    Li, Jianjun; Li, Xiao; Yang, Ran; Qu, Lingbo; Harrington, Peter de B.

    2013-01-01

    Graphical abstract: A very sensitive and simple electrochemical sensor for chlorophenols (CPs) based on nanocomposite of cetyltrimethylammonium bromide (CTAB) and ZnSe quantum dots (ZnSe–CTAB) through electrostatic self-assembly technology was built for the first time. The nanocomposite of ZnSe–CTAB introduced a favorable access for the electron transfer and showed excellent electrocatalytic activity for the oxidation of CPs. -- Highlights: •Nanocomposite based ZnSe QDs and CTAB was prepared and characterized. •A novel electrochemical sensor for the determination of CPs was built. •The proposed sensor was more sensitive, simple and environment-friendly. -- Abstract: In this work, a very sensitive and simple electrochemical sensor for chlorophenols (CPs) based on a nanocomposite of cetyltrimethylammonium bromide (CTAB) and ZnSe quantum dots (ZnSe–CTAB) through electrostatic self-assembly technology was built for the first time. The composite of ZnSe–CTAB introduced a favorable access for the electron transfer and gave superior electrocatalytic activity for the oxidation of CPs than ZnSe QDs and CTAB alone. Differential pulse voltammetry (DPV) was used for the quantitative determination of the CPs including 2-chlorophenol (2-CP), 2,4-dichlorophenol (2,4-DCP) and pentachlorophenol (PCP). Under the optimum conditions, the peak currents of the CPs were proportional to their concentrations in the range from 0.02 to 10.0 μM for 2-CP, 0.006 to 9.0 μM for 2,4-DCP, and 0.06 to 8.0 for PCP. The detection limits were 0.008 μM for 2-CP, 0.002 μM for 2,4-DCP, and 0.01 μM for PCP, respectively. The method was successfully applied for the determination of CPs in waste water with satisfactory recoveries. This ZnSe–CTAB electrode system provides operational access to design environment-friendly CPs sensors

  8. Fluorescence resonance energy transfer between ZnSe ZnS quantum dots and bovine serum albumin in bioaffinity assays of anticancer drugs

    Science.gov (United States)

    Shu, Chang; Ding, Li; Zhong, Wenying

    2014-10-01

    In the current work, using ZnSe ZnS quantum dots (QDs) as representative nanoparticles, the affinities of seven anticancer drugs for bovine serum albumin (BSA) were studied using fluorescence resonance energy transfer (FRET). The FRET efficiency of BSA-QD conjugates can reach as high as 24.87% by electrostatic interaction. The higher binding constant (3.63 × 107 L mol-1) and number of binding sites (1.75) between ZnSe ZnS QDs and BSA demonstrated that the QDs could easily associate to plasma proteins and enhance the transport efficacy of drugs. The magnitude of binding constants (103-106 L mol-1), in the presence of QDs, was between drugs-BSA and drugs-QDs in agreement with common affinities of drugs for serum albumins (104-106 L mol-1) in vivo. ZnSe ZnS QDs significantly increased the affinities for BSA of Vorinostat (SAHA), Docetaxel (DOC), Carmustine (BCNU), Doxorubicin (Dox) and 10-Hydroxycamptothecin (HCPT). However, they slightly reduced the affinities of Vincristine (VCR) and Methotrexate (MTX) for BSA. The recent work will not only provide useful information for appropriately understanding the binding affinity and binding mechanism at the molecular level, but also illustrate the ZnSe ZnS QDs are perfect candidates for nanoscal drug delivery system (DDS).

  9. Long-time Luminescence Kinetics of Localized excitons and conduction Band Edges Smearing in ZnSe(1-c)Tec Solid Solutions

    DEFF Research Database (Denmark)

    Klochikhin, O.; Ogloblin, S. G.; Permogorov, S.

    2000-01-01

    It is shown that the integrated luminescence intensity of localized excitons in solid solutions ZnSe(1 - c)Tec has a component slowly decaying with time. After the excitation above the mobility threshold, the long-time intensity decreases exponentially, with a fractional exponent changing from...

  10. Lean start-up

    DEFF Research Database (Denmark)

    Rasmussen, Erik Stavnsager; Tanev, Stoyan

    2016-01-01

    The risk of launching new products and starting new firms is known to be extremely high. The Lean Start-up approach is a way of reducing these risks and enhancing the chances for success by validating the products and services in the market with customers before launching it in full scale. The ma...... and the final business model. In other words: The start-up must first nail the problem together with the customers, then develop the solution and test, and then in the end scale it to a full-grown business model.......The risk of launching new products and starting new firms is known to be extremely high. The Lean Start-up approach is a way of reducing these risks and enhancing the chances for success by validating the products and services in the market with customers before launching it in full scale. The main...

  11. Starting an aphasia center?

    Science.gov (United States)

    Elman, Roberta J

    2011-08-01

    Starting an aphasia center can be an enormous challenge. This article provides initial issues to review and consider when deciding whether starting a new organization is right for you. Determining the need for the program in your community, the best size and possible affiliation for the organization, and available resources, as well as developing a business plan, marketing the program, and building awareness in the community, are some of the factors that are discussed. Specific examples related to starting the Aphasia Center of California are provided. © Thieme Medical Publishers.

  12. Early Head Start Evaluation

    Data.gov (United States)

    U.S. Department of Health & Human Services — Longitudinal information from an evaluation where children were randomly assigned to Early Head Start or community services as usual;direct assessments and...

  13. FEMA DFIRM Station Start

    Data.gov (United States)

    Minnesota Department of Natural Resources — This table contains information about station starting locations. These locations indicate the reference point that was used as the origin for distance measurements...

  14. Head Start Impact Study

    Data.gov (United States)

    U.S. Department of Health & Human Services — Nationally representative, longitudinal information from an evaluation where children were randomly assigned to Head Start or community services as usual;direct...

  15. Photon- and electron-induced surface voltage in electron spectroscopies on ZnSe(0 0 1)

    International Nuclear Information System (INIS)

    Cantoni, M.; Bertacco, R.; Brambilla, A.; Ciccacci, F.

    2009-01-01

    The surface band bending in ZnSe(0 0 1), as a function of the temperature, is investigated both in the valence band (by photoemission) and in the conduction band (by inverse photoemission and absorbed current spectroscopies). Two different mechanisms are invoked for interpreting the experimental data: the band bending due to surface states, and the surface voltage induced by the incident beam. While the latter is well known in photoemission (surface photovoltage), we demonstrate the existence of a similar effect in inverse photoemission and absorbed current spectroscopies, induced by the incident electrons instead of photons. These results point to the importance of considering the surface voltage effect even in electron-in techniques for a correct evaluation of the band bending.

  16. Characterization of the CH4/H2/Ar high density plasma etching process for ZnSe

    Science.gov (United States)

    Eddy, C. R.; Leonhardt, D.; Shamamian, V. A.; Butler, J. E.

    2001-05-01

    High density plasma etching of zinc selenide using CH4/H2/Ar plasma chemistries is investigated. Mass spectrometry, using through-the-platen sampling, is used to identify and monitor etch products evolving from the surface during etching. The identifiable primary etch products are Zn, Se, ZnH2, SeH2, Zn(CH3)2, and Se(CH3)2. Their concentrations are monitored as ion and neutral fluxes (both in intensity and composition), ion energy, and substrate temperature are varied. General insights about the surface chemistry mechanisms of the etch process are given from these observations. Regions of process parameter space best suited for moderate rate, anisotropic, and low damage etching of ZnSe are proposed.

  17. Discretization of the total magnetic field by the nuclear spin bath in fluorine-doped ZnSe.

    Science.gov (United States)

    Zhukov, E A; Kirstein, E; Kopteva, N E; Heisterkamp, F; Yugova, I A; Korenev, V L; Yakovlev, D R; Pawlis, A; Bayer, M; Greilich, A

    2018-05-16

    The coherent spin dynamics of fluorine donor-bound electrons in ZnSe induced by pulsed optical excitation is studied in a perpendicular applied magnetic field. The Larmor precession frequency serves as a measure for the total magnetic field exerted onto the electron spins and, surprisingly, does not increase linearly with the applied field, but shows a step-like behavior with pronounced plateaus, given by multiples of the laser repetition rate. This discretization occurs by a feedback mechanism in which the electron spins polarize the nuclear spins, which in turn generate a local Overhauser field adjusting the total magnetic field accordingly. Varying the optical excitation power, we can control the plateaus, in agreement with our theoretical model. From this model, we trace the observed discretization to the optically induced Stark field, which causes the dynamic nuclear polarization.

  18. Getting started with Unity

    CERN Document Server

    Felicia, Patrick

    2013-01-01

    Getting Started with Unity is written in an easy-to-follow tutorial format.""Getting Started with Unity"" is for[ 3D game developers[/color] who would like to learn how to use Unity3D and become familiar with its core features. This book is also suitable for intermediate users who would like to improve their skills. No prior knowledge of Unity3D is required.

  19. Microstructure and optical studies of electron beam evaporated ZnSe1−xTex nanocrystalline thin films

    International Nuclear Information System (INIS)

    Emam-Ismail, M.; El-Hagary, M.; Shaaban, E.R.; Al-Hedeib, A.M.

    2012-01-01

    Highlights: ► The structural and optical properties of ZnSeTe thin films were studied. ► The micro structural parameters of the films have been determined. ► The room temperature reflectance and transmittance data are analyzed. ► The refractive index and energy gap are determined. ► The single oscillator parameters were calculated. - Abstract: Nanocrystalline thin films of ZnSe 1−x Te x (0.0 ≤ x ≤ 1.0) were deposited on glass substrate using electron beam deposition technique. The structure of the prepared films was examined using X-ray diffraction technique and revealed that the deposited films have polycrystalline zinc blend structure with lattice constant, a, increasing linearly from 0.55816 to 0.59989 nm as x varies from 0 to 1. The optical studies of the nanocrystalline ZnSe 1−x Te x films showed that the refractive index increases and fundamental band gap E g decreases from 2.58 to 2.21 eV as the tellurium concentration increases from 0 to 1. Furthermore, it was also found that the variation of E g with composition shows quadratic behavior with bowing parameter equal to 0.105. In addition, the thickness and annealing effects on the structure and optical properties of the deposited films were also investigated. The refractive index dispersion and its dependence on composition were discussed in terms of single oscillator model proposed by Wemple–DiDomenico.

  20. Discriminative detection of bivalent Cu by dual-emission ZnSe quantum dot fluorescence sensing via ratiometric fluorescence measurements

    International Nuclear Information System (INIS)

    Wang, Chunlei; Zhou, Shujie; Xu, Shuhong; Wang, Zhuyuan; Cui, Yiping

    2014-01-01

    In this work, we showed that 1-thioglycerol (TG)-capped ZnSe quantum dots (QDs) with dual-emission could perform ideal QD fluorescence sensing for ratiometric fluorescence measurements. By comparing the fluorescence ratios at two emission peaks before and after the addition of cations, the discriminative detection of Cu(II) was realized, even in the case of co-existing with large amounts of other sensitive cations, such as Ag(I). The discriminative detection of Cu(II) is accurate with co-existing Ag(I) below 10 μmol L −1 . By a joint investigation of the ionic diffuse dynamics and carrier recombination dynamics, we found that the adsorbed layer of QDs plays a key role in the discriminative detection of Cu(II) from Ag(I) or other sensitive cations. The moderate adsorption capacity with a QD adsorbed layer makes Cu(II) capable of travelling across the QD double-layer structure, following a surface doping process via chemical reactions between Cu(II) and the QD surface atoms. As a result of Cu(II) doping, there were three major carrier recombination channels: the non-radiation recombination between the QD conduction band to the Cu(II) energy level, together with the non-radiation recombination and radiation recombination between the trap state energy levels and the Cu(II) energy level. As for Ag(I) and other sensitive cations, they have a strong adsorption capacity with the QD adsorbed layer, making them mainly present on the adsorbed layer. Due to the blocking of the ligand layer, we only observed weak coupling of the ZnSe conduction band with the Ag(I) energy level via a non-radiation recombination channel. (paper)

  1. White random lasing in mixture of ZnSe, CdS and CdSSe micropowders

    Science.gov (United States)

    Alyamani, A. Y.; Leanenia, M. S.; Alanazi, L. M.; Aljohani, M. M.; Aljariwi, A. A.; Rzheutski, M. V.; Lutsenko, E. V.; Yablonskii, G. P.

    2016-03-01

    Room temperature random lasing with white light emission in a mixture of AIIBVI semiconductor powders was achieved for the first time. The scattering gain media was formed by the mixture of closely packed active micron sized crystallites of ZnSe, CdS, CdSSe semiconductors. The micropowders were produced by grinding bulk crystals of each compound. Optical excitation was performed by 10-nanosecond pulses of tuned Ti:Al2O3-laser at 390 nm. The lasing in the mixture of semiconductor powders was achieved simultaneously at four wavelengths in blue, green, yellow and red spectral regions after exceeding the threshold excitation power density. A drastic integral intensity increase, spectrum narrowing and appearance of mode structure accompanied the laser action. ZnSe crystallites produce the laser light at about 460 nm while CdS particles - at about 520 nm. Two types of CdSSe semiconductor micropowders with different sulfur content lase at 580 nm and 660 nm. The threshold excitation power densities for all laser lines in the emission spectrum are approximately the same of about 0.9 MW/cm2. The sum of the emission spectrum of the mixture of the micropowders forms white light with high brightness. Lasing is due to an appearance of random feedback for amplified radiation in the active medium of closely packed light scattering crystallites. The presented results may find their applications for visualization systems, lighting technology, data transmission, medicine as biosensors and in identification systems. The key feature of random lasers is low cost of its production and possibility to be deposited on any type of surface.

  2. The effects of the impurity distribution on the electrical and optical properties of Cr2+:ZnSe nanowires: First-principles study

    Directory of Open Access Journals (Sweden)

    Shenyu Dai

    2018-03-01

    Full Text Available The structural, electrical and mid-infrared optical properties of wurtzite structured ZnSe nanowires with different Chromium impurity distribution are investigated using first-principles calculation based on density-functional theory (DFT. The formation energies have been calculated to study the relative stabilities of different Cr doping positions. It is shown that when the Cr doping position shifted from the center to the edge, the splitting energy between 5T2 and 5E levels of Cr d-orbitals is decreased and a redshift is observed in the calculated infrared absorption spectra. A probable reason for these effects of the impurity distribution is discussed. Keywords: First-principles, Nanowires, Impurity distribution, Cr-doped ZnSe

  3. Formation of clusters and the percolation threshold in a two-phase system with a random distribution of ZnSe quantum points

    Science.gov (United States)

    Bondar', N. V.

    2009-03-01

    A characteristic feature due to the formation of a percolation phase transition of carriers has been observed in a two-phase system consisting of borosilicate glass with ZnSe quantum dots. For near-threshold quantum-dot concentrations, changes due to microscopic fluctuations of the quantum-dot density have been observed in the intensities of radiation emission bands. This phenomenon is reminiscent of critical opalescence, where similar fluctuations of the density of a pure substance arise near a phase transition. It is proposed that the dielectric mismatch between the matrix and ZnSe plays a large role in the carrier (exciton) delocalization, resulting in the appearance of a "dielectric trap" on the interface and the formation there of surface states of excitons. The spatial overlapping of states which occurs at the critical concentration of quantum dots results in carrier tunneling and the appearance of a percolation transition in such a system.

  4. Properties of the ZnSe/ZnTe heterojunction prepared by a multi-source evaporation of ZnTe:Sb on ZnSe single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Romeo, N [Parma Univ. (Italy). Ist. di Fisica; First, F [Uniwersytet Mikolaja Kopernika, Torun (Poland). Inst. Fizyki; Seuret, D [Universidad de La Habana, (Cuba). Facultad de Fisica-Matematica

    1979-07-16

    A new method of preparation is described of a ZnSe/ZnTe heterojunction in which Sb-doped ZnTe is deposited by a multi-source apparatus on ZnSe monocrystals. The properties of the heterojunction was studied, esp. the I-U characteristic, the 1/C/sup 2/ plot as a function of applied voltage, the photocurrent spectrum, and the electroluminescence spectrum.

  5. Cadmium-free aqueous synthesis of ZnSe and ZnSe@ZnS core-shell quantum dots and their differential bioanalyte sensing potential

    Science.gov (United States)

    Mir, Irshad Ahmad; Rawat, Kamla; Bohidar, H. B.

    2016-10-01

    Herein we report a facile and cadmium-free approach to prepare water-soluble fluorescent ZnSe@ZnS core-shell quantum dots (QDs), using thioglycolic acid (TGA) ligand as a stabilizer and thiourea as a sulfur source. The optical properties and morphology of the obtained core-shell QDs were characterized by UV-vis and fluorescence spectroscopy, transmission electron microscopy (TEM), energy-dispersive x-ray analysis (EDX), x-ray diffraction (XRD), electrophoresis and dynamic light scattering (DLS) techniques. TEM analysis, and electrophoresis data showed that ZnSe core had an average size of 3.60 ± 0.12 nm and zeta potential of -38 mV; and for ZnSe@ZnS QDs, the mean size was 4.80 ± 0.20 nm and zeta potential was -45 mV. Compared to the core ZnSe QDs, the quantum yield of these core-shell structures was higher (13% versus 32%). These were interacted with five common bioanalytes such as, ascorbic acid, citric acid, oxalic acid, glucose and cholesterol which revealed fluorescence quenching due to concentration dependent binding of analytes to the core only, and core-shell QDs. The binding pattern followed the sequence: cholesterol ascorbic acid acid acid for ZnSe, and cholesterol acid ascorbic acid acid for core-shell QDs. Thus, enhanced binding was noticed for the analyte citric acid which may facilitate development of a fluorescence-based sensor based on the ZnSe core-only quantum dot platform. Further, the hydrophilic core-shell structure may find use in cell imaging applications.

  6. Getting started with Go

    CERN Multimedia

    CERN. Geneva

    2015-01-01

    No, not the Chinese boardgame, the programming language that ironically Google made difficult to google for. You may have heard of Golang, and are wondering whether you should learn it. The answer is that of course you should, and this talk should explain why and point you at the best resources to get started.

  7. The renaissance starts here

    International Nuclear Information System (INIS)

    Nedderman, John.

    1997-01-01

    The Asian Pacific Basin region has the highest rate of growth of anywhere in the world and its need for electricity is staggering. This is leading, noted a senior Korean official speaking at the 10th Pacific Basin Nuclear Conference, to a ''renaissance of nuclear power'' in Asia. Judging by the optimism in evidence at the conference, perhaps it has already started. (Author)

  8. Smart Start Evaluation Plan.

    Science.gov (United States)

    Bryant, Donna; Burchinal, Margaret; Buysse, Virginia; Kotch, Jonathan; Maxwell, Kelly; Neenan, Peter; Noblit, George; Orthner, Dennis; Peisner-Feinberg, Ellen; Telfair, Joseph

    Smart Start is North Carolina's partnership between state government and local leaders, service providers, and families to better serve children under 6 years of age and their families. This report describes the comprehensive plan to evaluate the state and local goals and objectives of the program, focusing on the components addressing the…

  9. ATLAS starts moving in

    CERN Multimedia

    2004-01-01

    The first large active detector component was lowered into the ATLAS cavern on 1 March. It consisted of the 8 modules forming the lower part of the central barrel of the tile hadronic calorimeter. The work of assembling the barrel, which comprises 64 modules, started the following day.

  10. Getting started with UDOO

    CERN Document Server

    Palazzetti, Emanuele

    2015-01-01

    If you are an Android developer who wants to learn how to use UDOO to build Android applications that are capable of interacting with their surrounding environment, then this book is ideal for you. Learning UDOO is the next great step to start building your first real-world prototypes powered by the Android operating system.

  11. Starting up the upstarts.

    Science.gov (United States)

    Greene, J

    1997-12-20

    Venture capitalists pour $1 billion a year into health care--and that investment may be the most overlooked indicator of new business opportunities. Signs show that companies focused on consolidation and cost-cutting are off the A list for risk capital. Instead, venture capitalists are targeting start-ups that save money on the front lines by truly managing care.

  12. Hot exciton relaxation in multiple layers CdSe/ZnSe self-assembled quantum dots separated by thick ZnSe barriers

    International Nuclear Information System (INIS)

    Eremenko, M; Budkin, G; Reznitsky, A

    2015-01-01

    We have studied PL and PLE spectra of two samples (A and B) of MBE grown CdSe/ZnSe asymmetric double quantum wells with different amount of deposited CdSe layers separated by 14 nm ZnSe barrier. It has been found that PLE spectra of the states forming short wavelength side of the PL spectra of both deep and shallow QWs of the sample A as well as that of deep QW of the sample B demonstrate oscillating structure in the spectral ranges corresponding to exciton states of self-assembled quantum dots only. Meanwhile PLE spectra of the short wavelength states of shallow QW the sample B revealed pronounced oscillating structure with energy period of ZnSe LO phonon under excitation with photons in a wide energy range both in the regions of quantum-dot states and in that of free states in the ZnSe barrier. In these spectra creating of excitons with kinetic energies more than 0.3 eV was observed which considerably exceed the exciton binding energy as well as LO phonon energy (both appr. 0.03 eV). It has been concluded that oscillating structure of the PLE spectra arises due to cascade relaxation of hot excitons. We discuss the model which explains these experimental findings. (paper)

  13. Hot exciton relaxation in multiple layers CdSe/ZnSe self-assembled quantum dots separated by thick ZnSe barriers

    Science.gov (United States)

    Eremenko, M.; Budkin, G.; Reznitsky, A.

    2015-11-01

    We have studied PL and PLE spectra of two samples (A and B) of MBE grown CdSe/ZnSe asymmetric double quantum wells with different amount of deposited CdSe layers separated by 14 nm ZnSe barrier. It has been found that PLE spectra of the states forming short wavelength side of the PL spectra of both deep and shallow QWs of the sample A as well as that of deep QW of the sample B demonstrate oscillating structure in the spectral ranges corresponding to exciton states of self-assembled quantum dots only. Meanwhile PLE spectra of the short wavelength states of shallow QW the sample B revealed pronounced oscillating structure with energy period of ZnSe LO phonon under excitation with photons in a wide energy range both in the regions of quantum-dot states and in that of free states in the ZnSe barrier. In these spectra creating of excitons with kinetic energies more than 0.3 eV was observed which considerably exceed the exciton binding energy as well as LO phonon energy (both appr. 0.03 eV). It has been concluded that oscillating structure of the PLE spectra arises due to cascade relaxation of hot excitons. We discuss the model which explains these experimental findings.

  14. Getting Started with Hibernate 3

    CERN Document Server

    Elliott, James

    2008-01-01

    Hibernate has clearly arrived. Are you ready to benefit from its simple way of working with relational databases as Java objects? This PDF updates the introductory material from the award-winning Hibernate: A Developer's Notebook to teach you how to jump right in and get productive with the current release of Hibernate. You'll be walked through the ins and outs of setting up Hibernate and some related tools that make it easier to use--and that may give you new ideas about how to store information in your Java programs. In short, this PDF gives you exactly the information you need to start u

  15. Getting started with Simulink

    CERN Document Server

    Zamboni, Luca

    2013-01-01

    This practical and easy-to-understand learning tutorial is one big exciting exercise for students and engineers that are always short on their schedules and want to regain some lost time with the help of Simulink.This book is aimed at students and engineers who need a quick start with Simulink. Though it's not required in order to understand how Simulink works, knowledge of physics will help the reader to understand the exercises described.

  16. Getting started with JUCE

    CERN Document Server

    Robinson, Martin

    2013-01-01

    his book is a fast-paced, practical guide full of step-by-step examples which are easy to follow and implement.This book is for programmers with a basic grasp of C++. The examples start at a basic level, making few assumptions beyond fundamental C++ concepts. Those without any experience with C++ should be able to follow and construct the examples, although you may need further support to understand the fundamental concepts.

  17. Getting started with Hazelcast

    CERN Document Server

    Johns, Mat

    2013-01-01

    Written as a step-by-step guide, Getting Started with Hazelcast will teach you all you need to know to make your application data scalable.This book is a great introduction for Java developers, software architects, or developers looking to enable scalable and agile data within their applications. You should have programming knowledge of Java and a general familiarity with concepts like data caching and clustering.

  18. Start-up procedure

    International Nuclear Information System (INIS)

    Marchl, A.; Krebs, W.D.; Aleite, W.

    1975-01-01

    The start-up procedure will be shown on a pressurized water reactor, although most of the activities will occur similarly in other reactor types. The commissioning time can be divided into 5 sections, the phases A to E together lasting 26 months. Subsequently there are a test run of one month and the handling-over of the plant to the operator. A survey of the commissioning sections with several important main events is shown. (orig./TK) [de

  19. Jump Starting Entrepreneurship

    DEFF Research Database (Denmark)

    Burcharth, Ana; Smith, Pernille; Frederiksen, Lars

    How do laid-off employees become entrepreneurs after receiving a dream start into self-employment? This question is relevant for policy makers and entrepreneurship researchers alike since it raises the possibility of a reverse entrepreneurial opportunity, in which the chance of becoming an entrep......How do laid-off employees become entrepreneurs after receiving a dream start into self-employment? This question is relevant for policy makers and entrepreneurship researchers alike since it raises the possibility of a reverse entrepreneurial opportunity, in which the chance of becoming...... an entrepreneur emerges before the discovery of a profitable opportunity. We empirically examine this question on the unique setting of a corporate entrepreneurship program. In the midst of a corporate crisis, Nokia supported laid-off employees to start their own ventures under favorable conditions. We...... persevered in their endeavors and eventually became comfortable with their new career prospects. We discuss the psychological factors that impact career transition after organizational closure and theorize weather they encourage or discourage entrepreneurship....

  20. Nutriendo la Promesa: Materiales Para la Aplicacion de las Normas de Ejecucion del Programa Head Start. Guia Para la Utilizacion de los Materiales [y] Transparencias (Nurturing the Promise: Set of Training Materials on the Head Start Program Performance Standards. User's Guide [and] Set of Transparencies).

    Science.gov (United States)

    Educational Services, Inc., Washington, DC.

    Since 1975, the Head Start Program Performance Standards have defined the services that local programs are required to provide to enrolled children and families. With revisions effective in 1998, the Program Performance Standards translate the Head Start vision into quality practices implemented at the local level. This document is comprised of a…

  1. Theoretical investigation of electronic, magnetic and optical properties of ZnSe doped TM and co-doped with MnTM (TM: Fe, Cr, Co): AB-initio study

    Energy Technology Data Exchange (ETDEWEB)

    Behloul, M. [LMPHE (URAC 12), Departement of Physique, B.P. 1014, Faculty of Science, University Mohammed V, Rabat (Morocco); Salmani, E., E-mail: elmehdisalmani@gmail.com [LMPHE (URAC 12), Departement of Physique, B.P. 1014, Faculty of Science, University Mohammed V, Rabat (Morocco); Ez-Zahraouy, H. [LMPHE (URAC 12), Departement of Physique, B.P. 1014, Faculty of Science, University Mohammed V, Rabat (Morocco); Benyoussef, A. [LMPHE (URAC 12), Departement of Physique, B.P. 1014, Faculty of Science, University Mohammed V, Rabat (Morocco); The Institute for Nanomaterials and Nanotechnology, MAScIR (Moroccan Fondation for Advanced Science, Innovation and Research), Rabat (Morocco)

    2016-12-01

    Based upon the first principal spin density functional calculation, the electronic, magnetic and optical properties of ZnTMSe and ZnMnTMSe where TM=Fe, Cr, Co are studied using the Korringa-Kohn-Rostoker coherent potential approximation (KKR-CPA) method within the local density (LDA)and the self-interaction-corrected(SIC) approximation. The purpose of this study is to determine the effect of different type of dopant and concentration on ferromagnetic and half metallic behavior of ZnSe. Therefore the magnetic disorder local moment (DLM) and the ferromagnetic state are investigated for different concentrations of Mn, Fe, Cr and Co; also the advantages of co-doped ZnSe with TM elements, behavior at room temperature are discussed. The electronic structure and optical properties are studied employing the local density (LDA) and the self-interaction-corrected (SIC) approximation. Moreover, the X-ray spectra modeling are in good agreement with the electronic and magnetic properties results. - Highlights: • The magnetic properties of ZnSe codoped with MnY(Y: Fe, Cr, Co) has been investigated. • The half-metallic appears in ZnSe codoped with impurities at low concentration. • The advantages of codoped ZnSe with impurities at room temperature are discussed.

  2. En god start

    DEFF Research Database (Denmark)

    Sievertsen, Hans Henrik

    I Danmark er det muligt at afvige fra reglen om, at barnet skal starte i skole det kalenderår, hvor barnet fylder 6 år. Det gør 10-15 procent af en årgang, mens 80-90 procent af børnene følger normen, og 2-3 procent starter i skole et år tidligere end normen, viser en analyse baseret på børn født i...

  3. Getting Started with Processing

    CERN Document Server

    Reas, Casey

    2010-01-01

    Learn computer programming the easy way with Processing, a simple language that lets you use code to create drawings, animation, and interactive graphics. Programming courses usually start with theory, but this book lets you jump right into creative and fun projects. It's ideal for anyone who wants to learn basic programming, and serves as a simple introduction to graphics for people with some programming skills. Written by the founders of Processing, this book takes you through the learning process one step at a time to help you grasp core programming concepts. You'll learn how to sketch wi

  4. Getting started with Arduino

    CERN Document Server

    Banzi, Massimo

    2011-01-01

    Arduino is the open-source electronics prototyping platform that's taken the design and hobbyist world by storm. This thorough introduction, updated for Arduino 1.0, gives you lots of ideas for projects and helps you work with them right away. From getting organized to putting the final touches on your prototype, all the information you need is here! Inside, you'll learn about: Interaction design and physical computingThe Arduino hardware and software development environmentBasics of electricity and electronicsPrototyping on a solderless breadboardDrawing a schematic diagram Getting started

  5. Getting Started with Netduino

    CERN Document Server

    Walker, Chris

    2012-01-01

    Start building electronics projects with Netduino, the popular open source hardware platform that's captured the imagination of makers and hobbyists worldwide. This easy-to-follow book provides the step-by-step guidance you need to experiment with Netduino and the .NET Micro Framework. Through a set of simple projects, you'll learn how to create electronic gadgets-including networked devices that communicate over TCP/IP. Along the way, hobbyists will pick up the basics of .NET programming, and programmers will discover how to work with electronics and microcontrollers. Follow the projects in

  6. Ultrathin ZnSe nanowires: one-pot synthesis via a heat-triggered precursor slow releasing route, controllable Mn doping and application in UV and near-visible light detection.

    Science.gov (United States)

    Li, Dong; Xing, Guanjie; Tang, Shilin; Li, Xiaohong; Fan, Louzhen; Li, Yunchao

    2017-10-12

    We report herein a heat-triggered precursor slow releasing route for the one-pot synthesis of ultrathin ZnSe nanowires (NWs), which relies on the gradual dissolving of Se powder into oleylamine containing a soluble Zn precursor under heating. This route allows the reaction system to maintain a high monomer concentration throughout the entire reaction process, thus enabling the generation of ZnSe NWs with diameter down to 2.1 nm and length approaching 400 nm. The size-dependent optical properties and band-edge energy levels of the ZnSe NWs were then explored in depth by UV-visible spectroscopy and cyclic voltammetry, respectively. Considering their unique absorption properties, these NWs were specially utilized for fabricating photoelectrochemical-type photodetectors (PDs). Impressively, the PDs based on the ZnSe NWs with diameters of 2.1 and 4.5 nm exhibited excellent responses to UVA and near-visible light, respectively: both possessed ultrahigh on/off ratios (5150 for UVA and 4213 for near-visible light) and ultrawide linear response ranges (from 2.0 to 9000 μW cm -2 for UVA and 5.0 to 8000 μW cm -2 for near-visible light). Furthermore, these ZnSe NWs were selectively doped with various amounts of Mn 2+ to tune their emission properties. As a result, ZnSe NW film-based photochromic cards were creatively developed for visually detecting UVA and near-visible radiation.

  7. Starting physiology: bioelectrogenesis.

    Science.gov (United States)

    Baptista, Vander

    2015-12-01

    From a Cartesian perspective of rational analysis, the electric potential difference across the cell membrane is one of the fundamental concepts for the study of physiology. Unfortunately, undergraduate students often struggle to understand the genesis of this energy gradient, which makes the teaching activity a hard task for the instructor. The topic of bioelectrogenesis encompasses multidisciplinary concepts, involves several mechanisms, and is a dynamic process, i.e., it never turns off during the lifetime of the cell. Therefore, to improve the transmission and acquisition of knowledge in this field, I present an alternative didactic model. The design of the model assumes that it is possible to build, in a series of sequential steps, an assembly of proteins within the membrane of an isolated cell in a simulated electrophysiology experiment. Initially, no proteins are inserted in the membrane and the cell is at a baseline energy state; the extracellular and intracellular fluids are at thermodynamic equilibrium. Students are guided through a sequence of four steps that add key membrane transport proteins to the model cell. The model is simple at the start and becomes progressively more complex, finally producing transmembrane chemical and electrical gradients. I believe that this didactic approach helps instructors with a more efficient tool for the teaching of the mechanisms of resting membrane potential while helping students avoid common difficulties that may be encountered when learning this topic. Copyright © 2015 The American Physiological Society.

  8. LEP dismantling starts

    CERN Multimedia

    2000-01-01

    Since the end of November, various teams have been getting stuck into dismantling the LEP accelerator and its four experiments. After making the installations safe, the dismantling and removal of 40,000 tonnes of equipment is underway. Down in the tunnel, it is a solemn moment. It is 10 o'clock on 13 December and Daniel Regin, one of those heading the dismantling work, moves in on a magnet, armed with a hydraulic machine. Surrounded by teams gathered there for a course in dismantling, he makes the first cut into LEP. The great deconstruction has begun. In little over than a year, the accelerator will have been cleared away to make room for its successor, the LHC. The start of the operation goes back to 27 November. Because before setting about the machine with hydraulic shears and monkey wrenches, LEP had first to be made safe - it was important to make sure the machine could be taken apart without risk. All the SPS beam injection systems to LEP were cut off. The fluids used for cooling the magnets and superc...

