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Sample records for diluted ii-vi oxide

  1. Degree of circular polarization in II-VI diluted magnetic semiconductor quantum dots

    NASA Astrophysics Data System (ADS)

    Rana, Shivani; Sen, Pratima; Sen, Pranay Kumar

    2012-07-01

    Degree of circular polarization (DCP) in II-VI diluted magnetic semiconductor quantum dots (QDs) has been studied analytically. Energy levels have been calculated using Luttinger-Kohn Hamiltonian and effective mass approximation. Effects due to application of externa magnetic field have been investigated, followed by calculation of transition dipole moment and DCP. Numerical estimates made for Mn-doped CdSe/ZnSe QDs show that DCP in undoped QDs is negligible while transition metal ion doping yields substantial polarization rotation (≈-2.20%) even at moderate magnetic fields (≈0.5T).

  2. Ultrafast spin dynamics in II-VI diluted magnetic semiconductors with spin-orbit interaction

    NASA Astrophysics Data System (ADS)

    Ungar, F.; Cygorek, M.; Tamborenea, P. I.; Axt, V. M.

    2015-05-01

    We study theoretically the ultrafast spin dynamics of II-VI diluted magnetic semiconductors in the presence of spin-orbit interaction. Our goal is to explore the interplay or competition between the exchange sd coupling and the spin-orbit interaction in both bulk and quantum-well systems. For bulk materials we concentrate on Zn1 -xMnxSe and take into account the Dresselhaus interaction, while for quantum wells we examine Hg1 -x -yMnxCdyTe systems with a strong Rashba coupling. Our calculations were performed with a recently developed formalism which incorporates electronic correlations beyond mean-field theory originating from the exchange sd coupling. For both bulk and quasi-two-dimensional systems we find that, by varying the system parameters within realistic ranges, either of the two interactions can be chosen to play a dominant role or they can compete on an equal footing with each other. The most notable effect of the spin-orbit interaction in both types of system is the appearance of strong oscillations where the exchange sd coupling by itself causes only an exponential decay of the mean electronic spin components. The mean-field approximation is also studied and an analytical interpretation is given as to why it shows a strong suppression of the spin-orbit-induced dephasing of the spin component parallel to the Mn magnetic field.

  3. Diluted II-VI oxide semiconductors with multiple band gaps.

    PubMed

    Yu, K M; Walukiewicz, W; Wu, J; Shan, W; Beeman, J W; Scarpulla, M A; Dubon, O D; Becla, P

    2003-12-12

    We report the realization of a new mult-band-gap semiconductor. Zn(1-y)Mn(y)OxTe1-x alloys have been synthesized using the combination of oxygen ion implantation and pulsed laser melting. Incorporation of small quantities of isovalent oxygen leads to the formation of a narrow, oxygen-derived band of extended states located within the band gap of the Zn(1-y)Mn(y)Te host. When only 1.3% of Te atoms are replaced with oxygen in a Zn0.88Mn0.12Te crystal the resulting band structure consists of two direct band gaps with interband transitions at approximately 1.77 and 2.7 eV. This remarkable modification of the band structure is well described by the band anticrossing model. With multiple band gaps that fall within the solar energy spectrum, Zn(1-y)Mn(y)OxTe1-x is a material perfectly satisfying the conditions for single-junction photovoltaics with the potential for power conversion efficiencies surpassing 50%.

  4. Materials and device design with III-V and II-VI compound-based diluted magnetic semiconductors

    NASA Astrophysics Data System (ADS)

    Katayama-Yoshida, Hiroshi; Sato, Kazunori

    2002-03-01

    Since the discovery of the carrier induced ferromagnetism in (In, Mn)As and (Ga, Mn)As, diluted magnetic semiconductors (DMS) have been of much interest from the industrial viewpoint because of their potentiality as a new functional material (spintronics). In this paper, the magnetism in DMS is investigated based on the first principles calculations, and materials and device design with the DMS is proposed toward the spintronics. The electronic structure is calculated by the Korringa-Kohn-Rostoker method combined with the coherent potential approximation based on the local spin density approximation. We calculate the electronic structure of ferromagnetic and spin-glass DMS, and total energy difference between them is calculated to estimate whether the ferromagnetic state is stable or not. It is shown that V-, Cr- and Mn-doped III-V compounds, V- and Cr-doped II-VI compounds and Fe-, Co- and Ni-doped ZnO are promising candidates for a high-Curie temperature ferromagnet. A chemical trend in the ferromagnetism is well understood based on the double exchange mechanism [1]. Based upon this material design, some prototypes of the spintronics devices, such as a spin-FET, a photo-induced-magnetic memory and a coherent-spin-infection device, are proposed. [1] K. Sato and H. Katayama-Yoshida, Jpn. J. Appl. Phys. 39 (2000) L555, 40 (2001) L334, L485 and L651.

  5. Isocrystalline core/shell synthesis of high quality II-VI diluted magnetic semiconductor quantum dots: ligand-field spectroscopic studies

    NASA Astrophysics Data System (ADS)

    Radovanovic, Pavle V.; Gamelin, Daniel R.

    2002-11-01

    Ligand field electronic absorption spectroscopy has been applied as a direct probe of Co2+ dopant ions in II-VI based diluted magnetic semiconductor quantum dots. Synthesis of Co2+-doped CdS (Co2+:CdS) quantum dots by simple coprecipitation in inverted micelle solutions has been found to yield predominantly surface bound dopant ions, which are unstable with respect to solvation in a coordinating solvent (pyridine). The solvation kinetics are biphasic, involving two transient intermediates. In contrast, Co2+ ions are doped much more isotropically in ZnS QDs, and this difference is attributed to the similar ionic radii of Co2+ and Zn2+ ions (0.74 Å), as opposed to Cd2+ ions (0.97 Å). We have developed an isocrystalline core/shell synthetic methodology that enables us to synthesize high quality internally doped Co2+:CdS quantum dots. The effect of Co2+ binding on the surface energies of CdS and ZnS quantum dots is discussed and related to the growth mechanism of diluted magnetic semiconductor quantum dots.

  6. Carrier-impurity spin transfer dynamics in paramagnetic II-VI diluted magnetic semiconductors in the presence of a wave-vector-dependent magnetic field

    NASA Astrophysics Data System (ADS)

    Cygorek, M.; Tamborenea, P. I.; Axt, V. M.

    2016-05-01

    Quantum kinetic equations of motion for carrier and impurity spins in paramagnetic II-VI diluted magnetic semiconductors in a k -dependent effective magnetic field are derived, where the carrier-impurity correlations are taken into account. In the Markov limit, rates for the electron-impurity spin transfer can be derived for electron spins parallel and perpendicular to the impurity spins corresponding to measurable decay rates in Kerr experiments in Faraday and Voigt geometry. Our rigorous microscopic quantum kinetic treatment automatically accounts for the fact that, in an individual spin flip-flop scattering process, a spin flip of an electron is necessarily accompanied by a flop of an impurity spin in the opposite direction and the corresponding change of the impurity Zeeman energy influences the final energy of the electron after the scattering event. This shift in the electron energies after a spin flip-flop scattering process, which usually has been overlooked in the literature, turns out to be especially important in the case of extremely diluted magnetic semiconductors in an external magnetic field. As a specific example for a k -dependent effective magnetic field the effects of a Rashba field on the dynamics of the carrier-impurity correlations in a Hg1 -x -yCdyMnxTe quantum well are described. It is found that, although accounting for the Rashba interaction in the dynamics of the correlations leads to a modified k -space dynamics, the time evolution of the total carrier spin is not significantly influenced. Furthermore, a connection between the present theory and the description of collective carrier-impurity precession modes is presented.

  7. Electron-beam-enhanced oxidation processes in II-VI compound semiconductors observed by high-resolution electron microscopy

    SciTech Connect

    Thangaraj, N.; Wessels, B.W.

    1990-02-01

    Enhanced oxidation of ZnS and ZnSe semiconductor surfaces has been observed in situ during electron irradiation in a high-resolution electron microscope. The phase present at the surface region has been identified as ZnO by optical diffractogram and selected area electron diffraction techniques. For ZnS oxidation, both hexagonal ZnO having a random orientation and cubic ZnO in perfect epitaxial relationship with the bulk ZnS were observed. Enhanced oxidation of ZnSe to ZnO has also been observed under electron beam irradiation. However, only the hexagonal form was observed. The oxidation rates for both ZnS and ZnSe depended on electron flux but was independent of orientation. A model in which the oxidation process is limited by diffusion through the oxide film is proposed. By electron irradiation the diffusion rate is enhanced presumably by a nonthermal process.

  8. Monolayer II-VI semiconductors: A first-principles prediction

    NASA Astrophysics Data System (ADS)

    Zheng, Hui; Li, Xian-Bin; Chen, Nian-Ke; Xie, Sheng-Yi; Tian, Wei Quan; Chen, Yuanping; Xia, Hong; Zhang, S. B.; Sun, Hong-Bo

    2015-09-01

    A systematic study of 32 honeycomb monolayer II-VI semiconductors is carried out by first-principles methods. While none of the two-dimensional (2D) structures can be energetically stable, it appears that BeO, MgO, CaO, ZnO, CdO, CaS, SrS, SrSe, BaTe, and HgTe honeycomb monolayers have a good dynamic stability. The stability of the five oxides is consistent with the work published by Zhuang et al. [Appl. Phys. Lett. 103, 212102 (2013), 10.1063/1.4831972]. The rest of the compounds in the form of honeycomb are dynamically unstable, revealed by phonon calculations. In addition, according to the molecular dynamic (MD) simulation evolution from these unstable candidates, we also find two extra monolayers dynamically stable, which are tetragonal BaS [P 4 /n m m (129 ) ] and orthorhombic HgS [P 21/m (11 ) ] . The honeycomb monolayers exist in the form of either a planar perfect honeycomb or a low-buckled 2D layer, all of which possess a band gap and most of them are in the ultraviolet region. Interestingly, the dynamically stable SrSe has a gap near visible light, and displays exotic electronic properties with a flat top of the valence band, and hence has a strong spin polarization upon hole doping. The honeycomb HgTe has recently been reported to achieve a topological nontrivial phase under appropriate in-plane tensile strain and spin-orbital coupling (SOC) [J. Li et al., arXiv:1412.2528]. Some II-VI partners with less than 5 % lattice mismatch may be used to design novel 2D heterojunction devices. If synthesized, potential applications of these 2D II-VI families could include optoelectronics, spintronics, and strong correlated electronics.

  9. II-VI nanowire radial heterostructures

    NASA Astrophysics Data System (ADS)

    Kahen, K. B.; Goldthorpe, Irene A.; Holland, M.

    2013-11-01

    There are many reports of ZnSe nanowire synthesis, but photoluminescence measurements on these nanowires indicate weak band-edge and high sub-bandgap defect emission. The two main contributors to the non-optimal photoluminescence are nanowire growth at high temperatures and unpassivated surface states. In this paper, the synthesis of II-VI core-shell nanowires by metal organic vapor phase epitaxy is reported. We demonstrate that larger bandgap shells that passivate the nanowire surface states can be deposited around the nanowires by increasing the partial pressures of the shell reactants without a large increase in growth temperature, allowing high quality material to be obtained. The deposition of nearly lattice-matched ZnMgSSe shells on the ZnSe nanowires increases the band-edge luminescent intensity of the ZnSe nanowires by more than four orders of magnitude and improves the band-edge to defect photoluminescence intensity ratio to 12 000:1. The corresponding full widths at half maximum of the band-edge exciton peaks of the core-shell nanowires can be as narrow as 2.8 nm. It is also shown that magnesium and chlorine can be incorporated into the ZnSe nanowire cores, which shortens the emission wavelength and is known to act as an n-type dopant, respectively.

  10. Chemistry of the Colloidal Group II-VI Nanocrystal Synthesis

    SciTech Connect

    Liu, Haitao

    2007-05-17

    In the last two decades, the field of nanoscience andnanotechnology has witnessed tremendous advancement in the synthesis andapplication of group II-VI colloidal nanocrystals. The synthesis based onhigh temperature decomposition of organometallic precursors has becomeone of the most successful methods of making group II-VI colloidalnanocrystals. This methodis first demonstrated by Bawendi and coworkersin 1993 to prepare cadmium chalcogenide colloidal quantum dots and laterextended by others to prepare other group II-VI quantum dots as well asanisotropic shaped colloidal nanocrystals, such as nanorod and tetrapod.This dissertation focuses on the chemistry of this type of nanocrystalsynthesis. The synthesis of group II-VI nanocrystals was studied bycharacterizing the molecular structures of the precursors and productsand following their time evolution in the synthesis. Based on theseresults, a mechanism was proposed to account for the 2 reaction betweenthe precursors that presumably produces monomer for the growth ofnanocrystals. Theoretical study based on density functional theorycalculations revealed the detailed free energy landscape of the precursordecomposition and monomerformation pathway. Based on the proposedreaction mechanism, a new synthetic method was designed that uses wateras a novel reagent to control the diameter and the aspect ratio of CdSeand CdS nanorods.

  11. Chemistry of the Colloidal Group II-VI Nanocrystal Synthesis

    SciTech Connect

    Liu, Haitao

    2007-05-17

    In the last two decades, the field of nanoscience andnanotechnology has witnessed tremendous advancement in the synthesis andapplication of group II-VI colloidal nanocrystals. The synthesis based onhigh temperature decomposition of organometallic precursors has becomeone of the most successful methods of making group II-VI colloidalnanocrystals. This method is first demonstrated by Bawendi and coworkersin 1993 to prepare cadmium chalcogenide colloidal quantum dots and laterextended by others to prepare other group II-VI quantum dots as well asanisotropic shaped colloidal nanocrystals, such as nanorod and tetrapod.This dissertation focuses on the chemistry of this type of nanocrystalsynthesis. The synthesis of group II-VI nanocrystals was studied bycharacterizing the molecular structures of the precursors and productsand following their time evolution in the synthesis. Based on theseresults, a mechanism was proposed to account for the 2 reaction betweenthe precursors that presumably produces monomer for the growth ofnanocrystals. Theoretical study based on density functional theorycalculations revealed the detailed free energy landscape of the precursordecomposition and monomerformation pathway. Based on the proposedreaction mechanism, a new synthetic method was designed that uses wateras a novel reagent to control the diameter and the aspect ratio of CdSeand CdS nanorods.

  12. Recent Progress in Photocatalysis Mediated by Colloidal II-VI Nanocrystals.

    PubMed

    Wilker, Molly B; Schnitzenbaumer, Kyle J; Dukovic, Gordana

    2012-12-01

    The use of photoexcited electrons and holes in semiconductor nanocrystals as reduction and oxidation reagents is an intriguing way of harvesting photon energy to drive chemical reactions. This review focuses on recent research efforts to understand and control the photocatalytic processes mediated by colloidal II-VI nanocrystalline materials, such as cadmium and zinc chalcogenides. First, we highlight how nanocrystal properties govern the rates and efficiencies of charge-transfer processes relevant to photocatalysis. We then describe the use of nanocrystal catalyst heterostructures for fuel-forming reactions, most commonly H2 generation. Finally, we review the use of nanocrystal photocatalysis as a synthetic tool for metal-semiconductor nano-heterostructures.

  13. Taming excitons in II-VI semiconductor nanowires and nanobelts

    NASA Astrophysics Data System (ADS)

    Xu, Xinlong; Zhang, Qing; Zhang, Jun; Zhou, Yixuan; Xiong, Qihua

    2014-10-01

    Excitons are one of the most important fundamental quasi-particles, and are involved in a variety of processes forming the basis of a wide range of opto-electronic and photonic devices based on II-VI semiconductor nanowires and nanobelts, such as light-emitting diodes, photovoltaic cells, photodetectors and nanolasers. A clear understanding of their properties and unveiling the potential engineering for excitons is of particular importance for the design and optimization of nanoscale opto-electronic and photonic devices. Herein, we present a comprehensive review on discussing the fundamental behaviours of the excitons in one-dimensional (1D) II-VI semiconductor nanomaterials (nanowires and nanobelts). We will start with a focus on the unique properties (origin, generation, etc) and dynamics of excitons and exciton complexes in the II-VI semiconductor nanowires and nanobelts. Then we move to the recent progress on the excitonic response in 1D nanomaterials and focus on the tailoring and engineering of excitonic properties through rational controlling of the physical parameters and conditions, intrinsically and extrinsically. These include (1) exciton-exciton interaction, which is important for 1D nanomaterial nanolasing; (2) exciton-phonon interaction, which has interesting applications for laser cooling; and (3) exciton-plasmon interaction, which is the cornerstone towards the realization of plasmonic lasers. The potential of electric field, morphology and size control for excitonic properties is also discussed. Unveiling and controlling excitonic properties in II-VI semiconductor nanowires and nanobelts would promote the development of 1D nanoscience and nanotechnology.

  14. Electronic Structure of II-Vi Semiconductors and Their Alloys

    NASA Astrophysics Data System (ADS)

    Wei, Su-Huai

    The II-VI semiconductors ZnXVI, CdXVI, and HgXVI are known to have a metal d band inside the main valence band. Using all-electron self-consistent electronic structure techniques, we study their effects on valence properties. For II-VI semiconductors, we find that p-d repulsion and hybridization (i) lower the band gaps, (ii) alter the sign of the crystal-field splitting, (iii) reduce the spin-orbit splitting, (iv) change the valence band offset between common-anion semiconductors, and (v) increase the equilibrium lattice parameters, p-d repulsion is also shown to be responsible for the anomalously small band gaps in chalcopyrites, and for the negative exchange splitting in MnTe. We also study the electronic structure of ordered and random II-VI substitutional alloys and identify the mechanism for their band gap narrowing. The random {A_{1-x}^{II}B_{x}^{II}C^{VI}} alloys are represented by the "special quasirandom structures." We show how chemical and structural perturbations lead to (i) distinct A-like and B-like features in the density of states and (ii) different C-like features associated with fluctuations in the local environments around the common sublattice.

  15. Electron Paramagnetic Resonance in II-Vi Semiconductor Heterostructures

    NASA Astrophysics Data System (ADS)

    Yang, Gui-Lin

    This dissertation is devoted to investigation of the electron paramagnetic resonance (EPR) of Mn ^{++} ions in II-VI semiconductor heterostructures, in order to determine how EPR is affected by this layered environment and what new information can be extracted by this technique. We first introduce the concept of the effective spin, and we review the theoretical background of the spin Hamiltonian, for describing the ground state of a paramagnetic ion in a solid. The physical origin of the constituent terms in the spin Hamiltonion are discussed, and their characteristics described, for use at later stages in the thesis. We then analyze the effect on EPR of the potential exchange interaction between the localized d-electrons of the Mn^{++} ions and the band electrons. We predict that such exchange interaction can lead to significant changes in the g-factors of Mn ^{++} ions due to the spin polarization of band electrons, resulting in line shifts of EPR spectra. Although such shifts would be too small to be observed for Mn^{++} ions introduced into bulk semiconductors, we show that the shifts can be significantly larger for Mn^ {++} ions in quantum wells, superlattices, and similar heterostructures, due to the electron confinement effect. This effect of the potential exchange interaction on the EPR spectra of Mn^{++} ions leads us to propose to use the Mn ^{++} ions as built-in localized probes for mapping the wave functions of electronic states in II-VI semiconductor quantum wells and superlattices. We then consider the influence of internal strain on the EPR transitions of Mn^{++} in II-VI semiconductor heterostructures. Our analysis of the changes of the Mn^{++} fine structure indicates that EPR can be used to detect even minute amounts of strain (e.g., strain resulting from as little as 0.01% lattice mismatch can readily be measured). Accordingly, we demonstrate EPR to be an ultrasensitive and probably unique tool for small strain measurements in II-VI

  16. Large area radiation detectors based on II VI thin films

    NASA Astrophysics Data System (ADS)

    Quevedo-Lopez, Manuel

    2015-03-01

    The development of low temperature device technologies that have enabled flexible displays also present opportunities for flexible electronics and flexible integrated systems. Of particular interest are possible applications in flexible, low metal content, sensor systems for unattended ground sensors, smart medical bandages, electronic ID tags for geo-location, conformal antennas, neutron/gamma-ray/x-ray detectors, etc. In this talk, our efforts to develop novel CMOS integration schemes, circuits, memory, sensors as well as novel contacts, dielectrics and semiconductors for flexible electronics are presented. In particular, in this presentation we discuss fundamental materials properties including crystalline structure, interfacial reactions, doping, etc. defining performance and reliability of II-VI-based radiation sensors. We investigate the optimal thickness of a semiconductor diode for thin-film solid state thermal neutron detectors. Besides II-VI materials, we also evaluated several diode materials, Si, CdTe,GaAs, C (diamond), and ZnO, and two neutron converter materials,10B and 6LiF. We determine the minimum semiconductor thickness needed to achieve maximum neutron detection efficiency. By keeping the semiconductor thickness to a minimum, gamma rejection is kept as high as possible. In this way, we optimize detector performance for different thin-film semiconductor materials.

  17. Recent Progress in Photocatalysis Mediated by Colloidal II-VI Nanocrystals

    PubMed Central

    Wilker, Molly B; Schnitzenbaumer, Kyle J; Dukovic, Gordana

    2012-01-01

    The use of photoexcited electrons and holes in semiconductor nanocrystals as reduction and oxidation reagents is an intriguing way of harvesting photon energy to drive chemical reactions. This review focuses on recent research efforts to understand and control the photocatalytic processes mediated by colloidal II-VI nanocrystalline materials, such as cadmium and zinc chalcogenides. First, we highlight how nanocrystal properties govern the rates and efficiencies of charge-transfer processes relevant to photocatalysis. We then describe the use of nanocrystal catalyst heterostructures for fuel-forming reactions, most commonly H2 generation. Finally, we review the use of nanocrystal photocatalysis as a synthetic tool for metal–semiconductor nano-heterostructures. PMID:24115781

  18. Ballistic transport in II-VI semiconductor compounds and alloys

    NASA Technical Reports Server (NTRS)

    Berding, M. A.; Krishnamurthy, S.; Sher, A.; Chen, A.-B.

    1988-01-01

    Realistic band structures are used in calculating the group velocity and scattering rates for electrons with injection energies up to 1 eV in ZnTe, CdTe, and the low-effective-mass alloy Hg(0.7)Cd(0.3)Te. Scattering from longitudinal optical phonons, ionized impurities, and alloy disorder have been included in the full band-structure calculation, which automatically includes both intra- and intervalley scattering. Of the II-VI materials considered, at 77 K HgCdTe is superior for low injection energies (up to 0.25 eV) while CdTe is superior at higher injection energies (1 eV) at room temperature. The attainable mean free paths (equal to or greater than 1000 A) and group velocities (equal to or greater than 10 to the 8th cm/s) for both systems are comparable to values found in III-V systems.

  19. Magnetization and Hysteresis of Dilute Magnetic-Oxide Nanoparticles

    NASA Astrophysics Data System (ADS)

    Skomski, Ralph; Balamurugan, B.; Sellmyer, D. J.

    2014-03-01

    Real-structure imperfections in dilute magnetic oxides tend to create small concentrations of local magnetic moments that are coupled by fairly long-range exchange interactions, mediated by p-electrons. The robustness of these interactions is caused by the strong overlap of the p orbitals, as contrasted to the much weaker interatomic exchange involving iron-series 3d electrons. The net exchange between defect moments can be positive or negative, which gives rise to spin structures with very small net moments. Similarly, the moments exhibit magnetocrystalline anisotropy, reinforced by electron hopping to and from 3d states and generally undergoing some random-anuisotropy averaging. Since the coercivity scales as 2K1/M and M is small, this creates pronounced and -- in thin films -- strongly anisotropic hysteresis loops. In finite systems with N moments, both K1 and M are reduced by a factor of order N1/2 due to random anisotropy and moment compensation, respectively, so that that typical coercivities are comparable to bulk magnets. Thermal activation readily randomizes the net moment of small oxide particles, so that the moment is easier to measure in compacted or aggregated particle ensembles. This research is supported by DOE (BES).

  20. II-VI wide band gap semiconductors under hydrostatic pressure

    NASA Astrophysics Data System (ADS)

    Baquero, R.; Decoss, R.; Olguin, D.

    1993-08-01

    We set an analytical expression for the gap as a function of hydrostatic deformation, E(sub g)(epsilon), by diagonalizing in Gamma the corresponding empirical tight-binding Hamiltonian (ETBH). In the ETBH we use the well known d(exp -2) Harrison scaling law (HSL) to adjust the TB parameter (TBP) to the changes in interatomic distances. We do not consider cation-anion charge transfer. We calculate E(sub g)(epsilon) for wide band gap II-VI semiconductors with zincblende crystal structure for deformations under pressure up to -5 percent. Results are in good agreement with experiment for the compounds of lower ionicity but deviate as the ionicity of the compound increases. This is due to the neglect of charge transfer which should be included self-consistently. Within the approximation we always find a positive second derivative of E(sub g)(epsilon) with respect to epsilon, independent of the material. Furthermore, the inclusion of deviations from HSL appear to be unimportant to this problem.

  1. Multi-crystalline II-VI based multijunction solar cells and modules

    SciTech Connect

    Hardin, Brian E.; Connor, Stephen T.; Groves, James R.; Peters, Craig H.

    2015-06-30

    Multi-crystalline group II-VI solar cells and methods for fabrication of same are disclosed herein. A multi-crystalline group II-VI solar cell includes a first photovoltaic sub-cell comprising silicon, a tunnel junction, and a multi-crystalline second photovoltaic sub-cell. A plurality of the multi-crystalline group II-VI solar cells can be interconnected to form low cost, high throughput flat panel, low light concentration, and/or medium light concentration photovoltaic modules or devices.

  2. Equilibrium composition in II?VI telluride MOCVD systems

    NASA Astrophysics Data System (ADS)

    Ben-Dor, L.; Greenberg, J. H.

    1999-03-01

    Thermodynamic calculations, or computer simulation of the equilibrium composition, offer an excellent possibility to reduce drastically the elaborate trial-and-error experimental efforts of finding the optimal preparation conditions for MOCVD processes (temperature T, pressure P, initial composition of the vapors X), to limit them only to the P- T- X field of existence of the solid to be prepared and an acceptable yield of the product. In this communication equilibrium composition was investigated for MOCVD processes of CdTe, ZnTe, HgTe and solid solutions Cd xZn 1- xTe and Hg xCd 1- xTe. A number of volatile organometallic compounds have been used as precursors for MOCVD growth. These are dimethylcadmium (CH 3) 2Cd, DMCd; diethylzinc (C 2H 5) 2Zn, DEZn; diisopropylzinc [CH(CH 3) 2] 2Zn, DiPZn; diethyltellurium (C 2H 5) 2Te, DETe; diisopropyltellurium [CH(CH 3) 2] 2Te, DiPTe; methylallyltellurium CH 3TeCH 2CHCH 2, MATe. A choice of the particular combination of the precursors largely depends on the desired composition of the film to be prepared, especially in cases of solid solutions Cd xZn 1- xTe and Hg xCd 1- xTe where the vapor pressure of the precursors is instrumental for the composition of the vapor in the reaction zone and, ultimately, for the composition x of the solid solution. Equilibrium composition for II-VI telluride MOCVD systems was investigated at temperatures up to 873 K in hydrogen and inert gas atmospheres at pressures up to 1 atm. P- T- X regions of existence were outlined for each of the five materials.

  3. Quantum Dot Channel (QDC) FETs with Wraparound II-VI Gate Insulators: Numerical Simulations

    NASA Astrophysics Data System (ADS)

    Jain, F.; Lingalugari, M.; Kondo, J.; Mirdha, P.; Suarez, E.; Chandy, J.; Heller, E.

    2016-11-01

    This paper presents simulations predicting the feasibility of 9-nm wraparound quantum dot channel (QDC) field-effect transistors (FETs). In particular, II-VI lattice-matched layers which reduce the density of interface states, serving as top (tunnel gate), side, and bottom gate insulators, have been simulated. Quantum simulations show FET operation with voltage swing of ~0.2 V. Incorporation of cladded quantum dots, such as SiO x -Si and GeO x -Ge, under the gate tunnel oxide results in electrical transport in one or more quantum dot layers which form a quantum dot superlattice (QDSL). Long-channel QDC FETs have experimental multistate drain current ( I D)-gate voltage ( V G) and drain current ( I D)-drain voltage ( V D) characteristics, which can be attributed to the manifestation of extremely narrow energy minibands formed in the QDSL. An approach for modeling the multistate I D- V G characteristics is reported. The multistate characteristics of QDC FETs permit design of compact two-bit multivalued logic circuits.

  4. Four-State Sub-12-nm FETs Employing Lattice-Matched II-VI Barrier Layers

    NASA Astrophysics Data System (ADS)

    Jain, F.; Chan, P.-Y.; Suarez, E.; Lingalugari, M.; Kondo, J.; Gogna, P.; Miller, B.; Chandy, J.; Heller, E.

    2013-11-01

    Three-state behavior has been demonstrated in Si and InGaAs field-effect transistors (FETs) when two layers of cladded quantum dots (QDs), such as SiO x -cladded Si or GeO x -cladded Ge, are assembled on the thin tunnel gate insulator. This paper describes FET structures that have the potential to exhibit four states. These structures include: (1) quantum dot gate (QDG) FETs with dissimilar dot layers, (2) quantum dot channel (QDC) with and without QDG layers, (3) spatial wavefunction switched (SWS) FETs with multiple coupled quantum well channels, and (4) hybrid SWS-QDC structures having multiple drains/sources. Four-state FETs enable compact low-power novel multivalued logic and two-bit memory architectures. Furthermore, we show that the performance of these FETs can be enhanced by the incorporation of II-VI nearly lattice-matched layers in place of gate oxides and quantum well/dot barriers or claddings. Lattice-matched high-energy gap layers cause reduction in interface state density and control of threshold voltage variability, while providing a higher dielectric constant than SiO2. Simulations involving self-consistent solutions of the Poisson and Schrödinger equations, and transfer probability rate from channel (well or dot layer) to gate (QD layer) are used to design sub-12-nm FETs, which will aid the design of multibit logic and memory cells.

  5. Quantum Dot Channel (QDC) FETs with Wraparound II-VI Gate Insulators: Numerical Simulations

    NASA Astrophysics Data System (ADS)

    Jain, F.; Lingalugari, M.; Kondo, J.; Mirdha, P.; Suarez, E.; Chandy, J.; Heller, E.

    2016-08-01

    This paper presents simulations predicting the feasibility of 9-nm wraparound quantum dot channel (QDC) field-effect transistors (FETs). In particular, II-VI lattice-matched layers which reduce the density of interface states, serving as top (tunnel gate), side, and bottom gate insulators, have been simulated. Quantum simulations show FET operation with voltage swing of ~0.2 V. Incorporation of cladded quantum dots, such as SiO x -Si and GeO x -Ge, under the gate tunnel oxide results in electrical transport in one or more quantum dot layers which form a quantum dot superlattice (QDSL). Long-channel QDC FETs have experimental multistate drain current (I D)-gate voltage (V G) and drain current (I D)-drain voltage (V D) characteristics, which can be attributed to the manifestation of extremely narrow energy minibands formed in the QDSL. An approach for modeling the multistate I D-V G characteristics is reported. The multistate characteristics of QDC FETs permit design of compact two-bit multivalued logic circuits.

  6. Jet fuel deposition and oxidation: Dilution, materials, oxygen, and temperature effects

    SciTech Connect

    Zabarnick, S.; Zelesnik, P.; Grinstead, R.R.

    1996-04-01

    Quartz crystal microbalance (QCM) and pressure measurements are used for determination of jet fuel thermal stability in a batch reactor. The QCM is able to monitor extremely small amounts of deposition in situ, while the pressure measurements provide qualitative data on the oxidation process. The dependence of the deposition amount was monitored as a function of the oxygen availability for two fuels. Also, the effect of QCM electrode materials was investigated. Deposition and oxidation were compared for the following electrode materials: gold, aluminum, silver, and platinum. The authors also studied the effect of dilution on oxidation and deposition. Jet fuel was diluted with increasing amounts of hydrocarbon solvent. It was observed that this dilution procedure can help characterize a fuel`s effective antioxidant concentration. Fuel dilution is also shown to be a good technique for improving thermal stability characteristics of poor fuels. Additionally they have studied the temperature effect on deposition for two fuels over the range 140 to 180 C.

  7. Study of the Local Structure of II-Vi Ternary Alloys by Extended X-Ray Absorption Fine Structure

    NASA Astrophysics Data System (ADS)

    Pong, Way-Faung

    Bondlengths, Debye-Waller factors, and site occupancy in the diluted magnetic semiconductors Zn_ {rm 1 - x}Mn_{ rm x}Se and Hg_{ rm 1 - x}Mn_{rm x}Te, and the narrow-gap semiconductor Hg _{rm 1 - x}Cd _{rm x}Te have been measured using extended x-ray absorption fine structure (EXAFS). The nearest-neighbor bond lengths in all of these alloys are found to be constant as a function of alloy composition within the experimental uncertainty of 0.01A. Because the average cation-cation distance changes with Mn composition, these results necessarily imply distortion of the tetrahedral bond angles. In the case of Zn_{rm 1 - x}Mn_{rm x} Se, the anion sublattice is shown to suffer the largest distortion, but the cation sublattice also exhibits some relaxation. The repercussions of these results are discussed, in terms of the amount of cation and anion sublattice distortion at low temperature and its connection to the superexchange mechanism occurring between the Mn ^{+2} ions and mediated by the intervening anion in Zn_{rm 1 - x}Mn_{rm x} Se. From the NN bond length relaxation results shown in this study and those reported elsewhere for the III -V-based and II-VI-based ternary compounds and DMS alloys, it appears that substitution of Mn^{+2 } ions into II-VI-based compounds causes greater local distortion, in general, than otherwise observed when group II cations are substituted for one another. We believe that the tetrahedral bond weakening in DMS is due to MN 3d-orbital (t_2) and anion p-orbital hybridization in DMS, leaving fewer p-orbitals available for tetrahedral bonding. This leads to the weakening of the bond force constants alpha, beta, as well as the bond becoming more ionic as Mn^{+2} is substituted into the II-VI-based compounds. Finally, the experimentally extended electron energy loss fine structure (EXELFS) technique, with modulations in the differential inelastic electron scattering cross -section above an absorption core edge, has been used in recent years to

  8. Photophysical Properties of II-VI Semiconductor Nanocrystals

    NASA Astrophysics Data System (ADS)

    Gong, Ke

    As it is well known, semiconductor nanocrystals (also called quantum dots, QDs) are being actively pursued for use in many different types of luminescent optical materials. These materials include the active media for luminescence downconversion in artificial lighting, lasers, luminescent solar concentrators and many other applications. Chapter 1 gives general introduction of QDs, which describe the basic physical properties and optical properties. Based on the experimental spectroscopic study, a semiquantitative method-effective mass model is employed to give theoretical prediction and guide. The following chapters will talks about several topics respectively. A predictive understanding of the radiative lifetimes is therefore a starting point for the understanding of the use of QDs for these applications. Absorption intensities and radiative lifetimes are fundamental properties of any luminescent material. Meantime, achievement of high efficiency with high working temperature and heterostructure fabrication with manipulation of lattice strain are not easy and need systematic investigation. To make accurate connections between extinction coefficients and radiative recombination rates, chapter 2 will consider three closely related aspects of the size dependent spectroscopy of II-VI QDs. First, it will consider the existing literature on cadmium selenide (CdSe) QD absorption spectra and extinction coefficients. From these results and fine structure considerations Boltzmann weighted radiative lifetimes are calculated. These lifetimes are compared to values measured on very high quality CdSe and CdSe coated with zinc selenide (ZnSe) shells. Second, analogous literature data are analyzed for cadmium telluride (CdTe) nanocrystals and compared to lifetimes measured for very high quality QDs. Furthermore, studies of the absorption and excitation spectra and measured radiative lifetimes for CdTe/CdSe Type-II core/shell QDs are reported. These results are also analyzed in

  9. Spectroscopic characterization of iron-doped II-VI compounds for laser applications

    NASA Astrophysics Data System (ADS)

    Martinez, Alan

    The middle Infrared (mid-IR) region of the electromagnetic spectrum between 2 and 15 ?m has many features which are of interest to a variety of fields such as molecular spectroscopy, biomedical applications, industrial process control, oil prospecting, free-space communication and defense-related applications. Because of this, there is a demand for broadly tunable, laser sources operating over this spectral region which can be easily and inexpensively produced. II-VI semiconductor materials doped with transition metals (TM) such as Co 2+, Cr2+, or Fe2+ exhibit highly favorable spectroscopic characteristics for mid-IR laser applications. Among these TM dopants, Fe2+ has absorption and emission which extend the farthest into the longer wavelength portion of the mid-IR. Fe2+:II-VI crystals have been utilized as gain elements in laser systems broadly tunable over the 3-5.5 microm range [1] and as saturable absorbers to Q -switch [2] and mode-lock [3] laser cavities operating over the 2.7-3 microm. TM:II-VI laser gain elements can be fabricated inexpensively by means of post-growth thermal diffusion with large homogeneous dopant concentration and good optical quality[4,5]. The work outlined in this dissertation will focus on the spectroscopic characterization of TM-doped II-VI semiconductors. This work can be categorized into three major thrusts: 1) the development of novel laser materials, 2) improving and extending applications of TM:II-VI crystals as saturable absorbers, and 3) fabrication of laser active bulk crystals. Because current laser sources based on TM:II-VI materials do not cover the entire mid-IR spectral region, it is necessary to explore novel laser sources to extend available emissions toward longer wavelengths. The first objective of this dissertation is the spectroscopic characterization of novel ternary host crystals doped with Fe2+ ions. Using crystal field engineering, laser materials can be prepared with emissions placed in spectral regions not

  10. 77 FR 21586 - II-VI, Incorporated, Infrared Optics-Saxonburg Division, Saxonburg, PA; Notice of Affirmative...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-04-10

    ... was published in the Federal Register on February 14, 2012 (77 FR 8281). The workers were engaged in... Employment and Training Administration II-VI, Incorporated, Infrared Optics--Saxonburg Division, Saxonburg... former workers of II-VI, Incorporated, Infrared Optics--Saxonburg Division, Saxonburg,...

  11. Exploration of oxide-based diluted magnetic semiconductors toward transparent spintronics

    NASA Astrophysics Data System (ADS)

    Fukumura, T.; Yamada, Y.; Toyosaki, H.; Hasegawa, T.; Koinuma, H.; Kawasaki, M.

    2004-02-01

    A review is given for the recent progress of research in the field of oxide-based diluted magnetic semiconductor (DMS), which was triggered by combinatorial discovery of transparent ferromagnet. The possible advantages of oxide semiconductor as a host of DMS are described in comparison with conventional compound semiconductors. Limits and problems for identifying novel ferromagnetic DMS are described in view of recent reports in this field. Several characterization techniques are proposed in order to eliminate unidentified ferromagnetism of oxide-based DMS unidentified ferromagnetic oxide (UFO). Perspectives and possible devices are also given.

  12. Dry Blending to Achieve Isotopic Dilution of Highly Enriched Uranium Oxide Materials

    SciTech Connect

    Henry, Roger Neil; Chipman, Nathan Alan; Rajamani, R. K.

    2001-04-01

    The end of the cold war produced large amounts of excess fissile materials in the United States and Russia. The Department of Energy has initiated numerous activities to focus on identifying material management strategies for disposition of these excess materials. To date, many of these planning strategies have included isotopic dilution of highly enriched uranium as a means of reducing the proliferation and safety risks. Isotopic dilution by dry blending highly enriched uranium with natural and/or depleted uranium has been identified as one non-aqueous method to achieve these risk (proliferation and criticality safety) reductions. This paper reviews the technology of dry blending as applied to free flowing oxide materials.

  13. Anti-stokes photoluminescence of II-VI nanoparticles with different emitting states

    NASA Astrophysics Data System (ADS)

    Ozturk, Birol; Wang, Yimg; Chen, Wei; Kotov, Nicholas A.

    2003-03-01

    Anti-stokes photoluminescence of II-VI nanoparticles with different emitting states Birol Ozturk(a), Wei Chen(b), Yimg Wang(a), Nicholas Kotov (a) (a) Department of Chemistry, Oklahoma State University,Stillwater,OK 74078,USA (b) Nomadics Inc., 1024South Innovation Way, Stillwater, OK 74074, USA Abstract Anti-stokes photoluminescence (ASPL) in II-VI colloidal nanoparticles of CdTe and CdSe was studied in dispersions. The measurements showed that photoluminescence PL and ASPL were likely to originate from different although close-lying electronic states. Temperature dependence measurements between 10K and 300K showed that there is no thermal excitation step involved in ASPL emission. Emission intensity dependence on excitation intensity is linear which indicates deviation from the classical two-photon absorption mechanism. The ASPL excitation scheme involving a long-lived intermediate state is discussed.

  14. Nonvolatile Memories Using Quantum Dot (QD) Floating Gates Assembled on II-VI Tunnel Insulators

    NASA Astrophysics Data System (ADS)

    Suarez, E.; Gogna, M.; Al-Amoody, F.; Karmakar, S.; Ayers, J.; Heller, E.; Jain, F.

    2010-07-01

    This paper presents preliminary data on quantum dot gate nonvolatile memories using nearly lattice-matched ZnS/Zn0.95Mg0.05S/ZnS tunnel insulators. The GeO x -cladded Ge and SiO x -cladded Si quantum dots (QDs) are self-assembled site-specifically on the II-VI insulator grown epitaxially over the Si channel (formed between the source and drain region). The pseudomorphic II-VI stack serves both as a tunnel insulator and a high- κ dielectric. The effect of Mg incorporation in ZnMgS is also investigated. For the control gate insulator, we have used Si3N4 and SiO2 layers grown by plasma- enhanced chemical vapor deposition.

  15. Misfit accommodation and dislocations in heteroepitaxial semiconductor layers: II-VI compounds on GaAs

    NASA Astrophysics Data System (ADS)

    Patriarche, G.; Rivière, J. P.; Castaing, J.

    1993-06-01

    We suggest a model for the nucleation and expansion of dislocations which accommodate the parameter misfit of an epitaxial layer on a substrate, applied, in this work, to a II-VI compound on GaAs. We examine in particular the dislocations threading through the layer, which must be kept as low as possible in density. Nous proposons un mécanisme de germination et de développement des dislocations permettant de compenser l'écart de paramètres d'une couche épitaxiée sur un substrat, par exemple dans notre cas, un composé II-VI sur GaAs. On porte une attention particulière aux dislocations résiduelles dans la couche dont on cherche à minimiser la densité.

  16. Process for forming shaped group II-VI semiconductor nanocrystals, and product formed using process

    DOEpatents

    Alivisatos, A. Paul; Peng, Xiaogang; Manna, Liberato

    2001-01-01

    A process for the formation of shaped Group II-VI semiconductor nanocrystals comprises contacting the semiconductor nanocrystal precursors with a liquid media comprising a binary mixture of phosphorus-containing organic surfactants capable of promoting the growth of either spherical semiconductor nanocrystals or rod-like semiconductor nanocrystals, whereby the shape of the semiconductor nanocrystals formed in said binary mixture of surfactants is controlled by adjusting the ratio of the surfactants in the binary mixture.

  17. Deuterium oxide dilution kinetics to predict body composition in dairy goats

    SciTech Connect

    Brown, D.L.; Taylor, S.J.

    1986-04-01

    Body composition and D2O dilution kinetics were studied in 15 female goats ranging from 38.0 to 70.1 kg live weight. Infrared spectrophotometric analyses of blood samples drawn during the 4 d following D2O injections were used to estimate D2O space. All does were slaughtered without shrinking and analyzed for dry matter, fat, nitrogen, and ash content. Estimates of D2O space from the late slope of the dilution curve, together with live weight, were used to predict body composition. Conclusions were 1) deuterium oxide space with live body weight accounts for about 90% of the variation in dairy goat empty body fat, empty body nitrogen, and empty body dry matter; 2) less than half the variation in empty body ash is related to live weight and D2O space; and 3) D2O space estimates would be biased by accelerations in water turnover.

  18. Quantification of Nitrous Oxide from Fugitive Emissions by Tracer Dilution Method using a Mobile Real-time Nitrous Oxide Analyzer

    NASA Astrophysics Data System (ADS)

    Mønster, J.; Rella, C.; Jacobson, G. A.; He, Y.; Hoffnagle, J.; Scheutz, C.

    2012-12-01

    Nitrous oxide is a powerful greenhouse gas considered 298 times stronger than carbon dioxide on a hundred years term (Solomon et al. 2007). The increasing global concentration is of great concern and is receiving increasing attention in various scientific and industrial fields. Nitrous oxide is emitted from both natural and anthropogenic sources. Inventories of source specific fugitive nitrous oxide emissions are often estimated on the basis of modeling and mass balance. While these methods are well-developed, actual measurements for quantification of the emissions can be a useful tool for verifying the existing estimation methods as well as providing validation for initiatives targeted at lowering unwanted nitrous oxide emissions. One approach to performing such measurements is the tracer dilution method (Galle et al. 2001), in which a tracer gas is released at the source location at a known flow. The ratio of downwind concentrations of both the tracer gas and nitrous oxide gives the ratios of the emissions rates. This tracer dilution method can be done with both stationary and mobile measurements; in either case, real-time measurements of both tracer and analyte gas is required, which places high demands on the analytical detection method. To perform the nitrous oxide measurements, a novel, robust instrument capable of real-time nitrous oxide measurements has been developed, based on cavity ring-down spectroscopy and operating in the near-infrared spectral region. We present the results of the laboratory and field tests of this instrument in both California and Denmark. Furthermore, results are presented from measurements using the mobile plume method with a tracer gas (acetylene) to quantify the nitrous oxide and methane emissions from known sources such as waste water treatment plants and composting facilities. Nitrous oxide (blue) and methane (yellow) plumes downwind from a waste water treatment facility.

  19. Novel photoinduced phase transitions in transition metal oxides and diluted magnetic semiconductors

    PubMed Central

    2012-01-01

    Some transition metal oxides have frustrated electronic states under multiphase competition due to strongly correlated d electrons with spin, charge, and orbital degrees of freedom and exhibit drastic responses to external stimuli such as optical excitation. Here, we present photoemission studies on Pr0.55(Ca1 − ySry)0.45MnO3 (y = 0.25), SrTiO3, and Ti1 − xCoxO2 (x = 0.05, 0.10) under laser illumination and discuss electronic structural changes induced by optical excitation in these strongly correlated oxides. We discuss the novel photoinduced phase transitions in these transition metal oxides and diluted magnetic semiconductors on the basis of polaronic pictures such as orbital, ferromagnetic, and ferroelectric polarons. PMID:23092248

  20. Self-organized MBE growth of II VI epilayers on patterned GaSb substrates

    NASA Astrophysics Data System (ADS)

    Wissmann, H.; Tran Anh, T.; Rogaschewski, S.; von Ortenberg, M.

    1999-05-01

    We report on the self-organized MBE growth of II-VI epilayers on patterned and unpatterned GaSb substrates resulting in quantum wires and quantum wells, respectively. The HgSe : Fe quantum wires were grown on (0 0 1)GaSb substrates with a buffer of lattice-matched ZnTe 1- xSe x. Due to the anisotropic growth of HgSe on the A-oriented stripes roof-like overgrowth with a definite ridge was obtained. Additional Fe doping in the direct vicinity of the ridge results in a highly conductive quantum wire.

  1. Crystal-Phase Control by Solution-Solid-Solid Growth of II-VI Quantum Wires.

    PubMed

    Wang, Fudong; Buhro, William E

    2016-02-10

    A simple and potentially general means of eliminating the planar defects and phase alternations that typically accompany the growth of semiconductor nanowires by catalyzed methods is reported. Nearly phase-pure, defect-free wurtzite II-VI semiconductor quantum wires are grown from solid rather than liquid catalyst nanoparticles. The solid-catalyst nanoparticles are morphologically stable during growth, which minimizes the spontaneous fluctuations in nucleation barriers between zinc blende and wurtzite phases that are responsible for the defect formation and phase alternations. Growth of single-phase (in our cases the wurtzite phase) nanowires is thus favored. PMID:26731426

  2. Structural Fluctuations and Thermophysical Properties of Molten II-VI Compounds

    NASA Technical Reports Server (NTRS)

    Su, Ching-Hua; Zhu, Shen; Li, Chao; Scripa, R.; Lehoczky, Sandra L.; Kim, Y. W.; Baird, J. K.; Lin, B.; Ban, Heng; Benmore, Chris

    2003-01-01

    The objectives of the project are to conduct ground-based experimental and theoretical research on the structural fluctuations and thermophysical properties of molten II-VI compounds to enhance the basic understanding of the existing flight experiments in microgravity materials science programs as well as to study the fundamental heterophase fluctuation phenomena in these melts by: 1) conducting neutron scattering analysis and measuring quantitatively the relevant thermophysical properties of the II-VI melts (such as viscosity, electrical conductivity, thermal diffusivity and density) as well as the relaxation characteristics of these properties to advance the understanding of the structural properties and the relaxation phenomena in these melts and 2) performing theoretical analyses on the melt systems to interpret the experimental results. All the facilities required for the experimental measurements have been procured, installed and tested. It has long been recognized that liquid Te presents a unique case having properties between those of metals and semiconductors. The electrical conductivity for Te melt increases rapidly at melting point, indicating a semiconductor-metal transition. Te melts comprise two features, which are usually considered to be incompatible with each other: covalently bound atoms and metallic-like behavior. Why do Te liquids show metallic behavior? is one of the long-standing issues in liquid metal physics. Since thermophysical properties are very sensitive to the structural variations of a melt, we have conducted extensive thermophysical measurements on Te melt.

  3. Bulk Growth of Wide Band Gap II-VI Compound Semiconductors by Physical Vapor Transport

    NASA Technical Reports Server (NTRS)

    Su, Ching-Hua

    1997-01-01

    The mechanism of physical vapor transport of II-VI semiconducting compounds was studied both theoretically, using a one-dimensional diffusion model, as well as experimentally. It was found that the vapor phase stoichiometry is critical in determining the vapor transport rate. The experimental heat treatment methods to control the vapor composition over the starting materials were investigated and the effectiveness of the heat treatments was confirmed by partial pressure measurements using an optical absorption technique. The effect of residual (foreign) gas on the transport rate was also studies theoretically by the diffusion model and confirmed experimentally by the measurements of total pressure and compositions of the residual gas. An in-situ dynamic technique for the transport rate measurements and a further extension of the technique that simultaneously measured the partial pressures and transport rates were performed and, for the first time, the experimentally determined mass fluxes were compared with those calculated, without any adjustable parameters, from the diffusion model. Using the information obtained from the experimental transport rate measurements as guideline high quality bulk crystal of wide band gap II-VI semiconductor were grown from the source materials which undergone the same heat treatment methods. The grown crystals were then extensively characterized with emphasis on the analysis of the crystalline structural defects.

  4. Vapor transport epitaxy: an advanced growth process for III-V and II-VI semiconductors

    NASA Astrophysics Data System (ADS)

    Gurary, Alexander; Tompa, Gary S.; Nelson, Craig R.; Stall, Richard A.; Lu, Yicheng; Liang, Shaohua

    1992-09-01

    The Vapor Transport Epitaxy (VTE) thin film deposition technique for the deposition of III - V and II - VI compound semiconductors and material results are reviewed. The motivation for development of the VTE technique is the elimination of several problems common to molecular beam epitaxy/chemical beam epitaxy and metalorganic chemical vapor deposition systems. In VTE, vapors from sources feed through throttling valves into a common manifold which is located directly below the inverted wafer. A high degree of film uniformity is achieved by controlling the flux distribution from the common manifold. The technique operates in the 10-4 - 10-6 Torr range using elemental, metalorganic or gaseous precursors. The system is configurated for 2 inch diameter wafers but the geometry may easily be scaled for larger diameters. Using elemental sources, we have demonstrated oval defect free growth of GaAs on GaAs (100) and (111) 2 degree(s) off substrates, through several microns of thickness at growth rates up to ten microns per hour. GaAs films which were grown without the manifold exhibit classic oval defects. The deposition rate of ZnSe films as a function of elemental flux, VI/II ratio, and growth temperature are described. The ZnSe films exhibited smooth surface morphologies on GaAs (100) 2 degree(s) off substrates. X- ray analysis shows that III - V and II - VI films exhibited crystallinities comparable to films produced by molecular beam epitaxy and metalorganic chemical vapor deposition techniques.

  5. Growth of Wide Band Gap II-VI Compound Semiconductors by Physical Vapor Transport

    NASA Technical Reports Server (NTRS)

    Su, Ching-Hua; Sha, Yi-Gao

    1995-01-01

    The studies on the crystal growth and characterization of II-VI wide band gap compound semiconductors, such as ZnTe, CdS, ZnSe and ZnS, have been conducted over the past three decades. The research was not quite as extensive as that on Si, III-V, or even narrow band gap II-VI semiconductors because of the high melting temperatures as well as the specialized applications associated with these wide band gap semiconductors. In the past several years, major advances in the thin film technology such as Molecular Beam Epitaxy (MBE) and Metal Organic Chemical Vapor Deposition (MOCVD) have demonstrated the applications of these materials for the important devices such as light-emitting diode, laser and ultraviolet detectors and the tunability of energy band gap by employing ternary or even quaternary systems of these compounds. At the same time, the development in the crystal growth of bulk materials has not advanced far enough to provide low price, high quality substrates needed for the thin film growth technology.

  6. Lattice dynamics of II-VI mixed semiconductor ZnS 1- xSe x

    NASA Astrophysics Data System (ADS)

    Kushwaha, A. K.

    2008-09-01

    Lattice dynamical properties of II-VI compounds having zinc-blende structure have been calculated by three-body shell model. This model incorporates the effect of the short-range repulsive interactions up to and including the second nearest neighbours, in addition to the long-range Coulombic interactions in the frame work of the rigid-shell model with both the ions are polarizable. The model involves in total eleven disposable parameters. Using the above proposed model the phonon dispersion relations for mixed II-VI semiconductor ZnS 1- xSe x are plotted. We find an overall good agreement with the experimental results. The application of the present model has been made to calculate the phonon dispersion relations of ZnS, ZnSe and mixed semiconductor ZnS 1- xSe x. The comparison of the theoretical results with the available experimental has been made along high symmetry directions. A reasonably good agreement is observed between theory and experiments.

  7. Boîtes quantiques II-VI comme sources de photons uniques

    NASA Astrophysics Data System (ADS)

    Couteau, C.; Moehl, S.; Tinjod, F.; Suffczynski, J.; Romestain, R.; Vial, J.-C.; Gérard, J.-M.; Kheng, K.; Poizat, J.-P.

    2004-11-01

    Dans le cadre de l'information et de la communication quantique, la nécessité d'avoir des photons uniques monomodes et à la demande se révèle cruciale. De récents travaux théoriques ont montré la possibilité de réaliser des portes logiques quantiques n'utilisant que de l'optique linéaire. C'est dans ce contexte que s'insère notre travail sur l'élaboration et l'utilisation de boîtes quantiques semi-conductrices II-VI comme “pistolet” à photons. Des expériences de dégroupement et d'interférences à 2 photons sont les premiers pas nécessaires pour caractériser notre source.

  8. Characterization of convection related defects in II-VI compound semiconductors

    NASA Technical Reports Server (NTRS)

    Witt, August F.

    1993-01-01

    The research carried out under NAG8-913, 'Characterization of Convection Related Defects in II-VI Compound Semiconductors', was aimed at exploration of the potential of axial magnetic fields for melt stabilization when applied in Bridgman geometry to the growth of HgMnTe. The thrust of the work was directed at the experimental establishment of the limits of magnetic melt stabilization during crystal growth and at the analytical verification of the effects of stabilization on critical materials properties. The data obtained indicate noticeable stabilization effects, particularly as far as the formation of microscopic compositional inhomogeneities is concerned. The effects of magnetic fields on precipitate formation are found to be minor. Magnetic field effects were investigated for both 'Bridgman' and 'travelling heater' geometries. The research was conducted during the period from May 22 to September 30, 1992.

  9. Mid-IR gain media based on transition metal-doped II-VI chalcogenides

    NASA Astrophysics Data System (ADS)

    Mirov, S. B.; Fedorov, V. V.; Martyshkin, D. V.; Moskalev, I. S.; Mirov, M. S.; Gafarov, O.; Martinez, A.; Peppers, J.; Smolski, V.; Vasilyev, S.; Gapontsev, V.

    2016-02-01

    Progress in fabrication and mid-IR lasing of Cr and Fe thermal-diffusion and radiation enhanced thermal diffusion doped II-VI binary and ternary polycrystals is reported. We demonstrate novel design of mid-IR Fe:ZnSe and Cr:ZnSe/S solid state lasers with significant improvement of output average power up to 35W@4.1 μm and 57W@2.5 μm and 20W@2.94 μm. We report significantly improved output characteristics of polycrystalline Cr:ZnS/Se lasers in gain-switched regime: 16 mJ at 200 Hz, pulse duration 5 ns with tunability over 2400-3000 nm as well as Kerr-Lens-Mode-Locked regime in terms of average power (up to 2 W), peak power and pulse energy (0.5 MW and 24 nJ, respectively), and pulse duration (less than 29 fs).

  10. Theoretical and experimental studies of stressed nanoparticles of II-VI semiconductors.

    PubMed

    Ferreira, D Lourençoni; Silva, F Oliveira; Viol, L Cristina de Souza; Licínio, P; Schiavon, M Antônio; Alves, J Luiz Aarestrup

    2010-01-01

    A theoretical and experimental study of isolated nanoparticles of II-VI semiconductor materials has been done. Using the framework of the effective mass model, the optical absorption spectrum of distributions of spherical quantum dots, freestanding, and under compressive or tensile stress, has been examined theoretically. The theoretical results allow one to foresee the absorption spectra of quantum dots made of a series of materials and having any size. The syntheses of colloidal quantum dots of CdS and CdSe has also been performed through wet chemical routes and characterized by means of optical techniques. The values of the strains in the synthesized quantum dots were inferred from a correlation established between the theoretical and the experimental results. PMID:20078149

  11. Quantification of methane and nitrous oxide emissions from various waste treatment facilities by tracer dilution method

    NASA Astrophysics Data System (ADS)

    Mønster, Jacob; Rella, Chris; Jacobson, Gloria; Kjeldsen, Peter; Scheutz, Charlotte

    2013-04-01

    Urban activities generate solid and liquid waste, and the handling and aftercare of the waste results in the emission of various compounds into the surrounding environment. Some of these compounds are emitted as gasses into the atmosphere, including methane and nitrous oxide. Methane and nitrous oxide are strong greenhouse gases and are considered to have 25 and 298 times the greenhouse gas potential of carbon dioxide on a hundred years term (Solomon et al. 2007). Global observations of both gasses have shown increasing concentrations that significantly contribute to the greenhouse gas effect. Methane and nitrous oxide are emitted from both natural and anthropogenic sources and inventories of source specific fugitive emissions from the anthropogenic sources of methane and nitrous oxide of are often estimated on the basis of modeling and mass balance. Though these methods are well-developed, actual measurements for quantification of the emissions is a very useful tool for verifying the modeling and mass balance as well as for validation initiatives done for lowering the emissions of methane and nitrous oxide. One approach to performing such measurements is the tracer dilution method (Galle et al. 2001, Scheutz et al. 2011), where the exact location of the source is located and a tracer gas is released at this source location at a known flow. The ratio of downwind concentrations of the tracer gas and the methane and nitrous oxide gives the emissions rates of the greenhouse gases. This tracer dilution method can be performed using both stationary and mobile measurements and in both cases, real-time measurements of both tracer and quantified gas are required, placing high demands on the analytical detection method. To perform the methane and nitrous oxide measurements, two robust instruments capable of real-time measurements were used, based on cavity ring-down spectroscopy and operating in the near-infrared spectral region. One instrument measured the methane and

  12. Crystal Growth of II-VI Semiconducting Alloys by Directional Solidification

    NASA Technical Reports Server (NTRS)

    Lehoczky, Sandor L.; Szofran, Frank R.; Su, Ching-Hua; Cobb, Sharon D.; Scripa, Rosalia A.; Sha, Yi-Gao

    1999-01-01

    This research study is investigating the effects of a microgravity environment during the crystal growth of selected II-VI semiconducting alloys on their compositional, metallurgical, electrical and optical properties. The on-going work includes both Bridgman-Stockbarger and solvent growth methods, as well as growth in a magnetic field. The materials investigated are II-VI, Hg(1-x)Zn(x)Te, and Hg(1-x)Zn(x)Se, where x is between 0 and 1 inclusive, with particular emphasis on x-values appropriate for infrared detection and imaging in the 5 to 30 micron wavelength region. Wide separation between the liquidus and solidus of the phase diagrams with consequent segregation during solidification and problems associated with the high volatility of one of the components (Hg), make the preparation of homogeneous, high-quality, bulk crystals of the alloys an extremely difficult nearly an impossible task in a gravitational environment. The three-fold objectives of the on-going investigation are as follows: (1) To determine the relative contributions of gravitationally-driven fluid flows to the compositional redistribution observed during the unidirectional crystal growth of selected semiconducting solid solution alloys having large separation between the liquidus and solidus of the constitutional phase diagram; (2) To ascertain the potential role of irregular fluid flows and hydrostatic pressure effects in generation of extended crystal defects and second-phase inclusions in the crystals; and, (3) To obtain a limited amount of "high quality" materials needed for bulk crystal property characterizations and for the fabrication of various device structures needed to establish ultimate material performance limits. The flight portion of the study was to be accomplished by performing growth experiments using the Crystal Growth Furnace (CGF) manifested to fly on various Spacelab missions.

  13. Diluted bitumen causes deformities and molecular responses indicative of oxidative stress in Japanese medaka embryos.

    PubMed

    Madison, Barry N; Hodson, P V; Langlois, V S

    2015-08-01

    This study characterized the toxicity and physiological effects of unweathered diluted bitumen (Access Western Blend dilbit; AWB) to fish. Embryos of Japanese medaka (Oryzias latipes) were exposed for 17 days to dilutions of physically-dispersed (water accommodated fraction; WAF) and chemically-dispersed (chemically-enhanced WAF; CEWAF) dilbit. AWB dilbit exposure was not lethal to medaka, but resulted in a high prevalence of blue sac disease (BSD), impaired development, and abnormal or un-inflated swim bladders at hatch. Physiological effects were indicated by the relative mRNA levels of key genes associated with, among others, cell cycling and the response to mutations (p53), xenobiotic metabolism (ahr, arnt2), phase I (cyp1a) and II processes associated with oxidative stress (cat, g6pdh, hsp70, gst, gpx, gsr, nfe2, and sod). AWB dilbit treatment increased p53 and cyp1a transcript levels (1.5-fold and >15-fold, respectively), with significant, but less pronounced changes in indicators of oxidative stress and metabolism. The exposure-related changes in embryotoxicity and mRNA synthesis were consistent with metabolism of polycyclic aromatic hydrocarbons (PAHs) to reactive and toxic metabolites. Medaka embryos responded similarly to WAF and CEWAF treatments, but CEWAF was about 100 times more efficient in delivering toxic concentrations of PAHs. The toxicity of chemically-dispersed nujol, a non-toxic mineral oil used as an experimental control, suggested that a portion of the observed effects of AWB could be attributed to excess dispersant in solution. This first study of the physiological effects of dilbit toxicity to fish embryos provides a baseline to compare toxicity between dilbit and conventional crude oils, and the groundwork for the development of molecular biomarkers of the sensitivity and level of risk of native Canadian fish species to dilbit exposure. PMID:26118968

  14. 77 FR 36579 - II-VI, Inc., Infrared Optics-Saxonburg Division, Saxonburg, PA; Leased Workers From Adecco, Carol...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-06-19

    ... in the Federal Register on February 14, 2012 (77 FR 8281). The workers' firm is engaged in activities... Employment and Training Administration II-VI, Inc., Infrared Optics-Saxonburg Division, Saxonburg, PA; Leased...., Infrared Optics-Saxonburg Division, Saxonburg, PA; Notice of Revised Determination on Reconsideration...

  15. All-vapor processing of P-type tellurium-containing II-VI semiconductor and ohmic contacts thereof

    SciTech Connect

    McCandless, Brian E.

    2000-03-01

    An all dry method for producing solar cells is provided comprising first heat-annealing a II-VI semiconductor; enhancing the conductivity and grain size of the annealed layer; modifying the surface and depositing a tellurium layer onto the enhanced layer; and then depositing copper onto the tellurium layer so as to produce a copper tellurium compound on the layer.

  16. All-vapor processing of p-type tellurium-containing II-VI semiconductor and ohmic contacts thereof

    DOEpatents

    McCandless, Brian E.

    2001-06-26

    An all dry method for producing solar cells is provided comprising first heat-annealing a II-VI semiconductor; enhancing the conductivity and grain size of the annealed layer; modifying the surface and depositing a tellurium layer onto the enhanced layer; and then depositing copper onto the tellurium layer so as to produce a copper tellurium compound on the layer.

  17. Origin and enhancement of spin polarized current in diluted magnetic oxides by oxygen vacancies

    NASA Astrophysics Data System (ADS)

    Chou, Hsiung; Yang, Kung-Shang; Tsao, Yao-Chung; Dwivedi, G. D.; Lin, Cheng-Pang; Sun, Shih-Jye; Lin, L. K.; Lee, S. F.

    2016-04-01

    Spin polarized current (SPC) is a crucial characteristic of diluted magnetic oxides due to the potential application of oxides in spintronic devices. However, most research has been focused on ferromagnetic properties rather than polarization of electric current, because direct measurements are difficult and the origin of SPC has yet to be fully understood. The method to increase the SPC percentage is beyond practical consideration at present. To address this problem, we focus on the role of oxygen vacancies (VO) on SPC, which are controlled by growing the Co-doped ZnO thin-films at room temperature in a reducing atmosphere [Ar + (1%-30%)H2]. We found that the conductivity increases with an increase of VO via two independent channels: the variable range hopping (VRH) within localized states and the itinerant transport in the conduction band. The point contact Andreev reflection measurements at 4.2 K, where the electric conduction is governed only by the VRH mechanism, prove that the current flowing in the VRH hopping channel is SPC. The percentage of SPC increases with the introduction of VO and increase in its concentration. The transport measurement shows that by manipulating VO, one can control the percentage of VRH hopping conduction such that it can even dominate room temperature conduction. The highest achieved SPC ratio at room temperature was 80%.

  18. Analytical Electron Diffraction from Iii-V and II-Vi Semiconductors

    NASA Astrophysics Data System (ADS)

    Spellward, Paul

    Available from UMI in association with The British Library. This thesis describes the development and evaluation of a number of new TEM-based techniques for the measurement of composition in ternary III-V and II-VI semiconductors. New methods of polarity determination in binary and ternary compounds are also presented. The theory of high energy electron diffraction is outlined, with particular emphasis on zone axis diffraction from well-defined strings. An account of TEM microstructural studies of Cd_{rm x}Hg _{rm 1-x}Te and CdTe epitaxial layers, which provided the impetus for developing the diffraction-based analytical techniques, is given. The wide range of TEM-based compositional determination techniques is described. The use of HOLZ deficiency lines to infer composition from a lattice parameter measurement is evaluated. In the case of Cd_{ rm x}Hg_{rm 1-x}Te, it is found to be inferior to other techniques developed. Studies of dynamical aspects of HOLZ diffraction can yield information about the dispersion surface from which a measure of composition may be obtained. This technique is evaluated for Al_{rm x}Ga_{rm 1-x} As, in which it is found to be of some use, and for Cd_{rm x}Hg _{rm 1-x}Te, in which the large Debye-Waller factor associated with mercury in discovered to render the method of little value. A number of critical voltages may be measured in medium voltage TEMs. The (111) zone axis critical voltage of Cd_{rm x}Hg _{rm 1-x}Te is found to vary significantly with x and forms the basis of an accurate technique for composition measurement in that ternary compound. Other critical voltage phenomena are investigated. In Al _{rm x}Ga_ {rm 1-x}As and other light ternaries, a non-systematic critical voltage is found to vary with x, providing a good indicator of composition. Critical voltage measurements may be made by conventional CBED or by various other techniques, which may also simultaneously yield information on the spatial variation of composition. The

  19. Epitaxial growth and characterization of II-VI-semiconductor, one-dimensional nanostructures and thin films

    NASA Astrophysics Data System (ADS)

    Zhu, Zuoming

    In this thesis, I present the results of three material science studies on II-VI semiconductor nanostructures and thin films: (1) epitaxial growth and characterization of one-dimensional ZnO nanostructures, (2) crystal structure and self-assembly of ultrathin ZnO nanorods, and (3) investigations of surface chemistry for atomic layer epitaxy of ZnS thin film on silicon with chemical precursors. First, in Chapter 3, I present a comparative study of metal-surface-catalyzed growth of ZnO nanowires using four different metal catalysts and using substrates of differing materials and crystal orientation. Multiple material diagnostics were employed to compare the material, structural, and optical properties of the nanowires grown using these different surface systems. My study showed that the growth modes of nanowires are dependent on the choice of surface catalysts. Further, the study revealed that these differences in growth modes are also closely related to the differences in materials properties of these wires including the degree of nanowire alignment on substrates, and the atomic composition ratio of Zn/O, as well as the relative intensity of the oxygen vacancy-related emission in photoluminescence spectra. Second, in Chapter 4, I investigated the growth and self-assembly of ultrathin ZnO nanorods using a combination of small-angle and wide-angle synchrotron X-ray diffraction (SAXRD and WAXRD), and TEM. SAXRD and TEM were used to investigate nanorod self-assembly and the influence of surfactant/precursor ratio on self-assembly; WAXRD were used to study the effects of growth chemistry and physical parameters on the nanorod size and lattice constants. These measurements revealed that these rods self-assemble into periodic superstructures and that the surfactant ligands are important in controlling self-assembly. WAXRD results suggest that surface-dependent changes, such as the binding of surface ligands or other adsorbed species may dominate the changes in nanorod

  20. Validity of deuterium oxide dilution for the measurement of body fat among Singaporeans.

    PubMed

    Deurenberg-Yap, Mabel; Deurenberg, Paul

    2002-09-01

    Body fat percent (BF%) was measured in 108 adult Chinese, 76 Malays, and 107 Indians in Singapore by densitometry, deuterium oxide dilution (hydrometry), dual energy x-ray absorptiometry (DXA) and a chemical four-compartment model (BF%4c). The hydration of the fat-free mass (FFM) was calculated. Subjects ranged in age from 18 to 69 years and their body mass index ranged from 16 to 40 kg/m2. BF%4c for the various subgroups were: Chinese females (33.5 +/- 7.5%), Chinese males (24.4 +/- 6.1%), Malay females (37.8 +/- 6.3%), Malay males (26.0 +/- 7.6%), Indian females (38.2 +/- 7.0%) and Indian males (28.1 +/- 5.5%). Biases were found between BF%4c and BF% measured by 2-compartment models (hydrometry, densitometry, DXA), with systematic underestimation by DXA and densitometry. On a group level hydrometry had the lowest bias while DXA gave the highest bias. When validated against BF%4c, 2-compartment models were found to be unsuitable for accurate measures of body fat due to high biases at the individual level and the violation of assumptions of constant hydration of FFM and density FFM among the ethnic groups. On a group level the best 2-compartment model for measuring body fat was found to be hydrometry. PMID:12362808

  1. Large-area x-ray topographic screening of II-VI substrates and epilayers

    NASA Astrophysics Data System (ADS)

    Di Marzio, Don; Larson, David J., Jr.; Casagrande, Louis G.; Wu, Jun; Dudley, Michael; Tobin, Stephen P.; Norton, Peter W.

