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Sample records for centre dot 2h2o

  1. Production of graphene quantum dots by ultrasound-assisted exfoliation in supercritical CO2/H2O medium.

    Gao, Hanyang; Xue, Chen; Hu, Guoxin; Zhu, Kunxu

    2017-07-01

    In this research, three kinds of graphene quantum dots (GQDs)-pristine graphene quantum dots (PGQDs), expanded graphene quantum dots (EGQDs) and graphene oxide quantum dots (GOQDs)-were produced from natural graphite, expanded graphite, and oxide graphite respectively in an ultrasound-assisted supercritical CO 2 (scCO 2 )/H 2 O system. The effects of aqueous solution content ratio, system pressure, and ultrasonic power on the yields of different kinds of GQDs were investigated. According to these experiment results, the combination of the intense knocking force generated from high-pressure acoustic cavitation in a scCO 2 /H 2 O system and the superior penetration ability of scCO 2 was considered to be the key to the successful exfoliation of such tiny pieces from bulk graphite. An interesting result was found that, contrary to common experience, the yield of PGQDs from natural graphite was much higher than that of GOQDs from graphite oxide. Based on the experimental analysis, the larger interlayer resistance of natural graphite, which hindered the insertion of scCO 2 molecules, and the hydrophobic property of natural graphite surface, which made the planar more susceptible to the attack of ultrasonic collapsing bubbles, were deduced to be the two main reasons for this result. The differences in characteristics among the three kinds of GQDs were also studied and compared in this research. In our opinion, this low-cost and time-saving method may provide an alternative green route for the production of various kinds of GQDs, especially PGQDs. Copyright © 2017 Elsevier B.V. All rights reserved.

  2. H2-H2O-HI Hydrogen Separation in H2-H2O-HI Gaseous Mixture Using the Silica Membrane

    Pandiangan, Tumpal

    2002-01-01

    It was evaluated aiming at the application for hydrogen iodide decomposition in the thermochemical lS process. Porous alumina tube having pore size of 0.1 μm was modified by chemical vapor deposition using tetraethoxysilane. The permeance single gas of He, H 2 , and N 2 was measured at 300-600 o C. Hydrogen permeance of the modified membrane at a permeation temperature of 600 o C was about 5.22 x 10 -08 mol/Pa m 2 s, and 3.2 x 10 -09 of using gas mixture of H 2 -H 2 O-HI, where as HI permeances was below 1 x 10 -10 mol/Pa m 2 s. The Hydrogen permeance relative was not changed after 25 hours exposure in a mixture of H 2 -H 2 O-HI gas at the temperature of 450 o C. (author)

  3. Nanosecond pulsed discharges in N2 and N2/H2O mixtures

    Joosten, R.M.; Verreycken, T.; Veldhuizen, van E.M.; Bruggeman, P.J.

    2011-01-01

    Nanosecond pulsed discharges in N2 and N2/H2O at atmospheric pressure between two pin-shaped electrodes are studied. The evolution of the discharge is investigated with time-resolved imaging and optical emission spectroscopy. The discharge consists of three phases, the ignition (mainly molecular

  4. Relaxation phenomena in CsCoCl3·2 H2O

    Flokstra, Jakob; Gerritsma, G.J.; Vermeulen, A.J.W.A; Botterman, A.C.

    1973-01-01

    Dynamic susceptibility measurements have been performed on a single crystal of CsCoCl3·2H2O at liquid temperatures by means of a Hartshorn mutual inductance bridge. At the magnetic phase transition a maximum in τabs(H) has been observed. A jump in τabs(T) has been found at the λ-point of liquid

  5. High purity H2/H2O/Ni/SZ electrodes at 500º C

    Høgh, Jens Valdemar Thorvald; Hansen, Karin Vels; Norrman, Kion

    2013-01-01

    of stabilized zirconia (SZ) with 10, 13 and 18 mol% yttria and one with 6 mol% scandia plus 4 mol% yttria were studied at open circuit voltage at 400-500 C in mixtures of H2/H2O over 46 days. The polarization resistances (Rp) for all samples increased significantly during the first 10-20 days at 500 C...

  6. VUV photoionization cross sections of HO2, H2O2, and H2CO.

    Dodson, Leah G; Shen, Linhan; Savee, John D; Eddingsaas, Nathan C; Welz, Oliver; Taatjes, Craig A; Osborn, David L; Sander, Stanley P; Okumura, Mitchio

    2015-02-26

    The absolute vacuum ultraviolet (VUV) photoionization spectra of the hydroperoxyl radical (HO2), hydrogen peroxide (H2O2), and formaldehyde (H2CO) have been measured from their first ionization thresholds to 12.008 eV. HO2, H2O2, and H2CO were generated from the oxidation of methanol initiated by pulsed-laser-photolysis of Cl2 in a low-pressure slow flow reactor. Reactants, intermediates, and products were detected by time-resolved multiplexed synchrotron photoionization mass spectrometry. Absolute concentrations were obtained from the time-dependent photoion signals by modeling the kinetics of the methanol oxidation chemistry. Photoionization cross sections were determined at several photon energies relative to the cross section of methanol, which was in turn determined relative to that of propene. These measurements were used to place relative photoionization spectra of HO2, H2O2, and H2CO on an absolute scale, resulting in absolute photoionization spectra.

  7. Direct Coupling of Thermo- and Photocatalysis for Conversion of CO2 -H2 O into Fuels.

    Zhang, Li; Kong, Guoguo; Meng, Yaping; Tian, Jinshu; Zhang, Lijie; Wan, Shaolong; Lin, Jingdong; Wang, Yong

    2017-12-08

    Photocatalytic CO 2 reduction into renewable hydrocarbon solar fuels is considered as a promising strategy to simultaneously address global energy and environmental issues. This study focused on the direct coupling of photocatalytic water splitting and thermocatalytic hydrogenation of CO 2 in the conversion of CO 2 -H 2 O into fuels. Specifically, it was found that direct coupling of thermo- and photocatalysis over Au-Ru/TiO 2 leads to activity 15 times higher (T=358 K; ca. 99 % CH 4 selectivity) in the conversion of CO 2 -H 2 O into fuels than that of photocatalytic water splitting. This is ascribed to the promoting effect of thermocatalytic hydrogenation of CO 2 by hydrogen atoms generated in situ by photocatalytic water splitting. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Synthesis and crystal structure of trans-[Ni(pyzdcH)M 2 (H 2 O) 2 ...

    The determined structure of the title compound C24H20Ni2N8O20 consists of the mononuclear trans-[Ni(pyzdc)2(H2O)2], (pyzdc = pyrazine-2,3- dicarboxylate). The Ni(II) atom is hexa-coordinated by two (pyzdcH)- groups and two water molecules. The coordinated water molecules are in trans-diaxial positions and the ...

  9. Magnetic excitations in (VO)HPO4· 1/2 H2O

    Garrett, A.W.; Nagler, S.E.; Tennant, D.A.

    1997-01-01

    The magnetic excitations of an antiferromagnetic spin dimer system, (VO)HPO 4 · 1/2 H 2 O, are examined using inelastic neutron scattering. A dispersionless mode is found, consistent with expectations for a dimer excitation. The intensity variation of the mode reveals a V 4+ - V 4+ dimer separation of 4.43 angstrom, almost 50% larger than the originally expected length

  10. Free radical behaviours during methylene blue degradation in the Fe2+/H2O2 system.

    Wang, Zhonghua; Zhao, Haiqian; Qi, Hanbing; Liu, Xiaoyan; Liu, Yang

    2017-12-22

    Behaviours of the free radicals during the methylene blue (MB) oxidation process in the Fe 2+ /H 2 O 2 system were studied to reveal the reason for the low utilization efficiency of H 2 O 2 . The roles of [Formula: see text], [Formula: see text] and [Formula: see text] radicals were proven to be different in the MB oxidation process. The results showed that [Formula: see text] radicals had a strong ability to oxidize MB; however, they were not the main active substances for MB degradation due to the low concentration in the traditional Fe 2+ /H 2 O 2 system. [Formula: see text] radicals could not oxidize MB. [Formula: see text] radicals were the main active substances for MB oxidation. In the short initial stage, the utilization efficiency of H 2 O 2 was high, because the generation rate of [Formula: see text] was much higher than that of [Formula: see text]. More [Formula: see text] radicals were involved in the MB oxidation reaction. In the long deceleration stage (after the short initial stage), a large amount of H 2 O 2 was consumed, but the amount of oxidized MB was very small. Most of the [Formula: see text] radicals were consumed via the rapid useless reaction between [Formula: see text] and [Formula: see text] in this stage, resulting in the serious useless consumption of H 2 O 2 . It is a feasible method to improve the utilization efficiency of H 2 O 2 by adding suitable additives into the Fe 2+ /H 2 O 2 system to weaken the useless reaction between [Formula: see text] and [Formula: see text].

  11. Dehydration of MoO 3 · 2H 2O: A Neutron Thermodiffractometry Study

    Boudjada, N.; Rodríguez-Carvajal, J.; Anne, M.; Figlarz, M.

    1993-07-01

    A neutron powder thermodiffractometric study of the dehydration reactions MoO 3 · 2H 2O → MoO 3 · H 2O → MoO 3 has been carried out in order to investigate the topotactic mechanism previously reported. The topotactic character of the reactions is confirmed and an approximate model for the crystal structure of MoO 3 · H 2O is proposed. Quantitative data about the relative amount of the existing phases, as a function of temperature, have been deduced from multiphase profile analysis. The anomalous behavior of the cell parameters of MoO 3 · H 2O, at about 100°C, indicates the existence of a new phase transition. The evolution of the crystallite size of MoO 3 has also been obtained from the broadening of Bragg reflections at high temperature. The preferred direction of growth is along [021].

  12. Viscosity of HI-I2-H2O solution at atmospheric pressure

    Chen, Songzhe; Zhang, Ping; Wang, Laijun; Xu, Jingming; Gao, Mengxue

    2014-01-01

    Iodine-Sulfur thermochemical cycle (IS-cycle) is one of the most promising massive hydrogen production methods. Basic properties data of the HI-I 2 -H 2 O solution involved in the HI decomposition section of IS-cycle are found to be very important. HI, I 2 , and H 2 O make up a highly non-ideal solution system. Viscosity and its variation with the composition/temperature are very essential for the flowsheet work and HI-H 2 O-I 2 solution’s fluid simulation, especially in the distillation and electro-electrodialysis processes. In this paper, viscosity values of HI-H 2 O-I 2 solutions were measured at atmospheric pressure and varying temperatures (from 20 to 125 ºC). As for the composition, the HI/H2O molar ratio of the samples ranged from 1:5.36 to 1:12.00, while the HI/I 2 molar ratio from 1.0 to 1.4.0. Both temperature and composition have dramatic influence on the viscosity. Increasing temperature or H 2 O/HI molar ratio will lead to the reduction of viscosity; while increasing of I 2 /HI molar ratio results in the increase of viscosity. It was also found that I 2 content has a larger and more complex influence on the viscosity of the HI-H 2 O-I 2 solution than H 2 O content does, especially at low temperature (<50 °C). (author)

  13. A model for radiolysis of water and aqueous solutions of H2, H2O2 and O2

    Ershov, B.G.; Gordeev, A.V.

    2008-01-01

    Kinetic model for the radiolysis of pure water describing the formation of H 2 , H 2 O 2 and O 2 and the radiation chemical transformations of aqueous solutions containing these compounds over a broad range of concentrations, pH, absorbed doses and dose rates is proposed and substantiated. The model includes a set of chemical reactions with optimized rate constants and the radiation chemical yields of radiolysis products. The model applicability to the description of the whole set of data on the radiation chemical transformations of water and aqueous solutions of H 2 , H 2 O 2 and O 2 is demonstrated

  14. Weak ferrimagnetism, compensation point and magnetization reversal in Ni(HCOO)2x2H2O

    Kageyama, H.; Khomskii, D.I.; Levitin, R.Z.; Vasiliev, A.N.

    2003-01-01

    Nickel (II) format dihydrate Ni(HCOO) 2 x2H 2 O shows peculiar magnetic response at T N =15.5 K. The magnitude of weak magnetic moment increases initially below T N , equals zero at T*=8.5 K and increases again at lowering temperature. The sign of low field magnetization at any given temperature is determined by the sample's magnetic prehistory and the signs are opposite to each other at T N . This behavior suggests that Ni(HCOO) 2 x2H 2 O is a weak ferrimagnet and T* is a compensation point

  15. On the optimal design of forward osmosis desalination systems with NH3-CO2-H2O solutions

    Gazzani, Matteo; Pérez-Calvo, José Francisco; Sutter, Daniel; Mazzotti, Marco

    2017-01-01

    Membrane-based forward osmosis, especially when NH3-CO2-H2O mixtures are adopted as draw solutions, is a promising new process for clean water production, including seawater desalination and wastewater treatment. In such a process, water is first removed from the feed (e.g. seawater) by exploiting

  16. Adsorbed Layers of D2, H2, O2, and 3He on Graphite Studied by Neutron Scattering

    Nielsen, Mourits; McTague, J. P.; Ellenson, W. D.

    1977-01-01

    The phase diagrams of adsorbed monolayers of D2, H2, O2, and 3He on graphite have been measured by neutron diffraction. H2 and D2-layers have a registered √3 structure at low coverages, and at monolayer completion they have a dense triangular structure, which is incommensurate with the substrate...

  17. Production of 34S-labeled gypsum (Ca34SO4.2H2O Produção de gesso (Ca34SO4.2H2O, marcado com 34S

    Alexssandra Luiza Rodrigues Molina Rossete

    2006-08-01

    Full Text Available Agricultural gypsum (CaSO4.2H2O stands out as an effective source of calcium and sulfur, and to control aluminum saturation in the soil. Labeled as 34S it can elucidate important aspects of the sulfur cycle. Ca34SO4.2H2O was obtained by chemical reaction between Ca(OH2 and H2(34SO4, performed under slow agitation. The acid was produced by ion exchange chromatography using the Dowex 50WX8 cation exchange resin and a Na2(34SO4 eluting solution. After precipitation, the precipitate was separated and dried in a ventilated oven at 60ºC. From 2.2 L H2SO4 0.2 mol L-1 and 33.6 g Ca(OH2, 73.7 ± 0.6 g Ca34SO4.2H2O were produced on average in the tests, representing a mean yield of 94.6 ± 0.8%, with 98% purity. The 34SO2 gas was obtained from Ca34SO4.2H2O in the presence of NaPO3 in a high vacuum line and was used for the isotopic determination of S in an ATLAS-MAT model CH-4 mass spectrometer.O gesso agrícola (CaSO4.2H2O destaca-se como fonte eficiente de cálcio e enxofre e na redução da saturação de alumínio no solo. O 34S como traçador isotópico pode elucidar aspectos importantes no ciclo do enxofre. Para tanto o Ca34SO4.2H2O foi obtido por reação química entre o Ca(OH2 e solução de H2(34SO4, realizada sob agitação lenta. O ácido foi produzido por cromatografia de troca iônica, utilizando resina catiônica Dowex 50WX8 e solução eluente de Na2(34SO4. Após a precipitação foi separado o precipitado e realizada a secagem em estufa ventilada à temperatura de 60ºC. Nos testes, a partir de 2,2 L de H2SO4 0,2 mol L-1 e 33,6 g de Ca(OH2, foram produzidos em média 73,7 ± 0,6 g de Ca34SO4.2H2O representando um rendimento médio de 94,6 ± 0,8%, com pureza de 98%. A partir do Ca34SO4.2H2O na presença de NaPO3, em linha de alto vácuo, obteve-se o gás 34SO2 utilizado para a determinação isotópica do S no espectrômetro de massas ATLAS-MAT modelo CH-4.

  18. One-dimensional ferromagnetic array compound [Co3(SBA)2(OH)2(H2O)2]n, (SBA = 4-sulfobenzoate)

    Honda, Zentaro; Nomoto, Naoyuki; Fujihara, Takashi; Hagiwara, Masayuki; Kida, Takanori; Sawada, Yuya; Fukuda, Takeshi; Kamata, Norihiko

    2018-06-01

    We report on the syntheses, crystal structure, and magnetic properties of the transition metal coordination polymer [Co3(SBA)2(OH)2(H2O)2]n, (SBA = 4-sulfobenzoate) in which CoO6 octahedra are linked through their edges, forming one-dimensional (1D) Co(II) arrays running along the crystal a-axis. These arrays are further perpendicularly bridged by SBA ligand to construct a three-dimensional framework. Its magnetic properties have been investigated, and ferromagnetic interactions within the arrays have been found. From heat capacity measurements, we have found that this compound exhibits a three-dimensional ferromagnetic phase transition at TC = 1.54 K, and the specific heat just above TC shows a Schottky anomaly which originates from an energy gap caused by uniaxial magnetic anisotropy. These results suggest that [Co3(SBA)2(OH)2(H2O)2]n consists of weakly coupled 1D ferromagnetic Ising arrays.

  19. Measuring gluconeogenesis using a low dose of 2H2O: advantage of isotope fractionation during gas chromatography.

    Katanik, Jill; McCabe, Brendan J; Brunengraber, Daniel Z; Chandramouli, Visvanathan; Nishiyama, Fumie J; Anderson, Vernon E; Previs, Stephen F

    2003-05-01

    The contribution of gluconeogenesis to glucose production can be measured by enriching body water with (2)H(2)O to approximately 0.5% (2)H and determining the ratio of (2)H that is bound to carbon-5 vs. carbon-2 of blood glucose. This labeling ratio can be measured using gas chromatography-mass spectrometry after the corresponding glucose carbons are converted to formaldehyde and then to hexamethylenetetramine (HMT). We present a technique for integrating ion chromatograms that allows one to use only 0.05% (2)H in body water (i.e., 10 times less than the current dose). This technique takes advantage of the difference in gas chromatographic retention times of naturally labeled HMT and [(2)H]HMT. We discuss the advantage(s) of using a low dose of (2)H(2)O to quantify the contribution of gluconeogenesis.

  20. A Critical Review of Models of the H-2/H2O/Ni/SZ Electrode Kinetics

    Mogensen, Mogens Bjerg; Høgh, Jens Valdemar Thorvald; Hansen, Karin Vels

    2007-01-01

    Various models of the H-2/H2O/Ni/SZ (SZ = stabilized zirconia) electrode kinetics have been presented in the literature in order to explain the reported experimental data. However, there has been a strong tendency of using a limited set of data to "verify" a given model, disregarding other data...... sets, which do not fit the model. We have inspected some models in the literature, and problems (e.g. no quantitative model has explained the large variation in reported values of apparent activation energy of the electrode kinetics) as well as strengths of the models are discussed. We point out...... important for any realistic and useful mathematical model of the H-2/H2O/Ni/SZ electrode....

  1. System of Sr(NO2)2-Sr(OH)2-H2O at 25 deg C

    Popova, T.B.; Berdyukova, V.A.; Khutsistova, F.M.

    1990-01-01

    Sr(NO 2 ) 2 -Sr(OH) 2 -H 2 O system was investigated by the methods of solubility, density, viscosity, electric conductivity and refractometry. It was established that its compoments form the compound 4Sr(NO 2 ) 2 xSr(OH) 2 x8H 2 O. The compound was separated from solution; its density, decomposition temperature were determined; IR spectra and X-ray patterns of prepared and initial compounds were obtained

  2. Photo-Induced Spin State Switching In [Fe(bpp)2](NCS)2·2H2O

    Bhattacharjee, Ashis; Goodwin, Harry A.; Guetlich, Philipp

    2010-01-01

    We present the results of our investigation into the effect of irradiation of green light on the high spin low spin transition behavior of the mononuclear iron(II) compound [Fe(bpp) 2 ](NCS) 2 ·2H 2 O explored with the help of magnetic as well as Moessbauer spectroscopic studies. It has been found that the compound exhibits molecular bistability under irradiation of light due to LIESST effect.

  3. The vibration-rotation-tunneling levels of N2-H2O and N2-D2O

    Wang, Xiao-Gang; Carrington, Tucker

    2015-07-01

    In this paper, we report vibration-rotation-tunneling levels of the van der Waals clusters N2-H2O and N2-D2O computed from an ab initio potential energy surface. The only dynamical approximation is that the monomers are rigid. We use a symmetry adapted Lanczos algorithm and an uncoupled product basis set. The pattern of the cluster's levels is complicated by splittings caused by H-H exchange tunneling (larger splitting) and N-N exchange tunneling (smaller splitting). An interesting result that emerges from our calculation is that whereas in N2-H2O, the symmetric H-H tunnelling state is below the anti-symmetric H-H tunnelling state for both K = 0 and K = 1, the order is reversed in N2-D2O for K = 1. The only experimental splitting measurements are the D-D exchange tunneling splittings reported by Zhu et al. [J. Chem. Phys. 139, 214309 (2013)] for N2-D2O in the v2 = 1 region of D2O. Due to the inverted order of the split levels, they measure the sum of the K = 0 and K = 1 tunneling splittings, which is in excellent agreement with our calculated result. Other splittings we predict, in particular those of N2-H2O, may guide future experiments.

  4. CO2/H2O adsorption equilibrium and rates on metal-organic frameworks: HKUST-1 and Ni/DOBDC.

    Liu, Jian; Wang, Yu; Benin, Annabelle I; Jakubczak, Paulina; Willis, Richard R; LeVan, M Douglas

    2010-09-07

    Metal-organic frameworks (MOFs) have recently attracted intense research interest because of their permanent porous structures, huge surface areas, and potential applications as novel adsorbents and catalysts. In order to provide a basis for consideration of MOFs for removal of carbon dioxide from gases containing water vapor, such as flue gas, we have studied adsorption equilibrium of CO(2), H(2)O vapor, and their mixtures and also rates of CO(2) adsorption in two MOFs: HKUST-1 (CuBTC) and Ni/DOBDC (CPO-27-Ni or Ni/MOF-74). The MOFs were synthesized via solvothermal methods, and the as-synthesized products were solvent exchanged and regenerated before experiments. Pure component adsorption equilibria and CO(2)/H(2)O binary adsorption equilibria were studied using a volumetric system. The effects of H(2)O adsorption on CO(2) adsorption for both MOF samples were determined, and the results for 5A and NaX zeolites were included for comparison. The hydrothermal stabilities for the two MOFs over the course of repetitive measurements of H(2)O and CO(2)/H(2)O mixture equilibria were also studied. CO(2) adsorption rates from helium for the MOF samples were investigated by using a unique concentration-swing frequency response (CSFR) system. Mass transfer into the MOFs is rapid with the controlling resistance found to be macropore diffusion, and rate parameters were established for the mechanism.

  5. Degradation of Pentachlorophenol in Aqueous Solution by the UV/ZrO 2 /H 2 O 2 Photocatalytic Process

    Mohammad Reza Samarghandi

    2015-12-01

    Full Text Available Pentachlorophenol (PCP, which is one of the resistant phenolic compounds, has been classified in the category of EPA’s priority pollutants due to its high toxicity and carcinogenic potential. Therefore, its removal from water and wastewater is very important. Various methods have been studied for removing the compound, among which advanced oxidation processes (AOPs have attracted much attention because of ease of application and high efficiency. Thus the aim of this study was to investigate the efficiency of the UV/ZrO2/H2O2 process, as an AOP, for PCP removal from aquatic environments. The effects of several parameters such as ultraviolet (UV exposure time, initial PCP concentration, pH, concentration of zirconium dioxide (ZrO2 nanoparticles, and H2O2 concentration were studied. Kinetics of the reaction was also detected. The concentration of the stated materials in the samples was determined using a spectrophotometer at 500 nm. The results showed that the highest efficiency (approximately 100% was reached at optimized conditions of pH 6, contact time of 30 minutes, initial PCP concentration of 20 mg/L, the nanoparticles concentration of 0.1 g/L and H2O2 concentration of 14.7 mM/L. Also, the process followed the first order kinetics reaction. The obtained results illustrated that the UV/ZrO2/H2O2 process has a high ability in removing PCP.

  6. Weather resistance of CaSO4 ṡ 1/2H2O-based sand-fixation material

    Liu, Xin; Tie, Shengnian

    2017-07-01

    Searching for an economical and effective sand-fixing material and technology is of great importance in Northwest China. This paper described the use of a semihydrated gypsum-(CaSO4 ṡ 1/2H2O-)based composite as a sand-fixing material. Its morphology and composition were characterized by SEM, and its water resistance, freezing-thawing resistance and wind erosion resistance were tested in the field. The results indicated that semihydrated gypsum-(CaSO4 ṡ 1/2H2O-)based sand-fixing composite has good water resistance and water-holding capacity. Its strength is maintained at 1.42 MPa after 50 freezing and thawing cycles, and its wind erosion increases with increasing wind speed and slope. Its compressive strength starts to decrease after nine months of field tests with no change in appearance, but it still satisfies the requirements of fixation technology. This sand-fixing material should have wide application owing to its good weather resistance.

  7. SYSTEMATIC VARIATIONS IN CO2/H2O ICE ABUNDANCE RATIOS IN NEARBY GALAXIES FOUND WITH AKARI NEAR-INFRARED SPECTROSCOPY

    Yamagishi, M.; Kaneda, H.; Ishihara, D.; Oyabu, S.; Onaka, T.; Shimonishi, T.; Suzuki, T.

    2015-01-01

    We report CO 2 /H 2 O ice abundance ratios in seven nearby star-forming galaxies based on the AKARI near-infrared (2.5–5.0 μm) spectra. The CO 2 /H 2 O ice abundance ratios show clear variations between 0.05 and 0.2 with the averaged value of 0.14 ± 0.01. The previous study on M82 revealed that the CO 2 /H 2 O ice abundance ratios strongly correlate with the intensity ratios of the hydrogen recombination Brα line to the polycyclic aromatic hydrocarbon (PAH) 3.3 μm feature. In the present study, however, we find no correlation for the seven galaxies as a whole due to systematic differences in the relation between CO 2 /H 2 O ice abundance and Brα/PAH 3.3 μm intensity ratios from galaxy to galaxy. This result suggests that there is another parameter that determines the CO 2 /H 2 O ice abundance ratios in a galaxy in addition to the Brα/PAH 3.3 μm ratios. We find that the CO 2 /H 2 O ice abundance ratios positively correlate with the specific star formation rates of the galaxies. From these results, we conclude that CO 2 /H 2 O ice abundance ratios tend to be high in young star-forming galaxies

  8. Two-component, ab initio potential energy surface for CO2-H2O, extension to the hydrate clathrate, CO2@(H2O)20, and VSCF/VCI vibrational analyses of both.

    Wang, Qingfeng Kee; Bowman, Joel M

    2017-10-28

    We report an ab initio, full-dimensional, potential energy surface (PES) for CO 2 -H 2 O, in which two-body interaction energies are fit using a basis of permutationally invariant polynomials and combined with accurate potentials for the non-interacting monomers. This approach which we have termed "plug and play" is extended here to improve the precision of the 2-body fit in the long range. This is done by combining two separate fits. One is a fit to 47 593 2-body energies in the region of strong interaction and approaching the long range, and the second one is a fit to 6244 2-body energies in the long range. The two fits have a region of overlap which permits a smooth switch from one to the other. All energies are obtained at the CCSD(T)-F12b/aug-cc-pVTZ level of theory. Properties of the full PES, i.e., stationary points, harmonic frequencies of the global minimum, etc., are shown to be in excellent agreement with direct CCSD(T)-F12b/aug-cc-pVTZ results. Diffusion Monte Carlo calculations of the dimer zero-point energy (ZPE) are performed, and a dissociation energy, D 0 , of 787 cm -1 is obtained using that ZPE, D e , and the rigorous ZPEs of the monomers. Using a benchmark D e , D 0 is 758 cm -1 . Vibrational self-consistent field (VSCF)/virtual state configuration interaction (VCI) MULTIMODE calculations of intramolecular fundamentals are reported and are in good agreement with available experimental results. Finally, the full dimer PES is combined with an existing ab initio water potential to develop a potential for the CO 2 hydrate clathrate CO 2 (H 2 O) 20 (5 12 water cage). A full normal-mode analysis of this hydrate clathrate is reported as are local-monomer VSCF/VCI calculations of the fundamentals of CO 2 .

  9. Application of UV/TiO2/H2O2 Advanced Oxidation to Remove Naphthalene from Water

    Behroz Karimi

    2016-11-01

    Full Text Available Naphthalene is released into the environment by burning such organic materials as fossil fuels and wood and in industrial and vehicle exhaust emissions. Naphthalene is used in the manufacture of plastics, resins, fuels, and dyes. The aim of this study was to evaluate the performance of UV/TiO2/H2O2 process to decompose naphthalene in aqueous solutions. For this purpose, the photocatalytic degradation of naphthalene was investigated under UV light irradiation in the presence of TiO2 and H2O2 under a variety of conditions. Photodegradation efficiencies of H2O2/UV, TiO2/UV, and H2O2/TiO2/UV processes were compared in a batch reactor using the low pressure mercury lamp irradiation. The effects of operating parameters such as reaction time (min; solution pH; and initial naphthalene, TiO2, and H2O2 concentrations on photodegradation were examined. In the UV/TiO2/H2O2 system with a naphthalene concentration of 15 mg/L, naphthalene removal efficiencies of 63, 75, 80, 88, 92, 95, 96.5, and 98% were achieved, respectively, for reaction times of 5, 10, 20, 30, 40, 50, 60, 100 and 120 min. This is while removal efficienciesof 50, 59.5, 69, 80, 85, 88, 91, and 95% were obtained in the UV/TiO2 system under the same conditions. For initial pH values of 3, 4, 5, 6, 7,9, 10, and 12, naphthalene removal efficiencies of approximately 96.8, 85.5, 86, 75.5, 68.8, 57.8, and 52.5% were acheived, respectively, with the UV/TiO2/H2O2 system. Thus, it may be claiomed that, compared to either H2O2/UV or TiO2/UV process, the H2O2/TiO2/UV process yielded a far more efficient photodegradation.

  10. Determination of muscle protein synthesis rates in fish using (2)H2O and (2)H NMR analysis of alanine.

    Marques, Cátia; Viegas, Filipa; Rito, João; Jones, John; Viegas, Ivan

    2016-09-15

    Following administration of deuterated water ((2)H2O), the fractional synthetic rate (FSR) of a given endogenous protein can be estimated by (2)H-enrichment quantification of its alanine residues. Currently, this is measured by mass spectrometry following a derivatization procedure. Muscle FSR was measured by (1)H/(2)H NMR analysis of alanine from seabass kept for 6 days in 5% (2)H-enriched saltwater, following acid hydrolysis and amino acid isolation by cation-exchange chromatography of muscle tissue. The analysis is simple and robust, and provides precise measurements of excess alanine (2)H-enrichment in the 0.1-0.4% range from 50 mmol of alanine recovered from muscle protein. Copyright © 2016 Elsevier Inc. All rights reserved.

  11. Hydrothermal synthesis and crystal structures of new uranyl oxalate hydroxides: α- and β-[(UO2)2(C2O4)(OH)2(H2O)2] and [(UO2)2(C2O4)(OH)2(H2O)2].H2O

    Duvieubourg, Laurence; Nowogrocki, Guy; Abraham, Francis; Grandjean, Stephane

    2005-01-01

    Two modifications of the new uranyl oxalate hydroxide dihydrate [UO 2 ) 2 (C 2 O 4 )(OH) 2 (H 2 O) 2 ] (1 and 2) and one form of the new uranyl oxalate hydroxide trihydrate [(UO 2 ) 2 (C 2 O 4 )(OH) 2 (H 2 O) 2 ].H 2 O (3) were synthesized by hydrothermal methods and their structures determined from single-crystal X-ray diffraction data. The crystal structures were refined by full-matrix least-squares methods to agreement indices R(wR)=0.0372(0.0842) and 0.0267(0.0671) calculated for 1096 and 1167 unique observed reflections (I>2σ(I)), for α (1) and β (2) forms, respectively and to R(wR)=0.0301(0.0737) calculated for 2471 unique observed reflections (I>2σ(I)), for 3. The α-form of the dihydrate is triclinic, space group P1-bar , Z=1, a=6.097(2), b=5.548(2), c=7.806(3)A, α=89.353(5), β=94.387(5), γ=97.646(5) o , V=260.88(15)A 3 , β-form is monoclinic, space group C2/c, Z=4, a=12.180(3), b=8.223(2), c=10.777(3)A, β=95.817(4), V=1073.8(5)A 3 . The trihydrate is monoclinic, space group P2 1 /c, Z=4, a=5.5095(12), b=15.195(3), c=13.398(3)A, β=93.927(3), V=1119.0(4)A 3 . In the three structures, the coordination of uranium atom is a pentagonal bipyramid composed of dioxo UO 2 2+ cation perpendicular to five equatorial oxygen atoms belonging to one bidentate oxalate ion, one water molecule and two hydroxyl ions in trans configuration in 2 and in cis configuration in 1 and 3. The UO 7 polyhedra are linked through hydroxyl oxygen atoms to form different structural building units, dimers [U 2 O 10 ] obtained by edge-sharing in 1, chains [UO 6 ] ∼ and tetramers [U 4 O 26 ] built by corner-sharing in 2 and 3, respectively. These units are further connected by oxalate entities that act as bis-bidentate to form one-dimensional chains in 1 and bi-dimensional network in 2 and 3. These chains or layers are connected in frameworks by hydrogen-bond arrays

  12. Compound effect of CaCO3 and CaSO4·2H2O on the strength of steel slag: cement binding materials

    Qi, Liqian; Liu, Jiaxiang; Liu, Qian

    2016-01-01

    In this study, we replaced 30% of the cement with steel slag to prepare binding material; additionally, small amounts of CaCO 3 and CaSO 4 ·2H 2 O were added. This was done to study the compound effect of CaCO 3 and CaSO 4 ·2H 2 O on the strength of steel slag-cement binding materials. The hydration degree of the steel slag cementitious material was analyzed by XRD, TG and SEM. The results showed that the optimum proportions of CaCO 3 and CaSO 4 ·2H 2 O were 3% and 2%, respectively. Compared with the steel slag-cement binders without adding CaCO 3 and CaSO 4 ·2H 2 O, the compressive strength increased by 59.9% at 3 days and by 17.8% at 28 days. Acting as the nucleation matrix, CaCO 3 could accelerate the hydration of C 3 S. In addition, CaCO 3 was involved in the hydration reaction, generating a new hydration product, which could stably exist in a slurry. Meanwhile, CaSO 4 ·2H 2 O could increase the number of AFt. The compound effect of CaCO 3 and CaSO 4 ·2H 2 O enhanced the intensity of steel slag-cement binding materials and improved the whole hydration behavior. (author)

  13. Synthesis of Nanoscale CaO-Al2O3-SiO2-H2O and Na2O-Al2O3-SiO2-H2O Using the Hydrothermal Method and Their Characterization

    Jingbin Yang

    2017-06-01

    Full Text Available C-A-S-H (CaO-Al2O3-SiO2-H2O and N-A-S-H (Na2O-Al2O3-SiO2-H2O have a wide range of chemical compositions and structures and are difficult to separate from alkali-activated materials. Therefore, it is difficult to analyze their microscopic properties directly. This paper reports research on the synthesis of C-A-S-H and N-A-S-H particles with an average particle size smaller than 300 nm by applying the hydrothermal method. The composition and microstructure of the products with different CaO(Na2O/SiO2 ratios and curing conditions were characterized using XRD, the RIR method, FTIR, SEM, TEM, and laser particle size analysis. The results showed that the C-A-S-H system products with a low CaO/SiO2 ratio were mainly amorphous C-A-S-H gels. With an increase in the CaO/SiO2 ratio, an excess of Ca(OH2 was observed at room temperature, while in a high-temperature reaction system, katoite, C4AcH11, and other crystallized products were observed. The katoite content was related to the curing temperature and the content of Ca(OH2 and it tended to form at a high-temperature and high-calcium environment, and an increase in the temperature renders the C-A-S-H gels more compact. The main products of the N-A-S-H system at room temperature were amorphous N-A-S-H gels and a small amount of sodalite. An increase in the curing temperature promoted the formation of the crystalline products faujasite and zeolite-P. The crystallization products consisted of only zeolite-P in the high-temperature N-A-S-H system and its content were stable above 70%. An increase in the Na2O/SiO2 ratio resulted in more non-bridging oxygen and the TO4 was more isolated in the N-A-S-H structure. The composition and microstructure of the C-A-S-H and N-A-S-H system products synthesized by the hydrothermal method were closely related to the ratio of the raw materials and the curing conditions. The results of this study increase our understanding of the hydration products of alkali

  14. Synthesis and vibrational spectra of cooper(II) and erbium(III) complexes with 2-diazo[2'-(oxymethyldiphenylphosphinyl)phenyl]-4-tert-butylphenol (HL) - [CuL2]·2H2O and Er(NO3)3·2HL·2H2O. Crystal structure of [CuL2]·2H2O

    Tsivadze, A.Yu.; Minacheva, L.Kh.; Ivanova, I.S.; Pyatova, E.N.; Sergienko, V.S.; Baulin, V.E.

    2008-01-01

    Paper describes synthesis of CuL 2 ·2H 2 O (I) complex cupric salt and of Er(NO 3 ) 3 ·2HL·2H 2 O (II) erbium nitrate complex (HL=2-diazo-[2'(oxymethyl-diphenyl-phosphinyl)phenyl]-4-tert-butylphenol). One interprets the fundamental frequencies within the IR-spectra of (I) and (II) compounds. One has performed X-ray diffraction analysis of I compound. The crystals are monoclinic ones, a=15.157(3), b=17.080(2), c=22.451(9) A, β=106.09(3) Deg, V=5584(3) A 3 , Z=4, C2/c sp.gr., R=0.0546 as to 1152 reflections with I>2σ(I). The copper atom coordination polyhedron (C 2 symmetry) may be described as a symmetrically-prolonged square bipyramid (4+2). Cu polyhedron central square is formed by substituted phenol oxygen atom and by one of diazo-group nitrogen atoms of either of two deprotonated ligands, namely: L - (Cu-N 1.969(6), Cu-O 1.899(5) A). The angles between lying opposite O and N atoms constitute 157.6 Deg, while the rest equatorial angles range within 90.6 Deg-95.9 Deg. The axial positions are occupied by O(2) and O(2A) anisole atoms (Cu-O 2.737(6) A, O(2)Cu(1)O(2A) angle constitutes 132.3 Deg). Within crystal I the complex molecules and the crystallization molecules of water are combined by by the hydrogen bond system. According to the IR-spectra data, within complex II in contrast to compound I erbium atom coordination by HL ligand involves oxygen phosphoryl atom [ru

  15. Theoretical studies on photoelectron and IR spectral properties of Br2.-(H2O)n clusters.

    Pathak, A K; Mukherjee, T; Maity, D K

    2007-07-28

    We report vertical detachment energy (VDE) and IR spectra of Br2.-.(H2O)n clusters (n=1-8) based on first principles electronic structure calculations. Cluster structures and IR spectra are calculated at Becke's half-and-half hybrid exchange-correlation functional (BHHLYP) with a triple split valence basis function, 6-311++G(d,p). VDE for the hydrated clusters is calculated based on second order Moller-Plesset perturbation (MP2) theory with the same set of basis function. On full geometry optimization, it is observed that conformers having interwater hydrogen bonding among solvent water molecules are more stable than the structures having double or single hydrogen bonded structures between the anionic solute, Br2.-, and solvent water molecules. Moreover, a conformer having cyclic interwater hydrogen bonded network is predicted to be more stable for each size hydrated cluster. It is also noticed that up to four solvent H2O units can reside around the solute in a cyclic interwater hydrogen bonded network. The excess electron in these hydrated clusters is localized over the solute atoms. Weighted average VDE is calculated for each size (n) cluster based on statistical population of the conformers at 150 K. A linear relationship is obtained for VDE versus (n+3)(-1/3) and bulk VDE of Br2.- aqueous solution is calculated as 10.01 eV at MP2 level of theory. BHHLYP density functional is seen to make a systematic overestimation in VDE values by approximately 0.5 eV compared to MP2 data in all the hydrated clusters. It is observed that hydration increases VDE of bromine dimer anion system by approximately 6.4 eV. Calculated IR spectra show that the formation of Br2.--water clusters induces large shifts from the normal O-H stretching bands of isolated water keeping bending modes rather insensitive. Hydrated clusters, Br2.-.(H2O)n, show characteristic sharp features of O-H stretching bands of water in the small size clusters.

  16. Ferroelastoelectric phase transition in (NH4)2CuCl4·2H2O single crystal

    Tylczyński, Zbigniew; Wiesner, Maciej

    2015-01-01

    The (NH 4 ) 2 CuCl 4 ·2H 2 O crystal exhibits anomalous thermal, piezoelectric, dielectric and elastic properties in the vicinity of the ferroelastoelectric phase transition at T C  = 200 K. Macroscopic order parameter is the h 36 component of the spontaneous piezoelectric tensor connecting polarisation P 3 and strain η 6 . The temperature change in h 36 component was proportional to (T C  − T) α , where α = 0.58 ± 0.05. Close to T C changes in dielectric permittivity were negligible. High value of ac conductivity in the high-temperature phase results from protons jumping between disordered ions NH 4 + and between molecules of crystallisation water. Only longitudinal ultrasonic waves exhibited an abrupt change upon the phase transition. The relaxation time of the order parameter was determined from anomalous changes in attenuation of the longitudinal waves. - Highlights: • Low-temperature phase shows higher-order ferroicity: ferroelastoelectricity. • Temperature change of spontaneous piezoelectricity was studied in the ordered phase. • Dispersion of complex dielectric constant was investigated in wide temperature range. • At high-temperature phase ac conductivity is caused by proton jumps. • Anomalies of ultrasonic waves at T C were analysed using phenomenological theory

  17. Equilibrium Measurements of the NH3-CO2-H2O System: Speciation Based on Raman Spectroscopy and Multivariate Modeling

    Maths Halstensen

    2017-01-01

    Full Text Available Liquid speciation is important for reliable process design and optimization of gas-liquid absorption process. Liquid-phase speciation methods are currently available, although they involve tedious and time-consuming laboratory work. Raman spectroscopy is well suited for in situ monitoring of aqueous chemical reactions. Here, we report on the development of a method for speciation of the CO2-NH3-H2O equilibrium using Raman spectroscopy and PLS-R modeling. The quantification methodology presented here offers a novel approach to provide rapid and reliable predictions of the carbon distribution of the CO2-NH3-H2O system, which may be used for process control and optimization. Validation of the reported speciation method which is based on independent, known, NH3-CO2-H2O solutions shows estimated prediction uncertainties for carbonate, bicarbonate, and carbamate of 6.45 mmol/kg H2O, 34.39 mmol/kg H2O, and 100.9 mmol/kg H2O, respectively.

  18. Behaviour of high purity UO2/H2O interfaces under helium beam irradiation in deaerated conditions

    Mendes, E.

    2005-11-01

    A question put within the framework of the nuclear fuel storage worn in geological site is what become to them in the presence of water. The aim of a fundamental program, of PRECCI project (ECA), is to highlight the behaviour of interfaces which can be used as models for the interfaces nuclear spent fuel/water if the fuel is uranium UO 2 dioxide. This doctorate is interested in the effect of the alpha activity which is the only one that exist in the spent fuel after long periods. The aim is to identify the mechanisms of alteration and of leaching of surfaces under alpha irradiation. A method is developed to irradiate UO 2 /H 2 O interfaces in deaerated conditions with the beam of He 2+ produced by a cyclotron. The He 2+ ions cross an UO 2 disc and emerge in water with an energy of 5 MeV. Leachings under irradiation are carried with a large range of particles flux. The post-irradiation characterization of the surface of the discs realised by micro-Raman spectroscopy allowed to identify the alteration layer. It is made up of studtite UO 2 (O 2 ),4H 2 O, and of schoepite UO 3 ,xH 2 O. The analysis of the solutions shows that the uranium release strongly increases. The electrochemical properties of the interfaces under irradiation strongly differ from those before irradiation. This work allows to propose that the radiolytic species seen by the interface are it during the heterogeneous phase of evolution of the traces and are species of short lives. Modeling show that the radiolytic radicals species can migrate toward the interface and react with the UO 2 surface. (author)

  19. Ordering of calcium and vacancies in calcium catapleiite CaZr[Si3O9] • 2H2O

    Aksenov, S. M.; Portnov, A. M.; Chukanov, N. V.; Rastsvetaeva, R. K.; Nelyubina, Yu. V.; Kononkova, N. N.; Akimenko, M. I.

    2016-01-01

    A sample of holotypic calcium catapleiite from the Burpala alkaline massif (Northern Baikal, Russia) is studied by single crystal X-ray analysis at 120 K and IR spectroscopy. The empirical formula of calcium catapleiite is Ca 0.97 Na 0.02 Zr 1.01 Si 3 O 9 • 2H 2 O (Z = 4). The X-ray diffraction study confirms the orthorhombic unit cell with the following parameters: a = 7.406(1), b = 12.687(1), and c = 10.112(1) Å; V = 950.1(2) Å 3 ; space group Pbnn. The crystal structure is refined in the anisotropic approximation of atomic displacement parameters using 1177 reflections with I > 2σ(I) to the final R = 2.91%. The structure of calcium catapleiite under study is based on the microporous heteropolyhedral framework formed by ZrO 6 octahedra and threemembered silicon–oxygen rings [Si 3 O 9 ]. It is on the whole analogous to the structures of the samples studied earlier, but differs from them by a high degree of ordering of calcium and vacancies at extraframework positions. The distribution of calcium over Ca1 and Ca2 positions in the calcium catapleiite structure leads to the formation of zigzag chains of the …Ca1–Zr–Ca1–Zr… and …Ca2–h–Ca2–□… types. Low occupancy of the Ca2 position and its alternation with the vacancy are prerequisites for potential Ca 2+ cationic conduction.

  20. Zoledronate complexes. III. Two zoledronate complexes with alkaline earth metals: [Mg(C(5)H(9)N(2)O(7)P(2))(2)(H(2)O)(2)] and [Ca(C(5)H(8)N(2)O(7)P(2))(H(2)O)](n).

    Freire, Eleonora; Vega, Daniel R; Baggio, Ricardo

    2010-06-01

    Diaquabis[dihydrogen 1-hydroxy-2-(imidazol-3-ium-1-yl)ethylidene-1,1-diphosphonato-kappa(2)O,O']magnesium(II), [Mg(C(5)H(9)N(2)O(7)P(2))(2)(H(2)O)(2)], consists of isolated dimeric units built up around an inversion centre and tightly interconnected by hydrogen bonding. The Mg(II) cation resides at the symmetry centre, surrounded in a rather regular octahedral geometry by two chelating zwitterionic zoledronate(1-) [or dihydrogen 1-hydroxy-2-(imidazol-3-ium-1-yl)ethylidene-1,1-diphosphonate] anions and two water molecules, in a pattern already found in a few reported isologues where the anion is bound to transition metals (Co, Zn and Ni). catena-Poly[[aquacalcium(II)]-mu(3)-[hydrogen 1-hydroxy-2-(imidazol-3-ium-1-yl)ethylidene-1,1-diphosphonato]-kappa(5)O:O,O':O',O''], [Ca(C(5)H(8)N(2)O(7)P(2))(H(2)O)](n), consists instead of a Ca(II) cation in a general position, a zwitterionic zoledronate(2-) anion and a coordinated water molecule. The geometry around the Ca(II) atom, provided by six bisphosphonate O atoms and one water ligand, is that of a pentagonal bipyramid with the Ca(II) atom displaced by 0.19 A out of the equatorial plane. These Ca(II) coordination polyhedra are ;threaded' by the 2(1) axis so that successive polyhedra share edges of their pentagonal basal planes. This results in a strongly coupled rhomboidal Ca(2)-O(2) chain which runs along [010]. These chains are in turn linked by an apical O atom from a -PO(3) group in a neighbouring chain. This O-atom, shared between chains, generates strong covalently bonded planar arrays parallel to (100). Finally, these sheets are linked by hydrogen bonds into a three-dimensional structure. Owing to the extreme affinity of zoledronic acid for bone tissue, in general, and with calcium as one of the major constituents of bone, it is expected that this structure will be useful in modelling some of the biologically interesting processes in which the drug takes part.

  1. Molecular beam scattering experiments with polar molecules. 1. Differential elastic scattering of H2+NH3 and H2+H2O

    Bickes, R.W. Jr.; Scoles, G.; Smith, K.M.

    1974-01-01

    Differential elastic scattering cross sections with well resolved quantum oscillations have been measuremed for the systems H 2 +NH 3 and H 2 +H 2 O. Assuming a spherically symmetric interaction the data show that a simple spherical potential (i.e. Lennard-Jones) does not properly describe the scattering

  2. Physical properties and the Peierls instability of Li0.82[Pt(S2C2(CN)2)2] · 2H2O

    Ahmad, M. M.; Turner, D. J.; Underhill, A. E.

    1984-01-01

    The infrared reflectivity, the temperature-dependent conductivity, and thermopower of the one-dimensional conductor Li0.82[Pt(S2C2(CN)2)2] · 2H2O, LiPt(mnt), is presented. It undergoes a simple Peierls transition at Tc=215 K, which is not influenced by correlations or by cation ordering. The meta...

  3. An efficient solvent-free synthesis of meso-substituted dipyrromethanes using SnCl2•2H2O catalysis

    Kabeer Ahmed Shaikh

    2012-07-01

    Full Text Available Highly rapid and simple methodology has been developed for the quantitative synthesis of meso-substituted dipyrromethanes from lowest pyrrole/aldehyde ratio. The method was carried out by using SnCl2•2H2O as a catalyst under solvent free condition. The method is environmentally friendly, easy to workup, and gives excellent yield of the products.

  4. LiOH - H2O2 - H2O trinary system study for the selection of optimal conditions of lithium peroxide synthesis

    Nefedov, R A; Ferapontov, Yu A; Kozlova, N P

    2016-01-01

    Using solubility method the decay kinetics of peroxide products contained in liquid phase of LiOH - H 2 O 2 - H 2 O trinary system with 2 to 6% by wt hydrogen peroxide content in liquid phase in 21 to 33 °C temperature range has been studied. Conducted studies have allowed to determine temperature and concentration limits of solid phase existence of Li 2 O 2 ·H 2 O content, distinctness of which has been confirmed using chemical and qualitative X- ray phase analysis. Stabilizing effect of solid phase of Li 2 O 2 ·H 2 O content on hydrogen peroxide decay contained in liquid phase of LiOH - H 2 O 2 - H 2 O trinary system under conditions of experiments conducted has been shown. (paper)

  5. LiOH - H2O2 - H2O trinary system study for the selection of optimal conditions of lithium peroxide synthesis

    Nefedov, R. A.; Ferapontov, Yu A.; Kozlova, N. P.

    2016-01-01

    Using solubility method the decay kinetics of peroxide products contained in liquid phase of LiOH - H2O2 - H2O trinary system with 2 to 6% by wt hydrogen peroxide content in liquid phase in 21 to 33 °C temperature range has been studied. Conducted studies have allowed to determine temperature and concentration limits of solid phase existence of Li2O2·H2O content, distinctness of which has been confirmed using chemical and qualitative X- ray phase analysis. Stabilizing effect of solid phase of Li2O2·H2O content on hydrogen peroxide decay contained in liquid phase of LiOH - H2O2 - H2O trinary system under conditions of experiments conducted has been shown.

  6. Hydrothermal crystallization in the KOH-TiO2-GeO2-H2O system at 500 deg C and 0.1 GPa

    Ilyushin, G.D.

    2003-01-01

    The identification of structural phases and crystallochemical analysis of phases in a KOH-TiO 2 -GeO 2 -H 2 O system under conditions of high temperatures and pressures are performed. A comparison is made with earlier obtained results for a system of KOH-GeO 2 (quartz-like structure)-H 2 O. It is established that K 2 Ti 6 O 13 skeleton potassium titanate is a basic phase in the system of KOH-TiO 2 -GeO 2 -H 2 O at 500 deg C and 0.1 GPa within a wide range of varying TiO 2 :GeO 2 and KOH concentrations [ru

  7. Improvement in surface hydrophilicity and resistance to deformation of natural leather through O2/H2O low-temperature plasma treatment

    You, Xuewei; Gou, Li; Tong, Xingye

    2016-01-01

    The natural leather was modified through O2/H2O low-temperature plasma treatment. Surface morphology was characterized by scanning electron microscopy (SEM) and the results showed that the pores on the leather surface became deeper and larger with enhanced permeability of water and vapor. XPS and FTIR-ATR was performed to determine the chemical composition of natural leather surface. Oxygen-containing groups were successfully grafted onto the surface of natural leather and oxygen content increased with longer treatment time. After O2/H2O plasma treatment, initial water contact angle was about 21° and water contact angles were not beyond 55° after being stored for 3 days. Furthermore, the tensile test indicated that the resistance to deformation had a prominent transform without sacrificing the tensile strength.

  8. Influence of chromium III ions on the electrical properties of NaNH4SO4.2H2O crystals

    Kassem, M.E.; El-Wahidy, E.F.; Hedewy, S.; Darwish, H.G.; Ramadan, T.

    1991-07-01

    The dielectric constant, ε, and electric conductivity, σ, of pure and Cr +3 doped samples of NaNH 4 SO 4 .2H 2 O are measured in the temperature range 20-300 K. The maximum value of dielectric constant in different crystallographic axes is presented and discussed. The effect of foreign ions on the critical behaviour and transition temperature T c is studied. (author). 18 refs, 2 figs, 1 tab

  9. Synthesis, solvatochromism and crystal structure of trans-[Cu(Et2NCH2CH2NH2)2.H2O](NO3)2 complex: Experimental with DFT combination

    Warad, Ismail; Musameh, Sharif; Badran, Ismail; Nassar, Nashaat N.; Brandao, Paula; Tavares, Carlos Jose; Barakat, Assem

    2017-11-01

    In this study, two dicationic asymmetrical diamine/copper(II) nitrate salt complexes of the general formula trans-[CuII(NN‧)2.H2O](NO3)2 were successfully synthesized using N,N-dimethylethylenediamine and N,N-diethylethylenediamine as asymmetrical diamine ligands. The structure of complex 2 was identified by X-ray single crystal diffraction analysis confirming that the bidentate ligand N,N-dimethylethylenediamine forms a penta-coordinated complex with an H2O molecule located around the copper(II) ion in a trans configuration. It was found that the metal centre is coordinated in a distorted square pyramidal fashion with a τ value of 0.274. The desired complexes were fully characterized using, MS, UV-Vis, CV, FTIR, TG/DTA, and Hirshfeld surface computational analysis. High level theoretical calculations were also performed in order to investigate the complexes structure, conformers, vibrational frequencies, and their excited states.

  10. Syntheses, characterization and nonlinear optical properties of sodium-scandium carbonate Na5Sc(CO3)4·2H2O

    Chen, Jie; Luo, Min; Ye, Ning

    2014-10-01

    A novel nonlinear optical (NLO) material Na5Sc(CO3)4·2H2O has been synthesized under a subcritical hydrothermal condition. The structure is determined by single-crystal X-ray diffraction and further characterized by TG analyses and UV-vis-NIR diffuse reflectance spectrum. It crystallizes in the tetragonal space group P-421c, with a = b = 7.4622(6) Å, C = 11.5928(15) Å. The Second-harmonic generation (SHG) on polycrystalline samples was measured using the Kurtz and Perry technique, which indicated that Na5Sc(CO3)4·2H2O was a phase-matchable material, and its measured SHG coefficient was about 1.8 times as large as that of d36 (KDP). The results from the UV-vis diffuse reflectance spectroscopy study of the powder samples indicated that the short-wavelength absorption edges of Na5Sc(CO3)4·2H2O is about 220 nm, suggesting that this crystal is a promising UV nonlinear optical (NLO) materials.

  11. Ionothermal Synthesis of a Novel 3D Cobalt Coordination Polymer with a Uniquely Reported Framework: [BMI]2[Co2(BTC2(H2O2

    Il-Ju Ko

    2017-01-01

    Full Text Available The framework of [RMI]2[Co2(BTC2(H2O2] (RMI = 1-alkyl-3-methylimidazolium, alkyl; ethyl (EMI; propyl (PMI; butyl (BMI, which has uniquely occurred in ionothermal reactions of metal salts and H3BTC (1,3,5-benzenetricarboxylic acid, an organic ligand, reappeared in this work. Ionothermal reaction of cobalt acetate and H3BTC with [BMI]Br ionic liquid as the reaction medium yielded the novel coordination polymer [BMI]2[Co2(BTC2(H2O2] (compound B2. Similar ionothermal reactions with different [EMI]Br and [PMI]Br as the reaction media have been previously reported to produce [EMI]2[Co3(BTC2(OAc2] (compound A1 and [PMI]2[Co2(BTC2(H2O2] (compound B1, respectively. In contrast with the trinuclear secondary building unit of A1, the framework structure of B1 and B2 consists of dinuclear secondary building units in common, but with subtle distinction posed by the different size of the incorporated cations. These structural differences amidst the frameworks showed interesting aspects, including guest and void volume, and were used to explain the chemical trend observed in the system. Moreover, the physicochemical properties of the newly synthesized compound have been briefly discussed.

  12. Availability of S from superphosphate and CaSO4.2H2O to alfafa (Medicago sativa L. Pers.) using tracer technique

    Aulakh, M.S.; Dev, G.

    1977-01-01

    The availability of S from superphosphate to alfalfa was evaluated and compared with CaSO 4 .2H 2 O (as the standard) in the greenhouse on a S deficient arid brown soil at 4 levels of applied S (0, 5, 10 and 20 ppm). A basal dose of N, P, K and Ca was made and the effect was studied for two growth stages (80 and 120 days). Sulphur application significantly increased the yield of dry matter, S content and total S removal in both the cuttings individually and for total harvest. In this effect, superphosphate was found to be more efficient. The radio-assay data confirmed that with graded levels of applied S, the fraction of fertilizer S in the plant increased without much off-setting S fraction from the native soil source, the effect being more with superphosphate treatment compared to CaSO 4 .2H 2 O. Phosphorus concentration in alfalfa decreased significantly with increasing level of applied S. The first cutting of alfalfa recorded higher P content in superphosphate series and in the second cutting, this difference between the two sources decreased. At optimum level of 20 ppm S, superphosphate was more effective than CaSO 4 .2H 2 O in narrowing N:S ratio to 11:1 and increasing S:P ratio to more than 1:1. (author)

  13. Improvement in surface hydrophilicity and resistance to deformation of natural leather through O_2/H_2O low-temperature plasma treatment

    You, Xuewei; Gou, Li; Tong, Xingye

    2016-01-01

    Graphical abstract: - Highlights: • O_2/H_2O can increase oxygen concentration in the plasma compared to the pure O_2 atmosphere. • Pores at the surface of natural leather became larger and deeper with enhanced permeability of water. • The initial water contact angle was about 21°. • Its preferable surface hydrophilicity kept for 3 days, which gives guidance for next process. • The elongation of the treated sample for 10 min was twice as large as that of the untreated sample. - Abstract: The natural leather was modified through O_2/H_2O low-temperature plasma treatment. Surface morphology was characterized by scanning electron microscopy (SEM) and the results showed that the pores on the leather surface became deeper and larger with enhanced permeability of water and vapor. XPS and FTIR-ATR was performed to determine the chemical composition of natural leather surface. Oxygen-containing groups were successfully grafted onto the surface of natural leather and oxygen content increased with longer treatment time. After O_2/H_2O plasma treatment, initial water contact angle was about 21° and water contact angles were not beyond 55° after being stored for 3 days. Furthermore, the tensile test indicated that the resistance to deformation had a prominent transform without sacrificing the tensile strength.

  14. (Solid + liquid) phase equilibria of (Ca(H2PO2)2 + CaCl2 + H2O) and (Ca(H2PO2)2 + NaH2PO2 + H2O) ternary systems at T = 323.15 K

    Cao, Hong-yu; Zhou, Huan; Bai, Xiao-qin; Ma, Ruo-xin; Tan, Li-na; Wang, Jun-min

    2016-01-01

    Graphical abstract: Solubility diagram of the (Ca(H 2 PO 2 ) 2 + NaH 2 PO 2 + H 2 O) system at T = (323.15 and 298.15) K. - Highlights: • Phase diagrams of Ca 2+ -H 2 PO 2 − -Cl − -H 2 O, Ca 2+ -Na + -H 2 PO 2 − -H 2 O at 323.15 K were obtained. • Incompatible double salt of NaCa(H 2 PO 2 ) 3 in Ca 2+ -Na + -H 2 PO 2 − -H 2 O system was determined. • Density diagram of the corresponding liquid were simultaneously measured. - Abstract: Calcium hypophosphite has been widely used as an anti-corrosive agent, flame retardant, fertilizer, assistant for Ni electroless plating, and animal nutritional supplement. High purity calcium hypophosphite can be synthesized via the replacement reaction of sodium hypophosphite and calcium chloride. In this work, the (solid + liquid) phase equilibria of (Ca(H 2 PO 2 ) 2 + CaCl 2 + H 2 O) and (Ca(H 2 PO 2 ) 2 + NaH 2 PO 2 + H 2 O) ternary systems at T = 323.15 K were studied experimentally via the classical isothermal solubility equilibrium method, and the phase diagrams for these two systems were obtained. It was found that two solid salts of CaCl 2 ·2H 2 O and Ca(H 2 PO 2 ) 2 exist in the (Ca(H 2 PO 2 ) 2 + CaCl 2 + H 2 O) system, and three salts of Ca(H 2 PO 2 ) 2 , NaH 2 PO 2 ·H 2 O and one incompatible double salt, NaCa(H 2 PO 2 ) 3 occur in the (Ca(H 2 PO 2 ) 2 + NaH 2 PO 2 + H 2 O) system.

  15. Hydrothermal synthesis and structural characterization of an organic–inorganic hybrid sandwich-type tungstoantimonate [Cu(en)2(H2O)]4[Cu(en)2(H2O)2][Cu2Na4(α-SbW9O33)2]·6H2O

    Liu, Yingjie; Cao, Jing; Wang, Yujie; Li, Yanzhou; Zhao, Junwei; Chen, Lijuan; Ma, Pengtao; Niu, Jingyang

    2014-01-01

    An organic–inorganic hybrid sandwich-type tungstoantimonate [Cu(en) 2 (H 2 O)] 4 [Cu(en) 2 (H 2 O) 2 ][Cu 2 Na 4 (α-SbW 9 O 33 ) 2 ]·6H 2 O (1) has been synthesized by reaction of Sb 2 O 3 , Na 2 WO 4 ·2H 2 O, CuCl 2 ·2H 2 O with en (en=ethanediamine) under hydrothermal conditions and structurally characterized by elemental analysis, inductively coupled plasma atomic emission spectrometry, IR spectrum and single-crystal X-ray diffraction. 1 displays a centric dimeric structure formed by two equivalent trivacant Keggin [α-SbW 9 O 33 ] 9− subunits sandwiching a hexagonal (Cu 2 Na 4 ) cluster. Moreover, those related hexagonal hexa-metal cluster sandwiched tungstoantimonates have been also summarized and compared. The variable-temperature magnetic measurements of 1 exhibit the weak ferromagnetic exchange interactions within the hexagonal (Cu 2 Na 4 ) cluster mediated by the oxygen bridges. - Graphical abstract: An organic–inorganic hybrid (Cu 2 Na 4 ) sandwiched tungstoantimonate [Cu(en) 2 (H 2 O)] 4 [Cu (en) 2 (H 2 O) 2 ][Cu 2 Na 4 (α-SbW 9 O 33 ) 2 ]·6H 2 O was synthesized and magnetic properties was investigated. Display Omitted - Highlights: • Organic–inorganic hybrid sandwich-type tungstoantimonate. • (Cu 2 Na 4 sandwiched) tungstoantimonate [Cu 2 Na 4 (α-SbW 9 O 33 ) 2 ] 10− . • Ferromagnetic tungstoantimonate

  16. The quantification of gluconeogenesis in healthy men by (2)H2O and [2-(13)C]glycerol yields different results: rates of gluconeogenesis in healthy men measured with (2)H2O are higher than those measured with [2-(13)C]glycerol

    Ackermans, M. T.; Pereira Arias, A. M.; Bisschop, P. H.; Endert, E.; Sauerwein, H. P.; Romijn, J. A.

    2001-01-01

    The quantification of gluconeogenesis (GNG) by (2)H2O and [2-(13)C]glycerol and the mass isotopomer dilution analysis of glucose does not involve assumptions regarding the enrichment of the oxaloacetate precursor pool. To compare these two methods we measured GNG in six healthy postabsorptive males

  17. A Cadmium Anionic 1-D Coordination Polymer {[Cd(H2O6][Cd2(atr2(μ2-btc2(H2O4] 2H2O}n within a 3-D Supramolecular Charge-Assisted Hydrogen-Bonded and π-Stacking Network

    Anas Tahli

    2016-03-01

    Full Text Available The hydrothermal reaction of 4,4′-bis(1,2,4-triazol-4-yl (btr and benzene-1,3,5-tricarboxylic acid (H3btc with Cd(OAc2·2H2O at 125 °C in situ forms 4-amino-1,2,4-triazole (atr from btr, which crystallizes to a mixed-ligand, poly-anionic chain of [Cd2(atr2(µ2-btc2(H2O4]2–. Together with a hexaaquacadmium(II cation and water molecules the anionic coordination-polymeric forms a 3-D supramolecular network of hexaaquacadmium(II-catena-[bis(4-amino-1,2,4-triazoletetraaquabis(benzene-1,3,5-tricarboxylatodicadmate(II] dihydrate, 1-D-{[Cd(H2O6][Cd2(atr2(µ2-btc2(H2O4] 2H2O}n which is based on hydrogen bonds (in part charge-assisted and π–π interactions.

