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Sample records for aluminum-induced crystallization comparison

  1. Poly-Si films with low aluminum dopant containing by aluminum-induced crystallization

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Typically, highly p-doped (2×10 18 cm -3 ) poly-Si films fabricated by the aluminum induced layer exchange (ALILE) process are not suitable for solar cell absorber layers. In this paper, the fabrication of high-quality, continuous polycrystalline silicon (poly-Si) films with lower doping concentrations (2×10 16 cm -3 ) using aluminum-induced crystallization (AIC) is reported. Secondary-ion-mass spectroscopy (SIMS) results showed that annealing at different temperature profiles leads to a variety of Al concentrations. Hall Effect measurements revealed that Al dopant concentration depends on the annealing temperature and temperature profile. Raman spectral analysis indicated that samples prepared via AIC contain some regions with small grains.

  2. Aluminum induced crystallization of strongly (111) oriented polycrystalline silicon thin film and nucleation analysis

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    A polycrystalline silicon thin film was fabricated on glass substrate by means of aluminum induced crystallization (AIC). Al and α-Si layers were deposited by magnetron sputtering respectively and annealed at 480°C for 1 h to realize layer exchange. The polycrystalline silicon thin film was continuous and strongly (111) oriented. By analyzing the structure variation of the oxidation membrane and lattice mismatch between γ-Al2O3 and Si, it was concluded that aluminum promoted the formation of (111) oriented silicon nucleus by controlling the orientation of γ-Al2O3, which was formed at the early stage of annealing.

  3. Study of polycrystalline silicon obtained by aluminum-induced crystallization depending on process conditions

    Science.gov (United States)

    Pereyaslavtsev, Alexander; Sokolov, Igor; Sinev, Leonid

    2016-11-01

    In this paper, we have decided to consider an alternative method of producing polycrystalline silicon and study change of its electrophysical characteristics depending on process parameters. As an alternative low-pressure chemical vapor deposition method appears aluminum-induced crystallization (AIC), which allows to obtain a polycrystalline silicon film is significantly larger grain size, thereby reducing contribution of grain boundaries. A comprehensive study of polycrystalline silicon was carried out using a variety of microscopic (OM, SEM) and spectroscopic (RAMAN, XPS) and diffraction (EBSD, XRD) analytic methods. We also considered possibility of self-doping in AIC, result of which was obtained polycrystalline silicon with different resistance. Additionally considered changes in temperature coefficient of resistance depending on technological parameters of AIC process.

  4. Deposition and characterization of silicon thin-films by aluminum-induced crystallization

    Science.gov (United States)

    Ebil, Ozgenc

    Polycrystalline silicon (poly-Si) as a thin-film solar cell material could have major advantages compared to non-silicon thin-film technologies. In theory, thin-film poly-Si may retain the performance and stability of c-Si while taking advantage of established manufacturing techniques. However, poly-Si films deposited onto foreign substrates at low temperatures typically have an average grain size of 10--50 nm. Such a grain structure presents a potential problem for device performance since it introduces an excessive number of grain boundaries which, if left unpassivated, lead to poor solar cell properties. Therefore, for optimum device performance, the grain size of the poly-Si film should be at least comparable to the thickness of the films. For this project, the objectives were the deposition of poly-Si thin-films with 2--5 mum grain size on glass substrates using in-situ and conventional aluminum-induced crystallization (AIC) and the development of a model for AIC process. In-situ AIC experiments were performed using Hot-Wire Chemical Vapor Deposition (HWCVD) both above and below the eutectic temperature (577°C) of Si-Al binary system. Conventional AIC experiments were performed using a-Si layers deposited on aluminum coated glass substrates by Electron-beam deposition, Plasma Enhanced Chemical Vapor Deposition (PECVD) and HWCVD. Continuous poly-Si films with an average grain size of 10 mum on glass substrates were achieved by both in-situ and conventional aluminum-induced crystallization of Si below eutectic temperature. The grain size was determined by three factors; the grain structure of Al layer, the nature of the interfacial oxide, and crystallization temperature. The interface oxide was found to be crucial for AIC process but not necessary for crystallization itself. The characterization of interfacial oxide layer formed on Al films revealed a bilayer structure containing Al2O3 and Al(OH)3 . The effective activation energy for AIC process was determined

  5. Poly-crystalline thin-film by aluminum induced crystallization on aluminum nitride substrate

    Science.gov (United States)

    Bhopal, Muhammad Fahad; Lee, Doo Won; Lee, Soo Hong

    2016-09-01

    Thin-film polycrystalline silicon ( pc-Si) on foreign (non-silicon) substrates has been researched by various research groups for the production of photovoltaic cells. High quality pc-Si deposition on foreign substrates with superior optical properties is considered to be the main hurdle in cell fabrication. Metal induced crystallization (MIC) is one of the renowned techniques used to produce this quality of material. In the current study, an aluminum induced crystallization (AIC) method was adopted to produce pc-Si thin-film on aluminum nitride (AlN) substrate by a seed layer approach. Aluminum and a-Si layer were deposited using an e-beam evaporator. Various annealing conditions were used in order to investigate the AIC grown pc-Si seed layers for process optimization. The effect of thermal annealing on grain size, defects preferentially crystallographic orientation of the grains were analyzed. Surface morphology was studied using an optical microscope. Poly-silicon film with a crystallinity fraction between 95-100% and an FWHM between 5-6 cm-1 is achievable at low temperatures and for short time intervals. A grain size of about 10 micron can be obtained at a low deposition rate on an AIN substrate. Similarly, Focused ion beam (FIB) also showed that at 425 °C sample B and at 400 °C sample A were fully crystallized. The crystalline quality of pc-Si was evaluated using μ-Raman spectroscopy as a function of annealed conditions and Grazing incidence X-ray diffraction (GIXRD) was used to determine the phase direction of the pc-Si layer. The current study implicates that a poly-silicon layer with good crystallographic orientation and crystallinity fraction is achievable on AIN substrate at low temperatures and short time frames.

  6. Effect on thickness of Al layer in poly-crystalline Si thin films using aluminum(Al) induced crystallization method.

    Science.gov (United States)

    Jeong, Chaehwan; Na, Hyeon Sik; Lee, Suk Ho

    2011-02-01

    The polycrystalline silicon (poly-Si) thin films were prepared by aluminum induced crystallization. Aluminum (Al) and amorphous silicon (a-Si) layers were deposited using DC sputtering and plasma enhanced chemical vapor deposition method, respectively. For the whole process Al properties of bi-layers can be one of the important factors. In this paper we investigated the structural and electrical properties of poly-crystalline Si thin films with a variation of Al thickness through simple annealing process. All samples showed the polycrystalline phase corresponding to (111), (311) and (400) orientation. Process time, defined as the time required to reach 95% of crystalline fraction, was within 60 min and Al(200 nm)/a-Si(400 nm) structure of bi-layer showed the fast response for the poly-Si films. The conditions with a variation of Al thickness were executed in preparing the continuous poly-Si films for solar cell application.

  7. P-type poly-Si prepared by low-temperature aluminum-induced crystallization and doping for solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Matsumoto, Yasuhiro; Yu, Zhenrui; Morales-Acevedo, Arturo [CINVESTAV-IPN, Mexico, D.F. (Mexico)

    2000-07-01

    P-type poly-Si thin films prepared by low temperature aluminum-induced crystallization and doping are reported. The starting material was boron-doped a-Si:H prepared by PECVD on glass substrates. Aluminum layers with different thickness were evaporated on a-Si:H surface and conventional thermal annealing was performed at temperatures ranging from 300 to 550 Celsius degrees. XRD, SIMS, and Hall effect measurements were carried out to characterize the annealed Al could be crystallized at temperature as low as 300 Celsius degrees in 60 minutes. This material has high carrier concentration as well as high Hall mobility and can be used as a p-layer of seed layer for thin film poly-Si solar cells. The technique reported here is compatible with PECVD process. [Spanish] Se informa sobre la preparacion de peliculas delgadas tipo P y Poli-Si mediante la cristalizacion inducida de aluminio a baja temperatura y el dopado. El material inicial era de boro dopado y a-Si:H preparado PECVD sobre substratos de vidrio. Se evaporaron capas de aluminio de diferente espesor sobre una superficie de a-Si:H y se llevo a cabo un destemplado termico convencional a temperaturas que varian entre 300 y 500 grados Celsius. Se llevaron a cabo mediciones de XRB, SIMS y del efecto Hall para caracterizar el aluminio destemplado para que pudiera ser cristalizado a temperaturas tan bajas como 300 grados Celsius en 60 minutos. Este material tiene una alta concentracion portadora asi como una alta movilidad Hall y puede usarse como una capa de semilla para celdas solares de pelicula delgada Poli-Si. La tecnica reportada aqui es compatible con el proceso PECVD.

  8. Quercetin attenuates neuronal death against aluminum-induced neurodegeneration in the rat hippocampus.

    Science.gov (United States)

    Sharma, D R; Wani, W Y; Sunkaria, A; Kandimalla, R J; Sharma, R K; Verma, D; Bal, A; Gill, K D

    2016-06-02

    Aluminum is a light weight and toxic metal present ubiquitously on earth, which has gained considerable attention due to its neurotoxic effects. It also has been linked ecologically and epidemiologically to several neurological disorders, including Alzheimer's disease (AD), Parkinson's disease (PD), Guamanian-Parkinsonian complex and Amyotrophic lateral sclerosis (ALS). The mechanism of aluminum neurotoxicity is poorly understood, but it is well documented that aluminum generates reactive oxygen species (ROS). Enhanced ROS production leads to disruption of cellular antioxidant defense systems and release of cytochrome c (cyt-c) from mitochondria to cytosol resulting in apoptotic cell death. Quercetin (a natural flavonoid) protects it from oxidative damage and has been shown to decrease mitochondrial damage in various animal models of oxidative stress. We hypothesized that if oxidative damage to mitochondria does play a significant role in aluminum-induced neurodegeneration, and then quercetin should ameliorate neuronal apoptosis. Administration of quercetin (10 mg/kg body wt/day) reduced aluminum (10 mg/kg body wt/day)-induced oxidative stress (decreased ROS production, increased mitochondrial superoxide dismutase (MnSOD) activity). In addition, quercetin also prevents aluminum-induced translocation of cyt-c, and up-regulates Bcl-2, down-regulates Bax, p53, caspase-3 activation and reduces DNA fragmentation. Quercetin also obstructs aluminum-induced neurodegenerative changes in aluminum-treated rats as seen by Hematoxylin and Eosin (H&E) staining. Further electron microscopic studies revealed that quercetin attenuates aluminum-induced mitochondrial swelling, loss of cristae and chromatin condensation. These results indicate that treatment with quercetin may represent a therapeutic strategy to attenuate the neuronal death against aluminum-induced neurodegeneration.

  9. Improving the Microstructure and Electrical Properties of Aluminum Induced Polysilicon Thin Films Using Silicon Nitride Capping Layer

    Directory of Open Access Journals (Sweden)

    Min-Hang Weng

    2014-01-01

    Full Text Available We investigated the capping layer effect of SiNx (silicon nitride on the microstructure, electrical, and optical properties of poly-Si (polycrystalline silicon prepared by aluminum induced crystallization (AIC. The primary multilayer structure comprised Al (30 nm/SiNx (20 nm/a-Si (amorphous silicon layer (100 nm/ITO coated glass and was then annealed in a low annealing temperature of 350°C with different annealing times, 15, 30, 45, and 60 min. The crystallization properties were analyzed and verified by X-ray diffraction (XRD and Raman spectra. The grain growth was analyzed via optical microscope (OM and scanning electron microscopy (SEM. The improved electrical properties such as Hall mobility, resistivity, and dark conductivity were investigated by using Hall and current-voltage (I-V measurements. The results show that the amorphous silicon film has been effectively induced even at a low temperature of 350°C and a short annealing time of 15 min and indicate that the SiNx capping layer can improve the grain growth and reduce the metal content in the induced poly-Si film. It is found that the large grain size is over 20 μm and the carrier mobility values are over 80 cm2/V-s.

  10. Metal-induced crystallization fundamentals and applications

    CERN Document Server

    Wang, Zumin; Mittemeijer, Eric J

    2014-01-01

    Introduction to Metal-Induced CrystallizationAtomic Mechanisms and Interface Thermodynamics of Metal-Induced Crystallization of Amorphous Semiconductors at Low TemperaturesThermodynamics and Kinetics of Layer Exchange upon Low-Temperature Annealing Amorphous Si/Polycrystalline Al Layered StructuresMetal-Induced Crystallization by Homogeneous Insertion of Metallic Species in Amorphous SemiconductorsAluminum-Induced Crystallization: Applications in Photovoltaic TechnologiesApplications of Metal-Induced Crystallization for Advanced Flat-Panel DisplaysLaser-Assisted Meta

  11. Focusing characteristics of diamond crystal x-ray monochromators. An experimental and theoretical comparison

    DEFF Research Database (Denmark)

    Rio, M.S. del; Grübel, G.; Als-Nielsen, J.

    1995-01-01

    Perfect crystals in transmission (Laue) geometry can be used effectively for x-ray monochromators, and moreover, perfect Laue crystals show an interesting focusing effect when the incident beam is white and divergent. This focusing is directly dependent on the incident beam divergence and on the ...... from a diamond crystal in Lane geometry, and we analyze and explain the results by comparison with ray-tracing simulations. (C) 1995 American Institute of Physics....

  12. Protective effects of low-intensity pulsed ultrasound on aluminum-induced cerebral damage in Alzheimer's disease rat model

    OpenAIRE

    Lin, Wei-Ting; Chen, Ran-Chou; Lu, Wen-Wei; Liu,Shing-Hwa; Yang, Feng-Yi

    2015-01-01

    The protein expressions of neurotrophic factors can be enhanced by low-intensity pulsed ultrasound (LIPUS) stimulation in the brain. The purpose of this study was to demonstrate the protective effect of LIPUS stimulation against aluminum-induced cerebral damage in Alzheimer's disease rat model. LIPUS was administered 7 days before each aluminum chloride (AlCl3) administration, and concomitantly given with AlCl3 daily for a period of 6 weeks. Neurotrophic factors in hippocampus were measured b...

  13. Comparison of High Temperature Crystal Lattice and Bulk Thermal Expansion Measurements of LGT Single Crystal

    Energy Technology Data Exchange (ETDEWEB)

    Beaucage, Timothy R [University of Maine; Beenfeldt, Eric P [University of Maine; Speakman, Scott A [ORNL; Porter, Wallace D [ORNL; Payzant, E Andrew [ORNL; Pereira da Cunha, Mauricio [University of Maine

    2006-01-01

    Among the langasite family of crystals (LGX), the three most popular materials are langasite (LGS, La3Ga5SiO14), langatate (LGT, La3Ga5.5Ta0.5O14) and langanite (LGN, La3Ga5.5Nb0.5O14). The LGX crystals have received significant attention for acoustic wave (AW) device applications due to several properties, which include: (1) piezoelectric constants about two and a half times those of quartz, thus allowing the design of larger bandwidth filters; (2) existence of temperature compensated orientations; (3) high density, with potential for reduced vibration and acceleration sensitivity; and (4) possibility of operation at high temperatures, since the LGX crystals do not present phase changes up to their melting point above 1400degC. The LGX crystals' capability to operate at elevated temperatures calls for an investigation on the growth quality and the consistency of these materials' properties at high temperature. One of the fundamental crystal properties is the thermal expansion coefficients in the entire temperature range where the material is operational. This work focuses on the measurement of the LGT thermal expansion coefficients from room temperature (25degC) to 1200degC. Two methods of extracting the thermal expansion coefficients have been used and compared: (a) dual push-rod dilatometry, which provides the bulk expansion; and (b) x-ray powder diffraction, which provides the lattice expansion. Both methods were performed over the entire temperature range and considered multiple samples taken from <001> Czochralski grown LGT material. The thermal coefficients of expansion were extracted by approximating each expansion data set to a third order polynomial fit over three temperature ranges reported in this work: 25degC to 400degC, 400degC to 900degC, 900degC to 1200degC. An accuracy of fit better than 35ppm for the bulk expansion and better than 10ppm for the lattice expansion have been obtained with the aforementioned polynomial fitting. The

  14. Comparison between high-energy proton and charged pion induced damage in Lead Tungstate calorimeter crystals

    CERN Document Server

    Lecomte, P; Nessi-Tedaldi, F; Pauss, F; Renker, D

    2007-01-01

    A Lead Tungstate crystal produced for the electromagnetic calorimeter of the CMS experiment at the LHC was cut into three equal-length sections. The central one was irradiated with 290 MeV/c positive pions up to a fluence of (5.67 +- 0.46)x10^13 /cm^2, while the other two were exposed to a 24 GeV/c proton fluence of (1.17 +- 0.11) x 10^13/ cm^2. The damage recovery in these crystals, stored in the dark at room temperature, has been followed over two years. The comparison of the radiation-induced changes in light transmission for these crystals shows that damage is proportional to the star densities produced by the irradiation.

  15. Systematic comparison of crystal and NMR protein structures deposited in the protein data bank.

    Science.gov (United States)

    Sikic, Kresimir; Tomic, Sanja; Carugo, Oliviero

    2010-09-03

    Nearly all the macromolecular three-dimensional structures deposited in Protein Data Bank were determined by either crystallographic (X-ray) or Nuclear Magnetic Resonance (NMR) spectroscopic methods. This paper reports a systematic comparison of the crystallographic and NMR results deposited in the files of the Protein Data Bank, in order to find out to which extent these information can be aggregated in bioinformatics. A non-redundant data set containing 109 NMR - X-ray structure pairs of nearly identical proteins was derived from the Protein Data Bank. A series of comparisons were performed by focusing the attention towards both global features and local details. It was observed that: (1) the RMDS values between NMR and crystal structures range from about 1.5 Å to about 2.5 Å; (2) the correlation between conformational deviations and residue type reveals that hydrophobic amino acids are more similar in crystal and NMR structures than hydrophilic amino acids; (3) the correlation between solvent accessibility of the residues and their conformational variability in solid state and in solution is relatively modest (correlation coefficient = 0.462); (4) beta strands on average match better between NMR and crystal structures than helices and loops; (5) conformational differences between loops are independent of crystal packing interactions in the solid state; (6) very seldom, side chains buried in the protein interior are observed to adopt different orientations in the solid state and in solution.

  16. Strength of orthoenstatite single crystals at mantle pressure and temperature and comparison with olivine

    Science.gov (United States)

    Raterron, Paul; Fraysse, Guillaume; Girard, Jennifer; Holyoke, Caleb W.

    2016-09-01

    Oriented single crystals of orthopyroxenes (OPx) were deformed in axisymmetric compression in the D-DIA at pressure and temperature in excess of 3 GPa and 1040 °C. Two crystal orientations were tested with the compression axis parallel to either [101]c crystallographic direction, to investigate [001](100) dislocation slip-system strength, or [011]c direction to investigate [001](010) slip-system strength. These slip systems are the most active in orthopyroxenes. Applied differential stresses and specimen strain rates were measured in situ by synchrotron X-ray diffraction and radiography. We used these data and comparison with previously reported low-pressure flow laws for protoenstatite and orthoenstatite to determine the power law parameters for the deformation of orthoenstatite crystals, which characterize OPx dislocation slip-system strengths. Applying these laws at reasonable mantle stresses along oceanic and continental geotherms indicates that OPx [001](100) slip system is weaker than OPx [001](010) slip system to ∼260 km depth where the strengths converge. It also indicates that both OPx slip systems are significantly stronger than olivine slip systems throughout the upper mantle, except in the upper most mantle, in the lithosphere, were OPx [001](100) slip system may be as weak or even weaker than olivine [100](010) easy slip system.

  17. Determination of interfacial tension from crystallization and dissolution data: a comparison with other methods.

    Science.gov (United States)

    Wu, W; Nancollas, G H

    1999-02-01

    Methods for the determination of interfacial tension between a solid and a liquid are reviewed including solubility/particle size, crystallization and dissolution kinetics. The use of solubility as a function of particle size, originally put forward by Ostwald and later corrected by Freundlich, may be unjustified for determining interfacial tension at solid-liquid interfaces. The interfacial tension values between solutions and sparingly soluble minerals such as hydroxyapatite, fluorapatite, brushite, octacalcium phosphate, calcium oxalate monohydrate, barium sulfate, calcium sulfate, calcite, and divalent metal fluorides are discussed. A comparison of these results is made with contact angle or wetting measurements. The interfacial tension values obtained from constant composition reaction kinetics are of the same order of magnitude as those determined using a contact angle method involving thin layer wicking techniques.

  18. Protective effects of low-intensity pulsed ultrasound on aluminum-induced cerebral damage in Alzheimer's disease rat model

    Science.gov (United States)

    Lin, Wei-Ting; Chen, Ran-Chou; Lu, Wen-Wei; Liu, Shing-Hwa; Yang, Feng-Yi

    2015-04-01

    The protein expressions of neurotrophic factors can be enhanced by low-intensity pulsed ultrasound (LIPUS) stimulation in the brain. The purpose of this study was to demonstrate the protective effect of LIPUS stimulation against aluminum-induced cerebral damage in Alzheimer's disease rat model. LIPUS was administered 7 days before each aluminum chloride (AlCl3) administration, and concomitantly given with AlCl3 daily for a period of 6 weeks. Neurotrophic factors in hippocampus were measured by western blot analysis. Behavioral changes in the Morris water maze and elevated plus maze were examined in rats after administration of AlCl3. Various biochemical analyses were performed to evaluate the extent of brain damages. LIPUS is capable of prompting levels of brain-derived neurotrophic factor (BDNF), glial cell line-derived neurotrophic factor (GDNF), and vascular endothelial growth factor (VEGF) in rat brain. AlCl3 administration resulted in a significant increase in the aluminum concentration, acetylcholinesterase activity and beta-amyloid (Aβ) deposition in AlCl3 treated rats. LIPUS stimulation significantly attenuated aluminum concentration, acetylcholinesterase activity, Aβ deposition and karyopyknosis in AlCl3 treated rats. Furthermore, LIPUS significantly improved memory retention in AlCl3-induced memory impairment. These experimental results indicate that LIPUS has neuroprotective effects against AlCl3-induced cerebral damages and cognitive dysfunction.

  19. Investigation of phase explosion in aluminum induced by nanosecond double pulse technique

    Energy Technology Data Exchange (ETDEWEB)

    Jafarabadi, Marzieh Akbari; Mahdieh, Mohammad Hossein, E-mail: mahdm@iust.ac.ir

    2015-08-15

    Highlights: • Single and collinear double pulse configurations were used for laser ablation of aluminum target in air. • The 5, 10, 15 and 20 ns delay times between pre pulse and main pulse in double pulse arrangement was investigated. • In comparison between single and double pulse regimes, the phase explosion threshold fluence is decreased in double pulse configuration. • The plasma shielding effect reduces the crater depth in lower laser fluence in double pulse configuration rather that its in single pulse configuration. - Abstract: In this paper, the influence of double pulse technique on phase explosion threshold in laser ablation of an aluminum target is investigated. Single and double pulse laser ablation of aluminum target was performed by a high power Nd:YAG laser beam in ambient air. In the double pulse excitation, the two pulses were from a single laser source which separated by a delay time in the range of 5–20 ns. Measuring ablation depth and rate, the phase explosion threshold was estimated in double pulse configuration as well as in the single pulse regime. The results show that in comparison between single and double pulse regimes, the phase explosion threshold fluence is decreased in double pulse configuration. The lowest phase explosion threshold fluence of 0.9 J/cm{sup 2} was obtained at 5 ns delay time. The results also show that plasma shielding effect reduced crater depth at a laser fluence which depended on the laser ablation configuration (single pulse or double pulse). The reduction of crater depth occurs at lower laser fluences for double pulse regime.

  20. Comparison of spectroscopic properties of Yb:YAP and Yb:YAG crystals

    Institute of Scientific and Technical Information of China (English)

    Xiaoming He; Guangjun Zhao; Xiaodong Xu; Xionghui Zeng; Jun Xu

    2007-01-01

    The Yb:YAG and Yb:YAP crystals have been grown by Czochralski method. The absorption spectra and the fluorescence spectra of Yb:YAG and Yb:YAP crystals have been investigated. It is shown that the Yb:YAG crystal has better laser properties and smaller threshold power than Yb:YAP crystal. In addition, the absorption cross-section of the Yb:YAP crystal is 2.16 times of that of the Yb:YAG crystal,so laser diode pumped Yb:YAG lasing can be easily realized. Because YAP single crystal is anisotropic, it is provided with polarization characteristics.

  1. Description of hard-sphere crystals and crystal-fluid interfaces: a comparison between density functional approaches and a phase-field crystal model.

    Science.gov (United States)

    Oettel, M; Dorosz, S; Berghoff, M; Nestler, B; Schilling, T

    2012-08-01

    In materials science the phase-field crystal approach has become popular to model crystallization processes. Phase-field crystal models are in essence Landau-Ginzburg-type models, which should be derivable from the underlying microscopic description of the system in question. We present a study on classical density functional theory in three stages of approximation leading to a specific phase-field crystal model, and we discuss the limits of applicability of the models that result from these approximations. As a test system we have chosen the three-dimensional suspension of monodisperse hard spheres. The levels of density functional theory that we discuss are fundamental measure theory, a second-order Taylor expansion thereof, and a minimal phase-field crystal model. We have computed coexistence densities, vacancy concentrations in the crystalline phase, interfacial tensions, and interfacial order parameter profiles, and we compare these quantities to simulation results. We also suggest a procedure to fit the free parameters of the phase-field crystal model. Thereby it turns out that the order parameter of the phase-field crystal model is more consistent with a smeared density field (shifted and rescaled) than with the shifted and rescaled density itself. In brief, we conclude that fundamental measure theory is very accurate and can serve as a benchmark for the other theories. Taylor expansion strongly affects free energies, surface tensions, and vacancy concentrations. Furthermore it is phenomenologically misleading to interpret the phase-field crystal model as stemming directly from Taylor-expanded density functional theory.

  2. A comparison study on the melt crystallization kinetics of long chain branched and linear isotactic polypropylenes

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The isothermal and non-isothermal crystallization kinetics of LCBPP and linear-iPP was investigated by optical microscopy and differential scanning calorimetry (DSC). The optical microscopy results in the isothermal crystallization process show that the crystals of LCBPP grow slower than the crystals of the linear-iPP. This originates from the low chain mobility, or in other words, the lower chain diffusion rate of LCBPP due to the existence of long side chains. The DSC results in the isothermal crystallization process show that the LCBPP exhibits, however, a higher overall crystallization rate with respect to the linear-iPP. This is related to the higher nucleation ability of LCBPP since the isothermal crystallization process of both LCBPP and linear-iPP are nucleation-dominated. Avrami analysis indicates that the nucleation nature and crystal growth manner of LCBPP and linear-iPP are about the same. The analyses of the non-isothermal crystallization processes indicate an increment in crystallization rate with increasing cooling rate. But at any cooling rate, the linear-iPP crystallizes more quickly than the LCBPP.This implies that the non-isothermal crystallization processes of LCBPP and linear-iPP are diffusion-dominated, in which the lower chain diffusion rate of LCBPP results in the slower crystallization of it.

  3. Comparison of the luminescent properties of LuAG:Pr nanopowders, crystals and films using synchrotron radiation

    Science.gov (United States)

    Gorbenko, V.; Zych, E.; Voznyak, T.; Nizankovskiy, S.; Zorenko, T.; Zorenko, Yu.

    2017-04-01

    Comparison of the luminescent properties of nanopowder, single crystal and single crystalline film of Pr3+ doped Pr-doped Lu3Al5O12 garnet (LuAG:Pr) prepared by the different technological methods is performed in this work using the time-resolved emission spectroscopy under excitation by synchrotron radiation with an energy of 3.7-25 eV at 300 K and 10 K. The notable differences in the properties of the Pr3+ luminescence are observed in LuAG:Pr crystals and films caused by involving the LuAl antisite defects and oxygen vacancies in crystals and Pb2+ flux related dopant in films in the excitation processes of the Pr3+ luminescence. At the same time, we have also found that the influence of host defects on the Pr3+ luminescence is significantly smaller in the LuAG:Pr nanopowders.

  4. Crystal growth and comparison of vibrational and thermal properties of semi-organic nonlinear optical materials

    Indian Academy of Sciences (India)

    S Gunasekaran; G Anand; R Arun Balaji; J Dhanalakshmi; S Kumaresan

    2010-10-01

    Single crystals of urea thiourea mercuric sulphate (UTHS) and urea thiourea mercuric chloride (UTHC), semi-organic nonlinear optical materials, were grown by low-temperature solution growth technique by slow evaporation method using water as the solvent. Good quality single crystals were grown within three weeks. The nonlinear nature of the crystals was confirmed by SHG test. The UV–Vis spectrum showed the transmitting ability of the crystals in the entire visible region. FTIR spectrum was recorded and vibrational assignments were made. The degree of dopant inclusion was ascertained by AAS. The TGA–DTA studies showed the thermal properties of the crystals.

  5. Comparison of polarization switching in ferroelectric TGS and relaxor SBN crystals

    Directory of Open Access Journals (Sweden)

    K. Matyjasek

    2013-01-01

    Full Text Available The comparative experimental analysis of polarization reversal kinetics in conventional homogeneous triglycine sulfate (NH2 CH2 COOH3 ˙ H2SO4; TGS and relaxor strontium barium niobate (Sr0.61Ba0.39Nb2O6; SBN crystals have been performed in a broad range of measurement conditions. The experimental data have been collected from microscopic observation of the domain structure, switching current and D-E hysteresis loop registration. The hysteresis loop and dielectric spectra has a strong link to the configuration of ferroelectric microdomains. The domain structure dynamics was examined by the nematic liquid crystal (NLC method.

  6. Comparison of measurements and simulation results in 300 mm CZ silicon crystal growth

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A special thermal modeling tool, CrysVUn, which was developed by Crystal Growth Laboratory (CGL) of Fraunhofer Institute of Integrated Systems and Devices Technology in Erlangen of Germany, was used for numerical analysis of growth Interface situation. The heat transportation, argon flow and melt convection have been considered. Cauchy's first and second laws of motion have been the governing partial equations for stress calculation. The measurement results and simulation results were compared and the interface shape and thermal stress distribution during 300 mm Czochralski (CZ) silicon crystal growth with different growth rates were predicted.

  7. Comparison of measured and computed phase functions of individual tropospheric ice crystals

    Science.gov (United States)

    Stegmann, Patrick G.; Tropea, Cameron; Järvinen, Emma; Schnaiter, Martin

    2016-07-01

    Airplanes passing the incuda (lat. anvils) regions of tropical cumulonimbi-clouds are at risk of suffering an engine power-loss event and engine damage due to ice ingestion (Mason et al., 2006 [1]). Research in this field relies on optical measurement methods to characterize ice crystals; however the design and implementation of such methods presently suffer from the lack of reliable and efficient means of predicting the light scattering from ice crystals. The nascent discipline of direct measurement of phase functions of ice crystals in conjunction with particle imaging and forward modelling through geometrical optics derivative- and Transition matrix-codes for the first time allow us to obtain a deeper understanding of the optical properties of real tropospheric ice crystals. In this manuscript, a sample phase function obtained via the Particle Habit Imaging and Polar Scattering (PHIPS) probe during a measurement campaign in flight over Brazil will be compared to three different light scattering codes. This includes a newly developed first order geometrical optics code taking into account the influence of the Gaussian beam illumination used in the PHIPS device, as well as the reference ray tracing code of Macke and the T-matrix code of Kahnert.

  8. Bandwidth comparison of photonic crystal fibers and conventional single mode fibers

    DEFF Research Database (Denmark)

    Nielsen, Martin Dybendal; Folkenberg, Jacob Riis; Mortensen, Niels Asger;

    2004-01-01

    We experimentally compare the optical bandwidth of a conventional single-mode fiber (SMF) with 3 different photonic crystal fibers (PCF) all optimized for visible applications. The spectral attenuation, single-turn bend loss, and mode-field diameters (MFD) are measured and the PCF is found to have...... a significantly larger bandwidth than the SMF for an identical MFD. It is shown how this advantage can be utilized for realizing a larger MFD for the PCF while maintaining a bending resistant fiber....

  9. Comparison of Lithium Gadolinium Borate Crystal Shards in Scintillating and Nonscintillating Plastic Matrices

    CERN Document Server

    Kazkaz, Kareem; Pedretti, Marisa

    2011-01-01

    We present a method for detecting neutrons using scintillating lithium gadolinium borate crystal shards in a plastic matrix while maintaining high gamma rejection. We have procured two cylindrical detectors, 5"\\times5", containing 1% crystal by mass. Crystal shards have a typical dimension of 1 mm. One detector was made with scintillating plastic, and one with nonscintillating plastic. Pulse shape analysis was used to reject gamma ray backgrounds. The scintillating detector was measured to have an intrinsic fast fission neutron efficiency of 0.4% and a gamma sensitivity of less than 2.3 \\times 10-9, while the nonscintillating detector had a neutron efficiency of 0.7% and gamma sensitivity of (4.75\\pm3.94)\\times10-9. We determine that increasing the neutron detection efficiency by a factor of 2 will make the detector competitive with moderated 3He tubes, and we discuss several simple and straightforward methods for obtaining or surpassing such an improvement. We end with a discussion of possible applications, ...

  10. Crystallization of Ice in Aqueous Solutions of Glycerol and Dimethyl Sulfoxide. 1. A Comparison of Mechanisms

    Science.gov (United States)

    Hey; Macfarlane

    1996-04-01

    The crystallization of ice from aqueous solutions of glycerol and dimethyl sulfoxide (Me2SO) has been studied using differential scanning calorimetry. In particular, the ice crystallization behavior of glycerol and Me2SO solutions containing approximately the same mole percent solute concentration (i.e., approximately 16 mol%) has been compared. These solutions (45 w/w% Me2SO (15.9 mol%) and 50 w/w% glycerol (16.4 mol%)) were shown to exhibit markedly different ice crystallization properties. For example, the peak homogeneous nucleation temperature of the Me2SO solution was observed to be 3°C above Tg, whereas the peak homogeneous nucleation temperature of the glycerol solution was shown to be 20°C above Tg. Further, the 50 w/w% glycerol solution was shown to devitrify at temperatures close to those of the peak nucleation rate, whereas the Me2SO solution was found to devitrify at temperatures much higher than the peak nucleation temperature. This, along with evidence from emulsion-based calorimetry experiments, indicates that the nucleation leading to devitrification in 45 w/w% Me2SO solutions is largely heterogeneous in nature.

  11. Multiscale modeling of polycrystalline graphene: A comparison of structure and defect energies of realistic samples from phase field crystal models

    Science.gov (United States)

    Hirvonen, Petri; Ervasti, Mikko M.; Fan, Zheyong; Jalalvand, Morteza; Seymour, Matthew; Vaez Allaei, S. Mehdi; Provatas, Nikolas; Harju, Ari; Elder, Ken R.; Ala-Nissila, Tapio

    2016-07-01

    We extend the phase field crystal (PFC) framework to quantitative modeling of polycrystalline graphene. PFC modeling is a powerful multiscale method for finding the ground state configurations of large realistic samples that can be further used to study their mechanical, thermal, or electronic properties. By fitting to quantum-mechanical density functional theory (DFT) calculations, we show that the PFC approach is able to predict realistic formation energies and defect structures of grain boundaries. We provide an in-depth comparison of the formation energies between PFC, DFT, and molecular dynamics (MD) calculations. The DFT and MD calculations are initialized using atomic configurations extracted from PFC ground states. Finally, we use the PFC approach to explicitly construct large realistic polycrystalline samples and characterize their properties using MD relaxation to demonstrate their quality.

  12. Optimum performance investigation of LYSO crystal pixels: A comparison between GATE simulation and experimental data

    CERN Document Server

    Chen, Ze; Chen, Jin-Da; Zhang, Xiu-Ling; Sun, Zhi-Yu; Huang, Wen-Xue; Wang, Jian-Song; Guo, Zhong-Yan; Xiao, Guo-Qing

    2013-01-01

    Monte Carlo simulation plays an important role in the study of time of flight (TOF) positron emission tomography (PET) prototype. As it can incorporate accurate physical modeling of scintillation detection process, from scintillation light generation, the transport of scintillation photos through the crystal(s), to the conversion of these photons into electronic signals. The Geant4 based simulation software GATE can provide a user-friendly simulation platform containing the properties needed. In this work, we developed a dedicated module in GATE simulation tool. Using this module, we simulated the light yield, energy resolution, time resolution of LYSO pixels with the same cross-section ($4\\times4 mm^{2}$) of different lengths: 5 mm, 10 mm, 15 mm, 20 mm, 25 mm, coupled to a PMT. The experiments were performed to validate the GATE simulation results. The results indicate that the best time resolution (484.0$\\pm$67.5 ps) and energy resolution (13.3$\\pm$0.4 %) could be produced by using pixel with length of 5 mm...

  13. Technical and radiological image quality comparison of different liquid crystal displays for radiology

    Directory of Open Access Journals (Sweden)

    Dams FE

    2014-10-01

    Full Text Available Francina EM Dams,2 KY Esther Leung,1 Pieter HM van der Valk,2 Marc CJM Kock,2 Jeroen Bosman,1 Sjoerd P Niehof1 1Medical Physics and Technology, 2Department of Radiology, Albert Schweitzer Hospital, Dordrecht, The Netherlands Background: To inform cost-effective decisions in purchasing new medical liquid crystal displays, we compared the image quality in displays made by three manufacturers. Methods: We recruited 19 radiologists and residents to compare the image quality of four liquid crystal displays, including 3-megapixel Barco®, Eizo®, and NEC® displays and a 6-megapixel Barco display. The evaluators were blinded to the manufacturers' names. Technical assessments were based on acceptance criteria and test patterns proposed by the American Association of Physicists in Medicine. Radiological assessments were performed on images from the American Association of Physicists in Medicine Task Group 18. They included X-ray images of the thorax, knee, and breast, a computed tomographic image of the thorax, and a magnetic resonance image of the brain. Image quality was scored on an analog scale (range 0–10. Statistical analysis was performed with repeated-measures analysis of variance. Results: The Barco 3-megapixel display passed all acceptance criteria. The Eizo and NEC displays passed the acceptance criteria, except for the darkest pixel value in the grayscale display function. The Barco 6-megapixel display failed criteria for the maximum luminance response and the veiling glare. Mean radiological assessment scores were 7.8±1.1 (Barco 3-megapixel, 7.8±1.2 (Eizo, 8.1±1.0 (NEC, and 8.1±1.0 (Barco 6-megapixel. No significant differences were found between displays. Conclusion: According to the tested criteria, all the displays had comparable image quality; however, there was a three-fold difference in price between the most and least expensive displays. Keywords: data display, humans, radiographic image enhancement, user-computer interface

  14. Shock Compression of Metal Crystals: A Comparison of Eulerian and Lagrangian Elastic-Plastic Theories

    Science.gov (United States)

    2014-11-01

    temperature equation-of-state (EOS) [ Luscher et al., 2013] for the pressure. For isotropic (e.g., untextured polycrystalline) solids, nonlinear elasticity...elastoplasticity [ Luscher et al., 2013]. 1450048-12 2nd Reading October 15, 2014 11:4 WSPC-255-IJAM S1758-8251 1450048 Shock Compression of Metal Crystals...Clayton, 2011; Luscher et al., 2013] S̄ = ∂Ū ∂E = ∂Ψ̄ ∂E = JFE−1σFE−T, θ = ∂Ū/∂η, η = −∂Ψ̄/∂θ, χ̄ = −∂Ψ̄/∂ζ, (3.7) c̄θ̇ = ∑ α τ̄αγ̇α + θ ∂S̄ ∂θ : Ė

  15. Crystal structure of trirubidium citrate from laboratory X-ray powder diffraction data and DFT comparison

    Science.gov (United States)

    Kaduk, James A.

    2017-01-01

    The crystal structure of trirubidium citrate, 3Rb+·C6H5O7 3−, has been solved and refined using laboratory X-ray powder diffraction data, and optimized using density functional techniques. The two independent Rb+ cations are seven- and eight-coordinate, with bond-valence sums of 0.99 and 0.92 valence units. The coordination polyhedra share edges and corners to form a three-dimensional framework. The only hydrogen bond is an intra­molecular one between the hy­droxy group and the central carboxyl­ate, with graph set S(5). The hydro­phobic methyl­ene groups lie in pockets in the framework. PMID:28217353

  16. Crystal structure of trirubidium citrate from laboratory X-ray powder diffraction data and DFT comparison.

    Science.gov (United States)

    Rammohan, Alagappa; Kaduk, James A

    2017-02-01

    The crystal structure of trirubidium citrate, 3Rb(+)·C6H5O7(3-), has been solved and refined using laboratory X-ray powder diffraction data, and optimized using density functional techniques. The two independent Rb(+) cations are seven- and eight-coordinate, with bond-valence sums of 0.99 and 0.92 valence units. The coordination polyhedra share edges and corners to form a three-dimensional framework. The only hydrogen bond is an intra-molecular one between the hy-droxy group and the central carboxyl-ate, with graph set S(5). The hydro-phobic methyl-ene groups lie in pockets in the framework.

  17. Comparison of the sensitivity of air and dielectric modes in photonic crystal slab sensors.

    Science.gov (United States)

    Tomljenovic-Hanic, Snjezana; Rahmani, Adel; Steel, M J; de Sterke, C Martijn

    2009-08-17

    Optical cavities provide a route to sensing through the shift of the optical resonant peak. However, effective sensing with optical cavities requires the optimization of the modal quality factor, Q, and the field overlap with the sample, f. For a photonic crystal slab (PCS) this figure of merit, M = fQ, involves two competing effects. The air modes usually have large f but small Q, whereas the dielectric modes have high-Q and small f. We compare the sensitivity of air and dielectric modes for different PCS cavity designs and account for loss associated with absorption by the sensed sample or its host liquid. We find that optimizing Q at the expense of f is the most beneficial strategy, and modes deriving from the dielectric bands are thus preferred.

  18. Comparison of different methods for rigorous modeling of photonic crystal fibers.

    Science.gov (United States)

    Szpulak, Marcin; Urbanczyk, Waclaw; Serebryannikov, Evgenii; Zheltikov, Aleksei; Hochman, Amit; Leviatan, Yehuda; Kotynski, Rafal; Panajotov, Krassimir

    2006-06-12

    We present a summary of the simulation exercise carried out within the EC Cost Action P11 on the rigorous modeling of photonic crystal fiber (PCF) with an elliptically deformed core and noncircular air holes with a high fill factor. The aim of the exercise is to calculate using different numerical methods and to compare several fiber characteristics, such as the spectral dependence of the phase and the group effective indices, the birefringence, the group velocity dispersion and the confinement losses. The simulations are performed using four rigorous approaches: the finite element method (FEM), the source model technique (SMT), the plane wave method (PWM), and the localized function method (LFM). Furthermore, we consider a simplified equivalent fiber method (EFM), in which the real structure of the holey fiber is replaced by an equivalent step index waveguide composed of an elliptical glass core surrounded by air cladding. All these methods are shown to converge well and to provide highly consistent estimations of the PCF characteristics. Qualitative arguments based on the general properties of the wave equation are applied to explain the physical mechanisms one can utilize to tailor the propagation characteristics of nonlinear PCFs.

  19. Comparison between AlN thin films with different crystal orientations for MEMS applications

    Science.gov (United States)

    Ababneh, A.; Marchand, G.; Seidel, H.; Hernando, J.; Sánchez-Rojas, J. L.; Sökmen, Ü.; Peiner, E.; Schmid, U.

    2009-05-01

    Aluminium nitride (AlN) reactively sputter deposited from an aluminium target is an interesting compound material due to its CMOS compatible fabrication process and its piezoelectric properties. The crystal structure obtained during sputtering is a very importance criterion to obtain a good piezoelectric performance. To demonstrate this, we focused our investigations on two types of films. The first type shows a good c- axis orientation with round grain geometry. The second type is (101) oriented having a triangular grain shape. For measuring the out-of-plane displacements for dij determination, a MSV 400 Polytec scanning laser Doppler vibrometer was used. To obtain the piezoelectric constants d33 and d31 a fitting procedure between experimental and theoretical predicted results is used. Effective values for d33 and d31 in c-axis oriented films are about 3.0 pm/V and -1.0 pm/V, respectively. By contrast, films with (101) orientation show a lower effective longitudinal piezoelectric coefficients, consistent with this different orientation. Finally, both types of AlN layers were deposited on 640 μm long micro-cantilevers. The average displacement of the first mode on the vertical axis was about 12 nm for the film with good c -axis orientation and 0.3 nm for that with (101)- orientation when applying the same excitation.

  20. Comparison of viewing angle and observer performances in different types of liquid-crystal display monitors.

    Science.gov (United States)

    Hatanaka, Shiro; Morishita, Junji; Hiwasa, Takeshi; Dogomori, Kiyoshi; Toyofuku, Fukai; Ohki, Masafumi; Higashida, Yoshiharu

    2009-07-01

    It is known that the performance of liquid-crystal display (LCD) monitors, such as the luminance and contrast ratio, is dependent on the viewing angle. Our purpose in this study was to compare the angular performance and the effect on observer performance of different types of LCD monitors. The luminance performance and contrast ratio as a function of viewing angle (-60 degrees to 60 degrees) in each direction for two types of LCD monitors, namely, a general-purpose LCD monitor and one especially designed for medical use, were measured in this study. Furthermore, the observer performance at various viewing angles in the horizontal direction for a medical-grade LCD monitor was investigated by eight observers based on a contrast-detail diagram. The two types of LCD monitors showed notable variations in luminance and contrast ratio as a function of the viewing angle. Acceptable viewing angles in terms of the contrast ratio were much smaller in each direction than those for nominal viewing angles in the specifications provided by the manufacturers, and those for the medical-grade LCD monitor in the horizontal and vertical directions were broader than those of the general-purpose LCD monitor. There was no significant difference in observer performance between 0 degrees and 40 degrees. On the other hand, our results showed a statistically significant difference in observer performance between 0 degrees and 60 degrees.

  1. Aluminum-induced dreierketten chain cross-links increase the mechanical properties of nanocrystalline calcium aluminosilicate hydrate

    Science.gov (United States)

    Geng, Guoqing; Myers, Rupert J.; Li, Jiaqi; Maboudian, Roya; Carraro, Carlo; Shapiro, David A.; Monteiro, Paulo J. M.

    2017-03-01

    The incorporation of Al and increased curing temperature promotes the crystallization and cross-linking of calcium (alumino)silicate hydrate (C-(A-)S-H), which is the primary binding phase in most contemporary concrete materials. However, the influence of Al-induced structural changes on the mechanical properties at atomistic scale is not well understood. Herein, synchrotron radiation-based high-pressure X-ray diffraction is used to quantify the influence of dreierketten chain cross-linking on the anisotropic mechanical behavior of C-(A-)S-H. We show that the ab-planar stiffness is independent of dreierketten chain defects, e.g. vacancies in bridging tetrahedra sites and Al for Si substitution. The c-axis of non-cross-linked C-(A-)S-H is more deformable due to the softer interlayer opening but stiffens with decreased spacing and/or increased zeolitic water and Ca2+ of the interlayer. Dreierketten chain cross-links act as ‘columns’ to resist compression, thus increasing the bulk modulus of C-(A-)S-H. We provide the first experimental evidence on the influence of the Al-induced atomistic configurational change on the mechanical properties of C-(A-)S-H. Our work advances the fundamental knowledge of C-(A-)S-H on the lowest level of its hierarchical structure, and thus can impact the way that innovative C-(A-)S-H-based cementitious materials are developed using a ‘bottom-up’ approach.

  2. Aluminum-induced dreierketten chain cross-links increase the mechanical properties of nanocrystalline calcium aluminosilicate hydrate

    Science.gov (United States)

    Geng, Guoqing; Myers, Rupert J.; Li, Jiaqi; Maboudian, Roya; Carraro, Carlo; Shapiro, David A.; Monteiro, Paulo J. M.

    2017-01-01

    The incorporation of Al and increased curing temperature promotes the crystallization and cross-linking of calcium (alumino)silicate hydrate (C-(A-)S-H), which is the primary binding phase in most contemporary concrete materials. However, the influence of Al-induced structural changes on the mechanical properties at atomistic scale is not well understood. Herein, synchrotron radiation-based high-pressure X-ray diffraction is used to quantify the influence of dreierketten chain cross-linking on the anisotropic mechanical behavior of C-(A-)S-H. We show that the ab-planar stiffness is independent of dreierketten chain defects, e.g. vacancies in bridging tetrahedra sites and Al for Si substitution. The c-axis of non-cross-linked C-(A-)S-H is more deformable due to the softer interlayer opening but stiffens with decreased spacing and/or increased zeolitic water and Ca2+ of the interlayer. Dreierketten chain cross-links act as ‘columns’ to resist compression, thus increasing the bulk modulus of C-(A-)S-H. We provide the first experimental evidence on the influence of the Al-induced atomistic configurational change on the mechanical properties of C-(A-)S-H. Our work advances the fundamental knowledge of C-(A-)S-H on the lowest level of its hierarchical structure, and thus can impact the way that innovative C-(A-)S-H-based cementitious materials are developed using a ‘bottom-up’ approach. PMID:28281635

  3. COMPARISON OF ANALYTICAL SOLUTIONS FOR CMSMPR CRYSTALLIZER WITH QMOM POPULATION BALANCE MODELING IN FLUENT

    Institute of Scientific and Technical Information of China (English)

    Bin Wan; Terry A. Ring; Kumar M. Dhanasekharan; Jayanta Sanyal

    2005-01-01

    Fluent version 6.2 computational fluid dynamics environment has been enhanced with a population balance capability that operates in conjunction with its multiphase calculations to predict the particle size distribution within the flow field. The population balance is solved by the quadrature method of moments (QMOM). Fluent's prediction capabilities are tested by using a 2-dimensional analogy of a constantly stirred tank reactor with a fluid flow compartment that mixes the fluid quickly and efficiently using wall movement and has a feed stream and a product stream. The results of these Fluent simulations using QMOM population balance solver are compared to steady state analytical solutions for the population balance in a stirred tank where 1) growth, 2) aggregation, and 3) breakage, take place separately and 4)combined nucleation and growth and 5) combined nucleation, growth and aggregation take place. The results of these comparisons show that the moments of the population balance are accurately predicted for nucleation, growth, aggregation and breakage when the flow field is turbulent. With laminar flow the mixing is not ideal and as a result the steady state well mixed solutions are not accurately simulated.

  4. Up-regulation of heme oxygenase-1 contributes to the amelioration of aluminum-induced oxidative stress in Medicago sativa.

    Science.gov (United States)

    Cui, Weiti; Zhang, Jing; Xuan, Wei; Xie, Yanjie

    2013-10-15

    In this report, pharmacological, histochemical and molecular approaches were used to investigate the effect of heme oxygenase-1 (HO-1) up-regulation on the alleviation of aluminum (Al)-induced oxidative stress in Medicago sativa. Exposure of alfalfa to AlCl3 (0-100 μM) resulted in a dose-dependent inhibition of root elongation as well as the enhancement of thiobarbituric acid reactive substances (TBARS) content. 1 and 10 μM (in particular) Al(3+) increased alfalfa HO-1 transcript or its protein level, and HO activity in comparison with the decreased changes in 100 μM Al-treated samples. After recuperation, however, TBARS levels in 1 and 10 μM Al-treated alfalfa roots returned to control values, which were accompanied with the higher levels of HO activity. Subsequently, exogenous CO, a byproduct of HO-1, could substitute for the cytoprotective effects of the up-regulation of HO-1 in alfalfa plants upon Al stress, which was confirmed by the alleviation of TBARS and Al accumulation, as well as the histochemical analysis of lipid peroxidation and loss of plasma membrane integrity. Theses results indicated that endogenous CO generated via heme degradation by HO-1 could contribute in a critical manner to its protective effects. Additionally, the pretreatments of butylated hydroxytoluene (BHT) and hemin, an inducer of HO-1, exhibited the similar cytoprotective roles in the alleviation of oxidative stress, both of which were impaired by the potent inhibitor of HO-1, zinc protoporphyrin IX (ZnPP). However, the Al-induced inhibition of root elongation was not influenced by CO, BHT and hemin, respectively. Together, the present results showed up-regulation of HO-1 expression could act as a mechanism of cell protection against oxidative stress induced by Al treatment.

  5. Nanomolar aluminum induces expression of the inflammatory systemic biomarker C-reactive protein (CRP) in human brain microvessel endothelial cells (hBMECs).

    Science.gov (United States)

    Alexandrov, Peter N; Kruck, Theodore P A; Lukiw, Walter J

    2015-11-01

    C-reactive protein (CRP; also known as pentraxin 1, PTX1), a 224 amino acid soluble serum protein organized into a novel pentameric ring-shaped structure, is a highly sensitive pathogenic biomarker for systemic inflammation. High CRP levels are found in practically every known inflammatory state, and elevated CRP levels indicate an increased risk for several common age-related human degenerative disorders, including cardiovascular disease, cancer, diabetes, and Alzheimer's disease (AD). While the majority of CRP is synthesized in the liver for secretion into the systemic circulation, it has recently been discovered that an appreciable amount of CRP is synthesized in highly specialized endothelial cells that line the vasculature of the brain and central nervous system (CNS). These highly specialized cells, the major cell type lining the human CNS vasculature, are known as human brain microvessel endothelial cells (hBMECs). In the current pilot study we examined (i) CRP levels in human serum obtained from AD and age-matched control patients; and (ii) analyzed the effects of nanomolar aluminum sulfate on CRP expression in primary hBMECs. The three major findings in this short communication are: (i) that CRP is up-regulated in AD serum; (ii) that CRP serum levels increased in parallel with AD progression; and (iii) for the first time show that nanomolar aluminum potently up-regulates CRP expression in hBMECs to many times its 'basal abundance'. The results suggest that aluminum-induced CRP may in part contribute to a pathophysiological state associated with a chronic systemic inflammation of the human vasculature.

  6. 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

  7. Suppression of Raman electron spin relaxation of radicals in crystals. Comparison of Cu2+ and free radical relaxation in triglycine sulfate and Tutton salt single crystals.

    Science.gov (United States)

    Hoffmann, S K; Goslar, J; Lijewski, S

    2011-08-31

    Electron spin-lattice relaxation was measured by the electron spin echo method in a broad temperature range above 4.2 K for Cu(2+) ions and free radicals produced by ionizing radiation in triglycine sulfate (TGS) and Tutton salt (NH4)(2)Zn(SO4)2 ⋅ 6H2O crystals. Localization of the paramagnetic centres in the crystal unit cells was determined from continuous wave electron paramagnetic resonance spectra. Various spin relaxation processes and mechanisms are outlined. Cu(2+) ions relax fast via two-phonon Raman processes in both crystals involving the whole phonon spectrum of the host lattice. This relaxation is slightly slower for TGS where Cu(2+) ions are in the interstitial position. The ordinary Raman processes do not contribute to the radical relaxation which relaxes via the local phonon mode. The local mode lies within the acoustic phonon band for radicals in TGS but within the optical phonon range in (NH4)(2)Zn(SO4)2 ⋅ 6H2O. In the latter the cross-relaxation was considered. A lack of phonons around the radical molecules suggested a local crystal amorphisation produced by x- or γ-rays.

  8. Comments on: “Crystal growth and comparison of vibrational and thermal properties of semi-organic nonlinear optical materials”

    Indian Academy of Sciences (India)

    Srinivasan Bikshandarkoil R; Fernandes Royle

    2016-03-01

    In {\\it Pramana – J. Phys. } 75, 683 (2010), Gunasekaran et al reported that they have grown the nonlinear optical crystals, urea thiourea mercuric chloride (UTHC) and urea thiourea mercuric sulphate (UTHS).We argue that UTHC and UTHS are dubious crystals and are not what the authors propose.

  9. Crystal structure of dicesium hydrogen citrate from laboratory single-crystal and powder X-ray diffraction data and DFT comparison

    Science.gov (United States)

    Rammohan, Alagappa; Sarjeant, Amy A.; Kaduk, James A.

    2017-01-01

    The crystal structure of dicesium hydrogen citrate, 2Cs+·C6H6O7 2−, has been solved using laboratory X-ray single-crystal diffraction data, refined using laboratory powder X-ray data, and optimized using density functional techniques. The Cs+ cation is nine-coordinate, with a bond-valence sum of 0.92 valence units. The CsO9 coordination polyhedra share edges and corners to form a three-dimensional framework. The citrate anion is located on a mirror plane. Its central hy­droxy/carboxyl­ate O—H⋯O hydrogen bond is short, and (unusually) inter­molecular. The centrosymmetric end-end carboxyl­ate hydrogen bond is exceptionally short (O⋯O = 2.416 Å) and strong. These hydrogen bonds contribute 16.5 and 21.7 kcal mol−1, respectively, to the crystal energy. The hydro­phobic methyl­ene groups occupy pockets in the framework. PMID:28217349

  10. Crystal structure of dicesium hydrogen citrate from laboratory single-crystal and powder X-ray diffraction data and DFT comparison.

    Science.gov (United States)

    Rammohan, Alagappa; Sarjeant, Amy A; Kaduk, James A

    2017-02-01

    The crystal structure of dicesium hydrogen citrate, 2Cs(+)·C6H6O7(2-), has been solved using laboratory X-ray single-crystal diffraction data, refined using laboratory powder X-ray data, and optimized using density functional techniques. The Cs(+) cation is nine-coordinate, with a bond-valence sum of 0.92 valence units. The CsO9 coordination polyhedra share edges and corners to form a three-dimensional framework. The citrate anion is located on a mirror plane. Its central hy-droxy/carboxyl-ate O-H⋯O hydrogen bond is short, and (unusually) inter-molecular. The centrosymmetric end-end carboxyl-ate hydrogen bond is exceptionally short (O⋯O = 2.416 Å) and strong. These hydrogen bonds contribute 16.5 and 21.7 kcal mol(-1), respectively, to the crystal energy. The hydro-phobic methyl-ene groups occupy pockets in the framework.

  11. Fabrication and comparison of PMN-PT single crystal, PZT and PZT-based 1-3 composite ultrasonic transducers for NDE applications.

    Science.gov (United States)

    Kim, Ki-Bok; Hsu, David K; Ahn, Bongyoung; Kim, Young-Gil; Barnard, Daniel J

    2010-08-01

    This paper describes fabrication and comparison of PMN-PT single crystal, PZT, and PZT-based 1-3 composite ultrasonic transducers for NDE applications. As a front matching layer between test material (Austenite stainless steel, SUS316) and piezoelectric materials, alumina ceramics was selected. The appropriate acoustic impedance of the backing materials for each transducer was determined based on the results of KLM model simulation. Prototype ultrasonic transducers with the center frequencies of approximately 2.25 and 5MHz for contact measurement were fabricated and compared to each other. The PMN-PT single crystal ultrasonic transducer shows considerably improved performance in sensitivity over the PZT and PZT-based 1-3 composite ultrasonic transducers.

  12. 液晶指向矢分布的模拟和比较研究%SIMULATION AND COMPARISON STUDY OF LIQUID CRYSTAL DIRECTOR DISTRIBUTIONS

    Institute of Scientific and Technical Information of China (English)

    王谦; 何赛灵

    2001-01-01

    用差分迭代法计算了扭曲、超扭曲以及混合排列丝状液晶在电场中指向矢的空间分布,与牛顿法和张弛法的计算作了比较;并应用于液晶电光特性的模拟计算.%A new finite-difference iterative method is used to calculate the distribution of the liquid crystal directors under an applied voltage.Numerical results for twisted nematic,super twisted nematic,and hybrid nematic cells are given.In comparison with Newton's method and the relaxation method, it in shown that the new method is simpler,more stable to give accurate results for various types of liquid crystal cells.

