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Sample records for aluminum-induced crystallization comparison

  1. Controlling silicon crystallization in aluminum-induced crystallization via substrate plasma treatment

    NASA Astrophysics Data System (ADS)

    Hainey, Mel F.; Innocent-Dolor, Jon-L.; Choudhury, Tanushree H.; Redwing, Joan M.

    2017-03-01

    The effect of reactive ion etching using chlorine or fluorine-based plasmas on aluminum-induced crystallization (AIC) of silicon on fused silica glass substrates was investigated with the goal of chemically modifying the substrate surface and thereby influencing the crystallization behavior. Chlorine etching of the glass prior to AIC resulted in six times faster silicon crystallization times and smaller grain sizes than films formed on untreated substrates while fluorine etching resulted in crystallization times double than those on untreated surfaces. The differences in crystallization behavior were attributed to changes in surface chemistry and surface energy of the glass as a result of the plasma treatment as supported by X-ray photoelectron spectroscopy and contact angle measurements. The different surface treatments were then combined with optical lithography to control the location of crystallization on the substrate surface to realize the production of patterned polycrystalline silicon films from initially continuous aluminum and silicon.

  2. Structural properties of a-Si films and their effect on aluminum induced crystallization

    SciTech Connect

    Tankut, Aydin; Ozkol, Engin; Karaman, Mehmet; Turan, Rasit; Canli, Sedat

    2015-10-15

    In this paper, we report the influence of the structural properties of amorphous silicon (a-Si) on its subsequent crystallization behavior via the aluminum induced crystallization (AIC) method. Two distinct a-Si deposition techniques, electron beam evaporation and plasma enhanced chemical vapor deposition (PECVD), are compared for their effect on the overall AIC kinetics as well as the properties of the final poly-crystalline (poly-Si) silicon film. Raman and FTIR spectroscopy results indicate that the PECVD grown a-Si films has higher intermediate-range order, which is enhanced for increased hydrogen dilution during deposition. With increasing intermediate-range order of the a-Si, the rate of AIC is diminished, leading larger poly-Si grain size.

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

    NASA Astrophysics Data System (ADS)

    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

    NASA Astrophysics Data System (ADS)

    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

    NASA Astrophysics Data System (ADS)

    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. Controlled aluminum-induced crystallization of an amorphous silicon thin film by using an oxide-layer diffusion barrier

    NASA Astrophysics Data System (ADS)

    Hwang, Ji-Hyun; Kwak, Hyunmin; Kwon, Myeung Hoi

    2014-03-01

    Aluminum-induced crystallization (AIC) of amorphous silicon with an Al2O3 diffusion barrier was investigated for controlling Si crystallization and preventing layer exchange during the annealing process. An Al2O3 layer was deposited between the a-Si and the Al films (a-Si/Al2O3/Al/Glass) and was blasted with an air spray gun with alumina beads to form diffusion channels between the Si and the Al layers. During the annealing process, small grain Si x Al seeds were formed at the channels. Then, the Al2O3 diffusion barrier was restructured to close the channels and prevent further diffusion of Al atoms into the a-Si layer. A polycrystalline Si film with (111), (220) and (311) crystallization peaks in the X-ray diffraction pattern was formed by annealing at 560 °C in a conventional furnace. That film showed a p-type semiconducting behavior with good crystallinity and a large grain size of up to 14.8 µm. No layer conversion occurred between the Si and the Al layers, which had been the fundamental obstacle to the applications in the crystallization of a-Si films by using the AIC method.

  7. On the Discontinuity of Polycrystalline Silicon Thin Films Realized by Aluminum-Induced Crystallization of PECVD-Deposited Amorphous Si

    NASA Astrophysics Data System (ADS)

    Pan, Qingtao; Wang, Tao; Yan, Hui; Zhang, Ming; Mai, Yaohua

    2017-04-01

    Crystallization of glass/Aluminum (50, 100, 200 nm) /hydrogenated amorphous silicon (a-Si:H) (50, 100, 200 nm) samples by Aluminum-induced crystallization (AIC) is investigated in this article. After annealing and wet etching, we found that the continuity of the polycrystalline silicon (poly-Si) thin films was strongly dependent on the double layer thicknesses. Increasing the a-Si:H/Al layer thickness ratio would improve the film microcosmic continuity. However, too thick Si layer might cause convex or peeling off during annealing. Scanning electron microscopy (SEM) and Energy Dispersive X-ray spectroscopy (EDX) are introduced to analyze the process of the peeling off. When the thickness ratio of a-Si:H/Al layer is around 1 to 1.5 and a-Si:H layer is less than 200 nm, the poly-Si film has a good continuity. Hall measurements are introduced to determine the electrical properties. Raman spectroscopy and X-ray diffraction (XRD) results show that the poly-Si film is completely crystallized and has a preferential (111) orientation.

  8. On the Discontinuity of Polycrystalline Silicon Thin Films Realized by Aluminum-Induced Crystallization of PECVD-Deposited Amorphous Si

    NASA Astrophysics Data System (ADS)

    Pan, Qingtao; Wang, Tao; Yan, Hui; Zhang, Ming; Mai, Yaohua

    2017-01-01

    Crystallization of glass/Aluminum (50, 100, 200 nm) /hydrogenated amorphous silicon (a-Si:H) (50, 100, 200 nm) samples by Aluminum-induced crystallization (AIC) is investigated in this article. After annealing and wet etching, we found that the continuity of the polycrystalline silicon (poly-Si) thin films was strongly dependent on the double layer thicknesses. Increasing the a-Si:H/Al layer thickness ratio would improve the film microcosmic continuity. However, too thick Si layer might cause convex or peeling off during annealing. Scanning electron microscopy (SEM) and Energy Dispersive X-ray spectroscopy (EDX) are introduced to analyze the process of the peeling off. When the thickness ratio of a-Si:H/Al layer is around 1 to 1.5 and a-Si:H layer is less than 200 nm, the poly-Si film has a good continuity. Hall measurements are introduced to determine the electrical properties. Raman spectroscopy and X-ray diffraction (XRD) results show that the poly-Si film is completely crystallized and has a preferential (111) orientation.

  9. The effect of hydrogen in the mechanism of aluminum-induced crystallization of sputtered amorphous silicon using scanning auger microanalysis

    SciTech Connect

    Hossain, Maruf; Meyer III, Harry M; Abu-Safe, Husam H; Naseem, Hameed; Brown, Walter D

    2006-01-01

    The metal-induced crystallization (MIC) of hydrogenated sputtered amorphous silicon (a-Si:H) using aluminum has been investigated using Xray diffraction (XRD) and scanning Auger microanalysis (SAM). Hydrogenated, as well as non-hydrogenated, amorphous silicon (a-Si) films were sputtered on glass substrates, then capped with a thin layer of Al. Following the depositions, the samples were annealed in the temperature range 200 C to 400 C for varying periods of time. Crystallization of the samples was confirmed by XRD. Non-hydrogenated films started to crystallize at 350 C. On the other hand, crystallization of the samples with the highest hydrogen (H2) content initiated at 225 C. Thus, the crystallization temperature is affected by the H2 content of the a-Si. Material structure following annealing was confirmed by SAM. In this paper, a comprehensive model for MIC of a-Si is developed based on these experimental results.

  10. Aluminum-induced granulomas in a tattoo

    SciTech Connect

    McFadden, N.; Lyberg, T.; Hensten-Pettersen, A.

    1989-05-01

    A patient who developed localized, granulomatous reactions in a tattoo is described. With the use of scanning electron microscopy and energy dispersive x-ray microanalysis, both aluminum and titanium particles were found in the involved skin sections. Intradermal provocation testing with separate suspensions of aluminum and titanium induced a positive response only in the case of aluminum. Examination by scanning electron microscopy and energy dispersive x-ray microanalysis of the provoked response established aluminum as the only nonorganic element present in the test site tissue. This is the first report of confirmed aluminum-induced, delayed-hypersensitivity granulomas in a tattoo.

  11. Comparison of Germanium Telluride (GeTe) Crystals

    NASA Technical Reports Server (NTRS)

    2004-01-01

    Comparison of Germanium Telluride (GeTe) Crystals grown on Earth (left) and in space (right) during the Skylab SL-3 mission. These crystals were grown using a vapor transport crystal growth method in the Multipurpose Electric Furnace System (MEFS). Crystals grown on earth are needles and platelettes with distorted surfaces and hollow growth habits. The length of the ground-based needle is approximately 2 mm and the average lenth of the platelets is 1 mm. The dull appearance of the Skylab crystals resulted from condensation of the transport agent during the long cooling period dictated by the Skylab furnace. In a dedicated process, this would be prevented by removing the ampoule from the furnace and quenching the vapor source.

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

    DTIC Science & Technology

    2014-11-01

    Shock Compression of Metal Crystals: A Comparison of Eulerian and Lagrangian Elastic- Plastic Theories by JD Clayton ARL-RP-0513...of Metal Crystals: A Comparison of Eulerian and Lagrangian Elastic- Plastic Theories JD Clayton Weapons and Materials Research Directorate, ARL...SUBTITLE Shock Compression of Metal Crystals: A Comparison of Eulerian and Lagrangian Elastic- Plastic Theories 5a. CONTRACT NUMBER 5b. GRANT

  13. EFFECTS OF ALUMINUM-INDUCED AGGREGATION ON THE FLUORESCENCE OF HUMIC SUBSTANCES. (R822251)

    EPA Science Inventory

    Aluminum-induced aggregates of terrestrial and aquatic humic acid standards from the International Humic Substances Society are shown to be fluorescent by means of a multiwavelength fluorescence anisotropy experiment in which the data was treated with a model for nonspherical ...

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

    PubMed

    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.

  15. A comparison between protein crystals grown with vapor diffusion methods in microgravity and protein crystals using a gel liquid-liquid diffusion ground-based method

    NASA Technical Reports Server (NTRS)

    Miller, Teresa Y.; He, Xiao-Min; Carter, Daniel C.

    1992-01-01

    Crystals of human serum albumin have been successfully grown in a variety of gels using crystallization conditions otherwise equivalent to those utilized in the popular hanging-drop vapor-equilibrium method. Preliminary comparisons of gel grown crystals with crystals grown by the vapor diffusion method via both ground-based and microgravity methods indicate that crystals superior in size and quality may be grown by limiting solutal convection. Preliminary X-ray diffraction statistics are presented.

  16. Comparison of hexagonal crystal structures between fluorapatite and polytetrafluoroethylene.

    PubMed

    Okazaki, Masayuki

    2017-01-01

    The crystallographic properties of fluorapatite (FAp) and polytetrafluoroethylene (PTFE) as biomedical materials were compared. Both materials contain fluorine and casually belong to the hexagonal crystal system. It is interesting that FAp is an inorganic ionic crystal, while PTFE is an organic covalent-bond crystal. Generally, fluorine contributes to the physicochemical stability and in some cases to the biocompatibility. The crystal structure of FAp was initially analyzed in 1930 by Náray-Szabó, although the analysis of hydroxyapatite (HAp) was markedly delayed until 1964. The computer graphics display demonstrated that fluoride ions serve to stabilize the hydroxyapatite crystals and prevent dental caries. On the other hand, PTFE crystal analysis was reported in 1954 by Bunn and Howells. The PTFE temperature-pressure phase diagram accepted for over 60 years is very complicated and insufficient. PTFE delicately changes its phase near room temperature, although at a glance it appears to have a simple form compared with DNA.

  17. Density comparison measurements of silicon crystals by a pressure-of-flotation method at NMIJ

    NASA Astrophysics Data System (ADS)

    Waseda, A.; Fujii, K.

    2004-04-01

    A new density comparison apparatus based on a pressure-of-flotation method (PFM) is presented. Density comparison measurements are performed for a new silicon crystal of the National Metrology Institute of Japan (NMIJ) for the density standard and determination of the Avogadro constant. The density comparison measurement of silicon crystals by the new PFM apparatus has an estimated relative standard uncertainty of 4.0 × 10-8. Adjusted values of density are evaluated from the data of the PFM and absolute measurements using a least-squares algorithm, where correlations are taken into consideration.

  18. Optimal dose of zinc supplementation for preventing aluminum-induced neurotoxicity in rats

    PubMed Central

    Lu, Hao; Hu, Jianyang; Li, Jing; Pang, Wei; Hu, Yandan; Yang, Hongpeng; Li, Wenjie; Huang, Chengyu; Zhang, Mingman; Jiang, Yugang

    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 orally 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 supplemented 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 pathological 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 aluminum-induced neurotoxicity in rats, and the optimal dosages are 100 and 200 mg/kg. PMID:25206586

  19. Crystallization of silicon films on glass: a comparison of methods

    SciTech Connect

    Lemons, R.A.; Bosch, M.A.; Herbst, D.

    1983-01-01

    The lure of flat panel displays has stimulated much research on the crystallization of silicon films deposited on large-area transparent substrates. In most respects, fused quartz is ideal. It has high purity, thermal shock resistance, and a softening point above the silicon melting temperature. Unfortunately, fused quartz has such a small thermal expansion that the silicon film cracks as it cools. This problem has been attacked by patterning with islands or moats before and after crystallization, by capping, and by using silicate glass substrates that match the thermal expansion of silicon. The relative merits of these methods are compared. Melting of the silicon film to achieve high mobility has been accomplished by a variety of methods including lasers, electron beams, and strip heaters. For low melting temperature glasses, surface heating with a laser or electron beam is essential. Larger grains are obtained with the high bias temperature, strip heater techniques. The low-angle grain boundaries characteristic of these films may be caused by constitutional undercooling. A model is developed to predict the boundary spacing as a function of scan rate and temperature gradient.

  20. In situ Crystallization of RF sputtered ITO thin films: A comparison with annealed samples

    SciTech Connect

    John, K. Aijo; Manju, T.

    2014-01-28

    Tin doped Indium Oxide (ITO) is a wide band gap semiconductor with high conductivity and transparency in the visible region of the solar spectrum. One of the most popular and exploited applications of ITO is the realization of the transparent conductive layers needed for the electrodes of light sensitive devices, such as photovoltaic cells. The thermal energy for the crystallization of ITO films is very low (150°C). The crystallization can be achieved by the continuous energetic bombardment of the ions in the sputtering chamber without annealing or substrate heating. The accumulated energy will ensure the thermal energy necessary for the crystallization. With the help of sufficiently high sputtering power and sufficient duration, crystallized ITO films can be produced without annealing. In this report, a comparison of the conductivity and transparency of ITO films under two crystallization conditions ((1) crystallization of the sputtered films by annealing; (2) in situ crystallization of the films by providing high sputtering power and long sputtering duration) will be presented.

  1. A quality comparison of protein crystals grown under containerless conditions generated by diamagnetic levitation, silicone oil and agarose gel.

    PubMed

    Cao, Hui-Ling; Sun, Li-Hua; Li, Jian; Tang, Lin; Lu, Hui-Meng; Guo, Yun-Zhu; He, Jin; Liu, Yong-Ming; Xie, Xu-Zhuo; Shen, He-Fang; Zhang, Chen-Yan; Guo, Wei-Hong; Huang, Lin-Jun; Shang, Peng; He, Jian-Hua; Yin, Da-Chuan

    2013-10-01

    High-quality crystals are key to obtaining accurate three-dimensional structures of proteins using X-ray diffraction techniques. However, obtaining such protein crystals is often a challenge. Several containerless crystallization techniques have been reported to have the ability to improve crystal quality, but it is unknown which is the most favourable way to grow high-quality protein crystals. In this paper, a quality comparison of protein crystals which were grown under three containerless conditions provided by diamagnetic levitation, silicone oil and agarose gel was conducted. A control experiment on a vessel wall was also simultaneously carried out. Seven different proteins were crystallized under the four conditions, and the crystal quality was assessed in terms of the resolution limit, the mosaicity and the Rmerge. It was found that the crystals grown under the three containerless conditions demonstrated better morphology than those of the control. X-ray diffraction data indicated that the quality of the crystals grown under the three containerless conditions was better than that of the control. Of the three containerless crystallization techniques, the diamagnetic levitation technique exhibited the best performance in enhancing crystal quality. This paper is to our knowledge the first report of improvement of crystal quality using a diamagnetic levitation technique. Crystals obtained from agarose gel demonstrated the second best improvement in crystal quality. The study indicated that the diamagnetic levitation technique is indeed a favourable method for growing high-quality protein crystals, and its utilization is thus potentially useful in practical efforts to obtain well diffracting protein crystals.

  2. Image Correlation Applied to Single Crystal Plasticity Experiments and Comparison to Strain Gage Data

    SciTech Connect

    LeBlanc, M M; Florando, J N; Lassila, D H; Schmidt, T; Tyson II, J

    2005-06-29

    Full-field optical techniques are becoming increasingly popular for measuring the deformation of materials, especially in materials that exhibit non-uniform behavior. While there are many full-field techniques available (e.g. moire interferometry, electronic speckle pattern interferometry (ESPI), holography, and image correlation [1]), for our study of the deformation of single crystals, the image correlation technique was chosen for its insensitivity to vibrations and ability to measure large strains. While the theory and development of the algorithms for image correlation have been presented elsewhere [2,3] a comparative study to a conventional strain measurement device, such as a strain gage rosette, is desired to test the robustness and accuracy of the technique. The 6 Degrees of Freedom (6DOF) experiment, which was specifically designed to validate dislocation dynamics (DD) simulations [4], is ideally suited to compare the two methods. This experiment is different from previous experiments on single crystals in that it allows the crystal to deform essentially unconstrained, in both the elastic and plastic regimes, by allowing the bottom of the sample to move as the sample is being compressed. This unconstrained motion prevents the internal crystal planes from rotating during the deformation as typically seen in the pioneering work of Schmid [5] and Taylor [6]. In the early development of the 6DOF apparatus, stacked strain gage rosettes were used to provide the strain data [7]. While very accurate at small strains, strain gages provide an averaged measurement over a small area and cannot be used to measure the inhomogeneous plastic strains that typically occur during the 6DOF experiment. An image correlation technique can measure the full-field in-plane and out-of-plane deformation that occurs in single crystals, and a comparison to the strain gage data at small strains can test the accuracy of the method.

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

    NASA Astrophysics Data System (ADS)

    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.

  4. Comparison of four different crystal forms of the Mycobacterium tuberculosis ESX-1 secreted protein regulator EspR.

    PubMed

    Gangwar, Shanti P; Meena, Sita R; Saxena, Ajay K

    2014-04-01

    The Mycobacterium tuberculosis ESX-1 secreted protein regulator (EspR, Rv3849) is the key protein that delivers bacterial proteins into the host cell during mycobacterial infection. EspR binds directly to the espACD operon and is involved in transcriptional activation. In the current study, M. tuberculosis EspR has been crystallized and its X-ray structure has been determined at 3.3 Å resolution in a P3221 crystal form. EspR forms a physiological dimer in the crystal. Each EspR monomer contains an N-terminal helix-turn-helix DNA-binding domain and a C-terminal dimerization domain. The EspR structure in the P3221 crystal form was compared with previously determined EspR structures in P32, P21 and P212121 crystal forms. Structural comparison analysis indicated that the N-terminal helix-turn-helix domain of EspR acquires a rigid structure in the four crystal forms. However, significant structural differences were observed in the C-terminal domain of EspR in the P21 crystal form when compared with the P3221 and P32 crystal forms. The interaction, stabilization energy and buried surface area analysis of EspR in the four different crystal forms have provided information about the physiological dimer interface of EspR.

  5. Light scattering by ice crystals of cirrus clouds: comparison of the physical optics methods

    NASA Astrophysics Data System (ADS)

    Konoshonkin, Alexander V.; Kustova, Natalia V.; Borovoi, Anatoli G.; Grynko, Yevgen; Förstner, Jens

    2016-10-01

    The physical optics approximations are derived from the Maxwell equations. The scattered field equations by Kirchhoff, Stratton-Chu, Kottler and Franz are compared and discussed. It is shown that in the case of faceted particles, these equations reduce to a sum of the diffraction integrals, where every diffraction integral is associated with one plane-parallel optical beam leaving a particle facet. In the far zone, these diffraction integrals correspond to the Fraunhofer diffraction patterns. The paper discusses the E-, M- and (E, M)-diffraction theories as applied to ice crystals of cirrus clouds. The comparison to the exact solution obtained by the discontinuous Galerkin time domain method shows that the Kirchhoff diffraction theory is preferable.

  6. Crystal growth of pure substances: Phase-field simulations in comparison with analytical and experimental results

    NASA Astrophysics Data System (ADS)

    Nestler, B.; Danilov, D.; Galenko, P.

    2005-07-01

    A phase-field model for non-isothermal solidification in multicomponent systems [SIAM J. Appl. Math. 64 (3) (2004) 775-799] consistent with the formalism of classic irreversible thermodynamics is used for numerical simulations of crystal growth in a pure material. The relation of this approach to the phase-field model by Bragard et al. [Interface Science 10 (2-3) (2002) 121-136] is discussed. 2D and 3D simulations of dendritic structures are compared with the analytical predictions of the Brener theory [Journal of Crystal Growth 99 (1990) 165-170] and with recent experimental measurements of solidification in pure nickel [Proceedings of the TMS Annual Meeting, March 14-18, 2004, pp. 277-288; European Physical Journal B, submitted for publication]. 3D morphology transitions are obtained for variations in surface energy and kinetic anisotropies at different undercoolings. In computations, we investigate the convergence behaviour of a standard phase-field model and of its thin interface extension at different undercoolings and at different ratios between the diffuse interface thickness and the atomistic capillary length. The influence of the grid anisotropy is accurately analyzed for a finite difference method and for an adaptive finite element method in comparison.

  7. Optical, thermal, and mechanical characterization of photonic crystal fibers: results and comparisons

    NASA Astrophysics Data System (ADS)

    Borzycki, Krzysztof; Kobelke, Jens; Schuster, Kay; Wójcik, Jan

    2010-04-01

    Six photonic crystal fibers (PCFs) were characterized at NIT laboratory participating in COST Action 299 "FIDES", allowing for comparisons of properties and their dependence on fiber design. Samples tested included three nonlinear fibers with germanium doped core, two fibers with un-doped core and honeycomb photonic structure, and a "PANDAlike" PCF with a pair of large holes along an un-doped core. Tests included optical time domain reflectometer (OTDR) measurements, spectral loss, polarization mode dispersion (PMD) and its variations with temperature, fiber twist and axial strain. Elastooptic coefficient was measured for 2 fibers. Most samples exhibited high PMD, up to 3 ps/m. PMD was usually reduced by twisting the fiber, but twist sensitivity varied widely. The "PANDA-like" PCF, however, had PMD virtually unaffected by both twist and tensile strain; the latter property made it different from true PANDA fiber tested for comparison. Intensity of backscattering in each PCF was stronger compared to a standard telecom single mode fiber (SMF), by a factor up to 110x.

  8. Nanomolar aluminum induces pro-inflammatory and pro-apoptotic gene expression in human brain cells in primary culture.

    PubMed

    Lukiw, Walter J; Percy, Maire E; Kruck, Theo P

    2005-09-01

    Aluminum, the most abundant neurotoxic metal in our biosphere, has been implicated in the etiology of several neurodegenerative disorders including Alzheimer's disease (AD). To further understand aluminum's influence on gene expression, we examined total messenger RNA levels in untransformed human neural cells exposed to 100 nanomolar aluminum sulfate using high density DNA microarrays that interrogate the expression of every human gene. Preliminary data indicate that of the most altered gene expression levels, 17/24 (70.8%) of aluminum-affected genes, and 7/8 (87.5%) of aluminum-induced genes exhibit expression patterns similar to those observed in AD. The seven genes found to be significantly up-regulated by aluminum encode pro-inflammatory or pro-apoptotic signaling elements, including NF-kappaB subunits, interleukin-1beta precursor, cytosolic phospholipase A2, cyclooxygenase-2, beta-amyloid precursor protein and DAXX, a regulatory protein known to induce apoptosis and repress transcription. The promoters of genes up-regulated by aluminum are enriched in binding sites for the stress-inducible transcription factors HIF-1 and NF-kappaB, suggesting a role for aluminum, HIF-1 and NF-kappaB in driving atypical, pro-inflammatory and pro-apoptotic gene expression. The effect of aluminum on specific stress-related gene expression patterns in human brain cells clearly warrant further investigation.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Astrophysics Data System (ADS)

    Jafarabadi, Marzieh Akbari; Mahdieh, Mohammad Hossein

    2015-08-01

    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/cm2 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.

  11. Water in quartz? - A comparison of naturally and experimentally deformed crystals

    NASA Astrophysics Data System (ADS)

    Thust, A.; Kilian, R.; Heilbronner, R.; Stunitz, H.; Holyoke, C. W.; Kronenberg, A. K.

    2011-12-01

    promote the distribution of H2O in the quartz crystal and thus influence the strength of the material The comparison of both situations, - experimental deformation of wetted, single crystal quartz by dislocation glide and natural deformation of dry quartz with wet grain boundaries by dislocation creep - raises a number of questions. (1) Assuming that wet grain boundaries control the mechanical behavior of quartz (recovery) implies that the presence of intra-crystalline water is not critical. (2) Assuming that intra-crystalline water is crucial and - at the same time - measuring very low intra-crystalline water content in nature implies that either the water is lost (i.e. was transient) or else even the low contents of 200 H/10^6Si are sufficient to enable intra-crystalline plasticity.

  12. Design and comparison of composite rod crystals for power scaling of diode end-pumped Nd:YAG lasers.

    PubMed

    Wilhelm, Ralf; Freiburg, Denis; Frede, Maik; Kracht, Dietmar; Fallnich, Carsten

    2009-05-11

    A comparison of composite Nd:YAG laser rod crystals with one, two and three doped segments for high-power diode end-pumping is presented. An approach based on an expansion of the heat generation density and temperature distributions into a Fourier-Bessel basis set for solving the stationary heat conduction equation is used for choosing adequate segment lengths and dopant concentrations. A maximum laser output power of 167.5 W at an optical-to-optical efficiency of 53.6% was achieved by longitudinal pumping a crystal with three doped segments with fibre-coupled laser diodes.

  13. Comparison between numerical modeling and experimental measurements of the interface shape in Kyropoulos growth of Ti-doped sapphire crystals

    NASA Astrophysics Data System (ADS)

    Stelian, C.; Sen, G.; Barthalay, N.; Duffar, T.

    2016-11-01

    Numerical modeling is applied to investigate the factors affecting the shape of the crystal-melt interface during the growth of Ti-doped sapphire crystals by using the Kyropoulos method. Numerical results are compared to experimental visualization of the growth interface in the case of ingots grown in crucibles of 15 cm in diameter. The transient computations of the heat transfer and melt convection show that the interface curvature depends on the internal radiative effect in the sapphire crystal. The effective thermal conductivity increases significantly in the case of Ti-doped crystals, leading to conical shapes of the interface with large curvatures. The growth interface is less curved in the case of non-doped sapphire crystals which have a smaller absorption coefficient. The convection driven by buoyancy and Marangoni effects has also a strong effect on the interface shape. The intensity of the Marangoni flow increases significantly during the shouldering stage of the growth, leading to a more curved interface with a convex-concave shape. The comparison between numerically computed interface deflection and the experimental results shows a good agreement. According to present numerical analysis, the formation of a plateau and the temporal concave shape of the crystal are related to unfavorable thermal conditions at the beginning of the growth process.

  14. Luminescence of SiO2 and GeO2 crystals with rutile structure. Comparison with α-quartz crystals and relevant glasses (Review Article)

    NASA Astrophysics Data System (ADS)

    Trukhin, A. N.

    2016-07-01

    Luminescence properties of SiO2 in different structural states are compared. Similar comparison is made for GeO2. Rutile and α-quartz structures as well as glassy state of these materials are considered. Main results are that for α-quartz crystals the luminescence of self-trapped exciton is the general phenomenon that is absent in the crystal with rutile structure. In rutile structured SiO2 (stishovite) and GeO2 (argutite) the main luminescence is due to a host material defect existing in as-received (as-grown) samples. The defect luminescence possesses specific two bands, one of which has a slow decay (for SiO2 in the blue and for GeO2, in green range) and another, a fast ultraviolet (UV) band (4.75 eV in SiO2 and at 3 eV in GeO2). In silica and germania glasses, the luminescence of self-trapped exciton coexists with defect luminescence. The latter also contains two bands: one in the visible range and another in the UV range. The defect luminescence of glasses was studied in details during last 60-70 years and is ascribed to oxygen deficient defects. Analogous defect luminescence in the corresponding pure nonirradiated crystals with α-quartz structure is absent. Only irradiation of a α-quartz crystal by energetic electron beam, γ-rays and neutrons provides defect luminescence analogous to glasses and crystals with rutile structure. Therefore, in glassy state the structure containing tetrahedron motifs is responsible for existence of self-trapped excitons and defects in octahedral motifs are responsible for oxygen deficient defects.

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

    NASA Astrophysics Data System (ADS)

    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.

  16. Comparison of radiation damage in lead tungstate crystals under pion and gamma irradiation

    SciTech Connect

    Batarin, V.A.; Butler, J.; Davidenko, A.M.; Derevschikov, A.A.; Goncharenko, Y.M.; Grishin, V.N.; Kachanov, V.A.; Khodyrev, V.Y.; Konstantinov, A.S.; Kravtsov, V.I.; Kubota, Y.; Lukanin, V.S.; Matulenko, Y.A.; Melnick, Y.M.; Meschanin, A.P.; Mikhalin, N.E.; Minaev, N.G.; Mochalov, V.V.; Morozov, D.A.; Nogach, L.V.; Ryazantsev, A.V.; /Serpukhov, IHEP /Fermilab /Minnesota U. /Syracuse U. /Nanjing U.

    2003-12-01

    Studies of the radiation hardness of lead tungstate crystals produced by the Bogoroditsk Techno-Chemical Plant in Russia and the Shanghai Institute of Ceramics in China have been carried out at IHEP, Protvino. The crystals were irradiated by a 40 GeV pion beam. After full recovery, the same crystals were irradiated using a {sup 137}Cs {gamma}-ray source. The dose rate profiles along the crystal length were observed to be quite similar. We compare the effects of the two types of radiation on the crystals light output.

  17. A new single crystal diamond dosimeter for small beam: comparison with different commercial active detectors.

    PubMed

    Marsolat, F; Tromson, D; Tranchant, N; Pomorski, M; Le Roy, M; Donois, M; Moignau, F; Ostrowsky, A; De Carlan, L; Bassinet, C; Huet, C; Derreumaux, S; Chea, M; Cristina, K; Boisserie, G; Bergonzo, P

    2013-11-07

    Recent developments of new therapy techniques using small photon beams, such as stereotactic radiotherapy, require suitable detectors to determine the delivered dose with a high accuracy. The dosimeter has to be as close as possible to tissue equivalence and to exhibit a small detection volume compared to the size of the irradiation field, because of the lack of lateral electronic equilibrium in small beam. Characteristics of single crystal diamond (tissue equivalent material Z = 6, high density) make it an ideal candidate to fulfil most of small beam dosimetry requirements. A commercially available Element Six electronic grade synthetic diamond was used to develop a single crystal diamond dosimeter (SCDDo) with a small detection volume (0.165 mm(3)). Long term stability was studied by irradiating the SCDDo in a (60)Co beam over 14 h. A good stability (deviation less than ± 0.1%) was observed. Repeatability, dose linearity, dose rate dependence and energy dependence were studied in a 10 × 10 cm(2) beam produced by a Varian Clinac 2100 C linear accelerator. SCDDo lateral dose profile, depth dose curve and output factor (OF) measurements were performed for small photon beams with a micro multileaf collimator m3 (BrainLab) attached to the linac. This study is focused on the comparison of SCDDo measurements to those obtained with different commercially available active detectors: an unshielded silicon diode (PTW 60017), a shielded silicon diode (Sun Nuclear EDGE), a PinPoint ionization chamber (PTW 31014) and two natural diamond detectors (PTW 60003). SCDDo presents an excellent spatial resolution for dose profile measurements, due to its small detection volume. Low energy dependence (variation of 1.2% between 6 and 18 MV photon beam) and low dose rate dependence of the SCDDo (variation of 1% between 0.53 and 2.64 Gy min(-1)) are obtained, explaining the good agreement between the SCDDo and the efficient unshielded diode (PTW 60017) in depth dose curve

  18. Ostwald-Meyers Metastable Region in LiBr Crystallization-Comparison of Measurements with Predictions.

    PubMed

    Duvall, Kristin N.; Dirksen, James A.; Ring, Terry A.

    2001-07-15

    Experiments have been performed to measure the Ostwald-Meyers metastable region during crystallization from concentrated LiBr solutions. Solution thermodynamics shows that several hydrated LiBr salts and ice can crystallize depending upon the concentration of LiBr in aqueous solution. The available solubility data were interpreted to give solubility products of several hydrated LiBr salts using the formulation of Helgeson, which accounts for the activity of water. The crystallization temperature was measured by monitoring to +/-0.01 degrees C the temperature of solutions inside test tubes placed in a cooling bath programmed at a cooling rate of 20 degrees C/h. A release of the heat of crystallization identifies the temperature of crystallization. The equilibrium solubility was verified by crystallization with seed crystals present. The crystallization temperature without seeds present was 10 to 20 degrees C less than the equilibrium solubility temperature corresponding to the Ostwald-Meyers metastable region. This crystallization temperature measured at 20 degrees C/h was shown to correspond to nucleation on the surface of the test tube with an interface energy of 40+/-1.2 erg/cm(2). Homogeneous nucleation from solution data shows the crystallization temperature to be from 40 to 50 degrees C below the equilibrium solubility curve and to be accurately predicted by homogeneous nucleation with an interface energy of 26 erg/cm(2), the literature value of the ice/water interface. Since the hydrated LiBr salts have surfaces that expose structured water molecules to the solution, this value is believed to be an appropriate value of the interface energy of the hydrated LiBr crystals. Crystallization temperature measurements were performed at different cooling rates, showing that slower cooling rates gave a narrower Ostwald-Myers metastable zone as is expected. Induction time measurements showed that the time to spontaneous crystallization increases as the supersaturation

  19. A COMPARISON OF FAR INFRARED AND RAMAN SPECTRA OF SOME RARE EARTH GARNET SINGLE CRYSTALS,

    DTIC Science & Technology

    RARE EARTH COMPOUNDS, *INFRARED SPECTRA), (*GARNET, RARE EARTH COMPOUNDS), (* RAMAN SPECTROSCOPY, RARE EARTH COMPOUNDS), SINGLE CRYSTALS, ALUMINATES...PHONONS, YTTRIUM COMPOUNDS, YTTERBIUM COMPOUNDS, TERBIUM COMPOUNDS, DYSPROSIUM COMPOUNDS, CANADA

  20. Augmentation of aluminum-induced oxidative stress in rat cerebrum by presence of pro-oxidant (graded doses of ethanol) exposure.

