ZnSe/ZnSeTe Superlattice Nanotips

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Young SJ

2010-01-01

Full Text Available Abstract The authors report the growth of ZnSe/ZnSeTe superlattice nanotips on oxidized Si(100 substrate. It was found the nanotips exhibit mixture of cubic zinc-blende and hexagonal wurtzite structures. It was also found that photoluminescence intensities observed from the ZnSe/ZnSeTe superlattice nanotips were much larger than that observed from the homogeneous ZnSeTe nanotips. Furthermore, it was found that activation energies for the ZnSe/ZnSeTe superlattice nanotips with well widths of 16, 20, and 24 nm were 76, 46, and 19 meV, respectively.

Estudios y Observaciones Preliminares para Determinar la Posibilidad de Crear un Proyecto de Riego

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Trueba Coronel Samuel

1946-04-01

Full Text Available Es importante percatarse de que en el desarrollo y buen éxito de un proyecto de riego, intervienen diversos; elementos que es necesario estudiar detenidamente, tales como por ejemplo: modo de captación de las aguas (que puede ser almacenamiento, derivación o bombeo; el fin a que se destinan las aguas (ésto es, volúmenes para riego, para regulación, o para le generación de energía; el clima, así como la cantidad y calidad de agua, y terrenos disponibles; los mercados y vías de comunicación para la extracción de los productos agrícolas. Es, pues, muy importante tener la mayor información veraz respecto de cada uno de estos elementos y factores.

Interaction of Se and GaSe with Si(111)

International Nuclear Information System (INIS)

Meng, Shuang; Schroeder, B. R.; Olmstead, Marjorie A.

2000-01-01

Deposition of Se and GaSe on Si(111)7x7 surfaces was studied with low-energy electron diffraction, x-ray photoelectron spectroscopy, and x-ray photoelectron diffraction to probe initial nucleation and interface structure for GaSe/Si(111) heteroepitaxy. Room-temperature deposition of Se on Si(111)7x7 results in an amorphous film. Subsequent annealing leads to Se evaporation without ordering or interdiffusion. Se deposition at 450 degree sign C saturates at submonolayer coverage with no diffusion of Se into the substrate. There is no clear evidence of ordered sites for the Se. Growth of GaSe on Si(111)7x7 above 500 degree sign C results in a pseudomorphic bilayer, with Si-Ga-Se bonding. Additional GaSe does not stick to the bilayer above 525 degree sign C. The resulting Se lone pair at the surface leads to an ideally passivated surface similar to As/Si(111). This stable surface is similar to the layer termination in bulk GaSe. The single domain bilayer is oriented with the Ga-Se bond parallel to the substrate Si-Si bond. (c) 2000 The American Physical Society

Cúpulas y bóvedas de yeso proyectado sobre molde de metacrilato

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VMBC, Equipo

1986-07-01

Full Text Available Investigation on gypsum within the programme «Materials, Technologies and Prototypes for a Very Low Cost Housing», which is being carried out in the lETcc in order to reach a housing typology by means of materials and technologies that will facilitate a final product that will combine together these fundamental characteristics: adequacy for the physical, social and cultural needs of the zone where they are constructed and a very low cost execution.Investigación del material yeso dentro del programa «Materiales, Tecnologías y Prototipos para Viviendas de muy Bajo Coste», que se desarrolla actualmente en el lETcc, con el fin de llegar a la realización de unas tipologías de viviendas construidas mediante materiales y tecnologías que permitan facilitar un producto final que reúna como características fundamentales: adecuación a las necesidades físicas y socioculturales de la zona a la que se destinan, y un muy bajo costo de ejecución

Extended analyses of Se VII and Se VIII

International Nuclear Information System (INIS)

Vankleef, Th.A.M.; Joshi, Y.N.

1984-01-01

Joshi et al. (1984) have conducted an analysis of the 3d8 4s-3d8 4p transitions in As VII. The present investigation is concerned with an analysis of similar transitions in Se VIII. The selenium spectrum was photographed in the 400-1200-A wavelength region on a variety of normal-incidence spectrographs. Attention is given to least-squares-fit (LSF) and Hartree-Fock (HF) parameter values for the 3d9 4d configuration of Se VII, LSF and HF parameter values for the 3d8 4s and 3d8 4p configurations of Se VIII, the energy and composition of the levels of the 3d9 4d configuration of Se VII, classified lines in Se VII, energy levels and composition of the 3d8 4s configuration and the revised and newly determined levels of the 3d8 4p configuration of Se VIII, and newly classified lines of Se VIII. 15 references

The Ag2Se-HgSe-GeSe2 system and crystal structures of the compounds

International Nuclear Information System (INIS)

Parasyuk, O.V.; Gulay, L.D.; Romanyuk, Ya.E.; Olekseyuk, I.D.; Piskach, L.V.

2003-01-01

The phase diagram of the quasi-ternary Ag 2 Se-HgSe-GeSe 2 system at 298 K was investigated using X-ray phase analysis and metallography. The formation of five intermediate quaternary phases β (Ag ∼7.12-∼6.32 Hg ∼0.44-∼0.82 GeSe 6 ), γ (Ag ∼6.08-∼4.00 Hg ∼0.96-∼2.00 GeSe 6 ), δ (Ag 3.4 Hg 2.3 GeSe 6 ), ε (Ag ∼2.24-∼2.00 Hg ∼2.88-∼3.00 GeSe 6 ) and ∼Ag 1.4 Hg 1.3 GeSe 6 was established. The crystal structure of the β-phase (for the Ag 6.504 Hg 0.912 GeSe 6 composition) was determined using X-ray single crystal diffraction. It crystallizes in a cubic structure (space group F4-bar 3m) with the lattice parameter a=1.09026(4) nm. The crystal structure of the δ-phase (Ag 3.4 Hg 2.3 GeSe 6 ) was determined using X-ray powder diffraction (space group F4-bar 3m, a=1.07767(8) nm). The crystal structure determination of the γ-phase (space group Pmn2 1 ) was performed for the compositions Ag 5.6 Hg 1.2 GeSe 6 , Ag 4.8 Hg 1.6 GeSe 6 and Ag 4 Hg 2 GeSe 6 using X-ray powder diffraction. The crystal structure of the LT-Hg 2 GeSe 4 compound (space group I4-bar , a=0.56786(2), c=1.12579(5) nm) was confirmed by powder diffraction also.

Phase diagram of Se-CaIn4Se7 system

International Nuclear Information System (INIS)

Musaeva, R.I.; Aliev, I.I; Ismailova, F.I; Aliev, A.A

2011-01-01

Full text: The Se-CaIn 4 Se 7 system has been studied using methods of differential thermal analysis, X-ray diffraction, micro structural analysis, density measurements and its phase diagram has been constructed. It has been established that the section Se-CaIn 4 Se 7 is a quasibinary section of the ternary system Ca-In-Se. At room temperature, on the basis of CaIn 2 Se 4 and Se no solid solution has been found

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.

Semiconductor-metal transition of Se in Ru-Se Catalyst Nanoparticles

Science.gov (United States)

Babu, P. K.; Lewera, Adam; Oldfield, Eric; Wieckowski, Andrzej

2009-03-01

Ru-Se composite nanoparticles are promising catalysts for the oxygen reduction reaction (ORR) in fuel cells. Though the role of Se in enhancing the chemical stability of Ru nanoparticles is well established, the microscopic nature of Ru-Se interaction was not clearly understood. We carried out a combined investigation of ^77Se NMR and XPS on Ru-Se nanoparticles and our results indicate that Se, a semiconductor in elemental form, becomes metallic when interacting with Ru. ^77Se spin-lattice relaxation rates are found to be proportional to T, the well-known Korringa behavior characteristic of metals. The NMR results are supported by the XPS binding energy shifts which suggest that a possible Ru->Se charge transfer could be responsible for the semiconductor->metal transition of Se which also makes Ru less susceptible to oxidation during ORR.

Bio-fortification and isotopic labelling of Se metabolites in onions and carrots following foliar application of Se and 77Se

DEFF Research Database (Denmark)

Kápolna, Emese; Laursen, Kristian H.; Husted, Søren

2012-01-01

Se. The 77Se- labelled metabolites in onions were predominantly γ-glutamyl-77Se-selenomethyl-selenocysteine (γ-glu-Me77SeCys), 77Se-methylselenocysteine (Me77SeCys) and 77Se-selenomethionine (77SeMet). Furthermore, we report here for the first time the finding in carrots of the bioactive Me77SeCys...

El agua y las consecuencias que esta genera en la agricultura y el medio ambiente

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Julio Gabriel

2017-05-01

Full Text Available Según el Organismo Internacional de Energía Atómica (OIEA 2017, la degradación del medio ambiente y la falta de agua limpia plantean retos fundamentales para el desarrollo sostenible. Los avances socioeconómicos no pueden sostenerse si no hay aire limpio para respirar, agua salubre para beber, suelos sanos para la producción agropecuaria y un medio ambiente limpio y estable en el que se sustente el trabajo y la vida. Sobre el particular la OIEA (2017, mencionan que: 1. Más de mil millones de personas en países en desarrollo carecen de acceso al agua potable (WWAP 2006. 2. Las extracciones de agua para riego han aumentado en más del 60% desde 1960 y el 70% aproximadamente de toda el agua dulce disponible se utiliza para riego en la agricultura. Sin embargo, debido a los ineficaces sistemas de riego, particularmente en los países en desarrollo, el 60% de esa agua se pierde al evaporarse o vuelve a los ríos o los acuíferos subterráneos (OMC/UNICEF/WSSCC 2000. 3. Más de 2.2 millones de personas, en su mayoría en países en desarrollo, mueren cada año a causa de enfermedades relacionadas con la baja calidad del agua y las malas condiciones de saneamiento. 4. Un estudio de la OMS indica que cada dólar invertido en mejorar el agua potable y los servicios de saneamiento puede reportar beneficios económicos de entre 4 y 34 dólares dependiendo de la región. 5. Los ecosistemas de agua dulce han sido severamente dañados: se estima que se ha perdido cerca de la mitad de los humedales del planeta, y más del 20% de las 10000 especies conocidas de agua dulce en el mundo se han extinguido o están amenazadas o en peligro (Naciones Unidas, 2003. 6. Las concentraciones atmosféricas mundiales de CO2, CH4 y N2O han aumentado considerablemente como resultado de las actividades del hombre desde 1750 y actualmente superan con creces los valores preindustriales, determinados a partir de muestras de hielo que abarcan muchos miles de años (IPCC

One-step synthesis of PbSe-ZnSe composite thin film

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Abe Seishi

2011-01-01

Full Text Available Abstract This study investigates the preparation of PbSe-ZnSe composite thin films by simultaneous hot-wall deposition (HWD from multiple resources. The XRD result reveals that the solubility limit of Pb in ZnSe is quite narrow, less than 1 mol%, with obvious phase-separation in the composite thin films. A nanoscale elemental mapping of the film containing 5 mol% PbSe indicates that isolated PbSe nanocrystals are dispersed in the ZnSe matrix. The optical absorption edge of the composite thin films shifts toward the low-photon-energy region as the PbSe content increases. The use of a phase-separating PbSe-ZnSe system and HWD techniques enables simple production of the composite package.

Conservación de jugos de caña energética: solución a la cogeneración eléctrica con el bagazo originado en periodos inactivos de cualquier central azucarero.

Directory of Open Access Journals (Sweden)

Amilkar Failde López

2012-04-01

Full Text Available En la evaluación de la viabilidad industrial de conservación de los jugos de caña energética mezclados con melazas de caña azucarera, datos experimentales obtenidos de las principales variables químicas y microbiológicas a escala de banco fueron analizados. Procesados con la prueba no paramétrica de Mann-Whitney, a las variables que registraron diferencias significativas se le construyeron gráficos y se les halló las ecuaciones de las líneas de tendencias y los coeficientes de correlación. Fueron determinados que el número más probable de microorganismos (NMP y el % de acidez, son las de riesgos de contaminación para la conservación a 75% Brix nominal de estos jugos. Se precisó que 80 días es el tiempo de garantía máximo. Son propuestas especificaciones de calidad para los diferentes usos, incorpora microorganismos patógenos cuando se destinan a alimento animal. Este resultado soluciona que cualquier central azucarero en periodos inactivos, pueda moler y cogenerar electricidad con el bagazo de caña energética o destinarlo a la industria del papel y la celulosa entre otras potencialidades, y conservar sus jugos para distintos destinos. Evita que los jugos se conviertan en un residual líquido agresivo al medio ambiente.

Structure and optical properties of GaSe-CdSe composites driven by Cd intercalation in GaSe lamellar crystals

International Nuclear Information System (INIS)

Caraman, Iuliana; Kantser, Valeriu; Evtodiev, Igor; Untila, Dumitru; Dmitroglo, Liliana; Leontie, Liviu; Arzumanyan, Grigory

2015-01-01

A new composite material composed of GaSe and CdSe has been obtained by treatment of GaSe single-crystal lamellas in Cd vapors at temperatures of 773-853 K and intercalation of Cd interlayers. The structure and optical properties of the GaSe-CdSe composite material have been studied. The content of CdSe crystallites was found to grow with increasing treatment temperature or with increasing duration of treatment at a constant temperature. Analysis of XRD, PL, XPS, AFM, and Raman patterns has shown that the heterogeneous composite composed of micro and nanocrystallites of CdSe in GaSe can be obtained by Cd intercalation in a temperature range of 753-853 K. On the basis of Raman spectrum, the vibrational modes of the composite have been identified. The PL of these materials contains emission bands of free and bound excitons, donor-acceptor bands, and bands of recombination via impurity levels. The PL emission spectra measured at a temperature of 78 and 300 K for the composites result from the overlapping of the emission bands of the components of GaSe doped with Cd and the CdSe crystallites. (authors)

Stable and metastable phases in reciprocal systems PbSe + Ag2I2 Ag2Se + PbI2 and PbSe + CdI2 = CdSe + PbI2

International Nuclear Information System (INIS)

Odin, I.N.; Grin'ko, V.V.; Kozlovskij, V.F.; Safronov, E.V.

2005-01-01

Mutual system PbSe + Ag 2 I 2 = Ag 2 Se + PbI 2 is investigated. It is shown that diagonal Ag 2 Se-PbI 2 is stable. Liquidus surface and isothermal section at 633 K of phase diagram of PbSe-Ag 2 Se-PbI 2 system are built. Transformations directing to crystallization metastable ternary compound forming in PbSe-PbI 2 system and metastable polytype modifications of lead iodide in PbSe-Ag 2 Se-PbI 2 system at 620-685 K are studied. By hardening from molten state (1150-1220 K) new interstitial metastable phases crystallizing in CdCl 2 structural type are obtained in PbSe-Ag 2 Se-PbI 2 and PbSe + CdI 2 = CdSe + PbI 2 systems [ru

Synthesis and characterization of ZnSe:Fe/ZnSe core/shell nanocrystals

Energy Technology Data Exchange (ETDEWEB)

Yang, Lin; Zhu, Jianguo, E-mail: yanglin_1028@163.com; Xiao, Dingquan

2014-04-15

High-quality ZnSe:Fe/ZnSe core/shell nanocrystals were prepared via a hydrothermal microemulsion technique. Effective surface passivation of monodisperse ZnSe:Fe nanocrystals is achieved by overcoating them with a ZnSe shell. The samples were characterized by means of XRD, EDX, TEM, PSD, XPS, photoluminescence, and Raman spectrum. The results show that the as-synthesized nanocrystals are cubic zinc blende ZnSe structure with high purity and the average particle size of ZnSe:Fe/ZnSe core/shell nanocrystal is larger than that of ZnSe:Fe core. The growth of ZnSe shell causes a small red shift in PL spectra, and then the PL quantum yield (QY) increases from 16% before shell growth to the maximum of 37% after increasing shell thickness up to 1.2 monolayers (ML). Moreover, both transverse optic (TO) and longitudinal optic (LO) phonon modes of ZnSe are shifted toward lower frequency as compared with the reported ones. -- Highlights: • ZnSe:Fe/ZnSe core/shell QDs were prepared by a hydrothermal microemulsion method. • ZnSe shell efficiently passivates surface defects by serving as a physical barrier. • The particle size and PL properties can be turned with the growth of ZnSe shell. • The luminescence efficiency and stability of QDs could be improved in this manner.

Measurement of 76Se and 78Se (γ, n) cross sections

International Nuclear Information System (INIS)

Kitatani, Fumito; Harada, Hideo; Goko, Shinji; Utsunomiya, Hiroaki; Akimune, Hidetoshi; Toyokawa, Hiroyuki; Yamada, Kawakatsu

2011-01-01

The (γ, n) cross sections of Se isotopes ( 76 Se, 78 Se) were measured to supply fundamental data for estimating the inverse reaction cross section, i.e., the 79 Se(n, γ) 80 Se cross section. The enriched samples and a reference 197 Au sample were irradiated with laser-Compton scattering (LCS) γ-rays. The excitation function of each (γ, n) cross section was determined for the energy range from each near neutron separation energy to the threshold energy of (γ, 2n) reaction. The energy point corresponding to each cross section was deduced using the accurately determined energy distribution of LCS γ-rays. Systematic (γ, n) cross sections for Se isotopes including 80 Se were compared with those calculated by using a statistical model calculation code TALYS. (author)

Thermoelectric prospects of chemically deposited PbSe and SnSe thin films

Science.gov (United States)

Nair, P. K.; Martínez, Ana Karen; Rosa García Angelmo, Ana; Barrios Salgado, Enue; Nair, M. T. S.

2018-03-01

Thin films of PbSe of 400-600 nm in thickness, were obtained via chemical deposition from a solution containing lead nitrate, thiourea and selenosufate. SnSe thin films of 90-180 nm in thickness, were also obtained by chemical deposition from a solution containing selenosulfate. Optical and electrical properties of these thin films were significantly altered by heating them in selenium vapor at 300 °C. Thin film PbSe has a bandgap (Eg) of 1.17 eV (direct gap, forbidden transitions), which decreases to 0.77 eV when it has been heated. Its electrical conductivity (σ) is p-type: 0.18 Ω-1 cm-1 (as-prepared), and 6.4 Ω-1 cm-1 when heated. Thin film SnSe is of orthorhombic crystalline structure which remains stable when heated at 300 °C, but its Eg increases from 1.12 eV (indirect) in as-prepared film to 1.5 eV (direct, forbidden transitions) upon heating. Its electrical conductivity is p-type, which increases from 0.3 Ω-1 cm-1 (as-prepared) to 1 Ω-1 cm-1 when heated (without Se-vapor). When SnSe film is heated at 300 °C in the presence of Se-vapor, they transform to SnSe2, with Eg of 1.5 eV (direct, forbidden) with n-type electrical conductivity, 11 Ω-1 cm-1. The Seebeck coefficient for the PbSe films is: +0.55 mV K-1 (as prepared) and +0.275 mV K-1 (heated); for SnSe films it is: +0.3 mV K-1 (as prepared) and +0.20 mV K-1 (heated); and for SnSe2 film, - 0.35 mV K-1. A five-element PbSe-SnSe2-PbSe-SnSe2-PbSe thermoelectric device demonstrated 50 mV for a temperature difference ΔT = 20 °C (2.5 mV K-1). For SnSe-SnSe2-SnSe-SnSe2-SnSe device, the value is 15 mV for ΔT = 20 °C (0.75 mV K-1). Prospect of these thin films in thermoelectric devices of hybrid materials, in which the coatings may be applied on distinct substrate and geometries is attractive.

High enrichment to low enrichment core's conversion. Grid seismic calculation

International Nuclear Information System (INIS)

Magoia, J.E.; Benito, G.D.

1990-01-01

The grid of a reactor under severe seismic conditions was structurally verified, considering that it must have been maintained without failure. Values obtained from tensions and displacements are under the admissible ones, the existing grid responds to the structural assessment before a severe S2 earthquake (OIEA classification). (Author) [es

Expression and crystallization of SeDsbA, SeDsbL and SeSrgA from Salmonella enterica serovar Typhimurium

International Nuclear Information System (INIS)

Jarrott, R.; Shouldice, S. R.; Gunčar, G.; Totsika, M.; Schembri, M. A.; Heras, B.

2010-01-01

The cloning, purification, crystallization and preliminary crystallographic studies of three DsbA-like proteins present in S. enterica serovar Typhimurium, SeDsbA, SeDsbL and SeSrgA, are reported. Pathogens require protein-folding enzymes to produce functional virulence determinants. These foldases include the Dsb family of proteins, which catalyze oxidative folding in bacteria. Bacterial disulfide catalytic processes have been well characterized in Escherichia coli K-12 and these mechanisms have been extrapolated to other organisms. However, recent research indicates that the K-12 complement of Dsb proteins is not common to all bacteria. Importantly, many pathogenic bacteria have an extended arsenal of Dsb catalysts that is linked to their virulence. To help to elucidate the process of oxidative folding in pathogens containing a wide repertoire of Dsb proteins, Salmonella enterica serovar Typhimurium has been focused on. This Gram-negative bacterium contains three DsbA proteins: SeDsbA, SeDsbL and SeSrgA. Here, the expression, purification, crystallization and preliminary diffraction analysis of these three proteins are reported. SeDsbA, SeDsbL and SeSrgA crystals diffracted to resolution limits of 1.55, 1.57 and 2.6 Å and belonged to space groups P2 1 , P2 1 2 1 2 and C2, respectively

CuInSe2 nano-crystallite reaction kinetics using solid state reaction from Cu2Se and In2Se3 powders

International Nuclear Information System (INIS)

Hsiang, Hsing-I; Lu, Li-Hsin; Chang, Yu-Lun; Ray, Dahtong; Yen, Fu-Su

2011-01-01

Highlights: → CuInSe 2 phase increased gradually accompanied with a decrease in γ-In 2 Se 3 and no intermediate phase during calcination. → CuInSe 2 formation from Cu 2 Se and In 2 Se 3 powders follows a one-dimensional diffusion-controlled reaction with apparent activation energy of about 122.5 kJ/mol. → The solid reaction kinetics may be dominated by the diffusion of In 3+ ions. - Abstract: The reaction mechanism and CuInSe 2 formation kinetics using a solid state reaction from Cu 2 Se and In 2 Se 3 powders synthesized using a heating up process were investigated using X-ray diffractomy (XRD) and transmission electron microscopy (TEM). It was observed that the CuInSe 2 phase increased gradually, accompanied with a decrease in γ-In 2 Se 3 with no intermediate phase as the calcination temperature and soaking time were increased. The reaction kinetics was analyzed using the Avrami and polynomial kinetic model, suggesting that CuInSe 2 formation from Cu 2 Se and In 2 Se 3 powders follows a diffusion-controlled reaction with an apparent activation energy of about 122.5-182.3 kJ/mol. Cu 2 Se and In 2 Se 3 phases react and directly transform into CIS without the occurrence of any intermediate phase and the size of the newly formed CuInSe 2 crystallites was close to that of the Cu 2 Se reactant particle based on the TEM results, which indicated that the solid reaction kinetics may be dominated by the diffusion of In 3+ ions.

Controllable size reduction of CdSe nanowires through the intermediate formation of Se-coated CdSe nanowires using acid and thermal treatment

Energy Technology Data Exchange (ETDEWEB)

Lam, N S [Department of Physics, Chinese University of Hong Kong, Hong Kong (China); Wong, K W [Department of Physics, Chinese University of Hong Kong, Hong Kong (China); Li, Q [Department of Physics, Chinese University of Hong Kong, Hong Kong (China); Zheng, Z [Department of Physics, Chinese University of Hong Kong, Hong Kong (China); Lau, W M [Surface Science Western, University of Western Ontario, London, ON, N6A 5B7 (Canada)

2007-10-17

Thinning of CdSe nanowires (NWs) with controllable size was achieved by a simple acid treatment and subsequent annealing on thick CdSe NWs synthesized from vapour phase growth. During acid treatment, not only the undesired impurities such as native oxides of Cd and Se could be etched, but surface reactions of CdSe NWs were also observed, resulting in the formation of a layer of elemental Se around a thinner CdSe core. As a result, a heterostructure of Se - CdSe nanostructure formed after acid treatment of CdSe NWs. Upon thermal annealing, the Se shell was effectively removed and thinned stoichiometric single-crystalline CdSe NWs could be obtained. It was observed that NWs could be thinned by up to {approx}60% in diameter by acid treatment and subsequent Se thermal desorption. The degree of thinning was controllable by adjusting the duration of acid treatment. The success of the thinning of CdSe NWs by simple acid treatment and the annealing process reported here opens a new processing route for obtaining stoichiometric CdSe NWs with controllable size reduction and improved aspect ratio. This can undoubtedly broadly improve the range of applications of 1D CdSe nanostructures and allow more exploration of their uni-directional properties. A correction was made to the last paragraph of section 3 on 18 September 2007. The corrected electronic version is identical to the print version.

Controllable size reduction of CdSe nanowires through the intermediate formation of Se-coated CdSe nanowires using acid and thermal treatment

International Nuclear Information System (INIS)

Lam, N S; Wong, K W; Li, Q; Zheng, Z; Lau, W M

2007-01-01

Thinning of CdSe nanowires (NWs) with controllable size was achieved by a simple acid treatment and subsequent annealing on thick CdSe NWs synthesized from vapour phase growth. During acid treatment, not only the undesired impurities such as native oxides of Cd and Se could be etched, but surface reactions of CdSe NWs were also observed, resulting in the formation of a layer of elemental Se around a thinner CdSe core. As a result, a heterostructure of Se - CdSe nanostructure formed after acid treatment of CdSe NWs. Upon thermal annealing, the Se shell was effectively removed and thinned stoichiometric single-crystalline CdSe NWs could be obtained. It was observed that NWs could be thinned by up to ∼60% in diameter by acid treatment and subsequent Se thermal desorption. The degree of thinning was controllable by adjusting the duration of acid treatment. The success of the thinning of CdSe NWs by simple acid treatment and the annealing process reported here opens a new processing route for obtaining stoichiometric CdSe NWs with controllable size reduction and improved aspect ratio. This can undoubtedly broadly improve the range of applications of 1D CdSe nanostructures and allow more exploration of their uni-directional properties. A correction was made to the last paragraph of section 3 on 18 September 2007. The corrected electronic version is identical to the print version

Benefits of oxygen in CuInSe{sub 2} and CuGaSe{sub 2} containing Se-rich grain boundaries

Energy Technology Data Exchange (ETDEWEB)

Feng, Chunbao, E-mail: chunbaofeng@126.com [Department of Mathematics and Physics, Chongqing University of Posts and Telecommunications, Chongqing, 400065 (China); Luo, Min; Li, Bolin; Li, Dengfeng [Department of Mathematics and Physics, Chongqing University of Posts and Telecommunications, Chongqing, 400065 (China); Nie, Jinlan [Department of Applied Physics, University of Electronic Science and Technology of China, Chengdu, 610054 (China); Dong, Huining [Department of Mathematics and Physics, Chongqing University of Posts and Telecommunications, Chongqing, 400065 (China)

2014-05-01

Using density functional theory calculation, we show that oxygen (O) exhibits an interesting effect in CuInSe{sub 2} and CuGaSe{sub 2}. The Se atoms with dangling bonds in a Se-rich Σ3 (114) grain boundary (GB) create deep gap states due to strong interaction between Se atoms. However, when such a Se atom is substituted by an O atom, the deep gap states can be shifted into valence band, making the site no longer a harmful non-radiative recombination center. We find that O atoms prefer energetically to substitute these Se atoms and induce significant lattice relaxation due to their smaller atomic size and stronger electronegativity, which effectively reduces the anion–anion interaction. Consequently, the deep gap states are shifted to lower energy regions close or even below the top of the valence band.

Alternative syntheses of [73,75Se]selenoethers exemplified for homocysteine[73,75Se]selenolactone

International Nuclear Information System (INIS)

Ermert, J.; Blum, T.; Hamacher, K.; Coenen, H.H.

2001-01-01

The present work describes two radiosynthetic pathways to prepare homocysteine[ 75 Se]selenolactone 1 starting from n.c.a. [ 75 Se]selenite 2. It was achieved either by alkylation reaction of n.c.a. methyl[ 75 Se]selenide 4 or by hydrolysis of alkylated 1,3-dicyclohexyl[ 75 Se]selenourea 11. N.c.a. methyl[ 75 Se]selenide 4 is available using sulfur as non-isotopic carrier. However, the radiochemical yield of the substitution of 2-tert.-butoxycarbonylamino-4-bromobutyric acid ethylester 5 with n.c.a. methyl-[ 75 Se]selenide is only in the range of 15%-20%. Birch reduction of protected n.c.a. [ 75 Se]selenomethionine 6 formed leads to a RCY of 5%-10% homocysteine[ 75 Se]selenolactone 1. Alternatively, the synthesis of homocysteine[ 75 Se]selenolactone 1 is possible by hydrolysis of the corresponding [ 75 Se]selenouronium salt 11 available by addition of 2-tert.-butoxycarbonylamino-4-bromobutyric acid ethylester 5 to 1,3-dicyclohexyl[ 75 Se]selenourea 10. A method was developed for the synthesis of 1,3-dicyclohexyl[ 75 Se]selenourea 10 by addition of c.a. [ 75 Se]SeH 2 to 1,3-dicyclohexylcarbodiimide, which leads to 20%-30% RCY of c.a. homocysteine[ 75 Se]selenolactone 1. (orig.)

The determination of Se content in Se egg by NAA in MNSR

International Nuclear Information System (INIS)

Wang Ke; Hou Xiaolin

1994-01-01

The selenium contents in the yolk, albumin and shell of the egg which was laid by layer hen fed with various Se concentrations are determined by thermal neutron activation analysis with a nuclear reaction 78 Se(n, γ) 77 Se m on the miniature neutron source reactor (MNSR). The results show that the more the selenium added to the feed, the higher the Se content in the egg and that in the egg constituents, the highest Se content is in the egg yolk and the lowest in the egg albumin

Experiencias formativas, auto-adscripciones y conflictos ambientales en el sudoeste de Misiones (Argentina

Directory of Open Access Journals (Sweden)

Ana Padawer

2015-04-01

Full Text Available En este artículo abordaremos cómo se relacionan las experiencias formativas vinculadas al trabajo rural, las identificaciones y los conflictos ambientales en San Ignacio, Misiones (Argentina. Nos interesa problematizar cómo los aprendizajes ligados a las tareas rurales se vinculan con las auto-adscripciones de los sujetos, teniendo como referencia las categorías de actores sociales agrarios regionales y las denominaciones que provienen de agendas estatales de intervención. Estos procesos acontecen en un contexto de creciente concentración de propiedades que se destinan a la explotación forestal, donde observamos, en algunos casos, cierta ambientalización de los históricos conflictos territoriales.Utilizando materiales provenientes de un trabajo de campo etnográfico que iniciamos en 2008, presentaremos a dos familias de pobladores rurales. En ambos casos es posible ver cómo el acceso a la tierra es decisivo para las experiencias formativas en las actividades de reproducción social, y que se liga con identificaciones como “gente de la colonia” y una incipiente referencia a la “agricultura familiar” a partir de las intervenciones del Estado. Estas dos familias permiten mostrar cómo las experiencias e identificaciones se expresan en el contexto de la participación de los sujetos en conflictos sociales, que asumen en un caso la forma histórica de reclamos fundiarios mientras que, en el otro, es posible ver que el ambiente tiene protagonismo incipiente.

Luminescence spectra of CdSe/ZnSe double layers of quantum dots

Energy Technology Data Exchange (ETDEWEB)

Reznitsky, Alexander; Permogorov, Sergei; Korenev, Vladimir V.; Sedova, Irina; Sorokin, Sergey; Sitnikova, Alla; Ivanov, Sergei [A.F. Ioffe Physico-Technical Institute, Polytekhnicheskaya 26, 194021 St. Petersburg (Russian Federation); Klochikhin, Albert [B.P. Konstantinov Nuclear Physics Institute, St. Petersburg (Russian Federation)

2009-12-15

We have studied the emission spectra and structural properties of double CdSe/ZnSe quantum dot (QD) sheet structures grown by molecular beam epitaxy in order to elucidate the mechanisms of the electronic and strain field interaction between the QD planes. The thickness of the ZnSe barrier separating the CdSe sheets was in the range of 10-60 monolayers (ML) in the set of samples studied. We have found that coupling between dots in adjacent layers becomes relatively strong in CdSe/ZnSe double layers structures with 25-27 ML barrier, while it is rather weak when the barrier thickness exceeds 30 ML. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Hopping conduction in gamma-irradiated InSe and InSe:Sn single crystals

International Nuclear Information System (INIS)

MUSTAFAEVA, S.N.; ISMAILOV, A.A.; ASADOV, M.M.

2010-01-01

Full text : The semiconductive InSe layer compound is characterized by a strong covalent bond inside the layers and a weak Van der Waals bonding between them. It was shown that across the layers of InSe single crystals at low temperatures (T ≤ 200 K) at direct current (dc) hopping conduction through localized states near the Fermi level takes place. The results of dc-conductivity of gamma-irradiated p-InSe and n-InSe : Sn layer single crystals have been presented in this work. ρ-InSe single crystal specimens grown by the Bridgman method were used in the experiments. Plates of the crystals under study were obtained by cleaving along the layers of single crystal ingots. The single-crystal InSe samples for electric measurements had the form of planar capacitors normal to the C axis of the crystals, with silver-paste electrodes. The thickness of the InSe samples was 300 mkm. Co 60 serves as the source of irradiation with energy of gamma-quantum equal to 1.3 MeV. The electric properties of non-irradiated and gamma-irradiated InSe crystals were measured under the same conditions. It is revealed that InSe and InSe : Sn (0.2 and 0.4 mole percent Sn) single crystals exhibit a variable range hopping conduction along a normal to their natural layers at temperatures T≤200 K in a dc electric field. From experimental data the parameters of localized states of p-InSe and n-InSe : Sn were calculated before and after gamma-irradiation. It is revealed that gamma-irradiation of p-InSe and n-InSe : Sn (0.2 and 0.4 mole percent Sn) single crystals leads to significant change of localized states parameters. After gamma-irradiation the density of states near the Fermi level increased, but their energy spread and the average jump distance decreased. The concentrations of radiated defects were estimated in p-InSe (5.18*10 1 7 sm - 3) and n-InSe : Sn (2.5*10 1 7 - 2.7*10 1 8 sm - 3) single crystals. The present results demonstrate that gamma-irradiation offers the possibility of tuning

Structure of Se-rich As-Se glasses by high-resolution x-ray photoelectron spectroscopy

International Nuclear Information System (INIS)

Golovchak, R.; Kovalskiy, A.; Miller, A. C.; Jain, H.; Shpotyuk, O.

2007-01-01

To establish the validity of various proposed structural models, we have investigated the structure of the binary As x Se 100-x chalcogenide glass family (x≤40) by high-resolution x-ray photoelectron spectroscopy. From the composition dependence of the valence band, the contributions to the density of states from the 4p lone pair electrons of Se and the 4p bonding states and 4s electrons of Se and As are identified in the top part of the band. The analysis of Se 3d and As 3d core-level spectra supports the so-called chain crossing model for the atomic structure of Se-rich As x Se 100-x bulk glasses. The results also indicate small deviations (∼3-8%) from this model, especially for glass compositions with short Se chains (25 40 Se 60 and of Se-Se-Se fragments in a glass with composition x=30 is established

Phase diagram of SnTe-CdSe cross-section of SnTe+CdSe reversible SnSe+CdTe ternary reciprocal system

International Nuclear Information System (INIS)

Dubrovin, I.V.; Budennaya, L.D.; Mizetskaya, I.B.; Sharkina, Eh.V.

1986-01-01

Phase equilibrium diagram of SnTe-CdSe cross-section of Sn, Cd long Te, Se ternary reciprocal system is investigated using the methods of differential thermal, X-ray phase, and microstructural analyses. Maximum length of solid solutions on the base of SnTe corresponds to approximately 14 mol.% at 1050 K and approximately 3 mol.% of CdSe at 670 K. Region of solid solutions on the base of CdSe corresponds to less than 1 mol.% of SnTe at room temperature. SnTe-CdSe cross-section is not a quasibinar one. Equilibrium is shifted to the left in the SnTe+CdSe reversible SnSe+CdTe reciprocal system

Meteorological monitoring Program in the location to the Juragua Nuclear Power Plant

International Nuclear Information System (INIS)

Linares Gonzalez, M.E.; Ramos Biltres, E.O.; Prendes Alonso, M.

1998-01-01

The objective gives the work it is to present the meteorological Monitoring program in the Juragua nuclear power plant, which you makes according to the standards settled down by the OIEA, the standards give the World meteorological organization and the demands to the content and elaboration gives the Nuclear Power Plant security documents DTN-1.03.91

La lectura en el aula. Qué se hace, qué se debe hacer y qué se puede hacer

OpenAIRE

Pablo Lorente Muñoz

2011-01-01

Emilio Sánchez Miguel (Coord.). La lectura en el aula. Qué se hace, qué se debe hacer y qué se puede hacer. Graó, col. Crítica y Fundamentos, 27. Barcelona, 2010. 382 págs. ISBN: 978-84-7827-892-3

SE-VYZ

International Nuclear Information System (INIS)

Anon

2004-01-01

On this CD compact disc 6 video-films (A-1 NPP; Bituminization; Cementation; Pressing; The Interim spent fuel storage facility; Transport into the National radioactive waste repository Mochovce; Ignition; and Vitrification). In these films process of radioactive waste treatment in the Bohunice Radioactive Waste Processing Center (SE-VYZ) is presented. 2 presentations about radioactive wastes treatment in the SE-VYZ are included

Speciation of Se and DOC in soil solution and their relation to Se bioavailability.

Science.gov (United States)

Weng, Liping; Vega, Flora Alonso; Supriatin, Supriatin; Bussink, Wim; Van Riemsdijk, Willem H

2011-01-01

A 0.01 M CaCl(2) extraction is often used to asses the bioavailability of plant nutrients in soils. However, almost no correlation was found between selenium (Se) in the soil extraction and Se content in grass. The recently developed anion Donnan membrane technique was used to analyze chemical speciation of Se in the 0.01 M CaCl(2) extractions of grassland soils and fractionation of DOC (dissolved organic carbon). The results show that most of Se (67-86%) in the extractions (15 samples) are colloidal-sized Se. Only 13-34% of extractable Se are selenate, selenite and small organic Se (<1 nm). Colloidal Se is, most likely, Se bound to or incorporated in colloidal-sized organic matter. The dominant form of small Se compounds (selenate, selenite/small organic compounds) depends on soil. A total of 47-85% of DOC is colloidal-sized and 15-53% are small organic molecules (<1 nm). In combination with soluble S (sulfur) and/or P (phosphor), concentration of small DOC can explain most of the variability of Se content in grass. The results indicate that mineralization of organic Se is the most important factor that controls Se availability in soils. Competition with sulfate and phosphate needs to be taken into account. Further research is needed to verify if concentration of small DOC is a good indicator of mineralization of soil organic matter.

One-pot synthesis of hollow NiSe-CoSe nanoparticles with improved performance for hybrid supercapacitors

Science.gov (United States)

Chen, Haichao; Fan, Meiqiang; Li, Chao; Tian, Guanglei; Lv, Chunju; Chen, Da; Shu, Kangying; Jiang, Jianjun

2016-10-01

Hollow NiSe-CoSe samples have been synthesized for the first time via a one-pot solvothermal approach. The strategy is robust enough to synthesize NiSe-CoSe nanoparticles with different NiSe to CoSe ratios but with a similar hollow structure. Co ions in the NiSe-CoSe nanoparticles play decisive role for formation of the hollow structure; otherwise, the nanoparticles become solid for the NiSe sample. When used as the positive electroactive materials for energy storage, the NiSe-CoSe samples show excellent electrochemical activity in alkaline electrolyte. Using the synergistic effect between NiSe and CoSe, the electrochemical performance of NiSe-CoSe can be tuned by varying the NiSe to CoSe ratios. The NiSe-CoSe sample with a NiSe to CoSe ratio of 4:2 shows the best electrochemical performance in terms of superior specific capacity, improved rate capability and excellent cycling stability. In addition, the electrochemical performance of NiSe-CoSe sample with a NiSe to CoSe ratio of 4:2 is also evaluated via assembling hybrid supercapacitors with RGO, and the hybrid supercapacitor delivers both high power and energy densities (41.8 Wh kg-1 at 750 W kg-1 and 20.3 Wh kg-1 at 30 kW kg-1).

Excitons, biexcitons, and phonons in ultrathin CdSe/ZnSe quantum structures

DEFF Research Database (Denmark)

Gindele, F.; Woggon, Ulrike; Langbein, Wolfgang Werner

1999-01-01

The optical properties of CdSe nanostructures grown by migration-enhanced epitaxy of CdSe on ZnSe are studied by time-, energy-, and temperature-dependent photoluminescence and excitation spectroscopy, as well as by polarization-dependent four-wave mixing and two-photon absorption experiments...

Política Agrícola y Migración Campesina: El Caso del Municipio de San Juan Atenco, Puebla, México

Directory of Open Access Journals (Sweden)

Sasha Castillo Ordóñez

2008-12-01

Full Text Available A partir de la aplicación del modelo Neoliberal en México se han reducido los apoyos del estado a los agricultores minifundistas productores de granos. Esta política repercutió en el decremento de los rendimientos de maíz e ingresos económicos de los agricultores. Ante esta situación se ha acentuado la migración de la población del municipio de San Juan Atenco, Puebla hacia a los Estados Unidos, principalmente a Los Ángeles, California. Trabajan fundamentalmente en la jardinería, albañilería, en promedio ganan $6.18 (dólares la hora y la mayoría no tienen prestaciones laborales. Los entrevistados perciben que su situación económica ha mejorado a partir de que tienen a un familiar trabajando en los Estados Unidos, ya que reciben anualmente en promedio $1,277.76, que destinan a los gastos del hogar fundamentalmente y una parte es invertida en la agricultura, para la compra de fertilizantes, pago de labores, compra de tierras. La migración representa una alternativa de los campesinos para hacer frente a los problemas económicos en el campo y lograr mantener la producción familiar.

Improved photoluminescence quantum yield and stability of CdSe-TOP, CdSe-ODA-TOPO, CdSe/CdS and CdSe/EP nanocomposites

Science.gov (United States)

Wei, Shutian; Zhu, Zhilin; Wang, Zhixiao; Wei, Gugangfen; Wang, Pingjian; Li, Hai; Hua, Zhen; Lin, Zhonghai

2016-07-01

Size-controllable monodisperse CdSe nanocrystals with different organic capping were prepared based on the hot-injection method. The effective separation of nucleation and growth was achieved by rapidly mixing two highly reactive precursors. As a contrast, we prepared CdSe/CdS nanocrystals (NCs) successfully based on the selective ion layer adsorption and reaction (SILAR) technique. This inorganic capping obtained higher photoluminescence quantum yield (PLQY) of 59.3% compared with organic capping of 40.8%. Furthermore, the CdSe-epoxy resin (EP) composites were prepared by adopting a flexible ex situ method, and showed excellent stability in the ambient environment for one year. So the composites with both high PLQY of nanocrystals and excellent stability are very promising to device application.

Thermoelectric transport of Se-rich Ag2Se in normal phases and phase transitions

International Nuclear Information System (INIS)

Mi, Wenlong; Lv, Yanhong; Qiu, Pengfei; Shi, Xun; Chen, Lidong; Zhang, Tiansong

2014-01-01

Small amount of Se atoms are used to tune the carrier concentrations (n H ) and electrical transport in Ag 2 Se. Significant enhancements in power factor and thermoelectric figure of merit (zT) are observed in the compositions of Ag 2 Se 1.06 and Ag 2 Se 1.08 . The excessive Se atoms do not change the intrinsically electron-conducting character in Ag 2 Se. The detailed analysis reveals the experiment optimum carrier concentration in Ag 2 Se is around 5 × 10 18  cm −3 . We also investigate the temperature of maximum zT and the thermoelectric transport during the first order phase transitions using the recently developed measurement system

USO DE HIDROQUÍMICA E ISÓTOPOS AMBIENTALES PARA LA EVALUACIÓN DE LA CONEXIÓN HIDROLÓGICA ENTRE EL AGUA SUBTERRÁNEA Y EL HUMEDAL CIÉNAGA COLOMBIA. (UN PRIMER ACERCAMIENTO

Directory of Open Access Journals (Sweden)

SANTA ARANGO DIANA PATRICIA

2010-05-01

Full Text Available El entendimiento de las condiciones de flujo de agua desde y hacia un humedal se basa, en principio, en la interpretación de información hidrológica, pero además la incorporación de técnicas no convencionales como lo son la hidroquímica y la hidrología isotópica y permite un mayor nivel de comprensión de los sistemas hidrológicos, en la medida en que es posible identificar el origen, la evolución del agua y los tiempos de tránsito y residencia en los diferentes compartimientos del ciclo hidrológico. El sistema hidrológico Ciénaga Colombia representa un ecosistema estratégico en el Bajo Cauca antioqueño y en pro de su sostenibilidad, se requiere un mejor conocimiento de él. Se presentan aquí los primeros resultados del proyecto “Hydrochemical and Isotopic techniques for the assessment of hydrological processes in the wetlands of Bajo Cauca Antioqueño” que la Universidad de Antioquia adelanta en convenio con el Organismo Internacional de Energía Atómica, OIEA, inspirados en la idea de usar técnicas isotópicas para evaluar procesos hidrológicos en humedales.

Contenha-se, se for capaz

Directory of Open Access Journals (Sweden)

Mirna Feitoza Pereira

2008-11-01

Full Text Available Em O Instinto da Linguagem, Steven Pinker discorre sobre sua célebre tese: a linguagem não é a mais prodigiosa invenção cultural humana. Ela é uma peça da constituição biológica do cérebro. A linguagem é uma habilidade complexa e especializada, que se desenvolve espontaneamente na criança, sem qualquer esforço consciente ou instrução formal, que se manifesta sem que se perceba sua lógica subjacente, que é qualitativamente a mesma em todo indiví­duo, e que difere de capacidades mais gerais de processamento de informações ou de comportamento inteligente. Para Pinker, a concepção de linguagem como um tipo de instinto transmite a idéia de que as pessoas sabem falar mais ou menos da mesma maneira que as aranhas sabem tecer suas teias. Ele apóia suas idéias em Darwin e Chomsky. Palavras-chave linguagem, gramática universal, evolução Abstract In Language Instinct, Steven Pinker argues about his famous thesis: language is not the most prodigious human cultural invention. It is a distinct piece of the biological constitution of the brain. Language is a complex, specialized skill, which develops spontaneously in the child, without conscious effort or formal instruction. It reveals itself without awareness of its underlying logic, which is qualitatively the same in every individual, and which is distinct from more general abilities of information processing of intelligent behavior. According to Pinker, the conception of language as a kind of instinct conveys the idea that people know how to talk in more or less the same way as spiders know how to spin webs. His thesis is founded in Darwin and Chomsky-s theories. Keywords language, universal grammar, evolution

EPR of SeO2- and SeO3- radicals in alkaline borate glasses with 77Se isotope

International Nuclear Information System (INIS)

Galimov, D.G.; Tarzimanov, K.D.

1977-01-01

Alkaline borate glasses with 77 Se were investigated in order to establish the nature of selenium compounds and radicals in glasses. The relationship between alkali ions and the oxygen radical of selenium was determined by decoding the hyperfine structure of the alkaline borate glass EPR spectra obtained before and after γ-irradiation. The irradiated and non-irradiated glasses were characterized by hyperfine splitting of the EPR lines from the α- and β centres. Moreover, the irradiated samples were noted to have a line doublet (signal phi). With intenser reduction conditions of glass fusion, the intensities of α, β, and phi signals were noted to decline. This confirmes the suggestion that these centres were caused by oxygen compouds. The authors concluded that α and β signals were due to the paramagnetic centres of SeO 2 - and [SeO 2 - ]R + , and phi signal to the SeO 3 - radicals

Se-Se isoelectronic centers in high purity CdTe

Energy Technology Data Exchange (ETDEWEB)

Najjar, Rita; Andre, Regis; Mariette, Henri [CEA-CNRS, Nanophysique et Semiconducteurs, Institut Neel, 25 rue des martyrs, 38042 Grenoble (France); Golnik, Andrzej; Kossacki, Piotr; Gaj, Jan A. [Institute of Experimental Physics, University of Warsaw, Hoza 69, 00-681 Warsaw (Poland)

2010-06-15

We evidence zero-dimensional exciton states trapped on isoelectronic Se centers in CdTe quantum wells, {delta}-doped with Se. Thanks to special precautions taken to have very high purity CdTe heterostructures, it is possible to observe, in photoluminescence spectra, sharp discrete lines arising from individual centers related to the Se doping. These emission lines appear at about 40 meV below the CdTe band gap energy. The most prominent lines are attributed to the recombination of excitons bound to nearest-neighbor selenium pairs in a tetrahedral CdTe environment. This assignment is confirmed by a common linear polarization direction of the emitted light, parallel to <110>. These excitons localized on individual isoelectronic traps are good candidates as single photon emitters (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Sample Set (SE): SE30 [Metabolonote[Archive

Lifescience Database Archive (English)

Full Text Available SE30 Comparison of seed metabolites among soybean varieties Investigation of Glycine max. green seed metabol...ites. 3 varieties (Kamogawashichiri, Koitozairai, Tanbakuro) data are examined. Tak

Sample Set (SE): SE13 [Metabolonote[Archive

Lifescience Database Archive (English)

Full Text Available SE13 Comparison of leaf metabolites among spinach varieties Investigation of Spinacia oleracea leaf metaboli...tes. 4 cultivers (Nihon, Kanaji, Kurohaminstarland and Wasesaradaakari) and 3 repli

Influence of CdSe layer air-baking on physical properties of CdSe-As2Se3 heterostructures

International Nuclear Information System (INIS)

Schauer, F.; Heza, S.; Kosek, F.; Cimpl, Z.

1980-01-01

An investigation is made of the influence of the air-baking time on the physical properties of a CdSe layer, which is a part of the heterogeneous structure CdSe-As 2 Se 3 used as a camera tube target. The I-U characteristics, C-U characteristics, the dependence of both the real and imaginary part admittance on frequency, and the photoconductance characteristics are measured. All measurements are carried out on heterostructures prepared with variable air-baking time of the CdSe layer: t =0, 5, 15, 40, and 120 min. The results of measurements contribute to the finding of the optimal production procedure with a minimum baking time of tsub(min) = 15 min. The heterostructures exhibit satisfactory properties. The dark current Isub(d)(U =1 V, T = 300 K) = 10 -10 Acm -2 with a rectification factor g(U = 10 V) = 10 6 and a capacitance C (2 kHz) = 2900 pFcm -2 . (author)

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

SE PREVENINDO?

Directory of Open Access Journals (Sweden)

Ana Débora Assis Moura

2010-01-01

Full Text Available Este estudio tuvo como objetivo verificar el comportamiento de las prostitutas en relación a la prevención de enfermedades de transmisión sexual y del Síndrome de Inmunodeficiencia Adquirida-SIDA, así como investigar cómo se previenen de esas enfermedades. Se trata de una investigación exploratoria, con enfoque cualitativo, llevada a cabo en la Asociación de las Prostitutas en Ceará, Brazil, en septiembre de 2008, a través de una encuesta con 25 prostitutas. El análisis de los datos se hizo según el análisis de contenido, después de ser agrupados en cuatro categorías: conocimiento sobre las enfermedades de transmisión sexual/SIDA; convivencia con la(s enfermedad(es; prevención de la enfermedad de transmisión sexual/SIDA; y el uso de drogas. Se concluyó que las prostitutas no usan preservativos en todas las relaciones sexuales, por lo tanto, las enfermedades de transmisión sexual representan una realidad; la desinformación sobre la(s enfermedad(es es notable; el consumo de drogas lícitas e ilícitas es frecuente entre ellas, factor que las expone a situaciones más vulnerables con relación al VIH/SIDA.

Canaryseed Crop

Directory of Open Access Journals (Sweden)

Maximiliano Cogliatti

2012-01-01

Full Text Available El alpiste (Phalaris canariensis L. es una gramínea con un ciclo de cultivo y prácticas de producción similares a las de otros cereales invernales, tales como el trigo (Triticum aestivum L. y la avena (Avena sativa L.. Actualmente, sus granos se destinan, casi con exclusividad, a la alimentación de aves, solos o en mezcla con otros como mijo, girasol y lino. El alpiste es un cereal genuino con una composición única que sugiere un potencial para uso alimentario. P. canariensis se cultiva en muchas zonas de climas templados. En la actualidad, su producción se concentra en las provincias del suroeste de Canadá (Alberta, Saskatchewan y Manitoba y en menor escala en Argentina, Tailandia y Australia. A nivel mundial es considerado como un cultivo menor, con pertinencia regional, con una producción de alrededor de 250 mil toneladas al año, lo que restringe la inversión privada y la investigación pública en su mejoramiento genético y tecnológico. Por esta razón, el tipo de manejo del cultivo que se aplica a esta especie depende en gran medida a las innovaciones hechas en otros cultivos similares. Este trabajo ofrece una revisión actualizad a de la información disponible sobre esta especie, sus necesidades, distribución, recursos genéticos, prácticas de cultivo, usos potenciales, comercialización y otros temas de interés para los investigadores y productores.

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)

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.