    1994-07-01

    A crucial aspect of process control in II-VI based device fabrication is the detailed monitoring of material properties, particularly structural quality. We have developed a method of mapping structural defects over large wafer areas using synchrotron white beam x-ray topography and have used it to characterize large area single crystal CdZnTe substrates and LPE HgCdTe epilayers grown on them. The synchrotron white beam technique produces high resolution topographic images of whole wafers regardless of long range strain, and the multiple images generated as a result of the polychromatic white beam (Laue geometry) provide an automatic defect depth profiling. The topographs reveal various types of defect structure in the CdZnTe substrates, and we have compared these topographic images to IR micrographs and x-ray rocking curve maps. Defect structures as revealed by the x-ray topographs were then followed from the CdZnTe substrates to the LPE grown HgCdTe epilayers. Epilayer topographs were also compared to conventional optical micrographs as well as with x-ray rocking curve maps. Finally, a scanning stage was constructed to topographically image large wafers and boule slabs.

  2. Growth of II-VI Solid Solutions in the Presence of a Rotating Magnetic Field

    NASA Technical Reports Server (NTRS)

    Gillies, D. C; Motakef, S.; Dudley, M.; Matyi, R.; Volz, H.

    1999-01-01

    The application of a rotating magnetic field (RMF)in the frequency range 60-400 Hz and field strength of the order of 2-8 mT to crystal growth has received increasing attention in recent years. To take full advantage of the control of fluid flow by the forces applied by the field, the liquid column must be electrically conducting. Also, the application of RMF to the directional solidification of a column of liquid can result in complete mixing in the resultant solid. Thus, the technique of RMF is suited to solvent zones and float zones where the composition of the liquid is more readily controlled. In the work we report on, numerical modeling has been applied to II-VI systems, particularly tellurium based traveling heater techniques (THM). Results for a spectrum of field strengths and acceleration levels will be presented. These show clearly the effects of competing buoyancy forces and electromagnetic stirring. Crystals of cadmium zinc telluride and mercury cadmium telluride have been grown terrestrially from a tellurium solvent zone. The effects of the RMF during these experiments will be demonstrated with micrographs showing etch pits, white beam x-ray synchrotron topographs and triple axis x-ray diffraction.

  3. Surface stability and the selection rules of substrate orientation for optimal growth of epitaxial II-VI semiconductors

    SciTech Connect

    Yin, Wan-Jian; Yang, Ji-Hui; Zaunbrecher, Katherine; Gessert, Tim; Barnes, Teresa; Wei, Su-Huai; Yan, Yanfa

    2015-10-05

    The surface structures of ionic zinc-blende CdTe (001), (110), (111), and (211) surfaces are systematically studied by first-principles density functional calculations. Based on the surface structures and surface energies, we identify the detrimental twinning appearing in molecular beam epitaxy (MBE) growth of II-VI compounds as the (111) lamellar twin boundaries. To avoid the appearance of twinning in MBE growth, we propose the following selection rules for choosing optimal substrate orientations: (1) the surface should be nonpolar so that there is no large surface reconstructions that could act as a nucleation center and promote the formation of twins; (2) the surface structure should have low symmetry so that there are no multiple equivalent directions for growth. These straightforward rules, in consistent with experimental observations, provide guidelines for selecting proper substrates for high-quality MBE growth of II-VI compounds.

  4. Molecular beam epitaxial growth and characterization of Bi{sub 2}Se{sub 3}/II-VI semiconductor heterostructures

    SciTech Connect

    Chen, Zhiyi Zhao, Lukas; Krusin-Elbaum, Lia; Garcia, Thor Axtmann; Tamargo, Maria C.; Hernandez-Mainet, Luis C.; Deng, Haiming

    2014-12-15

    Surfaces of three-dimensional topological insulators (TIs) have been proposed to host quantum phases at the interfaces with other types of materials, provided that the topological properties of interfacial regions remain unperturbed. Here, we report on the molecular beam epitaxy growth of II-VI semiconductor–TI heterostructures using c-plane sapphire substrates. Our studies demonstrate that Zn{sub 0.49}Cd{sub 0.51}Se and Zn{sub 0.23}Cd{sub 0.25}Mg{sub 0.52}Se layers have improved quality relative to ZnSe. The structures exhibit a large relative upward shift of the TI bulk quantum levels when the TI layers are very thin (∼6nm), consistent with quantum confinement imposed by the wide bandgap II-VI layers. Our transport measurements show that the characteristic topological signatures of the Bi{sub 2}Se{sub 3} layers are preserved.

  5. Multi-band Bloch equations and gain spectra of highly excited II-VI semiconductor quantum wells

    SciTech Connect

    Girndt, A.; Jahnke, F.; Knorr, A.; Koch, S.W.; Chow, W.W.

    1997-04-21

    Quasi-equilibrium excitation dependent optical probe spectra of II-VI semiconductor quantum wells at room temperature are investigated within the framework of multi-band semiconductor Bloch equations. The calculations include correlation effects beyond the Hartree-Fock level which describe dephasing, interband Coulomb correlations and band-gap renormalization in second Born approximation. In addition to the carrier-Coulomb interaction, the influence of carrier-phonon scattering and inhomogeneous broadening is considered. The explicit calculation of single particle properties like band structure and dipole matrix elements using k {center_dot} p theory makes it possible to investigate various II-VI material combinations. Numerical results are presented for CdZnSe/ZnSe and CdZnSe/MnZnSSe semiconductor quantum-well systems.

  6. Surface stability and the selection rules of substrate orientation for optimal growth of epitaxial II-VI semiconductors

    NASA Astrophysics Data System (ADS)

    Yin, Wan-Jian; Yang, Ji-Hui; Zaunbrecher, Katherine; Gessert, Tim; Barnes, Teresa; Yan, Yanfa; Wei, Su-Huai

    2015-10-01

    The surface structures of ionic zinc-blende CdTe (001), (110), (111), and (211) surfaces are systematically studied by first-principles density functional calculations. Based on the surface structures and surface energies, we identify the detrimental twinning appearing in molecular beam epitaxy (MBE) growth of II-VI compounds as the (111) lamellar twin boundaries. To avoid the appearance of twinning in MBE growth, we propose the following selection rules for choosing optimal substrate orientations: (1) the surface should be nonpolar so that there is no large surface reconstructions that could act as a nucleation center and promote the formation of twins; (2) the surface structure should have low symmetry so that there are no multiple equivalent directions for growth. These straightforward rules, in consistent with experimental observations, provide guidelines for selecting proper substrates for high-quality MBE growth of II-VI compounds.

  7. Temperature Dependence of Density, Viscosity and Electrical Conductivity for Hg-Based II-VI Semiconductor Melts

    NASA Technical Reports Server (NTRS)

    Li, C.; Ban, H.; Lin, B.; Scripa, R. N.; Su, C.-H.; Lehoczky, S. L.

    2004-01-01

    The relaxation phenomenon of semiconductor melts, or the change of melt structure with time, impacts the crystal growth process and the eventual quality of the crystal. The thermophysical properties of the melt are good indicators of such changes in melt structure. Also, thermophysical properties are essential to the accurate predication of the crystal growth process by computational modeling. Currently, the temperature dependent thermophysical property data for the Hg-based II-VI semiconductor melts are scarce. This paper reports the results on the temperature dependence of melt density, viscosity and electrical conductivity of Hg-based II-VI compounds. The melt density was measured using a pycnometric method, and the viscosity and electrical conductivity were measured by a transient torque method. Results were compared with available published data and showed good agreement. The implication of the structural changes at different temperature ranges was also studied and discussed.

  8. Defect-Rich Dopant-Free ZrO2 Nanostructures with Superior Dilute Ferromagnetic Semiconductor Properties.

    PubMed

    Rahman, Md Anisur; Rout, S; Thomas, Joseph P; McGillivray, Donald; Leung, Kam Tong

    2016-09-14

    Control of the spin degree of freedom of an electron has brought about a new era in spin-based applications, particularly spin-based electronics, with the potential to outperform the traditional charge-based semiconductor technology for data storage and information processing. However, the realization of functional spin-based devices for information processing remains elusive due to several fundamental challenges such as the low Curie temperature of group III-V and II-VI semiconductors (<200 K), and the low spin-injection efficiencies of existing III-V, II-VI, and transparent conductive oxide semiconductors in a multilayer device structure, which are caused by precipitation and migration of dopants from the host layer to the adjacent layers. Here, we use catalyst-assisted pulsed laser deposition to grow, for the first time, oxygen vacancy defect-rich, dopant-free ZrO2 nanostructures with high TC (700 K) and high magnetization (5.9 emu/g). The observed magnetization is significantly greater than both doped and defect-rich transparent conductive oxide nanomaterials reported to date. We also provide the first experimental evidence that it is the amounts and types of oxygen vacancy defects in, and not the phase of ZrO2 that control the ferromagnetic order in undoped ZrO2 nanostructures. To explain the origin of ferromagnetism in these ZrO2 nanostructures, we hypothesize a new defect-induced bound polaron model, which is generally applicable to other defect-rich, dopant-free transparent conductive oxide nanostructures. These results provide new insights into magnetic ordering in undoped dilute ferromagnetic semiconductor oxides and contribute to the design of exotic magnetic and novel multifunctional materials. PMID:27533277

  9. Defect-Rich Dopant-Free ZrO2 Nanostructures with Superior Dilute Ferromagnetic Semiconductor Properties.

    PubMed

    Rahman, Md Anisur; Rout, S; Thomas, Joseph P; McGillivray, Donald; Leung, Kam Tong

    2016-09-14

    Control of the spin degree of freedom of an electron has brought about a new era in spin-based applications, particularly spin-based electronics, with the potential to outperform the traditional charge-based semiconductor technology for data storage and information processing. However, the realization of functional spin-based devices for information processing remains elusive due to several fundamental challenges such as the low Curie temperature of group III-V and II-VI semiconductors (<200 K), and the low spin-injection efficiencies of existing III-V, II-VI, and transparent conductive oxide semiconductors in a multilayer device structure, which are caused by precipitation and migration of dopants from the host layer to the adjacent layers. Here, we use catalyst-assisted pulsed laser deposition to grow, for the first time, oxygen vacancy defect-rich, dopant-free ZrO2 nanostructures with high TC (700 K) and high magnetization (5.9 emu/g). The observed magnetization is significantly greater than both doped and defect-rich transparent conductive oxide nanomaterials reported to date. We also provide the first experimental evidence that it is the amounts and types of oxygen vacancy defects in, and not the phase of ZrO2 that control the ferromagnetic order in undoped ZrO2 nanostructures. To explain the origin of ferromagnetism in these ZrO2 nanostructures, we hypothesize a new defect-induced bound polaron model, which is generally applicable to other defect-rich, dopant-free transparent conductive oxide nanostructures. These results provide new insights into magnetic ordering in undoped dilute ferromagnetic semiconductor oxides and contribute to the design of exotic magnetic and novel multifunctional materials.

  10. Vibrational signatures of isotopic impurities and complexes in II-VI compound semiconductors

    NASA Astrophysics Data System (ADS)

    Talwar, Devki N.; Feng, Zhe Chuan; Yang, Tzuen-Rong

    2012-05-01

    In II-VI compound semiconductors, we have used a comprehensive Green's function theory to study the vibrational properties of isotopic defects and to ascertain the microstructure of complex centers involving dopants and intrinsic impurities. The phonons generated by a realistic lattice-dynamical model for the host materials are integrated in simulating the Green's functions to help explicate the observed localized vibrational modes (LVMs) for various defect centers. Contrary to the distinct force constants required for isolated defects, the isotopic shift of LVMs has offered strong revelations for inflexible ‘impurity-host’ interactions in each isotopic defect. In compound semiconductors a unique force variation correlation with bond covalency is proposed providing corrections to the nearest-neighbor (NN) force constants for the closest mass isoelectronic and impurities carrying static charges. The articulation is extremely useful for defining perturbations and for analyzing the infrared absorption data on LVMs of complex defect centers. In corroboration with experiments, the Green's functions theory of impurity modes in Li-doped CdTe:Al (ZnSe:Al) has established second NN LiCd(Zn)-AlCd(Zn) pairs indicating the passivation of group-I acceptors via interaction with group-III elements as donors. The proposal of an antisite complex model AlZn-ZnSe-AlZn for the X center is consistent with the existing absorption results on impurity modes and is equally justified by theoretical considerations—making it the more likely identity for the native defect compensating neighboring AlZn donors in ZnSe.

  11. Microwave-assisted synthesis of II-VI semiconductor micro-and nanoparticles towards sensor applications

    NASA Astrophysics Data System (ADS)

    Majithia, Ravish Yogesh

    Engineering particles at the nanoscale demands a high degree of control over process parameters during synthesis. For nanocrystal synthesis, solution-based techniques typically include application of external convective heat. This process often leads to slow heating and allows decomposition of reagents or products over time. Microwave-assisted heating provides faster, localized heating at the molecular level with near instantaneous control over reaction parameters. In this work, microwave-assisted heating has been applied for the synthesis of II-VI semiconductor nanocrystals namely, ZnO nanopods and CdX (X = Se, Te) quantum dots (QDs). Based on factors such as size, surface functionality and charge, optical properties of such nanomaterials can be tuned for application as sensors. ZnO is a direct bandgap semiconductor (3.37 eV) with a large exciton binding energy (60 meV) leading to photoluminescence (PL) at room temperature. A microwave-assisted hydrothermal approach allows the use of sub-5 nm ZnO zero-dimensional nanoparticles as seeds for generation of multi-legged quasi one-dimensional nanopods via heterogeneous nucleation. ZnO nanopods, having individual leg diameters of 13-15 nm and growing along the [0001] direction, can be synthesized in as little as 20 minutes. ZnO nanopods exhibit a broad defect-related PL spanning the visible range with a peak at ~615 nm. Optical sensing based on changes in intensity of the defect PL in response to external environment (e.g., humidity) is demonstrated in this work. Microwave-assisted synthesis was also used for organometallic synthesis of CdX(ZnS) (X = Se, Te) core(shell) QDs. Optical emission of these QDs can be altered based on their size and can be tailored to specific wavelengths. Further, QDs were incorporated in Enhanced Green-Fluorescent Protein -- Ultrabithorax (EGFP-Ubx) fusion protein for the generation of macroscale composite protein fibers via hierarchal self-assembly. Variations in EGFP- Ubx˙QD composite

  12. Solidification of II-VI Compounds in a Rotating Magnetic Field

    NASA Technical Reports Server (NTRS)

    Gillies, D. C.; Volz, M. P.; Mazuruk, K.; Motakef, S.; Dudley, M.; Matyi, R.

    1999-01-01

    This project is aimed at using a rotating magnetic field (RMF) to control fluid flow and transport during directional solidification of elemental and compound melts. Microgravity experiments have demonstrated that small amounts of residual acceleration of less than a micro-g can initiate and prolong fluid flow, particularly when there is a static component of the field perpendicular to the liquid solid interface. Thus a true diffusion boundary layer is not formed, and it becomes difficult to verify theories of solidification or to achieve diffusion controlled solidification. The RMF superimposes a stirring effect on an electrically conducting liquid, and with appropriate field strengths and frequencies, controlled transport of material through a liquid column can be obtained. As diffusion conditions are precluded and complete mixing conditions prevail, the technique is appropriate for traveling solvent zone or float zone growth methods in which the overall composition of the liquid can be maintained throughout the growth experiment. Crystals grown by RMF techniques in microgravity in previous, unrelated missions have shown exceptional properties. The objective of the project is two-fold, namely (1) using numerical modeling to simulate the behavior of a solvent zone with applied thermal boundary conditions and demonstrate the effects of decreasing gravity levels, or an increasing applied RMF, or both, and (2) to grow elements and II-VI compounds from traveling solvent zones both with and without applied RMFs, and to determine objectively how well the modeling predicts solidification parameters. Numerical modeling has demonstrated that, in the growth of CdTe from a tellurium solution, a rotating magnetic field can advantageously modify the shape of the liquid solid interface such that the interface is convex as seen from the liquid. Under such circumstances, the defect structure is reduced as any defects which are formed tend to grow out and not propagate. The flow

  13. Precipitation of anion inclusions and plasticity under hydrostatic pressure in II-VI crystals

    NASA Astrophysics Data System (ADS)

    Lindberg, G. P.; Weinstein, B. A.

    2016-10-01

    Precipitation of anion nanocrystals (NCs) in initially stoichiometric II-VI crystals under hydrostatic pressure and light exposure is explored by Raman spectroscopy, and the mechanism for this effect is analyzed by model calculations. ZnSe, ZnTe, and CdSe crystals are studied in bulk and/or epitaxial-film forms. Se and Te NCs in the trigonal (t) phase precipitate in ZnSe and ZnTe, but the effect is absent or minimal in CdSe. The precipitation is induced by pressure and assisted by sub-band-gap light. In ZnSe, t-Se NCs appear for pressure exceeding 4.8 GPa and light flux above 50 -70 W /m m2 . In ZnTe, the precipitation of t-Te NCs requires less pressure to initiate, and there is a clear upper-pressure limit for t-Te nuclei to form. We find also that ZnTe samples with cleavage damage or elevated zinc-vacancy content are more prone to form t-Te NCs at lower pressures (even 1 atm in some cases) and lower flux. The precipitation seen in ZnSe and ZnTe occurs at pressures far below their phase transitions, and cannot be due to those transitions. Rather, we propose that the NCs nucleate on dislocations that arise from hydrostatic-pressure induced plastic flow triggered by noncubic defect sites. Calculations of the kinetic barrier for growth of an optimally shaped nucleus are performed, including hydrostatic pressure in the energy minimization scheme. Using sensible values for the model parameters related to the cohesive energies of Se and Te, the calculations account for our main observations, including the existence of an upper pressure limit for precipitation, and the absence of precipitation in CdSe. We consider the effects of pressure-induced precipitate formation on the I-II phase transitions in a variety of binary semiconductors and make predictions of when this effect should be important.

  14. Ground-based research of crystal growth of II-VI compound semiconductors by physical vapor transport

    NASA Technical Reports Server (NTRS)

    Volz, M. P.; Gillies, D. C.; Szofran, F. R.; Lehoczky, S. L.; Su, Ching-Hua; Sha, Yi-Gao; Zhou, W.; Dudley, M.; Liu, Hao-Chieh; Brebrick, R. F.; Wang, J. C.

    1994-01-01

    Ground-based investigation of the crystal growth of II-VI semiconductor compounds, including CdTe, CdS, ZnTe, and ZnSe, by physical vapor transport in closed ampoules was performed. The crystal growth experimental process and supporting activities--preparation and heat treatment of starting materials, vapor partial pressure measurements, and transport rate measurements are reported. The results of crystal characterization, including microscopy, microstructure, optical transmission photoluminescence, synchrotron radiation topography, and chemical analysis by spark source mass spectrography, are also discussed.

  15. Study on the oxygen vacancy redistribution and the mechanism of electrical manipulation of ferromagnetism in diluted magnetic oxides

    SciTech Connect

    Ren, Shuxia; Dong, Jingyu; Chen, Wei Zhang, Liyong; Guo, Jiajun; Zhang, Li; Zhao, Jing; Zhao, Xu

    2015-12-21

    Electrical manipulation of room temperature ferromagnetism (RTFM) has been observed in several kinds of transition metal doped diluted magnetic oxide films. We demonstrate using X-ray photoelectron spectroscopy that the redistribution of the oxygen vacancies in a film under an electric field plays a crucial role in the enhancement of the RTFM. Based on a detailed analysis of the X-ray photoelectron spectroscopy data for the oxygen vacancy distribution in different resistive states, a unified mechanism has been proposed. This work points out a new direction for improving the magnetic properties of these materials by controlling oxygen vacancies in the interior of the films.

  16. Self-Interaction Corrections to the Electronic Structure of II-VI and III-V Nitride Semiconductors

    NASA Astrophysics Data System (ADS)

    Pollmann, J.

    1998-03-01

    II-VI and group-III nitride semiconductors have paramount technological potential for applications in micro- and optoelectronics. A most accurate description of their bulk electronic structure as a basis for studying defect properties, band-edge properties in respective ternary or quaternary alloys and electronic properties of their surfaces and interfaces is of major importance, therefore. Standard LDA band-structure calculations for these wide-band-gap compounds using nonlocal normconserving pseudopotentials yield gap energies and semicore d-band positions that are largely at variance with experimental data. Actually, InN even turns out to be a semimetal with a negative gap of about --0.4 eV in standard LDA, in contrast to the experimental gap of 1.9 eV. To improve the theoretical basis for the above mentioned studies, we have developed self-interaction- and relaxation-corrected pseudopotentials (SIRC-PPs) which are very efficient and physically well-founded. The properties of the constituent atoms are incorporated in these SIRC-PPs as accurately as possible from the start by taking atomic SIC contributions and electronic relaxation in the atoms fully into account. By this construction, we arrive at very useful pseudopotentials and effective one-particle Hamiltonians for the solids that can readily be employed in ab-initio LDA codes. This approach is computationally not more involved than any LDA calculation and, nevertheless, overcomes to a large extent the above mentioned shortcomings of standard LDA calculations employing 'state-of-the-art' pseudopotentials. Applications of our approach to II-VI and group-III nitride semiconductors have shown very gratifying results. The approach has also proven very useful for Hg-chalcogenides, as well as, for Ag- and Cu-halides. The calculations yield band structures, d-band positions, gap energies, densities of states, lattice constants, bulk moduli and effective masses in very good agreement with experiment. Due to the

  17. Effect of diluted and preheated oxidizer on the emission of methane flameless combustion

    NASA Astrophysics Data System (ADS)

    Hosseini, Seyed Ehsan; Salehirad, Saber; Wahid, M. A.; Sies, Mohsin Mohd; Saat, Aminuddin

    2012-06-01

    In combustion process, reduction of emissions often accompanies with output efficiency reduction. It means, by using current combustion technique it is difficult to obtainlow pollution and high level of efficiency in the same time. In new combustion system, low NOxengines and burners are studied particularly. Recently flameless or Moderate and Intensive Low oxygen Dilution (MILD) combustion has received special attention in terms of low harmful emissions and low energy consumption. Behavior of combustion with highly preheated air was analyzed to study the change of combustion regime and the reason for the compatibility of high performance and low NOx production. Sustainability of combustion under low oxygen concentration was examined when; the combustion air temperature was above the self-ignition temperature of the fuel. This paper purposes to analyze the NOx emission quantity in conventional combustion and flameless combustion by Chemical Equilibrium with Applications (CEA) software.

  18. Liquid chromatography, chemical oxidation, and online carbon isotope dilution mass spectrometry as a universal quantification system for nonvolatile organic compounds.

    PubMed

    Díaz, Sergio Cueto; Encinar, Jorge Ruiz; Sanz-Medel, Alfredo; Alonso, J Ignacio García

    2013-02-01

    A procedure for the universal detection and quantification of polar organic compounds separated by liquid chromatography (LC) based on postcolumn carbon isotope dilution mass spectrometry (IDMS) was developed. The eluent from the LC column is mixed online with a continuous flow of (13)C-enriched sodium bicarbonate, and the sodium persulfate oxidation reaction in acidic media is employed to achieve isotope equilibration. All carbon-containing compounds eluting from the column are oxidized to (12)CO(2) and (13)CO(2), respectively, and the carbon dioxide is separated from the aqueous phase using a gas-permeable membrane. The gaseous carbon dioxide is then carried to the mass spectrometer for isotope ratio measurements. Different water-soluble organic compounds were evaluated using a flow injection configuration to assess the efficiency of the oxidation process. Most water-soluble organic compounds tested showed quantitative oxidation. However, chemical structures involving conjugated C═N double bounds and guanidinium-like structures were found to be resistant to the oxidation and were further studied. For this purpose, (13)C(1)-labeled creatine (with the isotopic label in the guanidinium group) was employed as model compound. Specific conditions for the quantitative oxidation of these compounds required lower flow rates and the addition of metallic catalysts. This novel approach was tested as a universal detection and quantification system for LC. A simple standard mixture of four amino acids was separated under 100% aqueous conditions and quantified without the need for specific standards with good accuracy and precision using potassium hydrogen phthalate as internal standard. The main field of application of the developed method is for the purity assessment of organic standards with direct traceability to the International System of Units (SI). PMID:23252800

  19. Effect of Residual Accelerations on the Crystal Growth of II-VI Semiconductors in Low Earth Orbit

    NASA Technical Reports Server (NTRS)

    Gillies, D. C.; Su, C.-H.; Szofran, F. R.; Scripa, R. N.; Cobb, S. D.; Lehoczky, S. L.; Curreri, Peter A. (Technical Monitor)

    2002-01-01

    The paper compares and summarizes the effects of residual acceleration during crystal growth on the compositional variation of two II-VI solid solution binary alloys (Hg(0.8)Cd(0.2)Te and Hg(0.84)Zn(0.16)Te). The crystals were grown by directional solidification on the second United States Microgravity Payload (USMP-2) and the first United States Microgravity Laboratory (USML-1) missions, respectively. For both alloys, changes in the direction and magnitude of the quasisteady acceleration vector (approximately 0.4- 1 mu g) caused large changes in the radial compositional distribution that demonstrates the importance of residual accelerations, even in the submicrogravity range, for large density gradients in the melt and slow solidification rates. The observed compositional variations will be correlated to changes in the radial flow velocities ahead of the solidification interface.

  20. Engineering the cell-semiconductor interface: a materials modification approach using II-VI and III-V semiconductor materials.

    PubMed

    Bain, Lauren E; Ivanisevic, Albena

    2015-02-18

    Developing functional biomedical devices based on semiconductor materials requires an understanding of interactions taking place at the material-biosystem interface. Cell behavior is dependent on the local physicochemical environment. While standard routes of material preparation involve chemical functionalization of the active surface, this review emphasizes both biocompatibility of unmodified surfaces as well as use of topographic features in manipulating cell-material interactions. Initially, the review discusses experiments involving unmodified II-VI and III-V semiconductors - a starting point for assessing cytotoxicity and biocompatibility - followed by specific surface modification, including the generation of submicron roughness or the potential effect of quantum dot structures. Finally, the discussion turns to more recent work in coupling topography and specific chemistry, enhancing the tunability of the cell-semiconductor interface. With this broadened materials approach, researchers' ability to tune the interactions between semiconductors and biological environments continues to improve, reaching new heights in device function.

  1. II-VI Compounds 1991; Proceedings of the 5th International Conference, Tamano, Japan, Sept. 8-13, 1991

    NASA Astrophysics Data System (ADS)

    Fujita, Shigeo; Nishino, Taneo; Taguchi, Tsunemasa

    1992-02-01

    The present conference discusses topics concerning the crystal growth processing methods for narrow-gap and wide-gap materials, characterization methods for both material types, doping techniques, quantum well and heterostructure characteristics, quantum dots, defect and impurity effects, optical properties and excitons, semimagnetic materials, and applications of II-VI semiconductor compound-based devices. Among the applications discussed are compact blue lasers, bistable CdS-film optical devices, single-insulating thin-film cold cathodes, high-efficiency thin-film electroluminescent devices, CdS/CdTe heterojunction solar cells, double-insulating electroluminescent devices, full-color TV projectors based on electron beam-pumped semiconductor lasers, and blue/green lasers.

  2. Synthesis, functionalization, and biological tagging applications of II-VI semiconductor nanocrystals

    NASA Astrophysics Data System (ADS)

    Wang, Jun

    Fluorescent labeling of biological molecules is a technique that is used widely for analytical purposes in biotechnology and bioengineering. It typically involves the use of an organic dye molecule linked to a moiety that selectively bonds a particular biological molecule, allowing the detection of the latter by the fluorescence of the dye molecule. Semiconductor nanocrystals or quantum dots have emerged as a new class of fluorescent markers with distinct advantages over the traditional organic dyes. Their attractive properties include narrow, symmetric, and bright emission, continuous excitation by any wavelength smaller than the emission wavelength, broad absorption spectrum, long lifetime, resistance to photobleaching, as well as excellent optical and chemical stability that allows their use in lengthy experiments. The focus of this thesis is the synthesis and surface functionalization of ZnSe quantum dots and (ZnSe)ZnS core-shell nanostructures, and their biological conjugation with DNA and protein. The ability to synthesize different populations of quantum dots with narrow emission spectra permits multiplexing, a property that is very important for simultaneous detection of several analytes, which would be very tedious and expensive if done sequentially. Highly luminescent ZnSe nanocrystals have been synthesized using a hot-injection colloidal method. The synthesis was performed in a stirred batch reactor containing liquid hexadecylamine at 310°C. The precursors were diethylzinc diluted in heptane and selenium powder mixed with trioctylphosphine. The mixture of reactants was injected into the batch reactor and the time of reaction was used to control the size and luminescence emission wavelength of the quantum dots. In order to optimize the process various parameters that can influence the photoluminescence property of quantum dots obtained were investigated, such as surfactant addition, temperature, precursor ratio, and mixing conditions. Capping of the Zn

  3. Coupling digestion in a pilot-scale UASB reactor and electrochemical oxidation over BDD anode to treat diluted cheese whey.

    PubMed

    Katsoni, Alphathanasia; Mantzavinos, Dionissios; Diamadopoulos, Evan

    2014-11-01

    The efficiency of the anaerobic treatment of cheese whey (CW) at mesophilic conditions was investigated. In addition, the applicability of electrochemical oxidation as an advanced post-treatment for the complete removal of chemical oxygen demand (COD) from the anaerobically treated cheese whey was evaluated. The diluted cheese whey, having a pH of 6.5 and a total COD of 6 g/L, was first treated in a 600-L, pilot-scale up-flow anaerobic sludge blanket (UASB) reactor. The UASB process, which was operated for 87 days at mesophilic conditions (32 ± 2 °C) at a hydraulic retention time (HRT) of 3 days, led to a COD removal efficiency between 66 and 97 %, while the particulate matter of the wastewater was effectively removed by entrapment in the sludge blanket of the reactor. When the anaerobic reactor effluent was post-treated over a boron-doped diamond (BDD) anode at 9 and 18 A and in the presence of NaCl as the supporting electrolyte, complete removal of COD was attained after 3-4 h of reaction. During electrochemical experiments, three groups of organochlorinated compounds, namely trihalomethanes (THMs), haloacetonitriles (HANs), and haloketons (HKs), as well as 1,2-dichloroethane (DCA) and chloropicrin were identified as by-products of the process; these, alongside free chlorine, are thought to increase the matrix ecotoxicity to Artemia salina. PMID:24793070

  4. Mechanism of Oxidation of Ethane to Ethanol at Iron(IV)-Oxo Sites in Magnesium-Diluted Fe2(dobdc).

    PubMed

    Verma, Pragya; Vogiatzis, Konstantinos D; Planas, Nora; Borycz, Joshua; Xiao, Dianne J; Long, Jeffrey R; Gagliardi, Laura; Truhlar, Donald G

    2015-05-01

    The catalytic properties of the metal-organic framework Fe2(dobdc), containing open Fe(II) sites, include hydroxylation of phenol by pure Fe2(dobdc) and hydroxylation of ethane by its magnesium-diluted analogue, Fe0.1Mg1.9(dobdc). In earlier work, the latter reaction was proposed to occur through a redox mechanism involving the generation of an iron(IV)-oxo species, which is an intermediate that is also observed or postulated (depending on the case) in some heme and nonheme enzymes and their model complexes. In the present work, we present a detailed mechanism by which the catalytic material, Fe0.1Mg1.9(dobdc), activates the strong C-H bonds of ethane. Kohn-Sham density functional and multireference wave function calculations have been performed to characterize the electronic structure of key species. We show that the catalytic nonheme-Fe hydroxylation of the strong C-H bond of ethane proceeds by a quintet single-state σ-attack pathway after the formation of highly reactive iron-oxo intermediate. The mechanistic pathway involves three key transition states, with the highest activation barrier for the transfer of oxygen from N2O to the Fe(II) center. The uncatalyzed reaction, where nitrous oxide directly oxidizes ethane to ethanol is found to have an activation barrier of 280 kJ/mol, in contrast to 82 kJ/mol for the slowest step in the iron(IV)-oxo catalytic mechanism. The energetics of the C-H bond activation steps of ethane and methane are also compared. Dehydrogenation and dissociation pathways that can compete with the formation of ethanol were shown to involve higher barriers than the hydroxylation pathway. PMID:25882096

  5. Sequential treatment of diluted olive pomace leachate by digestion in a pilot scale UASB reactor and BDD electrochemical oxidation.

    PubMed

    Katsoni, Alphathanasia; Mantzavinos, Dionissios; Diamadopoulos, Evan

    2014-06-15

    The efficiency of the anaerobic treatment of olive pomace leachate (OPL) at mesophilic conditions was investigated. Daily and cumulative biogas production was measured during the operational period. The maximum biogas flowrate was 65 L/d, of which 50% was methane. In addition, the applicability of electrochemical oxidation as an advanced post-treatment method for the complete removal of chemical oxygen demand (COD) from the anaerobically treated OPL was evaluated. The diluted OPL, having a pH of 6.5 and a total COD of 5 g/L, was first treated in a 600 L, pilot-scale up-flow anaerobic sludge blanket (UASB) reactor. The UASB reactor was operated for 71 days at mesophilic conditions (32 ± 2 °C) in a temperature-controlled environment at a hydraulic retention time of 3 days, and organic loading rates (OLR) between 0.33 and 1.67 g COD/(L.d). The UASB process led to a COD removal efficiency between 35 and 70%, while the particulate matter of the wastewater was effectively removed by entrapment in the sludge blanket of the reactor. When the anaerobic reactor effluent was post-treated over a boron-doped diamond (BDD) anode at 18 A and in the presence of 0.17% NaCl as the supporting electrolyte, complete removal of COD was attained after 7 h of treatment predominantly through total oxidation reactions. During electrochemical experiments, three groups of organo-chlorinated compounds, namely trihalomethanes (THMs), haloacetonitriles (HANs) and haloketons (HKs), as well as 1,2-dichloroethane (DCA) and chloropicrin were identified as by-products of the process; these, along with the residual chlorine are thought to increase the matrix ecotoxicity to Artemia salina. PMID:24704905

  6. Transforming common III-V/II-VI insulating building blocks into topological heterostructure via the intrinsic electric polarization

    NASA Astrophysics Data System (ADS)

    Zunger, Alex; Zhang, Xiuwen; Abdalla, Leonardo; Liu, Qihang

    Currently known topological insulators (TIs) are limited to narrow gap compounds incorporating heavy elements, thus severely limiting the material pool available for such applications. We show how a heterovalent superlattice made of common semiconductor building blocks can transform its non-TI components into a topological heterostructure. The heterovalent nature of such interfaces sets up, in the absence of interfacial atomic exchange, a natural internal electric field that along with the quantum confinement leads to band inversion, transforming these semiconductors into a topological phase while also forming a giant Rashba spin splitting. We demonstrate this paradigm of designing TIs from ordinary semiconductors via first-principle calculations on III-V/II-VI superlattice InSb/CdTe. We illustrate the relationship between the interfacial stability and the topological transition, finding a ``window of opportunity'' where both conditions can be optimized. This work illustrates the general principles of co-evaluation of TI functionality with thermodynamic stability as a route of identifying realistic combination of common insulators that could produce topological heterostructures. This work was supported by Basic Energy Science, MSE division (Grant DE-FG02-13ER46959).

  7. Correlation of Schottky constants with interatomic distances of selected I-VII and II-VI compounds

    NASA Astrophysics Data System (ADS)

    Wiedemeier, Heribert

    2013-10-01

    The observed linear (Na-, K-halides) and near-linear (Mg-, Sr-, Zn-, Cd-, and Hg-chalcogenides) dependences of Schottky constants on reciprocal interatomic distances yield the relation logKS=((ss1/T)+is)1/d(A-B)+(si1/T)+ii, where KS is the product of metal and non-metal thermal equilibrium vacancy concentrations, and ss, is, si and ii are the group specific slope and intercept values obtained from an extended analysis of the above log KS versus 1/d(A-B) data. The previously reported linear dependences of log KS on the Born-Haber lattice energies [1] are the basis for combining the earlier results [1] with the Born-Mayer lattice energy equation to yield a new thermodynamic relationship, namely logKS=-(2.303(c(B-M)/d(A-B)-Ie), where c(B-M) is the product of the constants of the Born-Mayer equation and Ie is the metal ionization energy of the above compounds. These results establish a correlation between point defect concentrations and basic thermodynamic, coulombic, and structural solid state properties for selected I-VII and II-VI semiconductor materials.

  8. Extraction of beryllium from refractory beryllium oxide with dilute ammonium bifluoride and determination by fluorescence: a multiparameter performance evaluation.

    PubMed

    Goldcamp, Michael J; Goldcamp, Diane M; Ashley, Kevin; Fernback, Joseph E; Agrawal, Anoop; Millson, Mark; Marlow, David; Harrison, Kenneth

    2009-12-01

    Beryllium exposure can cause a number of deleterious health effects, including beryllium sensitization and the potentially fatal chronic beryllium disease. Efficient methods for monitoring beryllium contamination in workplaces are valuable to help prevent dangerous exposures to this element. In this work, performance data on the extraction of beryllium from various size fractions of high-fired beryllium oxide (BeO) particles (from < 32 microm up to 212 microm) using dilute aqueous ammonium bifluoride (ABF) solution were obtained under various conditions. Beryllium concentrations were determined by fluorescence using a hydroxybenzoquinoline fluorophore. The effects of ABF concentration and volume, extraction temperature, sample tube types, and presence of filter or wipe media were examined. Three percent ABF extracts beryllium nearly twice as quickly as 1% ABF; extraction solution volume has minimal influence. Elevated temperatures increase the rate of extraction dramatically compared with room temperature extraction. Sample tubes with constricted tips yield poor extraction rates owing to the inability of the extraction medium to access the undissolved particles. The relative rates of extraction of Be from BeO of varying particle sizes were examined. Beryllium from BeO particles in fractions ranging from less than 32 microm up to 212 microm were subjected to various extraction schemes. The smallest BeO particles are extracted more quickly than the largest particles, although at 90 degrees C even the largest BeO particles reach nearly quantitative extraction within 4 hr in 3% ABF. Extraction from mixed cellulosic-ester filters, cellulosic surface-sampling filters, wetted cellulosic dust wipes, and cotton gloves yielded 90% or greater recoveries. Scanning electron microscopy of BeO particles, including partially dissolved particles, shows that dissolution in dilute ABF occurs not just on the exterior surface but also via accessing particles' interiors due to porosity

  9. Metalorganic vapor phase epitaxy of wide-gap II VI semiconductors for optoelectronic applications: current status and future trends

    NASA Astrophysics Data System (ADS)

    Heuken, Michael

    1995-01-01

    The current status and future trends to overcome the major problems of wide-gap II-VI compounds grown by metalorganic vapor phase epitaxy (MOVPE) which are p-type doping and the understanding of interface properties of {ZnSSe}/{ZnSe-based} heterostructures will be discussed. Since a low growth temperature is required to reduce defects and impurities and to increase the sticking coefficient of dopant atoms, a matched precursor combination of zinc and selenium compounds or an additional growth assistance (e.g. plasma stimulation) must be employed. The optical and electrical properties of ZnSe doped with nitrogen will be discussed. Emphasis will be put on the fact that most of the MOVPE grown ZnSe:N layers remain highly resistive or that they show only low free hole concentrations. Occurring compensation mechanisms such as parasitic compensating donors associated with nitrogen or compensating nitrogen-hydrogen complexes may be the reason. The ability of MOVPE to handle high vapor pressure elements such as sulphur favours this technology for the growth of sophisticated quantum wells and superlattices to achieve electrical and optical confinement in laser structures and to push the emission wavelength further into the blue. Scanning transmission electron microscope, photoluminescence (PL) and X-ray measurements were used for the analysis of the interface properties. Growth optimization of {ZnSSe}/{ZnSe} interfaces results in monolayer fluctuations at the interfaces. High excitation PL experiments show that room temperature stimulated emission is possible with this kind of structures. To realize high bit rate data transmission in the blue spectral range at 2.7 eV the physical properties of optoelectronic modulators based on {ZnSSe}/{ZnSe} superlattices were examined.

  10. Photoinduced electron donor/acceptor processes in colloidal II-VI semiconductor quantum dots and nitroxide free radicals

    NASA Astrophysics Data System (ADS)

    Dutta, Poulami

    Electron transfer (ET) processes are one of the most researched topics for applications ranging from energy conversion to catalysis. An exciting variation is utilizing colloidal semiconductor nanostructures to explore such processes. Semiconductor quantum dots (QDs) are emerging as a novel class of light harvesting, emitting and charge-separation materials for applications such as solar energy conversion. Detailed knowledge of the quantitative dissociation of the photogenerated excitons and the interfacial charge- (electron/hole) transfer is essential for optimization of the overall efficiency of many such applications. Organic free radicals are the attractive counterparts for studying ET to/from QDs because these undergo single-electron transfer steps in reversible fashion. Nitroxides are an exciting class of stable organic free radicals, which have recently been demonstrated to be efficient as redox mediators in dye-sensitized solar cells, making them even more interesting for the aforementioned studies. This dissertation investigates the interaction between nitroxide free radicals TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl), 4-amino-TEMPO (4-amino- 2,2,6,6-tetramethylpiperidine-1-oxyl) and II-VI semiconductor (CdSe and CdTe) QDs. The nature of interaction in these hybrids has been examined through ground-state UV-Vis absorbance, steady state and time-resolved photoluminescence (PL) spectroscopy, transient absorbance, upconversion photoluminescence spectroscopy and electron paramagnetic resonance (EPR). The detailed analysis of the PL quenching indicates that the intrinsic charge transfer is ultrafast however, the overall quenching is still limited by the lower binding capacities and slower diffusion related kinetics. Careful analysis of the time resolved PL decay kinetics reveal that the decay rate constants are distributed and that the trap states are involved in the overall quenching process. The ultrafast hole transfer from CdSe QDs to 4-Amino TEMPO observed

  11. II-VI oxides phase separate whereas the corresponding carbonates order: The stabilizing role of anionic groups

    NASA Astrophysics Data System (ADS)

    Chan, J. A.; Zunger, Alex

    2009-10-01

    The formation enthalpies of isovalent, isostructural rocksalt alloys, (A,B) , where X=O such as (Ca,Mg)O, are typically unfavorable (positive) for both ordered and random phases. Simple replacement of the single-atom anion, X , by a larger anionic group, such as CO3 or SO4 , is able to induce a favorable (negative) formation enthalpy, leading to the formation of the ordered alternate monolayer, (CaCO3)1/(MgCO3)1 , dolomite structure. The underlying cause of this behavior is analyzed by breaking down the formation process in a Born-Haber-like cycle into volume and cell-shape deformation, chemical exchange, and cell-internal relaxation using first-principles density-functional theory calculations in the generalized gradient approximation. It is found that when the anion is a group (CO3) , rather than a single atom (O), the energy gained from the internal relaxation overcomes the energy required to compensate the volume mismatch. This explains the general experimental trends of phase separation in isovalent, isostructural alloys without internal-anion structure, compared to ordering tendencies when the anionic group removes internal strain. The importance of obtaining structural ideality in the design of stable solid solutions is highlighted.

  12. Evolving biomolecular control and peptide specificity for the synthesis and assembly of II-VI semiconductor nanomaterials

    NASA Astrophysics Data System (ADS)

    Flynn, Christine Elizabeth

    Peptides were selected using an evolutionary screening process utilizing engineered virus libraries to isolated peptides that recognized, nucleated and controlled II-VI semiconductor materials. Specifically, materials screened for this project included polycrystalline and single crystal surfaces of ZnS, CdS, PbS, and ZnSe. Once a positive peptide recognition sequence was isolated using phage display screening, the population of peptides found for ZnS or CdS were successfully tested to decipher relative binding affinities, results that further verified the consensus motifs identified. The peptides selected were then used to nucleate nanocrystals, specifically controlling nanoparticle sizes and directing crystal phases of ZnS and CdS. The ZnS-specific A7 and Z8 peptides were isolated from virus screenings of ZnS and tested for ZnS nucleation ability. Upon HRTEM analysis of the resultant nanocrystals, two different phases of ZnS were grown in the presence of A7 and Z8. A7 directed the wurtzite structure crystal phase of ZnS while Z8 directed the sphalerite crystal phase of ZnS. Two CdS-specific peptides, J140 and J182, were isolated from virus screenings of CdS and were further tested, not only for their CdS recognition ability, but for their CdS nucleating ability. Upon HRTEM analysis of the resultant nanocrystals, two different phases of CdS were grown in the presence of J140 and J182, a trend parallel to that seen with ZnS specific phage grown nanocrystals. J140 directed the wurtzite structure crystal phase while J182 directed the zinc blende crystal phase. Further, orientation of the materials using display of the specific peptides as fusions on the viral protein coat indicated that relative order of nanocrystals over several hundred nanometers could be achieved, while maintaining the crystal phase and size selectivity that was seen on the smaller scale.

  13. Dilution Confusion: Conventions for Defining a Dilution

    ERIC Educational Resources Information Center

    Fishel, Laurence A.

    2010-01-01

    Two conventions for preparing dilutions are used in clinical laboratories. The first convention defines an "a:b" dilution as "a" volumes of solution A plus "b" volumes of solution B. The second convention defines an "a:b" dilution as "a" volumes of solution A diluted into a final volume of "b". Use of the incorrect dilution convention could affect…

  14. A two-stage pretreatment process using dilute hydrochloric acid followed by Fenton oxidation to improve sugar recovery from corn stover.

    PubMed

    Li, Wenzhi; Liu, Qiyu; Ma, Qiaozhi; Zhang, Tingwei; Ma, Longlong; Jameel, Hasan; Chang, Hou-Min

    2016-11-01

    A two-stage pretreatment process is proposed in this research in order to improve sugar recovery from corn stover. In the proposed process, corn stover is hydrolyzed by dilute hydrochloric acid to recover xylose, which is followed by a Fenton reagent oxidation to remove lignin. 0.7wt% dilute hydrochloric acid is applied in the first stage pretreatment at 120°C for 40min, resulting in 81.0% xylose removal. Fenton reagent oxidation (1g/L FeSO4·7H2O and 30g/L H2O2) is performed at room temperature (about 20°C) for 12 has a second stage which resulted in 32.9% lignin removal. The glucose yield in the subsequent enzymatic hydrolysis was 71.3% with a very low cellulase dosage (3FPU/g). This two-stage pretreatment is effective due to the hydrolysis of hemicelluloses in the first stage and the removal of lignin in the second stage, resulting in a very high sugar recovery with a low enzyme loading. PMID:27543312

  15. Electrochemical photovoltaic cells stabilization and optimization of II-VI semiconductors. Third technical progress report, 1 October 1980 to 31 December 1980

    SciTech Connect

    Noufi, R.; Tench, D.; Warren, L.

    1981-01-20

    A program to provide the basis for designing a practical electrochemical solar cell based on the II-VI compound semiconductors is described. Emphasis is on developing new electrolyte redox systems and electrode surface modifications which will stabilize the II-VI compounds against photodissolution without seriously degrading the long-term solar response. Work on redox couple stabilization of n-CdX photoanodes has focused on fast metal-based one-electron couples in various nonaqueous solvents which represent an extension of work with the methanol/ferro-ferricyanide system, which, although stabilizing for n-CdSe photoanodes, has been found to be photolytically unstable. Very promising results which were obtained for the FeCl/sub 4//sup 1-/2-/ couple in acetonitrile suggest that related chloro-couples should be considered, including the colorless two-electron tin (II, IV) and antimony (III, V) systems. Conducting polymer films of polyrrole photoelectrochemically deposited onto n-type semiconductors were previously shown to protect these electrode materials from photodecomposition while permitting electron exchange with the electrolyte, but poor adhesion has remained a key problem. Recently, improved adhesion has been attained for roughened semiconductor surfaces. It now appears that polypyrrole films are to some extent permeable to solvent/solute species since the film stability depends on the nature of the redox electrolyte, and semiconductor decomposition products seem to form underneath the film in some cases. One possibility for circumventing this problem is to incorporate larger species, e.g., phthalocyanine dyes, within the film matrix.

  16. Leaching of lead slag component by sodium chloride and diluted nitric acid and synthesis of ultrafine lead oxide powders

    NASA Astrophysics Data System (ADS)

    Shu, Yuehong; Ma, Cheng; Zhu, Longguan; Chen, Hongyu

    2015-05-01

    The compounds in lead slag are transformed into [PbCl4]2- in a mixed solution of HNO3 and NaCl, which is converted into PbC2O4 by the addition of sodium oxalate and polyethylene glycol dispersant. Novel lead oxides are prepared via a combustion-calcination process from lead oxalate precursor. Key properties of the new oxides, such as crystalline phases and morphology, have been characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results show that lead oxides synthesized at different calcination temperatures comprise mainly α-PbO and β-PbO phases. In battery testing, the results reveal that the α-PbO phase exhibits higher initial capacity as positive active material, discharging about 150 mAh g-1 at 20 mA g-1. While β-PbO yields a relatively improved cycle life, in 50 cycles, its capacity loss is 5%. Further work is being carried out with the aim to optimize the battery manufacturing process or to find out the optimum ratio of α-PbO to β-PbO in order to sustain high discharge capacity and acceptable cycle life.

  17. Internal correction of hafnium oxide spectral interferences and mass bias in the determination of platinum in environmental samples using isotope dilution analysis.

    PubMed

    Rodríguez-Castrillón, José Angel; Moldovan, Mariella; García Alonso, J Ignacio

    2009-05-01

    A method has been developed for the accurate determination of platinum by isotope dilution analysis, using enriched (194)Pt, in environmental samples containing comparatively high levels of hafnium without any chemical separation. The method is based on the computation of the contribution of hafnium oxide as an independent factor in the observed isotope pattern of platinum in the spiked sample. Under these conditions, the ratio of molar fractions between natural abundance and isotopically enriched platinum was independent of the amount of hafnium present in the sample. Additionally, mass bias was corrected by an internal procedure in which the regression variance was minimised. This was possible as the mass bias factor for hafnium oxide was very close to that of platinum. The final procedure required the measurement of three platinum isotope ratios (192/194, 195/194 and 196/194) to calculate the concentration of platinum in the sample. The methodology has been validated using the reference material "BCR-723 road dust" and has been applied to different environmental matrices (road dust, air particles, bulk wet deposition and epiphytic lichens) collected in the Aspe Valley (Pyrenees Mountains). A full uncertainty budget, using Kragten's spreadsheet method, showed that the total uncertainty was limited only by the uncertainty in the measured isotope ratios and not by the uncertainties of the isotopic composition of platinum and hafnium.

  18. Body composition in Mexican adults by air displacement plethysmography (ADP) with the BOD-POD and deuterium oxide dilution using infrared spectroscopy (IRS-DOD).

    PubMed

    Macías, Nayeli; Calderón de la Barca, Ana María; Bolaños, Adriana V; Alemán, Heliodoro; Esparza, Julián; Valencia, Mauro E

    2002-09-01

    Thirty four subjects (13 men and 21 women), 24 to 70 years old from northern Mexico, were measured for body density by air displacement plethysmography (ADP) with the BOD-POD, and for total body water by deuterium oxide dilution and infrared spectroscopy (IRS-DOD). Subjects were given a 30 g dose of deuterium oxide. Saliva samples were filtered, sublimated, and deuterium was measured using a Miran 1 FF, IRS. Linear regression of the fat mass (FM) derived from both methods showed that the intercept (0.071) was not different from zero (p = .96) and the slope was 0.96 (p < .0001) demonstrating the techniques to be equivalent. Further, mean FM was 26.7 +/- 12.4 and 25.6 +/- 12.4 kg, for IRS-DOD and ADP techniques, respectively (p = .08). Precision analysis by the model R2 showed that 92.3% of the variability was explained (SEM = 3.4 kg). Bland-Altman analysis showed no significant bias (r = 0.017; p = .93). Mean difference between methods was -1.08 (CI: -2.3 to + 0.13) kg FM.

  19. Abundance and activity of vinyl chloride (VC)-oxidizing bacteria in a dilute groundwater VC plume biostimulated with oxygen and ethene.

    PubMed

    Mattes, Timothy E; Jin, Yang Oh; Livermore, Joshua; Pearl, Meredith; Liu, Xikun

    2015-11-01

    Clean-up of vinyl chloride (VC)-contaminated groundwater could be enhanced by stimulating aerobic VC-oxidizing bacterial populations (e.g., methanotrophs) with amendments such as molecular oxygen. In addition, ethene gas injection could further stimulate a different group of aerobic ethene- and VC-oxidizing bacteria called "etheneotrophs." We estimated the abundance and activity of these different VC-oxidizing bacteria in portions of a dilute groundwater VC plume subjected to oxygen and ethene biostimulation. Pyrosequencing of 16S rRNA genes, amplified from community DNA extracted from five groundwater monitoring wells, revealed that Proteobacteria dominated the microbial community. Among the Proteobacteria, methanotroph relative abundance was 6.00 % (well RB52I), 2.81 % (well RB46D), 56.3 % (well RB58I), 23.8 % (well RB63I), and 2.57 % (well RB64I). Reverse transcription qPCR (RT-qPCR) analysis was used to determined methanotroph and etheneotroph functional gene expression from selected monitoring wells. Resulting transcript per gene ratios for methanotroph functional genes (pmoA and mmoX) were 0.013 (RB46D), 0.017 (RB63I), 0.112 (RB64I), and 0.004 (RB46D), 0.239 (RB63I), and 0.199 (RB64I), respectively. Transcript per gene ratios for etheneotroph functional genes (etnC and etnE) were 0.37 (RB46D), 0.81 (RB63I), 5.85 (RB64I), and 0.38 (RB46D), 0.67 (RB63I), and 2.28 (RB64I), respectively. When considered along with geochemical and contaminant data from these wells, our RT-qPCR results suggest that methanotrophs and etheneotrophs were participating in VC cometabolism. We conclude that these molecular diagnostic techniques could be helpful to site managers interested in documenting the effectiveness of VC bioremediation strategies.

  20. Study by ESI-FTICRMS and ESI-FTICRMS(n) of zinc and cadmium thiophenolate complexes used as precursors for the synthesis of II-VI nanosemiconductors.

    PubMed

    Arl, Didier; Aubriet, Frédéric; Gaumet, Jean-Jacques

    2009-05-01

    [M(4)(SC(6)H(5))(10)][(CH(3))N](2), [M(10)L(4)(SC(6)H(5))(16)][(CH(3))N](4) and [Cd(17)S(4)(SC(6)H(5))(28)][(CH(3))N](2)(M = Cd or Zn, and L = S or Se) zinc and cadmium thiophenolates have been studied by electrospray ionization (ESI) Fourier transform ion cyclotron resonance (FTICR) mass spectrometry (ESI-FTICRMS) and tandem ESI-FTICRMS (ESI-FTICRMS(n)). ESI-FTICRMS demonstrated its ability to characterize and study such compounds, which may be used as precursors of II-VI nanomaterials. The obtained mass spectrum has been found to be highly relevant of the investigated thiophenolate and the fragmentation behavior of some of the detected ions is indicative of its stability. More specifically, it has been demonstrated that ESI in-source activation or fragmentation experiments conducted in the Fourier transform ion cyclotron resonance mass spectrometry (FTICRMS) cell induced the formation of a very stable entity, which corresponds to the general formula M(4)L(4) (M = Zn or Cd and L = S or Se). The elimination of SC(6)H(5)(-) and/or M(SC(6)H(5))(2) moieties by various activation processes from the studied thiophenolates led systematically to this structure.

  1. Systematic defect donor levels in III-V and II-VI semiconductors revealed by hybrid functional density-functional theory

    NASA Astrophysics Data System (ADS)

    Petretto, Guido; Bruneval, Fabien

    2015-12-01

    The identification of defect levels from photoluminescence spectroscopy is a useful but challenging task. Density-functional theory (DFT) is a highly valuable tool to this aim. However, the semilocal approximations of DFT that are affected by a band gap underestimation are not reliable to evaluate defect properties, such as charge transition levels. It is now established that hybrid functional approximations to DFT improve the defect description in semiconductors. Here we demonstrate that the use of hybrid functionals systematically stabilizes donor defect states in the lower part of the band gap for many defects, impurities or vacancies, in III-V and in II-VI semiconductors, even though these defects are usually considered as acceptors. These donor defect states are a very general feature and, to the best of our knowledge, have been overlooked in previous studies. The states we identify here may challenge the older assignments to photoluminescent peaks. Though appealing to screen quickly through the possible stable charge states of a defect, semilocal approximations should not be trusted for that purpose.

  2. Scattering amplitudes and static atomic correction factors for the composition-sensitive 002 reflection in sphalerite ternary III-V and II-VI semiconductors.

    PubMed

    Schowalter, M; Müller, K; Rosenauer, A

    2012-01-01

    Modified atomic scattering amplitudes (MASAs), taking into account the redistribution of charge due to bonds, and the respective correction factors considering the effect of static atomic displacements were computed for the chemically sensitive 002 reflection for ternary III-V and II-VI semiconductors. MASAs were derived from computations within the density functional theory formalism. Binary eight-atom unit cells were strained according to each strain state s (thin, intermediate, thick and fully relaxed electron microscopic specimen) and each concentration (x = 0, …, 1 in 0.01 steps), where the lattice parameters for composition x in strain state s were calculated using continuum elasticity theory. The concentration dependence was derived by computing MASAs for each of these binary cells. Correction factors for static atomic displacements were computed from relaxed atom positions by generating 50 × 50 × 50 supercells using the lattice parameter of the eight-atom unit cells. Atoms were randomly distributed according to the required composition. Polynomials were fitted to the composition dependence of the MASAs and the correction factors for the different strain states. Fit parameters are given in the paper.

  3. Investigation of p-side contact layers for II-VI compound semiconductor optical devices fabricated on InP substrates by MBE

    NASA Astrophysics Data System (ADS)

    Takamatsu, Shingo; Nomura, Ichirou; Shiraishi, Tomohiro; Kishino, Katsumi

    2015-09-01

    N-doped p-type ZnTe and ZnSeTe contact layers were investigated to evaluate which is more suitable for use in II-VI compound semiconductor optical devices on InP substrates. Contact resistances (Rc) between the contact layers and several electrode materials (Pd/Pt/Au, Pd/Au, and Au) were measured by the circular transmission line model (c-TLM) method using p-n diode samples grown on InP substrates by molecular beam epitaxy (MBE). The lowest Rc (6.5×10-5 Ω cm2) was obtained in the case of the ZnTe contact and Pd/Pt/Au electrode combination, which proves that the combination is suitable for obtaining low Rc. Yellow light-emitting diode devices with a ZnTe and ZnSeTe p-contact layer were fabricated by MBE to investigate the effect of different contact layers. The devices were characterized under direct current injections at room temperature. Yellow emission at around 600 nm was observed for each device. Higher emission intensity and lower slope resistance were obtained for the device with the ZnTe contact layer and Pd/Pt/Au electrode compared with other devices. These device performances are ascribed to the low Rc of the ZnTe contact and Pd/Pt/Au electrode combination.

  4. The impact of graphene oxide particles on viscosity stabilization for diluted polymer solutions using in enhanced oil recovery at HTHP offshore reservoirs

    NASA Astrophysics Data System (ADS)

    Dung Nguyen, Ba; Kien Ngo, Trung; Bui, Truong Han; Khanh Pham, Duy; Loc Dinh, Xuan; Nguyen, Phuong Tung

    2015-03-01

    Over 60% of the original oil in a place (OOIP) is retained in a reservoir after conventional methods have been exploited. Application of enhanced oil recovery (EOR) technology gives an additional chance to get out possibly about 20% more oil from the reservoir. The use of water-soluble polymers improves the water-oil mobility ratio, therefore, the displacement efficiency increased, and leads to enhanced oil recovery. High-molecular-weight polyacrylamide group is widely and successfully used in EOR. But no commercial polymer composition can be used in conditions of high temperature and hardness brine offshore reservoirs yet. To avoid the time consumption and high expense for selection and synthesis of the appropriate-structural polymer for EOR application, we attempt to find additives to enhance the thermal stability of polymer solutions. In this paper, we report the results of improved viscosity stability of diluted polymer/seawater solutions aged at reservoir conditions for 31days by adding graphite-oxide particles (GOs). In the presence of 300 ppm of GOs, the viscosity stability of 1700 ppm acrylamide-based polymer in sea water solution increases from 92 °C to 135 °C. FESEM pictures show good distribution of GOs in polymer network, which is a result of integration of functional groups in GOs surfaces and hydrophilic polymer chains.

  5. Preparation of II-VI semiconductor nanocrystallites in a glass matrix using chalcogenizing agent: Application to CdSe

    SciTech Connect

    Marc, J.L.; Granier, W.; Pradel, A.; Ribes, M.; Richard, T.; Allegre, J.; Lefebvre, P.

    1994-12-31

    A new route for preparing CdX (X = S, Se, Te, S+Se) nanocrystallites dispersed in a sodium borosilicate glass matrix from a hydrogel is proposed. Chalcogenizing complexing molecules -- for instance a mixture of NH{sub 4}SCN + H{sub 2}SeO{sub 3} -- introduced in the starting solution allowed an in situ crystallite preparation concomitant to gel densification. Prevention of crystallite oxidation is thus obtained. Moreover, coalescence is minimized because of the low gel-glass transition temperature. Low temperature absorption spectra have been interpreted in terms of exciton and electron-hole confinements, accounting for both an intrinsic broadening of energy states inside each nanocrystal and a Gaussian size distribution. Crystallite sizes and size dispersion can be adjusted by changing the initial Cd concentration. The crystallinity of the nanoparticles without change in dispersion is strongly improved by thermal treatment above the T{sub g} of the glass matrix.

  6. Real-time observation of morphological transformations in II-VI semiconducting nanobelts via environmental transmission electron microscopy

    SciTech Connect

    Agarwal, Rahul; Zakharov, Dmitri N.; Krook, Nadia M.; Liu, Wenjing; Berger, Jacob; Stach, Eric A.; Agarwal, Ritesh

    2015-05-01

    It has been observed that wurtzite II–VI semiconducting nanobelts transform into single-crystal, periodically branched nanostructures upon heating. The mechanism of this novel transformation has been elucidated by heating II–VI nanobelts in an environmental transmission electron microscope (ETEM) in oxidizing, reducing and inert atmospheres while observing their structural changes with high spatial resolution. The interplay of surface reconstruction of high-energy surfaces of the wurtzite phase and environment-dependent anisotropic chemical etching of certain crystal surfaces in the branching mechanism of nanobelts has been observed. Understanding of structural and chemical transformations of materials via in situ microscopy techniques and their role in designing new nanostructured materials is discussed.

  7. Real-time observation of morphological transformations in II-VI semiconducting nanobelts via environmental transmission electron microscopy

    DOE PAGES

    Agarwal, Rahul; Zakharov, Dmitri N.; Krook, Nadia M.; Liu, Wenjing; Berger, Jacob; Stach, Eric A.; Agarwal, Ritesh

    2015-05-01

    It has been observed that wurtzite II–VI semiconducting nanobelts transform into single-crystal, periodically branched nanostructures upon heating. The mechanism of this novel transformation has been elucidated by heating II–VI nanobelts in an environmental transmission electron microscope (ETEM) in oxidizing, reducing and inert atmospheres while observing their structural changes with high spatial resolution. The interplay of surface reconstruction of high-energy surfaces of the wurtzite phase and environment-dependent anisotropic chemical etching of certain crystal surfaces in the branching mechanism of nanobelts has been observed. Understanding of structural and chemical transformations of materials via in situ microscopy techniques and their role in designingmore » new nanostructured materials is discussed.« less

  8. Thermodynamics of Dilute Solutions.

    ERIC Educational Resources Information Center

    Jancso, Gabor; Fenby, David V.

    1983-01-01

    Discusses principles and definitions related to the thermodynamics of dilute solutions. Topics considered include dilute solution, Gibbs-Duhem equation, reference systems (pure gases and gaseous mixtures, liquid mixtures, dilute solutions), real dilute solutions (focusing on solute and solvent), terminology, standard states, and reference systems.…

  9. In vivo prediction of goat kids body composition from the deuterium oxide dilution space determined by isotope-ratio mass spectrometry.

    PubMed

    Lerch, S; Lastel, M L; Grandclaudon, C; Brechet, C; Rychen, G; Feidt, C

    2015-09-01

    Deuterium oxide dilution space (DOS) determination is one of the most accurate methods for in vivo estimation of ruminant body composition. However, the time-consuming vacuum sublimation of blood preceding infrared spectroscopy analysis, which is traditionally used to determine deuterium oxide (DO) concentration, limits its current use. The use of isotope-ratio mass spectrometry (IRMS) to determine the deuterium enrichment and thus quantify DO in plasma could counteract this limitation by reducing the sample preparation for plasma deproteinisation through centrifugal filters. The aim of this study was to validate the DOS technique using IRMS in growing goat kids to establish in vivo prediction equations of body composition. Seventeen weaned male Alpine goat kids (8.6 wk old) received a hay-based diet supplemented with 2 types of concentrates providing medium ( = 9) or high ( = 8) energy levels. Kids were slaughtered at 14.0 ( = 1, medium-energy diet), 17.2 ( = 4, medium-energy diet, and = 4, high-energy diet), or 21.2 wk of age ( = 4, medium-energy diet, and = 4, high-energy diet). Two days before slaughter, DOS was determined after an intravenous injection of 0.2 g DO/kg body mass (BM) and the resulting study of DO dilution kinetics from 4 plasma samples (+5, +7, +29, and +31 h after injection). The deuterium enrichment was analyzed by IRMS. After slaughter, the gut contents were discarded, the empty body (EB) was minced, and EB water, lipid, protein, ash, and energy contents were measured by chemical analyses. Prediction equations for body components measured postmortem were computed from in vivo BM and DOS. The lack of postmortem variation of fat-free EB composition was confirmed (mean of 75.3% [SD 0.6] of water), and the proportion of lipids in the EB tended ( = 0.06) to be greater for the high-energy diet (13.1%) than for the medium-energy diet (11.1%). There was a close negative relationship (residual CV [rCV] = 3.9%, = 0.957) between EB water and lipid

  10. Modeling the movement and equilibrium of water in the body of ruminants in relation to estimating body composition by deuterium oxide dilution

    SciTech Connect

    Arnold, R.N.