    PubMed

    Nayak, Prasunpriya; Sharma, Shiv Bhushan; Chowdary, Nadella Vijaya Subbaraya

    2010-11-01

    Both aluminum and ethanol are pro-oxidants and neurotoxic. Considering the possibilities of co-exposure and sharing mechanisms of producing neurotoxicity, the present study was planned to identify the level of aluminum-induced oxidative stress in altered pro-oxidant (ethanol exposure) status of cerebrum. Male rats were coexposed to aluminum and ethanol for 4 weeks. After the exposure period, cerebral levels of protein, reduced glutathione (GSH), lipid peroxidation (TBARS) were measured. Activities of catalase, superoxide dismutase (SOD), glutathione reductase (GR) and glutathione perioxidase (GPx) of cerebrum were estimated. In most of the cases significant correlations were observed between the alterations and graded ethanol doses, suggesting a dose-dependency in pushing the oxidant equilibrium toward pro-oxidants. Aluminum is found to influence significantly all the studied parameters of oxidative stress. Likewise, ethanol also influenced these parameters significantly, except GR, while the interaction between ethanol and aluminum could significantly influence only the GSH content and GR activity of cerebrum. Present study demonstrate that coexposure of aluminum with pro-oxidant might favor development of aluminum-induced oxidative stress in cerebrum. This observation might be helpful in understanding of mechanism of neurodegenerative disorders and ameliorate them.

  1. Comparison of the crystal and solution structures of calmodulin and troponin C

    SciTech Connect

    Heidorn, D.B.; Trewhella, J.

    1988-02-09

    X-ray solution scattering data from skeletal muscle troponin C and from calmodulin have been measured. Modeling studies based on the crystal structure coordinates for these proteins show discrepancies between the solution data and the crystal structure that indicate that if the size and shape of the globular domains are the same in solution as in the crystal, the distances between them must be smaller by several angstroms. Bringing the globular domains closer together requires structural changes in the interconnecting helix that joins them.

  2. Comparison of silver and molybdenum microfocus X-ray sources for single-crystal structure determination

    PubMed Central

    Krause, Lennard; Herbst-Irmer, Regine; Sheldrick, George M.; Stalke, Dietmar

    2015-01-01

    The quality of diffraction data obtained using silver and molybdenum microsources has been compared for six model compounds with a wide range of absorption factors. The experiments were performed on two 30 W air-cooled Incoatec IµS microfocus sources with multilayer optics mounted on a Bruker D8 goniometer with a SMART APEX II CCD detector. All data were analysed, processed and refined using standard Bruker software. The results show that Ag Kα radiation can be beneficial when heavy elements are involved. A numerical absorption correction based on the positions and indices of the crystal faces is shown to be of limited use for the highly focused microsource beams, presumably because the assumption that the crystal is completely bathed in a (top-hat profile) beam of uniform intensity is no longer valid. Fortunately the empirical corrections implemented in SADABS, although originally intended as a correction for absorption, also correct rather well for the variations in the effective volume of the crystal irradiated. In three of the cases studied (two Ag and one Mo) the final SHELXL R1 against all data after application of empirical corrections implemented in SADABS was below 1%. Since such corrections are designed to optimize the agreement of the intensities of equivalent reflections with different paths through the crystal but the same Bragg 2θ angles, a further correction is required for the 2θ dependence of the absorption. For this, SADABS uses the transmission factor of a spherical crystal with a user-defined value of μr (where μ is the linear absorption coefficient and r is the effective radius of the crystal); the best results are obtained when r is biased towards the smallest crystal dimension. The results presented here suggest that the IUCr publication requirement that a numerical absorption correction must be applied for strongly absorbing crystals is in need of revision. PMID:26089746

  3. Comparison of silver and molybdenum microfocus X-ray sources for single-crystal structure determination.

    PubMed

    Krause, Lennard; Herbst-Irmer, Regine; Sheldrick, George M; Stalke, Dietmar

    2015-02-01

    The quality of diffraction data obtained using silver and molybdenum microsources has been compared for six model compounds with a wide range of absorption factors. The experiments were performed on two 30 W air-cooled Incoatec IµS microfocus sources with multilayer optics mounted on a Bruker D8 goniometer with a SMART APEX II CCD detector. All data were analysed, processed and refined using standard Bruker software. The results show that Ag Kα radiation can be beneficial when heavy elements are involved. A numerical absorption correction based on the positions and indices of the crystal faces is shown to be of limited use for the highly focused microsource beams, presumably because the assumption that the crystal is completely bathed in a (top-hat profile) beam of uniform intensity is no longer valid. Fortunately the empirical corrections implemented in SADABS, although originally intended as a correction for absorption, also correct rather well for the variations in the effective volume of the crystal irradiated. In three of the cases studied (two Ag and one Mo) the final SHELXL R1 against all data after application of empirical corrections implemented in SADABS was below 1%. Since such corrections are designed to optimize the agreement of the intensities of equivalent reflections with different paths through the crystal but the same Bragg 2θ angles, a further correction is required for the 2θ dependence of the absorption. For this, SADABS uses the transmission factor of a spherical crystal with a user-defined value of μr (where μ is the linear absorption coefficient and r is the effective radius of the crystal); the best results are obtained when r is biased towards the smallest crystal dimension. The results presented here suggest that the IUCr publication requirement that a numerical absorption correction must be applied for strongly absorbing crystals is in need of revision.

  4. Comparison of templating abilities of urea and thioruea during photodimerization of bipyridylethyelene and stilbazole crystals.

    PubMed

    Bhogala, Balakrishna R; Captain, Burjor; Ramamurthy, Vaidhyanathan

    2015-01-01

    Photodimerization of cocrystals of four bispyridylethylenes and two stilbazoles with urea as a template in the solid state has been investigated following our success with thiourea. Four investigated olefins photodimerized quantitatively to a single dimer in the crystalline state only. The reactivity of urea-olefin crystals is understood on the basis of their packing arrangements in the crystalline state. In reactive crystals the adjacent reactive molecules are within 4.2 Å and parallel, whereas the unreactive ones have their adjacent molecules are farther than 4.6Å and nonparallel. Thus, with the knowledge of crystal packing the reactivity of urea-olefin crystals is predictable on the basis of Schmidt's topochemical postulates. The templating property of urea, similar to thiourea, derives from its ability to form hydrogen bonds with itself and the guest olefins. Despite the similarities in molecular structures of urea and thiourea their subtle electronic properties, yet to be fully understood, affect the crystal packing and consequently their reactivity in the crystalline state. Further work is needed to fully exploit the templating properties of urea.

  5. Defect Density Comparison of Detached versus Attached Bridgman Grown Germanium Crystals

    NASA Technical Reports Server (NTRS)

    Schweizer, M.; Cobb, S. D.; Volz, M. P.; Szofran, F. R.; Whitaker, Ann F. (Technical Monitor)

    2001-01-01

    Semiconductor Bridgman growth without contact between the growing crystal and the growth ampoule has been observed on Earth in the last few years during several experiments. Previously, this so-called detached or dewetted growth phenomenon occurred preferentially under microgravity conditions due to the absence of the hydrostatic pressure. Many theoretical as well as experimental investigations helped to provide a better understanding of the mechanism and to identify the parameters leading to the detachment. Thus, recent attempts to get stable detached growth under terrestrial conditions by Duffar et al. growing III-V compounds and our own group with germanium and germanium-silicon alloys were frequently successful. At this conference we present the results of several germanium growth experiments performed in pyrolytic boron nitride containers. To exert an influence on the pressure ratio above and below the melt we used closed-bottom and open-bottom containers. This resulted in mainly detached-grown single crystals with the closed-bottom crucibles and attached single crystals with the open-bottom tubes. Evidence of detached growth is obtained from the crystal surface with a combination of axial profilometer scans and optical and electron microscopy. Detailed investigations of the defect structure, which is the main focus of this presentation, have shown an improvement of the crystal quality in the detached-grown samples, with a strong reduction of the etch pit density by about two orders of magnitude.

  6. Comparison of ordered and disordered silicon nanowire arrays: experimental evidence of photonic crystal modes.

    PubMed

    Dhindsa, Navneet; Saini, Simarjeet S

    2016-05-01

    We experimentally compared the reflectance between ordered and disordered silicon nanowires to observe the evidence of photonic crystal modes. For similar diameters, the resonance peaks for the ordered nanowires at a spacing of 400 nm was at a shorter wavelength than the disordered nanowires, consistent to the excitation of photonic crystal modes. Furthermore, the resonant wavelength didn't shift while changing the density of the disordered nanowires, whereas there was a significant shift observed in the ordered ones. At an ordered spacing of 800 nm, the resonance wavelength approached that of the disordered structures, indicating that the ordered structures were starting to behave like individual waveguides. To our knowledge, this is the first direct experimental observation of photonic crystal modes in vertical periodic silicon nanowire arrays.

  7. Comparison of tunable lasers based on diode pumped Tm-doped crystals

    NASA Astrophysics Data System (ADS)

    Šulc, Jan; Jelínková, Helena; Koranda, Petr; Černý, Pavel; Jabczyński, Jan K.; Żendzian, Waldemar; Kwiatkowski, Jacek; Urata, Yoshiharu; Higuchi, Mikio

    2008-12-01

    We report on continuously tunable operation of a diode pumped lasers based on Tm-doped materials, emitting in the 1.8 - 2.μ1 m spectral band. In our study we compare results obtained with three various single crystals doped by Tm3+ ions: Yttrium Aluminum perovskite YAP (YAlO3), Gadolinium orthovanadate GdVO4, and Yttrium Lithium Fluoride YLF (YLiF4). Following samples were available: the 3mm long a-cut crystal rod of Tm:YAP with 4% at. Tm/Y (diameter 3 mm); the 8mm long b-cut crystal rod of Tm:YLF with 3.5% at. Tm/Y (diameter 3 mm); the 2.7mm long a-cut crystal block of Tm:GdVO4 with 2% at. Tm/Gd (crystal face 5×3 mm). For active medium pumping, the laser diode radiation was used. Because the tested samples differs significantly in absorption spectra, two fibre-coupled (core diameter 400 µm) temperature-tuned laser diodes were used: first operating at wavelength 793nm was used for Tm:YAP and Tm:YLF; the second operating at wavelength 802nm was used for Tm:GdVO4. In both cases, the continuous power up to 20W was available for pumping. The diode radiation was focused into the active crystal by two achromatic doublet lenses with the focal length f = 75 mm. The measured radius of pumping beam focus inside the crystal was 260 µm. The longitudinally diode pumped crystals were tested in linear, 80mm long, hemispherical laser cavity. The curved (radius 150mm) output coupler reflectivity was ~ 97 % in range from 1.8 up to 2.1 μm. The pumping flat mirror had maximal reflectivity in this range and it had high transmission around 0.8 μm. A 1.5mm thick birefringent plate made from quartz (Lyot filter) inserted under a Brewster's angle was used as a tuning element. This plate was placed inside the resonator between the crystal and the output coupler. Using Tm:YAP crystal, the maximal output power of 2.8W in this set-up was obtained. The laser could be tuned from 1865nm up to 2036nm with a maximum at 1985 nm. Laser based on Tm:YLF crystal was tunable from 1835nm up to

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

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed

    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.

  10. Comparison of optical properties and crystal structures of the praseodymium and europium chloroderivatives of acetates

    NASA Astrophysics Data System (ADS)

    Oczko, Grażyna; Starynowicz, Przemysław

    2005-04-01

    The praseodymium and europium dichloroacetates were obtained in the form of monocrystals. Crystal structures of the Ln(HCl 2CCOO) 3·2H 2O (Ln=Pr, Eu) compounds were determined by X-ray analysis. Both crystals proved to be isomorphous. They are monoclinic, space group P2 1/ n with: a=9.747(6), b=13.857(7), and c=23.595(9) Å, β=95.03(4)°, U=3175(3) Å 3, Z=8 for C 6H 7Cl 6O 8Pr and a=9.634(7), b=13.757(11), and c=23.524(14) Å, β=94.84(4)°, U=3107(4) Å 3, Z=8 for C 6H 7Cl 6O 8Eu. There are two symmetry independent lanthanide cations, which adopt a nine-coordinate geometry with seven oxygen atoms from carboxylate groups and two oxygen atoms from water molecules. Absorption (Pr 3+, Eu 3+), emission and emission excitation (Eu 3+) spectra of single crystals of Ln(HCl 2CCOO) 3·2H 2O were recorded at room temperature and low temperatures down to 4.2 K. Spectral intensities of the investigated systems are parametrized in terms of the Judd-Ofelt theory and compared to those of lanthanide trichloroacetates and acetates crystals. The relationship between the hypersensitivity and covalency is discussed. The nephelauxetic ratio β and Sinha's parameter δ are calculated based on the absorption spectra. The variation of these parameters and their correlation with the nature of metal-ligand bond is discussed. The bond polarity and bond strength of coordination complex determine the activity and stereospecifity of the catalyst thus the study of these properties are very important because of the application of lanthanide carboxylates as precursors of catalysts. The spectroscopic results are correlated with those from the crystal structure studies, especially with Ln-O distances and the co-ordinating forms of the carboxylate ions. The vibronic coupling in the f-f transitions were analysed. In order to determine the vibronic coupling quantitatively, calculations of the R= IVIB./ I0-phonon rates were performed from the low temperature absorption spectra. The correlation

  11. Comparison of the local and the average crystal structure of proton conducting lanthanum tungstate and the influence of molybdenum substitution.

    PubMed

    Magrasó, Anna; Frontera, Carlos

    2016-03-07

    We report on the comparison of the local and average structure reported recently for proton conducting lanthanum tungstate, of general formula La28-xW4+xO54+δv2-δ, and the impact of molybdenum-substitution on the crystal structure of the material. Partial replacement of W with 10 and 30 mol% Mo is investigated here, i.e. La27(W1-xMox)5O55.5 for x = 0.1 and 0.3. This study addresses the interpretation and the description of a disordered cation and anion sublattice in this material, which enables the understanding of the fundamental properties related to hydration, transport properties and degradation in lanthanum tungstate. The report shows that Mo-substituted lanthanum tungstate is a promising material as a dense oxide membrane for hydrogen separation at intermediate temperatures.

  12. Experimental Comparison of Tantalum Material Strength between Single Crystal [100] and [111] Samples at High Pressure and Strain Rates

    NASA Astrophysics Data System (ADS)

    Plechaty, Christopher; Park, Hye-Sook; Cavallo, Rob; Rudd, Robert; Prisbrey, Shon; Maddox, Brian; Wehrenberg, Christopher; May, Mark; Remington, Bruce

    2013-06-01

    Experiments were performed using the OMEGA laser to investigate the strength difference between single crystal [100] and [111] Ta samples at high pressure (1 Mbar), and high strain rates (106- 108 s-1) . To achieve these pressures and strain rates in experiment without melting the sample, a quasi-isentropic drive was employed to drive the growth of pre-imposed sinusoidal perturbations on the surface of the Ta samples, via the Rayleigh-Taylor (RT) instability. By measuring the ripple amplitude using face-on high energy (~22 KeV) radiography, the strength of the Ta sample is inferred from the amount of RT growth observed. Under these experimental conditions, the Ta material strength can be modeled by the Multiscale (MS) model, developed at LLNL. The value of the ``Taylor Factor'' (a MS model parameter), is thought to vary for [100] and [111] crystal orientations. To investigate this difference under these conditions, a comparison of the ripple growth was performed on the two samples for the same shot and drive conditions. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  13. Shock compression modeling of metallic single crystals: comparison of finite difference, steady wave, and analytical solutions

    SciTech Connect

    Lloyd, Jeffrey T.; Clayton, John D.; Austin, Ryan A.; McDowell, David L.

    2015-07-10

    Background: The shock response of metallic single crystals can be captured using a micro-mechanical description of the thermoelastic-viscoplastic material response; however, using a such a description within the context of traditional numerical methods may introduce a physical artifacts. Advantages and disadvantages of complex material descriptions, in particular the viscoplastic response, must be framed within approximations introduced by numerical methods. Methods: Three methods of modeling the shock response of metallic single crystals are summarized: finite difference simulations, steady wave simulations, and algebraic solutions of the Rankine-Hugoniot jump conditions. For the former two numerical techniques, a dislocation density based framework describes the rate- and temperature-dependent shear strength on each slip system. For the latter analytical technique, a simple (two-parameter) rate- and temperature-independent linear hardening description is necessarily invoked to enable simultaneous solution of the governing equations. For all models, the same nonlinear thermoelastic energy potential incorporating elastic constants of up to order 3 is applied. Results: Solutions are compared for plate impact of highly symmetric orientations (all three methods) and low symmetry orientations (numerical methods only) of aluminum single crystals shocked to 5 GPa (weak shock regime) and 25 GPa (overdriven regime). Conclusions: For weak shocks, results of the two numerical methods are very similar, regardless of crystallographic orientation. For strong shocks, artificial viscosity affects the finite difference solution, and effects of transverse waves for the lower symmetry orientations not captured by the steady wave method become important. The analytical solution, which can only be applied to highly symmetric orientations, provides reasonable accuracy with regards to prediction of most variables in the final shocked state but, by construction, does not provide insight

  14. Shock compression modeling of metallic single crystals: comparison of finite difference, steady wave, and analytical solutions

    DOE PAGES

    Lloyd, Jeffrey T.; Clayton, John D.; Austin, Ryan A.; ...

    2015-07-10

    Background: The shock response of metallic single crystals can be captured using a micro-mechanical description of the thermoelastic-viscoplastic material response; however, using a such a description within the context of traditional numerical methods may introduce a physical artifacts. Advantages and disadvantages of complex material descriptions, in particular the viscoplastic response, must be framed within approximations introduced by numerical methods. Methods: Three methods of modeling the shock response of metallic single crystals are summarized: finite difference simulations, steady wave simulations, and algebraic solutions of the Rankine-Hugoniot jump conditions. For the former two numerical techniques, a dislocation density based framework describes themore » rate- and temperature-dependent shear strength on each slip system. For the latter analytical technique, a simple (two-parameter) rate- and temperature-independent linear hardening description is necessarily invoked to enable simultaneous solution of the governing equations. For all models, the same nonlinear thermoelastic energy potential incorporating elastic constants of up to order 3 is applied. Results: Solutions are compared for plate impact of highly symmetric orientations (all three methods) and low symmetry orientations (numerical methods only) of aluminum single crystals shocked to 5 GPa (weak shock regime) and 25 GPa (overdriven regime). Conclusions: For weak shocks, results of the two numerical methods are very similar, regardless of crystallographic orientation. For strong shocks, artificial viscosity affects the finite difference solution, and effects of transverse waves for the lower symmetry orientations not captured by the steady wave method become important. The analytical solution, which can only be applied to highly symmetric orientations, provides reasonable accuracy with regards to prediction of most variables in the final shocked state but, by construction, does not provide

  15. Numerical comparison between conventional dispersion compensating fibers and photonic crystal fibers as lumped Raman amplifiers.

    PubMed

    Castellani, C E S; Cani, S P N; Segatto, M E V; Pontes, M J; Romero, M A

    2009-12-07

    In this paper we discuss the use of photonic crystal fibers (PCFs) as discrete devices for simultaneous wideband dispersion compensation and Raman amplification. The performance of the PCFs in terms of gain, ripple, optical signal-to-noise ratio (OSNR) and required fiber length for complete dispersion compensation is compared with conventional dispersion compensating fibers (DCFs). The main goal is to determine the minimum PCF loss beyond which its performance surpasses a state-of-the-art DCF and justifies practical use in telecommunication systems.

  16. Comparison of modeled and measured performance of a GSO crystal as gamma detector

    SciTech Connect

    Parno, Diana Syemour; Friend, Megan Lynn; Mamyan, Vahe; Benmokhtar, Fatiha; Camsonne, Alexandre; Franklin, Gregg B.; Paschke, Kent D.; Quinn, Brian Patrick

    2013-11-01

    We have modeled, tested, and installed a large, cerium-activated Gd{sub 2}SiO{sub 5} crystal scintillator for use as a detector of gamma rays. We present the measured detector response to two types of incident photons: nearly monochromatic photons up to 40 MeV, and photons from a continuous Compton backscattering spectrum up to 200 MeV. Our GEANT4 simulations, developed to determine the analyzing power of the Compton polarimeter in Hall A of Jefferson Lab, reproduce the measured spectra well.

  17. Comparison of crystal and solution hemoglobin binding of selected antigelling agents and allosteric modifiers

    SciTech Connect

    Mehanna, A.S.; Abraham, D.J. )

    1990-04-24

    This paper details comprehensive binding studies (solution and X-ray) of human hemoglobin A with a group of halogenated carboxylic acids that were investigated as potential antisickling agents. It is, to our knowledge, the first study to compare solution and crystal binding for a series of compounds under similar high-salt conditions used for cocrystallization. The compounds include ((3,4-dichlorobenzyl)oxy)acetic acid, ((p-bromobenzyl)oxy)acetic acid, clofibric acid, and bezafibrate. The location and stereochemistry of binding sites have been established by X-ray crystallography, while the number of binding sites and affinity constants were measured by using equilibrium dialysis. The observed crystal structures are consistent with the binding observed in solution and that the number of binding sites is independent of salt concentration, while the binding constant increases with increasing salt concentration. The studies also reveal that relatively small changes in the chemical structure of a drug molecule can result in entirely different binding sites on the protein. Moreover, the X-ray studies provide a possible explanation for the multiplicity in function exhibited by these compounds as allosteric modulators and/or antisickling agents. Finally, the studies indicate that these compounds bind differently to the R and T states of hemoglobin, and observation of special significance to the original design of these agents.

  18. Wettability of ultrananocrystalline diamond and graphite nanowalls films: a comparison with their single crystal analogs.

    PubMed

    Ostrovskaya, L Y u; Ralchenko, V G; Bolshakov, A P; Saveliev, A V; Dzbanovsky, N N; Shmegera, S V

    2009-06-01

    Dramatic changes in wettability of diamond and graphite are observed when these materials are prepared in nanostructured forms--undoped and nitrogen-doped ultrananocrystalline diamond (UNCD) films, and graphite nanowalls (GNW), respectively. The nanostructured carbon films were deposited on Si by microwave plasma CVD processes. The advancing contact angle theta for water on hydrogenated undoped UNCD films increases to 106 +/- 3 degrees compared to hydrogenated single crystal diamond (theta = 92 degrees). Nitrogen doping (N2 addition to plasma) during UNCD growth makes the film more hydrophilic. The GNW films exhibited superhydrophobic behavior with theta = 144 +/- 3 degrees for water, which is higher than the contact angle of monocrystalline graphite (the basal plane) by a factor of 1.8. No chemical surface treatment is necessary to achieve such high hydrophobicity, it is accomplished solely by a specific (nanoporous, high aspect ratio) surface morphology with very low free surface energy inherent in it. The wetting behaviour of nanostructured films can be described with the Cassie-Baxter equation for heterophase nanoporous surfaces. Oxidation and hydrogenation of UNCD films make it possible to control theta over a much wider range as compared to a single crystal diamond. The influence of diamond grain size on wetting is considered taking into account the surface treatment. The corresponding variation in surface energy has been determined by the modified Young's equation.

  19. Crystallization of silicon films on glass: a comparison of methods. [Flat panel displays

    SciTech Connect

    Lemons, R.A.; Bosch, M.A.; Herbst, D.

    1982-01-01

    The lure of flat panel displays has stimulated much research on the crystallization of silicon films deposited on large-area transparent substrates. In most respects, fused quartz is ideal. It has high purity, thermal shock resistance, and a softening point above the silicon melting temperature. Unfortunately, fused quartz has such a small thermal expansion that the silicon film cracks as it cools. This problem has been attacked by patterning with islands or moats before and after crystallization, by capping, and by using silicate glass substrates that match the thermal expansion of silicon. The relative merits of these methods are compared. Melting of the silicon film to achieve high mobility has been accomplished by a variety of methods including lasers, electron beams, and strip heaters. For low melting temperature glasses, surface heating with a laser or electron beam is essential. Larger grains are obtained with the high bias temperature, strip heater techniques. The low-angle grain boundaries characteristic of these films may be caused by constitutional undercooling. A model is developed to predict the boundary spacing as a function of scan rate and temperature gradient. 11 figures.

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

    PubMed

    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.

  1. Comparison of Phase Field Crystal and Molecular Dynamics Simulations for a Shrinking Grain

    SciTech Connect

    Radhakrishnan, Balasubramaniam; Gorti, Sarma B; Nicholson, Don M

    2012-01-01

    The Phase-Field Crystal (PFC) model represents the atomic density as a continuous function, whose spatial distribution evolves at diffusional, rather than vibrational time scales. PFC provides a tool to study defect interactions at the atomistic level but over longer time scales than in molecular dynamics (MD). We examine the behavior of the PFC model with the goal of relating the PFC parameters to physical parameters of real systems, derived from MD simulations. For this purpose we model the phenomenon of the shrinking of a spherical grain situated in a matrix. By comparing the rate of shrinking of the central grain using MD and PFC we obtain a relationship between PFC and MD time scales for processes driven by grain boundary diffusion. The morphological changes in the central grain including grain shape and grain rotation are also examined in order to assess the accuracy of the PFC in capturing the evolution path predicted by MD.

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

    PubMed Central

    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

  3. Comparison of CSD-YBCO growth on different single crystal substrates

    NASA Astrophysics Data System (ADS)

    Kunert, J.; Bäcker, M.; Falter, M.; Schroeder-Obst, D.

    2008-02-01

    2G HTS Coated Conductors properties can be improved by comparing different raw materials, precursor production routes and coating and annealing conditions. To suppress the influence of varying substrate tapes and buffer layer qualities on the HTS layers, a standard substrate is needed to improve the Jc values. In this work various pure single crystal substrates (SrTiO3 [STO], (LaAlO3)0.3(Sr2AlTaO6)0.7 [LSAT], LaAlO3 [LAO], NdGaO3 [NdGaO]) are investigated to find the material which is best in terms of price, texture and morphological layout and instantaneous availability. YBCO films deposited onto these substrates via chemical solution deposition (CSD) are analysed using XRD texture analysis, surface morphology analysis (high resolution AFM) and inductive measurement of the critical current density.

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

    PubMed

    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.

  5. Comparison in Schemes for Simulating Depositional Growth of Ice Crystal between Theoretical and Laboratory Data

    NASA Astrophysics Data System (ADS)

    Zhai, Guoqing; Li, Xiaofan

    2015-04-01

    The Bergeron-Findeisen process has been simulated using the parameterization scheme for the depositional growth of ice crystal with the temperature-dependent theoretically predicted parameters in the past decades. Recently, Westbrook and Heymsfield (2011) calculated these parameters using the laboratory data from Takahashi and Fukuta (1988) and Takahashi et al. (1991) and found significant differences between the two parameter sets. There are two schemes that parameterize the depositional growth of ice crystal: Hsie et al. (1980), Krueger et al. (1995) and Zeng et al. (2008). In this study, we conducted three pairs of sensitivity experiments using three parameterization schemes and the two parameter sets. The pre-summer torrential rainfall event is chosen as the simulated rainfall case in this study. The analysis of root-mean-squared difference and correlation coefficient between the simulation and observation of surface rain rate shows that the experiment with the Krueger scheme and the Takahashi laboratory-derived parameters produces the best rain-rate simulation. The mean simulated rain rates are higher than the mean observational rain rate. The calculations of 5-day and model domain mean rain rates reveal that the three schemes with Takahashi laboratory-derived parameters tend to reduce the mean rain rate. The Krueger scheme together with the Takahashi laboratory-derived parameters generate the closest mean rain rate to the mean observational rain rate. The decrease in the mean rain rate caused by the Takahashi laboratory-derived parameters in the experiment with the Krueger scheme is associated with the reductions in the mean net condensation and the mean hydrometeor loss. These reductions correspond to the suppressed mean infrared radiative cooling due to the enhanced cloud ice and snow in the upper troposphere.

  6. Si-O Bonded Interactions in Silicate Crystals and Molecules: A Comparison

    SciTech Connect

    Gibbs, Gerald V.; Jayatilaka, Dylan; Spackman, M. A.; Cox, David F.; Rosso, Kevin M.

    2006-11-16

    Bond critical point, local kinetic energy density, G(rc), and local potential energy density, V(rc), properties of the electron density distributions, ρ(r), calculated for silicates like quartz and molecules like disiloxane are similar, indicating that the forces that govern the Si-O bonded interactions in crystals are short-ranged and molecular-like. Using the G(rc)/ρ(rc) ratio as a measure of bond character, the ratio increases as the Si-O bond length, the local electronic energy density, H(rc) = G(rc) + V(rc), and the oordination number of the Si atom decrease, and as the value of the electron density at the bond critical point, ρ(rc) and the Laplacian, ∇2ρ(rc), increase. The G(rc)/ρ(rc) and H(rc)/ρ(rc) ratios categorize the bond as observed for other second row atom M-O bonds into nonequivalent classes with the covalent character of each of the M-O bonds increasing with the H(rc)/ρ(rc) ratio. Some workers consider the Si-O bond to be highly ionic and others considered it to be either intermediate or substantially covalent. The character of the bond is examined in terms of the large net atomic basin charges conferred on the Si atoms comprising disiloxane, stishovite, quartz and forsterite, the domains of localized electron density along the Si-O bond vectors and on the reflex side of the Si-O-Si angle together with the close similarity of the Si-O bonded interactions observed for a variety of hydroxyacid silicate molecules and a large number of silicate crystals. The bond critical point and local energy density properties of the electron density distribution indicate that the bond is intermediate in character between Al-O and P-O bonded interations rather than being ionic or covalent.

  7. Comparison of the three-dimensional structures of a human Bence-Jones dimer crystallized on Earth and aboard US Space Shuttle Mission STS-95.

    PubMed

    Terzyan, Simon S; Bourne, Christina R; Ramsland, Paul A; Bourne, Philip C; Edmundson, Allen B

    2003-01-01

    Crystals of a human (Sea) Bence-Jones dimer were produced in a capillary by vapor diffusion under microgravity conditions in the 9 day US Space Shuttle Mission STS-95. In comparison to ground-based experiments, nucleation was facile and spontaneous in space. Appearance of a very large (8 x 1.6 x 1.0 mm) crystal in a short time period is a strong endorsement for the use of microgravity to produce crystals sufficiently large for neutron diffraction studies. The Sea dimer crystallized in the orthorhombic space group P2(1)2(1)2(1), with a = 48.9 A, b = 85.2 A, and c = 114.0 A. The crystals grown in microgravity exhibited significantly lower mosaicities than those of ground-based crystals and the X-ray diffraction data had a lower overall B factor. Three-dimensional structures determined by X-ray analysis at two temperatures (100 and 293 K) were indistinguishable from those obtained from ground-based crystals. However, both the crystallographic R factor and the free R factor were slightly lower in the models derived from crystals produced in microgravity. The major difference between the two crystal growth systems is a lack of convection and sedimentation in a microgravity environment. This environment resulted in the growth of much larger, higher-quality crystals of the Sea Bence-Jones protein. Structurally, heretofore unrecognized grooves on the external surfaces of the Sea and other immunoglobulin-derived fragments are regular features and may offer supplementary binding regions for super antigens and other elongated ligands in the bloodstream and perivascular tissues.

  8. A comparison of specific surface area and crystallization kinetics in compact and porous amorphous solid water

    NASA Astrophysics Data System (ADS)

    Herrero, V. J.; Mate, B.; Roriguez-Lazcano, Y.; Galvez, O.; Moreno, M. A.; Escribano, R. M.

    2011-12-01

    In astronomical ices, both compact and porous morphologies can be expected depending on the particular ice history [1]. These different morphologies might be relevant for the interpretation of astronomical observations as demonstrated in recent works [2], where the characteristic ν4 band of NH4+ at 6.85 μm, used in tentative identifications of this ion in astronomical observations, was shown to broaden and virtually disappear, when embedded in compact ice samples. In this work we present a more detailed characterization of the compact ices used in ref. [2], which are produced in the laboratory through the sudden freezing of water droplets on a cold substrate, a procedure similar to that reported by Loerting et al. [3] for the generation of hyperquenched (HQ) glassy water. The present study is based on infrared (IR) vibrational spectroscopy measurements of the solids. The compactness, specific surface area (SSA), and crystallization kinetics of the HQ samples is compared to that of vapour deposited (VD) ices. SSA values are estimated from the isothermal adsorption of CH4 and CO2 at 40 and 90 K. The rates of crystallization are determined at several temperatures up to 150 K by monitoring the position and width of the OD stretching band of isolated HDO molecules in ice samples with a 4% HDO content (see ref. [4] for a previous application of the method). From these experiments we derive the conclusions that follow. The much higher porosity of the VD samples is immediately evidenced by the IR absorption peak of uncoordinated OH dangling bonds, which is practically absent in the HQ ices. The SSA values for the HQ ices are about one order of magnitude lower than those for VD ices, and likewise, the rates of crystallization, are also found to be lower in HQ than in VD ices. These results, and their likely astrophysical implications, will be discussed at the conference. This work has been funded by the Spanish Ministry of Science under Grants FIS2007-61686 and FIS2010

  9. Comparison of Hall effect near T c in YBCO 123 single crystal and 124 ceramics

    NASA Astrophysics Data System (ADS)

    Affronte, M.; Decroux, M.; Sadowski, W.; Graf, T.; Fischer, Ø.

    1990-12-01

    We have measured the Hall voltage VH as a function of temperature and magnetic field B (up to 6 T) near Tc in Y 1Ba 2Cu 3 O 7-δ (“123”) single crystal and in Y 1Ba 2Cu 4O 8 (“124”) ceramics. Near Tc, VH shows a sign reversal in the 123 crysta l ( B parallel to the c-axis) and the tangents to the VH versus B curves at 6 T do not cross the origin. These features are not observed in the 124 phase. The fact that a negative VH appears in the 123 phase and not in 124 seems to reflect different conditions for the flux flow dynamics in the two compounds. We also report measurements of the normal state Hall coefficient RH obtained in single phase 124 ceramics. The very small value of RH (1.5×10 -10m 3/C for T > 140 K) is rather unusual in the superconducting oxide family.

  10. Effect of different struvite crystallization methods on gaseous emission and the comprehensive comparison during the composting.

    PubMed

    Jiang, Tao; Ma, Xuguang; Yang, Juan; Tang, Qiong; Yi, Zhigang; Chen, Maoxia; Li, Guoxue

    2016-10-01

    This study compared 4 different struvite crystallization process (SCP) during the composting of pig feces. Four combinations of magnesium and phosphate salts (H3PO4+MgO (PMO), KH2PO4+MgSO4 (KPM), Ca(H2PO4)2+MgSO4 (CaPM), H3PO4+MgSO4 (PMS)) were assessed and were also compared to a control group (CK) without additives. The magnesium and phosphate salts were all supplemented at a level equivalent to 15% of the initial nitrogen content on a molar basis. The SCP significantly reduced NH3 emission by 50.7-81.8%, but not the N2O. Although PMS group had the lowest NH3 emission rate, the PMO treatment had the highest struvite content in the end product. The addition of sulphate decreased CH4 emission by 60.8-74.6%. The CaPM treatment significantly decreased NH3 (59.2%) and CH4 (64.9%) emission and yielded compost that was completely matured. Due to its effective performance and low cost, the CaPM was suggested to be used in practice.

  11. Comparison of spectroscopic properties of Tm and Ho in YAG and YLF crystals

    NASA Technical Reports Server (NTRS)

    Armagan, G.; Buoncristiani, A. M.; Inge, A. T.; Di Bartolo, B.