Sample Set (SE): SE53 [Metabolonote[Archive

Lifescience Database Archive (English)

Full Text Available SE53 Covering chemical diversity of genetically-modified tomatoes using metabolomics...signature. We conclude that multi-platform metabolomics is an approach that is both sensitive and robust and

Sample Set (SE): SE10 [Metabolonote[Archive

Lifescience Database Archive (English)

Full Text Available SE10 Effect of phosphorus nutrition for cabbage metabolites Investigation of Brassi...ca oleracea var. capitata Hatukoi leaf metabolites. 3 growth conditions (high, low and no phosphorus nutrition

Sample Set (SE): SE31 [Metabolonote[Archive

Lifescience Database Archive (English)

Full Text Available SE31 Comparison of seed metabolites among eggplant fruit tissues Investigation of S...olanum melongena Senryounigou metabolites. 3 tissues (flesh, fruit, peel) data are examined. Takeshi Ara 1,

Sample Set (SE): SE28 [Metabolonote[Archive

Lifescience Database Archive (English)

Full Text Available SE28 Comparison of leaf metabolites among developmental stages of Hevea brasiliensi...s Investigation of Hevea brasiliensis leaf metabolites. 4 developmental stages and 6 replicates data are exa

Superconductivity in the ferecrystals (PbSe){sub 1.14}(NbSe{sub 2}){sub n}

Energy Technology Data Exchange (ETDEWEB)

Grosse, Corinna; Chiatti, Olivio; Fischer, Saskia F. [Novel Materials Group, Humboldt-Universitaet Berlin (Germany); Alemayehu, Matti B.; Falmbigl, Matthias; Johnson, David C. [Department of Chemistry, University of Oregon, Eugene, OR (United States)

2016-07-01

The ferecrystals (PbSe){sub 1.14}(NbSe{sub 2}){sub n} are artificially layered materials consisting of n NbSe{sub 2} single-layers stacked alternately with atomic double layers of PbSe. NbSe{sub 2} is a transition metal dichalcogenide with interesting electrical properties such as superconductivity and charge density waves. The influence of turbostratic disorder, a random rotation between the NbSe{sub 2} and PbSe layers, on the superconducting transition temperature has been unknown so far. We investigate the structural and temperature-dependent electrical properties of the ferecrystals (PbSe){sub 1.14}(NbSe{sub 2}){sub n} by means of scanning transmission electron microscopy, X-ray diffraction, in-plane resistivity and Hall measurements and compare them to those of analogous non-disordered misfit layer compound (MLC) polymorphs. We observe a superconducting transition in the resistivity of the ferecrystals. The transition temperatures are reduced by up to 55 % with respect to the analogous MLC polymorphs. This indicates that turbostratic disorder substantially weakens the electron-phonon coupling in (PbSe){sub 1.14}(NbSe{sub 2}){sub n}. We discuss the results of the structural and electrical properties of the ferecrystals with respect to their MLC analogues and also with respect to ultra-thin NbSe{sub 2} layers.

Synthesis and optical study of green light emitting polymer coated CdSe/ZnSe core/shell nanocrystals

Energy Technology Data Exchange (ETDEWEB)

Tripathi, S.K., E-mail: surya@pu.ac.in [Department of Physics, Center of Advanced Study in Physics, Panjab University, Chandigarh 160 014 (India); Sharma, Mamta [Department of Physics, Center of Advanced Study in Physics, Panjab University, Chandigarh 160 014 (India)

2013-05-15

Highlights: ► Synthesis of Polymer coated core CdSe and CdSe/ZnSe core/shell NCs. ► From TEM image, the spherical nature of CdSe and CdSe/ZnSe is obtained. ► Exhibiting green band photoemission peak at 541 nm and 549 nm for CdSe core and CdSe/ZnSe core/shell NCs. ► The shell thickness has been calculated by using superposition of quantum confinement energy model. - Abstract: CdSe/ZnSe Core/Shell NCs dispersed in PVA are synthesized by chemical method at room temperature. This is characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), UV/Vis spectra and photoluminescence spectroscopy (PL). TEM image shows the spherical nature of CdSe/ZnSe core/shell NCs. The red shift of absorption and emission peak of CdSe/ZnSe core/shell NCs as compared to CdSe core confirmed the formation of core/shell. The superposition of quantum confinement energy model is used for calculation of thickness of ZnSe shell.

Sample Set (SE): SE20 [Metabolonote[Archive

Lifescience Database Archive (English)

Full Text Available SE20 Arabidopsis thaliana leaf metabolite analysis for a software test Investigatio...es that were investigated to optimize the parameters of PowerGet software for better metabolite annotation i

Sample Set (SE): SE18 [Metabolonote[Archive

Lifescience Database Archive (English)

Full Text Available in by Orbitrap MS and automated search engine Lipid Search A comprehensive and precise identification of pho...SE18 Global identification of phospholipid molecular species in mouse liver and bra

Electrochemical synthesis of nanostructured Se-doped SnS: Effect of Se-dopant on surface characterizations

International Nuclear Information System (INIS)

Kafashan, Hosein; Azizieh, Mahdi; Balak, Zohre

2017-01-01

Highlights: • Nanostructured SnS_1_-_xSe_x thin films were prepared by using electrodeposition method. • The XRD patterns obviously showed that the synthesized films were polycrystalline. • The PL spectra of SnS_1_-_xSe_x thin films showed four emission peaks. • The UV–vis spectra shows a variation in the optical band gap energy of SnS_1_-_xSe_x thin films from 1.22 to 1.65 eV. • SnS_1_-_xSe_x thin films would be suitable for use as absorber layers. - Abstract: SnS_1_-_xSe_x nanostructures with different Se-dopant concentrations were deposited on fluorine doped tin oxide (FTO) substrate through cathodic electrodeposition technique. The pH, temperature, applied potential (E), and deposition time remained were 2.1, 60 °C, −1 V, and 30 min, respectively. SnS_1_-_xSe_x nanostructures were characterized using X-ray diffraction (XRD), field emission scanning electron microcopy (FESEM), energy dispersive X-ray spectroscopy (EDX), room temperature photoluminescence (PL), and UV–vis spectroscopy. The XRD patterns revealed that the SnS_1_-_xSe_x nanostructures were polycrystalline with orthorhombic structure. FESEM showed various kinds of morphologies in SnS_1_-_xSe_x nanostructures due to Se-doping. PL and UV–vis spectroscopy were used to evaluate the optical properties of SnS_1_-_xSe_x thin films. The PL spectra of SnS_1_-_xSe_x nanostructures displayed four emission peaks, those are a blue, a green, an orange, and a red emission. UV–vis spectra showed that the optical band gap energy (E_g) of SnS_1_-_xSe_x nanostructures varied between 1.22–1.65 eV, due to Se-doping.

Complejo industrial en Ballymena, Irlanda del Norte

Directory of Open Access Journals (Sweden)

Gibb, Alexander

1966-06-01

Full Text Available These two industrial buildings serve for the manufacture of cigarettes. The main nave is 274 m long and 32 m wide. There are additional secondary buildings, which house the services and offices. This type of industry requires a close control of temperature and humidity, and it is necessary that these factors remain very constant during the process of manufacture. The naves have been covered with shed type sheeting. These sheets are prefabricated and rest on hollow arches, which are manufactured in sections, and are then prestressed and suitably spaced. The inner hollow part of these arches, and the columns on which they rest, also serve to carry the air conditioning conduits, and lighting cables. The large number of skylights ensures a good daylight illumination.Estas dos naves industriales se destinan a la fabricación de cigarrillos. La principal tiene 374 m de longitud y 32 m de anchura, completando el conjunto una serie de edificios para servicios y administración. Este tipo de industrias requiere que se preste especial atención a la temperatura y humedad del ambiente interior, lo cual exige asegurar la continuidad del estado previsto durante la fabricación. Las naves se han cubierto con una serie de láminas tipo shed, prefabricadas, que se apoyan en arcos huecos, prefabricados por trozos, pretensados y convenientemente espaciados. La parte hueca interior de estos arcos y de los montantes que los soportan se han aprovechado para colocar en ellos los conductos de aire acondicionado y otras canalizaciones para el alumbrado artificial. La gran profusión de lucernarios asegura una buena iluminación natural diurna.

Sample Set (SE): SE14 [Metabolonote[Archive

Lifescience Database Archive (English)

Full Text Available SE14 Effect of agricultural films for tomato fruit metabolites Investigation of Sol...anum lycopersicum fruit metabolites. 3 growth conditions (covered with normal or UV cut agricultural film or no agricultura

Properties of the CuGaSe2 and CuInSe2 (001) surface

International Nuclear Information System (INIS)

Deniozou, T.

2005-01-01

The main task of this work was to investigate the (001) CuGaSe 2 and CuInSe 2 surface in dependence of preparation and stoichiometry. The knowledge of the atomic structure as well as other surface properties is important in respect to optimization of novel thin film solar cells. For the characterization of the layers mainly Auger electron Spectroscopy, low-energy electron diffraction and photoelectron spectroscopy were implemented. The development of an appropriate procedure with Ar + sputtering and annealing combined with decapping enabled the preparation of clean and well-ordered surfaces. Different surface structures were observed in dependence of the layer preparation and composition. A (4 x 1) reconstruction was observed for the first time on CuGaSe 2 layers grown with a moderate Cu-excess after preparation by sputtering and annealing. Similarly a (4 x 2) reconstruction was detected on CuInSe2 surfaces of Cu-poor layers. A reconstruction could be also observed on Cu-poorer layers, however the facets/steps could not be completely removed. Cu-richer layers were facet-free, however the observed reconstruction was also weaker. Thus it was shown that in contrary to recent expectations, according to which only the (112) surface is stable, also the (001) can be stable under particular conditions. The appearance of facets or steps is correlated with the presence of CuIn 3 Se 5 or CuGa 3 Se 5 phases. This information is furthermore important for the understanding of grain boundaries in polycrystalline CuGaSe 2 and CuInSe 2 . Binding energy shifts were observed for the first time on all Se3d, In4d, Ga3d, Cu3d core levels of the reconstructed surfaces. By comparison with results from the literature from the similar ZnSe (100) surface a modell for the (4 x 2) reconstruction was proposed. The surface components in the Se3d, In4d and Cu3d emission were attributed to Se dimers or In and Cu adatoms respectively. The x 1 periodicity of the (4 x 1) reconstruction of CuGaSe 2 is

Sample Set (SE): SE16 [Metabolonote[Archive

Lifescience Database Archive (English)

Full Text Available SE16 Effect of agricultural films for spinach leaf metabolites 2 Investigation of S...pinacia oleracea leaf metabolites. 3 growth conditions (covered with normal or UV cut agricultural film or no agricultura

Sample Set (SE): SE26 [Metabolonote[Archive

Lifescience Database Archive (English)

Full Text Available SE26 Effect of compost for cabbage metabolites Investigation of Brassica oleracea v...ar. capitata YR Seisyun leaf metabolites. 2 growth conditions (with or without 6t compost treatment) and 3 r

Stable and metastable equilibria in PbSe + SnI2=SnSe + PbI2

International Nuclear Information System (INIS)

Odin, I.N.; Grin'ko, V.V.; Kozlovskij, V.F.; Demidova, E.D.

2003-01-01

T-x-y phase diagrams of the PbSe + SnI 2 =SnSe + PbI 2 mutual system (stable states) are plotted for the first time. It is shown that melt, solid solutions on the base of components of the mutual system and phase on the base of Sn 2 SeI 4 take part in phase equilibria. Transformations in the PbSe + SnI 2 =SnSe + PbI 2 mutual system leading to crystallization of metastable polytype modifications of lead iodides and metastable ternary compound forming in PbSe-PbI 2 system are investigated for the first time [ru

Copper Selenidophosphates Cu4P2Se6, Cu4P3Se4, Cu4P4Se3, and CuP2Se, Featuring Zero-, One-, and Two-Dimensional Anions.

Science.gov (United States)

Kuhn, Alexander; Schoop, Leslie M; Eger, Roland; Moudrakovski, Igor; Schwarzmüller, Stefan; Duppel, Viola; Kremer, Reinhard K; Oeckler, Oliver; Lotsch, Bettina V

2016-08-15

Five new compounds in the Cu/P/Se phase diagram have been synthesized, and their crystal structures have been determined. The crystal structures of these compounds comprise four previously unreported zero-, one-, and two-dimensional selenidophosphate anions containing low-valent phosphorus. In addition to two new modifications of Cu4P2Se6 featuring the well-known hexaselenidohypodiphosphate(IV) ion, there are three copper selenidophosphates with low-valent P: Cu4P3Se4 contains two different new anions, (i) a monomeric (zero-dimensional) selenidophosphate anion [P2Se4](4-) and (ii) a one-dimensional selenidophosphate anion [Formula: see text], which is related to the well-known gray-Se-like [Formula: see text] Zintl anion. Cu4P4Se3 contains one-dimensional [Formula: see text] polyanions, whereas CuP2Se contains the 2D selenidophosphate [Formula: see text] polyanion. It consists of charge-neutral CuP2Se layers separated by a van der Waals gap which is very rare for a Zintl-type phase. Hence, besides black P, CuP2Se constitutes a new possible source of 2D oxidized phosphorus containing layers for intercalation or exfoliation experiments. Additionally, the electronic structures and some fundamental physical properties of the new compounds are reported. All compounds are semiconducting with indirect band gaps of the orders of around 1 eV. The phases reported here add to the structural diversity of chalcogenido phosphates. The structural variety of this family of compounds may translate into a variety of tunable physical properties.

Exciton dephasing and biexciton binding in CdSe/ZnSe islands

DEFF Research Database (Denmark)

Wagner, Hans Peter; Tranitz, H.-P.; Preis, H

1999-01-01

The dephasing of excitons and the formation of biexcitons in self-organized CdSe/ZnSe islands grown by molecular-beam epitaxy is investigated using spectrally resolved four-wave mixing. A distribution of exciton-exciton scattering efficiencies and dephasing times in the range of 0.5-10 ps...

Simultaneous tracing of 76Se-selenite and 77Se-selenomethionine by absolute labeling and speciation

International Nuclear Information System (INIS)

Suzuki, Kazuo T.; Somekawa, Layla; Kurasaki, Kazuki; Suzuki, Noriyuki

2006-01-01

Nutritional selenocompounds are transformed into the assumed common intermediate selenide, which is utilized for the synthesis of selenoenzymes or transformed into methylated metabolites for excretion. Hence, selenocompound metabolites can be traced only with labeled selenium. Here we applied a new tracer method for the metallomics of biometals using simultaneous speciation of each metallome labeled with different homo-elemental isotopes to metabolism and availability of selenium. Rats were depleted of endogenous natural abundance selenium by feeding a single selenium stable isotope ( 82 Se-selenite) and then administered 76 Se-selenite and 77 Se-selenomethionine ( 77 Se-SeMet)simultaneously. Biological samples were subjected to quantification and speciation analysis by HPLC-ICPMS. Metabolites of the labeled 76 Se and 77 Se and interaction with endogenous selenium were traced and examined without interference from the corresponding endogenous natural abundance isotopes. Differences in the distribution and metabolism among organs and between the two nutritional selenocompounds were compared under exactly identical biological and analytical conditions: (1) selenite was distributed more efficiently than SeMet in organs and body fluids except the pancreas. (2) SeMet was taken up by organs in its intact form. (3) Selenium of SeMet origin was distributed selectively in the pancreas and mostly bound to a protein together with intact SeMet. (4) Selenosugars A and B but not trimethylselenonium (TMSe) were detected in the liver. (5) Selenosugar B and TMSe were detected in the kidneys

Electrochemical synthesis of nanostructured Se-doped SnS: Effect of Se-dopant on surface characterizations

Energy Technology Data Exchange (ETDEWEB)

Kafashan, Hosein, E-mail: hosein840521@gmail.com; Azizieh, Mahdi; Balak, Zohre

2017-07-15

Highlights: • Nanostructured SnS{sub 1-x}Se{sub x} thin films were prepared by using electrodeposition method. • The XRD patterns obviously showed that the synthesized films were polycrystalline. • The PL spectra of SnS{sub 1-x}Se{sub x} thin films showed four emission peaks. • The UV–vis spectra shows a variation in the optical band gap energy of SnS{sub 1-x}Se{sub x} thin films from 1.22 to 1.65 eV. • SnS{sub 1-x}Se{sub x} thin films would be suitable for use as absorber layers. - Abstract: SnS{sub 1-x}Se{sub x} nanostructures with different Se-dopant concentrations were deposited on fluorine doped tin oxide (FTO) substrate through cathodic electrodeposition technique. The pH, temperature, applied potential (E), and deposition time remained were 2.1, 60 °C, −1 V, and 30 min, respectively. SnS{sub 1-x}Se{sub x} nanostructures were characterized using X-ray diffraction (XRD), field emission scanning electron microcopy (FESEM), energy dispersive X-ray spectroscopy (EDX), room temperature photoluminescence (PL), and UV–vis spectroscopy. The XRD patterns revealed that the SnS{sub 1-x}Se{sub x} nanostructures were polycrystalline with orthorhombic structure. FESEM showed various kinds of morphologies in SnS{sub 1-x}Se{sub x} nanostructures due to Se-doping. PL and UV–vis spectroscopy were used to evaluate the optical properties of SnS{sub 1-x}Se{sub x} thin films. The PL spectra of SnS{sub 1-x}Se{sub x} nanostructures displayed four emission peaks, those are a blue, a green, an orange, and a red emission. UV–vis spectra showed that the optical band gap energy (E{sub g}) of SnS{sub 1-x}Se{sub x} nanostructures varied between 1.22–1.65 eV, due to Se-doping.

A transferable force field for CdS-CdSe-PbS-PbSe solid systems

Science.gov (United States)

Fan, Zhaochuan; Koster, Rik S.; Wang, Shuaiwei; Fang, Changming; Yalcin, Anil O.; Tichelaar, Frans D.; Zandbergen, Henny W.; van Huis, Marijn A.; Vlugt, Thijs J. H.

2014-12-01

A transferable force field for the PbSe-CdSe solid system using the partially charged rigid ion model has been successfully developed and was used to study the cation exchange in PbSe-CdSe heteronanocrystals [A. O. Yalcin et al., "Atomic resolution monitoring of cation exchange in CdSe-PbSe heteronanocrystals during epitaxial solid-solid-vapor growth," Nano Lett. 14, 3661-3667 (2014)]. In this work, we extend this force field by including another two important binary semiconductors, PbS and CdS, and provide detailed information on the validation of this force field. The parameterization combines Bader charge analysis, empirical fitting, and ab initio energy surface fitting. When compared with experimental data and density functional theory calculations, it is shown that a wide range of physical properties of bulk PbS, PbSe, CdS, CdSe, and their mixed phases can be accurately reproduced using this force field. The choice of functional forms and parameterization strategy is demonstrated to be rational and effective. This transferable force field can be used in various studies on II-VI and IV-VI semiconductor materials consisting of CdS, CdSe, PbS, and PbSe. Here, we demonstrate the applicability of the force field model by molecular dynamics simulations whereby transformations are initiated by cation exchange.

A transferable force field for CdS-CdSe-PbS-PbSe solid systems

Energy Technology Data Exchange (ETDEWEB)

Fan, Zhaochuan; Vlugt, Thijs J. H., E-mail: t.j.h.vlugt@tudelft.nl [Process and Energy Department, Delft University of Technology, Leeghwaterstraat 39, 2628 CB Delft,The Netherlands (Netherlands); Koster, Rik S.; Fang, Changming; Huis, Marijn A. van [Debye Institute for Nanomaterials Science and Center for Extreme Matter and Emergent Phenomena, Utrecht University, Princetonplein 5, 3584 CC Utrecht (Netherlands); Wang, Shuaiwei [Institute of Nanostructured Functional Materials, Huanghe Science and Technology College, Zhengzhou, Henan 450006 (China); Yalcin, Anil O.; Tichelaar, Frans D.; Zandbergen, Henny W. [Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft (Netherlands)

2014-12-28

A transferable force field for the PbSe-CdSe solid system using the partially charged rigid ion model has been successfully developed and was used to study the cation exchange in PbSe-CdSe heteronanocrystals [A. O. Yalcin et al., “Atomic resolution monitoring of cation exchange in CdSe-PbSe heteronanocrystals during epitaxial solid-solid-vapor growth,” Nano Lett. 14, 3661–3667 (2014)]. In this work, we extend this force field by including another two important binary semiconductors, PbS and CdS, and provide detailed information on the validation of this force field. The parameterization combines Bader charge analysis, empirical fitting, and ab initio energy surface fitting. When compared with experimental data and density functional theory calculations, it is shown that a wide range of physical properties of bulk PbS, PbSe, CdS, CdSe, and their mixed phases can be accurately reproduced using this force field. The choice of functional forms and parameterization strategy is demonstrated to be rational and effective. This transferable force field can be used in various studies on II-VI and IV-VI semiconductor materials consisting of CdS, CdSe, PbS, and PbSe. Here, we demonstrate the applicability of the force field model by molecular dynamics simulations whereby transformations are initiated by cation exchange.

Determination of K shell fluorescence cross-section and Kβ/Kα intensity ratios for Fe, Se, Te, FeSe, FeTe and TeSe

International Nuclear Information System (INIS)

Saydam, M.; Aksoy, C.; Cengiz, E.; Alaşalvar, C.; Tıraşoğlu, E.; Apaydın, G.

2012-01-01

The fluorescence cross-sections (σ Ki ) and the intensity ratios K β /K α for pure Fe, Se, Te elements and FeSe, FeTe, TeSe complexes have been investigated. The samples were excited by 59.5 keV γ-rays from 241 Am annular radioactive source and emitted X-rays. They were counted by an Ultra-LEGe detector with resolution of 150 eV at 5.9 keV. For pure elements results have been compared with the theoretical calculated values. According to our results band length and mutual interaction of atoms affected the results. We claimed that these effects would help researchers who study on superconductors, especially determining which compound can be show the superconductor properties. - Highlights: ► TeSe, FeSe and FeTe complexes have affected each other in terms of charge transfer. ► Fe excitement and enhancement have been made by Se and Te. ► Attractive interactions between electrons can help to becoming superconductivity.

AgSbSe2 and AgSb(S,Se)2 thin films for photovoltaic applications

International Nuclear Information System (INIS)

Garza, J.G.; Shaji, S.; Rodriguez, A.C.; Das Roy, T.K.; Krishnan, B.

2011-01-01

Silver antimony selenide (AgSbSe 2 ) thin films were prepared by heating sequentially deposited multilayers of antimony sulphide (Sb 2 S 3 ), silver selenide (Ag 2 Se), selenium (Se) and silver (Ag). Sb 2 S 3 thin film was prepared from a chemical bath containing SbCl 3 and Na 2 S 2 O 3 , Ag 2 Se from a solution containing AgNO 3 and Na 2 SeSO 3 and Se thin films from an acidified solution of Na 2 SeSO 3 , at room temperature on glass substrates. Ag thin film was deposited by thermal evaporation. The annealing temperature was 350 deg. C in vacuum (10 -3 Torr) for 1 h. X-ray diffraction analysis showed that the thin films formed were polycrystalline AgSbSe 2 or AgSb(S,Se) 2 depending on selenium content in the precursor films. Morphology and elemental analysis of these films were done using scanning electron microscopy and energy dispersive X-ray spectroscopy. Optical band gap was evaluated from the UV-visible absorption spectra of these films. Electrical characterizations were done using Hall effect and photocurrent measurements. A photovoltaic structure: glass/ITO/CdS/AgSbSe 2 /Al was formed, in which CdS was deposited by chemical bath deposition. J-V characteristics of this structure showed V oc = 435 mV and J sc = 0.08 mA/cm 2 under illumination using a tungsten halogen lamp. Preparation of a photovoltaic structure using AgSbSe 2 as an absorber material by a non-toxic selenization process is achieved.

Highly luminescent CdSe/ZnSe core-shell quantum dots of one-pot preparation in octadecene

NARCIS (Netherlands)

Zeng, Q.; Kong, X.; Zhang, Y.; Zhang, H.

2008-01-01

CdSe/ZnSe core-shell quantum dots were synthesized using a new one-pot procedure where the core was prepared in octadecene. A ZnSe shell around a CdSe nanoparticle was formed by the reaction of selenium-richness on the surfaces of CdSe nanoparticles with Zn2+ from the injected zinc stearate

Study of the 76788082Se(d,p)77798183Se reactions using polarized deuterons

International Nuclear Information System (INIS)

Montestruque, L.A.

1978-01-01

Differential cross sections and vector analyzing powers were measured at an incident deuteron energy of 12.5 MeV for the 76 78 80 82 Se(d,p) 77 79 81 83 Se reactions. The data are compared with the predictions of the DWBA theory to determine the l-value, spin, parity and spectroscopic factor of the resolved states. High resolution measurements were made with a 100 cm broad-range magnetic spectrograph to determine the excitation energies of the states studied, and the possible existence of contaminants in the targets. Definitive spin and parity assignments are made to 16 states in 77 Se, 22 states in 79 Se, 17 states in 81 Se, and 18 states in 83 Se, fifteen of which were previously assigned. In addition, tentative spin assignments were made to one state in 83 Se. The spectrograph measurements allowed the determination of the excitation energies of anumber of additional states in each isotope. Among the 76 states studied in this work, ther are 8 2P/sub 3/2/ states, 4 1F/sub 5/2/ states 6 2P/sub 1/2/ states 4 1G/sub 9/2/ states, 31 2D/sub 5/2/ states, 10 3S/sub 1/2/ states, and 13 2D/sub 3/2 states. A sum-rule analysis was made and the results compared to previous work and to the predictions of the simple pairing theory

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...

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.

Theoretical and experimental studies of the ZnSe/CuInSe2 heterojunction band offset

International Nuclear Information System (INIS)

Nelson, A.J.; Schwerdtfeger, C.R.; Wei, S.; Zunger, A.; Rioux, D.; Patel, R.; Hoechst, H.

1993-01-01

We report first-principles band structure calculations that show that ZnSe/CuInSe 2 has a significant valence band offset (VBO, ΔE v ): 0.70±0.05 eV for the relaxed interface and 0.60±0.05 eV for the coherent interface. These large values demonstrate the failure of the common anion rule. This is traced to a stronger Cu,d-Se,p level repulsion in CuInSe 2 than the Zn,d-Se,p repulsion in ZnSe. The VBO was then studied by synchrotron radiation soft x-ray photoemission spectroscopy. ZnSe overlayers were sequentially grown in steps on n-type CuInSe 2 (112) single crystals at 200 degree C. In situ photoemission measurements were acquired after each growth in order to observe changes in the valence band electronic structure as well as changes in the In 4d and Zn 3d core lines. Results of these measurements reveal that the VBO is ΔE v =0.70±0.15 eV, in good agreement with the first-principles prediction

Que se vea lo que se oye: a vueltas con los fonemas y las letras

Directory of Open Access Journals (Sweden)

Gómez del Estal Villarino, Mario

2011-03-01

Full Text Available Partiendo de lo que el refrán “La letra con sangre entra” viene a decir a quien se deje escucharlo, se abre una descripción de las diferencias radicales que se dan entre aprender a hablar y aprender a escribir. La relación entre ambas actividades no se puede entender sin analizar la tan extendida perversión que supone hablar lo que se escribe en vez de escribir lo que se habla. A continuación, se detallan algunos de los síntomas más frecuentes de dicha perversión, caracterizados todos por la intromisión de la conciencia en terrenos donde lo único que hace es estorbar, en especial la pronunciación pedantesca de ciertos finales silábicos o de palabra, como en traNSporte, aBStraKción, óPtico, oBjeto, fúTbol, libertaD, diGno o fraK, así como las distintas deformaciones que sufren las palabras que la ortografía académica prescribe que se escriban con la letra equis.

Synthesis and properties of new CdSe-AgI-As2Se3 chalcogenide glasses

International Nuclear Information System (INIS)

Kassem, M.; Le Coq, D.; Fourmentin, M.; Hindle, F.; Bokova, M.; Cuisset, A.; Masselin, P.; Bychkov, E.

2011-01-01

Research highlights: → Determination of the glass-forming region in the pseudo-ternary CdSe-AgI-As 2 Se 3 system. → Characterization of macroscopic properties of the new CdSe-AgI-As 2 Se 3 glasses. → Far infrared transmission of chalcogenide glasses. → Characterization of the total conductivity of CdSe-AgI-As 2 Se 3 glasses. -- Abstract: The glass-forming region in the pseudo-ternary CdSe-AgI-As 2 Se 3 system was determined. Measurements including differential scanning calorimetry (DSC), density, and X-ray diffraction were performed. The effect resulting from the addition of CdSe or AgI has been highlighted by examining three series of different base glasses. The characteristic temperatures of the glass samples, including glass transition (T g ), crystallisation (T x ), and melting (T m ) temperatures are reported and used to calculate their ΔT = T x - T g and their Hruby, H r = (T x - T g )/(T m - T x ), criteria. Evolution of the total electrical conductivity σ and the room temperature conductivity σ 298 was also studied. The terahertz transparency domain in the 50-600 cm -1 region was pointed for different chalcogenide glasses (ChGs) and the potential of the THz spectroscopy was suggested to obtain structural information on ChGs.

SeP, ApoER2 and megalin as necessary factors to maintain Se homeostasis in mammals.

Science.gov (United States)

Krol, Magdalena Beata; Gromadzinska, Jolanta; Wasowicz, Wojciech

2012-10-01

Selenoprotein P (SeP) is an extracellular protein containing ten selenium atoms in the form of selenocysteine, secreted mainly from the liver. About 60% of the whole plasma selenium level is present in SeP, which makes it a useful biomarker of selenium nutritional status. The main functions of SeP are transport and storage of selenium in plasma. It is especially an important protein for the brain, testes and kidneys where the supplementation of the proper amount of Se ensures the synthesis of selenoenzymes with antioxidant properties.Recently, it has been found that SeP uptake in kidneys, testes and brain depends on the apolipoprotein receptor 2 (ApoER2) and lipoprotein megalin receptor (Lrp2). Megalin receptor represents a physiological SeP receptor in kidneys, mediating the re-uptake of secreted SeP from the primary urine. The absence of a functional megalin receptor causes a significant reduction of plasma selenium and the SeP levels as a result of Se excretion. ApoER2 is a SeP receptor in the brain and testes which uptakes Se from the extracellular fluid. Deletion of ApoER2 in mice leads to a lowered selenium level in the brain and testes, neurological dysfunction, production of abnormal spermatozoa, infertility and even death when the subjects are fed a low-selenium diet. Copyright © 2012 Elsevier GmbH. All rights reserved.

Dynamical properties and their strain-dependence of ZnSe(ZnSe:N: Zinc-blende and wurtzite

Directory of Open Access Journals (Sweden)

Dandan Wang

2014-06-01

Full Text Available The lattice dynamical properties of ZnSe and ZnSe with substitutional N incorporation(ZnSe:N are investigated in both the zinc-blend(ZB and wurtzite(WZ structures using first-principles calculations. The optical phonon modes of ZB-ZnSe at the Γ-point locate at 250 cm−1 for LO and 213 cm−1 for TO. The characteristic E2 phonon modes at about 50 cm−1 and the E1 and another E2 phonon modes around 200 cm−1 of WZ-ZnSe are suggested to be the fingerprint for distinguishing the two polytypes of ZnSe. For substitutional N incorporated ZnSe, the N incorporation introduces three new high energy modes above 500 cm−1, and the splitting of them is much larger in the WZ phase than that in ZB phase. The strain dependence of phonon frequency which could be useful for corresponding spectroscopic strain characterization are also studied. The simple linear dependence is determined for ZB-ZnSe, while the situation for WZ-ZnSe looks more complicated.

Sample Set (SE): SE50 [Metabolonote[Archive

Lifescience Database Archive (English)

Full Text Available oids We report that flavonoids with radical scavenging activity mitigate against ox...ress. These data confirm the usefulness of flavonoids for enhancing both biotic and abiotic stress tolerance...SE50 Enhancement of oxidative and drought tolerance in arabidopsis by overaccumulation of antioxidant flavon

Sample Set (SE): SE52 [Metabolonote[Archive

Lifescience Database Archive (English)

Full Text Available SE52 Mass spectra-based framework for automated structural elucidation of metabolom...e data to explore phytochemical diversity A novel framework for automated elucidation of metabolite structur...te ontology system was also introduced to attain putative characterization of the metabolite signals.The automate

Microstructure and thermoelectric properties of CuInSe2/In2Se3 compound

Science.gov (United States)

Wang, Kang; Feng, Jing; Ge, Zhen-Hua; Qin, Peng; Yu, Jie

2018-01-01

CuInSe2 powders were synthesized by solvothermal method, and then the CuInSe2/In2Se3 bulk samples were fabricated by spark plasma sintering (SPS) technique. To investigate the phase composition, the powders were determined by X-ray diffraction (XRD). The microstructures of the powders and bulk samples were observed by scanning electron microscopy (SEM). The transportation of the electronic properties and thermal conductivity were measured at room temperature to 700 K. According to the results, the CuInSe2 powders appeared in flower-like patterns which ranged from 3 μm to 6 μm. CuInSe2 powders were synthesized at 180∘C with a chalcopyrite structure. The Seebeck coefficient increased significantly in composite thermoelectric materials up to 200μVṡK-1 at 623 K. The thermal conductivity of the sample significantly decreases from the room temperature to 700 K. The CuInSe2 bulk composite by solvothermal method achieves the highest ZT value of 0.187 at 700 K.

Phase diagram of the Sb-Se-I system and thermodynamic properties of SbSeI

International Nuclear Information System (INIS)

Aliev, Z.S.; Musaeva, S.S.; Babanly, D.M.; Shevelkov, A.V.; Babanly, M.B.

2010-01-01

The Sb-Se-I system was investigated by using the DTA and XRD analyses and EMF measurements with an antimony electrode. The T-x diagram of the binary Sb-I system was accurately redefined. A number of polythermal sections and the projection of the liquidus surface were constructed. The fields of the primary crystallization, as well as the types and coordinates of non- and monovariant equilibria were determined. It is shown that the quasi-binary sections Sb 2 Se 3 -SbI 3 , Sb-SbSeI, SbI 3 -Se, and SbSeI-Se triangulate the Sb-Se-I system, leading to five independent subsystems. A broad area of immiscibility, that overlaps a certain part of the antimony primary crystallization field, was found. From the EMF measurements, the partial molar functions of antimony (ΔG-bar, ΔH-bar, ΔS-bar) as well as standard integral thermodynamic functions of SbSeI were calculated. The latter were found to have the following values: ΔG f,298 0 =-80.12±1.81kJ/mol; ΔH f,298 0 =-77.3±1.8kJ/mol; S 298 0 =155.2±9.5J/(molK).

Phase diagram of the Sb-Se-I system and thermodynamic properties of SbSeI

Energy Technology Data Exchange (ETDEWEB)

Aliev, Z S; Musaeva, S S; Babanly, D M [Baku State University, General and Inorganic Chemistry Department (Azerbaijan); Shevelkov, A.V., E-mail: shev@inorg.chem.msu.r [Moscow Lomonosov State University, Chemistry Department (Russian Federation); Babanly, M.B., E-mail: Babanly_mb@rambler.r [Baku State University, General and Inorganic Chemistry Department (Azerbaijan)

2010-09-03

The Sb-Se-I system was investigated by using the DTA and XRD analyses and EMF measurements with an antimony electrode. The T-x diagram of the binary Sb-I system was accurately redefined. A number of polythermal sections and the projection of the liquidus surface were constructed. The fields of the primary crystallization, as well as the types and coordinates of non- and monovariant equilibria were determined. It is shown that the quasi-binary sections Sb{sub 2}Se{sub 3}-SbI{sub 3}, Sb-SbSeI, SbI{sub 3}-Se, and SbSeI-Se triangulate the Sb-Se-I system, leading to five independent subsystems. A broad area of immiscibility, that overlaps a certain part of the antimony primary crystallization field, was found. From the EMF measurements, the partial molar functions of antimony ({Delta}G-bar, {Delta}H-bar, {Delta}S-bar) as well as standard integral thermodynamic functions of SbSeI were calculated. The latter were found to have the following values: {Delta}G{sub f,298}{sup 0}=-80.12{+-}1.81kJ/mol; {Delta}H{sub f,298}{sup 0}=-77.3{+-}1.8kJ/mol; S{sub 298}{sup 0}=155.2{+-}9.5J/(molK).

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.)

Structural and optical properties of nanocrystalline CdSe and Al:CdSe thin films for photoelectrochemical application

Energy Technology Data Exchange (ETDEWEB)

Gawali, Sanjay A. [Electrochemical Materials Laboratory, Department of Physics, Shivaji University, Kolhapur - 416 004 (India); Bhosale, C.H., E-mail: bhosale_ch@yahoo.com [Electrochemical Materials Laboratory, Department of Physics, Shivaji University, Kolhapur - 416 004 (India)

2011-10-03

Highlights: {yields} The CdSe and Al:CdSe thin films have been successfully deposited by SPT. {yields} Hexagonal cubic structured CdSe and Al: CdSe thin films are observed. {yields} Large number of fine grains, Uniform and compact growth morphology. {yields} Hydrophilic surface nature. {yields} Al:CdSe have better PEC performance than CdSe. - Abstract: Nanocrystalline CdSe and Al:CdSe semiconductor thin films have been successfully synthesized onto amorphous and FTO glass substrates by spray pyrolysis technique. Aqueous solutions containing precursors of Cd and Se have been used to obtain good quality films. The optimized films have been characterized for their structural, morphological, wettability and optical properties. X-ray diffraction (XRD) studies show that the films are polycrystalline in nature with hexagonal crystal structure. Scanning electron microscopy (SEM) studies show that the film surface is smooth, uniform and compact in nature. Water wettability study reveals that the films are hydrophilic behavior. The formation of CdSe and Al:CdSe thin film were confirmed with the help of FTIR spectroscopy. UV-vis spectrophotometric measurement showed a direct allowed band gap lying in the range 1.673-1.87 eV. Output characteristics were studied by using cell configuration n- CdSe/Al:CdSe |1 M (NaOH + Na{sub 2} + S)|C. An efficient solar cell having a power conversion efficiency of 0.38% at illumination 25 mW cm{sup -2} was fabricated.

Señas Mexicano

Directory of Open Access Journals (Sweden)

Juan F. García Mejía

2007-01-01

Full Text Available En este artículo se muestra un sistema que permite el estudio y práctica del Lenguaje de Señas Mexicano (LMS, el cual es el método de comunicación de las personas que padecen un trastorno de procesamiento auditivo. El sistema propuesto en este artículo consta de un guante de tela instrumentado con sensores de flexión, una etapa de acondicionamiento de señales y una tarjeta de adquisición de datos; que en su conjunto constituyen el Hardware. El software esta formado por un programa de adquisición de datos y una interfaz de usuario, ambos codificados en Visual Basic Net. El sistema propuesto se modela por medio del lenguaje de modelado unificado (UML, ya que Visual Basic es un lenguaje orientado a eventos.

Sample Set (SE): SE27 [Metabolonote[Archive

Lifescience Database Archive (English)

Full Text Available SE27 Effect of agricultural films for cabbage leaf metabolites Investigation of Bra...ssica oleracea var. capitata YR Tenkuu leaf metabolites. 3 growth conditions (covered with normal or UV cut agricultura...l film or no agricultural film), 3 replicates data are examined. Takeshi Ara 1, Naoki Yamamoto 1,

Antiphase Boundaries in the Turbostratically Disordered Misfit Compound (BiSe)(1+δ)NbSe2.

Science.gov (United States)

Mitchson, Gavin; Falmbigl, Matthias; Ditto, Jeffrey; Johnson, David C

2015-11-02

(BiSe)(1+δ)NbSe2 ferecrystals were synthesized in order to determine whether structural modulation in BiSe layers, characterized by periodic antiphase boundaries and Bi-Bi bonding, occurs. Specular X-ray diffraction revealed the formation of the desired compound with a c-axis lattice parameter of 1.21 nm from precursors with a range of initial compositions and initial periodicities. In-plane X-ray diffraction scans could be indexed as hk0 reflections of the constituents, with a rectangular basal BiSe lattice and a trigonal basal NbSe2 lattice. Electron micrographs showed extensive turbostratic disorder in the samples and the presence of periodic antiphase boundaries (approximately 1.5 nm periodicity) in BiSe layers oriented with the [110] direction parallel to the zone axis of the microscope. This indicates that the structural modulation in the BiSe layers is not due to coherency strain resulting from commensurate in-plane lattices. Electrical transport measurements indicate that holes are the dominant charge carrying species, that there is a weak decrease in resistivity as temperature decreases, and that minimal charge transfer occurs from the BiSe to NbSe2 layers. This is consistent with the lack of charge transfer from the BiX to the TX2 layers reported in misfit layer compounds where antiphase boundaries were observed. This suggests that electronic considerations, i.e., localization of electrons in the Bi-Bi pairs at the antiphase boundaries, play a dominant role in stabilizing the structural modulation.

Heterojunctions formed by annealing of GaSe and InSe layered crystals in zinc vapor

Directory of Open Access Journals (Sweden)

Kudrynskyi Z. R.

2012-12-01

Full Text Available The article presents a method of creating heterojunc¬tions based on semiconductors with different lattice types. Substrates manufactured from GaSe and InSe layered crystals were annealed in Zn vapor. This way, n-ZnSe–p-GaSe and n-ZnSe–p-InSe heterojunctions were obtained. The obtained heterojunctions are photo¬sensitive in near and infrared spectral regions. This method opens up greate possibilities of producing heterostructures with a desired sensitivity band.

Thermoelectric study of Ag doped SnSe-Sb2Se3 based alloy

Science.gov (United States)

Das, Anish; Talukdar, M.; Kumar, Aparabal; Sarkar, Kalyan Jyoti; Dhama, P.; Banerji, P.

2018-05-01

In this article we have synthesized p-type alloy of SnSe and Sb2Se3 (10 atomic %) to study the thermoelectric transport properties. The alloy was prepared by melt grown technique followed by spark plasma sintering and latter doped with 2 atomic % Ag to compensate the carrier density in order to achieve higher electrical conductivity (σ). Out of these, the doped sample resulted in the maximum figure of merit, ZT˜0.7 at 773 K due to the existence of the secondary phase AgSbSe2 and reduced lattice thermal conductivity (0.61 W m-1 K-1 at 300 K). The fitted lattice thermal conductivity shows that point defect and Umklapp scattering are the primary process of phonon scattering for all the samples whereas the fitted mobility data confirms acoustic phonon scattering along with point defect and grain boundary scattering to be the main carrier scattering mechanism. More over room temperature carrier density and electrical conductivity are found to increase for the doped sample which further corroborate (90%)SnSe-(10%)Sb2Se3:2%Ag to be a potential candidate for highly efficient thermoelectric materials.

Optical properties of thermally annealed CdZnSe/ZnSe quantum dots

International Nuclear Information System (INIS)

Margapoti, Emanuela

2010-01-01

To analyse the diffusion characteristics, photoluminescence (PL) spectroscopy has been carried out in extensive detail on single, as well as, ensembles of thermally annealed (TA) CdSe/ZnSe QDs. For a series of QD-ensembles, each annealed for t A = 30 s at temperatures from T A = 300-550 C, the change in the QD-composition has been calculated from the blue-shift of the exciton ground-state PL-emission, using a concentration function based on Fick's laws of diffusion. The diffusion length (L D ) and the activation energy (E A ) have been determined thereof. For the studied QDs, E A has been evaluated to be 2.2 eV. Additionally, TA results also in an enhancement of the PL-intensity and reduction of the full-width-at-half maximum (FWHM) of the spectra. This point towards an increased homogeneity of the QD-size and composition, and decrease in the concentration of defects around the QDs. For single CdSe/ZnSe QDs, TA has been varied from 100-240 C, in steps for 20 C, with t A kept fixed at 30 s. Finally, the evolution of the magneto-optic response with post-growth thermal annealing has been studied for both individual QDs and QD-ensembles. An external magnetic field, applied perpendicular to the plane of the QDs (Faraday configuration), results in Zeeman spin splitting of the ground exciton state. The emissions from the Zeeman-split states are left and right circularly polarized and from the degree of circular polarization (DCP), as well as, the spectral separation of the PL-peaks, the g-factor can be estimated. For CdSe/ZnSe QD-ensembles, the g-factor has been observed to change sign with TA. (orig.).

Optical properties of thermally annealed CdZnSe/ZnSe quantum dots

Energy Technology Data Exchange (ETDEWEB)

Margapoti, Emanuela

2010-07-01

To analyse the diffusion characteristics, photoluminescence (PL) spectroscopy has been carried out in extensive detail on single, as well as, ensembles of thermally annealed (TA) CdSe/ZnSe QDs. For a series of QD-ensembles, each annealed for t{sub A} = 30 s at temperatures from T{sub A} = 300-550 C, the change in the QD-composition has been calculated from the blue-shift of the exciton ground-state PL-emission, using a concentration function based on Fick's laws of diffusion. The diffusion length (L{sub D}) and the activation energy (E{sub A}) have been determined thereof. For the studied QDs, E{sub A} has been evaluated to be 2.2 eV. Additionally, TA results also in an enhancement of the PL-intensity and reduction of the full-width-at-half maximum (FWHM) of the spectra. This point towards an increased homogeneity of the QD-size and composition, and decrease in the concentration of defects around the QDs. For single CdSe/ZnSe QDs, TA has been varied from 100-240 C, in steps for 20 C, with t{sub A} kept fixed at 30 s. Finally, the evolution of the magneto-optic response with post-growth thermal annealing has been studied for both individual QDs and QD-ensembles. An external magnetic field, applied perpendicular to the plane of the QDs (Faraday configuration), results in Zeeman spin splitting of the ground exciton state. The emissions from the Zeeman-split states are left and right circularly polarized and from the degree of circular polarization (DCP), as well as, the spectral separation of the PL-peaks, the g-factor can be estimated. For CdSe/ZnSe QD-ensembles, the g-factor has been observed to change sign with TA. (orig.).

Thermally stimulated properties in ZnSe:Tb and ZnSe:(Mn, Tb) phosphors

Science.gov (United States)

Mishra, A. K.; Mishra, S. K.; Pandey, S. P.; Lakshmi Mishra, Kshama

2018-02-01

Thermoluminescence studies were performed of ZnSe:Tb and ZnSe:(Mn, Tb) phosphors. A method of preparation for ZnSe phosphors doped with Tb and (Mn, Tb) has been discussed. The thermoluminescence (TL) properties of these phosphors have been studied from 100 to 370 K temperature after exciting by UV radiation (365 nm) at three uniform heating rates 0.4, 0.6 and 0.9 K/s. The trapping parameters like trap depth, lifetime of electrons and capture cross-section have also been determined using various methods.

Ab initio phonon thermal transport in monolayer InSe, GaSe, GaS, and alloys

Energy Technology Data Exchange (ETDEWEB)

Pandey, Tribhuwan; Parker, David S.; Lindsay, Lucas

2017-10-17

We compare vibrational properties and phonon thermal conductivities (κ) of monolayer InSe, GaSe and GaS systems using density functional theory and Peierls-Boltzmann transport methods. In going from InSe to GaSe to GaS, system mass decreases giving both increasing acoustic phonon velocities and decreasing scattering of these heat-carrying modes with optic phonons, ultimately giving κInSe< κGaSe< κGaS. This behavior is demonstrated by correlating the scattering phase space limited by fundamental conservation conditions with mode scattering rates and phonon dispersions for each material. We also show that, unlike flat monolayer systems such as graphene, thermal transport is governed by in-plane vibrations in InSe, GaSe and GaS, similar to buckled monolayer materials such as silicene. Alloying of InSe, GaSe and GaS systems provides an effective method for modulating their κ through intrinsic vibrational modifications and phonon scattering from mass disorder giving reductions ~2-3.5 times. This disorder also suppresses phonon mean free paths in the alloy systems compared to those in their crystalline counterparts. This work provides fundamental insights of lattice thermal transport from basic vibrational properties for an interesting set of two-dimensional materials.

Sample Set (SE): SE59 [Metabolonote[Archive

Lifescience Database Archive (English)

Full Text Available idopsis thaliana (Arabidopsis). However, the behavior of flavonoids during drough...t stress is still not well documented. Herein we investigated the time-series alternation of flavonoids in t...vonoids, a class of specialized metabolites, including flavonols and anthocyanins w...SE59 Alternation of flavonoid accumulation under drought stress in Arabidopsis thaliana We reported that fla

Intercalation compounds of NbSe2 und SnSe2. Model systems for low-dimensional superconductors

International Nuclear Information System (INIS)

Herzinger, Michael

2013-01-01

Quasi-two-dimensional (2D) metal dichalcogenides have received considerable research interest since their complex anisotropic electronic properties can be controlled by the intercalation of donor species. Although layered dichalcogenides have been studied by many aspects of chemical and physical properties, their two-dimensional character is only poorly understood. The present work deals with the layer-shaped dichalcogenides SnSe 2 and NbSe 2 . The host-material SnSe 2 was synthesized by chemical transport with Iodine as transport agent in sealed quartz ampoules. The intercalation of the semiconducting layered single crystals SnSe 2 with the organometallic compound cobaltocene (CoCp 2 ) leads to superconductivity up to T = 8 K. Ex-situ intercalation studies show an intercalation-mechanism outgoing from the host material 2H-SnSe 2 in a stage-2 phase which goes over in a stage-1 phase for higher intercalation degrees. In addition, SnSe 2 {CoCp 2 } x show remarkable low-temperature properties e.g. the coexistence of superconductivity and magnetism in dependence of the staging and cobaltocene-content of the material. Starting from an intercalation degree of 17% CoCp 2 long range ordered magnetism (with increasing saturation magnetization) was observed in 18R-SnSe 2 {CoCp 2 } x . Furthermore SnSe 2 {CoCp 2 } x show an extremely sensitive superconducting pinning behavior in very small magnetic fields partially below B 2 -content. A phase diagram was developed in dependence of the degree of intercalation over the whole range of intercalation between 0 % and 33 %. For comparison of the low-temperature character of SnSe 2 {CoCp 2 } x , another layer-shaped superconductor NbSe 2 was intercalated with CoCp 2 . The layered high-k s-wave superconductor 2H-NbSe 2 belongs to the most prominent low-dimensional materials studied during the past fifty years. After the discovery of the high temperature superconductor MgB 2 , a benchmark system for multi-band superconductivity, NbSe 2

IR and Raman spectra of LaH(SeO3)2 and FeH(SeO3)2

International Nuclear Information System (INIS)

Ratheesh, R.; Suresh, G.; Nayar, V.U.; Morris, R.E.

1995-01-01

The infrared and Raman spectra of LaH(SeO 3 ) 2 and FeH(SeO 3 ) 2 crystals are recorded and analysed. Bands confirm the coexistence of HSeO 3 - and SeO 3 2- ions in both LaH(SeO 3 ) 2 and FeH(SeO 3 ) 2 crystals. The Se-OH stretching vibrations are observed to be at lower wavenumbers in LaH(SeO 3 ) 2 than that in the iron compound in agreement with the short O-O distance in the former. Observed bands indicate that the SeO 3 2- ions are more angularly distorted in FeH(SeO 3 ) 2 crystal. ABC bands, characteristic of strong hydrogen bonded systems are observed in the infrared spectra of both the crystals. (author). 15 refs., 2 figs., 1 tab

Simultaneous speciation of arsenic (As(III), MMA, DMA, and As(V)) and selenium (Se(IV), Se(VI), and SeCN{sup -}) in petroleum refinery aqueous streams

Energy Technology Data Exchange (ETDEWEB)

Tonietto, Gisele B.; Godoy, Jose M.; Oliveira, Ana Cristina [Pontificia Universidade Catolica do Rio de Janeiro, Rio de Janeiro, RJ (Brazil); Souza, Marcia V. de [Petrobras/Cenpes, Research and Development Center, Rio de Janeiro (Brazil)

2010-07-15

High-performance liquid chromatography (HPLC) coupled to an ICP-MS with an octapole reaction system (ORS) has been used to carry out quantitative speciation of selenium (Se) and arsenic (As) in the stream waters of a refining process. The argon dimers interfering with the {sup 78}Se and {sup 80}Se isotopes were suppressed by pressurizing the octapole chamber with 3.1 mL min{sup -1} H{sub 2} and 0.5 mL min{sup -1} He. Four arsenic species arsenite - As(III), arsenate (As(V)), monomethylarsonic acid (MMA), and dimethylarsinic acid (DMA) - and three inorganic Se species - selenite Se(IV), selenate Se(VI), and selenocyanate (SeCN{sup -}) - were separated in a single run by ion chromatography (IC) using gradient elution with 100 mmol L{sup -1} NH{sub 4}NO{sub 3}, pH 8.5, adjusted by addition of NH{sub 3}, as eluent. Repeatabilities of peak position and of peak area evaluation were better than 1% and about 3%, respectively. Detection limits (as 3{sigma} of the baseline noise) were 81, 56, and 75 ng L{sup -1} for Se(IV), Se(VI), and SeCN{sup -}, respectively, and 22, 19, 25, and 16 ng L{sup -1} for As(III), As(V), MMA, and DMA, respectively. Calibration curve R {sup 2} values ranged between 0.996 and 0.999 for the arsenic and selenium species. Column recovery for ion chromatography was calculated to be 97 {+-} 6% for combined arsenic species and 98 {+-} 3% for combined selenium species. Because certified reference materials for As and Se speciation studies are still not commercially available, in order to check accuracy and precision the method was applied to certified reference materials, BCR 714, BCR 1714, and BCR 715 and to two different refinery samples - inlet and outlet wastewater. The method was successfully used to study the quantitative speciation of selenium and arsenic in petroleum refinery wastewaters. (orig.)