  9. An impressive start

    CERN Multimedia

    2011-01-01

    This has been an excellent week for the LHC, with a succession of fills rapidly increasing the number of proton bunches to 194 per beam. This has allowed the experiments to reach a peak luminosity of 2.5 × 1032 cm-2s-1, thereby surpassing the record for 2010 where we reached 2.0 × 1032 cm-2s-1. At the time of writing, the integrated luminosity delivered by the LHC in 2011 is around 28 inverse picobarns, which is already more than half of the total 2010 dataset.   These are impressive numbers, but what impresses me most is how quickly the LHC operators are now able to turn the machine around between fills, and how well LHC running has been incorporated into the overall operation of CERN’s accelerator complex. The flexibility of the LHC was illustrated on Thursday when we started a short phase of running at 1.38 TeV per beam, equivalent to the energy-per-nucleon of a lead-ion run. This lower energy data will be used by the experiments, in particular by ALICE, to compare...

  10. ATLAS starts moving in

    CERN Multimedia

    Della Mussia, S

    2004-01-01

    The first large active detector component was lowered into the ATLAS cavern on 1st March. It consisted of the 8 modules forming the lower part of the central barrel of the tile hadronic calorimeter. The work of assembling the barrel, which comprises 64 modules, started the following day. Two road trailers each with 64 wheels, positioned side by side. This was the solution chosen to transport the lower part of the central barrel of ATLAS' tile hadronic calorimeter from Building 185 to the PX16 shaft at Point 1 (see Figure 1). The transportation, and then the installation of the component in the experimental cavern, which took place over three days were, to say the least, rather spectacular. On 25 February, the component, consisting of eight 6-metre modules, was loaded on to the trailers. The segment of the barrel was transported on a steel support so that it wouldn't move an inch during the journey. On 26 February, once all the necessary safety checks had been carried out, the convoy was able to leave Buildi...

  11. Molecular beam epitaxial growth mechanism of ZnSe epilayers on (100) GaAs as determined by reflection high-energy electron diffraction, transmission electron microscopy and X-ray diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Ruppert, P.; Hommel, D.; Behr, T.; Heinke, H.; Waag, A.; Landwehr, G. (Physikalisches Inst., Univ. Wuerzburg (Germany))

    1994-04-14

    The properties of molecular beam epitaxial growth of ZnSe epilayers deposited directly on a GaAs substrate are compared to those grown on a GaAs buffer layer. The superior quality of the latter is confirmed by RHEED, TEM and X-ray diffraction. Based on RHEED oscillation studies, a model explaining the dependence of the ZnSe growth rate on Zn and Se fluxes and the substrate temperature is developed taking into account physisorbed and chemisorbed states. For partially relaxed epilayers, the correlation between the relaxation state and the crystalline mosaicity, as found by high resolution X-ray diffraction, is discussed

  12. Semiconductor laser with longitudinal electron-beam pumping and based on a quantum-well ZnCdSe/ZnSe structure grown on a ZnSe substrate by molecular beam epitaxy

    International Nuclear Information System (INIS)

    Kozlovskii, Vladimir I; Korostelin, Yurii V; Skasyrsky, Yan K; Shapkin, P V; Trubenko, P A; Dianov, Evgenii M

    1998-01-01

    The method of molecular beam epitaxy on a ZnSe substrate was used to grow a ZnCdSe/ZnSe structure with 115 quantum wells. This structure was made up into a cavity which included part of the substrate. Lasing was excited by longitudinal pumping with a scanning electron beam of E e = 40 - 70 keV energy. At T = 80 K for E e = 65 keV the threshold current density was 60 A cm -2 and the output power was 0.15 W at the 465 nm wavelength. At T= 300 K the lasing (λ= 474 nm) occurred in the ZnSe substrate. (lasers)

  13. From Head Start to Sure Start: Reflections on Policy Transfer

    Science.gov (United States)

    Welshman, John

    2010-01-01

    This article uses the history of debates over the US Head Start programme (1965), Early Head Start (1994) and the UK Sure Start initiative (1998), as a window on to policy transfer. In all the three, the aim was that early intervention could offer a means of boosting children's educational attainment and of countering the wider effects of poverty…

  14. Materialism.

    Science.gov (United States)

    Melnyk, Andrew

    2012-05-01

    Materialism is nearly universally assumed by cognitive scientists. Intuitively, materialism says that a person's mental states are nothing over and above his or her material states, while dualism denies this. Philosophers have introduced concepts (e.g., realization and supervenience) to assist in formulating the theses of materialism and dualism with more precision, and distinguished among importantly different versions of each view (e.g., eliminative materialism, substance dualism, and emergentism). They have also clarified the logic of arguments that use empirical findings to support materialism. Finally, they have devised various objections to materialism, objections that therefore serve also as arguments for dualism. These objections typically center around two features of mental states that materialism has had trouble in accommodating. The first feature is intentionality, the property of representing, or being about, objects, properties, and states of affairs external to the mental states. The second feature is phenomenal consciousness, the property possessed by many mental states of there being something it is like for the subject of the mental state to be in that mental state. WIREs Cogn Sci 2012, 3:281-292. doi: 10.1002/wcs.1174 For further resources related to this article, please visit the WIREs website. Copyright © 2012 John Wiley & Sons, Ltd.

  15. Radioactive starting aids for electrodeless light sources

    International Nuclear Information System (INIS)

    Proud, J.M.; Regan, R.J.; Haugsjaa, P.O.; Baird, D.H.

    1980-01-01

    The use of radioactive sources of α particles, β particles or γ rays as aids in starting a discharge in an electrodeless light source is discussed. The advantages of siting the sources at various positions in the device are discussed. Preferred materials are 85 Kr and 241 Am. (U.K.)

  16. Starting a New Chapter

    Directory of Open Access Journals (Sweden)

    Loza-Murguia Manuel G.

    2011-08-01

    Full Text Available In this new stage we want to improve the magazine to make it useful for readers, on the one hand we intend to maintain their accreditation project of the contents of the magazine and on the other hand, the boost in indexing websites popularity, who raise the visibility and therefore coverage to authors and readers who have honored us with their support and we receive frequent visits. Obviously all the works received will remain subject to internal assessment and peer review as usual. Your acceptance will be based on significance, originality and validity of the material presented. The journal is indexed by the time DIALNET. The half-yearly, from 2012 we intend to be a leader in information that is intended to finding solutions to the problems latent, on the other side seeks to raise awareness among professionals and researchers that the publication is a prerequisite to in order to will be clear what is being done as has research in the region. The Journal of the Selva Andina Research Society is a journal founded no more than two years, having failed to publish any number of this enormous amount of material in all this time. We are currently under evaluation by the SciELO Project, Bolivia and have the confidence to be meeting all the criteria that are required to be visible on the website of international prestige. We want to be a reference publication in the journal Public areas both in the international literature (particularly in Latin America and in Bolivia. As Director and Editor in Chief continued in front of it, I thank the Board of the Supreme Council on Science and Biotechnology Research Society Selva Andina renewed confidence in me during these early years, all the items they want be published should be sent to infoselvandina@gmail.com or boliviamanloza@yahoo.com. Following the usual guidelines and rules are expressed in the publication. There is an Editorial Board comprised of leading national and international professional experts who

  17. School Starting Age and Crime

    DEFF Research Database (Denmark)

    Landersø, Rasmus; Nielsen, Helena Skyt; Simonsen, Marianne

    This paper investigates the effects of school starting age on crime while relying on variation in school starting age induced by administrative rules; we exploit that Danish children typically start first grade in the calendar year they turn seven, which gives rise to a discontinuity in children......’s school starting age. Analyses are carried out using register-based Danish data. We find that higher age at school start lowers the propensity to commit crime, but that this reduction is caused by incapacitation while human capital accumulation is unaffected. Importantly, we also find that the individuals...

  18. Influence of pH on luminescence from water-soluble colloidal Mn-doped ZnSe quantum dots capped with different mercaptoacids

    International Nuclear Information System (INIS)

    Hardzei, Maryia; Artemyev, Mikhail

    2012-01-01

    Water-soluble ZnSe/ZnS core–shell quantum dots with ZnSe core doped by manganese ions show different luminescence response to pH changes in aqueous solutions depending on the type of solubilizing agents (thioglycolic acid, mercaptoundecanoic acid, sodium mercaptopropylsulfonate). In the case of long-chain mercaptoundecanoic acid only excitonic emission is affected by pH changes. Short-chain thioglycolic acid brings about equal excitonic/Mn emission variations with pH, while mercaptopropylsulfonate-stabilized quantum dots are insensitive to pH. The mechanism discussed here is based on the competition between different relaxation channels for excited excitons in ZnSe: excitonic radiative recombination, energy transfer to Mn ion and the photogenerated electron trapping due to the presence of protonated carboxyl group. ZnSe:Mn/ZnS quantum dots stabilized with long-chain mercaptoacids may be used as a new type of fluorescence ratiometric pH-sensor or indicator. - Highlights: ► Prepared ZnSe:Mn/ZnS quantum dots capped with different mercaptoacids in water. ► Photoluminescence intensity of ZnSe:Mn/ZnS quantum dots varied with pH. ► Character of luminescence variations depends on the sort of mercaptoacid capping. ► Competition between different excitonic relaxation channels for different caps.

  19. Structure and properties of ZnSxSe1-x thin films deposited by thermal evaporation of ZnS and ZnSe powder mixtures

    Science.gov (United States)

    Valeev, R. G.; Romanov, E. A.; Vorobiev, V. L.; Mukhgalin, V. V.; Kriventsov, V. V.; Chukavin, A. I.; Robouch, B. V.

    2015-02-01

    Interest to ZnSxSe1-x alloys is due to their band-gap tunability varying S and Se content. Films of ZnSxSe1-x were grown evaporating ZnS and ZnSe powder mixtures onto SiO2, NaCl, Si and ITO substrates using an original low-cost method. X-ray diffraction patterns and Raman spectroscopy, show that the lattice structure of these films is cubic ZnSe-like, as S atoms replace Se and film compositions have their initial S/Se ratio. Optical absorption spectra show that band gap values increase from 2.25 to 3 eV as x increases, in agreement with the literature. Because S atomic radii are smaller than Se, EXAFS spectra confirm that bond distances and Se coordination numbers decrease as the Se content decreases. The strong deviation from linearity of ZnSe coordination numbers in the ZnSxSe1-x indicate that within this ordered crystal structure strong site occupation preferences occur in the distribution of Se and S ions. The behavior is quantitatively confirmed by the strong deviation from the random Bernoulli distribution of the three sight occupation preference coefficients of the strained tetrahedron model. Actually, the ternary ZnSxSe1-x system is a bi-binary (ZnS+ZnSe) alloy with evanescent formation of ternary configurations throughout the x-range.

  20. Formation and reconstruction of Se nanoislands at the surface of thin epitaxial ZnSe layers grown on GaAs substrates

    Energy Technology Data Exchange (ETDEWEB)

    Kozlovskiy, V. I.; Krivobok, V. S., E-mail: krivobok@lebedev.ru [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation); Kuznetsov, P. I.; Nikolaev, S. N.; Onistchenko, E. E.; Pruchkina, A. A.; Temiryazev, A. G. [Russian Academy of Sciences, Kotel’nikov Institute of Radio-Engineering and Electronics (Russian Federation)

    2016-05-15

    Strained epitaxial ZnSe layers are grown on GaAs substrates by the method of vapor-phase epitaxy from metal-organic compounds. It is found that Se nanoislands with a density of 10{sup 8} to 10{sup 9} cm{sup –2} are formed at the surface of such layers. It is established that an increase in the size of Se islands and a decrease in their density take place after completion of growth. Annealing in a H{sub 2} atmosphere at a temperature higher than 260°C leads to the disappearance of Se islands and to a decrease in the surface roughness. It is shown that annealing does not lead to deterioration of the structural perfection of the epitaxial ZnSe films; rather, annealing gives rise to a decrease in the intensity of impurity–defect luminescence and to an increase in the intensity of intrinsic radiation near the bottom of the exciton band.

  1. Materials

    CSIR Research Space (South Africa)

    Van Wyk, Llewellyn V

    2009-02-01

    Full Text Available . It is generally included as part of a structurally insulated panel (SIP) where the foam is sandwiched between external skins of steel, wood or cement. Cement composites Cement bonded composites are an important class of building materials. These products... for their stone buildings, including the Egyptians, Aztecs and Inca’s. As stone is a very dense material it requires intensive heating to become warm. Rocks were generally stacked dry but mud, and later cement, can be used as a mortar to hold the rocks...

  2. Later Start, Longer Sleep: Implications of Middle School Start Times

    Science.gov (United States)

    Temkin, Deborah A.; Princiotta, Daniel; Ryberg, Renee; Lewin, Daniel S.

    2018-01-01

    Background: Although adolescents generally get less than the recommended 9 hours of sleep per night, research and effort to delay school start times have generally focused on high schools. This study assesses the relation between school start times and sleep in middle school students while accounting for potentially confounding demographic…

  3. Tips for Starting Physical Activity

    Science.gov (United States)

    ... Legislative Information Advisory & Coordinating Committees Strategic Plans & Reports Research Areas FAQs ... Starting Physical Activity Related Topics Section Navigation Tips to Help You Get Active ...

  4. Scheduling with target start times

    NARCIS (Netherlands)

    Hoogeveen, J.A.; Velde, van de S.L.; Klein Haneveld, W.K.; Vrieze, O.J.; Kallenberg, L.C.M.

    1997-01-01

    We address the single-machine problem of scheduling n independent jobs subject to target start times. Target start times are essentially release times that may be violated at a certain cost. The goal is to minimize an objective function that is composed of total completion time and maximum

  5. Contribution to the study of electronic structure of crystalline semiconductors (Si, Ge, GaAs, Gap, ZnTe, ZnSe

    Directory of Open Access Journals (Sweden)

    Bouhafs B.

    2012-06-01

    Full Text Available The band structure of semiconductors was described by several theorists since the Fifties. The main objective of the present paper is to do a comparative study between various families of semi-conductors IV (Si,Ge, III-V (GaAs, GaP and II-VI (ZnSe, ZnTe with both methods; tight Binding1 method and pseudo potential method2. This work enables us to understand as well as the mechanism of conduction process in these semiconductors and powers and limits of the above methods. The obtained results allow to conclude that both methods are in a good agreement to describe the morphology of band structures of the cited semiconductors. This encourages us to study in the future the electronic behaviour through the structure of bands for more complex systems such as the heterostructures.

  6. Jahn-Teller coupling of Cr2+ ion with degenerate modes in ZnS, ZnSe, and ZnTe crystals: microscopic treatment

    International Nuclear Information System (INIS)

    Natadze, A.L.; Ryskin, A.I.

    1980-01-01

    The Jahn-Teller (JT) interaction energy is calculated for 5 T 2 and 5 E states of the Cr 2+ ion in ZnS, ZnSe, and ZnTe crystals. The calculations are made within the framework of a particular microscopic model of the crystal field in the distorted crystal (model of point-like exchange charges), the multimode interaction is taken into account. For the 5 T 2 term the energies of interaction with tetragonal and trigonal modes are of the same order of magnitude. This circumstance results in a small height of the barriers that separate various minima of the adiabatic potential and is responsible for the dynamic aspect of the static JT effect in these systems. (author)

  7. Pressure dependence of elastic and dynamical properties of zinc-blende ZnS and ZnSe from first principle calculation

    Directory of Open Access Journals (Sweden)

    H.Y. Wang

    2012-03-01

    Full Text Available The density-functional theory (DFT and density-functional perturbation theory (DFPT are employed to study the pressure dependence of elastic and dynamical properties of zinc-blende ZnS and ZnSe. The calculated elastic constants and phonon spectra from 0 GPa to 15 GPa are compared with the available experimental data. Generally, our calculated values are overestimated with experimental data, but agree well with recent other theoretical values. The discrepancies with experimental data are due to the use of local density approximation (LDA and effect of temperature. In this work, in order to compare with experimental data, we calculated and discussed the pressure derivatives of elastic constants, the pressure dependence of dynamical effect charge, and mode Grüneisen parameter at Γ.

  8. Improving NPT safeguards. Particularly at the natural uranium starting point

    International Nuclear Information System (INIS)

    Harry, J.; Klerk, P. de

    1996-03-01

    According to the Non Proliferation Treaty (NPT) all nuclear material is subject to safeguards, but according to INFCIRC/153 the full range of safeguards is only applied beyond the 'starting point of safeguards', that is: The point at which nuclear material has reached a composition and purity suitable for fuel fabrication or enrichment. This paper addresses the two questions: (a) is the starting point adequately defined, and (b) what mesures could be applied to nuclear material before the starting point? Those questions have been asked before, some of the answers in this paper are new. (orig.)

  9. Improving NPT safeguards. Particularly at the natural uranium starting point

    Energy Technology Data Exchange (ETDEWEB)

    Harry, J. [Netherlands Energy Research Foundation (ECN), Petten (Netherlands); Klerk, P. de [Ministry of Foreign Affairs, The Hague (Netherlands)

    1996-03-01

    According to the Non Proliferation Treaty (NPT) all nuclear material is subject to safeguards, but according to INFCIRC/153 the full range of safeguards is only applied beyond the `starting point of safeguards`, that is: The point at which nuclear material has reached a composition and purity suitable for fuel fabrication or enrichment. This paper addresses the two questions: (a) is the starting point adequately defined, and (b) what mesures could be applied to nuclear material before the starting point? Those questions have been asked before, some of the answers in this paper are new. (orig.).

  10. Psychiatric Advance Directives: Getting Started

    Science.gov (United States)

    ... News Legal Issues Search for: About PADs A psychiatric advance directive (PAD) is a legal document that ... decisions during a mental health crisis. Getting Started Psychiatric advance directives (PADs) are relatively new legal instruments ...

  11. STARTing Again: What Happens After START I Expires?

    International Nuclear Information System (INIS)

    Mladineo, Stephen V.; Durbin, Karyn R.; Eastman, Christina M.

    2007-01-01

    The Strategic Arms Reduction Treaty (START I), a seminal arms control agreement that substantially reduced the levels of deployed strategic nuclear arms in the United States and Russia, will expire in December 2009. At this time, it is unclear what - if anything - will replace it. While the treaty remains relevant, more than a simple extension is appropriate. Instead the authors advocate for a successor regime that builds on the START I legacy but does not rely on the traditional tools of arms control. This paper examines the strategic context in which a successor regime would be developed and proposes several recommendations for future action

  12. Secondary Circuit Start Up Chemistry Optimisation

    International Nuclear Information System (INIS)

    Fontan, Guillaume; Morel, Pascal

    2012-09-01

    In a context of investment and renewal of equipment, Electricite De France (EDF) put enhanced efforts on operating practices during start-up of the secondary circuit, in order to improve operational performance and materials lifetime. This article focuses on the objective of optimizing the filling, the chemical conditioning and the thermal conditioning of the secondary fluid, while taking into account the following issues: - Limiting the time required to obtain a proper chemistry, - Limiting the amount of water and steam used, - Limiting the amount of effluent generated. The scope is all start-up conditions of secondary circuit, both after refuelling outage or fortuitous shutdowns of the plant. The recommendations produced are based on existing local procedures and good practices, which were collected and developed in order to propose a generic methodology understandable and useful both for operators, chemists and managers. (authors)

  13. Electrosíntesis y caracterización de materiales moleculares a partir de derivados n-trifluorometansulfonil-1-azahexa-1,3,5-trienos. // Electrosintesis and characterization of molecular materials starting from having derived.

    Directory of Open Access Journals (Sweden)

    M. E. Sánchez Vergara

    2008-01-01

    Full Text Available Actualmente existe un interés creciente en los Materiales Moleculares, ya que estos pueden presentar diferentescomportamientos eléctricos que van desde aislantes, semiconductores o bien conductores. En el presente estudio fueronsintetizados materiales de este tipo, a partir de derivados N-Trifluorometansulfonil-1-azahexa-1,3,5-trienos yK3[Cr(C2O43]•3H2O debido a que estos compuestos representan un gran interés por sus variadas aplicaciones en camposcomo la química analítica, además los derivados N-Trifluorometansulfonil-1-azahexa-1,3,5-trienos resultan especialmenteatractivos desde el punto de vista estructural ya que en su forma neutra presentan una extensa deslocalización electrónica locual les confiere un comportamiento químico muy particular. En esta comunicación, se forman mediante electrosíntesisconvencional y mediante electrosíntesis en el módulo de electrocristalización del microscopio de fuerza atómica (AFM,algunos materiales moleculares. Una vez obtenidos dichos materiales, se caracterizan por análisis elemental sobresuperficies (SEM-EDS.Palabras claves: Materiales moleculares, anisotropía, electrocristalización._____________________________________________________________________________Abstract.Recently, molecular materials have been developed because of their electrical properties which give conductor,semiconductor, or superconductor behavior. In this work, the synthesis of new materials formed from Ntrifluoromethanesulfonyl-1-azahexa-1, 3, 5-triene species and K3[Cr(C2O43]•3H2O is reported. NTrifluoromethanesulfonyl-1-azahexa-1,3,5-trienes compounds, which are highly functionalised pentametines, have alsobeen studied due to its interesting physical and chemical properties. These compounds are especially interesting from astructural point of view for some reasons; in a neutral form, they show an extensive electronic delocalisation, which confersthem a very particular chemical behaviour. This study is focused on

  14. Ratiometric Phosphorescent Probe for Thallium in Serum, Water, and Soil Samples Based on Long-Lived, Spectrally Resolved, Mn-Doped ZnSe Quantum Dots and Carbon Dots.

    Science.gov (United States)

    Lu, Xiaomei; Zhang, Jinyi; Xie, Ya-Ni; Zhang, Xinfeng; Jiang, Xiaoming; Hou, Xiandeng; Wu, Peng

    2018-02-20

    Thallium (Tl) is an extremely toxic heavy metal and exists in very low concentrations in the environment, but its sensing is largely underexplored as compared to its neighboring elements in the periodic table (especially mercury and lead). In this work, we developed a ratiometric phosphorescent nanoprobe for thallium detection based on Mn-doped ZnSe quantum dots (QDs) and water-soluble carbon dots (C-dots). Upon excitation with 360 nm, Mn-doped ZnSe QDs and C-dots can emit long-lived and spectrally resolved phosphorescence at 580 and 440 nm, respectively. In the presence of thallium, the phosphorescence emission from Mn-doped ZnSe QDs could be selectively quenched, while that from C-dots retained unchanged. Therefore, a ratiometric phosphorescent probe was thus developed, which can eliminate the potential influence from both background fluorescence and other analyte-independent external environment factors. Several other heavy metal ions caused interferences to thallium detection but could be efficiently masked with EDTA. The proposed method offered a detection limit of 1 μg/L, which is among the most sensitive probes ever reported. Successful application of this method for thallium detection in biological serum as well as in environmental water and soil samples was demonstrated.

  15. Synthesis of ZnSe and ZnSe:Cu quantum dots by a room temperature photochemical (UV-assisted) approach using Na2 SeO3 as Se source and investigating optical properties.

    Science.gov (United States)

    Khafajeh, R; Molaei, M; Karimipour, M

    2017-06-01

    In this study, ZnSe and ZnSe:Cu quantum dots (QDs) were synthesized using Na 2 SeO 3 as the Se source by a rapid and room temperature photochemical (UV-assisted) approach. Thioglycolic acid (TGA) was employed as the capping agent and UV illumination activated the chemical reactions. Synthesized QDs were successfully characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), photoluminescence (PL) and UV-visible (UV-vis) spectroscopy, Fourier transform-infrared (FT-IR), and energy dispersive X-ray spectroscopy (EDX). XRD analysis demonstrated the cubic zinc blend phase QDs. TEM images indicated that round-shaped particles were formed, most of which had a diameter of about 4 nm. The band gap of the ZnSe QDs was higher than that for ZnSe in bulk. PL spectra indicated an emission with three peaks related to the excitonic, surface trap states and deep level (DL) states. The band gap and QD emission were tunable only by UV illumination time during synthesis. ZnSe:Cu showed green emission due to transition of electrons from the Conduction band (CB) or surface trap states to the 2 T 2 acceptor levels of Cu 2 + . The emission was increased by increasing the Cu 2 + ion concentration, such that the optimal value of PL intensity was obtained for the nominal mole ratio of Cu:Zn 1.5%. Copyright © 2016 John Wiley & Sons, Ltd.

  16. Start Where Your Students Are

    Science.gov (United States)

    Jackson, Robyn R.

    2010-01-01

    Starting where your students are means understanding how currencies are negotiated and traded in the classroom. Any behavior that students use to acquire the knowledge and skills needed in the classroom functions as currency. Teachers communicate the kinds of currencies they accept in their classrooms, such as getting good grades; students do…

  17. Start-up of Rapsodie

    International Nuclear Information System (INIS)

    Pontier, R.

    1967-01-01

    After giving a general description of Rapsodie this report presents the conditions in which the start-up occurred and in which the tests were carried out. A chronological account is given of the operations and of the main events which occurred. The modifications made to the reactor during this period are described and a synthesis of the results obtained is presented. (author) [fr

  18. When to Start Antiretroviral Therapy

    Science.gov (United States)

    ... illnesses and coinfections Recent HIV infection Pregnancy All pregnant women with HIV should take HIV medicines to prevent mother-to- ... protect the health of the pregnant woman. All pregnant women with HIV should start taking HIV medicines as soon as ...

  19. Head Start Center Design Guide.

    Science.gov (United States)

    Administration for Children, Youth, and Families (DHHS), Washington, DC. Head Start Bureau.

    This guide contains suggested criteria for planning, designing, and renovating Head Start centers so that they are safe, child-oriented, developmentally appropriate, beautiful, environmentally sensitive, and functional. The content is based on the U.S. General Services Administration's Child Care Center Design Guide, PBS-P140, which was intended…

  20. Nanocrystalline ceramic materials

    Science.gov (United States)

    Siegel, Richard W.; Nieman, G. William; Weertman, Julia R.

    1994-01-01

    A method for preparing a treated nanocrystalline metallic material. The method of preparation includes providing a starting nanocrystalline metallic material with a grain size less than about 35 nm, compacting the starting nanocrystalline metallic material in an inert atmosphere and annealing the compacted metallic material at a temperature less than about one-half the melting point of the metallic material.

  1. Getting started with Drupal commerce

    CERN Document Server

    Jones, Richard

    2013-01-01

    A simple yet concise step-by-step tutorial that starts from scratch and builds up your knowledge with focused examples that will enable you to set up and run an e-commerce website.This book is for beginners and will take you through the installation and configuration of Drupal Commerce from scratch, but some familiarity with Drupal 7 will be an advantage. All examples are based on development on a local computer - you do not need a hosted Drupal environment.

  2. Getting started with Twitter Flight

    CERN Document Server

    Hamshere, Tom

    2013-01-01

    Getting Started with Twitter Flight is written with the intention to educate the readers, helping them learn how to build modular powerful applications with Flight, Twitter's cutting-edge JavaScript framework.This book is for anyone with a foundation in JavaScript who wants to build web applications. Flight is quick and easy to learn, built on technologies you already understand such as the DOM, events, and jQuery.

  3. School start times for adolescents.

    Science.gov (United States)

    2014-09-01

    The American Academy of Pediatrics recognizes insufficient sleep in adolescents as an important public health issue that significantly affects the health and safety, as well as the academic success, of our nation's middle and high school students. Although a number of factors, including biological changes in sleep associated with puberty, lifestyle choices, and academic demands, negatively affect middle and high school students' ability to obtain sufficient sleep, the evidence strongly implicates earlier school start times (ie, before 8:30 am) as a key modifiable contributor to insufficient sleep, as well as circadian rhythm disruption, in this population. Furthermore, a substantial body of research has now demonstrated that delaying school start times is an effective countermeasure to chronic sleep loss and has a wide range of potential benefits to students with regard to physical and mental health, safety, and academic achievement. The American Academy of Pediatrics strongly supports the efforts of school districts to optimize sleep in students and urges high schools and middle schools to aim for start times that allow students the opportunity to achieve optimal levels of sleep (8.5-9.5 hours) and to improve physical (eg, reduced obesity risk) and mental (eg, lower rates of depression) health, safety (eg, drowsy driving crashes), academic performance, and quality of life. Copyright © 2014 by the American Academy of Pediatrics.

  4. Starting of nuclear power stations

    International Nuclear Information System (INIS)

    Kotyza, V.

    1988-01-01

    The procedure is briefly characterized of jobs in nuclear power plant start-up and the differences are pointed out from those used in conventional power generation. Pressure tests are described oriented to tightness, tests of the secondary circuit and of the individual nodes and facilities. The possibility is shown of increased efficiency of such jobs on an example of the hydraulic tests of the second unit of the Dukovany nuclear power plant where the second and the third stages were combined in the so-colled integrated hydraulic test. (Z.M.). 5 figs

  5. Getting started With Amazon Redshift

    CERN Document Server

    Bauer, Stefan

    2013-01-01

    Getting Started With Amazon Redshift is a step-by-step, practical guide to the world of Redshift. Learn to load, manage, and query data on Redshift.This book is for CIOs, enterprise architects, developers, and anyone else who needs to get familiar with RedShift. The CIO will gain an understanding of what their technical staff is working on; the technical implementation personnel will get an in-depth view of the technology, and what it will take to implement their own solutions.

  6. Predicting emergency diesel starting performance

    International Nuclear Information System (INIS)

    DeBey, T.M.

    1989-01-01

    The US Department of Energy effort to extend the operational lives of commercial nuclear power plants has examined methods for predicting the performance of specific equipment. This effort focuses on performance prediction as a means for reducing equipment surveillance, maintenance, and outages. Realizing these goals will result in nuclear plants that are more reliable, have lower maintenance costs, and have longer lives. This paper describes a monitoring system that has been developed to predict starting performance in emergency diesels. A prototype system has been built and tested on an engine at Sandia National Laboratories. 2 refs

  7. Starting a nursing consultation practice.

    Science.gov (United States)

    Schulmeister, L

    1999-03-01

    Because the clinical nurse specialist (CNS) role has been changed or eliminated in many hospital organizations, many CNSs in career transition are considering establishing collaborative or independent nursing consultation practices. Opportunities for consultants exist in diverse practice settings and specialties. Before starting a consultation practice, the CNS should carefully examine goals, identify resources, and begin contacting potential referral sources. He or she must also decide what form of business organization to establish and write a business plan to solidify ideas and prepare for the unexpected. Most CNS consultants rely on personal savings to cover initial business and personal expenses, and many continue working as a CNS until the consultation practice is established. Fees can be set based on community standards, what the market will bear, desired projected income, or a third-party payor's fee schedule. The consultation practice can be marketed by word of mouth, inexpensive advertising techniques such as distributing flyers and business cards, direct mall, and media advertising. In today's healthcare marketplace, opportunities abound for the CNS risk-taker interested in starting a nursing consultation practice.

  8. The start of the harvest

    CERN Multimedia

    2011-01-01

    The first major particle physics summer conference has just started this week in Grenoble. After the Quark-Matter conference, the Europhysics Conference on High-Energy Physics marks the start of a promising harvest for the LHC experiments.   For the first time, the collaborations will be presenting their latest results based on all luminosity taken until end of June, which will provide more precise measurements in many areas. Thanks to the excellent performance of the LHC, the experiments have already accumulated a substantial quantity of data allowing them to push back the known limits and refine measurements in many fields ranging from b physics to the search for the Higgs boson and for dark matter. At the time of writing, the LHC collaborations are about to present these new results in an energy range which has never previously been explored. I have congratulated all the teams involved in getting the LHC into operation in record time with great efficiency. Today I would like to acknowledge the...

  9. Extended X-ray absorption fine structure studies of impulsive-type hardening in the heavily Be-doped ZnSe ternaries

    Energy Technology Data Exchange (ETDEWEB)

    Khan, Shabina; Singh, Pankaja [Barkatullah University, Bhopal (India); Mazher, Javed [Addis Ababa University, Addis Ababa (Ethiopia)

    2014-02-15

    Inherently soft zinc-selenides have been hardened through beryllium doping. High-quality stoichiometric ternaries of Be{sub x}Zn{sub 1-x}Se have been synthesized by using the Bridgeman technique. State-of-art X-ray absorption spectroscopy is performed by varying the concentration of the cationic dopant, Be, from 6% to 55% in the host ZnSe. Extended X-ray absorption fine structure analyses are carried out to study the next-neighbor and next nearest neighbor atomic positions, nature of the substitutional doping, extent of bond length homogeneity, the presence of involuntary contrast among path distances, and the crossover from a soft to a hard character of the ternary with increasing Be concentration. Our results indicate the presence of a non-regular impulsive hardening in the ternary with a disparity at the lower and the higher Be-doping levels, which are discussed vis-a-vis self-accommodation of substitutional dopants in the host lattice.

  10. Inhomogeneous nuclear spin polarization induced by helicity-modulated optical excitation of fluorine-bound electron spins in ZnSe

    Science.gov (United States)

    Heisterkamp, F.; Greilich, A.; Zhukov, E. A.; Kirstein, E.; Kazimierczuk, T.; Korenev, V. L.; Yugova, I. A.; Yakovlev, D. R.; Pawlis, A.; Bayer, M.

    2015-12-01

    Optically induced nuclear spin polarization in a fluorine-doped ZnSe epilayer is studied by time-resolved Kerr rotation using resonant excitation of donor-bound excitons. Excitation with helicity-modulated laser pulses results in a transverse nuclear spin polarization, which is detected as a change of the Larmor precession frequency of the donor-bound electron spins. The frequency shift in dependence on the transverse magnetic field exhibits a pronounced dispersion-like shape with resonances at the fields of nuclear magnetic resonance of the constituent zinc and selenium isotopes. It is studied as a function of external parameters, particularly of constant and radio frequency external magnetic fields. The width of the resonance and its shape indicate a strong spatial inhomogeneity of the nuclear spin polarization in the vicinity of a fluorine donor. A mechanism of optically induced nuclear spin polarization is suggested based on the concept of resonant nuclear spin cooling driven by the inhomogeneous Knight field of the donor-bound electron.