    1991-01-01

    The paper compares the cross-relaxation, energy transfer and loss processes in Tm- and Ho-doped YAG and YLF as a function of temperature, Tm concentration, and excitation power. Significant differences in the behavior of Tm and Tm,Ho in YAG and YLF crystals were found. The cross-relaxation rates of Tm(6 pct) are faster in YLF (about 5 microsec) than YAG (about 10 microsec). The energy transfer rates between Tm and Ho are faster in YLF than YAG. The time it takes for the maximum intensity of 1.7-micron emission to drop 10 percent is 25 microsec for YLF:Tm(6 pct),Ho(0.6 pct) and 65 microsec YAG:Tm(6 pct),Ho(0.5 pct). The losses occurring with increasing pump power for 2.1-micron emission of the above samples are 30 percent less in YLF than YAG. These qualitative differences point to YLF as a valuable 2-micron laser host material.

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

    PubMed

    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.

  13. Comparison of silicon photonic crystal resonator designs for optical trapping of nanomaterials.

    PubMed

    Serey, X; Mandal, S; Erickson, D

    2010-07-30

    The use of silicon photonic devices for optical manipulation has recently enabled the direct handling of objects like nucleic acids and nanoparticles that are much smaller than could previously be trapped using traditional laser tweezers. The ability to manipulate even smaller matter however requires the development of photonic structures with even stronger trapping potentials. In this work we investigate theoretically several photonic crystal resonator designs and characterize the achievable trapping stiffness and trapping potential depth (sometimes referred to as the trapping stability). Two effects are shown to increase these trapping parameters: field enhancement in the resonator and strong field containment. We find trapping stiffness as high as 22.3 pN nm(-1) for 100 nm polystyrene beads as well as potential depth of 51,000 k(B)T at T = 300 K, for one Watt of power input to the bus waveguide. Under the same conditions for 70 nm polystyrene beads, we find a stiffness of 69 pN nm(-1) and a potential depth of 177,000 k(B)T. Our calculations suggest that with input power of 10 mW we could trap particles as small as 7.7 nm diameter with a trapping depth of 500 k(B)T. We expect these traps to eventually enable the manipulation of small matter such as single proteins, carbon nanotubes and metallic nanoparticles.

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

    PubMed

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed Central

    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

  17. Pulse shape discrimination properties of Gd3Ga3Al2O12:Ce,B single crystal in comparison with CsI:Tl

    NASA Astrophysics Data System (ADS)

    Rawat, S.; Tyagi, Mohit; Netrakanti, P. K.; Kashyap, V. K. S.; Mitra, A.; Singh, A. K.; Desai, D. G.; Kumar, G. Anil; Gadkari, S. C.

    2016-12-01

    Single crystals of Gd3Ga3Al2O12:Ce,B and CsI:Tl were grown by Czochralski and Bridgman techniques, respectively. While both the crystals exhibited similar emission at about 550 nm, their scintillation decay times showed significantly different characteristics. The average scintillation decay time of Gd3Ga3Al2O12:Ce,B crystal was found to be about 284 ns for alpha excitation compared to 108 ns measured for a gamma source. On the other hand in CsI:Tl crystals, the alpha excitation resulted in a lower average decay time of 600 ns compared to 1200 ns with gamma excitation. Their pulse shape discrimination (PSD) for gamma and alpha radiations were studied by coupling the scintillators with photomultiplier tube or SiPM and employing an advanced digitizer as well as a conventional zero-crossing setup. In spite of having a poor α/γ light yield ratio, the PSD figure of merit and the difference of zero-crossing time in Gd3Ga3Al2O12:Ce,B crystals were found to be superior in comparison to CsI:Tl crystals.

  18. Si-O Bonded Interactions in Silicate Crystals and Molecules:  A Comparison

    SciTech Connect

    Gibbs, G. V.; Jayatilaka, D.; Spackman, M. A.; Cox, D. F.; Rosso, K. M.

    2006-11-01

    Bond critical point, local kinetic energy density, G(rc), and local potential energy density, V(rc), properties of the electron density distributions, ρ(r), calculated for silicates such as quartz and gas-phase molecules such as disiloxane are similar, indicating that the forces that govern the Si-O bonded interactions in silica are short-ranged and molecular-like. Using the G(rc)/ρ(rc) ratio as a measure of bond character, the ratio increases as the Si-O bond length, the local electronic energy density, H(rc) = G(rc) + V(rc), and the coordination number of the Si atom decrease and as the accumulation of the electron density at the bond critical point, ρ(rc), and the Laplacian, ∇2ρ(rc), increase. The G(rc)/ρ(rc) and H(rc)/ρ(rc) ratios categorize the bonded interaction as observed for other second row atom M-O bonds into discrete categories with the covalent character of each of the M-O bonds increasing with the H(rc)/ρ(rc) ratio. The character of the bond is examined in terms of the large net atomic charges conferred on the Si atoms comprising disiloxane, stishovite, quartz, and forsterite and the domains of localized electron density along the Si-O bond vectors and on the reflex side of the Si-O-Si angle together with the close similarity of the Si-O bonded interactions observed for a variety of hydroxyacid silicate molecules and a large number of silicate crystals. Finally, the bond critical point and local energy density properties of the electron density distribution indicate that the bond is an intermediate interaction between Al-O and P-O bonded interactions rather than being a closed-shell or a shared interaction.

  19. Experimental Comparison of Tantalum Material Strength between Single Crystal [100] and [111] Samples at High Pressure and Strain Rates

    NASA Astrophysics Data System (ADS)

    Plechaty, Christopher; Park, Hye-Sook; Cavallo, Rob; Prisbrey, Shon; Rudd, Robert; Wehrenberg, Christopher; Huntington, Channing; Maddox, Brian; May, Mark; Remington, Bruce

    2013-10-01

    Experiments were performed using the OMEGA laser to investigate Ta material strength at high pressure (1 Mbar), and high strain rates (106-108 s-1) . To achieve these pressures and strain rates in experiment without melting the sample, a quasi-isentropic drive was employed to drive the growth of pre-imposed sinusoidal perturbations embedded on the surface of the Ta sample, via the Rayleigh-Taylor (RT) instability. By measuring the ripple amplitude using face-on high energy (~ 22 KeV) radiography, the strength of the Ta sample was inferred from the amount of RT growth observed. Under these experimental conditions, the Ta material strength can be modeled by the Multiscale (MS) model, developed at LLNL. In this study, we performed a side-by-side comparison of the ripple growth on [100] and [111] orientated single-crystal Ta samples for the same shot and drive conditions. The objective was to determine if a difference in the growth predicted by the MS model could be observed at the high pressure and strain rates present in our experiments, and within the error bars of the experimental technique. Prepared by LLNL under Contract DE-AC52-07NA27344.

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

    PubMed

    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.

  1. Effects of 1 alpha,25- and 24R,25-dihydroxyvitamin D3 on aluminum-induced rickets in growing uremic rats.

    PubMed

    Vukicević, S; Krempien, B; Stavljenić, A

    1987-12-01

    Rats were subjected to a two-stage subtotal nephrectomy or sham operation, and treated with aluminum (Al) or both aluminum and vitamin D3 metabolites for 5 weeks with a cumulative dose of 13.6 mg aluminum. Animals were injected with 3H-thymidine and 3H-proline. The following analyses were performed: quantitative histology of tibial metaphyses and cytomorphometric electron microscopy of osteoclasts, quantitative (ICP-spectroscopy) and qualitative determination (histochemical staining) of aluminum within organs, and serum biochemistry (Ca, P, Mg, vitamin D3 metabolites, alkaline phosphatase, urea). The following new facts of the aluminum-related bone disease became evident: (a) Application of aluminum to growing uremic rats induced rickets, whose major epiphyseal growth plate changes were 1 alpha,25(OH)2D3-dependent. Addition of 1 alpha,25(OH)2D3 prevented the formation of rachitic metaphysis, but failed to prevent osteoid accumulation on epiphyseal and metaphyseal trabecular surfaces. Moreover, calcitriol produced hyperosteoidosis and osteosclerosis in the same rats. Aluminum did not alter the function of osteoblasts, while osteoclasts seemed inactivated. (b) The development of rickets was associated with suppressed serum levels of 1,25(OH)2D3, reduced phosphorus level and the high content of aluminum in the bone, kidney, and liver. The addition of 24R,25(OH)2D3 markedly exaggerated the reduction of serum levels of calcitriol. We suggested that aluminum induces rickets in growing uremic rats, which consists of two components: vitamin D refractory osteomalacia and 1 alpha,25(OH)2D3-dependent epiphyseal growth plate changes.

  2. 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.

    PubMed

    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.

  3. A comparison of the binding of urinary calcium oxalate monohydrate and dihydrate crystals to human kidney cells in urine

    PubMed Central

    Wang, Tingting; Thurgood, Lauren A.; Grover, Phulwinder K.; Ryall, Rosemary L.

    2010-01-01

    Objective To compare the binding kinetics of urinary calcium oxalate monohydrate (COM) and dihydrate (COD) crystals to human kidney (HK-2) cells in ultra-filtered (UF), and centrifuged and filtered (CF) human urine; and to quantify the binding of COM and COD crystals to cultured HK-2 cells in UF and CF urine samples collected from different individuals. Materials and methods Urine was collected from healthy subjects, pooled, centrifuged and filtered. 14C-oxalate-labelled COM and COD crystals were precipitated from the urine by adding oxalate after adjustment of two aliquots of the urine to 2 and 8 mm Ca2+, respectively. For the kinetic study, the crystals were incubated with HK-2 cells for up to 120 min in pooled CF urine adjusted to 2 and 8 mm Ca2+. Identical experiments were also carried out in UF urine samples collected from the same individuals. For the quantitative study, the same radioactively labelled COM and COD crystals were incubated with HK-2 cells for 50 min in separate CF and UF urines collected from eight healthy individuals at the native Ca2+ concentrations of the urines. Field emission electron microscopy and Fourier transform-infrared spectroscopy were used to confirm crystal morphology. Results Binding of both COM and COD crystals generally bound more strongly at 8 mm than at 2 mm Ca2+. The kinetic binding curves of COM were smooth, while those of COD were consistently biphasic, suggesting that the two crystal types induce different cellular metabolic responses: HK-2 cells crystals appear to possess a transitory mechanism for detaching COD, but not COM crystals. In UF urine, COM binding was significantly greater than that of COD at 2 mm Ca2+, but at 8 mm Ca2+ the binding of COD was greater at early and late time points. COD also bound significantly more strongly at early time points in CF urine at both 2 and 8 mm Ca2+. In both CF and UF urine, there was no difference between the binding affinity of urinary COM and COD crystals. Conclusion

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

    PubMed

    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.

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

    PubMed Central

    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

  6. Perdeuteration, crystallization, data collection and comparison of five neutron diffraction data sets of complexes of human galectin-3C

    PubMed Central

    Manzoni, Francesco; Saraboji, Kadhirvel; Sprenger, Janina; Kumar, Rohit; Noresson, Ann-Louise; Nilsson, Ulf J.; Leffler, Hakon; Fisher, S. Zoë; Schrader, Tobias E.; Ostermann, Andreas; Coates, Leighton; Blakeley, Matthew P.; Oksanen, Esko; Logan, Derek T.

    2016-01-01

    Galectin-3 is an important protein in molecular signalling events involving carbohydrate recognition, and an understanding of the hydrogen-bonding patterns in the carbohydrate-binding site of its C-terminal domain (galectin-3C) is important for the development of new potent inhibitors. The authors are studying these patterns using neutron crystallography. Here, the production of perdeuterated human galectin-3C and successive improvement in crystal size by the development of a crystal-growth protocol involving feeding of the crystallization drops are described. The larger crystals resulted in improved data quality and reduced data-collection times. Furthermore, protocols for complete removal of the lactose that is necessary for the production of large crystals of apo galectin-3C suitable for neutron diffraction are described. Five data sets have been collected at three different neutron sources from galectin-3C crystals of various volumes. It was possible to merge two of these to generate an almost complete neutron data set for the galectin-3C–lactose complex. These data sets provide insights into the crystal volumes and data-collection times necessary for the same system at sources with different technologies and data-collection strategies, and these insights are applicable to other systems. PMID:27841752

  7. Capillary stability of vapor-liquid-solid crystallization processes and their comparison to Czochralski and Stepanov growth methods

    NASA Astrophysics Data System (ADS)

    Nebol'sin, Valery A.; Suyatin, Dmitry B.; Dunaev, Alexander I.; Tatarenkov, Alexander F.

    2017-04-01

    Epitaxial semiconductor nanowires grown with vapor-liquid-solid crystallization processes are very attractive nanoscale objects for many different applications. Despite extensive studies of the growth mechanism, there is still a lack of understanding of the growth process; in particular, the stability of the vapor-liquid-solid crystallization process has not previously been studied. Here we examine the capillary stability of the vapor-liquid-solid growth of nanowires and filamentary crystals with different diameters and demonstrate that the growth is stable for small Bond numbers when the meniscus height is linearly dependent on catalyst diameter. The capillary stability of vapor-liquid-solid growth is also compared with capillary stability in the Stepanov and Czochralski crystal growth methods; it is shown that capillary stability is not possible in the Czochralski method, although it is possible in the Stepanov growth method when the ratio of crystal diameter to shaper diameter is >1/2. These findings are important for better understanding and improved control of the growth of nanowires and filamentary crystals and indicate, for example, that large diameter filamentary crystals can be grown via a vapor-liquid-solid mechanism if the influence of gravity forces on the liquid catalytic particle shape can be reduced.

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

    PubMed

    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.

  9. Comparison of the crystal structure and molecular models of N,N-diisobutyl-2-(octylphenylphosphinyl)acetamide (CMPO)

    SciTech Connect

    Rogers, R.D.; Rollins, A.N.; Gatrone, R.C.; Horwitz, E.P.

    1994-06-01

    The compound crystallizes in the space group P2{sub 1}/c with a=13. 446(6), b=22.280(7) {Angstrom}, b=92.07(4){degrees}, and D{sub calc}=1.05 g/cm{sup 3} for Z=8 (@20{degrees}C). Molecular mechanics, molecular dynamics, and MNDO calculations were also performed on CMPO utilizing the SYBYL{sup 2} suite of programs. Results from these calculations are compared to the crystal structure and to similar calculations performed on CMPO using ALCHEMY. The calculations agree fairly well with the crystal structure.

  10. Comparison of the crystal structure and molecular models of N,N-dissobutyl-2-(octylphenylphosphinyl)acetamide(CMPO).

    SciTech Connect

    Rogers, R. D.; Rollins, A. N.; Gatrone, R. C.; Horwitz, E. P.; Chemistry; Northern Illinois Univ.

    1995-01-01

    The crystal structure of N,N-diisobutyl-2-(octylphenylphosphinyl)acetamide, or CMPO was recently determined. The compound crystallizes in the space group P2{sub 1}/c with a=13.446(6),b=22.280(7),c=17.217(7) Angstroms, {beta}=92.07(4) degrees, and D{sub calc}=1.05 g/cm3 for Z=8 @20 C. Molecular mechanics, molecular dynamics, and MNDO calculations were also performed on CMPO utilizing the SYBYL suite of programs. The results from these calculations are compared to the crystal structure and to similar calculations performed on CMPO using ALCHEMY. In general, the results from the calculations agree fairly well with the parameters from the crystal structure.

  11. Comparison of the optical parameters of a CaF{sub 2} single crystal and optical ceramics

    SciTech Connect

    Palashov, O V; Khazanov, E A; Mukhin, I B; Mironov, I A; Smirnov, A N; Dukel'skii, K V; Fedorov, Pavel P; Osiko, Vyacheslav V; Basiev, Tasoltan T

    2007-01-31

    Single crystal and optical ceramic CaF{sub 2} samples are studied by the method of thermally induced depolarisation of laser radiation at 1076 nm. The absorption coefficients of the single crystal and ceramics are estimated as {alpha} < 4.5x10{sup -4} cm{sup -1} and {alpha} < 1.33x10{sup -3} cm{sup -1}, respectively. (letters)

  12. Comparison of BBL Crystal ANR ID Kit and API rapid ID 32 A for identification of anaerobic bacteria.

    PubMed

    Moll, W M; Ungerechts, J; Marklein, G; Schaal, K P

    1996-07-01

    BBL Crystal ANR ID Kit and the API System rapid ID 32 A are miniaturized identification systems for anaerobes using enzymatic tests. The incubation period of both systems is 4 hours. A comparative evaluation of the BBL Crystal Identification System Anaerobe ID Kit (Becton Dickinson Microbiology Systems, Cockeysville, USA) with anaerobes grown on Columbia and Schaedler agar plates (Becton Dickinson Microbiology Systems, Cockeysville, USA) and the API System rapid ID 32 A (BioMérieux SA, Lyon, France) with bacteria grown on Columbia agar (Becton Dickinson Microbiology Systems, Cockeysville, USA) which is recommended by the manufacturer as cultivation medium, was performed with 207 mostly fresh clinical anaerobe isolates, including 104 gram-negative bacilli, 12 gram-negative cocci, 15 gram-positive cocci, 14 gram-positive sporeforming bacilli and 62 representatives of gram-positive non-sporeforming bacilli. With supplemental testing the Crystal system with inocula from Columbia and Schaedler agar and API inoculates from Columbia agar identified to genus level 144 (69.6%), 152 (73.4%) and 109 (52.7%) isolates, respectively. Misidentification to genus level was found by Crystal from Columbia and Schaedler agar and by API from Columbia agar in 17 (8.2%), 15 (7.3%) and 12 (5.8%) isolates, respectively. 36 isolates were not determined to species level by classical anaerobic methods or the systems only identified to genus level. 26 anaerobes were not included in the database of the Crystal or API system. From the remaining 145 clinical isolates with supplemental testing, Crystal from Columbia and Schaedler agar plates correctly identified 91 (62.8%) and 102 (70.3%), respectively, and API, 69 (47.6%) isolates. For the correct identification to genus and species level of the 207 clinical isolates tested, the Crystal system from Columbia and Schaedler agar and API system from Columbia agar required supplemental testing, as specified by the manufacturer, for 39 (27.1%), 34 (22

  13. Comparison of OARE Accelerometer Data with Dopant Distribution in Se-Doped GaAs Crystals Grown During USML-1

    NASA Technical Reports Server (NTRS)

    Moskowitz, Milton E.; Bly, Jennifer M.; Matthiesen, David H.

    1997-01-01

    Experiments were conducted in the crystal growth furnace (CGF) during the first United States Microgravity Laboratory (USML-1), the STS-50 flight of the Space Shuttle Columbia, to determine the segregation behavior of selenium in bulk GaAs in a microgravity environment. After the flight, the selenium-doped GaAs crystals were sectioned, polished, and analyzed to determine the free carrier concentration as a function of position, One of the two crystals initially exhibited an axial concentration profile indicative of diffusion controlled growth, but this profile then changed to that predicted for a complete mixing type growth. An analytical model, proposed by Naumann [R.J. Naumann, J. Crystal Growth 142 (1994) 253], was utilized to predict the maximum allowable microgravity disturbances transverse to the growth direction during the two different translation rates used for each of the experiments. The predicted allowable acceleration levels were 4.86 microgram for the 2.5 micrometers/s furnace translation rate and 38.9 microgram for the 5.0 micrometers/s rate. These predicted values were compared to the Orbital Acceleration Research Experiment (OARE) accelerometer data recorded during the crystal growth periods for these experiments. Based on the analysis of the OARE acceleration data and utilizing the predictions from the analytical model, it is concluded that the change in segregation behavior was not caused by any acceleration events in the microgravity environment.

  14. An orthorhombic crystal form of cyclohexaicosaose, CA26.32.59 H(2)O: comparison with the triclinic form.

    PubMed

    Nimz, O; Gessler, K; Usón, I; Saenger, W

    2001-11-08

    Cycloamylose containing 26 glucose residues (cyclohexaicosaose, CA26) crystallized from water and 30% (v/v) polyethyleneglycol 400 in the orthorhombic space group P2(1)2(1)2(1) in the highly hydrated form CA26.32.59 H(2)O. X-ray analysis of the crystals at 0.85 A resolution shows that the macrocycle of CA26 is folded into two short left-handed V-amylose helices in antiparallel arrangement and related by a twofold rotational pseudosymmetry as reported recently for the (CA26)(2).76.75 H(2)O triclinic crystal form [Gessler, K. et al. Proc. Natl. Acad. Sci. USA 1999, 96, 4246-4251]. In the orthorhombic crystal form, CA26 molecules are packed in motifs reminiscent of V-amylose in hydrated and anhydrous forms. The intramolecular interface between the V-helices in CA26 is dictated by formation of an extended network of interhelical C-H...O hydrogen bonds; a comparable molecular arrangement is also evident for the intermolecular packing, suggesting that it is a characteristic feature of V-amylose interaction. The hydrophobic channels of CA26 are filled with disordered water molecules arranged in chains and held in position by multiple C-H...O hydrogen bonds. In the orthorhombic and triclinic crystal forms, the structures of CA26 molecules are equivalent but the positions of the individual water molecules are different, suggesting that the patterns of water chains are perturbed even by small structural changes associated with differences in packing arrangements in the two crystal lattices rather than with differences in the CA26 geometry.

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

    PubMed

    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.

  16. Comparison of helical scan and standard rotation methods in single-crystal X-ray data collection strategies.

    PubMed

    Polsinelli, Ivan; Savko, Martin; Rouanet-Mehouas, Cecile; Ciccone, Lidia; Nencetti, Susanna; Orlandini, Elisabetta; Stura, Enrico A; Shepard, William

    2017-01-01

    X-ray radiation in macromolecular crystallography can chemically alter the biological material and deteriorate the integrity of the crystal lattice with concomitant loss of resolution. Typical alterations include decarboxylation of glutamic and aspartic residues, breaking of disulfide bonds and the reduction of metal centres. Helical scans add a small translation to the crystal in the rotation method, so that for every image the crystal is shifted to expose a fresh part. On beamline PROXIMA 2A at Synchrotron SOLEIL, this procedure has been tested with various parameters in an attempt to understand how to mitigate the effects of radiation damage. Here, the strategies used and the crystallographic metrics for various scenarios are reported. Among these, the loss of bromine from bromophenyl moieties appears to be a useful monitor of radiation damage as the carbon-bromine bond is very sensitive to X-ray irradiation. Two cases are focused on where helical scans are shown to be superior in obtaining meaningful data compared with conventional methods. In one case the initial resolution of the crystal is extended over time, and in the second case the anomalous signal is preserved to provide greater effective multiplicity and easier phasing.

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

    NASA Astrophysics Data System (ADS)

    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.

  18. Comparison of dislocation density tensor fields derived from discrete dislocation dynamics and crystal plasticity simulations of torsion

    SciTech Connect

    Jones, Reese E.; Zimmerman, Jonathan A.; Po, Giacomo; Mandadapu, Kranthi

    2016-02-01

    Accurate simulation of the plastic deformation of ductile metals is important to the design of structures and components to performance and failure criteria. Many techniques exist that address the length scales relevant to deformation processes, including dislocation dynamics (DD), which models the interaction and evolution of discrete dislocation line segments, and crystal plasticity (CP), which incorporates the crystalline nature and restricted motion of dislocations into a higher scale continuous field framework. While these two methods are conceptually related, there have been only nominal efforts focused at the global material response that use DD-generated information to enhance the fidelity of CP models. To ascertain to what degree the predictions of CP are consistent with those of DD, we compare their global and microstructural response in a number of deformation modes. After using nominally homogeneous compression and shear deformation dislocation dynamics simulations to calibrate crystal plasticity ow rule parameters, we compare not only the system-level stress-strain response of prismatic wires in torsion but also the resulting geometrically necessary dislocation density fields. To establish a connection between explicit description of dislocations and the continuum assumed with crystal plasticity simulations we ascertain the minimum length-scale at which meaningful dislocation density fields appear. Furthermore, our results show that, for the case of torsion, that the two material models can produce comparable spatial dislocation density distributions.

  19. Comparison of dislocation density tensor fields derived from discrete dislocation dynamics and crystal plasticity simulations of torsion

    DOE PAGES

    Jones, Reese E.; Zimmerman, Jonathan A.; Po, Giacomo; ...

    2016-02-01

    Accurate simulation of the plastic deformation of ductile metals is important to the design of structures and components to performance and failure criteria. Many techniques exist that address the length scales relevant to deformation processes, including dislocation dynamics (DD), which models the interaction and evolution of discrete dislocation line segments, and crystal plasticity (CP), which incorporates the crystalline nature and restricted motion of dislocations into a higher scale continuous field framework. While these two methods are conceptually related, there have been only nominal efforts focused at the global material response that use DD-generated information to enhance the fidelity of CPmore » models. To ascertain to what degree the predictions of CP are consistent with those of DD, we compare their global and microstructural response in a number of deformation modes. After using nominally homogeneous compression and shear deformation dislocation dynamics simulations to calibrate crystal plasticity ow rule parameters, we compare not only the system-level stress-strain response of prismatic wires in torsion but also the resulting geometrically necessary dislocation density fields. To establish a connection between explicit description of dislocations and the continuum assumed with crystal plasticity simulations we ascertain the minimum length-scale at which meaningful dislocation density fields appear. Furthermore, our results show that, for the case of torsion, that the two material models can produce comparable spatial dislocation density distributions.« less

  20. Effects of Pre-Existing Ice Crystals on Cirrus Clouds and Comparison between Different Ice Nucleation Parameterizations with the Community Atmosphere Model (CAM5)

    SciTech Connect

    Shi, Xiangjun; Liu, Xiaohong; Zhang, Kai

    2015-01-01

    In order to improve the treatment of ice nucleation in a more realistic manner in the Community Atmospheric Model version 5.3 (CAM5.3), the effects of preexisting ice crystals on ice nucleation in cirrus clouds are considered. In addition, by considering the in-cloud variability in ice saturation ratio, homogeneous nucleation takes place spatially only in a portion of cirrus cloud rather than in the whole area of cirrus cloud. With these improvements, the two unphysical limiters used in the representation of ice nucleation are removed. Compared to observations, the ice number concentrations and the probability distributions of ice number concentration are both improved with the updated treatment. The preexisting ice crystals significantly reduce ice number concentrations in cirrus clouds, especially at mid- to high latitudes in the upper troposphere (by a factor of ~10). Furthermore, the contribution of heterogeneous ice nucleation to cirrus ice crystal number increases considerably.Besides the default ice nucleation parameterization of Liu and Penner (2005, hereafter LP) in CAM5.3, two other ice nucleation parameterizations of Barahona and Nenes (2009, hereafter BN) and Kärcher et al. (2006, hereafter KL) are implemented in CAM5.3 for the comparison. In-cloud ice crystal number concentration, percentage contribution from heterogeneous ice nucleation to total ice crystal number, and preexisting ice effects simulated by the three ice nucleation parameterizations have similar patterns in the simulations with present-day aerosol emissions. However, the change (present-day minus pre-industrial times) in global annual mean column ice number concentration from the KL parameterization (3.24×106 m-2) is obviously less than that from the LP (8.46×106 m-2) and BN (5.62×106 m-2) parameterizations. As a result, experiment using the KL parameterization predicts a much smaller anthropogenic aerosol longwave indirect forcing (0.24 W m-2) than that using the LP (0.46 W m-2

  1. Comparison of the crystal structures of the human manganese superoxide dismutase and the homologous Aspergillus fumigatus allergen at 2-A resolution.

    PubMed

    Flückiger, Sabine; Mittl, Peer R E; Scapozza, Leonardo; Fijten, Helmi; Folkers, Gerd; Grütter, Markus G; Blaser, Kurt; Crameri, Reto

    2002-02-01

    Manganese superoxide dismutase (MnSOD) of Aspergillus fumigatus, a fungus involved in many pulmonary complications, has been identified as IgE-binding protein. It has been shown also that MnSODs from other organisms, including human, are recognized by IgE Abs from individuals sensitized to A. fumigatus MnSOD. Comparison of the fungal and the human crystal structure should allow the identification of structural similarities responsible for IgE-mediated cross-reactivity. The three-dimensional structure of A. fumigatus MnSOD has been determined at 2-A resolution by x-ray diffraction analysis. Crystals belonged to space group P2(1)2(1)2(1) with unit cell dimensions of a = 65.88 A, b = 98.7 A, and c = 139.28 A. The structure was solved by molecular replacement using the structure of the human MnSOD as a search model. The final refined model included four chains of 199-200 amino acids, four manganese ions, and 745 water molecules, with a crystallographic R-factor of 19.4% and a free R-factor of 23.3%. Like MnSODs of other eukaryotic organisms, A. fumigatus MnSOD forms a homotetramer with the manganese ions coordinated by three histidines, one aspartic acid, and one water molecule. The fungal and the human MnSOD share high similarity on the level of both primary and tertiary structure. We identified conserved amino acids that are solvent exposed in the fungal and the human crystal structure and are therefore potentially involved in IgE-mediated cross-reactivity.

  2. Crystal structure of anhydrous tripotassium citrate from laboratory X-ray powder diffraction data and DFT comparison

    PubMed Central

    Rammohan, Alagappa; Kaduk, James A.

    2016-01-01

    The crystal structure of anhydrous tripotassium citrate, [K3(C6H5O7)]n, has been solved and refined using laboratory X-ray powder diffraction data, and optimized using density functional techniques. The three unique potassium cations are 6-, 8-, and 6-coordinate (all irregular). The [KOn] coordination polyhedra share edges and corners to form a three-dimensional framework, with channels running parallel to the c axis. The only hydrogen bond is an intra­molecular one involving the hy­droxy group and the central carboxyl­ate group, with graph-set motif S(5). PMID:27536403

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

    PubMed

    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.

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

    PubMed Central

    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

  5. Comparison of standard mercury thermometer and the liquid crystal device skin contact thermometer in febrile children at Eldoret District Hospital.

    PubMed

    Esamai, F

    1994-03-01

    The purpose of this study was to compare the temperature readings obtained from febrile children using the conventional glass mercury thermometer and the liquid crystal device skin contact thermometer. 56 children with fever were studied irrespective of the cause. In 30 children, the mercury thermometer recorded higher readings than the LCD skin contact thermometer by an average of 0.67 degree C while in 12 children the LCD thermometer recorded higher readings than the mercury thermometer by an average of 0.34 degree C. There was no temperature reading difference in 14 children between the two methods. It is concluded that LCD thermometer is a useful, cost effective, safe and durable alternative to mercury thermometers especially in developing countries.

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

    PubMed Central

    Kaduk, James A.

    2017-01-01

    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. PMID:28217327

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

    PubMed Central

    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

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

    PubMed Central

    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 carb­oxy­lic acid group forms helical chains of very strong hydrogen bonds (O⋯O ∼ 2.42 Å) along the b axis. The hy­droxy group participates in a chain of intra- and inter­molecular 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 inter­layer contacts are composed of the hydro­phobic methyl­ene groups. PMID:28083145

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

    PubMed

    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.

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

    PubMed

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Technical Reports Server (NTRS)

    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.

  13. Experience with exchange and archiving of raw data: comparison of data from two diffractometers and four software packages on a series of lysozyme crystals.

    PubMed

    Tanley, Simon W M; Schreurs, Antoine M M; Helliwell, John R; Kroon-Batenburg, Loes M J

    2013-02-01

    The International Union of Crystallography has for many years been advocating archiving of raw data to accompany structural papers. Recently, it initiated the formation of the Diffraction Data Deposition Working Group with the aim of developing standards for the representation of these data. A means of studying this issue is to submit exemplar publications with associated raw data and metadata. A recent study on the effects of dimethyl sulfoxide on the binding of cisplatin and carboplatin to histidine in 11 different lysozyme crystals from two diffractometers led to an investigation of the possible effects of the equipment and X-ray diffraction data processing software on the calculated occupancies and B factors of the bound Pt compounds. 35.3 Gb of data were transferred from Manchester to Utrecht to be processed with EVAL. A systematic comparison shows that the largest differences in the occupancies and B factors of the bound Pt compounds are due to the software, but the equipment also has a noticeable effect. A detailed description of and discussion on the availability of metadata is given. By making these raw diffraction data sets available via a local depository, it is possible for the diffraction community to make their own evaluation as they may wish.

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

    PubMed

    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.

  15. Comparison of CALIPSO-Like, LaRC, and MODIS Retrievals of Ice Cloud Properties over SIRTA in France and Florida during CRYSTAL-FACE

    NASA Technical Reports Server (NTRS)

    Chiriaco, M.; Chepfer, H.; Haeffelin, M.; Minnis, P.; Noel, V.; Platnick, S.; McGill, M.; Baumgardner, D.; Dubuisson, P.; Pelon, J.; Spangenberg, D.; Sun-Mack, S.; Wind, G.

    2007-01-01

    This study compares cirrus particle effective radius retrieved by a CALIPSO-like method with two similar methods using MODIS, MODI Airborne Simulator (MAS), and GOES imagery. The CALIPSO-like method uses lidar measurements coupled with the split-window technique that uses the infrared spectral information contained at the 8.65-micrometer, 11.15-micrometer and 12.05-micrometer bands to infer the microphysical properties of cirrus clouds. The two other methods, sing passive remote sensing at visible and infrared wavelengths, are the operational MODIS cloud products (referred to by its archival product identifier MOD06 for MODIS Terra) and MODIS retrievals performed by the CERES team at LaRC (Langley Research Center) in support of CERES algorithms; the two algorithms will be referred to as MOD06- and LaRC-method, respectively. The three techniques are compared at two different latitudes: (i) the mid-latitude ice clouds study uses 18 days of observations at the Palaiseau ground-based site in France (SIRTA: Site Instrumental de Recherche par Teledetection Atmospherique) including a ground-based 532 nm lidar and the Moderate Resolution Imaging Spectrometer (MODIS) overpasses on the Terra Platform, (ii) the tropical ice clouds study uses 14 different flight legs of observations collected in Florida, during the intensive field experiment CRYSTAL-FACE (Cirrus Regional Study of Tropical Anvils and cirrus Layers-Florida Area Cirrus Experiment), including the airborne Cloud Physics Lidar (CPL) and the MAS. The comparison of the three methods gives consistent results for the particle effective radius and the optical thickness, but discrepancies in cloud detection and altitudes. The study confirms the value of an active remote-sensing method (CALIPSO-like) for the study of sub-visible ice clouds, in both mid-latitudes and tropics. Nevertheless, this method is not reliable in optically very thick tropical ice clouds.

  16. Engineering crystals that facilitate the acyl-transfer reaction: insight from a comparison of the crystal structures of myo-inositol-1,3,5-orthoformate-derived benzoates and carbonates.