Third-order nonlinear optical properties of GeSe2-Ga2Se3-PbI2 glasses

International Nuclear Information System (INIS)

Tang Gao; Liu Cunming; Luo Lan; Chen Wei

2010-01-01

The third-order nonlinear optical (NLO) properties of new selenium-based GeSe 2 -Ga 2 Se 3 -PbI 2 glasses have been measured using the optical Kerr effect (OKE) technique, with picosecond and femtosecond laser pulses. The 0.70GeSe 2 -0.15Ga 2 Se 3 -0.15PbI 2 glass has the largest third-order optical nonlinear susceptibility in GeSe 2 -Ga 2 Se 3 -PbI 2 glass system with χ (3) of 5.28x10 12 esu. In addition, the response time of glasses is sub-picosecond, which is predominantly associated with electron cloud. Local structure of the glasses has been identified by using Raman studies, while the origins of the observed nonlinear optical response are discussed. The [Ge(Ga)Se 4 ] tetrahedral and lone-pair electrons from highly polarizable Pb atom in glasses play an important role in enhanced NLO response. These results as well as their good chemical stability indicate that GeSe 2 -Ga 2 Se 3 -PbI 2 glasses are promising materials for photonic applications of third-order nonlinear optical signal processing.

EMERGENCIA SOCIAL. Sobre Decretos-Ley de la Emergencia Social

Directory of Open Access Journals (Sweden)

Gustavo Malagón Londoño

2010-01-01

Full Text Available

La Academia Nacional de Medicina de Colombia expresa su profunda preocupación con motivo de los decretos-ley que han sido expedidos en el marco de la Emergencia Social decretada por el Gobierno.

En conjunto, tales decretos representan un grave atentado contra la medicina como ciencia y profesión, atentado que nunca se había registrado en el país ni en país alguno.

El Sistema General de Seguridad Social de Colombia (SGSSS atraviesa por una situación crítica que afecta por una parte a los afiliados y personas cubiertas total o parcialmente, y por otra, muy grave, a prestadores de servicios, médicos y profesiones de la salud e instituciones hospitalarias públicas y privadas. Los cuantiosos recursos que van al SGSSS son consumidos por la intermediación, entidades aseguradoras, que destinan buena parte de estos recursos a fines ajenos a la atención de la salud. Expertos aseguran que en el sistema norteamericano, que fue copiado en gran parte para crear el SGSSS colombiano, en las HMO (Health Maintenance Organizations, las EPS de los EUA, se queda la mitad de los recursos. Algunos creen que en Colombia no es menos, y que tal vez puede superar este 50%. Así pues, los costos que han llevado a la crisis financiera del SGSSS residen fundamentalmente en la intermediación y en todo el pertinente andamiaje administrativo que se ha construido.

Enhancement of hole mobility in InSe monolayer via an InSe and black phosphorus heterostructure.

Science.gov (United States)

Ding, Yi-Min; Shi, Jun-Jie; Xia, Congxin; Zhang, Min; Du, Juan; Huang, Pu; Wu, Meng; Wang, Hui; Cen, Yu-Lang; Pan, Shu-Hang

2017-10-05

To enhance the low hole mobility (∼40 cm 2 V -1 s -1 ) of InSe monolayer, a novel two-dimensional (2D) van der Waals heterostructure made of InSe and black phosphorus (BP) monolayers with high hole mobility (∼10 3 cm 2 V -1 s -1 ) has been constructed and its structural and electronic properties are investigated using first-principles calculations. We find that the InSe/BP heterostructure exhibits a direct band gap of 1.39 eV and type-II band alignment with electrons (holes) located in the InSe (BP) layer. The band offsets of InSe and BP are 0.78 eV for the conduction band minimum and 0.86 eV for the valence band maximum, respectively. Surprisingly, the hole mobility in the InSe/BP heterostructure exceeds 10 4 cm 2 V -1 s -1 , which is one order of magnitude larger than the hole mobility of BP and three orders larger than that of the InSe monolayer. The electron mobility is also increased to 3 × 10 3 cm 2 V -1 s -1 . The physical reason has been analyzed deeply, and a universal method is proposed to improve the carrier mobility of 2D materials by forming heterostructures with them and other 2D materials with complementary properties. The InSe/BP heterostructure can thus be widely used in nanoscale InSe-based field-effect transistors, photodetectors and photovoltaic devices due to its type-II band alignment and high carrier mobility.

Complexing in (NH4)2SeO4-UO2SeO4 H2O system

International Nuclear Information System (INIS)

Serezhkina, L.B.

1994-01-01

Isotherm of solubility in the (NH 4 ) 2 SeO 4 -UO 2 SeO 4 -H 2 O system has been constructed at 25 deg C. (NH 4 ) 2 (UO 2 ) 2 (SeO 4 ) 3 x6H 2 O formation is established for the first time and certain its physicochemical properties are determined. Regularities of complexing in the R 2 Se) 4 -UO 2 SeO 4 -H 2 O systems, where R-univalent cation are under discussion. 6 refs.; 3 tabs

Flexible one-dimensional carbon-selenium composite nanofibers with superior electrochemical performance for Li-Se/Na-Se batteries

Science.gov (United States)

Zeng, Linchao; Wei, Xiang; Wang, Jiaqing; Jiang, Yu; Li, Weihan; Yu, Yan

2015-05-01

A facile strategy is developed to synthesis selenium/carbon composites (Se@CNFs-CNT) by co-heating Se powder and electrospun Polyacrylonitrile (PAN)-CNT nanofibers at 600°Cin a sealed vessel. The Se molecules are chemically bonded and physical encapsulated by carbonized PAN-CNT composite (CNFs-CNT), which leads to prevent the dissolution of polyselenide intermediates in carbonate based electrolyte. When directly used as flexible free-standing cathode material for Li-Se batteries in low cost carbonate-based electrolyte, the Se@CNFs-CNT electrode exhibits improved cyclability (517 mAh g-1 after 500 cycles at 0.5 A g-1) and rate capability (485 mAh g-1 at 1 A g-1). Moreover, when tested as sodium batteries, it maintains a reversible capacity of 410 mAh g-1 after 240 cycles at 0.5 A g-1. The superior electrochemical performance (especially at high rates) of Se@CNFs-CNT is attributed to synergistic effect of the additive of CNT, the well confine of Se in the CNFs-CNT matrix through chemical bonding and the 3D interconnected carbon nanofibers (CNFs). This simple yet efficient process thus provides a promising route towards fabrication of a variety of high performance flexible Li-Se and Na-Se batteries.

Achieving tunable doping of MoSe2 based devices using GO@MoSe2 heterostructure

Science.gov (United States)

Maji, Tuhin Kumar; Tiwary, Krishna Kanhaiya; Karmakar, Debjani

2017-05-01

Doping nature of MoSe2, one of the promising Graphene analogous device material, can be tuned by controlling the concentration of functional groups in Graphene oxide (GO)@MoSe2 heterostructure. In this study, by first-principles simulation, we have observed that GO can be used as a carrier injection layer for MoSe2, where n or p type carriers are introduced within MoSe2 layer depending on the type and concentration of functional moieties in it. Both n and p-type Schottky barrier height modulations are investigated for different modeled configurations of the heterostructure. This combinatorial heterostructure can be a promising material for future electronic device application.

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.

Dipole strength in 80Se below the neutron-separation energy for the nuclear transmutation of 79Se

Directory of Open Access Journals (Sweden)

Makinaga Ayano

2017-01-01

Full Text Available The γ-ray strength function (γSF in 80Se is an important parameter to estimate the neutron-capture cross section of 79Se which is one of the long-lived fission products (LLFPs. Until now, the γSF method was applied for 80Se only above the neutron-separation energy (Sn and the evaluated 79Se(n,γ cross section has an instability caused by the GSF below Sn. We studied the dipole-strength distribution of 80Se in a photon-scattering experiment using bremsstrahlung produced by an electron beam of an energy of 11.5 MeV at the linear accelerator ELBE at HZDR. The present photoabsorption cross section of 80Se was combined with results of (γ,n experiments and are compared with predictions usinmg the TALYS code. We also estimated the 79Se(n,γ cross sections and compare them with TALYS predictionms and earlier work by other groups.

Dipole strength in 80Se below the neutron-separation energy for the nuclear transmutation of 79Se

Science.gov (United States)

Makinaga, Ayano; Massarczyk, Ralph; Beard, Mary; Schwengner, Ronald; Otsu, Hideaki; Müller, Stefan; Röder, Marko; Schmidt, Konrad; Wagner, Andreas

2017-09-01

The γ-ray strength function (γSF) in 80Se is an important parameter to estimate the neutron-capture cross section of 79Se which is one of the long-lived fission products (LLFPs). Until now, the γSF method was applied for 80Se only above the neutron-separation energy (Sn) and the evaluated 79Se(n,γ) cross section has an instability caused by the GSF below Sn. We studied the dipole-strength distribution of 80Se in a photon-scattering experiment using bremsstrahlung produced by an electron beam of an energy of 11.5 MeV at the linear accelerator ELBE at HZDR. The present photoabsorption cross section of 80Se was combined with results of (γ,n) experiments and are compared with predictions usinmg the TALYS code. We also estimated the 79Se(n,γ) cross sections and compare them with TALYS predictionms and earlier work by other groups.

Fundamental absorption edge in CuIn5Se8 and CuGa3Se5 single crystals

International Nuclear Information System (INIS)

Leon, M.; Merino, J.M.; Levcenko, S.; Nateprov, A.; Tezlevan, V.; Arushanov, E.; Syrbu, N.N.

2006-01-01

Optical absorption spectra of CuIn 5 Se 8 and CuGa 3 Se 5 single crystals have been investigated. The energy gap E g for CuIn 5 Se 8 (CuGa 3 Se 5 ) was found to be varied from 1.27(1.79) to 1.21(1.71) eV in the temperature range between 10 and 300 K. The temperature dependence of E g was studied by means of the Einstein model and the Paessler model. The Einstein temperature {222(267)K}, the Debye temperature {310(380)K}, a dimensionless constant related to the electron-phonon coupling {1.62(2.65)} as well as an effective energy {20 (24) meV} and a cut-off phonon energy {35(39) meV} have been estimated for CuIn 5 Se 8 (CuGa 3 Se 5 ). It was also found that the major contribution of phonons to the shift of E g versus temperature in CuIn 5 Se 8 (CuGa 3 Se 5 ) is mainly from optical phonons. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (Abstract Copyright [2006], Wiley Periodicals, Inc.)

Charge confinements in CdSe-ZnSe symmetric double quantum wells

International Nuclear Information System (INIS)

Tit, Nacir; Obaidat, Ihab M

2008-01-01

The bound states in the (CdSe) N w (ZnSe) N b (CdSe) N w -ZnSe(001) symmetric double quantum wells are investigated versus the well width (N w ) and the barrier thickness (N b ). A calculation based on the sp 3 s * tight-binding method which includes the spin-orbit interactions is employed to calculate the bandgap energy, quantum-confinement energy, and band structures. The studied systems possess a vanishing valence-band offset (VBO = 0) in consistency with the well known common-anion rule, and a large conduction-band offset (CBO ≅ 1 eV), which plays an essential role in the confinement of electrons within the CdSe wells. The biaxial strain, on the other hand, plays another role in confining the holes at the interfaces (within the well regions) and thus enhancing the radiative efficiency. The induced-strain energy is estimated to be ∼35 meV. More importantly, the results show that, for a fixed barrier thickness, the double wells are able to confine a pair of bound states when they are very thin. By increasing the wells' width (N w ), further, a new pair of states from the conduction-band continuum falls into the wells every time N w hits a multiple of four monolayers (more specifically, for 4n w ≤4(n+1), the number of bound states is 2(n+1), where n is an integer). On the other hand, the barrier thickness (N b ) is shown to have no effect on the number of bound states, but it solely controls their well-to-well interactions. A critical barrier thickness to switch off these latter interactions is estimated to occur at about N crit b ≅ 9 (L crit b ≅ 25∼AA. Rules governing the variation of the quantum-confinement energy versus both barrier thickness (N b ) and well width (N w ) have been derived. Our theoretical results are also shown to have excellent agreement with the available experimental photoluminescence data

AgSbSe{sub 2} and AgSb(S,Se){sub 2} thin films for photovoltaic applications

Energy Technology Data Exchange (ETDEWEB)

Garza, J.G. [Facultad de Ingenieria Mecanica y Electrica, Universidad Autonoma de Nuevo Leon, San Nicolas de los Garza, Nuevo Leon (Mexico); Shaji, S. [Facultad de Ingenieria Mecanica y Electrica, Universidad Autonoma de Nuevo Leon, San Nicolas de los Garza, Nuevo Leon (Mexico); Facultad de Ingenieria Mecanica y Electrica, CIIDIT - Universidad Autonoma de Nuevo Leon, Apodaca, Nuevo Leon (Mexico); Rodriguez, A.C.; Das Roy, T.K. [Facultad de Ingenieria Mecanica y Electrica, Universidad Autonoma de Nuevo Leon, San Nicolas de los Garza, Nuevo Leon (Mexico); Krishnan, B., E-mail: kbindu_k@yahoo.com [Facultad de Ingenieria Mecanica y Electrica, Universidad Autonoma de Nuevo Leon, San Nicolas de los Garza, Nuevo Leon (Mexico); Facultad de Ingenieria Mecanica y Electrica, CIIDIT - Universidad Autonoma de Nuevo Leon, Apodaca, Nuevo Leon (Mexico)

2011-10-01

Silver antimony selenide (AgSbSe{sub 2}) thin films were prepared by heating sequentially deposited multilayers of antimony sulphide (Sb{sub 2}S{sub 3}), silver selenide (Ag{sub 2}Se), selenium (Se) and silver (Ag). Sb{sub 2}S{sub 3} thin film was prepared from a chemical bath containing SbCl{sub 3} and Na{sub 2}S{sub 2}O{sub 3}, Ag{sub 2}Se from a solution containing AgNO{sub 3} and Na{sub 2}SeSO{sub 3} and Se thin films from an acidified solution of Na{sub 2}SeSO{sub 3}, at room temperature on glass substrates. Ag thin film was deposited by thermal evaporation. The annealing temperature was 350 deg. C in vacuum (10{sup -3} Torr) for 1 h. X-ray diffraction analysis showed that the thin films formed were polycrystalline AgSbSe{sub 2} or AgSb(S,Se){sub 2} depending on selenium content in the precursor films. Morphology and elemental analysis of these films were done using scanning electron microscopy and energy dispersive X-ray spectroscopy. Optical band gap was evaluated from the UV-visible absorption spectra of these films. Electrical characterizations were done using Hall effect and photocurrent measurements. A photovoltaic structure: glass/ITO/CdS/AgSbSe{sub 2}/Al was formed, in which CdS was deposited by chemical bath deposition. J-V characteristics of this structure showed V{sub oc} = 435 mV and J{sub sc} = 0.08 mA/cm{sup 2} under illumination using a tungsten halogen lamp. Preparation of a photovoltaic structure using AgSbSe{sub 2} as an absorber material by a non-toxic selenization process is achieved.

Porøse materialer

DEFF Research Database (Denmark)

Hansen, Ernst Jan de Place

2000-01-01

Dette undervisningsnotat er en samling af noter, der refererer til den indledende del af kurset Materialmekanik og Porøse materailer på Insitut for Bærende Konstruktiner og Materialer (BKM).......Dette undervisningsnotat er en samling af noter, der refererer til den indledende del af kurset Materialmekanik og Porøse materailer på Insitut for Bærende Konstruktiner og Materialer (BKM)....

Synthesis and properties of new CdSe-AgI-As{sub 2}Se{sub 3} chalcogenide glasses

Energy Technology Data Exchange (ETDEWEB)

Kassem, M. [Univ Lille Nord de France, F-59000 Lille (France); ULCO, LPCA, EAC CNRS 4493 F-59140 Dunkerque (France); Le Coq, D., E-mail: david.lecoq@univ-littoral.fr [Univ Lille Nord de France, F-59000 Lille (France); ULCO, LPCA, EAC CNRS 4493 F-59140 Dunkerque (France); Fourmentin, M.; Hindle, F.; Bokova, M.; Cuisset, A.; Masselin, P.; Bychkov, E. [Univ Lille Nord de France, F-59000 Lille (France); ULCO, LPCA, EAC CNRS 4493 F-59140 Dunkerque (France)

2011-02-15

Research highlights: {yields} Determination of the glass-forming region in the pseudo-ternary CdSe-AgI-As{sub 2}Se{sub 3} system. {yields} Characterization of macroscopic properties of the new CdSe-AgI-As{sub 2}Se{sub 3} glasses. {yields} Far infrared transmission of chalcogenide glasses. {yields} Characterization of the total conductivity of CdSe-AgI-As{sub 2}Se{sub 3} glasses. -- Abstract: The glass-forming region in the pseudo-ternary CdSe-AgI-As{sub 2}Se{sub 3} system was determined. Measurements including differential scanning calorimetry (DSC), density, and X-ray diffraction were performed. The effect resulting from the addition of CdSe or AgI has been highlighted by examining three series of different base glasses. The characteristic temperatures of the glass samples, including glass transition (T{sub g}), crystallisation (T{sub x}), and melting (T{sub m}) temperatures are reported and used to calculate their {Delta}T = T{sub x} - T{sub g} and their Hruby, H{sub r} = (T{sub x} - T{sub g})/(T{sub m} - T{sub x}), criteria. Evolution of the total electrical conductivity {sigma} and the room temperature conductivity {sigma}{sub 298} was also studied. The terahertz transparency domain in the 50-600 cm{sup -1} region was pointed for different chalcogenide glasses (ChGs) and the potential of the THz spectroscopy was suggested to obtain structural information on ChGs.

Effect of dietary sodium selenite, Se-enriched yeast and Se-enriched Chlorella on egg Se concentration, physical parameters of eggs and laying hen production

Czech Academy of Sciences Publication Activity Database

Skřivan, M.; Šimáně, J.; Dlouhá, G.; Doucha, Jiří

2006-01-01

Roč. 51, č. 4 (2006), s. 163-167 ISSN 1212-1819 Institutional research plan: CEZ:AV0Z50200510 Keywords : sodium selenite * se-yeast * se-chlorella Subject RIV: EE - Microbiology, Virology Impact factor: 0.421, year: 2006

Effect of the ITO substrate on the growth of Cu(In,Ga)Se{sub 2}, CuGa{sub 3}Se{sub 5}, CuGa{sub 5}Se{sub 8} and CuIn{sub 3}Se{sub 5} thin films by flash evaporation

Energy Technology Data Exchange (ETDEWEB)

Friedrich, E J; Merino, J M; Leon, M [Department of Applied Physics, Universidad Autonoma de Madrid (UAM), Cantoblanco, 28049 Madrid (Spain); Trigo, J F; Guillen, C [Department of Energy, CIEMAT, Avda Complutense, 22, 28040 Madrid (Spain); Ramiro, J, E-mail: josue.friedrich@uam.e [Department of Theory of Signal and Communications, URJC, Campus Fuenlabrada, 122, 28943 Madrid (Spain)

2009-04-21

Structural, compositional, electrical and morphological properties of CuIn{sub 1-x}Ga{sub x}Se{sub 2} (x = 0.15, 0.30) and ordered defect compounds (ODC) CuGa{sub 3}Se{sub 5}, CuGa{sub 5}Se{sub 8}, CuIn{sub 3}Se{sub 5} thin films grown by flash evaporation onto soda lime glass substrates (SLG) and ITO/SLG have been studied. Polycrystalline thin films with accentuated preferential orientation in the (1 1 2) plane of the tetragonal structure have been obtained. Annealing in Se atmosphere improves the structural, morphological, electrical and optical properties of the evaporated films, but provokes the formation of a CuIn{sub x}Se{sub y} phase on the surface of the films. Band gap values ranging between 1.01 and 1.21 eV have been obtained for the as-grown CuIn{sub 1-x}Ga{sub x}Se{sub 2} thin films and between 1.09 and 2.01 eV for the CuGa{sub 3}Se{sub 5}, CuGa{sub 5}Se{sub 8} and CuIn{sub 3}Se{sub 5} thin films.

Cu(InGa)Se{sub 2} absorber formation by in-situ, low-temperature annealing of co-evaporated bilayer (InGa){sub 2}Se{sub 3}/CuSe precursors

Energy Technology Data Exchange (ETDEWEB)

Moon, Kyeongchan; Kim, Woo Kyoung, E-mail: wkim@ynu.ac.kr

2015-12-01

Chalcopyrite Cu(InGa)Se{sub 2} (CIGS) absorbers were fabricated by the formation of bilayer stacked glass/Mo/(InGa){sub 2}Se{sub 3}/CuSe precursors followed by in-situ thermal annealing at 450 °C for approximately 10 min in a vacuum evaporator. The material properties (e.g., crystal orientation, compositional depth profile, and overall composition) and device performance of the resulting CIGS absorbers were compared with those of the CIGS absorbers formed by conventional 1-stage and 3-stage CIGS formation processes at a similar temperature. X-ray diffraction confirmed that the 1-stage co-evaporation and in-situ annealing of the bilayer precursor produced a polycrystalline CIGS absorber without a specific texture, whereas the CIGS absorber formed by the 3-stage process showed a highly (220) preferred orientation. Secondary ion mass spectrometry revealed Ga accumulation at the bottom of CIGS formed by in-situ annealing of the bilayer precursors. The cell efficiency of the device with the CIGS absorber formed by the in-situ, low-temperature (450 °C) annealing of bilayer stacked glass/Mo/(InGa){sub 2}Se{sub 3}/CuSe precursors was comparable to that produced by the conventional 3-stage process at a similar temperature. - Highlights: • Annealing of (InGa){sub 2}Se{sub 3}/CuSe precursors was compared with coevaporation process. • In-situ annealing of (InGa){sub 2}Se{sub 3}/CuSe precursors at 450 °C produced about 9% solar cell. • Ga profile within Cu(InGa)Se{sub 2} depended on process profile during co-evaporation.

Short and medium range structures of 80GeSe2–20Ga2Se3 chalcogenide glasses

Science.gov (United States)

Petracovschi, Elena; Calvez, Laurent; Cormier, Laurent; Le Coq, David; Du, Jincheng

2018-05-01

The short and medium range structures of 80GeSe2–20Ga2Se3 (or Ge23.5Ga11.8Se64.7) chalcogenide glasses have been studied by combining ab initio molecular dynamics (AIMD) simulations and experimental neutron diffraction studies. The structure factor and total correlation function were calculated from glass structures generated from AIMD simulations and compared with neutron diffraction experiments showing reasonable agreement. The atomic structures of ternary chalcogenide glasses were analyzed in detail, and it was found that gallium atoms are four-fold coordinated by selenium (Se) and form [GaSe4] tetrahedra. Germanium atoms on average also have four-fold coordination, among which Se is 3.5 with the remaining being Ge–Ge homo-nuclear bonds. Ga and Ge tetrahedra link together mainly through corner-sharing and some edge-sharing of Se. No homo-nuclear bonds were observed among Ga atoms or between Ge and Ga. In addition, Se–Se homo-nuclear bonds and Se chains with various lengths were observed. A small fraction of Se atom triclusters that bond to three cations of Ge and Ga were also observed, confirming earlier proposals from 77Se solid state nuclear magnetic resonance studies. Furthermore, the electronic structures of ternary chalcogenide glasses were studied in terms of atomic charge and electronic density of states in order to gain insights into the chemical bonding and electronic properties, as well as to provide an explanation of the observed atomic structures in these ternary chalcogenide glasses.

Absorption Spectra of CuGaSe2 and CuInSe2 Semiconducting Nanoclusters

KAUST Repository

Mokkath, Junais Habeeb; Singh, Nirpendra; Schwingenschlö gl, Udo

2015-01-01

The structural and optical properties of the chalcopyrite CunGanSe2n and CunInnSe2n nanoclusters (n = 2, 4, 6, and 8) are investigated as a function of the size using a combination of basin-hopping global optimization and time-dependent density

Mujeres receptoras de remesas y trabajo no remunerado en el Ecuador

OpenAIRE

Tello Torres, Nanci Leonor

2010-01-01

En el Ecuador las mujeres son protagonistas de dos aspectos importantes, las que destinan mayor carga global de trabajo respecto de los hombres, especialmente el trabajo no remunerado o doméstico; y las mayores receptoras de remesas de los emigrantes que están fuera del país y por ende administradoras de estos recursos. El resultado más importante de este estudio fue constatar que las mujeres, aumentaron su carga de trabajo no remunerado por los compromisos que adquieren con los familiares m...

Assessment of the anticancer compounds Se-methylselenocysteine and glucosinolates in Se-biofortified broccoli (Brassica oleracea L. var. italica) sprouts and florets.

Science.gov (United States)

Ávila, Fabricio William; Faquin, Valdemar; Yang, Yong; Ramos, Silvio Junio; Guilherme, Luiz Roberto G; Thannhauser, Theodore W; Li, Li

2013-07-03

Broccoli (Brassica oleracea L. var. italica) is a rich source of chemopreventive compounds. Here, we evaluated and compared the effect of selenium (Se) treatment on the accumulation of anticancer compounds Se-methylselenocysteine (SeMSCys) and glucosinolates in broccoli sprouts and florets. Total Se and SeMSCys content in sprouts increased concomitantly with increasing Se doses. Selenate was superior to selenite in inducing total Se accumulation, but selenite is equally effective as selenate in promoting SeMSCys synthesis in sprouts. Increasing sulfur doses reduced total Se and SeMSCys content in sprouts treated with selenate, but not in those with selenite. Examination of five broccoli cultivars reveals that sprouts generally have better fractional ability than florets to convert inorganic Se into SeMSCys. Distinctive glucosinolate profiles between sprouts and florets were observed, and sprouts contained approximately 6-fold more glucoraphanin than florets. In contrast to florets, glucosinolate content was not affected by Se treatment in sprouts. Thus, Se-enriched broccoli sprouts are excellent for simultaneous accumulation of chemopreventive compounds SeMSCys and glucoraphanin.

Enhanced thermoelectric properties of N-type polycrystalline In4Se3-x compounds via thermally induced Se deficiency

Science.gov (United States)

Zhao, Ran; Shu, Yu-Tian; Guo, Fu

2014-03-01

In4Se3-x compound is considered as a potential thermoelectric material due to its comparably low thermal conductivity among all existing ones. While most studies investigated In4Se3-x thermoelectric properties by controlling selennium or other dopants concentrations, in the current study, it was found that even for a fixed initial In/Se ratio, the resulting In/Se ratio varied significantly with different thermal processing histories (i.e., melting and annealing), which also resulted in varied thermoelectric properties as well as fracture surface morphologies of In4Se3-x polycrystalline specimens. Single phase polycrystalline In4Se3-x compounds were synthesized by combining a sequence of melting, annealing, pulverizing, and spark plasma sintering. The extension of previous thermal history was observed to significantly improve the electrical conductivity (about 121%) and figure of merit (about 53%) of In4Se3-x polycrystalline compounds. The extended thermal history resulted in the increase of Se deficiency (x) from 0.39 to 0.53. This thermally induced Se deficiency was observed to associate with increasing carrier mobility but decreasing concentration, which differs from the general trend observed for the initially adjusted Se deficiency at room temperature. Unusually large dispersed grains with nanosize layers were observed in specimens with the longest thermal history. The mechanism(s) by which previous thermal processing enhances carrier mobility and affect microstructural evolution are briefly discussed.

Effect of Silver Doping on Transport Properties of Bi2Se3: AgxBi2Se3 and Bi2-xAgxSe3

Science.gov (United States)

Zhang, Min; Wei, Zhan-Tao

2018-03-01

Ag-doped Bi2Se3 with the formula AgxBi2Se3 and Bi2-xAgxSe3 were prepared and their electrical and magnetic transport properties have been investigated to study the influence of silver doping on transport properties of Bi2Se3 with different Ag-doped method. All samples exhibited metallic resistivity and the resistivity increased with increasing Ag concentration. The lattice parameter c of Ag-substituted and Ag-intercalated samples displays a contrary change as the Ag concentration increased. For the Ag-intercalated samples, both the resistance upturn were observed in the curves of temperature dependent of resistivity and temperature dependent of magnetoresistance, respectively, indicating that the enhanced surface effect was obtained in those samples. Monotonously, field-induced MR peaks around 200 K were also observed in those samples. Similar behaviors were not observed in the Ag-substituted samples.

Effect of Silver Doping on Transport Properties of Bi2Se3: AgxBi2Se3 and Bi2-xAgxSe3

Science.gov (United States)

Zhang, Min; Wei, Zhan-Tao

2018-05-01

Ag-doped Bi2Se3 with the formula AgxBi2Se3 and Bi2-xAgxSe3 were prepared and their electrical and magnetic transport properties have been investigated to study the influence of silver doping on transport properties of Bi2Se3 with different Ag-doped method. All samples exhibited metallic resistivity and the resistivity increased with increasing Ag concentration. The lattice parameter c of Ag-substituted and Ag-intercalated samples displays a contrary change as the Ag concentration increased. For the Ag-intercalated samples, both the resistance upturn were observed in the curves of temperature dependent of resistivity and temperature dependent of magnetoresistance, respectively, indicating that the enhanced surface effect was obtained in those samples. Monotonously, field-induced MR peaks around 200 K were also observed in those samples. Similar behaviors were not observed in the Ag-substituted samples.

Formation of ZnSe/Bi2Se3 QDs by surface cation exchange and high photothermal conversion

Directory of Open Access Journals (Sweden)

Guozhi Jia

2015-08-01

Full Text Available Water-dispersed core/shell structure ZnSe/Bi2Se3 quantum dots were synthesized by ultrasonicwave-assisted cation exchange reaction. Only surface Zn ion can be replaced by Bi ion in ZnSe quantum dots, which lead to the ultrathin Bi2Se3 shell layer formed. It is significance to find to change the crystal of QDs due to the acting of ultrasonicwave. Cation exchange mechanism and excellent photothermal conversion properties are discussed in detail.

Absorption Spectra of CuGaSe2 and CuInSe2 Semiconducting Nanoclusters

KAUST Repository

Mokkath, Junais Habeeb

2015-10-01

The structural and optical properties of the chalcopyrite CunGanSe2n and CunInnSe2n nanoclusters (n = 2, 4, 6, and 8) are investigated as a function of the size using a combination of basin-hopping global optimization and time-dependent density functional theory. Although the lowest energy structures are found to show almost random geometries, the band gaps and absorption spectra still are subject to systematic blue shifts for decreasing cluster size in the case of CunGanSe2n, indicating strong electron confinement. The applicability of the nanoclusters in photovoltaics is discussed. © 2015 American Chemical Society.

Die tema van God se spraak in Hebreërs se inleidingsformules

Directory of Open Access Journals (Sweden)

Albert J. Coetsee

2015-03-01

Full Text Available Alhoewel die voorkoms en gebruik van die Ou Testament in die meeste navorsing oor Hebreërs besonder baie aandag geniet, is dit nie die geval met die Hebreërskrywer se gebruik van inleidingsformules vir sy Ou-Testamentiese aanhalings nie. Die gevolg is dat daar tot op hede betreklik min selfstandige navorsing oor die Hebreërskrywer se tema van God se spraak by sy inleidingsformules gedoen is. In hierdie artikel word Hebreërs se inleidingsformules in besonderhede nagegaan om te bepaal wat die aard en inhoud van die Hebreërskrywer se verwysings na die tema van God se spraak in sy inleidingsformules is. Daar word onder andere bepaal dat Hebreërs 38 direkte aanhalings vanuit die Ou Testament bevat, dat die Hebreërskrywer, met slegs een uitsondering, elke inleidingsformule met ’n werkwoord van sêinlei, dat ’n Persoon van die Drie-eenheid in 34 van die 38 direkte aanhalings (± 89% die onderwerp en gevolglike Spreker van die Ou-Testamentiese woorde is, dat die Hebreërskrywer al drie Persone van die Drie-eenheid as God beskou, en dat die Hebreërskrywer oortuig is dat die Ou Testament geïnspireer is en God se geldige en relevante openbaring bly. The theme of God’s speech in Hebrews’ introduction formulae. Whilst the occurance and function of the Old Testament in research on Hebrews enjoys a lot of attention, this is not the case for the writer of Hebrews’ use of introduction formulae for his Old Testament quotations. The result is that up to date relatively few independent studies have been made on the writer of Hebrews’ theme of God’s speech in his introduction formulae. In this article the introduction formulae in Hebrews are researched in detail to determine the nature and content of the writer of Hebrews’ reference to the theme of God’s speech in his introduction formulae. Amongst other things it is determined that Hebrews has 38 direct quotations from the Old Testament, that with the exception of one

SE debt restructuring plan

International Nuclear Information System (INIS)

Janoska, J.

2003-01-01

Slovenske elektrarne, a.s. (SE) plans to restructure one's own debts in 2003-2005. Debt restructuring plan is following: 2003: Collection of pre-payment on electricity - 60 million Euro (2.5 billion Slovak crowns), consumer unknown. Own promissory notes in total value of 100 million US$ (3.5 billion Slovak crowns) - in process. Sale of claims worth 2.4 billion Slovak crowns (57.21 million Euro) - negotiations in process. 2003/2004: Restructuring of loans payable IV. quarter 2003 and at the beginning of 2004 in value of 200 million Euro (8.3 billion Slovak crowns). Aim of SE is a new credit payable within 7 years, with instalments payable in the last two to three without any state subsidies. 2005: Loans worth 460 million Euro (189 billion Slovak crowns) will still remain. SE want to negotiate them with banks without state support

Sample Set (SE): SE47 [Metabolonote[Archive

Lifescience Database Archive (English)

Full Text Available SE47 Metabolomic correlation-network modules in Arabidopsis based on a graph-cluste...as a system. Typical metabolomics data show a few but significant correlations among metabolite levels when ...itions. Although several studies have assessed topologies in metabolomic correlation networks, it remains un... (mto1), and transparent testa4 (tt4) to compare systematically the metabolomic correlation...s in samples of roots and aerial parts. We then applied graph clustering to the constructed correlation

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.

CdSe/ZnSe quantum dot structures grown by molecular beam epitaxy with a CdTe submonolayer stressor

International Nuclear Information System (INIS)

Sedova, I. V.; Lyublinskaya, O. G.; Sorokin, S. V.; Sitnikova, A. A.; Toropov, A. A.; Donatini, F.; Dang, Si Le; Ivanov, S. V.

2007-01-01

A procedure for formation of CdSe quantum dots (QDs) in a ZnSe matrix is suggested. The procedure is based on the introduction of a CdTe submonolayer stressor deposited on the matrix surface just before deposition of the material of the QDs. (For CdTe/ZnSe structure, the relative lattice mismatch is Δa/a ∼ 14%.) The stressor forms small strained islands at the ZnSe surface, thus producing local fields of high elastic stresses controlling the process of the self-assembling of the QDs. According to the data of transmission electron microscopy, this procedure allows a considerable increase in the surface density of QDs, with a certain decrease in their lateral dimensions (down to 4.5 ± 1.5 nm). In the photoluminescence spectra, a noticeable (∼150 meV) shift of the peak to longer wavelengths from the position of the reference CdSe/ZnSe QD structure is observed. The shift is due to some transformation of the morphology of the QDs and an increase in the Cd content in the QDs. Comprehensive studies of the nanostructures by recording and analyzing the excitation spectra of photoluminescence, the time-resolved photoluminescence spectra, and the cathodoluminescence spectra show that the emission spectra involve two types of optical transitions, namely, the type-I transitions in the CdSeTe/ZnSe QDs and the type-II transitions caused mainly by the low cadmium content (Zn,Cd)(Se,Te)/ZnSe layer formed between the QDs

Effective mRNA Inhibition in PANC-1 Cells in Vitro Mediated via an mPEG-SeSe-PEI Delivery System.

Science.gov (United States)

Zhang, Yuefeng; Yang, Bin; Liu, Yajie; Qin, Wenjie; Li, Chao; Wang, Lantian; Zheng, Wen; Wu, Yulian

2016-05-01

RNA interference (RNAi)-mediated gene therapy is a promising approach to cure various diseases. However, developing an effective, safe, specific RNAi delivery system remains a major challenge. In this study, a novel redox-responsive polyetherimide (PEI)-based nanovector, mPEG-SeSe-PEI, was developed and its efficacy evaluated. We prepared three mPEG-SeSe-PEI vector candidates for small interfering glyceraldehyde-3-phosphate dehydrogenase (siGADPH) and determined their physiochemical properties and transfection efficiency using flow cytometry and PEG11.6-SeSe-PEI polymer. We investigated the silencing efficacy of GADPH mRNA expression in PANC-1 cells and observed that PEG11.6-SeSe-PEI/siGADPH (N/P ratio=10) polyplexes possessed the appropriate size and zeta-potential and exhibited excellent in vitro gene silencing effects with the least cytotoxicity in PANC-1 cells. In conclusion, we present PEG11.6-SeSe-PEI as a potential therapeutic gene delivery system for small interfering RNA (siRNA).

Negative ion photoelectron spectroscopy of SeO-

International Nuclear Information System (INIS)

Coe, J.V.; Snodgrass, J.T.; Freidhoff, C.B.; McHugh, K.M.; Bowen, K.H.

1985-01-01

Negative ion photoelectron spectroscopy (NIPES) involves a kinetic energy analysis of electrons which are photodetached when a mass selected beam of negative ions is crossed with a fixed frequency laser beam. The photodetachment spectra of SeO - displays transitions from the X 2 PI state of SeO - to both the X 3 Σ - and a 1 Δ states of SeO. The singlet-triplet splitting of SeO is readily observable since selection rules regarding spin do not apply in the bound to free state process of photodetachment. The electron affinity of SeO and the negative ion potential parameters of SeO - have been determined

Syntheses, structures, and properties of Ag4(Mo2O5)(SeO4)2(SeO3) and Ag2(MoO3)3SeO3

International Nuclear Information System (INIS)

Ling Jie; Albrecht-Schmitt, Thomas E.

2007-01-01

Ag 4 (Mo 2 O 5 )(SeO 4 ) 2 (SeO 3 ) has been synthesized by reacting AgNO 3 , MoO 3 , and selenic acid under mild hydrothermal conditions. The structure of this compound consists of cis-MoO 2 2+ molybdenyl units that are bridged to neighboring molybdenyl moieties by selenate anions and by a bridging oxo anion. These dimeric units are joined by selenite anions to yield zigzag one-dimensional chains that extended down the c-axis. Individual chains are polar with the C 2 distortion of the Mo(VI) octahedra aligning on one side of each chain. However, the overall structure is centrosymmetric because neighboring chains have opposite alignment of the C 2 distortion. Upon heating Ag 4 (Mo 2 O 5 )(SeO 4 ) 2 (SeO 3 ) looses SeO 2 in two distinct steps to yield Ag 2 MoO 4 . Crystallographic data: (193 K; MoKα, λ=0.71073 A): orthorhombic, space group Pbcm, a=5.6557(3), b=15.8904(7), c=15.7938(7) A, V=1419.41(12), Z=4, R(F)=2.72% for 121 parameters with 1829 reflections with I>2σ(I). Ag 2 (MoO 3 ) 3 SeO 3 was synthesized by reacting AgNO 3 with MoO 3 , SeO 2 , and HF under hydrothermal conditions. The structure of Ag 2 (MoO 3 ) 3 SeO 3 consists of three crystallographically unique Mo(VI) centers that are in 2+2+2 coordination environments with two long, two intermediate, and two short bonds. These MoO 6 units are connected to form a molybdenyl ribbon that extends along the c-axis. These ribbons are further connected together through tridentate selenite anions to form two-dimensional layers in the [bc] plane. Crystallographic data: (193 K; MoKα, λ=0.71073 A): monoclinic, space group P2 1 /n, a=7.7034(5), b=11.1485(8), c=12.7500(9) A, β=105.018(1) V=1002.7(2), Z=4, R(F)=3.45% for 164 parameters with 2454 reflections with I>2σ(I). Ag 2 (MoO 3 ) 3 SeO 3 decomposes to Ag 2 Mo 3 O 10 on heating above 550 deg. C. - Graphical abstract: A view of the one-dimensional [(Mo 2 O 5 )(SeO 4 ) 2 (SeO 3 )] 4- chains that extend down the c-axis in the structure of Ag 4 (Mo 2 O 5 )(SeO 4

Edificio de oficinas en Haaga - Helsinki – Finlandia

Directory of Open Access Journals (Sweden)

Heikki Castrén y Cía., Arquitectos

1974-05-01

Full Text Available This building has been constructed to house the head office of the company. It occupies eleven floors above ground and three subterranean ones, in addition to the lift shafts and its machinery tower. Since the lowest level is situated lower than and very close to the sea level a retaining wall has been constructed that is separated from the building by an inspection corridor which in addition isolates it from the possible humidity. Total foundation on the rock; beams and double pillars that allow pipes to be placed inside; mobile layout of partitions, aluminum windows with isolating glass; various airconditioning installations; pneumatic communications, etc. In addition to the premises for which it is actually intended it includes a spacious auditorium, a staff dining room, and a gymnasium with swimmingpool.Este edificio ha sido construido para albergar la sede central de la compañía. Se distribuye en once plantas sobre la rasante y tres subterráneas, además del foso de ascensores y la torre de maquinaria de los mismos. Dado que el nivel inferior se encuentra más bajo que el del mar y muy próximo a éste, se ha creado un muro de contención separado del edificio por un corredor de inspección que, además, lo aísla de las humedades posibles. Cimentación total sobre roca; estructura de hormigón armado; vigas y pilares dobles, que permiten el paso de conductos por su interior; tabiquería móvil; ventanas de aluminio con cristal aislante; toda suerte de instalaciones de acondicionamiento, comunicaciones neumáticas, etc. Además de las dependencias propias del uso a que se destinan, comprende un amplio auditorio, comedor de empleados y gimnasio con piscina.

Pulsed laser deposited heterogeneous mixture of Li2Se-Sb2Se3 nanocomposite as a new storage lithium material

International Nuclear Information System (INIS)

Yu Le; Chen Jie; Fu Zhengwen

2010-01-01

Li 2 Se-Sb 2 Se 3 nanocomposites with a highly heterogeneous mixture have been fabricated by reactive pulsed laser deposition method. The electrochemical properties of the as-deposited Li 2 Se-Sb 2 Se 3 thin film during the first charging and discharging have been investigated by the galvanostatic cycling and cyclic voltammetry measurements for the first time. By using ex situ X-ray diffraction (XRD), X-ray photoelectron spectra (XPS), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and selected-area electron diffraction (SAED) measurements, the decomposition of Li 2 Se driven by Sb 2 Se 3 under the electrochemical potential is revealed. In the first cycle, the oxidation peaks at 2.5 V and 3.2 V and the reduction peaks at 2.0 V can be attributed to the decomposition and formation of Li 2 Se with the conversion reaction of Sb 2 Se 3 into Sb 2 Se 5 . Our findings demonstrate that nanocomposite Li 2 Se-Sb 2 Se 3 can possess very high electrochemical activity. These results present a special case of solid-state heterogeneous electrochemistry with both nanostructured binary materials.

Surface Passivation of CdSe Quantum Dots in All Inorganic Amorphous Solid by Forming Cd1-xZnxSe Shell.

Science.gov (United States)

Xia, Mengling; Liu, Chao; Zhao, Zhiyong; Wang, Jing; Lin, Changgui; Xu, Yinsheng; Heo, Jong; Dai, Shixun; Han, Jianjun; Zhao, Xiujian

2017-02-07

CdSe quantum dots (QDs) doped glasses have been widely investigated for optical filters, LED color converter and other optical emitters. Unlike CdSe QDs in solution, it is difficult to passivate the surface defects of CdSe QDs in glass matrix, which strongly suppress its intrinsic emission. In this study, surface passivation of CdSe quantum dots (QDs) by Cd 1-x Zn x Se shell in silicate glass was reported. An increase in the Se/Cd ratio can lead to the partial passivation of the surface states and appearance of the intrinsic emission of CdSe QDs. Optimizing the heat-treatment condition promotes the incorporation of Zn into CdSe QDs and results in the quenching of the defect emission. Formation of CdSe/Cd 1-x Zn x Se core/graded shell QDs is evidenced by the experimental results of TEM and Raman spectroscopy. Realization of the surface passivation and intrinsic emission of II-VI QDs may facilitate the wide applications of QDs doped all inorganic amorphous materials.

Phase diagrams of novel Tl{sub 4}SnSe{sub 4}–TlSbSe{sub 2}–Tl{sub 2}SnSe{sub 3} quasi-ternary system following DTA and X-ray diffraction

Energy Technology Data Exchange (ETDEWEB)

Barchiy, I.E.; Tatzkar, A.R. [Department of Chemistry, Uzhgorod National University, Pidgirna St., 46, Uzhgorod 88000 (Ukraine); Fedorchuk, A.O. [Department of Inorganic and Organic Chemistry, Lviv National University of Veterinary Medicine and Biotechnologies, Pekarska St., 50, Lviv 79010 (Ukraine); Plucinski, K., E-mail: kpluc2006@wp.pl [Electronics Department, Military University Technology, Warsaw, Kaliskiego 2, Warsaw 00-908 (Poland)

2016-06-25

Phase relation in the Tl{sub 4}SnSe{sub 4}–TlSbSe{sub 2}–Tl{sub 2}SnSe{sub 3} quasiternary system were studied by the DTA and X-ray diffraction in combination with mathematical modeling. The phase diagrams of the Tl{sub 4}SnSe{sub 4}–TlSbSe{sub 2} and Tl{sub 2}SnSe{sub 3}–TlSbSe{sub 2} systems, the perspective views of the phase interaction in the ternary system, the liquidus surface projection, the isothermal section at 423 K were built for the first time. The Tl{sub 4}SnSe{sub 4}–TlSbSe{sub 2}–Tl{sub 2}SnSe{sub 3} system is of the invariant eutectic type and is characterized by the formation of limited solid solutions following initial ternary compounds. New complex compounds are not formed. - Highlights: • Two Tl{sub 4}SnSe{sub 4}–TlSbSe{sub 2},Tl{sub 2}SnSe{sub 3}–TlSbSe{sub 2} systems were explored. • Invariant processes in the ternary system were determined. • New complex compounds were not observed in ternary system.

Two anionically derivatized scandium oxoselenates(IV): ScF[SeO3] and Sc2O2[SeO3

Science.gov (United States)

Greiner, Stefan; Chou, Sheng-Chun; Schleid, Thomas

2017-02-01

Scandium fluoride oxoselenate(IV) ScF[SeO3] and scandium oxide oxoselenate(IV) Sc2O2[SeO3] could be synthesized through solid-state reactions. ScF[SeO3] was obtained phase-pure, by reacting mixtures of Sc2O3, ScF3 and SeO2 (molar ratio: 1:1:3) together with CsBr as fluxing agent in corundum crucibles embedded into evacuated glassy silica ampoules after firing at 700 °C for seven days. Sc2O2[SeO3] first emerged as by-product during the attempts to synthesize ScCl[SeO3] following aforementioned synthesis route and could later be reproduced from appropriate Sc2O3/SeO3 mixtures. ScF[SeO3] crystallizes monoclinically in space group P21/m with a=406.43(2), b =661.09(4), c=632.35(4) pm, β=93.298(3)° and Z=2. Sc2O2[SeO3] also crystallizes in the monoclinic system, but in space group P21/n with a=786.02(6), b=527.98(4), c=1086.11(8) pm, β=108.672(3)° for Z=4. The crystal structures of both compounds are strongly influenced by the stereochemically active lone pairs of the ψ1-tetrahedral [SeO3]2- anions. They also show partial structures, where the derivatizing F- or O2- anions play an important role. For ScF[SeO3] chains of the composition 2+∞ 1[FS c 2 / 2 ] form from connected [FSc2]5+ dumbbells, while [OSc3]7+ pyramids and [OSc4]10+ tetrahedra units are condensed to layers according to 2+ ∞ 2[O2Sc2 ] in Sc2O2[SeO3].

Possibility of using BeMgZnSe as a new cladding material for ZnSe-based blue laser diodes

International Nuclear Information System (INIS)

Kim, D. C.; Choi, J. H.; Yoo, K. H.; Kim, T. W.; Yao, T.

1999-01-01

We calculated the gain and the radiative recombination current density of ZnSe/Be x Mg y Zn 1-x-y Se/Be x Mg y Zn 1-x - y Se separate confinement heterostructure (SCH) laser diodes and compared the results with those for the more popular ZnSe/Zn 1-x Mg x S y Se 1-y /Zn 1-x Mg x S y Se 1-y system. For five different values of the cladding-layer energy gap (E g,c ), we sought the optimum SCH structure that had a minimum threshold current density for both quaternaries, and we compared the corresponding current densities. For the same E g,c , ZnMgSSe was found to have a smaller threshold current density. The threshold current density decreased rapidly with increasing. E g,c in both materials. Therefore, if the available energy gap of the BeMgZnSe cladding is larger than that of ZnMGZnSSe, BeMgZnSe may be the better choice

Cs2UPd3Se6

Directory of Open Access Journals (Sweden)

George N. Oh

2011-02-01

Full Text Available Dicaesium uranium(IV tripalladium(II hexaselenide, Cs2UPd3Se6, crystallizes in the space group Fmmm in the Ba2NaCu3O6 structure type. The asymmetric unit comprises the following atoms with site symmetries as shown: U1 (mm2, Cs1 (222, Cs2 (m2m, Pd1 (.m., Pd2 (2mm, Se1 (m.., and Se2 (1. This layered structure contains six edge-sharing square-planar [PdSe4] units that form a hexagon. These, in turn, edge-share with [USe6] trigonal–prismatic units, forming an extended layer parallel to (010. The layers are stacked along [010]. They are staggered, and are separated by the Cs atoms. The Cs atoms are either coordinated in a square antiprism of Se atoms or are ten-coordinate, with one square face and the opposite face hexagonal.

C-type Nd2Se3

Directory of Open Access Journals (Sweden)

2009-03-01

Full Text Available The title compound, neodymium sesquiselenide, is isotypic with the other known rare-earth metal(III selenides M2Se3 (M = La–Pr and Sm–Lu with the cubic C-type structure. It adopts a cation-defective Th3P4-type arrangement with close to 8/9 of the unique neodymium-cation site occupied, leading to the composition Nd2.667Se4 (Z = 4 or Nd2Se3 (Z = 5.333, respectively. The Nd3+ cations are thus surrounded by eight selenide anions, forming trigonal [NdSe8]13− dodecahedra, whereas the Se2− anions exhibit a sixfold coordination, but due to the under-occupation of neodymium, each one is statistically surrounded by only 5.333 cations. The crystal studied was a merohedral twin with a 0.31 (6:0.69 (6 domain ratio.

Opportunities and challenges for a sustainable energy policy in SE Europe: SE European Energy Community Treaty

International Nuclear Information System (INIS)

Mihajlov, Andjelka

2010-01-01

Energy demand continues to increase in turn raising concerns about energy supply. In this paper, the author has tried to systematize the role of the energy sector in South Eastern (SE) Europe in the context of the European energy policy process. This should make the energy sector in SE Europe more visible and open to substantial activities and appropriate funding. This is important to assure its full alignment with the European energy policy process, and in so doing, make it less fragile. According to the SE European Energy Community Treaty, parties to the Treaty are obliged to implement reforms in the energy and environmental sector in accordance with the European Union's respective policy. This paper raises awareness of the environmental requirements that have been set, of renewable energy and its implementation, at the same time pointing out that the response in SE Europe has been at a low level. It is believed that this paper could draw attention to the existing problems and could contribute to the establishment of a common integrated energy market in SE Europe and the EU. (author)

E-beam irradiation effect on CdSe/ZnSe QD formation by MBE: deep level transient spectroscopy and cathodoluminescence studies

International Nuclear Information System (INIS)

Kozlovsky, V I; Litvinov, V G; Sadofyev, Yu G

2004-01-01

CdSe/ZnSe structures containing 1 or 15 thin (3-5 monolayers) CdSe layers were studied by cathodoluminescence (CL) and deep level transient spectroscopy (DLTS). The DLTS spectra consisted of peaks from deep levels (DLs) and an additional intense peak due to electron emission from the ground quantized level in the CdSe layers. Activation energy of this additional peak correlated with an energy of the CdSe-layer emission line in the CL spectra. Electron-beam irradiation of the structure during the growth process was found to influence the DLTS and CL spectra of the CdSe layers, shifting the CdSe-layer emission line to the long-wave side. The obtained results are explained using the assumption that e-beam irradiation stimulates the formation of quantum dots of various sizes in the CdSe layers

¿ Como se hace una Telenovela ?

Directory of Open Access Journals (Sweden)

Iván Gavaldón

2015-01-01

Full Text Available La autora relata la historia de las Relaciones Públicas y dice que surgieron y se desarrollaron para legitimar ante el público los intereses económicos y políticos de quienes detentan el poder. Se cuestiona sobre el por qué no aplicar las relaciones públicas, en organizaciones populares, para que mejoren su publicación y orienten sus propósitos de desarrollo. El tema que aborda las Políticas culturales en América Latina acopia un extracto de lo más trascendente de los ensayos del libro editado por Néstor García Canclini. Sobre la telenovela se afirma que esta ha llegado a ser uno de los instrumentos más importantes de la comunicación popular: por ella desfilan las identidades de las más variadas culturas brasileñas. Y en cuanto a la caricatura se relata lo que ocurrió en el Seminario taller " Caricatura y Periodismo", realizado el(9-11 de Nov.- 1987 en el CIESPAL. El estudio sobre el mercado del vídeo se ve dificultado por la imprecisión de los datos obtenidos. Los datos oficiales no siempre se aproximan a la realidad, pues el mercado de vídeo se instauró en América Latina partiendo de una lógica totalmente diversa de los equipos de sonido e imagen.