    1986-01-01

    Deuterium oxide (D/sub 2/O) dilution was evaluated for use in estimating body composition of ruminants. Empty body composition of cattle could not be accurately estimated by two- or three-compartment models when solved on the basis of clearance of D/sub 2/O from blood. A 29-compartment blood-flow model was developed from measured blood flow rates and water volumes of tissues of sheep. The rates of equilibration of water in tissues that were simulated by the blood-flow model were much faster than actual rates measured in sheep and cattle. The incorporation of diffusion hindrances for movement of water into tissues enabled the blood flow model to simulate the measured equilibration rates in tissues, but the values of the diffusion coefficients were different for each tissue. The D/sub 2/O-disappearance curve for blood simulated by the blood-flow model with diffusion limitations was comprised for four exponential components. The tissues and gastrointestinal tract contents were placed into five groups based upon the rate of equilibration. Water in the organs of the body equilibrated with water in blood within 3 min. Water in visceral fat, head, and some of the gastrointestinal tract tissues equilibrated within 8 to 16 min. Water in skeletal muscle, fat, and bone and the contents of some segments of the gastrointestinal tract equilibrated within 30 to 36 min. Water in the tissues and contents of the cecum and upper-large intestine equilibrated within 160 to 200 min. Water in ruminal tissue and contents equilibrated within 480 min.

  11. Pressure-induced phonon freezing in the ZnSeS II-VI mixed crystal: phonon-polaritons and ab initio calculations

    NASA Astrophysics Data System (ADS)

    Hajj Hussein, R.; Pagès, O.; Polian, A.; Postnikov, A. V.; Dicko, H.; Firszt, F.; Strzałkowski, K.; Paszkowicz, W.; Broch, L.; Ravy, S.; Fertey, P.

    2016-05-01

    Near-forward Raman scattering combined with ab initio phonon and bond length calculations is used to study the ‘phonon-polariton’ transverse optical modes (with mixed electrical-mechanical character) of the II-VI ZnSe1-x S x mixed crystal under pressure. The goal of the study is to determine the pressure dependence of the poorly-resolved percolation-type Zn-S Raman doublet of the three oscillator [1  ×  (Zn-Se), 2  ×  (Zn-S)] ZnSe0.68S0.32 mixed crystal, which exhibits a phase transition at approximately the same pressure as its two end compounds (~14 GPa, zincblende  →  rocksalt), as determined by high-pressure x-ray diffraction. We find that the intensity of the lower Zn-S sub-mode of ZnSe0.68S0.32, due to Zn-S bonds vibrating in their own (S-like) environment, decreases under pressure (Raman scattering), whereas its frequency progressively converges onto that of the upper Zn-S sub-mode, due to Zn-S vibrations in the foreign (Se-like) environment (ab initio calculations). Ultimately, only the latter sub-mode survives. A similar ‘phonon freezing’ was earlier evidenced with the well-resolved percolation-type Be-Se doublet of Zn1-x Be x Se (Pradhan et al 2010 Phys. Rev. B 81 115207), that exhibits a large contrast in the pressure-induced structural transitions of its end compounds. We deduce that the above collapse/convergence process is intrinsic to the percolation doublet of a short bond under pressure, at least in a ZnSe-based mixed crystal, and not due to any pressure-induced structural transition.

  12. Microbial toxicity of ionic species leached from the II-VI semiconductor materials, cadmium telluride (CdTe) and cadmium selenide (CdSe).

    PubMed

    Ramos-Ruiz, Adriana; Zeng, Chao; Sierra-Alvarez, Reyes; Teixeira, Luiz H; Field, Jim A

    2016-11-01

    This work investigated the microbial toxicity of soluble species that can potentially be leached from the II-VI semiconductor materials, cadmium telluride and cadmium selenide. The soluble ions tested included: cadmium, selenite, selenate, tellurite, and tellurate. Their toxicity towards the acetoclastic and hydrogen-consuming trophic groups in a methanogenic consortium as well as towards a bioluminescent marine bacterium, Aliivibrio fischeri (Microtox(®) test), was assessed. The acetoclastic methanogenic activity was the most affected as evidenced by the low 50% inhibiting concentrations (IC50) values obtained of 8.6 mg L(-1) for both cadmium and tellurite, 10.2 mg L(-1) for tellurate, and 24.1 mg L(-1) for selenite. Both tellurium oxyanions caused a strong inhibition of acetoclastic methanogenesis at low concentrations, each additional increment in concentration provided progressively less inhibition increase. In the case of the hydrogenotrophic methanogenesis, cadmium followed by selenite caused the greatest inhibition with IC50 values of 2.9 and 18.0 mg L(-1), respectively. Tellurite caused a moderate effect as evidenced by a 36.8% inhibition of the methanogenic activity at the highest concentration tested, and a very mild effect of tellurate was observed. Microtox(®) analyses showed a noteworthy inhibition of cadmium, selenite, and tellurite with 50% loss in bioluminescence after 30 min of exposure of 5.5, 171.1, and 458.6 mg L(-1), respectively. These results suggest that the leaching of cadmium, tellurium and selenium ions from semiconductor materials can potentially cause microbial toxicity. PMID:27494313

  13. Microbial toxicity of ionic species leached from the II-VI semiconductor materials, cadmium telluride (CdTe) and cadmium selenide (CdSe).

    PubMed

    Ramos-Ruiz, Adriana; Zeng, Chao; Sierra-Alvarez, Reyes; Teixeira, Luiz H; Field, Jim A

    2016-11-01

    This work investigated the microbial toxicity of soluble species that can potentially be leached from the II-VI semiconductor materials, cadmium telluride and cadmium selenide. The soluble ions tested included: cadmium, selenite, selenate, tellurite, and tellurate. Their toxicity towards the acetoclastic and hydrogen-consuming trophic groups in a methanogenic consortium as well as towards a bioluminescent marine bacterium, Aliivibrio fischeri (Microtox(®) test), was assessed. The acetoclastic methanogenic activity was the most affected as evidenced by the low 50% inhibiting concentrations (IC50) values obtained of 8.6 mg L(-1) for both cadmium and tellurite, 10.2 mg L(-1) for tellurate, and 24.1 mg L(-1) for selenite. Both tellurium oxyanions caused a strong inhibition of acetoclastic methanogenesis at low concentrations, each additional increment in concentration provided progressively less inhibition increase. In the case of the hydrogenotrophic methanogenesis, cadmium followed by selenite caused the greatest inhibition with IC50 values of 2.9 and 18.0 mg L(-1), respectively. Tellurite caused a moderate effect as evidenced by a 36.8% inhibition of the methanogenic activity at the highest concentration tested, and a very mild effect of tellurate was observed. Microtox(®) analyses showed a noteworthy inhibition of cadmium, selenite, and tellurite with 50% loss in bioluminescence after 30 min of exposure of 5.5, 171.1, and 458.6 mg L(-1), respectively. These results suggest that the leaching of cadmium, tellurium and selenium ions from semiconductor materials can potentially cause microbial toxicity.

  14. Serial Dilution Simulation Lab

    ERIC Educational Resources Information Center

    Keler, Cynthia; Balutis, Tabitha; Bergen, Kim; Laudenslager, Bryanna; Rubino, Deanna

    2010-01-01

    Serial dilution is often a difficult concept for students to understand. In this short dry lab exercise, students perform serial dilutions using seed beads. This exercise helps students gain skill at performing dilutions without using reagents, bacterial cultures, or viral cultures, while being able to visualize the process.

  15. Influence of the electron-phonon interaction on the temperature dependence of the phonon mode frequency in the II-VI compound solid solutions

    SciTech Connect

    Woźny, M. Cebulski, J.; Sheregii, E. M.; Marcelli, A.; Piccinini, M.

    2015-01-14

    We present an experimental investigation of the temperature dependence of the TO-phonon mode frequencies for the HgTe-based II-VI semiconductor solid solutions. In the case of the ternary Hg{sub 0.9}Zn{sub 0.1}Te solid solution was shown a discontinuity in the temperature dependence of the HgTe-like T{sub 0}-mode and of the ZnTe-like T{sub 1}-mode, similar to the Hg{sub 0.85}Cd{sub 0.15}Te system [Sheregii et al., Phys. Rev. Lett. 102, 045504 (2009)]. A generalization of the theoretical temperature shift of the phonon mode frequency as analytic equation is derived that includes both the anharmonic contribution and the electron-phonon e-p interaction which in this case is returnable—the electron subsystem effect on the phonon one. Data show that our equation satisfactorily describes the temperature shift of both Hg{sub 0.85}Cd{sub 0.15}Te and Hg{sub 0.90}Zn{sub 0.10}Te containing Dirac point (E{sub g} ≡ Γ{sub 6} – Γ{sub 8} = 0) although one of the two constants describing the anharmonic shift of the HgTe-like mode should be positive what is abnormal too. In the case of the Hg{sub 0.80}Cd{sub 0.20}Te and Hg{sub 0.763}Zn{sub 0.237}Te solid solution, the role of the returnable e-p contribution is negligible but a positive temperature shift for the HgTe-like modes occurs. This result does not allow to explain the positive temperature shift of these modes merely by the contribution of the (e-p) interaction. Indeed, the relativistic contribution to the chemical bonds induces an abnormal temperature shift of the electron states in Hg-based semiconductors—the effect is expected since the Hg d spin-orbit split contribution to chemical bonds may lead to an abnormal temperature shift of the HgTe-like modes.

  16. Characterization of optoelectronic properties of mercury cadmium telluride and zinc oxide II-VI semiconductors for infrared and ultraviolet detector applications

    NASA Astrophysics Data System (ADS)

    Moazzami, Kaveh

    Infrared (IR) and Ultraviolet (UV) light detectors have numerous applications including thermal imaging and chemical and biological spectroscopy. In this work, key aspects of HgCdTe and ZnO semiconductor materials are studied in accordance to their importance to state of the art IR and UV detector technologies. The leading material technology for IR detectors today is the lattice matched HgCdTe alloy. The model for optical absorption in this material has not been reexamined after major improvements in HgCdTe material growth technology. Access to an accurate model for absorption coefficient of this material is important for understanding of detector behavior, where the degree of accuracy required continues to grow as detector structures continue to add complexity. In this work, the optical absorption coefficient of HgCdTe is studied in detail using theoretical bandstructure calculations, temperature dependent optical spectroscopy, and infrared spectroscopic ellipsometry. A new model for the optical absorption coefficient of this material as a function of composition and temperature is presented based on a proposed empirical relationship. A significant improvement in the prediction of photovoltaic detector spectral response is observed based on this proposed model. ZnO is emerging as an important material for short wavelength optoelectronic devices, and may have a major impact on high-performance UV detectors. In this work, the steady-state and time-resolved response of ZnO photoconductors are studied. A sharp turn on is observed in the UV for these photodetectors, corresponding to the bandgap energy of 3.4eV for the ZnO material. Photoconductive decay transients show a fast (nanoseconds) and slow (milliseconds) time constant that are attributed to minority carrier relaxation and trapping processes, respectively. Persistent photoconductivity was observed, with time constant on the order of minutes, in response to both visible and UV excitation and is attributed to deep hole traps in the material. The trap density spectra are extracted from these transients based on a rate equation model, where the peak hole trap energies are found to be at 0.75 and 0.9 eV from the edge of the valence band for photoconductors with and without SiO2 passivation.

  17. Unraveling the nature of carrier-mediated ferromagnetism in diluted magnetic semiconductors

    NASA Astrophysics Data System (ADS)

    Bouzerar, Georges; Bouzerar, Richard

    2015-10-01

    After more than a decade of intensive research in the field of diluted magnetic semiconductors (DMS), the nature and origin of ferromagnetism, especially in III-V compounds, is still controversial. Many questions and open issues are under intensive debates. Why after so many years of investigations, Mn-doped GaAs remains the candidate with the highest Curie temperature among the broad family of III-V materials doped with transition metal (TM) impurities? How can one understand that these temperatures are almost two orders of magnitude larger than that of hole-doped (Zn,Mn)Te or (Cd,Mn)Se? Is there any intrinsic limitation or is there any hope to reach room-temperature ferromagnetism in the dilute regime? How can one explain the proximity of (Ga,Mn)As to the metal-insulator transition and the change from Ruderman-Kittel-Kasuya-Yosida (RKKY) couplings in II-VI compounds to double-exchange type in (Ga,Mn)N? In spite of the great success of density functional theory-based studies to provide accurately the critical temperatures in various compounds, till very lately a theory that provides a coherent picture and understanding of the underlying physics was still missing. Recently, within a minimal model, it has been possible to show that among the physical parameters, the key one is the position of the TM acceptor level. By tuning the value of that parameter, one is able to explain quantitatively both magnetic and transport properties in a broad family of DMS. We will see that this minimal model explains in particular the RKKY nature of the exchange in (Zn,Mn)Te/(Cd,Mn)Te and the double exchange type in (Ga,Mn)N and simultaneously the reason why (Ga,Mn)As exhibits the highest critical temperature among both II-VI and III-V DMS's. xml:lang="fr"

  18. Microfluidic serial dilution ladder.

    PubMed

    Ahrar, Siavash; Hwang, Michelle; Duncan, Philip N; Hui, Elliot E

    2014-01-01

    Serial dilution is a fundamental procedure that is common to a large number of laboratory protocols. Automation of serial dilution is thus a valuable component for lab-on-a-chip systems. While a handful of different microfluidic strategies for serial dilution have been reported, approaches based on continuous flow mixing inherently consume larger amounts of sample volume and chip real estate. We employ valve-driven circulatory mixing to address these issues and also introduce a novel device structure to store each stage of the dilution process. The dilution strategy is based on sequentially mixing the rungs of a ladder structure. We demonstrate a 7-stage series of 1 : 1 dilutions with R(2) equal to 0.995 in an active device area of 1 cm(2).

  19. The mathematics of dilution.

    PubMed

    Chatterjee, Barun Kumar

    2014-04-01

    The major objection to homeopathic medicine is that the doses of medicine prescribed in some cases are too dilute for any active ingredient to be present. The medicines would hence be rendered inactive, necessitating novel explanations for the action. A further examination of dilution in the light of the Langmuir equation shows that homeopathic medicines may not be as dilute as a simplistic application of Avogadro's Principle suggests, due to surface effects.

  20. ECUT: Energy Conversion and utilization Technologies program biocatalysis research activity. Generation of chemical intermediates by catalytic oxidative decarboxylation of dilute organic acids

    NASA Technical Reports Server (NTRS)

    Distefano, S.; Gupta, A.; Ingham, J. D.

    1983-01-01

    A rhodium-based catalyst was prepared and preliminary experiments were completed where the catalyst appeared to decarboxylate dilute acids at concentrations of 1 to 10 vol%. Electron spin resonance spectroscoy was used to characterize the catalyst as a first step leading toward modeling and optimization of rhodium catalysts. Also, a hybrid chemical/biological process for the production of hydrocarbons has been assessed. These types of catalysts could greatly increase energy efficiency of this process.

  1. Effect of oxidation on the removal CU{sup 2+}, Cd{sup 2+} and Mn (VII) from dilute aqueous solutions by Upper Freeport bituminous coal. Quarterly report, June--August 1995

    SciTech Connect

    Bodine, D.L.

    1995-12-31

    Upper Freeport bituminous coal was able to remove Mn (VII) from dilute aqueous solution by concurrent adsorption and reduction of the manganese to lower valence, less toxic states. This type of reaction indicated the potential of using coal to remove oxidizing contaminants from effluents. Since oxidizing anions can degrade ion exchange resins and membranes, coal may be a viable alternative for detoxification. On analysis of the kinetics of copper and cadmium uptake from dilute aqueous solution, adsorption equilibria and functional groups analyses, it was apparent that the different oxidative pre-treatments affected both the surfaces and pore structure of Upper Freeport coal. The large amount of carboxyl and phenolic functional groups remaining after contact with copper and cadmium solutions, as determined by functional groups analyses, indicated the low affinity of the surface acid groups for these cations. Furthermore, there was almost no metal ion removal at low solution pH`s, which precludes the use of Upper Freeport for treating acidic wastes and effluents such as acid mine drainage. The coal surface functional groups are indeed able to exchange with cations, since the amount of these groups are measured by ion exchange with Na{sup +} and Ba{sup 2+}, however, it may be more difficult to displace the waters of hydration around Cu{sup 2+} and Cd{sup 2+}, to allow their uptake on the coal surface functional groups. Improved metal ion removal might be obtained using a lower rank coal, such as a subbituminous coal, which would be more susceptible to oxidation.

  2. EDITORIAL: Focus on Dilute Magnetic Semiconductors FOCUS ON DILUTE MAGNETIC SEMICONDUCTORS

    NASA Astrophysics Data System (ADS)

    Chambers, Scott A.; Gallagher, Bryan

    2008-05-01

    Chisholm, J D Budai and D P Norton Role of charge carriers for ferromagnetism in cobalt-doped rutile TiO2 T Fukumura, H Toyosaki, K Ueno, M Nakano and M Kawasaki Ab-initio study of exchange constants and electronic structure in diluted magnetic group-IV semiconductors Silvia Picozzi and Marjana Ležaić Phase coherent transport in (Ga,Mn)As D Neumaier, K Wagner, U Wurstbauer, M Reinwald, W Wegscheider and D Weiss Hydrogen interstitials-mediated ferromagnetism in MnxGe1-x magnetic semiconductors Xin-Xin Yao, Shi-Shen Yan, Shu-Jun Hu, Xue-Ling Lin, Chong Han, Yan-Xue Chen, Guo-Lei Liu and Liang-Mo Mei Electronic structures of magnetic semiconductors FeCr2Se4 and Fe0.5Cu0.5Cr2Se4 B I Min, Seung Su Baik, H C Choi, S K Kwon and J-S Kang Investigation of pure and Co2+-doped ZnO quantum dot electronic structures using the density functional theory: choosing the right functional Ekaterina Badaeva, Yong Feng, Daniel R Gamelin and Xiaosong Li Magnetic properties of sol-gel-derived doped ZnO as a potential ferromagnetic semiconductor: a synchrotron-based study N R S Farley, K W Edmonds, A A Freeman, G van der Laan, C R Staddon, D H Gregory and B L Gallagher Local electronic structure of Cr in the II-VI diluted ferromagnetic semiconductor Zn1-xCrxTe M Kobayashi, Y Ishida, J I Hwang, G S Song, A Fujimori, C S Yang, L Lee, H-J Lin, D J Huang, C T Chen, Y Takeda, K Terai, S-I Fujimori, T Okane, Y Saitoh, H Yamagami, K Kobayashi, A Tanaka, H Saito and K Ando Lack of ferromagnetism in n-type cobalt-doped ZnO epitaxial thin films T C Kaspar, T Droubay, S M Heald, P Nachimuthu, C M Wang, V Shutthanandan, C A Johnson, D R Gamelin and S A Chambers XMCD studies on Co and Li doped ZnO magnetic semiconductors Thomas Tietze, Milan Gacic, Gisela Schütz, Gerhard Jakob, Sebastian Brück and Eberhard Goering Ferromagnetic semiconductors and the role of disorder B W Wessels An extensive comparison of anisotropies in MBE grown (Ga,Mn)As material C Gould, S Mark, K Pappert, R G Dengel, J Wenisch, R P

  3. Body composition of adult cystic fibrosis patients and control subjects as determined by densitometry, bioelectrical impedance, total-body electrical conductivity, skinfold measurements, and deuterium oxide dilution

    SciTech Connect

    Newby, M.J.; Keim, N.L.; Brown, D.L. )

    1990-08-01

    This study contrasts body compositions (by six methods) of eight cystic fibrosis (CF) subjects with those of eight control subjects matched for age, height, and sex. CF subjects weighed 84% as much as control subjects. Densitometry and two bioelectrical impedance-analysis methods suggested that reduced CF weights were due to less lean tissue (10.7, 9.5, and 10.4 kg). Total-body electrical conductivity (TOBEC) and skinfold-thickness measurements indicated that CF subjects were leaner than control subjects and had less fat (5.4 and 3.6 kg) and less lean (5.2 and 7 kg) tissue. D2O dilution showed a pattern similar to TOBEC (8.3 kg less lean, 2.7 kg less fat tissue). Densitometry estimates of fat (mass and percent) were not correlated (r less than 0.74, p greater than 0.05) with any other method for CF subjects but were correlated with all other methods for control subjects. CF subjects contained less fat and lean tissue than did control subjects. Densitometry by underwater weighing is unsuitable for assessing body composition of CF patients.

  4. Quantification of the 2-deoxyribonolactone and nucleoside 5’-aldehyde products of 2-deoxyribose oxidation in DNA and cells by isotope-dilution gas chromatography mass spectrometry: Differential effects of γ-radiation and Fe2+-EDTA

    PubMed Central

    Chan, Wan; Chen, Bingzi; Wang, Lianrong; Taghizadeh, Koli; Demott, Michael S.; Dedon, Peter C.

    2010-01-01

    The oxidation of 2-deoxyribose in DNA has emerged as a critical determinant of the cellular toxicity of oxidative damage to DNA, with oxidation of each carbon producing a unique spectrum of electrophilic products. We have developed and validated an isotope-dilution gas chromatography-coupled mass spectrometry (GC-MS) method for the rigorous quantification of two major 2-deoxyribose oxidation products: the 2-deoxyribonolactone abasic site of 1’-oxidation and the nucleoside 5’-aldehyde of 5’-oxidation chemistry. The method entails elimination of these products as 5-methylene-2(5H)-furanone (5MF) and furfural, respectively, followed by derivatization with pentafluorophenylhydrazine (PFPH), addition of isotopically labeled PFPH derivatives as internal standards, extraction of the derivatives, and quantification by GC-MS analysis. The precision and accuracy of the method were validated with oligodeoxynucleotides containing the 2-deoxyribonolactone and nucleoside 5’-aldehyde lesions. Further, the well defined 2-deoxyribose oxidation chemistry of the enediyne antibiotics, neocarzinostatin and calicheamicin γ1I, was exploited in control studies, with neocarzinostatin producing 10 2-deoxyribonolactone and 300 nucleoside 5’-aldehyde per 106 nt per µM in accord with its established minor 1’- and major 5’-oxidation chemistry. Calicheamicin unexpectedly caused 1’-oxidation at a low level of 10 2-deoxyribonolactone per 106 nt per µM in addition to the expected predominance of 5’-oxidation at 560 nucleoside 5’-aldehyde per 106 nt per µM. The two hydroxyl radical-mediated DNA oxidants, γ-radiation and Fe2+-EDTA, produced nucleoside 5’-aldehyde at a frequency of 57 per 106 nt per Gy (G-value 74 nmol/J) and 3.5 per 106 nt per µM, respectively, which amounted to 40% and 35%, respectively, of total 2-deoxyribose oxidation as measured by a plasmid nicking assay. However, γ-radiation and Fe2+-EDTA produced different proportions of 2-deoxyribonolactone at 7

  5. Helium dilution refrigeration system

    DOEpatents

    Roach, Patrick R.; Gray, Kenneth E.

    1988-01-01

    A helium dilution refrigeration system operable over a limited time period, and recyclable for a next period of operation. The refrigeration system is compact with a self-contained pumping system and heaters for operation of the system. A mixing chamber contains .sup.3 He and .sup.4 He liquids which are precooled by a coupled container containing .sup.3 He liquid, enabling the phase separation of a .sup.3 He rich liquid phase from a dilute .sup.3 He-.sup.4 He liquid phase which leads to the final stage of a dilution cooling process for obtaining low temperatures. The mixing chamber and a still are coupled by a fluid line and are maintained at substantially the same level with the still cross sectional area being smaller than that of the mixing chamber. This configuration provides maximum cooling power and efficiency by the cooling period ending when the .sup.3 He liquid is depleted from the mixing chamber with the mixing chamber nearly empty of liquid helium, thus avoiding unnecessary and inefficient cooling of a large amount of the dilute .sup.3 He-.sup.4 He liquid phase.

  6. Helium dilution refrigeration system

    DOEpatents

    Roach, P.R.; Gray, K.E.

    1988-09-13

    A helium dilution refrigeration system operable over a limited time period, and recyclable for a next period of operation is disclosed. The refrigeration system is compact with a self-contained pumping system and heaters for operation of the system. A mixing chamber contains [sup 3]He and [sup 4]He liquids which are precooled by a coupled container containing [sup 3]He liquid, enabling the phase separation of a [sup 3]He rich liquid phase from a dilute [sup 3]He-[sup 4]He liquid phase which leads to the final stage of a dilution cooling process for obtaining low temperatures. The mixing chamber and a still are coupled by a fluid line and are maintained at substantially the same level with the still cross sectional area being smaller than that of the mixing chamber. This configuration provides maximum cooling power and efficiency by the cooling period ending when the [sup 3]He liquid is depleted from the mixing chamber with the mixing chamber nearly empty of liquid helium, thus avoiding unnecessary and inefficient cooling of a large amount of the dilute [sup 3]He-[sup 4]He liquid phase. 2 figs.

  7. Dilution, Concentration, and Flotation

    ERIC Educational Resources Information Center

    Liang, Ling; Schmuckler, Joseph S.

    2004-01-01

    As both classroom teaching practice and literature show, many students have difficulties learning science concepts such as density. Here are some investigations that identify the relationship between density and floating through experimenting with successive dilution of a liquid, or the systematic change of concentration of a saltwater solution.…

  8. Atmospheric evolution of sulfur emissions from Kı̅lauea: real-time measurements of oxidation, dilution, and neutralization within a volcanic plume.

    PubMed

    Kroll, Jesse H; Cross, Eben S; Hunter, James F; Pai, Sidhant; Wallace, Lisa M M; Croteau, Philip L; Jayne, John T; Worsnop, Douglas R; Heald, Colette L; Murphy, Jennifer G; Frankel, Sheila L

    2015-04-01

    The high atmospheric concentrations of toxic gases, particulate matter, and acids in the areas immediately surrounding volcanoes can have negative impacts on human and ecological health. To better understand the atmospheric fate of volcanogenic emissions in the near field (in the first few hours after emission), we have carried out real-time measurements of key chemical components of the volcanic plume from Kı̅lauea on the Island of Hawai'i. Measurements were made at two locations, one ∼ 3 km north-northeast of the vent and the other 31 km to the southwest, with sampling at each site spanning a range of meteorological conditions and volcanic influence. Instrumentation included a sulfur dioxide monitor and an Aerosol Chemical Speciation Monitor, allowing for a measurement of the partitioning between the two major sulfur species (gas-phase SO2 and particulate sulfate) every 5 min. During trade wind conditions, which sent the plume toward the southwest site, sulfur partitioning exhibited a clear diurnal pattern, indicating photochemical oxidation of SO2 to sulfate; this enabled the quantitative determination of plume age (5 h) and instantaneous SO2 oxidation rate (2.4 × 10(-6) s(-1) at solar noon). Under stagnant conditions near the crater, the extent of SO2 oxidation was substantially higher, suggesting faster oxidation. The particles within the plume were extremely acidic, with pH values (controlled largely by ambient relative humidity) as low as -0.8 and strong acidity (controlled largely by absolute sulfate levels) up to 2200 nmol/m(3). The high variability of sulfur partitioning and particle composition underscores the chemically dynamic nature of volcanic plumes, which may have important implications for human and ecological health. PMID:25734883

  9. Mechanistic model to predict colostrum intake based on deuterium oxide dilution technique data and impact of gestation and prefarrowing diets on piglet intake and sow yield of colostrum.

    PubMed

    Theil, P K; Flummer, C; Hurley, W L; Kristensen, N B; Labouriau, R L; Sørensen, M T

    2014-12-01

    The aims of the present study were to quantify colostrum intake (CI) of piglets using the D2O dilution technique, to develop a mechanistic model to predict CI, to compare these data with CI predicted by a previous empirical predictive model developed for bottle-fed piglets, and to study how composition of diets fed to gestating sows affected piglet CI, sow colostrum yield (CY), and colostrum composition. In total, 240 piglets from 40 litters were enriched with D2O. The CI measured by D2O from birth until 24 h after the birth of first-born piglet was on average 443 g (SD 151). Based on measured CI, a mechanistic model to predict CI was developed using piglet characteristics (24-h weight gain [WG; g], BW at birth [BWB; kg], and duration of CI [D; min]: CI, g=-106+2.26 WG+200 BWB+0.111 D-1,414 WG/D+0.0182 WG/BWB (R2=0.944). This model was used to predict the CI for all colostrum suckling piglets within the 40 litters (n=500, mean=437 g, SD=153 g) and was compared with the CI predicted by a previous empirical predictive model (mean=305 g, SD=140 g). The previous empirical model underestimated the CI by 30% compared with that obtained by the new mechanistic model. The sows were fed 1 of 4 gestation diets (n=10 per diet) based on different fiber sources (low fiber [17%] or potato pulp, pectin residue, or sugarbeet pulp [32 to 40%]) from mating until d 108 of gestation. From d 108 of gestation until parturition, sows were fed 1 of 5 prefarrowing diets (n=8 per diet) varying in supplemented fat (3% animal fat, 8% coconut oil, 8% sunflower oil, 8% fish oil, or 4% fish oil+4% octanoic acid). Sows fed diets with pectin residue or sugarbeet pulp during gestation produced colostrum with lower protein, fat, DM, and energy concentrations and higher lactose concentrations, and their piglets had greater CI as compared with sows fed potato pulp or the low-fiber diet (P<0.05), and sows fed pectin residue had a greater CY than potato pulp-fed sows (P<0.05). Prefarrowing diets affected

  10. Investigation of local structural environments and room-temperature ferromagnetism in (Fe,Cu)-codoped In2O3 diluted magnetic oxide films.

    PubMed

    An, Yukai; Xing, Yaya; Pan, Fei; Wu, Zhonghua; Liu, Jiwen

    2016-05-11

    The local structural, optical, magnetic and transport properties of (In0.95-xFexCu0.05)2O3 (0.06 ≤ x ≤ 0.20) films deposited by RF-magnetron sputtering have been systemically studied by different experimental techniques. Detailed structural analyses using XRD, XPS, EXAFS and full multiple-scattering ab initio theoretical calculations of Fe K-edge XANES show that the (In0.95-xFexCu0.05)2O3 films have the same cubic bixbyite structure as pure In2O3. The doped Fe ions exist at both +2 and +3 oxidation states, substituting for the In(3+) sites in the In2O3 lattice and forming a FeIn + 2VO complex with the O vacancy in the first coordination shell of Fe. However, the co-doped Cu atoms are not incorporated into the In2O3 lattice and form the Cu metal clusters due to high ionization energy. UV-Vis measurements show that the optical band gap Eg decreases monotonically with the increase of Fe concentration, implying an increasing s-pd exchange interaction in the films. All the films display intrinsic room-temperature (RT) ferromagnetism and the saturated magnetization (Ms) increases monotonically with Fe doping. The temperature dependence of the resistivity data suggests the conduction mechanism of Mott variable-range hopping (VRH) at low temperature, confirming that the carriers are localized. It can be concluded that the observed RT ferromagnetism in the films originates from the overlapping of polarons mediated by oxygen vacancies based on the bound magnetic polaron (BMP) model. The variation of the localization effect of carriers with Fe doping can obviously adjust the magnetic exchange interaction in the (In0.95-xFexCu0.05)2O3 films. PMID:27139011

  11. Investigation of local structural environments and room-temperature ferromagnetism in (Fe,Cu)-codoped In2O3 diluted magnetic oxide films.

    PubMed

    An, Yukai; Xing, Yaya; Pan, Fei; Wu, Zhonghua; Liu, Jiwen

    2016-05-11

    The local structural, optical, magnetic and transport properties of (In0.95-xFexCu0.05)2O3 (0.06 ≤ x ≤ 0.20) films deposited by RF-magnetron sputtering have been systemically studied by different experimental techniques. Detailed structural analyses using XRD, XPS, EXAFS and full multiple-scattering ab initio theoretical calculations of Fe K-edge XANES show that the (In0.95-xFexCu0.05)2O3 films have the same cubic bixbyite structure as pure In2O3. The doped Fe ions exist at both +2 and +3 oxidation states, substituting for the In(3+) sites in the In2O3 lattice and forming a FeIn + 2VO complex with the O vacancy in the first coordination shell of Fe. However, the co-doped Cu atoms are not incorporated into the In2O3 lattice and form the Cu metal clusters due to high ionization energy. UV-Vis measurements show that the optical band gap Eg decreases monotonically with the increase of Fe concentration, implying an increasing s-pd exchange interaction in the films. All the films display intrinsic room-temperature (RT) ferromagnetism and the saturated magnetization (Ms) increases monotonically with Fe doping. The temperature dependence of the resistivity data suggests the conduction mechanism of Mott variable-range hopping (VRH) at low temperature, confirming that the carriers are localized. It can be concluded that the observed RT ferromagnetism in the films originates from the overlapping of polarons mediated by oxygen vacancies based on the bound magnetic polaron (BMP) model. The variation of the localization effect of carriers with Fe doping can obviously adjust the magnetic exchange interaction in the (In0.95-xFexCu0.05)2O3 films.

  12. Systematic approach for simultaneously correcting the band-gap andp-dseparation errors of common cation III-V or II-VI binaries in density functional theory calculations within a local density approximation

    DOE PAGES

    Wang, Jianwei; Zhang, Yong; Wang, Lin-Wang

    2015-07-31

    We propose a systematic approach that can empirically correct three major errors typically found in a density functional theory (DFT) calculation within the local density approximation (LDA) simultaneously for a set of common cation binary semiconductors, such as III-V compounds, (Ga or In)X with X = N,P,As,Sb, and II-VI compounds, (Zn or Cd)X, with X = O,S,Se,Te. By correcting (1) the binary band gaps at high-symmetry points , L, X, (2) the separation of p-and d-orbital-derived valence bands, and (3) conduction band effective masses to experimental values and doing so simultaneously for common cation binaries, the resulting DFT-LDA-based quasi-first-principles methodmore » can be used to predict the electronic structure of complex materials involving multiple binaries with comparable accuracy but much less computational cost than a GW level theory. This approach provides an efficient way to evaluate the electronic structures and other material properties of complex systems, much needed for material discovery and design.« less

  13. Determination of total sulfur at microgram per gram levels in geological materials by oxidation of sulfur into sulfate with in situ generation of bromine using isotope dilution high-resolution ICPMS.

    PubMed

    Makishima, A; Nakamura, E

    2001-06-01

    We have developed a new, simple, and accurate method for the determination of total sulfur at microgram per gram levels in milligram-sized silicate materials with isotope dilution high-resolution inductively coupled plasma mass spectrometry equipped with a flow injection system. In this method, sulfur can be quantitatively oxidized by bromine into sulfate with achievement of isotope equilibrium between the sample and spike. Detection limits for 32S+ and 34S+ in the ideal solution and silicate samples were 1 and 6 ng mL(-1) and 0.07 and 0.3 microg g(-1), respectively. The total blank was 46 ng, so that a 40-mg silicate sample containing 10 mirog g(-1) sulfur can be measured with a blank correction of < 10%. This total blank can be lowered to 8 ng if a low-blank air system is used for evaporations. To evaluate the applicability of this method, we analyzed not only silicate reference materials with sulfur content of 5.25-489 microg g(-1) and sample sizes of 13-40 mg but also the Allende meteorite with a sulfur content of 2%. The reproducibility for various rock types was < 9%, even though blank corrections in some samples of low sulfur content were up to 24%. This method is suitable for analyzing geological samples as well environmental samples such as soils, sediments, and water samples.

  14. Dispersion serial dilution methods using the gradient diluter device.

    PubMed

    Walling, Leslie; Schulz, Craig; Johnson, Michael

    2012-12-01

    A solute aspirated into a prefilled tube of diluent undergoes a dilution effect known as dispersion. Traditionally the effects of dispersion have been considered a negative consequence of using liquid-filled fixed-tip liquid handlers. We present a novel device and technique that utilizes the effects of dispersion to the benefit of making dilutions. The device known as the Gradient Diluter extends the dilution range of practical serial dilutions to six orders of magnitude in final volumes as low as 10 μL. Presented are the device, dispersion methods, and validation tests using fluorescence detection of sulforhodamine and the high-performance liquid chromatography/ultraviolet detection of furosemide. In addition, a T-cell inhibition assay of a relevant downstream protein is used to demonstrate IC(50) curves made with the Gradient Diluter compare favorably with those generated by hand.

  15. Diluted magnetic semiconductors

    NASA Astrophysics Data System (ADS)

    Anderson, James R.

    1990-03-01

    Growth and physical properties of diluted magnetic semiconductors (DMS) were investigated. Growth included Bridgman, solid state recrystallization, and liquid phase epitaxy of Mercury(1-x)Manganese(x)Telluride and Mercury(1-x-y)Manganese(x)Cadmium(y)Telluride. Very uniform crystals were produced by solid state recrystallization. Physical properties studied included magnetization, optical response, and magnetotransport. From magnetization, the exchange interactions among magnetic ions have been deduced. Modulated spectroscopy gave details of the electronic structure of DMS and the quality of the material was indicated by the line widths. Magnetotransport, carried out in some cases to 30 T, showed a large negative magnetoresistance and subsequent increase. The Hg(1-x-y)Mn(x)Cd(y)Te has considerable promise for avalanche photodiodes between 1.2 and 1.8 micrometers.

  16. Dilution jet mixing program

    NASA Technical Reports Server (NTRS)

    Srinivasan, R.; Coleman, E.; Johnson, K.

    1984-01-01

    Parametric tests were conducted to quantify the mixing of opposed rows of jets (two-sided injection) in a confined cross flow. Results show that jet penetrations for two sided injections are less than that for single-sided injections, but the jet spreading rates are faster for a given momentum ratio and orifice plate. Flow area convergence generally enhances mixing. Mixing characteristics with asymmetric and symmetric convergence are similar. For constant momentum ratio, the optimum S/H(0) with in-line injections is one half the optimum value for single sided injections. For staggered injections, the optimum S/H(0) is twice the optimum value for single-sided injection. The correlations developed predicted the temperature distributions within first order accuracy and provide a useful tool for predicting jet trajectory and temperature profiles in the dilution zone with two-sided injections.

  17. Synthesis and Characterization of Co-doped ZnO Dilute Magnetic Semiconducting Nanorods

    NASA Astrophysics Data System (ADS)

    Das, N.; Khanra, S.; Bhamidipati, S.; Manivannan, K.; Kahol, P.; Ghosh, K.

    2012-02-01

    Transition-metal doped ZnO dilute magnetic semiconducting nanomaterials are considered as ideal systems for carrying out research in the field of spintronics as they can successfully combine magnetism and electronics in a single substance. ZnO is a wurtzite-type wide-bandgap semiconductor of the II-VI semiconductor group with band gap energy of 3.37 eV. Hydrothermal synthesis of undoped ZnO and Co-doped ZnO nanorods is carried out using aqueous solutions of Zn(NO3)2.6H2O, Co(C2H3OO)2.4 H2O, and using NH4OH as hydrolytic catalyst. Nanomaterials of different sizes and shapes were synthesized by varying the process parameters such as molarity (0.15M, 0.3M, 0.5M) and pH (8-11) of the precursors, growth temperature (130^oC), and annealing time during the hydrothermal Process. Structural, morphological, optical and magnetic properties are studied using various techniques such as XRD, SEM, UV-vis spectroscopy, and SQUID magnetometer. XRD and SEM studies reveal nanorods with hexagonal wurtzite structure with length in the range of 200 to 500 nm, and cross section in the range of 30 to 60 nm. Detailed structural, optical, and magnetic properties will be discussed in this presentation.

  18. Exploration of the new class of layered III-VI Diluted Magnetic Semiconductors (DMS)

    NASA Astrophysics Data System (ADS)

    Pekarek, Thomas; Miotkowski, I.; Ramdas, A. K.

    2014-03-01

    We have explored a new class of quasi-two-dimensional III-VI Diluted Magnetic Semiconductors (DMS) exhibiting a wide range of magnetic behavior. Several are good candidates for potential device applications. In In1-xMnxSe, we found a remarkably large thermal hysteresis (Delta T is approximately 200 K) extending up to room temperature. This is an important material because a typical thermal hysteresis in most materials has a Delta T approximately 20 K occurring well below room temperature. The thermal hysteresis is also seen in transport measurements for In1-xMnxSe. To date, we have found good agreement between experiment and theory for the 1st three III-VI DMS systems (In1-xMnxSe, In1-xMnxS, and Ga1-xMnxS). Ga1-xFexSe is unique amount the III-VI DMS exhibiting substantial magnetic anisotropy. In Ga1-xMnxS, we have found a spin glass transition and critical exponents (γ = 4.0, β = 0.8, and δ = 5.5) that are in agreement with the theory. We surprisingly found that the spin glass transition in the 2-D IIIVI DMS similar to spin glass in 3-D II-VI DMS. [This research was supported by the UNF Terry Presidential Professorship, a Purdue University Academic Reinvestment Program and by the National Science Foundation (NSF) Grant Nos. DMR-07-06593 and DMR-04-05082.

  19. Tuning magnetic disorder in diluted magnetic semiconductors using high fields to 89 Tesla

    SciTech Connect

    Crooker, Scott A; Samarth, Nitin

    2008-01-01

    We describe recent and ongoing studies at the National High Magnetic Field Laboratory at Los Alamos using the new '100 Tesla Multi-Shot Magnet', which is presently delivering fields up to {approx}89 T during its commissioning. We discuss the first experiments performed in this magnet system, wherein the linewidth of low-temperature photoluminescence spectra was used to directly reveal the degree of magnetic alloy disorder 'seen' by excitons in single Zn{sub 0.80}Cd{sub 0.22}Mn{sub 0.08}Se quantum wells. The magnetic potential landscape in II-VI diluted magnetic semiconductors (DMS) is typically smoothed when the embedded Mn{sup 2+} spins align in an applied field. However, an important (but heretofore untested) prediction of current models of compositional disorder is that magnetic alloy fluctuations in many DMS compounds should increase again in very large magnetic fields approaching 100 T. We observed precisely this increase above {approx}70 T, in agreement with a simple model of magnetic alloy disorder.

  20. Stress in dilute suspensions

    NASA Technical Reports Server (NTRS)

    Passman, Stephen L.

    1989-01-01

    Generally, two types of theory are used to describe the field equations for suspensions. The so-called postulated equations are based on the kinetic theory of mixtures, which logically should give reasonable equations for solutions. The basis for the use of such theory for suspensions is tenuous, though it at least gives a logical path for mathematical arguments. It has the disadvantage that it leads to a system of equations which is underdetermined, in a sense that can be made precise. On the other hand, the so-called averaging theory starts with a determined system, but the very process of averaging renders the resulting system underdetermined. A third type of theory is proposed in which the kinetic theory of gases is used to motivate continuum equations for the suspended particles. This entails an interpretation of the stress in the particles that is different from the usual one. Classical theory is used to describe the motion of the suspending medium. The result is a determined system for a dilute suspension. Extension of the theory to more concentrated systems is discussed.

  1. Dilution refrigeration for space applications

    NASA Technical Reports Server (NTRS)

    Israelsson, U. E.; Petrac, D.

    1990-01-01

    Dilution refrigerators are presently used routinely in ground based applications where temperatures below 0.3 K are required. The operation of a conventional dilution refrigerator depends critically on the presence of gravity. To operate a dilution refrigerator in space many technical difficulties must be overcome. Some of the anticipated difficulties are identified in this paper and possible solutions are described. A single cycle refrigerator is described conceptually that uses forces other than gravity to function and the stringent constraints imposed on the design by requiring the refrigerator to function on the earth without using gravity are elaborated upon.

  2. Intermittency in dilute granular flows

    NASA Astrophysics Data System (ADS)

    Guo, Wenxuan; Zhang, Qiang; Wylie, Jonathan J.

    2016-07-01

    In this letter, we show that dilute granular systems can exhibit a type of intermittency that has no analogue in gas dynamics. We consider a simple system in which a very dilute set of granular particles falls under gravity through a nozzle. This setting is analogous to the classical problem of high-speed nozzle flow in the study of compressible gases. It is well known that very dilute granular systems exhibit behavior qualitatively similar to gases, and that gas flowing through a nozzle does not exhibit intermittency. Nevertheless, we show that the intermittency in dilute granular nozzle flows can occur and corresponds to complicated transitions between supersonic and subsonic regimes. We also provide detailed explanations of the mechanism underlying this phenomenon.

  3. Cluster approach to dilute magnetism

    NASA Astrophysics Data System (ADS)

    Holvorcem, Paulo R. C.; Osório, Roberto

    1988-10-01

    A cluster algebra is developed for the definition of independent correlation functions in the cluster-variation method (CVM) for the spin-1 Ising model. A scheme is then introduced for the study of site-dilute spin- {1}/{2} Ising models by means of the CVM. The procedure regards the site-dilute spin- {1}/{2} model as the spin-1 model with additional constraints due to dilution. The Desjardins-Steinsvoll algortihm is used for the transformation of the CVM equations into a set of differential equations for the independent correlation functions with the inverse temperature as parameter. The evolution of the correlation functions with temperature and the behavior of response functions such as the specific heat and the susceptability are then obtained for any degree of dilution. As an introduction to this scheme, its detailed application is presented here for the simple case of the pair approximation.

  4. 40 CFR 1065.240 - Dilution air and diluted exhaust flow meters.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... dilution system, you may use a laminar flow element, an ultrasonic flow meter, a subsonic venturi, a... § 1065.240 Dilution air and diluted exhaust flow meters. (a) Application. Use a diluted exhaust flow meter to determine instantaneous diluted exhaust flow rates or total diluted exhaust flow over a...

  5. DAVINCI: Dilute Aperture VIsible Nulling Coronagraphic Imager

    NASA Technical Reports Server (NTRS)

    Shao, Michael; Levine, B. M.; Vasisht, G.; Lane, B. F.; Woodruff, R.; Vasudevan, G.; Samuele, R.; Lloyd, C. A.; Clampin, M.; Lyon, R.; Guyon, O.

    2008-01-01

    This slide presentation gives an overview of DAVINCI (Dilute Aperture VIsible Nulling Coronagraphic Imager). The presentation also includes information about dilute aperture coronagraph, and lyot efficiency.

  6. Dilute Oxygen Combustion - Phase 3 Report

    SciTech Connect

    Riley, Michael F.

    2000-05-31

    Dilute Oxygen Combustion (DOC) burners have been successfully installed and operated in the reheat furnace at Auburn Steel Co., Inc., Auburn, NY, under Phase 3 of the Dilute Oxygen Combustion project. Two new preheat zones were created employing a total of eight 6.5 MMBtu/hr capacity burners. The preheat zones provide a 30 percent increase in maximum furnace production rate, from 75 tph to 100 tph. The fuel rate is essentially unchanged, with the fuel savings expected from oxy-fuel combustion being offset by higher flue gas temperatures. When allowance is made for the high nitrogen level and high gas phase temperature in the furnace, measured NOx emissions are in line with laboratory data on DOC burners developed in Phase 1 of the project. Burner performance has been good, and there have been no operating or maintenance problems. The DOC system continues to be used as part of Auburn Steel's standard reheat furnace practice. High gas phase temperature is a result of the high firing density needed to achieve high production rates, and little opportunity exists for improvement in that area. However, fuel and NOx performance can be improved by further conversion on furnace zones to DOC burners, which will lower furnace nitrogen levels. Major obstacles are cost and concern about increased formation of oxide scale on the steel. Oxide scale formation may be enhanced by exposure of the steel to higher concentrations of oxidizing gas components (primarily products of combustion) in the higher temperature zones of the furnace. Phase 4 of the DOC project will examine the rate of oxide scale formation in these higher temperature zones and develop countermeasures that will allow DOC burners to be used successfully in these furnace zones.

  7. Dilute Oxygen Combustion Phase 3 Final Report

    SciTech Connect

    Riley, M.F.; Ryan, H.M.

    2000-05-31

    Dilute Oxygen Combustion (DOC) burners have been successfully installed and operated in the reheat furnace at Auburn Steel Co., Inc., Auburn, NY, under Phase 3 of the Dilute Oxygen Combustion project. Two new preheat zones were created employing a total of eight 6.5 MMBtu/hr capacity burners. The preheat zones provide a 30 percent increase in maximum furnace production rate, from 75 tph to 100 tph. The fuel rate is essentially unchanged, with the fuel savings expected from oxy-fuel combustion being offset by higher flue gas temperatures. When allowance is made for the high nitrogen level and high gas phase temperature in the furnace, measured NOx emissions are in line with laboratory data on DOC burners developed in Phase 1 of the project. Burner performance has been good and there have been no operating or maintenance problems. The DOC system continues to be used as part of Auburn Steel?s standard reheat furnace practice. High gas phase temperature is a result of the high firing density needed to achieve high production rates, and little opportunity exists for improvement in that area. However, fuel and NOx performance can be improved by further conversion of furnace zones to DOC burners, which will lower furnace nitrogen levels. Major obstacles are cost and concern about increased formation of oxide scale on the steel. Oxide scale formation may be enhanced by exposure of the steel to higher concentrations of oxidizing gas components (primarily products of combustion) in the higher temperature zones of the furnace. Phase 4 of the DOC project will examine the rate of oxide scale formation in these higher temperature zones and develop countermeasures that will allow DOC burners to be used successfully in these furnace zones.

  8. Bicosomes: Bicelles in Dilute Systems

    PubMed Central

    Rodríguez, Gelen; Soria, Guadalupe; Coll, Elisenda; Rubio, Laia; Barbosa-Barros, Lucyanna; López-Iglesias, Carmen; Planas, Anna M.; Estelrich, Joan; de la Maza, Alfons; López, Olga

    2010-01-01

    Abstract Bicelles are discoidal phospholipid nanostructures at high lipid concentrations. Under dilute conditions, bicelles become larger and adopt a variety of morphologies. This work proposes a strategy to preserve the discoidal morphology of bicelles in environments with high water content. Bicelles were formed in concentrated conditions and subsequently encapsulated in liposomes. Later dilution of these new structures, called bicosomes, demonstrated that lipid vesicles were able to isolate and protect bicelles entrapped inside them from the medium. Characterization of systems before and after dilution by dynamic light-scattering spectroscopy and cryo-transmission electron microscopy showed that free bicelles changed in size and morphology, whereas encapsulated bicelles remained unaltered by the effect of dilution. Free and entrapped bicelles (containing the paramagnetic contrast agent gadodiamide) were injected into rat brain lateral ventricles. Coronal and sagittal visualization was performed by magnetic resonance imaging. Whereas rats injected with free bicelles did not survive the surgery, those injected with bicosomes did, and a hyperintensity effect due to gadodiamide was observed in the cerebrospinal fluid. These results indicate that bicosomes are a good means of preserving the morphology of bicelles under dilution conditions. PMID:20643066

  9. 30 CFR 36.49 - Tests of exhaust-gas dilution system.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Tests of exhaust-gas dilution system. 36.49 Section 36.49 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR TESTING... carbon dioxide, carbon monoxide, oxides of nitrogen, and aldehydes in the diluted exhaust shall be...

  10. 30 CFR 36.49 - Tests of exhaust-gas dilution system.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Tests of exhaust-gas dilution system. 36.49 Section 36.49 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR TESTING... carbon dioxide, carbon monoxide, oxides of nitrogen, and aldehydes in the diluted exhaust shall be...

  11. Dilution and the elusive baseline.

    PubMed

    Likens, Gene E; Buso, Donald C

    2012-04-17

    Knowledge of baseline conditions is critical for evaluating quantitatively the effect of human activities on environmental conditions, such as the impact of acid deposition. Efforts to restore ecosystems to prior, "pristine" condition require restoration targets, often based on some presumed or unknown baseline condition. Here, we show that rapid and relentless dilution of surface water chemistry is occurring in the White Mountains of New Hampshire, following decades of acid deposition. Extrapolating measured linear trends using a unique data set of up to 47 years, suggest that both precipitation and streamwater chemistry (r(2) >0.84 since 1985) in the Hubbard Brook Experimental Forest (HBEF) will approximate demineralized water within one to three decades. Because such dilute chemistry is unrealistic for surface waters, theoretical baseline compositions have been calculated for precipitation and streamwater: electrical conductivity of 3 and 5 μS/cm, base cation concentrations of 7 and 39 μeq/liter, acid-neutralizing capacity values of <1 and 14 μeq/liter, respectively; and pH 5.5 for both. Significantly large and rapid dilution of surface waters to values even more dilute than proposed for Pre-Industrial Revolution (PIR) conditions has important ecological, biogeochemical and water resource management implications, such as for the success of early reproductive stages of aquatic organisms.

  12. Dilution and the elusive baseline.

    PubMed

    Likens, Gene E; Buso, Donald C

    2012-04-17

    Knowledge of baseline conditions is critical for evaluating quantitatively the effect of human activities on environmental conditions, such as the impact of acid deposition. Efforts to restore ecosystems to prior, "pristine" condition require restoration targets, often based on some presumed or unknown baseline condition. Here, we show that rapid and relentless dilution of surface water chemistry is occurring in the White Mountains of New Hampshire, following decades of acid deposition. Extrapolating measured linear trends using a unique data set of up to 47 years, suggest that both precipitation and streamwater chemistry (r(2) >0.84 since 1985) in the Hubbard Brook Experimental Forest (HBEF) will approximate demineralized water within one to three decades. Because such dilute chemistry is unrealistic for surface waters, theoretical baseline compositions have been calculated for precipitation and streamwater: electrical conductivity of 3 and 5 μS/cm, base cation concentrations of 7 and 39 μeq/liter, acid-neutralizing capacity values of <1 and 14 μeq/liter, respectively; and pH 5.5 for both. Significantly large and rapid dilution of surface waters to values even more dilute than proposed for Pre-Industrial Revolution (PIR) conditions has important ecological, biogeochemical and water resource management implications, such as for the success of early reproductive stages of aquatic organisms. PMID:22455659

  13. Evaluation of heavy water for indicator dilution cardiac output measurement

    SciTech Connect

    Schreiner, M.S.; Leksell, L.G.; Neufeld, G.R. )

    1989-10-01

    We evaluated deuterium oxide (D2O) as a tracer for cardiac output measurements. Cardiac output measurements made by thermodilution were compared with those made by indicator dilution with D2O and indocyanine green as tracers. Five triplicate measurements for each method were made at intervals of 30 minutes in each of 9 anesthetized, mechanically ventilated goats. Cardiac output ranged between 0.68 and 3.79 L/min. The 45 data points yielded a correlation coefficient of 0.948 for the comparison of D2O indicator dilution cardiac output measurements with thermodilution measurements and a linear regression slope of 1.046. D2O indicator dilution measurements were biased by -0.11 +/- 0.22 L/min compared with thermodilution measurements and had a standard deviation of +/- 0.12 L/min for triplicate measurements. Hematocrits ranging between 20 and 50 vol% had no effect on optical density for D2O. D2O is more stable than indocyanine green and approximately one-tenth the price (40 cents per injection compared with $4). The basic instrumentation cost of approximately $9,000 is an additional initial expense, but provides the ability to perform pulmonary extravascular water measurements with a double-indicator dilution technique. D2O has potential as a tracer for the clinical determination of indicator dilution cardiac output measurements and pulmonary extravascular water measurements.

  14. Dilute oxygen combustion. Phase I report

    SciTech Connect

    1997-10-01

    A novel burner, in which fuel (natural gas) and oxidant (oxygen or air) are separately injected into a furnace, shows promise for achieving very low nitrogen oxide(s) (NO{sub x}) emissions for commercial furnace applications. The dilute oxygen combustion (DOC) burner achieves very low NO{sub x} through in-furnace dilution of the oxidant stream prior to combustion, resulting in low flame temperatures, thus inhibiting thermal NO{sub x} production. The results of a fundamental and applied research effort on the development of the DOC burner are presented. In addition, the results of a market survey detailing the potential commercial impact of the DOC system are disclosed. The fundamental aspects of the burner development project involved examining the flame characteristics of a natural gas turbulent jet in a high-temperature ({approximately}1366 K) oxidant (7-27% O{sub 2} vol. wet). Specifically, the mass entrainment rate, the flame lift-off height, the velocity field and major species field of the jet were evaluated as a function of surrounding-gas temperature and composition. The measured entrainment rate of the fuel jet decreased with increasing oxygen content in the surrounding high-temperature oxidant, and was well represented by the d{sup +} scaling correlation found in the literature. The measured flame lift-off height decreased with increasing oxygen content and increasing temperature of the surrounding gas. An increase in surrounding-gas oxygen content and/or temperature inhibited the velocity decay within the jet periphery as a function of axial distance as compared to isothermal turbulent jets. However, the velocity measurements were only broadly represented by the d{sup +} scaling correlation. Several DOC burner configurations were tested in a laboratory-scale furnace at a nominal firing rate of 185 kW ({approximately}0.63 MMBtu/h). The flue gas composition was recorded as a function of furnace nitrogen content, furnace temperature, burner geometric

  15. Dilute Oxygen Combustion Phase 2 Final Report

    SciTech Connect

    Ryan, H.M.; Riley, M.F.; Kobayashi, H.

    2005-09-30

    A novel burner, in which fuel (natural gas) and oxidant (oxygen or air) are separately injected into a furnace, shows promise for achieving very low nitrogen oxide(s) (NOx) emissions for commercial furnace applications. The dilute oxygen combustion (DOC) burner achieves very low NOx through in-furnace dilution of the oxidant stream prior to combustion, resulting in low flame temperatures, thus inhibiting thermal NOx production. The results of a fundamental and applied research effort on the development of the DOC burner are presented. In addition, the results of a market survey detailing the potential commercial impact of the DOC system are disclosed. The fundamental aspects of the burner development project involved examining the flame characteristics of a natural gas turbulent jet in a high-temperature (~1366 K) oxidant (7-27% O2 vol. wet). Specifically, the mass entrainment rate, the flame lift-off height, the velocity field and major species field of the jet were evaluated as a function of surrounding-gas temperature and composition. The measured entrainment rate of the fuel jet decreased with increasing oxygen content in the surrounding high-temperature oxidant, and was well represented by the d+ scaling correlation found in the literature. The measured flame lift-off height decreased with increasing oxygen content and increasing temperature of the surrounding gas. An increase in surrounding-gas oxygen content and/or temperature inhibited the velocity decay within the jet periphery as a function of axial distance as compared to isothermal turbulent jets. However, the velocity measurements were only broadly represented by the d+ scaling correlation. Several DOC burner configurations were tested in a laboratory-scale furnace at a nominal firing rate of 185 kW (~0.63 MMBtu/h). The flue gas composition was recorded as a function of furnace nitrogen content, furnace temperature, burner geometric arrangement, firing rate, and fuel injection velocity. NOx emissions

  16. Dilute Oxygen Combustion Phase I Final Report

    SciTech Connect

    Ryan, H.M.; Riley, M.F.; Kobayashi, H.

    1997-10-31

    A novel burner, in which fuel (natural gas) and oxidant (oxygen or air) are separately injected into a furnace, shows promise for achieving very low nitrogen oxide(s) (NOx) emissions for commercial furnace applications. The dilute oxygen combustion (DOC) burner achieves very low NOx through in-furnace dilution of the oxidant stream prior to combustion, resulting in low flame temperatures, thus inhibiting thermal NOx production. The results of a fundamental and applied research effort on the development of the DOC burner are presented. In addition, the results of a market survey detailing the potential commercial impact of the DOC system are disclosed. The fundamental aspects of the burner development project involved examining the flame characteristics of a natural gas turbulent jet in a high-temperature (~1366 K) oxidant (7-27% O2 vol. wet). Specifically, the mass entrainment rate, the flame lift-off height, the velocity field and major species field of the jet were evaluated as a function of surrounding-gas temperature and composition. The measured entrainment rate of the fuel jet decreased with increasing oxygen content in the surrounding high-temperature oxidant, and was well represented by the d+ scaling correlation found in the literature. The measured flame lift-off height decreased with increasing oxygen content and increasing temperature of the surrounding gas. An increase in surrounding-gas oxygen content and/or temperature inhibited the velocity decay within the jet periphery as a function of axial distance as compared to isothermal turbulent jets. However, the velocity measurements were only broadly represented by the d+ scaling correlation. Several DOC burner configurations were tested in a laboratory-scale furnace at a nominal firing rate of 185 kW (~0.63 MMBtu/h). The flue gas composition was recorded as a function of furnace nitrogen content, furnace temperature, burner geometric arrangement, firing rate, and fuel injection velocity. NOx emissions

  17. Science Notes: Dilution of a Weak Acid

    ERIC Educational Resources Information Center

    Talbot, Christopher; Wai, Chooi Khee

    2014-01-01

    This "Science note" arose out of practical work involving the dilution of ethanoic acid, the measurement of the pH of the diluted solutions and calculation of the acid dissociation constant, K[subscript a], for each diluted solution. The students expected the calculated values of K[subscript a] to be constant but they found that the…

  18. Dilute Acid and Autohydrolysis Pretreatment

    NASA Astrophysics Data System (ADS)

    Yang, Bin; Wyman, Charles E.

    Exposure of cellulosic biomass to temperatures of about 120-210°C can remove most of the hemicellulose and produce cellulose-rich solids from which high glucose yields are possible with cellulase enzymes. Furthermore, the use of dilute sulfuric acid in this pretreatment operation can increase recovery of hemicellulose sugars substantially to about 85-95% of the maximum possible versus only about 65% if no acid is employed. The use of small-diameter tubes makes it possible to employ high solids concentrations similar to those preferred for commercial operations, with rapid heat-up, good temperature control, and accurate closure of material balances. Mixed reactors can be employed to pretreat larger amounts of biomass than possible in such small-diameter tubes, but solids concentrations are limited to about 15% or less to provide uniform temperatures. Pretreatment of large amounts of biomass at high solids concentrations is best carried out using direct steam injection and rapid pressure release, but closure of material balances in such “steam gun” devices is more difficult. Although flow of water alone or containing dilute acid is not practical commercially, such flow-through configurations provide valuable insight into biomass deconstruction kinetics not possible in the batch tubes, mixed reactors, or steam gun systems.

  19. A Microgravity Helium Dilution Cooler

    NASA Technical Reports Server (NTRS)

    Roach, Pat R.; Sperans, Joel (Technical Monitor)

    1994-01-01

    We are developing a He-3-He-4 dilution cooler to operate in microgravity. It uses charcoal adsorption pumps and heaters for its operation; it has no moving parts. It currently operates cyclically to well below 0.1 K and we have designed a version to operate continuously. We expect that the continuous version will be able to provide the long-duration cooling that many experiments need at temperatures down to 0.040 K. More importantly, such a dilution cooler could provide the precooling that enables the use of adiabatic demagnetization techniques that can reach temperatures below 0.001 K. At temperatures below 0.002 K many fascinating microgravity experiments on superfluid He-3 become possible. Among the possibilities are: research into a superfluid He-3 gyroscope, study of the nucleation of the B-phase of superfluid He-3 when the sample is floating out of contact with walls, study of the anisotropy of the surface tension of the B-phase, and NMR experiments on tiny free-floating clusters of superfluid He-3 atoms that should model the shell structure of nuclei.

  20. Propofol solubilization and structural transformations in dilutable microemulsion.

    PubMed

    Perlstein, My; Aserin, Abraham; Wachtel, Ellen J; Garti, Nissim

    2015-12-01

    Propofol (2,6-diisopropylphenol) is a drug for both induction and maintenance of anesthesia. Pure propofol cannot be injected because of its lipophilic character, low water-solubility, and low bioavailability. Presently, propofol is formulated in an unstable emulsion, easily oxidized, and easily contaminated with bacteria. We are proposing new, propofol-loaded modified microemulsions, stable thermodynamically, and microbiologically safe; the microemulsions are fully dilutable with water. Structural characterization of the empty and the propofol-loaded systems as a function of water dilution was accomplished using advanced analytical tools such as SD-NMR, SAXS, cryo-TEM, DSC, electrical conductivity, and viscosity. Upon water dilution the propofol-loaded concentrate forms swollen reverse micelles that upon further dilution (40 wt% water) progressively transform into a bicontinuous mesophase and then invert (>65 wt% water) into O/W nanodroplets without "losing" the solubilized propofol. The drug exhibits strong interactions with the surfactant (DSC and SD-NMR). Propofol increases the size of the microemulsion nanodroplets, but does not modify the microemulsion behavior. Water, ethanol, and PG are essential structural components, but do not interact directly with propofol.

  1. XAFS in dilute magnetic semiconductors.

    PubMed

    Sun, Zhihu; Yan, Wensheng; Yao, Tao; Liu, Qinghua; Xie, Yi; Wei, Shiqiang

    2013-10-14

    X-Ray absorption fine structure (XAFS) spectroscopy has experienced a rapid development in the last four decades and has proved to be a powerful structure characterization technique in the study of local environments in condensed matter. In this article, we first introduce the XAFS basic principles including theory, data analysis and experiment in some detail. Then we attempt to make a review on the applications of XAFS to the study of atomic and electronic structure in dilute magnetic semiconductor (DMS) systems. The power of XAFS in characterizing this interesting material system, such as determining the occupation sites and distribution of the dopants, detecting the presence of metal clusters or secondary phases, as well as identifying the defect types and dopant valence, will be illuminated by selected examples. This review should be of interest both to newcomers in the DMS field and to an interdisciplinary community of researchers working in synthesis, characterization and utilization of DMS materials. PMID:23884341

  2. Desynchronization in diluted neural networks

    SciTech Connect

    Zillmer, Ruediger; Livi, Roberto; Politi, Antonio; Torcini, Alessandro

    2006-09-15

    The dynamical behavior of a weakly diluted fully inhibitory network of pulse-coupled spiking neurons is investigated. Upon increasing the coupling strength, a transition from regular to stochasticlike regime is observed. In the weak-coupling phase, a periodic dynamics is rapidly approached, with all neurons firing with the same rate and mutually phase locked. The strong-coupling phase is characterized by an irregular pattern, even though the maximum Lyapunov exponent is negative. The paradox is solved by drawing an analogy with the phenomenon of 'stable chaos', i.e., by observing that the stochasticlike behavior is 'limited' to an exponentially long (with the system size) transient. Remarkably, the transient dynamics turns out to be stationary.

  3. Band anticrossing in dilute nitrides

    SciTech Connect

    Shan, W.; Yu, K.M.; Walukiewicz, W.; Wu, J.; Ager III, J.W.; Haller, E.E.

    2003-12-23

    Alloying III-V compounds with small amounts of nitrogen leads to dramatic reduction of the fundamental band-gap energy in the resulting dilute nitride alloys. The effect originates from an anti-crossing interaction between the extended conduction-band states and localized N states. The interaction splits the conduction band into two nonparabolic subbands. The downward shift of the lower conduction subband edge is responsible for the N-induced reduction of the fundamental band-gap energy. The changes in the conduction band structure result in significant increase in electron effective mass and decrease in the electron mobility, and lead to a large enhance of the maximum doping level in GaInNAs doped with group VI donors. In addition, a striking asymmetry in the electrical activation of group IV and group VI donors can be attributed to mutual passivation process through formation of the nearest neighbor group-IV donor nitrogen pairs.

  4. XAFS in dilute magnetic semiconductors.

    PubMed

    Sun, Zhihu; Yan, Wensheng; Yao, Tao; Liu, Qinghua; Xie, Yi; Wei, Shiqiang

    2013-10-14

    X-Ray absorption fine structure (XAFS) spectroscopy has experienced a rapid development in the last four decades and has proved to be a powerful structure characterization technique in the study of local environments in condensed matter. In this article, we first introduce the XAFS basic principles including theory, data analysis and experiment in some detail. Then we attempt to make a review on the applications of XAFS to the study of atomic and electronic structure in dilute magnetic semiconductor (DMS) systems. The power of XAFS in characterizing this interesting material system, such as determining the occupation sites and distribution of the dopants, detecting the presence of metal clusters or secondary phases, as well as identifying the defect types and dopant valence, will be illuminated by selected examples. This review should be of interest both to newcomers in the DMS field and to an interdisciplinary community of researchers working in synthesis, characterization and utilization of DMS materials.

  5. Dilution in single pass arc welds

    SciTech Connect

    DuPont, J.N.; Marder, A.R.

    1996-06-01

    A study was conducted on dilution of single pass arc welds of type 308 stainless steel filler metal deposited onto A36 carbon steel by the plasma arc welding (PAW), gas tungsten arc welding (GTAW), gas metal arc welding (GMAW), and submerged arc welding (SAW) processes. Knowledge of the arc and melting efficiency was used in a simple energy balance to develop an expression for dilution as a function of welding variables and thermophysical properties of the filler metal and substrate. Comparison of calculated and experimentally determined dilution values shows the approach provides reasonable predictions of dilution when the melting efficiency can be accurately predicted. The conditions under which such accuracy is obtained are discussed. A diagram is developed from the dilution equation which readily reveals the effect of processing parameters on dilution to aid in parameter optimization.

  6. Materials Design of CuAlO2-Based Dilute Magnetic Semiconductors by First-Principles Calculations and Monte Carlo Simulations

    NASA Astrophysics Data System (ADS)

    Kizaki, Hidetoshi; Sato, Kazunori; Katayama-Yoshida, Hiroshi

    2008-08-01

    In order to propose a new dilute magnetic semicoductors (DMS) other than II-VI and III-V semiconductor based DMS, magnetism of CuAlO2 based DMS is investigated by the Korringa-Kohn-Rostoker method combined with the coherent potential approximation within the local spin density approximation and Monte Carlo simulations (MCS). We found that effective exchange interactions (Jij) between magnetic ions are short-ranged and Jij's between magnetic ions in the same Cu-plane are ferromagnetic and ones between the different Cu-planes are nearly negligible in CuAlO2-based DMS. In comparison to this, Jij's between magnetic impurities occupied at Al-sites are slightly longer-ranged due to the stronger hybridization effect. According to MCS calculations, it is found that the value of the Curie temperature (TC) exceeds 80 K in (Cu,Fe)AlO2- and (Cu,Co)AlO2-DMS and that the TC is suppressed due to the strong percolation effect. This effect also appears in Cu(Al,TM)O2, where TM denote 3d-transition metal elements.

