WorldWideScience

Sample records for crystals formation double

  1. Formation and transformation of metastable double salts from the crystallization of mixed ammonium nitrate and ammonium sulfate particles.

    Science.gov (United States)

    Ling, Tsz Yan; Chan, Chak K

    2007-12-01

    Ammonium nitrate (AN) and ammonium sulfate (AS) are ubiquitous components of atmospheric aerosols. Thermodynamic models predict formation of pure (AN and AS) and double salts (3AN. AS and 2AN. AS) for the AN/AS system. Because of the high supersaturation at which a droplet crystallizes, metastable crystal formation is possible. In this study, the identity of the crystals formed from the crystallization of equimolar AN/AS mixed droplets was investigated in an electrodynamic balance coupled with a Raman spectroscopic system. Raman spectra of bulk AN/AS double salts possibly formed in this system are first reported for comparison with the single particle Raman results. The double-salt 3AN. AS, not predicted from thermodynamics, was observed in the freshly crystallized single particles. The degree of metastability can be different among several crystallization processes of the same particles. The metastable salt 3AN. AS gradually transformed into stable 2AN. AS, and the rate of such transformation increased with increasing relative humidity. This study illustrates the possibility of occurrence of metastable salts in atmospheric aerosols.

  2. Formation of nematic liquid crystals of sterically stabilized layered double hydroxide platelets

    NARCIS (Netherlands)

    Mourad, M.C.D.; Devid, E.J.; van Schooneveld, M.M.; Vonk, Ch.; Lekkerkerker, H.N.W.

    2008-01-01

    Colloidal platelets of hydrotalcite, a layered double hydroxide, have been prepared by coprecipitation at pH 11−12 of magnesium nitrate and aluminum nitrate at two different magnesium to aluminum ratios. Changing the temperature and ionic strength during hydrothermal treatment, the platelets were ta

  3. Frequency doubling crystals

    Science.gov (United States)

    Wang, Francis; Velsko, Stephan P.

    1989-01-01

    A systematic approach to the production of frequency conversion crystals is described in which a chiral molecule has attached to it a "harmonic generating unit" which contributes to the noncentrosymmetry of the molecule. Certain preferred embodiments of such harmonic generating units include carboxylate, guanadyly and imidazolyl units. Certain preferred crystals include L-arginine fluoride, deuterated L-arginine fluoride, L-arginine chloride monohydrate, L-arginine acetate, dithallium tartrate, ammonium N-acetyl valine, N-acetyl tyrosine and N-acetyl hydroxyproline. Chemical modifications of the chiral molecule, such as deuteration, halogenation and controlled counterion substitution are available to adapt the dispersive properties of a crystal in a particular wavelength region.

  4. Frequency Doubling Broadband Light in Multiple Crystals

    Energy Technology Data Exchange (ETDEWEB)

    ALFORD,WILLIAM J.; SMITH,ARLEE V.

    2000-07-26

    The authors compare frequency doubling of broadband light in a single nonlinear crystal with doubling in five crystals with intercrystal temporal walk off compensation, and with doubling in five crystals adjusted for offset phase matching frequencies. Using a plane-wave, dispersive numerical model of frequency doubling they study the bandwidth of the second harmonic and the conversion efficiency as functions of crystal length and fundamental irradiance. For low irradiance the offset phase matching arrangement has lower efficiency than a single crystal of the same total length but gives a broader second harmonic bandwidth. The walk off compensated arrangement gives both higher conversion efficiency and broader bandwidth than a single crystal. At high irradiance, both multicrystal arrangements improve on the single crystal efficiency while maintaining broad bandwidth.

  5. Double phase conjugation in tungsten bronze crystals.

    Science.gov (United States)

    Sharp, E J; Clark Iii, W W; Miller, M J; Wood, G L; Monson, B; Salamo, G J; Neurgaonkar, R R

    1990-02-20

    In this paper we report a new method for double phase conjugation particularly suited to the tungsten bronze crystal strontium barium niobate. It has also been observed to produce conjugate waves in BaTiO(3) and BSKNN. This new arrangement is called the bridge conjugator because the two beams enter opposing [100] crystal faces and fan together to form a bridge without reflection off a crystal face. Our measurements indicate that the bridge conjugator is competitive with previously reported double phase conjugate mirrors in reflectivity, response time, ease of alignment, and fidelity.

  6. Double Dirac cones in phononic crystals

    KAUST Repository

    Li, Yan

    2014-07-07

    A double Dirac cone is realized at the center of the Brillouin zone of a two-dimensional phononic crystal (PC) consisting of a triangular array of core-shell-structure cylinders in water. The double Dirac cone is induced by the accidental degeneracy of two double-degenerate Bloch states. Using a perturbation method, we demonstrate that the double Dirac cone is composed of two identical and overlapping Dirac cones whose linear slopes can also be accurately predicted from the method. Because the double Dirac cone occurs at a relatively low frequency, a slab of the PC can be mapped onto a slab of zero refractive index material by using a standard retrieval method. Total transmission without phase change and energy tunneling at the double Dirac point frequency are unambiguously demonstrated by two examples. Potential applications can be expected in diverse fields such as acoustic wave manipulations and energy flow control.

  7. Crystal sedimentation and stone formation.

    Science.gov (United States)

    Baumann, Johannes Markus; Affolter, Beat; Meyer, Rolf

    2010-02-01

    Mechanisms of crystal collision being the first step of aggregation (AGN) were analyzed for calcium oxalate monohydrate (COM) directly produced in urine. COM was produced by oxalate titration in urine of seven healthy men, in solutions of urinary macromolecules and in buffered distilled water (control). Crystal formation and sedimentation were followed by a spectrophotometer and analyzed by scanning electron microscopy. Viscosity of urine was measured at 37 degrees C. From results, sedimentation rate (v (S)), particle diffusion (D) and incidences of collision of particles in suspension by sedimentation (I (S)) and by diffusion (I (D)) were calculated. Calculations were related to average volume and urinary transit time of renal collecting ducts (CD) and of renal pelvis. v (S) was in urine 0.026 +/- 0.012, in UMS 0.022 +/- 0.01 and in control 0.091 +/- 0.02 cm min(-1) (mean +/- SD). For urine, a D of 9.53 +/- 0.97 mum within 1 min can be calculated. At maximal crystal concentration, I (S) was only 0.12 and I (D) was 0.48 min(-1) cm(-3) which, even at an unrealistic permanent and maximal crystalluria, would only correspond to less than one crystal collision/week/CD, whereas to the same tubular wall being in horizontal position 1.3 crystals/min and to a renal stone 624 crystals/cm(2) min could drop by sedimentation. Sedimentation to renal tubular or pelvic wall, where crystals can accumulate and meet with a tissue calcification or a stone, is probably essential for stone formation. Since v (S) mainly depends on particle size, reducing urinary supersaturation and crystal growth by dietary oxalate restriction seems to be an important measure to prevent aggregation.

  8. Crystal formation in furunculosis agar

    Science.gov (United States)

    Bullock, G.L.; Ross, A.J.

    1964-01-01

    SINCE ITS INTRODUCTION SOME MONTHS AGO, FURUNCULOSIS AGAR has been employed in the diagnosis of suspect furunculosis and also as a general purpose medium. During our work with this medium we have noticed discrete "colonies," of crystalline material, which very closely resemble microbial colonies. These crystal colonies are compact and appear on both the surface and subsurface; they occur in inoculated slants and plates incubated for long periods (2 to 3 weeks), as well as in uninoculated stored medium. As the crystal colonies could be confusing to workers using this medium, we decided to attempt to identify them and also to determine whether storage conditions and different lots of medium affect crystal formation.

  9. Realisation of a novel crystal bender for a fast double crystal monochromator

    Energy Technology Data Exchange (ETDEWEB)

    Zaeper, R.; Richwin, M. E-mail: richwin@uni-wuppertal.de; Wollmann, R.; Luetzenkirchen-Hecht, D.; Frahm, R

    2001-07-21

    A novel crystal bender for an X-ray undulator beamline as part of a fast double crystal monochromator development for full EXAFS energy range was characterized. Rocking curves of the monochromator crystal system were recorded under different heat loads and bending forces of the indirectly cooled first Si(1 1 1) crystal. The monochromator development implements new piezo-driven tilt tables with wide angular range to adjust the crystals' Bragg angles and a high pressure actuated bender mechanism for the first crystal.

  10. Realisation of a novel crystal bender for a fast double crystal monochromator

    CERN Document Server

    Zaeper, R; Wollmann, R; Luetzenkirchen-Hecht, D; Frahm, R

    2001-01-01

    A novel crystal bender for an X-ray undulator beamline as part of a fast double crystal monochromator development for full EXAFS energy range was characterized. Rocking curves of the monochromator crystal system were recorded under different heat loads and bending forces of the indirectly cooled first Si(1 1 1) crystal. The monochromator development implements new piezo-driven tilt tables with wide angular range to adjust the crystals' Bragg angles and a high pressure actuated bender mechanism for the first crystal.

  11. Angular vibrations of cryogenically cooled double-crystal monochromators.

    Science.gov (United States)

    Sergueev, I; Döhrmann, R; Horbach, J; Heuer, J

    2016-09-01

    The effect of angular vibrations of the crystals in cryogenically cooled monochromators on the beam performance has been studied theoretically and experimentally. A simple relation between amplitude of the vibrations and size of the focused beam is developed. It is shown that the double-crystal monochromator vibrations affect not only the image size but also the image position along the optical axis. Several methods to measure vibrations with the X-ray beam are explained and analyzed. The methods have been applied to systematically study angular crystal vibrations at monochromators installed at the PETRA III light source. Characteristic values of the amplitudes of angular vibrations for different monochromators are presented.

  12. Vibrational stability of a cryocooled horizontal double-crystal monochromator

    Science.gov (United States)

    Kristiansen, Paw; Johansson, Ulf; Ursby, Thomas; Jensen, Brian Norsk

    2016-01-01

    The vibrational stability of a horizontally deflecting double-crystal monochromator (HDCM) is investigated. Inherently a HDCM will preserve the vertical beam stability better than a ‘normal’ vertical double-crystal monochromator as the vibrations of a HDCM will almost exclusively affect the horizontal stability. Here both the relative pitch vibration between the first and second crystal and the absolute pitch vibration of the second crystal are measured. All reported measurements are obtained under active cooling by means of flowing liquid nitrogen (LN2). It is found that it is favorable to circulate the LN2 at high pressures and low flow rates (up to 5.9 bar and down to 3 l min−1 is tested) to attain low vibrations. An absolute pitch stability of the second crystal of 18 nrad RMS, 2–2500 Hz, and a relative pitch stability between the two crystals of 25 nrad RMS, 1–2500 Hz, is obtained under cryocooling conditions that allow for 1516 W to be adsorbed by the LN2 before it vaporizes. PMID:27577758

  13. Selectivity of Crystal Growth Direction in Layered Double Hydroxides

    Institute of Scientific and Technical Information of China (English)

    赵芸; 梁吉; 李峰; 段雪

    2004-01-01

    Investigation of selectivity of crystal growth direction in layered double hydroxides is helpful to control their particle sizes in different directions. Mg-Al layered double hydroxides (LDHs) were synthesized using a coprecipitation method. The influences of aging temperature, aging time, and Mg/Al molar ratio on the crystal structure, the LDHs particle size, and the selectivity of crystal growth in different directions were investigated. The results show that the size of the crystallites in the a direction is larger than that in the c direction for all experimental conditions, indicating faster crystal growth in the a direction than in the c direction. The crystallite sizes in the a and c directions both increase with decreasing Mg/Al molar ratio but with less difference between the sizes in the two directions. Therefore, the crystal growth rate in the c direction increases more than that in the a direction as the Mg/Al molar ratio decreases. The influence of the aging time, aging temperature, and Mg/Al molar ratio on the selectivity of the crystal growth direction can be used to prepare LDHs with selected sizes in the a and c directions.

  14. Microwave studies on double rare earth oxalate crystals

    Energy Technology Data Exchange (ETDEWEB)

    Elizabeth, Anit [School of Pure and Applied Physics, Mahatma Gandhi University, Kottayam 686560 (India); Joseph, Cyriac [School of Pure and Applied Physics, Mahatma Gandhi University, Kottayam 686560 (India); Paul, Issac [School of Pure and Applied Physics, Mahatma Gandhi University, Kottayam 686560 (India); Ittyachen, M.A. [School of Pure and Applied Physics, Mahatma Gandhi University, Kottayam 686560 (India); Mathew, K.T. [Microwave Imaging and Material Research Laboratory, Department of Electronics, Cochin University of Science and Technology, Kochi 682022 (India)]. E-mail: ktm@cusat.ac.in; Lonappan, Anil [Microwave Imaging and Material Research Laboratory, Department of Electronics, Cochin University of Science and Technology, Kochi 682022 (India); Jacob, Joe [Microwave Imaging and Material Research Laboratory, Department of Electronics, Cochin University of Science and Technology, Kochi 682022 (India)

    2005-01-25

    Rare earth compounds are recognized for outstanding physical, magnetic and optical properties. The oxalates and molybdates have gained importance for their various properties, which find applications in electro and accusto optical devices. This paper reports the microwave dielectric studies on double rare earth oxalate crystals. Using the cavity perturbation technique dielectric parameters such as complex permittivity and conductivity at microwave frequencies is determined. Using X-ray diffraction study the crystalline nature of the samples was established. The molecular and crystal structures were identified by IR analysis.

  15. Facile synthesis of Graphene Oxide/Double-stranded DNA composite liquid crystals and Hydrogels

    Indian Academy of Sciences (India)

    Rajendra Kurapati; Ashok M Raichur; U Venkateswara Reddy; N Suryaprakash

    2016-03-01

    Investigation of the interactions between graphene oxide (GO) and biomolecules is very crucialfor the development of biomedical applications based on GO. This study reports the first observation of thespontaneous formation of self-assembled liquid crystals and three-dimensional hydrogels of graphene oxidewith double-stranded DNA by simple mixing in an aqueous buffer media without unwinding double-strandedDNA to single-stranded DNA. The GO/dsDNA hydrogels have shown controlled porosity by changing the concentration of the components. The strong binding between dsDNA and graphene is proved by Ramanspectroscopy

  16. A magnetically adsorbed fine adjustment mechanism of the second crystal in a double-crystal monochromator

    Institute of Scientific and Technical Information of China (English)

    CAO Chong-Zhen; GAO Xue-Guan; MA Pei-Sun; WANG Feng-Qin; HE Dong-Qing; HUANG Yu-Ying; LIU Peng

    2005-01-01

    In a fine adjustment mechanism of the second crystal in a double-crystal monochromator, a compression spring is usually used as a return force element, but it often produces permanent deform after some time. A novel fine adjustment mechanism is put forward, which utilizes permanent-magnet as the return force element instead of a compression spring. Its principle and advantages of adjusting the pitch angle and the roll angle are analyzed, and the structure parameters of the permanent-magnet, which is the key pa rt of the fine adjustment mechanism, are optimized. The magnetically adsorbed fine adjustment mechanism has been testified and applied successfully in the double-crystal monochromator of 4W1B beam line in Beijing Synchrotron Radiation Facility (BSRF).

  17. Double twist helical nanofilaments in bent-core liquid crystals

    Science.gov (United States)

    Zhang, Cuiyu; Diorio, Nicholas; Lavrentovich, Oleg D.; Jakli, Antal

    2014-03-01

    Cryo-TEM observations on 40-150 nm films of four bent-core liquid crystal materials in their helical nanofilament (HNF) phase show that the filaments get deformed near the substrate, and the subsequent arrays of nanofilaments are not parallel, but twisted with respect to each other. The effect can explain the mysterious properties of the HNF materials, such as structural color and ambidextrous optical activity. The observed double twist structure was not expected in the previous models of this phase. Being principally different from the packing of molecules in the twist grain boundary (TGB) and blue (BP) phases, the double-twist structure of HNF expands the rich word of nanostructured organic materials. This work was financially supported by NSF DMR-0964765 and DMR 1104850. The cryo-TEM facility was supported by the Ohio Research Scholars Program. We are grateful for Prof. G. Heppke and Dr. D. Lotsch for providing the PnOPIMB materials for us.

  18. Formation of double-$\\Lambda$ hypernuclei at PANDA

    CERN Document Server

    Gaitanos, T; Lenske, H; Mosel, U

    2011-01-01

    We study the formation of single- and double-$\\Lambda$ hypernuclei in antiproton-induced reactions relevant for the forthcoming PANDA experiment at FAIR. We use the Giessen Boltzmann-Uehling-Uhlenbeck (GiBUU) transport model with relativistic mean-fields for the description of non-equilibrium dynamics and the statistical multifragmentation model (SMM) for fragment formation. This combined approach describes the dynamical properties of strangeness and fragments in low energy $\\bar{p}$-induced reactions fairly well. We then focus on the formation of double-$\\Lambda$ hypernuclei in high energy $\\bar{p}$-nucleus collisions on a primary target including the complementary $\\Xi$-induced reactions to a secondary one, as proposed by the PANDA collaboration. Our results show that a copious production of double-$\\Lambda$ hyperfragments is possible at PANDA. In particular, we provide first theoretical estimations on the double-$\\Lambda$ production cross section, which strongly rises with decreasing energy of the secondar...

  19. A Star-shaped Oligo(phenylenevinylene) Liquid Crystal Host with an Anthracene Guest-A Double Nanosegregating Supermesogen.

    Science.gov (United States)

    Maier, Philipp; Grüne, Matthias; Lehmann, Matthias

    2017-01-23

    Hexasubstituted C3 -symmetric benzenes with three elongated shape-persistent oligo(phenylenevinylene) arms and three pyridyl hydrogen-bond acceptors have been synthesized. These mesogens assemble in a double-helical columnar liquid crystal (LC) structure, owing to the compensation of free spaces between conjugated arms by dimer formation. The void is filled also by up to three anthracene carboxylic acids as guests forming hydrogen bonded supermesogens assembling in columnar LC and soft-crystal phases. Thin film fluorescence and solid-state NMR spectroscopy imply a transition from a disordered columnar LC to an unexpected double nanosegregated morphology of a filled soft columnar crystal phase. An additional intracolumnar separation of anthracene and oligo(phenylenevinylene) chromophores occurs, separate to the general segregation of aliphatic and aromatic building blocks in LC structures. The new type of supermesogens will enable the rational design of host-guest double cables with a wide range of different conjugated building blocks.

  20. Formation of Piroxicam Polymorphism in Solution Crystallization

    DEFF Research Database (Denmark)

    Bruun Hansen, Thomas; Qu, Haiyan

    2015-01-01

    also explored, and new insights into polymorphic control are documented and discussed. The crystal landscape was mapped for cooling crystallization of piroxicam from acetone/water mixtures (0.5 K/min) and for antisolvent crystallization from acetone with water as the antisolvent. Varying cooling rates...

  1. Formation of Double Neutron Stars, Millisecond Pulsars and Double Black Holes

    Science.gov (United States)

    van den Heuvel, Edward P. J.

    2017-09-01

    The 1982 model for the formation of Hulse-Taylor binary radio pulsar PSR B1913+16 is described, which since has become the `standard model' for the formation of the double neutron stars, confirmed by the 2003 discovery of the double pulsar system PSR J0737-3039AB. A brief overview is given of the present status of our knowledge of the double neutron stars, of which 15 systems are presently known. The binary-recycling model for the formation of millisecond pulsars is described, as put forward independently by Alpar et al. (1982), Radhakrishnan & Srinivasan (1982) and Fabian et al. (1983). This now is the `standard model' for the formation of these objects, confirmed by the discovery in 1998 of the accreting millisecond X-ray pulsars. It is noticed that the formation process of close double black holes has analogies to that of close double neutron stars, extended to binaries with larger initial component masses, although there are also considerable differences in the physics of the binary evolution at these larger masses.

  2. Formation of Double Neutron Stars, Millisecond Pulsars and Double Black Holes

    Indian Academy of Sciences (India)

    Edward P. J. Van Den Heuvel

    2017-09-01

    The 1982 model for the formation of Hulse–Taylor binary radio pulsar PSR B1913+16 is described, which since has become the ‘standard model’ for the formation of the double neutron stars, confirmed by the 2003 discovery of the double pulsar system PSR J0737-3039AB. A brief overview is given of the present status of our knowledge of the double neutron stars, of which 15 systems are presently known. The binary-recycling model for the formation of millisecond pulsars is described, as put forward independently by Alpar et al. (1982), Radhakrishnan & Srinivasan (1982) and Fabian et al. (1983). This now is the ‘standard model’ for the formation of these objects, confirmed by the discovery in 1998 of the accreting millisecond X-ray pulsars. It is noticed that the formation process of close double black holes has analogies to that of close double neutron stars, extended to binaries with larger initial component masses, although there are also considerable differences in the physics of the binary evolution at these larger masses.

  3. Accidental degeneracy of double Dirac cones in a phononic crystal

    KAUST Repository

    Chen, Ze-Guo

    2014-04-09

    Artificial honeycomb lattices with Dirac cone dispersion provide a macroscopic platform to study the massless Dirac quasiparticles and their novel geometric phases. In this paper, a quadruple-degenerate state is achieved at the center of the Brillouin zone in a two-dimensional honeycomb lattice phononic crystal, which is a result of accidental degeneracy of two double-degenerate states. In the vicinity of the quadruple-degenerate state, the dispersion relation is linear. Such quadruple degeneracy is analyzed by rigorous representation theory of groups. Using method, a reduced Hamiltonian is obtained to describe the linear Dirac dispersion relations of this quadruple-degenerate state, which is well consistent with the simulation results. Near such accidental degeneracy, we observe some unique properties in wave propagating, such as defect-insensitive propagating character and the Talbot effect.

  4. Design and performance of the ALS double-crystal monochromator

    Energy Technology Data Exchange (ETDEWEB)

    Jones, G.; Ryce, S.; Perera, R.C.C. [Lawrence Berkeley National Lab., CA (United States)] [and others

    1997-04-01

    A new {open_quotes}Cowan type{close_quotes} double-crystal monochromator, based on the boomerang design used at NSLS beamline X-24A, has been developed for beamline 9.3.1 at the ALS, a windowless UHV beamline covering the 1-6 keV photon-energy range. Beamline 9.3.1 is designed to simultaneously achieve the goals of high energy resolution, high flux, and high brightness at the sample. The mechanical design has been simplified, and recent developments in technology have been included. Measured mechanical precision of the monochromator shows significant improvement over existing designs. In tests with x-rays at NSLS beamline X-23 A2, maximum deviations in the intensity of monochromatic light were just 7% during scans of several hundred eV in the vicinity of the Cr K edge (6 keV) with the monochromator operating without intensity feedback. Such precision is essential because of the high brightness of the ALS radiation and the overall length of beamline 9.3.1 (26 m).

  5. Mode mixing in asymmetric double trench photonic crystal waveguides

    CERN Document Server

    Vlasov, Y A; McNab, S J; Vlasov, Yu. A.

    2003-01-01

    e investigate both experimentally and theoretically the waveguiding properties of a novel double trench waveguide where a conventional single-mode strip waveguide is embedded in a two dimensional photonic crystal (PhC) slab formed in silicon on insulator (SOI) wafers. We demonstrate that the bandwidth for relatively low-loss (50dB/cm) waveguiding is significantly expanded to 250nm covering almost all the photonic band gap owing to nearly linear dispersion of the TE-like waveguiding mode. The flat transmission spectrum however is interrupted by numerous narrow stop bands. We found that these stop bands can be attributed to anti-crossing between TE-like (positive parity) and TM-like (negative parity) modes. This effect is a direct result of the strong asymmetry of the waveguides that have an upper cladding of air and lower cladding of oxide. To our knowledge this is the first demonstration of the effects of cladding asymmetry on the transmission characteristics of the PhC slab waveguides.

  6. FBRM and PVM investigations of the double feed semi-batch crystallization of 6-aminopenicillanic acid

    Institute of Scientific and Technical Information of China (English)

    Min SU; Lin WANG; Hua SUN; Jingkang WANG

    2009-01-01

    6-Aminopenicillanic acid (6-APA) is a crucial pharmaceutical intermediate in the chemistry of semi-synthetic antibiotics. The focused beam reflectance measurement (FBRM) technology and particle vision measurement (PVM) technology were employed to the processes of online-monitoring of 6-APA crystallization behavior in a double-feeding semi-batch crystallizer. Experiments were carried out with four kinds of double-feeding policies and the results were compared with the traditional single-feeding. Records and analysis of FBRM indicated that the nucleation of double feeding policy was much higher than single policy, and chord length of 6-APA was almost determined and had little change after the nucleation peak. Ostwald ripening process had no significant effect on further growth of 6-APA crystal. PVM images showed that the crystal habit of 6-APA was continuously changed during the crystallization process. The development of (002) face in the final crystal for the five feeding policies were different.

  7. Real-time molecular scale observation of crystal formation.

    Science.gov (United States)

    Schreiber, Roy E; Houben, Lothar; Wolf, Sharon G; Leitus, Gregory; Lang, Zhong-Ling; Carbó, Jorge J; Poblet, Josep M; Neumann, Ronny

    2017-04-01

    How molecules in solution form crystal nuclei, which then grow into large crystals, is a poorly understood phenomenon. The classical mechanism of homogeneous crystal nucleation proceeds via the spontaneous random aggregation of species from liquid or solution. However, a non-classical mechanism suggests the formation of an amorphous dense phase that reorders to form stable crystal nuclei. So far it has remained an experimental challenge to observe the formation of crystal nuclei from five to thirty molecules. Here, using polyoxometallates, we show that the formation of small crystal nuclei is observable by cryogenic transmission electron microscopy. We observe both classical and non-classical nucleation processes, depending on the identity of the cation present. The experiments verify theoretical studies that suggest non-classical nucleation is the lower of the two energy pathways. The arrangement in just a seven-molecule proto-crystal matches the order found by X-ray diffraction of a single bulk crystal, which demonstrates that the same structure was formed in each case.

  8. Structures of an asymmetrically coupled double-well superlattice by double-crystal X-ray diffraction

    Institute of Scientific and Technical Information of China (English)

    马文全; 庄岩; 王玉田; 江德生

    1997-01-01

    An asymmetrically coupled ( GaAs/AlAs/GaAs/AlAs)/GaAs(001) double-well supperlattice isstudied by HRDCD (high resolution double-crystal X-ray diffractometry).The intensity of satellite peaks is modulated by wave packet of different sublayers.In the course of simulation,the satellite peaks in the vicinity of the node points of wave packet are very informative for precise determination of sublayer thickness and for improving accuracy.

  9. Crystal orbital study on the double walls made of nanotubes encapsulated inside zigzag carbon nanotubes

    Science.gov (United States)

    Zhao, Xin; Qiao, Weiye; Li, Yuliang; Huang, Yuanhe

    2015-01-01

    The structure stabilities and electronic properties are investigated by using ab initio self-consistent-field crystal orbital method based on density functional theory for the one-dimensional (1D) double-wall nanotubes made of n-gon SiO2 nanotubes encapsulated inside zigzag carbon nanotubes. It is found that formation of the combined systems is energetically favorable when the distance between the two constituents is around the Van der Waals scope. The obtained band structures show that all the combined systems are semiconductors with nonzero energy gaps. The frontier energy bands (the highest occupied band and the lowest unoccupied band) of double-wall nanotubes are mainly derived from the corresponding carbon nanotubes. The mobilities of charge carriers are calculated to be within the range of 102-104 cm2 V-1 s-1 for the hybrid double-wall nanotubes. Young's moduli are also calculated for the combined systems. For the comparison, geometrical and electronic properties of n-gon SiO2 nanotubes are also calculated and discussed.

  10. Formation of nuclei during precipitation in metallic mixed crystals

    Science.gov (United States)

    Becker, R.

    1988-01-01

    Assuming that the energy of a mixed crystal can be calculated by simple addition of neighboring bonds, the nuclear formation energy is calculated for precipation in a super-saturated binary mixed crystal. From this can be determined the frequency of the formation of nuclei. From the calculation of a numerical example we can obtain, for the degree of sub-cooling at which the frequency of the formation of nuclei reaches its maximum, satisfactory agreement with available measurements of the rate of precipitation.

  11. Cartilage formation in the CELLS 'double bubble' hardware

    Science.gov (United States)

    Duke, P. J.; Arizpe, Jorge; Montufar-Solis, Dina

    1991-01-01

    The CELLS experiment scheduled to be flown on the first International Microgravity Laboratory is designed to study the effect of microgravity on the cartilage formation, by measuring parameters of growth in a differentiating cartilage cell culture. This paper investigates the conditions for this experiment by studying cartilage differentiation in the 'bubble exchange' hardware with the 'double bubble' design in which the bubbles are joined by a flange which also overlays the gasket. Four types of double bubbles (or double gas permeable membranes) were tested: injection-molded bubbles 0.01- and 0.005-in. thick, and compression molded bubbles 0.015- and 0.01-in. thick. It was found that double bubble membranes of 0.005- and 0.010-in. thickness supported cartilage differentiation, while the 0.015-in. bubbles did not. It was also found that nodule count, used in this study as a parameter, is not the best measure of the amount of cartilage differentiation.

  12. Role of nucleation of bile liquid crystal in gallstone formation

    Institute of Scientific and Technical Information of China (English)

    Hai-Ming Yang; Jie Wu; Jin-Yi Li; Lin Gu; Min-Fei Zhou

    2003-01-01

    AIM: To explore the role of bile liquid crystal in the process of gallbladder stone formation and to provide bases for preventing and treating cholelithiasis.METHODS: 46 guinea pigs, half males and half females,were randomly divided into control group and stone-causing group. Normal feed and stoneleading feed were used respectively to raise guinea pigs in the control group and stone-causing group. The guinea pigs were killed in three batches during the raising period. Under polarizing microscope, the pattern changes of bile liquid crystal in the gallbladder biles of the guinea pigs in the control group and stone-causing group were dynamicly observed respectively in single-blind trial.RESULTS: It was found that there were few crystals in the guinea pigs′biles of the control group, and their Malta cross was small and scattered, and existed in single form. With the increase of the feeding days, bile liquid crystals grew and Malta cross became bigger with their distribution densified, denser somewhere, but always existed in single form. While those of the stone-causing group had more bile liquid crystals, Malta cross was big and merged in strings.With the increase of the feeding days, bile liquid crystals grew in amount and strings of Malta cross increased and became bigger. The crosses in strings were arranged more and more regularly and they gradually changed into stone crystals.CONCLUSION: Formation of gallbladder stone is a process of nucleation from different substances, and the causing-stone gallbladder bile is a constantly supersaturated solution, and bile liquid crystal is a nucleation factor in the formation of gallbladder stones. The process of nucleation includes gathering, merging and phase-changing of bile liquid crystals.The process of gathering, merging of bile liquid crystal is the key to nucleation.

  13. Crystal-free Formation of Non-Oxide Optical Fiber

    Science.gov (United States)

    Nabors, Sammy A.

    2015-01-01

    Researchers at NASA Marshall Space Flight Center have devised a method for the creation of crystal-free nonoxide optical fiber preforms. Non-oxide fiber optics are extensively used in infrared transmitting applications such as communication systems, chemical sensors, and laser fiber guides for cutting, welding and medical surgery. However, some of these glasses are very susceptible to crystallization. Even small crystals can lead to light scatter and a high attenuation coefficient, limiting their usefulness. NASA has developed a new method of non-oxide fiber formation that uses axial magnetic fields to suppress crystallization. The resulting non-oxide fibers are crystal free and have lower signal attenuation rates than silica based optical fibers.

  14. Lamb wave band gaps in one-dimensional radial phononic crystal plates with periodic double-sided corrugations

    Energy Technology Data Exchange (ETDEWEB)

    Li, Yinggang [School of Mechanical Engineering and State Key Laboratory for Strength and Vibration of Mechanical Structures, Xi’an Jiaotong University, Xi’an, 710049 (China); School of Transportation, Wuhan University of Technology, Wuhan 430070 (China); Chen, Tianning [School of Mechanical Engineering and State Key Laboratory for Strength and Vibration of Mechanical Structures, Xi’an Jiaotong University, Xi’an, 710049 (China); Wang, Xiaopeng, E-mail: xpwang@mail.xjtu.edu.cn [School of Mechanical Engineering and State Key Laboratory for Strength and Vibration of Mechanical Structures, Xi’an Jiaotong University, Xi’an, 710049 (China); Li, Suobin [School of Mechanical Engineering and State Key Laboratory for Strength and Vibration of Mechanical Structures, Xi’an Jiaotong University, Xi’an, 710049 (China)

    2015-11-01

    In this paper, we present the theoretical investigation of Lamb wave propagation in one-dimensional radial phononic crystal (RPC) plates with periodic double-sided corrugations. The dispersion relations, the power transmission spectra, and the displacement fields of the eigenmodes are studied by using the finite element method based on two-dimensional axial symmetry models in cylindrical coordinates. Numerical results show that the proposed RPC plates with periodic double-sided corrugations can yield several band gaps with a variable bandwidth for Lamb waves. The formation mechanism of band gaps in the double-sided RPC plates is attributed to the coupling between the Lamb modes and the in-phase and out-phases resonant eigenmodes of the double-sided corrugations. We investigate the evolution of band gaps in the double-sided RPC plates with the corrugation heights on both sides arranged from an asymmetrical distribution to a symmetrical distribution gradually. Significantly, with the introduction of symmetric double-sided corrugations, the antisymmetric Lamb mode is suppressed by the in-phase resonant eigenmodes of the double-sided corrugations, resulting in the disappearance of the lowest band gap. Furthermore, the effects of the geometrical parameters on the band gaps are further explored numerically.

  15. Crystal orbital study on the double walls made of nanotubes encapsulated inside zigzag carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Xin [College of Chemistry, Beijing Normal University, Beijing 100875 (China); Qiao, Weiye [College of Chemical Engineering and Biological Technology, Xingtai University, Xingtai 054001 (China); Li, Yuliang [College of Chemistry, Beijing Normal University, Beijing 100875 (China); Huang, Yuanhe, E-mail: yuanhe@bnu.edu.cn [College of Chemistry, Beijing Normal University, Beijing 100875 (China)

    2015-01-15

    The structure stabilities and electronic properties are investigated by using ab initio self-consistent-field crystal orbital method based on density functional theory for the one-dimensional (1D) double-wall nanotubes made of n-gon SiO{sub 2} nanotubes encapsulated inside zigzag carbon nanotubes. It is found that formation of the combined systems is energetically favorable when the distance between the two constituents is around the Van der Waals scope. The obtained band structures show that all the combined systems are semiconductors with nonzero energy gaps. The frontier energy bands (the highest occupied band and the lowest unoccupied band) of double-wall nanotubes are mainly derived from the corresponding carbon nanotubes. The mobilities of charge carriers are calculated to be within the range of 10{sup 2}–10{sup 4} cm{sup 2} V{sup −1} s{sup −1} for the hybrid double-wall nanotubes. Young’s moduli are also calculated for the combined systems. For the comparison, geometrical and electronic properties of n-gon SiO{sub 2} nanotubes are also calculated and discussed. - Graphical abstract: Structures and band structures of the optimum 1D Double walls nanotubes. The optimized structures are 3-gon SiO2@(15,0), 5-gon SiO2@(17,0), 6-gon SiO2@(18,0) and 7-gon SiO2@(19,0). - Highlights: • The structure and electronic properties of the 1D n-gon SiO{sub 2}@(m,0)s are studied using SCF-CO method. • The encapsulation of 1D n-gon SiO{sub 2} tubes inside zigzag carbon nanotubes can be energetically favorable. • The 1D n-gon SiO{sub 2}@(m,0)s are all semiconductors. • The mobility of charge carriers and Young’s moduli are calculated.

  16. Young's double-slit experiment in photonic crystals

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Lei, E-mail: mywaters@iastate.edu [Ames Laboratory - U.S. DOE and Department of Physics and Astronomy, Iowa State University, Ames, IA 50011 (United States); Koschny, Thomas [Ames Laboratory - U.S. DOE and Department of Physics and Astronomy, Iowa State University, Ames, IA 50011 (United States); Soukoulis, C.M. [Ames Laboratory - U.S. DOE and Department of Physics and Astronomy, Iowa State University, Ames, IA 50011 (United States); Institute of Electronic Structure and Lasers (IESL), FORTH, 71110 Heraklion, Crete (Greece)

    2012-10-15

    We present an experimental and numerical study of the transmission of a photonic crystal perforated by two subwavelength slits, separated by two wavelengths. The experimental near-field image of the double-slit design of the photonic crystal shows an interference pattern, which is analogous to Young's experiment. This interference arises as a consequence of the excitation of surface states of the photonic crystals and agrees very well with the simulations.

  17. Young's double-slit experiment in photonic crystals

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Lei; Koschny, Thomas; Soukoulis, Costas M.

    2012-10-01

    We present an experimental and numerical study of the transmission of a photonic crystal perforated by two sub-wavelength slits, separated by two wavelengths.The experimental near-field image of the double-slit design of the photonic crystal shows an interference pattern, which is analogous to Young’s experiment. This interference arises as a consequence of the excitation of surface states of the photonic crystals and agrees very well with the simulations.

  18. Double-bridge bonding of aluminium and hydrogen in the crystal structure of gamma-AlH3.

    Science.gov (United States)

    Yartys, Volodymyr A; Denys, Roman V; Maehlen, Jan Petter; Frommen, Christoph; Fichtner, Maximilian; Bulychev, Boris M; Emerich, Hermann

    2007-02-19

    Aluminum trihydride (alane) is one of the most promising among the prospective solid hydrogen-storage materials, with a high gravimetric and volumetric density of hydrogen. In the present work, the alane, crystallizing in the gamma-AlH3 polymorphic modification, was synthesized and then structurally characterized by means of synchrotron X-ray powder diffraction. This study revealed that gamma-AlH3 crystallizes with an orthorhombic unit cell (space group Pnnm, a = 5.3806(1) A, b = 7.3555(2) A, c = 5.77509(5) A). The crystal structure of gamma-AlH3 contains two types of AlH6 octahedra as the building blocks. The Al-H bond distances in the structure vary in the range of 1.66-1.79 A. A prominent feature of the crystal structure is the formation of the bifurcated double-bridge bonds, Al-2H-Al, in addition to the normal bridge bonds, Al-H-Al. This former feature has not been previously reported for Al-containing hydrides so far. The geometry of the double-bridge bond shows formation of short Al-Al (2.606 A) and Al-H (1.68-1.70 A) bonds compared to the Al-Al distances in Al metal (2.86 A) and Al-H distances for Al atoms involved in the formation of normal bridge bonds (1.769-1.784 A). The crystal structure of gamma-AlH3 contains large cavities between the AlH6 octahedra. As a consequence, the density is 11% less than for alpha-AlH3.

  19. Application prospects of cadmium-containing crystals based on tungstates and double tungstates

    CERN Document Server

    Nagornaya, L; Apanasenko, A; Tupitsyna, I; Chernikov, V; Vostretsov, V

    2002-01-01

    Tungstate and double tungstate crystals of high scintillation efficiency and detectors based on them are applied widely in the medical imaging and radiation monitoring because of their high sensitivity to the ionizing radiation, small radiation length, high radiation hardness, low afterglow level. In this work a possibility to broaden the application field of CWO crystals have been investigated by improvement of their spectrometric quality and decreasing of their afterglow level. CWO crystals with improved characteristics have been obtained (resolution for sup 1 sup 3 sup 7 Cs <8%, afterglow <0.02% after 20 ms). A possibility is considered to use these crystals for spectrometry of thermal and resonance neutrons, which is possible due to the presence of nuclei with large cross-section for these neutrons in the crystal lattice. Compounds of a new type based on Cd, La-containing double tungstates doped with rare earth elements have been synthesized, and their luminescent characteristics have been studied. ...

  20. Crystal Structure Representations for Machine Learning Models of Formation Energies

    CERN Document Server

    Faber, Felix; von Lilienfeld, O Anatole; Armiento, Rickard

    2015-01-01

    We introduce and evaluate a set of feature vector representations of crystal structures for machine learning (ML) models of formation energies of solids. ML models of atomization energies of organic molecules have been successful using a Coulomb matrix representation of the molecule. We consider three ways to generalize such representations to periodic systems: (i) a matrix where each element is related to the Ewald sum of the electrostatic interaction between two different atoms in the unit cell repeated over the lattice; (ii) an extended Coulomb-like matrix that takes into account a number of neighboring unit cells; and (iii) an Ansatz that mimics the periodicity and the basic features of the elements in the Ewald sum matrix by using a sine function of the crystal coordinates of the atoms. The representations are compared for a Laplacian kernel with Manhattan norm, trained to reproduce formation energies using a data set of 3938 crystal structures obtained from the Materials Project. For training sets consi...

  1. Holographic Polymer-Dispersed Liquid Crystals: Materials, Formation, and Applications

    Directory of Open Access Journals (Sweden)

    Y. J. Liu

    2008-01-01

    Full Text Available By combining polymer-dispersed liquid crystal (PDLC and holography, holographic PDLC (H-PDLC has emerged as a new composite material for switchable or tunable optical devices. Generally, H-PDLC structures are created in a liquid crystal cell filled with polymer-dispersed liquid crystal materials by recording the interference pattern generated by two or more coherent laser beams which is a fast and single-step fabrication. With a relatively ideal phase separation between liquid crystals and polymers, periodic refractive index profile is formed in the cell and thus light can be diffracted. Under a suitable electric field, the light diffraction behavior disappears due to the index matching between liquid crystals and polymers. H-PDLCs show a fast switching time due to the small size of the liquid crystal droplets. So far, H-PDLCs have been applied in many promising applications in photonics, such as flat panel displays, switchable gratings, switchable lasers, switchable microlenses, and switchable photonic crystals. In this paper, we review the current state-of-the-art of H-PDLCs including the materials used to date, the grating formation dynamics and simulations, the optimization of electro-optical properties, the photonic applications, and the issues existed in H-PDLCs.

  2. Defective urinary crystallization inhibition and urinary stone formation

    Directory of Open Access Journals (Sweden)

    Mauricio Carvalho

    2006-06-01

    Full Text Available INTRODUCTION: Nephrocalcin (NC is a glycoprotein produced in the kidney and inhibits calcium oxalate crystal formation. It has been separated into 4 isoforms (A, B, C, and D and found that (A + B are more abundant than (C + D in urine of healthy subjects, but the reverse is seen in human urine of kidney stone patients. To further examine the role of this protein in inhibition of urinary crystallization, nephrocalcin isoforms were purified from 2 genetically pure dog species. MATERIALS AND METHODS: We studied healthy Beagles, known to be non-stone forming dogs, and Mini-Schnauzers, known to be calcium oxalate stone formers. NC was isolated and purified from each group. Urinary biochemistry and calcium oxalate crystal growth inhibition were measured. RESULTS: Specific crystal growth inhibition activity was significantly higher in non-stone forming dogs (9.79 ± 2.25 in Beagles vs. 2.75 ± 1.34 of Mini-Schnauzers, p < 0.005. Dissociation constants toward calcium oxalate monohydrate were 10-fold different, with Beagles' isoforms being 10 times stronger inhibitors compare to those of Mini-Schnauzers'. Isoforms C + D of NC were the main isoforms isolated in stone-forming dogs. CONCLUSION: NC of these two species of dogs differently affects calcium oxalate crystallization and might have a role in determining ulterior urinary stone formation.

  3. Double Charged Surface Layers in Lead Halide Perovskite Crystals

    KAUST Repository

    Sarmah, Smritakshi P.

    2017-02-01

    Understanding defect chemistry, particularly ion migration, and its significant effect on the surface’s optical and electronic properties is one of the major challenges impeding the development of hybrid perovskite-based devices. Here, using both experimental and theoretical approaches, we demonstrated that the surface layers of the perovskite crystals may acquire a high concentration of positively charged vacancies with the complementary negatively charged halide ions pushed to the surface. This charge separation near the surface generates an electric field that can induce an increase of optical band gap in the surface layers relative to the bulk. We found that the charge separation, electric field, and the amplitude of shift in the bandgap strongly depend on the halides and organic moieties of perovskite crystals. Our findings reveal the peculiarity of surface effects that are currently limiting the applications of perovskite crystals and more importantly explain their origins, thus enabling viable surface passivation strategies to remediate them.

  4. Dual roles of brushite crystals in calcium oxalate crystallization provide physicochemical mechanisms underlying renal stone formation.

    Science.gov (United States)

    Tang, R; Nancollas, G H; Giocondi, J L; Hoyer, J R; Orme, C A

    2006-07-01

    Calcium oxalate monohydrate (COM) crystals are the major mineral component of most kidney stones, and thus have an important role in chronic human disease. However, the physicochemical mechanisms leading to calcium oxalate (CaOx) stone disease are only partially defined. As spontaneous precipitation of CaOx is rare under renal conditions, an alternative pathway for CaOx crystallization seems necessary to resolve this central issue. We performed kinetic studies using the dual constant composition method to simultaneously analyze the crystallization of COM and brushite, the form of calcium phosphate that is most readily formed in the typical slightly acidic urinary milieu. These studies were supported by parallel analysis by scanning electron and atomic force microscopy. In these studies, mineralization of a thermodynamically stable phase (COM) was induced by the presence of brushite, a more readily precipitated inorganic phase. Furthermore, once formed, the COM crystals grew at the expense of brushite crystals causing the dissolution of the brushite crystals. These studies show that brushite may play crucial roles in the formation of COM crystals. The definition of these two roles for brushite thereby provides physicochemical explanations for the initiation of COM crystallization and also for the relative paucity of calcium phosphate detected in the majority of CaOx renal stones.

  5. Entropy-driven crystal formation on highly strained substrates

    KAUST Repository

    Savage, John R.

    2013-05-20

    In heteroepitaxy, lattice mismatch between the deposited material and the underlying surface strongly affects nucleation and growth processes. The effect of mismatch is well studied in atoms with growth kinetics typically dominated by bond formation with interaction lengths on the order of one lattice spacing. In contrast, less is understood about how mismatch affects crystallization of larger particles, such as globular proteins and nanoparticles, where interparticle interaction energies are often comparable to thermal fluctuations and are short ranged, extending only a fraction of the particle size. Here, using colloidal experiments and simulations, we find particles with short-range attractive interactions form crystals on isotropically strained lattices with spacings significantly larger than the interaction length scale. By measuring the free-energy cost of dimer formation on monolayers of increasing uniaxial strain, we show the underlying mismatched substrate mediates an entropy-driven attractive interaction extending well beyond the interaction length scale. Remarkably, because this interaction arises from thermal fluctuations, lowering temperature causes such substrate-mediated attractive crystals to dissolve. Such counterintuitive results underscore the crucial role of entropy in heteroepitaxy in this technologically important regime. Ultimately, this entropic component of lattice mismatched crystal growth could be used to develop unique methods for heterogeneous nucleation and growth of single crystals for applications ranging from protein crystallization to controlling the assembly of nanoparticles into ordered, functional superstructures. In particular, the construction of substrates with spatially modulated strain profiles would exploit this effect to direct self-assembly, whereby nucleation sites and resulting crystal morphology can be controlled directly through modifications of the substrate.

  6. Intracavity frequency doubling of CW Ti:Sapphire laser utilising BiBO nonlinear crystal

    DEFF Research Database (Denmark)

    Thorhauge, Morten; Mortensen, Jesper Liltorp; Tidemand-Lichtenberg, Peter

    Utilising BiBO nonlinear crystal frequency doubling a Ti:Sapphire CW laser gave 100 mW at 405 nm and 53 mW at 392 nm. Stability proved excellent without servo control. Broad tunability was shown around 392 nm.......Utilising BiBO nonlinear crystal frequency doubling a Ti:Sapphire CW laser gave 100 mW at 405 nm and 53 mW at 392 nm. Stability proved excellent without servo control. Broad tunability was shown around 392 nm....

  7. The green light generation by self-frequency-doubled Yb:YCOB crystal

    CERN Document Server

    Fang, Qiannan; Zhang, Huaijin; Wang, Jiyang

    2016-01-01

    Taking advantages of the broad emission bands of a Yb3+ doped calcium yttrium oxoborate (Yb:YCOB) crystal cut along the optimized direction out of principle planes with the maximum effective nonlinear coefficient, the self-frequency-doubled green light based on the self-frequency-doubling behavior of Yb:YCOB was achieved with a maximum output power of 710 mW at 523 nm.

  8. Experimental observation of robust surface states on photonic crystals possessing single and double Weyl points

    CERN Document Server

    Chen, Wen-Jie; Chan, C T

    2015-01-01

    We designed and fabricated a time-reversal invariant Weyl photonic crystal that possesses single Weyl nodes with topological charge of 1 and double Weyl nodes with a higher topological charge of 2. Using numerical simulations and microwave experiment, nontrivial band gaps with nonzero Chern numbers for a fixed kz was demonstrated. The robustness of the surface state between the Weyl photonic crystal and PEC against kz-conserving scattering was experimentally observed.

  9. Effect of urea on formation of hydroxyapatite through double-step hydrothermal processing

    Energy Technology Data Exchange (ETDEWEB)

    Parthiban, S. Prakash, E-mail: prakashparthiban@gmail.com; Kim, Ill Yong; Kikuta, Koichi; Ohtsuki, Chikara

    2011-10-10

    The effect of urea on the formation of hydroxyapatite (HAp) was studied by employing the double-step hydrothermal processing of a powder mixture of beta-tricalcium phosphate ({beta}-TCP) and dicalcium phosphate dihydrate (DCPD). Co-existence of urea was found to sustain morphology of HAp crystals in the compacts under an initial concentration of 2 mol dm{sup -3} and less. Homogenous morphology of needle-like crystals was observed on the compacts carbonated owing to decomposition of urea. Carbonate ions (CO{sub 3}{sup 2-}) was found to be substituted in both the phosphate and hydroxide sites of HAp lattice. The synthesized HAp was calcium deficient, as it had a Ca/P atomic ratio of 1.62 and the phase was identified as calcium deficient hydroxyapatite (CDHA). The release of CO{sub 3}{sup 2-} ions from urea during the hydrothermal treatment determined the morphology of the CDHA in the compacts. The usage of urea in the morphological control of carbonate-substituted HAp (CHAp) employing the double-step hydrothermal method is established. Highlights: {yields} Carbonate substituted hydroxyapatite (CHAp) compacts were developed by a new method, namely double-step hydrothermal processing. {yields} CHAp compacts with uniform micromorphology were obtained by using urea as solvent. {yields} Morphology was sustained even at higher concentration of urea, which emphasized the versatility of urea. {yields} Homogenous morphology of CHAp compacts were obtained for higher concentration of urea. Pores were also formed at higher concentration on the CHAp compacts. {yields} The slow dissociation of urea under hydrothermal conditions is the reason for morphology control.

  10. Defect formation energy in pyrochlore: the effect of crystal size

    Science.gov (United States)

    Wang, Jianwei; Ewing, Rodney C.; Becker, Udo

    2014-09-01

    Defect formation energies of point defects of two pyrochlores Gd2Ti2O7 and Gd2Zr2O7 as a function of crystal size were calculated. Density functional theory with plane-wave basis sets and the projector-augmented wave method were used in the calculations. The results show that the defect formation energies of the two pyrochlores diverge as the size decreases to the nanometer range. For Gd2Ti2O7 pyrochlore, the defect formation energy is higher at nanometers with respect to that of the bulk, while it is lower for Gd2Zr2O7. The lowest defect formation energy for Gd2Zr2O7 is found at 15-20 Å. The different behaviors of the defect formation energies as a function of crystal size are caused by different structural adjustments around the defects as the size decreases. For both pyrochlore compositions at large sizes, the defect structures are similar to those of the bulk. As the size decreases, for Gd2Ti2O7, additional structure distortions appear at the surfaces, which cause the defect formation energy to increase. For Gd2Zr2O7, additional oxygen Frenkel pair defects are introduced, which reduce the defect formation energy. As the size further decreases, increased structure distortions occur at the surfaces, which cause the defect formation energy to increase. Based on a hypothesis that correlates the energetics of defect formation and radiation response for complex oxides, the calculated results suggest that at nanometer range Gd2Ti2O7 pyrochlore is expected to have a lower radiation tolerance, and those of Gd2Zr2O7 pyrochlore to have a higher radiation tolerance. The highest radiation tolerance for Gd2Zr2O7 pyrochlore is expected to be found at ˜2 nanometers.

  11. STRUCTURE FORMATION OF COLLOIDS IN NEMATIC LIQUID CRYSTALS

    Directory of Open Access Journals (Sweden)

    B.I.Lev

    2003-01-01

    Full Text Available We investigated the behaviour of colloidal particles suspended in nematic liquid crystals. These colloidal particles interact through elastic deformation of the nematic director field which can result in nontrivial collective behavior, leading to the formation of spatially modulated structures. In this paper, the formation of lattice structures is described both by computer simulations and by analytical theory. Effective interactions of the pairs of spherical macroparticles suspended in nematic liquid crystals have been suggested by many authors. Using these pairwise interactions, spatial structures are obtained by means of dynamic simulations. We have suggested a number of possible structures, which may be formed in multi-macroparticle systems. Regions of temperatures and concentrations are determined in which such a structure might appear.

  12. Formation of nanophases by crystallization of amorphous alloys

    Energy Technology Data Exchange (ETDEWEB)

    Baricco, M. [Turin Univ. (Italy). Dipt. di Chimica Inorganica; Tiberto, P. [Istituto Elettrotecnico Nazionale, Turin (Italy); Battezzati, L. [Turin Univ. (Italy). Dipt. di Chimica Inorganica

    1995-12-31

    A comparison is made of crystallization mechanisms in Fe-based amorphous alloys (Fe{sub 73.5}Cu{sub 1}Nb{sub 3}Si{sub 13.5}B{sub 9}, Fe{sub 90}Zr{sub 7}B{sub 3}), which lead to a nanocrystalline bcc phase with peculiar soft magnetic properties through primary crystallization. In all samples, the nucleation takes place uniformely throughout the material. The presence of atoms with low diffusivity (Zr, Nb) reduces the grain growth rate so that a small size of crystals is maintained. On the contrary, even extremely fast heating and short heat treatment do not produce nanocrystals in Fe{sub 40}Ni{sub 40}B{sub 20} although the crystallization mechanism is modified. However milling the ribbon leads to nanostructured crystalline phases. The formation of nanophases by crystallization is discussed considering the temperature dependence of nucleation frequency and growth rate. The effects of various thermodynamic and kinetic parameters are analyzed and the most favourable conditions for nanocrystallization are outlined. (orig.)

  13. Diffraction imaging for in-situ characterization of double-crystal x-ray monochromators

    CERN Document Server

    Stoupin, Stanislav; Heald, Steve M; Brewe, Dale; Meron, Mati

    2015-01-01

    Imaging of the Bragg reflected x-ray beam is proposed and validated as an in-situ method for characterization of performance of double-crystal monochromators under the heat load of intense synchrotron radiation. A sequence of images is collected at different angular positions on the reflectivity curve of the second crystal and analyzed. The method provides rapid evaluation of the wavefront of the exit beam, which relates to local misorientation of the crystal planes along the beam footprint on the thermally distorted first crystal. The measured misorientation can be directly compared to results of finite element analysis. The imaging method offers an additional insight on the local intrinsic crystal quality over the footprint of the incident x-ray beam.

  14. Measurement & Minimization of Mount Induced Strain on Double Crystal Monochromator Crystals

    Science.gov (United States)

    Kelly, J.; Alcock, S. G.

    2013-03-01

    Opto-mechanical mounts can cause significant distortions to monochromator crystals and mirrors if not designed or implemented carefully. A slope measuring profiler, the Diamond-NOM [1], was used to measure the change in tangential slope as a function of crystal clamping configuration and load. A three point mount was found to exhibit the lowest surface distortion (Diamond Light Source.

  15. Highly birefringent extruded elliptical-hole photonic crystal fibers with single defect and double defects

    Institute of Scientific and Technical Information of China (English)

    Zhongjiao He

    2009-01-01

    Highly birefringent elliptical-hole photonic crystal fibers(PCFs)with single defect and double defects are proposed,which are suppoosed to be achieved by extruding normal circular-hole PCFs based on a triangular lattice photonic crystal structure.Comparative research on the birefringence and the confinement loss of the proposed PCFs with single defect and double defects is presented.Simulation results show that the proposed PCFs with single defect and double defects can be with high birefringence(even up to the order of 10-2).The confinement loss increases when the ellipticity of the air hole of the PCFs increases,which nevertheless can be overconle by increasing the ring number or the area of the air holes in the fiber cladding.

  16. ZnWO_4 crystals as detectors for double beta decay and dark matter experiments

    CERN Document Server

    Danevich, F A; Nagorny, S S; Poda, D V; Tretyak, V I; Yurchenko, S S; Zdesenko, Y G; Zdesenko, Yu.G.

    2004-01-01

    Energy resolution, alpha/beta ratio, and the pulse shape discrimination ability of the ZnWO_4 crystal scintillators were studied. The radioactive contamination of a ZnWO_4 crystal was investigated in the Solotvina Underground Laboratory. Possibilities to apply ZnWO_4 crystals for the dark matter and double beta decay searches are discussed. New improved half-life limits on double beta decay in zinc isotopes were established, in particular, for EC\\beta^+ decay of 64-Zn as: T_1/2^2nu > 8.9 10^18 yr and T_1/2^0nu > 3.6 10^18 yr, both at 68% CL.

  17. Formation of Cu/Pd bimetallic crystals by electrochemical deposition

    Energy Technology Data Exchange (ETDEWEB)

    Alvarez, A.E. [Instituto de Ingenieria Electroquimica y Corrosion (INIEC), Departamento de Ingenieria Quimica, Universidad Nacional del Sur, Avda. Alem 1253, 8000 Bahia Blanca (Argentina); Salinas, D.R., E-mail: dsalinas@uns.edu.a [Instituto de Ingenieria Electroquimica y Corrosion (INIEC), Departamento de Ingenieria Quimica, Universidad Nacional del Sur, Avda. Alem 1253, 8000 Bahia Blanca (Argentina)

    2010-04-15

    The early stages of the palladium electrodeposition process onto a vitreous carbon (VC) substrate as well as the deposition of Cu on such Pd/VC modified surface were investigated using classical electrochemical techniques, atomic force microscopy (AFM) and scanning electron microscopy (SEM). Within the potential range considered the kinetics of the Pd electrodeposition from a PdCl{sub 2} acid solution can be described by a model involving progressive nucleation on active sites and diffusion-controlled 3D growth. The nucleation rate constant, A{sub 0}, and the number of active sites of the substrate, N{sub 0}, were determined from the analysis of potentiostatic current transients on the basis of an existing theoretical model. The AFM images corroborated the progressive nucleation mechanism showing irregular palladium crystals randomly distributed over the VC surface, with different sizes and 3D morphological characteristics. The electrodeposition of Cu was carried out onto the characterized Pd/VC modified surface from a Cu{sup 2+} containing solution using a well defined polarization routine. The SEM/EDX images confirmed the formation of Cu/Pd bimetallic crystals uniformly distributed on the VC surface and the in situ AFM images obtained during this process corroborated that Cu formed a core-shell structure with the Pd crystals. Nevertheless, the subsequent anodic stripping produced only a partial dissolution of the Cu deposits, and therefore, the formation of a Cu/Pd alloy could be inferred.

  18. Intracavity doubling of CW Ti:sapphire laser to 392.5 nm using BiBO-crystal

    DEFF Research Database (Denmark)

    Mortensen, Jesper Liltorp; Thorhauge, Morten; Tidemand-Lichtenberg, Peter

    2005-01-01

    In this work we present results obtained for intra-cavity frequency-doubling of a 785 nm CW Ti:sapphire laser utilising BiBO as the non-linear crystal. Intracavity doubling offers several advantages compared to extra-cavity doubling, such as no need to couple to an external resonance cavity...

  19. NONISOTHERMAL CRYSTALLIZATION AND MORPHOLOGY OF POLY(BUTYLENE SUCCINATE)/LAYERED DOUBLE HYDROXIDE NANOCOMPOSITES

    Institute of Scientific and Technical Information of China (English)

    Mei-qiu Zhan; Guang-yi Chen; Zhi-yong Wei; Yu-mei Shi; Wan-xi Zhang

    2013-01-01

    Biodegradable poly(butylene succinate) (PBS) and layered double hydroxide (LDH) nanocomposites were prepared via melt blending in a twin-screw extruder.The morphology and dispersion of LDH nanoparticles within PBS matrix were characterized by transmission electron microscopy (TEM),which showed that LDH nanoparticles were found to be well distributed at the nanometer level.The nonisothermal crystallization behavior of nanocomposites was extensively studied using differential scanning calorimetry (DSC) technique at various cooling rates.The crystallization rate of PBS was accelerated by the addition of LDH due to its heterogeneous nucleation effect; however,the crystallization mechanism and crystal structure of PBS remained almost unchanged.In kinetics analysis of nonisothermal crystallization,the Ozawa approach failed to describe the crystallization behavior of PBS/LDH nanocomposites,whereas both the modified Avrami model and the Mo method well represented the crystallization behavior of nanocomposites.The effective activation energy was estimated as a function of the relative degree of crystallinity using the isoconversional analysis.The subsequent melting behavior of PBS and PBS/LDH nanocomposites was observed to be dependent on the cooling rate.The POM showed that the small and less perfect crystals were formed in nanocomposites.

  20. Microwave plasma formation within a 2D photonic crystal

    Science.gov (United States)

    Parsons, Stephen; Gregório, José; Hopwood, Jeffrey

    2017-05-01

    Experiments demonstrate that an electromagnetic wave incident on a photonic crystal (PhC) containing a single point-defect causes gas breakdown. After breakdown we report the formation of a stable microwave plasma within this free-space vacancy. We show that gas breakdown is possible in low-pressure argon (10 Torr) using as little as 1.4 W of microwave power if the frequency of the incident wave is equal to the resonance of the vacancy (8.614 GHz). During formation, the plasma-filled defect decreases the transmission of energy through the photonic crystal by approximately two orders of magnitude. Plasma formation time is measured to be as fast as 100 ns at relatively high power (9 W). Using the transmission of energy through the PhC as a diagnostic tool, we report that the electron density of the microwave plasma is 1016-1017 m-3 for argon pressures between 10 and 50 Torr. Finally, we consider the application of the self-initiated plasma within the PhC as a simple power limiter.

  1. Doubled heterogeneous crystal nucleation in sediments of hard sphere binary-mass mixtures.

    Science.gov (United States)

    Löwen, Hartmut; Allahyarov, Elshad

    2011-10-07

    Crystallization during the sedimentation process of a binary colloidal hard spheres mixture is explored by Brownian dynamics computer simulations. The two species are different in buoyant mass but have the same interaction diameter. Starting from a completely mixed system in a finite container, gravity is suddenly turned on, and the crystallization process in the sample is monitored. If the Peclet numbers of the two species are both not too large, crystalline layers are formed at the bottom of the cell. The composition of lighter particles in the sedimented crystal is non-monotonic in the altitude: it is first increasing, then decreasing, and then increasing again. If one Peclet number is large and the other is small, we observe the occurrence of a doubled heterogeneous crystal nucleation process. First, crystalline layers are formed at the bottom container wall which are separated from an amorphous sediment. At the amorphous-fluid interface, a secondary crystal nucleation of layers is identified. This doubled heterogeneous nucleation can be verified in real-space experiments on colloidal mixtures. © 2011 American Institute of Physics

  2. Double-double radio galaxies : Further insights into the formation of the radio structures

    NARCIS (Netherlands)

    Brocksopp, C.; Kaiser, C.R.; Schoenmakers, A. P.; de Bruyn, A. G.

    2011-01-01

    Double-double radio galaxies (DDRGs) offer a unique opportunity for us to study multiple episodes of jet activity in large-scale radio sources. We use radio data from the Very Large Array and the literature to model two DDRGs, B1450+333 and B1834+620, in terms of their dynamical evolution. We find t

  3. Double-double radio galaxies: further insights into the formation of the radio structures

    NARCIS (Netherlands)

    Brocksopp, C.; Kaiser, C. R.; Schoenmakers, A. P.; de Bruyn, A. G.

    2011-01-01

    Double-double radio galaxies (DDRGs) offer a unique opportunity for us to study multiple episodes of jet activity in large-scale radio sources. We use radio data from the Very Large Array and the literature to model two DDRGs, B1450+333 and B1834+620, in terms of their dynamical evolution. We find t

  4. Diagenetic Crystal Growth in the Murray Formation, Gale Crater, Mars

    Science.gov (United States)

    Kah, L. C.; Kronyak, R. E.; Ming, D. W.; Grotzinger, J. P.; Schieber, J.; Sumner, D. Y.; Edgett, K. S.

    2015-01-01

    The Pahrump region (Gale Crater, Mars) marks a critical transition between sedimentary environments dominated by alluvial-to-fluvial materials associated with the Gale crater rim, and depositional environments fundamentally linked to the crater's central mound, Mount Sharp. At Pahrump, the Murray formation consists of an approximately 14-meter thick succession dominated by massive to finely laminated mudstone with occasional interbeds of cross-bedded sandstone, and is best interpreted as a dominantly lacustrine environment containing tongues of prograding fluvial material. Murray formation mudstones contain abundant evidence for early diagenetic mineral precipitation and its subsequent removal by later diagenetic processes. Lenticular mineral growth is particularly common within lacustrine mudstone deposits at the Pahrump locality. High-resolution MAHLI images taken by the Curiosity rover permit detailed morphological and spatial analysis of these features. Millimeter-scale lenticular features occur in massive to well-laminated mudstone lithologies and are interpreted as pseudomorphs after calcium sulfate. The distribution and orientation of lenticular features suggests deposition at or near the sediment-water (or sediment-air) interface. Retention of chemical signals similar to host rock suggests that original precipitation was likely poikilotopic, incorporating substantial amounts of the primary matrix. Although poikilotopic crystal growth is common in burial environments, it also occurs during early diagenetic crystal growth within unlithified sediment where high rates of crystal growth are common. Loss of original calcium sulfate mineralogy suggests dissolution by mildly acidic, later-diagenetic fluids. As with lenticular voids observed at Meridiani by the Opportunity Rover, these features indicate that calcium sulfate deposition may have been widespread on early Mars; dissolution of depositional and early diagenetic minerals is a likely source for both calcium

  5. CdWO4 crystal scintillators from enriched isotopes for double beta decay experiments

    CERN Document Server

    Poda, D V; Belli, P; Bernabei, R; Boiko, R S; Brudanin, V B; Cappella, F; Caracciolo, V; Castellano, S; Cerulli, R; Chernyak, D M; Danevich, F A; d'Angelo, S; Degoda, V Ya; Di Vacri, M L; Dossovitskiy, A E; Galashov, E N; Incicchitti, A; Kobychev, V V; Konovalov, S I; Kovtun, G P; Laubenstein, M; Mikhlin, A L; Mokina, V M; Nikolaiko, A S; Nisi, S; Podviyanuk, R B; Polischuk, O G; Shcherban, A P; Shlegel, V N; Solopikhin, D A; Tretyak, V I; Umatov, V I; Vasiliev, Ya V; Virich, V D

    2013-01-01

    Cadmium tungstate crystal scintillators enriched in 106Cd and 116Cd were developed. The produced scintillators exhibit good optical and scintillation properties, and a low level of radioactive contamination. Experiments to search for double beta decay of 106Cd and 116Cd are in progress at the Gran Sasso National Laboratories of the INFN (Italy). Prospects to further improve the radiopurity of the detectors by recrystallization are discussed.

  6. Dynamics of two coupled chaotic multimode Nd:YAG lasers with intracavity frequency doubling crystal

    Indian Academy of Sciences (India)

    Thomas Kuruvilla; V M Nandakumaran

    2000-03-01

    The effect of coupling two chaotic Nd:YAG lasers with intracavity KTP crystal for frequency doubling is numerically studied for the case of the laser operating in three longitudinal modes. It is seen that the system goes from chaotic to periodic and then to steady state as the coupling constant is increased. The intensity time series and phase diagrams are drawn and the Lyapunov characteristic exponent is calculated to characterize the chaotic and periodic regions.

  7. Double-crystal monochromator for a PF 60-period soft x-ray undulator (abstract)

    Science.gov (United States)

    Ishikawa, T.; Maezawa, H.; Nomura, M.; Ando, M.

    1989-07-01

    Since undulator light is sharply collimated itself, it can be effectively monochromatized by a perfect crystal. An x-ray double-crystal monochromator with a fixed exit has been designed and built for the use of undulator light from a 60-period undulator at Photon Factory (beamline 2A). Available Bragg angle ranges from 7° to 80°. Angle scan is made by means of a goniometer outside the vacuum chamber, with the finest step of 0.1 arcsec. Magnetic fluid is used as the vacuum seal of the feedthrough. The fixed exit beam position is kept by translating the second crystal along the two mechanical guides: one for normal and the other for parallel to the crystal surface. Adjustment of the parallelity of two crystals is made manually with flexible wires. Since a total power in the central coherent portion which is limited by a 1×1-mm2 slit is not so much, a stable operation is possible without cooling the crystal. Currently, InSb (111) reflection is used. The diffracting planes of the first cyrstal is 1° off from the surface and the second is the symmetric reflection. At its fifth harmonics, brilliant undulator light of approximately 1012 photons/s mm2 with 1-eV energy resolution is available (E=2 keV).

  8. Double-crystal monochromator as the first optical element in BESSRC-CAT beamlines (abstract)

    Science.gov (United States)

    Beno, Mark A.; Ramanathan, Mohan

    1996-09-01

    The first optical element in the BESSRC-CAT beamlines at the Advanced Photon Source will be a monochromator, so that a standard design for this critical component is advantageous. The monochromator we have designed is a double-crystal, fixed-exit scheme with a constant offset designed for UHV operation, thereby allowing windowless operation of the beamlines. The crystals are mounted on a turntable with the first crystal at the center of rotation. A mechanical linkage is used to correctly position the second crystal and maintain a constant offset. The main drive for the rotary motion is provided by a vacuum-compatible Huber goniometer isolated from the main vacuum chamber. Rotary motion of the primary monochromator stage is accomplished by using two adjacent vacuum chambers connected only by the small annular opening around a hollow stainless steel shaft, which connects the Huber goniometer to the turntable on which the crystals are mounted. The design of the monochromator is such that it can accommodate both water and liquid nitrogen cooling for the crystal optics. The basic design for the monochromator linkage mechanism will be presented along with details of the monochromator chamber. The results of initial optical tests of the monochromator system using tilt sensors and a precision autocollimator will also be given.

  9. Double-clad hollow core photonic crystal fiber for coherent Raman endoscope.

    Science.gov (United States)

    Brustlein, Sophie; Berto, Pascal; Hostein, Richard; Ferrand, Patrick; Billaudeau, Cyrille; Marguet, Didier; Muir, Alistair; Knight, Jonathan; Rigneault, Hervé

    2011-06-20

    Performing label free coherent anti-Stokes Raman scattering (CARS) and stimulated Raman scattering (SRS) in endoscope imaging is a challenge, with huge potential clinical benefit. To date, this goal has remained inaccessible because of the inherent coherent Raman noise that is generated in the fiber itself. By developing double-clad hollow core photonic crystal fiber, we demonstrate coherent anti-Stokes Raman scattering and stimulated Raman scattering in an 'endoscope-like' scheme. Both the excitation beams and the collected CARS and SRS signals travel through the same fiber. No CARS and SRS signals are generated within the hollow core fiber even for temporally overlapping pump and Stokes beams, leading to excellent image quality. The CARS and SRS signals generated in the sample are coupled back into a high numerical aperture multimode cladding surrounding the central photonic crystal cladding. We demonstrate this scheme by imaging molecular vibrational bonds of organic crystal deposited on a glass surface.

  10. Double-slit dynamical diffraction of X-rays in ideal crystals (Laue case).

    Science.gov (United States)

    Balyan, Minas K

    2010-11-01

    The theoretical investigation of double-slit dynamical X-ray diffraction in ideal crystals shows that, on the exit surface of crystals, interference fringes similar to Young's fringes are formed. An expression for the period of the fringes was obtained. The visibility of the fringes depending on temporal and spatial coherent properties of the incident beam is studied. The polarization state of the incident beam also affects the visibility of the fringes, which in turn depends on the size of the slits. The deviation from Bragg's exact angle causes a shift of the fringes and can also affect the amplitude of the intensity. One of the parameters on which the visibility of the fringes depends is the source-crystal distance. The proposed scheme can be used as a Rayleigh X-ray interferometer. Use of the scheme as a Michelson X-ray stellar interferometer is also possible.

  11. Evolutionary Channels for the Formation of Double Neutron Stars

    CERN Document Server

    Andrews, Jeff J; Kalogera, Vicky; Willems, Bart

    2014-01-01

    We analyze binary population models of double-neutron stars and compare results to the accurately measured orbital periods and eccentricities of the eight known such systems in our Galaxy. In contrast to past similar studies, we especially focus on the dominant evolutionary channels (we identify three); for the first time, we use a detailed understanding of the evolutionary history of three double neutron stars as actual constraints on the population models. We find that the evolutionary constraints derived from the double pulsar are particularly tight, and less than half of the examined models survive the full set of constraints. The top-likelihood surviving models yield constraints on the key binary evolution parameters, but most interestingly reveal (i) the need for electron-capture supernovae from relatively low-mass degenerate, progenitor cores, and (ii) the most likely evolutionary paths for the rest of the known double neutron stars. In particular, we find that J1913+16 likely went through a phase of C...

  12. Crystallization in Earth's Core after High-Temperature Core Formation

    Science.gov (United States)

    Hirose, K.; Morard, G.; Hernlund, J. W.; Helffrich, G. R.; Ozawa, H.