Facile fabrication of CNTs@C@MoSe2@Se hybrids with amorphous structure for high performance anode in lithium-ion batteries.

Science.gov (United States)

Jin, Rencheng; Cui, Yuming; Wang, Qingyao; Li, Guihua

2017-12-15

Amorphous MoSe 2 and Se anchored on amorphous carbon coated multiwalled carbon nanotubes (CNTs@C@MoSe 2 @Se) have been synthesized by a facile solvothermal strategy. The one dimensional CNTs@C@MoSe 2 @Se can effectively buffer the volume variation, prohibit the aggregation and facilitate electron and ion transport throughout the electrode. Furthermore, the combination of MoSe 2 and Se also provides buffer spaces for the volumetric change during cycling. Thus, the obtained CNTs@C@MoSe 2 @Se hybrids display the enhanced cycle stability and excellent high rate capacity. The reversible capacity of 1010mAhg -1 can be achieved after 100 cycles at the current density of 0.1Ag -1 . Even after 500 cycles, a reversible capacity of 508mAhg -1 is still retained at 5Ag -1 . Copyright © 2017 Elsevier Inc. All rights reserved.

PbSe Quantum Well VECSEL on Si

Science.gov (United States)

Fill, M.; Khiar, A.; Rahim, M.; Felder, F.; Zogg, H.

2011-12-01

Vertical external cavity surface emitting lasers in the wavelength region from 3-5 μm are presented. They are based on PbSe quantum wells grown on Si substrates. As host material Pb1-xEuxSe and Pb1-xSrxSe are used. With Pb1-xSrxSe as host material maximum operation temperatures of 325 K are achieved, while with Pb1-xEuxSe an operation temperature of 245 K could not be overcome. This may be explained by a band alignment transition from type I to type II with increasing temperature.

Investigation of short and ballistic coupling in vertical NbSe2 - graphene - NbSe2 Josephson junctions

Science.gov (United States)

Kim, Minsoo; Park, Geon-Hyoung; Yi, Jongyoon; Lee, Jae Hyeong; Park, Jinho; Lee, Hu-Jong

2H-NbSe2 is a layered two-dimensional superconducting material, which can be constructed into a van der Waals heterostructure with versatile functionality. Here we fabricated a vertically stacked NbSe2 - graphene - NbSe2 heterostructure by the dry transfer technique, where defect-free contact via van der Waals force provides the high interfacial transparency. Insertion of an atomically thin graphene layer between two NbSe2 flakes ensures the formation of highly coherent proximity Josephson coupling. Observed temperature dependence of the junction critical current (Ic) and large value of IcRn product (as large as 2.3ΔNbSe 2) reveal the short and ballistic Josephson coupling characteristics. Large junction critical current density of 104 A/cm2, multiple Andreev reflection in the subgap structure of the differential conductance, and magnetic field modulation of Ic also suggest the strong Josephson coupling via the graphene layer.

PHEIFFER SE TAALPOLITIEK JC Steyn

African Journals Online (AJOL)

sigself maak tog nie Chomsky se teorie oor n aangebore taalaanleg en die konsekwensie daarvan nl. dat elke taal opgebou moet wees volgens dieselfde grondprinsipes, ongeldig nie? Taalpolitieke oortuigingskrag het hierdie argument nog minder. Sal jy in alle erns vir mense kan se: "Ons moet aanhou om die taal te praat ...

Assessing the anticancer compounds Se-methylselenocysteine and glucosinolates in Se-biofortified broccoli (brassica oleracea L. var. italica) sprouts and florets

Science.gov (United States)

Broccoli (Brassica oleracea L. var. italica) is a rich source of chemopreventive compounds. Here, we evaluated and compared the effect of selenium (Se) treatment on the accumulation of anticancer compound Se-methylselenocysteine (SeMSCys) and glucosinolates in broccoli sprouts and florets. Total Se ...

The effects of staggered bandgap in the InP/CdSe and CdSe/InP core/shell quantum dots.

Science.gov (United States)

Kim, Sunghoon; Park, Jaehyun; Kim, Sungwoo; Jung, Won; Sung, Jaeyoung; Kim, Sang-Wook

2010-06-15

New type-II structures of CdSe/InP and InP/CdSe core-shell nanocrystals which have staggered bandgap alignment were fabricated. Using a simple model for the wave function for electrons and holes in InP/CdSe and CdSe/InP core/shell nanocrystals showed the wave function of the electron and hole spread into the shell, respectively. The probability density of the InP/CdSe and CdSe/InP core/shell QDs also showed a similar tendency. As a result, the structure exhibits increased delocalization of electrons and holes, leading to a red-shift in absorption and emission. Quantum yield increased in the InP/CdSe, however decreased in the CdSe/InP. The reason may be due to the surface trap and high activation barrier for de-trapping in the InP shell. 2010 Elsevier Inc. All rights reserved.

Glass forming tendencies of chalcogenides of the system (As2Se3)sub(1-x):(T12Se)sub(x)

International Nuclear Information System (INIS)

Majid, C.A.

1982-07-01

In this paper glass forming capabilities of chalcogenide glasses based on As 2 Se 3 with T1 2 Se concentrations are discussed. The studies were made using the differential thermal analysis (DTA) technique. These studies show that the glass forming tendency of As 2 Se 3 decreases as the concentrations of T1 2 Se molecules are increased. Also these studies show that with addition of T1 2 Se, the glass transition temperature Tsub(g) of As 2 Se 3 decreases, suggesting a tendency for weaker bonding and hence less stability of T1-rich compositions. (author)

Synthesis of dextran/Se nanocomposites for nanomedicine application

International Nuclear Information System (INIS)

Shen Yuhua; Wang Xiufang; Xie Anjian; Huang Lachun; Zhu Jinmiao; Chen Long

2008-01-01

In this study, spherical Se nanoparticles were prepared by the reduction of aqueous selenious acid with ice bath through a simple, conventional, and one-step method without the aid of any surfactant, or template. The nanoparticles were characterized by transmission electron microscopy (TEM), photon correlation spectroscopy (PCS), X-ray powder diffraction (XRD), Ultraviolet-visible spectroscopy (UV-vis), Zeta potential, respectively. The results show the Se nanoparticles have good particle dispersion with the average diameters of 36 nm and are amorphous (α-Se). Tablets A and B containing dextran and Se nanoparticles were synthesized with different preparation methods. Se nanoparticles studded equably in the interior and the surface of the tablets, and there are strong interactions between Se and dextran. The release of Se from tablets is investigated in the simulated gastric and intestinal conditions. It is found that the pH environment and different synthetical methods have significant influence on the release rate of Se. The release mechanism of Se nanoparticles is also discussed. The nanocomposites can be applied in controlled releasing of Se nanomedicine

Molecular structure of virgin and Tg cycled (Ag2Se)x (AsSe)1-x bulk glasses

Science.gov (United States)

Wachtman, Jacob; Chen, Ping; Boochand, P.

2009-03-01

AsSe, the base glass (x = 0) in the titled ternary, is an interesting example of a chalcogenide that is partially de-mixed into As4Se4 molecules segregated from a connected AsSe network, with the latter determining glass network properties. Raman scattering reveals sharp modes of the Realgar molecules that are superimposed on broad modes coming from of the backbone. Upon Tg cycling virgin samples (as quenched melts), the concentration of de-mixed As4Se4 molecules decreases, suggesting that thermally induced polymerization occurs; molecules break up to form part of the connective tissue. Modulated DSC experiments reveal a broad exotherm near 140 ^oC in virgin samples, which becomes nearly extinct in Tg cycled samples. The exotherm may represent Realgar molecules nano-crystallizing as the temperature approaches Tg. Compositional trends in thermal parameters such as Tg(x), δCp(x), and the δHnr(x) as a function of Ag2Se content `x' of the glasses will be reported.

Autismos que se 'curan'

OpenAIRE

Artigas, Josep, 1948-; Paula Pérez, Isabel, 1970-

2016-01-01

Introducción. La investigación sobre el autismo, basada principalmente en el modelo categórico del Manual diagnóstico y estadístico de los trastornos mentales, se ha centrado de forma preferente en la epidemiología, las manifestaciones clínicas, los mecanismos cognitivos y los determinantes biológicos y ambientales; sin embargo, se ha prestado escaso interés a las trayectorias evolutivas, las cuales son decisivas de cara al pronóstico a medio y largo plazo. Objetivo. Revisar el curso evolutiv...

Cs[FeSe{sub 2}], Cs{sub 3}[FeSe{sub 2}]{sub 2}, and Cs{sub 7}[Fe{sub 4}Se{sub 8}]. Missing links of known chalcogenido ferrate series

Energy Technology Data Exchange (ETDEWEB)

Stueble, Pirmin; Roehr, Caroline [Institut fuer Anorganische und Analytische Chemie, Universitaet Freiburg (Germany)

2017-11-17

The three cesium selenido ferrate title compounds with an Se:Fe ratio of 2:1 were synthesized from stoichiometric samples reacting elemental Cs either (A) with Fe and Se in a double-crucible setup (Cs[FeSe{sub 2}], Cs{sub 3}[FeSe{sub 2}]{sub 2}) or (B) with previously prepared FeSe{sub 2} (Cs{sub 3}[FeSe{sub 2}]{sub 2}, Cs{sub 7}[Fe{sub 4}S{sub 8}]) (T{sub max} = 800-1000 C). The pure Fe{sup III} ferrate Cs[FeSe{sub 2}] crystallizes in the Tl[FeSe{sub 2}] type [monoclinic, space group C2/m, a = 1392.95(10), b = 564.43(3), c = 737.44(6) pm, β = 119.163(5) , Z = 4, R{sub 1} = 0.0550]. It is thus not isotypic to all other alkali ferrates(III) A[FeS{sub 2}] and A[FeSe{sub 2}] containing chains of edge-sharing tetrahedra, but crystallizes in a t2 subgroup of the Immm structure of Cs[FeS{sub 2}]. The mixed-valent chain compound Cs{sub 3}[FeSe{sub 2}]{sub 2} is isotypic to its sulfido analogue [orthorhombic, space group Pnma, a = 777.88(6), b = 1151.02(6), c = 1341.61(7) pm, Z = 4, R{sub 1} = 0.0470]. In contrast to the isopunctal Na{sub 3}[FeSe{sub 2}]{sub 2} type K/Rb compounds the chains are only slightly corrugated. The monoclinic, likewise mixed-valent Fe{sup II/III} selenido ferrate Cs{sub 7}[Fe{sub 4}Se{sub 8}] [monoclinic, space group C2/c, a = 1953.79(10), b = 879.71(5), c = 1717.03(10) pm, β = 117.890(2) , Z = 4, R{sub 1} = 0.0816] is isostructural both to the cesium sulfido and tellurido compound. The structure contains oligomeric moieties of four edge sharing [FeSe{sub 4}] tetrahedra forming slightly distorted tetrahedral clusters [Fe{sub 4}Se{sub 8}]{sup 7-}, which are surrounded by a cube of 26 Cs cations. Based on a structure map, the crystal chemistry of the three title compounds is discussed together with all chain/cluster ferrates of the general series A{sub 1+x}[Fe{sup III}{sub 1-x}Fe{sup II}{sub x}Q{sub 2}] (x = 0-1; A = Na, K, Rb, Cs; Q = S, Se, Te). (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

A simple and facile synthesis of MPA capped CdSe and CdSe/CdS core/shell nanoparticles

Science.gov (United States)

Sukanya, D.; Sagayaraj, P.

2015-06-01

II-VI semiconductor nanostructures, in particular, CdSe quantum dots have drawn a lot of attention because of their promising potential applications in biological tagging, photovoltaic, display devices etc. due to their excellent optical properties, high emission quantum yield, size dependent emission wavelength and high photostability. In this paper, we describe the synthesis and properties of mercaptopropionic acid capped CdSe and CdSe/CdS nanoparticles through a simple and efficient co-precipitation method followed by hydrothermal treatment. The growth process, characterization and the optical absorption as a function of wavelength for the synthesized MPA capped CdSe and CdSe/CdS nanoparticles have been determined using X-ray diffraction study (XRD), Ultraviolet-Visible spectroscopy (UV-Vis), Fourier transform infrared spectroscopy (FT-IR) and High Resolution Transmission Electron Microscopy (HRTEM).

A simple and facile synthesis of MPA capped CdSe and CdSe/CdS core/shell nanoparticles

International Nuclear Information System (INIS)

Sukanya, D.; Sagayaraj, P.

2015-01-01

II-VI semiconductor nanostructures, in particular, CdSe quantum dots have drawn a lot of attention because of their promising potential applications in biological tagging, photovoltaic, display devices etc. due to their excellent optical properties, high emission quantum yield, size dependent emission wavelength and high photostability. In this paper, we describe the synthesis and properties of mercaptopropionic acid capped CdSe and CdSe/CdS nanoparticles through a simple and efficient co-precipitation method followed by hydrothermal treatment. The growth process, characterization and the optical absorption as a function of wavelength for the synthesized MPA capped CdSe and CdSe/CdS nanoparticles have been determined using X-ray diffraction study (XRD), Ultraviolet-Visible spectroscopy (UV-Vis), Fourier transform infrared spectroscopy (FT-IR) and High Resolution Transmission Electron Microscopy (HRTEM)

Como Perseu se defendeu de Medusa?

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Rose Lumertz de Freitas

2012-04-01

Full Text Available Na psicanálise francesa, principalmente com Lacan, o conceito de falta passou a ser de grande importância. Ao que, então, perguntamos: o que é a falta? E quando esta falta? O que acontece? O que acontece quando o não especularizável não está excluído, se fazendo, assim, especular? Quando Perseu vai ao encontro de Medusa, guiando-se por sua imagem refletida em um espelho de bronze polido, segurado por Atena, como pôde este herói defender-se de Medusa? Qual foi a forma encontrada por ele para se defender da presença do objeto que introduz a dimensão do real nu?

Comparing the influence of selenite (Se4+) and selenate (Se6+) on the inhibition of the mercury (Hg) phytotoxicity to pak choi.

Science.gov (United States)

Tran, Thi Anh Thu; Dinh, Quang Toan; Cui, Zeiwei; Huang, Jie; Wang, Dan; Wei, Tianjiao; Liang, Dongli; Sun, Xin; Ning, Ping

2018-01-01

Selenite (Se (IV)) and selenate (Se (IV)) have recently been demonstrated to be equally effective in inhibiting mercury (Hg) phytotoxicity to plants. This assertion is still unclear. In this study, we aimed to explore the potential effects of Se species (Se 4+ and Se 6+ ) on the inhibition of the mercury (Hg) bioavailability to pak choi in dry land. Pot experiments with exposure to different dosages of mercuric chloride (HgCl 2 ) and selenite (Na 2 SeO 3 ) or selenate (Na 2 SeO 4 ) were treated. To compare the influence of Se (IV) and Se (VI) on the bioaccumulation and bioavailability of Hg, the levels of total Hg in different pak choi (Brassica chinensis L.) tissues (roots and shoots) and the distribution changes of Hg fractions in soil before planting and after harvest were determined as well as the Hg I R values in soils (relative binding intensity) were analyzed. Results showed that application Se (IV) reduced the concentrations of Hg in pak choi roots more than Se (VI). Hg concentrations were also decreased in pak choi shoots in Se (IV) treatments, while which notably increased in Se (VI) treatments. Thus, Se (IV) plays a more important role than Se (VI) in limiting the absorption and bioaccumulation of Hg in pak choi. Moreover, this inhibition may only significantly occur when Se (IV) is at an appropriate level (2.5mg/kg). In addition, the good correlations between the proportions of mobile Hg fractions (soluble and exchangeable fractions), I R values with the Hg concentrations in plants were observed. This affirmed the importance of the Hg fractions transformation and the I R indicator of Hg in the assessment of their bioavailability. Our findings regarding the importance of Se (IV) influence in reducing Hg bioaccumulation not only provided the correct appraisal about the effect of Se species on the inhibition of the Hg phytotoxicity to pak choi in dry land, but also be a good reference for selecting Se fertilizer forms (Se 4+ or Se 6+ ). Copyright © 2017

Surface half-metallicity of half-Heusler compound FeCrSe and interface half-metallicity of FeCrSe/GaP

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Khalaf Al-zyadi, Jabbar M., E-mail: jabbar_alzyadi@yahoo.com [Department of Physics, College of Education for Pure Sciences, University of Basrah (Iraq); Jolan, Mudhahir H. [Department of Physics, College of Education for Pure Sciences, University of Basrah (Iraq); Yao, Kai-Lun, E-mail: klyao@mail.hust.edu.cn [School of Physics and Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, Wuhan 430074 (China); International Center of Materials Physics, Chinese Academy of Sciences, Shenyang 110015 (China)

2016-04-01

Recent studies showed that half-Heusler FeCrSe exhibits half-metallic ferromagnetism (Huang et al. [20]). In this paper, we investigate extensively the electronic, magnetic, and half-metallic properties of the half-Heusler alloy FeCrSe (111) and (001) surfaces and the interface with GaP (111) substrate by using the first-principles calculations within the density functional theory. The atomic density of states demonstrates that the half-me tallicity verified in the bulk FeCrSe is maintained at the CrSe-terminated (001) and Se-terminated (111) surfaces, but lost at both Cr- and Fe-terminated (111) surfaces and the Fe-terminated (001) surface. Alternatively, for the interface of FeCrSe/GaP (111), the bulk half-metallicity is destroyed at Se–P configuration while Se–Ga interface and subinterface show nearly 100% spin polarization. Moreover, the calculated interfacial adhesion energies exhibit that Se–Ga shape is more stable than the Se–P one. The calculated magnetic moments of Se, Ga at the Se–Ga (111) interface and P at the Se–P (111) interface increase with respect to the corresponding bulk values while the atomic magnetic moment of Se atom at the Se–P (111) interface decreases. We also notice that the magnetic moments of subinterface Fe at both Se–Ga and Se–P (111) interfaces decrease compared to the bulk values. - Highlights: • The half-metallicity verified in the bulk FeCrSe is kept at the CrSe-terminated (001) and Se-terminated (111) surfaces. • The calculated interfacial adhesion energies exhibit that Se–Ga shape is more stable than Se–P. • The magnetic moments of Se, Ga and P atoms at the interface increase. • The Se–Ga interface shows nearly 100% spin polarization.

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.

Li diffusion in NbSe/sub 2/ and Ag/sub 0.25/NbSe/sub 2/ single crystals

International Nuclear Information System (INIS)

Folinsbee, J.T.; Simpson, A.M.; Jericho, M.H.

1986-01-01

Measurements are reported of the diffusion of Lithium into NbSe/sub 2/ and into NbSe/sub 2/ preintercalated with silver. Diffusion parallel to the layers is found to be at least 2 orders of magnitude greater than perpendicular to the layers, but not to be greatly affected by the presence of intercalated silver. The activation energy for Li hopping in NbSe/sub 2/ is estimated to be 520 meV. The staging structure of Ag/sub x/NbSe/sub 2/ is also reported. These results have implications for the characterization of cathode materials in intercalation batteries

Luminescence of nanocrystalline ZnSe:Mn2+

NARCIS (Netherlands)

Suyver, J.F.; Wuister, S.F.; Kelly, J.J.; Meijerink, A.

2000-01-01

The luminescence properties of nanocrystalline ZnSe:Mn^(2+) prepared via an inorganic chemical synthesis are described. Photoluminescence spectra show distinct ZnSe and Mn^(2+) related emissions, both of which are excited via the ZnSe host lattice. The Mn^(2+) emission wavelength and the

The Influence of Interfaces on Properties of Thin-Film Inorganic Structural Isomers Containing SnSe-NbSe2 Subunits.

Science.gov (United States)

Alemayehu, Matti B; Falmbigl, Matthias; Ta, Kim; Johnson, David C

2015-04-28

Inorganic isomers ([SnSe]1+δ)m(NbSe2)n([SnSe]1+δ)p(NbSe2)q([SnSe]1+δ)r(NbSe2)s where m, n, p, q, r, and s are integers and m + p + r = n + q + s = 4 were prepared using the modulated elemental reactant technique. This series of all six possible isomers provides an opportunity to study the influence of interface density on properties while maintaining the same unit cell size and composition. As expected, all six compounds were observed to have the same atomic compositions and an almost constant c-axis lattice parameter of ≈4.90(5) nm, with a slight trend in the c-axis lattice parameter correlated with the different number of interfaces in the isomers: two, four and six. The structures of the constituents in the ab-plane were independent of one another, confirming the nonepitaxial relationship between them. The temperature dependent electrical resistivities revealed metallic behavior for all the six compounds. Surprisingly, the electrical resistivity at room temperature decreases with increasing number of interfaces. Hall measurements suggest this results from changes in carrier concentration, which increases with increasing thickness of the thickest SnSe block in the isomer. Carrier mobility scales with the thickness of the thickest NbSe2 block due to increased interfacial scattering as the NbSe2 blocks become thinner. The observed behavior suggests that the two constituents serve different purposes with respect to electrical transport. SnSe acts as a charge donor and NbSe2 acts as the charge transport layer. This separation of function suggests that such heterostructures can be designed to optimize performance through choice of constituent, layer thickness, and layer sequence. A simplistic model, which predicts the properties of the complex isomers from a weighted sum of the properties of building blocks, was developed. A theoretical model is needed to predict the optimal compound for specific properties among the many potential compounds that can be prepared.

Removal of selenite by zero-valent iron combined with ultrasound: Se(IV) concentration changes, Se(VI) generation, and reaction mechanism.

Science.gov (United States)

Fu, Fenglian; Lu, Jianwei; Cheng, Zihang; Tang, Bing

2016-03-01

In this paper, the performance and application of zero-valent iron (ZVI) assisted by ultrasonic irradiation for the removal of selenite (Se(IV)) in wastewater was evaluated and reaction mechanism of Se(IV) with ZVI in such systems was investigated. A series of batch experiments were conducted to determine the effects of ultrasound power, pH, ZVI concentration, N2 and air on Se(IV) removal. ZVI before and after reaction with Se(IV) was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Results indicated that ultrasound can lead to a significant synergy in the removal of Se(IV) by ZVI because ultrasound can promote the generation of OH and accelerate the advanced Fenton process. The primary reaction products of ZVI and Se(IV) were Se(0), ferrihydrite, and Fe2O3. Copyright © 2015 Elsevier B.V. All rights reserved.

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)

SE-72/AS-72 generator system based on Se extraction/ As reextraction

Science.gov (United States)

Fassbender, Michael Ernst; Ballard, Beau D

2013-09-10

The preparation of a .sup.72Se/.sup.72As radioisotope generator involves forming an acidic aqueous solution of an irradiated alkali bromide target such as a NaBr target, oxidizing soluble bromide in the solution to elemental bromine, removing the elemental bromine, evaporating the resulting solution to a residue, removing hydrogen chloride from the residue, forming an acidic aqueous solution of the residue, adding a chelator that selectively forms a chelation complex with selenium, and extracting the chelation complex from the acidic aqueous solution into an organic phase. As the .sup.72Se generates .sup.72As in the organic phase, the .sup.72As may be extracted repeatedly from the organic phase with an aqueous acid solution.

¿Como se hace publicidad por internet?

Directory of Open Access Journals (Sweden)

Franz Del Pozo

2015-01-01

Full Text Available Internet es el medio de comunicación y venta con el mayor potencial de crecimiento y efectividad al más bajo precio. Para vender se usan tarjetas de crédito, depósitos bancarios, franqueo, comercio electrónico. Explica qué y cómo se hace publicidad por Internet. La Red se usa para difundir y para vender y hay la posibilidad de hacer algo diferente a más de llegar directamente al público objetivo se interactúa con él.

Different effect of quenching temperature on Fe1+σTe0.5Se0.5 and β-FeSe

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Zhongnan Guo

2015-02-01

Full Text Available In this work, we have demonstrated a different effect on Fe1+σTe0.5Se0.5 and β-FeSe by changing the quenching temperature. Tc is clearly reduced in Fe1+σTe0.5Se0.5 after increasing the quenching temperature from 300 °C to 500 °C, while that of β-FeSe is almost unchanged. Structure refinement indicates that after quenched at 500 °C, FeTe4 tetrahedron exhibits an expansion with the stretched Fe-Te bond, together with the increased amount of interstitial iron. These particular changes on structure are believed to be responsible for the suppression of superconductivity in Fe1+σTe0.5Se0.5.

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.

Laser-induced luminescence of multilayer structures based on polyimides and CdSe and CdSe/ZnS nanocrystals

International Nuclear Information System (INIS)

Chistyakov, A A; Dayneko, S V; Zakharchenko, K V; Kolesnikov, V A; Tedoradze, M G; Mochalov, K E; Oleinikov, V A

2009-01-01

Laser-induced luminescence of multilayer structures based on the solids of CdSe and CdSe/ZnS nanocrystals, different organic semiconductors and on the layers of organic semiconductors with embedded nanocrystals has been investigated. Drastic decrease of luminescence quantum yield is observed in the films of CdSe nanocrystals on organic semiconductors compared to those on optical glasses. The luminescence of the nanocrystals in the matrices of organic semiconductors and in multilayer structures is shown to be suppressed. The effects observed are explained by the transfer of photogenerated carriers from the nanocrystals to the molecules of organic semiconductors. The presence of the charge transfer is confirmed by a drastic increase in the conductivity (by 2 – 4 orders of magnitude) and in photovoltaic effect at the presence of CdSe and CdSe/ZnS nanocrystals in the structures under investigation. The prospects of using the multilayer structures for development new materials for solar cells are discussed

The MgSeO4-UO2SeO4-H2O system at 25 deg C

International Nuclear Information System (INIS)

Serezhkina, L.B.; Serezhkin, V.N.

1984-01-01

The method of isothermal solubility at 25 deg C has been used to study MgSeO 4 -UO 2 SeO 4 -H 2 O system. Formation of the new compound Mg 2 (UO 2 ) 3 (SeO 4 ) 5 X32H 2 O, congruently soluble in water is stated. Thermographic and X-ray diffraction investigations of the prepared magnesium selenato-uranylate and products of its dehydration are conducted

Local structure and defect chemistry of [(SnSe)1.15]m(TaSe2) ferecrystals – A new type of layered intergrowth compound

International Nuclear Information System (INIS)

Grosse, Corinna; Atkins, Ryan; Kirmse, Holm; Mogilatenko, Anna; Neumann, Wolfgang; Johnson, David C.

2013-01-01

Highlights: •The crystal structure of [(SnSe) 1.15 ] m (TaSe 2 ) ferecrystals was analyzed by TEM. •The layers exhibit turbostratic disorder, but we also observed a local ordering. •The structures of the SnSe and TaSe 2 layers are similar to binary SnSe and 2H-TaSe 2 . •An increasing in-plane SnSe grain size with increasing m was observed. •Defect areas with missing, substituted or additional layers were found. -- Abstract: The atomic structure of the family of ferecrystals [(SnSe) 1.15 ] m (TaSe 2 ) (m = 1, 3, and 6) was investigated by means of transmission electron microscopy. The tantalum in the TaSe 2 layers was observed to have trigonal prismatic coordination similar to that found in the 2H polytype of bulk TaSe 2 . The structure of the SnSe constituent was found to be similar to that of orthorhombic α-SnSe. In the compounds with m = 1 and m = 3, regions with a local ordering of the layers along a commensurate axis, similar to the ordering in conventional misfit layer compounds, were observed. However, on a longer range the ferecrystals were found to exhibit a turbostratically disordered structure. Stacking defects were occasionally found in the samples in which a layer is interrupted and the surrounding layers are bent around these defects, while maintaining abrupt interfaces instead of interdiffusing. Volume defects were found in one sample of [(SnSe) 1.15 ] 1 (TaSe 2 ) 1 in which a SnSe layer locally substitutes a part of a TaSe 2 layer without interrupting the surrounding layers

Validación de un cuestionario de contexto para evaluar sistemas educativos con Modelos de Ecuaciones Estructurales. [Validation of a context questionnaire for the evaluation of educational systems with Structural Equations Modeling].

Directory of Open Access Journals (Sweden)

González-Montesinos, Manuel-Jorge

2010-12-01

Full Text Available This work shows the use of Structural Equations Modeling (SEM methodology to validate the conceptual structure of context questionnaires employed in national and international studies that evaluate the educational achievement of students. Unfortunately, evaluation agencies do not assign the same amount of technical resources to context questionnaires as those allotted to achievement tests, consequently the former are rarely subject to validity studies. In order to show the use of SEM methodology, a questionnaire was selected, which was employed by the National Institute for the Evaluation of Education to investigate the background factors associated with educational achievement of elementary school students in the third grade. It was administered to a national representative sample of 55,312 students. This questionnaire is analyzed according to SEM procedures of confirmatory factor analysis (CFA. The obtained results provide evidence for the constructive validity of this tool. Este trabajo tiene el propósito de mostrar el uso de la metodología de Modelos de Ecuaciones Estructurales (SEM para validar la estructura conceptual de cuestionarios de contexto que se utilizan en los estudios nacionales e internacionales para evaluar el logro educativo de los escolares. Desgraciadamente, los organismos evaluadores no destinan los mismos recursos técnicos a los cuestionarios de contexto que a las pruebas de aprendizaje, por lo que rara vez los primeros son sujetos a estudios de validez. Para mostrar el uso de la metodología SEM, se seleccionó el cuestionario dirigido a alumnos que utilizó el Instituto Nacional para la Evaluación de la Educación (INEE para conocer los factores de contexto asociados el logro educativo de los estudiantes de tercero de primaria, el que se aplicó a una muestra representativa nacional de 55, 312 alumnos. A dicho instrumento se le aplican los supuestos y procedimientos del análisis factorial confirmatorio (AFC y se

Diagnóstico de la inserción de la ética en la carrera de medicina en Brasil

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M.R.C.G. Novaes

Full Text Available Objetivo. Realizar el diagnóstico sobre la inserción de temas relacionados con la ética en cursos de pregrado de medicina en Brasil. Materiales y métodos. Estudio de corte transversal, retrospectivo histórico y exploratorio descriptivo. Se analizaron proyectos pedagógicos de 175 escuelas de Brasil. Se realizó una búsqueda activa en los documentos a través del análisis de aparición de términos con base en indexadores DeCS/MeSH. Los datos se correlacionaron con las informaciones relativas a los modelos pedagógicos de aprendizaje utilizados: metodologías activas (discusiones tutoriales en pequeños grupos y proyecto pedagógico integrado en módulos/ejes o metodologías tradicionales (clases expositivas para grupo numeroso y proyecto pedagógico separado por disciplinas, y se realizaron los siguientes análisis: frecuencia de la inserción de temas agrupados y carga horaria media semestral de estos temas. Resultados. En los currículos analizados se observó que 95 cursos de pregrado en medicina utilizaban metodologías tradicionales de aprendizaje. Los temas agrupados más frecuentes fueron: ética médica; conducta profesional; deontología médica; procedimientos éticos; teología, filosofía, sociología y humanismo; ética en investigación; bioética en salud colectiva; y donación, muerte y eutanasia. La prueba de correlación de Spearman entre la presencia de metodologías activas y tradicionales fue Ps = 0,814 (α = 0,014; IC 95%. Conclusión. Más del 80% de escuelas con metodología activa presentan una carga horaria sobre ética de 50-100 h, mientras que más del 60% de escuelas con metodología tradicional destinan una carga horaria inferior a 50 h para estos temas.

Análisis de la tecnología local de producción de frijol caraota (Phaseolus vulgaris L. en la zona de vega del rio Arauca Local technology analysis of black bean production (Phaseolus vulgaris L. in area shore of the Arauca river

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Valderrama N. Yhovana

1997-12-01

Full Text Available El cultivo del fríjol negro o caraota constituye un importante renglón agrícola de impacto económico y social en el municipio de Arauquita (Arauca, donde cerca de 500 hectáreas se destinan para su siembra en los mesessecos de Octubre y Noviembre. En este municipio la caraota es un cultivo tradicional, en el cual se emplea poca tecnología y existe poca investigación. El producto se comercializa, principalmente, en Venezuela donde existe una alta demanda. Para analizar la Tecnología Local de Producción (TLP, se realizaron encuestas entre agricultores representativos en diferentes veredas del municipio de Arauquita, encontrándose que es un cultivo en donde la mano de obra es contratada con personal de la región y cuyas labores se resumen en: siembra"a chuzo" sobre terrenos previamente quemados, el control de malezas, y finalmente cosecha y beneficio.
En la cadena de comercialización entre Colombia y Venezuela existen por lo menos 7 pasos entre el productor y el consumidor final.
The black bean crop is an important economic and social activity in Arauquita (east of Colombia. In thal region, about 500 hectares are devoted to planting seeds in dry months (October-November. This is a traditional crop, wich used not much technology and there is little research. The product is marketed mainly in Venezuela, where it has high demando This study was carried out making surveys to representative farmers on the region. In the black bean crop the farms work are contracted with personal of the region and its agricultural practices in summary are: burn of the vegetation, sowing, wich is done to random hill ("chuzo", putting several seeds by hill. Except the control of weeds, no fitosanitary control is done, isn't fertilized and its harvest and thresh are manual. Marketing between Colombia and Venezuela has at least seven steps from the producer to final costumer.

Composition-controlled optical properties of colloidal CdSe quantum dots

Energy Technology Data Exchange (ETDEWEB)

Ayele, Delele Worku [Department of Chemical Engineering, National Taiwan University of Science and Technology, Taipei 106, Taiwan (China); Department of Chemistry, Bahir Dar University, Bahir Dar (Ethiopia); Su, Wei-Nien, E-mail: wsu@mail.ntust.edu.tw [Graduate Institute of Applied Science and Technology, National Taiwan University of Science and Technology, Taipei 106, Taiwan (China); Chou, Hung-Lung [Graduate Institute of Applied Science and Technology, National Taiwan University of Science and Technology, Taipei 106, Taiwan (China); Pan, Chun-Jern [Department of Chemical Engineering, National Taiwan University of Science and Technology, Taipei 106, Taiwan (China); Hwang, Bing-Joe, E-mail: bjh@mail.ntust.edu.tw [Department of Chemical Engineering, National Taiwan University of Science and Technology, Taipei 106, Taiwan (China); National Synchrotron Radiation Research Center, Hsinchu 300, Taiwan (China)

2014-12-15

Graphical abstract: - Highlights: • The surface of CdSe QDs are modified with cadmium followed by selenium. • The optical properties of CdSe QDs can be controlled by manipulating the composition. • Surface compositional change affects the surface defects or traps and recombination. • The surface trapping state can be controlled by tuning the surface composition. • A change in composition shows a change in the carrier life time. - Abstract: A strategy with respect to band gap engineering by controlling the composition of CdSe quantum dots (QDs) is reported. After the CdSe QDs are prepared, their compositions can be effectively manipulated from 1:1 (Cd:Se) CdSe QDs to Cd-rich and then to Se-rich QDs. To obtain Cd-rich CdSe QDs, Cd was deposited on equimolar CdSe QDs. Further deposition of Se on Cd-rich CdSe QDs produced Se-rich CdSe QDs. The compositions (Cd:Se) of the as-prepared CdSe quantum dots were acquired by Energy-dispersive X-ray spectroscopy (EDX). By changing the composition, the overall optical properties of the CdSe QDs can be manipulated. It was found that as the composition of the QDs changes from 1:1 (Cd:Se) CdSe to Cd-rich and then Se-rich CdSe, the band gap decreases along with a red shift of UV–vis absorption edges and photoluminescence (PL) peaks. The quantum yield also decreases with surface composition from 1:1 (Cd:Se) CdSe QDs to Cd-rich and then to Se-rich, largely due to the changes in the surface state. Because of the involvement of the surface defect or trapping state, the carrier life time increased from the 1:1 (Cd:Se) CdSe QDs to the Cd-rich to the Se-rich CdSe QDs. We have shown that the optical properties of CdSe QDs can be controlled by manipulating the composition of the surface atoms. This strategy can potentially be extended to other semiconductor nanocrystals to modify their properties.

Composition-controlled optical properties of colloidal CdSe quantum dots

International Nuclear Information System (INIS)

Ayele, Delele Worku; Su, Wei-Nien; Chou, Hung-Lung; Pan, Chun-Jern; Hwang, Bing-Joe

2014-01-01

Graphical abstract: - Highlights: • The surface of CdSe QDs are modified with cadmium followed by selenium. • The optical properties of CdSe QDs can be controlled by manipulating the composition. • Surface compositional change affects the surface defects or traps and recombination. • The surface trapping state can be controlled by tuning the surface composition. • A change in composition shows a change in the carrier life time. - Abstract: A strategy with respect to band gap engineering by controlling the composition of CdSe quantum dots (QDs) is reported. After the CdSe QDs are prepared, their compositions can be effectively manipulated from 1:1 (Cd:Se) CdSe QDs to Cd-rich and then to Se-rich QDs. To obtain Cd-rich CdSe QDs, Cd was deposited on equimolar CdSe QDs. Further deposition of Se on Cd-rich CdSe QDs produced Se-rich CdSe QDs. The compositions (Cd:Se) of the as-prepared CdSe quantum dots were acquired by Energy-dispersive X-ray spectroscopy (EDX). By changing the composition, the overall optical properties of the CdSe QDs can be manipulated. It was found that as the composition of the QDs changes from 1:1 (Cd:Se) CdSe to Cd-rich and then Se-rich CdSe, the band gap decreases along with a red shift of UV–vis absorption edges and photoluminescence (PL) peaks. The quantum yield also decreases with surface composition from 1:1 (Cd:Se) CdSe QDs to Cd-rich and then to Se-rich, largely due to the changes in the surface state. Because of the involvement of the surface defect or trapping state, the carrier life time increased from the 1:1 (Cd:Se) CdSe QDs to the Cd-rich to the Se-rich CdSe QDs. We have shown that the optical properties of CdSe QDs can be controlled by manipulating the composition of the surface atoms. This strategy can potentially be extended to other semiconductor nanocrystals to modify their properties

PbSe Nanocrystal Excitonic Solar Cells

KAUST Repository

Choi, Joshua J.

2009-11-11

We report the design, fabrication, and characterization of colloidal PbSe nanocrystal (NC)-based photovoltaic test structures that exhibit an excitonic solar cell mechanism. Charge extraction from the NC active layer is driven by a photoinduced chemical potential energy gradient at the nanostructured heterojunction. By minimizing perturbation to PbSe NC energy levels and thereby gaining insight into the "intrinsic" photovoltaic properties and charge transfer mechanism of PbSe NC, we show a direct correlation between interfacial energy level offsets and photovoltaic device performance. Size dependent PbSe NC energy levels were determined by cyclic voltammetry and optical spectroscopy and correlated to photovoltaic measurements. Photovoltaic test structures were fabricated from PbSe NC films sandwiched between layers of ZnO nanoparticles and PEDOT:PSS as electron and hole transporting elements, respectively. The device current-voltage characteristics suggest a charge separation mechanism that Is distinct from previously reported Schottky devices and consistent with signatures of excitonic solar cells. Remarkably, despite the limitation of planar junction structure, and without film thickness optimization, the best performing device shows a 1-sun power conversion efficiency of 3.4%, ranking among the highest performing NC-based solar cells reported to date. © 2009 American Chemical Society.

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.

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.

Wide emission-tunable CdTeSe/ZnSe/ZnS core–shell quantum dots and their conjugation with E. coli O-157

Energy Technology Data Exchange (ETDEWEB)

Zhou, Haifeng [State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100 (China); Zhou, Guangjun, E-mail: gjzhou@sdu.edu.cn [State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100 (China); Zhou, Juan [Center for Disease Control and Prevention of Jinan Military Command, Jinan 250014 (China); Xu, Dong; Zhang, Xingshuang; Kong, Peng; Yang, Zhongsen [State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100 (China)

2015-05-15

Highlights: • QDs with variety morphology were obtained via an injection controlled process. • 3-D PL spectra of core–shell QDs show different excitation wavelength dependence. • The PL intensity of QDs with ZnSe transition layer increases dramatically. • Core–shell QDs were processed into aqueous phase and conjugated with E. coli O-157. - Abstract: Wide emission-tunable and different morphological alloyed CdTeSe quantum dots (QDs), CdTeSe/ZnS and CdTeSe/ZnSe/ZnS core–shell QDs were successfully synthesized via an injection controlled process. The effect of injection procedure and reaction temperature were systematically discussed and the growth mechanism was proposed. Most efficient PL wavelength was correlated with reaction time and temperature. The 3-D PL spectra of spherical bare CdTeSe and core–shell QDs with different passivation showed different excitation wavelength dependency. The PL intensity of CdTeSe/ZnSe/ZnS core–shell QDs increased greatly in comparison with that of CdTeSe and CdTeSe/ZnSe QDs. ZnSe transition layer played an important role in improving the PL intensity by providing a smoothened interface and gradient band offsets. The core–shell QDs were transferred into aqueous phase and successfully conjugated with Escherichia coli O-157. The proposed phase-transfer and bio-labeling strategy may be applicable to various QDs with different compositions.

Complexation in the system K2SeO4-UO2SeO4-H2O

International Nuclear Information System (INIS)

Serezhkina, L.B.; Kuchumova, N.V.; Serezhkin, V.N.

1994-01-01

Complexation in the system K 2 SeO 4 -UO 2 SeO 4 -H 2 O at 25 degrees C is studied by isothermal solubility. Congruently soluble K 2 UO 2 (SeO 4 ) 2 ·4H 2 O (I) and incongruently soluble K 2 (UO 2 ) 2 (SeO 4 ) 3 ·6H 2 O (II) are observed. The unit-cell constants of I and II are determined from an X-ray diffraction investigation. For I, a = 12,969, b = 11.588, c = 8.533 angstrom, Z = 4, space group Pmmb. For II, a = 23.36, b = 6.784, c = 13.699 angstrom, β = 104.42 degrees, Z = 4, space group P2/m, P2, or Pm. Complexes I and II are representatives of the crystal-chemical groups AB 2 2 M 1 and A 2 T 3 3 M 1 , respectively, of uranyl complexes

Origin of low thermal conductivity in SnSe

Science.gov (United States)

Xiao, Yu; Chang, Cheng; Pei, Yanling; Wu, Di; Peng, Kunling; Zhou, Xiaoyuan; Gong, Shengkai; He, Jiaqing; Zhang, Yongsheng; Zeng, Zhi; Zhao, Li-Dong

2016-09-01

We provide direct evidence to understand the origin of low thermal conductivity of SnSe using elastic measurements. Compared to state-of-the-art lead chalcogenides Pb Q (Q =Te , Se, S), SnSe exhibits low values of sound velocity (˜1420 m /s ) , Young's modulus (E ˜27.7 GPa ) , and shear modulus (G ˜9.6 GPa ) , which are ascribed to the extremely weak Sn-Se atomic interactions (or bonds between layers); meanwhile, the deduced average Grüneisen parameter γ of SnSe is as large as ˜3.13, originating from the strong anharmonicity of the bonding arrangement. The calculated phonon mean free path (l ˜ 0.84 nm) at 300 K is comparable to the lattice parameters of SnSe, indicating little room is left for further reduction of the thermal conductivity through introducing nanoscale microstructures and microscale grain boundaries. The low elastic properties indicate that the weak chemical bonding stiffness of SnSe generally causes phonon modes softening which eventually slows down phonon propagation. This work provides insightful data to understand the low lattice thermal conductivity of SnSe.

Attempting to realize n-type BiCuSeO

Science.gov (United States)

Zhang, Xiaoxuan; Feng, Dan; He, Jiaqing; Zhao, Li-Dong

2018-02-01

As an intrinsic p-type semiconductor, BiCuSeO has been widely researched in the thermoelectric community, however, n-type BiCuSeO has not been reported so far. In this work, we successfully realized n-type BiCuSeO through carrying out several successive efforts. Seebeck coefficient of BiCuSeO was increased through introducing extra Bi/Cu to fill the Bi/Cu vacancies that may produce holes, and the maximum Seebeck coefficient was increase from +447 μVK-1 for undoped BiCuSeO to +638 μVK-1 for Bi1.04Cu1.05SeO. The Seebeck coefficient of Bi1.04Cu1.05SeO was changed from p-type to n-type through electron doping through introducing Br/I in Se sites, the maximum negative Seebeck coefficient can reach ∼ -465 μVK-1 and -543 μVK-1 for Bi1.04Cu1.05Se1-xIxO and Bi1.04Cu1.05Se1-xBrxO, respectively. Then, after compositing Bi1.04Cu1.05Se0.99Br0.01O with Ag, n-type BiCuSeO can be absolutely obtained in the whole temperature range of 300-873 K, the maximum ZT 0.05 was achieved at 475 K in the Bi1.04Cu1.05Se0.99Br0.01O+15% Ag. Our report indicates that it is possible to realize n-type conducting behaviors in BiCuSeO system.

Immobilization of Se and U by iron sulfides

International Nuclear Information System (INIS)

Kang Mingliang; Ma Bin; Yang Zhuanwei; Liu Chunli; Chen Fanrong

2014-01-01

Both uranium and selenium are redox-sensitive, and can occur in several oxidation states. In reducing environments, they exist as insoluble forms. Therefore, reductive precipitation is the most effective way to immobilize U and Se. The interaction of aqueous Se (IV) and uranylwithiron sulfidesweresystematically investigated in light of thermodynamic calculations, X-ray Absorption Spectroscopy (XAS), and X-ray Photoelectron Spectroscopy (XPS). The results from the speciation study revealed that the reduction product was Se (O) when natural pyrite and pyrrhotitereacted with Se (IV), although FeSe 2 is the thermodynamically predicted product from nearly neural to alkaline conditions. This discrepancy is attributed to the oxidizing ability of Se (IV) towards FeSe 2 , of which produce the insoluble Se (0) as the stable product in short-term experiments. In contrast to the thermodynamic calculations, with a reaction product of mixed U (IV) and U (VI) (e.g., U 3 O 8 ), redox reaction was observed only at pH ∼ 8.5 and ∼ 4.5 for U (VI) reduction by nanosized pyrite and natural pyrite, respectively. We proposed that oxidation of pyrite needs an intermediate (e.g., Fe 2+ ), and the reaction between the uranyl and the intermediate is thermodynamically or kinetically limited. Moreover, trace elements generally held within pyrite structure can also greatly influence its reactivity. This study demonstrated that reaction kinetics play a significant role on the reaction product. From a geological time scale, Se and U are likely to be immobilized by iron sulfides via the form of FeSe 2 and UO 2 . (authors)

Chemical and structural evolution in the Th-SeO3(2-)/SeO4(2-) system: from simple selenites to cluster-based selenate compounds.

Science.gov (United States)

Xiao, Bin; Langer, Eike; Dellen, Jakob; Schlenz, Hartmut; Bosbach, Dirk; Suleimanov, Evgeny V; Alekseev, Evgeny V

2015-03-16

While extensive success has been gained in the structural chemistry of the U-Se system, the synthesis and characterization of Th-based Se structures are widely unexplored. Here, four new Th-Se compounds, α-Th(SeO3)2, β-Th(SeO3)2, Th(Se2O5)2, and Th3O2(OH)2(SeO4)3, have been obtained from mild hydrothermal or low-temperature (180-220 °C) flux conditions and were subsequently structurally and spectroscopically characterized. The crystal structures of α-Th(SeO3)2 and β-Th(SeO3)2 are based on ThO8 and SeO3 polyhedra, respectively, featuring a three-dimensional (3D) network with selenite anions filling in the Th channels along the a axis. Th(Se2O5)2 is a 3D framework composed of isolated ThO8 polyhedra interconnected by [Se2O5](2-) dimers. Th3O2(OH)2(SeO4)3 is also a 3D framework constructed by octahedral hexathorium clusters [Th6(μ3-O)4(μ3-OH)4](12+), which are interlinked by selenate groups SeO4(2-). The positions of the vibrational modes associated with both Se(IV)O3(2-) and Se(VI)O4(2-) units, respectively, were determined for four compounds, and the Raman spectra of α- and β-Th(SeO3)2 are compared and discussed in detail.

79Se: geochemical and crystallo-chemical retardation mechanisms

International Nuclear Information System (INIS)

Chen, F.; Ewing, R.C.

1999-01-01

79 Se is a long-lived (1.1 x 10 6 yrs) fission product which is chemically and radiologically toxic. Under Eh-pH conditions typical of oxidative alteration of spent nuclear fuel, selenite, SeO 3 2- or HSeO 3 - or selenate, SeO 4 2- , are the dominant aqueous species of selenium. Because of the high solubility of metal-selenites and metal-selenates and the low adsorption of selenite and selenate aqueous species by geological materials under alkaline conditions, selenium may be highly mobile. However, 79 Se released from altered fuel may become immobilized by incorporation into secondary uranyl phases as low concentration impurities, and this may significantly reduce the mobility of selenium. Analysis and comparison of the known structures of uranyl phases indicate that (SeO 3 ) may substitute for (SiO 3 OH) in structures of α-uranophane and boltwoodite that are expected to be the dominant alteration products of UO 2 in Si-rich groundwater. The substitutions (SeO 3 ) (SiO 3 OH) in sklodowskite, Mg[(UO 2 )(SiO 3 OH)] 2 (H 2 O) 6 and (SeO 3 ) (PO 4 ) in phurcalite, Ca 2 [(UO 2 ) 3 (PO 4 ) 2 O 2 ](H 2 O) 7 , may occur with the eliminated apical anion being substituted for by an H 2 O group, but experimental investigation is required. The close similarity between the sheets in the structures of rutherfordine, [(UO 2 )(CO 3 )] and [(UO 2 )(SeO 3 )] implies that the substitution (SeO 3 ) (CO 3 ) can occur in rutherfordine, and possibly other uranyl carbonates. However, the substitutions: (SeO 3 ) (SiO 4 ) in soddyite and (SeO 3 ) (PO 4 ) in phosphuranylite may disrupt their structural connectivity and are, therefore, unlikely. (orig.)

Exotic topological insulator states and topological phase transitions in Sb2Se3-Bi2Se3 heterostructures

KAUST Repository

Zhang, Qianfan

2012-03-27

Topological insulator is a new state of matter attracting tremendous interest due to its gapless linear dispersion and spin momentum locking topological states located near the surface. Heterostructures, which have traditionally been powerful in controlling the electronic properties of semiconductor devices, are interesting for topological insulators. Here, we studied the spatial distribution of the topological state in Sb 2Se 3-Bi 2Se 3 heterostructures by first-principle simulation and discovered that an exotic topological state exists. Surprisingly, the state migrates from the nontrivial Bi 2Se 3 into the trivial Sb 2Se 3 region and spreads across the entire Sb 2Se 3 slab, extending beyond the concept of "surface" state while preserving all of the topological surface state characteristics. This unusual topological state arises from the coupling between different materials and the modification of electronic structure near Fermi energy. Our study demonstrates that heterostructures can open up opportunities for controlling the real-space distribution of the topological state and inducing quantum phase transitions between topologically trivial and nontrivial states. © 2012 American Chemical Society.

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.)

In-situ XRD study of alloyed Cu2ZnSnSe4-CuInSe2 thin films for solar cells

International Nuclear Information System (INIS)

Hartnauer, Stefan; Wägele, Leonard A.; Jarzembowski, Enrico; Scheer, Roland

2015-01-01

We investigate the growth of Cu 2 ZnSnSe 4 -CuInSe 2 (CZTISe) thin films using a 2-stage (Cu-rich/Cu-free) co-evaporation process under simultaneous application of in-situ angle dispersive X-ray diffraction (XRD). In-situ XRD allows monitoring the phase formation during preparation. A variation of the content of indium in CZTISe leads to a change in the lattice constant. Single phase CZTISe is formed in a wide range, while at high In contents a phase separation is detected. Because of different thermal expansion coefficients, the X-ray diffraction peaks of ZnSe and CZTISe can be distinguished at elevated substrate temperatures. The formation of ZnSe appears to be inhibited even for low indium content. In-situ XRD shows no detectable sign for the formation of ZnSe. First solar cells of CZTISe have been prepared and show comparable performance to CZTSe. - Highlights: • In-situ XRD study of two-stage co-evaporated Cu 2 ZnSnSe 4 -CuInSe 2 alloyed thin films. • No detection of ZnSe with in-situ XRD due to Indium incorporation • Comparable efficiency of alloyed solar cells

Lattice thermal conductivity of LaSe

Energy Technology Data Exchange (ETDEWEB)

Li, Wei, E-mail: tolwwt@163.com [School of Physics and Telecommunication Engineering, South China Normal University, 510006 Guangzhou (China); Pan, Zhong-liang; Chen, Jun-fang; He, Qin-yu [School of Physics and Telecommunication Engineering, South China Normal University, 510006 Guangzhou (China); Wang, Teng [School of Computer, South China Normal University, 510631 Guangzhou (China)

2015-07-15

The phonon dispersions and phonon density of states of LaSe are obtained, based on density functional perturbation theory and the norm-conserving pseudo-potential method. An anomaly in calculated phonon dispersion curves is presented and interpreted as a Kohn anomaly. The heat capacity of LaSe is calculated then. For the three-phonon process scattering, the lowest non-harmonic cubic terms of the interatomic potential are considered to obtain single-phonon relaxation rate by applying the Fermi's golden rule. For the boundary scattering, the average phonon relaxation time was obtained. Considering two kinds of phonon scattering mechanisms, we obtain the lattice thermal conductivity of LaSe.

In situ observation of the formation of FeSe

DEFF Research Database (Denmark)

Grivel, Jean-Claude; Wulff, Anders Christian; Yue, Zhao

2011-01-01

The formation of the FeSe compound from a mixture of Fe and Se powders encased in a composite Cu/Nb sheath was studied in situ by means of high-energy synchrotron x-ray diffraction. Tetragonal beta-FeSe does not seem to form directly from the starting elements. Instead, a sequence of FeSe2, Fe3Se...