  11. Longitudinal and transverse spin dynamics of donor-bound electrons in fluorine-doped ZnSe: Spin inertia versus Hanle effect

    Science.gov (United States)

    Heisterkamp, F.; Zhukov, E. A.; Greilich, A.; Yakovlev, D. R.; Korenev, V. L.; Pawlis, A.; Bayer, M.

    2015-06-01

    The spin dynamics of strongly localized donor-bound electrons in fluorine-doped ZnSe epilayers is studied using pump-probe Kerr rotation techniques. A method exploiting the spin inertia is developed and used to measure the longitudinal spin relaxation time T1 in a wide range of magnetic fields, temperatures, and pump densities. The T1 time of the donor-bound electron spin of about 1.6 μ s remains nearly constant for external magnetic fields varied from zero up to 2.5 T (Faraday geometry) and in a temperature range 1.8-45 K. These findings impose severe restrictions on possible spin relaxation mechanisms. In our opinion they allow us to rule out scattering between free and donor-bound electrons, jumping of electrons between different donor centers, scattering between phonons and donor-bound electrons, and with less certainty charge fluctuations in the environment of the donors caused by the 1.5 ps pulsed laser excitation.

  12. Long range surface plasmon resonance enhanced electro-optically tunable Goos-Hänchen shift and Imbert-Fedorov shift in ZnSe prism

    Science.gov (United States)

    Goswami, Nabamita; Kar, Aparupa; Saha, Ardhendu

    2014-11-01

    A new theoretical approach towards the tuning of Goos-Hänchen shift and Imbert-Fedorov shift for the reflected light beam is observed, designed and simulated in this paper through electro-optically tunable liquid crystal at an incident wavelength of 1550 nm within the communication window. Here the considered Kretschmann-Raether geometry comprises a ZnSe prism and a liquid crystal layer of E44 between two metal layers of silver, where with the application of electric field from (0-10) V electro-optically tuning of the Goos-Hänchen shift from 64.09 μm to -53.408 μm and the Imbert-Fedorov shift from 122.8 μm to -32.5 μm for a change in refractive index of the liquid crystal layer from 1.52-1.79 are envisaged. This idea expedites the scope of fine tuning in optical switching within the μm ranges.

  13. 30 CFR 75.1913 - Starting aids.

    Science.gov (United States)

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Starting aids. 75.1913 Section 75.1913 Mineral... SAFETY STANDARDS-UNDERGROUND COAL MINES Diesel-Powered Equipment § 75.1913 Starting aids. (a) Volatile fuel starting aids shall be used in accordance with recommendations provided by the starting aid...

  14. (+)-Aromadendrene as chiral starting material for the synthesis of sesquiterpenes

    NARCIS (Netherlands)

    Gijsen, H.J.M.

    1993-01-01

    One of the distillation tails of the oil of Eucalyptus globulus, which is commercially available, contains about 55-70% of (+)-aromadendrene ( 2 ), together with 10-15% of alloaromadendrene ( 3 ). In this thesis has been described

  15. Starting material radiation source for Moessbauer investigations of tellurium compounds

    International Nuclear Information System (INIS)

    Alexandrov, A.J.; Grushko, J.S.; Makarov, E.F.; Mishin, K.Y.; Baltrunas, D.A.J.

    1977-01-01

    A method is described of preparing a radiation source for Mossbauer investigations of tellurium compounds manufactured on the basis of 5 MgO . Te 124 O 3 . 5 MgO . Te 124 O 3 is irradiated in a reactor by means of thermal neutrons, followed by annealing at a temperature ranging from 600 0 to 1,100 0 C for a period of from 5 to 10 hours

  16. Starting up the Saturne synchrotron

    International Nuclear Information System (INIS)

    Salvat, M.

    1958-02-01

    Illustrated by many drawings and graphs, this report describes and comments all operations and measurements to be performed for starting up the Saturne synchrotron until particle acceleration exclusively. The author reports the study of beam as it goes out of the Van de Graaff: experiment of position and stability of the beam axis, study of beam current and geometric characteristics (calibration of the induction probe), experiment of mass separation and proton percentage, and adjustment of regulation and Van de Graaff fall law. In a second part, he reports the optics alignment and the study of optics property (installation of the different sectors, study of inflector end voltage, and influence of inflector position in the chamber). The third part addresses the examination of phenomena associated with injection: injection method and definition of the initial instant, search for injection optimum conditions, study of particle lifetime and of phenomena on the inner probe. The fourth part proposes theoretical additional elements regarding the movement of particles at the injection in the useful area, and phenomena occurring on targets and on the inner probe

  17. In situ observation on the dynamic process of evaporation and crystallization of sodium nitrate droplets on a ZnSe substrate by FTIR-ATR.

    Science.gov (United States)

    Zhang, Qing-Nuan; Zhang, Yun; Cai, Chen; Guo, Yu-Cong; Reid, Jonathan P; Zhang, Yun-Hong

    2014-04-17

    Sodium nitrate is a main component of aging sea salt aerosol, and its phase behavior has been studied repeatedly with wide ranges observed in the efflorescence relative humidity (RH) in particular. Studies of the efflorescence dynamics of NaNO3 droplets deposited on a ZnSe substrate are reported, using an in situ Fourier transform infrared attenuated total reflection (FTIR-ATR) technique. The time-dependence of the infrared spectra of NaNO3 aerosols accompanying step changes in RH have been measured with high signal-to-noise ratio. From the IR difference spectra recorded, changes of the time-dependent absorption peak area of the O-H stretching band (ν-OH, ∼3400 cm(-1)) and the nitrate out-of-plane bending band (ν2-NO3(-), ∼836 cm(-1)) are obtained. From these measurements, changes in the IR signatures can be attributed to crystalline and solution phase nitrate ions, allowing the volume fraction of the solution droplets that have crystallized to be determined. Then, using these clear signatures of the volume fraction of droplets that have yet to crystallize, the homogeneous and heterogeneous nucleation kinetics can be studied from conventional measurements using a steady decline in RH. The nucleation rate measurements confirm that the rate of crystallization in sodium nitrate droplets is considerably less than in ammonium sulfate droplets at any particular degree of solute supersaturation, explaining the wide range of efflorescence RHs observed for sodium nitrate in previous studies. We demonstrate that studying nucleation kinetics using the FTIR-ATR approach has many advantages over brightfield imaging studies on smaller numbers of larger droplets or measurements made on single levitated particles.

  18. Spin-polarized structural, elastic, electronic and magnetic properties of half-metallic ferromagnetism in V-doped ZnSe

    Energy Technology Data Exchange (ETDEWEB)

    Monir, M. El Amine.; Baltache, H. [Laboratoire de Physique Quantique de la Matière et de la Modélisation Mathématique (LPQ3M), Faculté des Sciences, Université de Mascara, Mascara 29000 (Algeria); Murtaza, G., E-mail: murtaza@icp.edu.pk [Materials Modeling Lab, Department of Physics, Islamia College University, Peshawar (Pakistan); Khenata, R., E-mail: khenata_rabah@yahoo.fr [Laboratoire de Physique Quantique de la Matière et de la Modélisation Mathématique (LPQ3M), Faculté des Sciences, Université de Mascara, Mascara 29000 (Algeria); Ahmed, Waleed K. [ERU, Faculty of Engineering, United Arab Emirates University, Al Ain (United Arab Emirates); Bouhemadou, A. [Laboratory for Developing New Materials and their Characterization, Department of Physics, Faculty of Science, University of Setif, 19000 Setif (Algeria); Omran, S. Bin [Department of Physics and Astronomy, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451 (Saudi Arabia); Seddik, T. [Laboratoire de Physique Quantique de la Matière et de la Modélisation Mathématique (LPQ3M), Faculté des Sciences, Université de Mascara, Mascara 29000 (Algeria)

    2015-01-15

    Based on first principles spin-polarized density functional theory, the structural, elastic electronic and magnetic properties of Zn{sub 1−x}V{sub x}Se (for x=0.25, 0.50, 0.75) in zinc blende structure have been studied. The investigation was done using the full-potential augmented plane wave method as implemented in WIEN2k code. The exchange-correlation potential was treated with the generalized gradient approximation PBE-GGA for the structural and elastic properties. Moreover, the PBE-GGA+U approximation (where U is the Hubbard correlation terms) is employed to treat the “d” electrons properly. A comparative study between the band structures, electronic structures, total and partial densities of states and local moments calculated within both GGA and GGA+U schemes is presented. The analysis of spin-polarized band structure and density of states shows the half-metallic ferromagnetic character and are also used to determine s(p)-d exchange constants N{sub 0}α (conduction band ) and N{sub 0}β (valence band) due to Se(4p)–V(3d) hybridization. It has been clearly evidence that the magnetic moment of V is reduced from its free space change value of 3 µ{sub B} and the minor atomic magnetic moment on Zn and Se are generated. - Highlights: • Half metallicity origins by doping V in ZnSe. • PBE-GGA+U approximation is employed to treat the “d” electrons properly. • s(p)-d Exchange constants N{sub 0}α (conduction band ) and N{sub 0}β (valence band) are due to Se(4p)-V(3d) hybridization.

  19. Process parameters for high quality on-contour starting of laser cutting of steel

    NARCIS (Netherlands)

    Meijer, C.Z.; Meijer, C.Z.; Meijer, J.; Bakkers, E.P.M.

    1997-01-01

    Laser cut initiation in full material usually results in a start hole with bad quality. Starting strategies have been developed to avoid these crater-like holes. Start areas were obtained showing almost the same quality as the rest of the cut. As a result of the experiments and literature research

  20. Preschool Facilities - MDC_HeadStart

    Data.gov (United States)

    NSGIC Local Govt | GIS Inventory — A label (point) feature class of Head Start / Early Head Start/ Delegate Agencies/ Child Care Partnership & Family Day Care Homes Programs location in Miami-Dade...

  1. Drug Abuse Prevention Starts with Parents

    Science.gov (United States)

    ... Stages Listen Español Text Size Email Print Share Drug Abuse Prevention Starts with Parents Page Content Article Body ... for a time when drugs may be offered. Drug abuse prevention starts with parents learning how to talk ...

  2. What Happens at the Lesson Start?

    Science.gov (United States)

    Saloviita, Timo

    2016-01-01

    Transitional periods, such as lesson starts, are necessary steps from one activity to another, but they also compete with time for actual learning. The aim of the present study was to replicate a previous pilot study on lesson starts and explore possible disturbances. In total, 130 lesson starts in Finnish basic education in grades 1-9 were…

  3. Health Coordination Manual. Head Start Health Services.

    Science.gov (United States)

    Administration for Children, Youth, and Families (DHHS), Washington, DC. Head Start Bureau.

    Part 1 of this manual on coordinating health care services for Head Start children provides an overview of what Head Start health staff should do to meet the medical, mental health, nutritional, and/or dental needs of Head Start children, staff, and family members. Offering examples, lists, action steps, and charts for clarification, part 2…

  4. Teaching iSTART to Understand Spanish

    Science.gov (United States)

    Dascalu, Mihai; Jacovina, Matthew E.; Soto, Christian M.; Allen, Laura K.; Dai, Jianmin; Guerrero, Tricia A.; McNamara, Danielle S.

    2017-01-01

    iSTART is a web-based reading comprehension tutor. A recent translation of iSTART from English to Spanish has made the system available to a new audience. In this paper, we outline several challenges that arose during the development process, specifically focusing on the algorithms that drive the feedback. Several iSTART activities encourage…

  5. Start II, red ink, and Boris Yeltsin

    International Nuclear Information System (INIS)

    Arbatov, A.

    1993-01-01

    Apart from the vulnerability implied by the START II treaty, it will bear the burden of the general political opposition to the Yeltsin administration. START II will be seen as part of an overall Yeltsin-Andrei Kozyrev foreign policy that is under fire for selling out Russian national interests in Yugoslavia, the Persian Gulf, and elsewhere. This article discusses public opinion concerning START II, the cost of its implementation, and the general purpose of the treaty

  6. Starting a business through a franchise

    OpenAIRE

    Dubravka Mahaček; Maja Martinko Lihtar

    2013-01-01

    A business can be launched by establishing a new entity, purchasing an existing entity or through a franc - hise. There are certain prerequisites for starting a business, the most important ones being a quality idea and start-up capital. Potential start-up difficulties are inadequate financing, existing competition as well as the process of building your own market position. By purchasing an existing business some risks may be avoided and the opportunity for gaining profit may ...

  7. From START to NEW START. The dilemma and future of nuclear disarmament; Von START zu NEW START. Das Dilemma und die Zukunft der Nuklearen Abruestung

    Energy Technology Data Exchange (ETDEWEB)

    Plettenberg, Lars

    2012-07-01

    The report describes the existing four agreements on nuclear disarmament: START I (1991). START II (1993), SORT (2002) and NEW START (2010). The chapter on the dependence between nuclear disarmament and strategic stability covers the issues mutual assured destruction (MAD), credibility, overkill capacity; the role of nuclear weapons in the national strategies of the USA and NATO, Russia, Great Britain, France, China and the other nuclear states. Ways out of MAD include disarmament, de-alerting and mutual assured protection (MAP).

  8. Getting started with SBT for Scala

    CERN Document Server

    Saxena, Shiti

    2013-01-01

    A practical and fast-paced guide, Getting Started with SBT for Scala walks you through the setup of Scala projects in SBT with sample code for common as well as critical scenarios.Getting Started with SBT for Scala is for developers working on Scala projects who are interested in learning and utilizing Simple Build Tool to manage the build process.

  9. Families & the North Carolina Smart Start Initiative.

    Science.gov (United States)

    Lowman, Betsy; Bryant, Donna; Zolotor, Adam

    Smart Start is North Carolina's partnership between state government and local leaders, service providers, and families to better serve children under 6 years and their families. This study examined characteristics of families participating in Smart Start, their child care arrangements and family activities, and their need for and use of community…

  10. Start-up analysis for marketing strategy.

    Science.gov (United States)

    Griffith, M J; Baloff, N

    1984-01-01

    The complex start-up effect on utilization of health care services is too often overlooked or underestimated by marketing planners, leading to a range of negative consequences for both the users of services and the provider organization. Start-up analysis allows accurate estimation of these utilization effects for coordinated strategic planning among marketing finance, and operations.

  11. Head Start Impact Study. Technical Report

    Science.gov (United States)

    Puma, Michael; Bell, Stephen; Cook, Ronna; Heid, Camilla; Shapiro, Gary; Broene, Pam; Jenkins, Frank; Fletcher, Philip; Quinn, Liz; Friedman, Janet; Ciarico, Janet; Rohacek, Monica; Adams, Gina; Spier, Elizabeth

    2010-01-01

    This Technical Report is designed to provide technical detail to support the analysis and findings presented in the "Head Start Impact Study Final Report" (U.S. Department of Health and Human Services, January 2010). Chapter 1 provides an overview of the Head Start Impact Study and its findings. Chapter 2 provides technical information on the…

  12. New infrared solid state laser materials for CALIOPE

    International Nuclear Information System (INIS)

    DeLoach, L.D.; Page, R.H.; Wilke, G.D.

    1994-01-01

    Tunable infrared laser light may serve as a useful means by which to detect the presence of the targeted effluents. Since optical parametric oscillators (OPOs) have proven to be a versatile method of generating coherent light from the ultraviolet to the mid-infrared, this technology is a promising choice by which to service the CALIOPE applications. In addition, since some uncertainty remains regarding the precise wavelengths and molecules that will be targeted, the deployment of OPOs retains the greatest amount of wavelength flexibility. Another approach that the authors are considering is that of generating tunable infrared radiation directly with a diode-pumped solid state laser (DPSSL). One important advantage of a DPSSL is that it offers flexible pulse format modes that can be tailored to meet the needs of a particular application and target molecule. On the other hand, direct generation by a tunable DPSSL will generally be able to cover a more limited wavelength range than is possible with OPO technology. In support of the CALIOPE objectives the authors are exploring the potential for laser action among a class of materials comprised of transition metal-doped zinc chalcogenide crystals (i.e., ZnS, ZnSe and ZnTe). The Cr 2+ , Co 2+ and Ni 2+ dopants were selected as the most favorable candidates, on the basis of their documented spectral properties in the scientific literature. Thus far, the authors have characterized the absorption and emission properties of these ions in the ZnS and ZnSe crystals. The absorption spectra are used to determine the preferred wavelength at which the crystal should be pumped, while the emission spectra reveal the extent of the tuning range potentially offered by the material. In addition, measurements of the emission lifetime as a function of temperature turn out to be quite useful, since this data is suggestive of the room temperature emission yield

  13. Start 2: Thinking one move ahead

    Energy Technology Data Exchange (ETDEWEB)

    Gaines, L.L.

    1991-11-01

    At their summit meeting in the spring of 1990, Presidents Bush and Gorbachev issued a joint statement expressing their intentions to continue the process of strategic arms control beyond the Strategic Arms Reduction Treaty (START), which was eventually signed in July 1991, toward agreement on further reductions. They set general goals for negotiation of a follow-on treaty to START, which has been called START II. President Bush`s historic speech on September 27, 1991, reinforced those goals and specified several actions the US would take. It is the purpose of this report to examine possible provisions of START II and the implications of those provisions for achievement of the goals set at the 1990 summit, for verifiability, and for US force planning. This look ahead will contribute to advance planning of appropriate negotiating positions, verification research and development (R&D), and force modernization and restructuring. This report describes the goals for a START II treaty and possible means for achieving them. It postulates one set of provisions for such a treaty, while it examines force structures for the US that could result from adoption of a treaty with these provisions. The adequacy of methods for verifying START II are examined and the implications of a START II treaty are postulated.

  14. Start 2: Thinking one move ahead

    Energy Technology Data Exchange (ETDEWEB)

    Gaines, L.L.

    1991-11-01

    At their summit meeting in the spring of 1990, Presidents Bush and Gorbachev issued a joint statement expressing their intentions to continue the process of strategic arms control beyond the Strategic Arms Reduction Treaty (START), which was eventually signed in July 1991, toward agreement on further reductions. They set general goals for negotiation of a follow-on treaty to START, which has been called START II. President Bush's historic speech on September 27, 1991, reinforced those goals and specified several actions the US would take. It is the purpose of this report to examine possible provisions of START II and the implications of those provisions for achievement of the goals set at the 1990 summit, for verifiability, and for US force planning. This look ahead will contribute to advance planning of appropriate negotiating positions, verification research and development (R D), and force modernization and restructuring. This report describes the goals for a START II treaty and possible means for achieving them. It postulates one set of provisions for such a treaty, while it examines force structures for the US that could result from adoption of a treaty with these provisions. The adequacy of methods for verifying START II are examined and the implications of a START II treaty are postulated.

  15. Spectral and power characteristics of a 5% Tm : KLu(WO4)2 Nm-cut minislab laser passively Q-switched by a Cr2+ : ZnSe crystal

    Science.gov (United States)

    Vatnik, S. M.; Vedin, I. A.; Kurbatov, P. F.; Smolina, E. A.; Pavlyuk, A. A.; Korostelin, Yu. V.; Skasyrsky, Ya. K.

    2017-12-01

    Laser characteristics of a 5%Tm : KLu(WO4)2 Nm-cut minislab laser passively Q-switched by a Cr2+ : ZnSe saturable absorber are presented. At a pump power of 21 W, the average laser power at a wavelength of 1.91 μm was 3.2 W (pulse duration 35 ns, pulse energy 0.3 mJ). The maximum slope efficiency of the laser in the Q-switched regime was 31%; the loss in power with respect to the cw regime did not exceed 17%. At pump powers above 15 W, the dependence of the output power in the Q-switched regime on the pump power considerably differed from linear, which was explained by the formation of a thermal lens in the saturable absorber volume. The experimental energies and durations of laser pulses well agree with the values calculated from rate equations.

  16. A Healthy Start Can Begin Now

    Science.gov (United States)

    A healthy pregnancy begins before you ever become pregnant. Give yourself the best chance for a healthy pregnancy and healthy baby before you start down the road to motherhood. If you smoke, now’s a great time to quit.

  17. The physics of tokamak start-up

    International Nuclear Information System (INIS)

    Mueller, D.

    2013-01-01

    Tokamak start-up on present-day devices usually relies on inductively induced voltage from a central solenoid. In some cases, inductive startup is assisted with auxiliary power from electron cyclotron radio frequency heating. International Thermonuclear Experimental Reactor, the National Spherical Torus Experiment Upgrade and JT60, now under construction, will make use of the understanding gained from present-day devices to ensure successful start-up. Design of a spherical tokamak (ST) with DT capability for nuclear component testing would require an alternative to a central solenoid because the small central column in an ST has insufficient space to provide shielding for the insulators in the solenoid. Alternative start-up techniques such as induction using outer poloidal field coils, electron Bernstein wave start-up, coaxial helicity injection, and point source helicity injection have been used with success, but require demonstration of scaling to higher plasma current

  18. Start small and build toward business intelligence.

    Science.gov (United States)

    Kirby, Sean; Robertson, Brian

    2009-01-01

    To use business intelligence effectively, healthcare organizations should start small, align organizationally, and leverage success. Organizations should determine which measures they need and how to present them. Organizations should reinvest savings to continually improve.

  19. Lean Start-up in Established Companies

    DEFF Research Database (Denmark)

    Goduscheit, René Chester

    2018-01-01

    Lean start-up is an emergent perspective on how entrepreneurs can bring new products and services to the market. This approach challenges the dominant role of lengthy business plans, linear product development processes, and seeking complete overview of the potential of the new products....../services before market launch. Instead it suggests that start-ups could benefit from a ‘minimum-viable product’ approach where products and services are launched when they contain critical features. The emphasis in the lean start-up approach is on business models rather than the elaborate business plan...... at the companies (strategy meetings, development workshops etc.). The aim is to shed light on the implications for companies that seek to employ lean start-up. These implications will be aimed at aspects like innovation management, organizational structure, customer relations etc....

  20. 76 FR 37174 - Capital Investment Program-New Starts and Small Starts Program Funds

    Science.gov (United States)

    2011-06-24

    ... DEPARTMENT OF TRANSPORTATION Federal Transit Administration Capital Investment Program--New Starts... apportionment of the FY 2011 Capital Investment (New Starts and Small Starts) program funds. The funds will be... FY 2011, $1,596,800,000 was appropriated for the Capital Investments Grant Account, which includes...

  1. START: the creation of a spherical tokamak

    International Nuclear Information System (INIS)

    Sykes, Alan

    1992-01-01

    The START (Small Tight Aspect Ratio Tokamak) plasma fusion experiment is now operational at AEA Fusion's Culham Laboratory. It is the world's first experiment to explore an extreme limit of the tokamak - the Spherical Tokamak - which theoretical studies predict may have substantial advantages in the search for economic fusion power. The Head of the START project, describes the concept, some of the initial experimental results and the possibility of developing a spherical tokamak power reactor. (author)

  2. Materials science

    International Nuclear Information System (INIS)

    Anon.

    1977-01-01

    The Materials Science Division is engaged in research on physical properties of materials and the effects of radiation upon them. This involves solid state materials undergoing phase transitions, energy storing materials, and biomaterials. The Division also offers research facilities for M.S. and Ph.D. thesis work in the fields of physics, chemistry, materials, and radiation sciences in cooperation with the various colleges and departments of the UPR Mayaguez Campus. It is anticipated that it will serve as a catalyst in starting energy-related research programs in cooperation with UPR faculty, especially programs involving solar energy. To encourage and promote cooperative efforts, contact is maintained with former graduate students and with visiting scientists from Latin American research institutions

  3. Classroom Writing Environments and Children's Early Writing Skills: An Observational Study in Head Start Classrooms

    Science.gov (United States)

    Zhang, Chenyi; Hur, Jinhee; Diamond, Karen E.; Powell, Douglas

    2015-01-01

    This study examined the classroom writing environment in 31 Head Start classrooms, and explored the relations between the writing environment, children's (N = 262) name-writing, and children's letter knowledge using pathway analysis. Our analyses showed that Head Start classrooms provided opportunities (i.e., writing materials and teachers'…

  4. The impact of dry-land sprint start training on the short track speed skating start.

    Science.gov (United States)

    Haug, William B; Drinkwater, Eric J; Cicero, Nicholas J; Barthell, J Anthony; Chapman, Dale W

    2017-05-05

    This investigation sought to determine the effects of dry-land sprint start training on short track speed skating (STSS) start performance. Nine highly trained short track athletes completed a control period of normal STSS training followed by a four-week training intervention. Before and after the control and intervention periods, athletes performed three electronically timed dry-land and on-ice 14.43 m maximal sprint start efforts. The intervention consisted of two sprint sessions per week consisting of nine electronically timed 14.43 m dry-land sprint starts in addition to normal STSS training. The control period resulted in no substantial change in on-ice start performance (Mean Δ: -0.01 s, 95% Confidence Limits (CL): -0.08 to 0.05 s; Effect Size (ES): -0.05; Trivial) however, a small change was observed in dry-land start performance (Mean Δ: -0.07 s, 95% CL: -0.13 to -0.02 s; ES: -0.49). Following brief specific dry-land sprint start training a small improvement was observed in both on-ice (Mean Δ: -0.07 s, 95% CL: -0.13 to -0.01 s; ES: -0.33) and dry-land (Mean Δ: -0.04 s, 95% CL: -0.09 to 0.00 s; ES: -0.29) start performance. This investigation suggests STSS start performance can be improved through a brief dry-land sprint start training program.

  5. Guidelines for starting today's private practice

    Directory of Open Access Journals (Sweden)

    Schmitz ED

    2012-11-01

    Full Text Available No abstract available. Article truncated at 150 words. Starting a new practice may seem like a daunting task. The purpose of this article is to demystify the process of creating a new practice from the beginning. The cardinal rule is to keep costs low and not to outsource work that can easily be performed by any competent physician and staff. You do not need a manager, lawyer, business partner, coder or biller individually; you may be able to perform many of these services yourself. What you do need is a commitment to making your practice a success. Do not spend too much on your office space, furnishings or equipment. Start with the bare essentials. Immediately start applying to all insurance companies especially Medicare. Request an employer identification number. Set up a basic business banking account and submit the account number to the insurance companies you plan to work with. You can purchase an entire electronic healthcare record (EHR …

  6. Starting a business through a franchise

    Directory of Open Access Journals (Sweden)

    Dubravka Mahaček

    2013-12-01

    Full Text Available A business can be launched by establishing a new entity, purchasing an existing entity or through a franc - hise. There are certain prerequisites for starting a business, the most important ones being a quality idea and start-up capital. Potential start-up difficulties are inadequate financing, existing competition as well as the process of building your own market position. By purchasing an existing business some risks may be avoided and the opportunity for gaining profit may arise. Profitable operation is possible only if this business has up-to-date products and no outstanding liabilities. This paper discusses franchising business opportunities and the requisite investments and costs, which will bring success if they are accompanied by franchisee’s efforts. The paper aims to present the main characteristics of a franchise business, the necessary investment and the costs which arise in the process, as well as advantages, disadvantages and experiences with this kind of business

  7. Research nuclear reactor start-up simulator

    International Nuclear Information System (INIS)

    Sofo Haro, M.; Cantero, P.

    2009-01-01

    This work presents the design and FPGA implementation of a research nuclear reactor start-up simulator. Its aim is to generate a set of signals that allow replacing the neutron detector for stimulated signals, to feed the measurement electronic of the start-up channels, to check its operation, together with the start-up security logic. The simulator presented can be configured on three independent channels and adjust the shape of the output pulses. Furthermore, each channel can be configured in 'rate' mode, where you can specify the growth rate of the pulse frequency in %/s. Result and details of the implementation on FPGA of the different functional blocks are given. (author)

  8. Smart or Diverse Start-up Teams?

    DEFF Research Database (Denmark)

    Hoogendoorn, Sander; Parker, Simon C.; Van Praag, Mirjam

    2017-01-01

    This paper explores the relationship between cognitive abilities and team performance in a start-up setting. We argue that performance in this setting hinges on three tasks: opportunity recognition, problem solving, and implementation. We theorize that cognitive ability at the individual level has...... others can be assigned to tasks that impose a greater cognitive load (problem solving or opportunity recognition). We present the results of a field experiment in which 573 students in 49 teams started up and managed real companies. We ensured exogenous variation in—otherwise random—team composition...... by assigning students to teams based on their measured cognitive abilities. Each team performed a variety of tasks, often involving complex decision making. The key result of the experiment is that the performance of start-up teams first increases and then decreases with ability dispersion. Strikingly, average...

  9. Choice and validation of a near infrared spectroscopic application for the identity control of starting materials. practical experience with the EU draft Note for Guidance on the use of near infrared spectroscopy by the pharmaceutical industry and the data to be forwarded in part II of the dossier for a marketing authorization.

    Science.gov (United States)

    Vredenbregt, M J; Caspers, P W J; Hoogerbrugge, R; Barends, D M

    2003-11-01

    Recently the CPMP/CVMP sent out for consultation the draft Note for Guidance (dNfG) on the use of near infrared spectroscopy (NIRS) by the pharmaceutical industry and the data to be forwarded in part II of the dossier for a marketing authorization. We explored the practicability of this dNfG with respect to the verification of the correct identity of starting materials in a generic tablet-manufacturing site. Within the boundaries of the dNfG, a release procedure was developed for 12 substances containing structurally related compounds and substances differing only in particle size. For the method development literature data were also taken into consideration. Good results were obtained with wavelength correlation (WC), applied on raw spectra or second derivative spectra both without smoothing. The defined threshold of 0.98 for raw spectra differentiated between all molecular structures. Both methods were found to be robust over a period of 1 year. For the differentiation between the different particle sizes a subsequent second chemometric technique had to be used. Soft independent modelling of class analogy (SIMCA) with a probability level of 0.01 proved suitable. Internal and external validation I according to the dNfG showed no incorrect rejections or false acceptances. External validation II according to the dNfG was carried out with 95 potentially interfering substances from which 46 were tested experimentally. Macrogol 400 was not distinguished from macrogol 300. For the complete verification of the identity of macrogol 300 test A of the European Pharmacopoeia is needed in addition to the NIRS application. A release procedure developed with WC applied on raw spectra and SIMCA as a second method, which is different from the preferred method of the dNfG, was tested in practice with good results. We conclude that the dNfG has good practicability and that deviations from the preferred methods of the dNfG can also give good differentiation.

  10. Start up testing for the secure automated fabrication line

    International Nuclear Information System (INIS)

    Gerber, E.W.; Benson, E.M.; Dahl, R.E.

    1986-01-01

    The Secure Automated Fabrication (SAF) Line has been designed and built by Westinghouse Hanford Company for the Department of Energy at the Hanford Site near Richland, Washington. The SAF Line will provide the capability for remote manufacture of fuel for Liquid Metal Reactors, and will supply fuel for the Fast Flux Test Facility (FFTF). The SAF process is highly automated and represents a major advancement in nuclear fuel manufacturing, offering significant improvements in product quality, productivity, safety, and accountability of Special Nuclear Materials. The construction phase of the project is complete, and testing has been initiated to accomplish start up of the plant for manufacture of FFTF fuel. This paper describes the test methodology used for SAF Line start up

  11. Two-Man Bobsled Push Start Analysis

    Directory of Open Access Journals (Sweden)

    Lopes Alexandre Dias

    2016-04-01

    Full Text Available The importance of push start times on bobsled performance was evidenced by some studies, but at this moment there is no article to the authors’ knowledge that describes the bobsled push start. Thus, the objectives of this study were to describe the two-man bobsled push start, analyze the differences between teams, and estimate the most important variable analyzed. We hypothesized that the pilot and brakeman athletes’ movement patterns during a bobsled pushing start can be described. The images used in this study were obtained during the men’s two-man XIV World Championship of Bobsled (2004. Fifteen best teams participating in the championship were recorded, and four start runs for each team were analyzed. The videos were captured by two digital video cameras. The pilot athletes were analyzed during the moment that they touched the lateral push bar of the sled, and the brakemen were analyzed during the first take-off and first landing. The teams were pooled in three groups of five teams using the final ranking of pushing time. We concluded that there was a distinct pattern movement for pilots and brakemen. The initial position of the majority of the pilots was localized slightly behind the bar. After touching the lateral bar, the pilots remained in a semi-squat position, pushing the sled forward in a pattern of marching movement. All brakemen used the board attached to the track as a support for both feet at the start. The brakeman gave the greatest contribution to break the inertia of the sled. There was no significant difference of movement between the three groups analyzed for the pilot and the brakeman.