  18. Experimental study of the vapour-liquid equilibria of HI-I-2-H2O ternary mixtures, Part 2: Experimental results at high temperature and pressure

    Larousse, B.; Lovera, P.; Borgard, J.M.; Roehrich, G.; Mokrani, N.; Maillault, C.; Doizi, D.; Dauvois, V.; Roujou, J.L.; Lorin, V.; Fauvet, P.; Carles, P.; Hartmann, J.M.

    2009-01-01

    In order to assess the choice of the sulphur-iodine thermochemical cycle for massive hydrogen production, a precise knowledge of the concentrations of the gaseous species (HI, I 2 , and H 2 O) in thermodynamic equilibrium with the liquid phase of the HI-I 2 -H 2 O ternary mixture is required, in a wide range of concentrations and for temperatures and pressures up to 300 degrees C and 50 bar. In the companion paper (Part 1) the experimental device was described, which enables the measurement of the total pressure and concentrations of the vapour phase (and thus the knowledge of the partial pressures of the different gaseous species) for the HI-I 2 -H 2 O mixture in the 20-140 degrees C range and up to 2 bar. This (Part 2) article describes the experimental device which enables similar measurements but now in the process domain. The results concerning concentrations in the vapour phase for the HI-I 2 -H 2 O initial mixture (with a global composition) in the 120-270 degrees C temperature range and up to 30 bar are presented. As previously, optical online diagnostics are used, based on recordings of infrared transmission spectra for HI and H 2 O and on UV/visible spectrometry for I 2 . The concentrations measured in the vapour phase are the first to describe the vapour composition under thermophysical conditions close to those of the distillation column. The experimental results are compared with a thermodynamic model and will help us to scale up and optimize the reactive distillation column we promote for the HI section of the sulphur-iodine cycle. (authors)

  19. Calculating Equilibrium Constants in the SnCl2-H2O-NaOH System According to Potentiometric Titration Data

    Maskaeva, L. N.; Fedorova, E. A.; Yusupov, R. A.; Markov, V. F.

    2018-05-01

    The potentiometric titration of tin chloride SnCl2 is performed in the concentration range of 0.00009-1.1 mol/L with a solution of sodium hydroxide NaOH. According to potentiometric titration data based on modeling equilibria in the SnCl2-H2O-NaOH system, basic equations are generated for the main processes, and instability constants are calculated for the resulting hydroxo complexes and equilibrium constants of low-soluble tin(II) compounds. The data will be of interest for specialists in the field of theory of solutions.

  20. Ab initio molecular dynamics simulations reveal localization and time evolution dynamics of an excess electron in heterogeneous CO2-H2O systems.

    Liu, Ping; Zhao, Jing; Liu, Jinxiang; Zhang, Meng; Bu, Yuxiang

    2014-01-28

    In view of the important implications of excess electrons (EEs) interacting with CO2-H2O clusters in many fields, using ab initio molecular dynamics simulation technique, we reveal the structures and dynamics of an EE associated with its localization and subsequent time evolution in heterogeneous CO2-H2O mixed media. Our results indicate that although hydration can increase the electron-binding ability of a CO2 molecule, it only plays an assisting role. Instead, it is the bending vibrations that play the major role in localizing the EE. Due to enhanced attraction of CO2, an EE can stably reside in the empty, low-lying π(*) orbital of a CO2 molecule via a localization process arising from its initial binding state. The localization is completed within a few tens of femtoseconds. After EE trapping, the ∠OCO angle of the core CO2 (-) oscillates in the range of 127°∼142°, with an oscillation period of about 48 fs. The corresponding vertical detachment energy of the EE is about 4.0 eV, which indicates extreme stability of such a CO2-bound solvated EE in [CO2(H2O)n](-) systems. Interestingly, hydration occurs not only on the O atoms of the core CO2 (-) through formation of O⋯H-O H-bond(s), but also on the C atom, through formation of a C⋯H-O H-bond. In the latter binding mode, the EE cloud exhibits considerable penetration to the solvent water molecules, and its IR characteristic peak is relatively red-shifted compared with the former. Hydration on the C site can increase the EE distribution at the C atom and thus reduce the C⋯H distance in the C⋯H-O H-bonds, and vice versa. The number of water molecules associated with the CO2 (-) anion in the first hydration shell is about 4∼7. No dimer-core (C2O4 (-)) and core-switching were observed in the double CO2 aqueous media. This work provides molecular dynamics insights into the localization and time evolution dynamics of an EE in heterogeneous CO2-H2O media.

  1. Reactivity of the biphasic trichloroacetonitrile-CH2Cl2/H2O2 system in the epoxidation of soybean oil

    Martinelli, Márcia

    2002-06-01

    Full Text Available In this work we report on the epoxidation of soybean oil by the trichloroacetonitrile -CH2Cl2/H2O2 byphasic system. The reaction was carried out at room temperature and, most importantly, in non acid conditions which prevent the opening of the oxirane ring. The epoxidized soybean oil was characterized by infrared, 1H and 13C NMR. A maximum conversion of 81 % was achieved in two hours with 86% of selectivity in epoxy groupsEn el presente trabajo informamos sobre la epoxidación de aceite de soja mediante el sistema bifásico tricloroacetonitrilo-CH2Cl2/H2O2. La reacción fue realizada bajo condiciones de temperatura ambiente y, lo más importante, en condición no ácida, lo que evita la apertura del anillo oxirano. El aceite de soja fue caracterizado por infrarrojo y RMN de 1H and 13C. En dos horas se alcanzó una conversión máxima del 81 % obteniéndose una selectividad del 86 % en grupos epóxidos

  2. Effect of coatings on long term behaviour of a commercial stainless steel for solid oxide electrolyser cell interconnect application in H2/H2O atmosphere

    Ardigo, M.R.; Popa, I.; Chevalier, S.; Girardon, P.; Perry, F.; Laucournet, R.; Brevet, A.; Desgranges, C.

    2014-01-01

    K41X (AISI 441) stainless steel evidenced a high electrical conductivity after 3000 h ageing in H 2 /H 2 O side when used as interconnect for solid oxide electrolyser cells (SOEC) working at 800 C. Perovskite (La 1-x Sr x MnO 3-δ ) and spinel (Co 3 O 4 ) oxides coatings were applied on the surface of the ferritic steel for ageing at 800 C for 3000 h. Both coatings improved the behaviour of the steel and give interesting opportunities to use the K41X steel as interconnect for hydrogen production via high temperature steam electrolysis. Co 3 O 4 reduced into Co leading to a very good Area Specific Resistance (ASR) parameter, 0.038 Ωcm 2 . Despite a good ASR (0.06 Ωcm 2 ), La 1-x Sr x MnO 3-δ was less promising because it partially decomposed into MnO and La 2 O 3 during ageing in H 2 /H 2 O atmosphere. (authors)

  3. Synthesis and Crystal Structure of an Unprecedented Supramolecular Complex[Co(μ2-ClO4)2(H2O)2]·2MA

    XU,Jing; BAI,Zhengshuai; SUN,Weiyin

    2009-01-01

    A new supramolecular framework[Co(μ2-C104)2(H2O)2]·2MA(1)[MA=melamine(C3H6N6)]has been syn-thesized by a hydrothermal method.Interestingly,there ale inorganic and organic building blocks with two different supramolecular synthons:(a)2D(4,4)network constructed by infinite inorganic 1D chains through interchain hy-drogen bonding interactions;(b)1D zigzag organic chains formed by hydrogen bonds, which further stack up through,ππ-interactions between the two adjacent MA molecules.The entire structure of 1 is a 3D supramolecular framework resulting from the presence of abundant hydrogen bonds between infinite[CO(μ2-C1O4)2(H2O)2]n chains and zigzag MA chains in different sheets.1 gives a nice example of supramolecular framework based on non-covalent interactions including hydrogen bonding and π-π interactions.

  4. Measurements and modeling of absorption by CO2 + H2O mixtures in the spectral region beyond the CO2 ν3-band head

    Tran, H.; Turbet, M.; Chelin, P.; Landsheere, X.

    2018-05-01

    In this work, we measured the absorption by CO2 + H2O mixtures from 2400 to 2600 cm-1 which corresponds to the spectral region beyond the ν3 band head of CO2. Transmission spectra of CO2 mixed with water vapor were recorded with a high-resolution Fourier-transform spectrometer for various pressure, temperature and concentration conditions. The continuum absorption by CO2 due to the presence of water vapor was determined by subtracting from measured spectra the contribution of local lines of both species, that of the continuum of pure CO2 as well as of the self- and CO2-continua of water vapor induced by the H2O-H2O and H2O-CO2 interactions. The obtained results are in very good agreement with the unique previous measurement (in a narrower spectral range). They confirm that the H2O-continuum of CO2 is significantly larger than that observed for pure CO2. This continuum thus must be taken into account in radiative transfer calculations for media involving CO2+ H2O mixture. An empirical model, using sub-Lorentzian line shapes based on some temperature-dependent correction factors χ is proposed which enables an accurate description of the experimental results.

  5. Investigation of the Na2(H2PO2)2 - Ba(H2PO2)2 - H2O Water-Salt Ternary System at Room Temperature

    Erge, Hasan; Turan, Hakan; Kul, Ali Riza

    2016-01-01

    Objective: In this study, the solubility, density, conductivity and phase equilibria of the Na2(H2PO2)2-Ba(H2PO2)2-H2O ternary system located in the structure of the Na+, Ba2+, (H2PO2)-//H2O quaternary reciprocal water-salt system were investigated using physicochemical analysis methods. Material and Methods: Riedel-de Haen and Merck salts were used to investigate the solubility and phase equilibria of the Na2(H2PO2)2 -Ba(H2PO2)2-H2O ternary water–salt system at room temperature Res...

  6. Theoretical studies of the optical and EPR spectra for VO^{2+} in Na_3C_6H_5O_7·2H_2O single crystal

    Ch.-Y. Li

    2015-06-01

    Full Text Available On the basis of the perturbation formulas for a d^1 configuration ion in a tetragonal crystal field, the three optical absorption bands and electron paramagnetic resonance (EPR parameters (g factors g_i and hyperfine structure constants A_i for i = || and ⊥, respectively of VO^{2+} in Na_3C_6H_5O_7·2H_2O (TSCD single crystals were studied using the perturbation theory method. By simulating the calculated optical and EPR spectra to the observed values, local structure parameters and negative signs of the hyperfine structure constants A_i of the octahedral (VO_6^{8-} cluster in TSCD single crystal can be obtained.

  7. Bunsen Reaction using a HIx Solution (HI-I2-H2O with Countercurrent Flow for Sulfur-Iodine Hydrogen Production Process

    Kim Hyo-Sub

    2016-01-01

    Full Text Available In the sulfur-iodine hydrogen production process, the Bunsen reaction is a crucial section because of the linkage with the H2SO4 and HI decomposition sections. The HIx solution (HI-I2-H2O mixture was fed to the Bunsen reaction section as a reactant from the HI decomposition section. In this study, the Bunsen reaction using the HIx solution with countercurrent flow was performed. The production rate of HIx phase solution increased while that of H2SO4 phase solution was maintained constant when increasing the flow rate of HIx solution. As the SO2 flow rate increased, the production rates of H2SO4 and HIx phase solutions increased. The amount of resultant H2SO4 phase was very lower than that of resultant HIx phase under the conditions examined in this study.

  8. Solute activity coefficients in dilute aqueous electrolyte mixutes. III. The ternary system HCLO4 + UO2(CLO4)2 + H2O at 250C

    Boyd, G.E.

    1977-01-01

    Isopiestic vapor pressure comparison measurements were conducted with the three-component system HClO 4 + UO 2 (ClO 4 ) 2 + H 2 O in the concentration range between I = 0.05 and 1.9 m. Analysis of the mixture composition and concentration dependence of the osmotic coefficients with the Scatchard neutral-electrolyte and ion-component methods and with the Pitzer ion-component methods gave equally satisfactory results. Prediction of the observed osmotic coefficients by two-component approximations was satisfactory, and the data agreed well with values estimated with a model based on the osmolal fraction. A fair concordance was also found between predicted solute activity coefficients from simple models and values derived from complete treatments which included interaction terms

  9. Pure exciton- and magnon-assisted optical transitionsin the one-dimensional antiferromagnet CsMnCl3x2H2O (CMC)

    Jia, W.; Strauss, E.; Yen, W.M.

    1981-01-01

    We report the first observation of the pure electronic transitions in the 4 T 1 state of Mn 2+ ions in the one-dimensional antiferromagnet CsMnCl 3 x2H 2 O (CMC) in the absorption, excitation, and fluorescence spectra. Selection rules are analyzed: the exciton transition is electric dipole allowed, the magnon sideband in emission is a single-ion process, and is both electric and magnetic dipole allowed; however, the magnon sideband in absorption is an ion-pair process and is a weakened-electric-dipole and magnetic-dipole transition. The density of magnon states and the line profile of the magnon sideband have been calculated. The results explain the peculiar line shapes of the observed sideband emission. An exponential decay of the exciton is observed with a lifetime of 0.576 ms

  10. Ab initio studies of O-2(-) (H2O)(n) and O-3(-) (H2O)(n) anionic molecular clusters, n

    Bork, Nicolai Christian; Kurten, T.; Enghoff, Martin Andreas Bødker

    2011-01-01

    that anionic O-2(-)(H2O)n and O-3(-)(H2O)n clusters are thermally stabilized at typical atmospheric conditions for at least n = 5. The first 4 water molecules are strongly bound to the anion due to delocalization of the excess charge while stabilization of more than 4 H2O is due to normal hydrogen bonding....... Although clustering up to 12 H2O, we find that the O-2 and O-3 anions retain at least ca. 80 % of the charge and are located at the surface of the cluster. The O-2(-) and O-3(-) speicies are thus accessible for further reactions. We consider the distributions of cluster sizes as function of altitude before...

  11. Synthesis, structure, optical, photoluminescence and magnetic properties of K2[Co(C2O4)2(H2O)2]·4H2O

    Narsimhulu, M.; Hussain, K. A.

    2018-06-01

    The synthesis, crystal structure, optical, photoluminescence and magnetic behaviour of potassium bis(oxalato)cobaltate(II)tertrahydrate{K2[Co(C2O4)2(H2O)2]·4H2O} are described. The compound was grown at room temperature from mixture of aqueous solutions by slow evaporation method. The X-ray crystallographic data showed that the compound belongs to the monoclinic crystal system with P21/n space group and Z = 4. The UV-visible diffuse absorbance spectra exhibited bands at 253, 285 and 541 nm in the visible and ultraviolet regions. The optical band gap of the compound was estimated as 3.4 eV. At room temperature, an intense photoluminescence was observed from this material around 392 nm when it excited at 254 nm. The variable temperature dc magnetic susceptibility measurements exposed paramagnetic behaviour at high temperatures and antiferromagnetic ordering at low temperatures.

  12. Infrared spectroscopic investigation of M(H2PO4)2x2H2O (M=Mg, Mn, Cd) dehydration products

    Pechkovskij, V.V.; Dzyuba, E.D.; Mel'nikova, R.Ya.; Salonets, G.I.; Kovalishina, V.I.; Malashonok, I.E.

    1982-01-01

    Using the method of IR spectroscopy the composition of products separated at different stages of M(H 2 PO 4 ) 2 x2H 2 O dehydration, where M=Mg, Mn, Cd, has been investigated. It is shown that cation influence is expressed in strengthening of bond of proton-containing groups in the structure of initial compounds from magnesium to cadmium. A supposition is made that the difference in bond character of the groups more evidently expressed for partially dehydrated products of the composition M(H 2 PO 4 ) 2 , conditions a possibility of dehydration in two directions- with the formation of intermediate phase MH 2 P 2 O 7 or with separation of three phosphoric acid

  13. Multicomponent Biginelli's synthesis of 3,4-dihydropyrimidin-2(1H-ones promoted by SnCl2.2H2O

    Russowsky Dennis

    2004-01-01

    Full Text Available The ability of SnCl2.2H2O as catalyst to promote the Biginelli three-component condensation reaction from a diversity of aromatic aldehydes, ethyl acetoacetate and urea or thiourea is described. The reaction was carried out in acetonitrile or ethanol as solvents in neutral media and represents an improvement of the classical Biginelli protocol and an advantage in comparison with FeCl3.6H2O, NiCl2.6H2O and CoCl2.6H2O which were used with HCl as co-catalyst. The synthesis of 3,4-dihydropyrimidinones was achieved in good to excelent yields.

  14. Proton conducting system (ImH2)2SeO4·2H2O investigated with vibrational spectroscopy

    Zięba, Sylwia; Mizera, Adam; Pogorzelec-Glaser, Katarzyna; Łapiński, Andrzej

    2017-06-01

    Imidazolium selenate dihydrate (ImH2)2SeO4·2H2O crystals have been investigated using Raman and IR spectroscopy. Experimental data were supported by the quantum-chemical calculations (DFT), Hirshfield surfaces and fingerprint plots analysis, and Bader theory calculations. The imidazolium selenate dihydrate crystal exhibits high proton conductivity of the order of 10- 1 S/m at T = 333 K. The spectra of this compound are dominated by bands related to the lattice modes, the internal vibrations of the protonated imidazole cation, selenate anion, water molecules, and hydrogen bonds network. For the imidazolium selenate dihydrate crystal, the formal classification of the fundamental modes has been carried out.

  15. High-temperature entropy of anionic model for the phase transition in SnCl2.2H2O

    Freitas, L.C. de; Salinas, S.R.

    1975-01-01

    The basic model of the phase transition in the hydrogen-bonded layered crystal SnCl 2 .2H 2 O to account for the presence of ionic defects is modified. It is easy to obtain a series expansion for the high-temperature entropy of the ionic model in terms of closed subgraphs, with vertices of degree two, of the original three-coordinated 4-8 lattice. High-temperature entropy of the ionic model is shown to be identical to the residual entropy of a simple antiferromagnetic Ising model in a 3-4-8 lattice. This latter model can be solved exact by a set of transformations which lead to a well studied Ising model in a Union Jack lattice [pt

  16. Demonstration of diet-induced decoupling of fatty acid and cholesterol synthesis by combining gene expression array and 2H2O quantification.

    Jensen, Kristian K; Previs, Stephen F; Zhu, Lei; Herath, Kithsiri; Wang, Sheng-Ping; Bhat, Gowri; Hu, Guanghui; Miller, Paul L; McLaren, David G; Shin, Myung K; Vogt, Thomas F; Wang, Liangsu; Wong, Kenny K; Roddy, Thomas P; Johns, Douglas G; Hubbard, Brian K

    2012-01-15

    The liver is a crossroad for metabolism of lipid and carbohydrates, with acetyl-CoA serving as an important metabolic intermediate and a precursor for fatty acid and cholesterol biosynthesis pathways. A better understanding of the regulation of these pathways requires an experimental approach that provides both quantitative metabolic flux measurements and mechanistic insight. Under conditions of high carbohydrate availability, excess carbon is converted into free fatty acids and triglyceride for storage, but it is not clear how excessive carbohydrate availability affects cholesterol biosynthesis. To address this, C57BL/6J mice were fed either a low-fat, high-carbohydrate diet or a high-fat, carbohydrate-free diet. At the end of the dietary intervention, the two groups received (2)H(2)O to trace de novo fatty acid and cholesterol synthesis, and livers were collected for gene expression analysis. Expression of lipid and glucose metabolism genes was determined using a custom-designed pathway focused PCR-based gene expression array. The expression analysis showed downregulation of cholesterol biosynthesis genes and upregulation of fatty acid synthesis genes in mice receiving the high-carbohydrate diet compared with the carbohydrate-free diet. In support of these findings, (2)H(2)O tracer data showed that fatty acid synthesis was increased 10-fold and cholesterol synthesis was reduced by 1.6-fold in mice fed the respective diets. In conclusion, by applying gene expression analysis and tracer methodology, we show that fatty acid and cholesterol synthesis are differentially regulated when the carbohydrate intake in mice is altered.

  17. Overtone vibrational spectroscopy in H2-H2O complexes: a combined high level theoretical ab initio, dynamical and experimental study.

    Ziemkiewicz, Michael P; Pluetzer, Christian; Nesbitt, David J; Scribano, Yohann; Faure, Alexandre; van der Avoird, Ad

    2012-08-28

    First results are reported on overtone (v(OH) = 2 ← 0) spectroscopy of weakly bound H(2)-H(2)O complexes in a slit supersonic jet, based on a novel combination of (i) vibrationally mediated predissociation of H(2)-H(2)O, followed by (ii) UV photodissociation of the resulting H(2)O, and (iii) UV laser induced fluorescence on the nascent OH radical. In addition, intermolecular dynamical calculations are performed in full 5D on the recent ab initio intermolecular potential of Valiron et al. [J. Chem. Phys. 129, 134306 (2008)] in order to further elucidate the identity of the infrared transitions detected. Excellent agreement is achieved between experimental and theoretical spectral predictions for the most strongly bound van der Waals complex consisting of ortho (I = 1) H(2) and ortho (I = 1) H(2)O (oH(2)-oH(2)O). Specifically, two distinct bands are seen in the oH(2)-oH(2)O spectrum, corresponding to internal rotor states in the upper vibrational manifold of Σ and Π rotational character. However, none of the three other possible nuclear spin modifications (pH(2)-oH(2)O, pH(2)-pH(2)O, or oH(2)-pH(2)O) are observed above current signal to noise level, which for the pH(2) complexes is argued to arise from displacement by oH(2) in the expansion mixture to preferentially form the more strongly bound species. Direct measurement of oH(2)-oH(2)O vibrational predissociation in the time domain reveals lifetimes of 15(2) ns and <5(2) ns for the Σ and Π states, respectively. Theoretical calculations permit the results to be interpreted in terms of near resonant energy levels and intermolecular alignment of the H(2) and H(2)O wavefunctions, providing insight into predissociation dynamical pathways from these metastable levels.

  18. Two different one-dimensional structural motifs in [catena-{Cu(tacn)}2Pd(CN)4]Br2.[catena-Cu(tacn)Pd(CN)4]2.H2O (tacn is 1,4,7-triazacyclononane).

    Kuchár, Juraj; Cernák, Juraj

    2009-07-01

    The title compound, catena-poly[[bis[(triazacyclononane-kappa(3)N,N',N'')copper(II)]-di-mu-cyanido-kappa(4)N:C-palladate(II)-di-mu-cyanido-kappa(4)C:N] dibromide bis[[(triazacyclononane-kappa(3)N,N',N'')copper(II)]-mu-cyanido-kappa(2)N:C-[dicyanidopalladate(II)]-mu-cyanido-kappa(2)C:N] monohydrate], {[Cu(2)Pd(CN)(4)(C(6)H(15)N(3))(2)]Br(2).[Cu(2)Pd(2)(CN)(8)(C(6)H(15)N(3))(2)].H(2)O}(n), (I), was isolated from an aqueous solution containing tacn.3HBr (tacn is 1,4,7-triazacyclononane), Cu(2+) and tetracyanidopalladate(2-) anions. The crystal structure of (I) is essentially ionic and built up of 2,2-electroneutral chains, viz. [Cu(tacn)(NC)-Pd(CN)(2)-(CN)-], positively charged 2,4-ribbons exhibiting the composition {[Cu(tacn)(NC)(2)-Pd(CN)(2)-Cu(tacn)](2n+)}(n), bromide anions and one disordered water molecule of crystallization. The O atom of the water molecule occupies two unique crystallographic positions, one on a centre of symmetry, which is half occupied, and the other in a general position with one-quarter occupancy. One of the tacn ligands also exhibits disorder. The formation of two different types of one-dimensional structural motif within the same structure is a unique feature of this compound.

  19. Thermal decomposition of [Co(en)3][Fe(CN)6]∙ 2H2O: Topotactic dehydration process, valence and spin exchange mechanism elucidation.

    Trávníček, Zdeněk; Zbořil, Radek; Matiková-Maľarová, Miroslava; Drahoš, Bohuslav; Cernák, Juraj

    2013-01-01

    The Prussian blue analogues represent well-known and extensively studied group of coordination species which has many remarkable applications due to their ion-exchange, electron transfer or magnetic properties. Among them, Co-Fe Prussian blue analogues have been extensively studied due to the photoinduced magnetization. Surprisingly, their suitability as precursors for solid-state synthesis of magnetic nanoparticles is almost unexplored. In this paper, the mechanism of thermal decomposition of [Co(en)3][Fe(CN)6] ∙∙ 2H2O (1a) is elucidated, including the topotactic dehydration, valence and spins exchange mechanisms suggestion and the formation of a mixture of CoFe2O4-Co3O4 (3:1) as final products of thermal degradation. The course of thermal decomposition of 1a in air atmosphere up to 600°C was monitored by TG/DSC techniques, (57)Fe Mössbauer and IR spectroscopy. As first, the topotactic dehydration of 1a to the hemihydrate [Co(en)3][Fe(CN)6] ∙∙ 1/2H2O (1b) occurred with preserving the single-crystal character as was confirmed by the X-ray diffraction analysis. The consequent thermal decomposition proceeded in further four stages including intermediates varying in valence and spin states of both transition metal ions in their structures, i.e. [Fe(II)(en)2(μ-NC)Co(III)(CN)4], Fe(III)(NH2CH2CH3)2(μ-NC)2Co(II)(CN)3] and Fe(III)[Co(II)(CN)5], which were suggested mainly from (57)Fe Mössbauer, IR spectral and elemental analyses data. Thermal decomposition was completed at 400°C when superparamagnetic phases of CoFe2O4 and Co3O4 in the molar ratio of 3:1 were formed. During further temperature increase (450 and 600°C), the ongoing crystallization process gave a new ferromagnetic phase attributed to the CoFe2O4-Co3O4 nanocomposite particles. Their formation was confirmed by XRD and TEM analyses. In-field (5 K / 5 T) Mössbauer spectrum revealed canting of Fe(III) spin in almost fully inverse spinel structure of CoFe2O4. It has been found that the thermal

  20. Saturated phase densities of (CO_2 + H_2O) at temperatures from (293 to 450) K and pressures up to 64 MPa

    Efika, Emmanuel C.; Hoballah, Rayane; Li, Xuesong; May, Eric F.; Nania, Manuela; Sanchez-Vicente, Yolanda; Martin Trusler, J.P.

    2016-01-01

    Highlights: • Saturated phase densities of CO_2 + H_2O were measured with a 1.5 kg · m"−"3 uncertainty. • Aqueous phase densities can be predicted within 3 kg · m"−"3 using empirical models. • The CO_2-rich phase density was within 8 kg · m"−"3 of pure CO_2 at the same (p, T). • The cubic EOS of Spycher and Pruess deviates from the data by up to about 8 kg · m"−"3. - Abstract: An apparatus consisting of an equilibrium cell connected to two vibrating tube densimeters and two syringe pumps was used to measure the saturated phase densities of (CO_2 + H_2O) at temperatures from (293 to 450) K and pressures up to 64 MPa, with estimated average standard uncertainties of 1.5 kg · m"−"3 for the CO_2-rich phase and 1.0 kg · m"−"3 for the aqueous phase. The densimeters were housed in the same thermostat as the equilibrium cell and were calibrated in situ using pure water, CO_2 and helium. Following mixing, samples of each saturated phase were displaced sequentially at constant pressure from the equilibrium cell into the vibrating tube densimeters connected to the top (CO_2-rich phase) and bottom (aqueous phase) of the cell. The aqueous phase densities are predicted to within 3 kg · m"−"3 using empirical models for the phase compositions and partial molar volumes of each component. However, a recently developed multi-parameter equation of state (EOS) for this binary mixture, Gernert and Span [32], was found to under predict the measured aqueous phase density by up to 13 kg · m"−"3. The density of the CO_2-rich phase was always within about 8 kg · m"−"3 of the density for pure CO_2 at the same pressure and temperature; the differences were most positive near the critical density, and became negative at temperatures above about 373 K and pressures below about 10 MPa. For this phase, the multi-parameter EOS of Gernert and Span describes the measured densities to within 5 kg · m"−"3, whereas the computationally-efficient cubic EOS model of

  1. Obtention of agricultural gypsum traced on 34 S (Ca34 SO4.2H2O), by chemical reaction between H234 SO4 and Ca(OH)2

    Rossete, Alessandra L.R.M.; Bendassolli, Jose A.; Ignoto, Raquel de Fatima; Batagello, Hugo Henrique

    2002-01-01

    The gypsum (CaSO 4 .2H 2 O) has double function in the soil: as source of calcium and sulfur and reducing agent of aluminum saturation. The sulfur for the plants has acting in the vital functions and it is proven fact increase of the S deficiency in Brazilian soils. The isotope tracer 34 S can elucidate important aspects in the sulfur cycle. The Ca 34 SO 4 .2H 2 O was obtained by chemical reaction between Ca(OH) 2 and H 2 34 SO 4 solution. The acid was obtained by chromatography ionic change, using cationic resin Dowex 50WX8 and Na 2 34 SO 4 solution. The reaction was realized under slow agitation. After the reaction, the precipitate was separated and dried in ventilated stove at 60 deg C temperature. The Mass of the Ca 34 SO 4 .2H 2 O produced was determined by method gravimetric. This way, a system contends resin 426 cm 3 , considering volume of 2.2 liters can be obtained a solution contends 44.2 g of H 2 34 SO 4 , theoretically could be produced 78.0 g of Ca 34 SO 4 .2H 2 O approximately. With results of the tests were verified that there was not total precipitation of the Ca 34 SO 4 .2H 2 O. Were produced 73.7± 0.6 g of Ca 34 SO 4 .2H 2 O representing average income 94.6±0.8 %. The purity of the produced CaSO 4 .2H 2 O was 98%. (author)

  2. Preparation of rat gastric heavy and light microsomal membranes enriched in (H+-K+)-ATPase using 2H2O and Percoll gradients

    Im, W.B.; Davis, J.P.; Blakeman, D.P.

    1985-01-01

    Gastric heavy microsomal membranes highly enriched in (H + -K + )-ATPase were obtained from cimetidine- or carbachol-treated rats through 2 H 2 O and Percoll gradient centrifugations. Both the resting (cimetidine-treated) and the stimulated (carbachol-treated) heavy membranes which presumably represent the apical membrane of gastric parietal cells were enriched with the polypeptides of 81,000 and 45,000 besides that of 93,000 representing (H + -K + )-ATPase. No apparent differences could be detected between the resting and the stimulated heavy membranes in their polypeptide profiles or their specific activity of (H + -K + )-ATPase. Nevertheless, the level of 86 RbCl uptake was greater in the stimulated than the resting heavy microsomal membrane vesicles. The light gastric microsomes which abound in intracellular tubulovesicles containing reserve (H + -K + )-ATPase as isolated from cimetidine-treated rats were similarly purified with respect to (H + -K + )-ATPase. The purified light gastric membranes were largely devoid of the polypeptides of 81,000 and 45,000 found in the heavy gastric membranes. These observations further support the current hypothesis that secretagogues bring about changes in the environment of (H + -K + )-ATPase and induce KCl permeability in the apical membrane of the parietal cells, although at present the authors have been unable to identify the polypeptide(s) responsible for the KCl pathway

  3. Variscite (AlPO4 2H2O from Cioclovina Cave (Sureanu Mountains, Romania: a tale of a missing phosphate

    Bogdan P. Onac

    2004-04-01

    Full Text Available Recent investigations on a phosphatized sediment sequence in the Cioclovina Cave led to the identification of a second occurrence in Romania (first time in the cave environment of variscite, AlPO4·2H2O. The mineral exists as dull-white, tiny crusts and veinlets within the thick argillaceous material accumulated on the cave floor. Under scanning electron microscope (SEM variscite appears as subhedral to euhedral micron-size crystals. The {111} pseudo-octahedral form is rather common. Variscite was further characterized by means of X-ray diffraction, thermal, vibrational FT-IR and FT-Raman spectroscopy, and by SEM energy-dispersive spectrometry (EDS. The calculated orthorhombic cell parameters are a = 9.823(4, b = 8.562(9, c = 9.620(5 Å, and V = 809.167(6 Å3. The ED spectrum of variscite shows well-resolved Al and P lines confirming thus the presence of the major elements in our compound. The formation of variscite is attributed to the reaction between the phosphate-rich leachates derived from guano and the underlying clay sediments.

  4. Gypsum (CaSO4·2H2O) Scaling on Polybenzimidazole and Cellulose Acetate Hollow Fiber Membranes under Forward Osmosis

    Chen, Si Cong; Su, Jincai; Fu, Feng-Jiang; Mi, Baoxia; Chung, Tai-Shung

    2013-01-01

    We have examined the gypsum (CaSO4·2H2O) scaling phenomena on membranes with different physicochemical properties in forward osmosis (FO) processes. Three hollow fiber membranes made of (1) cellulose acetate (CA), (2) polybenzimidazole (PBI)/polyethersulfone (PES) and (3) PBI-polyhedral oligomeric silsesquioxane (POSS)/polyacrylonitrile (PAN) were studied. For the first time in FO processes, we have found that surface ionic interactions dominate gypsum scaling on the membrane surface. A 70% flux reduction was observed on negatively charged CA and PBI membrane surfaces, due to strong attractive forces. The PBI membrane surface also showed a slightly positive charge at a low pH value of 3 and exhibited a 30% flux reduction. The atomic force microscopy (AFM) force measurements confirmed a strong repulsive force between gypsum and PBI at a pH value of 3. The newly developed PBI-POSS/PAN membrane had ridge morphology and a contact angle of 51.42° ± 14.85° after the addition of hydrophilic POSS nanoparticles and 3 min thermal treatment at 95 °C. Minimal scaling and an only 1.3% flux reduction were observed at a pH value of 3. Such a ridge structure may reduce scaling by not providing a locally flat surface to the crystallite at a pH value of 3; thus, gypsum would be easily washed away from the surface. PMID:24957062

  5. An investigation on the structure, spectroscopy and thermodynamic aspects of Br2((-))(H2O)n clusters using a conjunction of stochastic and quantum chemical methods.

    Naskar, Pulak; Chaudhury, Pinaki

    2016-06-28

    In this work we obtained global as well as local structures of Br2((-))(H2O)n clusters for n = 2 to 6 followed by the study of IR-spectral features and thermochemistry for the structures. The way adopted by us to obtain structures is not the conventional one used in most cases. Here we at first generated excellent quality pre-optimized structures by exploring the suitable empirical potential energy surface using stochastic optimizer simulated annealing. These structures are then further refined using quantum chemical calculations to obtain the final structures, and spectral and thermodynamic features. We clearly showed that our approach results in very quick and better convergence which reduces the computational cost and obviously using the strategy we are able to get one [i.e. global] or more than one [i.e. global and local(s)] energetically lower structures than those which are already reported for a given cluster size. Moreover, IR-spectral results and the evolutionary trends in interaction energy, solvation energy and vertical detachment energy for global structures of each size have also been presented to establish the utility of the procedure employed.

  6. Pharmacokinetics of enrofloxacin HCl-2H2O (ENRO-C) in dogs and PK/PD Monte Carlo simulations against Leptospira sp.

    Sumano, Hector; Ocampo, Luis; Tapia, Graciela; Mendoza, C de Jesus; Gutierrez, Lilia

    2018-04-12

    Pharmacokinetics/pharmacodynamics (PK/PD) ratios of reference enrofloxacin (Enro-R) and enrofloxacin as HCl-2H 2 O (Enro-C), as well as Monte Carlo simulations based on composite MIC 50 and MIC 90 vs. Leptospira sp., were carried out in dogs after their IM and oral administration (10 mg/kg). Plasma determination of enrofloxacin was achieved by means of high performance liquid chromatography (HPLC). Maximum plasma concentration values after oral administration were 1.47 ± 0.19 µg/mL and 5.3 ± 0.84 µg/mL for Enro-R and Enro-C, respectively, and 1.6 ± 0.12 µg/mL and 7.6 ± 0.93 µg/mL after IM administration. Area under the plasma vs. time concentrations in 24 h (AUC 0-24 ) were 8.02 µg/mL/h and 36.2 µg/mL/h for Enro-R oral and Enro-C oral , respectively, and 8.55 ± 0.85 µg/mL/h and 56.4 ± 6.21 µg/mL/h after IM administration of these drugs. Only PK/PD ratios and Monte Carlo simulations obtained with Enro-C, anticipate that its IM administration to dogs will result in therapeutic concentrations to treat leptospirosis. This is the first time enrofloxacin has been recommended to treat this disease in dogs.

  7. Redetermination of Ce[B5O8(OH(H2O]NO3·2H2O

    Ya-Xi Huang

    2012-05-01

    Full Text Available The crystal structure of Ce[B5O8(OH(H2O]NO3·2H2O, cerium(III aquahydroxidooctaoxidopentaborate nitrate dihydrate, has been redetermined from single-crystal X-ray diffraction data. In contrast to the previous determination [Li et al. (2003. Chem. Mater. 15, 2253–2260], the present study reveals the location of all H atoms, slightly different fundamental building blocks (FBBs of the polyborate anions, more reasonable displacement ellipsoids for all non-H atoms, as well as a model without disorder of the nitrate anion. The crystal structure is built from corrugated polyborate layers parallel to (010. These layers, consisting of [B5O8(OH(H2O]2− anions as FBBs, stack along [010] and are linked by Ce3+ ions, which exhibit a distorted CeO10 coordination sphere. The layers are additionally stabilized via O—H...O hydrogen bonds between water molecules and nitrate anions, located at the interlayer space. The [BO3(H2O]-group shows a [3 + 1] coordination and is considerably distorted from a tetrahedral configuration. Bond-valence-sum calculation shows that the valence sum of boron is only 2.63 valence units (v.u. when the contribution of the water molecule (0.49 v.u. is neglected.

  8. Thermochemical Properties of the Complexes RE(HSal)3·2H2O (RE=La, Ce, Pr, Nd, Sm)

    2006-01-01

    Five solid rare earth salicylate complexes were synthesized by low hydrated lathanide chloride and salicylic acid. The complexes in this experiment were identified as the general formula RE(Hsal)3·2H2O(RE=La, Ce, Pr, Nd, Sm) by elemental analysis and EDTA volumetric analysis. IR spectra of the complexes show that carboxyl of salicylic acid coordinates to RE3+ ions. Electrochemical behaviors of the complexes on the glass-carbon electrode were researched with cyclic voltammetry (CV). It is indicated that the electrochemical process of the complexes is a one-electron redox process and the electrochemical reversibility of complexes is less than that of the lanthanide chlorides. The constant-volume combustion energies of complexes, ΔcU, were determined with a precise rotating-bomb calorimeter at 298.15 K. Their standard molar enthalpies of combustion, ΔcHθm, and standard molar enthalpies of formation, ΔfHθm, were calculated.

  9. Controlled Surface Modification of Polyamide 6.6 Fibres Using CaCl2/H2O/EtOH Solutions

    Barbara Rietzler

    2018-02-01

    Full Text Available Polyamide 6.6 is one of the most widely used polymers in the textile industry due to its durability; however, it has rather limited modification potential. In this work, the controlled surface modification of polyamide 6.6 fibres using the solvent system CaCl2/H2O/EtOH was studied. The effects of solvent composition (relative proportions of the three components and treatment time on fibre properties were studied both in situ (with fibres in solvent and ex situ (after the solvent was washed off. The fibres swell and/or dissolve in the solvent depending on its composition and the treatment time. We believe that the fibre–solvent interaction is through complex formation between the fibre carbonyl groups and the CaCl2. On washing, there is decomplexation and precipitation of the polymer. The treated fibres exhibit greater diameters and surface roughness, structural difference between an outer shell and an inner core is observable, and water retention is higher. The solvent system is more benign than current alternatives, and through suitable tailoring of the treatment conditions, e.g., composition and time, it may be used in the design of advanced materials for storage and release of active substances.

  10. Thermally activated 3D to 2D structural transformation of [Ni2(en)2(H2O)6(pyr)]·4H2O flexible coordination polymer

    Begović, Nebojša N.; Blagojević, Vladimir A.; Ostojić, Sanja B.; Radulović, Aleksandra M.; Poleti, Dejan; Minić, Dragica M.

    2015-01-01

    Thermally activated 3D to 2D structural transformation of the binuclear [Ni 2 (en) 2 (H 2 O) 6 (pyr)]·4H 2 O complex was investigated using a combination of theoretical and experimental methods. Step-wise thermal degradation (dehydration followed by release of ethylene diamine) results in two layered flexible coordination polymer structures. Dehydration process around 365 K results in a conjugated 2D structure with weak interlayer connectivity. It was shown to be a reversible 3D to 2D framework transformation by a guest molecule, and rehydration of the dehydration product occurs at room temperature in saturated water vapor. Rehydrated complex exhibits lower dehydration temperature, due to decreased average crystalline size, with higher surface area resulting in easier release and diffusion of water during dehydration. Thermal degradation of dehydration around 570 K, results in loss of ethylene diamine, producing a related 2D layered polymer structure, without interconnectivity between individual polymer layers. - Highlights: • Reversible 3D to 2D framework topochemical transformation on dehydration around 365 K. • Resulting polymer exhibits 2D layered structure with weak interlayer connectivity. • Dehydration is fully reversible in saturated water vapor at room temperature. • Further degradation around 570 K yields 2D polymer without interlayer connectivity. • 2D polymer exhibits conjugated electronic system

  11. Synthesis, crystal structure and thermal decomposition mechanism of the complex [Sm(p-BrBA)3bipy.H2O]2.H2O

    Zhang Haiyan; Zhang Jianjun; Ren Ning; Xu Suling; Tian Liang; Bai Jihai

    2008-01-01

    A new binuclear samarium (III) complex [Sm(p-BrBA) 3 bipy.H 2 O] 2 .H 2 O (p-BrBA = p-bromobenzoic acid; bipy = 2,2'-bipyridine) has been synthesized and characterized by elemental analysis, UV, IR, molar conductance and TG-DTG techniques. The structure of the complex was established by single crystal X-ray diffraction. It crystallizes in triclinic, space group P1-bar with a = 8.2476(7) A, b = 13.3483(10) A, c = 15.9035(13) A, α 73.9160(10) o , β = 78.9630(10) o , γ = 74.4770(10) o , Z = 1, D c 1.947 g cm -3 , F(000) = 910. The carboxylic groups are bonded to the samarium ion in two modes: bidentate bridging, monodentate. Each center Sm 3+ ion is eight-coordinated by one 2,2'-bipyridine molecular, four bidentate bridging and a monodentate carboxylic group, as well as one water molecular. The coordination polyhedron around each Sm 3+ ion can be described as bi-capped triangular prism geometry. The thermal decomposition behavior of the title complex in a static air atmosphere was investigated by TG-DTG and IR techniques

  12. Structure of Chloro bis(1,10-phenanthroline)Cobalt(II) Complex, [Co(phen)2(Cl)(H2O)]Cl · 2H2O

    Zhao, Pu Su; Lu, Lu De; Jian, Fang Fang

    2003-01-01

    The crystal structure of [Co(phen) 2 (Cl)(H 2 O)] Cl · 2H 2 O(phen=1,10-phenanthroline) has been determined by X-ray crystallography. It crystallizes in the triclinic system, space group P 1 , with lattice parameters a=9.662(2), b=11.445(1), c=13.037(2)A, α=64.02(1), β=86.364(9), γ=78.58(2) .deg., and Z=2. The coordinated cations contain a six-coordinated cobalt atom chelated by two phen ligands and one chloride anion and one water ligand in cis arrangement. In addition to the chloride coordinated to the cobalt, there are one chloride ion and four water molecules which complete the crystal structure. In the solid state, the title compound forms three dimensional network structure through hydrogen bonds, within which exists the strongest hydrogen bond (O(3)-O(4)=2.33A). The intermolecular hydrogen bonds connect the [Co(phen) 2 (Cl)(H 2 O)] 1+ , H 2 O moieties and chloride ion

  13. Density functional theory investigation of the geometric and electronic structures of [UO2(H2O)m(OH)n](2 - n) (n + m = 5).

    Ingram, Kieran I M; Häller, L Jonas L; Kaltsoyannis, Nikolas

    2006-05-28

    Gradient corrected density functional theory has been used to calculate the geometric and electronic structures of the family of molecules [UO2(H2O)m(OH)n](2 - n) (n + m = 5). Comparisons are made with previous experimental and theoretical structural and spectroscopic data. r(U-O(yl)) is found to lengthen as water molecules are replaced by hydroxides in the equatorial plane, and the nu(sym) and nu(asym) uranyl vibrational wavenumbers decrease correspondingly. GGA functionals (BP86, PW91 and PBE) are generally found to perform better for the cationic complexes than for the anions. The inclusion of solvent effects using continuum models leads to spurious low frequency imaginary vibrational modes and overall poorer agreement with experimental data for nu(sym) and nu(asym). Analysis of the molecular orbital structure is performed in order to trace the origin of the lengthening and weakening of the U-O(yl) bond as waters are replaced by hydroxides. No evidence is found to support previous suggestions of a competition for U 6d atomic orbitals in U-O(yl) and U-O(hydroxide)pi bonding. Rather, the lengthening and weakening of U-O(yl) is attributed to reduced ionic bonding generated in part by the sigma-donating ability of the hydroxide ligands.

  14. Synthesis, crystal structure and magnetic properties of [Cu(mal(abpt(H2O].3/2H2O and [Cu2(sq(abpt 2].2H2O (mal = malonate, sq = squarate, abpt = 4-amino-3,5-di-2-pyridyl-4H-1,2,4 triazole

    Eno A. Ededet

    2011-04-01

    Full Text Available Two new mixed-ligand complexes of formula [Cu(mal(abpt(H2O].3/2H2O (1 and [Cu2(sq(abpt2].2H2O (2 [mal = malonate, abpt = 4-amino-3,5-di-2-pyridyl-4H-1,2,4 triazole and sq = squarate], have been prepared and characterized by X-ray crystal structure determination and magnetic studies. Complex 1 crystallizes in the monoclinic system, space group C2/c, with a = 14.0086(2 Å, b = 10.0980(2 Å, c = 25.630(4 Å; β = 97.5900(10 o, and Z = 8. Complex 2 crystallizes in the triclinic system, space group P-1 with a = 7.5696(15 Å, b = 8.4697(17 Å, c = 11.049(2 Å; β = 93.00(3o, α = 96.98(3, γ = 90.111(3 and Z = 1. Complex 1 consist of a neutral mononuclear [Cu(mal(abpt(H2O] unit and water molecule of crystallization in a distorted square pyramidal coordination sphere, while complex 2 is viewed as being made up of [Cu(sq(abpt2] units with the squarato ligand bridging the two copper(II cations. Variable temperature magnetic behaviour of the complexes reveals the existence of weak antiferromagnetic interaction for complex 1 and weak ferromagnetic intrachain interaction for complex 2.

  15. Flat-topped emission centred at 1 250 nm from quantum dot superluminescent diodes

    R.A. Hogg

    2010-01-01

    Full Text Available We present a method for tailoring a broadband and flat-topped emission spectrum in quantum dot superluminescent diodes based upon modification of the dots-in-compositionally-modulated-well (DCMWELL technique. We demonstrate flat-topped emission with 95 nm full width at half maximum (FWHM, centred at 1 250 nm, and with output power in excess of 8 mW.

  16. Carbon dioxide induced bubble formation in a CH4-CO2-H2O ternary system: a molecular dynamics simulation study.

    Sujith, K S; Ramachandran, C N

    2016-02-07

    The extraction of methane from its hydrates using carbon dioxide involves the decomposition of the hydrate resulting in a CH4-CO2-H2O ternary solution. Using classical molecular dynamics simulations, we investigate the evolution of dissolved gas molecules in the ternary system at different concentrations of CO2. Various compositions considered in the present study resemble the solution formed during the decomposition of methane hydrates at the initial stages of the extraction process. We find that the presence of CO2 aids the formation of CH4 bubbles by causing its early nucleation. Elucidation of the composition of the bubble revealed that in ternary solutions with high concentration of CO2, mixed gas bubbles composed of CO2 and CH4 are formed. To understand the role of CO2 in the nucleation of CH4 bubbles, the structure of the bubble formed was analyzed, which revealed that there is an accumulation of CO2 at the interface of the bubble and the surrounding water. The aggregation of CO2 at the bubble-water interface occurs predominantly when the concentration of CO2 is high. Radial distribution function for the CH4-CO2 pair indicates that there is an increasingly favorable direct contact between dissolved CH4 and CO2 molecules in the bubble-water interface. It is also observed that the presence of CO2 at the interface results in the decrease in surface tension. Thus, CO2 leads to greater stability of the bubble-water interface thereby bringing down the critical size of the bubble nuclei. The results suggest that a rise in concentration of CO2 helps in the removal of dissolved CH4 thereby preventing the accumulation of methane in the liquid phase. Thus, the presence of CO2 is predicted to assist the decomposition of methane hydrates in the initial stages of the replacement process.

  17. Corrosion study on high power feeding of telecomunication copper cable in 5 wt.% CaSO4.2H2O solution

    Shamsudin, Shaiful Rizam; Hashim, Nabihah; Ibrahim, Mohd Saiful Bahri; Rahman, Muhammad Sayuzi Abdul; Idrus, Muhammad Amin; Hassan, Mohd Rezadzudin; Abdullah, Wan Razli Wan

    2016-07-01

    The studies were carried out to find out the best powering scheme over the copper telephone line. It was expected that the application of the higher power feeding could increase the data transfer and capable of providing the customer's satisfaction. To realize the application of higher remote power feeding, the potential of corrosion problem on Cu cables was studied. The natural corrosion behaviour of copper cable in the 0.5% CaSO4.2H2O solution was studied in term of open circuit potential for 30 days. The corrosion behaviour of higher power feeding was studied by the immersion and the planned interval test to determine the corrosion rate as well as the effect of voltage magnitudes and the current scheme i.e. positive direct (DC+) and alternating current (AC) at about 0.40 ± 0.01 mA/ cm2 current density. In the immersion test, both DC+ and AC scheme showed the increasing of feeding voltage magnitude has increased the corrosion rate of Cu samples starting from 60 to 100 volts. It was then reduced at about 100 - 120 volts which may due to the passive and transpassive mechanism. The corrosion rate was slowly reduced further from 120 to 200 volts. Visually, the positively charged of Cu cable was seems susceptible to severe corrosion, while AC scheme exhibited a slight corrosion reaction on the surface. However, the planned interval test and XRD results showed the corrosion activity of the copper cable in the studied solution was a relatively slow process and considered not to be corroded as a partially protective scale of copper oxide formed on the surface.

  18. Enhanced performance of wet compression-resorption heat pumps by using NH_3-CO_2-H_2O as working fluid

    Gudjonsdottir, V.; Infante Ferreira, C.A.; Rexwinkel, Glenn; Kiss, Anton A.

    2017-01-01

    Upgrading waste heat by compression resorption heat pumps (CRHP) has the potential to make a strong impact in industry. The efficiency of CRHP can be further improved by using alternative working fluids. In this work, the addition of carbon dioxide to aqueous ammonia solutions for application in CRHP is investigated. The previously published thermodynamic models for the ternary mixture are evaluated by comparing their results with experimental thermodynamic data, and checking their advantages and disadvantages. Then the models are used to investigate the impact of adding CO_2 to NH_3-H_2O in wet compression resorption heat pump applications. For an application where a waste stream is heated from 60 to 105 °C, a COP increase of up to 5% can be attained by adding CO_2 to the ammonia-water mixture, without any risk of salt formation. Additional advantages of adding CO_2 to the ammonia-water mixture in that case are decreased pressure ratio, as well as an increase in the lower pressure level. When practical pressure restrictions are considered the benefits of the added CO_2 become even larger or around 25% increase in the COP. Nonetheless, when the waste stream was considered to be additionally cooled down, no significant benefits were observed. - Highlights: • NH_3-CO_2-H_2O mixture is proposed as a working fluid for CRHP. • COP improvements of 5% are achieved compared to NH_3-H_2O. • Additional advantages of the added CO_2 are decreased pressure ratio.

  19. LiFePO4 Nanostructures Fabricated from Iron(III) Phosphate (FePO4 x 2H2O) by Hydrothermal Method.

    Saji, Viswanathan S; Song, Hyun-Kon

    2015-01-01

    Electrode materials having nanometer scale dimensions are expected to have property enhancements due to enhanced surface area and mass/charge transport kinetics. This is particularly relevant to intrinsically low electronically conductive materials such as lithium iron phosphate (LiFePO4), which is of recent research interest as a high performance intercalation electrode material for Li-ion batteries. Many of the reported works on LiFePO4 synthesis are unattractive either due to the high cost of raw materials or due to the complex synthesis technique. In this direction, synthesis of LiFePO4 directly from inexpensive FePO4 shows promise.The present study reports LiFePO4 nanostructures prepared from iron (III) phosphate (FePO4 x 2H2O) by precipitation-hydrothermal method. The sintered powder was characterized by X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), Inductive coupled plasma-optical emission spectroscopy (ICP-OES), and Electron microscopy (SEM and TEM). Two synthesis methods, viz. bulk synthesis and anodized aluminum oxide (AAO) template-assisted synthesis are reported. By bulk synthesis, micro-sized particles having peculiar surface nanostructuring were formed at precipitation pH of 6.0 to 7.5 whereas typical nanosized LiFePO4 resulted at pH ≥ 8.0. An in-situ precipitation strategy inside the pores of AAO utilizing the spin coating was utilized for the AAO-template-assisted synthesis. The template with pores filled with the precipitate was subsequently subjected to hydrothermal process and high temperature sintering to fabricate compact rod-like structures.

  20. Determination and modeling for the solubility of Na_2WO_4·2H_2O and Na_2MoO_4·2H_2O in the (Na"+ + MoO_4"2"− + WO_4"2"− + SO_4"2"− + H_2O) system

    Ning, Pengge; Xu, Weifeng; Cao, Hongbin; Xu, Hongbin

    2016-01-01

    Highlights: • The solubility of Na_2MoO_4·2H_2O and Na_2WO_4·2H_2O in Na_2MoO_4–Na_2WO_4–Na_2SO_4–H_2O were performed. • The solubility of sodium tungstate dihydrate in Na_2WO_4–Na_2SO_4–H_2O was determined. • The new model was established via regressing the published and the determined data. • The Pitzer parameter and the solubility product constant of the salt in solution were calculated. • The model was used to estimate the solubility of the sodium molybdate and sodium tungstate. - Abstract: The solubility of sodium tungstate dihydrate and sodium molybdate dihydrate in the (Na_2MoO_4 + Na_2WO_4 + Na_2SO_4 + H_2O) system was studied using experimental and calculated methods. The osmotic coefficient of sodium tungstate was fitted to calculate the thermodynamics parameters of (Na_2WO_4 + H_2O) system. The solubility of sodium tungstate dihydrate was determined using the dynamic method in Na_2WO_4–Na_2SO_4–H_2O to establish the new model which can provide an estimate the solubility of sodium tungstate dihydrate in various conditions, combined with the data published, the solubility of sodium tungstate dihydrate and the sodium molybdate dihydrate in quaternary system of (Na_2MoO_4 + Na_2WO_4 + Na_2SO_4 + H_2O) was estimated using the parameters of the two ternary systems of (Na_2WO_4 + Na_2SO_4 + H_2O) and (Na_2MoO_4 + Na_2SO_4 + H_2O). The results show that the AARD is always small and the calculated value is basically consistent with the experimental values for the system studied.

  1. Redox process catalysed by growing crystal-strengite, FePO4,2H2O, crystallizing from solution with iron(II) and hydroxylamine

    Lundager Madsen, Hans Erik

    2014-09-01

    In an attempt to grow pure crystals of the iron(II) phosphate vivianite, Fe3(PO4)2,8H2O, from a solution of Mohr's salt, Fe(NH4)2(SO4)2,6H2O, added to a solution of ammonium phosphate, hydroxylammonium chloride, NH3OHCl, was added to the iron(II) stock solution to eliminate oxidation of iron(II) by oxygen from the air. However, the effect turned out to be the opposite of the expected: whereas hydroxylamine reduces iron(III) in bulk solution, it acted as a strong oxidant in the presence of growing iron phosphate crystals, causing the crystallization of the iron(III) phosphate strengite, FePO4,2H2O, as the only solid phase. Evidently the crystal surface catalyses oxidation of iron(II) by hydroxylamine. The usual composite kinetics of spiral growth and surface nucleation was found. The surface-nucleation part yielded edge free energy λ in the range 12-45 pJ/m, virtually independent of temperature and in the range typical for phosphates of divalent metals. The scatter of values for λ presumably arises from contributions from different crystal forms to the overall growth rate. The low mean value points to strong adsorption of iron(II), which is subsequently oxidized at the crystal surface, forming strengite. The state of the system did not tend to thermodynamic equilibrium, but to a metastable state, presumably controlled by the iron(II) rich surface layer of the crystal. In addition to crystal growth, it was possible to measure nucleation kinetics by light scattering (turbidimetry). A point of transition from heterogeneous to homogeneous nucleation was found, and from the results for the homogeneous domain a rather precise value of crystal surface free energy γ=55 mJ/m2 was found. This is a relatively low value as well, indicating that the redox process plays a role already at the nucleation stage.

  2. Theoretical study of the gas-phase reactions of iodine atoms ((2)P(3/2)) with H(2), H(2)O, HI, and OH.

    Canneaux, Sébastien; Xerri, Bertrand; Louis, Florent; Cantrel, Laurent

    2010-09-02

    The rate constants of the reactions of iodine atoms with H(2), H(2)O, HI, and OH have been estimated using 39, 21, 13, and 39 different levels of theory, respectively, and have been compared to the available literature values over the temperature range of 250-2500 K. The aim of this methodological work is to demonstrate that standard theoretical methods are adequate to obtain quantitative rate constants for the reactions involving iodine-containing species. Geometry optimizations and vibrational frequency calculations are performed using three methods (MP2, MPW1K, and BHandHLYP) combined with three basis sets (cc-pVTZ, cc-pVQZ, and 6-311G(d,p)). Single-point energy calculations are performed with the highly correlated ab initio coupled cluster method in the space of single, double, and triple (pertubatively) electron excitations CCSD(T) using the cc-pVnZ (n = T, Q, and 5), aug-cc-pVnZ (n = T, Q, and 5), 6-311G(d,p), 6-311+G(3df,2p), and 6-311++G(3df,3pd) basis sets. Canonical transition state theory with a simple Wigner tunneling correction is used to predict the rate constants as a function of temperature. CCSD(T)/cc-pVnZ//MP2/cc-pVTZ (n = T and Q), CCSD(T)/6-311+G(3df,2p)//MP2/6-311G(d,p), and CCSD(T)/6-311++G(3df,3pd)//MP2/6-311G(d,p) levels of theory provide accurate kinetic rate constants when compared to available literature data. The use of the CCSD(T)/cc-pVQZ//MP2/cc-pVTZ and CCSD(T)/6-311++G(3df,3pd) levels of theory allows one to obtain a better agreement with the literature data for all reactions with the exception of the I + H(2) reaction R(1) . This computational procedure has been also used to predict rate constants for some reactions where no available experimental data exist. The use of quantum chemistry tools could be therefore extended to other elements and next applied to develop kinetic networks involving various fission products, steam, and hydrogen in the absence of literature data. The final objective is to implement the kinetics of gaseous

  3. Tinnunculite, C5H4N4O3 · 2H2O: Occurrences on the Kola Peninsula and Redefinition and Validation as a Mineral Species

    Pekov, I. V.; Chukanov, N. V.; Yapaskurt, V. O.; Belakovskiy, D. I.; Lykova, I. S.; Zubkova, N. V.; Shcherbakova, E. P.; Britvin, S. N.; Chervonnyi, A. D.

    2017-12-01

    Based on a study of samples found in the Khibiny (Mt. Rasvumchorr: the holotype) and Lovozero (Mts Alluaiv and Vavnbed) alkaline complexes on the Kola Peninsula, Russia, tinnunculite was approved by the IMA Commission on New Minerals, Nomenclature, and Classification as a valid mineral species (IMA no. 2015-02la) and, taking into account a revisory examination of the original material from burnt dumps of coal mines in the southern Urals, it was redefined as crystalline uric acid dihydrate (UAD), C5H4N4O3 · 2H2O. Tinnunculite is poultry manure mineralized in biogeochemical systems, which could be defined as "guano microdeposits." The mineral occurs as prismatic or tabular crystals up to 0.01 × 0.1 × 0.2 mm in size and clusters of them, as well as crystalline or microglobular crusts. Tinnunculite is transparent or translucent, colorless, white, yellowish, reddish or pale lilac. Crystals show vitreous luster. The mineral is soft and brittle, with a distinct (010) cleavage. D calc = 1.68 g/cm3 (holotype). Tinnunculite is optically biaxial (-), α = 1.503(3), β = 1.712(3), γ = 1.74(1), 2 V obs = 40(10)°. The IR spectrum is given. The chemical composition of the holotype sample (electron microprobe data, content of H is calculated by UAD stoichiometry) is as follows, wt %: 37.5 O, 28.4 C, 27.0 N, 3.8 Hcalc, total 96.7. The empirical formula calculated on the basis of (C + N+ O) = 14 apfu is: C4.99H8N4.07O4.94. Tinnunculite is monoclinic, space group (by analogy with synthetic UAD) P21/ c. The unit cell parameters of the holotype sample (single crystal XRD data) are a = 7.37(4), b = 6.326(16), c = 17.59(4) Å, β = 90(1)°, V = 820(5) Å3, Z = 4. The strongest reflections in the XRD pattern ( d, Å- I[ hkl]) are 8.82-84[002], 5.97-15[011], 5.63-24[102̅, 102], 4.22-22[112], 3.24-27[114̅,114], 3.18-100[210], 3.12-44[211̅, 211], 2.576-14[024].

  4. Carbon Dioxide and Water Vapor Concentrations, Co-spectra and Fluxes from Latest Standardized Automated CO2/H2O Flux Systems versus Established Analyzer Models

    Burba, G. G.; Kathilankal, J. C.; Begashaw, I.; Franzen, D.; Welles, J.; McDermitt, D. K.

    2017-12-01

    Spatial and temporal flux data coverage have improved significantly in recent years, due to standardization, automation and management of data collection, and better handling of the generated data. With more stations and networks, larger data streams from each station, and smaller operating budgets, modern tools are required to effectively and efficiently handle the entire process.These tools should produce standardized verifiable datasets, and provide a way to cross-share the standardized data with external collaborators to leverage available funding, and promote data analyses and publications. In 2015, new open-path and enclosed flux measurement systems1 were developed, based on established gas analyzer models2,3, with the goal of improving stability in the presence of contamination, refining temperature control and compensation, and providing more accurate gas concentration measurements. In 2017, the new open-path system was further refined to simplify hardware configuration, and to reduce power consumption and cost. Additionally, all new systems incorporate complete automated on-site flux calculations using EddyPro® Software4 run by a weatherized remotely-accessible microcomputer to provide standardized traceable data sets for fluxes and supporting variables. This presentation will describe details and results from the field tests of the new flux systems, in comparison to older models and reference instruments. References:1 Burba G., W. Miller, I. Begashaw, G. Fratini, F. Griessbaum, J. Kathilankal, L. Xu, D. Franz, E. Joseph, E. Larmanou, S. Miller, D. Papale, S. Sabbatini, T. Sachs, R. Sakai, D. McDermitt, 2017. Comparison of CO2 Concentrations, Co-spectra and Flux Measurements between Latest Standardized Automated CO2/H2O Flux Systems and Older Gas Analysers. 10th ICDC Conference, Switzerland: 21-25/08 2 Metzger, S., G. Burba, S. Burns, P. Blanken, J. Li, H. Luo, R. Zulueta, 2016. Optimization of an enclosed gas analyzer sampling system for measuring eddy

  5. The effect of CO2, H2O and SO2 on the kinetics of NO reduction by CH4 over La2O3

    Toops, Todd J.; Walters, Arden B.; Vannice, M.A.

    2002-01-01

    The effect of CO 2 , H 2 O and SO 2 on the kinetics of NO reduction by CH 4 over unsupported La 2 O 3 has been examined between 773 and 973K in the presence of O 2 in the feed. La 2 O 3 can maintain a stable, high specific activity (mol/(sm 2 )) for NO reduction with high concentrations of CO 2 and H 2 O in the feed; however, either of these two products reversibly inhibits the activity by about one-half in the presence of excess O 2 . The catalyst is poisoned by SO 2 at these temperatures and an oxysulfate phase is formed, but partial regeneration can be achieved at 1023K. CO 2 in the feed causes the formation of lanthanum oxycarbonate, which reverts to La 2 O 3 when CO 2 is removed, but no bulk La oxyhydroxide is detected after quenching with H 2 O in the feed. The influence of CO 2 and H 2 O on kinetic behavior can be described by assuming they compete with reactants for adsorption on surface sites, including them in the site balance equation, and using the rate expression proposed previously for NO reduction by CH 4 in excess O 2 . With O 2 in the feed, integral conversions of CH 4 and O 2 frequently occurred due to the direct combustion of CH 4 by O 2 , although NO conversions remained differential; thus, an integral reactor model was chosen to analyze the data which utilized a recently determined rate equation for CH 4 combustion on La 2 O 3 in conjunction with a previously proposed model for NO reduction by CH 4 . The following rate expression described the rate of N 2 formation: N 2 T = ' NO P NO P CH 4 P O 2 0.5 / 1 + K NO P NO + K CH 4 P CH 4 + K O 2 0.5 P O 2 0.5 + K CO 2 P CO 2 + K H 2 O P H 2 O 2 . It gave a good fit to the experimental rate data for NO reduction, as well as providing enthalpies and entropies of adsorption obtained from the fitting parameters that demonstrated thermodynamic consistency and were similar to previous values. The heats of adsorption were altered somewhat when either CO 2 or H 2 O was added to the feed, and the following

  6. Bulk modulus of basic sodalite, Na8[AlSiO4]6(OH)2·2H2O, a possible zeolitic precursor in coal-fly-ash-based geopolymers

    Oh, Jae Eun; Moon, Juhyuk; Mancio, Mauricio; Clark, Simon M.; Monteiro, Paulo J.M.