Histotopography of the radiopharmaceuticals 75Se-selenomethionine and 75Se-selenite in critical organs of adult and embryonic mice

International Nuclear Information System (INIS)

Khant, S.E.; Norets, T.A.

1981-01-01

Adult male and pregnant mice received 75 Se-labelled methionine and selenite, resp. The critical organs and the embryos were examined histoautoradiographically at different time intervals as to the organ distribution of the radiopharmaceuticals. All organs revealed a heterogeneity of the 75 Se distribution with an intensity being unequally organo-specific and depending on the type of the radiopharmaceutical. 75 Se-selenomethionine was deposited mainly in functional areas of kidneys, liver, bone marrow and testes thus causing a long-term retention and an intensive irradiation of these organs. In the embryos 75 Se-seleno-methionine was distributed unequally preferring liver, hematopoietic areas of the bone marrow and the lens

Influence of defect structure on magnetic and electronic properties of Hg1-x Crx Se and Hg1-x Cox Se

International Nuclear Information System (INIS)

Prozorovskij, V.D.; Reshidova, I.Yu.; Puzynya, A.I.; Paranchich, Yu.S.

1996-01-01

The results of experimental investigations of the Shubnikov-de Haas oscillations at superhigh frequencies, electron spin resonance, magnetic susceptibility, relaxation dielectric losses, and galvanomagnetic measurements in the Hg 1-x Cr x Se and Hg 1-x Co x Se single crystal samples are presented. Analysis of the results Hg 1-x Cr x Se and Hg 1-x Co x Se depend on the defect structure of the substance and the type of defects making this structure. The manifestation of critical phenomena in Hg 1-x Cr x Se also depends on the defect structure

Solving the shape conundrum in $^{70}$Se

CERN Multimedia

We propose a multi-step Coulomb-excitation study of $^{70}$Se at HIE-ISOLDE using the $^{208}$Pb( $^{70}$Se, $^{70}$Se*)$^{208}$Pb* reaction at a safe energy of 5.0 MeV/u. We aim at a precise measurement of the $\\left \\langle 2^{+}_{1} \\hspace{0.1cm} || \\hspace{0.1cm}\\hat{E}2 \\hspace{0.1cm} || \\hspace{0.1cm}2^{+}_{ 1} \\right \\rangle$ diagonal matrix element as well as gaining information on additional matrix elements. Such information will shed light onto the shape conundrum of the 2$^{+}_{1}$ state in $^{70}$Se as well as foreseeing the opportunity for a more detailed understanding of the shape-coexistence phenomenon in this region.

Relevamientos semicuantitativo para el estudio de la morfología de playa

OpenAIRE

Marcos, Angel; Fernández, Elba; Caló, Jorge; Huespe, Ricardo

2009-01-01

El cambio climático global y sus efectos sobre las ambientalmente sensibles áreas costeras han llevado, tanto a los organismos científicos como económicos, a poner en ejecución planes de manejo costero. Un punto débil de este esquema es la falta de datos estadísticos, sobre todo en países del llamado Tercer Mundo, que por sus características económicas no destinan fondos para este tipo de estudio. Es por ello interesante ejecutar metodologías de relevamiento de bajo costo, accesibles aún a pe...

Novel red-emission of ternary ZnCdSe semiconductor nanocrystals

Science.gov (United States)

Chung, Shu-Ru; Wang, Kuan-Wen; Chen, Hong-Shuo; Chen, Hong-Hong

2015-02-01

The effect of chain lengths of fatty acids on the physical properties of CdSe and ZnCdSe semiconductor nanocrystals (NCs) synthesized by the colloidal chemistry procedure is investigated. The fatty acids, lauric acid (LA), and stearic acid (SA), with different lengths of carbon chains, are used to prepare CdSe and ZnCdSe NCs when hexyldecylamine (HDA) is applied as the sole surfactant. For CdSe-SA and ZnCdSe-SA, they have the same emission wavelength at 592 nm and the same particle size of 3.3 nm; however, their quantum yield (QY) is 75 and 16 %, respectively. In contrast, the emission wavelength of CdSe-LA and ZnCdSe-LA NCs is 609 and 615 nm, the particle size is about 3.5 and 4 nm under the same reaction time, and the QY of them are 33 and 59 %, respectively. The X-ray diffraction pattern shows that ZnCdSe NCs all have the wurtzite structure, and their main peaks are located between those of pure CdSe and ZnSe materials. The main phase of ZnCdSe-SA and ZnCdSe-LA is ZnSe and CdSe, respectively, implying that alloyed ZnCdSe NC can be prepared and ZnSe and CdSe phase can be promoted by SA and LA, respectively. Moreover, the QY of red-emission ZnCdSe-LA is higher than 50 %. These results suggest that the growth rate of CdSe as well as ZnCdSe NC can be enhanced by using LA as complex reagent and HDA as sole surfactant. It is expected that the reported effective synthetic strategy can be developed as a very practical, easy and not time-consuming approach to prepare red emissive NCs with high QY and high reproducibility.

Liquidus Projection and Isothermal Section of the Sb-Se-Sn System

Science.gov (United States)

Chang, Jui-shen; Chen, Sinn-wen

2017-12-01

Sb-Se-Sn ternary alloys are promising chalcogenide materials. The liquidus projection and 673.2 K (400 °C) isothermal section of the Sb-Se-Sn ternary system are determined. Numerous Sb-Se-Sn alloys are prepared, and their primary solidification phases are examined. In addition to the three terminal phases, (Sb), (Se) and (Sn), there are Sb2Sn3, SbSn, SnSe, SnSe2, Sb2Se3, Sn2Sb9Se9, and SnSb2Se4 phases. In addition, there are two miscibility gaps along the Sb-Se and Se-Sn and sides. There are ten invariant reactions in the Sb-Se-Sn ternary system, and seven of them are experimentally determined in this study. The lowest reaction temperature of determined invariant reaction is L + SbSn = (Sn) + SnSe at 515.4 K ± 5 K (242.2 °C ± 5 °C). There are nine tie-triangles, which are Liquid + SbSn + SnSe, SbSn + SnSe + (Sb), SnSe + (Sb) + Sn2Sb9Se9, (Sb) + Sb2Se3 + Sn2Sb9Se9, SnSe + Sn2Sb9Se9 + SnSb2Se4, Sb2Se3 + Sn2Sb9Se9 + SnSb2Se4, SnSe + SnSe2 + SnSb2Se4, SnSe2 + SnSb2Se4 + Sb2Se3, and SnSe2 + Sb2Se3 + Liquid in the 673.2 K (400 °C) isothermal section of the Sb-Se-Sn ternary system.

Synthesis, crystal structure, optical, and electronic study of the new ternary thorium selenide Ba{sub 3}ThSe{sub 3}(Se{sub 2}){sub 2}

Energy Technology Data Exchange (ETDEWEB)

Prakash, Jai [Department of Chemistry, Northwestern University, Evanston, IL 60208-3113 (United States); Mesbah, Adel [Department of Chemistry, Northwestern University, Evanston, IL 60208-3113 (United States); ICSM, UMR 5257 CEA/CNRS/UM2/ENSCM, Site de Marcoule-Bât. 426, BP 17171, 30207 Bagnols-sur-Cèze cedex (France); Beard, Jessica [Department of Chemistry, Northwestern University, Evanston, IL 60208-3113 (United States); Lebègue, Sébastien [Laboratoire de Cristallographie, Résonance Magnétique et Modélisations (CRM2, UMR CNRS 7036), Institut Jean Barriol, Université de Lorraine, BP 239, Boulevard des Aiguillettes, 54506 Vandoeuvre-lès-Nancy (France); Malliakas, Christos D. [Department of Chemistry, Northwestern University, Evanston, IL 60208-3113 (United States); Ibers, James A., E-mail: ibers@chem.northwestern.edu [Department of Chemistry, Northwestern University, Evanston, IL 60208-3113 (United States)

2015-11-15

The compound Ba{sub 3}ThSe{sub 3}(Se{sub 2}){sub 2} has been synthesized by solid-state methods at 1173 K. Its crystal structure features one-dimensional chains of {sup 1}{sub ∞}[Th(Se){sub 3}(Se{sub 2}){sub 2}{sup 6−}] separated by Ba{sup 2+} cations. Each Th atom in these chains is coordinated to two Se–Se single-bonded pairs and four Se atoms to give rise to a pseudooctahedral geometry around Th. The Th–Se distances are consistent with Th{sup 4+} and hence charge balance of Ba{sub 3}ThSe{sub 3}(Se{sub 2}){sub 2} is achieved as 3×Ba{sup 2+}, 1×Th{sup 4+}, 3×Se{sup 2−}, and 2×Se{sub 2}{sup 2−}. From optical measurements the band gap of Ba{sub 3}ThSe{sub 3}(Se{sub 2}){sub 2} is 1.96(2) eV. DFT calculations indicate that the compound is a semiconductor. - Graphical abstract: Local coordination environment of Th atoms in the Ba{sub 3}ThSe{sub 3}(Se{sub 2}){sub 2} structure. - Highlights: • Ba{sub 3}ThSe{sub 3}(Se{sub 2}){sub 2} has been synthesized by solid-state methods at 1173 K. • The structure features chains of {sup 1}{sub ∞}[Th(Se){sub 3}(Se{sub 2}){sub 2}{sup 6−}] separated by Ba{sup 2+} cations. • Ba{sub 3}ThSe{sub 3}(Se{sub 2}){sub 2} is a semiconductor with a band gap of 1.96(2) eV.

Por uma cidade que se move e se comunica: corpo, rua e improviso

Directory of Open Access Journals (Sweden)

Julia Saldanha Vieira de Aguiar

2009-06-01

Full Text Available Este trabalho trata da relação de um lugar com suas pessoas. A reflexão acontece a partir de um estudo de caso: o Camelódromo da Praça XV. O Camelódromo foi uma grande feira, que durante 40 anos ocupou um espaço importante no centro de Porto Alegre/RS. (Auto organizado e vivido principalmente pelo povo, o fenômeno se configurava em um lugar onde improviso e estética constituiam o modo de ser e agir no cotidiano da rua. Ironicamente, no início de 2009, o Camelódromo foi transferido para dentro de um prédio. Hoje, onde se desenrolava o espetáculo do imprevisível, encontra-se um estacionamento para carros. Este trabalho foi produzido nos últimos meses do Camelódromo; em um espírito de elogio à estética do improviso e à auto-organização. Buscamos articular idéias da teoria da complexidade, do urbanismo, das artes e da comunicação, para tentar compreender um pouco essa manifestação espontânea, tão característica da urbe no século XXI.

Synthesis of CdSe Quantum Dots Using Fusarium oxysporum

Directory of Open Access Journals (Sweden)

Takaaki Yamaguchi

2016-10-01

Full Text Available CdSe quantum dots are often used in industry as fluorescent materials. In this study, CdSe quantum dots were synthesized using Fusarium oxysporum. The cadmium and selenium concentration, pH, and temperature for the culture of F. oxysporum (Fusarium oxysporum were optimized for the synthesis, and the CdSe quantum dots obtained from the mycelial cells of F. oxysporum were observed by transmission electron microscopy. Ultra-thin sections of F. oxysporum showed that the CdSe quantum dots were precipitated in the intracellular space, indicating that cadmium and selenium ions were incorporated into the cell and that the quantum dots were synthesized with intracellular metabolites. To reveal differences in F. oxysporum metabolism, cell extracts of F. oxysporum, before and after CdSe synthesis, were compared using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE. The results suggested that the amount of superoxide dismutase (SOD decreased after CdSe synthesis. Fluorescence microscopy revealed that cytoplasmic superoxide increased significantly after CdSe synthesis. The accumulation of superoxide may increase the expression of various metabolites that play a role in reducing Se4+ to Se2− and inhibit the aggregation of CdSe to make nanoparticles.

Mechanical and magneto-electronic properties of half-metallic ferromagnetism in Ti-doped ZnSe and CdSe alloys: Ab initio study

Science.gov (United States)

El Amine Monir, Mohammed; Ullah, Hayat; Baltach, Hadj; Gulbahar Ashiq, M.; Khenata, R.

2017-11-01

In this article we have studied the structural, elastic, electronic and magnetic properties of Zn1-xTixSe and Cd1-xTixSe alloys at (x = 0.25, 0.50, 0.75) using first principles density functional theory calculations with local spin density approximation (LSDA) and generalized gradient approximation plus Hubbard parameter (GGA+U) as exchange-correlation potential. The physical properties of both alloys were investigated in the zinc-blend phase. The structural parameters at equilibrium are consistent with experimental and earlier theoretical predictions. The elastic constants are also computed and compared with the literature. The DOS curves of Zn1-xTixSe and Cd1-xTixSe alloys for all the concentrations show the existence of hybridization among Ti (3d) and Se (4p) states. The calculated exchange constants N0α(s-d) and N0β (p-d) are useful to determine the contribution in the valence band and conduction band and are also shows the magnetic character of these alloys. In addition, the p-d hybridization in the PDOS reduces local magnetic moment of Ti from its free space charge of 2 μB and results small magnetic moments on the nonmagnetic Zn, Cd and Se sites. The calculated negative values of formation energy (Ef) reveal that all the Zn1-xTixSe and Cd1-xTixSe alloys are thermodynamically stables. A larger/Smaller value of Curie temperature (TC) for all the Zn1-xTixSe and Cd1-xTixSe alloys shows the strong/low interaction among the magnetic atoms respectively.

Microbial Precipitation of Cr(III)-Hydroxide and Se(0) Nanoparticles During Anoxic Bioreduction of Cr(VI)- and Se(VI)-Contaminated Water.

Science.gov (United States)

Kim, Yumi; Oh, Jong-Min; Roh, Yul

2017-04-01

This study examined the microbial precipitations of Cr(III)-hydroxide and Se(0) nanoparticles during anoxic bioreductions of Cr(VI) and Se(VI) using metal-reducing bacteria enriched from groundwater. Metal-reducing bacteria enriched from groundwater at the Korea Atomic Energy Research Institute (KAERI) Underground Research Tunnel (KURT), Daejeon, S. Korea were used. Metal reduction and precipitation experiments with the metal-reducing bacteria were conducted using Cr(VI)- and Se(VI)-contaminated water and glucose as a carbon source under an anaerobic environment at room temperature. XRD, SEM-EDX, and TEM-EDX analyses were used to characterize the mineralogy, crystal structure, chemistry, shape, and size distribution of the precipitates. The metal-reducing bacteria reduced Cr(VI) of potassium chromate (K₂CrO₄) to Cr(III) of chromium hydroxide [Cr(OH)3], and Se(VI) of sodium selenate (Na₂SeO₄) to selenium Se(0), with changes of color and turbidity. XRD, SEM-EDX, and TEM-EDX analyses revealed that the chromium hydroxide [Cr(OH)₃] was formed extracellularly with nanoparticles of 20–30 nm in size, and elemental selenium Se(0) nanoparticles had a sphere shape of 50–250 nm in size. These results show that metal-reducing bacteria in groundwater can aid or accelerate precipitation of heavy metals such as Cr(VI) and Se(VI) via bioreduction processes under anoxic environments. These results may also be useful for the recovery of Cr and Se nanoparticles in natural environments.

Ud at se med Erasmus

DEFF Research Database (Denmark)

Frandsen, Pernille

2009-01-01

Få lidt luft under vingerne, kom ud at møde udenlandske kolleger og se, hvordan man også kan lave uddannelsesbibliotek. Med begejstring fortæller tre bibliotekarer om deres oplevelser i det store udland – alt sammen finansieret af Erasmus.......Få lidt luft under vingerne, kom ud at møde udenlandske kolleger og se, hvordan man også kan lave uddannelsesbibliotek. Med begejstring fortæller tre bibliotekarer om deres oplevelser i det store udland – alt sammen finansieret af Erasmus....

Effects of hydrostatic pressure on the thermoelectric properties of the ɛ-polytype of InSe, GaSe, and InGaSe2 semiconductor compounds: an ab initio study

Science.gov (United States)

Elsayed, H.; Olguín, D.; Cantarero, A.

2017-12-01

This work presents an ab initio study of the effects of hydrostatic pressure on the Seebeck coefficients and thermoelectric power factors of the ɛ-polytype of InSe, GaSe, and InGaSe2 semiconductor compounds. Our study is performed using the semi-classical Boltzmann theory and the rigid band approach. The electronic band structures of these materials are calculated using the full-potential linearized augmented plane-wave method. The obtained thermoelectric properties are discussed in terms of the results of the electronic structure calculations. As we will show, our calculated Seebeck coefficient values indicate that these materials are good alternatives to other well-studied thermoelectric systems.

VerSeDa: vertebrate secretome database.

Science.gov (United States)

Cortazar, Ana R; Oguiza, José A; Aransay, Ana M; Lavín, José L

2017-01-01

Based on the current tools, de novo secretome (full set of proteins secreted by an organism) prediction is a time consuming bioinformatic task that requires a multifactorial analysis in order to obtain reliable in silico predictions. Hence, to accelerate this process and offer researchers a reliable repository where secretome information can be obtained for vertebrates and model organisms, we have developed VerSeDa (Vertebrate Secretome Database). This freely available database stores information about proteins that are predicted to be secreted through the classical and non-classical mechanisms, for the wide range of vertebrate species deposited at the NCBI, UCSC and ENSEMBL sites. To our knowledge, VerSeDa is the only state-of-the-art database designed to store secretome data from multiple vertebrate genomes, thus, saving an important amount of time spent in the prediction of protein features that can be retrieved from this repository directly. VerSeDa is freely available at http://genomics.cicbiogune.es/VerSeDa/index.php. © The Author(s) 2017. Published by Oxford University Press.

Raman scattering and structural analysis of electrodeposited CuInSe2 and S-rich quaternary CuIn(S,Se)2 semiconductors for solar cells

International Nuclear Information System (INIS)

Izquierdo-Roca, Victor; Fontane, Xavier; Morante, Joan Ramon; Saucedo, Edgardo; Ruiz, Carmen M.; Grand, Pierre-Philippe; Jaime-Ferrer, Jesus Salvador; Bermudez, Veronica; Calvo-Barrio, Lorenzo; Alvarez-Garcia, Jacobo; Perez-Rodriguez, Alejandro

2009-01-01

This work reports the Raman scattering characterisation of CuInSe 2 precursors grown by single step electrodeposition and the corresponding layers recrystallised under sulphurising conditions for solar cell devices. The analysis of the spectra measured on the as-grown precursors has allowed identifying the main secondary phases in these layers with elemental Se, Cu-Se phases and chalcopyrite Cu-poor ordered vacancy domains. To deepen in the identification of the Cu-Se phases, these measurements have been correlated with the analysis of binary Cu-Se layers. The experimental data indicate that formation of both Se and Cu-Se phases is likely controlled by the Se content in the layers. For values of stoichiometry below 1.15, excess Cu in the layers is accommodated in a phase with very low Raman efficiency (as Cu 2 Se). Increasing the content of Se leads to an increase in the spectral contribution from both Se and Cu 2-x Se, being the formation of these phases likely favoured under high excess Se conditions. The characterisation of the corresponding recrystallised layers has allowed analysing the impact of the presence of the secondary phases in the as-grown absorbers on the performance of the final solar cells. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Determination of the optimal conditions for simultaneous production of 73SE and 75SE radioisotopes in a 30 MeV cyclotron

International Nuclear Information System (INIS)

Pejman Rowshanfazad; Amirreza Jalilian; Mahsheed Sabet

2004-01-01

Purpose: 73 Se and 75 Se radioisotopes are widely used in medicine, industry and agriculture. 75 Se is used in high activity brachytherapy (1), assessment of pancreatic exocrine function (2, 3), study of bile acids and evaluation of illeal function (4, 5, 6), industrial radiography (7, 8) and as a tracer in the assessment of chemical, biochemical, biophysical processes, metabolic research and agricultural studies. 73 Se is used in pancreas scanning (9), hyperthyroidism diagnosis(10), adrenal scanning (11), tumor detection (12, 13, 14), detection of brain dopamine receptors (15), parathyroid tumor detection (10) and detection of brain blood flow (16). These radioisotopes were selected to be produced in the country according to their wide range of applications. The idea of simultaneous production of 73 Se and 75 Se arouse after the completion of primary studies. Important physical characteristics of these radioisotopes are shown in table l. Methods: 1 Selection of the Best Reaction. Various nuclear reactions which may be used for the production of 73 Se and 75 Se are shown in table 2 (17, 18, 19). Among the above reactions, those which use α and 3 He as the projectile particles were discarded since high energy and high intensity beams of α and 3 He are not available in the country at present. Those reactions which used 74 Se and 76 Se as the target material could not be used, since these isotopes have low isotopic values (0.87% and 9.02% respectively), and their chemical separation processes are difficult, expensive and time-taking, due to the equal chemical properties of the product and the target material (20). Thus 75 As(p, n) 75 Se seemed to be the most appropriate reaction for the production of 75 Se. The 75 As(d, 4n) 73 Se reaction is not as suitable as 75 As(p, 3n) 73 Se, because of the lower radionuclidic purity of the product (18). Thus the best reaction for the production of 73 Se was determined to be 75 As(p, 3n) 73 Se. There was no need for an isotopic

Seed-mediated direct growth of CdSe nanoclusters on substrates

International Nuclear Information System (INIS)

Pan Shangke; Ebrahim, Shaker; Soliman, Moataz; Qiao Qiquan

2013-01-01

Different shapes of CdSe nanostructures were obtained by hydrothermal method with varied Se sources and buffer layers. Hexagonal nanoparticles of CdSe with Wurtzite structure were synthesized from Se powder resource, while CdSe nanoclusters with Wurtzite structure were grown from Na 2 SeO 3 aqueous solution resources at 165 °C using cetyltrimethylammonium bromide as surfactant. Using ZnO nanoparticles as a seed layer, CdSe nanostructures only partially covered the indium tin oxide (ITO) substrates. With ZnO/CdSe quantum dots composite seed layer, CdSe nanostructures fully covered the ITO substrates.

Exotic topological insulator states and topological phase transitions in Sb2Se3-Bi2Se3 heterostructures

KAUST Repository

Zhang, Qianfan; Zhang, Zhiyong; Zhu, Zhiyong; Schwingenschlö gl, Udo; Cui, Yi

2012-01-01

in controlling the electronic properties of semiconductor devices, are interesting for topological insulators. Here, we studied the spatial distribution of the topological state in Sb 2Se 3-Bi 2Se 3 heterostructures by first-principle simulation and discovered

Spatial and temporal variability of stable isotope composition of precipitation over the south american continent

Directory of Open Access Journals (Sweden)

1995-01-01

Full Text Available VARIABILITE SPATIALE ET TEMPORELLE DE LA COMPOSITION EN ISOTOPES STABLES DE LA PRECIPITATION SUR LE CONTINENT SUDAMERICAIN. L’Agence Internationale de l’Energie Atomique, en coopération avec l’Organisation Météorologique Mondiale, exploite un réseau mondial de stations pour la prise d’échantillons mensuels de précipitation. Actuellement, à peu près 60 stations fournissent des informations sur la composition isotopique de la précipitation sur le continent sudaméricain. Ces dernières années plusieurs réseaux d’échantillonnage d’un caractère national (Argentine, Brésil, Chili, Equateur, Pérou ont été initiés. Les données apportées par ces réseaux contribuent au réseau mondial de l’AIEA/OMM. Ces travaux se concentrent sur l’étude de la variabilité spatiale et temporelle de la composition isotopique stable de la précipitation sur le continent. Dans cette étude, est examinée en détail la relation entre la composition isotopique de la précipitation dans la région et quelques paramètres climatiques, tels que la quantité de précipitation et la température de l’air. VARIABILIDAD ESPACIAL Y TEMPORAL DE LA COMPOSICIÓN DE ISÓTOPOS ESTABLES DE LA PRECIPITACIÓN EN EL CONTINENTE SUDAMERICANO. El Organismo Internacional de Energía Atómica (OIEA, en colaboración con la Organización Meteorológica Mundial (OMM, está llevando a cabo un estudio a escala global de la composición isotópica de la precipitación a partir de muestras mensuales de lluvia recogidas en estaciones meteorológicas. En la actualidad alrededor de 60 estaciones proporcionan información sobre la composición isotópica de la precipitación en el continente sudamericano. Durante los últimos años se han establecido en la región varias redes de control con carácter nacional (Argentina, Brasil, Chile, Ecuador, Perú. Los datos aportados por estas redes representan una valiosa contribución a la red mundial del OIEA/OMM. Este trabajo se

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.

¿Y, cómo se hacen?

Directory of Open Access Journals (Sweden)

Juan Ruiz

2015-01-01

Full Text Available El mundo de los dibujos animados es producto de la imaginación, de la fantasía que vuela en los sueños de los hombres de cualquier edad. El artículo relata la forma en cómo estos simpáticos personajes, que vemos a diario en el cine o la televisión, pueden moverse tan libremente y con tanto desenfado. Se parte de la idea o argumento, el guionista narra la historia de lo que será el animado. Luego el director con un dibujante trazan las escenas principales de la historia (storyboard o guión dibujado se discute con los artistas y realizadores del filme; una vez aprobado este se perfila el diseño de los personajes, se realiza la escenografía (maquetas de ser necesario. Se hacen los parlamentos o diálogos de los personajes para que actores(as pongan las voces y sigue el proceso más fino y técnico.

Methodology for the application of the probabilistic safety analysis to the cobalto therapy units in Cuba

International Nuclear Information System (INIS)

Vilaragut Llanes, Juan Jose; Ferro Fernandez, Ruben; Troncoso Fleitas, Mayra; Lozano Lima, Berta; De la Fuente Puch, Andres; Perez Reyes, Yolanda; Dumenigo Gonzalez, Cruz

2001-01-01

Presently work the main elements are discussed kept in mind for the use of the Analyses Probabilistas of Security in the evaluation of the security of the units of cobalto therapy of Cuba and it is presented, like part of the results of the first stage of the Study, the Methodological Guide that is being used in a Contract of Investigation of the OIEA that at the moment carries out the community of authors of the CNSN, of group with other specialists of the Ministry of Public Health (MINSAP)

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.

Variation of Se, Zn, Co, Fe and Rb distribution in rats upon sequence of injection with SeO2 and glutathione

International Nuclear Information System (INIS)

Czauderna, M.; Samochocka, K.; Kwiathkowska, J.

1984-01-01

The contents of Se, Zn, Co, Fe and Rb in several organs of Wistar rats were determined by instrumental neutron activation analysis (INAA) after injections of SeO 2 and glutathione (GSH). Se was incorporated in all the examined organs, and the efficiency of incorporation does not depend upon the sequence of injection with SeO 2 and GSH. The sequence of these injections affects the contents of the other elements in all the examined organs. (author)

Instantaneous preparation of CuInSe2 films from elemental In, Cu, Se particles precursor films in a non-vacuum process

International Nuclear Information System (INIS)

Kaigawa, R.; Uesugi, T.; Yoshida, T.; Merdes, S.; Klenk, R.

2009-01-01

CuInSe 2 (CIS) films are successfully prepared by means of non-vacuum, instantaneous, direct synthesis from elemental In, Cu, Se particles precursor films without prior synthesis of CIS nanoparticle precursors and without selenization with H 2 Se or Se vapor. Our precursor films were prepared on metal substrates by spraying the solvent with added elemental In, Cu, and Se particles. Precursor films were instantaneously sintered using a spot welding machine. When the electric power was fixed to 0.6 kVA, elemental In, Cu, or Se peaks were not observed and only peaks of CIS are observed by X-ray diffraction (XRD) on the film sintered for 7/8 s. We can observe XRD peaks indicative of the chalcopyrite-type structure, such as (101), (103) and (211) diffraction peaks. We conclude that the synthesized CIS crystals have chalcopyrite-type structure with high crystallinity

Constraining the cross section of 82Se(n, γ)83Se to validate the β-Oslo method

Science.gov (United States)

Childers, K.; Liddick, S. N.; Crider, B. P.; Dombos, A. C.; Lewis, R.; Spyrou, A.; Couture, A.; Mosby, S.; Prokop, C. J.; Naqvi, F.; Larsen, A. C.; Guttormsen, M.; Campo, L. C.; Renstrom, T.; Siem, S.; Bleuel, D. L.; Perdikakis, G.; Quinn, S.

2017-09-01

Neutron capture cross sections of short-lived nuclei are important for a variety of basic and applied nuclear science problems. However, because of the short half-lives of the nuclei involved and the nonexistence of a neutron target, indirect measurement methods are required. One such method is the β-Oslo method. The nuclear level density and γ strength function of a nucleus are extracted after β-decay and used in a statistical reaction model to constrain the neutron capture cross section. This method has been used previously, but must be validated against a directly measured neutron capture cross section. The neutron capture cross section of 82Se has been measured previously, and 83Se can be accessed by the β-decay of 83As. The β-decay of 83As to 83Se was studied using the SuN detector at the NSCL and the β-Oslo method was utilized to constrain the neutron capture cross section of 82Se, which is compared to the directly measured value.

Layer structured bismuth selenides Bi2Se3 and Bi3Se4 for high energy and flexible all-solid-state micro-supercapacitors

Science.gov (United States)

Hao, Chunxue; Wang, Lidan; Wen, Fusheng; Xiang, Jianyong; Li, Lei; Hu, Wentao; Liu, Zhongyuan

2018-02-01

In this work, bismuth selenides (Bi2Se3 and Bi3Se4), both of which have a layered rhombohedral crystal structure, have been found to be useful as electrode materials for supercapacitor applications. In a liquid electrolyte system (6M KOH), Bi2Se3 nanoplates exhibit much better performance as an electrode material than Bi3Se4 nanoparticles do, delivering a higher specific capacitance (272.9 F g-1) than that of Bi3Se4 (193.6 F g-1) at 5 mV s-1. This result may be attributed to the fact that Bi2Se3 nanoplates possess more active electrochemical surfaces for the reversible surface redox reactions owing to their planar quintuple stacked layers (septuple layers for Bi3Se4). To meet the demands of electronic skin, we used a novel flexible annular interdigital structure electrode to support the all-solid-state micro-supercapacitors (AMSCs). The Bi2Se3 AMSC device delivers a much better supercapacitor performance, exhibits a large stack capacitance of 89.5 F cm-3 at 20 mV s-1 (Bi3Se4: 79.1 F cm-3), a high energy density of 17.9 mWh cm-3 and a high power density of 18.9 W cm-3. The bismuth selenides also exhibit good cycle stability, with 95.5% retention after 1000 c for Bi2Se3 (Bi3Se4:90.3%). Clearly, Bi2Se3 nanoplates can be promising electrode materials for flexible annular interdigital AMSCs.

Production of Se-methylselenocysteine in transgenic plants expressing selenocysteine methyltransferase

Directory of Open Access Journals (Sweden)

Harris Hugh

2004-01-01

Full Text Available Abstract Background It has become increasingly evident that dietary Se plays a significant role in reducing the incidence of lung, colorectal and prostate cancer in humans. Different forms of Se vary in their chemopreventative efficacy, with Se-methylselenocysteine being one of the most potent. Interestingly, the Se accumulating plant Astragalus bisulcatus (Two-grooved poison vetch contains up to 0.6% of its shoot dry weight as Se-methylselenocysteine. The ability of this Se accumulator to biosynthesize Se-methylselenocysteine provides a critical metabolic shunt that prevents selenocysteine and selenomethionine from entering the protein biosynthetic machinery. Such a metabolic shunt has been proposed to be vital for Se tolerance in A. bisulcatus. Utilization of this mechanism in other plants may provide a possible avenue for the genetic engineering of Se tolerance in plants ideally suited for the phytoremediation of Se contaminated land. Here, we describe the overexpression of a selenocysteine methyltransferase from A. bisulcatus to engineer Se-methylselenocysteine metabolism in the Se non-accumulator Arabidopsis thaliana (Thale cress. Results By over producing the A. bisulcatus enzyme selenocysteine methyltransferase in A. thaliana, we have introduced a novel biosynthetic ability that allows the non-accumulator to accumulate Se-methylselenocysteine and γ-glutamylmethylselenocysteine in shoots. The biosynthesis of Se-methylselenocysteine in A. thaliana also confers significantly increased selenite tolerance and foliar Se accumulation. Conclusion These results demonstrate the feasibility of developing transgenic plant-based production of Se-methylselenocysteine, as well as bioengineering selenite resistance in plants. Selenite resistance is the first step in engineering plants that are resistant to selenate, the predominant form of Se in the environment.

Optical band gap study of a-Se and Se-Sb thin films

International Nuclear Information System (INIS)

Kaur, Ramandeep; Singh, Palwinder; Thakur, Anup

2016-01-01

Amorphous selenium (a-Se) and a-Se_9_5Sb_5 alloy were prepared using melt quenching technique. X-ray diffraction (XRD) pattern confirmed the amorphous nature of the prepared samples. Composition of the prepared samples has been determined using Energy dispersive X-ray fluorescence (EDXRF) technique. Differential thermal analysis (DTA) confirmed the glassy nature of the prepared samples. Thin films of the prepared samples were deposited on glass substrate using thermal evaporation method. Amorphous nature of the deposited films was confirmed using XRD. Optical properties of these films were obtained from the UV-VIS transmission spectra, at normal incidence, over 200-1100 nm spectral range. The optical absorption edge was described by using the model given by the Tauc. Optical band gap of the deposited films was calculated using Tauc plot. Optical characterization showed that average transmission and optical band gap decreased with the addition of antinomy.

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

de drogas que se consumen en su medio

Directory of Open Access Journals (Sweden)

José F. Enríquez Bielma

2006-01-01

Full Text Available Las adicciones son un problema de salud pública. Se estima que en México 3.5 millones de personas entre 12 a los 65 años han consumido algún tipo de drogas. A pesar de los avances en los estudios, se ha dejado de lado el carácter cultural que tiene la adicción. Con este estudio, se deseba conocer qué saben los estudiantes de segundo de secundaria sobre cuáles son las drogas que se consumen en su medio. Se llevó a cabo un estudio observacional con un muestreo aleatorio, con múltiples etapas y proporcional al tamaño en escuelas públicas y privadas. En total se estudiaron 42 escuelas del municipio de León, Gto., México de las cuales el 76.2% lo conformaron las escuelas públicas y el resto las escuelas privadas. Refirieron que conocen que se consumen, en su medio, 11 tipos de drogas. El 88% mencionó a la cocaína en primer lugar, en segundo lugar con un 85% la marihuana, siguiendo las tachas en un 62% y el pegamento en un 49%. En cuanto a los nombres que los estudiantes le dan a las drogas, estos van desde 23 hasta los 4 nombres, siendo la marihuana a la que se le da el mayor número de nombres, seguidos de la cocaína y el éxtasis.

Future strategy of SE

International Nuclear Information System (INIS)

Arcelli, M.

2006-01-01

In this presentation author (General Director of Slovenske elektrarne, a. s.) presents structure and investment plans of SE. The feasibility study of construction of the blocks 3 and 4 of the Mochovce NPP is presented

Magnetic excitation and local magnetic susceptibility of the excitonic insulator Ta2NiSe5 investigated by 77Se NMR

Science.gov (United States)

Li, Shang; Kawai, Shunsuke; Kobayashi, Yoshiaki; Itoh, Masayuki

2018-04-01

77Se NMR measurements were made on polycrystalline and single-crystalline samples to elucidate local magnetic susceptibility and magnetic excitation of Ta2NiSe5 , which is proposed to undergo an exciton condensation accompanied by a structural transition at Tc=328 K . We determine the 77Se Knight shift tensors for the three Se sites and analyze their anisotropy based on the site symmetry. The temperature dependence of the Knight shift is discussed on the basis of spin and orbital susceptibilities calculated for two-chain and two-dimensional three-band models. The large fraction of the Se 4 p orbital polarization due to the mixing between Ni 3 d and Se 4 p orbitals is estimated from the analysis of the transferred hyperfine coupling constant. Also the nuclear spin-lattice relaxation rate 1 /T1 is found not to show a coherent peak just below Tc and to obey the thermally activated temperature dependence with a spin gap energy of 1770 ±40 K . This behavior of 1 /T1 monitors the exciton condensation as proposed by the theoretical study of 1 /T1 based on the three-chain Hubbard model for the excitonic insulator.

Thermoelectric and mechanical properties of spark plasma sintered Cu3SbSe3 and Cu3SbSe4: Promising thermoelectric materials

Science.gov (United States)

Tyagi, Kriti; Gahtori, Bhasker; Bathula, Sivaiah; Toutam, Vijaykumar; Sharma, Sakshi; Singh, Niraj Kumar; Dhar, Ajay

2014-12-01

We report the synthesis of thermoelectric compounds, Cu3SbSe3 and Cu3SbSe4, employing the conventional fusion method followed by spark plasma sintering. Their thermoelectric properties indicated that despite its higher thermal conductivity, Cu3SbSe4 exhibited a much larger value of thermoelectric figure-of-merit as compared to Cu3SbSe3, which is primarily due to its higher electrical conductivity. The thermoelectric compatibility factor of Cu3SbSe4 was found to be ˜1.2 as compared to 0.2 V-1 for Cu3SbSe3 at 550 K. The results of the mechanical properties of these two compounds indicated that their microhardness and fracture toughness values were far superior to the other competing state-of-the-art thermoelectric materials.

Determination of total, and bound Se in sera by INAA

International Nuclear Information System (INIS)

Spate, V.L.; Mason, M.M.; Reams, C.L.; Baskett, C.K.; Morris, J.S.; Mills, D.S.

1994-01-01

The comparison between the total selenium in serum ('total Se') with that which is apparently bound to high molecular weight (> 12.000 D) species, presumably proteins ('bound Se') was reported. Nine hundred seventy seven (977) serum samples arising out of a population-based epidemiological study were prepared in duplicate for the determination of 'total Se' by pipeting directly into irradiation vials; and separate duplicate aliquots were dialyzed against DI water for the determination of 'bound Se'. All samples were analyzed by neutron activation analysis via 77m Se (17.4s) A small dialyzable Se component (∼ 6%) ('free Se'), defined as the difference between the 'total Se' minus the 'bound Se', was identified. (author) 2 refs.; 3 figs.; 5 tabs

Structural and optical properties of CdSe nanosheets

Science.gov (United States)

Solanki, Rekha Garg; Rajaram, P.; Arora, Aman

2018-04-01

Nanosheets of CdSe have been synthesized using a solvothermal route using citric acid as an additive. It is found that the citric acid effectively controls the structural and optical properties of CdSe nanostructures. XRD studies confirm the formation of hexagonal wurtzite phase of CdSe. The FESEM micrographs show that the obtained CdSe nanocrystals are in the form of very thin sheets (nanosheets). Optical absorption studies as well as Photoluminescence spectra show that the optical gap is around 1.76 eV which is close to the reported bulk value of 1.74 eV. The prepared CdSe nanosheets because of large surface area may be useful for catalytic activities in medicine, biotechnology and environmental chemistry and in biomedical imaging for in vitro detection of a breast cancer cells.

PySE: Software for extracting sources from radio images

Science.gov (United States)

Carbone, D.; Garsden, H.; Spreeuw, H.; Swinbank, J. D.; van der Horst, A. J.; Rowlinson, A.; Broderick, J. W.; Rol, E.; Law, C.; Molenaar, G.; Wijers, R. A. M. J.

2018-04-01

PySE is a Python software package for finding and measuring sources in radio telescope images. The software was designed to detect sources in the LOFAR telescope images, but can be used with images from other radio telescopes as well. We introduce the LOFAR Telescope, the context within which PySE was developed, the design of PySE, and describe how it is used. Detailed experiments on the validation and testing of PySE are then presented, along with results of performance testing. We discuss some of the current issues with the algorithms implemented in PySE and their interaction with LOFAR images, concluding with the current status of PySE and its future development.

Synthesis and biodistribution of 75Se-dinonyl-diselenide

International Nuclear Information System (INIS)

Liu, Y.F.; Qian, H.Q.; Zhang, Q.X.; Wang, X.Y.; Sun, J.G.; Li, B.Z.; Zhang, W.J.

1985-01-01

Selenium-75-labelled dinonyl-diselenide, C 9 H 19 75 SeSeC 9 H 19 , was synthesized and identified. It was injected into white rats in order to observe the selenium distribution in the tissues using inorganic 75 SeO 2 as the control agent. The sequence order of the 75 Se-dinonyl-diselenide uptake by tissues was: pancreas, muscles, stomach, liver, kidneys, spleen, blood, lungs, heart, brain, eyes. A very high accumulation of 75 Se-dinonyl-diselenide in the pancreas was observed, similar to that of the pancreatic imaging agent 75 Se-methionine. Furthermore, the enzymatic activity of glutathione peroxidase in the case of organic diselenide injection was higher than that measured for selenite. Selenium of dinonyl-diselenide was more effective and retainable in the process of converting itself to selenium-containing enzyme via the metabolic reactions. It may be advisable to replace inorganic sodium selenite by organic selenium compounds. Sodium selenite has been widely used in the prevention of the Keshan disease in China. (author)

PbSe nanocubes obtained by high-energy milling

Energy Technology Data Exchange (ETDEWEB)

Rojas-Chavez, H., E-mail: hrojasc@ipn.mx [Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada - IPN (Mexico); Reyes-Carmona, F. [Facultad de Quimica - UNAM (Mexico); Achimovicova, M. [Slovak Academy of Sciences, Institute of Geotechnics (Slovakia); Daneu, N. [Jozef Stefan Institute, Department for Nanostructured Materials (Slovenia); Jaramillo-Vigueras, D. [Centro de Investigacion e Innovacion Tecnologica - IPN (Mexico)

2012-06-15

In this study, PbSe nanocubes were obtained by high-energy milling, and their optical properties were investigated by measuring the UV-VIS-IR spectra in the range of 200-2,000 nm. The optical absorption of all samples showed a strong UV emission band at 1.45 eV. Previously, to obtain only PbSe nanocubes, an intermediate phase was identified, PbSeO{sub 3}. Although both PbSeO{sub 3} and PbSe were traced through this study, a major effort is devoted to characterize the latter. To trace how chemical transitions evolve from precursors to PbSe, X-ray diffraction and Rietveld refinement were carried out. Therefore, the following parameters were evaluated as a function of milling time: phase percentages, area-to-volume ratio, average crystallite dimensions, specific surface area, and morphology changes. To corroborate previous findings, nitrogen adsorption and transmission electron microscopy techniques were used. All the set experimental results unambiguously confirm that crystallites show a cubic morphology, with its average crystallite size distribution being around 24 nm.

Selective Cytotoxic Activity of Se-Methyl-Seleno-L-Cysteine- and Se-Polysaccharide-Containing Extracts from Shiitake Medicinal Mushroom, Lentinus edodes (Agaricomycetes).

Science.gov (United States)

Klimaszewska, Marzenna; Górska, Sandra; Dawidowski, Maciej; Podsadni, Piotr; Szczepanska, Agnieszka; Orzechowska, Emilia; Kurpios-Piec, Dagmara; Grosicka-Maciag, Emilia; Rahden-Staroń, Iwonna; Turło, Jadwiga

2017-01-01

Numerous formulations derived from the shiitake medicinal mushroom, Lentinus edodes, demonstrate anticancer activities. We hypothesized that isolates from selenium (Se)-enriched mycelia of L. edodes would possess stronger cancer-preventive properties than current preparations. The aim of this study was to investigate whether the presence of Se-methyl-seleno-L-cysteine in mycelial extracts of L. edodes affects their cytotoxic activity (makes them stronger) or whether they are as effective as Se-containing polysaccharides. Extracts were prepared from Se-containing mycelia under various conditions and assayed for cytotoxic activity in cancer (PC3 and HeLa) and normal (HMEC-1) cell lines. The chemical composition of the extracts was examined; specifically, the amounts of potentially cytotoxic Se compounds (methylselenocysteine, selenomethionine, and Se-containing polysaccharides) were measured. The relationship between extract composition and biological activity was characterized. Mycelial cultures were cultivated in a 10-L bioreactor in medium enriched with sodium selenite. Mycelial extracts were prepared either at 100°C or at 4°C in acidic solution. Total Se content was determined using the atomic absorption spectrometry method, and methylselenocysteine and selenomethionine contents were measured using reverse-phase high-performance liquid chromatography. Protein, carbohydrate, and polyphenolic contents were determined with spectrophotometric methods, and Se-containing polysaccharides were measured with the use of precipitation. Anticancer activity of mycelial extracts was examined using the MTT cell viability assay. Extracts containing Se-methyl-seleno-L-cysteine or Se-polysaccharides prepared at 4°C and 100°C, respectively, display moderate, time-dependent, specific cytotoxic activity in HeLa and PC3 cell lines. The effect in HeLa cells is more pronounced in the extract prepared at 4°C than at 100°C. The effect is almost equal for the PC3 cell line. However

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.

Thermoelectric Performance of Na-Doped GeSe

NARCIS (Netherlands)

Shaabani, Laaya; Aminorroaya-Yamini, Sima; Byrnes, Jacob; Akbar Nezhad, Ali; Blake, Graeme R

2017-01-01

Recently, hole-doped GeSe materials have been predicted to exhibit extraordinary thermoelectric performance owing largely to extremely low thermal conductivity. However, experimental research on the thermoelectric properties of GeSe has received less attention. Here, we have synthesized

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.

Chemical synthesis of Cu2Se nanoparticles at room temperature

International Nuclear Information System (INIS)

Rong, Fengxia; Bai, Yan; Chen, Tianfeng; Zheng, Wenjie

2012-01-01

Graphical abstract: The Cu 2 Se nanoparticles were synthesized by a simple and rapid method at room temperature. The TEM and SEM images show that the Cu 2 Se nanoparticles were spherical. Highlights: ► Cu 2 Se nanoparticles were synthesized by the reaction of nanoSe 0 sol with Cu + ions. ► The Cu 2 Se nanoparticles were spherical with cubic structure and well crystallized. ► Optical and electrochemical properties of Cu 2 Se nanoparticles were observed. ► The formation mechanism of Cu 2 Se nanoparticles was proposed. -- Abstract: A simple and rapid method has been developed to synthesize cuprous selenide (Cu 2 Se) nanoparticles by the reaction of selenium nanoparticles sol with copper sulfate solution containing ascorbic acid at room temperature. Cu 2 Se nanoparticles were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and energy dispersive X-ray analysis (EDX). The results indicated that Cu 2 Se nanoparticles were cubic crystal structure and spherical with the diameter about 75 nm. The ultraviolet–visible absorption spectrum (UV–vis) and cyclic voltammetry of Cu 2 Se nanoparticles were also investigated. The optical band gap energy of Cu 2 Se nanoparticles was 1.94 eV. On the basis of a series of experiments and characterizations, the formation mechanism of Cu 2 Se nanoparticles was discussed.

Electronic structure and superconductivity of FeSe-related superconductors.

Science.gov (United States)

Liu, Xu; Zhao, Lin; He, Shaolong; He, Junfeng; Liu, Defa; Mou, Daixiang; Shen, Bing; Hu, Yong; Huang, Jianwei; Zhou, X J

2015-05-13

FeSe superconductors and their related systems have attracted much attention in the study of iron-based superconductors owing to their simple crystal structure and peculiar electronic and physical properties. The bulk FeSe superconductor has a superconducting transition temperature (Tc) of ~8 K and it can be dramatically enhanced to 37 K at high pressure. On the other hand, its cousin system, FeTe, possesses a unique antiferromagnetic ground state but is non-superconducting. Substitution of Se with Te in the FeSe superconductor results in an enhancement of Tc up to 14.5 K and superconductivity can persist over a large composition range in the Fe(Se,Te) system. Intercalation of the FeSe superconductor leads to the discovery of the AxFe2-ySe2 (A = K, Cs and Tl) system that exhibits a Tc higher than 30 K and a unique electronic structure of the superconducting phase. A recent report of possible high temperature superconductivity in single-layer FeSe/SrTiO3 films with a Tc above 65 K has generated much excitement in the community. This pioneering work opens a door for interface superconductivity to explore for high Tc superconductors. The distinct electronic structure and superconducting gap, layer-dependent behavior and insulator-superconductor transition of the FeSe/SrTiO3 films provide critical information in understanding the superconductivity mechanism of iron-based superconductors. In this paper, we present a brief review of the investigation of the electronic structure and superconductivity of the FeSe superconductor and related systems, with a particular focus on the FeSe films.

Exploration work function and optical properties of monolayer SnSe allotropes

Science.gov (United States)

Cui, Zhen; Wang, Xia; Ding, Yingchun; Li, Meiqin

2018-02-01

The work function and optical properties are investigated with density functional theory for three monolayer SnSe allotropes. The calculated results indicate that the α-SnSe, δ-SnSe, ε-SnSe are semiconductor with the band gaps of 0.90, 1.25, and 1.50 eV, respectively. Meanwhile, the work function of δ-SnSe is lower than α-SnSe and ε-SnSe, which indicates that the δ-SnSe can be prepared of photoemission and field emission nanodevices. More importantly, the α-SnSe, δ-SnSe, ε-SnSe with the large static dielectric constants are 4.22, 5.48, and 3.61, which demonstrate that the three monolayer SnSe allotropes can be fabricated the capacitor. In addition, the static refractive index of δ-SnSe is larger than α-SnSe and ε-SnSe. The different optical properties with three monolayer SnSe allotropes reveal that the allotropes can regulate the properties of the materials. Moreover, our researched results show that the three monolayer SnSe allotropes are sufficient for fabrication of optoelectronic nanodevices.

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.

Shell Thickness Dependence of Interparticle Energy Transfer in Core-Shell ZnSe/ZnSe Quantum Dots Doping with Europium

Science.gov (United States)

Liu, Ni; Li, Shuxin; Wang, Caifeng; Li, Jie

2018-04-01

Low-toxic core-shell ZnSe:Eu/ZnS quantum dots (QDs) were prepared through two steps in water solution: nucleation doping and epitaxial shell grown. The structural and morphological characteristics of ZnSe/ZnS:Eu QDs with different shell thickness were explored by transmission electron microscopy (TEM) and X-ray diffraction (XRD) results. The characteristic photoluminescence (PL) intensity of Eu ions was enhanced whereas that of band-edge luminescence and defect-related luminescence of ZnSe QDs was decreased with increasing shell thickness. The transformation of PL intensity revealed an efficient energy transfer process between ZnSe and Eu. The PL intensity ratio of Eu ions ( I 613) to ZnSe QDs ( I B ) under different shell thickness was systemically analyzed by PL spectra and time-resolved PL spectra. The obtained results were in agreement with the theory analysis results by the kinetic theory of energy transfer, revealing that energy was transmitted in the form of dipole-electric dipole interaction. This particular method of adjusting luminous via changing the shell thickness can provide valuable insights towards the fundamental understanding and application of QDs in the field of optoelectronics.

Novel mechanical behaviors of wurtzite CdSe nanowires

Energy Technology Data Exchange (ETDEWEB)

Fu, Bing [Shanghai Normal University, Department of Physics (China); Chen, Li [MCPHS University, School of Arts and Sciences (United States); Xie, Yiqun; Feng, Jie; Ye, Xiang, E-mail: yexiang@shnu.edu.cn [Shanghai Normal University, Department of Physics (China)

2015-09-15

As an important semiconducting nanomaterial, CdSe nanowires have attracted much attention. Although many studies have been conducted in the electronic and optical properties of CdSe NWs, the mechanical properties of Wurtzite (WZ) CdSe nanowires remain unclear. Using molecular dynamics simulations, we have studied the tensile mechanical properties and behaviors of [0001]-oriented Wurtzite CdSe nanowires. By monitoring the stretching processes of CdSe nanowires, three distinct structures are found: the WZ wire, a body-centered tetragonal structure with four-atom rings (denoted as BCT-4), and a structure that consists of ten-atom rings with two four-atom rings (denoted as TAR-4) which is observed for the first time. Not only the elastic tensile characteristics are highly reversible under unloading, but a reverse transition between TAR-4 and BCT-4 is also observed. The stretching processes also have a strong dependence on temperature. A tubular structure similar to carbon nanotubes is observed at 150 K, a single-atom chain is formed at 300, 350 and 450 K, and a double-atom chain is found at 600 K. Our findings on tensile mechanical properties of WZ CdSe nanowires does not only provide inspiration to future study on other properties of CdSe nanomaterials but also help design and build efficient nanoscale devices.

Los jóvenes se incomunican

Directory of Open Access Journals (Sweden)

Margarita Ferro

2015-01-01

Full Text Available Hace años los jóvenes se comunicaban y relacionaban con sus amigos del barrio o de la escuela por lo que desde pequeños desarrollaban una comunicación interpersonal fluida. Hoy los video-juegos han sustituido la amistad y se han transformado en elementos de la comunicación. La autora analiza el mundo del nintendo y su influencia en las personas

SeRLoc: Robust Localization for Wireless Sensor Networks

National Research Council Canada - National Science Library

Lazos, Loukas; Poovendran, Radha

2005-01-01

.... We show that SeRLoc is robust against known attacks on WSNs such as the wormhole attack, the Sybil attack, and compromise of network entities and analytically compute the probability of success for each attack. We also compare the performance of SeRLoc with state-of-the-art range-independent localization schemes and show that SeRLoc has better performance.

Nematicity, magnetism and superconductivity in FeSe.