  12. Getting started with Microsoft Lync server 2013

    CERN Document Server

    Volpe, Fabrizio

    2013-01-01

    This book has a practical approach with a lot of step-by-step guides and explanations as to where and why we're doing the various operations.Getting Started with Microsoft Lync Server 2013 is a starting point for system administrators, IT pros, unified communication technicians, and decision makers in companies or in the consultancy business. For people who have never managed Lync (or a U.C. product), the book will guide you through the basic concepts and mistakes. If you are already managing a Lync deployment you will find important explanations and ideas put together in a single text. If you

  13. Soft start technique for diesel generator sets

    Energy Technology Data Exchange (ETDEWEB)

    Fredlund, Lars [Swedish State Power Board, Ringhals Nuclear Power Plant, S-430 22, Vaeroebacka (Sweden)

    1986-02-15

    A diesel motor in a nuclear power plant should be of a well-proven design. It is designed for long periods of trouble-free duty, but not for the frequent and rapid test starts called for by the technical specifications. In order to decrease the dynamic forces and thermal stresses, a soft-start scheme has been implemented. By limiting the fuel injection the diesel generator will reach full speed in appr. 30 seconds. The fuel limiter is a pneumatic cylinder which mechanically limits the travel of the terminal shaft of the governor. (author)

  14. Soft start technique for diesel generator sets

    International Nuclear Information System (INIS)

    Fredlund, Lars

    1986-01-01

    A diesel motor in a nuclear power plant should be of a well-proven design. It is designed for long periods of trouble-free duty, but not for the frequent and rapid test starts called for by the technical specifications. In order to decrease the dynamic forces and thermal stresses, a soft-start scheme has been implemented. By limiting the fuel injection the diesel generator will reach full speed in appr. 30 seconds. The fuel limiter is a pneumatic cylinder which mechanically limits the travel of the terminal shaft of the governor. (author)

  15. The Lean and Global Start-up

    DEFF Research Database (Denmark)

    Tanev, Stoyan; Rasmussen, Erik Stavnsager

    For several decades researchers have studied start-up companies with a focus on international markets, suppliers and networks from their inception and on companies that are establishing new, agile business models. This has resulted in two streams of research: The Born Global and International New...... Ventures research and research with a focus on the Lean Start-up company. It is our intention in this paper to give a short presentation of the two research streams and show how they can be merged into one with a focus on newly established technology oriented firms that are lean and global from...

  16. Entrepreneur How to Start an Online Business

    CERN Document Server

    Tobin, Lucy

    2012-01-01

    The secrets of the UK’s biggest online entrepreneurs revealed   Thinking of starting a business? Already have a business online and looking to take it to the next level? The wonderful world wide web has made creating a start-up that much easier. Thousands of people are out there reaping the rewards the web can bring. If you want to join them, you’ve come to the right place.  Profiling today’s foremost web entrepreneurs, Lucy Tobin - who meets successful business founders every week writing an enterprise column for The Evening Standard – takes us throug

  17. Start time delays in operating room: Different perspectives

    Directory of Open Access Journals (Sweden)

    Babita Gupta

    2011-01-01

    Full Text Available Background: Healthcare expenditure is a serious concern, with escalating costs failing to meet the expectations of quality care. The treatment capacities are limited in a hospital setting and the operating rooms (ORs. Their optimal utilization is vital in efficient hospital management. Starting late means considerable wait time for staff, patients and waste of resources. We planned an audit to assess different perspectives of the residents in surgical specialities and anesthesia and OR staff nurses so as to know the causative factors of operative delay. This can help develop a practical model to decrease start time delays in operating room (ORs. Aims: An audit to assess different perspectives of the Operating room (OR staff with respect to the varied causative factors of operative delay in the OR. To aid in the development of a practical model to decrease start time delays in ORs and facilitate on-time starts at Jai Prakash Narayan Apex Trauma centre (JPNATC, All India Institute of Medical Sciences (AIIMS, New Delhi. Methods: We prepared a questionnaire seeking the five main reasons of delay as per their perspective. Results: The available data was analysed. Analysis of the data demonstrated the common causative factors in start time operative delays as: a lack of proper planning, deficiencies in team work, communication gap and limited availability of trained supporting staff. Conclusions: The preparation of the equipment and required material for the OR cases must be done well in advance. Utilization of newer technology enables timely booking and scheduling of cases. Improved inter-departmental coordination and compliance with preanesthetic instructions needs to be ensured. It is essential that the anesthesiologists perform their work promptly, well in time . and supervise the proceedings as the OR manager. This audit is a step forward in defining the need of effective OR planning for continuous quality improvement.

  18. From START to NEW START. The dilemma and future of nuclear disarmament

    International Nuclear Information System (INIS)

    Plettenberg, Lars

    2012-01-01

    The report describes the existing four agreements on nuclear disarmament: START I (1991). START II (1993), SORT (2002) and NEW START (2010). The chapter on the dependence between nuclear disarmament and strategic stability covers the issues mutual assured destruction (MAD), credibility, overkill capacity; the role of nuclear weapons in the national strategies of the USA and NATO, Russia, Great Britain, France, China and the other nuclear states. Ways out of MAD include disarmament, de-alerting and mutual assured protection (MAP).

  19. Liquid phase sintered SiC ceramics from starting materials of different grade Cerâmicas à base de SiC sinterizadas via fase líquida a partir de matérias-primas de diferentes purezas

    Directory of Open Access Journals (Sweden)

    V. A. Izhevskyi

    2004-09-01

    Full Text Available Possibility of high performance ceramics manufactured from commercial SiC powder of technical grade has been shown. Sintering behavior and microstructure formation under conditions of liquid phase sintering (LPS with oxynitride sintering aids (AlN-Y2O3 of three SiC-based compositions have been investigated. Two of the compositions were based on Alcoa 1000 SiC powder of technical grade, and the third one, which was used as a reference, was based on H.C. Starck UF-15 fine grade commercial powder. Milling process used for Alcoa 1000 SiC powder granulometry improvement has been investigated in detail, while chemical treatment of milled SiC powders has been used for pick-up impurities removal. Dilatometric experiments showed that SiC powder of technical grade after appropriate treatment exhibits sinterability comparable with the fine grade SiC. Microstructural investigations performed on sintered samples showed that the final microstructure of the Alcoa 1000 SiC based materials was practically identical with the H.C. Starck SiC based reference ones. Preliminary investigations of hardness and fracture toughness were carried out revealing excellent results for the materials produced from cheaper, nationally produced starting powder.Neste trabalho é apresentada a possibilidade de obtenção de cerâmicas de SiC de alto desempenho a partir de matéria-prima comercial de grau técnico. Foi realizado o estudo de sinterização via fase líquida e desenvolvimento microestrutural de três composições à base de SiC tendo como aditivos de sinterização AlN e Y2O3 . Duas destas composições são à base de SiC-1000 da Alcoa, grau técnico, e a terceira, utilizada como referência, à base do UF-15 da H.C. Starck - Alemanha, pó comercial de granulometria fina. O processo de moagem do pó SiC-1000 da Alcoa foi acompanhado por medidas de distribuição granulométrica e posterior ataque químico, para remoção de impurezas. Os pós de grau técnico, ap

  20. The Start of a Tech Revolution

    Science.gov (United States)

    Dyrli, Kurt O.

    2009-01-01

    We are at the start of a revolution in the use of computers, one that analysts predict will rival the development of the PC in its significance. Companies such as Google, HP, Amazon, Sun Microsystems, Sony, IBM, and Apple are orienting their entire business models toward this change, and software maker SAS has announced plans for a $70 million…

  1. START to Get Ready for Breastfeeding

    Science.gov (United States)

    Breastfeeding is a great way to give your baby the nutrients he or she needs to grow and develop. Breastfeeding also can help you and your baby form a special bond. Breastfeeding can be good for both of you if you know where to S-T-A-R-T.

  2. Automobile Starting and Lighting System Maintenance Training ...

    African Journals Online (AJOL)

    The purpose of this study is to develop automobile starting and lighting system maintenance training manual for technical college students. Research and Development (R and D) design was adopted for the study. The population of the study is 348, comprising of 76 auto-mechanics teachers, 36 automobile supervisors and ...

  3. Addressing Tooth Decay in Head Start Children

    Science.gov (United States)

    Knowlden, Adam P.; Hill, Lawrence F.; Alles-White, Monica L.; Cottrell, Randall R.

    2012-01-01

    Tooth decay is the most prevalent chronic disease of childhood. Oral health education and dental services are crucial to reducing the number of children afflicted with dental cavities. Due to limited access to preventative care, Head Start children are particularly vulnerable to tooth decay. This article outlines practical implications of a…

  4. Single phase induction motor with starting performance

    Energy Technology Data Exchange (ETDEWEB)

    Popescu, M.; Demeter, E. [Research Institute for Electrical Machines, ICPE-ME, Bucharest (Romania); Navrapescu, V. [University `Politehnica` Bucharest, Electrical Engineering Faculty Splaiul Independentei, Bucharest (Romania)

    1997-12-31

    The paper presents problems related to a special type of single phase induction motor. The main novelty consists in the use of a conducting (aluminium casted) shell distributed on the periferic region of the rotor. As a result the starting performance, as well as the rated ones, is much improved in comparison with the conventional construction. (orig.) 4 refs.

  5. From Jam to Start-up

    DEFF Research Database (Denmark)

    Bering Kjæhr, Emil; Lyngbye Hvid Jensen, Jane; Schoenau-Fog, Henrik

    2015-01-01

    the foundation for new start-up companies. There are, however, an even larger group of very creative and innovative games and artifacts with great potential that go unpublished. This potentially leads to a loss of entrepreneurial opportunities and ultimately the jobs and careers such games could have fostered...

  6. An Overview of Head Start Program Studies

    Science.gov (United States)

    Hines, Jeanne Morris

    2017-01-01

    Johnson's "War on Poverty" administrative team campaigned for committee members to join the War on Poverty efforts to create and develop programs for children born into poverty (Zigler, 2003). Poverty based programs, such as the Head Start program, continue to put into place proactive measures to increase preschooler's cognitive…

  7. School Start Time and Teen Sleep.

    Science.gov (United States)

    Wahlstrom, Kyla L.

    2000-01-01

    Sleep studies have shown that teenagers' internal clocks are incompatible with most high schools' early hours. Research in two Minnesota districts indicates that later school starting times can benefit teens and everyone dealing with them. Student participation in sports and other afterschool activities remained high. (MLH)

  8. Getting started with Magento module development

    CERN Document Server

    Ajzele, Branko

    2013-01-01

    This project-based tutorial gives you a strong foundation and guides you through practical, real-world examples.This book contains valuable insights for both newbies and already established Magento developers. This book is targeted at new and intermediate PHP developers starting afresh with Magento module development.

  9. Getting started with OrientDB

    CERN Document Server

    Tesoriero, Claudio

    2013-01-01

    A standard tutorial aimed at making you an OrientDB expert, through the use of practical examples, explained in a step-by-step format.Getting Started with OrientDB 1.3.0 is great for database designers, developers, and systems engineers. It is assumed that you are familiar with NoSQL concepts, Java, and networking principles.

  10. An Alternative Starting Point for Fraction Instruction

    Science.gov (United States)

    Cortina, José Luis; Višnovská, Jana; Zúñiga, Claudia

    2015-01-01

    We analyze the results of a study conducted for the purpose of assessing the viability of an alternative starting point for teaching fractions. The alternative is based on Freudenthal's insights about fraction as comparison. It involves portraying the entities that unit fractions quantify as always being apart from the reference unit, instead of…

  11. Evaluation of Hawaii's Healthy Start Program.

    Science.gov (United States)

    Duggan, Anne K.; McFarlane, Elizabeth C.; Windham, Amy M.; Rohde, Charles A.; Salkever, David S.; Fuddy, Loretta; Rosenberg, Leon A.; Buchbinder, Sharon B.; Sia, Calvin C. J.

    1999-01-01

    Describes Hawaii's Healthy Start Program (HST), its ongoing evaluation study, and evaluation findings at the end of two of a planned three years of family-program participation and follow-up. HST uses home visitors to help prevent abusive and neglectful parenting. Found significant differences in program implementation among the three…

  12. Starting Up after 50. CELCEE Digest.

    Science.gov (United States)

    Seymour, Nicole

    Researchers are finding that older entrepreneurs are an increasing population in many Western countries. It is important to distinguish between entrepreneurs who have simply reached the age of 50 versus those who start up businesses after this age. The latter group is of particular interest because these people have presumably never faced the…

  13. Starting Small, Thinking Big - Continuum Magazine | NREL

    Science.gov (United States)

    , Thinking Big Stories NREL Helps Agencies Target New Federal Sustainability Goals Student Engagements Help solar power in the territory. Photo by Don Buchanan, VIEO Starting Small, Thinking Big NREL helps have used these actions to optimize that energy use.'" NREL's cross-organizational work supports

  14. 76 FR 70009 - Head Start Program

    Science.gov (United States)

    2011-11-09

    ... importance of the early years of a child's growth and development. On December 12, 2007, the Improving Head... education, serving nearly one million of our nation's most vulnerable young children and their families. It... Administration for Children and Families 45 CFR Part 1307 Head Start Program; Final Rule #0;#0;Federal Register...

  15. Early Start DENVER Model: A Meta - analysis

    Directory of Open Access Journals (Sweden)

    Jane P. Canoy

    2015-11-01

    Full Text Available Each child with Autism Spectrum Disorder has different symptoms, skills and types of impairment or disorder with other children. This is why the word “spectrum” is included in this disorder. Eapen, Crncec, and Walter, 2013 claimed that there was an emerging evidence that early interventions gives the greatest capacity of child’s development during their first years of life as “brain plasticity” are high during this period. With this, the only intervention program model for children as young as 18 months that has been validated in a randomized clinical trial is “Early Start Denver Model” (ESDM. This study aimed to determine the effectiveness of the outcome of “Early Start Denver Model” (ESDM towards young children with Autism Spectrum Disorders. This study made use of meta-analysis method. In this study, the researcher utilized studies related to “Early Start Denver Model (ESDM” which is published in a refereed journal which are all available online. There were five studies included which totals 149 children exposed to ESDM. To examine the “pooled effects” of ESDM in a variety of outcomes, a meta-analytic procedure was performed after the extraction of data of the concrete outcomes. Comprehensive Meta Analysis Version 3.3.070 was used to analyze the data.  The effectiveness of the outcome of “Early Start Denver Model” towards young children with Autism Spectrum Disorders (ASD highly depends on the intensity of intervention and the younger child age. This study would provide the basis in effectively implementing an early intervention to children with autism such as the “Early Start Denver Model” (ESDM that would show great outcome effects to those children that has “Autism Spectrum Disorder”.

  16. 45 CFR 1308.21 - Parent participation and transition of children into Head Start and from Head Start to public...

    Science.gov (United States)

    2010-10-01

    ... into Head Start and from Head Start to public school. 1308.21 Section 1308.21 Public Welfare... AND HUMAN SERVICES THE ADMINISTRATION FOR CHILDREN, YOUTH AND FAMILIES, HEAD START PROGRAM HEAD START... Standards § 1308.21 Parent participation and transition of children into Head Start and from Head Start to...

  17. Software for physical start-up console

    International Nuclear Information System (INIS)

    Arbet, L.; Suchy, R.

    1991-01-01

    The physical start-up console comprises an PC AT-based control unit equipped with an 80386 processor, and information input/output units. The basic functions to be fulfilled by the control unit software include data acquisition related to the following parameters: neutron physics properties of the reactor core (neutron fluxes recorded by ionization chambers and reactivity recorded by a digital reactimeter), positions of the reactor core control elements (by the digital position meter) and reactor core control measurements, and technological quantities requisite for evaluating physical start-up tests. The measured and calculated data are shown on the control unit display. The setup of the data acquisition system and of user programs is dealt with, and characteristics of the user processes are briefly described. (Z.S.)

  18. Single start multiple stop time digitizer

    International Nuclear Information System (INIS)

    Deshpande, P.A.; Mukhopadhyay, P.K.; Gopalakrishnan, K.R.

    1997-01-01

    A single start multiple stop time digitizer has been developed which can digitize the time between a start pulse and multiple stop pulses. The system has been designed as a PC add on card. The resolution of the instrument is 10 nSecs and the maximum length of time that it can measure is 1.28 milliseconds. Apart from time digitization, it can also resolve the height of the incoming pulses into 64 levels. After each input pulse the system dead time is less than 300 nSecs. The driver software for this card has been developed on DOS platform. It uses graphical user interface to provide a user friendly environment. The system is intended to be used in time of flight mass spectroscopy experiments. It can also be used for time of flight experiments in nuclear physics. (author). 2 figs

  19. Lean and global technology start-ups

    DEFF Research Database (Denmark)

    Tanev, Stoyan; Rasmussen, Erik Stavnsager; Zijdemans, Erik

    2015-01-01

    In this paper the authors introduce the concept of Lean Global Start-up (LGS) as a way of emphasizing the impossibility for new technology start-ups to deal separately with business development, innovation and early internationalization. For a newly established technology firm the task of being...... global and innovative at the same time should be seen as one process. The paper has two components – an introductory conceptual part and an empirical part that should be considered as basis for the preliminary validation of the conceptual insights. The research sample includes six firms – three from...... Canada and three from Denmark. The firms have had significant problems with the complexity, uncertainties and risks of being innovative on a global scale. They have however found ways of addressing these problems by a disciplined knowledge sharing and IP protection strategy and the efficient use...

  20. Starting apparatus for internal combustion engines

    Science.gov (United States)

    Dyches, Gregory M.; Dudar, Aed M.

    1997-01-01

    An internal combustion engine starting apparatus uses a signal from a curt sensor to determine when the engine is energized and the starter motor should be de-energized. One embodiment comprises a transmitter, receiver, computer processing unit, current sensor and relays to energize a starter motor and subsequently de-energize the same when the engine is running. Another embodiment comprises a switch, current transducer, low-pass filter, gain/comparator, relay and a plurality of switches to energize and de-energize a starter motor. Both embodiments contain an indicator lamp or speaker which alerts an operator as to whether a successful engine start has been achieved. Both embodiments also contain circuitry to protect the starter and to de-energize the engine.

  1. Starting procedure for internal combustion vessels

    Science.gov (United States)

    Harris, Harry A.

    1978-09-26

    A vertical vessel, having a low bed of broken material, having included combustible material, is initially ignited by a plurality of ignitors spaced over the surface of the bed, by adding fresh, broken material onto the bed to buildup the bed to its operating depth and then passing a combustible mixture of gas upwardly through the material, at a rate to prevent back-firing of the gas, while air and recycled gas is passed through the bed to thereby heat the material and commence the desired laterally uniform combustion in the bed. The procedure permits precise control of the air and gaseous fuel mixtures and material rates, and permits the use of the process equipment designed for continuous operation of the vessel.

  2. Getting started with MariaDB

    CERN Document Server

    Bartholomew, Daniel

    2013-01-01

    A practical, hands-on, beginner-friendly guide to installing and using MariaDB.Getting Started with MariaDB is for anyone who wants to learn more about databases in general or MariaDB in particular. No prior database experience is required. It is assumed that you have basic knowledge of software installation, editing files with a text editor, and using the command line and terminal.

  3. The 2002 Starting Artificial Intelligence Researchers Symposium

    OpenAIRE

    Vidal, Thierry

    2003-01-01

    During the 2002 European Conference on Artificial Intelligence (ECAI-02) was introduced the Starting Artificial Intelligence Researchers Symposium STAIRS), the first-ever international symposium specifically aimed at Ph.D. students in AI. The outcome was a thorough, high-quality, and successful event, with all the features one usually finds in the best international conferences: large international committees, comprehensive coverage, published proceedings, renowned speakers and panelists, sub...

  4. The rotating converter GKN II starts operation

    International Nuclear Information System (INIS)

    Jergas, E.

    1989-01-01

    At the beginning of 1989 the energy supply and consumption of the 110-kV-railway mains has changed considerably with starting the rotating converter of the German Federal Railways (DB) in the joint nuclear power station Neckar GmbH (GKN) block II. A description is given of the planned utilization of the rotating converters at baseload operation and possibilities for optimal energy use are shown. (orig.) [de

  5. Business Models for Start up Business

    OpenAIRE

    Boban, Nitin

    2010-01-01

    Gamingdom is a new start up venture that provides online gaming service utilising the latest cloud computing technology. The high demand, popularity and exponential growth in the number of gaming enthusiasts and the market have brought about this innovative idea. This new venture aims to provide an easy method of gaming through the internet without heavy expenses on hardware and software and also minimising the existing high rate of piracy. A business model is an essential tool for buildin...

  6. New Start of “Psychological Thought”

    Directory of Open Access Journals (Sweden)

    Stanislava Stoyanova

    2012-05-01

    Full Text Available The history and the mission of Psychological Thought are presented. The scientific journal “Psychological Thought” started its existence as an idea of the colleagues at the Department of Psychology at South-West University “Neofit Rilski” in 2006. Seven print issues were published from 2006 to 2009 (2 issues per year. Each issue included average ten articles published in Bulgarian or in English.

  7. Getting started with nopCommerce

    CERN Document Server

    Atkinson, Brandon

    2013-01-01

    A friendly, tutorial style book, which will help you learn your way through creating a live storefront with nopCommerce in a step-by-step manner.Getting Started with nopCommerce is for anyone who wants to sell products online using nopCommerce. If you are a non-technical person and are discouraged by the complexity of this powerful e-commerce application, then this book is for you.

  8. Starting and developing a surveying business

    CERN Document Server

    Imber, Austen

    2013-01-01

    Starting and Developing a Surveying Business shows how surveyors can develop their own successful small business. For surveyors thinking of taking this step, guidance is provided on the pros and cons which will help the right decision to be made, and the key factors which help see the business through its early stages. For surveyors already running their own small business, consideration is given to factors which will help profitability and growth potential.

  9. A Fast-Starting Robotic Fish

    Science.gov (United States)

    Modarres-Sadeghi, Yahya; Watts, Matthew; Conte, Joe; Hover, Franz; Triantafyllou, Michael

    2009-11-01

    We have built a simple mechanical system to emulate the fast-start performance of fish. The system consisted of a thin metal beam covered by a urethane rubber fish body. The body form of the mechanical fish in this work was modeled from a pike species, which is the most successfully studied fast-start specialist species. The mechanical fish was held in curvature and hung in water by two restraining lines, which were simultaneously released by pneumatic cutting mechanisms. The potential energy in the beam was transferred into the fluid, thereby accelerating the fish, similar to a pike. We measured the resulting velocity and acceleration, as well as the efficiency of propulsion for the mechanical fish model and also ran a series of flow visualization tests to observe the resulting flow pattern. We also studied the influence of stiffness and geometry of the tail on the efficiency of propulsion and flow pattern. The hydrodynamic efficiency of the fish, calculated by the transfer of energy, was around 10%. Flow visualization of the mechanical fast-start wake was also analyzed, showing that the acceleration is associated with the fast movement of an intense vortex in a near-lateral direction.

  10. Method of starting up PWR type reactor

    International Nuclear Information System (INIS)

    Kadokami, Akira; Ueno, Ryuji; Tsuge, Ayao; Onimura, Kichiro; Ochi, Tatsuya.

    1988-01-01

    Purpose: To start-up a PWR type reactor so as to effectively impregnate and concentrate corrosion inhibitors in intergranular corrosive faces. Method: Upon reactor start-up, after transferring from the warm zero output state to thermal power loaded state and injecting corrosion inhibitors, thermal power is returned to zero and, subsequently, increased up to a rated power. By selecting the thermal power upon injecting the corrosion inhibitors to a steam generator body, that is, by selecting a thermal power load that starts to boil in heat conduction tubes, feedwater in the clavis portion can be formed into an appropriate boiling convection and, accordingly, the corrosion inhibitors can be penetrated to the clevis portion at a higher rate and in a greater amount as compared with those under zero power condition. Subsequently, when the thermal power is reduced, a sub-cooled state is attained in the clevis portion, in which steams present in the intergranular corrosion faces in the heat conduction tubes are condensated. As a result, the corrosion inhibitors at high concentration are impregnated into the intergranular corrosive faces to provide excellent effects. (Kamimura, M.)

  11. Exercise starts and ends in the brain.

    Science.gov (United States)

    Kayser, Bengt

    2003-10-01

    Classically the limit to endurance of exercise is explained in terms of metabolic capacity. Cardio-respiratory capacity and muscle fatigue are thought to set the limit and the majority of studies on factors limiting endurance exercise discuss issues such as maximal oxygen uptake (VO2max), aerobic enzyme capacity, cardiac output, glycogen stores, etc. However, this paradigm does not explain the limitation to endurance exercise with large muscle groups at altitude, when at exhaustion exercise is ended without limb locomotor muscle fatigue and with sub-maximal cardiac output. A simple fact provides a basis for an explanation. Voluntary exercise starts and ends in the brain. It starts with spatial and temporal recruitment of motor units and ends with their de-recruitment. A conscious decision precedes a voluntary effort. The end of effort is again volitional and a forced conscious decision to stop precedes it, but it is unknown what forces the off-switch of recruitment at exhaustion although sensation of exertion certainly plays a role. An alternative model explaining the limitation of exercise endurance thus proposes that the central nervous system integrates input from various sources all related to the exercise and limits the intensity and duration of recruitment of limb skeletal muscle to prevent jeopardizing the integrity of the organism. This model acknowledges the cardio-respiratory and muscle metabolic capacities as prime actors on the performance scene, while crediting the central nervous system for its pivotal role as the ultimate site where exercise starts and ends.

  12. Modelling magnetic laminations under arbitrary starting state and flux waveform

    International Nuclear Information System (INIS)

    Bottauscio, Oriano; Chiampi, Mario; Ragusa, Carlo

    2005-01-01

    A numerical model able to predict the behaviour of a magnetic sheet under arbitrary supply conditions has been developed. The electromagnetic field problem is formulated in terms of an electric vector potential, which provides the magnetic field strength evolution. The hysteretic behaviour of the material is represented through the dynamic Preisach model where the activation law of the bi-state operators is modified in order to guarantee a smooth response. The problem has been solved through a time step procedure using the fixed Point technique for handling nonlinearity. The model has been validated by comparison with suitable experiments and it is applied to the investigation of the influence of the materials' starting state on the magnetic behaviour

  13. Key parameters of the swimming start and their relationship to start performance.

    Science.gov (United States)

    Tor, Elaine; Pease, David L; Ball, Kevin A

    2015-01-01

    The swimming start is typically broken into three sub-phases; on-block, flight, and underwater phases. While overall start performance is highly important to elite swimming, the contribution of each phase and important technical components within each phase, particularly with the new kick-start technique, has not been established. The aim of this study was to identify technical factors associated with overall start performance, with a particular focus on the underwater phase. A number of parameters were calculated from 52 starts performed by elite freestyle and butterfly swimmers. These parameters were split into above-water and underwater groupings, before factor analysis was used to reduce parameter numbers for multiple regression. For the above-water phases, 81% of variance in start performance was accounted for by take-off horizontal velocity. For the underwater water phase, 96% of variance was accounted for with time underwater in descent, time underwater in ascent and time to 10 m. Therefore, developing greater take-off horizontal velocity and focussing on the underwater phase by finding the ideal trajectory will lead to improved start performance.

  14. 46 CFR 112.50-7 - Compressed air starting.

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 4 2010-10-01 2010-10-01 false Compressed air starting. 112.50-7 Section 112.50-7... air starting. A compressed air starting system must meet the following: (a) The starting, charging... air compressors addressed in paragraph (c)(3)(i) of this section. (b) The compressed air starting...

  15. Ageing significantly at Temelin start-up process

    International Nuclear Information System (INIS)

    Brumovsky, M.; Zdarek, J.; Hahn, J.

    2002-01-01

    Full text: NPP Temelin is a unique case in Plant Life Management Programme application as it is now only in the period of start-up and thus all measures can be easily prepared and implemented in advance based on the experience of similar plants already in operation. Detailed analyses of potential damaging mechanisms as well as of initial conditions and properties of main components have been already done. Regarding this analysis, several measures have been prepared and put into operation: List of important parameters to be measured, saved and periodically analysed have been prepared - some of these parameters are measured in the framework of standard I and C system; new sets of sensors were installed for some additional ones; Special software for on-line evaluation of stress/temperature conditions and subsequently also fatigue damage in some chosen parts (with flow stratification etc.) have been installed and during reactor start-up tests have been checked; Surveillance specimen programme for reactor pressure vessel material monitoring was modified for better and fuller characterisation of material changes during operation; Ex-vessel neutron flux measurement has been established as a part of surveillance specimen programme. The whole Plant Life Management Programme is governed by a special PLIM Group in the plant with necessary links and responsibilities and rules with other necessary plant departments. (author)

  16. START: an advanced radiation therapy information system.

    Science.gov (United States)

    Cocco, A; Valentini, V; Balducci, M; Mantello, G

    1996-01-01

    START is an advanced radiation therapy information system (RTIS) which connects direct information technology present in the devices with indirect information technology for clinical, administrative, information management integrated with the hospital information system (HIS). The following objectives are pursued: to support decision making in treatment planning and functional and information integration with the rest of the hospital; to enhance organizational efficiency of a Radiation Therapy Department; to facilitate the statistical evaluation of clinical data and managerial performance assessment; to ensure the safety and confidentiality of used data. For its development a working method based on the involvement of all operators of the Radiation Therapy Department, was applied. Its introduction in the work activity was gradual, trying to reuse and integrate the existing information applications. The START information flow identifies four major phases: admission, visit of admission, planning, therapy. The system main functionalities available to the radiotherapist are: clinical history/medical report linking function; folder function; planning function; tracking function; electronic mail and banner function; statistical function; management function. Functions available to the radiotherapy technician are: the room daily list function; management function: to the nurse the following functions are available: patient directing function; management function. START is a departmental client (pc-windows)-server (unix) developed on an integrated database of all information of interest (clinical, organizational and administrative) coherent with the standard and with a modular architecture which can evolve with additional functionalities in subsequent times. For a more thorough evaluation of its impact on the daily activity of a radiation therapy facility, a prolonged clinical validation is in progress.

  17. Getting started with Zurb Foundation 4

    CERN Document Server

    Patterson, Andrew D

    2013-01-01

    The book starts with the basics of Foundation and helps you build your skills as you advance from installation to design, configuration, and customization with examples at every step.This book will be of great benefit to web architects, designers, and builders. While it helps to be a programmer, it isn't necessary for this book. You should be familiar with the basic principles of responsive web design and have a desire to create a professional website that looks great on both mobile devices and regular displays.

  18. Getting started in 3D with Maya

    CERN Document Server

    Watkins, Adam

    2012-01-01

    Deliver professional-level 3D content in no time with this comprehensive guide to 3D animation with Maya. With over 12 years of training experience, plus several award winning students under his belt, author Adam Watkins is the ideal mentor to get you up to speed with 3D in Maya. Using a structured and pragmatic approach Getting Started in 3D with Maya begins with basic theory of fundamental techniques, then builds on this knowledge using practical examples and projects to put your new skills to the test. Prepared so that you can learn in an organic fashion, each chapter builds on the know

  19. Getting started with FortiGate

    CERN Document Server

    Fabbri, Rosato

    2013-01-01

    This book is a step-by-step tutorial that will teach you everything you need to know about the deployment and management of FortiGate, including high availability, complex routing, various kinds of VPN working, user authentication, security rules and controls on applications, and mail and Internet access.This book is intended for network administrators, security managers, and IT pros. It is a great starting point if you have to administer or configure a FortiGate unit, especially if you have no previous experience. For people that have never managed a FortiGate unit, the book helpfully walks t

  20. Getting started with the Lazarus IDE

    CERN Document Server

    Person, Roderick

    2013-01-01

    This book is written in a simple, easy-to-understand format with lots of screenshots and step-by-step explanations.This book is geared toward developers that have a familiarity with Delphi or Free Pascal and would like to start using the open source Lazarus Integrated Development Environment. You should have knowledge of creating a console and GUI applications as well as creating basic components. Example source code and projects are provided to help learn the differences between Delphi and Lazarus projects.

  1. Participation in testing and start up operations

    International Nuclear Information System (INIS)

    Prasad, Y.S.R.

    1977-01-01

    Testing and start up operations of a nuclear power plant require careful planning. A detailed program of tests and the responsibility of implementing them is discussed. Requirement of documentation covering the tests and operating procedures is explained. The performance of the system during normal and abnomal operating conditions is analysed and required are modifications carried out. Various phases of commissioning and their significance are explained. Preparation of maintenance documentation and training of operating and maintenance staff during this period are discussed. Necessity of close liaison between the regulatory body and the operating organization is explained. (orig.) [de

  2. EU Emission Trading: Starting with Carbon Dioxide

    DEFF Research Database (Denmark)

    Vesterdal, Morten; Svendsen, Gert Tinggaard

    2003-01-01

    The Commission of the European Union wants to start a limited emission trading scheme by 2005 within the Community to enable "learning-by-doing" prior to the Kyoto Protocol. This to accomplish the desired 8% target level for six different greenhouse gases. However, in the EU it is not clear whether...... all the six relevant greenhouse gases or only CO2 should be traded. What is the simplest and most practicable solution? We argue in favour of the latter option for three main reasons: the possible dominating global warming potential of CO2, expected future developments in CO2 emissions and the fact...

  3. Start-up tests of NSRR

    International Nuclear Information System (INIS)

    1976-12-01

    Start up tests of the Nuclear Safety Research Reactor (NSRR) were carried out from June 25 to August 15, 1975. The course of tests is in three stage, i.e. critical approach and zero power, power-up and pulse operation. Performance of the reactor was shown to be in good agreement with the design specifications in both steady-state and pulse operations. Test procedures and the results are presented in four parts: (I) general, (II) zero-power tests, (III) power-up tests, and (IV) pulse operation tests. (auth.)

  4. Particle Physics at the LHC Start

    CERN Document Server

    Altarelli, Guido

    2011-01-01

    I present a concise review of the major issues and challenges in particle physics at the start of the LHC era. After a brief overview of the Standard Model and of QCD, I will focus on the electroweak symmetry breaking problem which plays a central role in particle physics today. The Higgs sector of the minimal Standard Model is so far just a mere conjecture that needs to be verified or discarded by the LHC. Probably the reality is more complicated. I will summarize the motivation for new physics that should accompany or even replace the Higgs discovery and a number of its possible forms that could be revealed by the LHC.

  5. Getting started with ownCloud

    CERN Document Server

    Patawari, Aditya

    2013-01-01

    This is a standard, precise, and short tutorial for setting up ownCloud and includes advanced topics like encryption, user management, and server security. This ownCloud book would be an ideal starting point for anyone who wants to store their data and also share it.This book is for first time users as well as administrators who are interested or responsible for managing an ownCloud instance. You do not need any prior experience with any of the technology, including Linux/Windows, Apache/IIS, SQLite/MySQL, or even PHP. It is a beginner-friendly book, written with a first time user in mind.

