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Sample records for center dot cl

  1. Cold white light generation through the simultaneous emission from Ce{sup 3+}, Dy{sup 3+} and Mn{sup 2+} in 90Al{sub 2}O{sub 3}{center_dot}2CeCl{sub 3}{center_dot}3DyCl{sub 3}{center_dot}5MnCl{sub 2} thin film

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez, W. [Departamento de Fisica, Universidad Autonoma Metropolitana-Iztapalapa, P.O. Box 55-534, Mexico, D.F. 09340 (Mexico); Alvarez, E. [Departamento de Fisica, Universidad de Sonora (UNISON), Boulevard Luis Encinas y Rosales s/n, Hermosillo, Sonora 83000 (Mexico); Martinez-Martinez, R.; Yescas-Mendoza, E. [Instituto de Fisica y Matematicas, Universidad Tecnologica de la Mixteca, Carretera a Acatlima Km. 2.5, Huajuapan de Leon, Oaxaca 69000 (Mexico); Camarillo, I. [Departamento de Fisica, Universidad Autonoma Metropolitana-Iztapalapa, P.O. Box 55-534, Mexico, D.F. 09340 (Mexico); Caldino, U., E-mail: cald@xanum.uam.mx [Departamento de Fisica, Universidad Autonoma Metropolitana-Iztapalapa, P.O. Box 55-534, Mexico, D.F. 09340 (Mexico)

    2012-08-15

    The photoluminescence of a CeCl{sub 3}, DyCl{sub 3} and MnCl{sub 2} doped aluminum oxide film deposited by ultrasonic spray pyrolysis was characterized by excitation, emission and decay time spectroscopy. A nonradiative energy transfer from Ce{sup 3+} to Dy{sup 3+} and Mn{sup 2+} is observed upon UV excitation at 278 nm (peak emission wavelength of AlGaN-based LEDs). Such energy transfer leads to a simultaneous emission of these ions in the blue, green, yellow and red regions, resulting in white light emission with CIE1931 chromaticity coordinates, x=0.34 and y=0.23, which correspond to cold white light with a color temperature of 4900 K. - Highlights: Black-Right-Pointing-Pointer 90Al{sub 2}O{sub 3}{center_dot}2CeCl{sub 3}{center_dot}3DyCl{sub 3}{center_dot}5MnCl{sub 2} thin film (AOCDM) could be prepared by spray pyrolysis. Black-Right-Pointing-Pointer Non-radiative energy transfer from Ce{sup 3+} to Dy{sup 3+} and Mn{sup 2+} takes place in AOCDM. Black-Right-Pointing-Pointer AOCDM (pumped with 278 nm-UV light) can generate 4900 K cold white light.

  2. Critical and superciritcal properties of 0.3 to 3.0 mol{center_dot}kg{sup {minus}1} CaCl{sub 2}(aq)

    Energy Technology Data Exchange (ETDEWEB)

    Oakes, C.S.; Bodnar, R.J.; Pitzer, K.S. [State Univ., Blacksburg, VA (United States)]|[Lawrence Berkeley Lab., CA (United States); Simonson, J.M. [Oak Ridge National Lab., TN (United States)

    1994-06-01

    Critical temperatures (T{sub c}) and densities (p{sub c}) for aqueous CaCl{sub 2} solutions were measured using two different optical techniques. Fluid inclusions with compositions of 0.5 to 4.0 mol{center_dot}ks{sup {minus}1} were synthesized from 600 to 820{degrees}C and at 1500 and 2500 bars in both the single and two-fluid phase fields. Critical temperatures were determined from measured homogenization temperatures and the observed mode of homogenization (i.e., to the liquid or vapor phase or by fading of the meniscus between apparent equal volumes of liquid and vapor). Critical temperatures determined by this method for 0.5, 1.0, 2.0, and 3.0 molal CaCl{sub 2}(aq) solutions are 395, 406, 466, and 565{degrees}C, respectively. T{sub c} for 4.0 molal CaCl{sub 2}(aq) was found to be in excess of 662{degree}C. Critical pressures (P{sub c}) could not be accurately determined from these measurements but were estimated from another source. Measurements of T{sub c} were also made using sealed silica capillaries containing 0.3, 0.5, 1.0, and 2.0 molal Cal{sub 2}(aq) solutions. T{sub c} values from these measurements are 388, 393, 405, and 465{degrees}C, respectively. Our data are in fair agreement with previously published data at and below 1.0 mol{center_dot}kg{sup {minus}1}, data from the two published sources of CaCl{sub 2}(aq) T{sub 2} measurements show substantially different trends, with the data from this study agreeing with the more recent of the two reports. Estimated values of p{sub c} are given for the solutions examined in the capillary tube experiments. Critical isochores are presented with new synthetic fluid inclusion derived isochores for 1.0 and 2.0 mol{center_dot}kg{sup {minus}1} Cal{sub 2}(aq) liquids to form a complete arrays of isochores for temperatures form {approximately} 100{degrees}C to those along the critical isochore and pressures to 5000 bars. 18 refs., 6 figs., 5 tabs.

  3. Magnetic Bloch oscillations in the near-Ising antiferromagnet CoCl2#center dot#2D2O

    DEFF Research Database (Denmark)

    Christensen, N.B.; Lefmann, K.; Johannsen, I.;

    2000-01-01

    We have investigated the possible occurrence of magnetic Bloch oscillations in CoCl2 . 2D(2)O. We were unable to observe these oscillations at 20.0 K, just above T-N. In an attempt to explain this result, we studied spin waves in the a*-c* plane in order to estimate the effect of the interchain...

  4. Diphosphine- and CO-Induced Fragmentation of Chloride-bridged Dinuclear Complex and Cp*Ir(mu-Cl)(3)Re(CO)(3) and Attempted Synthesis of Cp*Ir(mu-Cl)(3)Mn(CO)(3): Spectroscopic Data and X-ray Diffraction Structures of the Pentamethylcyclopentadienyl Compounds [Cp*IrCl{(Z)-Ph2PCH = CHPPh2}][Cl]center dot 2CHCl(3) and Cp*Ir(CO)Cl-2

    Energy Technology Data Exchange (ETDEWEB)

    Hammons, Casey [University of North Texas; Wang, Xiaoping [ORNL; Nesterov, Vladimir [University of North Texas; Richmond, Michael G. [University of North Texas

    2010-01-01

    The confacial bioctahedral compound Cp*Ir(mu-Cl)(3)Re(CO)(3) (1) undergoes rapid fragmentation in the presence of the unsaturated diphosphine ligand (Z)-Ph2PCH = CHPPh2 to give the mononuclear compounds [Cp*IrCl {(Z)-Ph2PCH = CHPPh2}][Cl] (2) and fac-ClRe(CO)(3)[(Z)-Ph2PCH = CHPPh2] (3). 2 has been characterized by H-1 and P-31 NMR spectroscopy and X-ray diffraction analysis. 2 center dot 2CHCl(3) crystallizes in the monoclinic space group C2/c, a = 35.023 (8) angstrom, b = 10.189 (2) angstrom, c = 24.003 (6) angstrom, b = 103.340 (3), V = 8,335 (3) angstrom 3, Z = 8, and d(calc) = 1.647 Mg/m(3); R = 0.0383, R-w = 0.1135 for 8,178 reflections with I> 2 sigma(I). The Ir(III) center in 2 exhibits a six-coordinate geometry and displays a chelating diphosphine group. Compound 1 reacts with added CO with fragmentation to yield the known compounds Cp*Ir(CO)Cl-2 (4) and ClRe(CO)(5) (5) in near quantitative yield by IR spectroscopy. Using the protocol established by our groups for the synthesis of 1, we have explored the reaction of [Cp*IrCl2](2) with ClMn(CO)(5) as a potential route to Cp*Ir(mu-Cl)(3)Mn(CO)(3); unfortunately, 4 was the only product isolated from this reaction. The solid-state structure of 4 was determined by X-ray diffraction analysis. 4 crystallizes in the triclinic space group P-1, a = 7.4059 (4) angstrom, b = 7.8940 (4) angstrom, c = 11.8488 (7) angstrom, alpha = 80.020 (1), beta = 79.758 (1), gamma = 68.631 (1), V = 630.34 (6) angstrom(3), Z = 2, and d(calc) = 2.246 Mg/m(3); R = 0.0126, R-w = 0.0329 for 2,754 reflections with I> 2 sigma(I). The expected three-legged piano-stool geometry in 4 has been crystallographically confirmed.

  5. Effects of Shannon entropy and electric field on polaron in RbCl triangular quantum dot

    Science.gov (United States)

    M, Tiotsop; A, J. Fotue; S, C. Kenfack; N, Issofa; H, Fotsin; L, C. Fai

    2016-04-01

    In this paper, the time evolution of the quantum mechanical state of a polaron is examined using the Pekar type variational method on the condition of the electric-LO-phonon strong-coupling and polar angle in RbCl triangular quantum dot. We obtain the eigenenergies, and the eigenfunctions of the ground state, and the first excited state respectively. This system in a quantum dot can be treated as a two-level quantum system qubit and the numerical calculations are performed. The effects of Shannon entropy and electric field on the polaron in the RbCl triangular quantum dot are also studied.

  6. Fabrication of CuCl quantum dots and the size dependence of the biexciton binding energy

    CERN Document Server

    Park, S T; Kim, H Y; Kim, I G

    2000-01-01

    We fabricated CuCl quantum dots (QDs) in an aluminoborosilicate glass matrix. The photoluminescence of the CuCl QDs was surveyed by using the band-to-band excitation and the site selective luminescence methods. The excitation density dependence of the exciton and the biexciton luminescence was measured, and the saturation effects of the luminescence intensities were observed. The biexciton binding energies measured using the site selective luminescence method increased with decreasing QD size. The data were well fitted by a function resulting from the numerical matrix-diagonalization method.

  7. Dynamic [Cl{sup -}]{sub i} measurement with chloride sensing quantum dots nanosensor in epithelial cells

    Energy Technology Data Exchange (ETDEWEB)

    Wang Yuchi; Mao Hua; Wong, Lid B, E-mail: ywang@biotechplex.com [BioTechPlex Corporation, 1205 Linda Vista Drive Suite A, San Marcos, CA 92078 (United States); Cytoptics Corporation, 1205 Linda Vista Drive Suite B, San Marcos, CA 92078 (United States)

    2010-02-05

    We have synthesized a chloride sensing quantum dots (QD) nanosensor, Cl-QD, for the dynamic measurements of chloride ion concentration in the millimolar range, a sensitivity that is applicable to most physiological intracellular chloride ion concentration ([Cl{sup -}]{sub i}) measurements in epithelial cells. The Cl-QD is synthesized by conjugating an anion receptor, 1-(2-mercapto-ethyl)-3-phenyl-thiourea (MEPTU) to a water soluble CdSe/ZnS QD at an emission wavelength of 620 nm. Upon binding of chloride ions to the Cl-QD, a photo-induced electron transfer mechanism caused the fluorescence of the QD to quench. This resulted in an inversely proportional relationship between the chloride ion concentration and the fluorescence intensity of the Cl-QD. We have utilized this Cl-QD to measure [Cl{sup -}]{sub i} in T84 and CF-PAC cultured cells, with either the C1C-2 or CFTR chloride channels being manipulated by pharmacological chloride channel activators and inhibitors. Activations of C1C-2 and CFTR chloride channels in T84 by the respective lubiprostone and genistein caused predictive increases in the fluorescence of the Cl-QD, i.e., a decrease of [Cl{sup -}]{sub i}. Conversely, glibenclamide, a chloride channel inhibitor, applied to the CF-PAC cells caused a predictable decrease in the fluorescence of Cl-QD due to the increase of [Cl{sup -}]{sub i}. These are the first data in using QD-based chloride ion sensors for dynamic measurements of intracellular chloride ion concentrations in epithelial cells.

  8. Combined MTX{center_dot}5-FU{center_dot}CDGP for the treatment of head and neck cancer

    Energy Technology Data Exchange (ETDEWEB)

    Sakoda, Takema; Kitano, Hiroya [Tottori Univ., Yonago (Japan). Faculty of Medicine; Saitoh, Yuko; Ikeda, Hiroki; Dake, Yoshihiro; Enomoto, Tadao [Japanese Red Cross Society Wakayama Medical Center (Japan); Seno, Satoshi [Shiga Univ. of Medical Science, Otsu (Japan); Kawano, Atsushi [Tokyo Medical Coll. (Japan)

    2003-05-01

    Combination chemotherapy including 5-fluorouracil (5-FU) and nedaplatin (CDGP) with methotrexate (MTX) and leucovorin (LV) was administered for modulation in patients with head and neck cancer. We treated 19 patients with MTX{center_dot}5-FU{center_dot}CDGP consisting of 150 mg/body of MTX on day 1 followed by a 3-day continuous infusion of 5-FU at 3,500 mg/m{sup 2} and 17 injections of LV at 15 mg and infusion of CDGP at 100 mg/m{sup 2}. Six patients had recurrent head and neck cancer, and 13 had newly diagnosed disease. Eleven of the new patients were concurrently treated with radiation therapy. Treatment-associated toxicity was significant, including mucositis and myelosuppression, but acceptable. Sixteen patients were eligible for evaluation of response. The overall complete response rate was 75.0% (12/16). Patients treated with radiotherapy had a 90.0% (9/10) overall complete response rate. (author)

  9. Structure of Na{sub 2}O{center_dot}MO{center_dot}SiO{sub 2}{center_dot}CaF{sub 2} (M=Mg, Ca) oxyfluoride glasses

    Energy Technology Data Exchange (ETDEWEB)

    Cheng Jinshu [State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan 430070 (China); Deng Wei, E-mail: dengwei@whut.edu.cn [State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan 430070 (China); Wang Mitang [School of Materials and Metallurgy, Inner Mongolia University of Science and Technology, Baotou 014010 (China)

    2012-07-15

    (9-x)CaO{center_dot}xMgO{center_dot}15Na{sub 2}O{center_dot}60SiO{sub 2}{center_dot}16CaF{sub 2}(x=0, 2, 4, 6, and 9) oxyfluoride glasses were prepared. Utilizing the Raman scattering technique together with {sup 29}Si and {sup 19}F MAS NMR, the effect of alkaline metal oxides on the Q species of glass was characterized. Raman results show that as magnesia is added at the expense of calcium oxide, the disproportional reaction Q{sup 3}{yields}Q{sup 4}+Q{sup 2} (Q{sup n} is a SiO{sub 4} tetrahedron with n bridging oxygens) prompted due to the high ionic field strength of magnesia, magnesium oxide entered into the silicate network as tetrahedral MgO{sub 4}, and removed other modifying ions for charge compensation. This reaction was confirmed by {sup 29}Si MAS NMR. {sup 19}F MAS NMR results show that fluorine exists in the form of mixed calcium sodium fluoride species in all glasses and no Si-F bonds were formed. As CaO is gradually replaced by MgO (x=6, 9), a proportion of the magnesium ions combines with fluorine to form the MgF{sup +} species. Meanwhile, some part of Na{sup +} ions complex F{sup -} in the form of F-Na(6).

  10. Off-Center D- Centers in a Quantum Dot in the Presence of a Perpendicular Magnetic Fields

    Institute of Scientific and Technical Information of China (English)

    XIE Wen-Fang

    2001-01-01

    We investigate the effect of the position of the donor in quantum dots on the energy spectrum in the presence ofa perpendicular magnetic field by using the method of few-body physics. As a function of the magnetic field, we find, when D- centers are placed sufficiently off-center, discontinuous ground-state transitions which are similar to those found in many-electron parabolic quantum dots. Series of magic numbers of angular momentum which minimize the ground-state electron-electron interaction energy have been discovered. The dependence of the binding energy of the ground-state of the 1D- center on the dot radius for a few values of the magnetic field strength is obtained and compared with other results.

  11. Design of columnar quantum dots for polarization-independent emission using 8-band k{center_dot}p method

    Energy Technology Data Exchange (ETDEWEB)

    Andrzejewski, J; Sek, G; Misiewicz, J [Institute of Physics, Wroclaw University of Technology, Wybrze z-dot e Wyspianskiego 27, 50-370 Wroclaw (Poland); O' Reilly, E [Department of Physics, University College Cork and Tyndall National Institute, Lee Maltings, Cork (Ireland); Fiore, A, E-mail: janusz.andrzejewski@pwr.wroc.p [CORBA Research Institute, Eindhoven University of Technology, PO Box 513, 5600 MB Eindhoven (Netherlands)

    2010-09-01

    Control of the polarization of the emitted light can be highly beneficial for certain optoelectronic applications such as optical amplifiers. It has been recently demonstrated experimentally that semiconductor quantum dots with large height to base length aspect ratio are able to emit polarization-independent light from the edge of the wafer. However, analysis of the physics responsible for the observed polarization properties of such nano-objects (like columnar quantum dots or quantum rods) is still rather limited. In particular, the role of the material surrounding the columnar QD on the strain and thus on the polarization properties has not been considered previously. We report here, based on original software, the results of eight-band k{center_dot}p calculations of the electronic and polarization properties of columnar In{sub y}Ga{sub 1-y}As quantum dots (CQD) with high aspect ratio (up to 6) embedded in an In{sub x}Ga{sub 1-x}As/GaAs quantum well. We calculate the relative intensities of transverse-magnetic (TM) and transverse-electric (TE) linear polarized light emitted from the edge of the semiconductor wafer as a function of the two main factors affecting the heavy hole - light hole valence band mixing and hence the polarization dependent selection rules for the optical transitions, namely i) the composition contrast y/x between the dot material and the surrounding well, and ii) the dot aspect ratio. Our numerical results show, in contrast to the previously reported expectations, that the former is the main driving parameter for tuning the polarization properties. This is explained analyzing the biaxial strain in the CQD, based on which it is possible to predict on the TM to TE intensity ratio.

  12. Binding Energy of D- and D0 Centers Confined by Spherical Quantum Dots

    Institute of Scientific and Technical Information of China (English)

    BAO Yuan-Peng; XIE Wen-Fang

    2008-01-01

    We study a negative donor center, a neutral donor in a spherical Gaussian potential quantum dot by using the matrix diagonalization of Hamiltonian within the effective-mass approximation. We calculate the energy E(D-) as functions of Gaussian potential size and depth, the same calculations as performed with the parabolic approximation. The dependence of the ground state of the neutral shallow donor and the negatively charged donor on the dot size and the potential depth is investigated.

  13. Binding Energies of D- Centers Trapped by a Quantum Dot in a Magnetic Field

    Institute of Scientific and Technical Information of China (English)

    XIE Wen-Fang

    2009-01-01

    A investigation of the properties of the bound states of D- centers confined in a parabolic quantum dot has been performed for the case with the presence of a perpendicular magnetic field.Calculations are carried out by using the method of numerical diagonalization of Hamiltonian matrix within the effective-mass approximation.The binding energies of the ground and some bound-excited states are obtained as a function of the applied magnetic field strength.Detailed calculations of the binding energies for a number of low-lying states show that for field strength less than B = 2.1 T, the D- center confined in a quantum dot possesses two bound states, for 2.1 ≤ B < 2.4 T, there exist three bound states, etc.Further relevant characteristics of the D- center quantum dots in magnetic fields are provided.

  14. Measurement of HO{sub x}{center_dot} production rate due to radon decay in air

    Energy Technology Data Exchange (ETDEWEB)

    Ding, Huiling

    1993-08-01

    Radon in indoor air may cause the exposure of the public to excessive radioactivity. Radiolysis of water vapor in indoor air due to radon decay could produce ({center_dot}OH and HO{sub 2} {center_dot}) that may convert atmospheric constituents to compounds of lower vapor pressure. These lower vapor pressure compounds might then nucleate to form new particles in the indoor atmosphere. Chemical amplification was used to determine HO{sub x}{center_dot} production rate in indoor air caused by radon decay. Average HO{sub x}{center_dot} production rate was found to be (4.31{plus_minus}0.07) {times} 10{sup 5} HO{sub x}{center_dot} per Rn decay per second (Bq) 3.4 to 55.0% at 22C. This work provided G{sub (HO{sub x}{center_dot})}-value, 7.86{plus_minus}0.13 No./100 eV in air by directly measuring [HO{sub x}{center_dot}] formed from the radiolysis procedure. This G value implies that HO{sub x}{center_dot} produced by radon decay in air might be formed by multiple processes and may be result of positive ion-molecule reactions, primary radiolysis, and radical reactions. There is no obvious relation between HO{sub x}{center_dot} production rate and relative humidity. A laser-induced fluorescence (LIF) system has been used for {center_dot}OH production rate measurement; it consists of an excimer laser, a dye laser, a frequency doubler, a gaseous fluorescence chamber, and other optical and electronic parts. This system needs to be improved to eliminate the interferences of light scattering and artificial {center_dot}OH produced from the photolysis of O{sub 3}/H{sub 2}O.

  15. Color centers in NaCl by hybrid functionals

    OpenAIRE

    Chen, Wei; Tegenkamp, Christoph; Pfnür, Herbert; Bredow, Thomas

    2010-01-01

    We present in this work the electronic structure and transition energies (both thermodynamic and optical) of Cl vacancies in NaCl by hybrid density functionals. The underestimated transition energies by the semi-local functional inherited from the band gap problem are recovered by the PBE0 hybrid functional through the non-local exact exchange, whose amount is adjusted to reproduce the experimental band gap. The hybrid functional also gives a better account of the lattice relaxation for the d...

  16. Thermoluminescence and F centers of manganese doped NaCl and NaCl-CKl crystals exposed to gamma radiation

    Energy Technology Data Exchange (ETDEWEB)

    Somera, L.; Cruz Z, E.; Roman L, J. [UNAM, Instituto de Ciencias Nucleares, Circuito Exterior, Ciudad Universitaria, 04510 Mexico D. F. (Mexico); Hernandez A, J. M.; Murrieta S, H., E-mail: ecruz@nucleares.unam.mx [UNAM, Instituto de Fisica, Circuito Exterior, Ciudad Universitaria, 04510 Mexico D. F. (Mexico)

    2015-10-15

    Alkali halides crystals doped with rare earths or transition metals have been widely studied due to the luminescence properties. In particular, NaCl and KCl single crystals present thermally stimulated luminescence (Tl) after gamma irradiation. The NaCl and the NaCl KCl mixed crystal doped with manganese (MnCl{sub 2}) impurity were grown by using the Czochralski method. The emission characteristic of Mn{sup 2+} was observed at 543 nm. The crystals were exposed between 0.02 and 10 kGy gamma dose from {sup 60}Co irradiator. Optical absorption at room temperature shows the peaked band at 452 nm corresponding to the manganese impurity. The F bands, was ascribed to the electron trapped in the anion vacancy in the lattice, were obtained at 452 nm and 455 nm belonging to NaCl:Mn and NaCl KCl:Mn, respectively. The F band increases as the doses increase and it was bleaching by the UV light at 470 nm. The glow curves of the samples show the first glow peak between 92-103 degrees C, while the second main peak was observed at 183 degrees C for the undoped NaCl and at 148 and 165 degrees C for the NaCl:Mn and NaCl-KCl:Mn, respectively. The main peak was slowly bleaching when the irradiated sample was illuminated with F (470 nm) light. Optical bleaching confirms that the F center has an important participation in the thermoluminescent response. The glow curves structure from the thermal bleaching suggests the participation of different kind of traps. Also, the kinetics parameters such as activation energy (E), frequency factor (s) and the kinetic order (b) were investigated. (Author)

  17. "Dot COM", a nuclear transit center for the primary piRNA pathway in Drosophila.

    Science.gov (United States)

    Dennis, Cynthia; Zanni, Vanessa; Brasset, Emilie; Eymery, Angeline; Zhang, Liang; Mteirek, Rana; Jensen, Silke; Rong, Yikang S; Vaury, Chantal

    2013-01-01

    The piRNA pathway protects genomes by silencing mobile elements. Despite advances in understanding the processing events that generate piRNAs for silencing, little is known about how primary transcripts are transported from their genomic clusters to their processing centers. Using a model of the Drosophila COM/flamenco locus in ovarian somatic cells, we identified a prominent nuclear structure called Dot COM, which is enriched in long transcripts from piRNA clusters but located far from their transcription sites. Remarkably, transcripts from multiple clusters accumulate at Dot COM, which is often juxtaposed with Yb-bodies, the cytoplasmic processing centers for cluster transcripts. Genetic evidence suggests that the accumulation of precursor transcripts at Dot COM represents one of the most upstream events in the piRNA pathway. Our results provide new insights into the initial steps of the piRNA pathway, and open up a new research area important for a complete understanding of this conserved pathway. PMID:24039799

  18. Binding energy and optical properties of an off-center hydrogenic donor impurity in a spherical quantum dot placed at the center of a cylindrical nano-wire

    International Nuclear Information System (INIS)

    The binding energy as well as the linear, third-order nonlinear and total optical absorption coefficient and refractive index changes of an off-center hydrogenic donor impurity in an InAs spherical quantum dot placed at the center of a GaAs cylindrical nano-wire have been investigated. In this regard, the effective-mass approximation approach is considered and eigenvalues and corresponding eigenfunctions are calculated via the finite element method. The binding energy is plotted as a function of the dot size and impurity position along with optical properties as a function of photon energy. In this study two different directions have been considered for impurity position, along the nano-wire axis and perpendicular to it. It has been found that the binding energy, absorption coefficient and refractive index changes are impressively affected not only by the dot radius but also by the position of the impurity and its direction. Additionally, the optical saturation can be tuned by the direction of the impurity and incident optical intensity. -- Highlights: • We consider spherical quantum dot located at the center of a cylindrical nano-wire. • An off-center hydrogenic donor impurity is considered in the system. • Binding energy is affected by orientation of impurity and its distance from center. • Saturation depends on the orientation of impurity position. • By shifting impurity position, orientation and dot radius blue- and red-shifts appear

  19. Assessing the occurrence of the dibromide radical (Br{sub 2}{sup -{center_dot}}) in natural waters: Measures of triplet-sensitised formation, reactivity, and modelling

    Energy Technology Data Exchange (ETDEWEB)

    De Laurentiis, Elisa; Minella, Marco; Maurino, Valter; Minero, Claudio [Universita degli Studi di Torino, Dipartimento di Chimica, Via P. Giuria 5, 10125 Torino (Italy); Mailhot, Gilles; Sarakha, Mohamed [Clermont Universite, Universite Blaise Pascal, Institut de Chimie de Clermont-Ferrand, BP 10448, F-63000 Clermont-Ferrand (France); CNRS, UMR 6296, ICCF, F-63171 Aubiere (France); Brigante, Marcello, E-mail: marcello.brigante@univ-bpclermont.fr [Clermont Universite, Universite Blaise Pascal, Institut de Chimie de Clermont-Ferrand, BP 10448, F-63000 Clermont-Ferrand (France); CNRS, UMR 6296, ICCF, F-63171 Aubiere (France); Vione, Davide, E-mail: davide.vione@unito.it [Universita degli Studi di Torino, Dipartimento di Chimica, Via P. Giuria 5, 10125 Torino (Italy); Universita degli Studi di Torino, Centro Interdipartimentale NatRisk, Via Leonardo da Vinci 44, 10095 Grugliasco (Italy)

    2012-11-15

    The triplet state of anthraquinone-2-sulphonate (AQ2S) is able to oxidise bromide to Br{sup {center_dot}}/Br{sub 2}{sup -{center_dot}}, with rate constant (2-4) Dot-Operator 10{sup 9} M{sup -1} s{sup -1} that depends on the pH. Similar processes are expected to take place between bromide and the triplet states of naturally occurring chromophoric dissolved organic matter ({sup 3}CDOM*). The brominating agent Br{sub 2}{sup -{center_dot}} could thus be formed in natural waters upon oxidation of bromide by both {sup {center_dot}}OH and {sup 3}CDOM*. Br{sub 2}{sup -{center_dot}} would be consumed by disproportionation into bromide and bromine, as well as upon reaction with nitrite and most notably with dissolved organic matter (DOM). By using the laser flash photolysis technique, and phenol as model organic molecule, a second-order reaction rate constant of {approx} 3 Dot-Operator 10{sup 2} L (mg C){sup -1} s{sup -1} was measured between Br{sub 2}{sup -{center_dot}} and DOM. It was thus possible to model the formation and reactivity of Br{sub 2}{sup -{center_dot}} in natural waters, assessing the steady-state [Br{sub 2}{sup -{center_dot}}] Almost-Equal-To 10{sup -13}-10{sup -12} M. It is concluded that bromide oxidation by {sup 3}CDOM* would be significant compared to oxidation by {sup {center_dot}}OH. The {sup 3}CDOM*-mediated process would prevail in DOM-rich and bromide-rich environments, the latter because elevated bromide would completely scavenge {sup {center_dot}}OH. Under such conditions, {sup {center_dot}}OH-assisted formation of Br{sub 2}{sup -{center_dot}} would be limited by the formation rate of the hydroxyl radical. In contrast, the formation rate of {sup 3}CDOM* is much higher compared to that of {sup {center_dot}}OH in most surface waters and would provide a large {sup 3}CDOM* reservoir for bromide to react with. A further issue is that nitrite oxidation by Br{sub 2}{sup -{center_dot}} could be an important source of the nitrating agent {sup {center_dot

  20. Low-mass lepton pair production in Pb-Au collisions at 40 A center dot GeV

    CERN Document Server

    Adamova, D; Appelshäuser, H; Belaga, V; Braun-Munzinger, P; Cherlin, A; Damjanovic, S; Dietel, T; Dietrich, L; Drees, A; Esumi, S I; Filimonov, K; Fomenko, K; Fraenkel, Zeev; Garabatos, C; Glässel, P; Hering, G; Holeczek, J; Kushpil, V; Lenkeit, B C; Maas, A; Marin, A; Milosevic, J; Milov, A; Miskowiec, D; Panebratsev, Yu A; Petchenova, O Yu; Petrácek, V; Pfeiffer, A; Rak, J; Ravinovich, I; Rehak, P; Richter, M; Sako, H; Schmitz, W; Schükraft, Jürgen; Sedykh, S; Seipp, W; Shimansky, S S; Slívova, J; Specht, H J; Stachel, J; Sumbera, M; Tilsner, H; Tserruya, Itzhak; Wessels, J P; Wienold, T; Windelband, B; Wurm, J P; Xie, W; Yurevich, S; Yurevich, V

    2003-01-01

    The CERES/NA45 experiment at the CERN SPS has previously measured e **+e**- pair production in 160 A center dot GeV Pb-Au collisions. In the mass region m greater than 0.2 GeV/c**2, an enhancement of 2.7 plus or minus 0.4(stat.) plus or minus 0.5(syst.) compared to the expectation from known hadronic decay sources was observed. In the 40 A center dot GeV data taken in 1999, an enhancement is again found; a preliminary analysis gives an even larger value of 5.0 plus or minus 1.3(stat.). The results are compared to theoretical model calculations based on pi**+ pi**- annihilation with a modified rho- propagator; they may be related to chiral symmetry restoration. 17 Refs.

  1. Formation of Cu-related emission centers under thermal doping of ZnS powders with CuCl and CuCl2

    International Nuclear Information System (INIS)

    The photoluminescence (PL), PL excitation and electron paramagnetic resonance spectra of powderlike ZnS doped with Cu from CuCl and CuCl2 compounds at 800 °C with restricted access of atmospheric air or in He flow were investigated. It is shown that the contribution of blue and green PL bands to PL spectra depends on the compounds used for doping and on the annealing conditions. The appearance of Cu clusters on the surface of ZnS microcrystals for both doping compounds is found. These clusters manifest themselves in the presence of broad line in electron paramagnetic resonance spectra and are the additional source for the doping of ZnS powder. The chemical reactions upon doping are analyzed. It is shown that these reactions control the concentration of the recombination centers responsible for blue and green PL bands and are also the reason of Cu clusters appearance. Under annealing in He flow when volatile components are removed by flowing gas, the dominant process can be the doping of ZnS from Cu clusters. This allows obtaining the blue band mainly. The localization of recombination centers responsible for blue and green emissions is discussed. - Highlights: • ZnS powder doped from CuCl and CuCl2 under different conditions was investigated. • The doping from different compounds results in the different ratio of B- and G-centers concentration. • The chemical reactions in the charge control the B- and G-center formation. • Under annealing in He flow the dominant process can be ZnS doping from Cu clusters

  2. Holes resonant tunneling through double-barrier structure with InAs quantum dots in the center of the GaAs quantum well

    International Nuclear Information System (INIS)

    The influence of InAs quantum dots grown in the center of GaAs quantum well on the tunnel characteristics of the resonant-tunnel diodes based on the p-type AlAs/GaAs/AlAs heterostructure is investigated. The introduction of quantum dots results in the shift and the diffusion of resonant peaks of the volt-ampere characteristics of diodes. However this effect essentially depends on the number of the 2D-subband involving into tunneling. The causes of such dependence are qualitatively explained by generation of the fluctuation potential in the vicinity of the quantum dots layer

  3. Ternary Isothermal Diffusion Coefficients of NaCl-MgCl2-H2O at 25 C. 7. Seawater Composition

    Energy Technology Data Exchange (ETDEWEB)

    Miller, D G; Lee, C M; Rard, J A

    2007-02-12

    The four diffusion coefficients D{sub ij} of the ternary system NaCl-MgCl{sub 2}-H{sub 2}O at the simplified seawater composition 0.48877 mol {center_dot} dm{sup -3} NaCl and 0.05110 mol {center_dot} dm{sup -3} MgCl{sub 2} have been remeasured at 25 C. The diffusion coefficients were obtained using both Gouy and Rayleigh interferometry with the highly precise Gosting diffusiometer. The results, which should be identical in principle, are essentially the same within or very close to their combined 'realistic' errors. This system has a cross-term D{sub 12} that is larger than the D{sub 22} main-term, where subscript 1 denotes NaCl and 2 denotes MgCl{sub 2}. The results are compared with earlier, less-precise measurements. Recommended values for this system are (D{sub 11}){sub V} = 1.432 x 10{sup -9} m{sup 2} {center_dot} sec{sup -1}, (D{sub 12}){sub V} = 0.750 x 10{sup -9} m{sup 2} {center_dot} sec{sup -1}, (D{sub 21}){sub V} = 0.0185 x 10{sup -9} m{sup 2} {center_dot} sec{sup -1}, and (D{sub 22}){sub V} = 0.728 x 10{sup -9} m{sup 2} {center_dot} sec{sup -1}.

  4. Optical excitation in doped quasi-one-dimensional antiferromagnet (CsMnCl3 centre dot 2H2O+Cu2+)

    International Nuclear Information System (INIS)

    In the wide range of wavelengths and temperatures, the spectra of light absorption and luminescence excitation as well as the emission decay kinetics of a quasi-one-dimensional dielectric crystal CsMnCl3 centre dot 2H2O doped with copper ions (molar concentration 0-3%) are studied. The conclusion is made of the exchange of electronic excitation energy being possible between the matrix and dopant subsystems only in the lowest excited state due to migration of excitation and their trapping by excitation traps of the copper origin. From the analysis of the shape of decay kinetics curves of the matrix luminescence of the crystal, the values of hopping (along the chains of manganese ions) and trapping rates of magnetic excitons are determined

  5. AB INITIO STUDY OF THE POSSIBLE SINGLE-CENTER UNITS FOR BINUCLEAR IRON COMPLEX [Fe2(bpym3Cl4

    Directory of Open Access Journals (Sweden)

    Tihonovschi Andrei

    2008-12-01

    Full Text Available In present work we study two possible single-center units for binuclear iron complex Fe2(bpym3Cl4 –[Fe(bpym3]2+ and Fe(bpym2Cl2. The obtained ground states for both studied systems are singlet states. In the case of Fe(bpym2Cl2 the lowest excited states were calculated to be 240cm-1 (triplet and 660cm-1 (quintet above the ground state and so are placed according to Lande rule. These states could be populated at room temperatures. For [Fe(bpym3]2+ first excited state was found to be about 6000cm-1 above the ground state and so cannot be populated at normal temperatures.

  6. Temperature-Dependent Exciton and Trap-Related Photoluminescence of CdTe Quantum Dots Embedded in a NaCl Matrix: Implication in Thermometry.

    Science.gov (United States)

    Kalytchuk, Sergii; Zhovtiuk, Olga; Kershaw, Stephen V; Zbořil, Radek; Rogach, Andrey L

    2016-01-27

    Temperature-dependent optical studies of semiconductor quantum dots (QDs) are fundamentally important for a variety of sensing and imaging applications. The steady-state and time-resolved photoluminescence properties of CdTe QDs in the size range from 2.3 to 3.1 nm embedded into a protective matrix of NaCl are studied as a function of temperature from 80 to 360 K. The temperature coefficient is found to be strongly dependent on QD size, with the highest sensitivity obtained for the smallest size of QDs. The emission from solid-state CdTe QD-based powders is maintained with high color purity over a wide range of temperatures. Photoluminescence lifetime data suggest that temperature dependence of the intrinsic radiative lifetime in CdTe QDs is rather weak, and it is mostly the temperature-dependent nonradiative decay of CdTe QDs which is responsible for the thermal quenching of photoluminescence intensity. By virtue of the temperature-dependent photoluminescence behavior, high color purity, photostability, and high photoluminescence quantum yield (26%-37% in the solid state), CdTe QDs embedded in NaCl matrices are useful solid-state probes for thermal imaging and sensing over a wide range of temperatures within a number of detection schemes and outstanding sensitivity, such as luminescence thermochromic imaging, ratiometric luminescence, and luminescence lifetime thermal sensing. PMID:26618345

  7. Time-resolved photoluminescence of type-II quantum dots and isoelectronic centers in Zn-Se-Te superlattice structures

    Science.gov (United States)

    Cheung, M. C.-K.; Cartwright, A. N.; Sellers, I. R.; McCombe, B. D.; Kuskovsky, I. L.

    2008-01-01

    Spectrally and time-resolved photoluminescence of a ZnTe /ZnSe superlattice reveals a smooth transition of the photoluminescence (PL) lifetime from ˜100ns at 2.35eV to less than a few nanoseconds at 2.8eV. The significant increase of the lifetime in the low energy region is strong evidence to support the formation of type-II quantum dots (QDs), since in these nanostructures the spatial separation of carriers is increased. The shorter lived emission above 2.5eV is attributed to excitons bound to Te isoelectronic centers in the ZnSe matrix. The smooth transition of the PL lifetime confirms that clusters of these Te atoms evolve into type-II ZnTe /ZnSe QDs.

  8. Solution and single crystal spectroscopic characterization of (PPh4)(2)[Fe(CN)(5)(imidazole)]center dot 2H(2)O

    NARCIS (Netherlands)

    Tchouka, Heloise; Meetsma, Auke; Molnar, Gabor; Rechignat, Lionel; Browne, Wesley R.

    2011-01-01

    The compound (PPh4)(2)[Fe-III(CN)(5)(im)]center dot 2H(2)O (1) together with its C-13 labeled analogue have been synthesized (where im is imidazole) and characterized by UV/Vis, LD, IR, Raman and resonance Raman spectroscopy both in solution, powder and single crystalline form. The low spin state of

  9. A administração clássica: um estudo aplicado a centrais de atendimento (call center

    Directory of Open Access Journals (Sweden)

    Jairo Moran Carvalho Ribeiro

    2015-04-01

    Full Text Available As organizações modernas, a exemplo de operações de centrais de atendimento, ou call centers, tem atuado em diversas áreas de negócios, que pode ser do simples atendimento, como os serviços de atendimento a clientes - SAC, a grandes empresas com foco em cobrança, televendas ou operações diversas. Assim, a pesquisa buscou apresentar evidências do emprego das teorias clássicas da administração, através de estudo de casos, em dois Call Centers de empresas do Rio Grande do Sul vinculados à rede varejista de eletroeletrônicos e a distribuidora de energia elétrica. Embora, a natureza de atuação diversa entre as duas centrais analisadas, os princípios clássicos da administração se mostraram evidenciados em ambas as operações, a exemplo da racionalização do trabalho, controle das atividades, supervisão atuante, jornadas definidas, prêmios por produção, dentre outros elementos característicos dos princípios defendidos por Taylor, Fayol, Ford entre outros clássicos da administração.

  10. 75 FR 37994 - Airworthiness Directives; Bombardier, Inc. Model CL-600-1A11 (CL-600), CL-600-2A12 (CL-601), CL...

    Science.gov (United States)

    2010-07-01

    ... FR 6862). That NPRM proposed to correct an unsafe condition for the specified products. The MCAI... ``significant rule'' under the DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and 3..., Inc. Model CL-600-1A11 (CL- 600), CL-600-2A12 (CL-601), CL-600-2B16 (CL-601-3A, CL-601-3R, and CL-...

  11. Thermodynamic properties of potassium nitrate-magnesium nitrate compound [2KNO{sub 3}{center_dot}Mg(NO{sub 3}){sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Reddy, Ramana G., E-mail: rreddy@eng.ua.edu [Department of Metallurgical and Materials Engineering, The University of Alabama, Tuscaloosa, AL 35487-0202 (United States); Wang, Tao; Mantha, Divakar [Department of Metallurgical and Materials Engineering, The University of Alabama, Tuscaloosa, AL 35487-0202 (United States)

    2012-03-10

    Highlights: Black-Right-Pointing-Pointer Thermodynamic properties of 2KNO{sub 3}{center_dot}Mg(NO{sub 3}){sub 2} compound were experimentally determined. Black-Right-Pointing-Pointer The 2KNO{sub 3}{center_dot}Mg(NO{sub 3}){sub 2} compound melting point and heat capacity were determined. Black-Right-Pointing-Pointer The enthalpies of transitions were determined. Black-Right-Pointing-Pointer The enthalpy, entropy and Gibbs energies as function of temperature were reduced. - Abstract: The Mg(NO{sub 3}){sub 2}-KNO{sub 3} binary system phase diagram has a congruent melting compound, 2KNO{sub 3}{center_dot}Mg(NO{sub 3}){sub 2}. The thermodynamic properties for this compound are not available in the literature. In this study, the nitrate compound was synthesized and the melting point and heat capacity were determined using differential scanning calorimetry (DSC). Two endothermic peaks were observed at 404.8 K and 468.83 K corresponding to solid state transition and melting of the compound with the enthalpies of transitions as 2.71 kJ/mol and 20.73 kJ/mol, respectively. The heat capacity data as function of temperature are fit to polynomial function and thermodynamic properties like enthalpy, entropy and Gibbs energies of the compound as function of temperature are subsequently deduced.

  12. Reaction of sulphate radical anion (SO{sub 4}{sup {center_dot}}{sup -}) with cyanuric acid. A potential reaction for its degradation?

    Energy Technology Data Exchange (ETDEWEB)

    Manoj, P.; Varghese, R.; Manoj, V.M.; Aravindakumar, C.T. [Mahatma Gandhi University, School of Chemical Sciences, Kottayam (India)

    2002-01-01

    A novel reaction between sulfate radical anion (SO{sub 4}{sup {center_dot}}{sup -}) and cyanuric acid (CA), a non-degradable end product of the oxidative degradation of the triazine based herbicide, atrazine, is presented using laser flash photolysis and steady state radiolysis techniques at pH 5. A second order rate constant of 1.9x10{sup 7} dm{sup 3} mol{sup -1} s{sup -1} has been determined and the transient intermediate ({lambda}{sub max}=330 nm) is assigned to a radical cation of CA (CA{sup {center_dot}}{sup +}). The degradation profile indicated that about 76% of CA have been decomposed after an absorbed {gamma}-radiation dose of 18 kGy. It is therefore proposed that the reaction of SO{sub 4}{sup {center_dot}}{sup -} could be utilised for the degradation of CA in aqueous medium which is normally stable to any Advanced Oxidation Processes. (author)

  13. Synthesis and photoluminescence properties of aqueous CdWO4 quantum dots with WO66- luminescence center

    International Nuclear Information System (INIS)

    Aqueous CdWO4 QDs were synthesized by the reaction of CdCl2 and Na2WO4 in the presence of mercaptoacetic acid (TGA) as capping reagent. The crystal morphology, particle size and its distribution of as-prepared products were characterized by transmission electron microscopy (TEM, SAED) atomic force microscopy (AFM), high-resolution transmission electron microscopy (HRTEM), and photon correlation spectroscopy (PCS), respectively. Qualitative assays for functional groups on the QDs' surface were measured by fourier transform infrared spectroscopy (FTIR). Photoluminescence properties of QDs were studied by photoluminescence spectroscopy (PL). The results showed that the single QD with diameter of about 8 ± 2 nm was single-crystal. The particle size distribution of QDs was normal. Infrared absorption bands of carboxylic group on the surface of CdWO4 QDs were observed around 1610-1550 cm-1 (nonsymmetrical vibration of -COO-) and 1400 cm-1 (symmetric vibration of C-O). With reaction-time going, PL peak position shifted from 498 to 549 nm and intensity of PL increased first and then decreased. PL peak position of QDs was blue-shift compared with 570 nm WO66- luminescence center of bulk CdWO4.

  14. Targeting the environmental assessment of veterinary drugs with the multi-species-soil system (MS{center_dot}3) agricultural soil microcosms: the ivermectin case study

    Energy Technology Data Exchange (ETDEWEB)

    Carbonell-Martin, G.; Pro-Gonzalez, J.; Aragones-Grunert, P.; Babib-Vich, M. M.; Fernandez-Rorija, C.; Tarazona-Lafarga, J. V.

    2011-07-01

    The environmental risk assessment of the veterinary pharmaceutical ivermectin is receiving significant attention. This paper assesses the capacity of the MS{center_dot}3 soil microcosm as a tool for targeting the environmental impact assessment of veterinary drugs, using ivermectin as model. Two screening MS{center_dot}3 were performed using different European soils; one with a soil collected in an agricultural station near to Madrid, Spain and a second with a soil collected in a farm area close to York, UK. Soils were fortified with ivermectin at the following ranges: 0.01-10 mg kg{sup -}1 and 0.1-100 mg kg{sup -}1 in the Madrid and York studies, respectively. The effects on earthworms, plants and soil microorganisms were assessed in the Madrid soil. Toxicity tests on aquatic organisms (algae, cladocerans and in vitro fish cell line RTLW1) were also conducted with the leachates. No effects were observed in earthworms and plants at any tested concentration; reduction in the respiration rate (< 5%) of soil microorganisms was detected. Earthworm/soil bioconcentration factors decreased with the increase in soil concentrations and were higher for the York soil. Effects on daphnids were observed in tested leachates; based on measured levels of ivermectin in the leachates an EC50 of about 0.5{mu}gL{sup -}1 can be estimated. Comparisons based on toxicity data and equilibrium partitioning confirmed that the main risk is expected to be related to the high sensitivity of cladocerans. The results confirm that MS{center_dot}3 systems are cost-effective tools for assessing the impact of veterinary pharmaceuticals when applied to agricultural land, as previously demonstrated for antimicrobials. (Author) 39 refs.

  15. 76 FR 59067 - Airworthiness Directives; Bombardier, Inc. Model CL-600-2B16 (CL-601-3A, CL-601-3R, and CL-604...

    Science.gov (United States)

    2011-09-23

    ... ``significant rule'' under the DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and 3.... Model CL-600-2B16 (CL- 601-3A, CL-601-3R, and CL-604 Variants) Airplanes AGENCY: Federal Aviation...) events have occurred where the Air-Driven Generator (ADG) failed to provide power on CL-600-2B19...

  16. Single to quadruple quantum dots with tunable tunnel couplings

    Energy Technology Data Exchange (ETDEWEB)

    Takakura, T.; Noiri, A.; Obata, T.; Yoneda, J.; Yoshida, K. [Department of Applied Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Otsuka, T.; Tarucha, S. [Department of Applied Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); RIKEN, Center for Emergent Matter Science, 3-1 Wako-shi, Saitama 351-0198 (Japan)

    2014-03-17

    We prepare a gate-defined quadruple quantum dot to study the gate-tunability of single to quadruple quantum dots with finite inter-dot tunnel couplings. The measured charging energies of various double dots suggest that the dot size is governed by the gate geometry. For the triple and quadruple dots, we study the gate-tunable inter-dot tunnel couplings. For the triple dot, we find that the effective tunnel coupling between side dots significantly depends on the alignment of the center dot potential. These results imply that the present quadruple dot has a gate performance relevant for implementing spin-based four-qubits with controllable exchange couplings.

  17. Study on the distribution of active centers in novel low Ti-loading MgCl2-supported Ziegler-Natta catalyst

    Institute of Scientific and Technical Information of China (English)

    王剑峰; 王立; 赵振荣; 王文钦; 陈涛

    2004-01-01

    Novel MgCl2-supported Ziegler-Natta (Z-N) catalysts prepared using a new one-pot ball milling method can effectively control the amounts of Ti-loading in the catalysts. Complex GPC data on polypropylene synthesized by these novel catalysts were analyzed using the method of fitting the molecular weight distribution (MWD) curves with a multiple Flory-Schulz function. It was found that multiple active centers exist in these novel catalysts. Detailed study of the effects of the Ti-loadings in the catalysts on the distribution of the active centers showed that the Ti-loadings in the novel MgCl2-supported Z-N catalysts might affect the proportion of each type of active centers; and might be the main factor responsible for the effect of the Ti-loadings on the microstructure, the molecular weight and molecular weight distribution width of the resultant polymer, the catalytic activity and polymerization kinetics.

  18. Formation of the center of ignition in a CH3Cl-Cl2 mixture under the action of UV light

    Science.gov (United States)

    Begishev, I. R.; Belikov, A. K.; Komrakov, P. V.; Nikitin, I. S.

    2016-07-01

    The dependence of temperature on time is investigated using a microthermocouple at different distances from a UV light source in a mixture of chlorine and chloromethane. These relationships give an idea of the size and location of a center of photoignition. It is found that if the size of the reaction vessel in the direction of the luminous flux is much greater than the dimensions of the ignition center, the thermal expansion of a reacting gas mixture has a huge impact on such photoignition parameters as the critical concentration limits and the critical intensity of UV radiation. It is found that by increasing the length of the vessel, some chlorinated combustible mixtures lose the ability to ignite when exposed to UV light.

  19. 76 FR 41653 - Airworthiness Directives; Bombardier, Inc. Model CL-600-2A12 (CL-601) and CL-600-2B16 (CL-601-3A...

    Science.gov (United States)

    2011-07-15

    ... products. That NPRM was published in the Federal Register on January 5, 2011 (76 FR 477). That NPRM...; 2. Is not a ``significant rule'' under the DOT Regulatory Policies and Procedures (44 FR 11034.... Model CL-600-2A12 (CL- 601) and CL-600-2B16 (CL-601-3A, CL-601-3R, and CL-604 Variants) Airplanes...

  20. Silica-supported (nBuCp)2ZrCl2: Effect of catalyst active center distribution on ethylene-1-hexene copolymerization

    KAUST Repository

    Atiqullah, Muhammad

    2013-08-12

    Metallocenes are a modern innovation in polyolefin catalysis research. Therefore, two supported metallocene catalysts-silica/MAO/(nBuCp)2ZrCl2 (Catalyst 1) and silica/nBuSnCl3/MAO/(nBuCp)2ZrCl2 (Catalyst 2), where MAO is methylaluminoxane-were synthesized, and subsequently used to prepare, without separate feeding of MAO, ethylene-1-hexene Copolymer 1 and Copolymer 2, respectively. Fouling-free copolymerization, catalyst kinetic stability and production of free-flowing polymer particles (replicating the catalyst particle size distribution) confirmed the occurrence of heterogeneous catalysis. The catalyst active center distribution was modeled by deconvoluting the measured molecular weight distribution and copolymer composition distribution. Five different active center types were predicted for each catalyst, which was corroborated by successive self-nucleation and annealing experiments, as well as by an extended X-ray absorption fine structure spectroscopy report published in the literature. Hence, metallocenes impregnated particularly on an MAO-pretreated support may be rightly envisioned to comprise an ensemble of isolated single sites that have varying coordination environments. This study shows how the active center distribution and the design of supported MAO anions affect copolymerization activity, polymerization mechanism and the resulting polymer microstructures. Catalyst 2 showed less copolymerization activity than Catalyst 1. Strong chain transfer and positive co-monomer effect-both by 1-hexene-were common. Each copolymer demonstrated vinyl, vinylidene and trans-vinylene end groups, and compositional heterogeneity. All these findings were explained, as appropriate, considering the modeled active center distribution, MAO cage structure repeat units, proposed catalyst surface chemistry, segregation effects and the literature that concerns and supports this study. While doing so, new insights were obtained. Additionally, future research, along the direction

  1. Studies on the Local Angular Distortion and Spin Hamiltonian Parameters for the Trigonal Co2+ Center in MgCl2

    Science.gov (United States)

    Hu, Xian-Fen; Wu, Shao-Yi; Kuang, Min-Quan; Li, Guo-Liang

    2014-11-01

    The local angular distortion and spin Hamiltonian parameters (g factors g||, g⊥ and the hyperfine structure constants) for the trigonal Co2+ center in MgCl2 are theoretically studied by diagonalizing the 6×6 energy matrix of ground 4T1 state for a trigonally distorted octahedral 3d7 cluster. Based on the cluster approach, the contributions from the admixtures of various J (= 1/2;3/2;5/2) states and the ligand orbital and spin-orbit coupling interactions are taken into account in a uniform way. The local impurity-ligand bond angle in the Co2+ center is found to be about 3.44° larger than the host metal-ligand bond angle in the pure crystal due to substitution of smaller Mg2+ by bigger Co2+, inducing a further compressed ligand octahedron. The calculated spin Hamiltonian parameters using the above local angular distortion are in good agreement with the experimental data. The present studies on the local structure and the spin Hamiltonian parameters for Co2+ in MgCl2 are tentatively extended to a more general case by comparing the relevant impurity behaviours for Co2+ in various trigonal environments.

  2. 75 FR 59071 - Airworthiness Directives; Bombardier, Inc. Model CL-600-2B16 (CL-604 Variants (Including CL-605...

    Science.gov (United States)

    2010-09-27

    ... in the Federal Register on June 2, 2010 (75 FR 30740). That NPRM proposed to correct an unsafe...'' under the DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and 3. Will not have.... Model CL-600-2B16 (CL- 604 Variants (Including CL-605 Marketing Variant)) Airplanes AGENCY:...

  3. Effects of Supported ( n BuCp) 2 ZrCl 2 Catalyst Active-Center Distribution on Ethylene–1-Hexene Copolymer Backbone Heterogeneity and Thermal Behaviors

    KAUST Repository

    Atiqullah, Muhammad

    2013-07-10

    Two catalysts, denoted as catalyst 1 [silica/MAO/(nBuCp) 2ZrCl2] and catalyst 2 [silica/nBuSnCl 3/MAO/(nBuCp)2ZrCl2] were synthesized and subsequently used to prepare, without separate feeding of methylaluminoxane (MAO), ethylene homopolymer 1 and homopolymer 2, respectively, and ethylene-1-hexene copolymer 1 and copolymer 2, respectively. Gel permeation chromatography (GPC), Crystaf, differential scanning calorimetry (DSC) [conventional and successive self-nucleation and annealing (SSA)], and 13C nuclear magnetic resonance (NMR) polymer characterization results were used, as appropriate, to model the catalyst active-center distribution, ethylene sequence (equilibrium crystal) distribution, and lamellar thickness distribution (both continuous and discrete). Five different types of active centers were predicted in each catalyst, as corroborated by the SSA experiments and complemented by an extended X-ray absorption fine structure (EXAFS) report published in the literature. 13C NMR spectroscopy also supported this active-center multiplicity. Models combined with experiments effectively illustrated how and why the active-center distribution and the variance in the design of the supported MAO anion, having different electronic and steric effects and coordination environments, influence the concerned copolymerization mechanism and polymer properties, including inter- and intrachain compositional heterogeneity and thermal behaviors. Copolymerization occurred according to the first-order Markovian terminal model, producing fairly random copolymers with minor skewedness toward blocky character. For each copolymer, the theoretical most probable ethylene sequences, nE MPDSC-GT and n E MPNMR-Flory, as well as the weight-average lamellar thicknesses, Lwav DSC-GT and Lwav SSA DSC, were found to be comparable. To the best of our knowledge, such a match has not previously been reported. The percentage crystallinities of the homo- and copolymers increased linearly as a function of

  4. Magnetic susceptibility of Co sup 2 sup + pairs in [Co sub 2 (ox)tpmc](ClO sub 4) sub 2 centre dot 3H sub 2 O cluster complex

    CERN Document Server

    Spasojevic, V; Sovilj, S P; Mrozinski, J

    2000-01-01

    Calculation of the magnetic susceptibility of Co sup 2 sup + pairs in the recently synthesized cobaltous cluster complex [Co sub 2 (ox)tpmc](ClO sub 4) sub 2 centre dot 3H sub 2 O has been conducted by the use of two different theoretical models. The calculated results were compared to the experimental data collected in a wide temperature region. Conclusions on both the magnetic properties of Co sup 2 sup + dimers and the validity of the proposed models have been drawn. In the temperature region above chi(T) maximum, the best results are obtained with the Heisenberg model that includes spin-orbit coupling and excited single-ion levels. In the low-temperature region anisotropy of the magnetic properties dominates and Ising dimer ground-state model gives a more appropriate description. Obtained g-values (g sub p sub a sub r sub a sub l sub l sub e sub l a=5.67, g sub p sub a sub r sub a sub l sub l sub e sub l b=5.73, and g sub p sub e sub r sub p sub e sub n sub d sub i sub c sub u sub l sub a sub r =1.54) con...