Science.gov (United States)

Böhmer, Anna E; Kreisel, Andreas

2018-01-17

Iron-based superconductors are well known for their complex interplay between structure, magnetism and superconductivity. FeSe offers a particularly fascinating example. This material has been intensely discussed because of its extended nematic phase, whose relationship with magnetism is not obvious. Superconductivity in FeSe is highly tunable, with the superconducting transition temperature, T c , ranging from 8 K in bulk single crystals at ambient pressure to almost 40 K under pressure or in intercalated systems, and to even higher temperatures in thin films. In this topical review, we present an overview of nematicity, magnetism and superconductivity, and discuss the interplay of these phases in FeSe. We focus on bulk FeSe and the effects of physical pressure and chemical substitutions as tuning parameters. The experimental results are discussed in the context of the well-studied iron-pnictide superconductors and interpretations from theoretical approaches are presented.

Lateral structure of (TiSe2)n(NbSe2)m superlattices

International Nuclear Information System (INIS)

Noh, M.; Shin, H.; Jeong, K.; Spear, J.; Johnson, D.C.; Kevan, S.D.; Warwick, T.

1997-01-01

The structures of a series of (TiSe 2 ) n (NbSe 2 ) m superlattices grown through controlled crystallization of designed multilayer reactants have been studied. X-ray diffraction of the data of the superlattices after crystallization show considerable preferred orientation, with the basal plane of the dichalcogenide structure parallel to the substrate to within 0.1 degree. Lattice refinement using the observed (00scr(l)) diffraction maxima yields lattice parameters along the c axis that are consistent with those expected based on the target superlattices and lattice parameters of the binary constituents. These (00scr(l)) diffraction data, however, contain no information about the crystalline structure in the ab plane of the superlattice associated with the preferred c-axis orientation. Off-specular x-ray diffraction (XRD), scanning electron microscopy, and scanning transmission x-ray microscopy (STXM) were used to explore the structure and homogeneity of the superlattices in the ab plane. XRD results rule out preferred long-range orientational order of the ab plane. Between grains, both the backscattered electron images and STXM images show grain domain structure in the ab plane with a characteristic grain domain size of approximately 50 μm. X-ray absorption microscopy in the STXM mode obtained at the Ti L 2,3 edge shows that the titanium in the superlattices is present as both octahedral Ti consistent with the TiSe 2 structure and metallic Ti. A comparison of the data obtained from these techniques highlights chemical information, which can be deduced on a submicrometer range from the space resolved spectra obtained using STXM. copyright 1997 American Institute of Physics

Unusually large chemical potential shift in a degenerate semiconductor: Angle-resolved photoemission study of SnSe and Na-doped SnSe

Science.gov (United States)

Maeda, M.; Yamamoto, K.; Mizokawa, T.; Saini, N. L.; Arita, M.; Namatame, H.; Taniguchi, M.; Tan, G.; Zhao, L. D.; Kanatzidis, M. G.

2018-03-01

We have studied the electronic structure of SnSe and Na-doped SnSe by means of angle-resolved photoemission spectroscopy. The valence-band top reaches the Fermi level by the Na doping, indicating that Na-doped SnSe can be viewed as a degenerate semiconductor. However, in the Na-doped system, the chemical potential shift with temperature is unexpectedly large and is apparently inconsistent with the degenerate semiconductor picture. The large chemical potential shift and anomalous spectral shape are key ingredients for an understanding of the novel metallic state with the large thermoelectric performance in Na-doped SnSe.

NaviSE: superenhancer navigator integrating epigenomics signal algebra.

Science.gov (United States)

Ascensión, Alex M; Arrospide-Elgarresta, Mikel; Izeta, Ander; Araúzo-Bravo, Marcos J

2017-06-06

Superenhancers are crucial structural genomic elements determining cell fate, and they are also involved in the determination of several diseases, such as cancer or neurodegeneration. Although there are pipelines which use independent pieces of software to predict the presence of superenhancers from genome-wide chromatin marks or DNA-interaction protein binding sites, there is not yet an integrated software tool that processes automatically algebra combinations of raw data sequencing into a comprehensive final annotated report of predicted superenhancers. We have developed NaviSE, a user-friendly streamlined tool which performs a fully-automated parallel processing of genome-wide epigenomics data from sequencing files into a final report, built with a comprehensive set of annotated files that are navigated through a graphic user interface dynamically generated by NaviSE. NaviSE also implements an 'epigenomics signal algebra' that allows the combination of multiple activation and repression epigenomics signals. NaviSE provides an interactive chromosomal landscaping of the locations of superenhancers, which can be navigated to obtain annotated information about superenhancer signal profile, associated genes, gene ontology enrichment analysis, motifs of transcription factor binding sites enriched in superenhancers, graphs of the metrics evaluating the superenhancers quality, protein-protein interaction networks and enriched metabolic pathways among other features. We have parallelised the most time-consuming tasks achieving a reduction up to 30% for a 15 CPUs machine. We have optimized the default parameters of NaviSE to facilitate its use. NaviSE allows different entry levels of data processing, from sra-fastq files to bed files; and unifies the processing of multiple replicates. NaviSE outperforms the more time-consuming processes required in a non-integrated pipeline. Alongside its high performance, NaviSE is able to provide biological insights, predicting cell

Layer Structured Bismuth Selenides of Bi2Se3 and Bi3Se4 for High Energy and Flexible All-Solid-State Micro-Supercapacitors.

Science.gov (United States)

Hao, Chunxue; Wang, Lidan; Wen, Fusheng; Xiang, Jianyong; Li, Lei; Hu, Wentao; Liu, Zhongyuan

2017-12-20

Bismuth selenides (Bi2Se3 and Bi3Se4), both of which have the layered rhombohedral crystal structure, and found to be useful as electrode materials for supercapacitor application in this work. Bi2Se3 nanoplates as electrode material exhibit much better performance than that of Bi3Se4 nanoparticles in liquid electrolyte system (6 M KOH), which delivers a higher specific capacitance (272.9 F/g) than that of Bi3Se4 (193.6 F/g) at 5 mV/s. This result would may be attributed to that Bi2Se3 nanoplates possess more active electrochemical surfaces for the reversible surface redox reactions owing to its planar quintuple stacked layers (septuple layers for Bi3Se4). For the demand of electronic skin, we used a novel flexible annular interdigital structure electrode applying for all-solid-state micro-supercapacitors (AMSCs). Bi2Se3 AMSCs device delivers a much more excellent supercapacitor performance, exhibits a large stack capacitance 89.5 F/cm3 (Bi3Se4: 79.1 F/cm3) at 20 mV/s, a high energy density 17.9 mWh/cm3 and high power density 18.9 W/cm3. The bismuth selenides also exhibit good cycle stability, retention 95.5% (90.3%) after 1000 c for Bi2Se3 (Bi3Se4). Obviously, Bi2Se3 nanoplates can be promising electrode materials for flexible annular interdigital all-solid-sate supercapacitor. © 2017 IOP Publishing Ltd.

Absorbed dose to man from the Se-75 labeled conjugated bile salt SeHCAT: concise communication

International Nuclear Information System (INIS)

Soundy, R.G.; Simpson, J.D.; Ross, H.M.; Merrick, M.V.

1982-01-01

The absorbed radiation dose that would result from the oral or intravenous administration of SeHCAT (23-[ 75 Se]selena-25-homotaurocholate) has been calculated using the MIRD tables and formulas and data from measurements of whole-body distribution and from long-term whole-body counting in rats, mice, and man. When SeHCAT is administered to normal subjects, the gallbladder is the critical organ, receiving 12 mrad (oral dose) or 22 mrad (i.v.) per microcurie. The whole-body dose is 1 mrad/μCi, whatever the route of administration. In severe hepatic failure the liver might receive 200 mrad/μCi. The activity likely to be used in routine clinical practice is 10 μCi. Where a whole-body counter is used, an activity of 1 μCi has proved adequate. Even at an administered activity of 25 μCi, the absorbed dose is small compared with established techniques of investigating the gastrointestinal tract

Absorbed dose to man from the Se-75 labeled conjugated bile salt SeHCAT: concise communication

International Nuclear Information System (INIS)

Soundy, R.G.; Simpson, J.D.; Ross, H.M.; Merrick, M.V.

1982-01-01

The absorbed radiation dose that would result from the oral or intravenous administration of SeHCAT (23-[75Se]selena-25-homotaurocholate) has been calculated using the MIRD tables and formulas and data from measurements of whole-body distribution and from long-term whole-body counting in rats, mice, and man. When SeHCAT is administered to normal subjects, the gallbladder is the critical organ, receiving 12 mrad (oral dose) or 22 mrad (i.v.) per microcurie. The whole-body dose is 1 mrad/microCi, whatever the route of administration. In severe hepatic failure the liver might receive 200 mrad/microCi. The activity likely to be used in routine clinical practice is 10 microCi. Where a whole-body counter is used, an activity of 1 microCi has proved adequate. Even at an administered activity of 25 microCi, the absorbed dose is small compared with established techniques of investigating the gastrointestinal tract

Structural manifestations of aging in Se-rich glasses

Science.gov (United States)

Dash, S.; Ravindren, S.; Chen, P.; Boolchand, P.

2015-03-01

We examine weakly cross-linked GexSe100-x (0%modulated DSC and Raman scattering experiments. Homogeneity of melts was carefully verified using FT-Raman line profiling. Upon aging at RT for 4 months, we find the width of the glass transition W(x) steadily decreasing from 10C at 7% Ge to 2C for pure Se. The 5-fold reduction of W(x) with a decrease of Ge content is accompanied by a 2-fold increase in the non-reversing enthalpy. Rejuvenation of the aged glasses changes W(x) from 15C at 7% Ge to 7C for pure Se. Tg is found to decrease upon rejuvenation with the difference (Tg(aged)-Tg(rejuv)) showing a maximum near 3% Ge and vanishing for pure Se and 6% of Ge, which are topological thresholds. These results in Se-rich glasses are consistent with aging induced decoupling of Se8 crowns and growth of extended range structural correlations between polymeric Sen chains due to lone pair interactions. At higher x, near 8-10% of Ge, eutectic effects are manifested. Work supported by NSF Grant DMR 08-53957.

Social Set Visualizer (SoSeVi) II

DEFF Research Database (Denmark)

Flesch, Benjamin; Vatrapu, Ravi

2016-01-01

This paper reports the second iteration of the Social Set Visualizer (SoSeVi), a set theoretical visual analytics dashboard of big social data. In order to further demonstrate its usefulness in large-scale visual analytics tasks of individual and collective behavior of actors in social networks......, the current iteration of the Social Set Visualizer (SoSeVi) in version II builds on recent advancements in visualizing set intersections. The development of the SoSeVi dashboard involved cutting-edge open source visual analytics libraries (D3.js) and creation of new visualizations such as of actor mobility...

Reversible ultrafast melting in bulk CdSe

International Nuclear Information System (INIS)

Wu, Wenzhi; He, Feng; Wang, Yaguo

2016-01-01

In this work, transient reflectivity changes in bulk CdSe have been measured with two-color femtosecond pump-probe spectroscopy under a wide range of pump fluences. Three regions of reflectivity change with pump fluences have been consistently revealed for excited carrier density, coherent phonon amplitude, and lattice temperature. For laser fluences from 13 to 19.3 mJ/cm 2 , ultrafast melting happens in first several picoseconds. This melting process is purely thermal and reversible. A complete phase transformation in bulk CdSe may be reached when the absorbed laser energy is localized long enough, as observed in nanocrystalline CdSe

Transition probabilities in neutron-rich Se,8684

Science.gov (United States)

Litzinger, J.; Blazhev, A.; Dewald, A.; Didierjean, F.; Duchêne, G.; Fransen, C.; Lozeva, R.; Sieja, K.; Verney, D.; de Angelis, G.; Bazzacco, D.; Birkenbach, B.; Bottoni, S.; Bracco, A.; Braunroth, T.; Cederwall, B.; Corradi, L.; Crespi, F. C. L.; Désesquelles, P.; Eberth, J.; Ellinger, E.; Farnea, E.; Fioretto, E.; Gernhäuser, R.; Goasduff, A.; Görgen, A.; Gottardo, A.; Grebosz, J.; Hackstein, M.; Hess, H.; Ibrahim, F.; Jolie, J.; Jungclaus, A.; Kolos, K.; Korten, W.; Leoni, S.; Lunardi, S.; Maj, A.; Menegazzo, R.; Mengoni, D.; Michelagnoli, C.; Mijatovic, T.; Million, B.; Möller, O.; Modamio, V.; Montagnoli, G.; Montanari, D.; Morales, A. I.; Napoli, D. R.; Niikura, M.; Pollarolo, G.; Pullia, A.; Quintana, B.; Recchia, F.; Reiter, P.; Rosso, D.; Sahin, E.; Salsac, M. D.; Scarlassara, F.; Söderström, P.-A.; Stefanini, A. M.; Stezowski, O.; Szilner, S.; Theisen, Ch.; Valiente Dobón, J. J.; Vandone, V.; Vogt, A.

2015-12-01

Reduced quadrupole transition probabilities for low-lying transitions in neutron-rich Se,8684 are investigated with a recoil distance Doppler shift (RDDS) experiment. The experiment was performed at the Istituto Nazionale di Fisica Nucleare (INFN) Laboratori Nazionali di Legnaro using the Cologne Plunger device for the RDDS technique and the AGATA Demonstrator array for the γ -ray detection coupled to the PRISMA magnetic spectrometer for an event-by-event particle identification. In 86Se the level lifetime of the yrast 21+ state and an upper limit for the lifetime of the 41+ state are determined for the first time. The results of 86Se are in agreement with previously reported predictions of large-scale shell-model calculations using Ni78-I and Ni78-II effective interactions. In addition, intrinsic shape parameters of lowest yrast states in 86Se are calculated. In semimagic 84Se level lifetimes of the yrast 41+ and 61+ states are determined for the first time. Large-scale shell-model calculations using effective interactions Ni78-II, JUN45, jj4b, and jj4pna are performed. The calculations describe B (E 2 ;21+→01+) and B (E 2 ;61+→41+) fairly well and point out problems in reproducing the experimental B (E 2 ;41+→21+) .

Extraction, characterization and antioxidant activities of Se-enriched tea polysaccharides.

Science.gov (United States)

Wang, Yuanfeng; Li, Yongfu; Liu, Yangyang; Chen, Xueqing; Wei, Xinlin

2015-01-01

Se-polysaccharides from Se-enriched tea leaves were purified by DEAE-sepharose fast flow gel column (2.5×60cm) and three polysaccharide fractions (Se-TPS1, Se-TPS2, and Se-TPS3) were isolated and purified with yields of 6.5, 37.14, and 8.57%, respectively. The average sizes of Se-TPS1 and Se-TPS2 were determined by HPGPC system, with molecular weights of 1.1×10(5) and 2.4×10(5)Da, respectively. Se-TPS3 was a polysaccharide polymer with two peaks with molecular weights of 9.2×10(5) and 2.5×10(5)Da. Monosaccharide components analysis by ion chromatography revealed Se-polysaccharides were acidic polysaccharoses and different from each other in monosaccharide kinds and molar ratio. Elements of Se, C, H, N, S, and 14 kinds of mineral elements were analyzed by AFS, EA, and ICP-AES, respectively. Spectral analysis (IR and UV) indicated Se-polysaccharides were typical glycoproteins. Morphological analyses of the samples were determined by SEM and AFM. In addition, the DPPH and superoxide radicals scavenging activities were also discussed to assess antioxidant activities of the samples, and Se-polysaccharides showed higher antioxidant activities compared to the ordinary polysaccharides. Copyright © 2015 Elsevier B.V. All rights reserved.

Atomic Defects and Doping of Monolayer NbSe2.

Science.gov (United States)

Nguyen, Lan; Komsa, Hannu-Pekka; Khestanova, Ekaterina; Kashtiban, Reza J; Peters, Jonathan J P; Lawlor, Sean; Sanchez, Ana M; Sloan, Jeremy; Gorbachev, Roman V; Grigorieva, Irina V; Krasheninnikov, Arkady V; Haigh, Sarah J

2017-03-28

We have investigated the structure of atomic defects within monolayer NbSe 2 encapsulated in graphene by combining atomic resolution transmission electron microscope imaging, density functional theory (DFT) calculations, and strain mapping using geometric phase analysis. We demonstrate the presence of stable Nb and Se monovacancies in monolayer material and reveal that Se monovacancies are the most frequently observed defects, consistent with DFT calculations of their formation energy. We reveal that adventitious impurities of C, N, and O can substitute into the NbSe 2 lattice stabilizing Se divacancies. We further observe evidence of Pt substitution into both Se and Nb vacancy sites. This knowledge of the character and relative frequency of different atomic defects provides the potential to better understand and control the unusual electronic and magnetic properties of this exciting two-dimensional material.

Thermal analysis of chalcogenide glasses of the system (As/sub/2Se/sub/3)/sub/(1-x):(Tl/sub/2Se)/sub/x

International Nuclear Information System (INIS)

Majid, C.A.

1987-01-01

In this paper differential thermal analysis (DTA) measurements of chalcogenide glasses of the system (As/sub/2Se/sub/3)/sub/(1-x): (Tl/sub/2Se)/sub/x, with x=0, 0.125, 0.25 and 0.50 are reported. The glass-forming tendencies of these materials have been calculated. The glass-forming tendency of As/sub/2Se/sub/3 has been found to be the highest among the member glasses of this family of chalcogenides. It was found that the glass-forming tendency of As/sub/2Se/sub/3 decreasing gradually at the Tl/sub/2/Se concentration increases. Tl/sub/2Se additions lower the glass transition temperature T/sub/q and the area under the endothermic peak for glass transition temperature, suggesting a tendency for relatively weaker bonding and hence less stability of Tl-rich glass compositions. These studies show that Tl/sub/2Se concentrations result in glasses with progressively higher crystallization tendencies. (author)

Tests for the absorption of /sup 75/Se-labelled homocholic acid conjugated with taurine (/sup 75/Se-HCAT)

Energy Technology Data Exchange (ETDEWEB)

Schroth, H.J.; Berberich, R.; Mueller, K.P.; Feifel, G.; Ecker, K.W.

1985-05-01

The absorption of selenomethionine Se 75-labelled homocholic acid conjugated with taurine (/sup 75/-SE-HCAT) was tested in 46 patients. Retention measurements using (1) an uncollimated gamma camera and (2) a measuring arrangement similar to a human-body counter were compared in order to obtain a quantitative assessment of the absorption capacity of the terminal ileum for bile acids. The retention curve obtained after the oral administration of the /sup 75/Se-labelled bile-acid analogue showed a monoexponential decline; in the case of unimpaired absorption, the half-life was greater than 2.5 days. When more than 30 cm of the ileum had been eliminated by inflammatory infection or resection, the measured half-life was below 0.5 days due to malabsorption. We also performed a quantitative determination of the hepatic secretion of /sup 75/-Se-HCAT into the gall bladder. If more than 80% of the activity administered is found in the gall bladder, disturbed absorption of bile acids in the terminal ileum can be excluded. Values smaller than 80%, however, do not provide proof of disturbed absorption.

Symmetry effects in neutron scattering from isotopically enriched Se isotopes

Energy Technology Data Exchange (ETDEWEB)

Lachkar, J.; Haouat, G.; McEllistrem, M. T.; Patin, Y.; Sigaud, J.; Cocu, F.

1975-06-01

Differential cross sections for neutron elastic and inelastic scattering from {sup 76}Se, {sup 78}Se, {sup 80}Se and {sup 82}Se, have been measured at 8-MeV incident neutron energy and from {sup 76}Se and {sup 82}Se at 6- and 10-MeV incident energies. The differences observed in the elastic scattering cross sections are interpretable as the effects of isospin term in the scattering potentials. A full analysis of the elastic scattering data are presented.

Detailed Visualization of Phase Evolution during Rapid Formation of Cu(InGa)Se2 Photovoltaic Absorber from Mo/CuGa/In/Se Precursors.

Science.gov (United States)

Koo, Jaseok; Kim, Sammi; Cheon, Taehoon; Kim, Soo-Hyun; Kim, Woo Kyoung

2018-03-02

Amongst several processes which have been developed for the production of reliable chalcopyrite Cu(InGa)Se 2 photovoltaic absorbers, the 2-step metallization-selenization process is widely accepted as being suitable for industrial-scale application. Here we visualize the detailed thermal behavior and reaction pathways of constituent elements during commercially attractive rapid thermal processing of glass/Mo/CuGa/In/Se precursors on the basis of the results of systematic characterization of samples obtained from a series of quenching experiments with set-temperatures between 25 and 550 °C. It was confirmed that the Se layer crystallized and then melted between 250 and 350 °C, completely disappearing at 500 °C. The formation of CuInSe 2 and Cu(InGa)Se 2 was initiated at around 450 °C and 550 °C, respectively. It is suggested that pre-heat treatment to control crystallization of Se layer should be designed at 250-350 °C and Cu(InGa)Se 2 formation from CuGa/In/Se precursors can be completed within a timeframe of 6 min.

Investigation of CuGaSe2/CuInSe2 double heterojunction interfaces grown by molecular beam epitaxy

Directory of Open Access Journals (Sweden)

Sathiabama Thiru

2015-02-01

Full Text Available In-situ reflection high-energy electron diffraction (RHEED observation and X-ray diffraction measurements were performed on heterojunction interfaces of CuGaSe2/CnInSe2/CuGaSe2 grown on GaAs (001 using migration-enhanced epitaxy. The streaky RHEED pattern and persistent RHEED intensity oscillations caused by the alternate deposition of migration-enhanced epitaxy sequence are observed and the growths of smooth surfaces are confirmed. RHEED observation results also confirmed constituent material interdiffusion at the heterointerface. Cross-sectional transmission electron microscopy showed a flat and abrupt heterointerface when the substrate temperature is as low as 400 °C. These have been confirmed even by X-ray diffraction and photoluminescence measurements.

Effect of nonstoichiometry properties of CuInSe2

International Nuclear Information System (INIS)

Rogacheva, E.I.; Tavrina, T.V.

1997-01-01

The homogeneity area size of the CuInSe 2 semiconductor compound is determined by the (CuIn)-Se profile of the Cu-In-Se ternary system at 350 deg C. The microhardness and thermo-electromotive force dependences on Se content are studied after various kind of thermal treatment. Interpretation of the results obtained is given with and account of defects formation character by deviations from stoichiometry [ru

Transient and modulated charge separation at CuInSe{sub 2}/C{sub 60} and CuInSe{sub 2}/ZnPc hybrid interfaces

Energy Technology Data Exchange (ETDEWEB)

Morzé, Natascha von, E-mail: natascha.von_morze@helmholtz-berlin.de; Dittrich, Thomas, E-mail: dittrich@helmholtz-berlin.de; Calvet, Wolfram, E-mail: wolfram.calvet@helmholtz-berlin.de; Lauermann, Iver, E-mail: iver.lauermann@helmholtz-berlin.de; Rusu, Marin, E-mail: rusu@helmholtz-berlin.de

2017-02-28

Highlights: • Surface physical properties of non- and Na-treated CuInSe{sub 2} layers studied. • Evidence of exciton dissociation and charge separation at CuInSe{sub 2}/ZnPc interface. • Strong band bending at the CuInSe{sub 2} surface in contact with C{sub 60} observed. • No evidence for exciton dissociation at the CuInSe{sub 2}/C{sub 60} interface found. • Cu-poor phase at CuInSe{sub 2}/organic interface crucial for charge separation. - Abstract: Spectral dependent charge transfer and exciton dissociation have been investigated at hybrid interfaces between inorganic polycrystalline CuInSe{sub 2} (untreated and Na-conditioned) thin films and organic C{sub 60} as well as zinc phthalocyanine (ZnPc) layers by transient and modulated surface photovoltage measurements. The stoichiometry and electronic properties of the bare CuInSe{sub 2} surface were characterized by photoelectron spectroscopy which revealed a Cu-poor phase with n-type features. After the deposition of the C{sub 60} layer, a strong band bending at the CuInSe{sub 2} surface was observed. Evidence for dissociation of excitons followed by charge separation was found at the CuInSe{sub 2}/ZnPc interface. The Cu-poor layer at the CuInSe{sub 2} surface was found to be crucial for transient and modulated charge separation at CuInSe{sub 2}/organic hybrid interfaces.

SeO2 adsorption on CaO surface: DFT study on the adsorption of a single SeO2 molecule

Science.gov (United States)

Fan, Yaming; Zhuo, Yuqun; Lou, Yu; Zhu, Zhenwu; Li, Liangliang

2017-08-01

Selenium is a hazardous element in coal. During coal combustion, most of the selenium will convert to SeO2 in the flue gas. Ca-based adsorbents, especially CaO, have been considered as a potential sorbent to adsorb SeO2 due to its low cost. In this paper, the adsorption mechanisms of single SeO2 on CaO surface were investigated by density functional theory (DFT) calculation. Both the physisorption and chemisorption structures were determined. It has been identified that the adsorption of SeO2 on CaO surface is primarily chemisorption, while physisorption takes effects at the initial stage of the process. Under O2 atmosphere, selenate is hard to form. Most of the adsorption products are selenite. Additionally, the electron density maps were obtained to reveal the surface active sites. The partial density of states (PDOS) was calculated for analyzing the electronic structural change of SeO2 and CaO surface during adsorption. The results provide fundamental information of the adsorption process, which could be meaningful for the development of new absorbents.

Photoacoustic spectroscopy of thin films of As2S3, As2Se3 and GeSe2

Indian Academy of Sciences (India)

Photoacoustic spectroscopy (PAS) is one of the important branches of spectroscopy, which enables one to detect light-induced heat production following the absorption of pulsed radiation by the sample. As2S3, As2Se3 and GeSe2 exhibit a wide variety of photo-induced phenomena that enable them to be used as optical ...

Cs2SeO4-UO2SeO4-H2O system at 25 deg C

International Nuclear Information System (INIS)

Serezhkina, L.B.; Serezhkin, V.N.

1987-01-01

Using the method of isothermal solubility at 25 deg C the interaction of cesium and uranyl selenates in aqueous solution is studied. Formation of congruently soluble Cs 2 UO 2 (SeO 4 ) 2 x2H 2 O and Cs 2 (UO 2 ) 2 x(SeO 4 ) 3 is ascertained, their crystallographic characteristics being determined

Estudio etnobotánico de especias, plantas aromáticas y medicinales utilizadas en La Molana, Atrato-Chocó, Colombia: Bases para la conservación de la biodiversidad

Directory of Open Access Journals (Sweden)

Miller Marmolejo Liloy

2018-01-01

Full Text Available Se realizó la caracterización y análisis de los sistemas productivos de plantas aromáticas, medicinales y condimentarias (PAMC de La Molana, Atrato-Chocó, Colombia a través de la identificación de sus características biofísicas, socioeconómicas y financieras, con el fin de proponer alternativas agroecológicas que solucionen los problemas y necesidades identificados en dichos sistemas; aplicando las metodologías e indicadores de evaluación de sistemas agrícolas hacia el desarrollo sostenible, Diseño, implementación y evaluación de arreglos agroforestales, Sistemas Agroforestales acompañado del análisis DOFA, y planificación agroforestal de unidades productivas (PAF, dicha información fue recopilada a través de la aplicación de un taller focal y cuestionarios semiestructurados a 40 productores. Se caracterizaron ocho unidades productivas (UP, cuatro parcelas y cuatro azoteas, a través de un muestreo aleatorio simple sin reposición. Los resultados señalan que estos productores destinan 15.6 ha a la producción de PAMC, de las cuales 11 ha son de cultivos en parcelas dentro de bosques y 4.6 ha son destinadas a cultivos en azoteas alrededor de las viviendas. Las unidades producen en promedio, 110 unidades (manojos semanales que son ofrecidos a vendedores informales en la plaza de mercado de Quibdó-Chocó, Colombia a precios que van desde COP $1000 hasta COP $3000 de acuerdo al tamaño y la especie. De igual modo se determinó que los ingresos económicos de las UP de PAMC dependen principalmente de las siguientes especies sembradas en las parcelas: Cilantro (Coriandrum sativum L., cimarrón (Eryngium foetidum L., Albahaca (Ocimum basilicum L. y Orégano (Origanum vulgare L., las cuales son las especies de mayor importancia económica en la zona de estudio.

Uma questão para a educacão inclusiva: expor-se ou resguardar-se?

Directory of Open Access Journals (Sweden)

Marie Claire Sekkel

Full Text Available Este artigo discute as relações entre os atores institucionais que participam de uma proposta de educação escolar inclusiva. Com essa finalidade, foram utilizados recortes dos dados coletados em uma pesquisa sobre a construção de ambientes inclusivos, realizada em uma escola municipal de educação infantil em São Paulo, no período de 2006 a 2008. Os dados foram organizados em torno da questão expor-se ou resguardar-se?, que dá visibilidade aos movimentos presentes nas relações institucionais. A pesquisa utilizou a etnografia como método de coleta de dados, e a análise foi feita com base no referencial da teoria crítica da sociedade. Os resultados apontam a presença do sentimento de ameaça, que gera a necessidade de resguardo, e também de situações de abertura à experiência no trabalho desenvolvido com as crianças, que pressupõem a necessidade de expor-se diante de si e do(s outro(s. Segundo autores da Escola de Frankfurt, a origem desse sentimento de ameaça é social, e o medo deve tornar-se consciente para que seus efeitos destrutivos para o indivíduo e para as relações sociais possam ser evitados. A abertura à experiência, por outro lado, é necessária para a produção de uma consciência verdadeira, que é o principal objetivo da educação segundo Theodor Adorno, e deve ser considerada elemento fundamental para os processos educacionais inclusivos.

Novel red-emission of ternary ZnCdSe semiconductor nanocrystals

Energy Technology Data Exchange (ETDEWEB)

Chung, Shu-Ru, E-mail: srchung@nfu.edu.tw [National Formosa University, Graduate Institute of Materials Science and Green Energy Engineering (China); Wang, Kuan-Wen [National Central University, Institute of Materials Science and Engineering (China); Chen, Hong-Shuo; Chen, Hong-Hong [National Formosa University, Graduate Institute of Materials Science and Green Energy Engineering (China)

2015-02-15

The effect of chain lengths of fatty acids on the physical properties of CdSe and ZnCdSe semiconductor nanocrystals (NCs) synthesized by the colloidal chemistry procedure is investigated. The fatty acids, lauric acid (LA), and stearic acid (SA), with different lengths of carbon chains, are used to prepare CdSe and ZnCdSe NCs when hexyldecylamine (HDA) is applied as the sole surfactant. For CdSe–SA and ZnCdSe–SA, they have the same emission wavelength at 592 nm and the same particle size of 3.3 nm; however, their quantum yield (QY) is 75 and 16 %, respectively. In contrast, the emission wavelength of CdSe–LA and ZnCdSe–LA NCs is 609 and 615 nm, the particle size is about 3.5 and 4 nm under the same reaction time, and the QY of them are 33 and 59 %, respectively. The X-ray diffraction pattern shows that ZnCdSe NCs all have the wurtzite structure, and their main peaks are located between those of pure CdSe and ZnSe materials. The main phase of ZnCdSe–SA and ZnCdSe–LA is ZnSe and CdSe, respectively, implying that alloyed ZnCdSe NC can be prepared and ZnSe and CdSe phase can be promoted by SA and LA, respectively. Moreover, the QY of red-emission ZnCdSe–LA is higher than 50 %. These results suggest that the growth rate of CdSe as well as ZnCdSe NC can be enhanced by using LA as complex reagent and HDA as sole surfactant. It is expected that the reported effective synthetic strategy can be developed as a very practical, easy and not time-consuming approach to prepare red emissive NCs with high QY and high reproducibility.

Novel red-emission of ternary ZnCdSe semiconductor nanocrystals

International Nuclear Information System (INIS)

Chung, Shu-Ru; Wang, Kuan-Wen; Chen, Hong-Shuo; Chen, Hong-Hong

2015-01-01

The effect of chain lengths of fatty acids on the physical properties of CdSe and ZnCdSe semiconductor nanocrystals (NCs) synthesized by the colloidal chemistry procedure is investigated. The fatty acids, lauric acid (LA), and stearic acid (SA), with different lengths of carbon chains, are used to prepare CdSe and ZnCdSe NCs when hexyldecylamine (HDA) is applied as the sole surfactant. For CdSe–SA and ZnCdSe–SA, they have the same emission wavelength at 592 nm and the same particle size of 3.3 nm; however, their quantum yield (QY) is 75 and 16 %, respectively. In contrast, the emission wavelength of CdSe–LA and ZnCdSe–LA NCs is 609 and 615 nm, the particle size is about 3.5 and 4 nm under the same reaction time, and the QY of them are 33 and 59 %, respectively. The X-ray diffraction pattern shows that ZnCdSe NCs all have the wurtzite structure, and their main peaks are located between those of pure CdSe and ZnSe materials. The main phase of ZnCdSe–SA and ZnCdSe–LA is ZnSe and CdSe, respectively, implying that alloyed ZnCdSe NC can be prepared and ZnSe and CdSe phase can be promoted by SA and LA, respectively. Moreover, the QY of red-emission ZnCdSe–LA is higher than 50 %. These results suggest that the growth rate of CdSe as well as ZnCdSe NC can be enhanced by using LA as complex reagent and HDA as sole surfactant. It is expected that the reported effective synthetic strategy can be developed as a very practical, easy and not time-consuming approach to prepare red emissive NCs with high QY and high reproducibility

Electrochemical synthesis of nanostructured Se-doped SnS: Effect of Se-dopant on surface characterizations

Science.gov (United States)

Kafashan, Hosein; Azizieh, Mahdi; Balak, Zohre

2017-07-01

SnS1-xSex nanostructures with different Se-dopant concentrations were deposited on fluorine doped tin oxide (FTO) substrate through cathodic electrodeposition technique. The pH, temperature, applied potential (E), and deposition time remained were 2.1, 60 °C, -1 V, and 30 min, respectively. SnS1-xSex nanostructures were characterized using X-ray diffraction (XRD), field emission scanning electron microcopy (FESEM), energy dispersive X-ray spectroscopy (EDX), room temperature photoluminescence (PL), and UV-vis spectroscopy. The XRD patterns revealed that the SnS1-xSex nanostructures were polycrystalline with orthorhombic structure. FESEM showed various kinds of morphologies in SnS1-xSex nanostructures due to Se-doping. PL and UV-vis spectroscopy were used to evaluate the optical properties of SnS1-xSex thin films. The PL spectra of SnS1-xSex nanostructures displayed four emission peaks, those are a blue, a green, an orange, and a red emission. UV-vis spectra showed that the optical band gap energy (Eg) of SnS1-xSex nanostructures varied between 1.22-1.65 eV, due to Se-doping.

The influence of thermal treatment and irradiation on specific resistance of (SnSe)1-x - (PrSe)x solid solutions

International Nuclear Information System (INIS)

Huseynov, J.I.; Murguzov, M.I.; Ismayilov, Sh.S.; Jafarov, T.A.

2014-01-01

Full text: It was studied some kinetic coefficients in cluding specific resistance of (SnSe) 1 -x - (PrSe) x solid solutions as well. Special interest was caused by composetions of above mentioned system for which the influence of irradiation and thermal treatment following this irradiation was explored. By its electric characteristics praseodymium monoselenide belongs to metals because a metallic link is formed among cation atoms in PrSe, at the expense of cohich praseodymium atoms possess an oxidation degree equalling to 3+

Anisotropy in CdSe quantum rods

Energy Technology Data Exchange (ETDEWEB)

Li, Liang-shi [Univ. of California, Berkeley, CA (United States)

2003-01-01

The size-dependent optical and electronic properties of semiconductor nanocrystals have drawn much attention in the past decade, and have been very well understood for spherical ones. The advent of the synthetic methods to make rod-like CdSe nanocrystals with wurtzite structure has offered us a new opportunity to study their properties as functions of their shape. This dissertation includes three main parts: synthesis of CdSe nanorods with tightly controlled widths and lengths, their optical and dielectric properties, and their large-scale assembly, all of which are either directly or indirectly caused by the uniaxial crystallographic structure of wurtzite CdSe. The hexagonal wurtzite structure is believed to be the primary reason for the growth of CdSe nanorods. It represents itself in the kinetic stabilization of the rod-like particles over the spherical ones in the presence of phosphonic acids. By varying the composition of the surfactant mixture used for synthesis we have achieved tight control of the widths and lengths of the nanorods. The synthesis of monodisperse CdSe nanorods enables us to systematically study their size-dependent properties. For example, room temperature single particle fluorescence spectroscopy has shown that nanorods emit linearly polarized photoluminescence. Theoretical calculations have shown that it is due to the crossing between the two highest occupied electronic levels with increasing aspect ratio. We also measured the permanent electric dipole moment of the nanorods with transient electric birefringence technique. Experimental results on nanorods with different sizes show that the dipole moment is linear to the particle volume, indicating that it originates from the non-centrosymmetric hexagonal lattice. The elongation of the nanocrystals also results in the anisotropic inter-particle interaction. One of the consequences is the formation of liquid crystalline phases when the nanorods are dispersed in solvent to a high enough

Electrodeposition of epitaxial CdSe on (111) gallium arsenide

Energy Technology Data Exchange (ETDEWEB)

Cachet, H.; Cortes, R.; Froment, M. [Universite Pierre et Marie Curie, Paris (France). Phys. des Liquides et Electrochimie; Etcheberry, A. [Institut Lavoisier (IREM) UMR CNRS C0173, Universite de Versailles- St Quentin en Yvelynes, 45 Avenue des Etats Unis, 78035, Versailles (France)

2000-02-21

Epitaxial growth of CdSe has been achieved on GaAs(111) by electrodeposition from an aqueous electrolyte. The structure of the film corresponds to the cubic modification of CdSe. The quality of epitaxy has been investigated by reflection high energy electron diffraction, transmission electron microscopy and X-ray diffraction techniques. By XPS measurements the chemistry of the CdSe/GaAs interface and the composition of CdSe are determined. (orig.)

An x-ray study of InSe

International Nuclear Information System (INIS)

Nagpal, K.C.; Ali, Z.

1975-01-01

Complete X-ray powder pattern of InSe, so far not available to literature, has been analyzed. The layer structure is based on a rhombohedral lattice cell, with space group R 3m, a sub(o) = 4.0046 +- 0.0005 A, csub(o) = 25.960 +- 0.004 A, and atomic position in 3 (a) of the space group : Zsub(In) = +-0.0555, Zsub(se) = 2/3 +- 0.106. Extreme softness and initial observe-reverse orientation of the rhombohedral cell in adjacent parts of a crystal or in thin lamellae parallel to the basal cleavage planes appear to be the main factors responsible for the characteristic sets of sharp and diffuse lines in the powder patterns normally obtained. These and Gandolfi camera powder patterns for several crystals are given. Heat treatment of powders obtained through cold work has indicated that comparatively short duration of 'annealing' at 600 deg C improves the powder pattern to some extent, but longer periods give products consisting of other phases of the In-Se system with small amount of InSe. The relative proportion of free space over the InSe powders in capsules as well as the amount of cold work seem to be the two main factors affecting the decomposition of InSe and appearance of other phases. Large platy crystals, on the other hand, withstand the heat treatment for a longer time. Even they undergo drastic changes in the sructure on prolonged heating at 600 deg C, yielding hexagonal phases with a common csub(o) = 19.26 A and a sub(o) = 4.0 and 7.11 respectively. (author)

Communication Received from Switzerland Concerning its Policies Regarding the Management of Plutonium; Comunicacion recibida de Suiza en relacion con sus polIticas referentes a la gestion del plutonio

Energy Technology Data Exchange (ETDEWEB)

NONE

2009-10-10

The Secretariat has received a note verbale dated 4 August 2009 from the Permanent Mission of Switzerland to the IAEA in the enclosures of which the Government of Switzerland, in keeping with its commitment under the Guidelines for the Management of Plutonium (contained in INFCIRC/5491 of 16 March 1998 and hereinafter referred to as 'Guidelines') and in accordance with Annexes B and C of the Guidelines, has made available annual figures for its holdings of civil unirradiated plutonium and the estimated amounts of plutonium contained in spent civil reactor fuel as of 31 December 2008 [Spanish] La Secretaria ha recibido una nota verbal, de fecha 4 de agosto de 2009, de la Mision Permanente de Suiza ante el OIEA, en cuyos anexos el Gobierno de Suiza, en cumplimiento de su compromiso contraido en virtud de las Directrices para la gestion del plutonio (transcritas en el documento INFCIRC/5491 de 16 de marzo de 1998 y a las que en adelante se denominara 'directrices') y de conformidad con los anexos B y C de esas directrices, ha presentado las cifras anuales de sus existencias de plutonio no irradiado de uso civil y las cantidades estimadas de plutonio contenido en el combustible gastado de reactores de uso civil, al 31 de diciembre de 2008.

Communication Received from Switzerland Concerning its Policies Regarding the Management of Plutonium; Comunicacion recibida de Suiza en relacion con sus politicas referentes a la gestion del plutonio

Energy Technology Data Exchange (ETDEWEB)

NONE

2010-06-01

The Secretariat has received a note verbale dated 4 May 2010 from the Permanent Mission of Switzerland to the IAEA in the enclosures of which the Government of Switzerland, in keeping with its commitment under the Guidelines for the Management of Plutonium (contained in INFCIRC/549 of 16 March 1998 and hereinafter referred to as 'Guidelines') and in accordance with Annexes B and C of the Guidelines, has made available annual figures for its holdings of civil unirradiated plutonium and the estimated amounts of plutonium contained in spent civil reactor fuel as of 31 December 2009 [Spanish] La Secretaria ha recibido una nota verbal, de fecha 4 de mayo de 2010, de la Mision Permanente de Suiza ante el OIEA, en cuyos anexos el Gobierno de Suiza, en cumplimiento de su compromiso contraido en virtud de las Directrices para la gestion del plutonio (transcritas en el documento INFCIRC/549 de 16 de marzo de 1998 y a las que en adelante se denominara 'directrices') y de conformidad con los anexos B y C de esas directrices, ha presentado las cifras anuales de sus existencias de plutonio no irradiado de uso civil y las cantidades estimadas de plutonio contenido en el combustible gastado de reactores de uso civil, al 31 de diciembre de 2009.

Communication Received from Switzerland Concerning its Policies Regarding the Management of Plutonium; Comunicacion recibida de Suiza en relacion con sus politicas referentes a la gestion del plutonio

Energy Technology Data Exchange (ETDEWEB)

NONE

2007-12-04

The Secretariat has received a Note Verbale dated 3 September 2007 from the Permanent Mission of Switzerland to the IAEA in the enclosures of which the Government of Switzerland, in keeping with Switzerland's commitment under the Guidelines for the Management of Plutonium (contained in INFCIRC/549 of 16 March 1998 and hereinafter referred to as 'Guidelines') and in accordance with Annexes B and C of the Guidelines, has made available annual figures for its holdings of civil unirradiated plutonium and the estimated amounts of plutonium contained in spent civil reactor fuel as of 31 December 2006 [Spanish] La Secretaria ha recibido una nota verbal, de fecha 3 de septiembre de 2007, de la Mision Permanente de Suiza ante el OIEA, en cuyos anexos el Gobierno de Suiza, en cumplimiento de su compromiso contraido en virtud de las Directrices para la gestion del plutonio (transcritas en el documento INFCIRC/549 de 22 de junio de 1998 y a las que en adelante se denominara 'directrices') y de conformidad con los anexos B y C de esas directrices, ha presentado las cifras anuales de sus existencias de plutonio no irradiado de uso civil y las cantidades estimadas de plutonio contenido en el combustible gastado de reactores de uso civil, al 31 de diciembre de 2006.

Study of structural phase transition in KD3 (Se O3)2 and Na H3(Se O3)2 by EPR

International Nuclear Information System (INIS)

Silva, J.C.M. da.

1988-01-01

The electron paramagnetic resonance of Se O - 2 centers in KD 3 (Se O 3 ) 2 and Na H 3 (Se O 3 ) 2 was done in the temperature ranges of -170 0 C o +80 0 C and +25 0 C to -185 0 C, respectively. (A.C.A.S.)

The system SnTe-InSe

International Nuclear Information System (INIS)

Gurshumov, A.P.; Alidzhanov, M.A.; Aliev, A.S.; Gadzhiev, T.G.; Mamedov, N.A.

1986-01-01

This paper discusses the nature of the interaction and physicochemical properties of the alloys of the system SnTe-InSe. The DTA was performed on an NTR-74 pyrometer, XPA on a Dron-2.0 diffractometer and MSA on an MIM-7 metallographic microscope. The microhardness of the samples was determined on a PMT-3 microhardness tester. The congruently melting compound SnInTeSe and solid solutions based on the starting components are formed in the system

Electronic Properties of Graphene-PtSe2 Contacts.

Science.gov (United States)

Sattar, Shahid; Schwingenschlögl, Udo

2017-05-10

In this article, we study the electronic properties of graphene in contact with monolayer and bilayer PtSe 2 using first-principles calculations. It turns out that there is no charge transfer between the components because of the weak van der Waals interaction. We calculate the work functions of monolayer and bilayer PtSe 2 and analyze the band bending at the contact with graphene. The formation of an n-type Schottky contact with monolayer PtSe 2 and a p-type Schottky contact with bilayer PtSe 2 is demonstrated. The Schottky barrier height is very low in the bilayer case and can be reduced to zero by 0.8% biaxial tensile strain.

Electronic Properties of Graphene–PtSe2 Contacts

KAUST Repository

Sattar, Shahid

2017-04-26

In this article, we study the electronic properties of graphene in contact with monolayer and bilayer PtSe2 using first-principles calculations. It turns out that there is no charge transfer between the components because of the weak van der Waals interaction. We calculate the work functions of monolayer and bilayer PtSe2 and analyze the band bending at the contact with graphene. The formation of an n-type Schottky contact with monolayer PtSe2 and a p-type Schottky contact with bilayer PtSe2 is demonstrated. The Schottky barrier height is very low in the bilayer case and can be reduced to zero by 0.8% biaxial tensile strain.

Electronic Properties of Graphene–PtSe2 Contacts

KAUST Repository

Sattar, Shahid; Schwingenschlö gl, Udo

2017-01-01

In this article, we study the electronic properties of graphene in contact with monolayer and bilayer PtSe2 using first-principles calculations. It turns out that there is no charge transfer between the components because of the weak van der Waals interaction. We calculate the work functions of monolayer and bilayer PtSe2 and analyze the band bending at the contact with graphene. The formation of an n-type Schottky contact with monolayer PtSe2 and a p-type Schottky contact with bilayer PtSe2 is demonstrated. The Schottky barrier height is very low in the bilayer case and can be reduced to zero by 0.8% biaxial tensile strain.

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.

Core–shell interaction and its impact on the optical absorption of pure and doped core-shell CdSe/ZnSe nanoclusters

Energy Technology Data Exchange (ETDEWEB)

Wang, Xinqin; Cui, Yingqi; Zeng, Qun; Yang, Mingli, E-mail: myang@scu.edu.cn [Institute of Atomic and Molecular Physics, Key Laboratory of High Energy Density Physics and Technology of Ministry of Education, Sichuan University, Chengdu 610065 (China); Yu, Shengping [College of Chemistry and Environment Protection Engineering, Southwest University for Nationalities, Chengdu 610041 (China)

2016-04-07

The structural, electronic, and optical properties of core-shell nanoclusters, (CdSe){sub x}@(CdSe){sub y} and their Zn-substituted complexes of x = 2–4 and y = 16–28, were studied with density functional theory calculations. The substitution was applied in the cores, the shells, and/or the whole clusters. All these clusters are characterized by their core-shell structures in which the core-shell interaction was found different from those in core or in shell, as reflected by their bondlengths, volumes, and binding energies. Moreover, the core and shell combine together to compose a new cluster with electronic and optical properties different from those of separated individuals, as reflected by their HOMO-LUMO gaps and optical absorptions. With the substitution of Cd by Zn, the structural, electronic, and optical properties of clusters change regularly. The binding energy increases with Zn content, attributed to the strong Zn–Se bonding. For the same core/shell, the structure with a CdSe shell/core has a narrower gap than that with a ZnSe shell/core. The optical absorption spectra also change accordingly with Zn substitution. The peaks blueshift with increasing Zn concentration, accompanying with shape variations in case large number of Cd atoms are substituted. Our calculations reveal the core-shell interaction and its influence on the electronic and optical properties of the core-shell clusters, suggesting a composition–structure–property relationship for the design of core-shell CdSe and ZnSe nanoclusters.

The Antiphagocytic Activity of SeM of Streptococcus equi Requires Capsule.

Science.gov (United States)

Timoney, John F; Suther, Pranav; Velineni, Sridhar; Artiushin, Sergey C

2014-01-01

Resistance to phagocytosis is a crucial virulence property of Streptococcus equi (Streptococcus equi subsp. equi; Se), the cause of equine strangles. The contribution and interdependence of capsule and SeM to killing in equine blood and neutrophils were investigated in naturally occurring strains of Se. Strains CF32, SF463 were capsule and SeM positive, strains Lex90, Lex93 were capsule negative and SeM positive and strains Se19, Se1-8 were capsule positive and SeM deficient. Phagocytosis and killing of Se19, Se1-8, Lex90 and Lex93 in equine blood and by neutrophils suspended in serum were significantly (P ≤ 0.02) greater compared to CF32 and SF463. The results indicate capsule and SeM are both required for resistance to phagocytosis and killing and that the anti-phagocytic property of SeM is greatly reduced in the absence of capsule.

Electrodeposition and Thermoelectric Properties of Cu-Se Binary Compound Films

Science.gov (United States)

Yang, Mengqian; Shen, Zhengwu; Liu, Xiaoqing; Wang, Wei

2016-03-01

Cu-Se binary compound films have been prepared by electrodeposition from solutions containing CuSO4, H2SeO3, and H2SO4 and their composition, structure, and thermoelectric performance analyzed. Moving the depositing potential negatively increased the Cu content in the film, remarkably so for relatively low Cu2+ concentration in the solution. X-ray diffraction analysis showed that the phase composition of the films varied with their Cu content. Cu-Se binary compound films electrodeposited from solutions with different concentration ratios of CuSO4 to H2SeO3 showed two different phases: α-Cu2- x Se (monoclinic) with Se content in the range of 33.3 at.% to 33.8 at.%, and β-Cu2Se (cubic) with Se content in the range of 35.3 at.% to 36.0 at.%. The highest power factor for electrodeposited Cu2- x Se film was 0.13 mW/(K2 m) with Seebeck coefficient of 56.0 μV/K.

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.)

SeO2 adsorption on CaO surface: DFT and experimental study on the adsorption of multiple SeO2 molecules

Science.gov (United States)

Fan, Yaming; Zhuo, Yuqun; Li, Liangliang

2017-10-01

SeO2 adsorption mechanisms on CaO surface were firstly investigated by both density functional theory (DFT) calculations and adsorption experiments. Adsorption of multiple SeO2 on the CaO (001) surface was investigated using slab model. Based on the results of adsorption energy and surface property, a double-layer adsorption mechanisms were proposed. In experiments, the SeO2 adsorption products were prepared in a U-shaped quartz reactor at 200 °C. The surface morphology was investigated by field emission scanning electron microscopy (FE-SEM). The superficial and total SeO2 mass fractions were measured by X-ray photoelectron spectroscopy (XPS) and inductively coupled plasma atomic emission spectroscopy (ICP-AES), respectively. The surface valence state and bulk structure are determined by XPS and X-Ray Diffraction (XRD). The experimental results are in good agreement with the DFT results. In conclusion, the fundamental SeO2 chemisorption mechanisms on CaO surface were suggested.

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.

Crystal structure, Raman scattering and magnetic properties of CuCr2-xZrxSe4 and CuCr2-xSnxSe4 selenospinels

Science.gov (United States)

Pinto, C.; Galdámez, A.; Barahona, P.; Moris, S.; Peña, O.

2018-06-01

Selenospinels, CuCr2-xMxSe4 (M = Zr and Sn), were synthesized via conventional solid-state reactions. The crystal structure of CuCr1.5Sn0.5Se4, CuCr1.7Sn0.3Se4, CuCr1.5Zr0.5Se4, and CuCr1.8Zr0.2Se4 were determined using single-crystal X-ray diffraction. All the phases crystallized in a cubic spinel-type structure. The chemical compositions of the single-crystals were examined using energy-dispersive X-ray analysis (EDS). Powder X-ray diffraction patterns of CuCr1.3Sn0.7Se4 and CuCr1.7Sn0.3Se4 were consistent with phases belonging to the Fd 3 bar m Space group. An analysis of the vibrational properties on the single-crystals was performed using Raman scattering measurements. The magnetic properties showed a spin glass behavior with increasing Sn content and ferromagnetic order for CuCr1.7Sn0.3Se4.

The absolute age of SE-RF-6 (Ngamanie) and its relation to SE-RF-2 (Nenumbo) : two decorated lapita sites in the southeast Solomon Islands

International Nuclear Information System (INIS)

Green, R.C.; Jones, M.