    2015-12-01

    Recent core formation models based on the metal-silicate partitioning of siderophile elements suggest that the Earth's core was formed by metal segregation at high pressure and high temperature in a deep magma ocean. It is also thought that the simultaneous solubility of silicon and oxygen in liquid iron are strongly enhanced at high pressure and high temperature, such that at the end of accretion the core was rich in both silicon and oxygen. Here we performed crystallization experiments on the Fe-Si binary and Fe-Si-O ternary systems up to core pressure in a laser-heated diamond-anvil cell. The starting material for the latter was a homogeneous mixture of fine-grain Fe-Si and SiO2 (sustain without extreme degrees of secular cooling. However, even for modest degrees of joint Si-O incorporation into the early core, the buoyancy released by crystallization of SiO2 is sufficient to overcome thermal stratification and sustain the geodynamo.

  13. A Unified Theory of Melting, Crystallization and Glass Formation

    DEFF Research Database (Denmark)

    Cotterill, R. M. J.; Jensen, F. J.; Damgaard Kristensen, W.

    1975-01-01

    -atomic dimensions, and the demonstration by Kotze and Kuhlmann-Wilsdorf that the solid-liquid interfacial energy is proportional to the grain boundary energy for a number of elements. These developments suggest the possibility of a relatively simple picture of crystallization and glass formation. In the liquid...... state dislocations, at the saturation density, are in constant motion and the microscopic grain boundary structure that they form is constantly changing due to dislocation-dislocation interaction. As the liquid is cooled below the melting point the free energy favors the crystalline form and grains...... especially on the amount of dislocation motion that can take place during the critical period when nucleation and growth becomes favored thermodynamically. Thus the glassy form will have a better chance of being formed if either the liquid is particularly viscous or if the cooling rate is particularly rapid....

  14. Fat crystal migration and aggregation and polymorphism evolution during the formation of granular crystals in beef tallow and palm oil.

    Science.gov (United States)

    Meng, Zong; Geng, Wenxin; Wang, Xingguo; Liu, Yuanfa

    2013-12-26

    Six rectangular block all beef tallow (BT)-based and all palm oil (PO)-based model shortenings prepared on a laboratory scale, denoted BTMS and POMS, respectively, were stored under two storage conditions, (1) constant temperatures (5 and 20 °C, respectively and (2) temperature fluctuations (5 °C for 12 h and 20 °C for 12 h for a cycle), to induce granular crystals. The fat crystal migration and aggregation, sensory evaluations, and polymorphism evolutions during the formation of granular crystals in the above samples were investigated systematically. In comparison to the constant temperature storage, the crystal growth and hierarchical aggregation process were more quick and the conversion rate of the β-form crystal was also faster in both BTMS and POMS under temperature cycling storage and, concomitantly, easier to induce the formation of granular crystals. From the comprehensive analysis of crystal sizes and the sensory evaluation results, it can be concluded that the detection threshold for graininess ranged from 40 to 90 μm, with the smaller size being perceived only at higher crystal concentrations. The possible formation mechanism and the realistic control approaches for granular crystals in plastic fats also are clarified in the present study.

  15. Aluminium substitution in iron(II III)-layered double hydroxides: Formation and cationic order

    Science.gov (United States)

    Ruby, Christian; Abdelmoula, Mustapha; Aissa, Rabha; Medjahdi, Ghouti; Brunelli, Michela; François, Michel

    2008-09-01

    The formation and the modifications of the structural properties of an aluminium-substituted iron(II-III)-layered double hydroxide (LDH) of formula Fe4IIFe(2-6y)IIIAl6yIII (OH) 12 SO 4, 8H 2O are followed by pH titration curves, Mössbauer spectroscopy and high-resolution X-ray powder diffraction using synchrotron radiation. Rietveld refinements allow to build a structural model for hydroxysulphate green rust, GR(SO 42-), i.e. y=0, in which a bilayer of sulphate anions points to the Fe 3+ species. A cationic order is proposed to occur in both GR(SO 42-) and aluminium-substituted hydroxysulphate green rust when yhydroxides. Adsorption of more soluble Al III species onto the initially formed ferric oxyhydroxide may be responsible for this slowdown of crystal growth. Therefore, the insertion of low aluminium amount ( y˜0.01) could be an interesting way for increasing the surface reactivity of iron(II-III) LDH that maintains constant the quantity of the reactive Fe II species of the material.

  16. Spontaneous formation of non-uniform double helices for elastic rods under torsion

    Energy Technology Data Exchange (ETDEWEB)

    Li, Hongyuan [Department of Applied Physics, School of Science, Xi' an Jiaotong University, Shaanxi 710049 (China); Zhao, Shumin, E-mail: zhaosm@mail.xjtu.edu.cn [Department of Applied Physics, School of Science, Xi' an Jiaotong University, Shaanxi 710049 (China); Xia, Minggang [Department of Optical Information Science and Technology, School of Science, Xi' an Jiaotong University, 710049 (China); Laboratory of Nanostructure and Physics Properties, School of Science, Xi' an Jiaotong University, 710049 (China); He, Siyu [Department of Applied Physics, School of Science, Xi' an Jiaotong University, Shaanxi 710049 (China); Yang, Qifan [Department of Biomedical Engineering, School of Life Science and Technology, Xi' an Jiaotong University, Shaanxi 710049 (China); Yan, Yuming [Department of Electrical Engineering and Automation, School of Electrical Engineering, Xi' an Jiaotong University, Shaanxi 710049 (China); Zhao, Hanqiao [Department of Biomedical Engineering, School of Life Science and Technology, Xi' an Jiaotong University, Shaanxi 710049 (China)

    2017-02-19

    The spontaneous formation of double helices for filaments under torsion is common and significant. For example, the research on the supercoiling of DNA is helpful for understanding the replication and transcription of DNA. Similar double helices can appear in carbon nanotube yarns, cables, telephone wires and so forth. We noticed that non-uniform double helices can be produced due to the surface friction induced by the self-contact. Therefore an ideal model was presented to investigate the formation of double helices for elastic rods under torque. A general equilibrium condition which is valid for both the smooth surface and the rough surface situations is derived by using the variational method. By adding further constraints, the smooth and rough surface situations are investigated in detail respectively. Additionally, the model showed that the specific process of how to twist and slack the rod can determine the surface friction and hence influence the configuration of the double helix formed by rods with rough surfaces. Based on this principle, a method of manufacturing double helices with designed configurations was proposed and demonstrated. Finally, experiments were performed to verify the model and the results agreed well with the theory. - Highlights: • An ideal model is conceived to investigate the spontaneous formation of double helices for rods under torsion. • Variational method is used to obtain a universal result for the double helix formation process • Self-contact and surface friction is considered to analyze the non-uniform double helix. • A novel method of producing double helix with arbitrary configuration is proposed and demonstrated. • The experiment results agree well with the theory.

  17. Double Doppler effect in two-dimensional photonic crystal with negative effective index

    Science.gov (United States)

    Jiang, Qiang; Chen, Jiabi; Liang, Binming; Zhuang, Songlin

    2016-11-01

    The inverse Doppler effect in photonic crystal with negative refractive index had been proofed experimentally in our previous research. In this paper, we studied the spatial harmonics of Bloch wave propagating in such PhCs by FFT method. The lagging and front phase evolutions reveal that both backward wave and forward wave exist in these harmonics. Subsequently, we studied the double Doppler effect phenomenon that both the normal and inverse Doppler exist in one photonic crystal simultaneously by using the improved dynamic FDTD method which we made it suitable for dealing with moving objects. The simulative Doppler frequency shifts were consistent with the theoretical values. Our study provides a potential technology in measurement area.

  18. Diffusion model of the formation of growth microdefects: A new approach to defect formation in crystals (Review)

    Science.gov (United States)

    Talanin, V. I.; Talanin, I. E.

    2016-03-01

    Theoretical studies of defect formation in semiconductor silicon play an important role in the creation of breakthrough ideas for next-generation technologies. A brief comparative analysis of modern theoretical approaches to the description of interaction of point defects and formation of the initial defect structure of dislocation-free silicon single crystals has been carried out. Foundations of the diffusion model of the formation of structural imperfections during the silicon growth have been presented. It has been shown that the diffusion model is based on high-temperature precipitation of impurities. The model of high-temperature precipitation of impurities describes processes of nucleation, growth, and coalescence of impurities during cooling of a crystal from 1683 to 300 K. It has been demonstrated that the diffusion model of defect formation provides a unified approach to the formation of a defect structure beginning with the crystal growth to the production of devices. The possibilities of using the diffusion model of defect formation for other semiconductor crystals and metals have been discussed. It has been shown that the diffusion model of defect formation is a platform for multifunctional solution of many key problems in modern solid state physics. Fundamentals of practical application of the diffusion model for engineering of defects in crystals with modern information technologies have been considered. An algorithm has been proposed for the calculation and analysis of a defect structure of crystals.

  19. Formation of liquid inclusion induced light scatter in KDP (DKDP) crystals

    Institute of Scientific and Technical Information of China (English)

    孙洵; 孙大亮; 许心光; 王正平; 付有君; 王圣来; 曾红; 李毅平; 于锡玲; 高樟寿

    2001-01-01

    We describe in this paper the formation of liquid inclusion induced light scatter in potassium dihydrogen phosphate (KDP) crystal and deuterated potassium dihydrogen phosphate (DKDP) crystals. The measurement has been done with an atomic force microscope (AFM). The mechanism of formation of liquid inclusion scatter has been proposed and the effect of super-saturation discussed.

  20. Application of PbWO4 crystal scintillators in experiment to search for double beta decay of 116Cd

    CERN Document Server

    Danevich, F A; Kobychev, V V; Kropivyansky, B N; Nagorny, S S; Nikolaiko, A S; Poda, D V; Tretyak, V I; Yurchenko, S S; Grinyov, B V; Nagornaya, L L; Pirogov, E N; Ryzhikov, V D; Brudanin, V B; Fedorov, M; Korzhik, M; Lobko, A; Miussevitch, O; Solsky, I M

    2004-01-01

    PbWO4 crystal scintillators are discussed as an active shield and light-guides in 116Cd double beta decay experiment with CdWO4 scintillators. Scintillation properties and radioactive contamination of PbWO4 scintillators were investigated. Energy resolution of CdWO4 detector, coupled to PbWO4 crystal as a light-guide, was tested. Efficiency of PbWO4-based active shield to suppress background from the internal contamination of PbWO4 crystals was calculated. Using of lead tungstate crystal scintillators as high efficiency 4-pi active shield could allow to build sensitive double beta experiment with 116CdWO4 crystal scintillators.

  1. Liquid Crystal Formation from Sunflower Oil: Long Term Stability Studies.

    Science.gov (United States)

    da Rocha-Filho, Pedro Alves; Maruno, Mônica; Ferrari, Márcio; Topan, José Fernando

    2016-06-09

    The Brazilian biodiversity offers a multiplicity of raw materials with great potential in cosmetics industry applications. Some vegetable oils and fatty esters increase skin hydration by occlusivity, keeping the skin hydrated and with a shiny appearance. Sunflower (Helianthus annus L.) oil is widely employed in cosmetic emulsions in the form of soaps, creams, moisturizers and skin cleansers due to the presence of polyphenols and its high vitamin E content. Liquid crystals are systems with many applications in both pharmaceutical and cosmetic formulations and are easily detected by microscopy under polarized light due to their birefringence properties. The aim of this research was to develop emulsions from natural sunflower oil for topical uses. Sunflower oil (75.0% w/w) was combined with liquid vaseline (25.0% w/w) employing a natural self-emulsifying base (SEB) derivative. The high temperature of the emulsification process did not influence the antioxidant properties of sunflower oil. Fatty esters were added to cosmetic formulations and extended stability tests were performed to characterize the emulsions. Fatty esters like cetyl palmitate and cetyl ester increase the formation of anisotropic structures. O/W emulsions showed acidic pH values and pseudoplastic behavior. The presence of a lamellar phase was observed after a period of 90 days under different storage conditions.

  2. Liquid Crystal Formation from Sunflower Oil: Long Term Stability Studies

    Directory of Open Access Journals (Sweden)

    Pedro Alves da Rocha-Filho

    2016-06-01

    Full Text Available The Brazilian biodiversity offers a multiplicity of raw materials with great potential in cosmetics industry applications. Some vegetable oils and fatty esters increase skin hydration by occlusivity, keeping the skin hydrated and with a shiny appearance. Sunflower (Helianthus annus L. oil is widely employed in cosmetic emulsions in the form of soaps, creams, moisturizers and skin cleansers due to the presence of polyphenols and its high vitamin E content. Liquid crystals are systems with many applications in both pharmaceutical and cosmetic formulations and are easily detected by microscopy under polarized light due to their birefringence properties. The aim of this research was to develop emulsions from natural sunflower oil for topical uses. Sunflower oil (75.0% w/w was combined with liquid vaseline (25.0% w/w employing a natural self-emulsifying base (SEB derivative. The high temperature of the emulsification process did not influence the antioxidant properties of sunflower oil. Fatty esters were added to cosmetic formulations and extended stability tests were performed to characterize the emulsions. Fatty esters like cetyl palmitate and cetyl ester increase the formation of anisotropic structures. O/W emulsions showed acidic pH values and pseudoplastic behavior. The presence of a lamellar phase was observed after a period of 90 days under different storage conditions.

  3. Double-double radio galaxies: further insights into the formation of the radio structures

    CERN Document Server

    Brocksopp, Catherine; Schoenmakers, Arno; de Bruyn, Ger

    2010-01-01

    Double-double radio galaxies (DDRGs) offer a unique opportunity for us to study multiple episodes of jet activity in large-scale radio sources. We use radio data from the Very Large Array and the literature to model two DDRGs, B1450+333 and B1834+620, in terms of their dynamical evolution. We find that the standard Fanaroff-Riley II model is able to explain the properties of the two outer lobes of each source, whereby the lobes are formed by ram-pressure balance of a shock at the end of the jet with the surrounding medium. The inner pairs of lobes, however, are not well-described by the standard model. Instead we interpret the inner lobes as arising from the emission of relativistic electrons within the outer lobes, which are compressed and re-accelerated by the bow-shock in front of the restarted jets and within the outer lobes. The predicted rapid progression of the inner lobes through the outer lobes requires the eventual development of a hotspot at the edge of the outer lobe, causing the DDRG ultimately t...

  4. A triple axis double crystal multiple reflection camera for ultra small angle X-ray scattering

    Science.gov (United States)

    Lambard, Jacques; Lesieur, Pierre; Zemb, Thomas

    1992-06-01

    To extend the domain of small angle X-ray scattering requires multiple reflection crystals to collimate the beam. A double crystal, triple axis X-ray camera using multiple reflection channel cut crystals is described. Procedures for measuring the desmeared scattering cross-section on absolute scale are described as well as the measurement from several typical samples : fibrils of collagen, 0.3 μm diameter silica spheres, 0.16 μm diameter interacting latex spheres, porous lignite coal, liquid crystals in a surfactant-water system, colloidal crystal of 0.32 μm diameter silica spheres. L'extension du domaine de diffusion des rayons-X vers les petits angles demande l'emploi de cristaux à réflexions multiples pour collimater le faisceau. Nous décrivons une caméra à rayons-X à trois axes où les réflexions multiples sont réalisées dans deux cristaux à gorge. Nous donnons ensuite les procédures de déconvolution pour obtenir la section efficace de diffusion en échelle absolue, ainsi que les résultats des mesures effectuées avec plusieurs échantillons typiques : fibres de collagène, sphères de silice de 0,3 μm de diamètre, sphères de latex de 0,16 μm de diamètre en interaction, charbon lignite poreux, cristaux liquides formés dans un système eau-tensioactif, solution colloïdale de sphères de silice de 0,32 μm de diamètre.

  5. Formation of D{sup -} by double radiative recombination of D{sup +}

    Energy Technology Data Exchange (ETDEWEB)

    Schuch, R.; Belkic, Dz.; Justiniano, E.; Zong, W.; Gao, H. [Stockholm Univ. (Sweden). Dept. of Atomic Phys.

    1997-04-01

    We have investigated double radiative recombination of D{sup +} ions stored in CRYRING by searching for the formation of D{sup -} in the electron cooler. An upper limit for the double electron recombination rate coefficient and a ratio of this coefficient over the single electron radiative recombination rate coefficient of (3.8 {+-} 1.5) x 10{sup -8} are obtained experimentally. Theoretical calculations of the rates and a discussion in comparison with double photoionization of H{sup -} are given. (orig.). 19 refs.

  6. Stone Formation and Fragmentation in Forgotten Ureteral Double J Stent

    Directory of Open Access Journals (Sweden)

    Okan Bas

    2014-02-01

    Full Text Available Aim: Nowadays, ureteral stents play an essential role in various endourological and open surgical procedures and common procedures performed in daily urological practice. However, stents can cause significant complications such as migration, infection, fragmentation, stone formation and encrustation, especially when forgotten for a long period. Objectives: We present our experience in endoscopic management of forgotten ureteral stents with a brief review of current literature. Case presentation: A total of 2 patients with forgotten ureteral stents were treated with endourological approaches in our department. Indwelling durations were 18 months and 36 months. After treatment both patients were stone and stent free. Conclusion: An endourological approach is effective for stent and stone removal after a single anesthesia session with minimal morbidity and short hospital stay. However, therapeutic strategy is also determined by the technology available. The best treatment would be the prevention of this complication by providing detailed patient education.

  7. An all-solid-state electrochemical double-layer capacitor based on a plastic crystal electrolyte

    Directory of Open Access Journals (Sweden)

    Ali eaabouimrane

    2015-08-01

    Full Text Available A plastic crystal, solid electrolyte was prepared by mixing tetrabutylammonium hexafluorophosphate salt, (C4H94NPF6, (10 molar % with succinonitrile, SCN, (N C−CH2−CH2−C N, [SCN-10%TBA-PF6]. The resultant waxy material shows a plastic crystalline phase that extend from -36 °C up to its melting at 23 °C. It shows a high ionic conductivity reaching 4 × 10−5 S/cm in the plastic crystal phase (15 °C and ~ 3 × 10−3 S/cm in the molten state (25 °C. These properties along with the high electrochemical stability rendered the use of this material as an electrolyte in an electrochemical double-layer capacitor (EDLC. The EDLC was assembled and its performance was tested by cyclic voltammetry, AC impedance spectroscopy and galvanostatic charge-discharge methods. Specific capacitance values in the range of 4-7 F/g. (of electrode active material were obtained in the plastic crystal phase at 15 °C, that although compare well with those reported for some polymer electrolytes, can be still enhanced with further development of the device and its components, and only demonstrate their great potential use for capacitors as a new application.

  8. Insights into the synthesis of layered double hydroxide (LDH) nanoparticles: Part 2. Formation mechanisms of LDH.

    Science.gov (United States)

    Sun, Xiaodi; Dey, Sandwip K

    2015-11-15

    This study demonstrates the effect of (co)intercalated anion compositions on nanostructure evolution to understand the formation mechanisms of layered double hydroxide (LDH) nanoparticles following coprecipitation and hydrothermal treatments (HT). Initially, the room temperature coprecipitation resulted in amorphous primary nanoparticles that agglomerated at the edges due to low surface charge densities. The reversibility of such agglomeration was determined by the crystalline quality upon HT and consequent surface charge density, which in turn were strongly influenced by the composition of the intercalated anions. Upon crystallization, the agglomerated Zn2Al(OH)6(NO3)0.3(CO3)0.35⋅xH2O primary nanoparticles re-dispersed, but the Zn2Al(OH)6(NO3)⋅xH2O nanoparticles with much lower stability and higher disorder (especially at the edges) exhibited irreversible agglomeration, and transformed into secondary nanoparticles via aggregational growth. Additionally, the stability studies on Zn2Al(OH)6(NO3)y(CO3)0.5(1-y)⋅xH2O nanoparticles (y=0-1) showed that the size difference between the cointercalated anions caused phase separation when 0.9⩾y⩾0.6, leading to bimodal size distributions. Moreover, the coarsening rates were controlled through the cointercalated anion compositions. By gradually varying the ratio of cointercalated NO3(-) to CO3(2-), monodispersed Zn2Al(OH)6(NO3)y(CO3)0.5(1-y)⋅xH2O (0.5⩾y⩾0) nanoparticles with systematic variation in the particle size of ∼200-400nm were obtained after HT at 85°C for 12h.

  9. Formation of porous crystals via viscoelastic phase separation

    Science.gov (United States)

    Tsurusawa, Hideyo; Russo, John; Leocmach, Mathieu; Tanaka, Hajime

    2017-10-01

    Viscoelastic phase separation of colloidal suspensions can be interrupted to form gels either by glass transition or by crystallization. With a new confocal microscopy protocol, we follow the entire kinetics of phase separation, from homogeneous phase to different arrested states. For the first time in experiments, our results unveil a novel crystallization pathway to sponge-like porous crystal structures. In the early stages, we show that nucleation requires a structural reorganization of the liquid phase, called stress-driven ageing. Once nucleation starts, we observe that crystallization follows three different routes: direct crystallization of the liquid phase, the Bergeron process, and Ostwald ripening. Nucleation starts inside the reorganized network, but crystals grow past it by direct condensation of the gas phase on their surface, driving liquid evaporation, and producing a network structure different from the original phase separation pattern. We argue that similar crystal-gel states can be formed in monatomic and molecular systems if the liquid phase is slow enough to induce viscoelastic phase separation, but fast enough to prevent immediate vitrification. This provides a novel pathway to form nanoporous crystals of metals and semiconductors without dealloying, which may be important for catalytic, optical, sensing, and filtration applications.

  10. Unstitching the nanoscopic mystery of zeolite crystal formation.

    Science.gov (United States)

    Brent, Rhea; Cubillas, Pablo; Stevens, Sam M; Jelfs, Kim E; Umemura, Ayako; Gebbie, James T; Slater, Ben; Terasaki, Osamu; Holden, Mark A; Anderson, Michael W

    2010-10-06

    A molecular-scale understanding of crystal growth is critical to the development of important materials such as pharmaceuticals, semiconductors and catalysts. Only recently has this been possible with the advent of atomic force microscopy that permits observation of nanoscopic features on solid surfaces under a liquid or solution environment. This allows in situ measurement of important chemical transformations such as crystal growth and dissolution. Further, the microscope can access not only an accurate height measurement of surface topography, important to deduce structural elements, but also the forces involved during nanoscopic processes. We have discovered that it is possible to use these features to "illuminate" critical nanoscopic chemical events at crystal surfaces and at the same time extract the associated energies and unstitch the details of the stepwise mechanism of growth and dissolution. This approach has been developed using nanoporous crystals of the heterogeneous catalyst zeolite L; however, in principle the approach could be adapted to many crystal growth problems.

  11. Spontaneous formation of non-uniform double helices for elastic rods under torsion

    Science.gov (United States)

    Li, Hongyuan; Zhao, Shumin; Xia, Minggang; He, Siyu; Yang, Qifan; Yan, Yuming; Zhao, Hanqiao

    2017-02-01

    The spontaneous formation of double helices for filaments under torsion is common and significant. For example, the research on the supercoiling of DNA is helpful for understanding the replication and transcription of DNA. Similar double helices can appear in carbon nanotube yarns, cables, telephone wires and so forth. We noticed that non-uniform double helices can be produced due to the surface friction induced by the self-contact. Therefore an ideal model was presented to investigate the formation of double helices for elastic rods under torque. A general equilibrium condition which is valid for both the smooth surface and the rough surface situations is derived by using the variational method. By adding further constraints, the smooth and rough surface situations are investigated in detail respectively. Additionally, the model showed that the specific process of how to twist and slack the rod can determine the surface friction and hence influence the configuration of the double helix formed by rods with rough surfaces. Based on this principle, a method of manufacturing double helices with designed configurations was proposed and demonstrated. Finally, experiments were performed to verify the model and the results agreed well with the theory.

  12. Anomalous double layer step formation on Si(100) in hydrogen ambient

    Energy Technology Data Exchange (ETDEWEB)

    Doescher, Henning; Kleinschmidt, Peter; Dobrich, Anja; Brueckner, Sebastian; Supplie, Oliver; Luczak, Johannes; Hannappel, Thomas [Helmholtz-Zentrum Berlin fuer Materialien und Energie, Berlin (Germany)

    2011-07-01

    Generation of double layer steps on Si(100) is desirable for subsequent anti-phase domain-free heteroepitaxy of III-V semiconductors. In UHV established procedures exist for the formation of double layer steps at the clean Si(100) surface. In the (metal-organic) vapour phase epitaxy environment the situation is more complicated due to the presence of hydrogen in the process ambient. Both theory and experiment of the hydrogenated surfaces suggest that under equilibrium conditions no preference for double layer steps is to be expected. Previously, we have shown that annealing in hydrogen at near atmospheric pressure leads to termination of the surface by monohydride. Here, we show that a process using Si(100) with an intermediate offcut of 2 in <011> can lead to a double layer stepped surface. Our process consists of deoxidation, homoepitaxial growth employing silane, annealing and slow cooling to 500 C in hydrogen ambient. We observe the formation of double layer steps using Fourier-transform infrared spectroscopy, low-energy electron diffraction and scanning tunneling microscopy. In sharp contrast to established UHV results, the double layer steps are of the D{sub A} type, where dimer rows of the reconstructed surface are parallel to the step edges.

  13. Red and Blue Light Generation in an LiTaO3 Crystal with a Double Grating Domain Structure

    Institute of Scientific and Technical Information of China (English)

    LIU Zhao-Wei; ZHU Shi-Ning; ZHU Yong-Yuan; WANG Hui-Tian; LUO Guo-Zhen; LIU Hui; MIN Nai-Ben; LIANG Xiao-Yan; XU Zu-Yan

    2001-01-01

    Simultaneous red and blue light generation in an LiTaOs crystal with a double grating structure is reported for the first time. The double grating consists of two separate domain reversal sequences (superlattices) in seriesand is fabricated by the field poling technique at room temperature. Using a picosecond 532 nm laser as a pump source, the red light at 631 nm and blue light at 460nm are generated at the same time. A possible applicationof the superlattice crystal is presented. X

  14. Comparison and characterization of efficient frequency doubling at 397.5 nm with PPKTP, LBO and BiBO crystals

    CERN Document Server

    Wen, Xin; Wang, Junmin

    2016-01-01

    A continuous-wave Ti:sapphire laser at 795 nm is frequency doubled in a bow-tie type enhancement four-mirror ring cavity with LiB3O5 (LBO), BiB3O6 (BiBO), and periodically polled KTiOPO4 (PPKTP) crystals, respectively. The properties of 397.5 nm ultra-violet (UV) output power, beam quality, stability for these different nonlinear crystals are investigated and compared. For PPKTP crystal, the highest doubling efficiency of 58.1% is achieved from 191 mW of 795 nm mode-matched fundamental power to 111 mW of 397.5 nm UV output. For LBO crystal, with 1.34 W of mode-matched 795 nm power, 770 mW of 397.5 nm UV output is achieved, implying a doubling efficiency of 57.4%. For BiBO crystal, with 323 mW of mode-matched 795 nm power, 116 mW of 397.5 nm UV output is achieved, leading to a doubling efficiency of 35.9%. The generated UV radiation has potential applications in the fields of quantum physics

  15. Search for double beta decay processes in 106Cd with the help of 106CdWO4 crystal scintillator

    CERN Document Server

    Belli, P; Boiko, R S; Brudanin, V B; Cappella, F; Caracciolo, V; Cerulli, R; Chernyak, D M; Danevich, F A; d'Angelo, S; Galashov, E N; Incicchitti, A; Kobychev, V V; Laubenstein, M; Mokina, V M; Poda, D V; Podviyanuk, R B; Polischuk, O G; Shlegel, V N; Stenin, Yu G; Suhonen, J; Tretyak, V I; Vasiliev, Ya V

    2011-01-01

    A search for the double beta processes in 106Cd was realized at the Gran Sasso National Laboratories of the INFN (Italy) with the help of a 106CdWO4 crystal scintillator (215 g) enriched in 106Cd up to 66%. After 6590 h of data taking, new improved half-life limits on the double beta processes in 106Cd were established at the level of 10^{19}-10^{21} yr; in particular, T_{1/2}(2\

  16. Ultrafast thermal dynamics of nano-ripples formation via laser double pulses excitation

    Science.gov (United States)

    Du, Guangqing; Wu, Yanmin; Uddin, Noor; Yang, Qing; Chen, Feng; Lu, Yu; Bian, Hao; Hou, Xun

    2016-09-01

    The ultrafast thermal dynamics of nano-ripples formation on gold film via ultrafast laser double pulses excitation is theoretically investigated by numerical simulations. The non-equilibrium thermal modulations with respect to the electron and phonon energy transfers within gold film is proposed for predicting the nano-ripples formation. It is revealed that the nano-ripples contrast on gold film surface can be well controlled via tuning the pulse energy ratio, pulse separation and pulse exchange of ultrafast laser double-pulse. It is attributed to the tunable energy transfer routes between the electron thermal diffusion and the electron-phonon coupling via tuning double pulses parameters. The study provides theoretical basis for producing high-contrast ripples for a wide range application in the fields such as high-absorptive solar cells, surface friction devices and super-hydrophobic surface.

  17. Probe spectrum of a four-level atom in a double-band photonic crystal

    Institute of Scientific and Technical Information of China (English)

    Wen Qing-Bo; Wang Jian; Zhang Han-Zhuang

    2004-01-01

    In this paper, the probe absorption spectrum of an atom in a double-band photonic crystal have been studied. In the modes, we assume that one of the two atomic transitions in a A-type atomic system is interacting with free vacuum modes, and another transition is interacting with free vacuum modes, isotropic photonic band gap (PBG) modes and anisotropic PBG modes, separately. The effects of the fine structure of the atomic lower levels on the probe absorption spectrum are investigated in detail in the three cases. The most interesting thing is that the two (four) transparencies at one (two) probe absorption peak(s), caused by the fine structure of the lower levels of an atom, are predicted in the case of isotropic PBG modes.

  18. Spontaneous emission spectrum of a four-level atom in a double-band photonic crystal

    Institute of Scientific and Technical Information of China (English)

    Wang Jian; Yang Dong; Zhang Han-Zhang

    2005-01-01

    The spontaneous emission spectrum from a four-level atom in a double-band photonic crystal has been investigated.We use the model which assumes three atomic transitions. One of the transitions interacts with the free vacuum modes,and the other two transitions couple to the modes of the isotropic photonic band gap (PBG), the anisotropic PBG and another free vacuum. The effects of the fine structure of the lower levels on the spontaneous emission spectrum of an atom are investigated in detail in the three cases. New features of four (two) transparencies with two (one) spontaneous emission peaks, resulting from the fine structure of the lower levels of an atom, are predicted in the case of isotropic PBG modes.

  19. Enhancement of luminescence from Er-doped Si by photonic crystal gradient double-heterostructuremicrocavity

    Science.gov (United States)

    Wang, Y.; An, J. M.; Wu, Y. D.; Hu, X. W.

    2017-03-01

    We experimentally demonstrate efficient enhancements of luminescence at wavelength of 1550 nm from two-dimensional (2D)-slab hexagonal photonic crystal (PC) non-airbridge and air bridge gradient double-heterostructure microcavities with Er/O co-implanted silicon (Si) as light emitters on silicon-on-insulator (SOI) wafer. The maximum measured Q-factor of 6284 of airbridge cavity has been achieved at the pumping power of 1.5 mW at room temperature. The airbridge cavity has stronger enhancement, but weaker heat dissipation than the non-airbridge one. The obvious red-shift and degraded Q-factor of resonant peak are present with the pumping power increasing. The resonant peak is observed to shift depending on the structural parameters of PC, which indicates a possible method to control the wavelength of enhanced luminescence for Si-based light emitters based on PC microcavity.

  20. Modified photoreactivity due to mixed crystal formation. I. Three mixed crystals between isostructural cobaloxime complexes.

    Science.gov (United States)

    Vithana, Champika; Uekusa, Hidehiro; Sekine, Akiko; Ohashi, Yuji

    2002-04-01

    Three crystals of 2-cyanoethyl cobaloxime complexes with 3-chloropyridine, 3-bromopyridine and 3-methylpyridine as axial base ligands are isostructural to one another. Three mixed crystals were formed between the pairs: (3-bromopyridine)(2-cyanoethyl)cobaloxime-(2-cyanoethyl)(3-methylpyridine)cobaloxime(0.45/0.55);(3-chloropyridine)(2-cyanoethyl)cobaloxime-(2-cyanoethyl)(3bromopyridine)cobaloxime (0.61/0.39); (3-chloropyridine)(2-cyanoethyl)cobaloxime-(2-cyanoethyl)(3-methylpyridine)cobaloxime (0.44/0.56). The X-ray crystal structure analysis revealed that the mixed compounds are also isostructural to the component crystals. It was found from the change in IR spectra that the 2-cyanoethyl groups in the three mixed crystals isomerized to 1-cyanoethyl groups on exposure to a xenon lamp, as observed for the 2-cyanoethyl groups in the component crystals. Rate constants for the three mixed and three component crystals, measured under the same conditions, are approximately the same, as the reaction cavities for the 2-cyanoethyl groups in the six crystals have almost the same size. For the mixed crystal between 3-chloropyridine and 3-methylpyridine complexes, the isomerization proceeded with retention of the single-crystal form. The conformation and configuration of the 1-cyanoethyl group that was produced were well explained by the shape of the reaction cavity before irradiation.

  1. Formation of deformation substructures in FCC crystals under the influence of point defect fluxes

    OpenAIRE

    Matveev, M. V.; Selivanikova, Olga Valerievna; Cherepanov, Dmitry Nikolaevich

    2016-01-01

    The article deals with sub-structural transformations in FCC crystals under the influence of point defect fluxes. Different relationships between accumulation of point defects in crystal and substructure transformations, in particular during the process of fragmented dislocation structure formation have been received.

  2. Structural and crystal chemical properties of rare-earth double phosphates and rare-earth titanate pyrochlores

    Science.gov (United States)

    Farmer, J. Matt

    Alkali rare-earth double phosphates have been studied for use as long-wavelength scintillators for gamma-ray detection using Si photodiodes. These compounds exhibit layered crystal structures, built from roughly hexagonal atomic layers in the sequence lanthanide, phosphate-alkali, alkali, alkali-phosphate. Details of the crystal symmetry depend on the relative sizes of the rare-earth and alkali metal ions. Single-crystal X-ray diffraction (SXRD) has been used to study these structures at room temperature for K3RE(PO4) 2 (where RE = Lu-Ce, Y, and Sc). The compound K3Lu(PO 4)2 crystallizes with a hexagonal unit cell, space group P-3. The Lu ion is six-coordinated to the oxygen atoms of the phosphate groups. Two lower-temperature phases of K3Lu(PO4) 2 were observed and characterized. The lower-temperature transition results in an increase in coordination of the Lu ion to seven fold. This new structure is isostructural with the room-temperature form of K3Yb(PO 4)2. High-temperature powder neutron diffraction and high-temperature powder XRD have revealed a large thermal expansion anisotropy for K3Lu(PO4)2. The K3RE(PO 4)2 formation enthalpies were determined using high-temperature oxide-melt solution calorimetry. The formation enthalpy from oxides becomes more exothermic with increasing rare-earth radius. Rare-earth titanates, RE2Ti2O7 (where RE = a rare-earth), with the pyrochlore structure are currently being studied for use as potential nuclear, actinide-rich waste forms. Single-crystals were synthesized using a high-temperature flux technique and characterized using single-crystal X-ray diffraction. The cubic lattice parameters display an approximately linear correlation with the RE-site cation radius. The Sm and Eu titanates exhibit a covalency increase between the REO8 and TiO6 polyhedra resulting in a deviation from the increasing linear lattice parameter through the series. Gd2Ti2O7 exhibits the lowest 48f oxygen positional parameter, an effect that can be

  3. Propagating and evanescent properties of double-point defects in sonic crystals

    Energy Technology Data Exchange (ETDEWEB)

    Romero-Garcia, V; Sanchez-Perez, J V [Centro de tecnologIas fisicas: Acustica, Materiales y Astrofisica, Universidad Politecnica de Valencia, Camino de Vera s/n, 46022 Valencia (Spain); Garcia-Raffi, L M, E-mail: virogar1@mat.upv.e [Instituto Universitario de Matematica Pura y Aplicada, Universidad Politecnica de Valencia, Camino de Vera s/n, 46022 Valencia (Spain)

    2010-08-15

    Complex band structures and multiple scattering theory have been used in this paper to analyze the overlapping of the evanescent waves localized in point defects in sonic crystals (SCs). The extended plane wave expansion (EPWE) with supercell approximation gives the imaginary part of the Bloch vectors that produces the decay of the localized modes inside the periodic system. Double cavities can present a coupling between the evanescent modes localized in the defect, showing a symmetric or antisymmetric mode. When point defects are close, the complex band structures reveal a splitting of the frequencies of the localized modes. Both the real part and the imaginary values of k of the localized modes in the cavities present different values for each localized mode, which gives different properties for each mode. The novel measurements, in very good agreement with analytical data, show experimental evidence of the symmetric and antisymmetric localized modes for a double-point defect in SCs. The investigation of the localization phenomena and the coupling between defects in periodic systems has fundamental importance in both pure and applied physics.

  4. POE/PLGA composite microspheres: formation and in vitro behavior of double walled microspheres.

    Science.gov (United States)

    Yang, Yi-Yan; Shi, Meng; Goh, Suat-Hong; Moochhala, Shabbir M; Ng, Steve; Heller, Jorge

    2003-03-07

    The poly(ortho ester) (POE) and poly(D,L-lactide-co-glycolide) 50:50 (PLGA) composite microspheres were fabricated by a water-in-oil-in-water (w/o/w) double emulsion process. The morphology of the composite microspheres varied depending on POE content. When the POE content was 50, 60 or 70% in weight, the double walled microspheres with a dense core of POE and a porous shell of PLGA were formed. The formation of the double walled POE/PLGA microspheres was analysed. Their in vitro degradation behavior was characterized by scanning electron microscopy, gel permeation chromatography, Fourier-transform infrared microscopy and nuclear magnetic resonance spectroscopy (NMR). It was found that compared to the neat POE or PLGA microspheres, distinct degradation mechanism was achieved in the double walled POE/PLGA microspheres system. The degradation of the POE core was accelerated due to the acidic microenvironment produced by the hydrolysis of the outer PLGA layer. The formation of hollow microspheres became pronounced after the first week in vitro. 1H NMR spectra showed that the POE core was completely degraded after 4 weeks. On the other hand, the outer PLGA layer experienced slightly retarded degradation after the POE core disappeared. PLGA in the double walled microspheres kept more than 32% of its initial molecular weight over a period of 7 weeks.

  5. Photorefractive grating formation in piezoelectric La3Ga5SiO14:Pr3+ crystals

    DEFF Research Database (Denmark)

    Dam-Hansen, C.; Johansen, P.M.; Fridkin, V.M.

    1996-01-01

    Photorefractive grating formation and erasure in piezoelectric crystals of La3Ga5SiO14:Pr3+ are presented. The specific photoconductivity and the photorefractive sensitivity are determined. The polarization dependence of the grating formation due to the bulk photovoltaic effect is shown and compa......Photorefractive grating formation and erasure in piezoelectric crystals of La3Ga5SiO14:Pr3+ are presented. The specific photoconductivity and the photorefractive sensitivity are determined. The polarization dependence of the grating formation due to the bulk photovoltaic effect is shown...

  6. The Arabidopsis thaliana DSB formation (AtDFO) gene is required for meiotic double-strand break formation.

    Science.gov (United States)

    Zhang, Cheng; Song, Yao; Cheng, Zhi-hao; Wang, Ying-xiang; Zhu, Jun; Ma, Hong; Xu, Ling; Yang, Zhong-Nan

    2012-10-01

    DNA double-strand break (DSB) formation is the initial event for meiotic recombination catalyzed by the conserved Spo11 protein. In Arabidopsis, several proteins have been reported to be involved in DSB formation. Here, we report an Arabidopsis DSB forming (DFO) gene in Arabidopsis that is involved in DSB formation. The dfo mutant exhibits reduced fertility, producing polyads with an abnormal number of microspores, unlike the tetrads in the wild type. The dfo meiocytes were defective in homologous chromosome synapsis and segregation. Genetic analysis revealed that the homologous recombination of Atdfo-1 is severely affected in meiotic prophase I. DFO encodes a protein without any known conserved domain. There was no homologue identified outside the plant kingdom, indicating that AtDFO is a plant-specific protein. AtMRE11 has been reported to be responsible for processing SPO11-generated DSBs. The Atmre11 mutant displays chromosome fragmentation during meiosis. However, the Atdfo Atmre11 double mutant had no such chromosome fragmentation, indicating that AtDFO is required for DSB formation.

  7. Development of CaMoO4 crystal scintillators for double beta decay experiment with 100-Mo

    CERN Document Server

    Annenkov, A N; Danevich, F A; Georgadze, A S; Kim, S K; Kim, H J; Kim, Y D; Kobychev, V V; Kornoukhov, V N; Korzhik, M; Lee, J I; Missevitch, O; Mokina, V M; Nagorny, S S; Nikolaiko, A S; Poda, D V; Podviyanuk, R B; Sedlak, D J; Shkulkova, O G; So, J H; Solsky, I M; Tretyak, V I; Yurchenko, S S

    2007-01-01

    Energy resolution, alpha/beta ratio, pulse-shape discrimination for gamma rays and alpha particles, temperature dependence of scintillation properties, and radioactive contamination were studied with CaMoO4 crystal scintillators. A high sensitivity experiment to search for neutrinoless double beta decay of 100-Mo by using CaMoO4 scintillators is discussed.

  8. Crystallization behavior and glass formation of selected lunar compositions.

    Science.gov (United States)

    Scherer, G.; Hopper, R. W.; Uhlmann, D. R.

    1972-01-01

    The kinetics of crystal growth have been determined over a wide range of temperature, from 800 to 1219 C, for lunar compositions 14259 and 14310. At all temperatures for both compositions the extent of crystal growth is found to be a linear function of time. For both materials, the growth rate versus temperature relations exhibit the form generally found with glass-forming materials. At all temperatures measured, the crystal growth rate of composition 14259 is smaller than that of composition 14310. The maximum growth rate for both compositions occurs at a temperature of about 1120 C. The growth rate data are combined with viscosity data obtained on the same compositions to construct the reduced growth rate versus undercooling relations.

  9. Classical crystal formation of dipoles in two dimensions

    DEFF Research Database (Denmark)

    Hansen, Kenneth Christian Klochmann; Fedorov, D. V.; Jensen, A. S.;

    2015-01-01

    We consider a two-dimensional layer of dipolar particles in the regime of strong dipole moments. Here we can describe the system using classical methods and determine the crystal structure that minimizes the total energy. The dipoles are assumed to be aligned by an external field and we consider...... different orientations of the dipolar moments with respect to the two-dimensional plane of motion. We observe that when the orientation angle changes away from perpendicular and towards the plane, the crystal structure will change from a hexagonal form to one that has the dipoles sitting in equidistant rows...

  10. Formation Enthalpy Calculation of Oxygen Vacancy Defect in Doped Lithium Niobate Crystals

    Institute of Scientific and Technical Information of China (English)

    QIANG Liang-sheng; LI Yao; TANG Dong-yan; XU Chong-quan; WEI Yong-de

    2004-01-01

    The relationship between temperature and oxygen vacancy concentration is deduced in this paper. Based on the data of thermal weight-loss experiment, the formation enthalpies of congruent and several doped LN crystals have been calculated. It was found that the formation enthalpy of oxygen vacancies can be decreased evidently by doping valence-changeable ions. The experimental results were discussed and a new reduction process of the photorefractive LN crystal at a relatively low temperature was proposed, and the reduced crystals showed a good effect in practical use.

  11. Allantoin crystal formation in Bagrada hilaris (Burmeister) (Hemiptera: Pentatomidae) females

    Science.gov (United States)

    Bagrada hilaris is a polyphagous herbivore recently reported as an invasive pest in the U.S. During the course of dissecting B. hilaris to understand ovarian morphology in relation to egg production and to determine sperm viability, unique crystals were observed in both the midgut and oviducts. Crys...

  12. Layered double hydroxide stability. 2. Formation of Cr(III)-containing layered double hydroxides directly from solution

    Science.gov (United States)

    Boclair, J. W.; Braterman, P. S.; Jiang, J.; Lou, S.; Yarberry, F.

    1999-01-01

    Solutions containing divalent metal [M(II) = Mg2+, Zn2+, Co2+, Ni2+, Mn2+] chlorides and CrCl3 6H2O were titrated with NaOH to yield, for M(II) = Zn, Co, and Ni, hydrotalcite-like layered double hydroxides (LDHs), [[M(II)]1-z[Cr(III)]z(OH)2][Cl]z yH2O, in a single step, without intermediate formation of chromium hydroxide. Analysis of the resultant titration curves yields solubility constants for these compounds. These are in the order Zn < Ni approximately Co, with a clear preference for formation of the phase with z = 1/3. With Mg2+ as chloride, titration gives a mixture of Cr(OH)3 and Mg(OH)2, but the metal sulfates give Mg2Cr(OH)6 1/2(SO4) by a two-step process. Titrimetric and spectroscopic evidence suggests short-range cation order in the one-step LDH systems.

  13. Simulation of Electronic Center Formation by Irradiation in Silicon Crystals

    Science.gov (United States)

    Yeritsyan, H. N.; Sahakyan, A. A.; Grigoryan, N. E.; Harutyunyan, V. V.; Tsakanov, V. M.; Grigoryan, B. A.; Yeremyan, A. S.; Amatuni, G. A.

    2017-02-01

    We present the results of a study on localized electronic centers formed in crystals by external influences (impurity introduction and irradiation). The main aim is to determine the nature of these centers in the forbidden gap of the energy states of the crystal lattice. For the case of semiconductors, silicon (Si) was applied as model material to determine the energy levels and concentration of radiation defects for application to both doped and other materials. This method relies on solving the appropriate equation describing the variation of the charge carrier concentration as a function of temperature n( T) for silicon crystals with two different energy levels and for a large set of N 1, N 2 (concentrations of electronic centers at each level), and n values. A total of almost 500 such combinations were found. For silicon, energy level values of ɛ 1 = 0.22 eV and ɛ 2 = 0.34 eV were used for the forbidden gap (with corresponding slopes determined from experimental temperature-dependent Hall-effect measurements) and compared with photoconductivity spectra. Additionally, it was shown that, for particular correlations among N 1, N 2, and n, curve slopes of ɛ 1/2 = 0.11 eV, ɛ 2/2 = 0.17 eV, and α = 1/2( ɛ 1 + ɛ 2) = 0.28 eV also apply. Comparison between experimental results for irradiation of silicon crystals by 3.5-MeV energy electrons and Co60 γ-quanta revealed that the n( T) curve slopes do not always coincide with the actual energy levels (electronic centers).

  14. Insights into the Synthesis of Layered Double Hydroxide (LDH) Nanoparticles: Part 2. Formation Mechanisms of LDH

    OpenAIRE

    Sun, Xiaodi; Dey, Sandwip K.

    2015-01-01

    This study demonstrates the effect of (co)intercalated anion compositions on nanostructure evolution to understand the formation mechanisms of layered double hydroxide (LDH) nanoparticles following coprecipitation and hydrothermal treatments (HT). Initially, the room temperature coprecipitation resulted in amorphous primary nanoparticles that agglomerated at the edges due to low surface charge densities. The reversibility of such agglomeration was determined by the crystalline quality upon HT...

  15. Cholesteric liquid crystal formation in suspensions of cellulose nanocrystals

    Science.gov (United States)

    Honorato-Rios, Camilla; Bruckner, Johanna; Schütz, Christina; Wagner, Sammy; Tosheva, Zornitza; Bergström, Lennart; Lagerwall, Jan P. F.

    With the strong current trend in nanotechnology to focus on sustainably produced nanomaterials, cellulose nanocrystals (CNC) are emerging as a particularly interesting candidate. They are mechanically strong, optically transparency and birefringent, have low weight and low thermal expansion coefficient. A most desirable feature of CNC is that aqueous suspensions form cholesteric liquid crystal phases already at low concentration, and when dried into thin solid films, the periodicity of the helical structure can be reduced to the range of visible selective reflection, in practice making the film a photonic crystal paper. We begin the chapter by briefly explaining how CNC is extracted from cellulose-rich bioresources, followed by a summary of the typical characteristics in terms of dimensions and surface charge, and how these depend on the production method. The current understanding of the phase diagram of CNC suspensions is then discussed, from the low-concentration regime around the isotropic-cholesteric transition to the less well understood regime where the system is kinetically arrested in a non-equilibrium state. We discuss the influences on phase behavior and cholesteric pitch of the solvent and its ionic strength. Finally, we discuss the production of photonic crystal films and we give a brief outlook.

  16. THE RESULTS OF TESTING TO EVALUATE CRYSTAL FORMATION AND SETTLING IN THE COLD CRUCIBLE INDUCTION MELTER

    Energy Technology Data Exchange (ETDEWEB)

    Marra, J.

    2009-06-30

    The Cold Crucible Induction Melter (CCIM) technology offers the potential to increase waste loading for High Level Waste (HLW) glasses leading to significant improvements in waste throughput rates compared to the reference Joule Heated Melter (JHM). Prior to implementation of a CCIM in a production facility it is necessary to better understand processing constraints associated with the CCIM. The glass liquidus temperature requirement for processing in the CCIM is an open issue. Testing was conducted to evaluate crystal formation and crystal settling during processing in the CCIM to gain insight into the effects on processing. A high aluminum/high iron content glass composition with known crystal formation tendencies was selected for testing. A continuous melter test was conducted for approximately 51 hours. To evaluate crystal formation, glass samples were obtained from pours and from glass receipt canisters where the glass melt had varying residence time in the melter. Additionally, upon conclusion of the testing, glass samples from the bottom of the melter were obtained to assess the degree of crystal settling. Glass samples were characterized in an attempt to determine quantitative fractions of crystals in the glass matrix. Crystal identity and relative composition were determined using a combination of x-ray diffraction (XRD) and scanning electron microscopy coupled with energy dispersive spectroscopy (SEM/EDS). Select samples were also analyzed by digesting the glass and determining the composition using inductively coupled atomic emission spectroscopy (ICP-AES). There was evidence of crystal formation (primarily spinels) in the melt and during cooling of the collected glass. There was evidence of crystal settling in the melt over the duration of the melter campaign.

  17. Crystallization of the avian reovirus double-stranded RNA-binding and core protein σA

    Energy Technology Data Exchange (ETDEWEB)

    Hermo-Parrado, X. Lois; Guardado-Calvo, Pablo [Departamento de Bioquímica y Biología Molecular, Facultad de Farmacia, Universidad de Santiago de Compostela, Campus Sur, E-15782 Santiago de Compostela (Spain); Llamas-Saiz, Antonio L. [Unidad de Difracción de Rayos X, Laboratorio Integral de Dinámica y Estructura de Biomoléculas José R. Carracido, Edificio CACTUS, Universidad de Santiago de Compostela, Campus Sur, E-15782 Santiago de Compostela (Spain); Fox, Gavin C. [Spanish CRG Beamline BM16, European Synchrotron Radiation Facility (ESRF), 6 Rue Jules Horowitz, BP 220, F-38043 Grenoble (France); Vazquez-Iglesias, Lorena; Martínez-Costas, José; Benavente, Javier [Departamento de Bioquímica y Biología Molecular, Facultad de Farmacia, Universidad de Santiago de Compostela, Campus Sur, E-15782 Santiago de Compostela (Spain); Raaij, Mark J. van, E-mail: vanraaij@usc.es [Departamento de Bioquímica y Biología Molecular, Facultad de Farmacia, Universidad de Santiago de Compostela, Campus Sur, E-15782 Santiago de Compostela (Spain); Unidad de Difracción de Rayos X, Laboratorio Integral de Dinámica y Estructura de Biomoléculas José R. Carracido, Edificio CACTUS, Universidad de Santiago de Compostela, Campus Sur, E-15782 Santiago de Compostela (Spain)

    2007-05-01

    The avian reovirus double-stranded RNA-binding and core protein σA has been crystallized in space group P1, with unit-cell parameters a = 103.2, b = 129.9, c = 144.0 Å, α = 93.8, β = 105.1, γ = 98.2°. A complete data set has been collected to 2.3 Å resolution and analyzed. The avian reovirus protein σA plays a dual role: it is a structural protein forming part of the transcriptionally active core, but it has also been implicated in the resistance of the virus to interferon by strongly binding double-stranded RNA and thus inhibiting the double-stranded RNA-dependent protein kinase. The σA protein has been crystallized from solutions containing ammonium sulfate at pH values around 6. Crystals belonging to space group P1, with unit-cell parameters a = 103.2, b = 129.9, c = 144.0 Å, α = 93.8, β = 105.1, γ = 98.2° were grown and a complete data set has been collected to 2.3 Å resolution. The self-rotation function suggests that σA may form symmetric arrangements in the crystals.

  18. Polarity Formation in Molecular Crystals as a Symmetry Breaking Effect

    Directory of Open Access Journals (Sweden)

    Luigi Cannavacciuolo

    2016-03-01

    Full Text Available The transition of molecular crystals into a polar state is modeled by a one-dimensional Ising Hamiltonian in multipole expansion and a suitable order parameter. Two symmetry breakings are necessary for the transition: the translational and the spin flip invariance—the former being broken by geometric constraints, the latter by the interaction of the first non-zero multipole with the next order multipole. Two different behaviors of the thermal average of the order parameter as a function of position are found. The free energy per lattice site converges to a finite value in the thermodynamic limit showing the consistency of the model in a macroscopic representation.

  19. Crystallization and glass formation in multi-component liquids

    Science.gov (United States)

    Zhang, Kai; Wang, Minglei; Papanikolaou, Stefanos; Schroers, Jan; O'Hern, Corey

    2013-03-01

    When a liquid is cooled faster than the critical cooling rate, crystallization is avoided, and amorphous solids are formed. What sets the critical cooling rate? We perform molecular dynamics simulations of model metallic alloys--polydisperse spheres with hard-sphere and modified Lennard-Jones interactions--to study the critical cooling rate as a function of the particle size ratio, stoichiometry, and strength of the attractive interactions. We also characterize the structural properties of glassy and crystalline states that form at rapid and slow cooling/compression rates, respectively, using local order parameters, position correlation functions, and Voronoi and other tessellations. NSF MRSEC DMR-1119826

  20. Formation of cholesterol bilayer domains precedes formation of cholesterol crystals in cholesterol/dimyristoylphosphatidylcholine membranes: EPR and DSC studies.

    Science.gov (United States)

    Mainali, Laxman; Raguz, Marija; Subczynski, Witold K

    2013-08-01

    Saturation-recovery EPR along with DSC were used to determine the cholesterol content at which pure cholesterol bilayer domains (CBDs) and cholesterol crystals begin to form in dimyristoylphosphatidylcholine (DMPC) membranes. To preserve compositional homogeneity throughout the membrane suspension, lipid multilamellar dispersions were prepared using a rapid solvent exchange method. The cholesterol content increased from 0 to 75 mol %. With spin-labeled cholesterol analogues, it was shown that the CBDs begin to form at ~50 mol % cholesterol. It was confirmed by DSC that the cholesterol solubility threshold for DMPC membranes is detected at ~66 mol % cholesterol. At levels above this cholesterol content, monohydrate cholesterol crystals start to form. The major finding is that the formation of CBDs precedes formation of cholesterol crystals. The region of the phase diagram for cholesterol contents between 50 and 66 mol % is described as a structured one-phase region in which CBDs have to be supported by the surrounding DMPC bilayer saturated with cholesterol. Thus, the phase boundary located at 66 mol % cholesterol separates the structured one-phase region (liquid-ordered phase of DMPC with CBDs) from the two-phase region where the structured liquid-ordered phase of DMPC coexists with cholesterol crystals. It is likely that CBDs are precursors of monohydrate cholesterol crystals.

  1. Study of optical reflectance properties in 1D annular photonic crystal containing double negative (DNG) metamaterials

    Science.gov (United States)

    Srivastava, Sanjeev K.; Aghajamali, Alireza

    2016-05-01

    Theoretical investigation of photonic band gaps or reflection bands in one-dimensional annular photonic crystal (APC) containing double negative (DNG) metamaterials and air has been presented. The proposed structure consists of the alternate layers of dispersive DNG material and air immersed in free space. In order to study photonic band gaps we obtain the reflectance spectrum of the annular PC by employing the transfer matrix method (TMM) in the cylindrical waves for both TE and TM polarizations. In this work we study the effect of azimuthal mode number (m) and starting radius (ρ0) on the three band gaps viz. zero averaged refractive index (zero-nbar) gap, zero permittivity (zero- ε) and zero permeability (zero- μ) gaps. It is found that for m ≥ 1 , zero- μ gap appears in TE mode and zero- ε gap appears in TM mode. The width of both zero- μ and zero- ε gap increases by increasing m values, but the enhancement of zero- μ gap is more appreciable. Also, the effect of ρ0 on the three band gaps (reflection bands) of annular PC structure at the given m-number has been studied, for both TE and TM polarizations. The result shows that in both polarizations zero- ε and zero- μ gaps decreases when ρ0 increases, whereas zero-nbar gap remains invariant.

  2. Double crystal monochromator controlled by integrated computing on BL07A in New SUBARU, Japan

    Energy Technology Data Exchange (ETDEWEB)

    Okui, Masato, E-mail: okui@kohzu.co.jp [Kohzu Precision Co., Ltd., 2-6-15, Kurigi, Asao-ku, Kawasaki-shi, Kanagawa 215-8521 (Japan); Laboratory of Advanced Science and Technology for Industry, University of Hyogo (Japan); Yato, Naoki; Watanabe, Akinobu; Lin, Baiming; Murayama, Norio [Kohzu Precision Co., Ltd., 2-6-15, Kurigi, Asao-ku, Kawasaki-shi, Kanagawa 215-8521 (Japan); Fukushima, Sei, E-mail: FUKUSHIMA.Sei@nims.go.jp [Laboratory of Advanced Science and Technology for Industry, University of Hyogo (Japan); National Institute for Material Sciences (Japan); Kanda, Kazuhiro [Laboratory of Advanced Science and Technology for Industry, University of Hyogo (Japan)

    2016-07-27

    The BL07A beamline in New SUBARU, University of Hyogo, has been used for many studies of new materials. A new double crystal monochromator controlled by integrated computing was designed and installed in the beamline in 2014. In this report we will discuss the unique features of this new monochromator, MKZ-7NS. This monochromator was not designed exclusively for use in BL07A; on the contrary, it was designed to be installed at low cost in various beamlines to facilitate the industrial applications of medium-scale synchrotron radiation facilities. Thus, the design of the monochromator utilized common packages that can satisfy the wide variety of specifications required at different synchrotron radiation facilities. This monochromator can be easily optimized for any beamline due to the fact that a few control parameters can be suitably customized. The beam offset can be fixed precisely even if one of the two slave axes is omitted. This design reduces the convolution of mechanical errors. Moreover, the monochromator’s control mechanism is very compact, making it possible to reduce the size of the vacuum chamber can be made smaller.

  3. Out-of-plane nanomechanical tuning of double-coupled one-dimensional photonic crystal cavities.

    Science.gov (United States)

    Tian, Feng; Zhou, Guangya; Du, Yu; Chau, Fook Siong; Deng, Jie; Akkipeddi, Ramam

    2013-06-15

    We demonstrate tuning of double-coupled one-dimensional photonic crystal cavities by their out-of-plane nanomechanical deformations. The coupled cavities are pulled by the vertical electrostatic force generated by the potential difference between the device layer and the handle layer in a silicon-on-insulator chip, and the induced deformations are analyzed by the finite element method. Applied with a voltage of 12 V, the cavities obtain a redshift of 0.0405 nm (twice the linewidth) for their second-order odd resonance mode and a blueshift of 0.0635 nm (three times the linewidth) for their second-order even resonance mode, which are mainly attributed to out-of-plane relative displacement. Out-of-plane tuning of coupled cavities does not need actuators and corresponding circuits; thus the device is succinct and compact. This working principle can be potentially applied in chip-level optoelectronic devices, such as sensors, switches, routers, and tunable filters.

  4. Design of Nearly Zero Dispersion Flattened Photonic Crystal Fiber with Double Cladding

    Institute of Scientific and Technical Information of China (English)

    WANG Wei; HOU Lan-Tian; SONG Jun-Jie; ZHOU Gui-Yao

    2009-01-01

    A novel design of nearly zero dispersion flattened photonic crystal fiber (PCF) with double cladding is proposed.To employ traditional stack and draw technology, the cladding is composed of a traditional triangular lattice of air-holes and silica. The dispersion of the fiber is mainly engineered by the small air holes in the inner cladding,which are easily preserved in the fiber drawing procedure. The large air-holes in the outer cladding are mainly for light confinement. Thus, the dispersion property of the PCF is insensitive to the deformation of the air holes in the outer cladding. Using 8 layers of air-hole ring, the loss of the fundamental mode for the PCF is as low as 0.13dB/km at 1.55μm. The dispersion of the PCF fluctuates from -0.023 to 0.021ps.km-1nm-1 in the range 1.45-1.625 μm.

  5. Formation and growth mechanism of TiC crystal in TiCp/Ti composites

    Institute of Scientific and Technical Information of China (English)

    金云学; 王宏伟; 曾松岩; 张二林

    2002-01-01

    Ti-C and Ti-Al-C alloys were prepared using gravity and directional solidification processes. Morphologies of TiC crystal were investigated by using SEM, XRD and EDX. Also, the formation and growth mechanism of TiC crystal have been analyzed on the basis of coordination polyhedron growth unit theory. During solidification of titanium alloys, the coordination polyhedron growth unit is TiC6. TiC6 growth units stack in a linking mode of edge to edge and form octahedral TiC crystal with {111} planes as present faces. Although the growing geometry of TiC crystal is decided by its lattice structure, the final morphology of TiC crystal depends on the effects of its growth environment. In solute concentration distribution, the super-saturation of C or TiC6 at the corners of octahedral TiC crystal is much higher than that of edges and faces of octahedral TiC crystal. At these corners the driving force for crystal growth is greater and the interface is instable which contribute to quick stacking rate of growth units at these corners and result in secondary dendrite arms along TiC crystallographic 〈100〉 directions. TiC crystal finally grows to be dendrites.

  6. Modulation of nanotube formation in apatite single crystal via organic molecule incorporation

    Energy Technology Data Exchange (ETDEWEB)

    Matsumoto, Takuya, E-mail: tmatsu@dent.osaka-u.ac.jp [Department of Oromaxillofacial Regeneration, Osaka University, 1-8 Yamada-Oka, Suita 565-0871 (Japan); Uddin, Mohammad Hafiz; An, Sang Hyun [Department of Oromaxillofacial Regeneration, Osaka University, 1-8 Yamada-Oka, Suita 565-0871 (Japan); Arakawa, Kazuto; Taguchi, Eiji [Research Center for Ultra-High Voltage Electron Microscopy, Osaka University, 7-1 Mihogaoka, Ibaraki 567-0047 (Japan); Nakahira, Atsushi [Department of Material Sciences, Osaka Prefecture University, 1-1 Gakuen-cho, Sakai 599-8531 (Japan); Okazaki, Masayuki [Department of Biomaterials Science, Hiroshima University Faculty of Dentistry, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8553 (Japan)

    2011-08-15

    Highlights: {yields} Hydroxyapatite incorporating amino acid was fabricated. {yields} The synthesized crystals showed linearly aligned nano-pores in their structure after their EB irradiation or heating. {yields} Amino acid is considered as an effective porogen for the modulation of internal structure of apatite single crystal. - Abstract: Hydroxyapatite materials are potentially useful for biomedical application, especially as vehicles for functional molecules. Structural control of bulk apatite materials, such as in the fabrication of hollow microspheres or porous structures, has been studied for this purpose. However, control of the internal structure of the source apatite crystal itself is still a challenge. Here, we show that small organic molecules incorporated in apatite crystals act as porogens which control the porous structure of apatite single crystal. The presence of amino acid under apatite synthesis conditions leads to firm bindings and encapsulation of the amino acid in apatite single crystals. Amino acid elimination by heating or electron beam irradiation enhances the pore formation in apatite single crystal. Moreover, incorporation of an acidic amino acid in apatite induces peapod like nanotubes in apatite single crystals. This study suggests the potential of using small organics for nano-structural control of apatite single crystals which would be valuable for enhancing drug loadings or modulating material digestion in vivo.

  7. Development of High-Thrust and Double-Sided Linear Synchronous Motor Module For Liquid Crystal Display Equipment

    Institute of Scientific and Technical Information of China (English)

    Myung-jin; CHUNG; Sang-yeon; HWANG

    2010-01-01

    <正>Recently,there is an increasing requirement for controlling linear motion up to a few hundred of millimeter strokes in the area of the liquid crystal display(LCD) production equipment.The requirements of the motion system for LCD production equipment are high acceleration and high velocity with positioning accuracy.To satisfy these requirements,it has to be designed with the high-thrust force and low velocity ripple.In this work, high-thrust and double-sided linear synchronous motor (LSM)module is proposed and the developed high-thrust and double-sided LSM module is verified by performance test.

  8. Search for double beta decay of zinc and tungsten with low background ZnWO{sub 4} crystal scintillators

    Energy Technology Data Exchange (ETDEWEB)

    Bernabei, R; Nozzoli, F [Dip. di Fisica, Universita di Roma ' Tor Vergata' , I-00133 Rome (Italy); Belli, P [INFN, sez. Roma ' Tor Vergata' , I-00133 Rome (Italy); Cappella, F; Prosperi, D [Dip. di Fisica, Universita di Roma ' La Sapienza' , I-00185 Rome (Italy); Cerulli, R; Nisi, S [INFN, Laboratori Nazionali del Gran Sasso, 67010 Assergi (Italy); Danevich, F A; Kobychev, V V; Mokina, V M; Nagorny, S S; Poda, D V; Tretyak, V I; Yurchenko, S S [Institute for Nuclear Research, MSP 03680 Kyiv (Ukraine); Grinyov, B V; Nagornaya, L L [Institute for Scintillation Materials, 61001 Kharkiv (Ukraine); Incicchitti, A [INFN, sez. Roma, I-00185 Rome (Italy)

    2010-01-01

    Double beta processes in {sup 64}Zn, {sup 70}Zn, {sup 180}W, and {sup 186}W have been searched for with the help of low background ZnWO4 crystal scintillators at the Gran Sasso National Laboratories of the INFN (Italy). The total measurement time exceeds ten thousand hours. New improved half-life (T{sub 1/2}) limits on double electron capture and electron capture with positron emission in {sup 64}Zn have been set. New T{sub 1/2} bounds were also set on different modes of 2{beta} processes in {sup 70}Zn, {sup 180}W, and {sup 186}W. Future perspectives are considered.

  9. Spore and crystal formation in Bacillus thuringiensis var thuringiensis during growth in cystine and cysteine.

    OpenAIRE

    Rajalakshmi, S.; Shethna, YI

    1980-01-01

    The effect of the addition of different concentratons of cystine and cysteine on sporulation and parasporal crystal formation in Bacillus thuringiensis var. thuringiensis was studied. The effect was well pronounced when the systine/cysteine additions were made after the stationary phase. Heat stable spores and crystals were formed when the culture was provided with a low concentration of cystine/cysteine (0.05 per cent w/v). At a moderate concentration of cystine or cysteine (0.15%), only ...

  10. Unsaturated glycerophospholipids mediate heme crystallization: biological implications for hemozoin formation in the kissing bug Rhodnius prolixus.

    Directory of Open Access Journals (Sweden)

    Renata Stiebler

    Full Text Available Hemozoin (Hz is a heme crystal produced by some blood-feeding organisms, as an efficient way to detoxify heme derived from hemoglobin digestion. In the triatomine insect Rhodnius prolixus, Hz is essentially produced by midgut extracellular phospholipid membranes known as perimicrovillar membranes (PMVM. Here, we investigated the role of commercial glycerophospholipids containing serine, choline and ethanolamine as headgroups and R. prolixus midgut lipids (RML in heme crystallization. All commercial unsaturated forms of phospholipids, as well as RML, mediated fast and efficient β-hematin formation by means of two kinetically distinct mechanisms: an early and fast component, followed by a late and slow one. The fastest reactions observed were induced by unsaturated forms of phosphatidylethanolamine (uPE and phosphatidylcholine (uPC, with half-lives of 0.04 and 0.7 minutes, respectively. β-hematin crystal morphologies were strikingly distinct among groups, with uPE producing homogeneous regular brick-shaped crystals. Interestingly, uPC-mediated reactions resulted in two morphologically distinct crystal populations: one less representative group of regular crystals, resembling those induced by uPE, and the other largely represented by crystals with numerous sharp edges and tapered ends. Heme crystallization reactions induced by RML were efficient, with a heme to β-hematin conversion rate higher than 70%, but clearly slower (t1/2 of 9.9-17.7 minutes than those induced by uPC and uPE. Interestingly, crystals produced by RML were homogeneous in shape and quite similar to those mediated by uPE. Thus, β-hematin formation can be rapidly and efficiently induced by unsaturated glycerophospholipids, particularly uPE and uPC, and may play a role on biological heme crystallization in R. prolixus midgut.

  11. The laser radiation action on the crystal formation processes in the biological fluids

    Science.gov (United States)

    Malov, Alexander N.; Vaichas, Andrey A.; Novikova, Evgeniya A.

    2016-11-01

    The results of an experimental study of the laser radiation effect on the crystal`s formation in the volume of biological fluids that are complex multi-component solutions have been discussing. Are investigated white and natural bile in vitro. The qualitative changes were observed. Thus, at the bottom of the cell in which bile is not exposed to the laser radiation, the crystals are formed. In the irradiated bile gallstone has a thin layer of a homogeneous viscous colloidal liquid with very small, visible in polarized light crystalline formations was got. Irradiated laser bile's gallstone was covered evenly white deposit without surface defect unlike gallstone in bile without radiation exposure. A possible mechanism to explain the laser radiation action on the mineral formation in biological fluids and also practical application of this effect have been suggesting too.

  12. Double Layers: Potential Formation and Related Nonlinear Phenomena in Plasmas: Proceedings of the 5th Symposium

    Science.gov (United States)

    Iizuka, S.

    1998-02-01

    The Table of Contents for the book is as follows: * PREFACE * INTERNATIONAL SCIENTIFIC COMMITTEE * LOCAL ORGANIZING COMMITTEE AT TOHOKU UNIVERSITY * CHAPTER 1: DOUBLE LAYERS, SHEATHS, AND POTENTIAL STRUCTURES * 1.1 Double Layers * On Fluid Models of Stationary, Acoustic Double Layers (Invited) * Particle Simulation of Double Layer (Invited) * Space-Time Dependence of Non-Steady Double Layers * The Role of Low Energy Electrons for the Generation of Anode Double Layers in Glow Discharges * Arbitrary Amplitude Ion-Acoustic Double Layers in a Dusty Plasma * 1.2 Sheaths * Bounded Plasma Edge Physics as Observed from Simulations in 1D and 2D (Invited) * Control of RF Sheath Structure in RF Diode Discharge * Observation of Density Gradients with Fine Structures and Low Frequency Wave Excitation at the Plasma-Sheath Boundary * Double Sheath Associated with an Electron Emission to a Plasma Containing Negative Ions * Sheath Edge and Floating Potential for Multi-Species Plasmas Including Dust Particles * 1.3 Potential Structures and Oscillations * Potential Structure Formed at a Constriction of a DC He Positive Column and its Coupling with Ionization Wave * Potential Structure in a New RF Magnetron Device with a Hollow Electrode * Potential Disruption in a RF Afterglow Electronegative Plasma * Potential Oscillation in a Strongly Asymmetry RF Discharge Containing Negative Ions * Effects of External Potential Control on Coulomb Dust Behavior * Potential Structure of Carbon Arc Discharge for High-Yield Fullerenes Formation * Control of Axial and Radial Potential Profiles in Tandem Mirrors (Invited) * CHAPTER 2: FIELD-ALIGNED ELECTRIC FIELDS AND RELATED PARTICLE ACCELERATIONS * 2.1 Field-Aligned Potential Formation * Formation of Large Potential Difference in a Plasma Flow along Converging Magnetic Field Lines (Invited) * Presheath Formation in front of an Oblique End-Plate in a Magnetized Sheet Plasma * Plasma Potential Formation Due to ECRH in a Magnetic Well * Electrostatic

  13. PRELIMINARY STUDY ON RELATIONSHIP BETWEEN DOUBLE VORTICES SELF-ORGANIZATION AND TYPHOON FORMATION IN BAROCLINIC ENVIRONMENT

    Institute of Scientific and Technical Information of China (English)

    TENG Dai-gao; LUO Zhe-xian; PAN Jing-song; YU Hui

    2010-01-01

    The relationship between the self-organization of double vortices(SODVs)and the formation of typhoons was discussed based on six numerical experiments with the Fifth-Generation National Center for Atmospheric Research/Penn State Mesoscale Model(MM5)and further discussion was made with a real typhoon case.The results showed that there is a critical distance dc for SODVs in baroclinic atmosphere.When the distance between separated vortices is smaller than or equal to dc,the double vortices self-organize into a typhoon-like vortex with two spiral bands.But the double vortices cannot have such organization if the distance between them is larger than dc.The value of dc is about 380 km in the context of ideal conditions in this paper,larger than that achieved in a barotropic model.A typical typhoon case in2005(Haitang)was selected to verify the above-mentioned conclusions.It was found that the SODV is one of the important and typical ways for the formation of typhoons.

  14. Stability and chirality effect on twist formation of collapsed double wall carbon nanotubes

    Institute of Scientific and Technical Information of China (English)

    XIAO Jian-liang; LIU Bin; HUANG Yong-gang; HWANG Ke-zhi; YU Min-feng

    2006-01-01

    This study is to reveal the effect of interlayer lattice registry on the formation of collapsed double wall carbon nanotubes (DWCNTs). It is found that collapsed carbon nanotubes can be energetically unstable,metastable or stable,depending mainly on the diameter of the CNT. A fully collapsed DWCNT can adopt different structural morphologies,such as a straight ribbon,a warping ribbon or a twisted ribbon,depending on the chirality of the CNT,which is similar to single wall carbon nanotubes (SWCNTs). Different from SWCNTs,this study also shows some unique phenomena in the formation of collapsed DWCNTs. A fully collapsed DWCNT can have different combinations of the interlayer lattice registry effect within the inner and outer tube,thus the outer tube can influence the formation of the collapsed CNT via lattice registry effect,sometimes even dominates the twist of the CNT.