  5. Effects of supported (nBuCp)2ZrCl2 catalyst active center multiplicity on crystallization kinetics of ethylene homo- and copolymers

    KAUST Repository

    Atiqullah, Muhammad

    2014-07-01

    Two different supported zirconocene, that is, bis(n-butylcyclopentadienyl) zirconium dichloride (nBuCp)2ZrCl2, catalysts were synthesized. Each catalyst was used to prepare one ethylene homopolymer and one ethylene-1-hexene copolymer. Catalyst active center multiplicity and polymer crystallization kinetics were modeled. Five separate active center types were predicted, which matched the successive self-nucleation and annealing (SSA) peak temperatures. The predicted crystallinity well matched the differential scanning calorimetric (DSC) values for a single Avrami-Erofeev index, which ranged between 2 and 3 for the polymers experimented. The estimated apparent crystallization activation energy Ea did not vary with cooling rates, relative crystallinity α, and crystallization time or temperature. Therefore, the concept of variable/instantaneous activation energy was not found to hold. Ea linearly increased with the weight average lamellar thickness Lwav DSC-GT; and for each homopolymer, it exceeded that of the corresponding copolymer. Higher Ea, hence slower crystallization, was identified as a pre-requisite to attain higher crystallinity. Crystallization parameters were correlated to polymer backbone parameters, which are influenced by catalyst active center multiplicity. © 2013 Taiwan Institute of Chemical Engineers.

  6. The relationship between the hardness and the point-defect-density in neutron-irradiated MgO{center_dot}3.0Al{sub 2}O{sub 3} and AlN

    Energy Technology Data Exchange (ETDEWEB)

    Suematsu, H.; Yatsui, K. [Nagaoka Univ. of Technology, Extreme Energy-Density Research Institute, Nagaoka, Niigata (Japan); Yano, T. [Tokyo Institute of Technology, Research Laboratory for Nuclear Reactors, Tokyo (Japan)

    2001-09-01

    MgO{center_dot}3.0Al{sub 2}O{sub 3} single crystals and sintered AlN polycrystals were irradiated with fast neutrons in various conditions and the hardness of the irradiated and unirradiated samples was measured with a Vickers hardness tester. The hardness of as-irradiated MgO{center_dot}3.0Al{sub 2}O{sub 3} and AlN samples increased by 23 and 51%, respectively. After isochronal annealing, the hardness gradually decreased and mostly recovered to that of the unirradiated one up to 1400degC. Volume of the sample also increased after the irradiation and changed in the same way as the hardness by annealing. A relationship between the hardness and the density of point defects is proposed and the experimental results agree with the relationship. It implies that the point defects generated by the irradiation pin down dislocations and increase the hardness of neutron irradiated MgO{center_dot}3.0Al{sub 2}O{sub 3} samples. (author)

  7. Investigation of the structure and properties of K{sub 9}H{sub 7}(SO{sub 4}){sub 8} {center_dot} H{sub 2}O single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Makarova, I. P., E-mail: secr@ns.crys.ras.ru; Chernaya, T. S.; Grebenev, V. V.; Dolbinina, V. V.; Verin, I. A.; Simonov, A. A. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation)

    2011-11-15

    The features of the conductivity of K{sub 9}H{sub 7}(SO{sub 4}){sub 8} {center_dot} H{sub 2}O single-crystal samples in the temperature range of superprotonic phase transition have been investigated. The K{sub 9}H{sub 7}(SO{sub 4}){sub 8} {center_dot} H{sub 2}O crystal structure is determined and refined taking into account hydrogen atoms by X-ray diffraction analysis at a temperature of 295 K: monoclinic symmetry, sp. gr. P2{sub 1}/c, Z = 4, a = 7.059(1), b = 19.773(1), c = 23.449(1) Angstrom-Sign , {beta} = 95.33(1) Degree-Sign , R{sub 1}/wR{sub 2} = 2.71/1.71. The structural data obtained suggest that the occurrence of high conductivity in K{sub 9}H{sub 7}(SO{sub 4}){sub 8} {center_dot} H{sub 2}O crystals with an increase in temperature is related to the diffusion of crystallization water and motion of K ions, as well as to the transformation of the system of hydrogen bonds and protonic motion. The stabilization of the high-temperature superprotonic phase and its supercooling to low temperatures are due to the presence of channels for the motion of K ions and slow backward diffusion of water in the crystal.

  8. Organically-Templated Zinc Hydrogen Phosphites: Syntheses, Structures and Properties of {alpha}- and {Beta}-ZnHOP{sub 3}{center_dot}N{sub 4}C{sub 2}H{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    HARRISON,WILLIAM T.A.; PHILLIPS,MARK L.F.; STANCHFIELD,JESSE; NENOFF,TINA M.

    2000-07-14

    The syntheses, crystal structures and some properties of {alpha}- and {beta}-ZnHPO{sub 3}{center_dot}N{sub 4}C{sub 2}H{sub 4} are reported. These two polymorphs are the first organically-templated hydrogen phosphites. They are built up from vertex-sharing HPO{sub 3} pseudo pyramids and ZnO{sub 3}N tetrahedra, where the Zn-N bond represents a direct link between zinc and the neutral 2-cyanoguanidine template. {alpha}-ZnHPO{sub 3}{center_dot}N{sub 4}C{sub 2}H{sub 4} is built up from infinite layers of vertex-sharing ZnO{sub 3}N and HPO{sub 3} groups forming 4-rings and 8-rings. {beta}-ZnHPO{sub 3}{center_dot}N{sub 4}C{sub 2}H{sub 4} has strong one-dimensional character, with the polyhedral building units forming 4-ring ladders. Similarities and differences to related zinc phosphates are discussed. Crystal data: {alpha}-ZnHPO{sub 3}{center_dot}N{sub 4}C{sub 2}H{sub 4}, M{sub r} = 229.44, monoclinic, P2{sub 1}/c, a = 9.7718 (5) {angstrom}, b = 8.2503 (4) {angstrom}, c = 9.2491 (5) {angstrom}, {beta} = 104.146 (1){sup 0}, V = 723.1 (1) {angstrom}{sup 3}, R(F) = 2.33%, wR(F) = 2.52%. {beta}-ZnHPO{sub 3}{center_dot}N{sub 4}C{sub 2}H{sub 4}, M{sub r} = 229.44, monoclinic, C2/c, a = 14.5092 (9) {angstrom}, b = 10.5464 (6) {angstrom}, c = 10.3342 (6) {angstrom}, {beta} = 114.290 (1){sup 0}, V = 1441.4 (3) {angstrom}{sup 3}, R(F) = 3.01%, wR(F) = 3.40%.

  9. Structure and stability of a DNA triple helix in solution: NMR studies on d(T) sub 6 ter dot d(T) sub 6 and its complex with a minor groove binding drug

    Energy Technology Data Exchange (ETDEWEB)

    Umemoto, Kimiko; Sarma, Mukti H.; Gupta, Goutam; Luo, Jia; Sarma, Ramaswamy H. (State Univ. of New York, Albany (USA))

    1990-05-23

    The possibility of both Watson-Crick and Hoogsteen A{center dot}T pairs can result in a triple helical structure for d(T){sub 6}{center dot}d(A){sub 6}{center dot}d(T){sub 6} in solution. In the triple helix the Watson-Crick paired T strand can run antiparallel, while the Hoogsteen paired T strand can run parallel to the A strand. On the basis of 1D/2D NMR studies, we have characterized the structural properties of the triple helix in terms of (a) nature of H-bonding, (b) chain conformations and relative chain orientations, (c) location of triplets T{center dot}A{center dot}T with respect to the helix axis, and (d) effects of NaCl and MgCl{sub 2}. In addition, we experimentally demonstrate that a minor groove specific drug Dst2 (a distamycin analogue) can bind to the triple helix. We show that the nature of thermal transition is altered by Dst2 binding; i.e., the host triple helix shows triple {yields} coil (monophasic) transition in the absence of Dst2, while in its presence the helix shows a triplex {yields} duplex {yields} coil (biphasic) transition.

  10. Synthesis and photoluminescence properties of aqueous CdWO{sub 4} quantum dots with WO{sub 6}{sup 6-} luminescence center

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Guoxin, E-mail: zhangguoxin@sinap.ac.cn [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, 2019 JiaLuo Roud, Shanghai 201800 (China); Yang Sefei [Department of Stomatology, Chinese PLA General Hospital, Beijing 100853 (China); Li Zheng; Zhang Lan; Zhou Wei [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, 2019 JiaLuo Roud, Shanghai 201800 (China); Zhang Haiying [Department of Chemical Engineering, Shanghai Institute of Technology, Shanghai 200235 (China); Shen Hua; Wang Yongxian [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, 2019 JiaLuo Roud, Shanghai 201800 (China)

    2010-10-15

    Aqueous CdWO{sub 4} QDs were synthesized by the reaction of CdCl{sub 2} and Na{sub 2}WO{sub 4} in the presence of mercaptoacetic acid (TGA) as capping reagent. The crystal morphology, particle size and its distribution of as-prepared products were characterized by transmission electron microscopy (TEM, SAED) atomic force microscopy (AFM), high-resolution transmission electron microscopy (HRTEM), and photon correlation spectroscopy (PCS), respectively. Qualitative assays for functional groups on the QDs' surface were measured by fourier transform infrared spectroscopy (FTIR). Photoluminescence properties of QDs were studied by photoluminescence spectroscopy (PL). The results showed that the single QD with diameter of about 8 {+-} 2 nm was single-crystal. The particle size distribution of QDs was normal. Infrared absorption bands of carboxylic group on the surface of CdWO{sub 4} QDs were observed around 1610-1550 cm{sup -1} (nonsymmetrical vibration of -COO{sup -}) and 1400 cm{sup -1} (symmetric vibration of C-O). With reaction-time going, PL peak position shifted from 498 to 549 nm and intensity of PL increased first and then decreased. PL peak position of QDs was blue-shift compared with 570 nm WO{sub 6}{sup 6-} luminescence center of bulk CdWO{sub 4}.

  11. Training effects on peak (VO2)-O-center dot, specific of the mode of movement, in rehabilitation of patients with coronary artery disease

    NARCIS (Netherlands)

    Nieuwland, W; Berkhuysen, MA; Landsman, MLJ; Lie, KI; Rispens, P

    1998-01-01

    Training effects on peak oxygen consumption ((V) over dot O-2), specific to the mode of movement, are well-known in exercise training of young, healthy adults. However, these specific training effects were never studied in patients with coronary artery disease, but may be important in the evaluation

  12. Synthesis and characterization of hepta coordinated tin(IV) complexes. X-ray crystal structure of [{sup n}Bu{sub 2} Sn(dappt)]{center_dot}(Me{sub 2} CO){sub 0.5} [H{sub 2}dappt 2,6-diacetyl pyridine bis(4-phenyl thiosemicarbazone)

    Energy Technology Data Exchange (ETDEWEB)

    Sousa, Gerimario F. de; Deflon, Victor M. [Universidade de Brasilia (UnB), DF (Brazil). Inst. de Quimica; Niquet, Elke [Tuebingen Univ. (Germany). Inst. fuer Anorganische Chemie; Abras, Anuar [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte (Brazil). Dept. de Fisica

    2001-08-01

    The reactions of the 2,6-diacetyl pyridine bis(4-phenyl thiosemicarbazone) ligand, H{sub 2}dappt, with R{sub 4-m} SnX{sub m} (m = 2, 3; R = Me, {sup n}Bu, Ph and X = Cl) led to the formation of four new hepta coordinated organotin(IV) complexes, which were characterized by microanalyses and by IR and Moessbauer spectroscopies. The n-butyl derivative [{sup n}Bu{sub 2} Sn(dappt)]{center_dot}(Me{sub 2} CO){sub 0.5} was also analyzed by a single crystal X-ray diffraction study. It crystallized in the monoclinic system with a space group C 2/c, with a = 36.164(14), b 9.7050(15), c = 26.194(11) Angstrom, {beta} = 132.00(2) deg C, Z=8. The structure determination revealed a neutral complex of Sn(IV) in a distorted pentagonal bipyramidal (PBP) geometry, with the equatorial plane defined by the SNNNS donor system of the ligand and with the two n-butyl groups in the axial positions. Also, a correlation between Moessbauer and X-ray data based on the point-charge model is discussed. (author)

  13. Thermodynamic properties of LiNO{sub 3}-NaNO{sub 3}-KNO{sub 3}-2KNO{sub 3}{center_dot}Mg(NO{sub 3}){sub 2} system

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Tao; Mantha, Divakar [Department of Metallurgical and Materials Engineering, The University of Alabama, Tuscaloosa, AL 35487-0202 (United States); Reddy, Ramana G., E-mail: rreddy@eng.ua.edu [Department of Metallurgical and Materials Engineering, The University of Alabama, Tuscaloosa, AL 35487-0202 (United States)

    2013-01-10

    Highlights: Black-Right-Pointing-Pointer Novel LiNO{sub 3}-NaNO{sub 3}-KNO{sub 3}-2KNO{sub 3}{center_dot}Mg(NO{sub 3}){sub 2} quaternary system was developed. Black-Right-Pointing-Pointer The melting point of the salt mixture was determined. Black-Right-Pointing-Pointer The heat capacity of the salt mixture was determined. Black-Right-Pointing-Pointer The enthalpy, entropy and Gibbs energies as function of temperature were deduced. - Abstract: A novel low melting eutectic salt was predicted in the LiNO{sub 3}-NaNO{sub 3}-KNO{sub 3}-2KNO{sub 3}{center_dot}Mg(NO{sub 3}){sub 2} quaternary system using thermodynamic modeling. The melting point of the eutectic salt was predicted to be 374.90 K. Differential scanning calorimetry (DSC) was used to experimentally determine the melting point and specific heat capacity of the quaternary system. The mixture was measured to be completely melted at 373.90 {+-} 0.78 K which is in an excellent agreement with the predicted value. The measured heat capacity data as function of temperature are fit to polynomial function. Subsequently, the thermodynamic properties such as enthalpy, entropy and Gibbs energies of this novel quaternary eutectic salt were deduced as function of temperature.

  14. Temperature-induced changes in the single-crystal structure of K{sub 9}H{sub 7}(SO{sub 4}){sub 8} {center_dot} H{sub 2}O

    Energy Technology Data Exchange (ETDEWEB)

    Makarova, I. P., E-mail: makarova@crys.ras.ru; Grebenev, V. V.; Chernaya, T. S.; Verin, I. A.; Dolbinina, V. V. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation); Chernyshov, D. Yu. [European Synchrotron Radiation Facility (France); Koval' chuk, M. V. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation)

    2013-05-15

    Interest in superprotonic crystals of M{sub m}H{sub n}(XO{sub 4}){sub (m+n)/2} is associated with the solution to the fundamental problem of modern condensed matter physics: investigations of structural phase transitions and the stabilization of phases with high proton conductivity with the aim of designing new functional materials. The available data suggest that changes in the physical properties in these crystals can occur through different structural mechanisms. To reveal the structural conditionality for anomalies in the physical properties, the crystals of K{sub 9}H{sub 7}(SO{sub 4}){sub 8} {center_dot} H{sub 2}O were studied by X-ray diffraction in the temperature range of 25-463 K, and the crystal structure of the high-temperature phase was determined at 418 K (sp. gr. Pcan). The results of the study indicate that the occurrence of high conductivity in K{sub 9}H{sub 7}(SO{sub 4}){sub 8} {center_dot} H{sub 2}O crystals at high temperatures is associated with the diffusion of water of crystallization, the hydrogen-bond network rearrangement, and the motion of K ions. The hydrogen-bond rearrangement and the hindered back diffusion of water to the crystal stabilize the high-temperature phase and ensure its supercooling to low temperatures.

  15. Perfil de sujeitos de pesquisa clínica em um centro ambulatorial independente Profile of clinical research subjects in an independent outpatient center

    Directory of Open Access Journals (Sweden)

    Paulo Gustavo Sampaio Lacativa

    2008-06-01

    Full Text Available Este artigo tem como objetivos avaliar a qualidade de atendimento de um centro de pesquisa clínica e o entendimento do termo de consentimento informado (TCLE; determinar os motivos da participação e detalhar níveis socioeconômicos. Foi feito um estudo transversal em centro de pesquisa ambulatorial, através de questionário auto-explicativo. Dos cem questionários avaliados, todos os sujeitos de pesquisa consideraram o centro como ótimo (86% ou bom (9%. A quase totalidade foi bem informada do conteúdo do TCLE e o conhecimento do direito "confidencialidade", comum a todos os TCLEs, foi seis vezes maior que " acesso aos dados", que não faz parte. Os principais motivos para participarem foram para "saber mais sobre a sua saúde" (59% e para "beneficiar outras pessoas no futuro" (47%. A principal faixa de renda salarial dos participantes foi entre dois e cinco salários mínimos (48% e a maioria (66% concluiu pelo menos até a 4º série do ensino fundamental. A população possui o mesmo perfil econômico do Rio de Janeiro, nível de escolaridade suficiente para assinar e compreender o que está assinando, conhecendo não só a existência do TCLE, mas demonstrando conhecer seu conteúdo. O motivo principal para participação é para autobenefício e por atitude altruísta.This paper assesses the quality of assistance in a clinical trial outpatient center as well as the patients´understanding of the informed consent (IC; determine the reasons why they participate and detail socio-economic levels. A cross-sectional study was adopted in a clinical trial outpatient center using a self-explanatory questionnaire. All 100 respondents considered the assistance at the center excellent (86% or good (9%. Almost all of them were well informed about the content of the IC. Their knowledge about the right to "confidentiality", present in all ICs, was 6 times higher than their knowledge about their right to "access the results", generally not included

  16. Chemiluminescence behavior of the carbon dots and the reduced state carbon dots

    Energy Technology Data Exchange (ETDEWEB)

    Teng, Ping [Key Laboratory on Luminescence and Real-Time Analysis, Ministry of Education, College of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715 (China); Xie, Jianxin [College of Resources and Environment, Yuxi Normal University, Yuxi, Yunnan 653100 (China); Long, Yijuan; Huang, Xiaoxiao; Zhu, Rui; Wang, Xiliang; Liang, Liping [Key Laboratory on Luminescence and Real-Time Analysis, Ministry of Education, College of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715 (China); Huang, Yuming, E-mail: ymhuang@swu.edu.cn [Key Laboratory on Luminescence and Real-Time Analysis, Ministry of Education, College of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715 (China); Zheng, Huzhi, E-mail: zhenghz@swu.edu.cn [Key Laboratory on Luminescence and Real-Time Analysis, Ministry of Education, College of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715 (China)

    2014-02-15

    Potassium permanganate (KMnO{sub 4}) can react with two different carbon nanoparticles, i.e., carbon dots (CDs) and reduced state carbon dots (r-CDs), in a strong acid medium to generate chemiluminescence (CL). Furthermore, the different CL intensities and CL behaviors due to the different surface groups on these two kinds of carbon nanoparticles were confirmed. CL spectra, fluorescence spectra, UV–vis absorption spectra, and electron paramagnanetic resonance spectra were applied to investigate the CL mechanism. The main reaction pathways were proposed as follows: for the CL reaction between CDs and KMnO{sub 4}, the excited states of CDs (CDs{sup ⁎}) and Mn(II) (Mn(II){sup ⁎}) emerged as KMnO{sub 4} could inject holes into CDs, then, the CDs{sup ⁎} and Mn(II){sup ⁎} acted as luminophors to yield CL; in the r-CDs-KMnO{sub 4} system, r-CDs were oxidized by KMnO{sub 4} directly, and CDs{sup ⁎} and Mn(II){sup ⁎} were produced, at the same time, CL occurred. What is more interesting is that the CL intensity of the r-CD system is stronger than that of the CD system, which confirms that functional groups have strong effect on the CL behavior. It inspired us that new carbon nanoparticles with excellent luminous performance can be designed by tuning their surface groups. -- Highlights: • Carbon dots (CDs) and reduced state carbon dots (r-CDs) can react with potassium permanganate (KMnO{sub 4}) in a strong acid to generate chemiluminescence (CL). • With different surface groups, the CL intensity of r-CDs-KMnO{sub 4} system is different from that of CDs-KMnO{sub 4} system. • The CL mechanisms of the two systems were investigated.

  17. Activation of silicon quantum dots for emission

    Institute of Scientific and Technical Information of China (English)

    Huang Wei-Qi; Miao Xin-Jian; Huang Zhong-Mei; Liu Shi-Rong; Qin Chao-Jian

    2012-01-01

    The emission of silicon quantum dots is weak when their surface is passivated well. Oxygen or nitrogen on the surface of silicon quantum dots can break the passivation to form localized electronic states in the band gap to generate active centers where stronger emission occurs.From this point of view,we can build up radiative matter for emission.Emissions of various wavelengths can be obtained by controlling the surface bonds of silicon quantum dots.Our experimental results demonstrate that annealing is important in the treatment of the activation,and stimulated emissions at about 600 and 700 nm take place on active silicon quantum dots.

  18. Small non-polar complexes exhibiting significant piezoelectric properties: Solvothermal synthesis and crystal structures of MO{sub 5}V(tren){center_dot}H{sub 2}O (M=Mo and W; tren=tris(2-aminoethyl)amine)

    Energy Technology Data Exchange (ETDEWEB)

    Rasmussen, M.; Naether, C. [Institut fuer Anorganische Chemie, Christian-Albrechts-Universitaet Kiel, Max-Eyth-Str. 2, D-24118 Kiel (Germany); Bismayer, U. [Mineralogisch-Petrographisches Institut, Universitaet Hamburg, Grindelallee 48 20146 Hamburg (Germany); Bensch, W., E-mail: wbensch@ac.uni-kiel.de [Institut fuer Anorganische Chemie, Christian-Albrechts-Universitaet Kiel, Max-Eyth-Str. 2, D-24118 Kiel (Germany)

    2012-11-15

    The two isostructural complexes MO{sub 5}V(tren){center_dot}H{sub 2}O (M=Mo (1) and W (2)) were synthesized under solvothermal conditions at pH Almost-Equal-To 12 crystallizing in the non-centrosymmetric space group P2{sub 1}2{sub 1}2{sub 1}. The structures are constructed by a distorted tetrahedral [MO{sub 4}]{sup 2-} anion bound via one shared oxygen atom to a severely distorted [V{sup IV}N{sub 4}O]{sup 2+} complex completing the octahedral coordination around the V centre. The two O atoms in the VN{sub 4}O{sub 2} octahedron are in cis position. The two compounds represent rare examples where the [MO{sub 4}]{sup 2-} anion is acting as a ligand. Both compounds exhibit a piezoelectric effect which is more pronounced for M=Mo. The samples are further characterized with IR and UV/Vis spectroscopy and thermal analysis. - Graphical abstract: The complexes [(V(tren)O)(MO4)]{center_dot}H2O (M = Mo, W; tren = tris(2-aminoethyl)amine)) composed of vertex-linked [MO4]{sup 2-} tetrahedron and [VN4O6]{sup 2+}octahedron. Highlights: Black-Right-Pointing-Pointer [MO{sub 4}]{sup 2-} tetrahedron (M=Mo, W) acting as ligand. Black-Right-Pointing-Pointer Jahn-Teller and steric distortion of the [VN{sub 4}O{sub 2}]{sup 2+} octahedron. Black-Right-Pointing-Pointer Non-centrosymmetric complexes exhibiting pronounced piezoelectric effect.

  19. Analytical investigation of AlCl[3]/SO[2]Cl[2] catholyte materials for secondary fuze reserve batteries.

    Energy Technology Data Exchange (ETDEWEB)

    Butler, Paul Charles; Rodriguez, Mark Andrew; Segall, Judith M.; Malizia, Louis A., Jr.; Cherry, Brian Ray; Andrews, Nicholas L.; Clark, Nancy H.; Alam, Todd Michael; Ingersoll, David T.; Tallant, David Robert; Simpson, Regina Lynn; Boyle, Timothy J.; Garcia, Manuel Joseph

    2004-05-01

    Exploration of the fundamental chemical behavior of the AlCl{sub 3}/SO{sub 2}Cl{sub 2} catholyte system for the ARDEC Self-Destruct Fuze Reserve Battery Project under accelerated aging conditions was completed using a variety of analytical tools. Four different molecular species were identified in this solution, three of which are major. The relative concentrations of the molecular species formed were found to depend on aging time, initial concentrations, and storage temperature, with each variable affecting the kinetics and thermodynamics of this complex reaction system. We also evaluated the effect of water on the system, and determined that it does not play a role in dictating the observed molecular species present in solution. The first Al-containing species formed was identified as the dimer [Al({mu}-Cl)Cl{sub 2}]{sub 2}, and was found to be in equilibrium with the monomer, AlCl{sub 3}. The second species formed in the reaction scheme was identified by single crystal X-ray diffraction studies as [Cl{sub 2}Al({mu}-O{sub 2}SCl)]{sub 2} (I), a scrambled AlCl{sub 3}{center_dot}SO{sub 2} adduct. The SO{sub 2}(g) present, as well as CL{sub 2}(g), was formed through decomposition of SO{sub 2}CL{sub 2}. The SO{sub 2}(g) generated was readily consumed by AlCl{sub 3} to form the adduct 1 which was experimentally verified when 1 was also isolated from the reaction of SO{sub 2}(g) and AlCl {sub 3}. The third species found was tentatively identified as a compound having the general formula {l_brace}[Al(O)Cl{sub 2}][OSCl{sub 2}]{r_brace}{sub n}. This was based on {sup 27}Al NMR data that revealed a species with tetrahedrally coordinated Al metal centers with increased oxygen coordination and the fact that the precipitate, or gel, that forms over time was shown by Raman spectroscopic studies to possess a component that is consistent with SOCl{sub 2}. The precursor to the precipitate should have similar constituents, thus the assignment of {l_brace}[Al(O)Cl{sub 2}][OSCl{sub 2

  20. Synthesis and structure of bismuth(III)-containing noncentrosymmetric phosphates, Cs3KBi2M4(PO4)6Cl (M = Mn, Fe). Monoclinic (Cc) and tetragonal (P43) polymorphs templated by chlorine-centered Cl(Bi2Cs) acentric units.

    Science.gov (United States)

    West, J Palmer; Sulejmanovic, Dino; Hwu, Shiou-Jyh; He, Jian; VanDerveer, Don; Johnson, B Keith

    2012-09-17

    Single crystals of three new noncentrosymmetric (NCS) phosphates, α (1) and β (2) forms of Cs(3)KBi(2)Mn(4)(PO(4))(6)Cl and α-Cs(3)KBi(2)Fe(4)(PO(4))(6)Cl (3), were grown in a reactive CsCl/KCl molten-salt media. Their structures were determined by single-crystal X-ray diffraction methods showing that the α form crystallizes in the space group Cc (No. 9), which is in one of the 10 NCS polar crystal classes, m (2/m) while the β form crystallizes in P4(3) (No. 78) of another polar class, 4 (4/m). The unit cell parameters of the α form can be approximately correlated with that of the β form via the 3 × 3 orientation matrix [0.5, 0.5, 0; -0.5, 0.5, 0; 0, 0, 2 sin β]. The structures of these otherwise complicated phosphates exhibit two types of channels with circular and elliptical windows where the Cl-centered Cl(Bi(2)Cs) acentric unit is located. The neighboring acentric units are arranged in a parallel fashion in the α form, resulting in the monoclinic (Cc) lattice, but "antiparallel" in the β form, thus giving the tetragonal (P4(3)) unit cell. 1-3 feature the compatible M-O-P unit that contains four crystallographically independent MO(x) (x = 4, 5) polyhedra, which are connected to the Cl(Bi(2)Cs) acentric unit through one short and one long M(II)···Cl bond. The compositions of 1 and 2 consist of three Mn(2+) (d(5)) and one Mn(3+) (d(4)) per formula unit and that of 3 has three Fe(2+) (d(6)) and one Fe(3+) (d(5)). Bond valence sums reveal that, in the α phase, the trivalent site adopts distorted tetrahedral M(1)(3+)O(4) coordination and, in the β phase, distorted trigonal-bipyramidal M(4)(3+)O(5). Thus far, the iron phase has only been isolated in the α form presumably because of little extra stabilization energy gain if the Fe(2+) d(6) ion were to occupy the M(1)O(4) site. The possible origins pertaining to the structural differences in the α and β forms are discussed. PMID:22924609

  1. The first 3D malonate bridged copper [Cu(O{sub 2}C-CH{sub 2}-CO{sub 2}H){sub 2}{center_dot}2H{sub 2}O]: Structure, properties and electronic structure

    Energy Technology Data Exchange (ETDEWEB)

    Seguatni, A., E-mail: seguatni@gmail.com [LBPC-INSERM U 698, Institut Galilee, Universite Paris XIII, 99, avenue J. B. Clement 93430, Villetaneuse (France); Fakhfakh, M. [Unite de recherche UR 12-30, Synthese et Structure de Materiaux Inorganiques, Faculte des Sciences de Bizerte, 7021 Zarzouna (Tunisia); Departement de Chimie, Universite du Quebec a Montreal, C.P. 8888, Succ. Centre-ville, Montreal, Que., H3C 3P8 (Canada); Smiri, L.S. [Unite de recherche UR 12-30, Synthese et Structure de Materiaux Inorganiques, Faculte des Sciences de Bizerte, 7021 Zarzouna (Tunisia); Gressier, P.; Boucher, F. [Institut des Materiaux Jean Rouxel, Universite de Nantes, CNRS, 2 rue de la Houssiniere, BP 32229, 44322 Nantes Cedex 3 (France); Jouini, N. [Departement de Chimie, Universite du Quebec a Montreal, C.P. 8888, Succ. Centre-ville, Montreal, Que., H3C 3P8 (Canada)

    2012-03-15

    A new inorganic-organic compound [Cu(O{sub 2}C-CH{sub 2}-CO{sub 2}H){sub 2}{center_dot}2H{sub 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{sub 2}O. Its framework is built up through carboxyl bridged copper where CuO{sub 6} octahedra are elongated with an almost D{sub 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{sub eff} value of about 6 eV is necessary for a better correlation with the experiment. - Graphical abstract: [Cu(O{sub 2}C-CH{sub 2}-CO{sub 2}H){sub 2}{center_dot}2H{sub 2}O]: the first 3D hybrid organic-inorganic compound built up carboxyl groups. The network presents a diamond-like structure achieved via carboxyl. Highlights: Black-Right-Pointing-Pointer A new organic-inorganic material with an unprecedented topology is synthesized. Black-Right-Pointing-Pointer Crystallographic structure is determined using single crystal X-ray diffraction. Black-Right-Pointing-Pointer Electronic structure is obtained from DFT, GGA+U calculation. Black-Right-Pointing-Pointer Framework can be described as formed from CuC{sub 4} tetrahedron sharing four corners. Black-Right-Pointing-Pointer This structure can be classified as an extended diamond structure.

  2. 75 FR 38011 - Airworthiness Directives; Bombardier, Inc. Model CL-600-2B16 (CL-604 Variant) Airplanes

    Science.gov (United States)

    2010-07-01

    ... products. That NPRM was published in the Federal Register on January 4, 2010 (75 FR 91). That NPRM proposed... Order 12866; 2. Is not a ``significant rule'' under the DOT Regulatory Policies and Procedures (44 FR.... Model CL-600-2B16 (CL- 604 Variant) Airplanes AGENCY: Federal Aviation Administration (FAA),...

  3. Isopiestic Investigation of the Osmotic and Activity Coefficients of {yMgCl2 + (1 - y)MgSO4}(aq) and the Osmotic Coefficients of Na2SO4.MgSO4(aq) at 298.15 K

    Energy Technology Data Exchange (ETDEWEB)

    Miladinovic, J; Ninkovic, R; Todorovic, M; Rard, J A

    2007-06-06

    Isopiestic vapor pressure measurements were made for {l_brace}yMgCl{sub 2} + (1-y)MgSO{sub 4}{r_brace}(aq) solutions with MgCl{sub 2} ionic strength fractions of y = 0, 0.1997, 0.3989, 0.5992, 0.8008, and (1) at the temperature 298.15 K, using KCl(aq) as the reference standard. These measurements for the mixtures cover the ionic strength range I = 0.9794 to 9.4318 mol {center_dot} kg{sup -1}. In addition, isopiestic measurements were made with NaCl(aq) as reference standard for mixtures of {l_brace}xNa{sub 2}SO{sub 4} + (1-x)MgSO{sub 4}{r_brace}(aq) with the molality fraction x = 0.50000 that correspond to solutions of the evaporite mineral bloedite (astrakanite), Na{sub 2}Mg(SO{sub 4}){sub 2} {center_dot} 4H{sub 2}O(cr). The total molalities, m{sub T} = m(Na{sub 2}SO{sub 4}) + m(MgSO{sub 4}), range from m{sub T} = 1.4479 to 4.4312 mol {center_dot} kg{sup -1} (I = 5.0677 to 15.509 mol {center_dot} kg{sup -1}), where the uppermost concentration is the highest oversaturation molality that could be achieved by isothermal evaporation of the solvent at 298.15 K. The parameters of an extended ion-interaction (Pitzer) model for MgCl2(aq) at 298.15 K, which were required for an analysis of the {l_brace}yMgCl{sub 2} + (1-y)MgSO{sub 4}{r_brace}(aq) mixture results, were evaluated up to I = 12.025 mol {center_dot} kg{sup -1} from published isopiestic data together with the six new osmotic coefficients obtained in this study. Osmotic coefficients of {l_brace}yMgCl{sub 2} + (1-y)MgSO{sub 4}{r_brace}(aq) solutions from the present study, along with critically-assessed values from previous studies, were used to evaluate the mixing parameters of the extended ion-interaction model.

  4. The Characteristics of YAG:Ce Phosphor Powder Prepared Using a NO{sub 3}{sup -}-Malonic Acid-NH{sub 4}NO{sub 3}-NH{sub 3}{center_dot}H{sub 2}O System

    Energy Technology Data Exchange (ETDEWEB)

    Jeong, Jin An [NJS Cablecar Co., Jeongeup (Korea, Republic of); Park, Kyung Hwan [Jeonju University High School, Jeonju (Korea, Republic of); Lee, Dong Hoon [Tech4M Co., Suwon (Korea, Republic of); Kim, Hong Gun; Kim, Yoo Young [Jeonju University, Jeonju (Korea, Republic of)

    2012-04-15

    Ce-doped Y{sub 3}Al{sub 5}O{sub 12} (YAG:Ce) phosphor powder was prepared using a NO{sub 3}{sup -}-malonic acid-NH{sub 4}NO{sub 3}-NH{sub 3}{center_dot}H{sub 2}O system. The YAG:Ce precursor was ignited at 240 .deg. C and the resulting powder contained YAG:Ce crystallites (42%) - active in the visible region at 460 nm - amorphous particles (53%) - inactive at visible wavelengths - and less than 3% oxide (3%) crystallite impurities. The impurities transformed to active YAG:Ce crystallites at above 800 .deg. C. At above 1000 .deg. C, the amorphous phase became YAG phase and isolated Ce{sub 2}O crystallites emerged. The powder particles comprised < 4 {mu}m secondary aggregates of 20 nm primary particles. The thermal dusting of the secondary particles coincided with the aggregation of the secondary particles at above 900 .deg. C

  5. Dynamics of the superprotonic conductor K{sub 9}H{sub 7}(SO{sub 4}){sub 8}{center_dot}H{sub 2}O studied by means of nuclear magnetic resonance

    Energy Technology Data Exchange (ETDEWEB)

    Vrtnik, S [J Stefan Institute, University of Ljubljana, Jamova 39, SI-1000 Ljubljana (Slovenia); Apih, T [J Stefan Institute, University of Ljubljana, Jamova 39, SI-1000 Ljubljana (Slovenia); Klanjsek, M [J Stefan Institute, University of Ljubljana, Jamova 39, SI-1000 Ljubljana (Slovenia); Jeglic, P [J Stefan Institute, University of Ljubljana, Jamova 39, SI-1000 Ljubljana (Slovenia); Lahajnar, G [J Stefan Institute, University of Ljubljana, Jamova 39, SI-1000 Ljubljana (Slovenia); Kirpichnikova, L F [Shubnikov Institute of Crystallography, Russian Academy of Sciences, Leninskii Prospekt 59, Moscow, 117333 (Russian Federation); Baranov, A I [Shubnikov Institute of Crystallography, Russian Academy of Sciences, Leninskii Prospekt 59, Moscow, 117333 (Russian Federation); Dolinsek, J [J Stefan Institute, University of Ljubljana, Jamova 39, SI-1000 Ljubljana (Slovenia)

    2004-11-17

    The dynamics of a recently discovered superprotonic conductor K{sub 9}H{sub 7}(SO{sub 4}){sub 8}{center_dot} H{sub 2}O has been studied between 40 and 425 K by techniques based on the NMR spectrum shape, spin-lattice and spin-spin relaxation. At low temperatures (such as 40 K), proton intra-H-bond hopping is already intensive. At higher temperatures, water 180 deg. reorientations become observable in the NMR experiments, whereas above 250 K, proton interbond jumps-a precursor of the superprotonic conductivity above the transition temperature T{sub sp} = 398 K-become frequent. Above T{sub sp}, a large increase in the proton spin-spin relaxation time T{sub 2} indicates that proton long-range diffusion becomes significant. Proton interbond jumps are assisted by reorientations of the SO{sub 4} tetrahedra, which also cause breaking of the water bonds, so water molecules become free and consequently diffuse out of the crystal. The loss of water allows rearrangement of the lattice, so the number of structurally equivalent proton sites in the superprotonic phase is increased, resulting in a very open structure for the hydrogen interbond transfer.

  6. Quantum dot spectroscopy

    DEFF Research Database (Denmark)

    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...

  7. Preparation, configurational and DFT-NBO analysis of nickel(II) complexes with edta-type ligands containing six-membered backbone ring : crystal structure of [Ni(H2O)(6)][Ni(1,3-pdta)]center dot 2H(2)O

    NARCIS (Netherlands)

    Belosevic, Svetlana; Vasojevic, Miorad M.; Jeremic, Marija S.; Meetsma, Auke; Matovic, Zoran D.

    2013-01-01

    New hexadentate nickel(II) complex Mg[Ni(1,3-pd3ap)]center dot 10H(2)O containing unsymmetrical edta-type ligand, 1,3-propanediamine-N,N,N '-triacetate-N-3-propionate (1,3-pd3ap), has been prepared, chromatographically separated, and characterized. Only one [trans(O-5)] of the two possible geometric

  8. La Clínica del Pueblo: a model of collaboration between a private media broadcasting corporation and an academic medical center for health education for North Carolina Latinos.

    Science.gov (United States)

    Calles-Escandón, Jorge; Hunter, Jaimie C; Langdon, Sarah E; Gómez, Eva M; Duren-Winfield, Vanessa T; Woods, Kristy F

    2009-12-01

    La Clínica del Pueblo, a health education collaboration between the Maya Angelou Center for Health Equity at Wake Forest University School of Medicine and Qué Pasa Media, Inc., disseminates culturally appropriate health information to the North Carolina (NC) Latino community. The program includes a weekly radio show and corresponding newspaper column addressing four areas: childhood health, adult health, safety, and utilization. The radio show format includes a didactic presentation followed by a call-in question and answer period. Over 200 consecutive weeks of programming have been completed, averaging 11 calls per show. A Latino healthcare resource guide and hotline also provide resource information. Participant demographic information indicates that 50% of the target population comes from Mexico, 60% are women, and 70% of the community is younger than 38 years. There was an increase in the use of the media as a source of health information over the course of the project, from an initial 33% of respondents to 58% in the last survey. Listenership to La Clínica del Pueblo displayed a pronounced increase (18% initial survey to 55% in last survey, P education level (P < 0.0001), female gender (P < 0.01) and radio listenership (P < 0.05). The first three variables predicted higher scores; however, radio listening recognition of our radio program was more common among individuals who had lower scores. In conclusion, La Clínica del Pueblo is a model for a novel approach that can reach the Latino community to improve medical knowledge and possibly affect health behaviors in a positive manner.

  9. Outline in 1997 Japan compound material academic meeting technological prize winning technology; Kenchiku, doboku kozobutsu no hoshu{center_dot}hokyo yo forukatousito no kaihatsu

    Energy Technology Data Exchange (ETDEWEB)

    Iba, Yoshitomo.; Uemura, Masahiko.; Murakami, Shinkichi.; Saito, Makoto.; Kobayashi, Akira. [Nittetsu Composite Corp., Tokyo (Japan)

    1999-03-15

    That function declines in the sutra time target, and it is finally destroyed, or a construction structure thing bears putting off that life by managing efficient maintenance it is possible. The factor of the function decline of the structure thing, the degree of the decline, and so on are grasped quantitatively, and efficient repair reinforcement time and a method of construction are chosen, and you must carry it out for that. It is paying attention to the development of the method of construction to reinforce the maintenance repair of the construction structure thing by using the tip compound factor from such a viewpoint. In the beginning, a material cost was very expensive, and the recognition not to use it was very general in such a construction field. In such recognition, in Tonen Corp. incorporated company, it has paid attention to the use possibility in the construction field of the tip compound factor since early, research and development have been done continuously from 1980, that It succeeds in, and it is the method of construction that a repair reinforces a concrete structure thing by the tip material that the method of construction which got the technological prize of the Japan compound material academic meeting in 1997 moved carbon fiber to the center. (NEDO)

  10. Outline in 1997 Japan compound material academic meeting technological prize winning technology. Kenchiku, doboku kozobutsu no hoshu[center dot]hokyo yo forukatousito no kaihatsu

    Energy Technology Data Exchange (ETDEWEB)

    Iba, Yoshitomo.; Uemura, Masahiko.; Murakami, Shinkichi.; Saito, Makoto.; Kobayashi, Akira. (Nittetsu Composite Corp., Tokyo (Japan))

    1999-03-15

    That function declines in the sutra time target, and it is finally destroyed, or a construction structure thing bears putting off that life by managing efficient maintenance it is possible. The factor of the function decline of the structure thing, the degree of the decline, and so on are grasped quantitatively, and efficient repair reinforcement time and a method of construction are chosen, and you must carry it out for that. It is paying attention to the development of the method of construction to reinforce the maintenance repair of the construction structure thing by using the tip compound factor from such a viewpoint. In the beginning, a material cost was very expensive, and the recognition not to use it was very general in such a construction field. In such recognition, in Tonen Corp. incorporated company, it has paid attention to the use possibility in the construction field of the tip compound factor since early, research and development have been done continuously from 1980, that It succeeds in, and it is the method of construction that a repair reinforces a concrete structure thing by the tip material that the method of construction which got the technological prize of the Japan compound material academic meeting in 1997 moved carbon fiber to the center. (NEDO)

  11. 75 FR 17884 - Airworthiness Directives; Bombardier, Inc. Model CL-600-2B19 (Regional Jet Series 100 & 440...

    Science.gov (United States)

    2010-04-08

    ... rule'' under the DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and 3. Will.... Model CL-600-2B19 (Regional Jet Series 100 & 440) Airplanes; Model CL-600-2C10 (Regional Jet Series 700, 701, & 702) Airplanes; Model CL-600-2D15 (Regional Jet Series 705) and Model CL-600-2D24 (Regional...

  12. Photocatalytic production of {sup 1}O{sub 2} and {center_dot}OH mediated by silver oxidation during the photoinactivation of Escherichia coli with TiO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Castro, Camilo A. [Centro de Investigaciones en Catalisis, Escuela de Ingenieria Quimica, Universidad Industrial de Santander (UIS), A.A. 678, Bucaramanga (Colombia); Institute of Chemical Sciences and Engineering, GGEC, Swiss Federal Institute of Technology (EPFL), Station 6, CH-1015, Lausanne (Switzerland); Osorio, Paula [Institute of Chemical Sciences and Engineering, GGEC, Swiss Federal Institute of Technology (EPFL), Station 6, CH-1015, Lausanne (Switzerland); Sienkiewicz, Andrzej [Laboratory of Complex Matter Physics, Institute of Physics of Condensed Matter, EPFL, Station 3, CH-1015, Lausanne (Switzerland); Pulgarin, Cesar, E-mail: cesar.pulgarin@epfl.ch [Institute of Chemical Sciences and Engineering, GGEC, Swiss Federal Institute of Technology (EPFL), Station 6, CH-1015, Lausanne (Switzerland); Centeno, Aristobulo [Centro de Investigaciones en Catalisis, Escuela de Ingenieria Quimica, Universidad Industrial de Santander (UIS), A.A. 678, Bucaramanga (Colombia); Giraldo, Sonia A., E-mail: sgiraldo@uis.edu.co [Centro de Investigaciones en Catalisis, Escuela de Ingenieria Quimica, Universidad Industrial de Santander (UIS), A.A. 678, Bucaramanga (Colombia)

    2012-04-15

    Highlights: Black-Right-Pointing-Pointer Metallic silver enhances the Ag-TiO{sub 2} photoinactivation of Escherichia coli under Vis irradiation. Black-Right-Pointing-Pointer {sup 1}O{sub 2} and {center_dot}OH were identified in Vis irradiated Ag-TiO{sub 2} suspensions. Black-Right-Pointing-Pointer UV oxidized the Ag metallic species in the material decreasing photoactivity. Black-Right-Pointing-Pointer Dark contact of the UV oxidized material with E. coli regenerates the photocatalyst. - Abstract: Ag loaded TiO{sub 2} was applied in the photocatalytic inactivation of Escherichia coli under ultraviolet (UV) and visible (Vis) light irradiations. Ag enhanced the TiO{sub 2} photodisinfecting effect under Vis irradiation promoting the formation of singlet oxygen and hydroxyl radicals as identified by EPR analyses. Ag nanoparticles, determined on TEM analyses, undergo an oxidation process on the TiO{sub 2}'s surface under UV or Vis irradiation as observed by XPS. In particular, UV pre-irradiation of the material totally diminished its photodisinfection activity under a subsequent Vis irradiation test. Under UV, photodegradation of dichloroacetic acid (DCA), attributed to photoproduced holes in TiO{sub 2}, was inhibited by the presence of Ag suggesting that oxidation of Ag{sup 0} to Ag{sup +} and Ag{sup 2+} is faster than the oxidative path of the TiO{sub 2}'s holes on DCA molecules. Furthermore, photoassisted increased of Ag{sup +} concentration on TiO{sub 2}'s surface enhances the bacteriostatic activity of the material in dark periods. Indeed, this latter dark contact of Ag{sup +}-TiO{sub 2} and E. coli seems to induce recovering of the Vis light photoactivity promoted by the surface Ag photoactive species.

  13. Quantum Dots Investigated for Solar Cells

    Science.gov (United States)

    Bailey, Sheila G.; Castro, Stephanie L.; Raffaelle, Ryne P.; Hepp, Aloysius F.

    2001-01-01

    The NASA Glenn Research Center has been investigating the synthesis of quantum dots of CdSe and CuInS2 for use in intermediate-bandgap solar cells. Using quantum dots in a solar cell to create an intermediate band will allow the harvesting of a much larger portion of the available solar spectrum. Theoretical studies predict a potential efficiency of 63.2 percent, which is approximately a factor of 2 better than any state-of-the-art devices available today. This technology is also applicable to thin-film devices--where it offers a potential four-fold increase in power-to-weight ratio over the state of the art. Intermediate-bandgap solar cells require that quantum dots be sandwiched in an intrinsic region between the photovoltaic solar cell's ordinary p- and n-type regions (see the preceding figure). The quantum dots form the intermediate band of discrete states that allow sub-bandgap energies to be absorbed. However, when the current is extracted, it is limited by the bandgap, not the individual photon energies. The energy states of the quantum dot can be controlled by controlling the size of the dot. Ironically, the ground-state energy levels are inversely proportional to the size of the quantum dots. We have prepared a variety of quantum dots using the typical organometallic synthesis routes pioneered by Ba Wendi et al., in the early 1990's. The most studied quantum dots prepared by this method have been of CdSe. To produce these dots, researchers inject a syringe of the desired organometallic precursors into heated triocytlphosphine oxide (TOPO) that has been vigorously stirred under an inert atmosphere (see the following figure). The solution immediately begins to change from colorless to yellow, then orange and red/brown, as the quantum dots increase in size. When the desired size is reached, the heat is removed from the flask. Quantum dots of different sizes can be identified by placing them under a "black light" and observing the various color differences in

  14. Polyol-mediated C-dot formation showing efficient Tb3+/Eu3+ emission.

    Science.gov (United States)

    Dong, Hailong; Kuzmanoski, Ana; Gössl, Dorothee M; Popescu, Radian; Gerthsen, Dagmar; Feldmann, Claus

    2014-07-18

    C-dots (3-5 nm in diameter) obtained by most simple heating of polyols (glycerol, diethylene glycol and PEG 400) show intense blue and green emission (50% quantum yield). Upon modification with TbCl3/EuCl3, energy transfer from the C-dots to the rare-earth metal results in line-type Tb(3+) (green)/Eu(3+) (red) emission with quantum yields up to 85%. PMID:24887063

  15. Quantum dot spectroscopy

    DEFF Research Database (Denmark)

    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...

  16. Quantum Dots: Theory

    Energy Technology Data Exchange (ETDEWEB)

    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.

  17. Ultrasmall silicon quantum dots

    NARCIS (Netherlands)

    Zwanenburg, F.A.; Van Loon, A.A.; Steele, G.A.; Rijmenam, C.E.W.M.; Balder, T.; Fang, Y.; Lieber, C.M.; Kouwenhoven, L.P.

    2009-01-01

    We report the realization of extremely small single quantum dots in p-type silicon nanowires, defined by Schottky tunnel barriers with Ni and NiSi contacts. Despite their ultrasmall size the NiSi–Si–NiSi nanowire quantum dots readily allow spectroscopy of at least ten consecutive holes, and addition

  18. Nuclear magnetic relaxation in the ferrimagnetic chain compound NiCu(C{sub 7}H{sub 6}N{sub 2}O{sub 6})(H{sub 2}O){sub 3}{center_dot}2H{sub 2}O : three-magnon scattering?

    Energy Technology Data Exchange (ETDEWEB)

    Hori, Hiromitsu; Yamamoto, Shoji [Division of Physics, Hokkaido University, Sapporo 060-0810 (Japan)

    2004-12-15

    Recent proton spin-lattice relaxation-time (T{sub 1}) measurements on the ferrimagnetic chain compound NiCu(C{sub 7}H{sub 6}N{sub 2}O{sub 6})(H{sub 2}O){sub 3}{center_dot}2H{sub 2}O are explained by an elaborately modified spin-wave theory. We give strong evidence of the major contribution to 1/T{sub 1} being made by the three-magnon scattering rather than the Raman scattering.

  19. Environmental conditions influence for real-time hologram formation on dichromated polyvinyl alcohol NiCl{sub 2}{center_dot}6H{sub 2}O doped films

    Energy Technology Data Exchange (ETDEWEB)

    Fontanilla-Urdaneta, R C; Olivares-Perez, A; Fuentes-Tapia, I; Rios-Velasco, M A, E-mail: rfontanilla@inaoep.mx, E-mail: olivares@inaoep.mx, E-mail: ifuentes@inaoep.mx, E-mail: moni_arv@hotmail.com [Instituto Nacional de Astrofisica, Optica y Electronica (INAOE), Luis Enrique Erro No. 1 Tonantzintla, Puebla (Mexico)

    2011-01-01

    The real-time holographic gratings recording are studied by the presence of a metallic salt. The experimental process refers to analysis of diffraction efficiency by the influence of humidity in the coating solution on holograms formation in presence of electrical potential. The diffraction efficiency is measured as a function of the exposure energy until reach the saturation. The influence of the hologram parameters to get the diffraction efficiency is studied at room conditions.

  20. Barrier Li Quantum Dots in Magnetic Fields

    Institute of Scientific and Technical Information of China (English)

    LIUYi-Min; LIXiao-Zhu; YANWen-Hong; BAOCheng-Guang

    2003-01-01

    The methods for the few-body system are introduced to investigate the states of the barrier Li quantum dots (QDs) in an arbitrary strength of magnetic field. The configuration, which consists of a positive ion located on the z-axis at a distaneed from the two-dimensional QD plane (the x-y plane) and three electrons in the dot plane bound by the positive ion, is called a barrier Li center. The system, which consists of three electrons in the dot plane bound by the ion,is called a barrier Li QD. The dependence of energy of the state of the barrier Li QD on an external magnetic field B and the distance d is obtained. The angular momentum L of the ground states is found to jump not only with the variation orB but also with d.

  1. Preparation an Mechanical Properties of NaCl Ceramics; NaCl seramikkusu no sakusei to kikaiteki seishitsu

    Energy Technology Data Exchange (ETDEWEB)

    Sata, Toshiyuki. [Kumamoto Institute of Technology, Kumamoto (Japan), Department of Industrial Chmistry

    1999-02-01

    NaCl powder specimens composed of equally sized (approximately 108 {mu}m), cubic single crystals were prepared by additions of acetone to saturated NaCl solution at -21 degree C under various preparation conditions. Grain growth during storage of the powder specimens was found to be greatly influenced by moisture in the ambient atmosphere. Storage of the specimens n a furnace at 400 degree C prevented grain growth. Compacts of the powder specimens produced by cold pressing (CP) and cold isostatic pressing (CIP) were sintered, or the powders were directly hot-pressed (HP). Relative densities (RD) of the resulting sintered bodies depended on the compaction or sintering conditions. From these sintered bodies, appropriate equationsrealating bending strength with porosity and grain size were obtained. The high-temperature bending strength increased up to 300 degree C and then decreased at higher temperatures. Deflections observed in the bending tests incerased with sintering temperature, that is, with the increase in grain size. Observed tensile strength values (5-10 MPa) were smaller than observed bending strength values (8-20 MP). Measured values of the Weibull coefficient and fracture toughness were m=5.34 and K{sub 1c}=1.05 MPa{center_dot}m{sup 1/2}, respectively. Single crystal specimens obtained frommelts by the Czochralski method were also subjected to bending test. These specimens showed large deflections above 200 degree C, and strain-hardening phenomena were also observed. Tension tests for single crystal whiskers prepared by condensatin of vaporized NaCl in a flowing air conducted along the [100] direction, and showed that the strength increased with the whisker cross sectional area up to a maximumvalue and then decreased. The highest strength value was obtained in vacuum with lower values being obtained in dry air and moist air because of the effects of oxygen and moisture, respectively. (author)

  2. Tunable Room Temperature Second Harmonic Generation in Glasses Doped with CuCI Nanocrystalline Quantum Dots

    Energy Technology Data Exchange (ETDEWEB)

    Thantu, Napoleon; Schley, Robert Scott; B. L. Justus

    2003-05-01

    Two-photon excited emission centered at 379-426 nm in photodarkening borosilicate glass doped with CuCl nanocrystalline quantum dots at room temperature has been observed. The emission is detected in the direction of the fundamental near-infrared beam. Time- and frequency-resolved measurements at room temperature and 77 K indicate that the emission is largely coherent light characteristic of second harmonic generation (SHG). An average conversion efficiency of ~10-10 is obtained for a 2 mm thick sample. The observed SHG can originate in the individual noncentrosymmetric nanocrystals, leading to a bulk-like contribution, and at the nanocrystal-glass interface, leading to a surface contribution. The bulk-like conversion efficiency is estimated using previously reported values of coherence length (5m) and bulk nonlinear susceptibility. This bulk-like conversion efficiency estimate is found to be smaller than the measured value, suggesting a more prominent surface contribution.

  3. 76 FR 33658 - Airworthiness Directives; Bombardier, Inc. Model CL-600-2B19 (Regional Jet Series 100 & 440...

    Science.gov (United States)

    2011-06-09

    ... rule'' under the DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979), 3. Will not... Directives; Bombardier, Inc. Model CL-600-2B19 (Regional Jet Series 100 & 440); Model CL-600-2C10 (Regional Jet Series 700, 701, & 702); Model CL-600-2D15 (Regional Jet Series 705); and Model...

  4. 75 FR 34657 - Airworthiness Directives; Bombardier, Inc. Model CL-600-2B19 (Regional Jet Series 100 & 440...

    Science.gov (United States)

    2010-06-18

    ... rule'' under the DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and 3. Will.... Model CL-600-2B19 (Regional Jet Series 100 & 440) Airplanes; Model CL-600-2C10 (Regional Jet Series 700, 701, & 702) Airplanes; Model CL-600-2D15 (Regional Jet Series 705) Airplanes; and Model...

  5. Dielectrophoretic Manipulation and Separation of Microparticles Using Microarray Dot Electrodes

    Directory of Open Access Journals (Sweden)

    Bashar Yafouz

    2014-04-01

    Full Text Available This paper introduces a dielectrophoretic system for the manipulation and separation of microparticles. The system is composed of five layers and utilizes microarray dot electrodes. We validated our system by conducting size-dependent manipulation and separation experiments on 1, 5 and 15 μm polystyrene particles. Our findings confirm the capability of the proposed device to rapidly and efficiently manipulate and separate microparticles of various dimensions, utilizing positive and negative dielectrophoresis (DEP effects. Larger size particles were repelled and concentrated in the center of the dot by negative DEP, while the smaller sizes were attracted and collected by the edge of the dot by positive DEP.