    PubMed

    Tamboli, Majid I; Krishanaswamy, Shobhana; Gonnade, Rajesh G; Shashidhar, Mysore S

    2016-11-01

    Minor variations in the molecular structure of constituent molecules of reactive crystals often yield crystals with significantly different properties due to altered modes of molecular association in the solid state. Hence, these studies could provide a better understanding of the complex chemical processes occurring in the crystalline state. However, reactions that proceed efficiently in molecular crystals are only a small fraction of the reactions that are known to proceed (with comparable efficiency) in the solution state. Hence, for consistent progress in this area of research, investigation of newer reactive molecular crystals which support different kinds of reactions and their related systems is essential. The crystal structures and acyl-transfer reactivity of a myo-inositol-1,3,5-orthoformate-derived dibenzoate and its carbonate (4-O-benzoyl-2-O-phenoxycarbonyl-myo-inositol 1,3,5-orthoformate, C21H18O9) and thiocarbonate (4-O-benzoyl-2-O-phenoxythiocarbonyl-myo-inositol 1,3,5-orthoformate, C21H18O8S) analogs are compared with the aim of understanding the relationship between crystal structure and acyl-transfer reactivity. Insertion of an O atom in the acyl (or thioacyl) group of an ester gives the corresponding carbonate (or thiocarbonate). This seemingly minor change in molecular structure results in a considerable change in the packing of the molecules in the crystals of myo-inositol-1,3,5-orthoformate-derived benzoates and the corresponding carbonates. These differences result in a lack of intermolecular acyl-transfer reactivity in crystals of myo-inositol-1,3,5-orthoformate-derived carbonates. Hence, this study illustrates the sensitivity of the relative orientation of molecules, their packing and ensuing changes in the reactivity of resulting crystals to minor changes in molecular structure.

  17. Crystal Meth

    MedlinePlus

    ... from Other Parents Stories of Hope Crystal meth Crystal meth Story of Hope by giovanni January 3, ... about my drug addiction having to deal with Crystal meth. I am now in recovery and fighting ...

  18. Crystal Meth

    MedlinePlus

    ... Navigation Home / Stories of Hope / Crystal meth Crystal meth Story Of Hope By giovanni January 3rd, 2013 ... my drug addiction having to deal with Crystal meth. I am now in recovery and fighting my ...

  19. Crystal Creations.

    ERIC Educational Resources Information Center

    Whipple, Nona; Whitmore, Sherry

    1989-01-01

    Presents a many-faceted learning approach to the study of crystals. Provides instructions for performing activities including crystal growth and patterns, creating miniature simulations of crystal-containing rock formations, charcoal and sponge gardens, and snowflakes. (RT)

  20. Ziegler-Natta and metallocene-catalyzed isotactic polypropylene: A comprehensive investigation and comparison using crystallization kinetics, fiber spinning and thermal spunbonding

    NASA Astrophysics Data System (ADS)

    Bond, Eric Bryan

    Isotactic polypropylene (iPP) can be synthesized using conventional heterogeneous Ziegler-Natta (zniPP) and homogenous metallocene catalysts (miPP). The purpose of this work was to investigate and compare and contrast miPP resins to zniPP resins. The resins in this study were thoroughly characterized by cNMR and solution fractionation to determine the number, type and distribution of defects. The resins were then studied under isothermal and nonisothermal quiescent crystallization conditions to determine the bulk and crystal growth kinetics, crystal structure, crystallinity and thermal properties. The cNMR and xylene fractionation studies indicated the miPP resins had substantially more total defects in the crystallizable material than either of the zniPP resins in this study. Combined results from DSC, SAXS and WAXD indicated the miPP and zniPP resins have similar alpha-monoclinic equilibrium melting temperatures (T m0), despite the differences in defect content, type and distribution. The presence of atactic material was found to lower the observed equilibrium melting temperature of a particular resin, whether miPP or zniPP. The isothermal crystallization studies showed the miPP resins readily produce the gamma-crystal structure. The zniPP resins also produced small amounts of the gamma-structure, at high crystallization temperatures. Defects were found to be excluded from the crystal under isothermal crystallization conditions. For crystallization under isothermal crystallization conditions, the observed linear growth rates were found to be dependent upon defect content. Under nonisothermal conditions, the growth rate was found to depend mostly on the molecular weight. Fiber spinning studies showed that the molecular weight and molecular weight distribution of an iPP resin is largely determined by the point of crystallization in the spinline, the crystallization temperature and as-spun filament properties. Increasing the molecular weight (also increasing the

  1. Comparison of crystallization kinetics in a-Si/Cu and a-Si/Al bilayer recording films under thermal annealing and pulsed laser irradiation

    NASA Astrophysics Data System (ADS)

    Her, Yung-Chiun; Chen, Chih-Wei; Wu, Chun-Lin

    2006-06-01

    Under thermal annealing, the crystallization temperatures of a-Si in a-Si/Cu and a-Si/Al bilayer recording films were significantly reduced to around 485 and 357 °C, respectively, and the activation energies for crystallization were reduced to about 3.3 eV. The formation of Cu3Si phase prior to crystallization of a-Si was found to occur at around 175 °C in a-Si/Cu, while no Al silicide was observed in a-Si/Al before crystallization of a-Si. The reaction exponents for a-Si/Cu and a-Si/Al were determined to be around 1.8 and 1.6, respectively, corresponding to a crystallization process in which grain growth occurs with nucleation, and the nucleation rate decreases with the progress of grain growth. Under pulsed laser irradiation, the precipitation of Cu3Si phases and crystallization of a-Si were observed in a-Si/Cu, while the crystallization and reamorphization of a-Si took place sequentially in a-Si/Al. The reaction exponents for a-Si/Cu and a-Si/Al, determined to be about 2.0 and 2.2, respectively, are slightly higher than those under thermal annealing, indicating that the crystallization processes of a-Si/Cu and a-Si/Al under pulsed laser irradiation are similar to those under thermal annealing. However, the decrease of nucleation rate with the progress of grain growth is slower. At the same time, the activation energies for crystallization of a-Si/Cu and a-Si/Al, estimated to be about 0.18 and 0.22 eV, respectively, are nearly an order of magnitude lower than those under thermal annealing. This may be explained by the explosive crystallization of a-Si by mechanical impact, with a high power pulsed laser.

  2. Geometrical parameterization of the crystal chemistry of P6(3)/m apatites: comparison with experimental data and ab initio results.

    PubMed

    Mercier, Patrick H J; Le Page, Yvon; Whitfield, Pamela S; Mitchell, Lyndon D; Davidson, Isobel J; White, T J

    2005-12-01

    Experimental structure refinements and ab initio simulation results for 18 published, fully ordered P6(3)/m (A;{\\rm I}_4)(A;{\\rm II}_6)(BO4)6X2 apatite end-member compositions have been analyzed in terms of a geometric crystal-chemical model that allows the prediction of unit-cell parameters (a and c) and all atom coordinates. To an accuracy of +/- 0.025 A, the magnitude of c was reproduced from crystal-chemical parameters characterizing chains of ...-A(II)-O3-B-O3-A(II)-... atoms, whereas that of a was determined from those describing (A(I)O6)-(BO4) polyhedral arrangements. The c/a ratio could be predicted to +/-0.2% using multi-variable functions based on geometric crystal-chemical model predictions, but could not be ascribed to the adjustment of a single crystal-chemical parameter. The correlations observed between algebraically independent crystal-chemical parameters representing the main observed polyhedral distortions reveal them as the minimum-energy solution to accommodate misfit components within this flexible structure type. For materials with given composition, good agreement (within +/- 0.5-2.0%) of ab initio crystal-chemical parameters was observed with only those from single-crystal refinements with R crystal work with R > 4.0% was not as good, while the scatter with those from Rietveld refinements was considerable. Accordingly, ab initio cell data, atomic coordinates and crystal-chemical parameters were reported here for the following compositions awaiting experimental work: (Zn,Hg)10(PO4)6(Cl,F)2, (Ca,Cd)10(VO4)6Cl2 and (Ca,Pb,Cd)10(CrO4)6Cl2.

  3. Protein Crystal Bovine Insulin

    NASA Technical Reports Server (NTRS)

    1991-01-01

    The comparison of protein crystal, Bovine Insulin space-grown (left) and earth-grown (right). Facilitates the incorporation of glucose into cells. In diabetics, there is either a decrease in or complete lack of insulin, thereby leading to several harmful complications. Principal Investigator is Larry DeLucas.

  4. Characterization and comparison of lidocaine-tetracaine and lidocaine-camphor eutectic mixtures based on their crystallization and hydrogen-bonding abilities.

    PubMed

    Gala, Urvi; Chuong, Monica C; Varanasi, Ravi; Chauhan, Harsh

    2015-06-01

    Eutectic mixtures formed between active pharmaceutical ingredients and/or excipients provide vast scope for pharmaceutical applications. This study aimed at the exploration of the crystallization abilities of two eutectic mixtures (EM) i.e., lidocaine-tetracaine and lidocaine-camphor (1:1 w/w). Thermogravimetric analysis (TGA) for degradation behavior whereas modulated temperature differential scanning calorimetry (MTDSC) set in first heating, cooling, and second heating cycles, was used to qualitatively analyze the complex exothermic and endothermic thermal transitions. Raman microspectroscopy characterized vibrational information specific to chemical bonds. Prepared EMs were left at room temperature for 24 h to visually examine their crystallization potentials. The degradation of lidocaine, tetracaine, camphor, lidocaine-tetracaine EM, and lidocaine-camphor EM began at 196.56, 163.82, 76.86, 146.01, and 42.72°C, respectively, which indicated that eutectic mixtures are less thermostable compared to their individual components. The MTDSC showed crystallization peaks for lidocaine, tetracaine, and camphor at 31.86, 29.36, and 174.02°C, respectively (n = 3). When studying the eutectic mixture, no crystallization peak was observed in the lidocaine-tetracaine EM, but a lidocaine-camphor EM crystallization peak was present at 18.81°C. Crystallization occurred in lidocaine-camphor EM after being kept at room temperature for 24 h, but not in lidocaine-tetracaine EM. Certain peak shifts were observed in Raman spectra which indicated possible interactions of eutectic mixture components, when a eutectic mixture was formed. We found that if the components forming a eutectic mixture have crystallization peaks close to each other and have sufficient hydrogen-bonding capability, then their eutectic mixture is least likely to crystallize out (as seen in lidocaine-tetracaine EM) or vice versa (lidocaine-camphor EM).

  5. Aluminum induced proteome changes in tomato cotyledons

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Cotyledons of tomato seedlings that germinated in a 20 µM AlK(SO4)2 solution remained chlorotic while those germinated in an aluminum free medium were normal (green) in color. Previously, we have reported the effect of aluminum toxicity on root proteome in tomato seedlings (Zhou et al. J Exp Bot, 20...

  6. 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

    NASA Astrophysics Data System (ADS)

    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.

  7. 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

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Astrophysics Data System (ADS)

    Wen, Xin; Han, Yashuai; Wang, Junmin

    2016-04-01

    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.

  9. Virtual Crystallizer

    SciTech Connect

    Land, T A; Dylla-Spears, R; Thorsness, C B

    2006-08-29

    Large dihydrogen phosphate (KDP) crystals are grown in large crystallizers to provide raw material for the manufacture of optical components for large laser systems. It is a challenge to grow crystal with sufficient mass and geometric properties to allow large optical plates to be cut from them. In addition, KDP has long been the canonical solution crystal for study of growth processes. To assist in the production of the crystals and the understanding of crystal growth phenomena, analysis of growth habits of large KDP crystals has been studied, small scale kinetic experiments have been performed, mass transfer rates in model systems have been measured, and computational-fluid-mechanics tools have been used to develop an engineering model of the crystal growth process. The model has been tested by looking at its ability to simulate the growth of nine KDP boules that all weighed more than 200 kg.

  10. Crystal growing

    NASA Technical Reports Server (NTRS)

    Neville, J. P.

    1990-01-01

    One objective is to demonstrate the way crystals grow and how they affect the behavior of material. Another objective is to compare the growth of crystals in metals and nonmetals. The procedures, which involve a supersaturated solution of a salt that will separate into crystals on cooling and the pouring off of an eutectic solution to expose the crystals formed by a solid solution when an alloy of two metals forms a solid and eutectic solution on cooling, are described.

  11. Determination of the Thickness of the Back Dead-Layer of GRETINA Crystals via Comparisons of Measured Photopeak Efficiencies with GEANT4 Simulations

    NASA Astrophysics Data System (ADS)

    Jarvis, L. R.; Stine, C. G.; Riley, L. A.

    2016-09-01

    Measurements of the photopeak efficiency of the GRETINA array up to 3.5 MeV made at the National Superconducting Cyclotron Laboratory with 152Eu and 56Co sources were compared with GEANT 4 simulations. We developed a method of determining the average thickness of the back dead layers of the GRETINA crystals by considering the partial photopeak efficiencies of events including gamma-ray interactions in the back slice of the crystals. The impact of dead-layer thicknesses on the accuracy of simulated photopeak efficiencies and the ratio of photopeak counts measured in the two GRETINA crystal types is discussed. This work was supported by the National Science Foundation under Grant Nos. PHY-1303480 and PHY-1102511 and by the US Department of Energy under Grant No. DE-AC02-05CH11231.

  12. Comparison of Sn-doped and nonstoichiometric vertical-Bridgman-grown crystals of the topological insulator Bi{sub 2}Te{sub 2}Se

    SciTech Connect

    Kushwaha, S. K. Gibson, Q. D.; Cava, R. J.; Xiong, J.; Ong, N. P.; Pletikosic, I.; Weber, A. P.; Fedorov, A. V.; Valla, T.

    2014-04-14

    A comparative study of the properties of topological insulator Bi{sub 2}Te{sub 2}Se (BTS) crystals grown by the vertical Bridgeman method is described. Two defect mechanisms that create acceptor impurities to compensate for the native n-type carriers are compared: Bi excess, and light Sn doping. Both methods yield low carrier concentrations and an n-p crossover over the length of the grown crystal boules, but lower carrier concentrations and higher resistivities are obtained for the Sn-doped crystals, which reach carrier concentrations as low as 8 × 10{sup 14} cm{sup −3}. Further, the temperature dependent resistivities for the Sn-doped crystals display strongly activated behavior at high temperatures, with a characteristic energy of half the bulk band gap. The (001) cleaved Sn-doped BTS crystals display high quality Shubnikov de Haas (SdH) quantum oscillations due to the topological surface state electrons. Angle resolved photoelectron spectroscopy (ARPES) characterization shows that the Fermi energy (E{sub F}) for the Sn-doped crystals falls cleanly in the surface states with no interference from the bulk bands, which the Dirac point for the surface states lies approximately 60 meV below the top of the bulk valence band maximum, and allows for a determination of the bulk and surface state carrier concentrations as a function of Energy near E{sub F}. Electronic structure calculations that compare Bi excess and Sn dopants in BTS demonstrate that Sn acts as a special impurity, with a localized impurity band that acts as a charge buffer occurring inside the bulk band gap. We propose that the special resonant level character of Sn in BTS gives rise to the exceptionally low carrier concentrations and activated resistivities observed.

  13. Apoferritin crystals

    NASA Technical Reports Server (NTRS)

    2001-01-01

    Dr. Alexander Chernov, of the Universities Space Research Association (USRA) and based at Marshall Space Flight Center, is investigating why protein crystals grown in space are, in about 20 percent of cases, better-ordered than those grown on the ground. They are testing the idea that the amount of impurities trapped by space-grown crystals may be different than the amount trapped by crystals grown on Earth because convection is negligible in microgravity. The concentrations or impurities in many space-grown crystals turned out to be several times lower than that in the terrestrial ones, sometimes below the detection limit. The ground-based experiment also showed that the amount of impurities per unit volume of the crystals was usually higher than the amount per unit volume of the solution. This means that a growing crystal actually purifies the solution in its immediate vicinity. Here, an impurity depletion zone is created around apoferritin crystals grown in gel, imitating microgravity conditions.

  14. Comparison of LuAP and LuYAP crystal properties from statistically significant batches produced with two different growth methods

    NASA Astrophysics Data System (ADS)

    Trummer, J.; Auffray, E.; Lecoq, P.; Petrosyan, A.; Sempere-Roldan, P.

    2005-10-01

    Measurements of the light yield, decay time and transmission were carried out on LuAP:Ce and mixed LuYAP:Ce crystals, which are new scintillation materials considered for Positron Emission Tomography (PET) and are used in the ClearPET™ [Auffray et al., Nucl. Sci. Methods A 527 (2004) 171 [15

  15. Lysozyme Crystal

    NASA Technical Reports Server (NTRS)

    2004-01-01

    To the crystallographer, this may not be a diamond but it is just as priceless. A Lysozyme crystal grown in orbit looks great under a microscope, but the real test is X-ray crystallography. The colors are caused by polarizing filters. Proteins can form crystals generated by rows and columns of molecules that form up like soldiers on a parade ground. Shining X-rays through a crystal will produce a pattern of dots that can be decoded to reveal the arrangement of the atoms in the molecules making up the crystal. Like the troops in formation, uniformity and order are everything in X-ray crystallography. X-rays have much shorter wavelengths than visible light, so the best looking crystals under the microscope won't necessarily pass muster under the X-rays. In order to have crystals to use for X-ray diffraction studies, crystals need to be fairly large and well ordered. Scientists also need lots of crystals since exposure to air, the process of X-raying them, and other factors destroy them. Growing protein crystals in space has yielded striking results. Lysozyme's structure is well known and it has become a standard in many crystallization studies on Earth and in space.

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

    ERIC Educational Resources Information Center

    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)

  17. RNA Crystallization

    NASA Technical Reports Server (NTRS)

    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.

  18. 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.

    PubMed

    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.

  19. Experimental and numerical analysis of penetration/removal response of endodontic instrument made of single crystal Cu-based SMA: comparison with NiTi SMA instruments

    NASA Astrophysics Data System (ADS)

    Vincent, M.; Xolin, P.; Gevrey, A.-M.; Thiebaud, F.; Engels-Deutsch, M.; Ben Zineb, T.

    2017-04-01

    This paper presents an experimental and numerical study showing that single crystal shape memory alloy (SMA) Cu-based endodontic instruments can lead to equivalent mechanical performances compared to NiTi-based instruments besides their interesting biological properties. Following a previous finite element analysis (FEA) of single crystal CuAlBe endodontic instruments (Vincent et al 2015 J. Mater. Eng. Perform. 24 4128–39), prototypes with the determined geometrical parameters were machined and experimentally characterized in continuous rotation during a penetration/removal (P/R) protocol in artificial canals. The obtained mechanical responses were compared to responses of NiTi endodontic files in the same conditions. In addition, FEA was conducted and compared with the experimental results to validate the adopted modeling and to evaluate the local quantities inside the instrument as the stress state and the distribution of volume fraction of martensite. The obtained results highlight that single crystal CuAlBe SMA prototypes show equivalent mechanical responses to its NiTi homologous prototypes in the same P/R experimental conditions.

  20. Crystal structure of carnidazole form II from synchrotron X-ray powder diffraction: structural comparison with form I, the hydrated form and the low energy conformations in vacuo.

    PubMed

    de Armas, Héctor Novoa; Peeters, Oswald M; Blaton, Norbert; Van den Mooter, Guy; De Ridder, Dirk J A; Schenk, Henk

    2006-10-01

    The crystal structure of carnidazole form II, O-methyl [2-(2-methyl-5-nitro-1H-imidazole-1-yl)ethyl]thiocarbamate, has been determined using synchrotron X-ray powder diffraction in combination with simulated annealing and whole profile pattern matching, and refined by the Rietveld method. For structure solution, 12 degrees of freedom were defined: one motion group and six torsions. Form II crystallizes in space group P2(1)/n, Z=4, with unit cell parameters after Rietveld refinement: a=13.915(4), b=8.095(2), c=10.649(3) A, beta=110.83(1) degrees, and V=1121.1(5) A3. The two polymorphic forms, as well as the hydrate, crystallize in the monoclinic space group P2(1)/n having four molecules in the cell. In form II, the molecules are held together by forming two infinite zig-zag chains via hydrogen bonds of the type N--H...N, the same pattern as in form I. A conformational study of carnidazole, at semiempirical PM3 level, was performed using stochastic approaches based on modification of the flexible torsion angles. The values of the torsion angles for the molecules of the two polymorphic forms and the hydrate of carnidazole are compared to those obtained from the conformational search. Form I and form II are enantiotropic polymorphic pairs this agrees with the fact that the two forms are conformational polymorphs.

  1. Protein Crystallization

    NASA Technical Reports Server (NTRS)

    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.

  2. Computational crystallization.

    PubMed

    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.

  3. Structure and dynamics of the antitumor drugs nogalamycin and disnogalamycin complexed to d(CGTACG)2: comparison of crystal and solution structures.

    PubMed

    Robinson, H; Yang, D; Wang, A H

    1994-11-04

    The nuclear magnetic resonance (NMR) solution structures of the 2:1 complexes of nogalamycin-d(CGTACG)2 (Ng-CGTACG) and disnogalamycin-d(CGTACG)2 (DNg-CGTACG) have been determined by a quantitative treatment of two-dimensional nuclear Overhauser effect (2D-NOE) crosspeak intensities. The 1.3 A resolution crystal structure of the 2:1 complex of Ng-CGTACG was used as a starting model for refinement using the procedure, SPEDREF [Robinson and Wang, Biochemistry 31 (1992) 3524-3533], which incorporates full matrix relaxation theory and simulated annealing minimization. The refined solution structures have R-factors of 16.1 and 19.6% between the observed and simulated NOEs for Ng-CGTACG and DNg-CGTACG, respectively. The refined NMR structures retain major features of the crystal structure in which the elongated aglycone chromophore is intercalated between the CpG steps with its nogalose and aminoglucose lying in the minor and major grooves, respectively. The root mean square deviation between the solution and crystal structure for the complexes is 1.01 A (Ng-CGTACG) and 1.20 A (DNg-CGTACG) for the drug, plus the three base pairs surrounding the drug, indicating a very similar local structure at the intercalation site. In the NMR structure, the two G:C Watson-Crick base pairs (C1:G12 and G2:C11) that wrap around the aglycone have large buckles, as do those seen in the crystal structure. There is a 22 degree bend at the T3-A4 step in the refined solution structure. This rearrangement of the solution conformation is likely due to the absence of crystal packing. Specific hydrogen bonds between the drug and G:C bases in both grooves of the helix are preserved in the solution structure. A separate study of the 2:1 complex at low pH showed that the terminal G-C base pairing is destabilized.

  4. Protein Crystal Recombinant Human Insulin

    NASA Technical Reports Server (NTRS)

    1994-01-01

    The comparison of protein crystal, Recombiant Human Insulin; space-grown (left) and earth-grown (right). On STS-60, Spacehab II indicated that space-grown crystals are larger and of greater optical clarity than their earth-grown counterparts. Recombiant Human Insulin facilitates the incorporation of glucose into cells. In diabetics, there is either a decrease in or complete lack of insulin, thereby leading to several harmful complications. Principal Investigator is Larry DeLucas.

  5. Analysis of incurred crystal violet in Atlantic salmon (Salmo salar L.): comparison between the analysis of crystal violet as an individual parent and leucocrystal violet and as total crystal violet after oxidation with 2,3-dichloro-5,6-dicyanobenzoquinone.

    PubMed

    Chan, D; Tarbin, J A; Stubbings, G; Kay, J; Sharman, M

    2012-01-01

    Due to on-going concern about the occurrence of triphenylmethane dye residues in fish destined for human consumption, a depletion study of crystal violet in salmon was carried out. Atlantic salmon less than 12 months old were exposed to crystal violet in fresh water at 15°C and subsequently sampled at 1, 7, 14, 28, 63 and 91 days after exposure. The salmon were then analysed by two analytical methods. In the first method, 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) was used to oxidise leucocrystal violet to its parent form. Total parent crystal violet was then analysed by LC-MS/MS. In the second method, crystal violet and leucocrystal violet were analysed individually by LC-MS/MS without oxidation. Both methods gave comparable results for total crystal violet concentrations, with a correlation of r(2)=0.69. Statistical treatment for 88 incurred salmon samples showed no significant difference between the two sets of results with t=1.68 and t(crit)=1.99. Up to 98% of crystal violet was metabolised to its leuco form in the salmon after 1 day of exposure and could be detected at significant concentrations (approximately 20 µg kg(-1)) 91 days after exposure. The depletion data also suggest that crystal violet has a half-life of approximately 15-16 days in salmon.

  6. Crystal Data

    National Institute of Standards and Technology Data Gateway

    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.

  7. 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.

    PubMed

    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.

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

    PubMed

    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.

  9. Radiometric ages of the Fire Clay tonstein [Pennsylvanian (Upper Carboniferous), Westphalian, Duckmantian]: A comparison of U-Pb zircon single-crystal ages and 40Ar/39Ar sanidine single-crystal plateau ages

    USGS Publications Warehouse

    Lyons, P.C.; Krogh, T.E.; Kwok, Y.Y.; Davis, D.W.; Outerbridge, W.F.; Evans, H.T.

    2006-01-01

    The Fire Clay tonstein [Pennsylvanian (Upper Carboniferous), Westphalian Series, Duckmantian Stage]-a kaolinized, volcanic-ash deposit occurring in Kentucky, West Virginia, Tennessee, and Virginia-is the most widespread bed in the Middle Pennsylvanian of the central Appalachian basin, USA. A concordant single-crystal U-Pb zircon datum for this tonstein gives a 206Pb/238U age of 314.6 ?? 0.9 Ma (2??). This age is in approximate agreement with a mean sanidine plateau age of 311.5 ?? 1.3 Ma (1??, n = 11) for the Fire Clay tonstein. The difference between the two ages may be due to bias between the 40K and 238U decay constants and other factors. The age of the Fire Clay tonstein has important implications for Duckmantian Stage (Westphalian Series) sedimentation rates, correlations with the Westphalian Series of Europe, Middle Pennsylvanian volcanic events, and the late Paleozoic time scale. ?? 2006 Elsevier B.V. All rights reserved.

  10. Homology among acid proteases: comparison of crystal structures at 3A resolution of acid proteases from Rhizopus chinensis and Endothia parasitica.

    PubMed Central

    Subramanian, E; Swan, I D; Liu, M; Davies, D R; Jenkins, J A; Tickle, I J; Blundell, T L

    1977-01-01

    The molecular structures of two fungal acid proteases at 3 A resolution have been compared, and found to have similar secondary and tertiary folding. These enzymes are bilobal and have a pronounced cleft between the two lobes. This cleft has been identified as the active site region from inhibitor binding studies. The results of the comparison are discussed in terms of homology among the acid proteases in general. Images PMID:322132

  11. [Diagnostic detection performance of a simulated nodule in chest computed tomography images and gray and color nuclear medicine images: comparison between a medical liquid crystal display monitor and an ordinary liquid crystal display monitor].

    PubMed

    Okumura, Eiichiro; Kamimae, Riyou; Miyashita, Kenta; Ueda, Rina; Kanmae, Yusuke; Kubo, Mikayo; Shirasaka, Natsumi; Takeda, Taiki; Hashimoto, Noriyuki

    2014-08-01

    The purpose of this study was to evaluate the detection performance of simulated nodules in chest computed tomography (CT) images and nuclear medicine images with an ordinary liquid crystal display (LCD) and a medical LCD (grayscale standard display function: GSDF) and gamma 2.2. We collected 72 chest CT image slices obtained from an LSCT phantom with simulated signals composed of various sizes and CT values and 78 slices of monochrome and color nuclear medicine images obtained from a digital phantom with a simulated signal composed of various sizes and radiation levels. Six observers performed receiver operating characteristic (ROC) analysis using a continuous scale. The area under the ROC curve (AUC) was calculated for each monitor. The average AUC values for detection of chest CT images on a medical LCD (GSDF), medical LCD (gamma 2.2), and ordinary LCD were 0.71, 0.67, and 0.73, respectively. The average AUC values for detection of monochrome nuclear medicine images using a medical LCD (GSDF), medical LCD (gamma 2.2), and ordinary LCD were 0.81, 0.75, and 0.72, respectively. The average AUC values for detection of color nuclear medicine images on a medical LCD (GSDF), medical LCD (gamma 2.2), and ordinary LCD were 0.88, 0.86, and 0.90, respectively. Observer performance for detection of simulated nodules in chest CT images and nuclear medicine images was not significantly different between the three LCD monitors. We therefore conclude that an ordinary LCD monitor can be used to detect simulated nodules in chest CT images and nuclear medicine images.

  12. Comparison of precursor infiltration into polymer thin films via atomic layer deposition and sequential vapor infiltration using in-situ quartz crystal microgravimetry

    SciTech Connect

    Padbury, Richard P.; Jur, Jesse S.

    2014-07-01

    Previous research exploring inorganic materials nucleation behavior on polymers via atomic layer deposition indicates the formation of hybrid organic–inorganic materials that form within the subsurface of the polymer. This has inspired adaptations to the process, such as sequential vapor infiltration, which enhances the diffusion of organometallic precursors into the subsurface of the polymer to promote the formation of a hybrid organic–inorganic coating. This work highlights the fundamental difference in mass uptake behavior between atomic layer deposition and sequential vapor infiltration using in-situ methods. In particular, in-situ quartz crystal microgravimetry is used to compare the mass uptake behavior of trimethyl aluminum in poly(butylene terephthalate) and polyamide-6 polymer thin films. The importance of trimethyl aluminum diffusion into the polymer subsurface and the subsequent chemical reactions with polymer functional groups are discussed.

  13. A Comparison of DEF X-Ray Film and a Photodiode Array (Reticon) as Detectors for an X-Ray Crystal Spectrometer.

    PubMed

    Goodman, D A; Eason, R W; Shiwai, B; Allinson, N; Magorrian, B; Grande, M; Ridgley, A

    1989-01-01

    A crystal spectrometer with a photodiode array (PDA) detector was tested for a range of x-ray energies between 1 and 2 keV. A laser-produced plasma has been used as an x-ray source and was generated by the high-power (Vulcan) glass laser system at the SERC Rutherford Appleton Laboratory, UK. The performance of the array was directly compared with the response of Kodak DEF x-ray film. In order to compare quantitatively the performances of the PDA and the film, detective quantum efficiency (DQE) considerations are presented for both devices. It is demonstrated that the PDA has a useful dynamic range which is approximately seven times greater than that of film, a peak DQE of approximately six times that of film, and a greatly superior low-signal performance. The operational characteristics of the PDA are discussed.

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

    NASA Astrophysics Data System (ADS)

    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.

  15. Liquid crystal television spatial light modulators

    NASA Technical Reports Server (NTRS)

    Liu, Hua-Kuang; Chao, Tien-Hsin

    1989-01-01

    The spatial light modulation characteristics and capabilities of the liquid crystal television (LCTV) spatial light modulators (SLMs) are discussed. A comparison of Radio Shack, Epson, and Citizen LCTV SLMs is made.

  16. Crystal clear

    NASA Astrophysics Data System (ADS)

    2012-02-01

    A semiconductor is usually opaque to any light whose photon energy is larger than the semiconductor bandgap. Nature Photonics spoke to Stephen Durbin about how to render GaAs semiconductor crystals transparent using intense X-ray pulses.

  17. Comparison of the use of liquid crystal thermometers with glass mercury thermometers in febrile children in a children's ward at Port Moresby General Hospital, Papua New Guinea.

    PubMed

    Mauta, L; Vince, J; Ripa, P

    2009-12-01

    We compared the temperatures recorded, in febrile children admitted to a children's ward at Port Moresby General Hospital, by a doctor and by a group of nurses using glass mercury thermometers (GMT) and liquid crystal thermometers (LCT, Nextemp and Traxit. The mean difference (with 95% confidence intervals) in temperatures between GMT and Nextemp were -0.12 degrees C (-0.16 degrees C to -0.08 degrees C) for the doctor and 0.12 degrees C (0.04-0.20 degrees C) for nurses. The mean difference in temperatures between GMT and Traxit were -0.05 degrees C (-0.09 degrees C to -0.01 degrees C) for the doctor and 0.19 degrees C (0.10-0.28 degrees C) for the nurses. A similar result was obtained when one of the Nextemp thermometers used in the initial study was compared with GMT on a small sample of patients by the doctor 8 months later. Limited evaluation showed nursing staff were in favour of using the LCTs. Nextemp and Traxit thermometers can be used interchangeably with GMT in this setting.

  18. Utilisation of Quartz Crystal Microbalance Sensors with Dissipation (QCM-D) for a Clauss Fibrinogen Assay in Comparison with Common Coagulation Reference Methods.

    PubMed

    Oberfrank, Stephanie; Drechsel, Hartmut; Sinn, Stefan; Northoff, Hinnak; Gehring, Frank K

    2016-02-24

    The determination of fibrinogen levels is one of the most important coagulation measurements in medicine. It plays a crucial part in diagnostic and therapeutic decisions, often associated with time-critical conditions. The commonly used measurement is the Clauss fibrinogen assay (CFA) where plasma is activated by thrombin reagent and which is conducted by mechanical/turbidimetric devices. As quartz crystal microbalance sensors with dissipation (QCM-D) based devices have a small footprint, can be operated easily and allow measurements independently from sample transportation time, laboratory location, availability and opening hours, they offer a great opportunity to complement laboratory CFA measurements. Therefore, the objective of the work was to (1) transfer the CFA to the QCM-D method; (2) develop an easy, time- and cost-effective procedure and (3) compare the results with references. Different sensor coatings (donor's own plasma; gold surface) and different QCM-D parameters (frequency signal shift; its calculated turning point; dissipation signal shift) were sampled. The results demonstrate the suitability for a QCM-D-based CFA in physiological fibrinogen ranges. Results were obtained in less than 1 min and in very good agreement with a standardized reference (Merlin coagulometer). The results provide a good basis for further investigation and pave the way to a possible application of QCM-D in clinical and non-clinical routine in the medical field.

  19. Optimal design for studying mucoadhesive polymers interaction with gastric mucin using a quartz crystal microbalance with dissipation (QCM-D): Comparison of two different mucin origins.

    PubMed

    Oh, Sejin; Wilcox, Matthew; Pearson, Jeffrey P; Borrós, Salvador

    2015-10-01

    The objective of this present study was to develop an efficient and simple method, based on the use of a quartz crystal microbalance with dissipation (QCM-D), to evaluate the mucoadhesive characteristics of cationic polymers; chitosan, thiolated chitosan (chitosan-SH), and polyallylamine hydrochloride (PAH), and anionic polymers; hyaluronic acid (HA) and thiolated hyaluronic acid (HA-SH). The experiments were carried out at pH 4 to assess the interaction between mucoadhesive polymers and a mucin-coated gold surface. A key point in the QCM-D protocol development was to evaluate two sources of mucin: native porcine gastric mucin (NPGM) and commercially available porcine gastric mucin (CPGM). QCM-D has shown its potential as a highly sensitive technique that provides information about the interaction of mucoadhesive polymers with gastric mucin. The technique would allow the classification of these polymers in order to further assess their application as base materials for nanocarriers, designed to interact with the mucosal barrier which represents a stumbling block for drug adsorption.

  20. Protein crystal growth in low gravity

    NASA Technical Reports Server (NTRS)

    Feigelson, Robert S.

    1990-01-01

    The effect of low gravity on the growth of protein crystals and those parameters which will affect growth and crystal quality was studied. The proper design of the flight hardware and experimental protocols are highly dependent on understanding the factors which influence the nucleation and growth of crystals of biological macromolecules. Thus, those factors are investigated and the body of knowledge which has been built up for small molecule crystallization. These data also provide a basis of comparison for the results obtained from low-g experiments. The flows around growing crystals are detailed. The preliminary study of the growth of isocitrate lyase, the crystal morphologies found and the preliminary x ray results are discussed. The design of two apparatus for protein crystal growth by temperature control are presented along with preliminary results.