    2011-01-01

    Synthetic basic sodalite, Na8[AlSiO4] 6(OH)2•2H2O, cubic, P43n, (also known as hydroxysodalite hydrate) was prepared by the alkaline activation of amorphous aluminosilicate glass, obtained from the phase separation of Class F fly ash. The sample

  7. Magnetic structure and phase transitions of Co1-xMnxCl2.2H2O and Co1-xMnxCl2.2D2O

    Brueckel, T.; Lippert, M.; Kubo, H.; Zenmyo, K.; Mayer, H.M.; Pfeiffer, F.; Hohlwein, D.; Krimmel, A.

    1995-01-01

    We present neutron diffraction results of the magnetic structure, phase transitions and magnetic short-range order of Co 1-x Mn x Cl 2 .2H 2 O/D 2 O single crystals. For samples in an intermediate composition range, where a spin glass phase exists, we found the coexistence of spin glass and long-range antiferromagnetic order. ((orig.))

  8. Jensenite, Cu3 Te (super 6+) O6 .2H2O, a new mineral species from the Centennial Eureka Mine, Tintic District, Juab County, Utah

    Roberts, Andrew C.; Grice, Joel D.; Groat, Lee A.; Criddle, Alan J.; Gault, Robert A.; Erd, Richard C.; Moffatt, Elizabeth A.

    1996-01-01

    Jensenite, ideally Cu 3 Te (super 6+) O 6 .2H 2 O, is monoclinic, P2 1 /n (14), with unit-cell parameters refined from powder data: a 9.204(2), b 9.170(2), c 7.584(1) Aa, beta 102.32(3) degrees , V 625.3(3) Aa 3 , a:b:c 1.0037:1:0.8270, Z = 4. The strongest six reflections of the X-ray powder-diffraction pattern [d in Aa(I)(hkl)] are: 6.428(100)(101,110), 3.217(70)(202), 2.601(40)(202), 2.530(50)(230), 2.144(35)(331) and 1.750(35)(432). The mineral is found on the dumps of the Centennial Eureka mine, Juab County, Utah, where it occurs as isolated crystals or as groups of crystals on drusy white quartz. Associated minerals are mcalpineite, xocomecatlite and unnamed Cu(Mg,Cu,Fe,Zn) 2 Te (super 6+) O 6 .6H 2 O. Individual crystals of jensenite are subhedral to euhedral, and form simple rhombs that are nearly equant. Some crystals are slightly elongate [101], with a length-to-width ratio up to 2:1. The largest crystal is approximately 0.4 mm in size; the average size is between 0.1 and 0.2 mm. Cleavage {101} fair. Forms are: {101} major; {110} medium; {100} minor; {301}, {201}, {203}, {102}, {010} very small. The mineral is transparent, emerald green, with a less intense streak of the same color and an uneven fracture. Jensenite is adamantine, brittle and nonfluorescent; H (Mohs) 3-4; D (calc.) 4.78 for the idealized formula, 4.76 g/cm 3 for the empirical formula. In a polished section, jensenite is very weakly bireflectant and nonpleochroic. In reflected plane-polarized light in air, it is a nondescript grey, and in oil, it is a much darker grey in color with a brownish tint, with ubiquitous bright green internal reflections. Anisotropy is not detectable. Measured values of reflectance, in air and in oil, are tabulated. Electron-microprobe analyses yielded CuO 50.91, ZnO 0.31, TeO 3 38.91, H 2 O (calc.) [8.00], total [98.13] wt.%. The empirical formula, derived from crystal-structure analysis and electron-microprobe analyses, is (Cu (sub 2.92) Zn (sub 0.02) ) (sub

  9. Crystal structure and spectroscopic behavior of synthetic novgorodovaite Ca2(C2O4)Cl2·2H2O and its twinned triclinic heptahydrate analog

    Piro, Oscar E.; Echeverría, Gustavo A.; González-Baró, Ana C.; Baran, Enrique J.

    2018-02-01

    Synthetic novgorodovaite analog Ca2(C2O4)Cl2·2H2O is identical to its natural counterpart. It crystallizes in the monoclinic I2/ m space group with a = 6.9352(3), b = 7.3800(4), c = 7.4426(3) Å, β = 94.303(4)°, V = 379.85(3) Å3 and Z = 2. The heptahydrate analog, Ca2(C2O4)Cl2·7H2O, crystallizes as triclinic twins in the P \\overline{1} space group with a = 7.3928(8), b = 8.9925(4), c = 10.484(2) Å, α = 84.070(7), β = 70.95(1), γ = 88.545(7)°, V = 655.3(1) Å3 and Z = 2. The crystal packing of both calcium oxalate-chloride double salts favors the directional bonding of oxalate, C2O4 2-, ligands to calcium ions as do other related calcium oxalate minerals. The π-bonding between C and O atoms of the C2O4 2- oxalate group leaves sp 2-hydridised orbitals of the oxygen atoms available for bonding to Ca. Thus, the Ca-O bonds in both calcium oxalate-chloride double salts are directed so as to lie in the plane of the oxalate group. This behavior is reinforced by the short O···O distances between the oxygens attached to a given carbon atom, which favors them bonding to a shared Ca atom in bidentate fashion. Strong bonding in the plane of the oxalate anion and wide spacing perpendicular to that plane due to repulsion between oxalate π-electron clouds gives rise to a polymerized structural units which are common to both hydrates, explaining the nearly equal cell constants 7.4 Å which are defined by the periodicity of Ca-oxalate chains in the framework (monoclinic b ≈ triclinic a). When compared with novgorodovaite, the higher water content of Ca2(C2O4)Cl2·7H2O leads to some major differences in their structures and ensuing physical properties. While novgorodovaite has a three-dimensional framework structure, in the higher hydrate, the highly polar water molecules displace chloride ions from the calcium coordination sphere and surround them through OwH···Cl hydrogen bonds. As a result, polymerization in Ca2(C2O4)Cl2·7H2O solid is limited to the formation

  10. Attikaite, Ca3Cu2Al2(AsO4)4(OH)4 · 2H2O, a new mineral species

    Chukanov, N. V.; Pekov, I. V.; Zadov, A. E.

    2007-12-01

    Attikaite, a new mineral species, has been found together with arsenocrandalite, arsenogoyazite, conichalcite, olivenite, philipsbornite, azurite, malachite, carminite, beudantite, goethite, quartz, and allophane at the Christina Mine No. 132, Kamareza, Lavrion District, Attiki Prefecture (Attika), Greece. The mineral is named after the type locality. It forms spheroidal segregations (up to 0.3 mm in diameter) consisting of thin flexible crystals up to 3 × 20 × 80 μm in size. Its color is light blue to greenish blue, with a pale blue streak. The Mohs’ hardness is 2 to 2.5. The cleavage is eminent mica-like parallel to {001}. The density is 3.2(2) g/cm3 (measured in heavy liquids) and 3.356 g/cm3 (calculated). The wave numbers of the absorption bands in the infrared spectrum of attikaite are (cm-1; sh is shoulder; w is a weak band): 3525 sh, 3425, 3180, 1642, 1120 w, 1070 w, 1035 w, 900 sh, 874, 833, 820, 690 w, 645 w, 600 sh, 555, 486, 458, and 397. Attikaite is optically biaxial, negative, α = 1.642(2), β = γ = 1.644(2) ( X = c) 2 V means = 10(8)°, and 2 V calc = 0°. The new mineral is microscopically colorless and nonpleochroic. The chemical composition (electron microprobe, average over 4 point analyses, wt %) is: 0.17 MgO, 17.48 CaO, 0.12 FeO, 16.28 CuO, 10.61 Al2O3, 0.89 P2O5, 45.45 As2O5, 1.39 SO3, and H2O (by difference) 7.61, where the total is 100.00. The empirical formula calculated on the basis of (O,OH,H2O)22 is: Ca2.94Cu{1.93/2+} Al1.97Mg0.04Fe{0.02/2+} [(As3.74S0.16P0.12)Σ4.02O16.08](OH)3.87 · 2.05H2 O. The simplified formula is Ca3Cu2Al2(AsO4)4(OH)4 · 2H2O. Attikaite is orthorhombic, space group Pban, Pbam or Pba2; the unit-cell dimensions are a = 10.01(1), b = 8.199(5), c = 22.78(1) Å, V = 1870(3) Å3, and Z = 4. In the result of the ignition of attikaite for 30 to 35 min at 128 140°, the H2O bands in the IR spectrum disappear, while the OH-group band is not modified; the weight loss is 4.3%, which approximately corresponds to two H2O

  11. Electrical Conductivity of Cancrinite-Type Na8 - 2 x Ca x [Al6Si6O24][CO3] · 2H2O ( x ≤ 0.03) Crystals

    Sorokin, N. I.

    2018-05-01

    The electrical conductivity of crystals of artificial cancrinite Na8 - 2 x Ca x [Al6Si6O24][CO3] · 2H2O ( x ≤ 0.03) has been studied in the temperature range of 498-604 K. These crystals were grown by hydrothermal synthesis on a seed in the Na2O-Al2O3-SiO2-H2O system ( t = 380-420°C, P = 3 × 107-9 × 107 Pa). The ionic conductivity of a single-crystal sample (sp. gr. P63), measured along the crystallographic axis c, is low: σ = 8 × 10-7 S/cm at 300°C. The electric transport activation energy is E a = 0.81 ± 0.05 eV. The relationship between the ionic conductivity and specific features of the atomic structure of cancrinites is discussed.

  12. Thermal gravimetric analysis of the CsCuCl3, Cs2CuCl4 and Cs2CuCl4x2H2O crystals

    Soboleva, L.V.; Vasil'eva, M.G.

    1977-01-01

    The thermal characteristics of crystals of Cs 2 CuCl 4 , Cs 2 CuCl 4 x2H 2 O, and CsCuCl 3 were investigated thermogravimetrically. The derivatogram of the Cs 2 CuCl 4 crystal is characterized by the presence of a single endothermal effect at 505 deg C. The derivatogram of the Cs 2 CuCl 4 x2H 2 O crystal contains three endothermal effects: at 40, 135, and 480 deg C. The derivatogram of the CsCuCl 3 crystal shows the presence of two endothermal effects at 142 and 455 deg C. The thermogravimetric data on Cs 2 CuCl 4 and CsCuCl 3 crystals reveal crystal decomposition on melting; hence, these crystals cannot be grown from melts

  13. Self-assembly of red-blood-cell-like (NH4)[Fe2(OH)(PO4)2]·2H2O architectures from 2D nanoplates by sonochemical method.

    Wu, Kaipeng; Liu, Diwei; Tang, Yun

    2018-01-01

    Red-blood-cell-like (RBC-like) (NH 4 )[Fe 2 (OH)(PO 4 ) 2 ]·2H 2 O architectures assembled from 2D nanoplates are successfully synthesized via a facile sonochemical method. XRD measurement indicates that the as-prepared sample is well crystallized with a monoclinic structure. The morphology of the sample is characterized by SEM analysis, which shows that the (NH 4 )[Fe 2 (OH)(PO 4 ) 2 ]·2H 2 O particles exhibit a unique biconcave red blood cell morphology with an average diameter of 4um and thickness of 1.5um. The detailed time-dependent experiments are conducted to investigate the morphological evolution process. It reveals that the ultrasonic time is crucial to the morphology of the products, and the RBC-like (NH 4 )[Fe 2 (OH)(PO 4 ) 2 ]·2H 2 O proceeds in steps of crystallization, formation of thin plates, and the subsequent self-assembly. Compared to the available methods that are typically time-consuming and complicated, this smart sonochemical strategy proposed herein is efficient and simple. Moreover, these obtained special RBC-like architectures will be more fascinating for application in many areas. Copyright © 2017 Elsevier B.V. All rights reserved.

  14. Thermal, spectroscopic and magnetic properties of the Co xNi1-x(SeO3).2H2O (x = 0, 0.4, 1) phases

    Larranaga, A.; Mesa, J.L.; Pizarro, J.L.; Pena, A.; Chapman, J.P.; Arriortua, M.I.; Rojo, T.

    2005-01-01

    The Co x Ni 1-x (SeO 3 ).2H 2 O (x = 0, 0.4, 1) family of compounds has been hydrothermally synthesized under autogeneous pressure and characterized by elemental analysis, infrared and UV-vis spectroscopies and thermogravimetric and thermodiffractometric techniques. The crystal structure of Co 0.4 Ni 0.6 (SeO 3 ).2H 2 O has been solved from single-crystal X-ray diffraction data. This phase is isostructural with the M(SeO 3 ).2H 2 O (M = Co and Ni) minerals and crystallizes in the P2 1 /n space group, with a 6.4681(7), b = 8.7816(7), c = 7.5668(7) A, β = 98.927(9) deg and Z = 4. The crystal structure of this series of compounds consists of a three-dimensional framework formed by (SeO 3 ) 2- selenite oxoanions and edge-sharing M 2 O 10 dimeric octahedra in which the metallic cations are coordinated by the oxygens belonging to both the selenite groups and water molecules. The diffuse reflectance spectra show the essential characteristics of Co(II) and Ni(II) cations in slightly distorted octahedral environments. The calculated values of the Dq and Racah (B and C) parameters are those habitually found for the 3d 7 and 3d 8 cations in octahedral coordination. The magnetic measurements indicate the existence of antiferromagnetic interactions in all the compounds. The magnetic exchange pathways involve the metal orbitals from edge-sharing dimeric octahedra and the (SeO 3 ) 2- anions which are linked to the M 2 O 10 polyhedra in three dimensions

  15. Controllable synthesis of (NH4)Fe2(PO4)2(OH)·2H2O using two-step route: Ultrasonic-intensified impinging stream pre-treatment followed by hydrothermal treatment.

    Dong, Bin; Li, Guang; Yang, Xiaogang; Chen, Luming; Chen, George Z

    2018-04-01

    (NH 4 )Fe 2 (PO 4 ) 2 (OH)·2H 2 O samples with different morphology are successfully synthesized via two-step synthesis route - ultrasonic-intensified impinging stream pre-treatment followed by hydrothermal treatment (UIHT) method. The effects of the adoption of ultrasonic-intensified impinging stream pre-treatment, reagent concentration (C), pH value of solution and hydrothermal reaction time (T) on the physical and chemical properties of the synthesised (NH 4 )Fe 2 (PO 4 ) 2 (OH)·2H 2 O composites and FePO 4 particles were systematically investigated. Nano-seeds were firstly synthesized using the ultrasonic-intensified T-mixer and these nano-seeds were then transferred into a hydrothermal reactor, heated at 170 °C for 4 h. The obtained samples were characterized by utilising XRD, BET, TG-DTA, SEM, TEM, Mastersizer 3000 and FTIR, respectively. The experimental results have indicated that the particle size and morphology of the obtained samples are remarkably affected by the use of ultrasonic-intensified impinging stream pre-treatment, hydrothermal reaction time, reagent concentration, and pH value of solution. When such (NH 4 )Fe 2 (PO 4 ) 2 (OH)·2H 2 O precursor samples were transformed to FePO 4 products after sintering at 650 °C for 10 h, the SEM images have clearly shown that both the precursor and the final product still retain their monodispersed spherical microstructures with similar particle size of about 3 μm when the samples are synthesised at the optimised condition. Copyright © 2017 Elsevier B.V. All rights reserved.

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

    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

  17. Thermodynamic properties of scorodite and parascorodite (FeAsO4 center dot 2H(2)O), kankite (FeAsO4 center dot 3.5H(2)O), and FeAsO4

    Majzlan, J.; Drahota, P.; Filippi, Michal; Grevel, K.-D.; Kahl, W.-A.; Plášil, J.; Boerio-Goates, J.; Woodfield, B. F.

    117/118, April (2012), s. 47-56 ISSN 0304-386X Institutional research plan: CEZ:AV0Z30130516 Keywords : scorodite * ferric arsenates * formation enthalpy * entropy * solubility Subject RIV: DD - Geochemistry Impact factor: 2.169, year: 2012

  18. Determination and modeling for the solubility of Na_2MoO_4·2H_2O in the (Na"+ + MoO_4"2"− + SO_4"2"−) system

    Ning, Pengge; Xu, Weifeng; Cao, Hongbin; Lin, Xiao; Xu, Hongbin

    2016-01-01

    Highlights: • The solubility of Na_2MoO_4·2H_2O in Na"+ + MoO_4"2"− + SO_4"2"− system was performed. • The new model was established via regressing the published and the determined data. • The Pitzer parameter and the solubility product constant of the salts in solution were calculated. • The model was applied to estimate the solubility of the sodium molybdate in various conditions. - Abstract: The solubility of Na_2MoO_4·2H_2O in (Na"+ + MoO_4"2"− + SO_4"2"−) system was carried out using a dynamic method within the temperature range from 293.15 K to 343.15 K. The new model was established via regression of the published and the determined values to predict the solubility. From the results, the solubility of sodium molybdate increases with the temperature increase, however, it decreases with the increasing concentration of sodium sulfate. The Pitzer parameters and the solubility product constant of sodium sulfate and sodium molybdate in aqueous solution were obtained using the literature data. The solubilities of the sodium molybdate in the sodium sulfate solution as well as the thermodynamic parameters were calculated based on the experimental values obtained. The new model was also applied to estimate the solubility of the sodium molybdate under various conditions. The calculated values agree well with the experiment results.

  19. Synthesis and crystal structure of a new neodymium(III) selenate-selenite: Nd2(SeO4)(SeO3)2(H2O)2

    Feng Meiling; Mao Jianggao

    2005-01-01

    The title new neodymium(III) selenate-selenite was obtained by hydrothermal reactions of neodymium(III) oxide, H 2 SeO 4 and 1,10-phenanthroline at 140 o C. Its structure was established by single-crystal X-ray diffraction. The title compound crystallizes in the monoclinic space group C2/c with cell parameters of a = 12.258(2) A, b 7.1024(15) A, c = 13.391(3) A, β = 104.250(2) o . The structure of Nd 2 (SeO 4 )(SeO 3 ) 2 (H 2 O) 2 is isomorphous with that of Er 2 (SeO 4 )(SeO 3 ) 2 (H 2 O) 2 , which was refined in the monoclinic space group C2 with the disordered selenate group. It features an ordered 3D network with channels along b-axis. The selenate or selenite groups alone can form a 2D layer with the Nd(III) ions. IR spectrum, TGA and luminescent studies have also been performed

  20. Investigation of dehydration reaction of BaCl2.2H2O and SrCl2.6H2O by thermal analysis under pressure

    Homma, Tsuneyuki; Yamada, Tetsuo

    1978-01-01

    The dehydration reactions of BaCl 2 .2H 2 O and SrCl 2 .6H 2 O were investigated by the techniques of thermal analysis, i.e. thermogravimetry (TG and DTG) and differential thermal analysis (DTA) under pressures of 1, 4, 10 and 40 atm. For BaCl 2 .2H 2 O, the DTA curves showed two peaks at 1 atm and three or four peaks at pressures above 4 atm, and the TG curves showed two steps over the range of 1 -- 10 atm and 3 steps at 40 atm. For SrCl 2 .6H 2 O, the DTA curves showed five peaks at respective pressure, and the TG curves showed three steps at 1 atm and two steps at pressures above 4 atm. As a common effect of pressure to the dehydration of these two salts, DTG peaks and some of DTA peaks shifted to higher temperatures with a increase in pressure, but a few peaks remained unshifted on DTA curves in spite of increasing pressure. The peaks which corresponded to these unshifted peaks on DTA curves were not observed on DTG curves. The unshifted peaks on DTA curves were attributed to the endothermic reaction accompanied by the dissociation of coordination water. The DTA and TG curves suggested that both salts formed the intermediate state between anhydrous and monohydrate states. (auth.)

  1. KNOWLEDGE AND MISCONCEPTIONS OF PULMONARY TUBERCULOSIS PATIENTS AT DOTS CENTRE, URBAN MEERUT.

    R Bansal

    2013-06-01

    Full Text Available Background: India is the second most populated country in the world; it has more new TB cases annually than any other country. In 2008, 1.98 million were estimated to have occurred in India, of whom 0.87 million were infectious cases, thus amounting to a fifth of the global burden of TB.With the entire country geographically covered under the DOTS program, research into socioeconomic impact of TB on patients and their households is crucial for providing comprehensive patient-friendly TB services and to document the benefits of DOTS. Objective: The present study was undertaken with the following objectives: (1 To determine the socio-demographic variables of registered patients for DOTS Treatment at Urban Health Training center Meerut. (2 To assess knowledge, awareness and attitude regarding Pulmonary Tuberculosis and its treatment among the patients. Materials and Methods: A cross-sectional study of 200 TB patients was done using a pre-tested semi-quantitative questionnaire in UHTC Meerut Period of Study: During 2010-2012. Results: Knowledge and awareness regarding Pulmonary Tuberculosis in patients at DOTS centre, Urban Meerut was very poor. There is a great need to educate the people about misconceptions like food and utensils as mode of transmission. BCC using the person to person contact in community , at health center and awareness campaigns are crucial in educating the ignorance seen in our field practice area. Conclusion: Poor knowledge and misconceptions concerning tuberculosis was quite concern in the patients. TB control program will remain ineffective unless myths and fears of TB patients are addressed related to causation of tuberculosis, mode of spread, and methods of prevention.

  2. KNOWLEDGE AND MISCONCEPTIONS OF PULMONARY TUBERCULOSIS PATIENTS AT DOTS CENTRE, URBAN MEERUT.

    R Bansal

    2013-08-01

    Full Text Available Background: India is the second most populated country in the world; it has more new TB cases annually than any other country. In 2008, 1.98 million were estimated to have occurred in India, of whom 0.87 million were infectious cases, thus amounting to a fifth of the global burden of TB.With the entire country geographically covered under the DOTS program, research into socioeconomic impact of TB on patients and their households is crucial for providing comprehensive patient-friendly TB services and to document the benefits of DOTS. Objective: The present study was undertaken with the following objectives: (1 To determine the socio-demographic variables of registered patients for DOTS Treatment at Urban Health Training center Meerut. (2 To assess knowledge, awareness and attitude regarding Pulmonary Tuberculosis and its treatment among the patients. Materials and Methods: A cross-sectional study of 200 TB patients was done using a pre-tested semi-quantitative questionnaire in UHTC Meerut Period of Study: During 2010-2012. Results: Knowledge and awareness regarding Pulmonary Tuberculosis in patients at DOTS centre, Urban Meerut was very poor. There is a great need to educate the people about misconceptions like food and utensils as mode of transmission. BCC using the person to person contact in community , at health center and awareness campaigns are crucial in educating the ignorance seen in our field practice area. Conclusion: Poor knowledge and misconceptions concerning tuberculosis was quite concern in the patients. TB control program will remain ineffective unless myths and fears of TB patients are addressed related to causation of tuberculosis, mode of spread, and methods of prevention.

  3. Preparation of Zr(Mo,W)2O8 with a larger negative thermal expansion by controlling the thermal decomposition of Zr(Mo,W)2(OH,Cl)2∙2H2O.

    Petrushina, Mariya Yu; Dedova, Elena S; Filatov, Eugeny Yu; Plyusnin, Pavel E; Korenev, Sergei V; Kulkov, Sergei N; Derevyannikova, Elizaveta A; Sharafutdinov, Marat R; Gubanov, Alexander I

    2018-03-28

    Solid solutions of Zr(Mo,W) 2 O 7 (OH,Cl) 2 ∙2H 2 O with a preset ratio of components were prepared by a hydrothermal method. The chemical composition of the solutions was determined by energy dispersive X-ray spectroscopy (EDX). For all the samples of ZrMo x W 2-x O 7 (OH,Cl) 2 ∙2H 2 O (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0, 1.2, 1.4, 1.6, 1.8, and 2.0), TGA and in situ powder X-ray diffraction (PXRD) studies (300-1100 K) were conducted. For each case, the boundaries of the transformations were determined: Zr(Mo,W) 2 O 7 (OH,Cl) 2 ∙2H 2 O → orthorhombic-ZrMo x W 2-x O 8 (425-525 K), orthorhombic-ZrMo x W 2-x O 8  → cubic-ZrMo x W 2-x O 8 (700-850 K), cubic-ZrMo x W 2-x O 8  → trigonal-ZrMo x W 2-x O 8 (800-1050 K for x > 1) and cubic-ZrMo x W 2-x O 8  → oxides (1000-1075 K for x ≤ 1). The cell parameters of the disordered cubic-ZrMo x W 2-x O 8 (space group Pa-3) were measured within 300-900 K, and the thermal expansion coefficients were calculated: -3.5∙10 -6  - -4.5∙10 -6  K -1 . For the ordered ZrMo 1.8 W 0.2 O 8 (space group P2 1 3), a negative thermal expansion (NTE) coefficient -9.6∙10 -6  K -1 (300-400 K) was calculated. Orthorhombic-ZrW2O 8 is formed upon the decomposition of ZrW 2 O 7 (OH,Cl) 2 ∙2H 2 O within 500-800 K.

  4. Structures, physicochemical and cytoprotective properties of new oxidovanadium(IV) complexes -[VO(mIDA)(dmbipy)]·1.5H2O and [VO(IDA)(dmbipy)]·2H2O

    Drzeżdżon, Joanna; Jacewicz, Dagmara; Wyrzykowski, Dariusz; Inkielewicz-Stępniak, Iwona; Sikorski, Artur; Tesmar, Aleksandra; Chmurzyński, Lech

    2017-09-01

    New oxidovanadium(IV) complexes with a modification of the ligand in the VO2+ coordination sphere were synthesized. [VO(mIDA)(dmbipy)]•1.5H2O and [VO(IDA)(dmbipy)]•2H2O were obtained as dark green crystals and grey-green powder, respectively (mIDA = N-methyliminodiacetic anion, IDA = iminodiacetic anion, dmbipy = 4,4‧-dimethoxy-2,2‧-dipyridyl). The crystal structure of [VO(mIDA)(dmbipy)]·1.5H2O has been determined by the X-ray diffraction method. The studies of structure of [VO(mIDA)(dmbipy)]•1.5H2O have shown that this compound occurs in the crystal as two rotational conformers. Furthermore, the stability constants of [VO(mIDA)(dmbipy)]•1.5H2O and [VO(IDA)(dmbipy)]•2H2O complexes in aqueous solutions were studied by using the potentiometric titration method and, consequently, determined using the Hyperquad2008 program. Moreover, the title complexes were investigated as antioxidant substances. The impact of the structure modification in the VO2+ complexes on the radical scavenging activity has been studied. The ability to scavenge the superoxide radical by two complexes - [VO(mIDA)(dmbipy)]·1.5H2O and [VO(IDA)(dmbipy)]·2H2O was studied by cyclic voltammetry (CV) and nitrobluetetrazolium (NBT) methods. The title complexes were also examined by the spectrophotometric method as scavengers of neutral organic radical - 1,1-diphenyl-2-picrylhydrazyl (DPPH•) and radical cation - 2,2'-azinobis-(3-ethylbenzothiazoline)-6-sulfonic acid (ABTS•+). Furthermore, the biological properties of two oxidovanadium(IV) complexes were investigated in relation to its cytoprotective properties by the MTT and LDH tests based on the hippocampal HT22 neuronal cell line during the oxidative damage induced by hydrogen peroxide. Finally, the results presented in this paper have shown that the both new oxidovanadium(IV) complexes with the 4,4‧-dimethoxy-2,2‧-dipyridyl ligand can be treated as the cytoprotective substances.

  5. Coordination polymers of scandium sulfate. Crystal structures of (H2Bipy)[Sc(H2O)(SO4)2]2·2H2O and (H2Bipy)[HSO4]2

    Petrosyants, S.P.; Ilyukhin, A.B.

    2005-01-01

    Compounds with general formula Cat x [Sc(H 2 O) z (SO 4 ) y ]·nH 2 O (Cat=NH 4 , H 2 Bipy (Bipy - 4,4'-bipyridine), HEdp (Edp - ethylene dipyridine)) identified on element analysis data and IR spectra are synthesized. X-ray diffraction analysis of (H 2 Bipy)[Sc(H 2 O)(SO 4 ) 2 ] 2 ·2H 2 O shows that in structure of the compound chains of ScO 6 octahedron and SO 4 tetrahedrons are joined in bands by tridentate coordination of sulfate ions. Bands form skeleton in endless emptiness of which there are H 2 Bipy 2+ cations [ru

  6. DNA-Binding Study of Tetraaqua-bis(p-nitrobenzoatocobalt(II Dihydrate Complex: [Co(H2O4(p-NO2C6H4COO2]·2H2O

    Hacali Necefoglu

    2007-06-01

    Full Text Available The interaction of [Co(H2O4(p-NO2C6H4COO2]. 2H2O with sheep genomicDNA has been investigated by spectroscopic studies and electrophoresis measurements.The interaction between cobalt(II p-nitrobenzoate and DNA has been followed by gelelectrophoresis while the concentration of the complex was increased from 0 to 14 mM.The spectroscopic study and electrophoretic experiments support the fact that the complexbinds to DNA by intercalation via p-nitrobenzoate into the base pairs of DNA. Themobility of the bands decreased as the concentration of complex was increased, indicatingthat there was increase in interaction between the metal ion and DNA.

  7. A Study of the Spin-State Transition and Phase Transformation in [Fe(bpp)(2)][CF(3)SO(3)](2).H(2)O and [Fe(bpp)(2)][BF(4)](2) Using Mn(2+) Electron Spin Resonance.

    Sung, Raymond C. W.; McGarvey, Bruce R.

    1999-08-09

    X-band ESR powder studies have been done on the spin transition in Mn(2+)-doped [Fe(bpp)(2)][CF(3)SO(3)](2).H(2)O and [Fe(bpp)(2)][BF(4)](2) (bpp = 2,6-bis(pyrazol-3-yl) pyridine). The change in D value of Mn(2+) during the thermally induced high-spin (HS) low-spin (LS) transition shows that the spin transition is accompanied by a phase transformation involving a domain mechanism. Irradiation experiments at 77 K have shown that a LS --> HS spin change occurs without a change in the crystalline phase. The rate of the change from the HS phase to the LS phase in the vicinity of 100 K has been measured and is found to be the same as that measured for the corresponding spin change obtained from Mössbauer spectroscopy and magnetic susceptibility studies.

  8. SYNTHESIS AND STRUCTURAL CHARACTERISTICS OF BIS(CITRATEGERMANATES(IV (Hbipy2[Ge(HCit2]•2H2O AND [CuCl(bipy2]2[Ge(HCit2]•8H2O

    Inna Seifullina

    2016-12-01

    Full Text Available The crystalline compounds (Hbipy2[Ge(HCit2]·2H2O (1 and CuCl(bipy2]2[Ge(HCit2]·8H2O (2 (where H4Cit is citric acid, bipy is 2,2ʹ-bipyridine were obtained for the fi rst time and their structures were determined by the single-crystal X-ray diffraction method. Compounds were characterized by IR spectroscopy, thermogravimetric (TGA and elemental analyses. Both compounds are formed with complex bis(citrategermanate anion and protonated 2,2’-bipyridine or [Cu(bipy2Cl]+ as cations in compounds 1 and 2, respectively.

  9. Examination of the Effects of Activated Carbon Produced from Coal Using Single-Step H3PO4/N2+H2O Vapor Activation on the Adsorption of Bovine Serum Albumin at Different Temperatures and pH Values

    Atakan Toprak

    2017-12-01

    Full Text Available This study examined protein adsorption equilibrium and kinetics on activated carbon (AC that we obtained from coal by single-step H3PO4 activation under N2+H2O vapor at 800 °C. Surface properties, pore size distribution, and volumes of AC were determined using the volumetric method with N2 adsorption at 77 K. Also, the textural properties were characterized by SEM-EDAX and XRD. The zeta potential values were measured to elucidate the electrostatic interactions between the protein and AC. The obtained AC discrete system was also used as an adsorbent for adsorbing bovine serum albumin (BSA from aqueous solution. The effects of pH (4.0, 5.0, and 7.4 and temperatures (20, 30 and 40 °C on the adsorption of BSA on AC were examined. The surface area, micropore, mesopore and total pore volumes of AC were found to be 1175 m2/g, 0.477 cm3/g, 0.061 cm3/g and 0.538 cm3/g, respectively. The optimum temperature for AC in BSA adsorption was found to be 40 °C and the pH was found to be 4.0. The highest BSA adsorption was found to be 159 mg/g and pH to be 4.0. The experimental equilibrium data were compared with the Langmuir and Freundlich models and found to be compatible with both models. The adsorption process is best described by the pseudo-first-order kinetic model. As a result, it was found out that AC obtained by single step H3PO4/N2+H2O vapor activation is an effective adsorbent for the adsorption of BSA from aqueous solution.

  10. Thermodynamic Modeling of Poorly Complexing Metals in Concentrated Electrolyte Solutions: An X-Ray Absorption and UV-Vis Spectroscopic Study of Ni(II) in the NiCl2-MgCl2-H2O System

    Zhang, Ning; Brugger, Joël; Etschmann, Barbara; Ngothai, Yung; Zeng, Dewen

    2015-01-01

    Knowledge of the structure and speciation of aqueous Ni(II)-chloride complexes is important for understanding Ni behavior in hydrometallurgical extraction. The effect of concentration on the first-shell structure of Ni(II) in aqueous NiCl2 and NiCl2-MgCl2 solutions was investigated by Ni K edge X-ray absorption (XAS) and UV-Vis spectroscopy at ambient conditions. Both techniques show that no large structural change (e.g., transition from octahedral to tetrahedral-like configuration) occurs. Both methods confirm that the Ni(II) aqua ion (with six coordinated water molecules at R Ni-O = 2.07(2) Å) is the dominant species over the whole NiCl2 concentration range. However, XANES, EXAFS and UV-Vis data show subtle changes at high salinity (> 2 mol∙kg-1 NiCl2), which are consistent with the formation of small amounts of the NiCl+ complex (up to 0.44(23) Cl at a Ni-Cl distance of 2.35(2) Å in 5.05 mol∙kg-1 NiCl2) in the pure NiCl2 solutions. At high Cl:Ni ratio in the NiCl2-MgCl2-H2O solutions, small amounts of [NiCl2]0 are also present. We developed a speciation-based mixed-solvent electrolyte (MSE) model to describe activity-composition relationships in NiCl2-MgCl2-H2O solutions, and at the same time predict Ni(II) speciation that is consistent with our XAS and UV-Vis data and with existing literature data up to the solubility limit, resolving a long-standing uncertainty about the role of chloride complexing in this system. PMID:25885410

  11. The first 3D malonate bridged copper [Cu(O2C–CH2–CO2H)2·2H2O]: Structure, properties and electronic structure

    Seguatni, A.; Fakhfakh, M.; Smiri, L.S.; Gressier, P.; Boucher, F.; Jouini, N.

    2012-01-01

    A new inorganic-organic compound [Cu(O 2 C–CH 2 –CO 2 H) 2 ·2H 2 O] ([Cumal]) was hydrothermally synthesized and characterized by IR spectroscopy, thermal analysis and single crystal X-ray diffraction. [Cumal] is the first three-dimensional compound existing in the system Cu(II)–malonic acid–H 2 O. Its framework is built up through carboxyl bridged copper where CuO 6 octahedra are elongated with an almost D 4h symmetry (4+2) due to the Jahn–Teller effect. The magnetic properties were studied by measuring its magnetic susceptibility in the temperature range of 2–300 K indicating the existence of weak ferromagnetic interactions. The electronic structure of [Cumal] was calculated within the density functional theory (DFT) framework. Structural features are well reproduced using DFT structural optimizations and the optical spectra, calculated within the dielectric formalism, explain very well the light blue colour of the compound. It is shown that a GGA+U approach with a U eff value of about 6 eV is necessary for a better correlation with the experiment. - Graphical abstract: [Cu(O 2 C–CH 2 –CO 2 H) 2 ·2H 2 O]: the first 3D hybrid organic–inorganic compound built up carboxyl groups. The network presents a diamond-like structure achieved via carboxyl. Highlights: ► A new organic–inorganic material with an unprecedented topology is synthesized. ► Crystallographic structure is determined using single crystal X-ray diffraction. ► Electronic structure is obtained from DFT, GGA+U calculation. ► Framework can be described as formed from CuC 4 tetrahedron sharing four corners. ► This structure can be classified as an extended diamond structure.

  12. The effect of carbonic anhydrase on the kinetics and equilibrium of the oxygen isotope exchange in the CO2-H2O system: Implications for δ18O vital effects in biogenic carbonates

    Uchikawa, Joji; Zeebe, Richard E.

    2012-10-01

    Interpretations of the primary paleoceanographic information recorded in stable oxygen isotope values (δ18O) of biogenic CaCO3 can be obscured by disequilibrium effects. CaCO3 is often depleted in 18O relative to the δ18O values expected for precipitation in thermodynamic equilibrium with ambient seawater as a result of vital effects. Vital effects in δ18O have been explained in terms of the influence of fluid pH on the overall δ18O of the sum of dissolved inorganic carbon (DIC) species (often referred to as "pH model") and in terms of 18O depletion as a result of the kinetic effects associated with CO2 hydration (CO2 + H2O ↔ H2CO3 ↔ HCO3- + H+) and CO2 hydroxylation (CO2 + OH- ↔ HCO3-) in the calcification sites (so-called "kinetic model"). This study addresses the potential role of an enzyme, carbonic anhydrase (CA), that catalyzes inter-conversion of CO2 and HCO3- in relation to the underlying mechanism of vital effects. We performed quantitative inorganic carbonate precipitation experiments in order to examine the changes in 18O equilibration rate as a function of CA concentration. Experiments were performed at pH 8.3 and 8.9. These pH values are comparable to the average surface ocean pH and elevated pH levels observed in the calcification sites of some coral and foraminiferal species, respectively. The rate of uncatalyzed 18O exchange in the CO2-H2O system is governed by the pH-dependent DIC speciation and the kinetic rate constant for CO2 hydration and hydroxylation, which can be summarized by a simple mathematical expression. The results from control experiments (no CA addition) are in agreement with this expression. The results from control experiments also suggest that the most recently published kinetic rate constant for CO2 hydroxylation has been overestimated. When CA is present, the 18O equilibration process is greatly enhanced at both pH levels due to the catalysis of CO2 hydration by the enzyme. For example, the time required for 18O

  13. Ferroelectric phase transition in hydrogen-bonded 2-aminopyridine phosphate (NC sub 4 H sub 4 NH sub 2)centre dot H sub 3 PO sub 4

    Czapla, Z; Waskowska, A

    2003-01-01

    A new crystal of 2-aminopyridine phosphate (NC sub 4 H sub 4 NH sub 2)centre dot H sub 3 PO sub 4 has been grown and its x-ray structure and physical properties were studied. At room temperature the crystals are monoclinic, space group C2/c. The flat 2-aminopyridine cations are hydrogen bonded to the anionic [PO sub 4 ] groups. The interesting feature of the crystal structure is the three-dimensional network of hydrogen bonds including, among others, two strong, symmetrical O centre dot centre dot centre dot H, H centre dot centre dot centre dot O interactions with disordered proton locations. Symmetrically related PO sub 4 anions linked through these protons form infinite (PO sub 4) subinfinity chains along the crystal a-axis. The anomalies in the temperature dependence of the electric permittivity showed that the crystal undergoes ferroelectric phase transition at T sub c = 103.5 K. The spontaneous polarization takes place along the crystal a-axis, being parallel to the chains of the hydrogen-bonded PO sub ...

  14. Hydrothermal synthesis of copper zirconium phosphate hydrate [Cu(OH)2Zr(HPO4)2·2H2O] and an investigation of its lubrication properties in grease.

    Zhang, Xiaosheng; Xu, Hong; Zuo, Zhijun; Lin, Zhi; Ferdov, Stanislav; Dong, Jinxiang

    2013-08-28

    Copper zirconium phosphate hydrate (Cu(OH)2Zr(HPO4)2·2H2O, hereafter referred to as Cu-α-ZrP) with high crystallinity was directly synthesized in a NaF-CuO-ZrO-P2O5-H2O system under hydrothermal conditions. The copper ion was confirmed to be an exchangeable cation in the Cu-α-ZrP through elemental analysis and a proton ion exchange process. The crystal structure of the Cu-α-ZrP was determined ab initio by using X-ray powder diffraction data. In the structure, the CuO6 octahedron would be located in an exchangeable atom position. Moreover, Cu-α-ZrP was evaluated as an additive in grease in a four ball test. The maximum nonseizure load (PB, representing the load-carrying capacity) of the base grease containing Cu-α-ZrP was increased from 353 to 1235 N. The excellent load-carrying capacity may be explained by the easier adherence of the material to the worn surface forming a tight protective film.

  15. Study of defects in solids. I. Chemical effects related to the (n,γ) reaction and electron capture. II. dehydration of Ba(ClO3)2,H2O

    Mathieu, J.-P.

    1975-01-01

    The first part of this work concerns the Moessbauer effect study of two groups of phenomena: those related to the (n,γ) reaction and those connected with radioactive disintegration of 57 Co by electron capture. Hf compounds were chosen for the first group, and a chemical study was also devoted to the effects of the (n,γ) reaction in organic complexes of Cr(III). Nuclear recoil and thermal annealing of these compounds were investigated. For the second group an attempt was made to show the effects of the environment on the chemical state of the 57 Fe detected. In part two the Ba(ClO 3 ) 2 ,H 2 O dehydratation mechanism was examined by quadrupolar nuclear resonance. By this technique, combined with X-ray diffraction and Raman spectroscopy, the effects of dehydration on the characteristics of the quadrupolar interaction and on the crystal structure of the compound were demonstrated. A model of the dehydration process is proposed [fr

  16. First identification and thermodynamic characterization of the ternary U(VI) species, UO2(O2)(CO3)2(4-), in UO2-H2O2-K2CO3 solutions.

    Goff, George S; Brodnax, Lia F; Cisneros, Michael R; Peper, Shane M; Field, Stephanie E; Scott, Brian L; Runde, Wolfgang H

    2008-03-17

    In alkaline carbonate solutions, hydrogen peroxide can selectively replace one of the carbonate ligands in UO2(CO3)3(4-) to form the ternary mixed U(VI) peroxo-carbonato species UO2(O2)(CO3)2(4-). Orange rectangular plates of K4[UO2(CO3)2(O2)].H2O were isolated and characterized by single crystal X-ray diffraction studies. Crystallographic data: monoclinic, space group P2(1)/ n, a = 6.9670(14) A, b = 9.2158(10) A, c = 18.052(4) A, Z = 4. Spectrophotometric titrations with H 2O 2 were performed in 0.5 M K 2CO 3, with UO2(O2)(CO3)2(4-) concentrations ranging from 0.1 to 0.55 mM. The molar absorptivities (M(-1) cm(-1)) for UO2(CO3)3(4-) and UO2(O2)(CO3)2(4-) were determined to be 23.3 +/- 0.3 at 448.5 nm and 1022.7 +/- 19.0 at 347.5 nm, respectively. Stoichiometric analyses coupled with spectroscopic comparisons between solution and solid state indicate that the stable solution species is UO2(O2)(CO3)2(4-), which has an apparent formation constant of log K' = 4.70 +/- 0.02 relative to the tris-carbonato complex.

  17. A 2D rhomboidal system of manganese(ii) [Mn(3-MeC6H4COO)2(H2O)2]n with spin canting: rationalization of the magnetic exchange.

    Garcia-Cirera, Beltzane; Costa, Ramon; Moreira, Ibério de P R; Font-Bardia, Mercè; Corbella, Montserrat

    2018-03-12

    The crystal structure of Mn(ii) carboxylate with 3-methylbenzoate as a bridging ligand [Mn(3-MeC 6 H 4 COO) 2 (H 2 O) 2 ] n shows a rhomboidal layer, where each pair of neighbor Mn(ii) ions are bridged through only one carboxylate group with a syn-anti conformation. The magnetic exchange between neighbor ions is weakly antiferromagnetic (J = -0.52 cm -1 , g = 2.04), and at low temperature the system shows spin canting with T B = 3.8 K. Computational studies, based on periodic calculations of the energies of the significant spin states on the magnetic cell and some higher supercells, corroborate the weak AF interaction between the adjacent Mn(ii) ions and preclude the negligible effect of frustration caused by very weak interactions between the non-adjacent ions in the magnetic response of the system. The results provide compelling evidence that the observed spin canting is due to the local coordination geometry of the manganese ions leading to two antiferromagnetically coupled subnets with different axial vectors.

  18. Bulk modulus of basic sodalite, Na8[AlSiO4]6(OH)2·2H2O, a possible zeolitic precursor in coal-fly-ash-based geopolymers

    Oh, Jae Eun

    2011-01-01

    Synthetic basic sodalite, Na8[AlSiO4] 6(OH)2•2H2O, cubic, P43n, (also known as hydroxysodalite hydrate) was prepared by the alkaline activation of amorphous aluminosilicate glass, obtained from the phase separation of Class F fly ash. The sample was subjected to a process similar to geopolymerization, using high concentrations of a NaOH solution at 90 °C for 24 hours. Basic sodalite was chosen as a representative analogue of the zeolite precursor existing in Na-based Class F fly ash geopolymers. To determine its bulk modulus, high-pressure synchrotron X-ray powder diffraction was applied using a diamond anvil cell (DAC) up to a pressure of 4.5 GPa. A curve-fit with a truncated third-order Birch-Murnaghan equation of state with a fixed K\\'o = 4 to pressure-normalized volume data yielded the isothermal bulk modulus, K o = 43 ± 4 GPa, indicating that basic sodalite is more compressible than sodalite, possibly due to a difference in interactions between the framework host and the guest molecules. © 2010 Elsevier Ltd.

  19. Facile and Scalable Synthesis of Zn3V2O7(OH)2·2H2O Microflowers as a High-Performance Anode for Lithium-Ion Batteries.

    Yan, Haowu; Luo, Yanzhu; Xu, Xu; He, Liang; Tan, Jian; Li, Zhaohuai; Hong, Xufeng; He, Pan; Mai, Liqiang

    2017-08-23

    The employment of nanomaterials and nanotechnologies has been widely acknowledged as an effective strategy to enhance the electrochemical performance of lithium-ion batteries (LIBs). However, how to produce nanomaterials effectively on a large scale remains a challenge. Here, the highly crystallized Zn 3 V 2 O 7 (OH) 2 ·2H 2 O is synthesized through a simple liquid phase method at room temperature in a large scale, which is easily realized in industry. Through suppressing the reaction dynamics with ethylene glycol, a uniform morphology of microflowers is obtained. Owing to the multiple reaction mechanisms (insertion, conversion, and alloying) during Li insertion/extraction, the prepared electrode delivers a remarkable specific capacity of 1287 mA h g -1 at 0.2 A g -1 after 120 cycles. In addition, a high capacity of 298 mA h g -1 can be obtained at 5 A g -1 after 1400 cycles. The excellent electrochemical performance can be attributed to the high crystallinity and large specific surface area of active materials. The smaller particles after cycling could facilitate the lithium-ion transport and provide more reaction sites. The facile and scalable synthesis process and excellent electrochemical performance make this material a highly promising anode for the commercial LIBs.

  20. Hydrothermal synthesis, structural elucidation, spectroscopic studies, thermal behavior and luminescence properties of a new 3-d compound: FeAlF2(C10H8N2)(HPO4)2(H2O)

    Bouzidia, Nabaa; Salah, Najet; Hamdi, Besma; Ben Salah, Abdelhamid

    2017-04-01

    The study of metal phosphate has been a proactive field of research thanks to its applied and scientific importance, especially in terms of the development of optical devices such as solid state lasers as well as optical fibers. The present paper seeks to investigate the synthesis, crystal structure, elemental analysis and properties of FeAlF2(C10H8N2)(HPO4)2(H2O) compound investigated by spectroscopic studies (FT-IR and FT-Raman), thermal behavior and luminescence. The Hirshfeld surface analysis and 2-D fingerprint plot have been performed to explore the behavior of these weak interactions and crystal cohesion. This investigation shows that the molecules are connected by hydrogen bonds of the type Osbnd H⋯O and Osbnd H⋯F. In addition, the 2,2'‒bipyridine ligand plays a significant role in the construction of 3-D supramolecular framework via π‒π stacking. FT‒IR and FT‒Raman spectra were used so as to ease the responsibilities of the vibration modes of the title compound. The thermal analysis (TGA) study shows a mass loss evolution as a temperature function. Finally, the optical properties were evaluated by photoluminescence spectroscopy.

  1. Synthesis, crystal structures, and characterization of double complex salts [Au(en)2][Rh(NO2)6]·2H2O and [Au(en)2][Rh(NO2)6

    Plyusnin, Pavel E.; Makotchenko, Evgenia V.; Shubin, Yury V.; Baidina, Iraida A.; Korolkov, Ilya V.; Sheludyakova, Liliya A.; Korenev, Sergey V.

    2015-11-01

    Double complex salts of rhodium(III) and gold(III) of the composition [Au(en)2][Rh(NO2)6]·2H2O (1) and [Au(en)2][Rh(NO2)6] (2) have been prepared. Crystal structures of the compounds have been determined by single crystal X-ray diffraction. The compounds have been characterized by PXRD, IR, far-IR, CHN and DTA. The complexes have a layered structures. The presence of water in 1 makes the structure of the hydrated DCS less dense as compared to the anhydrous one. The environment of the cation and the anion in the two structures is the same, oxygen atoms of the nitro groups are involved in hydrogen bonds N-H⋯O, N⋯O distances being approximately the same. The structures of 1 and 2 are notable in having shortened contacts between the gold atoms and the oxygen atoms of the nitro groups of the neighboring complex anions. The thermal behavior of the complexes in a hydrogen atmosphere was investigated. The final product of thermolysis prepared at the temperature 600°C is a two-phase mixture of pure metallic gold and the solid solution Rh0.93Au0.07.

  2. Symmetry and topology code of the cluster self-assembly of framework MT structures of alumophosphates AlPO4(H2O)2 (metavariscite and variscite) and Al2(PO4)2(H2O)3 (APC)

    Ilyushin, G. D.; Blatov, V. A.

    2017-03-01

    The supramolecular chemistry of alumophosphates, which form framework 3D MT structures from polyhedral AlO4(H2O)2 clusters with octahedral O coordination (of M polyhedra) and PO4 and AlO4 with tetrahedral O coordination (of T polyhedra), is considered. A combinatorial-topological modeling of the formation of possible types of linear (six types) and ring (two types) tetrapolyhedral cluster precursors M2T2 from MT monomers is carried out. Different versions of chain formation from linked (MT)2 rings (six types) are considered. The model, which has a universal character, has been used to simulate the cluster selfassembly of the crystal structure of AlPO4(H2O)2 minerals (metavariscite, m-VAR, and variscite, VAR) and zeolite [Al2(PO4)2(H2O)2] · H2O (APC). A tetrapolyhedral linear precursor is established for m-VAR and a ring precursor (MT)2 is established for VAR and APC. The symmetry and topology code of the processes of crystal structure self-assembly from cluster precursors is completely reconstructed. The functional role of the O-H···O hydrogen bonds is considered for the first time. The cluster self-assembly model explains the specific features of the morphogenesis of single crystals: m-VAR prisms, flattened VAR octahedra, and needleshaped APC square-base prisms.

  3. Hydrothermal synthesis, thermal, structural, spectroscopic and magnetic studies of the Mn5-x Co x (HPO4)2(PO4)2(H2O)4 (x=1.25, 2, 2.5 and 3) finite solid solution

    Larrea, Edurne S.; Mesa, Jose L.; Pizarro, Jose L.; Arriortua, Maria I.; Rojo, Teofilo

    2007-01-01

    The Mn 5- x Co x (HPO 4 ) 2 (PO 4 ) 2 (H 2 O) 4 (x=1.25, 2, 2.5, 3) finite solid solution has been synthesized by mild hydrothermal conditions under autogeneous pressure. The phases crystallize in the C2/c space group with Z=4, belonging to the monoclinic system. The unit-cell parameters obtained from single crystal X-ray diffraction are: a=17.525(1), b=9.0535(6), c=9.4517(7) A, β=96.633(5) o being R1=0.0436, wR2=0.0454 for Mn75Co25; a=17.444(2), b=9.0093(9), c=9.400(1) A, β=96.76(1) o being R1=0.0381, wR2=0.0490 for Mn60Co40; a=17.433(2), b=8.9989(9), c=9.405(1) A, β=96.662(9) o being R1=0.0438, wR2=0.0515 for Mn50Co50 and a=17.4257(9), b=8.9869(5), c=9.3935(5) A, β=96.685(4) o being R1=0.0296, wR2=0.0460 for Mn40Co60. The structure consists of a three dimensional network formed by octahedral pentameric entities (Mn,Co) 5 O 16 (H 2 O) 6 sharing vertices with the (PO 4 ) 3- and (HPO 4 ) 2- tetrahedra. The limit of thermal stability of these compounds is, approximately, 165 deg. C, near to this mean temperature the phases loose their water content in two successive steps. IR spectra show the characteristic bands of the water molecules and the phosphate and hydrogen-phosphate oxoanions. The diffuse reflectance spectra are consistent with the presence of MO 6 octahedra environments in slightly distorted octahedral geometry, except for the M(3)O 6 octahedron which presents a remarkable distortion and so a higher Dq parameter. The mean value for the Dq and B-Racah parameter for the M(1),(2)O 6 octahedra is 685 and 850 cm -1 , respectively. These parameters for the most distorted M(3)O 6 polyhedron are 825 and 880 cm -1 , respectively. The four phases exhibit antiferromagnetic couplings as the major magnetic interactions. However, a small spin canting phenomenon is observed at low temperatures for the two phases with major content in the anisotropic-Co(II) cation. - Graphical abstract: Crystal structure of the finite solid solution Mn 5-x Co x (HPO 4 ) 2 (PO 4 ) 2 (H

  4. A novel highly efficient adsorbent {[Co4(L)2(μ3-OH)2(H2O)3(4,4‧-bipy)2]·(H2O)2}n: Synthesis, crystal structure, magnetic and arsenic (V) absorption capacity

    Zhang, Chong; Xiao, Yu; Qin, Yan; Sun, Quanchun; Zhang, Shuhua

    2018-05-01

    A novel highly efficient adsorbent-microporous tetranuclear Co(II)-based polymer, {[Co4(L)2(μ3-OH)2(H2O)3(4,4‧-bipy)2]·(H2O)2}n (1, H3L = 4-(N,N‧-bis(4-carboxybenzyl)amino) benzenesulfonic acid, 4,4‧-bipy = 4,4‧-bipyridine), was hydrothermally synthesized. The complex 1 is a metal-organic framework (MOF) material which was characterized by single-crystal X-ray diffraction, BET and platon software. Co-MOF (complex 1) reveals excellent adsorption property. The capacity of Co-MOF to remove arsenic As(V) from sodium arsenate aqueous solutions was investigated (The form of As(V) is AsO43-). The experimental results showed that Co-MOF had a higher stable and relatively high As(V) removal rate (> 98%) at pH 4-10. The adsorption kinetics followed a pseudo-second-order kinetic model, and the adsorption isotherm followed the Langmuir equation. Co-MOF exhibits a very high adsorption capacity of As(V) in aqueous solution (Qmax of 96.08 mg/g). Finally, the optimal adsorption conditions for the model were obtained through a Box-Behnken response surface experiment which was designed with adsorption time, dose, temperature and rotational speed of the shaker as the influencing factors to determine two-factor interaction effects. Co-MOF was further characterized using FTIR, PXRD, X-ray photoelectron spectroscopy before and after adsorption As (V). The magnetism of Co-MOF was also discussed.

  5. X-Ray Diffraction and μ-Raman Investigation of the Monoclinic-Orthorhombic Phase Transition in Th1-xUx(C2O4)2. 2H2O Solid Solutions

    Clavier, N.; Dacheux, N.; Clavier, N.; Hingant, N.; Dacheux, N.; Barre, N.; Rivenet, M.; Obbade, S.; Abraham, F.

    2010-01-01

    A complete Th 1-x U x (C 2 O 4 ) 2 . 2H 2 O solid solution was prepared by mild hydrothermal synthesis from a mixture of hydrochloric solutions containing cations and oxalic acid. The crystal structure has been solved from twinned single crystals for x=0, 0. 5, and 1 with monoclinic symmetry, space group C2/c, leading to unit cell parameters of a ≅ to 10. 5 Angstroms, b ≅ 8. 5 Angstrom, and c ≅ 9. 6 Angstrom. The crystal structure consists of a two-dimensional arrangement of actinide centers connected through bis-bidentate oxalate ions forming squares. The actinide metal is coordinated by eight oxygen atoms from four oxalate entities and two water oxygen atoms forming a bi-capped square anti-prism. The connection between the layers is assumed by hydrogen bonds between the water molecules and the oxygen of oxalate of an adjacent layer. Under these conditions, the unit cell contains two independent oxalate ions. From high-temperature μ-Raman and X-ray diffraction studies, the compounds were found to undergo a transition to an orthorhombic form (space group Ccca). The major differences in the structural arrangement concern the symmetry of uranium, which decreases from C2 to D2, leading to a unique oxalate group. Consequently, the ν s (C-O) double band observed in the Raman spectra recorded at room temperature turned into a singlet. This transformation was then used to make the phase transition temperature more precise as a function of the uranium content of the sample. (authors)

  6. Estudo de oxidação avançada de corantes básicos via reação Fenton (Fe2+/H2O2

    Thiago Romário Soares Paulino

    2015-09-01

    Full Text Available RESUMOO processo de oxidação avançada do tipo reação Fenton (Fe2+/H2O2 foi estudado neste trabalho para descoloração de dois efluentes sintéticos, contendo os corantes Azul de Metileno (AM e Rodamina B (RB. Experimentalmente, soluções em concentração de 10 mg L-1 dos corantes foram submetidas a diferentes dosagens de agente oxidante (H2O2 e catalisador (Fe2+ em uma temperatura de 27 °C e pH 3. Os resultados obtidos apresentaram altos níveis de remoção de cor, com eficiência da ordem de 96% para o AM e 86% no RB. Os dados mostraram bom ajuste ao modelo cinético. O monitoramento do espectro de absorção dos corantes mostrou uma diminuição da amplitude dos picos relacionados aos grupos cromóforos em ambos compostos, corroborando com os níveis de eficiência alcançados. A análise de remoção de matéria orgânica em termos de Demanda Química de Oxigênio (DQO não acompanhou a mesma taxa de decréscimo de descoloração, obtendo-se reduções de 40,9% para o AM e 25,5% para o RB.

  7. Two-component, ab initio potential energy surface for CO2—H2O, extension to the hydrate clathrate, CO2@(H2O)20, and VSCF/VCI vibrational analyses of both

    Wang, Qingfeng Kee; Bowman, Joel M.

    2017-10-01

    We report an ab initio, full-dimensional, potential energy surface (PES) for CO2—H2O, in which two-body interaction energies are fit using a basis of permutationally invariant polynomials and combined with accurate potentials for the non-interacting monomers. This approach which we have termed "plug and play" is extended here to improve the precision of the 2-body fit in the long range. This is done by combining two separate fits. One is a fit to 47 593 2-body energies in the region of strong interaction and approaching the long range, and the second one is a fit to 6244 2-body energies in the long range. The two fits have a region of overlap which permits a smooth switch from one to the other. All energies are obtained at the CCSD(T)-F12b/aug-cc-pVTZ level of theory. Properties of the full PES, i.e., stationary points, harmonic frequencies of the global minimum, etc., are shown to be in excellent agreement with direct CCSD(T)-F12b/aug-cc-pVTZ results. Diffusion Monte Carlo calculations of the dimer zero-point energy (ZPE) are performed, and a dissociation energy, D0, of 787 cm-1 is obtained using that ZPE, De, and the rigorous ZPEs of the monomers. Using a benchmark De, D0 is 758 cm-1. Vibrational self-consistent field (VSCF)/virtual state configuration interaction (VCI) MULTIMODE calculations of intramolecular fundamentals are reported and are in good agreement with available experimental results. Finally, the full dimer PES is combined with an existing ab initio water potential to develop a potential for the CO2 hydrate clathrate CO2(H2O)20(512 water cage). A full normal-mode analysis of this hydrate clathrate is reported as are local-monomer VSCF/VCI calculations of the fundamentals of CO2.

  8. X-Ray diffraction and mu-Raman investigation of the monoclinic-orthorhombic phase transition in Th(1-x)U(x)(C(2)O(4))(2).2H(2)O solid solutions.

    Clavier, Nicolas; Hingant, Nina; Rivenet, Murielle; Obbade, Saïd; Dacheux, Nicolas; Barré, Nicole; Abraham, Francis

    2010-02-15

    A complete Th(1-x)U(x)(C(2)O(4))(2).2H(2)O solid solution was prepared by mild hydrothermal synthesis from a mixture of hydrochloric solutions containing cations and oxalic acid. The crystal structure has been solved from twinned single crystals for x = 0, 0.5, and 1 with monoclinic symmetry, space group C2/c, leading to unit cell parameters of a approximately 10.5 A, b approximately 8.5 A, and c approximately 9.6 A. The crystal structure consists of a two-dimensional arrangement of actinide centers connected through bis-bidentate oxalate ions forming squares. The actinide metal is coordinated by eight oxygen atoms from four oxalate entities and two water oxygen atoms forming a bicapped square antiprism. The connection between the layers is assumed by hydrogen bonds between the water molecules and the oxygen of oxalate of an adjacent layer. Under these conditions, the unit cell contains two independent oxalate ions. From high-temperature mu-Raman and X-ray diffraction studies, the compounds were found to undergo a transition to an orthorhombic form (space group Ccca). The major differences in the structural arrangement concern the symmetry of uranium, which decreases from C2 to D2, leading to a unique oxalate group. Consequently, the nu(s)(C-O) double band observed in the Raman spectra recorded at room temperature turned into a singlet. This transformation was then used to make the phase transition temperature more precise as a function of the uranium content of the sample.

  9. Bulk Kosterlitz-Thouless Type Molecular Superconductor β″-(BEDT-TTF)2[(H2O)(NH4)2Cr(C2O4)3]·18-crown-6.

    Martin, Lee; Lopez, Jordan R; Akutsu, Hiroki; Nakazawa, Yasuhiro; Imajo, Shusaku

    2017-11-20

    A new molecular superconductor, β″-(BEDT-TTF) 2 [(H 2 O)(NH 4 ) 2 Cr(C 2 O 4 ) 3 ]·18-crown-6, has been synthesized from the organic donor molecule BEDT-TTF with the anion Cr(C 2 O 4 ) 3 3- . The crystal structure consists of conducting organic layers of BEDT-TTF molecules which adopt the β″ packing motif (layer A), layers of NH 4 + and Λ-Cr(C 2 O 4 ) 3 3- (layer B), layers of (H 2 O)(NH 4 )18-crown-6 (layer C), and layers of NH 4 + and Δ-Cr(C 2 O 4 ) 3 3- (layer D) which produce a superstructure with a repeating pattern of ABCDABCDA. As a result of this packing arrangement, this is the 2D superconductor with the widest gap between conducting layers where only a single donor packing motif is present (β″). Superconducting critical temperatures at ambient pressure observed by electrical transport and magnetic measurements are 4.0-4.9 and 2.5 K, respectively. The strong 2D nature of this system, the broad transition to T zero at 1.8K, and the transition of α of V ∝ I α from 1 to 3 on I-V curves strongly suggest that the superconducting transition is very close to a Kosterlitz-Thouless transition. The magnetic field dependence of the superconducting critical temperature parallel to the conducting plane gives an upper critical field μ 0 H c2∥ > 8 T, which is over the calculated Pauli-Clogston limit for this material.

  10. Single-molecule magnets: structure and properties of [Mn18O14(O2CMe)18(hep)4(hepH)2(H2O)2](ClO4)2 with spin S = 13.

    Brechin, E K; Sañudo, E C; Wernsdorfer, W; Boskovic, C; Yoo, J; Hendrickson, D N; Yamaguchi, A; Ishimoto, H; Concolino, T E; Rheingold, A L; Christou, G

    2005-02-07

    The reaction of 2-(hydroxyethyl)pyridine (hepH) with a 2:1 molar mixture of [Mn3O(O2CMe)6(py)3]ClO4 and [Mn3O(O2CMe)6(py)3] in MeCN afforded the new mixed-valent (16Mn(III), 2Mn(II)), octadecanuclear complex [Mn18O14(O2CMe)18(hep)4(hepH)2(H2O)2](ClO4)2 (1) in 20% yield. Complex 1 crystallizes in the triclinic space group P. Direct current magnetic susceptibility studies in a 1.0 T field in the 5.0-300 K range, and variable-temperature variable-field dc magnetization studies in the 2.0-4.0 K and 2.0-5.0 T ranges were obtained on polycrystalline samples. Fitting of magnetization data established that complex 1 possesses a ground-state spin of S = 13 and D = -0.18 K. This was confirmed by the value of the in-phase ac magnetic susceptibility signal. Below 3 K, the complex exhibits a frequency-dependent drop in the in-phase signal, and a concomitant increase in the out-of-phase signal, consistent with slow magnetization relaxation on the ac time scale. This suggests the complex is a single-molecule magnet (SMM), and this was confirmed by hysteresis loops below 1 K in magnetization versus dc field sweeps on a single crystal. Alternating current and direct current magnetization data were combined to yield an Arrhenius plot from which was obtained the effective barrier (U(eff)) for magnetization reversal of 21.3 K. Below 0.2 K, the relaxation becomes temperature-independent, consistent with relaxation only by quantum tunneling of the magnetization (QTM) through the anisotropy barrier via the lowest-energy MS = +/-13 levels of the S = 13 spin manifold. Complex 1 is thus the SMM with the largest ground-state spin to display QTM.