  15. Have a break: determinants of meiotic DNA double strand break (DSB) formation and processing in plants.

    Science.gov (United States)

    Edlinger, Bernd; Schlögelhofer, Peter

    2011-03-01

    Meiosis is an essential process for sexually reproducing organisms, leading to the formation of specialized generative cells. This review intends to highlight current knowledge of early events during meiosis derived from various model organisms, including plants. It will particularly focus on cis- and trans-requirements of meiotic DNA double strand break (DSB) formation, a hallmark event during meiosis and a prerequisite for recombination of genetic traits. Proteins involved in DSB formation in different organisms, emphasizing the known factors from plants, will be introduced and their functions outlined. Recent technical advances in DSB detection and meiotic recombination analysis will be reviewed, as these new tools now allow analysis of early meiotic recombination in plants with incredible accuracy. To anticipate future directions in plant meiosis research, unpublished results will be included wherever possible.

  16. Analysis of ripple formation in single crystal spot welds

    Science.gov (United States)

    Rappaz, M.; Corrigan, D.; Boatner, L. A.

    1997-01-01

    Stationary spot welds have been made at the (001) surface of Fe-l5%Ni-15%Cr single crystals using a Gas Tungsten Arc (GTA). On the top surface of the spot welds, very regular and concentric ripples were observed after solidification by differential interference color microscopy. Their height (typically 1--5 micrometers and spacing, typically approximately 60 micrometers) decreased with the radius of the pool. These ripples were successfully accounted for in terms of capillary-wave theory using the fundamental mode frequency f(sub 0) given by the first zero of the zero-order Bessel function. The spacing d between the ripples was then equated to v(sub s)/f(sub 0), where v(sub s) is the solidification rate. From the measured ripple spacing, the velocity of the pool was deduced as a function of the radius, and this velocity was in good agreement with the results of a heat-flow simulation.

  17. Frequency doubling of incoherent light from a superluminescent diode in a periodically poled lithium niobate waveguide crystal

    Science.gov (United States)

    Kurzke, Henning; Kiethe, Jan; Heuer, Axel; Jechow, Andreas

    2017-05-01

    The amplified spontaneous emission from a superluminescent diode was frequency doubled in a periodically poled lithium niobate waveguide crystal. The temporally incoherent radiation of such a superluminescent diode is characterized by a relatively broad spectral bandwidth and thermal-like photon statistics, as the measured degree of second order coherence, {{g}(2)}(0)=1.9+/- 0.1 , indicates. Despite the non-optimized scenario in the spectral domain, we achieve six orders of magnitude higher conversion efficiency than previously reported with truly incoherent light. This is possible by using single spatial mode radiation and quasi phase matched material with a waveguide architecture. This work is a principle step towards efficient frequency conversion of temporally incoherent radiation in one spatial mode to access wavelengths where no radiation from superluminescent diodes is available, especially with tailored quasi phase matched crystals. The frequency doubled light might find application in imaging, metrology and quantum optics experiments.

  18. The cosmological Kibble mechanism in the laboratory string formation in liquid crystals

    CERN Document Server

    Bowick, M J; Schiff, E A; Srivastava, A M

    1994-01-01

    We have observed the production of strings (disclination lines and loops) via the Kibble mechanism of domain (bubble) formation in the isotropic to nematic phase transition of a sample of uniaxial nematic liquid crystal. The probablity of string formation per bubble is measured to be $0.33 \\pm 0.01$. This is in good agreement with the theoretical value $1/ \\pi$ expected in two dimensions for the order parameter space $S^2/{\\bf Z}_2$ of a simple uniaxial nematic liquid crystal.

  19. Turbulent mixing and layer formation in double-diffusive convection: 3D numerical simulations and theory

    CERN Document Server

    Rosenblum, Erica; Traxler, Adrienne; Stellmach, Stephan

    2010-01-01

    Double-diffusive convection, often referred to as semi-convection in astrophysics, occurs in thermally and compositionally stratified systems which are stable according to the Ledoux-criterion but unstable according to the Schwarzchild criterion. This process has been given relatively little attention so far, and its properties remain poorly constrained. In this paper, we present and analyze a set of three-dimensional simulations of this phenomenon in a Cartesian domain under the Boussinesq approximation. We find that in some cases the double-diffusive convection saturates into a state of homogeneous turbulence, but with turbulent fluxes several orders of magnitude smaller than those expected from direct overturning convection. In other cases the system rapidly and spontaneously develops closely-packed thermo-compositional layers, which later successively merge until a single layer is left. We compare the output of our simulations with an existing theory of layer formation in the oceanographic context, and fi...

  20. Search for double beta decay of $^{116}$Cd with enriched $^{116}$CdWO$_4$ crystal scintillators (Aurora experiment)

    CERN Document Server

    Danevich, F A; Belli, P; Bernabei, R; Cappella, F; Caracciolo, V; Cerulli, R; Chernyak, D M; d'Angelo, S; Incicchitti, A; Kobychev, V V; Konovalov, S I; Laubenstein, M; Mokina, V M; Poda, D V; Polischuk, O G; Shlegel, V N; Tretyak, V I; Umatov, V I

    2016-01-01

    The Aurora experiment to investigate double beta decay of $^{116}$Cd with the help of 1.162 kg cadmium tungstate crystal scintillators enriched in $^{116}$Cd to 82\\% is in progress at the Gran Sasso Underground Laboratory. The half-life of $^{116}$Cd relatively to the two neutrino double beta decay is measured with the highest up-to-date accuracy $T_{1/2}=(2.62\\pm0.14)\\times10^{19}$ yr. The sensitivity of the experiment to the neutrinoless double beta decay of $^{116}$Cd to the ground state of $^{116}$Sn is estimated as $T_{1/2} \\geq 1.9\\times10^{23}$ yr at 90\\% CL, which corresponds to the effective Majorana neutrino mass limit $\\langle m_{\

  1. Formation and crystallization of Zr-Ni-Ti metallic glass

    Institute of Scientific and Technical Information of China (English)

    刘雄军; 惠希东; 焦建廷; 陈国良

    2004-01-01

    The metallic Zr65 Ni25 Ti10 (mole fraction, %) glass has been fabricated by a single roller melt-spinning method. The glass forming ability(GFA) and thermal stability of the Zr65 Ni25 Ti10 melt-spun ribbons were investiga ted by using X-ray diffraction(XRD) and differential scanning calorimetry(DSC) in the mode of continuous heating.It is shown that the reduced glass transition temperature (Trg) is 0. 506 and the supercooled liquid region (△Tx) is 30 K. Two exothermic peaks were observed in the DSC curves of the as-quenched ribbon, which indicates that the crystallization process undergoes two different stages. The phase transformation during the isothermal annealing was investigated by X-ray diffraction(XRD) and transmission electronic microscope(TEM). It is observed that the meta stable FCC Zr2 Ni(Fd3m, α= 12.27 (A)) precipitated while annealing in the suppercooled region(615 K) and the stable BCT Zr2Ni(I4/mcm, α=6. 499 (A), c=5. 270 (A)) precipitated while annealing at higher temperature(673 K or 723K). The crystallines are on nanoscale, with grain size of 15 -30 nm. The reason for the precipitation of the different structural Zr2 Ni from the glassy matrix under different annealing conditions was discussed based on the concept of multi-component chemical short range order(MCSRO).

  2. Functional Implications of Photosystem II Crystal Formation in Photosynthetic Membranes*

    Science.gov (United States)

    Tietz, Stefanie; Puthiyaveetil, Sujith; Enlow, Heather M.; Yarbrough, Robert; Wood, Magnus; Semchonok, Dmitry A.; Lowry, Troy; Li, Zhirong; Jahns, Peter; Boekema, Egbert J.; Lenhert, Steven; Niyogi, Krishna K.; Kirchhoff, Helmut

    2015-01-01

    The structural organization of proteins in biological membranes can affect their function. Photosynthetic thylakoid membranes in chloroplasts have the remarkable ability to change their supramolecular organization between disordered and semicrystalline states. Although the change to the semicrystalline state is known to be triggered by abiotic factors, the functional significance of this protein organization has not yet been understood. Taking advantage of an Arabidopsis thaliana fatty acid desaturase mutant (fad5) that constitutively forms semicrystalline arrays, we systematically test the functional implications of protein crystals in photosynthetic membranes. Here, we show that the change into an ordered state facilitates molecular diffusion of photosynthetic components in crowded thylakoid membranes. The increased mobility of small lipophilic molecules like plastoquinone and xanthophylls has implications for diffusion-dependent electron transport and photoprotective energy-dependent quenching. The mobility of the large photosystem II supercomplexes, however, is impaired, leading to retarded repair of damaged proteins. Our results demonstrate that supramolecular changes into more ordered states have differing impacts on photosynthesis that favor either diffusion-dependent electron transport and photoprotection or protein repair processes, thus fine-tuning the photosynthetic energy conversion. PMID:25897076

  3. Functional Implications of Photosystem II Crystal Formation in Photosynthetic Membranes.

    Science.gov (United States)

    Tietz, Stefanie; Puthiyaveetil, Sujith; Enlow, Heather M; Yarbrough, Robert; Wood, Magnus; Semchonok, Dmitry A; Lowry, Troy; Li, Zhirong; Jahns, Peter; Boekema, Egbert J; Lenhert, Steven; Niyogi, Krishna K; Kirchhoff, Helmut

    2015-05-29

    The structural organization of proteins in biological membranes can affect their function. Photosynthetic thylakoid membranes in chloroplasts have the remarkable ability to change their supramolecular organization between disordered and semicrystalline states. Although the change to the semicrystalline state is known to be triggered by abiotic factors, the functional significance of this protein organization has not yet been understood. Taking advantage of an Arabidopsis thaliana fatty acid desaturase mutant (fad5) that constitutively forms semicrystalline arrays, we systematically test the functional implications of protein crystals in photosynthetic membranes. Here, we show that the change into an ordered state facilitates molecular diffusion of photosynthetic components in crowded thylakoid membranes. The increased mobility of small lipophilic molecules like plastoquinone and xanthophylls has implications for diffusion-dependent electron transport and photoprotective energy-dependent quenching. The mobility of the large photosystem II supercomplexes, however, is impaired, leading to retarded repair of damaged proteins. Our results demonstrate that supramolecular changes into more ordered states have differing impacts on photosynthesis that favor either diffusion-dependent electron transport and photoprotection or protein repair processes, thus fine-tuning the photosynthetic energy conversion.

  4. Investigation of optical inhomogeneity of MgO:PPLN crystals for frequency doubling of 1560 nm laser

    Science.gov (United States)

    Guo, Shanlong; Ge, Yulong; Han, Yashuai; He, Jun; Wang, Junmin

    2014-09-01

    The asymmetrical phase-matching temperature tuning curves of periodically-poled 5%-mol MgO-doped lithium niobate (MgO:PPLN) bulk crystals for frequency doubling of 1560 nm telecom laser have been observed experimentally and analyzed theoretically. We find that the asymmetrical phenomena are resulted from the variation in the extraordinary refractive index by the doping concentration inhomogeneity of the crystals. The critical parameters of phase-matching temperature mismatching γ(γ=δTpm/ΔT, in which δTpm is the change of the phase-matching temperature due to the doping concentration inhomogeneity, and ΔT is the temperature acceptance bandwidth) and the thermal refractive index ∂(Δn)/∂T are investigated. Our analysis method is not only a reasonable explanation to the experiment, but also can be a simple evaluation way of optical quality of the given MgO:PPLN bulk crystals. Moreover, the MgO:PPLN bulk crystal is used in single-pass configuration for frequency doubling a 4.4 W Erbium-doped fiber amplifier boosted 1560 nm telecom laser, and 300 mW of tunable 780 nm laser is obtained, corresponding to a conversion efficiency of 6.9%. This source provides a simple and compact laser system for rubidium atom cooling and manipulation experiments.

  5. Performance of ZnMoO4 crystal as cryogenic scintillating bolometer to search for double beta decay of molybdenum

    CERN Document Server

    Gironi, L; Beeman, J W; Cremonesi, O; Danevich, F A; Degoda, V Ya; Ivleva, L I; Nagornaya, L L; Pavan, M; Pessina, G; Pirro, S; Tretyak, V I; Tupitsyna, I A

    2010-01-01

    Zinc molybdate (ZnMoO4) single crystals were grown for the first time by the Czochralski method and their luminescence was measured under X ray excitation in the temperature range 85-400 K. Properties of ZnMoO4 crystal as cryogenic low temperature scintillator were checked for the first time. Radioactive contamination of the ZnMoO4 crystal was estimated as <0.3 mBq/kg (228-Th) and 8 mBq/kg (226-Ra). Thanks to the simultaneous measurement of the scintillation light and the phonon signal, the alpha particles can be discriminated from the gamma/beta interactions, making this compound extremely promising for the search of neutrinoless Double Beta Decay of 100-Mo. We also report on the ability to discriminate the alpha-induced background without the light measurement, thanks to a different shape of the thermal signal that characterizes gamma/beta and alpha particle interactions.

  6. Design, Build & Test of a Double Crystal Monochromator for Beamlines I09 & I23 at the Diamond Light Source

    Science.gov (United States)

    Kelly, J.; Lee, T.; Alcock, S.; Patel, H.

    2013-03-01

    A high stability Double Crystal Monochromator has been developed at The Diamond Light Source for beamlines I09 and I23. The design specification was a cryogenic, fixed exit, energy scanning monochromator, operating over an energy range of 2.1 - 25 keV using a Si(111) crystal set. The novel design concepts are the direct drive, air bearing Bragg axis, low strain crystal mounts and the cooling scheme. The instrument exhibited superb stability and repeatability on the B16 Test Beamline. A 20 keV Si(555), 1.4 μrad rocking curve was demonstrated. The DCM showed good stability without any evidence of vibration or Bragg angle nonlinearity.

  7. Pattern Formation in Double-Layer Kerr Resonators with Coupled Modes

    CERN Document Server

    Bois, Antoine

    2016-01-01

    A double-layer Kerr resonator in which both coupled modes are excited and interact with each other via incoherent cross-phase modulation is investigated to reveal stable localized solutions beyond the usual formation mechanism involving a single mode. Periodic solutions from modulational instability are found to occur at a slight penalty on the nonlinear efficiency, but they stabilize the spatial dynamics, leading to dissipative solitons in previously unattainable regimes. Numerical simulations show paired breather solitons in addition to temporally stable solutions. The results demonstrate coupled modes can increase the stability of Kerr frequency comb generation.

  8. Insights into the Tectonic Evolution of the North American Cordilleran Hinterland from Detrital Zircon Double Dating of the Eocene Elko Formation

    Science.gov (United States)

    Canada, A.; Cassel, E. J.; Smith, M. E.; Stockli, D. F.; Jicha, B. R.; Singer, B. S.

    2015-12-01

    The North American Cordilleran hinterland, from eastern Nevada to western Utah, is the product of Mesozoic crustal thickening and eventual orogen collapse. In NE Nevada, the Eocene Elko Formation represents ~10 Myr of high-elevation (up to 3.5 km) lacustrine deposition within a Paleogene orogenic plateau interior, prior to Neogene extensional collapse. Detrital zircon U-Pb and (U-Th)/He (ZHe) double dating from the Elko Formation constrains the timing and magnitude of tectonic-scale processes as well as the evolution of hinterland paleohydrology and magmatism. Eocene maximum depositional ages from detrital zircon are largely consistent with new single crystal sanidine 40Ar/39Ar ages for Elko Formation tuff beds. U-Pb-He double dating of Eocene sediments supports several phases of exhumation and surface uplift in the hinterland. ZHe ages, combined with U-Pb geochronology, clast assemblages, and paleocurrent analysis suggest a significant amount of detritus from the Roberts Mountain Allochthon (RMA) and back-arc plutons was transported to the Elko Basin during the middle Eocene. Detrital zircons sourced from the RMA record progressive unroofing and are characterized by Archean-Paleoproterozoic crystallization ages and Mesoproterozoic-Triassic cooling ages. The preponderance of Precambrian ZHe ages during the middle-late Eocene and the absence of reset ZHe ages throughout the basin imply that sediment burial did not exceed depths of >6 km during the Phanerozoic. Double dating of several grains from a sandstone below the base of the lacustrine section also confirms the presence of volcanic detritus derived from the Challis volcanic field of central Idaho 400 kilometers to the northeast. Lag time analysis permits discrimination of syndepositional volcanic grains from grains derived from rapidly exhumed sources. Lag time analysis (excluding volcanic grains) indicates that several source areas west of the Elko Basin have undergone major exhumation during the late Eocene.

  9. Matrix Gla Protein is Involved in Crystal Formation in Kidney of Hyperoxaluric Rats

    Directory of Open Access Journals (Sweden)

    Xiuli Lu

    2013-02-01

    Full Text Available Background: Matrix Gla protein (MGP is a molecular determinant regulating vascular calcification of the extracellular matrix. However, it is still unclear how MGP may be invovled in crystal formation in the kidney of hyperoxaluric rats. Methods: Male Sprague-Dawley rats were divided into the hyperoxaluric group and control group. Hyperoxaluric rats were administrated by 0.75% ethylene glycol (EG for up to 8 weeks. Renal MGP expression was detected by the standard avidin-biotin complex (ABC method. Renal crystal deposition was observed by a polarizing microscope. Total RNA and protein from the rat kidney tissue were extracted. The levels of MGP mRNA and protein expression were analyzed by the real-time polymerase chain reaction (RT-PCR and Western blot. Results: Hyperoxaluria was induced successfully in rats. The MGP was polarly distributed, on the apical membrane of renal tubular epithelial cells, and was found in the ascending thick limbs of Henle's loop (cTAL and the distal convoluted tubule (DCT in hyperoxaluric rats, its expression however, was present in the medullary collecting duct (MCD in stone-forming rats. Crystals with multilaminated structure formed in the injurious renal tubules with lack of MGP expression.MGP mRNA expression was significantly upregulated by the crystals' stimulations. Conclusion: Our results suggested that the MGP was involved in crystals formation by the continuous expression, distributing it polarly in the renal tubular cells and binding directly to the crystals.

  10. Lattice Boltzmann Simulation of Kinetic Isotope Effect During Snow Crystal Formation

    Science.gov (United States)

    Lu, G.; Depaolo, D. J.; Kang, Q.; Zhang, D.

    2007-12-01

    The isotopic composition of precipitation, especially that of snow, plays a special role in the global hydrological cycle and in reconstruction of past climates using polar ice cores. The fractionation of the major water isotope species (HHO, HDO, HHO-18) during ice crystal formation is critical to understanding the global distribution of isotopes in precipitation. Ice crystal growth in clouds is traditionally treated with a spherically-symmetric steady state diffusion model, with semi-empirical modifications added to account for ventilation and for complex crystal morphology. Although it is known that crystal growth rate, which depends largely on the degree of vapor over- saturation, determines crystal morphology, there are no quantitative models that relate morphology to the vapor saturation factor. Since kinetic (vapor phase diffusion-controlled) isotopic fractionation also depends on growth rate, there should be direct relationships between vapor saturation, crystal morphology, and crystal isotopic composition. We use a 2D lattice Boltzmann model to simulate diffusion-controlled ice crystal growth from vapor- oversaturated air. In the model, crystals grow solely according to the diffusive fluxes just above the crystal surfaces, and hence crystal morphology arises from the initial and boundary conditions in the model and does not need to be specified a priori. Crystal growth patterns can be varied between random growth and deterministic growth (along the maximum concentration gradient for example). The input parameters needed are the isotope- dependent vapor deposition rate constant (k) and the water vapor diffusivity in air (D). The values of both k and D can be computed from kinetic theory, and there are also experimentally determined values of D. The deduced values of k are uncertain to the extent that the condensation coefficient for ice is uncertain. The ratio D/k is a length (order 1 micron) that determines the minimum scale of dendritic growth features

  11. Refractive Index Change and Color Center Formation in LiYF_4 Crystal Induced by a Femtosecond Laser

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The refractive index change and color centers formation in LiYF4 crystal at room temperature are induced by a femtosecond laser irradiation. A mechanism for refractive index change and color centers formation is proposed.

  12. Refractive Index Change and Color Center Formation in LiYF4 Crystal Induced by a Femtosecond Laser

    Institute of Scientific and Technical Information of China (English)

    Quanzhong Zhao; Jianrong Qiu; Lüyun Yang; Xiongwei Jiang; Congshan Zhu

    2003-01-01

    The refractive index change and color centers formation in LiYF4 crystal at room temperature are induced by a femtosecond laser irradiation. A mechanism for refractive index change and color centers formation is proposed.

  13. Dynamics of Crystal Formation in the Greenland NorthGRIP Ice Core

    CERN Document Server

    Mathiesen, J; Jensen, M H; Levinsen, M; Olesen, P; Dahl-Jensen, D; Svensson, A; Mathiesen, Joachim; Ferkinghoff-Borg, Jesper; Jensen, Mogens H.; Levinsen, Mogens; Olesen, Poul; Dahl-Jensen, Dorthe; Svensson, Anders

    2003-01-01

    The North Greenland Ice Core Project (NorthGRIP) provides paleoclimatic information back to at least 115 kyr before present [Dahl-Jensen et al., 2002]. Each year, precipitation on the ice sheet covers it with a new layer of snow, which gradually transforms into ice crystals as the layer sinks into the ice sheet. The size distribution of ice crystals has been measured at selected depths in the upper 880 m of the NorthGRIP ice core [Svensson et al., 2003b], which cover a time span of 5300 years. The distributions change with time toward a universal curve, indicating a common underlying physical process in the formation of crystals. We identify this process as an interplay between fragmentation of the crystals and diffusion of their grain boundaries. The process is described by a two-parameter differential equation to which we obtain the exact solution. The solution is in excellent agreement with the experimentally observed distributions.

  14. Characterization of Si/SiGe/Si Deposited on SIMOX SOI by Synchrotron Radiation X-Ray Double-crystal Topography

    Institute of Scientific and Technical Information of China (English)

    Ma Tongda; Tu Hailing; Hu Guangyong; Wang Jing

    2004-01-01

    The synchrotron X-ray double-crystal topography was employed to investigate the structure of Si/SiGe/Si deposited on SIMOX SOI. Rocking curves with three diffraction peaks were acquired before and after 180° rotation of samples. Double-crystal topographs taken at the full width at half maximum (FWHM) of the three peaks differ from each other. Many defects appear in the Si layers that are likely related to the tilt between SOI and epitaxial layers.

  15. Dynamical entanglement formation and dissipation effects in two double quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Contreras-Pulido, L D [Centro de Investigacion CientIfica y de Educacion Superior de Ensenada, Apartado Postal 2732, Ensenada, BC 22860 (Mexico); Rojas, F [Departamento de Fisica Teorica, Centro de Ciencias de la Materia Condensada, Universidad Nacional Autonoma de Mexico, Ensenada, Baja California 22800 (Mexico)

    2006-11-01

    We study the static and dynamic formation of entanglement in charge states of a two double quantum dot array with two mobile electrons under the effect of an external driving field. We include dissipation via contact with a phonon bath. By using the density matrix formalism and an open quantum system approach, we describe the dynamical behaviour of the charge distribution (polarization), concurrence (measure of the degree of entanglement) and Bell state probabilities (two qubit states with maximum entanglement) of such a system, including the role of dot asymmetry and temperature effects. Our results show that it is possible to obtain entangled states as well as a most probable Bell state, which can be controlled by the driving field. We also evaluate how the entanglement formation based on charge states deteriorates as the temperature or asymmetry increases.

  16. Search for double beta processes in {sup 106}Cd with enriched {sup 106}CdWO{sub 4} crystal scintillator in coincidence with four crystals HPGe detector

    Energy Technology Data Exchange (ETDEWEB)

    Danevich, F. A., E-mail: danevich@kinr.kiev.ua; Chernyak, D. M.; Mokina, V. M. [Institute for Nuclear Research, MSP 03680 Kyiv (Ukraine); Belli, P.; Bernabei, R.; D’Angelo, S. [Dipartimento di Fisica, Università di Roma ”Tor Vergata”, I-00133 Rome (Italy); INFN sezione Roma ”Tor Vergata”, I-00133 Rome (Italy); Brudanin, V. B. [Joint Institute for Nuclear Research, 141980 Dubna (Russian Federation); Cappella, F.; Caracciolo, V.; Cerulli, R.; Laubenstein, M. [INFN, Laboratori Nazionali del Gran Sasso, I-67100 Assergi (AQ) (Italy); Incicchitti, A. [INFN, sezione di Roma ”La Sapienza”, I-00185 Rome (Italy); Dipartimento di Fisica, Università di Roma ”La Sapienza”, I-00185 Rome (Italy); Poda, D. V. [Institute for Nuclear Research, MSP 03680 Kyiv (Ukraine); Centre de Sciences Nucléaires et de Sciences de la Matière, 91405 Orsay (France); Polischuk, O. G.; Tretyak, V. I. [Institute for Nuclear Research, MSP 03680 Kyiv (Ukraine); INFN, sezione di Roma ”La Sapienza”, I-00185 Rome (Italy); Tupitsyna, I. A. [Institute of Scintillation Materials, 61001 Kharkiv (Ukraine)

    2015-10-28

    A radiopure cadmium tungstate crystal scintillator, enriched in {sup 106}Cd ({sup 106}CdWO{sub 4}), was used to search for double beta decay processes in {sup 106}Cd in coincidence with an ultra-low background set-up containing four high purity germanium (HPGe) detectors in a single cryostat. The experiment has been completed after 13085 h of data taking. New improved limits on most of the double beta processes in {sup 106}Cd have been set on the level of 10{sup 20}−10{sup 21} yr. Tn particular, the half-life limit on the two neutrino electron capture with positron emission, T{sub 1/2} ≥ 1.8 × 10{sup 21} yr, reached the region of theoretical predictions.

  17. The Formation of Crystal Defects in a Fe-Mn-Si Alloy Under Cyclic Martensitic Transformations.

    Science.gov (United States)

    Bondar, Vladimir I; Danilchenko, Vitaliy E; Iakovlev, Viktor E

    2016-12-01

    Formation of crystalline defects due to cyclic martensitic transformations (CMT) in the iron-manganese Fe-18 wt.% Mn-2 wt.% Si alloy was investigated using X-ray diffractometry. Conditions for accumulation of fragment sub-boundaries with low-angle misorientations and chaotic stacking faults in crystal lattice of austenite and ε-martensite were analyzed.

  18. Physical properties and crystal structure analysis of double-perovskite NdBaMn2O6 by using single crystals

    Science.gov (United States)

    Yamada, S.; Sagayama, H.; Higuchi, K.; Sasaki, T.; Sugimoto, K.; Arima, T.

    2017-01-01

    We have succeeded in growing large single crystals of double-perovskite NdBaMn2O6 with the c axis aligned, and carried out a crystal structure analysis and measurements of resistivity and magnetization. A first-order metal-insulator transition at TM I≃290 K is accompanied by a large jump of magnetization and lattice constants. The distortion of MnO6 octahedra is consistent with a ferroic orbital order of x2-y2 type, although other orbital orders cannot be completely discarded. Néel temperature TN is determined to be 235 K, which is fairly lower than TM I, on the basis of the onset of a large magnetic anisotropy. Another structural phase transition from tetragonal to orthorhombic is found at 370 K, which arises from staggered tilting of MnO6 octahedra and little affects the transport and magnetic properties.

  19. Formation of laser induced periodic surface structures (LIPSS) on Ti upon double fs pulse exposure

    Science.gov (United States)

    Gemini, Laura; Hashida, Masaki; Nishii, Takaya; Miyasaka, Yasuhiro; Inoue, Shunsuke; Limpouch, Jiri; Mocek, Tomas; Sakabe, Shuji

    2015-03-01

    Recently a parametric decay model was proposed in order to foresee LIPSS interspaces, and experimental results are in reasonable agreement. To confirm the possibility assumed by the model of pre-formed plasma generation, Ti surface was irradiated by a femtosecond (fs) laser beam composed by double fs pulses, with a fixed delay of 160 fs. The fluence of the first pulse (FPP), responsible for surface plasma formation, was varied in the range 10-50 mJ cm-2 and always kept below the LIPSS formation threshold fluence (FLIPSS) of Ti for 50-single-shots exposure. The fluence of the delayed pulse (FLP), responsible for LIPSS formation, was varied in the range 60-150 mJ cm-2 and always kept above FLIPSS. Regardless the specific fluence FLP of the delayed pulse, the interspace of the grating structures increases with the increase of FPP, that is the increase of the surface plasma density. This tendency suggests that a variation of the surface plasma density, due to a variation of FPP, actually leads to a modification of the grating features, highlighting the driving role of the first pulse in LIPSS formation. Moreover, we observed that the LIPSS periodicities after double pulse exposures are in quite good agreement with data on LIPSS periodicities after single 160 fs pulse irradiations on Ti surface and with the curve predicted by the parametric decay model. This experimental result suggests that the preformed plasma might be produced in the rising edge of the temporal profile of the laser pulse.

  20. Production of 82Se enriched Zinc Selenide (ZnSe) crystals for the study of neutrinoless double beta decay

    Science.gov (United States)

    Dafinei, I.; Nagorny, S.; Pirro, S.; Cardani, L.; Clemenza, M.; Ferroni, F.; Laubenstein, M.; Nisi, S.; Pattavina, L.; Schaeffner, K.; di Vacri, M. L.; Boyarintsev, A.; Breslavskii, I.; Galkin, S.; Lalayants, A.; Rybalka, I.; Zvereva, V.; Enculescu, M.

    2017-10-01

    High purity Zinc Selenide (ZnSe) crystals are produced starting from elemental Zn and Se to be used for the search of the neutrinoless double beta decay (0νDBD) of 82Se. In order to increase the number of emitting nuclides, enriched 82Se is used. Dedicated production lines for the synthesis and conditioning of the Zn82Se powder in order to make it suitable for crystal growth were assembled compliant with radio-purity constraints specific to rare event physics experiments. Besides routine check of impurities concentration, high sensitivity measurements are made for radio-isotope concentrations in raw materials, reactants, consumables, ancillaries and intermediary products used for ZnSe crystals production. Indications are given on the crystals perfection and how it is achieved. Since very expensive isotopically enriched material (82Se) is used, a special attention is given for acquiring the maximum yield in the mass balance of all production stages. Production and certification protocols are presented and resulting ready-to-use Zn82Se crystals are described.

  1. Formation of large (≃100 μm ice crystals near the tropical tropopause

    Directory of Open Access Journals (Sweden)

    D. S. Sayres

    2007-05-01

    Full Text Available Recent high-altitude aircraft measurements with in situ imaging instruments indicated the presence of relatively large (≃100 μm length, thin (aspect ratios of ≃6:1 or larger hexagonal plate ice crystals near the tropical tropopause in very low concentrations (<0.01 L−1. These crystals were not produced by deep convection or aggregation. We use simple growth-sedimentation calculations as well as detailed cloud simulations to evaluate the conditions required to grow the large crystals. Uncertainties in crystal aspect ratio leave a range of possibilities, which could be constrained by knowledge of the water vapor concentration in the air where the crystal growth occurred. Unfortunately, water vapor measurements made in the cloud formation region near the tropopause ranged from <2 ppmv to ≃3.5 ppmv. The higher water vapor concentrations correspond to very large ice supersaturations (relative humidities with respect to ice of about 200%. If the aspect ratios of the hexagonal plate crystals are as small as the image analysis suggests (6:1, see companion paper Lawson et al., 2007 then growth of the large crystals before they sediment out of the supersaturated layer would only be possible if the water vapor concentration were on the high end of the range indicated by the different measurements (>3 ppmv. On the other hand, if the crystal aspect ratios are quite a bit larger (≃14, then H2O concentrations toward the low of the measurement range (≃2–2.3 ppmv would suffice to grow the large crystals. Gravity-wave driven temperature and vertical wind perturbations only slightly modify the H2O concentrations needed to grow the crystals. We find that it would not be possible to grow the large crystals with water concentrations less than 2 ppmv, even with assumptions of a very high aspect ratio of 15 and steady upward motion of 2 cm s−1 to loft the crystals in the tropopause region. These calculations would seem to imply that the measurements

  2. On the sagittal focusing of synchrotron radiation with a double crystal monochromator

    Energy Technology Data Exchange (ETDEWEB)

    Kushnir, V.I.; Quintana, J.P.; Georgopoulos, P. (DUNU Synchrotron Research Center, Robert R. McCormick School of Engineering and Applied Science, Northwestern Univ., Evanston, IL (United States))

    1993-05-01

    A method to avoid the anticlastic bending of the second crystal in a two-crystal monochromator for synchrotron radiation is proposed. It is analytically shown that the anticlastic curvature is zero at the center of the crystal for a simply supported isotropic crystal loaded with a constant moment provided that the crystal's aspect ratio is equal to a 'golden value' dependent on the Poisson coefficient [nu]. For [nu]=0.262 (equal to [nu] in the Si(111) plane) this ratio is 2.360. Finite element results are presented on the case of the clamped crystal and show that there is a similar 'golden value' approximately equal to 1.42 for [nu]=0.262. (orig.).

  3. A unique growth mechanism of donut-shaped Mg–Al layered double hydroxides crystals revealed by AFM and STEM–EDX

    NARCIS (Netherlands)

    Budhysutanto, W.N.; Van Den Bruele, F.J.; Rossenaar, B.D.; Van Agterveld, D.; Van Enckevort, W.J.P.; Kramer, H.J.M.

    2010-01-01

    Donut-like crystals of Mg–Al layered double hydroxides (LDH) are synthesized using a hydrothermal method with microwave heating. This morphology provides enlargement of the specific surface area of the {h k 0} faces, needed for adsorption application. The growth mechanism for donut-shaped crystals i

  4. 100 mW of blue light at 405 nm from intracavity doubling of CW Ti:Sapphire laser utilising BiBO-crystal

    DEFF Research Database (Denmark)

    Thorhauge, Morten; Mortensen, Jesper Liltorp; Tidemand-Lichtenberg, Peter

    2006-01-01

    100 mW of coherent blue light with a wavelength of 405 nm was generated utilising a BiB3O6 (BiBO) nonlinear crystal to frequency double a Ti:Sapphire laser. Phase match curves as well as sensitivity to angular misalignment was calculated. The BiBO crystal was found to be excellent for this applic...

  5. Crystal structure induced residue formation on 4H-SiC by reactive ion etching

    Directory of Open Access Journals (Sweden)

    Yi-hong Liu

    2016-06-01

    Full Text Available The (000 1 ¯ C face of 4H-SiC wafer was etched by reactive ion etching in SF6/O2 plasma. The effect of etching parameters, such as work pressure, SF6:O2 ratio and etching time, on the residue formation were systematically investigated. The residue morphologies were observed by scanning electron microscopy and atomic force microscopy, respectively. The residues have spike shape and their facets are defined as { 1 1 ¯ 0 2 ¯ } crystal planes. They are formed at beginning of the etching and no new spikes are generated as prolonging etching time. Both work pressure and SF6:O2 ratio play significant role in the spike formation. The residues can be eliminated completely by increasing the SF6:O2 ratio and work pressure. On the basis of experimental results and of 4H-SiC crystal structure, the spike formation model is proposed.

  6. Femtosecond-laser inscribed double-cladding waveguides in Nd:YAG crystal: a promising prototype for integrated lasers.

    Science.gov (United States)

    Liu, Hongliang; Chen, Feng; Vázquez de Aldana, Javier R; Jaque, D

    2013-09-01

    We report on the design and implementation of a prototype of optical waveguides fabricated in Nd:YAG crystals by using femtosecond-laser irradiation. In this prototype, two concentric tubular structures with nearly circular cross sections of different diameters have been inscribed in the Nd:YAG crystals, generating double-cladding waveguides. Under 808 nm optical pumping, waveguide lasers have been realized in the double-cladding structures. Compared with single-cladding waveguides, the concentric tubular structures, benefiting from the large pump area of the outermost cladding, possess both superior laser performance and nearly single-mode beam profile in the inner cladding. Double-cladding waveguides of the same size were fabricated and coated by a thin optical film, and a maximum output power of 384 mW and a slope efficiency of 46.1% were obtained. Since the large diameters of the outer claddings are comparable with those of the optical fibers, this prototype paves a way to construct an integrated single-mode laser system with a direct fiber-waveguide configuration.

  7. Quantum-chemical approach to defect formation processes in non-metallic crystals

    Energy Technology Data Exchange (ETDEWEB)

    Kotomin, E.A.; Shluger, A.L. (Latvijskij Gosudarstvennyj Univ., Riga (USSR))

    1989-01-01

    Results of the quantum-chemical simulation of the formation of structural and radiation defects are reviewed, using ice, silicon, and silicon dioxide as examples. The relationship between the structural elements of these crystals and the structural defects is analysed. Models of the main defects, their optical characteristics, and the activation energy of their migration are discussed. The relationship between the characteristics obtained by quantum-chemical calculations and the parameters of the macroscopic kinetics of the processes induced by defects in dielectric crystals is considered. (author).

  8. Shock response of single crystal and nanocrystalline pentaerythritol tetranitrate: Implications to hotspot formation in energetic materials.

    Science.gov (United States)

    Cai, Y; Zhao, F P; An, Q; Wu, H A; Goddard, W A; Luo, S N

    2013-10-28

    We investigate shock response of single crystal and nanocrystalline pentaerythritol tetranitrate (PETN) with a coarse-grained model and molecular dynamics simulations, as regards mechanical hotspot formation in the absence or presence of grain boundaries (GBs). Single crystals with different orientations, and columnar nanocrystalline PETN with regular hexagonal, irregular hexagonal, and random GB patterns, are subjected to shock loading at different shock strengths. In single crystals, shock-induced plasticity is consistent with resolved shear stress calculations and the steric hindrance model, and this deformation leads to local heating. For regular-shaped hexagonal columnar nanocrystalline PETN, different misorientation angles lead to activation of different/same slip systems, different deformation in individual grains and as a whole, different GB friction, different temperature distributions, and then, different hotspot characteristics. Compared to their regular-shaped hexagonal counterpart, nanocrystalline PETN with irregular hexagonal GB pattern and that with random GBs, show deformation and hotspot features specific to their GBs. Driven by stress concentration, hotspot formation is directly related to GB friction and GB-initiated crystal plasticity, and the exact deformation is dictated by grain orientations and resolved shear stresses. GB friction alone can induce hotspots, but the hotspot temperature can be enhanced if it is coupled with GB-initiated crystal plasticity, and the slip of GB atoms has components out of the GB plane. The magnitude of shearing can correlate well with temperature, but the slip direction of GB atoms relative to GBs may play a critical role. Wave propagation through varying microstructure may also induce differences in stress states (e.g., stress concentrations) and loading rates, and thus, local temperature rise. GB-related friction and plasticity induce local heating or mechanical hotspots, which could be precursors to chemical

  9. The double reflection on the interface of uniaxial crystals in the Savart polariscope

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The reflection in the Savart polariscope is different from the isotropic medium. The double reflection of rays in the Savart polariscope is analyzed and discussed on the basis of the Snell law. The double reflection formulae of the extraordinary ray and the ordinary ray are given. These results may provide a theoretical and practical guide for studying, developing and engineering polarization interference imaging spectrometers.

  10. The double reflection on the interface of uniaxial crystals in the Savart polariscope

    Science.gov (United States)

    Wu, Junfang; Zhang, Chunmin

    2009-07-01

    The reflection in the Savart polariscope is different from the isotropic medium. The double reflection of rays in the Savart polariscope is analyzed and discussed on the basis of the Snell law. The double reflection formulae of the extraordinary ray and the ordinary ray are given. These results may provide a theoretical and practical guide for studying, developing and engineering polarization interference imaging spectrometers.

  11. CW frequency doubling of 1029 nm radiation Using single pass bulk and waveguide PPLN crystals

    CERN Document Server

    Chiodo, Nicola; Hrabina, Jan; Candela, Yves; Wallerand, Jean-Pierre; Acef, Ouali

    2013-01-01

    Following various works on second harmonic process using periodically poled Lithium Niobate crystals (PPLN), we report on the performances comparison between commercial bulk and waveguide crystals at 1029 nm. We use a continuous wave (CW) amplified Yb doped single fibre laser delivering up to 500mW in single mode regime. In case of bulk crystal we generate 4 mW using 400 mW IR power. The use of waveguide crystal leads to an increase of the harmonic power up to 33mW with input IR power limited to 200mW. Nevertheless, this impressive efficiency was affected by the long term degradation of the non-linear waveguide crystal.

  12. Formation of large (≃100 μm ice crystals near the tropical tropopause

    Directory of Open Access Journals (Sweden)

    M. J. Alexander

    2008-03-01

    Full Text Available Recent high-altitude aircraft measurements with in situ imaging instruments indicated the presence of relatively large (≃100 μm length, thin (aspect ratios of ≃6:1 or larger hexagonal plate ice crystals near the tropical tropopause in very low concentrations (<0.01 L−1. These crystals were not produced by deep convection or aggregation. We use simple growth-sedimentation calculations as well as detailed cloud simulations to evaluate the conditions required to grow the large crystals. Uncertainties in crystal aspect ratio leave a range of possibilities, which could be constrained by knowledge of the water vapor concentration in the air where the crystal growth occurred. Unfortunately, water vapor measurements made in the cloud formation region near the tropopause with different instruments ranged from <2 ppmv to ≃3.5 ppmv. The higher water vapor concentrations correspond to very large ice supersaturations (relative humidities with respect to ice of about 200%. If the aspect ratios of the hexagonal plate crystals are as small as the image analysis suggests (6:1, see companion paper (Lawson et al., 2008 then growth of the large crystals before they sediment out of the supersaturated layer would only be possible if the water vapor concentration were on the high end of the range indicated by the different measurements (>3 ppmv. On the other hand, if the crystal aspect ratios are quite a bit larger (≃10:1, then H2O concentrations toward the low end of the measurement range (≃2–2.5 ppmv would suffice to grow the large crystals. Gravity-wave driven temperature and vertical wind perturbations only slightly modify the H2O concentrations needed to grow the crystals. We find that it would not be possible to grow the large crystals with water concentrations less than 2 ppmv, even with assumptions of a very high aspect ratio of 15 and steady upward motion of 2 cm s−1 to loft the crystals in the tropopause region. These calculations would seem

  13. Development of a bent Laue beam-expanding double-crystal monochromator for biomedical X-ray imaging

    Energy Technology Data Exchange (ETDEWEB)

    Martinson, Mercedes, E-mail: mercedes.m@usask.ca [University of Saskatchewan, 116 Science Place, Room 163, Saskatoon, Saskatchewan (Canada); Samadi, Nazanin [University of Saskatchewan, 107 Wiggins Road, Saskatoon, Saskatchewan (Canada); Belev, George [Canadian Light Source, 44 Innovation Boulevard, Saskatoon, Saskatchewan (Canada); Bassey, Bassey [University of Saskatchewan, 116 Science Place, Room 163, Saskatoon, Saskatchewan (Canada); Lewis, Rob [University of Saskatchewan, 107 Wiggins Road, Saskatoon, Saskatchewan (Canada); Monash University, Clayton, Victoria 3800 (Australia); Aulakh, Gurpreet [University of Saskatchewan, 107 Wiggins Road, Saskatoon, Saskatchewan (Canada); Chapman, Dean [University of Saskatchewan, 116 Science Place, Room 163, Saskatoon, Saskatchewan (Canada); University of Saskatchewan, 107 Wiggins Road, Saskatoon, Saskatchewan (Canada)

    2014-03-13

    A bent Laue beam-expanding double-crystal monochromator was developed and tested at the Biomedical Imaging and Therapy beamline at the Canadian Light Source. The expander will reduce scanning time for micro-computed tomography and allow dynamic imaging that has not previously been possible at this beamline. The Biomedical Imaging and Therapy (BMIT) beamline at the Canadian Light Source has produced some excellent biological imaging data. However, the disadvantage of a small vertical beam limits its usability in some applications. Micro-computed tomography (micro-CT) imaging requires multiple scans to produce a full projection, and certain dynamic imaging experiments are not possible. A larger vertical beam is desirable. It was cost-prohibitive to build a longer beamline that would have produced a large vertical beam. Instead, it was proposed to develop a beam expander that would create a beam appearing to originate at a source much farther away. This was accomplished using a bent Laue double-crystal monochromator in a non-dispersive divergent geometry. The design and implementation of this beam expander is presented along with results from the micro-CT and dynamic imaging tests conducted with this beam. Flux (photons per unit area per unit time) has been measured and found to be comparable with the existing flat Bragg double-crystal monochromator in use at BMIT. This increase in overall photon count is due to the enhanced bandwidth of the bent Laue configuration. Whilst the expanded beam quality is suitable for dynamic imaging and micro-CT, further work is required to improve its phase and coherence properties.

  14. Angular Multiplexing Storage in Azo-polymer Liquid Crystal Films Using Shearing Interferometer of Double-frequency Grating

    Institute of Scientific and Technical Information of China (English)

    ZHANG Jiangying; MING Hai; WANG Pei; WU Yunxia; XIE Jianping; ZHANG Qijin; LIU Jian

    2002-01-01

    In this paper, the shearing interferometer of a double-frequency grating (DFG) and a small compact Nd∶YVO4 double frequency laser at 532 nm are used to study the multiple storage in azo-polymer liquid crystal (PLC) films. In a principle experiment, the angle-encoded multiple gratings are recorded and the experimental results give triplex gratings at the same region in azo-PLC films, the angle between two adjacent grating vectors being 45°. Compared to the two-beam interferometer and four-wave mixing method, this method has simple configuration, high fringe contrast and quake-proof. A compatible angular multiplexing storage system in azo-PLC films is proposed.

  15. Crystallization and chain reorganization of debranched rice starches in relation to resistant starch formation.

    Science.gov (United States)

    Kiatponglarp, Worawikunya; Tongta, Sunanta; Rolland-Sabaté, Agnès; Buléon, Alain

    2015-05-20

    The effects of chain distribution, concentration, temperature and hydrothermal treatments on the recrystallization behavior and formation of resistant starch (RS) were investigated. Waxy and normal rice starches were debranched at 10 and 21% w/w solid concentrations, incubated at 25 or 50 °C, and further subjected to annealing or heat moisture treatment (HMT) to enhance RS formation. The crystallization at 25 °C favored the formation of the B-type structure, whereas crystallization at 50 °C led to the A-type structure with a higher melting temperature (100-120 °C) and a higher RS content (52%). All incubated samples showed an increase in RS content after subsequent hydrothermal treatments. The sample incubated at a high temperature contained the highest RS content (74.5%) after HMT with larger/perfect crystallites. These results suggested that the RS formation could be manipulated by crystallization conditions and improved by hydrothermal treatments which are dependent on the initial crystalline perfection.

  16. Cut-off analysis of 19-cell Yb-doped double-cladding rod-type photonic crystal fibers.

    Science.gov (United States)

    Poli, F; Coscelli, E; Alkeskjold, T T; Passaro, D; Cucinotta, A; Leick, L; Broeng, J; Selleri, S

    2011-05-09

    Yb-doped double-cladding large mode area rod-type photonic crystal fibers are a key component for power scaling in fiber laser systems. Recently, designs with 19-cell core defect, that is with 19 missing air-holes in the center of the photonic crystal cladding, have been proposed, with reported core diameter up to 100 μm. In this paper an analysis of the cut-off wavelength of the first high-order mode in such low-NA fibers is reported, accounting for different approaches for the definition of the cladding effective index. Results have shown that taking into account the finite fiber cross-section and considering the first cladding mode of the actual fiber is mandatory to obtain a correct estimate of the cut-off wavelength.

  17. Transmission properties of one-dimensional Photonic crystals containing double-negative and single-negative materials

    Institute of Scientific and Technical Information of China (English)

    Xia Li; Kang Xie; Haiming Jiang

    2008-01-01

    The transmission properties of one-dimensional photonic crystals containing double-negative and singlenegative materials are studied theoretically.A special kind of photonic band gap is found in this structure.This gap is invariant with scaling and insensitive to thickness fluctuation.But when changing the ratio of the thickness of two media.the width of the gap could be enlarged.The defect modes are analyzed by inducing a linear defect layer in the structure.It is found that the number of defect modes will increase when the thickness of the defect layer becomes larger.

  18. A vacuum double-crystal spectrometer for reference-free highly charged ions X-ray spectroscopy

    CERN Document Server

    Amaro, P; Schlesser, S; Gumberidze, Alexandre; Kessler, Ernest G; Henins, Albert; Bigot, E -O Le; Trassinelli, M; Isac, Jean-Michel; Travers, Pascal; Guerra, Mauro; Santos, J P; Indelicato, Paul

    2012-01-01

    We have built a vacuum double crystal spectrometer, which coupled to an electron-cyclotron resonance ion source, allows to measure low-energy x-ray transitions in highly-charged ions with accuracies of the order of a few parts per million. We describe in detail the instrument and its performances. Furthermore, we present a few spectra of transitions in Ar$^{14+}$, Ar$^{15+}$ and Ar$^{16+}$. We have developed an \\emph{ab initio} simulation code that allows us to obtain accurate line profiles. It can reproduce experimental spectra with unprecedented accuracy. The quality of the profiles allows the direct determination of line width.

  19. Crystallization and cooling conditions for diogenite formation in the turbulent magma ocean of asteroid 4 Vesta

    Science.gov (United States)

    Kawabata, Yusuke; Nagahara, Hiroko

    2017-01-01

    Despite its small size, the asteroid 4 Vesta has been completely differentiated to core and mantle. Its composition is similar to howardite-eucrite-diogenite (HED) meteorites of which the detailed petrology is known. Therefore, 4 Vesta is a good target for understanding the differentiation of terrestrial planets. A new differentiation model for crust formation has been developed by taking magma ocean fluid dynamics, chemical equilibrium, the presence of 26Al, and cooling into consideration with a special focus on crystal separation. The role of crystal size, thickness of the conductive lid, and fO2 are evaluated as parameters. The results show that large crystals of at least 1 cm settled and formed a kilometer-thick cumulate layer of orthopyroxene with Mg # of 0.70-0.90 in ∼20 thousand years, which almost agrees with the Mg # of diogenites. Smaller grain sizes formed thinner layers.

  20. Clinical evaluation of a novel herbal dental cream in plaque formation: a double-blind, randomized, controlled clinical trial

    OpenAIRE

    amrutesh, sunita; Malini, J; Tandur, Prakash S; Pralhad S. Patki

    2010-01-01

    Background The aim of this study was to evaluate the efficacy and safety of herbal dental cream in comparison to fluoride dental cream. Objectives Clinical evaluation of a novel herbal dental cream in plaque formation: a double-blind, randomized, controlled clinical trial. Methods One hundred and two patients with established dental plaque were randomly assigned to either herbal dental group or fluoride dental group for six weeks in a double-blind design. Improvement in plaque index, oral hyg...

  1. Monotropic smectic A to double layer smectic C transition of biphenyl containing liquid crystal acetylene

    Institute of Scientific and Technical Information of China (English)

    Zhen Qiang Yu; Cai Zhen Zhu; Zhe Zhang; Jian Hong Liu; Jacky W.Y. Lam; Ben Zhong Tang

    2011-01-01

    5-[(4'-Heptoxy-4-biphenylyl)carbonyloxy]-l-pentyne (A-3, 7) was synthesized and the phase structures and transitions were investigated by differential scanning calorimetry (DSC), wide angle X-ray diffraction (WAXD), polarized light microscopy (PLM) and the molecular packing in the crystal and liquid crystalline phases were simulated by molecular dynamic simulation. The results showed that the sample formed thermodynamically metastable SmA and SmC2 phases before crystallized during cooling and the crystal phase directly transformed into isotropic phase during heating.

  2. Direct observation of two-step crystallization in nanoparticle superlattice formation

    Energy Technology Data Exchange (ETDEWEB)

    Park, Jungwon; Zheng, Haimei; Lee, Won Chul; Geissler, Phillip L.; Rabani, Eran; Alivisatos, A. Paul

    2011-10-06

    Direct imaging of nanoparticle solutions by liquid phase transmission electron microscopy has enabled unique in-situ studies of nanoparticle motion and growth. In the present work, we report on real-time formation of two-dimensional nanoparticle arrays in the very low diffusive limit, where nanoparticles are mainly driven by capillary forces and solvent fluctuations. We find that superlattice formation appears to be segregated into multiple regimes. Initially, the solvent front drags the nanoparticles, condensing them into an amorphous agglomerate. Subsequently, the nanoparticle crystallization into an array is driven by local fluctuations. Following the crystallization event, superlattice growth can also occur via the addition of individual nanoparticles drawn from outlying regions by different solvent fronts. The dragging mechanism is consistent with simulations based on a coarse-grained lattice gas model at the same limit.

  3. The double reflection on the interface of uniaxial crystals in the Savart polariscope

    Institute of Scientific and Technical Information of China (English)

    WU JunFang; ZHANG ChunMin

    2009-01-01

    The reflection in the Savart polariscope is different from the isotropic medium. The double reflection of rays in the Savart polariscope is analyzed and discussed on the basis of the Snell law. The double re-flection formulae of the extraordinary ray and the ordinary ray are given. These results may provide a theoretical and practical guide for studying, developing and engineering polarization interference im-aging spectrometers.

  4. Do carboximide–carboxylic acid combinations form co-crystals? The role of hydroxyl substitution on the formation of co-crystals and eutectics

    Directory of Open Access Journals (Sweden)

    Ramanpreet Kaur

    2015-05-01

    Full Text Available Carboxylic acids, amides and imides are key organic systems which provide understanding of molecular recognition and binding phenomena important in biological and pharmaceutical settings. In this context, studies of their mutual interactions and compatibility through co-crystallization may pave the way for greater understanding and new applications of their combinations. Extensive co-crystallization studies are available for carboxylic acid/amide combinations, but only a few examples of carboxylic acid/imide co-crystals are currently observed in the literature. The non-formation of co-crystals for carboxylic acid/imide combinations has previously been rationalized, based on steric and computed stability factors. In the light of the growing awareness of eutectic mixtures as an alternative outcome in co-crystallization experiments, the nature of various benzoic acid/cyclic imide combinations is established in this paper. Since an additional functional group can provide sites for new intermolecular interactions and, potentially, promote supramolecular growth into a co-crystal, benzoic acids decorated with one or more hydroxyl groups have been systematically screened for co-crystallization with one unsaturated and two saturated cyclic imides. The facile formation of an abundant number of hydroxybenzoic acid/cyclic carboximide co-crystals is reported, including polymorphic and variable stoichiometry co-crystals. In the cases where co-crystals did not form, the combinations are shown invariably to result in eutectics. The presence or absence and geometric disposition of hydroxyl functionality on benzoic acid is thus found to drive the formation of co-crystals or eutectics for the studied carboxylic acid/imide combinations.

  5. Do carboximide-carboxylic acid combinations form co-crystals? The role of hydroxyl substitution on the formation of co-crystals and eutectics.

    Science.gov (United States)

    Kaur, Ramanpreet; Gautam, Raj; Cherukuvada, Suryanarayan; Guru Row, Tayur N

    2015-05-01

    Carboxylic acids, amides and imides are key organic systems which provide understanding of molecular recognition and binding phenomena important in biological and pharmaceutical settings. In this context, studies of their mutual interactions and compatibility through co-crystallization may pave the way for greater understanding and new applications of their combinations. Extensive co-crystallization studies are available for carboxylic acid/amide combinations, but only a few examples of carboxylic acid/imide co-crystals are currently observed in the literature. The non-formation of co-crystals for carboxylic acid/imide combinations has previously been rationalized, based on steric and computed stability factors. In the light of the growing awareness of eutectic mixtures as an alternative outcome in co-crystallization experiments, the nature of various benzoic acid/cyclic imide combinations is established in this paper. Since an additional functional group can provide sites for new intermolecular inter-actions and, potentially, promote supramolecular growth into a co-crystal, benzoic acids decorated with one or more hydroxyl groups have been systematically screened for co-crystallization with one unsaturated and two saturated cyclic imides. The facile formation of an abundant number of hydroxybenzoic acid/cyclic carboximide co-crystals is reported, including polymorphic and variable stoichiometry co-crystals. In the cases where co-crystals did not form, the combinations are shown invariably to result in eutectics. The presence or absence and geometric disposition of hydroxyl functionality on benzoic acid is thus found to drive the formation of co-crystals or eutectics for the studied carboxylic acid/imide combinations.

  6. FORMATION MECHANISM OF TITANIUM CARBIDE CRYSTAL IN LASER SYNTHESIZED METAL-CERAMIC COMPOSITE COATING

    OpenAIRE

    BAOSHUAI DU; ZHONGWEN. ZHANG; XINHONG WANG; ZENGDA ZOU

    2011-01-01

    In situ titanium carbide reinforced iron-based composite coating was deposited on mild carbon steel using laser surface engineering (LSE) with ferrotitanium and graphite as precursor. The microstructure and phase constituents of the deposited coating were characterized. Formation mechanism of titanium carbide crystal in the composite coating was elucidated by correlating the morphology of titanium carbide and the thermal cycle experienced by the precursor during the laser treatment. It was de...

  7. Relationship between Multi-Phase Formation and Molecular Structure for Liquid Crystal System

    Institute of Scientific and Technical Information of China (English)

    LI Zhenxin; MA Heng; LI Shipu

    2005-01-01

    A mechanical model of liquid crystals ( LCs ) was used to explain the phase formation and thermal properties. The LC phases in the model are micro-machine systems consisting of an ensemble of molecular rotors, and some dynamic parameters in a semi-experiment molecular orbit method. A novel explanation on the multi-phase formation of LC system is obtained. It is found that the value of the critical rotational velocity is a key parameter for the characterization of each homologous series. The dipole moment of the molecules was also discussed.

  8. Glass formation and crystallization of high lead content PbO-B2O3 compositions

    Science.gov (United States)

    Weinberg, Michael C.; Smith, Gary L.; Neilson, George F.

    1986-01-01

    The glass-forming and undercooling ability of PbO-B2O3 melts in the 2PbO.B2O3 to 4PbO.B2O3 composition range were studied. The glass formation propensities were investigated as a function of cooling rate and sample mass. A qualitative investigation of the crystallization process(es) preventing glass formation was made, and it was concluded that under normal circumstances heterogeneous nucleation was the common occurrence. Hence, it was concluded that such compositions are prime candidates for containerless experiments aboard the Space Shuttle.

  9. Effect of adiponectin on kidney crystal formation in metabolic syndrome model mice via inhibition of inflammation and apoptosis.

    Science.gov (United States)

    Fujii, Yasuhiro; Okada, Atsushi; Yasui, Takahiro; Niimi, Kazuhiro; Hamamoto, Shuzo; Hirose, Masahito; Kubota, Yasue; Tozawa, Keiichi; Hayashi, Yutaro; Kohri, Kenjiro

    2013-01-01

    The aims of the present study were to elucidate a possible mechanism of kidney crystal formation by using a metabolic syndrome (MetS) mouse model and to assess the effectiveness of adiponectin treatment for the prevention of kidney crystals. Further, we performed genome-wide expression analyses for investigating novel genetic environmental changes. Wild-type (+/+) mice showed no kidney crystal formation, whereas ob/ob mice showed crystal depositions in their renal tubules. However, this deposition was remarkably reduced by adiponectin. Expression analysis of genes associated with MetS-related kidney crystal formation identified 259 genes that were >2.0-fold up-regulated and 243 genes that were metabolism. Expression analysis of adiponectin-induced genes related to crystal prevention revealed that the numbers of up- and down-regulated genes were 154 and 190, respectively. GO analyses indicated that the up-regulated genes belonged to the categories of cellular and mitochondrial repair, whereas the down-regulated genes belonged to the categories of immune and inflammatory reactions and apoptosis. The results of this study provide compelling evidence that the mechanism of kidney crystal formation in the MetS environment involves the progression of an inflammation and immunoresponse, including oxidative stress and adhesion reactions in renal tissues. This is the first report to prove the preventive effect of adiponectin treatment for kidney crystal formation by renoprotective activities and inhibition of inflammation and apoptosis.

  10. Formation of anorthosite on the Moon through magma ocean fractional crystallization

    Directory of Open Access Journals (Sweden)

    Tatsuyuki Arai

    2017-03-01

    Full Text Available Lunar anorthosite is a major rock of the lunar highlands, which formed as a result of plagioclase-floatation in the lunar magma ocean (LMO. Constraints on the sufficient conditions that resulted in the formation of a thick pure anorthosite (mode of plagioclase >95 vol.% is a key to reveal the early magmatic evolution of the terrestrial planets. To form the pure lunar anorthosite, plagioclase should have separated from the magma ocean with low crystal fraction. Crystal networks of plagioclase and mafic minerals develop when the crystal fraction in the magma (φ is higher than ca. 40–60 vol.%, which inhibit the formation of pure anorthosite. In contrast, when φ is small, the magma ocean is highly turbulent, and plagioclase is likely to become entrained in the turbulent magma rather than separated from the melt. To determine the necessary conditions in which anorthosite forms from the LMO, this study adopted the energy criterion formulated by Solomatov. The composition of melt, temperature, and pressure when plagioclase crystallizes are constrained by using MELTS/pMELTS to calculate the density and viscosity of the melt. When plagioclase starts to crystallize, the Mg# of melt becomes 0.59 at 1291 °C. The density of the melt is smaller than that of plagioclase for P > 2.1 kbar (ca. 50 km deep, and the critical diameter of plagioclase to separate from the melt becomes larger than the typical crystal diameter of plagioclase (1.8–3 cm. This suggests that plagioclase is likely entrained in the LMO just after the plagioclase starts to crystallize. When the Mg# of melt becomes 0.54 at 1263 °C, the density of melt becomes larger than that of plagioclase even for 0 kbar. When the Mg# of melt decreases down to 0.46 at 1218 °C, the critical diameter of plagioclase to separate from the melt becomes 1.5–2.5 cm, which is nearly equal to the typical plagioclase of the lunar anorthosite. This suggests that plagioclase could separate from the

  11. Time-varying formation control for double-integrator multi-agent systems with jointly connected topologies

    Science.gov (United States)

    Dong, Xiwang; Han, Liang; Li, Qingdong; Ren, Zhang

    2016-12-01

    Time-varying formation analysis and design problems for double-integrator multi-agent systems with jointly connected topologies are investigated. Different from the previous work on formation control, in this paper, the formation is specified by time-varying piecewise continuously differentiable vectors and the topology can be disconnected at any time instant. First, a distributed formation control protocol is constructed using local neighbour-to-neighbour information. In the case where the switching topology is jointly connected, necessary and sufficient conditions for double-integrator multi-agent systems to achieve time-varying formations are proposed, where the formation feasibility constraint is also derived. To describe the macroscopic movement of the whole formation, explicit expressions of the formation reference are presented, the motion modes of which can be partially assigned. Moreover, an approach to design the formation control protocol is given, which is fully distributed and requires no global information about the topology. Finally, the obtained theoretical results are applied to deal with the time-varying formation control problems of multi-vehicle systems.

  12. Zeolite Beta Formation from Clear Sols: Silicate Speciation, Particle Formation and Crystallization Monitored by Complementary Analysis Methods.

    Science.gov (United States)

    Castro, Maria; Haouas, Mohamed; Lim, Ivy; Bongard, Hans J; Schüth, Ferdi; Taulelle, Francis; Karlsson, Gunnel; Alfredsson, Viveka; Breyneart, Eric; Kirschhock, Christine E A; Schmidt, Wolfgang

    2016-10-17

    The formation of silicate nanoaggregates (NAs) at the very early stages of precursor sols and zeolite beta crystallization from silicate nanoparticles (NPs) are investigated in detail using a combination of different analysis methods, including liquid-state (29) Si, (27) Al, (14) N, and (1) H NMR spectroscopy, mass spectrometry (MS), small-angle X-ray scattering (SAXS), X-ray diffraction (XRD), and transmission electron microscopy at cryogenic temperatures (cryo-TEM). Prior to hydrothermal treatment, silicate NAs are observed if the Si/OH ratio in the reaction mixture is greater than 1. Condensation of oligomers within the NAs then generates NPs. Aluminum doped into the synthesis mixtures is located exclusively in the NPs, and is found exclusively in a state that is fourfold connected to silicate, favoring their condensation and aggregation. These results are in agreement with general trends observed for other systems. Silicate NAs are essential intermediates for zeolite formation and are generated by the aggregation of hydrated oligomers, aluminate, and templating cations. Subsequent further intra-nanoaggregate silicate condensation results in the formation of NPs. (1) H and (14) N liquid NMR as well as diffusion ordered spectroscopy (DOSY) experiments provide evidence for weakly restricted rotational and translational mobility of the organic template within NAs as a consequence of specific silicate-template interactions. NAs thus appear as key species in clear sols, and their presence in the precursor sol favors silicate condensation and further crystallization, promoted either by increasing the Si/OH ratio or by heating. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Characterization and Crystal Structures of Two Copper(Ⅱ) Complexes Constructed by a Flexible Double Betaine Ligand

    Institute of Scientific and Technical Information of China (English)

    JIANG Ning-Yi; LI Song-Lin

    2007-01-01

    A flexible double betaine 1,4-bis(pyridinil-4-carboxylato)-1,4-dimethylbenzene L has been used to generate two Cu(Ⅱ)-containing metal complexes that exhibit different polymeric structures: [Cu(H2O)2 L]·2NO3 1 and [Cu(H2O)3 L]·2Cl·H2O 2. The crystal structures of 1 and 2have been determined by single-crystal X-ray diffraction method. Crystal data for 1: triclinic, space group P1-, a = 5.253(2), b = 7.406(3), c = 14.792(5) (A), α = 84.195(5), β = 80.014(5), γ =78.053(5)°, V = 553.2(3) (A)3, Z = 1, F(000) = 293, Dc = 1.717 g/cm3, the final R = 0.0385 and wR =0.1079 for 1883 observed reflections (I> 2σ(Ⅰ)); and those for 2: monoclinic, space group P21/c, a =10.222(3), b = 25.287(7), c = 9.277(3) (A),β = 93.572(5)°, V = 2393.2(12) (A)3, Z = 4, F(000) = 1140,Dc = 1.540 g/cm3, the final R = 0.0472 and wR = 0.0956 for 3204 observed reflections (I >2σ(Ⅰ)).

  14. Anisotropic magnetic properties and superzone gap formation in CeGe single crystal.

    Science.gov (United States)

    Das, Pranab Kumar; Kumar, Neeraj; Kulkarni, R; Dhar, S K; Thamizhavel, A

    2012-04-11

    Single crystals of CeGe and its non-magnetic analog LaGe have been grown by the Czochralski method. The CeGe compound crystallizes in the orthorhombic FeB-type crystal structure with the space group Pnma (#62). The anisotropic magnetic properties have been investigated for well oriented single crystals by measuring the magnetic susceptibility, electrical resistivity and heat capacity. It has been found that CeGe orders antiferromagnetically at 10.5 K. Both transport and magnetic studies have revealed large anisotropy, reflecting the orthorhombic crystal structure. The magnetization data at 1.8 K reveal metamagnetic transitions along the [010] direction at 4.8 and 6.4 T and along the [100] direction at a critical field of 10.7 T, while the magnetization along the [001] direction increases linearly without any anomaly up to a field of 16 T. From the magnetic susceptibility and the magnetization measurements it has been found that the [010] direction is the easy axis of magnetization. The electrical resistivity along the three crystallographic directions exhibits an upturn at T(N), indicating superzone gap formation below T(N) in this compound. We have performed crystal electric field analysis on the magnetic susceptibility and the heat capacity data and found that the ground state is a doublet, and the energies of splitting from the ground state to the first and second excited doublet states were estimated to be 39 and 111 K, respectively.

  15. Formation and properties of reverse micellar cubic liquid crystals and derived emulsions.

    Science.gov (United States)

    Rodríguez-Abreu, Carlos; Shrestha, Lok Kumar; Varade, Dharmesh; Aramaki, Kenji; Maestro, Alicia; Quintela, Arturo López; Solans, Conxita

    2007-10-23

    The structure of the reverse micellar cubic (I2) liquid crystal and the adjacent micellar phase in amphiphilic block copolymer/water/oil systems has been studied by small-angle X-ray scattering (SAXS), rheometry, and differential scanning calorimetry (DSC). Upon addition of water to the copolymer/oil mixture, spherical micelles are formed and grow in size until a disorder-order transition takes place, which is related to a sudden increase in the viscosity and shear modulus. The transition is driven by the packing of the spherical micelles into a Fd3m cubic lattice. The single-phase I2 liquid crystals show gel-like behavior and elastic moduli higher than 104 Pa, as determined by oscillatory measurements. Further addition of water induces phase separation, and it is found that reverse water-in-oil emulsions with high internal phase ratio and stabilized by I2 liquid crystals can be prepared in the two-phase region. Contrary to liquid-liquid emulsions, both the elastic modulus and the viscosity decrease with the fraction of dispersed water, due to a decrease in the crystalline fraction in the sample, although the reverse emulsions remain gel-like even at high volume fractions of the dispersed phase. A temperature induced order-disorder transition can be detected by calorimetry and rheometry. Upon heating the I2 liquid crystals, two thermal events associated with small enthalpy values were detected: one endothermic, related to the "melting" of the liquid crystal, and the other exothermic, attributed to phase separation. The melting of the liquid crystal is associated with a sudden drop in viscosity and shear moduli. Results are relevant for understanding the formation of cubic-phase-based reverse emulsions and for their application as templates for the synthesis of structured materials.

  16. Content analyses in GaMnAs by double-crystal X-ray diffraction

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    A model for analyzing point defects in compound crystals was improved. Based on this modified model,a method for measuring Mn content in GaMnAs was established. A technique for eliminating the zero-drift-error was also established in the experiments of X-ray diffraction. With these methods, the Mn content in GaMnAs single crystals fabricated by the ion-beam epitaxy system was analyzed.Kevwords: GaMnAs, diluted magnetic semiconductor, X-ray dff fraction, lattice parameter, content of Mn.

  17. Superlocalization and Formation of Grain Structure in Ni3ge Single Crystals with Different Orientations of Deformation Axes

    Science.gov (United States)

    Solov'eva, Yu. V.; Lipatnikova, Ya. D.; Starenchenko, S. V.; Solov'ev, A. N.; Starenchenko, V. A.

    2017-09-01

    The paper describes the influence of orientation of Ni3Ge single crystal deformation axes on the high-temperature superlocalization of plastic deformation. Mechanical properties of single crystals with different orientations are studied in this paper as well as the slip traces and the evolution of the dislocation structure. Based on these investigations, the observing conditions are described for the superlocalization bands and the formation of the grain structure in local areas of the original single crystal.

  18. Laser-induced periodic surface structures on zinc oxide crystals upon two-colour femtosecond double-pulse irradiation

    Science.gov (United States)

    Höhm, S.; Rosenfeld, A.; Krüger, J.; Bonse, J.

    2017-03-01

    In order to study the temporally distributed energy deposition in the formation of laser-induced periodic surface structures (LIPSS) on single-crystalline zinc oxide (ZnO), two-colour double-fs-pulse experiments were performed. Parallel or cross-polarised double-pulse sequences at 400 and 800 nm wavelength were generated by a Mach–Zehnder interferometer, exhibiting inter-pulse delays up to a few picoseconds between the sub-ablation 50-fs-pulses. Twenty two-colour double-pulse sequences were collinearly focused by a spherical mirror to the sample surface. The resulting LIPSS periods and areas were analysed by scanning electron microscopy. The delay-dependence of these LIPSS characteristics shows a dissimilar behaviour when compared to the semiconductor silicon, the dielectric fused silica, or the metal titanium. A wavelength-dependent plasmonic mechanism is proposed to explain the delay-dependence of the LIPSS on ZnO when considering multi-photon excitation processes. Our results support the involvement of nonlinear processes for temporally overlapping pulses. These experiments extend previous two-colour studies on the indirect semiconductor silicon towards the direct wide band-gap semiconductor ZnO and further manifest the relevance of the ultrafast energy deposition for LIPSS formation.

  19. Crystal structure of listeriolysin O reveals molecular details of oligomerization and pore formation

    Science.gov (United States)

    Köster, Stefan; van Pee, Katharina; Hudel, Martina; Leustik, Martin; Rhinow, Daniel; Kühlbrandt, Werner; Chakraborty, Trinad; Yildiz, Özkan

    2014-04-01

    Listeriolysin O (LLO) is an essential virulence factor of Listeria monocytogenes that causes listeriosis. Listeria monocytogenes owes its ability to live within cells to the pH- and temperature-dependent pore-forming activity of LLO, which is unique among cholesterol-dependent cytolysins. LLO enables the bacteria to cross the phagosomal membrane and is also involved in activation of cellular processes, including the modulation of gene expression or intracellular Ca2+ oscillations. Neither the pore-forming mechanism nor the mechanisms triggering the signalling processes in the host cell are known in detail. Here, we report the crystal structure of LLO, in which we identified regions important for oligomerization and pore formation. Mutants were characterized by determining their haemolytic and Ca2+ uptake activity. We analysed the pore formation of LLO and its variants on erythrocyte ghosts by electron microscopy and show that pore formation requires precise interface interactions during toxin oligomerization on the membrane.

  20. Measuring birefringence of curved sheet and single crystals by double-exposure speckle photography

    Science.gov (United States)

    El-Dessouki, T. A.; Hendawy, N. I.; Zaki, A. A.

    2009-06-01

    In this work, a new theoretical and experimental approach for measuring birefringence of solid materials was described. Dispersions of birefringence of quartz, calcite crystals and Fortypan sheet were determined in the visible region. The results were compared with other interferometric methods to verify the accuracy of this approach.