  1. Liquid Crystals

    NASA Technical Reports Server (NTRS)

    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.

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

    NASA Technical Reports Server (NTRS)

    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.

  3. SYMMETRICAL LASER CRYSTALS.

    DTIC Science & Technology

    CRYSTAL GROWTH , SYMMETRY(CRYSTALLOGRAPHY), LASERS, SYNTHESIS, FERROELECTRIC CRYSTALS , FLUORESCENCE, IMPURITIES, BARIUM COMPOUNDS, ZIRCONATES...STRONTIUM COMPOUNDS, TITANATES, STANNATES, SAMARIUM, MANGANESE, REFRACTORY MATERIALS, OXIDES, SINGLE CRYSTALS .

  4. Therapeutic Crystals

    ERIC Educational Resources Information Center

    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…

  5. Comparing Crystals

    ERIC Educational Resources Information Center

    Sharp, Janet; Hoiberg, Karen; Chumbley, Scott

    2003-01-01

    This standard lesson on identifying salt and sugar crystals expands into an opportunity for students to develop their observation, questioning, and modeling skills. Although sugar and salt may look similar, students discovered that they looked very different under a magnifying glass and behaved differently when dissolved in water. In addition,…

  6. Optical Crystals

    ERIC Educational Resources Information Center

    Bergsten, Ronald

    1974-01-01

    Discusses the production and structure of a sequence of optical crystals which can serve as one-, two-, and three-dimensional diffraction plates to illustrate diffraction patterns by using light rather than x-rays or particles. Applications to qualitative presentations of Laue theory at the secondary and college levels are recommended. (CC)

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

    PubMed

    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.

  8. Hydrothermal crystal growth of the potassium niobate and potassium tantalate family of crystals

    SciTech Connect

    Mann, Matthew; Jackson, Summer; Kolis, Joseph

    2010-11-15

    Single crystals of KNbO{sub 3} (KN), KTaO{sub 3} (KT), and KTa{sub 1-x}Nb{sub x}O{sub 3} (x=0.44, KTN) have been prepared by hydrothermal synthesis in highly concentrated KOH mineralizer solutions. The traditional problems of inhomogeneity, non-stoichiometry, crystal striations and crystal cracking resulting from phase transitions associated with this family compounds are minimized by the hydrothermal crystal growth technique. Crystals of good optical quality with only minor amounts of metal ion reduction can be grown this way. Reactions were also designed to provide homogeneous distribution of tantalum and niobium metal centers throughout the KTN crystal lattice to maximize its electro-optic properties. Synthesis was performed at relatively low (500-660 {sup o}C) temperatures in comparison to the flux and Czochralski techniques. This work represents the largest crystals of this family of compounds grown by hydrothermal methods to date. -- Graphical Abstract:

  9. Protein crystal growth - Growth kinetics for tetragonal lysozyme crystals

    NASA Technical Reports Server (NTRS)

    Pusey, M. L.; Snyder, R. S.; Naumann, R.

    1986-01-01

    Results are reported from theoretical and experimental studies of the growth rate of lysozyme as a function of diffusion in earth-gravity conditions. The investigations were carried out to form a comparison database for future studies of protein crystal growth in the microgravity environment of space. A diffusion-convection model is presented for predicting crystal growth rates in the presence of solutal concentration gradients. Techniques used to grow and monitor the growth of hen egg white lysozyme are detailed. The model calculations and experiment data are employed to discuss the effects of transport and interfacial kinetics in the growth of the crystals, which gradually diminished the free energy in the growth solution. Density gradient-driven convection, caused by presence of the gravity field, was a limiting factor in the growth rate.

  10. Na-doped optical Germanium bulk crystals

    NASA Astrophysics Data System (ADS)

    Pekar, G. S.; Singaevsky, A. F.

    2012-09-01

    In an effort to develop a material for infrared (IR) optics with improved parameters, bulk crystals of optical germanium doped with Na have been first grown and studied. Single-crystalline and coarse-crystalline Ge:Na boules of different shapes and dimensions, up to 10 kg by weight, have been grown. Sodium was incorporated into the Ge crystal during the crystal growing from the melt. Despite the fact that Na contamination in the source material was not strictly controlled, the density of Na in the grown crystals determined by the neutron activation analysis as well as by the glow discharge mass spectrometry did not exceed 1015 cm-3. Just this value may be supposed to be close to the solubility limit of Na incorporated in Ge in the course of bulk crystal growth. A first demonstration of donor behavior of Na in bulk Ge crystals is made by means of a thermoelectric type of testing. An interstitial location of Na impurity has been verified by experiments on donor drift in the dc electric field. The crystals are grown with free electron density in the range from 5ṡ1013 to 4ṡ1014 cm-3 which is optimal for using Ge crystals as an optical material for fabricating passive elements of the IR technique. A comparison between the properties of Ge:Na crystals and Ge crystals doped with Sb, a conventional impurity in optical germanium, grown under the same technological conditions and from the same intrinsic Ge as a source material, revealed a number of advantages of Ge:Na crystals; among them, the higher transparency in the IR region, smaller radiation scattering and higher regular optical transmission, lower dislocation density, more uniform distribution of electrical and optical characteristics over the crystal volume, the identity of optical parameters in the single-crystalline, and coarse-crystalline boules. No degradation of optical elements fabricated from Ge:Na crystals was detected in the course of their commercial application, starting from 1998.

  11. Biological Macromolecule Crystallization Database

    National Institute of Standards and Technology Data Gateway

    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.

  12. F 3 - molecular ions in fluoride crystals

    NASA Astrophysics Data System (ADS)

    Radzhabov, E. A.

    2016-02-01

    The UV absorption spectra of F 3 - molecular ions in LaF3, SrF2, CaF2, and BaF2 crystals doped with rare-earth elements are studied. Comparison of radiation-colored and additively colored crystals reveals the absorption bands of F 3 - hole centers in the region near 6 eV. Nonempirical calculations of optical transitions agree well with experimental results.

  13. Nonlinear effects in photorefractive crystals

    NASA Astrophysics Data System (ADS)

    Erbschloe, Donald R.

    Photorefractive crystals are materials whose index of refraction is altered under illumination by light. These crystals are both photoconductive and electrooptic. When a nonuniform light intensity pattern is present in the material, photocarriers are generated and redistributed, creating space charge electric fields which change the refractive index locally. These crystals are ideal media for real time holography, and applications include wave amplification, image processing, phase conjugation, and laser beam steering for optical interconnects. This thesis investigates many novel aspects of the photorefractive effect. A study of nonreciprocal behavior identifies a new important consideration in the theory of two-wave mixing between counterpropagating beams-namely the presence of a photocurrent, or frequency detuning between the beams results in a spatially varying beam coupling. A numerical treatment of these important cases provides the first systematic theoretical assessment the control of nonreciprocal transmission and phase shift in lithium niobate, a representative photorefractive crystal. A comparison between crystal types suggests candidates for nonreciprocal applications such as an optical diode.

  14. Crystallization process

    DOEpatents

    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.

  15. Liquid Crystal Devices.

    ERIC Educational Resources Information Center

    Bradshaw, Madeline J.

    1983-01-01

    The nature of liquid crystals and several important liquid crystal devices are described. Ideas for practical experiments to illustrate the properties of liquid crystals and their operation in devices are also described. (Author/JN)

  16. Liquid Crystal Inquiries.

    ERIC Educational Resources Information Center

    Marroum, Renata-Maria

    1996-01-01

    Discusses the properties and classification of liquid crystals. Presents a simple experiment that illustrates the structure of liquid crystals and the differences between the various phases liquid crystals can assume. (JRH)

  17. Nonlinear Effects in Photorefractive Crystals.

    NASA Astrophysics Data System (ADS)

    Erbschloe, Donald Ross

    1988-12-01

    Available from UMI in association with The British Library. Requires signed TDF. Photorefractive crystals are materials whose index of refraction is altered under illumination by light. These crystals are both photoconductive and electrooptic. When a nonuniform light intensity pattern is present in the material, photocarriers are generated and redistributed, creating space charge electrical fields which change the refractive index locally. These crystals are ideal media for real-time holography, and applications include wave amplification, image processing, phase conjugation, and laser beam steering for optical interconnects. This thesis investigates many novel aspects of the photorefractive effect. A study of nonreciprocal behaviour identifies a new important consideration in the theory of two-wave mixing between counterpropagating beams--namely the presence of a photocurrent, or frequency detuning between the beams results in a spatially varying beam coupling. A numerical treatment of these important cases provides the first systematic theoretical assessment of the control of nonreciprocal transmission and phase shift in lithium niobate, a representative protorefractive crystal. A comparison between crystal types suggests candidates for nonreciprocal applications such as an optical diode. A study of bismuth silicon oxide, Bi_ {12}SiO_{20} , as the active gain medium in an oscillator reveals a novel feature, the presence of a light intensity threshold. For one crystal sample no oscillation occurred for incident intensities less than 0.8 mW/cm^2. A surprising new result is the appearance of higher diffracted orders in a crystal sample with a small wedge angle (0.036 ^circ) due to wave mixing between an incident beam and its first codirectional multiple reflection. Several applications for this new means of obtaining beam interaction are discussed--including the study of the photorefractive coupling for very large grating spacings, the investigation of transient

  18. PARAMAGNETIC RELAXATION IN CRYSTALS.

    DTIC Science & Technology

    CRYSTALS, PARAMAGNETIC RESONANCE, RELAXATION TIME , CRYSTAL DEFECTS, QUARTZ, GLASS, STRAIN(MECHANICS), TEMPERATURE, NUCLEAR SPINS, HYDROGEN, CALCIUM COMPOUNDS, FLUORIDES, COLOR CENTERS, PHONONS, OXYGEN.

  19. 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

    PubMed Central

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

    2010-01-01

    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

  20. 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.

    PubMed

    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

  1. Using Inorganic Crystals To Grow Protein Crystals

    NASA Technical Reports Server (NTRS)

    Shlichta, Paul J.; Mcpherson, Alexander A.

    1989-01-01

    Solid materials serve as nucleating agents. Protein crystals induced by heterogeneous nucleation and in some cases by epitaxy to grow at lower supersaturations than needed for spontaneous nucleation. Heterogeneous nucleation makes possible to grow large, defect-free single crystals of protein more readily. Such protein crystals benefits research in biochemistry and pharmacology.

  2. Laser-induced crystallization and crystal growth.

    PubMed

    Sugiyama, Teruki; Masuhara, Hiroshi

    2011-11-04

    Recent streams of laser studies on crystallization and crystal growth are summarized and reviewed. Femtosecond multiphoton excitation of solutions leads to their ablation at the focal point, inducing local bubble formation, shockwave propagation, and convection flow. This phenomenon, called "laser micro tsunami" makes it possible to trigger crystallization of molecules and proteins from their supersaturated solutions. Femtosecond laser ablation of a urea crystal in solution triggers the additional growth of a single daughter crystal. Intense continuous wave (CW) near infrared laser irradiation at the air/solution interface of heavy-water amino acid solutions results in trapping of the clusters and evolves to crystallization. A single crystal is always prepared in a spatially and temporally controlled manner, and the crystal polymorph of glycine depends on laser power, polarization, and solution concentration. Upon irradiation at the glass/solution interface, a millimeter-sized droplet is formed, and a single crystal is formed by shifting the irradiation position to the surface. Directional and selective crystal growth is also possible with laser trapping. Finally, characteristics of laser-induced crystallization and crystal growth are summarized.

  3. Molecular tectonics: from crystals to crystals of crystals.

    PubMed

    Marinescu, Gabriela; Ferlay, Sylvie; Kyritsakas, Nathalie; Hosseini, Mir Wais

    2013-12-11

    The in situ combination of M(II) cations (Co, Ni, Cu or Zn) with 2,4,6-pyridinetricarboxylic acid as a ligand, a bisamidinium dication as a H-bond donor tecton and NaOH leads to the formation of anionic metal complexes ML2(2-) and their interconnection into isomorphous 3D H-bonded networks displaying different colours which were used as preformed seed crystals for the formation of crystals of crystals by 3D epitaxial growth.

  4. Comparison of crystal growth and thermoelectric properties of n-type Bi-Se-Te and p-type Bi-Sb-Te nanocrystalline thin films: Effects of homogeneous irradiation with an electron beam

    SciTech Connect

    Takashiri, Masayuki Imai, Kazuo; Uyama, Masato; Nishi, Yoshitake; Hagino, Harutoshi; Miyazaki, Koji; Tanaka, Saburo

    2014-06-07

    The effects of homogenous electron beam (EB) irradiation on the crystal growth and thermoelectric properties of n-type Bi-Se-Te and p-type Bi-Sb-Te thin films were investigated. Both types of thin films were prepared by flash evaporation, after which homogeneous EB irradiation was performed at an acceleration voltage of 0.17 MeV. For the n-type thin films, nanodots with a diameter of less than 10 nm were observed on the surface of rice-like nanostructures, and crystallization and crystal orientation were improved by EB irradiation. The resulting enhancement of mobility led to increased electrical conductivity and thermoelectric power factor for the n-type thin films. In contrast, the crystallization and crystal orientation of the p-type thin films were not influenced by EB irradiation. The carrier concentration increased and mobility decreased with increased EB irradiation dose, possibly because of the generation of defects. As a result, the thermoelectric power factor of p-type thin films was not improved by EB irradiation. The different crystallization behavior of the n-type and p-type thin films is attributed to atomic rearrangement during EB irradiation. Selenium in the n-type thin films is more likely to undergo atomic rearrangement than the other atoms present, so only the crystallinity of the n-type Bi-Se-Te thin films was enhanced.

  5. Ultrasonic attenuation in molecular crystals

    NASA Astrophysics Data System (ADS)

    Perrin, Bernard

    1981-11-01

    It is now well established from an experimental point of view that, concerning the ultrasonic attenuation, molecular crystals exhibit a specific behavior among dielectric crystals. This fact suggests the presence of a relaxation process. Liebermann, who has introduced this field, has proposed a way to analyze this problem and in particular has given an expression for the ultrasonic absorption coefficient in terms of a relaxation time and some thermodynamic quantities. In contrast to Liebermann's approach, a solid-state viewpoint is presented here, and it is shown that this ultrasonic relaxation can be taken into account in the framework of Akhieser's theory. A general expression of the ultrasonic absorption coefficient is calculated in terms of the phonon collision operator using the Boltzmann-equation approach of Woodruff and Ehrenreich. The collision-time approximation widely used in dielectric crystals fails in molecular crystals for which the presence of slow relaxation times in the collision operator prevents the thermalization of the whole set of phonons and gives rise to an ultrasonic relaxation. Thus a more suitable approximation is suggested here, which leads to a new expression of the ultrasonic attenuation valid in molecular crystals. Different forms of this expression are discussed, and comparison with Liebermann's expression used in most of the previous papers shows that the present treatment takes better account of the anisotropy of the solid state. The fit of experimental results obtained for some ionic-molecular crystals also shows that the expression derived here gives better agreement than does Liebermann's. Finally, it is shown that in the framework of the present treatment and under rather general conditions, the anisotropy affects primarily the magnitude of the ultrasonic absorption due to the molecular relaxation, but it does not affect its frequency dependence.

  6. Crystallization and nucleation kinetics in volcanic systems

    NASA Astrophysics Data System (ADS)

    Agostini, C.; Fortunati, A.; Carroll, M. R.; Scaillet, B.; Landi, P.

    2011-12-01

    The main objective of this experimental study is to constrain and quantitatively model the complex solidification process that transforms a magma in a solid material. Of major interest are crystal nucleation and growth driven by isothermal decompression of hydrous magmas, and comparison with results from more abundant crystal growth/nucleation data obtained in isobaric cooling experiments. This research concerns two different volcanic systems, Pantelleria (peralkaline rhyolite) and Stromboli (basalt), to better understand how crystallization kinetics can affect different magma compositions. For Stromboli volcanic system TZM apparatus has been used to perform decompression runs at Bayerisches Geoinstitut in Bayreuth (DE). As for Pantelleria composition, cooling experiments has been done using IHPV devices at ISTO of Orléans (FR), on the basis of previous phase equilibrium work (Di Carlo et al., 2010). First obtained results for Stromboli case show high rates of nucleation and crystal growth during the initial stages of crystallization which were followed by crystal growth at approximately constant number densities as equilibrium was approached. Shapes of crystals growing in melts are controlled by the kinetics of crystallization and may provide information about the degree of undercooling experienced by batches of magma en route to the surface (Lofgren, 1980). The study of crystallization kinetics through phases growth rates (Couch et al., 2003), together with the calculation of nucleation density and nucleation rates (Hammer et al., 1999) represent a step toward the estimation of the time scales of magmatic processes in volcanic systems and the interpretation of shallow magmatic processes. The results for Stromboli suggest average crystal growth timescales on the order of weeks, but this is complicated by clear evidence that some crystals have experienced repeated periods of both dissolution and growth (Landi et al., 2004).

  7. Drilling technique for crystals

    NASA Technical Reports Server (NTRS)

    Hunter, T.; Miyagawa, I.

    1977-01-01

    Hole-drilling technique uses special crystal driller in which drill bit rotates at fixed position at speed of 30 rpm while crystal slowly advances toward drill. Technique has been successfully applied to crystal of Rochell salt, Triglycine sulfate, and N-acetyglycine. Technique limits heat buildup and reduces strain on crystal.

  8. Mixed crystal organic scintillators

    DOEpatents

    Zaitseva, Natalia P; Carman, M Leslie; Glenn, Andrew M; Hamel, Sebastien; Hatarik, Robert; Payne, Stephen A; Stoeffl, Wolfgang

    2014-09-16

    A mixed organic crystal according to one embodiment includes a single mixed crystal having two compounds with different bandgap energies, the organic crystal having a physical property of exhibiting a signal response signature for neutrons from a radioactive source, wherein the signal response signature does not include a significantly-delayed luminescence characteristic of neutrons interacting with the organic crystal relative to a luminescence characteristic of gamma rays interacting with the organic crystal. According to one embodiment, an organic crystal includes bibenzyl and stilbene or a stilbene derivative, the organic crystal having a physical property of exhibiting a signal response signature for neutrons from a radioactive source.

  9. Pressure cryocooling protein crystals

    DOEpatents

    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.

  10. Dielectric, magnetic, and lattice dynamics properties of Y-type hexaferrite Ba0.5Sr1.5Zn2Fe12O22: Comparison of ceramics and single crystals

    NASA Astrophysics Data System (ADS)

    Kamba, S.; Goian, V.; Savinov, M.; Buixaderas, E.; Nuzhnyy, D.; Maryško, M.; Kempa, M.; Bovtun, V.; Hlinka, J.; Knížek, K.; Vaněk, P.; Novák, P.; Buršík, J.; Hiraoka, Y.; Kimura, T.; Kouřil, K.; Štěpánková, H.

    2010-05-01

    We prepared multiferroic Y-type hexaferrite Ba0.5Sr1.5Zn2Fe12O22 ceramics and compared their magnetic and dielectric properties with single crystal. Magnetic susceptibility and microwave resonance measurement revealed magnetic phase transition at TC=312 K, similar as in single crystal. Ferroelectric (FE) phase can be induced by external magnetic field in all investigated samples and the phase diagram in ceramics qualitatively resembles that of the single crystal. The range of magnetic fields, where the FE phase is induced, broadens after annealing of single crystal. Ceramics quenched after sintering exhibit several orders of magnitude lower conductivity than the single crystal. Heavily damped magnetic resonance was discovered in terahertz spectra at 10 K and its frequency softens below 5 GHz near TC. Number and symmetry of observed infrared (IR) and Raman active phonons correspond to paraelectric phase with D3d5 hexagonal structure. No evidence for a structural phase transition was found in the IR and Raman spectra on cooling (in zero magnetic field) or in the room-temperature IR spectra with external static magnetic field up to 0.3 T.

  11. Mathematical Simulation of the Crystallization Process in a Continuous Linear Crystallizer

    NASA Astrophysics Data System (ADS)

    Veselov, S. N.; Volk, V. I.; Kashcheev, V. A.; Podymova, T. V.; Posenitskiy, E. A.

    2017-01-01

    A mathematical model of the crystallization of uranium in a continuous linear crystallizer, designed for the crystallization separation of desired products in the processing of an irradiated nuclear fuel, is proposed. This model defines the dynamics of growth/dissolution of uranyl nitrate hexahydrate crystals in a nitric acid solution of uranyl nitrate. Results of a numerical simulation of the indicated process, pointing to the existence of stationary conditions in the working space of the crystallizer, are presented. On the basis of these results, the characteristic time of establishment of the stationary regime at different parameters of the process was estimated. The mathematical model proposed was validated on the basis of a comparison of the results of calculations carried out within its framework with experimental data.

  12. Sigmoid kinetics of protein crystal nucleation

    NASA Astrophysics Data System (ADS)

    Nanev, Christo N.; Tonchev, Vesselin D.

    2015-10-01

    A non-linear differential equation expressing the new phase nucleation rate in the different steps of the process (non-stationary and stationary nucleation and in the plateau region) is derived from basic principles of the nucleation theory. It is shown that one and the same sigmoid (logistic) function describes both nucleation scenarios: the one according to the classical theory, and the other according to the modern two-stage mechanism of protein crystal formation. Comparison to experimental data on both insulin crystal nucleation kinetics and on bovine β-lactoglobulin crystallization indicates a good agreement with the sigmoidal prediction. Experimental data for electrochemical nucleation and glass crystallization obey the same sigmoid time dependence, and suggest universality of this nucleation kinetics law.

  13. Optical characteristics of Er3+ ion in Er/Yb:LiNbO3 crystal: Comparison with the dissimilar effect of anti-photorefractive ions Zn2+, In3+ and Zr4+

    NASA Astrophysics Data System (ADS)

    Qian, Yannan; Wang, Rui; Wang, Biao; Xu, Chao; Xu, Wei; Xing, Lili; Xu, Yanling

    2013-11-01

    The different influences of Zn2+, In3+ and Zr4+ ions on the optical characteristics of Er3+ ion in Er/Yb:LiNbO3 crystals were discussed. An enhanced 1.54 μm emission was observed for Zr/Er/Yb:LiNbO3 crystal, but the Zn2+ tri-doping resulted in a decreased one, and the intensity of 1.54 μm emission remained about same in In/Er/Yb:LiNbO3 crystal. The populations of the green emitting 4S3/2/2H11/2 states were achieved through the three-, two- and two-phonon processes in Zn/Er/Yb:LiNbO3, In/Er/Yb:LiNbO3 and Zr/Er/Yb:LiNbO3 crystals, respectively. Zn2+ and In3+ ions affected the optical characteristics of Er3+ ion via modifying the Er3+ ion occupancy in Er/Yb:LiNbO3 crystal. The formation of ErLi2+-ErNb2- ion pairs caused by the Zn2+ and In3+ ions could increase the rate of cross relaxation process. The OH- absorption spectra showed that the incorporation of Zr4+ ions increased OH- content, which increased the probability of the nonradiative relaxation process of 4I11/2→4I13/2 (Er) in Zr/Er/Yb:LiNbO3 crystal. The J-O intensity parameters Ωt (t=2, 4 and 6), the radiative lifetime (τrad) and fluorescence branching ratio (β) in Zr/Er/Yb:LiNbO3 crystal were predicted by Judd-Ofelt theory. Füchtbauer-Ladenburg and McCumber methods were carried out to calculate the emission cross-sections at 1.54 μm emission. The gain cross-section, estimated as a function of the population inversion ratio, allowed us to evaluate a potential laser performance of Zr/Er/Yb:LiNbO3 crystal.

  14. CRYSTALLIZATION IN MULTICOMPONENT GLASSES

    SciTech Connect

    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.

  15. A new hybrid phononic crystal in low frequencies

    NASA Astrophysics Data System (ADS)

    Zhang, Z.; Han, X. K.

    2016-11-01

    A novel hybrid phononic crystal is designed to obtain wider band gaps in low frequency range. The hybrid phononic crystal consists of rubber slab with periodic holes and plumbum stubs. In comparison with the phononic crystal without periodic holes, the new designed phononic crystal can obtain wider band gaps and better vibration damping characteristics. The wider band gap can be attributed to the interaction of local resonance and Bragg scattering. The controlling of the BG is explained by the strain energy of the hybrid PC and the introduced effective mass. The effects of the geometrical parameters and the shapes of the stubs and holes on the controlling of waves are further studied.

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

    PubMed

    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.

  17. Aluminum Induces Oxidative Stress Genes in Arabidopsis thaliana1

    PubMed Central

    Richards, Keith D.; Schott, Eric J.; Sharma, Yogesh K.; Davis, Keith R.; Gardner, Richard C.

    1998-01-01

    Changes in gene expression induced by toxic levels of Al were characterized to investigate the nature of Al stress. A cDNA library was constructed from Arabidopsis thaliana seedlings treated with Al for 2 h. We identified five cDNA clones that showed a transient induction of their mRNA levels, four cDNA clones that showed a longer induction period, and two down-regulated genes. Expression of the four long-term-induced genes remained at elevated levels for at least 48 h. The genes encoded peroxidase, glutathione-S-transferase, blue copper-binding protein, and a protein homologous to the reticuline:oxygen oxidoreductase enzyme. Three of these genes are known to be induced by oxidative stresses and the fourth is induced by pathogen treatment. Another oxidative stress gene, superoxide dismutase, and a gene for Bowman-Birk protease inhibitor were also induced by Al in A. thaliana. These results suggested that Al treatment of Arabidopsis induces oxidative stress. In confirmation of this hypothesis, three of four genes induced by Al stress in A. thaliana were also shown to be induced by ozone. Our results demonstrate that oxidative stress is an important component of the plant's reaction to toxic levels of Al. PMID:9449849

  18. Aluminum induces cross-resistance of potato to Phytophthora infestans.

    PubMed

    Arasimowicz-Jelonek, Magdalena; Floryszak-Wieczorek, Jolanta; Drzewiecka, Kinga; Chmielowska-Bąk, Jagna; Abramowski, Dariusz; Izbiańska, Karolina

    2014-03-01

    The phenomenon of cross-resistance allows plants to acquire resistance to a broad range of stresses after previous exposure to one specific factor. Although this stress-response relationship has been known for decades, the sequence of events that underpin cross-resistance remains unknown. Our experiments revealed that susceptible potato (Solanum tuberosum L. cv. Bintje) undergoing aluminum (Al) stress at the root level showed enhanced defense responses correlated with reduced disease symptoms after leaf inoculation with Phytophthora infestans. The protection capacity of Al to subsequent stress was associated with the local accumulation of H2O2 in roots and systemic activation of salicylic acid (SA) and nitric oxide (NO) dependent pathways. The most crucial Al-mediated changes involved coding of NO message in an enhanced S-nitrosothiol formation in leaves tuned with an abundant SNOs accumulation in the main vein of leaves. Al-induced distal NO generation was correlated with the overexpression of PR-2 and PR-3 at both mRNA and protein activity levels. In turn, after contact with a pathogen we observed early up-regulation of SA-mediated defense genes, e.g. PR1, PR-2, PR-3 and PAL, and subsequent disease limitation. Taken together Al exposure induced distal changes in the biochemical stress imprint, facilitating more effective responses to a subsequent pathogen attack.

  19. Apparatus for growing crystals

    NASA Technical Reports Server (NTRS)

    Jasinski, Thomas J. (Inventor); Witt, August F. (Inventor)

    1986-01-01

    An improved apparatus and method for growing crystals from a melt employing a heat pipe, consisting of one or more sections, each section serving to control temperature and thermal gradients in the crystal as it forms inside the pipe.

  20. Crystal structure and prediction.

    PubMed

    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.

  1. Growth of dopamine crystals

    NASA Astrophysics Data System (ADS)

    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.

  2. Crystal Structure and Prediction

    NASA Astrophysics Data System (ADS)

    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.

  3. Crystallization Pathways in Biomineralization

    NASA Astrophysics Data System (ADS)

    Weiner, Steve; Addadi, Lia

    2011-08-01

    A crystallization pathway describes the movement of ions from their source to the final product. Cells are intimately involved in biological crystallization pathways. In many pathways the cells utilize a unique strategy: They temporarily concentrate ions in intracellular membrane-bound vesicles in the form of a highly disordered solid phase. This phase is then transported to the final mineralization site, where it is destabilized and crystallizes. We present four case studies, each of which demonstrates specific aspects of biological crystallization pathways: seawater uptake by foraminifera, calcite spicule formation by sea urchin larvae, goethite formation in the teeth of limpets, and guanine crystal formation in fish skin and spider cuticles. Three representative crystallization pathways are described, and aspects of the different stages of crystallization are discussed. An in-depth understanding of these complex processes can lead to new ideas for synthetic crystallization processes of interest to materials science.

  4. Apparatus for mounting crystal

    DOEpatents

    Longeway, Paul A.

    1985-01-01

    A thickness monitor useful in deposition or etching reactor systems comprising a crystal-controlled oscillator in which the crystal is deposited or etched to change the frequency of the oscillator. The crystal rests within a thermally conductive metallic housing and arranged to be temperature controlled. Electrode contacts are made to the surface primarily by gravity force such that the crystal is substantially free of stress otherwise induced by high temperature.

  5. Photonic Crystal Fibers

    DTIC Science & Technology

    2005-12-01

    passive and active versions of each fiber designed under this task. Crystal Fibre shall provide characteristics of the fiber fabricated to include core...passive version of multicore fiber iteration 2. 15. SUBJECT TERMS EOARD, Laser physics, Fibre Lasers, Photonic Crystal, Multicore, Fiber Laser 16...9 00* 0 " CRYSTAL FIBRE INT ODUCTION This report describes the photonic crystal fibers developed under agreement No FA8655-o5-a- 3046. All

  6. CRYSTAL FILTER TEST SET

    DTIC Science & Technology

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

  7. Crystallization from Gels

    NASA Astrophysics Data System (ADS)

    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

  8. Food Crystalization and Eggs

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Food Crystalization and Eggs Deana R. Jones, Ph.D. USDA Agricultural Research Service Egg Safety and Quality Research Unit Athens, Georgia, USA Deana.Jones@ars.usda.gov Sugar, salt, lactose, tartaric acid and ice are examples of constituents than can crystallize in foods. Crystallization in a foo...

  9. Artistic Crystal Creations

    ERIC Educational Resources Information Center

    Lange, Catherine

    2008-01-01

    In this inquiry-based, integrative art and science activity, Grade 5-8 students use multicolored Epsom salt (magnesium sulfate) crystallizing solutions to reveal beautiful, cylindrical, 3-dimensional, needle-shaped structures. Through observations of the crystal art, students analyze factors that contribute to crystal size and formation, compare…

  10. Annealing macromolecular crystals.

    PubMed

    Hanson, B Leif; Bunick, Gerard J

    2007-01-01

    The process of crystal annealing has been used to improve the quality of diffraction from crystals that would otherwise be discarded for displaying unsatisfactory diffraction after flash cooling. Although techniques and protocols vary, macromolecular crystals are annealed by warming the flash-cooled crystal, then flash cooling it again. To apply macromolecular crystal annealing, a flash-cooled crystal displaying unacceptably high mosaicity or diffraction from ice is removed from the goniometer and immediately placed in cryoprotectant buffer. The crystal is incubated in the buffer at either room temperature or the temperature at which the crystal was grown. After about 3 min, the crystal is remounted in the loop and flash cooled. In situ annealing techniques, where the cold stream is diverted and the crystal allowed to warm on the loop prior to flash cooling, are variations of annealing that appears to work best when large solvent channels are not present in the crystal lattice or the solvent content of the crystal is relatively low.

  11. Protein Crystal Based Nanomaterials

    NASA Technical Reports Server (NTRS)

    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.

  12. Stability of Detached Grown Germanium Single Crystals

    NASA Technical Reports Server (NTRS)

    Schweizer, M.; Volz, M. P.; Cobb, S. D.; Vujisic, L.; Szofran, F. R.; Rose, M. Franklin (Technical Monitor)

    2001-01-01

    Detachment of the melt meniscus from the crucible during semiconductor Bridgman growth experiments has been observed in recent years, especially under microgravity experiments. Under earth conditions, the hydrostatic pressure counteracts the mechanism, whereby it is more difficult to achieve detached Bridgman growth. Attempts to get stable detached growth under terrestrial conditions have been discussed in the literature and have been the subject of recent experiments in our own group. The advantage of crystals grown without wall contact is obvious: In general, they possess a higher crystal quality than conventional Bridgman grown crystals with wall contact. However, due to the interaction of different parameters such as the wetting behavior of the melt with the crucible, and the dependence of the growth angle with the shape of the melt meniscus, the mechanism leading to detachment is very complicated and not completely understood. We have grown several doped and undoped Germanium crystals with the detached Bridgman and the normal Bridgman growth technique. Pyrolytic boron nitride containers were used for all growth experiments. In the detached grown crystals the typical gap thickness between the pBN crucible and the crystal is in the range of 10 to 100 micrometers, which was determined by performing profilometer measurements. Etch pit density measurements were also performed and a comparison between detached and attached grown crystals will be given. An interesting feature was detected on the surface of a detached grown crystal. Strong surface striations with an average axial distance of 0.5 mm were observed around the whole circumference. The maximum fluctuation of the gap thickness is in the range of 5-10 micrometers. These variations of the detached gap along the crystal axis can be explained by a kind of stiction of the melt/crucible interface and thus by a variation of the meniscus shape. This phenomenon leading to the fluctuation of the gap thickness will be

  13. Stability of Detached Grown Germanium Single Crystals

    NASA Technical Reports Server (NTRS)

    Schweizer, M.; Volz, M. P.; Cobb, S. D.; Motakef, S.; Szofran, F. R.; Curreri, Peter A. (Technical Monitor)

    2002-01-01

    Detachment of the melt meniscus from the crucible during semiconductor Bridgman growth experiments has been observed in recent years especially, under microgravity experiments. Under earth conditions, the hydrostatic pressure counteracts the mechanism, whereby it is more difficult to achieve detached Bridgman growth. Attempts to get stable detached growth under terrestrial conditions have been discussed in the literature and have been the subject of recent experiments in our own group. The advantage of crystals grown without wall contact is obvious: In general, they possess a higher crystal quality than conventional Bridgman grown crystals with wall contact. However, due to the interaction of different parameters such as the wetting behavior of the melt with the crucible, and the dependence of the growth angle with the shape of the melt meniscus, the mechanism leading to detachment is very complicated and not completely understood. We have grown several doped and undoped Germanium crystals with the detached Bridgman and the normal Bridgman growth technique. Pyrolytic boron nitride containers were used for all growth experiments. In the detached grown crystals the typical gap thickness between the pBN crucible and the crystal is in the range of 10 to 100 microns, which was determined by performing profilometer measurements. Etch pit density measurements were also performed and a comparison between detached and attached grown crystals will be given. An interesting feature was detected on the surface of a detached grown crystal. Strong surface striations with an average axial distance of 0.5mm were observed around the whole circumference. The maximum fluctuation of the gap thickness is in the range of 5-10 microns. These variations of the detached gap along the crystal axis can be explained by a kind of stiction of the melt/crucible interface and thus by a variation of the meniscus shape. This phenomenon leading to the fluctuation of the gap thickness will be

  14. Protein crystallization with paper

    NASA Astrophysics Data System (ADS)

    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.