  11. Local structure of Rb2Li4(SeO4)3·2H2O by the modeling of X-ray diffuse scattering — from average-structure to microdomain model

    Komornicka, Dorota; Wołcyrz, Marek; Pietraszko, Adam

    2012-01-01

    Local structure of dirubidium tetralithium tris(selenate(VI)) dihydrate — Rb 2 Li 4 (SeO 4 ) 3 · 2H 2 O has been determined basing on the modeling of X-ray diffuse scattering. The origin of observed structured diffuse streaks is SeO 4 tetrahedra switching between two alternative positions in two quasi-planar layers existing in each unit cell and formation of domains with specific SeO 4 tetrahedra configuration locally fulfilling condition for C-centering in the 2a×2b×c superstructure cell. The local structure solution is characterized by a uniform distribution of rather large domains (ca. thousand of unit cells) in two layers, but also monodomains can be taken into account. Inside a single domain SeO 4 tetrahedra are ordered along ab-diagonal forming two-string ribbons. Inside the ribbons SeO 4 and LiO 4 tetrahedra share the oxygen corners, whereas ribbons are bound to each other by a net of hydrogen bonds and fastened by corner sharing SeO 4 tetrahedra of the neighboring layers. - Graphical abstract: Experimental sections of the reciprocal space showing diffraction effects observed for RLSO. Bragg spots are visible on sections with integer indices (1 kl section — on the left), streaks — on sections with fractional ones (1.5 kl section — on the right). At the center: resulting local structure of the A package modeled as a microdomain: two-string ribbons of ordered oxygen-corners-sharing SeO 4 and LiO 4 terahedra extended along ab-diagonal are seen; ribbons are bound by hydrogen bonds (shown in pink); the multiplied 2a×2b unit cell is shown. Highlights: ► X-ray diffuse scattering in RLSO was registered and modeled. ► The origin of diffuse streaks is SeO 4 tetrahedra switching in two structure layers. ► The local structure is characterized by a uniform distribution of microdomains. ► Inside a single domain SeO 4 tetrahedra are ordered along ab-diagonal forming ribbons. ► The ribbons are bound to each other by a net of hydrogen bonds.

  12. Carbonate mineral solubility at low temperatures in the Na-K-Mg-Ca-H-Cl-SO 4-OH-HCO 3-CO 3-CO 2-H 2O system

    Marion, Giles M.

    2001-06-01

    Carbonate minerals have played an important role in the geochemical evolution of Earth, and may have also played an important role in the geochemical evolution of Mars and Europa. Several models have been published in recent years that describe chloride and sulfate mineral solubilities in concentrated brines using the Pitzer equations. Few of these models are parameterized for subzero temperatures, and those that are do not include carbonate chemistry. The objectives of this work are to estimate Pitzer-equation bicarbonate-carbonate parameters and carbonate mineral solubility products and to incorporate them into the FREZCHEM model to predict carbonate mineral solubilities in the Na-K-Mg-Ca-H-Cl-SO 4-OH-HCO 3-CO 3-CO 2-H 2O system at low temperatures (≤25°C) with a special focus on subzero temperatures. Most of the Pitzer-equation parameters and equilibrium constants are taken from the literature and extrapolated into the subzero temperature range. Solubility products for 14 sodium, potassium, magnesium, and calcium bicarbonate and carbonate minerals are included in the model. Most of the experimental data are at temperatures ≥ -8°C; only for the NaHCO 3-NaCl-H 2O and Na 2CO 3-NaCl-H 2O systems are there bicarbonate and carbonate data to temperatures as low as -21.6°C. In general, the fit of the model to the experimental data is good. For example, calculated eutectic temperatures and compositions for NaHCO 3, Na 2CO 3, and their mixtures with NaCl and Na 2SO 4 salts are in good agreement with experimental data to temperatures as low as -21.6°C. Application of the model to eight saline, alkaline carbonate waters give predicted pHs ranging from 9.2 to 10.2, in comparison with measured pHs that range from 8.7 to 10.2. The model suggests that the CaCO 3 mineral that precipitates during seawater freezing is probably calcite and not ikaite. The model demonstrates that a proposed salt assemblage for the icy surface of Europa consisting of highly hydrated MgSO 4

  13. Nanodiamond-based nanostructures for coupling nitrogen-vacancy centres to metal nanoparticles and semiconductor quantum dots.

    Gong, Jianxiao; Steinsultz, Nat; Ouyang, Min

    2016-06-08

    The ability to control the interaction between nitrogen-vacancy centres in diamond and photonic and/or broadband plasmonic nanostructures is crucial for the development of solid-state quantum devices with optimum performance. However, existing methods typically employ top-down fabrication, which restrict scalable and feasible manipulation of nitrogen-vacancy centres. Here, we develop a general bottom-up approach to fabricate an emerging class of freestanding nanodiamond-based hybrid nanostructures with external functional units of either plasmonic nanoparticles or excitonic quantum dots. Precise control of the structural parameters (including size, composition, coverage and spacing of the external functional units) is achieved, representing a pre-requisite for exploring the underlying physics. Fine tuning of the emission characteristics through structural regulation is demonstrated by performing single-particle optical studies. This study opens a rich toolbox to tailor properties of quantum emitters, which can facilitate design guidelines for devices based on nitrogen-vacancy centres that use these freestanding hybrid nanostructures as building blocks.

  14. Synthetic, spectroscopic and structural studies on 4-aminobenzoate complexes of divalent alkaline earth metals: x-ray crystal structures of [[Mg(H2O)6] (4-aba)2].2H2O and [Ca(H2O)2(4-aba)2] (4-aba=4-aminobenzoate)

    Murugavel, Ramaswamy; Karambelkar, Vivek V.; Anantharaman, Ganapathi

    2000-01-01

    Reactions between MCl 2 .nH 2 O (M = Mg, Ca, Sr, and Ba) and 4-aminobenzoic acid (4-abaH) result in the formation of complexes [(Mg(H 2 O) 6 )(4-aba) 2 ) .2H 2 O (I), [Ca(4-aba) 2 (H2 O ) 2 ] (2), [Sr(4-aba) 2 (H2 O ) 2 ] (3), and [Ba(4-aba) 2 Cl] (4), respectively. The new compounds 1 and 2, as well as the previously reported 3 and 4 form an extended intra- and intermolecular hydrogen bonded network in the solid-state. The compounds have been characterized by elemental analysis, pH measurements, thermogravimetric studies, and IR, NMR, and UV-Vis spectroscopy. The solid state structures of the molecules 1 and 2 have been determined by single crystal x-ray diffraction studies. In the case of magnesium complex 1, the dipositively charged Mg cation is surrounded by six water molecules and the two 4-aminobenzoate ligands show no direct bonding to the metal ion. The calcium ion in 2 is octa-coordinated with direct coordination of the 4-aminobenzoate ligands to the metal ion. The Ca-Ca separation in the polymeric chain of 2 is 3.9047(5) A. (author)

  15. Competition of the Peierls relief and structural defects in damping the domain walls in [Mn left brace (R/S)-pn right brace]2[Mn left brace(R/S)-pn right brace2(H2O)][Cr(CN)6]2 ferrimagnet

    Talantsev, A.D.; Kollak, O.V.; Kirman, M.V.; Morgunov, R.B.

    2015-01-01

    The [ [Mn left brace (R/S)-pn right brace] 2 [Mn left brace(R/S)-pn right brace 2 (H 2 O)][Cr(CN) 6 ] 2 molecular ferrimagnet exhibits an inverse sequence of changes in the domain wall motion regimes with increasing temperature in alternative magnetic field of 0.04-1400 Hz frequency. Initiation of the relaxation regime on the background of creep indicates that there are two different systems of the domain walls damping. The threshold amplitude of the alternative magnetic field corresponds to the Peierls relief contribution to the domain wall dynamics as well as the defect contribution usually considered.

  16. The topotactic dehydration of monoclinic {[Co(pht)(bpy)(H2O)2]·2H2O}n into orthorhombic [Co(pht)(bpy)(H2O)2]n (pht is phthalate and bpy is 4,4'-bipyridine).

    Harvey, Miguel Angel; Suarez, Sebastián; Cukiernik, Fabio D; Baggio, Ricardo

    2014-10-01

    Controlled heating of single crystals of the previously reported [Köferstein & Robl (2007). Z. Anorg. Allg. Chem. 633, 1127-1130] dihydrate {[Co(pht)(bpy)(H2O)2]·2H2O}n, (II) [where pht is phthalate (C8H4O4) and bpy is 4,4'-bipyridine (C10H8N2)], produced a topotactic transformation into an unreported diaqua anhydrate, namely poly[diaqua(μ2-benzene-1,2-dicarboxylato-κ(2)O(1):O(2))(μ2-4,4'-bipyridine-κ(2)N:N')cobalt(II)], [Co(C8H4O4)(C10H8N2)(H2O)2]n, (IIa). The structural change consists of the loss of the two solvent water molecules linking the original two-dimensional covalent substructures which are the `main frame' of the monoclinic P2/n hydrate (strictly preserved during the transformation), with further reaccommodation of the latter. The anhydrate organizes itself in the orthorhombic system (space group Pmn2(1)) in a disordered fashion, where the space-group-symmetry restrictions are achieved only in a statistical sense, with mirror-related two-dimensional planar substructures, mirrored in a plane perpendicular to [100]. Thus, the asymmetric unit in the refined model is composed of two superimposed mirror-related `ghosts' of half-occupancy each. Similarities and differences with the parent dihydrate and some other related structures in the literature are discussed.

  17. New family of lanthanide-based inorganic-organic hybrid frameworks: Ln2(OH)4[O3S(CH2)nSO3]·2H2O (Ln = La, Ce, Pr, Nd, Sm; n = 3, 4) and their derivatives.

    Liang, Jianbo; Ma, Renzhi; Ebina, Yasuo; Geng, Fengxia; Sasaki, Takayoshi

    2013-02-18

    We report the synthesis and structure characterization of a new family of lanthanide-based inorganic-organic hybrid frameworks, Ln(2)(OH)(4)[O(3)S(CH(2))(n)SO(3)]·2H(2)O (Ln = La, Ce, Pr, Nd, Sm; n = 3, 4), and their oxide derivatives. Highly crystallized samples were synthesized by homogeneous precipitation of Ln(3+) ions from a solution containing α,ω-organodisulfonate salts promoted by slow hydrolysis of hexamethylenetetramine. The crystal structure solved from powder X-ray diffraction data revealed that this material comprises two-dimensional cationic lanthanide hydroxide {[Ln(OH)(2)(H(2)O)](+)}(∞) layers, which are cross-linked by α,ω-organodisulfonate ligands into a three-dimensional pillared framework. This hybrid framework can be regarded as a derivative of UCl(3)-type Ln(OH)(3) involving penetration of organic chains into two {LnO(9)} polyhedra. Substitutional modification of the lanthanide coordination promotes a 2D arrangement of the {LnO(9)} polyhedra. A new hybrid oxide, Ln(2)O(2)[O(3)S(CH(2))(n)SO(3)], which is supposed to consist of alternating {[Ln(2)O(2)](2+)}(∞) layers and α,ω-organodisulfonate ligands, can be derived from the hydroxide form upon dehydration/dehydroxylation. These hybrid frameworks provide new opportunities to engineer the interlayer chemistry of layered structures and achieve advanced functionalities coupled with the advantages of lanthanide elements.

  18. Variable dimensionality and framework found in a series of quaternary zinc selenites, A2Zn3(SeO3)4·xH2O (A = Na, Rb, and Cs; 0≤x≤1) and Cs2Zn2(SeO3)3·2H2O

    Lü, Minfeng; Jo, Hongil; Oh, Seung-Jin; Ok, Kang Min

    2017-01-01

    Five new alkali metal zinc selenites, A2Zn3(SeO3)4·xH2O (A = Na, Rb, and Cs; 0≤x≤1) and Cs2Zn2(SeO3)3·2H2O have been synthesized by heating a mixture of ZnO, SeO2 and A2CO3 (A = Na, Rb, and Cs), and characterized by X-ray diffraction (XRD) and spectroscopic analyses techniques. All of the reported materials revealed a rich structural chemistry with different frameworks and connection modes of Zn2+. While Rb2Zn3(SeO3)4 and Cs2Zn3(SeO3)4·H2O revealed three-dimensional frameworks consisting of isolated ZnO4 tetrahedra and SeO3 polyhedra, Na2Zn3(SeO3)4, Cs2Zn3(SeO3)4, and Cs2Zn2(SeO3)3·2H2O contained two-dimensional [Zn3(SeO3)4]2- layers. Specifically, whereas isolated ZnO4 tetrahedra and SeO3 polyhedra are arranged into two-dimensional [Zn3(SeO3)4]2- layers in two cesium compounds, circular [Zn3O10]14- chains and SeO3 linkers are formed in two-dimensional [Zn3(SeO3)4]2- layers in Na2Zn3(SeO3)4. Close structural examinations suggest that the size of alkali metal is significant in determining the framework geometry as well as connection modes of transition metal cations.

  19. Ferroelectric TGS ((NH sub 2 CH sub 2 COOH) sub 3 centre dot H sub 2 SO sub 4) under high pressure

    Kobayashi, Y; Furuta, H; Endo, S; Deguchi, K

    2002-01-01

    The ferroelectric transition temperature T sub c of (NH sub 2 CH sub 2 COOH) sub 3 centre dot H sub 2 SO sub 4 (TGS), which is a typical order-disorder-type ferroelectric, was determined by dielectric constant and Raman scattering measurements under high pressure. T sub c increased, passed through a maximum and then decreased slightly with increasing pressure, and then abruptly dropped at about 2.5 GPa, where a transition to a new high-pressure phase was confirmed to exist. A tentative p-T phase diagram was proposed for TGS.

  20. Variable dimensionality and framework found in a series of quaternary zinc selenites, A2Zn3(SeO3)4·xH2O (A = Na, Rb, and Cs; 0≤x≤1) and Cs2Zn2(SeO3)3·2H2O

    Lü, Minfeng; Jo, Hongil; Oh, Seung-Jin; Ok, Kang Min

    2017-01-01

    Five new alkali metal zinc selenites, A 2 Zn 3 (SeO 3 ) 4 ·xH 2 O (A = Na, Rb, and Cs; 0≤x≤1) and Cs 2 Zn 2 (SeO 3 ) 3 ·2H 2 O have been synthesized by heating a mixture of ZnO, SeO 2 and A 2 CO 3 (A = Na, Rb, and Cs), and characterized by X-ray diffraction (XRD) and spectroscopic analyses techniques. All of the reported materials revealed a rich structural chemistry with different frameworks and connection modes of Zn 2+ . While Rb 2 Zn 3 (SeO 3 ) 4 and Cs 2 Zn 3 (SeO 3 ) 4 ·H 2 O revealed three-dimensional frameworks consisting of isolated ZnO 4 tetrahedra and SeO 3 polyhedra, Na 2 Zn 3 (SeO 3 ) 4 , Cs 2 Zn 3 (SeO 3 ) 4 , and Cs 2 Zn 2 (SeO 3 ) 3 ·2H 2 O contained two-dimensional [Zn 3 (SeO 3 ) 4 ] 2- layers. Specifically, whereas isolated ZnO 4 tetrahedra and SeO 3 polyhedra are arranged into two-dimensional [Zn 3 (SeO 3 ) 4 ] 2- layers in two cesium compounds, circular [Zn 3 O 10 ] 14- chains and SeO 3 linkers are formed in two-dimensional [Zn 3 (SeO 3 ) 4 ] 2- layers in Na 2 Zn 3 (SeO 3 ) 4 . Close structural examinations suggest that the size of alkali metal is significant in determining the framework geometry as well as connection modes of transition metal cations. - Graphical abstract: Variable dimensions and frameworks were found in a series of quaternary zinc selenites, A 2 Zn 3 (SeO 3 ) 4 (A = Na, Rb and Cs). - Highlights: • Five novel quaternary zinc selenites are synthesized. • All the selenites with different structures contain polarizable d 10 and lone pair cations. • The size of alkali metal cations is significant in determining the framework geometry.

  1. Ferromagnetic Coupling between Copper(II) Centers through the Diamagnetic Zinc(II) Ion: Crystal Structure and Magnetic Properties of [Cu(2)Zn(Hdmg)(2)(dmg)(2)(H(2)O)].0.5H(2)dmg.H(2)O (H(2)dmg = Dimethylglyoxime).

    Ruiz, Rafael; Julve, Miguel; Faus, Juan; Lloret, Francesc; Muñoz, M. Carmen; Journaux, Yves; Bois, Claudette

    1997-07-30

    A new heterotrinuclear complex of formula [Cu(2)Zn(Hdmg)(2)(dmg)(2)(H(2)O)].0.5H(2)dmg.H(2)O (C(18)H(34)Cu(2)N(9)O(11)Zn, 1) (H(2)dmg = dimethylglyoxime) has been synthesized and its crystal structure determined by single-crystal X-ray diffraction. It crystallizes in the triclinic system, space group P&onemacr;, with a = 11.414(1) Å, b = 11.992(3) Å, c =12.567(10) Å, alpha = 91.27(6) degrees, beta = 111.46(2) degrees, gamma = 112.24(2) degrees, and Z = 2. The structure consists of a chain of neutral [Cu(2)Zn(Hdmg)(2)(dmg)(2)(H(2)O)] trinuclear units and noncoordinated H(2)dmg and water molecules. The configuration around the zinc atom is distorted trigonal bipyramidal with four oximate oxygens from two [Cu(Hdmg)(dmg)](-) fragments (each one acting as a bidentate ligand through its deprotonated oximate oxygens in cis positions) occupying one axial and the three equatorial positions and an additional oximate oxygen from a symmetry-related [Cu(Hdmg)(dmg)](-) fragment filling the remaining axial position. The environment around Cu(1) and Cu(2) is distorted square pyramidal with four oximate nitrogen atoms building the equatorial plane. An oxygen atom [O(9)] from a water molecule and an oximate oxygen from a symmetry-related [Cu(Hdmg)(dmg)](-) fragment occupy the apical position of the square pyramids around Cu(1) and Cu(2), respectively. The trinuclear units are repeated through inversion centers standing at the middle of the Zn(1).Zn(1)(i) and Cu(2).Cu(2)(ii) vectors leading to a chain which runs parallel to the diagonal of the ac-plane. The Cu(1).Cu(2), Zn(1).Zn(1)(i), and Cu(2).Cu(2)(ii) separations are 5.506(2), 3.390(2), and 3.930(2) Å, respectively. 1 exhibits a characteristic ferromagnetic behavior with a continuous increase of the chi(M)T product as the temperature is lowered from 300 to 2.0 K. The field dependence of the magnetization at 2.0 K is consistent with a low-lying quintet state. The only efficient exchange pathways responsible for the overall

  2. Three new d10 transition metal selenites containing PO4 tetrahedron: Cd7(HPO4)2(PO4)2(SeO3)2, Cd6(PO4)1.34(SeO3)4.66 and Zn3(HPO4)(SeO3)2(H2O)

    Ma, Yun-Xiang; Gong, Ya-Ping; Hu, Chun-li; Mao, Jiang-Gao; Kong, Fang

    2018-06-01

    Three new d10 transition metal selenites containing PO4 tetrahedron, namely, Cd7(HPO4)2(PO4)2(SeO3)2 (1), Cd6(PO4)1.34(SeO3)4.66 (2) and Zn3(HPO4)(SeO3)2(H2O) (3), have been synthesized by hydrothermal reaction. They feature three different structural types. Compound 1 exhibits a novel 3D network composed of 3D cadmium selenite open framework with phosphate groups filled in the 1D helical tunnels. The structure of compound 2 displays a new 3D framework consisted of 2D cadmium oxide layers bridged by SeO3 and PO4 groups. Compound 3 is isostructural with the reported solids of Co3(SeO3)3-x(PO3OH)x(H2O) when x is equal to 1.0. Its structure could be viewed as a 3D zinc oxide open skeleton with SeO3 and HPO4 polyhedra attached on the wall of the tunnels. They represent the only examples in metal selenite phosphates in addition to the above cobalt compounds. Optical diffuse reflectance spectra revealed that these solids are insulators, which are consistent with the results of band structure computations based on DFT algorithm.

  3. Investigation into the dehydration of selenate doped Na2M(SO4)2·2H2O (M = Mn, Fe, Co and Ni): Stabilisation of the high Na content alluaudite phases Na3M1.5(SO4)3-1.5x(SeO4)1.5x (M = Mn, Co and Ni) through selenate incorporation

    Driscoll, L. L.; Kendrick, E.; Knight, K. S.; Wright, A. J.; Slater, P. R.

    2018-02-01

    In this paper we report an investigation into the phases formed on dehydration of Na2M(SO4)2-x(SeO4)x·2H2O (0 ≤ x ≤ 1; M = Mn, Fe, Co and Ni). For the Fe series, all attempts to dehydrate the samples doped with selenate resulted in amorphous products, and it is suspected that a side redox reaction involving the Fe and selenate may be occurring leading to phase decomposition and hence the lack of a crystalline product on dehydration. For M = Mn, Co, Ni, the structure observed was shown to depend upon the transition metal cation and level of selenate doping. An alluaudite phase, Na3M1.5(SO4)3-1.5x(SeO4)1.5x, was observed for the selenate doped compositions, with this phase forming as a single phase for x ≥ 0.5 M = Co, and x = 1.0 M = Ni. For M = Mn, the alluaudite structure is obtained across the series, albeit with small impurities for lower selenate content samples. Although the alluaudite-type phases Na2+2y(Mn/Co)2-y(SO4)3 have recently been reported [1,2], doping with selenate appears to increase the maximum sodium content within the structure. Moreover, the selenate doped Ni based samples reported here are the first examples of a Ni sulfate/selenate containing system exhibiting the alluaudite structure.

  4. Removal of pharmaceutically active compounds from synthetic and real aqueous mixtures and simultaneous disinfection by supported TiO2/UV-A, H2O2/UV-A, and TiO2/H2O2/UV-A processes.

    Bosio, Morgana; Satyro, Suéllen; Bassin, João Paulo; Saggioro, Enrico; Dezotti, Márcia

    2018-05-01

    Pharmaceutically active compounds are carried into aquatic bodies along with domestic sewage, industrial and agricultural wastewater discharges. Psychotropic drugs, which can be toxic to the biota, have been detected in natural waters in different parts of the world. Conventional water treatments, such as activated sludge, do not properly remove these recalcitrant substances, so the development of processes able to eliminate these compounds becomes very important. Advanced oxidation processes are considered clean technologies, capable of achieving high rates of organic compounds degradation, and can be an efficient alternative to conventional treatments. In this study, the degradation of alprazolam, clonazepam, diazepam, lorazepam, and carbamazepine was evaluated through TiO 2 /UV-A, H 2 O 2 /UV-A, and TiO 2 /H 2 O 2 /UV-A, using sunlight and artificial irradiation. While using TiO 2 in suspension, best results were found at [TiO 2 ] = 0.1 g L -1 . H 2 O 2 /UV-A displayed better results under acidic conditions, achieving from 60 to 80% of removal. When WWTP was used, degradation decreased around 50% for both processes, TiO 2 /UV-A and H 2 O 2 /UV-A, indicating a strong matrix effect. The combination of both processes was shown to be an adequate approach, since removal increased up to 90%. H 2 O 2 /UV-A was used for disinfecting the aqueous matrices, while mineralization was obtained by TiO 2 -photocatalysis.

  5. Novel optical and structural properties of porous GaAs formed by anodic etching of n±GaAs in a HF:C_2H_5OH:HCl:H_2O_2:H_2O electrolyte: effect of etching time

    Naddaf, M.; Saad, M.

    2014-01-01

    Porous GaAs layers have been formed by anodic etching of n±type GaAs (10.0) substrates in a HF:C_2H_5OH:HCl:H_2O_2:H_2O electrolyte. A dramatic impact of etching time on the optical and structural properties of porous GaAs layer is demonstrated. The nano/micro-features of porous GaAs layers are revealed by scanning electron microscopy (SEM) imaging. Two-peak room temperature photoluminescence (PL), "blue-green"and "green-yellow", is obtained in all prepared porous GaAs samples. Proper adjustment of etching time is found to produce a white color layer, instead of the usual dark gray color of porous GaAs. This is found to cause vast enhancement in the intensity of the visible PL in porous GaAs layer. Chemical composition and structural characterization by means of X-ray photoelectron spectroscopic (XPS), X-ray diffraction (XRD), and micro-Raman spectroscopy, confirm that this layer is characterized with monoclinic β-Ga_2O_3 rich surface. Etching time induced-modification of structural and chemical properties of porous GaAs layer is discussed and correlated to its PL behavior. It is inferred that the "blue-green"PL in porous GaAs can be ascribed to different degrees of quantum confinement in GaAs nano crystallites, whereas, the "green-yellow"PL is highly influenced by the As_2O_3 and Ga_2O_3, content in the porous GaAs layer. In addition, the reflectance measurements reveal an anti-refection trend of behavior of porous GaAs layers in the spectral range (500-1,100 nm). (author)

  6. Crystal and molecular structure of the coordination compounds of Er3+ with 1-(methoxydiphenylphosphoryl)-2-diphenylphosphorylbenzene [ErL21(NO3)2]2[Er(NO3)2(H2O)5]0.333(NO3)2.333 · 2.833H2O and its ethyl substituted derivative [ErL22(NO3)2][Er(NO3)5]0.5 · 0.5H2O

    Polyakova, I. N.; Baulin, V. E.; Ivanova, I. S.; Pyatova, E. N.; Sergienko, V. S.; Tsivadze, A. Yu.

    2015-01-01

    The coordination compounds of Er 3+ with 1-(methoxydiphenylphosphoryl)-2-diphenylphosphorylbenzene [ErL 2 1 (NO 3 ) 2 ] 2 [Er(NO 3 ) 2 (H 2 O) 5 ] 0.333 (NO 3 ) 2.333 · 2.833H 2 O (I) and its ethyl substituted derivative [ErL 2 2 (NO 3 ) 2 ][Er(NO 3 ) 5 ] 0.5 · 0.5H 2 O (II) are synthesized and their crystal structures are studied. I and II contain [ErL 2 (NO 3 ) 2 ] + complex cations of identical composition and close structure. The eight-vertex polyhedron of the Er atom in the shape of a distorted octahedron with two split trans vertices is formed by the O atoms of the phosphoryl groups of L ligands and nitrate anions. L ligands close nine-membered metallocycles. The structures contain spacious channels which are populated differently, namely, by disordered [Er(NO 3 ) 2 (H 2 O) 5 ] + complex cations, NO 3 − anions, and crystallization water molecules in I and disordered [Er(NO 3 ) 5 ] 2− complex anions and crystallization water molecules in II. The IR spectra of I and II are studied

  7. Metamorphic reprocessing of a serpentinized carbonate-bearing peridotite after detachment from the mantle wedge: A P-T path constrained from textures and phase diagrams in the system CaO-MgO-Al 2O 3-SiO 2-CO 2-H 2O

    Mposkos, E.; Baziotis, I.; Proyer, A.

    2010-08-01

    In the central Rhodope mountains of Greece a carbonate-bearing metaperidotite lens ˜ 200 × 500 m in size crops out as part of the high- to ultrahigh-pressure metamorphic Upper Sidironero Complex ˜ 500 m SE of the Gorgona Village, north of Xanthi town. It is composed primarily of coarse grained (3-20 mm in size) olivine and orthopyroxene, medium grained clinohumite and medium to fine grained tremolite, chlorite, dolomite, magnesite, talc, antigorite and various spinel phases. Whole-rock chemistry, mineral textures and compositions, and phase diagram calculations show that the metaperidotite was subjected to a prograde HP metamorphism, isofacial with the surrounding migmatitic gneisses, metapelites and amphibolites. The prograde character of metamorphism is demonstrated by inclusions of talc, antigorite, chlorite, dolomite, magnesite and Ti-clinohumite in ferrit-chromite, olivine, and orthopyroxene, as well as of olivine in orthopyroxene, and by the typical change in composition of zoned spinel minerals from ferrit-chromite in the core to chromian spinel at the rim. The prograde path is characterized by successive growth of amphibole, Ti-clinohumite, olivine and orthopyroxene, followed by the breakdown of Ti-clinohumite to olivine + Mg-ilmenite and of chlorite to olivine + spinel, probably during exhumation. The construction of a partial petrogenetic P- T grid in the system CaO-MgO-Al 2O 3-SiO 2-CO 2-H 2O (CMASCH) for Ca-poor ultramafic bulk compositions has proven highly useful for the reconstruction of the metamorphic evolution and a P- T path, indicating that the use of univariant reactions in mixed volatile systems is highly warranted. The P- T path is clearly constrained to pressures below 1.5-1.7 GPa by the absence of clinopyroxene. These pressures are slightly lower than those recorded in the closely associated Jurassic eclogites and much lower than those recorded in the diamond-bearing gneisses 5 km to the south in the same tectonic unit. The carbonate

  8. NMR investigation on isotope effect of glycinium phosphite H sub 3 NCH sub 2 COOH centre dot H sub 2 PO sub 3

    Ishibashi, T

    2003-01-01

    The motions of the phosphite anions and glycinium cations in H sub 3 NCH sub 2 COOH centre dot H sub 2 PO sub 3 (GPI) and its deuterated analogue (DGPI) were investigated by sup 1 H, sup 1 sup 3 C and sup 3 sup 1 P spin-lattice relaxation times T sub 1. For both GPI and DGPI, T sub 1 's of the sup 1 H, sup 1 sup 3 C and sup 3 sup 1 P nuclei reflect the amino rotation, methylene libration and motion of the phosphite anions, respectively. Activation energies obtained from T sub 1 's of sup 1 H, sup 1 sup 3 C and sup 3 sup 1 P nuclei are 28.6(2), 26.0(4) and 26.2(4) kJ/mol for GPI and are 34.9(6), 27(1), 47(2) kJ/mol for DGPI, respectively. The deuterium substitution increases E sub a for the motion influenced by the hydrogen bonding. In all the observed motions, correlation times of DGPI are larger than those of GPI. (author)

  9. Aspects of the historical development of targetry for heavy ions of 0.05-2000 A centre dot MeV at GSI

    Folger, H

    1999-01-01

    The progressively improved GSI accelerators provide beams of heavy ions from energies of 0.05-2000 A centre dot MeV at high particle intensities now. Therefore, a wide variety of common and new heavy-ion target techniques had to be installed and developed during the past 25 years to prepare and characterize self-supported or backed heavy-ion-targets of chemical elements and compounds from hydrogen (as polyethylene) to uranium. The thickness ranged from 2x10 sup - sup 6 to 20 g/cm sup 2 for beam spots of about 5 mm in diameter. Homogeneity, surface structure or individual shape had to be adapted to the needs of each experiment. Special setups were required for targets of poisonous materials, of highly enriched stable isotopes or those of radioactive species in minute amounts. The capability of thin-layer technologies was as well applied to prepare and measure stripper foils or various high-vacuum deposits for experimental or accelerator purposes. The development of different rotating target wheels and control ...

  10. A study of the x-irradiated Cs sub 5 H sub 3 (SO sub 4) sub 4 centre dot H sub 2 O crystal by EPR in the 80-415 K temperature range

    Waplak, S; Baranov, A I; Shuvalov, L A

    1997-01-01

    The EPR spectra of the x-irradiated fast proton conductor Cs sub 5 H sub 3 (SO sub 4) sub 4 centre dot H sub 2 O were investigated in the temperature range of 80-415 K. Two kinds of paramagnetic SO sub 4 sup - centres with different proton configurations below about 370 K and freeze-out behaviour of one of them below about 200 K were observed. The role of acid proton dynamics with respect to the glassy-like transition is discussed. (author)

  11. Variable dimensionality and new uranium oxide topologies in the alkaline-earth metal uranyl selenites AE[UO2)(SeO3)2] (AE=Ca, Ba) and Sr[UO2)(SeO3)2] · 2H2O

    Almond, Philip M.; Peper, Shane M.; Bakker, Eric; Albrecht-Schmitt, Thomas E.

    2002-01-01

    Three new alkaline-earth metal uranyl selenites, Ca[UO 2 )(SeO 3 ) 2 ] (1), Sr[UO 2 )(SeO 3 ) 2 ] · 2H 2 O (2), and Ba[UO 2 )(SeO 3 ) 2 ] (3), have been prepared from the reactions of CaCO 3 and Ca(OH) 2 , SrCl 2 and Sr(OH) 2 , or BaCl 2 and Ba(OH) 2 with UO 3 and SeO 2 under mild hydrothermal conditions. Single-crystal X-ray diffraction experiments reveal that the structures of 1-3 differ in both connectivity and dimensionality even though all contain the same fundamental building unit, namely [UO 2 (SeO 3 ) 4 ]. This polyhedron consists of a linear uranyl unit that is bound by one chelating and three bridging selenite anions creating a pentagonal bipyramidal environment around the U(VI) center. The crystal structure of 1 contains one-dimensional ribbons where the edges are terminated by monodentate selenite anions. The interior of the ribbons are constructed from edge-sharing pentagonal bipyramidal UO 7 units. The structure of 2 is also one-dimensional; however, here there are chains of edge-sharing pentagonal bipyramidal UO 7 dimers that are connected by bridging selenite anions. Ba[(UO 2 )(SeO 3 ) 2 ] (3) is two-dimensional, and the highly ruffled anionic sheets present in this structure are formed from both bridging and chelating/bridging selenite anions bound to uranyl moieties. The anionic substructures in 1-3 are separated by Ca 2+ , Sr 2+ , or Ba 2+ cations. Crystallographic data (193 K, MoKα, λ=0.71073): 1, triclinic, space group P1-bar, a=5.5502(6) A, b=6.6415(7) A, c=11.013(1) A, α=104.055(2) deg., β=93.342(2) deg., γ=110.589(2) deg. , Z=2, R(F)=4.56% for 100 parameters with 1530 reflections with I>2σ(I); 2, triclinic, space group P1-bar, a=7.0545(5) A, b=7.4656(5) A, c=10.0484(6) A, α=106.995(1) deg., β=108.028(1) deg., γ=98.875(1) deg., Z=2, R(F)= 2.43% for 128 parameters with 2187 reflections with I>2σ(I); 3, monoclinic, space group P2 1 /c, a=7.3067(6) A, b=8.1239(7) A, c=13.651(1) A, β=100.375(2) deg., Z=4, R(F)=4.31% for 105 parameters

  12. TO EVALUATE PREVALENCE OF DIABETES AND HIV IN NEWLY-DIAGNOSED MULTIDRUGRESISTANT TUBERCULOSIS PATIENTS ADMITTED FOR PRETREATMENT EVALUATION IN DOTS PLUS CENTRE, THANJAVUR

    Namasivayam Kuppusamy

    2017-07-01

    Full Text Available BACKGROUND More than 9 million people fall sick with tuberculosis every year in the world. People with weak immune system as a result of disease like diabetes and HIV are at high risk of developing MDR-TB infection. Proper monitoring and evaluation are needed to control MDR-TB in HIV and diabetes patients. The aim of the study is to find the prevalence of diabetes and HIV among MDR-TB patients admitted for pretreatment evaluation in Dots Plus Centre, Thanjavur Medical College, Tamilnadu. MATERIALS AND METHODS The medical records with datas of 96 patients with MDR-TB who are having diabetes and HIV infection were examined. These cases were diagnosed and registered during January 2015 to December 2015. These patients had drug resistant to first line antituberculosis drugs (isoniazid and rifampicin. Duration of diabetes and HIV infection were noted. Age were categorised in to four groups- 20-29 years, 30-39 years, 40-49 years and above 50 years. The potential risk of association of diabetes, HIV or both with MDR-TB was evaluated by univariate conditional logistic regression model. RESULTS Out of 96 newly-diagnosed MDR-TB patients, prevalence of diabetes is about 34.37%, out of which (84.84% were males and (15.15% were females. Out of 34.37%, 38.54% of patients had controlled diabetes, 61.45% patients had uncontrolled diabetes. Nearly, more than half of diabetes patient falls under uncontrolled diabetes. More number of male patients had diabetes with MDR-TB when compared to females. 10.4% of these persons got oral hypoglycaemic agent and 6.3% got insulin as treatment for diabetes. 1% had irregular treatment with poor compliance. Prevalence of HIV is about 4.16% out of which 75% were males and 25% were females. One patient had both diabetes and HIV with MDR tuberculosis. CONCLUSION In our retrospective study, prevalence of diabetes in MDR-TB patients were more common in males than in females, most of them were in the age groups of 40 years and above

  13. Energies and wave functions of an off-centre donor in hemispherical quantum dot: Two-dimensional finite difference approach and ritz variational principle

    Nakra Mohajer, Soukaina; El Harouny, El Hassan [Laboratoire de Physique de la Matière Condensée, Département de Physique, Faculté des Sciences, Université Abdelmalek Essaadi, B.P. 2121 M’Hannech II, 93030 Tétouan (Morocco); Ibral, Asmaa [Equipe d’Optique et Electronique du Solide, Département de Physique, Faculté des Sciences, Université Chouaïb Doukkali, B. P. 20 El Jadida Principale, El Jadida (Morocco); Laboratoire d’Instrumentation, Mesure et Contrôle, Département de Physique, Faculté des Sciences, Université Chouaïb Doukkali, B. P. 20 El Jadida Principale, El Jadida (Morocco); El Khamkhami, Jamal [Laboratoire de Physique de la Matière Condensée, Département de Physique, Faculté des Sciences, Université Abdelmalek Essaadi, B.P. 2121 M’Hannech II, 93030 Tétouan (Morocco); and others

    2016-09-15

    Eigenvalues equation solutions of a hydrogen-like donor impurity, confined in a hemispherical quantum dot deposited on a wetting layer and capped by an insulating matrix, are determined in the framework of the effective mass approximation. Conduction band alignments at interfaces between quantum dot and surrounding materials are described by infinite height barriers. Ground and excited states energies and wave functions are determined analytically and via one-dimensional finite difference approach in case of an on-center donor. Donor impurity is then moved from center to pole of hemispherical quantum dot and eigenvalues equation is solved via Ritz variational principle, using a trial wave function where Coulomb attraction between electron and ionized donor is taken into account, and by two-dimensional finite difference approach. Numerical codes developed enable access to variations of donor total energy, binding energy, Coulomb correlation parameter, spatial extension and radial probability density with respect to hemisphere radius and impurity position inside the quantum dot.

  14. Energies and wave functions of an off-centre donor in hemispherical quantum dot: Two-dimensional finite difference approach and ritz variational principle

    Nakra Mohajer, Soukaina; El Harouny, El Hassan; Ibral, Asmaa; El Khamkhami, Jamal

    2016-01-01

    Eigenvalues equation solutions of a hydrogen-like donor impurity, confined in a hemispherical quantum dot deposited on a wetting layer and capped by an insulating matrix, are determined in the framework of the effective mass approximation. Conduction band alignments at interfaces between quantum dot and surrounding materials are described by infinite height barriers. Ground and excited states energies and wave functions are determined analytically and via one-dimensional finite difference approach in case of an on-center donor. Donor impurity is then moved from center to pole of hemispherical quantum dot and eigenvalues equation is solved via Ritz variational principle, using a trial wave function where Coulomb attraction between electron and ionized donor is taken into account, and by two-dimensional finite difference approach. Numerical codes developed enable access to variations of donor total energy, binding energy, Coulomb correlation parameter, spatial extension and radial probability density with respect to hemisphere radius and impurity position inside the quantum dot.

  15. Contribution of dot-blot assay to the diagnosis and management of myositis: a three-year practice at a university hospital centre.

    Martel, Clothilde; Vignaud, Guillaume; Liozon, Eric; Magy, Laurent; Gallouedec, Gael; Ly, Kim; Bezanahary, Holly; Cypierre, Anne; Lapébie, François-Xavier; Palat, Sylvain; Gondran, Guillaume; Jauberteau, Marie-Odile; Fauchais, Anne-Laure

    2016-01-01

    Idiopathic inflammatory myopathies (IIM) are heterogeneous autoimmune diseases with wide clinical spectrum that may lead to delayed diagnosis. The aim of this study was to examine the impact of IIM-specific dot-blot assay on diagnostic process of patients presenting with muscular or systemic symptoms evocating of IIM. We collected all the prescriptions of an IIM specific dot-blot assay (8 autoantigens including Jo-1, PL-7, PL-12, SRP, Mi-2, Ku, PM/Scl and Scl-70) over a 38-month period. 316 myositis dot-blot assays (MSD) were performed in 274 patients (156 women, mean age 53±10.6 years) referring for muscular and/or systemic symptoms suggesting IIM. The timing of dot prescription through the diagnostic process was highly variable: without (35%), concomitantly (16%) or after electromyographic studies (35%). Fifty-nine patients (22%) had IIM according to Bohan and Peter's criteria. Among them, 29 (49%) had positive dot (8 Jo-1, 6 PM-Scl, 5 PL-12, 5 SRP, 2 Mi-2, 2 PL-7 and 1 Ku). Various other diagnoses were performed including 35 autoimmune disease or granulomatosis (12%), 19 inflammatory rheumatic disease (7%), 16 non inflammatory muscular disorders (6%), 10 drug-induced myalgia (4%), 11 infectious myositis (4%). Except 11 borderline SRP results and one transient PM-Scl, MSD was positive only in one case of IIM. Dot allowed clinicians to correct diagnosis in 4 cases and improved the diagnosis of IIM subtypes in 4 cases. This study reflects the interest of myositis dot in the rapid diagnosis process of patients with non-specific muscular symptoms leading to various diagnoses including IIM.

  16. Inversion of spin levels in Ni sup 2 sup + : Zn(BF sub 4) sub 2 centre dot 6H sub 2 O at all -round compression and effect of transition coincidence

    Krygin, I M; Nejlo, G N; Prokhorov, A D

    2001-01-01

    The study of the EPR spectrum of the Ni sup 2 sup + ion, replacing Zn sup 2 sup + in the Zn(BF sub 4) centre dot 6H sub 2 O crystals in the wide temperature range by the all-round compression in the X- and Q-ranges is carried out. The basic changes by varying temperature and pressure occur with the D parameter, characterizing the initial splitting by practically unchanged g-factor. The increase in the temperature is accompanied by the D nonlinear growth. The all-round compression linearly changes the initial splitting and leads to the change in the D-sign, signifying the spin levels inversion by 3.5 kbar. Coincidence of EPR lines, relative to different transitions, leads to the crevasse appearance in the outline of this one, that is connected with cross-relaxation inside the spin system

  17. Quadra-Quantum Dots and Related Patterns of Quantum Dot Molecules: Basic Nanostructures for Quantum Dot Cellular Automata Application

    Somsak Panyakeow

    2010-10-01

    Full Text Available Laterally close-packed quantum dots (QDs called quantum dot molecules (QDMs are grown by modified molecular beam epitaxy (MBE. Quantum dots could be aligned and cross hatched. Quantum rings (QRs created from quantum dot transformation during thin or partial capping are used as templates for the formations of bi-quantum dot molecules (Bi-QDMs and quantum dot rings (QDRs. Preferable quantum dot nanostructure for quantum computation based on quantum dot cellular automata (QCA is laterally close-packed quantum dot molecules having four quantum dots at the corners of square configuration. These four quantum dot sets are called quadra-quantum dots (QQDs. Aligned quadra-quantum dots with two electron confinements work like a wire for digital information transmission by Coulomb repulsion force, which is fast and consumes little power. Combination of quadra-quantum dots in line and their cross-over works as logic gates and memory bits. Molecular Beam Epitaxial growth technique called 'Droplet Epitaxy' has been developed for several quantum nanostructures such as quantum rings and quantum dot rings. Quantum rings are prepared by using 20 ML In-Ga (15:85 droplets deposited on a GaAs substrate at 390'C with a droplet growth rate of 1ML/s. Arsenic flux (7'8'10-6Torr is then exposed for InGaAs crystallization at 200'C for 5 min. During droplet epitaxy at a high droplet thickness and high temperature, out-diffusion from the centre of droplets occurs under anisotropic strain. This leads to quantum ring structures having non-uniform ring stripes and deep square-shaped nanoholes. Using these peculiar quantum rings as templates, four quantum dots situated at the corners of a square shape are regrown. Two of these four quantum dots are aligned either or, which are preferable crystallographic directions of quantum dot alignment in general.

  18. Ni2Sr(PO42·2H2O

    Lahcen El Ammari

    2010-12-01

    Full Text Available The title compound, dinickel(II strontium bis[orthophosphate(V] dihydrate, was obtained under hydrothermal conditions. The crystal structure consists of linear chains ∞1[NiO2/2(OH22/2O2/1] of edge-sharing NiO6 octahedra (overline{1} symmetry running parallel to [010]. Adjacent chains are linked to each other through PO4 tetrahedra (m symmetry and arranged in such a way to build layers parallel to (001. The three-dimensional framework is accomplished by stacking of adjacent layers that are held together by SrO8 polyhedra (2/m symmetry. Two types of O—H...O hydrogen bonds involving the water molecule are present, viz. one very strong hydrogen bond perpendicular to the layers and weak trifurcated hydrogen bonds parallel to the layers.

  19. Predicting CO2-H2O Interfacial Tension Using COSMO-RS

    Silvestri, Alessandro; Stipp, Susan Louise Svane; Andersson, Martin Peter

    2017-01-01

    us interpret results and gain insight under conditions where experiments are difficult or impossible. Here, we report predictions for CO2–water interfacial tension performed using density functional theory (DFT) combined with the COSMO-RS implicit solvent model. We predicted the IFT dependence...

  20. Separation of deuterium by H2/H2O reaction with hydrophobic platinum catalyst

    Kitamoto, A.; Takashima, Y.; Shimizu, M.

    The separation performance of a trickle bed exchange column packed with a hydrophobic or waterproof catalyst is related to operating conditions such as hydrogen surface velocity, water flow rate, and temperature. The optimum carrier type and catalyst platinum content were determined. The continuous injection of roughly 10 3 ppm O 2 regenerates the catalyst effectively. The ratio of hydrophobic catalyst to hydrophilic packing is an important factor in increasing the exchange rate in deuterium extraction

  1. Effect of the greenhouse gases (CO2, H2O, SO2) on Martian paleoclimate

    Postawko, S. E.; Kuhn, W. R.

    1986-01-01

    There is general agreement that certain surface features on Mars are indicative of the presence of liquid water at various times in the geologic past. In particular, the valley networks are difficult to explain by a mechanism other than the flow of liquid water. It has been suggested in several studies that a thick CO2 atmosphere on Mars early in its history could have provided a greenhouse warming that would have allowed the flow of water either on the surface or just below the surface. However, this effect was examined with a detailed radiation model, and it was found that if reduced solar luminosity early in the history of the solar system is taken into account, even three bars of CO2 will not provide sufficient greeenhouse warming. The addition of water vapor and sulflur dioxide (both plausible gases that may have been emitted by Martian volcanoes) to the atmosphere also fail to warm the surface above 273 K for reduced solar luminosity conditions. The increase in temperature may be large enough, however, for the formation of these features by brines.

  2. The Martian climate and energy balance models with CO2/H2O atmospheres

    Hoffert, M. I.

    1986-01-01

    The analysis begins with a seasonal energy balance model (EBM) for Mars. This is used to compute surface temperature versus x = sin(latitude) and time over the seasonal cycle. The core model also computes the evolving boundaries of the CO2 icecaps, net sublimational/condensation rates, and the resulting seasonal pressure wave. Model results are compared with surface temperature and pressure history data at Viking lander sites, indicating fairly good agreement when meridional heat transport is represented by a thermal diffusion coefficient D approx. 0.015 W/sq. m/K. Condensational wind distributions are also computed. An analytic model of Martian wind circulation is then proposed, as an extension of the EMB, which incorporates vertical wind profiles containing an x-dependent function evaluated by substitution in the equation defining the diffusion coefficient. This leads to a parameterization of D(x) and of the meridional circulation which recovers the high surface winds predicted by dynamic Mars atmosphere models (approx. 10 m/sec). Peak diffusion coefficients, D approx. 0.6 w/sq m/K, are found over strong Hadley zones - some 40 times larger than those of high-latitude baroclinic eddies. When the wind parameterization is used to find streamline patterns over Martian seasons, the resulting picture shows overturning hemispheric Hadley cells crossing the equator during solstices, and attaining peak intensities during the south summer dust storm season, while condensational winds are most important near the polar caps.

  3. Quantum Dots

    Tartakovskii, Alexander

    2012-07-01

    Part I. Nanostructure Design and Structural Properties of Epitaxially Grown Quantum Dots and Nanowires: 1. Growth of III/V semiconductor quantum dots C. Schneider, S. Hofling and A. Forchel; 2. Single semiconductor quantum dots in nanowires: growth, optics, and devices M. E. Reimer, N. Akopian, M. Barkelid, G. Bulgarini, R. Heeres, M. Hocevar, B. J. Witek, E. Bakkers and V. Zwiller; 3. Atomic scale analysis of self-assembled quantum dots by cross-sectional scanning tunneling microscopy and atom probe tomography J. G. Keizer and P. M. Koenraad; Part II. Manipulation of Individual Quantum States in Quantum Dots Using Optical Techniques: 4. Studies of the hole spin in self-assembled quantum dots using optical techniques B. D. Gerardot and R. J. Warburton; 5. Resonance fluorescence from a single quantum dot A. N. Vamivakas, C. Matthiesen, Y. Zhao, C.-Y. Lu and M. Atature; 6. Coherent control of quantum dot excitons using ultra-fast optical techniques A. J. Ramsay and A. M. Fox; 7. Optical probing of holes in quantum dot molecules: structure, symmetry, and spin M. F. Doty and J. I. Climente; Part III. Optical Properties of Quantum Dots in Photonic Cavities and Plasmon-Coupled Dots: 8. Deterministic light-matter coupling using single quantum dots P. Senellart; 9. Quantum dots in photonic crystal cavities A. Faraon, D. Englund, I. Fushman, A. Majumdar and J. Vukovic; 10. Photon statistics in quantum dot micropillar emission M. Asmann and M. Bayer; 11. Nanoplasmonics with colloidal quantum dots V. Temnov and U. Woggon; Part IV. Quantum Dot Nano-Laboratory: Magnetic Ions and Nuclear Spins in a Dot: 12. Dynamics and optical control of an individual Mn spin in a quantum dot L. Besombes, C. Le Gall, H. Boukari and H. Mariette; 13. Optical spectroscopy of InAs/GaAs quantum dots doped with a single Mn atom O. Krebs and A. Lemaitre; 14. Nuclear spin effects in quantum dot optics B. Urbaszek, B. Eble, T. Amand and X. Marie; Part V. Electron Transport in Quantum Dots Fabricated by

  4. Quantum dots

    Kouwenhoven, L.; Marcus, C.

    1998-01-01

    Quantum dots are man-made ''droplets'' of charge that can contain anything from a single electron to a collection of several thousand. Their typical dimensions range from nanometres to a few microns, and their size, shape and interactions can be precisely controlled through the use of advanced nanofabrication technology. The physics of quantum dots shows many parallels with the behaviour of naturally occurring quantum systems in atomic and nuclear physics. Indeed, quantum dots exemplify an important trend in condensed-matter physics in which researchers study man-made objects rather than real atoms or nuclei. As in an atom, the energy levels in a quantum dot become quantized due to the confinement of electrons. With quantum dots, however, an experimentalist can scan through the entire periodic table by simply changing a voltage. In this article the authors describe how quantum dots make it possible to explore new physics in regimes that cannot otherwise be accessed in the laboratory. (UK)

  5. Quadra-quantum Dots and Related Patterns of Quantum Dot Molecules:

    Somsak Panyakeow

    2010-10-01

    Full Text Available Abstract Laterally close-packed quantum dots (QDs called quantum dot molecules (QDMs are grown by modified molecular beam epitaxy (MBE. Quantum dots could be aligned and cross hatched. Quantum rings (QRs created from quantum dot transformation during thin or partial capping are used as templates for the formations of bi-quantum dot molecules (Bi-QDMs and quantum dot rings (QDRs. Preferable quantum dot nanostructure for quantum computation based on quantum dot cellular automata (QCA is laterally close-packed quantum dot molecules having four quantum dots at the corners of square configuration. These four quantum dot sets are called quadra-quantum dots (QQDs. Aligned quadra-quantum dots with two electron confinements work like a wire for digital information transmission by Coulomb repulsion force, which is fast and consumes little power. Combination of quadra-quantum dots in line and their cross-over works as logic gates and memory bits. Molecular Beam Epitaxial growth technique called ‘‘Droplet Epitaxy” has been developed for several quantum nanostructures such as quantum rings and quantum dot rings. Quantum rings are prepared by using 20 ML In-Ga (15:85 droplets deposited on a GaAs substrate at 390°C with a droplet growth rate of 1ML/s. Arsenic flux (7–8×10-6Torr is then exposed for InGaAs crystallization at 200°C for 5 min. During droplet epitaxy at a high droplet thickness and high temperature, out-diffusion from the centre of droplets occurs under anisotropic strain. This leads to quantum ring structures having non-uniform ring stripes and deep square-shaped nanoholes. Using these peculiar quantum rings as templates, four quantum dots situated at the corners of a square shape are regrown. Two of these four quantum dots are aligned either or , which are preferable crystallographic directions of quantum dot alignment in general.

  6. Incommensurate phases in the improper ferroelastic MgGeF sub 6 centre dot 6H sub 2 O:Mn sup 2 sup + studied by means of EPR

    Skrylnik, P G

    2002-01-01

    The results of an EPR study of the inhomogeneous phases existing in the temperature interval T sub C = 311.0 +- 0.3 K < T < T sub i sub 1 = 403 +- 0.3 K in improper ferroelastic crystals of MgGeF sub 6 centre dot 6H sub 2 O:Mn sup 2 sup + are presented. On the basis of the analysis of the temperature and angle dependences of the experimental parameters and numerical calculations, the conclusion has been drawn that at T sub i sub 1 the crystals considered undergo a transition to a structurally modulated phase and the order parameter of this transition may be the angle of the Mg[H sub 2 O] sub 6 sup 2 sup + octahedra rotation around the crystal C sub 3 -axis. From T sub i sub 1 to T sub C the modes of the modulated phase follow according to a completely classical scenario for incommensurate crystals: the origin of the incommensurate structure with plane-wave modulation at T sub i sub 1 , the appearance of structural phase solitons below T sub i sub 2 = 380 +- 0.3 K and decrease of the soliton density to v...

  7. DOT's CAFE rulemaking analysis.

    2013-02-13

    Presentation discusses what DOT needs to consider in setting CAFE standards. How DOT's use of the CAFE Compliance and Effects Modeling System helps to analyze potential CAFE Standards. How DOT might approach the next round of CAFE standards for model...

  8. PVTx properties of the CO2-H2O and CO2-H2O-NaCl systems below 647 K: assessment of experimental data and thermodynamic models

    Hu, Jiawen; Duan, Zhenhao; Zhu, Chen; Chou, I.-Ming

    2007-01-01

    Evaluation of CO2 sequestration in formation brine or in seawater needs highly accurate experimental data or models of pressure–volume–temperature-composition (PVTx) properties for the CO2–H2O and CO2–H2O–NaCl systems. This paper presents a comprehensive review of the experimental PVTx properties and the thermodynamic models of these two systems. The following conclusions are drawn from the review: (1) About two-thirds of experimental data are consistent with each other, where the uncertainty in liquid volumes is within 0.5%, and that in gas volumes within 2%. However, this accuracy is not sufficient for assessing CO2 sequestration. Among the data sets for liquids, only a few are available for accurate modeling of CO2 sequestration. These data have an error of about 0.1% on average, roughly covering from 273 to 642 K and from 1 to 35 MPa; (2) There is a shortage of volumetric data of saturated vapor phase. (3) There are only a few data sets for the ternary liquids, and they are inconsistent with each other, where only a couple of data sets can be used to test a predictive density model for CO2 sequestration; (4) Although there are a few models with accuracy close to that of experiments, none of them is accurate enough for CO2 sequestration modeling, which normally needs an accuracy of density better than 0.1%. Some calculations are made available on www.geochem-model.org.

  9. The mechanism of the dehydration reaction of solid HIO 4. 2H 2O and the role of radiation

    Takriti, S.

    1998-01-01

    A thermal and kinetic study of dehydration reaction of periodic acid dehydrate has been carried out with isothermal and physical measurements. Isothermal dehydration curves have been studied in the temperature ranges between 333 0 K respectively. Both dehydration processes involve the loss two molecules of water in the studied temperature ranges. Thermodynamic and kinetic parameters have been calculated using different physical models proposed. The data analysis illustrated that activation energy is about 1 eV for the first step and 1.2 eV for second

  10. Investigation of Laser Plasma Chemistry in CO2-N-2-H2O Using O-18 Labeled Water

    Ferus, Martin; Kubelík, Petr; Juha, Libor; Civiš, Svatopluk

    2009-01-01

    Roč. 39, 3-4 (2009), s. 245-245 ISSN 0169-6149 R&D Projects: GA MŠk LC510; GA MŠk(CZ) LC528; GA ČR GA203/06/1278; GA MŠk LA08024 Institutional research plan: CEZ:AV0Z40400503; CEZ:AV0Z10100523 Keywords : LIDB plasma * atmosphere * isotopes Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.053, year: 2009

  11. Theoretical studies on photoelectron and IR spectral properties of Br2.-(H2O)n clusters

    Pathak, A. K.; Mukherjee, T.; Maity, D. K.

    2007-07-01

    We report vertical detachment energy (VDE) and IR spectra of Br2•-•(H2O)n clusters (n=1-8) based on first principles electronic structure calculations. Cluster structures and IR spectra are calculated at Becke's half-and-half hybrid exchange-correlation functional (BHHLYP) with a triple split valence basis function, 6-311++G(d,p). VDE for the hydrated clusters is calculated based on second order Moller-Plesset perturbation (MP2) theory with the same set of basis function. On full geometry optimization, it is observed that conformers having interwater hydrogen bonding among solvent water molecules are more stable than the structures having double or single hydrogen bonded structures between the anionic solute, Br2•-, and solvent water molecules. Moreover, a conformer having cyclic interwater hydrogen bonded network is predicted to be more stable for each size hydrated cluster. It is also noticed that up to four solvent H2O units can reside around the solute in a cyclic interwater hydrogen bonded network. The excess electron in these hydrated clusters is localized over the solute atoms. Weighted average VDE is calculated for each size (n) cluster based on statistical population of the conformers at 150K. A linear relationship is obtained for VDE versus (n+3)-1/3 and bulk VDE of Br2•- aqueous solution is calculated as 10.01eV at MP2 level of theory. BHHLYP density functional is seen to make a systematic overestimation in VDE values by ˜0.5eV compared to MP2 data in all the hydrated clusters. It is observed that hydration increases VDE of bromine dimer anion system by ˜6.4eV. Calculated IR spectra show that the formation of Br2•--water clusters induces large shifts from the normal O-H stretching bands of isolated water keeping bending modes rather insensitive. Hydrated clusters, Br2•-•(H2O)n, show characteristic sharp features of O-H stretching bands of water in the small size clusters.

  12. Preparation of Pt-SDB hydrophobic catalyst used in H2-H2O isotope exchange reaction

    Li Junhua; Kang Yi; Ruan Hao; Dou Qincheng; Han Yande; Hu Shilin

    2001-01-01

    The preparation of Pt-SDB hydrophobic catalyst is studied, in which platinum as active metal and polystyrene divinylbenzene (SDB) as the carrier. Hydrogen isotope exchange reaction is carried out with Pt-SDB catalyst in counter-current in the trickle bed. The effect of preparing condition on the activity of catalyst is discussed. The results show that the excellent catalyst is obtained by reduced at the temperature of 200 degree C over 8 hours. Hydrophobic catalyst is high activity and stability as the amount of platinum content is 3%, the platinum can reach the economic use with the content of (1-2)%

  13. The reaction of uranium in the U-O2-H2O and U-H2O systems

    Pearce, R.J.; Kay, P.

    1987-09-01

    The reaction of uranium in dry air, moist air and oxygen free moisture has been studied thermogravimetrically over the temperature range 105-325 0 C and at water vapour pressures up to 100 kPa. It has been shown that in dry air the kinetics are complex and appear to result from parallel reactions involving both parabolic and linear rate laws. In oxygen free moisture, linear kinetics were obeyed and a near stoichiometric UO 2 reaction product was formed. Oxygen markedly inhibited the moisture reaction at the lower temperatures in the range examined but the degree of inhibition, as shown by weight gain measurements, decreased with increasing temperature such that, at the higher temperatures, there was little difference in reaction rates. At all temperatures, the production of hydrogen was markedly inhibited by the presence of air suggesting that the principal reaction was with free oxygen. However in moist conditions the reaction rate exhibited a dependency on the water vapour pressure according to k α psup(n) where n ∼ 0.3 in air and ∼ 0.5 in oxygen free conditions. The mechanism of the oxidation reaction is discussed. (author)

  14. Characterisation of the coke formed during metal dusting of iron in CO-H2-H2O gas mixtures

    Zhang, J.; Schneider, A.; Inden, G.

    2003-01-01

    Carbon deposits formed on the surface of iron samples during carburisation at 700 deg. C in a gas mixture of 75%CO-24.81%H 2 -0.19%H 2 O were characterised by using scanning electron microscopy (SEM), X-ray diffraction (XRD), Moessbauer spectroscopy and transmission electron microscopy (TEM). Cross-section observation of the iron sample by light optical microscopy revealed the formation of cementite after only 10 min reaction, together with a thin layer of graphite. After 4 h reaction, a thick coke layer was formed on top of the cementite surface. SEM surface observation indicated the formation of filamentous carbon in the coke layer. Further analysis of the coke by XRD and Moessbauer showed the presence of mainly Fe 3 C and small amount of Fe 2 C but no metallic iron in the carbon deposit. TEM analysis of the coke detected very convoluted filaments with iron-containing particles at the tip or along their length. These particles were identified to be cementite by selected area diffraction. Carbon deposits produced at the same temperature but with other gas compositions were also analysed by using XRD. It was found that with a low content of CO, e.g. 5%, both α-Fe and Fe 3 C were detected in the coke. Increasing CO content to more than 30%, iron carbide was the only iron-containing phase

  15. TG-FTIR measurement of CO2-H2O co-adsorption for CO2 air capture sorbent screening

    Smal, I.M.; Yu, Qian; Veneman, Rens; Fränzel-Luiten, B.; Brilman, Derk Willem Frederik

    2014-01-01

    Capturing atmospheric CO2 using solid sorbents is gaining interest. As ambient air normally contains much more (up to 100 times) water than CO2, a selective sorbent is desirable as co-adsorption will most likely occur. In this study, a convenient method based on an TG-FTIR analysis system is

  16. REMEDIATION OF TEXTILE DYES MIXTURES USING TIO2/VIS PHOTOCATALYSIS AND FENTON FE2+/H2O2

    P. M. Andrade

    2015-12-01

    Full Text Available This study aimed to use the following treatment technology: TiO2 photocatalysis and Fenton reaction for the remediation of mixture of textile dyes.  For the photocatalytic treatment it was obtained a reduction in color of 80% and Chemical Oxygen Demand of 60% using for this 600 mg L-1 of TiO2, 1500  mL min-1 recirculation flow, temperature 40 oC/45 oC and pH = 6.3 for 60 minutes of treatment. By Fenton reaction it was reached color reduction at 95% and Chemical Oxygen Demand reduction at 75% employing 60 mg L-1 H2O2, 50 mg L-1 de Fe2+ and pH = 4.0 for 62 minutes of treatment.

  17. Manche centre

    1997-05-01

    After a general presentation of radioactivity and radioactive wastes and of the French national agency for the management of radioactive wastes (ANDRA), this brochure gives a general overview of the Manche low- and medium-level radioactive waste disposal centre: principles of storage safety, waste containers (first confinement barrier), storage facility and cover (second confinement barrier), the underground (third confinement barrier), the impact of the centre on its environment, and the control of radioactivity in the vicinity of the centre. (J.S.)

  18. Nonlinear Dot Plots.

    Rodrigues, Nils; Weiskopf, Daniel

    2018-01-01

    Conventional dot plots use a constant dot size and are typically applied to show the frequency distribution of small data sets. Unfortunately, they are not designed for a high dynamic range of frequencies. We address this problem by introducing nonlinear dot plots. Adopting the idea of nonlinear scaling from logarithmic bar charts, our plots allow for dots of varying size so that columns with a large number of samples are reduced in height. For the construction of these diagrams, we introduce an efficient two-way sweep algorithm that leads to a dense and symmetrical layout. We compensate aliasing artifacts at high dot densities by a specifically designed low-pass filtering method. Examples of nonlinear dot plots are compared to conventional dot plots as well as linear and logarithmic histograms. Finally, we include feedback from an expert review.