2007-01-01

The relative age of SE-RF-6, SE-RF-2 and SE-SZ-8, three decorative phase Lapita sites in the Reef/Santa Cruz region of the Outer Easter Islands of Solomon Islands, has been the subject of dispute. A review of the evidence recovered from SE-RF-6 (Ngamanie), in conjunction with a Bayesian calibration model, supports the notion that it postdates the nearby site of SE-RF-2 (Nenumbo). We conclude that the SE-RF-6 represents an occupation of 50 to 100 years duration (compared with 50 or less for SE-RF-2), beginning some time in the interval 2470-2910 BP. (author). 22 refs., 4 figs., 3 tabs

Raman scattering and structural analysis of electrodeposited CuInSe{sub 2} and S-rich quaternary CuIn(S,Se){sub 2} semiconductors for solar cells

Energy Technology Data Exchange (ETDEWEB)

Izquierdo-Roca, Victor; Fontane, Xavier; Morante, Joan Ramon [Departament d' Electronica, Universitat de Barcelona (Spain); Saucedo, Edgardo; Ruiz, Carmen M.; Grand, Pierre-Philippe; Jaime-Ferrer, Jesus Salvador; Bermudez, Veronica [Institut de Recherche et Developement sur l' Energie Photovoltaique (IRDEP), Chatou (France); Calvo-Barrio, Lorenzo [Departament d' Electronica, Universitat de Barcelona (Spain); Lab. Analisis de Superficies, SCT, Universitat de Barcelona (Spain); Alvarez-Garcia, Jacobo [Centre de Recerca i Investigacio de Catalunya (CRIC), Barcelona (Spain); Perez-Rodriguez, Alejandro

2009-05-15

This work reports the Raman scattering characterisation of CuInSe{sub 2} precursors grown by single step electrodeposition and the corresponding layers recrystallised under sulphurising conditions for solar cell devices. The analysis of the spectra measured on the as-grown precursors has allowed identifying the main secondary phases in these layers with elemental Se, Cu-Se phases and chalcopyrite Cu-poor ordered vacancy domains. To deepen in the identification of the Cu-Se phases, these measurements have been correlated with the analysis of binary Cu-Se layers. The experimental data indicate that formation of both Se and Cu-Se phases is likely controlled by the Se content in the layers. For values of stoichiometry below 1.15, excess Cu in the layers is accommodated in a phase with very low Raman efficiency (as Cu{sub 2}Se). Increasing the content of Se leads to an increase in the spectral contribution from both Se and Cu{sub 2-x}Se, being the formation of these phases likely favoured under high excess Se conditions. The characterisation of the corresponding recrystallised layers has allowed analysing the impact of the presence of the secondary phases in the as-grown absorbers on the performance of the final solar cells. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Properties of different temperature annealed Cu(In,Ga)Se{sub 2} and Cu(In,Ga){sub 2}Se{sub 3.5} films prepared by RF sputtering

Energy Technology Data Exchange (ETDEWEB)

Yu Zhou; Liu Lian; Yan Yong; Zhang Yanxia; Li Shasha; Yan Chuanpeng; Zhang Yong [Key Laboratory of Magnetic Suspension Technology and Maglev Vehicle, Ministry of Education of China, Superconductivity and New Energy R and D Center (SNERDC), Mail Stop 165, Southwest Jiaotong University, Chengdu 610031 (China); Zhao Yong, E-mail: yzhao@swjtu.edu.cn [Key Laboratory of Magnetic Suspension Technology and Maglev Vehicle, Ministry of Education of China, Superconductivity and New Energy R and D Center (SNERDC), Mail Stop 165, Southwest Jiaotong University, Chengdu 610031 (China); School of Materials Science and Engineering, University of New South Wales, Sydney 2052, NSW (Australia)

2012-11-15

Highlights: Black-Right-Pointing-Pointer The Cu(In,Ga)Se{sub 2} and Cu(In,Ga)2Se{sub 3.5} films follow different process to form CIGS phase. Black-Right-Pointing-Pointer Composition loss of the annealed Cu(In,Ga)Se{sub 2} and Cu(In,Ga){sub 2}Se{sub 3.5} films are different. Black-Right-Pointing-Pointer Hexagonal CuSe phase exhibits unique transport feature. Black-Right-Pointing-Pointer Conductivity of the CIGS films is affected by the 'variable range hopping' mechanism. - Abstract: We have investigated the effect of annealing temperature on structural, compositional, electrical properties of the one-step RF sputtered Cu(In,Ga)Se{sub 2} and Cu(In,Ga){sub 2}Se{sub 3.5} films. After the annealing at various temperatures, loss of Se element is significant for the Cu(In,Ga)Se{sub 2} films and meanwhile composition of the annealed Cu(In,Ga){sub 2}Se{sub 3.5} films keeps almost constant. The as-deposited Cu(In,Ga)Se{sub 2} and Cu(In,Ga){sub 2}Se{sub 3.5} films show amorphous structure and they follow different transformation process to form chalcopyrite structure. Electrical conductivity of the annealed CIGS films related to their chemical composition. Cu(In,Ga)Se{sub 2} films annealed at 150 Degree-Sign C show unique electron transport mechanism for the formation of hexagonal CuSe phase. Electrical conductivity of the chalcopyrite structure films are dominated by the 'variable range hopping' transport mechanism. The annealed Cu(In,Ga){sub 2}Se{sub 3.5} films present higher density of disorders than the annealed Cu(In,Ga)Se{sub 2} films for their significant Cu deficient composition.

Fe-vacancy and superconductivity in FeSe-based superconductors

Science.gov (United States)

Wang, C. H.; Chen, T. K.; Chang, C. C.; Lee, Y. C.; Wang, M. J.; Huang, K. C.; Wu, P. M.; Wu, M. K.

2018-06-01

This review summarizes recent advancements in FeSe and related systems. The FeSe and related superconductors are currently receiving considerable attention for the high Tcs observed and for many similar features to the high Tc cuprate superconductors. These similarities suggest that understanding the FeSe based compounds could potentially help our understanding of the cuprates. We shall first review the common features observed in the FeSe-based system. It was found that with a careful control of material synthesizing processes, numerous rich phases have been observed in the FeSe-based system. Detailed studies show that the Fe-vacancy ordered phases found in the FeSe based compounds, which are non-superconducting Mott insulators, are the parent compounds of the superconductors. Superconductivity emerges from the parent phases by disordering the Fe vacancy order, often by a simple annealing treatment. Recent high temperature X-ray diffraction experiments show that the degree of structural distortion associated with the disorder of Fe-vacancy is closely related to volume fraction of the superconductivity observed. These results suggest the strong lattice to spin coupling are important for the occurrence of superconductivity in FeSe based superconductors.

¿Qué se juega al jugar un juego?

Directory of Open Access Journals (Sweden)

Kalejman, Cecilia

2012-06-01

Full Text Available En el presente artículo se considera el juego en relación a la niñez. Se indaga acerca del papel que juega el juego en la niñez intentando responder a diversas preguntas, entre ellas la más importante: ¿Qué significa jugar? A lo largo de esta etapa del desarrollo en que comienza a constituirse la subjetividad del individuo el juego constituye, sin dudas, un factor central, una herramienta fundamental en el desarrollo. Juego no es sólo el juego dramático, también consideramos para nuestro análisis aquellas modalidades de juego que se transmiten de generación en generación, juegos de construcción, los dibujos, teniendo en cuenta asimismo los objetos utilizados en los juegos, los contenidos de los mismos, los espacios en los que se desarrollan. Se piensa y se interpreta al juego, como un derecho y como un modo de expresión del niño, se finaliza este desarrollo con una conclusión acera del juego y el espacio que ocupa en la vida cotidiana.

Low temperature magnetic structure of MnSe

Indian Academy of Sciences (India)

Abstract. In this paper we report low temperature neutron diffraction studies on MnSe in order to understand the anomalous behaviour of their magnetic and transport prop- erties. Our study indicates that at low temperatures MnSe has two coexisting crystal structures, high temperature NaCl and hexagonal NiAs. NiAs phase ...

Thermoelectric properties of SnSe compound

Energy Technology Data Exchange (ETDEWEB)

Guan, Xinhong [State Key Laboratory of Information Photonics and Optical Communications, Ministry of Education, Beijing University of Posts and Telecommunications, P.O. Box 72, Beijing 100876 (China); Lu, Pengfei, E-mail: photon@bupt.edu.cn [State Key Laboratory of Information Photonics and Optical Communications, Ministry of Education, Beijing University of Posts and Telecommunications, P.O. Box 72, Beijing 100876 (China); Wu, Liyuan; Han, Lihong [State Key Laboratory of Information Photonics and Optical Communications, Ministry of Education, Beijing University of Posts and Telecommunications, P.O. Box 72, Beijing 100876 (China); Liu, Gang [School of Electronic Engineering, Beijing University of Posts and Telecommunications, Beijing 100876 (China); Song, Yuxin [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China); Wang, Shumin [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China); Photonics Laboratory, Department of Microtechnology and Nanoscience, Chalmers University of Technology, 41296 Gothenburg (Sweden)

2015-09-15

Highlights: • The electronic and thermoelectric properties of SnSe bulk material are studied. • The ZT can reach as high as 1.87 along yy and 1.6 along zz direction at 800k. • SnSe is an indirect-band material, and SOC has little effect on the band structure. • The high ZT can be attributed to the intrinsically ultralow thermal conductivity. - Abstract: A first-principles study and Boltzmann transport theory have been performed to evaluate the electronic structure and thermoelectric properties of SnSe compound. The energy band structure and density of states are studied in detail. The electronic transport coefficients are then calculated as a function of chemical potential or temperature within the assumption of the constant relaxation time. The figure of merit ZT is obtained with the use of calculated thermoelectric properties and can reach as high as 1.87 along yy and 1.6 along zz direction at 800 K. Our theoretical result agrees well with previous experimental data.

Thermoelectric properties of SnSe compound

International Nuclear Information System (INIS)

Guan, Xinhong; Lu, Pengfei; Wu, Liyuan; Han, Lihong; Liu, Gang; Song, Yuxin; Wang, Shumin

2015-01-01

Highlights: • The electronic and thermoelectric properties of SnSe bulk material are studied. • The ZT can reach as high as 1.87 along yy and 1.6 along zz direction at 800k. • SnSe is an indirect-band material, and SOC has little effect on the band structure. • The high ZT can be attributed to the intrinsically ultralow thermal conductivity. - Abstract: A first-principles study and Boltzmann transport theory have been performed to evaluate the electronic structure and thermoelectric properties of SnSe compound. The energy band structure and density of states are studied in detail. The electronic transport coefficients are then calculated as a function of chemical potential or temperature within the assumption of the constant relaxation time. The figure of merit ZT is obtained with the use of calculated thermoelectric properties and can reach as high as 1.87 along yy and 1.6 along zz direction at 800 K. Our theoretical result agrees well with previous experimental data

Epitaxial CdSe-Au nanocrystal heterostructures by thermal annealing.

Science.gov (United States)

Figuerola, Albert; van Huis, Marijn; Zanella, Marco; Genovese, Alessandro; Marras, Sergio; Falqui, Andrea; Zandbergen, Henny W; Cingolani, Roberto; Manna, Liberato

2010-08-11

The thermal evolution of a collection of heterogeneous CdSe-Au nanosystems (Au-decorated CdSe nanorods, networks, vertical assemblies) prepared by wet-chemical approaches was monitored in situ in the transmission electron microscope. In contrast to interfaces that are formed during kinetically controlled wet chemical synthesis, heating under vacuum conditions results in distinct and well-defined CdSe/Au interfaces, located at the CdSe polar surfaces. The high quality of these interfaces should make the heterostructures more suitable for use in nanoscale electronic devices.

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.

Electronic structure and exchange interactions in diluted semimagnetic semiconductors (Zn,Co)Se and (Zn,Mn)Se

Science.gov (United States)

Mašek, J.

1991-05-01

A comparative study of the electronic structure of (Zn,Co)Se and (Zn,Mn)Se is done by using a tight-binding version of the coherent potential approximation. The densities of states, relevant for a photoemission experiment, are calculated for a magnetically disordered phase. The exchange constant Jpd is obtained from the splitting of the valence band top in the ferromagnetic phase of the mixed crystal; Jdd is estimated from the energy of a spin reversal. We explain the large exchange constant in the Co-based systems as a result of efficient hybridization of the d-states with the valence band.

Utility of the SeHCAT test in the investigation of different types of bile acid malabsorption; SeHCAT-scanning ved galdesyremalabsorption

Energy Technology Data Exchange (ETDEWEB)

Hornshoej Thomsen, Lars; Arveschough, Anne Kirstine; Gustenhoff, Peter; Qvist, Peter

1998-09-01

Chronic diarrhoea caused by bile acid malabsorption (BAM) is usually divided into three groups. Type 1 is associated with ileal disease or ileal resection; type 2 is idiopathic, and type 3 is BAM associated with certain predisposing conditions. We evaluated the applicability of the SeHCAT test as a routine investigation of different types of suspected BAM. Detailed information about 298 patients were obtained from retrospective review of patient records. All 68 patients with ileal resections had abnormal SeHCAT retention (median 0.6%; range 0-13%). Of 42 patients with non-resected Crohn`s disease or radiation injury, BAM was found in 28 cases. A diagnosis of BAM type 2 was established in 33 of 150 patients with unexplained chronic diarrhoea. For patients tested for possible BAM type 3, the SeHCAT values were significantly lower compared to type 2 patients. For BAM type 1, the SeHCAT test is only recommended in non-resected patients. Idiopathic BAM seems to be more common than recognized. The presence of certain predisposing conditions might strenghten the indication for SeHCAT testing. (au) 20 refs.

Hablando se entiende la gente

Directory of Open Access Journals (Sweden)

Mila Crespo Picó

2012-08-01

Full Text Available Habiendo observado que muchos cursos centrados en el desarrollo de la competencia comunicativa oral se limitan a ofrecer actividades inconexas que suponen un gran esfuerzo por parte de los participantes para situarse ante cada actividad y dificultan el establecimiento de relaciones profundas entre los exponentes nociofuncionales, los objetivos comunicativos y los recursos lingüísticos necesarios para realizarlas por contar con un tiempo limitado en el aula para ello, se presentó, bajo el mismo título que esta comunicación, una propuesta didáctica para un curso de conversación que pretende paliar estos aspectos en el I Foro de Profesores de E/LE en la Universitat de València.

Structure of ferroelastic K3H(SeO4)2

International Nuclear Information System (INIS)

Ichikawa, M.; Sato, S.; Komukae, M.; Osaka, T.

1992-01-01

Tripotassium hydrogenbis(selenate), K 3 H(SeO 4 ) 2 , M r = 404.2, monoclinic, A2/a, a = 10.1291 (8), b = 5.9038 (5), c = 14.961 (1) A, β = 103.640 (8) 0 , V = 869.5 (1) A 3 , Z = 4, D x = 3.086 Mg m -3 , λ(Mo Kα) = 0.71073 A, μ = 9.86 mm -1 , F(000) = 760, T = 299 K, R(F) = 0.0294 for 1670 unique reflections. K 3 H(SeO 4 ) 2 is isomorphous with most M 3 H(XO 4 ) 2 -type crystals (M=K,Rb and Cs; Cs; X = S and Se); two SeO 4 groups are connected by a crystallographically symmetric hydrogen bond into a dimer. The bond distances and angles in the SeO 4 group are similar to those in Rb 3 H(SeO 4 ) 2 and Rb 3 D(SeO 4 ) 2 . The hydrogen-bond length, 2.524 (5) A, is the shortest among the members of the M 3 H(SeO 4 ) 2 family exhibiting the low-temperature phase transition. (orig.)

Facile synthesis and characterization of hexagonal NbSe2 nanoplates

International Nuclear Information System (INIS)

Zhang, Xianghua; Zhang, Du; Tang, Hua; Ji, Xiaorui; Zhang, Yi; Tang, Guogang; Li, Changsheng

2014-01-01

Graphical abstract: - Highlights: • Uniform hexagonal NbSe 2 nanoplates were prepared by a simple solid state reaction. • The possible formation mechanism of the NbSe 2 nanoplates was discussed. • The formation of NbSe 2 nanoplates undergoes a series of phase transition. - Abstract: The NbSe 2 nanoplates with hexagonal morphology have been successfully prepared by a facile, environmentally friendly reaction in closed reactor at moderate temperature. The thermal (750 °C) solid-state reaction between the ball-milled mixture of micro-sized Nb and Se yielded a high yield of NbSe 2 nanoplates. The as-prepared products were characterized by XRD, EDS, and SEM. The results showed that the as-prepared products were hexagonal phase NbSe 2 nanoplates with uniform sizes and the formation of NbSe 2 nanoplates underwent a series of phase transition. On the basis of experimental results obtained at different temperatures, a reasonable reaction process and a formation mechanism were proposed. Moreover, the ball milling time played a crucial role in acquiring the homogeneous distribution nanoplates

Estudio preliminar de la mineralización uranífera en la cordillera oriental, San Ramón, Oxapampa

OpenAIRE

Valencia, Jacinto

2014-01-01

Rocas intrusivas del magmatismo permo-triásico de la cordillera oriental, constituidas por granitos de San Ramón y Oxapampa, presentan buena favorabilidad como rocas fértiles en uranio, un granito de facie roja denominado monzo-granito; esta condición es el resultado de la ejecución del proyecto de cooperación del OIEA PER 2/16, a cargo de IPEN, “Mejora del conocimiento del potencial uranífero del Perú”. Los trabajos de campo han consistido en la revisión geológico-radiométrica y toma de mues...

Experimental studies and nuclear model calculations on proton-induced reactions on $^{nat}$Se, $^{76}$Se and $^{77}$Se with particular reference to the production of the medically interesting radionuclides $^{76}$Br and $^{77}$Br

CERN Document Server

Hassan, H E; Coenen, H H; Morsy, M; Qaim, S M; Shubin, Yu; 10.1016/j.apradiso.2004.02.001

2004-01-01

Excitation functions of the reactions /sup nat/Se(p, x)/sup 75,76,77,82/Br, /sup 76/Se(p, xn)/sup 75,76/Br, /sup 76/Se(p, x)/sup 75/Se and /sup 77/Se(p, xn)/sup 76,77/Br were measured from their respective thresholds up to 40 MeV, with particular emphasis on data for the production of the medically important radionuclides /sup 76 /Br and /sup 77/Br. The conventional stacked-foil technique was used. The samples were prepared by a sedimentation process. Irradiations were performed using the compact cyclotron CV 28 and the injector of COSY, both at the Research Centre Julich. In order to validate the data, nuclear model calculations were performed using the code ALICE- IPPE which is based on the preequilibrium-evaporation model. Good agreement was found between the experimental and theoretical data, except in the high-energy region where the calculated data were somewhat higher. All the measured excitation curves were compared with the data available in the literature. From the experimental data the theoretical ...

La desaceleración económica colombiana: se cosecha lo que se siembra

Directory of Open Access Journals (Sweden)

Carlos Humberto Ortiz

2009-12-01

Full Text Available La desaceleración económica que experimenta Colombia desde 1980 se explica por el estancamiento estructural de la economía y por la escalada de violencia relacionada con la expansión del narcotráfico. Los datos disponibles no rechazan esta hipótesis. El artículo plantea que la desindustrialización y el narcotráfico se forjaron en el mismo crisol: un modelo de desarrollo que ha integrado progresivamente la economía nacional a los mercados mundiales al tiempo que ha renunciado, también progresivamente, a la opción industrialista. Además, argumenta que la explosión del narcotráfico obedece a la profundización de la guerra contra las drogas en un contexto de demanda mundial creciente e inelástica.

Det monstrøse i Ezekiels vision

DEFF Research Database (Denmark)

Nielsen, Kirsten

2011-01-01

Artiklen viser, hvordan det monstrøse introduceres i Ezekiels Bog kap. 1 i form af nogle sammensatte levende væsener, der har træk hentet fra både menneske- og dyreverdenen. Det monstrøse består i denne overskridelse af de gængse grænser og problematiserer dermed de velkendte klassifikationer. Og...

Anabolizantes: conceitos segundo praticantes de musculação em Aracaju (SE Anabolizantes: conceptos según practicantes de musculación en Aracaju (SE Anabolic steroids: concepts according to muscular activity practisers in Aracaju (SE

Directory of Open Access Journals (Sweden)

André Faro Santos

2006-08-01

Full Text Available A presente pesquisa objetivou delinear os principais conceitos acerca dos anabolizantes entre os praticantes de musculação nas academias de Aracaju (SE. Pretendeu-se, também, conhecer a prevalência da utilização destas substâncias na amostra selecionada. A amostra constituiu-se de 58 indivíduos do sexo masculino, entre 18 e 35 anos de idade, com predominância de formação de nível médio e superior. Como resultados, detectou-se que a concepção prevalente quanto aos anabolizantes e aos seus malefícios corresponde ao que é divulgado quanto à sua utilização sem a prescrição médica: o perigo do abuso. Já quanto aos benefícios observados, constatou-se que há a percepção de que estas substâncias podem gerar resultados imediatos. Percebeu-se um consumo elevado na população pesquisada, que geralmente adquire as drogas nas farmácias e utiliza doses acima do recomendado. Foi observada relação estatística significativa entre o uso dos anabolizantes na atualidade e no passado (pLa presente investigación tuvo como objetivo delinear los principales conceptos acerca de los anabolizantes entre los practicantes de musculación en los gimnasios de Aracaju (SE. Se pretendió también conocer la prevalencia de la utilización de estas sustancias en la muestra seleccionada, constituida de 58 individuos del sexo masculino, entre 18 y 35 años de edad, con predominancia de formación de nivel medio y superior. Como resultados, se detectó que la concepción prevalente en cuanto a los anabolizantes y a sus efectos negativos corresponde a lo que se divulga con relación a su divulgación sin receta médica: el peligro del abuso. Lo que se refiere a los beneficios observados, se constató que hay una percepción de que estas sustancias pueden generar resultados inmediatos. Se percibió un consumo elevado en la población investigada, que generalmente adquiere las drogas en las farmacias y utiliza dosis mayores de lo recomendado. Fue

Preparation and characterization of polycrystalline n-CdSe photoelectrode

Energy Technology Data Exchange (ETDEWEB)

Bandyopadhyay, T. K.

1979-01-01

Thin layers of polycrystalline p-CdSe were prepared by the simultaneous eletrodeposition of cadmium and selenium from cadmium sulfate and selenious acid in a sulfuric acid solution at pH 0-1 on a titanium substrate. The adherence of the layers to the substrate, stoichiometric ratio of Cd:Se and photovoltaic property of the film depend upon the molar ratio of CdSO/sub 4/ and H/sub 2/SeO/sub 3/ and current density as well as on the pH and temperature of the electrolysis bath. On increasing the current density or the ratio of CdSO/sub 4/:H/sub 2/SeO/sub 3/ in the electrolysis bath, the Cd:Se of the electrodeposit increased. The semiconductor films so prepared were annealed at 550/sup 0/C in a nitrogen atmosphere, followed by etching in an acid solution and then used to construct the photo-electrochemical cell, Ti/CdSe/Na/sub 2/S-Na/sub 2/S/sub x/(aq.)/Pt, and the current-voltage curves have been studied. 11 references.

Nd2(SeO3)2(SeO4) . 2H2O - a mixed-valence compound containing selenium in the oxidation states +IV and +VI

International Nuclear Information System (INIS)

Berdonosov, P.S.; Dityat'yev, O.A.; Dolgikh, V.A.; Schmidt, P.; Ruck, Michael; Lightfoot, P.

2004-01-01

Pale pink crystals of Nd 2 (SeO 3 ) 2 (SeO 4 ) . 2H 2 O were synthesized under hydrothermal conditions from H 2 SeO 3 and Nd 2 O 3 at about 200 C. X-ray diffraction on powder and single-crystals revealed that the compound crystallizes with the monoclinic space group C 2/c (a = 12.276(1) A, b = 7.0783(5) A, c = 13.329(1) A, β = 104.276(7) ). The crystal structure of Nd 2 (SeO 3 ) 2 (SeO 4 ) . 2H 2 O is an ordered variant of the corresponding erbium compound. Eight oxygen atoms coordinate the Nd III atom in the shape of a bi-capped trigonal prism. The oxygen atoms are part of pyramidal (Se IV O 3 ) 2- groups, (Se VI O 4 ) 2- tetrahedra and water molecules. The [NdO 8 ] polyhedra share edges to form chains oriented along [010]. The selenate ions link these chains into layers parallel to (001). The layers are interconnected by the selenite ions into a three-dimensional framework. The dehydration of Nd 2 (SeO 3 ) 2 (SeO 4 ) . 2H 2 O starts at 260 C. The thermal decomposition into Nd 2 SeO 5 , SeO 2 and O 2 at 680 C is followed by further loss of SeO 2 leaving cubic Nd 2 O 3 . (Abstract Copyright [2004], Wiley Periodicals, Inc.) [de

CdSe nanoparticles grown via radiolytic methods in aqueous solutions

International Nuclear Information System (INIS)

Singh, Shalini; Rath, M.C.; Singh, A.K.; Mukherjee, T.; Jayakumar, O.D.; Tyagi, A.K.; Sarkar, S.K.

2011-01-01

Cadmium selenide, CdSe, nanoparticles have been synthesized in aqueous solution containing equimolar ammoniated CdSO 4 and Na 2 SeSO 3 as the starting materials without any capping agents, using gamma and electron beam irradiation under a reducing condition. The radiolytic processes occurring in water result in the formation of CdSe nanoparticles through the reactions mediated by hydrated electrons, e aq - . TEM measurements revealed that the CdSe nanoparticles were found to exist in agglomerates of dimension of about 100 nm, consisting of primary nanoparticles of dimensions within 5 nm. The as-grown nanoparticles were of cubic crystalline phase as supported by the XRD measurements. These bare CdSe nanoparticles exhibit room temperature ferromagnetic (RTFM) behavior. However, the RTFM behavior was found to be 30% higher in the case of CdSe nanoparticles prepared on electron beam irradiation as compared to those obtained by gamma irradiation, which was attributed to their relatively smaller size (2-3 nm) and disordered structures as compared to those obtained in the later case (3-5 nm). -- Research highlights: → CdSe nanoparticles could be synthesized in aqueous solutions containing equimolar ammoniated CdSO 4 and Na 2 SeSO 3 as the starting materials using gamma and electron beam irradiation under a reducing condition. → CdSe nanoparticles were found to exist in agglomerates of dimension of about 100 nm, consisting of primary nanoparticles of dimensions within 5 nm. → CdSe nanoparticles exhibit room temperature ferromagnetic (RTFM) behavior. → The RTFM behavior was found to be 30% higher in the case of CdSe nanoparticles prepared on electron beam irradiation as compared to those obtained by gamma irradiation.

After four months new privatisation committee in SE

International Nuclear Information System (INIS)

Janoska, J.

2003-01-01

In spite of a delay the Minister of Economy of the Slovak Republic wants to meet the schedule set by Government. In middle of September 2002 six prospect submitted their tender offers for entering Slovenske elektrarne (SE), a.s, Bratislava. Representative of privatisation advisor of SE, PricewaterhouseCoopers, Peter Mitka told TREND that he was in contact with the investors but they were waiting for a signal from official authorities about the current state of the tender. And they have been waiting for four months. Only last week a new privatisation commission started dealing with the offers. In spite of these facts Minister of Economy, Robert Nemcsics does not consider the process slow and said that the Ministry would use all its efforts to adhere to the original privatisation schedule prepared by the former government. He further added that everything would depend on the offers submitted. Investors are not interest in SE as a whole but only in its parts. Several members of the committee do not agree with the privatisation and restructuring principles set by the government including a split of SE to conventional and nuclear parts. One of the opponents is the former manager of SE Tibor Mikus (HZDS) - representative of the Parliament or Vladimir Mojs representative of Slovak Energeticists Unions. This put a brake on the tender and changes in the management of SE as well. Privatisation Agency FNM still has not decided upon calling a Extraordinary General Meeting of SE that would elect new bodies. Spokeswoman of FNM, Tatjana Lesajova claims that the Fund is still missing a legal analysis that would review the possibility of changing SE's Articles of Association so that the Board of Directors could be assigned based on a tender (proposal of the Ministry). Members of SE Privatisation Committee: Eva Simkova - Secretary of State, Ministry of Economy SR; Laszlo Pomothy - Secretary of State, Ministry of Economy SR; Henrich Herceg - Advisor to the Minister of Economy SR

Growth of polycrystalline Cu(In,Ga)Se2 thin films using a radio frequency-cracked Se-radical beam source and application for photovoltaic devices

International Nuclear Information System (INIS)

Ishizuka, Shogo; Shibata, Hajime; Yamada, Akimasa; Fons, Paul; Sakurai, Keiichiro; Matsubara, Koji; Niki, Shigeru

2007-01-01

Cu(In,Ga)Se 2 (CIGS) thin films were grown using a rf-cracked Se-radical beam source. A unique combination of film properties, a highly dense and smooth surface with large grain size, is shown. These features seem to have no significant influence on the photovoltaic performance. Defect control in bulk CIGS leading to corresponding variations in the electrical and photoluminescence properties was found to be possible by regulating the Se-radical source parameters. A competitive energy conversion efficiency of 17.5%, comparable to that of a Se-evaporative source grown CIGS device, has been demonstrated from a solar cell fabricated using a Se-radical source grown CIGS absorber

Electronic structure and magnetic properties of KCrSe2

NARCIS (Netherlands)

Fang, C.M.; Tolsma, P.R.; Groot, R.A. de; Wiegers, G.A.; Haas, C.; vanBruggen, C.F.; deGroot, R.A.

1996-01-01

KCrSe2 characterized by x-ray powder diffraction is a layered compound isostructural with NaCrSe2: a = 3.80 Angstrom; c = 22.19 Angstrom; space group R (3) over bar m. The magnetic properties are similar to those of NaCrSe2 but with ari even more pronounced difference between the intralayer and

Two-dimensional n -InSe/p -GeSe(SnS) van der Waals heterojunctions: High carrier mobility and broadband performance

Science.gov (United States)

Xia, Cong-xin; Du, Juan; Huang, Xiao-wei; Xiao, Wen-bo; Xiong, Wen-qi; Wang, Tian-xing; Wei, Zhong-ming; Jia, Yu; Shi, Jun-jie; Li, Jing-bo

2018-03-01

Recently, constructing van der Waals (vdW) heterojunctions by stacking different two-dimensional (2D) materials has been considered to be effective strategy to obtain the desired properties. Here, through first-principles calculations, we find theoretically that the 2D n -InSe/p -GeSe(SnS) vdW heterojunctions are the direct-band-gap semiconductor with typical type-II band alignment, facilitating the effective separation of photogenerated electron and hole pairs. Moreover, they possess the high optical absorption strength (˜105 ), broad spectrum width, and excellent carrier mobility (˜103c m2V-1s-1 ). Interestingly, under the influences of the interlayer coupling and external electric field, the characteristics of type-II band alignment is robust, while the band-gap values and band offset are tunable. These results indicate that 2D n -InSe/p -GeSe(SnS) heterojunctions possess excellent optoelectronic and transport properties, and thus can become good candidates for next-generation optoelectronic nanodevices.

[Selenium uptake and transport of rice under different Se-enriched natural soils].

Science.gov (United States)

Jiang, Chao-qiang; Shen, Jia; Zu, Chao-long

2015-03-01

In this study, a pot experiment was conducted with "Wandao 205" as test materials to investigate Se uptake and translocation in rice under different Se concentrations (0.5, 1.0, and 1.5 mg . kg-1). Results showed that there was no significant change in rice yield when Se concentration in soil was lower than 1.5 mg . kg-1. Significant linear correlations existed between Se concentration in soil and different rice plant tissues. Se concentration in rice plant followed the order of root > straw > grain. Se concentration in different rice grain fractions followed the order of bran > polished rice > hull. The root absorption index of Se was more than 1.86, suggest that the rice could absorpt Se from soil effectively. However, the transport and accumulation of Se in seeds from Se-enriched soil was relatively constant. The Se transport index in seeds was between 0.53 and 0.59. Soil Se concentration within the range of 0.5 to 1.0 mg . kg-1 could produce Se-enriched rice, which might be enough for human requirement of 60-80 µg . d-1 Se. However, polished rice at high-Se treatment (1.5 mg . kg-1) exceeded the maximum standard limit of Se (0.3 mg . kg-1) for cereals in China. These results suggested that we could produce Se-enriched rice under soil Se concentration in the range of 0.5 to 1.0 mg . kg-1 without spraying Se fertilizer, thus reducing the cost and avoiding soil and water pollution caused by exogenous Se.

The Role of Intrinsic and Surface States on the Emission Properties of Colloidal CdSe and CdSe/ZnS Quantum Dots

Directory of Open Access Journals (Sweden)

Morello Giovanni

2007-01-01

Full Text Available AbstractTime Resolved Photoluminescence (TRPL measurements on the picosecond time scale (temporal resolution of 17 ps on colloidal CdSe and CdSe/ZnS Quantum Dots (QDs were performed. Transient PL spectra reveal three emission peaks with different lifetimes (60 ps, 460 ps and 9–10 ns, from the bluest to the reddest peak. By considering the characteristic decay times and by comparing the energetic separations among the states with those theoretically expected, we attribute the two higher energy peaks to ± 1Uand ± 1L bright states of the fine structure picture of spherical CdSe QDs, and the third one to surface states emission. We show that the contribution of surface emission to the PL results to be different for the two samples studied (67% in the CdSe QDs and 32% in CdSe/ZnS QDs, confirming the decisive role of the ZnS shell in the improvement of the surface passivation.

CdSe nanoparticles grown via radiolytic methods in aqueous solutions

Energy Technology Data Exchange (ETDEWEB)

Singh, Shalini [Radiation and Photochemistry Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Rath, M.C., E-mail: madhab@barc.gov.i [Radiation and Photochemistry Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Singh, A.K. [Radiation and Photochemistry Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Mukherjee, T. [Chemistry Group, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Jayakumar, O.D.; Tyagi, A.K. [Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Sarkar, S.K. [Radiation and Photochemistry Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India)

2011-06-15

Cadmium selenide, CdSe, nanoparticles have been synthesized in aqueous solution containing equimolar ammoniated CdSO{sub 4} and Na{sub 2}SeSO{sub 3} as the starting materials without any capping agents, using gamma and electron beam irradiation under a reducing condition. The radiolytic processes occurring in water result in the formation of CdSe nanoparticles through the reactions mediated by hydrated electrons, e{sub aq}{sup -}. TEM measurements revealed that the CdSe nanoparticles were found to exist in agglomerates of dimension of about 100 nm, consisting of primary nanoparticles of dimensions within 5 nm. The as-grown nanoparticles were of cubic crystalline phase as supported by the XRD measurements. These bare CdSe nanoparticles exhibit room temperature ferromagnetic (RTFM) behavior. However, the RTFM behavior was found to be 30% higher in the case of CdSe nanoparticles prepared on electron beam irradiation as compared to those obtained by gamma irradiation, which was attributed to their relatively smaller size (2-3 nm) and disordered structures as compared to those obtained in the later case (3-5 nm). -- Research highlights: {yields} CdSe nanoparticles could be synthesized in aqueous solutions containing equimolar ammoniated CdSO{sub 4} and Na{sub 2}SeSO{sub 3} as the starting materials using gamma and electron beam irradiation under a reducing condition. {yields} CdSe nanoparticles were found to exist in agglomerates of dimension of about 100 nm, consisting of primary nanoparticles of dimensions within 5 nm. {yields} CdSe nanoparticles exhibit room temperature ferromagnetic (RTFM) behavior. {yields} The RTFM behavior was found to be 30% higher in the case of CdSe nanoparticles prepared on electron beam irradiation as compared to those obtained by gamma irradiation.

The reductive immobilization of aqueous Se(IV) by natural pyrrhotite

International Nuclear Information System (INIS)

Ma, Bin; Kang, Mingliang; Zheng, Zhong; Chen, Fanrong; Xie, Jinglin; Charlet, Laurent; Liu, Chunli

2014-01-01

Graphical abstract: - Highlights: • The reduction of aqueous Se(IV) by natural pyrrhotite can be described by a pseudo-first-order equation. • Phosphate can significantly inhibit Se(IV) reduction by natural pyrrhotite. • HS − and Fe 2+ dominate Se(IV) reduction by natural pyrrhotite at low and high pH, respectively. • Se(0) is formed following Se(IV) reduction by natural pyrrhotite. - Abstract: The interaction of Se(IV) with natural pyrrhotite was investigated at pH conditions ranging from acidic to nearly neutral. The results indicate that the reduction rate can be described in terms of a pseudo-first order reaction. At pH ∼4.0 to ∼5.0, the rate decreased with increasing pH. Unexpectedly, at pH ∼5.0, the rate increased with increasing reaction time. This response was also observed at pH ∼6.0. Two different reaction mechanisms were proposed to explain pyrrhotite oxidation by Se(IV). Because pyrrhotite is acid-soluble and can be attacked by both Fe 3+ and protons, direct reduction by the released aqueous sulfide dominates the reaction at low pH, whereas the cyclic oxidation of aqueous Fe 2+ adsorbed on pyrrhotite surfaces becomes predominant at high pH. Phosphate, which can be irreversibly bound to Fe 3+ intermediates even under acidic conditions, can significantly decrease the reaction rate by an order of magnitude at pH ∼4.5. In contrast to the thermodynamic calculations and the predicted prevalence of FeSe based on previous reports of aqueous Se(IV) reduction by synthetic mackinawite or troilite, only Se(0) was observed as the reaction product in this study. This observation confirmed that a slow reaction favors the formation of Se(0) rather than iron selenides

Selenization of mixed metal oxides for dense and ZnSe-free Cu{sub 2}ZnSnSe{sub 4} absorber films

Energy Technology Data Exchange (ETDEWEB)

Deng, Yitao; Chen, Guilin; Pan, Bin; Li, JianMin; Jiang, Guoshun; Liu, Weifeng, E-mail: liuwf@ustc.edu.cn; Zhu, Changfei, E-mail: cfzhu@ustc.edu.cn

2014-04-05

Highlights: • ZnSe-free CZTSe films with large grains was prepared from mixed oxides nanopraticles. • Appearance of Zn{sub 2}SnO{sub 4} in mixed oxides precursors leads to the absence of ZnSe secondary phrase. • To obtain pure CZTSe phase, different treating temperature was used. -- Abstract: Cu{sub 2}ZnSnSe{sub 4} (CZTSe) films were prepared by direct selenization of Cu{sub 2}O, SnO{sub 2} and Zn{sub 2}SnO{sub 4} precursors. Oxides precursors were prepared by baking hydroxides precipitation. In order to obtain ZnSe-free CZTSe films, Zn{sub 2}SnO{sub 4} was used to replace separated ZnO and SnO{sub 2} as one of the precursors. Through X-ray diffraction (XRD), scanning electron microscopy (SEM), it was found that CZTSe films, with micron-sized dense grains, were obtained in our work. From Raman spectra, it was also found that the ZnSe secondary phase was absent after the selenization. An energy bandgap about 0.86 eV was obtained in our work, which confirmed the Stannite-CZTSe structure.

Removal efficiency of 75Se, 51Cr and 60Co from tidal water by mangrove sediments from Sepetiba Bay (SE Brazil)

International Nuclear Information System (INIS)

Suzuki, K.N.; Lopes, R.T.; Machado, E.C.; Machado, W.; Osso, J.A.Jr.

2014-01-01

Mangrove sediment cores sampled from Sepetiba Bay (SE Brazil) were covered with tidal water spiked with 75 Se, 51 Cr and 60 Co to evaluate the removal efficiency of these radiotracers by underlying sediments. Variable time-evolution trends were observed along 115 h experiments, with significant differences between removal efficiencies of all radiotracers observed only after 70 h ( 51 Cr > 60 Co > 75 Se). After an event of 60 Co release back to overlying water, there was a general trend of lower 60 Co removal than observed for other radiotracers during the period from 20 to 54 h. After this event, alternated periods of higher 60 Co and higher 75 Se removal trends were observed, attributed to behavioural differences expected for such anionic and cationic radiotracers. While 75 Se and 51 Cr showed uniform time-evolution curves, as typically found in the literature for most radiotracers, 60 Co removal rates presented oscillations, probably due to sensitivity to changes in redox conditions within underlying sediments. Results evidenced the role of mangrove sediments as trace element sinks, which have implications for coastal water quality and for possible uses of such sediments in wastewater treatment systems. (author)

Se interlayer in CIGS absorption layer for solar cell devices

Energy Technology Data Exchange (ETDEWEB)

Lee, Seung-Kyu; Sim, Jae-Kwan [Semiconductor Materials Process Laboratory, School of Advanced Materials Engineering, Research Center for Advanced Materials Development, Chonbuk National University, Deokjin-Dong 664-14, Jeonju 561-756 (Korea, Republic of); Kissinger, N.J. Suthan [Department of General Studies, Physics Group, Jubail University College, Royal Commission for Jubail, Jubail 10074 (Saudi Arabia); Song, Il-Seok; Kim, Jin-Soo; Baek, Byung-Joon [Semiconductor Materials Process Laboratory, School of Advanced Materials Engineering, Research Center for Advanced Materials Development, Chonbuk National University, Deokjin-Dong 664-14, Jeonju 561-756 (Korea, Republic of); Lee, Cheul-Ro, E-mail: crlee7@jbnu.ac.kr [Semiconductor Materials Process Laboratory, School of Advanced Materials Engineering, Research Center for Advanced Materials Development, Chonbuk National University, Deokjin-Dong 664-14, Jeonju 561-756 (Korea, Republic of)

2015-06-05

Highlights: • Se interlayer is deposited between the CuGa and CuIn/In/Mo/STS stacked layer. • Both CIG precursor layers were selenized at 500 °C for 1 h. • SIMS depth profile shows that Ga distribution is uniform by Se interlayer. • The efficiency was improved for the CIGS solar cell by Se interlayer. - Abstract: A CIGS absorber layer with high gallium contents in the space-charge region can reduce the carrier recombination and improve the open circuit voltage V{sub oc}. Therefore, controlling Ga grading on top of CIGS thin film solar cells is the main objective of this experiment. To reduce Selenium (Se) vacancy, it is important that the diffusion of Ga elements into Se vacancy between Mo back contact and CIGS absorption layer would be controlled. In order to reduce Se vacancy and confirm Ga inter-diffusion, two CIGS solar cells were fabricated by converting CIG precursor with and without Se interlayer. The copper-indium metallic precursors were fabricated corresponding to the sequence CuIn/In/Mo/STS on stainless steel (STS) substrates by sequential direct current magnetron sputtering while Se layer was evaporated by rapid thermal annealing (RTA) system to obtain a Se/CuIn/In/Mo/STS stack. CuGa precursor layer was also fabricated on the Se/CuIn/In/Mo/STS stack. Finally, both CuGa/Se/CuIn/In/Mo/STS and CuGa/CuIn/In/Mo/STS stacks were selenized at 500 °C for 1 h. It was clearly observed from the secondary ion mass spectroscopy (SIMS) and X-ray diffraction (XRD) that there was a change between the fabricated CIGS absorption layers and the amount of Ga elements. Furthermore, the Ga elements gradually decreased from the top to the bottom layer of the CIGS absorption layer. We also discussed the effect of Se interlayer in the CIGS absorption layer and its influence on the solar cell’s performance.

Se interlayer in CIGS absorption layer for solar cell devices

International Nuclear Information System (INIS)

Lee, Seung-Kyu; Sim, Jae-Kwan; Kissinger, N.J. Suthan; Song, Il-Seok; Kim, Jin-Soo; Baek, Byung-Joon; Lee, Cheul-Ro

2015-01-01

Highlights: • Se interlayer is deposited between the CuGa and CuIn/In/Mo/STS stacked layer. • Both CIG precursor layers were selenized at 500 °C for 1 h. • SIMS depth profile shows that Ga distribution is uniform by Se interlayer. • The efficiency was improved for the CIGS solar cell by Se interlayer. - Abstract: A CIGS absorber layer with high gallium contents in the space-charge region can reduce the carrier recombination and improve the open circuit voltage V oc . Therefore, controlling Ga grading on top of CIGS thin film solar cells is the main objective of this experiment. To reduce Selenium (Se) vacancy, it is important that the diffusion of Ga elements into Se vacancy between Mo back contact and CIGS absorption layer would be controlled. In order to reduce Se vacancy and confirm Ga inter-diffusion, two CIGS solar cells were fabricated by converting CIG precursor with and without Se interlayer. The copper-indium metallic precursors were fabricated corresponding to the sequence CuIn/In/Mo/STS on stainless steel (STS) substrates by sequential direct current magnetron sputtering while Se layer was evaporated by rapid thermal annealing (RTA) system to obtain a Se/CuIn/In/Mo/STS stack. CuGa precursor layer was also fabricated on the Se/CuIn/In/Mo/STS stack. Finally, both CuGa/Se/CuIn/In/Mo/STS and CuGa/CuIn/In/Mo/STS stacks were selenized at 500 °C for 1 h. It was clearly observed from the secondary ion mass spectroscopy (SIMS) and X-ray diffraction (XRD) that there was a change between the fabricated CIGS absorption layers and the amount of Ga elements. Furthermore, the Ga elements gradually decreased from the top to the bottom layer of the CIGS absorption layer. We also discussed the effect of Se interlayer in the CIGS absorption layer and its influence on the solar cell’s performance

Quasi-two-dimensional thermoelectricity in SnSe

Science.gov (United States)

Tayari, V.; Senkovskiy, B. V.; Rybkovskiy, D.; Ehlen, N.; Fedorov, A.; Chen, C.-Y.; Avila, J.; Asensio, M.; Perucchi, A.; di Pietro, P.; Yashina, L.; Fakih, I.; Hemsworth, N.; Petrescu, M.; Gervais, G.; Grüneis, A.; Szkopek, T.

2018-01-01

Stannous selenide is a layered semiconductor that is a polar analog of black phosphorus and of great interest as a thermoelectric material. Unusually, hole doped SnSe supports a large Seebeck coefficient at high conductivity, which has not been explained to date. Angle-resolved photoemission spectroscopy, optical reflection spectroscopy, and magnetotransport measurements reveal a multiple-valley valence-band structure and a quasi-two-dimensional dispersion, realizing a Hicks-Dresselhaus thermoelectric contributing to the high Seebeck coefficient at high carrier density. We further demonstrate that the hole accumulation layer in exfoliated SnSe transistors exhibits a field effect mobility of up to 250 cm2/V s at T =1.3 K . SnSe is thus found to be a high-quality quasi-two-dimensional semiconductor ideal for thermoelectric applications.

13.7%-efficient Zn(Se,OH){sub x}/Cu(In,Ga)(S,Se){sub 2} thin-film solar cell

Energy Technology Data Exchange (ETDEWEB)

Ennaoui, A. [Hahn-Meitner-Institut, Bereich Physikalische Chemie, Berlin (Germany); Blieske, U.; Lux-Steiner, M.Ch. [Hahn-Meitner-Institut, Bereich Festkoerperphysik, Berlin (Germany)

1998-12-01

Cu(In,Ga)Se{sub 2} (CIGS) and related semiconducting compounds have demonstrated their high potential for high-efficiency thin-film solar cells. The highest efficiency for CIGS based thin-film solar cells has been achieved with CdS buffer layers prepared by a solution growth method known as chemical based deposition (CBD). With the aim of developing Cd-free chalcopyrite-based thin-film solar cells, Zn(Se,OH){sub x} buffer layers were deposited by CBD on polycrystalline Cu(In,Ga)(S,Se){sub 2} (CIGSS). A total-area conversion efficiency of 13.7% was certified by the Fraunhofer Institute for Solar Energy Systems. The CIGSS absorber was fabricated by Siemens Solar Industries (California). For device optimisation, the thickness and good surface coverage were controlled by XPS-UPS photoemission spectroscopy. A Zn(Se,OH){sub x} thickness below 7 nm has been found to be optimum for achieving a homogeneous and compact buffer film on CIGSS, with open-circuit photovoltage V{sub oc} = 535 mV, fill factor FF = 70.76% and a high short-circuit photocurrent density J{sub sc} 36.1 mA cm{sup -2}. (Author)

Use of enriched 74Se and 77Se in combination with isotope pattern deconvolution to differentiate and determine endogenous and supplemented selenium in lactating rats

International Nuclear Information System (INIS)

Gonzalez Iglesias, H.; Fernandez Sanchez, M.L.; Garcia Alonso, J.I.; Sanz-Medel, A.

2007-01-01

A quantitative methodology has been developed to differentiate between endogenous and supplemented selenium in lactating rats using two enriched selenium isotopes. Lactating rats were fed for 2 weeks with formula milk containing one enriched Se isotope, 77 Se, as the metabolic tracer. The isotopic composition of selenium in serum and urine samples was then measured by collision cell ICP-MS after the addition of a solution containing another enriched isotope, 74 Se, as quantitation tracer, before analysis. Isotope pattern deconvolution allowed the transformation of measured Se isotopic abundances into concentrations of natural abundance (endogenous) selenium and enriched 77 Se (supplemented) present in the samples. The proposed methodology was validated using serum and urine reference materials spiked with both 77 Se and 74 Se. The obtained results are discussed in terms of selenium exchange and half-life in lactating rats (11-12 days) and selenium levels in serum in comparison with non-supplemented rats and control rats after maternal feeding. (orig.)

Neutron Activation Resonance Integrals of 74Se, 78Se, 80Se, 81Br, 127I, 130Te, 138Ba, 140Ce, and 142Ce

International Nuclear Information System (INIS)

Ricabarra, M. D.; Turjanskl, R.; Ricabarra, G. H.; Bigham, C.B.

1968-01-01

A lithium-drift germanium γ-ray spectrometer has been used to make accurate intercomparisons of the ratio of resonance-integral to thermal-activation cross section by measuring cadmium ratios or relative activation rates in two different neutron spectra. The standard, gold, or secondary standard, indium, was mixed uniformly in the samples and the activities resolved with the spectrometer. Expressed as Westcott S 0 values, the results relative to S 0 = 17.7 for gold were as follows: 74 Se = 10.3 +± 0.1, 78 Se = 12.3 ± 0.3, 80 Sc = 2.65 ± 0.02, 81 Br = 24.3 ± 0.5, 127 I = 27.8 ± 0.5, 130 Te = 2.10 ± 0.07, 138 Ba = 0.649 ± 0.004, 140 Ce = 0.476 ± 0.003, 142 Ce = 0.865 ± 0.005. (author)

Atomic-scale structure of GeSe2 glass revisited: a continuous or broken network of Ge-(Se1/2)4 tetrahedra?

International Nuclear Information System (INIS)

Petkov, V; Le Messurier, D

2010-01-01

The atomic-scale structure of germanium diselenide (GeSe 2 ) glass has been revisited using a combination of high-energy x-ray diffraction and constrained reverse Monte Carlo simulations. The study shows that the glass structure may be very well described in terms of a continuous network of corner- and edge-sharing Ge-Se 4 tetrahedra. The result is in contrast to other recent studies asserting that the chemical order and, hence, network integrity in GeSe 2 glass are intrinsically broken. It is suggested that more elaborate studies are necessary to resolve the controversy.

A Review of SnSe: Growth and Thermoelectric Properties

Science.gov (United States)

Nguyen, Van Quang; Kim, Jungdae; Cho, Sunglae

2018-04-01

SnSe is a 2D semiconductor with an indirect energy gap of 0.86 - 1 eV; it is widely used in solar cell, optoelectronics, and electronic device applications. Recently, SnSe has been considered as a robust candidate for energy conversion applications due to its high thermoelectric performance ( ZT = 2.6 in p-type and 2.2 in n-type), which is assigned mainly to its anhamornic bonding leading to an ultralow thermal conductivity. In this review, we first discuss the crystalline and electronic structures of SnSe and the source of its p-type characteristic. Then, some typical single crystal and polycrystal growth techniques, as well as an epitaxial thin film growth technique, are outlined. The reported thermoelectric properties of SnSe grown by using each technique are also reviewed. Finally, we will describe some remaining issues concerning the use of SnSe for thermoelectric applications.

Cultivation and characterization of GaInSe2 crystals

International Nuclear Information System (INIS)

Panakhov, T.M.; Kafarova, D.M.

2013-01-01

This work is the first systematic study devoted to the growth of GaInSe 2 crystals and their characterization by experimental methods such as X-ray diffraction, electron microscopy transmission with high resolution, sample electron diffraction. By the method of photoelectron roentgen spectroscopy it was studied the chemical structure of the GaInSe 2 crystals and the microprobe analysis indicated that the individual crystals have an excess of gallium. GaInSe 2 crystals were grown by the Bridgman method. Samples were prepared as single crystals by the Bridgman method. Studies showed that the GaInSe 2 crystals are hexagonal ones

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

Effects of Interaction between Cadmium (Cd) and Selenium (Se) on Grain Yield and Cd and Se Accumulation in a Hybrid Rice (Oryza sativa) System.

Science.gov (United States)

Huang, Baifei; Xin, Junliang; Dai, Hongwen; Zhou, Wenjing

2017-11-01

A pot experiment was conducted to investigate the interactive effects of cadmium (Cd) and selenium (Se) on their accumulation in three rice cultivars, which remains unclear. The results showed that Se reduced Cd-induced growth inhibition, and increased and decreased Se and Cd concentrations in brown rice, respectively. Cadmium concentrations in all tissues of the hybrid were similar to those in its male parent yet significantly lower than those in its female parent. Selenium reduced Cd accumulation in rice when Cd concentration exceeded 2.0 mg kg -1 ; however Se accumulation depended on the levels of Cd exposure. Finally, Cd had minimal effect on Se translocation within the three cultivars. We concluded that Cd concentration in brown rice is a heritable trait, making crossbreeding a feasible method for cultivating high-yield, low-Cd rice cultivars. Selenium effectively decreased the toxicity and accumulation of Cd, and Cd affected Se uptake but not translocation.

Band alignment in ZnSe/Zn1-x-yCdxMnySe quantum-well structures

International Nuclear Information System (INIS)

Yu, W.Y.; Salib, M.S.; Petrou, A.; Jonker, B.T.; Warnock, J.