  15. Improving marginal crystals.

    PubMed

    Carter, Charles W; Riès-Kautt, Madeleine

    2007-01-01

    The physical chemistry of crystal growth can help to identify directions in which to look for improved crystal properties. In this chapter, we summarize how crystal growth depends on parameters that can be controlled experimentally, and relate them to the tools available for optimizing a particular crystal form for crystal shape, volume, and diffraction quality. Our purpose is to sketch the conceptual basis of optimization and to provide sample protocols derived from those foundations. We hope to assist even those who chose not to use systematic methods by enabling them to carry out rudimentary optimization searches armed with a better understanding of how the underlying physical chemistry operates.

  16. Photonic crystal light source

    DOEpatents

    Fleming, James G.; Lin, Shawn-Yu; Bur, James A.

    2004-07-27

    A light source is provided by a photonic crystal having an enhanced photonic density-of-states over a band of frequencies and wherein at least one of the dielectric materials of the photonic crystal has a complex dielectric constant, thereby producing enhanced light emission at the band of frequencies when the photonic crystal is heated. The dielectric material can be a metal, such as tungsten. The spectral properties of the light source can be easily tuned by modification of the photonic crystal structure and materials. The photonic crystal light source can be heated electrically or other heating means. The light source can further include additional photonic crystals that exhibit enhanced light emission at a different band of frequencies to provide for color mixing. The photonic crystal light source may have applications in optical telecommunications, information displays, energy conversion, sensors, and other optical applications.

  17. Protein Crystal Growth

    NASA Technical Reports Server (NTRS)

    2003-01-01

    In order to rapidly and efficiently grow crystals, tools were needed to automatically identify and analyze the growing process of protein crystals. To meet this need, Diversified Scientific, Inc. (DSI), with the support of a Small Business Innovation Research (SBIR) contract from NASA s Marshall Space Flight Center, developed CrystalScore(trademark), the first automated image acquisition, analysis, and archiving system designed specifically for the macromolecular crystal growing community. It offers automated hardware control, image and data archiving, image processing, a searchable database, and surface plotting of experimental data. CrystalScore is currently being used by numerous pharmaceutical companies and academic and nonprofit research centers. DSI, located in Birmingham, Alabama, was awarded the patent Method for acquiring, storing, and analyzing crystal images on March 4, 2003. Another DSI product made possible by Marshall SBIR funding is VaporPro(trademark), a unique, comprehensive system that allows for the automated control of vapor diffusion for crystallization experiments.

  18. Crystallization Stages of the Bishop Tuff Magma Body Recorded in Crystal Textures in Pumice Clasts

    SciTech Connect

    Pamukcu, Ayla; Gualda, Guilherme A.R.; Anderson, Jr. , Alfred T.

    2012-07-25

    The Bishop Tuff is a giant silicic ignimbrite erupted at 0.76 Ma in eastern California, USA. Five pumice clasts from the late-erupted Bishop Tuff (Aeolian Buttes) were studied in an effort to better understand the pre- and syn-eruptive history of the Bishop magma body and place constraints on the timescales of its existence. This study complements and expands on a previous study that focused on early-erupted Bishop Tuff pumice clasts. Bulk densities of pumice clasts were measured using an immersion method, and phenocryst crystal contents were determined using a sieving and winnowing procedure. X-ray tomography was used to obtain qualitative and quantitative textural information, particularly crystal size distributions (CSDs). We have determined CSDs for crystals ranging in size from {approx}10 to {approx}1000 {micro}m for three groups of mineral phases: magnetite ({+-}ilmenite), pyroxene + biotite, quartz + feldspar. Similar to early-erupted pumice, late-erupted pumice bulk density and crystal contents are positively correlated, and comparison of crystal fraction vs size trends suggests that the proportion of large crystals is the primary control on crystallinity. Porosity is negatively correlated with crystal content, which is difficult to reconcile with closed-system crystallization. Magnetite and pyroxene + biotite size distributions are fractal in nature, often attributed to fragmentation; however, crystals are mostly whole and euhedral, such that an alternative mechanism is necessary to explain these distributions. Quartz + feldspar size distributions are kinked, with a shallow-sloped log-linear section describing large crystals (> 140 {micro}m) and a steep-sloped log-linear section describing small crystals (< 140 {micro}m). We interpret these two crystal populations as resulting from a shift in crystallization regime. We suggest that the shallow-sloped section describes a pre-eruptive quartz + feldspar growth-dominated regime, whereas the steep

  19. Insecticidal crystal proteins of Bacillus thuringiensis.

    PubMed Central

    Höfte, H; Whiteley, H R

    1989-01-01

    A classification for crystal protein genes of Bacillus thuringiensis is presented. Criteria used are the insecticidal spectra and the amino acid sequences of the encoded proteins. Fourteen genes are distinguished, encoding proteins active against either Lepidoptera (cryI), Lepidoptera and Diptera (cryII), Coleoptera (cryIII), or Diptera (cryIV). One gene, cytA, encodes a general cytolytic protein and shows no structural similarities with the other genes. Toxicity studies with single purified proteins demonstrated that every described crystal protein is characterized by a highly specific, and sometimes very restricted, insect host spectrum. Comparison of the deduced amino acid sequences reveals sequence elements which are conserved for Cry proteins. The expression of crystal protein genes is affected by a number of factors. Recently, two distinct sigma subunits regulating transcription during different stages of sporulation have been identified, as well as a protein regulating the expression of a crystal protein at a posttranslational level. Studies on the biochemical mechanisms of toxicity suggest that B. thuringiensis crystal proteins induce the formation of pores in membranes of susceptible cells. In vitro binding studies with radiolabeled toxins demonstrated a strong correlation between the specificity of B. thuringiensis toxins and the interaction with specific binding sites on the insect midgut epithelium. The expression of B. thuringiensis crystal proteins in plant-associated microorganisms and in transgenic plants has been reported. These approaches are potentially powerful strategies for the protection of agriculturally important crops against insect damage. Images PMID:2666844

  20. Macromolecular Crystallization in Microgravity

    NASA Technical Reports Server (NTRS)

    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

  1. Crystal Polymorphism and Multiple Crystal Forms

    NASA Astrophysics Data System (ADS)

    Braga, Dario; Grepioni, Fabrizia; Maini, Lucia; Polito, Marco

    This chapter discusses the phenomenon of polymorphism in organic and organometallic compounds. Polymorphism is first introduced and then, to give the work some context, background information is given concerning properties and techniques for characterizing the solid phases. In particular, desolvation and interconverstion are examined, and the gas-solid reactions are presented as a successful route to obtaining new crystalline phases. Co-crystal definition is then described and the problem in distinguishing co-crystals and salts is evaluated.

  2. Protein crystal growth

    NASA Technical Reports Server (NTRS)

    2001-01-01

    Atomic force microscopy uses laser technology to reveal a defect, a double-screw dislocation, on the surface of this crystal of canavalin, a major source of dietary protein for humans and domestic animals. When a crystal grows, attachment kinetics and transport kinetics are competing for control of the molecules. As a molecule gets close to the crystal surface, it has to attach properly for the crystal to be usable. NASA has funded investigators to look at those attachment kinetics from a theoretical standpoint and an experimental standpoint. Dr. Alex McPherson of the University of California, Irvine, is one of those investigators. He uses X-ray diffraction and atomic force microscopy in his laboratory to answer some of the many questions about how protein crystals grow. Atomic force microscopy provides a means of looking at how individual molecules are added to the surface of growing protein crystals. This helps McPherson understand the kinetics of protein crystal growth. McPherson asks, How fast do crystals grow? What are the forces involved? Investigators funded by NASA have clearly shown that such factors as the level of supersaturation and the rate of growth all affect the habit [characteristic arrangement of facets] of the crystal and the defects that occur in the crystal.

  3. Study of single crystals of metal solid solutions

    NASA Technical Reports Server (NTRS)

    Doty, J. P.; Reising, J. A.

    1973-01-01

    The growth of single crystals of relatively high melting point metals such as silver, copper, gold, and their alloys was investigated. The purpose was to develop background information necessary to support a space flight experiment and to generate ground based data for comparison. The ground based data, when compared to the data from space grown crystals, are intended to identify any effects which zero-gravity might have on the basic process of single crystal growth of these metals. The ultimate purposes of the complete investigation are to: (1) determine specific metals and alloys to be investigated; (2) grow single metal crystals in a terrestrial laboratory; (3) determine crystal characteristics, properties, and growth parameters that will be effected by zero-gravity; (4) evaluate terrestrially grown crystals; (5) grow single metal crystals in a space laboratory such as Skylab; (6) evaluate the space grown crystals; (7) compare for zero-gravity effects of crystal characteristics, properties, and parameters; and (8) make a recommendation as to production of these crystals as a routine space manufacturing proceses.

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

    PubMed

    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.

  5. Fragile phase stability in (1-x)Pb(Mg{sub 1/3}Nb{sub 2/3}O{sub 3})-xPbTiO{sub 3} crystals: A comparison of [001] and [110] field-cooled phase diagrams

    SciTech Connect

    Cao, Hu; Li, Jiefang; Viehland, D.; Xu, Guangyong

    2006-05-01

    Phase diagrams of [001] and [110] field-cooled (FC) (1-x)Pb(Mg{sub 1/3}Nb{sub 2/3}O{sub 3})-xPbTiO{sub 3} or PMN-xPT (0.15{<=}x{<=}0.38) crystals have been constructed, based on high-resolution x-ray diffraction data. Comparisons reveal several interesting findings. First, a region of abnormal thermal expansion (c{ne}a) above the dielectric maximum was found, whose stability range extended to higher temperatures on application of electric field (E). Second, the rhombohedral (R) phase of the zero-field-cooled (ZFC) state was replaced by monoclinic M{sub A} in the [001] FC diagram, but with monoclinic M{sub B} in the [110] FC. Third, the monoclinic M{sub C} phase in the ZFC and [001] FC diagram was replaced by an orthorhombic (O) phase in the [110] FC diagram. Finally, in the [001] FC diagram, the phase boundary between tetragonal (T) and M{sub A} phases was extended to lower PT content (x=0.25); whereas in the [110] FC diagram, this extended region was entirely replaced by the O phase. These results clearly demonstrate that the phase stability of PMN-xPT crystals is quite fragile--depending not only on modest changes in E, but also on the direction along which E is applied.

  6. Comparison of the crystal structures of methyl 4-bromo-2-(meth­oxy­meth­oxy)benzoate and 4-bromo-3-(meth­oxy­meth­oxy)benzoic acid

    PubMed Central

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

    2016-01-01

    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 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 inter­actions [inter-centroid distances = 3.6787 (18) and 3.8431 (17) Å], leading to the formation of slabs parallel to the bc plane. PMID:27375868

  7. Requirements for structure determination of aperiodic crystals

    SciTech Connect

    Li, X.; Stern, E.A.; Ma, Y. )

    1991-01-15

    Using computer simulation, we compared the Patterson functions of one-dimensional (1D) randomly packed and quasiperiodic Fibonacci lattices with or without disorder, and a 2D Penrose lattice and random packing of pentagons (icosahedral glass model). Based on these comparisons, we derived some empirical guidelines for distinguishing ideal quasicrystals from aperiodic crystals with disorder using diffraction data. In contrast to periodic crystals, it is essential to include the background to obtain correct Patterson functions of the average structure since the background contains unresolved peaks. In particular, a Bragg peak scattering measurement {ital cannot}, in general, determine the structure of aperiodic crystals. Instead, a diffuse scattering measurement is required, which determines the absolute value of the diffraction background, in addition to the Bragg peaks. We further estimate that, dependent upon the disorder present, it is necessary to include up to 75% of the total diffracted intensity in any analysis.

  8. Automated macromolecular crystallization screening

    DOEpatents

    Segelke, Brent W.; Rupp, Bernhard; Krupka, Heike I.

    2005-03-01

    An automated macromolecular crystallization screening system wherein a multiplicity of reagent mixes are produced. A multiplicity of analysis plates is produced utilizing the reagent mixes combined with a sample. The analysis plates are incubated to promote growth of crystals. Images of the crystals are made. The images are analyzed with regard to suitability of the crystals for analysis by x-ray crystallography. A design of reagent mixes is produced based upon the expected suitability of the crystals for analysis by x-ray crystallography. A second multiplicity of mixes of the reagent components is produced utilizing the design and a second multiplicity of reagent mixes is used for a second round of automated macromolecular crystallization screening. In one embodiment the multiplicity of reagent mixes are produced by a random selection of reagent components.

  9. Antarctic stratospheric ice crystals

    NASA Technical Reports Server (NTRS)

    Goodman, J.; Toon, O. B.; Pueschel, R. F.; Snetsinger, K. G.; Verma, S.

    1989-01-01

    Ice crystals were replicated over the Palmer Peninsula at approximately 72 deg S on six occasions during the 1987 Airboirne Antarctic Ozone Experiment. The sampling altitude was between 12.5 and 18.5 km (45-65 thousand ft pressure altitude) with the temperature between 190 and 201 K. The atmosphere was subsaturated with respect to ice in all cases. The collected crystals were predominantly solid and hollow columns. The largest crystals were sampled at lower altitudes where the potential temperature was below 400 K. While the crystals were larger than anticipated, their low concentration results in a total surface area that is less than one tenth of the total aerosol surface area. The large ice crystals may play an important role in the observed stratospheric dehydration processes through sedimentation. Evidence of scavenging of submicron particles further suggests that the ice crystals may be effective in the removal of stratospheric chemicals.

  10. Protein crystallization in microgravity.

    PubMed

    Aibara, S; Shibata, K; Morita, Y

    1997-12-01

    A space experiment involving protein crystallization was conducted in a microgravity environment using the space shuttle "Endeavour" of STS-47, on a 9-day mission from September 12th to 20th in 1992. The crystallization was carried out according to a batch method, and 5 proteins were selected as flight samples for crystallization. Two of these proteins: hen egg-white lysozyme and co-amino acid: pyruvate aminotransferase from Pseudomonas sp. F-126, were obtained as single crystals of good diffraction quality. Since 1992 we have carried out several space experiments for protein crystallization aboard space shuttles and the space station MIR. Our experimental results obtained mainly from hen egg-white lysozyme are described below, focusing on the effects of microgravity on protein crystal growth.

  11. Crystallization of Macromolecules

    PubMed Central

    Friedmann, David; Messick, Troy; Marmorstein, Ronen

    2014-01-01

    X-ray crystallography has evolved into a very powerful tool to determine the three-dimensional structure of macromolecules and macromolecular complexes. The major bottleneck in structure determination by X-ray crystallography is the preparation of suitable crystalline samples. This unit outlines steps for the crystallization of a macromolecule, starting with a purified, homogeneous sample. The first protocols describe preparation of the macromolecular sample (i.e., proteins, nucleic acids, and macromolecular complexes). The preparation and assessment of crystallization trials is then described, along with a protocol for confirming whether the crystals obtained are composed of macromolecule as opposed to a crystallization reagent. Next, the optimization of crystallization conditions is presented. Finally, protocols that facilitate the growth of larger crystals through seeding are described. PMID:18429252

  12. Crystallization of Macromolecules

    PubMed Central

    Friedmann, David; Messick, Troy; Marmorstein, Ronen

    2014-01-01

    X-ray crystallography has evolved into a very powerful tool to determine the three-dimensional structure of macromolecules and macromolecular complexes. The major bottleneck in structure determination by X-ray crystallography is the preparation of suitable crystalline samples. This unit outlines steps for the crystallization of a macromolecule, starting with a purified, homogeneous sample. The first protocols describe preparation of the macromolecular sample (i.e., proteins, nucleic acids, and macromolecular complexes). The preparation and assessment of crystallization trials is then described, along with a protocol for confirming whether the crystals obtained are composed of macromolecule as opposed to a crystallization reagent . Next, the optimization of crystallization conditions is presented. Finally, protocols that facilitate the growth of larger crystals through seeding are described. PMID:22045560

  13. Metal-assisted and microwave accelerated-evaporative crystallization: Application to lysozyme protein

    NASA Astrophysics Data System (ADS)

    Mauge-Lewis, Kevin

    In response to the growing need for new crystallization techniques that afford for rapid processing times along with control over crystal size and distribution, the Aslan Research Group has recently demonstrated the use of Metal-Assisted and Microwave-Accelerated Evaporative Crystallization MA-MAEC technique in conjunction with metal nanoparticles and nanostructures for the crystallization of amino acids and organic small molecules. In this study, we have employed the newly developed MA-MAEC technique to the accelerated crystallization of chicken egg-white lysozyme on circular crystallization platforms in order to demonstrate the proof-of-principle application of the method for protein crystallization. The circular crystallization platforms are constructed in-house from poly (methyl methacrylate) (PMMA) and silver nanoparticle films (SNFs), indium tin oxide (ITO) and iron nano-columns. In this study, we prove the MA-MAEC method to be a more effective technique in the rapid crystallization of macromolecules in comparison to other conventional methods. Furthermore, we demonstrate the use of the novel iCrystal system, which incorporates the use of continuous, low wattage heating to facilitate the rapid crystallization of the lysozyme while still retaining excellent crystal quality. With the incorporation of the iCrystal system, we observe crystallization times that are even shorter than those produced by the MA-MAEC technique using a conventional microwave oven in addition to significantly improved crystal quality.

  14. Phononic crystal devices

    DOEpatents

    El-Kady, Ihab F [Albuquerque, NM; Olsson, Roy H [Albuquerque, NM

    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.

  15. Liquid Crystal Optofluidics

    SciTech Connect

    Vasdekis, Andreas E.; Cuennet, J. G.; Psaltis, D.

    2012-10-11

    By employing anisotropic fluids and namely liquid crystals, fluid flow becomes an additional degree of freedom in designing optofluidic devices. In this paper, we demonstrate optofluidic liquid crystal devices based on the direct flow of nematic liquid crystals in microfluidic channels. Contrary to previous reports, in the present embodiment we employ the effective phase delay acquired by light travelling through flowing liquid crystal, without analysing the polarisation state of the transmitted light. With this method, we demonstrate the variation in the diffraction pattern of an array of microfluidic channels acting as a grating. We also discuss our recent activities in integrating mechanical oscillators for on-chip peristaltic pumping.

  16. Automation in biological crystallization.

    PubMed

    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.

  17. Tunable plasmonic crystal

    DOEpatents

    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.

  18. Liquid crystal optofluidics

    NASA Astrophysics Data System (ADS)

    Vasdekis, A. E.; Cuennet, J. G.; Psaltis, D.

    2012-10-01

    By employing anisotropic fluids and namely liquid crystals, fluid flow becomes an additional degree of freedom in designing optofluidic devices. In this paper, we demonstrate optofluidic liquid crystal devices based on the direct flow of nematic liquid crystals in microfluidic channels. Contrary to previous reports, in the present embodiment we employ the effective phase delay acquired by light travelling through flowing liquid crystal, without analysing the polarisation state of the transmitted light. With this method, we demonstrate the variation in the diffraction pattern of an array of microfluidic channels acting as a grating. We also discuss our recent activities in integrating mechanical oscillators for on-chip peristaltic pumping.

  19. Heroin crystal nephropathy.

    PubMed

    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.

  20. Automation in biological crystallization

    PubMed Central

    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

  1. Crystals in magma chambers

    NASA Astrophysics Data System (ADS)

    Higgins, M.

    2011-12-01

    Differentiation processes in igneous systems are one way in which the diversity of igneous rocks is produced. Traditionally, magmatic diversity is considered as variations in the overall chemical composition, such as basalt and rhyolite, but I want to extend this definition to include textural diversity. Such textural variations can be manifested as differences in the amount of crystalline (and immiscible liquid) phases and in the origin and identity of such phases. One important differentiation process is crystal-liquid separation by floatation or decantation, which clearly necessitates crystals in the magma. Hence, it is important to determine if magmas in chambers (sensu lato) have crystals. The following discussion is framed in generalities - many exceptions occur. Diabase (dolerite) dykes are a common, widespread result of regional mafic magmatism. The rims of most diabase dykes have few or no phenocrysts and crystals in the cores are commonly thought to have crystallized in place. Hence, this major mafic magmatic source did not have crystals, although compositional diversity of these dykes is commonly explained by crystal-liquid separation. This can be resolved if crystallisation was on the walls on the magma chamber. Similarly, most flood basalts are low in crystals and separation of those that are present cannot always explain the observed compositional diversity. Crystal-rich flows do occur, for example the 'Giant Plagioclase Basalts' of the Deccan series, but the crystals are thought to form or accumulate in a crystal-rich zone beneath the roof of the chamber - the rest of the chamber probably has few crystals. Some magmas from Hawaii contain significant amounts of olivine crystals, but most of these are deformed and cannot have crystallised in the chamber. In this case the crystals are thought to grow as the magma passes through a decollement zone. They may have grown on the walls or been trapped by filters. Basaltic andesite ignimbrites generally have

  2. Advanced Protein Crystallization Facility (APCF)

    NASA Technical Reports Server (NTRS)

    1998-01-01

    This section of the Life and Microgravity Spacelab (LMS) publication contains articles entitled: (1) Crystallization of EGFR-EGF; (2) Crystallization of Apocrustacyanin C1; (3) Crystallization and X-ray Analysis of 5S rRNA and the 5S rRNA Domain A; (4) Growth of Lysozyme Crystals at Low Nucleation Density; (5) Comparative Analysis of Aspartyl tRNA-synthetase and Thaumatin Crystals Grown on Earth and In Microgravity; (6) Lysosome Crystal Growth in the Advanced Protein Crystallization Facility Monitored via Mach-Zehnder Interferometry and CCD Video; (7) Analysis of Thaumatin Crystals Grown on Earth and in Microgravity; (8) Crystallization of the Nucleosome Core Particle; (9) Crystallization of Photosystem I; (10) Mechanism of Membrane Protein Crystal Growth: Bacteriorhodopsin-mixed Micelle Packing at the Consolution Boundary, Stabilized in Microgravity; (11) Crystallization in a Microgravity Environment of CcdB, a Protein Involved in the Control of Cell Death; and (12) Crystallization of Sulfolobus Solfataricus

  3. Direct detection of antihydrogen atoms using a BGO crystal

    NASA Astrophysics Data System (ADS)

    Nagata, Y.; Kuroda, N.; Ohtsuka, M.; Leali, M.; Lodi-Rizzini, E.; Mascagna, V.; Tajima, M.; Torii, H. A.; Zurlo, N.; Matsuda, Y.; Venturelli, L.; Yamazaki, Y.

    2016-12-01

    The ASACUSA collaboration has developed a detector consisting of a large size BGO crystal to detect an atomic antihydrogen beam, and performed the direct detection of antihydrogen atoms. Energy spectra from antihydrogen annihilation on the BGO crystal are discussed in comparison to simulation results from the GEANT4 toolkit. Background mainly originating from cosmic rays were strongly suppressed by analyzing the energy deposited in the BGO and requiring a multiplicity of charged pions. Thus antihydrogen events were identified.

  4. Channeling through Bent Crystals

    SciTech Connect

    Mack, Stephanie; /Ottawa U. /SLAC

    2012-09-07

    Bent crystals have demonstrated potential for use in beam collimation. A process called channeling is when accelerated particle beams are trapped by the nuclear potentials in the atomic planes within a crystal lattice. If the crystal is bent then the particles can follow the bending angle of the crystal. There are several different effects that are observed when particles travel through a bent crystal including dechanneling, volume capture, volume reflection and channeling. With a crystal placed at the edge of a particle beam, part of the fringe of the beam can be deflected away towards a detector or beam dump, thus helping collimate the beam. There is currently FORTRAN code by Igor Yazynin that has been used to model the passage of particles through a bent crystal. Using this code, the effects mentioned were explored for beam energy that would be seen at the Facility for Advanced Accelerator Experimental Tests (FACET) at a range of crystal orientations with respect to the incoming beam. After propagating 5 meters in vacuum space past the crystal the channeled particles were observed to separate from most of the beam with some noise due to dechanneled particles. Progressively smaller bending radii, with corresponding shorter crystal lengths, were compared and it was seen that multiple scattering decreases with the length of the crystal therefore allowing for cleaner detection of the channeled particles. The input beam was then modified and only a portion of the beam sent through the crystal. With the majority of the beam not affected by the crystal, most particles were not deflected and after propagation the channeled particles were seen to be deflected approximately 5mm. After a portion of the beam travels through the crystal, the entire beam was then sent through a quadrupole magnet, which increased the separation of the channeled particles from the remainder of the beam to a distance of around 20mm. A different code, which was developed at SLAC, was used to

  5. Protein crystal growth

    NASA Technical Reports Server (NTRS)

    Bugg, Charles E.

    1993-01-01

    Proteins account for 50% or more of the dry weight of most living systems and play a crucial role in virtually all biological processes. Since the specific functions of essentially all biological molecules are determined by their three-dimensional structures, it is obvious that a detailed understanding of the structural makeup of a protein is essential to any systematic research pertaining to it. At the present time, protein crystallography has no substitute, it is the only technique available for elucidating the atomic arrangements within complicated biological molecules. Most macromolecules are extremely difficult to crystallize, and many otherwise exciting and promising projects have terminated at the crystal growth stage. There is a pressing need to better understand protein crystal growth, and to develop new techniques that can be used to enhance the size and quality of protein crystals. There are several aspects of microgravity that might be exploited to enhance protein crystal growth. The major factor that might be expected to alter crystal growth processes in space is the elimination of density-driven convective flow. Another factor that can be readily controlled in the absence of gravity is the sedimentation of growing crystal in a gravitational field. Another potential advantage of microgravity for protein crystal growth is the option of doing containerless crystal growth. One can readily understand why the microgravity environment established by Earth-orbiting vehicles is perceived to offer unique opportunities for the protein crystallographer. The near term objectives of the Protein Crystal Growth in a Microgravity Environment (PCG/ME) project is to continue to improve the techniques, procedures, and hardware systems used to grow protein crystals in Earth orbit.

  6. Photonic crystal waveguide created by selective infiltration

    NASA Astrophysics Data System (ADS)

    Casas Bedoya, A.; Domachuk, P.; Grillet, C.; Monat, C.; Mägi, E. C.; Li, E.; Eggleton, B. J.

    2012-06-01

    The marriage of photonics and microfluidics ("optofluidics") uses the inherent mobility of fluids to reversibly tune photonic structures beyond traditional fabrication methods by infiltrating voids in said structures. Photonic crystals (PhCs) strongly control light on the wavelength scale and are well suited to optofluidic tuning because their periodic airhole microstructure is a natural candidate for housing liquids. The infiltration of a single row of holes in the PhC matrix modifies the effective refractive index allowing optical modes to be guided by the PhC bandgap. In this work we present the first experimental demonstration of a reconfigurable single mode W1 photonic crystal defect waveguide created by selective liquid infiltration. We modified a hexagonal silicon planar photonic crystal membrane by selectively filling a single row of air holes with ~300nm resolution, using high refractive index ionic liquid. The modification creates optical confinement in the infiltrated region and allows propagation of a single optical waveguide mode. We describe the challenges arising from the infiltration process and the liquid/solid surface interaction in the photonic crystal. We include a detailed comparison between analytic and numerical modeling and experimental results, and introduce a new approach to create an offset photonic crystal cavity by varying the nature of the selective infiltration process.

  7. Crystals for stellar spectrometers

    NASA Technical Reports Server (NTRS)

    Alexandropoulos, N. G.; Cohen, G. G.

    1974-01-01

    Crystal evaluation as it applies to instrumentation employed in X-ray astronomy is reviewed, and some solutions are offered to problems that are commonly encountered. A general approach for selecting the most appropriate crystals for a given problem is also suggested. The energy dependence of the diffraction properties of (002) PET, (111) Ge, (101) ADP, (101) KAP, and (001) RAP are reported.

  8. Walkout in Crystal City

    ERIC Educational Resources Information Center

    Barrios, Greg

    2009-01-01

    When students take action, they create change that extends far beyond the classroom. In this article, the author, who was a former teacher from Crystal City, Texas, remembers the student walkout that helped launch the Latino civil rights movement 40 years ago. The Crystal City student walkout remains a high point in the history of student activism…

  9. Crystal growth and crystallography

    NASA Technical Reports Server (NTRS)

    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.

  10. Crystal Shape Bingo.

    ERIC Educational Resources Information Center

    Rule, Audrey C.

    This document describes a game that provides students with practice in recognizing three dimensional crystal shapes and planar geometric shapes of crystal faces. It contains information on the objective of the game, game preparation, and rules for playing. Play cards are included (four to a page). (ASK)

  11. Demonstration of Crystal Structure.

    ERIC Educational Resources Information Center

    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)

  12. Bioengineered magnetic crystals

    NASA Astrophysics Data System (ADS)

    Kasyutich, O.; Sarua, A.; Schwarzacher, W.

    2008-07-01

    In this paper we report on the successful application of a protein crystallization technique to fabricate a three-dimensionally ordered array of magnetic nanoparticles, i.e. a novel type of metamaterial with unique magnetic properties. We utilize ferritin protein cages for the template-constrained growth of superparamagnetic nanoparticles of magnetite/maghemite Fe3O4-γ-Fe2O3 (magnetoferritin), followed by thorough nanoparticle bioprocessing and purification, and finally by protein crystallization. Protein crystallization is driven by the natural response of proteins to the supersaturation of the electrolyte, which leads to spontaneous nucleation and 3D crystal growth. Within a short period of time (hours to days) we were able to grow functional crystals on the meso-scale, with sizes of the order of tens, up to a few hundred micrometres. We present initial magnetic and Raman spectroscopy characterization results for the obtained 3D arrays of magnetic nanoparticles.

  13. Polymer Crystallization under Confinement

    NASA Astrophysics Data System (ADS)

    Floudas, George

    Recent efforts indicated that polymer crystallization under confinement can be substantially different from the bulk. This can have important technological applications for the design of polymeric nanofibers with tunable mechanical strength, processability and optical clarity. However, the question of how, why and when polymers crystallize under confinement is not fully answered. Important studies of polymer crystallization confined to droplets and within the spherical nanodomains of block copolymers emphasized the interplay between heterogeneous and homogeneous nucleation. Herein we report on recent studies1-5 of polymer crystallization under hard confinement provided by model self-ordered AAO nanopores. Important open questions here are on the type of nucleation (homogeneous vs. heterogeneous), the size of critical nucleus, the crystal orientation and the possibility to control the overall crystallinity. Providing answers to these questions is of technological relevance for the understanding of nanocomposites containing semicrystalline polymers. In collaboration with Y. Suzuki, H. Duran, M. Steinhart, H.-J. Butt.

  14. Dynamic crystallization experiments on chondrule melts in reduced gravity

    NASA Technical Reports Server (NTRS)

    Lofgren, Gary; Williams, R. J.

    1987-01-01

    Chondrules crystallized during the earliest formational history of the solar system; and, if crystal settling and flotation are indicators of crystallization in the presence of gravity, they formed without the influence of gravity. In fact, attempts to duplicate the crystallization history of chondrules in the laboratory have met with limited success, because of the difficulty of comparing objects formed under the influence of gravity with objects that did not. These comparisons are difficult because there are several recognized features introduced by the presence of gravity and no doubt some which are not yet recognized. As a result there are several microscale and macroscale aspects of chondrule petrology which are difficult to understand quantitatively. Most of the features relate to the settling or flotation of early formed crystals. The proposed experiments are briefly described.

  15. Studying the magnetic properties of CoSi single crystals

    SciTech Connect

    Narozhnyi, V. N. Krasnorussky, V. N.

    2013-05-15

    The magnetic properties of CoSi single crystals have been measured in a range of temperatures T = 5.5-450 K and magnetic field strengths H {<=} 11 kOe. A comparison of the results for crystals grown in various laboratories allowed the temperature dependence of magnetic susceptibility {chi}(T) = M(T)/H to be determined for a hypothetical 'ideal' (free of magnetic impurities and defects) CoSi crystal. The susceptibility of this ideal crystal in the entire temperature range exhibits a diamagnetic character. The {chi}(T) value significantly increases in absolute value with decreasing temperature and exhibits saturation at the lowest temperatures studied. For real CoSi crystals of four types, paramagnetic contributions to the susceptibility have been evaluated and nonlinear (with respect to the field) contributions to the magnetization have been separated and taken into account in the calculations of {chi}(T).

  16. Evolution of molecular crystal optical phonons near structural phase transitions

    NASA Astrophysics Data System (ADS)

    Michki, Nigel; Niessen, Katherine; Xu, Mengyang; Markelz, Andrea

    Molecular crystals are increasingly important photonic and electronic materials. For example organic semiconductors are lightweight compared to inorganic semiconductors and have inexpensive scale up processing with roll to roll printing. However their implementation is limited by their environmental sensitivity, in part arising from the weak intermolecular interactions of the crystal. These weak interactions result in optical phonons in the terahertz frequency range. We examine the evolution of intermolecular interactions near structural phase transitions by measuring the optical phonons as a function of temperature and crystal orientation using terahertz time-domain spectroscopy. The measured orientation dependence of the resonances provides an additional constraint for comparison of the observed spectra with the density functional calculations, enabling us to follow specific phonon modes. We observe crystal reorganization near 350 K for oxalic acid as it transforms from dihydrate to anhydrous form. We also report the first THz spectra for the molecular crystal fructose through its melting point.

  17. The different conformations and crystal structures of dihydroergocristine

    NASA Astrophysics Data System (ADS)

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

    PubMed

    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.

  19. Crystallization of macromolecular complexes: combinatorial complex crystallization

    NASA Astrophysics Data System (ADS)

    Stura, Enrico A.; Graille, Marc; Charbonnier, Jean-Baptiste

    2001-11-01

    The usefulness of antibody complexation, as a way of increasing the chances of crystallization needs to be re-evaluated after many antibody complexes have been crystallized and their structure determined. It is somewhat striking that among these, only a small number is a complex with a large protein antigen. The problem is that the effort of raising, cleaving and purifying an Fab is rewarded only by an extra chance of getting crystals; depending on the relative likelihood of crystallization of the complexed and uncomplexed protein. The example of the complex between HIV gp120, CD4 and an Fab fragment from a neutralizing antibody suggests that further complexation of an antigen-antibody complex with a third protein could, by increasing the number of possible combinations, improve the likelihood of crystallization. We propose the use of Ig-binding proteins as a way of extending the method from HIV gp120 to all proteins for which there are monoclonal antibodies. We discuss this technique, combinatorial complex crystallization (CCC), as part of a multi-component system for the enhancement of crystallization of macromolecular complexes. The method makes use of single Ig-binding domains from Staphylococcus aureus protein A (SpA), Peptostreptococcus magnus protein L (PpL) and the streptococcal protein G (SpG). The generality of the method depends on the ability of these domains to interact with a large repertoire of antibodies without affecting antigen binding. There is strong evidence to suggest that these Ig-binding domains bind outside the antigen-combining site of the antibody without perturbing antigen binding. It is clear from the crystal structure of the single SpG domain complexed with an Fab that the interaction involves mainly the immunoglobulin CH1 domain, a region not involved in antigen recognition. We have recently determined the structure of the complex between a human Fab and the domain D from SpA and found that steric hindrance is unlikely even for large

  20. Potential productivity benefits of float-zone versus Czochralski crystal growth

    NASA Technical Reports Server (NTRS)

    Abe, T.