  7. 40 CFR 1065.240 - Dilution air and diluted exhaust flow meters.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... interval. You may use the difference between a diluted exhaust flow meter and a dilution air meter to.... We recommend that you use a diluted exhaust flow meter that meets the specifications in Table 1 of... verification in § 1065.307 and the calibration and verifications in § 1065.340 and § 1065.341. You may use...

  8. 40 CFR 1065.240 - Dilution air and diluted exhaust flow meters.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... interval. You may use the difference between a diluted exhaust flow meter and a dilution air meter to.... We recommend that you use a diluted exhaust flow meter that meets the specifications in Table 1 of... verification in § 1065.307 and the calibration and verifications in § 1065.340 and § 1065.341. You may use...

  9. 40 CFR 1065.240 - Dilution air and diluted exhaust flow meters.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... interval. You may use the difference between a diluted exhaust flow meter and a dilution air meter to.... We recommend that you use a diluted exhaust flow meter that meets the specifications in Table 1 of... verification in § 1065.307 and the calibration and verifications in § 1065.340 and § 1065.341. You may use...

  10. 40 CFR 1065.240 - Dilution air and diluted exhaust flow meters.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... interval. You may use the difference between a diluted exhaust flow meter and a dilution air meter to.... We recommend that you use a diluted exhaust flow meter that meets the specifications in Table 1 of... verification in § 1065.307 and the calibration and verifications in § 1065.340 and § 1065.341. You may use...

  11. Electrocoalescence based serial dilution of microfluidic droplets.

    PubMed

    Bhattacharjee, Biddut; Vanapalli, Siva A

    2014-07-01

    Dilution of microfluidic droplets where the concentration of a reagent is incrementally varied is a key operation in drop-based biological analysis. Here, we present an electrocoalescence based dilution scheme for droplets based on merging between moving and parked drops. We study the effects of fluidic and electrical parameters on the dilution process. Highly consistent coalescence and fine resolution in dilution factor are achieved with an AC signal as low as 10 V even though the electrodes are separated from the fluidic channel by insulator. We find that the amount of material exchange between the droplets per coalescence event is high for low capillary number. We also observe different types of coalescence depending on the flow and electrical parameters and discuss their influence on the rate of dilution. Overall, we find the key parameter governing the rate of dilution is the duration of coalescence between the moving and parked drop. The proposed design is simple incorporating the channel electrodes in the same layer as that of the fluidic channels. Our approach allows on-demand and controlled dilution of droplets and is simple enough to be useful for assays that require serial dilutions. The approach can also be useful for applications where there is a need to replace or wash fluid from stored drops.

  12. Electrocoalescence based serial dilution of microfluidic droplets

    PubMed Central

    Bhattacharjee, Biddut; Vanapalli, Siva A.

    2014-01-01

    Dilution of microfluidic droplets where the concentration of a reagent is incrementally varied is a key operation in drop-based biological analysis. Here, we present an electrocoalescence based dilution scheme for droplets based on merging between moving and parked drops. We study the effects of fluidic and electrical parameters on the dilution process. Highly consistent coalescence and fine resolution in dilution factor are achieved with an AC signal as low as 10 V even though the electrodes are separated from the fluidic channel by insulator. We find that the amount of material exchange between the droplets per coalescence event is high for low capillary number. We also observe different types of coalescence depending on the flow and electrical parameters and discuss their influence on the rate of dilution. Overall, we find the key parameter governing the rate of dilution is the duration of coalescence between the moving and parked drop. The proposed design is simple incorporating the channel electrodes in the same layer as that of the fluidic channels. Our approach allows on-demand and controlled dilution of droplets and is simple enough to be useful for assays that require serial dilutions. The approach can also be useful for applications where there is a need to replace or wash fluid from stored drops. PMID:25379096

  13. Systematic approach for simultaneously correcting the band-gap andp-dseparation errors of common cation III-V or II-VI binaries in density functional theory calculations within a local density approximation

    SciTech Connect

    Wang, Jianwei; Zhang, Yong; Wang, Lin-Wang

    2015-07-31

    We propose a systematic approach that can empirically correct three major errors typically found in a density functional theory (DFT) calculation within the local density approximation (LDA) simultaneously for a set of common cation binary semiconductors, such as III-V compounds, (Ga or In)X with X = N,P,As,Sb, and II-VI compounds, (Zn or Cd)X, with X = O,S,Se,Te. By correcting (1) the binary band gaps at high-symmetry points , L, X, (2) the separation of p-and d-orbital-derived valence bands, and (3) conduction band effective masses to experimental values and doing so simultaneously for common cation binaries, the resulting DFT-LDA-based quasi-first-principles method can be used to predict the electronic structure of complex materials involving multiple binaries with comparable accuracy but much less computational cost than a GW level theory. This approach provides an efficient way to evaluate the electronic structures and other material properties of complex systems, much needed for material discovery and design.

  14. Calibration graphs in isotope dilution mass spectrometry.

    PubMed

    Pagliano, Enea; Mester, Zoltán; Meija, Juris

    2015-10-01

    Isotope-based quantitation is routinely employed in chemical measurements. Whereas most analysts seek for methods with linear theoretical response functions, a unique feature that distinguishes isotope dilution from many other analytical methods is the inherent possibility for a nonlinear theoretical response curve. Most implementations of isotope dilution calibration today either eliminate the nonlinearity by employing internal standards with markedly different molecular weight or they employ empirical polynomial fits. Here we show that the exact curvature of any isotope dilution curve can be obtained from three-parameter rational function, y = f(q) = (a0 + a1q)/(1 + a2q), known as the Padé[1,1] approximant. The use of this function allows eliminating an unnecessary source of error in isotope dilution analysis when faced with nonlinear calibration curves. In addition, fitting with Padé model can be done using linear least squares.

  15. Helium Dilution Cryocooler for Space Applications

    NASA Technical Reports Server (NTRS)

    Roach, Pat; Hogan, Robert (Technical Monitor)

    2001-01-01

    NASA's New Millenium Program Space Technology presents the Helium Dilution Cryocooler for Space Applications. The topics include: 1) Capability; 2) Applications; and 3) Advantages. This paper is in viewgraph form.

  16. Flux balance analysis accounting for metabolite dilution.

    PubMed

    Benyamini, Tomer; Folger, Ori; Ruppin, Eytan; Shlomi, Tomer

    2010-01-01

    Flux balance analysis is a common method for predicting steady-state flux distributions within metabolic networks, accounting for the growth demand for the synthesis of a predefined set of essential biomass precursors. Ignoring the growth demand for the synthesis of intermediate metabolites required for balancing their dilution leads flux balance analysis to false predictions in some cases. Here, we present metabolite dilution flux balance analysis, which addresses this problem, resulting in improved metabolic phenotype predictions. PMID:20398381

  17. Flux balance analysis accounting for metabolite dilution.

    PubMed

    Benyamini, Tomer; Folger, Ori; Ruppin, Eytan; Shlomi, Tomer

    2010-01-01

    Flux balance analysis is a common method for predicting steady-state flux distributions within metabolic networks, accounting for the growth demand for the synthesis of a predefined set of essential biomass precursors. Ignoring the growth demand for the synthesis of intermediate metabolites required for balancing their dilution leads flux balance analysis to false predictions in some cases. Here, we present metabolite dilution flux balance analysis, which addresses this problem, resulting in improved metabolic phenotype predictions.

  18. Estimation method for serial dilution experiments.

    PubMed

    Ben-David, Avishai; Davidson, Charles E

    2014-12-01

    Titration of microorganisms in infectious or environmental samples is a corner stone of quantitative microbiology. A simple method is presented to estimate the microbial counts obtained with the serial dilution technique for microorganisms that can grow on bacteriological media and develop into a colony. The number (concentration) of viable microbial organisms is estimated from a single dilution plate (assay) without a need for replicate plates. Our method selects the best agar plate with which to estimate the microbial counts, and takes into account the colony size and plate area that both contribute to the likelihood of miscounting the number of colonies on a plate. The estimate of the optimal count given by our method can be used to narrow the search for the best (optimal) dilution plate and saves time. The required inputs are the plate size, the microbial colony size, and the serial dilution factors. The proposed approach shows relative accuracy well within ±0.1log10 from data produced by computer simulations. The method maintains this accuracy even in the presence of dilution errors of up to 10% (for both the aliquot and diluent volumes), microbial counts between 10(4) and 10(12) colony-forming units, dilution ratios from 2 to 100, and plate size to colony size ratios between 6.25 to 200.

  19. Minimal Coital Dilution in Accra, Ghana

    PubMed Central

    Jenness, Samuel M.; Biney, Adriana A. E.; Ampofo, William Kwabena; Dodoo, F. Nii-Amoo; Cassels, Susan

    2015-01-01

    Background Coital dilution, the reduction in the coital frequency per partner when an additional ongoing partner is added, may reduce the transmission potential of partnership concurrency for HIV and other sexually transmitted infections. Empirical estimates of dilution, especially dilution of sexual acts unprotected by condoms, are needed to inform prevention research. Methods Sexually active adults in Accra, Ghana were recruited in a multi-stage household probability sample. Degree (number of ongoing partners), total acts, and unprotected acts were measured retrospectively for each month in the past year through an event-history calendar. Random effects negative binomial models estimated the association between degree and coital frequency. Results Compared to person-months with a single partner (monogamy), 2.06 times as many total acts and 1.94 times as many unprotected acts occurred in months with 2 partners. In months with 3 partners, 2.90 times as many total acts and 2.39 times as many unprotected acts occurred compared to monogamous months. Total acts but not unprotected acts also declined with partnership duration. Conclusions No dilution was observed for total acts with up to three concurrent partners, but a small amount of dilution was observed for unprotected acts for months with multiple concurrencies. This suggests moderate selective condom use in months with multiple concurrencies. The implications of the observed dilution for future HIV transmission must be investigated with mathematical models. PMID:25622062

  20. Gluconeogenesis from labeled carbon: estimating isotope dilution

    SciTech Connect

    Kelleher, J.K.

    1986-03-01

    To estimate the rate of gluconeogenesis from steady-state incorporation of labeled 3-carbon precursors into glucose, isotope dilution must be considered so that the rate of labeling of glucose can be quantitatively converted to the rate of gluconeogenesis. An expression for the value of this isotope dilution can be derived using mathematical techniques and a model of the tricarboxylic acid (TCA) cycle. The present investigation employs a more complex model than that used in previous studies. This model includes the following pathways that may affect the correction for isotope dilution: 1) flux of 3-carbon precursor to the oxaloacetate pool via acetyl-CoA and the TCA cycle; 2) flux of 4- or 5-carbon compounds into the TCA cycle; 3) reversible flux between oxaloacetate (OAA) and pyruvate and between OAA and fumarate; 4) incomplete equilibrium between OAA pools; and 5) isotope dilution of 3-carbon tracers between the experimentally measured pool and the precursor for the TCA-cycle OAA pool. Experimental tests are outlined which investigators can use to determine whether these pathways are significant in a specific steady-state system. The study indicated that flux through these five pathways can significantly affect the correction for isotope dilution. To correct for the effects of these pathways an alternative method for calculating isotope dilution is proposed using citrate to relate the specific activities of acetyl-CoA and OAA.

  1. Microfluidics Meets Dilute Solution Viscometry: An Undergraduate Laboratory to Determine Polymer Molecular Weight Using a Microviscometer

    ERIC Educational Resources Information Center

    Pety, Stephen J.; Lu, Hang; Thio, Yonathan S.

    2011-01-01

    This paper describes a student laboratory experiment to determine the molecular weight of a polymer sample by measuring the viscosity of dilute polymer solutions in a PDMS microfluidic viscometer. Sample data are given for aqueous solutions of poly(ethylene oxide) (PEO). A demonstration of shear thinning behavior using the microviscometer is…

  2. Detailed mechanism of benzene oxidation

    NASA Technical Reports Server (NTRS)

    Bittker, David A.

    1987-01-01

    A detailed quantitative mechanism for the oxidation of benzene in both argon and nitrogen diluted systems is presented. Computed ignition delay time for argon diluted mixtures are in satisfactory agreement with experimental results for a wide range of initial conditions. An experimental temperature versus time profile for a nitrogen diluted oxidation was accurately matched and several concentration profiles were matched qualitatively. Application of sensitivity analysis has given approximate rate constant expressions for the two dominant heat release reactions, the oxidation of C6H5 and C5H5 radicals by molecular oxygen.

  3. Dilute Oxygen Combustion Phase IV Final Report

    SciTech Connect

    Riley, M.F.

    2003-04-30

    Novel furnace designs based on Dilute Oxygen Combustion (DOC) technology were developed under subcontract by Techint Technologies, Coraopolis, PA, to fully exploit the energy and environmental capabilities of DOC technology and to provide a competitive offering for new furnace construction opportunities. Capital cost, fuel, oxygen and utility costs, NOx emissions, oxide scaling performance, and maintenance requirements were compared for five DOC-based designs and three conventional air5-fired designs using a 10-year net present value calculation. A furnace direct completely with DOC burners offers low capital cost, low fuel rate, and minimal NOx emissions. However, these benefits do not offset the cost of oxygen and a full DOC-fired furnace is projected to cost $1.30 per ton more to operate than a conventional air-fired furnace. The incremental cost of the improved NOx performance is roughly $6/lb NOx, compared with an estimated $3/lb. NOx for equ8pping a conventional furnace with selective catalytic reduction (SCCR) technology. A furnace fired with DOC burners in the heating zone and ambient temperature (cold) air-fired burners in the soak zone offers low capital cost with less oxygen consumption. However, the improvement in fuel rate is not as great as the full DOC-fired design, and the DOC-cold soak design is also projected to cost $1.30 per ton more to operate than a conventional air-fired furnace. The NOx improvement with the DOC-cold soak design is also not as great as the full DOC fired design, and the incremental cost of the improved NOx performance is nearly $9/lb NOx. These results indicate that a DOC-based furnace design will not be generally competitive with conventional technology for new furnace construction under current market conditions. Fuel prices of $7/MMBtu or oxygen prices of $23/ton are needed to make the DOC furnace economics favorable. Niche applications may exist, particularly where access to capital is limited or floor space limitations

  4. Declining ecosystem health and the dilution effect.

    PubMed

    Khalil, Hussein; Ecke, Frauke; Evander, Magnus; Magnusson, Magnus; Hörnfeldt, Birger

    2016-01-01

    The "dilution effect" implies that where species vary in susceptibility to infection by a pathogen, higher diversity often leads to lower infection prevalence in hosts. For directly transmitted pathogens, non-host species may "dilute" infection directly (1) and indirectly (2). Competitors and predators may (1) alter host behavior to reduce pathogen transmission or (2) reduce host density. In a well-studied system, we tested the dilution of the zoonotic Puumala hantavirus (PUUV) in bank voles (Myodes glareolus) by two competitors and a predator. Our study was based on long-term PUUV infection data (2003-2013) in northern Sweden. The field vole (Microtus agrestis) and the common shrew (Sorex araneus) are bank vole competitors and Tengmalm's owl (Aegolius funereus) is a main predator of bank voles. Infection probability in bank voles decreased when common shrew density increased, suggesting that common shrews reduced PUUV transmission. Field voles suppressed bank vole density in meadows and clear-cuts and indirectly diluted PUUV infection. Further, Tengmalm's owl decline in 1980-2013 may have contributed to higher PUUV infection rates in bank voles in 2003-2013 compared to 1979-1986. Our study provides further evidence for dilution effect and suggests that owls may have an important role in reducing disease risk. PMID:27499001

  5. Developments on drug discovery and on new therapeutics: highly diluted tinctures act as biological response modifiers

    PubMed Central

    2011-01-01

    Background In the search for new therapies novel drugs and medications are being discovered, developed and tested in laboratories. Highly diluted substances are intended to enhance immune system responses resulting in reduced frequency of various diseases, and often present no risk of serious side-effects due to its low toxicity. Over the past years our research group has been investigating the action of highly diluted substances and tinctures on cells from the immune system. Methods We have developed and tested several highly diluted tinctures and here we describe the biological activity of M1, M2, and M8 both in vitro in immune cells from mice and human, and in vivo in mice. Cytotoxicity, cytokines released and NF-κB activation were determined after in vitro treatment. Cell viability, oxidative response, lipid peroxidation, bone marrow and lymph node cells immunophenotyping were accessed after mice in vivo treatment. Results None of the highly diluted tinctures tested were cytotoxic to macrophages or K562. Lipopolysaccharide (LPS)-stimulated macrophages treated with all highly diluted tinctures decreased tumour necrosis factor alpha (TNF-α) release and M1, and M8 decreased IFN-γ production. M1 has decreased NF-κB activity on TNF-α stimulated reporter cell line. In vivo treatment lead to a decrease in reactive oxygen species (ROS), nitric oxide (NO) production was increased by M1, and M8, and lipid peroxidation was induced by M1, and M2. All compounds enhanced the innate immunity, but M1 also augmented acquired immunity and M2 diminished B lymphocytes, responsible to acquired immunity. Conclusions Based on the results presented here, these highly diluted tinctures were shown to modulate immune responses. Even though further investigation is needed there is an indication that these highly diluted tinctures could be used as therapeutic interventions in disorders where the immune system is compromised. PMID:22029602

  6. Drug susceptibility testing by dilution methods.

    PubMed

    Jeannot, Katy; Plésiat, Patrick

    2014-01-01

    Serial twofold dilution methods are widely used to assess the bacteriostatic activities of antibiotics. This can be achieved by dilution of considered drugs in agar medium or in culture broth, and inoculation by calibrated inoculums. Although seemingly simple, these methods are greatly influenced by the experimental conditions used and may lead to discrepant results, in particular with untrained investigators. The present step-by-step protocol has been validated for Pseudomonas species, including P. aeruginosa. Introduction of appropriate control strains is crucial to ascertain minimal inhibitory concentration values and compare the results of independent experiments.

  7. Automatic dilution gaging of rapidly varying flow

    USGS Publications Warehouse

    Duerk, M.D.

    1983-01-01

    The analysis showed that the discharges measured by dye-dilution techniques were generally within ± 10 percent of the discharges determined from ratings established by current-meter measurements. Larger differences were noted at the start of and on the rising limb of four hydrographs. Of the 20 storms monitored, dilution measurements on 17 were of acceptable accuracy. Peak discharges from the open-channel site ranged from 0 to 12 percent departures from the existing rating whereas the comparison of peak discharge at the storm sewer site ranged from 0 to 5 percent departures from the existing rating.

  8. Diluted magnetic semiconductor nanowires exhibiting magnetoresistance

    DOEpatents

    Yang, Peidong; Choi, Heonjin; Lee, Sangkwon; He, Rongrui; Zhang, Yanfeng; Kuykendal, Tevye; Pauzauskie, Peter

    2011-08-23

    A method for is disclosed for fabricating diluted magnetic semiconductor (DMS) nanowires by providing a catalyst-coated substrate and subjecting at least a portion of the substrate to a semiconductor, and dopant via chloride-based vapor transport to synthesize the nanowires. Using this novel chloride-based chemical vapor transport process, single crystalline diluted magnetic semiconductor nanowires Ga.sub.1-xMn.sub.xN (x=0.07) were synthesized. The nanowires, which have diameters of .about.10 nm to 100 nm and lengths of up to tens of micrometers, show ferromagnetism with Curie temperature above room temperature, and magnetoresistance up to 250 Kelvin.

  9. Serial dilution microchip for cytotoxicity test

    NASA Astrophysics Data System (ADS)

    Bang, Hyunwoo; Lim, Sun Hee; Lee, Young Kyung; Chung, Seok; Chung, Chanil; Han, Dong-Chul; Chang, Jun Keun

    2004-08-01

    Today's pharmaceutical industry is facing challenges resulting from the vast increases in sample numbers produced by high-throughput screening (HTS). In addition, the bottlenecks created by increased demand for cytotoxicity testing (required to assess compound safety) are becoming a serious problem. We have developed a polymer PDMS (polydimethylsiloxane) based microfluidic device that can perform a cytotoxicity test in a rapid and reproducible manner. The concept that the device includes is well adjustable to automated robots in huge HTS systems, so we can think of it as a potential dilution and delivery module. Cytotoxicity testing is all about the dilution and dispensing of a drug sample. Previously, we made a PDMS based microfluidic device which automatically and precisely diluted drugs with a buffer solution with serially increasing concentrations. This time, the serially diluted drug solution was directly delivered to 96 well plates for cytotoxicity testing. Cytotoxic paclitaxel solution with 2% RPMI 1640 has been used while carrying out cancerous cell based cytotoxicity tests. We believe that this rapid and robust use of the PDMS microchip will overcome the growing problem in cytotoxicity testing for HTS.

  10. Statistical inference for serial dilution assay data.

    PubMed

    Lee, M L; Whitmore, G A

    1999-12-01

    Serial dilution assays are widely employed for estimating substance concentrations and minimum inhibitory concentrations. The Poisson-Bernoulli model for such assays is appropriate for count data but not for continuous measurements that are encountered in applications involving substance concentrations. This paper presents practical inference methods based on a log-normal model and illustrates these methods using a case application involving bacterial toxins.

  11. Declining ecosystem health and the dilution effect

    PubMed Central

    Khalil, Hussein; Ecke, Frauke; Evander, Magnus; Magnusson, Magnus; Hörnfeldt, Birger

    2016-01-01

    The “dilution effect” implies that where species vary in susceptibility to infection by a pathogen, higher diversity often leads to lower infection prevalence in hosts. For directly transmitted pathogens, non-host species may “dilute” infection directly (1) and indirectly (2). Competitors and predators may (1) alter host behavior to reduce pathogen transmission or (2) reduce host density. In a well-studied system, we tested the dilution of the zoonotic Puumala hantavirus (PUUV) in bank voles (Myodes glareolus) by two competitors and a predator. Our study was based on long-term PUUV infection data (2003–2013) in northern Sweden. The field vole (Microtus agrestis) and the common shrew (Sorex araneus) are bank vole competitors and Tengmalm’s owl (Aegolius funereus) is a main predator of bank voles. Infection probability in bank voles decreased when common shrew density increased, suggesting that common shrews reduced PUUV transmission. Field voles suppressed bank vole density in meadows and clear-cuts and indirectly diluted PUUV infection. Further, Tengmalm’s owl decline in 1980–2013 may have contributed to higher PUUV infection rates in bank voles in 2003–2013 compared to 1979–1986. Our study provides further evidence for dilution effect and suggests that owls may have an important role in reducing disease risk. PMID:27499001

  12. Osmosis is not driven by water dilution.

    PubMed

    Kramer, Eric M; Myers, David R

    2013-04-01

    There is a misconception among plant scientists that osmosis is driven by the tendency of solutes to dilute water. In this opinion article, we discuss the quantitative and qualitative failures of this view, and go on to review the correct kinetic picture of osmosis as it appears in physics textbooks.

  13. Sulfuric Acid and Water: Paradoxes of Dilution

    ERIC Educational Resources Information Center

    Leenson, I. A.

    2004-01-01

    On equilibrium properties of aqueous solutions of sulfuric acid, Julius Thomsen has marked that the heat evolved on diluting liquid sulfuric acid with water is a continuous function of the water used, and excluded absolutely the acceptance of definite hydrates as existing in the solution. Information about thermochemical measurement, a discussion…

  14. Cathodoluminescence from II-VI quantum well light emitting diodes

    NASA Astrophysics Data System (ADS)

    Nikiforov, Alexey Yuriyevich

    The objectives of the present research were to advance understanding of luminescence degradation, defects, and bias-dependent carrier confinement and transport in ZnCd(Mg)Se-based quantum well (QW) LED structures grown by molecular beam epitaxy. Most data were obtained from three LED samples. One was a ZnCdSe QW-based red LED with Au coating on top, and two were ZnCdMgSe QW-based blue LEDs with Au coating or Au dots on top. Optical and carrier confinement properties were characterized by time-resolved and bias-dependent cathodoluminescence (CL) spectroscopy and imaging. Electrical behavior was characterized by I-V and electroluminescence (EL) measurements. Both reversible and irreversible effects of bias and electron bombardment on luminescence were observed. Reversible effects were QW CL energy shifts and QW CL intensity changes during bias cycling. No EL was detected from the blue LEDs. Irreversible effects were QW CL decreases for the red LED and QW CL intensity enhancements for the blue LEDs. Reversible effects of bias on CL were simulated using a model incorporating generation and transport of excess carriers, overlap of the electron and hole wave functions, carrier escape, and competition between radiative and nonradiative processes. Ground state energy levels of carriers in the QW heterostructure were calculated in the effective mass and envelope function approximations. Modification of energy levels and wave functions by bias was calculated for both infinite and finite QWs. The finite QW simulations predict the reversible bias-dependent CL intensity behaviors seen experimentally for both red and blue LEDs. The simulations predict qualitatively, but not quantitatively, the reversible photon energy shifts with bias for the red LED. The photon energy shifts for the blue LEDs differed in both direction and magnitude from the simulations. The CL experiments have not established the cause of irreversible intensity decreases observed for the red LED during electron bombardment and bias cycling. Experiments suggest that the observed enhancements of CL intensity in the blue LEDs result from buildup of internal fields due to charges in preexisting or electron bombardment created traps.

  15. Modeling of mechanical properties of II-VI materials

    NASA Technical Reports Server (NTRS)

    Sher, A.; Berding, M. A.; Van Schilfgaarde, M.; Chen, A.-B.; Patrick, R.

    1988-01-01

    This paper reviews some new developments in the theory of alloy correlations, order-disorder transitions, and solidus phase-transition curves. It is argued that semiconductor alloys are never truly random, and the various phenomena that drive deviations from random arrangements are introduced. Likely consequences of correlations on the ability to fine-tune the lattice match of epitaxial layers to substrates, on vacancy formation, on diffusion, and on vapor-phase crystal growth are discussed. Examples are chosen for the alloys Hg(1-x)Cd(x)Te, Hg(1-x)Zn(x)Te, Cd(1-y)Zn(y)Te, and CdSe(1-y)Te(y).

  16. Ab initio study of II-(VI)2 dichalcogenides.

    PubMed

    Olsson, P; Vidal, J; Lincot, D

    2011-10-12

    The structural stabilities of the (Zn,Cd)(S,Se,Te)(2) dichalcogenides have been determined ab initio. These compounds are shown to be stable in the pyrite phase, in agreement with available experiments. Structural parameters for the ZnTe(2) pyrite semiconductor compound proposed here are presented. The opto-electronic properties of these dichalcogenide compounds have been calculated using quasiparticle GW theory. Bandgaps, band structures and effective masses are proposed as well as absorption coefficients and refraction indices. The compounds are all indirect semiconductors with very flat conduction band dispersion and high absorption coefficients. The work functions and surface properties are predicted. The Te and Se based compounds could be of interest as absorber materials in photovoltaic applications.

  17. Ionizing radiation induced degradation of monuron in dilute aqueous solution

    NASA Astrophysics Data System (ADS)

    Kovács, Krisztina; He, Shijun; Míle, Viktória; Földes, Tamás; Pápai, Imre; Takács, Erzsébet; Wojnárovits, László

    2016-07-01

    The decomposition of monuron was investigated in dilute aqueous solutions using pulse radiolysis and γ-radiolysis in order to identify the intermediates and final products. The main reaction takes place between monuron and the hydroxyl radicals yielding hydroxycyclohexadienyl type radicals with a second order rate constant of (7.4±0.2)×109 mol-1 dm3 s-1. In •OH reactions, the aminyl and phenoxyl radicals may also form. Dechlorination was observed in both hydroxyl radical and hydrated electron reactions. The •OH induced dechlorination reactions are suggested to occur through OH substitution or phenoxyl radical formation. The rate of oxidation is very high in the presence of dissolved oxygen. Some of the results are also supported by quantum chemical calculations.

  18. Stable isotope dilution analysis of hydrologic samples by inductively coupled plasma mass spectrometry

    USGS Publications Warehouse

    Garbarino, J.R.; Taylor, H.E.

    1987-01-01

    Inductively coupled plasma mass spectrometry is employed in the determination of Ni, Cu, Sr, Cd, Ba, Ti, and Pb in nonsaline, natural water samples by stable isotope dilution analysis. Hydrologic samples were directly analyzed without any unusual pretreatment. Interference effects related to overlapping isobars, formation of metal oxide and multiply charged ions, and matrix composition were identified and suitable methods of correction evaluated. A comparability study snowed that single-element isotope dilution analysis was only marginally better than sequential multielement isotope dilution analysis. Accuracy and precision of the single-element method were determined on the basis of results obtained for standard reference materials. The instrumental technique was shown to be ideally suited for programs associated with certification of standard reference materials.

  19. Pinch-off dynamics, extensional viscosity and relaxation time of dilute and ultradilute aqueous polymer solutions

    NASA Astrophysics Data System (ADS)

    Biagioli, Madeleine; Dinic, Jelena; Jimenez, Leidy Nallely; Sharma, Vivek

    Free surface flows and drop formation processes present in printing, jetting, spraying, and coating involve the development of columnar necks that undergo spontaneous surface-tension driven instability, thinning, and pinch-off. Stream-wise velocity gradients that arise within the thinning neck create and extensional flow field, which induces micro-structural changes within complex fluids that contribute elastic stresses, changing the thinning and pinch-off dynamics. In this contribution, we use dripping-onto-substrate (DoS) extensional rheometry technique for visualization and analysis of the pinch-off dynamics of dilute and ultra-dilute aqueous polyethylene oxide (PEO) solutions. Using a range of molecular weights, we study the effect of both elasticity and finite extensibility. Both effective relaxation time and the transient extensional viscosity are found to be strongly concentration-dependent even for highly dilute solutions.

  20. A nanoliter microfluidic serial dilution bioreactor.

    PubMed

    Gu, Guo-Yue; Lee, Yi-Wei; Chiang, Chih-Chung; Yang, Ya-Tang

    2015-07-01

    Bacterial culture is a basic technique in both fundamental and applied microbiology. The excessive reagent consumption and laborious maintenance of bulk bioreactors for microbial culture have prompted the development of miniaturized on-chip bioreactors. With the minimal choice of two compartments (N = 2) and discrete time, periodic dilution steps, we realize a microfluidic bioreactor that mimics macroscopic serial dilution transfer culture. This device supports automated, long-term microbial cultures with a nanoliter-scale working volume and real-time monitoring of microbial populations at single-cell resolution. Because of the high surface-to-volume ratio, the device also operates as an effective biofilm-flow reactor to support cogrowth of planktonic and biofilm populations. We expect that such devices will open opportunities in many fields of microbiology.

  1. Kinetic model for dilute traffic flow

    NASA Astrophysics Data System (ADS)

    Balouchi, Ashkan; Browne, Dana A.

    The flow of traffic represents a many-particle non-equilibrium problem with important practical consequences. Traffic behavior has been studied using a variety of approaches, including fluid dynamics models, Boltzmann equation, and recently cellular automata (CA). The CA model for traffic flow that Nagel and Schreckenberg (NS) introduced can successfully mimic many of the known features of the traffic flow. We show that in the dilute limit of the NS model, where vehicles exhibit free flow, cars show significant nearest neighbor correlation primarily via a short-range repulsion. introduce an approximate analytic model to describe this dilute limit. We show that the distribution of the distance between consecutive vehicles obeys a drift-diffusion equation. We compared this model with direct simulations. The steady state solution and relaxation of this model agrees well with direct simulations. We explore how this model breaks down as the transition to jams occurs.

  2. Dilution jet mixing program, supplementary report

    NASA Technical Reports Server (NTRS)

    Srinivasan, R.; White, C.

    1986-01-01

    The velocity and temperature distributions predicted by a 3-D numerical model and experimental measurements are compared. Empirical correlations for the jet velocity trajectory developed are presented. The measured velocity distributions for all test cases of phase through phase 3 are presented in the form of contour and oblique plots. quantification of the effects of the following on the jet mixing characteristics with a confined crossflow are: (1) orifice geometry momentum flux ratio and density ratio; (2) nonuniform mainstream temperature and velocity profiles upstream of dilution orifices; (3) cold versus hot jet injection; (4) cross-stream flow are a convergence as encountered in practical dilution zone geometries; (5) 2-D slot versus circular orifices; (6) discrete noncirculcer orifices; (7) single-sided versus opposed jets; (8) single row of jets.

  3. Dilution physics modeling: Dissolution/precipitation chemistry

    SciTech Connect

    Onishi, Y.; Reid, H.C.; Trent, D.S.

    1995-09-01

    This report documents progress made to date on integrating dilution/precipitation chemistry and new physical models into the TEMPEST thermal-hydraulics computer code. Implementation of dissolution/precipitation chemistry models is necessary for predicting nonhomogeneous, time-dependent, physical/chemical behavior of tank wastes with and without a variety of possible engineered remediation and mitigation activities. Such behavior includes chemical reactions, gas retention, solids resuspension, solids dissolution and generation, solids settling/rising, and convective motion of physical and chemical species. Thus this model development is important from the standpoint of predicting the consequences of various engineered activities, such as mitigation by dilution, retrieval, or pretreatment, that can affect safe operations. The integration of a dissolution/precipitation chemistry module allows the various phase species concentrations to enter into the physical calculations that affect the TEMPEST hydrodynamic flow calculations. The yield strength model of non-Newtonian sludge correlates yield to a power function of solids concentration. Likewise, shear stress is concentration-dependent, and the dissolution/precipitation chemistry calculations develop the species concentration evolution that produces fluid flow resistance changes. Dilution of waste with pure water, molar concentrations of sodium hydroxide, and other chemical streams can be analyzed for the reactive species changes and hydrodynamic flow characteristics.

  4. THE ANISOTROPIC TRANSPORT EFFECTS ON DILUTE PLASMAS

    SciTech Connect

    Devlen, Ebru

    2011-04-20

    We examine the linear stability analysis of a hot, dilute, and differentially rotating plasma by considering anisotropic transport effects. In dilute plasmas, the ion Larmor radius is small compared with its collisional mean free path. In this case, the transport of heat and momentum along the magnetic field lines becomes important. This paper presents a novel linear instability that may be more powerful and greater than ideal magnetothermal instability and ideal magnetorotational instability in the dilute astrophysical plasmas. This type of plasma is believed to be found in the intracluster medium (ICM) of galaxy clusters and radiatively ineffective accretion flows around black holes. We derive the dispersion relation of this instability and obtain the instability condition. There is at least one unstable mode that is independent of the temperature gradient direction for a helical magnetic field geometry. This novel instability is driven by the gyroviscosity coupled with differential rotation. Therefore, we call it gyroviscous-modified magnetorotational instability (GvMRI). We examine how the instability depends on signs of the temperature gradient and the gyroviscosity and also on the magnitude of the thermal frequency and on the values of the pitch angle. We provide a detailed physical interpretation of the obtained results. The GvMRI is applicable not only to the accretion flows and ICM but also to the transition region between cool dense gas and the hot low-density plasma in stellar coronae, accretion disks, and the multiphase interstellar medium because it is independent of the temperature gradient direction.

  5. Sodium perxenate permits rapid oxidation of manganese for easy spectrophotometric determination

    NASA Technical Reports Server (NTRS)

    Bane, R. W.

    1967-01-01

    Sodium perxenate oxidizes manganese to permanganate almost instantaneously in dilute acid solution and without a catalyst. A solution is prepared by dissolving 200 mg of sodium perxenate in distilled water and diluting to 100 ml.

  6. Helium 3/Helium 4 dilution cryocooler for space

    NASA Technical Reports Server (NTRS)

    Hendricks, John B.; Dingus, Michael L.

    1991-01-01

    Prototype dilution cryocoolers based on dilution refrigeration and adiabatic demagnetization refrigeration (ADR) cycles were designed, constructed, and tested. Although devices the devices did not operate as fully functional dilution cryocoolers, important information was gathered. The porous metal phase separator was demonstrated to operate in the -1-g configuration; this phase separation is the critical element in the He-3 circulation dilution cryocooler. Improvements in instrumentation needed for additional tests and development were identified.

  7. 21 CFR 172.710 - Adjuvants for pesticide use dilutions.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Adjuvants for pesticide use dilutions. 172.710... HUMAN CONSUMPTION Other Specific Usage Additives § 172.710 Adjuvants for pesticide use dilutions. The following surfactants and related adjuvants may be safely added to pesticide use dilutions by a grower...

  8. 21 CFR 172.710 - Adjuvants for pesticide use dilutions.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Adjuvants for pesticide use dilutions. 172.710... HUMAN CONSUMPTION Other Specific Usage Additives § 172.710 Adjuvants for pesticide use dilutions. The following surfactants and related adjuvants may be safely added to pesticide use dilutions by a grower...

  9. Body composition of lactating and dry Holstein cows estimated by deuterium dilution

    SciTech Connect

    Martin, R.A.; Ehle, F.R.

    1986-01-01

    In three experiments patterns of water turnover and body composition estimated by deuterium oxide were studied in Holstein cows. In the first experiment, four lactating cows were infused with deuterium oxide, and blood samples were taken during 4-d collection. Milking was stopped; cows were reinfused with deuterium oxide and resampled. Slopes of deuterium oxide dilution curves indicated lactating cows turned water over more rapidly than nonlactating cows. In the second experiment with the same four cows, during 4-d collection, deuterium oxide concentrations in milk, urine, and feces showed dilution patterns similar to deuterium oxide in blood. Sampling milk may be an alternative to sampling blood. In the third experiment, 36 Holstein cows were fed 55, 65, or 75% alfalfa, smooth bromegrass, or equal parts of each forage as total mixed rations; remaining portions of rations were a grain mixture. Body composition was estimated at -1, 1, 2, 3, 4, and 5 mo postpartum. Empty body water, protein, mineral, fat, and fat percentage decreased from prepartum to postpartum. First calf heifers contained less empty body water, protein, and mineral than older cows. Cows fed diets with 55% forage had more body fat than those fed diets with 75% forage. Cows fed alfalfa-based diets had more gastrointestinal fill regardless of grain than cows fed diets that contained alfalfa and smooth bromegrass. Gastrointestinal fill of cows increased from prepartum to 5 mo postpartum.

  10. Solubility of solutes in compressed gases: Dilute solution theory

    SciTech Connect

    Wang, X.; Tavlarides, L.L. . Dept. of Chemical Engineering)

    1994-03-01

    A dilute solution theory is developed for describing the thermodynamic behavior of a compressed gaseous dilute solution. The considerations follow generally accepted statistical treatments for describing dilute liquid solutions. The theory is self-consistent with the ideal gas law for dilute gases and with Henry's law for dilute liquid (or solid) solutions. Further, it provides a simple linear relationship which represents well the solubility behavior of a heavy solute (solid or liquid) in a gaseous solvent over relatively wide density regions of the solvent (i.e., 0 [le] [rho] [le] 2.0/V[sub c]).

  11. Magnetopolaron effect in diluted semimagnetic semiconductors

    NASA Astrophysics Data System (ADS)

    Tarasov, Georgiy G.; Mazur, Yuri I.; Rakitin, Andrey S.; Lavoric, S. R.; Tomm, Jens W.; Hoerstel, W.

    1997-08-01

    Phonon-assisted self-trapping of free carrier is considered in diluted semimagnetics. It is shown that the binding energy of free magnetic polaron can be substantially larger when the 'spin-phonon' coupling is taken into account. For the particular case of 'soft' lattice dynamics the region of stability for hole-induced polaron can be promoted to the temperature of tenths of degrees and magnetic field of a few Tesla. The possible hybridized excitations with the partition of free magnetic polaron are discussed in semimagnetic semiconductors.

  12. Steadiness in Dilute Pyroclastic Density Currents

    NASA Astrophysics Data System (ADS)

    Andrews, B. J.

    2015-12-01

    Pyroclastic density currents (PDCs) are often unsteady, as evidenced by direct observations of dilute lobes or jets emerging from the fronts of larger currents and by deposits that indicate transient transport and depositional regimes. We used scaled experiments to investigate unsteadiness in dilute PDCs. The experimental currents were run in an 8.5x6.1x2.6 m tank and comprised heated or ambient temperature 20-μm talc powder turbulently suspended in air. Experiments were scaled such that densimetric and thermal Richardson numbers, Froude number, and particle Stokes and settling numbers were dynamically similar to natural dilute PDCs. Although the experiment Reynolds numbers are substantially lower than those of natural PDCs, the experiments are fully turbulent. Experiments were observed with video and high-speed cameras and high-frequency thermocouples. Currents were generated with total eruption durations of 100 s. Unsteadiness in source conditions was produced by interrupting supply for intervals, t, with durations of 1, 2.5, 5, and 10 s in the experimental runs at 35 and 70 s. When t<2.5 s, the currents are indistinguishable from currents with steady supply. In runs with t=2.5-5 s, the individual pulses comprising each current are readily apparent near the source, but decay with distance downstream until the currents appear as single (e.g. steady) flows. In experiments with t=10 s, the 3 pulses comprising each run never merge and the currents remain unsteady. Comparison with the integral turbulent timescale, τ, and current velocity, U, show that unsteadiness is persistent when t>3<τ but currents are steady when t<τ. In currents with 3τ>t>τ, unsteadiness decays such that at a distance of ~4Ut, the currents are again steady. Applied to natural dilute PDCs, our results suggest that currents and their resulting deposits, will only show evidence of unsteadiness if they are disrupted for many seconds and those breaks may "heal" over distances of 100s of meters.

  13. Diluted Magnetic Iv-Vi Compounds

    NASA Astrophysics Data System (ADS)

    Bauer, G.; Pascher, H.

    The following sections are included: * INTRODUCTION * MAGNETIC PROPERTIES * Susceptibility * High Field Magnetization * Spin Glass Phase * Free Carrier Induced Ferromagnetism * Magnetic Properties of Layered IV-VI Diluted Magnetic Semiconductors * CALCULATION OF LANDAU STATES: MEAN FIELD THEORY FOR IV-VI COMPOUNDS * MAGNETOTRANSPORT * OPTICAL INTERBAND TRANSITIONS * Photoluminescence Without Magnetic Field * Magnetooptical Interband Transitions * COHERENT RAMAN SCATTERING * Theory * Classical approach * Nonlinear susceptibility in semiconductors * Experimental Results and Discussion * Results: Pb1-xMnxTe * Results: Pb1-xEuxSe * Effective Electron and Hole g factors * FAR INFRARED SPECTROSCOPY * COMPARISON EXPERIMENT - MOLECULAR FIELD THEORY * Band and Exchange Parameters * Selection Rules * CONCLUSION * ACKNOWLEDGEMENTS * REFERENCES

  14. The Effect of Dilution on the Structure of Microbial Communities

    NASA Technical Reports Server (NTRS)

    Mills, Aaron L.

    2000-01-01

    To determine how dilution of microbial communities affects the diversity of the diluted assemblage a series of numerical simulations were conducted that determined the theoretical change in diversity, richness, and evenness of the community with serial dilution. The results of the simulation suggested that the effects are non linear with a high degree of dependence on the initial evenness of the community being diluted. A series of incubation experiments using a range of dilutions of raw sewage as an inoculum into sterile sewage was used for comparison to the simulations. The diluted communities were maintained in batch fed reactors (three day retention time) for nine days. The communities were harvested and examined by conventional plating and by molecular analysis of the whole-community DNA using AFLP and T-RFLP. Additional, CLPP analysis was also applied. The effects on richness predicted by the numerical simulations were confirmed by the analyses used. The diluted communities fell into three groups, a low dilution, intermediate dilution, and high dilution group, which corresponded well with the groupings obtained for community richness in simulation. The grouping demonstrated the non-linear nature of dilution of whole communities. Furthermore, the results implied that the undiluted community consisted of a few dominant types accompanied by a number of rare (low abundance) types as is typical in unevenly distributed communities.

  15. Neutron scattering study of dilute supercritical solutions

    NASA Astrophysics Data System (ADS)

    Cochran, H. D.; Wignall, G. D.; Shah, V. M.; Londono, J. D.; Bienkowski, P. R.

    Dilute solutions in supercritical solvents exhibit interesting microstructures that are related to their dramatic macroscopic behavior. In typical attractive solutions, solutes are believed to be surrounded by clusters of solvent molecules, and solute molecules are believed to congregate in the vicinity of one another. Repulsive solutions, on the other hand, exhibit a local region of reduced solvent density around the solute with solute-solute congregation. Such microstructures influence solubility, partial molar volume, reaction kinetics, and many other properties. We have undertaken to observe these interesting microstructures directly by neutron scattering experiments on dilute noble gas systems including Ar. The three partial structure factors for such systems and the corresponding pair correlation functions can be determined by using the isotope substitution technique. The systems studied are uniquely suited for our objectives because of the large coherent neutron scattering length of the isotope (sup 36)Ar and because of the accurate potential energy functions that are available for use in molecular simulations and theoretical calculations to be compared with the scattering results. We will describe our experiment, the unique apparatus we have built for it, and the neutron scattering results from our initial allocations of beam time. We will also describe planned scattering experiments to follow those with noble gases, including study of long-chain molecules in supercritical solvents. Such studies will involve hydrocarbon mixtures with and without deuteration to provide contrast.

  16. Neutron scattering study of dilute supercritical solutions

    SciTech Connect

    Cochran, H.D.; Wignall, G.D.; Shah, V.M.; Londono, J.D.; Bienkowski, P.R.

    1994-10-01

    Dilute solutions in supercritical solvents exhibit interesting microstructures that are related to their dramatic macroscopic behavior. In typical attractive solutions, solutes are believed to be surrounded by clusters of solvent molecules, and solute molecules are believed to congregate in the vicinity of one another. Repulsive solutions, on the other hand, exhibit a local region of reduced solvent density around the solute with solute-solute congregation. Such microstructures influence solubility, partial molar volume, reaction kinetics, and many other properties. We have undertaken to observe these interesting microstructures directly by neutron scattering experiments on dilute noble gas systems including Ar. The three partial structure factors for such systems and the corresponding pair correlation functions can be determined by using the isotope substitution technique. The systems studied are uniquely suited for our objectives because of the large coherent neutron scattering length of the isotope {sup 36}Ar and because of the accurate potential energy functions that are available for use in molecular simulations and theoretical calculations to be compared with the scattering results. We will describe our experiment, the unique apparatus we have built for it, and the neutron scattering results from our initial allocations of beam time. We will also describe planned scattering experiments to follow those with noble gases, including study of long-chain molecules in supercritical solvents. Such studies will involve hydrocarbon mixtures with and without deuteration to provide contrast.

  17. Capillary electrophoretic separation of DNA restriction fragments using dilute polymer solutions

    SciTech Connect

    Braun, B.; Blanch, W.; Prausnitz, J.M.

    1997-02-01

    Because the mechanism of DNA separation in capillary electrophoresis is not well understood, selection of polymers is a {open_quotes}trial-and-error{close_quotes} procedure. We investigated dilute-solution DNA separations by capillary electrophoresis using solutions of four polymers that differ in size, shape and stiffness. Hydroxyethylcellulose of high molecular weight provides excellent separation of large DNA fragments (2027 bp - 23130 bp). Polyvinylpyrrolidone separates DNA from 72 bp to 23 kbp and star-(polyethylene oxide), like linear poly (ethylene oxide), provides separation of fragments up to 1353 bp.

  18. Characterization of the Dilute Ising Antiferromagnet

    SciTech Connect

    Wiener, T.

    2000-09-12

    A spin glass is a magnetic ground state in which ferromagnetic and antiferromagnetic exchange interactions compete, thereby creating frustration and a multidegenerate state with no long range order. An Ising system is a system where the spins are constrained to lie parallel or antiparallel to a primary axis. There has been much theoretical interest in the past ten years in the effects of applying a magnetic field transverse to the primary axis in an Ising spin glass at low temperatures and thus study phase transitions at the T=0 limit. The focus of this study is to search for and characterize a new Ising spin glass system. This is accomplished by site diluting yttrium for terbium in the crystalline material TbNi{sub 2}Ge{sub 2}. The first part of this work gives a brief overview of the physics of rare earth magnetism and an overview of experimental characteristics of spin glasses. This is followed by the methodology used to manufacture the large single crystals used in this study, as well as the measurement techniques used. Next, a summary of the results of magnetic measurements on across the dilution series from pure terbium to pure yttrium is presented. This is followed by detailed measurements on particular dilutions which demonstrate spin glass behavior. Pure TbNi{sub 2}Ge{sub 2} is an Ising antiferromagnet with a several distinct metamagnetic states below 17 K. As the terbium is alloyed with yttrium, these magnetic states are weakened in a consistent manner, as is seen in measurements of the transition temperatures and analysis of Curie-Weiss behavior at high temperature. At low concentrations of terbium, below 35%, long range order is no longer present and a spin-glass-like state emerges. This state is studied through various measurements, dc and ac susceptibility, resistivity, and specific heat. This magnetic behavior was then compared to that of other well characterized spin glasses. It is concluded that there is a region of concentration s for which a spin

  19. Dynamical Threshold of Diluteness of Soft Colloids

    SciTech Connect

    Chen, Wei-Ren; Do, Changwoo; Egami, T; Falus, Peter; Li, Xin; Liu, Dazhi; Porcar, L.; Sanchez-Diaz, Luis E; Smith, Gregory Scott; Wu, Bin

    2014-01-01

    The dynamics of soft colloids in solutions is characterized by internal collective motion as well as center-of-mass diffusion. Using neutron scattering we demonstrate that the competition between the relaxation processes associated with these two degrees of freedom results in strong dependence of dynamics and structure on colloid concentration, c, well below the overlap concentration c*. Triggered by the increasing inter-particle collisions, substantial structural dehydration and slowing-down of internal dynamics occurs before geometrically defined colloidal overlap develops. This observation is surprising since it is generally believed that the internal dynamics and conformation of soft colloidal particles essentially remain invariant below c*. The competition between these two relaxation processes gives rise to a new dynamically-defined dilute threshold concentration well below c*.

  20. Maximum independent set on diluted triangular lattices

    NASA Astrophysics Data System (ADS)

    Fay, C. W., IV; Liu, J. W.; Duxbury, P. M.

    2006-05-01

    Core percolation and maximum independent set on random graphs have recently been characterized using the methods of statistical physics. Here we present a statistical physics study of these problems on bond diluted triangular lattices. Core percolation critical behavior is found to be consistent with the standard percolation values, though there are strong finite size effects. A transfer matrix method is developed and applied to find accurate values of the density and degeneracy of the maximum independent set on lattices of limited width but large length. An extrapolation of these results to the infinite lattice limit yields high precision results, which are tabulated. These results are compared to results found using both vertex based and edge based local probability recursion algorithms, which have proven useful in the analysis of hard computational problems, such as the satisfiability problem.

  1. Crystallization of a dilute atomic dipolar condensate

    NASA Astrophysics Data System (ADS)

    Bisset, Russell; Blakie, Blair

    2016-05-01

    A recent experiment found that a dilute BEC of highly-magnetic dysprosium atoms may spontaneously break up into a crystal of droplets, a process reminiscent of the Rosensweig instability [ArXiv:1508.05007]. We dynamically simulate this scenario and find that the standard dipolar Gross-Pitaevskii equation (GPE) cannot explain such a droplet crystal. Indeed, the GPE predicts too much heating during the violent droplet formation, and a droplet lifetime that is much shorter than observed in the experiment. We investigate the requisite properties of the unknown stabilization mechanism, and find that an effective repulsive interaction with a higher order density dependence than the usual two-body interactions is required to quantitatively reproduce the experimental results.

  2. Dilute acid saccharification of lignocellulosic biomass

    SciTech Connect

    Penner, M.H.; Hashimoto, A.G.

    1995-12-01

    Aqueous dilute sulfuric acid solutions have been evaluated in terms of their effectiveness for the saccharification of the insoluble xylan fraction of poplar and switchgrass feedstocks. Acid concentrations ranging from .6 to 1.2% have been tested at temperatures ranging from 120 to 160{degrees}C. Treatments at optimum time, temperature, and acid combinations provided xylose yields of approximately 90% theoretical. Rate constants associated with xylan hydrolysis and xylose degradation for each of the feed-stocks have been evaluated. In general, optimum yields were associated with high temperature treatments for relatively short reaction times. Results from our laboratory will be presented with reference to previously published studies on hemicellulose saccharification and in the general context of converting lignocellulosic biomass to useful products.

  3. Hyperuniformity in periodically sheared dilute suspensions

    NASA Astrophysics Data System (ADS)

    Wilken, Sam; Guerra, Rodrigo; Pine, David J.; Chaikin, Paul M.

    Periodically sheared dilute, non-Brownian suspensions explore new configurations through collisions in an otherwise reversible flow. Below a critical strain, the particles remain active until they find a configuration with no collisions and reach an absorbing state. Recent simulations by Hexner and Levine have shown that the configuration of particles in the critically absorbing state is hyperuniform. The particle number fluctuations of hyperuniform systems decrease with counting box size more rapidly than random systems (like the same suspension that is not in a critically absorbing state). We built a compact, lightweight uni-axial shear cell where particle coordinates can be measured while shearing with a confocal microscope. We have identified hyperuniform structures with density fluctuation measurements in colloidal suspensions of up to 40% volume fraction in the critically absorbing state with a strain ramp down protocol and find hyperuniform scaling of the density fluctuations.

  4. Shock waves in a dilute granular gas

    NASA Astrophysics Data System (ADS)

    Reddy, M. H. Lakshminarayana; Ansumali, Santosh; Alam, Meheboob

    2014-12-01

    We study the evolution of shock waves in a dilute granular gas which is modelled using three variants of hydrodynamic equations: Euler, 10-moment and 14-moment models. The one-dimensional shock-wave problem is formulated and the resulting equations are solved numerically using a relaxation-type scheme. Focusing on the specific case of blast waves, the results on the density, the granular temperature, the skew temperature, the heat flux and the fourth moment are compared among three models. We find that the shock profiles are smoother for the 14-moment model compared to those predicted by the standard Euler equations. A shock-splitting phenomenon is observed in the skew granular temperature profiles for a blast wave.

  5. Negative magnetophoresis in diluted ferrofluid flow.

    PubMed

    Hejazian, Majid; Nguyen, Nam-Trung

    2015-07-21

    We report magnetic manipulation of non-magnetic particles suspended in diluted ferrofluid. Diamagnetic particles were introduced into a circular chamber to study the extent of their deflection under the effect of a non-uniform magnetic field of a permanent magnet. Since ferrofluid is a paramagnetic medium, it also experiences a bulk magnetic force that in turn induces a secondary flow opposing the main hydrodynamic flow. Sheath flow rate, particle size, and magnetic field strength were varied to examine this complex behaviour. The combined effect of negative magnetophoresis and magnetically induced secondary flow leads to various operation regimes, which can potentially find applications in separation, trapping and mixing of diamagnetic particles such as cells in a microfluidic system. PMID:26054840

  6. Dilute spin-orbit Fermi gases

    NASA Astrophysics Data System (ADS)

    Maldonado-Mundo, Daniel; He, Lianyi; Öhberg, Patrik; Valiente, Manuel

    2014-03-01

    We study repulsive Fermi gases with Rashba spin-orbit coupling in two and three dimensions when they are dilute enough that a single branch of the spectrum is occupied in the non-interacting ground state. We develop an effective renormalizable theory for fermions in the lower branch and obtain the energy of the system in three dimensions to second order in the renormalized coupling constant. We then exploit the non-Galilean-relativistic nature of spin-orbit coupled gases. We find that at finite momentum, the two-dimensional Fermi sea is deformed in a non-trivial way. Using mean-field theory to include interactions, we show that the ground-state of the system acquires a finite momentum, and is consequently deformed, when the interaction is stronger than a critical value. Heriot-Watt University. CM-DTC. SUPA. EPSRC.

  7. Nucleation of flocs in dilute colloidal suspensions

    SciTech Connect

    Agrawal, D.C.; Raj, R.; Cohen, C. )

    1989-11-01

    In contrast to earlier theories which assume that coagulation of particles in dilute colloidal suspensions occurs by random collisions, the authors present evidence that coagulation is limited by a nucleation and growth phenomenon, typical of a phase transformation. They show that suspensions of well-dispersed particles, which are almost indefinitely stable, flocculate rapidly when seeded with pregrown flocs. The nucleation argument is supported further by the observation that flocs which are grown at low {zeta} potential, where the particles strongly attract, do not peptize when the pH is changed to high {zeta} potential, where the attraction is weak. The experiments were carried out with aqueous dispersions of alumina particles. The timedependent change in cluster sizes was measured by in situ photon correlation spectroscopy. The observations raise the question of agglomeration as a phase transformation, involving a change in entropy, when the system moves from a dispersed to a flocculated state.

  8. Diluted magnetic semiconductors with narrow band gaps

    NASA Astrophysics Data System (ADS)

    Gu, Bo; Maekawa, Sadamichi

    2016-10-01

    We propose a method to realize diluted magnetic semiconductors (DMSs) with p - and n -type carriers by choosing host semiconductors with a narrow band gap. By employing a combination of the density function theory and quantum Monte Carlo simulation, we demonstrate such semiconductors using Mn-doped BaZn2As2 , which has a band gap of 0.2 eV. In addition, we found a nontoxic DMS Mn-doped BaZn2Sb2 , of which the Curie temperature Tc is predicted to be higher than that of Mn-doped BaZn2As2 , the Tc of which was up to 230 K in a recent experiment.

  9. Biodiesel Impact on Engine Lubricant Dilution During Active Regeneration of Aftertreatment Systems

    SciTech Connect

    He, X.; Williams, A.; Christensen, E.; Burton, J.; McCormick, R.

    2011-12-01

    Experiments were conducted with ultra low sulfur diesel (ULSD) and 20% biodiesel blends (B20) to compare lube oil dilution levels and lubricant properties for systems using late in-cylinder fuel injection for aftertreatment regeneration. Lube oil dilution was measured by gas chromatography (GC) following ASTM method D3524 to measure diesel content, by Fourier transform infrared (FTIR) spectrometry following a modified ASTM method D7371 to measure biodiesel content, and by a newly developed back-flush GC method that simultaneously measures both diesel and biodiesel. Heavy-duty (HD) engine testing was conducted on a 2008 6.7L Cummins ISB equipped with a diesel oxidation catalyst (DOC) and diesel particle filter (DPF). Stage one of engine testing consisted of 10 consecutive repeats of a forced DPF regeneration event. This continuous operation with late in-cylinder fuel injection served as a method to accelerate lube-oil dilution. Stage two consisted of 16 hours of normal engine operation over a transient test cycle, which created an opportunity for any accumulated fuel in the oil sump to evaporate. Light duty (LD) vehicle testing was conducted on a 2010 VW Jetta equipped with DOC, DPF and a NOx storage catalyst (NSC). Vehicle testing comprised approximately 4,000 miles of operation on a mileage-accumulation dynamometer (MAD) using the U.S. Environmental Protection Agency's Highway Fuel Economy Cycle because of the relatively low engine oil and exhaust temperatures, and high DPF regeneration frequency of this cycle relative to other cycles examined. Comparison of the lube oil dilution analysis methods suggests that D3524 does not measure dilution by biodiesel. The new back-flush GC method provided analysis for both diesel and biodiesel, in a shorter time and with lower detection limit. Thus all lube oil dilution results in this paper are based on this method. Analysis of the HD lube-oil samples showed only 1.5% to 1.6% fuel dilution for both fuels during continuous

  10. Dilute acid/metal salt hydrolysis of lignocellulosics

    DOEpatents

    Nguyen, Quang A.; Tucker, Melvin P.

    2002-01-01

    A modified dilute acid method of hydrolyzing the cellulose and hemicellulose in lignocellulosic material under conditions to obtain higher overall fermentable sugar yields than is obtainable using dilute acid alone, comprising: impregnating a lignocellulosic feedstock with a mixture of an amount of aqueous solution of a dilute acid catalyst and a metal salt catalyst sufficient to provide higher overall fermentable sugar yields than is obtainable when hydrolyzing with dilute acid alone; loading the impregnated lignocellulosic feedstock into a reactor and heating for a sufficient period of time to hydrolyze substantially all of the hemicellulose and greater than 45% of the cellulose to water soluble sugars; and recovering the water soluble sugars.

  11. Droplet Size Distributions in Atomization of Dilute Viscoelastic Solutions

    NASA Astrophysics Data System (ADS)

    Keshavarz, Bavand; McKinley, Gareth; Houze, Eric; Moore, John; Pottiger, Michael; Cotts, Patricia; M. I. T. Collaboration; DuPont Collaboration

    2012-11-01

    The droplet size probability distribution functions (PDF) for atomization/fragmentation processes in Newtonian fluids are now generally accepted to be close to Gamma distributions. Despite the great practical importance, little is known about the nature of corresponding distributions for viscoelastic liquids, e.g. polymeric solutions such as pesticide sprays and paints. We present data from air-assisted atomization experiments for model viscoelastic solutions composed of very dilute solutions of polyethylene oxide. Although the addition of small amounts of high molecular weight polymer keeps the fluid shear viscosity and surface tension close to the solvent values, the size distributions are skewed towards higher values of the Sauter mean diameter. We show that the PDF curves for these weakly-elastic fluids are well described by Gamma distributions, but the exponent n is systematically decreased by fluid elasticity. Flow visualization images show that this behavior arises from the non-linear dynamics close to the break-up point which are dominated by an elasto-capillary force balance within the thinning ligaments and the magnitude of the extensional viscosity in the viscoelastic fluid. Mechanical Engineering Department, Cambridge, MA.

  12. Overlap amplitude and localization properties in aperiodic diluted and non-diluted direct electric transmission lines

    NASA Astrophysics Data System (ADS)

    Lazo, E.; Castro, C. E.; Cortés-Cortés, F.

    2016-09-01

    In this work we study the relationship existing between the localization properties of the diluted and non-diluted direct electrical transmission lines with the overlap amplitude Cijω = 2 | Iiω Ijω | , where Ijω is the amplitude of the electric current function at jth cell of the transmission line for the state with frequency ω. We distribute two values of inductances LA and LB, according to the generalized aperiodic Thue-Morse m-tupling sequence. We find that the behavior of Ci,jω is directly related to the localization properties of the aperiodic sequences measured by the ξ normalized participation number, the Rq Rényi entropies and the μq moments. In addition, we generalize the scaling relationship for the overlap amplitude Ci,jω, i.e., <(Ci,jω) 2 q > =(2/N) 2 q.

  13. Effects of oxygen cover gas and NaOH dilution on gas generation in tank 241-SY-101 waste

    SciTech Connect

    Person, J.C.

    1996-05-30

    Laboratory studies are reported of gas generation in heated waste from tank 241-SY-101. The rates of gas generation and the compositions of product gas were measured. Three types of tests are compared. The tests use: undiluted waste, waste diluted by a 54% addition of 2.5 M NaOH, and undiluted waste with a reactive cover gas of 30% Oxygen in He. The gas generation rate is reduced by dilution, increased by higher temperatures (which determines activation energies), and increased by reactions of Oxygen (these primarily produce H{sub 2}). Gases are generated as reduction products oxidation of organic carbon species by nitrite and oxygen.

  14. Dilute Surfactant Methods for Carbonate Formations

    SciTech Connect

    Kishore K. Mohanty

    2006-02-01

    There are many fractured carbonate reservoirs in US (and the world) with light oil. Waterflooding is effective in fractured reservoirs, if the formation is water-wet. Many fractured carbonate reservoirs, however, are mixed-wet and recoveries with conventional methods are low (less than 10%). The process of using dilute anionic surfactants in alkaline solutions has been investigated in this work for oil recovery from fractured oil-wet carbonate reservoirs both experimentally and numerically. This process is a surfactant-aided gravity drainage where surfactant diffuses into the matrix, lowers IFT and contact angle, which decrease capillary pressure and increase oil relative permeability enabling gravity to drain the oil up. Anionic surfactants have been identified which at dilute concentration of 0.05 wt% and optimal salinity can lower the interfacial tension and change the wettability of the calcite surface to intermediate/water-wet condition as well or better than the cationic surfactant DTAB with a West Texas crude oil. The force of adhesion in AFM of oil-wet regions changes after anionic surfactant treatment to values similar to those of water-wet regions. The AFM topography images showed that the oil-wetting material was removed from the surface by the anionic surfactant treatment. Adsorption studies indicate that the extent of adsorption for anionic surfactants on calcite minerals decreases with increase in pH and with decrease in salinity. Surfactant adsorption can be minimized in the presence of Na{sub 2}CO{sub 3}. Laboratory-scale surfactant brine imbibition experiments give high oil recovery (20-42% OOIP in 50 days; up to 60% in 200 days) for initially oil-wet cores through wettability alteration and IFT reduction. Small (<10%) initial gas saturation does not affect significantly the rate of oil recovery in the imbibition process, but larger gas saturation decreases the oil recovery rate. As the core permeability decreases, the rate of oil recovery reduces

  15. Activities of chromium in molten copper at dilute concentrations by solid-state electrochemical cell

    NASA Astrophysics Data System (ADS)

    Inouye, T. K.; Fujiwara, H.; Iwase, M.

    1991-08-01

    In order to obtain the activities of chromium in molten copper at dilute concentrations (<0.008 chromium mole fractions), liquid copper was brought to equilibrium with molten CaCl2 + Cr2O3 slag saturated with Cr2O3 (s), at temperatures between 1423 and 1573 K, and the equilibrium oxygen partial pressures were measured by means of solid-oxide galvanic cells of the type Mo/Mo + MoO2/ZrO2(MgO)/(Cu + Cr))alloy + Cr2O3 + (CaCl2 + Cr2O3)slag/Mo. The free energy changes for the dissolution of solid chromium in molten copper at infinite dilution referred to 1 wt pct were determined as Cr (s) = Cr(1 wt pct, in Cu) and Δ G° = + 97,000 + 73.3 (T/K) ± 2,000 J mol-1.

  16. Transport and sedimentation in unconfined experimental dilute pyroclastic density currents

    NASA Astrophysics Data System (ADS)

    Ramirez, G.; Andrews, B. J.; Dennen, R. L.

    2013-12-01

    We present results from experiments conducted in a new facility that permits the study of large, unconfined particle laden density currents that are dynamically similar to natural dilute pyroclastic density currents (PDCs). Experiments were run in a sealed, air-filled tank measuring 8.5 m long by 6.1 m wide by 2.6 m tall. Currents were generated by feeding mixture of heated particles (5 μm aluminum oxide, 25 μm talc, 27 μm walnut shell, 76 μm glass beads) down a chute at controlled rates to produce dilute, turbulent gravity currents. Comparison of experimental currents with natural PDCs shows good agreement between Froude, densimetric and thermal Richardson, and particle Stokes and settling numbers; experimental currents have lower Reynolds numbers than natural PDCs, but are fully turbulent. Currents were illuminated with 3 orthogonal laser sheets (650, 532, and 450 nm wavelengths) and recorded with an array of HD video cameras and a high speed camera (up to 3000 fps). Deposits were mapped using a grid of sedimentation traps. We observe distinct differences between ambient temperature and warm currents: * warm currents have shorter run out distances, narrow map view distributions of currents and deposits, thicken with distance from the source, and lift off to form coignimbrite plumes; * ambient temperature currents typically travel farther, spread out radially, do not thicken greatly with transport distance, and do not form coignimbrite plumes. Long duration currents (600 s compared to 30-100 s) oscillate laterally with time (e.g. transport to the right, then the left, and back); this oscillation happens prior to any interaction with the tank walls. Isopach maps of the deposits show predictable trends in sedimentation versus distance in response to eruption parameters (eruption rate, duration, temperature, and initial current mass), but all sedimentation curves can be fit with 2nd order polynomials (R2>.9). Proximal sedimentation is similar in comparable warm

  17. Three-dimensional structure of dilute pyroclastic density currents

    NASA Astrophysics Data System (ADS)

    Andrews, B. J.