  6. Starting a Chinese Sauce Company in Helsinki

    OpenAIRE

    Shu, Bing; Shi, Jianan

    2017-01-01

    The thesis is about starting-up a Chinese sauce company in Helsinki. The introduction is about the history of Laoganma company and the missions of a branch company in Helsinki, as well as the aims of the project. The part about market research includes the current situation of Finnish sauce market and a SWOT analysis for a Finnish market entrance. Also, a successful case reflects the developed way for the company. Then, the price and location are defined in the thesis. Sales strategi...

  7. Take Control of Getting Started with Dreamweaver

    CERN Document Server

    Keller, Arnie

    2009-01-01

    Learn fundamental Web design principles and become comfortable working in Dreamweaver's complex interface! Dreamweaver 8 is a great Web design tool for pros, but newcomers may be overwhelmed by its interface or want to know more about how to work creatively and intelligently in the program. Help is at hand in Take Control of Getting Started with Dreamweaver, which offers a detailed tutorial for making your first site in Dreamweaver. Author Arnie Keller, who teaches Web design at the University of Victoria, shows you how to style type the smart way with CSS, create a sophisticated page layout

  8. Aqueous-phase synthesis and color-tuning of core/shell/shell inorganic nanocrystals consisting of ZnSe, (Cu, Mn)-doped ZnS, and ZnS

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Jongwan; Yoon, Sujin [Department of Chemistry and Research Institute for Natural Science, Hanyang University, Seoul, 133-791 (Korea, Republic of); Kim, Felix Sunjoo, E-mail: fskim@cau.ac.kr [School of Chemical Engineering and Materials Science, Chung-Ang University, Seoul, 156-756 (Korea, Republic of); Kim, Nakjoong, E-mail: kimnj@hanyang.ac.kr [Department of Chemistry and Research Institute for Natural Science, Hanyang University, Seoul, 133-791 (Korea, Republic of)

    2016-06-25

    We report synthesis of colloidal nanocrystals based on ZnSe core, (Cu,Mn)-doped ZnS inner-shell, and ZnS outer-shell by using an eco-friendly method and their optical properties. Synthesis of core/shell/shell nanocrystals was performed by using a one-pot/three-step colloidal method with 3-mercaptopropionic acid as a stabilizer in aqueous phase at low temperature. A double-shell structure was employed with inner-shell as a host for doping and outer-shell as a passivation layer for covering surface defects. Copper and manganese were introduced as single- or co-dopants during inner-shell formation, providing an effective means to control the emission color of the nanocrystals. The synthesized nanocrystals showed fluorescent emission ranging from blue to green, to white, and to orange, adjusted by doping components, amounts, and ratios. The photoluminescence quantum yields of the core/doped-shell/shell nanocrystals approached 36%. - Highlights: • ZnSe/ZnS:(Cu,Ms)/ZnS core/(doped)shell/shell nanocrystals were synthesized in an aqueous phase. • Emission color of nanocrystals was controlled from blue to white to orange by adjusting the atomic ratio of Cu and Mn co-dopants. • Photoluminescence quantum yields of the colloidal nanocrystals approached 36%.

  9. ORGANIZING THE MUSIC CLASSES IN STARTING SCHOOLS

    Directory of Open Access Journals (Sweden)

    N. G. Tagiltseva

    2013-01-01

    Full Text Available The paper considers the issue of children preparation for school in so called starting schools. In author’s opinion, the arts disciplines such as music, drawing and choreography can develop the aesthetic sense, moral qualities, more optimistic world outlook and respectful  attitude; the child develops creative skills and beauty perception both in fine arts and wild life.The author looks at the problems of planning and organizing the music training of preschool children, the different requirements for and concepts of the preschool and primary school normative documents being analyzed. The paper substantiates the effectiveness of poly-artistic and activity approaches to the split-level teaching, in particular – the method of projecting the familiar actions onto some sort of artistic activities. Based on the succession of preschool and primary school training, the author specifies the goals of music classes in starting schools, and outlines the most relevant game activities of role plays, didactic plays and contests.The paper is addressed to preschool and primary school teachers, music teachers, as well as methodologists and researchers dealing with preschool teaching. 

  10. LHC Report: Rocky re-start

    CERN Multimedia

    Barbara Holzer for the LHC Team

    2012-01-01

    A rocky re-start with beam followed a successful machine development period and the first technical stop of 2012. Today, Friday 11 May, the machine began running again with 1380 bunches.   A short, two-day machine development period was successfully completed on 21-22 April. It focused on topics relevant for the 2012 physics beam operation. This was then followed by a five-day technical stop, the first of the year. The technical stop finished on time on Friday 26 April. The re-start with beam was somewhat tortuous and hampered by an unlucky succession of technical faults leading to extended periods of downtime. The planned intensity increase was put on hold for three days with the machine operating with 1092 bunches and a moderate bunch intensity of 1.3x1011 protons. This delivered a reasonable peak luminosity of 3.6x1033 cm-2s-1 to ATLAS and CMS. Higher than usual beam losses were observed in the ramp and squeeze, and time was required to investigate the causes and to implement mitigati...

  11. Danish Ophthalmology - from start to 1865.

    Science.gov (United States)

    Norn, Mogens

    2016-03-01

    This short paper mentioned the medical treatment using the 'holy' springs, the first 'eye doctor' in Denmark, the first picture of spectacles which was found in Viborg Cathedral of the high priest before he performs circumcisio praeputii on Jesus Christ, further cataract reclination in Denmark from around year zero and cataract extraction in 1667 in Denmark on a goose by Francisco Borri and on humans by the Danish Georg Heuermann in 1755. Epidemic military eye diseases in 1807, 1856 and 1865 are also described in this study. From 1856, a new ophthalmological period started in Denmark with the first eye hospital (lazaret only for eye diseases), and in 1864, patients with eye diseases were transported from the few beds in the surgical departments in the municipal hospital to the first civil eye department in Denmark, the eye hospital Sct. Annae in Copenhagen. The new scientific period started with Jacob Christian Bentz (ophthalmia granulosa, joint editor of the Danish Medical Journal) and Heinrich Lehmann. © 2016 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

  12. Inadvertent pump start with gas expansion modules

    International Nuclear Information System (INIS)

    Campbell, L.R.; Harris, R.A.; Heard, F.J.; Dautel, W.A.

    1992-01-01

    Previous testing demonstrated the effectiveness of gas expansion modules (GEMs) in mitigating the consequences of a loss-of-flow-without-scram transient in Fast Flux Test Facility (FFTF)-sized sodium cooled cores. As a result, GEMs have been included in the advance liquid-metal reactor (PRISM) design project sponsored by the US Department of Energy. The PRISM design is under review at the US Nuclear Regulatory Commission for licensability. In the unlikely event that the reactor does not scram during a loss of low, the GEMs quickly insert sufficient negative reactivity to limit fuel and cladding temperatures to acceptable values. This is the positive benefit of the GEMs; however, the reverse situation must be considered. A primary pump could be inadvertently started from near-critical conditions resulting in a positive reactivity insertion and a power transient. One mitigating aspect of this event is that as the reactivity associated with the GEMs is inserted, the increasing flow increases core cooling. A test was conducted in the FFTF to demonstrate that the GEM and feedback reactivity are well predicted following pump start, and the reactivity transient is benign

  13. Bauxite slurry pipeline: start up operation

    Energy Technology Data Exchange (ETDEWEB)

    Othon, Otilio; Babosa, Eder; Edvan, Francisco; Brittes, Geraldo; Melo, Gerson; Janir, Joao; Favacho, Orlando; Leao, Marcos; Farias, Obadias [Vale, Rio de Janeiro, RJ (Brazil); Goncalves, Nilton [Anglo Ferrous Brazil S.A., Rio de Janeiro, RJ (Brazil)

    2009-07-01

    The mine of Miltonia is located in Paragominas-PA, in the north of Brazil. Bauxite slurry pipeline starts at the Mine of Miltonia and finishes in the draining installation of Alunorte refinery at the port of Barcarena-PA, located approximately 244km away from the mine. The pipeline runs over seven cities and passes below four great rivers stream beds. The system was designed for an underground 24 inches OD steel pipe to carry 9.9 million dry metric tonnes per annum (dMTAs) of 50.5% solid concentration bauxite slurry, using only one pumping station. The system is composed by four storage tanks and six piston diaphragm pumps, supplying a flow of 1680 m3/h. There is a cathodic protection system along the pipeline extension to prevent external corrosion and five pressure monitoring stations to control hydraulic conditions, there is also a fiber optic cable interconnection between pump station and terminal station. Pipeline Systems Incorporated (PSI) was the designer and followed the commissioning program of the start up operations. This paper will describe the beginning of the pipeline operations, technical aspects of the project, the operational experiences acquired in these two years, the faced problems and also the future planning. (author)

  14. Giving start-ups a helping hand

    CERN Multimedia

    2008-01-01

    The French-Swiss foundation for research and technology (FFSRT) joined forces with CERN to organise an information day on setting up new businesses, at the Globe of Science and Innovation. The participants heard talks by entrepreneurs who started out at CERN, sharing their experiences and difficulties.CERN is a hot-bed of high-tech skills and know-how, and the Organization works actively to transfer this expertise to society. Some such innovations can lead to new business start-ups, but it can be extremely difficult to obtain the information and support you need to find your way through the inevitable administrative labyrinth. By opening its doors to the Fondation franco-suisse pour la recherche et la technologie (FFSRT) and hosting this "Entrepreneurial Day" on 7 March, CERN has clearly flagged its desire to assist budding entrepreneurs. The day was jointly kicked off by Olga Hooft, General Manager of the FFSRT, and Maximilian Metzger, CERN’s Se...

  15. Training Materials Developed for Latino Entrepreneurs

    Science.gov (United States)

    Abreo, Christina; Miller, Wayne; Farmer, Frank; Moon, Zola; McCullough, Stacey

    2014-01-01

    This article describes the materials and training program that Extension created to assist current and potential Latino immigrant entrepreneurs in starting businesses in Arkansas. The content-based educational materials describe the process for starting a new business, government regulatory requirements, start-up costs and considerations, and how…

  16. Fusion reactor start-up without an external tritium source

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, S., E-mail: Shanliang.Zheng@ccfe.ac.uk; King, D.B.; Garzotti, L.; Surrey, E.; Todd, T.N.

    2016-02-15

    Highlights: • Investigated the feasibility (including plasma physics, neutronics and economics) of starting a fusion reactor from running pure D–D fusion reactor to gradually move towards the D–T operation. • Proposed building up tritium from making use of neutrons generated by D–D fusion reactions. • Studied plasma physics feasibility for pure D–D operation and provided consistent fusion power and neutron yield in the plasma with different mixture of deuterium and tritium. • Discussed the economics aspect for operating a pure D–D fusion reactor towards a full-power D–T fusion reactor. - Abstract: It has long been recognised that the shortage of external tritium sources for fusion reactors using D–T, the most promising fusion fuel, requires all such fusion power plants (FPP) to breed their own tritium. It is also recognised that the initial start-up of a fusion reactor will require several kilograms of tritium within a scenario in which radioactive decay, ITER and subsequent demonstrator reactors are expected to have consumed most of the known tritium stockpile. To circumvent this tritium fuel shortage and ultimately achieve steady-state operation for a FPP, it is essential to first accumulate sufficient tritium to compensate for loss due to decay and significant retention in the materials in order to start a new FPP. In this work, we propose to accumulate tritium starting from D–D fusion reactions, since D exists naturally in water, and to gradually build up the D–T plasma targeted in fusion reactor designs. There are two likely D–D fusion reaction channels, (1) D + D → T + p, and (2) D + D → He3 + n. The tritium can be generated via the reaction channel ‘(1)’ and the 2.45 MeV neutrons from ‘(2)’ react with lithium-6 in the breeding blanket to produce more tritium to be fed back into plasma fuel. Quantitative evaluations are conducted for two blanket concepts to assess the feasibility and suitability of this approach to FPP

  17. High Time Resolution Measurements of VOCs from Vehicle Cold Starts: The Air Toxic Cold Start Pulse

    Science.gov (United States)

    Jobson, B. T.; Huangfu, Y.; Vanderschelden, G. S.

    2017-12-01

    Pollutants emitted during motor vehicle cold starts, especially in winter in some climates, is a significant source of winter time air pollution. While data exist for CO, NO, and total hydrocarbon emissions from federal testing procedures for vehicle emission certification, little is known about the emission rates of individual volatile organic compounds, in particular the air toxics benzene, formaldehyde, and acetaldehyde. Little is known about the VOC speciation and temperature dependence for cold starts. The US EPA vehicle emission model MOVES assumes that cold start emissions have the same speciation profile as running emissions. We examined this assumption by measuring cold start exhaust composition for 4 vehicles fueled with E10 gasoline over a temperature range of -4°C to 10°C in winter of 2015. The extra cold start emissions were determined by comparison with emissions during engine idling. In addition to CO and NOx measurements a proton transfer reaction mass spectrometer was used to measure formaldehyde, acetaldehyde, benzene, toluene, and C2-alkylbenzenes at high time resolution to compare with the cold start emission speciation profiles used in the EPA MOVES2014 model. The results show that after the vehicle was started, CO mixing ratios can reach a few percent of the exhaust and then drop to several ppmv within 2 minutes of idling, while NOx showed different temporal behaviors among the four vehicles. VOCs displayed elevated levels during cold start and the peak mixing ratios can be two orders higher than idling phase levels. Molar emission ratios relative to toluene were used to compare with the emission ratio used in MOVES2014 and we found the formaldehyde-to-toluene emission ratio was about 0.19, which is 5 times higher than the emission ratio used in MOVES2014 and the acetaldehyde-to-toluene emission ratios were 0.86-0.89, which is 8 times higher than the ones in MOVES2014. The C2-alkylbenzene-to-toluene ratio agreed well with moves. Our results

  18. African entrepreneurs: An analysis of their motivation for starting their own business

    Directory of Open Access Journals (Sweden)

    BC Mitchell

    2003-11-01

    Full Text Available This study analyses the motivation of entrepreneurs for starting a business.  More specifically, it aims to identify whether entrepreneurs have common  motives for starting their own business, and whether men and women have  different reasons for becoming entrepreneurs. A motivation scale and openended  questions were used to measure motivation on a sample of more than 100  entrepreneurs. The results of a factor analysis indicate that entrepreneurs have  various reasons for starting a business, and are primarily motivated by the needs  for independence, material incentives and achievement.

  19. The UK sugar tax - a healthy start?

    Science.gov (United States)

    Jones, C M

    2016-07-22

    The unexpected announcement by the UK Chancellor of the Exchequer of a levy on sugar sweetened beverages (SSBs) on the 16 March 2016, should be welcomed by all health professionals. This population based, structural intervention sends a strong message that there is no place for carbonated drinks, neither sugared nor sugar-free, in a healthy diet and the proposed levy has the potential to contribute to both general and dental health. The sugar content of drinks exempt from the proposed sugar levy will still cause tooth decay. Improving the proposed tax could involve a change to a scaled volumetric tax of added sugar with a lower exemption threshold. External influences such as the Common Agricultural Policy and the Transatlantic Trade and Investment Partnership may negate the benefits of the sugar levy unless it is improved. However, the proposed UK sugar tax should be considered as a start in improving the nation's diet.

  20. Start of the international tokamak physics activity

    International Nuclear Information System (INIS)

    Campbell, D.

    2001-01-01

    This newsletter comprises a summary on the start of the International Tokamak Physics activity (ITPA) by Dr. D. Campbell, Chair of the ITPA Co-ordinating Committee. As the ITER EDA drew to a close, it became clear that it was desirable to establish a new mechanism in order to promote the continued development of the physics basis for burning plasma experiments and to preserve the invaluable collaborations between the major international fusion communities which had been established through the ITER physics expert groups. As a result of the discussions of the representatives of the European Union, Japan, the Russian Federation and the United States the agreed principles for conducting the International Tokamak Physics Activity (ITPA) were elaborated and ITPA topical physics groups were organized

  1. Getting started with LevelDB

    CERN Document Server

    Dent, Andy

    2013-01-01

    The book is a concise guide for using LevelDB. It explains database concepts and the use of C++, ranging from the basics all the way to high level topics in an easy to follow, step-by-step format.The book is meant for developers who want an embedded database for their applications. Experienced programmers can pick up on the sophisticated data mapping patterns and tuning tips.Getting Started with LevelDB requires a minimal background in programming in C++ or Objective-C for OS/X or iOS and familiarity with XCode. Therefore it teaches enough C++ to use LevelDB without presuming any C++ knowledge

  2. [How to start a neuroimaging study].

    Science.gov (United States)

    Narumoto, Jin

    2012-06-01

    In order to help researchers understand how to start a neuroimaging study, several tips are described in this paper. These include 1) Choice of an imaging modality, 2) Statistical method, and 3) Interpretation of the results. 1) There are several imaging modalities available in clinical research. Advantages and disadvantages of each modality are described. 2) Statistical Parametric Mapping, which is the most common statistical software for neuroimaging analysis, is described in terms of parameter setting in normalization and level of significance. 3) In the discussion section, the region which shows a significant difference between patients and normal controls should be discussed in relation to the neurophysiology of the disease, making reference to previous reports from neuroimaging studies in normal controls, lesion studies and animal studies. A typical pattern of discussion is described.

  3. Start-up Strategy for Continuous Bioreactors

    Directory of Open Access Journals (Sweden)

    A.C. da Costa

    1997-06-01

    Full Text Available Abstract - The start-up of continuous bioreactors is solved as an optimal control problem. The choice of the dilution rate as the control variable reduces the dimension of the system by making the use of the global balance equation unnecessary for the solution of the optimization problem. Therefore, for systems described by four or less mass balance equations, it is always possible to obtain an analytical expression for the singular arc as a function of only the state variables. The steady state conditions are shown to satisfy the singular arc expression and, based on this knowledge, a feeding strategy is proposed which leads the reactor from an initial state to the steady state of maximum productivity

  4. Re-starting an Arnoldi iteration

    Energy Technology Data Exchange (ETDEWEB)

    Lehoucq, R.B. [Argonne National Lab., IL (United States)

    1996-12-31

    The Arnoldi iteration is an efficient procedure for approximating a subset of the eigensystem of a large sparse n x n matrix A. The iteration produces a partial orthogonal reduction of A into an upper Hessenberg matrix H{sub m} of order m. The eigenvalues of this small matrix H{sub m} are used to approximate a subset of the eigenvalues of the large matrix A. The eigenvalues of H{sub m} improve as estimates to those of A as m increases. Unfortunately, so does the cost and storage of the reduction. The idea of re-starting the Arnoldi iteration is motivated by the prohibitive cost associated with building a large factorization.

  5. Organoclays obtaining starting up of clays sodium

    International Nuclear Information System (INIS)

    Silva, M.M. da; Mota, M.F.; Oliveira, G.C. de; Rodrigues, M.G.F.

    2012-01-01

    Clays have several applications in many areas of fields of technology, however, modification of these materials using organic compounds can be performed to obtain further hydrophobic materials, for applications in the adsorption of organic pollutants. This study aimed to analyze the effects of modifying two clays using sodium quaternary ammonium surfactants through ion exchange reaction process, in obtaining organoclays. The samples with sodium and organoclays were characterized by the techniques of X-ray diffraction (XRD), Infrared Spectroscopy in the region (IV), Gravimetric and Differential Thermal Analysis (DTA / TG) and organic adsorption tests. The results show that the process of obtaining organoclay is efficient, and materials have the potential for future applications in removing organic contaminants. (author)

  6. Monitoring Start of Season in Alaska

    Science.gov (United States)

    Robin, J.; Dubayah, R.; Sparrow, E.; Levine, E.

    2006-12-01

    In biomes that have distinct winter seasons, start of spring phenological events, specifically timing of budburst and green-up of leaves, coincides with transpiration. Seasons leave annual signatures that reflect the dynamic nature of the hydrologic cycle and link the different spheres of the Earth system. This paper evaluates whether continuity between AVHRR and MODIS normalized difference vegetation index (NDVI) is achievable for monitoring land surface phenology, specifically start of season (SOS), in Alaska. Additionally, two thresholds, one based on NDVI and the other on accumulated growing degree-days (GDD), are compared to determine which most accurately predicts SOS for Fairbanks. Ratio of maximum greenness at SOS was computed from biweekly AVHRR and MODIS composites for 2001 through 2004 for Anchorage and Fairbanks regions. SOS dates were determined from annual green-up observations made by GLOBE students. Results showed that different processing as well as spectral characteristics of each sensor restrict continuity between the two datasets. MODIS values were consistently higher and had less inter-annual variability during the height of the growing season than corresponding AVHRR values. Furthermore, a threshold of 131-175 accumulated GDD was a better predictor of SOS for Fairbanks than a NDVI threshold applied to AVHRR and MODIS datasets. The NDVI threshold was developed from biweekly AVHRR composites from 1982 through 2004 and corresponding annual green-up observations at University of Alaska-Fairbanks (UAF). The GDD threshold was developed from 20+ years of historic daily mean air temperature data and the same green-up observations. SOS dates computed with the GDD threshold most closely resembled actual green-up dates observed by GLOBE students and UAF researchers. Overall, biweekly composites and effects of clouds, snow, and conifers limit the ability of NDVI to monitor phenological changes in Alaska.

  7. Hydrogen energy network start-up scenario

    International Nuclear Information System (INIS)

    Weingartner, S.; Ellerbrock, H.

    1994-01-01

    Hydrogen is widely discussed as future fuel and energy storage medium either to replace conventional fuels for automobiles, aircrafts and ships or to avoid the necessity of bulky battery systems for electricity storage, especially in connection with solar power systems. These discussions however started more than 25 years ago and up to now hydrogen has failed to achieve a major break-through towards wider application as energy storage medium in civil markets. The main reason is that other fuels are cheaper and very well implemented in our daily life. A study has been performed at Deutsche Aerospace in order to evaluate the boundary conditions, either political or economical, which would give hydrogen the necessary push, i.e. advantage over conventional fuels. The main goal of this study was to identify critical influence factors and specific start-up scenarios which would allow an economical and practically realistic use of hydrogen as fuel and energy medium in certain niche markets outside the space industry. Method and major results of this study are presented in detail in the paper. Certain niche markets could be identified, where with little initial governmental support, either by funding, tax laws or legislation, hydrogen can compete with conventional fuels. This however requires a scenario where a lot of small actions have to be taken by a high variety of institutions and industries which today are not interconnected with each other, i.e. it requires a new cooperative and proactive network between e.g. energy utilities, car industries, those who have a sound experience with hydrogen (space industry, chemical industry) and last, but certainly not the least, the government. Based on the developed scenario precise recommendations are drawn as conclusions

  8. 46 CFR 112.50-3 - Hydraulic starting.

    Science.gov (United States)

    2010-10-01

    ... POWER SYSTEMS Emergency Diesel and Gas Turbine Engine Driven Generator Sets § 112.50-3 Hydraulic starting. A hydraulic starting system must meet the following: (a) The hydraulic starting system must be a... 46 Shipping 4 2010-10-01 2010-10-01 false Hydraulic starting. 112.50-3 Section 112.50-3 Shipping...

  9. Hot-start Giant Planets Form with Radiative Interiors

    Energy Technology Data Exchange (ETDEWEB)

    Berardo, David; Cumming, Andrew, E-mail: david.berardo@mcgill.ca, E-mail: andrew.cumming@mcgill.ca [Department of Physics and McGill Space Institute, McGill University, 3600 rue University, Montreal, QC H3A 2T8 (Canada)

    2017-09-10

    In the hot-start core accretion formation model for gas giants, the interior of a planet is usually assumed to be fully convective. By calculating the detailed internal evolution of a planet assuming hot-start outer boundary conditions, we show that such a planet will in fact form with a radially increasing internal entropy profile, so that its interior will be radiative instead of convective. For a hot outer boundary, there is a minimum value for the entropy of the internal adiabat S {sub min} below which the accreting envelope does not match smoothly onto the interior, but instead deposits high entropy material onto the growing interior. One implication of this would be to at least temporarily halt the mixing of heavy elements within the planet, which are deposited by planetesimals accreted during formation. The compositional gradient this would impose could subsequently disrupt convection during post-accretion cooling, which would alter the observed cooling curve of the planet. However, even with a homogeneous composition, for which convection develops as the planet cools, the difference in cooling timescale will change the inferred mass of directly imaged gas giants.

  10. Let's start at the very beginning

    Science.gov (United States)

    Hossenfelder, Sabine

    2018-01-01

    How did this happen? You, reading this, sitting on a rock that orbits a bright ball of plasma, which itself undergoes nuclear fusion? How all this, and more, materialized is what you will learn from Jim Baggott’s book Origins: the Scientific Story of Creation - at least to the extent that scientists have the answers.

  11. Application of intelligent soft start in asynchronous motor

    Science.gov (United States)

    Du, Xue; Ye, Ying; Wang, Yuelong; Peng, Lei; Zhang, Suying

    2018-05-01

    The starting way of three phase asynchronous motor has full voltage start and step-down start. Direct starting brings large current impact, causing excessive local temperature to the power grid and larger starting torque will also impact the motor equipment and affect the service life of the motor. Aim at the problem of large current and torque caused by start-up, an intelligent soft starter is proposed. Through the application of intelligent soft start on asynchronous motor, highlights its application advantage in motor control.

  12. Photoemission starting of induction rf-driven multicusp ion sources

    International Nuclear Information System (INIS)

    Pickard, D.S.; Leung, K.N.; Perkins, L.T.; Ponce, D.M.; Young, A.T.

    1996-01-01

    It has been demonstrated that pulsed and continuous wave, rf-driven hydrogen discharges can be started with photoemission. The extracted H - current from a photoemission-started plasma has been investigated and does not differ significantly from that of a filament-started plasma. The minimum pressure for photoemissive starting was found to be higher than that of filament starting, 17 mTorr compared to 7 mTorr, respectively, in this particular configuration. copyright 1996 American Institute of Physics

  13. Spreading continents kick-started plate tectonics.

    Science.gov (United States)

    Rey, Patrice F; Coltice, Nicolas; Flament, Nicolas

    2014-09-18

    Stresses acting on cold, thick and negatively buoyant oceanic lithosphere are thought to be crucial to the initiation of subduction and the operation of plate tectonics, which characterizes the present-day geodynamics of the Earth. Because the Earth's interior was hotter in the Archaean eon, the oceanic crust may have been thicker, thereby making the oceanic lithosphere more buoyant than at present, and whether subduction and plate tectonics occurred during this time is ambiguous, both in the geological record and in geodynamic models. Here we show that because the oceanic crust was thick and buoyant, early continents may have produced intra-lithospheric gravitational stresses large enough to drive their gravitational spreading, to initiate subduction at their margins and to trigger episodes of subduction. Our model predicts the co-occurrence of deep to progressively shallower mafic volcanics and arc magmatism within continents in a self-consistent geodynamic framework, explaining the enigmatic multimodal volcanism and tectonic record of Archaean cratons. Moreover, our model predicts a petrological stratification and tectonic structure of the sub-continental lithospheric mantle, two predictions that are consistent with xenolith and seismic studies, respectively, and consistent with the existence of a mid-lithospheric seismic discontinuity. The slow gravitational collapse of early continents could have kick-started transient episodes of plate tectonics until, as the Earth's interior cooled and oceanic lithosphere became heavier, plate tectonics became self-sustaining.

  14. Impulsively started, steady and pulsated annular inflows

    Energy Technology Data Exchange (ETDEWEB)

    Abdel-Raouf, Emad [General Field Engineer, Halliburton Energy Services 719 Hangar Dr, New Iberia, LA 70560, United States of America (United States); Sharif, Muhammad A R; Baker, John, E-mail: abdelraouf.em@gmail.com, E-mail: msharif@eng.ua.edu, E-mail: john.baker@eng.ua.edu [Aerospace Engineering and Mechanics Department, The University of Alabama, Tuscaloosa, Alabama 35487, United States of America (United States)

    2017-04-15

    A computational investigation was carried out on low Reynolds number laminar inflow starting annular jets using multiple blocking ratios and atmospheric ambient conditions. The jet exit velocity conditions are imposed as steady, unit pulsed, and sinusoidal pulsed while the jet surroundings and the far-field jet inlet upstream conditions are left atmospheric. The reason is to examine the flow behavior in and around the jet inlet under these conditions. The pulsation mode behavior is analyzed based on the resultant of the momentum and pressure forces at the entry of the annulus, the circulation and vortex formation, and the propulsion efficiency of the inflow jets. The results show that under certain conditions, the net force of inflow jets (sinusoidal pulsed jets in particular) could point opposite to the flow direction due to the adverse pressure drops in the flow. The propulsion efficiency is also found to increase with pulsation frequency and the sinusoidal pulsed inflow jets are more efficient than the unit pulsed inflow jets. In addition, steady inflow jets did not trigger the formation of vortices, while unit and sinusoidal pulsed inflow jets triggered the formation of vortices under a certain range of frequencies. (paper)

  15. Starting manufacturing phase of ITER upper ports

    Energy Technology Data Exchange (ETDEWEB)

    Utin, Yuri, E-mail: yuri.utin@iter.org [ITER Organization, Route de Vinon-sur-Verdon, CS 90 046, 13067 St. Paul Lez Durance Cedex (France); Alekseev, Alexander; Sborchia, Carlo; Choi, Changho; Albin, Vincent; Barabash, Vladimir; Davis, James [ITER Organization, Route de Vinon-sur-Verdon, CS 90 046, 13067 St. Paul Lez Durance Cedex (France); Fabritsiev, Sergey [NTC Sintez, Efremov Inst., 189631 Metallostroy, St. Petersburg (Russian Federation); Giraud, Benoit; Guirao, Julio [ITER Organization, Route de Vinon-sur-Verdon, CS 90 046, 13067 St. Paul Lez Durance Cedex (France); Koenig, Werner [MAN Diesel & Turbo SE, Werftstrasse 17, Deggendorf (Germany); Kedrov, Igor; Kuzmin, Evgeny [NTC Sintez, Efremov Inst., 189631 Metallostroy, St. Petersburg (Russian Federation); Levesy, Bruno; Martinez, Jean-Marc [ITER Organization, Route de Vinon-sur-Verdon, CS 90 046, 13067 St. Paul Lez Durance Cedex (France); Prebeck, Markus [MAN Diesel & Turbo SE, Werftstrasse 17, Deggendorf (Germany); Privalova, Elena [NTC Sintez, Efremov Inst., 189631 Metallostroy, St. Petersburg (Russian Federation); Ranzinger, Franz [MAN Diesel & Turbo SE, Werftstrasse 17, Deggendorf (Germany); Savrukhin, Petr [Russian Federation ITER Domestic Agency, Kurchatov sq.1, 123182 Moscow (Russian Federation); Schiller, Thomas [MAN Diesel & Turbo SE, Werftstrasse 17, Deggendorf (Germany); and others

    2015-10-15

    Highlights: • The port plugs are attached to the ports with high-strength fasteners. • Tightening of the fasteners via inductive heating was tested. • A concept for the port/plug sealing with metal-type gaskets has progressed. • Manufacturing design of the Upper Ports is in progress. • A full-scale mock-up of double-wall part of the port stub extension is in manufacturing process – acceptable final tolerances are expected. - Abstract: The ITER Vacuum Vessel (VV) features upper, equatorial and lower ports. The upper and regular equatorial ports are occupied by the port plugs. Although the port design has been overall completed in the past, the design of some remaining interfaces was still in progress: in particular, the Sealing Flange package, which includes the high-vacuum seals and the plug fasteners. As the ITER construction phase has started, the procurement of the VV ports has been launched. The VV upper ports will be procured by the Russian Federation Domestic Agency. The main suppliers were selected and the manufacturing design of the first parts is in full progress now. Since the VV is classified at nuclear level N2, the design and manufacture of its components are to be compliant with the French RCC-MR code and regulations for nuclear pressure equipment in France. These regulations make a strong impact to the port design and manufacturing process.

  16. Starting manufacturing phase of ITER upper ports

    International Nuclear Information System (INIS)

    Utin, Yuri; Alekseev, Alexander; Sborchia, Carlo; Choi, Changho; Albin, Vincent; Barabash, Vladimir; Davis, James; Fabritsiev, Sergey; Giraud, Benoit; Guirao, Julio; Koenig, Werner; Kedrov, Igor; Kuzmin, Evgeny; Levesy, Bruno; Martinez, Jean-Marc; Prebeck, Markus; Privalova, Elena; Ranzinger, Franz; Savrukhin, Petr; Schiller, Thomas

    2015-01-01

    Highlights: • The port plugs are attached to the ports with high-strength fasteners. • Tightening of the fasteners via inductive heating was tested. • A concept for the port/plug sealing with metal-type gaskets has progressed. • Manufacturing design of the Upper Ports is in progress. • A full-scale mock-up of double-wall part of the port stub extension is in manufacturing process – acceptable final tolerances are expected. - Abstract: The ITER Vacuum Vessel (VV) features upper, equatorial and lower ports. The upper and regular equatorial ports are occupied by the port plugs. Although the port design has been overall completed in the past, the design of some remaining interfaces was still in progress: in particular, the Sealing Flange package, which includes the high-vacuum seals and the plug fasteners. As the ITER construction phase has started, the procurement of the VV ports has been launched. The VV upper ports will be procured by the Russian Federation Domestic Agency. The main suppliers were selected and the manufacturing design of the first parts is in full progress now. Since the VV is classified at nuclear level N2, the design and manufacture of its components are to be compliant with the French RCC-MR code and regulations for nuclear pressure equipment in France. These regulations make a strong impact to the port design and manufacturing process.

  17. On electrode erosion in fluorescent lamps during instant start

    Energy Technology Data Exchange (ETDEWEB)

    Hadrath, S.