  6. NMR structural studies of intramolecular (Y+) sub n ter dot (R+) sub n (Y minus ) sub n DNA triplexes in solution: Imino and amino proton and nitrogen markers of Gter dot TA base triple formation

    Energy Technology Data Exchange (ETDEWEB)

    Radhakrishnan, I.; de los Santos, C.; Patel, D.J. (Columbia Univ., New York, NY (United States)); Gao, Xiaolian (Glaxo Research Inst., Research Triangle Park, NC (United States)); Live, D. (California Inst. of Tech., Pasadena (United States))

    1991-09-17

    The authors reported previously on NMR studies of (Y+){sub n}{center dot}(R+){sub n}(Y{minus}){sub n}DNA triple helices containing one oligopurine strand (R){sub n} and two oligopyrimidine strands (Y){sub n} stabilized by T{center dot}AT and C{sup +}{center dot}GC base triples. Recently, it has been established that guanosine can recognize a thymidine{center dot}adenosine base pair to form a G{center dot}TA triple in an otherwise (Y+){sub n}{center dot}(R+){sub n}(Y{minus}){sub n} triple-helix motif. The present study extends the NMR research to the characterization of structural features of a 31-mer deoxyoligonucleotide that folds intramolecularly into a 7-mer (Y+){sub n}{center dot}(R+){sub n}(Y{minus}){sub n} triplex with the strands linked through two T{sub 5} loops and that contains a central G{center dot}TA triple flanked by T{center dot}AT triples. The NMR data are consistent with the proposed pairing alignment for the G{center dot}TA triple where the guanosine in an anti orientation pairs through a single hydrogen bond from one of its 2-amino protons to the 4-carbonyl group of thymidine in the Watson-Crick TA pair. They detect a set of NOEs between adjacent triples that establishes that the G{center dot}TA triple stacks between flanking T{center dot}AT triples in the G{center dot}TA triplex. These results demonstrate the capabilities of the NMR approach in monitoring individual base triples and their pairing alignments, as well as establishing that the G{center dot}TA triple can be readily accommodated in an otherwise intramolecular (Y+){sub n}{center dot}(R+){sub n}(Y{minus}){sub n} triple helix in solution.

  7. Graphene quantum dots

    CERN Document Server

    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. SPECTRAL PROPERTIES OF SHUNGITE QUANTUM DOTS

    OpenAIRE

    RAZBIRIN B.S.; ROZHKOVA N.N.; Sheka, E. F.; Nelson, D. K.; Starukhin, A. N.; Goryunov, A. S.

    2014-01-01

    A low-temperature study has been performed for aqueous shungite, carbon tetrachloride, and toluene dispersions. Spectral characteristics for graphene quantum dots (GQDs) of shungite, attributed to individual fragments of reduced graphene oxide (rGO), reveal a dual character of the dispersions emitting centers: individual GQDs are responsible for the spectra position while fractal structure of GQD colloids provides large broadening of the spectra due to structural inhomogeneity of the colloida...

  9. Hyperbolic metamaterials based on quantum-dot plasmon-resonator nanocomposites

    DEFF Research Database (Denmark)

    Zhukovsky, Sergei; Ozel, T.; Mutlugun, E.;

    2014-01-01

    We theoretically demonstrate that nanocomposites made of colloidal semiconductor quantum dot monolayers placed between metal nanoparticle monolayers can function as multilayer hyperbolic metamaterials. Depending on the thickness of the spacer between the quantum dot and nanoparticle layers...... metamaterials are capable of increasing the radiative decay rate of emission centers inside them. The proposed theoretical framework can also be used to design quantum-dot/nanoplasmonic composites with optimized luminescence enhancement....

  10. Quantum dot solar cells

    CERN Document Server

    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

  11. Inmunodeficiencias humorales: Un estudio en tres Centros de Inmunología Clínica de adultos en la Ciudad de Buenos Aires Antibody deficiencies: A survey from three Clinical Immunology Centers for adults in Buenos Aires City

    Directory of Open Access Journals (Sweden)

    Diego S. Fernández Romero

    2011-08-01

    Full Text Available Las inmunodeficiencias humorales (IDH comprenden a un grupo de enfermedades caracterizadas por la imposibilidad de desarrollar una respuesta inmune efectiva mediada por anticuerpos. Estos pacientes presentan infecciones, principalmente por bacterias extracelulares capsuladas, del tracto respiratorio. El objetivo de nuestro estudio fue describir las características clínicas de una población de 128 pacientes derivados con sospecha o diagnóstico de IDH a tres centros para inmunodeficiencias de adultos, asistidos entre junio de 2004 y diciembre de 2009. Tres (2.3% consultaron por infecciones recurrentes en una sola oportunidad sin datos suficientes para su adecuada clasificación y fueron excluidos del estudio. De los 125 pacientes restantes, en 21 (16.8% se descartó IDH, en 8 (6.4% se diagnosticó inmunodeficiencia humoral secundaria (IDHS y en 96 (76.8% inmunodeficiencia humoral primaria (IDHP. Las causas de IDHS fueron: en un caso enfermedad renal, en uno uso de fenitoína, dos casos: gammapatía monoclonal y en 4 linfoma B. Las causas de las 96 IDHP fueron: 57 inmunodeficiencia común variable, 12 agammaglobulinemia ligada al cromosoma X, 10 deficiencia selectiva de IgA, 7 deficiencia de IgG1, 3 síndrome hiper-IgM, 3 deficiencia de IgM, 2 síndrome linfoproliferativo ligado al cromosoma X, un síndrome de Good y una deficiencia funcional de anticuerpos. Sesenta y siete pacientes estaban en seguimiento en el momento de la finalización del estudio, 25 de ellos estaban en seguimiento al iniciarse el estudio. De los 58 pacientes en seguimiento con indicación de tratamiento sustitutivo con gammaglobulina, 54 se encontraban en tratamiento al finalizar el estudio. En cuatro pacientes no se pudo confirmar el diagnóstico de IDHP.Antibody deficiency (AD comprises a group of diseases characterized by the inability to develop an effective antibody mediated immune response. These patients suffer mainly of encapsulated extracellular bacterial

  12. Chemiluminescence of graphene quantum dots and its application to the determination of uric acid

    Energy Technology Data Exchange (ETDEWEB)

    Amjadi, Mohammad, E-mail: amjadi@tabrizu.ac.ir; Manzoori, Jamshid L.; Hallaj, Tooba

    2014-09-15

    We report on the chemiluminescence (CL) of graphene quantum dots (GQDs) induced by direct chemical oxidation. GQDs were prepared by a simple carbonization method and characterized by X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy and Raman spectroscopy. It was found that Ce(IV) could oxidize GQDs to produce a relatively intense CL emission. The mechanism of CL generation was investigated based on the fluorescence and CL emission spectra. It was attributed to the radiative recombination of oxidant-injected holes and thermally excited electrons in the GQDs. In order to show the analytical application potential of GQDs-Ce(IV) CL system, it was applied to the determination of uric acid. Under the optimized conditions, the proposed CL system exhibited excellent analytical performance for determination of uric acid in the range of 1.0×10{sup −6} M–5.0×10{sup −4} M with a limit of detection of 5.0×10{sup −7} M. The method was applied to the determination of uric acid in human plasma and urine samples, with satisfactory results. - Highlights: • Chemiluminescence of graphene quantum dots by direct oxidation was studied. • Intense CL is produced by reaction of graphene quantum dots with Ce(IV). • The new CL system was applied to determination of uric acid in plasma and urine.

  13. Carbon nanotube quantum dots

    NARCIS (Netherlands)

    Sapmaz, S.

    2006-01-01

    Low temperature electron transport measurements on individual single wall carbon nanotubes are described in this thesis. Carbon nanotubes are small hollow cylinders made entirely out of carbon atoms. At low temperatures (below ~10 K) finite length nanotubes form quantum dots. Because of its small si

  14. Magnetoconductance fluctuations in open bismuth quantum dots

    Science.gov (United States)

    Hackens, B.; Minet, J. P.; Farhi, G.; Crahay, A.; Faniel, S.; Gustin, C.; Bayot, V.

    2002-03-01

    We investigate the low temperature (300 mK - 10 K) magnetoconductance of open circular bismuth quantum dots (diameter: 500 nm). The structures are fabricated using a combination of electron beam lithography, lift off and plasma etching techniques on bismuth thin films evaporated on heated SiO2 substrates. We observe reproducible magnetoconductance fluctuations (UCFs) up to 5T, qualitatively similar to conductance fluctuations evidenced in open quantum dots patterned in high mobility semiconductor heterostructures. In our samples, UCFs are superposed on a slowly varying negative magnetoconductance background. We also observe a sharp conductance maximum centered in B=0, which is reminescent of the spin-orbit induced anti-localisation phenomenon. The behavior of UCFs and of the conductance maximum is discussed as a function of the temperature, thickness and degree of cristallinity of the cavity.

  15. Barrier Li Quantum Dots in Magnetic Fields

    Institute of Scientific and Technical Information of China (English)

    LIU Yi-Min; LI Xiao-Zhu; YAN Wen-Hong; BAO Cheng-Guang

    2003-01-01

    The methods for the few-body system are introduced to investigate the states of the barrier Li quantumdots (QDs) in an arbitrary strength of magnetic field. The configuration, which consists of a positive ion located on thez-axis at a distance d from the two-dimensional QD plane (the x-y plane) and three electrons in the dot plane boundby the positive ion, is called a barrier Li center. The system, which consists of three electrons in the dot plane bound bythe ion, is called a barrier Li QD. The dependence of energy of the state of the barrier Li QD on an external magneticfield B and the distance d is obtained. The angular momentum L of the ground states is found to jump not only withthe variation of B but also with d.

  16. Colloidal Double Quantum Dots.

    Science.gov (United States)

    Teitelboim, Ayelet; Meir, Noga; Kazes, Miri; Oron, Dan

    2016-05-17

    Pairs of coupled quantum dots with controlled coupling between the two potential wells serve as an extremely rich system, exhibiting a plethora of optical phenomena that do not exist in each of the isolated constituent dots. Over the past decade, coupled quantum systems have been under extensive study in the context of epitaxially grown quantum dots (QDs), but only a handful of examples have been reported with colloidal QDs. This is mostly due to the difficulties in controllably growing nanoparticles that encapsulate within them two dots separated by an energetic barrier via colloidal synthesis methods. Recent advances in colloidal synthesis methods have enabled the first clear demonstrations of colloidal double quantum dots and allowed for the first exploratory studies into their optical properties. Nevertheless, colloidal double QDs can offer an extended level of structural manipulation that allows not only for a broader range of materials to be used as compared with epitaxially grown counterparts but also for more complex control over the coupling mechanisms and coupling strength between two spatially separated quantum dots. The photophysics of these nanostructures is governed by the balance between two coupling mechanisms. The first is via dipole-dipole interactions between the two constituent components, leading to energy transfer between them. The second is associated with overlap of excited carrier wave functions, leading to charge transfer and multicarrier interactions between the two components. The magnitude of the coupling between the two subcomponents is determined by the detailed potential landscape within the nanocrystals (NCs). One of the hallmarks of double QDs is the observation of dual-color emission from a single nanoparticle, which allows for detailed spectroscopy of their properties down to the single particle level. Furthermore, rational design of the two coupled subsystems enables one to tune the emission statistics from single photon

  17. Electron correlations in quantum dots

    CERN Document Server

    Tipton, D L J

    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 p...

  18. Fuzzy Dot Structure of BG-algebras

    OpenAIRE

    Tapan Senapati; Monoranjan Bhowmik; Madhumangal Pal

    2014-01-01

    In this paper, the notions of fuzzy dot subalgebras is introduced together with fuzzy normal dot subalgebras and fuzzy dot ideals of BG-algebras. The homomorphic image and inverse image are investigated in fuzzy dot subalgebras and fuzzy dot ideals of BG-algebras. Also, the notion of fuzzy relations on the family of fuzzy dot subalgebras and fuzzy dot ideals of BG-algebras are introduced with some related properties.

  19. Mixed-valence, layered, cation radical salts of the ethane-bridged dimeric tetrathiafulvalene [(EDT-TTF-CH2-)2#centre dot#+] [X-][THF]0.5, X-=FeCl4-, GaCl4-

    DEFF Research Database (Denmark)

    Mézière, C.; Fourmigué, M.; Canadell, E.;

    2000-01-01

    other give rise to both 1D- and 2D-type HOMO ... HOMO interactions whose origin is correlated with the details of the peculiar overlap patterns obtained with those dimeric tetrathiafulvalenes. The weak paramagnetism observed in the GaCl4- salt due to the organic spins of the conducting slabs is hidden...

  20. 75 FR 35613 - Airworthiness Directives; Bombardier, Inc. Model CL-600-2C10 (Regional Jet Series 700 & 701...

    Science.gov (United States)

    2010-06-23

    ..., 2009 (74 FR 55493). That NPRM proposed to correct an unsafe condition for the specified products. The...'' under the DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and 3. Will not have.... Model CL-600-2C10 (Regional Jet Series 700 & 701) Airplanes, Model CL-600-2D15 (Regional Jet Series...

  1. 75 FR 59073 - Airworthiness Directives; Bombardier, Inc. Model CL-600-2B19 (Regional Jet Series 100 & 440...

    Science.gov (United States)

    2010-09-27

    ... to the specified products. That NPRM was published in the Federal Register on April 8, 2010 (75 FR... Order 12866; 2. Is not a ``significant rule'' under the DOT Regulatory Policies and Procedures (44 FR.... Model CL-600-2B19 (Regional Jet Series 100 & 440) Airplanes; Model CL-600-2C10 (Regional Jet Series...

  2. 75 FR 69609 - Airworthiness Directives; Bombardier, Inc. Model CL-600-2B19 (Regional Jet Series 100 & 440...

    Science.gov (United States)

    2010-11-15

    ... 12866; 2. Is not a ``significant rule'' under the DOT Regulatory Policies and Procedures (44 FR 11034.... Model CL-600-2B19 (Regional Jet Series 100 & 440) Airplanes AGENCY: Federal Aviation Administration (FAA... Part 2, ``Airworthiness Limitations,'' of the Bombardier CL-600-2B19 Maintenance Requirements...

  3. 75 FR 25788 - Airworthiness Directives; Bombardier, Inc. Model CL-600-2B19 (Regional Jet Series 100 & 440...

    Science.gov (United States)

    2010-05-10

    ... 12866; 2. Is not a ``significant rule'' under the DOT Regulatory Policies and Procedures (44 FR 11034.... Model CL-600-2B19 (Regional Jet Series 100 & 440) Airplanes AGENCY: Federal Aviation Administration (FAA...) sufficient heat switches/sensors on CL-600-2B19 aircraft are located at the inboard end of each wing...

  4. 75 FR 60604 - Airworthiness Directives; Bombardier, Inc. Model CL-600-2B19 (Regional Jet Series 100 & 440...

    Science.gov (United States)

    2010-10-01

    ... (75 FR 34657). That NPRM proposed to correct an unsafe condition for the specified products. The MCAI...'' under the DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and 3. Will not have.... Model CL-600-2B19 (Regional Jet Series 100 & 440) Airplanes; Model CL-600-2C10 (Regional Jet Series...

  5. Quantum Dot Sensitized Photoelectrodes

    OpenAIRE

    Thomas Nann; Thomas J. Macdonald

    2011-01-01

    Quantum Dots (QDs) are promising alternatives to organic dyes as sensitisers for photocatalytic electrodes. This review article provides an overview of the current state of the art in this area. More specifically, different types of QDs with a special focus on heavy-metal free QDs and the methods for preparation and adsorption onto metal oxide electrodes (especially titania and zinc oxide) are discussed. Eventually, the key areas of necessary improvements are identified and assessed.

  6. Quantum Dot Sensitized Photoelectrodes

    Directory of Open Access Journals (Sweden)

    Thomas Nann

    2011-11-01

    Full Text Available Quantum Dots (QDs are promising alternatives to organic dyes as sensitisers for photocatalytic electrodes. This review article provides an overview of the current state of the art in this area. More specifically, different types of QDs with a special focus on heavy-metal free QDs and the methods for preparation and adsorption onto metal oxide electrodes (especially titania and zinc oxide are discussed. Eventually, the key areas of necessary improvements are identified and assessed.

  7. Plasmonic fluorescent quantum dots

    OpenAIRE

    Jin, Yongdong; Gao, Xiaohu

    2009-01-01

    Combining multiple discrete components into a single multifunctional nanoparticle could be useful in a variety of applications. Retaining the unique optical and electrical properties of each component after nanoscale integration is, however, a long-standing problem1,2. It is particularly difficult when trying to combine fluorophores such as semiconductor quantum dots with plasmonic materials such as gold, because gold and other metals can quench the fluorescence3,4. So far, the combination of...

  8. Nanocrystal quantum dots

    CERN Document Server

    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

  9. Quantum dot nanostructures

    Directory of Open Access Journals (Sweden)

    Mohamed Henini

    2002-06-01

    These sophisticated technologies for the growth of high quality epitaxial layers of compound semiconductor materials on single crystal semiconductor substrates are becoming increasingly important for the development of the semiconductor electronics industry. This article is intended to convey the flavor of the subject by focusing on the technology and applications of self-assembled quantum dots (QDs and to give an introduction to some of the essential characteristics.

  10. 75 FR 6862 - Airworthiness Directives; Bombardier, Inc. Model CL-600-1A11 (CL-600), CL-600-2A12 (CL-601), CL...

    Science.gov (United States)

    2010-02-12

    ... Policies and Procedures (44 FR 11034, February 26, 1979); and 3. Will not have a significant economic.... Model CL-600-1A11 (CL- 600), CL-600-2A12 (CL-601), CL-600-2B16 (CL-601-3A, CL-601-3R, and CL- 604 Variants (Including CL-605 Marketing Variant)) Airplanes AGENCY: Federal Aviation Administration (FAA),...

  11. Polymorphs of Pridopidine Hydrochloride

    DEFF Research Database (Denmark)

    Zimmermann, A.; Frostrup, B.; Bond, A. D.

    2012-01-01

    Pridopidine hydrochloride (Huntexil, Neuro-Search A/S, Ballerup, Denmark) is a dopaminergic stabilizer, currently in development for the treatment of motor symptoms associated with Huntington's disease. In this study, two polymorphic forms are characterized, forms I and II. The crystal structures...... center dot center dot N+-H center dot center dot center dot Cl-center dot center dot center dot N+-H center dot center dot center dot motif between columns. Forms I and II have melting points of 199 and 210 degrees C, respectively. Following melting of form I, a kinetically controlled crystallization...

  12. Intracellular distribution of nontargeted quantum dots after natural uptake and microinjection

    Directory of Open Access Journals (Sweden)

    Damalakiene L

    2013-02-01

    Full Text Available Leona Damalakiene,1 Vitalijus Karabanovas,2 Saulius Bagdonas,1 Mindaugas Valius,3 Ricardas Rotomskis1,21Biophotonics Group, Laser Research Center, Faculty of Physics, 2Biomedical Physics Laboratory, Institute of Oncology, 3Proteomics Center, Institute of Biochemistry, Vilnius University, Vilnius, LithuaniaBackground: The purpose of this study was to elucidate the mechanism of natural uptake of nonfunctionalized quantum dots in comparison with microinjected quantum dots by focusing on their time-dependent accumulation and intracellular localization in different cell lines.Methods: The accumulation dynamics of nontargeted CdSe/ZnS carboxyl-coated quantum dots (emission peak 625 nm was analyzed in NIH3T3, MCF-7, and HepG2 cells by applying the methods of confocal and steady-state fluorescence spectroscopy. Intracellular colocalization of the quantum dots was investigated by staining with Lysotracker®.Results: The uptake of quantum dots into cells was dramatically reduced at a low temperature (4°C, indicating that the process is energy-dependent. The uptake kinetics and imaging of intracellular localization of quantum dots revealed three accumulation stages of carboxyl-coated quantum dots at 37°C, ie, a plateau stage, growth stage, and a saturation stage, which comprised four morphological phases: adherence to the cell membrane; formation of granulated clusters spread throughout the cytoplasm; localization of granulated clusters in the perinuclear region; and formation of multivesicular body-like structures and their redistribution in the cytoplasm. Diverse quantum dots containing intracellular vesicles in the range of approximately 0.5–8 µm in diameter were observed in the cytoplasm, but none were found in the nucleus. Vesicles containing quantum dots formed multivesicular body-like structures in NIH3T3 cells after 24 hours of incubation, which were Lysotracker-negative in serum-free medium and Lysotracker-positive in complete medium. The

  13. Inter-dot coupling effects on transport through correlated parallel coupled quantum dots

    Indian Academy of Sciences (India)

    Shyam Chand; G Rajput; K C Sharma; P K Ahluwalia

    2009-05-01

    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 of quantum dots. The effect of inter-dot tunnelling on transport properties has been explored. Results, in intermediate inter-dot coupling regime show signatures of merger of two dots to form a single composite dot and in strong coupling regime the behaviour of the system resembles the two decoupled dots.

  14. Templating growth of gold nanostructures with a CdSe quantum dot array

    Science.gov (United States)

    Paul, Neelima; Metwalli, Ezzeldin; Yao, Yuan; Schwartzkopf, Matthias; Yu, Shun; Roth, Stephan V.; Müller-Buschbaum, Peter; Paul, Amitesh

    2015-05-01

    In optoelectronic devices based on quantum dot arrays, thin nanolayers of gold are preferred as stable metal contacts and for connecting recombination centers. The optimal morphology requirements are uniform arrays with precisely controlled positions and sizes over a large area with long range ordering since this strongly affects device performance. To understand the development of gold layer nanomorphology, the detailed mechanism of structure formation are probed with time-resolved grazing incidence small-angle X-ray scattering (GISAXS) during gold sputter deposition. Gold is sputtered on a CdSe quantum dot array with a characteristic quantum dot spacing of ~7 nm. In the initial stages of gold nanostructure growth, a preferential deposition of gold on top of quantum dots occurs. Thus, the quantum dots act as nucleation sites for gold growth. In later stages, the gold nanoparticles surrounding the quantum dots undergo a coarsening to form a complete layer comprised of gold-dot clusters. Next, growth proceeds dominantly via vertical growth of gold on these gold-dot clusters to form an gold capping layer. In this capping layer, a shift of the cluster boundaries due to ripening is found. Thus, a templating of gold on a CdSe quantum dot array is feasible at low gold coverage.

  15. 对比分析三角Pr3+中心在CsCdBr3和GdCl3晶体中的能级分裂%Comparative analysis of energy levels splitting for the triagonal Pr3+ centers in CsCdBr3 and GdCl3 crystals

    Institute of Scientific and Technical Information of China (English)

    段美玲; 李晋红; 陈芳

    2015-01-01

    Based upon the combination of Racah’ s group-theoretical consideration with Slater’ s wavefunctions, the 91 × 91 complete energy matrix of 4f2 configuration ion Pr3+ in C3v and C3h crystal field have been constructed respectively. The calculated Stark energy levels of CsCdBr3:Pr3+ and GdCl3:Pr3+ present a good agreement with the experimental values, which implies that the complete energy matrix method can be received as a recommend-able tool to perform a theoretical analysis to the doped crystal. Besides, the detailed comparison has been per-formed about the influence of Pr3+ ions on the energy levels splitting of the host crystal CsCdBr3 and GdCl3 doped with Pr3+ ions, characterized by different point group symmetry. It indicates that the sixth order crystal field pa-rameters play an indispensable role in splitting the energy levels. Additionally, the two systems will experience different local distortion.%以Racah的群表示论和Slater的波函数理论为基础,分别建立了4f2组态离子Pr3+在三角晶体场C3v和C3h中的91×91完全能量矩阵,并对Pr3+离子掺杂在卤化物CsCdBr3和GdCl3中的Stark能级做了计算与分析。结果显示计算值与实验值吻合很好,表明在分析由稀土离子掺杂体系的能级分裂时,完全能量矩阵方法是有效的方法。此外,将两种具有不同点群对称的体系的能级分裂情况作了比较,结果显示六阶晶体场参量对能级分裂的影响是不能忽略的,而且CsCdBr3:Pr3+和GdCl3:Pr3+将产生不同程度的畸变。

  16. Reassessing the role of DotF in the Legionella pneumophila type IV secretion system.

    Directory of Open Access Journals (Sweden)

    Molly C Sutherland

    Full Text Available Legionella pneumophila, the causative agent of a severe pneumonia termed Legionnaires' Disease, survives and replicates within both protozoan hosts and human alveolar macrophages. Intracellular survival is dependent upon secretion of a plethora of protein effectors that function to form a replicative vacuole, evade the endocytic pathway and subvert host immune defenses. Export of these factors requires a type IV secretion system (T4SS called Dot/Icm that is composed of twenty-seven proteins. This report focuses on the DotF protein, which was previously postulated to have several different functions, one of which centered on binding Dot/Icm substrates. In this report, we examined if DotF functions as the T4SS inner membrane receptor for Dot/Icm substrates. Although we were able to recapitulate the previously published bacterial two-hybrid interaction between DotF and several substrates, the interaction was not dependent on the Dot/Icm substrates' signal sequences as predicted for a substrate:receptor interaction. In addition, binding did not require the cytoplasmic domain of DotF, which was anticipated to be involved in recognizing substrates in the cytoplasm. Finally, inactivation of dotF did not abolish intracellular growth of L. pneumophila or translocation of substrates, two phenotypes dependent on the T4SS receptor. These data strongly suggest that DotF does not act as the major receptor for Dot/Icm substrates and therefore likely performs an accessory function within the core-transmembrane subcomplex of the L. pneumophila Dot/Icm type IV secretion system.

  17. Effect of hydrostatic pressure and polaronic mass of the binding energy in a spherical quantum dot

    Institute of Scientific and Technical Information of China (English)

    A. Rejo Jeice; Sr. Gerardin Jayam; K. S. Joseph Wilson

    2015-01-01

    Simultaneous effect of hydrostatic pressure and polaronic mass on the binding energies of the ground and excited states of an on-center hydrogenic impurity confined in a GaAs/GaAlAs spherical quantum dot are theoretically investigated by the variational method within the effective mass approximation. The binding energy is calculated as a function of dot radius and pressure. Our findings proved that the hydrostatic pressure led to the decrease of confined energy and the increase of donor binding energy. Conduction band non-parabolicity and the polaron masses are effective in the donor binding energy which is significant for narrow dots not in the confined energy. The maximum donor binding energy achieved by the polaronic mass in the ground and excited states are 2%–19%for the narrow dots. The confined and donor binding energies approach zero as the dot size approaches infinity.

  18. One-Step Synthesis and Photoluminescence Eva-luation of Cadmium-containing Quantum Dots

    Institute of Scientific and Technical Information of China (English)

    Nisha Shukla; Michael M Nigra; Abigail D Ondeck

    2012-01-01

    We have developed a simple one-step process for synthesis of ternary quantum dots (ZnCdSe, MgCdSe) with photoluminescence wavelengths ranging from the red to the blue region of the visible spectrum. The primary aim of this work was to develop a synthesis for the preparation of Cd-containing quantum dots using a Cd precursor with lower toxicity than those used in common syntheses. This synthesis makes use of Cd(acac)2 which is significantly less toxic than precursors such as CdO and CdCl2 . We have studied the effect of solvent boiling point, precursors and reaction time on the photoluminescence properties of the ternary quantum dots. Ternary quantum dots synthesized from Cd(acac)2 in low boiling point solvents have photoluminescence wavelengths in the blue region, while those synthesized in high boiling point solvents have photoluminescence wavelengths in the red region.

  19. Determination of atropine using Mn-doped ZnS quantum dots as novel luminescent sensitizers

    International Nuclear Information System (INIS)

    A novel chemiluminescence (CL) method using water-soluble Mn-doped ZnS quantum dots (QDs) as sensitizers is proposed for the chemiluminometric determination of atropine in pharmaceutical formulation. Water-soluble Mn-doped ZnS QDs were synthesized by using L-cysteine as stabilizer in aqueous solutions. The nanoparticles were structurally and optically characterized by X-ray powder diffraction (XRD), dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FTIR), UV–vis absorption spectroscopy and photoluminescence (PL) emission spectroscopy. It was found that ZnS quantum dots acted as enhancers of the weak CL emission produced upon oxidation of sulfite by Ce(IV) in acidic medium. Trace amounts of atropine improved the sensitize effect of ZnS quantum dots yielding a significant chemiluminescence enhancement of the Ce(IV)–SO32−–ZnS QD system. Therefore, a new CL analysis system was developed for the determination of atropine. Under the optimum conditions, there is a good linear relationship between the relative chemiluminescence intensity and the concentration of atropine in the range of 1×10−9–1×10−6 M of atropine with a correlation coefficient (R2) of 0.9992. The limit of detection of this system was found to be 2.54×10−10 M. This method is not only simple, sensitive and low cost, but also reliable for practical applications. -- Highlights: • Mn-doped ZnS quantum dots could enhance the chemiluminescence (CL) of cerium(IV)–sodium sulfite system. • ZnS quantum dots were used as the nanocatalyst. • Trace amounts of atropine improved the sensitize effect of ZnS quantum dots. • This work is introduced as a new method for the determination of atropine commercial drugs. • Detection limit of atropine was obtained 2.54×10−10 mol L−1

  20. Quantifying Local and Cooperative Components in the Ferroelectric Distortion of BaTiO3: Learning from the Off-Center Motion in the MnCl65– Complex Formed in KCl:Mn+

    DEFF Research Database (Denmark)

    García Lastra, Juan Maria; García-Fernández, P.; Calle-Vallejo, F.;

    2014-01-01

    this is no longer true if the lattice is expanded by only ∼5%, stressing the high sensitivity of the local contribution to chemical and hydrostatic pressures. In order to further understand the effect of local contributions on the phase transition mechanism of ferroelectrics, we have investigated the surprising C3v......, the present calculations reproduce the experimental phase sequence and transition temperatures. Furthermore, our calculations show that the off-center instability in KCl:Mn+ would be suppressed by reducing by only 1% the lattice parameter, a situation that then becomes comparable to that found for BaTiO3...

  1. Wetting layers effect on InAs/GaAs quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Sun Chao [State Key Laboratory of Information Photonics and Optical Communications, Beijing University of Posts and Telecommunications, P.O. Box 49(BUPT), Xitucheng Road No. 10, Beijing 100876 (China); Lu Pengfei, E-mail: photon.bupt@gmail.com [State Key Laboratory of Information Photonics and Optical Communications, Beijing University of Posts and Telecommunications, P.O. Box 49(BUPT), Xitucheng Road No. 10, Beijing 100876 (China); Yu Zhongyuan; Cao Huawei; Zhang Lidong [State Key Laboratory of Information Photonics and Optical Communications, Beijing University of Posts and Telecommunications, P.O. Box 49(BUPT), Xitucheng Road No. 10, Beijing 100876 (China)

    2012-11-15

    FEM combining with the K{center_dot}P theory is adopted to systematically investigate the effect of wetting layers on the strain-stress profiles and electronic structures of self-organized InAs quantum dot. Four different kinds of quantum dots are introduced at the same height and aspect ratio. We found that 0.5 nm wetting layer is an appropriate thickness for InAs/GaAs quantum dots. Strain shift down about 3%{approx}4.5% for the cases with WL (0.5 nm) and without WL in four shapes of quantum dots. For band edge energy, wetting layers expand the potential energy gap width. When WL thickness is more than 0.8 nm, the band edge energy profiles cannot vary regularly. The electron energy is affected while for heavy hole this impact on the energy is limited. Wetting layers for the influence of the electronic structure is obviously than the heavy hole. Consequently, the electron probability density function spread from buffer to wetting layer while the center of hole's function moves from QDs internal to wetting layer when introduce WLs. When WLs thickness is larger than 0.8 nm, the electronic structures of quantum dots have changed obviously. This will affect the instrument's performance which relies on the quantum dots' optical properties.

  2. Optimization of Quantum-Dot Molecular Beam Epitaxy for Broad Spectral Bandwidth Devices

    KAUST Repository

    Majid, M. A.

    2012-12-01

    The optimization of the key growth parameters for broad spectral bandwidth devices based on quantum dots is reported. A combination of atomic force microscopy, photoluminescence of test samples, and optoelectronic characterization of superluminescent diodes (SLDs) is used to optimize the growth conditions to obtain high-quality devices with large spectral bandwidth, radiative efficiency (due to a reduced defective-dot density), and thus output power. The defective-dot density is highlighted as being responsible for the degradation of device performance. An SLD device with 160 nm of bandwidth centered at 1230 nm is demonstrated.

  3. Growth and micromagnetism of self-assembled epitaxial fcc(111) cobalt dots.

    Science.gov (United States)

    Fruchart, O; Masseboeuf, A; Toussaint, J C; Bayle-Guillemaud, P

    2013-12-11

    We develop the self-assembly of epitaxial submicrometer-sized face-centered-cubic (fcc) Co(111) dots using pulsed laser deposition. The dots display atomically flat facets, from which the ratios of surface and interface energies for fcc Co are deduced. Zero-field magnetic structures are investigated with magnetic force and Lorentz microscopies, revealing vortex-based flux-closure patterns. A good agreement is found with micromagnetic simulations.

  4. Donor Centers in a Gaussian Potential

    Institute of Scientific and Technical Information of China (English)

    XIE Wen-Fang

    2007-01-01

    We study a neutral donor center (D0) and a negatively charged donor center (D-) trapped by a quantum dot, which is subjected to a Gaussian potential confinement. Calculations are made by using the method of numerical diagonalization of Hamiltonian within the effective-mass approximation. The dependence of the ground state of the neutral shallow donor and the negatively charged donor on the dot size and the potential depth is investigated. The same calculations performed with the parabolic approximation of the Gaussian potential lead to the results that are qualitatively and quantitatively different from each other.

  5. Quantum dots: Rethinking the electronics

    Science.gov (United States)

    Bishnoi, Dimple

    2016-05-01

    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.

  6. Photonics of shungite quantum dots

    OpenAIRE

    Razbirin, Boris S.; Rozhkova, Natalia N.; Sheka, Elena F.

    2014-01-01

    Shungite quantum dots are associated with nanosize fragments of reduced graphene oxide similarly to synthetic graphene quantum dots thus forming a common class of GQDs. Colloidal dispersions of powdered shungite in water, carbon tetrachloride, and toluene form the ground for the GQD photonic peculiarities manifestation. Morphological study shows a steady trend of GQDs to form fractals and a drastic change in the colloids fractal structure caused by solvent was reliably established. Spectral s...

  7. Spin pumping through quantum dots

    OpenAIRE

    Rojek, Stephan; Governale, Michele; König, Jürgen

    2013-01-01

    We propose schemes for generating spin currents into a semiconductor by adiabatic or non-adiabatic pumping of electrons through interacting quantum dots. The appeal of such schemes lies in the possibility to tune the pumping characteristics via gate voltages that control the properties of the quantum dot. The calculations are based on a systematic perturbation expansion in the tunnel-coupling strength and the pumping frequency, expressed within a diagrammatic real-time technique. Special focu...

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

    Directory of Open Access Journals (Sweden)

    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.

  9. Estado nutricional de pacientes com esquizofrenia frequentadores do Centro de Atenção Psicossocial (CAPS do Hospital de Clínicas de Porto Alegre Nutritional status of patients with schizophrenia who attend the Psychosocial Care Center (CAPS, Hospital de Clínicas de Porto Alegre

    Directory of Open Access Journals (Sweden)

    Karine Zortéa

    2010-01-01

    Full Text Available OBJETIVO: Avaliar o estado nutricional de pacientes com esquizofrenia, atendidos por um programa de reabilitação social (CAPS. MÉTODOS: Foi realizado um estudo transversal com 40 pacientes com diagnóstico de esquizofrenia, em uso de antipsicóticos, atendidos no CAPS do Hospital de Clínicas de Porto Alegre. Foram verificados medidas antropométricas (peso, estatura, circunferência abdominal, percentual de gordura corporal, pressão arterial e tabagismo. RESULTADOS: A amostra constitui-se de 65% de homens. A média de peso encontrada foi de 75,39 ± 15,73 kg. O índice de massa corporal médio apresentou-se dentro dos parâmetros de sobrepeso (26,76 ± 4,78 kg/m², sendo 55% dos pacientes com sobrepeso ou obesidade segundo a classificação da OMS/1998. A circunferência abdominal e o percentual de gordura corporal apresentaram-se elevados na maioria dos pacientes (62,5% e 92,5%, respectivamente. Adicionalmente, não houve associação significativa entre IMC e a classificação de antipsicóticos (típicos, atípicos, clozapina. Encontrou-se uma correlação entre o tempo de doença com o percentual de gordura (r = 0,39, p = 0,033 e escolaridade com o peso (r = 0,362, p = 0,046 e IMC (r = 0,372, p = 0,039. Na regressão linear, 13% da variabilidade do percentual de gordura foi explicada pelo tempo de doença (r² = 0,131, B = 0,233, p = 0,049; 13% da variação do peso foi explicada pela escolaridade (r² = 0,131, B = 1,415, p = 0,046 e 13,8% da variação do IMC foi explicada pela escolaridade (r² = 0,138, B = 0,411, p = 0,039. CONCLUSÃO: Os pacientes apresentaram níveis aumentados de circunferência abdominal, percentual de gordura corporal e peso. Aparentemente, o ganho de peso ocorre em todos os pacientes expostos a antipsicóticos, independentemente do tipo de medicação e de resposta clínica, e a qualquer momento ao longo da evolução da doença. Sugere-se que, adicionalmente, a avaliação dos hábitos alimentares e o

  10. Felodipine-diazabicyclo 2.2.2 octane-water (1/1/1)

    DEFF Research Database (Denmark)

    Solanko, K. A.; Surov, A. O.; Perlovich, G. L.;

    2012-01-01

    The title compound, C18H19Cl2NO4 center dot C6H12N2 center dot H2O, is a cocrystal hydrate containing the active pharmaceutical ingredient felodipine and diazabicyclo[2.2.2]octane (DABCO). The DABCO and water molecules are linked through O-H center dot center dot center dot N hydrogen bonds into...

  11. Fractals of graphene quantum dots in photoluminescence of shungite

    OpenAIRE

    RAZBIRIN B.S.; ROZHKOVA N.N.; Sheka, E. F.; Nelson, D. K.; Starukhin, A. N.; Goryunov, A. S.

    2013-01-01

    Photoluminescence of graphene quantum dots (GQDs) of shungite, attributed to individual fragments of reduced graphene oxide (rGO), has been studied for the frozen rGO colloidal dispersions in water, carbon tetrachloride, and toluene. Morphological study shows a steady trend of GQDs to form fractals and a drastic change in the colloids fractal structure caused by solvent was reliably established. Spectral study reveals a dual character of emitting centers: individual GQDs are responsible for t...

  12. Fuzzy dot ideals and fuzzy dot H-ideals of BCH-algebras

    Institute of Scientific and Technical Information of China (English)

    PENG Jia-yin

    2008-01-01

    The notions of fuzzy dot ideals and fuzzy dot H-ideals in BCH-algebras are intro duced,several appropriate examples are provided,and their some properties are investigated.The relations among fuzzy ideal,fuzzy H-ideal,fuzzy dot ideal and fuzzy dot H-ideals in BCH algebras are discussed,several equivalent depictions of fuzzy dot ideal are obtained. How to deal with the homomorphic image and inverse image of fuzzy dot ideals (fuzzy dot H-ideals) are studied. The relations between a fuzzy dot ideal (fuzzy dot H-ideal) in BCH-algebras and a fuzzy dot ideal (fuzzy dot H-ideal) in the product algebra of BCH-algebras are given.

  13. Concerted evolution of the tandemly repeated genes encoding primate U2 small nuclear RNA (the RNU2 locus) does not prevent rapid diversification of the (CT){sub n} {center_dot} (GA){sub n} microsatellite embedded within the U2 repeat unit

    Energy Technology Data Exchange (ETDEWEB)

    Liao, D.; Weiner, A.M. [Yale Univ., New Haven, CT (United States)

    1995-12-10

    The RNU2 locus encoding human U2 small nuclear RNA (snRNA) is organized as a nearly perfect tandem array containing 5 to 22 copies of a 5.8-kb repeat unit. Just downstream of the U2 snRNA gene in each 5.8-kb repeat unit lies a large (CT){sub n}{center_dot}(GA){sub n} dinucleotide repeat (n {approx} 70). This form of genomic organization, in which one repeat is embedded within another, provides an unusual opportunity to study the balance of forces maintaining the homogeneity of both kinds of repeats. Using a combination of field inversion gel electrophoresis and polymerase chain reaction, we have been able to study the CT microsatellites within individual U2 tandem arrays. We find that the CT microsatellites within an RNU2 allele exhibit significant length polymorphism, despite the remarkable homogeneity of the surrounding U2 repeat units. Length polymorphism is due primarily to loss or gain of CT dinucleotide repeats, but other types of deletions, insertions, and substitutions are also frequent. Polymorphism is greatly reduced in regions where pure (CT){sub n} tracts are interrupted by occasional G residues, suggesting that irregularities stabilize both the length and the sequence of the dinucleotide repeat. We further show that the RNU2 loci of other catarrhine primates (gorilla, chimpanzee, ogangutan, and baboon) contain orthologous CT microsatellites; these also exhibit length polymorphism, but are highly divergent from each other. Thus, although the CT microsatellite is evolving far more rapidly than the rest of the U2 repeat unit, it has persisted through multiple speciation events spanning >35 Myr. The persistence of the CT microsatellite, despite polymorphism and rapid evolution, suggests that it might play a functional role in concerted evolution of the RNU2 loci, perhaps as an initiation site for recombination and/or gene conversion. 70 refs., 5 figs.

  14. Influence of calcium on transport properties, band spectrum and superconductivity of YBa{sub 2}Cu{sub 3}O{sub y} and YBa{sub 1.5}La{sub 0.5}Cu{sub 3}O{sub y}{sup {center_dot}}

    Energy Technology Data Exchange (ETDEWEB)

    Gasumyants, V.E.; Vladimirskaya, E.V. [State Technical Univ., St. Petersburg (Russian Federation); Patrina, I.B. [Institute of Silicate Chemistry, St. Petersburg (Russian Federation)

    1994-12-31

    The comparative investigation of transport phenomena in Y{sub 1-x}Ca{sub x}Ba{sub 2}Cu{sub 3}O{sub y} (0y>6.87 and 6.73y>6.96) and YBa{sub 2-x}La{sub x}Cu{sub 3}O{sub y} (0center_dot}}. The results obtained suggest that Ca gives rise to some peculiarities in band spectrum of this compound.

  15. 76 FR 46597 - Airworthiness Directives; Bombardier, Inc. Model CL-600-2A12 (CL-601) and CL-600-2B16 (CL-601-3A...

    Science.gov (United States)

    2011-08-03

    .... Model CL-600-2A12 (CL- 601) and CL-600-2B16 (CL-601-3A, CL-601-3R, and CL-604 Variants) Airplanes... Bombardier, Inc. model-- Task(s)-- Initial compliance time (whichever occurs later)-- CL-600-2A12 (CL-601... icing. accumulation of 4,800 after the effective inclusive; and CL-600-2B16 (CL- total flight hours;...

  16. A hydrochemical investigation using 36Cl/Cl in groundwaters

    OpenAIRE

    Metcalfe, R.

    2003-01-01

    This report describes 36Cl studies which were undertaken during the H14 financial year. 6 groundwater samples were collected for 36Cl analysis. The results of this study suggest that 36Cl data could potentially be useful for interpreting groundwater origins and flow paths.

  17. Translocation of PEGylated quantum dots across rat alveolar epithelial cell monolayers

    Directory of Open Access Journals (Sweden)

    Fazlollahi F

    2011-11-01

    Full Text Available Farnoosh Fazlollahi1,8, Arnold Sipos1,2, Yong Ho Kim1,2, Sarah F Hamm-Alvarez6, Zea Borok1–3, Kwang-Jin Kim1,2,5–7, Edward D Crandall1,2,4,8 1Will Rogers Institute Pulmonary Research Center, 2Department of Medicine, 3Department of Biochemistry and Molecular Biology, 4Department of Pathology, 5Department of Physiology and Biophysics, 6Department of Pharmacology and Pharmaceutical Sciences, 7Department of Biomedical Engineering, 8Mork Family Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, CA, USA Background: In this study, primary rat alveolar epithelial cell monolayers (RAECM were used to investigate transalveolar epithelial quantum dot trafficking rates and underlying transport mechanisms. Methods: Trafficking rates of quantum dots (PEGylated CdSe/ZnS, core size 5.3 nm, hydrodynamic size 25 nm in the apical-to-basolateral direction across RAECM were determined. Changes in bioelectric properties (ie, transmonolayer resistance and equivalent active ion transport rate of RAECM in the presence or absence of quantum dots were measured. Involvement of endocytic pathways in quantum dot trafficking across RAECM was assessed using specific inhibitors (eg, methyl-ß-cyclodextrin, chlorpromazine, and dynasore for caveolin-, clathrin-, and dynamin-mediated endocytosis, respectively. The effects of lowering tight junctional resistance on quantum dot trafficking were determined by depleting Ca2+ in apical and basolateral bathing fluids of RAECM using 2 mM EGTA. Effects of temperature on quantum dot trafficking were studied by lowering temperature from 37°C to 4°C. Results: Apical exposure of RAECM to quantum dots did not elicit changes in transmonolayer resistance or ion transport rate for up to 24 hours; quantum dot trafficking rates were not surface charge-dependent; methyl-ß-cyclodextrin, chlorpromazine, and dynasore did not decrease quantum dot trafficking rates; lowering of temperature

  18. Biosensing with Luminescent Semiconductor Quantum Dots

    Directory of Open Access Journals (Sweden)

    Hedi Mattoussi

    2006-08-01

    Full Text Available Luminescent semiconductor nanocrystals or quantum dots (QDs are a recentlydeveloped class of nanomaterial whose unique photophysical properties are helping tocreate a new generation of robust fluorescent biosensors. QD properties of interest forbiosensing include high quantum yields, broad absorption spectra coupled to narrow sizetunablephotoluminescent emissions and exceptional resistance to both photobleaching andchemical degradation. In this review, we examine the progress in adapting QDs for severalpredominantly in vitro biosensing applications including use in immunoassays, asgeneralized probes, in nucleic acid detection and fluorescence resonance energy transfer(FRET - based sensing. We also describe several important considerations when workingwith QDs mainly centered on the choice of material(s and appropriate strategies forattaching biomolecules to the QDs.

  19. Binding Energy of an Exciton Bound to Ionized Acceptor in Quantum Dots

    Institute of Scientific and Technical Information of China (English)

    XIE Wen-Fang

    2001-01-01

    Binding energiesfor an exciton (X ) trapped in the two-dimensional quantum dot by a negative ion located on the z axis at a distance from the dot plane are calculated by using the method of few-body physics.This configuration is called a barrier (A-,X) center.The dependence of the binding energy of the ground state of the barrier (A-,X)center on the electron-to-hole mass ratio for a few values of the distance d between the fixed negative ion on the z axis and the dot plane is obtained.We find that when d → 0,the barrier (A-,X) center has not any bound state.We also studied the stability and binding energy of the ground state of the barrier (A-,X) center in a parabolic quantum dot as a function of the distance d between the fixed negative ion on the z axis and the dot plane.``

  20. A novel chemiluminescence method for determination of bisphenol Abased on the carbon dot-enhanced HCO3−–H2O2 system

    International Nuclear Information System (INIS)

    A simple and sensitive chemiluminescence (CL) method on the basis of carbon dot (C-dot) enhanced HCO3−–H2O2 system, is designed for the determination of bisphenol A (BPA). The very weak CL of the HCO3−–H2O2 system is enhanced by a factor of ∼100 in the presence of C-dots. Possible mechanisms that lead to the effect were elucidated by recording fluorescence and CL spectra and studying the effect of some radical scavengers. This enhancement is inhibited by BPA in the concentration range from 1.0 to 100 µg L−1. This is exploited for its trace determination with a detection limit (3 s) of 0.3 µg L−1. The established method was applied to the determination of BPA in baby bottle and water samples with satisfactory results. - Highlights: • The effect of carbon dots on HCO3−–H2O2 chemiluminescence reaction is studied. • Carbon dots greatly enhance the CL signal of this reaction (∼100 fold). • The new CL system was applied to determination of bisphenol A in real samples

  1. Resonant electronic transport through a triple quantum-dot with Λ-type level structure under dual radiation fields

    International Nuclear Information System (INIS)

    Due to quantum interference, light can transmit through dense atomic media, a phenomenon known as electromagnetically induced transparency (EIT). We propose that EIT is not limited to light transmission and there is an electronic analog where resonant transparency in charge transport in an opaque structure can be induced by electromagnetic radiation. A triple-quantum-dots system with Λ-type level structure is generally opaque due to the level in the center dot being significantly higher and therefore hopping from the left dot to the center dot is almost forbidden. We demonstrate that an electromagnetically induced electron transparency (EIET) in charge of transport can indeed occur in the Λ-type system. The direct evidence of EIET is that an electron can travel from the left dot to the right dot, while the center dot apparently becomes invisible. We analyze EIET and the related shot noise in both the zero and strong Coulomb blockade regimes. It is found that the EIET (position, height, and symmetry) can be tuned by several controllable parameters of the radiation fields, such as the Rabi frequencies and detuning frequencies. The result offers a transparency/opaque tuning technique in charge transport using interfering radiation fields

  2. Optical Fiber Sensing Using Quantum Dots

    OpenAIRE

    Faramarz Farahi; José Luís Santos; Tito Trindade; Manuel António Martins; Pedro Jorge

    2007-01-01

    Recent advances in the application of semiconductor nanocrystals, or quantum dots, as biochemical sensors are reviewed. Quantum dots have unique optical properties that make them promising alternatives to traditional dyes in many luminescence based bioanalytical techniques. An overview of the more relevant progresses in the application of quantum dots as biochemical probes is addressed. Special focus will be given to configurations where the sensing dots are incorporated in sol...

  3. Biosynthesis of luminescent quantum dots in an earthworm

    Science.gov (United States)

    Stürzenbaum, S. R.; Höckner, M.; Panneerselvam, A.; Levitt, J.; Bouillard, J.-S.; Taniguchi, S.; Dailey, L.-A.; Khanbeigi, R. Ahmad; Rosca, E. V.; Thanou, M.; Suhling, K.; Zayats, A. V.; Green, M.

    2013-01-01

    The synthesis of designer solid-state materials by living organisms is an emerging field in bio-nanotechnology. Key examples include the use of engineered viruses as templates for cobalt oxide (Co3O4) particles, superparamagnetic cobalt-platinum alloy nanowires and gold-cobalt oxide nanowires for photovoltaic and battery-related applications. Here, we show that the earthworm's metal detoxification pathway can be exploited to produce luminescent, water-soluble semiconductor cadmium telluride (CdTe) quantum dots that emit in the green region of the visible spectrum when excited in the ultraviolet region. Standard wild-type Lumbricus rubellus earthworms were exposed to soil spiked with CdCl2 and Na2TeO3 salts for 11 days. Luminescent quantum dots were isolated from chloragogenous tissues surrounding the gut of the worm, and were successfully used in live-cell imaging. The addition of polyethylene glycol on the surface of the quantum dots allowed for non-targeted, fluid-phase uptake by macrophage cells.

  4. Constitutional Isomerism of BiW6Cl15: (BiCl)[W6Cl14] and (BiCl2)[W6Cl13

    OpenAIRE

    Meyer, Hans-Juergen

    2009-01-01

    Abstract The compound (BiCl)[W6Cl14] was previously characterized as a product of the reduction of tungsten hexachloride with elemental bismuth. Another modification of BiW6Cl15 is now presented as (BiCl2)[W6Cl13], based on the results of an X-ray single crystal structure determination (space group P21/c, a = 1354.3(2) pm, b = 1234.4(2) pm, c = 1538.9(2) pm, and ? = 118.76(1) ?). The structure of (BiCl2)[W6Cl13] contains chains of [(W6Cl8i)Cl4aCl2/2a-a]- clusters bridged by chlorin...

  5. A colloidal quantum dot spectrometer

    Science.gov (United States)

    Bao, Jie; Bawendi, Moungi G.

    2015-07-01

    Spectroscopy is carried out in almost every field of science, whenever light interacts with matter. Although sophisticated instruments with impressive performance characteristics are available, much effort continues to be invested in the development of miniaturized, cheap and easy-to-use systems. Current microspectrometer designs mostly use interference filters and interferometric optics that limit their photon efficiency, resolution and spectral range. Here we show that many of these limitations can be overcome by replacing interferometric optics with a two-dimensional absorptive filter array composed of colloidal quantum dots. Instead of measuring different bands of a spectrum individually after introducing temporal or spatial separations with gratings or interference-based narrowband filters, a colloidal quantum dot spectrometer measures a light spectrum based on the wavelength multiplexing principle: multiple spectral bands are encoded and detected simultaneously with one filter and one detector, respectively, with the array format allowing the process to be efficiently repeated many times using different filters with different encoding so that sufficient information is obtained to enable computational reconstruction of the target spectrum. We illustrate the performance of such a quantum dot microspectrometer, made from 195 different types of quantum dots with absorption features that cover a spectral range of 300 nanometres, by measuring shifts in spectral peak positions as small as one nanometre. Given this performance, demonstrable avenues for further improvement, the ease with which quantum dots can be processed and integrated, and their numerous finely tuneable bandgaps that cover a broad spectral range, we expect that quantum dot microspectrometers will be useful in applications where minimizing size, weight, cost and complexity of the spectrometer are critical.

  6. Quantum-dot emitters in photonic nanostructures

    DEFF Research Database (Denmark)

    Hvam, Jørn Märcher; Stobbe, Søren; Lodahl, Peter

    2010-01-01

    The spontaneous emission from self-assembled semiconductor quantum dots is strongly influenced by the environment in which they are placed. This can be used to determine fundamental optical properties of the quantum dots as well as to manipulate and control the quantum-dot emission itself....

  7. Beer's law in semiconductor quantum dots

    CERN Document Server

    Adamashvili, G T

    2010-01-01

    The propagation of a coherent optical linear wave in an ensemble of semiconductor quantum dots is considered. It is shown that a distribution of transition dipole moments of the quantum dots changes significantly the polarization and Beer's absorption length of the ensemble of quantum dots. Explicit analytical expressions for these quantities are presented.

  8. Fabrication and single-electron-transfer operation of a triple-dot single-electron transistor

    Energy Technology Data Exchange (ETDEWEB)

    Jo, Mingyu, E-mail: mingyujo@eis.hokudai.ac.jp; Uchida, Takafumi; Tsurumaki-Fukuchi, Atsushi; Arita, Masashi; Takahashi, Yasuo [Graduate School of Information Science and Technology, Hokkaido University, Sapporo 060-0814 (Japan); Fujiwara, Akira; Nishiguchi, Katsuhiko [NTT Basic Research Laboratories, NTT Corporation, 3-1 Morinosato Wakamiya, Atsugi 243-0198 (Japan); Ono, Yukinori [Graduate School of Science and Engineering, University of Toyama, 3190 Gofuku, Toyama 930-8555 (Japan); Inokawa, Hiroshi [Research Institute of Electronics, Shizuoka University, 3-5-1, Johoku, Hamamatsu 432-8011 (Japan)

    2015-12-07

    A triple-dot single-electron transistor was fabricated on silicon-on-insulator wafer using pattern-dependent oxidation. A specially designed one-dimensional silicon wire having small constrictions at both ends was converted to a triple-dot single-electron transistor by means of pattern-dependent oxidation. The fabrication of the center dot involved quantum size effects and stress-induced band gap reduction, whereas that of the two side dots involved thickness modulation because of the complex edge structure of two-dimensional silicon. Single-electron turnstile operation was confirmed at 8 K when a 100-mV, 1-MHz square wave was applied. Monte Carlo simulations indicated that such a device with inhomogeneous tunnel and gate capacitances can exhibit single-electron transfer.

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

    Energy Technology Data Exchange (ETDEWEB)

    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

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

    International Nuclear Information System (INIS)

    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 T1=20 ms at B=4 T and T=1 K. A strong magnetic field dependence T1∝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 T1∝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 T1h in the microsecond range, therefore, comparable with electron spin

  11. Atomic scale investigations on Cd{sub x}Zn{sub 1−x}Se quantum dots: Correlation between the composition and emission properties

    Energy Technology Data Exchange (ETDEWEB)

    Benallali, H., E-mail: hammouda.benallali@im2np.fr; Hoummada, K.; Mangelinck, D. [Aix-Marseille Université, IM2NP-CNRS, Case 142, 13397 Marseille Cedex 20 (France); Cremel, T.; André, R.; Tatarenko, S.; Kheng, K. [University of Grenoble Alpes, F-38000 Grenoble (France); CEA, INAC, F-38054 Grenoble (France); CNRS, Inst. NEEL, F-38042 Grenoble (France)

    2014-08-04

    Atom probe tomography and photoluminescence spectroscopy have been used to study Cd{sub x}Zn{sub 1−x}Se quantum dots embedded in a ZnSe layer grown on a (001) GaAs substrate. Atom probe tomography analyses show significant cadmium incorporation in the center of the dots surrounded by poor cadmium region. These measurements illustrate that the maximum cadmium concentration in the quantum dots is significantly higher than the concentration estimated by transmission electron microscopy. The composition and size of quantum dots obtained by atom probe tomography have been used to calculate the transition energies including excitonic and strain effects.