  1. Topology design and fabrication of an efficient double 90° photonic crystal waveguide bend

    DEFF Research Database (Denmark)

    Jensen, Jakob Søndergaard; Sigmund, Ole; Frandsen, Lars Hagedorn

    2005-01-01

    We have designed and fabricated a novel 90 bend in a photonic crystal waveguide. The design was obtained using topology optimization and the fabricated waveguide displays a bend loss for transverse-electric-polarized light of less than 1 dB per bend in a 200-nm wavelength range....

  2. Nucleation kinetics of the formation of low dimensional calcium sulfate dihydrate crystals in isopropyl alcohol medium

    Energy Technology Data Exchange (ETDEWEB)

    Sandhya, S.; Sureshbabu, S.; Varma, H.K.; Komath, Manoj [Biomedical Technology Wing, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum 695 012 (India)

    2012-07-15

    Calcium sulfate dihydrate, constituted as uniform crystals of low dimensions, is a potential biomaterial for clinical applications like bone graft substitution and drug delivery. In this work, isopropyl alcohol has been used as a solvent to obtain low dimensional calcium sulfate dihydrate crystals from calcium nitrate - sulfuric acid system. Reactants in 0.5 molar concentration at ambient conditions generated uniform rod-shaped crystals of length 3-5 {mu}m. Analysis using X-ray Diffractometry and Fourier Transform Infrared Spectrometry showed the material to be well crystallized, phase-pure calcium sulfate dihydrate. The nucleation kinetics has been studied by observing the induction time of phase formation in solutions of millimolar concentrations through turbidimetry at 300 K. The data have been analysed using classical nucleation theory to deduce parameters like interfacial tension (or surface free energy), nucleation rate and critical radius. The surface free energy obtained (5.6 mJ/m{sup 2}) is comparatively lower than that reported for aqueous precipitation, which could be attributed to the presence of isopropyl alcohol. On escalating the supersaturation ratio, the nucleation rate drastically increased and the critical radius decreased exponentially. Particles formed at supersaturation 1.39 showed a monomodal distribution centered at 8.2 nm in Dynamic Light Scattering analysis. Comparable particle sizes were obtained in Transmission Electron Microscopy. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  3. From colloidal nanoparticles to a single crystal: new insights into the formation of nacre's aragonite tablets.

    Science.gov (United States)

    Zhang, Gangsheng; Xu, Jun

    2013-04-01

    Nacre has long served as a model for understanding the biomineralization mechanism and designing bio-inspired materials. However, its basic building blocks, the aragonite tablets, are still under debate in terms of their fine structure at the nanoscale and corresponding formation mechanism. Here, using a field emission scanning electron microscope (SEM), high resolution transmission electron microscope (HRTEM), and X-ray diffractometer, we comparatively investigate the immature and mature tablet from the green mussel's nacre. We find that: (1) the early immature tablet consists of closely-packed colloidal nanoparticles, which contain nanocrystals surrounded by the amorphous calcium carbonate (ACC) phase. Moreover, these nanocrystals are generally different in shape, size, and orientation; (2) the immature tablet can grow via oriented attachment besides via transformation of the ACC phase; and (3) with growth, the colloidal nanoparticles gradually increase in crystallinity and size until fully crystallized and fused together, leading to a mature tablet that is a monolithic single crystal of aragonite. Based on these findings, we propose a new model showing how the mature tablet evolves from the primary colloidal ACC nanoparticles. We expect this work will provide new insights into the formation of single crystal biominerals via the amorphous precursor route.

  4. Magnesium-Calcite Crystal Formation Mediated by the Thermophilic Bacterium Geobacillus thermoglucosidasius Requires Calcium and Endospores.

    Science.gov (United States)

    Murai, Rie; Yoshida, Naoto

    2016-11-01

    Fresh Geobacillus thermoglucosidasius cells grown on soybean-casein digest nutrient agar were inoculated as a parent colony 1 cm in diameter on the surface of an agar gel containing acetate and calcium ions (calcite-promoting hydrogel) and incubated at 60 °C for 4 days, after which magnesium-calcite single crystals of 50-130 µm in size formed within the parent colony. Addition of EDTA, polyacrylic acid or N,N-dicyclohexylcarbodiimide to the calcite-forming hydrogel inhibited the parent colony from forming magnesium-calcite crystals. Inoculation of G. thermoglucosidasius on calcite-forming hydrogel containing 5 µM cadmium and 20 µM zinc resulted in a decrease in the sporulation rate from 55 to 7-8 %. Magnesium-calcite synthesis decreased relative to the sporulation rate. G. thermoglucosidasius exhibited higher adsorption/absorbance of calcium than other Geobacillus sp. that do not mediate calcite formation and higher levels of magnesium accumulation. Calcium ions contained in the calcite-promoting hydrogel and magnesium ions concentrated in G. thermoglucosidasius cells serve as the elements for magnesium-calcite synthesis. The observed decreases in sporulation rate and magnesium-calcite formation support the hypothesis that endospores act as nuclei for the synthesis of magnesium-calcite single crystals.

  5. Role of supramolecular synthons in the formation of the supramolecular architecture of molecular crystals revisited from an energetic viewpoint.

    Science.gov (United States)

    Shishkin, Oleg V; Zubatyuk, Roman I; Shishkina, Svitlana V; Dyakonenko, Viktoriya V; Medviediev, Volodymyr V

    2014-04-14

    Analysis of the strengths and directionality of intermolecular interactions in the crystals containing only one type of supramolecular synthon allows the suggestion of a general classification of molecular crystals depending on type of their basic structural motifs. All crystals may be divided on four classes namely (I) crystals with isotropic packing of the building units; (II) columnar crystals where the basic structural motif (BSM) is a chain/column; (III) layered crystals with layers as the BSM; (IV) columnar-layered crystals containing chains/columns as the primary basic structural motif and layers as the secondary BSM. Taking into account the participation of different supramolecular synthons in the formation of different levels of the organization of molecular crystals, they may be considered as basic (responsible for the formation of molecular complexes as building units of crystals), primary, secondary and auxiliary, which are involved in the agglomeration of molecules in primary or secondary basic structural motifs or in the packing of these motifs, respectively. The ranking of supramolecular synthons depends on values of energies of intermolecular interactions and it is individual for each crystal.

  6. Evaluation of Optical Properties of Self-Frequency-Doubling Crystal Yb:GdYAl3(BO3)4 for Laser Applications

    Institute of Scientific and Technical Information of China (English)

    LI Jing; LI Qiang; WANG Ji-Yang; ZHAO Hong-Yang

    2007-01-01

    @@ Yb:GdYAl3(BO3)4(Yb:GdYAB) is investigated as a new laser crystal for potential applications in self-frequency doubling. The emission and absorption properties of Yb:GdYAB crystal are studied, and the emission decay times of the upper laser level are measured. The emission cross sections are evaluated using the absorption cross section and principle of reciprocity. The other laser performance parameters, such as the minimum inversion fraction βmin, pump saturation intensity Isat and minimum pump intensity Imin, are also calculated. The results are discussed in the framework of requirements for an effective diode-pumped Yb3+ laser system. Yb:GdYAB is expected to exhibit the most useful laser properties and to be superior to Yb:YAB crystal that has been excellent self-frequency-doubling crystal at present in many key spectroscopic parameter values.

  7. Influence of crystal orientation on the formation of femtosecond laser-induced periodic surface structures and lattice defects accumulation

    Science.gov (United States)

    Sedao, Xxx; Maurice, Claire; Garrelie, Florence; Colombier, Jean-Philippe; Reynaud, Stéphanie; Quey, Romain; Pigeon, Florent

    2014-04-01

    The influence of crystal orientation on the formation of femtosecond laser-induced periodic surface structures (LIPSS) has been investigated on a polycrystalline nickel sample. Electron Backscatter Diffraction characterization has been exploited to provide structural information within the laser spot on irradiated samples to determine the dependence of LIPSS formation and lattice defects (stacking faults, twins, dislocations) upon the crystal orientation. Significant differences are observed at low-to-medium number of laser pulses, outstandingly for (111)-oriented surface which favors lattice defects formation rather than LIPSS formation.

  8. Influence of crystal orientation on the formation of femtosecond laser-induced periodic surface structures and lattice defects accumulation

    Energy Technology Data Exchange (ETDEWEB)

    Sedao, Xxx; Garrelie, Florence, E-mail: florence.garrelie@univ-st-etienne.fr; Colombier, Jean-Philippe; Reynaud, Stéphanie; Pigeon, Florent [Université de Lyon, CNRS, UMR5516, Laboratoire Hubert Curien, Université de Saint Etienne, Jean Monnet, F-42023 Saint-Etienne (France); Maurice, Claire; Quey, Romain [Ecole Nationale Supérieure des Mines de Saint-Etienne, CNRS, UMR5307, Laboratoire Georges Friedel, F-42023 Saint-Etienne (France)

    2014-04-28

    The influence of crystal orientation on the formation of femtosecond laser-induced periodic surface structures (LIPSS) has been investigated on a polycrystalline nickel sample. Electron Backscatter Diffraction characterization has been exploited to provide structural information within the laser spot on irradiated samples to determine the dependence of LIPSS formation and lattice defects (stacking faults, twins, dislocations) upon the crystal orientation. Significant differences are observed at low-to-medium number of laser pulses, outstandingly for (111)-oriented surface which favors lattice defects formation rather than LIPSS formation.

  9. Crystal Structure of Aspirin-Acetylated Human Cyclooxygenase-2: Insight into the Formation of Products with Reversed Stereochemistry.

    Science.gov (United States)

    Lucido, Michael J; Orlando, Benjamin J; Vecchio, Alex J; Malkowski, Michael G

    2016-03-01

    Aspirin and other nonsteroidal anti-inflammatory drugs target the cyclooxygenase enzymes (COX-1 and COX-2) to block the formation of prostaglandins. Aspirin is unique in that it covalently modifies each enzyme by acetylating Ser-530 within the cyclooxygenase active site. Acetylation of COX-1 leads to complete loss of activity, while acetylation of COX-2 results in the generation of the monooxygenated product 15(R)-hydroxyeicosatetraenoic acid (15R-HETE). Ser-530 has also been shown to influence the stereochemistry for the addition of oxygen to the prostaglandin product. We determined the crystal structures of S530T murine (mu) COX-2, aspirin-acetylated human (hu) COX-2, and huCOX-2 in complex with salicylate to 1.9, 2.0, and 2.4 Å, respectively. The structures reveal that (1) the acetylated Ser-530 completely blocks access to the hydrophobic groove, (2) the observed binding pose of salicylate is reflective of the enzyme-inhibitor complex prior to acetylation, and (3) the observed Thr-530 rotamer in the S530T muCOX-2 crystal structure does not impede access to the hydrophobic groove. On the basis of these structural observations, along with functional analysis of the S530T/G533V double mutant, we propose a working hypothesis for the generation of 15R-HETE by aspirin-acetylated COX-2. We also observe differential acetylation of COX-2 purified in various detergent systems and nanodiscs, indicating that detergent and lipid binding within the membrane-binding domain of the enzyme alters the rate of the acetylation reaction in vitro.

  10. THE CRYSTAL STRUCTURE OF ASPIRIN ACETYLATED HUMAN CYCLOOXYGENASE-2: INSIGHT INTO THE FORMATION OF PRODUCTS WITH REVERSED STEREOCHEMISTRY

    Science.gov (United States)

    Lucido, Michael J.; Orlando, Benjamin J.; Vecchio, Alex J.; Malkowski, Michael G.

    2016-01-01

    Aspirin and other nonsterroidal anti-inflammatory drugs target the Cyclooxygenase enzymes (COX-1 and COX-2) to block the formation of prostaglandins. Aspirin is unique in that it covalently modifies each enzyme by acetylating Ser-530 within the cyclooxygenase active site. Acetylation of COX-1 leads to complete loss of activity, while acetylation of COX-2 results in the generation of the mono-oxygenated product 15(R)-hydroxyeicosatetraenoic acid (15R-HETE). Ser-530 has also been shown to influence the stereochemistry for oxygen addition into the prostaglandin product. We determined the crystal structures of S530T murine (mu) COX-2, aspirin-acetylated human (hu) COX-2, and huCOX-2 in complex with salicylate to 1.9Å, 2.0Å, and 2.4Å, respectively. The structures reveal that: 1) the acetylated Ser-530 completely blocks access to the hydrophobic groove; 2) the observed binding pose of salicylate is reflective of the enzyme-inhibitor complex prior to acetylation; and 3) the observed Thr-530 rotamer in the S530T muCOX-2 crystal structure does not impede access to the hydrophobic groove. Based on these structural observations, along with functional analysis of the S530T/G533V double mutant, we propose a working hypothesis for the generation of 15R-HETE by aspirin-acetylated COX-2. We also observe differential acetylation of COX-2 purified in various detergent systems and nanodiscs, indicating that detergent and lipid binding within the membrane-binding domain of the enzyme alters the rate of the acetylation reaction in vitro. PMID:26859324

  11. Formation of Cosmic String network from black holes: Implications from liquid crystal experiments

    CERN Document Server

    Srivastava, A M

    2006-01-01

    We present observation of large, expanding string loops forming around a heated wire tip embedded in a nematic liquid crystal sample. Loops expand due to convective stretching. This observation leads to a new insight into phenomena which could occur in the early universe. We show that local heating of plasma in the early universe by evaporating primordial black holes can lead to formation of large, expanding cosmic string loops, just as observed in the liquid crystal experiment. Intercommutation of string loops from neighboring black holes can lead to percolation, thereby forming an infinite string network. This is remarkable as such an infinite string network is thought to arise only when the entire universe undergoes phase transition.

  12. Monte Carlo simulation for the formation of a mixed crystal from two solids in contact.

    Science.gov (United States)

    Yinnon, C A; Buch, V; Devlin, J P

    2004-06-15

    The study focuses on nucleation and growth of a binary mixed crystal phase from two pure crystals in contact. Monte Carlo simulations of this process are conducted, with the dynamics proceeding via activated atom-vacancy exchanges. Intermolecular interactions, ranging up to next-nearest neighbors, are of size typical of hydrogen bonded systems. The process is driven by the formation of strong AB bonds at the expense of weaker AA and BB bonds. In the resulting model, the material is channeled and transported through the mixed phase crust along antiphase boundaries. The flow of molecules through the channels is directed, due to molecular energy lowering via gradual acquisition of an increasing number of nearest neighbors of the second species. On the other hand, defect motion is quasirandom. The model accounts partially for the t(1/alpha) (alpha>3) time dependence observed for conversion of nanoparticles of HBr dihydrate to monohydrate, by exposure to acid adsorbate.

  13. Sub-picosecond double-clad photonic crystal fiber oscillator and amplifier system

    Science.gov (United States)

    Li, Pingxue; Zhang, Mengmeng; Liang, Boxing; Chi, Junjie

    2015-08-01

    A ytterbium-doped large mode area PCF sub-picosecond laser oscillator and amplifier system is experimentally studied. The oscillator which combines NPE and SESAM is operating on the all-normal-dispersion regime and the LMA PCF is used as the gain medium. In the CW mode-locking regime, the oscillator directly generates the pulse at the repetition rate of 83.7 MHz while the pulse duration is 960 fs. The double-clad fiber amplifier system directly generates a high average power of 12.53 W with a pulse duration of 4.1 ps corresponding to the pulse energy of 150 nJ and peak power of 36.6 KW after about 3 m ytterbium doped double clad fiber amplification.

  14. A kinetic and mechanistic study into the formation of the Cu-Cr layered double hydroxide.

    Science.gov (United States)

    Williams, Gareth R; Clout, Alexander; Burley, Jonathan C

    2013-06-14

    The formation of the layered double hydroxide [Cu2Cr(OH)6]Cl·yH2O from the reaction between CuO and aqueous CrCl3·6H2O was explored using synchrotron X-ray diffraction and ex situ analyses. The use of hard X-rays permitted time-resolved in situ studies to be performed as the reaction proceeded under a range of conditions. Additional information was obtained from ex situ experiments in which aliquots of the reaction mixture were removed, quenched, and subsequently analysed by laboratory X-ray diffraction, IR, UV-visible, and atomic emission spectroscopies. On the basis of these data, it is proposed that the reaction involves three steps. First, the solid CuO starting material is hydrolysed to give Cu(OH)2 chains, releasing Cu(2+) ions into solution. The Cu hydroxide chains subsequently condense with aqueous Cr(3+) species, Cl(-) ions and water molecules to give a hydrated form of the LDH. This material then extrudes some water to form a phase with a reduced interlayer spacing.

  15. Thermodynamics for the Formation of Double-Stranded DNA-Single-Walled Carbon Nanotube Hybrids.

    Science.gov (United States)

    Shiraki, Tomohiro; Tsuzuki, Akiko; Toshimitsu, Fumiyuki; Nakashima, Naotoshi

    2016-03-24

    For the first time, the thermodynamics are described for the formation of double-stranded DNA (ds-DNA)-single-walled carbon nanotube (SWNT) hybrids. This treatment is applied to the exchange reaction of sodium cholate (SC) molecules on SWNTs and the ds-DNAs d(A)20 -d(T)20 and nuclear factor (NF)-κB decoy. UV/Vis/near-IR spectroscopy with temperature variations was used for analyzing the exchange reaction on the SWNTs with four different chiralities: (n,m)=(8,3), (6,5), (7,5), and (8,6). Single-stranded DNAs (ss-DNAs), including d(A)20 and d(T)20, are also used for comparison. The d(A)20-d(T)20 shows a drastic change in its thermodynamic parameters around the melting temperature (Tm ) of the DNA oligomer. No such Tm dependency was measured, owing to high Tm in the NF-κB decoy DNA and no Tm in the ss-DNA.

  16. Kibble-Zurek Scaling during Defect Formation in a Nematic Liquid Crystal.

    Science.gov (United States)

    Fowler, Nicholas; Dierking, Dr Ingo

    2017-04-05

    Symmetry-breaking phase transitions are often accompanied by the formation of topological defects, as in cosmological theories of the early universe, superfluids, liquid crystals or solid-state systems. This scenario is described by the Kibble-Zurek mechanism, which predicts corresponding scaling laws for the defect density ρ. One such scaling law suggests a relation ρ≈τQ(-1/2) with τQ the change of rate of a control parameter. In contrast to the scaling of the defect density during annihilation with ρ≈t(-1) , which is governed by the attraction of defects of the same strength but opposite sign, the defect formation process, which depends on the rate of change of a physical quantity initiating the transition, has only rarely been investigated. Herein, we use nematic liquid crystals as a different system to demonstrate the validity of the predicted scaling relation for defect formation. It is found that the scaling exponent is independent of temperature and material employed, thus universal, as predicted. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Large-Mode-Area Double-Cladding Photonic Crystal Fiber Laser in the Watt Range at 980 nm

    Institute of Scientific and Technical Information of China (English)

    LI Ping-Xue; ZHANG Xue-Xia; LIU Zhi; CHI Jun-Jie

    2011-01-01

    @@ We report on a quasi-three-level large-mode-area double-clad Yb-doped fiber laser that adopts a linear cavity consisting of a 0°fiber end and a cavity mirror.Two kinds of Yb-doped photonic crystal fiber(PCF) with different inner-clads (170 μm and 200μm) and absorption coefficients (4.5 dB/m and 3 dB/m) are used as the gain media.By optimizing the structure and elements of the cavity, maximum output powers of 1.24 W and 1.1 W were yielded with optical conversion efficiencies of 7.8% and 6.8% when the fiber lengths were 25 cm and 40 cm with 170μm and 200 μm inner-claddings, respectively.

  18. Synthesis and Crystal Structure of a New Double 2D Layer Complex Assembled by H4btec

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Assembly of H4btec with cobalt(Ⅱ) acetate afforded a new double 2D layer coor- dination polymer, [Co(btec)1/2(H2O)4·2H2O]n (H4btec = benzene-1,2,4,5-tetracarboxylic acid) 1. The polymeric structure has been characterized by single-crystal X-ray diffraction, FT-IR and thermal analysis. The crystal is of triclinic, space group P with a = 10.8762(2), b = 11.1411(1), c = 11.5084(3)(A), α = 82.8950(10), β = 63.0050(10), γ = 62.1500(10)°, V = 1091.72(4)(A)3, C5H13CoO10, Mr = 292.08, Z = 4, Dc = 1.777 g/cm3, μ = 1.612 mm-1, F(000) = 600, R = 0.0578, and wR = 0.2162 for 3576 observed reflections (I > 2σ(I)). Complex 1 consists of a new double 2D layer structure [Co(btec)1/2(H2O)4]n, both consisting of 4 + 4 grids with the sizes of 11.3667(2)(A) × 11.5084(3)(A)(Co(1)-Co(1A) × Co(2A)-Co(2B)) and 11.5084(3)(A)× 11.3667(2)(A) (Co(3)-Co(3C) × Co(4)- Co(4A)), respectively. The phenyl rings are at the corners while the Co(Ⅱ) atoms are in the sides of the grids, and lattice water molecules decorate between the layers. Hydrogen bonds between the layers and lattice water molecules result in the final 3D framework.

  19. Formation of classical crystals of dipolar particles in a helical geometry

    DEFF Research Database (Denmark)

    K. Pedersen, J.; V. Fedorov, D.; S. Jensen, A.

    2014-01-01

    We consider crystal formation of particles with dipole-dipole interactions that are confined to move in a one-dimensional helical geometry with their dipole moments oriented along the symmetry axis of the confining helix. The stable classical lowest energy configurations are found to be chain...... revolution. A larger total number of dipoles leads to a clusterization where the dipolar chains move closer to each other. This implies a change in the local density and the emergence of two length scales, one for the cluster size and one for the inter-cluster distance along the helix. Starting from three...

  20. Formation Mechanism of Guided Resonances and Bound States in the Continuum in Photonic Crystal Slabs

    CERN Document Server

    Gao, Xingwei; Zhen, Bo; Lin, Xiao; Joannopoulos, John D; Soljačić, Marin; Chen, Hongsheng

    2016-01-01

    We develop a formalism, based on the mode expansion method, to describe the guided resonances and bound states in the continuum (BICs) in photonic crystal slabs with one-dimensional periodicity. This approach provides analytic insights to the formation mechanisms of these states: the guided resonances arise from the transverse Fabry-P\\'erot condition, and the divergence of the resonance lifetimes at the BICs is explained by a destructive interference of radiation from different propagating components inside the slab. We show BICs at the center and on the edge of the Brillouin zone protected by symmetry, as well as BICs at generic wave vectors not protected by symmetry.

  1. Network formation in colloid-liquid crystal mixtures studied by confocal microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Cleaver, J; Poon, W C K [School of Physics and the Collaborative Optical Spectroscopy, Micromanipulation and Imaging Centre (COSMIC), JCMB, University of Edinburgh, Kings Buildings, Mayfield Road, Edinburgh EH9 3JZ (United Kingdom)

    2004-05-19

    We studied the formation of particle networks in colloid + liquid crystal mixtures cooled below the isotropic-nematic transition temperature by time-resolved laser scanning confocal microscopy. Our observations confirm a recent suggestion that alkane impurities play a crucial role in slowing down the speed of the isotropic-nematic interface. This enables the growing nematic droplets to 'push' particles into increasingly concentrated regions, ultimately resulting in a cellular network solid. We also found that faster cooling rates resulted in increasingly hierarchical cellular structures.

  2. A possible formation mechanism of double-walled and multi-walled carbon nanotube: a molecular dynamics study

    Science.gov (United States)

    Han, Dianrong; Luo, Chenglin; Dai, Yafei; Zhu, Xingfeng

    2016-09-01

    Molecular dynamics simulations based on an empirical potential were performed to study the interaction of graphene nanoribbons and the single-walled carbon nanotubes. The results indicated that a piece of graphene nanoribbon can form a tube structure inside or outside single-walled carbon nanotubes spontaneously under certain condition. Based on this kind of spontaneous phenomenon, we proposed a new possible formation mechanism of double walled carbon nanotube and multi-walled carbon nanotube, and suggested the possibility of controlling the structure of double-walled carbon nanotube and/or multi-walled carbon nanotube.

  3. Properties of the Band Gaps in 1D Ternary Lossy Photonic Crystal Containing Double-Negative Materials

    Directory of Open Access Journals (Sweden)

    Alireza Aghajamali

    2014-01-01

    Full Text Available Theoretically, the characteristics matrix method is employed to investigate and compare the properties of the band gaps of the one-dimensional ternary and binary lossy photonic crystals which are composed of double-negative and double-positive materials. This study shows that by varying the angle of incidence, the band gaps for TM and TE waves behave differently in both ternary and binary lossy structures. The results demonstrate that, by increasing the angle of incidence for the TE wave, the width and the depth of zero-n¯, zero-μ, and Bragg gap increase in both ternary and binary structures. On the other hand, the enhancement of the angle of incidence for the TM wave contributes to reduction of the width and the depth of the zero-n¯ and Bragg gaps, and they finally disappear for incidence angles greater than 50° and 60° for the binary structure and 40° and 45° for the ternary structures, respectively. In addition, the details of the edges of the band gaps variations as a function of incidence angle for both structures are studied.

  4. Search for double beta decay of zinc and tungsten with low background ZnWO{sub 4} crystal scintillators

    Energy Technology Data Exchange (ETDEWEB)

    Belli, P. [Dipartimento di Fisica, Universita di Roma ' Tor Vergata' and INFN, Sezione di Roma Tor Vergata, I-00133 Rome (Italy); Bernabei, R. [Dipartimento di Fisica, Universita di Roma ' Tor Vergata' and INFN, Sezione di Roma Tor Vergata, I-00133 Rome (Italy)], E-mail: rita.bernabei@roma2.infn.it; Cappella, F. [Dipartimento di Fisica, Universita di Roma ' La Sapienza' and INFN, Sezione di Roma, I-00185 Rome (Italy); Cerulli, R. [INFN, Laboratori Nazionali del Gran Sasso, 67010 Assergi (AQ) (Italy); Danevich, F.A. [Institute for Nuclear Research, MSP 03680 Kyiv (Ukraine); Grinyov, B.V. [Institute for Scintillation Materials, 61001 Kharkiv (Ukraine); Incicchitti, A. [Dipartimento di Fisica, Universita di Roma ' La Sapienza' and INFN, Sezione di Roma, I-00185 Rome (Italy); Kobychev, V.V.; Mokina, V.M.; Nagorny, S.S. [Institute for Nuclear Research, MSP 03680 Kyiv (Ukraine); Nagornaya, L.L. [Institute for Scintillation Materials, 61001 Kharkiv (Ukraine); Nisi, S. [INFN, Laboratori Nazionali del Gran Sasso, 67010 Assergi (AQ) (Italy); Nozzoli, F. [Dipartimento di Fisica, Universita di Roma ' Tor Vergata' and INFN, Sezione di Roma Tor Vergata, I-00133 Rome (Italy); Poda, D.V. [Institute for Nuclear Research, MSP 03680 Kyiv (Ukraine); Prosperi, D. [Dipartimento di Fisica, Universita di Roma ' La Sapienza' and INFN, Sezione di Roma, I-00185 Rome (Italy); Tretyak, V.I.; Yurchenko, S.S. [Institute for Nuclear Research, MSP 03680 Kyiv (Ukraine)

    2009-08-01

    Double beta processes in {sup 64}Zn, {sup 70}Zn, {sup 180}W, and {sup 186}W have been searched for with the help of large volume (0.1-0.7 kg) low background ZnWO{sub 4} crystal scintillators at the Gran Sasso National Laboratories of the INFN (Italy). The total measurement time exceeds ten thousand hours. New improved half-life limits on double electron capture and electron capture with positron emission in {sup 64}Zn have been set, in particular (all the limits are at 90% C.L.): T{sub 1/2}{sup 0{nu}}{sup 2{epsilon}}{>=}1.1x10{sup 20} yr, T{sub 1/2}{sup 2{nu}}{sup {epsilon}}{sup {beta}{sup +}}{>=}7.0x10{sup 20} yr, and T{sub 1/2}{sup 0{nu}}{sup {epsilon}}{sup {beta}{sup +}}{>=}4.3x10{sup 20} yr. In addition, new T{sub 1/2} bounds were set for different modes of 2{beta} processes in {sup 70}Zn, {sup 180}W, and {sup 186}W at the level of 10{sup 17}-10{sup 20} yr.

  5. Low coherence technique to interrogate optical sensors based on selectively filled double-core photonic crystal fiber for temperature measurement

    Science.gov (United States)

    Li, Kun; Jiang, Meng; Zhao, Zhongze; Wang, Zeming

    2017-04-01

    In this paper, an optical fiber sensing system based on low coherence interferometry (LCI) is proposed and demonstrated to interrogate sensors comprised of selectively filled double-core photonic crystal fiber (SFDC-PCF). The sensor used here is made by selectively filling about 1/3 area of air holes in the cladding of photonic crystal fiber with distilled water. So the dual-core in the sensor has different effective refractive indices, resulting in a phase delay between two lights transmitting in the fiber. The phase delay of the sensor can be compensated by a Mach-Zehnder interferometer with a scanning optical tunable delay line in one arm of the interferometer, namely temporal interrogation. By tracking the value of phase delay, the change of the measurand can be detected. Temperature measurement is carried out to testify the system performance. An average sensitivity of 0.9 μm/°C is achieved within the temperature range of 29-92 °C. This work provides a new thinking for fiber sensing technology based on LCI. The proposed all-fiber sensing system, with the merits of cost-effective, stability, and flexibility, can demodulate the SFDC-PCF sensor signals well. Further improvements such as better sensitivity, larger measurement range and multiplexing efficiency can be realized by tailoring the PCF sensor's structure.

  6. The cone phase of liquid crystals: Triangular lattice of double-tilt cylinders

    Indian Academy of Sciences (India)

    Yashodhan Hatwalne; N V Madhusudana

    2003-08-01

    We predict the existence of a new defect-lattice phase near the nematic–smectic-C (NC) transition. This tilt-analogue of the blue phase is a lattice of double-tilt cylinders which are disclination lines in the smectic layer normal as well as the c-field. We discuss the structure and stability of the cone phase. We suggest that many ‘nematics’ exhibiting short range layering and tilt order may in fact be in the molten cone phase, which is a line liquid.

  7. Microparticle Formation and Crystallization Rate of HMX with Supercritical CO2 Antisolvent Recrystallization

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Microparticle formation and crystallization rate of 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane (HMX) in acetone solution using supercritical carbon dioxide antisolvent (GAS) recrystallization were studied. Scanning electronic microscopy, X-ray diffraction and infrared radiation were used to examine particle size, crystallinity and chemical structure. The results show that β-HMX microparticle in different average size (2-9.5μm) and with narrow size distribution were obtained by controlling the expansibility, expansion speed, initial concentration and temperature during recrystallization of HMX. The formation of nuclei may be a main cause of consumption of solute when the solution is expanded rapidly enough and the equilibrium concentration is lower, in which almost monodisperse microparticle can be obtained.

  8. Microparticle Formation and Crystallization Rate of HMX with Supercritical CO2 Antisolvent Recrystallization

    Institute of Scientific and Technical Information of China (English)

    蔡建国; 周展云; 邓修

    2001-01-01

    Microparticle formation and crystallization rate of 1,3,5,7-tetranitro-l,3,5,7-tetraazacyclooctane (HMX) in acetone solution using supercritical carbon dioxide antisolvent (GAS) recrystallization were studied. Scanning electronic microscopy, X-ray diffraction and infrared radiation were used to examine particle size, crystallinity and chemical structure. The results show that β-HMX microparticle in different average size (2--9.5μm) and with narrow size distribution were obtained by controlling the expansibility, expansion speed, initial concentration and temperature during recrystallization of HMX. The formation of nuclei may be a main cause of consumption of solute when the solution is expanded rapidly enough and the equilibrium concentration is lower, in which almost monodisperse microparticle can be obtained.

  9. Formation of Polymer Networks for Fast In-Plane Switching of Liquid Crystals at Low Temperatures

    Science.gov (United States)

    Yu, Byeong-Hun; Song, Dong Han; Kim, Ki-Han; Wok Park, Byung; Choi, Sun-Wook; Park, Sung Il; Kang, Sung Gu; Yoon, Jeong Hwan; Kim, Byeong Koo; Yoon, Tae-Hoon

    2013-09-01

    We formed a polymer structure to enable fast in-plane switching of liquid crystals at low temperatures. The problem of the inevitable slow response at low temperatures was reduced by the formation of in-cell polymer networks in in-plane switching (IPS) cells. The electro-optic characteristics of polymer-networked IPS cells were measured at temperatures ranging from -10 to 20 °C. The turn-on and turn-off times of an IPS cell were reduced by 44.5 and 47.2% at -10 °C by the formation of polymer networks. We believe that the proposed technology can be applied to emerging display devices such as mobile phones and automotive displays that may be used at low temperatures.

  10. Low background detector with enriched 116CdWO4 crystal scintillators to search for double beta decay of 116Cd

    CERN Document Server

    Barabash, A S; Bernabei, R; Boiko, R S; Cappella, F; Caracciolo, V; Chernyak, D M; Cerulli, R; Danevich, F A; Di Vacri, M L; Dossovitskiy, A E; Galashov, E N; Incicchitti, A; Kobychev, V V; Konovalov, S I; Kovtun, G P; Kudovbenko, V M; Laubenstein, M; Mikhlin, A L; Nisi, S; Poda, D V; Podviyanuk, R B; Polischuk, O G; Shcherban, A P; Shlegel, V N; Solopikhin, D A; Stenin, Yu G; Tretyak, V I; Umatov, V I; Vasiliev, Ya V; Virich, V D

    2011-01-01

    A cadmium tungstate crystal boule enriched in $^{116}$Cd to 82% with mass of 1868 g was grown by the low-thermal-gradient Czochralski technique. The isotopic composition of cadmium and the trace contamination of the crystal were estimated by High Resolution Inductively Coupled Plasma Mass-Spectrometry. The crystal scintillators produced from the boule were subjected to characterization that included measurements of transmittance and energy resolution. A low background scintillation detector with two $^{116}$CdWO$_4$ crystal scintillators (586 g and 589 g) was developed. The detector was running over 1727 h deep underground at the Gran Sasso National Laboratories of the INFN (Italy), which allowed to estimate the radioactive contamination of the enriched crystal scintillators. The radiopurity of a third $^{116}$CdWO$_4$ sample (326 g) was tested with the help of ultra-low background high purity germanium $\\gamma$ detector. Monte Carlo simulations of double $\\beta$ processes in $^{116}$Cd were used to estimate ...

  11. Dislocation formation in seed crystals induced by feedstock indentation during growth of quasimono crystalline silicon ingots

    Science.gov (United States)

    Trempa, M.; Beier, M.; Reimann, C.; Roßhirth, K.; Friedrich, J.; Löbel, C.; Sylla, L.; Richter, T.

    2016-11-01

    In this work the dislocation formation in the seed crystal induced by feedstock indentation during the growth of quasimono (QM) silicon ingots for photovoltaic application was investigated. It could be shown by special laboratory indentation experiments that the formed dislocations propagate up to several millimeters deep into the volume of the seed crystal in dependence on the applied pressure of the feedstock particles on the surface of the seed crystal. Further, it was demonstrated that these dislocations if they were not back-melted during the seeding process grow further into the silicon ingot and drastically reduce its material quality. An estimation of the apparent pressure values in a G5 industrial crucible/feedstock setup reveals that the indentation phenomenon is a critical issue for the industrial production of QM silicon ingots. Therefore, some approaches to avoid/reduce the indentation events were tested with the result, that the most promising solution should be the usage of suitable feedstock particles as coverage of the seed.

  12. Stability of mass transfer from massive giants: double black hole binary formation and ultraluminous X-ray sources

    Science.gov (United States)

    Pavlovskii, K.; Ivanova, N.; Belczynski, K.; Van, K. X.

    2017-02-01

    Mass transfer in binaries with massive donors and compact companions, when the donors rapidly evolve after their main sequence, determines the formation rates of merging double stellar-mass black hole (BH) binaries formed outside clusters. This mass transfer was previously postulated to be unstable and was expected to lead to a common envelope event. The common envelope event then ends with either the merger of the two stars or formation of a binary that eventually may become a merging double BH. We revisit the stability of this mass transfer and find an unanticipated third outcome: for a large range of binary orbital separations, this mass transfer is stable. This newly found stability allows us to reconcile the empirical rate obtained by LIGO, 9-240 Gpc-3 yr-1, with the theoretical rate for double BH binary mergers predicted by population synthesis studies by excluding a channel that predicts a merger rate above 1000 Gpc-3 yr-1. Furthermore, the stability of the mass transfer leads to the formation of ultraluminous X-ray sources. The theoretically predicted formation rates of bright ultraluminous X-ray sources powered by a stellar-mass BH are high enough to explain the number of observed bright ultraluminous X-ray sources.

  13. An electron spin double resonance study of x-ray irradiated phenacyl chloride single crystals

    Science.gov (United States)

    Hwang, J. S.; Wang, H. C.; Andersson, B.; Kispert, L. D.; Geoffroy, M.

    1981-10-01

    Single crystals of phenacyl chloride irradiated at room temperature give rise to an EPR spectrum that has been shown by ENDOR and ELDOR studies to be due to the radical The EPR spectra are complicated by the appearance of a large number of forbidden lines due to the presence of a chlorine quadrupole interaction similar in magnitude to the proton hyperfine coupling. Spectral assignment is not possible by considering the EPR spectra alone. Although ENDOR spectra are difficult to obtain, it is possible to obtain an ENDOR spectrum along one of the crystal axis that identifies the spectra as due to radical I. Furthermore, rather intense and highly resolved ELDOR spectra are obtained at -60 °C as a function of angle enabling the chlorine and proton magnetic hyperfine tensor components of the -ĊHCl fragment to be determined as -15.4, -8.3, +45.6 MHz and -26.5, -52.5, -80.0 MHz, respectively. The Qzz components of the chlorine quadrupole tensor is -11.2 MHz.

  14. Core temperature in super-Gaussian pumped air-clad photonic crystal fiber lasers compared with double-clad fiber lasers

    Indian Academy of Sciences (India)

    P Elahi; H Nadgaran; F Kalantarifard

    2007-03-01

    In this paper we investigate the core temperature of air-clad photonic crystal fiber (PCF) lasers pumped by a super-Gaussian (SG) source of order four. The results are compared with conventional double-clad fiber (DCF) lasers pumped by the same super-Gaussian and by top-hat pump profiles.

  15. Boric Acid Reduces the Formation of DNA Double Strand Breaks and Accelerates Wound Healing Process.

    Science.gov (United States)

    Tepedelen, Burcu Erbaykent; Soya, Elif; Korkmaz, Mehmet

    2016-12-01

    Boron is absorbed by the digestive and respiratory system, and it was considered that it is converted to boric acid (BA), which was distributed to all tissues above 90 %. The biochemical essentiality of boron element is caused by boric acid because it affects the activity of several enzymes involved in the metabolism. DNA damage repair mechanisms and oxidative stress regulation is quite important in the transition stage from normal to cancerous cells; thus, this study was conducted to investigate the protective effect of boric acid on DNA damage and wound healing in human epithelial cell line. For this purpose, the amount of DNA damage occurred with irinotecan (CPT-11), etoposide (ETP), doxorubicin (Doxo), and H2O2 was determined by immunofluorescence through phosphorylation of H2AX((Ser139)) and pATM((Ser1981)) in the absence and presence of BA. Moreover, the effect of BA on wound healing has been investigated in epithelial cells treated with these agents. Our results demonstrated that H2AX((Ser139)) foci numbers were significantly decreased in the presence of BA while wound healing was accelerated by BA compared to that in the control and only drug-treated cells. Eventually, the results indicate that BA reduced the formation of DNA double strand breaks caused by agents as well as improving the wound healing process. Therefore, we suggest that boric acid has important therapeutical effectiveness and may be used in the treatment of inflammatory diseases where oxidative stress and wound healing process plays an important role.

  16. A study on ice crystal formation behavior at intracellular freezing of plant cells using a high-speed camera.

    Science.gov (United States)

    Ninagawa, Takako; Eguchi, Akemi; Kawamura, Yukio; Konishi, Tadashi; Narumi, Akira

    2016-08-01

    Intracellular ice crystal formation (IIF) causes several problems to cryopreservation, and it is the key to developing improved cryopreservation techniques that can ensure the long-term preservation of living tissues. Therefore, the ability to capture clear intracellular freezing images is important for understanding both the occurrence and the IIF behavior. The authors developed a new cryomicroscopic system that was equipped with a high-speed camera for this study and successfully used this to capture clearer images of the IIF process in the epidermal tissues of strawberry geranium (Saxifraga stolonifera Curtis) leaves. This system was then used to examine patterns in the location and formation of intracellular ice crystals and to evaluate the degree of cell deformation because of ice crystals inside the cell and the growing rate and grain size of intracellular ice crystals at various cooling rates. The results showed that an increase in cooling rate influenced the formation pattern of intracellular ice crystals but had less of an effect on their location. Moreover, it reduced the degree of supercooling at the onset of intracellular freezing and the degree of cell deformation; the characteristic grain size of intracellular ice crystals was also reduced, but the growing rate of intracellular ice crystals was increased. Thus, the high-speed camera images could expose these changes in IIF behaviors with an increase in the cooling rate, and these are believed to have been caused by an increase in the degree of supercooling.

  17. Understanding the origin of liquid crystal ordering of ultrashort double-stranded DNA

    Science.gov (United States)

    Saurabh, Suman; Lansac, Yves; Jang, Yun Hee; Glaser, Matthew A.; Clark, Noel A.; Maiti, Prabal K.

    2017-03-01

    Recent experiments have shown that short double-stranded DNA (dsDNA) fragments having six- to 20-base pairs exhibit various liquid crystalline phases. This violates the condition of minimum molecular shape anisotropy that analytical theories demand for liquid crystalline ordering. It has been hypothesized that the liquid crystalline ordering is the result of end-to-end stacking of dsDNA to form long supramolecular columns which satisfy the shape anisotropy criterion necessary for ordering. To probe the thermodynamic feasibility of this process, we perform molecular dynamics simulations on ultrashort (four base pair long) dsDNA fragments, quantify the strong end-to-end attraction between them, and demonstrate that the nematic ordering of the self-assembled stacked columns is retained for a large range of temperature and salt concentration.

  18. MATHEMATICAL MODELLING OF HYDROTHERMAL GROWTH OF CRYSTALS AS A DOUBLE DIFFUSIVE MAGNETOCONVECTION PROBLEM IN A COMPOSITE LAYER BOUNDED BY RIGID WALLS.

    Directory of Open Access Journals (Sweden)

    R. Sumithra

    2012-02-01

    Full Text Available The Hydrothermal growth of crystals is mathematically modeled as the onset of double diffusive magnetoconvection in a two-layer system comprising an incompressible two component, electrically conducting fluid saturated porous layer over which lies a layer of the same fluid in the presence a vertical magnetic field. Both the upper boundary of the fluid layer and the lower boundary of the porous layer are rigid and insulating to both heat and mass. At the interface the velocity, shear stress, normal stress, heat, heat flux,mass and mass flux are assumed to be continuous conducive for Darcy-Brinkman model. The resulting eigenvalue problem is solved by regular perturbation technique. The critical Rayleigh number, which is thecriterion for stability of the system is obtained. The effects of different physical parameters on the onset of double diffusive magnetoconvection are investigated in detail which enables to control convection during the growth of crystals in order to obtain pure crystals.

  19. Simultaneous Q-switching and Frequency-doubling by a Single KTP Crystal in a Diode-pumped Nd: YVO4 Laser

    Institute of Scientific and Technical Information of China (English)

    CHEN Fei; HUO Yujing; HE Shufang; FENG Lichun

    2000-01-01

    The interrelation between the phase matching condition for second harmonic generation (SHG) and the electro-optic Q-switching in KTP was numerically analyzed. A diode-pumped Q-switched Nd: YVO4/KTP green laser was reported, where the KTP crystal was simultaneously used as both an electrooptic Q-switcher and a frequency-doubling crystal in type Ⅱ phase matching.Compared with the conventional frequency-doubling and Q-switching configuration, low loss and high efficiency characteristics were realized by using a single KTP crystal. The Q-switched green laser pulse with a peak power of 762 W and a pulse width of 12 ns was obtained with 1 W pump power.

  20. Double layers liquid-crystal microlens arrays used in optical switches

    Science.gov (United States)

    Wang, Cheng; Fan, Di; Zhang, Bo; Tong, Qing; Luo, Jun; Lei, Yu; Zhang, Xinyu; Xie, Changsheng

    2015-12-01

    Based on our previous works in liquid-crystal microlens arrays (LCMAs), a new kind of optical switches using the 24×24 fiber arrays coupled with the LCMAs, which have a key dual-mode function of the switches about on and off state and work in visible and infrared range, is proposed and fabricated in this paper. Different with other common LCMAs, this new kind of dual-mode LCMAs includes two layers of control electrodes deposited directly over the surface of the top glass substrate in LC microcavity fabricated. The first layer is the patterned electrode, which is designed into basic circular holes with suitable diameter, and the second is the planar electrode. Both layered electrodes are effectively separated by a thin SiO2 film with a typical thickness of about several micrometers, and then the dual-mode microlenses are driven by applied electrical signals with different root mean square (rms) voltage.

  1. Including crystal structure attributes in machine learning models of formation energies via Voronoi tessellations

    Science.gov (United States)

    Ward, Logan; Liu, Ruoqian; Krishna, Amar; Hegde, Vinay I.; Agrawal, Ankit; Choudhary, Alok; Wolverton, Chris

    2017-07-01

    While high-throughput density functional theory (DFT) has become a prevalent tool for materials discovery, it is limited by the relatively large computational cost. In this paper, we explore using DFT data from high-throughput calculations to create faster, surrogate models with machine learning (ML) that can be used to guide new searches. Our method works by using decision tree models to map DFT-calculated formation enthalpies to a set of attributes consisting of two distinct types: (i) composition-dependent attributes of elemental properties (as have been used in previous ML models of DFT formation energies), combined with (ii) attributes derived from the Voronoi tessellation of the compound's crystal structure. The ML models created using this method have half the cross-validation error and similar training and evaluation speeds to models created with the Coulomb matrix and partial radial distribution function methods. For a dataset of 435 000 formation energies taken from the Open Quantum Materials Database (OQMD), our model achieves a mean absolute error of 80 meV/atom in cross validation, which is lower than the approximate error between DFT-computed and experimentally measured formation enthalpies and below 15% of the mean absolute deviation of the training set. We also demonstrate that our method can accurately estimate the formation energy of materials outside of the training set and be used to identify materials with especially large formation enthalpies. We propose that our models can be used to accelerate the discovery of new materials by identifying the most promising materials to study with DFT at little additional computational cost.

  2. First results of the experiment to search for double beta decay of 106Cd with 106CdWO4 crystal scintillator in coincidence with four crystals HPGe detector

    CERN Document Server

    Tretyak, V I; Bernabei, R; Brudanin, V B; Cappella, F; Caracciolo, V; Cerulli, R; Chernyak, D M; Danevich, F A; d'Angelo, S; Incicchitti, A; Laubenstein, M; Mokina, V M; Poda, D V; Polischuk, O G; Podviyanuk, R B; Tupitsyna, I A

    2013-01-01

    An experiment to search for double beta processes in 106Cd by using cadmium tungstate crystal scintillator enriched in 106Cd (106CdWO4) in coincidence with the four crystals HPGe detector GeMulti is in progress at the STELLA facility of the Gran Sasso underground laboratory of INFN (Italy). The 106CdWO4 scintillator is viewed by a low-background photomultiplier tube through a lead tungstate crystal light-guide produced from deeply purified archaeological lead to suppress gamma quanta from the photomultiplier tube. Here we report the first results of the experiment after 3233 hours of the data taking. A few new improved limits on double beta processes in 106Cd are obtained, in particular T1/2(2nuECb+) > 8.4e20 yr at 90% C.L.

  3. Mean-field interactions between nucleic-acid-base dipoles can drive the formation of the double helix

    Science.gov (United States)

    He, Yi; Maciejczyk, Maciej; Ołdziej, Stanisław; Scheraga, Harold A.; Liwo, Adam

    2013-01-01

    A proposed coarse-grained model of nucleic acids demonstrates that average interactions between base dipoles, together with chain connectivity and excluded-volume interactions, are sufficient to form double-helical structures of DNA and RNA molecules. Additionally, local interactions determine helix handedness and direction of strand packing. This result, and earlier research on reduced protein models, suggest that mean-field multipole-multipole interactions are the principal factors responsible for the formation of regular structure of biomolecules. PMID:23496746

  4. Ageing behaviour of unary hydroxides in trivalent metal salt solutions: Formation of layered double hydroxide (LDH)-like phases

    Indian Academy of Sciences (India)

    Michael Rajamathi; P Vishnu Kamath

    2000-10-01

    The hydroxides of Mg, Ni, Cu and Zn transform into layered double hydroxide (LDH)-like phases on ageing in solutions of Al or Cr salts. This reaction is similar to acid leaching and proceeds by a dissolution–reprecipitation mechanism offering a simple method of LDH synthesis, with implications for the accepted theories of formation of LDH minerals in the earth’s crust.

  5. Spontaneous formation of two-dimensional and three-dimensional cholesterol crystals in single hydrated lipid bilayers.

    Science.gov (United States)

    Ziblat, Roy; Fargion, Iael; Leiserowitz, Leslie; Addadi, Lia

    2012-07-18

    Grazing incidence x-ray diffraction measurements were performed on single hydrated bilayers and monolayers of Ceramide/Cholesterol/1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocyholine at varying concentrations. There are substantial differences in the phase and structure behavior of the crystalline domains formed within the bilayers relative to the corresponding monolayers, due to interactions between the opposing lipid leaflets. Depending on the lipid composition, these interactions lead to phase separation and formation of cholesterol crystals. The cholesterol and ceramide/cholesterol mixed phases were further characterized at 37°C by immunolabeling with specific antibodies recognizing ordered molecular arrays of cholesterol. Previous studies have shown that cholesterol may nucleate in artificial membranes to form thick two-dimensional bilayer crystals. The study herein demonstrates further growth of cholesterol into three-dimensional crystals. We believe that these results may provide further insight into the formation of cholesterol crystals in early stages of atherosclerosis inflammation.

  6. 低温液相合成Engel复盐晶体研究%Low Temperature Liquid Synthesis of Engel Double Salt Crystal

    Institute of Scientific and Technical Information of China (English)

    张文辉; 张茜; 谷守玉; 万亚珍

    2013-01-01

    It was of great importance in plotting the phase diagram of the Engel double salt crystal for the aim to control the production process.The best conditions of synthesis Engel double salt by low temperature liquid synthesis method were studied.The results shown the basic magnesium carbonate was putting the saturated solution of potassium bicarbonate according to the ratio as following; potassium bicarbonate; basic magnesium carbonate ( wt.) = 39.0: 0.2 and then reacted under the hydrothermal condition as 40 ℃ for 10 min, the mixture solution was crystallized rapidly cooling down to 25℃ and water-bathed for 7 h for the crystal growth process , the Engel double salt crystal were synthesized.The crystal was tested by X-ray powder diffraction ( XRD), which proved that it was in agreeing with the standard spectra.The result showed that the crystal's morphology was of good crystallization.%Engel复盐晶体合成对于准确绘制Engel复盐相图及指导实际生产有重要意义.论文研究了低温条件下液相合成Engel复盐晶体的适宜条件,即碳酸氢钾饱和溶液中加入碱式碳酸镁,其重量比39.0 g/0.2 g,在40℃下水热反应10 min;然后反应溶液从40℃冷却降温到25℃进行析晶,析晶过程持续约7.0h,制备出Engel复盐晶体;对产物进行了XRD及晶体形貌分析,其衍射峰与标准图谱一致,晶体形貌规则,结晶良好.

  7. Two-dimensional photonic-crystal-based double switch-divider.

    Science.gov (United States)

    Dmitriev, Victor; Martins, Leno

    2016-05-01

    We propose and investigate a new multifunctional component, consisting of a T-junction of three waveguides in 2D photonic crystal with a square lattice. One waveguide is the input port, while the other two serve as output ports. This component can fulfil three functions: First, it can switch OFF the two output ports; second, our component can be used as a 3 dB divider of the input power; and third, it can switch ON any one of the two output ports. Changing the regime is achieved by a DC magnetic field that magnetizes a cylindrical ferrite resonator placed in the T-junction. We present an analysis of the scattering matrices of the component and calculated frequency characteristics in the low terahertz region. In the frequency band of about 1 GHz with a central frequency of f=98.46  GHz, the device has the following parameters: isolation of the output ports from the input port in the first regime is better than -30  dB, division of the input signal is about (-3.8±1.0)  dB in the second regime, and isolation in the regime switch ON, where any one of the two output ports is higher than -15  dB and the insertion loss is lower than -2.0  dB.

  8. Recombinant formate dehydrogenase from Arabidopsis thaliana: Preparation, crystal growth in microgravity, and preliminary X-ray diffraction study

    Energy Technology Data Exchange (ETDEWEB)

    Shabalin, I. G., E-mail: inna@ns.crys.ras.ru [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation); Serov, A. E.; Skirgello, O. E. [Moscow State University, Faculty of Chemistry (Russian Federation); Timofeev, V. I.; Samygina, V. R. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation); Popov, V. O. [Russian Academy of Sciences, Bach Institute of Biochemistry (Russian Federation); Tishkov, V. I. [Moscow State University, Faculty of Chemistry (Russian Federation); Kuranova, I. P. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation)

    2010-09-15

    Crystals of high-purity recombinant NAD{sup +}-dependent formate dehydrogenase from the higher plant Arabidopsis thaliana (AraFDH) were grown in microgravity in the Modul'-1 protein crystallization apparatus on the International Space Station. The space-grown crystals have larger sizes than those grown on Earth. X-ray diffraction data suitable for determining the three-dimensional structure were collected from the space-grown crystals to a resolution of 1.22 A using an X-ray synchrotron source. The crystals belong to sp. gr. P4{sub 3}2{sub 1}2; the unit-cell parameters are a = b = 107.865 A, c = 71.180 A, {alpha} = {beta} = {gamma} = 90 deg.

  9. Development of a Compact Snow Crystal Formation Apparatus Based on a Diffusion Method Using a Peltier Device

    Science.gov (United States)

    Kojima, Shinsuke; Endo, Hiroshi; Seki, Mitsuo

    We developed a compact snow crystal formation apparatus based on a diffusion method using a Peltier device. This apparatus does not need an assemblage and is small enough to be operated on a desk. Anyone can easily observe snow crystal formation in a normal temperature room. We adopted a diffusion method because the shape enable that several people can simultaneously observe the snow crystal formation from above. To estimate a performance of the apparatus, we investigated temperature profiles in the apparatus by measurement and simulations with (Case 1) and without (Case 2) natural convection. As results of the simulations, Case 1 and Case 2 reached a steady state. In each case, temperature stratification condition was formed in lower part of the apparatus. From the comparison of the results of measurement and simulations, finally, it is concluded that there is a natural convection, but the air current is not so strong as disturbing the temperature stratification condition in the apparatus.

  10. Impacts of crystal metal on secondary aliphatic amine aerosol formation during dust storm episodes in Beijing

    Science.gov (United States)

    Liu, Qingyang; Bei, Yiling

    2016-03-01

    Trimethylamine (TMA) enters the atmosphere from a variety of sources and is a ubiquitous atmospheric organic base. The atmospheric reaction mechanism of TMA with key atmospheric oxidants is important to predict its distribution and environmental behavior in the particle phase. While previous studies have extensively focused on the production of particle amine salts (i.e. trimethylamine-N-oxide (TMAO)) using chamber experiments, the atmospheric behavior of TMAO in the environment is still poorly understood. Ambient fine particulate matter (PM2.5) was collected at two sampling sites in Beijing from March 10 to May 10, 2012. We analyzed the samples for water-soluble ions, crystal metals, TMA, and TMAO. Water-soluble ions (e.g. SO42-, NO3-, NH4+), TMA, and TMAO were measured using ion chromatography, while crystal metal (e.g. Al, Fe, Mn) in PM2.5 was quantified by inductively coupled plasma mass spectrometry (ICP-MS). Two dust storms (DS) occurred during the sampling period on March 28 and April 28. Mineral dust impacted PM2.5 mass and composition greatly during dust storm days, as it contributed approximately 1.2-4.0 times greater on dust storm days versus non-dust storm days. We found TMAO concentrations were highly associated with aluminum in PM2.5. Further, we applied the density functional theory (DFT) method to confirm that aluminum plays a catalytic effect in the reaction of TMA with ozone (O3). Our work improves understanding of the effect of crystal metals on secondary aliphatic amine aerosol formation in the atmosphere.

  11. Development of photonic crystal based large format IR scene projection technology

    Science.gov (United States)

    Wilson, J. A.; Burckel, B.; Caulfield, J.; Cogan, S.; Massie, M.; Rapp, R.; Rose, R.; Snyder, D.

    2012-06-01

    This paper describes recent results from the Extremely High Temperature Photonic Crystal System Technology (XTEMPS) technology program. The XTEMPS program has developed a Photonic Crystal (PhC) based high efficiency IR emitter array for use in the emerging generation of wide field of view high performance scene projectors. Cyan's approach provides high dynamic range, multispectral emission from SWIR to LWIR and is uniquely capable of accurately simulating very realistic system spectral signatures. The PhC array is fabricated from refractory materials to provide high radiance and long service lifetime. Cyan is teamed with Sandia National Laboratories for design and fabrication of the emitter and with Nova sensors to utilize their advanced Read In Integrated Circuit (RIIC). PhC based emitters show improved inband output power efficiency when compared to broad band "graybody" emitters due to the absence of out-of-band emission. Less electrical power is required to achieve high operating temperature, and non-Lambertian emission pattern puts a large fraction of the emitted energy into a straight ahead beam. Both effects significantly boost effective radiance output. Cyan has demonstrated pixel designs compatible with Nova's medium format RIIC, which ensures high apparent output temperatures with modest drive currents and low operating voltages of less than five volts. Unit cell pixel structures for high radiative efficiency have been demonstrated and arrays using PhC optimized for up to four spectral bands have been successfully patterned and fabricated into high yield wafers.

  12. Polymer Wall Formation Using Liquid-Crystal/Polymer Phase Separation Induced on Patterned Polyimide Films

    Science.gov (United States)

    Murashige, Takeshi; Fujikake, Hideo; Sato, Hiroto; Kikuchi, Hiroshi; Kurita, Taiichiro; Sato, Fumio

    2004-12-01

    We could form lattice-shaped polymer walls in a liquid crystal (LC) layer through the thermal phase separation of an LC/polystyrene solution between substrates with polyimide films etched by short-wavelength ultraviolet irradiation using a photomask. The LC wetting difference between the polyimide and substrate surfaces caused the coalescence of growing LC droplets on patterned polyimide films with the progress of phase separation. Consequently, polymer walls were formed on substrate surface areas without polyimide films. The shape of the polymer wall formed became sharp with the use of rubbed polyimide films because the nucleation of growing LC droplets concentrated on the patterned polyimide films. It is thought that the increase in the alignment order of LC molecules in the solution near the rubbed polyimide films promotes the formation of LC molecular aggregation, which becomes the growth nuclei of LC droplets.

  13. Formation mechanism of guided resonances and bound states in the continuum in photonic crystal slabs.

    Science.gov (United States)

    Gao, Xingwei; Hsu, Chia Wei; Zhen, Bo; Lin, Xiao; Joannopoulos, John D; Soljačić, Marin; Chen, Hongsheng

    2016-08-25

    We develop a formalism, based on the mode expansion method, to describe the guided resonances and bound states in the continuum (BICs) in photonic crystal slabs with one-dimensional periodicity. This approach provides analytic insights to the formation mechanisms of these states: the guided resonances arise from the transverse Fabry-Pérot condition, and the divergence of the resonance lifetimes at the BICs is explained by a destructive interference of radiation from different propagating components inside the slab. We show BICs at the center and on the edge of the Brillouin zone protected by symmetry, BICs at generic wave vectors not protected by symmetry, and the annihilation of BICs at low-symmetry wave vectors.

  14. Specific features of the formation of dislocation structure in gallium arsenide single crystals obtained by the Czochralski method

    Science.gov (United States)

    Parfenteva, I. B.; Pugachev, B. V.; Pavlov, V. F.; Kozlova, Yu. P.; Knyazev, C. N.; Yugova, T. G.

    2017-03-01

    The influence of the deviation of seed orientation from the [100] direction on the formation of a dislocation structure of gallium arsenide single crystals grown by the Czochralski method has been revealed. The intensive multiplication of dislocations and formation of a block structure occur at deviation by an angle of more than 3° in the region that is radially shifted to one of crystal sides. The linear density of dislocations in the walls changes from 1 × 104 cm-1 in low-angle boundaries to 6 × 104 cm-1 in subboundaries.

  15. The mechanisms and temperature dependence of superlattice stacking fault formation in the single-crystal superalloy PWA 1480

    Science.gov (United States)

    Milligan, Walter W.; Antolovich, Stephen D.

    1991-01-01

    The mechanism of the formation of superlattice staking faults in the single-crystal nickel-base superalloy PWA 1480 was investigated by observing deformation microstructures in the superalloy single crystals in the temperature range 20-1100 C. Results showed that, in addition to superlattice stacking faults observed after slow strain rate deformation at temperatures from 700 to 950 C, a high-density of superlattice staking faults formed after deformation at 200 C and below. The mechanisms of fault formation, which are different in the high- and the low-temperature regimes, are discussed.

  16. Thermal stress induced void formation during 450 mm defect free silicon crystal growth and implications for wafer inspection

    Science.gov (United States)

    Kamiyama, E.; Vanhellemont, J.; Sueoka, K.; Araki, K.; Izunome, K.

    2013-02-01

    When pulling large diameter Si crystals from a melt close to the Voronkov criterion, small changes in pulling speed and thermal gradient can lead to the formation of voids leading to detrimental pits on the polished wafer surface. The creation of voids is mainly due to the lowering of the vacancy formation energy due to increased thermal compressive stress. The small size and low density of the formed voids when pulling crystals close to the Voronkov criterion conditions are a challenge for wafer surface inspection tools and possible solutions are discussed.

  17. A novel dendritic surfactant for enhanced microcystin-LR detection by double amplification in a quartz crystal microbalance biosensor.

    Science.gov (United States)

    Xia, Yuetong; Zhang, Jianping; Jiang, Long

    2011-08-01

    Enhanced sensitivity for the hepatotoxin microcystin-LR (MC-LR) was achieved in a quartz crystal microbalance (QCM) system via double amplification. For primary amplification, an innovative interface on the QCM was obtained as a matrix by the vesicle layer formed by our synthetic dendritic surfactant, bis (amidoethyl-carbamoylethyl) octadecylamine (C18N3). The vesicle matrix was then functionalised by an optimised concentration of monoclonal antibodies against MC-LR (anti-MC-LR) to detect the analyte. The results showed that a detection limit of 100 ng/mL was achieved by primary amplification. To achieve higher sensitivity, secondary amplification was implemented with anti-MC-LR gold nanoparticle (AuNPs) conjugates as probes, which lowered the detection limit for MC-LR to 1 ng/mL (the maximum concentration recommended by the World Health Organization [WHO] in drinking water for humans). The QCM immunosensor reported here has advantages such as high sensitivity, portability, simplicity, and cost-effectiveness for MC-LR detection. It would be uniquely superior compared with current MC-LR detection techniques for on-the-spot water detection. Furthermore, the methodology described here is also potentially significant in many fields for the routine monitoring of environmental and food safety.

  18. Crystal Structure of E. coli RecE Protein Reveals a Toroidal Tetramer for Processing Double-Stranded DNA Breaks

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Jinjin; Xing, Xu; Herr, Andrew B.; Bell, Charles E.; (OSU); (UCIN)

    2009-07-21

    Escherichia coli RecE protein is part of the classical RecET recombination system that has recently been used in powerful new methods for genetic engineering. RecE binds to free double-stranded DNA (dsDNA) ends and processively digests the 5{prime}-ended strand to form 5{prime}-mononucleotides and a 3{prime}-overhang that is a substrate for single strand annealing promoted by RecT. Here, we report the crystal structure of the C-terminal nuclease domain of RecE at 2.8 {angstrom} resolution. RecE forms a toroidal tetramer with a central tapered channel that is wide enough to bind dsDNA at one end, but is partially plugged at the other end by the C-terminal segment of the protein. Four narrow tunnels, one within each subunit of the tetramer, lead from the central channel to the four active sites, which lie about 15 {angstrom} from the channel. The structure, combined with mutational studies, suggests a mechanism in which dsDNA enters through the open end of the central channel, the 5{prime}-ended strand passes through a tunnel to access one of the four active sites, and the 3{prime}-ended strand passes through the plugged end of the channel at the back of the tetramer.

  19. Study on fire-retardant nanocrystalline Mg-Al layered double hydroxides synthesized by microwave-crystallization method

    Institute of Scientific and Technical Information of China (English)

    ZHANG Zejiang; XU Chenghua; QIU Fali; MEI Xiujuan; LAN Bin; ZHANG Shuosheng

    2004-01-01

    Nanocrystalline Mg-Al layered double hydroxides with the particle size being 10-40 nm were firstly prepared by the technology of the microwave-crystallization and the variable-speed addition of the alkali. The obtained samples were characterized by TEM and XRD. The roles of the microwave and addition rate of the alkali were also discussed in the present work. The thermal decomposition activation energy of the nano-LDHs was calculated according to their TG, DTG and DSC curves by the Ozawa method. The results showed that the thermal decomposition of the nano-LDHs had four steps. Thereby the decomposition model of the nano-LDHs was supposed according to the analysis of their thermal decomposition. After PS, ABS, HDPE and PVC were filled with the nano-LDHs, their LOI values could be increased up to 28, 27, 26 and 33, respectively. When the fire-retardant coating contained 1.9% of the nano-LDHs that was 0.27 times the dosage of the conventional TiO2, its fire endurance time reached 32.75min that was 7.05 min longer than that of the best coating containing TiO2 according to the model big-panel combustion test method.

  20. Refractive index sensing characteristics of D-shape double core photonic crystal fiber based on surface plasmon resonance

    Science.gov (United States)

    Liu, Feng; Li, Shi-tao; Guo, Xuan

    2016-10-01

    A refractive index (RI) sensor and its sensing characteristics based on surface plasmon resonance (SPR) of D-shape double core photonic crystal fiber (DC-PCF) are researched theoretically in this letter. The basic sensor principle is the SPR light intensity modulation of polished D-shape DC-PCF. The influence of the polished angle and depth on the DC-PCF SPR characteristics is discussed extensively by using the finite element method (FEM). The effects of the coated metal type and its layer thickness on the resonant intensity are also analyzed. The relationship between the analyte RI and resonant wavelength is numerically simulated. The theoretical results show that the sensor's RI sensitivity exhibits about 2000 nm/RIU with the structure parameters of 60° polished angle, 58.5μm polished depth and 70nm thickness of the silver layer. Furthermore, if the single wavelength laser is chosen, the detection of the two core light intensity difference will improve the ability of resistance to environmental interference. The simple sensor structure and high sensitivity can make this technology for online refractive index measurement in widespread areas.

  1. Bandgap properties in locally resonant phononic crystal double panel structures with periodically attached spring-mass resonators

    Science.gov (United States)

    Qian, Denghui; Shi, Zhiyu

    2016-10-01

    Bandgap properties of the locally resonant phononic crystal double panel structure made of a two-dimensional periodic array of a spring-mass resonator surrounded by n springs (n equals to zero at the beginning of the study) connected between the upper and lower plates are investigated in this paper. The finite element method is applied to calculate the band structure, of which the accuracy is confirmed in comparison with the one calculated by the extended plane wave expansion (PWE) method and the transmission spectrum. Numerical results and further analysis demonstrate that two bands corresponding to the antisymmetric vibration mode open a wide band gap but is cut narrower by a band corresponding to the symmetric mode. One of the regulation rules shows that the lowest frequency on the symmetric mode band is proportional to the spring stiffness. Then, a new design idea of adding springs around the resonator in a unit cell (n is not equal to zero now) is proposed in the need of widening the bandwidth and lowering the starting frequency. Results show that the bandwidth of the band gap increases from 50 Hz to nearly 200 Hz. By introducing the quality factor, the regulation rules with the comprehensive consideration of the whole structure quality limitation, the wide band gap and the low starting frequency are also discussed.

  2. In situ NMR and electrochemical quartz crystal microbalance techniques reveal the structure of the electrical double layer in supercapacitors.

    Science.gov (United States)

    Griffin, John M; Forse, Alexander C; Tsai, Wan-Yu; Taberna, Pierre-Louis; Simon, Patrice; Grey, Clare P

    2015-08-01

    Supercapacitors store charge through the electrosorption of ions on microporous electrodes. Despite major efforts to understand this phenomenon, a molecular-level picture of the electrical double layer in working devices is still lacking as few techniques can selectively observe the ionic species at the electrode/electrolyte interface. Here, we use in situ NMR to directly quantify the populations of anionic and cationic species within a working microporous carbon supercapacitor electrode. Our results show that charge storage mechanisms are different for positively and negatively polarized electrodes for the electrolyte tetraethylphosphonium tetrafluoroborate in acetonitrile; for positive polarization charging proceeds by exchange of the cations for anions, whereas for negative polarization, cation adsorption dominates. In situ electrochemical quartz crystal microbalance measurements support the NMR results and indicate that adsorbed ions are only partially solvated. These results provide new molecular-level insight, with the methodology offering exciting possibilities for the study of pore/ion size, desolvation and other effects on charge storage in supercapacitors.

  3. Elucidating the Effect of Biomolecule Structure on Calcium Carbonate Crystal Formation

    Science.gov (United States)

    Kulbok, K. E.; Duckworth, O.

    2011-12-01

    Anthropogenic emissions of carbon dioxide have lead to a steady increase in atmospheric concentration. This greenhouse gas has been identified as a key driver of climate change and also has lead to increased acidification of marine and terrestrial waters. Calcium carbonate precipitation at the Earth's surface is an integral linkage in the global carbon cycle, especially in regards to regulating atmospheric carbon dioxide. As concern for the effect of increasing atmospheric CO2 levels grows, the need to understand calcium carbonate systems escalates concurrently. Calcium carbonate phases are the most abundant group of biominerals; therefore, elucidating the mechanism of biomineralization is critical to understanding CaCO3 precipitation and may aid in the development of novel carbon sequestration strategies. The ubiquity of microorganisms leads to an extensive number of biomolecules present in the Earth's systems, and thus an extensive range of possible effects on CaCO3 formation. Carboxylic acids are very common biomolecules and have a relatively simple structure, thus making them an ideal family of model compounds. This study examines the kinetics, thermodynamics, phase, and morphology of calcium carbonate crystals precipitated in the presence of carboxylate-containing biomolecules, including citric acid, succinic acid, and aspartic acid. The experiments utilize a unique (NH4)2CO3 gas-diffusion reactor, which allows in-situ measurements of chemical conditions during the precipitation and growth of crystals. Continuous monitoring of the in-situ conditions of pCO2, pH, [Ca2+], and optical absorbance provides data on the supersaturation at which nucleation occurs and the kinetics of mineral growth. The use of scanning electron microscopy and X-ray diffraction provides information on the morphology and mineralogy of precipitates. The combination of these data sets will provide an in-depth view of the ideal concentration of calcium ions required for solution saturation

  4. Carotenoid crystal formation in Arabidopsis and carrot roots caused by increased phytoene synthase protein levels.

    Directory of Open Access Journals (Sweden)

    Dirk Maass

    Full Text Available BACKGROUND: As the first pathway-specific enzyme in carotenoid biosynthesis, phytoene synthase (PSY is a prime regulatory target. This includes a number of biotechnological approaches that have successfully increased the carotenoid content in agronomically relevant non-green plant tissues through tissue-specific PSY overexpression. We investigated the differential effects of constitutive AtPSY overexpression in green and non-green cells of transgenic Arabidopsis lines. This revealed striking similarities to the situation found in orange carrot roots with respect to carotenoid amounts and sequestration mechanism. METHODOLOGY/PRINCIPAL FINDINGS: In Arabidopsis seedlings, carotenoid content remained unaffected by increased AtPSY levels although the protein was almost quantitatively imported into plastids, as shown by western blot analyses. In contrast, non-photosynthetic calli and roots overexpressing AtPSY accumulated carotenoids 10 and 100-fold above the corresponding wild-type tissues and contained 1800 and 500 microg carotenoids per g dry weight, respectively. This increase coincided with a change of the pattern of accumulated carotenoids, as xanthophylls decreased relative to beta-carotene and carotene intermediates accumulated. As shown by polarization microscopy, carotenoids were found deposited in crystals, similar to crystalline-type chromoplasts of non-green tissues present in several other taxa. In fact, orange-colored carrots showed a similar situation with increased PSY protein as well as carotenoid levels and accumulation patterns whereas wild white-rooted carrots were similar to Arabidopsis wild type roots in this respect. Initiation of carotenoid crystal formation by increased PSY protein amounts was further confirmed by overexpressing crtB, a bacterial PSY gene, in white carrots, resulting in increased carotenoid amounts deposited in crystals. CONCLUSIONS: The sequestration of carotenoids into crystals can be driven by the

  5. The research of propagation characteristic and formation of double half-Gaussian hollow beams

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    A new kind of hollow beams, double half-Gaussian hollow beams,was put forward. With the help of the Collins formula, the analytical equation of propagation and transformation of the hollow laser beams in free space was deduced. The simulation shows that the intensity exhibits the three-dimensional trap distribution in the near-field, while the double half-Gaussian hollow beams turn into solid laser beams when propagating a certain distance, which shows the characteristics of self-focus. The double half-Gaussian hollow beams were obtained by means of the dual-reflecting splitting optical system. The intensity of the vertical loop in different distances was tested, which shows that the analytical equation of propagation and transformation is in agreement with the result.