    2013-12-01

    Unconfined experimental density currents dynamically similar to pyroclastic density currents (PDCs) suggest that cross-stream motions of the currents and air entrainment through currents' lateral margins strongly affects PDC behavior. Experiments are conducted within an air-filled tank 8.5 m long by 6.1 m wide by 2.6 m tall. Currents are generated by feeding heated powders down a chute into the tank at controlled rates to form dilute, particle-laden, turbulent gravity currents that are fed for 30 to 600 seconds. Powders include 5 μm aluminum oxide, 25 μm talc, 27 μm walnut, 76 μm glass beads and mixtures thereof. Experiments are scaled such that Froude, densimetric and thermal Richardson, particle Stokes and Settling numbers, and thermal to kinetic energy densities are all in agreement with dilute PDCs; experiments have lower Reynolds numbers that natural currents, but the experiments are fully turbulent, thus the large scale structures should be similar. The experiments are illuminated with 3 orthogonal laser sheets (650, 532, and 450 nm wavelengths) and recorded with an array of HD video cameras and a high speed camera (up to 3000 fps); this system provides synchronous observation of a vertical streamwise and cross-stream planes, and a horizontal plane. Ambient temperature currents tend to spread out radially from the source and have long run out distances, whereas warmer currents tend to focus along narrow sectors and have shorter run outs. In addition, when warm currents lift off to form buoyant plumes, lateral spreading ceases. The behavior of short duration currents are dominated by the current head; as eruption duration increases, current transport direction tends to oscillate back and forth (this is particularly true for ambient temperature currents). Turbulent structures in the horizontal plane show air entrainment and advection downstream. Eddies illuminated by the vertical cross-stream laser sheet often show vigorous mixing along the current margins

  18. DILUTE SURFACTANT METHODS FOR CARBONATE FORMATIONS

    SciTech Connect

    Kishore K. Mohanty

    2004-01-01

    There are many carbonate reservoirs in US (and the world) with light oil and fracture pressure below its minimum miscibility pressure (or reservoir may be naturally fractured). Many carbonate reservoirs are naturally fractured. Waterflooding is effective in fractured reservoirs, if the formation is water-wet. Many fractured carbonate reservoirs, however, are mixed-wet and recoveries with conventional methods are low (less than 10%). Thermal and miscible tertiary recovery techniques are not effective in these reservoirs. Surfactant flooding (or huff-n-puff) is the only hope, yet it was developed for sandstone reservoirs in the past. The goal of this research is to evaluate dilute (hence relatively inexpensive) surfactant methods for carbonate formations and identify conditions under which they can be effective. Anionic surfactants (SS-6656, Alfoterra 35, 38, 63,65,68) have been identified which can change the wettability of the calcite surface to intermediate/water-wet condition as well or better than the cationic surfactant DTAB with a West Texas crude oil in the presence of Na{sub 2}CO{sub 3}. All the carbonate surfaces (Lithographic Limestone, Marble, Dolomite and Calcite) show similar behavior with respect to wettability alteration with surfactant 4-22. Anionic surfactants (5-166, Alfoterra-33 and Alfoterra-38 and Alfoterra-68), which lower the interfacial tension with a West Texas crude oil to very low values (<10{sup -2} nM/m), have also been identified. Plans for the next quarter include conducting wettability, mobilization, and imbibition studies.

  19. DILUTE SURFACTANT METHODS FOR CARBONATE FORMATIONS

    SciTech Connect

    Kishore K. Mohanty

    2003-07-01

    There are many carbonate reservoirs in US (and the world) with light oil and fracture pressure below its minimum miscibility pressure (or reservoir may be naturally fractured). Many carbonate reservoirs are naturally fractured. Waterflooding is effective in fractured reservoirs, if the formation is water-wet. Many fractured carbonate reservoirs, however, are mixed-wet and recoveries with conventional methods are low (less than 10%). Thermal and miscible tertiary recovery techniques are not effective in these reservoirs. Surfactant flooding (or huff-n-puff) is the only hope, yet it was developed for sandstone reservoirs in the past. The goal of this research is to evaluate dilute (hence relatively inexpensive) surfactant methods for carbonate formations and identify conditions under which they can be effective. We have conducted adsorption, phase behavior and wettability studies. Addition of Na{sub 2}CO{sub 3} decreases IFT with a minimum at about 0.2 M. Addition of surfactant decreases IFT further. In the absence of surfactant the minerals are oil wet after aging with crude oil. Addition of surfactant solution decreases the contact angle to intermediate wettability. Addition of Na{sub 2}CO{sub 3} decreases anionic surfactant adsorption on calcite surface. Plans for the next quarter include conducting adsorption, phase behavior and wettability studies.

  20. DILUTE SURFACTANT METHODS FOR CARBONATE FORMATIONS

    SciTech Connect

    Kishore K. Mohanty

    2005-07-01

    There are many carbonate reservoirs in US (and the world) with light oil and fracture pressure below its minimum miscibility pressure (or reservoir may be naturally fractured). Many carbonate reservoirs are naturally fractured. Waterflooding is effective in fractured reservoirs, if the formation is water-wet. Many fractured carbonate reservoirs, however, are mixed-wet and recoveries with conventional methods are low (less than 10%). Thermal and miscible tertiary recovery techniques are not effective in these reservoirs. Surfactant flooding (or huff-n-puff) is the only hope, yet it was developed for sandstone reservoirs in the past. The goal of this research is to evaluate dilute (hence relatively inexpensive) surfactant methods for carbonate formations and identify conditions under which they can be effective. Laboratory imbibition tests show that imbibition rate is not very sensitive to the surfactant concentration (in the range of 0.05-0.2 wt%) and small amounts of trapped gas saturation. It is however very sensitive to oil permeability and water-oil-ratio. Less than 0.5 M Na2CO3 is needed for in situ soap generation and low adsorption; NaCl can be added to reach the necessary total salinity. The simulation result matches the laboratory imbibition experimental data. Small fracture spacing and high permeability would be needed for high rate of recovery.

  1. DILUTE SURFACTANT METHODS FOR CARBONATE FORMATIONS

    SciTech Connect

    Kishore K. Mohanty

    2003-10-01

    There are many carbonate reservoirs in US (and the world) with light oil and fracture pressure below its minimum miscibility pressure (or reservoir may be naturally fractured). Many carbonate reservoirs are naturally fractured. Waterflooding is effective in fractured reservoirs, if the formation is water-wet. Many fractured carbonate reservoirs, however, are mixed-wet and recoveries with conventional methods are low (less than 10%). Thermal and miscible tertiary recovery techniques are not effective in these reservoirs. Surfactant flooding (or huff-n-puff) is the only hope, yet it was developed for sandstone reservoirs in the past. The goal of this research is to evaluate dilute (hence relatively inexpensive) surfactant methods for carbonate formations and identify conditions under which they can be effective. We have conducted adsorption, phase behavior, interfacial tension (IFT) and wettability studies. Alfoterra-38 (0.05 wt%), Alfoterra-35 (0.05 wt%), SS-6656 (0.05 wt%), and DTAB (1 wt%) altered the wettability of the initially oil-wet calcite plate to an intermediate/water-wet state. Low IFT ({approx}10{sup -3} dynes/cm) is obtained with surfactants 5-166, Alfoterra-33 and Alfoterra-38. Plans for the next quarter include conducting wettability and mobilization studies.

  2. Dilute Surfactant Methods for Carbonate Formations

    SciTech Connect

    Kishore K. Mohanty

    2004-03-31

    There are many carbonate reservoirs in US (and the world) with light oil and fracture pressure below its minimum miscibility pressure (or reservoir may be naturally fractured). Many carbonate reservoirs are naturally fractured. Waterflooding is effective in fractured reservoirs, if the formation is water-wet. Many fractured carbonate reservoirs, however, are mixed-wet and recoveries with conventional methods are low (less than 10%). Thermal and miscible tertiary recovery techniques are not effective in these reservoirs. Surfactant flooding (or huff-n-puff) is the only hope, yet it was developed for sandstone reservoirs in the past. The goal of this research is to evaluate dilute (hence relatively inexpensive) surfactant methods for carbonate formations and identify conditions under which they can be effective. Anionic surfactants (Alfoterra 35, 38) recover more than 40% of the oil in about 50 days by imbibition driven by wettability alteration in the core-scale. Anionic surfactant, Alfoterra-68, recovers about 28% of the oil by lower tension aided gravity-driven imbibition in the core-scale. Residual oil saturation showed little capillary number dependence between 10{sup -5} and 10{sup -2}. Wettability alteration increases as the number of ethoxy groups increases in ethoxy sulfate surfactants. Plans for the next quarter include conducting mobilization, and imbibition studies.

  3. DILUTE SURFACTANT METHODS FOR CARBONATE FORMATIONS

    SciTech Connect

    Kishore K. Mohanty

    2004-10-01

    There are many carbonate reservoirs in US (and the world) with light oil and fracture pressure below its minimum miscibility pressure (or reservoir may be naturally fractured). Many carbonate reservoirs are naturally fractured. Waterflooding is effective in fractured reservoirs, if the formation is water-wet. Many fractured carbonate reservoirs, however, are mixed-wet and recoveries with conventional methods are low (less than 10%). Thermal and miscible tertiary recovery techniques are not effective in these reservoirs. Surfactant flooding (or huff-n-puff) is the only hope, yet it was developed for sandstone reservoirs in the past. The goal of this research is to evaluate dilute (hence relatively inexpensive) surfactant methods for carbonate formations and identify conditions under which they can be effective. Simulation studies indicate that both wettability alteration and gravity-driven flow play significant role in oil recovery from fractured carbonates. Anionic surfactants (Alfoterra 35, 38) recover about 55% of the oil in about 150 days by imbibition driven by wettability alteration and low tension in the core-scale. Anionic surfactant, Alfoterra-68, recovers about 40% of the oil by lower tension aided gravity-driven imbibition in the core-scale. Cationic surfactant, DTAB recovers about 35% of the oil. Plans for the next quarter include conducting simulation and imbibition studies.

  4. DILUTE SURFACTANT METHODS FOR CARBONATE FORMATIONS

    SciTech Connect

    Kishore K. Mohanty

    2005-01-01

    There are many carbonate reservoirs in US (and the world) with light oil and fracture pressure below its minimum miscibility pressure (or reservoir may be naturally fractured). Many carbonate reservoirs are naturally fractured. Waterflooding is effective in fractured reservoirs, if the formation is water-wet. Many fractured carbonate reservoirs, however, are mixed-wet and recoveries with conventional methods are low (less than 10%). Thermal and miscible tertiary recovery techniques are not effective in these reservoirs. Surfactant flooding (or huff-n-puff) is the only hope, yet it was developed for sandstone reservoirs in the past. The goal of this research is to evaluate dilute (hence relatively inexpensive) surfactant methods for carbonate formations and identify conditions under which they can be effective. Imbibition in an originally oil-wet 2D capillary is the fastest in the case of Alf-38 and slowest in the case of DTAB (among the surfactants studied). Force of adhesion studies and contact angle measurements show that greater wettability alteration is possible with these anionic surfactants than the cationic surfactant studied. The water imbibition rate does not increase monotonically with an increase in the surfactant concentration. A numerical model has been developed that fits the rate of imbibition. Plans for the next quarter include conducting simulation and imbibition studies.

  5. DILUTE SURFACTANT METHODS FOR CARBONATE FORMATIONS

    SciTech Connect

    Kishore K. Mohanty

    2003-01-01

    There are many carbonate reservoirs in US (and the world) with light oil and fracture pressure below its minimum miscibility pressure (or reservoir may be naturally fractured). Many carbonate reservoirs are naturally fractured. Waterflooding is effective in fractured reservoirs, if the formation is water-wet. Many fractured carbonate reservoirs, however, are mixed-wet and recoveries with conventional methods are low (less than 10%). Thermal and miscible tertiary recovery techniques are not effective in these reservoirs. Surfactant flooding (or huff-n-puff) is the only hope, yet it was developed for sandstone reservoirs in the past. The goal of this research is to evaluate dilute (hence relatively inexpensive) surfactant methods for carbonate formations and identify conditions under which they can be effective. We have acquired field oil and core samples and field brine compositions from Marathon. We have conducted preliminary adsorption and wettability studies. Addition of Na{sub 2}CO{sub 3} decreases anionic surfactant adsorption on calcite surface. Receding contact angles increase with surfactant adsorption. Plans for the next quarter include conducting adsorption, phase behavior and wettability studies.

  6. DILUTE SURFACTANT METHODS FOR CARBONATE FORMATIONS

    SciTech Connect

    Kishore K. Mohanty

    2003-07-01

    There are many carbonate reservoirs in US (and the world) with light oil and fracture pressure below its minimum miscibility pressure (or reservoir may be naturally fractured). Many carbonate reservoirs are naturally fractured. Waterflooding is effective in fractured reservoirs, if the formation is water-wet. Many fractured carbonate reservoirs, however, are mixed-wet and recoveries with conventional methods are low (less than 10%). Thermal and miscible tertiary recovery techniques are not effective in these reservoirs. Surfactant flooding (or huff-n-puff) is the only hope, yet it was developed for sandstone reservoirs in the past. The goal of this research is to evaluate dilute (hence relatively inexpensive) surfactant methods for carbonate formations and identify conditions under which they can be effective. We have conducted adsorption, phase behavior, interfacial tension (IFT) and wettability studies. Addition of Na{sub 2}CO{sub 3} decreases IFT with a minimum at about 0.2 M. Addition of surfactant decreases IFT further. In the absence of surfactant the minerals are oil-wet after aging with crude oil. Addition of surfactant solution decreases the contact angle to intermediate-wet for many surfactants and water-wet for one surfactant. Addition of Na{sub 2}CO{sub 3} decreases anionic surfactant adsorption on calcite surface. Plans for the next quarter include conducting core adsorption, phase behavior, wettability and mobilization studies.

  7. Chain Dynamics in a Dilute Magnetorheological Fluid

    NASA Technical Reports Server (NTRS)

    Liu, Jing; Hagenbuchle, Martin

    1996-01-01

    The structure, formation, and dynamics of dilute, mono-dispersive ferrofluid emulsions in an external magnetic field have been investigated using dynamic light scattering techniques. In the absence of the magnetic field, the emulsion particles are randomly distributed and behave like hard spheres in Brownian motion. An applied magnetic field induces a magnetic dipole moment in each particle. Dipolar interactions between particles align them into chains where correlation functions show two decay processes. The short-time decay shows the motion of straight chains as a whole where the apparent chain length increases with the applied magnetic field and the particle volume fraction. Good scaling results are obtained showing that the apparent chain length grows with time following a power law with exponent of 0.6 and depends on the applied field, particle volume fraction, and diffusion constant of the particles. The long-time decay in the correlation function shows oscillation when the chains reach a certain length with time and stiffness with threshold field This result shows that chains not only fluctuate, but move in a periodic motion with a frequency of 364 Hz at lambda = 15. It may suggest the existence of phonons. This work is the first step in the understanding of the structure formation, especially chain coarsening mechanism, of magnetorheological (MR) fluids at higher volume fractions.

  8. Dilute Surfactant Methods for Carbonate Formations

    SciTech Connect

    Kishore K. Mohanty

    2005-10-01

    There are many carbonate reservoirs in US (and the world) with light oil and fracture pressure below its minimum miscibility pressure (or reservoir may be naturally fractured). Many carbonate reservoirs are naturally fractured. Waterflooding is effective in fractured reservoirs, if the formation is water-wet. Many fractured carbonate reservoirs, however, are mixed-wet and recoveries with conventional methods are low (less than 10%). Thermal and miscible tertiary recovery techniques are not effective in these reservoirs. Surfactant flooding (or huff-n-puff) is the best hope, yet it was developed for sandstone reservoirs in the past. The goal of this research is to evaluate dilute (hence relatively inexpensive) surfactant methods for carbonate formations and identify conditions under which they can be effective. Laboratory-scale surfactant brine imbibition experiments give high oil recovery (35-62% OOIP) for initially oil-wet cores through wettability alteration and IFT reduction. Core-scale simulation results match those of the experiments. Initial capillarity-driven imbibition gives way to a final gravity-driven process. As the matrix block height increases, surfactant alters wettability to a lesser degree, or permeability decreases, oil production rate decreases. The scale-up to field scale will be further studied in the next quarter.

  9. DILUTE SURFACTANT METHODS FOR CARBONATE FORMATIONS

    SciTech Connect

    Kishore K. Mohanty

    2005-04-01

    There are many carbonate reservoirs in US (and the world) with light oil and fracture pressure below its minimum miscibility pressure (or reservoir may be naturally fractured). Many carbonate reservoirs are naturally fractured. Waterflooding is effective in fractured reservoirs, if the formation is water-wet. Many fractured carbonate reservoirs, however, are mixed-wet and recoveries with conventional methods are low (less than 10%). Thermal and miscible tertiary recovery techniques are not effective in these reservoirs. Surfactant flooding (or huff-n-puff) is the only hope, yet it was developed for sandstone reservoirs in the past. The goal of this research is to evaluate dilute (hence relatively inexpensive) surfactant methods for carbonate formations and identify conditions under which they can be effective. Laboratory imbibition tests show about 61% oil recovery in the case of Alf-38 and 37% in the case of DTAB. A numerical model has been developed that fits the rate of imbibition of the laboratory experiment. Field-scale fracture block simulation shows that as the fracture spacing increases, so does the time of recovery. Plans for the next quarter include simulation studies.

  10. Understanding Mental Models of Dilution in Thai Students

    ERIC Educational Resources Information Center

    Jansoon, Ninna; Coll, Richard K.; Somsook, Ekasith

    2009-01-01

    The purpose of this study was to investigate Thai students' understanding of dilution and related concepts. The literature suggests that a complete understanding of chemistry concepts such as dilution entails understanding of and the ability to integrate mental models across three levels of representation: the macroscopic, sub-microscopic and…

  11. 40 CFR 1065.667 - Dilution air background emission correction.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Calculations and Data Requirements § 1065.667 Dilution air background emission correction. (a) To determine the mass of background emissions to subtract... 40 Protection of Environment 34 2012-07-01 2012-07-01 false Dilution air background...

  12. 40 CFR 1065.667 - Dilution air background emission correction.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Calculations and Data Requirements § 1065.667 Dilution air background emission correction. (a) To determine the mass of background emissions to subtract... 40 Protection of Environment 34 2013-07-01 2013-07-01 false Dilution air background...

  13. 40 CFR 1065.667 - Dilution air background emission correction.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Calculations and Data Requirements § 1065.667 Dilution air background emission correction. (a) To determine the mass of background emissions to subtract... 40 Protection of Environment 33 2011-07-01 2011-07-01 false Dilution air background...

  14. 40 CFR 1065.667 - Dilution air background emission correction.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Calculations and Data Requirements § 1065.667 Dilution air background emission correction. (a) To determine the mass of background emissions to subtract... 40 Protection of Environment 33 2014-07-01 2014-07-01 false Dilution air background...

  15. 40 CFR 1065.667 - Dilution air background emission correction.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Calculations and Data Requirements § 1065.667 Dilution air background emission correction. (a) To determine the mass of background emissions to subtract... 40 Protection of Environment 32 2010-07-01 2010-07-01 false Dilution air background...

  16. Measuring dilution of microbicide gels with optical imaging.

    PubMed

    Drake, Tyler K; Shah, Tejen; Peters, Jennifer J; Wax, Adam; Katz, David F

    2013-01-01

    We present a novel approach for measuring topical microbicide gel dilution using optical imaging. The approach compares gel thickness measurements from fluorimetry and multiplexed low coherence interferometry in order to calculate dilution of a gel. As a microbicide gel becomes diluted at fixed thickness, its mLCI thickness measurement remains constant, while the fluorimetry signal decreases in intensity. The difference between the two measurements is related to the extent of gel dilution. These two optical modalities are implemented in a single endoscopic instrument that enables simultaneous data collection. A preliminary validation study was performed with in vitro placebo gel measurements taken in a controlled test socket. It was found that change in slope of the regression line between fluorimetry and mLCI based measurements indicates dilution. A dilution calibration curve was then generated by repeating the test socket measurements with serial dilutions of placebo gel with vaginal fluid simulant. This methodology can provide valuable dilution information on candidate microbicide products, which could substantially enhance our understanding of their in vivo functioning.

  17. Effects of dilution on vehicle emissions of primary particles

    NASA Astrophysics Data System (ADS)

    Hayden, K. L.; Li, S.; Liggio, G.; McCurdy, M.; Chan, T.; Rostkowski, J.

    2009-12-01

    Dilution of primary aerosols from vehicles into the ambient atmosphere can change their physical and chemical characteristics. In order to study these processes, experiments were conducted in an engine testing facility at Environment Canada in Ottawa, Ontario. Exhaust from a light duty diesel engine was vented into a constant volume sampling (CVS) system where it underwent primary dilution at an ambient temperature of 25oC, leading to a primary dilution ratio of 10-15. From the CVS, the exhaust was further diluted using a combination of a Dekati ejection diluter and mixing with zero air in a flow tube, achieving secondary dilution ratios of up to 3000. Particle and gas measurements were made through multi-ports in the CVS and the flow tube using an SMPS, FMPS, AMS, and SP2, and instruments to measure CO, CO2, NOx, and total hydrocarbons (THC). Preliminary results indicate that regardless of dilution ratios, primary particles contain significant amounts of organic material that appear to reside on small black carbon cores. With increasing dilution ratios, the primary particle sizes become progressively smaller, suggesting volatilization of the adsorbed organic material. Results from various engine operating modes (simulating different driving conditions) will be presented.

  18. 21 CFR 864.5240 - Automated blood cell diluting apparatus.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Automated blood cell diluting apparatus. 864.5240 Section 864.5240 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES... § 864.5240 Automated blood cell diluting apparatus. (a) Identification. An automated blood cell...

  19. 21 CFR 864.5240 - Automated blood cell diluting apparatus.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Automated blood cell diluting apparatus. 864.5240 Section 864.5240 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES... § 864.5240 Automated blood cell diluting apparatus. (a) Identification. An automated blood cell...

  20. 21 CFR 864.5240 - Automated blood cell diluting apparatus.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Automated blood cell diluting apparatus. 864.5240 Section 864.5240 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES... § 864.5240 Automated blood cell diluting apparatus. (a) Identification. An automated blood cell...

  1. 21 CFR 864.5240 - Automated blood cell diluting apparatus.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Automated blood cell diluting apparatus. 864.5240 Section 864.5240 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES... § 864.5240 Automated blood cell diluting apparatus. (a) Identification. An automated blood cell...

  2. 21 CFR 864.5240 - Automated blood cell diluting apparatus.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Automated blood cell diluting apparatus. 864.5240 Section 864.5240 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES... § 864.5240 Automated blood cell diluting apparatus. (a) Identification. An automated blood cell...

  3. 33 CFR 154.824 - Inerting, enriching, and diluting systems.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... Systems § 154.824 Inerting, enriching, and diluting systems. (a) A vapor control system which uses... vapor control system which uses an inerting, enriching, or diluting system must be equipped with a gas... the injection point; (c) A vapor control system that uses an inerting or enriching system may not...

  4. Efficacy comparison between simple mixed-dilution and simple mid-dilution on-line hemodiafiltration techniques: a crossover study.

    PubMed

    Susantitaphong, Paweena; Tiranathanagul, Khajohn; Katavetin, Pisut; Hanwiwatwong, Orawadee; Wittayalertpanya, Supeecha; Praditpornsilpa, Kearkiat; Tungsanga, Kriang; Eiam-Ong, Somchai

    2012-12-01

    Mid-dilution and mixed-dilution on-line hemodiafiltration (OL-HDF) techniques are innovated to overcome the limitations of two standard techniques including predilution and postdilution. Unfortunately, the head-to-head comparisons between these two novel techniques in the same study are still limited. Moreover, the original mid-dilution and mixed-dilution OL-HDF need special dialyzers and special machines. In the present study, simple mid-dilution and simple mixed-dilution OL-HDF were settled with the aim for clinical use in general hemodialysis (HD) centers. The efficacies of uremic toxins removal between both modalities were measured and compared. This prospective randomized crossover study was conducted on 12 stable HD patients undergoing simple mixed-dilution and simple mid-dilution OL-HDF techniques. HD prescriptions were similar in both techniques. The dialysis efficacies were determined by calculating small- (urea, creatinine, and phosphate) and middle-molecule (beta-2 microglobulin [β2M]) removal. Moreover, potential complications such as high transmembrane pressure (TMP) and protein loss were also observed. Simple mixed-dilution OL-HDF provided significantly greater clearances of urea, creatinine, and β2M when compared with the simple mid-dilution OL-HDF techniques. Phosphate clearances in both techniques were comparable. In addition, TMP and dialysate albumin loss were not different. There were no intradialytic complications in both techniques. Simple mixed-dilution OL-HDF could provide greater efficacy for small- and middle-molecule clearances and acceptable potential risks, while phosphate removal is comparable.

  5. Identification of cardiovascular dilution systems by contrast ultrasound.

    PubMed

    Mischi, Massimo; Jansen, Annemieke H M; Korsten, Hendrikus H M

    2007-03-01

    Indicator dilution techniques permit accurate measurements of important cardiovascular parameters, such as pulmonary blood volume (PBV) and ejection fraction (EF). However, their use is limited by the need for central catheterization. Contrast ultrasonography allows overcoming this problem. PBV and EF can be measured by a dilution system identification algorithm after detection of multiple dilution curves by an ultrasound scanner. In this paper, we present a system identification method that exploits the a priori knowledge on the dilution system and finds the optimum parameters for the parametric model representing the dilution system impulse response. No subsequent model interpolation is needed. Volume measurements show accurate in-vitro results and clinical feasibility, while 50 EF measurements in patients show a 0.88 correlation coefficient with echocardiographic biplane estimates. In conclusion, adding a priori knowledge to the system identification algorithm leads to increased accuracy and robustness of the method for PBV and EF measurements.

  6. Diluted magnetic semiconductor superlattices and heterostructures

    NASA Astrophysics Data System (ADS)

    Datta, S.; Furdyna, J. K.; Gunshor, R. L.

    Diluted magnetic semiconductors (DMS) are mixed semiconducting crystals whose lattice is made up in part of substitutional magnetic ions. Cd 1-xMn xTe and Hg 1-xMn xTe are examples of such materials. Their structural and band parameters can be "tuned" by composition over a wide range. They can thus be exploited in situations completely similar to those involving Ga 1-xAl xAs. Using molecular beam epitaxy, we have grown Cd 1-xMn xTe superlattices with alternating Mn content, having up to 150 layers, with layer thickness ranging from 50 to 100 Å. The superlattice structure is clearly revealed by transmission electron microscopy and by zone-folding of the phonon spectrum observed in Raman scattering. Photoluminescence observed on Cd 1-xMn xTe superlattices is several orders of magnitude greater than that from a Cd 1-xMn xTe film with uniform Mn content, or from bulk Cd 1-xMn xTe specimens. The presence of localized magnetic moments in DMS results in a strong exchange interaction between these moments and band electrons. This in turn leads to gigantic Zeeman splittings of impurity states, exciton levels, Landau levels, and the bands themselves. Zeeman splittings as large as 20 meV (which in non-magnetic semiconductors would require unrealistic megagauss fields) are easily achieved in DMS in fields of several kilogauss. Since the magnitude of this exchange-induced splitting in DMS can be comparable to the binding energies and to the minigaps encountered in multiple quantum wells, DMS superlattices hold promise of a host of novel effects of both fundamental and applied interest.

  7. Biodiversity inhibits parasites: Broad evidence for the dilution effect.

    PubMed

    Civitello, David J; Cohen, Jeremy; Fatima, Hiba; Halstead, Neal T; Liriano, Josue; McMahon, Taegan A; Ortega, C Nicole; Sauer, Erin Louise; Sehgal, Tanya; Young, Suzanne; Rohr, Jason R

    2015-07-14

    Infectious diseases of humans, wildlife, and domesticated species are increasing worldwide, driving the need to understand the mechanisms that shape outbreaks. Simultaneously, human activities are drastically reducing biodiversity. These concurrent patterns have prompted repeated suggestions that biodiversity and disease are linked. For example, the dilution effect hypothesis posits that these patterns are causally related; diverse host communities inhibit the spread of parasites via several mechanisms, such as by regulating populations of susceptible hosts or interfering with parasite transmission. However, the generality of the dilution effect hypothesis remains controversial, especially for zoonotic diseases of humans. Here we provide broad evidence that host diversity inhibits parasite abundance using a meta-analysis of 202 effect sizes on 61 parasite species. The magnitude of these effects was independent of host density, study design, and type and specialization of parasites, indicating that dilution was robust across all ecological contexts examined. However, the magnitude of dilution was more closely related to the frequency, rather than density, of focal host species. Importantly, observational studies overwhelmingly documented dilution effects, and there was also significant evidence for dilution effects of zoonotic parasites of humans. Thus, dilution effects occur commonly in nature, and they may modulate human disease risk. A second analysis identified similar effects of diversity in plant-herbivore systems. Thus, although there can be exceptions, our results indicate that biodiversity generally decreases parasitism and herbivory. Consequently, anthropogenic declines in biodiversity could increase human and wildlife diseases and decrease crop and forest production.

  8. Dynamics of atmospheres with a non-dilute condensible component

    NASA Astrophysics Data System (ADS)

    Pierrehumbert, Raymond T.; Ding, Feng

    2016-06-01

    The diversity of characteristics for the host of recently discovered exoplanets opens up a great deal of fertile new territory for geophysical fluid dynamics, particularly when the fluid flow is coupled to novel thermodynamics, radiative transfer or chemistry. In this paper, we survey one of these new areas-the climate dynamics of atmospheres with a non-dilute condensible component, defined as the situation in which a condensible component of the atmosphere makes up a substantial fraction of the atmospheric mass within some layer. Non-dilute dynamics can occur for a wide range of condensibles, generically applying near both the inner and the outer edges of the conventional habitable zone and in connection with runaway greenhouse phenomena. It also applies in a wide variety of other planetary circumstances. We first present a number of analytical results developing some key features of non-dilute atmospheres, and then show how some of these features are manifest in simulations with a general circulation model adapted to handle non-dilute atmospheres. We find that non-dilute atmospheres have weak horizontal temperature gradients even for rapidly rotating planets, and that their circulations are largely barotropic. The relative humidity of the condensible component tends towards 100% as the atmosphere becomes more non-dilute, which has important implications for runaway greenhouse thresholds. Non-dilute atmospheres exhibit a number of interesting organized convection features, for which there is not yet any adequate theoretical understanding.

  9. Coalescence of silver clusters by immersion in diluted HF solution

    SciTech Connect

    Milazzo, R. G.; Mio, A. M.; D’Arrigo, G.; Spinella, C.; Grimaldi, M. G.; Rimini, E.

    2015-07-14

    The galvanic displacement deposition of silver on H-terminated Si (100) in the time scale of seconds is instantaneous and characterized by a cluster density of 10{sup 11}-10{sup 12} cm{sup −2}. The amount of deposited Ag follows a t{sup 1/2} dependence in agreement with a Cottrell diffusion limited mechanism. At the same time, during the deposition, the cluster density reduces by a factor 5. This behavior is in contrast with the assumption of immobile clusters. We show in the present work that coalescence and aggregation occur also in the samples immersed in the diluted hydrofluoric acid (HF) solution without the presence of Ag{sup +}. Clusters agglomerate according to a process of dynamic coalescence, typical of colloids, followed by atomic redistribution at the contact regions with the generation of multiple internal twins and stacking-faults. The normalized size distributions in terms of r/r{sub mean} follow also the prediction of the Smoluchowski ripening mechanism. No variation of the cluster density occurs for samples immersed in pure H{sub 2}O solution. The different behavior might be associated to the strong attraction of clusters to oxide-terminated Si surface in presence of water. The silver clusters are instead weakly bound to hydrophobic H-terminated Si in presence of HF. HF causes then the detachment of clusters and a random movement on the silicon surface with mobility of about 10{sup −13} cm{sup 2}/s. Attractive interaction (probably van der Waals) among particles promotes coarsening.

  10. Transcriptome Profiling of Wheat Seedlings following Treatment with Ultrahigh Diluted Arsenic Trioxide

    PubMed Central

    Betti, Lucietta; Trebbi, Grazia; Borghini, Giovanni; Nani, Daniele; Dinelli, Giovanni

    2014-01-01

    Plant systems are useful research tools to address basic questions in homeopathy as they make it possible to overcome some of the drawbacks encountered in clinical trials (placebo effect, ethical issues, duration of the experiment, and high costs). The objective of the present study was to test the hypothesis whether 7-day-old wheat seedlings, grown from seeds either poisoned with a sublethal dose of As2O3 or unpoisoned, showed different significant gene expression profiles after the application of ultrahigh diluted As2O3 (beyond Avogadro's limit) compared to water (control). The results provided evidence for a strong gene modulating effect of ultrahigh diluted As2O3 in seedlings grown from poisoned seeds: a massive reduction of gene expression levels to values comparable to those of the control group was observed for several functional classes of genes. A plausible hypothesis is that ultrahigh diluted As2O3 treatment induced a reequilibration of those genes that were upregulated during the oxidative stress by bringing the expression levels closer to the basal levels normally occurring in the control plants. PMID:25525452

  11. Antiferromagnetic instability in Sr3Ru2O7: stabilized and revealed by dilute Mn impurities

    NASA Astrophysics Data System (ADS)

    Hossain, Muhammed; Bohnenbuck, B.; Chuang, Y.-D.; Cruz, E.; Wu, H.-H.; Tjeng, L. H.; Elfimov, I. S.; Hussain, Z.; Keimer, B.; Sawatzky, G. A.; Damascelli, A.

    2009-03-01

    X-ray Absorption Spectroscopy (XAS) and Resonant Elastic Soft X-ray Scattering (RESXS) studies have been performed on Mn-doped Sr3Ru2O7, both on the Ru and Mn L-edges, to investigate the origin of the metal insulator transition. Extensive simulations based on our experimental findings point toward an intrinsic antiferromagnetic instability in the parent Sr3Ru2O7 compound that is stabilized by the dilute Mn impurities. We show that the metal-insulator transition is a direct consequence of the antiferromagnetic order and we propose a phenomenological model that may be applicable also to metal-insulator transitions seen in other oxides. Moreover, a comparison of Ru and Mn L-edge data on 5% Mn doped system reveals that dilute Mn impurities are generating much more intense signal than Ru which is occupying 95% of the lattice sites. This suggests the embedding of dilute impurities as a powerful mean to probe weak and, possibly, spatially inhomogeneous order in solid-state systems. In collaboration with: Y. Yoshida (AIST), J. Geck, D.G. Hawthorn (UBC), M.W. Haverkort, Z. Hu, C. Sch"ußler-Langeheine (Cologne), R. Mathieu, Y. Tokura, S. Satow, H. Takagi (Tokyo), J.D. Denlinger (ALS).

  12. Effect of dilution on carboxymethylcellulase and xylanase assays

    SciTech Connect

    Cauchon, N.; LeDuy, A.

    1984-08-01

    It has been demonstrated that the dilution of samples prior to the carboxymethylcellulase and xylanase assays causes serious discrepancies in the numerical values obtained for the enzyme activities. Even when the sample is assayed with the identical procedure, one could obtain different numerical values of the enzyme activity U depending on how much this sample has been diluted before the enzyme assay. Two crude commercial cellulase samples of Aspergillus niger and Trichoderma viride as well as the culture filtrate of our newly isolated acidophilic fungus have been used for the demonstration. An empirical method for reporting the cellulolytic activity by taking into account this dilution effect is proposed.

  13. Two-stage dilute acid prehydrolysis of biomass

    DOEpatents

    Grohmann, Karel; Torget, Robert W.

    1992-01-01

    A two-stage dilute acid prehydrolysis process on xylan containing hemicellulose in biomass is effected by: treating feedstock of hemicellulosic material comprising xylan that is slow hydrolyzable and xylan that is fast hydrolyzable under predetermined low temperature conditions with a dilute acid for a residence time sufficient to hydrolyze the fast hydrolyzable xylan to xylose; removing said xylose from said fast hydrolyzable xylan and leaving a residue; and treating said residue having a slow hydrolyzable xylan with a dilute acid under predetermined high temperature conditions for a residence time required to hydrolyze said slow hydrolyzable xylan to xylose.

  14. Retroviral sequences located within an intron of the dilute gene alter dilute expression in a tissue-specific manner.

    PubMed Central

    Seperack, P K; Mercer, J A; Strobel, M C; Copeland, N G; Jenkins, N A

    1995-01-01

    The murine dilute coat color locus encodes an unconventional myosin heavy chain that is thought to be required for the elaboration or maintenance of dendrites or organelle transport in melanocytes and neurons. In previous studies we showed that the d mutation carried by many inbred strains of mice (now referred to as dilute viral, dv), is caused by the integration of an ecotropic murine leukemia virus (Emv-3) into the dilute gene and that phenotypic revertants of dv (termed d+) result from viral excision; a solo viral long terminal repeat (LTR) is all that remains in revertant DNA. In the studies described here we show that Emv-3 sequences are located within an intron of the dilute gene in a region of the C-terminal tail that is differentially spliced. We also show that these Emv-3 sequences result in the production of shortened and abnormally spliced dilute transcripts and that the level of this effect varies among tissues. This tissue-specific effect on dilute expression likely accounts for the absence of neurological abnormalities observed in dv mice. Surprisingly, we also found that the solo viral LTR present in revertant d+ DNA produces a tissue-specific effect on dilute expression, although this effect is less dramatic than with the full-length provirus and produces no obvious mutant phenotype. These findings have important implications for understanding the effects of viral sequences on mammalian gene expression. Images PMID:7774591

  15. Separation processes using expulsion from dilute supercritical solutions

    DOEpatents

    Cochran, Jr., Henry D.

    1993-01-01

    A process for separating isotopes as well as other mixtures by utilizing the behavior of dilute repulsive or weakly attractive elements of the mixtures as the critical point of the solvent is approached.

  16. Success, failure and ambiguity of the dilution effect among competitors.

    PubMed

    Strauss, Alexander T; Civitello, David J; Cáceres, Carla E; Hall, Spencer R

    2015-09-01

    It remains challenging to predict variation in the magnitude of disease outbreaks. The dilution effect seeks to explain this variation by linking multiple host species to disease transmission. It predicts that disease risk increases for a focal host when host species diversity declines. However, when an increase in species diversity does not reduce disease, we are often unable to diagnose why. Here, we increase mechanistic and predictive clarity of the dilution effect with a general trait-based model of disease transmission in multi-host communities. Then, we parameterise and empirically test our model with a multi-generational case study of planktonic disease. The model-experiment combination shows that hosts that vary in competitive ability (R*) and potential to spread disease (R0 ) can produce three qualitatively disparate outcomes of dilution on disease: the dilution effect can succeed, fail, or be ambiguous/irrelevant.

  17. Separation processes using expulsion from dilute supercritical solutions

    DOEpatents

    Cochran, H.D. Jr.

    1993-04-20

    A process is described for separating isotopes as well as other mixtures by utilizing the behavior of dilute repulsive or weakly attractive elements of the mixtures as the critical point of the solvent is approached.

  18. Anatomy of the symmetry energy of dilute nuclear matter

    SciTech Connect

    De, J. N.; Samaddar, S. K.; Agrawal, B. K.

    2010-10-15

    The symmetry energy coefficients of dilute clusters nuclear matter are evaluated in the S-matrix framework. Employing a few different definitions commonly used in the literature for uniform nuclear matter, it is seen that the different definitions lead to perceptibly different results for the symmetry coefficients for dilute nuclear matter. They are found to be higher compared to those obtained for uniform matter in the low density domain. The calculated results are in reasonable consonance with those extracted recently from experimental data.

  19. Radiolysis of paracetamol in dilute aqueous solution

    NASA Astrophysics Data System (ADS)

    Szabó, László; Tóth, Tünde; Homlok, Renáta; Takács, Erzsébet; Wojnárovits, László

    2012-09-01

    Using radiolytic experiments hydroxyl radical (main reactant in advanced oxidation processes) was shown to effectively destroy paracetamol molecules. The basic reaction is attachment to the ring. The hydroxy-cyclohexadienyl radical produced in the further reactions may transform to hydroxylated paracetamol derivatives or to quinone type molecules and acetamide. The initial efficiency of aromatic ring destruction in the absence of dissolved O2 is c.a. 10%. The efficiency is 2-3 times higher in the presence of O2 due to its reaction with intermediate hydroxy-cyclohexadienyl radical and the subsequent ring destruction reactions through peroxi radical. Upon irradiation the toxicity of solutions at low doses increases with the dose and then at higher doses it decreases. This is due to formation of compounds with higher toxicity than paracetamol (e.g. acetamide, hidroquinone). These products, however, are highly sensitive to irradiation and degrade easily.

  20. Dry dilute acid pretreatment by co-currently feeding of corn stover feedstock and dilute acid solution without impregnation.

    PubMed

    He, Yanqing; Zhang, Jian; Bao, Jie

    2014-04-01

    Impregnation of lignocellulose materials with dilute acid solution is a routine operation in conventional dilute acid pretreatment. The dry dilute acid pretreatment (DDAP) at high solids content up to 70% is naturally considered to require longer impregnation time. In this study, a co-currently feeding operation of corn stover and dilute sulfuric acid solution without any impregnation was tested for DDAP. The DDAP pretreated corn stover without impregnation is found to be essentially no difference in pretreatment efficiency compared to those with impregnation in the helically agitated reactor. The yield from cellulose to ethanol in SSF again shows no obvious difference between the DDAP pretreated corn stover with and without impregnation. This study suggests that impregnation in DDAP was not necessary under the helical agitation mixing. The results provided a useful way of cost reduction and process simplification in pretreatment. PMID:24630497

  1. Dry dilute acid pretreatment by co-currently feeding of corn stover feedstock and dilute acid solution without impregnation.

    PubMed

    He, Yanqing; Zhang, Jian; Bao, Jie

    2014-04-01

    Impregnation of lignocellulose materials with dilute acid solution is a routine operation in conventional dilute acid pretreatment. The dry dilute acid pretreatment (DDAP) at high solids content up to 70% is naturally considered to require longer impregnation time. In this study, a co-currently feeding operation of corn stover and dilute sulfuric acid solution without any impregnation was tested for DDAP. The DDAP pretreated corn stover without impregnation is found to be essentially no difference in pretreatment efficiency compared to those with impregnation in the helically agitated reactor. The yield from cellulose to ethanol in SSF again shows no obvious difference between the DDAP pretreated corn stover with and without impregnation. This study suggests that impregnation in DDAP was not necessary under the helical agitation mixing. The results provided a useful way of cost reduction and process simplification in pretreatment.

  2. Modeling syngas-fired gas turbine engines with two dilutants

    NASA Astrophysics Data System (ADS)

    Hawk, Mitchell E.

    2011-12-01

    Prior gas turbine engine modeling work at the University of Wyoming studied cycle performance and turbine design with air and CO2-diluted GTE cycles fired with methane and syngas fuels. Two of the cycles examined were unconventional and innovative. The work presented herein reexamines prior results and expands the modeling by including the impacts of turbine cooling and CO2 sequestration on GTE cycle performance. The simple, conventional regeneration and two alternative regeneration cycle configurations were examined. In contrast to air dilution, CO2 -diluted cycle efficiencies increased by approximately 1.0 percentage point for the three regeneration configurations examined, while the efficiency of the CO2-diluted simple cycle decreased by approximately 5.0 percentage points. For CO2-diluted cycles with a closed-exhaust recycling path, an optimum CO2-recycle pressure was determined for each configuration that was significantly lower than atmospheric pressure. Un-cooled alternative regeneration configurations with CO2 recycling achieved efficiencies near 50%, which was approximately 3.0 percentage points higher than the conventional regeneration cycle and simple cycle configurations that utilized CO2 recycling. Accounting for cooling of the first two turbine stages resulted in a 2--3 percentage point reduction in un-cooled efficiency, with air dilution corresponding to the upper extreme. Additionally, when the work required to sequester CO2 was accounted for, cooled cycle efficiency decreased by 4--6 percentage points, and was more negatively impacted when syngas fuels were used. Finally, turbine design models showed that turbine blades are shorter with CO2 dilution, resulting in fewer design restrictions.

  3. [Formation of oxalate in oxaliplatin injection diluted with infusion solutions].

    PubMed

    Eto, Seiji; Yamamoto, Kie; Shimazu, Kounosuke; Sugiura, Toshimune; Baba, Kaori; Sato, Ayaka; Goromaru, Takeshi; Hagiwara, Yoshiaki; Hara, Keiko; Shinohara, Yoshitake; Takahashi, Kojiro

    2014-01-01

    Oxaliplatin use can cause acute peripheral neuropathy characterized by sensory paresthesias, which are markedly exacerbated by exposure to cold temperatures, and is a dose-limiting factor in the treatment of colorectal cancer.Oxalate is eliminated in a series of nonenzymatic conversions of oxaliplatin in infusion solutions or biological fluids.Elimination of oxalate from oxaliplatin has been suggested as one of the reasons for the development of acute neuropathy.In this study, we developed a high-performance liquid chromatography(HPLC)-based method to detect oxalate formation, and investigated the time dependent formation of oxalate in oxaliplatin diluted with infusion solutions.The results obtained showed that the amount of oxalate in the solution corresponded to 1.6% of oxaliplatin 8 h after oxaliplatin dilution with a 5% glucose solution. On the other hand, oxalate formation from oxaliplatin diluted with a saline solution was ten-fold higher than that from oxaliplatin diluted with the 5% glucose solution.Most patients who were intravenously injected with oxaliplatin experienced venous pain.As a preventive measure against venous pain, dexamethasone was added to the oxaliplatin injection.We measured the amount of oxalate formed in the dexamethasone-containing oxaliplatin injection diluted with a 5% glucose solution.The amount of oxalate formed when dexamethasone was added did not differ significantly from that formed when dexamethasone was not added.Thus, there are no clinical problems associated with the stability of oxaliplatin solutions.

  4. Mobile Melt-Dilute Treatment for Russian Spent Nuclear Fuel

    SciTech Connect

    Peacock, H.

    2002-09-17

    Treatment of spent Russian fuel using a Melt-Dilute (MD) process is proposed to consolidate fuel assemblies into a form that is proliferation resistant and provides critically safety under storage and disposal configurations. Russian fuel elements contain a variety of fuel meat and cladding materials. The Melt-Dilute treatment process was initially developed for aluminum-based fuels so additional development is needed for several cladding and fuel meat combinations in the Russian fuel inventory (e.g. zirconium-clad, uranium-zirconium alloy fuel). A Mobile Melt-Dilute facility (MMD) is being proposed for treatment of spent fuels at reactor site storage locations in Russia; thereby, avoiding the costs of building separate treatment facilities at each site and avoiding shipment of enriched fuel assemblies over the road. The MMD facility concept is based on laboratory tests conducted at the Savannah River Technology Center (SRTC), and modular pilot-scale facilities constructed at the Savannah River Site for treatment of US spent fuel. SRTC laboratory tests have shown the feasibility of operating a Melt-Dilute treatment process with either a closed system or a filtered off-gas system. The proposed Mobile Melt-Dilute process is presented in this paper.

  5. Dilution mixing estimates of trace metal concentrations of suspended sediments

    SciTech Connect

    Marcus, W.A. )

    1989-02-01

    Dilution mixing equations, at first glance, appear to provide an easy and useful approach for estimating pollutant loads in sediments of unmonitored stream channels. Results from Left Hand Creek, Colorado, however, indicate that only under proper circumstances can dilution mixing models be used to estimate suspended metal concentrations in unmonitored channels with any accuracy. The utility of this technique is severely limited by errors at monitored sites in measuring metal concentrations within sediments and sediment discharge. Specifically, three general constraints must be met before making dilution mixing estimates of unmonitored concentrations: (1) estimated sediment discharges in an unmonitored tributary should be at least 30 percent of that in the main channel below the confluence; (2) there must be a significant difference between the estimated or monitored metal load in the channel below the confluence and the metal loads of the upstream channels; and (3) travel times between the monitoring sites must be incorporated within the calculations.

  6. Gas dilution system results and application to acid rain utilities

    SciTech Connect

    Jolley-Souders, K.; Geib, R.; Dunn, C.

    1997-12-31

    In 1997, the United States EPA will remove restrictions preventing acid rain utilities from using gas dilution systems for calibration or linearity studies for continuous emissions monitoring, Test Method 205 in 40CFR51 requires that a gas dilution system must produce calibration gases whose measured values are within {+-}2% of predicted values. This paper presents the evaluation of the Environics/CalMat 2020 Dilution System for use in calibration studies. Internal studies show that concentrations generated by this unit are within {+-}0.5% of predicted values. Studies are being conducted by several acid rain utilities to evaluate the Environics/CalMat system using single minor component calibration standards. In addition, an internally generated study is being performed to demonstrate the system`s accuracy using a multi-component gas mixture. Data from these tests will be presented in the final version of the paper.

  7. Dilution cycle control for an absorption refrigeration system

    DOEpatents

    Reimann, Robert C.

    1984-01-01

    A dilution cycle control system for an absorption refrigeration system is disclosed. The control system includes a time delay relay for sensing shutdown of the absorption refrigeration system and for generating a control signal only after expiration of a preselected time period measured from the sensed shutdown of the absorption refrigeration system, during which the absorption refrigeration system is not restarted. A dilution cycle for the absorption refrigeration system is initiated in response to generation of a control signal by the time delay relay. This control system is particularly suitable for use with an absorption refrigeration system which is frequently cycled on and off since the time delay provided by the control system prevents needless dilution of the absorption refrigeration system when the system is turned off for only a short period of time and then is turned back on.

  8. Acoustoelastic constants in dilute two-phase alloys

    NASA Technical Reports Server (NTRS)

    Salama, K.; Schneider, E.; Chu, S. L.

    1986-01-01

    Acoustoelastic constants are calculated for two-phase alloys containing dilute concentrations of precipitates in a solid-solution matrix, on the basis of a model in which the precipitates are represented as a dilute elastic suspension of spherical particle inclusions in an infinite matrix. The longitudinal propagation velocity in the alloy is thereby obtained in terms of the precipitates' concentration and the elastic moduli of the two phases. Results are presented which indicate that the acoustoelastic constant of longitudinal waves in a dilute two-phase alloy varies linearly with the concentration of second-phase precipitates, in agreement with recent measurements in aluminum and steel alloys where the acoustoelastic constants changed linearly with the second phase's volume fraction.

  9. Application of cryocoolers to a vintage dilution refrigerator

    NASA Astrophysics Data System (ADS)

    Schmitt, Richard L.; Smith, Gary; Ruschman, Mark; Beaty, Jim

    2012-06-01

    A dilution refrigerator is required for 50 mK detector operation of CDMS (Cryogenic Dark Matter Search). Besides shielding the dilution refrigerator itself, the liquid nitrogen shield and liquid helium bath in the refrigerator cool the detector cryostat heat shields and cool electronics, resulting in significant external heat loads at 80 K and at 4 K. An Oxford Instruments Kelvinox 400 has served this role for ten years but required daily transfers of liquid nitrogen and liquid helium. Complicating the cryogen supply is the location 800 meters below ground in an RF shielded, class 10000 clean room at Soudan, MN. Nitrogen and helium re-liquefiers using cryocoolers were installed outside the clean room and continuously condense room temperature gas and return the liquids to the dilution refrigerator through a transfer line. This paper will describe the design, installation, controls and performance of liquefaction systems.

  10. Process of concentrating ethanol from dilute aqueous solutions thereof

    DOEpatents

    Oulman, C.S.; Chriswell, C.D.

    1981-07-07

    Relatively dilute aqueous solutions of ethanol are concentrated by passage through a bed of a crystalline silica polymorph, such as silicalite, to adsorb the ethanol with residual dilute feed in contact with the bed, which is displaced by passing concentrated aqueous ethanol through the bed without displacing the adsorbed ethanol. A product concentrate is then obtained by removing the adsorbed ethanol from the bed together with at least a portion of the concentrated aqueous ethanol used as the displacer liquid. This process permits ethanol to be concentrated from dilute fermentation beers, which may contain from 6 to 10% ethanol, to obtain a concentrate product at very low energy cost having an ethanol concentration in excess of 95%, such as a concentration of from 98 to 99.5%. 5 figs.

  11. Process of concentrating ethanol from dilute aqueous solutions thereof

    DOEpatents

    Oulman, Charles S. [Ames, IA; Chriswell, Colin D. [Slater, IA

    1981-07-07

    Relatively dilute aqueous solutions of ethanol are concentrated by passage through a bed of a crystalline silica polymorph, such as silicalite, to adsorb the ethanol with residual dilute feed in contact with the bed, which is displaced by passing concentrated aqueous ethanol through the bed without displacing the adsorbed ethanol. A product concentrate is then obtained by removing the adsorbed ethanol from the bed together with at least a portion of the concentrated aqueous ethanol used as the displacer liquid. This process permits ethanol to be concentrated from dilute fermentation beers, which may contain from 6 to 10% ethanol, to obtain a concentrate product at very low energy cost having an ethanol concentration in excess of 95%, such as a concentration of from 98 to 99.5%.

  12. Application of Cryocoolers to a Vintage Dilution Refrigerator

    SciTech Connect

    Schmitt, Richard; Smith, Gary; Ruschman, Mark; Beaty, Jim; /Minnesota U.

    2011-06-06

    A dilution refrigerator is required for 50mK detector operation of CDMS (Cryogenic Dark Matter Search). Besides shielding the dilution refrigerator itself, the liquid nitrogen shield and liquid helium bath in the refrigerator cool the detector cryostat heat shields and cool electronics, resulting in significant external heat loads at 80K and at 4K. An Oxford Instruments Kelvinox 400 has served this role for ten years but required daily transfers of liquid nitrogen and liquid helium. Complicating the cryogen supply is the location 800 meters below ground in an RF shielded, class 10000 clean room at Soudan, MN. Nitrogen and helium re-liquefiers using cryocoolers were installed outside the clean room and continuously condense room temperature gas and return the liquids to the dilution refrigerator through a transfer line. This paper will describe the design, installation, controls and performance of liquefaction systems.

  13. 40 CFR 1065.140 - Dilution for gaseous and PM constituents.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Equipment Specifications § 1065.140 Dilution for gaseous and PM constituents. (a) General. You may dilute exhaust with ambient air, synthetic air, or... diluting exhaust at a location as close as possible to the location where ambient air dilution would...

  14. Energy efficient reconcentration of diluted human urine using ion exchange membranes in bioelectrochemical systems.

    PubMed

    Tice, Ryan C; Kim, Younggy

    2014-11-01

    Nutrients can be recovered from source separated human urine; however, nutrient reconcentration (i.e., volume reduction of collected urine) requires energy-intensive treatment processes, making it practically difficult to utilize human urine. In this study, energy-efficient nutrient reconcentration was demonstrated using ion exchange membranes (IEMs) in a microbial electrolysis cell (MEC) where substrate oxidation at the MEC anode provides energy for the separation of nutrient ions (e.g., NH4(+), HPO4(2-)). The rate of nutrient separation was magnified with increasing number of IEM pairs and electric voltage application (Eap). Ammonia and phosphate were reconcentrated from diluted human urine by a factor of up to 4.5 and 3.0, respectively (Eap = 1.2 V; 3-IEM pairs). The concentrating factor increased with increasing degrees of volume reduction, but it remained stationary when the volume ratio between the diluate (urine solution that is diluted in the IEM stack) and concentrate (urine solution that is reconcentrated) was 6 or greater. The energy requirement normalized by the mass of nutrient reconcentrated was 6.48 MJ/kg-N (1.80 kWh/kg-N) and 117.6 MJ/kg-P (32.7 kWh/kg-P). In addition to nutrient separation, the examined MEC reactor with three IEM pairs showed 54% removal of COD (chemical oxygen demand) in 47-hr batch operation. The high sulfate concentration in human urine resulted in substantial growth of both of acetate-oxidizing and H2-oxidizing sulfate reducing bacteria, greatly diminishing the energy recovery and Coulombic efficiency. However, the high microbial activity of sulfate reducing bacteria hardly affected the rate of nutrient reconcentration. With the capability to reconcentrate nutrients at a minimal energy consumption and simultaneous COD removal, the examined bioelectrochemical treatment method with an IEM application has a potential for practical nutrient recovery and sustainable treatment of source-separated human urine.

  15. Field observations of dilution on the Ipanema Beach outfall.

    PubMed

    Roldão, J; Carvalho, J L; Roberts, P J

    2001-01-01

    Field observations of the Ipanema Beach, Rio de Janeiro, ocean sewage outfall are presented. Measurements of dilution and other wastefield characteristics were obtained by adding dye tracer to the effluent and measuring in-situ. Simultaneous measurements of oceanographic conditions were made by Acoustic Doppler Current Profilers, thermistor strings, and profiling instruments. Four experiments were performed, two during unstratified conditions when the plume was surfacing, and two during conditions of strong stratification when the plume was submerged. The minimum dilution varied from 30 to 130. The measurements reflect the worst case conditions as the campaigns were all made for weak currents. PMID:11443984

  16. Dilutional Hyponatremia during Hysteroscpic Surgery: Prevention and Treatment.

    PubMed

    Lan, Ling; Zhang, Yu-Guan; Wang, Jin; Gong, Ya-Hong

    2016-08-01

    Dilutional hyponatremia caused by excess absorption of hypo-osmotic irrigation fluids is one of the severe complications during hysteroscopic surgery. Appropriate delivery system and distending media,proper distending pressure,and reducing destruction of uterine venous sinus may remarkably lower the morbidity. Meanwhile,early detection and timely treatment of moderate and severe hyponatremia to avoid the occurrence of secondary nervous system demyelination are particularly important during the surgery. This review summarizes the risk factors and the prevention and treatment strategies of dilutional hyponatremia during hysteroscopic surgery. PMID:27594163

  17. Computer registration of radioactive indicator-dilution curves.

    PubMed

    Shepherd, A P; Perry, M A; Alexander, G M; Granger, D N; Riedel, G L; Kvietys, P R; Franke, C P

    1983-12-01

    A system is described for recording indicator-dilution curves produced by gamma radiation-emitting tracers. The system consists of a flow-through cuvette in a well counter, appropriate commercially available gamma radiation-detecting equipment, an Apple II computer, and a two-channel pulse-counting interface of our own design. With the counting interface and the software described here, an investigator can simultaneously record two indicator-dilution curves produced by gamma emitters. Instead of having to wait hours or days for results, the investigator can watch the data being recorded and display the results in graphic form almost immediately after each injection.

  18. The electrochemistry of SIMFUEL in dilute alkaline hydrogen peroxide solutions

    NASA Astrophysics Data System (ADS)

    Goldik, Jon

    The work described in this thesis is a study of the electrochemistry of SIMFUEL (SIMulated nuclear FUEL) in dilute, alkaline hydrogen peroxide solutions. In the first set of experiments, the reaction of H2O 2 on SIMFUEL electrodes was studied electrochemically and under open circuit conditions in 0.1 mol L-1 NaCl solutions at pH 9.8. The composition of the oxidized UO2 surface was determined by X-ray photoelectron spectroscopy. Hydrogen peroxide reduction was found to be catalyzed by the formation of a mixed UIV/UV (UO 2+x) surface layer, but to be blocked by the accumulation of UVI species (UO3· yH2O or adsorbed (UO2)2+) on the electrode surface. The formation of this UVI layer blocks both H2O2 reduction and oxidation, thereby inhibiting the potentially rapid H2O2 decomposition reaction to H2O and O2. Decomposition is found to proceed at a rate controlled by the desorption of the adsorbed (UO2)2+ or reduction of adsorbed O2 species. Reduction of (O2) ads is coupled to the slow oxidative dissolution of UO2 and formation of a corrosion product deposit of UO3· yH2O. In the second series of experiments, the electrochemical reduction of hydrogen peroxide on SIMFUEL was studied using the steady-state polarization technique. Kinetic parameters for the reaction, such as Tafel slopes and reaction orders, were determined. The results were interpreted in terms of a chemical-electrochemical mechanism involving UIV/UV donor-acceptor reduction sites. The large values of the Tafel slopes and the fractional reaction orders with respect to H2O2 can be understood in terms of the potential-dependent surface coverage of active sites, similar to that observed in the reduction of hydrogen peroxide on oxidized copper surfaces. The effects of pH over the range 10-13 were also investigated. The H2O 2 reduction currents were nearly independent of pH in the range 10-11, but were slowed at more alkaline values. The change in pH dependence appears to be related to the acid-base properties

  19. Ethanol production with dilute acid hydrolysis using partially dried lignocellulosics

    DOEpatents

    Nguyen, Quang A.; Keller, Fred A.; Tucker, Melvin P.

    2003-12-09

    A process of converting lignocellulosic biomass to ethanol, comprising hydrolyzing lignocellulosic materials by subjecting dried lignocellulosic material in a reactor to a catalyst comprised of a dilute solution of a strong acid and a metal salt to lower the activation energy (i.e., the temperature) of cellulose hydrolysis and ultimately obtain higher sugar yields.

  20. Upper and lower bounds for a serial dilution test.

    PubMed

    Blodgett, Robert J

    2005-01-01

    A Poisson-binomial model estimates the concentration of a target microbe from a serial dilution test. The maximum likelihood procedure gives an equation whose solution equals the estimate of the concentration. This paper gives bounds for the solution to this equation that require only minimal calculations.

  1. Coffee-ring effect beyond the dilute limit

    NASA Astrophysics Data System (ADS)

    Kim, Jin Young; Ryu, Seul-A.; Kim, Hyungdae; Kim, Joon Heon; Park, Jung Su; Park, Yong Seok; Oh, Jeong Su; Weon, Byung Mook

    2015-11-01

    The coffee-ring effect, which is a natural generation of outward capillary flows inside drying coffee drops, is valid at the dilute limit of initial solute concentrations. If the solute is not dilute, the ring deposit is forced to have a non-zero width; higher initial concentration leads to a wider ring. Here we study the coffee-ring effect in the dense limit by demonstrating differences with various initial coffee concentrations from 0.1% to 60%. The coffee drops with high initial concentrations of real coffee particles show interesting evaporation dynamics: dense coffee drops tend to evaporate slowly. This result is different from the classic coffee-ring effect in the dilute limit. We suppose that the slow evaporation of dense coffee drops is associated with the ring growth dynamics. The coffee-ring effect becomes more significant in modern technologies such as self-assembly of nanoparticles, ink-jet printing, painting and ceramics. The complexity in evaporation dynamics of colloidal fluids would be able to be understood by expanding the coffee-ring effects in the dilute as well as the dense limits.

  2. Implementing Inquiry-Based Learning in Teaching Serial Dilutions

    ERIC Educational Resources Information Center

    Walker, Candace L.; McGill, Michael T.; Buikema, Arthur L., Jr.; Stevens, Ann M.

    2008-01-01

    The 5E model of inquiry-based learning was incorporated into a sophomore-level microbiology laboratory to increase student understanding of serial dilutions, a concept that is often difficult for most students to comprehend. Quantitative and qualitative assessments were conducted during the semester to determine the value of this approach for…

  3. 40 CFR 1065.340 - Diluted exhaust flow (CVS) calibration.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... SSV. (7) Incrementally close the restrictor valve or decrease the blower speed to decrease the flow... 40 Protection of Environment 33 2011-07-01 2011-07-01 false Diluted exhaust flow (CVS) calibration... POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Calibrations and Verifications Flow-Related Measurements §...

  4. Dilution and volatilization of groundwater contaminant discharges in streams

    NASA Astrophysics Data System (ADS)

    Aisopou, Angeliki; Bjerg, Poul L.; Sonne, Anne T.; Balbarini, Nicola; Rosenberg, Louise; Binning, Philip J.

    2015-01-01

    An analytical solution to describe dilution and volatilization of a continuous groundwater contaminant plume into streams is developed for risk assessment. The location of groundwater plume discharge into the stream (discharge through the side versus bottom of the stream) and different distributions of the contaminant plume concentration (Gaussian, homogeneous or heterogeneous distribution) are considered. The model considering the plume discharged through the bank of the river, with a uniform concentration distribution was the most appropriate for risk assessment due to its simplicity and limited data requirements. The dilution and volatilization model is able to predict the entire concentration field, and thus the mixing zone, maximum concentration and fully mixed concentration in the stream. It can also be used to identify groundwater discharge zones from in-stream concentration measurement. The solution was successfully applied to published field data obtained in a large and a small Danish stream and provided valuable information on the risk posed by the groundwater contaminant plumes. The results provided by the dilution and volatilization model are very different to those obtained with existing point source models, with a distributed source leading to a larger mixing length and different concentration field. The dilution model can also provide recommendations for sampling locations and the size of impact zones in streams. This is of interest for regulators, for example when developing guidelines for the implementation of the European Water Framework Directive.

  5. Analysis of boron dilution in a four-loop PWR

    SciTech Connect

    Sun, J.G.; Sha, W.T.

    1995-12-31

    Thermal mixing and boron dilution in a pressurized water reactor were analyzed with COMMIX codes. The reactor system was the four loop Zion reactor. Two boron dilution scenarios were analyzed. In the first scenario, the plant is in cold shutdown and the reactor coolant system has just been filled after maintenance on the steam generators. To flush the air out of the steam generator tubes, a reactor coolant pump (RCP) is started, with the water in the pump suction line devoid of boron and at the same temperature as the coolant in the system. In the second scenario, the plant is at hot standby and the reactor coolant system has been heated up to operating temperature after a long outage. It is assumed that an RCP is started, with the pump suction line filled with cold unborated water, forcing a slug of diluted coolant down the downcomer and subsequently through the reactor core. The subsequent transient thermal mixing and boron dilution that would occur in the reactor system is simulated for these two scenarios. The reactivity insertion rate and the total reactivity are evaluated.

  6. Color dilution alopecia in a blue Doberman pinscher crossbreed

    PubMed Central

    Perego, Roberta; Proverbio, Daniela; Roccabianca, Paola; Spada, Eva

    2009-01-01

    A 6-year-old male, blue Doberman pinscher crossbreed was presented with coat abnormalities; in particular, flank alopecia and pruritus. Based on medical the history, clinical evidence, and histopathological examination, color dilution alopecia was diagnosed. The dog was with oral melatonin treated for 3 months without success. PMID:19436637

  7. Simplified Method for Groundwater Treatment Using Dilution and Ceramic Filter

    NASA Astrophysics Data System (ADS)

    Musa, S.; Ariff, N. A.; Kadir, M. N. Abdul; Denan, F.

    2016-07-01

    Groundwater is one of the natural resources that is not susceptible to pollutants. However, increasing activities of municipal, industrial, agricultural or extreme land use activities have resulted in groundwater contamination as occured at the Research Centre for Soft Soil Malaysia (RECESS), Universiti Tun Hussein Onn Malaysia (UTHM). Thus, aims of this study is to treat groundwater by using rainwater and simple ceramic filter as a treatment agent. The treatment uses rain water dilution, ceramic filters and combined method of dilute and filtering as an alternate treatment which are simple and more practical compared to modern or chemical methods. The water went through dilution treatment processes able to get rid of 57% reduction compared to initial condition. Meanwhile, the water that passes through the filtering process successfully get rid of as much as 86% groundwater parameters where only chloride does not pass the standard. Favorable results for the combination methods of dilution and filtration methods that can succesfully eliminate 100% parameters that donot pass the standards of the Ministry of Health and the Interim National Drinking Water Quality Standard such as those found in groundwater in RECESS, UTHM especially sulfate and chloride. As a result, it allows the raw water that will use clean drinking water and safe. It also proves that the method used in this study is very effective in improving the quality of groundwater.

  8. 21 CFR 866.2500 - Microtiter diluting and dispensing device.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Microtiter diluting and dispensing device. 866.2500 Section 866.2500 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Microbiology Devices §...

  9. 21 CFR 866.2500 - Microtiter diluting and dispensing device.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Microtiter diluting and dispensing device. 866.2500 Section 866.2500 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Microbiology Devices §...

  10. 21 CFR 866.2500 - Microtiter diluting and dispensing device.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Microtiter diluting and dispensing device. 866.2500 Section 866.2500 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Microbiology Devices §...

  11. 21 CFR 866.2500 - Microtiter diluting and dispensing device.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Microtiter diluting and dispensing device. 866.2500 Section 866.2500 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Microbiology Devices §...

  12. 21 CFR 866.2500 - Microtiter diluting and dispensing device.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Microtiter diluting and dispensing device. 866.2500 Section 866.2500 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Microbiology Devices §...

  13. Current density and state density in diluted magnetic semiconductor nanostructures

    NASA Astrophysics Data System (ADS)

    Pérez Merchancano, S. T.; Paredes Gutiérrez, H.; Zuñiga, J. A.

    2016-02-01

    We study in this paper the spin-polarized current density components in diluted magnetic semiconductor tunnelling diodes with different sample geometries. We calculate the resonant JxV and the density of states. The differential conductance curves are analyzed as functions of the applied voltage and the magnetic potential strength induced by the magnetic ions.

  14. Thermodynamics of a dilute XX chain in a field

    NASA Astrophysics Data System (ADS)

    Timonin, P. N.

    2016-06-01

    Gapless phases in ground states of low-dimensional quantum spin systems are rather ubiquitous. Their peculiarity is a remarkable sensitivity to external perturbations due to permanent criticality of such phases manifested by a slow (power-low) decay of pair correlations and the divergence of the corresponding susceptibility. A strong influence of various defects on the properties of the system in such a phase can then be expected. Here, we consider the influence of vacancies on the thermodynamics of the simplest quantum model with a gapless phase, the isotropic spin-1/2 XX chain. The existence of the exact solution of this model gives a unique opportunity to describe in detail the dramatic effect of dilution on the gapless phase—the appearance of an infinite series of quantum phase transitions resulting from level crossing under the variation of a longitudinal magnetic field. We calculate the jumps in the field dependences of the ground-state longitudinal magnetization, susceptibility, entropy, and specific heat appearing at these transitions and show that they result in a highly nonlinear temperature dependence of these parameters at low T. Also, the effect of enhancement of the magnetization and longitudinal correlations in the dilute chain is established. The changes of the pair spin correlators under dilution are also analyzed. The universality of the mechanism of the quantum transition generation suggests that similar effects of dilution can also be expected in gapless phases of other low-dimensional quantum spin systems.