  12. High 36Cl/Cl ratios in Chernobyl groundwater

    International Nuclear Information System (INIS)

    After the explosion of the Chernobyl Nuclear Power Plant in April 1986, contaminated material was buried in shallow trenches within the exclusion zone. A 90Sr plume was evidenced downgradient of one of these trenches, trench T22. Due to its conservative properties, 36Cl is investigated here as a potential tracer to determine the maximal extent of the contamination plume from the trench in groundwater. 36Cl/Cl ratios measured in groundwater, trench soil water and leaf leachates are 1–5 orders of magnitude higher than the theoretical natural 36Cl/Cl ratio. This contamination occurred after the Chernobyl explosion and currently persists. Trench T22 acts as an obvious modern point source of 36Cl, however other sources have to be involved to explain such contamination. 36Cl contamination of groundwater can be explained by dilution of trench soil water by uncontaminated water (rainwater or deep groundwater). With a plume extending further than that of 90Sr, radionuclide which is impacted by retention and decay processes, 36Cl can be considered as a suitable tracer of contamination from the trench in groundwater provided that modern release processes of 36Cl from trench soil are better characterized. - Highlights: • High 36Cl/Cl ratios measured in the Chernobyl Pilot Site groundwater. • Trench T22 acts as a modern source of groundwater contamination by 36Cl but other sources are involved. • Contamination results from dilution of a contaminated “T22” soil water with rainwater. • Processes involved in the modern release need to be investigated

  13. Luminescent Surface Quaternized Carbon Dots

    KAUST Repository

    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.

  14. On triaxial ellipsoidal quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Voon, L C Lew Yan; Willatzen, M [Mads Clausen Institute, University of Southern Denmark, Grundtvigs Alle 150, DK-6400 Soenderborg (Denmark)

    2004-02-25

    The bound-state problem for triaxial ellipsoidal infinite-barrier quantum dots has been solved. It is exactly solvable in terms of ellipsoidal coordinates and the eigenmodes are written in terms of Lame wavefunctions. The need for all eight types of functions is shown. This presents a generalization over previous work on spheres and spheroids. Splitting of degeneracy and level crossing are obtained.

  15. DOT strategies versus orbiter strategies

    NARCIS (Netherlands)

    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

  16. Vertical asymmetric double quantum dots

    Science.gov (United States)

    Roßbach, R.; Reischle, M.; Beirne, G. J.; Schweizer, H.; Jetter, M.; Michler, P.

    2007-01-01

    Two layers of differently sized self-assembled InP-quantum dots (QDs) separated by a GaInP spacer layer with varying thickness were grown by metal organic vapor phase epitaxy (MOVPE). Photoluminescence measurements of the QD ensembles and of individual asymmetric double QDS show coupling due to the tunnelling of carriers.

  17. 75 FR 63054 - Airworthiness Directives; Bombardier, Inc. Model CL-600-2B19 (Regional Jet Series 100 & 440...

    Science.gov (United States)

    2010-10-14

    ... published in the Federal Register on January 5, 2010 (75 FR 258). That NPRM proposed to correct an unsafe...'' under the DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and 3. Will not have.... Model CL-600-2B19 (Regional Jet Series 100 & 440) Airplanes AGENCY: Federal Aviation Administration...

  18. 76 FR 8605 - Airworthiness Directives; Bombardier, Inc. Model CL-600-2B19 (Regional Jet Series 100 and 440...

    Science.gov (United States)

    2011-02-15

    ... Register on November 15, 2010 (75 FR 69609). That NPRM proposed to correct an unsafe condition for the...'' under the DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and 3. Will not have.... Model CL-600-2B19 (Regional Jet Series 100 and 440) Airplanes AGENCY: Federal Aviation...

  19. 75 FR 31324 - Airworthiness Directives; Bombardier, Inc. Model CL-600-2B19 (Regional Jet Series 100 & 440...

    Science.gov (United States)

    2010-06-03

    ... ``significant rule'' under the DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and 3.... Model CL-600-2B19 (Regional Jet Series 100 & 440) Airplanes AGENCY: Federal Aviation Administration (FAA..., dated May 7, 2008, to Appendix A--Certification Maintenance Requirements of Part 2 of the Bombardier...

  20. 75 FR 64636 - Airworthiness Directives; Bombardier, Inc. Model CL-600-2B19 (Regional Jet Series 100 & 440...

    Science.gov (United States)

    2010-10-20

    ... 12866; 2. Is not a ``significant rule'' under the DOT Regulatory Policies and Procedures (44 FR 11034.... Model CL-600-2B19 (Regional Jet Series 100 & 440) Airplanes AGENCY: Federal Aviation Administration (FAA... of on-ground hydraulic accumulator screw cap/end cap failure have been experienced on...

  1. 76 FR 18024 - Airworthiness Directives; Bombardier, Inc. Model CL-600-2B19 (Regional Jet Series 100 & 440...

    Science.gov (United States)

    2011-04-01

    ... (75 FR 25788). That NPRM proposed to correct an unsafe condition for the specified products. The MCAI... ``significant rule'' under the DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and 3.... Model CL-600-2B19 (Regional Jet Series 100 & 440) Airplanes AGENCY: Federal Aviation Administration...

  2. First far-infrared high resolution analysis of the ν6 band of phosgene 35Cl2CO and 35Cl37ClCO

    Science.gov (United States)

    Flaud, J.-M.; Tchana, F. Kwabia; Lafferty, W. J.; Manceron, L.; Ndao, M.

    2016-08-01

    A Fourier transform spectrum of phosgene (Cl2CO) has been recorded in the 22.5 μm spectral region at a resolution of 0.00102 cm-1 using a Bruker IFS125HR spectrometer coupled to synchrotron radiation leading to the observation of the ν6 vibrational bands of the two isotopologues 35Cl2CO and 35Cl37ClCO. The corresponding upper state ro-vibrational levels were fit using Watson-type Hamiltonians. In this way it was possible to reproduce the upper state ro-vibrational levels to within the experimental uncertainty i.e. ∼0.30 × 10-3 cm-1. Very accurate rotational and centrifugal distortion constants were derived from the fit together with the following band centers: ν0(ν6,35Cl2CO) = 443.172062(15) cm-1, ν0(ν6,35Cl37ClCO) = 440.534956(17) cm-1.

  3. Hyperdense dots mimicking microcalcifications : Mammographic findings

    Energy Technology Data Exchange (ETDEWEB)

    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.

  4. Hyperdense dots mimicking microcalcifications : Mammographic findings

    International Nuclear Information System (INIS)

    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

  5. Systematic safety evaluation on photoluminescent carbon dots

    Science.gov (United States)

    Wang, Kan; Gao, Zhongcai; Gao, Guo; Wo, Yan; Wang, Yuxia; Shen, Guangxia; Cui, Daxiang

    2013-03-01

    Photoluminescent carbon dots (C-dots) were prepared using the improved nitric acid oxidation method. The C-dots were characterized by tapping-mode atomic force microscopy, and UV-vis absorption spectroscopy. The C-dots were subjected to systematic safety evaluation via acute toxicity, subacute toxicity, and genotoxicity experiments (including mouse bone marrow micronuclear test and Salmonella typhimurium mutagenicity test). The results showed that the C-dots were successfully prepared with good stability, high dispersibility, and water solubility. At all studied C-dot dosages, no significant toxic effect, i.e., no abnormality or lesion, was observed in the organs of the animals. Therefore, the C-dots are non-toxic to mice under any dose and have potential use in fluorescence imaging in vivo, tumor cell tracking, and others.

  6. 75 FR 30740 - Airworthiness Directives; Bombardier, Inc. Model CL-600-2B16 (CL-604 Variants (Including CL-605...

    Science.gov (United States)

    2010-06-02

    ... Procedures (44 FR 11034, February 26, 1979); and 3. Will not have a significant economic impact, positive or... Directives; Bombardier, Inc. Model CL-600-2B16 (CL- 604 Variants (Including CL-605 Marketing Variant... addition to Bombardier Inc. Models CL-600-2B19, CL-600-2C10 and CL-600-2D24. The latter three models...

  7. Spin transport through quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Lima, A.T. da Cunha; Anda, Enrique V. [Pontificia Univ. Catolica do Rio de Janeiro (PUC-Rio), RJ (Brazil)

    2003-07-01

    Full text: We investigate the spin polarized transport properties of a nanoscopic device constituted by a quantum dot connected to two leads. The electrical current circulates with a spin polarization that is modulated via a gate potential that controls the intensity of the spin-orbit coupling, the Rashba effect. We study a polarized field-effect transistor when one of its parts is constituted by a small quantum dot, which energies are controlled by another gate potential operating inside the confined region. The high confinement and correlation suffered by the charges inside the dot gives rise to novel phenomena. We show that through the manipulation of the gate potential applied to the dot it is possible to control, in a very efficient way, the intensity and polarization of the current that goes along the system. Other crucial parameters to be varied in order to understand the behavior of this system are the intensity of the external applied electric and magnetic field. The system is represented by the Anderson Impurity Hamiltonian summed to a spin-orbit interaction, which describes the Rashba effect. To obtain the current of this out-of-equilibrium system we use the Keldysh formalism.The solution of the Green function are compatible with the Coulomb blockade regime. We show that under the effect of a external magnetic field, if the dot is small enough the device operates as a complete spin filter that can be controlled by the gate potential. The behavior of this device when it is injected into it a polarized current and modulated by the Rashba effect is as well studied. (author)

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

    Directory of Open Access Journals (Sweden)

    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.

  9. 76 FR 477 - Airworthiness Directives; Bombardier, Inc. Model CL-600-2A12 (CL-601) and CL-600-2B16 (CL-601-3A...

    Science.gov (United States)

    2011-01-05

    ... Policies and Procedures (44 FR 11034, February 26, 1979); and 3. Will not have a significant economic.... Model CL-600-2A12 (CL- 601) and CL-600-2B16 (CL-601-3A, CL-601-3R, and CL-604 Variants) Airplanes AGENCY... applicability of the directive for CL-600-2A12 aircraft, serial numbers 3001 through 3066, and for CL-...

  10. 76 FR 66203 - Airworthiness Directives; Bombardier, Inc. Model CL-600-2B16 (CL-601-3A, CL-601-3R, and CL-604...

    Science.gov (United States)

    2011-10-26

    ... Policies and Procedures (44 FR 11034, February 26, 1979); and 3. Will not have a significant economic.... Model CL-600-2B16 (CL- 601-3A, CL-601-3R, and CL-604 Variants) Airplanes AGENCY: Federal Aviation... Bombardier, Inc. Model CL-600-2B16 (CL- 601-3A, CL-601-3R, and CL-604 Variants) airplanes, certificated...

  11. Biomimetic, Mild Chemical Synthesis of CdTe-GSH Quantum Dots with Improved Biocompatibility

    OpenAIRE

    Pérez-Donoso, José M.; Monrás, Juan P; Denisse Bravo; Adam Aguirre; Quest, Andrew F.; Igor O Osorio-Román; Aroca, Ricardo F.; Chasteen, Thomas G.; Vásquez, Claudio C.

    2012-01-01

    Multiple applications of nanotechnology, especially those involving highly fluorescent nanoparticles (NPs) or quantum dots (QDs) have stimulated the research to develop simple, rapid and environmentally friendly protocols for synthesizing NPs exhibiting novel properties and increased biocompatibility. In this study, a simple protocol for the chemical synthesis of glutathione (GSH)-capped CdTe QDs (CdTe-GSH) resembling conditions found in biological systems is described. Using only CdCl(2), K(...

  12. Highly efficient potentiometric glucose biosensor based on functionalized InN quantum dots

    OpenAIRE

    Alvi, Naveed ul Hassan; Soto Rodríguez, Paul; Gómez Hernández, Víctor Jesús; Kumar, Praveen; Amin, G.; Nur, O; Willander, Magnus; Nötzel, R.

    2012-01-01

    We present a fast, highly sensitive, and efficient potentiometric glucose biosensor based on functionalized InN quantum-dots (QDs). The InN QDs are grown by molecular beam epitaxy. The InN QDs are bio-chemically functionalized through physical adsorption of glucose oxidase (GOD). GOD enzyme-coated InN QDs based biosensor exhibits excellent linear glucose concentration dependent electrochemical response against an Ag/AgCl reference electrode over a wide logarithmic glucose concentration range ...

  13. Novel Au+-doped Zn xCd1−xS/ZnS core/shell quantum dots

    International Nuclear Information System (INIS)

    Au+ ions have been successfully incorporated into the lattice of ZnxCd1−xS quantum dots as luminescent centers via an aqueous method. The dopant emission can be tuned in the range of 445 to 570 nm, and the highest quantum yield can reach as high as 30%. Our results showed that Au+ ions can be used as an excellent luminescent dopant in doped quantum dots. Finally, these water-soluble quantum dots can be used directly in PL imaging of HepG2 cells without conjugating any biological targets, indicating a high potential application in bio-labeling. (papers)

  14. 76 FR 6536 - Airworthiness Directives; Bombardier, Inc. Model CL-215-1A10 (CL-215), CL-215-6B11 (CL-215T...

    Science.gov (United States)

    2011-02-07

    ... products. That NPRM was published in the Federal Register on November 9, 2010 (75 FR 68728). That NPRM... Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and 3. Will not have a significant.... Model CL-215-1A10 (CL- 215), CL-215-6B11 (CL-215T Variant), and CL-215-6B11 (CL-415 Variant)...

  15. Perfil clínico-epidemiológico dos pacientes diagnosticados com hanseníase em um centro de referência na região nordeste do Brasil Clinical and epidemiological profile of patients diagnosed with leprosy in a reference center in the notheast of Brazil

    Directory of Open Access Journals (Sweden)

    Cícero Cláudio Dias Gomes

    2005-12-01

    Full Text Available FUNDAMENTOS: A hanseníase permanece sério problema de saúde pública mundial. O conhecimento das características epidemiológicas da doença é importante ferramenta para o controle da endemia. OBJETIVO: Descrever as características clínicas e epidemiológicas dos pacientes diagnosticados com hanseníase no ano de 2004 em um centro de referência da Região Nordeste do Brasil. MÉTODO: Foram avaliados prontuários de pacientes que deram entrada no registro ativo do Centro de Dermatologia Dona Libânia, em Fortaleza, Ceará, no período de janeiro a dezembro de 2004. RESULTADOS: dos 967 casos que deram entrada nesse Centro naquele ano, 909 foram casos novos. Cerca de 7,7% eram pacientes entre zero e 14 anos de idade, e a distribuição por gênero foi de 483 (49,95% homens e 484 (50,05% mulheres. A maioria apresentava a forma clínica dimorfa (54,6%, sendo 82,2% dos pacientes provenientes de Fortaleza, CE. Foi realizada a avaliação do grau de incapacidades no diagnóstico em 94,2% dos pacientes, com 21,7% apresentando grau diferente de zero no diagnóstico. CONCLUSÃO: Com base nos resultados obtidos, constatou-se a presença de elevado percentual (7,7% de casos detectados em menores de 15 anos, associado a baixo percentual (5,8% de pacientes diagnosticados na forma indeterminada e elevado percentual (21,7% de casos com incapacidade ao diagnóstico.BACKGROUND: Leprosy continues to represent a serious public health problem worldwide. Knowledge of epidemiological characteristics of the disease is an important tool for the endemy control. OBJECTIVES: To describe the clinical and epidemiological characteristics of patients diagnosed with leprosy during 2004, in a Reference Center in the Northeast of Brazil. METHODS: We analyzed the records referring to patients who entered de active register of the Center of Dermatology Dona Libânia, in Fortaleza, Ceará, from January to december 2004. RESULTS: Out of 967 cases that entered this Center in

  16. Spin wave eigenmodes in single and coupled sub-150 nm rectangular permalloy dots

    Energy Technology Data Exchange (ETDEWEB)

    Carlotti, G., E-mail: giovanni.carlotti@fisica.unipg.it; Madami, M. [Dipartimento di Fisica e Geologia, Università di Perugia, Perugia (Italy); Tacchi, S. [Istituto Officina dei Materiali del CNR (CNR-IOM), Dipartimento di Fisica e Geologia, Perugia (Italy); Gubbiotti, G.; Dey, H.; Csaba, G.; Porod, W. [Center for Nano Science and Technology, Department of Electrical Engineering, University of Notre Dame, Notre Dame, Indiana 46556 (United States)

    2015-05-07

    We present the results of a Brillouin light scattering investigation of thermally excited spin wave eigenmodes in square arrays of either isolated rectangular dots of permalloy or twins of dipolarly coupled elements, placed side-by-side or head-to-tail. The nanodots, fabricated by e-beam lithography and lift-off, are 20 nm thick and have the major size D in the range between 90 nm and 150 nm. The experimental spectra show the presence of two main peaks, corresponding to modes localized either at the edges or in the center of the dots. Their frequency dependence on the dot size and on the interaction with adjacent elements has been measured and successfully interpreted on the basis of dynamical micromagnetic simulations. The latter enabled us also to describe the spatial profile of the eigenmodes, putting in evidence the effects induced by the dipolar interaction between coupled dots. In particular, in twinned dots the demagnetizing field is appreciably modified in proximity of the “internal edges” if compared to the “external” ones, leading to a splitting of the edge mode. These results can be relevant for the exploitation of sub-150 nm magnetic dots in new applications, such as magnonic metamaterials, bit-patterned storage media, and nano-magnetic logic devices.

  17. ClEST cluster :Cl_singleton0355 [ClEST

    Lifescience Database Archive (English)

    Full Text Available Cl_singleton0355 acyl- synthetase long- isoform b Cimex lectularius nuclear gene 19...GGAAGGTGCATTGGGAGCAATAAAAGCGATCGCATTTGTCTGTGATATCATCACTTATCCAGTGTACCTTATTCTACAACGGCCATGGG fb18010 1 acyl-CoA synthetase [Gl

  18. ClEST cluster :Cl_singleton0763 [ClEST

    Lifescience Database Archive (English)

    Full Text Available Cl_singleton0763 aldo-keto reductase Cimex lectularius nuclear gene 591 CACCGGGTAGG...GTGAATAAAGGCTTAGTTAGGTCAATCGGACTATCCAATTTCAACAAAAGACAGATCGAAGATGTTT fs09012 1 aldo-keto reductase [Gl

  19. Interaction of different poisons with MgCl2/TiCl4 based Ziegler-Natta catalysts

    Science.gov (United States)

    Bahri-Laleh, Naeimeh

    2016-08-01

    Adsorption of different poison molecules on activated MgCl2 is investigated within DFT using a cluster model of the MgCl2 surface with (MgCl2)16 formula containing four 4-coordinated and eight 5-coordinated Mg atoms as (110) and (104) surfaces, respectively. Studied poison molecules are chosen as possible impurities in hydrocarbon solvents and monomer feeds and contain water, hydrogensulfide, carbondioxide, molecular oxygen and methanol. First, adsorption of 1-4 molecules of different poisons to the (104) and (110) lateral cuts of MgCl2, as well as their adsorption on [MgCl2]/TiCl2Et active center and AlEt3 cocatalyst is considered. Results reveal that poisons strongly stabilize both crystal surfaces, mostly Ti active center relative to the unpoisoned solid. Second, energy barrier (ETS) for ethylene insertion in the presence of different poisons located on the first and second Mg atom relative to the active Ti is calculated. While poison molecule located on the second Mg does not change ETS, coordination of it into the first Mg atom increases ETS by 0.9-1.2 kcal mol-1. In the last part of this manuscript, the stereoselective behavior of active Ti species, with and without poison molecules and external electron donor, is fully explored.

  20. Constructions from Dots and Lines

    CERN Document Server

    Rodriguez, Marko A

    2010-01-01

    A graph is a data structure composed of dots (i.e. vertices) and lines (i.e. edges). The dots and lines of a graph can be organized into intricate arrangements. The ability for a graph to denote objects and their relationships to one another allow for a surprisingly large number of things to be modeled as a graph. From the dependencies that link software packages to the wood beams that provide the framing to a house, most anything has a corresponding graph representation. However, just because it is possible to represent something as a graph does not necessarily mean that its graph representation will be useful. If a modeler can leverage the plethora of tools and algorithms that store and process graphs, then such a mapping is worthwhile. This article explores the world of graphs in computing and exposes situations in which graphical models are beneficial.

  1. Properties of strong-coupling magneto-bipolaron qubit in quantum dot under magnetic field

    Science.gov (United States)

    Xu-Fang, Bai; Ying, Zhang; Wuyunqimuge; Eerdunchaolu

    2016-07-01

    Based on the variational method of Pekar type, we study the energies and the wave-functions of the ground and the first-excited states of magneto-bipolaron, which is strongly coupled to the LO phonon in a parabolic potential quantum dot under an applied magnetic field, thus built up a quantum dot magneto-bipolaron qubit. The results show that the oscillation period of the probability density of the two electrons in the qubit decreases with increasing electron–phonon coupling strength α, resonant frequency of the magnetic field ω c, confinement strength of the quantum dot ω 0, and dielectric constant ratio of the medium η the probability density of the two electrons in the qubit oscillates periodically with increasing time t, angular coordinate φ 2, and dielectric constant ratio of the medium η the probability of electron appearing near the center of the quantum dot is larger, and the probability of electron appearing away from the center of the quantum dot is much smaller. Project supported by the Natural Science Foundation of Hebei Province, China (Grant No. E2013407119) and the Items of Institution of Higher Education Scientific Research of Hebei Province and Inner Mongolia, China (Grant Nos. ZD20131008, Z2015149, Z2015219, and NJZY14189).

  2. Perfil clínico-epidemiológico das doenças sexualmente transmissíveis em crianças atendidas em um centro de referência na cidade de Manaus, Amazonas, Brasil Clinical and epidemiological profile of sexually transmitted diseases in children attending a referral center in the city of Manaus, Amazonas, Brazil

    Directory of Open Access Journals (Sweden)

    Carla Barros da Rocha Ribas

    2011-02-01

    Full Text Available FUNDAMENTOS: Doenças Sexualmente Transmissíveis em crianças permanecem um problema de saúde pública pouco estudado, sendo ainda necessários esclarecimentos sobre seu manejo e a relação destas com o abuso sexual infantil. OBJETIVOS: Descrever o perfil clínico-epidemiológico das Doenças Sexualmente Transmissíveis em crianças atendidas em centro de referência na cidade de Manaus. MÉTODOS: Realizou-se estudo descritivo exploratório para verificar características clínicas, epidemiológicas e laboratoriais das Doenças Sexualmente Transmissíveis em crianças atendidas durante o período de janeiro/2003 a dezembro/2007. RESULTADOS: Foram incluídas no estudo 182 crianças que apresentavam DST. A maioria era do sexo feminino (65,4% e de cor parda; a média de idade foi de 8,5 anos; 89% eram procedentes da cidade de Manaus; os pais foram os principais acompanhantes na consulta; verruga genital foi o principal diagnóstico em ambos os sexos; e, 90,1% apresentavam apenas uma DST. CONCLUSÃO: As frequências e características clínicas das DST nas crianças do estudo não diferiram do encontrado na literatura. Embora, com base em sinais e sintomas referentes tão somente às DST nas crianças, não se tenham parâmetros fidedignos de confirmação de abuso, deve-se sempre estar alerta para esta possibilidade, visto que estas doenças podem ser sinalizadoras de ofensas sexuais, por vezes, dissimuladas e repetidas.BACKGROUND: Sexually transmitted diseases in children remain a public health concern that is relatively ignored. Further data are required on the management of these diseases and their association with child sexual abuse. OBJECTIVES: To describe the clinical and epidemiological profile of sexually transmitted diseases in children receiving care at a referral center in the city of Manaus, Amazonas, Brazil. METHODS: A descriptive, exploratory study was conducted to evaluate the clinical, epidemiological and laboratory

  3. Photoactivation of silicon quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Lockwood, R., E-mail: rossl@ualberta.c [Department of Physics, University of Alberta, Edmonton, Alberta, T6G 2G7 (Canada); McFarlane, S. [Department of Physics, University of Alberta, Edmonton, Alberta, T6G 2G7 (Canada); Rodriguez Nunez, J.R. [Department of Chemistry, University of Alberta, Edmonton, Alberta, T6G 2G2 (Canada); Wang, X.Y. [Department of Physics, University of Alberta, Edmonton, Alberta, T6G 2G7 (Canada); Veinot, J.G.C. [Department of Chemistry, University of Alberta, Edmonton, Alberta, T6G 2G2 (Canada); Meldrum, A. [Department of Physics, University of Alberta, Edmonton, Alberta, T6G 2G7 (Canada)

    2011-07-15

    We show that free-standing silicon quantum dots (QDs) can be photoactivated by blue or UV optical irradiation. The luminescence intensity increases by an order of magnitude for irradiation times of several minutes under moderate optical power. The cut-off energy for photoactivation is between 2.1 and 2.4 eV, not very different from the activation energy for hydrogen dissociation from bulk silicon surfaces. We propose the mechanism for this effect is associated with silicon-hydride bond breaking and the subsequent oxidation of dangling bonds. This phenomenon could be used to 'write' luminescent quantum dots into pre-determined arrays. - Research highlights: {yields}Laser light causes increased photoluminescence intensity in silicon quantum dots. {yields} The photoactivation process is effective for wavelengths of 514 nm and shorter. {yields} Hydrogen bound to the Si-QDs is replaced by oxygen in a two-step process. {yields} Patterning is possible but limited by physical dispersion of Si-QDs.

  4. Few-electron quantum dots

    International Nuclear Information System (INIS)

    We review some electron transport experiments on few-electron, vertical quantum dot devices. The measurement of current versus source-drain voltage and gate voltage is used as a spectroscopic tool to investigate the energy characteristics of interacting electrons confined to a small region in a semiconducting material. Three energy scales are distinguished: the single-particle states, which are discrete due to the confinement involved; the direct Coulomb interaction between electron charges on the dot; and the exchange interaction between electrons with parallel spins. To disentangle these energies, a magnetic field is used to reorganize the occupation of electrons over the single-particle states and to induce changes in the spin states. We discuss the interactions between small numbers of electrons (between 1 and 20) using the simplest possible models. Nevertheless, these models consistently describe a large set of experiments. Some of the observations resemble similar phenomena in atomic physics, such as shell structure and periodic table characteristics, Hund's rule, and spin singlet and triplet states. The experimental control, however, is much larger than for atoms: with one device all the artificial elements can be studied by adding electrons to the quantum dot when changing the gate voltage. (author)

  5. Determination of atropine using Mn-doped ZnS quantum dots as novel luminescent sensitizers

    Energy Technology Data Exchange (ETDEWEB)

    Azizi, Seyed Naser [Analytical Division, Faculty of Chemistry, University of Mazandaran, Babolsar 4741695447 (Iran, Islamic Republic of); Chaichi, Mohammad Javad, E-mail: jchaichi@yahoo.com [Analytical Division, Faculty of Chemistry, University of Mazandaran, Babolsar 4741695447 (Iran, Islamic Republic of); Shakeri, Parmis [Analytical Division, Faculty of Chemistry, University of Mazandaran, Babolsar 4741695447 (Iran, Islamic Republic of); Bekhradnia, Ahmadreza [Pharmaceutical Sciences Research Center, Department of Medicinal Chemistry, Mazandaran University of Medical Sciences, Sari (Iran, Islamic Republic of)

    2013-12-15

    A novel chemiluminescence (CL) method using water-soluble Mn-doped ZnS quantum dots (QDs) as sensitizers is proposed for the chemiluminometric determination of atropine in pharmaceutical formulation. Water-soluble Mn-doped ZnS QDs were synthesized by using L-cysteine as stabilizer in aqueous solutions. The nanoparticles were structurally and optically characterized by X-ray powder diffraction (XRD), dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FTIR), UV–vis absorption spectroscopy and photoluminescence (PL) emission spectroscopy. It was found that ZnS quantum dots acted as enhancers of the weak CL emission produced upon oxidation of sulfite by Ce(IV) in acidic medium. Trace amounts of atropine improved the sensitize effect of ZnS quantum dots yielding a significant chemiluminescence enhancement of the Ce(IV)–SO{sub 3}{sup 2−}–ZnS QD system. Therefore, a new CL analysis system was developed for the determination of atropine. Under the optimum conditions, there is a good linear relationship between the relative chemiluminescence intensity and the concentration of atropine in the range of 1×10{sup −9}–1×10{sup −6} M of atropine with a correlation coefficient (R{sup 2}) of 0.9992. The limit of detection of this system was found to be 2.54×10{sup −10} M. This method is not only simple, sensitive and low cost, but also reliable for practical applications. -- Highlights: • Mn-doped ZnS quantum dots could enhance the chemiluminescence (CL) of cerium(IV)–sodium sulfite system. • ZnS quantum dots were used as the nanocatalyst. • Trace amounts of atropine improved the sensitize effect of ZnS quantum dots. • This work is introduced as a new method for the determination of atropine commercial drugs. • Detection limit of atropine was obtained 2.54×10{sup −10} mol L{sup −1}.

  6. Hastings Center

    Science.gov (United States)

    ... Public Events October 19, Hastings Center Seminar, Garrison : Human Genetic Engineering: Wh at Can We Do? What Should We ... Public Events October 19, Hastings Center Seminar, Garrison : Human Genetic Engineering: Wh at Can We Do? What Should We ...

  7. Charge State Hysteresis in Semiconductor Quantum Dots

    OpenAIRE

    Yang, C. H.; Rossi, A; Lai, N. S.; Leon, R.; Lim, W. H.; Dzurak, A.S.

    2014-01-01

    Semiconductor quantum dots provide a two-dimensional analogy for real atoms and show promise for the implementation of scalable quantum computers. Here, we investigate the charge configurations in a silicon metal-oxide-semiconductor double quantum dot tunnel coupled to a single reservoir of electrons. By operating the system in the few-electron regime, the stability diagram shows hysteretic tunnelling events that depend on the history of the dots charge occupancy. We present a model which acc...

  8. Resonant electron transfer between quantum dots

    OpenAIRE

    Openov, Leonid A.

    1999-01-01

    An interaction of electromagnetic field with a nanostructure composed of two quantum dots is studied theoretically. An effect of a resonant electron transfer between the localized low-lying states of quantum dots is predicted. A necessary condition for such an effect is the existence of an excited bound state whose energy lies close to the top of the barrier separating the quantum dots. This effect may be used to realize the reversible quantum logic gate NOT if the superposition of electron s...

  9. Optical Fiber Sensing Using Quantum Dots

    Directory of Open Access Journals (Sweden)

    Faramarz Farahi

    2007-12-01

    Full Text Available Recent advances in the application of semiconductor nanocrystals, or quantumdots, as biochemical sensors are reviewed. Quantum dots have unique optical properties thatmake them promising alternatives to traditional dyes in many luminescence basedbioanalytical techniques. An overview of the more relevant progresses in the application ofquantum dots as biochemical probes is addressed. Special focus will be given toconfigurations where the sensing dots are incorporated in solid membranes and immobilizedin optical fibers or planar waveguide platforms.

  10. Computation of relativistic terms in a spherical quantum dot

    Energy Technology Data Exchange (ETDEWEB)

    Yakar, Yusuf, E-mail: yuyakar@yahoo.com [Physics Department, Faculty of Arts and Science, Aksaray University, Campus 68100 Aksaray (Turkey); Cak Latin-Small-Letter-Dotless-I r, Bekir, E-mail: bcakir@selcuk.edu.tr [Physics Department, Faculty of Science, Selcuk University, Campus 42031 Konya (Turkey); Oezmen, Ayhan [Physics Department, Faculty of Science, Selcuk University, Campus 42031 Konya (Turkey)

    2013-02-15

    We studied a hydrogenic impurity located at the center of a spherical quantum dot with an infinite spherical confining potential and calculated energy levels and wavefunctions using Quantum Genetic Algorithm(QGA) and Hartree-Fock Roothaan (HFR) method. In addition, we investigated the first-order relativistic terms such as the relativistic correction to the kinetic energy, Darwin and spin-orbit interaction term. These terms were calculated using the first-order perturbation theory. The electronic charge density for the Darwin term was carried out from a global operator defined by Hiller, Sucher and Feinberg. The results revealed that the relativistic corrections are important in small dot radii and they should not be neglected to improve the accuracy of calculations. - Highlights: Black-Right-Pointing-Pointer A spherical quantum dot with an infinite spherical confining potential has been considered. Black-Right-Pointing-Pointer Quantum Genetic Algorithm and Hartree-Fock Roothaan method have been used to calculate the wave functions and the total energy. Black-Right-Pointing-Pointer The relativistic terms have been calculated using the first-order perturbation theory. Black-Right-Pointing-Pointer The electronic charge density for the Darwin term was carried out from a global operator defined by Hiller, Sucher and Feinberg.

  11. Excel Center

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Citigroup,one of the World top 500 companies,has now settled in Excel Center,Financial Street. The opening ceremony of Excel Center and the entry ceremony of Citigroup in the center were held on March 31.Government leaders of Xicheng District,the Excel CEO and the heads of Asia-Pacific Region leaders of Citibank all participated in the ceremony.

  12. A new phenomenon of quantum-dot cellular automata

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    Ifan external point charge and the movable charges of an isolated quantum-dot cellular automata (QCA) cell have the same polarity, the point charge greatly affects the polarization (P) of the cell only when it is in a narrow band with periodically changing width. The center of the band is on a radius R circle. The ratio of R to the electric charge (q) is a constant determined by the parameters of the cell. A QCA cell can be used as charge detector based on the above phenomenon.

  13. Frecuencia de virus respiratorios y características clínicas de niños que acuden a un hospital en México Frequency of respiratory viruses and clinical characteristics in children attending a care center in Mexico City

    Directory of Open Access Journals (Sweden)

    Rosa María Wong-Chew

    2010-12-01

    Full Text Available OBJETIVO. Describir la frecuencia de virus respiratorios y características clínicas en niños con cuadros respiratorios de un hospital de tercer nivel en México. MATERIAL Y MÉTODOS. Se incluyeron niños con diagnóstico de infección respiratoria y un resultado positivo por inmunofluorescencia de enero 2004 a octubre 2006. RESULTADOS. De 986 muestras nasofaríngeas, 138 (14% fueron positivas. La frecuencia fue: 80% virus sincicial respiratorio (VSR, 8% parainfluenza 1, 5% parainfluenza3, 2% adenovirus, 2% influenza A, 1% parainfluenza 2 y 1% influenza B. CONCLUSIONES. La frecuencia de virus respiratorios fue de 14%. El VSR se identificó asociado con más frecuencia, a neumonía y bronquiolitis en menores de 3 años.OBJECTIVE. To describe the frequency of respiratory viruses and clinical characteristics in children with respiratory signs and symptoms in a tertiary care center in Mexico. MATERIAL AND METHODS. Patients with a clinical diagnosis of respiratory infection and a positive immunofluorescence result (Light Diagnostics from January 2004 to October 2006 were included. RESULTS. From the 986 nashopharyngeal samples, 138 (14% were positive by immunofluorescence. The frequency was: 80% RSV, 8% parainfluenza 1, 5% parainfluenza 3, 2% adenovirus, 2% influenza A, 1% parainfluenza 2 and 1% influenza B. CONCLUSIONS. Respiratory viruses were detected in 14% of samples tested. RSV was the most frequently identified virus and was associated with pneumonia and bronchiolitis in children younger than 3 years old.

  14. Thermoelectric energy harvesting with quantum dots.

    Science.gov (United States)

    Sothmann, Björn; Sánchez, Rafael; Jordan, Andrew N

    2015-01-21

    We review recent theoretical work on thermoelectric energy harvesting in multi-terminal quantum-dot setups. We first discuss several examples of nanoscale heat engines based on Coulomb-coupled conductors. In particular, we focus on quantum dots in the Coulomb-blockade regime, chaotic cavities and resonant tunneling through quantum dots and wells. We then turn toward quantum-dot heat engines that are driven by bosonic degrees of freedom such as phonons, magnons and microwave photons. These systems provide interesting connections to spin caloritronics and circuit quantum electrodynamics.

  15. POLARON IN CYLINDRICAL AND SPHERICAL QUANTUM DOTS

    Directory of Open Access Journals (Sweden)

    L.C.Fai

    2004-01-01

    Full Text Available Polaron states in cylindrical and spherical quantum dots with parabolic confinement potentials are investigated applying the Feynman variational principle. It is observed that for both kinds of quantum dots the polaron energy and mass increase with the increase of Frohlich electron-phonon coupling constant and confinement frequency. In the case of a spherical quantum dot, the polaron energy for the strong coupling is found to be greater than that of a cylindrical quantum dot. The energy and mass are found to be monotonically increasing functions of the coupling constant and the confinement frequency.

  16. Semiconductor quantum-dot lasers and amplifiers

    DEFF Research Database (Denmark)

    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...

  17. Enhanced chemiluminescence of CdTe quantum dots-H₂O₂ by horseradish peroxidase-mimicking DNAzyme.

    Science.gov (United States)

    Zhang, Junli; Li, Baoxin

    2014-05-01

    In this study, it was found that horseradish peroxidase (HRP)-mimicking DNAzyme could effectively enhance the CL emission of CdTe quantum dots (QDs)-H2O2 system, whereas HRP could not enhance the CL intensity. The CL enhancement mechanism was investigated, and the CL enhancement was supposed to originate from the catalysis of HRP-mimicking DNAzyme on the CL reaction between CdTe QDs and H2O2. Meantime, compared with CdTe QDs-H2O2 CL system, H2O2 concentration was markedly decreased in QDs-H2O2-HRP-mimicking DNAzyme CL system, improving the stability of QDs-H2O2 CL system. The QDs-based CL system was used to detect sensitively CdTe QDs and HRP-mimicking DNAzyme (as biologic labels). This work gives a path for enhancing CL efficiency of QDs system, and will be helpful to promote the step of QDs application in various fields such as bioassay and trace detection of analyte. PMID:24556131

  18. OpenCL programming guide

    CERN Document Server

    Munshi, Aaftab; Mattson, Timothy G; Fung, James; Ginsburg, Dan

    2011-01-01

    Using the new OpenCL (Open Computing Language) standard, you can write applications that access all available programming resources: CPUs, GPUs, and other processors such as DSPs and the Cell/B.E. processor. Already implemented by Apple, AMD, Intel, IBM, NVIDIA, and other leaders, OpenCL has outstanding potential for PCs, servers, handheld/embedded devices, high performance computing, and even cloud systems. This is the first comprehensive, authoritative, and practical guide to OpenCL 1.1 specifically for working developers and software architects. Written by five leading OpenCL authorities, OpenCL Programming Guide covers the entire specification. It reviews key use cases, shows how OpenCL can express a wide range of parallel algorithms, and offers complete reference material on both the API and OpenCL C programming language. Through complete case studies and downloadable code examples, the authors show how to write complex parallel programs that decompose workloads across many different devices. They...

  19. Evidència científica en l’ús dels antídots

    OpenAIRE

    Corominas Garcia, Núria

    2012-01-01

    L’objectiu principal d’aquesta tesi es identificar i avaluar l’evidència científica, pel que fa a l’eficàcia i seguretat, que recolza l’ús dels següents antídots inclosos a la Guia d’antídots de l’Hospital Clínic (GAHC): Anticossos Fab antidigoxina en la intoxicació per digoxina, Flumazenil per revertir els efectes centrals de la sobredosificació per benzodiazepines, Fomepizol en la intoxicació per la ingesta de metanol i etilenglicol, Hidroxocobalamina en la intoxicació per cianur, i N-acet...

  20. Job center

    Science.gov (United States)

    To better meet the needs of AGU members, a program has been started to increase the effectiveness of the Job Center activity at the Spring and Fall Meetings. As a result, participation in the Job Center at the 1988 AGU Spring Meeting in Baltimore increased substantially compared to previous Spring Meetings. The number of employers, applicants, and interviews scheduled more than doubled compared to the 1987 Spring Job Center.In order to make the meeting Job Centers even better, a survey is being conducted of employers and applicants who participated in the 1988 Spring Job Center. Evaluation of this survey will be useful in continuing increased participation in and the effectiveness of the Job Center at the 1988 Fall Meeting. Past participants and those interested in the future of the Job Center are encouraged to forward comments and suggestions to AGU, Member Programs Division, 2000 Florida Ave., N.W., Washington, DC 20009.

  1. Quantum Dot Spectrum Converters for Enhanced High Efficiency Photovoltaics Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This research proposes to enhance solar cell efficiency, radiation resistance and affordability. The Quantum Dot Spectrum Converter (QDSC) disperses quantum dots...

  2. PREFACE: Quantum dots as probes in biology

    Science.gov (United States)

    Cieplak, Marek

    2013-05-01

    photosynthetic systems. The next paper, by Olejnik et al, discussed metallic QDs which enhance photosynthetic function in light-harvesting biomolecular complexes. Such hybrid structures with gold QDs are shown to exhibit a strong increase in the fluorescence quantum yield. The next two papers, by Sikora et al and Kaminska et al deal with the ZnO nanoparticles passivated by MgO. In the first of these two papers, the authors describe the behavior of ZnO/MgO when introduced to human cancer cells. In the second, the authors describe the QDs with an extra outer layer of Fe2O3 which makes the nanoparticles superparamagnetic and also capable of generation of reactive oxygen species which could be applied to form localized centers of toxicity for cancer treatment. Finally, in the last paper by Yatsunenko et al, the authors discuss several semiconducting QDs like ZnO with various rare-earth dopands. They propose a microwave-driven hydrothermal technology to make them, characterize their luminescence and demonstrate their usefulness in the early recognition of cancer tissues. Quantum dots as probes in biology contents Quantum dots as probes in biologyMarek Cieplak Luminescent nanoparticles and their applications in the life sciencesVarun K A Sreenivasan, Andrei V Zvyagin and Ewa M Goldys Ferredoxin:NADP+ oxidoreductase in junction with CdSe/ZnS quantum dots: characteristics of an enzymatically active nanohybrid Krzysztof Szczepaniak, Remigiusz Worch and Joanna Grzyb Spectroscopic studies of plasmon coupling between photosynthetic complexes and metallic quantum dotsMaria Olejnik, Bartosz Krajnik, Dorota Kowalska, Guanhua Lin and Sebastian Mackowski Luminescence of colloidal ZnO nanoparticles synthesized in alcohols and biological application of ZnO passivated by MgOBożena Sikora, Krzysztof Fronc, Izabela Kamińska, Kamil Koper, Piotr Stępień and Danek Elbaum Novel ZnO/MgO/Fe2O3 composite optomagnetic nanoparticles I Kamińska, B Sikora, K Fronc, P Dziawa, K Sobczak, R Minikayev, W

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

    International Nuclear Information System (INIS)

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

  4. A novel chemiluminescence method for determination of bisphenol Abased on the carbon dot-enhanced HCO{sub 3}{sup −}–H{sub 2}O{sub 2} system

    Energy Technology Data Exchange (ETDEWEB)

    Amjadi, Mohammad, E-mail: amjadi@tabrizu.ac.ir; Manzoori, Jamshid L.; Hallaj, Tooba

    2015-02-15

    A simple and sensitive chemiluminescence (CL) method on the basis of carbon dot (C-dot) enhanced HCO{sub 3}{sup −}–H{sub 2}O{sub 2} system, is designed for the determination of bisphenol A (BPA). The very weak CL of the HCO{sub 3}{sup −}–H{sub 2}O{sub 2} system is enhanced by a factor of ∼100 in the presence of C-dots. Possible mechanisms that lead to the effect were elucidated by recording fluorescence and CL spectra and studying the effect of some radical scavengers. This enhancement is inhibited by BPA in the concentration range from 1.0 to 100 µg L{sup −1}. This is exploited for its trace determination with a detection limit (3 s) of 0.3 µg L{sup −1}. The established method was applied to the determination of BPA in baby bottle and water samples with satisfactory results. - Highlights: • The effect of carbon dots on HCO{sub 3}{sup −}–H{sub 2}O{sub 2} chemiluminescence reaction is studied. • Carbon dots greatly enhance the CL signal of this reaction (∼100 fold). • The new CL system was applied to determination of bisphenol A in real samples.

  5. Quantum Gates Between Two Spins in a Triple Dot System with an Empty Dot

    CERN Document Server

    Coello, Jose Garcia

    2011-01-01

    We propose a scheme for implementing quantum gates and entanglement between spin qubits in the outer dots of a triple-dot system with an empty central dot. The voltage applied to the central dot can be tuned to realize the gate. Our scheme exemplifies the possibility of quantum gates outside the regime where each dot has an electron, so that spin-spin exchange interaction is not the only relevant mechanism. Analytic treatment is possible by mapping the problem to a t-J model. The fidelity of the entangling quantum gate between the spins is analyzed in the presence of decoherence stemming from a bath of nuclear spins, as well as from charge fluctuations. Our scheme provides an avenue for extending the scope of two qubit gate experiments to triple-dots, while requiring minimal control, namely that of the potential of a single dot, and may enhance the qubit separation to ease differential addressability.

  6. Nitrogen-Doped Carbon Dots for "green" Quantum Dot Solar Cells.

    Science.gov (United States)

    Wang, Hao; Sun, Pengfei; Cong, Shan; Wu, Jiang; Gao, Lijun; Wang, Yun; Dai, Xiao; Yi, Qinghua; Zou, Guifu

    2016-12-01

    Considering the environment protection, "green" materials are increasingly explored for photovoltaics. Here, we developed a kind of quantum dots solar cell based on nitrogen-doped carbon dots. The nitrogen-doped carbon dots were prepared by direct pyrolysis of citric acid and ammonia. The nitrogen-doped carbon dots' excitonic absorption depends on the N-doping content in the carbon dots. The N-doping can be readily modified by the mass ratio of reactants. The constructed "green" nitrogen-doped carbon dots solar cell achieves the best power conversion efficiency of 0.79 % under AM 1.5 G one full sun illumination, which is the highest efficiency for carbon dot-based solar cells. PMID:26781285

  7. Quadro clínico e nutricional de pacientes com fibrose cística: 20 anos de seguimento no HC-UFMG Clinical and nutritional aspects of a Center of Cystic Fibrosis-HC-UFMG: 20 years of follow-up

    Directory of Open Access Journals (Sweden)

    F. J. C. Reis

    2000-10-01

    Full Text Available OBJETIVOS: A fibrose cística (FC é a doença genética letal, de herança autossômica recessiva, mais comum entre pacientes de cor branca. O presente estudo foi realizado com o objetivo de identificar o quadro clínico e nutricional à admissão dos pacientes no Centro de Tratamento de FC do HC-UFMG e avaliar a sobrevida a longo prazo. PACIENTES E MÉTODOS: Em um período de 20 anos, 127 pacientes portadores de FC foram acompanhados longitudinalmente e submetidos a protocolo previamente estabelecido, após confirmação do diagnóstico pelo teste do suor. Foram obtidos na admissão dados demográficos, da apresentação clínica, nutricionais e laboratoriais. O genótipo foi obtido de 106 pacientes pela técnica do PCR. Os pacientes foram seguidos por mediana de 44 meses. A análise de sobrevida foi realizada utilizando-se o método de Kaplan-Meier. RESULTADOS: A mediana da idade do diagnóstico da FC foi de 33 meses. A manifestação clínica predominante na época do diagnóstico foi a associação de sintomas respiratórios e gastrointestinais crônicos, presentes em 61% das crianças. A mutação mais freqüente encontrada foi a deltaF508: 17 pacientes (16% eram homozigotos para essa mutação e 30 (28% eram heterozigotos. Houve uma prevalência de desnutrição à admissão de 63% tendo sido reduzida para 45% ao final do seguimento. Um total 20 pacientes (15,7% evoluiu para o óbito. A probabilidade estimada de sobrevida nos primeiros 12 meses após o diagnóstico foi de 96% e após 5 anos de seguimento de 80%. CONCLUSÕES: O diagnóstico da FC é ainda tardio em nosso meio e a sobrevida é menor quando comparada a dados internacionais. O seguimento desses pacientes em centro especializado permitiu uma melhora no estado nutricional apesar da inerente evolução da doença.BACKGROUND: Cystic fibrosis (CF is the most common severe autosomal recessive disease in caucasian population. The life expectancy of patients with CF has improved

  8. Photoinduced electron transfers with carbon dots

    OpenAIRE

    Wang, Xin; Cao, Li; Lu, Fushen; Meziani, Mohammed J.; Li, Heting; Qi, Gang; Zhou, Bing; Harruff, Barbara A.; Kermarrec, Fabien; Sun, Ya-Ping

    2009-01-01

    The photoluminescence in carbon dots (surface-passivated small carbon nanoparticles) could be quenched efficiently by electron acceptor or donor molecules in solution, namely that photo-excited carbon dots are both excellent electron donors and excellent electron acceptors, thus offering new opportunities for their potential uses in light energy conversion and related applications.

  9. Thick-shell nanocrystal quantum dots

    Science.gov (United States)

    Hollingsworth, Jennifer A.; Chen, Yongfen; Klimov, Victor I.; Htoon, Han; Vela, Javier

    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.

  10. Optical Properties of Semiconductor Quantum Dots

    NARCIS (Netherlands)

    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 mad

  11. Detecting the chirality for coupled quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Cao Huijuan [Institute for Condensed Matter Physics, School of Physics and Telecommunication Engineering, South China Normal University, Guangzhou 510631 (China); Hu Lian [Institute for Condensed Matter Physics, School of Physics and Telecommunication Engineering, South China Normal University, Guangzhou 510631 (China)], E-mail: huliancaohj@yahoo.com

    2008-04-21

    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.

  12. Double Acceptor Interaction in Semimagnetic Quantum Dot

    Directory of Open Access Journals (Sweden)

    A. Merwyn Jasper D. Reuben

    2011-01-01

    Full Text Available The effect of geometry of the semimagnetic Quantum Dot on the Interaction energy of a double acceptor is computed in the effective mass approximation using the variational principle. A peak is observed at the lower dot sizes as a magnetic field is increased which is attributed to the reduction in confinement.

  13. Functional Centering

    CERN Document Server

    Hahn, M

    1996-01-01

    Based on empirical evidence from a free word order language (German) we propose a fundamental revision of the principles guiding the ordering of discourse entities in the forward-looking centers within the centering model. We claim that grammatical role criteria should be replaced by indicators of the functional information structure of the utterances, i.e., the distinction between context-bound and unbound discourse elements. This claim is backed up by an empirical evaluation of functional centering.

  14. Marshall Space Flight Center Technology Investments Overview

    Science.gov (United States)

    Tinker, Mike

    2014-01-01

    NASA is moving forward with prioritized technology investments that will support NASA's exploration and science missions, while benefiting other Government agencies and the U.S. aerospace enterprise. center dotThe plan provides the guidance for NASA's space technology investments during the next four years, within the context of a 20-year horizon center dotThis plan will help ensure that NASA develops technologies that enable its 4 goals to: 1.Sustain and extend human activities in space, 2.Explore the structure, origin, and evolution of the solar system, and search for life past and present, 3.Expand our understanding of the Earth and the universe and have a direct and measurable impact on how we work and live, and 4.Energize domestic space enterprise and extend benefits of space for the Nation.

  15. Aspectos clínicos de pacientes com pitiríase versicolor atendidos em um centro de referência em dermatologia tropical na cidade de Manaus (AM, Brasil Clinical aspects of patients with pityriasis versicolor seen at a referral center for tropical dermatology in Manaus, Amazonas, Brazil

    Directory of Open Access Journals (Sweden)

    Patrícia Motta de Morais

    2010-12-01

    Full Text Available FUNDAMENTOS: A pitiríase versicolor (tinha versicolor é uma micose superficial crônica, causada por leveduras do gênero Malassezia spp. comensais das camadas queratinizadas da pele e que, sob determinadas condições ainda não esclarecidas, se torna patogênica, determinando as manifestações clínicas da doença. É uma dermatose recidivante e, mesmo após tratamento, pode deixar hipopigmentação persistente, causando problemas sociais aos indivíduos acometidos. OBJETIVO: Descrever as características clínicas e epidemiológicas de pacientes com diagnóstico de tinha versicolor atendidos em uma unidade de referência em Dermatologia (Fundação Alfredo da Matta. MÉTODOS: Estudo de série de casos em que foram detalhadas as manifestações cutâneas e as características epidemiológicas de pacientes atendidos na Fundação Alfredo da Matta com diagnóstico de tinha versicolor. RESULTADOS: Cento e dezesseis pacientes foram incluídos no estudo no período de janeiro a agosto de 2008. A maioria dos indivíduos é do sexo masculino, de cor parda, da faixa etária jovem e formada por estudantes, que apresentavam fatores predisponentes ao surgimento das manchas. Também a maioria apresentava lesões extensas e história passada da doença. CONCLUSÃO: O estudo mostrou alta proporção de indivíduos com quadros extensos e de longa duração da doença.BACKGROUND: Pityriasis versicolor (tinea versicolor is a chronic superficial mycosis caused by yeasts of the Malassezia spp. genus commensal of the keratinized layers of the skin. Under conditions not yet understood, it becomes pathogenic determining the clinical manifestations of the disease. It is a recurrent skin condition and persistent hypopigmentation may remain after treatment, causing social problems to those affected. OBJECTIVE: To describe the clinical and epidemiological features of patients diagnosed with tinea versicolor treated at a referral center for dermatology (Alfredo da

  16. Model-based clustered-dot screening

    Science.gov (United States)

    Kim, Sang Ho

    2006-01-01

    I propose a halftone screen design method based on a human visual system model and the characteristics of the electro-photographic (EP) printer engine. Generally, screen design methods based on human visual models produce dispersed-dot type screens while design methods considering EP printer characteristics generate clustered-dot type screens. In this paper, I propose a cost function balancing the conflicting characteristics of the human visual system and the printer. By minimizing the obtained cost function, I design a model-based clustered-dot screen using a modified direct binary search algorithm. Experimental results demonstrate the superior quality of the model-based clustered-dot screen compared to a conventional clustered-dot screen.

  17. Substitutional impurity in the graphene quantum dots

    Science.gov (United States)

    Sierański, K.; Szatkowski, J.

    2015-09-01

    The process of formation of the localized defect states due to substitutional impurity in sp2-bonded graphene quantum dot is considered using a simple tight-binding-type calculation. We took into account the interaction of the quantum dot atoms surrounding the substitutional impurity from the second row of elements. To saturate the external dangling sp2 orbitals of the carbon additionally 18 hydrogen atoms were introduced. The chemical formula of the quantum dot is H18C51X, where X is the symbol of substitutional atom. The position of the localized levels is determined relative to the host-atoms (C) εp energies. We focused on the effect of substitutional doping by the B, N and O on the eigenstate energies and on the total energy change of the graphene dots including for O the effect of lattice distorsion. We conclude that B, N, and O can form stable substitutional defects in graphene quantum dot.

  18. 75 FR 68728 - Airworthiness Directives; Bombardier, Inc. Model CL-215-1A10 (CL-215), CL-215-6B11 (CL-215T...

    Science.gov (United States)

    2010-11-09

    ... Procedures (44 FR 11034, February 26, 1979); and 3. Will not have a significant economic impact, positive or.... Model CL-215-1A10 (CL- 215), CL-215-6B11 (CL-215T Variant), and CL-215-6B11 (CL-415 Variant) Airplanes...: * * * * * Seven cases of on-ground hydraulic accumulator screw cap or end cap failure have been experienced on...

  19. Effect of the Electron-Phonon Coupling on Barrier D- Quantum Dots in Magnetic Fields

    Institute of Scientific and Technical Information of China (English)

    XIE Wen-Fang

    2002-01-01

    The influence of the electron-phonon coupling on the energy of low-lying states of the barrier D- center,which consists of a positive ion located on the z-axis at a distance from the two-dimensional quantum dot plane and two electrons in the dot plane bound by the ion, is investigated at arbitrary strength of magnetic field by making use of the method of few-body physics. Discontinuous ground-state energy transitions induced by the magnetic field are reported.The dependence of the binding energy of the D- ground state on the quantum dot radius is obtained. A considerable enhancement of the binding is found for the D- ground state, which results from the confinement of electrons and electron-phonon coupling.

  20. ClEST cluster :Cl_contig0243 [ClEST

    Lifescience Database Archive (English)

    Full Text Available Cl_contig0243 barrier-to-autointegration factor Cimex lectularius nuclear gene 428 ...TAATAAATACAGTATGATGTGCG fb29038 fs25084 mb23031 3 barrier to autointegration factor [Rhodnius prolixus] AEL79235 5.9E-56 GO:0003677 ...

  1. ClEST cluster :Cl_singleton0416 [ClEST

    Lifescience Database Archive (English)

    Full Text Available Cl_singleton0416 ornithine aminotransferase Cimex lectularius nuclear gene 438 TATC...CAGTTTGCCGAGTATATCACCCGTTATTT fb20049 1 PREDICTED: probable ornithine aminotransferase-like [Glycine max] XP_003531161 4.30167E-26 GO:0008483 ...

  2. ClEST cluster :Cl_singleton2093 [ClEST

    Lifescience Database Archive (English)

    Full Text Available Cl_singleton2093 selenoprotein t Cimex lectularius nuclear gene 435 GAGAAGGAGATTCCG...GAGACGGGAAGAATA mb12059 1 selenoprotein T [Glossina morsitans morsitans] ADD19835 7.29481E-59 GO:0045454 GO:0008430 GO:0005575 ...