  13. A study of high-energy proton induced damage in Cerium Fluoride in comparison with measurements in Lead Tungstate calorimeter crystals

    CERN Document Server

    Dissertori, G; Luckey, D; Nessi-Tedaldi, F; Otto, Th; Pauss, F; Roesler, S; Urscheler, Ch

    2010-01-01

    A Cerium Fluoride crystal produced during early R&D studies for calorimetry at the CERN Large Hadron Collider was exposed to a 24 GeV/c proton fluence Phi_p=(2.78 +- 0.20) x 10EE13 cm-2 and, after one year of measurements tracking its recovery, to a fluence Phi_p=(2.12 +- 0.15) x 10EE14 cm-2. Results on proton-induced damage to the crystal and its spontaneous recovery after both irradiations are presented here, along with some new, complementary data on proton-damage in Lead Tungstate. A comparison with FLUKA Monte Carlo simulation results is performed and a qualitative understanding of high-energy damage mechanism is attempted.

  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. Crystal nucleation of hard spheres using molecular dynamics, umbrella sampling, and forward flux sampling: a comparison of simulation techniques

    NARCIS (Netherlands)

    Filion, L.C.; Hermes, M; Ni, R.; Dijkstra, M.

    2010-01-01

    Over the last number of years several simulation methods have been introduced to study rare events such as nucleation. In this paper we examine the crystal nucleation rate of hard spheres using three such numerical techniques: molecular dynamics, forward flux sampling, and a Bennett–Chandlertype the

  16. Confined crystallization of n-hexadecane located inside microcapsules or outside submicrometer silica nanospheres: a comparison study.

    Science.gov (United States)

    Fu, Dongsheng; Su, Yunlan; Gao, Xia; Liu, Yufeng; Wang, Dujin

    2013-05-23

    Crystallization and phase transition behaviors of n-hexadecane (n-C16H34, abbreviated as C16) confined in microcapsules and n-alkane/SiO2 nanosphere composites have been investigated by the combination of differential scanning calorimetry (DSC) and temperature-dependent X-ray diffraction (XRD). As evident from the DSC measurement, the surface freezing phenomenon of C16 is enhanced in both the microcapsules and SiO2 nanosphere composites because the surface-to-volume ratio is dramatically enlarged in both kinds of confinement. It is revealed from the XRD results that the novel solid-solid phase transition is observed only in the microencapsulated C16, which crystallizes into a stable triclinic phase via a mestastable rotator phase (RI). For the C16/SiO2 composite, however, no novel rotator phase emerges during the cooling process, and C16 crystallizes into a stable triclinic phase directly from the liquid state. Heterogeneous nucleation induced by the surface freezing phase is dominant in the microencapsulated sample and contributes to the emergence of the novel rotator phase, whereas heterogeneous nucleation induced by foreign crystallization nuclei dominates the C16/SiO2 composite, leading to phase transition behaviors similar to those of bulk C16.

  17. Comparison of slowness profiles of lamb wave with elastic moduli and crystal structure in single crystalline silicon wafers

    Energy Technology Data Exchange (ETDEWEB)

    Min, Young Jae; Yun, Gyeong Won; Kim, Kyung Min; Roh, Yuji; Kim, Young H. [Applied Acoustics Lab, Korea Science Academy of KAIST, Busan (Korea, Republic of)

    2016-02-15

    Single crystalline silicon wafers having (100), (110), and (111) directions are employed as specimens for obtaining slowness profiles. Leaky Lamb waves (LLW) from immersed wafers were detected by varying the incident angles of the specimens and rotating the specimens. From an analysis of LLW signals for different propagation directions and phase velocities of each specimen, slowness profiles were obtained, which showed a unique symmetry with different symmetric axes. Slowness profiles were compared with elastic moduli of each wafer. They showed the same symmetries as crystal structures. In addition, slowness profiles showed expected patterns and values that can be inferred from elastic moduli. This implies that slowness profiles can be used to examine crystal structures of anisotropic solids.

  18. Performance comparison between ceramic Ce:GAGG and single crystal Ce:GAGG with digital-SiPM

    Science.gov (United States)

    Park, C.; Kim, C.; Kim, J.; Lee, Y.; Na, Y.; Lee, K.; Yeom, J. Y.

    2017-01-01

    The Gd3Al2Ga3O12 (Ce:GAGG) is a new inorganic scintillator known for its attractive properties such as high light yield, stopping power and relatively fast decay time. In this study, we fabricated a ceramic Ce:GAGG scintillator as a cost-effective alternative to single crystal Ce:GAGG and, for the first time, investigated their performances when coupled to the digital silicon photomultiplier (dSiPM)—a new type of photosensor designed for applications in medical imaging, high energy and astrophysics. Compared to 3 × 3 × 2 mm3 sized single crystal Ce:GAGG, the translucent ceramic Ce:GAGG, which has a much lower transmittance than the single crystal, was determined to give an output signal amplitude that is approximately 61% of single crystal Ce:GAGG. The energy resolution of the 511 keV annihilation peak of a 22Na source was measured to be 9.9 ± 0.2% and 13.0 ± 0.3% for the single and ceramic scintillators respectively. On the other hand, the coincidence resolving time (CRT) of ceramic Ce:GAGG was 307 ± 23 ps, better than the 465 ± 37 ps acquired with single crystals—probably attributed to its slightly faster decay time and higher proportion of the fast decay component. The ceramic Ce:GAGG may be a promising cost-effective candidate for applications that do not require thick scintillators such as x-ray detectors and charged particle detectors, and those that require time-of-flight capabilities.

  19. Comparison of four computational methods for computing Q factors and resonance wavelengths in photonic crystal membrane cavities

    DEFF Research Database (Denmark)

    de Lasson, Jakob Rosenkrantz; Frandsen, Lars Hagedorn; Burger, Sven

    2016-01-01

    We benchmark four state-of-the-art computational methods by computing quality factors and resonance wavelengths in photonic crystal membrane L5 and L9 line defect cavities.The convergence of the methods with respect to resolution, degrees of freedom and number ofmodes is investigated. Special...... attention is paid to the influence of the size of the computational domain. Convergence is not obtained for some of the methods, indicating that some are moresuitable than others for analyzing line defect cavities....

  20. Comparison of the crystal structures of methyl 4-bromo-2-(methoxymethoxybenzoate and 4-bromo-3-(methoxymethoxybenzoic acid

    Directory of Open Access Journals (Sweden)

    P. A. Suchetan

    2016-04-01

    Full Text Available The title compounds, C10H11BrO4, (I, and C9H9BrO4, (II, are derivatives of bromo–hydroxy–benzoic acids. Compound (II crystallizes with two independent molecules (A and B in the asymmetric unit. In both (I and (II, the O—CH2—O—CH3 side chain is not in its fully extended conformation; the O—C—O—C torsion angle is 67.3 (3 ° in (I, and −65.8 (3 and −74.1 (3° in molecules A and B, respectively, in compound (II. In the crystal of (I, molecules are linked by C—H...O hydrogen bonds, forming C(5 chains along [010]. The chains are linked by short Br...O contacts [3.047 (2 Å], forming sheets parallel to the bc plane. The sheets are linked via C—H...π interactions, forming a three-dimensional architecture. In the crystal of (II, molecules A and B are linked to form R22(8 dimers via two strong O—H...O hydrogen bonds. These dimers are linked into ...A–B...A–B...A–B... [C22(15] chains along [011] by C—H...O hydrogen bonds. The chains are linked by slipped parallel π–π interactions [inter-centroid distances = 3.6787 (18 and 3.8431 (17 Å], leading to the formation of slabs parallel to the bc plane.

  1. A comparison between experiment and theory on few-quantum-dot nanolasing in a photonic-crystal cavity

    DEFF Research Database (Denmark)

    Liu, Jin; Ates, Serkan; Lorke, Michael;

    2013-01-01

    We present an experimental and theoretical study on the gain mechanism in a photonic-crystal-cavity nanolaser with embedded quantum dots. From time-resolved measurements at low excitation power we find that four excitons are coupled to the cavity. At high excitation power we observe a smooth low-......-dot microcavity lasers and find that the number of excitons that must be included to fit the data largely exceeds the measured number, which shows that transitions involving the wetting layer can provide a surprisingly large contribution to the gain....

  2. Comparison of thermomagnetic history effects in weakly pinned single crystals of 3Rh4Sn13(R=Yb, Ca)

    Indian Academy of Sciences (India)

    S Sarkar; S Ramakrishnan; A K Grover; C V Tomy; G Balakrishnan; D McK Paul

    2002-05-01

    A comparative study of the thermomagnetic memory effects of c in two weakly pinned low c superconductors, Ca3Rh4Sn13 (CaRhSn) and Yb3Rh4Sn13 (YbRhSn), is presented. In both the systems, the peak effect (PE) phenomenon appears as an order–disorder transformation through stepwise amorphization of the flux line lattice (FLL). However, in CaRhSn, we can witness another disorder-driven transition (Bragg glass (BG) to a vortex glass (VG)) in a distinct manner as in a single crystal of high c YBa2Cu3O7- for $H||c$.

  3. Crystal structure of caesium dihydrogen citrate from laboratory X-ray powder diffraction data and DFT comparison

    Directory of Open Access Journals (Sweden)

    Alagappa Rammohan

    2017-02-01

    Full Text Available The crystal structure of caesium dihydrogen citrate, Cs+·H2C6H5O7−, has been solved and refined using laboratory X-ray powder diffraction data, and optimized using density functional techniques. The coordination polyhedra of the nine-coordinate Cs+ cations share edges to form chains along the a-axis. These chains are linked by corners along the c-axis. The un-ionized carboxylic acid groups form two different types of hydrogen bonds; one forms a helical chain along the c-axis, and the other is discrete. The hydroxy group participates in both intra- and intermolecular hydrogen bonds.

  4. A comparison of BCF-12 organic scintillators and Al2O3:C crystals for real-time medical dosimetry

    DEFF Research Database (Denmark)

    Beierholm, Anders Ravnsborg; Andersen, Claus Erik; Lindvold, Lars;

    2008-01-01

    Radioluminescence (RL) from aluminium oxide (Al2O3:C) crystals and organic scintillators such as the blue-emitting BCF-12 can be used for precise real-time dose rate measurements during radiation therapy of cancer patients. Attaching the dosimeters to thin light-guiding fiber cables enables in vivo...... can be circumvented for pulsed beams due to the long life-time of the main luminescence center. In contrast, chromatic removal seems to be the most effective method for organic scintillators, but is found to yield some experimental complexities. In this paper, we report on dose rate measurements using...

  5. The crystal structure of UehA in complex with ectoine-A comparison with other TRAP-T binding proteins.

    Science.gov (United States)

    Lecher, Justin; Pittelkow, Marco; Zobel, Silke; Bursy, Jan; Bönig, Tobias; Smits, Sander H J; Schmitt, Lutz; Bremer, Erhard

    2009-05-29

    Substrate-binding proteins or extracellular solute receptors (ESRs) are components of both ABC (ATP binding cassette) and TRAP-T (tripartite ATP-independent periplasmic transporter). The TRAP-T system UehABC from Silicibacter pomeroyi DSS-3 imports the compatible solutes ectoine and 5-hydroxyectoine as nutrients. UehA, the ESR of the UehABC operon, binds both ectoine and 5-hydroxyectoine with high affinity (K(d) values of 1.4+/-0.1 and 1.1+/-0.1 microM, respectively) and delivers them to the TRAP-T complex. The crystal structure of UehA in complex with ectoine was determined at 2.9-A resolution and revealed an overall fold common for all ESR proteins from TRAP systems determined so far. A comparison of the recently described structure of TeaA from Halomonas elongata and an ectoine-binding protein (EhuB) from an ABC transporter revealed a conserved ligand binding mode that involves both directed and cation-pi interactions. Furthermore, a comparison with other known TRAP-T ESRs revealed a helix that might act as a selectivity filter imposing restraints on the ESRs that fine-tune ligand recognition and binding and finally might determine the selection of the cognate substrate.

  6. Comparison of optical transients during the picosecond laser pulse-induced crystallization of GeSbTe and AgInSbTe phase-change thin films: Nucleation-driven versus growth-driven processes

    Science.gov (United States)

    Liang, Guangfei; Li, Simian; Huang, Huan; Wang, Yang; Lai, Tianshu; Wu, Yiqun

    2013-09-01

    Direct comparison of the real-time in-situ crystallization behavior of as-deposited amorphous Ge2Sb2Te5 (GeSbTe) and Ag8In14Sb55Te23 (AgInSbTe) phase-change thin films driven by picosecond laser pulses was performed by a time-resolved optical pump-probe technique with nanosecond resolution. Different optical transients showed various crystallization processes because of the dissimilar nucleation- and growth-dominated mechanisms of the two materials. The effects of laser pulse fluence, thermal conductive structure, and successive pulse irradiation on their crystallization dynamics were also discussed. A schematic was then established to describe the different crystallization processes beginning from the as-deposited amorphous state. The results may provide further insight into the phase-change mechanism under extra-non-equilibrium conditions and aid the development of ultrafast phase-change memory materials.

  7. Comparison of laser performance of electro-optic Q-switched Nd:YAG ceramic/single crystal laser

    Institute of Scientific and Technical Information of China (English)

    Jianghua Ji; Xiaolei Zhu; Chunyu Wang; Yongwei Feng; Qihong Lou

    2006-01-01

    @@ An electro-optic Q-switched Nd:YAG ceramic laser operating at kHz repetition rate was demonstrated.Thermal induced lens' focus of ceramic rod was measured and compensated by plano-convex cavity structure. Depolarization loss at different output powers was measured in Nd:YAG single crystal and ceramic lasers. High-energy high-beam-quality laser pulse output was obtained in both laser structures. Pulse energy of about 20 mJ and pulse width of less than 12 ns were achieved, and the average power reached 20 W. The divergence of output laser beam was less than 1.2 mrad, and the beam propagation factor M2was about 1.4.

  8. Crystal structure of pentasodium hydrogen dicitrate from synchrotron X-ray powder diffraction data and DFT comparison

    Energy Technology Data Exchange (ETDEWEB)

    Rammohan, Alagappa; Kaduk, James A.

    2017-01-27

    The crystal structure of pentasodium hydrogen dicitrate, Na5H(C6H5O7)2, has been solved and refined using synchrotron X-ray powder diffraction data, and optimized using density functional techniques. Each of the two independent citrate anions is joined into a dimer by very strong centrosymmetric O—H...O hydrogen bonds, with O...O distances of 2.419 and 2.409 Å. Four octahedrally coordinated Na+ions share edges to form open layers parallel to theabplane. A fifth Na+ion in trigonal–bipyramidal coordination shares faces with NaO6octahedra on both sides of these layers.

  9. Crystal structure of penta­sodium hydrogen dicitrate from synchrotron X-ray powder diffraction data and DFT comparison

    Science.gov (United States)

    Kaduk, James A.

    2017-01-01

    The crystal structure of penta­sodium hydrogen dicitrate, Na5H(C6H5O7)2, has been solved and refined using synchrotron X-ray powder diffraction data, and optimized using density functional techniques. Each of the two independent citrate anions is joined into a dimer by very strong centrosymmetric O—H⋯O hydrogen bonds, with O⋯O distances of 2.419 and 2.409 Å. Four octa­hedrally coordinated Na+ ions share edges to form open layers parallel to the ab plane. A fifth Na+ ion in trigonal–bipyramidal coordination shares faces with NaO6 octahedra on both sides of these layers. PMID:28217360

  10. Crystal structure of trirubidium citrate monohydrate from laboratory X-ray powder diffraction data and DFT comparison

    Science.gov (United States)

    Kaduk, James A.

    2017-01-01

    The crystal structure of the title compound, 3Rb+·C6H5O7 3−·H2O, has been solved and refined using laboratory X-ray powder diffraction data, and optimized using density functional techniques. The hy­droxy group participates in an intra­molecular hydrogen bond to the deprotonated central carboxyl­ate group with graph-set motif S(5). The water mol­ecule acts as a hydrogen-bond donor to both terminal and central carboxyl­ate O atoms. The three independent rubidium cations are seven-, six- and six-coordinate, with bond-valence sums of 0.84, 1.02, and 0.95, respectively. In the extended structure, their polyhedra share edges and corners to form a three-dimensional network. The hydro­phobic methyl­ene groups occupy channels along the b axis. PMID:28217348

  11. Crystal structure of dirubidium hydrogen citrate from laboratory X-ray powder diffraction data and DFT comparison.

    Science.gov (United States)

    Rammohan, Alagappa; Kaduk, James A

    2017-01-01

    The crystal structure of dirubidium hydrogen citrate, 2Rb(+)·HC6H5O7(2-), has been solved and refined using laboratory X-ray powder diffraction data, and optimized using density functional techniques. The un-ionized carb-oxy-lic acid group forms helical chains of very strong hydrogen bonds (O⋯O ∼ 2.42 Å) along the b axis. The hy-droxy group participates in a chain of intra- and inter-molecular hydrogen bonds along the c axis. These hydrogen bonds result in corrugated hydrogen-bonded layers in the bc plane. The Rb(+) cations are six-coordinate, and share edges and corners to form layers in the ab plane. The inter-layer contacts are composed of the hydro-phobic methyl-ene groups.

  12. Crystal structure of caesium di-hydrogen citrate from laboratory X-ray powder diffraction data and DFT comparison.

    Science.gov (United States)

    Rammohan, Alagappa; Kaduk, James A

    2017-02-01

    The crystal structure of caesium di-hydrogen citrate, Cs(+)·H2C6H5O7(-), has been solved and refined using laboratory X-ray powder diffraction data, and optimized using density functional techniques. The coordination polyhedra of the nine-coordinate Cs(+) cations share edges to form chains along the a-axis. These chains are linked by corners along the c-axis. The un-ionized carb-oxy-lic acid groups form two different types of hydrogen bonds; one forms a helical chain along the c-axis, and the other is discrete. The hy-droxy group participates in both intra- and inter-molecular hydrogen bonds.

  13. Pharmacological characterization of nanoparticle-induced platelet microaggregation using quartz crystal microbalance with dissipation: comparison with light aggregometry

    Science.gov (United States)

    Santos-Martinez, Maria J; Tomaszewski, Krzysztof A; Medina, Carlos; Bazou, Despina; Gilmer, John F; Radomski, Marek W

    2015-01-01

    Background Engineered nanoparticles (NPs) can induce platelet activation and aggregation, but the mechanisms underlying these interactions are not well understood. This could be due in part to use of devices that study platelet function under quasi-static conditions with low sensitivity to measure platelet microaggregation. Therefore, in this study we investigated the pharmacological pathways and regulators of NP-induced platelet microaggregation under flow conditions at nanoscale using quartz crystal microbalance with dissipation (QCM-D) and compared the data thus obtained with those generated by light aggregometry. Methods Blood was collected from healthy volunteers, and platelet-rich plasma was obtained. Thrombin receptor-activating peptide, a potent stimulator of platelet function, and pharmacological inhibitors were used to modulate platelet microaggregation in the presence/absence of silica (10 nm and 50 nm) and polystyrene (23 nm) NPs. Light aggregometry was used to study platelet aggregation in macroscale. Optical, immunofluorescence, and scanning electron microscopy were also used to visualize platelet aggregates. Results Platelet microaggregation was enhanced by thrombin receptor-activating peptide, whereas prostacyclin, nitric oxide donors, acetylsalicylic acid, and phenanthroline, but not adenosine diphosphate (ADP) blockers, were able to inhibit platelet microaggregation. NPs caused platelet microaggregation, an effect not detectable by light aggregometry. NP-induced microaggregation was attenuated by platelet inhibitors. Conclusion NP-induced platelet microaggregation appears to involve classical proaggregatory pathways (thromboxane A2-mediated and matrix metalloproteinase-2-mediated) and can be regulated by endogenous (prostacyclin) and pharmacological (acetylsalicylic acid, phenanthroline, and nitric oxide donors) inhibitors of platelet function. Quartz crystal microbalance with dissipation, but not light aggregometry, is an appropriate method for

  14. Monitoring the effects of fibrinogen concentration on blood coagulation using quartz crystal microbalance (QCM) and its comparison with thromboelastography

    Science.gov (United States)

    Lakshmanan, Ramji S.; Efremov, Vitaly; Cullen, Sinéad; Byrne, Barry; Killard, Anthony J.

    2013-05-01

    Fibrinogen has been identified as a major risk factor in cardiovascular disorders. Fibrinogen (340 kDa) is a soluble dimeric glycoprotein found in plasma and is a major component of the coagulation cascade. It has been identified as a major risk factor in cardiovascular disorders. The time taken for its conversion to fibrin is usually used as an "endpoint" in most clot-based assays, without any information on dynamic changes in physical properties or kinetics of a forming clot. A global coagulation profile as measured by Thromboelastography® (TEG®) provides information on both the time and kinetics of changes in physical property of the forming clot. In this work, Quartz crystal microbalance (QCM), which is a piezoelectric resonator has been used to study coagulation of plasma and compared with TEG. The changes in resonant frequency (Δf) and half width at half maximum (HWHM or ΔΓ) were used to evaluate effect of fibrinogen concentration. It has been shown that TEG is less sensitive to low concentrations of fibrinogen and dilution while QCM is able to monitor clot formation in both the circumstances.

  15. Validation and Determination of Ice Water Content - Radar Reflectivity Relationships during CRYSTAL-FACE: Flight Requirements for Future Comparisons

    Science.gov (United States)

    Sayres, D. S.; Smith, J. B.; Pittman, J. V.; Weinstock, E. M.; Anderson, J. G.; Heymsfield, G.; Fridland, A. M.; Ackerman, A. S.

    2007-01-01

    In order for clouds to be more accurately represented in global circulation models (GCM), there is need for improved understanding of the properties of ice such as the total water in ice clouds, called ice water content (IWC), ice particle sizes and their shapes. Improved representation of clouds in models will enable GCMs to better predict for example, how changes in emissions of pollutants affect cloud formation and evolution, upper tropospheric water vapor, and the radiative budget of the atmosphere that is crucial for climate change studies. An extensive cloud measurement campaign called CRYSTAL-FACE was conducted during Summer 2002 using instrumented aircraft and a variety of instruments to measure properties of ice clouds. This paper deals with the measurement of IWC using the Harvard water vapor and total water instruments on the NASA WB-57 high-altitude aircraft. The IWC is measured directly by these instruments at the altitude of the WB-57, and it is compared with remote measurements from the Goddard Cloud Radar System (CRS) on the NASA ER-2. CRS measures vertical profiles of radar reflectivity from which IWC can be estimated at the WB-57 altitude. The IWC measurements obtained from the Harvard instruments and CRS were found to be within 20-30% of each other. Part of this difference was attributed to errors associated with comparing two measurements that are not collocated in time an space since both aircraft were not in identical locations. This study provides some credibility to the Harvard and CRS-derived IWC measurements that are in general difficult to validate except through consistency checks using different measurement approaches.

  16. Crystal structures of a halophilic archaeal malate synthase from Haloferax volcanii and comparisons with isoforms A and G

    Directory of Open Access Journals (Sweden)

    Thomas Geoffrey C

    2011-05-01

    Full Text Available Abstract Background Malate synthase, one of the two enzymes unique to the glyoxylate cycle, is found in all three domains of life, and is crucial to the utilization of two-carbon compounds for net biosynthetic pathways such as gluconeogenesis. In addition to the main isoforms A and G, so named because of their differential expression in E. coli grown on either acetate or glycolate respectively, a third distinct isoform has been identified. These three isoforms differ considerably in size and sequence conservation. The A isoform (MSA comprises ~530 residues, the G isoform (MSG is ~730 residues, and this third isoform (MSH-halophilic is ~430 residues in length. Both isoforms A and G have been structurally characterized in detail, but no structures have been reported for the H isoform which has been found thus far only in members of the halophilic Archaea. Results We have solved the structure of a malate synthase H (MSH isoform member from Haloferax volcanii in complex with glyoxylate at 2.51 Å resolution, and also as a ternary complex with acetyl-coenzyme A and pyruvate at 1.95 Å. Like the A and G isoforms, MSH is based on a β8/α8 (TIM barrel. Unlike previously solved malate synthase structures which are all monomeric, this enzyme is found in the native state as a trimer/hexamer equilibrium. Compared to isoforms A and G, MSH displays deletion of an N-terminal domain and a smaller deletion at the C-terminus. The MSH active site is closely superimposable with those of MSA and MSG, with the ternary complex indicating a nucleophilic attack on pyruvate by the enolate intermediate of acetyl-coenzyme A. Conclusions The reported structures of MSH from Haloferax volcanii allow a detailed analysis and comparison with previously solved structures of isoforms A and G. These structural comparisons provide insight into evolutionary relationships among these isoforms, and also indicate that despite the size and sequence variation, and the truncated C

  17. Comparison between experiment and theory in the temperature variation of film tension above the bulk isotropic transition in free-standing liquid-crystal films.

    Science.gov (United States)

    Veum, M; Duelge, L; Droske, J; Nguyen, H T; Huang, C C; Mirantsev, L V

    2009-09-01

    Using differential scanning calorimetry, the transition enthalpies and temperatures for the bulk smectic-isotropic phase transition have been measured for a series of liquid-crystal compounds. For five compounds, those values were used as parameters in a microscopic mean-field model to predict the temperature dependence of the difference in free-energy density between a sample of material in a free-standing smectic film and that in the bulk. The model predicts a weak temperature dependence below the bulk clearing point and a pronounced monotonic increase with temperature above the transition temperature. The compounds used in this study were chosen specifically because they were also the subject of a previous independent experimental study [M. Veum, Phys. Rev. E 74, 011703 (2006)] that demonstrated a sudden monotonic increase in the free-standing film tension with temperature, which is qualitatively consistent with the predictions of the above-mentioned mean-field model. This study presents a direct and quantitative comparison between the predictions of the mean-field model and the results from previous tension experiments.

  18. Crystals in crystals

    DEFF Research Database (Denmark)

    Christensen, Claus H.; Schmidt, I.; Carlsson, A.;

    2005-01-01

    A major factor governing the performance of catalytically active particles supported on a zeolite carrier is the degree of dispersion. It is shown that the introduction of noncrystallographic mesopores into zeolite single crystals (silicalite-1, ZSM-5) may increase the degree of particle dispersion...... of the zeolite particles, particularly after thermal treatment. When using mesoporous zeolites, the particles were evenly distributed throughout the mesopore system of the zeolitic support, even after calcination, leading to nanocrystals within mesoporous zeolite single crystals....

  19. Comparison of optical transients during the picosecond laser pulse-induced crystallization of GeSbTe and AgInSbTe phase-change thin films: Nucleation-driven versus growth-driven processes

    Energy Technology Data Exchange (ETDEWEB)

    Liang, Guangfei [Key Laboratory of High Power Laser Materials, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China); Li, Simian [State Key Laboratory of Optoelectronic Materials and Technology, Department of Physics, Sun Yat-Sen University, Guangzhou 510275 (China); Huang, Huan [Key Laboratory of High Power Laser Materials, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China); Wang, Yang, E-mail: ywang@siom.ac.cn [Key Laboratory of High Power Laser Materials, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China); Lai, Tianshu, E-mail: stslts@mail.sysu.edu.cn [State Key Laboratory of Optoelectronic Materials and Technology, Department of Physics, Sun Yat-Sen University, Guangzhou 510275 (China); Wu, Yiqun [Key Laboratory of High Power Laser Materials, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China)

    2013-09-01

    Direct comparison of the real-time in-situ crystallization behavior of as-deposited amorphous Ge{sub 2}Sb{sub 2}Te{sub 5} (GeSbTe) and Ag{sub 8}In{sub 14}Sb{sub 55}Te{sub 23} (AgInSbTe) phase-change thin films driven by picosecond laser pulses was performed by a time-resolved optical pump-probe technique with nanosecond resolution. Different optical transients showed various crystallization processes because of the dissimilar nucleation- and growth-dominated mechanisms of the two materials. The effects of laser pulse fluence, thermal conductive structure, and successive pulse irradiation on their crystallization dynamics were also discussed. A schematic was then established to describe the different crystallization processes beginning from the as-deposited amorphous state. The results may provide further insight into the phase-change mechanism under extra-non-equilibrium conditions and aid the development of ultrafast phase-change memory materials.

  20. Structural study of vapour phase deposited 3,4,9,10-perylene tetracarboxylicacid diimide: Comparison between single crystal and ultra thin films grown on Pt(100)

    Energy Technology Data Exchange (ETDEWEB)

    Guillermet, O. [Universite de la Mediterranee, Aix-Marseille II, CRMC-N, UPR CNRS 7251, Campus de Luminy, case 913, F-13288 Marseille Cedex 09 (France); Mossoyan-Deneux, M. [Universite de Provence, Aix-Marseille I, L2MP, UMR CNRS 6137, Faculte des Sciences de St Jerome, F-13397 Marseille Cedex 20 (France); Giorgi, M. [Service Commun de Cristallochimie, Universite Paul Cezanne, Aix-marseille III, Faculte des Sciences de St Jerome, F-13397 Marseille Cedex 20 (France); Glachant, A. [Universite de la Mediterranee, Aix-Marseille II, CRMC-N, UPR CNRS 7251, Campus de Luminy, case 913, F-13288 Marseille Cedex 09 (France)]. E-mail: glachant@crmcn.univ-mrs.fr; Mossoyan, J.C. [Universite de Provence, Aix-Marseille I, L2MP, UMR CNRS 6137, Faculte des Sciences de St Jerome, F-13397 Marseille Cedex 20 (France)

    2006-08-30

    Structural properties of a single crystal and of a thin film of 3,4,9,10-perylene-tetracarboxylic-acid-diimide are compared. The two samples are both obtained from the vapour phase, the latter being deposited at room temperature, in an ultrahigh vacuum environment, on a clean Pt(100) substrate. In the single crystal we have pointed out interactions between adjacent molecules by overlapping of the {pi} systems in the stacks and by hydrogen bonds between neighbouring stacks. The various surface unit cells of the nanocrystals from the film, identified by means of scanning tunnelling microscopy, are not comparable to those expected from the X-ray diffraction study of the single crystal and to those already published for other substrates. This fact clearly highlights the role played by the type of substrate chosen and/or the substrate-molecule interaction that affects the stacking and crystallinity of the growing crystal on top.

  1. A New Method for Simultaneous Measurement of the Integrated Reflectivity of Crystals at Multiple Orders of Reflection and Comparison with New Theoretical Calculations

    Energy Technology Data Exchange (ETDEWEB)

    S.G. Lee; J.G. Bak; Y.S. Jung; M. Bitter; K.W. Hill; G. Hoelzer; O. Wehrhan; E. Foerster

    2003-04-09

    This paper describes a new method for the simultaneous measurement of the integrated reflectivity of a crystal for multiple orders of reflection at a predefined Bragg angle. The technique is demonstrated with a mica crystal for Bragg angles of 43{sup o}, 47{sup o}, and 50{sup o}. The measured integrated reflectivity for Bragg reflections up to the 24th order is compared with new theoretical predictions, which are also presented in this paper.

  2. Mass flux response comparisons of a 200-MHz surface acoustic wave (SAW) resonator microbalance to a 15-MHz thermoelectric quartz crystal microbalance (TQCM) in a high-vacuum environment

    Science.gov (United States)

    Wallace, Donald A.; Bowers, William D.

    1994-10-01

    Using a 200 MHz Surface Acoustic Wave (SAW) resonator device as a high-vacuum molecular deposition microbalance, similar to a bulk quartz crystal microbalance (QCM), and an often-used 15 MHz thermoelectric QCM (TQCM), a comparison of various parameters was made during a high-vacuum outgassing experiment. The source of molecular outgassing was a bright aluminum foil which was cooled to liquid nitrogen temperature and alternately, to ambient temperature. The two sensors, the SAW QCM and the TQCM were placed next to each other and viewed only the aluminum foil. In this high-vacuum environment, a comparison between various parameters, i.e., mass sensitivity, long term drift rate, stability, thermal effects and dynamic range of the SAW and the TQCM, was obtained.

  3. Comparison of the inhibitory capacity of two groups of pure natural extract on the crystallization of two types of material compound urinary stones in vitro study

    Science.gov (United States)

    Beghalia, Mohamed; Ghalem, Said; Allali, Hocine

    2015-10-01

    Urolithiasis is defined as the result of an abnormal precipitation within the urinary tract. This precipitation is most often from the normal constituents of the urine. This is a fairly common condition in the population. She is happy and recurrent etiology is often unknown if hypothetical. In Algeria, as in many countries, a large number of patients use herbal medicines in the treatment of their diseases including urolithiasis. Thus the aim of this study is the most widely used to evaluate the effectiveness of aqueous extracts of medicinal plants, in the treatment of calcium urolithiasis oxalo-and magnesium-amoniaco in vitro. The study also examines the effect of these extracts on the states of crystallization (nucleation, crystal growth, crystal aggregation), followed by photography on polarized light microscope.In this regard, we are devoted to studying the crystallization steps from oxalo-calcium and phospho-calcic prepared as artificial urine and supersaturated aqueous solutions, maintained at 37 °C to remain close to biological conditions. Extracts of the first group of herbs: Ammodaucus leucotrichus, Ajuga iva, Globularia alypum, Atriplex halimus are studied on the crystallization calcium oxalate, we cite the Ammodaucus leucotrichus which acts on the stages of nucleation, growth and the aggregation with a total inhibition. The second group of extracts plants tested on calcium phosphate crystallization : Acacia raddiana, Citrullus colocynthis, Rhus tripartita, Pistacia lentiscu, Warionia saharae, are able to significantly reduce phosphate crystallization in vitro. It is easily proved by FTIR and optical microscope. In conclusion the results of our work allows us to confirm the use of these plants as an aqueous decoction, in the field of urolithiasis. These activities may help to strengthen the body in depressed situations.

  4. A comparison of the abilities of natural rubber (NR) and synthetic polyisoprene cis-1,4 rubber (IR) to crystallize under strain at high strain rates.

    Science.gov (United States)

    Candau, Nicolas; Chazeau, Laurent; Chenal, Jean-Marc; Gauthier, Catherine; Munch, Etienne

    2016-02-07

    Strain induced crystallization (SIC) of a natural rubber (NR) and a synthetic rubber (IR) with a high amount of cis-1,4 units (98.6%) is studied, thanks to in situ wide angle X-ray (WAXS) experiments at room temperature performed in a large range of strain rates. During stretching at a low strain rate (4.2 × 10(-3) s(-1)), SIC in IR occurs at a larger stretching ratio than in NR. As a result, the crystallinity index at a given stretching ratio is lower in IR than in NR, in spite of the similar crosslink densities of the chains involved in the crystallization in both materials. This lower ability for crystallization in IR is attributed to the presence of branching along its backbone and its lower stereoregularity. Conversely, dynamic experiments performed at high strain rates (10(1)/10(2) s(-1)) show for both materials a similar ability to crystallize. This unexpected result is confirmed by monotonic tensile tests performed in a large range of strain rates. The reason is thermodynamic: the chain extension plays a predominant role compared to the role of the microstructure defects when the strain rate is high, i.e. when the kinetics of the crystallite nucleation forces the crystallization to occur at a large stretching ratio. A thermodynamic model enables qualitative reproduction of the experimental results.

  5. Axion Crystals

    CERN Document Server

    Ozaki, Sho

    2016-01-01

    The low-energy effective theories for gapped insulators are classified by three parameters: permittivity $\\epsilon$, permeability $\\mu$, and theta angle $\\theta$. Crystals with periodic $\\epsilon$ are known as photonic crystals. We here study the band structure of photons in a new type of crystals with periodic $\\theta$ (modulo $2\\pi$) in space, which we call the axion crystals. We find that the axion crystals have a number of new properties that the usual photonic crystals do not possess, such as the helicity-dependent photonic band gaps and the nonrelativistic gapless dispersion relation at small momentum. We briefly discuss possible realizations of axion crystals in condensed matter systems as well as high-energy physics.

  6. CRYSTAL-STRUCTURE OF RECOMBINANT HUMAN TRIOSEPHOSPHATE ISOMERASE AT 2.8 ANGSTROM RESOLUTION - TRIOSEPHOSPHATE ISOMERASE-RELATED HUMAN GENETIC-DISORDERS AND COMPARISON WITH THE TRYPANOSOMAL ENZYME

    NARCIS (Netherlands)

    MANDE, SC; MAINFROID, [No Value; KALK, KH; GORAJ, K; MARTIAL, JA; HOL, WGJ

    1994-01-01

    The crystal structure of recombinant human triosephosphate isomerase (hTIM) has been determined complexed with the transition-state analogue 2-phosphoglycolate at a resolution of 2.8 Angstrom. After refinement, the R-factor is 16.7% with good geometry. The asymmetric unit contains 1 complete dimer o

  7. Comparison of ab initio molecular properties of EDO-TTF with the properties of the (EDO-TTF)(2)PF6 crystal

    NARCIS (Netherlands)

    Linker, Gerrit-Jan; van Loosdrecht, Paul H. M.; van Duijnen, Piet; Broer, Ria

    2010-01-01

    We performed ab initio quantum chemical calculations for the geometrical and electronic structure of the EDO-TTF (ethylenedioxy-tetrathiafulvalene) molecule using HF, CASSCF and DFT methods. We compare these in vacuo results with the properties of the (EDO-TTF)(2)PF6 crystal at near room temperature

  8. In-situ metrology for the optimization of bent crystals used in hard-X-ray monochromators: Comparison between measurement and simulation

    Energy Technology Data Exchange (ETDEWEB)

    Thomasset, Muriel, E-mail: muriel.thomasset@synchrotron-soleil.f [Synchrotron SOLEIL, L' orme des Merisiers, BP 48, 91192 Gif sur Yvette (France); Moreno, Thierry; Capitanio, Blandine; Idir, Mourad [Synchrotron SOLEIL, L' orme des Merisiers, BP 48, 91192 Gif sur Yvette (France); Bucourt, Samuel [Imagine Optic, 18 rue Charles de Gaulle, Orsay 91400 (France)

    2010-05-01

    Crystal sagittal focusing is known as one of the most efficient way of focusing synchrotron X-ray radiation from bending magnet sources, thus delivering increases photon flux at the sample position. To optimize the performance of a sagittaly bent crystal inside a monochromator, it is necessary to have knowledge of its radius of curvature. However, this measurement is not very easy to obtain. Even though the use of the X-ray beam is the ultimate source for optimizing the system, it is still necessary to have a prior knowledge of the radius of curvature as a function of the motor bender positions to avoid any catastrophic failure. In this paper, we describe a simple, efficient and accurate method of measuring the radius of curvature of sagitally bent monochromator crystals at several bending magnet beamlines at synchrotron SOLEIL. To optimize the crystal bending inside these monochromators, we used a Shack-Hartmann sensor (HP 26) developed by the Imagine Optic Company (Orsay/France). This high accuracy two-dimensional metrology tool was originally designed to be installed on a Long Trace Profiler translation stage to measure the mirrors profiles. During a period where the SOLEIL synchrotron was in shutdown, this instrument was directly mounted inside the monochromator so that the radius of curvature could be measured in-situ. This method allows us to optimize the curvature and eliminate twist before bending strongly the crystal below radii of curvature of less than 2 m. The second step in the optimization process was to use the X-ray beam for the final adjustments of the bending system, where X-ray images are then used to analyse the residual defaults of the system. Using SpotX, a ray-tracing simulation tool, these errors can be fully analysed and a fully optimized system can then be obtained. Overall, five beamlines at synchrotron SOLEIL have used in this method to optimize their monochromators.

  9. Tricaesium citrate monohydrate, Cs3C6H5O7·H2O: crystal structure and DFT comparison

    Directory of Open Access Journals (Sweden)

    Alagappa Rammohan

    2017-04-01

    Full Text Available The crystal structure of tricaesium citrate monohydrate, 3Cs+·C6H5O73−·H2O, has been solved and refined using laboratory X-ray single-crystal diffraction data, and optimized using density functional techniques. This compound is isostructural to the K+ and Rb+ compounds with the same formula. The three independent Cs cations are eight-, eight-, and seven-coordinate, with bond-valence sums of 0.91, 1.22, and 1.12 valence units. The coordination polyhedra link into a three-dimensional framework. The hydroxy group forms the usual S(5 hydrogen bond with the central carboxylate group, and the water molecule acts as a donor in two strong hydrogen bonds.

  10. Fourier Analysis and Structure Determination--Part III: X-ray Crystal Structure Analysis.

    Science.gov (United States)

    Chesick, John P.

    1989-01-01

    Discussed is single crystal X-ray crystal structure analysis. A common link between the NMR imaging and the traditional X-ray crystal structure analysis is reported. Claims that comparisons aid in the understanding of both techniques. (MVL)

  11. 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.

  12. More accurate determination of the quantity of ice crystallized at low cooling rates in the glycerol and 1,2-propanediol aqueous solutions: comparison with equilibrium.

    Science.gov (United States)

    Boutron, P

    1984-04-01

    It is generally assumed that when cells are cooled at rates close to those corresponding to the maximum of survival, once supercooling has ceased, above the eutectic melting temperature the extracellular ice is in equilibrium with the residual solution. This did not seem evident to us due to the difficulty of ice crystallization in cryoprotective solutions. The maximum quantities of ice crystallized in glycerol and 1,2-propanediol solutions have been calculated from the area of the solidification and fusion peaks obtained with a Perkin-Elmer DSC-2 differential scanning calorimeter. The accuracy has been improved by several corrections: better defined baseline, thermal variation of the heat of fusion of the ice, heat of solution of the water from its melting with the residual solution. More ice crystallizes in the glycerol than in the 1,2-propanediol solutions, of which the amorphous residue contains about 40 to 55% 1,2-propanediol. The equilibrium values are unknown in the presence of 1,2-propanediol. With glycerol, in our experiments, the maximum is first lower than the equilibrium but approaches it as the concentration increases. It is not completely determined by the colligative properties of the solutes.

  13. Protein Crystallization

    Science.gov (United States)

    Chernov, Alexander A.

    2005-01-01

    Nucleation, growth and perfection of protein crystals will be overviewed along with crystal mechanical properties. The knowledge is based on experiments using optical and force crystals behave similar to inorganic crystals, though with a difference in orders of magnitude in growing parameters. For example, the low incorporation rate of large biomolecules requires up to 100 times larger supersaturation to grow protein, rather than inorganic crystals. Nucleation is often poorly reproducible, partly because of turbulence accompanying the mixing of precipitant with protein solution. Light scattering reveals fluctuations of molecular cluster size, its growth, surface energies and increased clustering as protein ages. Growth most often occurs layer-by-layer resulting in faceted crystals. New molecular layer on crystal face is terminated by a step where molecular incorporation occurs. Quantitative data on the incorporation rate will be discussed. Rounded crystals with molecularly disordered interfaces will be explained. Defects in crystals compromise the x-ray diffraction resolution crucially needed to find the 3D atomic structure of biomolecules. The defects are immobile so that birth defects stay forever. All lattice defects known for inorganics are revealed in protein crystals. Contribution of molecular conformations to lattice disorder is important, but not studied. This contribution may be enhanced by stress field from other defects. Homologous impurities (e.g., dimers, acetylated molecules) are trapped more willingly by a growing crystal than foreign protein impurities. The trapped impurities induce internal stress eliminated in crystals exceeding a critical size (part of mni for ferritin, lysozyme). Lesser impurities are trapped from stagnant, as compared to the flowing, solution. Freezing may induce much more defects unless quickly amorphysizing intracrystalline water.

  14. 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.

  15. Crystal Data

    Science.gov (United States)

    SRD 3 NIST Crystal Data (PC database for purchase)   NIST Crystal Data contains chemical, physical, and crystallographic information useful to characterize more than 237,671 inorganic and organic crystalline materials. The data include the standard cell parameters, cell volume, space group number and symbol, calculated density, chemical formula, chemical name, and classification by chemical type.

  16. Comparison of the crystal structures of methyl 4-bromo-2-(meth-oxy-meth-oxy)benzoate and 4-bromo-3-(meth-oxy-meth-oxy)benzoic acid.

    Science.gov (United States)

    Suchetan, P A; Suneetha, V; Naveen, S; Lokanath, N K; Krishna Murthy, P

    2016-04-01

    The title compounds, C10H11BrO4, (I), and C9H9BrO4, (II), are derivatives of bromo-hy-droxy-benzoic acids. Compound (II) crystallizes with two independent mol-ecules (A and B) in the asymmetric unit. In both (I) and (II), the O-CH2-O-CH3 side chain is not in its fully extended conformation; the O-C-O-C torsion angle is 67.3 (3) ° in (I), and -65.8 (3) and -74.1 (3)° in mol-ecules A and B, respectively, in compound (II). In the crystal of (I), mol-ecules are linked by C-H⋯O hydrogen bonds, forming C(5) chains along [010]. The chains are linked by short Br⋯O contacts [3.047 (2) Å], forming sheets parallel to the bc plane. The sheets are linked via C-H⋯π inter-actions, forming a three-dimensional architecture. In the crystal of (II), mol-ecules A and B are linked to form R 2 (2)(8) dimers via two strong O-H⋯O hydrogen bonds. These dimers are linked into ⋯A-B⋯A-B⋯A-B⋯ [C 2 (2)(15)] chains along [011] by C-H⋯O hydrogen bonds. The chains are linked by slipped parallel π-π inter-actions [inter-centroid distances = 3.6787 (18) and 3.8431 (17) Å], leading to the formation of slabs parallel to the bc plane.

  17. Comparison between beryllium and diamond-backing plates in diamond-anvil cells: Application to single-crystal X-ray diffraction high-pressure data

    DEFF Research Database (Denmark)

    Periotto, Benedetta; Nestola, Fabrizio; Balic Zunic, Tonci;

    2011-01-01

    A direct comparison between two complete intensity datasets, collected on the same sample loaded in two identical diamond-anvil pressure cells equipped, respectively, with beryllium and diamond backing plates was performed. The results clearly demonstrate that the use of diamond-backing plates...

  18. Comparison of ab initio molecular properties of EDO-TTF with the properties of the (EDO-TTF) 2PF 6 crystal

    Science.gov (United States)

    Linker, Gerrit-Jan; Loosdrecht, Paul H. M. van; Duijnen, Piet van; Broer, Ria

    2010-03-01

    We performed ab initio quantum chemical calculations for the geometrical and electronic structure of the EDO-TTF (ethylenedioxy-tetrathiafulvalene) molecule using HF, CASSCF and DFT methods. We compare these in vacuo results with the properties of the (EDO-TTF) 2PF 6 crystal at near room temperature. We demonstrate that, by bending and charging the molecule in vacuum, the deformation that is thought to be the origin of charge ordering in this material is an inherent property of the EDO-TTF molecule. We further show that deformations can be readily made at ambient temperatures.

  19. The comparison of calculated transition probabilities with luminescence characteristics of erbium(III) in fluoride glasses and in the mixed yttrium-zirconium oxide crystal

    Science.gov (United States)

    Reisfeld, R.; Katz, G.; Jacoboni, C.; De Pape, R.; Drexhage, M. G.; Brown, R. N.; Jørgensen, C. K.

    1983-07-01

    Fluorozirconate glasses containing 2 mole% ErF 3 were prepared by melting the binary fluorides with ammonium bifluoride under an atmosphere of carbon tetrachloride and argon at 850°C. Absorption spectra of these glasses were obtained and the Judd-Ofelt parameters were calculated. Emission spectra and lifetimes of erbium in fluorozirconate glass, in lead-gallium-zinc fluoride glass, and in yttrium-zirconium oxide crystal were measured and compared with the theoretical calculations. Laser emission lines in these materials are deduced from these measurements. It is suggested that materials doped with erbium may serve as light sources for fiber optic waveguides made from the undoped materials.

  20. Comparison of the properties of tonpilz transducers fabricated with 001 fiber-textured lead magnesium niobate-lead titanate ceramic and single crystals.

    Science.gov (United States)

    Brosnan, Kristen H; Messing, Gary L; Markley, Douglas C; Meyer, Richard J

    2009-11-01

    Tonpilz transducers are fabricated from 001 fiber-textured 0.72Pb(Mg(1/3)Nb(2/3))O(3)-0.28PbTiO(3) (PMN-28PT) ceramics, obtained by the templated grain growth process, and PMN-28PT ceramic and Bridgman grown single crystals of the same composition. In-water characterization of single element transducers shows higher source levels, higher in-water coupling, and more usable bandwidth for the 81 vol % textured PMN-28PT device than for the ceramic PMN-28PT element. The 81 vol % textured PMN-28PT tonpilz element measured under large signals shows linearity in sound pressure levels up to 0.23 MV/m drive field but undergoes a phase transition due to a lowered transition temperature from the SrTiO(3) template particles. Although the textured ceramic performs well in this application, it could be further improved with compositional tailoring to raise the transition temperature and better processing to improve the texture quality. With these improvements textured piezoelectric ceramics will be viable options for medical ultrasound, actuators, and sonar applications because of their ease of processing, compositional homogeneity, and potentially lower cost than single crystal.

  1. Macromolecular crystallization and crystal perfection

    CERN Document Server

    Chayen, Naomi E; Snell, Edward H

    2010-01-01

    Structural biology is key to our understanding of the mechanisms of biological processes. This text describes current methods and future frontiers in crystal growth and use of X-ray and neutron crystallography, in the context of automation of crystallization and generation of synchrotron X-ray and neutron beams.

  2. Liquid crystal tunable photonic crystal dye laser

    DEFF Research Database (Denmark)

    Buss, Thomas; Christiansen, Mads Brøkner; Smith, Cameron;

    2010-01-01

    We present a dye-doped liquid crystal laser using a photonic crystal cavity. An applied electric field to the liquid crystal provides wavelength tunability. The photonic crystal enhances resonant interaction with the gain medium....

  3. Measurement of Light Collection of CMS PbWO4 Crystals Comparison with the Cristal Monte Carlo Simulation Program and Further Evaluation

    CERN Document Server

    Drobychev, Gleb; Peigneux, Jean-Pierre; Rivoalan, P

    1998-01-01

    The measurement of the signal for light collection limited by the effective area of the present APD detectors has been evaluated using a photomultiplier and co60 source. Comparison of the methods and experimental results for simple geometrical situations has been made with the results of the CRISTAL Monte Carlo program which is also used to evaluate more complicated geometries including evaluation of a wavelength shifter used with an APD as a photodetector.

  4. Crystal Dislocations

    Directory of Open Access Journals (Sweden)

    Ronald W. Armstrong

    2016-01-01

    Full Text Available Crystal dislocations were invisible until the mid-20th century although their presence had been inferred; the atomic and molecular scale dimensions had prevented earlier discovery. Now they are normally known to be just about everywhere, for example, in the softest molecularly-bonded crystals as well as within the hardest covalently-bonded diamonds. The advent of advanced techniques of atomic-scale probing has facilitated modern observations of dislocations in every crystal structure-type, particularly by X-ray diffraction topography and transmission electron microscopy. The present Special Issue provides a flavor of their ubiquitous presences, their characterizations and, especially, their influence on mechanical and electrical properties.

  5. Comparison and evaluation of cloud point extraction and low-temperature directed crystallization as preconcentration tools for the determination of trace elements in environmental samples

    Energy Technology Data Exchange (ETDEWEB)

    Giokas, D.L.; Eksperiandova, L.P.; Blank, A.B.; Karayannis, M.I

    2004-03-03

    A comparative study between cloud point extraction (CPE) and low-temperature directed crystallization (LTDC) is presented. Trace elements (Cd, Pb, Cr, Cu, Zn, Ni and Fe) were preconcentrated by both methods from model and natural water samples and the results were evaluated with respect to extraction efficiency, accuracy, precision, sample throughput and interferences. Flame atomic absorption spectrometry (FAAS) and inductively coupled plasma atomic emission spectrometry (ICP-AES) were used for the final measurements. The results indicate that these extraction and preconcentration procedures ensure the required accuracy and precision for the reliable identification and quantification of trace elements in natural waters. Drawbacks of each method identified can further assist the analyst towards a better application of each method depending on the target species, the detector employed and the application intended (routine analysis, trace analysis, speciation analysis, etc.)

  6. IV measurements of mc-Si solar cells. Comparison of results from institute and industry partners within the EU CrystalClear project

    Energy Technology Data Exchange (ETDEWEB)

    Hahn, G.; Herguth, A.; Helfricht, A. [University of Konstanz, Department of Physics, Jacob-Burckhardt-Str. 29, 78464 Konstanz (Germany); Hofmann, M; Warta, W. [Fraunhofer Institute for Solar Energy Systems ISE, Heidenhofstr. 2, 79110 Freiburg (Germany); Van der Borg, N.J.C.M.; Weeber, A.W. [ECN Solar Energy, PO Box 1, NL 1755 ZG Petten (Netherlands); John, J.; Beaucarne, G. [IMEC, Kapeldreef 75, B-3001 Leuven (Belgium); Bagus, S.; Nagel, H. [SCHOTT Solar GmbH, Carl-Zeiss-Strasse 4, 63755 Alzenau (Germany); Le Quang, N.; Nichiporuk, O. [Photowatt International S.A.S. 33, Rue St. Honore 38300 Bourgoin Jallieu (France); Vincueria, I. [BP Solar Espana SAU, P.I. Tres Cantos Zona Oeste, s/n 28760, Madrid (Spain); Brochs, M. [REC Scancell, 8512 Narvik (Norway)

    2008-10-15

    Determination of solar cell parameters by illuminated IV measurement is a standard characterisation technique used by many partners active in photovoltaics. The aim of this work is to carry out a cross check of different measurement set-ups used by different research partners of the EU CrystalClear project using industrial type multicrystalline Si solar cells. In a first round robin a significant spread of all cell parameters (Voc, jsc, FF and efficiency) could be observed. After distribution of sister cells to selected cells calibrated at ISE CalLab, a second round robin was carried out. The spread in FF and jsc could be significantly reduced. Repeatability tests showed that by using a photo diode fluctuations of light intensity can be minimised and variations in jsc can be decreased down to 0.2 mA/cm{sup 2}. Remaining systematic errors are control of cell temperature, contacting geometry, and use of appropriate reference cells.

  7. A spectroscopic comparison of IGZO thin films and the parent In2O3, Ga2O3, and ZnO single crystals

    Science.gov (United States)

    Haeberle, J.; Brizzi, S.; Gaspar, D.; Barquinha, P.; Galazka, Z.; Schulz, D.; Schmeißer, D.

    2016-10-01

    We use resonant photoelectron spectroscopy at the Zn 2p, Ga 2p, In 3d, and O 1s absorption edges to report on the electronic properties of indium-gallium-zinc-oxide thin films. We also compare the data with the respective data of the corresponding single crystals In2O3, Ga2O3, and ZnO. We focus on the elemental composition and, in particular, find no evidence for oxygen deficiency. The In, Ga, and Zn absorption data at resonance can be used to analyze the conduction band states in detail. We deduce that a configuration interaction between d10s0 and d9s1states is of importance. We provided a novel mechanism in which configuration interaction induced gap states create both, extended unoccupied states around E F as well as localized occupied states within the gap.

  8. A comparison of the suitability of cathode ray tube (CRT) and liquid crystal display (LCD) monitors as visual stimulators in mfERG diagnostics.

    Science.gov (United States)

    Kaltwasser, Christoph; Horn, Folkert K; Kremers, Jan; Juenemann, Anselm

    2009-06-01

    The aim of this study was to determine up to which extent the specific characteristics of cathode ray tube (CRT) and liquid crystal display (LCD) monitors influence the retinal biosignal when used as stimulators in ocular electrophysiology. In a conventional CRT monitor, each pixel lights up only for a duration of a few milliseconds during each frame. In contrast, liquid crystal displays are quasi-static, i.e. each pixel has a constant luminance during the whole length of the frame, but lights up only with a certain delay after the trigger. These different display characteristics may affect the mfERG signal. The temporal and spatial luminance distributions of a CRT and an LCD monitor were measured in white flashes. The total amount of emitted light was calculated by integration of the intensity versus time curves. By means of an mfERG recording system (RETIsystem, Roland Consult, Brandenburg, Germany) first-order kernel (FOK) mfERG signals were computed and then analysed using customized MATLAB (TheMathWorks, Natick, MA, USA) software. With the two stimulator monitors, differences in the mfERG signal were observed. The latencies of mfERG responses recorded with the LCD monitor were significantly increased by 7.1 ms for N1 and 9.5 ms for P1 compared to the CRT. Due to a higher luminance, the N1 amplitude was significantly higher by approx. 2 dB in measurements with the LCD monitor while no significant difference could be detected with regard to the more contrast sensitive P1 amplitude. When using LCD monitors as stimulators the increase in latencies and differences in the luminance versus time profile must be taken into account. Prior to clinical application, the establishment of guidelines for the use of LCD monitors is recommended.

  9. Experimental study of therapeutic effect of Haierfu on mice of aluminum induced Alzheimer's disease%海尔福对铝致老年痴呆症小鼠治疗效果的实验研究

    Institute of Scientific and Technical Information of China (English)

    李韬; 陈菊芳; 玉莹; 张元; 潘福玉; 李海; 张树球

    2012-01-01

    Objective To explore the therapeutic effect of Haierfu on mice of aluminum induced Alzheimer's disease(AD). Methods AD mice model was established first. 48 mice were divided into control group, model group, treatment group 1(large dose)and treatment group 2(small dose). All mice except those of the control group were induced with aluminum by feeding aluminum chloride mixed fodder and freely drinking aluminum nitrate solution for 3 months. After two months, different doses of Haierfu were given to mice of treatment group 1 and group 2. Same volume of distilled water was given to mice of the control group and model group till to the end of the experiment. Hemoglobin(Hb)and Morris water maze test were tested before and after experiment. At the end of experiment total calcium, total cholesteroKTC), triglyceride(TG) and urea in blood were determined. After mice were sacrificed, their brains were taken and weighed. Parts of the brain were made into homogenate* and centrifuged to get the supernatant, in which acetylcholinesterase (AchE), total sulfhydryl group (-SH), malondialdehyde ( MDA) and superoxide anion radical (O7 ) were determined. And another part of the brain was used for pathological examination after formaldehyde treatment. Results In all experimental groups the indices showed that AchE wa(l. 67±0. 36), (0.76± 0.16), (1. 60±0. 35), and, 47±0. 23)U/mg pro( -SH was100. 00±23. 78), (90. 36±14.14), (108.71 ±23. 80), and( 128. 79± 13. 44)mmol/mg pro. The index in model group was a bit lower compared with the control groupi the difference was statistically significant (P< 0. 01). was (17. 63 ± 3. 05)% , ( 5. 93 ±2.69 )The index in model group and treatment group 2 was a bitlower compared with the control groups the differencewas statistically significant (P < 0. 01). The pathological finding of pallium showed that the number of granular cell decreased obviously, and the neuron suffered from atrophy, degeneration and necrosis. Conclusions Aluminum can

  10. Comparison of Laser Performances of 5at.% Yb: Gd,2xY,2(1-xSiO,5 Crystals between Different Cutting Directions

    Institute of Scientific and Technical Information of China (English)

    YU Hai-Bo; XU Jun; LIANG Xiao-Yan; HE Jin-Ping; LENG Yu-Xin; LI Ru-Xin; XU Zhi-Zhan; ZHENG Li-He; ZHAO Guang-Jun; SU Liang-Bi

    2008-01-01

    We investigate the laser actions of 5at.% Yb: Cd,2x Y,2(1-xSiO,5 (Yb:GYSO; x = 0.1) crystals with different cutting directions, parallel and vertical to the growth axis. Our results show that the cutting direction of the sample plays an astonished role in the laser operation. The sample cut vertically to the growth axis possesses the favourable lasing characteristics. Its output power reaches 3.13W at 1060nm with a slope efficiency of 44.68% when the absorbed pump power is 8.9W. In contrast, the sample cut parallel reaches only 1.65W at 1044nm with a slope efficiency of 33.76% with absorbed pump power of 7.99W. The absorption and emission spectra of the two samples are examined and the merit factor M is calculated. Our analysis is in agreement well with the experimental results. The wavelength tuning range of the superior sample covers from 1013.68nm to 1084.82nm.

  11. Influence of microgravity on protein crystal structures

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Structural determination and comparison of microgravity and ground grown protein crystals have been carried out in order to investigate the effect of microgravity on the structure of protein crystals. Following the structural studies on the hen egg-white lysozyme cystals grown in space and on the ground, the same kind of comparative studies was performed with acidic phospholipase A2 crystals grown in different gravities. Based on the results obtained so far, a conclusion could be made that microgravity might not be strong enough to change the conformation of polypeptide chain of proteins, but it may improve the bound waters' structure, and this might be an important factor for microgravity to improve the protein crystal quality. In addition, the difference in the improvement between the two kinds of protein crystals may imply that the degree of improvement of a protein crystal in microgravity may be related to the solvent content in the protein crystal.