  19. From DOT to Dotty

    CERN. Geneva

    2017-01-01

    - Module types are interfaces, which can be abstracted. In this talk Martin will present DOT, a particularly simple calculus that can express systems following these principles. DOT has been developed as the foundation of the next version of Scala. He will also report on dotty, a new Scala compiler that implements the constructs of DOT in its core data structures and that uses the lessons learned to drive Scala’s evolution.

  20. Transport in quantum dots

    Deus, Fernanda; Continetino, Mucio

    2011-01-01

    Full text. In this work we study the time dependent transport in interacting quantum dot. This is a zero-dimensional nano structure system which has quantized electronic states. In our purpose, we are interested in studying such system in a Coulomb blockade regime where a mean-field treatment of the electronic correlations are appropriate. The quantum dot is described by an Anderson type of Hamiltonian where the hybridization term arises from the contact with the leads. We consider a time dependence of both the energy of the localized state in the quantum dot and of the hybridization-like term. These time dependent parameters, under certain conditions, induce a current in the quantum dot even in the absence of difference on the chemical potential of the leads. The approach to this non-equilibrium problem requires the use of a Keldysh formalism. We calculate the non- equilibrium Green's functions and obtain results for the average (equilibrium term) and the non-equilibrium values of the electronic occupation number in the dot. we consider the possibility of a magnetic solution, with different values for the average up and down spins in the quantum dot. Our results allow to obtain, for instance, the tunneling current through the dot. The magnetic nature of the dot, for a certain range of parameters should give rise also to an induced spin current through the dot

  1. Quantum Dots: Theory

    Vukmirovic, Nenad; Wang, Lin-Wang

    2009-11-10

    This review covers the description of the methodologies typically used for the calculation of the electronic structure of self-assembled and colloidal quantum dots. These are illustrated by the results of their application to a selected set of physical effects in quantum dots.

  2. Quantum dot spectroscopy

    Leosson, Kristjan

    1999-01-01

    Semiconductor quantum dots ("solid state atoms") are promising candidates for quantum computers and future electronic and optoelectronic devices. Quantum dots are zero-dimensional electronic systems and therefore have discrete energy levels, similar to atoms or molecules. The size distribution of...

  3. Quantum dot spectroscopy

    Leosson, Kristjan

    Semiconductor quantum dots ("solid-state atoms") are promising candidates for quantum computers and future electronic and optoelectronic devices. Quantum dots are zero-dimensional electronic systems and therefore have discrete energy levels, similar to atoms or molecules. The size distribution of...

  4. Synthesis of quantum dots

    McDaniel, Hunter

    2017-10-17

    Common approaches to synthesizing alloyed quantum dots employ high-cost, air-sensitive phosphine complexes as the selenium precursor. Disclosed quantum dot synthesis embodiments avoid these hazardous and air-sensitive selenium precursors. Certain embodiments utilize a combination comprising a thiol and an amine that together reduce and complex the elemental selenium to form a highly reactive selenium precursor at room temperature. The same combination of thiol and amine acts as the reaction solvent, stabilizing ligand, and sulfur source in the synthesis of quantum dot cores. A non-injection approach may also be used. The optical properties of the quantum dots synthesized by this new approach can be finely tuned for a variety of applications by controlling size and/or composition of size and composition. Further, using the same approach, a shell can be grown around a quantum dot core that improves stability, luminescence efficiency, and may reduce toxicity.

  5. Stark-shift of impurity fundamental state in a lens shaped quantum dot

    Aderras, L.; Bah, A.; Feddi, E.; Dujardin, F.; Duque, C. A.

    2017-05-01

    We calculate the Stark effect and the polarisability of shallow-donor impurity located in the centre of lens shaped quantum dot by a variational method and in the effective-mass approximation. Our theoretical model assumes an infinite confinement to describe the barriers at the dot boundaries and the electric field is considered to be applied in the z-direction. The systematic theoretical investigation contains results with the quantum dot size and the strength of the external field. Our calculations reveal that the interval wherein the polarisability varies depends strongly on the dot size.

  6. Quantum dot molecules

    Wu, Jiang

    2014-01-01

    This book reviews recent advances in the exciting and rapidly growing field of quantum dot molecules (QDMs). It offers state-of-the-art coverage of novel techniques and connects fundamental physical properties with device design.

  7. Graphene quantum dots

    Güçlü, Alev Devrim; Korkusinski, Marek; Hawrylak, Pawel

    2014-01-01

    This book reflects the current status of theoretical and experimental research of graphene based nanostructures, in particular quantum dots, at a level accessible to young researchers, graduate students, experimentalists and theorists. It presents the current state of research of graphene quantum dots, a single or few monolayer thick islands of graphene. It introduces the reader to the electronic and optical properties of graphite, intercalated graphite and graphene, including Dirac fermions, Berry's phase associated with sublattices and valley degeneracy, covers single particle properties of

  8. ESR investigation of the reactions of glutathione, cysteine and penicillamine thiyl radicals: competitive formation of RSOcenter dot, Rcenter dot, RSSRcenter dot-. , and RSScenter dot

    Becker, David; Swarts, Steven; Champagne, Mark; Sevilla, M D

    1988-05-01

    The reactions of cysteine, glutathione and penicillamine thiyl radicals with oxygen and their parent thiols in frozen solutions have been elucidated with e.s.r. The major sulfur radicals observed are: (1) thiyl radicals, RS center dot; (2) disulfide radical anions, RSSR anion radicals; (3) perthiyl radicals, RSS center dot and upon introduction of oxygen; (4) sulfinyl radicals, RSO center dot, where R represents the remainder of the cysteine, glutathione or penicillamine moiety. The radical product observed depends on pH, concentration of thiol, and presence or absence of molecular oxygen. The sulfinyl radical is a ubiquitous intermediate, peroxyl radical attack on thiols may lead to sulfinyl radicals. The authors elaborate the observed reaction sequences that lead to sulfinyl radicals and, using /sup 17/O isotopic substitution studies, demonstrate the oxygen atom in sulfinyl radicals originates from dissolved molecular oxygen. The glutathione radical is found to abstract hydrogen from the ..cap alpha..-carbon position on the cysteine residue of glutathione to form a carbon-centred radical.

  9. Formulating CdSe quantum dots for white light-emitting diodes with high color rendering index

    Li, Fei; Li, Wan-Nan; Fu, Shao-Yun; Xiao, Hong-Mei

    2015-01-01

    Generation of white light using CdSe quantum dots (QDs) alone presents exciting possibilities for solid state lighting technology. In this work, Cd(Ac) 2 ·2H 2 O and Na 2 SeSO 3 are used as precursors to synthesize CdSe-QDs with an average diameter ranging from 2.77 to 4.65 nm at the low temperature from 60 to 180 °C. Smaller CdSe-QDs with an average diameter of 2.29 nm are got by an oxidation etching process using H 2 O 2 as oxidant. The structural and optical properties of these QDs are investigated and proper formulation of CdSe QDs with various sizes is carefully designed to achieve white light with a high color rendering index (CRI). It is observed for the first time that the as-prepared white light-emitting diodes from single CdSe-QDs show the Commission Inernationale del’Eclairage coordinate (CIE) of (0.30,0.34) very close to that (0.33,0.33) of pure white light and a high CRI of 84. Owing to these advantages, the as-prepared white light-emitting diodes from a single compound are promising for lighting applications. - Highlights: • CdSe-quantum dots (QDs) with a continuously changing size from 2.31 to 4.74 nm are prepared. • The obtained CdSe-QDs emit lights with tunable colors in the whole visible range. • The obtained mixture sample generates white light with a high color rendering index of 84. • The sample yields white light with the CIE coordinate (0.30, 0.34) very close to that of pure white light

  10. Hexagonal graphene quantum dots

    Ghosh, Sumit; Schwingenschlö gl, Udo

    2016-01-01

    We study hexagonal graphene quantum dots, using density functional theory, to obtain a quantitative description of the electronic properties and their size dependence, considering disk and ring geometries with both armchair and zigzag edges. We show that the electronic properties of quantum dots with armchair edges are more sensitive to structural details than those with zigzag edges. As functions of the inner and outer radii, we find in the case of armchair edges that the size of the band gap follows distinct branches, while in the case of zigzag edges it changes monotonically. This behaviour is further analyzed by studying the ground state wave function and explained in terms of its localisation.

  11. Quantum dot solar cells

    Wu, Jiang

    2013-01-01

    The third generation of solar cells includes those based on semiconductor quantum dots. This sophisticated technology applies nanotechnology and quantum mechanics theory to enhance the performance of ordinary solar cells. Although a practical application of quantum dot solar cells has yet to be achieved, a large number of theoretical calculations and experimental studies have confirmed the potential for meeting the requirement for ultra-high conversion efficiency. In this book, high-profile scientists have contributed tutorial chapters that outline the methods used in and the results of variou

  12. Hexagonal graphene quantum dots

    Ghosh, Sumit

    2016-12-05

    We study hexagonal graphene quantum dots, using density functional theory, to obtain a quantitative description of the electronic properties and their size dependence, considering disk and ring geometries with both armchair and zigzag edges. We show that the electronic properties of quantum dots with armchair edges are more sensitive to structural details than those with zigzag edges. As functions of the inner and outer radii, we find in the case of armchair edges that the size of the band gap follows distinct branches, while in the case of zigzag edges it changes monotonically. This behaviour is further analyzed by studying the ground state wave function and explained in terms of its localisation.

  13. Complete quantum control of exciton qubits bound to isoelectronic centres.

    Éthier-Majcher, G; St-Jean, P; Boso, G; Tosi, A; Klem, J F; Francoeur, S

    2014-05-30

    In recent years, impressive demonstrations related to quantum information processing have been realized. The scalability of quantum interactions between arbitrary qubits within an array remains however a significant hurdle to the practical realization of a quantum computer. Among the proposed ideas to achieve fully scalable quantum processing, the use of photons is appealing because they can mediate long-range quantum interactions and could serve as buses to build quantum networks. Quantum dots or nitrogen-vacancy centres in diamond can be coupled to light, but the former system lacks optical homogeneity while the latter suffers from a low dipole moment, rendering their large-scale interconnection challenging. Here, through the complete quantum control of exciton qubits, we demonstrate that nitrogen isoelectronic centres in GaAs combine both the uniformity and predictability of atomic defects and the dipole moment of semiconductor quantum dots. This establishes isoelectronic centres as a promising platform for quantum information processing.

  14. Quantum dots and nanocomposites.

    Mansur, Herman Sander

    2010-01-01

    Quantum dots (QDs), also known as semiconducting nanoparticles, are promising zero-dimensional advanced materials because of their nanoscale size and because they can be engineered to suit particular applications such as nonlinear optical devices (NLO), electro-optical devices, and computing applications. QDs can be joined to polymers in order to produce nanocomposites which can be considered a scientific revolution of the 21st century. One of the fastest moving and most exciting interfaces of nanotechnology is the use of QDs in medicine, cell and molecular biology. Recent advances in nanomaterials have produced a new class of markers and probes by conjugating semiconductor QDs with biomolecules that have affinities for binding with selected biological structures. The nanoscale of QDs ensures that they do not scatter light at visible or longer wavelengths, which is important in order to minimize optical losses in practical applications. Moreover, at this scale, quantum confinement and surface effects become very important and therefore manipulation of the dot diameter or modification of its surface allows the properties of the dot to be controlled. Quantum confinement affects the absorption and emission of photons from the dot. Thus, the absorption edge of a material can be tuned by control of the particle size. This paper reviews developments in the myriad of possibilities for the use of semiconductor QDs associated with molecules producing novel hybrid nanocomposite systems for nanomedicine and bioengineering applications.

  15. PREFACE: Quantum Dot 2010

    Taylor, Robert A.

    2010-09-01

    These conference proceedings contain the written papers of the contributions presented at Quantum Dot 2010 (QD2010). The conference was held in Nottingham, UK, on 26-30 April 2010. The conference addressed topics in research on: 1. Epitaxial quantum dots (including self-assembled and interface structures, dots defined by electrostatic gates etc): optical properties and electron transport quantum coherence effects spin phenomena optics of dots in cavities interaction with surface plasmons in metal/semiconductor structures opto-electronics applications 2. Novel QD structures: fabrication and physics of graphene dots, dots in nano-wires etc 3. Colloidal quantum dots: growth (shape control and hybrid nanocrystals such as metal/semiconductor, magnetic/semiconductor) assembly and surface functionalisation optical properties and spin dynamics electrical and magnetic properties applications (light emitting devices and solar cells, biological and medical applications, data storage, assemblers) The Editors Acknowledgements Conference Organising Committee: Maurice Skolnick (Chair) Alexander Tartakovskii (Programme Chair) Pavlos Lagoudakis (Programme Chair) Max Migliorato (Conference Secretary) Paola Borri (Publicity) Robert Taylor (Proceedings) Manus Hayne (Treasurer) Ray Murray (Sponsorship) Mohamed Henini (Local Organiser) International Advisory Committee: Yasuhiko Arakawa (Tokyo University, Japan) Manfred Bayer (Dortmund University, Germany) Sergey Gaponenko (Stepanov Institute of Physics, Minsk, Belarus) Pawel Hawrylak (NRC, Ottawa, Canada) Fritz Henneberger (Institute for Physics, Berlin, Germany) Atac Imamoglu (ETH, Zurich, Switzerland) Paul Koenraad (TU Eindhoven, Nethehrlands) Guglielmo Lanzani (Politecnico di Milano, Italy) Jungil Lee (Korea Institute of Science and Technology, Korea) Henri Mariette (CNRS-CEA, Grenoble, France) Lu Jeu Sham (San Diego, USA) Andrew Shields (Toshiba Research Europe, Cambridge, UK) Yoshihisa Yamamoto (Stanford University, USA) Artur

  16. Structure-guided mutational analysis reveals the functional requirements for product specificity of DOT1 enzymes.

    Dindar, Gülcin; Anger, Andreas M; Mehlhorn, Christine; Hake, Sandra B; Janzen, Christian J

    2014-11-12

    DOT1 enzymes are conserved methyltransferases that catalyse the methylation of lysine 79 on histone H3 (H3K79). Most eukaryotes contain one DOT1 enzyme, whereas African trypanosomes have two homologues, DOT1A and DOT1B, with different enzymatic activities. DOT1A mediates mono- and dimethylation of H3K76, the homologue of H3K79 in other organisms, whereas DOT1B additionally catalyses H3K76 trimethylation. However, it is unclear how these different enzymatic activities are achieved. Here we employ a trypanosomal nucleosome reconstitution system and structure-guided homology modelling to identify critical residues within and outside the catalytic centre that modulate product specificity. Exchange of these residues transfers the product specificity from one enzyme to the other, and reveals the existence of distinct regulatory domains adjacent to the catalytic centre. Our study provides the first evidence that a few crucial residues in DOT1 enzymes are sufficient to catalyse methyl-state-specific reactions. These results might also have far-reaching consequences for the functional understanding of homologous enzymes in higher eukaryotes.

  17. Amino Acid Formation Induced by High-power Laser in CO2/CO-N2-H2O Gas Mixtures

    Civiš, Svatopluk; Juha, Libor; Babánková, Dagmar; Cvačka, Josef; Frank, O.; Jehlička, J.; Králiková, Božena; Krása, Josef; Kubát, Pavel; Muck, A.; Pfeifer, Miroslav; Skála, Jiří; Ullschmied, Jiří

    2004-01-01

    Roč. 386, 1/3 (2004), s. 169-173 ISSN 0009-2614 R&D Projects: GA MŠk LN00A100 Institutional research plan: CEZ:AV0Z4040901 Keywords : Prebiotic synthesis * organic-synthesis * spectroscopy Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.438, year: 2004

  18. Monte Carlo analysis of Pu-H2O and UO2-PuO2-H2O critical assemblies with ENDF/B-IV data

    Hardy, J. Jr.; Ullo, J.J.

    1981-04-01

    A set of critical experiments, comprising thirteen homogeneous Pu-H 2 O assemblies and twelve UO 2 -PuO 2 lattices, was analyzed with ENDF/B-IV data and the RCPO1 Monte Carlo program, which modeled the experiments explicitly. Some major data sensitivities were also evaluated. For the Pu-H 2 O assemblies, calculated K/sub eff/ averaged 1.011. The large (2.7%) scatter of K/sub eff/ values for these assemblies was attributed mostly to uncertainties in physical specifications since no clear trends of K/sub eff/ were evident and data sensitivities were insignificant. The UO 2 -PuO 2 lattices showed just one trend of K/sub eff/, which indicated an overprediction of U238 capture consistent with that observed for uranium-H 2 O experiments. There was however a approx. 1% discrepancy in calculated K/sub eff/ between the two sets of UO 2 -PuO 2 lattices studied

  19. Uptake and speciation of uranium in synthetic gypsum (CaSO4•2H2O): Applications to radioactive mine tailings.

    Lin, Jinru; Sun, Wei; Desmarais, Jacques; Chen, Ning; Feng, Renfei; Zhang, Patrick; Li, Dien; Lieu, Arthur; Tse, John S; Pan, Yuanming

    2018-01-01

    Phosphogypsum formed from the production of phosphoric acid represents by far the biggest accumulation of gypsum-rich wastes in the world and commonly contains elevated radionuclides, including uranium, as well as other heavy metals and metalloids. Therefore, billions-of-tons of phosphogypsum stockpiled worldwide not only possess serious environmental problems but also represent a potential uranium resource. Gypsum is also a major solid constituent in many other types of radioactive mine tailings, which stems from the common usage of sulfuric acid in extraction processes. Therefore, management and remediation of radioactive mine tailings as well as future beneficiation of uranium from phosphogysum all require detailed knowledge about the nature and behavior of uranium in gypsum. However, little is known about the uptake mechanism or speciation of uranium in gypsum. In this study, synthesis experiments suggest an apparent pH control on the uptake of uranium in gypsum at ambient conditions: increase in U from 16 μg/g at pH = 6.5 to 339 μg/g at pH = 9.5. Uranium L 3 -edge synchrotron X-ray absorption spectroscopic analyses of synthetic gypsum show that uranyl (UO 2 ) 2+ at the Ca site is the dominant species. The EXAFS fitting results also indicate that uranyl in synthetic gypsum occurs most likely as carbonate complexes and yields an average U-O distance ∼0.25 Å shorter than the average Ca-O distance, signifying a marked local structural distortion. Applications to phosphogypsum from the New Wales phosphoric acid plant (Florida, USA) and uranium mine tailings from the Key Lake mill (Saskatchewan, Canada) show that gypsum is an important carrier of uranium over a wide range of pH and controls the fate of this radionuclide in mine tailings. Also, development of new technologies for recovering U from phosphogypsum in the future must consider lattice-bound uranyl in gypsum. Copyright © 2017 Elsevier Ltd. All rights reserved.

  20. Experimental and kinetic study of the iodine reactivity in low pressure H2/O2/H2O/HI/Ar premixed flames

    Delicat, Y.G.

    2012-01-01

    To assess kinetics aspects of iodine chemistry in an environment of a severe accident in a Pressurized Water Reactor (PWR), at the laboratory scale, an experimental reactor named 'flat flame burner' has been implemented. Low pressure flames of H 2 /O 2 /Ar premixed gas seeded with known amounts of iodhydric acid and steam were studied. The quantification of chemical species (HI, H 2 O, OH) in such environment was obtained by specific analytical techniques (Fourier Transform Infrared absorption spectrometry, FTIR and Laser Induced Fluorescence, LIF), the evolution of the temperature was determined by LIF and by thermocouple measurements. Further assays were performed in a flow reactor in which gaseous molecular iodine was injected and transported in a stream or hydrogen flow and a strong temperature gradient, representative of the primary circuit in the case of a severe accident. The resulting gaseous species (I 2 and HI) were quantified by ICP-MS and UV-Visible spectrometry. This experimental database has been used as a support to develop a detailed kinetic mechanism for the {I, O, H} system. It is composed of 37 reversible reactions involving 5 iodinated species. The thermo-kinetic parameter database has been actualized by using theoretical chemistry tools and also completed with data found in the literature. Modelling was performed by using the PREMIX code for flame assays, and with the in IRSN's severe accident simulation code ASTEC/SOPHAREOS code for flow reactor assays. The comparison between experiment and modelling shows that this detailed mechanism is able to reproduce the iodine chemistry in conditions representative of a PWR severe accident. (author)

  1. High-resolution photoelectron spectroscopy of TiO3H2-: Probing the TiO2- + H2O dissociative adduct

    DeVine, Jessalyn A.; Abou Taka, Ali; Babin, Mark C.; Weichman, Marissa L.; Hratchian, Hrant P.; Neumark, Daniel M.

    2018-06-01

    Slow electron velocity-map imaging spectroscopy of cryogenically cooled TiO3H2- anions is used to probe the simplest titania/water reaction, TiO20/- + H2O. The resultant spectra show vibrationally resolved structure assigned to detachment from the cis-dihydroxide TiO(OH)2- geometry based on density functional theory calculations, demonstrating that for the reaction of the anionic TiO2- monomer with a single water molecule, the dissociative adduct (where the water is split) is energetically preferred over a molecularly adsorbed geometry. This work represents a significant improvement in resolution over previous measurements, yielding an electron affinity of 1.2529(4) eV as well as several vibrational frequencies for neutral TiO(OH)2. The energy resolution of the current results combined with photoelectron angular distributions reveals Herzberg-Teller coupling-induced transitions to Franck-Condon forbidden vibrational levels of the neutral ground state. A comparison to the previously measured spectrum of bare TiO2- indicates that reaction with water stabilizes neutral TiO2 more than the anion, providing insight into the fundamental chemical interactions between titania and water.

  2. KINETICS OF HO2 + HO2 -> H2O2 + O2: IMPLICATIONS FOR STRATOSPHERIC H2O2. (R826236)

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  3. Fundamental Understanding of Methane-Carbon Dioxide-Water (CH4-CO2-H2O) Interactions in Shale Nanopores under Reservoir Conditions.

    Wang, Yifeng [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2018-02-01

    Shale is characterized by the predominant presence of nanometer-scale (1-100 nm) pores. The behavior of fluids in those pores directly controls shale gas storage and release in shale matrix and ultimately the wellbore production in unconventional reservoirs. Recently, it has been recognized that a fluid confined in nanopores can behave dramatically differently from the corresponding bulk phase due to nanopore confinement (Wang, 2014). CO2 and H2O, either preexisting or introduced, are two major components that coexist with shale gas (predominately CH4) during hydrofracturing and gas extraction. Note that liquid or supercritical CO2 has been suggested as an alternative fluid for subsurface fracturing such that CO2 enhanced gas recovery can also serve as a CO2 sequestration process. Limited data indicate that CO2 may preferentially adsorb in nanopores (particularly those in kerogen) and therefore displace CH4 in shale. Similarly, the presence of water moisture seems able to displace or trap CH4 in shale matrix. Therefore, fundamental understanding of CH4-CO2-H2O behavior and their interactions in shale nanopores is of great importance for gas production and the related CO2 sequestration. This project focuses on the systematic study of CH4-CO2-H2O interactions in shale nanopores under high-pressure and high temperature reservoir conditions. The proposed work will help to develop new stimulation strategies to enable efficient resource recovery from fewer and less environmentally impactful wells.

  4. Analysis of points of dew and contents of humidity of gassy mixtures N2-H2 O and CH4 H2 O

    Bedoya M, D; Muller, C; Oellrich, L R

    1995-01-01

    The actual knowledge of the exact water content in saturated gas mixtures still is incomplete, especially in the high pressure and low temperature region. Hence, dew point measurements with nitrogen - water and methane-water mixtures were performed; at pressures of 3 and 6 MPa and temperatures from 258 K to 288 K. The dew points were determined with the dew point mirror method and the water content by means of the Karl-Fischer-titration. The experimental values were compared to correlations from the literature. The approach by Sharma-Campbell resulted in the best description of the system nitrogen - water. For temperatures below 273 K the assumption of ideal behavior proved to be sufficient for the system methane-water, whereas for temperatures above 273 K calculations with the two-parameter corresponding states principle in combination with a fugacity correction turned out to be the best

  5. Comprehensive cluster-theory analysis of the magnetic structures and excitations in CoCl2·2H2O

    Jensen, Jens; Larsen, Jacob; Hansen, Ursula B.

    2018-01-01

    The magnetic properties of CoCl2·2H2O are analyzed in the mean-field/random-phase approximation using a basis of clusters with four spins along the c-axis chains of Co ions. The model gives a unifying account of the bulk properties, the spin waves, and the higher-order cluster-spin excitations...... at a transverse field of 160 kOe and is found to agree closely with their observations....

  6. Major, Trace, and Volatile (CO2, H2O, S, F, and Cl) Elements from 1000+ Hawaiian Olivine-hosted Melt Inclusions Reveal the Dynamics of Crustal Recycling

    Marske, J. P.; Hauri, E. H.; Trusdell, F.; Garcia, M. O.; Pietruszka, A. J.

    2015-12-01

    Global cycling of volatile elements (H2O, CO2, F, S, Cl) via subduction to deep mantle followed by entrainment and melting within ascending mantle plumes is an enigmatic process that controls key aspects of hot spot volcanism (i.e. melting rate, magma supply, degassing, eruptive style). Variations in radiogenic isotope ratios (e.g.187Os/188Os) at hot spots such as Hawaii reveal magmatic processes within deep-seated mantle plumes (e.g. mantle heterogeneity, lithology, and melt transport). Shield-stage lavas from Hawaii likely originate from a mixed plume source containing peridotite and recycled oceanic crust (pyroxenite) based on variations of radiogenic isotopes. Hawaiian lavas display correlations among isotopes, major and trace elements [1] that might be expected to have an expression in the volatile elements. To investigate this link, we present Os isotopic ratios (n=51), and major, trace, and volatile elements from 1003 olivine-hosted melt inclusions (MI) and their host minerals from tephra from Koolau, Mauna Loa, Hualalai, Kilauea, and Loihi volcanoes. The data show a strong correlation between MI volatile contents and incompatible trace element ratios (La/Yb) with Os isotopes of the same host olivines and reveal large-scale volatile heterogeneity and zonation exists within the Hawaiian plume. 'Loa' chain lavas, which are thought to originate from greater proportions of recycled oceanic crust/pyroxenite, have MIs with lower H2O, S, F, and Cl contents compared to 'Kea' chain lavas that were derived from more peridotite-rich sources. The depletion of volatile elements in the 'Loa' volcano MIs can be explained if they tapped an ancient dehydrated oceanic crust component within the Hawaiian plume. Higher extents of melting beneath 'Loa' volcanoes can also explain these depletions. The presence of dehydrated recycled mafic material in the plume source suggests that subduction effectively devolatilizes part of the oceanic crust. These results are similar to the observed shifts in H2O/Ce ratios near the Easter and Samoan hotspots [2,3]. Thus, it appears that multiple hotspots may record relative H2O depletions and possibly other volatiles. [1] Hauri et al. 1996, Nature 382, 415-419. [2] Dixon et al. 2002, Nature 420:385-89 [3] Workman et al. 2006, EPSL 241:932-51.

  7. Ab initio studies of O2-(H2O)n and O3-(H2O)n anionic molecular clusters, n≤12

    Bork, Nicolai Christian; Kurtén, T.; Enghoff, Martin Andreas Bødker

    2011-01-01

    that anionic O2−(H2O)n and O3−(H2O)n clusters are thermally stabilized at typical atmospheric conditions for at least n = 5. The first 4 water molecules are strongly bound to the anion due to delocalization of the excess charge while stabilization of more than 4 H2O is due to normal hydrogen bonding. Although...... clustering up to 12 H2O, we find that the O2 and O3 anions retain at least ca. 80 % of the charge and are located at the surface of the cluster. The O2− and O3− speicies are thus accessible for further reactions. Finally, the thermodynamics of a few relevant cluster reactions are considered....

  8. C-A-S-H synthesis and thermodynamics modelling in CaO-Al2O3-SiO2-H2O system

    Haas, J.; Pochard, I.; Nonat, A.

    2015-01-01

    Ordinary Portland cement (OPC) is being increasingly replaced by blended cements, where part of the clinker is replaced by secondary cementitious materials (SCM) such as blast furnace or fly ash. The use of SCM enables to achieve various aims as the cost reduction by recovery of by-products, the CO 2 emission reduction, the obtaining of specific properties as low pH. So, blended cements are more and more current in different fields as civil engineering and nuclear waste repository. The use of silica and/or aluminium rich SCMs directly impacts the amount and the kind of hydrates formed, hence the volume and the porosity and finally the durability of these materials. Aluminates containing hydrates formation is not well understood. Al content can result from Al-uptake in C-S-H due to Al-substitution of Si-tetrahedra to well crystallised hydrates like straetlingite or katoite phases. This study proposes a surface dependant thermodynamic model to predict and to correlate the Al-uptake (substitution) of C-A-S-H with solutions representative of that of cement pores chemistry. For this purpose, pure C-A-S-H alkali-free were synthesized in diluted suspensions. On one hand, hydrates and their solutions were characterized at equilibrium. On the other hand, thermodynamics modelling were performed from these collected data to describe C-A-S-H in the equilibrium solutions. These results allowed evaluating the Al-availability in the cementitious system and especially for aluminates containing hydrates precipitation. (authors)

  9. Homogeneous catalysis of deuterium transfer by potassium hydroxide and potassium methoxide D2-H2O and D2-CH3OH exchange

    Strathdee, G.G.; Garner, D.M.; Given, R.M.

    1977-01-01

    The kinetics and mechanism of exchange of deuterium between D 2 and water and between D 2 and methanol, catalyzed respectively by concentrated potassium hydroxide and potassium methoxide, has been studied between 348 and 398 K. In the D 2 -KOH-H 2 O case, the transfer of deuterium was found to be controlled by the rate of activation of the D 2 molecule by OH - . Rapid exchange of D + with the aqueous solution followed. From the D 2 -KOCH 3 -CH 3 OH studies, it was concluded that deuterium exchange depended upon the rates of both D 2 activation by methoxide and interaction of the solvent with the transition, or encounter, complex. The dependence of second-order rate constants on solvent activity for both systems was determined by normalization of the exchange reaction rates to unit reagent activity. Analysis of the kinetic isotope effects for each system suggested that their increase with base concentration or temperature was due to solvation effects. (author)

  10. Crystallization of rare earth germanates in the K2O-Ln2O3-GeO2-H2O at 280 deg C

    Panasenko, E.B.; Begunova, R.G.; Sklokina, N.F.

    1980-01-01

    Crystallization of rare earth germanates in potassium hydroxide solutions is studied at 280 deg C. Stability limits for different crystalline phases are established. Diorthogermanates Ln 2 O 3 x2GeO 3 (three structural modifications) are formed with all lanthanides except lanthanum. Germanates-apatites 7Ln 2 O 3 x9GeO 2 are characteristic for ''large'' lanthanides La-Nd. Alkali germanate of the composition 0.5 K 2 OxLn 2 O 3 xGeO 2 xnH 2 O is realized with the elements of the end of rare earth series, i.e., Tm-Lu. Some properties of the germanates synthesized are considered [ru

  11. Fundamental study of CO2-H2O-mineral interactions for carbon sequestration, with emphasis on the nature of the supercritical fluid-mineral interface.

    Bryan, Charles R.; Dewers, Thomas A.; Heath, Jason E.; Wang, Yifeng; Matteo, Edward N.; Meserole, Stephen P.; Tallant, David Robert

    2013-09-01

    In the supercritical CO2-water-mineral systems relevant to subsurface CO2 sequestration, interfacial processes at the supercritical fluid-mineral interface will strongly affect core- and reservoir-scale hydrologic properties. Experimental and theoretical studies have shown that water films will form on mineral surfaces in supercritical CO2, but will be thinner than those that form in vadose zone environments at any given matric potential. The theoretical model presented here allows assessment of water saturation as a function of matric potential, a critical step for evaluating relative permeabilities the CO2 sequestration environment. The experimental water adsorption studies, using Quartz Crystal Microbalance and Fourier Transform Infrared Spectroscopy methods, confirm the major conclusions of the adsorption/condensation model. Additional data provided by the FTIR study is that CO2 intercalation into clays, if it occurs, does not involve carbonate or bicarbonate formation, or significant restriction of CO2 mobility. We have shown that the water film that forms in supercritical CO2 is reactive with common rock-forming minerals, including albite, orthoclase, labradorite, and muscovite. The experimental data indicate that reactivity is a function of water film thickness; at an activity of water of 0.9, the greatest extent of reaction in scCO2 occurred in areas (step edges, surface pits) where capillary condensation thickened the water films. This suggests that dissolution/precipitation reactions may occur preferentially in small pores and pore throats, where it may have a disproportionately large effect on rock hydrologic properties. Finally, a theoretical model is presented here that describes the formation and movement of CO2 ganglia in porous media, allowing assessment of the effect of pore size and structural heterogeneity on capillary trapping efficiency. The model results also suggest possible engineering approaches for optimizing trapping capacity and for monitoring ganglion formation in the subsurface.

  12. D/H fractionation in the H2-H2O system at supercritical water conditions: Compositional and hydrogen bonding effects

    Foustoukos, Dionysis I.; Mysen, Bjorn O.

    2012-06-01

    A series of experiments has been conducted in the H2-D2-D2O-H2O-Ti-TiO2 system at temperatures ranging from 300 to 800 °C and pressures between ∼0.3 and 1.3 GPa in a hydrothermal diamond anvil cell, utilizing Raman spectroscopy as a quantitative tool to explore the relative distribution of hydrogen and deuterium isotopologues of the H2 and H2O in supercritical fluids. In detail, H2O-D2O solutions (1:1) were reacted with Ti metal (3-9 h) in the diamond cell, leading to formation of H2, D2, HD, and HDO species through Ti oxidation and H-D isotope exchange reactions. Experimental results obtained in situ and at ambient conditions on quenched samples indicate significant differences from the theoretical estimates of the equilibrium thermodynamic properties of the H-D exchange reactions. In fact, the estimated enthalpy for the H2(aq)-D2(aq) disproportionation reaction (ΔHrxn) is about -3.4 kcal/mol, which differs greatly from the +0.16 kcal/mol predicted for the exchange reaction in the gas phase by statistical mechanics models. The exothermic behavior of the exchange reaction implies enhanced stability of H2 and D2 relative to HD. Accordingly, the significant energy difference of the internal H2(aq)-D2(aq)-HD(aq) equilibrium translates to strong differences of the fractionation effects between the H2O-H2 and D2O-D2 isotope exchange relationships. The D/H fractionation factors between H2O-H2(aq) and D2O-D2(aq) differ by 365‰ in the 600-800 °C temperature range, and are indicative of the greater effect of D2O contribution to the δD isotopic composition of supercritical fluids. The negative ΔHrxn values for the H2(aq)-D2(aq)-HD(aq) equilibrium and the apparent decrease of the equilibrium constant with increasing temperature might be because of differences of the Henry’s law constant between the H- and D-bearing species dissolved in supercritical aqueous solutions. Such effects may be attributed to the stronger hydrogen bonding in the O-H⋯O relative to the O-D⋯O environment. This difference allows enhanced gas solubility in the denser and more polar H2O clusters, and thus, affects the D/H exchange between the H2-D2 volatiles and the coexisting H2O-D2O mixtures. The proposed role of temperature in promoting differences in the density and polarity of hydrogen-bonded OHO and ODO molecules may be explained with isotope-specific molar volume effects similar to those suggested to account for the hydrogen isotope fractionation between H2O and hydroxide mineral phases (e.g. brucite) across large pressure intervals.

  13. Thermal decomposition of [Co(en)3][Fe(CN)6]? 2H2O: Topotactic dehydration process, valence and spin exchange mechanism elucidation

    Tr?vn??ek, Zden?k; Zbo?il, Radek; Matikov?-Ma?arov?, Miroslava; Draho?, Bohuslav; ?ern?k, Juraj

    2013-01-01

    Background The Prussian blue analogues represent well-known and extensively studied group of coordination species which has many remarkable applications due to their ion-exchange, electron transfer or magnetic properties. Among them, Co-Fe Prussian blue analogues have been extensively studied due to the photoinduced magnetization. Surprisingly, their suitability as precursors for solid-state synthesis of magnetic nanoparticles is almost unexplored. In this paper, the mechanism of thermal deco...

  14. Estudo da aplicação de foto-Fenton (Fe2+/H2O2 solar no pré-tratamento do chorume

    Alessandro Sampaio Cavalcanti

    2014-01-01

    Full Text Available O chorume em estudo é proveniente da cidade de Cachoeira Paulista no interior do estado de São Paulo apresenta as concentrações dos parâmetros COT (368.6 mg C L-1, DQO (3552.2 mg O2 L-1 e DBO (397.4 mg O2 L-1 que mostram a baixa razão de        biodegradabilidade (DBO/DQO = 0.11. Neste contexto, os processos oxidativos avançados surgem como alternativa para o seu pré-tratamento. O objetivo desse trabalho é utilizar a fotocatálise homogênea, empregando foto-Fenton (H2O2 + Fe2+ Solar num reator aberto com volume constante do efluente (3 L para verificar a eficiência e a avaliação econômica de remoção da carga orgânica. O reator possui um suporte de madeira que está direcionado ao Equador com um ângulo de inclinação de 23º, com uma placa metálica sem pigmentação denominada branco, numa vazão constante (13 L . min-1. Ao mesmo tempo, o volume do reagente de Fe2+ (0.82 mol L-1 foi adicionado totalmente no início da reação e o H2O2 (30 %  m/ m durante 60 min do tempo total de 2 h, sendo a radiação solar medida através de um radiômetro portátil. O processo foi otimizado por um planejamento fatorial fracionado (24-1, e os fatores estudados foram: pH, intervalo da radiação solar, quantidades de H2O2 (g e Fe2+ (g. A maior redução percentual de COT (Carbono Orgânico Total foi 82.12%, com um aumento de sua biodegradabilidade para 0.41 aliado ao custo otimizado de US$ 0.188 / 3 L. Desta forma, o processo fotocatalítico proposto mostrou grande viabilidade técnico-econômico em relação à degradação da carga orgânica do chorume.

  15. LIMS/Nimbus-7 Level 2 Vertical Profiles of O3, NO2, H2O, HNO3, Geopotential Height, and Temperature V006

    National Aeronautics and Space Administration — The Limb Infrared Monitor of the Stratosphere (LIMS) version 6 Level-2 data product consists of daily, geolocated, vertical profiles of temperature, geopotential...

  16. Fundamental Understanding of Methane-Carbon Dioxide-Water (CH4-CO2-H2O) Interactions in Shale Nanopores under Reservoir Conditions: Quarterly Report.

    Wang, Yifeng [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2017-11-01

    Shale is characterized by the predominant presence of nanometer-scale (1-100 nm) pores. The behavior of fluids in those pores directly controls shale gas storage and release in shale matrix and ultimately the wellbore production in unconventional reservoirs. Recently, it has been recognized that a fluid confined in nanopores can behave dramatically differently from the corresponding bulk phase due to nanopore confinement (Wang, 2014). CO2 and H2O, either preexisting or introduced, are two major components that coexist with shale gas (predominately CH4) during hydrofracturing and gas extraction. Note that liquid or supercritical CO2 has been suggested as an alternative fluid for subsurface fracturing such that CO2 enhanced gas recovery can also serve as a CO2 sequestration process. Limited data indicate that CO2 may preferentially adsorb in nanopores (particularly those in kerogen) and therefore displace CH4 in shale. Similarly, the presence of water moisture seems able to displace or trap CH4 in shale matrix. Therefore, fundamental understanding of CH4-CO2-H2O behavior and their interactions in shale nanopores is of great importance for gas production and the related CO2 sequestration. This project focuses on the systematic study of CH4-CO2-H2O interactions in shale nanopores under high-pressure and high temperature reservoir conditions. The proposed work will help to develop new stimulation strategies to enable efficient resource recovery from fewer and less environmentally impactful wells.

  17. Isotopic evidence for the infiltration of mantle and metamorphic CO2-H2O fluids from below in faulted rocks from the San Andreas Fault System

    Pili, E.; Kennedy, B.M.; Conrad, M.E.; Gratier, J.-P.

    2010-12-15

    To characterize the origin of the fluids involved in the San Andreas Fault (SAF) system, we carried out an isotope study of exhumed faulted rocks from deformation zones, vein fillings and their hosts and the fluid inclusions associated with these materials. Samples were collected from segments along the SAF system selected to provide a depth profile from upper to lower crust. In all, 75 samples from various structures and lithologies from 13 localities were analyzed for noble gas, carbon, and oxygen isotope compositions. Fluid inclusions exhibit helium isotope ratios ({sup 3}He/{sup 4}He) of 0.1-2.5 times the ratio in air, indicating that past fluids percolating through the SAF system contained mantle helium contributions of at least 35%, similar to what has been measured in present-day ground waters associated with the fault (Kennedy et al., 1997). Calcite is the predominant vein mineral and is a common accessory mineral in deformation zones. A systematic variation of C- and O-isotope compositions of carbonates from veins, deformation zones and their hosts suggests percolation by external fluids of similar compositions and origin with the amount of fluid infiltration increasing from host rocks to vein to deformation zones. The isotopic trend observed for carbonates in veins and deformation zones follows that shown by carbonates in host limestones, marbles, and other host rocks, increasing with increasing contribution of deep metamorphic crustal volatiles. At each crustal level, the composition of the infiltrating fluids is thus buffered by deeper metamorphic sources. A negative correlation between calcite {delta}{sup 13}C and fluid inclusion {sup 3}He/{sup 4}He is consistent with a mantle origin for a fraction of the infiltrating CO{sub 2}. Noble gas and stable isotope systematics show consistent evidence for the involvement of mantle-derived fluids combined with infiltration of deep metamorphic H{sub 2}O and CO{sub 2} in faulting, supporting the involvement of deep fluids percolating through and perhaps weakening the fault zone. There is no clear evidence for a significant contribution from meteoric water, except for overprinting related to late weathering.

  18. Simulation of Canopy CO2/H2O Fluxes for a Rubber (Hevea Brasiliensis) Plantation in Central Cambodia: The Effect of the Regular Spacing of Planted Trees

    Kumagai, Tomo' omi; Mudd, Ryan; Miyazawa, Yoshiyuki; Liu, Wen; Giambelluca, Thomas; Kobayashi, N.; Lim, Tiva Khan; Jomura, Mayuko; Matsumoto, Kazuho; Huang, Maoyi; Chen, Qi; Ziegler, Alan; Yin, Song

    2013-09-10

    We developed a soil-vegetation-atmosphere transfer (SVAT) model applicable to simulating CO2 and H2O fluxes from the canopies of rubber plantations, which are characterized by distinct canopy clumping produced by regular spacing of plantation trees. Rubber (Hevea brasiliensis Müll. Arg.) plantations, which are rapidly expanding into both climatically optimal and sub-optimal environments throughout mainland Southeast Asia, potentially change the partitioning of water, energy, and carbon at multiple scales, compared with traditional land covers it is replacing. Describing the biosphere-atmosphere exchange in rubber plantations via SVAT modeling is therefore essential to understanding the impacts on environmental processes. The regular spacing of plantation trees creates a peculiar canopy structure that is not well represented in most SVAT models, which generally assumes a non-uniform spacing of vegetation. Herein we develop a SVAT model applicable to rubber plantation and an evaluation method for its canopy structure, and examine how the peculiar canopy structure of rubber plantations affects canopy CO2 and H2O exchanges. Model results are compared with measurements collected at a field site in central Cambodia. Our findings suggest that it is crucial to account for intensive canopy clumping in order to reproduce observed rubber plantation fluxes. These results suggest a potentially optimal spacing of rubber trees to produce high productivity and water use efficiency.

  19. Mechanical and microstructural evolution of Hi-Nicalon Trade Mark SiC fibers annealed in O2-H2O-Ar atmospheres

    Li Siwei; Feng Zude; Mei Hui; Zhang Litong

    2008-01-01

    Hi-Nicalon fibers were exposed in 8% O 2 /78% Ar/14% H 2 O atmosphere for 1 h at 1300, 1400, 1500, 1600 deg. C, respectively. Residual tensile strength was evaluated by tensile test, phases in the fibers were identified using an X-ray diffractometer (XRD), morphology of the fracture surfaces and microstructure was observed by scanning electron microscope (SEM) and transmission electron microscope (TEM), respectively. Results indicated that residual tensile strength increased with increasing temperature from 1300 to 1500 deg. C, then decreased after annealing in 1600 deg. C. The grain size of β-SiC and the amount of the stacking faults increased under the elevated temperature as well. After annealing, a passive film with a structure of α-cristobalite crystals dispersed in amorphous SiO 2 phase formed on the fiber surface, the thickness of the film increased with the annealing temperature from 1300 to 1500 deg. C, after annealing in 1600 deg. C, fractional silica film spalled. Finally, relationship between the structural changes and the mechanical properties, the control effect of water vapor on formation and structural evolution of the passive film were discussed

  20. Vibrational mode frequencies of silica species in SiO2-H2O liquids and glasses from ab initio molecular dynamics.

    Spiekermann, Georg; Steele-MacInnis, Matthew; Schmidt, Christian; Jahn, Sandro

    2012-04-21

    Vibrational spectroscopy techniques are commonly used to probe the atomic-scale structure of silica species in aqueous solution and hydrous silica glasses. However, unequivocal assignment of individual spectroscopic features to specific vibrational modes is challenging. In this contribution, we establish a connection between experimentally observed vibrational bands and ab initio molecular dynamics (MD) of silica species in solution and in hydrous silica glass. Using the mode-projection approach, we decompose the vibrations of silica species into subspectra resulting from several fundamental structural subunits: The SiO(4) tetrahedron of symmetry T(d), the bridging oxygen (BO) Si-O-Si of symmetry C(2v), the geminal oxygen O-Si-O of symmetry C(2v), the individual Si-OH stretching, and the specific ethane-like symmetric stretching contribution of the H(6)Si(2)O(7) dimer. This allows us to study relevant vibrations of these subunits in any degree of polymerization, from the Q(0) monomer up to the fully polymerized Q(4) tetrahedra. Demonstrating the potential of this approach for supplementing the interpretation of experimental spectra, we compare the calculated frequencies to those extracted from experimental Raman spectra of hydrous silica glasses and silica species in aqueous solution. We discuss observed features such as the double-peaked contribution of the Q(2) tetrahedral symmetric stretch, the individual Si-OH stretching vibrations, the origin of the experimentally observed band at 970 cm(-1) and the ethane-like vibrational contribution of the H(6)Si(2)O(7) dimer at 870 cm(-1).

  1. Photocrystallography at TriCS/SINQ: light-induced structural changes in Na2[Fe(CN)5NO]2H2O

    Schefer, J.; Schaniel, D.; Woike, Th.; Imlau, M.

    2004-01-01

    Light-induced metastable electronic states as observed e.g. in sodium nitroprusside are of fundamental interest for data storage and optical computing. Structural functionality and therefore the light-induced structure itself is of basic interest in such systems. As neutrons are sensitive to the position of the nucleus and non-destructive with respect to the metastable electronic states, neutron photocrystallography provides a useful method to determine light-induced structural changes. A photocrystallographic experimental setup has been built-up at SINQ and has been successfully used at the single-crystal instrument TriCS and the test facility TOPSI (now called MORPHEUS)

  2. Gasification of algal biomass (Cladophora glomerata L.) with CO2/H2O/O2 in a circulating fluidized bed.

    Ebadi, Abdol Ghaffar; Hisoriev, Hikmat

    2017-11-28

    Gasification is one of the most important thermochemical routes to produce both synthesis gas (syngas) and chars. The quality of produced syngas wieldy depends on the operating conditions (temperature, residence time, heating rate, and gasifying agent), hydrodynamic properties of gasifier (particle size, minimum fluidization velocity, and gasifier size), and type of feedstock (coal, biomass, oil, and municipal solid wastes). In the present study, simulation of syngas production via circulating fluidized bed (CFB) gasification of algal biomass (Cladophora glomerata L.) at different gasifying agents and particle sizes was carried out, using Aspen Plus simulator. The model which has been validated by using experimental data of the technical literature was used to evaluate the influence of operating conditions on gas composition and performance parameters. The results show that biomass gasification using pure oxygen as the gasification agent has great potential to improve the caloric value of produced gas and performance indicators. It was also found that the produced gas caloric value, syngas yield, and performance parameters (CCE and CGE) increase with reaction temperature but are inversely proportional to the biomass particle size.

  3. Time-dependent one-dimensional simulation of atmospheric dielectric barrier discharge in N2/O2/H2O using COMSOL Multiphysics

    Sohbatzadeh, F.; Soltani, H.

    2018-04-01

    The results of time-dependent one-dimensional modelling of a dielectric barrier discharge (DBD) in a nitrogen-oxygen-water vapor mixture at atmospheric pressure are presented. The voltage-current characteristics curves and the production of active species are studied. The discharge is driven by a sinusoidal alternating high voltage-power supply at 30 kV with frequency of 27 kHz. The electrodes and the dielectric are assumed to be copper and quartz, respectively. The current discharge consists of an electrical breakdown that occurs in each half-period. A detailed description of the electron attachment and detachment processes, surface charge accumulation, charged species recombination, conversion of negative and positive ions, ion production and losses, excitations and dissociations of molecules are taken into account. Time-dependent one-dimensional electron density, electric field, electric potential, electron temperature, densities of reactive oxygen species (ROS) and reactive nitrogen species (RNS) such as: O, O-, O+, {O}2^{ - } , {O}2^{ + } , O3, {N}, {N}2^{ + } , N2s and {N}2^{ - } are simulated versus time across the gas gap. The results of this work could be used in plasma-based pollutant degradation devices.

  4. Oxidation of SO2 and formation of water droplets under irradiation of 20MeV protons in N2/H2O/SO2

    Tomita, Shigeo; Nakai, Yoichi; Funada, Shuhei

    2015-01-01

    We have performed an experiment on charged droplet formation in a humidified N2 gas with trace SO2 concentration and induced by 20MeV proton irradiation. It is thought that SO2 reacts with the chemical species, such as OH radicals, generated through the reactions triggered by N2+ production. Both...

  5. Nanocrystal quantum dots

    Klimov, Victor I

    2010-01-01

    ""Soft"" Chemical Synthesis and Manipulation of Semiconductor Nanocrystals, J.A. Hollingsworth and V.I. Klimov Electronic Structure in Semiconductor Nanocrystals: Optical Experiment, D.J. NorrisFine Structure and Polarization Properties of Band-Edge Excitons in Semiconductor Nanocrystals, A.L. EfrosIntraband Spectroscopy and Dynamics of Colloidal Semiconductor Quantum Dots, P. Guyot-Sionnest, M. Shim, and C. WangMultiexciton Phenomena in Semiconductor Nanocrystals, V.I. KlimovOptical Dynamics in Single Semiconductor Quantum Do

  6. Quantum Dot Photonics

    Kinnischtzke, Laura A.

    We report on several experiments using single excitons confined to single semiconductor quantum dots (QDs). Electric and magnetic fields have previously been used as experimental knobs to understand and control individual excitons in single quantum dots. We realize new ways of electric field control by changing materials and device geometry in the first two experiments with strain-based InAs QDs. A standard Schottky diode heterostructure is demonstrated with graphene as the Schottky gate material, and its performance is bench-marked against a diode with a standard gate material, semi-transparent nickel-chromium (NiCr). This change of materials increases the photon collection rate by eliminating absorption in the metallic NiCr layer. A second set of experiments investigates the electric field response of QDs as a possible metrology source. A linear voltage potential drop in a plane near the QDs is used to describe how the spatially varying voltage profile is also imparted on the QDs. We demonstrate a procedure to map this voltage profile as a preliminary route towards a full quantum sensor array. Lastly, InAs QDs are explored as potential spin-photon interfaces. We describe how a magnetic field is used to realize a reversible exchange of information between light and matter, including a discussion of the polarization-dependence of the photoluminesence, and how that can be linked to the spin of a resident electron or hole. We present evidence of this in two wavelength regimes for InAs quantum dots, and discuss how an external magnetic field informs the spin physics of these 2-level systems. This thesis concludes with the discovery of a new class of quantum dots. As-yet unidentified defect states in single layer tungsten diselenide (WSe 2 ) are shown to host quantum light emission. We explore the spatial extent of electron confinement and tentatively identify a radiative lifetime of 1 ns for these single photon emitters.

  7. Quantum dot solar cell

    Ahamefula, U.C.; Sulaiman, M.Y.; Sopian, K.; Ibarahim, Z.; Ibrahim, N.; Alghoul, M.A.; Haw, L.C.; Yahya, M.; Amin, N.; Mat, S.; Ruslan, M.H.

    2009-01-01

    Full text: The much awaited desire of replacing fossil fuel with photovoltaic will remain a fairy tale if the myriad of issues facing solar cell development are marginalized. Foremost in the list is the issue of cost. Silicon has reached a stage where its use on large scale can no longer be lavishly depended upon. The demand for high grade silicon from the microelectronics and solar industries has soared leading to scarcity. New approach has to be sought. Notable is the increased attention on thin films such as cadmium telluride, copper indium gallium diselenide, amorphous silicon, and the not so thin non-crystalline family of silicon. While efforts to address the issues of stability, toxicity and efficiency of these systems are ongoing, another novel approach is quietly making its appearance - quantum dots. Quantum dots seem to be promising candidates for solar cells because of the opportunity to manipulate their energy levels allowing absorption of a wider solar spectrum. Utilization of minute quantity of these nano structures is enough to bring the cost of solar cell down and to ascertain sustainable supply of useful material. The paper outlines the progress that has been made on quantum dot solar cells. (author)

  8. Human-centred Governance

    Bason, Christian

    2017-01-01

    Design approaches are now being applied all over the world as a powerful approach to innovating public policies and services. Christian Bason, author of Leading public design: Discovering human-centred governance, argues that by bringing design methods into play, public managers can lead change...... with citizens at the centre, and discover a new model for steering public organisations: human-centred governance....

  9. The Search for Centre

    Nunes, April

    2006-01-01

    This paper acknowledges the importance of a dancer's centre but likewise highlights the problematic nature of the communication of this concept from dance teacher to student. After a brief introduction of orthodox approaches in finding centre, this paper suggests a method of locating centre through the ancient somatic technique.

  10. Silicon quantum dots: surface matters

    Dohnalová, K.; Gregorkiewicz, T.; Kůsová, Kateřina

    2014-01-01

    Roč. 26, č. 17 (2014), 1-28 ISSN 0953-8984 R&D Projects: GA ČR GPP204/12/P235 Institutional support: RVO:68378271 Keywords : silicon quantum dots * quantum dot * surface chemistry * quantum confinement Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.346, year: 2014

  11. Phosphorene quantum dots

    Vishnoi, Pratap; Mazumder, Madhulika; Barua, Manaswee; Pati, Swapan K.; Rao, C. N. R.

    2018-05-01

    Phosphorene, a two-dimensional material, has been a subject of recent investigations. In the present study, we have prepared blue fluorescent phosphorene quantum dots (PQDs) by liquid phase exfoliation of black phosphorus in two non-polar solvents, toluene and mesitylene. The average particle sizes of PQDs decrease from 5.0 to 1.0 nm on increasing the sonicator power from 150 to 225 W. The photoluminescence spectrum of the PQDs is red-shifted in the 395-470 nm range on increasing the excitation-wavelength from 300 to 480 nm. Electron donor and acceptor molecules quench the photoluminescence, with the acceptors showing more marked effects.

  12. GRUNCLE, 1. Collision Source Calculation for Program DOT. DOT-3.5, 2-D Neutron Transport, Gamma Transport Program DOT with New Space-Scaling

    1996-01-01

    mesh. Anisotropic scattering is treated using a Legendre expansion of arbitrary order. Convergence can be accelerated by several optional schemes, including a pointwise rescaling technique. DOT-3.5/E: Differs from DOT-3.5 in that exponential supplementary equations, as well as the usual diamond and weighted schemes, may be used to find the mesh-centre flux from the fluxes at the faces of the mesh. The model: 1. always gives positive solutions and does not require any fix-up techniques provided that the source is non-negative; 2. improves convergence rate in most neutron deep-penetration problems and, for any practical spatial discretization, always requires CPU times not only smaller than those required by DOT-3 mixed (linear + step fix-up) model, but also shorter (generally 10-20%) than the times required by DOT-3.5 weighted difference model; 3. increasing spatial mesh size supplies solutions which are always reasonable overestimates of the exact solution and its numerical behaviour is more stable and coherent than the mixed mode. Experience up to now from several deep penetration problems in (r,z) and (x,y) geometry shows that, while for neutrons the exponential model almost always works very well, for gamma rays its behaviour may be critical and in some cases there is lack of convergence. C - Restrictions on the complexity of the problem: The total storage requirement is determined by a formula given in the input description. No other restrictions to problem size are applicable

  13. CMS Centre at CERN

    2007-01-01

    A new "CMS Centre" is being established on the CERN Meyrin site by the CMS collaboration. It will be a focal point for communications, where physicists will work together on data quality monitoring, detector calibration, offline analysis of physics events, and CMS computing operations. Construction of the CMS Centre begins in the historic Proton Synchrotron (PS) control room. The historic Proton Synchrotron (PS) control room, Opened by Niels Bohr in 1960, will be reused by CMS to built its control centre. TThe LHC@FNAL Centre, in operation at Fermilab in the US, will work very closely with the CMS Centre, as well as the CERN Control Centre. (Photo Fermilab)The historic Proton Synchrotron (PS) control room is about to start a new life. Opened by Niels Bohr in 1960, the room will be reused by CMS to built its control centre. When finished, it will resemble the CERN Contro...

  14. Printer model for dot-on-dot halftone screens

    Balasubramanian, Raja

    1995-04-01

    A printer model is described for dot-on-dot halftone screens. For a given input CMYK signal, the model predicts the resulting spectral reflectance of the printed patch. The model is derived in two steps. First, the C, M, Y, K dot growth functions are determined which relate the input digital value to the actual dot area coverages of the colorants. Next, the reflectance of a patch is predicted as a weighted combination of the reflectances of the four solid C, M, Y, K patches and their various overlays. This approach is analogous to the Neugebauer model, with the random mixing equations being replaced by dot-on-dot mixing equations. A Yule-Neilsen correction factor is incorporated to account for light scattering within the paper. The dot area functions and Yule-Neilsen parameter are chosen to optimize the fit to a set of training data. The model is also extended to a cellular framework, requiring additional measurements. The model is tested with a four color xerographic printer employing a line-on-line halftone screen. CIE L*a*b* errors are obtained between measurements and model predictions. The Yule-Neilsen factor significantly decreases the model error. Accuracy is also increased with the use of a cellular framework.

  15. Leaving the street and reconstructing lives: impact of DOTS in empowering homeless people in Tokyo, Japan.

    Kawatsu, L; Sato, N; Ngamvithayapong-Yanai, J; Ishikawa, N

    2013-07-01

    Since 2000, the Public Health Centre (PHC) in Shinjuku, an area of Tokyo with one of the largest homeless populations in Japan, has been implementing PHC-based DOTS treatment for homeless tuberculosis (TB) patients, with much epidemiological success. Anecdotal evidence indicates that homeless patients treated under DOTS have experienced various positive changes. However, this experience has not yet been systematically analysed. To explore the changes experienced by homeless TB patients, and to discuss the possible role of PHC-based DOTS treatment in effecting these changes. A qualitative study via in-depth interviews with 18 ex-homeless patients who completed DOTS-based treatment at Shinjuku City PHC. The data were analysed using the interpretive content analysis method. The various changes experienced by the participants were categorised into five sub-categories of empowerment, including improved mental health and interpersonal relationships. Some of these changes were attributable to the participants undergoing PHC-based DOTS, which, by addressing their various emotional needs, helped to trigger patient empowerment. Based on our findings, a model of empowerment using PHC-based DOTS was constructed. PHC-based DOTS not only successfully controlled TB, it also empowered homeless patients by addressing their emotional needs. The interpersonal skills of the nurses played a critical role in this process.

  16. Graphene based quantum dots.

    Zhang, H G; Hu, H; Pan, Y; Mao, J H; Gao, M; Guo, H M; Du, S X; Greber, T; Gao, H-J

    2010-08-04

    Laterally localized electronic states are identified on a single layer of graphene on ruthenium by low temperature scanning tunneling spectroscopy (STS). The individual states are separated by 3 nm and comprise regions of about 90 carbon atoms. This constitutes a highly regular quantum dot-array with molecular precision. It is evidenced by quantum well resonances (QWRs) with energies that relate to the corrugation of the graphene layer. The dI/dV conductance spectra are modeled by a layer height dependent potential-well with a delta-function potential that describes the barrier for electron penetration into graphene. The resulting QWRs are strongest and lowest in energy on the isolated 'hill' regions with a diameter of 2 nm, where the graphene is decoupled from the surface.

  17. SAP Nuclear Competence Centre

    Andrlova, Z.

    2009-01-01

    In this issue we continue and introduce the SAP Nuclear Competence Centre and its head Mr. Igor Dzama. SAP Nuclear Competence Centrum is one of the fi rst competence centres outside ENEL headquarters. It should operate in Slovakia and should have competencies within the whole Enel group. We are currently dealing with the issues of organisation and funding. We are trying to balance the accountability to the NPP directors and to the management of the competence centres at Enel headquarters; we are looking at the relations between the competence centres within the group and defining the services that we will provide for the NPPs. author)

  18. Canadian Irradiation Centre

    1987-05-01

    The Canadian Irradiation Centre is a non-profit cooperative project between Atomic Energy of Canada Limited, Radiochemical Company and Universite du Quebec, Institut Armand-Frappier, Centre for Applied Research in Food Science. The Centre's objectives are to develop, demonstrate and promote Canada's radiation processing technology and its applications by conducting applied research; training technical, professional and scientific personnel; educating industry and government; demonstrating operational and scientific procedures; developing processing procedures and standards, and performing product and market acceptance trials. This pamphlet outlines the history of radoation technology and the services offered by the Canadian Irradiation Centre

  19. PennDOT : fact book

    2008-06-01

    PennDOT was created in 1970 when the former : Department of Highways was merged with transportation related : functions from the Departments of Revenue, : Commerce, Community Affairs and Military Affairs. With : an annual budget of about $5.4 billion...

  20. Quantum dots: Rethinking the electronics

    Bishnoi, Dimple [Department of Physics, S. S. Jain Subodh PG College, Jaipur, Rajasthan Pin-302004 (India)

    2016-05-06

    In this paper, we demonstrate theoretically that the Quantum dots are quite interesting for the electronics industry. Semiconductor quantum dots (QDs) are nanometer-scale crystals, which have unique photo physical, quantum electrical properties, size-dependent optical properties, There small size means that electrons do not have to travel as far as with larger particles, thus electronic devices can operate faster. Cheaper than modern commercial solar cells while making use of a wider variety of photon energies, including “waste heat” from the sun’s energy. Quantum dots can be used in tandem cells, which are multi junction photovoltaic cells or in the intermediate band setup. PbSe (lead selenide) is commonly used in quantum dot solar cells.

  1. DOT Official County Highway Map

    Minnesota Department of Natural Resources — The County Highway Map theme is a scanned and rectified version of the original MnDOT County Highway Map Series. The cultural features on some of these maps may be...