  3. ClEST cluster :Cl_contig0231 [ClEST

    Lifescience Database Archive (English)

    Full Text Available Cl_contig0231 bcl2 adenovirus e1b 19 kda protein-interacting Cimex lectularius nucl...AGCCGTCCGGACCAATTTCCACCAAAGGATTGGAAACTGAGGCATCCGGCTCGGAAAACTCTCTCAATACGCACGAC fs06082 fw15056 mb10031 3 BCL2/adenovirus

  4. Delay in DOTS for new pulmonary tuberculosis patient from rural area of Wardha District, India

    Directory of Open Access Journals (Sweden)

    Shilpa Bawankule

    2010-07-01

    Full Text Available Vast majority of active tuberculosis patients seeks treatment, do so promptly, still many patients spend a great deal of time and money “shopping for health” and too often they do not receive either accurate diagnosis or effective treatment, despite spending considerable resources. Objective: To find out the time taken to, for diagnosis of tuberculosis and to put patient on DOTS from the onset of symptoms and pattern of health seeking behavior of new pulmonary tuberculosis patients. A cross-sectional rapid assessment using qualitative (FGD and quantitative (Interview methods conducted at DOTS center of tertiary care hospital from rural Wardha. Participants: 53 pulmonary tuberculosis patients already on DOTS, in intensive phase. Main outcome measure: Delay in initiation of DOTS & health seeking behavior Results: Median total delay for starting DOTS was 111 days, (range: 10 to 321 days. Patient delay was more than provider delay. Patients delay was more in patients above 60 years, illiterate, per-capita income below 650 Rupees and HIV TB co-infection. Pattern of health seeking behavior was complex. Family physician was the preferred health care provider. Patient visited on an average four providers and spent around 1450 rupees (only direct cost before DOTS begin. Time taken from the onset of symptoms and start of DOT is a cause of concern for the tuberculosis control program. Early case detection is important rather than mere achieving target of 70% new case detection. Program manager needs to implement locally relevant & focused strategies for early case detection to improve the treatment success, especially in rural area of India.

  5. Electron transport in quantum dots

    CERN Document Server

    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...

  6. Distribution center

    Institute of Scientific and Technical Information of China (English)

    2004-01-01

    Distribution center is a logistics link fulfill physical distribution as its main functionGenerally speaking, it's a large and hiahly automated center destined to receive goods from various plants and suppliers,take orders,fill them efficiently,and deliver goods to customers as quickly as possible.

  7. Electronic states in vertically ordered Ge/Si quantum dots detected by photocurrent spectroscopy

    Science.gov (United States)

    Yakimov, A. I.; Kirienko, V. V.; Armbrister, V. A.; Bloshkin, A. A.; Dvurechenskii, A. V.

    2014-07-01

    We report on intraband photocurrent spectroscopy of sixfold stacked Ge/Si quantum dots embedded in a Si matrix and aligned along the growth direction. The dots are formed in a shape of pyramids with the average lateral size of 18 nm. The n-type heterostructures show broad spectral response ranging from 5 to 20 μm, depending on the polarization of the incoming infrared light. The normal incidence photocurrent peak centered around 12-15 μm is attributed to the transitions from the electron states localized in the Si region adjacent to the dots to continuum states of the Si matrix. The electron confinement is caused by a modification of the conduction band alignment induced by inhomogeneous tensile strain in Si around the buried Ge/Si quantum dots. Using the Ge content and dot shape determined by Raman and scanning tunneling microscopy analysis as input parameters for three-dimensional band structure simulations, a good agreement between measured and calculated electron binding energy is obtained. Photoluminescence spectroscopy and measurements of temperature dependence of dark conductance are used to correlate photocurrent results.

  8. Ultra-large scale synthesis of high electrochemical performance SnO2 quantum dots within 5 min at room temperature following a growth self-termination mechanism

    International Nuclear Information System (INIS)

    Highlights: • SnO2 quantum dots were prepared at an ultra-large scale at room temperature within 5 min. • The grinding of SnCl2⋅2H2O and ammonium persulphate with morpholine produces quantum dots. • The reactions were self-terminated through the rapid consumption of water. • The obtained SnO2 quantum dots own high electrochemical performance. - Abstract: SnO2 quantum dots are prepared at an ultra-large scale by a productive synthetic procedure without using any organic ligand. The grinding of solid mixture of SnCl2⋅2H2O and ammonium persulphate with morpholine in a mortar at room temperature produces 1.2 nm SnO2 quantum dots within 5 min. The formation of SnO2 is initiated by the reaction between tin ions and hydroxyl groups generated from hydrolysis of morpholine in the released hydrate water from SnCl2⋅2H2O. It is considered that as water is rapidly consumed by the hydrolysis reaction of morpholine, the growth process of particles is self-terminated immediately after their transitory period of nucleation and growth. As a result of simple procedure and high toleration to scaling up of preparation, at least 50 g of SnO2 quantum dots can be produced in one batch in our laboratory. The as prepared quantum dots present high electrochemical performance due to the effective faradaic reaction and the alternative trapping of electrons and holes

  9. Carbon-dot-decorated TiO₂ nanotube arrays used for photo/voltage-induced organic pollutant degradation and the inactivation of bacteria.

    Science.gov (United States)

    Feng, Lingyan; Sun, Hanjun; Ren, Jinsong; Qu, Xiaogang

    2016-03-18

    Photoluminescent carbon dots (c-dots) have recently attracted growing interest as a new member of the carbon-nanomaterial family. Here, we report for the first time that c-dot-decorated TiO2 nanotube arrays (c-dot/TiNTs) exhibit highly enhanced abilities regarding photo/voltage-induced organic pollutant degradation and bacterial inactivation. By applying UV irradiation (365 nm) or an electrochemical potential over 3 V (versus Ag/AgCl), an organic dye and a herbicide were efficiently degraded. Moreover, the inactivation of Gram-positive S. aureus and Gram-negative E. coli bacteria was realized on a c-dot/TiNT film. The c-dots were able to absorb light efficiently resulting in multiple exciton generation and also a reduction in the recombination of the e(-)/h(+) pair produced in c-dot/TiNT film during photo/voltage-induced degradation. It was also possible to readily regenerate the surface using ultraviolet light irradiation, leaving the whole film structure undamaged and with high reproducibility and stability. PMID:26870882

  10. Carbon-dot-decorated TiO2 nanotube arrays used for photo/voltage-induced organic pollutant degradation and the inactivation of bacteria

    Science.gov (United States)

    Feng, Lingyan; Sun, Hanjun; Ren, Jinsong; Qu, Xiaogang

    2016-03-01

    Photoluminescent carbon dots (c-dots) have recently attracted growing interest as a new member of the carbon-nanomaterial family. Here, we report for the first time that c-dot-decorated TiO2 nanotube arrays (c-dot/TiNTs) exhibit highly enhanced abilities regarding photo/voltage-induced organic pollutant degradation and bacterial inactivation. By applying UV irradiation (365 nm) or an electrochemical potential over 3 V (versus Ag/AgCl), an organic dye and a herbicide were efficiently degraded. Moreover, the inactivation of Gram-positive S. aureus and Gram-negative E. coli bacteria was realized on a c-dot/TiNT film. The c-dots were able to absorb light efficiently resulting in multiple exciton generation and also a reduction in the recombination of the e-/h+ pair produced in c-dot/TiNT film during photo/voltage-induced degradation. It was also possible to readily regenerate the surface using ultraviolet light irradiation, leaving the whole film structure undamaged and with high reproducibility and stability.

  11. Extracellular biosynthesis of CdTe quantum dots by the fungus Fusarium oxysporum and their anti-bacterial activity

    Science.gov (United States)

    Syed, Asad; Ahmad, Absar

    2013-04-01

    The growing demand for semiconductor [quantum dots (Q-dots)] nanoparticles has fuelled significant research in developing strategies for their synthesis and characterization. They are extensively investigated by the chemical route; on the other hand, use of microbial sources for biosynthesis witnessed the highly stable, water dispersible nanoparticles formation. Here we report, for the first time, an efficient fungal-mediated synthesis of highly fluorescent CdTe quantum dots at ambient conditions by the fungus Fusarium oxysporum when reacted with a mixture of CdCl2 and TeCl4. Characterization of these biosynthesized nanoparticles was carried out by different techniques such as Ultraviolet-visible (UV-Vis) spectroscopy, Photoluminescence (PL), X-ray Diffraction (XRD), X-ray Photoelectron spectroscopy (XPS), Transmission Electron Microscopy (TEM) and Fourier Transformed Infrared Spectroscopy (FTIR) analysis. CdTe nanoparticles shows antibacterial activity against Gram positive and Gram negative bacteria. The fungal based fabrication provides an economical, green chemistry approach for production of highly fluorescent CdTe quantum dots.

  12. Fluorescent Quantum Dots for Biological Labeling

    Science.gov (United States)

    McDonald, Gene; Nadeau, Jay; Nealson, Kenneth; Storrie-Lomardi, Michael; Bhartia, Rohit

    2003-01-01

    Fluorescent semiconductor quantum dots that can serve as "on/off" labels for bacteria and other living cells are undergoing development. The "on/off" characterization of these quantum dots refers to the fact that, when properly designed and manufactured, they do not fluoresce until and unless they come into contact with viable cells of biological species that one seeks to detect. In comparison with prior fluorescence-based means of detecting biological species, fluorescent quantum dots show promise for greater speed, less complexity, greater sensitivity, and greater selectivity for species of interest. There are numerous potential applications in medicine, environmental monitoring, and detection of bioterrorism.

  13. Time-bin Entanglement from Quantum Dots

    CERN Document Server

    Weihs, Gregor; Predojević, Ana

    2016-01-01

    The desire to have a source of single entangled photon pairs can be satisfied using single quantum dots as emitters. However, we are not bound to pursue only polarization entanglement, but can also exploit other degrees of freedom. In this chapter we focus on the time degree of freedom, to achieve so-called time-bin entanglement. This requires that we prepare the quantum dot coherently into the biexciton state and also build special interferometers for analysis. Finally this technique can be extended to achieve time-bin and polarization hyper-entanglement from a suitable 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

    Science.gov (United States)

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

    2016-09-01

    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. Senior Centers

    Medline Plus

    Full Text Available ... Karen Albers] We provide a wide variety of activities -- physical, health, mental health programs with Senior Plus, cognitive ... of games. [Narrator] Many senior centers also offer exercise programs. [Karen Albers] We offer aerobics, tai chi, ...

  16. Senior Centers

    Medline Plus

    Full Text Available ... Living independently at home is something many older adults would like to do as long as they can. Senior centers, adult day care, transportation, and meals programs are long- ...

  17. Senior Centers

    Medline Plus

    Full Text Available ... variety of social and recreational activities. [Karen Albers] We provide a wide variety of activities -- physical, health, ... senior centers also offer exercise programs. [Karen Albers] We offer aerobics, tai chi, tap dancing, ballroom dancing, ...

  18. Senior Centers

    Medline Plus

    Full Text Available ... transportation, and meals programs are long-term care services available in the community which make it easier ... about senior centers and other long-term care services available in your community, contact the Eldercare Locator ...

  19. Senior Centers

    Medline Plus

    Full Text Available ... of games. [Narrator] Many senior centers also offer exercise programs. [Karen Albers] We offer aerobics, tai chi, ... chi, tap dancing, ballroom dancing, square dancing, chair exercise, arthritis classes, yoga, and lots of dancing. [Narrator] ...

  20. Cathodoluminescence Imaging Using Nanodiamond Color Centers

    Science.gov (United States)

    Glenn, David; Zhang, Huiliang; Kasthuri, Narayanan; Trifonov, Alexei; Schalek, Richard; Lichtman, Jeff; Walsworth, Ronald

    2011-05-01

    We demonstrate a nanoscale imaging technique based on cathodoluminescence (CL) emitted by color centers in nanodiamonds (NDs) under excitation by an electron beam in a scanning electron microscope (SEM). We have identified several classes of color centers that are spectrally distinct at room temperature and can be obtained with high reliability in NDs with diameters on the order of 50 nm or smaller. Compared to standard CL markers, ND color centers are bright and highly stable under SEM excitation. In conjunction with appropriate functionalization of the ND surfaces, ND-CL will provide nanoscale information about molecular function to augment the structural information obtained with standard SEM techniques. We discuss an exciting application of this approach to neuroscience, specifically in the generation of high-resolution maps of the connections between neurons (``Connectomics'').

  1. High-resolution photocurrent microscopy using near-field cathodoluminescence of quantum dots

    Directory of Open Access Journals (Sweden)

    Heayoung P. Yoon

    2013-06-01

    Full Text Available We report a fast, versatile photocurrent imaging technique to visualize the local photo response of solar energy devices and optoelectronics using near-field cathodoluminescence (CL from a homogeneous quantum dot layer. This approach is quantitatively compared with direct measurements of high-resolution Electron Beam Induced Current (EBIC using a thin film solar cell (n-CdS / p-CdTe. Qualitatively, the observed image contrast is similar, showing strong enhancement of the carrier collection efficiency at the p-n junction and near the grain boundaries. The spatial resolution of the new technique, termed Q-EBIC (EBIC using quantum dots, is determined by the absorption depth of photons. The results demonstrate a new method for high-resolution, sub-wavelength photocurrent imaging measurement relevant for a wide range of applications.

  2. Nonadiabatic dynamics in the CH3+HCl→CH4+Cl(2PJ) reaction

    International Nuclear Information System (INIS)

    Nonadiabatic dynamics in the title reaction have been investigated by 2+1 REMPI detection of the Cl(2P3/2) and Cl*(2P1/2) products. Reaction was initiated by photodissociation of CH3I at 266 nm within a single expansion of a dilute mixture of CH3I and HCl in argon, giving a mean collision energy of 7800 cm-1 in the center-of-mass frame. Significant production of Cl* was observed, with careful checks made to ensure that no additional photochemical or inelastic scattering sources of Cl* perturbed the measurements. The fraction of the total yield of Cl(2PJ) atoms formed in the J=(1/2) level at this collision energy was 0.150±0.024, and must arise from nonadiabatic dynamics because the ground potential energy surface correlates to CH4+Cl(2P3/2) products

  3. The white dot syndromes Síndromes dos pontos brancos retinianos

    Directory of Open Access Journals (Sweden)

    Raul Nunes Galvarro Vianna

    2007-06-01

    Full Text Available Several entities must be considered when a patient presents with a white dot syndrome. In most cases these can be distinguished from one another based on the appearance or distribution of the lesions, the clinical course, or patient variables such as age, sex, laterality, and functional and image examinations. In this paper we review the distinctive and shared features of the white dot syndromes, highlighting the clinical findings, diagnostic test results, proposed etiologies, treatment, and prognosis.Várias doenças devem ser consideradas quando nos deparamos com paciente com uma entidade clínica incluída no grupo das "síndromes dos pontos brancos retinianos". O diagnóstico diferencial na maioria das vezes é baseado na aparência e/ou na distribuição das lesões, no curso clínico, ou por algumas variáveis relacionadas ao paciente, tais como idade, sexo, lateralidade, bem como por meio de exames funcionais e de imagem. O presente artigo revisa os achados clínicos das doenças que fazem parte do grupo das "síndromes dos pontos brancos retinianos", enfatizando as similaridades e as diferenças entre essas entidades. Os exames complementares, bem como a etiologia, o tratamento e o prognóstico de cada uma delas são descritos e comentados.

  4. Study of thermoluminescence in K Cl crystals doped with Sr2+

    International Nuclear Information System (INIS)

    An attempt is made to correlate the F and Z1 (F center modified by the presence of a two-valence impurity pair and and positive ion vacancy) and a V center, with the T L curve peaks observed in pure K Cl crystals doped with Sr2+, irradiated at room temperature. (L.C.J.A.)

  5. Quantitative cathodoluminescence (CL) spectroscopy of minerals: possibilities and limitations

    International Nuclear Information System (INIS)

    The luminescence spectrum of a mineral contains complex information related to the intrinsic crystal and the defect structure. For quantitative analysis of cathodoluminescence (CL) the spectra have to be deconvoluted by fitting and filtering procedures to identify and measure individual peaks. Peak-width, peak-position and transition probability of the luminescence centers are influenced by effects such as interactions within the defects themselves, and interaction between defects and the surrounding crystal lattice. For calcite and feldspar a linear correlation between the defect concentration of manganese and the Mn2+-activated CL-intensity is documented. Combined micro-particle induced x-ray emission (μ-PIXE) and CL-spectroscopy analyses of REE-doped synthetic calcite suggest a linear correlation between REE-activated CL intensity and REE-concentration at REE-concentration levels below approximately 500 ppm. Sensitizing and quenching by other REE are dominant effects yielding strong variations in the correlation between the REE-activated CL-intensity and the REE-content. (author)

  6. The Cl Isotope Composition of the Moon as evidence for an Anhydrous Mantle (Invited)

    Science.gov (United States)

    Sharp, Z. D.; Shearer, C., Jr.; McKeegan, K. D.; Barnes, J.; Wang, Y.

    2010-12-01

    The chlorine isotope composition of primitive terrestrial basalts and carbonaceous chondrites cover a narrow range centered around 0‰ with a total variation of ± 0.5‰. In contrast, the chlorine isotope composition of bulk samples and in situ ion microprobe analyses of lunar basalts and glasses cover a range of 25‰. Three possibilities were considered to explain the large spread: 1) initial isotopic heterogeneities, 2) devolatilization from solar wind/micrometeorite bombardment, 3) degassing under anhydrous conditions. The first of these possibilities is rejected because the Moon went through an magma ocean stage which would have homogenized any isotopic heterogeneities. To examine surface effects, we chose samples that have extremely different degrees of surface exposure. We find no correlation between the Cl isotope composition and surface exposure. We also conducted a laboratory experiment in which a thin film of NaCl was bombarded with a proton source for 24 hours with no change in Cl isotope composition. The third possibility is that the fractionation is explained by the anhydrous character of the Moon. On Earth, the volatiling Cl species is HCl. HCl is known to preferentially incorporate 37Cl relative to 35Cl due to the high bond strength of the molecule. This is offset by the higher translational velocity of H35Cl, so that overall, there is very little Cl isotope fractionation during degassing. We propose that lunar basalts were anhydrous and the volatile Cl species were metal chlorides, such as ZnCl2, NaCl, FeCl2, etc. The bond strength of metal chlorides and Cl dissolved in a basalt are similar, so that fractionation is caused mainly by volatilization, with the light isotopologue preferentially lost to the vapor phase. This idea is supported by the consistent lower Cl isotope ratios of water soluble salt fraction (~10 ‰ lower) and the lowest lunar Cl isotope values close to those of bulk Earth. The H content of lunar magmas must have been lower

  7. Large quantum dots with small oscillator strength

    DEFF Research Database (Denmark)

    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...... oscillator strength due to Coulomb effects. This is in stark contrast to the measured oscillator strength, which turns out to be so small that it can be described by excitons in the strong confinement regime. We attribute these findings to exciton localization in local potential minima arising from alloy...

  8. Ge Quantum Dot Infrared Imaging Camera Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Luna Innovations Incorporated proposes to develop a high performance Ge quantum dots-based infrared (IR) imaging camera on Si substrate. The high sensitivity, large...

  9. A simple turn on fluorescent sensor for the selective detection of thiamine using coconut water derived luminescent carbon dots.

    Science.gov (United States)

    Purbia, Rahul; Paria, Santanu

    2016-05-15

    In this study microwave-assisted hydrothermal method was used to prepare highly luminescent carbon dots (1-6 nm size) within a minute from tender coconut (Cocos nucifera) water. The synthesized carbon dots (C-dots) exhibit emission of blue and green lights while excited at 390 and 450 nm wavelengths, respectively. As an application, these C-dots were tested for a simple "turn on" fluorescent sensor for rapid detection of thiamine (vitamin B1). The detection of thiamine in human body is very important to prevent various diseases such as beriberi, neurological disorders, optic neuropathy, etc. The fluorescence emission intensity of C-dots quenches after addition of Cu(2+) ion and then again increases selectively (turn on) after the addition of thiamine. The fluorescence emission intensity enhancement of Cu(2+) ion modified C-dots in the presence of thiamine exhibits a linear relationship within the thiamine concentration range of 10-50 μM. The limit of detection was found to be 280 nM from this study. The selectivity of the detection was also tested in the presence of different organic molecules and inorganic ions (Ca(2+), Mg(2+), Na(+), K(+), Cl(-), SO4(2-), and NO3(-)) which are present in blood serum and urine and found to be almost no interference in the detection. Finally, to see the applicability in real samples a commercial vitamin capsule was tested and found less than 3% error in the detected concentration. The C-dots were also used for bioimaging of fungus and the results show they are also suitable for this application too. PMID:26745793

  10. Spin current in double quantum dot

    Institute of Scientific and Technical Information of China (English)

    Zhao Hua; Zhang Guo-Feng; Yin Wen; Liang Jiu-Qing

    2004-01-01

    We have studied the dynamical behaviours of two electrons confined in a double quantum dot driven by rotating magnetic fields in terms of the theory of Lewis-Riesenfeld Hermitian invariants for the explicitly time-dependent Hamiltonian. The coherent spin oscillations in the dot provide a generation source for spin current. Exact solutions obtained allow us to investigate the dynamical properties of the spin localization for various initial localized states.

  11. Magnetic quantum dots and magnetic edge states

    International Nuclear Information System (INIS)

    Starting with defining the magnetic edge state in a magnetic quantum dot, which becomes quite popular nowadays conjunction with a possible candidate for a high density memory device or spintronic materials, various magnetic nano-quantum structures are reviewed in detail. We study the magnetic edge states of the two dimensional electron gas in strong perpendicular magnetic fields. We find that magnetic edge states are formed along the boundary of the magnetic dot, which is formed by a nonuniform distribution of magnetic fields. These magnetic edge states circulate either clockwise or counterclockwise, depending on the number of missing flux quanta, and exhibit quite different properties, as compared to the conventional ones which are induced by electrostatic confinements in the quantum Hall system. We also find that a close relation between the quantum mechanical eigenstates and the classical trajectories in the magnetic dot. When a magnetic dot is located inside a quantum wire, the edge-channel scattering mechanism by the magnetic quantum dot is very different from that by electrostatic dots. Here, the magnetic dot is formed by two different magnetic fields inside and outside the dot. We study the ballistic edge-channel transport and magnetic edge states in this situation. When the inner field is parallel to the outer one, the two-terminal conductance is quantized and shows the features of a transmission barrier and a resonator. On the other hand, when the inner field is reversed, the conductance is not quantized and all channels can be completely reflected in some energy ranges. The difference between the above two cases results from the distinct magnetic confinements. We also describe successfully the edge states of magnetic quantum rings and others in detail

  12. Coherent scattering in a small quantum dot

    International Nuclear Information System (INIS)

    Ballistic transport in an open small (100 nm) three-terminal quantum dot based on the high-mobility two-dimensional electron gas of the AlGaAs/GaAs heterojunction has been analyzed. It has been shown that the gate oscillations of resistance of such a dot arise due to the coherent scattering of electrons on its quasidiscrete levels being suppressed by a weak magnetic field

  13. Exploring Extragalactic Emission: The Hα Dot Survey

    Science.gov (United States)

    Rampalli, Rayna; Salzer, John Joseph

    2016-01-01

    The Hα Dot Survey was established as a result of finding point sources of strong line emission in the data obtained for the ALFALFA Hα Survey (Van Sistine et al. 2015). In the latter survey, broad-band R and narrow-band Hα filters were used to examine target galaxies from the ALFALFA blind HI survey (Giovanelli et al. 2005, Haynes et al. 2011). In the process of reducing the ALFALFA Hα Survey data the "Hα Dots" were discovered (Kellar et al. 2008, 2012). Using specialized image analysis tools, a large population of dots has already been detected in the more than 1500 ALFALFA Hα narrow-band images taken with the 0.9m WIYN and 2.1m KPNO telescopes. Follow-up spectra of over 200 Hα Dots discovered from the 0.9m images reveal that these objects are a mix of nearby low-luminosity star-forming galaxies, compact starbursts and Seyfert 2 galaxies at intermediate redshifts, and high-redshift QSOs. Here we present the first list of Hα Dots detected using 2.1m telescope data. The 2.1m images yield a sample of Dots that average almost two magnitudes fainter than those detected with the 0.9m. The current REU project is designed to characterize the set of Hα Dots detected in the deeper 2.1m telescope images, while the broad goals of the Hα Dot Survey include the desire to understand better the chemical evolution of galaxies over cosmic time. This project was supported in part by the NSF REU grant 1358980, by the Maria Mitchell Association (Nantucket, MA), and by the Massachusetts Space Grant Consortium.

  14. Synthesis, characterization, and third-order nonlinear optical properties of copper quantum dots embedded in sodium borosilicate glass

    International Nuclear Information System (INIS)

    Highlights: ► The sodium borosilicate glass doped Cu quantum dots have been prepared by sol–gel route. ► The crystal structure and composition of as-prepared glass were investigated by XRD and XPS. ► Size and distribution of indium nanocrystals was determined by TEM and STEM. ► The third-order optical nonlinearity was investigated by using Z-scan technique. - Abstract: Copper quantum dots embedded in sodium borosilicate glass matrix were fabricated and analyzed in terms of their structural, chemical, and optical properties. X-ray powder diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses revealed that copper quantum dots were in face-centered-cubic crystalline phase and in the metallic state. Size and distribution of the quantum dots were measured by transmission electron microscopy (TEM) as well as high-resolution transmission electron microscopy (HRTEM). The results showed spherical shape have formed uniformly in the glass, and the size of these quantum dots were range from 1.5 to 5 nm with the average particle size about 2.7 nm. The third-order nonlinear optical properties of copper quantum dots doped glass were investigated by using Z-scan technique at the wavelength of 800 nm with femtosecond Ti: sapphire laser radiation. The value of third-order optical nonlinear susceptibility χ(3) of the glass was estimated to be 2.41 × 10−11 esu.

  15. Density of Trap States and Auger-mediated Electron Trapping in CdTe Quantum-Dot Solids.

    Science.gov (United States)

    Boehme, Simon C; Azpiroz, Jon Mikel; Aulin, Yaroslav V; Grozema, Ferdinand C; Vanmaekelbergh, Daniël; Siebbeles, Laurens D A; Infante, Ivan; Houtepen, Arjan J

    2015-05-13

    Charge trapping is an ubiquitous process in colloidal quantum-dot solids and a major limitation to the efficiency of quantum dot based devices such as solar cells, LEDs, and thermoelectrics. Although empirical approaches led to a reduction of trapping and thereby efficiency enhancements, the exact chemical nature of the trapping mechanism remains largely unidentified. In this study, we determine the density of trap states in CdTe quantum-dot solids both experimentally, using a combination of electrochemical control of the Fermi level with ultrafast transient absorption and time-resolved photoluminescence spectroscopy, and theoretically, via density functional theory calculations. We find a high density of very efficient electron traps centered ∼0.42 eV above the valence band. Electrochemical filling of these traps increases the electron lifetime and the photoluminescence quantum yield by more than an order of magnitude. The trapping rate constant for holes is an order of magnitude lower that for electrons. These observations can be explained by Auger-mediated electron trapping. From density functional theory calculations we infer that the traps are formed by dicoordinated Te atoms at the quantum dot surface. The combination of our unique experimental determination of the density of trap states with the theoretical modeling of the quantum dot surface allows us to identify the trapping mechanism and chemical reaction at play during charge trapping in these quantum dots. PMID:25853555

  16. Spin-dynamics simulations of vortex precession in 2-D magnetic dots

    Energy Technology Data Exchange (ETDEWEB)

    Depondt, Ph., E-mail: depondt@insp.jussieu.fr [Institut des NanoSciences de Paris, Universite Pierre et Marie Curie, UMR 7588 CNRS, 75252 Paris Cedex 05 (France); Levy, J.-C.S., E-mail: jean-claude.levy@univ-paris-diderot.fr [Materiaux et Phenomenes Quantiques, Universite Denis Diderot, UMR 7162 CNRS, 75013 Paris (France)

    2011-10-31

    Highlights: → Vortex precession was simulated in two-dimensional magnetic dots of finite size. → A simple qualitative explanation of the observed behaviors is proposed, including seemingly erratic ones. → Pinning of the vortex motion, unconnected with defects, is also observed and an explanation thereof provided. -- Abstract: Vortex precession was simulated in two-dimensional magnetic dots. The Landau-Lifshitz equation with exchange and dipolar interactions was integrated at a low temperature with initial conditions consisting in a single vortex situated aside from the central position. This vortex precesses around the center of the sample and either can be expelled or converges towards the center. These relaxation processes are systematically studied. A simple qualitative explanation of the observed behaviors is proposed, including seemingly somewhat erratic ones. Intrinsic pinning of the vortex motion, unconnected with defects, is also observed and an explanation thereof provided.

  17. Formation and ordering of epitaxial quantum dots

    Science.gov (United States)

    Atkinson, Paola; Schmidt, Oliver G.; Bremner, Stephen P.; Ritchie, David A.

    2008-10-01

    Single quantum dots (QDs) have great potential as building blocks for quantum information processing devices. However, one of the major difficulties in the fabrication of such devices is the placement of a single dot at a pre-determined position in the device structure, for example, in the centre of a photonic cavity. In this article we review some recent investigations in the site-controlled growth of InAs QDs on GaAs by molecular beam epitaxy. The method we use is ex-situ patterning of the GaAs substrate by electron beam lithography and conventional wet or dry etching techniques to form shallow pits in the surface which then determine the nucleation site of an InAs dot. This method is easily scalable and can be incorporated with marker structures to enable simple post-growth lithographic alignment of devices to each site-controlled dot. We demonstrate good site-control for arrays with up to 10 micron spacing between patterned sites, with no dots nucleating between the sites. We discuss the mechanism and the effect of pattern size, InAs deposition amount and growth conditions on this site-control method. Finally we discuss the photoluminescence from these dots and highlight the remaining challenges for this technique. To cite this article: P. Atkinson et al., C. R. Physique 9 (2008).

  18. Quantum-dot-in-perovskite solids

    KAUST Repository

    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.

  19. Coherent transport through interacting quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    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

  20. ClEST cluster :Cl_singleton1538 [ClEST

    Lifescience Database Archive (English)

    Full Text Available Cl_singleton1538 dead (asp-glu-ala-asp) box polypeptide 5 Cimex lectularius nuclear...fw14079 1 similar to DEAD/H (Asp-Glu-Ala-Asp/His) box polypeptide 5 (RNA helicase 68kDa) [Xenopus laevis] NP_001079703 6.59566E-23 ...

  1. Orifice diseases project - experience of the "Hospital das Clínicas" University of São Paulo Medical Center in day-hospital of anorectal disease Projeto doenças orificiais experiência do HCFMUSP em hospital-dia e doenças anorretais

    Directory of Open Access Journals (Sweden)

    Sergio Carlos Nahas

    1999-06-01

    Full Text Available The treatment of malignant or benign colorectal pathologies that require more complex management are priorities in tertiary hospitals such as "Hospital das Clínicas" University of São Paulo Medical Center (HCFMUSP. Therefore, benign, uncomplicated orifice conditions are relegated to second place. The number of patients with hemorrhoids, perianal fistulas, fissures, condylomas and pilonidal cysts who seek treatment at the HFMUSP is very great, resulting in over-crowding in the outpatient clinics and a long waiting list for recommended surgical treatment (at times over 18 months. The authors describe the experience of the HCFMUSP over an eight-day period with day-hospital surgery in which 140 patients underwent surgery. Data was prospectively taken on the patients undergoing surgery for benign orifice pathologies including age, sex, diagnosis, surgery performed, immediate and late postoperative complications, and follow-up. 140 patients operated on over eight days were studied. 68 were males (48.75% with ages ranging from 25 to 62 (mean 35.2 yrs.. Hemorrhoids was the most frequent condition encountered (82 hemorrhoidectomies, 58.6%, followed by perineal fistula (28 fistula repairs, 20.0%. The most common complication was headache secondary to rachianesthesia occurring in 9 patients (6.4%. One patient (0.7% developed bleeding immediately PO that required reoperation. Mean follow-up was 104 days. Day-surgery characterized by quality care and low morbidity is feasible in tertiary public hospitals, permitting surgery for benign orifice pathologies on many patients within a short period of time.O tratamento das patologias colorretais malignas ou benignas, que necessitam tratamento com maior grau de complexidade são prioridades em hospitais terciários, como é o Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo (HCFMUSP, permanecendo assim as patologias orificiais benignas em um segundo plano. Todavia devido à sua

  2. Dot-dye-immunoassay for the diagnosis of schistosomiasis mansoni

    Directory of Open Access Journals (Sweden)

    Ana Lúcia Teles Rabello

    1992-06-01

    Full Text Available A new serological assay dot-dye-immunoassay (dot-DIA was evaluated for the diagnosis of schistosomiasis mansoni. This method consist of four steps: (a biding of antigens to a nitrocellulose membrane (NC; (b blocking of free sites of the NC; (c incubation in specific primary antibody; (d detection of primary antibody reactivity by color development using second antibody coupled to textile dyes. Sera from 82 individuals, 61 with Schistosoma mansoni eggs in the stool and 21 stool negative were tested by ELISA, dot-ELISA, and dotDIA. A high level of agreement between the methods tested was observed for all sera tested: ELISA x dot-ELISA: 95.1%, ELISA x dot-DIA: 92.7% and dot-ELISA x dot-DIA: 97.6%. In this study, dot-DIA proved to be a feasible, sensitive, rapid and practical test for the diagnosis of shcistosomiasis.

  3. Study on Interaction Between Chitosan and CdS Quantum Dots via Photoluminescence Spectra

    Institute of Scientific and Technical Information of China (English)

    Zhan LI; Yu Min DU; Yan WEN

    2004-01-01

    The interaction between CdS quantum dots and amino polysaccharide chitosan in aqueous solution was studied via photoluminescence(PL)spectra. The surface binding of chitosan with different molecular weight(MW)quenched the luminescence of QDs due to the elimination of radioactive anion vacancy centers.This process fits well with the Perrin model;lower MW chitosan exhibits higher quenching efficiency due to better availability to the surface.

  4. Templating growth of gold nanostructures with a CdSe quantum dot array

    OpenAIRE

    Paul, Neelima; Metwalli, Ezzeldin; Yao, Yuan; Schwartzkopf, Matthias; Yu, Shun; Roth, Stephan V.; Müller-Buschbaum, Peter; Paul, Amitesh

    2015-01-01

    In optoelectronic devices based on quantum dot arrays, thin nanolayers of gold are preferred as stable metal contacts and for connecting recombination centers. The optimal morphology requirements are uniform arrays with precisely controlled positions and sizes over a large area with long range ordering since this strongly affects device performance. To understand the development of gold layer nanomorphology, the detailed mechanism of structure formation are probed with time-resolved grazing i...

  5. Sociodemographic and clinical characteristics of a diabetic population at a primary level health care center Características sociodemográficas y clínicas de una población diabética en el nivel primario de atención a la salud Características sociodemográficas e clínicas de portadores de diabetes em um serviço de atenção básica à saúde

    Directory of Open Access Journals (Sweden)

    Liudmila Miyar Otero

    2007-10-01

    Full Text Available This study aimed to analyze the social-demographic, clinical and life habits characteristics of a diabetic population being treated in the primary level of a healthcare center. A total of 52 diabetic patients, enrolled, in 2006, in a Research and Extension Center linked to a University in Sao Paulo, participated in the study. The data were collected through interviews, using appropriated forms, after the patients consent. The results showed other illness associated to diabetes and an unsatisfactory metabolic control. These data can support health professionals' actions in order to effectively prevent and manage diabetes in the basic health services. The conclusion, in face of the obtained results, is that there is the need to develop courses to the health professionals of education in diabetes, aiming to meet the complexity of the care and progression of the disease in this clientele.Este estudio tiene como objetivo analizar las características sociodemográficas, clínicas y los hábitos de vida de una población diabética atendida en el nivel primario de atención a la salud. Participaron 52 diabéticos registrados en un Centro de Investigación y Extensión Universitaria en el interior del Estado de San Paulo, en 2006. Los datos fueron recolectados mediante entrevista, utilizando-se dos formularios, después del consentimiento de los sujetos. Los resultados mostraron que los sujetos presentaban otras enfermedades asociadas a la diabetes y controle metabólico insatisfactorio. Esos datos pueden subsidiar las acciones de los profesionales de salud para la efectiva prevención y el manejo de la diabetes en los servicios de atención básica de salud. Ante los resultados conseguidos, se concluye que es necesario incrementar cursos de calificación en educación en la diabetes para los profesionales de salud, con el objetivo de atender a la complejidad del cuidado y a la progresión de la enfermedad en esta población.Este estudo teve como

  6. Temporal Evolution of Velocity and Magnetic Field in and around Umbral Dots

    OpenAIRE

    Watanabe, Hiroko; Rubio, Luis R. Bellot; Rodriguez, Jaime de la Cruz; van der Voort, Luc Rouppe

    2012-01-01

    We study the temporal evolution of umbral dots (UDs) using measurements from the CRISP imaging spectropolarimeter at the Swedish 1-m Solar Telescope. Scans of the magnetically sensitive 630 nm iron lines were performed under stable atmospheric conditions for 71 min with a cadence of 63 s. These observations allow us to investigate the magnetic field and velocity in and around UDs at a resolution approaching 0.13". From the analysis of 339 UDs, we draw the following conclusions: (1)UDs show cl...

  7. Effect of tunneling injection on the modulation response of quantum dot lasers

    Directory of Open Access Journals (Sweden)

    Y. Yekta kiya

    2014-03-01

    Full Text Available In this paper, modulation bandwidth characteristics of InGaAs/GaAs quantum dot (QD laser were theoretically investigated. Simulation was done by using the fourth order Runge-Kutta method. Effect of carrier relaxation life time, temperature and current density on characteristics of tunneling injection QD laser (TIL and conventional QD laser (CL were analyzed. Results showed that tunneling injection in QD laser increases the modulation bandwidth indicating that it is very useful for using in the fiber optic communication systems.

  8. Experiments towards size and dopant control of germanium quantum dots for solar applications

    OpenAIRE

    Brittany L. Oliva-Chatelain; Barron, Andrew R.

    2015-01-01

    While the literature for the doping of silicon quantum dots (QDs) and nanocrystals (NCs) is extensive, reports of doping their germanium analogs are sparse. We report a range of attempts to dope Ge QDs both during and post-synthesis. The QDs have been characterized by TEM, XPS, and I/V measurements of SiO2 coated QD thin films in test cells using doped Si substrates. The solution synthesis of Ge QDs by the reduction of GeCl4 with LiAlH4 results in Ge QDs with a low level of chlorine atoms on ...

  9. Magnetic resonance study of the radiolysis products in chlorinated SrCl2:Fe crystals

    International Nuclear Information System (INIS)

    The main objective of the research presented in this thesis has been to investigate by magnetic resonance techniques and Electron Nuclear Double Resonance (EPR and ENDOR) the atomic structure and properties of the impurity associated paramagnetic point defects produced by X-ray irradiation at low temperature (T=80 K) in chlorinated SrCl2 crystals doped with iron. The original results can be summarized as follows: 1. The tetragonal Fe+ (I) center, produced after X-ray irradiation at liquid nitrogen temperature of chlorinated SrCl2:Fe2+ single crystals and stable up to 700 K, has been studied with X- and Q- band ENDOR. The shf interactions of the unpaired electrons with the Cl nuclei of the first ligand shell and with the central 57Fe nucleus have been identified in the ENDOR spectra. The reconstruction of the X-band EPR spectrum using the ENDOR data showed that all eight Cl ions in the first shell are equivalent. Hence the center has D4h symmetry. Moreover, the ENDOR data strongly suggested that the first shell of Cl ions exhibits a tetragonal compression, confirming the EPR analysis. The simplest structural model which can explain all experimental data consists of an interstitial Fe+ ion with two neighboring substitutional cation impurities, most likely K+, on opposite sites along the tetragonal axis of the center. 2. The tetragonal Fe+ (II) center, produced after X-ray irradiation at liquid nitrogen temperature of chlorinated SrCl2:Fe crystals, which is unstable at RT, has been studied by X- and Q- band ENDOR. Interaction of the unpaired electrons with the Cl nuclei of the first ligand shell and with an impurity lying along the tetragonal axis of the center have been identified and analyzed in the ENDOR spectra. The experimental values of the isotropic and anisotropic shf constants for the first 3''5Cl shell have been used to determine the unpaired spin densities in the 3s and 3p chlorine orbitals as f3s = 0.27% and f3p = 1.95 % respectively, resulting in a total

  10. Measurement of the absorption cross sections of SiCl_4, SiCl_3, SiCl_2 and Cl at H Lyman-α wavelength

    OpenAIRE

    Mével, R.; Catoire, L.; M. Fikri; Roth, P.

    2013-01-01

    Atomic resonance absorption spectroscopy coupled with a shock tube is a powerful technique for studying high temperature dynamics of reactive systems. Presently, high temperature pyrolysis of SiCl_4–Ar mixtures has been studied behind reflected shock waves. Using time-resolved absorption profiles at 121.6 nm and a detailed reaction model, the absorption cross sections of SiCl_4, SiCl_3, SiCl_2 and Cl have been measured. Results agree well with available data for SiCl_4 and constitute, to our ...

  11. Realistic model of a vertical pillar quantum dot: Analysis of individual dot data

    NARCIS (Netherlands)

    Maksym, P.A.; Nishi, Y.; Austing, D.G.; Hatano, T.; Kouwenhoven, L.P.; Aoki, H.; Tarucha, S.

    2009-01-01

    An accurate model of a vertical pillar quantum dot is described. The full three-dimensional structure of the device containing the dot is taken into account and this leads to an effective two-dimensional model in which electrons move in the two lateral dimensions, the confinement is parabolic, and t

  12. Performance characterization of Watson Ahumada motion detector using random dot rotary motion stimuli.

    Directory of Open Access Journals (Sweden)

    Siddharth Jain

    Full Text Available The performance of Watson & Ahumada's model of human visual motion sensing is compared against human psychophysical performance. The stimulus consists of random dots undergoing rotary motion, displayed in a circular annulus. The model matches psychophysical observer performance with respect to most parameters. It is able to replicate some key psychophysical findings such as invariance of observer performance to dot density in the display, and decrease of observer performance with frame duration of the display.Associated with the concept of rotary motion is the notion of a center about which rotation occurs. One might think that for accurate estimation of rotary motion in the display, this center must be accurately known. A simple vector analysis reveals that this need not be the case. Numerical simulations confirm this result, and may explain the position invariance of MST(d cells. Position invariance is the experimental finding that rotary motion sensitive cells are insensitive to where in their receptive field rotation occurs.When all the dots in the display are randomly drawn from a uniform distribution, illusory rotary motion is perceived. This case was investigated by Rose & Blake previously, who termed the illusory rotary motion the omega effect. Two important experimental findings are reported concerning this effect. First, although the display of random dots evokes perception of rotary motion, the direction of motion perceived does not depend on what dot pattern is shown. Second, the time interval between spontaneous flips in perceived direction is lognormally distributed (mode approximately 2 s. These findings suggest the omega effect fits in the category of a typical bistable illusion, and therefore the processes that give rise to this illusion may be the same processes that underlie much of other bistable phenomenon.

  13. Senior Centers

    Medline Plus

    Full Text Available ... dancing. [Narrator] These centers can provide entree to new activities and expand a person’s social contacts. [Karen ... meeting all their interests and introducing them to new things; whether it’s an arts and crafts project, ...

  14. clOpenCL - supporting distributed heterogeneous computing in HPC clusters

    OpenAIRE

    Alves, Albano; Rufino, José; Pina, António; Santos, Luis Paulo

    2013-01-01

    Clusters that combine heterogeneous compute device architectures, coupled with novel programming models, have created a true alternative to traditional (homogeneous) cluster computing, allowing to leverage the performance of parallel applications. In this paper we introduce clOpenCL, a platform that supports the simple deployment and efficient running of OpenCL-based parallel applications that may span several cluster nodes, expanding the original single-node OpenCL model. clOpenCL is deploye...

  15. Submonolayer Quantum Dot Infrared Photodetector

    Science.gov (United States)

    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.

  16. Comparison of two methods for selegiline determination: A flow-injection chemiluminescence method using cadmium sulfide quantum dots and corona discharge ion mobility spectrometry

    Science.gov (United States)

    Khataee, Alireza; Lotfi, Roya; Hasanzadeh, Aliyeh; Iranifam, Mortaza; Zarei, Mahmoud; Joo, Sang Woo

    2016-01-01

    Two analytical approaches including chemiluminescence (CL) and corona discharge ionization ion mobility spectrometry (CD-IMS) were developed for sensitive determination of selegiline (SG). We found that the CL intensity of the KMnO4-Na2S2O3 CL system was significantly enhanced in the presence of L-cysteine capped CdS quantum dots (QDs). A possible CL mechanism for this CL reaction is proposed. In the presence of SG, the enhanced CL system was inhibited. Based on this inhibition, a simple and sensitive flow-injection CL method was proposed for the determination of SG. Under optimum experimental conditions, the decreased CL intensity was proportional to SG concentration in the range of 0.01 to 30.0 mg L- 1. The detection limit (3σ) was 0.004 mg L- 1. Also, SG was determined using CD-IMS, and under optimum conditions of CD-IMS, calibration curves were linear in the range of 0.15 to 42.0 mg L- 1, with a detection limit (3σ) of 0.03 mg L- 1. The precision of the two methods was calculated by analyzing samples containing 5.0 mg L- 1 of SG (n = 11). The relative standard deviations (RSDs%) of the flow-injection CL and CD-IMS methods are 2.17% and 3.83%, respectively. The proposed CL system exhibits a higher sensitivity and precision than the CD-IMS method for the determination of SG.

  17. Understanding electronic systems in semiconductor quantum dots

    Science.gov (United States)

    Ciftja, Orion

    2013-11-01

    Systems of confined electrons are found everywhere in nature in the form of atoms where the orbiting electrons are confined by the Coulomb attraction of the nucleus. Advancement of nanotechnology has, however, provided us with an alternative way to confine electrons by using artificial confining potentials. A typical structure of this nature is the quantum dot, a nanoscale system which consists of few confined electrons. There are many types of quantum dots ranging from self-assembled to miniaturized semiconductor quantum dots. In this work we are interested in electrostatically confined semiconductor quantum dot systems where the electrostatic confining potential that traps the electrons is generated by external electrodes, doping, strain or other factors. A large number of semiconductor quantum dots of this type are fabricated by applying lithographically patterned gate electrodes or by etching on two-dimensional electron gases in semiconductor heterostructures. Because of this, the whole structure can be treated as a confined two-dimensional electron system. Quantum confinement profoundly affects the way in which electrons interact with each other, and external parameters such as a magnetic field. Since a magnetic field affects both the orbital and the spin motion of the electrons, the interplay between quantum confinement, electron-electron correlation effects and the magnetic field gives rise to very interesting physical phenomena. Thus, confined systems of electrons in a semiconductor quantum dot represent a unique opportunity to study fundamental quantum theories in a controllable atomic-like setup. In this work, we describe some common theoretical models which are used to study confined systems of electrons in a two-dimensional semiconductor quantum dot. The main emphasis of the work is to draw attention to important physical phenomena that arise in confined two-dimensional electron systems under various quantum regimes.

  18. Structure and function of collectin liver 1 (CL-L1) and collectin 11 (CL-11, CL-K1)

    DEFF Research Database (Denmark)

    Selman, Lana; Hansen, Soren

    2012-01-01

    to l-fucose and d-mannose, whereas CL-L1 shows preference for d-mannose, d-fucose, N-acetylglucosamine, and surprisingly also d-galactose. CL-11 binds to various microorganisms including Escherichia coli, Candida albicans and Influenza A virus. Polymorphisms in the CL-11 gene (COLEC11) leading...

  19. The interaction of CsCl with films of solid water

    CERN Document Server

    Borodin, A; Krischok, S; Kempter, V

    2003-01-01

    The interaction of CsCl molecules with films of solid water (three layers thick, typically), deposited on a tungsten crystal at 130 K, was studied. Metastable impact electron spectroscopy (MIES) and UPS(HeI) were applied to study the emission from Cl3p and Cs5p and the highest occupied states 1b sub 1 , 3a sub 1 and 1b sub 2 of molecular water. Below a critical stoichiometry of about CsCl centre dot nH sub 2 O with n=6 the UPS spectra are quite similar to those from chlorides solvated in liquid water in as much as the relative positions and intensities of the water and salt features are concerned; very little emission from the ionization of Cl3p and Cs5p is observed with MIES. We conclude that the CsCl molecules become solvated in the water film. As long as n>6, the water spectrum remains characteristic for condensed water; at n6, water molecules not involved directly into the hydration of the salt molecules desorb around 140 K. Around 160 K all water has disappeared from the surface. Above this temperature o...

  20. Condensation of flowing steam with binary nucleation of NaCl and water

    OpenAIRE

    Šejna M.; Šťastný M.

    2007-01-01

    The effects of chemistry on the flowing steam nucleation are in particular unexplained. An approach is used in the paper which is based on binary nucleation of main impurity NaCl and water. Physical and mathematical models are described and are applied on the steam flow with condensation in convergent-divergent nozzle. Binary nucleation numerical model is applied for the calculation of the flow with condensation in nozzle with expansion rate in divergent nozzle part dot{ar{P}} = 4 500 1/s. Th...

  1. Diamagnetic susceptibility of a confined donor in inhomogeneous quantum dots

    Science.gov (United States)

    Rahmani, K.; Zorkani, I.; Jorio, A.

    2011-03-01

    The binding energy and diamagnetic susceptibility χdia are estimated for a shallow donor confined to move in GaAs-GaAlAs inhomogeneous quantum dots. The calculation was performed within the effective mass approximation and using the variational method. The results show that the binding energy and the diamagnetic susceptibility χdia depend strongly on the core radius and the shell radius. We have demonstrated that there is a critical value of the ratio of the inner radius to the outer radius which may be important for nanofabrication techniques. The binding energy Eb shows a minimum for a critical value of this ratio depending on the value of the outer radius and shows a maximum when the donor is placed at the center of the spherical layer. The diamagnetic susceptibility is more sensitive to variations of the radius for a large spherical layer. The binding energy and diamagnetic susceptibility depend strongly on the donor position.

  2. Magnetic alteration of entanglement in two-electron quantum dots

    CERN Document Server

    Simonovic, N S

    2015-01-01

    Quantum entanglement is analyzed thoroughly in the case of the ground and lowest states of two-electron axially symmetric quantum dots under a perpendicular magnetic field. The individual-particle and the center-of-mass representations are used to study the entanglement variation at the transition from interacting to noninteracting particle regimes. The mechanism of symmetry breaking due to the interaction, that results in the states with symmetries related to the later representation only, being entangled even at the vanishing interaction, is discussed. The analytical expression for the entanglement measure based on the linear entropy is derived in the limit of noninteracting electrons. It reproduces remarkably well the numerical results for the lowest states with the magnetic quantum number M>2 in the interacting regime. It is found that the entanglement of the ground state is a discontinuous function of the field strength. A method to estimate the entanglement of the ground state, characterized by the quan...

  3. Diamagnetic susceptibility of a confined donor in inhomogeneous quantum dots

    International Nuclear Information System (INIS)

    The binding energy and diamagnetic susceptibility χdia are estimated for a shallow donor confined to move in GaAs-GaAlAs inhomogeneous quantum dots. The calculation was performed within the effective mass approximation and using the variational method. The results show that the binding energy and the diamagnetic susceptibility χdia depend strongly on the core radius and the shell radius. We have demonstrated that there is a critical value of the ratio of the inner radius to the outer radius which may be important for nanofabrication techniques. The binding energy Eb shows a minimum for a critical value of this ratio depending on the value of the outer radius and shows a maximum when the donor is placed at the center of the spherical layer. The diamagnetic susceptibility is more sensitive to variations of the radius for a large spherical layer. The binding energy and diamagnetic susceptibility depend strongly on the donor position.

  4. Impurity-modulated Aharonov-Bohm oscillations and intraband optical absorption in quantum dot-ring nanostructures

    Science.gov (United States)

    Barseghyan, M. G.; Manaselyan, A. Kh.; Laroze, D.; Kirakosyan, A. A.

    2016-07-01

    In this work we study the electronic states in quantum dot-ring complex nanostructures with an on-center hydrogenic impurity. The influence of the impurity on Aharonov-Bohm energy spectra oscillations and intraband optical absorption is investigated. It is shown that in the presence of a hydrogenic donor impurity the Aharonov-Bohm oscillations in quantum dot-ring structures become highly tunable. Furthermore, the presence of the impurity drastically changes the intraband absorption spectra due to the strong controllability of the electron localization type.

  5. IRASM Center

    International Nuclear Information System (INIS)

    IRASM is a national center for radiation processing developed around an industrial Co60 gamma irradiator. Being a department in an R and D national institute, IRASM Center is dealing with radiation treatment, pre/post microbiological control, validation of irradiation sterilization, detection of irradiated foodstuffs. Training is available for operators of new irradiation facilities focused on radiation technologies, dosimetry, sterilization, food treatment, conservation by irradiation of cultural heritage, quality assurance. Expertise on proper choosing the plastics for packaging versus dose is offered to the potential clients. IRASM Center is also involved in interdisciplinary applied research like chitosan treatment, sterile male technique or implementation of irradiation step in production of pharmaceuticals. All important activities: irradiation treatment, dosimetry, microbiology, detection of irradiated food, radioprotection, nuclear safety, physical protection. are performed in accordance with the proper standards in the frame of a certified quality management system. In this way Co60 industrial sources, a byproduct of certain nuclear power plants like Candu type, appear to be the key of a large technical and R and D domain. (authors)

  6. Surface plasmon-assisted optical bistability in the quantum dot-metal nanoparticle hybrid system

    Science.gov (United States)

    Bao, Chengjun; Qi, Yihong; Niu, Yueping; Gong, Shangqing

    2016-07-01

    We theoretically investigated optical bistability (OB) of a coupled excition-plasmon hybrid system in a unidirectional ring cavity. It is found that the threshold and the region of OB can be tuned by adjusting the center-center distance between the quantum dot and metal nanoparticle (MNP), the Rabi frequency of the control field and the radius of the MNP. Due to the significantly enhanced optical nonlinearity by the surface plasmon effect, the threshold of OB can be decreased greatly when the probe field is parallel to the major axis of the hybrid system. The enhanced OB may have promising applications in optical switching and optical storage.

  7. Donor energy levels of a spherical quantum dot subject to parallel electric and magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Souza, Gustavo V.B. de; Bruno-Alfonso, Alexys [UNESP, SP (Brazil)

    2011-07-01

    Full text. Quantum dots are quasi-zero-dimensional semiconductor structures that have been intensively investigated in the last two decades. On the one hand, they are interesting for basic science, because they can be seen as artificial atoms. Therefore, the theories of one and several particles in atoms and molecules may be tested and developed in a different scale. On the other hand, they are technologically relevant because their absorption and emission of light may be tailored by controlling their sizes, shapes and composition. Moreover, the addition of impurities and the application of electromagnetic fields further affect the electronic and optical properties of the quantum dots. In this work, the ground and excited states of a donor impurity at the center of a spherical semiconductor quantum dot, in the presence of parallel electric and magnetic fields, are calculated within the effective-mass approximation. The confining barrier of the dot is assumed to be infinitely high and the Schroedinger equation is solved by a finite-difference technique. This involves the derivation of appropriate boundary conditions and the computational diagonalization of large sparse matrices. The numerical results for the energy levels and the binding and transition energies are compared with available variational values. The iso-probability surfaces of the calculated states are displayed for different strengths of the applied fields. In this way, we are able to discuss the confining and ionizing effects of the fields

  8. Colloidal Quantum dot photovoltaics: Tuning optoelectronic properties

    International Nuclear Information System (INIS)

    Full text: Colloidal quantum dots combine processing from the solution phase with tunability of the bandgap. Via the size-effect the optical properties can be matched to the solar spectrum for a wide-range photon harvesting. To engineer photovoltaic devices, quantum dots are compressed from their colloidal form into a close-packed nanocrystal matrix, while undergoing a systematic layer-by-layer process. The resulting quantum dot solid is treated as semiconductor medium - one having electron-hole mobilites, free carrier densities and a dielectric constant. While the size-effect determined the band-gap before, it is now the nature of ligand and the treatment route, that influences mentioned electronic parameters. We took the view on the processing steps and found a concept for analysing trap states, moblility and device performance in real quantum dot solids. Our findings emphasize the interplay of mobility and trap-distribution with routes that take special care on the nanocrystal surface and hence conserve optoelectronic qualities of quantum dots for efficient photovoltaic cells. (author)

  9. Photoluminescence of carbon dots from mesoporous silica

    Science.gov (United States)

    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.

  10. Satisfaction levels among patients availing DOTS services in Bundelkhand Region (UP, India: Evidence from patient exit-interviews

    Directory of Open Access Journals (Sweden)

    Shalini Srivastav

    2014-01-01

    Full Text Available Context: Patient satisfaction is a determinant of treatment uptake and adherence to Directly Observed Treatment Short course (DOTS therapy for Tuberculosis (TB. Waiting time, staff′s attitude and improvement in symptoms may affect patient′s satisfaction. Aims: The rationale of the present study is to assess the levels of satisfaction among patients utilizing the DOTS services and the factors contributing toward patient satisfaction. Settings and Design: Cross-sectional study. Study Duration: Jan 2009 to March 2009. Study Area: Four Designated Microscopic Centers (DMCs of District Jhansi. Materials and Methods: Exit interviews of all the patients who were diagnosed as TB cases and put on DOTS in the first quarter of 2009 (i.e., subjects registered from 1 st January 2009 to 31 st March 2009 at four selected DMCs were taken on pre-tested questionnaire. Statistical Analysis: Results are expressed in percentages. Results: Average waiting time at center reported was 5-10 minutes by majority of cases (42.7%. Approx.78.6% patients were fully satisfied with the services provided at the centers. Lack of financial burden was the most common reason for satisfaction (95.4%, followed by improvement in symptoms (75%. Most common problems faced by the patients was difficult in coming on alternate days (30.0% followed by loss of wages and transport charges (26.8%. Conclusion: The study findings could potentially be explored to improve DOTS services to attain maximum satisfaction among TB patients.