  6. The research of propagation characteristic and formation of double half-Gaussian hollow beams

    Institute of Scientific and Technical Information of China (English)

    DONG Yuan; ZHANG XiHe; NING GuoBin; JIN GuangYong; LIANG Wei; L(U) YanFei; ZHANG Kai

    2009-01-01

    A new kind of hollow beams, double half-Gaussian hollow beams, was put forward. With the help of the Collins formula, the analytical equation of propagation and transformation of the hollow laser beams in free space was deduced. The simulation shows that the intensity exhibits the three-dimensional trap distribution in the near-field, while the double half-Gaussian hollow beams turn into solid laser beams when propagating a certain distance, which shows the characteristics of self-focus. The double half-Gaussian hollow beams were obtained by means of the dual-reflecting splitting optical system. The intensity of the vertical loop in different distances was tested, which shows that the analytical equation of propagation and transformation is in agreement with the result.

  7. Formation and rejoining of deoxyribonucleic acid double-strand breaks induced in isolated cell nuclei by antineoplastic intercalating agents.

    Science.gov (United States)

    Pommier, Y; Schwartz, R E; Kohn, K W; Zwelling, L A

    1984-07-03

    The biochemical characteristics of the formation and disappearance of intercalator-induced DNA double-strand breaks (DSB) were studied in nuclei from mouse leukemia L1210 cells by using filter elution methodology [Bradley, M. O., & Kohn, K.W. (1979) Nucleic Acids Res. 7, 793-804]. The three intercalators used were 4'-(9-acridinylamino)-methanesulfon-m-anisidide (m-AMSA), 5-iminodaunorubicin (5-ID), and ellipticine. These compounds differ in that they produced predominantly DNA single-strand breaks (SSB) (m-AMSA) or predominantly DNA double-strand breaks (ellipticine) or a mixture of both SSB and DSB (5-ID) in whole cells. In isolated nuclei, each intercalator produced DSB at a frequency comparable to that which is produced in whole cells. Moreover, these DNA breaks reversed within 30 min after drug removal. It thus appeared that neither ATP nor other nucleotides were necessary for intercalator-dependent DNA nicking-closing reactions. The formation of the intercalator-induced DSB was reduced at ice temperature. Break formation was also reduced in the absence of magnesium, at a pH above 6.4 and at NaCl concentrations above 200 mM. In the presence of ATP and ATP analogues, the intercalator-induced cleavage was enhanced. These results suggest that the intercalator-induced DSB are enzymatically mediated and that the enzymes involved in these reactions can catalyze DNA double-strand cleavage and rejoining in the absence of ATP, although the occupancy of an ATP binding site might convert the enzyme to a form more reactive to intercalators. Three inhibitors of DNA topoisomerase II--novobiocin, nalidixic acid, and norfloxacin--reduced the formation of DNA strand breaks.(ABSTRACT TRUNCATED AT 250 WORDS)

  8. Double Neutron Stars: Evidence For Two Different Neutron-Star Formation Mechanisms

    OpenAIRE

    Heuvel, E. P. J. van den

    2007-01-01

    Six of the eight double neutron stars known in the Galactic disk have low orbital eccentricities (< 0.27) indicating that their second-born neutron stars received only very small velocity kicks at birth. This is similar to the case of the B-emission X-ray binaries, where a sizable fraction of the neutron stars received hardly any velocity kick at birth (Pfahl et al. 2002). The masses of the second-born neutron stars in five of the six low-eccentricity double neutron stars are remarkably low (...

  9. Development of radiopure cadmium tungstate crystal scintillators from enriched {sup 106}Cd and {sup 116}Cd to search for double beta decay

    Energy Technology Data Exchange (ETDEWEB)

    Danevich, F. A.; Boiko, R. S.; Chernyak, D. M.; Kobychev, V. V.; Kropivyansky, B. N.; Mokina, V. M.; Nikolaiko, A. S.; Poda, D. V.; Podviyanuk, R. B.; Tretyak, V. I. [Institute for Nuclear Research, Kyiv (Ukraine); Barabash, A. S.; Konovalov, S. I.; Umatov, V. I. [Institute of Theoretical and Experimental Physics, Moscow (Russian Federation); Belli, P.; Bernabei, R.; D' Angelo, S. [INFN, Section of Rome Tor Vergata, Rome, Italy and Department of Physics, University of Rome Tor Vergata, Rome (Italy); Brudanin, V. B. [Joint Institute for Nuclear Research, Dubna (Russian Federation); Cappella, F.; Incicchitti, A. [INFN, Section of Rome La Sapienza, Rome, Italy and Department of Physics, University of Rome La Sapienza, Rome (Italy); Caracciolo, V. [INFN, Gran Sasso National Laboratories, Assergi (Aq), Italy and Department of Physics, University of L' Aquila, L' Aquila (Italy); and others

    2013-08-08

    Cadmium tungstate crystal scintillators enriched in {sup 106}Cd up to 66% ({sup 106}CdWO{sub 4}) and in {sup 116}Cd up to 82% ({sup 116}CdWO{sub 4}) have been developed. The low radioactive contamination of the crystals measured on the level of ≤ 1.5 mBq/kg ({sup 40}K), ≤ 0.005 - 0.012 mBq/kg ({sup 226}Ra), 0.04 - 0.07 mBq/kg ({sup 228}Th) allows to carry out high sensitivity experiments to search for double beta processes in {sup 106}Cd and {sup 116}Cd.

  10. Comparative study of optical properties of the one-dimensional multilayer Period-Doubling and Thue-Morse quasi-periodic photonic crystals

    Directory of Open Access Journals (Sweden)

    Yassine Bouazzi

    2012-10-01

    Full Text Available The last decades have witnessed the growing interest in the use of photonic crystal as a new material that can be used to control electromagnetic wave. Actually, not only the periodic structures but also the quasi-periodic systems have become significant structures of photonic crystals. This work deals with optical properties of dielectric Thue-Morse multilayer and Period-Doubling multilayer. We use the so-called Transfer Matrix Method (TMM to determine the transmission spectra of the structures. Based on the representation of the transmittance spectra in the visible range a comparative analysis depending on the iteration number, number of layers and incidence angle is presented.

  11. Formation of oriented nickel aggregates in rutile single crystals by Ni implantation

    Energy Technology Data Exchange (ETDEWEB)

    Cruz, M.M., E-mail: mmcruz@fc.ul.pt [CFMC, Universidade de Lisboa, Campo Grande, 1749-016 Lisboa (Portugal); Dep. Física, Fac. Ciências, Universidade de Lisboa, Campo Grande, 1749-016 Lisboa (Portugal); Silva, R.C. da [IST/ITN, Instituto Superior Técnico, Universidade de Lisboa, Campus Tecnológico e Nuclear, E.N.10, 2686-953 Sacavém (Portugal); CFNUL, Av. Prof. Gama Pinto 2, 1649-003 Lisboa (Portugal); Pinto, J.V. [CFMC, Universidade de Lisboa, Campo Grande, 1749-016 Lisboa (Portugal); CFNUL, Av. Prof. Gama Pinto 2, 1649-003 Lisboa (Portugal); Borges, R.P. [CFMC, Universidade de Lisboa, Campo Grande, 1749-016 Lisboa (Portugal); Franco, N. [IST/ITN, Instituto Superior Técnico, Universidade de Lisboa, Campus Tecnológico e Nuclear, E.N.10, 2686-953 Sacavém (Portugal); CFNUL, Av. Prof. Gama Pinto 2, 1649-003 Lisboa (Portugal); Casaca, A. [CFMC, Universidade de Lisboa, Campo Grande, 1749-016 Lisboa (Portugal); Instituto Superior de Engenharia de Lisboa—ISEL, R. Cons. Emídio Navarro 1, 1959-007 Lisboa (Portugal); Alves, E. [IST/ITN, Instituto Superior Técnico, Universidade de Lisboa, Campus Tecnológico e Nuclear, E.N.10, 2686-953 Sacavém (Portugal); CFNUL, Av. Prof. Gama Pinto 2, 1649-003 Lisboa (Portugal); Godinho, M. [CFMC, Universidade de Lisboa, Campo Grande, 1749-016 Lisboa (Portugal); Dep. Física, Fac. Ciências, Universidade de Lisboa, Campo Grande, 1749-016 Lisboa (Portugal)

    2013-08-15

    The magnetic and electrical properties of Ni implanted single crystalline TiO{sub 2} rutile were studied for nominal implanted fluences between 0.5×10{sup 17} cm{sup −2} and 2.0×10{sup 17} cm{sup −2} with 150 keV energy, corresponding to maximum atomic concentrations between 9 at% and 27 at% at 65 nm depth, in order to study the formation of metallic oriented aggregates. The results indicate that the as implanted crystals exhibit superparamagnetic behavior for the two higher fluences, which is attributed to the formation of nanosized nickel clusters with an average size related with the implanted concentration, while only paramagnetic behavior is observed for the lowest fluence. Annealing at 1073 K induces the aggregation of the implanted nickel and enhances the magnetization in all samples. The associated anisotropic behavior indicates preferred orientations of the nickel aggregates in the rutile lattice consistent with Rutherford backscattering spectrometry—channelling results. Electrical conductivity displays anisotropic behavior but no magnetoresistive effects were detected. - Author-Highlights: • Ni nano-aggregates were grown on TiO{sub 2} using Ni implantation with different fluences. • In the as implanted state, the aggregates size is a function of the implanted fluence. • Ni aggregates are oriented within the rutile structure-2 orientations are proposed.

  12. Stochastic polarity formation in molecular crystals, composite materials and natural tissues

    Directory of Open Access Journals (Sweden)

    Jürg Hulliger

    2017-07-01

    Full Text Available This topical review summarizes the theoretical and experimental findings obtained over the last 20 years on the subject of growth-induced polarity formation driven by a Markov chain process. When entering the growing surface of a molecular crystal, an inorganic–organic composite or a natural tissue, the building blocks may undergo 180° orientational disorder. Driven by configurational entropy, faulted orientations can promote the conversion of a growing non-polar seed into an object showing polar domains. Similarly, orientational disorder at the interface may change a polar seed into a two-domain state. Analytical theory and Monte Carlo simulations were used to model polarity formation. Scanning pyroelectric, piezoresponse force and phase-sensitive second-harmonic microscopies are methods for investigating the spatial distribution of polarity. Summarizing results from different types of materials, a general principle is provided for obtaining growth-induced polar domains: a non-zero difference in the probabilities for 180° orientational misalignments of building blocks, together with uni-directional growth, along with Markov chain theory, can produce objects showing polar domains.

  13. Double Neutron Stars: Evidence For Two Different Neutron-Star Formation Mechanisms

    NARCIS (Netherlands)

    van den Heuvel, E.P.J.

    2007-01-01

    Six of the eight double neutron stars known in the Galactic disk have low orbital eccentricities (< 0.27) indicating that their second-born neutron stars received only very small velocity kicks at birth. This is similar to the case of the B-emission X-ray binaries, where a sizable fraction of the ne

  14. 双程腔内倍频激光器的谐波晶体腔内位置的理论研究%The Theory Research on the Location of a Frequency Doubling Crystal in a Double-pass Intracavity Frequency Doubling Laser

    Institute of Scientific and Technical Information of China (English)

    程一斌

    2000-01-01

    In this paper, the location of a frequency doubling crystal in a double-pass intra cavity frequency doubling and plano- concave confignration' s laser whose output was inone direc tion was analyzed in theory, and the formula of the suitable space between the frequency doubling crystal and the fiat mirror was obtained.%从理论上分析了平-凹腔结构的双程谐波、单方向输出的腔内谐波激光器的谐 波晶体腔内位置的选择,获得了谐波晶体与全反射镜的合理间距的解析式。

  15. Carboxy-terminal extension effects on crystal formation and insecticidal properties of colorado potato beetle-active Bacillus thuringiensis d-endotoxins

    NARCIS (Netherlands)

    Naimov, S.; Martens-Uzunova, E.S.; Weemen, W.M.J.; Dukiandjiev, S.; Minkov, I.; Maagd, de R.A.

    2006-01-01

    Many Bacillus thuringiensis crystal proteins, particularly those active against lepidopteran insects, have carboxy-terminal extensions that mediate bipyramidal crystal formation. These crystals are only soluble at high (>10.0) pH in reducing conditions such as generally found in the lepidopteran

  16. Stimulated crystallization of melt-quenched Ge{sub 2}Sb{sub 2}Te{sub 5} films employing femtosecond laser double pulses

    Energy Technology Data Exchange (ETDEWEB)

    Cotton, Rebecca L.; Siegel, Jan [Laser Processing Group, Instituto de Optica, CSIC, Serrano 121, E-28006 Madrid (Spain)

    2012-12-15

    The phase transformation of Ge{sub 2}Sb{sub 2}Te{sub 5} films from the melt-quenched amorphous phase into the crystalline phase induced by 800 nm, 100 fs laser pulses has been studied. For partly amorphized films, progressive crystallization could be induced by single pulses, which can be explained by growth of already existing crystalline embryos. For completely amorphized films, it was not possible to induce crystallization with one or two consecutive pulses; three pulses being the threshold for the onset of crystallization. By employing a fs laser double pulse with an adjustable inter-pulse delay, partial crystallization could be triggered for a delay range of 200 fs-100 ps, while for longer delays no crystallization was possible. The time window for stimulated crystallization can be related to the relaxation dynamics of free electrons excited by the first pulse, which are further excited by the second pulse still remaining in the excited state. Our results indicate that the lifetime of excited electrons in melt-quenched amorphous Ge{sub 2}Sb{sub 2}Te{sub 5} is Almost-Equal-To 100 ps.

  17. In situ platelets formation into aqueous polymer colloids: The topochemical transformation from single to double layered hydroxide (LSH-LDH) uncovered.

    Science.gov (United States)

    Stimpfling, Thomas; Langry, Arthur; Hintze-Bruening, Horst; Leroux, Fabrice

    2016-01-15

    Layered Single Hydroxide (LSH) of chemical composition Zn5(OH)8(acetate)2·nH2O is synthesized under in situ condition in an aqueous dispersion of an amphiphilic, carboxylate bearing polyester via a modified polyol route. The one-pot LSH generation yields agglomerates of well intercalated platelets, 9-10nm separated from each other. However the corresponding Layered Double Hydroxide (LDH) of formal composition Zn2Al(OH)6 (acetate)·nH2O is found to proceed via the formation of crystallized, similarly spaced LSH sheets in the neighborhood of amorphous Al rich domains as evidenced by X-ray diffraction and transmission electron micrographs. The initial phase segregation effaces over time while LSH platelets convert into the LDH phase. Fingerprinted by the change of in-plane cation accommodation, the associated topochemical reaction of the edge-sharing octahedral LSH platelets involves the transformation of metal lacunae, adjacently covered by one tetrahedral coordinated cation on each side to balance the negative surcharge, into fully occupied and monolayered platelets of edge-sharing octahedral LDH, the former voids being occupied by trivalent cations. This replenishing process of empty sites, coupled with the dissolution of tetrahedral sites is likely to be observed for the first time due to the presence of well separated, polymer intercalated platelets. TEM pictures vision crystal growth arising from the zone of the LSH edge-slab and by using solid state kinetics formalism the associated high activation energy of the first-order reaction agrees well with a plausible dissolution re-precipitation mechanism. The conversion of LSH into LDH platelets may be extended to others cations as Co(2+), Cu(2+), as well as the aluminum source (AlCl3) and the water-soluble polymer (NVP), thus indicating it is a new prevalent facet of LDH.

  18. Formating double layer mechanism by electric charged particle stream in plasma

    Science.gov (United States)

    Shan-jun, Ma; Qian-li, Yang; Xiao-qing, Li

    1998-08-01

    In this paper, two-fluid equations have been solved after having considered magnetic field generated by charged particle stream. Finally, the distribution of electric field Ez(z, r) and its growth rate γ in plasma have been obtained. From the expression of Ez(z, r) it can be known that the double layer has been formed. With the increase of disturbance γ will be larger, and finally this will result in the interruption of electric current and occurrence of burst.

  19. Nonlinear Localization due to a Double Negative Defect Layer in a One-Dimensional Photonic Crystal Containing Single Negative Material Layers

    Institute of Scientific and Technical Information of China (English)

    Munazza Zulfiqar Ali; Tariq Abdullah

    2008-01-01

    We investigate the effects of introducing a defect layer in a one-dimensional photonic crystal containing single negative material layers on the transmission properties.The width of the defect layer js taken to be the same or smaller than the period of the structure.Different cases of the defect layer being linear or nonlinear and double positive or double negative are discussed.It is found that only a nonlinear double negative layer givas rises to a localized mode within the zero-φeff gap in this kind of structure.It is also shown that the important characteristics of the nonlinear defect mode such as its frequency,its FWHM and the threshold of the associated bistability can be controlled by changing the widths of the defect layer and the host layers.

  20. Search for double beta decay of Zinc and Tungsten with the help of low-background ZnWO4 crystal scintillators

    CERN Document Server

    Belli, P; Cappella, F; Cerulli, R; Danevich, F A; Grinyov, B V; Incicchitti, A; Kobychev, V V; Mokina, V M; Nagorny, S S; Nagornaya, L L; Nisi, S; Nozzoli, F; Poda, D V; Prosperi, D; Tretyak, V I; Yurchenko, S S

    2008-01-01

    Double beta processes in 64-Zn, 70-Zn, 180-W, and 186-W have been searched for with the help of large volume (0.1-0.7 kg) low background ZnWO4 crystal scintillators at the Gran Sasso National Laboratories of the INFN. Total time of measurements exceeds 10 thousands hours. New improved half-life limits on double electron capture and electron capture with positron emission in 64-Zn have been set, in particular (all the limits are at 90% C.L.): T1/2(0nu2EC)> 1.1e20 yr, T1/2(2nuECbeta+)>7.0e20 yr, and T1/2(0nuECbeta+)>4.3e20 yr. The different modes of double beta processes in 70-Zn, 180-W, and 186-W have been restricted at the level of 1e17-1e20 yr.

  1. THE DOUBLE PULSAR: EVIDENCE FOR NEUTRON STAR FORMATION WITHOUT AN IRON CORE-COLLAPSE SUPERNOVA

    Energy Technology Data Exchange (ETDEWEB)

    Ferdman, R. D.; Kramer, M.; Stappers, B. W.; Lyne, A. G. [School of Physics and Astronomy, University of Manchester, Jodrell Bank Centre for Astrophysics, Alan Turing Building, Oxford Road, Manchester M13 9PL (United Kingdom); Stairs, I. H. [Department of Physics and Astronomy, University of British Columbia, Vancouver, BC V6T 1Z1 (Canada); Breton, R. P. [School of Physics and Astronomy, University of Southampton, Highfield, Southampton SO17 1BJ (United Kingdom); McLaughlin, M. A. [Department of Physics, West Virginia University, Morgantown, WV 26505 (United States); Freire, P. C. C. [Max-Planck-Institut fuer Radioastronomie, Auf dem Huegel 69, D-53121 Bonn (Germany); Possenti, A. [INAF-Osservatorio Astronomico di Cagliari, Loc. Poggio dei Pini, I-09012 Capoterra (Italy); Kaspi, V. M. [Department of Physics, McGill University, Ernest Rutherford Physics Building, 3600 University Street, Montreal, QC H3A 2T8 (Canada); Manchester, R. N., E-mail: ferdman@jb.man.ac.uk [CSIRO Astronomy and Space Science, Australia Telescope National Facility, Epping, NSW 1710 (Australia)

    2013-04-10

    The double pulsar system PSR J0737-3039A/B is a double neutron star binary, with a 2.4 hr orbital period, which has allowed measurement of relativistic orbital perturbations to high precision. The low mass of the second-formed neutron star, as well as the low system eccentricity and proper motion, point to a different evolutionary scenario compared to most other known double neutron star systems. We describe analysis of the pulse profile shape over 6 years of observations and present the resulting constraints on the system geometry. We find the recycled pulsar in this system, PSR J0737-3039A, to be a near-orthogonal rotator with an average separation between its spin and magnetic axes of 90 Degree-Sign {+-} 11 Degree-Sign {+-} 5 Degree-Sign . Furthermore, we find a mean 95% upper limit on the misalignment between its spin and orbital angular momentum axes of 3. Degree-Sign 2, assuming that the observed emission comes from both magnetic poles. This tight constraint lends credence to the idea that the supernova that formed the second pulsar was relatively symmetric, possibly involving electron capture onto an O-Ne-Mg core.

  2. The double pulsar: evidence for neutron star formation without an iron core-collapse supernova

    CERN Document Server

    Ferdman, R D; Kramer, M; Breton, R P; McLaughlin, M A; Freire, P C C; Possenti, A; Stappers, B W; Kaspi, V M; Manchester, R N; Lyne, A G

    2013-01-01

    The double pulsar system PSR J0737-3039A/B is a double neutron star binary, with a 2.4-hour orbital period, which has allowed measurement of relativistic orbital perturbations to high precision. The low mass of the second-formed neutron star, as well as the low system eccentricity and proper motion, point to a different evolutionary scenario compared to most other known double neutron star systems. We describe analysis of the pulse profile shape over 6 years of observations, and present the resulting constraints on the system geometry. We find the recycled pulsar in this system, PSR J0737-3039A, to be a near-orthogonal rotator, with an average separation between its spin and magnetic axes of 90 +/- 11 +/- 5 deg. Furthermore, we find a mean 95% upper limit on the misalignment between its spin and orbital angular momentum axes of 3.2 deg, assuming that the observed emission comes from both magnetic poles. This tight constraint lends credence to the idea that the supernova that formed the second pulsar was relat...

  3. A compact low cost “master–slave” double crystal monochromator for x-ray cameras calibration of the Laser MégaJoule Facility

    Energy Technology Data Exchange (ETDEWEB)

    Hubert, S., E-mail: sebastien.hubert@cea.fr; Prévot, V.

    2014-12-21

    The Alternative Energies and Atomic Energy Commission (CEA-CESTA, France) built a specific double crystal monochromator (DCM) to perform calibration of x-ray cameras (CCD, streak and gated cameras) by means of a multiple anode diode type x-ray source for the MégaJoule Laser Facility. This DCM, based on pantograph geometry, was specifically modeled to respond to relevant engineering constraints and requirements. The major benefits are mechanical drive of the second crystal on the first one, through a single drive motor, as well as compactness of the entire device. Designed for flat beryl or Ge crystals, this DCM covers the 0.9–10 keV range of our High Energy X-ray Source. In this paper we present the mechanical design of the DCM, its features quantitatively measured and its calibration to finally provide monochromatized spectra displaying spectral purities better than 98%.

  4. Double modulation of X radiation diffracted in a quartz single crystal by high and low frequency acoustic waves

    CERN Document Server

    Kocharyan, L A; Bornazyan, H S

    1986-01-01

    The time dependence of X radiation diffracted in a quartz single crystal is experimentally investigated when surface acoustic waves modulated by low frequency oscillations of different frequencies and forms are excited in the crystal.

  5. Splicing stimulates siRNA formation at Drosophila DNA double-strand breaks.

    Directory of Open Access Journals (Sweden)

    Karin Merk

    2017-06-01

    Full Text Available DNA double-strand breaks trigger the production of locus-derived siRNAs in fruit flies, human cells and plants. At least in flies, their biogenesis depends on active transcription running towards the break. Since siRNAs derive from a double-stranded RNA precursor, a major question is how broken DNA ends can generate matching sense and antisense transcripts. We performed a genome-wide RNAi-screen in cultured Drosophila cells, which revealed that in addition to DNA repair factors, many spliceosome components are required for efficient siRNA generation. We validated this observation through site-specific DNA cleavage with CRISPR-cas9 followed by deep sequencing of small RNAs. DNA breaks in intron-less genes or upstream of a gene's first intron did not efficiently trigger siRNA production. When DNA double-strand breaks were induced downstream of an intron, however, this led to robust siRNA generation. Furthermore, a downstream break slowed down splicing of the upstream intron and a detailed analysis of siRNA coverage at the targeted locus revealed that unspliced pre-mRNA contributes the sense strand to the siRNA precursor. Since splicing factors are stimulating the response but unspliced transcripts are entering the siRNA biogenesis, the spliceosome is apparently stalled in a pre-catalytic state and serves as a signaling hub. We conclude that convergent transcription at DNA breaks is stimulated by a splicing dependent control process. The resulting double-stranded RNA is converted into siRNAs that instruct the degradation of cognate mRNAs. In addition to a potential role in DNA repair, the break-induced transcription may thus be a means to cull improper RNAs from the transcriptome of Drosophila melanogaster. Since the splicing factors identified in our screen also stimulated siRNA production from high copy transgenes, it is possible that this surveillance mechanism serves in genome defense beyond DNA double-strand breaks.

  6. Evaluation of the Quality of Sapphire Using X-Ray Rocking Curves and Double-Crystal X-Ray Topography

    Science.gov (United States)

    1994-05-01

    hard, high-strength, chemically resistant optical windows; and sub- srates for the growth of epitaxial films. The quality of a sapphire crystal can... crystal diffractometer. Single- crystal sapphire may be grown by a variety of different methods, of which the more common are Verneuil (flame fusion...Linear features (L), which may represent slight variations in lattice parameter along the crystal growth front, or dislocation networks, ad small

  7. Formation of laser-induced periodic surface structures on fused silica upon two-color double-pulse irradiation

    Science.gov (United States)

    Höhm, S.; Herzlieb, M.; Rosenfeld, A.; Krüger, J.; Bonse, J.

    2013-12-01

    The formation of laser-induced periodic surface structures (LIPSS) upon irradiation of fused silica with multiple irradiation sequences consisting of laser pulse pairs (50 fs single-pulse duration) of two different wavelengths (400 and 800 nm) is studied experimentally. Parallel polarized double-pulse sequences with a variable delay Δt between -10 and +10 ps and between the individual fs-laser pulses were used to investigate the LIPSS periods versus Δt. These two-color experiments reveal the importance of the ultrafast energy deposition to the silica surface by the first laser pulse for LIPSS formation. The second laser pulse subsequently reinforces the previously seeded spatial LIPSS frequencies.

  8. Formation of laser-induced periodic surface structures on fused silica upon two-color double-pulse irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Höhm, S.; Herzlieb, M.; Rosenfeld, A. [Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie (MBI), Max-Born-Straße 2A, D-12489 Berlin (Germany); Krüger, J.; Bonse, J. [BAM Bundesanstalt für Materialforschung und –prüfung, Unter den Eichen 87, D-12205 Berlin (Germany)

    2013-12-16

    The formation of laser-induced periodic surface structures (LIPSS) upon irradiation of fused silica with multiple irradiation sequences consisting of laser pulse pairs (50 fs single-pulse duration) of two different wavelengths (400 and 800 nm) is studied experimentally. Parallel polarized double-pulse sequences with a variable delay Δt between −10 and +10 ps and between the individual fs-laser pulses were used to investigate the LIPSS periods versus Δt. These two-color experiments reveal the importance of the ultrafast energy deposition to the silica surface by the first laser pulse for LIPSS formation. The second laser pulse subsequently reinforces the previously seeded spatial LIPSS frequencies.

  9. Cystone, a well-known herbal formulation, inhibits struvite crystal growth formation in single diffusion gel growth technique

    Directory of Open Access Journals (Sweden)

    Pralhad S. Patki

    2013-02-01

    Full Text Available Objective: The present study was aimed to evaluate the beneficial effect of Cystone® against struvite crystal growth in in vitro conditions. Methods: Various concentrations of Cystone® was prepared in 1 M magnesium acetate solution and evaluated for crystal growth inhibition assay by a well-known method called single diffusion gel growth technique in vitro. Results: Cystone®, a well-known polyherbal formulation, at 0.5, 1 and 2% concentrations showed significant and dose-dependent inhibition of struvite crystal growth formation in in vitro by reducing number, total mass and total volume of the struvite crystals formed and also caused fragmentation of grown struvite crystals in the gel matrix. Conclusion: The results of the present study indicate, Cystone® significantly retards the formation of struvite stones and also brings about its fragmentation. This could be one of the probable mechanisms behind the beneficial effect offered by Cystone® in the clinical management of urolithiasis and urinary tract infections. [J Exp Integr Med 2013; 3(1: 51-55

  10. Demonstration of periodic nanostructure formation with less ablation by double-pulse laser irradiation on titanium

    Science.gov (United States)

    Furukawa, Yuki; Sakata, Ryoichi; Konishi, Kazuki; Ono, Koki; Matsuoka, Shusaku; Watanabe, Kota; Inoue, Shunsuke; Hashida, Masaki; Sakabe, Shuji

    2016-06-01

    By pairing femtosecond laser pulses (duration ˜40 fs and central wavelength ˜810 nm) at an appropriate time interval, a laser-induced periodic surface structure (LIPSS) is formed with much less ablation than one formed with a single pulse. On a titanium plate, a pair of laser pulses with fluences of 70 and 140 mJ/cm2 and a rather large time interval (>10 ps) creates a LIPSS with an interspace of 600 nm, the same as that formed by a single pulse of 210 mJ/cm2, while the double pulse ablates only 4 nm, a quarter of the ablation depth of a single pulse.

  11. Two-dimensional colloidal crystal assisted formation of conductive porous gold films with flexible structural controllability.

    Science.gov (United States)

    Lu, Zhicheng; Liu, Chen; Han, Heyou

    2015-01-01

    Two-dimensional (2D) colloidal crystals of polystyrene (PS) particles were used as a structure-controlling template to fabricate conductive Au films with an ordered array of nanoholes. The fabrication mainly involved the functionalization of the supporting substrate with polyelectrolyte (PE) functional layers, self-assembly of Au nanoparticles, and electroless deposition of gold. The self-assembly of Au nanoparticles and electroless deposition of gold were macroscopically monitored using ultraviolet-visible (UV-vis) spectroscopy based on the changes in both the extinction spectra of Au nanoparticles and the optical responses of ordered arrays of PS particles. By scanning electron microscopy (SEM) characterization, it was found that Au nanoparticles were assembled into a film structure with orderly dispersed nanoholes and the deposition of gold was confined to the preformed Au nanoparticle films. During the formation of Au films, PE layer structure, Au nanoparticle size and heating treatment applied to the PS template could influence the structures of conductive porous Au films such as the hole diameter, film thickness, and hole diameter/wall thickness ratio (D/W). In addition, this paper also described electrochemical cyclic voltammetry (CV) employed to demonstrate the porosity of the ultimate Au films.

  12. On the formation of shocks of electromagnetic plane waves in non-linear crystals

    CERN Document Server

    Christodoulou, Demetrios

    2015-01-01

    An influential result of F. John states that no genuinely non-linear strictly hyperbolic quasi-linear first order system of partial differential equations in two variables has a global $C^2$-solution for small enough initial data. Inspired by recent work of D. Christodoulou, we revisit John's original proof and extract a more precise description of the behaviour of solutions at the time of shock. We show that John's singular first order quantity, when expressed in characteristic coordinates, remains bounded until the final time, which is then characterised by an inverse density of characteristics tending to zero in one point. Moreover, we study the derivatives of second order, showing again their boundedness when expressed in appropriate coordinates. We also recover John's upper bound for the time of shock formation and complement it with a lower bound. Finally, we apply these results to electromagnetic plane waves in a crystal with no magnetic properties and cubic electric non-linearity in the energy density...

  13. On the formation of shocks of electromagnetic plane waves in non-linear crystals

    Science.gov (United States)

    Christodoulou, Demetrios; Perez, Daniel Raoul

    2016-08-01

    An influential result of F. John states that no genuinely non-linear strictly hyperbolic quasi-linear first order system of partial differential equations in two variables has a global C2-solution for small enough initial data. Inspired by recent work of D. Christodoulou, we revisit John's original proof and extract a more precise description of the behaviour of solutions at the time of shock. We show that John's singular first order quantity, when expressed in characteristic coordinates, remains bounded until the final time, which is then characterised by an inverse density of characteristics tending to zero in one point. Moreover, we study the derivatives of second order, showing again their boundedness when expressed in appropriate coordinates. We also recover John's upper bound for the time of shock formation and complement it with a lower bound. Finally, we apply these results to electromagnetic plane waves in a crystal with no magnetic properties and cubic electric non-linearity in the energy density, assuming no dispersion.

  14. Inhibition of cholesterol crystallization under bilirubin deconjugation: partial characterization of mechanisms whereby infected bile accelerates pigment stone formation.

    Science.gov (United States)

    Nakai, Kuniharu; Tazuma, Susumu; Nishioka, Tomoji; Chayama, Kazuaki

    2003-06-10

    Pigment gallstones have been reported to be closely associated with biliary tract infection. We previously reported that addition of unconjugated bilirubin (UCB), which is deconjugated by beta-glucuronidase in infected bile, could enhance cholesterol crystal formation in supersaturated model bile (MB). The present study evaluated the effect of beta-glucuronidase on the processes of pigment gallstone formation and cholesterol crystallization. Supersaturated MB (taurocholate/lecithin/cholesterol at 71:18:11, a total lipid concentration of 10.0 g/dl and a cholesterol saturation index (CSI) of 2.0) and native rat bile were mixed at a ratio of 3:1. Then, mixed bile was incubated with or without beta-glucuronidase and changes of the following parameters were investigated over time: (1) the UCB/total bilirubin ratio; (2) cholesterol crystal formation; (3) the precipitate weight and the cholesterol concentration in the precipitate and supernatant; and (4) the lipid distribution of vesicles in the supernatant. Compared with beta-glucuronidase-free bile, (1) beta-glucuronidase-containing bile showed a significant increase of the UCB/total bilirubin ratio, (2) as well as a significantly longer nucleation time (96+/-17.0 vs. 114+/-20.0) and fewer cholesterol crystals. (3) The precipitate weight and the cholesterol concentration in the precipitate were significantly increased, while the cholesterol concentration in supernatant was decreased. (4) When mixed bile was incubated with beta-glucuronidase, the cholesterol concentration in the vesicles was lower than in bile without beta-glucuronidase. The precipitate weight and the cholesterol concentration in the precipitate was increased by incubation with beta-glucuronidase, while cholesterol concentration was decreased in the supernatant (especially in the vesicles). This means that bile vesicles were more stable and it was more difficult for cholesterol crystals to form. Thus, the presence of beta-glucuronidase may inhibit the

  15. THE DOUBLE SERPENT: POLITICAL AND ECONOMIC POWER IN THE FORMATION OF CAPITALISM.

    Directory of Open Access Journals (Sweden)

    Gerardo Cerdas Vega

    2013-06-01

    Full Text Available This paper analyzes the historical links between political and economic power in the formation of capitalism, from the standpoint of long-time periods and the role that power had in shaping the economy and society in Europe since the sixteenth century. The result of this process is an capitalist interstate system whose expansive dynamic reached the entire globe and whose entanglement we need to solve in order to overcome naturalized readings on the formative process of global economic and political order.

  16. Model-free kinetic analysis of Sr2FeMoO6 re-crystallization process used for double-perovskite monocrystals grown by Bridgman method

    Science.gov (United States)

    Bartha, Cristina; Plapcianu, Carmen; Palade, Petru; Vizman, Daniel

    2015-12-01

    The synthesis routes for polycrystalline bulk Sr2FeMoO6 (SFMO), offer various possibilities, but in all the cases it is difficult to obtain a single phase of this compound. A new challenge in the field is to achieve mono-crystals using different growing routes and the Bridgman method represents one of them. In order to establish the optimal conditions of mono-crystals growing process, a complex thermal investigation of bulk double perovskite has been performed. Differential thermal analysis investigation in argon inert atmosphere, starting from room temperature up to 1650°C provided information about melting and re-crystallization temperature range. Both, the activation energy of Sr2FeMoO6 re-crystallization process and the re-crystallization mechanism were comparatively analyzed by two free-model estimations (Friedman and Ozawa-Flynn-Wall analysis). The resulted data are very important in order to set up the heating program of Bridgman furnace.

  17. Expansion of lower-frequency locally resonant band gaps using a double-sided stubbed composite phononic crystals plate with composite stubs

    Energy Technology Data Exchange (ETDEWEB)

    Li, Suobin; Chen, Tianning [School of Mechanical Engineering and State Key Laboratory for Strength and Vibration of Mechanical Structures, Xi' an Jiaotong University, Xi' an, Shaanxi 710049 (China); Wang, Xiaopeng, E-mail: xpwang@mail.xjtu.edu.cn [School of Mechanical Engineering and State Key Laboratory for Strength and Vibration of Mechanical Structures, Xi' an Jiaotong University, Xi' an, Shaanxi 710049 (China); Li, Yinggang [Key Laboratory of High Performance Ship Technology of Ministry of Education, Wuhan University of Technology, Wuhan, 430070 (China); Chen, Weihua [School of Mechanical Engineering and State Key Laboratory for Strength and Vibration of Mechanical Structures, Xi' an Jiaotong University, Xi' an, Shaanxi 710049 (China)

    2016-06-03

    We studied the expansion of locally resonant complete band gaps in two-dimensional phononic crystals (PCs) using a double-sided stubbed composite PC plate with composite stubs. Results show that the introduction of the proposed structure gives rise to a significant expansion of the relative bandwidth by a factor of 1.5 and decreases the opening location of the first complete band gap by a factor of 3 compared to the classic double-sided stubbed PC plate with composite stubs. Furthermore, more band gaps appear in the lower-frequency range (0.006). These phenomena can be attributed to the strong coupling between the “analogous rigid mode” of the stub and the anti-symmetric Lamb modes of the plate. The “analogous rigid mode” of the stub is produced by strengthening the localized resonance effect of the composite plates through the double-sided stubs, and is further strengthened through the introduction of composite stubs. The “analogous rigid mode” of the stubs expands the out-of-plane band gap, which overlaps with in-plane band gap in the lower-frequency range. As a result, the complete band gap is expanded and more complete band gaps appear. - Highlights: • Expansion of lower-frequency locally resonant BGs using novel composite phononic crystals plates. • The proposed structure expands the relative bandwidth 1.5 times compared to classic doubled-sided stubbed PC plates. • The opening location of the first complete BG decreases 3 times compared to the classic doubled-sided stubbed PC plates. • The concept “analogous rigid mode” is put forward to explain the expansion of lower-frequency BGs.

  18. Double layer formation in the expanding region of an inductively coupled electronegative plasma

    CERN Document Server

    Plihon, N; Chabert, P

    2015-01-01

    Double-layers (DLs) were observed in the expanding region of an inductively coupled plasma with $\\text{Ar}/\\text{SF}\\_6$ gas mixtures. No DL was observed in pure argon or $\\text{SF}\\_6$ fractions below few percent. They exist over a wide range of power and pressure although they are only stable for a small window of electronegativity (typically between 8\\% and 13\\% of $\\text{SF}\\_6$ at 1mTorr), becoming unstable at higher electronegativity. They seem to be formed at the boundary between the source tube and the diffusion chamber and act as an internal boundary (the amplitude being roughly 1.5$\\frac{kT\\_e}{e}$)between a high electron density, high electron temperature, low electronegativity plasma upstream (in the source), and a low electron density, low electron temperature, high electronegativity plasma downstream.

  19. Up and down translocation events and electric double-layer formation inside solid-state nanopores.

    Science.gov (United States)

    Zanjani, Mehdi B; Engelke, Rebecca E; Lukes, Jennifer R; Meunier, Vincent; Drndić, Marija

    2015-08-01

    We present a theoretical study of nanorod translocation events through solid-state nanopores of different sizes which result in positive or negative ion conductance changes. Using theoretical models, we show that positive conductance changes or up events happen for nanopore diameters smaller than a transition diameter dt, and negative conductance changes or down events occur for nanopore diameters larger than dt. We investigate the underlying physics of such translocation phenomena and describe the significance of the electric double-layer effects for nanopores with small diameters. Furthermore, for nanopores with large diameters, it is shown that a geometric model, formulated based on the nanoparticle blockade inside the nanopore, provides a straightforward and reasonably accurate prediction of ion conductance change. Based on this concept, we also implement a method to distinguish and detect nanorods of different sizes by focusing solely on the sign and not the exact value of the conductance change.

  20. Double shock front formation in cylindrical radiative blast waves produced by laser irradiation of krypton gas

    Energy Technology Data Exchange (ETDEWEB)

    Kim, I.; Quevedo, H. J.; Feldman, S.; Bang, W.; Serratto, K.; McCormick, M.; Aymond, F.; Dyer, G.; Bernstein, A. C.; Ditmire, T. [Center for High Energy Density Science, Department of Physics, The University of Texas at Austin, C1510, Austin, Texas 78712 (United States)

    2013-12-15

    Radiative blast waves were created by irradiating a krypton cluster source from a supersonic jet with a high intensity femtosecond laser pulse. It was found that the radiation from the shock surface is absorbed in the optically thick upstream medium creating a radiative heat wave that travels supersonically ahead of the main shock. As the blast wave propagates into the heated medium, it slows and loses energy, and the radiative heat wave also slows down. When the radiative heat wave slows down to the transonic regime, a secondary shock in the ionization precursor is produced. This paper presents experimental data characterizing both the initial and secondary shocks and numerical simulations to analyze the double-shock dynamics.

  1. Effect of double quaternary ammonium groups on micelle formation of partially fluorinated surfactant.

    Science.gov (United States)

    Matsuoka, Keisuke; Chiba, Nagisa; Yoshimura, Tomokazu; Takeuchi, Emi

    2011-04-15

    To investigate the effect of divalency on the micelle properties, we synthesized divalent cationic surfactants composed of fluorocarbons and double quaternary ammonium groups N,N-dimethyl-N-[2-(N'-trimethylammonium)ethyl]-1-(3-perfluoroalkyl-2-hydroxypropyl) ammonium bromide [C(n)(F)C(3)-2Am; where n (=8 or 10) represents the number of carbon atoms in the fluorocarbon chain]. The double quaternary ammonium groups are continuously combined by the ethylene spacer in the surfactant head group, which clearly distinguishes the molecular design of the surfactant from those of the other typical divalent surfactants, bolaform and gemini types. The presence of the divalent head group results in an advantageous increase in their solubility [i.e., rise in the critical micelle concentration (cmc)]; however, the extra electrostatic repulsion between divalent cations decreases the surface activity in comparison with monovalent homologous fluorinated surfactants. The cmc, surface tension at cmc, and area occupied by a surfactant molecule in aqueous solution at 298.2K are 4.32 mM, 30.6 mN m(-1), and 0.648 nm(2 )molecule(-1), respectively, for C(8)(F)C(3)-2Am, and 1.51 mM, 30.4 mN m(-1), and 0.817 nm(2) molecule(-1), respectively, for C(10)(F)C(3)-2Am. The micellar size and shape were investigated by dynamic light scattering and freeze-fracture transmission electron microscopy (TEM). The TEM micrographs show that C(n)(F)C(3)-2Am (n=8 and 10) mainly forms ellipsoidal micelles approximately 10-100 nm in size for n=8 and approximately 10-20 nm in size for n=10. The degree of counterion binding to micelle was determined by selective electrode potential measurements, and the results of 0.7-0.8 agree with the average values for conventional monovalent ionic surfactants.

  2. Formation processes of CuCl and regenerated Cu crystals on bronze surfaces in neutral and acidic media

    Energy Technology Data Exchange (ETDEWEB)

    Wang Julin [Institute of Materials Science and Engineering, Beijing University of Chemical Technology, Beijing 100029 (China)]. E-mail: julinwang@126.com; Xu Chunchun [Institute of Materials Science and Engineering, Beijing University of Chemical Technology, Beijing 100029 (China); Lv Guocheng [Institute of Materials Science and Engineering, Beijing University of Chemical Technology, Beijing 100029 (China)

    2006-07-15

    The paper is devoted to investigating the formation of CuCl and regenerated Cu crystals on bronze. Electrochemical behaviour of bronze in simulated anoxic edaphic media and occluded cell (O.C.) solutions was studied with cycle voltammetry (CV) and X-ray diffraction (XRD). Within potential range of -800 to +800 mV, oxidation occurred was largely a process in which Cu is oxidized to CuCl and the reduction process was a reverse of it. An atomic force microscopy (AFM) was used to observe the morphology of CuCl crystals, regenerated Cu crystals and corrosion interface at nm level. The deposition of regenerated Cu on simulated archaeological bronzes was simulated under experimental conditions for the first time. CuCl could be thoroughly reduced to pure Cu if reduction time interval were sufficiently prolonged. This provided a theoretical and experimental basis for getting rid of harmful CuCl patina from archaeological bronzes with electrochemical means.

  3. Crystallization and cooling conditions for the diogenite formation in the turbulent magma ocean of the asteroid 4 Vesta

    CERN Document Server

    Kawabata, Yusuke

    2016-01-01

    The asteroid 4 Vesta has been completely differentiated to core and mantle despite its small size, of which surface materials are howardite-eucrite-diogenite (HED) meteorites that we know the detailed petrology, and therefore, is a good target for understanding differentiation of terrestrial planets. A new differentiation model for crust formation was developed by taking magma ocean fluid dynamics, chemical equilibrium, presence of $^{26}$Al, and cooling into consideration with special care to crystal separation. The role of crystal size, thickness of the conductive lid, and fO2 are evaluated as parameters. The results show that large crystals (1cm) settle and form a km-thick cumulate layer of orthopyroxene with Mg# of 0.70-0.90 in ~20 thousand years, which almost agrees with the Mg# of diogenites, whereas thinner layers are formed if the grain size is smaller.

  4. EXTERNAL ACTION EFFECT ON THE STRUCTURE OF THE LIQUID PHASE, THE CRYSTALLIZATION PROCESS, STRUCTURE FORMATION OF COPPER

    Directory of Open Access Journals (Sweden)

    Mr. Eduard A. Dmitriev

    2016-09-01

    Full Text Available The paper presents the research results of a fluid phase overheating and alloying effect on cuprum mechanical characteristics. Careful analysis of poly-thermal cross-sections of electro-resistance proved that in order to obtain the maximum values of cuprum mechanical properties, it should be overheated 30 °С above the temperature threshold of abnormal electro-resistance change of a fluid phase (1320 °С. The paper presents the research results of the influence of thermal and thermo-high-speed treatment of cuprum melting on its structure, crystallization and structure formation processes. Regularities of structure change, crystallization parameters and structure formation depending on overheating and cooling rate of the melt are stated.

  5. Constraints on the Formation of Double Neutron Stars from the Observed Eccentricities and Current Limits on Merger Rates

    Science.gov (United States)

    Chruslinska, M.; Belczynski, K.; Bulik, T.; Gladysz, W.

    2017-03-01

    We employ population synthesis method to model the double neutron star (DNS) population and test various possibilities on natal kick velocities gained by neutron stars after their formation. We first choose natal kicks after standard core collapse supernovae (CCSN) from a Maxwellian distribution with velocity dispersion of σ = 265 km/s as proposed by Hobbs and then modify this distribution by changing σ toward smaller and larger kick values. We also take into account the possibility of NS formation through electron capture supernova. In this case we test two scenarios: zero natal kick or small natal kick, drawn from Maxwellian distribution with σ = 26.5 km/s. We calculate the present-day orbital parameters of binaries and compare the resulting eccentricities with those known for observed DNSs. As an additional test we calculate Galactic merger rates for our model populations and confront them with observational limits. We do not find any model unequivocally consistent with both observational constraints simultaneously. The models with low kicks after CCSN for binaries with the second NS forming through core collapse SN are marginally consistent with the observations. This means that either 14 observed DNSs are not representative of the intrinsic Galactic population, or that our modeling of DNS formation needs revision.

  6. Research on the Depression Effect for the Formation of Fine Crystals during ZBLAN Glass Rapid Resolidification in Variable Gravity

    Science.gov (United States)

    2012-01-10

    Formation of Fine Crystals during ZBLAN Glass Rapid Resolidification in Variable Gravity 5a. CONTRACT NUMBER FA23861114067 5b. GRANT NUMBER 5c...ABSTRACT This research aims at investigating the rapid resolidification of ZBLAN (Zr, Ba, La, Al, Na, Fluoride compound) glasses . The complex...synthesis of ZBLAN glass in normal gravity yields crystalline forms that are undesired for the transmission properties of the glass . This research takes

  7. Photophysical Analysis of the Formation of Organic–Inorganic Trihalide Perovskite Films: Identification and Characterization of Crystal Nucleation and Growth

    OpenAIRE

    Anaya, Miguel; Galisteo-López, Juan F.; Calvo, Mauricio E.; López, Cefe; Míguez, Hernán

    2016-01-01

    In this work we demonstrate that the different processes occurring during hybrid organic–inorganic lead iodide perovskite film formation can be identified and analyzed by a combined in situ analysis of their photophysical and structural properties. Our observations indicate that this approach permits unambiguously identifying the crystal nucleation and growth regimes that lead to the final material having a cubic crystallographic phase, which stabilizes to the well-known tetragonal phase upon...

  8. CCDC 1446069: Experimental Crystal Structure Determination : tris(Pentafluorophenyl)-(triethylsilyl formate)-aluminium

    KAUST Repository

    Chen, Jiawei

    2016-01-01

    An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

  9. CCDC 1446070: Experimental Crystal Structure Determination : tris(Pentafluorophenyl)-(triethylsilyl formate)-boron

    KAUST Repository

    Chen, Jiawei

    2016-01-01

    An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

  10. Body-centered cubic dissipative crystal formation in a dispersive and diffractive optical parametric oscillator.

    Science.gov (United States)

    Tlidi, M; Pieroux, D; Mandel, Paul

    2003-09-15

    We show that coupling diffraction and chromatic dispersion lead to body-centered cubic and hexagonally packed cylinders of dissipative optical crystals in a degenerate optical parametric oscillator. The stabilization of these crystals is a direct consequence of the interaction between the modulational and the quasi-neutral modes.

  11. Coke Formation in a Zeolite Crystal During the Methanol-to-Hydrocarbons Reaction as Studied with Atom Probe Tomography.

    Science.gov (United States)

    Schmidt, Joel E; Poplawsky, Jonathan D; Mazumder, Baishakhi; Attila, Özgün; Fu, Donglong; de Winter, D A Matthijs; Meirer, Florian; Bare, Simon R; Weckhuysen, Bert M

    2016-09-01

    Understanding the formation of carbon deposits in zeolites is vital to developing new, superior materials for various applications, including oil and gas conversion processes. Herein, atom probe tomography (APT) has been used to spatially resolve the 3D compositional changes at the sub-nm length scale in a single zeolite ZSM-5 crystal, which has been partially deactivated by the methanol-to-hydrocarbons reaction using (13) C-labeled methanol. The results reveal the formation of coke in agglomerates that span length scales from tens of nanometers to atomic clusters with a median size of 30-60 (13) C atoms. These clusters correlate with local increases in Brønsted acid site density, demonstrating that the formation of the first deactivating coke precursor molecules occurs in nanoscopic regions enriched in aluminum. This nanoscale correlation underscores the importance of carefully engineering materials to suppress detrimental coke formation.

  12. Formation of crystal-like structures and branched networks from nonionic spherical micelles

    Science.gov (United States)

    Cardiel, Joshua J.; Furusho, Hirotoshi; Skoglund, Ulf; Shen, Amy Q.

    2015-12-01

    Crystal-like structures at nano and micron scales have promise for purification and confined reactions, and as starting points for fabricating highly ordered crystals for protein engineering and drug discovery applications. However, developing controlled crystallization techniques from batch processes remain challenging. We show that neutrally charged nanoscale spherical micelles from biocompatible nonionic surfactant solutions can evolve into nano- and micro-sized branched networks and crystal-like structures. This occurs under simple combinations of temperature and flow conditions. Our findings not only suggest new opportunities for developing controlled universal crystallization and encapsulation procedures that are sensitive to ionic environments and high temperatures, but also open up new pathways for accelerating drug discovery processes, which are of tremendous interest to pharmaceutical and biotechnological industries.

  13. Segregation/Mixing Behavior ofBinary Particles and Formation of Doubl e-Density-Fl uidized Bed

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The current separator with air-dense-medium fluidized bed can only turn out two products at the sametime with a single separating density. The double-density-fluidized bed means that two separating areas with differ-ent densities are formed in a fluidized cascade. In each separating area, the bed density is uniform and meets thetechnical requirement of coal preparation respectively. Therefore, the processed materials can be separated intcthree products according to density. In this paper, the fluidized behaviors of binary dense media were experimental-ly studied and the distribution characteristics of particle concentration and bed density in different bed structurewere discussed. The segregation and mixing mechanisms of binary dense media were analyzed. It was testified thatthe pyramidal part designed in the bed structure played a key role in the formation of double-density-fluidized bed.The pyramidal part intensified the segregation of binary particles between two separating areas and strengthened themixing in the low density area, which made for the density uniform of the area.

  14. Formation of the Double Neutron Star System PSR J1930$-$1852

    CERN Document Server

    Shao, Yong

    2015-01-01

    The spin period (185 ms) and period derivative ($1.8\\times10^{-17}\\,\\rm s\\,s^{-1}$) of the double neutron star (DNS) system PSR J1930$-$1852 recently discovered indicate that the pulsar was mildly recycled through the process of Roche-lobe overflow. This system has the longest orbital period (45 days) of the known DNS systems, and can be formed from a helium star-NS binary if the initial mass of the helium star was $ \\lesssim 4.0M_{\\odot} $; otherwise the helium star would never fill its Roche-lobe \\citep{t15}. At the moment of the supernova explosion, the mass of the helium star was $ \\lesssim3.0M_{\\odot} $. We find that the probability distribution of the velocity kick imparted to the new-born neutron star has a maximum at about $30 \\,\\rm km\\,s^{-1}$ (and a tail up to $ 260 \\,\\rm km\\,s^{-1}$), indicating that this NS most probably received a low kick velocity at birth.

  15. Anomalous or regular capacitance? The influence of pore size dispersity on double-layer formation

    Science.gov (United States)

    Jäckel, N.; Rodner, M.; Schreiber, A.; Jeongwook, J.; Zeiger, M.; Aslan, M.; Weingarth, D.; Presser, V.

    2016-09-01

    The energy storage mechanism of electric double-layer capacitors is governed by ion electrosorption at the electrode surface. This process requires high surface area electrodes, typically highly porous carbons. In common organic electrolytes, bare ion sizes are below one nanometer but they are larger when we consider their solvation shell. In contrast, ionic liquid electrolytes are free of solvent molecules, but cation-anion coordination requires special consideration. By matching pore size and ion size, two seemingly conflicting views have emerged: either an increase in specific capacitance with smaller pore size or a constant capacitance contribution of all micro- and mesopores. In our work, we revisit this issue by using a comprehensive set of electrochemical data and a pore size incremental analysis to identify the influence of certain ranges in the pore size distribution to the ion electrosorption capacity. We see a difference in solvation of ions in organic electrolytes depending on the applied voltage and a cation-anion interaction of ionic liquids in nanometer sized pores.

  16. Host–Guest Chirality Interplay: A Mutually Induced Formation of a Chiral ZMOF and Its Double-Helix Polymer Guests

    KAUST Repository

    Luo, Xiaolong

    2016-01-12

    A novel homochiral zeolite-like metal-organic framework (ZMOF), [(Cu4I4) (dabco)2]·[Cu2(bbimb)]·3DMF (JLU-Liu23, dabco =1,4-diazabicyclo[2.2.2]-octane, H2bbimb =1,3-bis(2-benzimidazol)benzene, DMF = N,N-dimethylformamide), has been successfully constructed to host unprecedented DNA-like [Cu2(bbimb)]n polymers with double-helicity. The host-guest chirality interplay permitted the induced formation of an unusual gyroid MOF with homochirality and helical channels in the framework for the first time, JLU-Liu23. Importantly, the enantiomeric pairs (23P, 23M) can be promoted and isolated in the presence of appropriate chiral inducing agents, affording enantioselective separation of chiral molecules as well as small gas molecules. © 2016 American Chemical Society.

  17. Al-Si alloy point contact formation and rear surface passivation for silicon solar cells using double layer porous silicon

    Science.gov (United States)

    Moumni, Besma; Ben Jaballah, Abdelkader; Bessais, Brahim

    2012-10-01

    Lowering the rear surface recombination velocities by a dielectric layer has fascinating advantages compared with the standard fully covered Al back-contact silicon solar cells. In this work the passivation effect by double layer porous silicon (PS) (wide band gap) and the formation of Al-Si alloy in narrow p-type Si point contact areas for rear passivated solar cells are analysed. As revealed by Fourier transform infrared spectroscopy, we found that a thin passivating aluminum oxide (Al2O3) layer is formed. Scanning electron microscopy analysis performed in cross sections shows that with bilayer PS, liquid Al penetrates into the openings, alloying with the Si substrate at depth and decreasing the contact resistivity. At the solar cell level, the reduction in the contact area and resistivity leads to a minimization of the fill factor losses.

  18. Modified photoreactivity due to mixed crystal formation. II. Enhanced reactivity upon conformational mimicry and cavity enlargement.

    Science.gov (United States)

    Vithana, Champika; Uekusa, Hidehiro; Sekine, Akiko; Ohashi, Yuji

    2002-12-01

    The 2-cyanopropyl (beta-cyanopropyl) group in the cobaloxime complex of (2-cyanopropyl)(3-methylpyridine)bis(dimethylglyoximato)cobalt(III) takes a trans conformation around the Co-C-C-CN bond in the crystal and undergoes isomerization to the 1-cyanopropyl (alpha-cyanopropyl) group with a low reaction rate when the powdered crystals are irradiated with a xenon lamp. When the complex was mixed with (2-cyanoethyl)(3-methylpyridine)bis(dimethylglyoximato)cobalt(III) or (2-cyanoethyl)(3-ethylpyridine)bis(dimethylglyoximato)cobalt(III), a mixed crystal, Mix-I or Mix-II, was obtained. The cell parameters of Mix-I and Mix-II were considerably different. When the crystals of Mix-I and Mix-II were irradiated with the xenon lamp, the 2-cyanopropyl group and the 2-cyanoethyl group isomerized to the 1-cyanopropyl and 1-cyanoethyl groups, respectively, in the crystalline state as well as in the solid state. The isomerization rates of the 2-cyanopropyl and 2-cyanoethyl groups of the mixed crystals became significantly higher than the corresponding rates in the component crystals. For the 2-cyanopropyl group, the conformational change from trans to cis in the mixed crystals caused reaction rates to be enhanced, and the expanded volume of the reaction cavity in the mixed crystals increased the reactivity for the 2-cyanoethyl group, when compared with the reactivity of each component crystal. A quantitative discussion of the increased rate constants is presented, which is based on the crystal structures. The shapes of the reaction cavities for the reactive groups undergoing isomerization control the conformation and configuration of the produced 1-cyanoethyl and 1-cyanopropyl groups.

  19. Double template effect in [4 + 4] Schiff base macrocycle formation; an ESI-MS study.

    Science.gov (United States)

    Barreira-Fontecha, Julia; Kulmaczewski, Rafal; Ma, Xiaomei; McKee, Vickie

    2011-12-07

    The mechanism of self-assembly of a polynuclear complex of a [4 + 4] Schiff base iminomethylenediphenolate macrocycle [BaCu(4)(4 + 4)](2+) via a non-macrocyclic dialdehyde intermediate has been followed using ESI-MS of the reaction solutions. Both assembly of the intermediate and Schiff-base condensation with diamine give rise to single products; formation of the intermediate metallacycle is fast but Schiff-base condensation is much slower. Both intermediate complex and macrocyclic product have been structurally characterised.

  20. First bolometric measurement of the two neutrino double beta decay of $^{100}$Mo with a ZnMoO$_4$ crystals array

    CERN Document Server

    Cardani, L; Iachellini, N Ferreiro; Pattavina, L; Beeman, J W; Bellini, F; Casali, N; Cremonesi, O; Dafinei, I; Di Domizio, S; Ferroni, F; Galashov, E; Gotti, C; Nagorny, S; Orio, F; Pessina, G; Piperno, G; Pirro, S; Previtali, E; Rusconi, C; Tomei, C; Vignati, M

    2013-01-01

    The large statistics collected during the operation of a ZnMoO$_4$ array, for a total exposure of 1.3 kg $\\cdot$ day of $^{100}$Mo, allowed the first bolometric observation of the two neutrino double beta decay of $^{100}$Mo. The observed spectrum of each crystal was reconstructed taking into account the different background contributions due to environmental radioactivity and internal contamination. The analysis of coincidences between the crystals allowed the assignment of constraints to the intensity of the different background sources, resulting in a reconstruction of the measured spectrum down to an energy of $\\sim$300 keV. The half-life extracted from the data is T$_{1/2}^{2\

  1. Study of CdMoO4 crystal for a neutrinoless double beta decay experiment with 116Cd and 100Mo nuclides

    Science.gov (United States)

    Xue, Ming-Xuan; Zhang, Yun-Long; Peng, Hai-Ping; Xu, Zi-Zong; Wang, Xiao-Lian

    2017-04-01

    The scintillation properties of a CdMoO4 crystal have been investigated experimentally. The fluorescence yields and decay times measured from 22 K to 300 K demonstrate that CdMoO4 crystal is a good candidate for an absorber for a bolometer readout, for both heat and scintillation signals. The results from Monte Carlo studies, taking the backgrounds from 2ν2β of and internal trace nuclides 214Bi and 208Tl into account, show that the expected sensitivity of a CdMoO4 bolometer for neutrinoless double beta decay experiments with an exposure of 100 kg·years is one order of magnitude higher than those of the current sets of the of and Supported by National Natural Science Foundation of China (11275199)

  2. Single Crystal Growth of Multiferroic Double Perovskites: Yb2CoMnO6 and Lu2CoMnO6

    Directory of Open Access Journals (Sweden)

    Hwan Young Choi

    2017-02-01

    Full Text Available We report on the growth of multiferroic Yb2CoMnO6 and Lu2CoMnO6 single crystals which were synthesized by the flux method with Bi2O3. Yb2CoMnO6 and Lu2CoMnO6 crystallize in a double-perovskite structure with a monoclinic P21/n space group. Bulk magnetization measurements of both specimens revealed strong magnetic anisotropy and metamagnetic transitions. We observed a dielectric anomaly perpendicular to the c axis. The strongly coupled magnetic and dielectric states resulted in the variation of both the dielectric constant and the magnetization by applying magnetic fields, offering an efficient approach to accomplish intrinsically coupled functionality in multiferroics.

  3. Broadly wavelength- and pulse width-tunable high-repetition rate light pulses from soliton self-frequency shifting photonic crystal fiber integrated with a frequency doubling crystal.

    Science.gov (United States)

    Lanin, Aleksandr A; Fedotov, Andrei B; Zheltikov, Aleksei M

    2012-09-01

    Soliton self-frequency shift (SSFS) in a photonic crystal fiber (PCF) pumped by a long-cavity mode-locked Cr:forsterite laser is integrated with second harmonic generation (SHG) in a nonlinear crystal to generate ultrashort light pulses tunable within the range of wavelengths from 680 to 1800 nm at a repetition rate of 20 MHz. The pulse width of the second harmonic output is tuned from 70 to 600 fs by varying the thickness of the nonlinear crystal, beam-focusing geometry, and the wavelength of the soliton PCF output. Wavelength-tunable pulses generated through a combination of SSFS and SHG are ideally suited for coherent Raman microspectroscopy at high repetition rates, as verified by experiments on synthetic diamond and polystyrene films.

  4. Optical, luminescence and thermal properties of radiopure ZnMoO{sub 4} crystals used in scintillating bolometers for double beta decay search

    Energy Technology Data Exchange (ETDEWEB)

    Chernyak, D.M. [Institute for Nuclear Research, MSP 03680 Kyiv (Ukraine); Centre de Sciences Nucléaires et de Sciences de la Matière, 91405 Orsay (France); Danevich, F.A. [Institute for Nuclear Research, MSP 03680 Kyiv (Ukraine); Degoda, V.Ya.; Dmitruk, I.M. [Kyiv National Taras Shevchenko University, MSP 03680 Kyiv (Ukraine); Ferri, F. [Dipartimento di Scienza e Alta Tecnologia dell' Università dell' Insubria, Como I-22100 (Italy); Galashov, E.N. [Nikolaev Institute of Inorganic Chemistry, 630090 Novosibirsk (Russian Federation); Giuliani, A., E-mail: Andrea.Giuliani@csnsm.in2p3.fr [Centre de Sciences Nucléaires et de Sciences de la Matière, 91405 Orsay (France); Dipartimento di Scienza e Alta Tecnologia dell' Università dell' Insubria, Como I-22100 (Italy); Sezione INFN di Milano-Bicocca, I-20126 Italy (Italy); Ivanov, I.M. [Nikolaev Institute of Inorganic Chemistry, 630090 Novosibirsk (Russian Federation); Kobychev, V.V. [Institute for Nuclear Research, MSP 03680 Kyiv (Ukraine); Mancuso, M.; Marnieros, S. [Centre de Sciences Nucléaires et de Sciences de la Matière, 91405 Orsay (France); Dipartimento di Scienza e Alta Tecnologia dell' Università dell' Insubria, Como I-22100 (Italy); Mokina, V.M. [Institute for Nuclear Research, MSP 03680 Kyiv (Ukraine); Nones, C.; Olivieri, E. [Service de Physique des Particules, CEA-Saclay, F-91191 Gif sur Yvette (France); Pessina, G. [Sezione INFN di Milano-Bicocca, I-20126 Italy (Italy); Rusconi, C. [Dipartimento di Scienza e Alta Tecnologia dell' Università dell' Insubria, Como I-22100 (Italy); Sezione INFN di Milano-Bicocca, I-20126 Italy (Italy); and others

    2013-11-21

    Zinc molybdate (ZnMoO{sub 4}) crystals are an excellent candidate material to fabricate scintillating bolometers for the study of neutrinoless double beta decay of {sup 100}Mo, provided that the crystal quality meets strict optical, thermal and radiopurity requirements. This paper addresses the characterization of improved crystalline samples grown by the low-thermal-gradient Czochralski technique. Transmittance measurements confirm significant improvement of the material with respect to previously developed samples. Luminescence properties (emission spectra, dependence of intensity on temperature, thermally stimulated luminescence and phosphorescence) have been studied under X-ray excitation from liquid-helium to room temperature. The index of refraction was measured in the wavelength interval 406–655 nm. Samples of ZnMoO{sub 4} crystals with masses of 5.07 g and 23.8 g were operated as scintillating bolometers at temperatures below 30 mK, with simultaneous detection of scintillation and heat signals, confirming an excellent alpha/beta rejection power. Background measurements allowed encouraging radiopurity level estimations. The light collection from ZnMoO{sub 4} scintillators was Monte Carlo simulated, analysing different crystal size, shape and surface properties and different photodetector sizes.

  5. Model of phosphorus precipitation and crystal formation in electric arc furnace steel slag filters.

    Science.gov (United States)

    Claveau-Mallet, Dominique; Wallace, Scott; Comeau, Yves

    2012-02-07

    The objective of this study was to develop a phosphorus retention mechanisms model based on precipitation and crystallization in electric arc furnace slag filters. Three slag columns were fed during 30 to 630 days with a reconstituted mining effluent at different void hydraulic retention times. Precipitates formed in columns were characterized by X-ray diffraction and transmission electronic microscopy. The proposed model is expressed in the following steps: (1) the rate limiting dissolution of slag is represented by the dissolution of CaO, (2) a high pH in the slag filter results in phosphorus precipitation and crystal growth, (3) crystal retention takes place by filtration, settling and growth densification, (4) the decrease in available reaction volume is caused by crystal and other particulate matter accumulation (and decrease in available reaction time), and (5) the pH decreases in the filter over time if the reaction time is too low (which results in a reduced removal efficiency). Crystal organization in a slag filter determines its phosphorus retention capacity. Supersaturation and water velocity affect crystal organization. A compact crystal organization enhances the phosphorus retention capacity of the filter. A new approach to define filter performance is proposed: saturation retention capacity is expressed in units of mg P/mL voids.

  6. Constraints on the formation of double neutron stars from the observed eccentricities and current limits on merger rates

    CERN Document Server

    Chruslinska, Martyna; Bulik, Tomasz; Gladysz, Wojciech

    2016-01-01

    We employ population synthesis method to model the double neutron star (DNS) population and test various possibilities on natal kick velocities gained by neutron stars after their formation. We first choose natal kicks after standard core collapse SN from a Maxwellian distribution with velocity dispersion of sigma=265 km/s as proposed by Hobbs et al. (2005) and then modify this distribution by changing the velocity dispersion towards smaller and larger kick values. We also take into account the possibility of NS formation through electron capture supernova. In this case we test two scenarios: zero natal kick or small natal kick, drawn from Maxwellian distribution with sigma = 26.5 km/s. We calculate the present-day orbital parameters of binaries and compare the resulting eccentricities with those known for observed DNSs. As an additional test we calculate Galactic merger rates for our model populations and confront them with observational limits. We do not find any model unequivocally consistent with both obs...

  7. A Double-Porosity Model for Pumping Test in a Fractured Formation of a Large Dip Angle

    Science.gov (United States)

    Ho, Shin-Wei; Chen, chia-shyun

    2016-04-01

    A Cenozoic sandstone fractured formation is found to have a dip angle, θ, as large as 47 degree. Assuming the dip angle creates a uniform regional flow in the fractured formation, the flow field due to pumping is no longer radially symmetric with respect to the pumping. Instead, a capture zone will appear in the neighborhood of the pumping well. A double porosity model is developed for the problem of interest, where the matrix flow is taken into account by the distributed parameter approach. Neglecting fracture storage, there are three hydrogeological parameters in the model; namely, fracture transmissivity Tf, matrix hydraulic conductivity Km, and matrix storage coefficient Sm. A Laplace-domain solution is determined, and its large time asymptotic solution analytically inverted, which indicates that the drawdown variation of large times exhibits a straight line in a semilog plot. When the dip angle is known, the slope of this straight line can be used to determine Tf, and the intercept of the logarithmic time axis can be used to estimate Sm. The remaining Km can be uniquely determined by the curve-matching method for drawdown of small and intermediate times without difficulty. The larger the dip angle, the closer the stagnation point to the pumping well, and the smaller the capture zone. An overestimate of Tf by a factor of cosθ results if the dip angle effect is neglected. However, neglecting the dip angle has less effect on the estimates of Km and Sm.

  8. Formation of a Double-decker Magnetic Flux Rope in the Sigmoidal Solar Active Region 11520

    CERN Document Server

    Cheng, X; Zhang, J; Sun, X D; Guo, Y; Wang, Y M; Kliem, B; Deng, Y Y

    2014-01-01

    In this paper, we address the formation of a magnetic flux rope (MFR) that erupted on 2012 July 12 and caused a strong geomagnetic storm event on July 15. Through analyzing the long-term evolution of the associated active region observed by the Atmospheric Imaging Assembly and the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory, it is found that the twisted field of an MFR, indicated by a continuous S-shaped sigmoid, is built up from two groups of sheared arcades near the main polarity inversion line half day before the eruption. The temperature within the twisted field and sheared arcades is higher than that of the ambient volume, suggesting that magnetic reconnection most likely works there. The driver behind the reconnection is attributed to shearing and converging motions at magnetic footpoints with velocities in the range of 0.1--0.6 km s$^{-1}$. The rotation of the preceding sunspot also contributes to the MFR buildup. Extrapolated three-dimensional non-linear force-free field s...

  9. On the existence of ``l-threonine formate'', ``l-alanine lithium chloride'' and ``bis l-alanine lithium chloride'' crystals

    Science.gov (United States)

    Petrosyan, A. M.; Ghazaryan, V. V.; Fleck, M.

    2013-03-01

    We argue that the recently reported crystals "L-threonine formate" as well as "L-alanine lithium chloride" and "bis L-alanine lithium chloride" actually are the well-known crystals L-threonine and L-alanine, respectively.

  10. Effects of Ice-Crystal Structure on Halo Formation: Cirrus Cloud Experimental and Ray-Tracing Modeling Studies

    Science.gov (United States)

    Sassen, Kenneth; Knight, Nancy C.; Takano, Yoshihide; Heymsfield, Andrew J.

    1994-01-01

    During the 1986 Project FIRE (First International Satellite Cloud Climatology Project Regional Experiment) field campaign, four 22 deg halo-producing cirrus clouds were studied jointly from a ground-based polarization lidar and an instrumented aircraft. The lidar data show the vertical cloud structure and the relative position of the aircraft, which collected a total of 84 slides by impaction, preserving the ice crystals for later microscopic examination. Although many particles were too fragile to survive impaction intact, a large fraction of the identifiable crystals were columns and radial bullet rosettes, with both displaying internal cavitations and radial plate-column combinations. Particles that were solid or displayed only a slight amount of internal structure were relatively rare, which shows that the usual model postulated by halo theorists, i.e., the randomly oriented, solid hexagonal crystal, is inappropriate for typical cirrus clouds. With the aid of new ray-tracing simulations for hexagonal hollow-ended column and bullet-rosette models, we evaluate the effects of more realistic ice-crystal structures on halo formation and lidar depolarization and consider why the common halo is not more common in cirrus clouds.

  11. Effects of high-dose hydrogen implantation on defect formation and dopant diffusion in silver implanted ZnO crystals

    Science.gov (United States)

    Yaqoob, Faisal; Huang, Mengbing

    2016-07-01

    This work reports on the effects of a deep high-dose hydrogen ion implant on damage accumulation, defect retention, and silver diffusion in silver implanted ZnO crystals. Single-crystal ZnO samples were implanted with Ag ions in a region ˜150 nm within the surface, and some of these samples were additionally implanted with hydrogen ions to a dose of 2 × 1016 cm-2, close to the depth ˜250 nm. Rutherford backscattering/ion channeling measurements show that crystal damage caused by Ag ion implantation and the amount of defects retained in the near surface region following post-implantation annealing were found to diminish in the case with the H implantation. On the other hand, the additional H ion implantation resulted in a reduction of substitutional Ag atoms upon post-implantation annealing. Furthermore, the presence of H also modified the diffusion properties of Ag atoms in ZnO. We discuss these findings in the context of the effects of nano-cavities on formation and annihilation of point defects as well as on impurity diffusion and trapping in ZnO crystals.