  2. Complex dynamics in planar two-electron quantum dots

    Schroeter, Sebastian Josef Arthur

    2013-01-01

    Quantum dots play an important role in a wide range of recent experimental and technological developments. In particular they are promising candidates for realisations of quantum bits and further applications in quantum information theory. The harmonically confined Hooke's atom model is experimentally verified and separates in centre-of-mass and relative coordinates. Findings that are contradictory to this separability call for an extension of the model, in particular changing the confinement potential. In order to study effects of an anharmonic confinement potential on spectral properties of planar two-electron quantum dots a sophisticated numerical approach is developed. Comparison between the Helium atom, Hooke's atom and an anharmonic potential model are undertaken in order to improve the description of quantum dots. Classical and quantum features of complexity and chaos are investigated and used to characterise the dynamics of the system to be mixed regular-chaotic. Influence of decoherence can be described by quantum fidelity, which measures the effect of a perturbation on the time evolution. The quantum fidelity of eigenstates of the system depends strongly on the properties of the perturbation. Several methods for solving the time-dependent Schrödinger equation are implemented and a high level of accuracy for long time evolutions is achieved. The concept of offset entanglement, the entanglement of harmonic models in the noninteracting limit, is introduced. This concept explains different questions raised in the literature for harmonic quantum dot models, recently. It shows that only in the groundstate the electrons are not entangled in the fermionic sense. The applicability, validity, and origin of Hund's first rule in general quantum dot models is further addressed. In fact Hund's first rule is only applicable, and in this case also valid, for one pair of singlet and triplet states in Hooke's atom. For more realistic models of two-electron quantum dots an

  3. Complex dynamics in planar two-electron quantum dots

    Schroeter, Sebastian Josef Arthur

    2013-06-25

    Quantum dots play an important role in a wide range of recent experimental and technological developments. In particular they are promising candidates for realisations of quantum bits and further applications in quantum information theory. The harmonically confined Hooke's atom model is experimentally verified and separates in centre-of-mass and relative coordinates. Findings that are contradictory to this separability call for an extension of the model, in particular changing the confinement potential. In order to study effects of an anharmonic confinement potential on spectral properties of planar two-electron quantum dots a sophisticated numerical approach is developed. Comparison between the Helium atom, Hooke's atom and an anharmonic potential model are undertaken in order to improve the description of quantum dots. Classical and quantum features of complexity and chaos are investigated and used to characterise the dynamics of the system to be mixed regular-chaotic. Influence of decoherence can be described by quantum fidelity, which measures the effect of a perturbation on the time evolution. The quantum fidelity of eigenstates of the system depends strongly on the properties of the perturbation. Several methods for solving the time-dependent Schrödinger equation are implemented and a high level of accuracy for long time evolutions is achieved. The concept of offset entanglement, the entanglement of harmonic models in the noninteracting limit, is introduced. This concept explains different questions raised in the literature for harmonic quantum dot models, recently. It shows that only in the groundstate the electrons are not entangled in the fermionic sense. The applicability, validity, and origin of Hund's first rule in general quantum dot models is further addressed. In fact Hund's first rule is only applicable, and in this case also valid, for one pair of singlet and triplet states in Hooke's atom. For more realistic models of two

  4. Laser-induced positive ion and neutral atom/molecule emissions from single-crystal CaHPO4 center dot 2H20: The role of electron-beam-induced defects

    Dawes, Mary L.; Hess, Wayne P.; Kawaguchi, Yuji; Langford, S C.; Dickinson, J. Tom

    1998-01-01

    We examine laser-induced ion and neutral emissions from single-crystal CaHPO4 center dot 2H2O (brushite), a wide-band-gap, hydrated inorganic single crystal, with 248-nm excimer laser radiation. Both laser-induced ion and neutral emissions are several orders magnitude higher following exposure to 2keV electrons at current densities of 200 uA/cm2 and doses of 1 C/cm2. In addition to intense Ca+ signals, electron-irradiated surfaces yield substantial CaO+, PO+, and P+ signals. As-grown and as-cleaved brushite show only weak neutral O2 and Ca emissions, whereas electron-irradiated surfaces yield enhanced O2, Ca, PO, PO2, and P emissions. Electron irradiation (i) significantly heats the sample, leading to thermal dehydration (CaHPO4 formation) and pyrolysis (Ca2P2O7 formation)and (ii) chemically reduces the surface via electron stimulated desorption. The thermal effects are accompanied by morphological changes, including recrystallization. Although complex, these changes lead to high defect densities, which are responsible for the dramatic enhancements in the observed laser desorption

  5. The quantum mechanical description of the dot-dot interaction in ionic colloids

    Morais, P.C.; Qu, Fanyao

    2007-01-01

    In this study the dot-dot interaction in ionic colloids is systematically investigated by self-consistently solving the coupled Schroedinger and Poisson equations in the frame of finite difference method (FDM). In a first approximation the interacting two-dot system (dimer) is described using the picture of two coupled quantum wells. It was found that the dot-dot interaction changes the colloid characteristic by changing the hopping coefficient (t) and consequently the nanodot surface charge density (σ). The hopping coefficient and the surface charge density were investigated as a function of the dot size and dot-dot distance

  6. Red light emitting solid state hybrid quantum dot-near-UV GaN LED devices

    Song, Hongjoo; Lee, Seonghoon

    2007-01-01

    We produced core-shell (CdSe)ZnSe quantum dots by direct colloidal chemical synthesis and the surface-passivation method-an overcoating of the core CdSe with a larger-bandgap material ZnSe. The (CdSe)ZnSe quantum dots(QDs) play the role of a colour conversion centre. We call these quantum dots nanophosphors. We fabricated red light emitting hybrid devices of (CdSe)ZnSe QDs and a near-UV GaN LED by combining red light emitting (CdSe)ZnSe quantum dots (as a colour conversion centre) with a near-UV(NUV) GaN LED chip (as an excitation source). A few good red phosphors have been known for UV excitation wavelengths, and red phosphors for UV excitation have been sought for a long time. Here we tested the possibility of using (CdSe)ZnSe QDs as red nanophosphors for UV excitation. The fabricated red light emitting hybrid device of (CdSe)ZnSe and a NUV GaN LED chip showed a good luminance. We demonstrated that the (CdSe)ZnSe quantum dots were promising red nanophosphors for NUV excitation and that a red LED made of QDs and a NUV excitation source was a highly efficient hybrid device

  7. Client Centred Desing

    Ørngreen, Rikke; Nielsen, Janni; Levinsen, Karin

    2008-01-01

    In this paper we argue for the use of Client Centred preparation phases when designing complex systems. Through Client Centred Design human computer interaction can extend the focus on end-users to alse encompass the client's needs, context and resources....

  8. Electron correlations in quantum dots

    Tipton, Denver Leonard John

    2001-01-01

    Quantum dot structures confine electrons in a small region of space. Some properties of semiconductor quantum dots, such as the discrete energy levels and shell filling effects visible in addition spectra, have analogies to those of atoms and indeed dots are sometimes referred to as 'artificial atoms'. However, atoms and dots show some fundamental differences due to electron correlations. For real atoms, the kinetic energy of electrons dominates over their mutual Coulomb repulsion energy and for this reason the independent electron approximation works well. For quantum dots the confining potential may be shallower than that of real atoms leading to lower electron densities and a dominance of mutual Coulomb repulsion over kinetic energy. In this strongly correlated regime the independent electron picture leads to qualitatively incorrect results. This thesis concentrates on few-electron quantum dots in the strongly correlated regime both for quasi-one-dimensional and two-dimensional dots in a square confining potential. In this so-called 'Wigner' regime the ground-state electronic charge density is localised near positions of classical electrostatic minima and the interacting electronic spectrum consists of well separated spin multiplets. In the strongly correlated regime the structure of low-energy multiplets is explained by mapping onto lattice models with extended-Hubbard and Heisenberg effective Hamiltonians. The parameters for these effective models are calculated within a Hartree approximation and are shown to reproduce well the exact results obtained by numerical diagonalisation of the full interacting Hamiltonian. Comparison is made between square dots and quantum rings with full rotational symmetry. In the very low-density regime, direct diagonalisation becomes impractical due to excessive computer time for convergence. In this regime a numerical renormalisation group method is applied to one-dimensional dots, enabling effective spin-interactions to be

  9. Imaging and Manipulating Energy Transfer Among Quantum Dots at Individual Dot Resolution.

    Nguyen, Duc; Nguyen, Huy A; Lyding, Joseph W; Gruebele, Martin

    2017-06-27

    Many processes of interest in quantum dots involve charge or energy transfer from one dot to another. Energy transfer in films of quantum dots as well as between linked quantum dots has been demonstrated by luminescence shift, and the ultrafast time-dependence of energy transfer processes has been resolved. Bandgap variation among dots (energy disorder) and dot separation are known to play an important role in how energy diffuses. Thus, it would be very useful if energy transfer could be visualized directly on a dot-by-dot basis among small clusters or within films of quantum dots. To that effect, we report single molecule optical absorption detected by scanning tunneling microscopy (SMA-STM) to image energy pooling from donor into acceptor dots on a dot-by-dot basis. We show that we can manipulate groups of quantum dots by pruning away the dominant acceptor dot, and switching the energy transfer path to a different acceptor dot. Our experimental data agrees well with a simple Monte Carlo lattice model of energy transfer, similar to models in the literature, in which excitation energy is transferred preferentially from dots with a larger bandgap to dots with a smaller bandgap.

  10. A highly efficient single-photon source based on a quantum dot in a photonic nanowire

    Claudon, Julien; Bleuse, Joel; Malik, Nitin Singh

    2010-01-01

    –4 or a semiconductor quantum dot5–7. Achieving a high extraction efficiency has long been recognized as a major issue, and both classical solutions8 and cavity quantum electrodynamics effects have been applied1,9–12. We adopt a different approach, based on an InAs quantum dot embedded in a GaAs photonic nanowire......The development of efficient solid-state sources of single photons is a major challenge in the context of quantum communication,optical quantum information processing and metrology1. Such a source must enable the implementation of a stable, single-photon emitter, like a colour centre in diamond2...

  11. Record Charge Carrier Diffusion Length in Colloidal Quantum Dot Solids via Mutual Dot-To-Dot Surface Passivation.

    Carey, Graham H; Levina, Larissa; Comin, Riccardo; Voznyy, Oleksandr; Sargent, Edward H

    2015-06-03

    Through a combination of chemical and mutual dot-to-dot surface passivation, high-quality colloidal quantum dot solids are fabricated. The joint passivation techniques lead to a record diffusion length for colloidal quantum dots of 230 ± 20 nm. The technique is applied to create thick photovoltaic devices that exhibit high current density without losing fill factor. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. The Bruce Energy Centre

    Jones, R.I.

    1982-06-01

    The Bruce Energy Centre Development Corporation is a joint venture of the Ontario Energy Corporation and 6 private companies formed to market surplus steam from the Bruce Nuclear Power Development. The corporation will also sell or lease land near Bruce NPD. The Bruce Energy Centre has an energy output of 900 BTU per day per dollar invested. Potential customers include greenhouse operators, aquaculturalists, food and beverage manufacturers, and traditional manufacturers

  13. The Aube centre

    1996-07-01

    This educational booklet is devoted to a general presentation of the Aube radioactive wastes storage centre. After a short presentation of the Andra, the French national agency for the management of radioactive wastes, it gives some general information about radioactive wastes (origin, classification), containers (quality assurance and different types), wastes transportation (planning, safety), and about the Aube centre itself: description, treatment and conditioning of drums (compacting and injection), storage facilities, geological situation of the site, and environmental controls. (J.S.)

  14. CENTRE FOR GEOMETRICAL METROLOGY

    De Chiffre, Leonardo

    The objective of this Annual Report is to give a general introduction to CGM as well as to give an account of the tasks carried out using the facilities of CGM's Instrument Centre during 1998 and 1999.......The objective of this Annual Report is to give a general introduction to CGM as well as to give an account of the tasks carried out using the facilities of CGM's Instrument Centre during 1998 and 1999....

  15. InAs/GaAs quantum dots for THz generation

    Daghestani, N.S.; Cataluna, M.A.; Berry, G.; Rose, M.J.; Ross, G.

    2012-01-01

    We report pulsed terahertz generation from InAs/GaAs quantum-dot based photoconductive devices. For 800 nm optical excitation, the dots act as recombination centres for carriers generated in the GaAs layers. Using photoreflective pump-probe measurements we demonstrate that the photogenerated carrier lifetime decreases when a lateral bias is applied. This can be attributed to an increase in the capture area of the dots when under bias. Two types of antenna metallization were investigated; non-Ohmic, and quasi-Ohmic contacts. Non-Ohmic antennae displayed resilience to Joule heating when operated at a field strength of 46 MV/m. The breakdown field of the devices was 48 MV/m, which is comparable to the breakdown field of bulk GaAs (∝50 MV/m). The maximum estimated infrared-to-THz conversion efficiency is ∝1x10 -5 . (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  16. Spin storage in quantum dot ensembles and single quantum dots

    Heiss, Dominik

    2009-01-01

    This thesis deals with the investigation of spin relaxation of electrons and holes in small ensembles of self-assembled quantum dots using optical techniques. Furthermore, a method to detect the spin orientation in a single quantum dot was developed in the framework of this thesis. A spin storage device was used to optically generate oriented electron spins in small frequency selected quantum dot ensembles using circularly polarized optical excitation. The spin orientation can be determined by the polarization of the time delayed electroluminescence signal generated by the device after a continuously variable storage time. The degree of spin polarized initialization was found to be limited to 0.6 at high magnetic fields, where anisotropic effects are compensated. The spin relaxation was directly measured as a function of magnetic field, lattice temperature and s-shell transition energy of the quantum dot by varying the spin storage time up to 30 ms. Very long spin lifetimes are obtained with a lower limit of T 1 =20 ms at B=4 T and T=1 K. A strong magnetic field dependence T 1 ∝B -5 has been observed for low temperatures of T=1 K which weakens as the temperature is increased. In addition, the temperature dependence has been determined with T 1 ∝T -1 . The characteristic dependencies on magnetic field and temperature lead to the identification of the spin relaxation mechanism, which is governed by spin-orbit coupling and mediated by single phonon scattering. This finding is qualitatively supported by the energy dependent measurements. The investigations were extended to a modified device design that enabled studying the spin relaxation dynamics of heavy holes in self-assembled quantum dots. The measurements show a polarization memory effect for holes with up to 0.1 degree of polarization. Furthermore, investigations of the time dynamics of the hole spin relaxation reveal surprisingly long lifetimes T 1 h in the microsecond range, therefore, comparable with

  17. Spin storage in quantum dot ensembles and single quantum dots

    Heiss, Dominik

    2009-10-15

    This thesis deals with the investigation of spin relaxation of electrons and holes in small ensembles of self-assembled quantum dots using optical techniques. Furthermore, a method to detect the spin orientation in a single quantum dot was developed in the framework of this thesis. A spin storage device was used to optically generate oriented electron spins in small frequency selected quantum dot ensembles using circularly polarized optical excitation. The spin orientation can be determined by the polarization of the time delayed electroluminescence signal generated by the device after a continuously variable storage time. The degree of spin polarized initialization was found to be limited to 0.6 at high magnetic fields, where anisotropic effects are compensated. The spin relaxation was directly measured as a function of magnetic field, lattice temperature and s-shell transition energy of the quantum dot by varying the spin storage time up to 30 ms. Very long spin lifetimes are obtained with a lower limit of T{sub 1}=20 ms at B=4 T and T=1 K. A strong magnetic field dependence T{sub 1}{proportional_to}B{sup -5} has been observed for low temperatures of T=1 K which weakens as the temperature is increased. In addition, the temperature dependence has been determined with T{sub 1}{proportional_to}T{sup -1}. The characteristic dependencies on magnetic field and temperature lead to the identification of the spin relaxation mechanism, which is governed by spin-orbit coupling and mediated by single phonon scattering. This finding is qualitatively supported by the energy dependent measurements. The investigations were extended to a modified device design that enabled studying the spin relaxation dynamics of heavy holes in self-assembled quantum dots. The measurements show a polarization memory effect for holes with up to 0.1 degree of polarization. Furthermore, investigations of the time dynamics of the hole spin relaxation reveal surprisingly long lifetimes T{sub 1}{sup h

  18. Quantum optics with single quantum dot devices

    Zwiller, Valery; Aichele, Thomas; Benson, Oliver

    2004-01-01

    A single radiative transition in a single-quantum emitter results in the emission of a single photon. Single quantum dots are single-quantum emitters with all the requirements to generate single photons at visible and near-infrared wavelengths. It is also possible to generate more than single photons with single quantum dots. In this paper we show that single quantum dots can be used to generate non-classical states of light, from single photons to photon triplets. Advanced solid state structures can be fabricated with single quantum dots as their active region. We also show results obtained on devices based on single quantum dots

  19. Large quantum dots with small oscillator strength

    Stobbe, Søren; Schlereth, T.W.; Höfling, S.

    2010-01-01

    We have measured the oscillator strength and quantum efficiency of excitons confined in large InGaAs quantum dots by recording the spontaneous emission decay rate while systematically varying the distance between the quantum dots and a semiconductor-air interface. The size of the quantum dots...... is measured by in-plane transmission electron microscopy and we find average in-plane diameters of 40 nm. We have calculated the oscillator strength of excitons of that size assuming a quantum-dot confinement given by a parabolic in-plane potential and a hard-wall vertical potential and predict a very large...... intermixing inside the quantum dots....

  20. The interaction between d-dot's

    Hirayama, Masaki; Machida, Masahiko; Koyama, Tomio; Ishida, Takekazu; Kato, Masaru

    2005-01-01

    We investigated the interaction between two square d-dot's. The d-dot is the nano-scaled superconducting composite structure that is made of a d-wave superconducting dot embedded in the s-wave superconducting matrix. In the numerical calculation, using the finite element method, we solved the two-components Ginzburg-Landau equation self-consistently. We obtained two kinds of solutions, which can be considered as ferromagnetic and antiferromagnetic configurations, when two d-dot's are separated parallel and diagonally. Also we discuss the applicability of d-dot's as an artificial spin system where the interactions can be controlled by the fabrication

  1. Energy centre microgrid model

    Pasonen, R.

    2011-09-15

    A simulation model of Energy centre microgrid made with PSCAD simulation software version 4.2.1 has been built in SGEM Smart Grids and Energy Markets (SGEM) work package 6.6. Microgrid is an autonomous electric power system which can operate separate from common distribution system. The idea of energy centre microgrid concept was considered in Master of Science thesis 'Community Microgrid - A Building block of Finnish Smart Grid'. The name of energy centre microgrid comes from a fact that production and storage units are concentrated into a single location, an energy centre. This centre feeds the loads which can be households or industrial loads. Power direction flow on the demand side remains same compared to the current distribution system and allows to the use of standard fuse protection in the system. The model consists of photovoltaic solar array, battery unit, variable frequency boost converter, inverter, isolation transformer and demand side (load) model. The model is capable to automatically switch to islanded mode when there is a fault in outside grid and back to parallel operation mode when fault is removed. The modelled system responses well to load changes and total harmonic distortion related to 50Hz base frequency is kept under 1.5% while operating and feeding passive load. (orig.)

  2. Nuclear Spins in Quantum Dots

    Erlingsson, S.I.

    2003-01-01

    The main theme of this thesis is the hyperfine interaction between the many lattice nuclear spins and electron spins localized in GaAs quantum dots. This interaction is an intrinsic property of the material. Despite the fact that this interaction is rather weak, it can, as shown in this thesis,

  3. Luminescent Surface Quaternized Carbon Dots

    Bourlinos, Athanasios B.; Zbořil, Radek; Petr, Jan; Bakandritsos, Aristides; Krysmann, Marta; Giannelis, Emmanuel P.

    2012-01-01

    Thermal oxidation of a salt precursor made from the acid base combination of tris(hydroxymethyl)aminomethane and betaine hydrochloride results in light-emitting surface quaternized carbon dots that are water-dispersible, display anion exchange properties, and exhibit uniform size/surface charge. © 2011 American Chemical Society.

  4. Luminescent Surface Quaternized Carbon Dots

    Bourlinos, Athanasios B.

    2012-01-10

    Thermal oxidation of a salt precursor made from the acid base combination of tris(hydroxymethyl)aminomethane and betaine hydrochloride results in light-emitting surface quaternized carbon dots that are water-dispersible, display anion exchange properties, and exhibit uniform size/surface charge. © 2011 American Chemical Society.

  5. DOT strategies versus orbiter strategies

    Rutten, R.J.

    2001-01-01

    The Dutch Open Telescope is a high-resolution solar imager coming on-line at La Palma. The definition of the DOT science niche, strategies, and requirements resemble Solar Orbiter considerations and deliberations. I discuss the latter in the light of the former, and claim that multi-line observation

  6. Polymer-coated quantum dots

    Tomczak, N.; Liu, Rongrong; Vancso, Gyula J.

    2013-01-01

    Quantum Dots (QDs) are semiconductor nanocrystals with distinct photophysical properties finding applications in biology, biosensing, and optoelectronics. Polymeric coatings of QDs are used primarily to provide long-term colloidal stability to QDs dispersed in solutions and also as a source of

  7. Hyperdense dots mimicking microcalcifications : Mammographic findings

    Kim, Nam Hyeon; Park, Jeong Mi; Goo, Hyun Woo; Bang, Sun Woo

    1996-01-01

    To differentiate fine hyperdense dots mimicking microcalcifications from true microcalcifications on mammography. Mammograms showing hyperdense dots in ten patients (mean age, 59 years) were evaluated. Two radiologists were asked to differentiate with the naked eye the hyperdense dots seen on ten mammograms and proven microcalcifications seen on ten mammograms. Densitometry was also performed for all lesions and the contrast index was calculated. The shape and distribution of the hyperdense dots were evaluated and enquires were made regarding any history of breast disease and corresponding treatment. Biopsies were performed for two patients with hyperdense dots. Two radiologists made correct diagnoses in 19/20 cases(95%). The contrast index was 0.10-0.88 (mean 0.58) for hyperdense dots and 0.02-0.45 (mean 0.17) for true microcalcifications. The hyperdense dots were finer and homogeneously rounder than the microcalcifications. Distribution of the hyperdense dots was more superficial in subcutaneous fat (seven cases) and subareolar area (six cases). All ten patients with hyperdense dots had history of mastitis and abscesses and had been treated by open drainage (six cases) and/or folk remedy (four cases). In eight patients, herb patches had been attached. Biopsies of hyperdense dots did not show any microcalcification or evidence of malignancy. These hyperdense dots were seen mainly in older patients. Their characteristic density, shape, distribution and clinical history makes differential diagnosis from true microcalcifications easy and could reduce unnecessary diagnostic procedures such as surgical biopsy

  8. Hyperdense dots mimicking microcalcifications : Mammographic findings

    Kim, Nam Hyeon; Park, Jeong Mi; Goo, Hyun Woo; Bang, Sun Woo [Asan Medical Center, University of Ulsan College of Medicine, Seoul (Korea, Republic of)

    1996-12-01

    To differentiate fine hyperdense dots mimicking microcalcifications from true microcalcifications on mammography. Mammograms showing hyperdense dots in ten patients (mean age, 59 years) were evaluated. Two radiologists were asked to differentiate with the naked eye the hyperdense dots seen on ten mammograms and proven microcalcifications seen on ten mammograms. Densitometry was also performed for all lesions and the contrast index was calculated. The shape and distribution of the hyperdense dots were evaluated and enquires were made regarding any history of breast disease and corresponding treatment. Biopsies were performed for two patients with hyperdense dots. Two radiologists made correct diagnoses in 19/20 cases(95%). The contrast index was 0.10-0.88 (mean 0.58) for hyperdense dots and 0.02-0.45 (mean 0.17) for true microcalcifications. The hyperdense dots were finer and homogeneously rounder than the microcalcifications. Distribution of the hyperdense dots was more superficial in subcutaneous fat (seven cases) and subareolar area (six cases). All ten patients with hyperdense dots had history of mastitis and abscesses and had been treated by open drainage (six cases) and/or folk remedy (four cases). In eight patients, herb patches had been attached. Biopsies of hyperdense dots did not show any microcalcification or evidence of malignancy. These hyperdense dots were seen mainly in older patients. Their characteristic density, shape, distribution and clinical history makes differential diagnosis from true microcalcifications easy and could reduce unnecessary diagnostic procedures such as surgical biopsy.

  9. The ideal Atomic Centre

    Mas, R.

    1965-01-01

    The author presents considerations which should prove to be of interest to all those who have to design, to construct and to operate a nuclear research centre. A large number of the ideas presented can also be applied to non-nuclear scientific research centres. In his report the author reviews: various problems with which the constructor is faced: ground-plan, infrastructure, buildings and the large units of scientific equipment in the centre, and those problems facing the director: maintenance, production, supplies, security. The author stresses the relationship which ought to exist between the research workers and the management. With this aim in view he proposes the creation of National School for Administration in Research which would train administrative executives for public or private organisations; they would be specialised in the fields of fundamental or applied research. (author) [fr

  10. Modeling of the quantum dot filling and the dark current of quantum dot infrared photodetectors

    Ameen, Tarek A.; El-Batawy, Yasser M.; Abouelsaood, A. A.

    2014-01-01

    A generalized drift-diffusion model for the calculation of both the quantum dot filling profile and the dark current of quantum dot infrared photodetectors is proposed. The confined electrons inside the quantum dots produce a space-charge potential barrier between the two contacts, which controls the quantum dot filling and limits the dark current in the device. The results of the model reasonably agree with a published experimental work. It is found that increasing either the doping level or the temperature results in an exponential increase of the dark current. The quantum dot filling turns out to be nonuniform, with a dot near the contacts containing more electrons than one in the middle of the device where the dot occupation approximately equals the number of doping atoms per dot, which means that quantum dots away from contacts will be nearly unoccupied if the active region is undoped

  11. Engineering colloidal quantum dot solids within and beyond the mobility-invariant regime

    Zhitomirsky, David

    2014-05-06

    © 2014 Macmillan Publishers Limited. Colloidal quantum dots are attractive materials for efficient, low-cost and facile implementation of solution-processed optoelectronic devices. Despite impressive mobilities (1-30 cm2V-1 s-1) reported for new classes of quantum dot solids, it is-surprisingly-the much lower-mobility (10-3-10-2 cm2V-1 s-1) solids that have produced the best photovoltaic performance. Here we show that it is not mobility, but instead the average spacing among recombination centres that governs the diffusion length of charges in today\\'s quantum dot solids. In this regime, colloidal quantum dot films do not benefit from further improvements in charge carrier mobility. We develop a device model that accurately predicts the thickness dependence and diffusion length dependence of devices. Direct diffusion length measurements suggest the solid-state ligand exchange procedure as a potential origin of the detrimental recombination centres. We then present a novel avenue for in-solution passivation with tightly bound chlorothiols that retain passivation from solution to film, achieving an 8.5% power conversion efficiency.

  12. Netherlands Reactor Centre

    Anon.

    1976-01-01

    Briefly reviews the last year's work of the twenty year old Netherlands Reactor Centre (RCN) in the fields of reactor safety, fissile material, nuclear fission, non-nuclear energy systems and overseas co-operation. The annual report thus summarised is the last one to appear under the name of RCN. The terms of reference of the organisation having been broadened to include research into energy supply in general, it is to be known in future as the Netherlands Energy Research Centre (ECN). (D.J.B.)

  13. The Structural Integrity Centre

    Tomkins, B.

    1987-01-01

    The paper concerns the development and work of the Structural Integrity Centre (SIC) at Risley Nuclear Laboratories, United Kingdom. The centre was set up to provide authoritative advice to plant designers and operators on the integrity and life assessment of structures and components across the reactor projects in the United Kingdom. A description is given of the structure and role of the SIC, as well as the Structural Integrity Assessment work. The assessment methods are described for thermally loaded structures and welded structures. Finally, defect significance assessment and environmental effects are outlined. (U.K.)

  14. International research centre launched

    1965-01-01

    Full text: The first scientific research and educational institution to be set up on a completely international basis was officially inaugurated in Trieste on 5 October 1964 by the Director General of IAEA, Dr. Sigvard Eklund, when he opened the first seminar of the International Centre for Theoretical Physics. As evidence of the international nature of the institution he noted that the scientists who would work and teach there during the first year represented sixteen different countries. By the end of 1964, the Centre building was nearing completion and three of the five floors were occupied. A successful symposium had been held on the subject of plasma physics, and a score of professors and fellows were at work, from Bulgaria, Czechoslovakia, Greece, India, Japan, Jordan, the Netherlands, Norway, Pakistan, Poland, the United Kingdom, and the United States. A dozen scientific papers had been issued as preprints. The main purpose of the Centre is to foster the advancement of theoretical physics through training and research; at first the chief subject will be high-energy and elementary particle physics. Plasma physics, low energy physics and solid-state physics will also be dealt with. Special attention is paid to the needs of the developing countries. Of the 25 fellows selected for the academic year 1964-65, more than half are from South America, Africa and Asia. In conjunction with the Research Centre, there is an Advanced School for theoretical Physics to provide graduate training for fellows who need such preparation before they embark upon research. The Centre works under the guidance of a Scientific Council comprising the president, Prof. M. Sandoval-Vallarta (Nuclear Energy Commission of Mexico); Prof. A. Abragam (Saclay, France); Prof. R. Oppenheimer (Institute for Advanced Study, Princeton, USA); Dr. V. Soloviev (Dubna, USSR); Prof V.F. Weiskopf (Director General, CERN) ; Prof Abdus Salam (Imperial College, London) ; Prof. P. Budini (University of Trieste

  15. Centre for Political and

    user

    and definitions will be published and the data translated into the official ... The Centre provides a terminological and subject-related service to lecturers and ... postgraduate students in international politics, political studies and .... obtain financial contributions (cf. .... making of authoritative and enforceable rules (laws) for.

  16. Implementing Responsibility Centre Budgeting

    Vonasek, Joseph

    2011-01-01

    Recently, institutes of higher education (universities) have shown a renewed interest in organisational structures and operating methodologies that generate productivity and innovation; responsibility centre budgeting (RCB) is one such process. This paper describes the underlying principles constituting RCB, its origin and structural elements, and…

  17. Fuel cycle centres

    Hagen, M.

    1977-01-01

    The concept of co-locating and integrating fuel cycle facilities at one site is discussed. This concept offers considerable advantages, especially in minimizing the amount of radioactive material to be transported on public roads. Safeguards and physical protection as relating to such an integrated system of facilities are analysed in detail, also industrial and commercial questions. An overall risk-benefit evaluation turns out to be in favour of fuel cycle centres. These centres seem to be specifically attractive with regard to the back end of the fuel cycle, including on-site disposal of radioactive wastes. The respective German approach is presented as an example. Special emphasis is given to the site selection procedures in this case. Time scale and cost for the implementation of this concept are important factors to be looked at. Since participation of governmental institutions in these centres seems to be indispensable their respective roles as compared to industry must be clearly defined. The idea of adjusting fuel cycle centres to regional rather than national use might be an attractive option, depending on the specific parameters in the region, though results of existing multinational ventures are inconclusive in this respect. Major difficulties might be expected e.g. because of different national safety regulations and standards as well as commercial conditions among partner countries. Public acceptance in the host country seems to be another stumbling block for the realization of this type of multinational facilities

  18. Budapest Training Technology Centre.

    Budapest Training Technology Centre (Hungary).

    The Budapest Training Technology Centre (BTTC) grew out of a 1990 agreement calling for Great Britain to help Hungary develop and implement open and flexible training methods and technology-based training to support the labor force development and vocational training needs resulting from Hungary's transition to a market economy. The BTTC would be…

  19. Official Centre Hospitality

    Sylvain Dufour

    Approved by the Management Executive Committee. - 1 -. Version 3.1.0 effective 2017-06-28. Official Centre Hospitality. 1. Objective. 2. Application. 3. Definitions. 4. Roles and Responsibilities. 5. Authorization. 6. Consultants and Contractors. 7. Reimbursement. 1. Objective. To define the circumstances under which ...

  20. Academic Drug Discovery Centres

    Kirkegaard, Henriette Schultz; Valentin, Finn

    2014-01-01

    Academic drug discovery centres (ADDCs) are seen as one of the solutions to fill the innovation gap in early drug discovery, which has proven challenging for previous organisational models. Prior studies of ADDCs have identified the need to analyse them from the angle of their economic...

  1. ATLAS Visitors Centre

    claudia Marcelloni

    2009-01-01

    ATLAS Visitors Centre has opened its shiny new doors to the public. Officially launched on Monday February 23rd, 2009, the permanent exhibition at Point 1 was conceived as a tour resource for ATLAS guides, and as a way to preserve the public’s opportunity to get a close-up look at the experiment in action when the cavern is sealed.

  2. The electronic properties of semiconductor quantum dots

    Barker, J.A.

    2000-10-01

    This work is an investigation into the electronic behaviour of semiconductor quantum dots, particularly self-assembled quantum dot arrays. Processor-efficient models are developed to describe the electronic structure of dots, deriving analytic formulae for the strain tensor, piezoelectric distribution and diffusion- induced evolution of the confinement potential, for dots of arbitrary initial shape and composition profile. These models are then applied to experimental data. Transitions due to individual quantum dots have a narrow linewidth as a result of their discrete density of states. By contrast, quantum dot arrays exhibit inhomogeneous broadening which is generally attributed to size variations between the individual dots in the ensemble. Interpreting the results of double resonance spectroscopy, it is seen that variation in the indium composition of the nominally InAs dots is also present. This result also explains the otherwise confusing relationship between the spread in the ground-state and excited-state transition energies. Careful analysis shows that, in addition to the variations in size and composition, some other as yet unidentified broadening mechanism must also be present. The influence of rapid thermal annealing on dot electronic structure is also considered, finding that the experimentally observed blue-shift and narrowing of the photoluminescence linewidth may both be explained in terms of normal In/Ga interdiffusion. InAs/GaAs self-assembled quantum dots are commonly assumed to have a pyramidal geometry, so that we would expect the energy separation of the ground-state electron and hole levels in the dot to be largest at a positive applied field. This should also be the case for any dot of uniform composition whose shape tapers inwards from base to top, counter to the results of experimental Stark-shift spectroscopy which show a peak transition energy at a negative applied field. It is demonstrated that this inversion of the ground state

  3. dotNet som multimediaplattform

    Johansson, Glenn

    2008-01-01

    As the speed and complexity of computers have increased so have software and the expectations of users. Software development follows a straightforward evolution where complicated tasks are made easier by better tools; this repeats itself as those tasks in turn are automated. Software mechanics that were seen as revolutionary a decade ago are seen as obvious requirements that no multimedia application can be without. dotNet is the next step in line and makes it easier and faster to build softw...

  4. Dicke states in multiple quantum dots

    Sitek, Anna; Manolescu, Andrei

    2013-10-01

    We present a theoretical study of the collective optical effects which can occur in groups of three and four quantum dots. We define conditions for stable subradiant (dark) states, rapidly decaying super-radiant states, and spontaneous trapping of excitation. Each quantum dot is treated like a two-level system. The quantum dots are, however, realistic, meaning that they may have different transition energies and dipole moments. The dots interact via a short-range coupling which allows excitation transfer across the dots, but conserves the total population of the system. We calculate the time evolution of single-exciton and biexciton states using the Lindblad equation. In the steady state the individual populations of each dot may have permanent oscillations with frequencies given by the energy separation between the subradiant eigenstates.

  5. Hydrogenic impurity in double quantum dots

    Wang, X.F.

    2007-01-01

    The ground state binding energy and the average interparticle distances for a hydrogenic impurity in double quantum dots with Gaussian confinement potential are studied by the variational method. The probability density of the electron is calculated, too. The dependence of the binding energy on the impurity position is investigated for GaAs quantum dots. The result shows that the binding energy has a minimum as a function of the distance between the two quantum dots when the impurity is located at the center of one quantum dot or at the center of the edge of one quantum dot. When the impurity is located at the center of the two dots, the binding energy decreases monotonically

  6. Mononuclear, trinuclear, and hetero-trinuclear supramolecular complexes containing a new tri-sulfonate ligand and cobalt(II)/copper(II)-(1, 10-phenanthroline)(2) building blocks

    Yu, Yunfang; Wei, Yongqin; Broer, Ria; Sa, Rongjian; Wu, Kechen

    Novel mononuclear, trinuclear, and hetero-trinuclear supermolecular complexes, [Co(phen)(2)(H2O)(HTST)] center dot 2H(2)O (1), [CO3(phen)(6) (H2O)(2)(TST)(2)]center dot 7H(2)O (2), and [CO2Cu(phen)(6)(H2O)(2)(TST)(2)]center dot 10H(2)O (3), have been synthesized by the reactions of a new

  7. Elderly Care Centre

    Wagiman, Aliani; Haja Bava Mohidin, Hazrina; Ismail, Alice Sabrina

    2016-02-01

    The demand for elderly centre has increased tremendously abreast with the world demographic change as the number of senior citizens rose in the 21st century. This has become one of the most crucial problems of today's era. As the world progress into modernity, more and more people are occupied with daily work causing the senior citizens to lose the care that they actually need. This paper seeks to elucidate the best possible design of an elderly care centre with new approach in order to provide the best service for them by analysing their needs and suitable activities that could elevate their quality of life. All these findings will then be incorporated into design solutions so as to enhance the living environment for the elderly especially in Malaysian context.

  8. Sphere and dot product representations of graphs

    R.J. Kang (Ross); T. Müller (Tobias)

    2012-01-01

    textabstractA graph $G$ is a $k$-sphere graph if there are $k$-dimensional real vectors $v_1,\\dots,v_n$ such that $ij\\in E(G)$ if and only if the distance between $v_i$ and $v_j$ is at most $1$. A graph $G$ is a $k$-dot product graph if there are $k$-dimensional real vectors $v_1,\\dots,v_n$ such

  9. International Data Centre (IDC)

    Johansson, P.

    2002-01-01

    The presentation outlines the International Data Centre (Indc) mission, objective and historical background. The Indc progressive commissioning and organizational plans are presented on charts. The IMS stations providing data to Indc operations and the global communication infrastructure are plotted on world maps. The various types of IMS data are thus listed as seismic, hydroacoustic, infrasound and radionuclide. Finally Indc products and services together with its main achievements are listed

  10. Electronic transport through a quantum dot chain with strong dot-lead coupling

    Liu, Yu; Zheng, Yisong; Gong, Weijiang; Gao, Wenzhu; Lue, Tianquan

    2007-01-01

    By means of the non-equilibrium Green function technique, the electronic transport through an N-quantum-dot chain is theoretically studied. By calculating the linear conductance spectrum and the local density of states in quantum dots, we find the resonant peaks in the spectra coincides with the eigen-energies of the N-quantum-dot chain when the dot-lead coupling is relatively weak. With the increase of the dot-lead coupling, such a correspondence becomes inaccurate. When the dot-lead coupling exceeds twice the interdot coupling, such a mapping collapses completely. The linear conductance turn to reflect the eigen-energies of the (N-2)- or (N-1)-quantum dot chain instead. The two peripheral quantum dots do not manifest themselves in the linear conductance spectrum. More interestingly, with the further increase of the dot-lead coupling, the system behaves just like an (N-2)- or (N-1)-quantum dot chain in weak dot-lead coupling limit, since the resonant peaks becomes narrower with the increase of dot-lead coupling

  11. Today's DOT and the quest for more accountable organizational structures.

    2005-12-01

    This study investigates the impact of DOT organizational structures on effective transportation planning and performance. A review of the 50 state DOT authorizing statutes and DOT organizational charts found minimal differences in organizational stru...

  12. Historical centres: changing definitions

    Roberta Lazzarotti

    2014-02-01

    Full Text Available Since the end of the Second World War, the architectural and planning culture has been showing a fluctuating attention to the theme of historical centres and their enhancement. First of all this uneven progress explains the difficulty to reach a homogeneous definition and this is still lacking. During a long phase of this period, the historical parts of the town were considered as objects to be preserved in an integral way, as urban monuments. This is mostly due to the high symbolic value of these settlements, that represent fundamental landmarks. Identity building and empowerment of local communities are indispensable conditions for any development programme, especially in the case of centres or other historic environments at risk of abandonment. The progressive evolution of this concept brings awareness of the impossibility of separating – either in analytical or in planning terms ­ historical centres from their urban and territorial contexts, which are linked by mutual, deep relationships. This article attempts to retrace the steps signaled by the publication of international documents and conventions, from the Charter of Gubbio (1960 to the Charter of Krakow and the European Landscape Convention (2000; they obviously represent particular points of view, not exhaustive of the richness of the positions in the debate, but extremely significant in terms of diffusion and consensus.

  13. Quantum dots for quantum information technologies

    2017-01-01

    This book highlights the most recent developments in quantum dot spin physics and the generation of deterministic superior non-classical light states with quantum dots. In particular, it addresses single quantum dot spin manipulation, spin-photon entanglement and the generation of single-photon and entangled photon pair states with nearly ideal properties. The role of semiconductor microcavities, nanophotonic interfaces as well as quantum photonic integrated circuits is emphasized. The latest theoretical and experimental studies of phonon-dressed light matter interaction, single-dot lasing and resonance fluorescence in QD cavity systems are also provided. The book is written by the leading experts in the field.

  14. Semiconductor quantum-dot lasers and amplifiers

    Hvam, Jørn Märcher; Borri, Paola; Ledentsov, N. N.

    2002-01-01

    -power surface emitting VCSELs. We investigated the ultrafast dynamics of quantum-dot semiconductor optical amplifiers. The dephasing time at room temperature of the ground-state transition in semiconductor quantum dots is around 250 fs in an unbiased amplifier, decreasing to below 50 fs when the amplifier...... is biased to positive net gain. We have further measured gain recovery times in quantum dot amplifiers that are significantly lower than in bulk and quantum-well semiconductor optical amplifiers. This is promising for future demonstration of quantum dot devices with high modulation bandwidth...

  15. Millimeter Wave Modulators Using Quantum Dots

    Prather, Dennis W

    2008-01-01

    In this effort electro-optic modulators for millimeter wave sensing and imaging were developed and demonstrated via design, fabrication, and experimental characterization of multi layer quantum dot...

  16. Spin Switching via Quantum Dot Spin Valves

    Gergs, N. M.; Bender, S. A.; Duine, R. A.; Schuricht, D.

    2018-01-01

    We develop a theory for spin transport and magnetization dynamics in a quantum dot spin valve, i.e., two magnetic reservoirs coupled to a quantum dot. Our theory is able to take into account effects of strong correlations. We demonstrate that, as a result of these strong correlations, the dot gate voltage enables control over the current-induced torques on the magnets and, in particular, enables voltage-controlled magnetic switching. The electrical resistance of the structure can be used to read out the magnetic state. Our model may be realized by a number of experimental systems, including magnetic scanning-tunneling microscope tips and artificial quantum dot systems.

  17. Optical Signatures of Coupled Quantum Dots

    Stinaff, E. A.; Scheibner, M.; Bracker, A. S.; Ponomarev, I. V.; Korenev, V. L.; Ware, M. E.; Doty, M. F.; Reinecke, T. L.; Gammon, D.

    2006-02-01

    An asymmetric pair of coupled InAs quantum dots is tuned into resonance by applying an electric field so that a single hole forms a coherent molecular wave function. The optical spectrum shows a rich pattern of level anticrossings and crossings that can be understood as a superposition of charge and spin configurations of the two dots. Coulomb interactions shift the molecular resonance of the optically excited state (charged exciton) with respect to the ground state (single charge), enabling light-induced coupling of the quantum dots. This result demonstrates the possibility of optically coupling quantum dots for application in quantum information processing.

  18. Vectorization of DOT3.5 code

    Nonomiya, Iwao; Ishiguro, Misako; Tsutsui, Tsuneo

    1990-07-01

    In this report, we describe the vectorization of two-dimensional Sn-method radiation transport code DOT3.5. Vectorized codes are not only the NEA original version developed at ORNL but also the versions improved by JAERI: DOT3.5 FNS version for fusion neutronics analyses, DOT3.5 FER version for fusion reactor design, and ESPRIT module of RADHEAT-V4 code system for radiation shielding and radiation transport analyses. In DOT3.5, input/output processing time amounts to a great part of the elapsed time when a large number of energy groups and/or a large number of spatial mesh points are used in the calculated problem. Therefore, an improvement has been made for the speedup of input/output processing in the DOT3.5 FNS version, and DOT-DD (Double Differential cross section) code. The total speedup ratio of vectorized version to the original scalar one is 1.7∼1.9 for DOT3.5 NEA version, 2.2∼2.3 fro DOT3.5 FNS version, 1.7 for DOT3.5 FER version, and 3.1∼4.4 for RADHEAT-V4, respectively. The elapsed times for improved DOT3.5 FNS version and DOT-DD are reduced to 50∼65% that of the original version by the input/output speedup. In this report, we describe summary of codes, the techniques used for the vectorization and input/output speedup, verification of computed results, and speedup effect. (author)

  19. Perceptual strategies of pigeons to detect a rotational centre--a hint for star compass learning?

    Bianca Alert

    Full Text Available Birds can rely on a variety of cues for orientation during migration and homing. Celestial rotation provides the key information for the development of a functioning star and/or sun compass. This celestial compass seems to be the primary reference for calibrating the other orientation systems including the magnetic compass. Thus, detection of the celestial rotational axis is crucial for bird orientation. Here, we use operant conditioning to demonstrate that homing pigeons can principally learn to detect a rotational centre in a rotating dot pattern and we examine their behavioural response strategies in a series of experiments. Initially, most pigeons applied a strategy based on local stimulus information such as movement characteristics of single dots. One pigeon seemed to immediately ignore eccentric stationary dots. After special training, all pigeons could shift their attention to more global cues, which implies that pigeons can learn the concept of a rotational axis. In our experiments, the ability to precisely locate the rotational centre was strongly dependent on the rotational velocity of the dot pattern and it crashed at velocities that were still much faster than natural celestial rotation. We therefore suggest that the axis of the very slow, natural, celestial rotation could be perceived by birds through the movement itself, but that a time-delayed pattern comparison should also be considered as a very likely alternative strategy.

  20. DGNB certified Healthcare Centres

    Brunsgaard, Camilla; Larsen, Tine Steen

    2015-01-01

    for sustainability and wants a certification. This research investigates the decision‐making and design process (DMaDP) behind four DGNB certified Healthcare Centres (HCC) in Northern Jutland in Denmark. In general, knowledge about the DMaDP is important. However it is important to know what part DGNB plays...... a dialog about DGNB and energy concept is important even before anyone start sketching. Experiences with the different approaches will be further outlined in the paper.Future research has the intention to collect further knowledge about DGNB and DMaDP in practise. This project was limited to Healthcare...

  1. Town Centre Redevelopment Strategies

    Vagnby, Bo Hellisen

    After many years of urban growth Danish downtowns are facing some important choices. Shall the stake one-sidedly be on the town centres as driving forces for growth and 'city marketing', or do they still have a role to play in a broader socio-economic context? In the paper we look back on eight...... as slum clearence and urban renewal. To a certain extent parallels are drawn to international experiences, especially where these are of such a nature that they can be assumed transferred to Danish connctions. Conclusively, the strategies are discussed in the light of the turn of Danish urban planning...

  2. Stark shifting two-electron quantum dot

    Dineykhan, M.; Zhaugasheva, S.A.; Duysebaeva, K.S.

    2003-01-01

    Advances in modern technology make it possible to create semiconducting nano-structures (quantum dot) in which a finite number of electrons are 'captured' in a bounded volume. A quantum dot is associated with a quantum well formed at the interface, between two finite-size semiconductors owing to different positions of the forbidden gaps on the energy scale in these semiconductors. The possibility of monitoring and controlling the properties of quantum dots attracts considerable attention to these objects, as a new elemental basis for future generations of computers. The quantum-mechanical effects and image potential play a significant role in the description of the formation mechanism quantum dot, and determined the confinement potential in a two-electron quantum dot only for the spherical symmetric case. In the present talk, we considered the formation dynamics of two-electron quantum dot with violation of spherical symmetry. So, we have standard Stark potential. The energy spectrum two-electron quantum dot were calculated. Usually Stark interactions determined the tunneling phenomena between quantum dots

  3. Quantum Dots Coupled to a Superconductor

    Jellinggaard, Anders Robert

    are tuned electrostatically. This includes tuning the odd occupation of the dot through a quantum phase transition, where it forms a singlet with excitations in the superconductor. We detail the fabrication of these bottom gated devices, which additionally feature ancillary sensor dots connected...

  4. Detecting the chirality for coupled quantum dots

    Cao Huijuan; Hu Lian

    2008-01-01

    We propose a scheme to detect the chirality for a system consisting of three coupled quantum dots. The chirality is found to be determined by the frequency of the transition between chiral states under the chiral symmetry broken perturbation. The results are important to construct quantum gates and to demonstrate chiral entangle states in the triangle spin dots

  5. Optical Properties of Semiconductor Quantum Dots

    Perinetti, U.

    2011-01-01

    This thesis presents different optical experiments performed on semiconductor quantum dots. These structures allow to confine a small number of electrons and holes to a tiny region of space, some nm across. The aim of this work was to study the basic properties of different types of quantum dots

  6. Optical anisotropy in vertically coupled quantum dots

    Yu, Ping; Langbein, Wolfgang Werner; Leosson, Kristjan

    1999-01-01

    We have studied the polarization of surface and edge-emitted photoluminescence (PL) from structures with vertically coupled In0.5Ga0.5As/GaAs quantum dots (QD's) grown by molecular beam epitaxy. The PL polarization is found to be strongly dependent on the number of stacked layers. While single...... number due to increasing dot size....

  7. Thick-shell nanocrystal quantum dots

    Hollingsworth, Jennifer A [Los Alamos, NM; Chen, Yongfen [Eugene, OR; Klimov, Victor I [Los Alamos, NM; Htoon, Han [Los Alamos, NM; Vela, Javier [Los Alamos, NM

    2011-05-03

    Colloidal nanocrystal quantum dots comprising an inner core having an average diameter of at least 1.5 nm and an outer shell, where said outer shell comprises multiple monolayers, wherein at least 30% of the quantum dots have an on-time fraction of 0.80 or greater under continuous excitation conditions for a period of time of at least 10 minutes.

  8. Optical Spectroscopy Of Charged Quantum Dot Molecules

    Scheibner, M.; Bracker, A. S.; Stinaff, E. A.; Doty, M. F.; Gammon, D.; Ponomarev, I. V.; Reinecke, T. L.; Korenev, V. L.

    2007-04-01

    Coupling between two closely spaced quantum dots is observed by means of photoluminescence spectroscopy. Hole coupling is realized by rational crystal growth and heterostructure design. We identify molecular resonances of different excitonic charge states, including the important case of a doubly charged quantum dot molecule.

  9. Capture, relaxation and recombination in quantum dots

    Sreenivasan, D.

    2008-01-01

    Quantum dots (QDs) have attracted a lot of interest both from application and fundamental physics point of view. A semiconductor quantum dot features discrete atomiclike energy levels, despite the fact that it contains many atoms within its surroundings. The discrete energy levels give rise to very

  10. Densities and apparent molar volumes of atmospherically important electrolyte solutions. 2. The systems H(+)-HSO4(-)-SO4(2-)-H2O from 0 to 3 mol kg(-1) as a function of temperature and H(+)-NH4(+)-HSO4(-)-SO4)2-)-H2O from 0 to 6 mol kg(-1) at 25 °C using a Pitzer ion interaction model, and NH4HSO4-H2O and (NH4)3H(SO4)2-H2O over the entire concentration range.

    Clegg, S L; Wexler, A S

    2011-04-21

    A Pitzer ion interaction model has been applied to the systems H(2)SO(4)-H(2)O (0-3 mol kg(-1), 0-55 °C) and H(2)SO(4)-(NH(4))(2)SO(4)-H(2)O (0-6 mol kg(-1), 25 °C) for the calculation of apparent molar volume and density. The dissociation reaction HSO(4)(-)((aq)) ↔ H(+)((aq)) + SO(4)(2-)((aq)) is treated explicitly. Apparent molar volumes of the SO(4)(2-) ion at infinite dilution were obtained from part 1 of this work, (1) and the value for the bisulfate ion was determined in this study from 0 to 55 °C. In dilute solutions of both systems, the change in the degree of dissociation of the HSO(4)(-) ion with concentration results in much larger variations of the apparent molar volumes of the solutes than for conventional strong (fully dissociated) electrolytes. Densities and apparent molar volumes are tabulated. Apparent molar volumes calculated using the model are combined with other data for the solutes NH(4)HSO(4) and (NH(4))(3)H(SO(4))(2) at 25 °C to obtain apparent molar volumes and densities over the entire concentration range (including solutions supersaturated with respect to the salts).

  11. Biocompatible Quantum Dots for Biological Applications

    Rosenthal, Sandra J.; Chang, Jerry C.; Kovtun, Oleg; McBride, James R.; Tomlinson, Ian D.

    2011-01-01

    Semiconductor quantum dots are quickly becoming a critical diagnostic tool for discerning cellular function at the molecular level. Their high brightness, long-lasting, sizetunable, and narrow luminescence set them apart from conventional fluorescence dyes. Quantum dots are being developed for a variety of biologically oriented applications, including fluorescent assays for drug discovery, disease detection, single protein tracking, and intracellular reporting. This review introduces the science behind quantum dots and describes how they are made biologically compatible. Several applications are also included, illustrating strategies toward target specificity, and are followed by a discussion on the limitations of quantum dot approaches. The article is concluded with a look at the future direction of quantum dots. PMID:21276935

  12. Magnon-driven quantum dot refrigerators

    Wang, Yuan; Huang, Chuankun; Liao, Tianjun; Chen, Jincan, E-mail: jcchen@xmu.edu.cn

    2015-12-18

    Highlights: • A three-terminal quantum dot refrigerator is proposed. • The effects of magnetic field, applied voltage, and polarization are considered. • The region that the system can work as a refrigerator is determined. • Two different magnon-driven quantum dot refrigerators are compared. - Abstract: A new model of refrigerator consisting of a spin-splitting quantum dot coupled with two ferromagnetic reservoirs and a ferromagnetic insulator is proposed. The rate equation is used to calculate the occupation probabilities of the quantum dot. The expressions of the electron and magnon currents are obtained. The region that the system can work in as a refrigerator is determined. The cooling power and coefficient of performance (COP) of the refrigerator are derived. The influences of the magnetic field, applied voltage, and polarization of two leads on the performance are discussed. The performances of two different magnon-driven quantum dot refrigerators are compared.

  13. Multi-Excitonic Quantum Dot Molecules

    Scheibner, M.; Stinaff, E. A.; Doty, M. F.; Ware, M. E.; Bracker, A. S.; Gammon, D.; Ponomarev, I. V.; Reinecke, T. L.; Korenev, V. L.

    2006-03-01

    With the ability to create coupled pairs of quantum dots, the next step towards the realization of semiconductor based quantum information processing devices can be taken. However, so far little knowledge has been gained on these artificial molecules. Our photoluminescence experiments on single InAs/GaAs quantum dot molecules provide the systematics of coupled quantum dots by delineating the spectroscopic features of several key charge configurations in such quantum systems, including X, X^+,X^2+, XX, XX^+ (with X being the neutral exciton). We extract general rules which determine the formation of molecular states of coupled quantum dots. These include the fact that quantum dot molecules provide the possibility to realize various spin configurations and to switch the electron hole exchange interaction on and off by shifting charges inside the molecule. This knowledge will be valuable in developing implementations for quantum information processing.

  14. Mochovce waste treatment centre

    Sedliak, D.; Endrody, J.

    2000-01-01

    The first unit of the Mochovce NPP (WWER 440 MW) was put in a test operation in October 1998. The second unit with the same power output was put in the test operation in March 2000. The Nuclear Regulatory Authority of the Slovak Republic in its Decision No. 318/98 of 28 October 1998, by which an agreement with the operation of the Unit 1 of the Mochovce. Nuclear Power Plant was issued, requires to start the construction of the Liquid Radioactive Waste Treatment Centre until January 2004. The subject of this presentation is a system description of the Liquid Radioactive Waste (LRW) management in the Mochovce NPP. The initial part is dedicated to a short description of the radioactive waste management legislation requirements. Then the presentation continues with an information about the LRW production in the Mochovce NPP, LRW sources, chemical and radiochemical attributes, description of storage. The presentation also provides real values of its production in a comparison with the design data. The LRW production minimization principles are also mentioned there. Another part deals with the basic requirements for the technology proposal of the liquid RW treatment, especially concerning the acceptance criteria at the Republic RW Repository Mochovce. The final part is devoted to a short description of the investment procedure principles - design preparation levels and a proposed construction schedule of the centre. (authors)

  15. Electron transport in quantum dots

    2003-01-01

    When I was contacted by Kluwer Academic Publishers in the Fall of 200 I, inviting me to edit a volume of papers on the issue of electron transport in quantum dots, I was excited by what I saw as an ideal opportunity to provide an overview of a field of research that has made significant contributions in recent years, both to our understanding of fundamental physics, and to the development of novel nanoelectronic technologies. The need for such a volume seemed to be made more pressing by the fact that few comprehensive reviews of this topic have appeared in the literature, in spite of the vast activity in this area over the course of the last decade or so. With this motivation, I set out to try to compile a volume that would fairly reflect the wide range of opinions that has emerged in the study of electron transport in quantum dots. Indeed, there has been no effort on my part to ensure any consistency between the different chapters, since I would prefer that this volume instead serve as a useful forum for the...

  16. From micro- to nanomagnetic dots: evolution of the eigenmode spectrum on reducing the lateral size

    Carlotti, G; Madami, M; Gubbiotti, G; Tacchi, S; Hartmann, F; Emmerling, M; Kamp, M; Worschech, L

    2014-01-01

    Brillouin light scattering experiments and micromagnetic simulations have been exploited to investigate the spectrum of thermally excited magnetic eigenmodes in 10 nm-thick elliptical Permalloy dots, when the longer axis D is scaled down from about 1000 to 100 nm. It is shown that for D larger than about 200 nm the characteristics of the spin-wave eigenmodes are dominated by dipolar energy, while for D in the range of about 100 to 200 nm exchange energy effects cause qualitative and quantitative differences in the spin-wave spectrum. In this ‘mesoscopic’ regime, the usual classification scheme, involving one fundamental mode with large average magnetization and many other modes collected in families with specific symmetries, no longer holds. Rather, one finds the simultaneous presence of two modes with ‘fundamental’ character, i.e. with a significant and comparable value of the average dynamical magnetization: the former is at larger frequency and has its maximum amplitude at the dot's centre, while the latter occurs at lower frequency and is localized at the dot's edges. Interestingly, the maximum intensity swaps from the higher frequency mode to the lower frequency one, just when the dot size is reduced from about 200 to 100 nm. This is relevant in view of the exploitation of nanodots for the design of nanomagnetic devices with lateral dimensions in the above interval, such as memory cells, logic gates, reading heads and spin-torque oscillators. (paper)

  17. From micro- to nanomagnetic dots: evolution of the eigenmode spectrum on reducing the lateral size

    Carlotti, G.; Gubbiotti, G.; Madami, M.; Tacchi, S.; Hartmann, F.; Emmerling, M.; Kamp, M.; Worschech, L.

    2014-07-01

    Brillouin light scattering experiments and micromagnetic simulations have been exploited to investigate the spectrum of thermally excited magnetic eigenmodes in 10 nm-thick elliptical Permalloy dots, when the longer axis D is scaled down from about 1000 to 100 nm. It is shown that for D larger than about 200 nm the characteristics of the spin-wave eigenmodes are dominated by dipolar energy, while for D in the range of about 100 to 200 nm exchange energy effects cause qualitative and quantitative differences in the spin-wave spectrum. In this ‘mesoscopic’ regime, the usual classification scheme, involving one fundamental mode with large average magnetization and many other modes collected in families with specific symmetries, no longer holds. Rather, one finds the simultaneous presence of two modes with ‘fundamental’ character, i.e. with a significant and comparable value of the average dynamical magnetization: the former is at larger frequency and has its maximum amplitude at the dot's centre, while the latter occurs at lower frequency and is localized at the dot's edges. Interestingly, the maximum intensity swaps from the higher frequency mode to the lower frequency one, just when the dot size is reduced from about 200 to 100 nm. This is relevant in view of the exploitation of nanodots for the design of nanomagnetic devices with lateral dimensions in the above interval, such as memory cells, logic gates, reading heads and spin-torque oscillators.

  18. Inter-dot coupling effects on transport through correlated parallel

    Transport through symmetric parallel coupled quantum dot system has been studied, using non-equilibrium Green function formalism. The inter-dot tunnelling with on-dot and inter-dot Coulomb repulsion is included. The transmission coefficient and Landaur–Buttiker like current formula are shown in terms of internal states ...

  19. Call Centre- Computer Telephone Integration

    Dražen Kovačević

    2012-10-01

    Full Text Available Call centre largely came into being as a result of consumerneeds converging with enabling technology- and by the companiesrecognising the revenue opportunities generated by meetingthose needs thereby increasing customer satisfaction. Regardlessof the specific application or activity of a Call centre, customersatisfaction with the interaction is critical to the revenuegenerated or protected by the Call centre. Physical(v, Call centreset up is a place that includes computer, telephone and supervisorstation. Call centre can be available 24 hours a day - whenthe customer wants to make a purchase, needs information, orsimply wishes to register a complaint.

  20. Metamorphic quantum dots: Quite different nanostructures

    Seravalli, L.; Frigeri, P.; Nasi, L.; Trevisi, G.; Bocchi, C.

    2010-01-01

    In this work, we present a study of InAs quantum dots deposited on InGaAs metamorphic buffers by molecular beam epitaxy. By comparing morphological, structural, and optical properties of such nanostructures with those of InAs/GaAs quantum dot ones, we were able to evidence characteristics that are typical of metamorphic InAs/InGaAs structures. The more relevant are: the cross-hatched InGaAs surface overgrown by dots, the change in critical coverages for island nucleation and ripening, the nucleation of new defects in the capping layers, and the redshift in the emission energy. The discussion on experimental results allowed us to conclude that metamorphic InAs/InGaAs quantum dots are rather different nanostructures, where attention must be put to some issues not present in InAs/GaAs structures, namely, buffer-related defects, surface morphology, different dislocation mobility, and stacking fault energies. On the other hand, we show that metamorphic quantum dot nanostructures can provide new possibilities of tailoring various properties, such as dot positioning and emission energy, that could be very useful for innovative dot-based devices.

  1. 49 CFR 40.13 - How do DOT drug and alcohol tests relate to non-DOT tests?

    2010-10-01

    ... 49 Transportation 1 2010-10-01 2010-10-01 false How do DOT drug and alcohol tests relate to non... TRANSPORTATION WORKPLACE DRUG AND ALCOHOL TESTING PROGRAMS Employer Responsibilities § 40.13 How do DOT drug and... non-DOT drug and alcohol testing programs. This prohibition includes the use of the DOT forms with...

  2. Short-wavelength InAlGaAs/AlGaAs quantum dot superluminescent diodes

    Liang, De-Chun; An, Qi; Jin, Peng; Li, Xin-Kun; Wei, Heng; Wu, Ju; Wang, Zhan-Guo

    2011-10-01

    This paper reports the fabrication of J-shaped bent-waveguide superluminescent diodes utilizing an InAlGaAs/AlGaAs quantum dot active region. The emission spectrum of the device is centred at 884 nm with a full width at half maximum of 37 nm and an output power of 18 mW. By incorporating an Al composition into the quantum dot active region, short-wavelength superluminescent diode devices can be obtained. An intersection was found for the light power-injection current curves measured from the straight-waveguide facet and the bent-waveguide facet, respectively. The result is attributed to the conjunct effects of the gain and the additional loss of the bent waveguide. A numerical simulation is performed to verify the qualitative explanation. It is shown that bent waveguide loss is an important factor that affects the output power of J-shaped superluminescent diode devices.

  3. Quantum dot devices for optical communications

    Mørk, Jesper

    2005-01-01

    -low threshold currents and amplifiers with record-high power levels. In this tutorial we will review the basic properties of quantum dots, emphasizing the properties which are important for laser and amplifier applications, as well as devices for all-optical signal processing. The high-speed properties....... The main property of semiconductor quantum dots compared to bulk material or even quantum well structures is the discrete nature of the allowed states, which means that inversion of the medium can be obtained for very low electron densities. This has led to the fabrication of quantum dot lasers with record...

  4. Micromagnetic simulations of submicron cobalt dots

    Parker, G. J.; Cerjan, C.

    2000-01-01

    Numerical simulations of submicron Co extruded elliptical dots were performed to illustrate the relative importance of different physical parameters on the switching behavior in the easy direction. Shape, size, magnetic moment magnitude, and the magnitude and distribution of the crystalline anisotropicity were varied. The simulation represents magnetostatic, exchange, and crystalline anisotropicity fields on a structured mesh using finite difference techniques. The smooth boundary of the dots is accurately represented by use of the embedded curve boundary method. Agreement with experimental hysteresis measurements of submicron dot arrays is obtained when an appropriate angular distribution of the grain anisotropicity axes is invoked. (c) 2000 American Institute of Physics

  5. Entangled exciton states in quantum dot molecules

    Bayer, Manfred

    2002-03-01

    Currently there is strong interest in quantum information processing(See, for example, The Physics of Quantum Information, eds. D. Bouwmeester, A. Ekert and A. Zeilinger (Springer, Berlin, 2000).) in a solid state environment. Many approaches mimic atomic physics concepts in which semiconductor quantum dots are implemented as artificial atoms. An essential building block of a quantum processor is a gate which entangles the states of two quantum bits. Recently a pair of vertically aligned quantum dots has been suggested as optically driven quantum gate(P. Hawrylak, S. Fafard, and Z. R. Wasilewski, Cond. Matter News 7, 16 (1999).)(M. Bayer, P. Hawrylak, K. Hinzer, S. Fafard, M. Korkusinski, Z.R. Wasilewski, O. Stern, and A. Forchel, Science 291, 451 (2001).): The quantum bits are individual carriers either on dot zero or dot one. The different dot indices play the same role as a "spin", therefore we call them "isospin". Quantum mechanical tunneling between the dots rotates the isospin and leads to superposition of these states. The quantum gate is built when two different particles, an electron and a hole, are created optically. The two particles form entangled isospin states. Here we present spectrocsopic studies of single self-assembled InAs/GaAs quantum dot molecules that support the feasibility of this proposal. The evolution of the excitonic recombination spectrum with varying separation between the dots allows us to demonstrate coherent tunneling of carriers across the separating barrier and the formation of entangled exciton states: Due to the coupling between the dots the exciton states show a splitting that increases with decreasing barrier width. For barrier widths below 5 nm it exceeds the thermal energy at room temperature. For a given barrier width, we find only small variations of the tunneling induced splitting demonstrating a good homogeneity within a molecule ensemble. The entanglement may be controlled by application of electromagnetic field. For

  6. Circularly organized quantum dot nanostructures of Ge on Si substrates

    Cai, Qijia; Chen, Peixuan; Zhong, Zhenyang; Jiang, Zuimin; Lu, Fang; An, Zhenghua

    2009-01-01

    A novel circularly arranged structure of germanium quantum dots has been fabricated by combining techniques including electron beam lithography, wet etching and molecular beam epitaxy. It was observed that both pattern and growth parameters affect the morphology of the quantum dot molecules. Meanwhile, the oxidation mask plays a vital role in the formation of circularly organized quantum dots. The experimental results demonstrate the possibilities of investigating the properties of quantum dot molecules as well as single quantum dots

  7. A 2x2 quantum dot array with controllable inter-dot tunnel couplings

    Mukhopadhyay, Uditendu; Dehollain, Juan Pablo; Reichl, Christian; Wegscheider, Werner; Vandersypen, Lieven M. K.