  12. Liquid Crystals

    Science.gov (United States)

    1990-01-01

    Thermochromic liquid crystals, or TLCs, are a type of liquid crystals that react to changes in temperature by changing color. The Hallcrest/NASA collaboration involved development of a new way to visualize boundary layer transition in flight and in wind tunnel testing of aircraft wing and body surfaces. TLCs offered a new and potentially better method of visualizing the boundary layer transition in flight. Hallcrest provided a liquid crystal formulation technique that afforded great control over the sensitivity of the liquid crystals to varying conditions. Method is of great use to industry, government and universities for aerodynamic and hydrodynamic testing. Company's principal line is temperature indicating devices for industrial use, such as non-destructive testing and flaw detection in electric/electronic systems, medical application, such as diagnostic systems, for retail sale, such as room, refrigerator, baby bath and aquarium thermometers, and for advertising and promotion specials. Additionally, Hallcrest manufactures TLC mixtures for cosmetic applications, and liquid crystal battery tester for Duracell batteries.

  13. Searching for the Best Protein Crystals: Synchrotron Based Measurements of Protein Crystal Quality

    Science.gov (United States)

    Borgstahl, Gloria; Snell, Edward H.; Bellamy, Henry; Pangborn, Walter; Nelson, Chris; Arvai, Andy; Ohren, Jeff; Pokross, Matt

    1999-01-01

    We are developing X-ray diffraction methods to quantitatively evaluate the quality of protein crystals. The ultimate use for these crystal quality will be to optimize crystal growth and freezing conditions to obtain the best diffraction data. We have combined super fine-phi slicing with highly monochromatic, low divergence synchrotron radiation and the ADSC Quantum 4 CCD detector at the Stanford Synchrotron Radiation laboratory beamline 1.5 to accurately measure crystal mosaicity. Comparisons of microgravity versus earth-grown insulin crystals using these methods will be presented.

  14. Photonic crystals

    CERN Document Server

    Busch, Kurt; Wehrspohn, Ralf B; Föll, Helmut

    2006-01-01

    The majority of the contributions in this topically edited book stems from the priority program SPP 1113 ""Photonische Kristalle"" run by the Deutsche Forschungsgemeinschaft (DFG), resulting in a survey of the current state of photonic crystal research in Germany. The first part of the book describes methods for the theoretical analysis of their optical properties as well as the results. The main part is dedicated to the fabrication, characterization and modeling of two- and three-dimensional photonic crystals, while the final section presents a wide spectrum of applications: gas sensors, micr

  15. Ribbon Crystals

    DEFF Research Database (Denmark)

    Bohr, Jakob; Markvorsen, Steen

    2013-01-01

    A repetitive crystal-like pattern is spontaneously formed upon the twisting of straight ribbons. The pattern is akin to a tessellation with isosceles triangles, and it can easily be demonstrated with ribbons cut from an overhead transparency. We give a general description of developable ribbons...

  16. Therapeutic Crystals

    Science.gov (United States)

    Bond, Charles S.

    2014-01-01

    Some readers might not fully know what the difference is between crystallography, and the "new age" practice of dangling crystals around the body to capitalise on their healing energy. The latter is often considered to be superstition, while ironically, the former has actually resulted in real rationally-based healing of human diseases…

  17. Photonic crystals principles and applications

    CERN Document Server

    Gong, Qihuang

    2013-01-01

    IntroductionPrimary Properties of Photonic CrystalsFabrication of Photonic CrystalsPhotonic Crystal All-Optical SwitchingTunable Photonic Crystal FilterPhotonic Crystal LaserPhotonic Crystal Logic DevicesPhotonic Crystal Sensors

  18. Comparison of NIR chemical imaging with conventional NIR, Raman and ATR-IR spectroscopy for quantification of furosemide crystal polymorphs in ternary powder mixtures.

    Science.gov (United States)

    Schönbichler, S A; Bittner, L K H; Weiss, A K H; Griesser, U J; Pallua, J D; Huck, C W

    2013-08-01

    The aim of this study was to evaluate the ability of near-infrared chemical imaging (NIR-CI), near-infrared (NIR), Raman and attenuated-total-reflectance infrared (ATR-IR) spectroscopy to quantify three polymorphic forms (I, II, III) of furosemide in ternary powder mixtures. For this purpose, partial least-squares (PLS) regression models were developed, and different data preprocessing algorithms such as normalization, standard normal variate (SNV), multiplicative scatter correction (MSC) and 1st to 3rd derivatives were applied to reduce the influence of systematic disturbances. The performance of the methods was evaluated by comparison of the standard error of cross-validation (SECV), R(2), and the ratio performance deviation (RPD). Limits of detection (LOD) and limits of quantification (LOQ) of all methods were determined. For NIR-CI, a SECVcorr-spec and a SECVsingle-pixel corrected were calculated to assess the loss of accuracy by taking advantage of the spatial information. NIR-CI showed a SECVcorr-spec (SECVsingle-pixel corrected) of 2.82% (3.71%), 3.49% (4.65%), and 4.10% (5.06%) for form I, II, III. NIR had a SECV of 2.98%, 3.62%, and 2.75%, and Raman reached 3.25%, 3.08%, and 3.18%. The SECV of the ATR-IR models were 7.46%, 7.18%, and 12.08%. This study proves that NIR-CI, NIR, and Raman are well suited to quantify forms I-III of furosemide in ternary mixtures. Because of the pressure-dependent conversion of form II to form I, ATR-IR was found to be less appropriate for an accurate quantification of the mixtures. In this study, the capability of NIR-CI for the quantification of polymorphic ternary mixtures was compared with conventional spectroscopic techniques for the first time. For this purpose, a new way of spectra selection was chosen, and two kinds of SECVs were calculated to achieve a better comparability of NIR-CI to NIR, Raman, and ATR-IR.

  19. 基于混合液晶分子动力学模拟比较液晶分子旋转黏度大小∗%Rotational viscosity comparison of liquid crystals based on the molecular dynamics of mixtures

    Institute of Scientific and Technical Information of China (English)

    王启东; 彭增辉; 刘永刚; 姚丽双; 任淦; 宣丽

    2015-01-01

    It is critical to improve the response speed of a liquid crystal wavefront corrector in order to increase the band-width of a liquid crystal adaptive optics system. The design of liquid crystal molecules with small rotational viscosity becomes a basic method of increasing the response speed of a liquid crystal wavefront corrector. Various phases of liquid crystal from molecular dynamics simulation are given in this paper, and the detailed computational methods of order parameter and rotational viscosity are also presented. Rotational viscosities of liquid crystals are compared based on the molecular dynamics of mixtures. The data fluctuation is reduced effectively through several simulations and the multiple analysis of original data. A detailed process of molecular dynamics of mixtures is given in this paper and the result is greatly satisfactory. We believe that one can perform a better molecular design using this process and obtain a better understanding of molecular interactions of LCs.

  20. Biological Macromolecule Crystallization Database

    Science.gov (United States)

    SRD 21 Biological Macromolecule Crystallization Database (Web, free access)   The Biological Macromolecule Crystallization Database and NASA Archive for Protein Crystal Growth Data (BMCD) contains the conditions reported for the crystallization of proteins and nucleic acids used in X-ray structure determinations and archives the results of microgravity macromolecule crystallization studies.

  1. Crystallization process

    Science.gov (United States)

    Adler, Robert J.; Brown, William R.; Auyang, Lun; Liu, Yin-Chang; Cook, W. Jeffrey

    1986-01-01

    An improved crystallization process is disclosed for separating a crystallizable material and an excluded material which is at least partially excluded from the solid phase of the crystallizable material obtained upon freezing a liquid phase of the materials. The solid phase is more dense than the liquid phase, and it is separated therefrom by relative movement with the formation of a packed bed of solid phase. The packed bed is continuously formed adjacent its lower end and passed from the liquid phase into a countercurrent flow of backwash liquid. The packed bed extends through the level of the backwash liquid to provide a drained bed of solid phase adjacent its upper end which is melted by a condensing vapor.

  2. Ribbon crystals.

    Directory of Open Access Journals (Sweden)

    Jakob Bohr

    Full Text Available A repetitive crystal-like pattern is spontaneously formed upon the twisting of straight ribbons. The pattern is akin to a tessellation with isosceles triangles, and it can easily be demonstrated with ribbons cut from an overhead transparency. We give a general description of developable ribbons using a ruled procedure where ribbons are uniquely described by two generating functions. This construction defines a differentiable frame, the ribbon frame, which does not have singular points, whereby we avoid the shortcomings of the Frenet-Serret frame. The observed spontaneous pattern is modeled using planar triangles and cylindrical arcs, and the ribbon structure is shown to arise from a maximization of the end-to-end length of the ribbon, i.e. from an optimal use of ribbon length. The phenomenon is discussed in the perspectives of incompatible intrinsic geometries and of the emergence of long-range order.

  3. Single crystal U-Pb zircon age and Sr-Nd isotopic composition of impactites from the Bosumtwi impact structure, Ghana: Comparison with country rocks and Ivory Coast tektites.

    Science.gov (United States)

    Ferrière, Ludovic; Koeberl, Christian; Thöni, Martin; Liang, Chen

    2010-08-01

    The 1.07 Myr old Bosumtwi impact structure (Ghana), excavated in 2.1-2.2 Gyr old supracrustal rocks of the Birimian Supergroup, was drilled in 2004. Here, we present single crystal U-Pb zircon ages from a suevite and two meta-graywacke samples recovered from the central uplift (drill core LB-08A), which yield an upper Concordia intercept age of ca. 2145 ± 82 Ma, in very good agreement with previous geochronological data for the West African Craton rocks in Ghana. Whole rock Rb-Sr and Sm-Nd isotope data of six suevites (five from inside the crater and one from outside the northern crater rim), three meta-graywacke, and two phyllite samples from core LB-08A are also presented, providing further insights into the timing of the metamorphism and a possibly related isotopic redistribution of the Bosumtwi crater rocks. Our Rb-Sr and Sm-Nd data show also that the suevites are mixtures of meta-greywacke and phyllite (and possibly a very low amount of granite). A comparison of our new isotopic data with literature data for the Ivory Coast tektites allows to better constrain the parent material of the Ivory Coast tektites (i.e., distal impactites), which is thought to consist of a mixture of metasedimentary rocks (and possibly granite), but with a higher proportion of phyllite (and shale) than the suevites (i.e., proximal impactites). When plotted in a Rb/Sr isochron diagram, the sample data points (n = 29, including literature data) scatter along a regression line, whose slope corresponds to an age of 1846 ± 160 Ma, with an initial Sr isotope ratio of 0.703 ± 0.002. However, due to the extensive alteration of some of the investigated samples and the lithological diversity of the source material, this age, which is in close agreement with a possible "metamorphic age" of ∼ 1.8-1.9 Ga tentatively derived from our U-Pb dating of zircons, is difficult to consider as a reliable metamorphic age. It may perhaps reflect a common ancient source whose Rb-Sr isotope

  4. Comparison of the structure and the electric properties of ZnIn/sub 2/S/sub 4/(III)- and CdInGaS/sub 4/-layered crystals

    Energy Technology Data Exchange (ETDEWEB)

    Anagnostopoulos, A.N.; Manolikas, C.; Papadopoulos, D. (Aristoteles University, Thessaloniki (Greece). First Laboratory of Physics)

    1983-06-16

    ZnIn/sub 2/S/sub 4/(III) and CdInGaS/sub 4/ crystallize in the same space group R3m and have almost the same lattice constants. ZnIn/sub 2/S/sub 4/(III) appears as a layered crystal with composition faults between its layers, influencing the conductivity of this compound. CdInGaS/sub 4/ shows no composition faults. This fact explains the different electric properties of these compounds.

  5. Microbending in photonic crystal fibres - an ultimate loss limit?

    DEFF Research Database (Denmark)

    Bjarklev, Anders Overgaard; Hansen, Theis Peter; Hougaard, Kristian G.;

    2001-01-01

    Microbending losses are for the first time estimated in index-guiding photonic crystal fibres, and comparisons with standard step-index fibres are made. The results indicate that typical photonic crystal fibres are significantly less sensitive (one order of magnitude smaller loss) towards...

  6. Pressure cryocooling protein crystals

    Science.gov (United States)

    Kim, Chae Un; Gruner, Sol M.

    2011-10-04

    Preparation of cryocooled protein crystal is provided by use of helium pressurizing and cryocooling to obtain cryocooled protein crystal allowing collection of high resolution data and by heavier noble gas (krypton or xenon) binding followed by helium pressurizing and cryocooling to obtain cryocooled protein crystal for collection of high resolution data and SAD phasing simultaneously. The helium pressurizing is carried out on crystal coated to prevent dehydration or on crystal grown in aqueous solution in a capillary.

  7. Anticlastic curvature measurements on unribbed crystal optics for synchrotron radiation

    Energy Technology Data Exchange (ETDEWEB)

    Quintana, J.P.; Dolin, Y.; Georgopoulos, P. (DND-CAT Synchrotron Research Center, APS/ANL Sector 5, Building 400, 9700 South Cass Avenue, Argonne, Illinois 60439 (United States)); Kushnir, V.I. (APS/XFD, Bldg. 362, 9700 South Cass Ave., Argonne, Illinois 60439 (United States))

    1995-02-01

    Various methods have been proposed for measuring the distortion in perfect crystals using double-crystal methods. The majority of these methods rely on making comparisons between double-crystal rocking curve measurements under the spatial extent of an extended x-ray beam. Unless the beam is large and parallel (such as at a synchrotron bending magnet), these methods are not easily scalable to large crystals (e.g., crystal focusing elements for synchrotron beamlines) due to the mechanical inaccuracies inherent in moving the various optical components. We present a method based on a scanning source which simplifies the problems in scaling double-crystal methods to large optics. In addition, results using this method are presented on a ribless sagittal focusing Si(111) crystal demonstrating that the anticlastic deviation can be made to be less than [plus minus]1 s of arc over a 1-cm-long section parallel to the sagittal axis.

  8. Optical properties of 3d-ions in crystals spectroscopy and crystal field analysis

    CERN Document Server

    Brik, Mikhail

    2013-01-01

    "Optical Properties of 3d-Ions in Crystals: Spectroscopy and Crystal Field Analysis" discusses spectral, vibronic and magnetic properties of 3d-ions in a wide range of crystals, used as active media for solid state lasers and potential candidates for this role. Crystal field calculations (including first-principles calculations of energy levels and absorption spectra) and their comparison with experimental spectra, the Jahn-Teller effect, analysis of vibronic spectra, materials science applications are systematically presented. The book is intended for researchers and graduate students in crystal spectroscopy, materials science and optical applications. Dr. N.M. Avram is an Emeritus Professor at the Physics Department, West University of Timisoara, Romania; Dr. M.G. Brik is a Professor at the Institute of Physics, University of Tartu, Estonia.

  9. Trace element distribution in geological crystals

    Energy Technology Data Exchange (ETDEWEB)

    Den Besten, J.L.; Jamieson, D.N.; Weiser, P.S. [Melbourne Univ., Parkville, VIC (Australia). School of Physics

    1996-12-31

    Channelling is a useful microprobe technique for determining the structure of crystals, but until now has not been performed on geological crystals. The composition has been investigated rather than the structure, which can further explain the origin of the crystal and provide useful information on the substitutionality of trace elements. This may then lead to applications of extraction of valuable metals and semiconductor electronics. Natural crystals of pyrite, FeS{sub 2}, which contains a substantial concentration of gold were channeled and examined to identify the channel axis orientation. Rutherford Backscattering (RBS) and Particle Induced X-Ray Emission (PIXE) spectra using MeV ions were obtained in the experiment to provide a comparison of lattice and non-lattice trace elements. 3 figs.

  10. Silicon heterojunction solar cell and crystallization of amorphous silicon

    Science.gov (United States)

    Lu, Meijun

    -Si, but also use the well established manufacturing techniques on thin-film. One of the main difficulties of poly-Si thin-film solar cells is growing large-grained poly-Si films (grain sizes comparable to the film thickness of micrometers) onto foreign substrates. Aluminum-induced crystallization (AIC) is one technique that has been developed to transform the amorphous Si to large-grain poly-Si. In this dissertation, our systematic studies of AIC samples with different stack structures, with and without interface oxide layer, annealed both below and above eutectic temperature will be introduced, and a phenomenological model will be proposed to explain the experimental results.

  11. CRYSTALLIZATION IN MULTICOMPONENT GLASSES

    Energy Technology Data Exchange (ETDEWEB)

    KRUGER AA; HRMA PR

    2009-10-08

    In glass processing situations involving glass crystallization, various crystalline forms nucleate, grow, and dissolve, typically in a nonuniform temperature field of molten glass subjected to convection. Nuclear waste glasses are remarkable examples of multicomponent vitrified mixtures involving partial crystallization. In the glass melter, crystals form and dissolve during batch-to-glass conversion, melter processing, and product cooling. Crystals often agglomerate and sink, and they may settle at the melter bottom. Within the body of cooling glass, multiple phases crystallize in a non-uniform time-dependent temperature field. Self-organizing periodic distribution (the Liesegnang effect) is common. Various crystallization phenomena that occur in glass making are reviewed.

  12. Aluminum induces tau aggregation in vitro but not in vivo.

    Science.gov (United States)

    Mizoroki, Tatsuya; Meshitsuka, Shunsuke; Maeda, Sumihiro; Murayama, Miyuki; Sahara, Naruhiko; Takashima, Akihiko

    2007-07-01

    Etiological studies suggest that aluminum (Al) intake might increase an individual's risk of developing Alzheimer's disease (AD). Biochemical analysis data on the effects of Al, however, are inconsistent. Hence, the pathological involvement of Al in AD remains unclear. If Al is involved in AD, then it is reasonable to hypothesize that Al might be involved in the formation of either amyloid plaques or neurofibrillary tangles (NFTs). Here, we investigated whether Al might be involved in NFT formation by using an in vitro tau aggregation paradigm, a tau-overexpressing neuronal cell line (N2a), and a tau-overexpressing mouse model. Although Al induced tau aggregation in a heparin-induced tau assembly assay, these aggregates were neither thioflavin T positive nor did they resemble tau fibrils seen in human AD brains. With cell lysates from stable cell lines overexpressing tau, the accumulation of SDS-insoluble tau increased when the lysates were treated with at least 100 muM Al-maltolate. Yet Al-maltolate caused illness or death in transgenic mice overexpressing human tau and in non-transgenic littermates well before the Al concentration in the brain reached 100 muM. These results indicate that Al has no direct link to AD pathology.

  13. [Aluminum induces chromosome aberrations in wheat root meristem cells].

    Science.gov (United States)

    Bulanova, N V; Synzynys, B I; Koz'min, G V

    2001-12-01

    The yield and pattern of chromosome structure aberrations in wheat seedlings treated with aluminum nitrate and aluminum sulfate at various concentrations have been determined by the anaphase method. Aluminum has a genotoxic effect causing genome, chromatid, and chromosome aberrations in apical root meristem cells. The relationship between the total yield of structural mutations and the aluminum concentration follows a bell-shaped curve. The mutagenic activity of aluminum nitrate peaks at 10(-3) mg/ml, which is twice as high as the permissible concentration limit (PCL) of aluminum in potable water. The maximum of the mutagenic activity of aluminum sulfate is observed at 5 x 10(-4) mg/ml, i.e., one PCL. Tap water boiled for 2 h in an aluminum vessel has virtually no genotoxic effect on wheat cells.

  14. Growth of dopamine crystals

    Science.gov (United States)

    Patil, Vidya; Patki, Mugdha

    2016-05-01

    Many nonlinear optical (NLO) crystals have been identified as potential candidates in optical and electro-optical devices. Use of NLO organic crystals is expected in photonic applications. Hence organic nonlinear optical materials have been intensely investigated due to their potentially high nonlinearities, and rapid response in electro-optic effect compared to inorganic NLO materials. There are many methods to grow organic crystals such as vapor growth method, melt growth method and solution growth method. Out of these methods, solution growth method is useful in providing constraint free crystal. Single crystals of Dopamine have been grown by evaporating the solvents from aqueous solution. Crystals obtained were of the size of orders of mm. The crystal structure of dopamine was determined using XRD technique. Images of crystals were obtained using FEG SEM Quanta Series under high vacuum and low KV.

  15. Crystal structure and prediction.

    Science.gov (United States)

    Thakur, Tejender S; Dubey, Ritesh; Desiraju, Gautam R

    2015-04-01

    The notion of structure is central to the subject of chemistry. This review traces the development of the idea of crystal structure since the time when a crystal structure could be determined from a three-dimensional diffraction pattern and assesses the feasibility of computationally predicting an unknown crystal structure of a given molecule. Crystal structure prediction is of considerable fundamental and applied importance, and its successful execution is by no means a solved problem. The ease of crystal structure determination today has resulted in the availability of large numbers of crystal structures of higher-energy polymorphs and pseudopolymorphs. These structural libraries lead to the concept of a crystal structure landscape. A crystal structure of a compound may accordingly be taken as a data point in such a landscape.

  16. Temperature-mediated polymorphism in molecular crystals: The impact on crystal packing and charge transport

    KAUST Repository

    Stevens, Loah A.

    2015-01-13

    We report a novel synthesis to ultra high purity 7,14-bis((trimethylsilyl)ethynyl)dibenzo[b,def]-chrysene (TMS-DBC) and the use of this material in the growth of single crystals by solution and vapor deposition techniques. We observe that the substrate temperature has a dramatic impact on the crystal growth, producing two distinct polymorphs of TMS-DBC; low temperature (LT) fine red needles and high temperature (HT) large yellow platelets. Single crystal X-ray crystallography confirms packing structures where the LT crystals form a 1D slipped-stack structure, while the HT crystals adopt a 2D brickwork motif. These polymorphs also represent a rare example where both are extremely stable and do not interconvert to the other crystal structure upon solvent or thermal annealing. Single crystal organic field-effect transistors of the LT and HT crystals show that the HT 2D brickwork motif produces hole mobilities as high as 2.1 cm2 V-1 s-1, while the mobility of the 1D structure is significantly lower, at 0.028 cm2 V-1 s-1. Electronic-structure calculations indicate that the superior charge transport in the brickwork polymorph in comparison to the slipped-stack polymorph is due to the presence of an increased dimensionality of the charge migration pathways.

  17. Crystallization from Gels

    Science.gov (United States)

    Narayana Kalkura, S.; Natarajan, Subramanian

    Among the various crystallization techniques, crystallization in gels has found wide applications in the fields of biomineralization and macromolecular crystallization in addition to crystallizing materials having nonlinear optical, ferroelectric, ferromagnetic, and other properties. Furthermore, by using this method it is possible to grow single crystals with very high perfection that are difficult to grow by other techniques. The gel method of crystallization provides an ideal technique to study crystal deposition diseases, which could lead to better understanding of their etiology. This chapter focuses on crystallization in gels of compounds that are responsible for crystal deposition diseases. The introduction is followed by a description of the various gels used, the mechanism of gelling, and the fascinating phenomenon of Liesegang ring formation, along with various gel growth techniques. The importance and scope of study on crystal deposition diseases and the need for crystal growth experiments using gel media are stressed. The various crystal deposition diseases, viz. (1) urolithiasis, (2) gout or arthritis, (3) cholelithiasis and atherosclerosis, and (4) pancreatitis and details regarding the constituents of the crystal deposits responsible for the pathological mineralization are discussed. Brief accounts of the theories of the formation of urinary stones and gallstones and the role of trace elements in urinary stone formation are also given. The crystallization in gels of (1) the urinary stone constituents, viz. calcium oxalate, calcium phosphates, uric acid, cystine, etc., (2) the constituents of the gallstones, viz. cholesterol, calcium carbonate, etc., (3) the major constituent of the pancreatic calculi, viz., calcium carbonate, and (4) cholic acid, a steroidal hormone are presented. The effect of various organic and inorganic ions, trace elements, and extracts from cereals, herbs, and fruits on the crystallization of major urinary stone and gallstone

  18. CRYSTAL FILTER TEST SET

    Science.gov (United States)

    CRYSTAL FILTERS, *HIGH FREQUENCY, *RADIOFREQUENCY FILTERS, AMPLIFIERS, ELECTRIC POTENTIAL, FREQUENCY, IMPEDANCE MATCHING , INSTRUMENTATION, RADIOFREQUENCY, RADIOFREQUENCY AMPLIFIERS, TEST EQUIPMENT, TEST METHODS

  19. ALICE photon spectrometer crystals

    CERN Multimedia

    Maximilien Brice

    2006-01-01

    Members of the mechanical assembly team insert the last few crystals into the first module of ALICE's photon spectrometer. These crystals are made from lead-tungstate, a crystal as clear as glass but with nearly four times the density. When a high-energy particle passes through one of these crystals it will scintillate, emitting a flash of light allowing the energy of photons, electrons and positrons to be measured.

  20. Kinetics of barium sulphate reaction crystallization in crystallizers with internal circulation

    Directory of Open Access Journals (Sweden)

    J. Koralewska

    2008-06-01

    Full Text Available Kinetic calculation results describing the observed nucleation and growth rates of barium sulphate crystals precipitated in an integrated reaction-crystallization process in a barium sulphate-ammonium chloride-water system are presented and analyzed. The scope of experiments included two continuous model DTM-type crystallizers (Draft Tube Magma with internal circulation of the suspension forced by a liquid jet-pump device responsible for stable and intensive enough ascending/descending flow of BaSO4 crystal magma in a mixing chamber. For comparison purposes the experimental data corresponding to a continuous DT (Draft Tube crystallizer with propeller agitator are presented and discussed. The various types of laboratory crystallizers used were fed with concentrated water solution of barium chloride (of 10 or 24 mass % and - in a stoichiometric proportion - crystalline ammonium sulphate, assuming isothermal (348 K and hydrodynamic (average residence time of suspension in a crystallizer: 900 s process conditions. The observed nucleation and growth rates of barium sulphate crystals were estimated on the basis of crystal size distributions (CSDs using convenient calculation scheme derived for an MSMPR (Mixed Suspension Mixed Product Removal model approach. Considering the experimental population density distribution courses, a size-dependent growth (SDG phenomenon was taken into account in the kinetic calculations. Five SDG kinetic models recommended in the accessible literature were used for kinetic parameter values estimation. It was proved statistically, that Rojkowski’s two SDG models (hyperbolic and exponential best suit for our own experimental data description. The experimental data presented can be practically applied for improving the constructions of liquid jet-pump DTM crystallizers recommended for reaction crystallization of sparingly soluble inorganic salts (especially for high concentrations of reaction substrates in the modern

  1. Protein Crystal Based Nanomaterials

    Science.gov (United States)

    Bell, Jeffrey A.; VanRoey, Patrick

    2001-01-01

    This is the final report on a NASA Grant. It concerns a description of work done, which includes: (1) Protein crystals cross-linked to form fibers; (2) Engineering of protein to favor crystallization; (3) Better knowledge-based potentials for protein-protein contacts; (4) Simulation of protein crystallization.

  2. Microscopic verification of topological electron-vortex binding in the lowest Landau-level crystal state.

    Science.gov (United States)

    Chang, Chia-Chen; Jeon, Gun Sang; Jain, Jainendra K

    2005-01-14

    When two-dimensional electrons are subjected to a very strong magnetic field, they are believed to form a triangular crystal. By a direct comparison with the exact wave function, we demonstrate that this crystal is not a simple Hartree-Fock crystal of electrons but an inherently quantum mechanical crystal characterized by a nonperturbative binding of quantized vortices to electrons. It is suggested that this has qualitative consequences for experiment.

  3. Charged Frenkel biexcitons in organic molecular crystals

    CERN Document Server

    Agranovich, V M; Kamchatnov, A M

    2001-01-01

    It is known that the energy of the lowest electronic transition in neutral molecules of anthracene, tetracene and other polyacenes is blue shifted in comparison with the corresponding transition energy in mono-valent molecular ions. This effect in molecular crystal may be responsible for the attraction between molecular (Frenkel) exciton and charge carrier. Due to this attraction the bound state of Frenkel exciton and free charge (charged Frenkel exciton) may be formed. The same mechanism can be responsible for formation of charged biexcitons (bound state of two Frenkel excitons and a charge carrier). Calculations are performed for molecular crystals like tetracene by means of one-dimensional lattice model

  4. 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.

  5. Protein crystallization with paper

    Science.gov (United States)

    Matsuoka, Miki; Kakinouchi, Keisuke; Adachi, Hiroaki; Maruyama, Mihoko; Sugiyama, Shigeru; Sano, Satoshi; Yoshikawa, Hiroshi Y.; Takahashi, Yoshinori; Yoshimura, Masashi; Matsumura, Hiroyoshi; Murakami, Satoshi; Inoue, Tsuyoshi; Mori, Yusuke; Takano, Kazufumi

    2016-05-01

    We developed a new protein crystallization method that incorporates paper. A small piece of paper, such as facial tissue or KimWipes, was added to a drop of protein solution in the traditional sitting drop vapor diffusion technique, and protein crystals grew by incorporating paper. By this method, we achieved the growth of protein crystals with reducing osmotic shock. Because the technique is very simple and the materials are easy to obtain, this method will come into wide use for protein crystallization. In the future, it could be applied to nanoliter-scale crystallization screening on a paper sheet such as in inkjet printing.

  6. Macromolecular Crystallization in Microgravity

    Science.gov (United States)

    Snell, Edward H.; Helliwell, John R.

    2004-01-01

    The key concepts that attracted crystal growers, macromolecular or solid state, to microgravity research is that density difference fluid flows and sedimentation of the growing crystals are greatly reduced. Thus, defects and flaws in the crystals can be reduced, even eliminated, and crystal volume can be increased. Macromolecular crystallography differs from the field of crystalline semiconductors. For the latter, crystals are harnessed for their electrical behaviors. A crystal of a biological macromolecule is used instead for diffraction experiments (X-ray or neutron) to determine the three-dimensional structure of the macromolecule. The better the internal order of the crystal of a biological macromolecule then the more molecular structure detail that can be extracted. This structural information that enables an understanding of how the molecule functions. This knowledge is changing the biological and chemical sciences with major potential in understanding disease pathologies. Macromolecular structural crystallography in general is a remarkable field where physics, biology, chemistry, and mathematics meet to enable insight to the basic fundamentals of life. In this review, we examine the use of microgravity as an environment to grow macromolecular crystals. We describe the crystallization procedures used on the ground, how the resulting crystals are studied and the knowledge obtained from those crystals. We address the features desired in an ordered crystal and the techniques used to evaluate those features in detail. We then introduce the microgravity environment, the techniques to access that environment, and the theory and evidence behind the use of microgravity for crystallization experiments. We describe how ground-based laboratory techniques have been adapted to microgravity flights and look at some of the methods used to analyze the resulting data. Several case studies illustrate the physical crystal quality improvements and the macromolecular structural

  7. The contribution of polystyrene nanospheres towards the crystallization of proteins.

    Directory of Open Access Journals (Sweden)

    Johanna M Kallio

    Full Text Available BACKGROUND: Protein crystallization is a slow process of trial and error and limits the amount of solved protein structures. Search of a universal heterogeneous nucleant is an effort to facilitate crystallizability of proteins. METHODOLOGY: The effect of polystyrene nanospheres on protein crystallization were tested with three commercial proteins: lysozyme, xylanase, xylose isomerase, and with five research target proteins: hydrophobins HFBI and HFBII, laccase, sarcosine dimethylglycine N-methyltransferase (SDMT, and anti-testosterone Fab fragment 5F2. The use of nanospheres both in screening and as an additive for known crystallization conditions was studied. In screening, the addition of an aqueous solution of nanosphere to the crystallization drop had a significant positive effect on crystallization success in comparison to the control screen. As an additive in hydrophobin crystallization, the nanospheres altered the crystal packing, most likely due to the amphiphilic nature of hydrophobins. In the case of laccase, nanospheres could be used as an alternative for streak-seeding, which insofar had remained the only technique to produce high-diffracting crystals. With methyltransferase SDMT the nanospheres, used also as an additive, produced fewer, larger crystals in less time. Nanospheres, combined with the streak-seeding method, produced single 5F2 Fab crystals in shorter equilibration times. CONCLUSIONS: All in all, the use of nanospheres in protein crystallization proved to be beneficial, both when screening new crystallization conditions to promote nucleation and when used as an additive to produce better quality crystals, faster. The polystyrene nanospheres are easy to use, commercially available and close to being inert, as even with amphiphilic proteins only the crystal packing is altered and the nanospheres do not interfere with the structure and function of the protein.

  8. Revisiting the blind tests in crystal structure prediction: accurate energy ranking of molecular crystals.

    Science.gov (United States)

    Asmadi, Aldi; Neumann, Marcus A; Kendrick, John; Girard, Pascale; Perrin, Marc-Antoine; Leusen, Frank J J

    2009-12-24

    In the 2007 blind test of crystal structure prediction hosted by the Cambridge Crystallographic Data Centre (CCDC), a hybrid DFT/MM method correctly ranked each of the four experimental structures as having the lowest lattice energy of all the crystal structures predicted for each molecule. The work presented here further validates this hybrid method by optimizing the crystal structures (experimental and submitted) of the first three CCDC blind tests held in 1999, 2001, and 2004. Except for the crystal structures of compound IX, all structures were reminimized and ranked according to their lattice energies. The hybrid method computes the lattice energy of a crystal structure as the sum of the DFT total energy and a van der Waals (dispersion) energy correction. Considering all four blind tests, the crystal structure with the lowest lattice energy corresponds to the experimentally observed structure for 12 out of 14 molecules. Moreover, good geometrical agreement is observed between the structures determined by the hybrid method and those measured experimentally. In comparison with the correct submissions made by the blind test participants, all hybrid optimized crystal structures (apart from compound II) have the smallest calculated root mean squared deviations from the experimentally observed structures. It is predicted that a new polymorph of compound V exists under pressure.

  9. Synthesis of monoclinic zinc diphosphide single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Mowles, T.A.

    1978-05-01

    Monoclinic zinc diphosphide is a cheap, plentiful, direct-gap semiconductor with an optimum transition energy for solar absorption. Single crystals were grown from the vapor to be evaluated as a new photovoltaic material. Monoclinic and tetragonal crystal formed within evacuated quartz ampules that were charged with zinc and excess phosphorous and heated in a temperature gradient to give phosphorous pressures from 0.07 to 8.5 atmospheres. The monoclinic form melts incongruently near 990/sup 0/C. The tetragonal form is metastable; its growth is enhanced by impurities but retarded by high phosphorous pressures. The mechanism of the synthesis indicates that a tightly-controlled vapor deposition is possible and that high-quality thin films should form at temperatures from 950 to 990/sup 0/C at pressures below 10 atmospheres. By a modification of the technique, sesquizinc phosphide single crystals were grown for comparison.

  10. Synthesis and Crystal Structure of Dehydroandrographolide Dipolycyclophosphate

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    The title compound was synthesized and characterized by IR, NMR, H R S I-M S and MS, and its crystal structure was determined by single-crystal X-ray diffraction. The crystal is of orthorhombic system (C4oH52O11P2, Mr= 770.76), space group P21212, with a = 22.562(5), b =29.224(6), c = 7.1953(14) A, V = 4744.2(16) A3, Z = 4, Dc = 1.079 g/cm3, F(000) = 1640 andμ =0.141 mm-1. The final R = 0.0758 and wR = 0.1778 for 2794 observed reflections with I > 2o(I).Intermolecular hydrogen bonds are found between the O atom of carbonyl group and H atoms of olefinic carbon. The absolute configuration of this molecule was confirmed by comparison with that of the original material.

  11. Active Photonic Crystal Waveguides

    DEFF Research Database (Denmark)

    Ek, Sara

    This thesis deals with the fabrication and characterization of active photonic crystal waveguides, realized in III-V semiconductor material with embedded active layers. The platform offering active photonic crystal waveguides has many potential applications. One of these is a compact photonic...... crystal semiconductor optical amplier. As a step towards such a component, photonic crystal waveguides with a single quantum well, 10 quantum wells and three layers of quantum dots are fabricated and characterized. An experimental study of the amplied spontaneous emission and a implied transmission...... due to photonic crystal dispersion. The observations are explained by the enhancement of net gain by light slow down. Another application based on active photonic crystal waveguides is micro lasers. Measurements on quantum dot micro laser cavities with different mirror configurations and photonic...

  12. Polymer semiconductor crystals

    Directory of Open Access Journals (Sweden)

    Jung Ah Lim

    2010-05-01

    Full Text Available One of the long-standing challenges in the field of polymer semiconductors is to figure out how long interpenetrating and entangled polymer chains self-assemble into single crystals from the solution phase or melt. The ability to produce these crystalline solids has fascinated scientists from a broad range of backgrounds including physicists, chemists, and engineers. Scientists are still on the hunt for determining the mechanism of crystallization in these information-rich materials. Understanding the theory and concept of crystallization of polymer semiconductors will undoubtedly transform this area from an art to an area that will host a bandwagon of scientists and engineers. In this article we describe the basic concept of crystallization and highlight some of the advances in polymer crystallization from crystals to nanocrystalline fibers.

  13. Macromolecular crystallization in microgravity

    Energy Technology Data Exchange (ETDEWEB)

    Snell, Edward H [Biophysics Group, NASA Marshall Space Flight Center, Code XD42, Huntsville, AL 35812 (United States); Helliwell, John R [Department of Chemistry, The University of Manchester, Manchester, M13 9PL (United Kingdom)

    2005-04-01

    Density difference fluid flows and sedimentation of growing crystals are greatly reduced when crystallization takes place in a reduced gravity environment. In the case of macromolecular crystallography a crystal of a biological macromolecule is used for diffraction experiments (x-ray or neutron) so as to determine the three-dimensional structure of the macromolecule. The better the internal order of the crystal then the greater the molecular structure detail that can be extracted. It is this structural information that enables an understanding of how the molecule functions. This knowledge is changing the biological and chemical sciences, with major potential in understanding disease pathologies. In this review, we examine the use of microgravity as an environment to grow macromolecular crystals. We describe the crystallization procedures used on the ground, how the resulting crystals are studied and the knowledge obtained from those crystals. We address the features desired in an ordered crystal and the techniques used to evaluate those features in detail. We then introduce the microgravity environment, the techniques to access that environment and the theory and evidence behind the use of microgravity for crystallization experiments. We describe how ground-based laboratory techniques have been adapted to microgravity flights and look at some of the methods used to analyse the resulting data. Several case studies illustrate the physical crystal quality improvements and the macromolecular structural advances. Finally, limitations and alternatives to microgravity and future directions for this research are covered. Macromolecular structural crystallography in general is a remarkable field where physics, biology, chemistry and mathematics meet to enable insight to the fundamentals of life. As the reader will see, there is a great deal of physics involved when the microgravity environment is applied to crystallization, some of it known, and undoubtedly much yet to

  14. Analysis of liquid crystal properties for photonic crystal fiber devices

    DEFF Research Database (Denmark)

    Weirich, Johannes; Lægsgaard, Jesper; Wei, Lei;

    2009-01-01

    We analyze the bandgap structure of Liquid Crystal infiltrated Photonic Crystal Fibers depending on the parameters of the Liquid Crystals by means of finite element simulations. For a biased Liquid Crystal Photonic Crystal Fiber, we show how the tunability of the bandgap position depends on the L...

  15. Automation in biological crystallization.

    Science.gov (United States)

    Stewart, Patrick Shaw; Mueller-Dieckmann, Jochen

    2014-06-01

    Crystallization remains the bottleneck in the crystallographic process leading from a gene to a three-dimensional model of the encoded protein or RNA. Automation of the individual steps of a crystallization experiment, from the preparation of crystallization cocktails for initial or optimization screens to the imaging of the experiments, has been the response to address this issue. Today, large high-throughput crystallization facilities, many of them open to the general user community, are capable of setting up thousands of crystallization trials per day. It is thus possible to test multiple constructs of each target for their ability to form crystals on a production-line basis. This has improved success rates and made crystallization much more convenient. High-throughput crystallization, however, cannot relieve users of the task of producing samples of high quality. Moreover, the time gained from eliminating manual preparations must now be invested in the careful evaluation of the increased number of experiments. The latter requires a sophisticated data and laboratory information-management system. A review of the current state of automation at the individual steps of crystallization with specific attention to the automation of optimization is given.

  16. Heroin crystal nephropathy.

    Science.gov (United States)

    Bautista, Josef Edrik Keith; Merhi, Basma; Gregory, Oliver; Hu, Susie; Henriksen, Kammi; Gohh, Reginald

    2015-06-01

    In this paper we present an interesting case of acute kidney injury and severe metabolic alkalosis in a patient with a history of heavy heroin abuse. Urine microscopy showed numerous broomstick-like crystals. These crystals are also identified in light and electron microscopy. We hypothesize that heroin crystalizes in an alkaline pH, resulting in tubular obstruction and acute kidney injury. Management is mainly supportive as there is no known specific therapy for this condition. This paper highlights the utility of urine microscopy in diagnosing the etiology of acute kidney injury and proposes a novel disease called heroin crystal nephropathy.

  17. A crystal barrel

    CERN Multimedia

    2007-01-01

    The production of crystals for the barrel of the CMS electromagnetic calorimeter has been completed. This is an important milestone for the experiment, which received the last of its 62,960 crystals on 9 March. The members of the team responsible for the crystal acceptance testing at CERN display the last crystal for the CMS electromagnetic calorimeter barrel. From left to right: Igor Tarasov, Etiennette Auffray and Hervé Cornet.One of the six machines specially developed to measure 67 different parameters on each crystal. Igor Tarasov is seen inserting the last batch of crystals into the machine. The last of the 62,960 CMS barrel crystals arrived at CERN on 9 March. Once removed from its polystyrene protection, this delicate crystal, like thousands of its predecessors, will be inserted into the last of the 36 supermodules of the barrel electromagnetic calorimeter in a few days' time. This marks the end of an important chapter in an almost 15-year-long journey by the CMS crystals team, some of whose member...

  18. Automation in biological crystallization

    Science.gov (United States)

    Shaw Stewart, Patrick; Mueller-Dieckmann, Jochen

    2014-01-01

    Crystallization remains the bottleneck in the crystallographic process leading from a gene to a three-dimensional model of the encoded protein or RNA. Automation of the individual steps of a crystallization experiment, from the preparation of crystallization cocktails for initial or optimization screens to the imaging of the experiments, has been the response to address this issue. Today, large high-throughput crystallization facilities, many of them open to the general user community, are capable of setting up thousands of crystallization trials per day. It is thus possible to test multiple constructs of each target for their ability to form crystals on a production-line basis. This has improved success rates and made crystallization much more convenient. High-throughput crystallization, however, cannot relieve users of the task of producing samples of high quality. Moreover, the time gained from eliminating manual preparations must now be invested in the careful evaluation of the increased number of experiments. The latter requires a sophisticated data and laboratory information-management system. A review of the current state of automation at the individual steps of crystallization with specific attention to the automation of optimization is given. PMID:24915074

  19. Geometric and unipotent crystals

    OpenAIRE

    Berenstein, Arkady; Kazhdan, David

    1999-01-01

    In this paper we introduce geometric crystals and unipotent crystals which are algebro-geometric analogues of Kashiwara's crystal bases. Given a reductive group G, let I be the set of vertices of the Dynkin diagram of G and T be the maximal torus of G. The structure of a geometric G-crystal on an algebraic variety X consists of a rational morphism \\gamma:X-->T and a compatible family e_i:G_m\\times X-->X, i\\in I of rational actions of the multiplicative group G_m satisfying certain braid-like ...

  20. Phononic crystal devices

    Science.gov (United States)

    El-Kady, Ihab F.; Olsson, Roy H.

    2012-01-10

    Phononic crystals that have the ability to modify and control the thermal black body phonon distribution and the phonon component of heat transport in a solid. In particular, the thermal conductivity and heat capacity can be modified by altering the phonon density of states in a phononic crystal. The present invention is directed to phononic crystal devices and materials such as radio frequency (RF) tags powered from ambient heat, dielectrics with extremely low thermal conductivity, thermoelectric materials with a higher ratio of electrical-to-thermal conductivity, materials with phononically engineered heat capacity, phononic crystal waveguides that enable accelerated cooling, and a variety of low temperature application devices.

  1. Tunable plasmonic crystal

    Energy Technology Data Exchange (ETDEWEB)

    Dyer, Gregory Conrad; Shaner, Eric A.; Reno, John L.; Aizin, Gregory

    2015-08-11

    A tunable plasmonic crystal comprises several periods in a two-dimensional electron or hole gas plasmonic medium that is both extremely subwavelength (.about..lamda./100) and tunable through the application of voltages to metal electrodes. Tuning of the plasmonic crystal band edges can be realized in materials such as semiconductors and graphene to actively control the plasmonic crystal dispersion in the terahertz and infrared spectral regions. The tunable plasmonic crystal provides a useful degree of freedom for applications in slow light devices, voltage-tunable waveguides, filters, ultra-sensitive direct and heterodyne THz detectors, and THz oscillators.

  2. Crystallization Formulation Lab

    Data.gov (United States)

    Federal Laboratory Consortium — The Crystallization Formulation Lab fills a critical need in the process development and optimization of current and new explosives and energetic formulations. The...

  3. INTERFACIAL MASS TRANSPORT IN OXIDE CRYSTAL GROWTH

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    @@ A space high temperature in situobservation instrument (SHITISOI) is dedicated to visualize and record the whole growth process of oxide crystal in high temperature melts and solutions. Model experiments using transparent liquids such as KNbO3,Li2B4O7+KNbO3 were chosen to investigate effects of interracial mass transport in oxide crystal growth. For the scaling of the coupled velocity, heat and concentration fields in KNbO3 crystal growth, a rotating crystal growth process was performed and the widths of interfacial concentration, heat and momentum transition zones (The "boundary layers") are obtained, which are 7.5×10-a, 8.6×10-2 and 4.4×10-1 cm,respectively. Hence one can expect that interfacial concentration gradient will be confined to a narrow layer and in region of major concentration change at the in terface. In order to study a mechanism based on the interfacial mass transport resulting from hydrodynamics, the growth of KNbO3 grain in high temperature Li2B4O7 and KNbO3 solutin was studied. The result shows that the pivotal feature in the KNbO3 crystal growth is the initiated by KNbO3 solute surface tension gra dient which is caused by the slow diffusion of KNbO3 solutes. Direct comparison of the model predictions and experimental observed phenomena demonstrate the predictive capability of this model.

  4. Electronic structures of organometallic complexes of f elements LXXXIII: First comparison of experimental and calculated (on the basis of density functional theory) polarized Raman spectra of an oriented organometallic single crystal: Tris(pentamethylcyclopentadienyl)lanthanum.

    Science.gov (United States)

    Amberger, Hanns-Dieter; Reddmann, Hauke; Mueller, Thomas J; Evans, William J

    2014-10-15

    The polarized Raman spectra of an oriented La(η(5)-C5Me5)3 (1) single crystal (where the principal axes of the two molecules per unit cell are uniformly oriented) as well as the mid (ca. 90K) and far infrared spectra of pellets have been recorded. Applying the selection rules of C3h symmetry to the spectra obtained, the irreducible representations (irreps) of numerous lines/bands of intra-ligand character were derived. In the range theory (DFT) were performed. In the intra-ligand range >400cm(-1), the obtained results agree well with the experimental findings. Because of the strong mixing at lower wavenumbers, even the separation of calculated skeletal and intra-ligand modes and the identification of the former was only successful by comparing the calculated FIR and averaged Raman spectra of compound 1 with those of La(η(5)-C5Me4H)3 (2). Making use of both the calculated frequencies of normal modes and their polarizability tensors, the polarized Raman spectra of an oriented single crystal of 1 in the range <400cm(-1) were calculated and compared to the experimental ones. Because of an overestimation of the mixing of normal vibrations of A' symmetry, the experimental intensities of the lines of the symmetric stretch ν1(A') were not reproduced by the calculation for compound 1 but by that for Sm(η(5)-C5Me5)3 (3). Skeletal and intra-ligand modes were separated and designated. Neglecting νC-H modes, the DFT calculation for 1 achieved an r.m.s. deviation of 17.9cm(-1) for 72 assignments.

  5. Photonic Crystal Fiber Attenuator

    Institute of Scientific and Technical Information of China (English)

    Joo; Beom; Eom; Hokyung; Kim; Jinchae; Kim; Un-Chul; Paek; Byeong; Ha; Lee

    2003-01-01

    We propose a novel fiber attenuator based on photonic crystal fibers. The difference in the modal field diameters of a conventional single mode fiber and a photonic crystal fiber was used. A variable optical attenuator was also achieved by applying macro-bending on the PCF part of the proposed attenuator

  6. Manipulation of colloidal crystallization

    NARCIS (Netherlands)

    Vermolen, E.C.M.

    2008-01-01

    Colloidal particles (approximately a micrometer in diameter) that are dispersed in a fluid, behave thermodynamically similar to atoms and molecules: at low concentrations they form a fluid, while at high concentrations they can crystallize into a colloidal crystal to gain entropy. The analogy with m

  7. Crystal growth and crystallography

    Science.gov (United States)

    Chernov, A. A.

    1998-01-01

    Selected topics that may be of interest for both crystal-structure and crystal-growth communities are overviewed. The growth of protein crystals, along with that of some other compounds, is one of the topics, and recent insights into related phenomena are considered as examples of applications of general principles. The relationship between crystal growth shape and structure is reviewed and an attempt to introduce semiquantitative characterization of binding for proteins is made. The concept of kinks for complex structures is briefly discussed. Even at sufficiently low supersaturations, the fluctuation of steps may not be sufficient to implement the Gibbs-Thomson law if the kink density is low enough. Subsurface ordering of liquids and growth of rough interfaces from melts is discussed. Crystals growing in microgravity from solution should be more perfect if they preferentially trap stress-inducing impurities, thus creating an impurity-depleted zone around themselves. Evidently, such a zone is developed only around the crystals growing in the absence of convection. Under terrestrial conditions, the self-purified depleted zone is destroyed by convection, the crystal traps more impurity and grows stressed. The stress relief causes mosaicity. In systems containing stress-inducing but poorly trapped impurities, the crystals grown in the absence of convection should be worse than those of their terrestrial counterparts.

  8. Photonic crystal fibers

    DEFF Research Database (Denmark)

    Lægsgaard, Jesper; Hansen, K P; Nielsen, M D;

    2003-01-01

    Photonic crystal fibers having a complex microstructure in the transverse plane constitute a new and promising class of optical fibers. Such fibers can either guide light through total internal reflection or the photonic bandgap effect, In this paper, we review the different types and applications...... of photonic crystal fibers with particular emphasis on recent advances in the field....

  9. Crystals in the LHC

    CERN Multimedia

    Antonella Del Rosso

    2012-01-01

    Bent crystals can be used to deflect charged particle beams. Their use in high-energy accelerators has been investigated for almost 40 years. Recently, a bent crystal was irradiated for the first time in the HiRadMat facility with an extreme particle flux, which crystals would have to withstand in the LHC. The results were very encouraging and confirmed that this technology could play a major role in increasing the beam collimation performance in future upgrades of the machine.   UA9 bent crystal tested with a laser. Charged particles interacting with a bent crystal can be trapped in channelling states and deflected by the atomic planes of the crystal lattice (see box). The use of bent crystals for beam manipulation in particle accelerators is a concept that has been well-assessed. Over the last three decades, a large number of experimental findings have contributed to furthering our knowledge and improving our ability to control crystal-particle interactions. In modern hadron colliders, su...

  10. Demonstration of Crystal Structure.

    Science.gov (United States)

    Neville, Joseph P.

    1985-01-01

    Describes an experiment where equal parts of copper and aluminum are heated then cooled to show extremely large crystals. Suggestions are given for changing the orientation of crystals by varying cooling rates. Students are more receptive to concepts of microstructure after seeing this experiment. (DH)

  11. Recent results from Crystal Barrel

    CERN Document Server

    Doser, Michael

    2000-01-01

    The Crystal Barrel detector has collected data on antiproton annihilation on Hydrogen and Deuterium at rest and at momenta up to 1940 MeV/c, accumulating a total of 600 M events with the goal of studying meson spectroscopy and searching for non-qbarq states. This large amount of data has allowed high statistics studies of exclusive final states produced under various initial conditions. Comparisons between different initial and final states greatly constrain the interpretation of these data sets. In particular, the requirement of consistency between fits of 3-body final state Dalitz plots is a powerful tool in the search for non-standard model resonances [1]. More recently, the study of the same Dalitz plot produced from antiproton annihilation on liquid and gaseous hydrogen, on deuterium or on liquid hydrogen at different center-of-mass energies has extended this approach to higher mass resonances.

  12. Crystal structure of levomepromazine maleate

    Directory of Open Access Journals (Sweden)

    Gyula Tamás Gál

    2016-05-01

    Full Text Available The asymmetric unit of the title salt, C19H25N2OS+·C4H3O4− [systematic name: (S-3-(2-methoxyphenothiazin-10-yl-N,N,2-trimethylpropanaminium hydrogen maleate], comprises two (S-levomepromazine cations and two hydrogen maleate anions. The conformations of the two cations are similar. The major difference relates to the orientation of the methoxy substituent at the phenothiazine ring system. The crystal components form a three-dimensional supramolecular network via N—H...O, C—H...O and C—H...π interactions. A comparison of the conformations of the levomepromazine cations with those of the neutral molecule and similar protonated molecules reveals significant conformational flexibility of the phenothiazine ring system and the substituent at the phenothiazine N atom.

  13. Function Photonic Crystals

    CERN Document Server

    Wu, Xiang-Yao; Yang, Jing-Hai; Liu, Xiao-Jing; Ba, Nuo; Wu, Yi-Heng; Wang, Qing-Cai; Li, Jing-Wu

    2010-01-01

    In the paper, we present a new kind of function photonic crystals, which refractive index is a function of space position. Unlike conventional PCs, which structure grow from two materials, A and B, with different dielectric constants $\\epsilon_{A}$ and $\\epsilon_{B}$. By Fermat principle, we give the motion equations of light in one-dimensional, two-dimensional and three-dimensional function photonic crystals. For one-dimensional function photonic crystals, we study the dispersion relation, band gap structure and transmissivity, and compare them with conventional photonic crystals. By choosing various refractive index distribution function $n(z)$, we can obtain more width or more narrow band gap structure than conventional photonic crystals.

  14. Progress on photonic crystals

    CERN Document Server

    Lecoq, P; Gundacker, S; Hillemanns, H; Jarron, P; Knapitsch, A; Leclercq, J L; Letartre, X; Meyer, T; Pauwels, K; Powolny, F; Seassal, C

    2010-01-01

    The renewal of interest for Time of Flight Positron Emission Tomography (TOF PET) has highlighted the need for increasing the light output of scintillating crystals and in particular for improving the light extraction from materials with a high index of refraction. One possible solution to overcome the problem of total internal reflection and light losses resulting from multiple bouncing within the crystal is to improve the light extraction efficiency at the crystal/photodetector interface by means of photonic crystals, i.e. media with a periodic modulation of the dielectric constant at the wavelength scale. After a short reminder of the underlying principles this contribution proposes to present the very encouraging results we have recently obtained on LYSO pixels and the perspectives on other crystals such as BGO, LuYAP and LuAG. These results confirm the impressive predictions from our previously published Monte Carlo simulations. A detailed description of the sample preparation procedure is given as well ...

  15. Optically Anomalous Crystals

    CERN Document Server

    Shtukenberg, Alexander; Kahr, Bart

    2007-01-01

    Optical anomalies in crystals are puzzles that collectively constituted the greatest unsolved problems in crystallography in the 19th Century. The most common anomaly is a discrepancy between a crystal’s symmetry as determined by its shape or by X-ray analysis, and that determined by monitoring the polarization state of traversing light. These discrepancies were perceived as a great impediment to the development of the sciences of crystals on the basis of Curie’s Symmetry Principle, the grand organizing idea in the physical sciences to emerge in the latter half of the 19th Century. Optically Anomalous Crystals begins with an historical introduction covering the contributions of Brewster, Biot, Mallard, Brauns, Tamman, and many other distinguished crystallographers. From this follows a tutorial in crystal optics. Further chapters discuss the two main mechanisms of optical dissymmetry: 1. the piezo-optic effect, and 2. the kinetic ordering of atoms. The text then tackles complex, inhomogeneous crystals, and...

  16. Functional substitution of coordination polyhedron in crystal structure of silicates

    Institute of Scientific and Technical Information of China (English)

    叶大年; 马哲生; 赫伟; 李哲; 施倪承; D.Pushcharovsky

    2002-01-01

    On the bases of the study of comparative crystal chemistry of silicates it has been concluded that the octahedra and square pyramids of Ti-0 and Zr-O play functional role of tetrahedra of Si-O in the construction of crystal structures. Therefore, those silicates may be named titano-and zircono-silicates. Because of the functional similarity of coordination polyhedra, the structures of cristobalite and feldspar have been compared with those of perovskite and garnet, respectively. As a new concept, the functional replacement of tetrahedra by octahedra and/or pyramids is defined by the authors of this paper for favorable comparison of relative crystal structures.

  17. The different conformations and crystal structures of dihydroergocristine

    Science.gov (United States)

    Mönch, B.; Kraus, W.; Köppen, R.; Emmerling, F.

    2016-02-01

    The identification of different forms of dihydroergocristine (DHEC) was carried out by crystallization from different organic solvents. DHEC was identified as potential template for molecularly imprinted polymers (MIPs) for the epimeric specific analysis of ergot alkaloids (EAs) in food. DHEC was crystallized from different solvents in order to mimic the typical MIP synthesis conditions. Four new solvatomorphs of DHEC were obtained. All solvatomorphs contain a water molecule in the crystal structure, whereas three compounds contain an additional solvent molecule. Based on the conformation of DHEC a comparison with typical EA molecules was possible. The analysis showed that DHEC is a suitable template for MIPs for EAs.

  18. Crystallization phenomena of isotactic polystyrene

    NARCIS (Netherlands)

    Lemstra, Peter Jan

    1975-01-01

    In this thesis the crystallization behavior of isotactic polystyrene has been described. The kinetics of the crystallization process and the crystalline structure were studied both for crystallization in the bulk and from dilute solutions. ... Zie Summary

  19. 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.

  20. Shaped Crystal Growth

    Science.gov (United States)

    Tatartchenko, Vitali A.

    Crystals of specified shape and size (shaped crystals) with controlled crystal growth (SCG) defect and impurity structure have to be grown for the successful development of modern engineering. Since the 1950s many hundreds of papers and patents concerned with shaped growth have been published. In this chapter, we do not try to enumerate the successful applications of shaped growth to different materials but rather to carry out a fundamental physical and mathematical analysis of shaping as well as the peculiarities of shaped crystal structures. Four main techniques, based on which the lateral surface can be shaped without contact with the container walls, are analyzed: the Czochralski technique (CZT), the Verneuil technique (VT), the floating zone technique (FZT), and technique of pulling from shaper (TPS). Modifications of these techniques are analyzed as well. In all these techniques the shape of the melt meniscus is controlled by surface tension forces, i.e., capillary forces, and here they are classified as capillary shaping techniques (CST). We look for conditions under which the crystal growth process in each CST is dynamically stable. Only in this case are all perturbations attenuated and a crystal of constant cross section shaping technique (CST) grown without any special regulation. The dynamic stability theory of the crystal growth process for all CST is developed on the basis of Lyapunov's dynamic stability theory. Lyapunov's equations for the crystal growth processes follow from fundamental laws. The results of the theory allow the choice of stable regimes for crystal growth by all CST as well as special designs of shapers in TPS. SCG experiments by CZT, VT, and FZT are discussed but the main consideration is given to TPS. Shapers not only allow crystal of very complicated cross section to be grown but provide a special distribution of impurities. A history of TPS is provided later in the chapter, because it can only be described after explanation of the

  1. The LaH(PO sub 3 ) sub 2. 3H sub 2 O crystal structure; comparison with crystal structures of other phosphites acid compounds. Structure cristalline de LaH(PO sub 3 H) sub 2. 3H sub 2 O. Comparaison avec les autres phosphites acides

    Energy Technology Data Exchange (ETDEWEB)

    Loukili, M. (Ecole Superieure de Technologie, Fes (MA)); Rafiq, M.; Durand, J. (Faculte des Sciences, Fes (MA)); Cot, L. (Ecole Nationale Superieure de Chimie, 34 - Montpellier (FR))

    1991-10-01

    The end value R = 0.032 for the reliability factor is obtained for the 1018 considered, for absorption corrected independent reflections. All the atoms of the formula are located except the hydrogen atoms of the water molecule. The comparison of the stereochemistry with the other phosphite acid anions shows the existence of three types of arrangement anions, the Ln{sup 3+} cation is eight coordinated by seven oxygen atoms of phophite anions and one oxygen of one water molecule.