  12. Thermal formation of mesoporous single-crystal Co3O4 nano-needles and their lithium storage properties

    KAUST Repository

    Lou, Xiong Wen

    2008-01-01

    In this work, we report the simple solid-state formation of mesoporous Co3O4 nano-needles with a 3D single-crystalline framework. The synthesis is based on controlled thermal oxidative decomposition and re-crystallization of precursor β-Co(OH)2 nano-needles. Importantly, after thermal treatment, the needle-like morphology can be completely preserved, despite the fact that there is a large volume contraction accompanying the process: β-Co(OH)2 → Co3O 4. Because of the intrinsic crystal contraction, a highly mesoporous structure with high specific surface area has been simultaneously created. The textual properties can be easily tailored by varying the annealing temperature between 200-400 °C. Interestingly, thermal re-crystallization at higher temperatures leads to the formation of a perfect 3D single-crystalline framework. Thus derived mesoporous Co3O4 nano-needles serve as a good model system for the study of lithium storage properties. The optimized sample manifests very low initial irreversible loss (21%), ultrahigh capacity, and excellent cycling performance. For example, a reversible capacity of 1079 mA h g-1 can be maintained after 50 cycles. The superior electrochemical performance and ease of synthesis may suggest their practical use in lithium-ion batteries. © The Royal Society of Chemistry 2008.

  13. In-situ, variable thickness, liquid crystal film target formation at moderate repetition rate for intense laser applications

    CERN Document Server

    Poole, P L; Cochran, G E; Hanna, R J; Andereck, C D; Schumacher, D W

    2015-01-01

    Liquid crystal films have recently been demonstrated as variable thickness, planar targets for ultra-intense laser matter experiments and applications such as ion acceleration. By controlling the parameters of film formation, including liquid crystal temperature and volume, their thickness can be varied on-demand from 10 $nm$ to above 10 $\\mu m$. This thickness range enables for the first time real-time selection and optimization of various ion acceleration mechanisms using low cost, high quality targets. Our previous work employed these targets in single shot configuration, requiring chamber cycling after the pre-made films were expended. Presented here is a film formation device capable of drawing films from a bulk liquid crystal source volume to any thickness in the aforementioned range. This device will form films under vacuum within 2 $\\mu m$ of the same location each time, well within the Rayleigh range of even tight $F/ \\#$ systems. The repetition rate of the device exceeds 0.1 $Hz$ for sub-100 $nm$ fi...

  14. The Effect of Premixed Schedule on the Crystal Formation of Calcium Phosphate Cement-chitosan Composite with Added Tetracycline

    Institute of Scientific and Technical Information of China (English)

    Jing MAO; Yan LIU; Bin ZHOU; Liyun YAO

    2008-01-01

    In this study, calcium phosphate cements (CPC) were prepared by mixing cement powders of tetracalcium phosphate (TTCP) with a cement liquid of phosphate acid saline solution. Tetracycline (TTC)-CPC, chitosan-CPC and chitosan-TTC-CPC were investigated with different premixed schedule. It was demonstrate that both TTC and chitosan worked on the phase transition and crystal characteristics. TTCP mixed with phosphate acid saline solution had similar features of Fourier transform-infrared spectrometry (FT-IR) no matter it was mixed with chitosan or TTC or both. TTC premixed with cement liquid or powder had significant different features of FT-IR and 876 cm-1seemed to be a special peak for TTC when TTC was premixed with cement liquid. This was also supported by XRD analysis, which showed that TTC premixed with cement liquid improved phase transition of TTCP to OCP. Chitosan, as organic additive, regulates the regular crystal formation and inhibits the phase transition of TTCP to OCP, except when it is mingled with cement liquid premixed with TTC in field scanning electron microscope. It was concluded that the premixed schedule influences the crystal formation and phase transition, which may be associated with its biocompatibility and bioactivities in vivo.

  15. Double Reunion Event From Revisited Shungura Formation, Omo Valley, Southwest Ethiopia.

    Science.gov (United States)

    Birke, T. K.; Otofuji, Y.; Brown, F. H.; Takemoto, K.; Eshete, G.

    2006-12-01

    Two hundred fifty meters of fluvio-lacustrine deposit were sampled from the 760 meter thick fossil rich Shungura Formation to study magnetostratigraphy within the Matuyama Chron. This formation is exposed in the lower Omo valley in southwestern Ethiopia and is divided into 12 members (Basal, followed by A to L (but excluding I)) on the basis of volcanic ash layers (de Heinzelin, 1983). This study focuses on strata between Tuff F and the upper part of Member G. Two to three block samples were collected from 46 levels, from which four to five standard cube specimens were produced resulting in 240 laboratory specimens. Two sets of specimens were first subjected to a pilot step-wise Alternating Field (Af) and Thermal demagnetization (Th) with 17 to 21 steps for Af and 19 to 25 steps for Th. The remaining samples were treated with Th techniques. On average samples have strong Natural Remanent Magnetization Intensity (NRM) with a mean of μ= 0.21 A/m. In most cases, up to three components of magnetization were revealed by both demagnetization techniques. The Characteristic Remanent Magnetization (ChRM) is represented by the highest temperature- coercivity component and appears by demagnetization at temperatures between 390°C-620°C or alternating fields between 25-100mT. As shown by study of the magnetic mineralogy, ChRM is carried by detrital magnetite and maghemite. Directional analyses revealed three reversed and three normal polarity zones: R3-N3-R2-N2-R1-N1. Reversed polarity (R3) is observed in the bottom 60 m of section, the next 44 meters are normal (N3), followed by 36 meters of reversed (R2) sstrata, then 10 meters of normal (N2) strata, 84 meters of reversed (R1) section, and 16 meters (N1) of normal strata at the top. The overall mean direction Ds=359.5°, Is= -0.3°, α95=3.9°, N = 46 is not different from the expected direction D=1°, I=8.8°, α95= 2.3°, N = 26 obtained from the Apparent Polar Wander Path (APWP) curve for Africa at 2 Ma (Besse and

  16. Crystal structure, electronic and magnetic properties of double perovskite Ba2FeWO6: A combined experimental-theoretical study

    Science.gov (United States)

    Saad, H.-E, M. Musa; Rammeh, N.

    2016-01-01

    Double perovskite oxide Ba2FeWO6 has been synthesized in polycrystalline form by the solid-state ceramic method at 950 °C. Structural characterization was performed by using the X-ray powder diffraction (XRD) and neutron powder diffraction (NPD) followed by Rietveld analysis of these patterns. The crystal structure of Ba2FeWO6 is cubic; space group Fm-3m with lattice parameter of a=8.1351 Å. Also, a density functional theory (DFT) study of the crystal structure, electronic and magnetic properties of Ba2FeWO6 has been carried out using full potential linear muffin-tin orbital (FP-LMTO). We showed that the obtained symmetry lattice parameter agree well with the experimental results. The influence of Fe element on the magnetic and electronic properties of double perovskite oxide Ba2FeWO6 is analyzed. Band structure calculations for cubic Ba2FeWO6 predict an energy-gap in both spin-up and spin-down. The semiconductor antiferromagnetic (AFM) phase is stabilized by the hybridization of nonmagnetic W6+ (5d°) site positioned in between the magnetic Fe2+ (3d6) sites through the O2- anions in a long range O-Fe-O-W-O arrangement. 57Fe Mössbaur spectrum and DFT calculations suggest that the AFM behavior arises since the mixed valence Fe2+-Fe3+ effect introduces in Fe2+-O2--W6+ anticoupling.

  17. Synthesis, crystal structures, and magnetic properties of double perovskites SrLaNiOsO6 and BaLaNiOsO6

    Science.gov (United States)

    Feng, Hai L.; Schnelle, Walter; Tjeng, Liu Hao; Jansen, Martin

    2016-10-01

    New double perovskite oxides SrLaNiOsO6 and BaLaNiOsO6 were synthesized by solid state reactions from the respective binary metal oxides, and their crystal structures and magnetic properties were characterized. At room temperature SrLaNiOsO6 and BaLaNiOsO6 crystallize in ordered double perovskite structures with space groups of P21/n (monoclinic) and I4/m (tetragonal), respectively. They are electrically semiconducting with an activation energy of ≈0.35 eV. Specific heat and magnetic measurements indicate that SrLaNiOsO6 shows predominantly antiferromagnetic correlations and displays antiferromagnetic transition around 60 K. However, for the isoelectronic BaLaNiOsO6 ferromagnetic correlations are predominant and there is no clear feature of a magnetic transition detectable. The remarkable change in magnetic properties of ALaNiOsO6 (A = Sr and Ba) can be related to the degree of structure distortions, i.e. the bending of the O-B-O (B = Ni,Os) links.

  18. Structure Formation of Ultrathin PEO Films at Solid Interfaces—Complex Pattern Formation by Dewetting and Crystallization

    Directory of Open Access Journals (Sweden)

    Hans-Georg Braun

    2013-02-01

    Full Text Available The direct contact of ultrathin polymer films with a solid substrate may result in thin film rupture caused by dewetting. With crystallisable polymers such as polyethyleneoxide (PEO, molecular self-assembly into partial ordered lamella structures is studied as an additional source of pattern formation. Morphological features in ultrathin PEO films (thickness < 10 nm result from an interplay between dewetting patterns and diffusion limited growth pattern of ordered lamella growing within the dewetting areas. Besides structure formation of hydrophilic PEO molecules, n-alkylterminated (hydrophobic PEO oligomers are investigated with respect to self-organization in ultrathin films. Morphological features characteristic for pure PEO are not changed by the presence of the n-alkylgroups.

  19. Glass Formation of a Coordination Polymer Crystal for Enhanced Proton Conductivity and Material Flexibility.

    Science.gov (United States)

    Chen, Wenqian; Horike, Satoshi; Umeyama, Daiki; Ogiwara, Naoki; Itakura, Tomoya; Tassel, Cédric; Goto, Yoshihiro; Kageyama, Hiroshi; Kitagawa, Susumu

    2016-04-18

    The glassy state of a two-dimensional (2D) Cd(2+) coordination polymer crystal was prepared by a solvent-free mechanical milling process. The glassy state retains the 2D structure of the crystalline material, albeit with significant distortion, as characterized by synchrotron X-ray analyses and solid-state multinuclear NMR spectroscopy. It transforms to its original crystal structure upon heating. Thus, reversible crystal-to-glass transformation is possible using our new processes. The glass state displays superior properties compared to the crystalline state; specifically, it shows anhydrous proton conductivity and a dielectric constant two orders of magnitude greater than the crystalline material. It also shows material flexibility and transparency.

  20. Formation and crystallization of bulk Pd82Si18 amorphous alloys

    Institute of Scientific and Technical Information of China (English)

    蒲建; 王敬丰; 肖建中; 崔昆

    2003-01-01

    Bulk amorphous Pd82Si18 alloy with the largest diameter of 8 mm was prepared by water quenching the molten alloy with flux medium in a quartz tube. The calculation result indicates that the bulk Pd82Si18 amorphous alloys have a low critical cooling rate (Rc) of 4.589 K/s or less. The experimental results show that purifying melt may improve glass forming ability(GFA) of undercooled melt, while liquid phase separation (LPS) of undercooled melt will decrease its GFA. There are some differences in crystallization experiments between bulk metallic glass and amorphous ribbons of Pd82Si18 alloys. These include the numbers of exothermic peak, glass transition temperature Tg, crystallization temperature Tx, region of undercooling liquid (ΔT=Tx-Tg) respectively. The links of cooling rates of melt and crystallization of Pd82Si18 amorphous alloys are explored.

  1. Transient formation of bcc crystals in suspensions of poly(N-isopropylacrylamide)-based microgels.

    Science.gov (United States)

    Gasser, U; Lietor-Santos, J-J; Scotti, A; Bunk, O; Menzel, A; Fernandez-Nieves, A

    2013-11-01

    We present a small-angle x-ray scattering study of crystals formed by temperature-sensitive, swollen microgel particles consisting of poly(N-isopropylacrylamide) copolymerized with acrylic acid and 5 mol % of a cross-linker. As for hard spheres, the random hexagonal close-packed structure is predominant during crystal growth and slowly transforms toward the face-centered-cubic structure. However, a transient phase of body-centered-cubic crystal is observed in an intermediate range of effective volume fractions. We estimate that the studied suspensions are close to a transition from face-centered-cubic to body-centered-cubic structure that can be understood by the tendency of the system to maximize the excluded volume and minimize the contact area between the particles.

  2. Silicon Crystals Formation Using Silicatein-Like Cathepsin of Marine Sponge Latrunculia oparinae.

    Science.gov (United States)

    Kamenev, D G; Shkryl, Y N; Veremeichik, G N; Golotin, V A; Naryshkina, N N; Timofeeva, Y O; Kovalchuk, S N; Semiletova, I V; Bulgakov, V P

    2015-12-01

    The cDNA fragment encoding the catalytic domain of the new silicatein-like cathepsin enzyme LoCath was expressed in a strain Top10 of Escherichia coli, extracted and purified via nickel-affinity chromatography. Recombinant enzyme performed silica-polymerizing activity when mixed with water-soluble silica precursor-tetrakis-(2-hydroxyethyl)-orthosilicate. Scanning electron microscopy revealed hexagonal, octahedral and β-tridimit crystals. Energy dispersion fluorescence X-ray spectrometry analysis showed that all these crystals consist of pure silicon oxide. It is the first report about the ability of marine sponge's cathepsin to polymerize silicon, as well as about the structure and composition of the silicon oxide crystal formed by recombinant cathepsin. Further study of the catalytic activity of silicatein and cathepsin will help to understand the biosilification processes in vivo, and will create basis for biotechnological use of recombinant proteins for silicon polymerization.

  3. Metallic Na formation in NaCl crystals with irradiation of electron or vacuum ultraviolet photon

    Energy Technology Data Exchange (ETDEWEB)

    Owaki, Shigehiro [Osaka Prefecture Univ., Sakai, Osaka (Japan). Coll. of Integrated Arts and Sciences; Koyama, Shigeko; Takahashi, Masao; Kamada, Masao; Suzuki, Ryouichi

    1997-03-01

    Metallic Na was formed in NaCl single crystals with irradiation of a variety of radiation sources and analyzed the physical states with several methods. In the case of irradiation of 21 MeV electron pulses to the crystal blocks, the optical absorption and lifetime measurement of positron annihilation indicated appearance of Na clusters inside. Radiation effects of electron beam of 30 keV to the crystals in vacuum showed the appearance of not only metallic Na but atomic one during irradiation with Auger electron spectroscopy. Intense photon fluxes in vacuum ultraviolet region of synchrotron radiation were used as another source and an analyzing method of ultraviolet photoelectron spectroscopy. The results showed the metallic Na layered so thick that bulk plasmon can exist. (author)

  4. Ultrasound to stimulate early bone formation in a distraction gap : a double blind randomised clinical pilot trial in the edentulous mandible

    NARCIS (Netherlands)

    Schortinghuis, J; Bronckers, ALLJ; Stegenga, B; Raghoebar, GM; de Bont, LGM

    2005-01-01

    Objective: In a double blind randomised clinical pilot trial, it was investigated whether tow intensity pulsed ultrasound therapy stimulates early bone formation in a distraction gap created in a severely resorbed mandible. Design: Eight patients underwent a mandibular vertical distraction over an a

  5. Electron paramagnetic resonance and electron-nuclear double resonance study of the neutral copper acceptor in ZnGeP sub 2 crystals

    CERN Document Server

    Stevens, K T; Setzler, S D; Schünemann, P G; Pollak, T M

    2003-01-01

    Electron paramagnetic resonance (EPR) and electron-nuclear double resonance have been used to characterize the neutral copper acceptor in ZnGeP sub 2 crystals. The copper substitutes for zinc and behaves as a conventional acceptor (i.e. the 3d electrons do not play a dominant role). Because of a high degree of compensation from native donors, the copper acceptors in our samples were initially in the nonparamagnetic singly ionized state (Cu sub Z sub n sup -). The paramagnetic neutral state (Cu sub Z sub n sup 0) was observed when the crystals were exposed to 632.8 nm or 1064 nm laser light while being held at a temperature below 50 K. The g matrix of the neutral copper acceptor is axial g sub p sub a sub r = 2.049 and g sub p sub e sub r sub p = 2.030), with the unique principal direction parallel to the tetragonal c axis of the crystal. The hyperfine and nuclear quadrupole matrices also exhibit c-axis symmetry (A sub p sub a sub r = 87.6 MHz, A sub p sub e sub r sub p = 34.8 MHz and P = 0.87 MHz for sup 6 su...

  6. Crystal structure of human prion protein fragment reveals a motif for oligomer formation

    Science.gov (United States)

    Apostol, Marcin I.; Perry, Kay; Surewicz, Witold K.

    2013-01-01

    The structural transition of the prion protein from α-helical to β-sheet rich underlies its conversion into infectious and disease-associated isoforms. Here we describe the crystal structure of a fragment from human prion protein consisting of the disulfide bond linked portions of helices 2 and 3. Instead of forming a pair-of-sheets steric zipper structure characteristic of amyloid fibers, this fragment crystallized into an β-sheet rich assembly of hexameric oligomers. This study reveals a never before observed structural motif for ordered protein aggregates, and suggests a possible mechanism for self-propagation of misfolded conformations by such non-amyloid oligomers. PMID:23808589

  7. Crystal structure of a human prion protein fragment reveals a motif for oligomer formation.

    Science.gov (United States)

    Apostol, Marcin I; Perry, Kay; Surewicz, Witold K

    2013-07-17

    The structural transition of the prion protein from α-helical- to β-sheet-rich underlies its conversion into infectious and disease-associated isoforms. Here we describe the crystal structure of a fragment from human prion protein consisting of the disulfide-bond-linked portions of helices 2 and 3. Instead of forming a pair-of-sheets steric zipper structure characteristic of amyloid fibers, this fragment crystallized into a β-sheet-rich assembly of hexameric oligomers. This study reveals a never before observed structural motif for ordered protein aggregates and suggests a possible mechanism for self-propagation of misfolded conformations by such nonamyloid oligomers.

  8. Out-of-equilibrium processes in suspensions of oppositely charged colloids: liquid-to-crystal nucleation and gel formation

    Science.gov (United States)

    Sanz, Eduardo

    2009-03-01

    We study the kinetics of the liquid-to-crystal transformation and of gel formation in colloidal suspensions of oppositely charged particles. We analyse, by means of both computer simulations and experiments, the evolution of a fluid quenched to a state point of the phase diagram where the most stable state is either a homogeneous crystalline solid or a solid phase in contact with a dilute gas. On the one hand, at high temperatures and high packing fractions, close to an ordered-solid/disordered-solid coexistence line, we find that the fluid-to-crystal pathway does not follow the minimum free energy route. On the other hand, a quench to a state point far from the ordered-crystal/disordered-crystal coexistence border is followed by a fluid-to-solid transition through the minimum free energy pathway. At low temperatures and packing fractions we observe that the system undergoes a gas-liquid spinodal decomposition that, at some point, arrests giving rise to a gel-like structure. Both our simulations and experiments suggest that increasing the interaction range favors crystallization over vitrification in gel-like structures. [4pt] In collaboration with Chantal Valeriani, Soft Condensed Matter, Debye Institute for Nanomaterials Science, Utrecht University, Princetonplein 5, 3584 CC Utrecht, The Netherlands and SUPA, School of Physics, University of Edinburgh, JCMB King's Buildings, Mayfield Road, Edinburgh EH9 3JZ, UK; Teun Vissers, Andrea Fortini, Mirjam E. Leunissen, and Alfons van Blaaderen, Soft Condensed Matter, Debye Institute for Nanomaterials Science, Utrecht University; Daan Frenke, FOM Institute for Atomic and Molecular Physics, Kruislaan 407, 1098 SJ Amsterdam, The Netherlands and Department of Chemistry, University of Cambridge, Lensfield Road, CB2 1EW, Cambridge, UK; and Marjolein Dijkstra, Soft Condensed Matter, Debye Institute for Nanomaterials Science, Utrecht University.

  9. Evaluation of sulfated polysaccharides from the brown seaweed Dictyopteris justii as antioxidant agents and as inhibitors of the formation of calcium oxalate crystals.

    Science.gov (United States)

    Melo, Karoline Rachel Teodosio; Camara, Rafael Barros Gomes; Queiroz, Moacir Fernandes; Vidal, Arthur Anthunes Jacome; Lima, Camila Renata Machado; Melo-Silveira, Raniere Fagundes; Almeida-Lima, Jailma; Rocha, Hugo Alexandre Oliveira

    2013-11-25

    Oxalate crystals and other types of crystals are the cause of urolithiasis, and these are related to oxidative stress. The search for new compounds with antioxidant qualities and inhibitors of these crystal formations is therefore necessary. In this study, we extracted four sulfated polysaccharides, a fucoglucoxyloglucuronan (DJ-0.3v), a heterofucan (DJ-0.4v), and two glucans (DJ-0.5v and DJ-1.2v), from the marine alga Dictyopteris justii. The presence of sulfated polysaccharides was confirmed by chemical analysis and FT-IR. All the sulfated polysaccharides presented antioxidant activity under different conditions in some of the in vitro tests and inhibited the formation of calcium oxalate crystals. Fucan DJ-0.4v was the polysaccharide that showed the best antioxidant activity and was one of the best inhibitors of the crystallization of calcium oxalate. Glucan DJ-0.5v was the second most potent inhibitor of the formation of oxalate crystals, as it stabilized dehydrated oxalate crystals (less aggressive form), preventing them from transforming into monohydrate crystals (more aggressive form). The obtained data lead us to propose that these sulfated polysaccharides are promising agents for use in the treatment of urolithiasis.

  10. Evaluation of Sulfated Polysaccharides from the Brown Seaweed Dictyopteris Justii as Antioxidant Agents and as Inhibitors of the Formation of Calcium Oxalate Crystals

    Directory of Open Access Journals (Sweden)

    Karoline Rachel Teodosio Melo

    2013-11-01

    Full Text Available Oxalate crystals and other types of crystals are the cause of urolithiasis, and these are related to oxidative stress. The search for new compounds with antioxidant qualities and inhibitors of these crystal formations is therefore necessary. In this study, we extracted four sulfated polysaccharides, a fucoglucoxyloglucuronan (DJ-0.3v, a heterofucan (DJ-0.4v, and two glucans (DJ-0.5v and DJ-1.2v, from the marine alga Dictyopteris justii. The presence of sulfated polysaccharides was confirmed by chemical analysis and FT-IR. All the sulfated polysaccharides presented antioxidant activity under different conditions in some of the in vitro tests and inhibited the formation of calcium oxalate crystals. Fucan DJ-0.4v was the polysaccharide that showed the best antioxidant activity and was one of the best inhibitors of the crystallization of calcium oxalate. Glucan DJ-0.5v was the second most potent inhibitor of the formation of oxalate crystals, as it stabilized dehydrated oxalate crystals (less aggressive form, preventing them from transforming into monohydrate crystals (more aggressive form. The obtained data lead us to propose that these sulfated polysaccharides are promising agents for use in the treatment of urolithiasis.

  11. Subpicosecond pulse compression in nonlinear photonic crystal waveguides based on the formation of high-order optical solitons

    Institute of Scientific and Technical Information of China (English)

    Chen Xiong-Wen; Lin Xu-Sheng; Lan Sheng

    2005-01-01

    We investigate by numerical simulation the compression of subpicosecond pulses in two-dimensional nonlinear photonic crystal (PC) waveguides. The compression originates from the generation of high-order optical solitons through the interplay of the huge group-velocity dispersion and the enhanced self-phase modulation in nonlinear PC waveguides.Both the formation of Bragg grating solitons and gap solitons can lead to efficient pulse compression. The compression factors under different excitation power densities and the optimum length for subpicosecond pulse compression have been determined. As a compressor, the total length of the nonlinear PC waveguide is only ten micrometres and therefore can be easily incorporated into PC integrated circuits.

  12. Structure Formation of Ultrathin PEO Films at Solid Interfaces—Complex Pattern Formation by Dewetting and Crystallization.

    Science.gov (United States)

    Braun, Hans-Georg; Meyer, Evelyn

    2013-02-05

    The direct contact of ultrathin polymer films with a solid substrate may result in thin film rupture caused by dewetting. With crystallisable polymers such as polyethyleneoxide (PEO), molecular self-assembly into partial ordered lamella structures is studied as an additional source of pattern formation. Morphological features in ultrathin PEO films (thickness PEO molecules, n-alkylterminated (hydrophobic) PEO oligomers are investigated with respect to self-organization in ultrathin films. Morphological features characteristic for pure PEO are not changed by the presence of the n-alkylgroups.

  13. Formation of crystalline Zn-Al layered double hydroxide precipitates on γ-alumina: the role of mineral dissolution.

    Science.gov (United States)

    Li, Wei; Livi, Kenneth J T; Xu, Wenqian; Siebecker, Matthew G; Wang, Yujun; Phillips, Brian L; Sparks, Donald L

    2012-11-06

    To better understand the sequestration of toxic metals such as nickel (Ni), zinc (Zn), and cobalt (Co) as layered double hydroxide (LDH) phases in soils, we systematically examined the presence of Al and the role of mineral dissolution during Zn sorption/precipitation on γ-Al(2)O(3) (γ-alumina) at pH 7.5 using extended X-ray absorption fine structure spectroscopy (EXAFS), high-resolution transmission electron microscopy (HR-TEM), synchrotron-radiation powder X-ray diffraction (SR-XRD), and (27)Al solid-state NMR. The EXAFS analysis indicates the formation of Zn-Al LDH precipitates at Zn concentration ≥0.4 mM, and both HR-TEM and SR-XRD reveal that these precipitates are crystalline. These precipitates yield a small shoulder at δ(Al-27) = +12.5 ppm in the (27)Al solid-state NMR spectra, consistent with the mixed octahedral Al/Zn chemical environment in typical Zn-Al LDHs. The NMR analysis provides direct evidence for the existence of Al in the precipitates and the migration from the dissolution of γ-alumina substrate. To further address this issue, we compared the Zn sorption mechanism on a series of Al (hydr)oxides with similar chemical composition but differing dissolubility using EXAFS and TEM. These results suggest that, under the same experimental conditions, Zn-Al LDH precipitates formed on γ-alumina and corundum but not on less soluble minerals such as bayerite, boehmite, and gibbsite, which point outs that substrate mineral surface dissolution plays an important role in the formation of Zn-Al LDH precipitates.

  14. Supersmooth and modified surface of sapphire crystals: Formation, characterization, and applications in nanotechnologies

    Science.gov (United States)

    Muslimov, A. E.; Asadchikov, V. E.; Butashin, A. V.; Vlasov, V. P.; Deryabin, A. N.; Roshchin, B. S.; Sulyanov, S. N.; Kanevsky, V. M.

    2016-09-01

    The results of studying the state of the surface of sapphire crystals by a complex of methods in different stages of crystal treatment are considered by an example of preparing sapphire substrates with a supersmooth surface. The possibility of purposefully forming regular micro- and nanoreliefs and thin transition layers using thermal and thermochemical impacts are considered. The advantages of sapphire substrates with a modified surface for forming heteroepitaxial CdTe and ZnO semiconductor films and ordered ensembles of gold nanoparticles are described. The results of the experiments on the application of crystalline sapphire as a material for X-ray optical elements are reported. These elements include total external reflection mirrors and substrates for multilayer mirrors, output windows for synchrotron radiation, and monochromators working in the reflection geometry in X-ray spectrometers. In the latter case, the problems of the defect structure of bulk crystals sapphire and the choice of a method for growing sapphire crystals of the highest structural quality are considered.

  15. FORMATION (DECOMPOSITION) ENTHALPY CALCULATIONS FOR CRYSTAL LATTICES OF ALKALINE-EARTH FLUORIDES

    OpenAIRE

    Gruba, O.; Germanyuk, N.; Ryabukhin, A.

    2015-01-01

    A series of calculations of structural and thermochemical properties has been carried out for the alkaline-earth fluorides. The calculations have been carried out using the modified model of effective ionic radii and the model of enthalpy calculation for the crystal lattice. The results of the calculations are in accordance with the known experimental data within confidence intervals.

  16. Crystal Structure Formation of CH3NH3PbI3-xClx Perovskite

    Directory of Open Access Journals (Sweden)

    Shiqiang Luo

    2016-02-01

    Full Text Available Inorganic-organic hydride perovskites bring the hope for fabricating low-cost and large-scale solar cells. At the beginning of the research, two open questions were raised: the hysteresis effect and the role of chloride. The presence of chloride significantly improves the crystallization and charge transfer property of the perovskite. However, though the long held debate over of the existence of chloride in the perovskite seems to have now come to a conclusion, no prior work has been carried out focusing on the role of chloride on the electronic performance and the crystallization of the perovskite. Furthermore, current reports on the crystal structure of the perovskite are rather confusing. This article analyzes the role of chloride in CH3NH3PbI3-xClx on the crystal orientation and provides a new explanation about the (110-oriented growth of CH3NH3PbI3 and CH3NH3PbI3-xClx.

  17. Carboxy-terminal extension effects on crystal formation and insecticidal properties of Cry15Aa

    NARCIS (Netherlands)

    Naimov, S.; Valkova, R.; Dukjandiev, S.; Minkov, J.; Maagd, de R.A.

    2011-01-01

    Cry15Aa protein, produced by Bacillus thuringiensis serovar thompsoni HD542, in a crystal together with a 40 kDa accompanying protein, is one of a small group of non-typical, less well-studied members of the Cry family of insecticidal proteins, and may provide an alternative for the more commonly us

  18. Unsaturated Glycerophospholipids Mediate Heme Crystallization: Biological Implications for Hemozoin Formation in the Kissing Bug Rhodnius prolixus

    DEFF Research Database (Denmark)

    Stiebler, R.; Majerowicz, David; Knudsen, Jens

    2014-01-01

    Hemozoin (Hz) is a heme crystal produced by some blood-feeding organisms, as an efficient way to detoxify heme derived from hemoglobin digestion. In the triatomine insect Rhodnius prolixus, Hz is essentially produced by midgut extracellular phospholipid membranes known as perimicrovillar membrane...

  19. An Assessment of Engineered Calcium Oxalate Crystal Formation on Plant Growth and Development as a Step toward Evaluating Its Use to Enhance Plant Defense.

    Science.gov (United States)

    Nakata, Paul A

    2015-01-01

    The establishment of new approaches to control chewing insects has been sought not only for direct use in reducing crop loss but also in managing resistance to the pesticides already in use. Engineered formation of calcium oxalate crystals is a potential strategy that could be developed to fulfill both these needs. As a step toward this development, this study investigates the effects of transforming a non-calcium oxalate crystal accumulating plant, Arabidopsis thaliana, into a crystal accumulating plant. Calcium oxalate crystal accumulating A. thaliana lines were generated by ectopic expression of a single bacterial gene encoding an oxalic acid biosynthetic enzyme. Biochemical and cellular studies suggested that the engineered A. thaliana lines formed crystals of calcium oxalate in a manner similar to naturally occurring crystal accumulating plants. The amount of calcium oxalate accumulated in leaves also reached levels similar to those measured in the leaves of Medicago truncatula in which the crystals are known to play a defensive role. Visual inspection of the different engineered lines, however, suggested a phenotypic consequence on plant growth and development with higher calcium oxalate concentrations. The restoration of a near wild-type plant phenotype through an enzymatic reduction of tissue oxalate supported this observation. Overall, this study is a first to provide initial insight into the potential consequences of engineering calcium oxalate crystal formation in non-crystal accumulating plants.

  20. Double hexagonal close-packed structure revealed in a single colloidal crystal grain by Bragg rod analysis

    NARCIS (Netherlands)

    Meijer, J. M.; Shabalin, A.; Dronyak, R.; Yefanov, O. M.; Singer, A.; Kurta, R. P.; Lorenz, U.; Gorobstov, O.; Dzhigaev, D.; Gulden, J.; Byelov, D. V.; Zozulya, A. V.; Sprung, M.; Vartanyants, I. A.; Petukhov, Andrei V.

    2014-01-01

    A coherent X-ray diffraction study of a single colloidal crystal grain composed of silica spheres is reported. The diffraction data contain Bragg peaks and additional features in the form of Bragg rods, which are related to the stacking of the hexagonally close-packed layers. The profile of the Brag

  1. Polypropylene/Layered Double Hydroxide (LDH) Nanocomposites: Influence of LDH Particle Size on the Crystallization Behavior of Polypropylene.

    Science.gov (United States)

    Nagendra, Baku; Mohan, Kiran; Gowd, E Bhoje

    2015-06-17

    Highly dispersed isotactic polypropylene (iPP) nanocomposites were prepared by incorporating two different sized Mg-Al LDH nanoparticles with different loadings from 1 to 10 wt % using a modified solvent mixing method. Larger sized LDH nanoparticles (∼3-4 μm) were prepared from the gel form of Mg-Al LDH, and the smaller sized nanoparticles (∼50-200 nm) were prepared by sonication of as-synthesized LDH particles. Such obtained LDH nanoparticles were carefully characterized using wide-angle X-ray diffraction (WAXD), transmission electron microscopy, and scanning electron microscopy. WAXD and atomic force microscopy results indicate that the LDH nanoparticles were highly dispersed in the iPP matrix. The influence of LDH nanoparticles size and concentration on the thermal stability, spherulitic morphology, melting behavior, isothermal crystallization kinetics, and lamellar structure of iPP were investigated. Incorporation of low loadings of sonicated LDH particles (e.g., 1-2.5 wt %) show substantial effect on thermal stability, spherulite size, crystallinity, and crystallization half-time and lamellar morphology of iPP compared to the pure iPP and that of nanocomposites with larger LDH particles with same loadings. The better nucleation ability of iPP in the presence of sonicated LDH can be attributed to the high surface area of LDH nanoparticles along with its better dispersibility within the polymer matrix. The incorporation of LDH nanoparticles does not change the crystallization growth mechanism and crystal structure of iPP.

  2. On the electric double-layer structure at carbon electrode/organic electrolyte solution interface analyzed by ac impedance and electrochemical quartz-crystal microbalance responses

    Energy Technology Data Exchange (ETDEWEB)

    Kim, In-Tae; Egashira, Minato; Yoshimoto, Nobuko [Department of Applied Chemistry, Graduate School of Science and Engineering, Yamaguchi University, 2-16-1, Tokiwadai, Ube 755-8611 (Japan); Morita, Masayuki, E-mail: morita@yamaguchi-u.ac.jp [Department of Applied Chemistry, Graduate School of Science and Engineering, Yamaguchi University, 2-16-1, Tokiwadai, Ube 755-8611 (Japan)

    2011-08-30

    Highlights: {center_dot} We monitored resonance frequency change of smooth surface carbon electrode to determine mass changes during electrochemical polarization.{center_dot} This was done from viewpoints of ensuring the electric double-layer structure in organic electrolytes.{center_dot} Clear difference was observed in the mass changes among the electrolyte composition.{center_dot} It were related with differences in the double-layer capacitance at carbon. - Abstract: ac impedance and electrochemical quartz crystal microbalance (EQCM) techniques have been applied to analyze the structure of electric double-layer formed at carbon/organic electrolyte solution interface using a sputtered carbon electrode. The mass changes caused by electrochemical adsorption (accumulation) of ions have been estimated in the solutions of propylene carbonate (PC) dissolving tetrafluoroborate (BF{sub 4}{sup -}) salts of lithium (Li{sup +}), tetraethylammonium (TEA{sup +}) and tetra-n-butylammonium (TBA{sup +}) cations. The observed mass changes during the cathodic polarization in the solutions containing TEA{sup +} and TBA{sup +} were well consistent with those expected by the calculation based on mono-layer adsorption of the cations with giving the consideration to the surface roughness. On the other hand, the mass change observed in the solution containing Li{sup +} salt showed that the solvation of Li{sup +} with three or four molecules of PC would be the charge compensation species at the interface. Comparison of the quantity of the electricity passed during the EQCM measurements with that from theoretical calculation with simple Helmholtz-layer model revealed that the major part of the double-layer capacitance would be based on the electrostatic polarization of the solvent molecule directly adsorbed at the carbon surface.

  3. P2Y6 Receptor Antagonist MRS2578 Inhibits Neutrophil Activation and Aggregated Neutrophil Extracellular Trap Formation Induced by Gout-Associated Monosodium Urate Crystals.

    Science.gov (United States)

    Sil, Payel; Hayes, Craig P; Reaves, Barbara J; Breen, Patrick; Quinn, Shannon; Sokolove, Jeremy; Rada, Balázs

    2017-01-01

    Human neutrophils (polymorphonuclear leukocytes [PMNs]) generate inflammatory responses within the joints of gout patients upon encountering monosodium urate (MSU) crystals. Neutrophil extracellular traps (NETs) are found abundantly in the synovial fluid of gout patients. The detailed mechanism of MSU crystal-induced NET formation remains unknown. Our goal was to shed light on possible roles of purinergic signaling and neutrophil migration in mediating NET formation induced by MSU crystals. Interaction of human neutrophils with MSU crystals was evaluated by high-throughput live imaging using confocal microscopy. We quantitated NET levels in gout synovial fluid supernatants and detected enzymatically active neutrophil primary granule enzymes, myeloperoxidase, and human neutrophil elastase. Suramin and PPADS, general P2Y receptor blockers, and MRS2578, an inhibitor of the purinergic P2Y6 receptor, blocked NET formation triggered by MSU crystals. AR-C25118925XX (P2Y2 antagonist) did not inhibit MSU crystal-stimulated NET release. Live imaging of PMNs showed that MRS2578 represses neutrophil migration and blocked characteristic formation of MSU crystal-NET aggregates called aggregated NETs. Interestingly, the store-operated calcium entry channel inhibitor (SK&F96365) also reduced MSU crystal-induced NET release. Our results indicate that the P2Y6/store-operated calcium entry/IL-8 axis is involved in MSU crystal-induced aggregated NET formation, but MRS2578 could have additional effects affecting PMN migration. The work presented in the present study could lead to a better understanding of gouty joint inflammation and help improve the treatment and care of gout patients.

  4. Possibilities and limitations of synchrotron X-ray powder diffraction with double crystal and double multilayer monochromators for microscopic speciation studies

    Energy Technology Data Exchange (ETDEWEB)

    De Nolf, Wout [Department of Chemistry, University of Antwerp, Universiteitsplein 1, B-2610, Antwerpen (Wilrijk) (Belgium)], E-mail: wout.denolf@ua.ac.be; Jaroszewicz, Jakub [Department of Chemistry, University of Antwerp, Universiteitsplein 1, B-2610, Antwerpen (Wilrijk) (Belgium); Terzano, Roberto [Dipartimento di Biologia e Chimica Agro-forestale ed Ambientale, Via Amendola 165/A, I-70126, University of Bari, Bari (Italy); Lind, Ole Christian; Salbu, Brit [Isotope Laboratory, Norwegian University of Life Sciences, PO Box 5003, N-1432 As (Norway); Vekemans, Bart [Department of Analytical Chemistry, Ghent University, Krijgslaan 281 S12, B-9000 Gent (Belgium); Janssens, Koen [Department of Chemistry, University of Antwerp, Universiteitsplein 1, B-2610, Antwerpen (Wilrijk) (Belgium); Falkenberg, Gerald [HASYLAB at DESY, Beamline L, Notkestraat 85, D-22603, Hamburg (Germany)

    2009-08-15

    The performance of a combined microbeam X-ray fluorescence/X-ray powder diffraction (XRF/XRPD) measurement station at Hamburger Synchrotronstrahlungslabor (HASYLAB) Beamline L is discussed in comparison to that at European Synchrotron Radiation Facility (ESRF) ID18F/ID22. The angular resolution in the X-ray diffractograms is documented when different combinations of X-ray source, optics and X-ray diffraction detectors are employed. Typical angular resolution values in the range 0.3-0.5 deg. are obtained at the bending magnet source when a 'pink' beam form of excitation is employed. A similar setup at European Synchrotron Radiation Facility beamlines ID18F and ID22 allows to reach angular resolution values of 0.1-0.15 deg. In order to document the possibilities and limitations for speciation of metals in environmental materials by means of Hamburger Synchrotronstrahlungslabor Beamline L X-ray fluorescence/X-ray powder diffraction setup, two case studies are discussed, one involved in the identification of the crystal phases in which heavy metals such as chromium, iron, barium and lead are present in polluted soils of an industrial site (Val Basento, Italy) and another involved in the speciation of uranium in depleted uranium particles (Ceja Mountains, Kosovo). In the former case, the angular resolution is sufficient to allow identification of most crystalline phases present while in the latter case, it is necessary to dispose of an angular resolution of ca. 0.2 deg. to distinguish between different forms of oxidized uranium.

  5. Dynamics of the formation of laser-induced periodic surface structures (LIPSS) upon femtosecond two-color double-pulse irradiation of metals, semiconductors, and dielectrics

    Energy Technology Data Exchange (ETDEWEB)

    Höhm, S.; Herzlieb, M.; Rosenfeld, A. [Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie (MBI), Max-Born-Straße 2A, D-12489 Berlin (Germany); Krüger, J. [BAM Bundesanstalt für Materialforschung und –prüfung, Unter den Eichen 87, D-12205 Berlin (Germany); Bonse, J., E-mail: joern.bonse@bam.de [BAM Bundesanstalt für Materialforschung und –prüfung, Unter den Eichen 87, D-12205 Berlin (Germany)

    2016-06-30

    Graphical abstract: - Highlights: • LIPSS formation on Fused Silica, Silicon, and Titanium is studied upon parallel and cross-polarized two-color (400 and 800 nm) double-fs-pulse irradiation. • LIPSS orientation on Fused Silica follows the polarization of the first pulse. • LIPSS formation on Silicon and Titanium can be explained by a plasmonic model. - Abstract: In order to address the dynamics and physical mechanisms of LIPSS formation for three different classes of materials (metals, semiconductors, and dielectrics), two-color double-fs-pulse experiments were performed on Titanium, Silicon and Fused Silica. For that purpose a Mach–Zehnder interferometer generated polarization controlled (parallel or cross-polarized) double-pulse sequences at 400 nm and 800 nm wavelength, with inter-pulse delays up to a few picoseconds. Multiple of these two-color double-pulse sequences were collinearly focused by a spherical mirror to the sample surfaces. The fluence of each individual pulse (400 nm and 800 nm) was always kept below its respective ablation threshold and only the joint action of both pulses lead to the formation of LIPSS. Their resulting characteristics (periods, areas) were analyzed by scanning electron microscopy. The periods along with the LIPSS orientation allow a clear identification of the pulse which dominates the energy coupling to the material. For strong absorbing materials (Silicon, Titanium), a wavelength-dependent plasmonic mechanism can explain the delay-dependence of the LIPSS. In contrast, for dielectrics (Fused Silica) the first pulse always dominates the energy deposition and LIPSS orientation, supporting a non-plasmonic formation scenario. For all materials, these two-color experiments confirm the importance of the ultrafast energy deposition stage for LIPSS formation.

  6. Role of intermediary cells in Peltodon radicans (Lamiaceae in the transfer of calcium and formation of calcium oxalate crystals

    Directory of Open Access Journals (Sweden)

    Elder Antônio Sousa Paiva

    2005-01-01

    Full Text Available With the objective of studying the connection between calcium oxalate crystals formation and the phloem, fragments of leaves of Peltodon radicans Pohl (Lamiaceae were fixed and processed, for light and electron-transmission microscopes. It was observed that the crystals occurred in the cells of the bundle sheath, juxtaposed in relation to the phloem. Intermediary cells established a connection between the sieve element and crystal-bearing sheath cells. Calcium was present abundantly in the cytoplasm of sheath cells as calcium oxalate crystals. The presence of calcium was also detected in the intermediary cells, but in the sieve elements it was not detected. There was, therefore, an increasing concentration gradient of calcium in the sieve elements from sheath cells. Thus, we hypothesized that the formation of calcium oxalate crystals regulates calcium levels in the sieve elements.Com o objetivo de estudar a relação entre cristais de oxalato de cálcio e floema, fragmentos de folhas de Peltodon radicans foram fixados e processados, segundo métodos usuais, para estudos ao microscópio de luz e eletrônico de transmissão. Observou-se que os cristais ocorrem nas células da bainha do feixe, lateralmente em relação ao floema. Células intermediárias estabelecem conexão entre elemento crivado e células da bainha, portadoras de cristais, com crescimento intrusivo entre estas. Íons cálcio são abundantes no citoplasma das células da bainha que contém cristais de oxalato de cálcio. Nas células intermediárias a detecção ultra-citoquímica de cálcio também apresentou resultados positivos, enquanto nos elementos crivados a presença deste íon não foi constatada. Há, portanto, um gradiente crescente de concentração de cálcio dos elementos crivados para as células da bainha. Assim, formulamos a hipótese de que a formação de cristais de oxalato de cálcio tem, em P. radicans, o objetivo de controlar os níveis de cálcio citoss

  7. Self-catalytic crystal growth, formation mechanism, and optical properties of indium tin oxide nanostructures.

    Science.gov (United States)

    Liang, Yuan-Chang; Zhong, Hua

    2013-08-22

    In-Sn-O nanostructures with rectangular cross-sectional rod-like, sword-like, and bowling pin-like morphologies were successfully synthesized through self-catalytic growth. Mixed metallic In and Sn powders were used as source materials, and no catalyst layer was pre-coated on the substrates. The distance between the substrate and the source materials affected the size of the Sn-rich alloy particles during crystal growth in a quartz tube. This caused In-Sn-O nanostructures with various morphologies to form. An X-ray photoelectron spectroscope and a transmittance electron microscope with an energy-dispersive X-ray spectrometer were used to investigate the elemental binding states and compositions of the as-synthesized nanostructures. The Sn doping and oxygen vacancies in the In2O3 crystals corresponded to the blue-green and yellow-orange emission bands of the nanostructures, respectively.

  8. [Calcium carbide of different crystal formation synthesized by calcium carbide residue].

    Science.gov (United States)

    Lu, Zhong-yuan; Kang, Ming; Jiang, Cai-rong; Tu, Ming-jing

    2006-04-01

    To recycle calcium carbide residue effectively, calcium carbide of different crystal form, including global aragonite, calcite and acicular calcium carbide was synthesized. Both the influence of pretreatment in the purity of calcium carbide, and the influence of temperatures of carbonization reaction, release velocity of carbon dioxide in the apparition of calcium carbide of different crystal form were studied with DTA-TG and SEM. The result shows that calcium carbide residue can take place chemistry reaction with ammonia chlorinate straight. Under the condition that pH was above 7, the purity of calcium carbide was above 97%, and the whiteness was above 98. Once provided the different temperatures of carbonization reaction and the proper release velocity of carbon dioxide, global aragonite, calcite and acicular calcium carbide were obtained.

  9. Controlling ZIF-67 crystals formation through various cobalt sources in aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Xiangli [School of Chemistry and Chemical Engineering, Southeast University, Nanjing 211189 (China); Jiangsu Key Laboratory of Advanced Metallic Materials, Nanjing 211189 (China); Xing, Tiantian [School of Chemistry and Chemical Engineering, Southeast University, Nanjing 211189 (China); Lou, Yongbing [School of Chemistry and Chemical Engineering, Southeast University, Nanjing 211189 (China); Jiangsu Key Laboratory of Advanced Metallic Materials, Nanjing 211189 (China); Chen, Jinxi, E-mail: chenjinxi@seu.edu.cn [School of Chemistry and Chemical Engineering, Southeast University, Nanjing 211189 (China); Jiangsu Key Laboratory of Advanced Metallic Materials, Nanjing 211189 (China)

    2016-03-15

    Zeolitic imidazolate frameworks ZIF-67 were prepared under hydrothermal (120 °C) and non-hydrothermal (room temperature) from various cobalt sources and 2-methylimidazolate (Hmim) in aqueous solution within 30 min. The particle size and morphology were found to be related to the reactivity of the cobalt salt, Hmim/Co{sup 2+} molar ratios and experimental condition. Using Co(NO{sub 3}){sub 2} as cobalt source, small-sized ZIF-67 crystals with agglomeration were formed. For CoCl{sub 2}, small-sized rhombic dodecahedron were obtained. While large-sized crystals of rhombic dodecahedron structure were obtained from CoSO{sub 4} and Co(OAc){sub 2}. Under hydrothermal condition, the size of ZIF-67 crystals tended to be more uniform and the morphology were more regular comparing to non-hydrothermal condition. This study provides a simple way to control the size and morphology of ZIF-67 crystals prepared in aqueous solution. - Graphical abstract: Zeolitic imidazolate frameworks ZIF-67 were prepared under hydrothermal (120 °C) and non-hydrothermal (room temperature) from four different cobalt sources (Co(NO{sub 3}){sub 2}, CoCl{sub 2}, CoSO{sub 4} and Co(OAc){sub 2}) in aqueous solution within 30 min. The particle size and morphology were found to be related to the reactivity of the cobalt salt, Hmim/Co{sup 2+} molar ratios and experimental condition. - Highlights: • The particle size and morphology were determined by the reactivity of cobalt salt. • ZIF-67 could be prepared from CoSO{sub 4} and Co(OAc){sub 2} at Hmim/Co{sup 2+} molar ratio of 10. • Uniform and regular particles were obtained under hydrothermal condition.

  10. Crystal structure of the amyloid-β p3 fragment provides a model for oligomer formation in Alzheimer's disease.

    Science.gov (United States)

    Streltsov, Victor A; Varghese, Joseph N; Masters, Colin L; Nuttall, Stewart D

    2011-01-26

    Alzheimer's disease is a progressive neurodegenerative disorder associated with the presence of amyloid-β (Aβ) peptide fibrillar plaques in the brain. However, current evidence suggests that soluble nonfibrillar Aβ oligomers may be the major drivers of Aβ-mediated synaptic dysfunction. Structural information on these Aβ species has been very limited because of their noncrystalline and unstable nature. Here, we describe a crystal structure of amylogenic residues 18-41 of the Aβ peptide (equivalent to the p3 α/γ-secretase fragment of amyloid precursor protein) presented within the CDR3 loop region of a shark Ig new antigen receptor (IgNAR) single variable domain antibody. The predominant oligomeric species is a tightly associated Aβ dimer, with paired dimers forming a tetramer in the crystal caged within four IgNAR domains, preventing uncontrolled amyloid formation. Our structure correlates with independently observed features of small nonfibrillar Aβ oligomers and reveals conserved elements consistent with residues and motifs predicted as critical in Aβ folding and oligomerization, thus potentially providing a model system for nonfibrillar oligomer formation in Alzheimer's disease.

  11. Formation of Bragg Band Gaps in Anisotropic Phononic Crystals Analyzed With the Empty Lattice Model

    Directory of Open Access Journals (Sweden)

    Yan-Feng Wang

    2016-05-01

    Full Text Available Bragg band gaps of phononic crystals generally, but not always, open at Brillouin zone boundaries. The commonly accepted explanation stems from the empty lattice model: assuming a small material contrast between the constituents of the unit cell, avoided crossings in the phononic band structure appear at frequencies and wavenumbers corresponding to band intersections; for scalar waves the lowest intersections coincide with boundaries of the first Brillouin zone. However, if a phononic crystal contains elastically anisotropic materials, its overall symmetry is not dictated solely by the lattice symmetry. We construct an empty lattice model for phononic crystals made of isotropic and anisotropic materials, based on their slowness curves. We find that, in the anisotropic case, avoided crossings generally do not appear at the boundaries of traditionally defined Brillouin zones. Furthermore, the Bragg “planes” which give rise to phononic band gaps, are generally not flat planes but curved surfaces. The same is found to be the case for avoided crossings between shear (transverse and longitudinal bands in the isotropic case.

  12. The formation of organic (propolis films)/inorganic (layered crystals) interfaces for optoelectronic applications

    Science.gov (United States)

    Drapak, S. I.; Bakhtinov, A. P.; Gavrylyuk, S. V.; Kovalyuk, Z. D.; Lytvyn, O. S.

    2008-10-01

    Propolis (honeybee glue) organic films were prepared from an alcoholic solution on the surfaces of inorganic layered semiconductors (indium, gallium and bismuth selenides). Atomic force microscopy (AFM) and X-ray diffraction (XRD) are used to characterize structural properties of an organic/inorganic interfaces. It is shown that nanodimensional linear defects and nanodimensional cavities of various shapes are formed on the van der Waals (VDW) surfaces of layered crystals as a result of chemical interaction between the components of propolis (flavonoids, aminoacids and phenolic acids) and the VDW surfaces as well as deformation interaction between the VDW surfaces and propolis films during their polymerization. The nanocavities are formed as a result of the rupture of strong covalent bonds in the upper layers of layered crystals and have the shape of hexagons or triangles in the (0001) plane. The shape, lateral size and distribution of nanodimensional defects on the VDW surfaces depends on the type of crystals, the magnitude and distribution of surface stresses. We have obtained self-organized nanofold structures of propolis/InSe interface. It is established that such heterostructures have photosensitivity in the infrared range hνpropolis films at room temperature).

  13. Development of CaMoO{sub 4} crystal scintillators for a double beta decay experiment with {sup 100}Mo

    Energy Technology Data Exchange (ETDEWEB)

    Annenkov, A.N.; Buzanov, O.A. [Moscow Steel and Alloy Institute, 119049 Moscow (Russian Federation); Danevich, F.A. [Institute for Nuclear Research, MSP 03680 Kyiv (Ukraine)], E-mail: danevich@kinr.kiev.ua; Georgadze, A.Sh. [Institute for Nuclear Research, MSP 03680 Kyiv (Ukraine); Kim, S.K. [DMRC and School of Physics, Seoul National University, Seoul 151-742 (Korea, Republic of); Kim, H.J. [Physics Department, Kyungpook National University, Daegu 702-701 (Korea, Republic of); Kim, Y.D. [Sejong University, Seoul (Korea, Republic of); Kobychev, V.V. [Institute for Nuclear Research, MSP 03680 Kyiv (Ukraine); Kornoukhov, V.N. [Institute for Theoretical and Experimental Physics, 117218 Moscow (Russian Federation); Korzhik, M. [Institute for Nuclear Problems, 220030 Minsk (Belarus); Lee, J.I. [Sejong University, Seoul (Korea, Republic of); Missevitch, O. [Institute for Nuclear Problems, 220030 Minsk (Belarus); Mokina, V.M.; Nagorny, S.S.; Nikolaiko, A.S.; Poda, D.V.; Podviyanuk, R.B.; Sedlak, D.J.; Shkulkova, O.G. [Institute for Nuclear Research, MSP 03680 Kyiv (Ukraine); So, J.H. [Physics Department, Kyungpook National University, Daegu 702-701 (Korea, Republic of)] (and others)

    2008-01-11

    We have studied the energy resolution, {alpha}/{beta} ratio, temperature dependence of the scintillation properties, and the radioactive contamination of CaMoO{sub 4} crystal scintillators. We have also examined the use of pulse-shape discrimination to distinguish {gamma} rays and {alpha} particles. A high sensitivity experiment to search for the 0{nu}2{beta} decay of {sup 100}Mo using CaMoO{sub 4} scintillators is discussed.

  14. Investigation on quality of cubic GaN/GaAs (100) by double-crystal X-ray diffraction

    Institute of Scientific and Technical Information of China (English)

    徐大鹏; 王玉田; 杨辉; 郑联喜; 李建斌; 段俐宏; 吴荣汉

    1999-01-01

    Cubic GaN was grown on GaAs (100) by low pressure metal organic chemical vapor deposition (MOCVD). X-ray diffraction, scanning electron microscope (SEM) and photoluminescence (PL) spectra were performed to characterize the quality of the GaN film. The PL spectra of cubic GaN thin films being thicker than 1.5 μm were reported. Triple-crystal diffraction to analyze orientation distributions and strain of the thin films was also demonstrated.

  15. Effects of copper, iron and fluoride co-crystallized with sugar on caries development and acid formation in deslivated rats.

    Science.gov (United States)

    Rosalen, P L; Pearson, S K; Bowen, W H

    1996-11-01

    The purpose was to explore the effects of combinations of copper, iron and fluoride (Cu, Fe and F) incorporated in sucrose by co-crystallization on caries development in the deslivated rat model and to examine acid formation by bacteria in the rat mouth. Ninety-six Sprague-Dawley rats were infected with Streptococcus sobrinus 6715 and desalivated when aged 26 days. Eight groups were placed in a König-Höfer programmed feeder and received 17 meals daily at hourly intervals, and essential nutrition (NCP No. 2) by gavage twice daily for 21 days. The groups received (1) plain sucrose, (2) F (8 parts/10(6)) co-crystallized with sucrose, (3) Fe (88 parts/10(6)) sucrose, (4) Cu (75 parts/10(6)) sucrose, (5) Cu + F sucrose, (6) Cu + L Fe sucrose, (7) F + Fe sucrose, and (8) Cu + Fe + F sucrose. At death the jaws were removed and sonicated in 0.9% saline solution for microbial assessment. In addition, organic acid assays were performed for each animal. Keyes smooth-surface and sulcal caries scores were lowest in the Cu + Fe + F sucrose group, but not statistically significantly different from those of the other Cu groups. The numbers of Strep. sobrinus found in the groups that received Cu, Cu + Fe, Cu + F, F + Fe and Cu + Fe + F sugar were lower than in the control group. Lactic acid was found in lower concentrations in Fe, Cu, Cu + F, Cu + Fe and F + Fe groups than in the other groups. It appears that combinations of Cu; Fe and F co-crystallized with sugar may have an additive effect in reducing the cariogenic potential of sugar by affecting lactic acid formation and reducing bacterial colonization.

  16. The short range anion-H interaction is the driving force for crystal formation of ions in water.

    Science.gov (United States)

    Alejandre, José; Chapela, Gustavo A; Bresme, Fernando; Hansen, Jean-Pierre

    2009-05-07

    The crystal formation of NaCl in water is studied by extensive molecular dynamics simulations. Ionic solutions at room temperature and various concentrations are studied using the SPC/E and TIP4P/2005 water models and seven force fields of NaCl. Most force fields of pure NaCl fail to reproduce the experimental density of the crystal, and in solution some favor dissociation at saturated conditions, while others favor crystal formation at low concentration. A new force field of NaCl is proposed, which reproduces the experimental phase diagram in the solid, liquid, and vapor regions. This force field overestimates the solubility of NaCl in water at saturation conditions when used with standard Lorentz-Berthelot combining rules for the ion-water pair potentials. It is shown that precipitation of ions is driven by the short range interaction between Cl-H pairs, a term which is generally missing in the simulation of ionic solutions. The effects of intramolecular flexibility of water on the solubility of NaCl ions are analyzed and is found to be small compared to rigid models. A flexible water model, extending the rigid SPC/E, is proposed, which incorporates Lennard-Jones interactions centered on the hydrogen atoms. This force field gives liquid-vapor coexisting densities and surface tensions in better agreement with experimental data than the rigid SPC/E model. The Cl-H, Na-O, and Cl-O pair distribution functions of the rigid and flexible models agree well with experiment. The predicted concentration dependence of the electric conductivity is in fair agreement with available experimental data.

  17. Initial formation behaviour of polypyrrole on single crystal TiO2 through photo-electrochemical reaction.

    Science.gov (United States)

    Kawakita, Jin; Weitzel, Matthias

    2011-04-01

    Hybrid materials of the organic and inorganic semiconductors have a potential to show the better performance in the charge separation at the junction upon the photovoltaic action by the presence of the space charge layer in the inorganic semiconductor. In this study, the photo-anodic polymerization was selected as a fabrication method for the hybrid materials composed of TiO2 and polypyrrole on the basis of some advantages of this method. For the process control of the photo-anodic polymerization, it is important to elucidate the formation and growth mechanisms of the organic polymer. In this study, a flat sheet of single-crystal TiO2 was used as a well-defined surface for preparation of the organic polymer of pyrrole. Photo-anodic polarization behaviour was clarified and polypyrrole was prepared on TiO2. The formation process, especially the initial step was revealed by observation of polypyrrole with atomic force microscope (AFM) and statistical interpretation of the morphology of polypyrrole in the nano-scopic level. The formation process of polypyrrole on the TiO2 surface was summarized; (1) adsorption of precursors, (2) localized formation and growth of polypyrrole under the photo-illumination, and (3) homogenous growth of polypyrrole with the external current application under the photo-illumination.

  18. Crystal structure, electronic and magnetic properties of double perovskite Ba{sub 2}FeWO{sub 6}: A combined experimental–theoretical study

    Energy Technology Data Exchange (ETDEWEB)

    Musa Saad, H.-E., E-mail: musa.1964@gmail.com [Department of Physics, College of Science, Qassim University, P.O. 4466, Buraidah 51452 (Saudi Arabia); Rammeh, N. [Laboratoire de Physico-Chimie des Matériaux Minéraux et leurs Applications, Centre National de Recherches en Sciences des Matériaux, B. P. 95, Hammam-Lif 2050 (Tunisia)

    2016-01-15

    Double perovskite oxide Ba{sub 2}FeWO{sub 6} has been synthesized in polycrystalline form by the solid-state ceramic method at 950 °C. Structural characterization was performed by using the X-ray powder diffraction (XRD) and neutron powder diffraction (NPD) followed by Rietveld analysis of these patterns. The crystal structure of Ba{sub 2}FeWO{sub 6} is cubic; space group Fm-3m with lattice parameter of a=8.1351 Å. Also, a density functional theory (DFT) study of the crystal structure, electronic and magnetic properties of Ba{sub 2}FeWO{sub 6} has been carried out using full potential linear muffin-tin orbital (FP-LMTO). We showed that the obtained symmetry lattice parameter agree well with the experimental results. The influence of Fe element on the magnetic and electronic properties of double perovskite oxide Ba{sub 2}FeWO{sub 6} is analyzed. Band structure calculations for cubic Ba{sub 2}FeWO{sub 6} predict an energy-gap in both spin-up and spin-down. The semiconductor antiferromagnetic (AFM) phase is stabilized by the hybridization of nonmagnetic W{sup 6+} (5d°) site positioned in between the magnetic Fe{sup 2+} (3d{sup 6}) sites through the O{sup 2−} anions in a long range O–Fe–O–W–O arrangement. {sup 57}Fe Mössbaur spectrum and DFT calculations suggest that the AFM behavior arises since the mixed valence Fe{sup 2+}–Fe{sup 3+} effect introduces in Fe{sup 2+}–O{sup 2–}–W{sup 6+} anticoupling.

  19. Stability of mass transfer from massive giants: double black-hole binary formation and ultra-luminous X-ray sources

    CERN Document Server

    Pavlovskii, K; Belczynski, K; Van, K X

    2016-01-01

    The mass transfer in binaries with massive donors and compact companions, when the donors rapidly evolve after their main sequence, is one of the dominant formation channels of merging double stellar-mass black hole binaries. This mass transfer was previously postulated to be unstable and was expected to lead to a common envelope event. The common envelope event then would end with either double black hole formation, or with the merger of the two stars. We re-visit the stability of this mass transfer, and find that for a large range of the binary orbital separations this mass transfer is stable. This newly found stability allows us to reconcile the theoretical rate for double black hole binary mergers predicted by population synthesis studies, and the empirical rate obtained by LIGO. Futhermore, the stability of the mass transfer leads to the formation of ultra-luminous X-ray sources. The theoretically predicted formation rates of ultra-luminous X-ray sources powered by a stellar-mass BH, as well as the range...

  20. Dynamics of the formation of laser-induced periodic surface structures (LIPSS) upon femtosecond two-color double-pulse irradiation of metals, semiconductors, and dielectrics

    Science.gov (United States)

    Höhm, S.; Herzlieb, M.; Rosenfeld, A.; Krüger, J.; Bonse, J.

    2016-06-01

    In order to address the dynamics and physical mechanisms of LIPSS formation for three different classes of materials (metals, semiconductors, and dielectrics), two-color double-fs-pulse experiments were performed on Titanium, Silicon and Fused Silica. For that purpose a Mach-Zehnder interferometer generated polarization controlled (parallel or cross-polarized) double-pulse sequences at 400 nm and 800 nm wavelength, with inter-pulse delays up to a few picoseconds. Multiple of these two-color double-pulse sequences were collinearly focused by a spherical mirror to the sample surfaces. The fluence of each individual pulse (400 nm and 800 nm) was always kept below its respective ablation threshold and only the joint action of both pulses lead to the formation of LIPSS. Their resulting characteristics (periods, areas) were analyzed by scanning electron microscopy. The periods along with the LIPSS orientation allow a clear identification of the pulse which dominates the energy coupling to the material. For strong absorbing materials (Silicon, Titanium), a wavelength-dependent plasmonic mechanism can explain the delay-dependence of the LIPSS. In contrast, for dielectrics (Fused Silica) the first pulse always dominates the energy deposition and LIPSS orientation, supporting a non-plasmonic formation scenario. For all materials, these two-color experiments confirm the importance of the ultrafast energy deposition stage for LIPSS formation.

  1. Formation of interstitial-vacancy pairs by electronic excitation in pure ionic crystals

    Energy Technology Data Exchange (ETDEWEB)

    Itoh, Noriaki; Tanimura, Katsumi (Nagoya Univ. (Japan). Dept. of Physics)

    1990-01-01

    We review experiments and theories on defect formation induced by electronic excitation. Emphasis is placed on the microscopic mechanism of F-H pair formation in alkali halides and relevant phenomena in other systems such as alkaline earth fluorides, amorphous silicon dioxide and alkali halide surfaces. Dynamic and thermally-activated formation of the F-H pairs are discussed separately and it is pointed out that these two processes involve relaxation on different adiabatic potential surfaces. The mechanism of the temperature dependence is discussed in some detail. The significance of the value of S/D for the defect formation process in alkali halides, where S is the space between the halogen ion and D is the diameter of a halogen atom, is also discussed. Although understanding of the defect formation processes in systems other than alkali halides is not as deep as in alkali halides, the similarities and differences in the processes in alkali halides and other materials are discussed. Defect formation and sputtering of alkali halides are also compared. (author).

  2. High-resolution studies of double-layered ejecta craters: Morphology, inherent structure, and a phenomenological formation model

    Science.gov (United States)

    Wulf, Gerwin; Kenkmann, Thomas

    2015-02-01

    The ejecta blankets of impact craters in volatile-rich environments often possess characteristic layered ejecta morphologies. The so-called double-layered ejecta (DLE) craters are characterized by two ejecta layers with distinct morphologies. The analysis of high-resolution image data, especially HiRISE and CTX, provides new insights into the formation of DLE craters. A new phenomenological excavation and ejecta emplacement model for DLE craters is proposed based on a detailed case study of the Martian crater Steinheim—a well-preserved DLE crater—and studies of other DLE craters. The observations show that the outer ejecta layer is emplaced as medial and distal ejecta that propagate outwards in a debris avalanche or (if saturated with water) a debris flow mode after landing, overrunning previously formed secondary craters. In contrast, the inner ejecta layer is formed by a translational slide of the proximal ejecta deposits during the emplacement stage that overrun and superimpose parts of the outer ejecta layer. Based on our model, DLE craters on Mars are the result of an impact event into a rock/ice mixture that produces large amounts of shock-induced vaporization and melting of ground ice, leading to high ejection angles, proximal landing positions, and an ejecta curtain with relatively wet (in terms of water in liquid form) composition in the distal part versus dryer composition in the proximal part. As a consequence, basal melting of ice components in the ejecta at the transient crater rim, which is induced by frictional heating and the enhanced pressure at depth, initiates an outwards directed collapse of crater rim material in a translational slide mode. Our results indicate that similar processes may also be applicable for other planetary bodies with volatile-rich environments, such as Ganymede, Europa, and the Earth.

  3. Differential Roles of Peroxisome Proliferator-Activated Receptor-α and Receptor-γ on Renal Crystal Formation in Hyperoxaluric Rodents

    Directory of Open Access Journals (Sweden)

    Kazumi Taguchi

    2016-01-01

    Full Text Available Peroxisome proliferator-activated receptors (PPARs and related inflammatory and oxidative molecule expression were investigated in a hyperoxaluric rodent model to evaluate the in vivo efficacy of PPAR agonists in preventing renal crystal formation. PPAR expression was examined in a mouse hyperoxaluria kidney stone model induced by daily intra-abdominal glyoxylate injection. Therapeutic effects of the PPARα agonist fenofibrate and PPARγ agonist pioglitazone were also assessed in a 1% ethylene glycol-induced rat model of hyperoxaluria. Crystal formation, inflammation, cell injury, apoptosis, and oxidative stress were compared to those of vehicle-treated controls. Quantitative reverse transcription-polymerase chain reaction revealed that PPARα and PPARγ expression decrease and increase, respectively, during crystal formation in hyperoxaluric kidneys. In addition, PPARα localized to the cytoplasm of both proximal and distal tubular cells, whereas PPARγ accumulated in the nucleus of proximal tubular cells. Furthermore, renal crystal formation was significantly less prevalent in pioglitazone-treated rats but higher in the fenofibrate-treated and fenofibrate/pioglitazone-cotreated groups compared to controls, thus indicating that pioglitazone, but not fenofibrate, markedly decreased cell inflammation, oxidative stress, and apoptosis. Collectively, the results demonstrated that PPARγ suppressed renal crystal formation via its antioxidative and anti-inflammatory effects; however, the renotoxicity of PPARα may elicit the opposite effect.

  4. Formation of the Yandangshan volcanic-plutonic complex (SE China) by melt extraction and crystal accumulation

    Science.gov (United States)

    Yan, Li-Li; He, Zhen-Yu; Jahn, Bor-ming; Zhao, Zhi-Dan

    2016-12-01

    The association of volcanic and shallow plutonic rocks in caldera may provide important clues to the geochemical evolution of silicic magma systems. The Yandangshan caldera is a typical example of late Mesozoic volcanic-plutonic complex in SE China. It is composed of a series of rhyolitic extrusives and subvolcanic intrusions of porphyritic quartz syenites. In this work, we conducted petrological and geochemical studies, as well as zircon dating, on the coexisting volcanic and plutonic rocks from the Yandangshan caldera. The results of SHRIMP and LA-ICP-MS zircon U-Pb dating revealed that the crystallization of the rhyolitic extrusives and subvolcanic intrusions was contemporaneous within analytical errors and in a short period (104-98 Ma). Geochemically, the volcanic rocks are characterized by high Rb/Sr and Rb/Ba ratios and depletion in Ba, Sr, P, Eu and Ti, while the shallow plutons show high K, Ba, Al, Fe and low Rb/Sr and Rb/Ba ratios with insignificant negative Eu anomalies. The volcanic and plutonic rocks have a similar range of zircon Hf isotopic compositions (εHf(t) = - 10.0 to + 1.5) and TDM2 model ages of 2.10-1.23 Ga. They also have comparable whole-rock Sr and Nd isotopic compositions ((87Sr/86Sr)i = 0.7084-0.7090; εNd(t) = - 7.8 to - 6.5) and zircon oxygen isotopic compositions (δ18O mainly = 4.5 to 6.0‰). We argue that the volcanic-plutonic complex of the Yandangshan caldera was formed by reworking of Paleoproterozoic lower crusts in the eastern Cathaysia block, and that the complex could be linked by fractional crystallization and crystal accumulation in a shallow magma chamber. The volcanic rocks represent the highly fractionated end-member, whereas the subvolcanic intrusions of porphyritic quartz syenites could be the residual crystal mushes. This case study could have a general implication for the genetic relationship between volcanic and shallow plutonic rocks in calderas.

  5. Electric field induced domain formation in surface stabilized ferroelectric liquid crystal cells

    OpenAIRE

    Dierking, Ingo; Gießelmann, Frank; Schacht, Jochen; Zugenmaier, Peter

    1994-01-01

    Two types of domains have been observed for S sub(C) ferroelectric liquid crystals in surface stabilized cells (SSFLC) by application of a high electric field with the smectic layers tilted by the amount of the chevron angle with respect to the normal of the rubbing direction in the substrate plane. The layer structure resembles that of a chevron configuration in the plane of the substrate similar to the recently reported stripe-shaped SSFLC structure. The two domain types 'appear' to switch ...

  6. Enhanced shower formation in aligned thick germanium crystals and discrimination against charged hadrons

    Science.gov (United States)

    Baurichter, A.; Kirsebom, K.; Medewaldt, R.; Mikkelsen, U.; Møller, S.; Uggerhøj, E.; Worm, T.; Elsener, K.; Ballestrero, S.; Sona, P.; Romano, J.

    1995-11-01

    The distribution of the energy released in a thin silicon detector placed on the downstream side of a thick germanium single crystal bombarded with a 150 GeV electron or pion beam along directions close to the axis or along random directions has been investigated. In view of a possible application to very high energy gamma ray astronomy and particle physics, the intrinsic capability of such a device to reject, on the basis of energy discrimination, unwanted events due to charged hadrons together with the resulting loss of efficiency for the detection of showers initiated by high energy electrons, is determined as a function of the chosen energy threshold.

  7. Environmental scanning electron microscope (ESEM) evaluation of crystal and plaque formation associated with biocorrosion.

    Science.gov (United States)

    Geiger, S L; Ross, T J; Barton, L L

    1993-08-01

    The biofilm attributed to Desulfovibrio vulgaris growing in the presence of ferrous metals was examined with an environmental scanning electron microscope. This novel microscope produced images of iron sulfide colloids and other iron containing structures that had not been reported previously. A plaque composed of iron sulfide enveloped the surface of the corroding metal while crystals containing magnesium, iron, sulfur, and phosphorus were present in the culture where corrosion was in progress. A structure resembling the tubercule found in aerobic corrosion was observed on stainless steel undergoing biocorrosion and the elements present in this structure included sulfur, iron, chloride, calcium, potassium, and chromium.