    2018-01-01

    The interaction between electrons in arrays of electrostatically defined quantum dots is naturally described by a Fermi-Hubbard Hamiltonian. Moreover, the high degree of tunability of these systems make them a powerful platform to simulate different regimes of the Hubbard model. However, most quantum dot array implementations have been limited to one-dimensional linear arrays. In this letter, we present a square lattice unit cell of 2$\\times$2 quantum dots defined electrostatically in a AlGaA...

  8. [Analysis on workload for hospital DOTS service].

    Nagata, Yoko; Urakawa, Minako; Kobayashi, Noriko; Kato, Seiya

    2014-04-01

    A directly observed treatment short course (DOTS) trial was launched in Japan in the late 1990s and targeted patients with social depression at urban areas. Based on these findings, the Ministry of Health, Labour and Welfare established the Japanese DOTS Strategy in 2003, which is a comprehensive support service ensuring the adherence of tuberculosis patients to drug administration. DOTS services are initially provided at the hospital to patients with infectious tuberculosis who are hospitalized according to the Infectious Diseases Control Law. After being discharged from the hospital, the patients are referred to a public health center. However, a survey conducted in 2008 indicated that all the patients do not receive appropriate DOTS services at some hospitals. In the present study, we aimed to evaluate the protocols and workload of DOTS at hospitals that are actively involved in tuberculosis medical practice, including DOTS, to assess whether the hospital DOTS services were adequate. We reviewed a series of articles on hospital DOTS from a Japanese journal on nursing for tuberculosis patients and identified 25 activities regarding the hospital DOTS service. These 25 items were then classified into 3 categories: health education to patients, support for adherence, and coordination with the health center. In total, 20 hospitals that had > 20 authorized tuberculosis beds were selected--while considering the geographical balance, schedule of this survey, etc.--from 33 hospitals where an ex-trainee of the tuberculosis control expert training program in the Research Institute of Tuberculosis (RIT) was working and 20 hospitals that had collaborated with our previous survey on tuberculosis medical facilities. All the staff associated with the DOTS service were asked to record the total working time as well as the time spent for each activity. The data were collected and analyzed at the RIT. The working times for each activity of the DOTS service for nurses, pharmacists

  9. Thermoelectric transport through quantum dots

    Merker, Lukas Heinrich

    2016-06-30

    In this thesis the thermoelectric properties (electrical conductance, Seebeck coefficient and thermal conductance)of quantum dots described by the Anderson impurity model have been investigated by using the numerical renormalization group (NRG) method. In order to make accurate calculations for thermoelectric properties of quantum impurity systems, a number of recent developments and refinements of the NRG have been implemented. These include the z-averaging and Campo discretization scheme, which enable the evaluation of physical quantities on an arbitrary temperature grid and at large discretization parameter Λ and the full density matrix (FDM) approach, which allows a more accurate calculation of spectral functions and transport coefficients. The implementation of the z-averaging and Campo discretization scheme has been tested within a new method for specific heats of quantum impurities. The accuracy of this new method was established by comparison with the numerical solution of the Bethe-ansatz equations for the Anderson model. The FDM approach was implemented and tested within a new approach to the calculation of impurity contributions to the uniform susceptibilities. Within this method a non-negligible contribution from the ''environmental'' degrees of freedom needs to be taken into account to recover the correct susceptibility, as shown by comparison with the Bethe-ansatz approach. An accurate method to calculate the conductance of a quantum dot is implemented, enabling the extraction of the Fermi liquid scaling coefficients c{sub T} and c{sub B} to high accuracy, being able to verify the results of the renormalized super perturbation theory approach (within its regime of validity). The method was generalized to higher order moments of the local level spectral function. This, as well as reduction of the SU(2) code to the U(1) symmetry, enabled the investigation of the effect of a magnetic field on the thermoelectric properties of quantum

  10. Chiral Responsive Liquid Quantum Dots.

    Zhang, Jin; Ma, Junkai; Shi, Fangdan; Tian, Demei; Li, Haibing

    2017-08-01

    How to convert the weak chiral-interaction into the macroscopic properties of materials remains a huge challenge. Here, this study develops highly fluorescent, selectively chiral-responsive liquid quantum dots (liquid QDs) based on the hydrophobic interaction between the chiral chains and the oleic acid-stabilized QDs, which have been designated as (S)-1810-QDs. The fluorescence spectrum and liquidity of thermal control demonstrate the fluorescence properties and the fluidic behavior of (S)-1810-QDs in the solvent-free state. Especially, (S)-1810-QDs exhibit a highly chiral-selective response toward (1R, 2S)-2-amino-1,2-diphenyl ethanol. It is anticipated that this study will facilitate the construction of smart chiral fluidic sensors. More importantly, (S)-1810-QDs can become an attractive material for chiral separation. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Phonon impact on optical control schemes of quantum dots: Role of quantum dot geometry and symmetry

    Lüker, S.; Kuhn, T.; Reiter, D. E.

    2017-12-01

    Phonons strongly influence the optical control of semiconductor quantum dots. When modeling the electron-phonon interaction in several theoretical approaches, the quantum dot geometry is approximated by a spherical structure, though typical self-assembled quantum dots are strongly lens-shaped. By explicitly comparing simulations of a spherical and a lens-shaped dot using a well-established correlation expansion approach, we show that, indeed, lens-shaped dots can be exactly mapped to a spherical geometry when studying the phonon influence on the electronic system. We also give a recipe to reproduce spectral densities from more involved dots by rather simple spherical models. On the other hand, breaking the spherical symmetry has a pronounced impact on the spatiotemporal properties of the phonon dynamics. As an example we show that for a lens-shaped quantum dot, the phonon emission is strongly concentrated along the direction of the smallest axis of the dot, which is important for the use of phonons for the communication between different dots.

  12. Council celebrates CERN Control Centre

    2006-01-01

    With the unveiling of its new sign, the CERN Control Centre was officially inaugurated on Thursday 16 March. To celebrate its startup, CERN Council members visited the sleek centre, a futuristic-looking room filled with a multitude of monitoring screens.

  13. The Aube centre. 1997 statement

    1998-09-01

    Since January 1992 the Aube centre ensures the storage of 90% of the short life radioactive wastes produced in France. This educational booklet describes the organization of the activities in the centre from the storage of wastes to the radioactivity surveillance of the environment (air, surface and ground waters, river sediments, plants and milk). (J.S.)

  14. CANDU 9 Control Centre Mockup

    Webster, A.; Macbeth, M.J.

    1996-01-01

    This paper provides a summary of the design process being followed, the benefits of applying a systematic design using human factors engineering, presents an overview of the CANDU 9 control centre mockup facility, illustrates the control centre mockup with photographs of the 3D CADD model and the full scale mockup, and provides an update on the current status of the project. (author)

  15. RTEMS CENTRE- RTEMS Improvement

    Silva, Helder; Constantino, Alexandre; Freitas, Daniel; Coutinho, Manuel; Faustino, Sergio; Sousa, Jose; Dias, Luis; Zulianello, Marco

    2010-08-01

    During the last two years, EDISOFT's RTEMS CENTRE team [1], jointly with the European Space Agency and with the support of the worldwide RTEMS community [2], have been developing an activity to facilitate the qualification of the real-time operating system RTEMS (Real-Time Operating System for Multiprocessor Systems). This paper intends to give a high level visibility of the progress and the results obtained in the RTEMS Improvement [3] activity. The primary objective [4] of the project is to improve the RTEMS product, its documentation and to facilitate the qualification of RTEMS for future space missions, taking into consideration the specific operational requirements. The sections below provide a brief overview of the RTEMS operating system and the activities performed in the RTEMS Improvement project, which includes the selection of API managers to be qualified, the tailoring process, the requirements analysis, the reverse engineering and design of the RTEMS, the quality assurance process, the ISVV activities, the test campaign, the results obtained, the criticality analysis and the facilitation of qualification process.

  16. Thailand's nuclear research centre

    Yamkate, P.

    2001-01-01

    The Office of Atomic Energy for Peace, Thailand, is charged with three main tasks, namely, Nuclear Energy development Plan, Utilization of Nuclear Based technology Plan and Science and Technology Plan. Its activities are centred around the research reactor TRR-1/M1. The main areas of contribution include improvement in agricultural production, nuclear medicine and nuclear oncology, health care and nutrition, increasing industrial productivity and efficiency and, development of cadre competent in nuclear science and technology. The office also has the responsibility of ensuring nuclear safety, radiation safety and nuclear waste management. The office has started a new project in 1997 under which a 10 MWt research reactor, an isotope production facility and a waste processing and storage facility would be set up by General Atomic of USA. OAEP has a strong linkage with the IAEA and has been an active participant in RCA programmes. In the future OAEP will enhance its present capabilities in the use of radioisotopes and radiation and look into the possibility of using nuclear energy as an alternative energy resource. (author)

  17. The Adult Education Centre

    Olga Drofenik

    1997-01-01

    Full Text Available The Adult Education Centre has drafted the professional foundations for the Master Plan for Adult Education which, according to the provisions stipulated in the Adult Education Act, will be adopted by the Parliament. The Master Plan specifies the goals, priority target groups, priority areas and a draft financial projection. The professional foundations include the ratings of adult education in studies about adult education trends in Slovenia and abroad. The paper presents research results relevant to the Master Plan and documents issued by international organizations, including research into the Decisive Global Factors of EC Development after 1992, the Report of Ministers of the OECD, and the Economic Development Strategy of Slovenia . All the above-mentioned documents emphasize the importance of life­long learning in achieving a more fulfilling personal life, faster economic growth and maintenance of social ties. In principle, the same views are shared in Slovenia. However, in practice the "multi-dimensional" nature of adult education often gives way to "education for production". This is why we especially stress the importance of adult education in the social and cultural context.

  18. System and method for making quantum dots

    Bakr, Osman; Pan, Jun; El-Ballouli, Ala'a O.; Knudsen, Kristian Rahbek; Abdelhady, Ahmed L.

    2015-01-01

    Embodiments of the present disclosure provide for methods of making quantum dots (QDs) (passivated or unpassivated) using a continuous flow process, systems for making QDs using a continuous flow process, and the like. In one or more embodiments

  19. MoDOT research peer exchange.

    2011-04-01

    The Missouri Department of Transportation hosted a peer exchange on April 11-12, 2011 in Jefferson City, Missouri. Participants included representatives from four state DOTs, The National Academies, USDOT-RITA, FHWA, and both public and private resea...

  20. Electron Transport in Coupled Quantum Dots

    Antoniadis, D

    1998-01-01

    In the course of the investigation funded by this proposal we fabricated, modeled, and measured a variety of quantum dot structures in order to better understand how such nanostructures might be used for computation...

  1. Synthetic Developments of Nontoxic Quantum Dots.

    Das, Adita; Snee, Preston T

    2016-03-03

    Semiconductor nanocrystals, or quantum dots (QDs), are candidates for biological sensing, photovoltaics, and catalysis due to their unique photophysical properties. The most studied QDs are composed of heavy metals like cadmium and lead. However, this engenders concerns over heavy metal toxicity. To address this issue, numerous studies have explored the development of nontoxic (or more accurately less toxic) quantum dots. In this Review, we select three major classes of nontoxic quantum dots composed of carbon, silicon and Group I-III-VI elements and discuss the myriad of synthetic strategies and surface modification methods to synthesize quantum dots composed of these material systems. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Optical Studies of Single Quantum Dots

    Gammon, Daniel; Steel, Duncan G

    2002-01-01

    ...: the atomlike entities known as quantum dots (QDs). Measuring 1-100 nm across, QDs are semiconductor structures in which the electron wavefunction is confined in all three dimensions by the potential energy barriers that form the QD's boundaries...

  3. The evolving DOT enterprise : today toward tomorrow.

    2013-04-01

    Departments of transportation (DOTs) today are being shaped by a wide range of : factors some of which are directly managed and controlled within the transportation : industry while others are external factors shaping the demand for transportatio...

  4. Alternative energy resources for MoDOT

    2011-02-01

    This research investigates environmentally friendly alternative energy sources that could be used by MoDOT in various areas, and develops applicable and sustainable strategies to implement those energy sources.

  5. Colloidal Quantum Dot Photovoltaics: A Path Forward

    Kramer, Illan J.; Sargent, Edward H.

    2011-01-01

    spectrum. CQD materials' ease of processing derives from their synthesis, storage, and processing in solution. Rapid advances have brought colloidal quantum dot photovoltaic solar power conversion efficiencies of 6% in the latest reports. These achievements

  6. Silicon Quantum Dots for Quantum Information Processing

    2013-11-01

    S. Lai, C. Tahan, A. Morello and A. S. Dzurak, Electron Spin lifetimes in multi-valley sil- icon quantum dots, S3NANO Winter School Few spin solid...lifetimes in multi-valley sil- icon quantum dots, International Workshop on Silicon Quantum Electronics, Grenoble, France, February 2012 (Poster). C...typically plunger gates), PMMA A5 is spun at 5000 rpm for 30 seconds, resulting in a 280 nm resist thickness. The resists are baked for 90 seconds at 180

  7. Exciton in type-II quantum dot

    Sierra-Ortega, J; Escorcia, R A [Universidad del Magdalena, A. A. 731, Santa Marta (Colombia); Mikhailov, I D, E-mail: jsierraortega@gmail.co [Universidad Industrial de Santander, A. A. 678, Bucaramanga (Colombia)

    2009-05-01

    We study the quantum-size effect and the influence of the external magnetic field on the exciton ground state energy in the type-II InP quantum disk, lens and pyramid deposited on a wetting layer and embedded in a GaInP matrix. We show that the charge distribution over and below quantum dot and wetting layer induced by trapped exciton strongly depends on the quantum dot morphology and the strength of the magnetic field.

  8. Sol-Gel Chemistry for Carbon Dots.

    Malfatti, Luca; Innocenzi, Plinio

    2018-03-14

    Carbon dots are an emerging class of carbon-based nanostructures produced by low-cost raw materials which exhibit a widely-tunable photoluminescence and a high quantum yield. The potential of these nanomaterials as a substitute of semiconductor quantum dots in optoelectronics and biomedicine is very high, however they need a customized chemistry to be integrated in host-guest systems or functionalized in core-shell structures. This review is focused on recent advances of the sol-gel chemistry applied to the C-dots technology. The surface modification, the fine tailoring of the chemical composition and the embedding into a complex nanostructured material are the main targets of combining sol-gel processing with C-dots chemistry. In addition, the synergistic effect of the sol-gel precursor combined with the C-dots contribute to modify the intrinsic chemo-physical properties of the dots, empowering the emission efficiency or enabling the tuning of the photoluminescence over a wide range of the visible spectrum. © 2018 The Chemical Society of Japan & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Coherent transport through interacting quantum dots

    Hiltscher, Bastian

    2012-01-01

    The present thesis is composed of four different works. All deal with coherent transport through interacting quantum dots, which are tunnel-coupled to external leads. There a two main motivations for the use of quantum dots. First, they are an ideal device to study the influence of strong Coulomb repulsion, and second, their discrete energy levels can easily be tuned by external gate electrodes to create different transport regimes. The expression of coherence includes a very wide range of physical correlations and, therefore, the four works are basically independent of each other. Before motivating and introducing the different works in more detail, we remark that in all works a diagrammatic real-time perturbation theory is used. The fermionic degrees of freedom of the leads are traced out and the elements of the resulting reduced density matrix can be treated explicitly by means of a generalized master equation. How this equation is solved, depends on the details of the problem under consideration. In the first of the four works adiabatic pumping through an Aharonov-Bohm interferometer with a quantum dot embedded in each of the two arms is studied. In adiabatic pumping transport is generated by varying two system parameters periodically in time. We consider the two dot levels to be these two pumping parameters. Since they are located in different arms of the interferometer, pumping is a quantum mechanical effect purely relying on coherent superpositions of the dot states. It is very challenging to identify a quantum pumping mechanism in experiments, because a capacitive coupling of the gate electrodes to the leads may yield an undesired AC bias voltage, which is rectified by a time dependent conductance. Therefore, distinguishing features of these two transport mechanisms are required. We find that the dependence on the magnetic field is the key feature. While the pumped charge is an odd function of the magnetic flux, the rectified current is even, at least in

  10. Coherent transport through interacting quantum dots

    Hiltscher, Bastian

    2012-10-05

    The present thesis is composed of four different works. All deal with coherent transport through interacting quantum dots, which are tunnel-coupled to external leads. There a two main motivations for the use of quantum dots. First, they are an ideal device to study the influence of strong Coulomb repulsion, and second, their discrete energy levels can easily be tuned by external gate electrodes to create different transport regimes. The expression of coherence includes a very wide range of physical correlations and, therefore, the four works are basically independent of each other. Before motivating and introducing the different works in more detail, we remark that in all works a diagrammatic real-time perturbation theory is used. The fermionic degrees of freedom of the leads are traced out and the elements of the resulting reduced density matrix can be treated explicitly by means of a generalized master equation. How this equation is solved, depends on the details of the problem under consideration. In the first of the four works adiabatic pumping through an Aharonov-Bohm interferometer with a quantum dot embedded in each of the two arms is studied. In adiabatic pumping transport is generated by varying two system parameters periodically in time. We consider the two dot levels to be these two pumping parameters. Since they are located in different arms of the interferometer, pumping is a quantum mechanical effect purely relying on coherent superpositions of the dot states. It is very challenging to identify a quantum pumping mechanism in experiments, because a capacitive coupling of the gate electrodes to the leads may yield an undesired AC bias voltage, which is rectified by a time dependent conductance. Therefore, distinguishing features of these two transport mechanisms are required. We find that the dependence on the magnetic field is the key feature. While the pumped charge is an odd function of the magnetic flux, the rectified current is even, at least in

  11. Quantum-dot-in-perovskite solids

    Ning, Zhijun; Gong, Xiwen; Comin, Riccardo; Walters, Grant; Fan, Fengjia; Voznyy, Oleksandr; Yassitepe, Emre; Buin, Andrei; Hoogland, Sjoerd; Sargent, Edward H.

    2015-01-01

    © 2015 Macmillan Publishers Limited. All rights reserved. Heteroepitaxy - atomically aligned growth of a crystalline film atop a different crystalline substrate - is the basis of electrically driven lasers, multijunction solar cells, and blue-light-emitting diodes. Crystalline coherence is preserved even when atomic identity is modulated, a fact that is the critical enabler of quantum wells, wires, and dots. The interfacial quality achieved as a result of heteroepitaxial growth allows new combinations of materials with complementary properties, which enables the design and realization of functionalities that are not available in the single-phase constituents. Here we show that organohalide perovskites and preformed colloidal quantum dots, combined in the solution phase, produce epitaxially aligned 'dots-in-a-matrix' crystals. Using transmission electron microscopy and electron diffraction, we reveal heterocrystals as large as about 60 nanometres and containing at least 20 mutually aligned dots that inherit the crystalline orientation of the perovskite matrix. The heterocrystals exhibit remarkable optoelectronic properties that are traceable to their atom-scale crystalline coherence: photoelectrons and holes generated in the larger-bandgap perovskites are transferred with 80% efficiency to become excitons in the quantum dot nanocrystals, which exploit the excellent photocarrier diffusion of perovskites to produce bright-light emission from infrared-bandgap quantum-tuned materials. By combining the electrical transport properties of the perovskite matrix with the high radiative efficiency of the quantum dots, we engineer a new platform to advance solution-processed infrared optoelectronics.

  12. Semiconductor Quantum Dots with Photoresponsive Ligands.

    Sansalone, Lorenzo; Tang, Sicheng; Zhang, Yang; Thapaliya, Ek Raj; Raymo, Françisco M; Garcia-Amorós, Jaume

    2016-10-01

    Photochromic or photocaged ligands can be anchored to the outer shell of semiconductor quantum dots in order to control the photophysical properties of these inorganic nanocrystals with optical stimulations. One of the two interconvertible states of the photoresponsive ligands can be designed to accept either an electron or energy from the excited quantum dots and quench their luminescence. Under these conditions, the reversible transformations of photochromic ligands or the irreversible cleavage of photocaged counterparts translates into the possibility to switch luminescence with external control. As an alternative to regulating the photophysics of a quantum dot via the photochemistry of its ligands, the photochemistry of the latter can be controlled by relying on the photophysics of the former. The transfer of excitation energy from a quantum dot to a photocaged ligand populates the excited state of the species adsorbed on the nanocrystal to induce a photochemical reaction. This mechanism, in conjunction with the large two-photon absorption cross section of quantum dots, can be exploited to release nitric oxide or to generate singlet oxygen under near-infrared irradiation. Thus, the combination of semiconductor quantum dots and photoresponsive ligands offers the opportunity to assemble nanostructured constructs with specific functions on the basis of electron or energy transfer processes. The photoswitchable luminescence and ability to photoinduce the release of reactive chemicals, associated with the resulting systems, can be particularly valuable in biomedical research and can, ultimately, lead to the realization of imaging probes for diagnostic applications as well as to therapeutic agents for the treatment of cancer.

  13. Quantum-dot-in-perovskite solids

    Ning, Zhijun

    2015-07-15

    © 2015 Macmillan Publishers Limited. All rights reserved. Heteroepitaxy - atomically aligned growth of a crystalline film atop a different crystalline substrate - is the basis of electrically driven lasers, multijunction solar cells, and blue-light-emitting diodes. Crystalline coherence is preserved even when atomic identity is modulated, a fact that is the critical enabler of quantum wells, wires, and dots. The interfacial quality achieved as a result of heteroepitaxial growth allows new combinations of materials with complementary properties, which enables the design and realization of functionalities that are not available in the single-phase constituents. Here we show that organohalide perovskites and preformed colloidal quantum dots, combined in the solution phase, produce epitaxially aligned \\'dots-in-a-matrix\\' crystals. Using transmission electron microscopy and electron diffraction, we reveal heterocrystals as large as about 60 nanometres and containing at least 20 mutually aligned dots that inherit the crystalline orientation of the perovskite matrix. The heterocrystals exhibit remarkable optoelectronic properties that are traceable to their atom-scale crystalline coherence: photoelectrons and holes generated in the larger-bandgap perovskites are transferred with 80% efficiency to become excitons in the quantum dot nanocrystals, which exploit the excellent photocarrier diffusion of perovskites to produce bright-light emission from infrared-bandgap quantum-tuned materials. By combining the electrical transport properties of the perovskite matrix with the high radiative efficiency of the quantum dots, we engineer a new platform to advance solution-processed infrared optoelectronics.

  14. On the diameter of dot-critical graphs

    Doost Ali Mojdeh

    2009-01-01

    Full Text Available A graph G is \\(k\\-dot-critical (totaly \\(k\\-dot-critical if \\(G\\ is dot-critical (totaly dot-critical and the domination number is \\(k\\. In the paper [T. Burtona, D. P. Sumner, Domination dot-critical graphs, Discrete Math, 306 (2006, 11-18] the following question is posed: What are the best bounds for the diameter of a \\(k\\-dot-critical graph and a totally \\(k\\-dot-critical graph \\(G\\ with no critical vertices for \\(k \\geq 4\\? We find the best bound for the diameter of a \\(k\\-dot-critical graph, where \\(k \\in\\{4,5,6\\}\\ and we give a family of \\(k\\-dot-critical graphs (with no critical vertices with sharp diameter \\(2k-3\\ for even \\(k \\geq 4\\.

  15. Quantum measurement of coherent tunneling between quantum dots

    Wiseman, H. M.; Utami, Dian Wahyu; Sun, He Bi; Milburn, G. J.; Kane, B. E.; Dzurak, A.; Clark, R. G.

    2001-01-01

    We describe the conditional and unconditional dynamics of two coupled quantum dots when one dot is subjected to a measurement of its occupation number by coupling it to a third readout dot via the Coulomb interaction. The readout dot is coupled to source and drain leads under weak bias, and a tunnel current flows through a single bound state when energetically allowed. The occupation of the quantum dot near the readout dot shifts the bound state of the readout dot from a low conducting state to a high conducting state. The measurement is made by continuously monitoring the tunnel current through the readout dot. We show that there is a difference between the time scale for the measurement-induced decoherence between the localized states of the dots, and the time scale on which the system becomes localized due to the measurement

  16. Performance of local correlation methods for halogen bonding: The case of Br2-(H2O)n,n = 4,5 clusters and Br2@5(12)6(2) clathrate cage.

    Batista-Romero, Fidel A; Pajón-Suárez, Pedro; Bernal-Uruchurtu, Margarita I; Hernández-Lamoneda, Ramón

    2015-09-07

    The performance of local correlation methods is examined for the interactions present in clusters of bromine with water where the combined effect of hydrogen bonding (HB), halogen bonding (XB), and hydrogen-halogen (HX) interactions lead to many interesting properties. Local methods reproduce all the subtleties involved such as many-body effects and dispersion contributions provided that specific methodological steps are followed. Additionally, they predict optimized geometries that are nearly free of basis set superposition error that lead to improved estimates of spectroscopic properties. Taking advantage of the local correlation energy partitioning scheme, we compare the different interaction environments present in small clusters and those inside the 5(12)6(2) clathrate cage. This analysis allows a clear identification of the reasons supporting the use of local methods for large systems where non-covalent interactions play a key role.

  17. Concentrations and uncertainties of stratospheric trace species inferred from limb infrared monitor of the stratosphere data. I - Methodology and application to OH and HO2. II - Monthly averaged OH, HO2, H2O2, and HO2NO2

    Kaye, J. A.; Jackman, C. H.

    1986-01-01

    Difficulties arise in connection with the verification of multidimensional chemical models of the stratosphere. The present study shows that LIMS data, together with a photochemical equilibrium model, may be used to infer concentrations of a variety of zonally averaged trace Ox, OHx, and NOx species over much of the stratosphere. In the lower stratosphere, where the photochemical equilibrium assumption for HOx species breaks down, inferred concentrations should still be accurate to about a factor of 2 for OH and 2.5 for HO2. The algebraic nature of the considered model makes it possible to see easily to the first order the effect of variation of any model input parameter or its uncertainty on the inferred concontration of the HOx species and their uncertainties.

  18. High resolution spectroscopy of the Martian atmosphere - Study of seasonal variations of CO, O3, H2O, and T on the north polar cap and a search for SO2, H2O2, and H2CO

    Krasnopolsky, V. A.; Chakrabarti, S.; Larson, H.; Sandel, B. R.

    1992-01-01

    An overview is presented of an observational campaign which will measure (1) the seasonal variations of the CO mixing ratio on the Martian polar cap due to accumulation and depletion of CO during the condensation and evaporation of CO2, as well as (2) the early spring ozone and water vapor of the Martian north polar cap, and (3) the presence of H2CO, H2O2, and SO2. The lines of these compounds will be measured by a combined 4-m telescope and Fourier-transform spectrometer 27097.

  19. [Co(NH3)6]3[Cu4(OH)(CO3)8].2H2O--a new carbonato-copper(II) anion stabilized by extensive hydrogen bonding.

    Abrahams, Brendan F; Haywood, Marissa G; Robson, Richard

    2004-04-21

    Addition of Co(NH3)6(3+) to aqueous solutions of Cu(II) in excess carbonate promotes the assembly of a new highly charged carbonato-copper(II) anion, [Cu4(OH)(CO3)8](9-), which contains an unusual mu4 hydroxo-bridged square Cu4 arrangement, stabilised in the crystal by no less than forty hydrogen bonds (< 3 Angstrom) to hexammine cations.

  20. Análisis de puntos de rocío y contenidos de humedad de mezclas gaseosas N2-H2O y CH4-H2O

    D. Bogoya M.; C. Müller, I. Q.; L. R. Oellrich

    1995-01-01

    EI conocimiento actual del contenido de humedad de mezclas gaseosas saturadas es aún incompleto, especialmente en la región de altas presiones y bajas temperaturas. Por tanto se realizaron medidas experimentales de punta de rocío con los sistemas nitrógeno-agua y metano-agua, a presiones de 3 y 6 MPa y a temperaturas de 258 K a 288 K. Los puntos de rocío se determinaron con el método del espejo de punta de rocío y los contenidos de humedad por medio de la titulación de Karl-Fischer. Los valor...

  1. In Situ Raman Spectroscopic Study of Gypsum (CaSO4·2H2O) and Epsomite (MgSO4·7H2O) Dehydration Utilizing an Ultrasonic Levitator.

    Brotton, Stephen J; Kaiser, Ralf I

    2013-02-21

    We present an original apparatus combining an acoustic levitator and a pressure-compatible process chamber. To characterize in situ the chemical and physical modifications of a levitated, single particle while heated to well-defined temperatures using a carbon dioxide laser, the chamber is interfaced to a Raman spectroscopic probe. As a proof-of-concept study, by gradually increasing the heating temperature, we observed the variations in the Raman spectra as 150 μg of crystals of gypsum and epsomite were dehydrated in anhydrous nitrogen gas. We display spectra showing the decreasing intensities of the ν1 symmetric and ν3 asymmetric stretching modes of water with time and the simultaneous shift of the ν1(SO4(2-)) symmetric stretch mode to higher wavenumbers. Our results demonstrate that the new apparatus is well suited to study the dehydration of levitated species such as minerals and offers potential advantages compared with previous experiments on bulk samples.

  2. Mechanism of intercalation in protonic conductors: case of HUP (H3OUO2PO4, 3H2O) and the corresponding xerogel [(UO2)sub(1.5-x) PO4Hsub(2x),2H2O

    Colomban, P.; Pham Thi, M.

    1985-01-01

    Intercalation of acetone alkylammonium, methylviologen and cobalticinium ions in HUP framework (H 3 OUO 2 PO 4 .3H 2 O) have been studied with different methods (IR and Raman spectroscopies, X-ray diffraction, DSC and scanning electron microscopy). Various reactions have been pointed out: i.e. proton transfer from H 3 O + to PO 4 3- , ionisation of cobaltocene into cobalticinium. Species orientation is discussed and its influence on conductivity and phase transitions [fr

  3. Análisis de puntos de rocío y contenidos de humedad de mezclas gaseosas N2-H2O y CH4-H2O

    D. Bogoya M.

    1995-01-01

    Full Text Available EI conocimiento actual del contenido de humedad de mezclas gaseosas saturadas es aún incompleto, especialmente en la región de altas presiones y bajas temperaturas. Por tanto se realizaron medidas experimentales de punta de rocío con los sistemas nitrógeno-agua y metano-agua, a presiones de 3 y 6 MPa y a temperaturas de 258 K a 288 K. Los puntos de rocío se determinaron con el método del espejo de punta de rocío y los contenidos de humedad por medio de la titulación de Karl-Fischer. Los valores experimentales se compararon con correlaciones de la literatura. El método de Sharma-Campbell resultó ser la mejor descripción del sistema nitrógeno-agua. Para temperaturas inferiores a 273 K la suposición de comportamiento de gas ideal mostro ser suficiente para el sistema metano-agua, mientras que para temperaturas superiores a 273 K los cálculos mediante el principio de estados correspondientes con dos parámetros, en combinación con una corrección de fugacidad, manifestó ser la mejor.

  4. Delamination-restacking behaviour of surfactant intercalated layered hydroxy double salts, M 3Zn 2(OH) 8(surf) 2ṡ2H 2O [M = Ni, Co and surf = dodecyl sulphate (DS), dodecyl benzene sulphonate (DBS)

    Rajamathi, Jacqueline T.; Ravishankar, N.; Rajamathi, Michael

    2005-02-01

    Surfactant anion intercalated nickel-zinc and cobalt-zinc layered hydroxy double salts were prepared through a modified acetate hydrolysis route. These organo-inorganic hybrids delaminate readily in alcohols such as 1-butanol to give stable translucent colloids. The extent of delamination and the stability of the colloids obtained are comparable to what has been observed in the case of layered double hydroxides (LDHs). The original layered solid could be obtained either by evaporation of the colloid or precipitation by the addition of a polar solvent such as acetone.

  5. Correlation of the thermodynamic properties of the ideal gases Ar, CO, H2, N2, O2, CO2, H2O, CH4, and C2H4

    Sievers, U.; Schulz, S.; Dortmund Univ.

    1981-01-01

    The thermodynamic properties of pure substances in the state of the ideal gases serve as reference quantity for the calculation of the caloric quantities of real fluid pure substances and mixtures. All caloric quantities of pure ideal gases can be calculated as a function of temperature and density if the molar enthalpy and the molar entropy are known for a reference point and also the temperature dependence of the molar isochoric heat capacity exists. In this article the molar enthalpy, the molar entropy and the molar isochoric heat capacity are investigated more detailed. (RDE)

  6. Removal of binary dyes mixtures with opposite and similar charges by adsorption, coagulation/flocculation and catalytic oxidation in the presence of CeO2/H2O2 Fenton-like system.

    Issa Hamoud, Houeida; Finqueneisel, Gisèle; Azambre, Bruno

    2017-06-15

    In this study, the removal of binary mixtures of dyes with similar (Orange II/Acid Green 25) or opposite charges (Orange II/Malachite Green) was investigated either by simple adsorption on ceria or by the heterogeneous Fenton reaction in presence of H 2 O 2 . First, the CeO 2 nanocatalyst with high specific surface area (269 m 2 /g) and small crystal size (5 nm) was characterized using XRD, Raman spectroscopy and N 2 physisorption at 77 K. The adsorption of single dyes was studied either from thermodynamic and kinetic viewpoints. It is shown that the adsorption of dyes on ceria surface is highly pH-dependent and followed a pseudo-second order kinetic model. Adsorption isotherms fit well the Langmuir model with a complete monolayer coverage and higher affinity towards Orange II at pH 3, compared to other dyes. For the (Orange II/Acid Green 25) mixture, both the amounts of dyes adsorbed on ceria surface and discoloration rates measured from Fenton experiments were decreased by comparison with single dyes. This is due to the adsorption competition existing onto the same surface Ce x+ sites and the reaction competition with hydroxyl radicals, respectively. The behavior of the (Orange II/Malachite Green) mixture is markedly different. Dyes with opposite charges undergo paired adsorption on ceria as well as homogeneous and heterogeneous coagulation/flocculation processes, but can also be removed by heterogeneous Fenton process. Copyright © 2016 Elsevier Ltd. All rights reserved.

  7. A study on socio-demographic profile and feasibility of DOTS provider registered under RNTCP in Varanasi district Uttar Pradesh

    Mohd. Afzalul Haque

    2014-03-01

    Full Text Available Introduction: Tuberculosis is a major chronic disorder affecting the larger population more than any other disease in the country. DOTS was introduced in India in 1993 as part of the Revised National Tuberculosis Programme (RNTCP following a review of India’s National Tuberculosis Programme (NTP a year earlier (1 .Patient satisfaction is an important parameter for assessing the quality of patient care services. There is need to assess the health care provider regarding the consumer satisfaction as often as possible, this paper summarizes our experience about role of DOTS provider in the management of TB patient in rural population of Varanasi districts Utter Pradesh. Objective: (1 To assess the perception of registered tuberculosis patients regarding DOTS provider for the treatment of tuberculosis. (2 To assess the accessibility, acceptability & availability of community DOTS provider. Design: A longitudinal study. Setting: Three microscopic centre of Cholapur Tuberculosis unit of Varanasi districts. Methods: Registered patients were interviewed twice: once in the beginning and another at the completion of the treatment or after the permanent discontinuation of the treatment. Patients were interviewed for their socio-demographic profiles, opinion about DOTS and its providers. Side effects experienced and action taken etc. Data was collected on a semi-structured, pre-tested questionnaire. DOTS providers were interviewed and treatment cards analyzed for any interruption of treatment and action taken. Data was collected from 1st June 2004 to 31th June 2005 till the completion of the regimen. Results: Majority of DOTS providers were young males (82.7% of 26 years to 40 years, while the representation of females was only 5 (17.3%. Almost more than 80% of the patients started their treatment within 1-10 days. For majority of cases (83% the distance of DOTS provider from patient’s house was within 1 km. Mean time spent to go to DOTS provider was 27

  8. The Aube centre; Le Centre de l`Aube

    NONE

    1996-07-01

    This educational booklet is devoted to a general presentation of the Aube radioactive wastes storage centre. After a short presentation of the Andra, the French national agency for the management of radioactive wastes, it gives some general information about radioactive wastes (origin, classification), containers (quality assurance and different types), wastes transportation (planning, safety), and about the Aube centre itself: description, treatment and conditioning of drums (compacting and injection), storage facilities, geological situation of the site, and environmental controls. (J.S.)

  9. Introducing the PET Centre Prague

    Belohlavek, O.

    2001-01-01

    The PET Centre Prague (www.homolka.cz/nm) was established in 1999 as the outcome of a joint project of the public Na Homolce Hospital and the Nuclear Research Institute Rez, plc, the Czech radiopharmaceutical producer. Technical and financial assistance was provided by the International Atomic Energy Agency, which perceived the Centre as its model project that could serve as a guide for the development of PET centres in countries sharing a comparable level of development with the Czech Republic. The article maps the history of the project, its design, workplace lay-out and equipment, radiation protection arrangements and spectrum of the first approx. 3000 investigations. (author)

  10. Spin interactions in InAs quantum dots and molecules

    Doty, M.F.; Ware, M.E.; Stinaff, E.A.; Scheibner, M.; Bracker, A.S.; Ponomarev, I.V.; Badescu, S.C.; Reinecke, T.L.; Gammon, D. [Naval Research Lab, Washington, DC 20375 (United States); Korenev, V.L. [A.F. Ioffe Physical Technical Institute, St. Petersburg 194021 (Russian Federation)

    2006-12-15

    Spin interactions between particles in quantum dots or quantum dot molecules appear as fine structure in the photoluminescence spectra. Using the understanding of exchange interactions that has been developed from single dot spectra, we analyze the spin signatures of coupled quantum dots separated by a wide barrier such that inter-dot interactions are negligible. We find that electron-hole exchange splitting is directly evident. In dots charged with an excess hole, an effective hole-hole interaction can be turned on through tunnel coupling. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  11. Artful and multifaceted applications of carbon dot in biomedicine.

    Jaleel, Jumana Abdul; Pramod, K

    2018-01-10

    Carbon dots (C-dots) are luminescent carbon nanomaterial having good biocompatibility and low toxicity. The characteristic fluorescence emission property of C-dots establishes their role in optical imaging. C-dots which are superior to fluorescent dyes and semiconductor quantum dots act as a safer in vivo imaging probe. Apart from their bioimaging application, other applications in biomedicine such as drug delivery, cancer therapy, and gene delivery were studied. In this review, we present multifaceted applications of C-dots along with their synthesis, surface passivation, doping, and toxicity profile. Copyright © 2017 Elsevier B.V. All rights reserved.

  12. Submonolayer Quantum Dot Infrared Photodetector

    Ting, David Z.; Bandara, Sumith V.; Gunapala, Sarath D.; Chang, Yia-Chang

    2010-01-01

    A method has been developed for inserting submonolayer (SML) quantum dots (QDs) or SML QD stacks, instead of conventional Stranski-Krastanov (S-K) QDs, into the active region of intersubband photodetectors. A typical configuration would be InAs SML QDs embedded in thin layers of GaAs, surrounded by AlGaAs barriers. Here, the GaAs and the AlGaAs have nearly the same lattice constant, while InAs has a larger lattice constant. In QD infrared photodetector, the important quantization directions are in the plane perpendicular to the normal incidence radiation. In-plane quantization is what enables the absorption of normal incidence radiation. The height of the S-K QD controls the positions of the quantized energy levels, but is not critically important to the desired normal incidence absorption properties. The SML QD or SML QD stack configurations give more control of the structure grown, retains normal incidence absorption properties, and decreases the strain build-up to allow thicker active layers for higher quantum efficiency.

  13. Advancements in the Field of Quantum Dots

    Mishra, Sambeet; Tripathy, Pratyasha; Sinha, Swami Prasad.

    2012-08-01

    Quantum dots are defined as very small semiconductor crystals of size varying from nanometer scale to a few micron i.e. so small that they are considered dimensionless and are capable of showing many chemical properties by virtue of which they tend to be lead at one minute and gold at the second minute.Quantum dots house the electrons just the way the electrons would have been present in an atom, by applying a voltage. And therefore they are very judiciously given the name of being called as the artificial atoms. This application of voltage may also lead to the modification of the chemical nature of the material anytime it is desired, resulting in lead at one minute to gold at the other minute. But this method is quite beyond our reach. A quantum dot is basically a semiconductor of very tiny size and this special phenomenon of quantum dot, causes the band of energies to change into discrete energy levels. Band gaps and the related energy depend on the relationship between the size of the crystal and the exciton radius. The height and energy between different energy levels varies inversely with the size of the quantum dot. The smaller the quantum dot, the higher is the energy possessed by it.There are many applications of the quantum dots e.g. they are very wisely applied to:Light emitting diodes: LEDs eg. White LEDs, Photovoltaic devices: solar cells, Memory elements, Biology : =biosensors, imaging, Lasers, Quantum computation, Flat-panel displays, Photodetectors, Life sciences and so on and so forth.The nanometer sized particles are able to display any chosen colour in the entire ultraviolet visible spectrum through a small change in their size or composition.

  14. The centre of the action

    2008-01-01

    The CERN Control Centre (CCC) has all the ingredients of an action movie control room: hundreds of screens, technicians buzzing in and out, huge floor-to-ceiling windows revealing the looming vista of a mountain range, flashing lights, microphones… This is the place where not just the LHC, but the whole of CERN’s accelerator complex and technical support is based - truly the centre of the action at CERN.

  15. Dot gain compensation in the blue noise mask

    Yao, Meng; Parker, Kevin J.

    1995-04-01

    Frequency modulated (FM) halftoning or 'stochastic screening,' has attracted a great deal of attention in the printing industry in recent years. It has several advantages over conventional halftoning. But one serious problem that arises in FM halftoning is dot gain. One approach to stochastic screening uses a specially constructed halftone screen, the blue noise mask (BNM), to produce an unstructured and visually appealing pattern of halftone dots at any gray level. In this paper, we will present methods to correct dot gain with the BNM. Dot gain is related to the area-to-perimeter ration of printed spots. We can exploit this feature in different ways. At a medium level, a B>NM pattern will have 'connected' as well as 'isolated' dots. Normally, as we build down BNM patterns to lower levels, a specific number of white dots will be replace by black dots. Since connected white dots are more likely to be picked than isolated white dots, this will results in substantial dot gain because of the increasing number of isolated white dots. We show that it is possible to constrain the process of constructing a BNM such that isolated dots are preferentially removes, thus significantly reducing dot gain in a BNM.

  16. Training centres - organization and management

    Kovar, P.

    1986-01-01

    In the lecture 'Training centres - organization and management' some principles and requirements which influence the organization, management and activity pattern of nuclear training centres, are briefly introduced. It is demonstrated, step by step, how these general principles are implemented in the development of the Czechoslovak nuclear power programme, it means, how the training of the NPP personnel proceeds in Czechoslovak nuclear training centres. General principles which are selected: a connection between the capacity of the training centre and the scope and needs of the nuclear power programme, a position of the training center within the institutional set-up, a structure and organization of the training system which complies with the system of NPP construction, reflect the pattern and the activity of the nuclear training centre and nuclear power technical level, a research group of workers in the nuclear training centre, main tasks and technical facilities, management of the training process and a transfer of knowledge and research results into the training process. The lecture is supplemented by pictures and slides. (orig.)

  17. RTEMS Centre - Support and Maintenance Centre to RTEMS Operating System

    Silva, H.; Constantino, A.; Freitas, D.; Coutinho, M.; Faustino, S.; Mota, M.; Colaço, P.; Sousa, J.; Dias, L.; Damjanovic, B.; Zulianello, M.; Rufino, J.

    2009-05-01

    RTEMS CENTRE - Support and Maintenance Centre to RTEMS Operating System is a joint ESA/Portuguese Task Force initiative to develop a support and maintenance centre to the Real-Time Executive for Multiprocessor Systems (RTEMS). This paper gives a high level visibility of the progress, the results obtained and the future work in the RTEMS CENTRE [6] and in the RTEMS Improvement [7] projects. RTEMS CENTRE started officially in November 2006, with the RTEMS 4.6.99.2 version. A full analysis of RTEMS operating system was produced. The architecture was analysed in terms of conceptual, organizational and operational concepts. The original objectives [1] of the centre were primarily to create and maintain technical expertise and competences in this RTOS, to develop a website to provide the European Space Community an entry point for obtaining support (http://rtemscentre.edisoft.pt), to design, develop, maintain and integrate some RTEMS support tools (Timeline Tool, Configuration and Management Tools), to maintain flight libraries and Board Support Packages, to develop a strong relationship with the World RTEMS Community and finally to produce some considerations in ARINC-653, DO-178B and ECSS E-40 standards. RTEMS Improvement is the continuation of the RTEMS CENTRE. Currently the RTEMS, version 4.8.0, is being facilitated for a future qualification. In this work, the validation material is being produced following the Galileo Software Standards Development Assurance Level B [5]. RTEMS is being completely tested, errors analysed, dead and deactivated code removed and tests produced to achieve 100% statement and decision coverage of source code [2]. The SW to exploit the LEON Memory Management Unit (MMU) hardware will be also added. A brief description of the expected implementations will be given.

  18. Photoluminescence of carbon dots from mesoporous silica

    Nelson, D. K.; Razbirin, B. S.; Starukhin, A. N.; Eurov, D. A.; Kurdyukov, D. A.; Stovpiaga, E. Yu; Golubev, V. G.

    2016-09-01

    Photophysical properties of carbon dots were investigated under various excitation conditions and over a wide temperature region - from room to liquid helium temperatures. The carbon dots (CDs) were synthesized using mesoporous silica particles as a reactor and (3-aminopropyl)triethoxysilane (APTES) as a precursor. The photoluminescence spectra of CDs exhibit a strong dependence on the excitation wavelength and demonstrate a significant inhomogeneous broadening. Lowering sample temperature reveals the doublet structure of the spectra, which is associated with the vibronic structure of radiative transitions. The vibration energy ∼1200 cm-1 is close to the energy of Csbnd O stretching vibration. Long-lived phosphorescence of carbon dots with its decay time ∼0.2 s at T = 80 K was observed. The fluorescence and phosphorescence spectra are shown to be spectrally separated. The long-lived component of the emission was ascribed to optically forbidden triplet-singlet transitions. The value of the singlet-triplet splitting was found to be about 0.3 eV. Photo-induced polarization of the luminescence of carbon dots was revealed. The degree of the linear polarization is dependent on the wavelengths of both excitation and emitted light. The effect indicates a hidden anisotropy of optical dipole transitions in the dots and demonstrates the loss of the dipole orientation during the electron energy relaxation.

  19. Analysis of MoDOT communication and outreach effectiveness

    2008-07-01

    Personal interviews were held with MoDOT personnel to assess MoDOTs current communication practices and existing customer segmentation practices. Focus groups were then held to help gauge the effectiveness of existing communication practices and t...

  20. Coulomb Blockade of Tunnel-Coupled Quantum Dots

    Golden, John

    1997-01-01

    .... Though classical charging models can explain the Coulomb blockade of an isolated dot, they must be modified to explain the Coulomb blockade of dots coupled through the quantum mechanical tunneling of electrons...

  1. Surface treatment of nanocrystal quantum dots after film deposition

    Sykora, Milan; Koposov, Alexey; Fuke, Nobuhiro

    2015-02-03

    Provided are methods of surface treatment of nanocrystal quantum dots after film deposition so as to exchange the native ligands of the quantum dots for exchange ligands that result in improvement in charge extraction from the nanocrystals.

  2. Quantum dot optoelectronic devices: lasers, photodetectors and solar cells

    Wu, Jiang; Chen, Siming; Seeds, Alwyn; Liu, Huiyun

    2015-01-01

    Nanometre-scale semiconductor devices have been envisioned as next-generation technologies with high integration and functionality. Quantum dots, or the so-called ‘artificial atoms’, exhibit unique properties due to their quantum confinement in all 3D. These unique properties have brought to light the great potential of quantum dots in optoelectronic applications. Numerous efforts worldwide have been devoted to these promising nanomaterials for next-generation optoelectronic devices, such as lasers, photodetectors, amplifiers, and solar cells, with the emphasis on improving performance and functionality. Through the development in optoelectronic devices based on quantum dots over the last two decades, quantum dot devices with exceptional performance surpassing previous devices are evidenced. This review describes recent developments in quantum dot optoelectronic devices over the last few years. The paper will highlight the major progress made in 1.3 μm quantum dot lasers, quantum dot infrared photodetectors, and quantum dot solar cells. (topical review)

  3. Inorganic passivation and doping control in colloidal quantum dot photovoltaics

    Hoogland, Sjoerd H.; Ip, Alex; Thon, Susanna; Voznyy, Oleksandr; Tang, Jiang; Liu, Huan; Zhitomirsky, David; Debnath, Ratan K.; Levina, Larissa; Rollny, Lisa R.; Fischer, Armin H.; Kemp, Kyle W.; Kramer, Illan J.; Ning, Zhijun; Labelle, André J.; Chou, Kang Wei; Amassian, Aram; Sargent, E. H.

    2012-01-01

    We discuss strategies to reduce midgap trap state densities in colloidal quantum dot films and requirements to control doping type and magnitude. We demonstrate that these improvements result in colloidal quantum dot solar cells with certified 7.0% efficiency.

  4. TxDOT administration research : tasks completed in FY2009.

    2010-01-01

    Texas Department of Transportation (TxDOT) Project 0-6581-TI, TxDOT Administration : Research, encompasses multiple tasks that explore and support administrative aspects of : transportation research. : The project term began in October 2008 and has b...

  5. Filtering algorithm for dotted interferences

    Osterloh, K., E-mail: kurt.osterloh@bam.de [Federal Institute for Materials Research and Testing (BAM), Division VIII.3, Radiological Methods, Unter den Eichen 87, 12205 Berlin (Germany); Buecherl, T.; Lierse von Gostomski, Ch. [Technische Universitaet Muenchen, Lehrstuhl fuer Radiochemie, Walther-Meissner-Str. 3, 85748 Garching (Germany); Zscherpel, U.; Ewert, U. [Federal Institute for Materials Research and Testing (BAM), Division VIII.3, Radiological Methods, Unter den Eichen 87, 12205 Berlin (Germany); Bock, S. [Technische Universitaet Muenchen, Lehrstuhl fuer Radiochemie, Walther-Meissner-Str. 3, 85748 Garching (Germany)

    2011-09-21

    An algorithm has been developed to remove reliably dotted interferences impairing the perceptibility of objects within a radiographic image. This particularly is a major challenge encountered with neutron radiographs collected at the NECTAR facility, Forschungs-Neutronenquelle Heinz Maier-Leibnitz (FRM II): the resulting images are dominated by features resembling a snow flurry. These artefacts are caused by scattered neutrons, gamma radiation, cosmic radiation, etc. all hitting the detector CCD directly in spite of a sophisticated shielding. This makes such images rather useless for further direct evaluations. One approach to resolve this problem of these random effects would be to collect a vast number of single images, to combine them appropriately and to process them with common image filtering procedures. However, it has been shown that, e.g. median filtering, depending on the kernel size in the plane and/or the number of single shots to be combined, is either insufficient or tends to blur sharp lined structures. This inevitably makes a visually controlled processing image by image unavoidable. Particularly in tomographic studies, it would be by far too tedious to treat each single projection by this way. Alternatively, it would be not only more comfortable but also in many cases the only reasonable approach to filter a stack of images in a batch procedure to get rid of the disturbing interferences. The algorithm presented here meets all these requirements. It reliably frees the images from the snowy pattern described above without the loss of fine structures and without a general blurring of the image. It consists of an iterative, within a batch procedure parameter free filtering algorithm aiming to eliminate the often complex interfering artefacts while leaving the original information untouched as far as possible.

  6. Filtering algorithm for dotted interferences

    Osterloh, K.; Buecherl, T.; Lierse von Gostomski, Ch.; Zscherpel, U.; Ewert, U.; Bock, S.

    2011-01-01

    An algorithm has been developed to remove reliably dotted interferences impairing the perceptibility of objects within a radiographic image. This particularly is a major challenge encountered with neutron radiographs collected at the NECTAR facility, Forschungs-Neutronenquelle Heinz Maier-Leibnitz (FRM II): the resulting images are dominated by features resembling a snow flurry. These artefacts are caused by scattered neutrons, gamma radiation, cosmic radiation, etc. all hitting the detector CCD directly in spite of a sophisticated shielding. This makes such images rather useless for further direct evaluations. One approach to resolve this problem of these random effects would be to collect a vast number of single images, to combine them appropriately and to process them with common image filtering procedures. However, it has been shown that, e.g. median filtering, depending on the kernel size in the plane and/or the number of single shots to be combined, is either insufficient or tends to blur sharp lined structures. This inevitably makes a visually controlled processing image by image unavoidable. Particularly in tomographic studies, it would be by far too tedious to treat each single projection by this way. Alternatively, it would be not only more comfortable but also in many cases the only reasonable approach to filter a stack of images in a batch procedure to get rid of the disturbing interferences. The algorithm presented here meets all these requirements. It reliably frees the images from the snowy pattern described above without the loss of fine structures and without a general blurring of the image. It consists of an iterative, within a batch procedure parameter free filtering algorithm aiming to eliminate the often complex interfering artefacts while leaving the original information untouched as far as possible.

  7. Carbon quantum dots and a method of making the same

    Zidan, Ragaiy; Teprovich, Joseph A.; Washington, Aaron L.

    2017-08-22

    The present invention is directed to a method of preparing a carbon quantum dot. The carbon quantum dot can be prepared from a carbon precursor, such as a fullerene, and a complex metal hydride. The present invention also discloses a carbon quantum dot made by reacting a carbon precursor with a complex metal hydride and a polymer containing a carbon quantum dot made by reacting a carbon precursor with a complex metal hydride.

  8. Spectroscopy of Charged Quantum Dot Molecules

    Stinaff, E. A.; Scheibner, M.; Bracker, A. S.; Ponomarev, I. V.; Ware, M. E.; Doty, M. F.; Reinecke, T. L.; Gammon, D.; Korenev, V. L.

    2006-03-01

    Spins of single charges in quantum dots are attractive for many quantum information and spintronic proposals. Scalable quantum information applications require the ability to entangle and operate on multiple spins in coupled quantum dots (CQDs). To further the understanding of these systems, we present detailed spectroscopic studies of InAs CQDs with control of the discrete electron or hole charging of the system. The optical spectrum reveals a pattern of energy anticrossings and crossings in the photoluminescence as a function of applied electric field. These features can be understood as a superposition of charge and spin configurations of the two dots and represent clear signatures of quantum mechanical coupling. The molecular resonance leading to these anticrossings is achieved at different electric fields for the optically excited (trion) states and the ground (hole) states allowing for the possibility of using the excited states for optically induced coupling of the qubits.

  9. The ideal Atomic Centre; Le Centre Atomique ideal

    Mas, R [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1965-07-01

    The author presents considerations which should prove to be of interest to all those who have to design, to construct and to operate a nuclear research centre. A large number of the ideas presented can also be applied to non-nuclear scientific research centres. In his report the author reviews: various problems with which the constructor is faced: ground-plan, infrastructure, buildings and the large units of scientific equipment in the centre, and those problems facing the director: maintenance, production, supplies, security. The author stresses the relationship which ought to exist between the research workers and the management. With this aim in view he proposes the creation of National School for Administration in Research which would train administrative executives for public or private organisations; they would be specialised in the fields of fundamental or applied research. (author) [French] L'auteur propose une base de reflexions a tous ceux qui doivent concevoir, realiser et faire vivre un Centre d'Etudes Nucleaires. Un grand nombre des idees exprimees peut d'ailleurs s'appliquer a un Centre d'Etudes Scientifiques non nucleaires. Dans son ouvrage, l'auteur passe en revue les differents problemes qui se posent au constructeur: plan, masse, infrastructure, batiments et grands appareils du Centre, et ceux qu'a a resoudre le directeur: entretien, fabrication, approvisionnements, securite. L'auteur insiste sur l'aspect des rapports qui doivent exister entre les chercheurs et ceux qui les administrent. Il propose a cette fin la creation d'une Ecole Nationale d'Administration de la Recherche qui formerait des cadres administratifs pour les organismes publics ou prives, specialises dans la Recherche fondamentale ou appliquee. (auteur)

  10. 49 CFR 41.119 - DOT regulated buildings.

    2010-10-01

    ... 49 Transportation 1 2010-10-01 2010-10-01 false DOT regulated buildings. 41.119 Section 41.119 Transportation Office of the Secretary of Transportation SEISMIC SAFETY § 41.119 DOT regulated buildings. (a) Each DOT Operating Administration with responsibility for regulating the structural safety of buildings...

  11. Bright infrared LEDs based on colloidal quantum-dots

    Sun, Liangfeng; Choi, Joshua J.; Stachnik, David; Bartnik, Adam C.; Hyun, Byung-Ryool; Malliaras, George G.; Hanrath, Tobias; Wise, Frank W.

    2013-01-01

    Record-brightness infrared LEDs based on colloidal quantum-dots have been achieved through control of the spacing between adjacent quantum-dots. By tuning the size of quantum-dots, the emission wavelengths can be tuned between 900nm and 1650nm. © 2013 Materials Research Society.

  12. Double quantum dot as a minimal thermoelectric generator

    Donsa, S.; Andergassen, S.; Held, K.

    2014-01-01

    Based on numerical renormalization group calculations, we demonstrate that experimentally realized double quantum dots constitute a minimal thermoelectric generator. In the Kondo regime, one quantum dot acts as an n-type and the other one as a p-type thermoelectric device. Properly connected the double quantum dot provides a miniature power supply utilizing the thermal energy of the environment.

  13. Four-Wave Mixing Spectroscopy of Quantum Dot Molecules

    Sitek, A.; Machnikowski, P.

    2007-08-01

    We study theoretically the nonlinear four-wave mixing response of an ensemble of coupled pairs of quantum dots (quantum dot molecules). We discuss the shape of the echo signal depending on the parameters of the ensemble: the statistics of transition energies and the degree of size correlations between the dots forming the molecules.

  14. Coherence and dephasing in self-assembled quantum dots

    Hvam, Jørn Märcher; Leosson, K.; Birkedal, Dan

    2003-01-01

    We measured dephasing times in InGaAl/As self-assembled quantum dots at low temperature using degenerate four-wave mixing. At 0K, the coherence time of the quantum dots is lifetime limited, whereas at finite temperatures pure dephasing by exciton-phonon interactions governs the quantum dot...

  15. Optical localization of quantum dots in tapered nanowires

    Østerkryger, Andreas Dyhl; Gregersen, Niels; Fons, Romain

    2017-01-01

    In this work we have measured the far-field emission patterns of In As quantum dots embedded in a GaAs tapered nanowire and used an open-geometry Fourier modal method for determining the radial position of the quantum dots by computing the far-field emission pattern for different quantum dot...

  16. Circular polarization memory in single Quantum Dots

    Khatsevich, S.; Poem, E.; Benny, Y.; Marderfeld, I.; Gershoni, D.; Badolato, A.; Petroff, P. M.

    2010-01-01

    Under quasi-resonant circularly polarized optical excitation, charged quantum dots may emit polarized light. We measured various transitions with either positive, negative or no circular-polarization memory. We explain these observations and quantitatively calculate the polarization spectrum. Our model use the full configuration-interaction method, including the electron-hole exchange interaction, for calculating the quantum dot's confined many-carrier states, along with one assumption regarding the spin relaxation of photoexcited carriers: Electrons maintain their initial spin polarization, while holes do not.

  17. Bilayer graphene quantum dot defined by topgates

    Müller, André; Kaestner, Bernd; Hohls, Frank; Weimann, Thomas; Pierz, Klaus; Schumacher, Hans W., E-mail: hans.w.schumacher@ptb.de [Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig (Germany)

    2014-06-21

    We investigate the application of nanoscale topgates on exfoliated bilayer graphene to define quantum dot devices. At temperatures below 500 mK, the conductance underneath the grounded gates is suppressed, which we attribute to nearest neighbour hopping and strain-induced piezoelectric fields. The gate-layout can thus be used to define resistive regions by tuning into the corresponding temperature range. We use this method to define a quantum dot structure in bilayer graphene showing Coulomb blockade oscillations consistent with the gate layout.

  18. Polymers in Carbon Dots: A Review

    Yiqun Zhou

    2017-02-01

    Full Text Available Carbon dots (CDs have been widely studied since their discovery in 2004 as a green substitute of the traditional quantum dots due to their excellent photoluminescence (PL and high biocompatibility. Meanwhile, polymers have increasingly become an important component for both synthesis and modification of CDs to provide polymeric matrix and enhance their PL property. Furthermore, critical analysis of composites of CDs and polymers has not been available. Herein, in this review, we summarized the use of polymers in the synthesis and functionalization of CDs, and the applications of these CDs in various fields.

  19. Spectroscopic characteristics of carbon dots (C-dots) derived from carbon fibers and conversion to sulfur-bridged C-dots nanosheets.

    Vinci, John C; Ferrer, Ivonne M; Guterry, Nathan W; Colón, Verónica M; Destino, Joel F; Bright, Frank V; Colón, Luis A

    2015-09-01

    We synthesized sub-10 nm carbon nanoparticles (CNPs) consistent with photoluminescent carbon dots (C-dots) from carbon fiber starting material. The production of different C-dots fractions was monitored over seven days. During the course of the reaction, one fraction of C-dots species with relatively high photoluminescence was short-lived, emerging during the first hour of reaction but disappearing after one day of reaction. Isolation of this species during the first hour of the reaction was crucial to obtaining higher-luminescent C-dots species. When the reaction proceeded for one week, the appearance of larger nanostructures was observed over time, with lateral dimensions approaching 200 nm. The experimental evidence suggests that these larger species are formed from small C-dot nanoparticles bridged together by sulfur-based moieties between the C-dot edge groups, as if the C-dots polymerized by cross-linking the edge groups through sulfur bridges. Their size can be tailored by controlling the reaction time. Our results highlight the variety of CNP products, from sub-10 nm C-dots to ~200 nm sulfur-containing carbon nanostructures, that can be produced over time during the oxidation reaction of the graphenic starting material. Our work provides a clear understanding of when to stop the oxidation reaction during the top-down production of C-dots to obtain highly photoluminescent species or a target average particle size.

  20. The Belgian nuclear research centre

    Moons, F.

    2001-01-01

    The Belgian Nuclear Research Centre is almost exclusively devoted to nuclear R and D and services and is able to generate 50% of its resources (out of 75 million Euro) by contract work and services. The main areas of research include nuclear reactor safety, radioactive waste management, radiation protection and safeguards. The high flux reactor BR2 is extensively used to test fuel and structural materials. PWR-plant BR3 is devoted to the scientific analysis of decommissioning problems. The Centre has a strong programme on the applications of radioisotopes and radiation in medicine and industry. The centre has plans to develop an accelerator driven spallation neutron source for various applications. It has initiated programmes to disseminate correct information on issues of nuclear energy production and non-energy nuclear applications to different target groups. It has strong linkages with the IAEA, OECD-NEA and the Euratom. (author)

  1. Technical support and emergency centre

    Bohun, L.; Kapisovsk y, M.

    1997-01-01

    This paper presents technical support and emergency management center which will be on two places: Mochovce NPP Emergency Centre (Technical support center and Support working center) and Reserve Emergency Centre in Levice (Reserve emergency center and Environmental Evaluation Center). The main aims of the emergency management centers are: the management and coordination of all persons and organisations; provision of the all information needed to evaluation of the accident and its mitigation; continuous evaluation of the potential or real radiological consequences; taking measure for an early notification of the governmental bodies and the organizations, warning and protection of the public; and other aims. In the next part the data for technical support and emergency centre are discussed

  2. Presentation of TVO's visitor's centre

    Aemmaelae, V.M.

    1993-01-01

    There are four nuclear power plant units in Finland, two of which are PWR's owned by Imatran Voima Oy. The two BWR units are located at Olkiluoto and owned by Teollisuuden Voima Oy. This presentation tells about TVO's concept of informing the visitors at Olkiluoto. At the site there are located, in addition to the two nuclear power plant units, the intermediate storage for spent fuel, the repository for low and medium-active waste as well as the training centre. At the Olkiluoto Visitor's Centre all the activities of the company are presented using varied audio-visual aids. The centre has several exhibits and there are also different installations to show how the plant works. (author)

  3. International Development Research Centre Act Loi sur le Centre de ...

    1 juin 2009 ... research includes any scientific or technical inquiry or experimentation that is .... data centres and facilities for research and other activ- ities;. (b) initiate and ..... Loi sur la pension de la fonction publique ne s'applique pas aux ...

  4. Scheduling participants of Assessment Centres

    Lysgaard, Jens; Løber, Janni

      Assessment Centres are used as a tool for psychologists and coaches to observe a number of dimensions in a person's behaviour and test his/her potential within a number of chosen focus areas. This is done in an intense course, with a number of different exercises which expose each participant...... Centres usually last two days and involve 3-6 psychologists or trained coaches as assessors. An entire course is composed of a number of rounds, with each round having its individual duration. In each round, the participants are divided into a number of groups with prespecifed pairing of group sizes...