  2. [Spherical crystallization in pharmaceutical technology].

    Science.gov (United States)

    Szabóné, R P; Pintyéné, H K; Kása, P; Erös, I; Hasznosné, N M; Farkas, B

    1998-03-01

    Physical properties of crystals, such as size, crystal size distribution and morphology, may predetermine the usefulness of crystalline materials in many pharmaceutical application. The above properties can be regulated with the crystallization process. The spherical crystals are suitable for direct tablet-making because of their better flowability and compressibility properties. These crystals can be used in the filling of the capsule. In this work, the spherical crystals such as "single crystal", "poly-crystals" and agglomerates with other excipients are collected from the literature and the experimental results of the authors. A close cooperation between chemists and the pharmaceutical technologists can help for doing steps in this field.

  3. Quartz crystal growth

    Science.gov (United States)

    Baughman, Richard J.

    1992-01-01

    A process for growing single crystals from an amorphous substance that can undergo phase transformation to the crystalline state in an appropriate solvent. The process is carried out in an autoclave having a lower dissolution zone and an upper crystallization zone between which a temperature differential (.DELTA.T) is maintained at all times. The apparatus loaded with the substance, solvent, and seed crystals is heated slowly maintaining a very low .DELTA.T between the warmer lower zone and cooler upper zone until the amorphous substance is transformed to the crystalline state in the lower zone. The heating rate is then increased to maintain a large .DELTA.T sufficient to increase material transport between the zones and rapid crystallization. .alpha.-Quartz single crystal can thus be made from fused quartz in caustic solvent by heating to 350.degree. C. stepwise with a .DELTA.T of 0.25.degree.-3.degree. C., increasing the .DELTA.T to about 50.degree. C. after the fused quartz has crystallized, and maintaining these conditions until crystal growth in the upper zone is completed.

  4. Diagnostic performance of detecting breast cancer on computed radiographic (CR) mammograms: comparison of hard copy film, 3-megapixel liquid-crystal-display (LCD) monitor and 5-megapixel LCD monitor.

    Science.gov (United States)

    Yamada, Takayuki; Suzuki, Akihiko; Uchiyama, Nachiko; Ohuchi, Noriaki; Takahashi, Shoki

    2008-11-01

    The purpose was to compare observer performance in the detection of breast cancer using hard-copy film, and 3-megapixel (3-MP) and 5-megapixel (5-MP) liquid crystal display (LCD) monitors in a simulated screening setting. We amassed 100 sample sets, including 32 patients with surgically proven breast cancer (masses present, N = 12; microcalcifications, N = 10; other types, N = 10) and 68 normal controls. All the mammograms were obtained using computed radiography (CR; sampling pitch of 50 mum). Twelve mammographers independently assessed CR mammograms presented in random order for hard-copy and soft-copy reading at minimal 4-week intervals. Observers rated the images on seven-point (1 to 7) and continuous (0 to 100) malignancy scales. Receiver-operating-characteristics analysis was performed, and the average area under the curve (AUC) was calculated for each modality. The jackknife method with the Bonferroni correction was applied to multireader/multicase analysis. The average AUC values for the 3-MP LCD, 5-MP LCD, and hard-copy film were 0.954, 0.947, and 0.956 on the seven-point scale and 0.943, 0.923, and 0.944 on the continuous scale, respectively. There were no significant differences among the three modalities on either scale. Soft-copy reading using 3-MP and 5-MP LCDs is comparable to hard-copy reading for detecting breast cancer.

  5. Crystallization on prestructured seeds.

    Science.gov (United States)

    Jungblut, Swetlana; Dellago, Christoph

    2013-01-01

    The crystallization transition of an undercooled monodisperse Lennard-Jones fluid in the presence of small prestructured seeds is studied with transition path sampling combined with molecular dynamics simulations. Compared to the homogeneous crystallization, clusters of a few particles arranged into a face- and body-centered cubic structure enhance the crystallization, while icosahedrally ordered seeds do not change the reaction rate. We identify two distinct nucleation regimes-close to the seed and in the bulk. Crystallites form close to the face- and body-centered structures and tend to stay away from the icosahedrally ordered seeds.

  6. Raman scattering in crystals

    Energy Technology Data Exchange (ETDEWEB)

    Edwards, D.F.

    1988-09-30

    A tutorial presentation is given of Raman scattering in crystals. The physical concepts are emphasized rather than the detailed mathematical formalism. Starting with an introduction to the concepts of phonons and conservation laws, the effects of photon-phonon interactions are presented. This interaction concept is shown for a simple cubic crystal and is extended to a uniaxial crystal. The correlation table method is used for determining the number and symmetry of the Raman active modes. Finally, examples are given to illustrate the relative ease of using this group theoretical method and the predictions are compared with measured Raman spectra. 37 refs., 17 figs., 6 tabs.

  7. Molecules in crystals

    Science.gov (United States)

    Spackman, Mark A.

    2013-04-01

    Hirshfeld surface analysis has developed from the serendipitous discovery of a novel partitioning of the crystal electron density into discrete molecular fragments, to a suite of computational tools used widely for the identification, analysis and discussion of intermolecular interactions in molecular crystals. The relationship between the Hirshfeld surface and very early ideas on the internal structure of crystals is outlined, and applications of Hirshfeld surface analysis are presented for three molecules of historical importance in the development of modern x-ray crystallography: hexamethylbenzene, hexamethylenetetramine and diketopiperazine.

  8. Hypersonic phononic crystals.

    Science.gov (United States)

    Gorishnyy, T; Ullal, C K; Maldovan, M; Fytas, G; Thomas, E L

    2005-03-25

    In this Letter we propose the use of hypersonic phononic crystals to control the emission and propagation of high frequency phonons. We report the fabrication of high quality, single crystalline hypersonic crystals using interference lithography and show that direct measurement of their phononic band structure is possible with Brillouin light scattering. Numerical calculations are employed to explain the nature of the observed propagation modes. This work lays the foundation for experimental studies of hypersonic crystals and, more generally, phonon-dependent processes in nanostructures.

  9. The Crystal Hotel: A Microfluidic Approach to Biomimetic Crystallization.

    Science.gov (United States)

    Gong, Xiuqing; Wang, Yun-Wei; Ihli, Johannes; Kim, Yi-Yeoun; Li, Shunbo; Walshaw, Richard; Chen, Li; Meldrum, Fiona C

    2015-12-02

    A "crystal hotel" microfluidic device that allows crystal growth in confined volumes to be studied in situ is used to produce large calcite single crystals with predefined crystallographic orientation, microstructure, and shape by control of the detailed physical environment, flow, and surface chemistry. This general approach can be extended to form technologically important, nanopatterned single crystals.

  10. Crystallization Growth of Single Crystal Cu by ContinuousCasting

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Crystallization growth of single-crystal Cu by continuous casting has been investigated using selfdesigned horizontal continuous casting equipment and XRD. Experimental results showed that the crystallization plane of (311), (220) and (111) were eliminated sequentially in evolutionary process. The final growth plane of crystal was (200), the direction of crystallization was [100],the growth direction of both sides of the rod inclined to axis, and the degree of deviation of direction [100] from the crystal axis was less than 10. In order to produce high quality single crystal, the solid-liquid interface morphology must be smooth, even be planar.

  11. Crystal Electrostatic Energy

    CERN Document Server

    Ivanchin, Alexander

    2010-01-01

    It has been shown that to calculate the parameters of the electrostatic field of the ion crystal lattice it sufficient to take into account ions located at a distance of 1-2 lattice spacings. More distant ions make insignificant contribution. As a result, the electrostatic energy of the ion lattice in the alkaline halide crystal produced by both positive and negative ions is in good agreement with experiment when the melting temperature and the shear modulus are calculated. For fcc and bcc metals the ion lattice electrostatic energy is not sufficient to obtain the observed values of these parameters. It is possible to resolve the contradiction if one assumes that the electron density is strongly localized and has a crystal structure described by the lattice delta - function. As a result, positive charges alternate with negative ones as in the alkaline halide crystal. Such delta-like localization of the electron density is known as a model of nearly free electrons.

  12. Shaping Crystals using Electrophoresis

    Science.gov (United States)

    Palacci, Jeremie; Mackiewicz, Kristian

    2016-11-01

    Electrophoresis is size and shape independent as stressed by Morrison in his seminal paper. Here we present an original approach to reshape colloidal crystals using an electric field as a carving tool.

  13. Deformations of crystal frameworks

    CERN Document Server

    Borcea, Ciprian S

    2011-01-01

    We apply our deformation theory of periodic bar-and-joint frameworks to tetrahedral crystal structures. The deformation space is investigated in detail for frameworks modelled on quartz, cristobalite and tridymite.

  14. Inclusions in DKDP crystal

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The shape and the size of inclusions in DKDP crystal have been observed and measured microscopically.Three kinds of inclusions were found and the components of the inclusions were measured. The formation mechanisms were proposed and discussed.``

  15. Relations between structure and nicotine-like activity: X-ray crystal structure analysis of (-)-cytisine and (-)-lobeline hydrochloride and a comparison with (-)-nicotine and other nicotine-like compounds.

    Science.gov (United States)

    Barlow, R. B.; Johnson, O.

    1989-01-01

    1. Although (-)-cytisine is a rigid structure, it occurs in the crystal in two distinct but very similar conformations in which the pyridone ring is tilted relative to the charged nitrogen atom at much the same angle as the pyridine ring is in (-)-nicotine hydrogen iodide. The carbonyl group in the pyridone ring of (-)-cytisine, however, is on the side of the ring opposite to pyridine nitrogen in (-)-nicotine. 2. The pKa of (-)-lobeline HCl at 25 degrees C is 8.6 (approx), indicating that (-)-lobeline is at least 90% in the protonated form at physiological pH (7.6). It is probably the phenyl 2-keto-ethyl part of (-)-lobeline, rather than the phenyl 2-hydroxy-ethyl part, which interacts with the receptor. 3. The combination within one molecule of a charged ('onium') nitrogen atom lying out of the plane of, and some distance (4.5-6.5 A) from, an aromatic ring is common to many compounds with nicotine-like activity (e.g. nicotine, cytisine, choline phenyl ether bromide, dimethyl-phenyl-piperazinium (DMPP) iodide, coryneine iodide and m-hydroxyphenylpropyl trimethyl ammonium iodide). In some molecules the aromatic ring can be replaced by an unsaturated group, such as carbonyl (e.g. acetylcholine) or double-bonds (e.g. anatoxin). 4. Activity at nicotinic receptors appears to involve interactions between the positively charged nitrogen atom and a negatively charged group, probably close to cysteine residues 192 and 193 in the receptor. It is suggested that rather than specific groups in the molecule also being involved, activity at nicotinic receptors depends on interactions between a flat part of the drug containing double-bonds, or systems of double bonds, and a planar area in the receptor, possibly tyrosine or phenylalanine residues. PMID:2590771

  16. Detection of masses and microcalcifications of breast cancer on digital mammograms: comparison among hard-copy film, 3-megapixel liquid crystal display (LCD) monitors and 5-megapixel LCD monitors: an observer performance study.

    Science.gov (United States)

    Kamitani, Takeshi; Yabuuchi, Hidetake; Soeda, Hiroyasu; Matsuo, Yoshio; Okafuji, Takashi; Sakai, Shuji; Furuya, Akio; Hatakenaka, Masamitsu; Ishii, Nobuhide; Honda, Hiroshi

    2007-05-01

    The purpose of the study was to compare observer performance in the detection of masses and microcalcifications of breast cancer among hard-copy reading and soft-copy readings using 3-megapixel (3M) and 5-megapixel (5M) liquid crystal display (LCD) monitors. For the microcalcification detection test, we prepared 100 mammograms: 40 surgically verified cancer cases and 60 normal cases. For the mass detection test, we prepared 100 mammograms: 50 cancer cases and 50 normal cases. After six readers assessed both microcalcifications and masses set for each modality, receiver operating characteristic (ROC) analysis was performed. The average A(z)s for mass detection using a hard copy and 3M and 5M LCD monitors were 0.923, 0.927 and 0.920, respectively; there were no significant differences. The average A(z) for microcalcification detection using hard copy, 3M and 5M LCD monitors was 0.977, 0.954 and 0.972, respectively. There were no significant differences, but the P-values between the hard copy and 3M LCD monitor and that between the 3M and 5M LCD monitor were 0.08 and 0.09, respectively. In conclusion, the observer performances for detecting masses of breast cancers were comparable among the hard copy and two LCD monitors; however, soft-copy reading with a 3M LCD monitor showed slightly lower observer performance for detecting microcalcifications of breast cancers than hard-copy or 5M LCD monitor reading.

  17. Crystal Structures of Furazanes

    OpenAIRE

    Klapötke, Thomas; Schmid, Philipp; Stierstorfer, Jörg

    2015-01-01

    Several nitrogen-rich salts of 3-nitramino-4-nitrofurazane and dinitraminoazoxyfurazane were synthesized and characterized by various spectroscopic methods. The crystal structures were determined by low temperature single crystal X-ray diffraction. Moreover the sensitivities toward thermal and mechanical stimuli were determined by differential thermal analysis (DTA) and BAM (Bundesanstalt für Materialforschung und -prüfung) methods. The standard enthalpies of formation were calculated for all...

  18. SINGLE CRYSTAL NEUTRON DIFFRACTION.

    Energy Technology Data Exchange (ETDEWEB)

    KOETZLE,T.F.

    2001-03-13

    Single-crystal neutron diffraction measures the elastic Bragg reflection intensities from crystals of a material, the structure of which is the subject of investigation. A single crystal is placed in a beam of neutrons produced at a nuclear reactor or at a proton accelerator-based spallation source. Single-crystal diffraction measurements are commonly made at thermal neutron beam energies, which correspond to neutron wavelengths in the neighborhood of 1 Angstrom. For high-resolution studies requiring shorter wavelengths (ca. 0.3-0.8 Angstroms), a pulsed spallation source or a high-temperature moderator (a ''hot source'') at a reactor may be used. When complex structures with large unit-cell repeats are under investigation, as is the case in structural biology, a cryogenic-temperature moderator (a ''cold source'') may be employed to obtain longer neutron wavelengths (ca. 4-10 Angstroms). A single-crystal neutron diffraction analysis will determine the crystal structure of the material, typically including its unit cell and space group, the positions of the atomic nuclei and their mean-square displacements, and relevant site occupancies. Because the neutron possesses a magnetic moment, the magnetic structure of the material can be determined as well, from the magnetic contribution to the Bragg intensities. This latter aspect falls beyond the scope of the present unit; for information on magnetic scattering of neutrons see Unit 14.3. Instruments for single-crystal diffraction (single-crystal diffractometers or SCDs) are generally available at the major neutron scattering center facilities. Beam time on many of these instruments is available through a proposal mechanism. A listing of neutron SCD instruments and their corresponding facility contacts is included in an appendix accompanying this unit.

  19. Liquid Crystal Airborne Display

    Science.gov (United States)

    1977-08-01

    81/2X 11- 10 -9 .8 display using a large advertising alphanimeric ( TCI ) has been added to the front of the optical box used in the F-4 aircraft for HUD...properties over a wide range of tempera - tures, including normal room temperature. What are Liquid Crystals? Liquid crystals have been classified in three...natic fanctions and to present data needed for the semi- automatic and manual control of system functions. Existing aircraft using CRT display

  20. Physical properties of BeAl6O10 single crystals

    Science.gov (United States)

    Pestryakov, E. V.; Petrov, V. V.; Zubrinov, I. I.; Semenov, V. I.; Trunov, V. I.; Kirpichnikov, A. V.; Alimpiev, A. I.

    1997-10-01

    Single crystals of BeAl6O10, beryllium hexaaluminate, were grown by the Czochralski method. The optical, acousto-optical, elastic, and a number of thermo-mechanical properties of bulk crystals of BeAl6O10 were investigated in comparison with crystal of BeAl2O4, chrysoberyl. It has been demonstrated that this material is the promising host for active media of tunable solid state lasers.

  1. Building a crystal palace

    CERN Multimedia

    2007-01-01

    The end-caps of the CMS electromagnetic calorimeter (ECAL) take shape as the first quadrant was completed on Wednesday 3 October. 1831 crystals, organised into five by five blocks named ‘supercrystals’, make up the first quadrant of Dee 1.With the 61,200-crystal barrel of its electromagnetic calorimeter (ECAL) complete, CMS is now building the endcaps, on the tenth anniversary of their initial design. Crystals for the endcaps were the last to be made, so the race is now on to have them all in place and ready for the turn-on of the LHC next year. Assembly of the first of eight quadrants began in June and crystal mounting was completed on Wednesday 3 October. Each crystal is transparent, has a volume just larger than a CERN coffee cup yet weighs a huge 1.5kg. 1831 of these lead tungstate crystals went into the first quadrant from a total 14,648 in the endcaps. The lead and tungsten account for 86% of each crystal’s weight, but as project leader Dave Cockerill expl...

  2. Crystal growth of artificial snow

    Science.gov (United States)

    Kimura, S.; Oka, A.; Taki, M.; Kuwano, R.; Ono, H.; Nagura, R.; Narimatsu, Y.; Tanii, J.; Kamimiytat, Y.

    1984-01-01

    Snow crystals were grown onboard the space shuttle during STS-7 and STS-8 to facilitate the investigation of crystal growth under conditions of weightlessness. The experimental design and hardware are described. Space-grown snow crystals were polyhedrons looking like spheres, which were unlike snow crystals produced in experiments on Earth.

  3. High-throughput crystallization screening.

    Science.gov (United States)

    Skarina, Tatiana; Xu, Xiaohui; Evdokimova, Elena; Savchenko, Alexei

    2014-01-01

    Protein structure determination by X-ray crystallography is dependent on obtaining a single protein crystal suitable for diffraction data collection. Due to this requirement, protein crystallization represents a key step in protein structure determination. The conditions for protein crystallization have to be determined empirically for each protein, making this step also a bottleneck in the structure determination process. Typical protein crystallization practice involves parallel setup and monitoring of a considerable number of individual protein crystallization experiments (also called crystallization trials). In these trials the aliquots of purified protein are mixed with a range of solutions composed of a precipitating agent, buffer, and sometimes an additive that have been previously successful in prompting protein crystallization. The individual chemical conditions in which a particular protein shows signs of crystallization are used as a starting point for further crystallization experiments. The goal is optimizing the formation of individual protein crystals of sufficient size and quality to make them suitable for diffraction data collection. Thus the composition of the primary crystallization screen is critical for successful crystallization.Systematic analysis of crystallization experiments carried out on several hundred proteins as part of large-scale structural genomics efforts allowed the optimization of the protein crystallization protocol and identification of a minimal set of 96 crystallization solutions (the "TRAP" screen) that, in our experience, led to crystallization of the maximum number of proteins.

  4. Transmission measurement of the photonic band gap of GaN photonic crystal slabs

    NARCIS (Netherlands)

    Caro, J.; Roeling, E.M.; Rong, B.; Nguyen, H.M.; Van der Drift, E.W.J.M.; Rogge, S.; Karouta, F.; Van der Heijden, R.W.; Salemink, H.W.M.

    2008-01-01

    A high-contrast-ratio (30 dB) photonic band gap in the near-infrared transmission of hole-type GaN two-dimensional photonic crystals (PhCs) is reported. These crystals are deeply etched in a 650 nm thick GaN layer grown on sapphire. A comparison of the measured spectrum with finite difference time d

  5. Magnetic excitations of single-crystal PrBa2Cu3O6.2

    DEFF Research Database (Denmark)

    Lister, S.J.S.; Boothroyd, A.T.; Andersen, N.H.;

    2000-01-01

    Measurements of the low-energy magnetic excitations in single-crystal PrBa2Cu3O6.2, and in YBa2Cu3O6.2 for comparison, have been performed using inelastic neutron scattering. An excitation with weak dispersion is seen, which is compared to a spin-wave model based on the lowest lying crystal field...

  6. Photonic Crystal Sensors Based on Porous Silicon

    Directory of Open Access Journals (Sweden)

    Claudia Pacholski

    2013-04-01

    Full Text Available Porous silicon has been established as an excellent sensing platform for the optical detection of hazardous chemicals and biomolecular interactions such as DNA hybridization, antigen/antibody binding, and enzymatic reactions. Its porous nature provides a high surface area within a small volume, which can be easily controlled by changing the pore sizes. As the porosity and consequently the refractive index of an etched porous silicon layer depends on the electrochemial etching conditions photonic crystals composed of multilayered porous silicon films with well-resolved and narrow optical reflectivity features can easily be obtained. The prominent optical response of the photonic crystal decreases the detection limit and therefore increases the sensitivity of porous silicon sensors in comparison to sensors utilizing Fabry-Pérot based optical transduction. Development of porous silicon photonic crystal sensors which allow for the detection of analytes by the naked eye using a simple color change or the fabrication of stacked porous silicon photonic crystals showing two distinct optical features which can be utilized for the discrimination of analytes emphasize its high application potential.

  7. Photonic crystal sensors based on porous silicon.

    Science.gov (United States)

    Pacholski, Claudia

    2013-04-09

    Porous silicon has been established as an excellent sensing platform for the optical detection of hazardous chemicals and biomolecular interactions such as DNA hybridization, antigen/antibody binding, and enzymatic reactions. Its porous nature provides a high surface area within a small volume, which can be easily controlled by changing the pore sizes. As the porosity and consequently the refractive index of an etched porous silicon layer depends on the electrochemial etching conditions photonic crystals composed of multilayered porous silicon films with well-resolved and narrow optical reflectivity features can easily be obtained. The prominent optical response of the photonic crystal decreases the detection limit and therefore increases the sensitivity of porous silicon sensors in comparison to sensors utilizing Fabry-Pérot based optical transduction. Development of porous silicon photonic crystal sensors which allow for the detection of analytes by the naked eye using a simple color change or the fabrication of stacked porous silicon photonic crystals showing two distinct optical features which can be utilized for the discrimination of analytes emphasize its high application potential.

  8. Comparison of FDG PET and positron coincidence detection imaging using a dual-head gamma camera with 5/8-inch NaI(Tl) crystals in patients with suspected body malignancies.

    Science.gov (United States)

    Boren, E L; Delbeke, D; Patton, J A; Sandler, M P

    1999-04-01

    The purpose of this study was to compare the diagnostic accuracy of fluorine-18 fluorodeoxyglucose (FDG) images obtained with (a) a dual-head coincidence gamma camera (DHC) equipped with 5/8-inch-thick NaI(Tl) crystals and parallel slit collimators and (b) a dedicated positron emission tomograph (PET) in a series of 28 patients with known or suspected malignancies. Twenty-eight patients with known or suspected malignancies underwent whole-body FDG PET imaging (Siemens, ECAT 933) after injection of approximately 10 mCi of 18F-FDG. FDG DHC images were then acquired for 30 min over the regions of interest using a dual-head gamma camera (VariCam, Elscint). The images were reconstructed in the normal mode, using photopeak/photopeak, photopeak/Compton, and Compton/photopeak coincidence events. FDG PET imaging found 45 lesions ranging in size from 1 cm to 7 cm in 28 patients. FDG DHC imaging detected 35/45 (78%) of these lesions. Among the ten lesions not seen with FDG DHC imaging, eight were less than 1.5 cm in size, and two were located centrally within the abdomen suffering from marked attenuation effects. The lesions were classified into three categories: thorax (n=24), liver (n=12), and extrahepatic abdominal (n=9). FDG DHC imaging identified 100% of lesions above 1.5 cm in the thorax group and 78% of those below 1.5 cm, for an overall total of 83%. FDG DHC imaging identified 100% of lesions above 1.5 cm, in the liver and 43% of lesions below 1.5 cm, for an overall total of 67%. FDG DHC imaging identified 78% of lesions above 1.5 cm in the extrahepatic abdominal group. There were no lesions below 1.5 cm in this group. FDG coincidence imaging using a dual-head gamma camera detected 90% of lesions greater than 1.5 cm. These data suggest that DHC imaging can be used clinically in well-defined diagnostic situations to differentiate benign from malignant lesions.

  9. Design of Agglomerated Crystals of Ibuprofen During Crystallization: Influence of Surfactant

    Directory of Open Access Journals (Sweden)

    Maryam Maghsoodi

    2011-01-01

    Full Text Available Objective(sIbuprofen is a problematic drug in tableting, and dissolution due to its poor solubility, hydrophobicity, and tendency to stick to surface. Because of the bad compaction behavior ibuprofen has to be granulated usually before tableting. However, it would be more satisfactory to obtain directly during the crystallization step crystalline particles that can be directly compressed and quickly dissolved. Materials and Methods Crystallization of ibuprofen was carried out using the quasi emulsion solvent diffusion method in presence of surfactant (sodium lauryl sulfate (SLS, Tween 80. The particles were characterized by differential scanning calorimetry (DSC, powder X-ray diffraction (XRPD and were evaluated for particle size, flowability, drug release and tableting behavior. ResultsIbuprofen particles obtained in the presence of surfactants consisted of numerous plate- shaped crystals which had agglomerated together as near spherical shape. The obtained agglomerates exhibited significantly improved micromeritic properties as well as tableting behavior than untreated drug crystals. The agglomerates size and size distribution was largely controlled by surfactant concentration, but there was no significant influence found on the tableting properties. The dissolution tests showed that the agglomerates obtained in presence of SLS exhibited enhanced dissolution rate while the agglomerates made in the presence of Tween 80 had no significant impact on dissolution rate of ibuprofen in comparison to untreated sample. The XRPD and DSC results showed that during the agglomeration process, ibuprofen did not undergo any polymorphic changes.Conclusion The study highlights the influence of surfactants on crystallization process leading to modified performance.

  10. Crystal Growth Models of Dexamethasone Sodium Phosphate in a MSMPR Reactive Crystallizer

    Institute of Scientific and Technical Information of China (English)

    郝红勋; 王静康; 王永莉; 侯宝红

    2005-01-01

    The reactive crystallization process of dexamethasone sodium phosphate was investigated in a continuous mixed-suspension, mixed-product-removal(MSMPR) crystallizer. Analyzing experimental data, it was found that the growth of product crystal was size-dependent. The Bransom, CR, ASL, M J2 and M J3 size-dependent growth models were discussed in details. Using experimental steady state population density data of dexamethasone sodium phosphate, parameters of five size-dependent growth models were determined by the method of non-linear least-squares. By comparison of experimental population density and linear growth rate data with those obtained from the five size-dependent growth models, it was found that the MJ3 model predicts the growth more accurately than do the other four models. Based on the theory of population balance, the crystal nucleation and growth rate equations of dexamethasone sodium phosphate were determined by non-linear regression method. The effects of different operation parameters such as supersaturation, magma density and temperature on the quality of product crystal were also discussed, and the optimal operation conditions were derived.

  11. Electrochemical deposition of silver crystals aboard Skylab 4

    Science.gov (United States)

    Grodzka, P. G.; Facemire, B. R.; Johnston, M. H.; Gates, D. W.

    1976-01-01

    Silver crystals were grown aboard Skylab 4 by an electro-chemical reaction and subsequently returned to earth for comparison with crystals grown at 1- and 5-g. Both the Skylab and earth-grown crystals show a variety of structures. Certain tendencies in structure dependency on gravity level, however, can be discerned. In addition, downward growing dendrite streamers; upward growing chunky crystal streamers; growth along an air/liquid interface; and ribbon, film, and fiber crystal habits were observed in experiments conducted on the ground with solutions of varying concentrations. It was also observed that the crystal structures of space and ground electro-deposited silver crystals were very similar to the structures of germanium selenide and germanium telluride crystals grown in space and on the ground by a vapor transport technique. Consideration of the data leads to the conclusions that: (1) the rate of electrochemical displacement of silver ions from a 5 percent aqueous solution by copper is predominantly diffussion controlled in space and kinetically controlled in 1- and higher-g because of augmentation of mass transport by convection; (2) downward and upward crystal streamers are the result of gravity-driven convection, the flow patterns of which can be delineated. Lateral growths along an air/liquid interface are the result of surface-tension-driven convection, the pattern of which also can be delineated; (3) electrolysis in space or low-g environments can produce either dendritic crystals with more perfect microcrystalline structures or massive, single crystals with fewer defects than those grown on ground or at higher g-levels. Ribbons or films of space-grown silicon crystals would find a ready market for electronic substrate and photocell applications. Space-grown dendritic, metal crystals present the possibility of unique catalysts. Large perfect crystals of various materials are desired for a number of electronic and optical applications; and (4) vapor

  12. Crystal Ball Functional Model

    Science.gov (United States)

    Plotnick, David

    2016-09-01

    The A2 collaboration of the MAinz MIkrotron is dedicated to studying meson production and nucleon structure and behavior via photon scattering. The photons are made via bremsstrahlung process and energy-tagged using the Glasgow Photon tagger. The photon beam then interacts in a variety of targets: cryogenic, polarized or solid state, and scattered particles deposit their energy within the NaI crystals. Scintillators are able to give results on particles energy and time. Events are reconstructed by combining information from the Tagging spectrometer, the Crystal Ball detector, the TAPS forward wall spectrometer, a Cherenkov detector, and multi-wire proportional chambers. To better understand the detector and experimental events, a live display was built to show energies deposited in crystals in real-time. In order to show a range of energies and particles, addressable LEDs that are individually programmable were used. To best replicate the Crystal Ball, 3D printing technology was employed to build a similar highly segmented icosahedron that can hold each LED, creating a 3D representation of what photons see during experiments. The LEDs were controlled via Arduino microcontroller. Finally, we implemented the Experimental Physics and Industrial Control System to grab live event data, and a simple program converts this data in to color and crystal number data that is able to communicate with the Arduino. Using these simple parts, we can better visualize and understand the tools used in nuclear physics. This material is based upon work supported by the National Science Foundation Grant No. IIA-1358175.

  13. Introduction to protein crystallization.

    Science.gov (United States)

    McPherson, Alexander; Gavira, Jose A

    2014-01-01

    Protein crystallization was discovered by chance about 150 years ago and was developed in the late 19th century as a powerful purification tool and as a demonstration of chemical purity. The crystallization of proteins, nucleic acids and large biological complexes, such as viruses, depends on the creation of a solution that is supersaturated in the macromolecule but exhibits conditions that do not significantly perturb its natural state. Supersaturation is produced through the addition of mild precipitating agents such as neutral salts or polymers, and by the manipulation of various parameters that include temperature, ionic strength and pH. Also important in the crystallization process are factors that can affect the structural state of the macromolecule, such as metal ions, inhibitors, cofactors or other conventional small molecules. A variety of approaches have been developed that combine the spectrum of factors that effect and promote crystallization, and among the most widely used are vapor diffusion, dialysis, batch and liquid-liquid diffusion. Successes in macromolecular crystallization have multiplied rapidly in recent years owing to the advent of practical, easy-to-use screening kits and the application of laboratory robotics. A brief review will be given here of the most popular methods, some guiding principles and an overview of current technologies.

  14. A novel lattice energy calculation technique for simple inorganic crystals

    Science.gov (United States)

    Kaya, Cemal; Kaya, Savaş; Banerjee, Priyabrata

    2017-01-01

    In this pure theoretical study, a hitherto unexplored equation based on Shannon radii of the ions forming that crystal and chemical hardness of any crystal to calculate the lattice energies of simple inorganic ionic crystals has been presented. To prove the credibility of this equation, the results of the equation have been compared with experimental outcome obtained from Born-Fajans-Haber- cycle which is fundamentally enthalpy-based thermochemical cycle and prevalent theoretical approaches proposed for the calculation of lattice energies of ionic compounds. The results obtained and the comparisons made have demonstrated that the new equation is more useful compared to other theoretical approaches and allows to exceptionally accurate calculation of lattice energies of inorganic ionic crystals without doing any complex calculations.

  15. Coherent Dynamics of Quantum Dots in Photonic-Crystal Cavities

    DEFF Research Database (Denmark)

    Madsen, Kristian Høeg

    deviations. Similar measurements on a quantum dot in a photonic-crystal cavity sow a Rabi splitting on resonance, while time-resolved measurements prove that the system is in the weak coupling regime. Whle tuning the quantum dot through resonance of the high-Q mode we observe a strong and surprisingly...... Successfully model the decay rates with a microscopic model that allows us to for the first time extract the effective phonon density of states, which we can model with bulk phonons. Studies on a quantum dot detuned from a low-Q mode of a photonic-crystal cavity show a high collection efficiency at the first......In this thesis we have performed quantum-electrodynamics experiments on quantum dots embedded in photonic-crystal cavities. We perform a quantitative comparison of the decay dynamics and emission spectra of quantum dots embedded in a micropillar cavity and a photonic-crystal cavity. The light...

  16. Photonic Crystal Microchip Laser

    Science.gov (United States)

    Gailevicius, Darius; Koliadenko, Volodymyr; Purlys, Vytautas; Peckus, Martynas; Taranenko, Victor; Staliunas, Kestutis

    2016-09-01

    The microchip lasers, being very compact and efficient sources of coherent light, suffer from one serious drawback: low spatial quality of the beam strongly reducing the brightness of emitted radiation. Attempts to improve the beam quality, such as pump-beam guiding, external feedback, either strongly reduce the emission power, or drastically increase the size and complexity of the lasers. Here it is proposed that specially designed photonic crystal in the cavity of a microchip laser, can significantly improve the beam quality. Experiments show that a microchip laser, due to spatial filtering functionality of intracavity photonic crystal, improves the beam quality factor M2 reducing it by a factor of 2, and increase the brightness of radiation by a factor of 3. This comprises a new kind of laser, the “photonic crystal microchip laser”, a very compact and efficient light source emitting high spatial quality high brightness radiation.

  17. Flexible ferroelectric organic crystals

    Science.gov (United States)

    Owczarek, Magdalena; Hujsak, Karl A.; Ferris, Daniel P.; Prokofjevs, Aleksandrs; Majerz, Irena; Szklarz, Przemysław; Zhang, Huacheng; Sarjeant, Amy A.; Stern, Charlotte L.; Jakubas, Ryszard; Hong, Seungbum; Dravid, Vinayak P.; Stoddart, J. Fraser

    2016-10-01

    Flexible organic materials possessing useful electrical properties, such as ferroelectricity, are of crucial importance in the engineering of electronic devices. Up until now, however, only ferroelectric polymers have intrinsically met this flexibility requirement, leaving small-molecule organic ferroelectrics with room for improvement. Since both flexibility and ferroelectricity are rare properties on their own, combining them in one crystalline organic material is challenging. Herein, we report that trisubstituted haloimidazoles not only display ferroelectricity and piezoelectricity--the properties that originate from their non-centrosymmetric crystal lattice--but also lend their crystalline mechanical properties to fine-tuning in a controllable manner by disrupting the weak halogen bonds between the molecules. This element of control makes it possible to deliver another unique and highly desirable property, namely crystal flexibility. Moreover, the electrical properties are maintained in the flexible crystals.

  18. Flexible ferroelectric organic crystals

    Science.gov (United States)

    Owczarek, Magdalena; Hujsak, Karl A.; Ferris, Daniel P.; Prokofjevs, Aleksandrs; Majerz, Irena; Szklarz, Przemysław; Zhang, Huacheng; Sarjeant, Amy A.; Stern, Charlotte L.; Jakubas, Ryszard; Hong, Seungbum; Dravid, Vinayak P.; Stoddart, J. Fraser

    2016-01-01

    Flexible organic materials possessing useful electrical properties, such as ferroelectricity, are of crucial importance in the engineering of electronic devices. Up until now, however, only ferroelectric polymers have intrinsically met this flexibility requirement, leaving small-molecule organic ferroelectrics with room for improvement. Since both flexibility and ferroelectricity are rare properties on their own, combining them in one crystalline organic material is challenging. Herein, we report that trisubstituted haloimidazoles not only display ferroelectricity and piezoelectricity—the properties that originate from their non-centrosymmetric crystal lattice—but also lend their crystalline mechanical properties to fine-tuning in a controllable manner by disrupting the weak halogen bonds between the molecules. This element of control makes it possible to deliver another unique and highly desirable property, namely crystal flexibility. Moreover, the electrical properties are maintained in the flexible crystals. PMID:27734829

  19. 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.

  20. Photonic Crystal Fibres

    DEFF Research Database (Denmark)

    Bjarklev, Anders Overgaard; Broeng, Jes; Sanchez Bjarklev, Araceli

    Photonic crystal fibres represent one of the most active research areas today in the field of optics. The diversity of applications that may be addressed by these fibres and their fundamental appeal, by opening up the possibility of guiding light in a radically new way compared to conventional...... optical fibres, have spun an interest from almost all areas of optics and photonics. The aim of this book is to provide an understanding of the different types of photonic crystal fibres and to outline some of the many new and exciting applications that these fibres offer. The book is intended for both...... readers with a general interest in photonic crystals, as well as for scientists who are entering the field and desire a broad overview as well as a solid starting point for further specialized stuides. Teh book, therefore, covers bothe general aspects such as the link from classical optics to photonic...

  1. Quantum Electrodynamics in Photonic Crystal Waveguides

    DEFF Research Database (Denmark)

    Nielsen, Henri Thyrrestrup

    In this thesis we have performed quantum electrodynamics (QED) experiments in photonic crystal (PhC) waveguides and cavity QED in the Anderson localized regime in disordered PhC waveguides. Decay rate measurements of quantum dots embedded in PhC waveguides has been used to map out the variations...... probability. The Q-factor distributions of Anderson localized modes have been measured in PhC waveguides with articial induced disorder with embedded emitters. The largest Q-factors are found in the sample with the smallest amount of disorder. From a comparison with the waveguide model the localization length...

  2. Anharmonicity in GaTe layered crystals

    Energy Technology Data Exchange (ETDEWEB)

    Aydinli, A. [Physics Department, Bilkent University, Ankara (Turkey); Gasanly, N.M.; Uka, A. [Physics Department, Middle East Technical University, Ankara (Turkey); Efeoglu, H. [Physics Department, Atatuerk University, Erzurum (Turkey)

    2002-07-01

    The temperature dependencies (10-300 K) of seven Raman-active mode frequencies in layered semiconductor gallium telluride have been measured in the frequency range from 25 to 300 cm{sup -1}. Softening and broadening of the optical phonon lines are observed with increasing temperature. Comparison between the experimental data and theories of the shift of the phonon lines during heating of the crystal showed that the experimental dependencies can be explained by contributions from thermal expansion and lattice anharmonicity. Lattice anharmonicity is determined to be due to three-phonon processes. (Abstract Copyright [2002], Wiley Periodicals, Inc.)

  3. Photonic crystals as metamaterials

    Science.gov (United States)

    Foteinopoulou, S.

    2012-10-01

    The visionary work of Veselago had inspired intensive research efforts over the last decade, towards the realization of man-made structures with unprecedented electromagnetic (EM) properties. These structures, known as metamaterials, are typically periodic metallic-based resonant structures demonstrating effective constitutive parameters beyond the possibilities of natural material. For example they can exhibit optical magnetism or simultaneously negative effective permeability and permittivity which implies the existence of a negative refractive index. However, also periodic dielectric and polar material, known as photonic crystals, can exhibit EM capabilities beyond natural materials. This paper reviews the conditions and manifestations of metamaterial capabilities of photonic crystal systems.

  4. High Birefringence Liquid Crystals

    Directory of Open Access Journals (Sweden)

    Jakub Herman

    2013-09-01

    Full Text Available Liquid crystals, compounds and mixtures with positive dielectric anisotropies are reviewed. The mesogenic properties and physical chemical properties (viscosity, birefringence, refractive indices, dielectric anisotropy and elastic constants of compounds being cyano, fluoro, isothiocyanato derivatives of biphenyl, terphenyl, quaterphenyl, tolane, phenyl tolane, phenyl ethynyl tolane, and biphenyl tolane are compared. The question of how to obtain liquid crystal with a broad range of nematic phases is discussed in detail. Influence of lateral substituent of different kinds of mesogenic and physicochemical properties is presented (demonstrated. Examples of mixtures with birefringence ∆n in the range of 0.2–0.5 are given.

  5. Crystal Structures of Furazanes

    Directory of Open Access Journals (Sweden)

    Thomas M. Klapötke

    2015-09-01

    Full Text Available Several nitrogen-rich salts of 3-nitramino-4-nitrofurazane and dinitraminoazoxyfurazane were synthesized and characterized by various spectroscopic methods. The crystal structures were determined by low temperature single crystal X-ray diffraction. Moreover the sensitivities toward thermal and mechanical stimuli were determined by differential thermal analysis (DTA and BAM (Bundesanstalt für Materialforschung und -prüfung methods. The standard enthalpies of formation were calculated for all compounds at the CBS-4M level of theory, and the energetic performance was predicted with the EXPLO5 V6.02 computer code.

  6. Liquid crystals fundamentals

    CERN Document Server

    Singh, Shri

    2001-01-01

    Liquid crystals are partially ordered systems without a rigid, long-range structure. The study of these materials covers a wide area: chemical structure, physical properties and technical applications. Due to their dual nature - anisotropic physical properties of solids and rheological behavior of liquids - and easy response to externally applied electric, magnetic, optical and surface fields liquid crystals are of greatest potential for scientific and technological applications. The subject has come of age and has achieved the status of being a very exciting interdisciplinary field of scienti

  7. Cirrus Crystal Terminal Velocities.

    Science.gov (United States)

    Heymsfield, Andrew J.; Iaquinta, Jean

    2000-04-01

    Cirrus crystal terminal velocities are of primary importance in determining the rate of transport of condensate from upper- to middle-tropospheric levels and profoundly influence the earth's radiation balance through their effect on the rate of buildup or decay of cirrus clouds. In this study, laboratory and field-based cirrus crystal drag coefficient data, as well as analytical descriptions of cirrus crystal shapes, are used to derive more physically based expressions for the velocities of cirrus crystals than have been available in the past.Polycrystals-often bullet rosettes-are shown to be the dominant crystal types in synoptically generated cirrus, with columns present in varying but relatively large percentages, depending on the cloud. The two critical parameters needed to calculate terminal velocity are the drag coefficient and the ratio of mass to cross-sectional area normal to their fall direction. Using measurements and calculations, it is shown that drag coefficients from theory and laboratory studies are applicable to crystals of the types found in cirrus. The ratio of the mass to area, which is shown to be relatively independent of the number of bullets in the rosette, is derived from an analytic model that represents bullet rosettes containing one to eight bullets in 19 primary geometric configurations. The ratio is also derived for columns. Using this information, a general set of equations is developed to calculate the terminal velocities and masses in terms of the aspect ratio (width divided by length), ice density, and rosette maximum dimension. Simple expressions for terminal velocity and mass as a function of bullet rosette maximum dimension are developed by incorporating new information on bullet aspect ratios.The general terminal velocity and mass relations are then applied to a case from the First International Satellite Cloud Climatology Project (ISCCP) Research Experiment (FIRE) 2, when size spectra from a balloon-borne ice crystal

  8. Enhanced crystallization of poly (lactic acid) through reactive aliphatic bisamide

    Science.gov (United States)

    Nanthananon, P.; Seadan, M.; Pivsa-Art, S.; Suttiruengwong, S.

    2015-07-01

    The poor crystallization rate of poly (lactic acid) (PLA) is a major drawback in terms of controlling the properties of final products. To overcome this, a nucleating agent is normally applied. In this work, the aliphatic bisamide, N, N'-(1,3-propylene) bis(10-undecenamide) (PBU), having reactive functional groups is used as a crystallization promoter for PLA by adding PBU in various concentration (0.1-0.7 wt%) into PLA together with peroxide via reactive melt blending. The conventional ethylene bis-stearamide(EBS) is used for a comparison. The extruded samples are characterized for gel content and FT-IR spectroscopy. The crystallization behaviour and rate, and spherulites morphology are investigated by differential scanning calorimetry (DSC) and polarized optical microscopy (POM), respectively. It is found that the addition of PBU into PLA results in the dramatic increase in crystallinity and crystallization rate of PLA compared with neat PLA and PLA added EBS. The crystallinity increases to 24.9-28.3% higher than neat PLA under even cooling rate of 7°C/min. The addition of 0.7 wt% PBU shows the fastest crystallization rate with t1/2 value isothermally crystallized at 130°C of only 6 min. POM images indicate the increase in the nucleation density and very fine spherulitesof PLA added PBU, promoting the fast crystallization.

  9. An analytical model for porous single crystals with ellipsoidal voids

    Science.gov (United States)

    Mbiakop, A.; Constantinescu, A.; Danas, K.

    2015-11-01

    A rate-(in)dependent constitutive model for porous single crystals with arbitrary crystal anisotropy (e.g., FCC, BCC, HCP, etc.) containing general ellipsoidal voids is developed. The proposed model, denoted as modified variational model (MVAR), is based on the nonlinear variational homogenization method, which makes use of a linear comparison porous material to estimate the response of the nonlinear porous single crystal. Periodic multi-void finite element simulations are used in order to validate the MVAR for a large number of parameters including cubic (FCC, BCC) and hexagonal (HCP) crystal anisotropy, various creep exponents (i.e., nonlinearity), several stress triaxiality ratios, general void shapes and orientations and various porosity levels. The MVAR model, which involves a priori no calibration parameters, is found to be in good agreement with the finite element results for all cases considered in the rate-dependent context. The model is then used in a predictive manner to investigate the complex response of porous single crystals in several cases with strong coupling between the anisotropy of the crystal and the (morphological) anisotropy induced by the shape and orientation of the voids. Finally, a simple way of calibrating the MVAR with just two adjustable parameters is depicted in the rate-independent context so that an excellent agreement with the FE simulation results is obtained. In this last case, this proposed model can be thought as a generalization of the Gurson model in the context of porous single crystals and general ellipsoidal void shapes and orientations.

  10. 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

  11. REFINEMENT OF THE CRYSTAL STRUCTURE OF GUANIDINIUM ALUMINUM SULFATE HEXAHYDRATE.

    Science.gov (United States)

    FERROELECTRIC CRYSTALS, * CRYSTAL STRUCTURE ), (*GUANIDINES, CRYSTAL STRUCTURE ), (*ALUMINUM COMPOUNDS, CRYSTAL STRUCTURE ), SULFATES, HYDRATES, X RAY DIFFRACTION, CHROMIUM COMPOUNDS, CRYSTAL LATTICES, CHEMICAL BONDS

  12. Terahertz Generation in Nonlinear Crystals with Mid-Infrared CO2 Laser

    Institute of Scientific and Technical Information of China (English)

    LU Yan-Zhao; WANG Xin-Bing; MIAO Liang; ZUO Du-Luo; CHENG Zu-Hai

    2011-01-01

    The terahertz(THz)generation based on difference frequency generation in nonlinear optical crystals pumped by mid-infrared C02 laser has been investigated.We present a comprehensive study of the phase-matching conditions in the GaSe, ZnGeP2 and GaAs crystals. A comparison of the characteristics of these crystals as the THz frequency generator is also presented. The investigation of the conversion efficiency shows that GaSe and GaAs are the most promising nonlinear crystals for the efficient and widely tunable THz generation.

  13. The CMS crystal calorimeter

    CERN Document Server

    Lustermann, W

    2004-01-01

    The measurement of the energy of electrons and photons with very high accuracy is of primary importance far the study of many physics processes at the Large Hadron Collider (LHC), in particular for the search of the Higgs Boson. The CMS experiment will use a crystal calorimeter with pointing geometry, almost covering 4p, as it offers a very good energy resolution. It is divided into a barrel composed of 61200 lead tungstate crystals, two end-caps with 14648 crystals and a pre-shower detector in front of the end-cap. The challenges of the calorimeter design arise from the high radiation environment, the 4 Tesla magnetic eld, the high bunch crossing rate of 40 MHz and the large dynamic range, requiring the development of fast, radiation hard crystals, photo-detectors and readout electronics. An overview of the construction and design of the calorimeter will be presented, with emphasis on some of the details required to meet the demanding performance goals. 19 Refs.

  14. Computer-assisted Crystallization.

    Science.gov (United States)

    Semeister, Joseph J., Jr.; Dowden, Edward

    1989-01-01

    To avoid a tedious task for recording temperature, a computer was used for calculating the heat of crystallization for the compound sodium thiosulfate. Described are the computer-interfacing procedures. Provides pictures of laboratory equipment and typical graphs from experiments. (YP)

  15. Liquid crystal colloids

    Directory of Open Access Journals (Sweden)

    2010-01-01

    Full Text Available This special issue of "Condensed Matter Physics" focuses on the most recent developments in the study of a fascinating soft matter system, representing colloidal particles in a liquid crystalline environment. Furthermore, some articles address pioneering steps in the discovery of liquid crystals going back to 1861 paper by Julius Planer.

  16. Crystal Ball Replica

    Science.gov (United States)

    Ajamian, John

    2016-09-01

    The A2 collaboration of the Institute for Nuclear Physics of Johannes Gutenberg University performs research on (multiple) meson photoproduction and nucleon structure and dynamics using a high energy polarized photon beam at specific targets. Particles scattered from the target are detected in the Crystal Ball, or CB. The CB is composed of 672 NaI crystals that surround the target and can analyze particle type and energy of ejected particles. Our project was to create a replica of the CB that could display what was happening in real time on a 3 Dimensional scale replica. Our replica was constructed to help explain the physics to the general public, be used as a tool when calibrating each of the 672 NaI crystals, and to better analyze the electron showering of particles coming from the target. This poster will focus on the hardware steps necessary to construct the replica and wire the 672 programmable LEDS in such a way that they can be mapped to correspond to the Crystal Ball elements. George Washington NSF Grant.

  17. The Crystal Set

    Science.gov (United States)

    Greenslade, Thomas B., Jr.

    2014-01-01

    In past issues of this journal, the late H. R. Crane wrote a long series of articles under the running title of "How Things Work." In them, Dick dealt with many questions that physics teachers asked themselves, but did not have the time to answer. This article is my attempt to work through the physics of the crystal set, which I thought…

  18. DIFFRACTION FROM MODEL CRYSTALS

    Science.gov (United States)

    Although calculating X-ray diffraction patterns from atomic coordinates of a crystal structure is a widely available capability, calculation from non-periodic arrays of atoms has not been widely applied to cellulose. Non-periodic arrays result from modeling studies that, even though started with at...

  19. NADAC Comparison

    Data.gov (United States)

    U.S. Department of Health & Human Services — The NADAC Weekly Comparison identifies the drug products with current NADAC rates that are replaced with new NADAC rates. Other changes (e.g. NDC additions and...

  20. Subcutaneous crystal deposition in pseudogout.

    Science.gov (United States)

    Rothschild, B M; Round, M J

    1980-11-07

    Aspiration of inflamed periarticular tissues in seven patients suspected of having gout on clinical examination revealed positively birefringent calcium pyrophosphate crystals. The identification of calcium pyrophosphate crystals within articular structures and in the surrounding soft tissues and radiologic findings of chondrocalcinosis, in the absence of identifiable uric acid crystals, emphasize the importance of crystal identification in all cases of probable gout and stress the diagnostic role of soft-tissue aspiration in cases of soft-tissue inflammation, especially when arthrocentesis is unsuccessful.

  1. Ultrafast photonic crystal optical switching

    Institute of Scientific and Technical Information of China (English)

    GONG Qi-huang; HU Xiao-yong

    2006-01-01

    Photonic crystal,a novel and artificial photonic material with periodic dielectric distribution,possesses photonic bandgap and can control the propagation states of photons.Photonic crystal has been considered to be a promising candidate for the future integrated photonic devices.The properties and the fabrication method of photonic crystal are expounded.The progresses of the study of ultrafast photonic crystal optical switching are discussed in detail.

  2. Intensified crystallization in complex media: heuristics for crystallization of platform chemicals

    NARCIS (Netherlands)

    Urbanus, J.; Roelands, C.P.M.; Verdoes, D.; Horst, J.H. ter

    2012-01-01

    This paper presents heuristics for the integration of fermentation with the appropriate crystallization based in-situ product recovery (ISPR) technique. Here techniques, such as co-crystallization (CC), evaporative crystallization (EC), template induced crystallization (TIC), cooling crystallization

  3. A Few Good Crystals Please

    Science.gov (United States)

    Judge, Russell A.; Snell, Edward H.

    1999-01-01

    Part of the challenge of macromolecular crystal growth for structure determination is obtaining an appropriate number of crystals with a crystal volume suitable for X-ray analysis. In this respect an understanding of the effect of solution conditions on macromolecule nucleation rates is advantageous. This study investigated the effects of solution conditions on the nucleation rate and final crystal size of two crystal systems; tetragonal lysozyme and glucose isomerase. Batch crystallization plates were prepared at given solution concentration and incubated at set temperatures over one week. The number of crystals per well with their size and axial ratios were recorded and correlated with solution conditions. Duplicate experiments indicate the reproducibility of the technique. Results for each system showing the effect of supersaturation, incubation temperature and solution pH on nucleation rates will be presented and discussed. In the case of lysozyme, having optimized solution conditions to produce an appropriate number of crystals of a suitable size, a batch of crystals were prepared under exactly the same conditions. Fifty of these crystals were analyzed by x-ray techniques. The results indicate that even under the same crystallization conditions, a marked variation in crystal properties exists.

  4. Classical and quantum Coulomb crystals

    CERN Document Server

    Bonitz, M; Baumgartner, H; Henning, C; Filinov, A; Block, D; Arp, O; Piel, A; Kading, S; Ivanov, Y; Melzer, A; Fehske, H; Filinov, V

    2008-01-01

    Strong correlation effects in classical and quantum plasmas are discussed. In particular, Coulomb (Wigner) crystallization phenomena are reviewed focusing on one-component non-neutral plasmas in traps and on macroscopic two-component neutral plasmas. The conditions for crystal formation in terms of critical values of the coupling parameters and the distance fluctuations and the phase diagram of Coulomb crystals are discussed.

  5. Transmission electron microscopy for the evaluation and optimization of crystal growth

    Energy Technology Data Exchange (ETDEWEB)

    Stevenson, Hilary P.; Lin, Guowu; Barnes, Christopher O.; Sutkeviciute, Ieva; Krzysiak, Troy; Weiss, Simon C.; Reynolds, Shelley; Wu, Ying; Nagarajan, Veeranagu; Makhov, Alexander M.; Lawrence, Robert; Lamm, Emily; Clark, Lisa; Gardella, Timothy J.; Hogue, Brenda G.; Ogata, Craig M.; Ahn, Jinwoo; Gronenborn, Angela M.; Conway, James F.; Vilardaga, Jean-Pierre; Cohen, Aina E.; Calero, Guillermo

    2016-04-26

    The crystallization of protein samples remains the most significant challenge in structure determination by X-ray crystallography. Here, the effectiveness of transmission electron microscopy (TEM) analysis to aid in the crystallization of biological macromolecules is demonstrated. It was found that the presence of well ordered lattices with higher order Bragg spots, revealed by Fourier analysis of TEM images, is a good predictor of diffraction-quality crystals. Moreover, the use of TEM allowed (i) comparison of lattice quality among crystals from different conditions in crystallization screens; (ii) the detection of crystal pathologies that could contribute to poor X-ray diffraction, including crystal lattice defects, anisotropic diffraction and crystal contamination by heavy protein aggregates and nanocrystal nuclei; (iii) the qualitative estimation of crystal solvent content to explore the effect of lattice dehydration on diffraction and (iv) the selection of high-quality crystal fragments for microseeding experiments to generate reproducibly larger sized crystals. Applications to X-ray free-electron laser (XFEL) and micro-electron diffraction (microED) experiments are also discussed.

  6. Antisolvent precipitation of novel xylitol-additive crystals to engineer tablets with improved pharmaceutical performance.

    Science.gov (United States)

    Kaialy, Waseem; Maniruzzaman, Mohammad; Shojaee, Saeed; Nokhodchi, Ali

    2014-12-30

    The purpose of this work was to develop stable xylitol particles with modified physical properties, improved compactibility and enhanced pharmaceutical performance without altering polymorphic form of xylitol. Xylitol was crystallized using antisolvent crystallization technique in the presence of various hydrophilic polymer additives, i.e., polyethylene glycol (PEG), polyvinylpyrrolidone (PVP) and polyvinyl alcohol (PVA) at a range of concentrations. The crystallization process did not influence the stable polymorphic form or true density of xylitol. However, botryoidal-shaped crystallized xylitols demonstrated different particle morphologies and lower powder bulk and tap densities in comparison to subangular-shaped commercial xylitol. Xylitol crystallized without additive and xylitol crystallized in the presence of PVP or PVA demonstrated significant improvement in hardness of directly compressed tablets; however, such improvement was observed to lesser extent for xylitol crystallized in the presence of PEG. Crystallized xylitols produced enhanced dissolution profiles for indomethacin in comparison to original xylitol. The influence of additive concentration on tablet hardness was dependent on the type of additive, whereas an increased concentration of all additives provided an improvement in the dissolution behavior of indomethacin. Antisolvent crystallization using judiciously selected type and concentration of additive can be a potential approach to prepare xylitol powders with promising physicomechanical and pharmaceutical properties.

  7. Detached Solidification of Germanium-Silicon Crystals on the ISS

    Science.gov (United States)

    Volz, M. P.; Mazuruk, K.; Croell, A.

    2016-01-01

    A series of Ge(sub 1-x) Si(sub x) crystal growth experiments are planned to be conducted in the Low Gradient Furnace (LGF) onboard the International Space Station. The primary objective of the research is to determine the influence of containment on the processing-induced defects and impurity incorporation in germanium-silicon alloy crystals. A comparison will be made between crystals grown by the normal and "detached" Bridgman methods and the ground-based float zone technique. Crystals grown without being in contact with a container have superior quality to otherwise similar crystals grown in direct contact with a container, especially with respect to impurity incorporation, formation of dislocations, and residual stress in crystals. "Detached" or "dewetted" Bridgman growth is similar to regular Bridgman growth in that most of the melt is in contact with the crucible wall, but the crystal is separated from the wall by a small gap, typically of the order of 10-100 microns. Long duration reduced gravity is essential to test the proposed theory of detached growth. Detached growth requires the establishment of a meniscus between the crystal and the ampoule wall. The existence of this meniscus depends on the ratio of the strength of gravity to capillary forces. On Earth, this ratio is large and stable detached growth can only be obtained over limited conditions. Crystals grown detached on the ground exhibited superior structural quality as evidenced by measurements of etch pit density, synchrotron white beam X-ray topography and double axis X-ray diffraction.

  8. Reactions of a cyclodimethylsiloxane (Me2SiO)6 with silver salts of weakly coordinating anions; crystal structures of [Ag(Me2SiO)6][Al] ([Al] = [FAl{OC(CF3)3}3], [Al{OC(CF3)3}4]) and their comparison with [Ag(18-crown-6)]2[SbF6]2.