    2006-09-15

    A fluorescent lamp driven with an 'instant start electronic control gear' starts in a glow mode. In the glow mode, which lasts typically for tens of milliseconds, the cathode fall exceeds hundreds of volts. This causes high energy ion bombardment of the electrode which heats the electrode, and induces a transition from glow to arc mode. In the arc mode the electrode emits thermionically and the cathode fall drops to the 12 - 15 V range. Unfortunately, the high energy ion bombardment during the glow mode leads also to intense sputtering of electrode material, including tungsten as well as emitter. Thus, instant started fluorescent lamps often suffer from early failures due to coil fracture. Therefore, the investigation of tungsten erosion during instant start is necessary and was the main goal of this work. The density of neutral atomic tungsten is determined by laser-induced fluorescence (LIF) and optical emission spectroscopy measurements (OES). Investigations are performed on a low-pressure argon dc discharge and on commercial fluorescent lamps. To include the entire temperature profile along the electrode the diffuse and spot operation modes of the dc lamp are studied experimentally and theoretically. The measured dependencies of the cathode temperature along the coil on the discharge and heating parameters are compared with the calculated results. For the first time the tungsten erosion during instant start of commercial fluorescent lamps was experimentally investigated in this work. The erosion process could be related to sputtering. A reconstruction of the temporal evolution of the absolute tungsten population density of the ground state during the glow mode was presented. The sputtered tungsten density increases immediately with the ignition, reaches a maximum where the discharge contracts at the end of the glow mode, and decreases some milliseconds before the glow-to-arc transition takes place. The maximum tungsten density was observed within a

  18. Nuclear power: time to start again

    International Nuclear Information System (INIS)

    Rezak, W.D.

    2004-01-01

    This paper presents data which support the construction and operating successes enjoyed by energy companies that operate nuclear power plants in the US. The result is that the US nuclear industry is alive and well. Perhaps it's time to start anew the building of nuclear power plants. Over 20% of the electricity generated in the United States comes from nuclear power plants. An adequate, reliable supply of reasonably priced electric energy is not a consequence of an expanding economy and gross national product; it is an absolute necessity before such expansion can occur. It is hard to imagine any aspect of our business or personal lives not, in some way, dependent upon electricity. All over the world (in over 30 countries) nuclear power is a low-cost, secure, safe, dependable, and environmentally friendly form of electric power generation. Nuclear plants in these countries are built in six to eight years using technology developed in the US, with good performance and safety records. This treatise addresses the success experienced by the US nuclear industry over the last 40 years, and makes the case that this reliable, cost-competitive source of electric power can help support the economic engine of the country and help prevent experiences like the recent crises in California and the Northeast. Successful operation of nuclear facilities is determined by examining capacity or load factors. Load factor is the percentage of design generating capacity that a power plant actually produces over the course of a year's operation. This paper makes the case that these operating performance indicators warrant renewed consideration of the nuclear option. Usage of electricity in the US now approaches total generating capacity. The Nuclear Regulatory Commission has pre-approved construction and operating licenses for several nuclear plant designs. State public service commissions are beginning to understand that dramatic reform is required. The economy is recovering and inflation

  19. Starting up microbial enhanced oil recovery.

    Science.gov (United States)

    Siegert, Michael; Sitte, Jana; Galushko, Alexander; Krüger, Martin

    2014-01-01

    This chapter gives the reader a practical introduction into microbial enhanced oil recovery (MEOR) including the microbial production of natural gas from oil. Decision makers who consider the use of one of these technologies are provided with the required scientific background as well as with practical advice for upgrading an existing laboratory in order to conduct microbiological experiments. We believe that the conversion of residual oil into natural gas (methane) and the in situ production of biosurfactants are the most promising approaches for MEOR and therefore focus on these topics. Moreover, we give an introduction to the microbiology of oilfields and demonstrate that in situ microorganisms as well as injected cultures can help displace unrecoverable oil in place (OIP). After an initial research phase, the enhanced oil recovery (EOR) manager must decide whether MEOR would be economical. MEOR generally improves oil production but the increment may not justify the investment. Therefore, we provide a brief economical assessment at the end of this chapter. We describe the necessary state-of-the-art scientific equipment to guide EOR managers towards an appropriate MEOR strategy. Because it is inevitable to characterize the microbial community of an oilfield that should be treated using MEOR techniques, we describe three complementary start-up approaches. These are: (i) culturing methods, (ii) the characterization of microbial communities and possible bio-geochemical pathways by using molecular biology methods, and (iii) interfacial tension measurements. In conclusion, we hope that this chapter will facilitate a decision on whether to launch MEOR activities. We also provide an update on relevant literature for experienced MEOR researchers and oilfield operators. Microbiologists will learn about basic principles of interface physics needed to study the impact of microorganisms living on oil droplets. Last but not least, students and technicians trying to understand

  20. Cross-linking of polymeric materials

    International Nuclear Information System (INIS)

    Bloom, L.I.; Du Plessis, T.A.; Meij, G.O.

    1991-01-01

    The invention provides a method of producing a cured polymeric artifact from a polymeric thermoplastic starting material, the material of the artifact having reduced thermoplasticity relative to the starting material and exhibiting an enhanced degree of cross-linking relative to the starting material. The method includes subjecting a polymeric thermoplastic starting material, which is capable of being cross-linked by irradiation, to sufficient irradiation partially to cross-linked the starting material to produce a thermoplastic partially cross-linked intermediate material. The thermoplasticity of the intermediate material is then reduced by heating it to raise its melting point. The invention also provides a method of making a partially cross-linked feedstocks and a master batch for use in making such artifacts

  1. Start a Research on Biopolymer Polyhydroxyalkanoate (PHA: A Review

    Directory of Open Access Journals (Sweden)

    Giin-Yu Amy Tan

    2014-03-01

    Full Text Available With the impending fossil fuel crisis, the search for and development of alternative chemical/material substitutes is pivotal in reducing mankind’s dependency on fossil resources. One of the potential substitute candidates is polyhydroxyalkanoate (PHA. PHA is a carbon-neutral and valuable polymer that could be produced from many renewable carbon sources by microorganisms, making it a sustainable and environmental-friendly material. At present, PHA is not cost competitive compared to fossil-derived products. Encouraging and intensifying research work on PHA is anticipated to enhance its economic viability in the future. The development of various biomolecular and chemical techniques for PHA analysis has led to the identification of many PHA-producing microbial strains, some of which are deposited in culture collections. Research work on PHA could be rapidly initiated with these ready-to-use techniques and microbial strains. This review aims to facilitate the start-up of PHA research by providing a summary of commercially available PHA-accumulating microbial cultures, PHA biosynthetic pathways, and methods for PHA detection, extraction and analysis.

  2. Technological start of T-15 tokamak. The start-up diagnostic complex

    International Nuclear Information System (INIS)

    Notkin, G.E.

    1989-01-01

    The T-15 tokamak with superconducting toroidal winding reached the technological start-up phase. The results of the first operating tests of the main tokamak components are reported. Due to improper function of both the vacuum and the cryogenic system, the nominal parameters of the vacuum and of the toroidal magnetic field have not been achieved. The non-optimum vacuum conditions made the discharge start-up difficult even when a pre-ionizing electron beam and a gyrotron generator were used. The pre-discharge plasma parametes were studied by means of a limited set of plasma diagnostic apparatus. Due to substantially deteriorated vacuum conditions, it was not possible to repeat the only one successful discharge with a current of 100 kA, lasting for 50 ms. (J.U.)

  3. Methods of materiality

    DEFF Research Database (Denmark)

    Aagaard, Jesper; Matthiesen, Noomi Christine Linde

    2016-01-01

    that researchers should start paying attention to the material world (consisting of both human bodies and material objects) and what it means for how people live their lives. It is argued that this can be done by incorporating the concept of material presence to capture embodied and material layers of existence......This article challenges the hegemonic status of “language” as the primary substance of qualitative research in psychology, whether through interviews or recordings of naturally occurring talk. It thereby questions the overt focus on analyzing linguistic “meaning.” Instead, it is suggested...... practical guidelines for incorporating attention to materiality in qualitative research....

  4. Quantifying climate risk - the starting point

    International Nuclear Information System (INIS)

    Fairweather, Helen; Luo, Qunying; Liu, De Li; Wiles, Perry

    2007-01-01

    Full text: All natural systems have evolved to their current state as a result inter alia of the climate in which they developed. Similarly, man-made systems (such as agricultural production) have developed to suit the climate experienced over the last 100 or so years. The capacity of different systems to adapt to changes in climate that are outside those that have been experienced previously is largely unknown. This results in considerable uncertainty when predicting climate change impacts. However, it is possible to quantify the relative probabilities of a range of potential impacts of climate change. Quantifying current climate risks is an effective starting point for analysing the probable impacts of future climate change and guiding the selection of appropriate adaptation strategies. For a farming system to be viable within the current climate, its profitability must be sustained and, therefore, possible adaptation strategies need to be tested for continued viability in a changed climate. The methodology outlined in this paper examines historical patterns of key climate variables (rainfall and temperature) across the season and their influence on the productivity of wheat growing in NSW. This analysis is used to identify the time of year that the system is most vulnerable to climate variation, within the constraints of the current climate. Wheat yield is used as a measure of productivity, which is also assumed to be a surrogate for profitability. A time series of wheat yields is sorted into ascending order and categorised into five percentile groupings (i.e. 20th, 40th, 60th and 80th percentiles) for each shire across NSW (-100 years). Five time series of climate data (which are aggregated daily data from the years in each percentile) are analysed to determine the period that provides the greatest climate risk to the production system. Once this period has been determined, this risk is quantified in terms of the degree of separation of the time series

  5. Pakistan/USAID to start CSM project.

    Science.gov (United States)

    1984-01-01

    Pakistan, with the assistance of funds for the US Agency for International Development (USAID), is about to start its novel approach to contraceptive social marketing (CSM). This new effort suggests a marked policy shift on the part of the Pakistan government toward intensifying its family planning activities. The program will be government-operated and supported by AID over the next 5 years with $20 million, more than double the cost of similar CSM projects elswhere. Distribution of a condom on a pilot project basis is expected to begin by December 1984. Sales of a low-dose oral contraceptive (OC) could begin in test market areas by mid-1985, with national launching of both products tentatively scheduled for January 1986. The Pakistan/USAID agreement represents the 1st time since the formation of India's Nirodh project in the late 1960s that a CSM program is being established without the involvement of either an international social marketing contractor or a country's family planning association. The Pakistan CSM program will be managed by a policy board composed of representatives from the government's Ministries of Planning, Health and Education; a resident advisor from USAID; and a local company responsible for product marketing and distribution. The approach has received a skeptical response among international social marketing experts about the program's chances for success. Their doubts extend to 2 other aspects of the proposed design: an official of the Ministry of Planning's Population and Welfare Division expects the CSM program to generate sufficient revenues to cover all operating costs following the 5-year subsidy period, while also providing attractive profit margins for the marketing/distribution company; and the government prohibits mass media advertising of contraceptives. According to AID, the issue of mass media contraceptive advertising has not yet been resolved, and a national survey will be conducted to determine what communication needs are

  6. Canola meal on starting pigs feeding

    Directory of Open Access Journals (Sweden)

    Lina Maria Peñuela-Sierra

    2015-12-01

    Full Text Available Three experiments were carried out to determine the nutritional values and evaluate the performance of piglets fed on canola meal. In experiment I, a digestibility assay was conducted using fourteen barrow pigs, with an initial body weight of 20.62±3.30 kg. The evaluated feedstuff was canola meal, with a level of 250 g/kg in the basal diet (corn + soybean meal-based. The experimental unit consisted of one pig, with a total of seven experimental units per diet. The values as (fed basis of digestible (DE and metabolizable (ME energy of canola meal were 2,995 kcal/kg and 2,796 kcal/kg, respectively. In experiment II, ileal digestibility assays were carried out to determine the apparent and true ileal digestibility coefficient and digestible amino acids. Three crossbred pigs were used, with a BW of 38.6±1.98 kg. The treatments consisted of two diets, with a single source of protein (canola meal and one protein-free diet (OFD. The values of digestible amino acids in canola meal were as follows: lysine: 11.8 g/kg; methionine+cystine: 9.1 g/kg; threonine: 7.9 g/kg; tryptophan: 2.4 g/kg; leucine: 15.7 g/kg; and isoleucine: 8.7 g/kg. In experiment III, 60 piglets (BW= 15.08±0.72 kg to 30.26±2.78 kg were allotted in a completely randomized design. The treatments consisted of four diets with increasing levels of canola meal (50, 100, 150 and 200 g/kg, six replicates and experimental unit consisted of two pigs. Additionally, a control diet was formulated containing 0.0 g/kg CM. Regression analysis indicates that there was no effect (P?0.05 of the level of canola meal inclusion on pigs performance. The performance results suggest that it is feasible to use up to 200 g/kg of canola meal in starting pigs diet, without impairing performance and the feeding cost.

  7. Environmental mitigation for SCC initiation of BWR core internals by hydrogen injection during start-up

    International Nuclear Information System (INIS)

    Dozaki, K.; Abe, A.; Nagata, N.; Takiguchi, H.

    2004-01-01

    Hydrogen injection into the reactor water has been applied to many BWR power stations. Since hydrogen injected accelerates recombination of oxidant generated by water radiolysis, oxidant concentration, such as dissolved oxygen concentration in reactor water can be reduced. As the result of the reduction of oxidant concentration, Electrochemical Corrosion Potential (ECP) at the surface of structural material can be lowered. Lowered ECP moderates Stress Corrosion Cracking (SCC) sensitivity of structural materials, such as stainless steels. As usual, hydrogen injection system begins to work after the plant start-up is finished, when the condition of normal operation is established. Accordingly, Hydrogen Water Chemistry (HWC) does not cover all the period of plant operation. As far as SCC crack growth is considered, loss of HWC during plant start-up does not result in significant crack growth, because of duration of plant start-up is much shorter than that of plant normal operation, when HWC condition is being satisfied. However, the reactor water environment and load conditions during a plant start-up may contribute to the initiation of SCC. It is estimated that the core internals are subjected to the strain rate that may cause susceptibility to SCC initiation during start-up. Dissolved oxygen (DO) and hydrogen peroxide (H 2 O 2 ) has a peak, and ECP is in high levels during start-up. Therefore it is beneficial to perform hydrogen injection during start-up as well in order to suppress SCC initiation. We call it HWC During Start-up (HDS) here. (orig.)

  8. Multigenerational Head Start Participation: An Unexpected Marker of Progress

    Science.gov (United States)

    Chor, Elise

    2018-01-01

    One-quarter of the Head Start population has a mother who participated in the program as a child. This study uses experimental Head Start Impact Study (HSIS) data on 3- and 4-year-olds (N = 2,849) to describe multigenerational Head Start families and their program experiences. In sharp contrast to full-sample HSIS findings, Head Start has large,…

  9. Enhancing start performance in the sport of skeleton

    OpenAIRE

    Colyer, Steffi

    2015-01-01

    A fast start is considered to be crucial in skeleton with marginal gains in start performance perceived to make meaningful improvements to overall chances of success. Currently, knowledge surrounding the underlying determinants of start performance is sparse and training practices are based on limited scientific evidence. A series of investigations were conducted to advance this understanding.Initial observations revealed similarities between dry-land push-starts and those on ice tracks. Howe...

  10. A point at the horizon. Start of an intersectoral Business Plan Biobased Economy

    International Nuclear Information System (INIS)

    2011-06-01

    This document is the starting point of a joint business plan for the transition to a Dutch biobased economy (BBE), in which the 6 top sectors chemistry, agro-food, horticulture and propagation materials, logistics, energy and water want to join forces to give more shape to the leading role of the Netherlands in the transition to a sustainable society. [nl

  11. Robotic surgery start-up with a fellow as the console surgeon

    DEFF Research Database (Denmark)

    Reinhardt, Susanne; Ifaoui, Inge Boetker; Thorup, Jorgen

    2017-01-01

    learning curve for robotic pyeloplasty will allow pediatric urology fellowship programs to be integrated in the start-up phase of a pediatric robotic program even though the case material is limited. Operative success rates were in accordance with the gold standard of open surgery....

  12. Users' Manual for Research: Translating Head Start Findings Into Action (Expanded Notebook Version).

    Science.gov (United States)

    Grotberg, Edith H.; Fowler, Austine

    This users' manual, intended for use with a Project Head Start teacher training notebook, describes the purpose, development and field testing of the training materials and suggests procedures for using the notebook as a resource in teacher training sessions. The training notebook to which the users' manual refers is based on 11 questions in the…

  13. Making a Simple Self-Starting Electric Motor

    Science.gov (United States)

    Hong, Seok-In; Choi, Jung-In; Hong, Seok-Cheol

    2009-01-01

    A simple electric motor has a problem in that the current applied to the motor per se can rarely trigger its rotation. Usually such motors begin to rotate after the rotor is slightly turned by hand (i.e., manual starting). In a "self-starting" motor, the rotor starts to rotate spontaneously as soon as the current is applied. This paper describes…

  14. Head Start Participants, Programs, Families and Staff in 2013

    Science.gov (United States)

    Walker, Christina

    2014-01-01

    Head Start programs provide poor children and their families with comprehensive early education and support services. Each year, programs are required to submit a Program Information Report (PIR) to the Office of Head Start on participating children, pregnant women, and families, as well as the staff serving the Head Start population. In 2013, the…

  15. The Role of Classroom Quality in Explaining Head Start Impacts

    Science.gov (United States)

    Connors, Maia C.; Friedman-Krauss, Allison H.; Morris, Pamela A.; Page, Lindsay C.; Feller, Avi

    2014-01-01

    This study seeks to answer the following question: Are impacts on Head Start classroom quality associated with impacts of Head Start on children's learning and development? This study employs a variety of descriptive and quasi-experimental methods to explore the role of classroom quality as a mediator or mechanism of Head Start impacts. This…

  16. Do Head Start Impacts Vary by Neighborhood Context?

    Science.gov (United States)

    Morris, Pamela A.; Connors, Maia C.; McCoy, Dana Charles; Gomez, Celia J.; Yoshikawa, Hiro; Aber, J. Lawrence

    2014-01-01

    This paper capitalizes on the addition of geocodes for Head Start centers in which children were randomly assigned to address questions about the role of neighborhood characteristics in moderating impacts of assignment to the Head Start program. Researchers explore the extent to which impacts of assignment to Head Start on outcomes for children…

  17. Head Start Instructional Professionals' Inclusion Perceptions and Practices

    Science.gov (United States)

    Muccio, Leah S.; Kidd, Julie K.; White, C. Stephen; Burns, M. Susan

    2014-01-01

    This study considered the facilitators and barriers of successful inclusion in Head Start classrooms by examining the perspectives and practices of instructional professionals. A cross-sectional survey design was combined with direct observation in inclusive Head Start classrooms. Survey data were collected from 71 Head Start instructional…

  18. Enhancing Early Childhood Outcomes: Connecting Child Welfare and Head Start

    Science.gov (United States)

    McCrae, Julie S.; Brown, Samantha M.; Yang, Jessica; Groneman, Sheila

    2016-01-01

    Head Start is a preschool program for families with low incomes and nearly 85% of child welfare-involved families are low-income, yet little is known about Head Start and child welfare collaboration. This study uses data from 28 Head Start directors to describe collaboration facilitators and barriers, and collaborative mechanisms in place. The…

  19. Experience in the Kola NPP start-up works

    International Nuclear Information System (INIS)

    Zakharov, S.I.; Omel'chuk, V.V.; Bodrukhin, Yu.M.

    1984-01-01

    Main stages and peculiar features of maintenance and start-up works at WWER-440 type reactor NPPs described. Remarks revealed during complex equipment testing, physical and power start-up will be useful for arrangement of maintenance and start-up works at newly built NPPs

  20. Personal and Public Start Pages in a library setting

    NARCIS (Netherlands)

    Kieft-Wondergem, Dorine

    Personal and Public Start Pages are web-based resources. With these kind of tools it is possible to make your own free start page. A Start Page allows you to put all your web resources into one page, including blogs, email, podcasts, RSSfeeds. It is possible to share the content of the page with

  1. Soft-Starting Power-Factor Motor Controller

    Science.gov (United States)

    Nola, F. J.

    1983-01-01

    Three-phase power-factor controller with soft start is based on earlier version that does not control starting transients. Additional components serve to turn off "run" command signal and substitute gradual startup command signal during preset startup interval. Improved controller reduces large current surge that usually accompanies starting. Controller applies power smoothly, without causing motor vibrations.

  2. 40 CFR 86.536-78 - Engine starting and restarting.

    Science.gov (United States)

    2010-07-01

    ... equipped with automatic chokes shall be operated according to the instructions in the manufacturer's... transmission shall be placed in gear 15 seconds after the engine is started. If necessary, braking may be... starting procedure, the engine (automatic and manual choke engines) shall be started by opening the...

  3. Methods of synthesizing thermoelectric materials

    Science.gov (United States)

    Ren, Zhifeng; Chen, Shuo; Liu, Wei-Shu; Wang, Hengzhi; Wang, Hui; Yu, Bo; Chen, Gang

    2016-04-05

    Methods for synthesis of thermoelectric materials are disclosed. In some embodiments, a method of fabricating a thermoelectric material includes generating a plurality of nanoparticles from a starting material comprising one or more chalcogens and one or more transition metals; and consolidating the nanoparticles under elevated pressure and temperature, wherein the nanoparticles are heated and cooled at a controlled rate.

  4. 76 FR 50813 - Major Capital Investment Projects; Guidance on News Starts/Small Starts Policies and Procedures

    Science.gov (United States)

    2011-08-16

    ... DEPARTMENT OF TRANSPORTATION Federal Transit Administration Major Capital Investment Projects; Guidance on News Starts/Small Starts Policies and Procedures AGENCY: Federal Transit Administration (FTA... Administration (FTA) to publish policy guidance on the New and Small Starts capital project review and evaluation...

  5. Handbook of the Properties of Optical Materials

    Science.gov (United States)

    1984-01-01

    EFFECTIVE MASS - - MOBILITY - - A-2 ARSEWIC SELENIOE (As2 Se3 ) OPTICAL PROPERTIES TRANSMISSION RANGE: 9 - 11n Optical Absorption Coefficient = 0.079...of 55 KRS-5 as a function of wavelength. A-2120 ZINC SELENIOE ZnSe 0 STRUCTURE CRYSTALLINE SYMMETRY = Cubic, 43m LATTICE CONSTANTS (A) = a = 5.667

  6. Are the new starting block facilities beneficial for backstroke start performance?

    Science.gov (United States)

    de Jesus, Karla; de Jesus, Kelly; Abraldes, J Arturo; Medeiros, Alexandre Igor Araripe; Fernandes, Ricardo J; Vilas-Boas, João Paulo

    2016-01-01

    We aimed to analyse the handgrip positioning and the wedge effects on the backstroke start performance and technique. Ten swimmers completed randomly eight 15 m backstroke starts (four with hands on highest horizontal and four on vertical handgrip) performed with and without wedge. One surface and one underwater camera recorded kinematic data. Standardised mean difference (SMD) and 95% confidence intervals (CI) were used. Handgrip positioning did not affect kinematics with and without wedge use. Handgrips horizontally positioned and feet over wedge displayed greater knee angular velocity than without it (SMD = -0.82; 95% CI: -1.56, -0.08). Hands vertically positioned and feet over wedge presented greater take-off angle (SMD = -0.81; 95% CI: -1.55, -0.07), centre of mass (CM) vertical positioning at first water contact (SMD = -0.97; 95% CI: -1.87, -0.07) and CM vertical velocity at CM immersion (SMD = 1.03; 95% CI: 0.08, 1.98) when comparing without wedge use. Swimmers extended the hip previous to the knee and ankle joints, except for the variant with hands vertically positioned without wedge (SMD = 0.75; 95% CI: -0.03, 1.53). Swimmers should preserve biomechanical advantages achieved during flight with variant with hands vertically positioned and wedge throughout entry and underwater phase.

  7. FORMATION OF THE PENUMBRA AND START OF THE EVERSHED FLOW

    Energy Technology Data Exchange (ETDEWEB)

    Murabito, M.; Guglielmino, S. L.; Zuccarello, F. [Dipartimento di Fisica e Astronomia—Sezione Astrofisica, Università degli Studi di Catania, Via S. Sofia 78, I-95123 Catania (Italy); Romano, P. [INAF—Osservatorio Astrofisico di Catania, Via S. Sofia 78, I-95123 Catania (Italy); Solanki, S. K., E-mail: mmurabito@oact.inaf.it [Max-Planck-Institut für Sonnensystemforschung Justus-von-Liebig-Weg 3, D-37077 Göttingen (Germany)

    2016-07-01

    We studied the variations of line of sight photospheric plasma flows during the formation phase of the penumbra around a pore in active region NOAA 11490. We used a high spatial, spectral, and temporal resolution data set acquired by the Interferometric BIdimensional Spectrometer operating at the NSO/Dunn Solar Telescope as well as data taken by the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory satellite ( SDO /HMI). Before the penumbra formed we observed a redshift of the spectral line in the inner part of the annular zone surrounding the pore as well as a blueshift of material associated with opposite magnetic polarity farther away from the pore. We found that the onset of the classical Evershed flow occurs on a very short timescale (1 to 3 hr) while the penumbra is forming. During the same time interval we found changes in the magnetic field inclination in the penumbra, with the vertical field actually changing sign near the penumbral edge, while the total magnetic field showed a significant increase, about 400 G. To explain these and other observations related to the formation of the penumbra and the onset of the Evershed flow we propose a scenario in which the penumbra is formed by magnetic flux dragged down from the canopy surrounding the initial pore. The Evershed flow starts when the sinking magnetic field dips below the solar surface and magnetoconvection sets in.

  8. Analysis of the start-up and control of a particle bed reactor

    International Nuclear Information System (INIS)

    Lazareth, O.W.; Araj, K.J.; Horn, F.L.; Ludewig, H.; Powell, J.R.

    1987-01-01

    This study describes the modeling of start-up transients in Particle Bed Reactors (PBR) for burst electric power. Two computer programs have been developed to analyze the start-up process. The first program (named KINETIC) analyzes the entire fuel element, calculating time dependent solutions for power and the temperature distribution in the packed bed. The second program (named SPHEAT, for Spherical Heating) calculates time-dependent temperatures inside individual, cladded fuel particles. The two programs provide powerful analytical tools for evaluation of material and geometrical options, power and time constraints, and conditions that could lead to element failures

  9. Nonlinear Optics: Materials, Fundamentals, and Applications. Postdeadline papers

    Science.gov (United States)

    1992-08-01

    The Nonlinear Optics: Materials, Fundamentals, and Applications conference was held on 17-21 Aug. 1992. The following topics were addressed: subpicosecond time resolved four-wave mixing spectroscopy in heteroepitaxial ZnSe thin layers; anisotropic two-photon transition in GaAs/AlGaAs multiple quantum well waveguides; two picosecond, narrow-band, tunable, optical parametric systems using BBO and LBO; second generation in an optically active liquid: experimental observation of a fourth-order optical nonlinearity due to molecular chirality; optical image recognition system implemented with a 3-D memory disk; phase-matched second-harmonic generation in waveguides of polymeric Langmuir-Blodgett films; fluence dependent dynamics observed in the resonant third-order optical response of C60 and C70 films; temporal modulation of spatial optical solitons: a variational approach; measurements of light-scattering noise during two-wave mixing in a Kerr medium; excess noise introduced by beam propagation through an atomic vapor; an approach to all-optical switching based on second-order nonlinearities; multilayer, nonlinear ARROW waveguides for surface emitted sum-frequency mixing; energy scaling of SBS phase conjugate mirrors to 4J; vector versus scalar theory for the double phase conjugate mirror; cross-talk and error probability in counter-beam lambda-multiplexed digital holograms; and modal growth of SHG in doped silica thin film waveguides.

  10. Modelling ohmic confinement experiments on the START tokamak

    International Nuclear Information System (INIS)

    Roach, C.M.

    1996-05-01

    Ohmic confinement data from the tight aspect ratio tokamak START has been analysed using the ASTRA transport simulation code. Neoclassical expressions have been modified to describe tight aspect ratio configurations, and the comparison between START data and models of anomalous transport has been made quantitative using the standard χ 2 test from statistics. Four confinement models (T11, Rebut-Lallia-Watkins, Lackner-Gottardi, and Taroni et al's Bohm model) have been compared with the START data. Three of the models are found to simulate START's electron temperature data moderately well, while Taroni et al's Bohm model overestimates electron temperatures in START by an order of magnitude. Thus comparison with START data tends to discriminate against Bohm models; these models are pessimistic or ITER. (author)

  11. Sleep, sleepiness and school start times: a preliminary study.

    Science.gov (United States)

    Dexter, Donn; Bijwadia, Jagdeep; Schilling, Dana; Applebaugh, Gwendolyn

    2003-01-01

    High school students are reported to be excessively sleepy, resulting in decreased academic performance, increased psycho-social problems and increased risk of morbidity and mortality from accidents. Early school start times have been noted to contribute to this problem. This report attempts to confirm the relationship of early school start times with decreased sleep and increased sleepiness. We examined sophomore and junior students in 2 local high schools with different start times and measured the amount of time slept and sleepiness. We found that students at the early start school reported reduced sleep time and more sleepiness than their counterparts at the later starting school. Early school start times are associated with student reports of less sleep and increased sleepiness. Further studies in larger groups are recommended in view of the potential significant impact of sleep deprivation in this age group.

  12. Linking Environmental Orientation to Start-ups’ Networking Activities

    DEFF Research Database (Denmark)

    Dickel, Petra; Ritter, Thomas

    Besides for-profit start-ups, an increasing number of firms start their existence with the purpose to “do good” for society – mirrored in an increasing academic discussion of sustainable firms. Yet, there is little research on the networking activities of start-ups that do not have profit...... generation as their primary focus. Addressing this research gap, we develop hypotheses on the different networking activities of environmentally oriented start-ups arguing that their societal focus has a positive impact on the frequency of their networking and the size of their network. For empirically...... investigating such networking differences, we use data from 179 technology-based start-ups and show that start-ups with a strong external environmental orientation have significantly higher networking frequency and build larger networks. On the contrary, strong internal environmental orientation is linked...

  13. Start-up simulations of the PULSAR pulsed tokamak reactor

    International Nuclear Information System (INIS)

    Werley, K.A.; Bathke, C.G.

    1993-01-01

    Start-up conditions are examined for a pulsed tokamak reactor that uses only inductively driven plasma current (and bootstrap current). A zero-dimensional (profile-averaged) model containing plasma power and particle balance equations is used to study several aspects of plasma start-up, including: (1) optimization of the start-up pathway; (2) tradeoffs of auxiliary start-up heating power versus start-up time; (3) volt-second consumption; (4) thermal stability of the operating point; (5) estimates of the diverter heat flux and temperature during the start-up transient; (6) the sensitivity of the available operating space to allowed values of the H confinement factor; and (7) partial-power operations

  14. Start up testing for the secure automated fabrication line

    International Nuclear Information System (INIS)

    Gerber, E.W.; Benson, E.M.; Dahl, R.E.

    1987-01-01

    The secure automated fabrication (SAF) line is a remotely operated, liquid metal reactor fuel fabrication process being built by Westinghouse Hanford Company for the Department of Energy. All process and control equipment is installed and start up testing has been initiated. Start up testing is comprised of five phases, each incorporating higher degrees of equipment integration, automation, and remote control. Testing methodology for SAF line start up is described in this report

  15. How to Start Growing Beef Calves on Feed

    OpenAIRE

    ZoBell, Dale R

    2003-01-01

    Starting calves on feed takes time and effort because of the stress young calves are susceptible to at this point in their lives. The reduction of stress will result in calves consuming more feed, thus remaining healthier. To successfully start calves on feed, dry matter intake must be maximized while minimizing health problems. The following is a 5-step applied method for starting calves on a silage-based ration.

  16. School Starting Age and the Crime-Age Profile

    DEFF Research Database (Denmark)

    Landersø, Rasmus; Nielsen, Helena Skyt; Simonsen, Marianne

    2017-01-01

    This paper uses register-based data to investigate the effects of school starting age on crime. Through this, we provide insights into the determinants of crime-age profiles. We exploit that Danish children typically start first grade in the calendar year they turn seven, which gives rise...... to a discontinuity in school starting age for children born around New Year. Our analysis speaks against a simple invariant crime-age profile as is popular in criminology: we find that higher school starting age lowers the propensity to commit crime at young ages. We also find effects on the number of crimes...

  17. De-escalatory confidence-building measures after START

    International Nuclear Information System (INIS)

    Stockton, P.N.

    1992-01-01

    The very notion of examining de-escalatory CBMs in the context of the START negotiations appears odd. Given the immense progress in US-Soviet relations, of which the proposed START agreement is emblematic, the risk of the two nations stumbling to the brink of war seems increasingly remote. Why bother analyzing CBMs designed to help resolve such an improbable event? The obvious answer is that relations between the US and the Soviet Union - or whatever array of nations succeed it - could take an unforeseeable turn for the worse. Once ratified, the START agreement is supposed to remain in force for seven years, more than enough time for political tensions to return with a vengeance. This suggests a more prudent question: if our two nations do stumble to the brink of war, will the START agreement affect the prospect of de-escalatory CBMs? And if the US and Soviet Union pursue deeper force-reductions in a follow-on START II agreement, could that agreement be designed to facilitate more effective de-escalatory measures? This paper sets the stage for addressing such questions by outlining the START agreement and offering a brief overview of how START might affect the prospects for CBMs. Then, after examining some specific CBM proposals in light of START, an analysis will be made of the de-escalatory problems and opportunities that a Start II treaty might create

  18. Cold starting characteristics analysis of hydraulic free piston engine

    International Nuclear Information System (INIS)

    Zhang, Shuanlu; Zhao, Zhenfeng; Zhao, Changlu; Zhang, Fujun; Wang, Shan

    2017-01-01

    The cold start characteristic of hydraulic free piston diesel engine may affect its stable operation. Therefore the specific cold start characteristics, such as BDC or TDC positions, pressure in-cylinder, heat release rate, should be investigated in detail. These parameters fluctuate in some regularity in the cod start process. With the development of the free piston engine prototype and the establishment of test bench, the results are obtained. For the dynamic results, the fluctuation range of TDC and BDC positions is 8 mm and decreases with time. The thermodynamic results show that the combustion process is not stable and the pressure in-cylinder fluctuates largely in the cold start process. In addition, the combustion is rapid and knock happens inevitably. In order to investigate the reasons, a CFD model is established for temperature analysis in-cylinder and heat transfer conditions. It is found that higher start wall temperature will lead to more uniform temperature distribution. The delay period may decreases and heat release will move forward. This reason is analyzed by thermodynamic derivation based on the first law of thermodynamics. Finally, the improvement suggestions of cold start strategy are proposed. - Highlights: • The cold start behaviors of HFPE are investigated in detail. • CFD method is used for simulating temperature distribution in start process. • Thermodynamic derivation uncovers the compression temperature distribution. • The improvement suggestions of cold start strategy are proposed.