  8. Ketoprofen sodium: preparation and its formation of mixed crystals with ketoprofen.

    Science.gov (United States)

    Hildebrand, G E; Müller-Goymann, C C

    1997-07-01

    A simple two-step process for the preparation of ketoprofen sodium was developed. The procedure involved dissolution of ketoprofen in ethanolic NaOH followed by evaporation of the solvent. The resulting amorphous solid was crystallized by controlled precipitation from 96% ethanol. The sodium salt proved to be stable for 4 years and its aqueous solutions for at least 1 year (investigated period). Ketoprofen sodium appears to be an alternative bulk form to ketoprofen acid for production of formulations after further characterization of the compound.

  9. Formation of H-type liquid crystal dimer at air-water interface

    Energy Technology Data Exchange (ETDEWEB)

    Karthik, C., E-mail: karthik.c@pilani.bits-pilani.ac.in; Gupta, Adbhut, E-mail: karthik.c@pilani.bits-pilani.ac.in; Joshi, Aditya, E-mail: karthik.c@pilani.bits-pilani.ac.in; Manjuladevi, V., E-mail: karthik.c@pilani.bits-pilani.ac.in; Gupta, Raj Kumar, E-mail: karthik.c@pilani.bits-pilani.ac.in [Department of Physics, Birla Institute of Technology and Science, Pilani, Rajasthan -333031 (India); Varia, Mahesh C.; Kumar, Sandeep [Raman Research Institute, Sadashivanagar, Bangalore - 560080 (India)

    2014-04-24

    We have formed the Langmuir monolayer of H-shaped Azo linked liquid crystal dimer molecule at the air-water interface. Isocycles of the molecule showed hysteresis suggesting the ir-reversible nature of the monolayer formed. The thin film deposited on the silicon wafer was characterized using Atomic Force Microscopy (AFM) and Field Emission Scanning Electron Microscopy (FESEM). The images showed uniform domains of the dimer molecule. We propose that these molecules tend to take book shelf configuration in the liquid phase.

  10. Inside and outside double poison in rhinosinusitis in the formation of meaning%"内外双毒"在鼻-鼻窦炎形成中的意义

    Institute of Scientific and Technical Information of China (English)

    刘敏; 张大铮; 张勤修

    2011-01-01

    张勤修教授从中西医结合的角度对鼻-鼻窦炎的发病机制进行了探讨.他认为"内外双毒互结"在鼻-鼻窦炎的形成中具有重要的意义,从而指出该病的治疗应从"解双毒"的角度进一步研究,以解除"双毒互结"的恶性循环,达到治疗的目的.%Tutor of combination of Chinese and western medicine Zhang Qinxiu professor from the perspective of thinosi nusitis the pathogenesis is discussed. He thinks "inside and outside double poison mutual tie" in thinosinusitis 's formation has an important meaning, thus pointed the treatment of the disease should "solution double poison" Angle, further studies to remove "double poison mutual tie" vicious circle, achieve the objective of treatment.

  11. Two novel CPs with double helical chains based rigid tripodal ligands: Syntheses, crystal structures, magnetic susceptibility and fluorescence properties

    Science.gov (United States)

    Wang, Xiao; Hou, Xiang-Yang; Zhai, Quan-Guo; Hu, Man-Cheng

    2016-11-01

    Two three-dimensional coordination polymers (CPs), namely [Cd(bpydb)- (H2bpydb)]n·0.5nH2O (1), and [Cu2(bpydb)2]n (2) (2,6-di-p-carboxyphenyl-4,4'- bipyridine1 = H2bpydb), containing a novel double-helical chains, which have been solvothermal synthesized, characterized, and structure determination. CPs 1-2 reveal the new (3,5)-net and (3,6)-net alb topology, respectively. The fluorescence properties of CPs 1-2 were investigated, and magnetic susceptibility measurements indicate that compound 1 has dominating antiferromagnetic couplings between metal ions.

  12. Crystal chemistry of M{sup II}M′{sup IV}(PO{sub 4}){sub 2} double monophosphates

    Energy Technology Data Exchange (ETDEWEB)

    Bregiroux, Damien, E-mail: damien.bregiroux@upmc.fr [Sorbonne Universités, UPMC Univ Paris 06, CNRS, Collège de France, Laboratoire de Chimie de la Matière Condensée de Paris, 11 place Marcelin Berthelot, 75005 Paris (France); Popa, Karin [“Al.I. Cuza” University, Department of Chemistry, 11-Carol I Blvd., 700506 Iasi (Romania); Wallez, Gilles [Institut de Recherche de Chimie Paris (IRCP), CNRS – Chimie ParisTech – Paris Sciences et Lettres PSL UMR8247, 11 rue Pierre et Marie Curie, 75005 Paris (France); Sorbonne Universités, UPMC Univ Paris 06 (France)

    2015-10-15

    M{sup II}M′{sup IV}(PO{sub 4}){sub 2} compounds have been extensively studied for several decades for their potential applications in the field of several domains such as matrices for actinides conditioning, phosphors etc. In this paper, the relationships between composition and crystal structure of these compounds are established. A review of the various processes used for the synthesis of these compounds is also proposed, as well as their most reported properties. M{sup II}M′{sup IV}(PO{sub 4}){sub 2} structures stem from two different archetypes: the cheralite and the yavapaiite structures, with some exceptions that are also described in this article. The ratio of the cations radii appears to be the most relevant parameter. The high ratio between the ionic radii of the divalent and tetravalent cations in yavapaiite derivates results in the ordering of these cations into well-differentiated polyhedra whereas cheralite is the only non-ordered structure encountered for M{sup II}M′{sup IV}(PO{sub 4}){sub 2} compounds. - Graphical abstract: In this paper, the relationships between composition and crystal structure of M{sup II}M′{sup IV}(PO{sub 4}){sub 2} compounds are established. A review of the various processes used for the synthesis of these compounds is also proposed, as well as their most reported properties. - Highlights: • Crystal structure–composition relationships of MIIM′IV(PO4)2 compounds. • Review of the various processes used for the synthesis of these compounds. • Their most reported properties are described and discussed.

  13. TEM monitoring of silver nanoparticles formation on the surface of lead crystal glass

    Energy Technology Data Exchange (ETDEWEB)

    Gil, C. [Fundacion Centro Nacional del Vidrio, Real Fabrica de Cristales, Po Pocillo, 1. 40100 La Granja de San Ildefonso, Segovia (Spain); Villegas, M.A. [Centro Nacional de Investigaciones Metalurgicas, CSIC, Avda. Gregorio del Amo, 8. 28040 Madrid (Spain)]. E-mail: mavillegas@cenim.csic.es; Navarro, J.M. Fernandez [Instituto de Optica Daza de Valdes, CSIC, C. Serrano, 121. 28006 Madrid (Spain)

    2006-12-15

    Silver nanoparticles have been formed on the surface of lead crystal glass by means of (i) ion-exchange of alkaline ions from the glass by Ag{sup +} ions from a molten salts bath, and (ii) silica based sol-gel coatings containing silver. All experimental variables concerning both ion-exchange process and sol-gel coatings application were combined and studied as main parameters governing the reduction of Ag{sup +} ions to Ag{sup 0} atoms and further aggregation to form nanosized colloids. The content of thermoreducing agents (arsenic or antimony oxides) in the lead crystal glass was essential to favour the reduction of silver ions to form nanoparticles. Optimal experimental conditions to be used for the obtaining of surface silver nanoparticles were determined. TEM was used as the principal characterisation technique for direct observation of the nanoparticles generated. The size of silver colloids varied in the 20-300 nm range for ion-exchanged samples and in the 10-80 nm range for sol-gel coated samples.

  14. [A study on the formation of apatite crystallized with gel method].

    Science.gov (United States)

    Endo, T; Amano, N; Yoshida, M; Murakami, H; Kosuge, N; Ohmi, Y; Kameda, A

    1989-10-01

    About apatite produced with a silicahydro gel method using calcium nitrate (group I) or calcium chloride (group II) and a gelatin gel method by use of calcium nitrate (group III) or calcium chloride (group IV), the formative volume as well as the formative condition of a periodic-layered precipitate (Liesegang ring), the pH measurement, calculation of Ca/P ratio, an estimation of the chlorine ion, morphological observation with a scanning electron microscope, qualitative analyses by X-ray diffraction (identification, crystallite size, lattice imperfections, lattice constants) and the composition analysis by infrared absorption spectroscopy were carried out to elucidate the formation of apatite using the gel method. The result showed that there were no distinct differences between group I-II and group III-IV, and it is suggested that it is possible to form satisfact fluorapatite with a gel method using calcium chloride as well as calcium nitrate.

  15. Formation and growth of crystal defects in directionally solidified multicrystalline silicon for solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Ryningen, Birgit

    2008-07-01

    Included in this thesis are five publications and one report. The common theme is characterisation of directionally solidified multicrystalline silicon for solar cells. Material characterisation of solar cell silicon is naturally closely linked to both the casting process and to the solar cell processing: Many of the material properties are determined by the casting process, and the solar cell processing will to some extend determine which properties will influence the solar cell performance. Solar grade silicon (SoG-Si) made by metallurgical refining route and supplied by Elkem Solar was directionally solidified and subsequently characterised, and a simple solar cell process was applied. Except from some metallic co-precipitates in the top of the ingot, no abnormalities were found, and it is suggested that within the limits of the tests performed in this thesis, the casting and the solar cell processing, rather than the assumed higher impurity content, was the limiting factor. It is suggested in this thesis that the main quality problem in multicrystalline silicon wafers is the existence of dislocation clusters covering large wafer areas. The clusters will reduce the effect of gettering and even if gettering could be performed successfully, the clusters will still reduce the minority carrier mobility and hence the solar cell performance. It has further been pointed out that ingots solidified under seemingly equal conditions might have a pronounced difference in minority carrier lifetime. Ingots with low minority carrier lifetime have high dislocation densities. The ingots with the substantially higher lifetime seem all to be dominated by twins. It is also found a link between a higher undercooling and the ingots dominated by twins. It is suggested that the two types of ingots are subject to different nucleation and crystal growth mechanisms: For the ingots dominated by dislocations, which are over represented, the crystal growth is randomly nucleated at the

  16. Dynamic Crystallization Experiments Using Conventional and Solar Furnace Techniques--implications For The Formation of Refractory Forsterite In Chondrites

    Science.gov (United States)

    Pack, A.; Sauerborn, M.; Klerner, S.; Palme, H.; Neumann, A.; Seboldt, W.

    A distinct generation of forsteritic olivine (Mg2SiO4) grains (RF) with unusually high concentrations of refractory components including CaO (0.7 wt.%), Al2O3 (0.4 wt.%), V, Sc, and REEs occurs in unequilibrated chondrites, including ordinary, carbonaceous, and the highly oxidized Rumurutiites. Contents of siderophile elements like FeO (1 wt.%), Ni, or Mn are extremly low in RF. It is inferred that formation of RF pre-dates the formation of chondrules and matrix as well as formation of the different types of parent bodies (CCs, OCs, oxidized R-chondrites). Hence, RF can help us to better understand the processes in the early stage of the solar system in the time between formation of CAIs and Si,Mg-chondrules. However, formation of RF is not well understood. Crystallization of RF in chon- drules requires chondrule melts with ca. 20 wt.% CaO. Most chondrules have typically <4 wt.% CaO (max. ca. 10 wt.% CaO). We have conducted dynamic crystallization experiments using a conventional furnace (1.5...1000 K·min-1) and the DLR solar furnace (approx. 100000 K·min-1) in order to test if rapid cooling of a chondrule- like melt would produce high CaO in RF. We demostrate that Ca-partitioning between olivine and silicate melt is only weakly influenced by rapid cooling even at extremly high cooling rates in the range of 105 K·min-1 as obtained in the solar furnace ex- periments. At a bulk composition of the starting melt of 7.5 wt.% CaO, no deviation from equilibrium fractionation was observed (T/t = 1.5 . . . 105 K·min-1). At a ol/melt bulk content of 17.5 wt.% CaO, in increase in DCa of approximately 10...20% was observed. Chondrules with CaO contents in the range of 10 wt.% (upper limit of CaO in chondrules) thus cannot be regarded to be the host of RF. Hence, there must have been an early generation of extremly CaO-rich chondrules (20 wt.% CaO). Alternatively, RF may have formed by other processes, e. g. direct condensation from the solar nebula.

  17. A Facile Method to Prepare Double-Layer Isoporous Hollow Fiber Membrane by In Situ Hydrogen Bond Formation in the Spinning Line.

    Science.gov (United States)

    Noor, Nazia; Koll, Joachim; Radjabian, Maryam; Abetz, Clarissa; Abetz, Volker

    2016-03-01

    A double-layer hollow fiber is fabricated where an isoporous surface of polystyrene-block-poly(4-vinylpyridine) is fixed on a support layer by co-extrusion. Due to the sulfonation of the support layer material, delamination of the two layers is suppressed without increasing the number of subsequent processing steps for isoporous composite membrane formation. Electron microscope-energy-dispersive X-ray spectroscopy images unveil the existence of a high sulfur concentration in the interfacial region by which in-process H-bond formation between the layers is evidenced. For the very first time, our study reports a facile method to fabricate a sturdy isoporous double-layer hollow fiber.

  18. Formation of laser-induced periodic surface structures on fused silica upon multiple cross-polarized double-femtosecond-laser-pulse irradiation sequences

    Energy Technology Data Exchange (ETDEWEB)

    Rohloff, M.; Das, S. K.; Hoehm, S.; Grunwald, R.; Rosenfeld, A. [Max-Born-Institut fuer Nichtlineare Optik und Kurzzeitspektroskopie (MBI), Max-Born-Strasse 2A, D-12489 Berlin (Germany); Krueger, J.; Bonse, J. [BAM Bundesanstalt fuer Materialforschung und -pruefung, Unter den Eichen 87, D-12205 Berlin (Germany)

    2011-07-01

    The formation of laser-induced periodic surface structures (LIPSS) upon irradiation of fused silica with multiple irradiation sequences consisting of five Ti:sapphire femtosecond (fs) laser pulse pairs (150 fs, 800 nm) is studied experimentally. A Michelson interferometer is used to generate near-equal-energy double-pulse sequences with a temporal pulse delay from -20 to +20 ps between the cross-polarized individual fs-laser pulses ({approx}0.2 ps resolution). The results of multiple double-pulse irradiation sequences are characterized by means of Scanning Electron and Scanning Force Microscopy. Specifically in the sub-ps delay domain striking differences in the surface morphologies can be observed, indicating the importance of the laser-induced free-electron plasma in the conduction band of the solids for the formation of LIPSS.

  19. Poly-β-hydroxybutyrate Metabolism Is Unrelated to the Sporulation and Parasporal Crystal Protein Formation in Bacillus thuringiensis

    Science.gov (United States)

    Wang, Xun; Li, Zhou; Li, Xin; Qian, Hongliang; Cai, Xia; Li, Xinfeng; He, Jin

    2016-01-01

    Poly-3-hydroxybutyrate (PHB) is a natural polymer synthesized by many bacteria as a carbon-energy storage material. It was accumulated maximally prior to the spore formation but was degraded during the process of sporulation in Bacillus thuringiensis. Intriguingly, B. thuringiensis also accumulates large amounts of insecticidal crystal proteins (ICPs) during sporulation, which requires considerable input of carbon and energy sources. How PHB accumulation affects sporulation and ICP formation remains unclear to date. Intuitively, one would imagine that accumulated PHB provides the energy required for ICP formation. Yet our current data indicate that this is not the case. First, growth curves of the deletion mutants of phaC (encoding the PHB synthase) and phaZ (encoding the PHB depolymerase) were found to be similar to the parent strain BMB171; no difference in growth rate could be observed. In addition we further constructed the cry1Ac10 ICP gene overexpression strains of BMB171 (BMB171-cry), as well as its phaC and phaZ deletion mutants ΔphaC-cry and ΔphaZ-cry to compare their spore and ICP production rates. Again, not much change of ICP production was observed among these strains either. In fact, PHB was still degraded in most ΔphaZ-cry cells as observed by transmission electron microscopy. Together these results indicated that there is no direct association between the PHB accumulation and the sporulation and ICP formation in B. thuringiensis. Some other enzymes for PHB degradation or other energy source may be responsible for the sporulation and/or ICP formation in B. thuringiensis. PMID:27379025

  20. Poly-β-hydroxybutyrate Metabolism Is Unrelated to the Sporulation and Parasporal Crystal Protein Formation in Bacillus thuringiensis.

    Science.gov (United States)

    Wang, Xun; Li, Zhou; Li, Xin; Qian, Hongliang; Cai, Xia; Li, Xinfeng; He, Jin

    2016-01-01

    Poly-3-hydroxybutyrate (PHB) is a natural polymer synthesized by many bacteria as a carbon-energy storage material. It was accumulated maximally prior to the spore formation but was degraded during the process of sporulation in Bacillus thuringiensis. Intriguingly, B. thuringiensis also accumulates large amounts of insecticidal crystal proteins (ICPs) during sporulation, which requires considerable input of carbon and energy sources. How PHB accumulation affects sporulation and ICP formation remains unclear to date. Intuitively, one would imagine that accumulated PHB provides the energy required for ICP formation. Yet our current data indicate that this is not the case. First, growth curves of the deletion mutants of phaC (encoding the PHB synthase) and phaZ (encoding the PHB depolymerase) were found to be similar to the parent strain BMB171; no difference in growth rate could be observed. In addition we further constructed the cry1Ac10 ICP gene overexpression strains of BMB171 (BMB171-cry), as well as its phaC and phaZ deletion mutants ΔphaC-cry and ΔphaZ-cry to compare their spore and ICP production rates. Again, not much change of ICP production was observed among these strains either. In fact, PHB was still degraded in most ΔphaZ-cry cells as observed by transmission electron microscopy. Together these results indicated that there is no direct association between the PHB accumulation and the sporulation and ICP formation in B. thuringiensis. Some other enzymes for PHB degradation or other energy source may be responsible for the sporulation and/or ICP formation in B. thuringiensis.

  1. Stress-induced formation mechanism of stacking fault tetrahedra in nano-cutting of single crystal copper

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Quanlong [School of Mechatronics Engineering, Harbin Institute of Technology, Harbin 150001 (China); Center for Precision Engineering, Harbin Institute of Technology, Harbin 150001 (China); Bai, Qingshun [School of Mechatronics Engineering, Harbin Institute of Technology, Harbin 150001 (China); Chen, Jiaxuan, E-mail: wangquanlong0@hit.edu.cn [Center for Precision Engineering, Harbin Institute of Technology, Harbin 150001 (China); Guo, Yongbo [Center for Precision Engineering, Harbin Institute of Technology, Harbin 150001 (China); Xie, Wenkun [School of Mechatronics Engineering, Harbin Institute of Technology, Harbin 150001 (China); Center for Precision Engineering, Harbin Institute of Technology, Harbin 150001 (China)

    2015-11-15

    Graphical abstract: In this paper, molecular dynamics simulation is performed to study the distribution of dislocation defects and local atomic crystal structure of single crystal copper. The stress distribution is investigated which is calculated by virial stress and analyzed by static pressure. The results are shown in (a)–(d). It is indicated that the compressive stress mainly spreads over the shear-slip zone, and the tensile stress is consisted in flank friction zone, shown in (a). The high tensile stress in subsurface is the source of stress, shown in (b). By the driven action of the stress source, the initial stair-rod dislocation nucleates. Then the dislocation climbs along four {1 1 1} planes under the stress driven action, shown in (d). Finally, the SFT is formed by the interaction of the compressive stress and the tensile stress which come from the shear-slip zone and friction zone, respectively. Besides, stair-rod dislocation, stacking faults and dislocation loop are also nucleated in the subsurface, shown in (c). Dislocation distribution, local atomic crystal structure state and stress-induced formation process of SFT by atomic. - Highlights: • A novel defect structure “stress-induced stacking fault tetrahedra” is revealed. • Atomic structural evolution and stress state distribution of the SFT are studied. • The stress-induced formation mechanism of the SFT is proposed. - Abstract: Stacking fault tetrahedra commonly existed in subsurface of deformed face center cubic metals, has great influence on machining precision and surface roughness in nano-cutting. Here we report, a stacking fault tetrahedra is formed in subsurface of workpiece during nano-cutting. The variation of cutting force and subsurface defects distribution are studied by using molecular dynamics simulation. The stress distribution is investigated which is calculated by virial stress and analyzed by static compression. The result shows that the cutting force has a rapidly

  2. TBAI-Catalyzed/Water-Assisted Double C-S Bond Formations: An Efficient Approach to Sulfides through Metal-Free Three-Component Reactions.

    Science.gov (United States)

    Chu, Xue-Qiang; Xu, Xiao-Ping; Ji, Shun-Jun

    2016-09-26

    An aqueous catalytic method for double C-S bond formations that involves alcohol derivatives, organic halides, and sodium thiosulfate has been developed. A diverse range of functionalized sulfides, including pharmaceutical and biological derivatives, can be obtained in an efficient and eco-friendly manner under air. The mechanistic studies revealed that this tetrabutylammonium-iodide-catalyzed/water-assisted reaction generated a mercaptan species as the key intermediate. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Process of negative-muon-induced formation of an ionized acceptor center ({sub μ}A){sup –} in crystals with the diamond structure

    Energy Technology Data Exchange (ETDEWEB)

    Belousov, Yu. M., E-mail: theorphys@phystech.edu [Moscow Institute of Physics and Technology (State University) (Russian Federation)

    2016-12-15

    The formation of an ionized acceptor center by a negative muon in crystals with the diamond structure is considered. The negative muon entering a target is captured by a nucleus, forming a muonic atom {sub μ}A coupled to a lattice. The appearing radiation-induced defect has a significant electric dipole moment because of the violation of the local symmetry of the lattice and changes the phonon spectrum of the crystal. The ionized acceptor center is formed owing to the capture of an electron interacting with the electric dipole moment of the defect and with the radiation of a deformation-induced local-mode phonon. Upper and lower bounds of the formation rate of the ionized acceptor center in diamond, silicon, and germanium crystals are estimated. It is shown that the kinetics of the formation of the acceptor center should be taken into account when processing μSR experimental data.

  4. Deterministic formation of interface states in some two-dimensional photonic crystals with conical dispersions

    CERN Document Server

    Huang, Xueqin; Zhang, Zhao-Qing; Chan, C T

    2014-01-01

    There is no assurance that interface states can be found at the boundary separating two materials. As a strong perturbation typically favors wave localization, it is natural to expect that an interface state should form more easily in the boundary that represents a strong perturbation. Here, we show on the contrary that in some two dimensional photonic crystals (PCs) with a square lattice possessing Dirac-like cone at k=0, a small perturbation guarantees the existence of interface states. More specifically, we find that single-mode localized states exist in a deterministic manner at an interface formed by two PCs each with system parameters slightly perturbed from the conical dispersion condition. The conical dispersion guarantees the existence of gaps in the projected band structure which allows interface states to form and the assured existence of interface states stems from the geometric phases of the bulk bands.

  5. Enhanced shower formation in aligned thick germanium crystals and discrimination against charged hadrons

    Energy Technology Data Exchange (ETDEWEB)

    Baurichter, A. [Aarhus Univ. (Denmark). Inst. for Synchrotron Radiat.; Kirsebom, K. [Aarhus Univ. (Denmark). Inst. for Synchrotron Radiat.; Medewaldt, R. [Aarhus Univ. (Denmark). Inst. for Synchrotron Radiat.; Mikkelsen, U. [Aarhus Univ. (Denmark). Inst. for Synchrotron Radiat.; Moeller, S. [Aarhus Univ. (Denmark). Inst. for Synchrotron Radiat.; Uggerhoej, E. [Aarhus Univ. (Denmark). Inst. for Synchrotron Radiat.; Worm, T. [Aarhus Univ. (Denmark). Inst. for Synchrotron Radiat.; Elsener, K. [European Organization for Nuclear Research, Geneva (Switzerland); Ballestrero, S. [Dipartimento di Fisica, University of Florence and INFN Sezione di Firenze, Largo E. Fermi 2, 50125 Florence (Italy); Sona, P. [Dipartimento di Fisica, University of Florence and INFN Sezione di Firenze, Largo E. Fermi 2, 50125 Florence (Italy); Romano, J. [Dipartimento di Fisica, University La Sapienza-Rome and INFN Sezione di Roma, P.le A. Moro 5, 00185 Rome (Italy)

    1995-11-01

    The distribution of the energy released in a thin silicon detector placed on the downstream side of a thick germanium single crystal bombarded with a 150 GeV electron or pion beam along directions close to the left angle 110 right angle axis or along random directions has been investigated. In view of a possible application to very high energy gamma ray astronomy and particle physics, the intrinsic capability of such a device to reject, on the basis of energy discrimination, unwanted events due to charged hadrons together with the resulting loss of efficiency for the detection of showers initiated by high energy electrons, is determined as a function of the chosen energy threshold. (orig.).

  6. Observation of nanostructured cluster formation of Tm ions in CaF{sub 2} crystals

    Energy Technology Data Exchange (ETDEWEB)

    Drazic, G.; Kobe, S. [Jozef Stefan Institute, Jamova 39, SI-1000 Ljubljana (Slovenia); Cefalas, A.C. [National Hellenic Research Foundation, TPCI, 48 Vassileos Constantinou Avenue, Athens 11635 (Greece)], E-mail: ccefalas@eie.gr; Sarantopoulou, E.; Kollia, Z. [National Hellenic Research Foundation, TPCI, 48 Vassileos Constantinou Avenue, Athens 11635 (Greece)

    2008-08-25

    Transmission electron microscopy, energy dispersive X-ray spectroscopy, and high-resolution scanning-transmission electron microscopy, with electron beam sizes ranging from 2 to 50 nm, were used to investigate the spatial distribution and homogeneity of doped Tm{sup 3+} ions in CaF{sub 2} host matrices with atomic resolution, in solid crystals grown from melts using the Bridgman-Stockbarger method. With the smallest size electron beam available of 2 nm, it was found that the Tm{sup 3+} ions were distributed inhomogeneously at the host sites. They took the form of sub-nm agglomerations of 3-5 atoms, rather than individual ions and the phase transition layer was 0.1 nm thick. The spatial extend of inhomogeneous Tm{sup 3+} concentration was 2.6-6 nm and originates from ionic density fluctuations in the liquid phase at the interface layer due to the local electrostatic field at the ionic sites.

  7. Formation of laser-induced periodic surface structures on fused silica upon multiple parallel polarized double-femtosecond-laser-pulse irradiation sequences

    Energy Technology Data Exchange (ETDEWEB)

    Rosenfeld, Arkadi, E-mail: rosenfeld@mbi-berlin.de [Max-Born-Institut fuer Nichtlineare Optik und Kurzzeitspektroskopie (MBI), Max-Born-Strasse 2A, D-12489 Berlin (Germany); Rohloff, Marcus; Hoehm, Sandra [Max-Born-Institut fuer Nichtlineare Optik und Kurzzeitspektroskopie (MBI), Max-Born-Strasse 2A, D-12489 Berlin (Germany); Krueger, Joerg [BAM Bundesanstalt fuer Materialforschung und -pruefung, Unter den Eichen 87, D-12205 Berlin (Germany); Bonse, Joern, E-mail: joern.bonse@bam.de [BAM Bundesanstalt fuer Materialforschung und -pruefung, Unter den Eichen 87, D-12205 Berlin (Germany)

    2012-09-15

    Highlights: Black-Right-Pointing-Pointer LIPSS formation studied for double-fs-pulses (160 fs, 800 nm) of different fluences. Black-Right-Pointing-Pointer Close to the damage threshold predominantly HSFL are observed. Black-Right-Pointing-Pointer The HSFL period remains almost constant {approx}375 nm (delay independent). Black-Right-Pointing-Pointer At high fluences and for short delays a transient metallic state is created (LSFL regime). Black-Right-Pointing-Pointer A transition of the LSFL period from 750 to 530 nm is observed in the sub-ps delay range. - Abstract: The formation of laser-induced periodic surface structures (LIPSS) upon irradiation of fused silica with multiple irradiation sequences of parallel polarized Ti:sapphire femtosecond laser pulse pairs (160 fs pulse duration, 800 nm central wavelength) was studied experimentally. For that purpose, a Michelson interferometer was used to generate near-equal-energy double-pulse sequences allowing the temporal pulse delay between the parallel-polarized individual fs-laser pulses to be varied between 0 and 40 ps with {approx}0.2 ps temporal resolution. The surface morphologies of the irradiated surface areas were characterized by means of scanning electron and scanning force microscopy. In the sub-ps delay range a strong decrease of the LIPSS periods and the ablation crater depths with the double-pulse delay was observed indicating the importance of the laser-induced free-electron plasma in the conduction band of the solids for the formation of LIPSS.

  8. Octamer formation in lysozyme solutions at the initial crystallization stage detected by small-angle neutron scattering.

    Science.gov (United States)

    Boikova, Anastasiia S; Dyakova, Yulia A; Ilina, Kseniia B; Konarev, Petr V; Kryukova, Alyona E; Kuklin, Alexandr I; Marchenkova, Margarita A; Nabatov, Boris V; Blagov, Alexandr E; Pisarevsky, Yurii V; Kovalchuk, Mikhail V

    2017-07-01

    Solutions of lysozyme in heavy water were studied by small-angle neutron scattering (SANS) at concentrations of 40, 20 and 10 mg ml(-1) with and without the addition of precipitant, and at temperatures of 10, 20 and 30°C. In addition to the expected protein monomers, dimeric and octameric species were identified in solutions at the maximum concentration and close to the optimal conditions for crystallization. An optimal temperature for octamer formation was identified and both deviation from this temperature and a reduction in protein concentration led to a significant decrease in the volume fractions of octamers detected. In the absence of precipitant, only monomers and a minor fraction of dimers are present in solution.

  9. Extensive ssDNA end formation at DNA double-strand breaks in non-homologous end-joining deficient cells during the S phase

    Directory of Open Access Journals (Sweden)

    Stenerlöw Bo

    2007-10-01

    Full Text Available Abstract Background Efficient and correct repair of DNA damage, especially DNA double-strand breaks, is critical for cellular survival. Defects in the DNA repair may lead to cell death or genomic instability and development of cancer. Non-homologous end-joining (NHEJ is the major repair pathway for DNA double-strand breaks in mammalian cells. The ability of other repair pathways, such as homologous recombination, to compensate for loss of NHEJ and the ways in which contributions of different pathways are regulated are far from fully understood. Results In this report we demonstrate that long single-stranded DNA (ssDNA ends are formed at radiation-induced DNA double-strand breaks in NHEJ deficient cells. At repair times ≥ 1 h, processing of unrejoined DNA double-strand breaks generated extensive ssDNA at the DNA ends in cells lacking the NHEJ protein complexes DNA-dependent protein kinase (DNA-PK or DNA Ligase IV/XRCC4. The ssDNA formation was cell cycle dependent, since no ssDNA ends were observed in G1-synchronized NHEJ deficient cells. Furthermore, in wild type cells irradiated in the presence of DNA-PKcs (catalytic subunit of DNA-PK inhibitors, or in DNA-PKcs deficient cells complemented with DNA-PKcs mutated in six autophosphorylation sites (ABCDE, no ssDNA was formed. The ssDNA generation also greatly influences DNA double-strand break quantification by pulsed-field gel electrophoresis, resulting in overestimation of the DNA double-strand break repair capability in NHEJ deficient cells when standard protocols for preparing naked DNA (i. e., lysis at 50°C are used. Conclusion We provide evidence that DNA Ligase IV/XRCC4 recruitment by DNA-PK to DNA double-strand breaks prevents the formation of long ssDNA ends at double-strand breaks during the S phase, indicating that NHEJ components may downregulate an alternative repair process where ssDNA ends are required.

  10. Kinetics of Schottky defect formation and annihilation in single crystal TlBr.

    Science.gov (United States)

    Bishop, Sean R; Tuller, Harry L; Kuhn, Melanie; Ciampi, Guido; Higgins, William; Shah, Kanai S

    2013-07-28

    The kinetics for Schottky defect (Tl and Br vacancy pair) formation and annihilation in ionically conducting TlBr are characterized through a temperature induced conductivity relaxation technique. Near room temperature, defect generation-annihilation was found to take on the order of hours before equilibrium was reached after a step change in temperature, and that mechanical damage imparted on the sample rapidly increases this rate. The rate limiting step to Schottky defect formation-annihilation is identified as being the migration of lower mobility Tl (versus Br), with an estimate for source-sink density derived from calculated diffusion lengths. This study represents one of the first investigations of Schottky defect generation-annihilation kinetics and demonstrates its utility in quantifying detrimental mechanical damage in radiation detector materials.

  11. AOT-microemulsions-based formation and evolution of PbWO$_{4}$ crystals

    CERN Document Server

    Chen, D; Tang Kai Bin; Liang Zhen Hua; Zheng Hua Gui

    2004-01-01

    Anionic surfactant-AOT-microemulsions-assisted formation and evolution of PbWO//4 nanostructures with bundles rodlike, ellipsoidlike, and spherelike prepared at different media conditions were studied by powder X-ray diffraction pattern, field emission scanning electron microscopy, and transmission electron microscopy. The possible mechanisms for the formation of PbWO//4 samples in series of microemulsion systems were discussed. Various comparison experiments show that several experimental parameters, such as the AOT concentration, the water content, and reaction temperature play important roles in the morphological control of PbWO//4 nanostructures. Room-temperature photoluminescence of PbWO//4 samples with different morphologies has also been investigated and the results reveal that all these samples showed similar features with emissions at 480 similar to 510 nm but different luminescence intensity. 40 Refs.

  12. Formation of Zn-rich phyllosilicate, Zn-layered double hydroxide and hydrozincite in contaminated calcareous soils

    Energy Technology Data Exchange (ETDEWEB)

    Jacquat, Olivier; Voegelin, Andreas; Villard, Andre; Marcus, Matthew A.; Kretzschmar, Ruben

    2007-10-15

    Recent studies demonstrated that Zn-phyllosilicate- and Zn-layered double hydroxide-type (Zn-LDH) precipitates may form in contaminated soils. However, the influence of soil properties and Zn content on the quantity and type of precipitate forming has not been studied in detail so far. In this work, we determined the speciation of Zn in six carbonate-rich surface soils (pH 6.2 to 7.5) contaminated by aqueous Zn in the runoff from galvanized power line towers (1322 to 30090 mg/kg Zn). Based on 12 bulk and 23 microfocused extended X-ray absorption fine structure (EXAFS) spectra, the number, type and proportion of Zn species were derived using principal component analysis, target testing, and linear combination fitting. Nearly pure Zn-rich phyllosilicate and Zn-LDH were identified at different locations within a single soil horizon, suggesting that the local availabilities of Al and Si controlled the type of precipitate forming. Hydrozincite was identified on the surfaces of limestone particles that were not in direct contact with the soil clay matrix. With increasing Zn loading of the soils, the percentage of precipitated Zn increased from {approx}20% to {approx}80%, while the precipitate type shifted from Zn-phyllosilicate and/or Zn-LDH at the lowest studied soil Zn contents over predominantly Zn-LDH at intermediate loadings to hydrozincite in extremely contaminated soils. These trends were in agreement with the solubility of Zn in equilibrium with these phases. Sequential extractions showed that large fractions of soil Zn ({approx}30% to {approx}80%) as well as of synthetic Zn-kerolite, Zn-LDH, and hydrozincite spiked into uncontaminated soil were readily extracted by 1 M NH{sub 4}NO{sub 3} followed by 1 M NH{sub 4}-acetate at pH 6.0. Even though the formation of Zn precipitates allows for the retention of Zn in excess to the adsorption capacity of calcareous soils, the long-term immobilization potential of these precipitates is limited.

  13. Formation of Cosmic Crystals in Highly-Supersaturated Silicate Vapor Produced by Planetesimal Bow Shocks

    CERN Document Server

    Miura, H; Yamamoto, T; Nakamoto, T; Yamada, J; Tsukamoto, K; Nozawa, J

    2010-01-01

    Several lines of evidence suggest that fine silicate crystals observed in primitive meteorite and interplanetary dust particles (IDPs) nucleated in a supersaturated silicate vapor followed by crystalline growth. We investigated evaporation of $\\mu$m-sized silicate particles heated by a bow shock produced by a planetesimal orbiting in the gas in the early solar nebula and condensation of crystalline silicate from the vapor thus produced. Our numerical simulation of shock-wave heating showed that these {\\mu}m-sized particles evaporated almost completely when the bow shock is strong enough to cause melting of chondrule precursor dust particles. We found that the silicate vapor cools very rapidly with expansion into the ambient unshocked nebular region; the cooling rate is estimated, for instance, to be as high as 2000 K s$^{-1}$ for a vapor heated by a bow shock associated with a planetesimal of radius 1 km. The rapid cooling of the vapor leads to nonequilibrium gas-phase condensation of dust at temperatures muc...

  14. Phosphate-intercalated Ca-Fe-layered double hydroxides: Crystal structure, bonding character, and release kinetics of phosphate

    Science.gov (United States)

    Woo, Myong A.; Woo Kim, Tae; Paek, Mi-Jeong; Ha, Hyung-Wook; Choy, Jin-Ho; Hwang, Seong-Ju

    2011-01-01

    The nitrate-form of Ca-Fe-layered double hydroxide (Ca-Fe-LDH) was synthesized via co-precipitation method, and its phosphate-intercalates were prepared by ion-exchange reaction. According to X-ray diffraction analysis, the Ca-Fe-LDH-NO 3- compound and its H 2PO 4--intercalate showed hexagonal layered structures, whereas the ion-exchange reaction with HPO 42- caused a frustration of the layer ordering of LDH. Fe K-edge X-ray absorption spectroscopy clearly demonstrated that the Ca-Fe-LDH lattice with trivalent iron ions was well-maintained after the ion-exchange with HPO 42- and H 2PO 4-. Under acidic conditions, phosphate ions were slowly released from the Ca-Fe-LDH lattice and the simultaneous release of hydroxide caused the neutralization of acidic media. Fitting analysis based on kinetic models indicated a heterogeneous diffusion process of phosphates and a distinct dependence of release rate on the charge of phosphates. This study strongly suggested that Ca-Fe-LDH is applicable as bifunctional vector for slow release of phosphate fertilizer and for the neutralization of acid soil.

  15. Molecular dynamics studies and quantification of the effect of chirality on the formation of liquid crystal mesophases

    Energy Technology Data Exchange (ETDEWEB)

    Solymosi, Miklos

    2002-07-01

    Results are presented from theoretical studies and from a series of molecular dynamics simulations undertaken to quantify the effect of chirality on the formation of liquid crystal mesophases. In the theoretical studies we have proposed a scaled chiral index with a formulation which allows comparison to be made between molecules comprising different numbers of atoms. We have undertaken chirality calculations utilizing the proposed scaled chiral index, G{sub 0S}, for one optimized static molecular geometry for a range of liquid crystal chiral dopants and ferroelectric liquid crystal molecules. The scaled chiral index, G{sub 0S}, allows a rapid calculation to be made of a pseudoscalar quantity which shows a good correlation with the helical twisting power of liquid crystal chiral dopants in a nematic liquid crystal solvent. This could prove a powerful aid in the design of novel dopant molecules where the dopant is rigid and the helical twisting is predominantly a steric effect. The same scaled chirality index, G{sub 0S}, calculation for ferroelectric liquid crystal molecules hints at an inverse correlation with spontaneous polarization agreeing with some experimental results. The scaled chiral index is a chemically useful index that can also be decomposed into atomic or functional group contributions, thereby creating a new measure of the asymmetric potential of functional groups and their different possible substitution positions. In the molecular dynamics simulation studies we have investigated two three-site Gay-Berne models, one chiral and the other achiral, each with a rotated central site forming a zigzag shape. In the chiral model one of the end site was additionally rotated out of the plane of the other two sites by a chiral angle {theta}{sub c}. Results from the achiral phase simulations support the theory that steric molecular shape can be associated with a driving force that leads to the smectic A - smectic C phase transition since such a transition was

  16. Growth and Characterization of Agar Gel Grown Brushite Crystals

    Directory of Open Access Journals (Sweden)

    V. B. Suryawanshi

    2014-01-01

    Full Text Available Brushite [CaHPO4·2H2O] or calcium hydrogen phosphate dihydrate (CHPD also known as urinary crystal is a stable form of calcium phosphate. The brushite crystals were grown by single and double diffusion techniques in agar-agar gel at room temperature. Effects of different growth parameters were discussed in single diffusion and double diffusion techniques. Good quality star, needle, platy, rectangular, and prismatic shaped crystals in single diffusion and nuclei with dendritic growth were obtained in double diffusion. These grown nuclei were characterized by scanning electron microscopy (SEM, Fourier transform infrared (FTIR spectroscopy, X-ray diffraction (XRD, and thermogravimetric analysis (TGA. SEM has shown the different morphologies of crystals; FTIR has confirmed the presence of functional groups; crystalline nature was supported by XRD, whereas the TGA indicates total 24.68% loss in weight and formation of stable calcium pyrophosphate (Ca2P2O7 at 500°C.

  17. Positive regulation of meiotic DNA double-strand break formation by activation of the DNA damage checkpoint kinase Mec1(ATR).

    Science.gov (United States)

    Gray, Stephen; Allison, Rachal M; Garcia, Valerie; Goldman, Alastair S H; Neale, Matthew J

    2013-07-31

    During meiosis, formation and repair of programmed DNA double-strand breaks (DSBs) create genetic exchange between homologous chromosomes-a process that is critical for reductional meiotic chromosome segregation and the production of genetically diverse sexually reproducing populations. Meiotic DSB formation is a complex process, requiring numerous proteins, of which Spo11 is the evolutionarily conserved catalytic subunit. Precisely how Spo11 and its accessory proteins function or are regulated is unclear. Here, we use Saccharomyces cerevisiae to reveal that meiotic DSB formation is modulated by the Mec1(ATR) branch of the DNA damage signalling cascade, promoting DSB formation when Spo11-mediated catalysis is compromised. Activation of the positive feedback pathway correlates with the formation of single-stranded DNA (ssDNA) recombination intermediates and activation of the downstream kinase, Mek1. We show that the requirement for checkpoint activation can be rescued by prolonging meiotic prophase by deleting the NDT80 transcription factor, and that even transient prophase arrest caused by Ndt80 depletion is sufficient to restore meiotic spore viability in checkpoint mutants. Our observations are unexpected given recent reports that the complementary kinase pathway Tel1(ATM) acts to inhibit DSB formation. We propose that such antagonistic regulation of DSB formation by Mec1 and Tel1 creates a regulatory mechanism, where the absolute frequency of DSBs is maintained at a level optimal for genetic exchange and efficient chromosome segregation.

  18. Picosecond laser-induced formation of spikes in a single crystal superalloy

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Wei [State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China); State Key Laboratory of Transient Optics and Photonics, Xi' an Institute of Optics and Precision Mechanics of Chinese Academy of Sciences, Xi' an Shaanxi 710119 (China); Cheng Guanghua [State Key Laboratory of Transient Optics and Photonics, Xi' an Institute of Optics and Precision Mechanics of Chinese Academy of Sciences, Xi' an Shaanxi 710119 (China); Feng Qiang, E-mail: qfeng@skl.ustb.edu.cn [State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China); National Center for Materials Service Safety, University of Science and Technology Beijing, Beijing 100083 (China); Cao Lamei [National Key Laboratory of Science and Technology on Advanced High Temperature Structural Materials, Beijing Institute of Aeronautical Materials, Beijing 100095 (China)

    2012-09-15

    Highlights: Black-Right-Pointing-Pointer Transition from ripples to spikes with pulse number. Black-Right-Pointing-Pointer Laser fluence has a significant effect on the spike separation. Black-Right-Pointing-Pointer Relationship between structures and their parametric dependence is established. Black-Right-Pointing-Pointer Capillary waves are responsible for the formation of spikes. - Abstract: The characteristics of laser-induced periodic surface structures (LIPSS) were investigated after laser irradiation with different pulse duration under a certain range of laser fluence (0.25 {<=} {Phi} {<=} 1.91 J/cm{sup 2}) and pulse number (11 {<=} N {<=} 560). Spikes were generated by picosecond laser irradiation in ambient air, in comparison with only periodic ripple structures introduced by nanosecond and femtosecond laser irradiation. Microstructural investigations indicate that these spikes were initiated by the fragment of periodic ripple ridges or corrugation on the smooth surface with subsequent pulses, and their separation increased with increasing the laser fluence. Surface capillary waves associated with the resolidification process can be employed to explain the formation of spikes by picosecond laser irradiation.

  19. Dynamic pattern formation of liquid crystals using binary self-assembled monolayers on an ITO surface under DC voltage.

    Science.gov (United States)

    Ishida, Takao; Oyama, Makiko; Terada, Kei-ichi; Haga, Masa-aki

    2014-12-07

    There have been numerous studies of liquid crystal (LC) convection using sandwich-type LC cells under AC voltage. In contrast to previous LC convection studies under AC voltage, we propose the use of a binary self-assembled monolayer (SAM) with a redox-active Ru complex and insulating octadecyl phosphonic acid (C18) molecules on an indium tin oxide (ITO) surface as the electrode of sandwich-type LC cells under DC bias voltage. This is because the functionalized molecules immobilized on the ITO surface are expected to control the LC orientation and electrical conduction of LC cells, under an exact DC bias voltage. We successfully achieved LC pattern formation using ITO electrodes with binary SAMs in LC cells. Moreover, we confirmed that the LC pattern size was increased by increasing the coverage of the Ru complex in binary SAMs. We consider that a combination of three factors, electrical conduction change, controlling of LC orientation in the initial stage and redox-activity of the Ru-complex, is the reason for LC convection although we cannot fully explain the distribution of these three factors. We believe that our LC pattern formation is promising for new type devices e.g., artificial compound eyes using the LC device technology.

  20. Photophysical Analysis of the Formation of Organic–Inorganic Trihalide Perovskite Films: Identification and Characterization of Crystal Nucleation and Growth

    Science.gov (United States)

    2016-01-01

    In this work we demonstrate that the different processes occurring during hybrid organic–inorganic lead iodide perovskite film formation can be identified and analyzed by a combined in situ analysis of their photophysical and structural properties. Our observations indicate that this approach permits unambiguously identifying the crystal nucleation and growth regimes that lead to the final material having a cubic crystallographic phase, which stabilizes to the well-known tetragonal phase upon cooling to room temperature. Strong correlation between the dynamic and static photoemission results and the temperature-dependent X-ray diffraction data allows us to provide a description and to establish an approximate time scale for each one of the stages and their evolution. The combined characterization approach herein explored yields key information about the kinetics of the process, such as the link between the evolution of the defect density during film formation, revealed by a fluctuating photoluminescence quantum yield, and the gradual changes observed in the PbI2-related precursor structure. PMID:26949439

  1. Basic building units, self-assembly and crystallization in the formation of complex inorganic open architectures

    Indian Academy of Sciences (India)

    C N R Rao

    2001-10-01

    Careful investigations of open-framework metal phosphates reveal that the formation of these complex architectures is likely to involve a process wherein one-dimensional ladders or chains, and possibly zero-dimens ional monomers, transform to higher dimensional structures. The one-dimensional ladder appears to be the primary building unit of these structures. At one stage of the building-up process, spontaneous self-assembly of a low-dimensional structure such as the ladder seems to occur, followed by crys tallization of a two- or three-dimensional structure. Accordingly, many of the higher dimensional structures retain the structural features of the 1D structure, indicating the occurrence of self-assembly. These findings mark the beginnings of our understan ding of complex supramolecular inorganic materials.

  2. Coke formation during the methanol-to-olefin conversion: in situ microspectroscopy on individual H-ZSM-5 crystals with different Brønsted acidity

    NARCIS (Netherlands)

    Mores, D.|info:eu-repo/dai/nl/314003401; Kornatowski, J.; Olsbye, U.; Weckhuysen, B.M.|info:eu-repo/dai/nl/285484397

    2011-01-01

    Coke formation during the methanol-to-olefin (MTO) conversion has been studied at the single-particle level with in situ UV/Vis and confocal fluorescence microscopy. For this purpose, large H-ZSM-5 crystals differing in their Si/Al molar ratio have been investigated. During MTO, performed at 623 and

  3. Adsorption and Formation of Small Na Clusters on Pristine and Double-Vacancy Graphene for Anodes of Na-Ion Batteries.

    Science.gov (United States)

    Liang, Zhicong; Fan, Xiaofeng; Zheng, Weitao; Singh, David J

    2017-05-24

    Layered carbon is a likely anode material for Na-ion batteries (NIBs). Graphitic carbon has a low capacity of approximately 35 (mA h)/g due to the formation of NaC64. Using first-principles methods including van der Waals interactions, we analyze the adsorption of Na ions and clusters on graphene in the context of anodes. The interaction between Na ions and graphene is found to be weak. Small Na clusters are not stable on the surface of pristine graphene in the electrochemical environment of NIBs. However, we find that Na ions and clusters can be stored effectively on defected graphene that has double vacancies. In addition, the adsorption energy of small Na clusters near a double vacancy is found to decrease with increasing cluster size. With high concentrations of vacancies the capacity of Na on defective graphene is found to be as much as 10-30 times higher than that of graphitic carbon.

  4. Influence of graded index materials on the photonic localization in one-dimensional quasiperiodic (Thue-Mosre and Double-Periodic) photonic crystals

    Science.gov (United States)

    Singh, Bipin K.; Pandey, Praveen C.

    2014-12-01

    In this paper, we present the investigation on the photonic localization and band gaps in quasi-periodic photonic crystals containing graded index materials using a transfer matrix method in region 150-750 THz of the electromagnetic spectrum. The graded layers have a space dispersive refractive index, which vary in a linear and exponential fashion as a function of the depth of layer. The considered quasiperiodic structures are taken in the form of Thue-Morse and Double-Periodic sequences. The grading profile in the layers affects the position of reflection dips and forbidden bands, and frequency region of the bands. We observed that vast number of forbidden band gaps and dips are developed in its reflection spectra by increasing the number of quasi-periodic generation. Moreover, we compare the total forbidden bandwidths with increasing the generation of the quasi-periodic sequences for the structures with linear and exponential graded layer. Results show that the different graded profiles with same boundary refractive index can change the position of localization modes, number of photonic bands and change the frequency region of the bands. Therefore, we can achieve suitable photonic band gaps and modes by choosing the different gradation profiles of the refractive index and generation of the quasi-periodic sequences.

  5. Fabrication of high-aspect-ratio double-slot photonic crystal waveguide in InP heterostructure by inductively coupled plasma etching using ultra-low pressure

    Directory of Open Access Journals (Sweden)

    Kaiyu Cui

    2013-02-01

    Full Text Available Double-slot photonic crystal waveguide (PCW in InP heterostructure is fabricated by inductively coupled plasma (ICP etching. Due to using an ultra-low pressure of 0.05 Pa, etch depths up to 3.5 μm for holes with diameter of 200 nm and 1.8 μm for slots of ∼40 nm are achieved, which indicate a record-high aspect-ratio, i.e. 45, for such narrow slots in InP heterostructure. Moreover, etching quality is evaluated based on both the transmission performance and the linewidth of micro-photoluminescence (μ-PL. In our measurement, a structure-dependent transmission-dip about 17 dB is obtained from a 17-μm-long W3 PCW, and a PL widening as small as 19 nm compared to the corresponding wafer is observed. These promising experimental results evidence the high etching quality realized in this work and confirm the feasibility of etching small-feature-size patterns by ICP technology for InP based devices in future mono-/hetero-integrated photonic circuits.

  6. Experimental and theoretical evaluation of the reactions leading to formation of internal double bonds in suspension PVC

    NARCIS (Netherlands)

    Purmova, Jindra; Pauwels, Kim F. D.; Agostini, Michela; Bruinsma, Maarten; Vorenkamp, Eltio J.; Schouten, Arend J.; Coote, Michelle L.

    2008-01-01

    The number of internal double bonds in poly(vinyl chloride) (PVC) samples was studied as a function of molecular weight at various monomer conversions. These defect structures were found to exhibit end-group-like characteristics: their concentration per chain was largely constant as a function of mo

  7. Formation of a solid solution between [N(C2H5)4][BF4] and [N(C2H5)4][PF6] in crystal and plastic crystal phases.

    Science.gov (United States)

    Matsumoto, Kazuhiko; Nonaka, Ryojun; Wang, Yushen; Veryasov, Gleb; Hagiwara, Rika

    2017-01-18

    The phase behavior of [N2222][BF4] and [N2222][PF6] (N2222(+) = tetraethylammonium cation) binary systems has been investigated in the present study. Differential scanning calorimetry revealed that the crystal-to-plastic-crystal transition temperature decreases upon mixing the two salts, with a minimum at x([N2222][PF6]) = 0.4, where x([N2222][PF6]) denotes the molar fraction of [N2222][PF6]. Powder X-ray diffraction analysis indicated the formation of a solid solution with a rock-salt type structure in the plastic crystal phase at all ratios and the lattice parameter a changes according to Vegard's law. In the crystal phase, two solid solution phases based on the structures of the single salts are observed. Raman spectroscopy confirmed the changes in the solid-solid transition temperature as observed by differential scanning calorimetry. Consequently, in the resulting phase diagram, the solid solution is formed in a wide x([N2222][PF6]) range for both the crystal and plastic crystal phases.

  8. High-Power Red Light Generation by Intra-Cavity Frequency-Doubling of a Side-Pumped Nd:YAG Laser in a LiB.3O5 Crystal

    Institute of Scientific and Technical Information of China (English)

    SUN Zhi-Pei; ZHANG Hong-Bo; CUI Da-Fu; XU Zu-Yan; LI Rui-Ning; BI Yong; YANG Xiao-Dong; BO Yong; HOU Wei; ZHANG Ying; WANG Gui-Ling; ZHAO Wu-Li

    2004-01-01

    We report the generation of high-power red light radiation of 11.2 W in a LiB3O5(LBO) crystal with intra-cavity frequency doubling of two compact and simple side-pumped Nd:YAG laser modules under a repetition rate of 3.5kHz. The pulse width of output is about 180 ± 20ns. The beam quality of the M2 value is 15 ± 3 in both the directions. This excellent laser performance demonstrates that the Nd:YAG laser with LBO intracavity frequency doubling is an promising method for generating red light with high brightness.

  9. Compact efficient Q-switched eye-safe laser at 1525 nm with a double-end diffusion-bonded Nd:YVO4 crystal as a self-Raman medium.

    Science.gov (United States)

    Chang, Y T; Su, K W; Chang, H L; Chen, Y F

    2009-03-16

    We report on an efficient Q-switched eye-safe laser at 1525 nm with a double-end diffusion-bonded Nd:YVO(4) crystal as a self-Raman gain medium. A diffusion-bonded crystal not only reduces the thermal effects but also increase the interaction length for the stimulated Raman scattering. With an input pump power of 17.2 W, average power of 2.23 W at the first- Stokes wavelength of 1525 nm is generated at a pulse repetition rate of 40 kHz, corresponding to a conversion efficiency of 13%.

  10. Polyoxometalate/Polyethylene Glycol Interactions in Water: From Nanoassemblies in Water to Crystal Formation by Electrostatic Screening.

    Science.gov (United States)

    Buchecker, Thomas; Le Goff, Xavier; Naskar, Bappaditya; Pfitzner, Arno; Diat, Olivier; Bauduin, Pierre

    2017-06-22

    In the last decade organic-inorganic hybrid materials have become essential in materials science as they combine properties of both building blocks. Nowadays the main routes for their synthesis involve electrostatic coupling, covalent grafting, and/or solvent effects. In this field, polyoxometalates (POMs) have emerged as interesting inorganic functional building blocks due to their outstanding properties. In the present work the well-known α-Keggin polyoxometalate, α-PW12 O40(3-) (PW), is shown to form hybrid crystalline materials with industrial (neutral) polyethylene glycol oligomers (PEG) under mild conditions, that is, in aqueous medium and at room temperature. The formation of these materials originates from the spontaneous self-assembly of PW with EOx , (EO=ethylene oxide) with at least four EO units (x>4). The PW-PEG nanoassemblies, made of a POM surrounded by about two PEG oligomers, are stabilized by electrostatic repulsions between the negatively charged PW anions. Addition of NaCl, aimed at screening the inter-nanoassembly repulsions, induces aggregation and formation of hybrid crystalline materials. Single-crystal analysis showed a high selectivity of PW towards EO5 -EO6 oligomers from PEG200, which is made of a mixture of EO3-8 . Therefore, a general "soft" route to produce POM-organic composites is proposed here through the control of electrostatic repulsions between spontaneously formed nanoassemblies in water. However, this rational design of new POM hybrid (crystalline) materials with hydrophilic blocks, using such a simple mixing procedure of the components, requires a deep understanding of the molecular interactions. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Comparison between Double Crystals X-ray Diffraction and Micro-Raman Measurement on Composition Determination of High Ge Content Si1-xGex Layer Epitaxied on Si Substrate

    Institute of Scientific and Technical Information of China (English)

    Lei ZHAO; Yuhua ZUO; Buwen CHENG; Jinzhong YU; Qiming WANG

    2006-01-01

    It is important to acquire the composition of Si1-xGex layer, especially that with high Ge content, epitaxied on Si substrate. Two nondestructive examination methods, double crystals X-ray diffraction(DCXRD)and micro-Raman measurement, were introduced comparatively to determine x value in Si1-xGex layer, which show that while the two methods are consistent with each other when x is low, the results obtained from double crystals X-ray diffraction are not credible due to the large strain relaxation occurring in Si1-xGex layers when Ge content is higher than about 20%. Micro-Raman measurement is more appropriate for determining high Ge content than DCXRD.

  12. Stable modification of PDMS surface properties by plasma polymerization: application to the formation of double emulsions in microfluidic systems.

    Science.gov (United States)

    Barbier, Valessa; Tatoulian, Michaël; Li, Hong; Arefi-Khonsari, Farzaneh; Ajdari, Armand; Tabeling, Patrick

    2006-06-06

    We describe a method based on plasma polymerization for the modification and control of the surface properties of poly(dimethylsiloxane) (PDMS) surfaces. By depositing plasma polymerized acrylic acid coatings on PDMS, we succeeded to fabricate stable (several days) hydrophilic and patterned hydrophobic/hydrophilic surfaces. We used this approach to generate direct and (for the first time in this material) double emulsions in PDMS microchannels.

  13. Formation of transgressive anorthosite seams in the Bushveld Complex via tectonically induced mobilisation of plagioclase-rich crystal mushes

    Institute of Scientific and Technical Information of China (English)

    Wolfgang D. Maier; Bartosz T. Karykowski; Sheng-Hong Yang

    2016-01-01

    The formation of anorthosites in layered intrusions has remained one of petrology’s most enduring enigmas. We have studied a sequence of layered chromitite, pyroxenite, norite and anorthosite overlying the UG2 chromitite in the Upper Critical Zone of the eastern Bushveld Complex at the Smokey Hills platinum mine. Layers show very strong medium to large scale lateral continuity, but abundant small scale irregularities and transgressive relationships. Particularly notable are irregular masses and seams of anorthosite that have intrusive relationships to their host rocks. An anorthosite layer locally transgresses several 10 s of metres into its footwall, forming what is referred to as a “pothole” in the Bushveld Complex. It is proposed that the anorthosites formed from plagioclase-rich crystal mushes that originally accumulated at or near the top of the cumulate pile. The slurries were mobilised during tectonism induced by chamber subsidence, a model that bears some similarity to that generally proposed for oceanic mass flows. The anorthosite slurries locally collapsed into pull-apart structures and injected their host rocks. The final step was down-dip drainage of Fe-rich intercumulus liquid, leaving behind anor-thosite adcumulates.

  14. Modeling of the pressure induced formation of a random network of a mixture of N2 and CO crystals

    Science.gov (United States)

    Batyrev, Iskander G.

    2017-01-01

    First principles calculations were performed to understand pressure induced transition to extended solid of substitutional mixtures of N2 and CO in crystalline delta phase. The transition occurs at ˜7-9 GPa and has a hysteresis allowing to stabilize covalently bonded random network down to much lower pressures. Only two atoms of N out of 24 were found to be incorporated in random network formed mainly by C and O atoms in 128 atom unit cell. Here, in search of a new route for the synthesis of poly-nitrogen materials, higher concentrations of N atoms (37.5%, 50%, and 90.625%) in delta molecular crystal phases under compression up to 50 GPa were calculated using density functional theory. Presence of CO is found to facilitate formation of the random network. To understand the importance of initial molecular crystalline structure the calculations were performed for the mixtures of N2 and CO in delta phases and at different sites with spherical and disk shaped disorder. Results calculated in linear response theory to obtain IR and Raman spectra are compared with recent experimental results.

  15. Spatially selective Er/Yb-doped CaF{sub 2} crystal formation by CO{sub 2} laser exposure

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Dong-Seon; Lee, Jin-Ho; Lim, Ki-Soo, E-mail: kslim@chungbuk.ac.kr

    2014-10-30

    Highlights: • Oxyfluoride glass–ceramics containing CaF{sub 2} nanocrystals doped with Er{sup 3+} and Yb{sup 3+} ions were formed on the glass surface by CO{sub 2} laser and a heat gun exposure. • Most of Er and Yb ions were distributed inside CaF{sub 2} nanocrystals and fluorine loss was observed in the EDS element maps. • IR-to-VIS upconversion emission efficiency of laser annealed glass ceramics was much increased and compared with that of the furnace-annealed glass ceramics. • Distributed volume of the glass ceramics were estimated by a confocal fluorescence microscope imaging. - Abstract: We report the glass–ceramic precipitation on the oxyfluoride glass surface by spatially selective annealing with a CO{sub 2} laser and a heat gun exposure. X-ray diffraction analysis showed the formation of major CaF{sub 2} and miner Ca{sub 2}SiO{sub 4} nanoparticles. We observed ∼100 nm nanoparticle aggregation by tunneling electron microscopy and element distribution in glass and crystal phases. Spatial distribution of glass ceramics near the glass surface was probed by confocal fluorescence microscope by using much enhanced emission from the Er ions in the laser-treated area. Strong emissions at 365 nm excitation and visible up-conversion emissions at 980 nm excitation also indicated well incorporation of Er and Yb ions into a crystalline environment.

  16. Spatially selective Er/Yb-doped CaF{sub 2} crystal formation by CO{sub 2} laser exposure

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Dong-Seon; Lee, Jin-Ho; Lim, Ki-Soo, E-mail: kslim@chungbuk.ac.kr

    2015-04-15

    Highlights: • Oxyfluoride glass–ceramics containing CaF{sub 2} nanocrystals doped with Er{sup 3+} and Yb{sup 3+} ions were formed on the glass surface by CO{sub 2} laser and a heat gun exposure. • Most of Er and Yb ions were distributed inside CaF{sub 2} nanocrystals and fluorine loss was observed in the EDS element maps. • IR-to-VIS upconversion emission efficiency of laser annealed glass ceramics was much increased and compared with that of the furnace-annealed glass ceramics. • Distributed volume of the glass ceramics were estimated by a confocal fluorescence microscope imaging. - Abstract: We report the glass–ceramic precipitation on the oxyfluoride glass surface by spatially selective annealing with a CO{sub 2} laser and a heat gun exposure. X-ray diffraction analysis showed the formation of major CaF{sub 2} and miner Ca{sub 2}SiO{sub 4} nanoparticles. We observed ∼100 nm nanoparticle aggregation by tunneling electron microscopy and element distribution in glass and crystal phases. Spatial distribution of glass ceramics near the glass surface was probed by confocal fluorescence microscope by using much enhanced emission from the Er ions in the laser-treated area. Strong emissions at 365 nm excitation and visible up-conversion emissions at 980 nm excitation also indicated well incorporation of Er and Yb ions into a crystalline environment.

  17. Experimental verification of the model for formation of double Shockley stacking faults in highly doped regions of PVT-grown 4H–SiC wafers

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Yu; Guo, Jianqiu; Goue, Ouloide; Raghothamachar, Balaji; Dudley, Michael; Chung, Gil; Sanchez, Edward; Quast, Jeff; Manning, Ian; Hansen, Darren

    2016-10-01

    Recently, we reported on the formation of overlapping rhombus-shaped stacking faults from scratches left over by the chemical mechanical polishing during high temperature annealing of PVT-grown 4H–SiC wafer. These stacking faults are restricted to regions with high N-doped areas of the wafer. The type of these stacking faults were determined to be Shockley stacking faults by analyzing the behavior of their area contrast using synchrotron white beam X-ray topography studies. A model was proposed to explain the formation mechanism of the rhombus shaped stacking faults based on double Shockley fault nucleation and propagation. In this paper, we have experimentally verified this model by characterizing the configuration of the bounding partials of the stacking faults on both surfaces using synchrotron topography in back reflection geometry. As predicted by the model, on both the Si and C faces, the leading partials bounding the rhombus-shaped stacking faults are 30° Si-core and the trailing partials are 30° C-core. Finally, using high resolution transmission electron microscopy, we have verified that the enclosed stacking fault is a double Shockley type.

  18. Synthesis, double-helix formation, and higher-assembly formation of chiral polycyclic aromatic compounds: conceptual development of polyketide aldol synthesis.

    Science.gov (United States)

    Yamaguchi, Masahiko; Shigeno, Masanori; Saito, Nozomi; Yamamoto, Koji

    2014-02-01

    Polycyclic aromatic compounds are an important group of substances in chemistry, and the study of their properties is a subject of interest in the development of drugs and materials. We have been conducting studies to develop chiral polycyclic aromatic compounds, i.e., helicenes and equatorenes. These helical molecules showed notable aggregate-forming properties and the capability for chiral recognition exerted by noncovalent bond interactions, which were not observed in compounds with central chirality. Homo- and hetero-double-helix-forming helicene oligomers were developed, and the latter self-assembled to form gels and vesicles. In this article, we describe such hierarchical studies of polycyclic aromatic compounds, which were started from polyketide aldol synthesis.

  19. Formation and Characterization of Mixed Crystals Based on Bis (Thiourea)Cadmium Chloride and Bis (Thiourea)Cadmium Iodide

    OpenAIRE

    2014-01-01

    Bis(thiourea)cadmium chloride(BTCC) and bis(thiourea)cadmium iodide (BTCI) are metal complexes of thiourea having better nonlinear optical properties than KH2PO4. An attempt has been made in the present study to form mixed crystals based on BTCC and BTCI (even though their crystal lattices mismatch) from aqueous solutions, the precursors mixed in proper proportions. A total of seven (including the end members) crystals were formed by the free evaporation method and characteriz...

  20. Formats

    Directory of Open Access Journals (Sweden)

    Gehmann, Ulrich

    2012-03-01

    Full Text Available In the following, a new conceptual framework for investigating nowadays’ “technical” phenomena shall be introduced, that of formats. The thesis is that processes of formatting account for our recent conditions of life, and will do so in the very next future. It are processes whose foundations have been laid in modernity and which will further unfold for the time being. These processes are embedded in the format of the value chain, a circumstance making them resilient to change. In addition, they are resilient in themselves since forming interconnected systems of reciprocal causal circuits.Which leads to an overall situation that our entire “Lebenswelt” became formatted to an extent we don’t fully realize, even influencing our very percep-tion of it.

  1. Designed Formation of Co₃O₄/NiCo₂O₄ Double-Shelled Nanocages with Enhanced Pseudocapacitive and Electrocatalytic Properties.

    Science.gov (United States)

    Hu, Han; Guan, Buyuan; Xia, Baoyu; Lou, Xiong Wen David

    2015-04-29

    Hollow structures with high complexity in shell architecture and composition have attracted tremendous interest because of their great importance for both fundamental studies and practical applications. Herein we report the designed synthesis of novel box-in-box nanocages (NCs) with different shell compositions, namely, Co3O4/NiCo2O4 double-shelled nanocages (DSNCs). Uniform zeolitic imidazolate framework-67/Ni-Co layered double hydroxides yolk-shelled structures are first synthesized and then transformed into Co3O4/NiCo2O4 DSNCs by thermal annealing in air. Importantly, this strategy can be easily extended to prepare other complex DSNCs. When evaluated as electrodes for pseudocapacitors, the Co3O4/NiCo2O4 DSNCs show a high specific capacitance of 972 F g(-1) at a current density of 5 A g(-1) and excellent stability with 92.5% capacitance retention after 12 000 cycles, superior to that of Co3O4 NCs with simple configuration and Co3O4/Co3O4 DSNCs. Besides, the Co3O4/NiCo2O4 DSNCs also exhibit much better electrocatalytic activity for the oxygen evolution reaction than Co3O4 NCs. The greatly improved electrochemical performance of Co3O4/NiCo2O4 DSNCs demonstrates the importance of rational design and synthesis of hollow structures with higher complexity.

  2. Theoretical and computational comparison of models for dislocation dissociation and stacking fault/core formation in fcc crystals

    Science.gov (United States)

    Mianroodi, J. R.; Hunter, A.; Beyerlein, I. J.; Svendsen, B.

    2016-10-01

    The purpose of the current work is the theoretical and computational comparison of selected models for the energetics of dislocation dissociation resulting in stacking fault and partial dislocation (core) formation in fcc crystals as based on the (generalized) Peierls-Nabarro (GPN: e.g., Xiang et al., 2008; Shen et al., 2014), and phase-field (PF: e.g., Shen and Wang, 2004; Hunter et al., 2011, 2013; Mianroodi and Svendsen, 2015), methodologies (e.g., Wang and Li, 2010). More specifically, in the current work, the GPN-based model of Xiang et al. (2008) is compared theoretically with the PF-based models of Shen and Wang (2004), Hunter et al. (2011, 2013), and Mianroodi and Svendsen (2015). This is carried out here with the help of a unified formulation for these models via a generalization of the approach of Cahn and Hilliard (1958) to mechanics. Differences among these include the model forms for the free energy density ψela of the lattice and the free energy density ψsli associated with dislocation slip. In the PF-based models, for example, ψela is formulated with respect to the residual distortion HR due to dislocation slip (e.g., Khachaturyan, 1983; Mura, 1987), and with respect to the dislocation tensor curl HR in the GPN model (e.g., Xiang et al., 2008). As shown here, both model forms for ψela are in fact mathematically equal and so physically equivalent. On the other hand, model forms for ψsli differ in the assumed dependence on the phase or disregistry fields ϕ, whose spatial variation represents the transition from unslipped to slipped regions in the crystal. In particular, Xiang et al. (2008) and Hunter et al. (2011, 2013) work with ψsli(ϕ). On the other hand, Shen and Wang (2004) and Mianroodi and Svendsen (2015) employ ψsli(ϕ , ∇ ϕ). To investigate the consequences of these differences for the modeling of the dislocation core, dissociation, and stacking fault formation, predictions from the models of Hunter et al. (2011, 2013) and Mianroodi

  3. Effects of micro electric current load during cooling of plant tissues on intracellular ice crystal formation behavior and pH.

    Science.gov (United States)

    Ninagawa, Takako; Kawamura, Yukio; Konishi, Tadashi; Narumi, Akira

    2016-08-01

    Cryopreservation techniques are expected to evolve further to preserve biomaterials and foods in a fresh state for extended periods of time. Long-term cryopreservation of living materials such as food and biological tissue is generally achieved by freezing; thus, intracellular freezing occurs. Intracellular freezing injures the cells and leads to cell death. Therefore, a dream cryopreservation technique would preserve the living materials without internal ice crystal formation at a temperature low enough to prevent bacterial activity. This study was performed to investigate the effect of micro electrical current loading during cooling as a new cryopreservation technique. The behavior of intracellular ice crystal formation in plant tissues with or without an electric current load was evaluated using the degree of supercooling, degree of cell deformation, and grain size and growing rate of intracellular ice crystal. Moreover, the transition of intracellular pH during plant tissue cooling with or without electric current loading was also examined using the fluorescence intensity ratio to comprehend cell activity at lower temperatures. The results indicated that micro electric current load did not only decrease the degree of cell deformation and grain size of intracellular ice crystal but also reduced the decline in intracellular pH due to temperature lowering, compared with tissues subjected to the same cooling rate without an electric current load. Thus, the effect of electric current load on cryopreservation and the potential of a new cryopreservation technique using electric current load were discussed based on these results.

  4. RNA Crystallization

    Science.gov (United States)

    Golden, Barbara L.; Kundrot, Craig E.

    2003-01-01

    RNA molecules may be crystallized using variations of the methods developed for protein crystallography. As the technology has become available to syntheisize and purify RNA molecules in the quantities and with the quality that is required for crystallography, the field of RNA structure has exploded. The first consideration when crystallizing an RNA is the sequence, which may be varied in a rational way to enhance crystallizability or prevent formation of alternate structures. Once a sequence has been designed, the RNA may be synthesized chemically by solid-state synthesis, or it may be produced enzymatically using RNA polymerase and an appropriate DNA template. Purification of milligram quantities of RNA can be accomplished by HPLC or gel electrophoresis. As with proteins, crystallization of RNA is usually accomplished by vapor diffusion techniques. There are several considerations that are either unique to RNA crystallization or more important for RNA crystallization. Techniques for design, synthesis, purification, and crystallization of RNAs will be reviewed here.

  5. Formation and Characterization of Mixed Crystals Based on Bis (ThioureaCadmium Chloride and Bis (ThioureaCadmium Iodide

    Directory of Open Access Journals (Sweden)

    I.S. Prameela Kumar

    2014-07-01

    Full Text Available Bis(thioureacadmium chloride(BTCC and bis(thioureacadmium iodide (BTCI are metal complexes of thiourea having better nonlinear optical properties than KH2PO4. An attempt has been made in the present study to form mixed crystals based on BTCC and BTCI (even though their crystal lattices mismatch from aqueous solutions, the precursors mixed in proper proportions. A total of seven (including the end members crystals were formed by the free evaporation method and characterized chemically, structurally, thermally, optically and electrically. The X-ray diffraction measurements indicate that (BTCCX(BTCI1-X crystals with x=1.0,0.8 and 0.6 are orthorhombic in structure with space group Pmn21 and that with x=0.5, 0.4, 0.2 and 0.0 are monoclinic in structure with space group P21/c. All the grown crystals are found to be thermally stable up to 215 °C and possessing wide optical transmission window (300-900 nm which is suitable for NLO applications. The electrical measurements indicate that the grown crystals exhibit a normal dielectric behavior. The results obtained in the present study indicate that mixed crystals can be formed from the isomorphous precursors directly even though the end member’s crystals have lattice mismatching.