  11. Inorganic passivation and doping control in colloidal quantum dot photovoltaics

    KAUST Repository

    Hoogland, Sjoerd 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.

  12. Nanosized Carbon Dots from Organic Matter and Biomass

    Institute of Scientific and Technical Information of China (English)

    LI Yuanyuan; CHEN Tong; MA Yulong

    2016-01-01

    Carbon nanoparticles (C-dots) were prepared by relfuxing the combustion soots of candles and corn stalk in nitric acid. The synthesized C-dots were characterized. The results showed a sharp increase in oxygen content and a sharp decrease in carbon content after oxidation. The C-dots had -OH and -CO2H groups introduced which made them hydrophilic. However, their difference was also obvious. The C-dots from candle soot had a 10-45 nm broad particle size distribution, and those from corn stalk soot had a 6-18 nm relatively small and narrow size distribution. The C-dots were mainly ofsp2 andsp3 carbon structure different from the C-dots of diamond-like structure from candle soot. Interestingly, two kinds of C-dots all exhibited unique photoluminescent properties. The obtained C-dots have potential applications in a broad range of areas.

  13. Origins and optimization of entanglement in plasmonically coupled quantum dots

    Science.gov (United States)

    Otten, Matthew; Larson, Jeffrey; Min, Misun; Wild, Stefan M.; Pelton, Matthew; Gray, Stephen K.

    2016-08-01

    A system of two or more quantum dots interacting with a dissipative plasmonic nanostructure is investigated in detail by using a cavity quantum electrodynamics approach with a model Hamiltonian. We focus on determining and understanding system configurations that generate multiple bipartite quantum entanglements between the occupation states of the quantum dots. These configurations include allowing for the quantum dots to be asymmetrically coupled to the plasmonic system. Analytical solution of a simplified limit for an arbitrary number of quantum dots and numerical simulations and optimization for the two- and three-dot cases are used to develop guidelines for maximizing the bipartite entanglements. For any number of quantum dots, we show that through simple starting states and parameter guidelines, one quantum dot can be made to share a strong amount of bipartite entanglement with all other quantum dots in the system, while entangling all other pairs to a lesser degree.

  14. Filtering algorithm for dotted interferences

    Energy Technology Data Exchange (ETDEWEB)

    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.

  15. Integration of informal medical practitioners in DOTS implementation to improve case detection rate

    International Nuclear Information System (INIS)

    To integrate informal registered medical practitioners (IRMP) in Directly Observed Therapy Short Course (DOTS) implementation to improve case detection rate. This interventional study was conducted in the settlement area of Malir district whereas New Karachi was taken as control, between February to November 2005. All registered health care providers within 5 kilometer around Tuberculosis (T8) DOTS center Malir were included. New sputum positive and sputum direct smear negative cases of pulmonary Tuberculosis above 15 years residing in the catechumen's area were included as target population. Informal registered medical practitioners were trained for the referral of suspected cases to the TB DOTs center where three sputum samples were taken, and X-ray chest was done to confirm if sputum direct smear (D/S) was negative. Demographic data regarding age, gender, address, case number, onset of symptoms, treatment given, response, compliance to treatment was all collected. Out of 64 health care providers there were a drop out of 6 leaving 58 informal registered medical practitioners (36 homeopathic/ 22 Hakims) who referred 54 cases, of these 16 cases were actual suspects. Two out of these 16 (12.5%) were Tuberculosis positive. One was Sputum D/S positive and the other sputum direct smear negative with X-ray chest positive. Comparison of data (Malir and New Karachi diagnostic center) showed that by incorporating homeopathic and Hakims an increase in the proportion of case identification (0.477) was significantly higher in Malir (intervention area) vs New Karachi (non-intervention area) (0.316). Integration of informal registered medical practitioners was found to be effective in DOTS implementation hence they can be incorporated in other national programmes to improve public health (JPMA 60:33; 2010). (author)

  16. Coherence and dephasing in self-assembled quantum dots

    DEFF Research Database (Denmark)

    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...... coherence. The inferred homogeneous line widths are significantly smaller than the line widths usually observed in the photoluminescence from single quantum dots indicating an additional inhomogeneours broadening mechanism in the latter....

  17. Short-wave infrared colloidal quantum dot photodetectors on silicon

    OpenAIRE

    Hu, Chen; Gassenq, Alban; Justo, Yolanda; Yakunin, Sergii; Heiss, Wolfgang; Hens, Zeger; Roelkens, Gunther

    2013-01-01

    In this paper, two kinds of colloidal quantum dots, PbS and HgTe, are explored for SWIR photodetectors application. The colloidal dots are prepared by hot injection chemical synthesis, with organic ligands around the dots keeping them stable in solution. For the purpose of achieving efficient carrier transport between the dots in a film, these long organic ligands are replaced by shorter, inorganic ligands. We report uniform, ultra-smooth colloidal QD films without cracks realized by dip-coat...

  18. Quantum Dots in Photonic Crystal Waveguides

    DEFF Research Database (Denmark)

    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...... quantum-dot-waveguide coupling. Such a structure is ideally suited for a number of applications in quantum information processing and among others we propose an on-chip spin-photon interface, a single photon transistor, and a deterministic cNOT gate....

  19. Charged-Exciton Complexes in Quantum Dots

    Institute of Scientific and Technical Information of China (English)

    XIE Wen-Fang

    2001-01-01

    It is known experimentally that stable charged-exciton complexes can exist in low-dimensional semiconductor nanostructures. Much less is known about the properties of such charged-exciton complexes since three-body problems are very difficult to be solved, even numerically. Here we introduce the correlated hyperspherical harmonics as basis functions to solve the hyperangular equation for negatively and positively charged excitons (trions) in a harmonic quantum dot. By using this method, we have calculated the energy spectra of the low-lying states of a charged exciton as a function of the radius of quantum dot. Based on symmetry analysis, the level crossover as the dot radius increases can be fully explained as the results of symmetry constraint.``

  20. Branch management into micropipeline joint dot

    Directory of Open Access Journals (Sweden)

    Dimitar Tyanev

    2011-11-01

    Full Text Available This paper considers problems related to hardware implementation of computational process with conditional jumps. Hardware refers to asynchronous pipeline organization at microoperational level. Exploration is dedicated to one of the tasks presented in (Tyanev, D., 2009 concerning to micropipeline controller design to control micropipeline stage into joint dot of branch algorithm. Joint dot is the point at which few preceding branches are combined. It appears inevitably into conditional jump structures and this is the reason for the actuality of its problem. Analysis of this new task is presented and request arbitration functioning principles are formulated for the incoming to joint dot requests. The arbiter is responsible for the fair choice on which depends steady peformance of separate pipeline brances. Paper also describes pipeline controller synthesis and analysis of its operation in two variants: about 2-phase and 4-phase data transfer protocol. The synthesized asynchronous arbiter scheme is invariant to the type of pipeline protocol.

  1. Biodegradation of the Nitramine Explosive CL-20

    OpenAIRE

    Trott, Sandra; Nishino, Shirley F.; Hawari, Jalal; Spain, Jim C.

    2003-01-01

    The cyclic nitramine explosive CL-20 (2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane) was examined in soil microcosms to determine whether it is biodegradable. CL-20 was incubated with a variety of soils. The explosive disappeared in all microcosms except the controls in which microbial activity had been inhibited. CL-20 was degraded most rapidly in garden soil. After 2 days of incubation, about 80% of the initial CL-20 had disappeared. A CL-20-degrading bacterial strain, Agrobact...

  2. Spectroelectrochemistry of EuCl3 in four molten salt eutectics; 3 LiCl – NaCl, 3 LiCl – 2 KCl, LiCl – RbCl, and 3 LiCl – 2 CsCl; at 873 K

    Energy Technology Data Exchange (ETDEWEB)

    Schroll, Cynthia A.; Chatterjee, Sayandev; Levitskaia, Tatiana G.; Heineman, William R.; Bryan, Samuel A.

    2016-05-17

    Key electrochemical properties affecting pyroprocessing of nuclear fuel were examined in four eutectic melts using using Eu3+/2+ as a representative probe. We report the electrochemical and spectroelectrochemical behavior of EuCl3 in four molten salt eutectics (3 LiCl – NaCl, 3 LiCl – 2 KCl, LiCl – RbCl and 3 LiCl – 2 CsCl) at 873 K. Cyclic voltammetry was used to determine the redox potential for Eu3+/2+ and the applied potentials for spectroelectrochemistry. Single step chronoabsorptometry and thin-layer spectroelectrochemistry were used to obtain the number of electrons transferred, redox potentials and diffusion coefficients for Eu3+ in each eutectic melt. The redox potentials determined by thin-layer spectroelectrochemistry were extremely close to those obtained using cyclic voltammetry. The redox potential for Eu3+/2+ was most positive in the 3 LiCl - NaCl melt, showed a negative shift in the 3 LiCl - 2 KCl melt, and was the most negative in the LiCl - RbCl and 3 LiCl - 2 CsCl eutectics. The diffusion coefficient for Eu3+ followed this same trend; it was the largest in the 3 LiCl - NaCl melt and the smallest in the LiCl - RbCl and 3 LiCl - 2 CsCl melts. The basic one-electron reversible electron transfer for Eu3+/2+ was not changed by melt composition.

  3. Reactions Between Humic Acid Solutions and Excessive ClO2 or Cl2

    Institute of Scientific and Technical Information of China (English)

    GE Yuan-xin; ZHU Zhi-liang; MA Hong-mei; ZHAO Jian-fu

    2007-01-01

    Reactions between humic acid solutions and excessive ClO2 or Cl2 have been investigated. Under various experimental conditions, the removal efficiency of TOC, UV254 and A140 from humic acid solutions were examined. The relationship between the removal efficiency and the consumption of ClO2 or Cl2 was discussed. The results showed that the maximum demand of ClO2 was 2.19 mg/mg TOC for the humic acid solution under the experimental conditions, and that of Cl2 was 1.88 mg/mg TOC. The variation tendency of ClO2 consumption was similar to that of Cl2. TOC of humic acid solutions decreased 15.2% and 15.6% after the reaction with ClO2 or Cl2 respectively. Under the experimental conditions, 21.4% of unsaturated bonds and 52.8% of humic acid color were removed by ClO2 in 168 h. As for Cl2, removal efficiency of unsaturated bonds and humic acid color were 16.8% and 41.7% respectively. Larger molecules from humic acid were oxidized to smaller molecules by ClO2 and Cl2. Higher oxidation potential of ClO2 than that of Cl2 was also indicated by variation of UV254/A410 ratios. The similar tendency, that exhibited faster variation in the initial 24 h, existed for all the research factors.

  4. CL from ZnO nanowires and microneedles Co-doped with N and Mn

    International Nuclear Information System (INIS)

    Cathodoluminescence (CL) was used to study the luminescence emission of ZnO : N, Mn nanowires and microneedles grown by thermal evaporation. CL spectra acquired at room temperature showed the presence of near band edge and defect-related emissions. The defect related emission comprised two bands centered at 2.28 and 2.5 eV. The first component was attributed to the formation of spinel ZnMn2O4 and the second to the well-known ZnO green emission. CL spectra acquired at 100 K showed two emissions centered at 3.22 and 3.25 eV that were attributed to donor–acceptor pair (DAP) and FA transitions, respectively. It was proposed that substitutional nitrogen (NO) and zinc interstitial (Zni) were acceptor and shallow-donor centers in the DAP transition. (paper)

  5. CL from ZnO nanowires and microneedles Co-doped with N and Mn

    Science.gov (United States)

    Herrera, M.; Morales, A.; Díaz, J. A.

    2014-05-01

    Cathodoluminescence (CL) was used to study the luminescence emission of ZnO : N, Mn nanowires and microneedles grown by thermal evaporation. CL spectra acquired at room temperature showed the presence of near band edge and defect-related emissions. The defect related emission comprised two bands centered at 2.28 and 2.5 eV. The first component was attributed to the formation of spinel ZnMn2O4 and the second to the well-known ZnO green emission. CL spectra acquired at 100 K showed two emissions centered at 3.22 and 3.25 eV that were attributed to donor-acceptor pair (DAP) and FA transitions, respectively. It was proposed that substitutional nitrogen (NO) and zinc interstitial (Zni) were acceptor and shallow-donor centers in the DAP transition.

  6. un clúster empresarial

    Directory of Open Access Journals (Sweden)

    Laura Marcela López Posada

    2006-01-01

    Full Text Available Los clústeres empresariales se han constituido en mecanismos para impulsar la competitividad de sectores en regiones y tradicionalmente han sido analizados desde la perspectiva económica (por su aporte en variables macroeconómicas, pero para su consolidación todo conglomerado empresarial requiere la comprensión de relaciones sociales, culturales y políticas. Resulta difícil estudiar estas relaciones desde teorías organizacionales tradicionales como la estructuralista o la contingencial, y se debe recurrir a otras perspectivas como el neoinstitucionalismo sociológico, enfoque que es utilizado en la presente investigación. La investigación fundamento del artículo se hizo en un sector considerado dinámico para el eje cafetero como es el de herramientas, la cual fue abordada desde un enfoque cualitativo mediante la aplicación de dos guías de entrevista semiestructurada (se aplicaron a treinta empresas de la cadena productiva y a nueve entidades de apoyo, diario de campo y análisis de fuentes documentales. Se concluye que en el clúster predominan el individualismo, la descon- fianza y la ausencia de elementos identitarios, simultáneamente con fuertes lazos comerciales y prácticas de gestión que se han institucionalizado por procesos isomórficos.

  7. Optical properties of charged semiconductor quantum dots

    Science.gov (United States)

    Jha, Praket P.

    The effect of n-type doping on the luminescence properties of II-VI quantum dots is studied. The addition of two shells of CdS on CdSe quantum dots prevents the creation of surface traps and makes the system stable under reducing environment. The injection of electrons into films of quantum dots leads to lower photoluminescence (PL) efficiency, with the extent of quenching dependent on both the number and the quantum states of the spectator charges in the nanocrystal. It is found that a 1Pe electron is an eightfold better PL quencher than the 1Se electron. Reduced threshold for stimulated emission is also observed in doped CdSe/CdS films. Time resolved photoluminescence measurements are used to extract the recombination rates of a charged exciton, called trion. It is observed that the negative trion has a radiative rate ˜2.2 +/- 0.4x faster than a neutral exciton, while its non-radiative recombination rate is slower than the biexciton non-radiative recombination rate by a factor of 7.5 +/- 1.7. The knowledge of the recombination rates of the trion enables us to calculate the quantum yield of a negative trion to be ˜10% for the nanocrystals investigated in our work. This is larger than the off state quantum yield from a single quantum dot photoluminescence trajectory and eliminates the formation of negative trion as the possible reason for the PL blinking of single quantum dots. Single quantum dot electrochemistry has also been achieved. It is shown that by varying the Fermi level of the system electrons can be reversibly injected into and extracted out of single CdSe/CdS and CdSe/ZnS nanoparticles to modulate the photoluminescence.

  8. Photoluminescence studies of single InGaAs quantum dots

    DEFF Research Database (Denmark)

    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...

  9. Imaging vasculature and lymphatic flow in mice using quantum dots

    DEFF Research Database (Denmark)

    Ballou, Byron; Ernst, Lauren A.; Andreko, Susan;

    2009-01-01

    Quantum dots are ideal probes for fluorescent imaging of vascular and lymphatic tissues. On injection into appropriate sites, red- and near-infrared-emitting quantum dots provide excellent definition of vasculature, lymphoid organs, and lymph nodes draining both normal tissues and tumors. We detail...... methods for use with commercially available quantum dots and discuss common difficulties....

  10. AHE measurements of very thin films and nanosized dots

    NARCIS (Netherlands)

    Kikuchi, N.; Murillo, R.; Lodder, J.C.

    2005-01-01

    In this paper we present anomalous Hall effect analysis from very thin Co (0.5 nm) film, Co/Pt multilayers and large areas of nanosized dots as well as from a few magnetic dots having a diameter of 120 nm. The dot arrayis prepared from Co/Pt multilayer by using laser interference lithography (LIL) w

  11. Bright infrared LEDs based on colloidal quantum-dots

    KAUST Repository

    Sun, Liangfeng

    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. Construction of magnetic-carbon-quantum-dots-probe-labeled apoferritin nanocages for bioimaging and targeted therapy

    Directory of Open Access Journals (Sweden)

    Yao HC

    2016-09-01

    Full Text Available Hanchun Yao,1,2 Li Su,1 Man Zeng,1 Li Cao,1 Weiwei Zhao,1 Chengqun Chen,3 Bin Du,1,2 Jie Zhou1,2 1School of Pharmaceutical Sciences, Zhengzhou University, 2Collaborative Innovation Center of Drug Research and Safety Evaluation, Henan Province, 3Department of Pharmacy, The First Affiliated Hospital of Zhengzhou University, Zhengzhou, People’s Republic of China Abstract: Carbon dots (CDs are one of the most highlighted carbon-based materials for biological applications, such as optical imaging nanoprobes, which are used for labeling cells in cancer treatment mainly due to their biocompatibility and unique optical properties. In this study, gadolinium (Gd-complex-containing CDs were obtained through a one-step microwave method to develop multimodal nanoprobes integrating the advantages of optical and magnetic imaging. The obtained Gd-CDs exhibited highly fluorescent properties with excellent water solubility and biological compatibility. Natural apoferritin (AFn nanocages, an excellent drug delivery carrier, are hollow in structure, with their pH-dependent, unfolding–refolding process at pH 2.0 and 7.4. The chemotherapeutic drug doxorubicin (DOX can be highly effective and encapsulated into AFn cavity. A widely used tumor-targeting molecule, folic acid (FA, functionalized the surface of AFn to obtain an active tumor targeting effect on MCF-7 cells and malignant tumors in mice models. In this study, an AFn nanocarrier encapsulating high concentration of DOX labeled with magnetic and fluorescent Gd-CDs probe was developed. Gd-CDs exhibited a unique green photoluminescence and almost no toxicity compared with free GdCl3. Furthermore, Gd-doped CDs significantly increased the circulation time and decreased the toxicity of Gd3+ in in vitro and in vivo magnetic resonance imaging, which demonstrated that the AFn nanocages labeled with Gd-CD compounds could serve as an excellent T1 contrast agent for magnetic resonance imaging. The self

  13. Biodegradation of the nitramine explosive CL-20.

    Science.gov (United States)

    Trott, Sandra; Nishino, Shirley F; Hawari, Jalal; Spain, Jim C

    2003-03-01

    The cyclic nitramine explosive CL-20 (2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane) was examined in soil microcosms to determine whether it is biodegradable. CL-20 was incubated with a variety of soils. The explosive disappeared in all microcosms except the controls in which microbial activity had been inhibited. CL-20 was degraded most rapidly in garden soil. After 2 days of incubation, about 80% of the initial CL-20 had disappeared. A CL-20-degrading bacterial strain, Agrobacterium sp. strain JS71, was isolated from enrichment cultures containing garden soil as an inoculum, succinate as a carbon source, and CL-20 as a nitrogen source. Growth experiments revealed that strain JS71 used 3 mol of nitrogen per mol of CL-20. PMID:12620886

  14. LiYbCl4(THF4

    Directory of Open Access Journals (Sweden)

    Lukas Richtera

    2011-06-01

    Full Text Available The title compound, di-μ-chlorido-dichlorido-1κ2Cl-tetrakis(tetrahydrofuran-1κ2O,2κ2O-lithiumytterbium(III, [LiYbCl4(C4H8O4], was prepared by the reaction of YbCl3(THF3 with LiCl in THF (THF is tetrahydrofuran. The central motif of the structure is a Yb(μ-Cl2Li ring. The Yb atom is hexacoordinated to four Cl atoms and two THF molecules oriented in a trans fashion. The Li atom has a tetrahedral environment and is coordinated to two Cl atoms and two THF molecules. No intermolecular interactions other than van der Waals forces were observed. Two of the THF molecules are disordered over two positions.

  15. Impact of Community-Based DOT on Tuberculosis Treatment Outcomes: A Systematic Review and Meta-Analysis.

    Directory of Open Access Journals (Sweden)

    HaiYang Zhang

    treatment outcomes according to the pooled results of included studies in this review. Studies on strategies for implementation of patient-centered and community-centered CB-DOT deserve further attention.

  16. Engineered Quantum Dot Single Photon Sources

    CERN Document Server

    Buckley, Sonia; Vuckovic, Jelena

    2012-01-01

    Fast, high efficiency, and low error single photon sources are required for implementation of a number of quantum information processing applications. The fastest triggered single photon sources to date have been demonstrated using epitaxially grown semiconductor quantum dots (QDs), which can be conveniently integrated with optical microcavities. Recent advances in QD technology, including demonstrations of high temperature and telecommunications wavelength single photon emission, have made QD single photon sources more practical. Here we discuss the applications of single photon sources and their various requirements, before reviewing the progress made on a quantum dot platform in meeting these requirements.

  17. Optical studies of capped quantum dots

    OpenAIRE

    Wuister, S.F.

    2005-01-01

    This thesis describes the synthesis and spectroscopy of CdSe and CdTe semiconductor quantum dots (QDs). The first chapter gives an introduction into the unique size dependent properties of semiconductor quantum dots. Highly luminescent QDs of CdSe and CdTe were prepared via a high temperature method in a glovebox. These QDs are soluble in organics but can be transferred into water or ethanol after exchange of the surfactants by various thiols (HS-R). For CdTe the exchange with thiols has a be...

  18. Cadmium telluride quantum dots advances and applications

    CERN Document Server

    Donegan, John

    2013-01-01

    Optical Properties of Bulk and Nanocrystalline Cadmium Telluride, Núñez Fernández and M.I. VasilevskiyAqueous Synthesis of Colloidal CdTe Nanocrystals, V. Lesnyak, N. Gaponik, and A. EychmüllerAssemblies of Thiol-Capped CdTe Nanocrystals, N. GaponikFörster Resonant Energy Transfer in CdTe Nanocrystal Quantum Dot Structures, M. Lunz and A.L. BradleyEmission of CdTe Nanocrystals Coupled to Microcavities, Y.P. Rakovich and J.F. DoneganBiological Applications of Cadmium Telluride Semiconductor Quantum Dots, A. Le Cign

  19. Resonant tunneling in graphene pseudomagnetic quantum dots.

    Science.gov (United States)

    Qi, Zenan; Bahamon, D A; Pereira, Vitor M; Park, Harold S; Campbell, D K; Neto, A H Castro

    2013-06-12

    Realistic relaxed configurations of triaxially strained graphene quantum dots are obtained from unbiased atomistic mechanical simulations. The local electronic structure and quantum transport characteristics of y-junctions based on such dots are studied, revealing that the quasi-uniform pseudomagnetic field induced by strain restricts transport to Landau level- and edge state-assisted resonant tunneling. Valley degeneracy is broken in the presence of an external field, allowing the selective filtering of the valley and chirality of the states assisting in the resonant tunneling. Asymmetric strain conditions can be explored to select the exit channel of the y-junction.

  20. Mitigation of quantum dot cytotoxicity by microencapsulation.

    Directory of Open Access Journals (Sweden)

    Amelia Romoser

    Full Text Available When CdSe/ZnS-polyethyleneimine (PEI quantum dots (QDs are microencapsulated in polymeric microcapsules, human fibroblasts are protected from acute cytotoxic effects. Differences in cellular morphology, uptake, and viability were assessed after treatment with either microencapsulated or unencapsulated dots. Specifically, QDs contained in microcapsules terminated with polyethylene glycol (PEG mitigate contact with and uptake by cells, thus providing a tool to retain particle luminescence for applications such as extracellular sensing and imaging. The microcapsule serves as the "first line of defense" for containing the QDs. This enables the individual QD coating to be designed primarily to enhance the function of the biosensor.

  1. Thermodynamic Optimization of DyCl3 -NaCl System

    Institute of Scientific and Technical Information of China (English)

    叶信宇; 孙益民; 张静; 谈君君

    2005-01-01

    In this paper, the phase diagram of the DyCl3 -NaCl system is optimized and calculated with CALPHAD ( calculation of phase diagram ) technology. A set of thermodynamic functions of compounds Na3 DyCl6, NaDyCl4, and NaDY2 Cl7 have been optimized and calculated based on an interactive computer-assisted analysis. The optimized thermodynamic parameters, calculated phase diagram and experimental phase diagram are thermodynamically serf-consistent.

  2. ESR of trapped centers in γ irradiated silver chlorates single crystals

    International Nuclear Information System (INIS)

    The paramagnetic centers O-3, ClO2, and (ClO2--Cl)- have been identified in irradiated AgClO3 single crystals by X and Q band ESR experiments at room temperatures and by the optical absorption bands at 480 and 360 nm, characteristic of the first two centers, respectively. The ESR spectrum and its angular dependence show that the first two centers have two magnetically inequivalent sites per unit cell. The third center was clearly observed only at certain orientations. The data for ClO2 show that the principal directions of the g and A tensors do not coincide; the two magnetically inequivalent sites have similar principal values of the g and A tensors related by a 900 rotation about the tetragonal crystal axis of symmetry, and can therefore be assumed to be chemically equivalent. It is found that the ClO2 center is formed substitutionally in the ClO-3 ion position, but that the ozonide O-3 is not. The thermal annealing of the γ irradiated AgClO3 has revealed an increase in the concentration of the O-3 radical that seems to be connected with the simultaneous destruction of the ClO2 center

  3. Chemiluminescence of carbon dots induced by diperiodato-nicklate (IV) in alkaline solution and its application to a quenchometric flow-injection assays of paracetamole, L-cysteine and glutathione

    International Nuclear Information System (INIS)

    Aqueous solutions of carbon dots (C-dots) were prepared by microwave-assisted thermal carbonization of poly(ethylene glycol). They were investigated by transmission electron microscopy, absorption and fluorescence spectra. It is shown that diperiodato-nicklate(IV), a strong oxidant, induces the chemiluminescence (CL) of C-dots in strongly alkaline solution without use of an additional reagent. A mechanism for this reaction is suggested. It is also found that the CL of the system is quenched by paracetamole, L-cysteine and glutathione. Under the optimized conditions, the calibration plot is linear with a correlation coefficient (r) of >0.995. The limits of detection are 90, 8, and 60 µg L-1 for paracetamole, L-cysteine, and glutathione, respectively. Spiked urine and serum samples were analyzed and gave recoveries in the range from 84.38 to 116.0 %, with an RSD of 1.2–2.7 %. (author)

  4. Nanoscale fluorescence lifetime imaging with a single diamond NV center

    CERN Document Server

    Beams, Ryan; Johnson, Timothy W; Oh, Sang-Hyun; Novotny, Lukas; Vamivakas, Nick

    2013-01-01

    Solid-state quantum emitters, such as artificially engineered quantum dots or naturally occurring defects in solids, are being investigated for applications ranging from quantum information science and optoelectronics to biomedical imaging. Recently, these same systems have also been studied from the perspective of nanoscale metrology. In this letter we study the near-field optical properties of a diamond nanocrystal hosting a single nitrogen vacancy center. We find that the nitrogen vacancy center is a sensitive probe of the surrounding electromagnetic mode structure. We exploit this sensitivity to demonstrate nanoscale fluorescence lifetime imaging microscopy (FLIM) with a single nitrogen vacancy center by imaging the local density of states of an optical antenna.

  5. Tuberculose associada à AIDS: características demográficas, clínicas e laboratoriais de pacientes atendidos em um serviço de referência do sul do Brasil Tuberculosis associated to AIDS: demographic, clinical and laboratory characteristics of patients cared for at a reference center in the south of Brazil

    OpenAIRE

    Maria Marta Santos Boffo; Ivo Gomes de Mattos; Marta Osório Ribeiro; Isabel Cristina de Oliveira Neto

    2004-01-01

    INTRODUÇÃO: A sinergia entre a tuberculose e o vírus da imunodeficiência humana é responsável pelo aumento da morbi-mortalidade dos pacientes com AIDS. OBJETIVO: Delinear o perfil de pacientes com tuberculose e AIDS na cidade de Rio Grande (RS) relacionando dados demográficos, clínicos e laboratoriais. MÉTODO: A amostra foi constituída por todos os casos de tuberculose confirmados pelo isolamento de Mycobacterium tuberculosis ocorridos no Serviço de AIDS do Hospital Universitário/FURG entre s...

  6. A study of the lunisolar secular resonance $2dot{omega}+dot{Omega}=0$

    Directory of Open Access Journals (Sweden)

    Alessandra eCelletti

    2016-03-01

    Full Text Available The dynamics of small bodies around the Earth has gained a renewed interest,since the awareness of the problems that space debris can cause in thenearby future. A relevant role in space debris is played by lunisolarsecular resonances, which might contribute to an increase of the orbitalelements, typically of the eccentricity. We concentrate our attention onthe lunisolar secular resonance described by the relation$2dot{omega}+dot{Omega}=0$, where $omega$ and $Omega$ denotethe argument of perigee and the longitude of the ascending node of the space debris.We introduce three different models with increasing complexity. We show that the growth in eccentricity, as observed in space debris located in the MEO region at the inclination about equal to $56^circ$, can be explained as a natural effect of the secular resonance $2dot{omega}+dot{Omega}=0$, while the chaotic variations of the orbital parameters are the result of interaction and overlapping of nearby resonances.

  7. A study of the lunisolar secular resonance 2dot{ω}+dot{Ω}=0

    Science.gov (United States)

    Celletti, Alessandra; Gales, Catalin

    2016-03-01

    The dynamics of small bodies around the Earth has gained a renewed interest, since the awareness of the problems that space debris can cause in the nearby future. A relevant role in space debris is played by lunisolar secular resonances, which might contribute to an increase of the orbital elements, typically of the eccentricity. We concentrate our attention on the lunisolar secular resonance described by the relation 2dot{ω}+dot{Ω}=0, where ω and Ω denote the argument of perigee and the longitude of the ascending node of the space debris. We introduce three different models with increasing complexity. We show that the growth in eccentricity, as observed in space debris located in the MEO region at the inclination about equal to 56°, can be explained as a natural effect of the secular resonance 2dot{ω}+dot{Ω}=0, while the chaotic variations of the orbital parameters are the result of interaction and overlapping of nearby resonances.

  8. A study of the lunisolar secular resonance $2\\dot{\\omega}+\\dot{\\Omega}=0$

    CERN Document Server

    Celletti, Alessandra

    2016-01-01

    The dynamics of small bodies around the Earth has gained a renewed interest, since the awareness of the problems that space debris can cause in the nearby future. A relevant role in space debris is played by lunisolar secular resonances, which might contribute to an increase of the orbital elements, typically of the eccentricity. We concentrate our attention on the lunisolar secular resonance described by the relation $2\\dot{\\omega}+\\dot{\\Omega}=0$, where $\\omega$ and $\\Omega$ denote the argument of perigee and the longitude of the ascending node of the space debris. We introduce three different models with increasing complexity. We show that the growth in eccentricity, as observed in space debris located in the MEO region at the inclination about equal to $56^\\circ$, can be explained as a natural effect of the secular resonance $2\\dot{\\omega}+\\dot{\\Omega}=0$, while the chaotic variations of the orbital parameters are the result of interaction and overlapping of nearby resonances.

  9. Ultra-large scale synthesis of high electrochemical performance SnO{sub 2} quantum dots within 5 min at room temperature following a growth self-termination mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Cui, Hongtao, E-mail: htcui@ytu.edu.cn; Xue, Junying; Ren, Wanzhong; Wang, Minmin

    2015-10-05

    Highlights: • SnO{sub 2} quantum dots were prepared at an ultra-large scale at room temperature within 5 min. • The grinding of SnCl{sub 2}⋅2H{sub 2}O and ammonium persulphate with morpholine produces quantum dots. • The reactions were self-terminated through the rapid consumption of water. • The obtained SnO{sub 2} quantum dots own high electrochemical performance. - Abstract: SnO{sub 2} quantum dots are prepared at an ultra-large scale by a productive synthetic procedure without using any organic ligand. The grinding of solid mixture of SnCl{sub 2}⋅2H{sub 2}O and ammonium persulphate with morpholine in a mortar at room temperature produces 1.2 nm SnO{sub 2} quantum dots within 5 min. The formation of SnO{sub 2} is initiated by the reaction between tin ions and hydroxyl groups generated from hydrolysis of morpholine in the released hydrate water from SnCl{sub 2}⋅2H{sub 2}O. It is considered that as water is rapidly consumed by the hydrolysis reaction of morpholine, the growth process of particles is self-terminated immediately after their transitory period of nucleation and growth. As a result of simple procedure and high toleration to scaling up of preparation, at least 50 g of SnO{sub 2} quantum dots can be produced in one batch in our laboratory. The as prepared quantum dots present high electrochemical performance due to the effective faradaic reaction and the alternative trapping of electrons and holes.

  10. Development of cadmium-free quantum dot for intracellular labelling through electroporation or lipid-calcium-phosphate

    Science.gov (United States)

    Liu, Ying-Feng; Hung, Wei-Ling; Hou, Tzh-Yin; Huang, Hsiu-Ying; Lin, Cheng-An J.

    2016-04-01

    Traditional fluorescent labelling techniques has severe photo-bleaching problem such as organic dyes and fluorescent protein. Quantum dots made up of traditional semiconductor (CdSe/ZnS) material has sort of biological toxicity. This research has developed novel Cd-free quantum dots divided into semiconductor (Indium phosphide, InP) and noble metal (Gold). Former has lower toxicity compared to traditional quantum dots. Latter consisting of gold (III) chloride (AuCl3) and toluene utilizes sonochemical preparation and different stimulus to regulate fluorescent wavelength. Amphoteric macromolecule surface technology and ligand Exchange in self-Assembled are involved to develop hydrophilic nanomaterials which can regulate the number of grafts per molecule of surface functional groups. Calcium phosphate (CaP) nanoparticle (NP) with an asymmetric lipid bilayer coating technology developed for intracellular delivery and labelling has synthesized Cd-free quantum dots possessing high brightness and multi-fluorescence successfully. Then, polymer coating and ligand exchange transfer to water-soluble materials to produce liposome nanomaterials as fluorescent probes and enhancing medical applications of nanotechnology.

  11. Electrically addressing a single self-assembled quantum dot

    CERN Document Server

    Ellis, D J P; Atkinson, P; Ritchie, D A; Shields, A J

    2006-01-01

    We report on the use of an aperture in an aluminum oxide layer to restrict current injection into a single self-assembled InAs quantum dot, from an ensemble of such dots within a large mesa. The insulating aperture is formed through the wet-oxidation of a layer of AlAs. Under photoluminescence we observe that only one quantum dot in the ensemble exhibits a Stark shift, and that the same single dot is visible under electroluminescence. Autocorrelation measurements performed on the electroluminescence confirm that we are observing emission from a single quantum dot.

  12. The Influence of Formulating a Damping Solution on Dot Gain

    Directory of Open Access Journals (Sweden)

    Povilas Mikalainis

    2011-02-01

    Full Text Available Difference in dot gain using various additives to the damping solution was investigated on two offset web presses. Dot gain was measured using a densitometer and calculated considering CIE L*a*b* coordinates. It was found that while using a non alcohol additive instead of the alcohol one, dot gain became smaller and printing stability was lower. Changes in dot gain depend on the ink that may vary in colours. The influence of changes in dot gain on the colour was determined. Besides, it was found that differences in colour were unacceptable in many cases.Article in Lithuanian

  13. Synthesis of CdSe quantum dots for quantum dot sensitized solar cell

    Energy Technology Data Exchange (ETDEWEB)

    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.

  14. Synthesis of CdSe quantum dots for quantum dot sensitized solar cell

    International Nuclear Information System (INIS)

    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

  15. Ostwald's ripening of nanostructures with quantum dots

    CERN Document Server

    Vengrenovich, R D; Yarema, S V

    2001-01-01

    The scenario of quantum dots shaping during ripening three-dimensional islands obtained by heteroepitaxy in a Stranski-Krastanow mode, is offered. It is shown that throughout the growth of dislocations with their subsequent separation from the island bottom, the size distribution function becomes narrower with noticeable diminishing the dispersion. The possible reasons for signal attenuation of Ostwald's ripening islands are analyzed

  16. Ostwald's ripening of nanostructures with quantum dots

    International Nuclear Information System (INIS)

    The scenario of quantum dots shaping during ripening three-dimensional islands obtained by heteroepitaxy in a Stranski-Krastanow mode, is offered. It is shown that throughout the growth of dislocations with their subsequent separation from the island bottom, the size distribution function becomes narrower with noticeable diminishing the dispersion. The possible reasons for signal attenuation of Ostwald's ripening islands are analyzed

  17. Saturating optical resonances in quantum dots

    Science.gov (United States)

    Nair, Selvakumar V.; Rustagi, K. C.

    Optical bistability in quantum dots, recently proposed by Chemla and Miller, is studied in a two-resonance model. We show that for such classical electromagnetic resonances the applicability of a two-resonance model is far more restrictive than for those in atoms.

  18. Quantum dot devices for optical communications

    DEFF Research Database (Denmark)

    Mørk, Jesper

    2005-01-01

    Semiconductor quantum dots are often described as "artificial atoms": They are small nanometre-sized structures in which electrons only are allowed to exist at certain discrete levels due to size quantization, thus allowing the engineering of fundamental properties such as the coupling to light. ...

  19. Single Molecule Applications of Quantum Dots

    DEFF Research Database (Denmark)

    Rasmussen, Thomas Elmelund; Jauffred, Liselotte; Brewer, Jonathan R.;

    2013-01-01

    Fluorescent nanocrystals composed of semiconductor materials were first introduced for biological applications in the late 1990s. The focus of this review is to give a brief survey of biological applications of quantum dots (QDs) at the single QD sensitivity level. These are described as follows: 1...

  20. Optical anisotropy in vertically coupled quantum dots

    DEFF Research Database (Denmark)

    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...

  1. Decoherence in Nearly-Isolated Quantum Dots

    DEFF Research Database (Denmark)

    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...

  2. Producing Quantum Dots by Spray Pyrolysis

    Science.gov (United States)

    Banger, Kulbinder; Jin, Michael H.; Hepp, Aloysius

    2006-01-01

    An improved process for making nanocrystallites, commonly denoted quantum dots (QDs), is based on spray pyrolysis. Unlike the process used heretofore, the improved process is amenable to mass production of either passivated or non-passivated QDs, with computer control to ensure near uniformity of size.

  3. System and method for making quantum dots

    KAUST Repository

    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.

  4. Amphoteric CdSe nanocrystalline quantum dots.

    Science.gov (United States)

    Islam, Mohammad A

    2008-06-25

    The nanocrystal quantum dot (NQD) charge states strongly influence their electrical transport properties in photovoltaic and electroluminescent devices, optical gains in NQD lasers, and the stability of the dots in thin films. We report a unique electrostatic nature of CdSe NQDs, studied by electrophoretic methods. When we submerged a pair of metal electrodes, in a parallel plate capacitor configuration, into a dilute solution of CdSe NQDs in hexane, and applied a DC voltage across the pair, thin films of CdSe NQDs were deposited on both the positive and the negative electrodes. Extensive characterizations including scanning electron microscopy (SEM), atomic force microscopy (AFM), Fourier transform infrared (FTIR) and Raman studies revealed that the films on both the positive and the negative electrodes were identical in every respect, clearly indicating that: (1) a fraction (<1%) of the CdSe NQDs in free form in hexane solution are charged and, more importantly, (2) there are equal numbers of positive and negative CdSe NQDs in the hexane solution. Experiments also show that the number of deposited dots is at least an order of magnitude higher than the number of initially charged dots, indicating regeneration. We used simple thermodynamics to explain such amphoteric nature and the charging/regeneration of the CdSe NQDs.

  5. Quantum Dot Devices for Optical Signal Processing

    DEFF Research Database (Denmark)

    Chen, Yaohui

    with other semiconductor materials. The understanding of such properties is important in order to improve the performance of existing devices and to trigger the development of new semiconductor devices for dierent optical signal processing functionalities in the future. We present a detailed quantum dot...

  6. Competing interactions in semiconductor quantum dots

    NARCIS (Netherlands)

    R. van den Berg; G.P. Brandino; O. El Araby; R.M. Konik; V. Gritsev; J.S. Caux

    2014-01-01

    We introduce an integrability-based method enabling the study of semiconductor quantum dot models incorporating both the full hyperfine interaction as well as a mean-field treatment of dipole-dipole interactions in the nuclear spin bath. By performing free-induction decay and spin-echo simulations w

  7. Enabling biomedical research with designer quantum dots

    NARCIS (Netherlands)

    Tomczak, N.; Janczewski, D.; Dorokhin, D.V.; Han, M-Y; Vancso, G.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.

  8. Quantum dot waveguides: ultrafast dynamics and applications

    DEFF Research Database (Denmark)

    Chen, Yaohui; Mørk, Jesper

    2009-01-01

    In this paper we analyze, based on numerical simulations, the dynamics of semiconductor devices incorporating quantum dots (QDs). In particular we emphasize the unique ultrafast carrier dynamics occurring between discrete QD bound states, and its influence on QD semiconductor optical amplifiers...

  9. Tunneling Processes in Optically Excited Quantum Dots

    Institute of Scientific and Technical Information of China (English)

    LI Xiu-Ping; WEI Hua-Rong; XU Li-Ping; GONG Jian-Ping; YAN Wei-Xian

    2011-01-01

    The single-electron tunneling processes in optically excited coupled quantum dots can be divided into two parts: the electron and the hole parts, which are analytically obtained in the framework of the Keldysh formalism. The tunneling process is selective tunneling, which results in dark tunneling states. The tunneling currents are co-determined by the resonance energies and probability distributions of the particular quantum channels defined by the electron-hole complex resonant states.%The single-electron tunneling processes in optically excited coupled quantum dots can be divided into two parts:the electron and the hole parts,which are analytically obtained in the framework of the Keldysh formalism.The tunneling process is selective tunneling,which results in dark tunneling states.The tunneling currents are co-determined by the resonance energies and probability distributions of the particular quantum channels defined by the electron-hole complex resonant states.Probing the fine-energy structure of the exciton complexes[1-10] in an optically excited quantum dot is an important way of exploring new mechanisms in nanostructures.Single electron tunneling (SET) devices consisting of a central quantum dot (QD) and a tunneling coupled source and drain have become important optoelectronic nano-devices.[11,12

  10. A circular dielectric grating for vertical extraction of single quantum dot emission

    CERN Document Server

    Davanco, M; Schuh, D; Badolato, A; Srinivasan, K

    2011-01-01

    We demonstrate a nanostructure composed of partially etched annular trenches in a suspended GaAs membrane, designed for efficient and moderately broadband (approx. 5 nm) emission extraction from single InAs quantum dots. Simulations indicate that a dipole embedded in the nanostructure center radiates upwards into free space with a nearly Gaussian far-field, allowing a collection efficiency > 80 % with a high numerical aperture (NA=0.7) optic, and with 12X Purcell radiative rate enhancement. Fabricated devices exhibit an approx. 10 % photon collection efficiency with a NA=0.42 objective, a 20X improvement over quantum dots in unpatterned GaAs. A fourfold exciton lifetime reduction indicates moderate Purcell enhancement.

  11. Strong reduction of the lattice thermal conductivity in superlattices and quantum dot superlattices

    Science.gov (United States)

    Fomin, V. M.; Nika, D. L.; Cocemasov, A. I.; Isacova, C. I.; Schmidt, O. G.

    2012-06-01

    Thermal transport is theoretically investigated in the planar Si/Ge superlattices and Si/Ge quantum dot superlattices. The phonon states in the considered nanostructures are obtained using the Face-centered Cubic Cell model of lattice dynamics. A significant reduction of the lattice thermal conductivity is revealed in both considered structures in a wide range of temperatures from 100 K to 400 K. This effect is explained by the removal of the high-energy and high-velocity phonon modes from the heat flux due to their localization in superlattice segments and the phonon scattering on the interfaces. The obtained results show prospects of the planar superlattices and quantum-dot superlattices for thermoelectric and thermo-insulating applications.

  12. High-Q submicron-diameter quantum-dot microcavity pillars for cavity QED experiments

    DEFF Research Database (Denmark)

    Gregersen, Niels; Lermer, Matthias; Dunzer, Florian;

    As/AlAs micropillar design where Bloch-wave engineering is employed to significally enhance the cavity mode confinement in the submicron diameter regime. We demonstrate a record-high vacuum Rabi splitting of 85 µeV of the strong coupling for pillars incorporating quantum dots with modest oscillator strength f ≈ 10...... and the DBR Bloch mode limits the Q to about 2000. [1] In our optimized design we have replaced the standard λ-spacer with a 3 segment tapered region. The layer thicknesses of these GaAs/AlAs segments are gradually reduced towards the center, effectively detuning the bandgap relative to that of the DBRs...... and allowing for a single localized mode inside the cavity. The fundamental Bloch mode experiences an adiabatic transition, leading to an improved mode matching and a reduced coupling to propagating Bloch modes in the DBRs. The central GaAs layer incorporating quantum dots is only 60 nm thick corresponding...

  13. Inter-dot strain field effect on the optoelectronic properties of realistic InP lateral quantum-dot molecules

    International Nuclear Information System (INIS)

    We report on numerical simulations of InP surface lateral quantum-dot molecules on In0.48Ga0.52 P buffer, using a model strictly derived by experimental results by extrapolation of the molecules shape from atomic force microscopy images. Our study has been inspired by the comparison of a photoluminescence spectrum of a high-density InP surface quantum dot sample with a numerical ensemble average given by a weighted sum of simulated single quantum-dot spectra. A lack of experimental optical response from the smaller dots of the sample is found to be due to strong inter-dot strain fields, which influence the optoelectronic properties of lateral quantum-dot molecules. Continuum electromechanical, k→·p→ bandstructure, and optical calculations are presented for two different molecules, the first composed of two dots of nearly identical dimensions (homonuclear), the second of two dots with rather different sizes (heteronuclear). We show that in the homonuclear molecule the hydrostatic strain raises a potential barrier for the electrons in the connection zone between the dots, while conversely the holes do not experience any barrier, which considerably increases the coupling. Results for the heteronuclear molecule show instead that its dots do not appear as two separate and distinguishable structures, but as a single large dot, and no optical emission is observed in the range of higher energies where the smaller dot is supposed to emit. We believe that in samples of such a high density the smaller dots result as practically incorporated into bigger molecular structures, an effect strongly enforced by the inter-dot strain fields, and consequently it is not possible to experimentally obtain a separate optical emission from the smaller dots

  14. Inter-dot strain field effect on the optoelectronic properties of realistic InP lateral quantum-dot molecules

    Energy Technology Data Exchange (ETDEWEB)

    Barettin, Daniele, E-mail: Daniele.Barettin@uniroma2.it; Auf der Maur, Matthias [Department of Electronic Engineering, University of Rome “Tor Vergata,” Via del Politecnico 1, 00133, Rome (Italy); De Angelis, Roberta; Prosposito, Paolo; Casalboni, Mauro [Department of Industrial Engineering, University of Rome Tor Vergata, Via del Politecnico 1 00133 Rome, Italy and INSTM, Unitá di ricerca dell' Universitá di Roma “Tor Vergata,” Via della Ricerca Scientifica 1, 00133, Rome (Italy); Pecchia, Alessandro [CNR-ISMN, via Salaria Km. 29.300, 00017 Monterotondo, Rome (Italy)

    2015-03-07

    We report on numerical simulations of InP surface lateral quantum-dot molecules on In{sub 0.48}Ga{sub 0.52 }P buffer, using a model strictly derived by experimental results by extrapolation of the molecules shape from atomic force microscopy images. Our study has been inspired by the comparison of a photoluminescence spectrum of a high-density InP surface quantum dot sample with a numerical ensemble average given by a weighted sum of simulated single quantum-dot spectra. A lack of experimental optical response from the smaller dots of the sample is found to be due to strong inter-dot strain fields, which influence the optoelectronic properties of lateral quantum-dot molecules. Continuum electromechanical, k{sup →}·p{sup →} bandstructure, and optical calculations are presented for two different molecules, the first composed of two dots of nearly identical dimensions (homonuclear), the second of two dots with rather different sizes (heteronuclear). We show that in the homonuclear molecule the hydrostatic strain raises a potential barrier for the electrons in the connection zone between the dots, while conversely the holes do not experience any barrier, which considerably increases the coupling. Results for the heteronuclear molecule show instead that its dots do not appear as two separate and distinguishable structures, but as a single large dot, and no optical emission is observed in the range of higher energies where the smaller dot is supposed to emit. We believe that in samples of such a high density the smaller dots result as practically incorporated into bigger molecular structures, an effect strongly enforced by the inter-dot strain fields, and consequently it is not possible to experimentally obtain a separate optical emission from the smaller dots.

  15. Annealing-induced change in quantum dot chain formation mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Park, Tyler D.; Colton, John S.; Farrer, Jeffrey K. [Department of Physics and Astronomy, Brigham Young University, Provo UT 84602 (United States); Yang, Haeyeon [Department of Nanoscience and Nanoengineering, South Dakota School of Mines and Technology, Rapid City, SD 57701 (United States); Kim, Dong Jun [IPG Photonics Corporation, Oxford, MA 01540 (United States)

    2014-12-15

    Self-assembled InGaAs quantum dot chains were grown using a modified Stranski-Krastanov method in which the InGaAs layer is deposited under a low growth temperature and high arsenic overpressure, which suppresses the formation of dots until a later annealing process. The dots are capped with a 100 nm GaAs layer. Three samples, having three different annealing temperatures of 460°C, 480°C, and 500°C, were studied by transmission electron microscopy. Results indicate two distinct types of dot formation processes: dots in the 460°C and 480°C samples form from platelet precursors in a one-to-one ratio whereas the dots in the sample annealed at 500°C form through the strain-driven self-assembly process, and then grow larger via an additional Ostwald ripening process whereby dots grow into larger dots at the expense of smaller seed islands. There are consequently significant morphological differences between the two types of dots, which explain many of the previously-reported differences in optical properties. Moreover, we also report evidence of indium segregation within the dots, with little or no indium intermixing between the dots and the surrounding GaAs barrier.

  16. Annealing-induced change in quantum dot chain formation mechanism

    Science.gov (United States)

    Park, Tyler D.; Colton, John S.; Farrer, Jeffrey K.; Yang, Haeyeon; Kim, Dong Jun

    2014-12-01

    Self-assembled InGaAs quantum dot chains were grown using a modified Stranski-Krastanov method in which the InGaAs layer is deposited under a low growth temperature and high arsenic overpressure, which suppresses the formation of dots until a later annealing process. The dots are capped with a 100 nm GaAs layer. Three samples, having three different annealing temperatures of 460°C, 480°C, and 500°C, were studied by transmission electron microscopy. Results indicate two distinct types of dot formation processes: dots in the 460°C and 480°C samples form from platelet precursors in a one-to-one ratio whereas the dots in the sample annealed at 500°C form through the strain-driven self-assembly process, and then grow larger via an additional Ostwald ripening process whereby dots grow into larger dots at the expense of smaller seed islands. There are consequently significant morphological differences between the two types of dots, which explain many of the previously-reported differences in optical properties. Moreover, we also report evidence of indium segregation within the dots, with little or no indium intermixing between the dots and the surrounding GaAs barrier.

  17. Annealing-induced change in quantum dot chain formation mechanism

    Directory of Open Access Journals (Sweden)

    Tyler D. Park

    2014-12-01

    Full Text Available Self-assembled InGaAs quantum dot chains were grown using a modified Stranski-Krastanov method in which the InGaAs layer is deposited under a low growth temperature and high arsenic overpressure, which suppresses the formation of dots until a later annealing process. The dots are capped with a 100 nm GaAs layer. Three samples, having three different annealing temperatures of 460°C, 480°C, and 500°C, were studied by transmission electron microscopy. Results indicate two distinct types of dot formation processes: dots in the 460°C and 480°C samples form from platelet precursors in a one-to-one ratio whereas the dots in the sample annealed at 500°C form through the strain-driven self-assembly process, and then grow larger via an additional Ostwald ripening process whereby dots grow into larger dots at the expense of smaller seed islands. There are consequently significant morphological differences between the two types of dots, which explain many of the previously-reported differences in optical properties. Moreover, we also report evidence of indium segregation within the dots, with little or no indium intermixing between the dots and the surrounding GaAs barrier.

  18. 76 FR 34014 - Airworthiness Directives; Bombardier, Inc. Model CL-215-1A10, CL-215-6B11 (CL-215T Variant), and...

    Science.gov (United States)

    2011-06-10

    ... Procedures (44 FR 11034, February 26, 1979); and 3. Will not have a significant economic impact, positive or.... Model CL-215-1A10, CL- 215-6B11 (CL-215T Variant), and CL-215-6B11 (CL-415 Variant) Airplanes AGENCY.... Model CL-215-1A10 airplanes, serial numbers 1051 through 1125 inclusive; Model CL-215- 6B11...

  19. Inhomogeneous charging and screening effects in semiconductor quantum dot arrays

    Energy Technology Data Exchange (ETDEWEB)

    Wetzler, R [Institut fuer Theoretische Physik, Technische Universitaet Berlin, Hardenbergstr. 36, 10623 Berlin (Germany); Kunert, R [Institut fuer Theoretische Physik, Technische Universitaet Berlin, Hardenbergstr. 36, 10623 Berlin (Germany); Wacker, A [Fysiska Institutionen, Lunds Universitet, Box 118, 22100 Lund (Sweden); Schoell, E [Institut fuer Theoretische Physik, Technische Universitaet Berlin, Hardenbergstr. 36, 10623 Berlin (Germany)

    2004-07-01

    The electronic properties of quantum dot (QD) arrays are strongly influenced by the Coulomb interaction of electrons within the dot as well as with those in neighbouring dots. In this paper, we investigate this behaviour taking into account screening by a free electron gas in the vicinity of the QDs. We find pronounced effects for standard capacitance[ndash]voltage (CV) measurements of QD structures embedded in a pn-diode. In particular, we show that the three-dimensional nature of the problem is crucial for devices with low dot-density, whereas the self-consistency between electron depletion in the bulk layer and dot occupation is important for high dot-densities. The Coulomb interaction between the dots induces a broadening of the peaks in the CV characteristic which is comparable with the effect of disordered QD arrays, where we considered realistic size and position fluctuations obtained by a kinetic Monte Carlo simulation.

  20. Heterogeneous computing with OpenCL

    CERN Document Server

    2013-01-01

    Heterogeneous Computing with OpenCL teaches OpenCL and parallel programming for complex systems that may include a variety of device architectures: multi-core CPUs, GPUs, and fully-integrated Accelerated Processing Units (APUs) such as AMD Fusion technology. Designed to work on multiple platforms and with wide industry support, OpenCL will help you more effectively program for a heterogeneous future. Written by leaders in the parallel computing and OpenCL communities, this book will give you hands-on OpenCL experience to address a range of fundamental parallel algorithms. The authors explore memory spaces, optimization techniques, graphics interoperability, extensions, and debugging and profiling. Intended to support a parallel programming course, Heterogeneous Computing with OpenCL includes detailed examples throughout, plus additional online exercises and other supporting materials.