  5. Training centres in Latin America

    NONE

    1959-04-15

    Early 1958 the Brazilian representative on the Board of Governors of the International Atomic Energy Agency - supported by the Governors from Argentina and Guatemala -proposed that a study should be made of the possibility of setting up one or more atomic energy training centres in Latin America. On the Board's recommendation, the Director General of the Agency appointed a fact-finding team to make anon-the-spot study. In drafting this report the team was invited to consider the following points: (a) The need for establishing one or more regional training centres; (b) Existing facilities that are being or could be used for training, together with technical data concerning them; (c) The general scientific technological and industrial conditions of the countries visited insofar as they have a bearing on their training needs and capabilities. The authors of the report conclude that 'a training centre in radio-botany should provide vitally needed knowledge and vitally needed specialists to all the agricultural installations in Latin America. A training centre like this might provide an excellent model upon which to base training centres in other areas'. The report recommends that: 1. The Agency should meet the requests of Latin American universities by, for example, supplying equipment and sending experts; 2. At least one specialized training centre should be established as soon as possible. Taking as an example the field of radio-botany, such a centre would provide trained specialists in radio-botany to agricultural institutions throughout Latin America and also provide basic research results vital to agriculture. The cost of new facilities might be of the order of $7 500 000, with an annual budget of approximately $650 000. Staff required: 40 scientists and 175 employees; 3. Whenever it appears feasible to gather necessary staff of high creative ability and established productivity and when funds can be made available for facilities, equipment and operating costs, at

  6. Training centres in Latin America

    1959-01-01

    Early 1958 the Brazilian representative on the Board of Governors of the International Atomic Energy Agency - supported by the Governors from Argentina and Guatemala -proposed that a study should be made of the possibility of setting up one or more atomic energy training centres in Latin America. On the Board's recommendation, the Director General of the Agency appointed a fact-finding team to make anon-the-spot study. In drafting this report the team was invited to consider the following points: (a) The need for establishing one or more regional training centres; (b) Existing facilities that are being or could be used for training, together with technical data concerning them; (c) The general scientific technological and industrial conditions of the countries visited insofar as they have a bearing on their training needs and capabilities. The authors of the report conclude that 'a training centre in radio-botany should provide vitally needed knowledge and vitally needed specialists to all the agricultural installations in Latin America. A training centre like this might provide an excellent model upon which to base training centres in other areas'. The report recommends that: 1. The Agency should meet the requests of Latin American universities by, for example, supplying equipment and sending experts; 2. At least one specialized training centre should be established as soon as possible. Taking as an example the field of radio-botany, such a centre would provide trained specialists in radio-botany to agricultural institutions throughout Latin America and also provide basic research results vital to agriculture. The cost of new facilities might be of the order of $7 500 000, with an annual budget of approximately $650 000. Staff required: 40 scientists and 175 employees; 3. Whenever it appears feasible to gather necessary staff of high creative ability and established productivity and when funds can be made available for facilities, equipment and operating costs, at

  7. Logistics centres development in Latvia

    I. Kabashkin

    2007-12-01

    Full Text Available In the situation where a large increase in trade and freight transport volumes in the Baltic Sea region (BSR is expected and in which the BSR is facing a major economic restructuring, eff orts to achieve more integrated and sustainable transport and communication links within the BSR are needed. One of these eff orts is the development of logistics centres (LCs and their networking, which will continue to have an impact on improving communication links, spatial planning practices and approaches, logistics chain development and the promotion of sustainable transport modes. These factors will refl ect on logistics processes both in major gateway cities and in remote BSR areas. The importance of logistics systems as a whole is not seen clearly enough. Logistics actors see that logistics operations are not appreciated as much as other fi elds of activity. In addition, logistics centres and the importance of logistics activities to the business life of areas and the employment rate should be brought up better. In the paper main goal and tasks of national approach to LCs development are discussed. Strategic focus of new activities in this area is on the integration of various networks within and between logistics centres in order to improve and develop the quality of logistics networks as well as to spatially widen the networking activities. The key objectives are to integrate the links between logistics centres, ports and other logistics operators in a functional and sustainable way, to promote spatial integration by creating sustainable and integrated approaches to spatial planning of logistics centres and transport infrastructure, to improve ICT-based networking and communication practices of the fi elds of transport and logistics and to increase the competence of logistics centres and associated actors by organising educational and training events. The current activities include, for example, the creation of measures for transport networking and

  8. Transport through overlapping states in quantum dots and double dot molecules

    Berkovits, R.

    2006-01-01

    Full Text: We shall review the transport properties of interacting quantum dots with overlapping orbitals for which the orthodox Coulomb blockade picture no longer holds. We shall concentrate on he conductance through a serial double dot structure for which the inter-dot tunneling is stronger than the tunneling to the leads. When the dots are occupied by 1 or 3 electrons the usual Kondo peak is observed. For the case in which 2 electrons occupy the molecule a singlet is formed. Nevertheless, the conductance in that case has a constant non-zero value, and might even be equal to the maximum conductance of 2e 2 /h for certain values of the molecule parameters. We show that this is the result of the subtle interplay between the symmetric and anti-symmetric orbitals of the molecule caused by interactions and interference

  9. Photoluminescence studies of single InGaAs quantum dots

    Leosson, Kristjan; Jensen, Jacob Riis; Hvam, Jørn Märcher

    1999-01-01

    Semiconductor quantum dots are considered a promising material system for future optical devices and quantum computers. We have studied the low-temperature photoluminescence properties of single InGaAs quantum dots embedded in GaAs. The high spatial resolution required for resolving single dots...... to resolve luminescence lines from individual quantum dots, revealing an atomic-like spectrum of sharp transition lines. A parameter of fundamental importance is the intrinsic linewidth of these transitions. Using high-resolution spectroscopy we have determined the linewidth and investigated its dependence...... on temperature, which gives information about how the exciton confined to the quantum dot interacts with the surrounding lattice....

  10. Kondo and mixed-valence regimes in multilevel quantum dots

    Chudnovskiy, A. L.; Ulloa, S. E.

    2001-01-01

    We investigate the dependence of the ground state of a multilevel quantum dot on the coupling to an external fermionic system and on the interactions in the dot. As the coupling to the external system increases, the rearrangement of the effective energy levels in the dot signals the transition from the Kondo regime to a mixed-valence (MV) regime. The MV regime in a two-level dot is characterized by an intrinsic mixing of the levels in the dot, resulting in nonperturbative subtunneling and supertunneling phenomena that strongly influence the Kondo effect

  11. Synthesis of CdSe quantum dots for quantum dot sensitized solar cell

    Singh, Neetu, E-mail: singh.neetu1985@gmail.com; Kapoor, Avinashi [Department of Electronic Science, University of Delhi South Campus, New Delhi-110 021 (India); Kumar, Vinod [Department of Physics, University of the Free State, Bloemfontein, ZA9300 (South Africa); Mehra, R. M. [School of Engineering and Technology, Sharda University, Greater Noida-201 306, U.P. (India)

    2014-04-24

    CdSe Quantum Dots (QDs) of size 0.85 nm were synthesized using chemical route. ZnO based Quantum Dot Sensitized Solar Cell (QDSSC) was fabricated using CdSe QDs as sensitizer. The Pre-synthesized QDs were found to be successfully adsorbed on front ZnO electrode and had potential to replace organic dyes in Dye Sensitized Solar Cells (DSSCs). The efficiency of QDSSC was obtained to be 2.06 % at AM 1.5.

  12. Entangled photons from small quantum dots

    Visser, P.M.; Allaart, K.; Lenstra, D.

    2003-01-01

    We discuss level schemes of small quantum-dot turnstiles and their applicability in the production of entanglement in two-photon emission. Due to the large energy splitting of the single-electron levels, only one single-electron level and one single-hole level can be made resonant with the levels in

  13. Coulomb Coupling Between Quantum Dots and Waveguides

    Porod, Wolfgang

    2000-01-01

    .... We considered both III-V and Si-based semiconductor systems. In later years, the AASERT award supported work on QCA realizations in Coulomb-blockade metal-dot systems, which were successful in demonstrating the basic QCA switching operation...

  14. System and method for making quantum dots

    Bakr, Osman M.

    2015-05-28

    Embodiments of the present disclosure provide for methods of making quantum dots (QDs) (passivated or unpassivated) using a continuous flow process, systems for making QDs using a continuous flow process, and the like. In one or more embodiments, the QDs produced using embodiments of the present disclosure can be used in solar photovoltaic cells, bio-imaging, IR emitters, or LEDs.

  15. Enabling biomedical research with designer quantum dots

    Tomczak, N.; Janczewski, D.; Dorokhin, D.V.; Han, M-Y; Vancso, Gyula J.; Navarro, Melba; Planell, Josep A.

    2012-01-01

    Quantum Dots (QDs) are a new class of semiconductor nanoparticulate luminophores, which are actively researched for novel applications in biology and nanomedicine. In this review, the recent progress in the design and applications of QD labels for in vitro and in vivo imaging of cells is presented.

  16. Effect of temperature on quantum dots

    MAHDI AHMADI BORJI

    2017-07-12

    Jul 12, 2017 ... Effect of temperature on InxGa1−xAs/GaAs quantum dots. MAHDI AHMADI BORJI1, ALI ... Attention should be given to the effects of temperature, ... tion 2 explains the model and method of the numerical simulation. Our results ...

  17. Featured Image: Bright Dots in a Sunspot

    Kohler, Susanna

    2018-03-01

    This image of a sunspot, located in in NOAA AR 12227, was captured in December 2014 by the 0.5-meter Solar Optical Telescope on board the Hinode spacecraft. This image was processed by a team of scientists led by Rahul Yadav (Udaipur Solar Observatory, Physical Research Laboratory Dewali, India) in order to examine the properties of umbral dots: transient, bright features observed in the umbral region (the central, darkest part) of a sunspot. By exploring these dots, Yadav and collaborators learned how their properties relate to the large-scale properties of the sunspots in which they form for instance, how do the number, intensities, or filling factors of dots relate to the size of a sunspots umbra? To find out more about the authors results, check out the article below.Sunspot in NOAA AR 11921. Left: umbralpenumbral boundary. Center: the isolated umbra from the sunspot. Right: The umbra with locations of umbral dots indicated by yellow plus signs. [Adapted from Yadav et al. 2018]CitationRahul Yadav et al 2018 ApJ 855 8. doi:10.3847/1538-4357/aaaeba

  18. Decoherence in Nearly-Isolated Quantum Dots

    Folk, J.; M. Marcus, C.; Harris jr, J.

    2000-01-01

    Decoherence in nearly-isolated GaAs quantum dots is investigated using the change in average Coulomb blockade peak height upon breaking time-reversal symmetry. The normalized change in average peak height approaches the predicted universal value of 1/4 at temperatures well below the single...

  19. Electron Spins in Semiconductor Quantum Dots

    Hanson, R.

    2005-01-01

    This thesis describes a series of experiments aimed at understanding and controlling the behavior of the spin degree of freedom of single electrons, confined in semiconductor quantum dots. This research work is motivated by the prospects of using the electron spin as a quantum bit (qubit), the basic

  20. Resistance to Black Dot in Potato

    Black dot fungus can colonize tubers on the surface, in the stolon end, or in a combination of both.On the surface the fungus is prevalent as sclerotia, and in the stolon end the fungus colonizes the vascular tissuesas hyphae. The fungus is introduced to non-infested soils mostly by infected potato ...

  1. Photoluminescence of hybrid quantum dot systems

    Král, Karel; Menšík, Miroslav

    2015-01-01

    Roč. 7, č. 4 (2015), 347-349 ISSN 2164-6627 R&D Projects: GA MŠk LH12236; GA MŠk LH12186 Institutional support: RVO:68378271 ; RVO:61389013 Keywords : quantum dots * energy transfer * electron-phonon interaction Subject RIV: BM - Solid Matter Physics ; Magnetism

  2. Many electron effects in semiconductor quantum dots

    Semiconductor quantum dots (QDs) exhibit shell structures, very similar to atoms. Termed as 'artificial atoms' by some, they are much larger (1 100 nm) than real atoms. One can study a variety of manyelectron effects in them, which are otherwise difficult to observe in a real atom. We have treated these effects within the ...

  3. Integrated photonics using colloidal quantum dots

    Menon, Vinod M.; Husaini, Saima; Okoye, Nicky; Valappil, Nikesh V.

    2009-11-01

    Integrated photonic devices were realized using colloidal quantum dot composites such as flexible microcavity laser, microdisk emitters and integrated active-passive waveguides. The microcavity laser structure was realized using spin coating and consisted of an all-polymer distributed Bragg reflector with a poly-vinyl carbazole cavity layer embedded with InGaP/ZnS colloidal quantum dots. These microcavities can be peeled off the substrate yielding a flexible structure that can conform to any shape and whose emission spectra can be mechanically tuned. Planar photonic devices consisting of vertically coupled microring resonators, microdisk emitters, active-passive integrated waveguide structures and coupled active microdisk resonators were realized using soft lithography, photo-lithography, and electron beam lithography, respectively. The gain medium in all these devices was a composite consisting of quantum dots embedded in SU8 matrix. Finally, the effect of the host matrix on the optical properties of the quantum dots using results of steady-state and time-resolved luminescence measurements was determined. In addition to their specific functionalities, these novel device demonstrations and their development present a low-cost alternative to the traditional photonic device fabrication techniques.

  4. Influence of the quantum dot geometry on p -shell transitions in differently charged quantum dots

    Holtkemper, M.; Reiter, D. E.; Kuhn, T.

    2018-02-01

    Absorption spectra of neutral, negatively, and positively charged semiconductor quantum dots are studied theoretically. We provide an overview of the main energetic structure around the p -shell transitions, including the influence of nearby nominally dark states. Based on the envelope function approximation, we treat the four-band Luttinger theory as well as the direct and short-range exchange Coulomb interactions within a configuration interaction approach. The quantum dot confinement is approximated by an anisotropic harmonic potential. We present a detailed investigation of state mixing and correlations mediated by the individual interactions. Differences and similarities between the differently charged quantum dots are highlighted. Especially large differences between negatively and positively charged quantum dots become evident. We present a visualization of energetic shifts and state mixtures due to changes in size, in-plane asymmetry, and aspect ratio. Thereby we provide a better understanding of the experimentally hard to access question of quantum dot geometry effects. Our findings show a method to determine the in-plane asymmetry from photoluminescence excitation spectra. Furthermore, we supply basic knowledge for tailoring the strength of certain state mixtures or the energetic order of particular excited states via changes of the shape of the quantum dot. Such knowledge builds the basis to find the optimal QD geometry for possible applications and experiments using excited states.

  5. Optical properties of quantum-dot-doped liquid scintillators

    Aberle, C; Winslow, L; Li, J J; Weiss, S

    2013-01-01

    Semiconductor nanoparticles (quantum dots) were studied in the context of liquid scintillator development for upcoming neutrino experiments. The unique optical and chemical properties of quantum dots are particularly promising for the use in neutrinoless double-beta decay experiments. Liquid scintillators for large scale neutrino detectors have to meet specific requirements which are reviewed, highlighting the peculiarities of quantum-dot-doping. In this paper, we report results on laboratory-scale measurements of the attenuation length and the fluorescence properties of three commercial quantum dot samples. The results include absorbance and emission stability measurements, improvement in transparency due to filtering of the quantum dot samples, precipitation tests to isolate the quantum dots from solution and energy transfer studies with quantum dots and the fluorophore PPO

  6. From quantum dots to quantum circuits

    Ensslin, K.

    2008-01-01

    Full text: Quantum dots, or artificial atoms, confine charge carriers in three-dimensional islands in a semiconductor environment. Detailed understanding and exquisite control of the charge and spin state of the electrically tunable charge occupancy have been demonstrated over the years. Quantum dots with best quality for transport experiments are usually realized in n-type AlGaAs/GaAs heterostructures. Novel material systems, such as graphene, nanowires and p-type heterostructures offer unexplored parameter regimes in view of spin-orbit interactions, carrier-carrier interactions and hyperfine coupling between electron and nuclear spins, which might be relevant for future spin qubits realized in quantum dots. With more sophisticated nanotechnology it has become possible to fabricate coupled quantum systems where classical and quantum mechanical coupling and back action is experimentally investigated. A narrow constriction, or quantum point contact, in vicinity to a quantum dot has been shown to serve as a minimally invasive sensor of the charge state of the dot. If charge transport through the quantum dot is slow enough (kHz), the charge sensor allows the detection of time-resolved transport through quantum-confined structures. This has allowed us to measure extremely small currents not detectable with conventional electronics. In addition the full statistics of current fluctuations becomes experimentally accessible. This way correlations between electrons which influence the current flow can be analyzed by measuring the noise and higher moments of the distribution of current fluctuations. Mesoscopic conductors driven out of equilibrium can emit photons which may be detected by another nearby quantum system with suitably tuned energy levels. This way an on-chip microwave single photon detector has been realized. In a ring geometry containing a tunable double quantum dot it has been possible to measure the self-interference of individual electrons as they traverse

  7. Formaldehyde in the Galactic Centre

    Cohen, R.J.; Few, R.W.

    1981-01-01

    Formaldehyde 6-cm absorption in the direction of the Galactic Centre has been surveyed using the Jodrell Bank MK II radio telescope (beam-width 10 x 9 arcmin). The observations sample the region - 2 0 = 0 and - 0 0 .5 = 0 .5, with a velocity range of 620 km s -1 , a velocity resolution of 2.1 km s -1 and an rms noise level of approximately 0.03 K. The data are presented as contour maps showing line temperature as a function of latitude and velocity (b-V maps) and as a function of longitude and velocity (l-V maps). Similar maps of the line-to-continuum ratio are also presented. The radial distribution of formaldehyde (H 2 CO) in the Galactic Centre region is derived using two different kinematic models which give similar results. Formaldehyde is strongly concentrated in the Galactic Centre in a layer of latitude extent approximately 0 0 .5 and longitude extent approximately 4 0 which contains one quarter of all the H 2 CO in the Galaxy. The distribution is centred on l approximately 1 0 . The individual H 2 CO features are described in detail. (author)

  8. The DEMETER Science Mission Centre

    Lagoutte, D.; Brochot, J.; Y.; de Carvalho, D.; Elie, F.; Harivelo, F.; Hobara, Y.; Madrias, L.; Parrot, M.; Pincon, J. L.; Berthelier, J. J.; Peschard, D.; Seran, E.; Gangloff, M.; Sauvaud, J. A.; Lebreton, J. P.; Štverák, Štěpán; Trávníček, Pavel M.; Grygorczuk, J.; Slominski, J.; Wronowski, R.; Barbier, S.; Bernard, P.; Gaboriaud, A.; Wallut, J. M.

    2006-01-01

    Roč. 54, č. 5 (2006), s. 428-440 ISSN 0032-0633 Institutional research plan: CEZ:AV0Z30420517 Keywords : Mission Centre * Data processing Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 1.509, year: 2006

  9. CENTRE OF THE MAIN INTERESTS

    DIANA DELEANU

    2013-05-01

    Full Text Available The centre of the main interests of the debtor is a legal tool meant to settle conflicts that can arise between jurisdictions in cross-border insolvencies, based on the principles of mutual recognition and co-operation.

  10. DotFETs: MOSFETs strained by a Single SiGE dot in a Low-Temperature ELA Technology

    Biasotto, C.

    2011-01-01

    The work presented in this thesis was performed in the context of the European Sixth Framework Program FP6 project “Disposable Dot Field Effect Transistor for High Speed Si Integrated Circuits”, referred to as the D-DotFET project. The project had the goal of realizing strain-enhanced mobility in CMOS transistors by transferring strain from a self-assembled germanium dot to the channel of a transistor fabricated above the dot. The initial idea was to dispose of the Ge dot underneath the chann...

  11. Study of InGaN/GaN quantum dot systems by TEM techniques and photoluminescence spectroscopy

    Kashtiban, R J; Bangert, U; Harvey, A J; Sherliker, B; Halsall, M P

    2010-01-01

    InGaN/GaN multilayer quantum dot structures produced by MOCVD techniques on c-plane sapphire were studied by transmission electron microscopy (TEM) and photoluminescence (PL) techniques. Indium fluctuations ranging from 1-4 nm were observed with both energy filtered TEM (EFTEM) and high angle annular dark field (HAADF) scanning TEM. The existence of V-shaped defects with nucleation centres at the termination of threading dislocation were observed in HAADF images. There was also evidence of the formation of large quantum dots at low densities from lattice HRTEM images. This was further confirmed by PL measurements through the observation of a single sharp line at low power with the typical saturation behaviour at higher power excitation.

  12. The CCCB is a cultural centre, not a tourist centre

    Elena Xirau

    2004-04-01

    Full Text Available Last February, Barcelona's Centre of Contemporary Culture (CCCB celebrated its first ten years in existence. During this time, this institution has looked to be a showcase to the most modern and innovative cultural expressions focused on reflecting on the concept of the city. In this interview, Josep Ramoneda offers his personal view, as the CCCB's director. He talks of how this cultural project was born, of how the concept of the institution took shape in the CCCB, of its relations with Barcelona's Strategic Plan, of how the project has evolved, of the architectural remodelling of the Casa de la Caritat building for its conversion into a cultural centre, of the relations with other institutions and its future.

  13. DOT for patients with limited access to health care facilities in a hill district of eastern Nepal.

    Wares, D F; Akhtar, M; Singh, S

    2001-08-01

    The hill district in Nepal, where access to health care facilities is difficult. To compare results before and after a decentralised directly observed treatment (DOT) intervention. Prospective study of patients registered in Dhankuta district, Nepal, 1996-1999. Patients received their intensive phase treatment under health worker supervision via one of three DOT options: 1) ambulatory from the peripheral government health facilities; 2) ambulatory from an international non-governmental organisation (INGO) TB clinic in district centre; or 3) resident in INGO TB hostel in district centre. Historical data from 1995-1996, with unsupervised short-course chemotherapy, were used for comparison. Of 307 new cases, respectively 126 (41%), 86 (28%) and 95 (31%) took their intensive phase treatment via options 1, 2 and 3. Smear conversion (at 2 months) and cure rates in new smear-positive pulmonary tuberculosis cases were respectively 81.6% (vs. 58.8% historical, P = 0.001) and 84.9% (vs. 76.7% historical, P = 0.03). Overall costs to the INGO provider fell by 7%, mainly as a result of staffing reductions in the INGO services made possible by rationalisation with government services during the intervention. By offering varied DOT delivery routes, including an in-patient option, satisfactory results are possible with DOT even in areas where access to health care facilities is difficult. Provision of in-patient care via an INGO TB hostel allowed a significant proportion of new cases (31%) to receive their intensive phase treatment who otherwise may have had difficulty accessing treatment, due either to the distance to the nearest health facility or to disease severity. Substitution of government hospital beds or local hotel beds for the INGO hostel beds may allow the model to be reproduced elsewhere in similar geographical conditions in Nepal, but further studies should be performed in a non-INGO supported district beforehand.

  14. Gestion du Centre | CRDI - Centre de recherches pour le ...

    Le Comité de gestion du Centre (CGC) est composé des membres de la haute direction du CRDI, notamment les directeurs de nos quatre bureaux régionaux et de nos principaux secteurs de programme. Le CGC travaille en collaboration avec le président afin de soutenir la recherche pour le développement, lui fournissant ...

  15. RTEMS CENTRE- Support and Maintenance CENTRE to RTEMS Operating System

    Silva, H.; Constantino, A.; Coutunho, M.; Freitas, D.; Faustino, S.; Mota, M.; Colaço, P.; Zulianello, M.

    2008-08-01

    RTEMS stands for Real-Time Operating System for Multiprocessor Systems. It is a full featured Real Time Operating System that supports a variety of open APIs and interface standards. It provides a high performance environment for embedded applications, including a fixed-priority preemptive/non-preemptive scheduler, a comprehensive set of multitasking operations and a large range of supported architectures. Support and maintenance CENTRE to RTEMS operating system (RTEMS CENTRE) is a joint initiative of ESA-Portugal Task force, aiming to build a strong technical competence in the space flight (on- board) software, to offer support, maintenance and improvements to RTEMS. This paper provides a high level description of the current and future activities of the RTEMS CENTRE. It presents a brief description of the RTEMS operating system, a description of the tools developed and distributed to the community [1] and the improvements to be made to the operating system, including facilitation for the qualification of RTEMS (4.8.0) [2] for the space missions.

  16. Hubble's View of Little Blue Dots

    Kohler, Susanna

    2018-02-01

    The recent discovery of a new type of tiny, star-forming galaxy is the latest in a zoo of detections shedding light on our early universe. What can we learn from the unique little blue dots found in archival Hubble data?Peas, Berries, and DotsGreen pea galaxies identified by citizen scientists with Galaxy Zoo. [Richard Nowell Carolin Cardamone]As telescope capabilities improve and we develop increasingly deeper large-scale surveys of our universe, we continue to learn more about small, faraway galaxies. In recent years, increasing sensitivity first enabled the detection of green peas luminous, compact, low-mass (10 billion solar masses; compare this to the Milky Ways 1 trillion solar masses!) galaxies with high rates of star formation.Not long thereafter, we discovered galaxies that form stars similarly rapidly, but are even smaller only 330 million solar masses, spanning less than 3,000 light-years in size. These tiny powerhouses were termed blueberries for their distinctive color.Now, scientists Debra and Bruce Elmegreen (of Vassar College and IBM Research Division, respectively) report the discovery of galaxies that have even higher star formation rates and even lower masses: little blue dots.Exploring Tiny Star FactoriesThe Elmegreens discovered these unique galaxies by exploring archival Hubble data. The Hubble Frontier Fields data consist of deep images of six distant galaxy clusters and the parallel fields next to them. It was in the archival data for two Frontier Field Parallels, those for clusters Abell 2744 and MAS J0416.1-2403, that the authors noticed several galaxies that stand out as tiny, bright, blue objects that are nearly point sources.Top: a few examples of the little blue dots recently identified in two Hubble Frontier Field Parallels. Bottom: stacked images for three different groups of little blue dots. [Elmegreen Elmegreen 2017]The authors performed a search through the two Frontier Field Parallels, discovering a total of 55 little blue dots

  17. Quantum dot-polymer conjugates for stable luminescent displays.

    Ghimire, Sushant; Sivadas, Anjaly; Yuyama, Ken-Ichi; Takano, Yuta; Francis, Raju; Biju, Vasudevanpillai

    2018-05-23

    The broad absorption of light in the UV-Vis-NIR region and the size-based tunable photoluminescence color of semiconductor quantum dots make these tiny crystals one of the most attractive antennae in solar cells and phosphors in electrooptical devices. One of the primary requirements for such real-world applications of quantum dots is their stable and uniform distribution in optically transparent matrices. In this work, we prepare transparent thin films of polymer-quantum dot conjugates, where CdSe/ZnS quantum dots are uniformly distributed at high densities in a chitosan-polystyrene copolymer (CS-g-PS) matrix. Here, quantum dots in an aqueous solution are conjugated to the copolymer by a phase transfer reaction. With the stable conjugation of quantum dots to the copolymer, we prevent undesired phase separation between the two and aggregation of quantum dots. Furthermore, the conjugate allows us to prepare transparent thin films in which quantum dots are uniformly distributed at high densities. The CS-g-PS copolymer helps us in not only preserving the photoluminescence properties of quantum dots in the film but also rendering excellent photostability to quantum dots at the ensemble and single particle levels, making the conjugate a promising material for photoluminescence-based devices.

  18. A novel POSS-coated quantum dot for biological application

    Rizvi SB

    2012-08-01

    Full Text Available Sarwat B Rizvi,1 Lara Yildirimer,1 Shirin Ghaderi,1 Bala Ramesh,1 Alexander M Seifalian,1,2 Mo Keshtgar1,21UCL Centre for Nanotechnology and Regenerative Medicine, Division of Surgery and Interventional Science, University College London, United Kingdom; 2Royal Free Hampstead NHS Trust Hospital, London, United KingdomAbstract: Quantum dots (QDs are fluorescent semiconductor nanocrystals that have the potential for major advancements in the field of nanomedicine through their unique photophysical properties. They can potentially be used as fluorescent probes for various biomedical imaging applications, including cancer localization, detection of micrometastasis, image guided surgery, and targeted drug delivery. Their main limitation is toxicity, which requires a biologically compatible surface coating to shield the toxic core from the surrounding environment. However, this leads to an increase in QD size that may lead to problems of excretion and systemic sequestration. We describe a one pot synthesis, characterization, and in vitro cytotoxicity of a novel polyhedral oligomeric silsesquioxane (POSS-coated CdTe-cored QD using mercaptosuccinic acid (MSA and D-cysteine as stabilizing agents. Characterization was performed using transmission electron microscopy Fourier transform infrared spectroscopy, and photoluminescence studies. POSS-coated QDs demonstrated high colloidal stability and enhanced photostability on high degrees of ultraviolet (UV excitation compared to QDs coated with MSA and D-cysteine alone (P value < 0.05. In vitro toxicity studies showed that both POSS and MSA-QDs were significantly less toxic than ionized salts of Cd+2 and Te-2. Confocal microscopy confirmed high brightness of POSS-QDs in cells at both 1 and 24 hours, indicating that these QDs are rapidly taken up by cells and remain photostable in a biological environment. We therefore conclude that a POSS coating confers biological compatibility, photostability, and colloidal

  19. Randomized study of initial treatment with radiationter dot MCNU or radiationter dot MCNUter dot interferon-. beta. for malignant glioma

    Kiya, Katsuzo; Uozumi, Tohru; Kurisu, Kaoru (Hiroshima Univ. (Japan). School of Medicine) (and others)

    1990-02-01

    The efficacy of radiation{center dot}MCNU (MR group) or radiation{center dot}MCNU{center dot}interferon-{beta} (IMR group) for malignant glioma was studied by a randomized trial at numerous medical facilities. MR group was irradiated with 50{approx}60 Gy and intravenously injected with 2 mg/kg of MCNU on the initial day of irradiation and 6 weeks later. IMR group was also given intravenous administration of interferon-{beta} at the dose of 2x10{sup 6}IU/m{sup 2} for 5 serial-days every eight weeks. There was no difference in background between the two groups. The response rate in MR group and IMR group was 44.4% (4/9) and 30.0% (3/10), respectively, showing no significant difference. The resected tumor volume before the start of these regimens seemed to correlate the response to the treatment in both groups. The major toxicity was myelosuppression, especially using MCNU with interferon-{beta}. These results indicated that this combined therapy is effective for malignant glioma, and should be executed further trials and follow up study. (author).

  20. Neighbourhood Centres – Organisation, Management and Finance

    Larsen, Jacob Norvig

    to identify different financial models and analyse economic sustainability. As regards organisational and management models data were collected through documentary sources and by means of personal interviews and field visits to ten centres. Even within the analysed limited population of centres economic...... public subsidy. Some of the centres have high number of users on a daily basis, whereas others are only rarely used. It is explored how organisation, management and financial set-up differs among the centres. Quantitative data on financial issues and annual accounts of fifteen centres were analysed...... and institutional sustainability varies significantly. In organisational terms centres range from fully-integrated in the municipal administration to independent voluntary managed centres. In terms of financial, or economic, models variation is less pronounced as all centres to some degree are dependent on current...

  1. Institutional Support : Centre for Research and Technology ...

    year-old science and technology research centre at Maseno University in western Kenya. The Centre focuses on science and technology research to influence both national policies and development practices at the community level. Currently ...

  2. Japanese maintenance centres strive for greater realism

    Nedderman, J.

    1987-01-01

    Japanese utilities have devoted considerable efforts to ensuring that realistic plant conditions are simulated at their maintenance centres. In some centres, eg that of Kansai Electric Power Co, realism extends to difficult access, limited lighting and restricted ventilation. (author)

  3. Report: Cultural Research Centre (CRC)

    Cross-Cultural Foundation of Uganda

    2010-01-01

    This report arises from research carried out in Iganga and Namutumba districts in late 2006/early 2007 by the Cultural Research Centre (CRC), based in Jinja. Our research focus was to gauge the impact of using Lusoga as a medium of instruction (since 2005 in "pilot" lower primary classes) within and outside the classroom. This initiative was in response to a new set of circumstances in the education sector in Uganda, especially the introduction by Government of teaching in local languages in ...

  4. Radwaste Treatment Centre Jaslovske Bohunice

    2000-01-01

    In this leaflet the Bohunice Radwaste Treatment Centre (BSC RAO) is presented. BSC RAO is designed to process and treat liquid and solid radwaste, arising from the NPP A-1 decommissioning, from NPPs V-1, V-2, and Mochovce operations, as well as institutional radwaste of diverse institutional (hospitals, research institutes) in the Slovak Republic. Transport, sorting, incineration, compacting, concentration and cementation of radwaste as well as monitoring of emission are described

  5. Family-centred care delivery

    Mayo-Bruinsma, Liesha; Hogg, William; Taljaard, Monica; Dahrouge, Simone

    2013-01-01

    Abstract Objective To determine whether models of primary care service delivery differ in their provision of family-centred care (FCC) and to identify practice characteristics associated with FCC. Design Cross-sectional study. Setting Primary care practices in Ontario (ie, 35 salaried community health centres, 35 fee-for-service practices, 32 capitation-based health service organizations, and 35 blended remuneration family health networks) that belong to 4 models of primary care service delivery. Participants A total of 137 practices, 363 providers, and 5144 patients. Main outcome measures Measures of FCC in patient and provider surveys were based on the Primary Care Assessment Tool. Statistical analyses were conducted using linear mixed regression models and generalized estimating equations. Results Patient-reported FCC scores were high and did not vary significantly by primary care model. Larger panel size in a practice was associated with lower odds of patients reporting FCC. Provider-reported FCC scores were significantly higher in community health centres than in family health networks (P = .035). A larger number of nurse practitioners and clinical services on-site were both associated with higher FCC scores, while scores decreased as the number of family physicians in a practice increased and if practices were more rural. Conclusion Based on provider and patient reports, primary care reform strategies that encourage larger practices and more patients per family physician might compromise the provision of FCC, while strategies that encourage multidisciplinary practices and a range of services might increase FCC. PMID:24235195

  6. Bright infrared quantum-dot light-emitting diodes through inter-dot spacing control

    Sun, Liangfeng; Choi, Joshua J.; Stachnik, David; Bartnik, Adam C.; Hyun, Byung-Ryool; Malliaras, George G.; Hanrath, Tobias; Wise, Frank W.

    2012-01-01

    Infrared light-emitting diodes are currently fabricated from direct-gap semiconductors using epitaxy, which makes them expensive and difficult to integrate with other materials. Light-emitting diodes based on colloidal semiconductor quantum dots, on the other hand, can be solution-processed at low cost, and can be directly integrated with silicon. However, so far, exciton dissociation and recombination have not been well controlled in these devices, and this has limited their performance. Here, by tuning the distance between adjacent PbS quantum dots, we fabricate thin-film quantum-dot light-emitting diodes that operate at infrared wavelengths with radiances (6.4 W sr '1 m '2) eight times higher and external quantum efficiencies (2.0%) two times higher than the highest values previously reported. The distance between adjacent dots is tuned over a range of 1.3 nm by varying the lengths of the linker molecules from three to eight CH 2 groups, which allows us to achieve the optimum balance between charge injection and radiative exciton recombination. The electroluminescent powers of the best devices are comparable to those produced by commercial InGaAsP light-emitting diodes. By varying the size of the quantum dots, we can tune the emission wavelengths between 800 and 1,850 nm.© 2012 Macmillan Publishers Limited.

  7. Transport properties of a Kondo dot with a larger side-coupled noninteracting quantum dot

    Liu, Y S; Fan, X H; Xia, Y J; Yang, X F

    2008-01-01

    We investigate theoretically linear and nonlinear quantum transport through a smaller quantum dot in a Kondo regime connected to two leads in the presence of a larger side-coupled noninteracting quantum dot, without tunneling coupling to the leads. To do this we employ the slave boson mean field theory with the help of the Keldysh Green's function at zero temperature. The numerical results show that the Kondo conductance peak may develop multiple resonance peaks and multiple zero points in the conductance spectrum owing to constructive and destructive quantum interference effects when the energy levels of the large side-coupled noninteracting dot are located in the vicinity of the Fermi level in the leads. As the coupling strength between two quantum dots increases, the tunneling current through the quantum device as a function of gate voltage applied across the two leads is suppressed. The spin-dependent transport properties of two parallel coupled quantum dots connected to two ferromagnetic leads are also investigated. The numerical results show that, for the parallel configuration, the spin current or linear spin differential conductance are enhanced when the polarization strength in the two leads is increased

  8. Bright infrared quantum-dot light-emitting diodes through inter-dot spacing control.

    Sun, Liangfeng; Choi, Joshua J; Stachnik, David; Bartnik, Adam C; Hyun, Byung-Ryool; Malliaras, George G; Hanrath, Tobias; Wise, Frank W

    2012-05-06

    Infrared light-emitting diodes are currently fabricated from direct-gap semiconductors using epitaxy, which makes them expensive and difficult to integrate with other materials. Light-emitting diodes based on colloidal semiconductor quantum dots, on the other hand, can be solution-processed at low cost, and can be directly integrated with silicon. However, so far, exciton dissociation and recombination have not been well controlled in these devices, and this has limited their performance. Here, by tuning the distance between adjacent PbS quantum dots, we fabricate thin-film quantum-dot light-emitting diodes that operate at infrared wavelengths with radiances (6.4 W sr(-1) m(-2)) eight times higher and external quantum efficiencies (2.0%) two times higher than the highest values previously reported. The distance between adjacent dots is tuned over a range of 1.3 nm by varying the lengths of the linker molecules from three to eight CH(2) groups, which allows us to achieve the optimum balance between charge injection and radiative exciton recombination. The electroluminescent powers of the best devices are comparable to those produced by commercial InGaAsP light-emitting diodes. By varying the size of the quantum dots, we can tune the emission wavelengths between 800 and 1,850 nm.

  9. Bright infrared quantum-dot light-emitting diodes through inter-dot spacing control

    Sun, Liangfeng

    2012-05-06

    Infrared light-emitting diodes are currently fabricated from direct-gap semiconductors using epitaxy, which makes them expensive and difficult to integrate with other materials. Light-emitting diodes based on colloidal semiconductor quantum dots, on the other hand, can be solution-processed at low cost, and can be directly integrated with silicon. However, so far, exciton dissociation and recombination have not been well controlled in these devices, and this has limited their performance. Here, by tuning the distance between adjacent PbS quantum dots, we fabricate thin-film quantum-dot light-emitting diodes that operate at infrared wavelengths with radiances (6.4 W sr \\'1 m \\'2) eight times higher and external quantum efficiencies (2.0%) two times higher than the highest values previously reported. The distance between adjacent dots is tuned over a range of 1.3 nm by varying the lengths of the linker molecules from three to eight CH 2 groups, which allows us to achieve the optimum balance between charge injection and radiative exciton recombination. The electroluminescent powers of the best devices are comparable to those produced by commercial InGaAsP light-emitting diodes. By varying the size of the quantum dots, we can tune the emission wavelengths between 800 and 1,850 nm.© 2012 Macmillan Publishers Limited.

  10. Quantum Dots in Photonic Crystal Waveguides

    Sollner, Immo Nathanael

    This Thesis is focused on the study of quantum electrodynamics in photonic crystal waveguides. We investigate the interplay between a single quantum dot and the fundamental mode of the photonic crystal waveguide. We demonstrate experimental coupling eciencies for the spontaneous emission...... into the mode exceeding 98% for emitters spectrally close to the band-edge of the waveguide mode. In addition we illustrate the broadband nature of the underlying eects, by obtaining coupling eciencies above 90% for quantum dots detuned from the band edge by as far as 20nm. These values are in good agreement...... with numerical simulations. Such a high coupling eciency implies that the system can be considered an articial 1D-atom, and we theoretically show that this system can generate strong photon-photon interaction, which is an essential functionality for deterministic optical quantum information processing. We...

  11. Conductance Peaks in Open Quantum Dots

    Ramos, J. G. G. S.; Bazeia, D.; Hussein, M. S.; Lewenkopf, C. H.

    2011-01-01

    We present a simple measure of the conductance fluctuations in open ballistic chaotic quantum dots, extending the number of maxima method originally proposed for the statistical analysis of compound nuclear reactions. The average number of extreme points (maxima and minima) in the dimensionless conductance T as a function of an arbitrary external parameter Z is directly related to the autocorrelation function of T(Z). The parameter Z can be associated with an applied gate voltage causing shape deformation in quantum dot, an external magnetic field, the Fermi energy, etc. The average density of maxima is found to be Z >=α Z /Z c , where α Z is a universal constant and Z c is the conductance autocorrelation length, which is system specific. The analysis of Z > does not require large statistic samples, providing a quite amenable way to access information about parametric correlations, such as Z c .

  12. Efficient Luminescence from Perovskite Quantum Dot Solids

    Kim, Younghoon; Yassitepe, Emre; Voznyy, Oleksandr; Comin, Riccardo; Walters, Grant; Gong, Xiwen; Kanjanaboos, Pongsakorn; Nogueira, Ana F.; Sargent, Edward H.

    2015-01-01

    © 2015 American Chemical Society. Nanocrystals of CsPbX3 perovskites are promising materials for light-emitting optoelectronics because of their colloidal stability, optically tunable bandgap, bright photoluminescence, and excellent photoluminescence quantum yield. Despite their promise, nanocrystal-only films of CsPbX3 perovskites have not yet been fabricated; instead, highly insulating polymers have been relied upon to compensate for nanocrystals' unstable surfaces. We develop solution chemistry that enables single-step casting of perovskite nanocrystal films and overcomes problems in both perovskite quantum dot purification and film fabrication. Centrifugally cast films retain bright photoluminescence and achieve dense and homogeneous morphologies. The new materials offer a platform for optoelectronic applications of perovskite quantum dot solids.

  13. Trajectory phases of a quantum dot model

    Genway, Sam; Hickey, James M; Garrahan, Juan P; Armour, Andrew D

    2014-01-01

    We present a thermodynamic formalism to study the trajectories of charge transport through a quantum dot coupled to two leads in the resonant-level model. We show that a close analogue of equilibrium phase transitions exists for the statistics of transferred charge; by tuning an appropriate ‘counting field’, crossovers to different trajectory phases are possible. Our description reveals a mapping between the statistics of a given device and current measurements over a range of devices with different dot–lead coupling strengths. Furthermore insight into features of the trajectory phases are found by studying the occupation of the dot conditioned on the transported charge between the leads; this is calculated from first principles using a trajectory biased two-point projective measurement scheme. (paper)

  14. Quantum features of semiconductor quantum dots

    Lozada-Cassou, M.; Dong Shihai; Yu Jiang

    2004-01-01

    The exact solutions of the two-dimensional Schrodinger equation with the position-dependent mass for the square well potential in the semiconductor quantum dots system are obtained. The eigenvalues, which are closely related to the position-dependent masses μ1 and μ2, the potential well depth V0 and the radius of the quantum dots r0, can be calculated from two boundary conditions. We generalize this quantum system to three-dimensional case. The special cases for the angular momentum quantum number l=0, 1, 2 are studied in some detail. We find that the energy levels are proportional to the parameters μ2, V0 and r0 for l=0. The relations between them for l=1, 2 become very complicated. The scattering states of this quantum system are mentioned briefly

  15. Dynamic localization in quantum dots: Analytical theory

    Basko, D.M.; Skvortsov, M.A.; Kravtsov, V.E.

    2003-02-01

    We analyze the response of a complex quantum-mechanical system (e.g., a quantum dot) to a time-dependent perturbation φ(t). Assuming the dot to be described by random matrix theory for GOE we find the quantum correction to the energy absorption rate as a function of the dephasing time t φ . If φ(t) is a sum of d harmonics with incommensurate frequencies, the correction behaves similarly to that to the conductivity δσ d (t φ ) in the d-dimensional Anderson model of the orthogonal symmetry class. For a generic periodic perturbation the leading quantum correction is absent as in the systems of the unitary symmetry class, unless φ(-t+τ)=φ(t+τ) for some τ, which falls into the quasi-1d orthogonal universality class. (author)

  16. Theory of Charged Quantum Dot Molecules

    Ponomarev, I. V.; Scheibner, M.; Stinaff, E. A.; Bracker, A. S.; Doty, M. F.; Ware, M. E.; Gammon, D.; Reinecke, T. L.; Korenev, V. L.

    2006-03-01

    Recent optical spectroscopy of excitonic molecules in coupled quantum dots (CQDs) tuned by electric field reveal a richer diversity in spectral line patterns than in their single quantum dot counterparts. We developed a theoretical model that allows us to classify energies and intensities of various PL transitions. In this approach the electric field induced resonance tunneling of the electron and hole states occurs at different biases due to the inherent asymmetry of CQDs. The truncated many-body basis configurations for each molecule are constructed from antisymmetrized products of single-particle states, where the electron occupies only one ground state level in single QD and the hole can occupy two lowest levels of CQD system. The Coulomb interaction between particles is treated with perturbation theory. As a result the observed PL spectral lines can be described with a small number of parameters. The theoretical predictions account well for recent experiments.

  17. Strain-tunable quantum dot devices

    Rastelli, A.; Trotta, R.; Zallo, E.; Atkinson, P.; Magerl, E.; Ding, F.; Plumhof, J.D.; Kumar, S.; Doerr, K.; Schmidt, O.G.

    2011-01-01

    We introduce a new class of quantum dot-based devices, in which the semiconductor structures are integrated on top of piezoelectric actuators. This combination allows on one hand to study in detail the effects produced by variable strains (up to about 0.2%) on the excitonic emission of single quantum dots and on the other to manipulate their electronic- and optical properties to achieve specific requirements. In fact, by combining strain with electric fields we are able to obtain (i) independent control of emission energy and charge-state of a QD, (II) wavelength-tunable single-QD light-emitting diodes and (III) frequency-stabilized sources of single photons at predefined wavelengths. Possible future extensions and applications of this technology will be discussed.

  18. Efficient Luminescence from Perovskite Quantum Dot Solids

    Kim, Younghoon

    2015-11-18

    © 2015 American Chemical Society. Nanocrystals of CsPbX3 perovskites are promising materials for light-emitting optoelectronics because of their colloidal stability, optically tunable bandgap, bright photoluminescence, and excellent photoluminescence quantum yield. Despite their promise, nanocrystal-only films of CsPbX3 perovskites have not yet been fabricated; instead, highly insulating polymers have been relied upon to compensate for nanocrystals\\' unstable surfaces. We develop solution chemistry that enables single-step casting of perovskite nanocrystal films and overcomes problems in both perovskite quantum dot purification and film fabrication. Centrifugally cast films retain bright photoluminescence and achieve dense and homogeneous morphologies. The new materials offer a platform for optoelectronic applications of perovskite quantum dot solids.

  19. Quantum Dot Devices for Optical Signal Processing

    Chen, Yaohui

    and the continuum. Additional to the conventional time-domain modeling scheme, a small-signal perturbation analysis has been used to assist the investigation of harmonic modulation properties. The static properties of quantum dot devices, for example high saturation power, have been quantitatively analyzed....... Additional to the static linear amplication properties, we focus on exploring the gain dynamics on the time scale ranging from sub-picosecond to nanosecond. In terms of optical signals that have been investigated, one is the simple sinusoidally modulated optical carrier with a typical modulation frequency....... We also investigate the gain dynamics in the presence of pulsed signals, in particular the steady gain response to a periodic pulse trains with various time periods. Additional to the analysis of high speed patterning free amplication up to 150-200 Gb/s in quantum dot semiconductor optical ampliers...

  20. Magnetic control of dipolaritons in quantum dots

    Rojas-Arias, J S; Vinck-Posada, H; Rodríguez, B A

    2016-01-01

    Dipolaritons are quasiparticles that arise in coupled quantum wells embedded in a microcavity, they are a superposition of a photon, a direct exciton and an indirect exciton. We propose the existence of dipolaritons in a system of two coupled quantum dots inside a microcavity in direct analogy with the quantum well case and find that, despite some similarities, dipolaritons in quantum dots have different properties and can lead to true dark polariton states. We use a finite system theory to study the effects of the magnetic field on the system, including the emission, and find that it can be used as a control parameter of the properties of excitons and dipolaritons, and the overall magnetic behaviour of the structure. (paper)

  1. The Aube storage centre: Annual report 2010

    2011-01-01

    After a presentation of the Aube storage centre, a storage centre for low and intermediate activity nuclear wastes, this report gives an overview of measures related to nuclear security, to radioprotection and to nuclear safety. It indicates the incidents and accidents which occurred in 2010, describes how the centre's wastes are managed, and indicates the actions performed in terms of public information

  2. The Silicon:Colloidal Quantum Dot Heterojunction

    Masala, Silvia; Adinolfi, Valerio; Sun, Jon Paul; Del Gobbo, Silvano; Voznyy, Oleksandr; Kramer, Illan J.; Hill, Ian G.; Sargent, Edward H.

    2015-01-01

    A heterojunction between crystalline silicon and colloidal quantum dots (CQDs) is realized. A special interface modification is developed to overcome an inherent energetic band mismatch between the two semiconductors, and realize the efficient collection of infrared photocarriers generated in the CQD film. This junction is used to produce a sensitive near infrared photodetector. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Biomedical application of carbon quantum dots

    Markovic, Z.

    2017-01-01

    In this presentation we will summarize and discuss the possibilities of application of carbon quantum dots (CQD) as agents for PDT. Considering their biocompatibility, photostability and optical properties, CQD seem to be good candidates as a photosensitizer. This lecture critically compares and discusses current state-of the-art use of CQD in PDT. We will analyze structural, morphological and optical properties of these nanomaterials as well as the mechanisms responsible for their photosensition and ROS production. (authors)

  4. Quantum Dots for Molecular Diagnostics of Tumors

    Zdobnova, T.A.; Lebedenko, E.N.; Deyev, S.М.

    2011-01-01

    Semiconductor quantum dots (QDs) are a new class of fluorophores with unique physical and chemical properties, which allow to appreciably expand the possibilities for the current methods of fluorescent imaging and optical diagnostics. Here we discuss the prospects of QD application for molecular diagnostics of tumors ranging from cancer-specific marker detection on microplates to non-invasive tumor imaging in vivo. We also point out the essential problems that require resolution in order to c...

  5. Silicon based quantum dot hybrid qubits

    Kim, Dohun

    2015-03-01

    The charge and spin degrees of freedom of an electron constitute natural bases for constructing quantum two level systems, or qubits, in semiconductor quantum dots. The quantum dot charge qubit offers a simple architecture and high-speed operation, but generally suffers from fast dephasing due to strong coupling of the environment to the electron's charge. On the other hand, quantum dot spin qubits have demonstrated long coherence times, but their manipulation is often slower than desired for important future applications. This talk will present experimental progress of a `hybrid' qubit, formed by three electrons in a Si/SiGe double quantum dot, which combines desirable characteristics (speed and coherence) in the past found separately in qubits based on either charge or spin degrees of freedom. Using resonant microwaves, we first discuss qubit operations near the `sweet spot' for charge qubit operation. Along with fast (>GHz) manipulation rates for any rotation axis on the Bloch sphere, we implement two independent tomographic characterization schemes in the charge qubit regime: traditional quantum process tomography (QPT) and gate set tomography (GST). We also present resonant qubit operations of the hybrid qubit performed on the same device, DC pulsed gate operations of which were recently demonstrated. We demonstrate three-axis control and the implementation of dynamic decoupling pulse sequences. Performing QPT on the hybrid qubit, we show that AC gating yields π rotation process fidelities higher than 93% for X-axis and 96% for Z-axis rotations, which demonstrates efficient quantum control of semiconductor qubits using resonant microwaves. We discuss a path forward for achieving fidelities better than the threshold for quantum error correction using surface codes. This work was supported in part by ARO (W911NF-12-0607), NSF (PHY-1104660), DOE (DE-FG02-03ER46028), and by the Laboratory Directed Research and Development program at Sandia National Laboratories

  6. The Silicon:Colloidal Quantum Dot Heterojunction

    Masala, Silvia

    2015-10-13

    A heterojunction between crystalline silicon and colloidal quantum dots (CQDs) is realized. A special interface modification is developed to overcome an inherent energetic band mismatch between the two semiconductors, and realize the efficient collection of infrared photocarriers generated in the CQD film. This junction is used to produce a sensitive near infrared photodetector. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Depleted Bulk Heterojunction Colloidal Quantum Dot Photovoltaics

    Barkhouse, D. Aaron R.

    2011-05-26

    The first solution-processed depleted bulk heterojunction colloidal quantum dot solar cells are presented. The architecture allows for high absorption with full depletion, thereby breaking the photon absorption/carrier extraction compromise inherent in planar devices. A record power conversion of 5.5% under simulated AM 1.5 illumination conditions is reported. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Research Progress of Photoanodes for Quantum Dot Sensitized Solar Cells

    LI Zhi-min

    2017-08-01

    Full Text Available This paper presents the development status and tendency of quantum dot sensitized solar cells. Photoanode research progress and its related technologies are analyzed in detail from the three ways of semiconductor thin films, quantum dot co-sensitization and quantum dot doping, deriving from the approach that the conversion efficiency can be improved by photoanode modification for quantum dot sensitized solar cells. According to the key factors which restrict the cell efficiency, the promising future development of quantum dot sensitized solar cells is proposed,for example,optimizing further the compositions and structures of semiconductor thin films for the photoanodes, exploring new quantum dots with broadband absorption and developing high efficient techniques of interface modification.

  9. Quantum Dots and Their Multimodal Applications: A Review

    Paul H. Holloway

    2010-03-01

    Full Text Available Semiconducting quantum dots, whose particle sizes are in the nanometer range, have very unusual properties. The quantum dots have band gaps that depend in a complicated fashion upon a number of factors, described in the article. Processing-structure-properties-performance relationships are reviewed for compound semiconducting quantum dots. Various methods for synthesizing these quantum dots are discussed, as well as their resulting properties. Quantum states and confinement of their excitons may shift their optical absorption and emission energies. Such effects are important for tuning their luminescence stimulated by photons (photoluminescence or electric field (electroluminescence. In this article, decoupling of quantum effects on excitation and emission are described, along with the use of quantum dots as sensitizers in phosphors. In addition, we reviewed the multimodal applications of quantum dots, including in electroluminescence device, solar cell and biological imaging.

  10. Central dot sign in entities other than Caroli disease

    Ahmadi, T.; Itai, Yuji; Minami, Manabu.

    1997-01-01

    The purpose of this study was to describe central dot sign (tiny dots with strong contrast enhancement of the portal vein within dilated hepatic bile ducts on computed tomography) in entities other than Caroli disease, especially in peribiliary cysts with or without autosomal-dominant polycystic kidney disease. Computed tomography in 74 cases of peribiliary cysts and 134 cases of other liver diseases and states possibly showing central dot sign were retrospectively reviewed to examine the central dot sign. In three cases of peribiliary cysts, some part of the liver showed strongly enhanced portal radicles surrounded completely or partially by low-attenuation, enlarged peribiliary cysts, presenting ''central dot sign'' on contrast-enhanced computed tomography. We suggest that in addition to Caroli disease, some other entities and diseases of the liver may demonstrate central dot sign and this sign should not be considered a specific finding of Caroli disease. (author)

  11. Central dot sign in entities other than Caroli disease

    Ahmadi, T.; Itai, Yuji [Tsukuba Univ., Ibaraki (Japan). Inst. of Clinical Medicine; Minami, Manabu

    1997-11-01

    The purpose of this study was to describe central dot sign (tiny dots with strong contrast enhancement of the portal vein within dilated hepatic bile ducts on computed tomography) in entities other than Caroli disease, especially in peribiliary cysts with or without autosomal-dominant polycystic kidney disease. Computed tomography in 74 cases of peribiliary cysts and 134 cases of other liver diseases and states possibly showing central dot sign were retrospectively reviewed to examine the central dot sign. In three cases of peribiliary cysts, some part of the liver showed strongly enhanced portal radicles surrounded completely or partially by low-attenuation, enlarged peribiliary cysts, presenting ``central dot sign`` on contrast-enhanced computed tomography. We suggest that in addition to Caroli disease, some other entities and diseases of the liver may demonstrate central dot sign and this sign should not be considered a specific finding of Caroli disease. (author)

  12. Templated self-assembly of SiGe quantum dots

    Dais, Christian

    2009-08-19

    This PhD thesis reports on the fabrication and characterization of exact aligned SiGe quantum dot structures. In general, SiGe quantum dots which nucleate via the Stranski-Krastanov growth mode exhibit broad size dispersion and nucleate randomly on the surface. However, to tap the full potential of SiGe quantum dots it is necessary to control the positioning and size of the dots on a nanometer length, e.g. for electronically addressing of individual dots. This can be realized by so-called templated self-assembly, which combines top-down lithography with bottom-up selfassembly. In this process the lithographically defined pits serve as pre-defined nucleation points for the epitaxially grown quantum dots. In this thesis, extreme ultraviolet interference lithography at a wavelength of e=13.4 nm is employed for prepatterning of the Si substrates. This technique allows the precise and fast fabrication of high-resolution templates with a high degree of reproducibility. The subsequent epitaxial deposition is either performed by molecular beam epitaxy or low-pressure chemical vapour deposition. It is shown that the dot nucleation on pre-patterned substrates depends strongly on the lithography parameters, e.g. size and periodicity of the pits, as well as on the epitaxy parameters, e.g. growth temperature or material coverage. The interrelations are carefully analyzed by means of scanning force microscopy, transmission electron microscopy and X-ray diffraction measurements. Provided that correct template and overgrowth parameters are chosen, perfectly aligned and uniform SiGe quantum dot arrays of different period, size as well as symmetry are created. In particular, the quantum dot arrays with the so far smallest period (35 nm) and smallest size dispersion are fabricated in this thesis. Furthermore, the strain fields of the underlying quantum dots allow the fabrication of vertically aligned quantum dot stacks. Combining lateral and vertical dot alignment results in three

  13. Biocompatible yogurt carbon dots: evaluation of utilization for medical applications

    Dinç, Saliha; Kara, Meryem; Demirel Kars, Meltem; Aykül, Fatmanur; Çiçekci, Hacer; Akkuş, Mehmet

    2017-09-01

    In this study, carbon dots (CDs) were produced from yogurt, a fermented milk product, via microwave-assisted process (800 W) in 30 min without using any additional chemical agents. Yogurt CDs had outstanding nitrogen and oxygen ratios. These dots were monodisperse and about 2 nm sized. The toxicological assessments of yogurt carbon dots in human cancer cells and normal epithelial cells and their fluorescence imaging in living cell system were carried out. Yogurt carbon dots had intense fluorescent signal under confocal microscopy and good fluorescence stability in living cell system. The resulting yogurt carbon dots exhibited high biocompatibility up to 7.1 mg/mL CD concentration which may find utilization in medical applications such as cellular tracking, imaging and drug delivery. Yogurt carbon dots have potential to be good diagnostic agents to visualize cancer cells which may be developed as a therapeutic carrier.

  14. The quantum Hall effect in quantum dot systems

    Beltukov, Y M; Greshnov, A A

    2014-01-01

    It is proposed to use quantum dots in order to increase the temperatures suitable for observation of the integer quantum Hall effect. A simple estimation using Fock-Darwin spectrum of a quantum dot shows that good part of carriers localized in quantum dots generate the intervals of plateaus robust against elevated temperatures. Numerical calculations employing local trigonometric basis and highly efficient kernel polynomial method adopted for computing the Hall conductivity reveal that quantum dots may enhance peak temperature for the effect by an order of magnitude, possibly above 77 K. Requirements to potentials, quality and arrangement of the quantum dots essential for practical realization of such enhancement are indicated. Comparison of our theoretical results with the quantum Hall measurements in InAs quantum dot systems from two experimental groups is also given

  15. Transient Dynamics of Double Quantum Dots Coupled to Two Reservoirs

    Fukadai, Takahisa; Sasamoto, Tomohiro

    2018-05-01

    We study the time-dependent properties of double quantum dots coupled to two reservoirs using the nonequilibrium Green function method. For an arbitrary time-dependent bias, we derive an expression for the time-dependent electron density of a dot and several currents, including the current between the dots in the wide-band-limit approximation. For the special case of a constant bias, we calculate the electron density and the currents numerically. As a result, we find that these quantities oscillate and that the number of crests in a single period of the current from a dot changes with the bias voltage. We also obtain an analytical expression for the relaxation time, which expresses how fast the system converges to its steady state. From the expression, we find that the relaxation time becomes constant when the coupling strength between the dots is sufficiently large in comparison with the difference of coupling strength between the dots and the reservoirs.

  16. Using of Quantum Dots in Biology and Medicine.

    Pleskova, Svetlana; Mikheeva, Elza; Gornostaeva, Ekaterina

    2018-01-01

    Quantum dots are nanoparticles, which due to their unique physical and chemical (first of all optical) properties, are promising in biology and medicine. There are many ways for quantum dots synthesis, both in the form of nanoislands self-forming on the surfaces, which can be used as single-photon emitters in electronics for storing information, and in the form of colloidal quantum dots for diagnostic and therapeutic purposes in living systems. The paper describes the main methods of quantum dots synthesis and summarizes medical and biological ways of their use. The main emphasis is laid on the ways of quantum dots surface modification. Influence of the size and form of nanoparticles, charge on the surfaces of quantum dots, and cover type on the efficiency of internalization by cells and cell compartments is shown. The main mechanisms of penetration are considered.

  17. Principles of conjugating quantum dots to proteins via carbodiimide chemistry

    Song Fayi; Chan, Warren C W

    2011-01-01

    The covalent coupling of nanomaterials to bio-recognition molecules is a critical intermediate step in using nanomaterials for biology and medicine. Here we investigate the carbodiimide-mediated conjugation of fluorescent quantum dots to different proteins (e.g., immunoglobulin G, bovine serum albumin, and horseradish peroxidase). To enable these studies, we developed a simple method to isolate quantum dot bioconjugates from unconjugated quantum dots. The results show that the reactant concentrations and protein type will impact the overall number of proteins conjugated onto the surfaces of the quantum dots, homogeneity of the protein–quantum dot conjugate population, quantum efficiency, binding avidity, and enzymatic kinetics. We propose general principles that should be followed for the successful coupling of proteins to quantum dots.

  18. The DIY Digital Medical Centre.

    Timmis, James Kenneth; Timmis, Kenneth

    2017-09-01

    Healthcare systems worldwide are confronted with major economic, organizational and logistical challenges. Historic evolution of health care has led to significant healthcare sector fragmentation, resulting in systemic inefficiencies and suboptimal resource exploitation. To attain a sustainable healthcare model, fundamental, system-wide improvements that effectively network, and ensure fulfilment of potential synergies between sectors, and include and facilitate coherent strategic planning and organisation of healthcare infrastructure are needed. Critically, they must be specifically designed to sustainably achieve peak performance within the current policy environment for cost-control, and efficiency and quality improvement for service delivery. We propose creation of a new healthcare cluster, to be embedded in existing healthcare systems. It consists of (i) local 24/7 walk-in virtually autonomous do-it-yourself Digital Medical Centres performing routine diagnosis, monitoring, prevention, treatment and standardized documentation and health outcome assessment/reporting, which are online interfaced with (ii) regional 24/7 eClinician Centres providing on-demand clinical supervision/assistance to Digital Medical Centre patients. Both of these are, in turn, online interfaced with (iii) the National Clinical Informatics Centre, which houses the national patient data centre (cloud) and data analysis units that conduct patient- and population-level, personalized and predictive(-medicine) intervention optimization analyses. The National Clinical Informatics Centre also interfaces with biomedical research and prioritizes and accelerates the translation of new discoveries into clinical practice. The associated Health Policy Innovation and Evaluation Centre rapidly integrates new findings with health policy/regulatory discussions. This new cluster would synergistically link all health system components in a circular format, enable not only access by all arms of the health

  19. Theory of the Quantum Dot Hybrid Qubit

    Friesen, Mark

    2015-03-01

    The quantum dot hybrid qubit, formed from three electrons in two quantum dots, combines the desirable features of charge qubits (fast manipulation) and spin qubits (long coherence times). The hybridized spin and charge states yield a unique energy spectrum with several useful properties, including two different operating regimes that are relatively immune to charge noise due to the presence of optimal working points or ``sweet spots.'' In this talk, I will describe dc and ac-driven gate operations of the quantum dot hybrid qubit. I will analyze improvements in the dephasing that are enabled by the sweet spots, and I will discuss the outlook for quantum hybrid qubits in terms of scalability. This work was supported in part by ARO (W911NF-12-0607), NSF (PHY-1104660), the USDOD, and the Intelligence Community Postdoctoral Research Fellowship Program. The views and conclusions contained in this presentation are those of the authors and should not be interpreted as representing the official policies or endorsements, either expressed or implied, of the US government.

  20. Quantum Dots for Solar Cell Application

    Poudyal, Uma

    Solar energy has been anticipated as the most important and reliable source of renewable energy to address the ever-increasing energy demand. To harvest solar energy efficiently, diverse kinds of solar cells have been studied. Among these, quantum dot sensitized solar cells have been an interesting group of solar cells mainly due to tunable, size-dependent electronic and optical properties of quantum dots. Moreover, doping these quantum dots with transition metal elements such as Mn opens avenue for improved performance of solar cells as well as for spin based technologies. In this dissertation, Mn-doped CdSe QDs (Mn-CdSe) have been synthesized by Successive Ionic Layer Adsorption and Reaction (SILAR) method. They are used in solar cells to study the effect of Mn doping in the performance of solar cells. Incident photon to current-conversion efficiency (IPCE) is used to record the effect of Mn-doping. Intensity modulated photovoltage and photocurrent spectroscopy (IMVS/PS) has been used to study the carrier dynamics in these solar cells. Additionally, the magnetic properties of Mn-CdSe QDs is studied and its possible origin is discussed. Moreover, CdS/CdSe QDs have been used to study the effect of liquid, gel and solid electrolyte in the performance and stability of the solar cells. Using IPCE spectra, the time decay measurements are presented and the possible reactions between the QD and the electrolytes are explained.