  15. Reusable chelating resins concentrate metal ions from highly dilute solutions

    NASA Technical Reports Server (NTRS)

    Bauman, A. J.; Weetal, H. H.; Weliky, N.

    1966-01-01

    Column chromatographic method uses new metal chelating resins for recovering heavy-metal ions from highly dilute solutions. The absorbed heavy-metal cations may be removed from the chelating resins by acid or base washes. The resins are reusable after the washes are completed.

  16. Activities of titanium in molten copper at dilute concentrations measured by solid- state electrochemical cells at 1373 K

    NASA Astrophysics Data System (ADS)

    Hoshino, H.; Shimada, T.; Yamamoto, M.; Iwase, M.

    1992-03-01

    In order to obtain the activities of titanium in molten copper at dilute concentrations, i.e., between 5 x 10-6 and 3.4 x 10-3 titanium mole fractions, liquid copper was brought into equilibrium with molten {CaCl2 + Ti2O3} slag saturated with Ti2O3 (s) at 1373 K and the equilibrium oxygen partial pressures were measured by means of a solid-oxide galvanic cell of the type Mo/Mo + MoO2/ZrO2(MgO)/(Cu + Ti)alloy + Ti2O3 + CaCl2 + Ti2O3 slag/Mo The free energy change for the dissolution of solid titanium in molten copper at infinite dilution referred to 1 wt pet was determined as Ti (s) = Ti(1 wt pet in Cu) ΔG°/J = -86,100 ± 8900 at 1373 K

  17. Combined Dilute Acid and Solvent Based Pretreatment of Agricultural Wastes for Efficient Lignocellulosic Fractionation and Biofuels Production

    SciTech Connect

    Brodeur, G.; Ramakrishnan, S.; Wilson, C.; Telotte, J.; Collier, J.; Stickel, J.

    2013-01-01

    A true biorefinery for processing lignocellulosic biomass should achieve maximum utilization of all major constituents (cellulose, hemicellulose, & lignin) within the feedstock. In this work a combined pretreatment process of dilute acid (DA) and N-methyl morpholine N-oxide (NMMO) is described that allows for both fractionation and subsequent complete hydrolysis of the feedstocks (corn stover and sugarcane bagasse). During this multi-step processing, the dilute acid pretreatment solubilizes the majority (>90%) of the hemicellulosic fraction, while the NMMO treatment yields a cellulosic fraction that is completely digestible within 48 hours at low enzyme loadings. With both the cellulosic and hemicellulosic fractions being converted into separate, dissolved sugar fractions, the remaining portion is nearly pure lignin. When used independently, DA and NMMO pretreatments are only able to achieve ~80% and ~45% cellulosic conversion, respectively. Mass balance calculations along with experimental results are used to illustrate the feasibility of separation and recycling of NMMO.

  18. Effects of Matrix Viscoelasticity on Rheology of Dilute and Semi-Dilute Suspensions of Non Brownian Rigid Spheres

    NASA Astrophysics Data System (ADS)

    Grizzuti, Nino; Pasquino, Rossana

    2008-07-01

    The rheology of non-Brownian, inertialess rigid spheres suspended in viscoelastic fluids was investigated in the dilute and semi-dilute regimes (volume fractions up to 10%), where interparticle interactions become increasingly relevant. PMMA spherical particles were suspended in viscoelastic Polydimethylsiloxanes (PDMS). A Newtonian fluid (Polyisobutilene, PIB) was also used as a reference system. As expected, both the viscosity and the viscoelastic moduli increased with increasing solid volume fraction. The rheological parameters showed a simple scaling behaviour when their normalized values (with respect to the pure fluid) were considered. Viscosity and moduli were found to be independent upon shear rate and frequency, respectively. Following Batchelor's approach for non-dilute Newtonian suspensions, a second order polynomial dependency for the rheological properties was assumed. While the Newtonian reference fluid was found to obey well Batchelor's theoretical predictions, the viscoelastic suspensions showed more pronounced deviations from the linear dilute behavior, resulting in a second order polynomial coefficient substantially larger than that predicted by Batchelor for Newtonian systems. It was also found that the same concentration dependence was followed by both elastic and loss modulus.

  19. Two-stage dilute-acid and organic-solvent lignocellulosic pretreatment for enhanced bioprocessing.

    PubMed

    Brodeur, G; Telotte, J; Stickel, J J; Ramakrishnan, S

    2016-11-01

    A two stage pretreatment approach for biomass is developed in the current work in which dilute acid (DA) pretreatment is followed by a solvent based pretreatment (N-methyl morpholine N oxide - NMMO). When the combined pretreatment (DAWNT) is applied to sugarcane bagasse and corn stover, the rates of hydrolysis and overall yields (>90%) are seen to dramatically improve and under certain conditions 48h can be taken off the time of hydrolysis with the additional NMMO step to reach similar conversions. DAWNT shows a 2-fold increase in characteristic rates and also fractionates different components of biomass - DA treatment removes the hemicellulose while the remaining cellulose is broken down by enzymatic hydrolysis after NMMO treatment to simple sugars. The remaining residual solid is high purity lignin. Future work will focus on developing a full scale economic analysis of DAWNT for use in biomass fractionation. PMID:27631703

  20. Self-recognition among different polyprotic macroions during assembly processes in dilute solution.

    PubMed

    Liu, Tianbo; Langston, Melissa L K; Li, Dong; Pigga, Joseph M; Pichon, Céline; Todea, Ana Maria; Müller, Achim

    2011-03-25

    We report a self-recognition phenomenon based on an assembly process in a homogeneous dilute aqueous solution of two nano-scaled, spherical polyprotic metal oxide-based macroions (neutral species in crystals), also called Keplerates of the type [(linker)₃₀(pentagon)₁₂]≡[{M(H₂O)}₃₀{(Mo)Mo₅}₁₂] where M is Fe(III) or Cr(III). Upon deprotonation of the neutral species, the resulting macroions assemble into hollow "blackberry"-type structures through very slow homogeneous dimer-oligomerization processes. Although the geometrical surface structures of the two macroions are practically identical, mixtures of these form homogeneous superstructures, rather than mixed species. The phase separation is based on the difference in macroionic charge densities present during the slow homogeneous dimer or oligomer formation. The surface water ligands' residence times of Cr(III) and Fe(III) differ markedly and lead to very different interfacial water mobilities between the Keplerates.

  1. Improved measurement of iodine in food samples using inductively coupled plasma isotope dilution mass spectrometry.

    PubMed

    Haldimann, M; Eastgate, A; Zimmerli, B

    2000-11-01

    A new ICP-MS method for the determination of iodine in food samples is presented. The method makes use of a new miniature cyclonic spray chamber and a concentric glass nebulizer that is designed for low sample uptakes and is operated in a self-aspirating mode. As a consequence the wash-out was accelerated over conventional systems. This configuration allows the direct determination of iodine in mineralized solutions following digestion with nitric acid only. No strong oxidizing reagents such as perchloric acid or lengthy sample preparation were necessary to alter the chemical form of potentially volatile species. The isotope dilution technique using the long-lived isotope 129I was applied to obtain freedom from matrix effects. The present study reports on results for total iodine in selected nutritional and biological reference materials and makes a comparison with instrumental neutron activation analysis.

  2. Two-stage dilute-acid and organic-solvent lignocellulosic pretreatment for enhanced bioprocessing.

    PubMed

    Brodeur, G; Telotte, J; Stickel, J J; Ramakrishnan, S

    2016-11-01

    A two stage pretreatment approach for biomass is developed in the current work in which dilute acid (DA) pretreatment is followed by a solvent based pretreatment (N-methyl morpholine N oxide - NMMO). When the combined pretreatment (DAWNT) is applied to sugarcane bagasse and corn stover, the rates of hydrolysis and overall yields (>90%) are seen to dramatically improve and under certain conditions 48h can be taken off the time of hydrolysis with the additional NMMO step to reach similar conversions. DAWNT shows a 2-fold increase in characteristic rates and also fractionates different components of biomass - DA treatment removes the hemicellulose while the remaining cellulose is broken down by enzymatic hydrolysis after NMMO treatment to simple sugars. The remaining residual solid is high purity lignin. Future work will focus on developing a full scale economic analysis of DAWNT for use in biomass fractionation.

  3. Deposition and characterization of pyrocarbon coatings produced by use of CO/sub 2/ dilution

    SciTech Connect

    Stinton, D.P.; Lackey, W.J.

    1981-10-01

    A Biso-coated fuel particle for the High-Temperature Gas-Cooled Reactor (HTGR) consists of a 500 ..mu..m ThO/sub 2/ kernel, an 85-..mu..m layer of low-density carbon, and a 75-..mu..m layer of high-density pyrocarbon. Coatings produced from mixtures of 50% propylene, 25% CO/sub 2/, and 25% Ar were found to be more gastight than were coatings produced from mixtures of propylene and argon, helium, or H/sub 2/. Higher concentrations of CO/sub 2/ in the gas mixture caused severe oxidation of graphite components within the coating furnace. The permeability of coatings deposited by use of CO/sub 2/ dilution was found to depend on the deposition temperature. Low deposition temperatures produced more gastight coatings. It was determined that CO/sub 2/ had little or no effect on coating anisotropy. 6 figures.

  4. Quantifying Methane Fluxes Simply and Accurately: The Tracer Dilution Method

    NASA Astrophysics Data System (ADS)

    Rella, Christopher; Crosson, Eric; Green, Roger; Hater, Gary; Dayton, Dave; Lafleur, Rick; Merrill, Ray; Tan, Sze; Thoma, Eben

    2010-05-01

    Methane is an important atmospheric constituent with a wide variety of sources, both natural and anthropogenic, including wetlands and other water bodies, permafrost, farms, landfills, and areas with significant petrochemical exploration, drilling, transport, or processing, or refining occurs. Despite its importance to the carbon cycle, its significant impact as a greenhouse gas, and its ubiquity in modern life as a source of energy, its sources and sinks in marine and terrestrial ecosystems are only poorly understood. This is largely because high quality, quantitative measurements of methane fluxes in these different environments have not been available, due both to the lack of robust field-deployable instrumentation as well as to the fact that most significant sources of methane extend over large areas (from 10's to 1,000,000's of square meters) and are heterogeneous emitters - i.e., the methane is not emitted evenly over the area in question. Quantifying the total methane emissions from such sources becomes a tremendous challenge, compounded by the fact that atmospheric transport from emission point to detection point can be highly variable. In this presentation we describe a robust, accurate, and easy-to-deploy technique called the tracer dilution method, in which a known gas (such as acetylene, nitrous oxide, or sulfur hexafluoride) is released in the same vicinity of the methane emissions. Measurements of methane and the tracer gas are then made downwind of the release point, in the so-called far-field, where the area of methane emissions cannot be distinguished from a point source (i.e., the two gas plumes are well-mixed). In this regime, the methane emissions are given by the ratio of the two measured concentrations, multiplied by the known tracer emission rate. The challenges associated with atmospheric variability and heterogeneous methane emissions are handled automatically by the transport and dispersion of the tracer. We present detailed methane flux

  5. Spin-orbit dilution effects on the magnetism of frustrated spinel Ge(Co1-xMgx)2O4

    NASA Astrophysics Data System (ADS)

    Agata, Ryotaro; Takita, Shota; Ishikawa, Takashi; Watanabe, Tadataka

    2015-03-01

    We investigated magnetic properties of spinel oxides Ge(Co1-xMgx)2O4 with x = 0 ~ 0.5 to study the spin-orbit dilution effects on the magnetism of spin-orbit frustrated spinel GeCo2O4. We discovered that the magnetic moment per single Co2+ ion is decreased with increasing nonmagnetic Mg2+ concentration, which indicates the spin-orbit decoupling caused by the spin-orbit dilution. Additionally, small-amount substitution of Mg2+ for Co2+ causes the rapid increase of the positive Weiss temperature indicating the enhancement of ferromagnetic interactions, while the Mg2+ substitution suppresses the antiferromagnetic ordering resulting in the appearance of spin glass behavior. The present results suggest that the spin-orbit dilution causes the spin-orbit decoupling and the reinforcement of ferromagnetic frustration in GeCo2O4.

  6. Fabrication of Flexible Au/ZnO/ITO/PET Memristor Using Dilute Electrodeposition Method

    NASA Astrophysics Data System (ADS)

    Fauzi, F. B.; Ani, M. H.; Othman, R.; Azhar, A. Z. A.; Mohamed, M. A.; Herman, S. H.

    2015-11-01

    DRAM has been approaching its maximum physical limit due to the demand of smaller size and higher capacity memory resistor. The researchers have discovered the abilities of a memristor, a Non Volatile Memory (NVM) that could overcome the size and capacity obstacles. This paper discussed about the deposition of zinc oxide (ZnO) on indium tin oxide (ITO) coated polyethylene terephthalate (PET) substrate by electrodeposition. Metallic Zn film was deposited on substrates with varying deposition time from 15 to 120 seconds in very dilute zinc chloride (ZnCl2) aqueous and subsequently oxidized at 150 °C to form ZnO/ITO coated PET junction. The deposited thin film was characterized via x-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). The results from I-V measurement show the deposited ZnO exhibits pinched hysteresis loop. The hysteresis loop becomes smaller with increasing deposition time. The 15 seconds electrodeposition gave the largest hysteresis loop and largest value of resistive switching ratio of 1.067. The result of the synthesized ZnO on the flexible substrate can be one of the alternatives to replace the current memory system as the flexible memory system.

  7. Rapid NO 2 formation in diluted petrol-fuelled engine exhaust—A source of NO 2 in winter smog episodes

    NASA Astrophysics Data System (ADS)

    Shi, Ji Ping; Harrison, Roy M.

    Substantially enhanced rates of oxidation of nitric oxide have been found in petrol engine exhaust diluted with air in the dark. The main product of oxidation is nitrogen dioxide, but up to 20% of the oxidised NO can be in the form of other NO y species. Similarly enhanced NO oxidation rates are also found in the presence of petrol vapour. The kinetics of NO oxidation are close to zero order in NO, the rate being appreciably faster than the known thermal reaction 2NO + O 2 → 2NO 2. Attempts to isolate the chemical species responsible for this rate enhancement from petrol vapour and engine exhaust have led to identification of 1-methyl-1,3-cyclopentadiene and 1,3-cyclohexadiene. A mechanism has been developed in which addition of NO 2 to a conjugated diene causes initiation of a free-radical chain oxidation. A simple numerical model incorporating this process is capable of explaining the observed rate enhancements.

  8. Dilute nitric or nitrous acid solution containing halide ions as effective media for pure gold dissolution.

    PubMed

    Hojo, Masashi; Yamamoto, Masahiko; Okamura, Kei

    2015-08-14

    The greatly enhanced oxidation ability of dilute aqueous nitric acid (0.10-2.0 mol L(-1)) containing bromide and iodide salts as well as chloride salts has been examined based on the dissolution kinetics of pure gold at 30-60 °C. It has been found that bromide salts are more effective than chloride salts in gaining the ability of dissolving gold in dilute aqueous nitric acid solution. At 60 °C, a piece of gold-wire (ca. 20 mg) is dissolved in 20 mL of as low as 0.10 mol L(-1) HNO3 solution containing 1.0-5.0 mol L(-1) NaBr and the dissolution rate constant, log(k/s(-1)), increases linearly (from -5.78 to -4.52) with the increasing NaBr concentration. The addition of organic solvents, such as acetonitrile and acetic acid, causes acceleration of gold dissolution in LiBr and NaBr solutions. With increasing MeCN contents, for instance, the log(k/s(-1)) value of 0.10 mol L(-1) HNO3 solution containing 2.0 mol L(-1) NaBr increases linearly from -5.30 to -4.61 at 30% (v/v) MeCN. The bromide salts affect the gold dissolution rate constant in the order of KBr < NaBr < LiBr < CaBr2. With increasing NaI concentration (0.20-3.0 mol L(-1)), some acceleration in log(k/s(-1)) of 0.50 or 1.0 mol L(-1) HNO3 solution has been observed; however, the slope of acceleration as the function of NaI concentration is much smaller than that of NaCl or NaBr. The gold dissolution ability has been examined also for nitrous acid containing chloride and bromide ions at 35 °C. The NaNO2 solution containing twice or more amounts of HX (X = Cl, Br) gives the maximum efficiency for gold dissolution, according to the log(k/s(-1)) values of the mixed solutions of NaNO2 (0.10-2.0 mol L(-1)) and HX of various concentrations. The influence of oxidation by dilute nitric and nitrous acids on the gold dissolution is discussed from the standpoint of the redox potentials in "modified" aqueous solutions and not of the changes in the activity coefficients of ions.

  9. NUCLEAR ISOTOPIC DILUTION OF HIGHLY ENRICHED URANIUM BY DRY BLENDING VIA THE RM-2 MILL TECHNOLOGY

    SciTech Connect

    Raj K. Rajamani; Sanjeeva Latchireddi; Vikas Devrani; Harappan Sethi; Roger Henry; Nate Chipman

    2003-08-01

    DOE has initiated numerous activities to focus on identifying material management strategies to disposition various excess fissile materials. In particular the INEEL has stored 1,700 Kg of offspec HEU at INTEC in CPP-651 vault facility. Currently, the proposed strategies for dispositioning are (a) aqueous dissolution and down blending to LEU via facilities at SRS followed by shipment of the liquid LEU to NFS for fabrication into LWR fuel for the TVA reactors and (b) dilution of the HEU to 0.9% for discard as a waste stream that would no longer have a criticality or proliferation risk without being processed through some type of enrichment system. Dispositioning this inventory as a waste stream via aqueous processing at SRS has been determined to be too costly. Thus, dry blending is the only proposed disposal process for the uranium oxide materials in the CPP-651 vault. Isotopic dilution of HEU to typically less than 20% by dry blending is the key to solving the dispositioning issue (i.e., proliferation) posed by HEU stored at INEEL. RM-2 mill is a technology developed and successfully tested for producing ultra-fine particles by dry grinding. Grinding action in RM-2 mill produces a two million-fold increase in the number of particles being blended in a centrifugal field. In a previous study, the concept of achieving complete and adequate blending and mixing (i.e., no methods were identified to easily separate and concentrate one titanium compound from the other) in remarkably short processing times was successfully tested with surrogate materials (titanium dioxide and titanium mono-oxide) with different particle sizes, hardness and densities. In the current project, the RM-2 milling technology was thoroughly tested with mixtures of natural uranium oxide (NU) and depleted uranium oxide (DU) stock to prove its performance. The effects of mill operating and design variables on the blending of NU/DU oxides were evaluated. First, NU and DU both made of the same oxide

  10. Fluidized bed electrowinning of chromium from very dilute solutions

    SciTech Connect

    Hu, X.; Bautista, R.G.

    1988-10-01

    The Fluidized Bed Electrochemical Reactor (FBER) was used to electrowin chromium from very dilute solutions, ranging in concentration from 0.52 to 3.12 g Cr/1 at pH = 2. The cathode consisted of particulate chromium (450-600 ..mu..m diam.) with a current feeder made of carbon bars and a tubular lead anode in a cylindrical cell. The current efficiency was in the range of 0.08-0.22. The bed expansion, deposition rate, conversion ratio of Cr(VI) to Cr(III) and voltage - current characteristic of the cell were studied. The results indicate that the use of the FBER will make possible the removal of chromium from very dilute solutions without the introduction of other chemicals which would need to be removed or treated further downstream to satisfy environmental abatement codes.

  11. Derivation of Equivalent Continuous Dilution for Cyclic, Unsteady Driving Forces

    SciTech Connect

    Lawrence Berkeley National Laboratory; Technical University of Denmark, Department of Civil Engineering; Mortensen, Dorthe K.; Walker, Iain S.; Sherman, Max H.

    2010-12-15

    This article uses an analytical approach to determine the dilution of an unsteadily-generated solute in an unsteady solvent stream, under cyclic temporal boundary conditions. The goal is to find a simplified way of showing equivalence of such a process to a reference case where equivalent dilution is defined as a weighted average concentration. This derivation has direct applications to the ventilation of indoor spaces where indoor air quality and energy consumption cannot in general be simultaneously optimized. By solving the equation we can specify how much air we need to use in one ventilation pattern compared to another to obtain same indoor air quality. Because energy consumption is related to the amount of air exchanged by a ventilation system, the equation can be used as a first step to evaluate different ventilation patterns effect on the energy consumption. The use of the derived equation is demonstrated by representative cases of interest in both residential and non-residential buildings.

  12. Rheology of Dilute Aqueous Dispersions of Monodisperse Phytoglycogen Nanoparticles

    NASA Astrophysics Data System (ADS)

    Shamana, Hurmiz; Dutcher, John

    The viscosity of dilute colloidal dispersions is well described by the Einstein relation, which is linear in the volume fraction of the particles. For hard spheres, this allows the calculation of the specific volume of the spheres. For soft colloidal particles, the analysis of the data can be complicated by the uptake of the solvent by the particles. We have measured the concentration dependence of the zero shear viscosity of dilute aqueous dispersions of monodisperse phytoglycogen nanoparticles, which absorb a large amount of water (each nanoparticle contains about 250% of its mass in water). By using values of the particle size and the hydrated and dehydrated molecular weights determined using neutron scattering, we can interpret the measured viscosity-concentration data in terms of the Einstein relation to obtain the particle density and corresponding volume fraction of the dispersions.

  13. Fluorescence and absorbance of polystyrene in dilute and semidilute solutions

    SciTech Connect

    Torkelson, J.M.; Lipsky, S.; Tirrell, M.; Tirrell, D.A.

    1983-02-01

    The fluorescence and absorbance of polystyrene in solution have been measured over a wide concentration range for several molecular weights and solvents (cyclohexane, 1,2 dichloroethane). The absorbance at wavelengths below 280 nm for these molecular weights and solvents is found to be insensitive to the transition between dilute and semidilute solutions. Self-absorption of the fluorescence results in a much reduced observed monomer emission at high concentration. When this is corrected, the ratio of excimer to monomer fluorescence intensity, I/sub E//I/sub M/, is essentially constant at low concentrations and at most increases only very slowly and smoothly at higher concentrations. No significant molecular weight or solvent effects on the concentration dependence of I/sub E//I/sub M/ are manifested for these molecular weights and solvents over the concentration range studied. Contrary to previous reports, fluorescence spectroscopy reveals no abrupt transition between dilute and semidilute solutions. 30 references, 6 figures, 4 tables.

  14. Sibship Size and Gendered Resource Dilution in Different Societal Contexts

    PubMed Central

    Kalmijn, Matthijs

    2016-01-01

    Resource dilution theory hypothesizes that children’s educational attainment suffers from being raised with many siblings, as the parental resources have to be shared with more children. Based on economic and cultural theories, we hypothesize that resource dilution is gendered: especially a larger number of brothers is harmful to a person’s educational attainment. Using the Survey of Health, Ageing and Retirement in Europe, covering 18 European countries, we show that the number of brothers is more negatively related with the odds of obtaining a college degree than the number of sisters. This holds particularly for women. However, this pattern is weaker in countries that are known to have a more gender-egalitarian climate. PMID:27560371

  15. Electrolysis of dilute sodium chloride solution in a diaphragm cell

    SciTech Connect

    Kubasov, V.L.; Ivanter, I.A.; Druzhinin, E.A.; Vorob'eva, V.B.

    1986-02-10

    In some cases, as in the production of iodine and bromine, dilute solutions of sodium chloride remain unutilized. In view of the existence of large amounts of unutilized spent sodium chloride solutions and their harmful effect when discharged into the environment, it is desirable to develop a process for production of chlorine and alkali with high current efficiencies, satisfying industrial requirements, from dilute sodium chloride solutions. The authors have therefore studied electrolysis of solutions containing 160 and 180 kg/m/sup 3/ of sodium chloride, having pH of 11.0-11.5, close in composition to solutions from the Cheleken chemical factory. The chlorine and alkali current efficiencies and the compositions of the anolyte, catholyte, and anode gas were determined.

  16. Separation and concentration of lower alcohols from dilute aqueous solutions

    DOEpatents

    Moore, Raymond H.; Eakin, David E.; Baker, Eddie G.; Hallen, Richard T.

    1991-01-01

    A process for producing, from a dilute aqueous solution of a lower (C.sub.1 -C.sub.5) alcohol, a concentrated liquid solution of the alcohol in an aromatic organic solvent is disclosed. Most of the water is removed from the dilute aqueous solution of alcohol by chilling sufficiently to form ice crystals. Simultaneously, the remaining liquid is extracted at substantially the same low temperature with a liquid organic solvent that is substantially immiscible in aqueous liquids and has an affinity for the alcohol at that temperature, causing the alcohol to transfer to the organic phase. After separating the organic liquid from the ice crystals, the organic liquid can be distilled to enrich the concentration of alcohol therein. Ethanol so separated from water and concentrated in an organic solvent such as toluene is useful as an anti-knock additive for gasoline.

  17. Sibship Size and Gendered Resource Dilution in Different Societal Contexts.

    PubMed

    Kalmijn, Matthijs; van de Werfhorst, Herman G

    2016-01-01

    Resource dilution theory hypothesizes that children's educational attainment suffers from being raised with many siblings, as the parental resources have to be shared with more children. Based on economic and cultural theories, we hypothesize that resource dilution is gendered: especially a larger number of brothers is harmful to a person's educational attainment. Using the Survey of Health, Ageing and Retirement in Europe, covering 18 European countries, we show that the number of brothers is more negatively related with the odds of obtaining a college degree than the number of sisters. This holds particularly for women. However, this pattern is weaker in countries that are known to have a more gender-egalitarian climate. PMID:27560371

  18. Dry dilution refrigerator with He-4 precool loop

    SciTech Connect

    Uhlig, Kurt

    2014-01-29

    He-3/He-4 dilution refrigerators (DR) are very common in sub-Kelvin temperature research. We describe a pulse tube precooled DR where a separate He-4 circuit condenses the He-3 of the dilution loop. Whereas in our previous work the dilution circuit and the He-4 circuit were separate, we show how the two circuits can be combined. Originally, the He-4 loop with a base temperature of ∼ 1 K was installed to make an additional cooling power of up to 100 mW available to cool cold amplifiers and electrical lines. In the new design, the dilution circuit is run through a heat exchanger in the vessel of the He-4 circuit so condensation of the He-3 stream of the DR is done by the He-4 stage. A much reduced condensation time (factor of 2) of the He-3/He-4 gas mixture at the beginning of an experiment is achieved. A compressor is no longer needed with the DR as the condensation pressure remains below atmospheric pressure at all times; thus the risk of losing expensive He-3 gas is small. The performance of the DR has been improved compared to previous work: The base temperature of the mixing chamber at a small He-3 flow rate is now 4.1 mK; at the highest He-3 flow rate of 1.2 mmol/s this temperature increases to 13 mK. Mixing chamber temperatures were measured with a cerium magnesium nitrate (CMN) thermometer which was calibrated with a superconducting fixed point device.

  19. Theoretical behavior of microemulsions: geometrical aspects and dilution properties

    SciTech Connect

    Biais, J.; Bothorel, P.; Clin, B.; Lalanne, P.

    1981-03-01

    A very simple theoretical model for microemulsions is used; introducing the idea of pseudophases, and therefore equilibrium between them, one can account for many experimental properties of such systems. By using two partition coefficients respectively for alcohol and oil, the existence of dilution lines for microemulsions and of excluding domains for spherical objects is justified, and the evolution of some geometrical characteristics is predicted. 17 references.

  20. Nematic ordering in dilute solutions of rodlike polyelectrolytes

    NASA Astrophysics Data System (ADS)

    Potemkin, Igor I.; Khokhlov, Alexei R.

    2004-06-01

    Quantitative theory of orientational behavior of rodlike polyelectrolytes in dilute solution is developed. We find that in salt-free solutions many-body Coulomb interactions between macro- and counterions favor nematic ordering. It is shown that the orientationally isotropic phase of the solution becomes unstable toward nematic ordering at polymer concentration smaller than the overlap concentration. Our predictions are consistent with experimental observations for synthetic polyelectrolytes poly(p-phenylene)sulfonates in aqueous solutions.

  1. Characterizing storm water dispersion and dilution from small coastal streams

    NASA Astrophysics Data System (ADS)

    Romero, Leonel; Siegel, David A.; McWilliams, James C.; Uchiyama, Yusuke; Jones, Charles

    2016-06-01

    Characterizing the dispersion and dilution of storm water from small coastal creeks is important for understanding the importance of land-derived subsidies to nearby ecosystems and the management of anthropogenic pollutants. In Southern California, creek runoff is episodic, intense, and short-lived while the plumes are buoyant, all of which make the field sampling of freshwater plumes challenging. Numerical modeling offers a viable way to characterize these systems. The dilution and dispersion of freshwater from two creeks that discharge into the Santa Barbara Channel, California is investigated using Regional Ocean Modeling System (ROMS) simulations with a horizontal resolution of 100 m. Tight coupling is found among precipitation, hydrologic discharge, wind forcing, and submesoscale flow structures which all contribute to plume evolution. During flooding, plumes are narrow and attached to the coast, due to downwelling/onshore wind forcing and intense vorticity filaments lying parallel to the shelf. As the storm passes, the winds typically shift to offshore/upwelling favorable conditions and the plume is advected offshore which enhances its dilution. Plumes reach the bottom nearshore while they form thin layers a few meters thick offshore. Dilution field of passive tracers released with the runoff is strongly anisotropic with stronger cross-shelf gradients than along-shelf. Dispersion analysis of statistical moments of the passive tracer distribution results in scale-dependent diffusivities consistent with the particle-pair analysis of Romero et al. Model validation, the roles of submesoscale processes, and wind forcing on plume evolution and application to ecological issues and marine resource management are discussed.

  2. Development of a compact dilution refrigerator for zero gravity operation

    NASA Technical Reports Server (NTRS)

    Roach, Pat R.; Helvensteijn, Ben

    1990-01-01

    A compact dilution refrigerator design based on internal charcoal adsorption is being tested for operation in zero gravity. This refrigerator is self-contained with no external pumps or gas handling system and provides reliable operation since it has no moving parts. All operations are performed with heaters and are completely computer controlled. The refrigerator is capable of providing many hours of operation at very low temperature before the charcoal pumps must be recycled.

  3. Transmission of order in some unusual dilute systems

    NASA Technical Reports Server (NTRS)

    Adler, Joan; Palmer, R. G.; Meyer, H.

    1987-01-01

    As a system is diluted, the critical temperature T may fall to zero at a concentration X sub c greater than the percolation concentration, because mere connectivity does not guarantee the transmission of order even at T = 0. Detailed results, including bounds on X sub c, are presented for the three-state Potts antiferromagnet on a triangular lattice and for quadrupolar models of (o-H2)x(p-H2)1-x mixtures on fcc and triangular lattices.

  4. Underestimation of access flow by ultrasound dilution flow measurements

    NASA Astrophysics Data System (ADS)

    Bos, Clemens; Smits, Johannes H. M.; Zijlstra, Jan J.; Blankestijn, Peter J.; Bakker, Chris J. G.; Viergever, Max A.

    2002-02-01

    For hemodialysis access surveillance, flow measurements are increasingly considered important because they identify accesses at risk of thrombosis. Usually these flow measurements are performed with the ultrasound dilution technique. In a previous patient study it was observed that the resulting flow values were systematically low as compared to magnetic resonance flow measurements, but a satisfactory explanation was lacking. In the present study, we will demonstrate by hemodynamic calculations and in vitro experiments that this discrepancy can be explained by a temporary reduction of the access flow rate, caused by the reversed needle configuration during ultrasound dilution flow measurements. In this configuration, blood is injected retrogressively at one needle and flow between the needles is increased, causing an increased dissipation of energy. The proposed explanation is subsequently confirmed in a patient with a loop graft, by measuring the blood velocity by Doppler ultrasound as a function of reversed dialyzer flow rate. Apart from the ultrasound dilution technique, these findings are applicable to other recently proposed methods for measuring access flow that employ the reversed needle configuration.

  5. The Dilution Effect and Information Integration in Perceptual Decision Making

    PubMed Central

    Hotaling, Jared M.; Cohen, Andrew L.; Shiffrin, Richard M.; Busemeyer, Jerome R.

    2015-01-01

    In cognitive science there is a seeming paradox: On the one hand, studies of human judgment and decision making have repeatedly shown that people systematically violate optimal behavior when integrating information from multiple sources. On the other hand, optimal models, often Bayesian, have been successful at accounting for information integration in fields such as categorization, memory, and perception. This apparent conflict could be due, in part, to different materials and designs that lead to differences in the nature of processing. Stimuli that require controlled integration of information, such as the quantitative or linguistic information (commonly found in judgment studies), may lead to suboptimal performance. In contrast, perceptual stimuli may lend themselves to automatic processing, resulting in integration that is closer to optimal. We tested this hypothesis with an experiment in which participants categorized faces based on resemblance to a family patriarch. The amount of evidence contained in the top and bottom halves of each test face was independently manipulated. These data allow us to investigate a canonical example of sub-optimal information integration from the judgment and decision making literature, the dilution effect. Splitting the top and bottom halves of a face, a manipulation meant to encourage controlled integration of information, produced farther from optimal behavior and larger dilution effects. The Multi-component Information Accumulation model, a hybrid optimal/averaging model of information integration, successfully accounts for key accuracy, response time, and dilution effects. PMID:26406323

  6. Disappearance of high frequency modes in polymer dilute solution viscoelasticity

    NASA Astrophysics Data System (ADS)

    Larson, Ronald; Jain, Semant

    2009-03-01

    We address the problem of the ``missing modes'' in the high frequency rheology of dilute polymer solutions. According to the Rouse-Zimm theory, the slow viscoelastic response of dilute polymers is dominated by the collective motion of the chain, as described by a bead-spring model. However, one expects this description to break down at high frequencies at which chain motion on scales too small to be represented by beads and springs should be evident; this motion should be controlled by rotations of individual backbone bonds of the polymer. The viscoelastic response produced by these ``local modes'' is observable in polymer melts; however, for dilute polymer solutions, the ``local modes'' are absent from viscoelastic spectra, as shown by Schrag and coworkers (Peterson, et al., J. Polym. Sci. B, 39:2860 (2001)). Here we address this problem by directly simulating single polymer chains using Brownian dynamics simulations, with realistic bending and torsional potentials. We show using these simulations that the ``missing modes'' result from barriers to bond rotation that make the chain ``dynamically rigid'' at high frequencies. As a result, the ``dynamical Kuhn length'' of the chain exceeds the static one, and the chain at high frequencies is not able to explore local conformations as fast as would be needed for their relaxation to contribute to the mechanical relaxation spectrum.

  7. Dilution control and vibration studies at an underground mine

    SciTech Connect

    Mohanty, B. |; Yang, R.; Leblanc, M.; Kelly, C.

    1995-12-31

    A total of 33 blasts in the pillar recovery program at INCO-Crean Hill has been investigated by means of an extensive set of diagnostic techniques. These included, borehole deviation measurements, stope cavity survey, near-field seismics in both rock and backfill, in-hole VOD and fragment size analysis. The 200 mm diameter VCR blasts employed a variety of explosives types (ANFO, slurry and ANFO/Polystyrene) and deck sizes. The objective of the investigation was to control dilution and backbreak through optimal choice of explosive type and charge weight, without exceeding vibration limits in the adjacent backfill or causing significant degradation in fragmentation. The high quality experimental data, along with closely monitored borehole deviations and in-hole detonation properties of the explosive decks allowed the establishment of comprehensive near-field vibration vs. scaled distance relationship in both rock and backfill. The study helped identify the principal factors responsible for dilution from backfill at the mine. The analysis also showed that the two types of slurry explosive used in the mine and regular ANFO had equivalent damage potential to backfill. The key conclusions of the study were further confirmed in a second pillar recovery program, with significant potential benefits in terms of both dilution control and increased productivity. The paper details the steps in this investigation, and highlights the strengths and limitations of the methodology adopted in solving blasting problems in full-scale production blast environment.

  8. The Dilution Effect and Information Integration in Perceptual Decision Making.

    PubMed

    Hotaling, Jared M; Cohen, Andrew L; Shiffrin, Richard M; Busemeyer, Jerome R

    2015-01-01

    In cognitive science there is a seeming paradox: On the one hand, studies of human judgment and decision making have repeatedly shown that people systematically violate optimal behavior when integrating information from multiple sources. On the other hand, optimal models, often Bayesian, have been successful at accounting for information integration in fields such as categorization, memory, and perception. This apparent conflict could be due, in part, to different materials and designs that lead to differences in the nature of processing. Stimuli that require controlled integration of information, such as the quantitative or linguistic information (commonly found in judgment studies), may lead to suboptimal performance. In contrast, perceptual stimuli may lend themselves to automatic processing, resulting in integration that is closer to optimal. We tested this hypothesis with an experiment in which participants categorized faces based on resemblance to a family patriarch. The amount of evidence contained in the top and bottom halves of each test face was independently manipulated. These data allow us to investigate a canonical example of sub-optimal information integration from the judgment and decision making literature, the dilution effect. Splitting the top and bottom halves of a face, a manipulation meant to encourage controlled integration of information, produced farther from optimal behavior and larger dilution effects. The Multi-component Information Accumulation model, a hybrid optimal/averaging model of information integration, successfully accounts for key accuracy, response time, and dilution effects. PMID:26406323

  9. Infinitely dilute partial molar properties of proteins from computer simulation.

    PubMed

    Ploetz, Elizabeth A; Smith, Paul E

    2014-11-13

    A detailed understanding of temperature and pressure effects on an infinitely dilute protein's conformational equilibrium requires knowledge of the corresponding infinitely dilute partial molar properties. Established molecular dynamics methodologies generally have not provided a way to calculate these properties without either a loss of thermodynamic rigor, the introduction of nonunique parameters, or a loss of information about which solute conformations specifically contributed to the output values. Here we implement a simple method that is thermodynamically rigorous and possesses none of the above disadvantages, and we report on the method's feasibility and computational demands. We calculate infinitely dilute partial molar properties for two proteins and attempt to distinguish the thermodynamic differences between a native and a denatured conformation of a designed miniprotein. We conclude that simple ensemble average properties can be calculated with very reasonable amounts of computational power. In contrast, properties corresponding to fluctuating quantities are computationally demanding to calculate precisely, although they can be obtained more easily by following the temperature and/or pressure dependence of the corresponding ensemble averages.

  10. Breakdown of Cell Wall Nanostructure in Dilute Acid Pretreated Biomass

    SciTech Connect

    Pingali, Sai Venkatesh; Urban, Volker S; Heller, William T; McGaughey, Joseph; O'Neill, Hugh Michael; Foston, Marcus B; Myles, Dean A A; Ragauskas, Arthur J; Evans, Barbara R

    2010-01-01

    The generation of bioethanol from lignocellulosic biomass holds great promise for renewable and clean energy production. A better understanding of the complex mechanisms of lignocellulose breakdown during various pretreatment methods is needed to realize this potential in a cost and energy efficient way. Here, we use small-angle neutron scattering (SANS) to characterize morphological changes in switchgrass lignocellulose across molecular to sub-micron length scales resulting from the industrially-relevant dilute acid pretreatment method. Our results demonstrate that dilute acid pretreatment increases the cross-sectional radius of the crystalline cellulose fibril. This change is accompanied by removal of hemicellulose and the formation of Rg ~ 135 lignin aggregates. The structural signature of smooth cell wall surfaces is observed at length scales larger than 1000 , and it remains remarkably invariable during pretreatment. This study elucidates the interplay of the different biomolecular components in the break down process of switchgrass by dilute acid pretreatment. The results are important for the development of efficient strategies of biomass to biofuel conversion.

  11. A dilution effect in the emerging amphibian pathogen Batrachochytrium dendrobatidis

    PubMed Central

    Searle, Catherine L.; Biga, Lindsay M.; Spatafora, Joseph W.; Blaustein, Andrew R.

    2011-01-01

    Global declines in biodiversity are altering disease dynamics in complex and multifaceted ways. Changes in biodiversity can have several outcomes on disease risk, including dilution and amplification effects, both of which can have a profound influence on the effects of disease in a community. The dilution effect occurs when biodiversity and disease risk are inversely related, whereas the amplification effect is a positive relationship between biodiversity and disease risk. We tested these effects with an emerging fungal pathogen of amphibians, Batrachochytrium dendrobatidis (Bd), which is responsible for catastrophic amphibian population declines and extinctions worldwide. Despite the rapid and continued spread of Bd, the influence of host diversity on Bd dynamics remains unknown. We experimentally manipulated host diversity and density in the presence of Bd and found a dilution effect where increased species richness reduced disease risk, even when accounting for changes in density. These results demonstrate the general importance of incorporating community structure into studies of disease dynamics and have implications for the effects of Bd in ecosystems that differ in biodiversity. PMID:21930900

  12. Online Measurement of Exhaled NO Concentration and Its Production Sites by Fast Non-equilibrium Dilution Ion Mobility Spectrometry

    PubMed Central

    Peng, Liying; Jiang, Dandan; Wang, Zhenxin; Liu, Jiwei; Li, Haiyang

    2016-01-01

    Exhaled nitric oxide (NO) is one of the most promising breath markers for respiratory diseases. Its profile for exhalation and the respiratory NO production sites can provide useful information for medical disease diagnosis and therapeutic procedures. However, the high-level moisture in exhaled gas always leads to the poor selectivity and sensitivity for ion spectrometric techniques. Herein, a method based on fast non-equilibrium dilution ion mobility spectrometry (NED-IMS) was firstly proposed to directly monitor the exhaled NO profile on line. The moisture interference was eliminated by turbulently diluting the original moisture to 21% of the original with the drift gas and dilution gas. Weak enhancement was observed for humid NO response and its limit of detection at 100% relative humidity was down to 0.58 ppb. The NO concentrations at multiple exhalation flow rates were measured, while its respiratory production sites were determined by using two-compartment model (2CM) and Högman and Meriläinen algorithm (HMA). Last but not the least, the NO production sites were analyzed hourly to tentatively investigate the daily physiological process of NO. The results demonstrated the capacity of NED-IMS in the real-time analysis of exhaled NO and its production sites for clinical diagnosis and assessment. PMID:26975333

  13. PEM fuel cell stack performance using dilute hydrogen mixture. Implications on electrochemical engine system performance and design

    SciTech Connect

    Inbody, M.A.; Vanderborgh, N.E.; Hedstrom, J.C.; Tafoya, J.I.

    1996-12-31

    Onboard fuel processing to generate a hydrogen-rich fuel for PEM fuel cells is being considered as an alternative to stored hydrogen fuel for transportation applications. If successful, this approach, contrasted to operating with onboard hydrogen, utilizes the existing fuels infrastructure and provides required vehicle range. One attractive, commercial liquid fuels option is steam reforming of methanol. However, expanding the liquid methanol infrastructure will take both time and capital. Consequently technology is also being developed to utilize existing transportation fuels, such as gasoline or diesel, to power PEM fuel cell systems. Steam reforming of methanol generates a mixture with a dry gas composition of 75% hydrogen and 25% carbon dioxide. Steam reforming, autothermal reforming, and partial oxidation reforming of C{sub 2} and larger hydrocarbons produces a mixture with a more dilute hydrogen concentration (65%-40%) along with carbon dioxide ({approx}20%) and nitrogen ({approx}10%-40%). Performance of PEM fuel cell stacks on these dilute hydrogen mixtures will affect the overall electrochemical engine system design as well as the overall efficiency. The Los Alamos Fuel Cell Stack Test facility was used to access the performance of a PEM Fuel cell stack over the range of gas compositions chosen to replicate anode feeds from various fuel processing options for hydrocarbon and alcohol fuels. The focus of the experiments was on the anode performance with dilute hydrogen mixtures with carbon dioxide and nitrogen diluents. Performance with other anode feed contaminants, such as carbon monoxide, are not reported here.

  14. Use of seawater for the boron-doped diamond electrochemical treatment of diluted vinasse wastewater.

    PubMed

    Daskalaki, V M; Marakas, H; Mantzavinos, D; Katsaounis, A; Gikas, P

    2013-01-01

    Vinasse wastewater of high organic content (COD = 131,000 mg/L) and low biodegradability (BOD5/COD = 0.11) cannot be easily managed and usually require several consecutive treatment steps. The objective of this work was to dilute vinasse wastewater with seawater and then subject them to electrochemical oxidation over boron-doped diamond (BDD) electrodes. The use of seawater is a rational and novel approach for plants close to the seashore since it may achieve the desirable levels of effluent concentration and conductivity without consuming other water resources and extra electrolytes. Experiments were conducted at initial COD values of 830-8,400 mg/L, NaCl concentrations of 34-200 mM and current densities of 70-200 mA/cm(2) for up to 5 hours. The effect of current density and NaCl concentration was marginal on the electrochemical treatment, while the single most important parameter was the initial COD concentration. The order of reaction for COD reduction appears to be 'first' at low effluent concentrations and it decreases to 'zero' at higher concentrations, denoting the importance of the ratio of organics to reactive radicals concentration. Based on COD and total organic carbon data, it is postulated that degradation occurs predominantly through total oxidation (i.e. mineralization) to carbon dioxide and water, which is characteristic of BDD anodes. PMID:24334881

  15. Evaluation of online carbon isotope dilution mass spectrometry for the purity assessment of synthetic peptide standards.

    PubMed

    Cueto Díaz, Sergio; Ruiz Encinar, Jorge; García Alonso, J Ignacio

    2014-09-24

    We present a novel method for the purity assessment of peptide standards which is applicable to any water soluble peptide. The method is based on the online (13)C isotope dilution approach in which the peptide is separated from its related impurities by liquid chromatography (LC) and the eluent is mixed post-column with a continuous flow of (13)C-enriched sodium bicarbonate. An online oxidation step using sodium persulfate in acidic media at 99°C provides quantitative oxidation to (12)CO2 and (13)CO2 respectively which is extracted to a gaseous phase with the help of a gas permeable membrane. The measurement of the isotope ratio 44/45 in the mass spectrometer allows the construction of the mass flow chromatogram. As the only species that is finally measured in the mass spectrometer is CO2, the peptide content in the standard can be quantified, on the base of its carbon content, using a generic primary standard such as potassium hydrogen phthalate. The approach was validated by the analysis of a reference material (NIST 8327), and applied to the quantification of two commercial synthetic peptide standards. In that case, the results obtained were compared with those obtained using alternative methods, such as amino acid analysis and ICP-MS. The results obtained proved the value of the method for the fast, accurate and precise mass purity assignment of synthetic peptide standards. PMID:25172815

  16. Evaluation of online carbon isotope dilution mass spectrometry for the purity assessment of synthetic peptide standards.

    PubMed

    Cueto Díaz, Sergio; Ruiz Encinar, Jorge; García Alonso, J Ignacio

    2014-09-24

    We present a novel method for the purity assessment of peptide standards which is applicable to any water soluble peptide. The method is based on the online (13)C isotope dilution approach in which the peptide is separated from its related impurities by liquid chromatography (LC) and the eluent is mixed post-column with a continuous flow of (13)C-enriched sodium bicarbonate. An online oxidation step using sodium persulfate in acidic media at 99°C provides quantitative oxidation to (12)CO2 and (13)CO2 respectively which is extracted to a gaseous phase with the help of a gas permeable membrane. The measurement of the isotope ratio 44/45 in the mass spectrometer allows the construction of the mass flow chromatogram. As the only species that is finally measured in the mass spectrometer is CO2, the peptide content in the standard can be quantified, on the base of its carbon content, using a generic primary standard such as potassium hydrogen phthalate. The approach was validated by the analysis of a reference material (NIST 8327), and applied to the quantification of two commercial synthetic peptide standards. In that case, the results obtained were compared with those obtained using alternative methods, such as amino acid analysis and ICP-MS. The results obtained proved the value of the method for the fast, accurate and precise mass purity assignment of synthetic peptide standards.

  17. Treatment of dilute methylene blue-containing wastewater by coupling sawdust adsorption and electrochemical regeneration.

    PubMed

    Bouaziz, I; Chiron, C; Abdelhedi, R; Savall, A; Groenen Serrano, K

    2014-01-01

    In the present work, the coupling of adsorption and electrochemical oxidation on a boron-doped diamond (BDD) electrode to treat solutions containing dyes is studied. This coupling may be convenient for the treatment of diluted pollutant that is limited by the low rate of electrooxidation due to mass-transfer limitation. A pre-concentration step by adsorption could minimize the design of the electrochemical reactor. The adsorbent chosen was mixed with softwood sawdust, and methylene blue was chosen as the model dye molecule. Isotherms of adsorption and kinetics were investigated as well as the effects of current density and regeneration time. The BDD electrochemical oxidation of methylene blue adsorbed onto sawdust led simultaneously to its degradation and sawdust regeneration for the next adsorption. It was observed that multiple adsorption and electrochemical regeneration cycles led to an enhancement of adsorption capacity of the sawdust. This study demonstrated that adsorption–electrochemical degradation coupling offers a promising approach for the efficient elimination of organic dyes from wastewater.

  18. CO sub 2 induced inhibition of the localized corrosion of aluminum, Al-0. 5% Cu, and Al-2% Cu in dilute HF solution

    SciTech Connect

    Scully, J.R. . Dept. of Materials Science); Peebles, D.E. )

    1991-01-01

    This study presents work on corrosion of aluminum, Al-.5% Cu, and Al-2% Cu. Electrochemical tests were performed in dilute HF solutions both with and without CO{sub 2} sparging. It is suggested that CO{sub 2} or its reaction products interact with the passive film so that exposure of Cu in the oxide-solution interface is minimized. CO{sub 2} is investigated as a corrosion inhibitor. 4 refs. (JDL)

  19. Dynamic properties of dilute Bose-Einstein condensates

    NASA Astrophysics Data System (ADS)

    Durfee, Dallin S.

    In this thesis, a new apparatus for the study of Bose- Einstein condensation is described, and the first two experiments performed with the new device are discussed. The new instrument was constructed for the creation of dilute gas sodium Bose-Einstein condensates, and features an optical quality quartz cell, a high-flux spin-flip Zeeman slower, a tightly confining magnetic trap, and a high-resolution imaging system. The theory, design, and construction of each component is discussed, including a detailed explanation of non-destructive dispersive imaging. Bose-Einstein condensation was first achieved in the new apparatus in January of this year. Bose condensates consisting of 10 to 25 million atoms can be produced in this apparatus at a rate of two condensates per minute. The first two experiments performed with the new instrument probed the dynamic properties of dilute Bose condensates, allowing comparisons to be made with long standing theories of weakly-interacting degenerate Bose fluids. The first experiment was the study of ``surface wave'' excitations of Bose condensates. Standing and rotating quadrupole and octopole excitations were driven with a novel scanned optical dipole potential, a new tool which allows us to generate arbitrary two-dimensional perturbations to the trapping potential which confines the atoms. The second experiment studied the transition from dissipationless to dissipative flow in a Bose condensate. This study, performed by ``stirring'' the condensate with a focused laser, provided the first experimental evidence for the existence of a critical velocity for dissipation in dilute gas Bose condensates. This experiment is discussed in the context of earlier studies of the critical velocity of superfluid liquid helium. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253-1690.)

  20. Synthesis and processing of monosized oxide powders

    DOEpatents

    Barringer, E.A.; Fegley, M.B. Jr.; Bowen, H.K.

    1985-09-24

    Uniform-size, high-purity, spherical oxide powders are formed by hydrolysis of alkoxide precursors in dilute alcoholic solutions. Under controlled conditions (concentrations of 0.03 to 0.2 M alkoxide and 0.2 to 1.5 M water, for example) oxide particles on the order of about 0.05 to 0.7 microns can be produced. Methods of doping such powders and forming sinterable compacts are also disclosed. 6 figs.

  1. Synthesis and processing of monosized oxide powders

    DOEpatents

    Barringer, Eric A.; Fegley, Jr., M. Bruce; Bowen, H. Kent

    1985-01-01

    Uniform-size, high-purity, spherical oxide powders are formed by hydrolysis of alkoxide precursors in dilute alcoholic solutions. Under controlled conditions (concentrations of 0.03 to 0.2 M alkoxide and 0.2 to 1.5 M water, for example) oxide particles on the order of about 0.05 to 0.7 micron can be produced. Methods of doping such powders and forming sinterable compacts are also disclosed.

  2. Standardisation and comparison of serial dilution and single dilution enzyme linked immunosorbent assay (ELISA) using different antigenic preparations of the Babesia (Theileria) equi parasite.

    PubMed

    Kumar, Sanjay; Kumar, Yogesh; Malhotra, Dharam V; Dhar, Shruti; Nichani, Anil K

    2003-01-01

    Serial dilution and single dilution enzyme linked immunosorbent assays (ELISA) were standardised and their sensitivity and specificity were compared for serodiagnosis of Babesia equi infection. The antibody titres of 24 donkey sera of known identity were determined separately by serial dilution ELISA using three different B. equi antigens namely whole merozoite (WM), cell membrane (CM) and high speed supernatant (HSS). The ratios of the optical density (OD) of known positive and known negative sera at different serum dilutions were calculated and termed as the positive/negative (P/N) ratio. The coefficients of correlation (r) were calculated between the P/N ratios at different dilutions of sera and the log10 antibody titres of the same sera were ascertained by serial dilution ELISA. The highest value of 'r' was obtained at a serum dilution of 1:200. From log10 antibody titre of sera (y) and their P/N ratio at a dilution of 1:200 (x), regression equations (y = a + bx) were calculated separately for the three antigens. Test sera were diluted to 1:200, their OD were read in duplicate wells and were converted to the P/N ratio. Antibody titres were predicted from the P/N ratio using a regression equation separately for the three antigens. Titres obtained by both ELISAs were not significantly different from each other, thus confirming that single dilution ELISA could be successfully used to replace conventional serial dilution ELISA. The sensitivity, specificity and predictive value of single dilution ELISA was validated statistically using 42 B. equi disease-positive sera and 106 B. equi disease-negative sera. The WM antigen was found to be the most sensitive with a higher predictive value for negative test sera as compared to the CM or HSS antigens. Sera positive for other equine infections including Babesia caballi showed no cross-reaction with the three B. equi antigens in ELISA, thus the test was immunologically specific. Antibody titres of 109 unknown field donkey

  3. Dilution of axion dark radiation by thermal inflation

    NASA Astrophysics Data System (ADS)

    Hattori, Hironori; Kobayashi, Tatsuo; Omoto, Naoya; Seto, Osamu

    2015-07-01

    Axions in the Peccei-Quinn (PQ) mechanism provide a promising solution to the strong C P problem in the standard model of particle physics. Coherently generated PQ scalar fields could dominate the energy density in the early Universe and decay into relativistic axions, which would conflict with the current dark radiation constraints. We study the possibility that a thermal inflation driven by a U (1 ) gauged Higgs field dilutes such axions. A well-motivated extra gauged U (1 ) would be the local B -L symmetry. We also discuss the implication for the case of U (1 )B-L and an available baryogenesis mechanism in such cosmology.

  4. Modeling Corrosion Reactions of Steel in a Dilute Carbonate Solution

    NASA Astrophysics Data System (ADS)

    Eliyan, Faysal Fayez; Alfantazi, Akram

    2016-02-01

    This research models the corrosion reactions of a high-strength steel in an aerated, dilute, carbonate solution during a single-cycle voltammetry. Based on a previous study (Eliyan et al. in J Mater Eng Perform 24(6):1-8, 2015) and a literature survey, the corrosion reactions of the cathodic reduction, anodic dissolution, and passivation, as well as the interfacial interactions and the chemistry of the corrosion products are illustrated in schematics. The paper provides a visual guide on the corrosion reactions for steel in carbonate solutions based on the available mechanistic details that were reported and are still being investigated in literature.

  5. A lattice Boltzmann method for dilute polymer solutions.

    PubMed

    Singh, Shiwani; Subramanian, Ganesh; Ansumali, Santosh

    2011-06-13

    We present a lattice Boltzmann approach for the simulation of non-Newtonian fluids. The method is illustrated for the specific case of dilute polymer solutions. With the appropriate local equilibrium distribution, phase-space dynamics on a lattice, driven by a Bhatnagar-Gross-Krook (BGK) relaxation term, leads to a solution of the Fokker-Planck equation governing the probability density of polymer configurations. Results for the bulk rheological characteristics for steady and start-up shear flow are presented, and compare favourably with those obtained using Brownian dynamics simulations. The new method is less expensive than stochastic simulation techniques, particularly in the range of small to moderate Weissenberg numbers (Wi).

  6. Classical Equation of State for Dilute Relativistic Plasma

    NASA Astrophysics Data System (ADS)

    Hussein, N. A.; Eisa, D. A.; Sayed, E. G.

    2016-06-01

    The aim of this paper is to calculate the analytical form of the equation of state for dilute relativistic plasma. We obtained the excess free energy and pressure in the form of a convergent series expansion in terms of the thermal parameter μ where μ = {{m{c^2}} over {KT}}, m is the mass of charge, c is the speed of light, K is the Boltzmann's constant, and T is the absolute temperature. The results are discussed and compared with previous work of other authors.

  7. Wire-packed heat exchangers for dilution refrigerators.

    PubMed

    Polturak, E; Rappaport, M; Rosenbaum, R

    1978-03-01

    Very simple wire-packed step heat exchangers for dilution refrigerators are described. No sintering is used in fabrication. Flow impedances and thermal resistance between the liquid and the copper wires are low. A refrigerator with five wire-packed heat exchangers in addition to a countercurrent heat exchanger attains a temperature of 11.4 mK with a single mixing chamber and 6.1 mK with two mixing chambers. High cooling power is achieved at modest (3)He circulation rates. PMID:18699084

  8. Terahertz radiation from magnetic excitations in diluted magnetic semiconductors.

    PubMed

    Rungsawang, R; Perez, F; Oustinov, D; Gómez, J; Kolkovsky, V; Karczewski, G; Wojtowicz, T; Madéo, J; Jukam, N; Dhillon, S; Tignon, J

    2013-04-26

    We probed, in the time domain, the THz electromagnetic radiation originating from spins in CdMnTe diluted magnetic semiconductor quantum wells containing high-mobility electron gas. Taking advantage of the efficient Raman generation process, the spin precession was induced by low power near-infrared pulses. We provide a full theoretical first-principles description of spin-wave generation, spin precession, and of emission of THz radiation. Our results open new perspectives for improved control of the direct coupling between spin and an electromagnetic field, e.g., by using semiconductor technology to insert the THz sources in cavities or pillars.

  9. Dispersion of Sound in Dilute Suspensions with Nonlinear Particle Relaxation

    NASA Technical Reports Server (NTRS)

    Kandula, Max

    2010-01-01

    The theory accounting for nonlinear particle relaxation (viscous and thermal) has been applied to the prediction of dispersion of sound in dilute suspensions. The results suggest that significant deviations exist for sound dispersion between the linear and nonlinear theories at large values of Omega(Tau)(sub d), where Omega is the circular frequency, and Tau(sub d) is the Stokesian particle relaxation time. It is revealed that the nonlinear effect on the dispersion coefficient due to viscous contribution is larger relative to that of thermal conduction

  10. Phase transitions in pure and dilute thin ferromagnetic films

    NASA Astrophysics Data System (ADS)

    Korneta, W.; Pytel, Z.

    1983-10-01

    The mean-field model of a thin ferromagnetic film where the nearest-neighbor exchange coupling in surface layers can be different from that inside the film is considered. The phase diagram, equations for the second-order phase-transition lines, and the spontaneous magnetization profiles near the phase transitions are given. It is shown that there is no extra-ordinary transition in a thin film. If the thickness of the film tends to infinity the well-known results for the mean-field model of a semi-infinite ferromagnet are obtained. The generalization for disordered dilute thin ferromagnetic films and semi-infinite ferromagnets is also given.

  11. Dispersion of sound in dilute suspensions with nonlinear particle relaxation.

    PubMed

    Kandula, Max

    2010-03-01

    The theory accounting for nonlinear particle relaxation (viscous and thermal) has been applied to the prediction of dispersion of sound in dilute suspensions. The results suggest that significant deviations exist for sound dispersion between the linear and nonlinear theories at large values of omegatau(d), where omega is the circular frequency and tau(d) is the Stokesian particle relaxation time. It is revealed that the nonlinear effect on the dispersion coefficient due to viscous contribution is larger relative to that of thermal conduction. PMID:20329811

  12. Scaling of Greenwood Peierls conductance on a diluted square lattice

    NASA Astrophysics Data System (ADS)

    Schwalm, William; Schmitz, Albert

    The modified rectangle lattice of Dhar is a bond-diluted square lattice. The structure is self-similar and finitely ramified, like a fractal. Nevertheless certain discrete Schrödinger equation Green functions for the modified rectangle are known in closed form in the infinite lattice limit and the spectrum is continuous. By standard transfer matrix renormalization methods we present a study scaling properties of the Greenwood Peierls conductance distribution across the lattice with one dimensional lead wires attached as a function of lattice size and of additional disorder of several types.

  13. Self-Diffusion of Drops in a Dilute Sheared Emulsion

    NASA Technical Reports Server (NTRS)

    Loewenberg, Michael; Hinch, E. J.

    1996-01-01

    Self-diffusion coefficients that describe cross-flow migration of non-Brownian drops in a dilute sheared emulsion were obtained by trajectory calculations. A boundary integral formulation was used to describe pairwise interactions between deformable drops; interactions between undeformed drops were described with mobility functions for spherical drops. The results indicate that drops have large anisotropic self-diffusivities which depend strongly on the drop viscosity and modestly on the shear-rate. Pairwise interactions between drops in shear-flow do not appreciably promote drop breakup.

  14. Multicenter comparison of the ISO standard 20776-1 and the serial 2-fold dilution procedures to dilute hydrophilic and hydrophobic antifungal agents for susceptibility testing.

    PubMed

    Gomez-Lopez, Alicia; Arendrup, Maiken Cavling; Lass-Floerl, Cornelia; Rodriguez-Tudela, Juan-Luis; Cuenca-Estrella, Manuel

    2010-05-01

    A multicenter study was conducted to assess the accuracy of the ISO standard 20776-1 and the serial 2-fold dilution procedures for antifungal susceptibility testing. Fluconazole trays can be accurately prepared by following ISO and serial dilution schemes. However, itraconazole trays showed a significant lack of reproducibility that was independent of which method was followed.

  15. Dilute NiPt alloy interactions with Si

    NASA Astrophysics Data System (ADS)

    Corni, F.; Grignaffini Gregorio, B.; Ottaviani, G.; Queirolo, G.; Follegot, J. P.

    1993-11-01

    The reaction between a dilute Ni 95Pt 5 alloy and <111>Si has been investigated as a function of the annealing temperature and time, and the film thickness. Contrary to the concentrate alloys the first phase formed is Ni 2Si and the growth kinetics in the initial steps are similar to the case of pure Ni. Pt segregates in the alloy and its presence slows down the silicide growth rate suggesting that a new mechanism, namely the release of Ni from the alloy, is competing with the diffusion process in the silicide. In all the cases here considered NiSi starts to form only when all the Ni is reacted, indicating that the Pt never reaches high enough concentrations to inhibit the Ni 2Si growth. The further evolution of the system is similar to the ones reported for bilayers and non-dilute alloys. The I-V characteristics measured after annealing give a barrier height of 0.70 ± 0.01 eV.

  16. A miniature dilution refrigerator for sub-Kelvin detector arrays

    NASA Astrophysics Data System (ADS)

    Teleberg, Gustav; Chase, Simon T.; Piccirillo, Lucio

    2006-06-01

    We describe a miniature dilution refrigerator (MDR), operated in continuous mode and suitable for many detector applications at temperatures down to 50 mK. It distinguishes itself from other refrigerators in that it is self-contained and benefits from an internal cycle of the 3He gas. As a result, no external gas handling system is required so size, weight and complexity of the system is dramatically decreased. The system has no fine capillaries, moving parts or cooled O-rings. It is therefore mechanically very reliable, has no risk of blockages and is unlikely to develop cryogenic leaks. One direct application is balloon-borne or ground-based observations of the CMB using large detector arrays. When these experiments are operated remotely on platforms or at sites with limited infrastructure and maintenance support, a compact and reliable dilution refrigerator becomes essential. We describe a complete system incorporating an MDR which we have built and integrated with a pulse-tube refrigerator to achieve a cooling power of several micro Watt at 100 mK. This system is being developed for a CMB polarization experiment (CLOVER) which requires three independent cryostats to cool large TES detector arrays.

  17. Modeling the myocardial dilution curve of a pure intravascular indicator.

    PubMed

    Lee, J S; Karch, J; Jayaweera, A R; Lindner, J R; Lee, L P; Skyba, D M; Kaul, S

    1997-10-01

    The dispersion and dilution of contrast medium through the myocardial vasculature is examined first with a serial model comprised of arterial, capillary, and venous components in series to determine their time-concentration curves (TCC) and the myocardial dilution curve (MDC). Analysis of general characteristics shows that the first moment of the MDC, adjusted for that of the aortic TCC and mean transit time (MTT) from the aorta to the first intramyocardial artery, is one-half the MTT of the myocardial vasculature and that the ratio of the area of the MDC and aortic TCC is the fractional myocardial blood volume (MBV). The use of known coronary vascular morphometry and a set of transport functions indicates that the temporal change in MDC is primarily controlled by the MTT. An analysis of several models with heterogeneous flow distributions justifies the procedures to calculate MTT and MBV from the measured MDC. Compared with previously described models, the present model is more general and provides a physical basis for the effects of flow dispersion and heterogeneity on the characteristics of the MDC.

  18. Thermal conductivity and sound attenuation in dilute atomic Fermi gases

    SciTech Connect

    Braby, Matt; Chao Jingyi; Schaefer, Thomas

    2010-09-15

    We compute the thermal conductivity and sound attenuation length of a dilute atomic Fermi gas in the framework of kinetic theory. Above the critical temperature for superfluidity, T{sub c}, the quasiparticles are fermions, whereas below T{sub c}, the dominant excitations are phonons. We calculate the thermal conductivity in both cases. We find that at unitarity the thermal conductivity {kappa} in the normal phase scales as {kappa}{proportional_to}T{sup 3/2}. In the superfluid phase we find {kappa}{proportional_to}T{sup 2}. At high temperature the Prandtl number, the ratio of the momentum and thermal diffusion constants, is 2/3. The ratio increases as the temperature is lowered. As a consequence we expect sound attenuation in the normal phase just above T{sub c} to be dominated by shear viscosity. We comment on the possibility of extracting the shear viscosity of the dilute Fermi gas at unitarity using measurements of the sound absorption length.

  19. Stability Regimes of Turbulent Nitrogen-Diluted Hydrogen Jet Flames

    SciTech Connect

    Weiland, N.T.; Strakey, P.A.

    2007-03-01

    One option for combustion in zero-emission Integrated Gasification Combined Cycle (IGCC) power plants is non-premixed combustion of nitrogen-diluted hydrogen in air. An important aspect to non-premixed combustion is flame stability or anchoring, though only a few fundamental stability studies of these flames have taken place to date. The following paper presents the results of experiments investigating the effects of nitrogen diluent fraction, jet diameter, and exit velocity on the static stability limits of a turbulent hydrogen jet flame issuing from a thin-lipped tube into a quiescent atmosphere. Four different stability limits are observed: detachment from the burner lip, reattachment to the burner lip, transition from a laminar lifted flame base to blowout or to a turbulent lifted flame, and transition from a turbulent lifted flame to blowout. The applicability of existing theories and correlations to the stability results is discussed. These results are an important step in assessing the viability of a non-premixed combustion approach using hydrogen diluted with nitrogen as a fuel.

  20. Geochemical detection of carbon dioxide in dilute aquifers

    SciTech Connect

    Carroll, S; Hao, Y; Aines, R

    2009-03-27

    Carbon storage in deep saline reservoirs has the potential to lower the amount of CO{sub 2} emitted to the atmosphere and to mitigate global warming. Leakage back to the atmosphere through abandoned wells and along faults would reduce the efficiency of carbon storage, possibly leading to health and ecological hazards at the ground surface, and possibly impacting water quality of near-surface dilute aquifers. We use static equilibrium and reactive transport simulations to test the hypothesis that perturbations in water chemistry associated with a CO{sub 2} gas leak into dilute groundwater are important measures for the potential release of CO{sub 2} to the atmosphere. Simulation parameters are constrained by groundwater chemistry, flow, and lithology from the High Plains aquifer. The High Plains aquifer is used to represent a typical sedimentary aquifer overlying a deep CO{sub 2} storage reservoir. Specifically, we address the relationships between CO{sub 2} flux, groundwater flow, detection time and distance. The CO{sub 2} flux ranges from 10{sup 3} to 2 x 10{sup 6} t/yr (0.63 to 1250 t/m{sup 2}/yr) to assess chemical perturbations resulting from relatively small leaks that may compromise long-term storage, water quality, and surface ecology, and larger leaks characteristic of short-term well failure.

  1. Impaired Urine Dilution Capability in HIV Stable Patients

    PubMed Central

    Belloso, Waldo H.; de Paz Sierra, Mariana; Navarro, Matilde; Sanchez, Marisa L.; Perelsztein, Ariel G.; Musso, Carlos G.