  1. On the ClC halogen bond: a rotational study of CF3Cl-CO.

    Science.gov (United States)

    Caminati, Walther; Evangelisti, Luca; Feng, Gang; Giuliano, Barbara M; Gou, Qian; Melandri, Sonia; Grabow, Jens-Uwe

    2016-07-21

    The rotational spectra of two isotopologues (CF3(35)Cl-CO and CF3(37)Cl-CO) of the CF3Cl-CO adduct have been investigated and analyzed using supersonic-jet Fourier transform microwave spectroscopy, and found to have the features of a symmetric top. Rotational, centrifugal distortion, and nuclear quadrupole ((35)Cl and (37)Cl) coupling constants have been precisely obtained from high-resolution measurements. The two subunits of the complex are held together via a ClC halogen bond interaction. Information on the internal dynamics and the dissociation energy of the complex is provided. PMID:27049637

  2. Tuberculose associada à AIDS: características demográficas, clínicas e laboratoriais de pacientes atendidos em um serviço de referência do sul do Brasil Tuberculosis associated to AIDS: demographic, clinical and laboratory characteristics of patients cared for at a reference center in the south of Brazil

    Directory of Open Access Journals (Sweden)

    Maria Marta Santos Boffo

    2004-04-01

    Full Text Available INTRODUÇÃO: A sinergia entre a tuberculose e o vírus da imunodeficiência humana é responsável pelo aumento da morbi-mortalidade dos pacientes com AIDS. OBJETIVO: Delinear o perfil de pacientes com tuberculose e AIDS na cidade de Rio Grande (RS relacionando dados demográficos, clínicos e laboratoriais. MÉTODO: A amostra foi constituída por todos os casos de tuberculose confirmados pelo isolamento de Mycobacterium tuberculosis ocorridos no Serviço de AIDS do Hospital Universitário/FURG entre setembro de 1997 e dezembro de 2000, em 31 pacientes reportados como casos definidos de AIDS. Foram examinados 33 materiais clínicos pulmonares e extrapulmonares através da cultura pelo método de Ogawa-Kudoh e da baciloscopia pelo Kinyoun. A identificação de M. tuberculosis foi feita pelos métodos fenotípicos usuais. Para determinação da resistência das cepas isoladas foi empregado o método das proporções. RESULTADOS: A média de idade foi de 33,8 ± 9,9 anos, com uma relação homem/mulher de 2,87:1. Eram brancos 80,7% dos pacientes. Todos os pacientes apresentavam manifestações clínicas gerais e/ou específicas de tuberculose no momento da suspeita diagnóstica. Em 20 deles foram constatados fatores de risco: uso de droga endovenosa, alcoolismo, desnutrição, encarceramento. A doença pulmonar ocorreu em 19 casos, a extrapulmonar em 10 e a associada em 2 deles. Entre aqueles com a forma extrapulmonar, predominou o comprometimento ganglionar. As 33 cepas isoladas foram identificadas como M. tuberculosis, e 28 mostraram sensibilidade à isoniazida e à rifampicina. CONCLUSÃO: A tuberculose nos pacientes com AIDS apresentou-se com manifestações clínicas variáveis, comprometendo homens e mulheres em condições sociais desfavoráveis, em plena fase produtiva de suas vidas.BACKGROUND: Synergism between tuberculosis and HIV is responsible for the increased morbidity-mortality rate in AIDS patients. OBJECTIVE: To delineate the

  3. Effects of NaCl and NH4Cl on the initial atmospheric corrosion of zinc

    International Nuclear Information System (INIS)

    Effects of NaCl and NH4Cl on the initial atmospheric corrosion of zinc were investigated via quartz crystal microbalance (QCM) in laboratory at 80% RH and 25 deg C. The results show that both NaCl and NH4Cl can accelerate the initial atmospheric corrosion of zinc. The combined effect of NaCl and NH4Cl on the corrosion of zinc is greater than that caused by NH4Cl and less than that caused by NaCl. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy and electron dispersion X-ray analysis (SEM/EDAX) were used to characterize the corrosion products of zinc. (NH4)2ZnCl4, Zn5(OH)8Cl2 . H2O and ZnO present on zinc surface in the presence of NH4Cl while Zn5(OH)8Cl2 . H2O and ZnO are the dominant corrosion products on NaCl-treated zinc surface. Probable mechanisms are presented to explain the experimental results

  4. Dot-ELISA for the detection of anti-Cysticercus cellulosae antibodies in cerebrospinal fluid using a new solid phase (resin-treated polyester fabric and Cysticercus longicollis antigens Teste dot-ELISA para detecção de anticorpos anti-Cysticercus cellulosae em líquido cefalorraquiano utilizando um novo suporte (tecido de poliéster-resina e antígenos de Cysticercus longicollis

    Directory of Open Access Journals (Sweden)

    Adelaide José Vaz

    1996-12-01

    Full Text Available A dot-ELISA was developed for the detection of antibodies in CSF in the immunologic diagnosis of human neurocysticercosis, using antigen extracts of the membrane and scolex of Cysticercus cellulosae (M+S-Cc and, alternately, membrane (M and vesicular fluid (VF of Cysticercus longicollis (Cl covalently bound to a new solid phase consisting of polyester fabric treated with N-methylol-acrylamide resin (dot-RT. The test was performed at room temperature, with reduced incubation times and with no need for special care in the manipulation of the support. The sensitivity rates obtained were 95.1% for antigen Cc and 97.6% for antigen Cl. Specificity was 90.6% when Cc was used, and 96.9% and 100% when M-Cl and VF-Cl were used, respectively. No significant differences in titer were observed between tests carried out with homologous and heterologous antigens. The low cost and easy execution of the dot-RT test using antigen extracts of Cysticercus longicollis indicate the test for use in the immunodiagnosis of human neurocysticercosis.Foi desenvolvido o teste dot-ELISA para detecção de anticorpos em líquido cefalorraquiano (LCR no diagnóstico imunológico da neurocisticercose humana, utilizando antígenos de membrana e escólex de Cysticercus cellulosae (M+E-Cc e, alternativamente, membrana (M e líquido vesicular (LV de Cysticercus longicollis (Cl covalentemente ligados a um novo suporte constituído de tecido de poliéster-resina de N-metilol-acrilamida (dot-TR. O teste foi realizado à temperatura ambiente, com tempos de incubação reduzidos e sem necessidade de cuidados na manipulação do suporte. A sensibilidade obtida foi de 95,1% para o antígeno Cc e 97,6% para o Cl. A especificidade foi de 90,6% quando o antígeno Cc foi usado, e 96,9% e 100% para M-Cl e LV-Cl, respectivamente. Não foi observada diferença significativa entre os antígenos homólogo e heterólogo. O baixo custo e a fácil execução do teste dot-TR empregando extratos antig

  5. 77 FR 56525 - Special Conditions: Bombardier, Model CL-600-2B16 Airplane (CL-601-3A, CL-601-3R, and CL-604...

    Science.gov (United States)

    2012-09-13

    .../ , including any personal information the commenter provides. Using the search function of the docket web site... April 11, 2000 (65 FR 19477-19478), as well as at http://DocketsInfo.dot.gov/ . Docket: Background... with a crew of two. It is powered by two General Electric engines and has a maximum takeoff weight...

  6. 75 FR 28471 - Airworthiness Directives; Bombardier, Inc. Model CL-600-1A11 (CL-600), CL-600-2A12 (CL-601), and...

    Science.gov (United States)

    2010-05-21

    ... in the Federal Register on February 25, 2010 (75 FR 8559), and proposed to supersede AD 2007-14-02, Amendment 39- 15124 (72 FR 38004, July 12, 2007). That NPRM proposed to correct an unsafe condition for the... not a ``significant rule'' under the DOT Regulatory Policies and Procedures (44 FR 11034, February...

  7. 76 FR 66620 - Airworthiness Directives; Bombardier, Inc. Model CL-215-1A10, CL-215-6B11 (CL-215T Variant), and...

    Science.gov (United States)

    2011-10-27

    ... Procedures (44 FR 11034, February 26, 1979); and 3. Will not have a significant economic impact, positive or.... Model CL-215-1A10, CL- 215-6B11 (CL-215T Variant), and CL-215-6B11 (CL-415 Variant) Airplanes AGENCY... comments. SUMMARY: We are adopting a new airworthiness directive (AD) for certain Bombardier, Inc. Model...

  8. The protein amide {sup 1}H{sup N} chemical shift temperature coefficient reflects thermal expansion of the N-H{center_dot}{center_dot}{center_dot}O=C hydrogen bond

    Energy Technology Data Exchange (ETDEWEB)

    Hong Jingbo; Jing Qingqing; Yao Lishan, E-mail: yaols@qibebt.ac.cn [Chinese Academy of Sciences, Laboratory of Biofuels, Qingdao Institute of Bioenergy and Bioprocess Technology (China)

    2013-01-15

    The protein amide {sup 1}H{sup N} chemical shift temperature coefficient can be determined with high accuracy by recording spectra at different temperatures, but the physical mechanism responsible for this temperature dependence is not well understood. In this work, we find that this coefficient strongly correlates with the temperature coefficient of the through-hydrogen-bond coupling, {sup 3h}J{sub NC Prime }, based on NMR measurements of protein GB3. Parallel tempering molecular dynamics simulation suggests that the hydrogen bond distance variation at different temperatures/replicas is largely responsible for the {sup 1}H{sup N} chemical shift temperature dependence, from which an empirical equation is proposed to predict the hydrogen bond thermal expansion coefficient, revealing responses of individual hydrogen bonds to temperature changes. Different expansion patterns have been observed for various networks formed by {beta} strands.

  9. Equilibrium partial pressures, thermodynamic properties of aqueous and solid phases, and Cl{sub 2} production from aqueous HCl and HNO{sub 3} and their mixtures

    Energy Technology Data Exchange (ETDEWEB)

    Massucci, M.; Clegg, S.L.; Brimblecombe, P. [Univ. of East Anglia, Norwich (United Kingdom). School of Environmental Sciences

    1999-05-27

    Equilibrium total pressures have been measured above aqueous HNO{sub 3} and aqueous HCl using a capacitance manometer. Equilibrium partial pressures of the acids have also been determined, by mass spectrometry, from 274.8 to 234.6 K for both HCl solutions, and from 265.0 to 240.1 K for 15.73 mol kg{sup {minus}1} HNO{sub 3}. Results are generally consistent with model predictions, though with small systematic deviations for the total pressure measurements over aqueous HCl at about 220 K. Mixtures of HCl{minus}HNO{sub 3}{minus}H{sub 2}O composition yielded measured total pressures orders of magnitude greater than predicted for the gases H{sub 2}O, HNO{sub 3}, and HCl. Mass spectrometric determinations and equilibrium thermodynamic calculations suggest that Cl{sub 2} and NOCl were produced by the reaction: 4H{sup +}{sub aq} + NO{sub 3}{sup {minus}}{sub aq} + 3Cl{sup {minus}}{sub aq} {r_equilibrium} NOCl{sub aq} + Cl{sub 2(aq)} + 2H{sub 2}O{sub (1)}, which is known to occur in aqua regia. Calculations for aqueous solutions of stratospheric aerosol composition suggest, purely on equilibrium grounds, that the reaction could be a source of active chlorine in the stratosphere. The correlation of Clegg and Brimblecombe of the thermodynamic properties of aqueous HNO{sub 3} activities has been revised, and vapor pressure products assessed from literature studies. The activity product for the reaction HNO{sub 3}{center_dot}2H{sub 2}O{sub (cr)} {r_equilibrium} H{sup +}{sub (aq)} + NO{sub 3}{sup {minus}}{sub (aq)} + 2H{sub 2}O{sub (1)} has also been determined. The model of Carslaw et al. has been revised for the solubility of HBr in aqueous H{sub 2}SO{sub 4} to stratospheric temperatures.

  10. Quantum dot-sized organic fluorescent dots for long-term cell tracing

    Science.gov (United States)

    Li, Kai; Tang, Ben Zhong; Liu, Bin

    2014-03-01

    Fluorescence techniques have been extensively employed to develop non-invasive methodologies for tracking and understanding complex biological processes both in vitro and in vivo, which is of high importance in modern life science research. Among a variety of fluorescent probes, inorganic semiconductor quantum dots (QDs) have shown advantages in terms of better photostability, larger Stokes shift and more feasible surface functionalization. However, their intrinsic toxic heavy metal components and unstable fluorescence at low pH greatly impede the applications of QDs in in vivo studies. In this work, we developed novel fluorescent probes that can outperform currently available QD based probes in practice. Using conjugated oligomer with aggregation-induced emission characteristics as the fluorescent domain and biocompatible lipid-PEG derivatives as the encapsulation matrix, the obtained organic dots have shown higher brightness, better stability in biological medium and comparable size and photostability as compared to their counterparts of inorganic QDs. More importantly, unlike QD-based probes, the organic fluorescent dots do not blink, and also do not contain heavy metal ions that could be potentially toxic when applied for living biosubstrates. Upon surface functionalization with a cell-penetrating peptide, the organic dots greatly outperform inorganic quantum dots in both in vitro and in vivo long-term cell tracing studies, which will be beneficial to answer crucial questions in stem cell/immune cell therapies. Considering the customized fluorescent properties and surface functionalities of the organic dots, a series of biocompatible organic dots will be developed to serve as a promising platform for multifarious bioimaging tasks in future.

  11. Spectroscopic Interpretation: The High Vibrations of CDBrClF

    CERN Document Server

    Jung, C; Taylor, H S

    2004-01-01

    We extract the dynamics implicit in an algebraic fitted model Hamiltonian for the deuterium chromophore's vibrational motion in the molecule CDBrClF. The original model has 4 degrees of freedom, three positions and one representing interbond couplings. A conserved polyad allows in a semiclassical approach the reduction to 3 degrees of freedom. For most quantum states we can identify the underlying motion that when quantized gives the said state. Most of the classifications, identifications and assignments are done by visual inspection of the already available wave function semiclassically transformed from the number representation to a representation on the reduced dimension toroidal configuration space corresponding to the classical action and angle variables. The concentration of the wave function density to lower dimensional subsets centered on idealized simple lower dimensional organizing structures and the behavior of the phase along such organizing centers already reveals the atomic motion. Extremely li...

  12. Structure model and synthesis of NdCl3-FeCl3-graphite intercalation compounds

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The distribution of the elements and microstructure of NdCl3-FeCl3-graphite intercalation compounds (GICs) were shown by scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). The results show that Nd element intercalates into graphite, forming NdCl3-FeCl3-GICs, and the distribution of Nd and Fe is nearly even. On the basis of the data, a structure model for RECl3-GICs was founded, and the characteristic layer distance and the index of interval energy were calculated. The calculated results agree with experimental ones, and the relative errors are ±2%. Thus it can be seen that the (111) face is optimal direction for intercalation reaction of TbCl3 LuCl3, and the (001) face is that for LaCl3 GdCl3, because of the lowest interval energy.

  13. Metal halide hydrates as lewis acid catalysts for the conjugated friedel-crafts reactions of indoles and activated olefins

    Energy Technology Data Exchange (ETDEWEB)

    Schwalm, Cristiane S.; Ceschi, Marco Antonio; Russowsky, Dennis, E-mail: dennis@iq.ufrgs.b [Universidade Federal do Rio Grande do Sul (IQ/UFRGS), Porto Alegre, RS (Brazil). Inst. de Quimica

    2011-07-01

    Metal halide hydrates such as SnCl{sub 2{center_dot}}2H{sub 2}O, MnCl{sub 2{center_dot}}4H{sub 2}O, SrCl{sub 2{center_dot}}6H{sub 2}O, CrCl{sub 2{center_dot}}6H{sub 2}O, CoCl{sub 2{center_dot}}6H{sub 2}O e CeCl{sub 3{center_dot}}7H{sub 2}O were investigated as mild Lewis acids catalysts for the conjugate Friedel-Crafts reaction between indoles and activated olefins. The reactions were carried out with aliphatic unsaturated ketones over a period of days at room temperature, while chalcones reacted only under reflux conditions. The reactions with nitrostyrene s were either performed in solvent or under solventless conditions. In all cases reasonable to good yields were obtained. (author)

  14. CL møder sptogfagsdidaktikken

    DEFF Research Database (Denmark)

    Pedersen, Michael Svendsen

    2011-01-01

    I artiklen diskuteres den didaktiske kontekst for brugen af CL (Cooperative Learning) i sprogundervisningen. Indledningsvis stilles følgende spørgsmål: Hvor kommer de indholdsfrie CL-strukturer fra, og hvad sker der når man inddrager dem i sprogundervisningen? I besvarelsen af disse spørgsmål...

  15. Some Properties of CL-space and Almost CL-space%关于CL-空间和几乎CL-空间的一些性质

    Institute of Scientific and Technical Information of China (English)

    卢允照

    2006-01-01

    讨论具有"平坦性"凸性单位球结构的Banach空间的一些性质.首先根据CL-空间的定义证明了Banach空间l1是CL-空间.通过证明l31和l3∞具有非CL-子空间证明了维数大于2的CL空间不具继承性,即具有非CL-子空间,另外,总结了有限维CL-空间与其它一些Banach空间类的等价性.最后讨论了CL-空间和几乎CL-空间包含Banach空间c0与l1的一些性质以及实对偶空间成为几乎CL-空间的两个必要条件.

  16. Al/Cl2 molten salt battery

    Science.gov (United States)

    Giner, J.

    1972-01-01

    Molten salt battery has been developed with theoretical energy density of 5.2 j/kg (650 W-h/lb). Battery, which operates at 150 C, can be used in primary mode or as rechargeable battery. Battery has aluminum anode and chlorine cathode. Electrolyte is mixture of AlCl3, NaCl, and some alkali metal halide such as KCl.

  17. Atmospheric production rate of {sup 36}Cl

    Energy Technology Data Exchange (ETDEWEB)

    Parrat, Y.; Hajdas, W.; Baltensperger, U.; Synal, H.A.; Kubik, P.W.; Gaeggeler, H.W. [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Suter, M. [Eidgenoessische Technische Hochschule, Zurich (Switzerland)

    1997-09-01

    Using experimental cross sections, a new calculation of the atmospheric production rate of {sup 36}Cl was carried out. A mean production rate of 20 atoms m{sup -2}s{sup -1} was obtained, which is lower than mean {sup 36}Cl deposition rates. (author) 2 figs., 7 refs.

  18. Point defects and luminescence in single NaCl: Cu crystals

    International Nuclear Information System (INIS)

    Optical absorption, thermally stimulated luminescence and photoluminescence experiments were performed in NaCl:Cu(0.4%) and NaCl:Cu(0.8%) crystals blocks grown by Czochralski technique. The monocrystals NaCl:Cu were exposed to gamma rays from 60 Co source up to 30 kGy as well as to UV radiation. The radiation-induced defects were mainly in the F-centers form and their optical absorption bands were found to be dependent from the Cu impurity concentration. It was observed that the gamma induced absorption band at 256.7 nm was shifted toward 236.3 nm when the crystals were irradiated with UV light. At high radiation dose (20 kGy) the F-centers were bleached with F-light. The change in the glow curve after bleaching suggests that the recombination occurs around the impurity of the doped crystal. (Author)

  19. Point defects and luminescence in single NaCl: Cu crystals

    Energy Technology Data Exchange (ETDEWEB)

    Cruz Z, E.; Ramos B, S.; Negron M, A. [ICN-UNAM, A.P. 70-543, 04510 Mexico D.F. (Mexico); Chernov, V.; Melendrez, R.; Barboza F, M. [CIF, UNISON, A.P. 5-088, 83190 Hermosillo, Sonora (Mexico); Murrieta S, H.; Hernandez A, J. [IFUNAM, A.P. 20-364, 01000 Mexico D.F. (Mexico)

    2004-07-01

    Optical absorption, thermally stimulated luminescence and photoluminescence experiments were performed in NaCl:Cu(0.4%) and NaCl:Cu(0.8%) crystals blocks grown by Czochralski technique. The monocrystals NaCl:Cu were exposed to gamma rays from {sup 60} Co source up to 30 kGy as well as to UV radiation. The radiation-induced defects were mainly in the F-centers form and their optical absorption bands were found to be dependent from the Cu impurity concentration. It was observed that the gamma induced absorption band at 256.7 nm was shifted toward 236.3 nm when the crystals were irradiated with UV light. At high radiation dose (20 kGy) the F-centers were bleached with F-light. The change in the glow curve after bleaching suggests that the recombination occurs around the impurity of the doped crystal. (Author)

  20. STUDIES ON THE KINETICS OF PROPYLENE POLYMERIZATION WITH THE COMPLEX TYPE TiCl3 CATALYST

    Institute of Scientific and Technical Information of China (English)

    TANG Shipei; TAN Zhongjun; WANG Shemin; ZHANG Airong

    1984-01-01

    The active center concentration Cp, the rate constant kp, and the activation energy of chain propagation Ep in the polymerization of propylene with complex-type TiCl3-(C2H5)2AlCl catalyst system were studied. The Mn was corrected by (M)w/(M)n value determined by GPC. The values thus obtained for Cp, kp, and Ep at 50C were 3.01 mol/mol Ti, 6.27 1/mol . sec, and 5.10 Kcal/mol respectively.The kinetic parameters were compared with those obtained from conventional TiCl3. AlCl3 catalyst, showing that the higher activity of the complex-type catalyst over the conventional catalyst is not only due to the higher Cp of the former, but to a greater extent due to the increase of the kp value.

  1. Bright infrared quantum-dot light-emitting diodes through inter-dot spacing control

    KAUST Repository

    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.

  2. Interference effects in a double quantum dot system with inter-dot Coulomb correlations

    International Nuclear Information System (INIS)

    Electron transport through a double quantum dot system is studied with the use of the Green function formalism based on the equation of motion method, and an interplay between interference and Coulomb blockade effects due to inter-dot correlations is discussed. A double structure with two Fano resonances (or antiresonances) is found in the conductance spectrum. Fano features are weakly influenced by the presence of Coulomb interaction but the conductance is strongly suppressed in the energy region with the Fermi level in the leads close to the aligned levels of both dots. This Coulomb blockade effect takes place when the coupling between the dots is of repulsive character. On the other hand, the conductance of an artificial molecule with attractive inter-dot coupling is only slightly modified in this energy region. As a sign of the coupling can be easily changed in a presence of an external magnetic field by changes of the magnetic flux there is the possibility to control variations of the conductance, which may be important from the application point of view

  3. Cs3ScCl6

    Directory of Open Access Journals (Sweden)

    Matthew D. Ward

    2014-06-01

    Full Text Available Crystals of tricaesium scandium(III hexachloride were obtained as a side product from the reaction of U, SnCl2, Sc, and S in a CsCl flux at 1073 K. Cs3ScCl6 crystallizes in the Rb3YCl6 structure type. The asymmetric unit comprises three Cs sites, two Sc sites, and six Cl sites, all of which have site symmetry 1, except for the two Sc sites that have site symmetries of 2 and -1, respectively. The structure is composed of isolated [ScCl6]3− octahedra that are surrounded by Cs+ cations. Two Cs+ cations have interactions with eight Cl− anions, while the third has interactions with ten Cl− anions.

  4. Entangling distant quantum dots using classical interference

    Science.gov (United States)

    Busch, Jonathan; Kyoseva, Elica S.; Trupke, Michael; Beige, Almut

    2008-10-01

    We show that it is possible to employ reservoir engineering to turn two distant and relatively bad cavities into one good cavity with a tunable spontaneous decay rate. As a result, quantum computing schemes, which would otherwise require the shuttling of atomic qubits in and out of an optical resonator, can now be applied to distant quantum dots. To illustrate this we transform a recent proposal to entangle two qubits via the observation of macroscopic fluorescence signals [J. Metz , Phys. Rev. Lett. 97, 040503 (2006)] to the electron-spin states of two semiconductor quantum dots. Our scheme requires neither the coherent control of qubit-qubit interactions nor the detection of single photons. Moreover, the scheme is relatively robust against spin-bath couplings, parameter fluctuations, and the spontaneous emission of photons.

  5. Mesoscopic Cavity Quantum Electrodynamics with Quantum Dots

    CERN Document Server

    Childress, L I; Lukin, M D

    2003-01-01

    We describe an electrodynamic mechanism for coherent, quantum mechanical coupling between spacially separated quantum dots on a microchip. The technique is based on capacitive interactions between the electron charge and a superconducting transmission line resonator, and is closely related to atomic cavity quantum electrodynamics. We investigate several potential applications of this technique which have varying degrees of complexity. In particular, we demonstrate that this mechanism allows design and investigation of an on-chip double-dot microscopic maser. Moreover, the interaction may be extended to couple spatially separated electron spin states while only virtually populating fast-decaying superpositions of charge states. This represents an effective, controllable long-range interaction, which may facilitate implementation of quantum information processing with electron spin qubits and potentially allow coupling to other quantum systems such as atomic or superconducting qubits.

  6. Many electron effects in semiconductor quantum dots

    Indian Academy of Sciences (India)

    R K Pandey; Manoj K Harbola; V Ranjan; Vijay A Singh

    2003-01-01

    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 local density approximation (LDA) and the Harbola–Sahni (HS) scheme. HS is free of the selfinteraction error of the LDA. Our calculations have been performed in a three-dimensional quantum dot. We have carried out a study of the size and shape dependence of the level spacing. Scaling laws for the Hubbard ‘’ are established.

  7. Protease-activated quantum dot probes

    Science.gov (United States)

    Chang, Emmanuel; Sun, Jiantang; Miller, Jordan S.; Yu, William W.; Colvin, Vicki L.; West, Jennifer L.; Drezek, Rebekah

    2006-04-01

    We demonstrate a novel quantum dot based probe with inherent signal amplification upon interaction with a targeted proteolytic enzyme. This probe may be useful for imaging in cancer detection and diagnosis. In this system, quantum dots (QDs) are bound to gold nanoparticles (AuNPs) via a proteolytically-degradable peptide sequence to non-radiatively suppress luminescence. A 71% reduction in luminescence was achieved with conjugation of AuNPs to QDs. Peptide cleavage results in release of AuNPs and restores radiative QD photoluminescence. Initial studies observed a 52% rise in luminescence over 47 hours of exposure to 0.2 mg/mL collagenase. These probes can be customized for targeted degradation simply by changing the sequence of the peptide linker.

  8. Facile labeling of lipoglycans with quantum dots

    International Nuclear Information System (INIS)

    Bacterial endotoxins or lipopolysaccharides (LPS) are among the most potent activators of the innate immune system, yet mechanisms of their action and in particular the role of glycans remain elusive. Efficient non-invasive labeling strategies are necessary for studying interactions of LPS glycans with biological systems. Here we report a new method for labeling LPS and other lipoglycans with luminescent quantum dots. The labeling is achieved by partitioning of hydrophobic quantum dots into the core of various LPS aggregates without disturbing the native LPS structure. The biofunctionality of the LPS-Qdot conjugates is demonstrated by the labeling of mouse monocytes. This simple method should find broad applicability in studies concerned with visualization of LPS biodistribution and identification of LPS binding agents.

  9. Efficient Luminescence from Perovskite Quantum Dot Solids

    KAUST Repository

    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.

  10. Light emission from Si quantum dots

    Directory of Open Access Journals (Sweden)

    Philippe M. Fauchet

    2005-01-01

    Full Text Available Si quantum dots (QDs as small as ∼2 nm in diameter have been synthesized by a variety of techniques. Because of quantum confinement and the elimination of bulk or surface defects, these dots can emit light from the near infrared throughout the visible with quantum efficiencies in excess of 10%. The luminescence wavelength range has been extended to longer wavelengths by the addition of light-emitting rare earths such as erbium (Er. Light-emitting devices (LEDs have been fabricated and their performances are starting to approach those of direct band gap semiconductor or organic LEDs. A search for a Si QD-based laser is even under way. The state-of-the-art in the materials science, physics, and device development of luminescent Si QDs is reviewed and areas of future research are pointed out.

  11. Ratiometric Temperature Sensing with Semiconducting Polymer Dots

    OpenAIRE

    Ye, Fangmao; Wu, Changfeng; Jin, Yuhui; Chan, Yang-Hsiang; Zhang, Xuanjun; Chiu, Daniel T.

    2011-01-01

    This communication describes ultra-bright single-nanoparticle ratiometric temperature sensors based on semiconducting polymer dots (Pdots). We attached the temperature sensitive dye—Rhodamine B (RhB), whose emission intensity decreases with increasing temperature—within the matrix of Pdots. The as-prepared Pdot-RhB nanoparticle showed excellent temperature sensitivity and high brightness because it took advantage of the light harvesting and amplified energy transfer capability of Pdots. More ...

  12. The Silicon:Colloidal Quantum Dot Heterojunction

    KAUST Repository

    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.

  13. Adiabatic description of nonspherical quantum dot models

    Energy Technology Data Exchange (ETDEWEB)

    Gusev, A. A., E-mail: gooseff@jinr.ru; Chuluunbaatar, O.; Vinitsky, S. I. [Joint Institute for Nuclear Research (Russian Federation); Dvoyan, K. G.; Kazaryan, E. M.; Sarkisyan, H. A. [Russian-Armenian (Slavonic) University (Armenia); Derbov, V. L.; Klombotskaya, A. S.; Serov, V. V. [Saratov State University (Russian Federation)

    2012-10-15

    Within the effective mass approximation an adiabatic description of spheroidal and dumbbell quantum dot models in the regime of strong dimensional quantization is presented using the expansion of the wave function in appropriate sets of single-parameter basis functions. The comparison is given and the peculiarities are considered for spectral and optical characteristics of the models with axially symmetric confining potentials depending on their geometric size, making use of the complete sets of exact and adiabatic quantum numbers in appropriate analytic approximations.

  14. Shot noise of coupled semiconductor quantum dots

    OpenAIRE

    Kiesslich, G.; Wacker, A; Schoell, E.

    2003-01-01

    The low-frequency shot noise properties of two electrostatically coupled semiconductor quantum dot states which are connected to emitter/collector contacts are studied. A master equation approach is used to analyze the bias voltage dependence of the Fano factor as a measure of temporal correlations in tunneling current caused by Pauli's exclusion principle and the Coulomb interaction. In particular, the influence of the Coulomb interaction on the shot noise behavior is discussed in detail and...

  15. Semiconductor Quantum Dots for Biomedicial Applications

    OpenAIRE

    Lijia Shao; Feng Yan; Yanfang Gao

    2011-01-01

    Semiconductor quantum dots (QDs) are nanometre-scale crystals, which have unique photophysical properties, such as size-dependent optical properties, high fluorescence quantum yields, and excellent stability against photobleaching. These properties enable QDs as the promising optical labels for the biological applications, such as multiplexed analysis of immunocomplexes or DNA hybridization processes, cell sorting and tracing, in vivo imaging and diagnostics in biomedicine. Meanwhile, QDs can...

  16. Quantum dots: synthesis, bioapplications, and toxicity

    OpenAIRE

    Valizadeh, Alireza; Mikaeili, Haleh; Samiei, Mohammad; Farkhani, Samad Mussa; Zarghami, Nosratalah; Kouhi, Mohammad; Akbarzadeh, Abolfazl; Davaran, Soodabeh

    2012-01-01

    This review introduces quantum dots (QDs) and explores their properties, synthesis, applications, delivery systems in biology, and their toxicity. QDs are one of the first nanotechnologies to be integrated with the biological sciences and are widely anticipated to eventually find application in a number of commercial consumer and clinical products. They exhibit unique luminescence characteristics and electronic properties such as wide and continuous absorption spectra, narrow emission spectra...

  17. The pinning effect in quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Monisha, P. J., E-mail: pjmonisha@gmail.com [School of Physics, University of Hyderabad, Hyderabad-500046 (India); Mukhopadhyay, Soma [Department of Physics, D V R College of Engineering and Technology, Hyderabad-502285 (India)

    2014-04-24

    The pinning effect is studied in a Gaussian quantum dot using the improved Wigner-Brillouin perturbation theory (IWBPT) in the presence of electron-phonon interaction. The electron ground state plus one phonon state is degenerate with the electron in the first excited state. The electron-phonon interaction lifts the degeneracy and the first excited states get pinned to the ground state plus one phonon state as we increase the confinement frequency.

  18. Depleted Bulk Heterojunction Colloidal Quantum Dot Photovoltaics

    KAUST Repository

    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.

  19. Electronic spectrum of non-tetrahedral acceptors in CdTe:Cl and CdTe:Bi,Cl single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Krivobok, V. S., E-mail: krivobok@lebedev.ru [P.N. Lebedev Physical Institute, Russian Academy of Sciences, Moscow (Russian Federation); Moscow Institute of Physics and Technology (State University), Dolgoprudny, Moscow Region (Russian Federation); Nikolaev, S. N.; Bagaev, V. S.; Pruchkina, A. A.; Onishchenko, E. E.; Kolosov, S. A.; Klevkov, Yu. V.; Skorikov, M. L. [P.N. Lebedev Physical Institute, Russian Academy of Sciences, Moscow (Russian Federation)

    2016-02-07

    The electronic spectra of complex acceptors in compensated CdTe:Cl, CdTe:Ag,Cl, and CdTe:Bi,Cl single crystals are studied using low-temperature photoluminescence (PL) measurements under both nonresonant and resonant excitation of distant donor–acceptor pairs (DAP). The wavelength modulation of the excitation source combined with the analysis of the differential PL signal is used to enhance narrow spectral features obscured because of inhomogeneous line broadening and/or excitation transfer for selectively excited DAPs. For the well-known tetrahedral (T{sub D}) Ag{sub Cd} acceptor, the energies of four excited states are measured, and the values obtained are shown to be in perfect agreement with the previous data. Moreover, splitting between the 2P{sub 3/2} (Γ{sub 8}) and 2S{sub 3/2} (Γ{sub 8}) states is clearly observed for Ag{sub Cd} centers located at a short distance (5–7 nm) from a hydrogen-like donor (Cl{sub Te}). This splitting results from the reduction of the T{sub D} symmetry taking place when the acceptor is a member of a donor–acceptor pair. For the Cl-related complex acceptor with an activation energy of ∼121 meV (A-center), the energies of eight excited states are measured. It is shown that this defect produces low-symmetry central-cell correction responsible for the strong splitting of S-like T{sub D} shells. The energy spectrum of the Bi-related shallow acceptor with an activation energy of ∼36 meV is measured as well. The spectrum obtained differs drastically from the hydrogen-like set of levels, which indicates the existence of repulsive low-symmetry perturbation of the hydrogen-like Coulomb potential. It is also shown that the spectra of selectively excited PL recorded for a macroscopic ensemble of distant donor–acceptor pairs allow one to detect the low symmetry of acceptors of a given type caused by their complex nature or by the Jahn–Teller distortion. This method does not require any additional (external) field and is

  20. Electronic spectrum of non-tetrahedral acceptors in CdTe:Cl and CdTe:Bi,Cl single crystals

    International Nuclear Information System (INIS)

    The electronic spectra of complex acceptors in compensated CdTe:Cl, CdTe:Ag,Cl, and CdTe:Bi,Cl single crystals are studied using low-temperature photoluminescence (PL) measurements under both nonresonant and resonant excitation of distant donor–acceptor pairs (DAP). The wavelength modulation of the excitation source combined with the analysis of the differential PL signal is used to enhance narrow spectral features obscured because of inhomogeneous line broadening and/or excitation transfer for selectively excited DAPs. For the well-known tetrahedral (TD) AgCd acceptor, the energies of four excited states are measured, and the values obtained are shown to be in perfect agreement with the previous data. Moreover, splitting between the 2P3/2 (Γ8) and 2S3/2 (Γ8) states is clearly observed for AgCd centers located at a short distance (5–7 nm) from a hydrogen-like donor (ClTe). This splitting results from the reduction of the TD symmetry taking place when the acceptor is a member of a donor–acceptor pair. For the Cl-related complex acceptor with an activation energy of ∼121 meV (A-center), the energies of eight excited states are measured. It is shown that this defect produces low-symmetry central-cell correction responsible for the strong splitting of S-like TD shells. The energy spectrum of the Bi-related shallow acceptor with an activation energy of ∼36 meV is measured as well. The spectrum obtained differs drastically from the hydrogen-like set of levels, which indicates the existence of repulsive low-symmetry perturbation of the hydrogen-like Coulomb potential. It is also shown that the spectra of selectively excited PL recorded for a macroscopic ensemble of distant donor–acceptor pairs allow one to detect the low symmetry of acceptors of a given type caused by their complex nature or by the Jahn–Teller distortion. This method does not require any additional (external) field and is applicable to acceptors in diverse zinc-blende compound

  1. The quantum dot nanoconjugate tool box (Invited Paper)

    Science.gov (United States)

    Tomlinson, I. D.; Wright, D. W.; Giorgio, T. D.; Blakely, R. D.; Pennycook, S. J.; Hercules, D.; Bentzen, L.; Smith, R. A.; McBride, J.; Vergne, M. J.; Rosenthal, S.

    2005-04-01

    The surface coating of quantum dots has been characterised using Z-stem. Quantum dots have been pegylated to increase stability in aqueous solution. The fluorescence intensity of the quantum dots was modulated pegylation. PEG was coupled using different ratios of EDC, PEG and NHS. Optimum coupling conditions were found to occur when 2000 equivalents of PEG were reacted with 1 equivalent of dot in the presence of 1500 equivalents of NHS and EDC. Angiotensin II was also conjugated to quantum dots and these conjugates were shown to be biologically active. Quantum dots have also been surface functionalised with other peptides such as NGR with subsequent demonstration of cell surface binding and can be characterized by flow cytometry.

  2. Templated self-assembly of SiGe quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    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

  3. Mode Competition in Dual-Mode Quantum Dots Semiconductor Microlaser

    CERN Document Server

    Chusseau, Laurent; Viktorovitch, P; Letartre, Xavier

    2013-01-01

    This paper describes the modeling of quantum dots lasers with the aim of assessing the conditions for stable cw dual-mode operation when the mode separation lies in the THz range. Several possible models suited for InAs quantum dots in InP barriers are analytically evaluated, in particular quantum dots electrically coupled through a direct exchange of excitation by the wetting layer or quantum dots optically coupled through the homogeneous broadening of their optical gain. A stable dual-mode regime is shown possible in all cases when quantum dots are used as active layer whereas a gain medium of quantum well or bulk type inevitably leads to bistable behavior. The choice of a quantum dots gain medium perfectly matched the production of dual-mode lasers devoted to THz generation by photomixing.

  4. Modified magnetic quantum dot with electric confining potentials

    International Nuclear Information System (INIS)

    The electronic properties of a modified magnetic quantum dot are studied. The modified magnetic quantum dot is a quantum structure that is formed by spatially inhomogeneous distributions of magnetic fields. Electrons are magnetically confined to the plane where the magnetic fields inside and outside the dot are different from each other. The energy spectrum exhibits quite different features depending on the directions of the magnetic fields inside and outside the dot. In particular, the case of opposite directions of the fields is more interesting than that of the same direction. An electrostatic potential is introduced to the system to study the effects of an electric confining potential on the eigenenergy of a single electron in the modified magnetic quantum dot. The additional potential raises the whole energy spectrum and changes its shape. The ground-state angular momentum transitions occurring in a bare modified magnetic quantum dot disappear on introduction of the additional parabolic potential

  5. Ac response of a coupled double quantum dot

    Institute of Scientific and Technical Information of China (English)

    Xu Jie; W.Z. Shangguan; Zhan Shi-Chang

    2005-01-01

    The effect of phase-breaking process on the ac response of a coupled double quantum dot is studied in this paper based on the nonequilibrium Green function formalism. A general expression is derived for the ac current in the presence of electron-phonon interaction. The ac conductance is numerically computed and the results are compared with those in [Anatram M P and Datts S 1995 Phys. Rev. B 51 7632]. Our results reveal that the inter-dot electron tunnelling interplays with that between dots and electron reservoirs, and contributes prominently to the ac current when inter-dot tunnelling coupling is much larger than the tunnelling coupling between dots and electron reservoirs. In addition, the phase-breaking process is found to have a significant effect on the ac transport through the coupled double dot.

  6. Single quantum dots fundamentals, applications, and new concepts

    CERN Document Server

    2003-01-01

    This book reviews recent advances in the exciting and rapid growing field of semiconductor quantum dots by contributions from some of the most prominent researchers in the field. Special focus is given to the optical and electronic properties of single quantum dots due to their potential applications in devices operating with single electrons and/or single photons. This includes quantum dots in electric and magnetic fields, cavity-quantum electrodynamics, nonclassical light generation, and coherent optical control of excitons. Single Quantum Dots also addresses various growth techniques as well as potential device applications such as quantum dot lasers, and new concepts like a single-photon source, and a single quantum dot laser.

  7. Quantum Dots and Their Multimodal Applications: A Review

    Directory of Open Access Journals (Sweden)

    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.

  8. Controlled coupling of quantum dots to nanowire plasmons

    International Nuclear Information System (INIS)

    Full text: The diameter of dielectric waveguides is limited by the wavelength of the guided light. In contrast, gold and silver nanowires can sustain propagating plasmon modes even for significantly smaller dimensions. Furthermore the strong eld localization of the nanowire plasmon modes leads to a strong interaction with nearby quantum emitters such as quantum dots. We use electron beam lithography, rst, to fabricate silver nanowires and, second, to position a few dots close to one nanowire end in a template-assisted process. Scanning a focused laser spot over the nanowire ends, we demonstrate both, the excitation of nanowire modes by quantum dots and the addressing of the same dots by plasmons. We use the fluorescence signals to quantify the quantum dots/plasmon coupling and show that part of the plasmon-induced dot fluorescence couples back to plasmonic modes. (author)

  9. Quantum dot spectroscopy using a single phosphorus donor

    Science.gov (United States)

    Büch, Holger; Fuechsle, Martin; Baker, William; House, Matthew G.; Simmons, Michelle Y.

    2015-12-01

    Using a deterministic single P donor placed with atomic precision accuracy next to a nanoscale silicon quantum dot, we present a way to analyze the energy spectrum of small quantum dots in silicon by tunnel-coupled transport measurements. The energy-level structure of the quantum dot is observed as resonance features within the transport bias triangles when the donor chemical potential is aligned with states within the quantum dot as confirmed by a numeric rate equation solver SIMON. This technique allows us to independently extract the quantum dot level structure irrespective of the density of states in the leads. Such a method is useful for the investigation of silicon quantum dots in the few-electron regime where the level structure is governed by an intricate interplay between the spin- and the valley-orbit degrees of freedom.

  10. Formation of self-assembled quantum dots of iron oxide thin films by spray pyrolysis from non-aqueous medium

    International Nuclear Information System (INIS)

    Quantum dots (QDs) of iron oxide have been deposited onto ITO coated glass substrates by spray pyrolysis technique, using ferric chloride (FeCl3.7H2O) in non-aqueous medium as a starting material. The non-aqueous solvents namely methanol, ethanol, propanol, butanol and pentanol were used as solvents. The effect of solvents on the film structure and morphology was studied. The structural, morphological, compositional and optical properties were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive analysis of X-rays (EDAX), and optical absorption measurement techniques

  11. Linfoma não-Hodgkin na infância: características clínico-epidemiológicas e avaliação de sobrevida em um único centro no Nordeste do Brasil Non-Hodgkin's lymphoma in childhood: clinical and epidemiological characteristics and survival analysis at a single center in Northeast Brazil

    Directory of Open Access Journals (Sweden)

    Márcia Ferreira Pedrosa

    2007-12-01

    Full Text Available OBJETIVO: Descrever o perfil clínico-epidemiológico dos pacientes portadores de linfoma não-Hodgkin diagnosticados no Serviço de Oncologia Pediátrica do Instituto Materno-Infantil Professor Fernando Figueira em um período de 9 anos, bem como descrever sobrevida e possíveis associações prognósticas com as variáveis clínico-epidemiológicas estudadas. MÉTODOS: Estudo descritivo de corte transversal, realizado através da análise dos prontuários de 110 pacientes com linfoma não-Hodgkin admitidos na instituição no período de maio de 1994 a maio de 2003. As sobrevidas global e livre de doença foram analisadas através da técnica de Kaplan-Meier, e o teste de log rank foi utilizado para avaliar diferenças entre os grupos. RESULTADOS: A idade média foi de 6,1 anos, e a relação masculino-feminino, 2,4:1. O subtipo histológico mais freqüente foi o linfoma de Burkitt. A maioria dos pacientes foi diagnosticada em estádio III e IV da classificação de Murphy e provinha da zona rural. Renda familiar per capita inferior a 1/2 salário mínimo foi observada em 36,4%, e analfabetismo materno, em 12,7% dos casos. A probabilidade de sobrevida global e livre de doença aos 5 anos foi de 70±4% e 68±4%, respectivamente. Nenhuma das variáveis clínico-epidemiológicas analisadas mostrou associação estatística significante com a probabilidade de sobrevida dos pacientes (p > 0,05. CONCLUSÃO: Observamos incidência mais elevada do subtipo Burkitt e de crianças acometidas em idade mais jovem quando comparada à descrita em literatura estrangeira. A sobrevida observada aproximou-se dos resultados descritos pelos principais grupos cooperativos de tratamento de câncer infantil. As variáveis clínico-epidemiológicas analisadas não apresentaram associação prognóstica estatística significante.OBJECTIVE:To describe the clinical and demographic characteristics of non-Hodgkin's lymphoma patients diagnosed at the Pediatric Oncology Unit

  12. Roles of external and cellular Cl- ions on the activation of an apical electrodiffusional Cl- pathway in toad skin.

    Science.gov (United States)

    Procopio, J; Lacaz-Vieira, F

    1990-07-01

    This study is concerned with the short-circuit current, Isc, responses of the Cl(-)-transporting cells of toad skin submitted to sudden changes of the external Cl- concentration, [Cl]o. Sudden changes of [Cl]o, carried out under apical membrane depolarization, allowed comparison of the roles of [Cl]o and [Cl]cell on the activation of the apical Cl- pathways. Equilibration of short-circuited skins symmetrically in K-Ringer's solutions of different Cl- concentrations permitted adjustment of [Cl]cell to different levels. For a given Cl- concentration (in the range of 11.7 to 117 mM) on both sides of a depolarized apical membrane, this structure exhibits a high Cl- permeability, P(Cl)apical. On the other hand, for the same range of [Cl]cell but with [Cl]o = 0, P(Cl)apical is reduced to negligible values. These observations indicate that when the apical membrane is depolarized P(Cl)apical is modulated by [Cl]o; in the absence of external Cl- ions, intracellular Cl- is not sufficient to activate P(Cl)apical. Computer simulation shows that the fast Cl- currents induced across the apical membrane by sudden shifts of [Cl]o from a control equilibrium value strictly follow the laws of electrodiffusion. For each experimental group, the computer-generated Isc versus [( Cl]cell - [Cl]o) curve which best fits the experimental data can only be obtained by a unique pair of P(Cl)apical and Rb (resistance of the basolateral membrane), thus allowing the calculation of these parameters. The electrodiffusional behavior of the net Cl- flux across the apical membrane supports the channel nature of the apical Cl- pathways in the Cl(-)-transporting cells. Cl- ions contribute significantly to the overall conductance of the basolateral membrane even in the presence of a high K concentration in the internal solution. PMID:1698229

  13. The magnetic susceptibility of graphite biintercalated with CoCl2 and GaCl3

    OpenAIRE

    Rosenman, I.; Batallan, F.; Simon, Ch.; Hachim, L.

    1986-01-01

    We present the first results of magnetic susceptibility on CoCl2-GaCl 3 biintercalated in graphite, and compare them with those obtained in second stage CoCl2-graphite. A fit by a power law above the maximum of the susceptibility present two regimes : in the high temperature one, the γ values are high and even higher in the CoCl2-GaCl 3 compound. This indicates that the three-dimensional coupling is lower in the biintercalation compound. In the low temperature regime, near the transition, the...

  14. Study of inter-dot coupling in nano-patterned permalloy dots array

    International Nuclear Information System (INIS)

    We present a series of studies on interdot coupling in the nanometer-scaled permalloy dots array. A standard electron beam lithography in conjunction with lift-off process was employed for patterning 30 nm thick of millions of permalloy dots array with diameter (D) of 500 nm and the aspect ratio S/D of spacing (S) to diameter ranging from 0.2 to 1.25. The magnetization reversal processes were identified to evolve through the vortex nucleation, movement, and annihilation based on magnetic force microscopy (MFM) imaging in the presence of external magnetic fields. The nucleation field, annihilation field, and moving rate of vortex core were analyzed using M-H loops measured by the alternating gradient magnetometer (AGM). These behaviors are associated with the dipole-dipole interaction in dots array with various interdot spacings.

  15. Electron States of Few-Electron Quantum Dots

    Institute of Scientific and Technical Information of China (English)

    戴振宏; 孙金祚; 张立德; 李作宏; 黄士勇; 隋鹏飞

    2002-01-01

    We study few-electron semiconductor quantum dots using the unrestricted Hartree-Fock-Roothaan method based on the Gaussian basis. Our emphasis is on the energy level calculation for quantum dots. The confinement potential in a quantum dot is assumed to be in a form of three-dimensional spherical finite potential well. Some valuable results, such as the rearrangement of the energy level, have been obtained.

  16. Exciton dephasing in single InGaAs quantum dots

    DEFF Research Database (Denmark)

    Leosson, Kristjan; Østergaard, John Erland; Jensen, Jacob Riis;

    2000-01-01

    The homogeneous linewidth of excitonic transitions is a parameter of fundamental physical importance. In self-assembled quantum dot systems, a strong inhomogeneous broadening due to dot size fluctuations masks the homogeneous linewidth associated with transitions between individual states. The ho...... to fast dephasing. We present an investigation of the low-temperature homogeneous linewidth of individual PL lines from MBE-grown In0.5Ga0.5As/GaAs quantum dots....

  17. Exciton lifetime measurements on single silicon quantum dots.

    Science.gov (United States)

    Sangghaleh, Fatemeh; Bruhn, Benjamin; Schmidt, Torsten; Linnros, Jan

    2013-06-01

    We measured the exciton lifetime of single silicon quantum dots, fabricated by electron beam lithography, reactive ion etching and oxidation. The observed photoluminescence decays are of mono-exponential character with a large variation (5-45 μs) from dot to dot, even for the same emission energy. We show that this lifetime variation may be the origin of the heavily debated non-exponential (stretched) decays typically observed for ensemble measurements.

  18. Region-Dot Conversion Fusion Algorithm and Application

    OpenAIRE

    Zhouxing Fu; Mei Wang; Jingyi Du; Hsiung-Cheng Lin; Ningbo Xu; Hongyang Zan

    2014-01-01

    The interior decoration materials and the new furniture using formaldehyde, ammonia, and other poisonous substances are known as the main sources of indoor air pollutions. However, it is still a big challenge to estimate accurately the overall air quality by using the current measuring tools. Accordingly, the region-dot fusion (RDF) algorithm is proposed to evaluate the air quality in this paper. For the conversion from a region to a dot, the region-dot function is firstly defined as the summ...

  19. Nonlinear transport in coupled quantum dots: A stationary probability approach

    Institute of Scientific and Technical Information of China (English)

    GONG JianPing; DUAN SuQing; YAN WeiXian; ZHAO XianGeng

    2009-01-01

    The stationary tunneling current and differential conductance of the coupled quantum dots system with split-gates are calculated by generalizing the Beenaker's linear response theory for the description of the Coulomb-blockade oscillations of the conductance in the single quantum dot. The calculation of the charging diagram in parallel through the double dot as function of the two side-gate voltages shows a remarkable agreement with the recent experimental results by Hatano et al. (Science, 2005, 309: 268-271)

  20. Recent advances in carbon-based dots for electroanalysis.

    Science.gov (United States)

    Yulong, Ying; Xinsheng, Peng

    2016-04-25

    Carbon-based dots represent a new type of quantum dot with unique and well-defined properties owing to their quantum confinement and edge effects, which are widely employed in sensing, light-emitting diodes, nanomedicine, photocatalysis, electrocatalysis, bioimaging, etc. In this review, we update the latest research results of carbon-based dots in this rapidly evolving field of electroanalysis, place emphases on their applications as sensors and give future perspectives for developing more smart sensors.

  1. Polarization anisotropic luminescence of tunable single lateral quantum dot molecules

    Science.gov (United States)

    Hermannstädter, C.; Witzany, M.; Heldmaier, M.; Hafenbrak, R.; Jöns, K. D.; Beirne, G. J.; Michler, P.

    2012-03-01

    We investigate the photoluminescence polarization anisotropy of self-assembled individual lateral InGaAs/GaAs quantum dot molecules. In contrast to similarly grown single quantum dots, the dot molecules exhibit a remarkable degree of linear polarization, which remains almost unchanged when a lateral electric field is applied to tune the exciton wave function and, thus, the luminescence spectral properties. We discuss the nature of this polarization anisotropy and suggest possible causes based on the system's symmetry and heterostructure alloy composition.

  2. Reconfigurable quadruple quantum dots in a silicon nanowire transistor

    OpenAIRE

    Betz, A. C.; Tagliaferri, M. L. V.; Vinet, M.; Broström, M.; Sanquer, M.; Ferguson, A.J.; Gonzalez-Zalba, M. F.

    2016-01-01

    We present a novel reconfigurable metal-oxide-semiconductor multi-gate transistor that can host a quadruple quantum dot in silicon. The device consist of an industrial quadruple-gate silicon nanowire field-effect transistor. Exploiting the corner effect, we study the versatility of the structure in the single quantum dot and the serial double quantum dot regimes and extract the relevant capacitance parameters. We address the fabrication variability of the quadruple-gate approach which, paired...

  3. InAs/GaAs quantum-dot superluminescent diodes monolithically grown on a Ge substrate.

    Science.gov (United States)

    Jiang, Qi; Tang, Mingchu; Chen, Siming; Wu, Jiang; Seeds, Alwyn; Liu, Huiyun

    2014-09-22

    We report the first InAs/GaAs quantum-dot (QD) superluminescent diode (SLD) monolithically grown on a Ge substrate by molecular beam epitaxy. The QD SLD exhibits a 3 dB emission bandwidth of ~60 nm centered at 1252 nm with output power of 27 mW at room temperature. The 3 dB bandwidth is very stable over the temperature range from 20 °C to 100 °C, which highlights the potential for integration with high performance ICs.

  4. A novel high-efficiency single-mode quantum dot single photon source

    DEFF Research Database (Denmark)

    Gerard, J.M.; Gregersen, Niels; Nielsen, Torben Roland;

    2008-01-01

    We present a novel single-mode single photon source exploiting the emission of a semiconductor quantum dot (QD) located inside a photonic wire. Besides an excellent coupling (>95%) of QD spontaneous emission to the fundamental guided mode [1], we show that a single photon collection efficiency...... above 80% within a 0.5 numerical aperture can be achieved using a bottom Bragg mirror and a tapering of the nanowire tip. Because this photon collection strategy does not exploit the Purcell effect, it could also be efficiently applied to broadband single photon emitters such as F-centers in diamond....

  5. Spin effects in InAs self-assembled quantum dots.

    Science.gov (United States)

    Dos Santos, Ednilson C; Gobato, Yara Galvão; Brasil, Maria Jsp; Taylor, David A; Henini, Mohamed

    2011-01-01

    We have studied the polarized resolved photoluminescence in an n-type resonant tunneling diode (RTD) of GaAs/AlGaAs which incorporates a layer of InAs self-assembled quantum dots (QDs) in the center of a GaAs quantum well (QW). We have observed that the QD circular polarization degree depends on applied voltage and light intensity. Our results are explained in terms of the tunneling of minority carriers into the QW, carrier capture by InAs QDs and bias-controlled density of holes in the QW. PMID:21711647

  6. Spin effects in InAs self-assembled quantum dots

    OpenAIRE

    Brasil Maria; Taylor David; Henini Mohamed; dos Santos Ednilson; Gobato Yara

    2011-01-01

    Abstract We have studied the polarized resolved photoluminescence in an n-type resonant tunneling diode (RTD) of GaAs/AlGaAs which incorporates a layer of InAs self-assembled quantum dots (QDs) in the center of a GaAs quantum well (QW). We have observed that the QD circular polarization degree depends on applied voltage and light intensity. Our results are explained in terms of the tunneling of minority carriers into the QW, carrier capture by InAs QDs and bias-controlled density of holes in ...

  7. Spin effects in InAs self-assembled quantum dots

    Directory of Open Access Journals (Sweden)

    Brasil Maria

    2011-01-01

    Full Text Available Abstract We have studied the polarized resolved photoluminescence in an n-type resonant tunneling diode (RTD of GaAs/AlGaAs which incorporates a layer of InAs self-assembled quantum dots (QDs in the center of a GaAs quantum well (QW. We have observed that the QD circular polarization degree depends on applied voltage and light intensity. Our results are explained in terms of the tunneling of minority carriers into the QW, carrier capture by InAs QDs and bias-controlled density of holes in the QW.

  8. A novel LiCl-BaCl2:Eu2+ eutectic scintillator for thermal neutron detection

    Science.gov (United States)

    Wu, Yuntao; Lukosi, Eric D.; Zhuravleva, Mariya; Lindsey, Adam C.; Melcher, Charles L.

    2015-10-01

    A natLiCl-BaCl2:Eu2+ eutectic scintillator was synthesized by the vertical Bridgman method aiming at the application of thermal neutron detection. The molar ratio of LiCl and BaCl2 was 75.1/24.9, which corresponds to the eutectic composition in the LiCl-BaCl2 system. The grown eutectic showed a periodic microstructure of BaCl2:Eu2+ and LiCl phases with 2-3 μm thickness. The α-particle induced radioluminescence spectrum of the scintillator showed an intense emission peak at 406 nm due to the Eu2+ 5d1→4f emission from the BaCl2:Eu2+ phase and an additional weak emission peak at 526 nm. The scintillation decay time was 412 ns. LiCl-BaCl2:Eu2+ eutectic samples exhibited non-correlated neutron detection efficiency and light yield as a function of crystal length, suggesting material non-uniformities within the boule. The relative light yield was equal to or greater than that of Nucsafe lithium glass. Gamma-ray exposures indicate that gamma/neutron threshold discrimination for higher energy gamma-rays will be limited.

  9. Unbound states of 32Cl and the 31S(p,\\gamma)32Cl reaction rate

    CERN Document Server

    Matoš, M; Linhardt, L E; Bardayan, D W; Nesaraja, C D; Clark, J A; Deibel, C M; O'Malley, P D; Parker, P D

    2011-01-01

    The 31S(p,\\gamma)32Cl reaction is expected to provide the dominant break-out path from the SiP cycle in novae and is important for understanding enrichments of sulfur observed in some nova ejecta. We studied the 32S(3He,t)32Cl charge-exchange reaction to determine properties of proton-unbound levels in 32Cl that have previously contributed significant uncertainties to the 31S(p,\\gamma)32Cl reaction rate. Measured triton magnetic rigidities were used to determine excitation energies in 32Cl. Proton-branching ratios were obtained by detecting decay protons from unbound 32Cl states in coincidence with tritons. An improved 31S(p,\\gamma)32Cl reaction rate was calculated including robust statistical and systematic uncertainties.