  19. School Starting Age and the Crime-Age Profile

    OpenAIRE

    Landerso, Rasmus; Nielsen, Helena Skyt; Simonsen, Marianne

    2015-01-01

    This paper uses register-based data to investigate the effects of school starting age on crime. Through this, we provide insights into the determinants of crime-age profiles. We exploit that Danish children typically start first grade in the calendar year they turn seven, which gives rise to a discontinuity in school starting age for children born around New Year. Our analysis speaks against a simple invariant crime-age profile as is popular in criminology: we find that higher school starting...

  20. Product innovation and commercialization in lean global start-ups

    DEFF Research Database (Denmark)

    Tanev, Stoyan; Rasmussen, Erik Stavnsager; Zijdemans, Erik

    2015-01-01

    The paper examines the distinctive characteristics of product innovation and commercialization in Lean Global Start-up (LGS) – new technology firms which have adopted a lean and global path from or near to their inception. It suggests an uncertainty vs risk framework which allows integrating two...... research streams – Born Global (BG) firms and lean start-ups. In addition to its integrative theoretical value, the paper offers insights for lean start-up managers dealing with the challenges of a global start....

  1. Bypass line assisted start-up of a loop heat pipe with a flat evaporator

    International Nuclear Information System (INIS)

    Boo, Joon Hong; Jung, Eui Guk

    2009-01-01

    Loop heat pipes often experience start-up problems especially under low thermal loads. A bypass line was installed between the evaporator and the liquid reservoir to alleviate the difficulties associated with start-up of a loop heat pipe with flat evaporator. The evaporator and condenser had dimensions of 40 mm (W) by 50 mm (L). The wall and tube materials were stainless steel and the working fluid was methanol. Axial grooves were provided in the flat evaporator to serve as vapor passages. The inner diameters of liquid and vapor transport lines were 2 mm and 4 mm, respectively, and the length of the two lines was 0.5 m each. The thermal load range was up to 130 W for horizontal alignment with the condenser temperature of 10 .deg. C. The experimental results showed that the minimum thermal load for start-up was lowered by 37% when the bypass line was employed

  2. Impurity control and its impact upon start-up and transformer recharging in NET

    International Nuclear Information System (INIS)

    Harrison, M.F.A.

    1985-01-01

    Control of the release of impurities and their subsequent ingress and exhaust from tokamak plasmas has been the subject of intensive studies aimed at both the prediction of reactor burn condition and the interpretation of results from present experiments. Control concepts which are specific to current-initiation, current ramp-up and RF heating during start-up of a reactor such as NET have to date received little attention, according to the author. This paper presents an inductive start-up scenario which is typical of those presently being considered for NET. Shown are plasma configurations during start-up. Particularly significant issues are the advantages of forming the divertor configuration at the earliest practicable stage and the problems expected due to contamination of the limiter with divertor material

  3. Molecular Engineering of dosimetric materials

    International Nuclear Information System (INIS)

    Salas, P.; Castano, V.M.; Mendoza, D.; Gonzalez, P.

    1999-01-01

    It was studied the thermoluminescent response to the gamma radiation of a new family of solid materials of zircon-silica. In this study some materials have been prepared by the sol-gel method with different stoichiometric relations, finding that it is possible to control, at least, partially, the thermoluminescent behavior starting from the Molecular Engineering of those materials, since the mixture of both ceramics allows to produce materials with different spatial structures. (Author)

  4. Caregivers' attitudes regarding portion size served to Head Start children

    Science.gov (United States)

    The purpose of this study was to identify caregivers' attitudes regarding amounts and types of foods served to Head Start preschoolers using qualitative methods. Researchers conducted 8 focus groups (4 African American; 4 Hispanic) with 33 African American and 29 Hispanic Head Start caregivers. Mode...

  5. Head Start, 4 years After Completing the Program

    Science.gov (United States)

    Kim, Young-Joo

    2013-01-01

    This paper studies the effect of the Head Start program on children's achievements in reading and math tests during their first 4 years of schooling after completing the program. Using nationally representative data from the Early Childhood Longitudinal Study, I found large measurement error in the parental reports of Head Start attendance, which…

  6. Starting infants on antiretroviral therapy | Clayden | Southern African ...

    African Journals Online (AJOL)

    5 years or more, that most start at a late stage of the disease, and that mortality in the first few months of treatment remains high.5,6 A recent study shows that starting treatment in early infancy can be lifesaving, and this has informed revisions in World Health Organization (WHO) guidelines7,8 (see WHO 'Dear Health Care ...

  7. Head Start Impact Study. Final Report. Executive Summary

    Science.gov (United States)

    Puma, Michael; Bell, Stephen; Cook, Ronna; Heid, Camilla; Shapiro, Gary; Broene, Pam; Jenkins, Frank; Fletcher, Philip; Quinn, Liz; Friedman, Janet; Ciarico, Janet; Rohacek, Monica; Adams, Gina; Spier, Elizabeth

    2010-01-01

    This report summarizes the findings from a study on the impacts of Head Start on children and families during the children's preschool, kindergarten, and 1st grade years. Its study goals were to: (1) Determine the impact of Head Start on children's school readiness, and on parental practices that support children's development; and to (2)…

  8. Early Head Start Participants, Programs, Families, and Staff in 2014

    Science.gov (United States)

    Mohan, Anitha; Walker, Christina

    2016-01-01

    In 1994, the federal Early Head Start (EHS) program was created to address the comprehensive needs of low-income pregnant women and children under age 3. EHS was launched almost 30 years after Head Start was established in 1965 to serve low-income 3- and 4-year-old children and their families with comprehensive early education and support…

  9. 46 CFR 112.50-5 - Electric starting.

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 4 2010-10-01 2010-10-01 false Electric starting. 112.50-5 Section 112.50-5 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) ELECTRICAL ENGINEERING EMERGENCY LIGHTING AND POWER SYSTEMS Emergency Diesel and Gas Turbine Engine Driven Generator Sets § 112.50-5 Electric starting...

  10. Starting an Actuarial Science Major at a Liberal Arts College

    Science.gov (United States)

    Mills, Mark A.

    2014-01-01

    The article provides details of the process of starting an actuarial science major at a small, liberal arts college. Some critique of the major is included, as well as some challenges that may be faced by others wanting to start such a major at their institution.

  11. 40 CFR 86.136-90 - Engine starting and restarting.

    Science.gov (United States)

    2010-07-01

    ... automatic chokes shall be operated according to the manufacturer's operating instructions in the owner's...) The transmission shall be placed in gear 15 seconds after the engine is started. If necessary, braking... instructions in the owner's manual do not specify a warm engine starting procedure, the engine (automatic and...

  12. Start-up Costs, Taxes and Innovative Entrepreneurship

    NARCIS (Netherlands)

    P. Darnihamedani (Pourya); J.H. Block (Jörn); S.J.A. Hessels (Jolanda); A. Simonyan (Aram)

    2015-01-01

    markdownabstract__Abstract__ Prior research suggests that start-up costs and taxes negatively influence entry into entrepreneurship. Yet, no distinction is made regarding the type of entrepreneurship, particularly innovative versus non-innovative entrepreneurship. Start-up costs, being one-off

  13. 13 CFR 305.11 - Contract awards; early construction start.

    Science.gov (United States)

    2010-01-01

    ... 13 Business Credit and Assistance 1 2010-01-01 2010-01-01 false Contract awards; early construction start. 305.11 Section 305.11 Business Credit and Assistance ECONOMIC DEVELOPMENT ADMINISTRATION... § 305.11 Contract awards; early construction start. EDA must determine that the award of all contracts...

  14. Beyond Intentions--What Makes a Student Start a Firm?

    Science.gov (United States)

    Joensuu-Salo, Sanna; Varamäki, Elina; Viljamaa, Anmari

    2015-01-01

    Purpose: Entrepreneurial intentions have been extensively studied in student populations, with results suggesting that higher education does not promote formation of entrepreneurial intentions (e.g. Varamäki et al., 2013). However, the gap between intending to start a business and actually doing something to start one remains. The purpose of this…

  15. Dynamic usage of transcription start sites within core promoters

    DEFF Research Database (Denmark)

    Kawaji, Hideya; Frith, Martin C; Katayama, Shintaro

    2006-01-01

    BACKGROUND: Mammalian promoters do not initiate transcription at single, well defined base pairs, but rather at multiple, alternative start sites spread across a region. We previously characterized the static structures of transcription start site usage within promoters at the base pair level......, based on large-scale sequencing of transcript 5' ends. RESULTS: In the present study we begin to explore the internal dynamics of mammalian promoters, and demonstrate that start site selection within many mouse core promoters varies among tissues. We also show that this dynamic usage of start sites...... is associated with CpG islands, broad and multimodal promoter structures, and imprinting. CONCLUSION: Our results reveal a new level of biologic complexity within promoters--fine-scale regulation of transcription starting events at the base pair level. These events are likely to be related to epigenetic...

  16. University Knowledge Spillovers & Regional Start-up Rates

    DEFF Research Database (Denmark)

    Hellerstedt, Karin; Wennberg, Karl; Frederiksen, Lars

    2014-01-01

    how characteristics of the economic and political milieu within each region influence the ratio of firm births. We find that knowledge spillovers from universities and firm-based R&D strongly affect the start-up rates for both high-tech firms and knowledge-intensive services firms. Further, the start......This chapter investigates how regional start-up rates in the knowledge-intensive services and high-tech industries are influenced by knowledge spillovers from both universities and firm-based R&D activities. Integrating insights from economic geography and organizational ecology into the literature......-up rate of knowledge-intensive service firms is tied more strongly to the supply of university educated individuals and the political regulatory regime within the municipality than start-ups in high-tech industries. This suggests that knowledge-intensive service-start-ups are more susceptible to both...

  17. Starting lithium prophylaxis early v. late in bipolar disorder

    DEFF Research Database (Denmark)

    Kessing, Lars Vedel; Vradi, Eleni; Andersen, Per Kragh

    2014-01-01

    BACKGROUND: No study has investigated when preventive treatment with lithium should be initiated in bipolar disorder. AIMS: To compare response rates among patients with bipolar disorder starting treatment with lithium early v. late. METHOD: Nationwide registers were used to identify all patients...... with a diagnosis of bipolar disorder in psychiatric hospital settings who were prescribed lithium during the period 1995-2012 in Denmark (n = 4714). Lithium responders were defined as patients who, following a stabilisation lithium start-up period of 6 months, continued lithium monotherapy without being admitted...... to hospital. Early v. late intervention was defined in two ways: (a) start of lithium following first contact; and (b) start of lithium following a diagnosis of a single manic/mixed episode. RESULTS: Regardless of the definition used, patients who started lithium early had significantly decreased rates of non...

  18. PENGEMBANGAN DESAIN STARTING BLOCK KOLAM RENANG DENGAN MENGGUNAKAN THEORY OF INVENTIVE PROBLEM SOLVING (TRIZ

    Directory of Open Access Journals (Sweden)

    Denny Nurkertamanda

    2012-02-01

    Full Text Available Swimmingpool starting block is one of swimming equiptment that must be used in swimming sport competition.It used not only by senior athlete but also the beginner. In addition, it used not only in one swimmingpool butalso another pool which has different height of watersurface and swimmingpoll wallside.Now, the condition of starting block only fit with some of athlete. The other athlete had difficulties when use it.Because of that, design improvement need to be done for starting block to be adaptable for all athlete in anyage and adaptable for the condition of watersurface.Adaptability fitur improvement for starting block makes fitur stabilition of product composition getting worse,and those things is unwanted. So that Theory of Inventive Problem Solving (TRIZ method is needed to solvethe problem technical contradiction so the ideal final output can be reached.Adaptable starting block design can be reached after solve the technical contradiction happened when solvingthe problems used TRIZ. Reducing the parameters which had disadvantages for the ideal final product suchas: weight of the moving object, quantity of the material used, dangerous factor of the object, and dangerousfactors from environtment.

  19. Analysis of MBE-grown II-VI hetero-interfaces and quantum-dots by Raman spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Bass, Utz

    2012-10-16

    The material system of interest in this thesis are II-VI-semiconductors. The first part of this thesis focuses on the formation of self-assembled CdSe-based quantum dots (QD) on ZnSe. The lattice constants of ZnSe and CdSe differ as much as about 7% and therefore a CdSe layer grown on top of ZnSe experiences a huge strain. The aspired strain relief constitutes in the self-assembly of QDs (i.e. a roughened layer structure). Additionally, this QD layer is intermixed with Zn as this is also a possibility to decrease the strain in the layer. For CdSe on ZnSe, in Molecular Beam Epitaxy (MBE), various QD growth procedures were analysed with respect to the resulting Cd-content of the non-stoichiometric ternary (Zn,Cd)Se. The evaluation was performed by Raman Spectroscopy as the phonon frequency depends on the Cd-content. The second part of the thesis emphasis on the interface properties of n-ZnSe on n-GaAs. Different growth start procedures of the ZnSe epilayer may lead to different interface configurations with characteristic band-offsets and carrier depletion layer widths. The analysis is mainly focused on the individual depletion layer widths in the GaAs and ZnSe. This non-destructive analysis is performed by evaluating the Raman signal which comprises of phonon scattering from the depleted regions and coupled plasmon-phonon scattering from regions with free carriers.

  20. Analysis of MBE-grown II-VI hetero-interfaces and quantum-dots by Raman spectroscopy

    International Nuclear Information System (INIS)

    Bass, Utz

    2012-01-01

    The material system of interest in this thesis are II-VI-semiconductors. The first part of this thesis focuses on the formation of self-assembled CdSe-based quantum dots (QD) on ZnSe. The lattice constants of ZnSe and CdSe differ as much as about 7% and therefore a CdSe layer grown on top of ZnSe experiences a huge strain. The aspired strain relief constitutes in the self-assembly of QDs (i.e. a roughened layer structure). Additionally, this QD layer is intermixed with Zn as this is also a possibility to decrease the strain in the layer. For CdSe on ZnSe, in Molecular Beam Epitaxy (MBE), various QD growth procedures were analysed with respect to the resulting Cd-content of the non-stoichiometric ternary (Zn,Cd)Se. The evaluation was performed by Raman Spectroscopy as the phonon frequency depends on the Cd-content. The second part of the thesis emphasis on the interface properties of n-ZnSe on n-GaAs. Different growth start procedures of the ZnSe epilayer may lead to different interface configurations with characteristic band-offsets and carrier depletion layer widths. The analysis is mainly focused on the individual depletion layer widths in the GaAs and ZnSe. This non-destructive analysis is performed by evaluating the Raman signal which comprises of phonon scattering from the depleted regions and coupled plasmon-phonon scattering from regions with free carriers.

  1. From BookStart to BookSmart : about the importance of an early start with parent-child reading

    NARCIS (Netherlands)

    Berg, Heleen van den

    2015-01-01

    BookStart has been developed to enhance parent-child verbal interactions in early childhood by promoting book sharing. Parents receive a voucher for a baby book and free access to baby books in the library. In a large-scale research, we found that if parents complied with the BookStart suggestion to

  2. Dictionary materials engineering, materials testing

    International Nuclear Information System (INIS)

    1994-01-01

    This dictionary contains about 9,500 entries in each part of the following fields: 1) Materials using and selection; 2) Mechanical engineering materials -Metallic materials - Non-metallic inorganic materials - Plastics - Composites -Materials damage and protection; 3) Electrical and electronics materials -Conductor materials - Semiconductors - magnetic materials - Dielectric materials - non-conducting materials; 4) Materials testing - Mechanical methods - Analytical methods - Structure investigation - Complex methods - Measurement of physical properties - Non-destructive testing. (orig.) [de

  3. Zygomycota associated with traditional meju, a fermented soybean starting material for soy sauce and soybean paste

    NARCIS (Netherlands)

    Hong, S.B.; Kim, D.H.; Lee, M.; Baek, S.Y.; Kwon, S.; Houbraken, J.; Samson, R.A.

    2012-01-01

    Various zygomycota species were detected during a study of the mycobiota of meju, a brick of dried fermented soybeans, used in Korean cuisine. Two hundred and sixty-eight strains were isolated from 98 finished meju products collected in various regions of Korea from 2009 to 2011, and 96 strains were

  4. Stereospecific synthesis of specifically deuterated metoprolol enantiomers from chiral starting materials

    Energy Technology Data Exchange (ETDEWEB)

    Shetty, H.U.; Murthy, S.S.; Nelson, W.L. (Washington Univ., Seattle, WA (USA). Dept. of Medicinal Chemistry)

    1989-10-01

    Enantiomers of metoprolol (1) containing six deuterium atoms in the isopropyl methyl groups ((2R)), two deuterium atoms at C-2 and C-6 of the aromatic ring ((2S)), and two deuterium atoms at C-3 of the propanolamine side chain ((2S)) were prepared. Chiral 2,2-dimethyl-1,3-dioxolane-4-methanols ((4R) and (4S)) were key synthons. Sources of deuterium were ({sup 2}H{sub 6})-isopropyl-amine, 4-(2-methoxyethyl)-2,6-({sup 2}H{sub 2})-phenol, prepared by {sup 2}HCl/{sup 2}H{sub 2}O exchange, and (4S)-2,2-dimethyl-1,3-dioxolane-4-({sup 2}H{sub 2})-4-methanol, prepared by LiAl{sup 2}H{sub 4} reduction of (4S)-methyl 2,2-dimethyl-1,3-dioxolane-4-carboxylate. Enantiomeric excess was greater than 94% for each of the prepared enantiomers, as determined independently by {sup 1}H NMR spectroscopy on diastereomeric derivatives and by chiral column HPLC. (author).

  5. Comparative study of Bi-2223/Ag superconductors derived from particles size of starting materials

    Czech Academy of Sciences Publication Activity Database

    Sýkorová, D.; Smrčková, O.; Rubešová, K.; Vašek, Petr

    2007-01-01

    Roč. 21, 18/19 (2007), s. 3246-3249 ISSN 0217-9792 R&D Projects: GA ČR GA203/05/0114 Institutional research plan: CEZ:AV0Z10100521 Keywords : Ag-addition * sol-gel method Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.647, year: 2007

  6. Tokamak start-up with electron-cyclotron heating

    Energy Technology Data Exchange (ETDEWEB)

    Holly, D J; Prager, S C; Shepard, D A; Sprott, J C [Wisconsin Univ., Madison (USA)

    1981-11-01

    Experiments are described in which the start-up voltage in a tokamak is reduced by about a factor of two by the use of a modest amount of electron cyclotron resonance heating power for pre-ionization. The solution of the zero-dimensional start-up equations indicates that the effect is due to the high initial density which increases the rate at which the conductivity increases in the neutral-dominated initial plasma. The effect extrapolates favourably to larger tokamaks. A 50% reduction in the start-up volt-second requirement and impurity reflux is also observed.

  7. Tokamak start-up with electron-cyclotron heating

    International Nuclear Information System (INIS)

    Holly, D.J.; Prager, S.C.; Shepard, D.A.; Sprott, J.C.

    1981-01-01

    Experiments are described in which the start-up voltage in a tokamak is reduced by about a factor of two by the use of a modest amount of electron cyclotron resonance heating power for pre-ionization. The solution of the zero-dimensional start-up equations indicates that the effect is due to the high initial density which increases the rate at which the conductivity increases in the neutral-dominated initial plasma. The effect extrapolates favourably to larger tokamaks. A 50% reduction in the start-up volt-second requirement and impurity reflux is also observed. (author)

  8. Start-up of NPP Krsko; Pokusno obratovanje NE Krsko

    Energy Technology Data Exchange (ETDEWEB)

    Spiler, J; Aralica, J [Nuklearna elektrana Krsko, Krsko (Yugoslavia)

    1984-07-01

    The report describes a review of start-up program and its realisation. There are also described some more significant start-up results with their evaluation. The most significant operation criteria are compared between NPP Krsko and other similar plants in the world. The comparison shows that after the first contractors and operation personnel efforts have been accomplished, our first nuclear power plant is a safe and reliable source of electric power. At the end there are listed NPP Krsko start-up recommendations and experience. (author)

  9. Biomechanical Analysis of the Swim-Start: A Review

    Directory of Open Access Journals (Sweden)

    Julien Vantorre, Didier Chollet, Ludovic Seifert

    2014-06-01

    Full Text Available This review updates the swim-start state of the art from a biomechanical standpoint. We review the contribution of the swim-start to overall swimming performance, the effects of various swim-start strategies, and skill effects across the range of swim-start strategies identified in the literature. The main objective is to determine the techniques to focus on in swimming training in the contemporary context of the sport. The phases leading to key temporal events of the swim-start, like water entry, require adaptations to the swimmer’s chosen technique over the course of a performance; we thus define the swim-start as the moment when preparation for take-off begins to the moment when the swimming pattern begins. A secondary objective is to determine the role of adaptive variability as it emerges during the swim-start. Variability is contextualized as having a functional role and operating across multiple levels of analysis: inter-subject (expert versus non-expert, inter-trial or intra-subject (through repetitions of the same movement, and inter-preference (preferred versus non-preferred technique. Regarding skill effects, we assume that swim-start expertise is distinct from swim stroke expertise. Highly skilled swim-starts are distinguished in terms of several factors: reaction time from the start signal to the impulse on the block, including the control and regulation of foot force and foot orientation during take-off; appropriate amount of glide time before leg kicking commences; effective transition from leg kicking to break-out of full swimming with arm stroking; overall maximal leg and arm propulsion and minimal water resistance; and minimized energy expenditure through streamlined body position. Swimmers who are less expert at the swim-start spend more time in this phase and would benefit from training designed to reduce: (i the time between reaction to the start signal and impulse on the block, and (ii the time in transition (i

  10. Predicting start-up success with machine learning

    OpenAIRE

    Bento, Francisco Ramadas da Silva Ribeiro

    2018-01-01

    Start-ups are becoming the motor that moves our economy. Google, Apple, or more recently Airbnb and Uber are companies with tremendous impact in worldwide economy, social interactions and government. Over the past decade, both in the US and Europe, there has been an exponential growth in start-up formation. Thus, it seems a relevant challenge understanding what makes this type of high-risk ventures successful and as such, attractive to investors and entrepreneurs. Success for a start-up is de...

  11. Material Science

    Energy Technology Data Exchange (ETDEWEB)

    Won, Dong Yeon; Kim, Heung

    1987-08-15

    This book introduces material science, which includes key of a high-tech industry, new materials of dream like new metal material and semiconductor, classification of materials, microstructure of materials and characteristic. It mentions magic new materials such as shape memory alloy, fine ceramics, engineering fine ceramics, electronic ceramics, engineering plastic, glass, silicone conductor, optical fiber mixed materials and integrated circuit, challenge for new material and development of new materials.

  12. Material Science

    International Nuclear Information System (INIS)

    Won, Dong Yeon; Kim, Heung

    1987-08-01

    This book introduces material science, which includes key of a high-tech industry, new materials of dream like new metal material and semiconductor, classification of materials, microstructure of materials and characteristic. It mentions magic new materials such as shape memory alloy, fine ceramics, engineering fine ceramics, electronic ceramics, engineering plastic, glass, silicone conductor, optical fiber mixed materials and integrated circuit, challenge for new material and development of new materials.

  13. CERN confident of LHC start-up in 2007

    CERN Document Server

    2007-01-01

    "Delegates attending the 140th meeting of CERN Council heard a confident report from the Laboratory about the scheduled start-up of the world's highest energy particle accelerator, the Large Hadron Collier (LHC), in 2007." (1 page)

  14. Short-term treatment outcomes of children starting antiretroviral ...

    African Journals Online (AJOL)

    Short-term treatment outcomes of children starting antiretroviral therapy in the intensive care unit, general medical wards and outpatient HIV clinics at Red Cross War Memorial Children's Hospital, Cape Town, South Africa: A retrospective cohort study.

  15. Method of starting internal pumps of a nuclear reactor

    International Nuclear Information System (INIS)

    Kumagami, Shoji.

    1985-01-01

    Purpose: To reduce the noise effects by decreasing the invading current into the main line upon starting an internal pump type nuclear reactor adapted to forcively recycle the reactor water by a plurality of internal pumps. Method: A plurality of internal pumps are divided into several groups and, upon starting pumps belonging to the individual unit group, the starting instances for the respective pumps are deviated to reduce the surges applied to the main line and suppress the invading current lower to reduce the earth noises. As a result, effects caused to other devices or equipments can be moderated to improve the reliability. Furthermore, by actuating the respective pumps on every group units in a starting pattern along the orthogonal line, flow rate distribution in the reactor can be balanced. Then, the instability region during low rotation of pumps, that is, instability of the flow rate near the resonance frequency can be decreased. (Kawakami, Y.)

  16. School start times and teenage driver motor vehicle crashes.

    Science.gov (United States)

    2015-12-01

    There is substantial evidence that lack of sleep is a significant factor in motor vehicle crashes experienced by teenage drivers. This report examines the hypothesis that a later high school start time may reduce crash rates by reducing the interfere...

  17. Density and starting-energy dependent effective interaction

    International Nuclear Information System (INIS)

    Yamaguchi, Norio; Nagata, Sinobu; Kasuga, Teruo

    1979-01-01

    A new effective potential constructed from the reaction matrix calculation of nuclear matters is proposed, taking three-body effects into account. Starting from the two-body scattering equation for nuclear matters, an equation with averaged momentum is introduced as the definition of effective interaction. The parameters in the equation are the Fermi momentum and the starting energy. The nuclear density dependence and the starting energy dependence are independently treated in the potential. The effective interactions including three-body effects were calculated. The dependence on the starting energy is large. The effective interaction is more attractive in the triplet E state, and assures overall saturation without any artificial renormalization. The reaction matrix calculation can be well reproduced by the calculation with this effective potential. The results of calculation for the binding energy of He-4 and O-16 and the shell model matrix elements of O-16 are represented. (Kato, T.)

  18. 1-D hybrid code for FRM start-up

    International Nuclear Information System (INIS)

    Stark, R.A.; Miley, G.H.

    1982-01-01

    A one-D hybrid has been developed to study the start-up of the FRM via neutral-beam injection. The code uses a multi-group numerical model originally developed by J. Willenberg to describe fusion product dynamics in a solenoidal plasma. Earlier we described such a model for use in determining self-consistent ion currents and magnetic fields in FRM start-up. However, consideration of electron dynamics during start-up indicate that the electron current will oppose the injected ion current and may even foil the attempt to achieve reversal. For this reason, we have combined the multi-group ion (model) with a fluid treatment for electron dynamics to form the hybrid code FROST (Field Reversed One-dimensional STart-up). The details of this merger, along with sample results of operation of FROST, are given

  19. Getting started with digital collections scaling to fit your organization

    CERN Document Server

    Monson, D

    2017-01-01

    This easy-to-follow guide to digitization fundamentals will ensure that readers gain a solid grasp of the knowledge and resources available for getting started on their own digital collection projects.

  20. Dialysis access, infections, and hospitalisations in unplanned dialysis start patients

    DEFF Research Database (Denmark)

    Machowska, Anna; Alscher, Mark Dominik; Vanga, Satyanarayana Reddy

    2017-01-01

    Introduction: Unplanned dialysis start (UPS) associates with worse clinical outcomes, higher utilisation of healthcare resources, lower chances to select dialysis modality and UPS patients typically commenced in-centre haemodialysis (HD) with central venous catheter (CVC). We evaluated patient ou...

  1. CERN confirms goal of 2007 start-up for LHC

    CERN Document Server

    2005-01-01

    Speaking at the 131st session of CERN Council on 17 December 2004, the Director-General, Robert Aymar, confirmed that the top priority is to maintain the goal of starting up the Large Hadron Collider (LHC) in 2007.

  2. MASS TRANSIT: FTA Could Relieve New Starts Program Funding Constraints

    National Research Council Canada - National Science Library

    2001-01-01

    .... Much of this investment has come through the Federal Transit Administration's (FTA) New Starts program, which helps pay for certain rail, bus, and trolley projects through full-funding grant agreements...

  3. Spring 
start-up for the LHC

    CERN Multimedia

    2007-01-01

    A new schedule for the commissioning of the LHC was presented to the Council at its Session in June. The start-up of the accelerator is scheduled for May 2008, to allow all technical problems to be resolved.

  4. Materials and material testing

    International Nuclear Information System (INIS)

    Joergens, H.

    1978-01-01

    A review based on 105 literature quotations is given on the latest state of development in the steel sector and in the field of non-ferrous metals and plastics. The works quoted also include, preparation, working, welding including simulation methods, improvement of weldability, material mechanics (explanation of defects mechanisms by means of fracture mechanics), defect causes (corrosion, erosion, hydrogen influence), mechanical-technological and non-destructive material testing. Examples from the field of reactor building are also given within there topics. (IHOE) [de

  5. Self-starting aerodynamics analysis of vertical axis wind turbine

    OpenAIRE

    Jianyang Zhu; Hailin Huang; Hao Shen

    2015-01-01

    Vertical axis wind turbine is a special type of wind-force electric generator which is capable of working in the complicated wind environment. The self-starting aerodynamics is one of the most important considerations for this kind of turbine. This article aims at providing a systematic synthesis on the self-starting aerodynamic characteristics of vertical axis wind turbine based on the numerical analysis approach. First, the physical model of vertical axis wind turbine and its parameter defi...

  6. An eigenexpansion technique for modelling plasma start-up

    International Nuclear Information System (INIS)

    Pillsbury, R.D.

    1989-01-01

    An algorithm has been developed and implemented in a computer program that allows the estimation of PF coil voltages required to start-up an axisymmetric plasma in a tokamak in the presence of eddy currents in toroidally continuous conducting structures. The algorithm makes use of an eigen-expansion technique to solve the lumped parameter circuit loop voltage equations associated with the PF coils and passive (conducting) structures. An example of start-up for CIT (Compact Ignition Tokamak) is included

  7. University Start-ups: A Better Business Model

    Science.gov (United States)

    Dehn, J.; Webley, P. W.

    2015-12-01

    Many universities look to start-up companies as a way to attract faculty, supporting research and students as traditional federal sources become harder to come by. University affiliated start-up companies can apply for a broader suite of grants, as well as market their services to a broad customer base. Often university administrators see this as a potential panacea, but national statistics show this is not the case. Rarely do universities profit significantly from their start-ups. With a success rates of around 20%, most start-ups end up costing the university money as well as faculty-time. For the faculty, assuming they want to continue in academia, a start-up is often unattractive because it commonly leads out of academia. Running a successful business as well as maintaining a strong teaching and research load is almost impossible to do at the same time. Most business models and business professionals work outside of academia, and the models taught in business schools do not merge well in a university environment. To mitigate this a new business model is proposed where university start-ups are aligned with the academic and research missions of the university. A university start-up must work within the university, directly support research and students, and the work done maintaining the business be recognized as part of the faculty member's university obligations. This requires a complex conflict of interest management plan and for the companies to be non-profit in order to not jeopardize the university's status. This approach may not work well for all universities, but would be ideal for many to conserve resources and ensure a harmonious relationship with their start-ups and faculty.

  8. Strategic Management: Business Model Canvas for Start-Up Company

    OpenAIRE

    Sonninen, Anna

    2016-01-01

    Thesis is written about development of Kakunpala as a Start-Up Company, because development processes and ideas are the key factors for future success of the company. The aim of this thesis is to understand Strategic Management of the Company and Development processes,by using the SWOT analysis before and after development and by applying Business Model Canvas template to the Start-Up Company, and by describing Customer Journey: what relations Kakunpala has with clients and its processes...

  9. Later Start Time for Teens Improves Grades, Mood, and Safety

    Science.gov (United States)

    Wahlstrom, Kyla L.

    2017-01-01

    A recent study by the University of Minnesota looked at eight high schools across the U.S. that chose later start times, from 8:00 a.m. to 8:55 a.m. The study found significant decreases in absences and tardiness as well as greater academic benefits for schools with the latest start times. Among the 9,395 students in the study, those who slept…

  10. Application of STOPP and START criteria: interrater reliability among pharmacists.

    LENUS (Irish Health Repository)

    Ryan, Cristin

    2009-07-01

    Inappropriate prescribing is a well-documented problem in older people. The new screening tools, STOPP (Screening Tool of Older Peoples\\' Prescriptions) and START (Screening Tool to Alert doctors to Right Treatment) have been formulated to identify potentially inappropriate medications (PIMs) and potential errors of omissions (PEOs) in older patients. Consistent, reliable application of STOPP and START is essential for the screening tools to be used effectively by pharmacists.

  11. Dampak Mentoring Pada Keberhasilan Start-Up Business: Studi Kasus Pada Start-Up Business di Indonesia [Mentoring the Impact of Success of a Start-Up Business: A Case Study of a Start-Up Business in Indonesia

    OpenAIRE

    Christina Yanita Setyawati

    2016-01-01

    Entrepreneurship is a highly developed science today, as well as in the world of education in Indonesia. Teaching entrepreneurship at the university level, especially at some universities in Surabaya, the second largest city in Indonesia, shows the positive impact that there were 74.03% of start-up businesses that survived and thrived in 2014. Based on the previous observation, some business start-ups are accompanied by a mentor. Mentoring is a process of forming and maintaining lasting relat...