    Science.gov (United States)

    Cameron, T Stanley; Decken, Andreas; Krossing, Ingo; Passmore, Jack; Rautiainen, J Mikko; Wang, Xinping; Zeng, Xiaoqing

    2013-03-18

    Two silver-cyclodimethylsiloxane cation salts [AgD6][Al] ([Al] = [Al(ORF)4](1) or [FAl(OR(F))3](2), R(F) = C(CF3)3, D = Me2SiO) were prepared by the reactions of Ag[Al] with D6 in SO2(l). For a comparison the [Ag(18-crown-6)]2[SbF6]2(3) salt was prepared by the reaction of Ag[SbF6] and 18-crown-6 in SO2(l). The compounds were characterized by IR, multinuclear NMR, and single crystal X-ray crystallography. The structures of 1 and 2 show that D6 acts as a pseudo crown ether toward Ag(+). The stabilities and bonding of [MDn](+) and [M(18-crown-6)](+) (M = Ag, Li, n = 4-8) complexes were studied with theoretical calculations. The calculations predicted that D6 adopts a puckered C(i) symmetric structure in the gas phase in contrast to previous reports. 18-Crown-6 was calculated to bind more strongly to Li(+) and Ag(+) than D6. (29)Si[(1)H] NMR results in solution, and calculations in the gas phase established that a hard Lewis acid Li(+) binds more strongly to D6 than Ag(+). A comparison of the [MD(n)](+) complex stabilities showed D7 to form the most stable metal complexes in the gas phase and the solid state and explained why [AgD7][SbF6] was isolated in a previous reaction where ring transformations resulted in an equilibrium of [AgD(n)](+) complexes. In contrast, the isolations of 1 and 2 were possible because the corresponding equilibrium of [AgD(n)](+) complexes was not observed with [Al](-) anions. The formation of the dinuclear complex salt 3 instead of the corresponding mononuclear complex salt was shown to be driven by the gain in lattice enthalpy in the solid state. The bonding to Li(+) in D6 and 18-crown-6 metal complexes was described by a quantum theory of atoms in molecules (QTAIM) analysis to be mostly electrostatic while the bonding to Ag(+) also had a significant charge transfer component. The charge transfer from both D6 and 18-crown-6 to Ag(+) and Li(+) metal ions was depicted by the QTAIM analysis to be of similar strength, and the difference in the

  9. Timescales of storage and recycling of crystal mush at Krafla Volcano, Iceland

    Science.gov (United States)

    Cooper, Kari M.; Sims, Kenneth W. W.; Eiler, John M.; Banerjee, Neil

    2016-06-01

    Processes in upper-crustal magma reservoirs such as recharge, magma mixing, recycling of previously crystallized material, and eruption affect both the physical state and the chemical composition of magmas. A growing body of evidence shows that crystals in intermediate or silicic volcanic rocks preserve records of these processes that may be obscured due to mixing in the liquid fraction of magmas. Fewer studies have focused on crystals in basaltic lavas, but these show evidence for a more subtle, but still rich record of magmatic processes. We present new 238U-230Th-226Ra data for plagioclase, combined with δ18O and trace-element measurements of the same crystal populations, from basalts erupted at Krafla Volcanic Center, Iceland. These data document the presence of multiple crystal populations within each sample, with chemical and oxygen isotope heterogeneity at a variety of scales: within individual crystals, between crystals in a given population, between crystal populations within the same sample, and between crystals in lavas erupted from different vents during the same eruption. Comparison to whole-rock or groundmass data shows that the majority of macroscopic crystals are not in trace-element or oxygen isotope equilibrium with their host liquids. The most likely explanation for these data is that the macroscopic crystals originated within a highly heterogeneous crystal mush in the shallow magma reservoir system. U-series and diffusion data indicate that the crystals (and therefore the mush) formed recently (likely within a few thousand years of eruption, and with a maximum age of 8-9 ka), and that the crystals resided in their host magma prior to eruption for decades to a few centuries at most. These data, in conjunction with other recent studies, suggest a model where erupted Icelandic magmas are the result of diverse magmas entering the crust, followed by complex interactions between melts and previously crystallized material at all crustal levels.

  10. Band structures and localization properties of aperiodic layered phononic crystals

    Energy Technology Data Exchange (ETDEWEB)

    Yan Zhizhong, E-mail: zzyan@bit.edu.cn [Department of Applied Mathematics, Beijing Institute of Technology, Beijing 100081 (China); Zhang Chuanzeng [Department of Civil Engineering, University of Siegen, D-57078 Siegen (Germany)

    2012-03-15

    The band structures and localization properties of in-plane elastic waves with coupling of longitudinal and transverse modes oblique propagating in aperiodic phononic crystals based on Thue-Morse and Rudin-Shapiro sequences are studied. Using transfer matrix method, the concept of the localization factor is introduced and the correctness is testified through the Rytov dispersion relation. For comparison, the perfect periodic structure and the quasi-periodic Fibonacci system are also considered. In addition, the influences of the random disorder, local resonance, translational and/or mirror symmetries on the band structures of the aperiodic phononic crystals are analyzed in this paper.

  11. Band structures and localization properties of aperiodic layered phononic crystals

    Science.gov (United States)

    Yan, Zhi-Zhong; Zhang, Chuanzeng

    2012-03-01

    The band structures and localization properties of in-plane elastic waves with coupling of longitudinal and transverse modes oblique propagating in aperiodic phononic crystals based on Thue-Morse and Rudin-Shapiro sequences are studied. Using transfer matrix method, the concept of the localization factor is introduced and the correctness is testified through the Rytov dispersion relation. For comparison, the perfect periodic structure and the quasi-periodic Fibonacci system are also considered. In addition, the influences of the random disorder, local resonance, translational and/or mirror symmetries on the band structures of the aperiodic phononic crystals are analyzed in this paper.

  12. Crystallization-induced properties from morphology-controlled organic crystals.

    Science.gov (United States)

    Park, Chibeom; Park, Ji Eun; Choi, Hee Cheul

    2014-08-19

    During the past two decades, many materials chemists have focused on the development of organic molecules that can serve as the basis of cost-effective and flexible electronic, optical, and energy conversion devices. Among the potential candidate molecules, metal-free or metal-containing conjugated organic molecules offer high-order electronic conjugation levels that can directly support fast charge carrier transport, rapid optoelectric responses, and reliable exciton manipulation. Early studies of these molecules focused on the design and synthesis of organic unit molecules that exhibit active electrical and optical properties when produced in the form of thin film devices. Since then, researchers have worked to enhance the properties upon crystallization of the unit molecules as single crystals provide higher carrier mobilities and exciton recombination yields. Most recently, researchers have conducted in-depth studies to understand how crystallization induces property changes, especially those that depend on specific crystal surfaces. The different properties that depend on the crystal facets have been of particular interest. Most unit molecules have anisotropic structures, and therefore produce crystals with several unique crystal facets with dissimilar molecular arrangements. These structural differences would also lead to diverse electrical conductance, optical absorption/emission, and even chemical interaction properties depending on the crystal facet investigated. To study the effects of crystallization and crystal facet-dependent property changes, researchers must grow or synthesize crystals of highly conjugated molecules that have both a variety of morphologies and high crystallinity. Morphologically well-defined organic crystals, that form structures such as wires, rods, disks, and cubes, provide objects that researchers can use to evaluate these material properties. Such structures typically occur as single crystals with well-developed facets with

  13. Liquid crystals in tribology.

    Science.gov (United States)

    Carrión, Francisco-José; Martínez-Nicolás, Ginés; Iglesias, Patricia; Sanes, José; Bermúdez, María-Dolores

    2009-09-18

    Two decades ago, the literature dealing with the possible applications of low molar mass liquid crystals, also called monomer liquid crystals (MLCs), only included about 50 references. Today, thousands of papers, conference reports, books or book chapters and patents refer to the study and applications of MLCs as lubricants and lubricant additives and efforts are made to develop new commercial applications. The development of more efficient lubricants is of paramount technological and economic relevance as it is estimated that half the energy consumption is dissipated as friction. MLCs have shown their ability to form ordered boundary layers with good load-carrying capacity and to lower the friction coefficients, wear rates and contact temperature of sliding surfaces, thus contributing to increase the components service life and to save energy. This review includes the use of MLCs in lubrication, and dispersions of MLCs in conventional polymers (PDMLCs). Finally, new lubricating system composed of MLC blends with surfactants, ionic liquids or nanophases are considered.

  14. Nonlinear Photonic Crystal Fibers

    DEFF Research Database (Denmark)

    Hansen, Kim Per

    2004-01-01

    , leading to reduced mode confinement and dispersion flexibility. In this thesis, we treat the nonlinear photonic crystal fiber – a special sub-class of photonic crystal fibers, the core of which has a diameter comparable to the wavelength of the light guided in the fiber. The small core results in a large...... nonlinear coefficient and in various applications, it is therefore possible to reduce the required fiber lengths quite dramatically, leading to increased stability and efficiency. Furthermore, it is possible to design these fibers with zero-dispersion at previously unreachable wavelengths, paving the way...... for completely new applications, especially in and near the visible wavelength region. One such application is supercontinuum generation. Supercontinuum generation is extreme broadening of pulses in a nonlinear medium (in this case a small-core fiber), and depending on the dispersion of the fiber, it is possible...

  15. Liquid Crystal Motion Picture Projector①

    Institute of Scientific and Technical Information of China (English)

    SHIYongji

    1997-01-01

    A liquid crystal moving picture projector and method are described.Light incident on a liquid crystal display-type device is selectively scattered or transmitted by respective portions of liquid crystal display,and a projection mechanism projects an image formed by either such scattered light or such transmitted light.A liquid cystal moving picture projector includes a liquid crystal display for creating characteristics of an image,and projecttion optics for projecting images sequentially created by the display.The display includes a liquid crystal material capable of temporary storing information at respective areas.The temporary storage may be a function of charge storing directly on liquid crystal material.A method of projecting plural images in sequence includes:creating an image or characteristics of an image in a liquid crystal material,storing such image in such liquid crystal material,directing light at such liquid crystal material,projecting such image as a function of light transmitted through or scattered by such liquid crystal material,and creating a further image in such liquid crystal material for subsequent projection.

  16. Textures of liquid crystals

    CERN Document Server

    Dierking, Ingo

    2006-01-01

    A unique compendium of knowledge on all aspects of the texture of liquid crystals, providing not just detailed information on texture formation and determination, but also an in-depth discussion of different characterization methods. Experts as well as graduates entering the field will find all the information they need in this handbook, while the magnitude of the color images make it valuable hands-on-reference.

  17. Crystalizing the Spinon Basis

    OpenAIRE

    Nakayashiki, Atsushi; Yamada, Yasuhiko

    1995-01-01

    The quasi-particle structure of the higher spin XXZ model is studied. We obtained a new description of crystals associated with the level $k$ integrable highest weight $U_q(\\widehat{sl_2})$ modules in terms of the creation operators at $q=0$ (the crystaline spinon basis). The fermionic character formulas and the Yangian structure of those integrable modules naturally follow from this description. We have also derived the conjectural formulas for the multi quasi-particle states at $q=0$.

  18. Photonic crystal optical memory

    Science.gov (United States)

    Lima, A. Wirth; Sombra, A. S. B.

    2011-06-01

    After several decades pushing the technology and the development of the world, the electronics is giving space for technologies that use light. We propose and analyze an optical memory embedded in a nonlinear photonic crystal (PhC), whose system of writing and reading data is controlled by an external command signal. This optical memory is based on optical directional couplers connected to a shared optical ring. Such a device can work over the C-Band of ITU (International Telecommunication Union).

  19. Crystals against cancer

    CERN Multimedia

    2009-01-01

    This is a remarkable example of direct technology transfer from particle physics to medicine. Clinical trials have begun in Portugal on a new medical imaging system for the diagnosis of breast cancer, which uses positron emission tomography (PET). The system, developed by a Portuguese consortium in collaboration with CERN and laboratories participating in the Crystal Clear collaboration, will detect even the smallest tumours and thus help avoid unnecessary biopsies.

  20. Phononic crystals fundamentals and applications

    CERN Document Server

    Adibi, Ali

    2016-01-01

    This book provides an in-depth analysis as well as an overview of phononic crystals. This book discusses numerous techniques for the analysis of phononic crystals and covers, among other material, sonic and ultrasonic structures, hypersonic planar structures and their characterization, and novel applications of phononic crystals. This is an ideal book for those working with micro and nanotechnology, MEMS (microelectromechanical systems), and acoustic devices. This book also: Presents an introduction to the fundamentals and properties of phononic crystals Covers simulation techniques for the analysis of phononic crystals Discusses sonic and ultrasonic, hypersonic and planar, and three-dimensional phononic crystal structures Illustrates how phononic crystal structures are being deployed in communication systems and sensing systems.

  1. Modern trends in technical crystallization

    Science.gov (United States)

    Matz, G.

    1980-04-01

    Interesting and significant developments have occurred in the last decade in both crystallization equipment and in the theory of crystallization process. In the field of technical crystallization new crystallizers have been developed and computer modelling has become important in scaling up and in the achievement of increased performance. The DP-Kristaller developed by Escher-Wyss-Tsukishima, the Brodie purifier, the sieve tray column having dancing balls, the automated multiple crystallization process due to Mützenberg and Saxer and the double belt cooler, all of which represent technical developments, are described in the first section. The second part of the paper reviews computer modelling of the fluidized bed crystallizer, chemical precipitation, flaking and prilling. Finally, there is a brief discussion of the impact of technical crystallization processes on environmental protection.

  2. Crystallization of undercooled liquid fenofibrate.

    Science.gov (United States)

    Amstad, Esther; Spaepen, Frans; Weitz, David A

    2015-11-28

    Formulation of hydrophobic drugs as amorphous materials is highly advantageous as this increases their solubility in water and therefore their bioavailability. However, many drugs have a high propensity to crystallize during production and storage, limiting the usefulness of amorphous drugs. We study the crystallization of undercooled liquid fenofibrate, a model hydrophobic drug. Nucleation is the rate-limiting step; once seeded with a fenofibrate crystal, the crystal rapidly grows by consuming the undercooled liquid fenofibrate. Crystal growth is limited by the incorporation of molecules into its surface. As nucleation and growth both entail incorporation of molecules into the surface, this process likely also limits the formation of nuclei and thus the crystallization of undercooled liquid fenofibrate, contributing to the good stability of undercooled liquid fenofibrate against crystallization.

  3. Quartz Crystal Microbalance Data

    Energy Technology Data Exchange (ETDEWEB)

    Baxamusa, S H

    2011-11-16

    We are using a Qpod quartz crystal microbalance (manufactured by Inficon) for use as a low-volume non-volatile residue analysis tool. Inficon has agreed to help troubleshoot some of our measurements and are requesting to view some sample data, which are attached. The basic principle of an NVR analysis is to evaporate a known volume of solvent, and weigh the remaining residue to determine the purity of the solvent. A typical NVR analysis uses 60 g of solvent and can measure residue with an accuracy of +/- 0.01 mg. The detection limit is thus (0.01 mg)/(60 g) = 0.17 ppm. We are attempting to use a quartz crystal microbalance (QCM) to make a similar measurement. The attached data show the response of the QCM as a 5-20 mg drop of solvent evaporates on its surface. The change in mass registered by the QCM after the drop evaporates is the residue that deposits on the crystal. On some measurements, the change in mass in less than zero, which is aphysical since the drop will leave behind {>=}0 mass of residue. The vendor, Inficon, has agreed to look at these data as a means to help troubleshoot the cause.

  4. Living liquid crystals

    Science.gov (United States)

    Zhou, Shuang; Sokolov, Andrey; Lavrentovich, Oleg D.; Aranson, Igor S.

    2014-01-01

    Collective motion of self-propelled organisms or synthetic particles, often termed “active fluid,” has attracted enormous attention in the broad scientific community because of its fundamentally nonequilibrium nature. Energy input and interactions among the moving units and the medium lead to complex dynamics. Here, we introduce a class of active matter––living liquid crystals (LLCs)––that combines living swimming bacteria with a lyotropic liquid crystal. The physical properties of LLCs can be controlled by the amount of oxygen available to bacteria, by concentration of ingredients, or by temperature. Our studies reveal a wealth of intriguing dynamic phenomena, caused by the coupling between the activity-triggered flow and long-range orientational order of the medium. Among these are (i) nonlinear trajectories of bacterial motion guided by nonuniform director, (ii) local melting of the liquid crystal caused by the bacteria-produced shear flows, (iii) activity-triggered transition from a nonflowing uniform state into a flowing one-dimensional periodic pattern and its evolution into a turbulent array of topological defects, and (iv) birefringence-enabled visualization of microflow generated by the nanometers-thick bacterial flagella. Unlike their isotropic counterpart, the LLCs show collective dynamic effects at very low volume fraction of bacteria, on the order of 0.2%. Our work suggests an unorthodox design concept to control and manipulate the dynamic behavior of soft active matter and opens the door for potential biosensing and biomedical applications. PMID:24474746

  5. Cholesterol crystal embolism (atheroembolism)

    Science.gov (United States)

    VENTURELLI, CHIARA; JEANNIN, GUIDO; SOTTINI, LAURA; DALLERA, NADIA; SCOLARI, FRANCESCO

    2006-01-01

    Cholesterol crystal embolism, known as atheroembolic disease, is caused by showers of cholesterol crystals from an atherosclerotic plaque that occludes small arteries. Embolization can occur spontaneously or as an iatrogenic complication from an invasive vascular procedure (angiography or vascular surgery) and after anticoagulant therapy. The atheroembolism can give rise to different degrees of renal impairment. Some patients show a moderate loss of renal function, others severe renal failure requiring dialysis. Renal outcome can be variable: some patients deteriorate or remain on dialysis, some improve and some remain with chronic renal impairment. Clinically, three types of atheroembolic renal disease have been described: acute, subacute or chronic. More frequently a progressive loss of renal function occurs over weeks. Atheroembolization can involve the skin, gastrointestinal system and central nervous system. The diagnosis is difficult and controversial for the protean extrarenal manifestations. In the past, the diagnosis was often made post-mortem. In the last 10 yrs, awareness of atheroembolic renal disease has improved. The correct diagnosis requires the clinician to be alert. The typical patient is a white male aged >60 yrs with a history of hypertension, smoking and arterial disease. The presence of a classic triad (precipitating event, renal failure and peripheral cholesterol crystal embolization) suggests the diagnosis. This can be confirmed by a biopsy of the target organs. A specific treatment is lacking; however, it is an important diagnosis to make because an aggressive therapeutic approach can be associated with a more favorable clinical outcome. PMID:21977265

  6. Instabilities in liquid crystals

    CERN Document Server

    Barclay, G J

    1998-01-01

    and we examine the differences which occur for differing dielectric anisotropies. Finally, in Chapter 7 we study how a sample of smectic C liquid crystal behaves when it is subjected to a uniform shear flow within the smectic plane. We find travelling wave solutions for the behaviour of the c-director and adapt these solutions to incorporate the effects of an applied field. This thesis contains theoretical work dealing with the effects of magnetic and electric fields on samples of nematic, smectic A and smectic C liquid crystals. Some background material along with the continuum theory is introduced in Chapter 2. In Chapter 3 we consider the effect on the director within an infinite sample of nematic liquid crystal which is subjected to crossed electric and magnetic fields. In particular we examine the stability of the travelling waves which describe the director motion by considering the behaviour of the stable perturbations as time increases. The work of Chapter 4 examines a bounded sample of smectic A liqu...

  7. Few-quantum-dot lasing in photonic crystal nanocavities

    DEFF Research Database (Denmark)

    Liu, Jin; Ates, Serkan; Stobbe, Søren;

    2011-01-01

    Photonic crystal nanolasers have attracted great interest both for fundamental research and applications in the past decade. In photonic crystal cavities, the leakage to optical modes is strongly reduced, which increases the spontaneous emission coupling factor, β. This is a crucial parameter for...... advanced semiconductor models of photonic crystal nanolasers is still missing [2]. The goal of this work is to get a deep understanding of the quantum dots based nanocavity lasers by comparing experiments to theory.......Photonic crystal nanolasers have attracted great interest both for fundamental research and applications in the past decade. In photonic crystal cavities, the leakage to optical modes is strongly reduced, which increases the spontaneous emission coupling factor, β. This is a crucial parameter...... for the threshold characteristics of lasers. With increasing β, the well-known step-like threshold behavior becomes smoother. Although the smooth lasing transitions of photonic crystal nanolasers were observed and fitted by traditional rate equation models [1], a systematic comparison between experiments and more...

  8. On dewetting of thin films due to crystallization (crystallization dewetting).

    Science.gov (United States)

    Habibi, Mehran; Rahimzadeh, Amin; Eslamian, Morteza

    2016-03-01

    Drying and crystallization of a thin liquid film of an ionic or a similar solution can cause dewetting in the resulting thin solid film. This paper aims at investigating this type of dewetting, herein termed "crystallization dewetting", using PbI2 dissolved in organic solvents as the model solution. PbI2 solid films are usually used in X-ray detection and lead halide perovskite solar cells. In this work, PbI2 films are fabricated using spin coating and the effect of major parameters influencing the crystallization dewetting, including the type of the solvent, solution concentration, drying temperature, spin speed, as well as imposed vibration on the substrate are studied on dewetting, surface profile and coverage, using confocal scanning laser microscopy. Simplified hydrodynamic governing equations of crystallization in thin films are presented and using a mathematical representation of the process, it is phenomenologically demonstrated that crystallization dewetting occurs due to the absorption and consumption of the solution surrounding a growing crystal. Among the results, it is found that a low spin speed (high thickness), a high solution concentration and a low drying temperature promote crystal growth, and therefore crystallization dewetting. It is also shown that imposed vibration on the substrate can affect the crystal size and crystallization dewetting.

  9. The fluid phenomena in the crystallization of the protein crystal

    Institute of Scientific and Technical Information of China (English)

    Duan Li; Kang Qi

    2008-01-01

    This paper reports that an optical diagnostic system consisting of Maeh-Zehnder interferometer with a phase shift device and image processor has been used for study of the kinetics of protein crystal growing process. The crystallization process of protein crystal by vapour diffusion is investigated. The interference fringes are observed in real time. The present experiment demonstrates that the diffusion and the sedimentation influence the crystallization of protein crystal which grows in solution, and the concentration capillary convection associated with surface tension occurs at the vicinity of free surface of the protein mother liquor, and directly affects on the outcome of protein crystallization. So far the detailed analysis and the important role of the fluid phenomena in protein crystallization have been discussed a little in both space- and ground-based crystal growth experiments. It is also found that these fluid phenomena affect theoutcome of protein crystallization, regular growth, and crystal quality. This may explain the fact that many results of space-based investigation do not show overall improvement.

  10. Discrete breathers in crystals

    Science.gov (United States)

    Dmitriev, S. V.; Korznikova, E. A.; Baimova, Yu A.; Velarde, M. G.

    2016-05-01

    It is well known that periodic discrete defect-containing systems, in addition to traveling waves, support vibrational defect-localized modes. It turned out that if a periodic discrete system is nonlinear, it can support spatially localized vibrational modes as exact solutions even in the absence of defects. Since the nodes of the system are all on equal footing, it is only through the special choice of initial conditions that a group of nodes can be found on which such a mode, called a discrete breather (DB), will be excited. The DB frequency must be outside the frequency range of the small-amplitude traveling waves. Not resonating with and expending no energy on the excitation of traveling waves, a DB can theoretically conserve its vibrational energy forever provided no thermal vibrations or other perturbations are present. Crystals are nonlinear discrete systems, and the discovery in them of DBs was only a matter of time. It is well known that periodic discrete defect-containing systems support both traveling waves and vibrational defect-localized modes. It turns out that if a periodic discrete system is nonlinear, it can support spatially localized vibrational modes as exact solutions even in the absence of defects. Because the nodes of the system are all on equal footing, only a special choice of the initial conditions allows selecting a group of nodes on which such a mode, called a discrete breather (DB), can be excited. The DB frequency must be outside the frequency range of small-amplitude traveling waves. Not resonating with and expending no energy on the excitation of traveling waves, a DB can theoretically preserve its vibrational energy forever if no thermal vibrations or other perturbations are present. Crystals are nonlinear discrete systems, and the discovery of DBs in them was only a matter of time. Experimental studies of DBs encounter major technical difficulties, leaving atomistic computer simulations as the primary investigation tool. Despite

  11. Heat-labile enterotoxin crystal forms with variable A/B5 orientation. Analysis of conformational flexibility

    NARCIS (Netherlands)

    Sixma, Titia K.; Aguirre, Angel; Terwisscha van Scheltinga, Anke C.; Wartna, Ellen S.; Kalk, Kor H.; Hol, Wim G.J.

    1992-01-01

    A new native crystal form of heat-labile enterotoxin (LT) has two AB5 complexes in the asymmetric unit with different orientations of the A subunit with respect to the B pentamer. Comparison with other crystal forms of LT shows that there is considerable conformational freedom for orientating the A

  12. Heat-labile enterotoxin crystal forms with variable A/B5 orientation. Analysis of conformational flexibility

    NARCIS (Netherlands)

    Sixma, Titia K.; Aguirre, Angel; Terwisscha van Scheltinga, Anke C.; Wartna, Ellen S.; Kalk, Kor H.; Hol, Wim G.J.

    1992-01-01

    A new native crystal form of heat-labile enterotoxin (LT) has two AB, complexes in the asymmetric unit with different orientations of the A subunit with respect to the B pentamer. Comparison with other crystal forms of LT shows that there is considerable conformational freedom for orientating the A

  13. Investigations on the growth, optical, thermal, dielectric, and laser damage threshold properties of crystal violet dye-doped potassium acid phthalate single crystal

    Science.gov (United States)

    Rao, G. Babu; Rajesh, P.; Ramasamy, P.

    2016-03-01

    Influence of crystal violet dye with different concentration on potassium acid phthalate single crystal grown by conventional method has been studied. No change has been observed in the structure, whereas changes have been observed in the external morphology of the crystal when the dyes are incorporated in the crystal lattice. Thermogravimetric and differential thermal analyses show the onset decomposition temperatures to be at 302, 285, 284, and 285 °C for pure, 0.1, 0.3, and 0.5 mol% crystal violet-doped potassium acid phthalate crystals, respectively. The dielectric measurement was carried out on the grown crystals as a function of frequency at various temperatures. In addition, strong luminescent emission bands at 638, 648, and 640 nm were observed in which the relative intensity was found to be reversed as a result of doping concentration. The laser damage threshold value significantly increased for dye-doped crystal in comparison with pure crystal which may make it suitable for the solid-state dye laser applications.

  14. Additive manufacturing of micrometric crystallization vessels and single crystals

    Science.gov (United States)

    Halevi, Oded; Jiang, Hui; Kloc, Christian; Magdassi, Shlomo

    2016-11-01

    We present an all-additive manufacturing method that is performed at mild conditions, for the formation of organic single crystals at specific locations, without any photolithography prefabrication process. The method is composed of two steps; inkjet printing of a confinement frame, composed of a water soluble electrolyte. Then, an organic semiconductor solution is printed within the confinement to form a nucleus at a specific location, followed by additional printing, which led to the growth of a single crystal. The specific geometry of the confinement enables control of the specific locations of the single crystals, while separating the nucleation and crystal growth processes. By this method, we printed single crystals of perylene, which are suitable for the formation of OFETs. Moreover, since this method is based on a simple and controllable wet deposition process, it enables formation of arrays of single crystals at specific locations, which is a prerequisite for mass production of active organic elements on flexible substrates.

  15. Crystal growth in salt efflorescence

    Science.gov (United States)

    Zehnder, Konrad; Arnold, Andreas

    1989-09-01

    Salt efflorescences strongly affect wall paintings and other monuments. The external factors governing the crystal habits and aggregate forms are studied phenomenologically in laboratory experiments. As salt contaminated materials dry, slats crystallize forming distinct sequences of crystal habits and aggregate forms on and underneath the surfaces. Four phases may be distinguished: (1) Large individual crystals with equilibrium forms grow immersed in a thick solution film; (2) granular crusts of small isometric crystals grow covered by a thin solution film; (3) fibrous crusts of columnar crystals grow from a coherent but thin solution film so that the crystals are in contact with solution only at their base; (4) whiskers grow from isolated spots of very thin solution films into the air. The main factor governing these morphologies is the humidity of the substrate. A porous material cracks while granular crystals (approaching their equilibrium forms) grow within the large pores. As the fissures widen, the habits pass into columnar crystals and then into whiskers. Because this succession corresponds to the crystallization sequence on the substrate surface it can be traced back to the same growth conditions.

  16. DDA Computations of Porous Aggregates with Forsterite Crystals: Effects of Crystal Shape and Crystal Mass Fraction

    Science.gov (United States)

    Wooden, Diane H.; Lindsay, Sean S.; Harker, David; Woodward, Charles; Kelley, Michael S.; Kolokolova, Ludmilla

    2015-01-01

    Porous aggregate grains are commonly found in cometary dust samples and are needed to model cometary IR spectral energy distributions (SEDs). Models for thermal emissions from comets require two forms of silicates: amorphous and crystalline. The dominant crystal resonances observed in comet SEDs are from Forsterite (Mg2SiO4). The mass fractions that are crystalline span a large range from 0.0 25 AU at 1E6 yr) by inner disk materials (crystals) are challenged to yield the highend-range of cometary crystal mass fractions. However, in current thermal models, Forsterite crystals are not incorporated into larger aggregate grains but instead only are considered as discrete crystals. A complicating factor is that Forsterite crystals with rectangular shapes better fit the observed spectral resonances in wavelength (11.0-11.15 microns, 16, 19, 23.5, 27, and 33 microns), feature asymmetry and relative height (Lindley et al. 2013) than spherically or elliptically shaped crystals. We present DDA-DDSCAT computations of IR absorptivities (Qabs) of 3 micron-radii porous aggregates with 0.13 crystals. We can produce crystal resonances with similar appearance to the observed resonances of comet Hale- Bopp. Also, a lower mass fraction of crystals in aggregates can produce the same spectral contrast as a higher mass fraction of discrete crystals; the 11micron and 23 micron crystalline resonances appear amplified when crystals are incorporated into aggregates composed otherwise of spherically shaped amorphous Fe-Mg olivines and pyroxenes. We show that the optical properties of a porous aggregate is not linear combination of its monomers, so aggregates need to be computed. We discuss the consequence of lowering comet crystal mass fractions by modeling IR SEDs with aggregates with crystals, and the implications for radial transport models of our protoplanetary disk.

  17. Crystal growth and structural analysis of zirconium sulphoselenide single crystals

    Indian Academy of Sciences (India)

    K R Patel; R D Vaidya; M S Dave; S G Patel

    2008-08-01

    A series of zirconium sulphoselenide (ZrSSe3–, where = 0, 0.5, 1, 1.5, 2, 2.5, 3) single crystals have been grown by chemical vapour transport technique using iodine as a transporting agent. The optimum condition for the growth of these crystals is given. The stoichiometry of the grown crystals were confirmed on the basis of energy dispersive analysis by X-ray (EDAX) and the structural characterization was accomplished by X-ray diffraction (XRD) studies. The crystals are found to possess monoclinic structure. The lattice parameters, volume, particle size and X-ray density have been carried out for these crystals. The effect of sulphur proportion on the lattice parameter, unit cell volume and X-ray density in the series of ZrSSe3– single crystals have been studied and found to decrease in all these parameters with rise in sulphur proportion. The grown crystals were examined under optical zoom microscope for their surface topography study. Hall effect measurements were carried out on grown crystals at room temperature. The negative value of Hall coefficient implies that these crystals are -type in nature. The conductivity is found to decrease with increase of sulphur content in the ZrSSe3– series. The electrical resistivity parallel to c-axis as well as perpendicular to -axis have been carried out in the temperature range 303–423 K. The results obtained are discussed in detail.

  18. Extracting trends from two decades of microgravity macromolecular crystallization history

    Science.gov (United States)

    Judge, Russell A.; Snell, Edward H.; van der Woerd, Mark J.

    2005-01-01

    Since the 1980s hundreds of macromolecular crystal growth experiments have been performed in the reduced acceleration environment of an orbiting spacecraft. Significant enhancements in structural knowledge have resulted from X-ray diffraction of the crystals grown. Similarly, many samples have shown no improvement or degradation in comparison to those grown on the ground. A complex series of interrelated factors affect these experiments and by building a comprehensive archive of the results it was aimed to identify factors that result in success and those that result in failure. Specifically, it was found that dedicated microgravity missions increase the chance of success when compared with those where crystallization took place as a parasitic aspect of the mission. It was also found that the chance of success could not be predicted based on any discernible property of the macromolecule available to us.

  19. Functional substitution of coordination polyhedron in crystal structure of silicates

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    On the bases of the study of comparative crystal chemistry of silicates it has been concluded that the octahedra and square pyramids of Ti-O and Zr-O play functional role of tetrahedra of Si-O in the construction of crystal structures.Therefore,those silicates may be named titano- and zircono-silicates.Because of the functional similarity of coordination polyhedra,the structures of cristobalite and feldspar have been compared with those of perovskite and garnet,respectively.As a new concept,the functional replacement of tetrahedra by octahedra and/or pyramids is defined by the authors of this paper for favorable comparison of relative crystal structures.

  20. Semiconducting polymer single crystals and devices (Conference Presentation)

    Science.gov (United States)

    Dong, Huanli

    2016-11-01

    Highly ordered organic semiconductors in solid state with optimal molecular packing are critical to their electrical performance. Single crystals with long-range molecular orders and nearly perfect molecular packing are the best candidates, which already have been verified to exhibit the highest performance whether based on inorganic or small organic materials. However, in comparison, preparing high quality polymer crystals remains a big challenge in polymer science because of the easy entanglements of the long and flexible polymer chains during self-assembly process, which also significantly limits the development of their crystalline polymeric electronic devices. Here we have carried out systematical investigations to prepare high quality semiconducting polymers and high performance semiconducting polymer crystal optoelectronic devices have been successfully fabricated. The semiconducting polymeric devices demonstrate significantly enhanced charge carreir transport compared to their thin films, and the highest carreir mobiltiy could be approcahing 30 cm2 V-1s-1, one of the highest mobiltiy values for polymer semiconductors.

  1. Crystal structure of inactive form of Rab3B

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Wei; Shen, Yang; Jiao, Ronghong; Liu, Yanli; Deng, Lingfu; Qi, Chao (Hebei); (Toronto); (Huazhong)

    2012-06-28

    Rab proteins are the largest family of ras-related GTPases in eukaryotic cells. They act as directional molecular switches at membrane trafficking, including vesicle budding, cargo sorting, transport, tethering, and fusion. Here, we generated and crystallized the Rab3B:GDP complex. The structure of the complex was solved to 1.9 {angstrom} resolution and the structural base comparison with other Rab3 members provides a structural basis for the GDP/GTP switch in controlling the activity of small GTPase. The comparison of charge distribution among the members of Rab3 also indicates their different roles in vesicular trafficking.

  2. Dissipation by a crystallization process

    Science.gov (United States)

    Dorosz, Sven; Voigtmann, Thomas; Schilling, Tanja

    2016-01-01

    We discuss crystallization as a non-equilibrium process. In a system of hard spheres under compression at a constant rate, we quantify the amount of heat that is dissipated during the crystallization process. We interpret the dissipation as arising from the resistance of the system against phase transformation. An intrinsic compression rate is identified that separates a quasi-static regime from one of rapidly driven crystallization. In the latter regime the system crystallizes more easily, because new relaxation channels are opened, at the cost of forming a higher fraction of non-equilibrium crystal structures. We rationalize the change in the crystallization mechanism by analogy with shear thinning, in terms of a kinetic competition between near-equilibrium relaxation and external driving.

  3. Lasing from fluorescent protein crystals.

    Science.gov (United States)

    Oh, Heon Jeong; Gather, Malte C; Song, Ji-Joon; Yun, Seok Hyun

    2014-12-15

    We investigated fluorescent protein crystals for potential photonic applications, for the first time to our knowledge. Rod-shaped crystals of enhanced green fluorescent protein (EGFP) were synthesized, with diameters of 0.5-2 μm and lengths of 100-200 μm. The crystals exhibit minimal light scattering due to their ordered structure and generate substantially higher fluorescence intensity than EGFP or dye molecules in solutions. The magnitude of concentration quenching in EGFP crystals was measured to be about 7-10 dB. Upon optical pumping at 485 nm, individual EGFP crystals located between dichroic mirrors generated laser emission with a single-mode spectral line at 513 nm. Our results demonstrate the potential of protein crystals as novel optical elements for self-assembled, micro- or nano-lasers and amplifiers in aqueous environment.

  4. Crystal structure of cafenstrole

    Directory of Open Access Journals (Sweden)

    Gihaeng Kang

    2015-08-01

    Full Text Available The title compound (systematic name: N,N-diethyl-3-mesitylsulfonyl-1H-1,2,4-triazole-1-carboxamide, C16H22N4O3S, is a triazole herbicide. The dihedral angle between the planes of the triazole and benzene ring planes is 88.14 (10°. In the crystal, C—H...O hydrogen bonds and weak C—H...π interactions link adjacent molecules, forming one-dimensional chains along the a axis.

  5. Crystallization Behavior of Waxes

    OpenAIRE

    Jana, Sarbojeet

    2016-01-01

    Partially hydrogenated oil (PHO) has no longer GRAS status. However, PHO is one of the important ingredients in bakery and confectionary industry and therefore the food industry is seeking for an alternative fat to replace PHO. Waxes have shown promise to fulfill that demand because of its easy availability and cheap in price. Waxes with high melting points (> 40 °C) help in the crystallization process when mixed with low melting point oils. A crystalline network is formed in this wax/oil cry...

  6. Hardness of metallic crystals

    Indian Academy of Sciences (India)

    Wuhui Li; Fengzhang Ren; Juanhua Su; Zhanhong Ma; Ke Cao; Baohong Tian

    2011-07-01

    This paper presents a new formula for calculating the hardness of metallic crystals, resulted from the research on the critical grain size with stable dislocations. The formula is = 6 /[(1 – )], where is the hardness, the coefficient, the shear modulus, the Poisson’s ratio, a function of the radius of an atom () and the electron density at the atom interface (). The formula will not only be used to testify the critical grain size with stable dislocations, but also play an important role in the understanding of mechanical properties of nanocrystalline metals.

  7. Radiating dipoles in photonic crystals

    OpenAIRE

    Busch, Kurt; Vats, Nipun; John, Sajeev; Sanders, Barry C.

    2000-01-01

    The radiation dynamics of a dipole antenna embedded in a Photonic Crystal are modeled by an initially excited harmonic oscillator coupled to a non--Markovian bath of harmonic oscillators representing the colored electromagnetic vacuum within the crystal. Realistic coupling constants based on the natural modes of the Photonic Crystal, i.e., Bloch waves and their associated dispersion relation, are derived. For simple model systems, well-known results such as decay times and emission spectra ar...

  8. Inorganic Crystal Structure Database (ICSD)

    Science.gov (United States)

    SRD 84 FIZ/NIST Inorganic Crystal Structure Database (ICSD) (PC database for purchase)   The Inorganic Crystal Structure Database (ICSD) is produced cooperatively by the Fachinformationszentrum Karlsruhe(FIZ) and the National Institute of Standards and Technology (NIST). The ICSD is a comprehensive collection of crystal structure data of inorganic compounds containing more than 140,000 entries and covering the literature from 1915 to the present.

  9. Negative refraction in photonic crystals

    OpenAIRE

    Baba, T.; Matsumoto, T.; Asatsuma, T.

    2008-01-01

    Photonic crystals are multidimensional periodic gratings, in which the light propagation is dominated by Bragg diffraction that appears to be refraction at the flat surfaces of the crystals. The refraction angle from positive to negative, perfectly or only partially obeying Snell’s law, can be tailored based on photonic band theory. Negative refraction enables novel prism, collimation, and lens effects. Because photonic crystals usually consist of two transparent media, these effects occur at...

  10. Magnetic Field Applications in Semiconductor Crystal Growth and Metallurgy

    Science.gov (United States)

    Mazuruk, Konstantin; Ramachandran, Narayanan; Grugel, Richard; Curreri, Peter A. (Technical Monitor)

    2002-01-01

    The Traveling Magnetic Field (TMF) technique, recently proposed to control meridional flow in electrically conducting melts, is reviewed. In particular, the natural convection damping capability of this technique has been numerically demonstrated with the implication of significantly improving crystal quality. Advantages of the traveling magnetic field, in comparison to the more mature rotating magnetic field method, are discussed. Finally, results of experiments with mixing metallic alloys in long ampoules using TMF is presented

  11. Research on YB68 for Microwave Acoustic Crystals

    Science.gov (United States)

    1974-11-01

    techniques. Comparisons were made among sapphire crystals grown by Verneuil , Czochralski, and chemical vapor deposition tech- niques, and MgAlsO, spinel grown...long memory time, microwave ultrasonic delay lines. Information on sapphire , spinel, yttrium aluminum garnet, and yttrium boride is presented. At...and for longitudinal waves in P-rhombohedral boron and Al 0 3 ( sapphire ). At present, delay lines are constructed prircipally from sapphire , using

  12. Numerical methods for modeling photonic-crystal VCSELs

    DEFF Research Database (Denmark)

    Dems, Maciej; Chung, Il-Sug; Nyakas, Peter

    2010-01-01

    We show comparison of four different numerical methods for simulating Photonic-Crystal (PC) VCSELs. We present the theoretical basis behind each method and analyze the differences by studying a benchmark VCSEL structure, where the PC structure penetrates all VCSEL layers, the entire top-mirror DBR...... to the effective index method. The simulation results elucidate the strength and weaknesses of the analyzed methods; and outline the limits of applicability of the different models....

  13. Crystallization and Polymorphism of Felodipine

    DEFF Research Database (Denmark)

    Surov, A. O.; Solanko, K. A.; Bond, A. D.;

    2012-01-01

    . The crystal structures of the new forms III and IV were determined using single-crystal X-ray diffraction. Forms I, II, and III were obtained in bulk form and characterized by a variety of analytical methods, including thermal analysis, solution calorimetry, intrinsic dissolution rate measurement......, and solubility measurement. Form IV could be obtained only as a few isolated single crystals, and its crystallization could not be reproduced. On the basis of the measured thermochemical data and solubility studies, form I appears to be the thermodynamically most stable phase at ambient conditions, although...

  14. Crystal engineering: A brief overview

    Indian Academy of Sciences (India)

    Gautam R Desiraju

    2010-09-01

    Crystal structures of organic and metal-organic compounds have been determined in enormous numbers over the past century, and at the time of writing this review, the Cambridge Structural Database has just crossed the half million mark. The possibility of designing a particular crystal packing is, however, of more recent origin and the subject of crystal engineering has addressed this possibility, more or less systematically, during the past 30 years. Crystal engineering demands a detailed and thorough knowledge of intermolecular interactions, which act as the supramolecular glue that binds molecules into crystals. It also requires systematic strategies for the design of a crystal, the architectural blueprint as it were. Finally, this enterprise needs to be geared towards a useful property in that the crystal that is being designed is a functional one. All these features of the subject are directly or indirectly connected with the fact that there is a very large database of known crystal structures that is available to the crystal engineer. This review attempts to briefly survey the current scenario in this expanding subject.

  15. Photonic crystal fibers in biophotonics

    Science.gov (United States)

    Tuchin, Valery V.; Skibina, Julia S.; Malinin, Anton V.

    2011-12-01

    We observed recent experimental results in area of photonic crystal fibers appliance. Possibility of creation of fiberbased broadband light sources for high resolution optical coherence tomography is discussed. Using of femtosecond pulse laser allows for generation of optical radiation with large spectral width in highly nonlinear solid core photonic crystal fibers. Concept of exploitation of hollow core photonic crystal fibers in optical sensing is demonstrated. The use of photonic crystal fibers as "smart cuvette" gives rise to efficiency of modern optical biomedical analysis methods.

  16. Photonic Crystal Optical Tweezers

    CERN Document Server

    Wilson, Benjamin K; Bachar, Stephanie; Knouf, Emily; Bendoraite, Ausra; Tewari, Muneesh; Pun, Suzie H; Lin, Lih Y

    2009-01-01

    Non-invasive optical manipulation of particles has emerged as a powerful and versatile tool for biological study and nanotechnology. In particular, trapping and rotation of cells, cell nuclei and sub-micron particles enables unique functionality for various applications such as tissue engineering, cancer research and nanofabrication. We propose and demonstrate a purely optical approach to rotate and align particles using the interaction of polarized light with photonic crystal nanostructures to generate enhanced trapping force. With a weakly focused laser beam we observed efficient trapping and transportation of polystyrene beads with sizes ranging from 10 um down to 190 nm as well as cancer cell nuclei. In addition, we demonstrated alignment of non-spherical particles using a 1-D photonic crystal structure. Bacterial cells were trapped, rotated and aligned with optical intensity as low as 17 uW/um^2. Finite-difference time domain (FDTD) simulations of the optical near-field and far-field above the photonic c...

  17. Frustrated polymer crystal structures

    Science.gov (United States)

    Lotz, B.; Strasbourg, 67083

    1997-03-01

    Several crystal structures or polymorphs of chiral or achiral polymers and biopolymers with three fold conformation of the helix have been found to conform to a common and -with one exception(Puterman, M. et al, J. Pol. Sci., Pol. Phys. Ed., 15, 805 (1977))- hitherto unsuspected packing scheme. The trigonal unit-cell contains three isochiral helices; the azimuthal setting of one helix differs significantly from that of the other two, leading to a so-called frustrated packing scheme, in which the environment of conformationally identical helices differs. Two variants of the frustrated scheme are analyzed. Similarities with frustrated two dimensional magnetic systems are underlined. Various examples of frustration in polymer crystallography are illustrated via the elucidation or reinterpretation of crystal phases or polymorphs of polyolefins, polyesters, cellulose derivatives and polypeptides. Structural manifestations (including AFM evidence) and morphological consequences of frustration are presented, which help diagnose the existence of this original packing of polymers.(Work done with L. Cartier, D. Dorset, S. Kopp, T. Okihara, M. Schumacher, W. Stocker.)

  18. Tunable Topological Phononic Crystals

    KAUST Repository

    Chen, Ze-Guo

    2016-05-27

    Topological insulators first observed in electronic systems have inspired many analogues in photonic and phononic crystals in which remarkable one-way propagation edge states are supported by topologically nontrivial band gaps. Such band gaps can be achieved by breaking the time-reversal symmetry to lift the degeneracy associated with Dirac cones at the corners of the Brillouin zone. Here, we report on our construction of a phononic crystal exhibiting a Dirac-like cone in the Brillouin zone center. We demonstrate that simultaneously breaking the time-reversal symmetry and altering the geometric size of the unit cell result in a topological transition that we verify by the Chern number calculation and edge-mode analysis. We develop a complete model based on the tight binding to uncover the physical mechanisms of the topological transition. Both the model and numerical simulations show that the topology of the band gap is tunable by varying both the velocity field and the geometric size; such tunability may dramatically enrich the design and use of acoustic topological insulators.

  19. Crystal Compton Camera

    Energy Technology Data Exchange (ETDEWEB)

    Ziock, Klaus-Peter [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Braverman, Joshua B. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Harrison, Mark J. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Hornback, Donald Eric [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Fabris, Lorenzo [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Newby, Jason [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2013-09-26

    Stand-off detection is one of the most important radiation detection capabilities for arms control and the control of illicit nuclear materials. For long range passive detection one requires a large detector and a means of “seeing through” the naturally occurring and varying background radiation, i.e. imaging. Arguably, Compton imaging is the best approach over much of the emission band suitable for long range detection. It provides not only imaging, but more information about the direction of incidence of each detected gamma-ray than the alternate approach of coded-aperture imaging. The directional information allows one to reduce the background and hence improve the sensitivity of a measurement. However, to make an efficient Compton imager requires localizing and measuring the simultaneous energy depositions when gamma-rays Compton scatter and are subsequently captured within a single, large detector volume. This concept has been demonstrated in semi-conductor detectors (HPGe, CZT, Si) but at ~ $1k/cm3 these materials are too expensive to build the large systems needed for standoff detection. Scintillator detectors, such as NaI(Tl), are two orders of magnitude less expensive and possess the energy resolution required to make such an imager. However, they do not currently have the ability to localize closely spaced, simultaneous energy depositions in a single large crystal. In this project we are applying a new technique that should, for the first time ever, allow cubic-millimeter event localization in a bulk scintillator crystal.

  20. Electron spectroscopy of crystals

    CERN Document Server

    Nemoshkalenko, V V

    1979-01-01

    This book is conceived as a monograph, and represents an up-to-date collection of information concerning the use of the method of X-ray photoelectron spec­ troscopy in the study of the electron structure of crystals, as well as a personal interpretation of the subject by the authors. In a natural way, the book starts in Chapter 1 with a recapitulation of the fundamentals of the method, basic relations, principles of operation, and a com­ parative presentation of the characteristics and performances of the most com­ monly used ESCA instruments (from the classical ones-Varian, McPherson, Hewlett Packard, and IEEE-up to the latest model developed by Professor Siegbahn in Uppsala), and continues with a discussion of some of the difficult problems the experimentalist must face such as calibration of spectra, prepara­ tion of samples, and evaluation of the escape depth of electrons. The second chapter is devoted to the theory of photoemission from crystal­ line solids. A discussion of the methods of Hartree-Fo...

  1. Measurement of neutron detection efficiencies in NaI using the Crystal Ball detector

    Energy Technology Data Exchange (ETDEWEB)

    Stanislaus, T.D.S.; Koetke, D.D. E-mail: donald.koetke@valpo.edu; Allgower, C.; Bekrenev, V.; Benslama, K.; Berger, E.; Briscoe, W.J.; Clajus, M.; Comfort, J.R.; Craig, K.; Gibson, A.; Grosnick, D.; Huber, G.M.; Isenhower, D.; Kasprzyk, T.; Knecht, N.; Koulbardis, A.; Kozlenko, N.; Kruglov, S.; Kycia, T.; Lolos, G.J.; Lopatin, I.; Manley, D.M.; Manweiler, R.; Marusic, A.; McDonald, S.; Nefkens, B.M.K.; Olmsted, J.; Papandreou, Z.; Peaslee, D.; Peterson, R.J.; Phaisangittisakul, N.; Pulver, M.; Ramirez, A.F.; Sadler, M.; Shafi, A.; Slaus, I.; Spinka, H.; Starostin, A.; Staudenmaier, H.M.; Supek, I.; Thoms, J.; Tippens, W.B

    2001-04-21

    We report on a measurement of the neutron detection efficiency in NaI crystals in the Crystal Ball (CB) detector obtained from a study of {pi}{sup -}p{yields}{pi} degree sign n reactions at the Brookhaven National Laboratory AGS. A companion GEANT-based Monte Carlo study has been done to simulate these reactions in the CB, and a comparison with the data is provided.

  2. Preparation and thermal decomposition mechanism of Mg,Al-hydrotalcite nano-crystals with titania doping

    Institute of Scientific and Technical Information of China (English)

    REN Qing-li; LUO Qiang

    2006-01-01

    The highly pure nano-crystal Mg,Al-hydrotalcite with titania doping was synthesized by one-step liquid reaction method at atmospheric pressure. The preparation of the Mg,Al-hydrotalcite nano-crystal after doping titania was investigated according to the results of XRD,TEM,IR and DSC. Moreover,based on the DSC test results,the thermal mechanism functions of the Mg,Al-hydrotalcite with titania doping were studied after calculation and comparison.

  3. Measurement of neutron detection efficiencies in NaI using the Crystal Ball detector

    Science.gov (United States)

    Stanislaus, T. D. S.; Koetke, D. D.; Allgower, C.; Bekrenev, V.; Benslama, K.; Berger, E.; Briscoe, W. J.; Clajus, M.; Comfort, J. R.; Craig, K.; Gibson, A.; Grosnick, D.; Huber, G. M.; Isenhower, D.; Kasprzyk, T.; Knecht, N.; Koulbardis, A.; Kozlenko, N.; Kruglov, S.; Kycia, T.; Lolos, G. J.; Lopatin, I.; Manley, D. M.; Manweiler, R.; Marusic, A.; McDonald, S.; Nefkens, B. M. K.; Olmsted, J.; Papandreou, Z.; Peaslee, D.; Peterson, R. J.; Phaisangittisakul, N.; Pulver, M.; Ramirez, A. F.; Sadler, M.; Shafi, A.; Slaus, I.; Spinka, H.; Starostin, A.; Staudenmaier, H. M.; Supek, I.; Thoms, J.; Tippens, W. B.

    2001-04-01

    We report on a measurement of the neutron detection efficiency in NaI crystals in the Crystal Ball (CB) detector obtained from a study of π-p→ π°n reactions at the Brookhaven National Laboratory AGS. A companion GEANT-based Monte Carlo study has been done to simulate these reactions in the CB, and a comparison with the data is provided.

  4. Evaluation of CZT crystals from the former Soviet Union

    CERN Document Server

    Hermon, H; James, R B; Antolak, A J; Morse, D H; Brunett, B A; Hackett, C; Tarver, E; Komar, V; Goorsky, M S; Yoon, H; Kolesnikov, N N; Toney, J; Schlesinger, T E

    1999-01-01

    Vertical high-pressure Bridgman (VHPB) Cd sub 1 sub - sub x Zn sub x Te (0.04crystals grown in the Ukraine and Russia have been evaluated and compared to US-grown materials. Various analytical techniques were used to study the materials for trace impurities, precipitates, crystallinity, and electrical transport properties. Relatively, high concentrations of carbon and trace impurities such as Se, Nd and Si have been detected in the crystals. In most cases, the crystals showed lower resistivity than US-grown CZT. However, recent crystals grown in Russia exhibited better detector performance than those grown previously, and a good response to an sup 2 sup 4 sup 1 Am radioactive source was found. Electron lifetimes below 1 mu s were measured in crystals having significant numbers of micro-defects, compared to lifetimes of 5-15 mu s found in spectrometer grade materials produced in the US. Furthermore, the zinc composition along the growth axis showed better homogeneity in comparison with ...

  5. 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.)

  6. Optical Study of Liquid Crystal Lens Doped with Multiwalled Carbon Nanotubes

    Directory of Open Access Journals (Sweden)

    Hui LI

    2016-05-01

    Full Text Available In this paper, a new kind of electrically controlled liquid crystal lens, which respond in a relatively fast time, is presented. The multiwalled carbon nanotubes are doped into liquid crystal to fabricate the liquid crystal lens. As 0.02 % concentration of multiwalled carbon nanotubes is uniformly distributed in the liquid crystal, the optical features of the liquid crystal lens are obviously improved. The liquid crystal lens with a diameter of 2.0 mm was fabricated with about 0.2 s response time and less than 5 Vrms applied voltage. The focal length can vary from 16 to 510 mm, and the operation voltage changes from 1.0 to 5.5 Vrms. This liquid crystal lens has the very attractive feature of submillisecond response time, which is a much faster response time in comparison with conventional liquid crystal lens. Thus, this kind of liquid crystal lens has high potential for implementation in many practical imaging applications and imaging commercialisation.DOI: http://dx.doi.org/10.5755/j01.ms.22.2.12911

  7. Experiments testing the abatement of radiation damage in D-xylose isomerase crystals with cryogenic helium.

    Science.gov (United States)

    Hanson, B Leif; Harp, Joel M; Kirschbaum, Kristin; Schall, Constance A; DeWitt, Ken; Howard, Andrew; Pinkerton, A Alan; Bunick, Gerard J

    2002-11-01

    Helium is a more efficient cryogen than nitrogen, and for macromolecular data collection at high-flux beamlines will deliver lower temperatures. An open-flow helium cryostat developed at the University of Toledo (the Pinkerton Device) has been used for macromolecular data collection. This device differs from standard commercial He cryostats by having a much narrower aperture providing a high velocity stream of He around the crystal that maximizes convective and conductive heat exchange between the crystal and the cryogen. This paper details a series of experiments conducted at the IMCA-CAT 17ID beamline using one crystal for each experimental condition to examine whether helium at 16 K provided better radiation-damage abatement compared with nitrogen at 100 K. These studies used matched high-quality crystals (0.94 A diffraction resolution) of D-xylose isomerase derived from the commercial material Gensweet SGI. Comparisons show that helium indeed abates the indicators of radiation damage, in this case resulting in longer crystal diffractive lifetimes. The overall trend suggests that crystals maintain order and that high-resolution data are less affected by increased radiation load when crystals are cooled with He rather than N(2). This is probably the result of a lower effective temperature at the crystal with concomitant reduction in free-radical diffusion. Other features, such as an apparent phase transition in macromolecular crystals at lower temperatures, require investigation to broaden the utility of He use.

  8. THEORY OF INCOMMENSURATE CRYSTAL FACETS

    NARCIS (Netherlands)

    VANSMAALEN, S

    1993-01-01

    The morphology of incommensurately modulated crystals is considered. A surface free energy model is constructed which interprets the stabilization of the incommensurate facets as due to surface pinning of the phase of the modulation wave. The stepped nature of the true crystal surface restricts the

  9. Photonic-crystal fibers gyroscope

    Directory of Open Access Journals (Sweden)

    Ali Muse Haider

    2015-01-01

    Full Text Available In this paper we proposed to use of a photonic crystal fiber with an inner hollow defect. The use of such fibers is not affected by a material medium on the propagation of optical radiation. Photonic crystal fibers present special properties and capabilities that lead to an outstanding potential for sensing applications

  10. Handbook of nonlinear optical crystals

    CERN Document Server

    Dmitriev, Valentin G; Nikogosyan, David N

    1991-01-01

    This Handbook of Nonlinear Optical Crystals provides a complete description of the properties and applications of nonlinear crystals In addition, it presents the most important equations for calculating the main parameters of nonlinear frequency converters This comprehensive reference work will be of great value to all scientists and engineers working in nonlinear optics, quantum electronics and laser physics

  11. Photoelastic sphenoscopic analysis of crystals

    Energy Technology Data Exchange (ETDEWEB)

    Montalto, L. [DIISM, Dip. Di Ingegneria Industriale e Scienze Matematiche—Università Politecnica delle Marche, Ancona (Italy); SIMAU, Dip. Di Scienze e Ingegneria della Materia, dell’ambiente ed Urbanistica—Università Politecnica delle Marche, Ancona (Italy); Rinaldi, D. [SIMAU, Dip. Di Scienze e Ingegneria della Materia, dell’ambiente ed Urbanistica—Università Politecnica delle Marche, Ancona (Italy); Scalise, L.; Paone, N. [DIISM, Dip. Di Ingegneria Industriale e Scienze Matematiche—Università Politecnica delle Marche, Ancona (Italy); Davì, F. [DICEA, Dip. Di Ingegneria Civile, Edile e Architettura—Università Politecnica delle Marche, Ancona (Italy)

    2016-01-15

    Birefringent crystals are at the basis of various devices used in many fields, from high energy physics to biomedical imaging for cancer detection. Since crystals are the main elements of those devices, a great attention is paid on their quality and properties. Here, we present a methodology for the photoelastic analysis of birefringent crystals, based on a modified polariscope. Polariscopes using conoscopic observation are used to evaluate crystals residual stresses in a precise but time consuming way; in our methodology, the light beam shape, which impinges on the crystal surface, has been changed from a solid cone (conoscopy) to a wedge (sphenoscopy). Since the polarized and coherent light is focused on a line rather than on a spot, this allows a faster analysis which leads to the observation, at a glance, of a spatial distribution of stress along a line. Three samples of lead tungstate crystals have been observed using this technique, and the obtained results are compared with the conoscopic observation. The samples have been tested both in unloaded condition and in a loaded configuration induced by means of a four points bending device, which allows to induce a known stress distribution in the crystal. The obtained results confirm, in a reliable manner, the sensitivity of the methodology to the crystal structure and stress.

  12. Protein Crystal Growth in Microgravity

    Institute of Scientific and Technical Information of China (English)

    毕汝昌; 桂璐璐; 师珂; 王耀萍; 陈世芝; 韩青; 胡永林; 沈福苓; 牛秀田; 华子谦; 卢光莹; 张健; 李松林; 龚为民; 牛立文; 黄其辰

    1994-01-01

    Protein crystal growth is quite important for the determination of protein structureswhich are essential to the understanding of life at molecular level as well as to the development of molecu-lar biotechnology.The microgravity environment of space is an ideal place to study the complicated pro-tein crystallization and to grow good-quality protein crystals.A number of crystal-growth experiments of10 different proteins were carried out in August,1992 on the Chinese re-entry satellite FSW-2 in spaceusing a tube crystallization equipment made in China.A total of 25 samples from 6 proteins producedcrystals,and the effects of microgravity on protein crystal growth were observed,especially for an acidicphospholipase A2 and henegg-white lysozyme which gave better crystals in space than earth-grown crys-tals in ground control experiments.The results have shown that the microgravity in space favors the im-provement of the size,perfection,morphology and internal order of the grown protein crytals.