    2014-01-01

    Renal disease is a well-recognized complication among patients with HIV infection. Viral infection itself and the use of some antiretroviral drugs contribute to this condition. The thick ascending limb of Henle's loop (TALH) is the tubule segment where free water clearance is generated, determining along with glomerular filtration rate the kidney's ability to dilute urine. Objective. We analyzed the function of the proximal tubule and TALH in patients with HIV infection receiving or not tenofovir-containing antiretroviral treatment in comparison with healthy seronegative controls, by applying a tubular physiological test, hyposaline infusion test (Chaimowitz' test). Material & Methods. Chaimowitz' test was performed on 20 HIV positive volunteers who had normal renal functional parameters. The control group included 10 healthy volunteers. Results. After the test, both HIV groups had a significant reduction of serum sodium and osmolarity compared with the control group. Free water clearance was lower and urine osmolarity was higher in both HIV+ groups. Proximal tubular function was normal in both studied groups. Conclusion. The present study documented that proximal tubule sodium reabsorption was preserved while free water clearance and maximal urine dilution capability were reduced in stable HIV patients treated or not with tenofovir. PMID:24800076

  2. Analytical approaches to the OH radical induced degradation of sulfonamide antibiotics in dilute aqueous solutions.

    PubMed

    Sági, Gyuri; Csay, Tamás; Szabó, László; Pátzay, György; Csonka, Emil; Takács, Erzsébet; Wojnárovits, László

    2015-03-15

    By combining a large variety of analytical techniques this study aimed at elaborating methods to follow up the degradation of sulfonamides in an advanced oxidation process (AOP): irradiation with ionizing radiation in dilute aqueous solution. In this process, besides other radicals, hydroxyl radicals are produced. As pulse radiolysis experiments show the basic initial reaction is hydroxyl radical addition to the benzene ring, forming cyclohexadienyl radical intermediates. In aerated solutions these radicals transform to peroxy radicals. Among the first formed products aromatic molecules hydroxylated in the benzene rings or in some cases in the heterocyclic rings were observed by LC-MS/MS. Chemical oxygen demand (COD) measurements indicate that at the early reaction period of degradation one hydroxyl radical induces incorporation of 1.5 O atoms into the products. Comparison of the COD and TOC (total organic carbon content) results shows gradual oxidation. Simultaneously with hydroxylation ring opening also takes place. The kinetics of inorganic SO4(2-) and NH4(+) formation, analyzed by ion chromatography, is similar to the kinetics of ring degradation (UV spectroscopy), however, there is a delayed formation of NO3(-). The latter ions may be produced in oxidative degradation of smaller N containing fragments. The S atoms of the sulfonamides remain in the solution (ICP-MS measurements) after degradation, whereas some part of the N atoms leaves the solution probably in the form of N2 (total nitrogen content (TN) measurements). Degradation is accompanied by a high pH drop due to formation of SO4(2-), NO3(-) and smaller organic acids. The degradation goes through many simultaneous and consecutive reactions, and with the applied methods the different stages of degradation can be characterized.

  3. Direct oxidation of jet fuels and Pennsylvania crude oil in a solid oxide fuel cell

    NASA Astrophysics Data System (ADS)

    Zhou, Z. F.; Gallo, C.; Pague, M. B.; Schobert, H.; Lvov, S. N.

    A Cu-ceria solid oxide fuel cell (SOFC) is shown to generate electric power using jet fuels and Pennsylvania crude oil through direct oxidation of the fuels. The liquid fuels contained up to 910 ppm of sulfur and were injected into the anode compartment either with or without N 2 dilution. The performance of the fuel cell was stable over 30 h for jet fuels and Pennsylvania crude oil without N 2 dilution whereas N 2 dilution prolonged the stable power generation up to 100 h for jet fuel and up to 80 h for Pennsylvania crude oil. The generated power density was about 0.1 W cm -2 for both fuels.

  4. Influence of Oxygen Supply on Oxide Coarsening During the Internal Oxidation of Two-Phase Fe-Y Alloys

    NASA Astrophysics Data System (ADS)

    Kachur, Stephen J.; Webler, Bryan A.

    2016-09-01

    Fe-Y binary alloys underwent thermogravimetric analysis while exposed to low oxidant partial pressures using a mixture of 5 pct H2-95 pct Ar gas at two flow rates. The alloys experienced in situ internal oxidation of Y-rich intermetallic phases. Kinetics and microstructures were both affected by flowrate. Lower flow rates resulted in coarser oxides and decreased oxidation rates. Results show the possible impacts of rate-controlling processes in the gas phase on internal oxidation with dilute oxidants.

  5. Structural and Magnetic Properties of Dilute Ca²⁺ Doped Iron Oxide Nanoparticles.

    PubMed

    Samar Layek; Rout, K; Mohapatra, M; Anand, S; Verma, H C

    2016-01-01

    Undoped and calcium substituted hematite (α-Fe₂O₃) nanoparticles are synthesized by surfactant-directed co-precipitation and post annealing method. The annealed nanoparticles were found to be in single phase in nature and crystallize in the rhombohedral structure with space group R3c as confirmed by Rietveld refinement of the X-ray diffraction (XRD) data. Average crystallite sizes are calculated to be 20 to 30 nm and 50 to 60 nm for the nanoparticles annealed at 400 and 600 °C respectively. Mössbauer spectra for all the nanoparticles could be fitted with a sextet corresponding to the single magnetic state of the iron atoms in its Fe³⁺ state in the hematite matrix. The FTIR and Raman spectra of all the samples correspond to specific modes of α-Fe₂O₃. UV-Vis spectra of annealed samples showed broad peaks in the range of 525-630 nm resulting from spin-forbidden ligand field transition together with the spin-flip transition among the 2t₂g states. The estimated band gap energies were in the range of 1.6 to 1.9 eV which are much lower than the reported values for nano hematite. From the room temperature magnetic hysteresis loop measurements, weak ferromagnetic behavior is observed in all undoped and Ca²⁺ doped hematite samples. Morin temperature (T(M)) is calculated to be 257 and 237 K for 1.45% doped samples with particle size 54 and 27 nm respectively. The sample with Ca content of 1.45 wt% when annealed at 400 °C showed that the particles were of different shapes which included both quasi spherical and rod shaped. On annealing the same sample at 600 °C, the nanorods collapsed to form bigger spherical and ellipsoidal particles. PMID:27398469

  6. Terahertz electromagnons in spin-diluted cupric oxide: dynamics of twisted spin states

    NASA Astrophysics Data System (ADS)

    Lloyd-Hughes, James; Jones, Samuel; Wurz, Nicola; Failla, Michele; McConville, Chris; Prabhakaran, Dharmalingham

    2015-03-01

    Understanding the physics of magnetoelectric materials may lead to their application in actuators, sensors and solid state memories. Improper multiferroics also have novel quasiparticle excitations: electromagnons form when spin-waves become electric-dipole active. We investigated magnons, electromagnons and spin-lattice coupling in Cu(1-x)Zn(x)O (0

  7. Effect of dilution of stool soluble component on growth and development of Strongyloides stercoralis.

    PubMed

    Anamnart, Witthaya; Intapan, Pewpan Maleewong; Pattanawongsa, Attarat; Chamavit, Pennapa; Kaewsawat, Supreecha; Maleewong, Wanchai

    2015-01-01

    Dispersion or dilution of stool by water from heavy rainfall may affect Strongyloides stercoralis free-living development producing infective filariform larvae (FL). This study examined effect of water dilution of stool on survival of S. stercoralis free-living development. One g of stool was prepared in water so that its soluble component was diluted sequentially from 1:2 to 1:480. Three dishes were used to compare FL production in three culture conditions: stool suspension, stool sediment deposited in soil, and isolated rhabditiform larvae (RhL) deposited in soil. The fourth dish was for developmental observation of RhL into free-living stages. Numerous FL were generated from undiluted or 1:2 diluted stool and stool sediment placed on soil. However, starting from dilution 1:5, FL production continuously decreased in both stool suspensions and stool sediments placed on soil. RhL isolated from stool dilutions placed on soil gave rise to few FL. Worm mating were seen at 24-30 hours in dilutions 1:20-1:120 only. Highest numbers of FL from indirect free-living cycle were 1/3 of those from control. FL production decreased as stool dilution increased, and reached zero production at 1:160 dilution. Rainfall may disperse or dilute stool so that nutritional supplement for S. stercoralis free-living development is insufficient.

  8. Effect of dilution of stool soluble component on growth and development of Strongyloides stercoralis.

    PubMed

    Anamnart, Witthaya; Intapan, Pewpan Maleewong; Pattanawongsa, Attarat; Chamavit, Pennapa; Kaewsawat, Supreecha; Maleewong, Wanchai

    2015-01-01

    Dispersion or dilution of stool by water from heavy rainfall may affect Strongyloides stercoralis free-living development producing infective filariform larvae (FL). This study examined effect of water dilution of stool on survival of S. stercoralis free-living development. One g of stool was prepared in water so that its soluble component was diluted sequentially from 1:2 to 1:480. Three dishes were used to compare FL production in three culture conditions: stool suspension, stool sediment deposited in soil, and isolated rhabditiform larvae (RhL) deposited in soil. The fourth dish was for developmental observation of RhL into free-living stages. Numerous FL were generated from undiluted or 1:2 diluted stool and stool sediment placed on soil. However, starting from dilution 1:5, FL production continuously decreased in both stool suspensions and stool sediments placed on soil. RhL isolated from stool dilutions placed on soil gave rise to few FL. Worm mating were seen at 24-30 hours in dilutions 1:20-1:120 only. Highest numbers of FL from indirect free-living cycle were 1/3 of those from control. FL production decreased as stool dilution increased, and reached zero production at 1:160 dilution. Rainfall may disperse or dilute stool so that nutritional supplement for S. stercoralis free-living development is insufficient. PMID:26035061

  9. Determination of Trace Cadmium in Geological Samples by Aerosol Dilution ICP-MS with Inverse Aqua Regia Extraction

    NASA Astrophysics Data System (ADS)

    Xu, Q.; Guo, W.; Jin, L.; Hu, S.; Chai, X.

    2015-12-01

    Cadmium (Cd) is a trace element that occurs at ppb level in most terrestrial materials. The determination of Cd in geological samples by ICP-MS is subject to Zr and/or Mo based oxide/hydroxide interference. This study developed a valid method for the determination of Cd by Ar aerosol dilution ICP-MS with inverse aqua regia extraction (in a water bath at 95℃ for 2h). An Agilent 7700x ICP-MS (Agilent Technologies, USA) with an aerosol dilution system was used. The extraction procedure separated most of the Zr matrix (>90%) from the analyte, and the residual Zr- hydroxides and Mo-oxides or hydroxides were successfully eliminated by adding an amount of Ar to the sample aerosol prior to the plasma. Compared to the conventional operation, the amounts of oxide and hydroxide ions formed in the plasma were reduced by up to 10 times. The relative yields of the interfering oxides and hydroxides were as low as 0.012% ((94Mo16OH++95Mo16O+)/(94Mo++95Mo+)) and 0.007% (94Zr16OH+/94Zr+). Under the optimized dilution gas flow rate (0.85 L min-1) and carrier gas flow rate (0.24 L min-1), the limit of detection (LOD, 3s) for 111Cd was 1.3 ng g-1. The accuracy of the method was assessed by using two USGS SRMs (andesite AGV-2 and basalt BCR-2). The Cd contents determined for AGV-2 and BCR-2 are 0.058±0.004μg g-1 and 0.148±0.007μg g-1 (N=10), which are in good agreement with the USGS reference values (0.061μg g-1 and 0.14μg g-1). The proposed method was also applied to determine Cd contents in 65 IGGE SRMs (28 soils, 28 sediments and 9 rocks). The measured Cd levels in these samples agree well with their certified values. The developed method shows great potential for the direct determination of trace levels of Cd in geological samples.

  10. Optimization of the dilute maleic acid pretreatment of wheat straw

    PubMed Central

    2009-01-01

    Background In this study, the dilute maleic acid pretreatment of wheat straw is optimized, using pretreatment time, temperature and maleic acid concentration as design variables. A central composite design was applied to the experimental set up. The response factors used in this study are: (1) glucose benefits from improved enzymatic digestibility of wheat straw solids; (2) xylose benefits from the solubilization of xylan to the liquid phase during the pretreatment; (3) maleic acid replenishment costs; (4) neutralization costs of pretreated material; (5) costs due to furfural production; and (6) heating costs of the input materials. For each response factor, experimental data were fitted mathematically. After data translation to €/Mg dry straw, determining the relative contribution of each response factor, an economic optimization was calculated within the limits of the design variables. Results When costs are disregarded, an almost complete glucan conversion to glucose can be reached (90% from solids, 7%-10% in liquid), after enzymatic hydrolysis. During the pretreatment, up to 90% of all xylan is converted to monomeric xylose. Taking cost factors into account, the optimal process conditions are: 50 min at 170°C, with 46 mM maleic acid, resulting in a yield of 65 €/Mg (megagram = metric ton) dry straw, consisting of 68 €/Mg glucose benefits (from solids: 85% of all glucan), 17 €/Mg xylose benefits (from liquid: 80% of all xylan), 17 €/Mg maleic acid costs, 2.0 €/Mg heating costs and 0.68 €/Mg NaOH costs. In all but the most severe of the studied conditions, furfural formation was so limited that associated costs are considered negligible. Conclusions After the dilute maleic acid pretreatment and subsequent enzymatic hydrolysis, almost complete conversion of wheat straw glucan and xylan is possible. Taking maleic acid replenishment, heating, neutralization and furfural formation into account, the optimum in the dilute maleic acid pretreatment of

  11. Molecular dynamics of a dilute solution of hydrogen in palladium

    NASA Astrophysics Data System (ADS)

    Pratt, Lawrence R.; Eckert, J.

    1989-06-01

    Molecular-dynamics results on a dilute solution of H in Pd are presented and compared with available incoherent inelastic neutron-scattering results. The embedded-atom model adopted here does a good job of describing the H-Pd atomic forces probed by incoherent inelastic neutron scattering. The time correlation functions associated with the computed spectra are strongly damped and indicative of the anharmonicity that has been suggested as the principal contribution to the anomalous isotope dependence of the superconducting transition temperature in PdH. These results highlight the fact that the H-atom vibrations in Pd-H solutions are low-frequency, large-amplitude vibrations relative to vibrations of H atoms in usual covalent interactions. The rms displacement of the H atom from its mean position in the center of the Pd octahedron compares favorably with the available neutron-diffraction results.

  12. Elimination of charge carrier trapping in diluted semiconductors

    NASA Astrophysics Data System (ADS)

    Abbaszadeh, D.; Kunz, A.; Wetzelaer, G. A. H.; Michels, J. J.; Crăciun, N. I.; Koynov, K.; Lieberwirth, I.; Blom, P. W. M.

    2016-06-01

    In 1962, Mark and Helfrich demonstrated that the current in a semiconductor containing traps is reduced by N/Ntr, with N the amount of transport sites, Nt the amount of traps and r a number that depends on the trap energy distribution. For r > 1, the possibility opens that trapping effects can be nearly eliminated when N and Nt are simultaneously reduced. Solution-processed conjugated polymers are an excellent model system to test this hypothesis, because they can be easily diluted by blending them with a high-bandgap semiconductor. We demonstrate that in conjugated polymer blends with 10% active semiconductor and 90% high-bandgap host, the typical strong electron trapping can be effectively eliminated. As a result we were able to fabricate polymer light-emitting diodes with balanced electron and hole transport and reduced non-radiative trap-assisted recombination, leading to a doubling of their efficiency at nearly ten times lower material costs.

  13. Numerical studies of dilute and dense spray characteristics

    NASA Technical Reports Server (NTRS)

    Kim, Y. M.; Shang, H. M.; Chen, C. P.; Ziebarth, J. P.; Wang, T. S.

    1992-01-01

    Several issues involving the improvement of physical submodels and the computational efficiency in modeling dilute and dense spray combustion are discussed. First, the implementations of a dispersion width approach accounting for turbulent dispersion within each computational parcel is discussed. This is essentially a statistical transport model and the testings of this model confirm the capability of accurately representing dispersion in nearly-homogeneous and inhomogeneous turbulent flows with improved efficiency over the delta function stochastic separated flow model. To account for the dense spray effects, an existing drop collision and coalescence model and a Taylor analogy breakup (TAB) model were employed. These models were incorporated into a state-of-the-art multiphase all-speed transient flow solution procedure. Several examples including nonevaporating, evaporating, and burning dense spray cases were studied. The numerical results show reasonably good comparisons with available experimental data in terms of spray penetration, drop sizes, and overall configuration of a spray flame.

  14. Studies of the effects of curvature on dilution jet mixing

    NASA Astrophysics Data System (ADS)

    Holdeman, James D.; Srinivasan, Ram; Reynolds, Robert S.; White, Craig D.

    1992-02-01

    An analytical program was conducted using both three-dimensional numerical and empirical models to investigate the effects of transition liner curvature on the mixing of jets injected into a confined crossflow. The numerical code is of the TEACH type with hybrid numerics; it uses the power-law and SIMPLER algorithms, an orthogonal curvilinear coordinate system, and an algebraic Reynolds stress turbulence model. From the results of the numerical calculations, an existing empirical model for the temperature field downstream of single and multiple rows of jets injected into a straight rectangular duct was extended to model the effects of curvature. Temperature distributions, calculated with both the numerical and empirical models, are presented to show the effects of radius of curvature and inner and outer wall injection for single and opposed rows of cool dilution jets injected into a hot mainstream flow.

  15. Hydrodynamic properties of rodlike and disklike particles in dilute solution

    NASA Astrophysics Data System (ADS)

    Ortega, A.; García de la Torre, J.

    2003-11-01

    The hydrodynamic properties of cylindrical (rodlike and discoidal) particles in dilute solution have been computed using the bead-shell model treatment. Previous results [Tirado and Garcı´a de la Torre, J. Chem. Phys. 71, 2581 (1979); 73, 1993 (1980)] for rods with length-to-diameter ratio p>2 are now extended to short cylinders and disks down to p=0.1. The intrinsic viscosity is obtained for rods and disks, and results are presented for the three rotational relaxation times of a cylindrical particle. The hydrodynamic properties are expressed in forms that have a weak variation with p, and are therefore useful for the analysis of experimental values. We present examples of the determination of the length and diameter of the cylindrical particles, for DNA oligonucleotides and tobacco mosaic virus.

  16. Bose-Einstein condensation of dilute atomic gases

    NASA Astrophysics Data System (ADS)

    Wu, Biao

    The Bose-Einstein condensation of dilute atomic gases is studied. The focus is on the interesting properties and the dynamical behavior of Bose-Einstein condensates (BECs1) under various external manipulations. We investigate how the interaction affects the interference pattern between two BEC clouds, and show how the interference pattern can be calculated. We then present a theory on the generation of dark solitons in BECs with a new experimental technique called phase imprint. By mapping this problem into a classic pendulum problem, we show how to design the phase step imprinted on a BEC cloud to generate desired dark solitons. We finally study the system of a BEC in an optical lattice, a nonlinear periodic system, which exhibits interesting new effects on the tunneling and superfluidity in terms of its Bloch bands and Bloch waves. 1In the dissertation, BEC stands for Bose-Einstein condensate, not Bose-Einstein condensation.

  17. Statistical design for a small serial dilution series.

    PubMed

    Zelterman, Daniel; Tulupyev, Alexander; Heimer, Robert; Abdala, Nadia

    2010-02-10

    We describe statistical plans for a serial dilution series designed to detect and estimate the number of viral particles in a solution. The design addresses a problem when a very limited number of aliquots are available for proliferation. A gamma prior distribution on the number of viral particles allows us to describe the marginal probability distribution of all experimental outcomes. We examine a design that minimizes the expected reciprocal information and compare this with the maximum entropy design. We argue that the maximum entropy design is more useful from the point of view of the laboratory technician. The problem and design are motivated by our study of the viability of human immunodeficiency virus in syringes and other equipment that might mediate blood-borne viral transmission.

  18. Dilute Magnetic Semiconductors from Electrodeposited ZnO Nanowires

    SciTech Connect

    Athavan, Nadarajah; Konenkamp, R.

    2011-02-02

    We present experimental results on the magnetic properties of doped ZnO nanowires grown at 80 8C in electrodeposition. We show that impurities such as Al, Mn, Co, and Cu can be incorporated in the nanowires by adding the corresponding metal salts to the electrolyte solution. At concentration levels of a few atomic percent we find the impurity concentration in the solid to be approximately proportional to the precursor concentration in solution. ZnO nanowrires doped with Cu, Co, and Mn show superparamagnetic response at room temperature, while undoped and Al-doped wires show no discernible magnetic response. The results indicate that with Cu, Mn, and Co doping dilute magnetic semiconductors can be prepared.

  19. Muon hyperfine fields in iron and its dilute alloys

    NASA Technical Reports Server (NTRS)

    Stronach, C. E.; Squire, K. R.; Arrott, A. S.; Patterson, B. D.; Heinrich, B.; Lankford, W. F.; Fiory, A. T.; Kossler, W. J.; Singh, J. J.

    1981-01-01

    The temperature dependence of the interstitial magnetic field, B, as determined by the rotation of the spin of the muon, has been measured for dilute polycrystalline iron alloys with Mo, Ti, and Nb additions over a temperature range of 240 to 633 K. In all cases the behaviors differ from one another and from the Fe(Al) alloys previously studied. B, which is negative with respect to the magnetization, is increased in magnitude by Al and Mo, and decreased greatly by Ti. The addition of Nb creates a two-phase alloy from which the role of heterogeneity and/or strain on B in iron can be assessed. If the temperature dependence of the hyperfine field extracted from B for Fe(Mo) alloys is interpreted on the model previously used to discuss the Fe(Al) data, then the muon must be attracted to the Mo atom while repelled by the Al atoms as the temperature decreases.

  20. Dilute Aperture Visible Nulling Coronagraph Imaging (DAViNCI)

    NASA Technical Reports Server (NTRS)

    Shao, Michael; Levine, B. M.; Vasisht, G.; Lane, B. F.; Woodruff, R.; Vasudevan, G.; Samuele R.; Harvey, K.; Clampin, M.; Lyon, R.; Guyon, O.; Tolls, V.

    2008-01-01

    The presentation focuses on instrument and mission overview, science case, Team X study, and technology status. Topics include DAViNCI study milestones, number of targets versus inner working angle, planet orbit and IWA, combiner/nuller instrument, DAViNCI Team X costs, technology status and near future plans, and deep laser null 1.23 x 10(exp -7) suppression. Summary points are: dilute aperture concept advantages, lower cost than a comparable 7-8m coronagraph working at 2 lambda/D, technology progress prior to 2008 was seriously limited by available funding but showed 1e-y suppression (2006) of laser light needed for 1e-9 to approximately 1e-10 contrast, and current technology effort is off to a fast date with a demonstration of less than 100pm wavefront measurement in Nov 08.

  1. Criteria for the evaluation of a dilute decontamination demonstration

    SciTech Connect

    FitzPatrick, V.F.; Divine, J.R.; Hoenes, G.R.; Munson, L.F.; Card, C.J.

    1981-12-01

    This document provides the prerequisite technical information required to evaluate and/or develop a project to demonstrate the dilute chemical decontamination of the primary coolant system of light water reactors. The document focuses on five key areas: the basis for establishing programmatic prerequisites and the key decision points that are required for proposal evaluation and/or RFP (Request for Proposal) issuance; a technical review of the state-of-the-art to identify the potential impacts of a reactor's primary-system decontamination on typical BWR and PWR plants; a discussion of the licensing, recertification, fuel warranty, and institutional considerations and processes; a preliminary identification and development of the selection criteria for the reactor and the decontamination process; and a preliminary identification of further research and development that might be required.

  2. Scanning Hall probe microscopy of a diluted magnetic semiconductor

    SciTech Connect

    Kweon, Seongsoo; Samarth, Nitin; Lozanne, Alex de

    2009-05-01

    We have measured the micromagnetic properties of a diluted magnetic semiconductor as a function of temperature and applied field with a scanning Hall probe microscope built in our laboratory. The design philosophy for this microscope and some details are described. The samples analyzed in this work are Ga{sub 0.94}Mn{sub 0.06}As films grown by molecular beam epitaxy. We find that the magnetic domains are 2-4 mum wide and fairly stable with temperature. Magnetic clusters are observed above T{sub C}, which we ascribe to MnAs defects too small and sparse to be detected by a superconducting quantum interference device magnetometer.

  3. Detection of dilute sperm samples using photoacoustic flowmetry

    NASA Astrophysics Data System (ADS)

    Viator, J. A.; Sutovsky, P.; Weight, R. M.

    2008-02-01

    Detection of sperm cells in dilute samples may have application in forensic testing and diagnosis of male reproductive health. Due to the optically dense subcellular structures in sperm cells, irradiation by nanosecond laser pulses induces a photoacoustic response detectable using a custom flow cytometer. We determined the detection threshold of bull sperm using various concentrations, from 200 to 1,000,000 sperm cells per milliliter. Using a tunable laser system set to 450nm with a 5 ns pulse duration and 11-12 mJ/pulse, we obtained a detection threshold of 3 sperm cells. The flow rate was 4 ml/minute through the flow chamber. The acoustic sensor was a 100 μm PVDF film attached to the glass flow chamber. The acoustic signal was preamplified and sent to an oscilloscope. The threshold signal indicated a signal to noise ratio of approximately 6 to 1. Improved system design may decrease the threshold to single sperm cells.

  4. Pinning Susceptibility: The Effect of Dilute, Quenched Disorder on Jamming

    NASA Astrophysics Data System (ADS)

    Graves, Amy L.; Nashed, Samer; Padgett, Elliot; Goodrich, Carl P.; Liu, Andrea J.; Sethna, James P.

    2016-06-01

    We study the effect of dilute pinning on the jamming transition. Pinning reduces the average contact number needed to jam unpinned particles and shifts the jamming threshold to lower densities, leading to a pinning susceptibility, χp . Our main results are that this susceptibility obeys scaling form and diverges in the thermodynamic limit as χp∝|ϕ -ϕc∞|-γp where ϕc∞ is the jamming threshold in the absence of pins. Finite-size scaling arguments yield these values with associated statistical (systematic) errors γp=1.018 ±0.026 (0.291 ) in d =2 and γp=1.534 ±0.120 (0.822 ) in d =3 . Logarithmic corrections raise the exponent in d =2 to close to the d =3 value, although the systematic errors are very large.

  5. Forms of vitamin B12 in radioisotope dilution assays.

    PubMed Central

    Begley, J A; Hall, C A

    1981-01-01

    Since the presence of analogues of vitamin B12 (B12, cobalamin, Cbl) has been postulated as the basis for the high values obtained by some radioisotope dilution assays (RIDA) of serum Cbl we examined serum for analogues. None could be demonstrated in the extracts of serum prepared for RIDA as sought by both direct and indirect techniques. The natural forms of serum Cbl were converted to cyanocobalamin (CN Cbl) by this process of extraction which included cyanide (CN). The correctly performed RIDA for Cbl based on R binder gave higher values than a RIDA based on intrinsic factor or than by bioassay. By exclusion, the difference appeared to be due to unidentified factors rather than the presence of analogues. Images PMID:7019262

  6. Infinite dilution conductimetry of plasma and urine: correlation with osmolality.

    PubMed

    Genain, C; Tellier, P; Syrota, A; Pocidalo, J J; Hans, M

    1978-08-15

    The infinite dilution conductivity (IDC) of plasma and urine allows a measurement of the electrolyte content in small samples (5 to 15 microliter). The method was compared to the corrected osmolality (II'p) measured by the freezing-point depression. A linear correlation existed between II'p and the IDC: for plasma: II'p = 13.10 sigma o,p + 37.00 (n = 46 and r = 0.9949) for urine: II'u = 12.75 sigma o,u + 16.56 (n = 85 and r = 0.9504). The measurement of the IDC does not depend on protein concentration and can be used instead of the osmometer methods to determine the total plasma and urine electrolyte content.

  7. Split-plot designs for robotic serial dilution assays.

    PubMed

    Buzas, Jeffrey S; Wager, Carrie G; Lansky, David M

    2011-12-01

    This article explores effective implementation of split-plot designs in serial dilution bioassay using robots. We show that the shortest path for a robot to fill plate wells for a split-plot design is equivalent to the shortest common supersequence problem in combinatorics. We develop an algorithm for finding the shortest common supersequence, provide an R implementation, and explore the distribution of the number of steps required to implement split-plot designs for bioassay through simulation. We also show how to construct collections of split plots that can be filled in a minimal number of steps, thereby demonstrating that split-plot designs can be implemented with nearly the same effort as strip-plot designs. Finally, we provide guidelines for modeling data that result from these designs. PMID:21627628

  8. Cryogen-free dilution refrigerator for ACTPOL polarization- sensitive receiver

    NASA Astrophysics Data System (ADS)

    Shvarts, V.; Zhao, Z.; Devlin, M. J.; Klein, J.; Lungu, M.; Schmitt, B.; Thornton, R.

    2014-12-01

    We present a new cryogenic receiver for the Atacama Cosmology Telescope (ACT), a six-meter diameter off-axis Gregorian telescope located at an altitude of 5,200 meters (17,000 ft.) on Cerro Toco, in Northern Chile. The focal plane contains 3000 polarization-sensitive transition edge sensor (TES) bolometers, and is cooled to below 100 mK with a removable pulse-tube based customised JDry-100 dilution refrigerator insert. The optical tubes and the rest of the receiver are cooled with a dedicated pulse tube to below 3 K. Details of the receiver- to-telescope integration and first season on-site operation are described, including detector base temperature stability in vertical and tilted position as well as remote operation via Ethernet link.

  9. Split-plot designs for robotic serial dilution assays.

    PubMed

    Buzas, Jeffrey S; Wager, Carrie G; Lansky, David M

    2011-12-01

    This article explores effective implementation of split-plot designs in serial dilution bioassay using robots. We show that the shortest path for a robot to fill plate wells for a split-plot design is equivalent to the shortest common supersequence problem in combinatorics. We develop an algorithm for finding the shortest common supersequence, provide an R implementation, and explore the distribution of the number of steps required to implement split-plot designs for bioassay through simulation. We also show how to construct collections of split plots that can be filled in a minimal number of steps, thereby demonstrating that split-plot designs can be implemented with nearly the same effort as strip-plot designs. Finally, we provide guidelines for modeling data that result from these designs.

  10. Positive ion polymerization in hydrogen diluted silane plasmas

    SciTech Connect

    Nunomura, S.; Kondo, M.

    2008-12-08

    Mass spectra of positive ions (cations) and neutrals have been measured in hydrogen diluted silane plasmas at gas pressures of 0.1-10 Torr. The mass spectrum of ions changes with the pressure, while that of neutrals maintains a similar shape. The dominant ion species varies from a hydrogen ion group at < or approx. 0.5 Torr to a monosilicon hydride ion group at {approx_equal}0.5-1 Torr and polysilicon hydride ion groups at > or approx. 1 Torr, which is determined from ionization channels and consecutive ion-molecule reactions. The ion bombardment is suppressed with the pressure, from several tens of eV at < or approx. 1 Torr to a few eV at > or approx. 7 Torr.

  11. High-throughput ab-initio dilute solute diffusion database

    PubMed Central

    Wu, Henry; Mayeshiba, Tam; Morgan, Dane

    2016-01-01

    We demonstrate automated generation of diffusion databases from high-throughput density functional theory (DFT) calculations. A total of more than 230 dilute solute diffusion systems in Mg, Al, Cu, Ni, Pd, and Pt host lattices have been determined using multi-frequency diffusion models. We apply a correction method for solute diffusion in alloys using experimental and simulated values of host self-diffusivity. We find good agreement with experimental solute diffusion data, obtaining a weighted activation barrier RMS error of 0.176 eV when excluding magnetic solutes in non-magnetic alloys. The compiled database is the largest collection of consistently calculated ab-initio solute diffusion data in the world. PMID:27434308

  12. Pinning Susceptibility: The Effect of Dilute, Quenched Disorder on Jamming.

    PubMed

    Graves, Amy L; Nashed, Samer; Padgett, Elliot; Goodrich, Carl P; Liu, Andrea J; Sethna, James P

    2016-06-10

    We study the effect of dilute pinning on the jamming transition. Pinning reduces the average contact number needed to jam unpinned particles and shifts the jamming threshold to lower densities, leading to a pinning susceptibility, χ_{p}. Our main results are that this susceptibility obeys scaling form and diverges in the thermodynamic limit as χ_{p}∝|ϕ-ϕ_{c}^{∞}|^{-γ_{p}} where ϕ_{c}^{∞} is the jamming threshold in the absence of pins. Finite-size scaling arguments yield these values with associated statistical (systematic) errors γ_{p}=1.018±0.026(0.291) in d=2 and γ_{p}=1.534±0.120(0.822) in d=3. Logarithmic corrections raise the exponent in d=2 to close to the d=3 value, although the systematic errors are very large. PMID:27341244

  13. Band Anticrossing in Dilute Germanium Carbides Using Hybrid Density Functionals

    NASA Astrophysics Data System (ADS)

    Stephenson, Chad A.; O'brien, William A.; Qi, Meng; Penninger, Michael; Schneider, William F.; Wistey, Mark A.

    2016-04-01

    Dilute germanium carbides (Ge1- x C x ) offer a direct bandgap for compact silicon photonics, but widely varying properties have been reported. This work reports improved band structure calculations for Ge1- x C x using ab initio simulations that employ the HSE06 exchange-correlation density functional. Contrary to Vegard's law, the conduction band minimum at Γ is consistently found to decrease with increasing C content, while L and X valleys change much more slowly. The calculated Ge bandgap is within 11% of experimental values. A decrease in energy at the Γ conduction band valley of (170 meV ± 50)/%C is predicted, leading to a direct bandgap for x > 0.008. These results indicate a promising material for Group IV lasers.

  14. Dispersal and air entrainment in unconfined dilute pyroclastic density currents

    NASA Astrophysics Data System (ADS)

    Andrews, Benjamin J.

    2014-09-01

    Unconfined scaled laboratory experiments show that 3D structures control the behavior of dilute pyroclastic density currents (PDCs) during and after liftoff. Experiments comprise heated and ambient temperature 20 μm talc powder turbulently suspended in air to form density currents within an unobstructed 8.5 × 6 × 2.6-m chamber. Comparisons of Richardson, thermal Richardson, Froude, Stokes, and settling numbers and buoyant thermal to kinetic energy densities show good agreement between experimental currents and dilute PDCs. The experimental Reynolds numbers are lower than those of PDCs, but the experiments are fully turbulent; thus, the large-scale dynamics are similar between the two systems. High-frequency, simultaneous observation in three orthogonal planes shows that the currents behave very differently than previous 2D (i.e., confined) currents. Specifically, whereas ambient temperature currents show radial dispersal patterns, buoyancy reversal, and liftoff of heated currents focuses dispersal along narrow axes beneath the rising plumes. The aspect ratios, defined as the current length divided by a characteristic width, are typically 2.5-3.5 in heated currents and 1.5-2.5 in ambient temperature currents, reflecting differences in dispersal between the two types of currents. Mechanisms of air entrainment differ greatly between the two currents: entrainment occurs primarily behind the heads and through the upper margins of ambient temperature currents, but heated currents entrain air through their lateral margins. That lateral entrainment is much more efficient than the vertical entrainment, >0.5 compared to ˜0.1, where entrainment is defined as the ratio of cross-stream to streamwise velocity. These experiments suggest that generation of coignimbrite plumes should focus PDCs along narrow transport axes, resulting in elongate rather than radial deposits.

  15. The extrinsic hysteresis behavior of dilute binary ferrofluids.

    PubMed

    Lin, Lihua; Li, Jian; Lin, Yueqiang; Liu, Xiaodong; Chen, Longlong; Li, Junming; Li, Decai

    2014-10-01

    We report on the magnetization behavior of dilute binary ferrofluids based on γ-Fe(2)O(3)/Ni(2)O(3) composite nanoparticles (A particles), with diameter about 11 nm, and ferrihydrite (Fe(5)O(7)(OH) ・4H2O) nanoparticles (B particles), with diameter about 6 nm. The results show that for the binary ferrofluids with A-particle volume fraction φ(A) = 0.2% and B-particle volume fractions φ(B) = 0.1% and φ(B) = 0.6%, the magnetization curves exhibit quasi-magnetic hysteresis behavior. The demagnetizing curves coincide with the magnetizing curves at high fields. However, for single γ-Fe(2)O(3)/Ni(2)O(3) ferrofluids with φ(A) = 0.2% and binary ferrofluids with φ(A) = 0.2% and φ(B) = 1.0%, the magnetization curves do not behave in this way. Additionally, at high field (750 kA/m), the binary ferrofluid with φ(B) = 1.0% has the smallest magnetization. From the model-of-chain theory, the extrinsic hysteresis behavior of these samples is attributed to the field-induced effects of pre-existing A particle chains, which involve both Brownian rotation of the chains'moments and a Néel rotation of the particles' moments in the chains. The loss of magnetization for the ferrofluids with φ(B) = 1.0% is attributed to pre-existing ring-like A-particle aggregates. These magnetization behaviors of the dilute binary ferrofluids not only depend on features of the strongly magnetic A-particle system, but also modifications of the weaker magnetic B-particle system. PMID:25365919

  16. Radiotracer Dilution Method for Mercury Inventory Study in Electrolytic Cells

    SciTech Connect

    Sugiharto; Su'ud, Zaki; Kurniadi, Rizal; Waris, Abdul; Santoso, Sigit Budi; Abidin, Zainal; Santoso, Gatot Budi

    2010-06-22

    Purpose of the experiment is to demonstrate feasibility the use of radiotracer to measure weight of mercury in electrolytic cells of soda industry. The weight of mercury in each cell of the plant is designed approximately 1700 kg. Radiotracer is prepared by mixing {sup 203}Hg radioactive mercury with 2400 g of inactive mercury in a bath. The respective precisely weighted mercury aliquots to be injected into the cells are prepared by pouring approximately 130 g of radioactive mercury taken from the bath into 13 standard vials, in accordance with the number of the cells tested. Four standard references prepared by further dilution of {+-}2 g active mercury taken from the bath to obtain the dilution factors range of 12,000 to 20,000 from which the calibration graph is constructed. The injection process is conducting by pouring the radioactive mercury from aliquots into the flowing mercury at the inlet side of the cell and allows them to mix thoroughly. It is assumed that the mass of the radiotracer injected into a closed system remains constant, at least during the period of the test. From this experiment it was observed that the mixing time is two days after injection of radioactive mercury. The inactive mercury in each electrolytic cell calculated by the radiotracer method is of the range 1351.529 kg to 1966.354 kg with maximum error (95% confidence) is 1.52 %. The accuracy of measurement of the present method is better than gravimetric one which accounts 4 % of error on average.

  17. An inline QC method for determining serial dilution performance of DMSO-based systems.

    PubMed

    Walling, Leslie A

    2011-06-01

    Serial dilution of compounds solubilized in dimethylsulfoxide (DMSO) for dose-response curves is a common method for efficacy analysis of potential drug candidates. In general, serial dilution methods are particularly prone to error propagation because each dilution is dependent on the previous concentration. Moreover, assumptions about quality control parameters (i.e., dye linearity) can lead to an erroneous process. Here, an inline performance measurement is sought to improve the precision and accuracy of dilution plates. Sulforhodamine 101 (S101) dye is introduced as the quantitative fluorometric method of choice for DMSO-based systems. Although S101 in DMSO behaves in a nonlinear fashion over its detectable range, we account for this with a direct calibration method that includes every point of the dilution template. This report contains dye selection rationale for the S101 dye and its use in quantifying the performance of 96- and 384-well dilution protocols as tested on five identical instruments.

  18. Crystal growth of selected II-VI semiconducting alloys by directional solidification

    NASA Technical Reports Server (NTRS)

    Lehoczky, Sandor L.; Szofran, F. R.; Gillies, D. C.; Cobb, S. D.; Su, C.-H.; Sha, Y.-G.; Andrews, R. N.

    1994-01-01

    A Hg(0.84)Zn(0.16)Te alloy crystal was back-melted and partially resolidified during the first United States Microgravity Laboratory (USML-1) mission in the Marshall Space Flight Center's Crystal Growth Furnace. The experiment was inadvertently terminated at about 30% of planned completion. Nonetheless, it was successfully demonstrated that HgZnTe alloy ingots partially grown and quenched on the ground can be back-melted and regrown in space under nearly steady state growth conditions. An identical 'ground-truth' experiment was performed following the mission. Preliminary results are presented for both crystals, as well as for a series of other crystals grown prior to the mission for the purposes of optimizing in-flight growth conditions.

  19. High detectivity short-wavelength II-VI quantum cascade detector

    SciTech Connect

    Ravikumar, Arvind P. Gmachl, Claire F.; Garcia, Thor A.; Tamargo, Maria C.; Jesus, Joel De

    2014-08-11

    We report on the experimental demonstration of a ZnCdSe/ZnCdMgSe-based short-wavelength photovoltaic Quantum Cascade Detector (QCD). The QCD operates in two spectral bands centered around 2.6 μm and 3.6 μm. Calibrated blackbody measurements yield a peak responsivity of 0.1 mA/W or 2400 V/W at 80 K, and a corresponding 300 K background radiation limited infrared performance detectivity (BLIP) of ∼2.5 × 10{sup 10 }cm √Hz/W. Comparison of background illuminated and dark current-voltage measurements demonstrates a BLIP temperature of 200 K. The device differential resistance-area product, decreases from about 10{sup 6} Ω cm{sup 2} at 80 K to about 8000 Ω cm{sup 2} at 300 K, indicative of the ultra-low Johnson noise in the detectors.

  20. Effective g-factor control in II-VI quantum dots: morphological effects

    NASA Astrophysics Data System (ADS)

    Prado, S. J.; López-Richard, V.; Trallero-Giner, C.; Alcalde, A. M.; Marques, G. E.

    2004-03-01

    The Zeeman splitting in a single CdTe quantum dot (QD) is theoretically analyzed in the frame of Kane-Weiler 8 × 8 k . p model. The conduction g-factor was calculated as a function of the QD size. We discuss the effects of the dot geometry on the magnitude and on sign of the g-factor, that opens new channels towards control and manipulation of magneto-optical properties and spin in different confinement regimes.

  1. State of the art HOT performances for Sofradir II-VI extrinsic technologies

    NASA Astrophysics Data System (ADS)

    Rubaldo, Laurent; Brunner, Alexandre; Guinedor, Pierre; Taalat, Rachid; Sam-giao, Diane; Kerlain, Alexandre; Dargent, Loïc.; Nicolas, Péré-Laprene; Chaffraix, Vincent; Bourqui, Marie-Lise; Loquet, Yannick; Coussement, Jerome

    2016-05-01

    SOFRADIR is the worldwide leader on the cooled IR detector market for high-performance space, military and security applications thanks to a well mastered Mercury Cadmium Telluride (MCT) technology, and recently thanks to the acquisition of III-V technology: InSb, InGaAs, and QWIP quantum detectors. Strong and continuous development efforts are deployed to deliver cutting edge products with improved performances in terms of spatial and thermal resolution, low excess noise and high operability. The actual trend in quantum IR detector development is the design of very small pixel, with high operating temperature. To maintain the detector performances and operability at high temperature, the number of pixels exhibiting extra noise like 1/f and RTS noise must be limited. This paper presents the recent developments achieved in Sofradir in terms of HOT MCT extrinsic p on n technology, blue MW band (cut-off wavelength of 4.2μm at 150K) and extended MW band (cut-off wavelength of 5.3μm at 130K). Comparison between optimized and non-optimized technology will be presented in terms of NETD temperature dependency, MTF, 1/f noise and the corresponding impact on RFPN (Residual Fixe Pattern Noise) and its stability up to 170K will be shown.

  2. Recent advances in Sofradir IR on II-VI photodetectors for HOT applications

    NASA Astrophysics Data System (ADS)

    Rubaldo, Laurent; Brunner, Alexandre; Guinedor, Pierre; Taalat, Rachid; Berthoz, Jocelyn; Sam-giao, Diane; Kerlain, Alexandre; Dargent, Loic; Péré-Laperne, Nicolas; Chaffraix, Vincent; Bourqui, Marie-Lise; Loquet, Yannick; Coussement, Jerome

    2016-02-01

    SOFRADIR is the worldwide leader on the cooled IR detector market for high-performance space, military and security applications thanks to a well mastered Mercury Cadmium Telluride (MCT) technology, and recently thanks to the acquisition of III-V technology: InSb, InGaAs, and QWIP quantum detectors. Strong and continuous development efforts are deployed to deliver cutting edge products with improved performances in terms of spatial and thermal resolution, low excess noise and high operability. The actual trend in quantum IR detector development is the design of very small pixel, with high operating temperature. To maintain the detector performances and operability at high temperature, the number of pixels exhibiting extra noise like 1/f and RTS noise must be limited. This paper presents the recent developments achieved in Sofradir in terms of HOT MCT extrinsic p on n technology, blue MW band (cut-off wavelength of 4.2μm at 150K) and extended MW band (cut-off wavelength of 5.3μm at 130K). Comparison between optimized and non-optimized technology will be presented in terms of NETD temperature dependency, MTF, 1/f noise and the corresponding impact on RFPN (Residual Fixe Pattern Noise) and its stability up to 170K will be shown.

  3. MTF performance: measurements, modelisation, and optimization for Sofradir II-VI IR photodetectors

    NASA Astrophysics Data System (ADS)

    Berthoz, Jocelyn; Rubaldo, Laurent; Maillard, Magalie; Taalat, Rachid; Grille, Romain; Péré-Laperne, Nicolas; Kerlain, Alexandre; Ferron, Alexandre; Gravrand, Olivier

    2015-01-01

    SOFRADIR is widely present on the IR detector market for high-performance space, military and security applications thanks to a well mastered Mercury Cadmium Telluride (MCT) technology, and to the recent acquisition of the III-V InSb, InGaAs, and QWIP technologies. As a result, strong and continuous development efforts are deployed to deliver cutting edge products with improved performances in terms of sensitivity, spatial and thermal resolution. The actual trend in quantum IR detector development is the design of very small pixel, with high operating temperature. The selfconfinement of neighboring diodes may not be efficient enough to maintain optimal modulation transfert function (MTF). This paper presents the recent developments achieved in Sofradir in terms of MTF measurements protocol challenged by the pitch reduction. An overview of state of the art MTF results with optimized measurement technic will be shown, from SWIR to VLWIR MCT focal plane. In order to optimize device performances and reduce development cycle time, this experimental approach has been coupled with finite elements modelisation (FEM). Optimized MTF results for 10μm pitch and HOT MCT technology will be exposed.

  4. Asymmetric topological interfaces and charge transfer in epitaxial Bi2 Se3 /II-VI superlattices

    NASA Astrophysics Data System (ADS)

    Chen, Zhiyi; Zhao, Lukasf; Korzhovska, Inna; Garcia, Thor; Tamargo, Maria; Krusin-Elbaum, Lia; Park, Kyungwha

    Access to charge transport through Dirac surface states in topological insulators (TIs) can be challenging due to their intermixing with the bulk or with non-topological subsurface two-dimensional electron gas (2DEG) quantum well states. Formed by bending of bulk electronic bands near the surface, 2DEG states arise via charge transfer to the topological surfaces, so the choice of layers abutting these surfaces is critical. Here we report molecular beam epitaxial growth of Bi2Se3/ZnxCd1-xSe superlattices that support only one topological surface channel per TI layer. The topological nature of conducting channels is evidenced by π-Berry phase and by the two-dimensional weak antilocalization. Both density functional theory calculations and transport measurements suggest that a single topological Dirac cone per TI layer arises from the asymmetry between the Se-terminated and Zn-terminated interfaces of ZnxCd1-xSe with Bi2Se3. Our findings suggest that topological transport could be controlled by adjusting charge transfer from non-topological spacers in hybrid structures. Supported by NSF-DMR-1420634, NSF-DMR-1312483, DOD-W911NF-13-1-0159, NSF DMR-1206354 and computer resources from SDSC under DMR060009N and VT ARC.

  5. High- and Reproducible-Performance Graphene/II-VI Semiconductor Film Hybrid Photodetectors

    NASA Astrophysics Data System (ADS)

    Huang, Fan; Jia, Feixiang; Cai, Caoyuan; Xu, Zhihao; Wu, Congjun; Ma, Yang; Fei, Guangtao; Wang, Min

    2016-06-01

    High- and reproducible-performance photodetectors are critical to the development of many technologies, which mainly include one-dimensional (1D) nanostructure based and film based photodetectors. The former suffer from a huge performance variation because the performance is quite sensitive to the synthesis microenvironment of 1D nanostructure. Herein, we show that the graphene/semiconductor film hybrid photodetectors not only possess a high performance but also have a reproducible performance. As a demo, the as-produced graphene/ZnS film hybrid photodetector shows a high responsivity of 1.7 × 107 A/W and a fast response speed of 50 ms, and shows a highly reproducible performance, in terms of narrow distribution of photocurrent (38-65 μA) and response speed (40-60 ms) for 20 devices. Graphene/ZnSe film and graphene/CdSe film hybrid photodetectors fabricated by this method also show a high and reproducible performance. The general method is compatible with the conventional planar process, and would be easily standardized and thus pay a way for the photodetector applications.

  6. Thermophysical Properties of Te-based II-VI Semiconductors: Reduced Algorithms for Thermal Diffusivity Determination

    NASA Technical Reports Server (NTRS)

    Banish, R. Michael; Brantschen, Segolene; Pourpoint, Timothee L.; Wessling, Francis; Sekerka, Robert F.

    2003-01-01

    This paper presents methodologies for measuring the thermal diffusivity using the difference between temperatures measured at two, essentially independent, locations. A heat pulse is applied for an arbitrary time to one region of the sample; either the inner core or the outer wall. Temperature changes are then monitored versus time. The thermal diffusivity is calculated from the temperature difference versus time. No initial conditions are used directly in the final results.

  7. Interface demarcation in Bridgman-Stockbarger crystal growth of II-VI compounds

    NASA Technical Reports Server (NTRS)

    Gillies, Donald C.; Lehoczky, S. L.; Szofran, F. R.; Su, Ching-Hua; Larson, David

    1991-01-01

    In preparation for anticipated microgravity space missions carrying the Advanced Automated Directional Solidification Furnace, experiments were conducted to determine growth of interface in growing crystals of cadmium-doped germanium (test case), cadmium telluride, and mercury zinc telluride, using three different techniques. It was found that compositional variations detectable by microprobe and EDS techniques were most successful for detecting interfaces in materials with extensive transient regions, large segregation coefficients, and high alloy content.

  8. High- and Reproducible-Performance Graphene/II-VI Semiconductor Film Hybrid Photodetectors.

    PubMed

    Huang, Fan; Jia, Feixiang; Cai, Caoyuan; Xu, Zhihao; Wu, Congjun; Ma, Yang; Fei, Guangtao; Wang, Min

    2016-01-01

    High- and reproducible-performance photodetectors are critical to the development of many technologies, which mainly include one-dimensional (1D) nanostructure based and film based photodetectors. The former suffer from a huge performance variation because the performance is quite sensitive to the synthesis microenvironment of 1D nanostructure. Herein, we show that the graphene/semiconductor film hybrid photodetectors not only possess a high performance but also have a reproducible performance. As a demo, the as-produced graphene/ZnS film hybrid photodetector shows a high responsivity of 1.7 × 10(7) A/W and a fast response speed of 50 ms, and shows a highly reproducible performance, in terms of narrow distribution of photocurrent (38-65 μA) and response speed (40-60 ms) for 20 devices. Graphene/ZnSe film and graphene/CdSe film hybrid photodetectors fabricated by this method also show a high and reproducible performance. The general method is compatible with the conventional planar process, and would be easily standardized and thus pay a way for the photodetector applications. PMID:27349692

  9. Control of physical and optical properties of II-VI quantum dots

    NASA Astrophysics Data System (ADS)

    Sooklal, Kelly Sonja

    This thesis primarily concentrates on two semiconductors, CdS and ZnS, both of which have been widely used in the fabrication of electrical devices. Nanoparticles of CdS and ZnS have both been prepared using a variety of synthetic methods. These "quantum confined" particles exhibit a wide range of size dependent properties which can be modified by either altering their size and/or surface chemistry. In one set of experiments, it was found that the location of Mn 2+ profoundly affects the photophysics of ZnS nanoclusters. Mn 2+ substituted for Zn2+ in the ZnS lattice produced orange emission with lifetimes that were intermediate between those found for micron clusters and smaller nanoclusters. The addition of Mn2+ to the outside of the preformed ZnS nanoclusters showed near-band gap emission in the ultraviolet with even shorter lifetimes. We have also used these Mn2+ doped nanoclusters to fabricate electroluminescent devices. In another set of experiments, the effects of different ions on the photophysics of ZnS nanoclusters was investigated. Depending on the cation, we have been able to produce ZnS nanoclusters that emit in the blue, green, yellow and orange regions of the visible spectrum by incorporating Cu2+, Pb2+ and Mn2+. Quantum dots of CdS have also been prepared using several different stabilizing agents. CdS nanoparticles that have been synthesized using dendrimers as hosts exhibit striking optical and electronic features. Intense blue-green emission is observed when the CdS-dendrimer nanocomposites are formed in methanol and/or acidified methanol solutions. Bright yellow emission is observed when the semiconductor-dendrimer nanocomposites are prepared in water and/or basic methanol solutions. One additional experiment was performed using capping groups to modify the photophysics of CdS. Nanometer-sized CdS were prepared using a series of 4-substituted thiophenols as capping agents. The 4-substituents included both electron-donating and electron-withdrawing groups. We have found that it is possible to turn CdS luminescence off depending on the nature of the capping thiophenol ligand, illustrating that chemical control of the surface of the nanoclusters exerts a profound effect on their optical properties.

  10. Mediation of surface recombination in a II-VI powder by palladium microislands

    NASA Astrophysics Data System (ADS)

    Sahyun, M. R. V.

    1987-04-01

    The recombination mechanisms in a Zn(Cd)S:Ag phosphor powder have been probed by luminescence and flash-photolysis time-resolved dielectric loss techniques. The influence of Pd-microislands chemically deposited thereon, alone, and in conjunction with recombination mediators phenylhydrazine and phenylacetic acid (in xylene solution) on the recombination pathways was studied. The Pd deposit affects recombination by increasing the fraction of the particle volume dominated by the surface processes, by providing a pathway for photoelectrons to reach the (negative) surface to participate in surface recombination, and by providing recombination centers per se. The implications of these results for heterogeneous photocatalysis are discussed.

  11. Fabrication and characterization of II-VI semiconductor nanoparticles decorated electrospun polyacrylonitrile nanofibers.

    PubMed

    Nirmala, R; Jeon, Kyungsoo; Navamathavan, R; Kim, Byoung-Suhk; Khil, Myung-Seob; Kim, Hak Yong

    2013-05-01

    Semiconductor nanoparticles incorporated highly aligned electrospun polyacrylonitrile (PAN) composite nanofibers were obtained via a simple, scalable and low-cost dip coating technique at room temperature. The resultant PAN nanofibers exhibited good incorporation of CdS, ZnS and CoS semiconductor nanoparticles. The detailed characterizations of these composite nanofibers were investigated. The incorporation of semiconductor nanoparticles on the surfaces of PAN nanofibers were confirmed by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy and X-ray diffraction analysis. The current-voltage (I-V) characteristics revealed that the electrical conductivity of these composite nanofibers were higher than that of the pristine PAN nanofibers. Overall, the feasibility of obtaining uniformly dispersed semiconductor nanoparticles on PAN nanofibers can be utilized for the realization of various nanotechnological device applications. PMID:23453708

  12. Luminescence properties of II/VI semiconductor colloidal nanocrystals at collective and single scales

    NASA Astrophysics Data System (ADS)

    Vion, Céline; Barthou, Carlos; Coolen, Laurent; Bennaloul, Paul; Chinh, Vu Duc; Thuy Linh, Pham; Thi Bich, Vu; Thu Nga, Pham; Maître, Agnès

    2009-09-01

    Colloidal nanocrystals are crystalline spheres of semiconductors of a few nanometers, obtained by chemical synthesis. At this size scale, lower than Bohr radius of the exciton, emission properties are dominated by quantum confinement effects and depend crucially on the nanocrystal radius, which can be controlled by adjusting the synthesis parameters. Nanocrystals present high photostability and good quantum efficiency, even at room temperature. Their emission wavelength can be tuned over the whole visible range, making them very attractive solid state light sources which are already used in optoelectronic devices or for biological labeling. The luminescence properties of CdSe colloidal nanocrystals synthesized at the Institute of Materials Science in Hanoi are presented. At collective scale, the emission properties reveal the synthesis quality. Temperature effects from ambient to 4 K on spectra and decay rates will be presented and analyzed in terms of emitting level fine structure. The study of CdSe colloidal quantum dots at the single emitter scale is of great interest as it reveals properties which are hidden by collective studies, such as luminescence "blinking", a random switching from a fluorescent to a non fluorescent state, which is closely related to the crystalline defects of a nanocrystal and its interaction with its environment. We will present the blinking properties of the prepared nanocrystals, and relate them to the nanocrystals synthesis quality and shell quality.

  13. Theoretical studies of II-VI semiconductors, carbon-nitride compounds, fullerenes and nanotubes

    NASA Astrophysics Data System (ADS)

    Cote, Michel

    1998-12-01

    Under the Carl D. Perkins Act Vocational and Applied Technology Act Amendments of 1990, community colleges were mandated to integrate academic and occupational education for all students, though the Act did not specify the ways in which this might be accomplished or set guidelines for compliance. This dissertation offers a rubric by which compliance can be measured---the Domains of Career Preparation---a comprehensive taxonomy of academic and occupational competencies which prepares all students for work and for further education. Applying the Domains and the models of integration identified by Grubb and Kraskouskas (1992), the dissertation reports compliance among a random one-third of the community colleges of each state. In addition, the dissertation examines organizational characteristics and implementation attributes to understand how this federal policy has failed to change local practice. The data reveals that colleges are more likely to adopt isomorphic structures and curriculum than they are to risk the implementation of innovations. The final chapter of the dissertation builds on theories of organizational change and adoption of innovations and describes a research-practice-policy collaborative to foster substantive curricular reform among a select group of colleges, who might then be imitated by their counterparts. The combination of benchmarks and structures for innovation has the potential to expand capacity and will of community college leaders to meet the instructional needs of a highly diverse population.

  14. Development of MBE II-VI Epilayers on GaAs(211)B

    NASA Astrophysics Data System (ADS)

    Jacobs, R. N.; Nozaki, C.; Almeida, L. A.; Jaime-Vasquez, M.; Lennon, C.; Markunas, J. K.; Benson, D.; Smith, P.; Zhao, W. F.; Smith, D. J.; Billman, C.; Arias, J.; Pellegrino, J.

    2012-10-01

    Large-area, low-cost substrates are envisioned for next-generation HgCdTe infrared focal-plane arrays (IRFPA). Si, GaAs, Ge, and InSb have been previously examined as potential candidates. Fabrication of IRFPAs based on these substrates is limited by fundamental materials properties that potentially lead to lower detector performance and operability. Lattice and thermal mismatch between the substrate and epilayer are just two of several material factors that must be considered. We have reviewed these factors in the context of more recent data, and determined it worthwhile to revisit the use of GaAs substrates for epitaxial growth of HgCdTe. Our study starts with an evaluation of the surface quality (epireadiness) of commercially available (211) B-oriented GaAs substrates. Molecular beam epitaxial growth of CdTe buffer layers and subsequent HgCdTe absorber layers are performed in separate vacuum-interconnected chambers. The importance of optimization of the CdTe buffer layer growth for high-quality HgCdTe is detailed through surface morphology and x-ray studies. x-Ray diffraction rocking-curve full-width at half-maximum values as low as 52 arcsec have been obtained. Long-wave infrared Hg1- x Cd x Te ( x = 0.23) has been grown on these buffer layers, producing cross-hatch-dominated surface morphologies, with dislocation densities as low as ˜3 × 106 cm-2. We have also obtained (for optimized layers), 80-K Hall-effect n-type carrier concentration and electron mobility of approximately ~1.5 × 1015 cm-3 and 1 × 105 cm2 V-1 s-1, respectively. Finally, we briefly compare GaAs and Si in light of our preliminary investigation.

  15. High Resolution Triple Axis X-Ray Diffraction Analysis of II-VI Semiconductor Crystals

    NASA Technical Reports Server (NTRS)

    Volz, H. M.; Matyi, R. J.

    1999-01-01

    The objective of this research program is to develop methods of structural analysis based on high resolution triple axis X-ray diffractometry (HRTXD) and to carry out detailed studies of defect distributions in crystals grown in both microgravity and ground-based environments. HRTXD represents a modification of the widely used double axis X-ray rocking curve method for the characterization of grown-in defects in nearly perfect crystals. In a double axis rocking curve experiment, the sample is illuminated by a monochromatic X-ray beam and the diffracted intensity is recorded by a fixed, wide-open detector. The intensity diffracted by the sample is then monitored as the sample is rotated through the Bragg reflection condition. The breadth of the peak, which is often reported as the full angular width at half the maximum intensity (FWHM), is used as an indicator of the amount of defects in the sample. This work has shown that high resolution triple axis X-ray diffraction is an effective tool for characterizing the defect structure in semiconductor crystals, particularly at high defect densities. Additionally, the technique is complimentary to X-ray topography for defect characterization in crystals.

  16. High- and Reproducible-Performance Graphene/II-VI Semiconductor Film Hybrid Photodetectors

    PubMed Central

    Huang, Fan; Jia, Feixiang; Cai, Caoyuan; Xu, Zhihao; Wu, Congjun; Ma, Yang; Fei, Guangtao; Wang, Min

    2016-01-01

    High- and reproducible-performance photodetectors are critical to the development of many technologies, which mainly include one-dimensional (1D) nanostructure based and film based photodetectors. The former suffer from a huge performance variation because the performance is quite sensitive to the synthesis microenvironment of 1D nanostructure. Herein, we show that the graphene/semiconductor film hybrid photodetectors not only possess a high performance but also have a reproducible performance. As a demo, the as-produced graphene/ZnS film hybrid photodetector shows a high responsivity of 1.7 × 107 A/W and a fast response speed of 50 ms, and shows a highly reproducible performance, in terms of narrow distribution of photocurrent (38–65 μA) and response speed (40–60 ms) for 20 devices. Graphene/ZnSe film and graphene/CdSe film hybrid photodetectors fabricated by this method also show a high and reproducible performance. The general method is compatible with the conventional planar process, and would be easily standardized and thus pay a way for the photodetector applications. PMID:27349692

  17. 77 FR 27081 - II-VI, Incorporated, Infrared Optics-Saxonburg Division, Saxonburg, Pennsylvania; Notice of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-05-08

    ... was published in the Federal Register on February 14, 2012 (77 FR 8281). The workers were engaged in employment related to the production of infrared and CO 2 laser optics, and related materials. The initial... experienced a decline in the sales or production of infrared and CO 2 laser optics, and related...

  18. Structural Fluctuations and Thermophysical Properties of Molten II-VI Compounds

    NASA Technical Reports Server (NTRS)

    Su, Ching-Hua; Feth, Shari; Lehoczky, Sandor; Mook, Herb A.; Scripa, Rose; Zhu, Shen

    2001-01-01

    Recently, in support of the microgravity experiment entitled "Crystal Growth of Selected 11-VI Semiconducting Alloys by Directional Solidification," the viscosity of HgZnTe pseudobinary melt was measured using an oscillating-cup viscometer at NASA/Marshall Space Flight Center (MSFC). An unexpected time drift of the measured viscosity, which shows a slow relaxation phenomena at temperatures near the liquidus point, was reproducibly observed. Two sets of data were obtained by cooling the Hg(0.84)Zn(0.16)Te melt from 850 C and stabilizing at temperatures of 790 C, which is just above the liquidus temperature, and stabilizing at temperature of 810 C. While it took one day to reach equilibration at 810 C, five days were required at 790 C A similar relaxation phenomenon was also observed in the measured density of the same liquid. Furthermore, in the density measurements of the HgCdTe melts, which is the pseudobinary system studied in another flight experiment entitled "Growth of Solid Solution Single Crystals," a negative thermal expansion was reported. The liquid density increases from the liquidus point to a maximum value at a temperature approximately 700 C above the liquidus, where normal thermal expansion progressively resumes.

  19. Thermophysical analysis of II-VI semiconductors by PPE calorimetry and lock-in thermography

    SciTech Connect

    Streza, M.; Dadarlat, D.; Strzałkowski, K.

    2013-11-13

    An accurate determination of thermophysical properties such as thermal diffusivity, thermal effusivity and thermal conductivity is extremely important for characterization and quality assurance of semiconductors. Thermal diffusivity and effusivity of some binary semiconductors have been investigated. Two experimental techniques were used: a contact technique (PPE calorimetry) and a non contact technique (lock-in thermography). When working with PPE, in the back (BPPE) configuration and in the thermally thick regim of the pyroelectric sensor, we can get the thermal diffusivity of the sample by performing a scanning of the excitation frequency of radiation. Thermal effusivity is obtained in front configuration (sensor directly irradiated and sample in back position) by performing a thickness scan of a coupling fluid. By using the lock-in thermography technique, the thermal diffusivity of the sample is obtained from the phase image. The results obtained by the two techniques are in good agreement. Nevertheless, for the determination of thermal diffusivity, lock-in thermography is preferred.

  20. Time-resolved optical studies of wide-gap II-VI semiconductor heterostructures

    NASA Astrophysics Data System (ADS)

    Wang, Hong

    ZnSe and ZnSe-based quantum well and superlattice structures are potential candidates for light emitting devices and other optical devices such as switches and modulators working in the blue-green wavelength range. Carrier dynamics studies of these structures are important in evaluating device performance as well as understanding the underlying physical processes. In this thesis, a carrier dynamics investigation is conducted for temperature from 77K to 295K on CdZnSSe/ZnSSe single quantum well structure (SQW) and ZnSe/ZnSTe superlattice fabricated by molecular beam epitaxy (MBE). Two experimental techniques with femtosecond time resolution are used in this work: up-conversion technique for time- resolved photoluminescence (PL) and pump-probe technique for time-resolved differential absorption studies. For both heterostructures, the radiative recombination is dominated by exciton transition due to the large exciton binding energy as a result of quantum confinement effect. The measured decay time of free exciton PL in CdZnSSe/ZnSSe SQW increases linearly with increasing temperature which agrees with the theoretical prediction by considering the conservation of momentum requirement for radiative recombination. However, the recombination of free carriers is also observed in CdZnSSe/ZnSSe SQW for the whole temperature range studied. On the other hand, in ZnSe/ZnSTe superlattice structures, the non- radiative recombination processes are non-negligible even at 77K and become more important in higher temperature range. The relaxation processes such as spectral hole burning, carrier thermalization and hot-carrier cooling are observed in ZnSe/ZnSTe superlattices at room temperature (295K) by the femtosecond pump-probe measurements. A rapid cooling of the thermalized hot- carrier from 763K to 450K within 4ps is deduced. A large optical nonlinearity (i.e., the induced absorption change) around the heavy-hole exciton energy is also obtained.

  1. Recombination dynamics in heterostructures with two planar arrays of II-VI quantum dots

    NASA Astrophysics Data System (ADS)

    Mikhailov, T. N.; Belyaev, K. G.; Toropov, A. A.; Sorokin, S. V.; Pozina, G.; Shubina, T. V.

    2016-08-01

    We present time-resolved photoluminescence studies of epitaxial heterostructures with two arrays of Cd(Zn)Se/ZnSe quantum dots (QDs), which are formed by the successive insertion of CdSe fractional monolayers of different nominal thicknesses into a ZnSe matrix. Our data are suggestive of the appearance of effective channels of the energy transfer from the insertion comprising the array with smaller QDs, emitting at higher energy, towards the array with larger QDs, emitting at lower energy. The effect of dark excitons on characteristic times of radiative recombination is discussed.

  2. Precision of a field method for determination of pH in dilute lakes

    USGS Publications Warehouse

    Turk, J.T.

    1986-01-01

    Replicate pH measurements in three dilute lakes made during extreme conditions indicate that pH can be measured in the field with a variance due to measurement error of 0.005 unit. Error of the field technique in measuring the pH of dilute solutions in the laboratory ranges from less than 0.01 unit in dilute strong-acid solutions to about 0.05 unit in air-saturated deionized water.

  3. Electrical impedance and HV plasma images of high dilutions of sodium chloride.

    PubMed

    Assumpção, R

    2008-07-01

    This paper reports impedance data and high voltage plasma photographic plates of high dilutions of sodium chloride in water submitted to the homeopathic dilution and succession up to 30cH. Extremely low concentrations of the original salt, even beyond Avogadro number, clearly differ from 'pure' water and; the action of sodium chloride on the electrical properties of water is inverted at high dilution.

  4. ON-DEMAND SERIAL DILUTION USING QUANTIZED NANO/PICOLITER-SCALE DROPLETS

    SciTech Connect

    Jambovane, Sachin R.; Prost, Spencer A.; Sheen, Allison M.; Magnuson, Jon K.; Kelly, Ryan T.