    1985-01-01

    Efficient mass production of single-crystal silicon is necessary for the efficient silicon solar arrays needed in the coming decade. However, it is anticipated that there will be difficulty growing such volumes of crystals using conventional Czochralski (Cz) methods. While the productivity of single crystals might increase with a crystal diameter increase, there are two obstacles to the mass production of large diameter Czochralski crystals, the long production cycle due to slow growth rate and the high heat requirements of the furnaces. Also counterproductive would be the large resistivity gradient along the growth direction of the crystals due to impurity concentration. Comparison between Float zone (FZ) and Cz crystal growth on the basis of a crystal 150 mm in diameter is on an order of two to four times in favor of the FZ method. This advantage results from high growth rates and steady-state growth while maintaining a dislocation-free condition and impurity segregation.

  1. Origin of platy calcite crystals in hot-spring deposits in the Kenya Rift Valley

    SciTech Connect

    Jones, B.; Renault, R.W.

    1998-09-01

    Platy calcite crystals, which have their c axis parallel to their shortest length axis, are common components of travertine deposits found around some hot springs in the Kenya Rift Valley. They are composite crystals formed of numerous paper-thin subcrystals. Individual plates allowed to grow without obstruction develop a hexagonal motif. The Kenyan crystals typically form in hot (>75 C) waters that have a low Ca content (<10 mg/l), a high CO{sub 2} content, and a high rate of CO{sub 2} degassing. At Chemurkeu, aggregates of numerous small platy crystals collectively form lattice crystals that superficially resemble ray crystals. The walls of the lattice crystals are formed of large platy crystals that have their long and intermediate length axes aligned parallel to the plane of the long axis of the lattice crystal. Internally, the lattice crystals are formed of small platy calcite crystals arranged in a boxlike pattern that creates the appearance of a lattice when viewed in thin section. Lattice crystals are highly porous, with each pore being enclosed by platy crystals. At Lorusio, travertines are mainly formed of pseudodentrites that are constructed by numerous small platy crystals attached to a main stem which is a large platy crystal that commonly curves along its long axis. The pseudodentrites are the main construction blocks in ledges and lilypads that form in the vent pool and spring outflow channels, where the water is too hot for microbes other than hyperthermophiles. The platy calcite crystals in the Kenyan travertines are morphologically similar to platy calcite crystals that form as scale in pipes in the geothermal fields of New Zealand and hydrothermal angel wing calcite from the La Fe mine in Mexico. Comparison of the Kenyan and New Zealand crystals indicates that platy calcite crystals form from waters with a low Ca{sup 2+} content and a high CO{sub 3}/Ca ratio due to rapid rates of CO{sub 2} degassing.

  2. Shaped Crystal Growth

    NASA Astrophysics Data System (ADS)

    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

  3. Dispersion in photonic crystals

    NASA Astrophysics Data System (ADS)

    Witzens, Jeremy

    2005-11-01

    Investigations on the dispersive properties of photonic crystals, modified scattering in ring-resonators, monolithic integration of vertical-cavity surface-emitting lasers and advanced data processing techniques for the finite-difference time-domain method are presented. Photonic crystals are periodic mesoscopic arrays of scatterers that modify the propagation properties of electromagnetic waves in a similar way as "natural" crystals modify the properties of electrons in solid-state physics. In this thesis photonic crystals are implemented as planar photonic crystals, i.e., optically thin semiconductor films with periodic arrays of holes etched into them, with a hole-to-hole spacing of the order of the wavelength of light in the dielectric media. Photonic crystals can feature forbidden frequency ranges (the band-gaps) in which light cannot propagate. Even though most work on photonic crystals has focused on these band-gaps for application such as confinement and guiding of light, this thesis focuses on the allowed frequency regions (the photonic bands) and investigates how the propagation of light is modified by the crystal lattice. In particular the guiding of light in bulk photonic crystals in the absence of lattice defects (the self-collimation effect) and the angular steering of light in photonic crystals (the superprism effect) are investigated. The latter is used to design a planar lightwave circuit for frequency domain demultiplexion. Difficulties such as efficient insertion of light into the crystal are resolved and previously predicted limitations on the resolution are circumvented. The demultiplexer is also fabricated and characterized. Monolithic integration of vertical-cavity surface-emitting lasers by means of resonantly enhanced grating couplers is investigated. The grating coupler is designed to bend light through a ninety-degree angle and is characterized with the finite-difference time-domain method. The vertical-cavity surface-emitting lasers are

  4. Protein crystal growth in microgravity

    NASA Technical Reports Server (NTRS)

    Delucas, Lawrence J.; Smith, Craig D.; Smith, H. Wilson; Vijay-Kumar, Senadhi; Senadhi, Shobha E.; Ealick, Steven E.; Carter, Daniel C.; Snyder, Robert S.

    1989-01-01

    The crystals of most proteins or other biological macromolecules are poorly ordered and diffract to lower resolutions than those observed for most crystals of simple organic and inorganic compounds. Crystallization in the microgravity environment of space may improve crystal quality by eliminating convection effects near growing crystal surfaces. A series of 11 different protein crystal growth experiments was performed on U.S. Space Shuttle flight STS-26 in September 1988. The microgravity-grown crystals of gamma-interferon D1, porcine elastase, and isocitrate lyase are larger, display more uniform morphologies, and yield diffraction data to significantly higher resolutions than the best crystals of these proteins grown on earth.

  5. Crystal structures of the solute receptor GacH of Streptomyces glaucescens in complex with acarbose and an acarbose homolog: comparison with the acarbose-loaded maltose-binding protein of Salmonella typhimurium.

    PubMed

    Vahedi-Faridi, Ardeschir; Licht, Anke; Bulut, Haydar; Scheffel, Frank; Keller, Sandro; Wehmeier, Udo F; Saenger, Wolfram; Schneider, Erwin

    2010-04-02

    GacH is the solute binding protein (receptor) of the putative oligosaccharide ATP-binding cassette transporter GacFG, encoded in the acarbose biosynthetic gene cluster (gac) from Streptomyces glaucescens GLA.O. In the context of the proposed function of acarbose (acarviosyl-1,4-maltose) as a 'carbophor,' the transporter, in complex with a yet to be identified ATPase subunit, is supposed to mediate the uptake of longer acarbose homologs and acarbose for recycling purposes. Binding assays using isothermal titration calorimetry identified GacH as a maltose/maltodextrin-binding protein with a low affinity for acarbose but with considerable binding activity for its homolog, component 5C (acarviosyl-1,4-maltose-1,4-glucose-1,1-glucose). In contrast, the maltose-binding protein of Salmonella typhimurium (MalE) displays high-affinity acarbose binding. We determined the crystal structures of GacH in complex with acarbose, component 5C, and maltotetraose, as well as in unliganded form. As found for other solute receptors, the polypeptide chain of GacH is folded into two distinct domains (lobes) connected by a hinge, with the interface between the lobes forming the substrate-binding pocket. GacH does not specifically bind the acarviosyl group, but displays specificity for binding of the maltose moiety in the inner part of its binding pocket. The crystal structure of acarbose-loaded MalE showed that two glucose units of acarbose are bound at the same region and position as maltose. A comparative analysis revealed that in GacH, acarbose is buried deeper into the binding pocket than in MalE by exactly one glucose ring shift, resulting in a total of 18 hydrogen-bond interactions versus 21 hydrogen-bond interactions for MalE(acarbose). Since the substrate specificity of ATP-binding cassette import systems is determined by the cognate binding protein, our results provide the first biochemical and structural evidence for the proposed role of GacHFG in acarbose metabolism.

  6. 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.

    PubMed

    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 <400cm(-1), where 28 Raman-allowed lines and 20 FIR-allowed bands of both skeletal and intra-ligand character are expected, only few assignments based on symmetry considerations were possible. In order to increase the number of identifications, model calculations on the basis of density functional 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.

  7. An approach to engineer paracetamol crystals by antisolvent crystallization technique in presence of various additives for direct compression.

    PubMed

    Kaialy, Waseem; Larhrib, Hassan; Chikwanha, Brian; Shojaee, Saeed; Nokhodchi, Ali

    2014-04-10

    Paracetamol is a popular over-the-counter analgesic and a challenging model drug due to its poor technological and biopharmaceutical properties such as flowability, compressibility, compactibility and wettability. This work was aimed to alter the crystal habit of paracetamol from elongated to polyhedral-angular via particle engineering whilst maintaining the stable polymorphic form (form I: monoclinic form). The engineered paracetamol crystals obtained in the present investigation showed better technological and biopharmaceutical properties in comparison to the commercial paracetamol. Engineered paracetamol crystals were obtained using antisolvent crystallization technique in the presence of various concentrations (0.1, 0.5 and 1%, w/w) of additives, namely, polyvinyl alcohol (PVA), Avicel PH 102 (microcrystalline cellulose), Brij 58, methylcellulose (MC) and polyethylene glycol having different molecular weights (PEGs 1500, 6000 and 8000). Paracetamols crystallized in the presence of Avicel (or physically mixed with Avicel), Brij 58 and PEG 6000 demonstrated the best compactibility over a range of compaction pressures. Brij-crystallized paracetamol provided the fastest dissolution rate among all the paracetamol batches. Paracetamols crystallized in the presence of PVA or Avicel, or physically mixed with Avicel demonstrated a reduced degree of crystallinity in comparison to the other paracetamols. This study showed that the type, the grade and the concentration of additives could influence the physical stability such as flow, crystallinity and polymorphic transformation of paracetamol, the technological and biopharmaceutical properties of paracetamol. Stable polymorphic form of paracetamol with optimal tableting characteristics can be achieved through particle engineering.

  8. Quartz crystal growth

    DOEpatents

    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.

  9. Miscibility studies of two twist-bend nematic liquid crystal dimers with different average molecular curvatures. A comparison between experimental data and predictions of a Landau mean-field theory for the NTB-N phase transition.

    PubMed

    López, D O; Robles-Hernández, B; Salud, J; de la Fuente, M R; Sebastián, N; Diez-Berart, S; Jaen, X; Dunmur, D A; Luckhurst, G R

    2016-02-14

    We report a calorimetric study of a series of mixtures of two twist-bend liquid crystal dimers, the 1'',7''-bis(4-cyanobiphenyl)-4'-yl heptane (CB7CB) and 1''-(2',4-difluorobiphenyl-4'-yloxy)-9''-(4-cyanobiphenyl-4'-yloxy) nonane (FFO9OCB), the molecules of which have different effective molecular curvatures. High-resolution heat capacity measurements in the vicinity of the NTB-N phase transition for a selected number of binary mixtures clearly indicate a first order NTB-N phase transition for all the investigated mixtures, the strength of which decreases when the nematic range increases. Published theories predict a second order NTB-N phase transition, but we have developed a self-consistent mean field Landau model using two key order parameters: a symmetric and traceless tensor for the orientational order and a short-range vector field which is orthogonal to the helix axis and rotates around of the heliconical structure with an extremely short periodicity. The theory, in its simplified form, depends on two effective elastic constants and explains satisfactorily our heat capacity measurements and also predicts a first-order NTB-N phase transition. In addition, as a complementary source of experimental measurements, the splay (K1) and bend (K3) elastic constants in the conventional nematic phase for the pure compounds and some selected mixtures have been determined.

  10. Aluminum Nitride Crystal Growth

    DTIC Science & Technology

    1979-12-01

    increase the growth rate of AiN crystals from the vapor phase, and some new experiments to test this model conjecture are needed. if one’could operate...walls is much less severe,, and hence the crucible lifetime is about 88 times greater than for the -slycrystalline tungsten. In an effort to test this...added H2 to increase the growth rate is a better idea. One growth run, W253, Was made to test the single-crystal crucible method. The crystal from

  11. Analysis of Crystallization Kinetics

    NASA Technical Reports Server (NTRS)

    Kelton, Kenneth F.

    1997-01-01

    A realistic computer model for polymorphic crystallization (i.e., initial and final phases with identical compositions), which includes time-dependent nucleation and cluster-size-dependent growth rates, is developed and tested by fits to experimental data. Model calculations are used to assess the validity of two of the more common approaches for the analysis of crystallization data. The effects of particle size on transformation kinetics, important for the crystallization of many systems of limited dimension including thin films, fine powders, and nanoparticles, are examined.

  12. Crystallization on prestructured seeds.

    PubMed

    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.

  13. Crystals in light.

    PubMed

    Kahr, Bart; Freudenthal, John; Gunn, Erica

    2010-05-18

    We have made images of crystals illuminated with polarized light for almost two decades. Early on, we abandoned photosensitive chemicals in favor of digital electrophotometry with all of the attendant advantages of quantitative intensity data. Accurate intensities are a boon because they can be used to analytically discriminate small effects in the presence of larger ones. The change in the form of our data followed camera technology that transformed picture taking the world over. Ironically, exposures in early photographs were presumed to correlate simply with light intensity, raising the hope that photography would replace sensorial interpretation with mechanical objectivity and supplant the art of visual photometry. This was only true in part. Quantitative imaging accurate enough to render the separation of crystalloptical quantities had to await the invention of the solid-state camera. Many pioneers in crystal optics were also major figures in the early history of photography. We draw out the union of optical crystallography and photography because the tree that connects the inventors of photography is a structure unmatched for organizing our work during the past 20 years, not to mention that silver halide crystallites used in chemical photography are among the most consequential "crystals in light", underscoring our title. We emphasize crystals that have acquired optical properties such as linear birefringence, linear dichroism, circular birefringence, and circular dichroism, during growth from solution. Other crystalloptical effects were discovered that are unique to curiously dissymmetric crystals containing embedded oscillators. In the aggregate, dyed crystals constitute a generalization of single crystal matrix isolation. Simple crystals provided kinetic stability to include guests such as proteins or molecules in excited states. Molecular lifetimes were extended for the preparation of laser gain media and for the study of the photodynamics of single

  14. Swimming in a crystal.

    PubMed

    Brown, Aidan T; Vladescu, Ioana D; Dawson, Angela; Vissers, Teun; Schwarz-Linek, Jana; Lintuvuori, Juho S; Poon, Wilson C K

    2016-01-07

    We study catalytic Janus particles and Escherichia coli bacteria swimming in a two-dimensional colloidal crystal. The Janus particles orbit individual colloids and hop between colloids stochastically, with a hopping rate that varies inversely with fuel (hydrogen peroxide) concentration. At high fuel concentration, these orbits are stable for 100s of revolutions, and the orbital speed oscillates periodically as a result of hydrodynamic, and possibly also phoretic, interactions between the swimmer and the six neighbouring colloids. Motile E. coli bacteria behave very differently in the same colloidal crystal: their circular orbits on plain glass are rectified into long, straight runs, because the bacteria are unable to turn corners inside the crystal.

  15. Single crystals of chitosan.

    PubMed

    Cartier, N; Domard, A; Chanzy, H

    1990-10-01

    Lamellar single crystals of chitosan were prepared at 125 degrees C by adding ammonia to a low DP fraction of chitosan dissolved in water. The crystals gave sharp electron diffraction diagrams which could be indexed in an orthorhombic P2(1)2(1)2(1) unit cell with a = 8.07 A, b = 8.44 A, c = 10.34 A. The unit cell contained two anti-parallel chitosan chains and no water molecules. It was found that cellulose microfibrils from Valonia ventricosa could act as nuclei for inducing the crystallization of chitosan on cellulose. This produced a shish-kebab morphology.

  16. Molecules in crystals

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed

    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.

  18. Shaping Crystal-Crystal Phase Transitions

    NASA Astrophysics Data System (ADS)

    Du, Xiyu; van Anders, Greg; Dshemuchadse, Julia; Glotzer, Sharon

    Previous computational and experimental studies have shown self-assembled structure depends strongly on building block shape. New synthesis techniques have led to building blocks with reconfigurable shape and it has been demonstrated that building block reconfiguration can induce bulk structural reconfiguration. However, we do not understand systematically how this transition happens as a function of building block shape. Using a recently developed ``digital alchemy'' framework, we study the thermodynamics of shape-driven crystal-crystal transitions. We find examples of shape-driven bulk reconfiguration that are accompanied by first-order phase transitions, and bulk reconfiguration that occurs without any thermodynamic phase transition. Our results suggest that for well-chosen shapes and structures, there exist facile means of bulk reconfiguration, and that shape-driven bulk reconfiguration provides a viable mechanism for developing functional materials.

  19. Computer Modeling of Crystallization and Crystal Size distributions

    NASA Astrophysics Data System (ADS)

    Amenta, R. V.

    2002-05-01

    The crystal size distribution of an igneous rock has been shown to be related to the crystallization kinetics. In order to better understand crystallization processes, the nucleation and growth of crystals in a closed system is modeled computationally and graphically. Units of volume analogous to unit cells are systematically attached to stationary crystal nuclei. The number of volume units attached to each crystal per growth stage is proportional to the crystal size insuring that crystal dimensional growth rates are constant regardless of their size. The number of new crystal nuclei per total system volume that form in each growth stage increases exponentially Cumulative crystal size distributions (CCSD) are determined for various stages of crystallization (30 percent, 60 pct, etc) from a database generated by the computer model, and each distribution is fit to an exponential function of the same form. Simulation results show that CCSD functions appear to fit the data reasonably well (R-square) with the greatest misfit at 100 pct crystallization. The crystal size distribution at each pct crystallization can be obtained from the derivative of the respective CCSD function. The log form of each crystal size distribution (CSD) is a linear function with negative slope. Results show that the slopes of the CSD functions at pcts crystallization up to 90 pct are parallel, but the slope at 100 pct crystallization differs from the others although still in approximate alignment. We suggest that real crystallization of igneous rocks may show this pattern. In the early stages of crystallization crystals are far apart and CSD's are ideal as predicted by theory based on growth of crystals in a brine. At advanced stages of crystallization growth collision boundaries develop between crystals. As contiguity increases crystals become blocked and inactive because they can no longer grow. As crystallization approaches 100 pct a significant number of inactive crystals exist resulting in

  20. No warmup crystal oscillator

    NASA Technical Reports Server (NTRS)

    Phillips, D. H.

    1982-01-01

    During warmup, crystal oscillators often show a frequency offset as large as 1 part in 10 to the 5th power. If timing information is transferred to the oscillator and then the oscillator is allowed to warmup, a timing error greater than 1 millisecond will occur. For many applications, it is unsuitable to wait for the oscillator to warmup. For medium accuracy timing requirements where overall accuracies in the order of 1 millisecond are required, a no warmup crystal concept was developed. The concept utilizes two crystal oscillator, used sequentially to avoid using a crystal oscillator for timing much higher frequency accuracy once warmed up. The accuracy achieved with practical TCXOs at initial start over a range of temperatures is discussed. A second design utilizing two oven controlled oscillators is also discussed.

  1. Diffusion in Coulomb crystals

    SciTech Connect

    Hughto, J.; Schneider, A. S.; Horowitz, C. J.; Berry, D. K.

    2011-07-15

    Diffusion in Coulomb crystals can be important for the structure of neutron star crusts. We determine diffusion constants D from molecular dynamics simulations. We find that D for Coulomb crystals with relatively soft-core 1/r interactions may be larger than D for Lennard-Jones or other solids with harder-core interactions. Diffusion, for simulations of nearly perfect body-centered-cubic lattices, involves the exchange of ions in ringlike configurations. Here ions ''hop'' in unison without the formation of long lived vacancies. Diffusion, for imperfect crystals, involves the motion of defects. Finally, we find that diffusion, for an amorphous system rapidly quenched from Coulomb parameter {Gamma}=175 to Coulomb parameters up to {Gamma}=1750, is fast enough that the system starts to crystalize during long simulation runs. These results strongly suggest that Coulomb solids in cold white dwarf stars, and the crust of neutron stars, will be crystalline and not amorphous.

  2. Diffusion in Coulomb crystals.

    PubMed

    Hughto, J; Schneider, A S; Horowitz, C J; Berry, D K

    2011-07-01

    Diffusion in Coulomb crystals can be important for the structure of neutron star crusts. We determine diffusion constants D from molecular dynamics simulations. We find that D for Coulomb crystals with relatively soft-core 1/r interactions may be larger than D for Lennard-Jones or other solids with harder-core interactions. Diffusion, for simulations of nearly perfect body-centered-cubic lattices, involves the exchange of ions in ringlike configurations. Here ions "hop" in unison without the formation of long lived vacancies. Diffusion, for imperfect crystals, involves the motion of defects. Finally, we find that diffusion, for an amorphous system rapidly quenched from Coulomb parameter Γ=175 to Coulomb parameters up to Γ=1750, is fast enough that the system starts to crystalize during long simulation runs. These results strongly suggest that Coulomb solids in cold white dwarf stars, and the crust of neutron stars, will be crystalline and not amorphous.

  3. Crystal-Clear Technology.

    ERIC Educational Resources Information Center

    Ondris-Crawford, Renate J.; And Others

    1993-01-01

    Provides diagrams to aid in discussing polymer dispersed liquid crystal (PDLC) technology. Equipped with a knowledge of PDLC, teachers can provide students with insight on how the gap between basic science and technology is bridged. (ZWH)

  4. Crystallization behavior of anorthite

    NASA Technical Reports Server (NTRS)

    Klein, L.; Uhlmann, D. R.

    1974-01-01

    The growth rate of anorthite crystals from the melt is studied as a function of temperature with undercooling in the ranges 52-152 and 402-652 degrees C. The triclinic form is invariably observed as the crystallization product, growth is preferentially in the c direction, and the interface morphology is faceted. Significant growth rate anisotropy is indicated. The maximum growth rate of anorthite from the melt is higher than for anorthite-rich lunar compositions. Recent computer studies are combined with experimental data to estimate the heat of fusion of anorthite as 28000-45000 cal/mol; the corresponding range for entropy of fusion is (7.8-12)R (where R is the gas constant). The observations and kinetic data support Jackson's predictions concerning materials with large entropies of fusion and his suggestion that entropy of fusion is an important parameter for characterizing the crystal-liquid interface and the nature of the crystallization process.

  5. Crystallization of Silicon Ribbons

    NASA Technical Reports Server (NTRS)

    Leipold, M. H.

    1984-01-01

    Purity constraints for reasonable solar-cell efficiency require that silicon-ribbon growth for photovoltaics occur in a regime in which constitutional supercooling or other compositional effects on the crystallization front are not important. A major consideration in the fundamentals of crystallization is the removal of the latent heat of fusion. The direction of removal, compared with the growth direction, has a major influence on the crystallization rate and the development of localized stresses. The detailed shape of the crystallization front appears to have two forms: that required for dendritic-web growth, and that occurring in all others. After the removal of the latent heat of fusion, the thermal-mechanical behavior of all ribbons appears similar within the constraints of the exothermal gradient. The technological constraints in achieving the required thermal and mechanical conditions vary widely among the growth processes.

  6. Shaping Crystals using Electrophoresis

    NASA Astrophysics Data System (ADS)

    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.

  7. A new crystal form of a hyperthermophilic endocellulase

    SciTech Connect

    Kataoka, Misumi; Ishikawa, Kazuhiko

    2014-06-18

    The hyperthermostable endocellulase from P. furiosus was crystallized at pH 5.5. The new crystal form has symmetry consistent with space group C2 and exhibits a structure different from that of the protein crystallized at pH 9.0. The hyperthermophilic glycoside hydrolase family endocellulase 12 from the archaeon Pyrococcus furiosus (EGPf; Gene ID PF0854; EC 3.2.1.4) catalyzes the hydrolytic cleavage of the β-1,4-glucosidic linkage in β-glucan in lignocellulose biomass. A crystal of EGPf was previously prepared at pH 9.0 and its structure was determined at an atomic resolution of 1.07 Å. This article reports the crystallization of EGPf at the more physiologically relevant pH of 5.5. Structure determination showed that this new crystal form has the symmetry of space group C2. Two molecules of the enzyme are observed in the asymmetric unit. Crystal packing is weak at pH 5.5 owing to two flexible interfaces between symmetry-related molecules. Comparison of the EGPf structures obtained at pH 9.0 and pH 5.5 reveals a significant conformational difference at the active centre and in the surface loops. The interfaces in the vicinity of the flexible surface loops impact the quality of the EGPf crystal.

  8. Crystal Growth of Germanium-Silicon Alloys on the ISS

    NASA Technical Reports Server (NTRS)

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

    2015-01-01

    A series of Ge(1-x)Si(x) crystal growth experiments are planned to be conducted in the Low Gradient Furnace (LGF) onboard the International Space Station. The experiments are part of the investigation "Influence of Containment on the Growth of Silicon-Germanium" (ICESAGE). 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. This meniscus can exist over a much larger range of processing parameters in microgravity and the meniscus is more stable under microgravity conditions. The plans for the flight experiments will be described.

  9. A comparison study of aliphatic and aromatic structure directing agents influencing the crystal and electronic structures, and properties of iodoplumbate hybrids: water induced structure conversion and visible light photocatalytic properties.

    PubMed

    Liu, Guang-Ning; Shi, Jian-Ru; Han, Xiao-Jiang; Zhang, Xiao; Li, Ke; Li, Jie; Zhang, Tao; Liu, Qi-Sheng; Zhang, Zhen-Wei; Li, Cuncheng

    2015-07-28

    The introduction of the aliphatic amines en (ethylenediamine), aep (N-(2-aminoethyl)piperazine) and tepa (tetraethylenepentamine), and the aromatic species 2,2'-bipy (2,2'-bipyridine) and dpe (1,2-di(4-pyridyl)ethylene) as structure directing agents (SDAs) into inorganic iodoplumbates affords six hybrids, namely [(Hen)4(H2.5O)2I](PbI6) (1), Cs2n[Pb3I8(en)2]n (2), (H3tepa)n(PbI5)n (3), (H2aep)n(PbI4)n (4), (Et22,2'-bipy)n(Pb2I6)n (5) and (Et2dpe)n(Pb2I6)n (6). 1 contains a discrete octahedral (PbI6)(4-) anion generated under the direction of a novel co-template, [(Hen)4(H2.5O)2I](4+). 2 contains inorganic Cs(+) ions and a novel hybrid anionic layer [Pb3I8(en)2]n(2n-) that has never been encountered in iodoplumbate hybrids. 3 features a zigzag (PbI5)(3-) chain with the charge being compensated by a triprotonated tepa cation. 4 is composed of perovskite sheets of lead(ii) octahedra and aep cations that are generated from tepa via an unprecedented in situ ligand reaction. Both 5 and 6 have (Pb2I6)n(2n-) chains and represent the first example of introducing a 2,2'-bipy or dpe derivative cation in iodoplumbate hybrids, respectively. The comparative study reveals that aliphatic amines and aromatic species contribute differently to the crystal and electronic structures, and the properties of the hybrids. Importantly, 1-4 exhibit interesting water induced structure conversions, while 5 and 6 can be used as heterogeneous photocatalysts for dye wastewater treatment under visible light irradiation.

  10. SINGLE CRYSTAL NEUTRON DIFFRACTION.

    SciTech Connect

    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.

  11. Protein Crystal Quality Studies

    NASA Technical Reports Server (NTRS)

    1998-01-01

    Eddie Snell, Post-Doctoral Fellow the National Research Council (NRC) uses a reciprocal space mapping diffractometer for macromolecular crystal quality studies. The diffractometer is used in mapping the structure of macromolecules such as proteins to determine their structure and thus understand how they function with other proteins in the body. This is one of several analytical tools used on proteins crystallized on Earth and in space experiments. Photo credit: NASA/Marshall Space Flight Center (MSFC)

  12. Macromolecular Crystal Quality

    NASA Technical Reports Server (NTRS)

    Snell, Edward H.; Borgstahl, Gloria E. O.; Bellamy, Henry D.; Curreri, Peter A. (Technical Monitor)

    2001-01-01

    There are many ways of judging a good crystal. Which we use depends on the qualities we seek. For gemstones size, clarity and impurity levels (color) are paramount. For the semiconductor industry purity is probably the most important quality. For the structural crystallographer the primary desideratum is the somewhat more subtle concept of internal order. In this chapter we discuss the effect of internal order (or the lack of it) on the crystal's diffraction properties.

  13. Liquid Crystal Airborne Display

    DTIC Science & Technology

    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

  14. Crystal growth of drug materials by spherical crystallization

    NASA Astrophysics Data System (ADS)

    Szabó-Révész, P.; Hasznos-Nezdei, M.; Farkas, B.; Göcző, H.; Pintye-Hódi, K.; Erős, I.

    2002-04-01

    One of the crystal growth processes is the production of crystal agglomerates by spherical crystallization. Agglomerates of drug materials were developed by means of non-typical (magnesium aspartate) and typical (acetylsalicylic acid) spherical crystallization techniques. The growth of particle size and the spherical form of the agglomerates resulted in formation of products with good bulk density, flow, compactibility and cohesivity properties. The crystal agglomerates were developed for direct capsule-filling and tablet-making.

  15. Physical properties of BeAl6O10 single crystals

    NASA Astrophysics Data System (ADS)

    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.

  16. Engineering Crystal Morphology

    NASA Astrophysics Data System (ADS)

    Dandekar, Preshit; Kuvadia, Zubin B.; Doherty, Michael F.

    2013-07-01

    Crystallization is an important separation and particle formation technique in the manufacture of high-value-added products. During crystallization, many physicochemical characteristics of the substance are established. Such characteristics include crystal polymorph, shape and size, chemical purity and stability, reactivity, and electrical and magnetic properties. However, control over the physical form of crystalline materials has remained poor, due mainly to an inadequate understanding of the basic growth and dissolution mechanisms, as well as of the influence of impurities, additives, and solvents on the growth rate of individual crystal faces. Crystal growth is a surface-controlled phenomenon in which solute molecules are incorporated into surface lattice sites to yield the bulk long-range order that characterizes crystalline materials. In this article, we describe some recent advances in crystal morphology engineering, with a special focus on a new mechanistic model for spiral growth. These mechanistic ideas are simple enough that they can be made to work and accurate enough that they are useful.

  17. Phononic crystal diffraction gratings

    NASA Astrophysics Data System (ADS)

    Moiseyenko, Rayisa P.; Herbison, Sarah; Declercq, Nico F.; Laude, Vincent

    2012-02-01

    When a phononic crystal is interrogated by an external source of acoustic waves, there is necessarily a phenomenon of diffraction occurring on the external enclosing surfaces. Indeed, these external surfaces are periodic and the resulting acoustic diffraction grating has a periodicity that depends on the orientation of the phononic crystal. This work presents a combined experimental and theoretical study on the diffraction of bulk ultrasonic waves on the external surfaces of a 2D phononic crystal that consists of a triangular lattice of steel rods in a water matrix. The results of transmission experiments are compared with theoretical band structures obtained with the finite-element method. Angular spectrograms (showing frequency as a function of angle) determined from diffraction experiments are then compared with finite-element simulations of diffraction occurring on the surfaces of the crystal. The experimental results show that the diffraction that occurs on its external surfaces is highly frequency-dependent and has a definite relation with the Bloch modes of the phononic crystal. In particular, a strong influence of the presence of bandgaps and deaf bands on the diffraction efficiency is found. This observation opens perspectives for the design of efficient phononic crystal diffraction gratings.

  18. Photonic crystal sensors based on porous silicon.

    PubMed

    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.

  19. 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.

    PubMed

    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.

  20. Synthesis, crystal structure, and magnetic properties of Li3Mg2OsO6, a geometrically frustrated osmium(V) oxide with an ordered rock salt structure: comparison with isostructural Li3Mg2RuO6.

    PubMed

    Nguyen, Phuong-Hieu T; Ramezanipour, Farshid; Greedan, John E; Cranswick, Lachlan M D; Derakhshan, Shahab

    2012-11-05

    The novel osmium-based oxide Li(3)Mg(2)OsO(6) was synthesized in polycrystalline form by reducing Li(5)OsO(6) by osmium metal and osmium(IV) oxide in the presence of stoichiometric amounts of magnesium oxide. The crystal structure was refined using powder X-ray diffraction data in the orthorhombic Fddd space group with a = 5.88982(5) Å, b = 8.46873(6) Å, and c = 17.6825(2) Å. This compound is isostructural and isoelectronic with the ruthenium-based system Li(3)Mg(2)RuO(6). The magnetic ion sublattice Os(5+) (S = 3/2) consists of chains of interconnected corner- and edge-shared triangles, which brings about the potential for geometric magnetic frustration. The Curie-Weiss law holds over the range 80-300 K with C = 1.42(3) emu·K/mol [μ(eff) = 3.37(2) μ(B)] and θ(C) = -105.8(2) K. Below 80 K, there are three anomalies at 75, 30, and 8 K. Those at 75 and 30 K are suggestive of short-range antiferromagnetic correlations, while that at 8 K is a somewhat sharper maximum showing a zero-field-cooled/field-cooled divergence suggestive of perhaps spin freezing. The absence of magnetic Bragg peaks at 3.9 K in the neutron diffraction pattern supports this characterization, as does the absence of a sharp peak in the heat capacity, which instead shows only a very broad maximum at ∼12 K. A frustration index of f = 106/8 = 13 indicates a high degree of frustration. The magnetic properties of the osmium phase differ markedly from those of the isostructural ruthenium material, which shows long-range antiferromagnetic order below 17 K, f = 6, and no unusual features at higher temperatures. Estimates of the magnetic exchange interactions at the level of spin-dimer analysis for both the ruthenium and osmium materials support a more frustrated picture for the latter. Errors in the calculation and assignment of the exchange pathways in the previous report on Li(3)Mg(2)RuO(6) are identified and corrected.

  1. Crystal Structures of Sialyltransferase from Photobacterium damselae

    PubMed Central

    Huynh, Nhung; Li, Yanhong; Yu, Hai; Huang, Shengshu; Lau, Kam; Chen, Xi; Fisher, Andrew J.

    2014-01-01

    Sialyltransferase structures fall into either GT-A or GT-B glycosyltransferase fold. Some sialyltransferases from the Photobacterium genus have been shown to contain an additional N-terminal immunoglobulin (Ig)-like domain. Photobacterium damselae α2–6-sialyltransferase has been used efficiently in enzymatic and chemoenzymatic synthesis of α2–6-linked sialosides. Here we report three crystal structures of this enzyme. Two structures with and without a donor substrate analogue CMP-3F(a)Neu5Ac contain an immunoglobulin (Ig)-like domain and adopt the GT-B sialyltransferase fold. The binary structure reveals a non-productive pre-Michaelis complex, which are caused by crystal lattice contacts that prevent the large conformational changes. The third structure lacks the Ig-domain. Comparison of the three structures reveals small inherent flexibility between the two Rossmann-like domains of the GT-B fold. PMID:25451227

  2. Silicon heterojunction solar cell and crystallization of amorphous silicon

    NASA Astrophysics Data System (ADS)

    Lu, Meijun

    they use less materials resulting in lower cost. Polycrystalline silicon (poly-Si) is one promising thin-film material. It has the potential advantages to not only retain the performance and stability of c-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.