  13. Flow induced/ refined solution crystallization of a semiconducting polymer

    Science.gov (United States)

    Nguyen, Ngoc A.

    morphology formation in comparison to that of the pristine (as-received) P3HT. As a result, single P3HT crystals with high surface energy chain folds were analyzed and determined. Previous reported results of infinite melting enthalpy of extended chain P3HT crystals are much higher than the result discovered in this study. The findings in this study revealed that the infinite melting enthalpy of chain-folded P3HT crystals is considerably decreased due to the presence of this P3HT chain-folded surface energy. In this study, the kinetics and mechanism of P3HT crystallization under shear-flow was thoroughly investigated as well. A homogeneous nucleation of P3HT was observed that allows one dimensional fibril crystal growth. The micrometer long P3HT crystals are formed and limited by the contact time between the P3HT molecules. Furthermore, it was found that phenyl-C61-butyric acid methyl ester (PCBM) nanoparticles inhibit the crystallization of P3HT under shear. However, the shear-flow leads to nanophase agglomeration of PCBM and creates percolation of P3HT fibril crystal networks and the PCBM phase separated domains that apparently present better pathways for transporting electrons and holes. Interestingly, the structured liquid was simply applied onto substrates with a paintbrush resulting in similar device performance to those made with current techniques in which the morphology is commonly formed during application or post-processing steps. These detailed findings are given and discussed in the thesis.

  14. Modification of Hydroxyapatite Crystal Using IR Laser

    CERN Document Server

    Satoh, Saburoh; Goto, M; Guan, W; Hayashi, N; Ihara, S; Yamabe, C; Yamaguchi, Y

    2004-01-01

    The first application of laser technology to dentistry was for the removal of caries. However, reports of laser application on improvement of dental surface were emerged, much attention has been focused on the laser’s potential to enhance enamel’s hardness and resistance to acid. Most of the previous reports concentrated on the photo issue interaction. Few research has pursued the photochemical phenomenon occurred during laser irradiation on biological tissues. In order to find a creative method to remineralize the dissociating enamel and exposed coronal of dentine, the authors developed a novel procedure during laser irradiation. Slice of sound molar and artificial HAp pellet were irradiated separately, with CO2 laser under different laser parameters. Tow series of samples covered with saturation calcium ion solution were irradiated separately. To investigate the crystal morphology, XRD pattern were surveyed. The comparison of each cases show that the chemical coating affected the ablation process evidentl...

  15. Enhanced photoacoustic detection using photonic crystal substrate

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Yunfei; Liu, Kaiyang [Department of Electrical and Computer Engineering, Iowa State University, Ames, Iowa 50011 (United States); McClelland, John [Ames Laboratory-USDOE, Ames, Iowa 50011 (United States); Department of Mechanical Engineering, Iowa State University, Ames, Iowa 50011 (United States); Department of Biochemistry, Biophysics, and Molecular Biology, Iowa State University, Ames, Iowa 50011 (United States); Lu, Meng, E-mail: menglu@iastate.edu [Department of Electrical and Computer Engineering, Iowa State University, Ames, Iowa 50011 (United States); Department of Mechanical Engineering, Iowa State University, Ames, Iowa 50011 (United States)

    2014-04-21

    This paper demonstrates the enhanced photoacoustic sensing of surface-bound light absorbing molecules and metal nanoparticles using a one-dimensional photonic crystal (PC) substrate. The PC structure functions as an optical resonator at the wavelength where the analyte absorption is strong. The optical resonance of the PC sensor provides an intensified evanescent field with respect to the excitation light source and results in enhanced optical absorption by surface-immobilized samples. For the analysis of a light absorbing dye deposited on the PC surface, the intensity of photoacoustic signal was enhanced by more than 10-fold in comparison to an un-patterned acrylic substrate. The technique was also applied to detect gold nanorods and exhibited more than 40 times stronger photoacoustic signals. The demonstrated approach represents a potential path towards single molecule absorption spectroscopy with greater performance and inexpensive instrumentation.

  16. MyCrystals - a simple visual data management program for laboratory-scale crystallization experiments

    DEFF Research Database (Denmark)

    Løvgreen, Monika Nøhr; Løvgreen, Mikkel; Christensen, Hans Erik Mølager

    2009-01-01

    MyCrystals is designed as a user-friendly program to display crystal images and list crystallization conditions. The crystallization conditions entry fields can be customized to suit the experiments. MyCrystals is also able to sort the images by the entered crystallization conditions, which...

  17. Crystal structure of propaquizafop

    Directory of Open Access Journals (Sweden)

    Youngeun Jeon

    2014-12-01

    Full Text Available The title compound, C22H22ClN3O5 {systematic name: 2-(propan-2-ylideneaminooxyethyl (R-2-[4-(6-chloroquinoxalin-2-yloxyphenoxy]propionate}, is a herbicide. The asymmetric unit comprises two independent molecules in which the dihedral angles between the phenyl ring and the quinoxaline ring plane are 75.93 (7 and 82.77 (8°. The crystal structure features C—H...O, C—H...N, and C—H...Cl hydrogen bonds, as well as weak π–π interactions [ring-centroid separation = 3.782 (2 and 3.5952 (19 Å], resulting in a three-dimensional architecture.

  18. Lamella settler crystallizer

    Science.gov (United States)

    Maimoni, Arturo

    1990-01-01

    A crystallizer which incorporates a lamella settler and which is particularly applicable for use in batteries and power cells for electric vehicles or stationary applications. The lamella settler can be utilized for coarse particle separation or for agglomeration, and is particularly applicable to aluminum-air batteries or power cells for solving the hydrargillite (aluminum-hydroxide) removal problems from such batteries. This invention provides the advantages of very low energy consumption, turbulence, shear, cost and maintenance. Thus, due to the low shear and low turbulence of this invention, it is particularly effective in the control of aluminum hydroxide particle size distribution in the various sections of an aluminum-air system, as well as in other electrochemical systems requiring separation for phases of different densities.

  19. Frequency mixing crystal

    Science.gov (United States)

    Ebbers, Christopher A.; Davis, Laura E.; Webb, Mark

    1992-01-01

    In a laser system for converting infrared laser light waves to visible light comprising a source of infrared laser light waves and means of harmoic generation associated therewith for production of light waves at integral multiples of the frequency of the original wave, the improvement of said means of harmonic generation comprising a crystal having the chemical formula X.sub.2 Y(NO.sub.3).sub.5 .multidot.2 nZ.sub.2 o wherein X is selected from the group consisting of Li, Na, K, Rb, Cs, and Tl; Y is selected from the group consisting of Sc, Y, La, Ce, Nd, Pr, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Al, Ga, and In; Z is selected from the group consisting of H and D; and n ranges from 0 to 4.

  20. Crystal structure of nuarimol

    Directory of Open Access Journals (Sweden)

    Gihaeng Kang

    2015-08-01

    Full Text Available The title compound [systematic name: (RS-(2-chlorophenyl(4-fluorophenyl(pyrimidin-5-ylmethanol], C17H12ClFN2O, is a pyrimidine fungicide. The asymmetric unit comprises two independent molecules, A and B, in which the dihedral angles between the plane of the pyrimidine ring and those of the chlorophenyl and fluorophenyl rings are 71.10 (6 and 70.04 (5° in molecule A, and 73.24 (5 and 89.30 (5° in molecule B. In the crystal, O—H...N hydrogen bonds link the components into [010] chains of alternating A and B molecules. The chains are cross-linked by C—H...F hydrogen bonds and weak C—H...π and C—Cl...π [Cl...ring centroid = 3.7630 (8 Å] interactions, generating a three-dimensional network.

  1. Natural photonic crystals

    Energy Technology Data Exchange (ETDEWEB)

    Vigneron, Jean Pol, E-mail: jean-pol.vigneron@fundp.ac.be [Research Center in Physics of Matter and Radiation (PMR), University of Namur (FUNDP), rue de Bruxelles, 61, B-5000 Namur (Belgium); Simonis, Priscilla [Research Center in Physics of Matter and Radiation (PMR), University of Namur (FUNDP), rue de Bruxelles, 61, B-5000 Namur (Belgium)

    2012-10-15

    Photonic structures appeared in nature several hundred millions years ago. In the living world, color is used for communication and this important function strongly impacts the individual chances of survival as well as the chances to reproduce. This has a statistical influence on species populations. Therefore, because they are involved in evolution, natural color-generating structures are - from some point of view - highly optimized. In this short review, a survey is presented of the development of natural photonic crystal-type structures occurring in insects, spiders, birds, fishes and other marine animals, in plants and more, from the standpoint of light-waves propagation. One-, two-, and three-dimensional structures will be reviewed with selected examples.

  2. Growth habit of polar crystals

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Using coordination polyhedron rule, growth habit of polar crystals such as ZnO, ZnS and SiO2 is investigated. It shows that the growth rates in the positive and negative polar axis directions are different. The theoretical growth habit of ZnO crystal is hexagonal prism and the growth rates of its various faces are:V{0001}>V{0111}-->V{0110}->V{0111}->V{0001}-. The growth habit of ZnS crystal is tetrahedron and its growth rates of different crystal faces are: V{111}>V{001}>V{001} =V{100} =. The growth rate relationship between positive and negative polar axis directions of SiO2 crystal V[1120]-->V[1120]-.is These results are in agreement with the growth habits observed under hydrothermal conditions. The different growth rates between positive and negative polar axis directions cannot be explained by PBC theory.

  3. Springer Handbook of Crystal Growth

    CERN Document Server

    Dhanaraj, Govindhan; Prasad, Vishwanath; Dudley, Michael

    2010-01-01

    Over the years, many successful attempts have been made to describe the art and science of crystal growth. Most modern advances in semiconductor and optical devices would not have been possible without the development of many elemental, binary, ternary, and other compound crystals of varying properties and large sizes. The objective of the Springer Handbook of Crystal Growth is to present state-of-the-art knowledge of both bulk and thin-film crystal growth. The goal is to make readers understand the basics of the commonly employed growth processes, materials produced, and defects generated. Almost 100 leading scientists, researchers, and engineers from 22 different countries from academia and industry have been selected to write chapters on the topics of their expertise. They have written 52 chapters on the fundamentals of bulk crystal growth from the melt, solution, and vapor, epitaxial growth, modeling of growth processes and defects, techniques of defect characterization as well as some contemporary specia...

  4. Photonic crystals in epitaxial semiconductors

    CERN Document Server

    La Rue, R M de

    1998-01-01

    The title of the paper uses the expression "photonic crystals". By photonic crystals, we mean regular periodic structures with a substantial refractive index variation in one-, two- or three- dimensional space. Such crystals can $9 exist naturally, for example natural opal, but are more typically fabricated by people. Under sufficiently strong conditions, i.e., sufficiently large refractive index modulation, correct size of structural components, and $9 appropriate rotational and translational symmetry, these crystals exhibit the characteristics of a photonic bandgap (PBG) structure. In a full photonic bandgap structure there is a spectral stop band for electromagnetic waves $9 propagating in any direction through the structure and with an arbitrary state of polarization. This behavior is of interest both from a fundamental viewpoint and from the point of view of novel applications in photonic devices. The $9 paper gives an outline review of work on photonic crystals carried out by the Optoelectronics Researc...

  5. Crystallization of glycine with ultrasound

    DEFF Research Database (Denmark)

    Louhi-Kultanen, Marjatta; Karjalainen, Milja; Rantanen, Jukka;

    2006-01-01

    Sonocrystallization has proved to be an efficient tool to influence the external appearance and structure of a crystalline product obtained by various crystallization methods. The present work focuses on high intensity sonocrystallization of glycine by varying amplitude of ultrasound with an ultr......Sonocrystallization has proved to be an efficient tool to influence the external appearance and structure of a crystalline product obtained by various crystallization methods. The present work focuses on high intensity sonocrystallization of glycine by varying amplitude of ultrasound...... with an ultrasound frequency of 20kHz at two temperature ranges 40-50 and 20-30 degrees C in a jacketed 250-ml cooling crystallizer equipped with a stirrer. The polymorph composition of the obtained crystals was analyzed with a temperature variable X-ray powder diffractometer (XRPD). XRPD results showed that...... ultrasound power. This study also showed, the higher the ultrasound amplitude the smaller the crystals obtained....

  6. Prediction of molecular crystal structures

    CERN Document Server

    Beyer, T

    2001-01-01

    The ab initio prediction of molecular crystal structures is a scientific challenge. Reliability of first-principle prediction calculations would show a fundamental understanding of crystallisation. Crystal structure prediction is also of considerable practical importance as different crystalline arrangements of the same molecule in the solid state (polymorphs)are likely to have different physical properties. A method of crystal structure prediction based on lattice energy minimisation has been developed in this work. The choice of the intermolecular potential and of the molecular model is crucial for the results of such studies and both of these criteria have been investigated. An empirical atom-atom repulsion-dispersion potential for carboxylic acids has been derived and applied in a crystal structure prediction study of formic, benzoic and the polymorphic system of tetrolic acid. As many experimental crystal structure determinations at different temperatures are available for the polymorphic system of parac...

  7. Bacterial Ice Crystal Controlling Proteins

    Directory of Open Access Journals (Sweden)

    Janet S. H. Lorv

    2014-01-01

    Full Text Available Across the world, many ice active bacteria utilize ice crystal controlling proteins for aid in freezing tolerance at subzero temperatures. Ice crystal controlling proteins include both antifreeze and ice nucleation proteins. Antifreeze proteins minimize freezing damage by inhibiting growth of large ice crystals, while ice nucleation proteins induce formation of embryonic ice crystals. Although both protein classes have differing functions, these proteins use the same ice binding mechanisms. Rather than direct binding, it is probable that these protein classes create an ice surface prior to ice crystal surface adsorption. Function is differentiated by molecular size of the protein. This paper reviews the similar and different aspects of bacterial antifreeze and ice nucleation proteins, the role of these proteins in freezing tolerance, prevalence of these proteins in psychrophiles, and current mechanisms of protein-ice interactions.

  8. Scintillation properties of solution-grown trans-stilbene single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Zaitseva, Natalia, E-mail: zaitseva1@llnl.gov [Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94551 (United States); Glenn, Andrew; Carman, Leslie; Paul Martinez, H.; Hatarik, Robert [Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94551 (United States); Klapper, Helmut [Institut für Kristallographie, Jägerstraße 17-19, D-52066 Aachen (Germany); Payne, Stephen [Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94551 (United States)

    2015-07-21

    The scintillation properties of trans-stilbene crystals grown for the first time by application of the solution growth technique to the scale of 10 cm are reported. Measurements of the scintillation light output, pulse shape discrimination, and neutron detection efficiency were made with sets of crystals cut as 50 cm diameter cylinders of different lengths from 0.3 to 10 cm. Comparison to liquid scintillators and traditional melt-grown stilbene showed that at increasing sizes new solution-grown crystals exhibit better scintillation performance that makes them promising for use in large scale neutron detectors. Results are discussed in relation to structural imperfections attributed to different methods of growth. - Highlights: • 10-cm-scale trans-stilbene single crystals grown from organic solutions. • Crystals have high optical quality required for fast neutron detection. • Scintillation performance superior to liquids and melt-grown stilbene demonstrated.

  9. Characterization of pure and copper-doped iron tartrate crystals grown in silica gel

    Indian Academy of Sciences (India)

    V Mathivanan; M Haris

    2013-07-01

    Single crystal growth of pure and copper-doped iron tartrate crystals bearing composition Cu Fe(1−) C4H4O6 · H2O, where = 0, 0.07, 0.06, 0.05, 0.04, 0.03, is achieved using gel technique. The elemental analysis has been done using energy-dispersive X-ray analysis (EDAX) spectrum. The characterization studies such as Fourier transform infrared spectroscopy (FTIR), powder X-ray diffraction (XRD), magnetic analysis and thermal analysis have been done for crystals with = 0 for pure iron tartrate and with = 0.05 for copper-mixed iron tartrate crystals. A detailed comparison has been made between pure and doped crystals.

  10. Dynamic control of higher-order modes in hollow-core photonic crystal fibers.

    Science.gov (United States)

    Euser, T G; Whyte, G; Scharrer, M; Chen, J S Y; Abdolvand, A; Nold, J; Kaminski, C F; Russell, P St J

    2008-10-27

    We present a versatile method for selective mode coupling into higher-order modes of photonic crystal fibers, using holograms electronically generated by a spatial light modulator. The method enables non-mechanical and completely repeatable changes in the coupling conditions. We have excited higher order modes up to LP(31) in hollow-core photonic crystal fibers. The reproducibility of the coupling allows direct comparison of the losses of different guided modes in both hollow-core bandgap and kagome-lattice photonic crystal fibers. Our results are also relevant to applications in which the intensity distribution of the light inside the fiber is important, such as particle- or atom-guidance.

  11. Characterizing configurable transmission modes in plasma photonic crystals using scanning field mapping

    Science.gov (United States)

    Wang, Benjamin; Cappelli, Mark

    2016-10-01

    A fully tunable plasma photonic crystal is used to control the propagation of free space electromagnetic waves in the S to X band of the microwave spectrum. A structured array of discharge plasma tubes are arranged in a square crystal lattice with the individual plasma dielectric constant tuned through variation in the plasma density. Microwave field-mapping is used to characterize the transmitted electromagnetic fields of the tunable device operating in waveguiding and bending modes. These modes are obtained by introducing appropriate line defects in the photonic crystal structure by controlling the activity of individual plasma tubes. Comparisons are made of the measured fields to those simulated using commercially-available software.

  12. Physical properties of BeAl{sub 6}O{sub 10} single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Pestryakov, E.V.; Petrov, V.V.; Zubrinov, I.I.; Semenov, V.I.; Trunov, V.I.; Kirpichnikov, A.V. [Department of Quantum Electronics, Institute of Semiconductor Physics, Novosibirsk 630090 (Russia); Alimpiev, A.I. [Design and Technological Institute of Monocrystals, Novosibirsk 630058 (Russia)

    1997-10-01

    Single crystals of BeAl{sub 6}O{sub 10}, beryllium hexaaluminate, were grown by the Czochralski method. The optical, acousto-optical, elastic, and a number of thermo-mechanical properties of bulk crystals of BeAl{sub 6}O{sub 10} were investigated in comparison with crystal of BeAl{sub 2}O{sub 4}, chrysoberyl. It has been demonstrated that this material is the promising host for active media of tunable solid state lasers. {copyright} {ital 1997 American Institute of Physics.}

  13. Crystallization of Biological Macromolecules in Microgravity

    Science.gov (United States)

    Snell, Edward H.; Chayen, N. E.; Helliwell, J. R.

    2000-01-01

    An overview of microgravity crystallization explaining why microgravity is used, factors which affect crystallization, the method of crystallization and the environment itself. Also covered is how best to make use of microgravity and what the future might hold.

  14. Effects of impurities on crystal growth in fructose crystallization

    Science.gov (United States)

    Chu, Y. D.; Shiau, L. D.; Berglund, K. A.

    1989-10-01

    The influence of impurities on the crystallization of anhydrous fructose from aqueous solution was studied. The growth kinetics of fructose crystals in the fructose-water-glucose and fructose-water-difructose dianhydrides systems were investigated using photomicroscopic contact nucleation techniques. Glucose is the major impurity likely to be present in fructose syrup formed during corn wet milling, while several difructose dianhydrides are formed in situ under crystallization conditions and have been proposed as a cause in the decrease of overall yields. Both sets of impurities were found to cause inhibition of crystal growth, but the mechanisms responsible in each case are different. It was found that the presence of glucose increases the solubility of fructose in water and thus lowers the supersaturation of the solution. This is probably the main effect responsible for the decrease of crystal growth. Since the molecular structures of difructose dianhydrides are similar to that of fructose, they are probably "tailor-made" impurities. The decrease of crystal growth is probably caused by the incorporation of these impurities into or adsorption to the crystal surface which would accept fructose molecules in the orientation that existed in the difructose dianhydride.

  15. Effects of increasing size and changing europium activator concentration in KCaI3 scintillator crystals

    Science.gov (United States)

    Lindsey, Adam C.; Zhuravleva, Mariya; Wu, Yuntao; Stand, Luis; Loyd, Matthew; Gokhale, Sasmit; Koschan, Merry; Melcher, Charles L.

    2016-09-01

    KCaI3:Eu crystals have been identified as very promising for use in spectroscopic detector applications related to nuclear nonproliferation and domestic security efforts. Initial studies have shown for small crystals a few mm3 in size with 3% europium dopant concentration, a high light yield of >70,000 ph/MeV and energy resolution of ≈3% at 662 keV is attainable which is comparable with the highest performance scintillators discovered. In this work, single crystals of KCaI3 with a range of Eu2+ doping between 0 and 5 at% substituting for Ca2+ were grown at 22 mm diameter and their performance for gamma-ray spectroscopy studied. Comparisons among crystals approximately Ø22 mm×22 mm (8.4 cm3 or ≈0.5 in3) provide a more accurate understanding of how scintillation performance changes with Eu doping and increased crystal size. KCaI3 in the undoped form is shown to be a highly efficient intrinsic scintillator with a defect-related emission at 404 nm which coexists with the Eu2+ 5d-4f emission in low dopant concentrations and is completely re-absorbed in more heavily doped crystals. For larger crystals, effects from self-absorption due to Eu activation become more evident by a near doubling of decay time for 0.5 in3 crystals as the activator is increased from 0.5 to 5.0 at% Eu. Comparisons of pulse-height spectra obtained for Ø22 mm×22 mm cylinders with varying Eu concentration suggests best performance is achieved using lower Eu additions closer to 0.5-1.0 at%. Using a modified crystal packaging featuring an offset reflector geometry, 0.5 in3 crystals of KCaI3:Eu can attain under 4% energy resolution at 662 keV.

  16. Growth of KH/sub 2/PO/sub 4/ crystals at constant temperature and supersaturation. Final report, October 20, 1980-October 20, 1981

    Energy Technology Data Exchange (ETDEWEB)

    Loiacono, G.M.; Zola, J.; Kostecky, G.

    1982-02-01

    A large three-zone crystallizer system was constructed and successfully operated for growing KH/sub 2/PO/sub 4/ single crystals. Under conditions of constant crystallization temperature and supersaturation, growth rates exceding 5 mm per day were demonstrated for KH/sub 2/PO/sub 4/ crystals of 5 x 5 cm cross section. The optical quality of these crystals was equivalent to that of crystals grown at rates presently considered as state-of-the-art (approx. 1 mm/day). Sample crystals were supplied for comparison testing. The three-zone system appears to be ideally suitable for growth of large-diameter KH/sub 2/PO/sub 4/ crystals for the Laser Fusion Program.

  17. THE CRYSTAL STRUCTURE OF DIPHENYLTELLURIUM DIBROMIDE,

    Science.gov (United States)

    TELLURIUM COMPOUNDS, *ORGANOMETALLIC COMPOUNDS, CRYSTAL STRUCTURE , CRYSTAL STRUCTURE , BROMIDES, SYMMETRY(CRYSTALLOGRAPHY), X RAY DIFFRACTION, FOURIER ANALYSIS, LEAST SQUARES METHOD, MOLECULAR STRUCTURE, CHEMICAL BONDS.

  18. Crystal-field effects in fluoride crystals for optical refrigeration

    Energy Technology Data Exchange (ETDEWEB)

    Hehlen, Markus P [Los Alamos National Laboratory

    2010-01-01

    The field of optical refrigeration of rare-earth-doped solids has recently seen an important breakthrough. The cooling of a YLiF{sub 4} (YLF) crystal doped with 5 mol% Yb3+ to 155 K by Seletskiy et al [NPhot] has surpassed the lowest temperatures ({approx}170 K for {approx}100 mW cooling capacity) that are practical with commercial multi-stage thermoelectric coolers (TEC) [Glaister]. This record performance has advanced laser cooling into an application relevant regime and has put first practical optical cryocoolers within reach. The result is also relevant from a material perspective since for the first time, an Yb3+-doped crystal has outperformed an Yb3+-doped glass. The record temperature of 208 K was held by the Yb3+-doped fluorozirconate glass ZBLAN. Advanced purification and glass fabrication methods currently under development are expected to also advance ZBLAN:Yb3+ to sub-TEC temperatures. However, recent achievements with YLF:Yb3+ illustrate that crystalline materials may have two potentially game-changing advantajes over glassy materials. First, the crystalline environment reduces the inhomogeneous broadening of the Yb3+ electronic transitions as compared to a glassy matrix. The respective sharpening of the crystal-field transitions increases the peak absorption cross section at the laser excitation wavelength and allows for more efficient pumping of the Yb3+ ions, particularly at low temperatures. Second, many detrimental impurities present in the starting materials tend to be excluded from the crystal during its slow growth process, in contrast to a glass where all impurities present in the starting materials are included in the glass when it is formed by temperature quenching a melt. The ultra high purity required for laser cooling materials [PRB] therefore may be easier to realize in crystals than in glasses. Laser cooling occurs by laser excitation of a rare-earth ion followed by anti-Stokes luminescence. Each such laser-cooling cycle extracts

  19. Photonic crystal enhanced cytokine immunoassay.

    Science.gov (United States)

    Mathias, Patrick C; Ganesh, Nikhil; Cunningham, Brian T

    2009-01-01

    Photonic crystal surfaces are demonstrated as a means for enhancing the detection sensitivity and resolution for assays that use a fluorescent tag to quantify the concentration of an analyte protein molecule in a liquid test sample. Computer modeling of the spatial distribution of resonantly coupled electromagnetic fields on the photonic crystal surface are used to estimate the magnitude of enhancement factor compared to performing the same fluorescent assay on a plain glass surface, and the photonic crystal structure is fabricated and tested to experimentally verify the performance using a sandwich immunoassay for the protein Tumor Necrosis Factor-alpha (TNF-alpha). The demonstrated photonic crystal fabrication method utilizes a nanoreplica molding technique that allows for large-area inexpensive fabrication of the structure in a format that is compatible with confocal microarray laser scanners. The signal-to-noise ratio for fluorescent spots on the photonic crystal is increased by at least five-fold relative to the glass slide, allowing a TNF-alpha concentration of 1.6 pg/ml to be distinguished from noise on a photonic crystal surface. In addition, the minimum quantitative limit of detection on the photonic crystal surface is one-third the limit on the glass slide - a decrease from 18 pg/ml to 6 pg/ml. The increased performance of the immunoassay allows for more accurate quantitation of physiologically relevant concentrations of TNF-alpha in a protein microarray format that can be expanded to multiple cytokines.

  20. Spatial filtering with photonic crystals

    Energy Technology Data Exchange (ETDEWEB)

    Maigyte, Lina [Departament de Física i Enginyeria Nuclear, Universitat Politècnica de Catalunya, Rambla Sant Nebridi 22, Terrassa 08222 (Spain); Staliunas, Kestutis [Departament de Física i Enginyeria Nuclear, Universitat Politècnica de Catalunya, Rambla Sant Nebridi 22, Terrassa 08222 (Spain); Institució Catalana de Recerca i Estudis Avançats (ICREA), Pg. Lluís Companys 23, Barcelona 08010 (Spain)

    2015-03-15

    Photonic crystals are well known for their celebrated photonic band-gaps—the forbidden frequency ranges, for which the light waves cannot propagate through the structure. The frequency (or chromatic) band-gaps of photonic crystals can be utilized for frequency filtering. In analogy to the chromatic band-gaps and the frequency filtering, the angular band-gaps and the angular (spatial) filtering are also possible in photonic crystals. In this article, we review the recent advances of the spatial filtering using the photonic crystals in different propagation regimes and for different geometries. We review the most evident configuration of filtering in Bragg regime (with the back-reflection—i.e., in the configuration with band-gaps) as well as in Laue regime (with forward deflection—i.e., in the configuration without band-gaps). We explore the spatial filtering in crystals with different symmetries, including axisymmetric crystals; we discuss the role of chirping, i.e., the dependence of the longitudinal period along the structure. We also review the experimental techniques to fabricate the photonic crystals and numerical techniques to explore the spatial filtering. Finally, we discuss several implementations of such filters for intracavity spatial filtering.

  1. Radiation generation with pyroelectric crystals

    Science.gov (United States)

    Geuther, Jeffrey A.

    2007-12-01

    Pyroelectric crystals heated or cooled in vacuum have been used to produce low-energy x-ray devices since 1992. In the course of this thesis, experiments with lithium tantalate (LiTaO3) and lithium niobate (LiNbO 3) were performed to extend the usefulness of pyroelectric radiation sources. Paired-crystal x-ray generators were shown to double the x-ray energy and yield, and allow the k-shell fluorescence of any metal up to thorium (Z = 90). It was demonstrated that the electron emission from a single pyroelectric crystal could be transmitted through a beryllium window to allow the electron beam to be extracted from the vacuum chamber. The electron emission current and energy were measured, and a mathematical model was developed to predict emission current and energy. Magnetic deflection experiments were used to verify that the electric field produced by the pyroelectric effect in lithium tantalate was sufficient to ionize gas. Finally, a paired-crystal system was used to ionize a deuterium fill gas near a metallic tip mounted to a pyroelectric crystal, and accelerate these ions into a deuterated target mounted to the opposing crystal. This technique was used to produce a compact, low-power fusion neutron source driven by pyroelectric crystals.

  2. Spherical colloidal photonic crystals.

    Science.gov (United States)

    Zhao, Yuanjin; Shang, Luoran; Cheng, Yao; Gu, Zhongze

    2014-12-16

    CONSPECTUS: Colloidal photonic crystals (PhCs), periodically arranged monodisperse nanoparticles, have emerged as one of the most promising materials for light manipulation because of their photonic band gaps (PBGs), which affect photons in a manner similar to the effect of semiconductor energy band gaps on electrons. The PBGs arise due to the periodic modulation of the refractive index between the building nanoparticles and the surrounding medium in space with subwavelength period. This leads to light with certain wavelengths or frequencies located in the PBG being prohibited from propagating. Because of this special property, the fabrication and application of colloidal PhCs have attracted increasing interest from researchers. The most simple and economical method for fabrication of colloidal PhCs is the bottom-up approach of nanoparticle self-assembly. Common colloidal PhCs from this approach in nature are gem opals, which are made from the ordered assembly and deposition of spherical silica nanoparticles after years of siliceous sedimentation and compression. Besides naturally occurring opals, a variety of manmade colloidal PhCs with thin film or bulk morphology have also been developed. In principle, because of the effect of Bragg diffraction, these PhC materials show different structural colors when observed from different angles, resulting in brilliant colors and important applications. However, this angle dependence is disadvantageous for the construction of some optical materials and devices in which wide viewing angles are desired. Recently, a series of colloidal PhC materials with spherical macroscopic morphology have been created. Because of their spherical symmetry, the PBGs of spherical colloidal PhCs are independent of rotation under illumination of the surface at a fixed incident angle of the light, broadening the perspective of their applications. Based on droplet templates containing colloidal nanoparticles, these spherical colloidal PhCs can be

  3. Size effects in crystal plasticity

    DEFF Research Database (Denmark)

    Borg, Ulrik

    2007-01-01

    of plastic flow in a single crystal, grain boundary effects in a bicrystal, and grain size effects in a polycrystal are studied. Single crystals containing micro-scale voids have also been analyzed at different loading conditions with focus on the stress and deformation fields around the voids, on void......Numerical analyses of plasticity size effects have been carried out for different problems using a developed strain gradient crystal plasticiy theory. The theory employs higher order stresses as work conjugates to slip gradients and uses higher order boundary conditions. Problems on localization...

  4. Cost comparisons

    CERN Document Server

    CERN Bulletin

    2010-01-01

    How much does the LHC cost? And how much does this represent in other currencies? Below we present a table showing some comparisons with the cost of other projects. Looking at the figures, you will see that the cost of the LHC can be likened to that of three skyscrapers, or two seasons of Formula 1 racing! One year's budget of a single large F1 team is comparable to the entire materials cost of the ATLAS or CMS experiments.   Please note that all the figures are rounded for ease of reading.    CHF € $   LHC 4.6 billions 3 billions  4 billions   Space Shuttle Endeavour (NASA) 1.9 billion 1.3 billion 1.7 billion   Hubble Space Telescope (cost at launch – NASA/...

  5. Electrochemical Quartz Crystal Nanobalance

    Science.gov (United States)

    Inzelt, György

    The method of piezoelectric microgravimetry (nanogravimetry) using an electrochemical quartz crystal microbalance (EQCM) or nanobalance (EQCN) can be considered as a novel and much more sensitive version of electrogravimetry. The EQCN technique has become a widely used technique in several areas of electrochemistry, electroanalytical chemistry, bioelectrochemistry, etc. [1-10]. Obviously, mass changes occurring during adsorption, sorption, electrosorption, electrodeposition, or spontaneous deposition can be followed, which is very helpful for the elucidation of reaction mechanism via identification of the species accumulated on the surface. These investigations include metal and alloy deposition, underpotential deposition, electroplating, synthesis of conducting polymers by electropolymerization, adsorption of biologically active materials, and analytical determination of small ions and biomolecules. Of course, the opposite processes, i.e., spontaneous dissolution, electrodissolution, corrosion, can also be studied. Electrochemical oscillations, in which the formation and oxidation of chemisorbed molecular fragments play a determining role, have been studied, too. The majority of the investigations have been devoted to ion and solvent transport associated with the redox transformations of electrochemically active polymers. Similar studies have been carried out regarding polynuclear surface layers such as metal hexacyanometalates as well as inorganic and organic microcrystals of different compositions.

  6. Crystal structure of pymetrozine

    Directory of Open Access Journals (Sweden)

    Youngeun Jeon

    2015-07-01

    Full Text Available The title compound, C10H11N5O {systematic name: 6-methyl-4-[(E-(pyridin-3-ylmethylideneamino]-4,5-dihydro-1,2,4-triazin-3(2H-one}, C10H11N5O, is used as an antifeedant in pest control. The asymmetric unit comprises two independent molecules, A and B, in which the dihedral angles between the pyridinyl and triazinyl ring planes [r.m.s. deviations = 0.0132 and 0.0255 ] are 11.60 (6 and 18.06 (4°, respectively. In the crystal, N—H...O, N—H...N, C—H...N and C—H...O hydrogen bonds, together with weak π–π interactions [ring-centroid separations = 3.5456 (9 and 3.9142 (9 Å], link the pyridinyl and triazinyl rings of A molecules, generating a three-dimensional network.

  7. Single Crystal Surfaces

    Science.gov (United States)

    Aguilar-Santillan, Joaquin

    2014-06-01

    The present work studies (0001) Al2O3 and (111) Al2MgO4 wetting with pure molten Al by the sessile drop technique from 1073 K to 1473 K (800 °C to 1200 °C) under Ar at PO2 10-15 Pa. Al pure liquid wets a smooth and chemically homogeneous surface of an inert solid, the wetting driving force ( t, T) can be readily studied when surface solid roughness increases in the system. Both crystals planes (0001) Al2O3 and (111) Al2MgO4 have crystallographic surfaces with identical O-2 crystalline positions however considering Mg2+ content in Al2MgO4 structure may influence a reactive mode. Kinetic models results under similar experimental conditions show that Al wetting on (0001) Al2O3 is less reactive than (111) Al2MgO4, however at >1273 K (1000 °C) (0001) Al2O3 transformation occurs and a transition of wetting improves. The (111) Al2MgO4 and Al system promotes interface formations that slow its wetting process.

  8. Transport phenomena in the crystallization of lysozyme by osmotic dewatering and liquid-liquid diffusion in low gravity

    Science.gov (United States)

    Todd, Paul; Sportiello, Michael G.; Gregory, Derek; Cassanto, John M.; Alvarado, Ulises A.; Ostroff, Robert; Korszun, Z. R.

    1993-01-01

    Two methods of protein crystallization, osmotic dewatering and liquid-liquid diffusion, like the vapor diffusion (hanging-drop and sessile-drop) methods allow a gradual approach to supersaturation conditions. The crystallization of hen egg-white lysozyme, an extensively characterized protein crystal, in the presence of sodium chloride was used as an experimental model with which to compare these two methods in low gravity and in the laboratory. Comparisons of crystal growth rates by the two methods under the two conditions have, to date, indicated that the rate of crystal growth by osmotic dewatering is nearly the same in low gravity and on the ground, while much faster crystal growth rates can be achieved by the liquid-liquid diffusion method in low gravity.

  9. Radiating dipoles in photonic crystals

    Science.gov (United States)

    Busch; Vats; John; Sanders

    2000-09-01

    The radiation dynamics of a dipole antenna embedded in a photonic crystal are modeled by an initially excited harmonic oscillator coupled to a non-Markovian bath of harmonic oscillators representing the colored electromagnetic vacuum within the crystal. Realistic coupling constants based on the natural modes of the photonic crystal, i.e., Bloch waves and their associated dispersion relation, are derived. For simple model systems, well-known results such as decay times and emission spectra are reproduced. This approach enables direct incorporation of realistic band structure computations into studies of radiative emission from atoms and molecules within photonic crystals. We therefore provide a predictive and interpretative tool for experiments in both the microwave and optical regimes.

  10. Crystallization & Encapsulation in multicomponent mixtures

    NARCIS (Netherlands)

    Reus, M.A.

    2016-01-01

    In this dissertation crystallization and microencapsulation processes are used to produce multicomponent particulate products with different functionalities (improved stability, controlled release, protection from environment, etc.) and their performance is assessed. Additionally, the interactions b

  11. Absence of Quantum Time Crystals.

    Science.gov (United States)

    Watanabe, Haruki; Oshikawa, Masaki

    2015-06-26

    In analogy with crystalline solids around us, Wilczek recently proposed the idea of "time crystals" as phases that spontaneously break the continuous time translation into a discrete subgroup. The proposal stimulated further studies and vigorous debates whether it can be realized in a physical system. However, a precise definition of the time crystal is needed to resolve the issue. Here we first present a definition of time crystals based on the time-dependent correlation functions of the order parameter. We then prove a no-go theorem that rules out the possibility of time crystals defined as such, in the ground state or in the canonical ensemble of a general Hamiltonian, which consists of not-too-long-range interactions.

  12. High-resolution X-ray study of the effects of deuteration on crystal growth and the crystal structure of proteinase K.

    Science.gov (United States)

    Chatake, Toshiyuki; Ishikawa, Takuya; Yanagisawa, Yasuhide; Yamada, Taro; Tanaka, Ichiro; Fujiwara, Satoru; Morimoro, Yukio

    2011-11-01

    Deuteration of macromolecules is an important technique in neutron protein crystallography. Solvent deuteration of protein crystals is carried out by replacing water (H(2)O) with heavy water (D(2)O) prior to neutron diffraction experiments in order to diminish background noise. The effects of solvent deuteration on the crystallization of proteinase K (PK) with polyethylene glycol as a precipitant were investigated using high-resolution X-ray crystallography. In previous studies, eight NO(3)(-) anions were included in the PK crystal unit cell grown in NaNO(3) solution. In this study, however, the PK crystal structure did not contain NO(3)(-) anions; consequently, distortions of amino acids arising from the presence of NO(3)(-) anions were avoided in the present crystal structures. High-resolution (1.1 Å) X-ray diffraction studies showed that the degradation of PK crystals induced by solvent deuteration was so small that this degradation would be negligible for the purpose of neutron protein crystallography experiments at medium resolution. Comparison of the nonhydrogen structures of nondeuterated and deuterated crystal structures demonstrated very small structural differences. Moreover, a positive correlation between the root-mean-squared differences and B factors indicated that no systematic difference existed.

  13. Crystal growth of an organic non-linear optical material from the vapour phase

    CERN Document Server

    Hou, W

    1999-01-01

    Due to the potential applications of organic non-linear optical materials in the areas of optical processing and communication, the investigation of the crystal growth of new organic NLO materials has been an active field for the last 20 years. For such uses it is necessary to produce single crystals of high quality and perfection, free of strain and defects. When crystals are grown from the solution and the melt, solvent and the decomposition component in the melt can introduce impurities and imperfection to the as-grown crystals. For crystals grown from vapour phase, in the absence of the solvent, this cannot occur and the method promises to yield single crystals of higher quality. Despite this attraction, little attention has been paid to the vapour phase growth of organic NLO crystals. It was with this in mind that the following investigation was carried out. Using Methyl p-hydroxybenzoate (p-MHB), a potential organic NLO material, a comparison investigation was made of its crystal growth from both the va...

  14. Effects of protein engineering and rational mutagenesis on crystal lattice of single chain antibody fragments.

    Science.gov (United States)

    Kalyoncu, Sibel; Hyun, Jeongmin; Pai, Jennifer C; Johnson, Jennifer L; Entzminger, Kevin; Jain, Avni; Heaner, David P; Morales, Ivan A; Truskett, Thomas M; Maynard, Jennifer A; Lieberman, Raquel L

    2014-09-01

    Protein crystallization is dependent upon, and sensitive to, the intermolecular contacts that assist in ordering proteins into a three-dimensional lattice. Here we used protein engineering and mutagenesis to affect the crystallization of single chain antibody fragments (scFvs) that recognize the EE epitope (EYMPME) with high affinity. These hypercrystallizable scFvs are under development to assist difficult proteins, such as membrane proteins, in forming crystals, by acting as crystallization chaperones. Guided by analyses of intermolecular crystal lattice contacts, two second-generation anti-EE scFvs were produced, which bind to proteins with installed EE tags. Surprisingly, although noncomplementarity determining region (CDR) lattice residues from the parent scFv framework remained unchanged through the processes of protein engineering and rational design, crystal lattices of the derivative scFvs differ. Comparison of energy calculations and the experimentally-determined lattice interactions for this basis set provides insight into the complexity of the forces driving crystal lattice choice and demonstrates the availability of multiple well-ordered surface features in our scFvs capable of forming versatile crystal contacts.

  15. Molecular dynamics simulation of triclinic lysozyme in a crystal lattice.

    Science.gov (United States)

    Janowski, Pawel A; Liu, Chunmei; Deckman, Jason; Case, David A

    2016-01-01

    Molecular dynamics simulations of crystals can enlighten interpretation of experimental X-ray crystallography data and elucidate structural dynamics and heterogeneity in biomolecular crystals. Furthermore, because of the direct comparison against experimental data, they can inform assessment of molecular dynamics methods and force fields. We present microsecond scale results for triclinic hen egg-white lysozyme in a supercell consisting of 12 independent unit cells using four contemporary force fields (Amber ff99SB, ff14ipq, ff14SB, and CHARMM 36) in crystalline and solvated states (for ff14SB only). We find the crystal simulations consistent across multiple runs of the same force field and robust to various solvent equilibration schemes. However, convergence is slow compared with solvent simulations. All the tested force fields reproduce experimental structural and dynamic properties well, but Amber ff14SB maintains structure and reproduces fluctuations closest to the experimental model: its average backbone structure differs from the deposited structure by 0.37Å; by contrast, the average backbone structure in solution differs from the deposited by 0.65Å. All the simulations are affected by a small progressive deterioration of the crystal lattice, presumably due to imperfect modeling of hydrogen bonding and other crystal contact interactions; this artifact is smallest in ff14SB, with average lattice positions deviating by 0.20Å from ideal. Side-chain disorder is surprisingly low with fewer than 30% of the nonglycine or alanine residues exhibiting significantly populated alternate rotamers. Our results provide helpful insight into the methodology of biomolecular crystal simulations and indicate directions for future work to obtain more accurate energy models for molecular dynamics.

  16. Measuring phonons in protein crystals

    Science.gov (United States)

    Niessen, Katherine A.; Snell, Edward; Markelz, A. G.

    2013-03-01

    Using Terahertz near field microscopy we find orientation dependent narrow band absorption features for lysozyme crystals. Here we discuss identification of protein collective modes associated with the observed features. Using normal mode calculations we find good agreement with several of the measured features, suggesting that the modes arise from internal molecular motions and not crystal phonons. Such internal modes have been associated with protein function.

  17. The Growth of KLN Crystals

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    The growth temperature curve of the growth system for the potass ium li thium niobate (KLN) has been measured and the temperature decrease program has b een calculated. KLN crystals with a size up to 30mm × 15mm × 5 mm have be en grown by flux method. The primary factors of the cracking of KLN crystal hav e been discussed. A blue laser light output has been obtained by optical parame tric oscillator pumping.

  18. Charge transport in organic crystals

    Energy Technology Data Exchange (ETDEWEB)

    Ortmann, Frank

    2009-07-01

    The understanding of charge transport is one of the central goals in the research on semiconducting crystals. For organic crystals this is particularly complicated due to the strength of the electron-phonon interaction which requires the description of a seamless transition between the limiting cases of a coherent band-transport mechanism and incoherent hopping. In this thesis, charge transport phenomena in organic crystals are studied by theoretical means. A theory for charge transport in organic crystals is developed which covers the whole temperature range from low T, where it reproduces an expression from the Boltzmann equation for band transport, via elevated T, where it generalizes Holstein's small-polaron theory to finite bandwidths, up to high T, for which a temperature dependence equal to Marcus' electron-transfer theory is obtained. Thereby, coherent band transport and thermally induced hopping are treated on equal footing while simultaneously treating the electron-phonon interaction non-perturbatively. By avoiding the approximation of narrow polaron bands the theory allows for the description of large and small polarons and serves as a starting point for computational studies. The theoretical description is completed by using ab initio material parameters for the selected crystals under study. These material parameters are taken from density functional theory calculations for durene, naphthalene, and guanine crystals. Besides the analysis of the transport mechanism, special focus is put on the study of the relationship between mobility anisotropy and structure of the crystals. This study is supported by a 3D-visualization method for the transport channels in such crystals which has been derived in this thesis. (orig.)

  19. Semiconductor crystal high resolution imager

    Science.gov (United States)

    Levin, Craig S. (Inventor); Matteson, James (Inventor)

    2011-01-01

    A radiation imaging device (10). The radiation image device (10) comprises a subject radiation station (12) producing photon emissions (14), and at least one semiconductor crystal detector (16) arranged in an edge-on orientation with respect to the emitted photons (14) to directly receive the emitted photons (14) and produce a signal. The semiconductor crystal detector (16) comprises at least one anode and at least one cathode that produces the signal in response to the emitted photons (14).

  20. Liquid Crystals for Nondestructive Evaluation

    Science.gov (United States)

    1978-09-01

    Temperatures TI > T2 > - > TS defects was possible using the liquid crystal. are the Average TemperatursI Thes Resptivegi. Kapfer , Burns, Salvo, and Doyle...Means of Liquid Crystals,’ J. 38 .1; .1 of Sound and Vibration, Vol. 36, No. 3, pp. 407- 65. V.C. Kapfer , D.J. Bums, C.J. Salvo, and E.A. 15, Oct. 1974

  1. The application of NLC for detecting solid crystals surface homogeneity

    Energy Technology Data Exchange (ETDEWEB)

    Tomilin, M G, E-mail: mgtomilin@mail.r [St.-Petersburg State University of Information Technologies, Mechanics and Optics, Kronverksky pr. 49, St.-Petersburg, 197101 (Russian Federation)

    2010-11-01

    The goal of the paper is to demonstrate wide fields of new polarizing microscope application based on nematic liquid crystals (LCs) for detecting different solid crystals surface inhomogeneities. Optical polarizing microscope (OPM) based on LCs makes possible to observe the invisible physical fields' distribution on the objects' surfaces. The OPM novelty consists in LC spatial light modulator (SLM) introduction in optical scheme to detect local deformations in real time. LC SLM applied as recording media has to be in direct contact with the surface under investigation. It gives the possibility to detect the invisible physical fields on the surface: intermolecular interactions, electrical, magnetic fields, etc. The theory of LC layer deformations was developed to find the relation between real size of structural defect D and the size of its image D' visualized with NLC layer. OPM method was used for detecting different aspects of surface inhomogeneities for different types of solid crystals. The new results were obtained for twinning boundaries in piezo quartz resonator having industrial application. LC SLM demonstrates non destructive method and better accuracy in comparison with etching, and the simplicity in comparison with x-radiation detecting. LC SLM may be combined with interference, phase-contrast and even near-field microscopes.

  2. Adaptive Liquid Crystal Windows

    Energy Technology Data Exchange (ETDEWEB)

    Taheri, Bahman; Bodnar, Volodymyr

    2011-12-31

    Energy consumption by private and commercial sectors in the U.S. has steadily grown over the last decade. The uncertainty in future availability of imported oil, on which the energy consumption relies strongly, resulted in a dramatic increase in the cost of energy. About 20% of this consumption are used to heat and cool houses and commercial buildings. To reduce dependence on the foreign oil and cut down emission of greenhouse gases, it is necessary to eliminate losses and reduce total energy consumption by buildings. To achieve this goal it is necessary to redefine the role of the conventional windows. At a minimum, windows should stop being a source for energy loss. Ideally, windows should become a source of energy, providing net gain to reduce energy used to heat and cool homes. It is possible to have a net energy gain from a window if its light transmission can be dynamically altered, ideally electronically without the need of operator assistance, providing optimal control of the solar gain that varies with season and climate in the U.S. In addition, the window must not require power from the building for operation. Resolution of this problem is a societal challenge and of national interest and will have a broad global impact. For this purpose, the year-round, allclimate window solution to provide an electronically variable solar heat gain coefficient (SHGC) with a wide dynamic range is needed. AlphaMicron, Inc. (AMI) developed and manufactured 1ft × 1ft prototype panels for the world’s first auto-adjusting Adaptive Liquid Crystal Windows (ALCWs) that can operate from sunlight without the need for external power source and demonstrate an electronically adjustable SHGC. This novel windows are based on AlphaMicron’s patented e-Tint® technology, a guesthost liquid crystal system implemented on flexible, optically clear plastic films. This technology is suitable both for OEM and aftermarket (retro-fitting) lamination to new and existing windows. Low level of

  3. Bulk Crystal Growth of Piezoelectric PMN-PT Crystals Using Gradient Freeze Technique for Improved SHM Sensors

    Science.gov (United States)

    Aggarwal, Mohan D.; Kochary, F.; Penn, Benjamin G.; Miller, Jim

    2007-01-01

    There has been a growing interest in recent years in lead based perovskite ferroelectric and relaxor ferroelectric solid solutions because of their excellent dielectric, piezoelectric and electrostrictive properties that make them very attractive for various sensing, actuating and structural health monitoring (SHM) applications. We are interested in the development of highly sensitive and efficient PMN-PT sensors based on large single crystals for the structural health monitoring of composite materials that may be used in future spacecrafts. Highly sensitive sensors are needed for detection of defects in these materials because they often tend to fail by distributed and interacting damage modes and much of the damage occurs beneath the top surface of the laminate and not detectable by visual inspection. Research is being carried out for various combinations of solid solutions for PMN-PT piezoelectric materials and bigger size crystals are being sought for improved sensor applications. Single crystals of this material are of interest for sensor applications because of their high piezoelectric coefficient (d33 greater than 1700 pC/N) and electromechanical coefficients (k33 greater than 0.90). For comparison, the commonly used piezoelectric ceramic lead zirconate titanate (PZT) has a d33 of about 600 pC/N and electromechanical coefficients k33 of about 0.75. At the present time, these piezoelectric relaxor crystals are grown by high temperature flux growth method and the size of these crystals are rather small (3x4x5 mm(exp 3). In the present paper, we have attempted to grow bulk single crystals of PMN-PT in a 2 inch diameter platinum crucible and successfully grown a large size crystal of 67%PMN-33%PT using the vertical gradient freeze technique with no flux. Piezoelectric properties of the grown crystals are investigated. PMN-PT plates show excellent piezoelectric properties. Samples were poled under an applied electric field of 5 kV/cm. Dielectric properties at a

  4. Crystal growth, Judd–Ofelt analysis and radiative properties of Nd:YAG single crystal grown by HDS

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Huaixin, E-mail: guohuaixin@gmail.com; Zhang, Mingfu, E-mail: mfzhang1@hit.edu.cn; Han, Jiecai; Nie, Ying

    2013-08-15

    Nd{sup 3+}-doped Y{sub 3}A{sub l5}O{sub 12} single crystal was successfully grown by horizontal directional solidification (HDS) method; in addition optical absorption and fluorescence spectra were measured at room temperature. Base on the Judd–Ofelt theory, the intensity parameters of Nd{sup 3+} in YAG crystal grown by HDS were determined, and then three spectroscopic parameter Ω{sub t} (t=2,4,6), radiative transition probabilities, radiative lifetime and branching ratios were obtained according to the absorption spectra and fluorescence spectra, and the results were discussed as well. Furthermore, the stimulated emission cross-section of {sup 4}F{sub 3/2}–{sup 4}I{sub 11/2} transition of Nd{sup 3+} in YAG crystal grown by the HDS technique was calculated as 17.86×10{sup −20} cm{sup 2}. In comparison with Nd:YAG crystal grown by the Czochraiski technique, those results indicated that lowly Nd{sup 3+}-doped YAG crystal grown by HDS method had highly efficient stimulated emission for laser materials. -- Highlights: ► The intensity parameters of Nd{sup 3+} in YAG crystal grown by the HDS were determined base on the Judd–Ofelt theory. ► The spectroscopic quality factor Ω{sub 4}/Ω{sub 6} was stimulated to be 0.6497. ► Radiative transition probabilities, radiative lifetime and branching ratios were estimated. ► The emission cross-section calculated for the {sup 4}F{sub 3/2}→{sup 4}I{sub 11/2} transition was 17.86×10{sup −20} cm{sup 2}.

  5. Exploring Carbon Nanomaterial Diversity for Nucleation of Protein Crystals

    Science.gov (United States)

    Govada, Lata; Leese, Hannah S.; Saridakis, Emmanuel; Kassen, Sean; Chain, Benny; Khurshid, Sahir; Menzel, Robert; Hu, Sheng; Shaffer, Milo S. P.; Chayen, Naomi E.

    2016-02-01

    Controlling crystal nucleation is a crucial step in obtaining high quality protein crystals for structure determination by X-ray crystallography. Carbon nanomaterials (CNMs) including carbon nanotubes, graphene oxide, and carbon black provide a range of surface topographies, porosities and length scales; functionalisation with two different approaches, gas phase radical grafting and liquid phase reductive grafting, provide routes to a range of oligomer functionalised products. These grafted materials, combined with a range of controls, were used in a large-scale assessment of the effectiveness for protein crystal nucleation of 20 different carbon nanomaterials on five proteins. This study has allowed a direct comparison of the key characteristics of carbon-based nucleants: appropriate surface chemistry, porosity and/or roughness are required. The most effective solid system tested in this study, carbon black nanoparticles functionalised with poly(ethylene glycol) methyl ether of mean molecular weight 5000, provides a novel highly effective nucleant, that was able to induce crystal nucleation of four out of the five proteins tested at metastable conditions.

  6. Heterogeneous Crystallization on Pairs of Pre-Structured Seeds.

    Science.gov (United States)

    Jungblut, Swetlana; Dellago, Christoph

    2016-09-01

    Studying the effects of small pre-structured seeds on the crystallization transition in an undercooled monodisperse Lennard-Jones fluid with transition interface path sampling combined with molecular dynamics simulations, we analyze the impact of the simultaneous presence of two seeds with various structures. In the presence of seeds with face- and body-centered cubic structures, we find that decreasing the seed-to-seed distance enhances the probability of the crystalline clusters formed on one of the seeds to grow beyond the critical size, thus, increasing the crystal nucleation rates. In contrast, when seeds have an icosahedral structure, the crystalline clusters form mostly in the bulk. The crystal nucleation rate, however, is also determined by the distance between the seeds with regular structure in which the lattice spacing is equal to the bulk lattice constant, pointing to a heterogeneous crystal nucleation that occurs away from the icosahedrally structured seeds. For slightly squeezed seeds, the effects of the presence of seeds with face- and body-centered cubic structures are reduced in comparison to the regular seeds, and we do not see any effect of the presence of the second seed for seeds with squeezed icosahedral structure.

  7. Finding the Cold Needle in a Warm Haystack: Infrared Imaging Applied to Locating Cryo-cooled Crystals in Loops

    Science.gov (United States)

    Snell, Edward; vanderWoerd, Mark

    2003-01-01

    Thermally imaging the cryocooling processes of crystals has been demonstrated showing the progression of a cold wave through a crystal from the face closest to the origin of the coldstream ending at the point furthest away. During these studies large volume crystals were clearly distinguished from the loop holding them. Large volume crystals, used for neutron studies, were chosen deliberately to enhance the imaging. The different infrared transmission and reflectance properties of the crystal in comparison to the cryo-protectant are thought to be the parameter that produces the contrast making the crystal visible. As an application of the technology to locating crystals, more small crystals of lysozyme and a bFGF/dna complex were cryo-protected and imaged in large loops. The crystals were clearly distinguished from the vitrified solution. In the case of the bFGF/dna complex the illumination had to be carefully manipulated to enable the crystal to be seen in the visible spectrum. These preliminary results will be presented along with advantages and disadvantages of the technique and a discussion of how it might be applied.

  8. Stacking fault energy in some single crystals

    Institute of Scientific and Technical Information of China (English)

    Aditya M.Vora

    2012-01-01

    The stacking fault energy of single crystals has been reported using the peak shift method.Presently studied all single crystals are grown by using a direct vapor transport (DVT) technique in the laboratory.The structural characterizations of these crystals are made by XRD.Considerable variations are shown in deformation (α) and growth (β) probabilities in single crystals due to off-stoichiometry,which possesses the stacking fault in the single crystal.

  9. A Century of Sapphire Crystal Growth

    Science.gov (United States)

    2004-05-17

    Crystal growth storage cabinet from Frémy’s lab.5,6 Flame Fusion and the Verneuil Process In 1885 rubies selling for $1000-2500...1891: Working with his student, M. Pacquier, Verneuil had developed most of what we now call Verneuil flame-fusion crystal growth . Verneuil ... Verneuil ) Crystal Growth Nassau, Gems Made by Man 11 • 1892: Verneuil eliminated crystal cracking by making contact area between ruby crystal

  10. Synthesis, characterization, single crystal X-ray structure, EPR and theoretical studies of a new hybrid inorganic-organic compound [Cu(Hdien)2(H2O)2](pnb)4·4H2O and its structural comparison with related [Cu(en)2(H2O)2](pnb)2

    Science.gov (United States)

    Kumar, Santosh; Sharma, Raj Pal; Venugopalan, Paloth; Witwicki, Maciej; Ferretti, Valeria

    2016-11-01

    A new hybrid inorganic-organic compound [Cu(Hdien)2(H2O)2](pnb)4·4H2O (1) (where pnb = p-nitrobenzoate), in which the tridentate ligand diethylenetriamine (dien) shows an unusual coordination behavior acting as a bidentate ligand when present in its monoprotonated form (Hdien+) has been synthesized by the reaction of copper(II) p-nitrobenzoate and slight excess of dien in methanol-water mixture (4:1v/v). Re-crystallization of the violet precipitated product from hot water gave single crystals suitable for X-ray diffraction studies. The newly synthesized compound 1 has been characterized by spectroscopic techniques (UV-Vis, FT-IR, EPR), and theoretical methods (DFT and MRCI/SORCI). Single crystal X-ray structure determination revealed the existence of the cationic species [Cu(Hdien)2(H2O)2]4+, four p-nitrobenzoate as counter anions and four water molecules are present as solvent of crystallization. Packing analyses of title compound as well as of the structurally similar [Cu(en)2(H2O)2](pnb)2,2 has shown similarities in the crystalline architecture that both hybrid inorganic-organic compounds is stabilized by various non-covalent interactions such as N-H⋯O, C-H⋯O, O-H⋯O etc.

  11. theoretical analysis of finite-height semiconductor-on-insulator based planar photonic crystal waveguides

    DEFF Research Database (Denmark)

    Søndergaard, Thomas; Arentoft, Jesper

    2002-01-01

    A planar photonic crystal waveguide based on the semiconductor-on-insulator (SOI) materials system is analyzed theoretically. Two-dimensional (2-D) calculations and comparison with dispersion relations for the media above and below the finite-height waveguide are used to obtain design guidelines...

  12. Photoaligning and Photopatterning — A New Challenge in Liquid Crystal Photonics

    Directory of Open Access Journals (Sweden)

    Vladimir G. Chigrinov

    2013-03-01

    Full Text Available Photoalignment possesses obvious advantages in comparison with the usually “rubbing” treatment of the substrates of liquid crystal display (LCD cells. The application of the photoalignment and photopatterning nanotechnology for the new generation of photonic and display devices will be reviewed.