  10. The structure of the muscle protein complex 4Ca{sup 2+} {center_dot}troponin C {center_dot} troponin

    Energy Technology Data Exchange (ETDEWEB)

    Olah, G.A.; Trewhella, J. [Los Alamos National Laboratory, NM (United States)

    1994-12-31

    Analysis of scattering data based on a Monte Carlo integration method was used to 2+ obtain a low resolution model of the 4Ca{sup 2+}{circ} troponin C{circ}troponin I complex. This modeling method allows rapid testing of plausible structures where the best fit model can be ascertained by a comparison between model structure scattering profiles and measured scattering data. In the best fit model, troponin I appears as a spiral structure 2+ that wraps around 4Ca{sup 2+}{circ}troponin C which adopts an extended dumbbell conformation similar to that observed in the crystal structures of troponin C. The Monte Carlo modeling method can be applied to other biological systems in which detailed structural information is lacking.

  11. Polarized quantum dot emission in electrohydrodynamic jet printed photonic crystals

    Energy Technology Data Exchange (ETDEWEB)

    See, Gloria G. [Micro and Nanotechnology Laboratory, Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, 208 North Wright Street, Urbana, Illinois 61801 (United States); Xu, Lu; Nuzzo, Ralph G. [Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801 (United States); Sutanto, Erick; Alleyne, Andrew G. [Mechanical Science and Engineering Department, University of Illinois at Urbana-Champaign, 154 Mechanical Engineering Building, Urbana, Illinois 61801 (United States); Cunningham, Brian T. [Micro and Nanotechnology Laboratory, Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, 208 North Wright Street, Urbana, Illinois 61801 (United States); Department of Bioengineering, University of Illinois at Urbana-Champaign, 1270 Digital Computer Laboratory, MC-278, Urbana, Illinois 61801 (United States)

    2015-08-03

    Tailored optical output, such as color purity and efficient optical intensity, are critical considerations for displays, particularly in mobile applications. To this end, we demonstrate a replica molded photonic crystal structure with embedded quantum dots. Electrohydrodynamic jet printing is used to control the position of the quantum dots within the device structure. This results in significantly less waste of the quantum dot material than application through drop-casting or spin coating. In addition, the targeted placement of the quantum dots minimizes any emission outside of the resonant enhancement field, which enables an 8× output enhancement and highly polarized emission from the photonic crystal structure.

  12. Nonequilibrium Electron Transport Through a Quantum Dot from Kubo Formula

    Institute of Scientific and Technical Information of China (English)

    L(U) Rong; ZHANG Guang-Ming

    2005-01-01

    Based on the Kubo formula for an electron tunneling junction, we revisit the nonequilibrium transport properties through a quantum dot. Since the Fermi level of the quantum dot is set by the conduction electrons of the leads, we calculate the electron current from the left side by assuming the quantum dot coupled to the right lead as another side of the tunneling junction, and the other way round is used to calculate the current from the right side. By symmetrizing these two currents, an effective local density states on the dot can be obtained, and is discussed at high and low temperatures, respectively.

  13. Coupling of single quantum dots to a photonic crystal waveguide

    DEFF Research Database (Denmark)

    Lund-Hansen, Toke; Stobbe, Søren; Julsgaard, Brian;

    is coupled efficiently to a single enhanced mode. One popular approach has been to couple single quantum dots to a nanocavity but a limiting factor in this configuration is that in order to apply the photon it should subsequently be coupled out of the cavity, reducing the overall efficiency significantly....... An alternative approach is to couple the quantum dot directly to the propagating mode of a photonic waveguide. We demonstrate the coupling of single quantum dots to a photonic crystal waveguide using time-resolved spontaneous emission measurements. A pronounced effect is seen in the decay rates of dots coupled...

  14. An Exciton Bound to a Neutral Donor in Quantum Dots

    Institute of Scientific and Technical Information of China (English)

    解文方

    2002-01-01

    The binding energies for an exciton (X) trapped in a two-dimensional quantum dot by a neutral donor have been calculated using the method of few-body physics for the heavy hole (σ= 0.196) and the light hole (σr = 0.707).We find that the (D0, X) complex confined in a quantum dot has in general a larger binding energy than those in a two-dimensional quantum well and a three-dimensional bulk semiconductor, and the binding energy increases with the decrease of the dot radius. At dot radius R →∞, we compare our calculated result with the previous results.

  15. Core–shell quantum dots: Properties and applications

    Energy Technology Data Exchange (ETDEWEB)

    Vasudevan, D., E-mail: vasudevand@rediffmail.com [Electrodics and electrocatalysis division, CSIR-CECRI, Karaikudi 630006 (India); Gaddam, Rohit Ranganathan [Amity Institute of Nanotechnology, Amity University, Noida 201301 (India); Trinchi, Adrian; Cole, Ivan [CSIRO Materials Science and Engineering, Clayton South MDC, 3169 (Australia)

    2015-07-05

    Fluorescent quantum dots (QDs) are semiconducting nanocrystals (NCs) that find numerous applications in areas, such as bio labelling, sensors, lasers, light emitting diodes and medicine. Core–shell quantum dots were developed to improve the photoluminescence efficiency of single quantum dots. Capping their surface with organic ligands as well as their extraction into aqueous media enables their use in sensing applications. The current review highlights the importance and applications of core shell quantum dots as well as their surface modifications and applications in the field of medicine and as sensors for chemical and biochemical analysis.

  16. Carbon Dot Based Sensing of Dopamine and Ascorbic Acid

    OpenAIRE

    Upama Baruah; Neelam Gogoi; Achyut Konwar; Manash Jyoti Deka; Devasish Chowdhury; Gitanjali Majumdar

    2014-01-01

    We demonstrate carbon dot based sensor of catecholamine, namely, dopamine and ascorbic acid. Carbon dots (CDs) were prepared from a green source: commercially available Assam tea. The carbon dots prepared from tea had particle sizes of ∼0.8 nm and are fluorescent. Fluorescence of the carbon dots was found to be quenched in the presence of dopamine and ascorbic acid with greater sensitivity for dopamine. The minimum detectable limits were determined to be 33 μM and 98 μM for dopamine and ascor...

  17. Highly fluorescent xerogels with entrapped carbon dots for organic scintillators

    Energy Technology Data Exchange (ETDEWEB)

    Quaranta, A., E-mail: quaranta@ing.unitn.it [University of Trento, Department of Industrial Engineering, via Mesiano, 77, 38123 Trento (Italy); Laboratori Nazionali di Legnaro, INFN, Viale dell' Università, 2, 35020 Legnaro (PD) (Italy); Carturan, S. [Laboratori Nazionali di Legnaro, INFN, Viale dell' Università, 2, 35020 Legnaro (PD) (Italy); University of Padova, Department of Physics and Astronomy “Galileo Galilei”, Via Marzolo, 8, 35131 Padova (Italy); Campagnaro, A.; Dalla Palma, M. [University of Trento, Department of Industrial Engineering, via Mesiano, 77, 38123 Trento (Italy); Laboratori Nazionali di Legnaro, INFN, Viale dell' Università, 2, 35020 Legnaro (PD) (Italy); Giarola, M.; Daldosso, N. [University of Verona, Department of Informatics, Strada le Grazie,15, 37134 Verona (Italy); Maggioni, G. [Laboratori Nazionali di Legnaro, INFN, Viale dell' Università, 2, 35020 Legnaro (PD) (Italy); University of Padova, Department of Physics and Astronomy “Galileo Galilei”, Via Marzolo, 8, 35131 Padova (Italy); Mariotto, G. [University of Verona, Department of Informatics, Strada le Grazie,15, 37134 Verona (Italy)

    2014-02-28

    Organically modified silicate thin film and bulk samples were prepared using [3-(2-aminoethylamino)propyl]trimethoxysilane (AEAP-TMOS) as precursor with the addition of different amounts of AEAP-TMOS functionalized C-dots, prepared by reaction of AEAP-TMOS and citric acid at high temperature. The synthesis of surface functionalized C-dots was followed by Fourier Transform Infrared (FTIR) spectroscopy, and the C-dots optical properties were characterized by optical absorption and UV–vis fluorescence. Thin xerogel films and bulk samples were studied by FTIR, Raman and fluorescence spectroscopy. Intense blue-green emission was observed by UV excitation of functionalized C-dots. Carbon quantum dot (CQD) luminescence was preserved also in the xerogel matrices, and the energy transfer from the matrix to CQDs, which is a key characteristic for scintillation detectors, was investigated in the two systems. - Highlights: • Functionalized carbon dots were synthesized. • Carbon dots were dispersed in hybrid xerogel bulk and thin film. • Carbon dots exhibit a strong tunable blue luminescence. • Xerogels were characterized by FT-IR, Raman and fluorescence spectroscopies. • Energy transfer processes were evidenced between C-dots and xerogel matrix.

  18. 我是中国DotA的希望(一)

    Institute of Scientific and Technical Information of China (English)

    少小帅

    2010-01-01

    我叫贾鹏我叫贾鹏,我是中国DotA的希望。他们一直这么评价我,而我对此深信不疑。在这个全民DotA的时代,我也不例外。我DotA玩的怎么样,我不好去评价,和我一起DotA的兄弟们是这么评价我的,"前期打得没的说!"邱涵说;"Gank打得没的说!"程龙说;

  19. Polarized quantum dot emission in electrohydrodynamic jet printed photonic crystals

    International Nuclear Information System (INIS)

    Tailored optical output, such as color purity and efficient optical intensity, are critical considerations for displays, particularly in mobile applications. To this end, we demonstrate a replica molded photonic crystal structure with embedded quantum dots. Electrohydrodynamic jet printing is used to control the position of the quantum dots within the device structure. This results in significantly less waste of the quantum dot material than application through drop-casting or spin coating. In addition, the targeted placement of the quantum dots minimizes any emission outside of the resonant enhancement field, which enables an 8× output enhancement and highly polarized emission from the photonic crystal structure

  20. Electric and Magnetic Interaction between Quantum Dots and Light

    DEFF Research Database (Denmark)

    Tighineanu, Petru

    a future challenge for the droplet-epitaxy technique. A multipolar theory of spontaneous emission from quantum dots is developed to explain the recent observation that In(Ga)As quantum dots break the dipole theory. The analysis yields a large mesoscopic moment, which contains magnetic-dipole and electric......-matter interaction of both electric and magnetic character. Our study demonstrates that In(Ga)As quantum dots lack parity symmetry and, as consequence, can be employed for locally probing the parity symmetry of complex photonic nanostructures. This opens the prospect for interfacing quantum dots with optical...

  1. Second-harmonic imaging of semiconductor quantum dots

    DEFF Research Database (Denmark)

    Østergaard, John Erland; Bozhevolnyi, Sergey I.; Pedersen, Kjeld;

    2000-01-01

    Resonant second-harmonic generation is observed at room temperature in reflection from self-assembled InAlGaAs quantum dots grown on a GaAs (001) substrate. The detected second-harmonic signal peaks at a pump wavelength of similar to 885 nm corresponding to the quantum-dot photoluminescence maxim...... observe that second-harmonic images of the quantum-dot surface structure show wavelength-dependent spatial variations. Imaging at different wavelength is used to demonstrate second-harmonic generation from the semiconductor quantum dots. (C) 2000 American Institute of Physics....

  2. SMM DotA大赛结束中国DotA战队囊括三甲

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    11月27至29日,国外著名DotA大赛Sendi Mutiara Multimedia Grand National DotA Tournament:Grand Firlals 2009(以下简称SMM09)在马来西亚马六甲州进行了为期三天的精彩大战.最终来自中国的三支战队sGty、cD、EHOME囊括三甲。成为SMM09的最大赢家。

  3. Emission switching in carbon dots coated CdTe quantum dots driving by pH dependent hetero-interactions

    Energy Technology Data Exchange (ETDEWEB)

    Dai, Xiao; Wang, Hao; Yi, Qinghua; Wang, Yun; Cong, Shan; Zhao, Jie; Sun, Yinghui; Zou, Guifu, E-mail: zouguifu@suda.edu.cn, E-mail: jiexiong@uestc.edu.cn [College of Physics, Optoelectronics and Energy and Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215006 (China); Qian, Zhicheng [School of Electronic and Information Engineering, Xi' an Jiaotong University, Xi' an 710049 (China); Huang, Jianwen; Xiong, Jie, E-mail: zouguifu@suda.edu.cn, E-mail: jiexiong@uestc.edu.cn [State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054 (China); Luo, Hongmei [Department of Chemical and Materials Engineering, New Mexico State University, Las Cruces, New Mexico 88003 (United States)

    2015-11-16

    Due to the different emission mechanism between fluorescent carbon dots and semiconductor quantum dots (QDs), it is of interest to explore the potential emission in hetero-structured carbon dots/semiconducting QDs. Herein, we design carbon dots coated CdTe QDs (CDQDs) and investigate their inherent emission. We demonstrate switchable emission for the hetero-interactions of the CDQDs. Optical analyses indicate electron transfer between the carbon dots and the CdTe QDs. A heterojunction electron process is proposed as the driving mechanism based on N atom protonation of the carbon dots. This work advances our understanding of the interaction mechanism of the heterostructured CDQDs and benefits the future development of optoelectronic nanodevices with new functionalities.

  4. The Galactic Center Weather Forecast

    CERN Document Server

    Moscibrodzka, Monika; Gammie, Charles F; Dolence, Joshua C

    2012-01-01

    In accretion-based models for Sgr A* the X-ray, infrared, and millimeter emission arise in a hot, geometrically thick accretion flow close to the black hole. The spectrum and size of the source depend on the black hole mass accretion rate $\\dot{M}$. Since Gillessen et al. have recently discovered a cloud moving toward Sgr A* that will arrive in summer 2013, $\\dot{M}$ may increase from its present value $\\dot{M}_0$. We therefore reconsider the "best-bet" accretion model of Moscibrodzka et al., which is based on a general relativistic MHD flow model and fully relativistic radiative transfer, for a range of $\\dot{M}$. We find that for modest increases in $\\dot{M}$ the characteristic ring of emission due to the photon orbit becomes brighter, more extended, and easier to detect by the planned Event Horizon Telescope submm VLBI experiment. If $\\dot{M} \\gtrsim 8 \\dot{M}_0$ this "silhouette of the black hole will be hidden beneath the synchrotron photosphere at 230 GHz, and for $\\dot{M} \\gtrsim 16 \\dot{M}_0$ the silh...

  5. AcEST: CL39Contig1 [AcEST

    Lifescience Database Archive (English)

    Full Text Available CL39Contig1 913 36 Adiantum capillus-veneris contig: CL39contig1 sequence. Link to clone list Show CL39C...ontig1 Contig ID CL39Contig1 Length 913 Number of clones 36 Definition Adiantum capillus-veneris contig: CL39c

  6. AcEST: CL1509Contig1 [AcEST

    Lifescience Database Archive (English)

    Full Text Available CL1509Contig1 1477 3 Adiantum capillus-veneris contig: CL1509contig1 sequence. Link... to clone list Show CL1509Contig1 Contig ID CL1509Contig1 Length 1477 Number of clones 3 Definition Adiantum... capillus-veneris contig: CL1509contig1 sequence. Link to clone list Link to clone list Clone ID BP916497 DK

  7. AcEST: CL89Contig1 [AcEST

    Lifescience Database Archive (English)

    Full Text Available CL89Contig1 651 21 Adiantum capillus-veneris contig: CL89contig1 sequence. Link to clone list Show CL89C...ontig1 Contig ID CL89Contig1 Length 651 Number of clones 21 Definition Adiantum capillus-veneris contig: CL89c

  8. AcEST: CL49Contig1 [AcEST

    Lifescience Database Archive (English)

    Full Text Available CL49Contig1 701 14 Adiantum capillus-veneris contig: CL49contig1 sequence. Link to clone list Show CL49C...ontig1 Contig ID CL49Contig1 Length 701 Number of clones 14 Definition Adiantum capillus-veneris contig: CL49c

  9. AcEST: CL59Contig1 [AcEST

    Lifescience Database Archive (English)

    Full Text Available CL59Contig1 769 28 Adiantum capillus-veneris contig: CL59contig1 sequence. Link to clone list Show CL59C...ontig1 Contig ID CL59Contig1 Length 769 Number of clones 28 Definition Adiantum capillus-veneris contig: CL59c

  10. AcEST: CL227Contig1 [AcEST

    Lifescience Database Archive (English)

    Full Text Available CL227Contig1 1060 9 Adiantum capillus-veneris contig: CL227contig1 sequence. Link to clone list Show CL2...27Contig1 Contig ID CL227Contig1 Length 1060 Number of clones 9 Definition Adiantum capillus-veneris contig: CL2

  11. AcEST: CL22Contig1 [AcEST

    Lifescience Database Archive (English)

    Full Text Available CL22Contig1 1518 45 Adiantum capillus-veneris contig: CL22contig1 sequence. Link to clone list Show CL2...2Contig1 Contig ID CL22Contig1 Length 1518 Number of clones 45 Definition Adiantum capillus-veneris contig: CL2

  12. AcEST: CL267Contig1 [AcEST

    Lifescience Database Archive (English)

    Full Text Available CL267Contig1 922 8 Adiantum capillus-veneris contig: CL267contig1 sequence. Link to clone list Show CL2...67Contig1 Contig ID CL267Contig1 Length 922 Number of clones 8 Definition Adiantum capillus-veneris contig: CL2

  13. AcEST: CL270Contig1 [AcEST

    Lifescience Database Archive (English)

    Full Text Available CL270Contig1 687 7 Adiantum capillus-veneris contig: CL270contig1 sequence. Link to clone list Show CL2...70Contig1 Contig ID CL270Contig1 Length 687 Number of clones 7 Definition Adiantum capillus-veneris contig: CL2

  14. AcEST: CL265Contig1 [AcEST

    Lifescience Database Archive (English)

    Full Text Available CL265Contig1 1000 8 Adiantum capillus-veneris contig: CL265contig1 sequence. Link to clone list Show CL2...65Contig1 Contig ID CL265Contig1 Length 1000 Number of clones 8 Definition Adiantum capillus-veneris contig: CL2

  15. AcEST: CL230Contig1 [AcEST

    Lifescience Database Archive (English)

    Full Text Available CL230Contig1 829 9 Adiantum capillus-veneris contig: CL230contig1 sequence. Link to clone list Show CL2...30Contig1 Contig ID CL230Contig1 Length 829 Number of clones 9 Definition Adiantum capillus-veneris contig: CL2

  16. AcEST: CL29Contig1 [AcEST

    Lifescience Database Archive (English)

    Full Text Available CL29Contig1 903 40 Adiantum capillus-veneris contig: CL29contig1 sequence. Link to clone list Show CL2...9Contig1 Contig ID CL29Contig1 Length 903 Number of clones 40 Definition Adiantum capillus-veneris contig: CL2

  17. AcEST: CL253Contig1 [AcEST

    Lifescience Database Archive (English)

    Full Text Available CL253Contig1 644 8 Adiantum capillus-veneris contig: CL253contig1 sequence. Link to clone list Show CL2...53Contig1 Contig ID CL253Contig1 Length 644 Number of clones 8 Definition Adiantum capillus-veneris contig: CL2

  18. AcEST: CL204Contig1 [AcEST

    Lifescience Database Archive (English)

    Full Text Available CL204Contig1 503 2 Adiantum capillus-veneris contig: CL204contig1 sequence. Link to clone list Show CL2...04Contig1 Contig ID CL204Contig1 Length 503 Number of clones 2 Definition Adiantum capillus-veneris contig: CL2

  19. Standardization of dot-ELISA for the serological diagnosis of toxocariasis and comparision of the assay with ELISA Padronização do teste dot-ELISA para o diagnóstico da toxocaríase, estudo comparativo com o teste imunoenzimático ELISA

    Directory of Open Access Journals (Sweden)

    Eide Dias Camargo

    1992-02-01

    Full Text Available The dot-enzyme-linked immunosorbent assay (dot-ELISA was standardized using somatic (S and excretory-secretory (ES antigens of Toxocara-canis for the detection of specific antibodies in 22 serum samples from children aged 1 to 15 years, with clinical signs of toxocariasis. Fourteen serum samples from apparently normal individuals and 28 sera from patients with other pathologies were used as controls. All samples were used before and after absorption with Ascaris suum extract. When the results were evaluated in comparison with ELISA, the two tests were found to have similar sensitivity, but dot-ELISA was found to be more specific in the presence of the two antigens studied. Dot-ELISA proved to be effective for the diagnosis of human toxocariasis, presenting advantages in terms of yield, stability, time and ease of execution and low cost.Padronizou-se o teste imunoenzimático dot-ELISA, empregando-se os antígenos somático (S e excretor-secretor (ES de Toxocara canis, para pesquisa de anticorpos específicos em 22 soros de pacientes com idades entre 5 a 15 anos, com dados clínicos de toxocaríase. Como grupo controle, foram estudados 14 soros de indivíduos supostamente normais e 28 soros de pacientes com outras patologias. Todas as amostras em estudo foram empregadas antes e após absorção com extrato de Ascaris suum. Os resultados obtidos foram avaliados comparativamente com o teste ELISA evidenciando, nos dois testes estudados, comportamento semelhante quanto à sensibilidade e maior especificidade para o dot-ELISA, com qualquer dos dois antígenos estudados. O teste dot-ELISA mostrou-se eficiente para o diagnóstico da toxocaríase humana, apresentando vantagens quanto ao rendimento, estabilidade, tempo e facilidade de execução e baixo custo.

  20. The Electron-Hole Pair in a Single Quantum Dot and That in a Vertically Coupled Quantum Dot

    Institute of Scientific and Technical Information of China (English)

    XIE Wen-Fang; ZHU Wu

    2003-01-01

    The energy spectra of low-lying states of an exciton in a single and a vertically coupled quantum dots arestudied under the influence of a perpendicularly applied magnetic field. Calculations are made by using the method ofnumerical diagonalization of the Hamiltonian within the effective-mass approximation. We also calculated the bindingenergy of the ground and the excited states of an exciton in a single quantum dot and that in a vertically coupledquantum dot as a function of the dot radius for different values of the distance and the magnetic field strength.

  1. The Electron-Hole Pair in a Single Quantum Dot and That in a Vertically Coupled Quantum Dot

    Institute of Scientific and Technical Information of China (English)

    XIEWen-Fang; ZHUWu

    2003-01-01

    The energy spectra of low-lying states of an exciton in a single and a vertically coupled quantum dots are studied under the influence of a perpendicularly applied magnetic field. Calculations are made by using the method of numerical diagonalization of the Hamiltonian within the effective-mass approximation. We also calculated the binding energy of the ground and the excited states of an exciton in a single quantum dot and that in a vertically coupled quantum dot as a function of the dot radius for different vaJues of the distance and the magnetic field strength.

  2. Call Center ist nicht gleich Call Center

    OpenAIRE

    Baumgartner, Marc; Udris, Ivars

    2005-01-01

    Untersuchungen in 14 Schweizer Call Centers erbrachten vier Call Center-Typen, die sich hinsichtlich Arbeitstätigkeiten und Kommunikationsrichtung voneinander unterscheiden: (a) Beratungs- und Beschwerdemanagement, (b) Informationsmanagement, (c) Auftragsmanagement und (d) Kunden- und Kampagnenmanagement. Dies hat auch Auswirkungen auf die Personalstruktur, -selektion und -entwicklung der Call Center. Es wird der Frage nachgegangen, welche Kompetenzanforderungen in den unterschiedlichen Call ...

  3. On Sensitivity of HE CL-20

    Institute of Scientific and Technical Information of China (English)

    Yu. V. Sheikov; L. A. Andrievskikh; V. G. Vasipenko; S. A. Vakhmistrov; N. N. Zhbanova; V. B. Kosolapov; L.V.Fomicheva

    2004-01-01

    @@ 1 Introduction Recently a series of publications appeared in literature devoted to study of properties of hexanitrohexaazaisowurtzitan( CL-20), which is considered as an explosive with performance higher than that of HMX, and which has moderate sensitivity[1].

  4. Electron charging in epitaxial germanium quantum dots on silicon (100)

    Science.gov (United States)

    Ketharanathan, Sutharsan

    The electron charging behavior of self assembled epitaxial Ge quantum dots on Si(100) grown using molecular beam epitaxy has been studied. Ge quantum dots encapsulated in n-type Si matrix were incorporated into Schottky diodes to investigate their charging behavior using capacitance-voltage measurements. These experimental results were interpreted in the context of theoretical models to assess the degree of charge localization to the dot. Experiments involving Ge quantum dot growth, growth of Sb-doped Si and morphological evolution during encapsulation of the Ge dots during Si overgrowth were performed in order to optimize the conditions for obtaining distinct Ge quantum dot morphologies. This investigation included finding a suitable method to minimize Sb segregation while maintaining good dot epitaxy and overall crystal quality. Holes are confined to the Ge dots for which the valence band offsets are large (˜650 meV). Electrons are confined to the strained Si regions adjacent to the Ge quantum dots which have relatively smaller confinement potentials (˜100--150 meV). Experimentally, it was found that but and pyramid clusters in the range from 20--40 nm in diameter confine ˜1electron per dot while dome clusters in the range from 60--80 nm diameter confine ˜6--8 electrons per dot. Theoretical simulations predict that similar pyramid structures confine ˜0.4 electrons per dot and dome structures confine ˜2.2--3 electrons per dot. Even though the theory and the experimental results disagree due to various uncertainties and approximations, the ratio between theory and experiment agree remarkably well for both island types. We also investigated constructive three-dimensional nanolithography. Nanoscale Au rich dots and pure Ge dots were deposited on SiO2 and Si3N4 substrates by decomposing adsorbed precursors using a focused electron beam in an environmental transmission electron microscope. Dimethyl acetylacetonate gold was used for Au and digermane was used to

  5. Equations for calculation of NaCl/( NaCl + CaCl2 ) ratios and salinities from hydrohalite-melting and ice-melting temperatures in the H2O-NaCl-CaCl2 system%利用H2O-NaCl-CaCl2体系水盐化合物和冰的融化温度计算NaCl/(NaCl+CaCl2)比值和盐度的方程

    Institute of Scientific and Technical Information of China (English)

    Guoxiang Chi; Pei Ni

    2007-01-01

    The composition of fluid inclusions in the H2O-NaCl-CaCl2 system has been generally graphically estimated using the melting temperatures of hydrohalite ( Tm-HH ) and ice ( Tm-ice ). Here we present two equations that can be used to calculate the relative proportion of NaCl ( i. e. , NaCt/[ NaCl + CaCl2 ], or XNaCl) and the total salinity ( i. e. , NaCl + CaCl2, wt% ) for fluid inclusions with ice as the last melting phase. XNaCl can be calculated from Tm-HH using the following equation:y= ( a + bx)-1/c where y is XNaCl, x is Tm-HH, a =0. 33124402, b = -0.031518028, and c =0. 22932736. In the cases where only Tm-ice is measured and Tm-HH is not known, Tm-ice can be used as the maximum possible Tm-HH to calculate the maximum value of XNaCl using the above equation. In these cases, the following equation can be used to calculate the maximum total salinity: y = (a +bx +cx2) -1 where y is salinity, x is Tm-HH, a = 0. 057184817, b = 0. 00078565757, and c = 5. 7262766E-6. Because the isothems in the field of ice are sub-parallel to the NaCl-CaCl2 binary side in the H2O-NaCl-CaCl2 ternary system, the errors in salinity calculation introduced by the above approximation are small ( less than 2 wt% ). A Windows program for calculation of XNacl and salinity is available at: http ://uregina. ca/~ chiguox.

  6. Carrier relaxation processes in magnetic semiconductor quantum-dot systems

    International Nuclear Information System (INIS)

    The energy relaxation process of CdSe/ZnMnSe quantum dots (QDs) was investigated using polarization-selective magneto-photoluminescence (PL). Peaks from the Mn2+ internal transition, the CdSe QDs, and the ZnMnSe barrier were observed in the system. The CdSe QD peak was relatively weak while the intensity of the Mn2+ transition was strong in the spectrum taken at zero magnetic field. However, the peaks intensities changed significantly when a magnetic field was applied, and the situation became reversed (i.e., the CdSe QD peak become stronger than the peak due to the Mn2+ internal transition, specifically for σ+ polarization). The opposite intensity behavior was observed in the peak from the Mn2+ ions and in the PL of the CdSe QDs and revealed that these two carrier capture centers competed with each other for carriers excited in the ZnMnSe barrier. The variation in the Mn2+ internal transition with the magnetic field was well described by using a model developed under an angular momentum selection rule. This suggests that competition between the two energy transfer processes in the CdSe/ZnMnSe QD system is responsible for the observed PL intensity behavior.

  7. Fractals of graphene quantum dots in photoluminescence of shungite

    Science.gov (United States)

    Razbirin, B. S.; Rozhkova, N. N.; Sheka, E. F.; Nelson, D. K.; Starukhin, A. N.

    2014-05-01

    Viewing shungite as loosely packed fractal nets of graphene-based (reduced graphene oxide, rGO) quantum dots (GQDs), we consider photoluminescence of the latter as a convincing proof of the structural concept as well as of the GQD attribution to individual rGO fragments. We study emission from shungite GQDs for colloidal dispersions in water, carbon tetrachloride, and toluene at both room and low temperatures. As expected, the photoluminescence of the GQD aqueous dispersions is quite similar to that of synthetic GQDs of the rGO origin. The morphological study of shungite dispersions shows a steady trend of GQDs to form fractals and to drastically change the colloid fractal structure caused by the solvent exchange. Spectral study reveals a dual character of the emitting centers: individual GQDs are responsible for the spectra position while the fractal structure of GQD colloids ensures high broadening of the spectra due to structural inhomogeneity, thus causing a peculiar dependence of the photoluminescence spectra on the excitation wavelength. For the first time, photoluminescence spectra of individual GQDs were observed in frozen toluene dispersions, which paves the way for a theoretical treatment of the GQD photonics.

  8. OpenCL programming using Python syntax

    OpenAIRE

    Massimo Di Pierro

    2013-01-01

    We describe ocl, a Python library built on top of p yOpenCL and numpy. It allows programming GPU devices using Python. Python functions which ar e marked up using the provided decorator, are converted into C99/OpenCL and compil ed using the JIT at runtime. This approach lowers the barrier to entry to programming GPU devices since it requires only Python syntax and no external compilation or linkin g steps. The resulting Pyth...

  9. "JCE" Classroom Activity Connections: NaCl or CaCl[subscript 2], Smart Polymer Gel Tells More

    Science.gov (United States)

    Chen, Yueh-Huey; Lin, Jia-Ying; Wang, Yu-Chen; Yaung, Jing-Fun

    2010-01-01

    This classroom activity connection demonstrates the differences between the effects of NaCl (a salt of monovalent metal ions) and CaCl[subscript 2] (a salt of polyvalent metal ions) on swollen superabsorbent polymer gels. Being ionic compounds, NaCl and CaCl[subscript 2] both collapse the swollen polymer gels. The gel contracted by NaCl reswells…

  10. Radiocarbon dating and the 36Cl/Cl evolution of three Great Artesian Basin wells at Dalhousie, South Australia

    Science.gov (United States)

    Abu Risha, Usama A.

    2016-06-01

    The use of 14C (half-life = 5,730 years) in modeling the evolution of the 36Cl/Cl ratios in groundwater is reported for the first time. The complexity of the Cl-36Cl system due to the occurrence of different Cl and 36Cl sources and the difficulty of the determination of the initial groundwater 36Cl/Cl ratios have raised concerns about the reliability of using 36Cl (half-life = 301 thousand years, a) as a groundwater-dating tool. This work uses groundwater 14C age as a calibrating parameter of the Cl-36Cl/Cl decay-mixing models of three wells from the southwestern Great Artesian Basin (GAB), Australia. It aims to allow for the different sources of Cl and 36Cl in the southwestern GAB aquifer. The results show that the initial Cl concentrations range from 245 to 320 mg/l and stable Cl is added to groundwater along flowpaths at rates ranging from 1.4 to 3.5 mg/l/ka. The 36Cl content of the groundwater is assumed to be completely of atmospheric origin. The samples have different Cl-36Cl/Cl mixing-decay models reflecting recharge under different conditions as well as the heterogeneity of the aquifer.

  11. Highly efficient potentiometric glucose biosensor based on functionalized InN quantum dots

    Science.gov (United States)

    Alvi, N. H.; Soto Rodriguez, P. E. D.; Gómez, V. J.; Kumar, Praveen; Amin, G.; Nur, O.; Willander, M.; Nötzel, R.

    2012-10-01

    We present a fast, highly sensitive, and efficient potentiometric glucose biosensor based on functionalized InN quantum-dots (QDs). The InN QDs are grown by molecular beam epitaxy. The InN QDs are bio-chemically functionalized through physical adsorption of glucose oxidase (GOD). GOD enzyme-coated InN QDs based biosensor exhibits excellent linear glucose concentration dependent electrochemical response against an Ag/AgCl reference electrode over a wide logarithmic glucose concentration range (1 × 10-5 M to 1 × 10-2 M) with a high sensitivity of 80 mV/decade. It exhibits a fast response time of less than 2 s with good stability and reusability and shows negligible response to common interferents such as ascorbic acid and uric acid. The fabricated biosensor has full potential to be an attractive candidate for blood sugar concentration detection in clinical diagnoses.

  12. Phase diagrams for the binary systems NdCl3-LiCl and PrCl3-LiCl

    OpenAIRE

    Kim, I; 岡本芳浩

    1999-01-01

    NdCl3-LiCl及びPrCl3-LiClの各2成分系の相状態を、200~800circCの範囲における示差熱分析及び急冷したサンプルの室温X線回折によって調べた。NdCl3-LiCl系では、31mol%NdCl3の組成に共晶(456circC)が見られたのに加えて、包晶点(467circC)の存在が観測された。一方、PrCl3-LiCl系では同じく31mol%PrCl3の組成に共晶(464circC)が見いだされたのみで包晶の存在は確認されなかった。これらの結晶をもとに、各2成分系の状態図を作成した。...

  13. Stimulated emission and lasing from all-inorganic perovskite quantum dots

    Science.gov (United States)

    Sun, Handong; Wang, Yue; Li, Xiaoming; Haibo, Zeng

    We present superior optical gain and lasing properties in a new class of emerging quantum materials, the colloidal all-inorganic cesium lead halide perovskite quantum dots (IPQDs) (CsPbX3, X = Cl, Br, I). Our result has indicated that such material system show combined merits of both colloidal quantum dots and halide perovskites. Low-threshold and ultrastable stimulated emission was demonstrated under atmospheric condition. The flexibility and advantageous optical gain properties of these CsPbX3 IPQDs were manifested by demonstration of an optically pumped micro-laser. The nonlinear optical properties including the multi-photon absorption and resultant photoluminescence of the CsPbX3 nanocrystals were investigated. A large two-photon absorption cross-section of up to ~1.2×105 GM is determined from 9 nm-sized CsPbBr3 nanocrystals. Moreover, low-threshold frequency-upconverted stimulated emission by two-photon absorption was observed from the thin films of close-packed CsPbBr3 nanocrystals. We further realize the three-photon pumped stimulated emission in green spectra range from colloidal IPQD.

  14. Electric conductivity of PCl5-ZrCl4, PCl5-TaCl5, and PCl5-MoCl5 molten mixtures

    International Nuclear Information System (INIS)

    When mixing individual molecular melts of PCl5 with ZrCl4, TaCl5 or with MoCl5, an essential (by several orders) increase in electric conductivity (up to 0.02-0.1 Ohm-1·cm-1), which stems, in all probability, from the appearance of complex ions PCl4+, ZrCl5-, ZrCl62-, TaCl5- and MoCl6- in the molten mixtures as a result of chemical interaction

  15. Children's cancer centers

    Science.gov (United States)

    Pediatric cancer center; Pediatric oncology center; Comprehensive cancer center ... Treating childhood cancer is not the same as treating adult cancer. The cancers are different. So are the treatments and the ...

  16. Hybrid passivated colloidal quantum dot solids

    KAUST Repository

    Ip, Alex

    2012-07-29

    Colloidal quantum dot (CQD) films allow large-area solution processing and bandgap tuning through the quantum size effect. However, the high ratio of surface area to volume makes CQD films prone to high trap state densities if surfaces are imperfectly passivated, promoting recombination of charge carriers that is detrimental to device performance. Recent advances have replaced the long insulating ligands that enable colloidal stability following synthesis with shorter organic linkers or halide anions, leading to improved passivation and higher packing densities. Although this substitution has been performed using solid-state ligand exchange, a solution-based approach is preferable because it enables increased control over the balance of charges on the surface of the quantum dot, which is essential for eliminating midgap trap states. Furthermore, the solution-based approach leverages recent progress in metal:chalcogen chemistry in the liquid phase. Here, we quantify the density of midgap trap states in CQD solids and show that the performance of CQD-based photovoltaics is now limited by electrong-"hole recombination due to these states. Next, using density functional theory and optoelectronic device modelling, we show that to improve this performance it is essential to bind a suitable ligand to each potential trap site on the surface of the quantum dot. We then develop a robust hybrid passivation scheme that involves introducing halide anions during the end stages of the synthesis process, which can passivate trap sites that are inaccessible to much larger organic ligands. An organic crosslinking strategy is then used to form the film. Finally, we use our hybrid passivated CQD solid to fabricate a solar cell with a certified efficiency of 7.0%, which is a record for a CQD photovoltaic device. © 2012 Macmillan Publishers Limited. All rights reserved.

  17. Sociodemographic and clinical characteristics of a diabetic population at a primary level health care center Características sociodemográficas y clínicas de una población diabética en el nivel primario de atención a la salud Características sociodemográficas e clínicas de portadores de diabetes em um serviço de atenção básica à saúde

    OpenAIRE

    Liudmila Miyar Otero; Maria Lúcia Zanetti; Carla Regina de Souza Teixeira

    2007-01-01

    This study aimed to analyze the social-demographic, clinical and life habits characteristics of a diabetic population being treated in the primary level of a healthcare center. A total of 52 diabetic patients, enrolled, in 2006, in a Research and Extension Center linked to a University in Sao Paulo, participated in the study. The data were collected through interviews, using appropriated forms, after the patients consent. The results showed other illness associated to diabetes and an unsatisf...

  18. Reduction behavior of cerium(Ⅲ) ions in NaCl-2CsCl melt

    Institute of Scientific and Technical Information of China (English)

    QI Xue; ZHU Hongmin

    2005-01-01

    The cathodic process of cerium(Ⅲ) ions in NaCl-2CsCl melt was studied by cyclic voltammetry and square wave voltammetry with tungsten and gold electrodes at 873 K. The two electroanalytical methods yield similar results. The cathodic process of cerium(Ⅲ) ions consists of two reversible steps: Ce3+ + e-= Ce2+ and Ce2+ + 2e-= Ce. The half wave potentials of Ce3+/Ce2+ and Ce2+/Ce were determined as -2.525 V vs. Cl2/Cl- and -2.975 V vs. Cl2/Cl-, respectively. The diffusion coefficient of Ce3+ was also determined as 5.5 × 10-5 cm2·s-1.

  19. Inclusion of thiol DAB dendrimer/CdSe quantum dots based in a membrane structure: Surface and bulk membrane modification

    International Nuclear Information System (INIS)

    Highlights: ► Fluorescent nanocomposite based in CdSe quantum dots (QDs) coated by thiol polypropylenimine (DAB). ► Bulk chemical characterization by TEM and EDAX ► Inclusion of the S-DAB-CdSe QDs in a cellulosic support and its characterization by Fluorescence and XPS. ► Electrical characterization by Impedance Spectroscopy of dry and wet samples containing a heavy metal. -- Abstract: The behavior of a fluorescent nanocomposite, obtained by means of a thiol polypropylenimine dendrimer of third generation coated with CdSe quantum dots, and embedded in a hydrophilic cellulosic membrane as support is electrochemically studied in order to evaluate its applicability as a sensor in liquid media. The characterization of the nanocomposite by TEM and EDAX shows uniform nano morphology (size comprised in the range 60–90 nm) and composition, respectively. The analysis of the engineered hybrid cellulose-dendrimer quantum dots material by confocal fluorescence microscopy indicates almost mono-dispersion distribution of the nanocomposite when irradiated under UV light, while its presence on the film surface was determined by X-ray photoelectron spectroscopy. Impedance spectroscopy measurements performed with dry membrane samples show a decrease in the conductivity and dielectric constant of the modified membrane in comparison with the raw support. Electrical changes in the modified film associated to the presence of Cd(II) uptakes from a Cl2Cd solution were also obtained. These results support the possible application of this nanocomposite material as heavy metal sensor in liquid media

  20. Immobilizing water-soluble graphene quantum dots with gold nanoparticles for a low potential electrochemiluminescence immunosensor

    Science.gov (United States)

    Dong, Yongqiang; Wu, Huan; Shang, Pengxiang; Zeng, Xiaoting; Chi, Yuwu

    2015-10-01

    Hydrazide-modified graphene quantum dots (HM-GQDs) obtained by refluxing GQDs with hydrazine hydrate were hybridized with gold nanoparticles (AuNPs) through a redox reaction between HM-GQDs and AuCl4-. The obtained nano-hybrids (HM-GQD-AuNPs) possess the unique electrochemiluminescence (ECL) properties of HM-GQDs and the easy self-assembly with some bio-molecules of AuNPs, which have great potential applications in bio-sensors. HM-GQD-AuNPs were modified on a glassy carbon electrode to develop a novel ECL immunosensor of carcinoembryonic antigen (CEA) as a model target analyte. Due to the increment of electron-transfer resistance after immunoreaction, the ECL intensity decreased as the concentration of CEA was increased. The linear response range was between 0.02 and 80 ng mL-1, and the detection limit was 0.01 ng mL-1.Hydrazide-modified graphene quantum dots (HM-GQDs) obtained by refluxing GQDs with hydrazine hydrate were hybridized with gold nanoparticles (AuNPs) through a redox reaction between HM-GQDs and AuCl4-. The obtained nano-hybrids (HM-GQD-AuNPs) possess the unique electrochemiluminescence (ECL) properties of HM-GQDs and the easy self-assembly with some bio-molecules of AuNPs, which have great potential applications in bio-sensors. HM-GQD-AuNPs were modified on a glassy carbon electrode to develop a novel ECL immunosensor of carcinoembryonic antigen (CEA) as a model target analyte. Due to the increment of electron-transfer resistance after immunoreaction, the ECL intensity decreased as the concentration of CEA was increased. The linear response range was between 0.02 and 80 ng mL-1, and the detection limit was 0.01 ng mL-1. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr04328j

  1. Nonvolatile Quantum Dot Gate Memory (NVQDM): Tunneling Rate from Quantum Well Channel to Quantum Dot Gate

    Science.gov (United States)

    Hasaneen, El-Sayed; Heller, Evan; Bansal, Rajeev; Jain, Faquir

    2003-10-01

    In this paper, we compute the tunneling of electrons in a nonvolatile quantum dot memory (NVQDM) cell during the WRITE operation. The transition rate of electrons from a quantum well channel to the quantum dots forming the floating gate is calculated using a recently reported method by Chuang et al.[1]. Tunneling current is computed based on transport of electrons from the channel to the floating quantum dots. The maximum number of electrons on a dot is calculated using surface electric field and break down voltage of the tunneling dielectric material. Comparison of tunneling for silicon oxide and high-k dielectric gate insulators is also described. Capacitance-Voltage characteristics of a NVQDM device are calculated by solving the Schrodinger and Poisson equations self-consistently. In addition, the READ operation of the memory has been investigated analytically. Results for 70 nm channel length Si NVQDMs are presented. Threshold voltage is calculated including the effect of the charge on nanocrystal quantum dots. Current-voltage characteristics are obtained using BSIM3v3 model [2-3]. This work is supported by Office of Navel Research (N00014210883, Dr. D. Purdy, Program Monitor), Connecticut Innovations Inc./TranSwitch (CII # 00Y17), and National Science Foundation (CCR-0210428) grants. [1] S. L. Chuang and N. Holonyak, Appl. Phys. Lett., 80, pp. 1270, 2002. [2] Y. Chen et. al., BSIM3v3 Manual, Elect. Eng. and Comp. Dept., U. California, Berkeley, CA, 1996. [3] W. Liu, MOSFET Models for SPICE Simulation, John Wiley & Sons, Inc., 2001.

  2. Quantum dot density studies for quantum dot intermediate band solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Thomassen, Sedsel Fretheim; Zhou, Dayong; Vitelli, Stefano; Mayani, Maryam Gholami; Fimland, Bjoern-Ove; Reenaas, Turid Worren

    2010-07-01

    Quantum dots (QDs) have been an active area of research for many years and have been implemented in several applications, such as lasers and detectors. During the last years, some attempts have been made to increase the absorption and efficiency of solar cells by inserting QDs into the intrinsic region of pin solar cells. So far, these attempts have been successful in increasing the absorption, but not the cell efficiency. There are probably several reasons for this lack of efficiency increase, but we believe that one important reason is the low density of the implemented QDs. In this work, samples of single layer InAs QDs on n-GaAs(001) substrates have been grown by molecular beam epitaxy (MBE) and we have performed a systematic study of how deposition parameters affect the QD density. The aim is to achieve densities > 1011 cm-2. The nominal substrate temperature (360 - 500 deg. C), the InAs growth rate (0.085 - 1 ML/s) and thickness (2.0 - 2.8 ML) have been varied in a systematic way for two different deposition methods of InAs, i.e. continuous deposition or deposition with interruptions. In addition, we have for the continuous growth samples also varied the As-flux (0.5 - 6 centre dot10-6 torr). Scanning electron microscopy (SEM) has been the main characterization method to determine quantum dot sizes and densities, and atomic force microscopy (AFM) has been used for evaluation of the quantum dot heights. We find that the QD density increases with reduced growth temperature and that it is higher for samples grown continuously than for samples grown with growth interruptions. The homogeneity is also strongly affected by temperature, InAs deposition method and the As-flux. We have observed QD densities as high as 2.5 centre dot1011 cm-2 for the samples grown at the lowest growth temperatures. (Author)

  3. Ultra-bright alkylated graphene quantum dots

    Science.gov (United States)

    Feng, Lan; Tang, Xing-Yan; Zhong, Yun-Xin; Liu, Yue-Wen; Song, Xue-Huan; Deng, Shun-Liu; Xie, Su-Yuan; Yan, Jia-Wei; Zheng, Lan-Sun

    2014-10-01

    Highly efficient and stable photoluminescence (PL) are urgently desired for graphene quantum dots (GQDs) to facilitate their prospective applications as optical materials. Here, we report the facile and straightforward synthesis of alkylated graphene quantum dots (AGQDs) via the solvothermal reaction of propagatively alkylated graphene sheets (PAGenes). In contrast to most GQDs reported so far, the synthesized AGQDs process pH-independent and ultra-bright PL with a relative quantum yield of up to 65%. Structural and chemical composition characterization demonstrated that the synthesized AGQDs are nearly oxygen-defect-free with alkyl groups decorated on edges and basal plane, which may contribute to their greatly improved pH tolerance and high quantum efficiency. The photocatalytic performance of AGQDs-P25 nanocomposites was evaluated by the degradation of Rhodamine B under visible light. The photocatalytic rate is ca. 5.9 times higher than that of pure P25, indicating that AGQDs could harness the visible spectrum of sunlight for energy conversion or environmental therapy.Highly efficient and stable photoluminescence (PL) are urgently desired for graphene quantum dots (GQDs) to facilitate their prospective applications as optical materials. Here, we report the facile and straightforward synthesis of alkylated graphene quantum dots (AGQDs) via the solvothermal reaction of propagatively alkylated graphene sheets (PAGenes). In contrast to most GQDs reported so far, the synthesized AGQDs process pH-independent and ultra-bright PL with a relative quantum yield of up to 65%. Structural and chemical composition characterization demonstrated that the synthesized AGQDs are nearly oxygen-defect-free with alkyl groups decorated on edges and basal plane, which may contribute to their greatly improved pH tolerance and high quantum efficiency. The photocatalytic performance of AGQDs-P25 nanocomposites was evaluated by the degradation of Rhodamine B under visible light. The

  4. Quantum dot loaded immunomicelles for tumor imaging

    Directory of Open Access Journals (Sweden)

    Levchenko Tatyana

    2010-10-01

    Full Text Available Abstract Background Optical imaging is a promising method for the detection of tumors in animals, with speed and minimal invasiveness. We have previously developed a lipid coated quantum dot system that doubles the fluorescence of PEG-grafted quantum dots at half the dose. Here, we describe a tumor-targeted near infrared imaging agent composed of cancer-specific monoclonal anti-nucleosome antibody 2C5, coupled to quantum dot (QD-containing polymeric micelles, prepared from a polyethylene glycol/phosphatidylethanolamine (PEG-PE conjugate. Its production is simple and involves no special equipment. Its imaging potential is great since the fluorescence intensity in the tumor is twofold that of non-targeted QD-loaded PEG-PE micelles at one hour after injection. Methods Para-nitrophenol-containing (5% PEG-PE quantum dot micelles were produced by the thin layer method. Following hydration, 2C5 antibody was attached to the PEG-PE micelles and the QD-micelles were purified using dialysis. 4T1 breast tumors were inoculated subcutaneously in the flank of the animals. A lung pseudometastatic B16F10 melanoma model was developed using tail vein injection. The contrast agents were injected via the tail vein and mice were depilated, anesthetized and imaged on a Kodak Image Station. Images were taken at one, two, and four hours and analyzed using a methodology that produces normalized signal-to-noise data. This allowed for the comparison between different subjects and time points. For the pseudometastatic model, lungs were removed and imaged ex vivo at one and twenty four hours. Results The contrast agent signal intensity at the tumor was double that of the passively targeted QD-micelles with equally fast and sharply contrasted images. With the side views of the animals only tumor is visible, while in the dorsal view internal organs including liver and kidney are visible. Ex vivo results demonstrated that the agent detects melanoma nodes in a lung

  5. Fano-Rashba effect in quantum dots

    International Nuclear Information System (INIS)

    We consider the electronic transport through a Rashba quantum dot coupled to ferromagnetic leads. We show that the interference of localized electron states with resonant electron states leads to the appearance of the Fano-Rashba effect. This effect occurs due to the interference of bound levels of spin-polarized electrons with the continuum of electronic states with an opposite spin polarization. We investigate this Fano-Rashba effect as a function of the applied magnetic field and Rashba spin-orbit coupling

  6. Cotunneling effects in GaAs vertical double quantum dot

    OpenAIRE

    Badrutdinov, A. O.; Huang, S. M.; Kono, K; Ono, K.; Tayurskii, D. A.

    2010-01-01

    We observed lifting of Coulomb blockade in GaAs vertical double quantum dot with low potential barriers, induced by cotunneling mechanisms at dilution fridge temperature of 10 mK. Several distinct features were observed, compared to single dot case, and appropriate explanation for them was given

  7. A Multi-Chanel Speckle Imaging for the DOT

    NARCIS (Netherlands)

    Sütterlin, P.; Hammerschlag, R.H.; Bettonvil, F.C.M.; Rutten, R.J.; Skomorovsky, V.I.; Domyshev, G.N.

    2001-01-01

    The Dutch Open Telescope (DOT) had its initial observing campaighn in September 1999. Alhough only a simple video system was used, the results demonstrated the excellent high-resolution capabilities of the combination of the open-teloscope concept, the DOT optics, the remaining image degradation due

  8. High-resolution photoluminescence studies of single semiconductor quantum dots

    DEFF Research Database (Denmark)

    Leosson, Kristjan; Østergaard, John Erland; Jensen, Jacob Riis;

    2000-01-01

    Semiconductor quantum dots, especially those formed by self-organized growth, are considered a promising material system for future optical devices [1] and the optical properties of quantum dot ensembles have been investigated in detail over the past years. Recently, considerable interest has...

  9. DOE evaluation document for DOT 7A Type A packaging

    International Nuclear Information System (INIS)

    This document, DOE Evaluation Document for DOT 7A Type A Packaging, March 1987, presents approximately 100 different packagings which have been determined to meet the requirements for a DOT Spec 7A Type A packaging (49 CFR 178.350) and satisfies the requirements of 49 CFR 174.315(a) concerning the requirements for a document

  10. 49 CFR 15.15 - SSI disclosed by DOT.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 1 2010-10-01 2010-10-01 false SSI disclosed by DOT. 15.15 Section 15.15 Transportation Office of the Secretary of Transportation PROTECTION OF SENSITIVE SECURITY INFORMATION § 15.15 SSI... containing SSI are not available for public inspection or copying, nor does DOT release such records...

  11. Transport through Zero-Dimensional States in a Quantum Dot

    NARCIS (Netherlands)

    Kouwenhoven, Leo P.; Wees, Bart J. van; Harmans, Kees J.P.M.; Williamson, John G.

    1990-01-01

    We have studied the electron transport through zero-dimensional (0D) states. 0D states are formed when one-dimensional edge channels are confined in a quantum dot. The quantum dot is defined in a two-dimensional electron gas with a split gate technique. To allow electronic transport, connection to t

  12. Negative Trions Trapped by a Spherical Parabolic Quantum Dot

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    In this paper, a negatively charged exciton trapped by a spherical parabolic quantum dot has been investigated. The energy spectra of low-lying states are calculated by means of matrix diagonalization. The important feature of the low-lying states of the negatively charged excitons in a spherical quantum dot is obtained via an analysis of the energy spectra.

  13. Ultrafast gain and index dynamics in quantum dot amplifiers

    DEFF Research Database (Denmark)

    Borri, Paola; Langbein, Wolfgang; Mørk, Jesper;

    1999-01-01

    The ultrafast dynamics of gain and refractive index in an InAs/GaAs quantum dot amplifier are investigated at room temperature. The gain is observed to recover with a 90 fs time constant, ruling out problems of slow carrier capture into the dots, and making this component promising for high...

  14. Electronic properties of assemblies of zno quantum dots

    NARCIS (Netherlands)

    Roest, Aarnoud Laurens

    2003-01-01

    Electron transport in an assembly of ZnO quantum dots has been studied using an electrochemically gated transistor. The electron mobility shows a step-wise increase as a function of the electron occupation per quantum dot. When the occupation number is below two, transport occurs by tunnelling betwe

  15. Electron Transport in Quantum Dots and Heat Transport in Molecules

    DEFF Research Database (Denmark)

    Kirsanskas, Gediminas

    and to perform electrical transport experiments at temperatures below one Kelvin (1 K), and thus to address such question. In this thesis we are concerned with the theoretical description of one kind of such devices called quantum dots. As the name suggest a quantum dot is a system where particles are confined...

  16. Low temperature crystal growth and structure of ordered Ba7F12Cl2

    OpenAIRE

    Kubel, Frank; Bill, Hans; Hagemann, Hans-Rudolf

    1999-01-01

    Crystals of composition Ba[7]F[12]Cl[2] were obtained by areaction at room temperature between Ba[2+]/Cl[-]/F[-]in a gel of agar-agar/water. The hexagonal crystals have space group P6, a=1064.69(8), c=417.89(5)pm, V=410.24(8) 10[6] pm[3] and Z=l. The anions form a propeller type network located in tunnels parallel to the c[hex] axis; the chloride ions are located at the center on the propeller axes. The Ba[2+] ions are coordinated by a (distorted) tricapped trigonal environment of fluoride an...

  17. Womens Business Center

    Data.gov (United States)

    Small Business Administration — Women's Business Centers (WBCs) represent a national network of nearly 100 educational centers throughout the United States and its territories, which are designed...

  18. Characterization of the interaction between collectin 11 (CL-11, CL-K1) and nucleic acids

    DEFF Research Database (Denmark)

    Henriksen, Maiken Lumby; Brandt, Jette; Iyer, Sinduja S C;

    2013-01-01

    to changes in ionic strength and pH. Competition studies show that CL-11 binds to nucleic acids and carbohydrates via separate binding-sites and oligomericity appears crucial for binding activity. Combined interaction with DNA and mannan strongly increases binding avidity. By surface plasmon resonance we...... estimate the dissociation constant for the binding between CL-11 and double stranded DNA oligonucleotides to KD=9-20nM. In an in vitro assay we find that CL-11 binds to DNA coated surfaces, which leads to C4b deposition via MASP-2. We propose that CL-11, e.g. via complement, may play a role in response...

  19. Electrochemical Deposition of Aluminum from NaCl-AlCl3 Melts

    DEFF Research Database (Denmark)

    Li, Qingfeng; Hjuler, H. A.; Berg, Rolf W.;

    1990-01-01

    Electrochemical deposition of aluminum from NaAlCl4 melts saturated with NaCl onto a glassy carbon electrode at175°C has been studied by voltammetry, chronoamperometry, and constant current deposition. The deposition of aluminumwas found to proceed via a nucleation/growth mechanism, and the nucle......Electrochemical deposition of aluminum from NaAlCl4 melts saturated with NaCl onto a glassy carbon electrode at175°C has been studied by voltammetry, chronoamperometry, and constant current deposition. The deposition of aluminumwas found to proceed via a nucleation/growth mechanism...

  20. LUMINESCENCE OF CADMIUM SULFIDE QUANTUM DOTS IN FLUOROPHOSPHATE GLASSES

    Directory of Open Access Journals (Sweden)

    Z. O. Lipatova

    2015-03-01

    Full Text Available Cadmium sulfide quantum dots are perspective materials in optics, medicine, biology and optoelectronics. Fluorophosphate glasses, doped with cadmium sulfide quantum dots, were examined in the paper. Heat treatment led to the formation of quantum dots with diameters equal to 2.8 nm, 3.0 nm and 3.8 nm. In view of such changes in the quantum dots size the fundamental absorption edge shift and the luminescence band are being displaced to the long wavelengths. Luminescence lifetime has been found to be dependent on the registration wavelength in the range from 450 to 700 nm. Obtained fluorophosphate glasses with CdS quantum dots can find their application as fluorescent materials with intensive luminescence band and long excited-state natural lifetime.