    2014-10-29

    This paper describes a fully automated droplet-based microfluidic device for on-demand serial dilution that is capable of achieving a dilution ratio of >6000 (concentration ranges from 1 mM to 160nM) over 35 nanoliter-scale droplets. This serial diluter can be applied to high throughput and label-free kinetic assays by integrating with our previously developed on-demand droplet-based microfluidic with mass spectrometry detection.

  5. Effects of high-temperature diluted-H2 annealing on effective mobility of 4H-SiC MOSFETs with thermally-grown SiO2

    NASA Astrophysics Data System (ADS)

    Hirai, Hirohisa; Kita, Koji

    2016-04-01

    The impact of post-oxidation annealing (POA) in diluted-H2 ambient on a 4H-SiC/SiO2 interface was investigated with a cold wall furnace. Effective mobility (μeff) was extracted from lateral metal-oxide-semiconductor field-effect transistors (MOSFETs) by applying the split capacitance-voltage (C-V) technique to the determination of charge density and a calibration technique using two MOSFETs with different gate lengths to minimize the contribution of parasitic components. POA at 1150 °C in diluted-H2 ambient resulted in an enhancement of μeff compared with that for POA in N2 ambient. It was indicated that the effects of POA in diluted H2 should be attributed to the reduction in the density of near interface traps, which disturb the electron transportation in the inversion channel, from the measurement temperature dependence of μeff as well as from the C-V curves of MOS capacitors fabricated on n-type SiC.

  6. A serial dilution microfluidic device using a ladder network generating logarithmic or linear concentrations.

    PubMed

    Kim, Choong; Lee, Kangsun; Kim, Jong Hyun; Shin, Kyeong Sik; Lee, Kyu-Jung; Kim, Tae Song; Kang, Ji Yoon

    2008-03-01

    In this paper, we propose a serial dilution microfluidic chip which is able to generate logarithmic or linear step-wise concentrations. These concentrations were generated via adjustments in the flow rate of two converging fluids at the channel junctions of the ladder network. The desired dilution ratios are almost independent of the flow rate or diffusion length of molecules, as the dilution device is influenced only by the ratio of volumetric flow rates. Given a set of necessary dilution ratios, whether linear or logarithmic, a serial dilution chip can be constructed via the modification of a microfluidic resistance network. The design principle was suggested and both the logarithmic and linear dilution chips were fabricated in order to verify their performance in accordance with the fluorescence intensity. The diluted concentrations of a fluorescein solution in the microfluidic device evidenced relatively high linearity, and the cytotoxicity test of MCF-7 breast cancer cells via the logarithmic dilution chip was generally consistent with the results generated with manual dilution.

  7. Antimicrobial susceptibility testing of Australian isolates of Brachyspira hyodysenteriae using a new broth dilution method.

    PubMed

    Karlsson, Märit; Oxberry, Sophy L; Hampson, David J

    2002-01-01

    The antimicrobial susceptibilities of 76 field isolates of Brachyspira hyodysenteriae from different states of Australia were tested in a newly developed broth dilution procedure. The antimicrobial agents used were tiamulin, valnemulin, tylosin, erythromycin, lincomycin and clindamycin. The results from the broth dilution susceptibility testing of 39 of the isolates were compared with results obtained for the same isolates using the agar dilution method. Amongst the isolates tested by broth dilution, 17 were from three farms and had been collected over a number of years. Their pulsed field gel electrophoresis pattern previously had been determined. The broth dilution technique was simple to use, less labor intensive than agar dilution, and gave clear end points. The results obtained using the two methods generally corresponded well, although in a few cases the MIC obtained by broth dilution were lower than those with agar dilution. For the 76 isolates tested by broth dilution, the MIC(90) (mg/l) was: tiamulin, 1; valnemulin, 0.5; tylosin>256; erythromycin>256; lincomycin, 64 and clindamycin, 16. Only minor differences in susceptibility patterns were found amongst isolates from different Australian states. Over all the isolates, and also amongst the isolates obtained from different years on the three farms, there was no trend for the susceptibility of the isolates to alter with time. PMID:11731165

  8. Effects of diluting medium and holding time on sperm motility analysis by CASA in ram.

    PubMed

    Mostafapor, Somayeh; Farrokhi Ardebili, Farhad

    2014-01-01

    The aim of this study was to evaluate the effects of dilution rate and holding time on various motility parameters using computer-assisted sperm analysis (CASA). The semen samples were collected from three Ghezel rams. Samples were diluted in seminal plasma (SP), phosphate-buffered saline (PBS) containing 1% bovine serum albumin (BSA) and Bioexcell. The motility parameters that computed and recorded by CASA include curvilinear velocity (VCL), straight line velocity (VSL), average path velocity (VAP), straightness (STR), linearity (LIN), amplitude of lateral head displacement (ALH), and beat cross frequency (BCF). In all diluters, there was a decrease in the average of all three parameters of sperms movement velocity as the time passed, but density of this decrease was more intensive in SP. The average of ALH between diluters indicated a significant difference, as it was more in Bioexcell in comparison with the similar amount in SP and PBS. The average of LIN in the diluted sperms in Bioexcell was less than two other diluters in all three times. The motility parameters of the diluted sperms in Bioexcell and PBS indicated an important and considerable difference with the diluted sperms in SP. According to the gained results, the Bioexcell has greater ability in preserving motility of sperm in comparison with the other diluters but as SP is considered as physiological environment for sperm. It seems that the evaluation of the motility parameters in Bioexcell and PBS cannot be an accurate and comparable evaluation with SP.

  9. Temperature imaging of turbulent dilute spray flames using two-line atomic fluorescence

    NASA Astrophysics Data System (ADS)

    Medwell, Paul R.; Masri, Assaad R.; Pham, Phuong X.; Dally, Bassam B.; Nathan, Graham J.

    2014-11-01

    This paper reports the first application of nonlinear excitation regime two-line atomic fluorescence imaging (NTLAF) of indium to measure temperature in turbulent flames of dilute sprays. Indium chloride is dissolved in acetone fuel which is atomised with an ultrasonic nebuliser and supplied with carrier air into a standard piloted burner. It is found that the indium fluorescence signal is not affected by scattering from the droplets or fuel vapour and that no changes to the optical arrangement used with gaseous flames were required. Notwithstanding the lower temperature thresholds of 800 K imposed by the population of excitation species for the NTLAF method and of 1,200 K imposed by the mechanism of releasing gas-phase indium from its salt, the comparisons of conditional and pseudo-unconditional means with thermocouple measurements performed in a range of turbulent spray flames are quite favourable. The NTLAF signal quality deteriorates on the jet centreline at upstream locations and on the lean side of the flame, the former being largely due to insufficient conversion of indium chloride to indium atoms and the latter potentially due to indium oxidation. Nevertheless, the signal-to-noise ratios obtained in the reaction zone regions are good and the results reveal the expected temperature trends in the turbulent spray flames tested here. Further developments are necessary to resolve the mechanism of indium formation and to broaden the temperature range.

  10. Tuning oxygen impurities and microstructure of nanocrystalline silicon photovoltaic materials through hydrogen dilution

    PubMed Central

    2014-01-01

    As a great promising material for third-generation thin-film photovoltaic cells, hydrogenated nanocrystalline silicon (nc-Si:H) thin films have a complex mixed-phase structure, which determines its defectful nature and easy residing of oxygen impurities. We have performed a detailed investigation on the microstructure properties and oxygen impurities in the nc-Si:H thin films prepared under different hydrogen dilution ratio treatment by the plasma-enhanced chemical vapor deposition (PECVD) process. X-ray diffraction, transmission electron microscopy, Raman spectroscopy, and optical transmission spectroscopy have been utilized to fully characterize the microstructure properties of the nc-Si:H films. The oxygen and hydrogen contents have been obtained from infrared absorption spectroscopy. And the configuration state of oxygen impurities on the surface of the films has been confirmed by X-ray photoelectron spectroscopy, indicating that the films were well oxidized in the form of SiO2. The correlation between the hydrogen content and the volume fraction of grain boundaries derived from the Raman measurements shows that the majority of the incorporated hydrogen is localized inside the grain boundaries. Furthermore, with the detailed information on the bonding configurations acquired from the infrared absorption spectroscopy, a full explanation has been provided for the mechanism of the varying microstructure evolution and oxygen impurities based on the two models of ion bombardment effect and hydrogen-induced annealing effect. PMID:24994958

  11. Turbulent Flame Speeds and NOx Kinetics of HHC Fuels with Contaminants and High Dilution Levels

    SciTech Connect

    Peterson, Eric; Krejci, Michael; Mathieu, Olivier; Vissotski, Andrew; Ravi, Sankat; Plichta, Drew; Sikes, Travis; Levacque, Anthony; Camou, Alejandro; Aul, Christopher

    2014-01-24

    This final report documents the technical results of the 3-year project entitled, “Turbulent Flame Speeds and NOx Kinetics of HHC Fuels with Contaminants and High Dilution Levels,” funded under the NETL of DOE. The research was conducted under six main tasks: 1) program management and planning; 2) turbulent flame speed measurements of syngas mixtures; 3) laminar flame speed measurements with diluents; 4) NOx mechanism validation experiments; 5) fundamental NOx kinetics; and 6) the effect of impurities on NOx kinetics. Experiments were performed using primary constant-volume vessels for laminar and turbulent flame speeds and shock tubes for ignition delay times and species concentrations. In addition to the existing shock- tube and flame speed facilities, a new capability in measuring turbulent flame speeds was developed under this grant. Other highlights include an improved NOx kinetics mechanism; a database on syngas blends for real fuel mixtures with and without impurities; an improved hydrogen sulfide mechanism; an improved ammonia kintics mechanism; laminar flame speed data at high pressures with water addition; and the development of an inexpensive absorption spectroscopy diagnostic for shock-tube measurements of OH time histories. The Project Results for this work can be divided into 13 major sections, which form the basis of this report. These 13 topics are divided into the five areas: 1) laminar flame speeds; 2) Nitrogen Oxide and Ammonia chemical kinetics; 3) syngas impurities chemical kinetics; 4) turbulent flame speeds; and 5) OH absorption measurements for chemical kinetics.

  12. Application of Uranium Isotope Dilution Mass Spectrometry in the preparation of New Certified Reference Materials

    NASA Astrophysics Data System (ADS)

    Hasözbek, A.; Mathew, K. J.; Orlowicz, G.; Srinivasan, B.; Narayanan, U.

    2012-04-01

    Proven measurement techniques play a critical role in the preparation of Certified Reference Materials (CRMs) - those requiring high accuracy and precision in the measurement results. Isotope Dilution Mass Spectrometry (IDMS) is one such measurement method commonly used in the quantitative analysis of uranium in nuclear safeguards and isotope geology applications. In this project, we evaluated the possibility of using some of the uranium isotopic and assay CRMs made earlier by the New Brunswick laboratory as IDMS spikes to define the uranium mass fraction in future preparations of CRMs. Uranium solutions prepared from CRM 112-A (a highly pure uranium metal assay standard) and CRM 115 (a highly pure uranium oxide isotopic and assay standard) were used as spikes in the determination of uranium. Two different thermal ionization mass spectrometer instruments (MAT 261 and TRITON) were used for the isotopic measurements. Standard IDMS equation was used for data reduction to yield results for uranium mass fraction along with uncertainties, the latter calculated according to GUM. The results show that uranium mass fraction measurements can be made with the required accuracy and precision for defining the uranium concentration in new CRMs as well as in routine samples analyses.

  13. A liver stress-endocrine nexus promotes metabolic integrity during dietary protein dilution.

    PubMed

    Maida, Adriano; Zota, Annika; Sjøberg, Kim A; Schumacher, Jonas; Sijmonsma, Tjeerd P; Pfenninger, Anja; Christensen, Marie M; Gantert, Thomas; Fuhrmeister, Jessica; Rothermel, Ulrike; Schmoll, Dieter; Heikenwälder, Mathias; Iovanna, Juan L; Stemmer, Kerstin; Kiens, Bente; Herzig, Stephan; Rose, Adam J

    2016-09-01

    Dietary protein intake is linked to an increased incidence of type 2 diabetes (T2D). Although dietary protein dilution (DPD) can slow the progression of some aging-related disorders, whether this strategy affects the development and risk for obesity-associated metabolic disease such as T2D is unclear. Here, we determined that DPD in mice and humans increases serum markers of metabolic health. In lean mice, DPD promoted metabolic inefficiency by increasing carbohydrate and fat oxidation. In nutritional and polygenic murine models of obesity, DPD prevented and curtailed the development of impaired glucose homeostasis independently of obesity and food intake. DPD-mediated metabolic inefficiency and improvement of glucose homeostasis were independent of uncoupling protein 1 (UCP1), but required expression of liver-derived fibroblast growth factor 21 (FGF21) in both lean and obese mice. FGF21 expression and secretion as well as the associated metabolic remodeling induced by DPD also required induction of liver-integrated stress response-driven nuclear protein 1 (NUPR1). Insufficiency of select nonessential amino acids (NEAAs) was necessary and adequate for NUPR1 and subsequent FGF21 induction and secretion in hepatocytes in vitro and in vivo. Taken together, these data indicate that DPD promotes improved glucose homeostasis through an NEAA insufficiency-induced liver NUPR1/FGF21 axis. PMID:27548521

  14. Emerging Diluted Ferromagnetism in High‐T c Superconductors Driven by Point Defect Clusters

    PubMed Central

    Guzman, Roger.; Mishra, Rohan; Bartolomé, Elena; Salafranca, Juan; Magén, Cesar; Varela, Maria; Coll, Mariona; Palau, Anna; Valvidares, S. Manuel; Gargiani, Pierluigi; Pellegrin, Eric; Herrero‐Martin, Javier.; Pennycook, Stephen J.; Pantelides, Sokrates T.; Puig, Teresa; Obradors, Xavier

    2016-01-01

    Defects in ceramic materials are generally seen as detrimental to their functionality and applicability. Yet, in some complex oxides, defects present an opportunity to enhance some of their properties or even lead to the discovery of exciting physics, particularly in the presence of strong correlations. A paradigmatic case is the high‐temperature superconductor YBa2Cu3O7‐δ (Y123), in which nanoscale defects play an important role as they can immobilize quantized magnetic flux vortices. Here previously unforeseen point defects buried in Y123 thin films that lead to the formation of ferromagnetic clusters embedded within the superconductor are unveiled. Aberration‐corrected scanning transmission microscopy has been used for exploring, on a single unit‐cell level, the structure and chemistry resulting from these complex point defects, along with density functional theory calculations, for providing new insights about their nature including an unexpected defect‐driven ferromagnetism, and X‐ray magnetic circular dichroism for bearing evidence of Cu magnetic moments that align ferromagnetically even below the superconducting critical temperature to form a dilute system of magnetic clusters associated with the point defects. PMID:27812469

  15. Soot surface temperature measurements in pure and diluted flames at atmospheric and elevated pressures

    SciTech Connect

    Berry Yelverton, T.L.; Roberts, W.L.

    2008-10-15

    Soot surface temperature was measured in laminar jet diffusion flames at atmospheric and elevated pressures. The soot surface temperature was measured in flames at one, two, four, and eight atmospheres with both pure and diluted (using helium, argon, nitrogen, or carbon dioxide individually) ethylene fuels with a calibrated two-color soot pyrometry technique. These two dimensional temperature profiles of the soot aid in the analysis and understanding of soot production, leading to possible methods for reducing soot emission. Each flame investigated was at its smoke point, i.e., at the fuel flow rate where the overall soot production and oxidation rates are equal. The smoke point was chosen because it was desirable to have similar soot loadings for each flame. A second set of measurements were also taken where the fuel flow rate was held constant to compare with earlier work. These measurements show that overall flame temperature decreases with increasing pressure, with increasing pressure the position of peak temperature shifts to the tip of the flame, and the temperatures measured were approximately 10% lower than those calculated assuming equilibrium and neglecting radiation. (author)

  16. A thermodynamic assessment of the potential synthesis of condensed hydrocarbons during cooling and dilution of volcanic gases.

    PubMed

    Zolotov, M Y; Shock, E L

    2000-01-10

    The possibility for abiotic synthesis of condensed hydrocarbons in cooling/diluting terrestrial volcanic gases has been evaluated on the basis of the consideration of metastable chemical equilibria involving gaseous CO, CO2, H2 and H2O. The stabilities of n-alkanes and polycyclic aromatic hydrocarbons (PAHS) have been evaluated for several typical volcanic gas compositions under various conditions for cooling/diluting of quenched volcanic gas. The modeling shows that n-alkanes and PAHs have a thermodynamic potential to form metastably from H2 and CO below approximately 250 degrees C within the stability field of graphite. Despite the predominance of CO2 in volcanic gases, synthesis of hydrocarbons from CO2 and H2 is less favored energetically than from CO and H2. Both low temperature and a high H/C atomic ratio in volcanic gas generally favor stability of hydrocarbons with higher H/C ratios. PAHs are thermodynamically stable at temperatures approximately 10 degrees -50 degrees C higher than large n-alkanes; however, at lower temperatures, PAHs and n-alkanes have similar stabilities and are likely to form metastable mixtures. Both the energetic drive to form hydrocarbons and possible temperatures of formation increase as the oxidation state (fO2) of the volcanic gases decreases and as the cooling/dilution ratios of volcanic gases increase. Synthesis of hydrocarbons is energetically more likely in cooling trapped gases than in ashcloud eruptive columns. Mechanisms for hydrocarbon formation may include Fischer-Tropsch-type synthesis catalyzed by magnetite from solid volcanic products. On the early Earth, Mars, and Jupiter's satellite Europa, several factors would have provided more favorable conditions for hydrocarbon synthesis in volcanic gases than under current terrestrial conditions and might have contributed to the production of organic compounds required for the emergence of life.

  17. Mitochondrial DNA as a non-invasive biomarker: Accurate quantification using real time quantitative PCR without co-amplification of pseudogenes and dilution bias

    SciTech Connect

    Malik, Afshan N.; Shahni, Rojeen; Rodriguez-de-Ledesma, Ana; Laftah, Abas; Cunningham, Phil

    2011-08-19

    Highlights: {yields} Mitochondrial dysfunction is central to many diseases of oxidative stress. {yields} 95% of the mitochondrial genome is duplicated in the nuclear genome. {yields} Dilution of untreated genomic DNA leads to dilution bias. {yields} Unique primers and template pretreatment are needed to accurately measure mitochondrial DNA content. -- Abstract: Circulating mitochondrial DNA (MtDNA) is a potential non-invasive biomarker of cellular mitochondrial dysfunction, the latter known to be central to a wide range of human diseases. Changes in MtDNA are usually determined by quantification of MtDNA relative to nuclear DNA (Mt/N) using real time quantitative PCR. We propose that the methodology for measuring Mt/N needs to be improved and we have identified that current methods have at least one of the following three problems: (1) As much of the mitochondrial genome is duplicated in the nuclear genome, many commonly used MtDNA primers co-amplify homologous pseudogenes found in the nuclear genome; (2) use of regions from genes such as {beta}-actin and 18S rRNA which are repetitive and/or highly variable for qPCR of the nuclear genome leads to errors; and (3) the size difference of mitochondrial and nuclear genomes cause a 'dilution bias' when template DNA is diluted. We describe a PCR-based method using unique regions in the human mitochondrial genome not duplicated in the nuclear genome; unique single copy region in the nuclear genome and template treatment to remove dilution bias, to accurately quantify MtDNA from human samples.

  18. Heat Transfer in Boiling Dilute Emulsion with Strong Buoyancy

    NASA Astrophysics Data System (ADS)

    Freeburg, Eric Thomas

    Little attention has been given to the boiling of emulsions compared to that of boiling in pure liquids. The advantages of using emulsions as a heat transfer agent were first discovered in the 1970s and several interesting features have since been studied by few researchers. Early research focuses primarily on pool and flow boiling and looks to determine a mechanism by which the boiling process occurs. This thesis looks at the boiling of dilute emulsions in fluids with strong buoyant forces. The boiling of dilute emulsions presents many favorable characteristics that make it an ideal agent for heat transfer. High heat flux electronics, such as those seen in avionics equipment, produce high heat fluxes of 100 W/cm2 or more, but must be maintained at low temperatures. So far, research on single phase convection and flow boiling in small diameter channels have yet to provide an adequate solution. Emulsions allow the engineer to tailor the solution to the specific problem. The fluid can be customized to retain the high thermal conductivity and specific heat capacity of the continuous phase while enhancing the heat transfer coefficient through boiling of the dispersed phase component. Heat transfer experiments were carried out with FC-72 in water emulsions. FC-72 has a saturation temperature of 56 °C, far below that of water. The parameters were varied as follows: 0% ≤ epsilon ≤ 1% and 1.82 x 1012 ≤ RaH ≤ 4.42 x 1012. Surface temperatures along the heated surface reached temperature that were 20 °C in excess of the dispersed phase saturation temperature. An increase of ˜20% was seen in the average Nusselt numbers at the highest Rayleigh numbers. Holography was used to obtain images of individual and multiple FC-72 droplets in the boundary layer next to the heated surface. The droplet diameters ranged from 0.5 mm to 1.3 mm. The Magnus effect was observed when larger individual droplets were injected into the boundary layer, causing the droplets to be pushed

  19. Fast and accurate procedure for the determination of Cr(VI) in solid samples by isotope dilution mass spectrometry.

    PubMed

    Fabregat-Cabello, Neus; Rodríguez-González, Pablo; Castillo, Ángel; Malherbe, Julien; Roig-Navarro, Antoni F; Long, Stephen E; García Alonso, J Ignacio

    2012-11-20

    We present here a new environmental measurement method for the rapid extraction and accurate quantification of Cr(VI) in solid samples. The quantitative extraction of Cr(VI) is achieved in 10 minutes by means of focused microwave assisted extraction using 50 mmol/L Ethylendiamintetraacetic acid (EDTA) at pH 10 as extractant. In addition, it enables the separation of Cr species by anion exchange chromatography using a mobile phase which is a 1:10 dilution of the extracting solution. Thus, neutralization or acidification steps which are prone to cause interconversion of Cr species are not needed. Another benefit of using EDTA is that it allows to measure Cr(III)-EDTA complex and Cr(VI) simultaneously in an alkaline extraction solution. The application of a 10 minutes focused microwave assisted extraction (5 min at 90 °C plus 5 min at 110 °C) has been shown to quantitatively extract all forms of hexavalent chromium from the standard reference materials (SRM) candidate NIST 2700 and NIST 2701. A double spike isotope dilution mass spectrometry (IDMS) procedure was employed to study chromium interconversion reactions. It was observed that the formation of a Cr(III)-EDTA complex avoided Cr(III) oxidation for these two reference materials. Thus, the use of a double spiking strategy for quantification is not required and a single spike IDMS procedure using isotopically enriched Cr(VI) provided accurate results.

  20. Defect-induced magnetism: Test of dilute magnetism in Fe-doped hexagonal BaTiO3 single crystals

    NASA Astrophysics Data System (ADS)

    Chakraborty, Tanushree; Ray, Sugata; Itoh, Mitsuru

    2011-04-01

    Single crystalline Fe-doped hexagonal BaTiO3 samples with varying oxygen content are created by specifically intended post-growth annealing treatments, in order to check the influence of defects on the unusual high temperature ferromagnetism observed in this system. The various defects have been shown to play a crucial role in dilute magnetic systems and therefore, it is important to carry out this check for the Fe-doped BaTiO3 system also, in which unusual ferromagnetism was reported even in its bulk single crystalline form. The x-ray diffraction and dielectric studies carried out here have confirmed that the Fe doping of Ti is intrinsic, while the high resolution transmission electron microscopy (HRTEM) and x-ray photoemission spectroscopy (XPS) studies proved the absence of unwanted magnetic metal clusters in the sample. The transport studies show that the oxygen concentrations could be varied substantially by the thermal treatments. Finally, magnetization measurements on the samples demonstrated that ferromagnetism is stronger in samples with higher oxygen deficiency, which could interestingly be retreated under high oxygen atmosphere and reversibly be taken back to a lower magnetic state. The vacancy-induced ferromagnetism is further confirmed by EPR measurements, which is consistent with earlier studies and, consequently, put the doped BaTiO3 in the list of true dilute magnetic oxide (DMO) systems.

  1. Particle model analyses of N2O dilution with He on electrical characteristics of radio-frequency discharges

    NASA Astrophysics Data System (ADS)

    Younis, G.; Yousfi, M.; Despax, B.

    2009-05-01

    The electrical characteristics (voltage, electric field, charged particle densities, dissipated power, particle energy, etc.) are analyzed in the case of low pressure (0.5 and 1 Torr) radio-frequency (rf) discharges in nitrous oxide (N2O)/Helium (He) mixtures. An optimized and validated particle model has been used for these analyses in the case of gradual dilutions of N2O with He buffer gas. A specific care is carried on the power density evolution and variation which show a complex behavior as a function of He proportion (up to 85%). These analyses are based on a microscopic approach enabling one to show the contribution of the different inelastic processes mainly between electrons and respectively N2O and He gases. This approach enables also one to show the discharge region (the positive column or the plasma region) where the power is preferentially dissipated. The power density variation is found to be mainly proportional to the electron density variation. The latter is dependent on the different processes occurring between the charged particles [i.e., electrons, negative ions (O- and NO-), and positive ions (N2O+ and He+)] and the neutral gas mixture (N2O and He). Furthermore, the particle model shows the role of the electron-He collisions on the variation in the electron energy and distribution. This allows more particularly explaining the effects of N2O dilution with He on the dissipated power variation in terms of creation and loss of electrons through collision processes.

  2. Estimating lean mass over a wide range of body composition: a calibration of deuterium dilution in the arctic ground squirrel.

    PubMed

    Lee, Trixie N; Fridinger, Robert W; Barnes, Brian M; Loren Buck, C; O'Brien, Diane M

    2011-12-15

    Calculating body water through isotope dilution has become a useful way to nondestructively estimate body composition in many species. The most accurate estimates using this method require calibration against proximate chemical analysis of body composition for individual species, but no studies to our knowledge have calibrated this method on a hibernating mammal that seasonally undergoes dramatic changes in body composition. We use deuterium oxide to estimate total body water in captive arctic ground squirrels, Urocitellus parryii, and compare two approaches of calculating lean mass from total body water, both calibrated against lean mass based on proximate analysis. The first method uses a single tissue hydration constant to calculate lean mass from total body water; the second method uses a predictive equation to calculate lean mass from total body water and body mass. We found that the predictive equation performs better over the large range of body composition common to this species. Distillation of blood samples did not affect lean mass estimates from either calculation method. These findings indicate that isotope dilution using a predictive equation should work well as an alternative to destructive methods in other small mammals that undergo radical changes in body composition across their annual cycle.

  3. Glass transition of adsorbed stereoregular PPMA by inverse gas chromatography at infinite dilution

    NASA Astrophysics Data System (ADS)

    Hamieh, T.; Rezzaki, M.; Grohens, Y.; Schultz, J.

    1998-10-01

    In this paper, we used inverse gas chromatography (IGC) at infinite dilution that proved to be a powerful technique to determine glass transition and other transitions of PMMA adsorbed on α-alumina. We highlighted the glass transition temperature of the system PMMA/α-Al2O3 with defined polymer tacticity at various covered surface fractions. Thus, the Tg of the adsorbed isotactic PMMA increases strongly as compared to the bulk value. The study of the physical chemical properties of PMMA/α-alumina revealed an important difference in the acidic and basic behaviour, in Lewis terms, of aluminium oxide covered by various concentrations of PMMA. It appears that there is a stabilisation of the physical chemical properties of PMMA/α-Al2O3 for a surface coverage above 50%. This study also highlighted an important effect of the tacticity of the polymer on the acid-base character of the system PMMA/Al2O3. Dans cet article, nous montrons que la chromatographie gazeuse inverse (CGI) à dilution infinie se révèle être une technique très intéressante pour la détermination de la transition vitreuse de polymères stéréoréguliers adsorbés sur des substrats solides tels que l'alumine. Nous avons mis en évidence des transitions attribuées aux phénomènes de relaxation béta, transition vitreuse et autres transitions des systèmes PMMA/Al2O3 de tacticité définie à différents taux de recouvrement. Ainsi, la Tg du PMMA isotactique adsorbé augmente de façon significative par rapport a celle du polymère massique. L'étude des propriétés physico-chimiques du système PMMA/Al2O3, révèle une différence importante dans le comportement acido-basique, au sens de Lewis, de l'alumine pour de taux de recouvrement en PMMA variables. Il apparaît qu'il y a stabilisation des propriétés physico-chimiques de PMMA/Al2O3 pour un taux de recouvrement en PMMA supérieur à 50 %. Cette étude a montré également une influence importante de la tacticité du polymère sur le

  4. Uniform Doping in Quantum-Dots-Based Dilute Magnetic Semiconductor.

    PubMed

    Saha, Avijit; Shetty, Amitha; Pavan, A R; Chattopadhyay, Soma; Shibata, Tomohiro; Viswanatha, Ranjani

    2016-07-01

    Effective manipulation of magnetic spin within a semiconductor leading to a search for ferromagnets with semiconducting properties has evolved into an important field of dilute magnetic semiconductors (DMS). Although a lot of research is focused on understanding the still controversial origin of magnetism, efforts are also underway to develop new materials with higher magnetic temperatures for spintronics applications. However, so far, efforts toward quantum-dots(QDs)-based DMS materials are plagued with problems of phase separation, leading to nonuniform distribution of dopant ions. In this work, we have developed a strategy to synthesize highly crystalline, single-domain DMS system starting from a small magnetic core and allowing it to diffuse uniformly inside a thick CdS semiconductor matrix and achieve DMS QDs. X-ray absorption fine structure (XAFS) spectroscopy and energy-dispersive X-ray spectroscopy-scanning transmission electron microscopy (STEM-EDX) indicates the homogeneous distribution of magnetic impurities inside the semiconductor QDs leading to superior magnetic property. Further, the versatility of this technique was demonstrated by obtaining ultra large particles (∼60 nm) with uniform doping concentration as well as demonstrating the high quality magnetic response. PMID:27295453

  5. Breakdown of hierarchical architecture in cellulose during dilute acid pretreatments

    SciTech Connect

    Zhang, Yan; Inouye, Hideyo; Yang, Lin; Himmel, Michael E.; Tucker, Melvin; Makowski, Lee

    2015-02-28

    Cellulose can work as a feedstock for sustainable bioenergy because of its global abundance. Pretreatment of biomass has significant influence on the chemical availability of cellulose locked in recalcitrant microfibrils. Optimizing pretreatment depends on an understanding of its impact on the microscale and nanoscale molecular architecture. X-ray scattering experiments have been performed on native and pre-treated maize stover and models of cellulose architecture have been derived from these data. Ultra small-angle, very small-angle and small-angle X-ray scattering (USAXS, VSAXS and SAXS) probe three different levels of architectural scale. USAXS and SAXS have been used to study cellulose at two distinct length scales, modeling the fibrils as ~30 Å diameter rods packed into ~0.14 μm diameter bundles. VSAXS is sensitive to structural features at length scales between these two extremes. Detailed analysis of diffraction patterns from untreated and pretreated maize using cylindrical Guinier plots and the derivatives of these plots reveals the presence of substructures within the ~0.14 μm diameter bundles that correspond to grouping of cellulose approximately 30 nm in diameter. These sub-structures are resilient to dilute acid pretreatments but are sensitive to pretreatment when iron sulfate is added. Our results provide evidence of the hierarchical arrangement of cellulose at three length scales and the evolution of these arrangements during pre-treatments.

  6. Magnetoviscosity in dilute ferrofluids from rotational brownian dynamics simulations.

    PubMed

    Soto-Aquino, D; Rinaldi, C

    2010-10-01

    Ferrofluids are suspensions of magnetic nanoparticles which respond to imposed magnetic fields by changing their viscosity without losing their fluidity. Prior work on modeling the behavior of ferrofluids has focused on using phenomenological suspension-scale continuum equations. A disadvantage of this approach is the controversy surrounding the equation describing the rate of change of the ferrofluid magnetization, the so-called magnetization relaxation equation. In this contribution the viscosity of dilute suspensions of spherical magnetic nanoparticles suspended in a Newtonian fluid and under applied shear and constant magnetic fields is studied through rotational brownian dynamics simulations. Simulation results are compared with the predictions of suspension-scale models based on three magnetization relaxation equations. Excellent agreement is observed between simulation results and the predictions of an equation due to Martsenyuk, Raikher, and Shliomis. Good qualitative agreement is observed with predictions of other equations, although these models fail to accurately predict the magnitude and shear rate dependence of the magnetic-field-dependent effective viscosity. Finally, simulation results over a wide range of conditions are collapsed into master curves using a Mason number defined based on the balance of hydrodynamic and magnetic torques. PMID:21230393

  7. Multifractality in dilute magnetorheological fluids under an oscillating magnetic field.

    PubMed

    Moctezuma, R E; Arauz-Lara, J L; Donado, F

    2014-12-01

    A study of the multifractal characteristics of the structure formed by magnetic particles in a dilute magnetorheological fluid is presented. A quasi-two-dimensional magnetorheological fluid sample is simultaneously subjected to a static magnetic field and a sinusoidal magnetic field transverse to each other. We analyzed the singularity spectrum f(α) and the generalized dimension D(q) of the whole structure to characterize the distribution of the aggregates under several conditions of particle concentration, magnetic field intensities, and liquid viscosity. We also obtained the fractal dimension D(g), calculated from the radius of gyration of the chains, to describe the internal distribution of the particles. We present a thermodynamic interpretation of the multifractal analysis, and based on this, we discussed the characteristics of the structure formed by the particles and its relation with previous studies of the average chain length. We have found that this method is useful to quantitatively describe the structure of magnetorheological fluids, especially in systems with high particle concentration where the aggregates are more complex than simple chains or columns. PMID:25615089

  8. Nonequilibrium thermodynamics of dilute polymer solutions in flow

    SciTech Connect

    Latinwo, Folarin; Hsiao, Kai-Wen; Schroeder, Charles M.

    2014-11-07

    Modern materials processing applications and technologies often occur far from equilibrium. To this end, the processing of complex materials such as polymer melts and nanocomposites generally occurs under strong deformations and flows, conditions under which equilibrium thermodynamics does not apply. As a result, the ability to determine the nonequilibrium thermodynamic properties of polymeric materials from measurable quantities such as heat and work is a major challenge in the field. Here, we use work relations to show that nonequilibrium thermodynamic quantities such as free energy and entropy can be determined for dilute polymer solutions in flow. In this way, we determine the thermodynamic properties of DNA molecules in strong flows using a combination of simulations, kinetic theory, and single molecule experiments. We show that it is possible to calculate polymer relaxation timescales purely from polymer stretching dynamics in flow. We further observe a thermodynamic equivalence between nonequilibrium and equilibrium steady-states for polymeric systems. In this way, our results provide an improved understanding of the energetics of flowing polymer solutions.

  9. Dilutional Control of Prothrombin Activation at Physiologically Relevant Shear Rates

    PubMed Central

    Haynes, Laura M.; Dubief, Yves C.; Orfeo, Thomas; Mann, Kenneth G.

    2011-01-01

    The generation of proteolyzed prothrombin species by preassembled prothrombinase in phospholipid-coated glass capillaries was studied at physiologic shear rates (100–1000 s−1). The concentration of active thrombin species (α-thrombin and meizothrombin) reaches a steady state, which varies inversely with shear rate. When corrected for shear rate, steady-state levels of active thrombin species exhibit no variation and a Michaelis-Menten analysis reveals that chemistry of this reaction is invariant between open and closed systems; collectively, these data imply that variations with shear rate arise from dilutional effects. Significantly, the major products observed include nonreactive species arising from the loss of prothrombin's phospholipid binding domain (des F1 species). A numerical model developed to investigate the spatial and temporal distribution of active thrombin species within the capillary reasonably approximates the observed output of total thrombin species at different shears; it also predicts concentrations of active thrombin species in the wall region sufficient to account for observed levels of des FI species. The predominant feedback formation of nonreactive species and high levels of the primarily anticoagulant intermediate meizothrombin (∼40% of total active thrombin species) may provide a mechanism to prevent thrombus propagation downstream of a site of thrombosis or hemorrhage. PMID:21281592

  10. Automated spike preparation system for Isotope Dilution Mass Spectrometry (IDMS)

    SciTech Connect

    Maxwell, S.L. III; Clark, J.P.

    1990-12-31

    Isotope Dilution Mass Spectrometry (IDMS) is a method frequently employed to measure dissolved, irradiated nuclear materials. A known quantity of a unique isotope of the element to be measured (referred to as the ``spike``) is added to the solution containing the analyte. The resulting solution is chemically purified then analyzed by mass spectrometry. By measuring the magnitude of the response for each isotope and the response for the ``unique spike`` then relating this to the known quantity of the ``spike``, the quantity of the nuclear material can be determined. An automated spike preparation system was developed at the Savannah River Site (SRS) to dispense spikes for use in IDMS analytical methods. Prior to this development, technicians weighed each individual spike manually to achieve the accuracy required. This procedure was time-consuming and subjected the master stock solution to evaporation. The new system employs a high precision SMI Model 300 Unipump dispenser interfaced with an electronic balance and a portable Epson HX-20 notebook computer to automate spike preparation.

  11. Automated spike preparation system for Isotope Dilution Mass Spectrometry (IDMS)

    SciTech Connect

    Maxwell, S.L. III; Clark, J.P.

    1990-01-01

    Isotope Dilution Mass Spectrometry (IDMS) is a method frequently employed to measure dissolved, irradiated nuclear materials. A known quantity of a unique isotope of the element to be measured (referred to as the spike'') is added to the solution containing the analyte. The resulting solution is chemically purified then analyzed by mass spectrometry. By measuring the magnitude of the response for each isotope and the response for the unique spike'' then relating this to the known quantity of the spike'', the quantity of the nuclear material can be determined. An automated spike preparation system was developed at the Savannah River Site (SRS) to dispense spikes for use in IDMS analytical methods. Prior to this development, technicians weighed each individual spike manually to achieve the accuracy required. This procedure was time-consuming and subjected the master stock solution to evaporation. The new system employs a high precision SMI Model 300 Unipump dispenser interfaced with an electronic balance and a portable Epson HX-20 notebook computer to automate spike preparation.

  12. Efficiency dilution: long-term exergy conversion trends in Japan.

    PubMed

    Williams, Eric; Warr, Benjamin; Ayres, Robert U

    2008-07-01

    This analysis characterizes century-scale trends in exergy efficiency in Japan. Exergy efficiency captures the degree to which energy inputs (such as coal) are converted into useful work (such as electricity or power to move a vehicle). This approach enables the estimation of net efficiencies which aggregate different technologies. Sectors specifically analyzed are electricity generation, transport, steel production, and residential space heating. One result is that the aggregate exergy efficiency of the Japanese economy declined slightly over the last half of the 20th century, reaching a high of around 38% in the late 1970s and falling to around 33% by 1998. The explanation for this is that while individual technologies improved dramatically over the century, less exergy-efficient ones were progressively adopted, yielding a net stabilization or decline. In the electricity sector, for instance, adoption of hydropower was followed by fossil-fired plants and then by nuclear power, each technology being successively less efficient from an exergy perspective. The underlying dynamic of this trend is analogous to declining ore grades in the mining sector. Increasing demand for exergy services requires expended utilization of resources from which it is more difficult to extract utility (e.g., falling water versus coal). We term this phenomenon efficiency dilution. PMID:18678034

  13. Conformation of ionizable poly Para phenylene ethynylene in dilute solutions

    DOE PAGES

    Wijesinghe, Sidath; Maskey, Sabina; Perahia, Dvora; Grest, Gary S.

    2015-11-03

    The conformation of dinonyl poly para phenylene ethynylenes (PPEs) with carboxylate side chains, equilibrated in solvents of different quality is studied using molecular dynamics simulations. PPEs are of interest because of their tunable electro-optical properties, chemical diversity, and functionality which are essential in wide range of applications. The polymer conformation determines the conjugation length and their assembly mode and affects electro-optical properties which are critical in their current and potential uses. The current study investigates the effect of carboxylate fraction on PPEs side chains on the conformation of chains in the dilute limit, in solvents of different quality. The dinonylmore » PPE chains are modeled atomistically, where the solvents are modeled both implicitly and explicitly. Dinonyl PPEs maintained a stretched out conformation up to a carboxylate fraction f of 0.7 in all solvents studied. The nonyl side chains are extended and oriented away from the PPE backbone in toluene and in implicit good solvent whereas in water and implicit poor solvent, the nonyl side chains are collapsed towards the PPE backbone. Thus, rotation around the aromatic ring is fast and no long range correlations are seen within the backbone.« less

  14. Characterization and fermentation of dilute-acid hydrolyzates from wood

    SciTech Connect

    Taherzadeh, M.J.; Niklasson, C.; Liden, G.; Eklund, R.; Gustafsson, L.

    1997-11-01

    Dilute-acid hydrolyzates from alder, aspen, birch, willow, pine, and spruce were fermented without prior detoxification. The hydrolyzates were prepared by a one-stage hydrolysis process using sulfuric acid (5 g/L) at temperatures between 188 and 234 C and with a holding time of 7 min. The fermentations were carried out anaerobically by Saccharomyces cerevisiae (10 g of d.w./L) at a temperature of 30 C and an initial pH of 5.5. The fermentabilities were quite different for the different wood species, and only hydrolyzates of spruce produced at 188 and 198 C, hydrolyzates of pine produced at 188 C, and hydrolyzates of willow produced at 198 C could be completely fermented within 24 h. From the sum of the concentrations of the known inhibitors furfural and 5-(hydroxymethyl)furfural (HMF), a good prediction of the maximum ethanol production rate could be obtained, regardless of the origin of the hydrolyzate. Furthermore, in hydrolyzates that fermented well, furfural and HMF were found to be taken up and converted by the yeast, concomitant with the uptake of glucose.

  15. Antiphospholipid syndrome: analysis of dilute Russell's viper venom time titer.

    PubMed

    Martinez, Alan P; Cunningham, Mark T

    2016-07-01

    To evaluate the characteristic features of the dilute Russell's viper venom time (DRVVT) titer in the antiphospholipid syndrome (APS). The medical record of 3660 consecutive patients with DRVVT orders between 2006 and 2015 were examined for criteria satisfying the diagnosis of APS. DRVVT titer was studied as a function of titer distribution, titer stability, and clinicopathologic features. Twenty-six patients were diagnosed with APS based on a persistently positive DRVVT and a history of arterial or venous thrombosis. DRVVT titer was mostly of low magnitude (65-77% of patients), was of similar value between initial and repeat testing (mean DRVVT titer 1.40 vs. 1.38; P = 0.858; mean time interval 216 days), and was positively associated with anticardiolipin antibodies (IgG and IgM) and antibeta-2-glycoprotein I antibodies (IgG and IgM) (P < 0.020). Low titer and moderate/high titer DRVVT were associated with a triple positive antiphospholipid antibody profile in 0 and 62% of patients, respectively (P < 0.020). DRVVT titer in APS was predominantly low in magnitude, stable over time, and associated with specific antiphospholipid antibody profiles.

  16. Bioavailability of soilborne lead in adults, by stable isotope dilution.

    PubMed Central

    Maddaloni, M; Lolacono, N; Manton, W; Blum, C; Drexler, J; Graziano, J

    1998-01-01

    Using stable isotope dilution, we determined the bioavailability of soilborne lead (Pb) in human adult volunteers. Soil from a residential yard at a mining-impacted federal Superfund site that had negligible amounts of other priority pollutants was dried and screened through a 25-micron mesh sieve. The < 250-micron fraction, which likely represents that ingested via hand-to-mouth activity, was then sterilized by exposure to radiation. Ten replicate samples yielded a mean (SD) soil Pb concentration of 2924 +/- 36 ppm, and a mean 206Pb/207Pb ratio of 1.1083 +/- 0.0002, indicating remarkable soil homogeneity. Six adults with 206Pb/207Pb ratios of > 1.190 were admitted to the clinical research center and fasted overnight prior to dosing with 250 micrograms Pb/70 kg bw (i.e., 85.5 mg soil/70 kg) in a gelatin capsule. Blood for Pb and 206Pb/207Pb ratios was obtained at 14 time points through 30 hr. Results of the isotopic analyses from these subjects indicate that on average 26.2% +/- 8.1 of the administered dose was absorbed. Six additional subjects were subsequently studied but ingested soil immediately after a standardized breakfast. Bioavailability in this group was only 2.52% +/- 1.7. Collectively, this study provides the first experimental estimates of soil Pb absorption in humans, and should allow for more precise estimates of health risks due to Pb-contaminated soil. Images Figure 1 Figure 2 Figure 3 PMID:9860919

  17. Effect of dilute acid on the accelerated weathering of wood

    SciTech Connect

    Williams, R.S.

    1988-02-01

    Western red cedar (Thuja plicata) specimens were soaked in acid solutions to determine the effect of acid conditions (such as low pH fog) on the weathering of wood. Daily 1-hour soaking in dilute sulfurous, sulfuric, or nitric acid (pH 2.0, 2.5, 3.0, 3.5, or 4.0) increased the rate of accelerated (xenon arc) weathering of the specimens compared to controls soaked in distilled/deionized water. Weathering was manifested as the erosion rate of the wood surface and was determined gravimetrically be fitting the weight loss over time to a linear model. This method detected significant differences between acid-treated specimens and untreated controls within 300 hours of accelerated weathering. The erosion rate was dependent on the acid type and pH. Sulfurous acid treatment caused the fastest rate of erosion, followed by sulfuric then nitric acid. None of the acids affected the erosion rate at pH 3.5 or above. Below this threshold, the rate of erosion increased as the hydrogen ion concentration increased. Sugar analysis of residues from the acids and the distilled water used to soak the wood indicated acid-dependent degradation of polysaccharides.

  18. Breakdown of hierarchical architecture in cellulose during dilute acid pretreatments

    SciTech Connect

    Zhang, Yan; Inouye, Hideyo; Yang, Lin; Himmel, Michael E.; Tucker, Melvin; Makowski, Lee

    2015-02-28

    Cellulose is an attractive candidate as a feedstock for sustainable bioenergy because of its global abundance. Pretreatment of biomass has significant influence on the chemical availability of cellulose locked in recalcitrant microfibrils. Optimizing pretreatment depends on an understanding of its impact on the microscale and nanoscale molecular architecture. X-ray scattering experiments have been performed on native and pre-treated maize stover and models of cellulose architecture have been derived from these data. Ultra small-angle, very small-angle and small-angle X-ray scattering (USAXS, VSAXS and SAXS) probe three different levels of architectural scale. USAXS and SAXS have been used to study cellulose at two distinct length scales, modeling the fibrils as ~30 Å diameter rods packed into ~0.14 μm diameter bundles. VSAXS is sensitive to structural features at length scales between these two extremes. Detailed analysis of diffraction patterns from untreated and pretreated maize using cylindrical Guinier plots and the derivatives of these plots reveals the presence of substructures within the ~0.14 μm diameter bundles that correspond to grouping of cellulose approximately 30 nm in diameter. These sub-structures are resilient to dilute acid pretreatments but are sensitive to pretreatment when iron sulfate is added. Lastly, these results provide evidence of the hierarchical arrangement of cellulose at three length scales and the evolution of these arrangements during pre-treatments.

  19. Irradiation-induced patterning in dilute Cu-Fe alloys

    NASA Astrophysics Data System (ADS)

    Stumphy, B.; Chee, S. W.; Vo, N. Q.; Averback, R. S.; Bellon, P.; Ghafari, M.

    2014-10-01

    Compositional patterning in dilute Cu1-xFex (x ≈ 12%) induced by 1.8 MeV Kr+ irradiation was studied as a function of temperature using atom probe tomography. Irradiation near room temperature led to homogenization of the sample, whereas irradiation at 300 °C and above led to precipitation and macroscopic coarsening. Between these two temperatures the irradiated alloys formed steady state patterns of composition where precipitates grew to a fixed size. The size in this regime increased somewhat with temperature. It was also observed that the steady state concentrations of Fe in Cu matrix and Cu in the Fe precipitates both greatly exceeded their equilibrium solubilities, with the degree of supersaturation in each phase decreasing with increasing temperature. In the macroscopic coarsening regime, the Fe-rich precipitates showed indications of a “cherry-pit” structure, with Cu precipitates forming within the Fe precipitates. In the patterning regime, interfaces between Fe-rich precipitates and the Cu-rich matrix were irregular and diffuse.

  20. Efficiency dilution: long-term exergy conversion trends in Japan

    SciTech Connect

    Eric Williams; Benjamin Warr; Robert U. Ayres

    2008-07-01

    This analysis characterizes century-scale trends in exergy efficiency in Japan. Exergy efficiency captures the degree to which energy inputs (such as coal) are converted into useful work (such as electricity or power to move a vehicle). This approach enables the estimation of net efficiencies which aggregate different technologies. Sectors specifically analyzed are electricity generation, transport, steel production, and residential space heating. One result is that the aggregate exergy efficiency of the Japanese economy declined slightly over the last half of the 20th century, reaching a high of around 38% in the late 1970s and falling to around 33% by 1998. The explanation for this is that while individual technologies improved dramatically over the century, less exergy-efficient ones were progressively adopted, yielding a net stabilization or decline. In the electricity sector, for instance, adoption of hydropower was followed by fossil-fired plants and then by nuclear power, each technology being successively less efficient from an exergy perspective. The underlying dynamic of this trend is analogous to declining ore grades in the mining sector. Increasing demand for exergy services requires expended utilization of resources from which it is more difficult to extract utility (e.g., falling water versus coal). We term this phenomenon efficiency dilution. 30 refs., 4 figs., 1 tab.

  1. Chitosan sorbents for platinum sorption from dilute solutions

    SciTech Connect

    Guibal, E.; Larkin, A.; Vincent, T.; Tobin, J.M.

    1999-10-01

    Chitosan has proved efficient at removing platinum in dilute effluents. The maximum uptake capacity reaches 300 mg/g (almost 1.5 mmol/g). The optimum pH for sorption is pH 2. A glutaraldehyde cross-linking pretreatment is necessary to stabilize the biopolymer in acidic solutions. Sorption isotherms have been studied as a function of pH, sorbent particle size, and the cross-linking ratio. Surprisingly, the extent of the cross-linking (determined by the concentration of the cross-linking agent in the treatment bath) has no significant influence on uptake capacity. Competitor anions such as chloride or nitrate induce a large decrease in the sorption efficiency. Sorption kinetics show also that uptake rate is not significantly changed by increasing either the cross-linking ratio or the particle size of the sorbent. Mass transfer rates are significantly affected by the initial platinum concentration and by the conditioning of the biopolymer. Gel-bead conditioning appears to reduce the sorption rate. While for molybdate and vanadate ions, mass transfer was governed by intraparticle mass transfer, for platinum, both external and intraparticle diffusion control the uptake rate. In contrast with the former ions, platinum does not form polynuclear hydrolyzed species, which are responsible for steric hindrance of diffusion into the polymer network.

  2. Multielement stoichiometry in aquatic invertebrates: when growth dilution matters.

    PubMed

    Karimi, Roxanne; Fisher, Nicholas S; Folt, Carol L

    2010-12-01

    Element concentrations in organisms can be variable, often causing deviations from otherwise consistent, taxon-specific multielement stoichiometries. Such variation can have considerable ecological consequences, yet physiological mechanisms remain unclear. We tested the influence of somatic growth dilution (SGD) on multiple element concentrations under different bioenergetic conditions. SGD occurs when rapid individual growth causes a disproportional gain in biomass relative to gain of a specific element. SGD can strongly affect elements in various organisms, but we lack a general framework to unify results across studies and assess its overall importance. We derived the general conditions that trigger SGD from an element accumulation model. We parameterized the model with bioenergetic and element-specific rates summarized from the literature to compare SGD effects on 15 elements (nonessential metals, essential trace elements, macronutrients) in three aquatic invertebrate taxa. For all taxa, we found that SGD (1) occurs to some degree for all 15 elements over realistic ranges of growth and ingestion rates and (2) has the greatest effect on elements with low efflux (excretion) rates, including certain nonessential metals (e.g., MeHg, Po), essential trace elements, and macronutrients (e.g., N, Fe). Thus, SGD can strongly affect concentrations of a spectrum of elements under natural conditions. These results provide a framework for predicting variation in the elemental composition of animals.

  3. Stability of dilute solutions of uranium, lead, and thorium ions

    USGS Publications Warehouse

    Milkey, R.G.

    1954-01-01

    Standard solutions and samples containing a few micrograms of metallic ions per milliliter are frequently used in determination of trace elements. It is important to know whether the concentrations of such solutions remain constant from day to day. The stability of dilute solutions of three metallic ions-uranium, lead, and thorium-has been investigated. Solutions containing concentrations of metallic ions, ranging from 1000 to 0.1 ?? per milliliter, were allowed to stand for approximately 2.5 months, and then the metallic ion content of those solutions that had lost strength was determined. Both adsorption and hydrolysis variously influenced the solute loss, but the minimum pH at which loss of concentration of lead and uranium occurred seemed to coincide with the pH at which the hydrolyzed metal ions began to precipitate. No increase in the stability of the solutions was obtained by substituting polyethylene containers for borosilicate glass. The solutions that lost strength could not be restored promptly to the original concentration by manual means, such as shaking them vigorously for several minutes.

  4. Breakdown of hierarchical architecture in cellulose during dilute acid pretreatments

    DOE PAGES

    Zhang, Yan; Inouye, Hideyo; Yang, Lin; Himmel, Michael E.; Tucker, Melvin; Makowski, Lee

    2015-02-28

    Cellulose is an attractive candidate as a feedstock for sustainable bioenergy because of its global abundance. Pretreatment of biomass has significant influence on the chemical availability of cellulose locked in recalcitrant microfibrils. Optimizing pretreatment depends on an understanding of its impact on the microscale and nanoscale molecular architecture. X-ray scattering experiments have been performed on native and pre-treated maize stover and models of cellulose architecture have been derived from these data. Ultra small-angle, very small-angle and small-angle X-ray scattering (USAXS, VSAXS and SAXS) probe three different levels of architectural scale. USAXS and SAXS have been used to study cellulose atmore » two distinct length scales, modeling the fibrils as ~30 Å diameter rods packed into ~0.14 μm diameter bundles. VSAXS is sensitive to structural features at length scales between these two extremes. Detailed analysis of diffraction patterns from untreated and pretreated maize using cylindrical Guinier plots and the derivatives of these plots reveals the presence of substructures within the ~0.14 μm diameter bundles that correspond to grouping of cellulose approximately 30 nm in diameter. These sub-structures are resilient to dilute acid pretreatments but are sensitive to pretreatment when iron sulfate is added. Lastly, these results provide evidence of the hierarchical arrangement of cellulose at three length scales and the evolution of these arrangements during pre-treatments.« less

  5. Quantitation of DNA adducts by stable isotope dilution mass spectrometry

    PubMed Central

    Tretyakova, Natalia; Goggin, Melissa; Janis, Gregory

    2012-01-01

    Exposure to endogenous and exogenous chemicals can lead to the formation of structurally modified DNA bases (DNA adducts). If not repaired, these nucleobase lesions can cause polymerase errors during DNA replication, leading to heritable mutations potentially contributing to the development of cancer. Due to their critical role in cancer initiation, DNA adducts represent mechanism-based biomarkers of carcinogen exposure, and their quantitation is particularly useful for cancer risk assessment. DNA adducts are also valuable in mechanistic studies linking tumorigenic effects of environmental and industrial carcinogens to specific electrophilic species generated from their metabolism. While multiple experimental methodologies have been developed for DNA adduct analysis in biological samples – including immunoassay, HPLC, and 32P-postlabeling – isotope dilution high performance liquid chromatography-electrospray ionization-tandem mass spectrometry (HPLC-ESI-MS/MS) generally has superior selectivity, sensitivity, accuracy, and reproducibility. As typical DNA adducts concentrations in biological samples are between 0.01 – 10 adducts per 108 normal nucleotides, ultrasensitive HPLC-ESI-MS/MS methodologies are required for their analysis. Recent developments in analytical separations and biological mass spectrometry – especially nanoflow HPLC, nanospray ionization MS, chip-MS, and high resolution MS – have pushed the limits of analytical HPLC-ESI-MS/MS methodologies for DNA adducts, allowing researchers to accurately measure their concentrations in biological samples from patients treated with DNA alkylating drugs and in populations exposed to carcinogens from urban air, drinking water, cooked food, alcohol, and cigarette smoke. PMID:22827593

  6. Critical masses of highly enriched uranium diluted with matrix material

    SciTech Connect

    Sanchez, R.; Kimpland, R.; Jaegers, P.; Butterfield, K.; Casson, W.; Bounds, J.; Myers, W.; Densmore, J. Rendon, G.

    2000-07-01

    Radioactive waste containing fissile material is frequently encountered in decontamination and decommissioning activities. Most of this waste is placed in containers or drums and stored in storage facilities. The amount of fissile material in each drum is generally small because criticality safety limits have been calculated with computer transport codes utilizing cross-section sections with large uncertainties. To the best of their knowledge, no experimental critical mass data are available to ensure the correctness of these calculations or any calculations for systems containing fissile material ({sup 235}U, {sup 239}Pu, or {sup 233}U) in contact with matrix material such as Al{sub 2}O{sub 3}, CaO, SiO{sub 2}, Al, MgO, etc. The experiments discussed in this paper establish the critical masses of highly enriched uranium foils diluted in various X/{sup 235}U ratios with polyethylene and SiO{sub 2}, polyethylene and aluminum, and polyethylene and MgO. In addition, these critical mass experimental data will be used to validate computer transport codes and cross-section data.

  7. Development of a stable isotope dilution assay for tenuazonic acid.

    PubMed

    Asam, Stefan; Liu, Yang; Konitzer, Katharina; Rychlik, Michael

    2011-04-13

    A stable isotope dilution assay (SIDA) for the Alternaria mycotoxin tenuazonic acid was developed. Therefore, [(13)C(6),(15)N]-tenuazonic acid was synthesized from [(13)C(6),(15)N]-isoleucine by Dieckmann intramolecular cyclization after acetoacetylation with diketene. The synthesized [(13)C(6),(15)N]-tenuazonic acid was used as the internal standard for determination of tenuazonic acid in tomato products by liquid chromatography tandem mass spectrometry after derivatization with 2,4-dinitrophenylhydrazine. Method validation revealed a limit of detection of 0.1 μg/kg and a limit of quantitation of 0.3 μg/kg. Recovery was close to 100% in the range of 3-300 μg/kg. Determination of tenuazonic acid in two samples of different tomato ketchups (naturally contaminated) was achieved with a coefficient of variation of 2.3% and 4.7%. Different tomato products (n = 16) were analyzed for their content of tenuazonic acid using the developed SIDA. Values were between 15 and 195 μg/kg (tomato ketchup, n = 9), 363 and 909 μg/kg (tomato paste, n = 2), and 8 and 247 μg/kg (pureed tomatoes and comparable products, n = 5). PMID:21370870

  8. Uniform Doping in Quantum-Dots-Based Dilute Magnetic Semiconductor.

    PubMed

    Saha, Avijit; Shetty, Amitha; Pavan, A R; Chattopadhyay, Soma; Shibata, Tomohiro; Viswanatha, Ranjani

    2016-07-01

    Effective manipulation of magnetic spin within a semiconductor leading to a search for ferromagnets with semiconducting properties has evolved into an important field of dilute magnetic semiconductors (DMS). Although a lot of research is focused on understanding the still controversial origin of magnetism, efforts are also underway to develop new materials with higher magnetic temperatures for spintronics applications. However, so far, efforts toward quantum-dots(QDs)-based DMS materials are plagued with problems of phase separation, leading to nonuniform distribution of dopant ions. In this work, we have developed a strategy to synthesize highly crystalline, single-domain DMS system starting from a small magnetic core and allowing it to diffuse uniformly inside a thick CdS semiconductor matrix and achieve DMS QDs. X-ray absorption fine structure (XAFS) spectroscopy and energy-dispersive X-ray spectroscopy-scanning transmission electron microscopy (STEM-EDX) indicates the homogeneous distribution of magnetic impurities inside the semiconductor QDs leading to superior magnetic property. Further, the versatility of this technique was demonstrated by obtaining ultra large particles (∼60 nm) with uniform doping concentration as well as demonstrating the high quality magnetic response.

  9. Alyssum homolocarpum seed gum: Dilute solution and some physicochemical properties.

    PubMed

    Hesarinejad, M A; Razavi, Seyed M A; Koocheki, A

    2015-11-01

    The objective of this study was to investigate the effect of various temperatures (25-65°C) on some dilute solution properties of Alyssum homolocarpum seed gum (AHSG) as a novel potential source of hydrocolloid. Monosaccharide composition, FTIR analysis and molecular parameters were determined to provide more structural information. The results indicated that AHSG had a low molecular weight (3.66×10(5)Da), medium intrinsic viscosity (18.34dl/g) at 25°C, relatively flexible chain with a chain flexibility parameter of 618.54, and activation energy of 0.51×10(7)J/kgmol. With rise in temperature from 25 to 55°C, the intrinsic viscosity decreased as well as coil radius and volume of AHSG. The shape factor of AHSG macromolecule was spherical at all temperatures. The electrostatic interaction and particle size of AHSG solution were -25.81mV (at neutral pH) and 225.36nm, respectively. The results revealed that AHSG had high total sugar content (85.33%), small amount of uronic acids (5.63%) and it is likely a galactan-type polysaccharide. The FTIR spectra showed that AHSG behaved like a typical polyelectrolyte because of the presence of carboxyl and hydroxyl groups.

  10. Forward di-jet production in dilute-dense collisions

    NASA Astrophysics Data System (ADS)

    Petreska, E.; Kotko, P.; Kutak, K.; Marquet, C.; Sapeta, S.; van Hameren, A.

    2016-03-01

    We derive a factorization formula for forward production of two jets in dilutedense collisions that is valid for an arbitrary value of the momentum imbalance of the jets, kt. This generalizes the transverse momentum dependent (TMD) factorization formula that has been derived before by Dominguez et al. Their formula is valid only for small values of the transverse momentum of the small-x gluon from the target; it has kt dependent TMD gluon distributions, but on-shell hard matrix elements. We extend the TMD formula to all ranges of kt by including off-shell matrix elements. We also add finite Nc corrections. The new formula encompasses both, the TMD factorization for small kt on the order of the saturation scale, and the High Energy Factorization (HEF) for large kt on the order of the momentum of the jets. The TMD and HEF factorizations can be derived from the Color Glass Condensate (CGC) formula for forward di-jet production in the appropriate limits. We show explicitly the equivalence of HEF and CGC in the dilute target approximation.

  11. Transient Effects in Planar Solidification of Dilute Binary Alloys

    NASA Technical Reports Server (NTRS)

    Mazuruk, Konstantin; Volz, Martin P.

    2008-01-01

    The initial transient during planar solidification of dilute binary alloys is studied in the framework of the boundary integral method that leads to the non-linear Volterra integral governing equation. An analytical solution of this equation is obtained for the case of a constant growth rate which constitutes the well-known Tiller's formula for the solute transient. The more physically relevant, constant ramping down temperature case has been studied both numerically and analytically. In particular, an asymptotic analytical solution is obtained for the initial transient behavior. A numerical technique to solve the non-linear Volterra equation is developed and the solution is obtained for a family of the governing parameters. For the rapid solidification condition, growth rate spikes have been observed even for the infinite kinetics model. When recirculating fluid flow is included into the analysis, the spike feature is dramatically diminished. Finally, we have investigated planar solidification with a fluctuating temperature field as a possible mechanism for frequently observed solute trapping bands.

  12. 40 CFR 1065.546 - Validation of minimum dilution ratio for PM batch sampling.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... for PM batch sampling. 1065.546 Section 1065.546 Protection of Environment ENVIRONMENTAL PROTECTION... Specified Duty Cycles § 1065.546 Validation of minimum dilution ratio for PM batch sampling. Use continuous... dilution ratios for PM batch sampling as specified in § 1065.140(e)(2) over the test interval. You may...

  13. Chromogenic assay of human coagulation factor VIII: statistical comparison of 2 working dilution procedures.

    PubMed

    Alonso, C; Gonzalez, A; Frutos, G

    2005-08-01

    The effect of 2 different practices for preparation of working dilutions in the chromogenic substrate method for potency assay of factor VIII was evaluated. In this study the potency of several concentrate materials was shown to be statistically equivalent, whether performing the assay with independent or serial working dilutions.

  14. Thermoluminescence of ultra-high dilutions of lithium chloride and sodium chloride

    NASA Astrophysics Data System (ADS)

    Rey, Louis

    2003-05-01

    Ultra-high dilutions of lithium chloride and sodium chloride (10 -30 g cm -3) have been irradiated by X- and γ-rays at 77 K, then progressively rewarmed to room temperature. During that phase, their thermoluminescence has been studied and it was found that, despite their dilution beyond the Avogadro number, the emitted light was specific of the original salts dissolved initially.

  15. Response to Comment on “Dilution limits dissolved organic carbon utilization in the deep ocean”

    NASA Astrophysics Data System (ADS)

    Arrieta, Jesús M.; Mayol, Eva; Hansman, Roberta L.; Herndl, Gerhard J.; Dittmar, Thorsten; Duarte, Carlos M.

    2015-12-01

    Our recent finding that dilution limits dissolved organic carbon (DOC) utilization in the deep ocean has been criticized based on the common misconception that lability equates to rapid and complete utilization. Even when considering the redefinition of recalcitrant DOC recently proposed by Jiao et al., the dilution hypothesis best explains our experimental observations.

  16. Estimating dilutions for patch testing skin care products: a practical method.

    PubMed

    Sherertz, E F; Byers, S V

    1997-09-01

    When patch testing, it is helpful to patch test with the patient's own topical products. However, the thickness (viscosity) of the product often prevents easy measurement for dilution. A method of estimating volume: volume dilutions that requires minimal investment in supplies is presented. This method is only applicable to personal products and is not suitable for industrial or household chemicals.

  17. 30 CFR 36.49 - Tests of exhaust-gas dilution system.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Tests of exhaust-gas dilution system. 36.49 Section 36.49 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR TESTING... TRANSPORTATION EQUIPMENT Test Requirements § 36.49 Tests of exhaust-gas dilution system. The performance...

  18. 30 CFR 36.49 - Tests of exhaust-gas dilution system.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Tests of exhaust-gas dilution system. 36.49 Section 36.49 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR TESTING... TRANSPORTATION EQUIPMENT Test Requirements § 36.49 Tests of exhaust-gas dilution system. The performance...

  19. Two-Exon Skipping within MLPH Is Associated with Coat Color Dilution in Rabbits

    PubMed Central

    Lehner, Stefanie; Gähle, Marion; Dierks, Claudia; Stelter, Ricarda; Gerber, Jonathan; Brehm, Ralph; Distl, Ottmar

    2013-01-01

    Coat color dilution turns black coat color to blue and red color to cream and is a characteristic in many mammalian species. Matings among Netherland Dwarf, Loh, and Lionhead Dwarf rabbits over two generations gave evidence for a monogenic autosomal recessive inheritance of coat colour dilution. Histological analyses showed non-uniformly distributed, large, agglomerating melanin granules in the hair bulbs of coat color diluted rabbits. We sequenced the cDNA of MLPH in two dilute and one black rabbit for polymorphism detection. In both color diluted rabbits, skipping of exons 3 and 4 was present resulting in altered amino acids at p.QGL[37-39]QWA and a premature stop codon at p.K40*. Sequencing of genomic DNA revealed a c.111-5C>A splice acceptor mutation within the polypyrimidine tract of intron 2 within MLPH. This mutation presumably causes skipping of exons 3 and 4. In 14/15 dilute rabbits, the c.111-5C>A mutation was homozygous and in a further dilute rabbit, heterozygous and in combination with a homozygous frame shift mutation within exon 6 (c.585delG). In conclusion, our results demonstrated a colour dilution associated MLPH splice variant causing a strongly truncated protein (p.Q37QfsX4). An involvement of further MLPH-associated mutations needs further investigations. PMID:24376820

  20. The surface oxidation of pyrite

    NASA Astrophysics Data System (ADS)

    Buckley, A. N.; Woods, R.

    1987-02-01

    The surface oxidation in air and air-saturated aqueous solutions of the iron sulfide mineral, pyrite, has been studied by X-ray photoelectron spectroscopy. Iron sulfate was produced on fracture surfaces within the first few minutes of exposure to air under ambient conditions. Iron oxide was also included in the oxidation products after prolonged exposure which implies that a sulfur product in addition to sulfate must be formed. It is suggested that this product is an iron-deficient sulfide. Elemental sulfur was not evident at surfaces exposed to air. Iron oxide rather than sulfate was present at abraded surfaces exposed to air for a few minutes. Oxidation of pyrite in air-saturated acid solutions resulted in the formation of a surface sulfur layer the extent and nature of which depended on solution composition and exposure time. Sulfate was the only sulfur oxidation product identified in alkaline solutions not containing soluble sulfide, and iron oxide remained at the surface after such treatment. Thin layers of elemental sulfur were observed at fracture surfaces immersed in aerated, dilute sodium sulfide solutions.