  13. Liquid crystal TV-based white light optical tracking novelty filter.

    Science.gov (United States)

    Li, Y; Kostrzewski, A; Kim, D H; Eichmann, G

    1989-11-15

    A compact white light optical tracking novelty filter is demonstrated. Based on the use of two inexpensive liquid crystal televisions, a filtered and collimated white light source, digital delay, and video recorder, this portable white light device performs two major image comparison operations, a real time image subtraction and novelty tracking operations. Some preliminary experimental results are presented.

  14. Revealing of defects in CdTe crystals by DSL etching

    NARCIS (Netherlands)

    Bissoli, F.; Weyher, J.L.; Zappettini, A.; Zha, M.; Zanotti, L.

    2005-01-01

    The effect of DS(L) (Diluited Sirtl with or without Light) solution on CadmiumTelluride crystals has been studied in comparison with the actions due to Inoue and Nakagawa etching solutions. The use of chemical etching to reveal extended defects is a fast and useful technique for characterizing the c

  15. Crystal lattice dependency of the free radicals found in irradiated glycine

    NARCIS (Netherlands)

    Bie, M.J.A. de; Braams, R.

    1969-01-01

    The EPR spectra, and hence the stable free radicals, are different for the - or γ-irradiated α-, β- and γ-crystal forms of polycrystalline glycone. Therefore comparisons of the trideutero-glycine EPR spectrum with the EPR spectra of non-deuterated glycine are open to question

  16. A statistical approach for measuring dislocations in 2D photonic crystals

    DEFF Research Database (Denmark)

    Malureanu, Radu; Frandsen, Lars Hagedorn

    2008-01-01

    In this paper, a comparison between the placement accuracy of lattice atoms in photonic crystal structures fabricated with different lithographic techniques is made. Using atomic force microscopy measurements and self-developed algorithms for calculating the holes position within less than 0.01nm...

  17. Prediction of molecular crystal structures

    Energy Technology Data Exchange (ETDEWEB)

    Beyer, Theresa

    2001-07-01

    The ab initio prediction of molecular crystal structures is a scientific challenge. Reliability of first-principle prediction calculations would show a fundamental understanding of crystallisation. Crystal structure prediction is also of considerable practical importance as different crystalline arrangements of the same molecule in the solid state (polymorphs)are likely to have different physical properties. A method of crystal structure prediction based on lattice energy minimisation has been developed in this work. The choice of the intermolecular potential and of the molecular model is crucial for the results of such studies and both of these criteria have been investigated. An empirical atom-atom repulsion-dispersion potential for carboxylic acids has been derived and applied in a crystal structure prediction study of formic, benzoic and the polymorphic system of tetrolic acid. As many experimental crystal structure determinations at different temperatures are available for the polymorphic system of paracetamol (acetaminophen), the influence of the variations of the molecular model on the crystal structure lattice energy minima, has also been studied. The general problem of prediction methods based on the assumption that the experimental thermodynamically stable polymorph corresponds to the global lattice energy minimum, is that more hypothetical low lattice energy structures are found within a few kJ mol{sup -1} of the global minimum than are likely to be experimentally observed polymorphs. This is illustrated by the results for molecule I, 3-oxabicyclo(3.2.0)hepta-1,4-diene, studied for the first international blindtest for small organic crystal structures organised by the Cambridge Crystallographic Data Centre (CCDC) in May 1999. To reduce the number of predicted polymorphs, additional factors to thermodynamic criteria have to be considered. Therefore the elastic constants and vapour growth morphologies have been calculated for the lowest lattice energy

  18. Crystal growth in a three-phase system: diffusion and liquid-liquid phase separation in lysozyme crystal growth.

    Science.gov (United States)

    Heijna, M C R; van Enckevort, W J P; Vlieg, E

    2007-07-01

    In the phase diagram of the protein hen egg-white lysozyme, a region is present in which the lysozyme solution demixes and forms two liquid phases. In situ observations by optical microscopy show that the dense liquid droplets dissolve when crystals grow in this system. During this process the demixed liquid region retracts from the crystal surface. The spatial distribution of the dense phase droplets present special boundary conditions for Fick's second law for diffusion. In combination with the cylindrical symmetry provided by the kinetically roughened crystals, this system allows for a full numerical analysis. Using experimental data for setting the boundary conditions, a quasi-steady-state solution for the time-dependent concentration profile was shown to be valid. Comparison of kinetically rough growth in a phase separated system and in a nonseparated system shows that the growth kinetics for a three-phase system differs from a two-phase system, in that crystals grow more slowly but the duration of growth is prolonged.

  19. Structure and physical properties of single crystal PrCr{sub 2}Al{sub 20} and CeM{sub 2}Al{sub 20} (M=V, Cr): A comparison of compounds adopting the CeCr{sub 2}Al{sub 20} structure type

    Energy Technology Data Exchange (ETDEWEB)

    Kangas, Michael J.; Schmitt, Devin C.; Sakai, Akito; Nakatsuji, Satoru [Department of Chemistry, Louisiana State University, Baton Rouge, LA 70803 (United States); Institute of Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581 (Japan); Chan, Julia Y., E-mail: jchan@lsu.edu [Department of Chemistry, Louisiana State University, Baton Rouge, LA 70803 (United States); Institute of Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581 (Japan)

    2012-12-15

    Crystal growth and full structure determination of compounds adopting the CeCr{sub 2}Al{sub 20} structure type, LnTi{sub 2}Al{sub 20} (Ln=La-Pr, Sm, and Yb), LnV{sub 2}Al{sub 20} (Ln=La-Pr, and Sm), and LnCr{sub 2}Al{sub 20} (Ln=La-Pr, Sm, and Yb), are reported. Resistivity, magnetic susceptibility, and heat capacity of flux grown single crystals of the nonmagnetic CeM{sub 2}Al{sub 20} (Ln=Ce, Yb; M=Ti, V) compounds are compared to PrCr{sub 2}Al{sub 20}. Of particular interest is PrCr{sub 2}Al{sub 20} which does not show any phase transition down to the lowest temperature of the measurement (400 mK in resistivity measurement and 1.8 K for magnetic susceptibility measurements) and exhibits Kondo behavior at low temperatures. - Graphical abstract: Crystal structure of SmV{sub 2}Al{sub 20} showing the interpenetrating diamond-like samarium network and pyrochlore-like vanadium network. Highlights: Black-Right-Pointing-Pointer Single crystals of LnM{sub 2}Al{sub 20} were grown from a molten aluminum flux. Black-Right-Pointing-Pointer Magnetic, electrical, and specific heat of single crystal LnM{sub 2}Al{sub 20} are presented. Black-Right-Pointing-Pointer PrCr{sub 2}Al{sub 20} exhibits evidence of Kondo effect.

  20. Nanofluidics of Single-crystal Diamond Nanomechanical Resonators

    CERN Document Server

    Kara, V; Atikian, H; Yakhot, V; Loncar, M; Ekinci, K L

    2015-01-01

    Single-crystal diamond nanomechanical resonators are being developed for countless applications. A number of these applications require that the resonator be operated in a fluid, i.e., a gas or a liquid. Here, we investigate the fluid dynamics of single-crystal diamond nanomechanical resonators in the form of nanocantilevers. First, we measure the pressure-dependent dissipation of diamond nanocantilevers with different linear dimensions and frequencies in three gases, He, N$_2$, and Ar. We observe that a subtle interplay between the length scale and the frequency governs the scaling of the fluidic dissipation. Second, we obtain a comparison of the surface accommodation of different gases on the diamond surface by analyzing the dissipation in the molecular flow regime. Finally, we measure the thermal fluctuations of the nanocantilevers in water, and compare the observed dissipation and frequency shifts with theoretical predictions. These findings set the stage for developing diamond nanomechanical resonators o...

  1. The crystal structure of samarosporin I at atomic resolution.

    Science.gov (United States)

    Gessmann, Renate; Axford, Danny; Evans, Gwyndaf; Brückner, Hans; Petratos, Kyriacos

    2012-11-01

    The atomic resolution structures of samarosporin I have been determined at 100 and 293 K. This is the first crystal structure of a natural 15-residue peptaibol. The amino acid sequence in samarosporin I is identical to emerimicin IV and stilbellin I. Samarosporin is a peptide antibiotic produced by the ascomycetous fungus Samarospora rostrup and belongs to peptaibol subfamily 2. The structures at both temperatures are very similar to each other adopting mainly a 3₁₀-helical and a minor fraction of α-helical conformation. The helices are significantly bent and packed in an antiparallel fashion in the centered monoclinic lattice leaving among them an approximately 10-Å channel extending along the crystallographic twofold axis. Only two ordered water molecules per peptide molecule were located in the channel. Comparisons have been carried out with crystal structures of subfamily 2 16-residue peptaibols antiamoebin and cephaibols. The repercussion of the structural analysis of samarosporin on membrane function is discussed.

  2. Chirped photonic crystals: a natural strategy for broadband reflectance

    CERN Document Server

    Cook, Caleb Q

    2016-01-01

    One-dimensional photonic crystals with slowly varying, i.e. "chirped", lattice period are responsible for broadband light reflectance in many diverse biological contexts, ranging from the shiny coatings of various beetles to the eyes of certain butterflies. We present a quantum scattering analogy for light reflection from these adiabatically chirped photonic crystals (ACPCs) and apply a WKB-type approximation to obtain a closed-form expression for the reflectance. From this expression we infer several design principles, including a differential equation for the chirp pattern required to elicit a given reflectance spectrum and the minimal number of bilayers required to exceed a desired reflectance threshold. Comparison of the number of bilayers found in ACPCs throughout nature and our predicted minimal required number also gives a quantitative measure of the optimality of chirped biological reflectors. Together these results elucidate the design principles of chirped reflectors in nature and their possible app...

  3. Methods for synthesizing microporous crystals and microporous crystal membranes

    Energy Technology Data Exchange (ETDEWEB)

    Dutta, Prabir; Severance, Michael; Sun, Chenhu

    2017-02-07

    A method of making a microporous crystal material, comprising: a. forming a mixture comprising NaOH, water, and one or more of an aluminum source, a silicon source, and a phosphate source, whereupon the mixture forms a gel; b. heating the gel for a first time period, whereupon a first volume of water is removed from the gel and micoroporous crystal nuclei form, the nuclei having a framework; and c.(if a membrane is to be formed) applying the gel to a solid support seeded with microporous crystals having a framework that is the same as the framework of the nuclei; d. heating the gel for a second time period. during which a second volume of water is added to the gel; wherein the rate of addition of the second volume of water is between about 0.5 and about 2.0 fold the rate of removal of the first volume of water.

  4. Hot Views on Cold Crystals: The Application of Thermal Imaging in Cryo-crystallography

    Science.gov (United States)

    Snell, E. H.; vanderWoerd, M. J.; Deacon, A.

    2003-01-01

    In the past we have used thermal imaging techniques to visualize the cryocooling processes of macromolecular crystals. From these images it was clear that a cold wave progresses through a crystal starting at the face closest to the origin of the cold stream and ending at the point furthest away. During these studies we used large volume crystals, which were clearly distinguished from the loop holding them. These large crystals, originally grown for neutron diffraction studies, were chosen deliberately to enhance the imaging. As an extension to this work, we present used thermal imaging to study small crystals, held in a cryo-loop, in the presence of vitrified mother liquor. The different infrared transmission and reflectance properties of the crystal in comparison to the mother liquor surrounding it are thought to be the parameter that produces the contrast that makes the crystal visible. An application of this technology may be the determination of the exact location of small crystals in a cryo-loop. Data from initial tests in support of application development was recorded for lysozyme crystals and for bFGF/dna complex crystals, which were cryo-cooled and imaged in large loops, both with visible light and with infrared radiation. The crystals were clearly distinguished from the vitrified solution in the infrared spectrum, while in the case of the bFGF/dna complex the illumination had to be carefully manipulated to make the crystal visible in the visible spectrum. These results suggest that the thermal imaging may be more sensitive than visual imaging for automated location of small crystals. However, further work on small crystals robotically mounted at SSRL did not clearly visualize those crystals. The depth of field of the camera proved to be limiting and a different cooling geometry was used, compared to the previous, successful experiments. Analysis to exploit multiple images to improve depth of field and experimental work to understand cooling geometry

  5. Hot Views on Cold Crystals: The Application of Thermal Imaging in Cryocrystallography

    Science.gov (United States)

    Snell, Eddie H.

    2003-01-01

    In the past we have used thermal imaging techniques to visualize the cryocooling processes of macromolecular crystals. From these images it was clear that a cold wave progresses through a crystal starting at the face closest to the origin of the cold stream and ending at the point furthest away. During these studies we used large volume crystals, which were clearly distinguished from the loop holding them. These large crystals, originally grown for neutron diffraction studies, were chosen deliberately to enhance the imaging. As an extension to this work, we used thermal imaging to study small crystals, held in a cryo- loop, in the presence of vitrified mother liquor. The different infrared transmission and reflectance properties of the crystal in comparison to the mother liquor surrounding it are thought to be the parameter that produces the contrast that makes the crystal visible. An application of this technology may be the determination of the exact location of small crystals in a cryo-loop. Data from initial tests in support of application development was recorded for lysozyme crystals and for bFGF/dna complex crystals, which were cryo-cooled and imaged in large loops, both with visible light and with infrared radiation. The crystals were clearly distinguished from the vitrified solution in the infrared spectrum, while in the case of the bFGF/dna complex the illumination had to be carefully manipulated to make the crystal visible in the visible spectrum. These results suggest that the thermal imaging may be more sensitive than visual imaging for automated location of small crystals. However, further work on small crystals robotically mounted at SSRL did not clearly visualize those crystals. The depth of field of the camera proved to be limiting and a different cooling geometry was used, compared to the previous, successful experiments. Analysis to exploit multiple images to improve depth of field and experimental work to understand cooling geometry effects is

  6. Organic Crystals with Near-Infrared Amplified Spontaneous Emissions Based on 2'-Hydroxychalcone Derivatives: Subtle Structure Modification but Great Property Change.

    Science.gov (United States)

    Cheng, Xiao; Wang, Kai; Huang, Shuo; Zhang, Houyu; Zhang, Hongyu; Wang, Yue

    2015-07-13

    A series of highly efficient deep red to near-infrared (NIR) emissive organic crystals 1-3 based on the structurally simple 2'-hydroxychalcone derivatives were synthesized through a simple one-step condensation reaction. Crystal 1 displays the highest quantum yield (Φf) of 0.32 among the reported organic single crystals with an emission maximum (λem) over 710 nm. Comparison between the bright emissive crystals 1-3 and the nearly nonluminous compounds 4-7 clearly gives evidence that a subtle structure modification can arouse great property changes, which is instructive in designing new high-efficiency organic luminescent materials. Notably, crystals 1-3 exhibit amplified spontaneous emissions (ASE) with extremely low thresholds. Thus, organic deep red to NIR emissive crystals with very high Φf have been obtained and are found to display the first example of NIR fluorescent crystal ASE.

  7. Effects of Annealing Treatments on Luminescence and Scintillation Properties of Ce:Lu3Al5O12 Crystal Grown by Czochralski Method

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Ce:Lu3Al5O12 single crystals grown in pure N2 atmosphere by Czochralski method were annealed in oxidizing atmosphere (air) and reducing atmosphere (H2+N2), respectively. Effects of annealing treatments on luminescence and scintillation properties of the crystals were investigated. The crystal annealed in air showed the highest luminescence intensity under blue light or vacuum ultraviolet excitation in comparison with that annealed in reducing flux or the as-grown crystal. Under X-ray excitation, crystal annealed in reducing atmosphere had the lowest light yield, and crystal annealed in air had the fastest decay time under 137Cs 662 keV γ-ray excitation. Different annealing treatments resulted in different luminescence and scintillation properties, which might related with oxygen vacancies or defect existing in the crystals.

  8. Growth of KH/sub 2/PO/sub 4/ crystals at constant temperature and supersaturation. Final report, 20 October 1980-20 October 1981

    Energy Technology Data Exchange (ETDEWEB)

    Loiacono, G.M.; Zola, J.; Kostecky, G.

    1982-02-01

    A large three-zone cyrstallizer system was constructed and successfully operated for growing KH/sub 2/PO/sub 4/ single crystals. Under conditions of constant crystallization temperature and supersaturation, growth rates exceeding 5 mm per day were demonstrated for KH/sub 2/PO/sub 4/ crystals of 5 x 5 cm cross section. The optical quality of these crystals was equivalent to that of crystals grown at rates presently considered as state-of-the-art (approx. 1 mm/day). Sample crystals were supplied for comparison testing. The three-zone system appears to be ideally suitable for growth of large-diameter KH/sub 2/PO/sub 4/ crystals for the Laser Fusion Program.

  9. Role of Solvents in Improvement of Dissolution Rate of Drugs: Crystal Habit and Crystal Agglomeration

    Directory of Open Access Journals (Sweden)

    Maryam Maghsoodi

    2015-03-01

    Full Text Available Crystallization is often used for manufacturing drug substances. Advances of crystallization have achieved control over drug identity and purity, but control over the physical form remains poor. This review discusses the influence of solvents used in crystallization process on crystal habit and agglomeration of crystals with potential implication for dissolution. According to literature it has been known that habit modification of crystals by use of proper solvents may enhance the dissolution properties by changing the size, number and the nature of crystal faces exposed to the dissolution medium. Also, the faster dissolution rate of drug from the agglomerates of crystals compared with the single crystals may be related to porous structure of the agglomerates and consequently their better wettability. It is concluded from this review that in-depth understanding of role of the solvents in crystallization process can be applied to engineering of crystal habit or crystal agglomeration, and predictably dissolution improvement in poorly soluble drugs.

  10. Tunable Photonic Band Gaps In Photonic Crystal Fibers Filled With a Cholesteric Liquid Crystal

    Institute of Scientific and Technical Information of China (English)

    Thomas; Tanggaard; Larsen; David; Sparre; Hermann; Anders; Bjarklev

    2003-01-01

    A photonic crystal fiber has been filled with a cholesteric liquid crystal. A temperature sensitive photonic band gap effect was observed, which was especially pronounced around the liquid crystal phase transition temperature.

  11. Supramolecular chemistry and crystal engineering

    Indian Academy of Sciences (India)

    Ashwini Nangia

    2010-05-01

    Advances in supramolecular chemistry and crystal engineering reported from India within the last decade are highlighted in the categories of new intermolecular interactions, designed supramolecular architectures, network structures, multi-component host-guest systems, cocrystals, and polymorphs. Understanding self-assembly and crystallization through X-ray crystal structures is illustrated by two important prototypes - the large unit cell of elusive saccharin hydrate, Na16(sac)16 . 30H2O, which contains regular and irregular domains in the same structure, and by the Aufbau build up of zinc phosphate framework structures, e.g. ladder motif in [C3N2H12][Zn(HPO4)2] to layer structure in [C3N2H12][Zn2(HPO4)3] upon prolonged hydrothermal conditions. The pivotal role of accurate X-ray diffraction in supramolecular and structural studies is evident in many examples. Application of the bottomup approach to make powerful NLO and magnetic materials, design of efficient organogelators, and crystallization of novel pharmaceutical polymorphs and cocrystals show possible future directions for interdisciplinary research in chemistry with materials and pharmaceutical scientists. This article traces the evolution of supramolecular chemistry and crystal engineering starting from the early nineties and projects a center stage for chemistry in the natural sciences.

  12. Nucleation of Crystals in Solution

    Science.gov (United States)

    Vekilov, Peter G.

    2010-07-01

    Solution crystallization is an essential part of processes in the chemical and pharmaceutical industries and a major step in physiological and pathological phenomena. Crystallization starts with nucleation and control of nucleation is crucial for the control of the number, size, perfection, polymorphism and other characteristics of the crystalline materials. Recently, there have been significant advances in the understanding of the mechanism of nucleation of crystals in solution. The most significant of these is the two-step mechanism of nucleation, according to which the crystalline nucleus appears inside pre-existing metastable clusters of size several hundred nanometers, which consist of dense liquid and are suspended in the solution. While initially proposed for protein crystals, the applicability of this mechanism has been demonstrated for small molecule organic materials, colloids, and biominerals. This mechanism helps to explain several long-standing puzzles of crystal nucleation in solution: nucleation rates which are many orders of magnitude lower than theoretical predictions, nucleation kinetic dependencies with steady or receding parts at increasing supersaturation, the role of heterogeneous substrates for polymorph selection, the significance of the dense protein liquid, and others. More importantly, this mechanism provides powerful tools for control of the nucleation process by varying the solution thermodynamic parameters so that the volume occupied by the dense liquid shrinks or expands.

  13. Sublimation rate of molecular crystals - role of internal degrees of freedom

    Energy Technology Data Exchange (ETDEWEB)

    Maiti, A; Zepeda-Ruiz, L A; Gee, R H; Burnham, A

    2007-01-19

    It is a common practice to estimate site desorption rate from crystal surfaces with an Arrhenius expression of the form v{sub eff} exp(-{Delta}E/k{sub B}T), where {Delta}E is an activation barrier to desorb and v{sub eff} is an effective vibrational frequency {approx} 10{sup 12} sec{sup -1}. However, such a formula can lead to several to many orders of magnitude underestimation of sublimation rates in molecular crystals due to internal degrees of freedom. We carry out a quantitative comparison of two energetic molecular crystals with crystals of smaller entities like ice and Argon (solid) and uncover the errors involved as a function of molecule size. In the process, we also develop a formal definition of v{sub eff} and an accurate working expression for equilibrium vapor pressure.

  14. Quantum and classical theories of scattering of relativistic electrons in ultrathin crystals

    CERN Document Server

    Shulga, N F

    2016-01-01

    Quantum and classical theories are proposed of scattering of high energy electrons in ultrathin crystals. The quantum theory is based upon a special representation of the scattering amplitude in the form of the integral over the surface surrounding the crystal, and on the spectral method of determination of the wave function. The classical theory is based upon the solution of the equation of motion by numerical methods. The comparison is performed of quantum and classical differential cross-sections of scattering in the transitional range of crystal thicknesses, from those at which the channeling phenomenon is not developed up to those at which it is realized. It is shown that in this range of crystal thicknesses substantial difference of quantum and classical scattering cross-sections takes place for the electrons with the energy up to tens of MeV. With the energy increase such difference decreases but some quantum effects in scattering still remain.

  15. On the facet-skeletal transition of snow crystals - Experiments in high and low gravity

    Science.gov (United States)

    Alena, T.; Hallett, J.; Saunders, C. P. R.

    1990-01-01

    A laboratory investigation of the influence of air velocity on the growth of columnar ice crystals from the vapor over the range -3 to -5 C shows that the linear growth velocity increases and that columns transform to sheath crystals or needles as air velocity increases from a few cm/s to 40 cm/s. Comparison with a similar transition of plates to dendrites shows that, macroscopically, in both cases the facets sprout rounded tips at a critical velocity which is lower for higher ambient supersaturation. Studies in low gravity show that chamber scale convection under normal gravity may have significant influence on growth even in the absence of an imposed air velocity. Falling snow crystals become more skeletal in shape as they grow and fall with increasing velocity. This development depends critically on temperature (+ or - 0.5 C) and demonstrates that the snow crystal shape is even more dependent on environmental growth conditions that previously thought.

  16. Mechanical properties of layered InSe and GaSe single crystals

    Science.gov (United States)

    Mosca, D. H.; Mattoso, N.; Lepienski, C. M.; Veiga, W.; Mazzaro, I.; Etgens, V. H.; Eddrief, M.

    2002-01-01

    The mechanical properties of InSe and GaSe single crystals have been studied by means of nanoindentation tests. Both bulk crystals are well ordered and present a predominant γ-type interlayer stacking sequence as determined by x-ray diffraction and transmission electron microscopy measurements. The course of plastic deformation induced in the crystals by application of a definite shear stress through the penetration of a Berkovich tip indicates that the deformation occurs predominantly by pop-in events along easy slip directions having a fairly elastic character between displacements. Hardness anisotropy along crystal axes is clearly seen and the measured elastic modulus presents a discrepancy smaller than 5% in comparison with theoretical calculations performed using previous experimental values of the elastic constants.

  17. Crystallization in lactose refining-a review.

    Science.gov (United States)

    Wong, Shin Yee; Hartel, Richard W

    2014-03-01

    In the dairy industry, crystallization is an important separation process used in the refining of lactose from whey solutions. In the refining operation, lactose crystals are separated from the whey solution through nucleation, growth, and/or aggregation. The rate of crystallization is determined by the combined effect of crystallizer design, processing parameters, and impurities on the kinetics of the process. This review summarizes studies on lactose crystallization, including the mechanism, theory of crystallization, and the impact of various factors affecting the crystallization kinetics. In addition, an overview of the industrial crystallization operation highlights the problems faced by the lactose manufacturer. The approaches that are beneficial to the lactose manufacturer for process optimization or improvement are summarized in this review. Over the years, much knowledge has been acquired through extensive research. However, the industrial crystallization process is still far from optimized. Therefore, future effort should focus on transferring the new knowledge and technology to the dairy industry.

  18. Last crystals for the CMS chandelier

    CERN Multimedia

    2008-01-01

    In March, the last crystals for CMS’s electromagnetic calorimeter arrived from Russia and China. Like dedicated jewellers crafting an immense chandelier, the CMS ECAL collaborators are working extremely hard to install all the crystals before the start-up of the LHC. One of the last CMS end-cap crystals, complete with identification bar code. Lead tungstate crystals mounted onto one section of the CMS ECAL end caps. Nearly 10 years after the first production crystal arrived at CERN in September 1998, the very last shipment has arrived. These final crystals will be used to complete the end-caps of the electromagnetic calorimeter (ECAL) at CMS. All in all, there are more than 75,000 crystals in the ECAL. The huge quantity of CMS lead tungstate crystals used in the ECAL corresponds to the highest volume ever produced for a single experiment. The excellent quality of the crystals, both in ter...

  19. Homogeneous models for bianisotropic crystals

    CERN Document Server

    Ponti, S; Oldano, C

    2002-01-01

    We extend to bianisotropic structures a formalism already developed, based on the Bloch method for defining the effective dielectric tensor of anisotropic crystals in the long-wavelength approximation. More precisely, we provide a homogenization scheme which yields a wavevector-dependent effective medium for any 3D, 2D, or 1D bianisotropic crystal. We illustrate our procedure by applying this to a 1D magneto-electric smectic C*-type structure. The resulting equations confirm that the presence of dielectric and magnetic susceptibilities in the periodic structures generates magneto-electric pseudo-tensors for the effective medium. Their contribution to the optical activity of structurally chiral media can be of the same order of magnitude as the one present in dielectric helix-shaped crystals. Simple analytical expressions are found for the most important optical properties of smectic C*-type structures which are simultaneously dielectric and magnetic.

  20. Surface energies of elemental crystals

    Science.gov (United States)

    Tran, Richard; Xu, Zihan; Radhakrishnan, Balachandran; Winston, Donald; Sun, Wenhao; Persson, Kristin A.; Ong, Shyue Ping

    2016-09-01

    The surface energy is a fundamental property of the different facets of a crystal that is crucial to the understanding of various phenomena like surface segregation, roughening, catalytic activity, and the crystal’s equilibrium shape. Such surface phenomena are especially important at the nanoscale, where the large surface area to volume ratios lead to properties that are significantly different from the bulk. In this work, we present the largest database of calculated surface energies for elemental crystals to date. This database contains the surface energies of more than 100 polymorphs of about 70 elements, up to a maximum Miller index of two and three for non-cubic and cubic crystals, respectively. Well-known reconstruction schemes are also accounted for. The database is systematically improvable and has been rigorously validated against previous experimental and computational data where available. We will describe the methodology used in constructing the database, and how it can be accessed for further studies and design of materials.

  1. Phononic crystals of poroelastic spheres

    Science.gov (United States)

    Alevizaki, A.; Sainidou, R.; Rembert, P.; Morvan, B.; Stefanou, N.

    2016-11-01

    An extension of the layer-multiple-scattering method to phononic crystals of poroelastic spheres immersed in a fluid medium is developed. The applicability of the method is demonstrated on specific examples of close-packed fcc crystals of submerged water-saturated meso- and macroporous silica microspheres. It is shown that, by varying the pore size and/or the porosity, the transmission, reflection, and absorption spectra of finite slabs of these crystals are significantly altered. Strong absorption, driven by the slow waves in the poroelastic material and enhanced by multiple scattering, leads to negligible transmittance over an extended frequency range, which might be useful for practical applications in broadband acoustic shielding. The results are analyzed by reference to relevant phononic dispersion diagrams in the viscous and inertial coupling limits, and a consistent interpretation of the underlying physics is provided.

  2. 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.

  3. Optical Properties of Photonic Crystals

    CERN Document Server

    Sakoda, Kazuaki

    2005-01-01

    This is the first comprehensive textbook on the optical properties of photonic crystals. It deals not only with the properties of the radiation modes inside the crystals but also with their peculiar optical response to external fields. A general theory of linear and nonlinear optical response is developed in a clear and detailed fashion using the Green's function method. The symmetry of the eigenmodes is treated systematically using group theory to show how it affects the optical properties of photonic crystals. Important recent developments such as the enhancement of stimulated emission, second harmonic generation, quadrature-phase squeezing, and low-threshold lasing are also treated in detail and made understandable. Numerical methods are also emphasized. Thus this book provides both an introduction for graduate and undergraduate students and also key information for researchers in this field. This second edition has been updated and includes a new chapter on superfluorescence.

  4. Effect of crystal habit on the dissolution behaviour of simvastatin crystals and its relationship to crystallization solvent properties.

    Science.gov (United States)

    Bukovec, P; Benkic, P; Smrkolj, M; Vrecer, F

    2016-05-01

    Simvastatin crystals, having same crystal structure but different types of habits and hence different intrinsic dissolution rate, were prepared by recrystallization from solvents selected according to their polarity index. Scanning electron microscopy, laser diffraction, image analysis, X-ray powder diffractometry, Fourier transform infrared spectroscopy and differential scanning calorimetry were used to investigate the physicochemical characteristics of the prepared crystals. The isolated crystals exhibited different crystal habits but possessed the same internal crystal structure. In this study the comparative intrinsic dissolution behaviour of the simvastatin crystals with different types of habits was studied and explained by surface energy and correlated to different solvent systems that were used for crystallization. In our work we diminished the influence of all other physical parameters that could influence the dissolution rate, e.g. particle size, specific surface area and polymorphism in order to focus the study onto the impact of crystal shape itself on the dissolution rate of simvastatin crystals. Rod shaped crystals isolated from more hydrophilic solvent mixture dissolved faster than plate-like crystals obtained from solvent mixture with lower polarity index. We correlated this fact to the different growth rate of the individual faces which resulted in different relative size of the individual crystal faces exposed to the dissolution medium as well as the chemical nature of those faces which in turn influenced the wettability and subsequent dissolution of the active pharmaceutical ingredient.

  5. Fluorescence properties of photonic crystals doped with perylenediimide.

    Science.gov (United States)

    Diacon, Aurel; Rusen, Edina; Mocanu, Alexandra; Hudhomme, Piétrick; Cincu, Corneliu

    2011-06-21

    This study aims to present the fabrication of colloidal photonic crystals (PC) with increased fluorescence properties. The use of a highly fluorescent perylenediimide derivate (PDI) during the soap-free emulsion polymerization of styrene-acrylic acid resulted in monodisperse core-shell particles which allowed the fabrication of PC films. The properties of the hybrid material were studied in comparison with hybrid materials obtained by impregnation of films with chromophore solutions. In both cases an increase of the fluorescence response was observed in addition to a blue shift for the PDI core particles, proving the incorporation of the dye inside the copolymer particles.

  6. Photonic crystal digital alloys and their band structure properties.

    Science.gov (United States)

    Lee, Jeongkug; Kim, Dong-Uk; Jeon, Heonsu

    2011-09-26

    We investigated semi-disordered photonic crystals (PCs), digital alloys, and made thorough comparisons with their counterparts, random alloys. A set of diamond lattice PC digital alloys operating in a microwave regime were prepared by alternately stacking two kinds of sub-PC systems composed of alumina and silica spheres of the same size. Measured transmission spectra as well as calculated band structures revealed that when the digital alloy period is short, band-gaps of the digital alloys are practically the same as those of the random alloys. This study indicates that the concept of digital alloys holds for photons in PCs as well.

  7. Nucleation of insulin crystals in a wide continuous supersaturation gradient.

    Science.gov (United States)

    Penkova, Anita; Dimitrov, Ivaylo; Nanev, Christo

    2004-11-01

    Modifying the classical double pulse technique, by using a supersaturation gradient along an insulin solution contained in a glass capillary tube, we found conditions appropriate for the direct measurement of nucleation parameters. The nucleation time lag has been measured. Data for the number of crystal nuclei versus the nucleation time were obtained for this hormone. Insulin was chosen as a model protein because of the availability of solubility data in the literature. A comparison with the results for hen-egg-white lysozyme, HEWL was performed.

  8. Crystal structure of 3-bromo-2-hydroxybenzoic acid

    Directory of Open Access Journals (Sweden)

    Gerhard Laus

    2015-05-01

    Full Text Available Mutual carboxyl–carboxyl O—H...O hydrogen bonds link the molecules of the title compound, C7H5BrO3, into centrosymmetric dimers which display a central R22(8 ring motif. In addition, there is an intramolecular hydroxyl–carboxyl O—H...O interaction present. A comparison with the crystal structures of 59 other substituted derivatives of salicylic acid shows that both the centrosymmetric carboxyl–carboxyl O—H...O dimer and the stacking mode of molecules along the short a axis observed in the title structure are frequent packing motifs in this set.

  9. Lateral shift in one-dimensional quasiperiodic chiral photonic crystal

    Energy Technology Data Exchange (ETDEWEB)

    Da, Jian, E-mail: dajian521@sina.com [Department of Information Engineering, Huaian Senior Vocational and Technical School, Feiyao road, Huaian 223005, Jiangsu Province (China); Mo, Qi, E-mail: moqiyueyang@163.com [School of Software, Yunnan University, Cuihu Bai Road, Kunming City, Yunnan Province 650091 (China); Cheng, Yaokun [Department of Information Engineering, Huaian Senior Vocational and Technical School, Feiyao road, Huaian 223005, Jiangsu Province (China); Liu, Taixiang [Taishan Vocational College of Nursing, Shandong Province 271000 (China)

    2015-02-01

    We investigate the lateral shift of a one-dimensional quasiperiodic photonic crystal consisting of chiral and conventional dielectric materials. The effect of structural irregularity on lateral shift is evaluated by stationary-phase approach. Our results show that the lateral shift can be modulated by varying the structural irregularity in quasiperiodic structure. Besides, the position of peak in lateral shift spectrum stays sensitive to the chiral factor of chiral materials. In comparison with that of periodic structure, quasiperiodic structure provides an extra degree of freedom to manipulate the lateral shift.

  10. Growth of bulk gadolinium pyrosilicate single crystals for scintillators

    Science.gov (United States)

    Gerasymov, I.; Sidletskiy, O.; Neicheva, S.; Grinyov, B.; Baumer, V.; Galenin, E.; Katrunov, K.; Tkachenko, S.; Voloshina, O.; Zhukov, A.

    2011-03-01

    Ce, Pr, and La-doped gadolinium pyrosilicate Gd2Si2O7 (GPS) single crystals were grown by the Czochralski and Top Seeded Solution Growth (TSSG) techniques for the first time. Formation conditions of different pyrosilicate phases were determined. X-ray luminescence integral intensity of Ce-doped GPS is about one order of magnitude higher in comparison with gadolinium oxyorthosilicate Gd2SiO5:Ce (GSO:Ce). All samples demonstrate temperature stability of luminescence yield up to 400 K.

  11. Channeling and Radiation of 855 MeV Electrons and Positrons in Straight and Bent Tungsten (110) Crystals

    CERN Document Server

    Shen, H; Zhang, F S; Sushko, Gennady B; Korol, Andrei V; Solov'yov, Andrey V

    2016-01-01

    Planar channeling of 855 MeV electrons and positrons in straight and bent tungsten (110) crystal is simulated by means of the \\MBNExplorer software package. The results of simulations for a broad range of bending radii are analyzed in terms of the channel acceptance, dechanneling length, and spectral distribution of the emitted radiation. Comparison of the results with predictions of other theories as well as with the data for (110) oriented diamond, silicon and germanium crystals is carried out.

  12. Quantum crystals and spin chains

    Energy Technology Data Exchange (ETDEWEB)

    Dijkgraaf, Robbert [KdV Institute for Mathematics, University of Amsterdam, Plantage Muidergracht 24, 1018 TV Amsterdam (Netherlands); Institute for Theoretical Physics, University of Amsterdam, Valckenierstraat 65, 1018 XE Amsterdam (Netherlands); Orlando, Domenico [Institut de Physique, Universite de Neuchatel, Rue Breguet 1, CH-2000 Neuchatel (Switzerland); Reffert, Susanne [Institute for Theoretical Physics, University of Amsterdam, Valckenierstraat 65, 1018 XE Amsterdam (Netherlands)], E-mail: sreffert@gmail.com

    2009-04-21

    In this article, we discuss the quantum version of the melting crystal corner in one, two, and three dimensions, generalizing the treatment for the quantum dimer model. Using a mapping to spin chains we find that the two-dimensional case (growth of random partitions) is integrable and leads directly to the Hamiltonian of the Heisenberg XXZ ferromagnet. The three-dimensional case of the melting crystal corner is described in terms of a system of coupled XXZ spin chains. We give a conjecture for its mass gap and analyze the system numerically.

  13. Quantum crystals and spin chains

    Science.gov (United States)

    Dijkgraaf, Robbert; Orlando, Domenico; Reffert, Susanne

    2009-04-01

    In this article, we discuss the quantum version of the melting crystal corner in one, two, and three dimensions, generalizing the treatment for the quantum dimer model. Using a mapping to spin chains we find that the two-dimensional case (growth of random partitions) is integrable and leads directly to the Hamiltonian of the Heisenberg XXZ ferromagnet. The three-dimensional case of the melting crystal corner is described in terms of a system of coupled XXZ spin chains. We give a conjecture for its mass gap and analyze the system numerically.

  14. Manufacturing method of photonic crystal

    Science.gov (United States)

    Park, In Sung; Lee, Tae Ho; Ahn, Jin Ho; Biswas, Rana; Constant, Kristen P.; Ho, Kai-Ming; Lee, Jae-Hwang

    2013-01-29

    A manufacturing method of a photonic crystal is provided. In the method, a high-refractive-index material is conformally deposited on an exposed portion of a periodic template composed of a low-refractive-index material by an atomic layer deposition process so that a difference in refractive indices or dielectric constants between the template and adjacent air becomes greater, which makes it possible to form a three-dimensional photonic crystal having a superior photonic bandgap. Herein, the three-dimensional structure may be prepared by a layer-by-layer method.

  15. Crystal study and econometric model

    Science.gov (United States)

    1975-01-01

    An econometric model was developed that can be used to predict demand and supply figures for crystals over a time horizon roughly concurrent with that of NASA's Space Shuttle Program - that is, 1975 through 1990. The model includes an equation to predict the impact on investment in the crystal-growing industry. Actually, two models are presented. The first is a theoretical model which follows rather strictly the standard theoretical economic concepts involved in supply and demand analysis, and a modified version of the model was developed which, though not quite as theoretically sound, was testable utilizing existing data sources.

  16. Acoustooptic Diffraction in Borate Crystals

    CERN Document Server

    Martynyuk-Lototska, I; Krupych, O; Adamiv, V; Smirnov, Ye; Vlokh, R

    2004-01-01

    The efficiency of acoustooptic (AO) diffraction in a-BaB2O4 and Li2B4O7 crystals is studied experimentally. The crystals are shown to be quite good AO materials. The efficiency of AO diffraction in a-BaB2O4 reaches h=30% at the electric signal power of P=0.7W for the transverse acoustic wave and 15% at the power of P=0.56W for the longitudinal wave. The same parameter for Li2B4O7 reaches h=21% at P=0,81W for the longitudinal acoustic wave.

  17. Fundamentals of liquid crystal devices

    CERN Document Server

    Yang, Deng-Ke

    2014-01-01

    Revised throughout to cover the latest developments in the fast moving area of display technology, this 2nd edition of Fundamentals of Liquid Crystal Devices, will continue to be a valuable resource for those wishing to understand the operation of liquid crystal displays. Significant updates include new material on display components, 3D LCDs and blue-phase displays which is one of the most promising new technologies within the field of displays and it is expected that this new LC-technology will reduce the response time and the number of optical components of LC-modules. Prof. Yang is a pion

  18. Single crystal PMN-PT/epoxy 1-3 composite for energy-harvesting application.

    Science.gov (United States)

    Ren, Kailiang; Liu, Yiming; Geng, Xuecang; Hofmann, Heath F; Zhang, Qiming M

    2006-03-01

    One key parameter in using electroactive materials to harvest electric energy from mechanical sources is the energy conversion efficiency. Recently, it was shown that, in the relaxor ferroelectric PMN-PT single crystals, a very high longitudinal electromechanical coupling factor (>90%) can be obtained. This paper investigates energy harvesting using 1-3 composites of PMN-PT single crystals in a soft epoxy matrix. It is shown that 1-3 composites enable the single crystals operating in the longitudinal mode to achieve high efficiency for energy harvesting, and the soft-polymer, matrix-supported single-crystal rods maintain high mechanical integrity under different external loads. For comparison, 1-3 composites with piezoceramic PZT also are investigated in energy-harvesting applications, and the results show that the high coupling factor of single crystal PMN-PT 1-3 composites leads to much higher electric energy output for similar mechanical energy input. The harvested energy density of 1-3 composite with single crystal (22.1 mW/cm3 under a stress of 40.4 MPa) is about twice of that harvested with PZT ceramic 1-3 composite (12 mW/cm3 under a stress of 39 MPa). At a higher stress level, the harvested-energy density of 1-3 PMN-PT single crystal composite can reach 96 mW/cm3.

  19. Crystallization Analysis and Control of Ammonia-Based Air Source Absorption Heat Pump in Cold Regions

    Directory of Open Access Journals (Sweden)

    Wei Wu

    2013-01-01

    Full Text Available Energy consumption of heating and domestic hot water is very high and will keep increasing. Air source absorption heat pump (ASAHP was proposed to overcome the problems of low energy efficiency and high air pollution existing in boiler systems, as well as the problem of bad performance under low ambient temperatures for electrical heat pumps. In order to investigate the crystallization possibility of ammonia-salt ASAHP, crystallization margin (evaluated by solution mass concentration at generating temperature ranging from 100 to 150°C, evaporating temperature from −30 to 10°C, and condensing temperature from 30 to 65°C are analyzed. To prevent the NH3–NaSCN solution from crystallizing, ASAHP integrated with pressure booster located between the evaporator and absorber is simulated. Analysis and comparisons show that NH3–NaSCN is easy to crystallize at relatively high generating temperature, low evaporating temperature, and low condensing temperature. But crystallization margin of NH3–LiNO3 can always stay above 5% for most conditions, keeping away from crystallization. Pressure booster can effectively avoid the crystallization problem that will take place in the NH3–NaSCN ASAHP system.

  20. Benchmark of the FLUKA model of crystal channeling against the UA9-H8 experiment

    Science.gov (United States)

    Schoofs, P.; Cerutti, F.; Ferrari, A.; Smirnov, G.

    2015-07-01

    Channeling in bent crystals is increasingly considered as an option for the collimation of high-energy particle beams. The installation of crystals in the LHC has taken place during this past year and aims at demonstrating the feasibility of crystal collimation and a possible cleaning efficiency improvement. The performance of CERN collimation insertions is evaluated with the Monte Carlo code FLUKA, which is capable to simulate energy deposition in collimators as well as beam loss monitor signals. A new model of crystal channeling was developed specifically so that similar simulations can be conducted in the case of crystal-assisted collimation. In this paper, most recent results of this model are brought forward in the framework of a joint activity inside the UA9 collaboration to benchmark the different simulation tools available. The performance of crystal STF 45, produced at INFN Ferrara, was measured at the H8 beamline at CERN in 2010 and serves as the basis to the comparison. Distributions of deflected particles are shown to be in very good agreement with experimental data. Calculated dechanneling lengths and crystal performance in the transition region between amorphous regime and volume reflection are also close to the measured ones.

  1. Measurement of z-axis deviation angle of electro-optic crystal by conoscopic interference

    Science.gov (United States)

    Li, Dong; Liu, Yong; Liu, Xu; Jiang, Hongzhen; Zheng, Fanglan

    2016-09-01

    Properties of plasma electrode pockels cell is directly affected by the Z-axis deviation angle of the electro-optic crystal. Therefore, high precision measurement of the Z-axis deviation angle is indispensable. By using conoscopic interference technique, a measurement system for Z-axis deviation angle of electro-optic crystal is introduced. The principle of conoscopic interference method is described in detail, and a series of techniques are implied in this measurement system to improve the accuracy. High-precision positioning method of the crystal based on Michelson interference is proposed to determine the normal consistency of crystal, which can ensure the high positioning repeatability of crystal in the measurement process. The positioning comparison experiment of the crystal shows that the standard deviation of our method is less than 1pixel, which is much better than the traditional method (nearly 4pixels). Moreover, melatope extraction algorithm of optical axis based on image matching technique is proposed to ensure the melatope can be extracted in high precision. Calibration method of the normal of transmission surface of crystal is also proposed. The experiment results show that the PV and rms of Z-axis deviation angle is less than 0.05mrad and 0.02mrad, respectively. The repeatability accuracy is less than 0.01mrad.

  2. Circular patterns of calcium oxalate crystals induced by defective Langmuir-Blodgett film

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The injury of the renal epithelial cell membrane can promote the nucleation of nascent crystals, as well as adhesion of crystals on it. It thus accelerates the formation of renal calculi. In this paper, the defective Langmuir-Blodgett(LB)films were used as a model system to simulate the injured renal epithelial cell membrane. The microcosmic structure of the defective LB film and the molecular mechanism of the effect of this film on nucleation, growth, deposited patterns and adhesion of calcium oxalate monohydrate(COM)were investigated. The circular defective domains were formed in dipalmitoylphosphatidylcholine(DPPC)LB film after the film was treated by potassium oxalate. These domains could induce ring-shaped patterns of COM crystals. In comparison, the LB film without pretreatment by potassium oxalate only induced random growth of hexagonal COM crystals. As the crystallization time increased, the size of COM crystals in the patterns increased, the crystal patterns changed from empty circles to solid circles, and the number of the circular patterns with small size(5-20μm)increased. The results would shed light on the molecular mechanism of urolithiasis induced by injury of the renal epithelial membrane at the molecular and supramolecular level.

  3. Circular patterns of calcium oxalate crystals induced by defective Langmuir-Blodgett film

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The injury of the renal epithelial cell membrane can promote the nucleation of nascent crystals, as well as adhesion of crystals on it. It thus accelerates the formation of renal calculi. In this paper, the defective Langmuir-Blodgett (LB) films were used as a model system to simulate the injured renal epithelial cell membrane. The microcosmic structure of the defective LB film and the molecular mechanism of the effect of this film on nucleation, growth, deposited patterns and adhesion of calcium oxalate monohydrate (COM) were investigated. The circular defective domains were formed in dipalmitoylphosphatidylcholine (DPPC) LB film after the film was treated by potassium oxalate. These domains could induce ring-shaped patterns of COM crystals. In comparison, the LB film without pretreatment by potassium oxalate only induced random growth of hexagonal COM crystals. As the crystallization time increased, the size of COM crystals in the patterns increased, the crystal patterns changed from empty circles to solid circles, and the number of the circular patterns with small size (5-20 μm) increased. The results would shed light on the molecular mechanism of urolithiasis induced by injury of the renal epithelial membrane at the molecular and supramolecular level.

  4. Introduction to crystal growth and characterization

    CERN Document Server

    Benz, Klaus-Werner

    2014-01-01

    This new textbook provides for the first time a comprehensive treatment of the basics of contemporary crystallography and crystal growth in a single volume. The reader will be familiarized with the concepts for the description of morphological and structural symmetry of crystals. The architecture of crystal structures of selected inorganic and molecular crystals is illustrated. The main crystallographic databases as data sources of crystal structures are described. Nucleation processes, their kinetics and main growth mechanism will be introduced in fundamentals of crystal growth. Some phase d

  5. From optical MEMS to photonic crystal

    Science.gov (United States)

    Lee, Sukhan; Kim, Jideog; Lee, Hong-Seok; Moon, Il-Kwon; Won, JongHwa; Ku, Janam; Choi, Hyung; Shin, Hyungjae

    2002-10-01

    This paper presents the emergence of photonic crystals as significant optomechatronics components, following optical MEMS. It is predicted that, in the coming years, optical MEMS and photonic crystals may go through dynamic interactions leading to synergy as well as competition. First, we present the Structured Defect Photonic Crystal (SDPCTM) devised by the authors for providing the freedom of designing photonic bandgap structures, such that the application of photonic crystals be greatly extended. Then, we present the applications of optical MEMS and photonic crystals to displays and telecommunications. It is shown that many of the applications that optical MEMS can contribute to telecommunications and displays may be implemented by photonic crystals.

  6. Research on colored lyotropic liquid crystals

    Institute of Scientific and Technical Information of China (English)

    WEI Xilian; YIN Baolin; SUN Dezhi; LIU Jie; WANG Zhongni; LI Ganzuo

    2005-01-01

    Splendidly colored lyotropic liquid crystals formed in the ternary system of a novel cationic surfactant, 3-p-nonylphenoxy-2-hydroxypropyl trimethyl ammonium bromide (NPTAB)-n-butanol-water system, had been observed under polarized light microscope. Small-angle X-ray scattering (SAXS), 2H (deuterium) quadrupolar splitting (2H NMR) were employed to confirm the structures of these liquid crystals. The structural transformation of these special lyotropic liquid crystals had been confirmed by differential scanning calorimetry (DSC). The influences of liquid crystal film thickness, temperature and conserving time on the color of liquid crystals have been investigated. It is also theoretically discussed for forming and changing of liquid crystal color.

  7. Large fraction of crystal directions leads to ion channeling

    Science.gov (United States)

    Nordlund, K.; Djurabekova, F.; Hobler, G.

    2016-12-01

    It is well established that when energetic ions are moving in crystals, they may penetrate much deeper if they happen to be directed in some specific crystal directions. This `channeling' effect is utilized for instance in certain ion beam analysis methods and has been described by analytical theories and atomistic computer simulations. However, there have been very few systematic studies of channeling in directions other than the principal low-index ones. We present here a molecular dynamics-based approach to calculate ion channeling systematically over all crystal directions, providing ion `channeling maps' that easily show in which directions channeling is expected. The results show that channeling effects can be quite significant even at energies below 1 keV, and that in many cases, significant planar channeling occurs also in a wide range of crystal directions between the low-index principal ones. In all of the cases studied, a large fraction (˜20 -60 % ) of all crystal directions show channeling. A practical implication of this is that modern experiments on randomly oriented nanostructures will have a large probability of channeling. It also means that when ion irradiations are carried out on polycrystalline samples, channeling effects on the results cannot a priori be assumed to be negligible. The maps allow for easy selection of good `nonchanneling' directions in experiments or alternatively finding wide channels for beneficial uses of channeling. We implement channeling theory to also give the fraction of channeling directions in a manner directly comparable to the simulations. The comparison shows good qualitative agreement. In particular, channeling theory is very good at predicting which channels are active at a given energy. This is true down to sub-keV energies, provided the penetration depth is not too small.

  8. Fullerite crystal thermodynamic characteristics and the law of corresponding states.

    Science.gov (United States)

    Torrens, Francisco; Castellano, Gloria

    2010-02-01

    The existence of single-wall carbon nanotubes in organic solvents in the form of clusters is discussed. A theory is developed based on a bundlet model, which enables describing the cluster-size distribution function. Comparison of calculated solubilities with experiments would permit obtaining energetic parameters, characterizing the interaction of a nanotube with its surrounding. Fullerenes and nanotubes are objects whose behaviour in many physical situations is characterized by peculiarities, which show up in that these systems represent the only soluble forms of carbon, what is related to their molecular structures. The fullerene molecule is a virtually uniform closed spherical-spheroidal surface and a nanotube is a smooth cylindrical unit. Both structures give rise to weak interactions between the neighbouring units in a crystal and promote their interaction with solvent molecules. The phenomena have a unified explanation in the bundlet model, in which the free energy of a nanotube in a cluster is combined from two components: a volume one proportional to the number of molecules n in a cluster and a surface one proportional to n1/2. Growth mechanisms of fractal clusters in fullerene solutions are analyzed along with similarity laws, determining the thermodynamic characteristics of fullerite crystals. In accordance with the similarity laws, the dimensionless Debye temperatures theta0 for all crystals belonging to the considered class should be close. Temperatures theta0 are determined by a similarity relation from experimental and estimated data. Fullerite theta0 is twice that for inert-gas crystals because, near the Debye point, the fullerite crystal is orientationally ordered so that its structure is dissimilar to face-centred cubic. A fullerene molecule whose thermal rotation is frozen cannot be considered as a spherically symmetric particle. The fulfilment of the similarity laws, which are valuable for particles with spherically symmetric interaction

  9. Functional possibilities of nonlinear crystals for frequency conversion: uniaxial crystals

    Energy Technology Data Exchange (ETDEWEB)

    Andreev, Yu M [Institute of Monitoring of Climatic and Ecological Systems, Siberian Branch of the Russian Academy of Sciences, Tomsk (Russian Federation); Arapov, Yu D; Kasyanov, I V [E.I. Zababakhin All-Russian Scientific-Research Institute of Technical Physics, Russian Federal Nuclear Centre, Snezhinsk, Chelyabinsk region (Russian Federation); Grechin, S G; Nikolaev, P P [N.E. Bauman Moscow State Technical University, Moscow (Russian Federation)

    2016-01-31

    The method and results of the analysis of phase-matching and nonlinear properties for all point groups of symmetry of uniaxial crystals that determine their functional possibilities for solving various problems of nonlinear frequency conversion of laser radiation are presented. (nonlinear optical phenomena)

  10. Crystal structures of cristobalite-type and coesite-type PON redetermined on the basis of single-crystal X-ray diffraction data.

    Science.gov (United States)

    Bykov, Maxim; Bykova, Elena; Dyadkin, Vadim; Baumann, Dominik; Schnick, Wolfgang; Dubrovinsky, Leonid; Dubrovinskaia, Natalia

    2015-11-01

    Hitherto, phospho-rus oxonitride (PON) could not be obtained in the form of single crystals and only powder diffraction experiments were feasible for structure studies. In the present work we have synthesized two polymorphs of phospho-rus oxonitride, cristobalite-type (cri-PON) and coesite-type (coe-PON), in the form of single crystals and reinvestigated their crystal structures by means of in house and synchrotron single-crystal X-ray diffraction. The crystal structures of cri-PON and coe-PON are built from PO2N2 tetra-hedral units, each with a statistical distribution of oxygen and nitro-gen atoms. The crystal structure of the coe-PON phase has the space group C2/c with seven atomic sites in the asymmetric unit [two P and three (N,O) sites on general positions, one (N,O) site on an inversion centre and one (N,O) site on a twofold rotation axis], while the cri-PON phase possesses tetra-gonal I-42d symmetry with two independent atoms in the asymmetric unit [the P atom on a fourfold inversion axis and the (N,O) site on a twofold rotation axis]. In comparison with previous structure determinations from powder data, all atoms were refined with anisotropic displacement parameters, leading to higher precision in terms of bond lengths and angles.

  11. Crystal structures of cristobalite-type and coesite-type PON redetermined on the basis of single-crystal X-ray diffraction data

    Directory of Open Access Journals (Sweden)

    Maxim Bykov

    2015-11-01

    Full Text Available Hitherto, phosphorus oxonitride (PON could not be obtained in the form of single crystals and only powder diffraction experiments were feasible for structure studies. In the present work we have synthesized two polymorphs of phosphorus oxonitride, cristobalite-type (cri-PON and coesite-type (coe-PON, in the form of single crystals and reinvestigated their crystal structures by means of in house and synchrotron single-crystal X-ray diffraction. The crystal structures of cri-PON and coe-PON are built from PO2N2 tetrahedral units, each with a statistical distribution of oxygen and nitrogen atoms. The crystal structure of the coe-PON phase has the space group C2/c with seven atomic sites in the asymmetric unit [two P and three (N,O sites on general positions, one (N,O site on an inversion centre and one (N,O site on a twofold rotation axis], while the cri-PON phase possesses tetragonal I-42d symmetry with two independent atoms in the asymmetric unit [the P atom on a fourfold inversion axis and the (N,O site on a twofold rotation axis]. In comparison with previous structure determinations from powder data, all atoms were refined with anisotropic displacement parameters, leading to higher precision in terms of bond lengths and angles.

  12. Crystal structure of a new variety of lead dodecaborate Pb{sub 6}(Li{sub 0.65}Na{sub 0.19})[B{sub 12}O{sub 24}]I{sub 0.84} {center_dot} 0.168H{sub 2}O and its comparison with beryl and cordierite

    Energy Technology Data Exchange (ETDEWEB)

    Belokoneva, E. L., E-mail: elbel@geol.msu.ru; Derkach, I. K.; Dimitrova, O. V. [Moscow State University, Faculty of Geology (Russian Federation)

    2013-05-15

    Crystals of a new representative of ring-radical dodecaborates Pb{sub 6}(Li{sub 0.65}Na{sub 0.19})[B{sub 12}O{sub 24}]I{sub 0.84} {center_dot} 0.168H{sub 2}O, space group R3bar m , are obtained under hydrothermal conditions. The structure is determined with-out preliminary knowledge of the chemical formula. It is close to that of the Pb{sub 6}[B{sub 12}O{sub 24}] {center_dot} H{sub 2}O dodecaborate studied earlier, but unlike the latter structure it contains admixtures of iodide anion, lithium cation, and water molecule, which incompletely populate positions in channels. The formation of the second variety, which brings to light ion-exchange properties of the crystals, is due to mineralizing ions available in the concen-trated solution in the course of crystallization. The new compound is compared with beryl and cordierite, which have close structures with channels capable of capturing various groups. Structures of synthetic Na and Ag dodecaborates with analogous but distorted ring dodecaborate radicals are discussed.

  13. THE CRYSTAL STRUCTURE OF ANTIMONY (III) SULFOBROMIDE, SBSBR,

    Science.gov (United States)

    ANTIMONY COMPOUNDS, *SULFUR COMPOUNDS, CRYSTAL STRUCTURE , CRYSTAL STRUCTURE , BROMIDES, SYMMETRY(CRYSTALLOGRAPHY), FOURIER ANALYSIS, MOLECULAR STRUCTURE, CRYSTAL LATTICES, CHEMICAL BONDS, X RAY DIFFRACTION.

  14. Lunar Magma Ocean Crystallization: Constraints from Fractional Crystallization Experiments

    Science.gov (United States)

    Rapp, J. F.; Draper, D. S.