  12. An Ultra Low Noise Self-Starting Pulse Generator

    DEFF Research Database (Denmark)

    Lasri, J.; Bilenca, A.; Dahan, D.

    2002-01-01

    We describe a self-starting optical pulse source generating 10 GHz, 15 ps pulses with an average jitter of 43 fs and a o.15% amplitude noise over a frequency range of 500 Hz - 1 MHz.......We describe a self-starting optical pulse source generating 10 GHz, 15 ps pulses with an average jitter of 43 fs and a o.15% amplitude noise over a frequency range of 500 Hz - 1 MHz....

  13. Power start up of the Dalat nuclear research reactor

    International Nuclear Information System (INIS)

    Pham Duy Hien; Ngo Quang Huy; Vu Hai Long; Tran Khanh Mai

    1994-01-01

    After accomplishing the physical start-up of the reactor, the power start-up was carried out in February 1984. The power of the reactor has reached: 10 KW on 6/2/1984, 100 KW on 7/2/1984, 200 KW and 300 KW on 8/2/1984; 400 KW and nominal power 500 KW on 9/2/1984. The reactivity temperature coefficient and the xenon poisoning were determined. 3 figs., 12 tabs

  14. Sure start: voices of the 'hard-to-reach'.

    Science.gov (United States)

    Coe, C; Gibson, A; Spencer, N; Stuttaford, M

    2008-07-01

    This research aimed to look in depth at the factors affecting the ability of four Sure Start local programmes, based in a multicultural Midlands city, to engage with 'hard-to-reach' populations. A variety of research strategies and methods were employed. Geographical information systems, participatory research methods and interviews were used in order to understand the extent of the challenge, and hear first hand, why parents may not get involved with Sure Start. The mapping exercise involved collation and mapping of postcode data with respect to boundaries and potential and actual users of Sure Start services. This made possible the identification of any geographical patterning in the distribution of service users and non-users. Participatory research methods were used with parents, enabling them to conduct short interviews within their own communities and make sense of the data collected. Interviews were also conducted with 70 parents across the city, recruited through local schools. The results indicate that parental decisions regarding Sure Start are the product of a complex interaction between numerous factors which may act as either barriers or facilitators to service utilization. The results suggest that a multi-method approach to data collection is useful and appropriate in gaining access to those parents who are non-users of the Sure Start services and enabling their voices to be heard. These findings offer some explanations and insight into the apparent ambivalent attitudes of some families toward Sure Start services. Implications for future practice are discussed.

  15. The backstroke swimming start: state of the art.

    Science.gov (United States)

    de Jesus, Karla; de Jesus, Kelly; Fernandes, Ricardo J; Vilas-Boas, João Paulo; Sanders, Ross

    2014-09-29

    As sprint swimming events can be decided by margins as small as .01 s, thus, an effective start is essential. This study reviews and discusses the 'state of the art' literature regarding backstroke start biomechanics from 23 documents. These included two swimming specific publications, eight peer-reviewed journal articles, three from the Biomechanics and Medicine in Swimming Congress series, eight from the International Society of Biomechanics in Sports Conference Proceedings, one from a Biomechanics Congress and one academic (PhD) thesis. The studies had diverse aims, including swimmers' proficiency levels and data collection settings. There was no single consensus for defining phase descriptions; and kinematics, kinetics and EMG approaches were implemented in laboratory settings. However, researchers face great challenges in improving methods of quantifying valid, reliable and accurate data between laboratory and competition conditions. For example, starting time was defined from the starting signal to distances as disparate as ∼5 m to 22.86 m in several studies. Due to recent rule changes, some of the research outcomes now refer to obsolete backstroke start techniques, and only a few studies considered the actual international rules. This literature review indicated that further research is required, in both laboratory and competition settings focusing on the combined influences of the current rules and block configuration on backstroke starting performances.

  16. Ceramic piezoelectric materials

    International Nuclear Information System (INIS)

    Kaszuwara, W.

    2004-01-01

    Ceramic piezoelectric materials conert reversibility electric energy into mechanical energy. In the presence of electric field piezoelectric materials exhibit deformations up to 0.15% (for single crystals up to 1.7%). The deformation energy is in the range of 10 2 - 10 3 J/m 3 and working frequency can reach 10 5 Hz. Ceramic piezoelectric materials find applications in many modern disciplines such as: automatics, micromanipulation, measuring techniques, medical diagnostics and many others. Among the variety of ceramic piezoelectric materials the most important appear to be ferroelectric materials such as lead zirconate titanate so called PZT ceramics. Ceramic piezoelectric materials can be processed by methods widely applied for standard ceramics, i.e. starting from simple precursors e.g. oxides. Application of sol-gel method has also been reported. Substantial drawback for many applications of piezoelectric ceramics is their brittleness, thus much effort is currently being put in the development of piezoelectric composite materials. Other important research directions in the field of ceramic piezoelectric materials composite development of lead free materials, which can exhibit properties similar to the PZT ceramics. Among other directions one has to state processing of single crystals and materials having texture or gradient structure. (author)

  17. Preliminary study in development of glass-ceramic based on SiO2-LiO2 system, starting of different SiO2 starting powders

    International Nuclear Information System (INIS)

    Daguano, J.K.M.F.; Santos, F.A.; Santos, C.; Marton, L.F.M.; Conte, R.A.; Rodrigues Junior, D.; Melo, F.C.L.

    2009-01-01

    In this work, lithium disilicate glass-ceramics were developed starting of the rice ash- SiO 2 and Li 2 CO 3 powders. The results were compared with glass ceramics based on the lithium disilicate obtained by commercial SiO 2 powders. Glass were melted at 1580 deg C, and annealed at 850 deg C. X-Ray diffraction and scanning electron microscopy were used for characterization of the materials, and hardness and fracture toughness were evaluated using Vickers indentation method. Glasses with amorphous structure were obtained in both materials. After annealing, 'rice-ash' samples presented Li 2 SiO 3 and residual SiO 2 as crystalline phases. On the other side, commercial SiO 2 - Samples presented only Li 2 Si 2 O 5 as crystalline phases and the better results of hardness and fracture toughness. (author)

  18. Later School Start Times: What Informs Parent Support or Opposition?

    Science.gov (United States)

    Dunietz, Galit Levi; Matos-Moreno, Amilcar; Singer, Dianne C; Davis, Matthew M; O'Brien, Louise M; Chervin, Ronald D

    2017-07-15

    To investigate parental knowledge about adolescent sleep needs, and other beliefs that may inform their support for or objection to later school start times. In 2014, we conducted a cross-sectional, Internet-based survey of a nationally representative sample of parents as part of the C.S. Mott Children's Hospital National Poll on Children's Health. Parents with teens aged 13-17 years reported their children's sleep patterns and school schedules, and whether the parents supported later school start times (8:30 am or later). Responses associated with parental support of later school start times were examined with logistic regression analysis. Overall, 88% of parents reported school start times before 8:30 am, and served as the analysis sample (n = 554). In this group, 51% expressed support for later school start times. Support was associated with current school start times before 7:30 am (odds ratio [OR] = 3.1 [95% confidence interval (CI) 1.2, 8.4]); parental opinion that their teen's current school start time was "too early" (OR = 3.8 [1.8, 7.8]); and agreement with American Academy of Pediatrics recommendations about school start times (OR = 4.7 [2.2, 10.1]). Support also was associated with anticipation of improved school performance (OR = 3.0 [1.5, 5.9]) or increased sleep duration (OR = 4.0 [1.8, 8.9]) with later school start times. Conversely, parents who anticipated too little time for after-school activities (OR = 0.5 [0.3, 0.9]) and need for different transportation plans (OR = 0.5 [0.2, 0.9]) were often less supportive. Parental education about healthy sleep needs and anticipated health benefits may increase their support for later school start times. Educational efforts should also publicize the positive experiences of communities that have made this transition, with regard to limited adverse effect on after-school activity schedules and transportation. © 2017 American Academy of Sleep Medicine

  19. Internal combustion engine cold-start efficiency: A review of the problem, causes and potential solutions

    International Nuclear Information System (INIS)

    Roberts, Andrew; Brooks, Richard; Shipway, Philip

    2014-01-01

    Highlights: • The sources of I.C. engine cold start efficiency are reviewed and quantified. • Potential solutions are reviewed and the benefit quantified together. • Potential conflicts between different engine sub-systems are discussed. • Fuel consumption benefits of up to 7% are observed during cold start. • Emission reductions of up to 40% during cold start are observed. - Abstract: Legislation on vehicle emissions continues to become more stringent in an effort to minimise the impact of internal combustion engines on the environment. One area of significant concern in this respect is that of the cold-start; the thermal efficiency of the internal combustion engine is significantly lower at cold-start than when the vehicle reaches steady state temperatures owing to sub-optimal lubricant and component temperatures. The drive for thermal efficiency (of both the internal combustion engine and of the vehicle as a whole) has led to a variety of solutions being trialled to assess their merits and effects on other vehicle systems during this warm-up phase (and implemented where appropriate). The approaches have a common theme of attempting to reduce energy losses so that systems and components reach their intended operating temperature range as soon as possible after engine start. In the case of the engine, this is primarily focused on the lubricant system. Lubricant viscosity is highly sensitive to temperature and the increased viscosity at low temperatures results in higher frictional and pumping losses than would be observed at the target operating temperature. The approaches used to tackle the problem include the use of phase change materials (to reduce the cool-down rate during a period following engine running) [1,2] and the use of thermal barrier coatings in an attempt to insulate the cylinder bore and prevent heat loss (thus increasing the amount of energy utilised as brake work [3]). A range of system alterations have also been trialled including

  20. Head Start at Ages 3 and 4 versus Head Start Followed by State Pre-K: Which Is More Effective?

    Science.gov (United States)

    Jenkins, Jade Marcus; Farkas, George; Duncan, Greg J.; Burchinal, Margaret; Vandell, Deborah Lowe

    2016-01-01

    As policy-makers contemplate expanding preschool opportunities for low-income children, one possibility is to fund two, rather than one year of Head Start for children at ages 3 and 4. Another option is to offer one year of Head Start followed by one year of pre-k. We ask which of these options is more effective. We use data from the Oklahoma…

  1. Pre-start timing information is used to set final linear speed in a C-start manoeuvre.

    Science.gov (United States)

    Reinel, Caroline; Schuster, Stefan

    2014-08-15

    In their unique hunting behaviour, archerfish use a complex motor decision to secure their prey: based solely on how dislodged prey initially falls, they select an adapted C-start manoeuvre that turns the fish right towards the point on the water surface where their prey will later land. Furthermore, they take off at a speed that is set so as to arrive in time. We show here that the C-start manoeuvre and not subsequent tail beating is necessary and sufficient for setting this adaptive level of speed. Furthermore, the C-start pattern is adjusted to independently determine both the turning angle and the take-off speed. The selection of both aspects requires no a priori information and is done based on information sampled from the onset of target motion until the C-start is launched. Fin strokes can occur right after the C-start manoeuvre but are not required to fine-tune take-off speed, but rather to maintain it. By probing the way in which the fish set their take-off speed in a wide range of conditions in which distance from the later catching point and time until impact varied widely and unpredictably, we found that the C-start manoeuvre is programmed based on pre-C-start estimates of distance and time until impact. Our study hence provides the first evidence for a C-start that is fine-tuned to produce an adaptive speed level. © 2014. Published by The Company of Biologists Ltd.

  2. TrustRank: a Cold-Start tolerant recommender system

    Science.gov (United States)

    Zou, Haitao; Gong, Zhiguo; Zhang, Nan; Zhao, Wei; Guo, Jingzhi

    2015-02-01

    The explosive growth of the World Wide Web leads to the fast advancing development of e-commerce techniques. Recommender systems, which use personalised information filtering techniques to generate a set of items suitable to a given user, have received considerable attention. User- and item-based algorithms are two popular techniques for the design of recommender systems. These two algorithms are known to have Cold-Start problems, i.e., they are unable to effectively handle Cold-Start users who have an extremely limited number of purchase records. In this paper, we develop TrustRank, a novel recommender system which handles the Cold-Start problem by leveraging the user-trust networks which are commonly available for e-commerce applications. A user-trust network is formed by friendships or trust relationships that users specify among them. While it is straightforward to conjecture that a user-trust network is helpful for improving the accuracy of recommendations, a key challenge for using user-trust network to facilitate Cold-Start users is that these users also tend to have a very limited number of trust relationships. To address this challenge, we propose a pre-processing propagation of the Cold-Start users' trust network. In particular, by applying the personalised PageRank algorithm, we expand the friends of a given user to include others with similar purchase records to his/her original friends. To make this propagation algorithm scalable to a large amount of users, as required by real-world recommender systems, we devise an iterative computation algorithm of the original personalised TrustRank which can incrementally compute trust vectors for Cold-Start users. We conduct extensive experiments to demonstrate the consistently improvement provided by our proposed algorithm over the existing recommender algorithms on the accuracy of recommendations for Cold-Start users.

  3. Dynamic factors and electromyographic activity in a sprint start

    Directory of Open Access Journals (Sweden)

    M Čoh

    2009-07-01

    Full Text Available The aim of the study was to establish the major dynamic parameters as well as the EMG activation of muscles in a sprint start as the first derivative of sprint velocity. The subject of the analysis was block velocity, the production of force in the front and rear starting blocks, the block acceleration in the first two steps and the electromyographic activity (EMG of the following muscles: the erector spinae muscle, gluteus maximus muscle, rectus femoris muscle, vastus medialis muscle, vastus lateralis muscle, biceps femoris muscle and gastrocnemius–medialis muscle. One international-class female sprinter participated in the experiment. She performed eight starts in constant laboratory conditions. The 3-D kinematic analysis was made using a system of nine Smart-e 600 cameras operating at a frame rate of 60 Hz. Dynamic parameters were established by means of two separate force platforms to which the starting blocks were fixed. A 16-channel electromyograph was used to analyse electromyographic activity (EMG. It was established that the block velocity depended on the absolute force produced in the front and rear starting blocks and that it was 2.84±0.21 m.s-1. The maximal force on the rear and front blocks was 628±34 N and 1023±30 N, respectively. In view of the total impulse (210±11 Ns the force production/time ratio in the rear and front blocks was 34%:66%. The erector spinae muscle, vastus lateralis muscle and gastrocnemius–medialis muscle generate the efficiency of the start. The block acceleration in the first two steps primarily depends on the activation of the gluteus maximus muscle, rectus femoris muscle, biceps femoris muscle and gastrocnemius–medialis muscle. A sprint start is a complex motor stereotype requiring a high degree of integration of the processes of central movement regulation and an optimal level of biomotor abilities.

  4. START: An essential step in a new era

    International Nuclear Information System (INIS)

    Lockwood, D.

    1991-01-01

    After more than nine years of negotiations, the US and the Soviet Union signed the Strategic Arms Reduction Treaty (START) in Moscow on July 31, 1991. While the world has changed dramatically since 1982 when the START negotiations began, the treaty remains very much in the US interest. START exacts deep cuts in the most destabilizing and dangerous US and Soviet strategic weapons, and will lead to substantial overall reductions in the strategic nuclear forces of both sides. Moreover, the agreement will create a formal, structured, and predictable strategic environment. It will also impose on the Soviet Union or its successors a legally binding set of obligations that will be in effect for many years, regardless of changes in leadership or form of government. START, with its extensive series of intrusive, cooperative, and technical verification measures, will greatly enhance US knowledge about Soviet strategic nuclear forces and activities. The force reductions, predictability, and transparency that START will lock in will be especially valuable if the Soviet Union breaks into independent states or if there is a resurgence of hard-line political forces in Moscow. In addition, START will provide a framework for deeper reductions that could further reduce the risk of nuclear war, stimulate an increasingly cooperative relationship between the US and the Soviet Union or its successors, and save tens of billions of dollars. Finally, by demonstrating a US and Soviet commitment to reversing the arms race, START should reinforce efforts to stem the proliferation of nuclear weapons among both newly independent Soviet republics and nuclear threshold states, and to ensure success at the Nonproliferation Treaty (NPT) extension conference in 1995

  5. Stop and Restart Effects on Modern Vehicle Starting System Components

    Energy Technology Data Exchange (ETDEWEB)

    Windover, Paul R. [Argonne National Lab. (ANL), Argonne, IL (United States); Owens, Russell J. [Argonne National Lab. (ANL), Argonne, IL (United States); Levinson, Terry M. [Argonne National Lab. (ANL), Argonne, IL (United States); Laughlin, Michael [Argonne National Lab. (ANL), Argonne, IL (United States); Gaines, Linda [Argonne National Lab. (ANL), Argonne, IL (United States)

    2015-01-01

    Many drivers of personal and commercial vehicles believe that turning the vehicle off and on frequently instead of idling will cause premature wear of the starter system (starter motor and starter battery). As a result, they are concerned that the replacement cost of the starter motor and/or battery due to increased manual engine cycling would be more than the cumulative cost of the fuel saved by not idling unnecessarily. A number of variables play a role in addressing this complex concern, including the number of starting cycles per day, the time between starting cycles, the intended design life of the starting system, the amount of fuel used to restart an engine, and the cumulative cost of the saved fuel. Qualitative and quantitative information from a variety of sources was used to develop a life-cycle economic model to evaluate the cost and quantify the realistic factors that are related to the permissible frequency of starter motor cycles for the average vehicle to economically minimize engine idle time. Annual cost savings can be calculated depending on shutdown duration and the number of shutdown cycles per day. Analysis shows that cost savings are realized by eliminating idling exceeding one minute by shutting down the engine and restarting it. For a typical motorist, the damage to starting system components resulting from additional daily start cycles will be negligible. Overall, it was found that starter life is mostly dependent on the total number of start cycles, while battery life is more dependent on ensuring a full charge between start events.

  6. Preparation of Al/Fe-Pillared Clays: Effect of the Starting Mineral.

    Science.gov (United States)

    Muñoz, Helir-Joseph; Blanco, Carolina; Gil, Antonio; Vicente, Miguel-Ángel; Galeano, Luis-Alejandro

    2017-11-28

    Four natural clays were modified with mixed polyoxocations of Al/Fe for evaluating the effect of the physicochemical properties of the starting materials (chemical composition, abundance of expandable clay phases, cationic exchange capacity and textural properties) on final physicochemical and catalytic properties of Al/Fe-PILCs. The aluminosilicate denoted C2 exhibited the highest potential as starting material in the preparation of Al/Fe-PILC catalysts, mainly due to its starting cationic exchange capacity (192 meq/100 g) and the dioctahedral nature of the smectite phase. These characteristics favored the intercalation of the mixed (Al 13- x /Fe x ) 7+ Keggin-type polyoxocations, stabilizing a basal spacing of 17.4 Å and high increase of the BET surface (194 m²/g), mainly represented in microporous content. According to H₂-TPR analyses, catalytic performance of the incorporated Fe in the Catalytic Wet Peroxide Oxidation (CWPO) reaction strongly depends on the level of location in mixed Al/Fe pillars. Altogether, such physicochemical characteristics promoted high performance in CWPO catalytic degradation of methyl orange in aqueous medium at very mild reaction temperatures (25.0 ± 1.0 °C) and pressure (76 kPa), achieving TOC removal of 52% and 70% of azo-dye decolourization in only 75 min of reaction under very low concentration of clay catalyst (0.05 g/L).

  7. School start times and teenage driver motor vehicle crashes.

    Science.gov (United States)

    Foss, Robert D; Smith, Richard L; O'Brien, Natalie P

    2018-04-26

    Shifting school start times to 8:30 am or later has been found to improve academic performance and reduce behavior problems. Limited research suggests this may also reduce adolescent driver motor vehicle crashes. A change in the school start time from 7:30 am to 8:45 am for all public high schools in one North Carolina county presented the opportunity to address this question with greater methodologic rigor. We conducted ARIMA interrupted time-series analyses to examine motor vehicle crash rates of high school age drivers in the intervention county and 3 similar comparison counties with comparable urban-rural population distribution. To focus on crashes most likely to be affected, we limited analysis to crashes involving 16- & 17-year-old drivers occurring on days when school was in session. In the intervention county, there was a 14% downward shift in the time-series following the 75 min delay in school start times (p = .076). There was no change approaching statistical significance in any of the other three counties. Further analysis indicated marked, statistically significant shifts in hourly crash rates in the intervention county, reflecting effects of the change in school start time on young driver exposure. Crashes from 7 to 7:59 am decreased sharply (-25%, p = .008), but increased similarly from 8 to 8:59 am (21%, p = .004). Crashes from 2 to 2:59 pm declined dramatically (-48%, p = .000), then increased to a lesser degree from 3 to 3:59 pm (32%, p = .024) and non-significantly from 4 to 4:59 (19%, p = .102). There was no meaningful change in early morning or nighttime crashes, when drowsiness-induced crashes might have been expected to be most common. The small decrease in crashes among high school age drivers following the shift in school start time is consistent with the findings of other studies of teen driver crashes and school start times. All these studies, including the present one, have limitations, but the similar

  8. A novel induction motor starting method using superconduction

    International Nuclear Information System (INIS)

    Silva, F.B.B.; Orlando, M.T.D.; Fardin, J.F.; Simonetti, D.S.; Baldan, C.A.

    2014-01-01

    Highlights: • Alternative method for starting up induction motor. • Based on using a high-temperature superconductor. • A prototype of the limiter was constructed with a 2G-YBCO tape. • Prototype was tested with a 55-kW industrial induction motor in a 440-V/60-Hz. • Offers reduced current waveform distortion compared to the soft starter method. - Abstract: In this paper, an alternative method for starting up induction motors is proposed, taking into account experimental measurements. The new starting current limitation method is based on using a high-temperature superconductor. A prototype of the superconducting starting current limiter was constructed with a commercially available second-generation high-temperature superconductor YBCO tape, and this was tested with a 55-kW industrial induction motor in a 440-V/60-Hz three-phase power grid. Performance evaluations of the superconducting limiter method (applied to startup of the induction motor) were performed and were compared with a direct-on-line starter and an electronic soft starter. In addition, a computational model was developed and used for electromagnetic torque analysis of the system. As significant characteristics, our method offers the ability to limit the starting current of the induction motor with greater electromagnetic torque, reduced current waveform distortion and therefore lower harmonic pollution during startup when compared to the soft starter method

  9. Self-starting aerodynamics analysis of vertical axis wind turbine

    Directory of Open Access Journals (Sweden)

    Jianyang Zhu

    2015-12-01

    Full Text Available Vertical axis wind turbine is a special type of wind-force electric generator which is capable of working in the complicated wind environment. The self-starting aerodynamics is one of the most important considerations for this kind of turbine. This article aims at providing a systematic synthesis on the self-starting aerodynamic characteristics of vertical axis wind turbine based on the numerical analysis approach. First, the physical model of vertical axis wind turbine and its parameter definitions are presented. Secondary, the interaction model between the vertical axis wind turbine and fluid is developed by using the weak coupling approach; the numerical data of this model are then compared with the wind tunnel experimental data to show its feasibility. Third, the effects of solidity and fixed pitch angle on the self-starting aerodynamic characteristics of the vertical axis wind turbine are analyzed systematically. Finally, the quantification effects of the solidity and fixed pitch angle on the self-starting performance of the turbine can be obtained. The analysis in this study will provide straightforward physical insight into the self-starting aerodynamic characteristics of vertical axis wind turbine.

  10. Control device for start-up of reactor depressurization system

    International Nuclear Information System (INIS)

    Suzuki, Hiroshi; Saito, Minoru; Oda, Shingo; Miura, Satoshi; Hashimoto, Koji; Tate, Hitoshi; Fujii, Kazunobu

    1998-01-01

    The present invention concerns are emergency reactor core cooling system (ECCS) of a BWR type reactor and provides a control device for start-up of an automatic depressurization system. Namely, the device has an object of preventing erroneous opening of a main steam escape safety value when testing a start-up signal circuit of an automatic depressurization system for testing the automatic depressurization system. A start-up signal circuit receives both signals of a reactor container pressure high signal and a reactor pressure vessel water level low signal and outputs an automatic start-up signal for compulsorily opening a main steam escape safety valve automatically. A test switch having a self-holding circuit is disposed to a central control chamber. A test signal circuit is disposed for preventing transfer of an erroneous start-up signal to the main steam escape safety valve due to a simulation signal during output test signals by the test switch. (I.S.)

  11. Start-up Funding via Equity Crowdfunding in Germany

    DEFF Research Database (Denmark)

    Angerer, Martin; Brem, Alexander; Kraus, Sascha

    2017-01-01

    Entrepreneurs often struggle to find sufficient funding for their start-ups. A relatively new way for companies to attract capital is via an internet platform, locating investors who in return receive something in return for their ventures. Equity crowdfunding is one of several types of crowdfund......Entrepreneurs often struggle to find sufficient funding for their start-ups. A relatively new way for companies to attract capital is via an internet platform, locating investors who in return receive something in return for their ventures. Equity crowdfunding is one of several types...... of crowdfunding, and is also known as crowdinvesting in the German-speaking realm. This article predominantly advances the scientific knowledge regarding the success factors of equity crowdfunding for German start-ups. The study conducted nine qualitative interviews with start-ups and crowdinvesting platforms....... Its first result is that German start-ups select crowdinvesting because (1) it is a funding opportunity and (2) it has an expected marketing effect. To organize the results of relevant success factors, the Crowdinvesting Success Model was designed by the researchers. This supports German entrepreneurs...

  12. A novel induction motor starting method using superconduction

    Energy Technology Data Exchange (ETDEWEB)

    Silva, F.B.B., E-mail: flaviobarcelos@ifes.edu.br [Ifes – Federal Institute of Espírito Santo, Dept. of Industrial Automation, Serra, ES 29173087 (Brazil); UFES – Federal University of Espírito Santo, Dept. of Electrical Engineering, Vitória, ES (Brazil); Orlando, M.T.D. [UFES – Federal University of Espírito Santo, Dept. of Physics, Vitória, ES (Brazil); Fardin, J.F.; Simonetti, D.S. [UFES – Federal University of Espírito Santo, Dept. of Electrical Engineering, Vitória, ES (Brazil); Baldan, C.A. [EEL/USP – Engineering School from Lorena/University of São Paulo, SP (Brazil)

    2014-12-15

    Highlights: • Alternative method for starting up induction motor. • Based on using a high-temperature superconductor. • A prototype of the limiter was constructed with a 2G-YBCO tape. • Prototype was tested with a 55-kW industrial induction motor in a 440-V/60-Hz. • Offers reduced current waveform distortion compared to the soft starter method. - Abstract: In this paper, an alternative method for starting up induction motors is proposed, taking into account experimental measurements. The new starting current limitation method is based on using a high-temperature superconductor. A prototype of the superconducting starting current limiter was constructed with a commercially available second-generation high-temperature superconductor YBCO tape, and this was tested with a 55-kW industrial induction motor in a 440-V/60-Hz three-phase power grid. Performance evaluations of the superconducting limiter method (applied to startup of the induction motor) were performed and were compared with a direct-on-line starter and an electronic soft starter. In addition, a computational model was developed and used for electromagnetic torque analysis of the system. As significant characteristics, our method offers the ability to limit the starting current of the induction motor with greater electromagnetic torque, reduced current waveform distortion and therefore lower harmonic pollution during startup when compared to the soft starter method.

  13. The Rationality and Irrationality of Financing Green Start-Ups

    Directory of Open Access Journals (Sweden)

    Linda Bergset

    2015-11-01

    Full Text Available Green start-ups contribute towards a transition to a more sustainable economy by developing sustainable and environmentally friendly innovation and bringing it to the market. Due to specific product/service characteristics, entrepreneurial motivation and company strategies that might differ from that of other start-ups, these companies might struggle even more than usual with access to finance in the early stages. This conceptual paper seeks to explain these challenges through the theoretical lenses of entrepreneurial finance and behavioural finance. While entrepreneurial finance theory contributes to a partial understanding of green start-up finance, behavioural finance is able to solve a remaining explanatory deficit produced by entrepreneurial finance theory. Although some behavioural finance theorists are suggesting that the current understanding of economic rationality underlying behavioural finance research is inadequate, most scholars have not yet challenged these assumptions, which constrict a comprehensive and realistic description of the reality of entrepreneurial finance in green start-ups. The aim of the paper is thus, first, to explore the specifics of entrepreneurial finance in green start-ups and, second, to demonstrate the need for a more up-to-date conception of rationality in behavioural finance theory in order to enable realistic empirical research in this field.

  14. Start-up of spherical tokamak without a center solenoid

    International Nuclear Information System (INIS)

    Maekawa, Takashi; Nagata, Masayoshi

    2012-01-01

    For low-aspect tokamak reactors, spherical tokamak reactors, ST-type FESF/CTFs, it is essential to remove or minimize a central solenoid (CS). Even with the minimized CS, non-inductive start up of the plasma current is required. Rapid increase in the spontaneous plasma current at the final stage of current start-up drives ignition. At the initial stage, formation of plasma and magnetic surfaces are required. As non-inductive plasma start-up scenarios, ECH/ECCD, LHCD, HHFW, DC HELICITY injection, plasma merging and NBI have been studied. In the present article, the present status and future prospect of experimental and theoretical works on these subjects. (author)

  15. Starting characteristics of direct current motors powered by solar cells

    Science.gov (United States)

    Singer, S.; Appelbaum, J.

    1989-01-01

    Direct current motors are used in photovoltaic systems. Important characteristics of electric motors are the starting to rated current and torque ratios. These ratios are dictated by the size of the solar cell array and are different for the various dc motor types. Discussed here is the calculation of the starting to rated current ratio and starting to rated torque ratio of the permanent magnet, and series and shunt excited motors when powered by solar cells for two cases: with and without a maximum-power-point-tracker (MPPT) included in the system. Comparing these two cases, one gets a torque magnification of about 3 for the permanent magnet motor and about 7 for other motor types. The calculation of the torques may assist the PV system designer to determine whether or not to include an MPPT in the system.

  16. Applying behavioral insights to delay school start times.

    Science.gov (United States)

    Kohl Malone, Susan; Ziporyn, Terra; Buttenheim, Alison M

    2017-12-01

    Healthy People 2020 established a national objective to increase the proportion of 9th-to-12th-grade students reporting sufficient sleep. A salient approach for achieving this objective is to delay middle and high school start times. Despite decades of research supporting the benefits of delayed school start times on adolescent sleep, health, and well-being, progress has been slow. Accelerating progress will require new approaches incorporating strategies that influence how school policy decisions are made. In this commentary, we introduce four strategies that influence decision-making processes and demonstrate how they can be applied to efforts aimed at changing school start time policies. Copyright © 2017 National Sleep Foundation. All rights reserved.

  17. Small Vertical Axis Wind Turbines: aerodynamics and starting behavior

    Directory of Open Access Journals (Sweden)

    Horia DUMITRESCU

    2013-12-01

    Full Text Available In urban areas the wind is very turbulent and unstable with fast changes in direction andvelocity. In these environments, the use of small vertical axis wind turbines (VAWT becomesincreasingly attractive due to several advantages over horizontal axis wind turbines (HAWT.However, such designs have received much less attention than the more common propeller-typedesigns and the understanding of same aspects of their operation remains, to this day, incomplete.This is particularly true of their starting characteristics. Indeed, same authors heuristically maintainthat they cannot start without external assistance. This paper reviews the cause of the inability of thelow solidity fixed pitch vertical axis wind turbines to self-start, and investigates the way ofovercoming this draw back.

  18. Starting-up sequence of the AWEC-60 wind turbine

    International Nuclear Information System (INIS)

    Avia, F.; Cruz, M. de la.

    1991-01-01

    One of the most critical status of the wind turbines operation is the starting-up sequence and the connection to the grid, due to the actuating loads that could be several times the loads during operation at rated conditions. Due to this fact, the control strategy is very important during the starting-up sequence in order to minimize the loads on the machine. For this purpose it is necessary to analyze the behaviour of the wind turbine during that sequence in different wind conditions and machine conditions. This report shows the graphic information about fifty starting-up sequences of the AWEC-60 wind turbine of 60 m. diameter and 1200 kW of rated power, recorded in April 1991 and cut-out wind speed. (author)

  19. Start-up processes’ efficiency of turbine jet engines

    Directory of Open Access Journals (Sweden)

    Jankowski Antoni

    2016-12-01

    Full Text Available The paper presents diagnoses of example start-up processes of drive units built in military aircraft operated in the Dęblin's “School of Eaglets” during the flight. The significance of this process is very important, especially from the point of view of flight safety, especially as it concerns the training aircraft, on which officer cadets-candidates for pilots are trained. The diagnosis of the start-up process was conducted using data from on-board flight recorders recorded during a flight training, whose aim was an emergency launch of particular drive units, and with the help of the so-called phase mapping of the selected operating parameters of the particular flight drive systems. The standard diagram of typical start-up systems was shown, while presenting their base subassemblies. At the end, the obtained results and the main problems that need intervention were commented, as well as further preventive activities were proposed.

  20. Influence of Starting Powders on Hydroxyapatite Coatings Fabricated by Room Temperature Spraying Method.

    Science.gov (United States)

    Seo, Dong Seok; Lee, Jong Kook; Hwang, Kyu Hong; Hahn, Byung Dong; Yoon, Seog Young

    2015-08-01

    Three types of raw materials were used for the fabrication of hydroxyapatite coatings by using the room temperature spraying method and their influence on the microstructure and in vitro characteristics were investigated. Starting hydroxyapatite powders for coatings on titanium substrate were prepared by a heat treatment at 1100 °C for 2 h of bovine bone, bone ash, and commercial hydroxyapatite powders. The phase compositions and Ca/P ratios of the three hydroxyapatite coatings were similar to those of the raw materials without decomposition or formation of a new phase. All hydroxyapatite coatings showed a honeycomb structure, but their surface microstructures revealed different features in regards to surface morphology and roughness, based on the staring materials. All coatings consisted of nano-sized grains and had dense microstructure. Inferred from in vitro experiments in pure water, all coatings have a good dissolution-resistance and biostability in water.