  6. Exchange of interlayer terephthalate anions from a Mg Al layered double hydroxide: formation of intermediate interstratified phases

    Science.gov (United States)

    Kaneyoshi, Masami; Jones, William

    1998-10-01

    The exchange of interlayer terephthalate (TA) anions from a Mg-Al layered double hydroxide (LDH) by carbonate, sulfate, chloride and nitrate anions is reported. It is shown that TA is readily exchanged by CO 32- and SO 42- but only partly by Cl - and NO 3-. We demonstrate that during the exchange process interstratified phases are observed. Such interstratification has previously been reported only for directly synthesised materials. The origin of the interstratification is believed to be associated with two preferred orientations of TA anions within the layers, i.e. vertical or horizontal to the clay sheets. Two models for the possible exchange mechanism which is operating in these systems are proposed.

  7. A new model for mixing by double-diffusive convection (semi-convection): I. The conditions for layer formation

    CERN Document Server

    Mirouh, Giovanni M; Stellmach, Stephan; Traxler, Adrienne L; Wood, Toby S

    2011-01-01

    The process referred to as "semi-convection" in astrophysics and "double-diffusive convection in the diffusive regime" in Earth and planetary sciences, occurs in stellar and planetary interiors in regions which are stable according to the Ledoux criterion but unstable according to the Schwarzschild criterion. In this series of papers, we analyze the results of an extensive suite of 3D numerical simulations of the process, and ultimately propose a new 1D prescription for heat and compositional transport in this regime which can be used in stellar or planetary structure and evolution models. In a preliminary study of the phenomenon, Rosenblum et al. (2011) showed that, after saturation of the primary instability, a system can evolve in one of two possible ways: the induced turbulence either remains homogeneous, with very weak transport properties, or transitions into a thermo-compositional staircase where the transport rate is much larger (albeit still smaller than in standard convection). In this paper, we sho...

  8. Swelling and gel/sol formation of perchlorate-type layered double hydroxides in concentrated aqueous solutions of amino acid-related zwitterionic compounds.

    Science.gov (United States)

    Iyi, Nobuo; Ishihara, Shinsuke; Kaneko, Yoshiro; Yamada, Hirohisa

    2013-02-26

    ClO(4)(-)MgAl-LDH3, a MgAl (Mg/Al = 3) layered double hydroxide (LDH) containing perchlorate, swells and forms colloidal suspensions (sols) via the gel state in concentrated aqueous solutions of zwitterionic compounds related to amino acids. In total, 36 zwitterionic compounds with different molecular structures and additional functional groups were examined at various concentrations, and the sol-formation ability was judged by the transmittance (at λ = 589 nm) of the resulting suspensions. At low concentration, the obtained suspensions were turbid, with transmittances of ~0%. However, above the threshold concentration (0.3-1.0 M), osmotic swelling occurred and the transmittances of the suspensions increased sharply with increases in concentration to reach maximum values of 70-95%. The threshold concentration and maximum transmittance value depended on the structure and the location of the functional groups. The enhancement of the permittivity of water by the zwitterions and the formation of H-bond networks were assumed to be the reasons for the swelling phenomenon. Similar gel/sol formation was observed for ClO(4)(-)LDHs with Mg/Al = 2, Ni/Al = 2, 3, and Co/Al = 2 and some NO(3)(-)LDHs. Large ClO(4)(-)LDH films could be prepared by filtration of the colloidal suspensions followed by washing and drying processes.

  9. The role of superheating in the formation of Glass Mountain obsidians (Long Valley, CA) inferred through crystallization of sanidine

    Science.gov (United States)

    Waters, Laura E.; Andrews, Benjamin J.

    2016-10-01

    The Glass Mountain obsidians (Long Valley, CA) are crystal poor (obsidians. The obsidian in this study (GM-11) is saturated in nine phases (sanidine + quartz + plagioclase + titanomagnetite + ilmenite + zircon + apatite + allanite + biotite), and results of high-resolution SEM compositional mapping and electron microprobe analysis reveal that individual sanidine crystals are normally zoned and span a range of compositions (Or40-78). Sanidines have a "granophyric" texture, characterized by intergrowths of quartz and sanidine. Mineral phases in the natural sample are compared to H2O-saturated phase equilibrium experiments conducted in cold-seal pressure vessels, over a range of conditions (700-850 °C; 75-225 MPa), and all are found to be plausible phenocrysts. Comparison of sanidine compositions from the natural sample with those grown in phase equilibrium experiments demonstrates that sanidine in the natural sample occurs in a reduced abundance. Further comparison with phase equilibrium experiments suggests that sanidine compositions track progressive loss of dissolved melt water (±cooling), suggesting that crystallization in the natural obsidian was driven predominantly by degassing resulting from decompression. It is paradoxical that an effusively (slowly) erupted lava should contain multiple phenocryst phases, including sanidine crystals that span a range of compositions with granophyric textures, and yet remain so crystal poor. To resolve this paradox, it is necessary that the solidification mechanism (degassing or cooling) that produced the sanidine crystals (and other mineral phases) must have an associated kinetic effect(s) that efficiently hinders crystal nucleation and growth. Decompression experiments conducted in this study and from the literature collectively demonstrate that the simplest way to inhibit nucleation during degassing-induced crystallization is to initiate degassing ± cooling from superliquidus conditions, and therefore, the Glass

  10. Morphology transition of raft-model membrane induced by osmotic pressure: Formation of double-layered vesicle similar to an endo- and/or exocytosis

    Science.gov (United States)

    Onai, Teruaki; Hirai, Mitsuhiro

    2010-10-01

    The effect of osmotic pressure on the structure of large uni-lamellar vesicle (LUV) of the lipid mixtures of monosialoganglioside (GM1)-cholesterol-dioleoyl-phosphatidylcholine (DOPC) was studies by using wide-angle X-ray scattering (WAXS) method. The molar ratios of the mixtures were 0.1/0.1/1, 0/0.1/1, and 0/0/1. The ternary lipid mixture is a model of lipid rafts. The value of osmotic pressure was varied from 0 to 4.16×105 N/m2 by adding the polyvinylpyrrolidone (PVP) in the range from 0 to 25 % w/v. In the case of the mixtures without GM1, the rise of the osmotic pressure just enhances the multi-lamellar stacking with deceasing the inter-lamellar spacing. On the other hand, the mixture containing GM1 shows the structural transition from a uni-lamellar vesicle to a double-layered vesicle (a liposome including a smaller one inside) by the rise of osmotic pressure. In this morphology transition the total surface area of the double-layered vesicle is mostly as same as that of the LUV at the initial state. The polar head region of GM1 is bulky and highly hydrophilic due to the oligosaccharide chain containing a sialic acid residue. Then, the present results suggest that the existence of GM1 in the outer-leaflet of the LUV is essentially important for such a double-layered vesicle formation. Alternatively, a phenomenon similar to an endo- and/or exocytosis in cells can be caused simply by a variation of osmotic pressure.

  11. Morphology transition of raft-model membrane induced by osmotic pressure: Formation of double-layered vesicle similar to an endo- and/or exocytosis

    Energy Technology Data Exchange (ETDEWEB)

    Onai, Teruaki; Hirai, Mitsuhiro, E-mail: mhirai@fs.aramaki.gunma-u.ac.j [Department of Physics, Gunma University, Maebashi 371-8510 (Japan)

    2010-10-01

    The effect of osmotic pressure on the structure of large uni-lamellar vesicle (LUV) of the lipid mixtures of monosialoganglioside (G{sub M1})-cholesterol-dioleoyl-phosphatidylcholine (DOPC) was studies by using wide-angle X-ray scattering (WAXS) method. The molar ratios of the mixtures were 0.1/0.1/1, 0/0.1/1, and 0/0/1. The ternary lipid mixture is a model of lipid rafts. The value of osmotic pressure was varied from 0 to 4.16x10{sup 5} N/m{sup 2} by adding the polyvinylpyrrolidone (PVP) in the range from 0 to 25 % w/v. In the case of the mixtures without G{sub M1}, the rise of the osmotic pressure just enhances the multi-lamellar stacking with deceasing the inter-lamellar spacing. On the other hand, the mixture containing G{sub M1} shows the structural transition from a uni-lamellar vesicle to a double-layered vesicle (a liposome including a smaller one inside) by the rise of osmotic pressure. In this morphology transition the total surface area of the double-layered vesicle is mostly as same as that of the LUV at the initial state. The polar head region of G{sub M1} is bulky and highly hydrophilic due to the oligosaccharide chain containing a sialic acid residue. Then, the present results suggest that the existence of G{sub M1} in the outer-leaflet of the LUV is essentially important for such a double-layered vesicle formation. Alternatively, a phenomenon similar to an endo- and/or exocytosis in cells can be caused simply by a variation of osmotic pressure.

  12. Solid-state electric double layer capacitors fabricated with plastic crystal based flexible gel polymer electrolytes: Effective role of electrolyte anions

    Energy Technology Data Exchange (ETDEWEB)

    Suleman, Mohd; Kumar, Yogesh; Hashmi, S.A., E-mail: sahashmi@physics.du.ac.in

    2015-08-01

    Flexible gel polymer electrolyte (GPE) thick films incorporated with solutions of lithium trifluoromethanesulfonate (Li-triflate or LiTf) and lithium bis trifluoromethane-sulfonimide (LiTFSI) in a plastic crystal succinonitrile (SN), entrapped in poly(vinylidine fluoride-co-hexafluoropropylene) (PVdF-HFP) have been prepared and characterized. The films have been used as electrolytes in the electrical double layer capacitors (EDLCs). Coconut-shell derived activated carbon with high specific surface area (∼2100 m{sup 2} g{sup −1}) and mixed (micro- and meso-) porosity has been used as EDLC electrodes. The structural, thermal, and electrochemical characterization of the GPEs have been performed using scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), impedance measurements and cyclic voltammetry. The high ionic conductivity (∼10{sup −3} S cm{sup −1} at 25 °C), good electrochemical stability window (>4.0 V) and flexible nature of the free-standing films of GPEs show their competence in the fabrication of EDLCs. The EDLCs have been tested using electrochemical impedance spectroscopy, cyclic voltammetry, and charge–discharge studies. The EDLCs using LiTf based electrolyte have been found to give higher values of specific capacitance, specific energy, power density (240–280 F g{sup −1}, ∼39 Wh kg{sup −1} and ∼19 kW kg{sup −1}, respectively) than the EDLC cell with LiTFSI based gel electrolyte. EDLCs have been found to show stable performance for ∼10{sup 4} charge–discharge cycles. The comparative studies indicate the effective role of electrolyte anions on the capacitive performance of the solid-state EDLCs. - Graphical abstract: Display Omitted - Highlights: • Flexible EDLCs with succinonitrile based gel electrolyte membranes are reported. • Anionic size of salts in gel electrolytes plays important role on capacitive performance. • Li-triflate incorporated gel electrolyte shows better

  13. Ripples and the formation of anisotropic lipid domains: Imaging two-component double bilayers by atomic force microscopy_copy_03

    DEFF Research Database (Denmark)

    Leidy, C.; Kaasgaard, Thomas; Crowe, J.H.;

    2002-01-01

    . Intriguing straight-edged anisotropic fluid-phase domains were observed in the fluid-phase/ordered-phase coexistence temperature range, which resemble the fluid-phase/ordered-phase domain patterns observed in giant unilamellar vesicles composed of such phospholipid mixtures. With the high resolution provided......Direct visualization of the fluid-phase/ordered-phase domain structure in mica-supported bilayers composed of 1,2-dimyristoyl-sn-glycero-3-phosphocholine/1,2-distearoyl-sn-glycero-3-phosphocholine mixtures is performed with atomic force microscopy. The system studied is a double bilayer supported...... by atomic force microscopy, we investigated the origin of these anisotropic lipid domain patterns, and found that ripple phase formation is directly responsible for the anisotropic nature of these domains. The nucleation and growth of fluid-phase domains are found to be directed by the presence of ripples...

  14. Application of the Jones calculus for a modulated double-refracted light beam propagating in a homogeneous and nondepolarizing electro-optic uniaxial crystal.

    Science.gov (United States)

    Izdebski, Marek; Kucharczyk, Włodzimierz; Raab, Roger E

    2004-01-01

    The Jones matrix calculus is applied to an electro-optic crystal with uniaxial symmetry when the light beam is incident nearly normally on the crystal face. The approach allows one to treat refracted waves and rays that diverge in the crystal and are modulated by an external low-frequency field. The effect of partial interference of overlapping refracted beams is allowed for and calculated for the case of uniform intensity of the beam over its cross section. The method is employed to analyze optical systems containing an imprecisely cut and aligned electro-optic crystal plate.

  15. Dynamic crystallization experiments bearing on the origin of textures in impact-generated liquids. [for lunar rock formation

    Science.gov (United States)

    Lofgren, G. E.

    1977-01-01

    Dynamic crystallization experiments on a synthetic glass of 14310 composition show that the density and distribution of crystals present at the initiation of cooling can drastically affect the texture of the crystallized product. Experiments were performed in one-atmosphere gas-mixing furnaces at an oxygen fugacity slightly below iron-wustite, and precooling crystallization, cooling history, and melt history were systematically varied. When cooled from a complete liquid, the experimental charges were porphyritic with 1-2 mm phenocrysts set in a very fine-grained matrix (less than 0.1 mm). This result suggests that 14310 did not cool from a complete melt. When cooled from a crystal-liquid mixture, the experimental charges had widely varying textures depending on the density and distribution of crystals that act as nucleation sites. It is suggested that the close spatial association of widely divergent textures in the matrices of some breccias and rocks might arise in this manner; local variations in cooling rates are not required.

  16. Double-layered ejecta craters on Mars: morphology, formation, and a comparison with the Ries ejecta blanket

    Science.gov (United States)

    Kenkmann, Thomas; Wulf, Gerwin; Sturm, Sebastian; Pietrek, Alexa

    2015-04-01

    The ejecta blankets of impact craters in volatile-rich environments often show characteristic layered ejecta morphologies. The so-called double-layer ejecta (DLE) craters are probably the most confusing crater types showing two ejecta layers with distinct morphologies. A phenomenological ejecta excavation and emplacement model for DLE craters is proposed based on a detailed case study of the Martian crater Steinheim - a textbook like, pristine DLE crater - and studies of other DLE craters [1]. The observations show that DLE craters on Mars are the result of an impact event into a rock/ice mixture that produces large amounts of shock-induced vaporization and melting of ground ice. The deposits of the ejecta curtain are wet in the distal part and dryer in composition in the proximal part. As a result, the outer ejecta layer is emplaced as medial and distal ejecta that propagate outwards in a fluid saturated debris flow mode after landing overrunning previously formed secondary craters. In contrast, the inner ejecta layer is formed by a translational slide of the proximal ejecta deposits. This slide overruns and superimposes parts of the outer ejecta layer. Basal melting of the ice components of the ejecta volumes at the transient crater rim is induced by frictional heating and the enhanced pressure at depth. The results indicate similar processes also for other planetary bodies with volatile-rich environments, such as Ganymede, Europa or the Earth. The Ries crater on Earth has a similar ejecta thickness distribution as DLE craters on Mars [2]. Here basal sliding and fluidization of the ejecta increases outward by the entrainment of locally derived Tertiary sands and clays, that are saturated with groundwater. References: [1] Wulf, G. & Kenkmann, T. (2015) Met. Planet. Sci. (in press); [2] Sturm, S., Wulf. G., Jung, D. & Kenkmann, T. (2013) Geology 41, 531-534.

  17. Computational crystallization.

    Science.gov (United States)

    Altan, Irem; Charbonneau, Patrick; Snell, Edward H

    2016-07-15

    Crystallization is a key step in macromolecular structure determination by crystallography. While a robust theoretical treatment of the process is available, due to the complexity of the system, the experimental process is still largely one of trial and error. In this article, efforts in the field are discussed together with a theoretical underpinning using a solubility phase diagram. Prior knowledge has been used to develop tools that computationally predict the crystallization outcome and define mutational approaches that enhance the likelihood of crystallization. For the most part these tools are based on binary outcomes (crystal or no crystal), and the full information contained in an assembly of crystallization screening experiments is lost. The potential of this additional information is illustrated by examples where new biological knowledge can be obtained and where a target can be sub-categorized to predict which class of reagents provides the crystallization driving force. Computational analysis of crystallization requires complete and correctly formatted data. While massive crystallization screening efforts are under way, the data available from many of these studies are sparse. The potential for this data and the steps needed to realize this potential are discussed.

  18. Adsorption, Desorption, Surface Diffusion, Lattice Defect Formation, and Kink Incorporation Processes of Particles on Growth Interfaces of Colloidal Crystals with Attractive Interactions

    Directory of Open Access Journals (Sweden)

    Yoshihisa Suzuki

    2016-07-01

    Full Text Available Good model systems are required in order to understand crystal growth processes because, in many cases, precise incorporation processes of atoms or molecules cannot be visualized easily at the atomic or molecular level. Using a transmission-type optical microscope, we have successfully observed in situ adsorption, desorption, surface diffusion, lattice defect formation, and kink incorporation of particles on growth interfaces of colloidal crystals of polystyrene particles in aqueous sodium polyacrylate solutions. Precise surface transportation and kink incorporation processes of the particles into the colloidal crystals with attractive interactions were observed in situ at the particle level. In particular, contrary to the conventional expectations, the diffusion of particles along steps around a two-dimensional island of the growth interface was not the main route for kink incorporation. This is probably due to the number of bonds between adsorbed particles and particles in a crystal; the number exceeds the limit at which a particle easily exchanges its position to the adjacent one along the step. We also found novel desorption processes of particles from steps to terraces, attributing them to the assistance of attractive forces from additionally adsorbing particles to the particles on the steps.

  19. Search for double- {beta} decay processes in {sup 108}Cd and {sup 114}Cd with the help of the low-background CdWO{sub 4} crystal scintillator

    Energy Technology Data Exchange (ETDEWEB)

    Belli, P.; Bernabei, R.; D' Angelo, S.; Nozzoli, F.; Tretyak, V.I. [Universita di Roma Tor Vergata and INFN, Sezione di Roma Tor Vergata, Dipartimento di Fisica, Rome (Italy); Cappella, F.; Incicchitti, A.; Prosperi, D. [Universita di Roma La Sapienza and INFN, Sezione di Roma, Dipartimento di Fisica, Rome (Italy); Cerulli, R. [Laboratori Nazionali del Gran Sasso, INFN, Assergi (Italy); Danevich, F.A.; Kobychev, V.V.; Nagorny, S.S.; Mokina, V.M.; Poda, D.V. [MSP, Institute for Nuclear Research, Kyiv (Ukraine)

    2008-05-15

    The search for double-{beta} processes in {sup 108}Cd and {sup 114}Cd was realized by using data of the low-background experiment with the CdWO{sub 4} crystal scintillator at the Gran Sasso National Laboratories of the INFN. New improved half-life limits on double-beta processes were established, in particular T{sub 1/2}{sup 0{nu}}{sup 2{epsilon}}({sup 1}08Cd){>=}1.0(2.7) x 10{sup 18} yr, T{sub 1/2}{sup 2{nu}}{sup 2{beta}}({sup 1}14Cd){>=}1.3(2.1) x 10{sup 18} yr, and T{sub 1/2}{sup 0{nu}}{sup 2{beta}}({sup 1}14Cd){>=}1.1(2.5) x 10{sup 21} yr at 90(68)% C.L. (orig.)

  20. Ion beam damage assessment and waveguide formation induced by energetic Si-ion irradiation in lanthanum aluminate crystal

    Science.gov (United States)

    Liu, Y.; Huang, Q.; Crespillo, M. L.; Qiao, M.; Liu, P.; Wang, X. L.

    2017-02-01

    Lanthanum aluminate (LaAlO3) crystal has emerged as one of the most valuable functional-materials, and its physical, electronic and optical properties strongly depend on the crystal structure, which can be easily altered in an irradiation environment and therefore affect the performance of LaAlO3-based devices. On the other hand, the preparation of LaAlO3 waveguide is also a scientific challenge for its potential application prospects in optoelectronics field. In this work, the damage evolution behavior of LaAlO3 crystal under Si-ion irradiation has been discussed in detail utilizing complementary characterization techniques, and then, single-mode waveguide of LaAlO3 crystal in the visible band can be obtained based on ion-irradiation-induced lattice damage behavior. Waveguide optical-coupling techniques are used to show its competitive features. Thus, novel optical waveguides with optimized features in LaAlO3 crystals can be tailored by a proper selection of ion mass, energy and fluence using the modification of the target material during ion irradiation process.

  1. Time lapse microscopy of temperature control during self-assembly of 3D DNA crystals

    Science.gov (United States)

    Conn, Fiona W.; Jong, Michael Alexander; Tan, Andre; Tseng, Robert; Park, Eunice; Ohayon, Yoel P.; Sha, Ruojie; Mao, Chengde; Seeman, Nadrian C.

    2017-10-01

    DNA nanostructures are created by exploiting the high fidelity base-pairing interactions of double-stranded branched DNA molecules. These structures present a convenient medium for the self-assembly of macroscopic 3D crystals. In some self-assemblies in this system, crystals can be formed by lowering the temperature, and they can be dissolved by raising it. The ability to monitor the formation and melting of these crystals yields information that can be used to monitor crystal formation and growth. Here, we describe the development of an inexpensive tool that enables direct observation of the crystal growth process as a function of both time and temperature. Using the hanging-drop crystallization of the well-characterized 2-turn DNA tensegrity triangle motif for our model system, its response to temperature has been characterized visually.

  2. The "New Polyethylene Glycol Dilemma": Polyethylene Glycol Impurities and Their Paradox Role in mAb Crystallization.

    Science.gov (United States)

    Hildebrandt, Christian; Joos, Lea; Saedler, Rainer; Winter, Gerhard

    2015-06-01

    Polyethylene glycols (PEG) represent the most successful and frequently applied class of excipients used for protein crystallization. PEG auto-oxidation and formation of impurities such as peroxides and formaldehydes that foster protein drug degradation is known. However, their effect on mAb crystallization has not been studied in detail before. During the present study, a model IgG1 antibody (mAb1) was crystallized in PEG solutions. Aggregate formation was observed during crystallization and storage that was ascribed to PEG degradation products. Reduction of peroxide and formaldehyde levels prior to crystallization by vacuum and freeze-drying was investigated for its effect on protein degradation. Vacuum drying was superior in removal of peroxides but inferior in reducing formaldehyde residues. Consequently, double purification allowed extensive removal of both impurities. Applying of purified PEG led to 50% lower aggregate fractions. Surprisingly, PEG double purification or addition of methionine prior to crystallization prevented crystal formation. With increased PEG concentration or spiking with peroxides and formaldehydes, crystal formation could be recovered again. With these results, we demonstrate that minimum amounts of oxidizing impurities and thus in consequence chemically altered proteins are vital to initiate mAb1 crystallization. The present study calls PEG as good precipitant for therapeutic biopharmaceuticals into question.

  3. Formation of a regular domain structure in TGS–TGS + Cr crystals with a profile impurity distribution

    Energy Technology Data Exchange (ETDEWEB)

    Belugina, N. V., E-mail: alla@ns.crys.ras.ru; Gainutdinov, R. V.; Tolstikhina, A. L.; Ivanova, E. S. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation); Kashevich, I. F. [Vitebsk State University (Belarus); Shut, V. N.; Mozzharov, S. E. [Belarussian Academy of Sciences, Institute of Technical Acoustics (Belarus)

    2015-07-15

    A complex investigation of TGS–TGS + Cr crystals with a profile impurity distribution of chromium ions Cr{sup 3+} has been carried out at the macrolevel (measurement of dielectric properties by the method of nematic liquid crystals) and microlevel (domain structure according to atomic force microscopy data). It is established that periodic doped layers are formed only in individual growth pyramids in the regions where the polarization vector has a nonzero component along the normal to the growth faces rather than throughout the entire crystal volume. The domain configuration at the boundary of growth layers with different impurity compositions has been studied by piezoelectric force microscopy. The static unipolarity of layers with and without chromium impurity is approximately identical, whereas the domain-wall density in doped regions is higher than that in undoped ones by a factor of about 7.

  4. Crystallization field and rate study for the formation of single phase sodium-potassium and potassium clinoptilolite

    Energy Technology Data Exchange (ETDEWEB)

    Guevenir, Oe.; Kalipcilar, H.; Culfaz, A. [Middle East Technical University, Department of Chemical Engineering, 06531 Ankara (Turkey)

    2011-04-15

    Reproducible synthesis of clinoptilolite as the single crystalline phase was achieved in the narrow crystallization field at or around the nominal batch composition of 2.1(Na{sub 2}O+K{sub 2}O):Al{sub 2}O{sub 3}:10SiO{sub 2}:110H{sub 2}O at 140 C. Clinoptilolites of high purity were crystallized in the pure sodium or mixed sodium-potassium cation systems. Partial replacement of hydroxyl anions with the salts of carbonates or chlorides also yielded clinoptilolite as the single crystalline phase although at lower crystallization rates. (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  5. Formation mechanism of the low-frequency locally resonant band gap in the two-dimensional ternary phononic crystals

    Institute of Scientific and Technical Information of China (English)

    Wang Gang; Liu Yao-Zong; Wen Ji-Hong; Yu Dian-Long

    2006-01-01

    The low-frequency band gap and the corresponding vibration modes in two-dimensional ternary locally resonant phononic crystals are restudied successfully with the lumped-mass method. Compared with the work of C. Goffaux and J. Sanchez-Dehesa (Phys. Rev. B 67 14 4301(2003)), it is shown that there exists an error of about 50% in their calculated results of the band structure, and one band is missing in their results. Moreover, the in-plane modes shown in their paper are improper, which results in the wrong conclusion on the mechanism of the ternary locally resonant phononic crystals. Based on the lumped-mass method and better description of the vibration modes according to the band gaps, the locally resonant mechanism in forming the subfrequency gaps is thoroughly analysed. The rule used to judge whether a resonant mode in the phononic crystals can result in a corresponding subfrequency gap is also verified in this ternary case.

  6. H{sub 2}V{sub 3}O{sub 8} single-crystal nanobelts: Hydrothermal preparation and formation mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Chang, K.-H. [Department of Chemical Engineering, National Chung Cheng University, Chia-Yi 621, Taiwan (China); Hu, C.-C. [Department of Chemical Engineering, National Chung Cheng University, Chia-Yi 621, Taiwan (China)], E-mail: cchu@che.nthu.edu.tw

    2007-10-15

    The formation mechanism of highly pure H{sub 2}V{sub 3}O{sub 8} single-crystal nanobelts is clarified in a hydrothermal synthesis process with a specially designed precursor solution containing V{sup 5+} and V{sup 4+} in a fixed ratio of 2/1. This specially designed precursor solution provides an additional merit for the rapid fabrication of highly pure H{sub 2}V{sub 3}O{sub 8} nanobelts through a simple hydrothermal route. During the hydrothermal synthesis process, V{sup 5+} species initially reacts with some V{sup 4+} to form a metastable, whisker-like V{sub 10}O{sub 24} . nH{sub 2}O (n < 12). The V{sup 5+} species dissolved from the whisker-like V{sub 10}O{sub 24} . nH{sub 2}O reacts continuously with residual V{sup 4+} ions in the precursor solution to form seeds of H{sub 2}V{sub 3}O{sub 8} single-crystals. The anisotropic growth of H{sub 2}V{sub 3}O{sub 8} single-crystal nanobelts with length > 10 {mu}m and width between 50 and 150 nm occurs with prolonging the hydrothermal time. Finally, highly pure H{sub 2}V{sub 3}O{sub 8} single-crystal nanobelts are obtained when the hydrothermal time reaches 4 h. The textures of vanadium oxides prepared at different hydrothermal times are systematically compared through X-ray diffraction, transmission electron microscopic and X-ray photoelectron spectroscopic analyses to clarify the synthesis mechanism of H{sub 2}V{sub 3}O{sub 8} single-crystal nanobelts.

  7. Formation of one-dimensional helical columns and excimerlike excited states by racemic quinoxaline-fused [7]carbohelicenes in the crystal.

    Science.gov (United States)

    Sakai, Hayato; Shinto, Sho; Araki, Yasuyuki; Wada, Takehiko; Sakanoue, Tomo; Takenobu, Taishi; Hasobe, Taku

    2014-08-01

    A series of quinoxaline-fused [7]carbohelicenes (HeQu derivatives) was designed and synthesized to evaluate their structural and photophysical properties in the crystal state. The quinoxaline units were expected to enhance the light-emitting properties and to control the packing structures in the crystal. The electrochemical and spectroscopic properties and excited-state dynamics of these compounds were investigated in detail. The first oxidation potentials of HeQu derivatives are approximately the same as that of unsubstituted reference [7]carbohelicene (Heli), whereas their first reduction potentials are shifted to the positive by about 0.7 V. The steady-state absorption, fluorescence, and circular dichroism spectra also became redshifted compared to those of Heli. The molecular orbitals and energy levels of the HOMO and LUMO states, calculated by DFT methods, support these trends. Moreover, the absolute fluorescence quantum yields of HeQu derivatives are about four times larger than that of Heli. The structural properties of the aggregated states were analyzed by single-crystal analysis. Introduction of appropriate substituents (i.e., 4-methoxyphenyl) in the HeQu unit enabled the construction of one-dimensional helical columns of racemic HeQu derivatives in the crystal state. Helix formation is based on intracolumn π-stacking between two neighboring [7]carbohelicenes and intercolumn CH⋅⋅⋅N interaction between a nitrogen atom of a quinoxaline unit and a hydrogen atom of a helicene unit. The time-resolved fluorescence spectra of single crystals clearly showed an excimerlike delocalized excited state owing to the short distance between neighboring [7]carbohelicene units.

  8. Transmesenteric hernia due to double-loop formation in the small intestine: a fatal case involving a toddler.

    Science.gov (United States)

    Kakimoto, Yu; Abiru, Hitoshi; Kotani, Hirokazu; Ozeki, Munetaka; Tsuruyama, Tatsuaki; Tamaki, Keiji

    2012-01-10

    We report a unique case of transmesenteric hernia resulting in death, which went undiagnosed during a recent hospital visit. The victim was a 2.5-year-old girl who - with the exception of chronic constipation - had no medical history. One night she complained of abdominal pains and was taken to a pediatric hospital where doctors performed an abdominal X-ray and echography. No significant findings suggesting bowel obstruction (e.g. air-fluid levels or dilation of the bowel) were obtained on examinations and bloody feces were not observed in this particular episode. As her abdominal pain gradually attenuated, the doctor allowed her to return home. A few hours later, she lost consciousness and expired despite resuscitation efforts attempted at an emergency hospital. A subsequent autopsy revealed that the small bowel had herniated through a defect in the mesentery resulting in two consecutive and inversely forming loops, in which each loop protruded on either side of the mesentery. This rare morphological anatomy seems to have progressed in a two-step process. The girl's mild abdominal pain was likely induced by herniation and formation of the first intestinal loop, followed by severe shock occurring when the subsequent intestinal segment invaginated into the same defect forming the second loop on the opposite side of the mesentery. This case illustrates the difficulty of diagnosing transmesenteric hernia due to the presentation of unspecific symptoms; especially in infants and toddlers. Furthermore, this report demonstrates the value of a complete autopsy in cases of sudden and unexpected deaths involving children. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

  9. The role of trivalent cations and interlayer anions on the formation of layered double hydroxides in an oxic-CO2 medium

    Science.gov (United States)

    Paikaray, Susanta; Hendry, M. Jim

    2012-12-01

    Most common occurrences of magnesium (Mg2+), aluminum (Al3+), iron (Fe3+), carbonate (CO32-), and sulfate (SO42-) in environmental settings can lead to formation of layered double hydroxides. This study investigated the role of different trivalent cations and divalent interlayer anions on the physicochemical properties of hydrotalcite-like layered double hydroxides. Hydrotalcite-like compounds (HTLCs) were synthesized at ambient temperature by co-precipitation while maintaining Mg2+ as the primary divalent cation and varying Al3+ and Fe3+ as the trivalent cations and SO42- and CO32- as the interlayer anions. X-ray diffractograms, Raman and infrared spectra, and scanning electron microscopy images confirmed the precipitation of rounded fibrous HTLCs. BET analyses showed that the MgAlCO3-type HTLC had the greatest surface area (101.7 m2/g), followed by MgAlSO4 (93.9 m2/g), MgFeCO3 (81.3 m2/g), and MgFeSO4 (17.8 m2/g). Substitution of Fe3+ increased lattice parameters compared to Al3+ substitution. Incorporation of SO42- as an interlayer anion was favored during Fe3+ substitution but reduced the crystallinity of the HTLC. Carbonate was the preferred interlayer anion, but available SO42- occupied the interlayer spaces together with CO32- if a high charge deficiency was maintained during HTLC precipitation. Two major stages of mass loss occurred (≤250 and 250-450 °C) for all the samples with better thermal stability for SO42- vs. CO32- as interlayer anion and Al3+ vs. Fe3+ as trivalent cation.

  10. The study on formation and structure of double minutes%双微体的形成及结构研究

    Institute of Scientific and Technical Information of China (English)

    郭欢; 孟祥宁; 傅松滨

    2015-01-01

    基因扩增是人类肿瘤细胞中一种常见的基因组不稳定表现形式,其最主要的细胞遗传学表现形式为双微体.双微体的结构复杂,由一个或几个来源相同或不同的扩增子构成.扩增子之间的断裂融合接头连接方式多种多样,涉及非同源末端连接、同源重组和非同源末端连接基础上的新型修复机制等多种DNA断裂重接方式.分析双微体结构、了解扩增子连接方式对于阐明双微体的形成机制及进一步理解基因扩增有重要意义.%Gene amplification is one of the most frequent manifestations of genomic instability in human tumors,whose main cytogenetic structures are double minute chromosomes (DMs).DMs consist of different amplicons which have one or different origins.There are diverse connections of break-fusion junction between amplicons,including homologous recombination,non-homologous end joining and novel DNA repair mechanisms based on the non-homologous end joining,which suggested that more than one DNA double-strand break repair procedures contributed in the foemation of DMs.Thus,the structures of DMs and junction sequences can give us clues for interpreting the mechanism of gene amplification and DMs formation.

  11. Role of crystallographic anisotropy in the formation of surface layers of single NiTi crystals after ion-plasma alloying

    Energy Technology Data Exchange (ETDEWEB)

    Poletika, T. M., E-mail: poletm@ispms.tsc.ru; Girsova, S. L., E-mail: llm@ispms.tsc.ru [Institute of Strength Physics and Materials Science SB RAS, Tomsk, 634055 (Russian Federation); Meisner, L. L., E-mail: girs@ispms.tsc.ru; Meisner, S. N., E-mail: msn@ispms.tsc.ru [Institute of Strength Physics and Materials Science SB RAS, Tomsk, 634055 (Russian Federation); National Research Tomsk State University, Tomsk, 634050 (Russian Federation); Shulepov, I. A., E-mail: iashulepov@tpu.ru [National Research Tomsk Polytechnic University, Tomsk, 634050 (Russian Federation)

    2015-10-27

    The structure of the surface and near-surface layers of single crystals of NiTi, differently oriented relative to the direction of ion beam treatment was investigated. The role of the crystallographic orientation in formation of structure of surface layers after ion-plasma alloying was revealed. It was found that the orientation effects of selective sputtering and channeling determine the thickness of the oxide and amorphous layers, the depth of penetration of ions and impurities, the distribution of Ni with depth.

  12. Renal tubular injury induced by ischemia promotes the formation of calcium oxalate crystals in rats with hyperoxaluria.

    Science.gov (United States)

    Cao, Yanwei; Liu, Wanpeng; Hui, Limei; Zhao, Jianjun; Yang, Xuecheng; Wang, Yonghua; Niu, Haitao

    2016-10-01

    Hyperoxaluria and cell injury are key factors in urolithiasis. Oxalate metabolism may be altered by renal dysfunction and therefore, impact the deposition of calcium oxalate (CaOx) crystals. We investigated the relationship of renal function, oxalate metabolism and CaOx crystal deposition in renal ischemia. One hundred male Sprague-Dawley rats were randomly divided into four groups. Hyperoxaluria model (Group A and B) was established by feeding rats with 0.75 % ethylene glycol (EG). The left renal pedicle was clamped for 30 min to establish renal ischemia Groups (B and C), while Groups A and D underwent sham operation. Then, serum and urine oxalate (Ox), creatinine (Cr) and urea nitrogen (UN) levels were evaluated by liquid chromatography mass spectrometry (LCMS) and ion mass spectrum (IMS) at days 0, 2, 4, 7, and 14. CaOx crystallization was assessed by transmission electron microscope (TEM). A temporal and significant increase of serum Cr and UN levels was observed in Groups B and C compared to values obtained for Groups A and D (P renal tissue. Our results indicated that renal tubular injury induced by renal ischemia might not affect Ox levels but could promote CaOx crystal retention under hyperoxaluria.

  13. Mesoporous MEL, BEA, and FAU zeolite crystals obtained by in situ formation of carbon template over metal nanoparticles

    DEFF Research Database (Denmark)

    Abildstrøm, Jacob Oskar; Ali, Zahra Nasrudin; Mentzel, Uffe Vie

    2016-01-01

    nanoparticles supported on silica, a carbon–silica composite is obtained and exploited as a combined carbon template/silica source for the zeolite synthesis. The mesoporous zeolite materials were all prepared by hydrothermal crystallization in alkaline media followed by removal of the carbon template...

  14. Possible wave formation and martensitic transformation of iron particles in copper single crystals during argon ion bombardment

    DEFF Research Database (Denmark)

    Thölén, Anders Ragnar; Li, Chang-Hai; Easterling, K.E.

    1983-01-01

    Thin single crystal copper specimens (thickness ~250 nm) containing coherent iron particles (diameter 40–50 nm) have been bombarded with argon ions (5, 80, and 330 keV). During this process some of the iron particles transform to martensite. The transformation was observed near the exposed surface...

  15. Effect of a Transverse Magnetic Field on Stray Grain Formation of Ni-Based Single Crystal Superalloy During Directional Solidification

    Science.gov (United States)

    Xuan, Weidong; Liu, Huan; Lan, Jian; Li, Chuanjun; Zhong, Yunbo; Li, Xi; Cao, Guanghui; Ren, Zhongming

    2016-08-01

    The effect of a transverse magnetic field on stray grain formation during directional solidification of superalloy was investigated. Experimental results indicated that the transverse magnetic field effectively suppressed the stray grain formation on the side the primary dendrite diverges from the mold wall. Moreover, the quenched experimental results indicated that the solid/liquid interface shape was obviously changed in a transverse magnetic field. The effect of a transverse magnetic field on stray grain formation was discussed.

  16. Functionalizing Designer DNA Crystals

    Science.gov (United States)

    Chandrasekaran, Arun Richard

    Three-dimensional crystals have been self-assembled from a DNA tensegrity triangle via sticky end interaction. The tensegrity triangle is a rigid DNA motif containing three double helical edges connected pair-wise by three four-arm junctions. The symmetric triangle contains 3 unique strands combined in a 3:3:1 ratio: 3 crossover, 3 helical and 1 central. The length of the sticky end reported previously was two nucleotides (nt) (GA:TC) and the motif with 2-helical turns of DNA per edge diffracted to 4.9 A at beam line NSLS-X25 and to 4 A at beam line ID19 at APS. The purpose of these self-assembled DNA crystals is that they can be used as a framework for hosting external guests for use in crystallographic structure solving or the periodic positioning of molecules for nanoelectronics. This thesis describes strategies to improve the resolution and to incorporate guests into the 3D lattice. The first chapter describes the effect of varying sticky end lengths and the influence of 5'-phosphate addition on crystal formation and resolution. X-ray diffraction data from beam line NSLS-X25 revealed that the crystal resolution for 1-nt (G:C) sticky end was 3.4 A. Motifs with every possible combination of 1-nt and 2-nt sticky-ended phosphorylated strands were crystallized and X-ray data were collected. The position of the 5'-phosphate on either the crossover (strand 1), helical (strand 2), or central strand (3) had an impact on the resolution of the self-assembled crystals with the 1-nt 1P-2-3 system diffracting to 2.62 A at APS and 3.1 A at NSLS-X25. The second chapter describes the sequence-specific recognition of DNA motifs with triplex-forming oligonucleotides (TFOs). This study examined the feasibility of using TFOs to bind to specific locations within a 3-turn DNA tensegrity triangle motif. The TFO 5'-TTCTTTCTTCTCT was used to target the tensegrity motif containing an appropriately embedded oligopurine.oligopyrimidine binding site. As triplex formation involving cytidine

  17. Synthesis of YAG:Ce3+ Phosphor by Polyacrylamide Gel Method and Promoting Action of α-Al2O3 Seed Crystal on Phase Formation

    Institute of Scientific and Technical Information of China (English)

    Li Yongxiu; Li Yinyi; Min Yulin; Wu Yanli; Cheng Changming; Zhou Xuezhen; Gu Ziying

    2005-01-01

    YAG:Ce3+ phosphor particles were prepared using polyacrylamide gel method. The structure evolution of powders during annealing process was followed by X-ray diffraction determination. It is found that some intermediate phases, including θ-Al2O3, YAM and YAP, are formed when calcining polyacrylamide gel, however, the pure YAG phase can be formed directly when calcining polyacrylamide gel with α-Al2O3 as seed crystal. These facts show that the existence of α-Al2O3 seed crystal can block the formation of θ-Al2O3, YAM and YAP, and accelerate its reaction with Y2O3 to form YAG phase directly at lower temperature. The emission peak of prepared YAG:Ce3+ phosphor is wide with maximum at 550 nm and the exitation band has two peaks, the major one is around at 460 nm, which matches the blue emission of GaN LED and is suitable for the assemble of white LED. Some fluxes can enhance the photoluminescence intensity of phosphor particles, that can be attributed both to the improvement of crystallization processes of YAG and to the stabilization of trivalence cerium ion in YAG:Ce3+.

  18. The effect of crystal structure of TiO2 nanotubes on the formation of calcium phosphate coatings during biomimetic deposition

    Science.gov (United States)

    Liu, Yi; Kim, Sun; McLeod, John A.; Li, Jun; Guo, Xiaoxuan; Sham, Tsun-Kong; Liu, Lijia

    2017-02-01

    The crystallization process of bioactive calcium phosphate (CaP) species via biomimetic deposition onto anodic TiO2 nanotubes is investigated. The porous surface of nanostructured TiO2 provides an ideal substrate for CaP crystallization. The compositions of CaP coatings are studied using X-ray absorption near-edge structures (XANES) at the Ca K-edge. Using detection modes with different probing depths, both the surface of the CaP coating and the CaP-TiO2 interface are simultaneously analyzed. Calcium phosphate (CaP) species, such as hydroxyapatite (HAp), octacalcium phosphate (Ca8(HPO4)2(PO4)4·5H2O, OCP), brushite (CaHPO4·2H2O, DCPD), and amorphous calcium phosphate (ACP), are found in the CaP coatings. TiO2 nanotubes of amorphous and anatase phases are comparatively studied to determine their effect on the efficiency of CaP formation and the phase transformation among CaP species in prolonged deposition time. It is found the composition of CaP coating has a strong dependency on the crystal structure of TiO2 substrate and the kinetics (deposition time).

  19. Hot spot formation and chemical reaction initiation in shocked HMX crystals with nanovoids: a large-scale reactive molecular dynamics study.

    Science.gov (United States)

    Zhou, Tingting; Lou, Jianfeng; Zhang, Yangeng; Song, Huajie; Huang, Fenglei

    2016-07-14

    We report million-atom reactive molecular dynamic simulations of shock initiation of β-cyclotetramethylene tetranitramine (β-HMX) single crystals containing nanometer-scale spherical voids. Shock induced void collapse and subsequent hot spot formation as well as chemical reaction initiation are observed which depend on the void size and impact strength. For an impact velocity of 1 km s(-1) and a void radius of 4 nm, the void collapse process includes three stages; the dominant mechanism is the convergence of upstream molecules toward the centerline and the downstream surface of the void forming flowing molecules. Hot spot formation also undergoes three stages, and the principal mechanism is kinetic energy transforming to thermal energy due to the collision of flowing molecules on the downstream surface. The high temperature of the hot spot initiates a local chemical reaction, and the breakage of the N-NO2 bond plays the key role in the initial reaction mechanism. The impact strength and void size have noticeable effects on the shock dynamical process, resulting in a variation of the predominant mechanisms leading to void collapse and hot spot formation. Larger voids or stronger shocks result in more intense hot spots and, thus, more violent chemical reactions, promoting more reaction channels and generating more reaction products in a shorter duration. The reaction products are mainly concentrated in the developed hot spot, indicating that the chemical reactivity of the hmx crystal is greatly enhanced by void collapse. The detailed information derived from this study can aid a thorough understanding of the role of void collapse in hot spot formation and the chemical reaction initiation of explosives.

  20. Single crystal fibers growth of double lithium, lanthanium molybdate and adjustment of a micro-pulling down furnace for high vacuum setup; Crescimento de fibras de molibdato duplo de litio e lantanio e adaptacao de sistema de alto vacuo para micro pulling-down

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Fernando Rodrigues da

    2013-07-01

    In this work we investigated crystal growth procedures aiming the development of single crystal fiber (SCF) for laser applications. For quality optimization in the fabrication of fluorides SCF a new growth chamber for a micro-pulling down furnace ({mu}-PD) was constructed targeting the fibers fabrication with strict atmosphere control (high vacuum, gas flux and static atmospheres). Simultaneously, the SCF growth process of rare earth double molybdates was studied. The growth of pure and Nd{sup 3+}-doped SCF of LiLa(MoO{sub 4}){sub 2} (LLM) was studied in the range of 0,5 - 10mol% doping. The designed furnace growth chamber with controlled atmosphere was successfully constructed and tested under different conditions. Specially, it was tested with the growth of LiF SFC under CF{sub 4} atmosphere showing the expected results. Transparent and homogeneous SCF of Nd:LLM were grown. In the pure fibers was observed facets formation, however, these defects were minimized after tuning of the growth parameters and additionally with the fibers doping. X-ray analysis showed the crystallization of a single phase (space group I4{sub 1}/a); the optical coherence tomography showed the presence of scattering centers only in regions were some growth stability occurred due to the manual process control. The measured Nd{sup 3+} distribution showed uniform incorporation, indicative of a segregation coefficient close to unity in LLM. The potential laser gain of the system was determined using a numerical solution of the rate equations system for the 805nm, CW pumping regime, showing the maximum laser emission gain at 1.064 {mu}m for a Nd{sup 3+}-doping of 5mol%. (author)

  1. High-density transfection with HEK-293 cells allows doubling of transient titers and removes need for a priori DNA complex formation with PEI.

    Science.gov (United States)

    Backliwal, Gaurav; Hildinger, Markus; Hasija, Vivek; Wurm, Florian M

    2008-02-15

    Recombinant proteins are of great commercial and scientific interest. Yet, most production methods in mammalian cells involve the time- and labor-consuming step of creating stable cell lines. Production methods based on transient gene expression are advantageous in terms of speed and versatility; yet, depending on the transfection protocol, transient transfection faces some bottlenecks such as a priori complex formation, limitations in terms of transfection and production media used and the need for medium exchange prior to and/or after transfection. Published protocols for transfection of suspension-adapted HEK-293 cells with polyethyleneimine have shown great promise in overcoming some of these bottlenecks, but still require a priori complex formation for optimal yields and limit the choice of transfection and production media. Here, we report successful in situ transfection of suspension-adapted HEK-293 cells with 25-kDa linear polyethyleneimine at densities up to 20 x 10(6) cells/mL in complex media followed by production at lower cell densities (1 x 10(6) cells/mL). After concentrating cells to such high densities, transfection of HEK-293 cells becomes possible in most commonly used media and is not restricted to a specific medium. Furthermore, there is no need to make transfection complexes a priori, a step that prevents inline sterile filtration of the DNA bulk for transfection, an important consideration when scaling processes up to 100 or 1,000 L. Finally, transfecting HEK-293 cells at high density in complex media is superior to existing transfection protocols and doubles yields of recombinant protein obtainable by transient gene expression.

  2. Formation of a stable RuvA protein double tetramer is required for efficient branch migration in vitro and for replication fork reversal in vivo.

    Science.gov (United States)

    Bradley, Alison S; Baharoglu, Zeynep; Niewiarowski, Andrew; Michel, Bénédicte; Tsaneva, Irina R

    2011-06-24

    In bacteria, RuvABC is required for the resolution of Holliday junctions (HJ) made during homologous recombination. The RuvAB complex catalyzes HJ branch migration and replication fork reversal (RFR). During RFR, a stalled fork is reversed to form a HJ adjacent to a DNA double strand end, a reaction that requires RuvAB in certain Escherichia coli replication mutants. The exact structure of active RuvAB complexes remains elusive as it is still unknown whether one or two tetramers of RuvA support RuvB during branch migration and during RFR. We designed an E. coli RuvA mutant, RuvA2(KaP), specifically impaired for RuvA tetramer-tetramer interactions. As expected, the mutant protein is impaired for complex II (two tetramers) formation on HJs, although the binding efficiency of complex I (a single tetramer) is as wild type. We show that although RuvA complex II formation is required for efficient HJ branch migration in vitro, RuvA2(KaP) is fully active for homologous recombination in vivo. RuvA2(KaP) is also deficient at forming complex II on synthetic replication forks, and the binding affinity of RuvA2(KaP) for forks is decreased compared with wild type. Accordingly, RuvA2(KaP) is inefficient at processing forks in vitro and in vivo. These data indicate that RuvA2(KaP) is a separation-of-function mutant, capable of homologous recombination but impaired for RFR. RuvA2(KaP) is defective for stimulation of RuvB activity and stability of HJ·RuvA·RuvB tripartite complexes. This work demonstrates that the need for RuvA tetramer-tetramer interactions for full RuvAB activity in vitro causes specifically an RFR defect in vivo.

  3. Influence of clusters in melt on the subsequent glass-formation and crystallization of Fe-Si-B metallic glasses

    Institute of Scientific and Technical Information of China (English)

    Shaoxiong Zhou; Bangshao Dong; Rui Xiang; Guangqiang Zhang; Jingyu Qin; Xiufang Bian

    2015-01-01

    The liquid structure of seven representative Fe–Si–B alloys has been investigated by ab initio molecular dynamics simulation focusing on the role of clusters in terms of glass-forming ability (GFA) and crystallization. It is demonstrated that the type of primary phase precipitated from amorphous state under heat treatment is determined by the relative fraction and role of various clusters in melt. The alloy melt shows higher stability and resultantly larger GFA when there is no dominant cluster or several clusters coexist, which explains the different GFAs and crystallization processes at various ratios of Si and B in the Fe–Si–B system. The close correlation among clusters, crystalline phase and GFA is also studied.

  4. Influence of clusters in melt on the subsequent glass-formation and crystallization of Fe–Si–B metallic glasses

    Directory of Open Access Journals (Sweden)

    Shaoxiong Zhou

    2015-04-01

    Full Text Available The liquid structure of seven representative Fe–Si–B alloys has been investigated by ab initio molecular dynamics simulation focusing on the role of clusters in terms of glass-forming ability (GFA and crystallization. It is demonstrated that the type of primary phase precipitated from amorphous state under heat treatment is determined by the relative fraction and role of various clusters in melt. The alloy melt shows higher stability and resultantly larger GFA when there is no dominant cluster or several clusters coexist, which explains the different GFAs and crystallization processes at various ratios of Si and B in the Fe–Si–B system. The close correlation among clusters, crystalline phase and GFA is also studied.

  5. Cellulose nanocrystal-based materials : from liquid crystal self-assembly and glass formation to multifunctional thin films

    OpenAIRE

    Jan P. F. Lagerwall; Schütz, Christina; Salajkova, Michaela; Noh, Junghyun; PARK, JI HYUN; Scalia, Giusy; Bergström, Lennart

    2014-01-01

    Cellulose nanocrystals (CNCs), produced by the acid hydrolysis of wood, cotton or other cellulose-rich sources, constitute a renewable nanosized raw material with a broad range of envisaged uses: for example, in composites, cosmetics and medical devices. The intriguing ability of CNCs to self-organize into a chiral nematic (cholesteric) liquid crystal phase with a helical arrangement has attracted significant interest, resulting in much research effort, as this arrangement gives dried CNC fil...

  6. The Influence of Crystal Structure on the Lattice Sites and Formation Energies of Hydrogen in Wurtzite and Zinc-Blende GaN

    Energy Technology Data Exchange (ETDEWEB)

    Wright, A.F.

    1999-02-01

    Charge-state calculations based on density-functional theory are used to study the formation energy of hydrogen in wurtzite and zinc-blende GaN as a function of Fermi level Comparison of these results reveals notable differences including a 0.56 eV lower formation energy for H2 in wurtzite, and different configurations for H2 and H- in the two crystal structures. Furthermore, H+ is found to be equally stable at bond-centered and anti-bonding sites in wurtzite, whereas it is unstable at a bond-centered site in zinc blende. These differences are due to distinct features of the two crystal structures including: the lower symmetry of wurtzite which provides a wider selection of bonding sites for H+, and the existence of extended three-fold symmetric channels oriented along the c-axis in wurtzite which provide more favorable bonding configurations for H2 and H-.N-H+ stretch-mode vibration frequencies, clustering of ?3+ in p-type material, and diffusion barriers for H" are also investigated in wurtzite GaN. A diffusion barrier of 1.6 eV is found for H- in wurtzite GaN, significantly lower than a previous estimate, and a tendency for H+ clustering in p-type material is found.

  7. Anion effect on the binary and ternary phase diagrams of chiral medetomidine salts and conglomerate crystal formation.

    Science.gov (United States)

    Choobdari, Ebrahim; Fakhraian, Hossein; Peyrovi, Mohammad Hassan

    2014-03-01

    The binary phase diagrams of hydrogen halides salts of medetomidine (Med.HX, X:Br,I) and hydrogen oxalate salt of medetomidine (Med.Ox) were determined based on thermogravimetric/differential thermal analysis (TGA/DTA) and their crystal structure behavior was confirmed by comparison of the X-ray diffractometry and FT-IR spectroscopy of the racemate and pure enantiomer. All hydrogen halide salts presented racemic compound behavior. Heat of fusion of halides salt of (rac)-medetomidine decreased with ionic radius increase. Eutectic points for Med.HCl (previously reported), Med.HBr, and Med.HI rest were unchanged approximately. The solubility of different enantiomeric mixtures of Med.HBr and Med.HI were measured at 10, 20, and 30°C in 2-propanol showing a solubility increase with ionic radius. A binary phase diagram of Med.Ox shows a racemic conglomerate behavior. The solubility of enantiomeric mixtures of Med.Ox were measured at 10, 20, 30, and 40°C. The ternary phase diagram of Med.Ox in ethanol conforms to a conglomerate crystal forming system, favoring its enantiomeric purification by preferential crystallization.

  8. Low-frequency and tuning characteristic of band gap in a symmetrical double-sided locally resonant phononic crystal plate with slit structure

    Science.gov (United States)

    Wang, X. P.; Jiang, P.; Song, A. L.

    2016-09-01

    In this paper, the low-frequency and tuning characteristic of band gap in a two-dimensional phononic crystal structure, consisting of a square array of aluminum cylindrical stubs deposited on both sides of a thin rubber plate with slit structure, are investigated. Using the finite element method, the dispersion relationships and power transmission spectra of this structure are calculated. In contrast to a typical phononic crystal without slit structure, the proposed slit structure shows band gaps at lower frequencies. The vibration modes of the band gap edges are analyzed to clarify the mechanism of the lowest band gaps. Additionally, the influence of the slit parameters and stub parameters on the band gaps in slit structure are investigated. The geometrical parameters of the slits and stubs were found to influence the band gaps; this is critical to understand for practical applications. These results will help in fabricating phononic crystal structures whose band frequency can be modulated at lower frequencies.

  9. Influence of cerium doping on the dielectric relaxation of Sr{sub 0.75}Ba{sub 0.25}Nb{sub 2}O{sub 6} single crystal grown by the double crucible Stepanov technique

    Energy Technology Data Exchange (ETDEWEB)

    Bhaumik, Indranil, E-mail: neel@rrcat.gov.in [Crystal Growth Laboratory, LMDDD, Raja Ramanna Centre for Advanced Technology, Indore (India); Ganesamoorthy, S. [XS and CGS, CMPD, MSG, Indira Gandhi Centre for Atomic Research, Kalpakkam (India); Bhatt, R. [Crystal Growth Laboratory, LMDDD, Raja Ramanna Centre for Advanced Technology, Indore (India); Subramanian, N. [XS and CGS, CMPD, MSG, Indira Gandhi Centre for Atomic Research, Kalpakkam (India); Karnal, A.K.; Gupta, P.K. [Crystal Growth Laboratory, LMDDD, Raja Ramanna Centre for Advanced Technology, Indore (India); Takekawa, S.; Kitamura, K. [Polar Domain Engineering Group, NIMS, Namiki, Tsukuba (Japan)

    2015-02-05

    Highlights: • Incorporation of Ce in the lattice reduces dielectric maxima in Sr{sub 0.75}Ba{sub 0.25}Nb{sub 2}O{sub 6}. • It increases degree of diffusiveness and lowers the temperature of dielectric maxima. • These are due to introduction of addition random field via created point defects. • Both of the crystals undergo non-debye type relaxation. • VF fitting revealed that attempt frequency reduced by one order on Ce doping. - Abstract: The effect of Ce doping on the dielectric relaxation in Sr{sub 0.75}Ba{sub 0.25}Nb{sub 2}O{sub 6} single crystal grown by double crucible Stepanov technique has been investigated. It has been observed that the incorporation of Ce ion in the lattice reduces the dielectric maxima. It further increases the degree of diffusiveness and lowers the temperature of dielectric maxima as a result of the introduction of additional random field via created point defects. Both the undoped and Ce doped crystals undergo a non-debye type relaxation. Vogel–Fulcher fitting reveals that the attempt frequency reduced by one order of magnitude on Ce doping.

  10. Optical spectroscopy and crystal field studies of the Mn{sup 4+} ion (3d{sup 3}) in the double perovskite NaLaMgTeO{sub 6}

    Energy Technology Data Exchange (ETDEWEB)

    Srivastava, Alok M.; Camardello, Samuel J.; Comanzo, Holly A.; Garcia-Santamaria, Florencio [GE Global Research, Niskayuna, NY (United States); Brik, Mikhail G. [Tartu Univ. (Estonia). Inst. of Physics

    2014-02-15

    The spectroscopic properties of the Mn{sup 4+} ion (3d{sup 3}) in the double perovskite NaLaMgTeO{sub 6} are reported in this work. Evidence is presented for the occupation by the Mn{sup 4+} ion of both the six coordinated Mg{sup 2+} and Te{sup 6+} sites in the host structure. The Mn{sup 4+} energy levels are calculated using the exchange charge model of crystal field theory for both occupied sites. The results of our calculations yield the crystal field splitting and Racah parameters of Dq =2008 cm{sup -1}, B =790 cm{sup -1}, C =2881 cm{sup -1}, with C/B = 3.65 (Mg{sup 2+} site) and Dq =2008 cm{sup -1}, B =790 cm{sup -1}, C =2949 cm{sup -1}, with C/B = 3.73 (Te{sup 6+} site). A cross-cutting comparative study of the variations in the crystal field splitting and the Racah parameters of the six-coordinated Mn{sup 4+} ion in a series of materials with the perovskite structure are presented. (orig.)

  11. Calcium acetate induces calcium uptake and formation of calcium-oxalate crystals in isolated leaflets of Gleditsia triacanthos L.

    Science.gov (United States)

    Borchert, R

    1986-09-01

    During treatment of isolated, peeled leaflets of Gleditsia triacanthos with 0.5-2 mM [(45)Ca]acetate, saturation of the cell-wall free space with Ca(2+) occurred within 10 min and was followed by a period of 6-10 h during which there was no significant Ca-uptake into the protoplast, but apoplastic Ca(2+) was periodically released into the medium. Later, Ca(2+) was absorbed for 3-4 d at rates of up to 2.2 μmol Ca(2+)·h(-1)·(g FW)(-1) to final concentrations of 350 μmol Ca(2+)· (g FW)(-1). The distribution of absorbed Ca(2+) between cell wall, vacuole and Ca-oxalate crystals was determined during Ca-uptake. Wheras intact, cut leaflets deposited absorbed Ca(2+) as Ca-oxalate in the crystal cells, peeled leaflets lacking crystal cells accumulated at least 40-50 μmol·(g FW)(-1) soluble Ca(2+) before the absorbed Ca(2+) was precipitated as Ca-oxalate. These observations indicate that the mechanisms for the continuous uptake of Ca(2+), the synthesis of oxalate and the precipitation of Ca(2+) as Ca-oxalate are operational in the crystal cells of intact leaflets, but not in the mesophyll cells of peeled leaflets where they must be induced by exposure to Ca(2+). The precipitation of absorbed Ca(2+) as Ca-oxalate by the crystal cells of isolated Gleditsia leaflets illustrates the role of these cells in the excretion of surplus Ca(2+) which enters normal, attached leaves with the transpiration stream.In addition to acetate, only Ca-lactate and Ca-carbonate lead to Ca-uptake, but at rates well below those observed with Ca-acetate. Other small organic anions (citrate, glycolate, glyoxalate, malate) and inorganic anions (chloride, nitrate, sulfate) did not permit Ca-uptake. Acetate-(14)C was rapidly absorbed during Ca-uptake, but less than 20% was incorporated into Ca-oxalate; the rest remained mostly in the soluble fraction or was metabolized to CO2. Acetate, as a permeable weak acid, may enable rapid Ca-uptake by stimulating proton extrusion at the plasmalemma and by

  12. Effect of amino acid dopants on the spectral, optical, mechanical and thermal properties of potassium acid phthalate crystals for possible optoelectronic and frequency doubling applications

    Science.gov (United States)

    Prakash, J. Thomas Joseph; Gnanaraj, J. Martin Sam; Dhavud, S. Shek; Ekadevasena, S.

    2015-09-01

    Undoped and amino acid (L-Arginine and L-Valine) doped KAP crystals were grown by slow evaporation solution growth technique. The changes in the structural, spectral, optical, mechanical and thermal properties were observed. The sharp prominent peaks in the indexed powder XRD pattern confirms the crystalline nature of the sample. Optical studies reveal that the crystal is transparent in the entire visible light region. Thermal stability was checked by TG/DTA analysis. The mechanical stability was evaluated from Vicker's microhardness test. The SHG efficiency for the title materials was tested with different particle sizes by the Kurtz and Perry powder method, which established the existence of phase matching.

  13. ROS via BTK-p300-STAT1-PPARγ signaling activation mediates cholesterol crystals-induced CD36 expression and foam cell formation

    Directory of Open Access Journals (Sweden)

    Sivareddy Kotla

    2017-04-01

    Full Text Available In understanding the mechanisms of cholesterol in the pathogenesis of atherosclerosis, previous studies from other laboratories have demonstrated that cholesterol crystals (CC induce scavenger receptor CD36 expression and NLRP3-mediated inflammasome formation. In elucidating the mechanisms by which CC could enhance CD36 expression and foam cell formation, here we report that CC via NADPH and xanthine oxidases-mediated ROS production activates BTK, a non-receptor tyrosine kinase. In addition, CC induce p300 tyrosine phosphorylation and activation in a BTK-dependent manner, which in turn, leads to STAT1 acetylation and its interaction with PPARγ in CD36 expression, oxLDL uptake and foam cell formation. Furthermore, p300, STAT1 and PPARγ bound to a STAT binding site at −107 nt in CD36 promoter and enhanced its activity in ROS and BTK-dependent manner. Disruption of this STAT binding site by site-directed mutagenesis abolished CC-induced CD36 promoter activity. Together these results reveal for the first time that CC via producing ROS and activating BTK causes p300-mediated STAT1 acetylation and its interaction with PPARγ in CD36 expression, oxLDL uptake and foam cell formation.

  14. From surface science to catalysis: The importance of methoxy and formate species on Cu single crystals and industrial catalysts

    Science.gov (United States)

    Bowker, M.; Waugh, K. C.

    2016-08-01

    Early work from the Madix group identified a number of simple surface intermediate species which have proved to be of significance for industrial catalytic processes. Two of these intermediates are the methoxy and formate surface species. We discuss the formation and behavior of these on copper surfaces, and go on to highlight their role in two important industrial reactions, namely methanol synthesis and the selective oxidation of methanol to formaldehyde. The formate is the pivotal intermediate for methanol synthesis and is formed from the reaction of CO2 and H2, whereas it is important to avoid the formation of that intermediate for selective methanol oxidation, which proceeds through dehydrogenation of the methoxy species.

  15. Fe(II) sorption on pyrophyllite: Effect of structural Fe(III) (impurity) in pyrophyllite on nature of layered double hydroxide (LDH) secondary mineral formation

    Energy Technology Data Exchange (ETDEWEB)

    Starcher, Autumn N.; Li, Wei; Kukkadapu, Ravi K.; Elzinga, Evert J.; Sparks, Donald L.

    2016-11-01

    Fe(II)-Al(III)-LDH (layered double hydroxide) phases have been shown to form from reactions of aqueous Fe(II) with Fe-free Al-bearing minerals (phyllosilicate/clays and Al-oxides). To our knowledge, the effect of small amounts of structural Fe(III) impurities in “neutral” clays on such reactions, however, were not studied. In this study to understand the role of structural Fe(III) impurity in clays, laboratory batch studies with pyrophyllite (10 g/L), an Al-bearing phyllosilicate, containing small amounts of structural Fe(III) impurities and 0.8 mM and 3 mM Fe(II) (both natural and enriched in 57Fe) were carried out at pH 7.5 under anaerobic conditions (4% H2 – 96% N2 atmosphere). Samples were taken up to 4 weeks for analysis by Fe-X-ray absorption spectroscopy and 57Fe Mössbauer spectroscopy. In addition to the precipitation of Fe(II)-Al(III)-LDH phases as observed in earlier studies with pure minerals (no Fe(III) impurities in the minerals), the analyses indicated formation of small amounts of Fe(III) containing solid(s), most probably hybrid a Fe(II)-Al(III)/Fe(III)-LDH phase. The mechanism of Fe(II) oxidation was not apparent but most likely was due to interfacial electron transfer from the sorbed Fe(II) to the structural Fe(III) and/or surface-sorption-induced electron-transfer from the sorbed Fe(II) to the clay lattice. Increase in the Fe(II)/Al ratio of the LDH with reaction time further indicated the complex nature of the samples. This research provides evidence for the formation of both Fe(II)-Al(III)-LDH and Fe(II)-Fe(III)/Al(III)-LDH-like phases during reactions of Fe(II) in systems that mimic the natural environments. Better understanding Fe phase formation in complex laboratory studies will improve models of natural redox systems.

  16. Formation mechanisms of nano and microcones by laser radiation on surfaces of Si, Ge, and SiGe crystals.

    Science.gov (United States)

    Medvid, Artur; Onufrijevs, Pavels; Jarimaviciute-Gudaitiene, Renata; Dauksta, Edvins; Prosycevas, Igoris

    2013-06-04

    In this work we study the mechanisms of laser radiation interaction with elementary semiconductors such as Si and Ge and their solid solution SiGe. As a result of this investigation, the mechanisms of nanocones and microcones formation on a surface of semiconductor were proposed. We have shown the possibility to control the size and the shape of cones both by the laser. The main reason for the formation of nanocones is the mechanical compressive stresses due to the atoms' redistribution caused by the gradient of temperature induced by strongly absorbed laser radiation. According to our investigation, the nanocone formation mechanism in semiconductors is characterized by two stages. The first stage is characterized by formation of a p-n junction for elementary semiconductors or of a Ge/Si heterojunction for SiGe solid solution. The generation and redistribution of intrinsic point defects in elementary semiconductors and Ge atoms concentration on the irradiated surface of SiGe solid solution in temperature gradient field take place at this stage due to the thermogradient effect which is caused by strongly absorbed laser radiation. The second stage is characterized by formation of nanocones due to mechanical plastic deformation of the compressed Ge layer on Si. Moreover, a new 1D-graded band gap structure in elementary semiconductors due to quantum confinement effect was formed. For the formation of microcones Ni/Si structure was used. The mechanism of the formation of microcones is characterized by two stages as well. The first stage is the melting of Ni film after irradiation by laser beam and formation of Ni islands due to surface tension force. The second step is the melting of Ni and subsequent manifestations of Marangoni effect with the growth of microcones.

  17. Measurement of helium-like and hydrogen-like argon spectra using double-crystal X-ray spectrometers on EAST

    Science.gov (United States)

    Lyu, B.; Chen, J.; Hu, R. J.; Wang, F. D.; Li, Y. Y.; Fu, J.; Shen, Y. C.; Bitter, M.; Hill, K. W.; Delgado-Aparicio, L. F.; Pablant, N.; Lee, S. G.; Ye, M. Y.; Shi, Y. J.; Wan, B. N.

    2016-11-01

    A two-crystal assembly was deployed on the tangential X-ray crystal spectrometer to measure both helium-like and hydrogen-like spectra on EAST. High-quality helium-like and hydrogen-like spectra were observed simultaneously for the first time on one detector for a wide range of plasma parameters. Profiles of line-integrated core ion temperatures inferred from two spectra were consistent. Since tungsten was adopted as the upper divertor material, one tungsten line (W XLIV at 4.017 Å) on the short-wavelength side of the Lyman-α line (Lα1) was identified for typical USN discharges, which was diffracted by a He-like crystal (2d = 4.913 Å). Another possible Fe XXV line (1.85 Å) was observed to be located on the long-wavelength side of resonance line (w), which was diffracted from a H-like crystal (2d = 4.5622 Å) on the second order. Be-like argon lines were also observable that fill the detector space between the He-like and H-like spectra.

  18. Development of cryogenic low background detector based on enriched zinc molybdate crystal scintillators to search for neutrinoless double beta decay of $^{100}$Mo

    CERN Document Server

    Chernyak, Dmitry

    2015-01-01

    ZnMoO$_4$ scintillators with a mass of $\\sim$ 0.3 kg, as well as Zn$^{100}$MoO$_4$ crystals enriched in the isotope $^{100}$Mo were produced for the first time by using the low-thermal-gradient Czochralski technique. The optical and luminescent properties of the produced crystals were studied to estimate the progress in crystal growth quality. The low-temperature tests with a 313 g ZnMoO$_4$ and two enriched Zn$^{100}$MoO$_4$ crystals were performed aboveground in the Centre de Sciences Nucl\\'eaires et de Sciences de la Mati\\`ere. The low background measurements with a three ZnMoO$_4$ and two enriched detectors installed in the EDELWEISS set-up at the Laboratoire Souterrain de Modane were carried out. To optimize the light collection in ZnMoO$_4$ scintillating bolometers, we have simulated the collection of scintillation photons in a detector module for different geometries by Monte Carlo method using the GEANT4 package. Response to the 2$\

  19. Synthesis and Crystal Structure of (E)-4-(Benzyloxy)-2-(cinnamoyloxy)-N,N,N-trimethyl-4-oxobutan-1-aminium Chloride as a Double-prodrug

    Institute of Scientific and Technical Information of China (English)

    GONG Xiao-Wei; LI Xun; LI Wei-Lu; GAO Xu; XU Wen-Fang; ZHAI Hai-Min

    2008-01-01

    A novel hydrochloride quaternary ammonium salt (E)-4-(benzyloxy)-2-(cinnamo-yloxy)-N,N,N-trimethy1-4-oxobutan-1-aminium chloride(C23H29NO4Cl2,Mr=454.37)has been synthesized via the sequence of acetylation and esterification by using L-carnitine(L-4-N-trimethy-lammonium-3-hydroxybutyric acid,LC)and cinnamic acid as the starting materials,and its crystal structure was determined by single-crystal X-ray diffraction method.The crystal belongs to monoclinic,space group P212121 with a=10.1670(4),b=10.4488(4),c=22.9795(11)(A),V=2441.18(18)(A)3,Z=4,Dc=1.236 g/cm3,μ(MoKa)=0.293 mm-1,F(000)=960,Flack factor=-0.01(11).the final R=0.0489 and wR=0.1550 for 3350 observed reflections(I>2σ(I))and R=0.0953 for all 5648 unique reflections.The crystal structure involves a conjugated system which shows a reverse olefin structure.

  20. Beam tests of proton-irradiated PbWO$_4$ crystals and evaluation of double-sided read-out technique for mitigation of radiation damage effects

    CERN Document Server

    Lucchini, Marco Toliman

    2016-01-01

    The harsh radiation environment in which detectors will have to operate during the High Luminosity phase of the LHC (HL-LHC) represents a crucial challenge for many calorimeter technologies. In the CMS forward calorimeters, ionizing doses and hadron fluences will reach up to 300 kGy (at a dose rate of 30 Gy/h) and $2\\times10^{14}$ cm$^{-2}$, respectively, at the pseudorapidity region of $\\lvert \\eta\\rvert=2.6$. To evaluate the evolution of the CMS ECAL performance in such conditions, a set of PbWO$_4$ crystals, exposed to 24 GeV protons up to integrated fluences between $2.1\\times10^{13}$ cm$^{-2}$ and $1.3\\times10^{14}$ cm$^{-2}$, has been studied in beam tests. A degradation of the energy resolution and a non-linear response to electron showers are observed in damaged crystals. Direct measurements of the light output from the crystals show the amplitude decreasing and pulse becoming faster as the fluence increases. The evolution of the performance of the PbWO$_4$ crystals has been well understood and parame...