    2015-01-01

    The currently accepted paradigm of lunar formation is that of accretion from the ejecta of a giant impact, followed by crystallization of a global scale magma ocean. This model accounts for the formation of the anorthosite highlands crust, which is globally distributed and old, and the formation of the younger mare basalts which are derived from a source region that has experienced plagioclase extraction. Several attempts at modelling the crystallization of such a lunar magma ocean (LMO) have been made, but our ever-increasing knowledge of the lunar samples and surface have raised as many questions as these models have answered. Geodynamic models of lunar accretion suggest that shortly following accretion the bulk of the lunar mass was hot, likely at least above the solidus]. Models of LMO crystallization that assume a deep magma ocean are therefore geodynamically favorable, but they have been difficult to reconcile with a thick plagioclase-rich crust. A refractory element enriched bulk composition, a shallow magma ocean, or a combination of the two have been suggested as a way to produce enough plagioclase to account for the assumed thickness of the crust. Recently however, geophysical data from the GRAIL mission have indicated that the lunar anorthositic crust is not as thick as was initially estimated, which allows for both a deeper magma ocean and a bulk composition more similar to the terrestrial upper mantle. We report on experimental simulations of the fractional crystallization of a deep (approximately 100km) LMO with a terrestrial upper mantle-like (LPUM) bulk composition. Our experimental results will help to define the composition of the lunar crust and mantle cumulates, and allow us to consider important questions such as source regions of the mare basalts and Mg-suite, the role of mantle overturn after magma ocean crystallization and the nature of KREEP

  15. NATO Advanced Research Workshop on Incommensurate Crystals, Liquid Crystals, and Quasi-Crystals

    CERN Document Server

    Clark, N

    1988-01-01

    In this NATO-sponsored Advanced Research Workshop we succeeded in bringing together approximately forty scientists working in the three main areas of structurally incommensurate materials: incommensurate crystals (primarily ferroelectric insulators), incommensurate liquid crystals, and metallic quasi-crystals. Although these three classes of materials are quite distinct, the commonality of the physics of the origin and descrip­ tion of these incommensurate structures is striking and evident in these proceedings. A measure of the success of this conference was the degree to which interaction among the three subgroups occurred; this was facili­ tated by approximately equal amounts of theory and experiment in the papers presented. We thank the University of Colorado for providing pleasant housing and conference facilities at a modest cost, and we are especially grate­ ful to Ann Underwood, who retyped all the manuscripts into camera-ready form. J. F. Scott Boulder, Colorado N. A. Clark v CONTENTS PART I: INCO...

  16. Growth, structural, spectral, mechanical, thermal and dielectric characterization of phosphoric acid admixtured L-alanine (PLA) single crystals

    Science.gov (United States)

    Rose, A. S. J. Lucia; Selvarajan, P.; Perumal, S.

    2011-10-01

    Phosphoric acid admixtured L-alanine (PLA) single crystals were grown successfully by solution method with slow evaporation technique at room temperature. Crystals of size 18 mm × 12 mm × 8 mm have been obtained in 28 days. The grown crystals were colorless and transparent. The solubility of the grown samples has been found out at various temperatures. The lattice parameters of the grown crystals were determined by X-ray diffraction technique. The reflection planes of the sample were confirmed by the powder X-ray diffraction study and diffraction peaks were indexed. Fourier transform infrared (FTIR) studies were used to confirm the presence of various functional groups in the crystals. UV-visible transmittance spectrum was recorded to study the optical transparency of grown crystal. The nonlinear optical (NLO) property of the grown crystal was confirmed by Kurtz-Perry powder technique and a study of its second harmonic generation efficiency in comparison with potassium dihydrogen phosphate (KDP) has been made. The mechanical strength of the crystal was estimated by Vickers hardness test. The grown crystals were subjected to thermo gravimetric and differential thermal analysis (TG/DTA). The dielectric behavior of the sample was also studied.

  17. A simple technique to reduce evaporation of crystallization droplets by using plate lids with apertures for adding liquids.

    Science.gov (United States)

    Zipper, Lauren E; Aristide, Xavier; Bishop, Dylan P; Joshi, Ishita; Kharzeev, Julia; Patel, Krishna B; Santiago, Brianna M; Joshi, Karan; Dorsinvil, Kahille; Sweet, Robert M; Soares, Alexei S

    2014-12-01

    A method is described for using plate lids to reduce evaporation in low-volume vapor-diffusion crystallization experiments. The plate lids contain apertures through which the protein and precipitants were added to different crystallization microplates (the reservoir was filled before fitting the lids). Plate lids were designed for each of these commonly used crystallization microplates. This system minimizes the dehydration of crystallization droplets containing just a few nanolitres of protein and precipitant, and results in more reproducible diffraction from the crystals. For each lid design, changes in the weight of the plates were used to deduce the rate of evaporation under different conditions of temperature, air movement, droplet size and precipitant. For comparison, the state of dehydration was also visually assessed throughout the experiment. Finally, X-ray diffraction methods were used to compare the diffraction of protein crystals that were conventionally prepared against those that were prepared on plates with plate lids. The measurements revealed that the plate lids reduced the rate of evaporation by 63-82%. Crystals grown in 5 nl drops that were set up with plate lids diffracted to higher resolution than similar crystals from drops that were set up without plate lids. The results demonstrate that plate lids can be instrumental for improving few-nanolitre crystallizations.

  18. Single crystalline Co3O4 nanocrystals exposed with different crystal planes for Li-O2 batteries.

    Science.gov (United States)

    Su, Dawei; Dou, Shixue; Wang, Guoxiu

    2014-08-29

    Single crystalline Co3O4 nanocrystals exposed with different crystal planes were synthesised, including cubic Co3O4 nanocrystals enclosed by {100} crystal planes, pseudo octahedral Co3O4 enclosed by {100} and {110} crystal planes, Co3O4 nanosheets exposed by {110} crystal planes, hexagonal Co3O4 nanoplatelets exposed with {111} crystal planes, and Co3O4 nanolaminar exposed with {112} crystal planes. Well single crystalline features of these Co3O4 nanocrystals were confirmed by FESEM and HRTEM analyses. The electrochemical performance for Li-O2 batteries shows that Co3O4 nanocrystals can significantly reduce the discharge-charge over-potential via the effect on the oxygen evolution reaction (OER). From the comparison on their catalytic performances, we found that the essential factor to promote the oxygen evolution reactions is the surface crystal planes of Co3O4 nanocrystals, namely, crystal planes-dependent process. The correlation between different Co3O4 crystal planes and their effect on reducing charge-discharge over-potential was established: {100} < {110} < {112} < {111}.

  19. Crystal structure of inactive form of Rab3B

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Wei [Hubei Key Laboratory of Genetic Regulation and Integrative Biology, College of Life Science, Huazhong Normal University, Wuhan 430079 (China); Shen, Yang [Structural Genomics Consortium, University of Toronto, 101 College St., Toronto, Ontario, Canada M5G 1L7 (Canada); Jiao, Ronghong [Department of Function Inspection, Hebei Provincial People' s Hospital, Shijiazhuang 050051 (China); Liu, Yanli; Deng, Lingfu [Hubei Key Laboratory of Genetic Regulation and Integrative Biology, College of Life Science, Huazhong Normal University, Wuhan 430079 (China); Qi, Chao, E-mail: qichao@mail.ccnu.edu.cn [Hubei Key Laboratory of Genetic Regulation and Integrative Biology, College of Life Science, Huazhong Normal University, Wuhan 430079 (China)

    2012-02-24

    Highlights: Black-Right-Pointing-Pointer This is the first structural information of human Rab3B. Black-Right-Pointing-Pointer To provides a structural basis for the GDP/GTP switch in controlling the activity of Rab3. Black-Right-Pointing-Pointer The charge distribution of Rab3B indicates its unique roles in vesicular trafficking. -- Abstract: Rab proteins are the largest family of ras-related GTPases in eukaryotic cells. They act as directional molecular switches at membrane trafficking, including vesicle budding, cargo sorting, transport, tethering, and fusion. Here, we generated and crystallized the Rab3B:GDP complex. The structure of the complex was solved to 1.9 A resolution and the structural base comparison with other Rab3 members provides a structural basis for the GDP/GTP switch in controlling the activity of small GTPase. The comparison of charge distribution among the members of Rab3 also indicates their different roles in vesicular trafficking.

  20. Crystallization of a member of the recFOR DNA repair pathway, RecO, with and without bound oligonucleotide

    Energy Technology Data Exchange (ETDEWEB)

    Aono, Shelly; Hartsch, Thomas; Schulze-Gahmen, Ursula

    2003-01-22

    RecFOR proteins are important for DNA repair by homologous recombination in bacteria. The RecO protein from Thermus thermophilus was cloned, purified and characterized for its binding to oligonucleotides. The protein was crystallized alone and in complex with a 14-mer oligonucleotide. Both crystal forms grow under different crystallization conditions in the same space group, P3121 or P3221, with almost identical unit cell parameters. Complete data sets were collected to 2.8 Angstrom and 2.5 Angstrom for RecO alone and the RecO-oligonucleotide complex, respectively. Visual comparison of the diffraction patterns between the two crystal forms and calculation of an Rmerge of 33.9 percent on F indicate that one of the crystal forms is indeed a complex of RecO with bound oligonucleotide.

  1. LiCaTb5(BO3)6: A new magneto-optical crystal promising as Faraday rotator

    Science.gov (United States)

    Li, R. K.; Wu, C. C.; Xia, M. J.

    2016-12-01

    A properly engineered new ortho-borate with composition of LiCaTb5(BO3)6 (LCTB), shows 55% enhancement of Verdet constant over the widely used magneto-optical TGG crystal. Centimetre level LCTB crystal can be grown from the self-flux LiCaBO3. Transmittance and magnetic measurements reveal that LCTB crystal is highly transparent between 500 and 1500 nm and is paramagnetic down to 2 K with a magnetic easy axis along the [001] direction. Faraday rotation measurements show that the Verdet constant along [001] direction of LCTB crystal is 227 (3) rad/Tm at 633 nm, in comparison to that of TGG crystal (146(2) rad/Tm) under the same measurement conditions. The above results indicate that the title compound can be a promising candidate as a new MO material with high performance in a Faraday isolator.

  2. [Photonic crystals for analytical chemistry].

    Science.gov (United States)

    Chen, Yi; Li, Jincheng

    2009-09-01

    Photonic crystals, originally created to control the transmission of light, have found their increasing value in the field of analytical chemistry and are probable to become a hot research area soon. This review is hence composed, focusing on their analytical chemistry-oriented applications, including especially their use in chromatography, capillary- and chip-based electrophoresis.

  3. Neutron Transmission through Sapphire Crystals

    DEFF Research Database (Denmark)

    of simulations, in order to reproduce the transmission of cold neutrons through sapphire crystals. Those simulations were part of the effort of validating and improving the newly developed interface between the Monte-Carlo neutron transport code MCNP and the Monte Carlo ray-tracing code McStas....

  4. Irradiation Defects in Silicon Crystal

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The application of irradiation in silicon crystal is introduced.The defects caused by irradiation are reviewed and some major ways of studying defects in irradiated silicon are summarized.Furthermore the problems in the investigation of irradiated silicon are discussed as well as its properties.

  5. Photonic-crystal waveguide biosensor

    DEFF Research Database (Denmark)

    Skivesen, Nina; Têtu, Amélie; Kristensen, Martin

    2007-01-01

    A photonic-crystal waveguide sensor is presented for biosensing. The sensor is applied for refractive index measurements and detection of protein-concentrations. Concentrations around 10 μg/ml (0.15μMolar) are measured with excellent signal to noise ratio, and a broad, dynamic refractive index se...

  6. One-dimensional photonic crystals

    NARCIS (Netherlands)

    Shen, Huaizhong; Wang, Zhanhua; Wu, Yuxin; Yang, Bai

    2016-01-01

    A one-dimensional photonic crystal (1DPC), which is a periodic nanostructure with a refractive index distribution along one direction, has been widely studied by scientists. In this review, materials and methods for 1DPC fabrication are summarized. Applications are listed, with a special emphasis

  7. Imprinted photonic crystal chemical sensors

    NARCIS (Netherlands)

    Boersma, A.; Burghoorn, M.M.A.; Saalmink, M.

    2011-01-01

    In this paper we present the use of Photonic Crystals as chemical sensors. These 2D nanostructured sensors were prepared by nano-imprint lithography during which a nanostructure is transferred from a nickel template into a responsive polymer, that is be specifically tuned to interact with the chemic

  8. Growing Crystals with a Computer.

    Science.gov (United States)

    Berkowitz, S. J.; Haase, D. G.

    1987-01-01

    Describes an open-ended computer simulation project that can be used to illustrate the growth of solid crystals in different forms at any level from high school physics to graduate physics. Discusses a simple computer program in BASIC language on an IBM personal computer. Gives examples of simulations. (CW)

  9. SHG from centrosymmetric supermolecular crystal

    Institute of Scientific and Technical Information of China (English)

    郭文生; 刘祁涛; 邵宗书; 郭放; 周广勇; 魏春生; 王东

    2002-01-01

    Supermolecular crystal composed of p-nitrophenol, hexamethylenetetramine, phosphoric acid and water was obtained by supermolecular assembly. The crystal has a centrosymmetric structure with space group P21/c. The relative intensity and integral value of green frequency doubling of light from the crystal powder compared with that from KDP powder measured by pico-second Nd:YAG laser are 757.3 (KDP: 183.4) and 1771.7 (KDP: 423.98), respectively. In supermolecular crystal, due to the arrangement of centrosymmetric p-nitrophenol molecules in the inorganic-organic host framework formed by hexamethylenetetramine, phosphoric acid and water, the distances between the p-nitrophenol molecules with centrosymmetry are changed (N1A-O1A: 0.8158 nm, N1B’-O1B: 1.4450 nm, N1A-N1A’: 0.5837 nm, N1B’-N1B: 0.6898 nm), and the interaction between the dipoles becomes weak, which is easy for the ground state to turn into the excited state charge separated form, and generate the stable asymmetrical distribution of π-electron clo

  10. SHG from centrosymmetric supermolecular crystal

    Institute of Scientific and Technical Information of China (English)

    郭文生; 郭放; 魏春生; 刘祁涛; 周广勇; 王东; 邵宗书

    2002-01-01

    Supermolecular crystal composed of p-nitrophenol, hexamethylenetetramine, phosphoric acid and water was obtained by supermolecular assembly. The crystal has a centrosymmetric structure with space group P21/c. The relative intensity and integral value of green frequency doubling of light from the crystal powder compared with that from KDP powder measured by pico-second Nd:YAG laser are 757.3 (KDP: 183.4) and 1771.7 (KDP: 423.98), respectively. In supermolecular crystal, due to the arrangement of centrosymmetric p-nitrophenol molecules in the inorganic-organic host framework formed by hexamethylenetetramine, phosphoric acid and water, the distances between the p-nitrophenol molecules with centrosymmetry are changed (N1A-O1A: 0.8158 nm, N1B′-O1B: 1.4450 nm, N1A-N1A′: 0.5837 nm, N1B′-N1B: 0.6898 nm), and the interaction between the dipoles becomes weak, which is easy for the ground state to turn into the excited state charge separated form, and generate the stable asymmetrical distribution of (-electron cloud density of quinonal structure, thus exhibiting SHG effect.

  11. Cold Crystal Reflector Filter Concept

    CERN Document Server

    Muhrer, G

    2014-01-01

    In this paper the theoretical concept of a cold crystal reflector filter will be presented. The aim of this concept is to balance the shortcoming of the traditional cold polycrystalline reflector filter, which lies in the significant reduction of the neutron flux right above (in energy space) or right below (wavelength space) the first Bragg edge.

  12. Growth of Solid Solution Crystals

    Science.gov (United States)

    Lehoczky, S. L.; Szofran, F. R.; Holland, L. R.

    1985-01-01

    The major objective of this program is to determine the conditions under which single crystals of solid solutions can be grown from the melt in a Bridgman configuration with a high degree of chemical homogeneity. The central aim is to assess the role of gravity in the growth process and to explore the possible advantages for growth in the absence of gravity. The alloy system being investigated is the solid solution semiconductor with x-values appropriate for infrared detector applications in Hg sub (1-x) Cd sub x Te the 8 to 14 micro m wavelength region. Both melt and Te-solvent growth are being considered. The study consists of an extensive ground-based experimental and theoretical research effort followed by flight experimentation where appropriate. Experimental facilities have been established for the purification, casting, and crystal growth of the alloy system. Facilities have been also established for the metallurgical, compositional, electric and optical characterization of the alloys. Crystals are being grown by the Bridgman-Stockbarger method and are analyzed by various experimental techniques to evaluate the effects of growth conditions on the longitudinal and radial compositional variations and defect densities in the crystals.

  13. The Influence of Radiation Damage on the Deflection of High-Energy Beams in Bent Silicon Crystals

    CERN Document Server

    Biino, C; Doble, Niels T; Elsener, K; Gatignon, L; Grafström, P; Mikkelsen, U; Kirsebom, K; Møller, S P; Uggerhøj, Erik; Worm, T

    1996-01-01

    Experimental results obtained for deflection of 450 GeV/c protons channeling along the {111} planes in a bent, strongly irradiated silicon crystal are presented. A comparison between the deflection efficiencies in irradiated areas and non-irradiated areas in the crystal shows that irradiation by 2.4 · 1020 protons/cm2 leads to a reduction of around 30 % in deflection efficiency. As a consequence, beam-splitting and extraction from an accelerator by means of a bent crystal are feasible solutions at high energies even for intense beams and during long periods.

  14. Process for Encapsulating Protein Crystals

    Science.gov (United States)

    Morrison, Dennis R.; Mosier, Benjamin

    2003-01-01

    A process for growing protein crystals encapsulated within membranes has been invented. This process begins with the encapsulation of a nearly saturated aqueous protein solution inside semipermeable membranes to form microcapsules. The encapsulation is effected by use of special formulations of a dissolved protein and a surfactant in an aqueous first liquid phase, which is placed into contact with a second, immiscible liquid phase that contains one or more polymers that are insoluble in the first phase. The second phase becomes formed into the semipermeable membranes that surround microglobules of the first phase, thereby forming the microcapsules. Once formed, the microcapsules are then dehydrated osmotically by exposure to a concentrated salt or polymer solution. The dehydration forms supersaturated solutions inside the microcapsules, thereby enabling nucleation and growth of protein crystals inside the microcapsules. By suitable formulation of the polymer or salt solution and of other physical and chemical parameters, one can control the rate of transport of water out of the microcapsules through the membranes and thereby create physicochemical conditions that favor the growth, within each microcapsule, of one or a few large crystals suitable for analysis by x-ray diffraction. The membrane polymer can be formulated to consist of low-molecular-weight molecules that do not interfere with the x-ray diffraction analysis of the encapsulated crystals. During dehydration, an electrostatic field can be applied to exert additional control over the rate of dehydration. This protein-crystal-encapsulation process is expected to constitute the basis of protein-growth experiments to be performed on the space shuttle and the International Space Station. As envisioned, the experiments would involve the exposure of immiscible liquids to each other in sequences of steps under microgravitational conditions. The experiments are expected to contribute to knowledge of the precise

  15. Infrared Sensor with Liquid Crystal Chopper

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    An infrared sensor using the liquid crystal chopper is presented. The infrared sensor is designed to detect infrared rays with a pyroelectric element used as a liquid crystal chopper in such an infrared sensor or the like.

  16. Emerging Technologies of Liquid Crystal Displays

    Institute of Scientific and Technical Information of China (English)

    Sin-Doo Lee; Chang-Jae Yu; Jae-Hong Park; Min-Sik Jung

    2003-01-01

    The general features and the emerging technologies of liquid crystal displays are described from the viewpoints of wide viewing and fast response technologies. The device applications of liquid crystals for optical communications are also described.

  17. Purification of 5-hydroxymethylfurfural (hmf) by crystallization

    DEFF Research Database (Denmark)

    2013-01-01

    This invention relates to an efficient procedure for purifying HMF by crystallization at low temperature from an organic solvent.......This invention relates to an efficient procedure for purifying HMF by crystallization at low temperature from an organic solvent....

  18. Biased liquid crystal photonic bandgap fiber

    DEFF Research Database (Denmark)

    Weirich, Johannes; Lægsgaard, Jesper; Alkeskjold, Thomas Tanggaard;

    2008-01-01

    We simulate the director structure of all capillaries in a biased photonic crystal fiber infiltrated with liquid crystals. Various mode simulations for different capillaries show the necessity to consider the entire structure....

  19. Notizen: On some Crystals of "Lapis Lazuli"

    Science.gov (United States)

    Banerjee, A.; Häger, T.

    1992-10-01

    Some deep blue dodecahedral crystals from Afghanistan have been investigated by UV-, VIS- and IR-spectral photometry and x-ray powder diffraction technique. Contrary to earlier identification, the crystals have been identified as hauynite.

  20. Space-time crystals of trapped ions.

    Science.gov (United States)

    Li, Tongcang; Gong, Zhe-Xuan; Yin, Zhang-Qi; Quan, H T; Yin, Xiaobo; Zhang, Peng; Duan, L-M; Zhang, Xiang

    2012-10-19

    Spontaneous symmetry breaking can lead to the formation of time crystals, as well as spatial crystals. Here we propose a space-time crystal of trapped ions and a method to realize it experimentally by confining ions in a ring-shaped trapping potential with a static magnetic field. The ions spontaneously form a spatial ring crystal due to Coulomb repulsion. This ion crystal can rotate persistently at the lowest quantum energy state in magnetic fields with fractional fluxes. The persistent rotation of trapped ions produces the temporal order, leading to the formation of a space-time crystal. We show that these space-time crystals are robust for direct experimental observation. We also study the effects of finite temperatures on the persistent rotation. The proposed space-time crystals of trapped ions provide a new dimension for exploring many-body physics and emerging properties of matter.

  1. Needs and Opportunities in Crystal Growth.

    Science.gov (United States)

    Mroczkowski, Stanley

    1980-01-01

    Presents a survey of the scientific basis for single crystals production, discussing some of the theoretical and experimental advances in the area. Future prospects for semiconductors, magnetic lasers, nonlinear optics, piezoelectrics, and other crystals are surveyed. (Author/CS)

  2. Bacillus thuringiensis crystal proteins that target nematodes

    OpenAIRE

    Wei, Jun-Zhi; Hale, Kristina; Carta, Lynn; Platzer, Edward; Wong, Cynthie; Fang, Su-Chiung; Aroian, Raffi V.

    2003-01-01

    Bacillus thuringiensis (Bt) crystal proteins are pore-forming toxins used as insecticides around the world. Previously, the extent to which these proteins might also target the invertebrate phylum Nematoda has been mostly ignored. We have expressed seven different crystal toxin proteins from two largely unstudied Bt crystal protein subfamilies. By assaying their toxicity on diverse free-living nematode species, we demonstrate that four of these crystal proteins are active against multiple nem...

  3. Attachment of Thiobacillus thiooxidans to sulfur crystals.

    Science.gov (United States)

    SCHAEFFER, W I; HOLBERT, P E; UMBREIT, W W

    1963-01-01

    Schaeffer, W. I. (Rutgers, The State University, New Brunswick, N.J.), P. E. Holbert, and W. W. Umbreit. Attachment of Thiobacillus thiooxidans to sulfur crystals. J. Bacteriol. 85:137-140. 1963.-Electron micrographs of replicas of sulfur crystals before and after attack by Thiobacillus thiooxidans show that the microorganisms erode the crystal in the area immediately adjacent to the cell. When there are many cells, the entire crystal surface appears eroded.

  4. Thermo-optical characteristics of DKDP crystal

    Science.gov (United States)

    Mironov, E. A.; Vyatkin, A. G.; Starobor, A. V.; Palashov, O. V.

    2017-03-01

    This letter presents a theoretical and experimental investigation of thermally induced polarization distortions occurring in an optical element made of c-cut tetragonal crystals. Two material characteristics were defined for this class of crystals: the optical anisotropy parameter ξ and the thermo-optical constant Q. These were generalized with analogous characteristics of elastically isotropic cubic crystals. The experimental investigation of these characteristics for popular tetragonal deuterated potassium dihydrogen phosphate (DKDP) crystal was carried out.

  5. Pattern information extraction from crystal structures

    OpenAIRE

    Okuyan, Erhan

    2005-01-01

    Cataloged from PDF version of article. Determining crystal structure parameters of a material is a quite important issue in crystallography. Knowing the crystal structure parameters helps to understand physical behavior of material. For complex structures, particularly for materials which also contain local symmetry as well as global symmetry, obtaining crystal parameters can be quite hard. This work provides a tool that will extract crystal parameters such as primitive vect...

  6. Reporting with Visual Studio and Crystal Reports

    CERN Document Server

    Elkoush, Mahmoud

    2013-01-01

    A fast-paced, example-based guide to learn how to create a reporting application using Visual Studio and Crystal Reports.""Reporting with Visual Studio and Crystal Reports"" is for developers new to Crystal Reports. It will also prove useful to intermediate users who wish to explore some new techniques in Crystal Reports using Microsoft Visual Studio. Readers are expected to have basic knowledge of C#, Microsoft Visual Studio, and Structured Query Language (SQL).

  7. Orthoconic liquid crystals--a case study.

    Science.gov (United States)

    Lagerwall, Sven T

    2014-06-01

    Since the early investigations on liquid crystals it was realized how the confining surfaces often determine the textures and even properties of the material. This influence is particularly complex and important for chiral materials. When we come to chiral smectics the surfaces may have dramatic effects. These are illustrated on the ferroelectric liquid crystals; they then again increase in importance for the antiferroelectric liquid crystals where the most recent example is given by the orthoconic liquid crystals.

  8. Spatial solitons in nonlinear photonic crystals

    DEFF Research Database (Denmark)

    Corney, Joel Frederick; Bang, Ole

    2000-01-01

    We study solitons in one-dimensional quadratic nonlinear photonic crystals with periodic linear and nonlinear susceptibilities. We show that such crystals support stable bright and dark solitons, even when the effective quadratic nonlinearity is zero.......We study solitons in one-dimensional quadratic nonlinear photonic crystals with periodic linear and nonlinear susceptibilities. We show that such crystals support stable bright and dark solitons, even when the effective quadratic nonlinearity is zero....

  9. S-Allyl-Cysteines Reduce Amelioration of Aluminum Induced Toxicity in Rats

    Directory of Open Access Journals (Sweden)

    Sadhana Shrivastava

    2011-01-01

    Full Text Available Problem statement: Aluminum (Al is a trivalent cation found in its ionic form in most kinds of animal tissues and in natural waters everywhere. Approach: It is a potent neurotoxin and has been associated in the pathogenesis of several clinical disorders including Alzheimer’s disease. Results: The aim of the study was to demonstrate the protective effect of S-Allyl-Cysteines (SAC against Al-induced toxicity in rat model on certain biochemical parameters, lipid peroxidation and oxidative stress enzymes of white albino rats. Six rats per group were divided into various treatment groups. Group one rats were given normal saline and served as control group. Group two animals received Al as aluminum nitrate 32.5 mg (i.p. for the induction of toxicity. Group three to five received different doses of SAC (25, 50 and 100 mg kg-1 for 3 days after 24 h of Al toxicity. Rats were orally administered their respective doses every day for 3 days. Evaluations were made in blood and tissues. The activity of Acetylcholinesterase (AchE was inhibited in all the parts of brain after Al intoxication. Significant rise were observed the Activities of Serum Transaminases (AST and ALT after toxicant exposure. The activity of â-Aminolevulinic acid Dehydratase (ALAD in blood and â-Aminolevulinic Acid Synthetase (ALAS in brain was decreased after Al exposure. Al significant increased cholesterol, triglyceride, creatinine and urea level in serum. TBARS level was significantly higher and GSH content were significantly lower during toxicity. Total and esterified cholesterol in liver, kidney and brain were increased after Al exposure. Histopathological changes in liver, kidney and brain were also recouped with the therapy. Conclusion/Recommendations: Our data proved that SAC which is a bioactive and bioavailable component of garlic has organosulfur compounds which regulates the thiol status of the cell and scavenges free radicals and work as an antioxidant. Thus SAC effectively reduces cognitive dysfunction and oxidative damage induced by Al.

  10. Prophylactic and therapeutic effects of taurine against aluminum-induced acute hepatotoxicity in mice.

    Science.gov (United States)

    El-Sayed, Wael M; Al-Kahtani, Mohamed A; Abdel-Moneim, Ashraf M

    2011-08-30

    Aluminum is a well known neurotoxin and a possible candidate of hepatotoxins to humans. Using natural antioxidants against metal-induced hepatotoxicity is a modern approach. In the present study, Aluminum (AlCl(3)) intoxication (a single injection of 25mg Al(3+)/kg, i.p.) for 24h in mice resulted in elevations in serum alanine aminotransferase activity and serum tumor necrosis factor and hepatic malondialdehyde levels. Aluminum reduced the activities of glutathione peroxidase, glutathione S-transferase, quinone oxidoreductase, and catalase in liver. In addition, Al caused hepatic hemorrhage, cellular degeneration as well as necrosis of hepatocytes. Ultrastructure examination showed swelling of mitochondria, derangement of rough endoplasmic reticulum cisternae and pleomorphic nuclei with abnormal chromatin distribution. Taurine, a sulfur-containing amino acid was administered to mice daily for 5 days before (at 100mg/kg, i.p.) or 2h after (a single dose of 1g/kg, i.p.) aluminum administration. Treating mice with taurine at either dosing regimens, pre- or post-aluminum administration alleviated aluminum oxidative damaging effects. The rate of recovery was better when taurine was administered prior to Al. Taurine had anaphylactic and therapeutic activity against hepatotoxicity induced by aluminum in mice.

  11. Signal transduction events in aluminum-induced cell death in tomato suspension cells

    NARCIS (Netherlands)

    Iakimova, E.T.; Kapchina-Toteva, V.M.; Woltering, E.J.

    2007-01-01

    In this study, some of the signal transduction events involved in AlCl3-induced cell death in tomato (Lycopersicon esculentum Mill.) suspension cells were elucidated. Cells treated with 100 ¿M AlCl3 showed typical features of programmed cell death (PCD) such as nuclear and cytoplasmic condensation.

  12. Single and double long pulse laser ablation of aluminum induced in air and water ambient

    Science.gov (United States)

    Akbari Jafarabadi, Marzieh; Mahdieh, Mohammad Hossein

    2017-02-01

    In this paper, single pulse and double pulse laser ablation of an aluminum target in two interaction ambient was investigated experimentally. The interaction was performed by nanosecond Nd:YAG laser beam in air and four depths (i.e. 9, 13, 17, and 21 mm) of distilled water ambient. The irradiation was carried out in single and collinear double pulse configurations in both air and liquid ambient. Crater geometry (depth and diameter) was measured by an optical microscope. The results indicated that the crater geometry strongly depends on both single pulse and double pulse configurations and interaction ambient. In single pulse regime, the crater diameter is higher for all water depths compared to that of air. However, the crater depth, depend on water depth, is higher or lower than the crater depth in air. In double pulse laser ablation, there are greater values for both crater diameters and crater depths in the water.

  13. The metal transporter SMF-3/DMT-1 mediates aluminum-induced dopamine neuron degeneration.

    Science.gov (United States)

    VanDuyn, Natalia; Settivari, Raja; LeVora, Jennifer; Zhou, Shaoyu; Unrine, Jason; Nass, Richard

    2013-01-01

    Aluminum (Al(3+)) is the most prevalent metal in the earth's crust and is a known human neurotoxicant. Al(3+) has been shown to accumulate in the substantia nigra of patients with Parkinson's disease (PD), and epidemiological studies suggest correlations between Al(3+) exposure and the propensity to develop both PD and the amyloid plaque-associated disorder Alzheimer's disease (AD). Although Al(3+) exposures have been associated with the development of the most common neurodegenerative disorders, the molecular mechanism involved in Al(3+) transport in neurons and subsequent cellular death has remained elusive. In this study, we show that a brief exposure to Al(3+) decreases mitochondrial membrane potential and cellular ATP levels, and confers dopamine (DA) neuron degeneration in the genetically tractable nematode Caenorhabditis elegans (C. elegans). Al(3+) exposure also exacerbates DA neuronal death conferred by the human PD-associated protein α-synuclein. DA neurodegeneration is dependent on SMF-3, a homologue to the human divalent metal transporter (DMT-1), as a functional null mutation partially inhibits the cell death. We also show that SMF-3 is expressed in DA neurons, Al(3+) exposure results in a significant decrease in protein levels, and the neurodegeneration is partially dependent on the PD-associated transcription factor Nrf2/SKN-1 and caspase Apaf1/CED-4. Furthermore, we provide evidence that the deletion of SMF-3 confers Al(3+) resistance due to sequestration of Al(3+) into an intracellular compartment. This study describes a novel model for Al(3+)-induced DA neurodegeneration and provides the first molecular evidence of an animal Al(3+) transporter.

  14. Aluminum-Induced Entropy in Biological Systems: Implications for Neurological Disease

    Directory of Open Access Journals (Sweden)

    Christopher A. Shaw

    2014-01-01

    Full Text Available Over the last 200 years, mining, smelting, and refining of aluminum (Al in various forms have increasingly exposed living species to this naturally abundant metal. Because of its prevalence in the earth’s crust, prior to its recent uses it was regarded as inert and therefore harmless. However, Al is invariably toxic to living systems and has no known beneficial role in any biological systems. Humans are increasingly exposed to Al from food, water, medicinals, vaccines, and cosmetics, as well as from industrial occupational exposure. Al disrupts biological self-ordering, energy transduction, and signaling systems, thus increasing biosemiotic entropy. Beginning with the biophysics of water, disruption progresses through the macromolecules that are crucial to living processes (DNAs, RNAs, proteoglycans, and proteins. It injures cells, circuits, and subsystems and can cause catastrophic failures ending in death. Al forms toxic complexes with other elements, such as fluorine, and interacts negatively with mercury, lead, and glyphosate. Al negatively impacts the central nervous system in all species that have been studied, including humans. Because of the global impacts of Al on water dynamics and biosemiotic systems, CNS disorders in humans are sensitive indicators of the Al toxicants to which we are being exposed.

  15. Pattern of aluminum-induced secretion of organic acids differs between rye and wheat.

    Science.gov (United States)

    Li, X F; Ma, J F; Matsumoto, H

    2000-08-01

    Al-Induced secretion of organic acids from the roots has been considered as a mechanism of Al tolerance, but the processes leading to the secretion of organic acids are still unknown. In this study, the secretion pattern and alteration in the metabolism of organic acids under Al stress were examined in rye (Secale cereale L. cv King) and wheat (Triticum aestivum L. cv Atlas 66). Al induced rapid secretion of malate in the wheat, but a lag (6 and 10 h for malic and citric acids, respectively) between the exposure to Al and the secretion of organic acids was observed in the rye. The activities of isocitrate dehydrogenase, phosphoenolpyruvate carboxylase, and malate dehydrogenase were not affected by Al in either plant. The activity of citrate synthase was increased by the exposure to Al in the rye, but not in the wheat. The secretion of malate was not suppressed at low temperature in the wheat, but that of citrate was stopped in the rye. The Al-induced secretion of citrate from roots of the rye was inhibited by the inhibitors of a citrate carrier, which transports citrate from the mitochondria to the cytoplasm. All of these results suggest that alteration in the metabolism of organic acids is involved in the Al-induced secretion of organic acids in rye, but only activation of an anion channel seems to be responsible for the rapid secretion of malate in the wheat.

  16. Amelioration of iron toxicity: A mechanism for aluminum-induced growth stimulation in tea plants.

    Science.gov (United States)

    Hajiboland, Roghieh; Barceló, Juan; Poschenrieder, Charlotte; Tolrà, Roser

    2013-11-01

    Tea plants (Camellia sinensis) are well adapted to acid soils with high Al availability. These plants not only accumulate high leaf Al concentrations, but also respond to Al with growth stimulation. Decreased oxidative stress has been associated with this effect. Why tea plants not exposed to Al suffer from oxidative stress has not been clarified. In this study, hydroponically grown tea plants treated with 0 to 300 μM Al were analyzed for growth, Al and Fe accumulation, and Al distribution by means of morin and hematoxylin staining. Roots of control plants stained black with hematoxylin. This indicates the formation of a Fe-hematoxylin complex. Young leaves of controls accumulated more than 1000 mg Fe kg(-1) dry weight. This concentration is above the Fe-toxicity threshold in most species. Supply of Al stimulated growth and reduced Fe uptake and transport. These results indicate that Al-induced growth stimulation might be due to alleviation of a latent Fe toxicity occurring in tea plants without Al supply.

  17. Optimal dose of zinc supplementation for preventing aluminum-induced neurotoxicity in rats****

    Institute of Scientific and Technical Information of China (English)

    Hao Lu; Yugang Jiang; Jianyang Hu; Jing Li; Wei Pang; Yandan Hu; Hongpeng Yang; Wenjie Li; Chengyu Huang; Mingman Zhang

    2013-01-01

    Zinc supplementation can help maintain learning and memory function in rodents. In this study, we hypothesized that zinc supplementation could antagonize the neurotoxicity induced by aluminum in rats. Animals were fed a diet containing different doses of zinc (50, 100, 200 mg/kg) for 9 weeks, and oral y administered aluminum chloride (300 mg/kg daily) from the third week for 7 consecutive weeks. Open-field behavioral test results showed that the number of rearings in the group given the 100 mg/kg zinc supplement was significantly increased compared with the group given the 50 mg/kg zinc supplement. Malondialdehyde content in the cerebrum was significantly decreased, while dopamine and 5-hydroxytryptamine levels were increased in the groups given the diet plemented with 100 and 200 mg/kg zinc, compared with the group given the diet supplemented with 50 mg/kg zinc. The acetylcholinesterase activity in the cerebrum was significantly decreased in the group given the 100 mg/kg zinc supplement. Hematoxylin-eosin staining revealed evident patho-logical damage in the hippocampus of rats in the group given the diet supplemented with 50 mg/kg zinc, but the damage was attenuated in the groups given the diet supplemented with 100 and 200 mg/kg zinc. Our findings suggest that zinc is a potential neuroprotective agent against alumi-num-induced neurotoxicity in rats, and the optimal dosages are 100 and 200 mg/kg.

  18. Pretreatment with H2O2 Alleviates Aluminum-induced Oxidative Stress in Wheat Seedlings

    Institute of Scientific and Technical Information of China (English)

    Fang Jie Xu; Chong Wei Jin; Wen Jing Liu; Yong Song Zhang; Xian Yong Lin

    2011-01-01

    Hydrogen peroxide(H2O2)is a key reactive oxygen species(ROS)in signal transduction pathways Ieading to activation of plant defenses against biotic and abiotic stresses.In this study,we investigated the effects of H2O2 pretreatment on aluminum (Al)induced antioxidant responses in root tips of two wheat(Triticum aestivum L.)genotypes,Yangmai-5(Al-sensitive)and Jian-864(Al-tolerant).Al increased and root elongation inhibition in Yangmai-5 than in Jian-864.However,H2O2 pretreatment alleviated Alinduced deleterious effects in both genotypes.Under Al stress,H2O2 pretreatment increased the activities of superoxide dismutase,catalase,peroxidase,ascorbate peroxidase and monodehydroascorbate reductase,glutathione reductase and giutathione peroxidase as well as the levels of ascorbate and glutathione more significantly in Yangmai-5 than in Jian-864.Furthermore,H2O2 pretreatment also increased the total antioxidant capacity evaluated as the 2,2-diphenyl-1-picrylhydrazyl-radical scavenging activity and the ferric reducing/antioxidant power more significantly in Yangmai-5 than in Jian-864.Therefore,we conclude that H2O2 pretreatment improves wheat Al acclimation during subsequent Al exposure by enhancing the antioxidant defense capacity,which prevents ROS accumulation,and that the enhancement is greater in the Al-sensitive genotype than in the Al-tolerant genotype.

  19. Co-crystallization as a separation technology: controlling product concentrations by co-crystals

    NARCIS (Netherlands)

    Urbanus, J.; Roelands, C.P.M.; Verdoes, D.; Jansens, P.J.; Horst, J.H. ter

    2010-01-01

    Co-crystallization is known as a product formulation technology, but it can also be used as a tool to solve crystallization problems. Product removal by co-crystallization in fermentations is used as a showcase to demonstrate the potential of co-crystallization as a separation technique. In fermenta

  20. The objective crystal spectrometer OXS on the spectrum-X-gamma satellite crystal calibrations

    DEFF Research Database (Denmark)

    Abdali, S.; Christensen, Finn Erland; Schnopper, H.W.;

    1997-01-01

    The four kinds of crystals; RAP(001), Si(111), LiF(220) and the Co/C multilayer on the super polished Si(111) crystals, together make up the objective crystal spectrometer OXS. They cover a wide energy range extending from 0.16 eV to 8 keV. A study of crystal reflectivity and energy resolution...

  1. Robotic CCD microscope for enhanced crystal recognition

    Science.gov (United States)

    Segelke, Brent W.; Toppani, Dominique

    2007-11-06

    A robotic CCD microscope and procedures to automate crystal recognition. The robotic CCD microscope and procedures enables more accurate crystal recognition, leading to fewer false negative and fewer false positives, and enable detection of smaller crystals compared to other methods available today.

  2. A generalized crystal-cutting method for modeling arbitrarily oriented crystals in 3D periodic simulation cells with applications to crystal-crystal interfaces

    Science.gov (United States)

    Kroonblawd, Matthew P.; Mathew, Nithin; Jiang, Shan; Sewell, Thomas D.

    2016-10-01

    A Generalized Crystal-Cutting Method (GCCM) is developed that automates construction of three-dimensionally periodic simulation cells containing arbitrarily oriented single crystals and thin films, two-dimensionally (2D) infinite crystal-crystal homophase and heterophase interfaces, and nanostructures with intrinsic N-fold interfaces. The GCCM is based on a simple mathematical formalism that facilitates easy definition of constraints on cut crystal geometries. The method preserves the translational symmetry of all Bravais lattices and thus can be applied to any crystal described by such a lattice including complicated, low-symmetry molecular crystals. Implementations are presented with carefully articulated combinations of loop searches and constraints that drastically reduce computational complexity compared to simple loop searches. Orthorhombic representations of monoclinic and triclinic crystals found using the GCCM overcome some limitations in standard distributions of popular molecular dynamics software packages. Stability of grain boundaries in β-HMX was investigated using molecular dynamics and molecular statics simulations with 2D infinite crystal-crystal homophase interfaces created using the GCCM. The order of stabilities for the four grain boundaries studied is predicted to correlate with the relative prominence of particular crystal faces in lab-grown β-HMX crystals. We demonstrate how nanostructures can be constructed through simple constraints applied in the GCCM framework. Example GCCM constructions are shown that are relevant to some current problems in materials science, including shock sensitivity of explosives, layered electronic devices, and pharmaceuticals.

  3. Approaches to automated protein crystal harvesting

    Energy Technology Data Exchange (ETDEWEB)

    Deller, Marc C., E-mail: mdeller@scripps.edu; Rupp, Bernhard, E-mail: mdeller@scripps.edu

    2014-01-28

    Approaches to automated and robot-assisted harvesting of protein crystals are critically reviewed. While no true turn-key solutions for automation of protein crystal harvesting are currently available, systems incorporating advanced robotics and micro-electromechanical systems represent exciting developments with the potential to revolutionize the way in which protein crystals are harvested.

  4. Economic analysis of crystal growth in space

    Science.gov (United States)

    Ulrich, D. R.; Chung, A. M.; Yan, C. S.; Mccreight, L. R.

    1972-01-01

    Many advanced electronic technologies and devices for the 1980's are based on sophisticated compound single crystals, i.e. ceramic oxides and compound semiconductors. Space processing of these electronic crystals with maximum perfection, purity, and size is suggested. No ecomonic or technical justification was found for the growth of silicon single crystals for solid state electronic devices in space.

  5. Crystallization Kinetics within a Generic Modelling Framework

    DEFF Research Database (Denmark)

    Meisler, Kresten Troelstrup; von Solms, Nicolas; Gernaey, Krist;

    2013-01-01

    An existing generic modelling framework has been expanded with tools for kinetic model analysis. The analysis of kinetics is carried out within the framework where kinetic constitutive models are collected, analysed and utilized for the simulation of crystallization operations. A modelling...... procedure is proposed to gain the information of crystallization operation kinetic model analysis and utilize this for faster evaluation of crystallization operations....

  6. Framework for the analysis of crystallization operations

    DEFF Research Database (Denmark)

    Meisler, Kresten Troelstrup; Abdul Samad, Noor Asma Fazli Bin; Gernaey, Krist

    Crystallization is often applied in the production of salts and/oractive pharmaceutical ingredients (API), and the crystallization step is an essential part of the manufacturing process for many chemicals-based products.In recent years the monitoring and analysis of crystallization operations has...

  7. 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...

  8. Batch cooling crystallization and pressure filtration of sulphathiazole: the influence of solvent composition.

    Science.gov (United States)

    Häkkinen, Antti; Pöllänen, Kati; Karjalainen, Milja; Rantanen, Jukka; Louhi-Kultanen, Marjatta; Nyström, Lars

    2005-02-01

    Currently there is a great interest in new process analytical approaches to increase the process understanding of pharmaceutical unit operations. In the present study, the influence of the solvent composition on the material properties and, further, on the filtration characteristics, of different crystal suspensions obtained through an unseeded batch-cooling-crystallization process was studied. Sulphathiazole, which is an antibiotic agent with multiple polymorphic forms, was produced by performing laboratory-scale cooling crystallization experiments from five different mixtures of water and propan-1-ol (n-propanol). The size, shape and polymorphic composition of the crystals produced were characterized with a scanning electron microscope, with a novel automated image analyser and with an X-ray powder diffractometer. All of the monitored crystal properties were found to clearly differ between the samples obtained from different solvents. The crystals produced in the batch-cooling-crystallization experiments were separated from the crystallizing solvents using a batch-type pressure Nutsche filter, and the filtration characteristics of the suspensions were evaluated on the basis of average filter-cake porosities and average specific cake resistances, which were determined from the experimentally obtained filtration data. Comparison between the calculated filtration characteristics revealed that considerable differences existed between the different suspensions, and it could therefore be concluded that the pressure-filtration process was influenced by the composition of the crystallizing solvent. The filterability of all the studied sulphathiazole suspensions was considered to be rather good on the basis of the relatively low cake porosities (0.51-0.63), which were accompanied with low average specific cake resistances [(8.7 x 10(7))-(1.2 x 10(9)) m/kg].

  9. The crystal structure and crystal chemistry of fernandinite and corvusite

    Science.gov (United States)

    Evans, H.T.; Post, J.E.; Ross, D.R.; Nelen, J.A.

    1994-01-01

    Using type material of fernandinite from Minasragra, Peru, and corvusite from the Jack Claim, La Sal Mountains, Utah, the properties and crystal chemistry of these minerals have been determined by Rietveld analysis of the powder X-ray-diffraction patterns. The crystal structure of both species is isotypic with the V2O5 -type layer first found for ??-Ag0.68V2O5; it consists of chains of VO6 octahedra linked by opposite corners (parallel to b) condensed by edge-sharing to form the layer. The vanadium has average valence 4.8, and the resulting layer-charge is balanced by varying amounts of Ca, Na, and K in the interlayer region accompanied by labile water. This study has confirmed the validity of fernandinite as a unique mineral species. It is closely related to corvusite, from which it is distinguished on the basis of the dominant interlayer cation: Ca for fernandinite, Na for curvusite. -Authors

  10. Hot Views on Cold Crystals: The Application of Thermal Imaging in Cryocrystallography

    Science.gov (United States)

    Snell, Eddie

    2003-01-01

    We have used thermal imaging techniques to visualize the cryocooling processes of macromolecular crystals. Cryocooling is a common technique used for structural data collection to reduce radiation damage in intense X-ray beams and decrease the thermal motion of the atoms. From the thermal images it was clear that during cryocooling a cold wave progresses through a crystal starting at the face closest to the origin of the cold stream and ending at the point furthest away. As an extension to this work, we used thermal imaging to study small crystals, held in a cryo-loop, in the presence of vitrified mother liquor. The different infrared transmission and reflectance properties of the crystal in comparison to the mother liquor surrounding it are thought to be the parameter that produces the contrast that makes the crystal visible. An application of this technology may be the determination of the exact location of small crystals in a cryo-loop for automated structural genomics studies. Data from initial tests in support of application development was recorded for lysozyme crystals and for bFGF/dna complex crystals, which were cryocooled and imaged in large loops, both with visible light and with infrared radiation. The crystals were clearly distinguished from the vitrified solution in the infrared spectrum, while in the case of the bFGF/dna complex the illumination had to be carefully manipulated to make the crystal visible in the visible spectrum. These results suggest that the thermal imaging may be more sensitive than visual imaging for automated location of small crystals. However, further work on small crystals robotically mounted at SSRL did not clearly visualize those crystals. The depth of field of the camera proved to be limiting and a different cooling geometry was used, compared to the previous, successful experiments. Analysis to exploit multiple images to improve depth of field and experimental work to understand cooling geometry effects is ongoing. These

  11. Crystallization Behavior and Growing Process of Rutile Crystals in Ti-Bearing Blast Furnace Slag

    Science.gov (United States)

    Zhang, Wu; Zhang, Li; Li, Yuhai; Li, Xin

    2016-09-01

    The aim of the present work is to elucidate crystallization and growing process of rutile crystals in Ti-bearing blast furnace slag. The samples were taken from the liquid slag and quenched at once at elevated temperatures in order to analyze phase transaction of titanium and grain size of rutile crystals. Crystallization and growing kinetics of rutile crystals under elevated temperature conditions were calculated, and the crystallization process of rutile crystals under isothermal conditions was expressed by Avrami equation. The effects of experimental parameters, such as experimental temperatures, SiO2 addition, cooling rate, crystal seed addition and oxygen flow, were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM), the optimal conditions for rutile crystals to grow up were obtained. Distribution and movement state of rutile crystals in the slag were analyzed.

  12. Crystal coating via spray drying to improve powder tabletability.

    Science.gov (United States)

    Vanhoorne, V; Peeters, E; Van Snick, B; Remon, J P; Vervaet, C

    2014-11-01

    A continuous crystal coating method was developed to improve both flowability and tabletability of powders. The method includes the introduction of solid, dry particles into an atomized spray during spray drying in order to coat and agglomerate individual particles. Paracetamol was used as a model drug as it exhibits poor flowability and high capping tendency upon compaction. The particle size enlargement and flowability were evaluated by the mean median particle size and flow index of the resulting powders. The crystal coating coprocessing method was successful for the production of powders containing 75% paracetamol with excellent tableting properties. However, the extent of agglomeration achieved during coprocessing was limited. Tablets compressed on a rotary tablet press in manual mode showed excellent compression properties without capping tendency. A formulation with 75% paracetamol, 5% PVP and 20% amorphous lactose yielded a tensile strength of 1.9 MPa at a compression pressure of 288 MPa. The friability of tablets compressed at 188 MPa was only 0.6%. The excellent tabletability of this formulation was attributed to the coating of paracetamol crystals with amorphous lactose and PVP through coprocessing and the presence of brittle and plastic components in the formulation. The coprocessing method was also successfully applied for the production of directly compressible lactose showing improved tensile strength and friability in comparison to a spray dried direct compression lactose grade.

  13. Single crystal plasticity by modeling dislocation density rate behavior

    Energy Technology Data Exchange (ETDEWEB)

    Hansen, Benjamin L [Los Alamos National Laboratory; Bronkhorst, Curt [Los Alamos National Laboratory; Beyerlein, Irene [Los Alamos National Laboratory; Cerreta, E. K. [Los Alamos National Laboratory; Dennis-Koller, Darcie [Los Alamos National Laboratory

    2010-12-23

    The goal of this work is to formulate a constitutive model for the deformation of metals over a wide range of strain rates. Damage and failure of materials frequently occurs at a variety of deformation rates within the same sample. The present state of the art in single crystal constitutive models relies on thermally-activated models which are believed to become less reliable for problems exceeding strain rates of 10{sup 4} s{sup -1}. This talk presents work in which we extend the applicability of the single crystal model to the strain rate region where dislocation drag is believed to dominate. The elastic model includes effects from volumetric change and pressure sensitive moduli. The plastic model transitions from the low-rate thermally-activated regime to the high-rate drag dominated regime. The direct use of dislocation density as a state parameter gives a measurable physical mechanism to strain hardening. Dislocation densities are separated according to type and given a systematic set of interactions rates adaptable by type. The form of the constitutive model is motivated by previously published dislocation dynamics work which articulated important behaviors unique to high-rate response in fcc systems. The proposed material model incorporates thermal coupling. The hardening model tracks the varying dislocation population with respect to each slip plane and computes the slip resistance based on those values. Comparisons can be made between the responses of single crystals and polycrystals at a variety of strain rates. The material model is fit to copper.

  14. Methodology for fast evaluation of Bacillus thuringiensis crystal protein content

    Directory of Open Access Journals (Sweden)

    Alves Lúcia M. Carareto

    2000-01-01

    Full Text Available The development of the production and use of Bacillus thuringiensis in Brazil at a commercial scale faces certain difficulties, among them the establishment of efficient methodologies for the quantitation of toxic products to be commercialized. Presently, the amount of toxin is given in percentage by analyzing the samples total protein content. Such methodology however, does not measure the actual amount of active protein present in the product, since most strains express different endotoxin genes and might even produce b-toxin. Since the various types of toxins exhibit different antigenic characteristics, this work has as objective the utilization of fast immunological techniques to quantify the level of crystal protein. Crystal protein produced by a subspecies of Bacillus thuringiensis var. israelensis was purified by ultracentrifugation and utilized to immunize rabbits and to produce hiperimmune sera. Such sera were latter used to evaluate the level of proteins on commercial bioinsecticide and on laboratory cultures of B. thuringiensis through the immunodot technique. The results were obtained by comparison of data obtained from reactions with known concentrations of crystal protein permitting to evaluate the level of such protein on various materials.

  15. Crystal structure of lead(II) tartrate: a redetermination.

    Science.gov (United States)

    Weil, Matthias

    2015-01-01

    Single crystals of poly[μ4-tartrato-κ(6) O (1),O (3):O (1'):O (2),O (4):O (4')-lead], [Pb(C4H4O6)] n , were grown in a gel medium. In comparison with the previous structure determination of this compound from laboratory powder X-ray diffraction data [De Ridder et al. (2002 ▶). Acta Cryst. C58, m596-m598], the redetermination on the basis of single-crystal data reveals the absolute structure, all atoms with anisotropic displacement parameters and a much higher accuracy in terms of bond lengths and angles. It could be shown that a different space group or incorporation of water as reported for similarly gel-grown lead tartrate crystals is incorrect. In the structure, each Pb(2+) cation is bonded to eight O atoms of five tartrate anions, while each tartrate anion links four Pb(2+) cations. The resulting three-dimensional framework is stabilized by O-H⋯O hydrogen bonds between the OH groups of one tartrate anion and the carboxyl-ate O atoms of adjacent anions.

  16. Crystal structure of lead(II tartrate: a redetermination

    Directory of Open Access Journals (Sweden)

    Matthias Weil

    2015-01-01

    Full Text Available Single crystals of poly[μ4-tartrato-κ6O1,O3:O1′:O2,O4:O4′-lead], [Pb(C4H4O6]n, were grown in a gel medium. In comparison with the previous structure determination of this compound from laboratory powder X-ray diffraction data [De Ridder et al. (2002. Acta Cryst. C58, m596–m598], the redetermination on the basis of single-crystal data reveals the absolute structure, all atoms with anisotropic displacement parameters and a much higher accuracy in terms of bond lengths and angles. It could be shown that a different space group or incorporation of water as reported for similarly gel-grown lead tartrate crystals is incorrect. In the structure, each Pb2+ cation is bonded to eight O atoms of five tartrate anions, while each tartrate anion links four Pb2+ cations. The resulting three-dimensional framework is stabilized by O—H...O hydrogen bonds between the OH groups of one tartrate anion and the carboxylate O atoms of adjacent anions.

  17. Crystal structure of K[Hg(SCN)3] - a redetermination.

    Science.gov (United States)

    Weil, Matthias; Häusler, Thomas

    2014-09-01

    The crystal structure of the room-temperature modification of K[Hg(SCN)3], potassium tri-thio-cyanato-mercurate(II), was redetermined based on modern CCD data. In comparison with the previous report [Zhdanov & Sanadze (1952 ▶). Zh. Fiz. Khim. 26, 469-478], reliability factors, standard deviations of lattice parameters and atomic coordinates, as well as anisotropic displacement parameters, were revealed for all atoms. The higher precision and accuracy of the model is, for example, reflected by the Hg-S bond lengths of 2.3954 (11), 2.4481 (8) and 2.7653 (6) Å in comparison with values of 2.24, 2.43 and 2.77 Å. All atoms in the crystal structure are located on mirror planes. The Hg(2+) cation is surrounded by four S atoms in a seesaw shape [S-Hg-S angles range from 94.65 (2) to 154.06 (3)°]. The HgS4 polyhedra share a common S atom, building up chains extending parallel to [010]. All S atoms of the resulting (1) ∞[HgS2/1S2/2] chains are also part of SCN(-) anions that link these chains with the K(+) cations into a three-dimensional network. The K-N bond lengths of the distorted KN7 polyhedra lie between 2.926 (2) and 3.051 (3) Å.

  18. DIFFERENT APPROACHES TO CRYSTALLIZATION OF MEMBRANE PROTEINS

    Directory of Open Access Journals (Sweden)

    Prakash G. Doiphode

    2012-01-01

    Full Text Available Crystallography is more like an art than science. Crystallizing membrane proteins are a big challenge; membrane proteins are present in the cell membrane and serve as cell support. The most important feature of membrane protein is that it contains both hydrophobic and hydrophilic regions on its surface. They are generally much more difficult to study than soluble proteins. The problem becomes more difficult when trying to obtain crystals to determine the high resolution structures of membrane proteins. We want to utilize this opportunity to briefly examine various approaches for crystallization of membrane proteins. The important factors for determining the success of crystallization experiments for membrane proteins lies in the purification, preparation of membrane samples, the environment in which the crystals are grown and the technique used to grow the crystals. All the X-ray structures of membrane protein are grown from preparations of detergents by different methods developed to crystallize. In this review different techniques for the crystallization of membrane proteins are being described. The cubic phase method also known as in meso method is discussed along with other methods to understand about the crystallization of membrane proteins, its general applicability, salt, detergent and screening effects on crystallization. Low volumes as nano-liter of samples can be used for crystallization. The effects of different detergents on the crystallization of membrane protein, as well as the use of surfactants like polyoxyethylene. Approach based on the detergent complexation to prove the ability of cyclodextrins to remove detergent from ternary mixtures in order to get 2D crystals. Crystallization of membrane proteins using non-ionic surfactants as well as Lipidic sponge phase and with swollen lipidic mesophases is discussed to better understand the crystallization of membrane proteins.

  19. Morphology Changing at Incipient Crystallization Condition

    Science.gov (United States)

    Toshima, Takeshi; Hamai, Ryo; Fujita, Saya; Takemura, Yuka; Takamatsu, Saori; Tafu, Masamoto

    2015-04-01

    Brushite (Dicalcium phosphate dihydrate, (DCPD), CaHPO4·2H2O) is one of key components in calcium phosphate system due to wide attractive material not only as bioceramics but also environmental materials. Morphology of DCPD crystals is important factor when one uses its functionality with chemical reaction; because its surface crystal face, shape and size rule the chemical reactivity, responsiveness. Moreover, physical properties are also changed the morphology; such as cohesion, dispersiveness, permeability and so on. If one uses DCPD crystals as environmental renovation materials to catch the fluoride ions, their shape require 020 crystal surfaces; which usually restricts their shape as plate-like structure. After the chemical reaction, the shape of sludge is not good for handling due to their agglutinate property. Therefore searching an effective parameter and developing the method to control the morphology of DCPD crystals is required. In past, we reported that initial concentration and pH value of starting solution, prepared by dissolving calcium nitrate, Ca(NO3)2 and ammonium dihydrogen phosphate, NH4H2PO4, changes the morphology of DCPD crystals and phase diagram of morphology of DCPD crystal depend on those parameter. The DCPD crystallization shows unique behaviour; products obtained higher initial concentration form single crystal-like structure and under lower condition, they form agglomerate crystal-like structure. These results contradict usual crystallization. Here we report that the effect of mixing process of two solutions. The morphology of DCPD crystals is changed from plate structure to petal structure by the arrangement. Our result suggests that morphology of DCPD crystals strongly depends at incipient crystallization condition and growth form is controllable by setting initial crystallization condition.

  20. Numerical analysis and simulation of Czochralski growth processes for large diameter silicon crystals

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Numerical analysis and simulation have been an effective means to develop the advanced growth technology and to control the defects type, size and density for silicon crystals of 300 mm and beyond In the present paper, numerical analysis of the melt flow in the Czochralski (CZ) crystal growth configuration, the three dimensional (3D) modeling, the simulation of melt flow under the magnetic field, the inverse modeling and the time-dependent simulation are reviewed. Finally, comparison of numerical analysis with experimental measurements is discussed.