1997-01-01

We present a magneto-optical study of ZnSe/Zn 1-x-y Cd x Mn y Se quantum-well structures in which a suitable choice of the Cd composition leads to a system that is type I at zero magnetic field. When a magnetic field is applied perpendicular to the layers of the structure, the band edges split in such a way as to make the upper σ - (1/2, t 3/2) exciton transition type II, while the ground state σ + (-1/2, -3/2) exciton component remains type I at all field values. This alignment reduces the probability for carrier relaxation from the higher-energy exciton component and opens the possibility of hole-spin population inversion via optical pumping. copyright 1997 The American Physical Society

Colegio Nuestra Señora del Carmen-Ikastetxea

OpenAIRE

García Sedano, Esther

2012-01-01

Este trabajo se centra en la atención a la diversidad, enfocado en aquellos alumnos con necesidades educativas especiales por dificultades de aprendizaje, por trastorno de déficit de atención, dislexia, inteligencia límite (bordeline) y síndrome de triple X. Con él también se pretende la adaptación de niños de nacionalidad china a nuestros hábitos y se les ilustra en el método silábico para que aprendan el idioma del castellano con prontitud para evitar la dislexia, entre otros problemas. ...

Symmetry and optical anisotropy in CdSe/ZnSe quantum dots

Energy Technology Data Exchange (ETDEWEB)

Kiessling, Tobias

2009-10-29

The material system of choice for the investigations performed in the frame of this Thesis were self-assembled CdSe/ZnSe QDs. The reason for this choice is twofold. First, CdSe/ZnSe QDs can be grown with excellent optical quality, which is a prerequiste for optical studies. Second, due to the polar nature of II-VI compound semiconductors, optical anisotropies induced by various asymmetries are more pronounced than in their IIIV or element IV counterparts. Unlike in the III-V materials, where the self-organization of QDs is well described by the Stranski-Krastanow growth mode, the peculiarities of the QD formation are not entirely clear in II-VI alloys. For the purposes of the current work QDs emerging from two variants of Molecular Beam Epitaxy (MBE) growth were studied. In order to establish a clear connection between the optically observed anisotropies and the growth induced asymmetries in the QDs we start out by summarizing all available structural and morphological studies that were performed on the resultant QDs, including x-ray diffraction, atomic force microscopy, high resolution transmission electron microscopy and resonant Raman scattering. Extensive investigations by Photoluminescence (PL) and Photoluminescence Excitation (PLE) spectroscopy hence detail the resultant electronic structure of excitons confined to the above QDs as well as their energy relaxation across the latter. We find that for these small-sized strongly confining QDs k-vector conservation is entirely relaxed, which enables interaction of the excitons with a continuum of phonons and explains fast and efficient exciton capture by the QDs, even for excitation conditions far above the ground state. We demonstrate how this provides an alternative fast relaxation channel to Auger-like electron-hole scattering, that may also explain fast hole relaxation and adds to the understanding of the absence of a phonon bottleneck in the energy relaxation in these type of QDs. With the above analysis as a

Symmetry and optical anisotropy in CdSe/ZnSe quantum dots

International Nuclear Information System (INIS)

Kiessling, Tobias

2009-01-01

The material system of choice for the investigations performed in the frame of this Thesis were self-assembled CdSe/ZnSe QDs. The reason for this choice is twofold. First, CdSe/ZnSe QDs can be grown with excellent optical quality, which is a prerequiste for optical studies. Second, due to the polar nature of II-VI compound semiconductors, optical anisotropies induced by various asymmetries are more pronounced than in their IIIV or element IV counterparts. Unlike in the III-V materials, where the self-organization of QDs is well described by the Stranski-Krastanow growth mode, the peculiarities of the QD formation are not entirely clear in II-VI alloys. For the purposes of the current work QDs emerging from two variants of Molecular Beam Epitaxy (MBE) growth were studied. In order to establish a clear connection between the optically observed anisotropies and the growth induced asymmetries in the QDs we start out by summarizing all available structural and morphological studies that were performed on the resultant QDs, including x-ray diffraction, atomic force microscopy, high resolution transmission electron microscopy and resonant Raman scattering. Extensive investigations by Photoluminescence (PL) and Photoluminescence Excitation (PLE) spectroscopy hence detail the resultant electronic structure of excitons confined to the above QDs as well as their energy relaxation across the latter. We find that for these small-sized strongly confining QDs k-vector conservation is entirely relaxed, which enables interaction of the excitons with a continuum of phonons and explains fast and efficient exciton capture by the QDs, even for excitation conditions far above the ground state. We demonstrate how this provides an alternative fast relaxation channel to Auger-like electron-hole scattering, that may also explain fast hole relaxation and adds to the understanding of the absence of a phonon bottleneck in the energy relaxation in these type of QDs. With the above analysis as a

Lanthanide modification of CdSe/ZnS core/shell quantum dots

DEFF Research Database (Denmark)

Dethlefsen, Johannes Rytter; Mikhailovsky, Alexander A.; Burks, Peter T.

2012-01-01

Lanthanide-modified CdSe quantum dots (CdSe(Ln) QDs) have been prepared by heating a solution of Cd(oleate)(2), SeO2, and Ln(bipy)(S2CNEt2)(3) (bipy = 2,2'-bipyridine) to 180-190 degrees C for 10-15 min. The elemental compositions of the resulting CdSe(Ln) cores and CdSe(Ln)/ZnS core/shell QDs show...

Características generales, propiedades, yacimientos y aplicaciones de pirofilita. II. Yacimientos, aplicaciones y utilización como materia prima cerámica

Directory of Open Access Journals (Sweden)

Sánchez Soto, P. J.

1998-10-01

Full Text Available In this work, the main world deposits of pyrophyllite are indicated according to the literature, showing the available production data. It is emphasized the research focusing on mining and characterization of raw materials containing pyrophyllite, which shows a marked applied interest. It is described and reviewed the most relevant applications of pyrophyllite and pyrophyllite raw materials, in especial refractories and ceramics, fillers, building materials, catalysts and as a high-pressure medium for synthesis of materials. Finally, it is also described and reviewed its use as raw material for the preparation of advanced materials, such as sialon, emphasizing the possibilities of application of pyrophyllite raw materials in our country as a result of distinct investigations of relevant interest performed by several Research Institutes and University Departments. It is deduced that pyrophyllite and pyrophyllite raw materials are increasing in relative importance in many applied fields, as compared with other layer silicates, such as talc and kaolinite.

En este trabajo se indican los principales yacimientos mundiales de pirofilita según la bibliografía, los datos de producción disponibles, además de revisar las investigaciones más destacadas sobre prospección y caracterización de materias primas que contienen pirofilita y que presentan un marcado interés aplicado. Se realiza una amplia revisión de las principales aplicaciones a las que se destinan dichas materias primas, en especial para la preparación de materiales cerámicos y refractarios, su uso como carga, en la construcción, obtención de catalizadores y síntesis de materiales a alta presión debido a sus propiedades. Por último, se describen y revisan sus aplicaciones en la preparación de nuevos materiales y materiales avanzados, como son los sialones, destacando su potencial de utilización en nuestro país como resultado de diversas investigaciones de inter

Generalized stacking fault energies, cleavage energies, ionicity and brittleness of Cu(Al/Ga/In)Se2 and CuGa(S/Se/Te)2

Science.gov (United States)

Xue, H. T.; Tang, F. L.; Gruhn, T.; Lu, W. J.; Wan, F. C.; Rui, Z. Y.; Feng, Y. D.

2014-04-01

We calculate the generalized stacking fault (GSF) energies and cleavage energies γcl of the chalcopyrite compounds CuAlSe2, CuGaSe2, CuInSe2, CuGaS2 and CuGaTe2 using first principles. From the GSF energies, we obtain the unstable stacking fault energies γus and intrinsic stacking fault energies γisf. By analyzing γus and γisf, we find that the \\langle \\bar{{1}}\\,1\\,0\\rangle (1 1 2) direction is the easiest slip direction for these five compounds. Also, for CuInSe2, it is most possible to undergo a dislocation-nucleation-induced plastic deformation along the \\langle \\bar{{1}}\\,1\\,0\\rangle (1 1 2) slip direction. We show that the (1 1 2) plane is the preferable plane for fracture in the five compounds by comparing γcl of the (0 0 1) and (1 1 2) planes. It is also found that both γus and γcl decrease as the cationic or anionic radius increases in these chalcopyrites, i.e. along the sequences CuAlSe2 → CuGaSe2 → CuInSe2 and CuGaS2 → CuGaSe2 → CuGaTe2. Based on the values of the ratio γcl/γus, we discuss the brittle-ductile properties of these compounds. All of the compounds can be considered as brittle materials. In addition, a strong relationship between γcl/γus and the total proportion of ionic bonding in these compounds is found.

Complexing in the system Rb2SeO4-UO2SeO4-H2O

International Nuclear Information System (INIS)

Kuchumova, N.V.; Shtokova, I.P.; Serezhkina, L.B.; Serezhkin, V.N.

1989-01-01

Method of isothermal solubility at 25 deg C is used to study interaction of rubidium and uranyl selenates in aqueous solution. Formation of congruently soluble Rb 2 UO 2 (SeO 4 ) 2 x2H 2 O and Rb 2 (UO 2 ) 2 x(SeO 4 ) 3 x6H 2 O is stated. For the last compound crystallographic characteristics (a=10.668; b=14.935(9); c=13.891(7) A; β=104.94(1); Z=4, sp.gr. P2 1 /c) are determined. Thermal decomposition of a compound results in formation of Rb 2 U 2 O 7

SeO{sub 2} adsorption on CaO surface: DFT study on the adsorption of a single SeO{sub 2} molecule

Energy Technology Data Exchange (ETDEWEB)

Fan, Yaming; Zhuo, Yuqun; Lou, Yu; Zhu, Zhenwu [Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Thermal Engineering, Tsinghua University, Beijing 100084 (China); Li, Liangliang [Key Laboratory of Advanced Materials, Department of Material Science and Engineering, Tsinghua University, Beijing 100084 (China)

2017-08-15

Highlights: • Adsorption mechanisms of SeO{sub 2} on CaO surface under O{sub 2} were firstly studied by DFT. • The adsorption energies, bond length and electron density maps were calculated. • The electronic structure changes upon adsorption were studied. - Abstract: Selenium is a hazardous element in coal. During coal combustion, most of the selenium will convert to SeO{sub 2} in the flue gas. Ca-based adsorbents, especially CaO, have been considered as a potential sorbent to adsorb SeO{sub 2} due to its low cost. In this paper, the adsorption mechanisms of single SeO{sub 2} on CaO surface were investigated by density functional theory (DFT) calculation. Both the physisorption and chemisorption structures were determined. It has been identified that the adsorption of SeO{sub 2} on CaO surface is primarily chemisorption, while physisorption takes effects at the initial stage of the process. Under O{sub 2} atmosphere, selenate is hard to form. Most of the adsorption products are selenite. Additionally, the electron density maps were obtained to reveal the surface active sites. The partial density of states (PDOS) was calculated for analyzing the electronic structural change of SeO{sub 2} and CaO surface during adsorption. The results provide fundamental information of the adsorption process, which could be meaningful for the development of new absorbents.

Self-Assembled PbSe Nanowire:Perovskite Hybrids

KAUST Repository

Yang, Zhenyu

2015-12-02

© 2015 American Chemical Society. Inorganic semiconductor nanowires are of interest in nano- and microscale photonic and electronic applications. Here we report the formation of PbSe nanowires based on directional quantum dot alignment and fusion regulated by hybrid organic-inorganic perovskite surface ligands. All material synthesis is carried out at mild temperatures. Passivation of PbSe quantum dots was achieved via a new perovskite ligand exchange. Subsequent in situ ammonium/amine substitution by butylamine enables quantum dots to be capped by butylammonium lead iodide, and this further drives the formation of a PbSe nanowire superlattice in a two-dimensional (2D) perovskite matrix. The average spacing between two adjacent nanowires agrees well with the thickness of single atomic layer of 2D perovskite, consistent with the formation of a new self-assembled semiconductor nanowire:perovskite heterocrystal hybrid.

Self-Assembled PbSe Nanowire:Perovskite Hybrids

KAUST Repository

Yang, Zhenyu; Yassitepe, Emre; Voznyy, Oleksandr; Janmohamed, Alyf; Lan, Xinzheng; Levina, Larissa; Comin, Riccardo; Sargent, Edward H.

2015-01-01

© 2015 American Chemical Society. Inorganic semiconductor nanowires are of interest in nano- and microscale photonic and electronic applications. Here we report the formation of PbSe nanowires based on directional quantum dot alignment and fusion regulated by hybrid organic-inorganic perovskite surface ligands. All material synthesis is carried out at mild temperatures. Passivation of PbSe quantum dots was achieved via a new perovskite ligand exchange. Subsequent in situ ammonium/amine substitution by butylamine enables quantum dots to be capped by butylammonium lead iodide, and this further drives the formation of a PbSe nanowire superlattice in a two-dimensional (2D) perovskite matrix. The average spacing between two adjacent nanowires agrees well with the thickness of single atomic layer of 2D perovskite, consistent with the formation of a new self-assembled semiconductor nanowire:perovskite heterocrystal hybrid.

Coherent optical nonlinearities and phase relaxation of quasi-three-dimensional and quasi-two-dimensional excitons in ZnSxSe1 - x/ZnSe structures

DEFF Research Database (Denmark)

Wagner, Hans Peter; Schätz, A.; Maier, R.

1997-01-01

We investigate the dephasing of heavy-hole excitons in different free-standing ZnSxSe1-x/ZnSe layer structures by spectrally resolved transient four-wave mixing. ZnSe layers of 80, 8, and 4 nm thickness with ternary barriers are studied, representing the crossover from quasi-three-dimensional to ...

Empreendedorismo religioso: quando Weber se associa a Granovetter

Directory of Open Access Journals (Sweden)

Victor Silva Corrêa

2016-12-01

Full Text Available O fenômeno religioso no Brasil vem atraindo crescente atenção da academia, impulsionado, em grande parte, pela expansão das seitas protestantes no país, sobretudo de vertente pentecostal. Na esteira dessa transformação, um tema, em particular, reveste-se de especial importância. Trata-se do papel dos chamados empreendedores religiosos aqui compreendidos como os novos pastores evangélicos. No entanto, tais atores não vêm sendo muito estudados. O presente trabalho busca preencher essa lacuna. Recorre-se, para isso, às contribuições teóricas clássicas derivadas de Weber, em associação às contribuições contemporâneas originárias de Granovetter, em particular, sobre acoplamento e desacoplamento. Conclui-se o trabalho propondo um novo referencial para a análise de certas dimensões do empreendedorismo religioso.

Atomic defects and doping of monolayer NbSe2

OpenAIRE

Nguyen, Lan; Komsa, Hannu-Pekka; Khestanova, Ekaterina; Kashtiban, Reza J; Peters, Jonathan J.P.; Lawlor, Sean; Sanchez, Ana M.; Sloan, Jeremy; Gorbachev, Roman; Grigorieva, Irina; Krasheninnikov, Arkady V.; Haigh, Sarah

2017-01-01

We have investigated the structure of atomic defects within monolayer NbSe2 encapsulated in graphene by combining atomic resolution transmission electron microscope imaging, density functional theory (DFT) calculations, and strain mapping using geometric phase analysis. We demonstrate the presence of stable Nb and Se monovacancies in monolayer material and reveal that Se monovacancies are the most frequently observed defects, consistent with DFT calculations of their formation energy. We reve...

Banks offer SE more than it asked for

International Nuclear Information System (INIS)

Janoska, J.

2004-01-01

About a year ago, when new management took over the financial department of Slovenske elektrarne (SE), a.s. the company was in crisis. It faced an acute cash-flow deficit and due loans of over 20 bill. Sk (501.21 mil. Eur). SE could not provide adequate guarantees for the required loans and without state guarantees it was virtually impossible or too expensive to obtain additional loans. But last week the situation changed for the better. Despite the fact that due to the restructuring of SE's loan portfolio, the company will pay the banks 3 bill. Sk (75.18 mil. Eur) less interest over the next three years than under the original arrangements, even the bakers seemed satisfied. A loan portfolio full of non-standard agreements signed with about 30 banks had previously prevented decisions regarding the structure of the company's assets and liabilities.The cabinet refused to admit that SE was in crisis and offered SE for sale, although it could not be privatised due to its debt structure and the fact that it was close to default. Despite this unfavourable situation, company economists decided to make an offensive move -in cooperation with a small group of banks they converted the tens of company loan agreements into a new loan package that will be simpler, cheaper, and with longer maturity periods, which will not require state guarantees. SE managed to restructure debts with a total value of 550 mil. Eur and until these transactions are completed the banks offered SE a bridge loan of 110 mil. Eur. The transaction related to a syndicated loan of 350 mil. Eur which was concluded in April. Eurobonds with a total value of 200 mil. Eur were issued two months later. The banks offered the company more than it requested. Demand for the Eurobond issue exceeded the 200 mil. Eur of bonds on offer. (author)

Lustre filesystem for CMS storage element (SE)

International Nuclear Information System (INIS)

Wu, Y; Kim, B; Avery, P; Fu, Y; Bourilkov, D; Taylor, C; Prescott, C; Rodriguez, J

2011-01-01

This paper presents our effort to integrate the Lustre filesystem with BeStMan, GridFTP and Ganglia to make it a fully functional WLCG SE (Storage Element). We first describe the configuration of our Lustre filesystem at the University of Florida and our integration process. We then present benchmark performance figures and IO rates from the CMS analysis jobs and the WAN data transfer performance that are conducted on the Lustre SE.

Det stedløse fællesskab

DEFF Research Database (Denmark)

Andreasen, Torsten Arni Caleb

2009-01-01

Det værkløse, det uvedgåelige, det kommende fællesskab. I nr. 4 af tidsskriftet Aléa (1983) udkom første udgave af den franske filosof Jean-Luc Nancys artikel "La communauté désœuvrée" (Det værkløse fællesskab), der senere udkom med tilføjelser i bogen af samme navn (1986). Via en analyse af...

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).

Hjemløse borgeres sygdom og brug af sundhedsydelser

DEFF Research Database (Denmark)

Benjaminsen, Lars; Birkelund, Jesper Fels; Enemark, Morten Holm

sygdom er meget udbredt blandt hjemløse borgere. Men også når man korrigerer for misbrug og psykisk sygdom, har de hjemløse borgere forøget risiko for en række sygdomme som fx infektionssygdomme, lungebetændelse og KOL. Undersøgelsen identificerer også et merforbrug af sundhedsydelser blandt de hjemløse...... tandlæge og speciallæge. Den stærke oversygelighed i gruppen af hjemløse borgere peger generelt på et behov for at medtænke en sundhedsmæssig dimension i den sociale støtte til disse borgere. Undersøgelsen er finansieret af Helsefonden....

Structural and optical properties of alloyed quaternary CdSeTeS core and CdSeTeS/ZnS core–shell quantum dots

Energy Technology Data Exchange (ETDEWEB)

Adegoke, Oluwasesan, E-mail: adegoke.sesan@mailbox.co.za [Department of Chemistry, Faculty of Natural and Agricultural Sciences, University of Pretoria, Lynnwood Road, Pretoria 0002 (South Africa); Nyokong, Tebello, E-mail: t.nyokong@ru.ac.za [Department of Chemistry, Rhodes University, Grahamstown 6140 (South Africa); Forbes, Patricia B.C., E-mail: patricia.forbes@up.ac.za [Department of Chemistry, Faculty of Natural and Agricultural Sciences, University of Pretoria, Lynnwood Road, Pretoria 0002 (South Africa)

2015-10-05

Highlights: • Alloyed quaternary CdSeTeS core quantum dots (QDs) were synthesized. • Passivation was carried out using a ZnS shell. • Quaternary CdSeTeS core exhibited unique optical properties over CdSeTe/ZnS. • CdSeTeS can be employed as a useful alternative to core/shell QDs. - Abstract: Synthesis of fluorescent alloyed quantum dots (QDs) with unique optical properties suitable for a wide array of chemical, physical and biological applications is of research interest. In this work, highly luminescent and photostable alloyed quaternary CdSeTeS core QDs of two different sizes were fabricated via the organometallic hot-injection synthetic route. Characterization of the nanocrystals were performed using TEM, XRD, UV/vis and fluorescence spectrophotometric techniques. We have demonstrated in this work that the well fabricated alloyed quaternary CdSeTeS core QDs possess unique optical properties that are advantageous over conventional core/shell systems. Formation of the CdSeTeS/ZnS core/shell with the desired optical properties comes with a number of challenges, hence the advantages of the quaternary alloyed core over the core/shell QDs are (i) avoidance of the challenging process of determining the proper shell thickness which can provide the desired optical properties in the core/shell system and (ii) avoidance of the lattice-induced mismatch between the core and the shell material which can either lead to incomplete exciton confinement or dislocation at the core/shell interface.

Ocean to continent transfer of atmospheric Se as revealed by epiphytic lichens

International Nuclear Information System (INIS)

Wen Hanjie; Carignan, Jean

2009-01-01

There is still a long-term debate concerning the relative contributions of naturally emitted and anthropogenic Se at the regional and local scales. Here, Se and heavy metal concentrations are reported for epiphytic lichens collected in coastal and inland areas from the USA, Canada and France for assessing atmospheric Se source. Correlations found between Se and Cl in lichens confirmed the major marine biogenic source for atmospheric Se. Continental samples do not show systematic relationships between Se and other metal (Pb, Cu, In ...) contents, even for lichens collected in the vicinity of smelters or close to urban areas. Our results suggest that, although anthropogenic Se may be present, the marine biogenic Se source is a major contributor to atmospheric Se for our sampling locations. The contribution of naturally emitted atmospheric Se may be significant in urban and industrial areas and should be taken into account for further studies. - Although anthropogenic Se may be present, the contribution of naturally emitted atmospheric Se may be significant in urban and industrial areas and should be taken into account for further studies.

The processing of CdSe/Polymer nanocomposites via solution organometallic chemistry

International Nuclear Information System (INIS)

Khanna, P.K.; Singh, Narendra; Charan, Shobhit; Lonkar, Sunil P.; Reddy, A. Satyanarayana; Patil, Yogesh; Viswanath, A. Kasi

2006-01-01

This paper presents in situ preparation of CdSe nanoparticles using poly(vinyl alcohol) [PVA] and polymethylmethacrylate [PMMA] as matrices by use of organoselenium compound. Reaction of cadmium metal salt and 1,2,3-selenadiazole (the source of selenium) enabled formation of CdSe nanoparticles. Use of selenadiazole in the present work with polymer is first of its kind. The radical polymerization of methycrylate monomer with benzoyl peroxide followed by reaction of respective reagents have been successfully employed to synthesize CdSe/PMMA nanocomposite. Similarly, reaction between selenadiazole and cadmium metal salt in aq. PVA yielded polymer coated or mixed CdSe nanoparticles. The UV-vis absorption spectra showed blue shift of about 200 nm with respect to band-gap energy of bulk CdSe, due to size quantization effect in CdSe particles. An emission band was observed at 530 nm in photoluminescence spectrum (PL) of CdSe/PMMA. IR spectra indicated shifts in the values of the polymer functional group due to nanoparticles. X-ray measurement of CdSe/Polymer nano-composites showed broad pattern for cubic CdSe and particle size of CdSe was estimated to be <10 nm. TGA revealed gradual weight loss between 200 and 400 deg. C indicating increased thermal stability of the polymer

Photoelectrochemical (PEC) studies on CdSe thin films ...

Indian Academy of Sciences (India)

TECS

Thin films of CdSe were deposited by potentiostatic mode on different substrates such as ... trodeposited from aqueous acidic baths, but very few ... washed with liquid detergent (labolene) followed by ul- .... increases the ionic mobilities and hence the conductivity ... A PEC cell of configuration, CdSe/1 M polysulphide/.

Wittgenstein og respekten for det religiøse

DEFF Research Database (Denmark)

Albinus, Lars

2006-01-01

Fremstilling af den tidlige og den sene Wittgensteins forhold til det religiøse med særligt henblik på tabet af umiddelbarhed.......Fremstilling af den tidlige og den sene Wittgensteins forhold til det religiøse med særligt henblik på tabet af umiddelbarhed....

Forming Glasses from Se and Te

Directory of Open Access Journals (Sweden)

Pierre Lucas

2009-10-01

Full Text Available Despite being close neighbors on the Periodic Table, selenium and tellurium present a totally different abilities to form glasses. Se is a very good glass former, and gives rise to numerous glass compositions which are popular for their transparency in the infrared range and their stability against crystallization. These glasses can be shaped into sophisticated optical devices such as optical fibers, planar guides or lenses. Nevertheless, their transparencies are limited at about 12 μm (depending on the thickness of the optical systems due to the relatively small mass of the Se element. On the other hand, tellurium is heavier and its use in substitution for Se permits to shift the IR cutoff beyond 20 μm. However, the semimetallic nature of Te limits its glass formation ability and this glass family is known to be unstable and consequently has found application as phase change material in the Digital Versatile Disk (DVD technology. In this paper, after a review of selenide glasses and their applications, it will be shown how, in a recent past, it has been possible to stabilize tellurium glasses by introducing new elements like Ga or I in their compositions.

Qué se sabe de bullying

Directory of Open Access Journals (Sweden)

B. Ricardo Musalem, Ps.

2015-01-01

Full Text Available Se define bullying como una dinámica de maltrato sistemática que ocurre entre iguales de manera persistente. Es considerado un problema de salud pública debido a su prevalencia y las consecuencias que tiene en todos sus participantes: en los agresores, en las víctimas, en los espectadores, en los padres y familias, en la comunidad escolar y en la sociedad en general. Las investigaciones muestran efectos a corto, mediano y largo plazo en el desarrollo emocional y social de niños y adolescentes. Se ha constatado una relación del acoso escolar con las patologías físicas, psicosomática y de salud mental en niños, adolescentes y en la vida adulta. En este artículo se describen las características individuales, las relacionales, los factores conocidos como de riesgo y factores protectores, la prevalencia y los programas de abordaje integral del fenómeno. Son múltiples los estudios que muestran la efectividad de la aplicación de estos programas de intervención, diseñados en función de los conocimientos acumulados.

Influence of Se concentrations and species in hydroponic cultures on Se uptake, translocation and assimilation in non-accumulator ryegrass.

Science.gov (United States)

Versini, Antoine; Di Tullo, Pamela; Aubry, Emmanuel; Bueno, Maïté; Thiry, Yves; Pannier, Florence; Castrec-Rouelle, Maryse

2016-11-01

The success of biofortification and phytoremediation practices, addressing Se deficiency and Se pollution issues, hinges crucially on the fate of selenium in the plant media in response to uptake, translocation and assimilation processes. We investigate the fate of selenium in root and shoot compartments after 3 and 6 weeks of experiment using a total of 128 plants grown in hydroponic solution supplied with 0.2, 2, 5, 20 and 100 mg L -1 of selenium in the form of selenite, selenate and a mixture of both species. Selenate-treated plants exhibited higher root-to-shoot Se translocation and total Se uptake than selenite-treated plants. Plants took advantage of the selenate mobility and presumably of the storage capacity of leaf vacuoles to circumvent selenium toxicity within the plant. Surprisingly, 28% of selenate was found in shoots of selenite-treated plants, questioning the ability of plants to oxidize selenite into selenate. Selenomethionine and methylated organo-selenium amounted to 30% and 8% respectively in shoots and 35% and 9% in roots of the identified Se, suggesting that selenium metabolization occurred concomitantly in root and shoot plant compartments and demonstrating that non-accumulator plants can synthesize notable quantities of precursor compound for volatilization. The present study demonstrated that non-accumulator plants can develop the same strategies as hyper-accumulator plants to limit selenium toxicity. When both selenate and selenite were supplied together, plants used selenate in a storage pathway and selenite in an assimilation pathway. Plants might thereby benefit from mixed supplies of selenite and selenate by saving enzymes and energy required for selenate reduction. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

Phase transitions in thin films of Sn-Sb-Se system

International Nuclear Information System (INIS)

Samsudi Sakrani; Abdalla Belal Adam; Yussof Wahab

1998-01-01

The preparation and formation of covalent ternary Sn-Sb-Se system were investigated. A solid state reaction technique was employed whereby the evaporated multilayers of Sn/Se/Sb/Sn reacted chemically at a fixed temperature of 240 o C and were allowed to a room temperature slow-cooling. X-ray diffraction analysis showed that phase changes occurred in the system, with indication of amorphization for the predicted Sn 9 .3Sb 8 .1Se 4 4.9 and Sn 1 3.2Sb 4 3.4Se 4 3.4 compositions. These enabled the preliminary topological phase transitions of Sn-Sb-Se system according to the Gibb's triangle in which the areas of crystalline-amorphous were located. (Author)

Synthesis and crystal structure of three new quaternary compounds in the system (Cu-III-Se{sub 2}){sub 1-x}ZnSe{sub x} (III = Al, Ga, In), formed by Zn incorporation in Cu-III-Se{sub 2} chalcopyrite s

Energy Technology Data Exchange (ETDEWEB)

Delgado, G. E. [Universidad de Los Andes, Facultad de Ciencias, Departamento de Quimica, Laboratorio de Cristalografia, 5101 Merida (Venezuela, Bolivarian Republic of); Grima G, P.; Quintero, M., E-mail: gerzon@ula.ve [Universidad de Los Andes, Facultad de Ciencias, Departamento de Fisica, Centro de Estudios de Semiconductores, 5101 Merida (Venezuela, Bolivarian Republic of)

2016-11-01

The crystal structure of the chalcogenide alloys CuZnAlSe{sub 3}, CuZnCaSe{sub 3} and CuZnInSe{sub 3}, new members of the system I-II-III-VI{sub 3}, were characterized using X-ray powder diffraction data. All materials crystallize in the tetragonal space group P{sub -4} 2{sub c} (N 112) with a CuFeInSe{sub 3}- type structure. (Author)

Synthesis and crystal structure determination of Br2SeIBr ...

Indian Academy of Sciences (India)

Unknown

termined by single crystal X-ray diffraction method. This compound was ... company and SeBr4 was prepared from the reaction of Se powder (0⋅1 g) with Br2 ... angles of Br2SeIBr and table 4 shows anisotropic displace- ment parameters.

Magnetic study of Fe-doped CdSe nanomaterials

International Nuclear Information System (INIS)

Das, Sayantani; Banerjee, Sourish; Sinha, T. P.

2016-01-01

Nanoparticles of pure and iron (50 %) doped cadmium selenide (CdSe) have been synthesized by soft chemical route. EDAX analysis supports the inclusion of Fe into CdSe nanoparticles. The average particle size of pure and doped CdSe is found to be ∼50 nm from scanning electron microscopy (SEM). Magnetization of the samples are measured under the field cooled (FC) and zero field cooled (ZFC) modes in the temperature range from 5K to 300K applying a magnetic field of 500Oe. Field dependent magnetization (M-H) measurement indicates presence of room temperature (RT) paramagnetism and low temperature (5K) ferromagnetism of the sample.

Yield of 73Se for various reactions and its chemical processing

International Nuclear Information System (INIS)

Nozaki, T.; Itoh, Y.; Ogawa, K.

1979-01-01

Excitation curves for the formation of 73 Se by the following reactions were measured up to proton energy of 50 MeV and 3 He- and α-particle energies of 40 MeV, together with those for byproduct formation reactions: (1) 75 As(p, 3n) 73 Se, (2) Ge + 3 He → 73 Se, and (3) Ge + α → 73 Se. The proton reaction has proved to be much superior to the other reactions both in yield and product purity. Volatilization of 73 Se from a solution of condensed polyphosphoric acid was found to give an excellent method of 73 Se separation from various arsenic targets without carrier. Also, solvent extraction of red selenium 73 Se with a minute amount of carrier was shown to be a useful separation method. (author)

Experimental Conditions: SE48_S01_M01_D01 [Metabolonote[Archive

Lifescience Database Archive (English)

Full Text Available structure elucidation of 36 specialized metabolites from Oryza sativa (rice) by using MS/MS and NMR analyse...s SE48_S01 Habataki SE48_S01_M01 1 μL SE48_MS01 LC–QTOF-MS/MS analysis SE48_DS01 Data upload Default SE48_AM01 SE48_SS01 Isolation of specialized metabolites ...

Solid solutions in the system Nd2(SeO4)3 - Sm2(SeO4)3 - H2O

International Nuclear Information System (INIS)

Serebrennikov, V.V.; Tsybukova, T.N.; Velikov, A.A.

1984-01-01

Using the method of isothermal solubility at 25 deg C the system Nd 2 (SeO 4 ) 3 -Sm 2 (SeO 4 ) 3 -H 2 O has been studied. Roentgenographic recording of solid ''residues'' is realized. For solid solutions energies of interchange and formation heats are calculated. Formation heats of solid solutions on the basis of samarium selenates are also found experimentally

Core-Shell Zn x Cd1- x Se/Zn y Cd1- y Se Quantum Dots for Nonvolatile Memory and Electroluminescent Device Applications

Science.gov (United States)

Al-Amoody, Fuad; Suarez, Ernesto; Rodriguez, Angel; Heller, E.; Huang, Wenli; Jain, F.

2011-08-01

This paper presents a floating quantum dot (QD) gate nonvolatile memory device using high-energy-gap Zn y Cd1- y Se-cladded Zn x Cd1- x Se quantum dots ( y > x) with tunneling layers comprising nearly lattice-matched semiconductors (e.g., ZnS/ZnMgS) on Si channels. Also presented is the fabrication of an electroluminescent (EL) device with embedded cladded ZnCdSe quantum dots. These ZnCdSe quantum dots were embedded between indium tin oxide (ITO) on glass and a top Schottky metal electrode deposited on a thin CsF barrier. These QDs, which were nucleated in a photo-assisted microwave plasma (PMP) metalorganic chemical vapor deposition (MOCVD) reactor, were grown between the source and drain regions on a p-type silicon substrate of the nonvolatile memory device. The composition of QD cladding, which relates to the value of y in Zn y Cd1- y Se, was engineered by the intensity of ultraviolet light, which controlled the incorporation of zinc in ZnCdSe. The QD quality is comparable to those deposited by other methods. Characteristics and modeling of the II-VI quantum dots as well as two diverse types of devices are presented in this paper.

Information letter 2. Information about operation of plants SE-NPP Bohunice and SE-VYZ during February 2005

International Nuclear Information System (INIS)

2005-03-01

In this leaflet results of exploitation of four units of the Bohunice V-1 and V-2 NPPs are presented. The electricity and heat production in February 2005 are reviewed. Within a February 2005 the electricity was produced: 217 GWh (block 1), 281 GWh (block 2), 277 GWh (block 3), 282 GWh (block 4), totally 1057 GWh, and 2271 GWh within a January - February 2005. The heat production in February 2005 was 266 506 GJ, and within a January - February 2005 it was produced 531 849 GJ of heat. On February 17 Slovak minister of economy Pavol Rusko and general director of ENEL Paolo Scaroni signed the agreement on acquisition of 66 per cent of Slovenske elektrarne (SE) by Italian ENEL for 840 million Eur. SE has capacity of around 7 GW (83 per cent of total Slovakian capacity). In 2004 SE generated 26 TWh of electricity. Processing and storage of radioactive wastes in Decommissioning of Nuclear Installations and Spent Fuel and Rad-waste Management (SE-VYZ) is presented. Since beginning of this year 58 fibre-concrete containers have been filled up in Bohunice processing centre of radioactive wastes. Twenty-three pieces of fibre-concrete containers were processed into fibre-concrete containers in Bohunice processing centre of radioactive wastes (BSC RAO) in February 2005. Twenty fibre-concrete containers were stored into Republic storage of radioactive wastes (RU RAO). Total number in RU RAO reached 830 pieces of fibre-concrete containers, which represent 11.53 per cent of storage capacity (7200 containers). Bohunice processing centre of radioactive wastes was put into active operation just before five years

X = S, Se, Te) heterostructures

KAUST Repository

Zhang, Qingyun; Schwingenschlö gl, Udo

2018-01-01

Using first-principles calculations, we investigate the electronic properties of the two-dimensional GaX/MX2 (M = Mo, W; X = S, Se, Te) heterostructures. Orbital hybridization between GaX and MX2 is found to result in Rashba splitting at the valence

The Formation Mechanism of Cu(In0.7Ga0.3Se2 Nanoparticles and the Densification Trajectory of the Se-Rich Quaternary Target by Hot Pressing

Directory of Open Access Journals (Sweden)

Qiang Ma

2018-03-01

Full Text Available In this paper, a method to obtain the CuInGaSe2 (CIGS absorber layer with an appropriate selenium content is put forward, in which a Se-rich target is used to deposit a CIGS thin-film and this film is annealed in a Se-free inert atmosphere. The key issue of this method is the preparation of a Se-rich target with a homogeneous composition and a high-density. The formation mechanism of CuInSe2 and CuGaSe2 is investigated and the results point to the intermediate phase Cu2−xSe playing a role of a nucleation core. The sintering densification trajectory of the target with the addition of extra selenium is researched. Additionally, an effective way to avoid the sintering defects is proposed. Finally, a conversion efficiency of 11.2% for the CIGS solar cell is reached by sputtering from the obtained Se-rich target.

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.

La lengua castellana se encuentra en cada rincón

OpenAIRE

López de Armentia Llanos, Javier

2015-01-01

Nuestros alumnos acaban de comenzar el primer curso de primaria. En este primer momento, un mundo nuevo se abre ante ellos; nuevos profesores, nuevos espacios, nuevos materiales, nuevo modo de trabajo, nueva forma de distribución de las mesas, e incluso, en algunos casos, nuevo centro educativo. En primera instancia, los alumnos se ven desbordados a la hora de enfrentarse a nuevos retos. ¿Se podría encontrar una forma útil de suavizar este paso adelante? Este trabajo de fin de grado se va ...

Sc2[Se2O5]3: The First Rare-Earth Metal Oxoselenate(IV with Exclusively [Se2O5]2− Anions

Directory of Open Access Journals (Sweden)

Stefan Greiner

2018-04-01

Full Text Available The scandium oxodiselenate(IV Sc2[Se2O5]3 was synthesized via solid-state reactions between scandium sesquioxide (Sc2O3 and selenium dioxide (SeO2 with thallium(I chloride (TlCl as fluxing agent in molar ratios of 1:4:2. Evacuated fused silica ampoules were used as reactions vessels for annealing the mixtures for five days at 800 °C. The new scandium compound crystallizes in the triclinic space group P 1 ¯ with the lattice parameters a = 663.71(5 pm, b = 1024.32(7 pm, c = 1057.49(8 pm, α = 81.034(2°, β = 87.468(2°, γ = 89.237(2° and Z = 2. There are two distinct Sc3+ positions, which show six-fold coordination by oxygen atoms as [ScO6]9− octahedra (d(Sc–O = 205–212 pm. Three different [Se2O5]2− anions provide these oxygen atoms with their terminal ligands (Ot. Each of the six selenium(IV central atoms exhibit a stereochemically active lone pair of electrons, so that all [Se2O5]2− anions consist of two ψ1-tetrahedral [SeO3]2− subunits (d(Se–Ot = 164–167 pm, d(Se–Ob = 176–185 pm, ∢(O–Se–O = 93–104° sharing one bridging oxygen atom (Ob with ∢(Se–Ob–Se = 121–128°. The vibrational modes of the complex anionic [Se2O5]2− entities were characterized via single-crystal Raman spectroscopy.

How Correlated is the FeSe /SrTiO3 System?

Science.gov (United States)

Mandal, Subhasish; Zhang, Peng; Ismail-Beigi, Sohrab; Haule, K.

2017-08-01

Recent observation of ˜10 times higher critical temperature in a FeSe monolayer compared with its bulk phase has drawn a great deal of attention because the electronic structure in the monolayer phase appears to be different than bulk FeSe. Using a combination of density functional theory and dynamical mean field theory, we find electronic correlations have important effects on the predicted atomic-scale geometry and the electronic structure of the monolayer FeSe on SrTiO3 . The electronic correlations are dominantly controlled by the Se-Fe-Se angle either in the bulk phase or the monolayer phase. But the angle sensitivity increases and the orbital differentiation decreases in the monolayer phase compared to the bulk phase. The correlations are more dependent on Hund's J than Hubbard U . The observed orbital selective incoherence to coherence crossover with temperature confirms the Hund's metallic nature of the monolayer FeSe. We also find electron doping by oxygen vacancies in SrTiO3 increases the correlation strength, especially in the dx y orbital by reducing the Se-Fe-Se angle.

Chemistry in CESM-SE: Evaluation, Performance and Optimization

Energy Technology Data Exchange (ETDEWEB)

Lamarque, Jean-Francois [National Center for Atmospheric Research, Boulder, CO (United States); Conley, Andrew [National Center for Atmospheric Research, Boulder, CO (United States); Vitt, Francis [National Center for Atmospheric Research, Boulder, CO (United States); Drake, John [Univ. of Tennessee, Knoxville, TN (United States); Sun, Jian [Univ. of Tennessee, Knoxville, TN (United States)

2016-01-06

The purpose of the proposed work focused on development of chemistry representation within the Spectral Element (SE) dynamical core as implemented in the Community Earth System Model (CESM). More specifically, a main focus was on the ability of SE to accurately represent tracer transport. The proposed approach was to incrementally increase the complexity of the problem, starting from specified two-dimensional flow and tracers to simulations using specified dynamics and full chemistry. As demonstrated below, we have successfully studied all aspects of the proposed work, although only part of the work has been published in the refereed literature so far. Furthermore, because the SE dynamical core has been found to have several deficiencies that are still being investigated for solution, not all proposed tasks were finalized. In addition to the tests for SE performance, in an effort to decrease the computational burden of interactive chemistry, especially in the case of a large number of chemical species and chemical reactions, development on a faster chemical solver and implementation on GPUs has been implemented in CESM under the leadership of John Drake (U. Tennessee).

Distopie voor oë: Eben Venter se duister kuns

Directory of Open Access Journals (Sweden)

Harry Sewlall

2016-08-01

Full Text Available Sedert die verskyning van Joseph Conrad se novelle, Heart of Darkness, uitgegee as vervolgverhaal in 1899, was daar al verskeie pogings om Conrad se teks te ‘herskryf’, al was die verwantskap met die meesterteks dikwels gering of selfs twyfelagtig. Nog ’n herskrywing van Conrad se teks is Eben Venter se roman Trencherman, aanvanklik in Afrikaans uitgegee as Horrelpoot. Hierdie teks volg die meesterteks baie nougeset na, nie slegs deur aanhalings daaruit as motto’s vooraan elke hoofstuk te gebruik nie, maar ook deur beelde en woorde uit die oorspronklike teks op ooglopende of bedekte wyse in die narratief in te weef. Die vrae waarmee ’n leser soos ek, wat nie vertroud is met Afrikaans nie, gekonfronteer word, is of dit ’n geval van plagiaat is of ’n oefening in intertekstualiteit en ofdie boek eerder ’n poging is om sensasie te wek ten einde meer boeke te verkoop. Hierdie vraevorm die basis vir ’n intertekstuele verkenning van die twee tekste, wat neerkom op ’n stiplees van Conrad se teks langs Trencherman ten einde die intertekstuele skakels tussen die twee tekste te identifiseer. Teoreties is die artikel gebaseer op die werk van Kristeva en Barthes. Die ondersoek het bevestig dat Trencherman inderdaad ’n oefening in intertekstualiteit is, nie slegs as intertekstualiteit nie, maar eerder as ’n in-gesprek-tree met Conrad se meesterteks. Daaruit volg die slotsom dat Trencherman ’n geldige intertekstuele antwoord is op Heart of darkness wat Conrad se beroemde novelle dekonstrueer en die draaiboek daarvan transponeer na ’n distopiese, post-demokratiese Suid-Afrika.

Ud & se - med Claude Monet

DEFF Research Database (Denmark)

Bonde, Lisbeth

2015-01-01

Udstillingen 'Claude Monet - Lost in Translation - på ARoS stiller ind på Claud Monet og hans samtidige malerkolleger. Udstillingen forsøger at "genlæse" Monet fra et samtidskunstnerisk perspektiv - og vurderer hans indsats, inden hans værker er blevet reproduceret ihjel....

Optical studies of CdSe/PVA nanocomposite films

Science.gov (United States)

Kushwaha, Kamal Kumar; Ramrakhaini, Meera

2018-05-01

The nanocomposite films of CdSe nanocrystals in polyvinyl alcohol (PVA) matrix were synthesized by environmental friendly chemical method. These composites were characterized by X-ray diffraction which indicates the hexagonal crystalline structure of CdSe with crystal size up to a few nm. The crystal size is found to decrease by increasing PVA Concentration. The photoluminescence (PL) characteristics of these composite films with varying concentration of PVA as well as Cd2+ content have been investigated. The PL peak of CdSe was observed at 510 nm and higher intensity is observed by increasing PVA concentration without any change in position of PL peak. Due to proper passivation of surface states non-radiative transition are reduced which enhance the PL intensity. By increasing concentration of Cd2+ content in the CdSe/PVA nanocomposite films, smaller CdSe nanocrystals were obtained giving higher intensity and blue shift in the PL peak due to enhanced oscillator strength and quantum confinement effect. The PL peak in green and blue region makes these composite films promising materials for optical display devices. The Refractive index of these composites was also measured at sodium line with the help of Abee's refractometer and was found in the range of 2.20-2.45. It is seen that refractive index varies with polymer concentration. This may be useful for their potential application in anti-reflection coating, display devices and optical sensors.

V1.42In1.83Mo15Se19

Directory of Open Access Journals (Sweden)

Michel Potel

2010-10-01

Full Text Available The structure of the title compound, vanadium indium pentadecamolybdenum nonadecaselenide, V1.42In1.83Mo15Se19, is isotypic with In2.9Mo15Se19 [Grüttner et al. (1979. Acta Cryst. B35, 285–292]. It is characterized by two cluster units Mo6Sei8Sea6 and Mo9Sei11Sea6 (where i represents inner and a apical atoms that are present in a 1:1 ratio. The cluster units are centered at Wyckoff positions 2b and 2c and have point-group symmetry overline{3} and overline{6}, respectively. The clusters are interconnected through additional Mo—Se bonds. In the title compound, the V3+ cations replace the trivalent indium atoms present in In2.9Mo15Se19, and a deficiency is observed on the monovalent indium site. One Mo, one Se and the V atom are situated on mirror planes, and two other Se atoms and the In atom are situated on threefold rotation axes.

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.

Real-time in-situ monitoring of the topotactic transformation of TlCu3Se2 into TlCu2Se2

International Nuclear Information System (INIS)

Ångström, J.; Sahlberg, M.; Berger, R.

2015-01-01

Highlights: • Topotactic transition from TlCu 3 Se 2 to TlCu 2 Se 2 followed in situ. • Synchrotron radiation X-ray powder diffraction enabled short scans. • Relative abundance of phases refined from powder data. • Opens up for studying similar systems in the same manner. - Abstract: The solid state transformation of monoclinic TlCu 3 Se 2 into tetragonal TlCu 2 Se 2 by oxidative copper leaching in concentrated ammonia solution has been studied in situ by the use of synchrotron radiation. The diffraction patterns of parent and daughter phase are both sharp, indicating a strong topotactic relationship between them that effectuates a rapid change by “chimie douce” performed at +19 °C. The transformation rate is strongly connected to the access of oxygen from the surrounding air. The transformation was followed in a real-time mode, being almost complete after 2.5 h with 1 h incubation due to low oxygen content, as shown from refining the diffraction patterns by Rietveld profile technique

Experimental Conditions: SE3_S02_M01_D02 [Metabolonote[Archive

Lifescience Database Archive (English)

Full Text Available SE3_S02_M01_D02 SE3 Comparison of fruit metabolites among tomato varieties 1 SE3_S0...2 Solanum lycopersicum House Momotaro fruit SE3_S02_M01 6.7mg [MassBase ID] MDLC1_25529 SE3_MS1 LC-FT-ICR-MS

Experimental Conditions: SE3_S02_M02_D03 [Metabolonote[Archive

Lifescience Database Archive (English)

Full Text Available SE3_S02_M02_D03 SE3 Comparison of fruit metabolites among tomato varieties 1 SE3_S0...2 Solanum lycopersicum House Momotaro fruit SE3_S02_M02 6.7 mg [MassBase ID] MDLC1_25530 SE3_MS1 LC-FT-ICR-M

Experimental Conditions: SE3_S02_M01_D01 [Metabolonote[Archive

Lifescience Database Archive (English)

Full Text Available SE3_S02_M01_D01 SE3 Comparison of fruit metabolites among tomato varieties 1 SE3_S0...2 Solanum lycopersicum House Momotaro fruit SE3_S02_M01 6.7mg [MassBase ID] MDLC1_25529 SE3_MS1 LC-FT-ICR-MS

Experimental Conditions: SE3_S02_M03_D03 [Metabolonote[Archive

Lifescience Database Archive (English)

Full Text Available SE3_S02_M03_D03 SE3 Comparison of fruit metabolites among tomato varieties 1 SE3_S0...2 Solanum lycopersicum House Momotaro fruit SE3_S02_M03 6.7 mg [MassBase ID] MDLC1_25531 SE3_MS1 LC-FT-ICR-M

Experimental Conditions: SE3_S02_M03_D01 [Metabolonote[Archive

Lifescience Database Archive (English)

Full Text Available SE3_S02_M03_D01 SE3 Comparison of fruit metabolites among tomato varieties 1 SE3_S0...2 Solanum lycopersicum House Momotaro fruit SE3_S02_M03 6.7 mg [MassBase ID] MDLC1_25531 SE3_MS1 LC-FT-ICR-M

Experimental Conditions: SE3_S02_M01_D03 [Metabolonote[Archive

Lifescience Database Archive (English)

Full Text Available SE3_S02_M01_D03 SE3 Comparison of fruit metabolites among tomato varieties 1 SE3_S0...2 Solanum lycopersicum House Momotaro fruit SE3_S02_M01 6.7mg [MassBase ID] MDLC1_25529 SE3_MS1 LC-FT-ICR-MS

Experimental Conditions: SE3_S02_M02_D01 [Metabolonote[Archive

Lifescience Database Archive (English)

Full Text Available SE3_S02_M02_D01 SE3 Comparison of fruit metabolites among tomato varieties 1 SE3_S0...2 Solanum lycopersicum House Momotaro fruit SE3_S02_M02 6.7 mg [MassBase ID] MDLC1_25530 SE3_MS1 LC-FT-ICR-M

Experimental Conditions: SE3_S02_M03_D02 [Metabolonote[Archive

Lifescience Database Archive (English)

Full Text Available SE3_S02_M03_D02 SE3 Comparison of fruit metabolites among tomato varieties 1 SE3_S0...2 Solanum lycopersicum House Momotaro fruit SE3_S02_M03 6.7 mg [MassBase ID] MDLC1_25531 SE3_MS1 LC-FT-ICR-M

Experimental Conditions: SE3_S02_M02_D02 [Metabolonote[Archive

Lifescience Database Archive (English)

Full Text Available SE3_S02_M02_D02 SE3 Comparison of fruit metabolites among tomato varieties 1 SE3_S0...2 Solanum lycopersicum House Momotaro fruit SE3_S02_M02 6.7 mg [MassBase ID] MDLC1_25530 SE3_MS1 LC-FT-ICR-M

Structural, morphological and optical properties of pulsed laser deposited ZnSe/ZnSeO3 thin films

Science.gov (United States)

Hassan, Syed Ali; Bashir, Shazia; Zehra, Khushboo; Salman Ahmed, Qazi

2018-04-01

The effect of varying laser pulses on structural, morphological and optical behavior of Pulsed Laser Deposited (PLD) ZnSe/ZnSeO3 thin films has been investigated. The films were grown by employing Excimer laser (100 mJ, 248 nm, 18 ns, 30 Hz) at various number of laser pulses i.e. 3000, 4000, 5000 and 6000 with elevated substrate temperature of 300 °C. One film was grown at Room Temperature (RT) by employing 3000 number of laser pulses. In order to investigate the structural analysis of deposited films, XRD analysis was performed. It was observed that the room temperature is not favorable for the growth of crystalline film. However, elevated substrate temperature to 300°C, two phases with preferred orientation of ZnSeO3 (2 1 2) and ZnSe (3 3 1) were identified. AFM and SEM analysis were performed to explore the surface morphology of grown films. Morphological analysis also confirmed the non-uniform film growth at room temperature. At elevated substrate temperature (300 °C), the growth of dendritic rods and cubical crystalline structures are observed for lower number of laser pulses i.e. 3000 and 4000 respectively. With increased number of pulses i.e. 5000 and 6000, the films surface morphology becomes smooth which is confirmed by measurement of surface RMS roughness. Number of grains, skewness, kurtosis and other parameters have been evaluated by statistical analysis. In order to investigate the thickness, and optical properties of deposited films, ellipsometery and UV–Vis spectroscopy techniques were employed. The estimated band gap energy is 2.67 eV for the film grown at RT, whereas band gap values varies from 2.80 eV to 3.01 eV for the films grown at 300 °C with increasing number of laser pulses.

Far-Infrared Absorption of PbSe Nanorods

KAUST Repository

Hyun, Byung-Ryool

2011-07-13

Measurements of the far-infrared absorption spectra of PbSe nanocrystals and nanorods are presented. As the aspect ratio of the nanorods increases, the Fröhlich sphere resonance splits into two peaks. We analyze this splitting with a classical electrostatic model, which is based on the dielectric function of bulk PbSe but without any free-carrier contribution. Good agreement between the measured and calculated spectra indicates that resonances in the local field factors underlie the measured spectra. © 2011 American Chemical Society.

Stability studies of CdSe nanocrystals in an aqueous environment