  3. Ionic diffusion mastering using crystal-chemistry parameters: tau-Cu{sub 1/2}Ag{sub 1/2}V{sub 2}O{sub 5} structure determination and comparison with refined delta-Ag{sub x}V{sub 2}O{sub 5} and epsilon-Cu{sub x}V{sub 2}O{sub 5} ones

    SciTech Connect

    Rozier, P.; Dolle, M.; Galy, J.

    2009-06-15

    tau-Ag{sub 1/2}Cu{sub 1/2}V{sub 2}O{sub 5} compound crystallises in the monoclinic system space group C2/m with cell parameters a=11.757(4) A, b=3.6942(5) A, c=9.463(2) A, and beta=114.62(2){sup o}. The structure is build up with V{sub 4}O{sub 10} D4 double layer. The silver and copper ions are located in two different oxygenated tunnels. Examination of electronic density maps shows that while the silver ions are located in defined crystallographic sites, the copper ones are fully delocalised over the whole tunnel. Comparison with delta-Ag{sub x}V{sub 2}O{sub 5} and epsilon-Cu{sub x}V{sub 2}O{sub 5} refined structure allows to define crystal chemistry parameters governing the ionic delocalisation and give clues to predict from structural consideration the expected electrical behaviour with the aim to make possible a structural design to enhance guest species reactivity. - Graphical abstract: The role of nature and amount of guest species on their respective localisation Evidence for full delocalisation of copper ions and diffusion pathways visualisation Display Omitted

  4. Electrochemical deposition of silver crystals aboard Skylab 4

    NASA Technical Reports Server (NTRS)

    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

  5. Crystal Growth Control

    NASA Technical Reports Server (NTRS)

    Duval, Walter M. B.; Batur, Celal; Bennett, Robert J.

    1997-01-01

    We present an innovative design of a vertical transparent multizone furnace which can operate in the temperature range of 25 C to 750 C and deliver thermal gradients of 2 C/cm to 45 C/cm for the commercial applications to crystal growth. The operation of the eight zone furnace is based on a self-tuning temperature control system with a DC power supply for optimal thermal stability. We show that the desired thermal profile over the entire length of the furnace consists of a functional combination of the fundamental thermal profiles for each individual zone obtained by setting the set-point temperature for that zone. The self-tuning system accounts for the zone to zone thermal interactions. The control system operates such that the thermal profile is maintained under thermal load, thus boundary conditions on crystal growth ampoules can be predetermined prior to crystal growth. Temperature profiles for the growth of crystals via directional solidification, vapor transport techniques, and multiple gradient applications are shown to be easily implemented. The unique feature of its transparency and ease of programming thermal profiles make the furnace useful for scientific and commercial applications for the determination of process parameters to optimize crystal growth conditions.

  6. Introduction to protein crystallization

    PubMed Central

    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. PMID:24419610

  7. Crystal Ball Functional Model

    NASA Astrophysics Data System (ADS)

    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.

  8. Photocatalytic and photoelectrochemical hydrogen production on strontium titanate single crystals

    SciTech Connect

    Wagner, F.T.; Somorjai, G.A.

    1980-01-01

    Sustained photogeneration of hydrogen was observed on metal-free as well as on platinized SrTiO/sub 3/ single crystals illuminated in aqueous alkaline electrolytes or in the presence of electrolyte films. Hydrogen evolution rates increased with electrolyte hydroxide concentration, most strongly at hydroxide concentrations above 5 N. Both stoichiometric and prereduced metal-free crystals were active for hydrogen photoproduction. No activity was observed from crystals in neutral or acidic solutions or in water vapor in the absence of a crust of a basic deliquescent compounds. Metal-free crystals appear to evolve hydrogen via a photocatalytic mechanism in which all chemistry occurs at the illuminated surface. The results allow direct comparison of the photocatalytic and photoelectrochemical processes and have implications for the development of heterogeneous photocatalysis at the gas-solid interface.

  9. Surface acoustic-wave piezoelectric crystal aerosol mass microbalance

    NASA Astrophysics Data System (ADS)

    Bowers, W. D.; Chuan, R. L.

    1989-07-01

    The development of a particulate mass-sensing instrument based on a quartz-crystal microbalance and enhanced with the new surface acoustic-wave (SAW) technology is reported. Mass sensitivity comparisons of a 158-MHz SAW piezoelectric microbalance and a conventional 10-MHz quartz-crystal microbalance show that the SAW crystal is 266 times more sensitive, in good agreement with the theoretical value of 250. The frequency stability of a single SAW resonator is 6 parts in 10 to the 8th over 1 min. The response to temperature changes is found to be very linear over the range +30 to -30 C. A strong response to 15 ppm SO2 has been demonstrated on a chemically coated SAW crystal.

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

    NASA Astrophysics Data System (ADS)

    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.

  11. Protein Crystals and their Growth

    NASA Technical Reports Server (NTRS)

    Chernov, A. A.

    2004-01-01

    Recent results on binding between protein molecules in crystal lattice, crystal-solution surface energy, elastic properties and strength and spontaneous crystal cracking are reviewed and discussed in the first half of this paper (Sea 2-4). In the second par&, some basic approaches to solubility of proteins are followed by overview on crystal nucleation and growth (Sec 5). It is argued that variability of mixing in batch crystallization may be a source for scattering of crystal number ultimately appearing in the batch. Frequency at which new molecules join crystal lattice is measured by kinetic coefficient and related to the observable crystal growth rate. Numerical criteria to discriminate diffusion and kinetic limited growth are discussed on this basis in Sec 7. In Sec 8, creation of defects is discussed with the emphasis on the role of impurities and convection on macromolecular crystal I;erfection.

  12. Flexible ferroelectric organic crystals

    PubMed Central

    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

  13. Photonic Crystal Microchip Laser

    NASA Astrophysics Data System (ADS)

    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.

  14. Photonic Crystal Microchip Laser.

    PubMed

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

    2016-09-29

    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 M(2) 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.

  15. Flexible ferroelectric organic crystals

    NASA Astrophysics Data System (ADS)

    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.

  16. Photonic Crystal Microchip Laser

    PubMed Central

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

    2016-01-01

    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. PMID:27683066

  17. Frequency doubling crystals

    DOEpatents

    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.

  18. Microgravity crystal growth

    NASA Technical Reports Server (NTRS)

    2001-01-01

    Advanced finite element models are used to study three-dimensional, time-dependent flow and segregation in crystal growth systems. In this image of a prototypical model for melt and crystal growth, pathlines at one instant in time are shown for the flow of heated liquid silicon in a cylindrical container. The container is subjected to g-jitter disturbances along the vertical axis. A transverse magnetic field is applied to control them. Such computations are extremely powerful for understanding melt growth in microgravity where g-jitter drives buoyant flows. The simulation is part of the Theoretical Analysis of 3D, Transient Convection and Segregation in Microgravity Bridgman Crystal Growth investigation by Dr. Jeffrey J. Derby of the University of Mirnesota, Minneapolis.

  19. FRACTIONAL CRYSTALLIZATION FEED ENVELOPE

    SciTech Connect

    HERTING DL

    2008-03-19

    Laboratory work was completed on a set of evaporation tests designed to establish a feed envelope for the fractional crystallization process. The feed envelope defines chemical concentration limits within which the process can be operated successfully. All 38 runs in the half-factorial design matrix were completed successfully, based on the qualitative definition of success. There is no feed composition likely to be derived from saltcake dissolution that would cause the fractional crystallization process to not meet acceptable performance requirements. However, some compositions clearly would provide more successful operation than other compositions.

  20. Protein Crystal Malic Enzyme

    NASA Technical Reports Server (NTRS)

    1992-01-01

    Malic Enzyme is a target protein for drug design because it is a key protein in the life cycle of intestinal parasites. After 2 years of effort on Earth, investigators were unable to produce any crystals that were of high enough quality and for this reason the structure of this important protein could not be determined. Crystals obtained from one STS-50 were of superior quality allowing the structure to be determined. This is just one example why access to space is so vital for these studies. Principal Investigator is Larry DeLucas.

  1. Protein Crystal Quality Studies

    NASA Technical Reports Server (NTRS)

    1998-01-01

    Eddie Snell (standing), Post-Doctoral Fellow the National Research Council (NRC),and Marc Pusey of Marshall Space Flight Center (MSFC) use a reciprocal space mapping diffractometer for marcromolecular crystal quality studies. The diffractometer is used in mapping the structure of marcromolecules such as proteins to determine their structure and thus understand how they function with other proteins in the body. This is one of several analytical tools used on proteins crystalized on Earth and in space experiments. Photo credit: NASA/Marshall Space Flight Center (MSFC)

  2. Protein crystal quality in diffusive environments and its evaluation

    NASA Astrophysics Data System (ADS)

    Lopez-Jaramillo, F. J.; Otálora, F.; Gavira, J. A.

    2003-01-01

    We have analyzed the crystal quality along a capillary by a precise protocol that comprises the study of tetragonal lysozyme cylindrical crystals that fill the capillary diameter (i.e. rods), the careful definition of the diffraction parameters and the use of a single software for the data reduction in order to avoid any bias in the comparison of the quality of different data sets. Our results cannot be explained on the basis of the different redundancy of the data sets and they demonstrate that the gel acupuncture method promotes a gradient of supersaturation along the capillary that yields in the same experiment crystals of increasing quality as a function of the position. However, despite being single crystals, rods have regions that show different crystal quality because they grew at different supersaturations. Our data are in agreement with the existence of a relation between length of the c-axis and crystal quality reported by other groups, but a deeper analysis of the cell parameters reveals the existence of a significant linear relation ( R=0.87) with the c/ a-axis ratio. This result points to the hypothesis of an ideal unit cell that yields the best crystals in terms of I/ σ( I).

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

    NASA Astrophysics Data System (ADS)

    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.

  4. High Pressure Crystal Chemistry of Hydrous Ringwoodite

    NASA Astrophysics Data System (ADS)

    Holl, C. M.; Smyth, J. R.; Frost, D. J.; Jacobsen, S. D.

    2002-12-01

    Single crystals of hydrous Fo90 ringwoodite up to 800 μm in diameter have been synthesized in a multi-anvil press at 1400°C and 20 GPa. The crystals are deep blue in color and contain approximately 0.8 percent H2O by weight as measured by IR spectroscopy. The unit cell parameter of this material has been refined by single-crystal X-ray diffraction at 15 different pressures up to 3.8 GPa. Pressure was determined by refinement of the until cell volume of a standard quartz crystal. Preliminary values for the bulk modulus give a K0 = 172 +/- 9 GPa and K' = 5.1 +/- 1.6 over the range studied. The crystal structure of this material has been refined at six pressures up to 3.8 GPa. Refinements were obtained from an average of 13 unique data with values of Rf < 5%. Preliminary estimates of the polyhedral compressibilities are 1.0x10-2 GPa-1 (K = 100 GPa) for MgVI and 6.3x10-3 GPa-1 (K = 160 GPa) for SiIV. Comparison of the present data with previous results shows a systematic decrease in the bulk modulus of ringwoodite with H content. This decrease is larger than the effect of temperature within the allowable ranges of each so that an increase in H2O content of one percent would have an effect on the bulk modulus equivalent to raising the temperature by 500°C.

  5. Dynamically controlled crystallization method and apparatus and crystals obtained thereby

    NASA Technical Reports Server (NTRS)

    Arnowitz, Leonard (Inventor); Steinberg, Emanuel (Inventor)

    1999-01-01

    A method and apparatus for dynamically controlling the crystallization of proteins including a crystallization chamber or chambers for holding a protein in a salt solution, one or more salt solution chambers, two communication passages respectively coupling the crystallization chamber with each of the salt solution chambers, and transfer mechanisms configured to respectively transfer salt solution between each of the salt solution chambers and the crystallization chamber. The transfer mechanisms are interlocked to maintain the volume of salt solution in the crystallization chamber substantially constant. Salt solution of different concentrations is transferred into and out of the crystallization chamber to adjust the salt concentration in the crystallization chamber to achieve precise control of the crystallization process.

  6. Functionalizing Designer DNA Crystals

    NASA Astrophysics Data System (ADS)

    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

  7. Exotic crystal superstructures of colloidal crystals in confinement.

    PubMed

    Fontecha, Ana Barreira; Schöpe, Hans Joachim

    2008-06-01

    Colloidal model systems have been used for over three decades for investigating liquids, crystals, and glasses. Colloidal crystal superstructures have been observed in binary systems of repulsive spheres as well as oppositely charged sphere systems showing structures well known from atomic solids. In this work we study the structural transition of colloidal crystals under confinement. In addition to the known sequence of crystalline structures, crystal superstructures with dodecagonal and hexagonal symmetry are observed in one component systems. These structures have no atomic counterpart.

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

    DTIC Science & Technology

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

  9. DIFFRACTION FROM MODEL CRYSTALS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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...

  10. Crystal forms of naproxen.

    PubMed

    Song, Jung-Soon; Sohn, Young-Taek

    2011-01-01

    The objective of this work was to investigate the existence of polymorphs and pseudopolymorphs of naproxen and the transformation of crystal forms. Four crystal forms of naproxen have been isolated by recrystallization and characterized by differential scanning calorimetry, powder X-ray diffractometry and thermogravimetric analysis. The differential scanning calorimetry and powder X-ray diffractometry patterns of the four crystal forms were different respectively. In the dissolution studies in pH 6.8 ± 0.05 buffer equilibrated at 37 ± 0.5°C, the solubility of four crystal forms was similar (within the error range). After storage of 1 month at 0% RH (silica gel, 20°C), 52% RH (saturated solution of Na(2)Cr(2)O(7.2)H(2)O/20°C) and 95% RH (saturated solution of Na(2)HPO(4)/20°C), Form 2 and Form 4 were transformed to Form 1, but Form 3 and Form 1 were not transformed and they were shown to have a good physical stability at room temperature for 1 month.

  11. Pyrrolidinium ionic liquid crystals.

    PubMed

    Goossens, Karel; Lava, Kathleen; Nockemann, Peter; Van Hecke, Kristof; Van Meervelt, Luc; Driesen, Kris; Görller-Walrand, Christiane; Binnemans, Koen; Cardinaels, Thomas

    2009-01-01

    N-alkyl-N-methylpyrrolidinium cations have been used for the design of ionic liquid crystals, including a new type of uranium-containing metallomesogen. Pyrrolidinium salts with bromide, bis(trifluoromethylsulfonyl)imide, tetrafluoroborate, hexafluorophosphate, thiocyanate, tetrakis(2- thenoyltrifluoroacetonato)europate(III) and tetrabromouranyl counteranions were prepared. For the bromide salts and tetrabromouranyl compounds, the chain length of the alkyl group C(n)H(2n+1) was varied from eight to twenty carbon atoms (n = 8, 10-20). The compounds show rich mesomorphic behaviour: highly ordered smectic phases (the crystal smectic E phase and the uncommon crystal smectic T phase), smectic A phases, and hexagonal columnar phases were observed, depending on chain length and anion. This work gives better insight into the nature and formation of the crystal smectic T phase, and the molecular requirements for the appearance of this highly ordered phase. This uncommon tetragonal mesophase is thoroughly discussed on the basis of detailed powder X-ray diffraction experiments and in relation to the existing literature. Structural models are proposed for self-assembly of the molecules within the smectic layers. In addition, the photophysical properties of the compounds containing a metal complex anion were investigated. For the uranium-containing mesogens, luminescence can be induced by dissolving them in an ionic liquid matrix. The europium-containing compound shows intense red photoluminescence with high colour purity.

  12. Laser schlieren crystal monitor

    NASA Technical Reports Server (NTRS)

    Owen, Robert B. (Inventor); Johnston, Mary H. (Inventor)

    1987-01-01

    A system and method for monitoring the state of a crystal which is suspended in a solution is described which includes providing a light source for emitting a beam of light along an optical axis. A collimating lens is arranged along the optical axis for collimating the emitted beam to provide a first collimated light beam consisting of parallel light rays. By passing the first collimated light beam through a transparent container, a number of the parallel light rays are deflected off the surfaces of said crystal being monitored according to the refractive index gradient to provide a deflected beam of deflected light rays. A focusing lens is arranged along optical axis for focusing the deflected rays towards a desired focal point. A knife edge is arranged in a predetermined orientation at the focal point; and a screen is provided. A portion of the deflected beam is blocked with the knife edge to project only a portion of the deflected beam. A band is created at one edge of the image of the crystal which indicates the state of change of the surface of the crystal being monitored.

  13. Ferroelectric liquid crystal display

    NASA Technical Reports Server (NTRS)

    York, Paul K. (Inventor)

    1977-01-01

    A ferroelectric liquid crystal display device employs capacitance spoiling layers to minimize unneeded capacitances created by crossovers of X and Y address lines and to accurately define desired capacitances. The spoiler layers comprise low dielectric constant layers which space electrodes from the ferroelectric at crossover points where capacitance is not needed for device operation.

  14. The Crystal Set

    ERIC Educational Resources Information Center

    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…

  15. Poet Lake Crystal Approval

    EPA Pesticide Factsheets

    This September 19, 2016 letter from EPA approves the petition from Poet Biorefining-Lake Crystal, regarding non-grandfathered ethanol produced through a dry mill process, qualifying under the Clean Air Act for renewable fuel (D-code 6) RINs under the RFS

  16. Crystal Ball Replica

    NASA Astrophysics Data System (ADS)

    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. Controlling Chirality of Entropic Crystals.

    PubMed

    Damasceno, Pablo F; Karas, Andrew S; Schultz, Benjamin A; Engel, Michael; Glotzer, Sharon C

    2015-10-09

    Colloidal crystal structures with complexity and diversity rivaling atomic and molecular crystals have been predicted and obtained for hard particles by entropy maximization. However, thus far homochiral colloidal crystals, which are candidates for photonic metamaterials, are absent. Using Monte Carlo simulations we show that chiral polyhedra exhibiting weak directional entropic forces self-assemble either an achiral crystal or a chiral crystal with limited control over the crystal handedness. Building blocks with stronger faceting exhibit higher selectivity and assemble a chiral crystal with handedness uniquely determined by the particle chirality. Tuning the strength of directional entropic forces by means of particle rounding or the use of depletants allows for reconfiguration between achiral and homochiral crystals. We rationalize our findings by quantifying the chirality strength of each particle, both from particle geometry and potential of mean force and torque diagrams.

  18. Protein crystal growth in microgravity

    NASA Technical Reports Server (NTRS)

    Rosenblum, William M.; Delucas, Lawrence J.; Wilson, William W.

    1989-01-01

    Major advances have been made in several of the experimental aspects of protein crystallography, leaving protein crystallization as one of the few remaining bottlenecks. As a result, it has become important that the science of protein crystal growth is better understood and that improved methods for protein crystallization are developed. Preliminary experiments with both small molecules and proteins indicate that microgravity may beneficially affect crystal growth. For this reason, a series of protein crystal growth experiments using the Space Shuttle was initiated. The preliminary space experiments were used to evolve prototype hardware that will form the basis for a more advanced system that can be used to evaluate effects of gravity on protein crystal growth. Various optical techniques are being utilized to monitor the crystal growth process from the incipient or nucleation stage and throughout the growth phase. The eventual goal of these studies is to develop a system which utilizes optical monitoring for dynamic control of the crystallization process.

  19. Dichroism in Helicoidal Crystals.

    PubMed

    Cui, Xiaoyan; Nichols, Shane M; Arteaga, Oriol; Freudenthal, John; Paula, Froilanny; Shtukenberg, Alexander G; Kahr, Bart

    2016-09-21

    Accounting for the interactions of light with heterogeneous, anisotropic, absorbing, optically active media is part of the characterization of complex, transparent materials. Stained biological structures in thin tissue sections share many of these features, but systematic optical analyses beyond the employ of the simple petrographic microscopes have not be established. Here, this accounting is made for polycrystalline, spherulitic bundles of twisted d-mannitol lamellae grown from melts containing light-absorbing molecules. It has long been known that a significant percentage of molecular crystals readily grow as helicoidal ribbons with mesoscale pitches, but a general appreciation of the commonality of these non-classical crystal forms has been lost. Helicoidal crystal twisting was typically assayed by analyzing refractivity modulation in the petrographic microscope. However, by growing twisted crystals from melts in the presence of dissolved, light-absorbing molecules, crystal twisting can be assayed by analyzing the dichroism, both linear and circular. The term "helicoidal dichroism" is used here to describe the optical consequences of anisotropic absorbers precessing around radii of twisted crystalline fibrils or lamellae. d-Mannitol twists in two polymorphic forms, α and δ. The two polymorphs, when grown from supercooled melts in the presence of a variety of histochemical stains and textile dyes, are strongly dichroic in linearly polarized white light. The bis-azo dye Chicago sky blue is modeled because it is most absorbing when parallel and perpendicular to the radial axes in the respective spherulitic polymorphs. Optical properties were measured using Mueller matrix imaging polarimetry and simulated by taking into account the microstructure of the lamellae. The optical analysis of the dyed, patterned polycrystals clarifies aspects of the mesostructure that can be difficult to extract from bundles of tightly packed fibrils.

  20. Study of the growth atmosphere effect on optical and scintillation characteristics of large CsI(TI) crystals

    NASA Astrophysics Data System (ADS)

    Panova, A. N.; Goriletsky, V. I.; Grinyova, T. B.; Shakhova, K. V.; Vinograd, E. L.

    1999-03-01

    In contrast to the traditional growth method of large scintillation alkali halide crystals - in an inert atmosphere, CsI(TI) crystals have been grown in CO 2 atmosphere favoring changes of their impurity composition. Absorption and scintillation characteristics of crystals obtained have been studied in comparison to those grown in the inert gas medium. Effect of different radiation doses on variations in optical and scintillation characteristics has been studied for CsI(TI) crystals grown by various techniques. CsI(TI) crystals grown in CO 2 atmosphere are found to exhibit a higher radiation resistance and a faster restoration of their basic characteristics.

  1. Studies of Cubic Ice Crystals

    DTIC Science & Technology

    1989-12-11

    the nitrate ion concentration in the ice. We hypothesize that Br- was oxidized to bromine (Br2), hypobromous acid (HOBr), or bromic acid (HBr03). The...Crystals grown from solutions of ammonium carbonate at -16°C 35 10 Crystals grown from solutions of sulfuric acid at -16°C 36 11 Ice crystal aspect ratios...elaborate crystals. When we compare this with the results of Workman and Reynolds for acid solutions, which all yielded negligible freezing potentials, we

  2. Results of the TTF-TCNQ and the calcium carbonate crystallization on the Long Duration Exposure Facility

    NASA Technical Reports Server (NTRS)

    Nielsen, Kjeld Flemming; Lind, M. David

    1992-01-01

    Experiment A0139A on the Long Duration Exposure Facility (LDEF) carried four large containers into orbit five years with crystal growth solutions for lead sulfide, calcium carbonate, and TTF-TCNQ. Although temperature data was lost, the experimental program had been working since the valves in all containers had been opened. All four experiments produced crystals of varying quality. The calcium carbonate crystals had the best appearance. The TTF-TCNQ crystals were packed together near the valve openings of the container. When taken apart, the single crystals showed some unusual morphological properties. X ray investigations as well as conductivity measurements on long duration space grown TTF-TCNQ crystals will be presented. Comparisons will be made with our previous space solution growth experiments. The TTF-TCNQ crystals are no longer of the highest interest, so this activity has been terminated in favor of calcium carbonate and calcium phosphate crystallizations.

  3. Direct flow crystal growth system

    DOEpatents

    Montgomery, Kenneth E.; Milanovich, Fred P.

    1992-01-01

    A crystal is grown in a constantly filtered solution which is flowed directly into the growing face of a crystal. In a continuous flow system, solution at its saturation temperature is removed from a crystal growth tank, heated above its saturation temperature, filtered, cooled back to its saturation temperature, and returned to the tank.

  4. Growing Crystals for Infrared Detectors

    NASA Technical Reports Server (NTRS)

    Lehoczky, S. L.; Szofran, F. R.

    1984-01-01

    Unidirectional solidification yields bulk crystals with compositional homogeneity. Unidirectionaly crystal-growth furnace assembly travels vertically so crystal grows upward from bottom tapered end of ampoule. Separately controlled furnaces used for hot (upper) and cold (lower) zones. New process produces ingots with radial compositional homogeneity suitable for fabricating infrared detectors.

  5. Physical vapor transport crystal growth

    NASA Technical Reports Server (NTRS)

    Yoel, Dave W.; Anderson, Elmer; Wu, Maw-Kuen; Cheng, H. Y.

    1987-01-01

    The goals of this research are two-fold: to study effective means of growing ZnSe crystals of good optical quality and to determine the advantages of growing such crystals in microgravity. As of this date the optimal conditions for crystal growth have not been determined. However, successful growth runs were made in two furnances and the results are given.

  6. Chiral Crystallization of Ethylenediamine Sulfate

    ERIC Educational Resources Information Center

    Koby, Lawrence; Ningappa, Jyothi B.; Dakesssian, Maria; Cuccia, Louis A.

    2005-01-01

    The optimal conditions for the crystallization of achiral ethylenediamine sulfate into large chiral crystals that are ideal for polarimetry studies and observation using Polaroid sheets are presented. This experiment is an ideal undergraduate experiment, which clearly demonstrates the chiral crystallization of an achiral molecule.

  7. A Few Good Crystals Please

    NASA Technical Reports Server (NTRS)

    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.

  8. Small Business Innovations (Crystal Components)

    NASA Technical Reports Server (NTRS)

    1991-01-01

    Scientific Materials Corporation, Bozeman, MT developed the SciMax line of improved Nd:Yag crystals under an Small Business Innovation Research (SBIR) contract with Langley Research Center. They reduced the amount of water trapped in the crystals during growth to improve the optical quality and efficiency. Applications of the crystals include fiber optics, telecommunications, welding, drilling, eye surgery and medical instrumentation.

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

    SciTech Connect

    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.

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

    PubMed

    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.

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

    NASA Technical Reports Server (NTRS)

    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.

  12. Crystal Engineering of Hand-Twisted Helical Crystals.

    PubMed

    Saha, Subhankar; Desiraju, Gautam R

    2017-02-08

    A strategy is outlined for the design of hand-twisted helical crystals. The starting point in the exercise is the one-dimensional (1D) plastic crystal, 1,4-dibromobenzene, which is then changed to a 1D elastic crystal, exemplified by 4-bromophenyl 4'-chlorobenzoate, by introduction of a molecular synthon -O-CO- in lieu of the supramolecular synthon Br···Br in the precursor. The 1D elastic crystals are next modified to two-dimensional (2D) elastic crystals, of the type 4-bromophenyl 4'-nitrobenzoate where the halogen bonding and C-H···O hydrogen bonding are well-matched. Finally, varying the interaction strengths in these 2D elastic crystals gives plastic crystals with two pairs of bendable faces but without slip planes. Typical examples are 4-chlorophenyl and 4-bromophenyl 4'-nitrobenzoate. This type of 2D plasticity represents a new type of bendable crystals in which plastic behavior is seen with a fair degree of isotropic character in the crystal packing. The presence of two sets of bendable faces, generally orthogonal to each other, allows for the possibility of hand-twisting of the crystals to give grossly helical morphologies. Accordingly, we propose the name hand-twisted helical crystals for these substances.

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

    NASA Astrophysics Data System (ADS)

    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.

  14. Improving the Quality of Protein Crystals Using Stirring Crystallization

    NASA Astrophysics Data System (ADS)

    Adachi, Hiroaki; Matsumura, Hiroyoshi; Niino, Ai; Takano, Kazufumi; Kinoshita, Takayoshi; Warizaya, Masaichi; Inoue, Tsuyoshi; Mori, Yusuke; Sasaki, Takatomo

    2004-04-01

    Recent reports state that a high magnetic field improves the crystal quality of bovine adenosine deaminase (ADA) with an inhibitor [Kinoshita et al.: Acta Cryst. D59 (2003) 1333]. In this paper, we examine the effect of stirring solution on ADA crystallization using a vapor-diffusion technique with rotary and figure-eight motion shakers. The probability of obtaining high-quality crystals is increased with stirring in a figure-eight pattern. Furthermore, rotary stirring greatly increased the probability of obtaining high-quality crystals, however, nucleation time was also increased. The crystal structure with the inhibitor was determined at a high resolution using a crystal obtained from a stirred solution. These results indicate that stirring with simple equipment is as useful as the high magnetic field technique for protein crystallization.

  15. Laser alexandrite crystals grown by horizontal oriented crystallization technique

    NASA Astrophysics Data System (ADS)

    Gurov, V. V.; Tsvetkov, E. G.; Yurkin, A. M.

    2008-05-01

    Comparative studies were performed for alexandrite crystals, Al 2BeO 4:Cr 3+, employed in solid state lasers and grown by the horizontal oriented crystallization (HOC) technique and alexandrite crystals grown by the Czochralski (Cz) method. It was shown that the structural quality and possibilities of generation of stimulated emission HOC-crystals are similar to Cz-crystals, whereas their damage threshold is about three times higher. The obtained results and considerably lower cost price of HOC-alexandrite crystals prove their advantageous application in powerful laser systems, which require large laser rods with a higher resistance to laser beam. It is emphasized that application of HOC technique is promising for growth of laser crystals of other high-temperature oxide compounds.

  16. Anisotropy of sapphire single crystal sputtering

    SciTech Connect

    Minnebaev, K. F.; Tolpin, K. A.; Yurasova, V. E.

    2015-08-15

    We have studied the spatial distribution of particles sputtered from the base (0001) plane of a sapphire single crystal with trigonal crystalline lattice (α-Al{sub 2}O{sub 3}) that can be considered a superposition of two hexagonal close packed (hcp) structures–the ideal sublattice of oxygen and a somewhat deformed sublattice of aluminum. It is established that the particles sputtered from the base plane of sapphire are predominantly deposited along the sides of an irregular hexagon with spots at its vertices. The patterns of spots have been also studied for sputtering of particles from the (0001) face of a zinc single crystal with the hcp lattice. The spots of sputtered Zn atoms are arranged at the vertices of concentric equilateral hexagons. In both cases, the observed anisotropy of sputtering is related to focused collisions (direct and assisted focusing) and the channeling process. The chemical composition of spots has been determined in various regions of sputtered sapphire deposition. The results are discussed in comparison to analogous earlier data for secondary ion emission from an α-Al{sub 2}O{sub 3} single crystal.

  17. Extreme Nonlinear Optics With Liquid Crystals

    DTIC Science & Technology

    2006-10-31

    Photorefractive CdSe and gold nanowire -doped liquid crystals and polymer-dispersed-liquid-crystal photonic crystals,” Mol. Cryst. Liq. Cryst. 446: 233...Mallouk, “ Photorefractive CdSe and gold nanowire -doped liquid crystals and polymer-dispersed-liquid-crystal photonic crystals,” Mol. Cryst. Liq. Cryst...Williams, B. Lewis and T. Mallouk, “Photorefractive CdSe and gold nanowire -doped liquid crystals and polymer-dispersed-liquid-crystal photonic

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

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed

    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

  20. Plenum type crystal growth process

    DOEpatents

    Montgomery, Kenneth E.

    1992-01-01

    Crystals are grown in a tank which is divided by a baffle into a crystal growth region above the baffle and a plenum region below the baffle. A turbine blade or stirring wheel is positioned in a turbine tube which extends through the baffle to generate a flow of solution from the crystal growing region to the plenum region. The solution is pressurized as it flows into the plenum region. The pressurized solution flows back to the crystal growing region through return flow tubes extending through the baffle. Growing crystals are positioned near the ends of the return flow tubes to receive a direct flow of solution.

  1. Protein Crystals Grown in Space

    NASA Technical Reports Server (NTRS)

    2000-01-01

    A collage of protein and virus crystals, many of which were grown on the U.S. Space Shuttle or Russian Space Station, Mir. The crystals include the proteins canavalin; mouse monoclonal antibody; a sweet protein, thaumatin; and a fungal protease. Viruses are represented here by crystals of turnip yellow mosaic virus and satellite tobacco mosaic virus. The crystals are photographed under polarized light (thus causing the colors) and range in size from a few hundred microns in edge length up to more than a millimeter. All the crystals are grown from aqueous solutions and are useful for X-ray diffraction analysis. Credit: Dr. Alex McPherson, University of California, Irvine.

  2. Plenum type crystal growth chamber

    SciTech Connect

    Montgomery, K.E.

    1990-12-31

    Crystals are grown in a tank which is divided by a baffle into a crystal growth region above the baffle and a plenum region below the baffle. A turbine blade or stirring wheel is positioned in a turbine tube which extends through the baffle to generate a flow of solution from the crystal growing region to the plenum region. The solution is pressurized as it flows into the plenum region. The pressurized solution flows back to the crystal growing region through return flow tubes extending through the baffle. Growing crystals are positioned near the ends of the return flow tubes to receive a direct flow of solution.

  3. Surrogate Seeds For Growth Of Crystals

    NASA Technical Reports Server (NTRS)

    Shlichta, Paul J.

    1989-01-01

    Larger crystals of higher quality grown. Alternative method for starting growth of crystal involves use of seed crystal of different material instead of same material as solution. Intended for growing single-crystal proteins for experiments but applicable in general to growth of crystals from solutions and to growth of semiconductor or other crystals from melts.

  4. Mechanical properties of tricalcium phosphate single crystals grown by molten salt synthesis.

    PubMed

    Viswanath, B; Raghavan, R; Gurao, N P; Ramamurty, U; Ravishankar, N

    2008-09-01

    Mechanical properties of flux-grown tricalcium phosphate (TCP) single crystals ranging in size from 50 to 75microm have been characterized by performing micro- and nanoindentation on their facets. Notwithstanding the inherent brittleness and anisotropy, these single crystals exhibit nanoscale plasticity in the form of pile-up around the edges of indents. A similar plastic response was observed in hydroxyapatite (HA) single crystals during nanoindentation in an earlier study. The hardness and elastic modulus obtained during nanoindentation are discussed in comparison with the polycrystalline forms of both TCP and HA found in the literature. The indentation fracture toughness values of TCP single crystals were found to be higher than those of HA single crystals. The higher values are attributed not only to the difference in crystal structure and corresponding differences in surface energy, but also to extensive crack bridging by ligament formation across crack faces during crack propagation.

  5. Macromolecular crystal growing system

    NASA Technical Reports Server (NTRS)

    Snyder, Robert S. (Inventor); Herren, Blair J. (Inventor); Carter, Daniel C. (Inventor); Yost, Vaughn H. (Inventor); Bugg, Charles E. (Inventor); Delucas, Lawrence J. (Inventor); Suddath, Fred L. (Inventor)

    1991-01-01

    A macromolecular crystal growing system especially designed for growing crystals in the low gravity of space as well as the gravity of earth includes at least one tray assembly, a carrier assembly which receives the tray, and a refrigeration-incubation module in which the carrier assembly is received. The tray assembly includes a plurality of sealed chambers with a plastic syringe and a plug means for the double tip of the syringe provided therein. Ganging mechanisms operate the syringes and plugs simultaneously in a precise and smooth operation. Preferably, the tray assemblies are mounted on ball bearing slides for smooth operation in inserting and removing the tray assemblies into the carrier assembly. The plugging mechanism also includes a loading control mechanism. A mechanism for leaving a syringe unplugged is also provided.

  6. CRYSTAL/FACE

    NASA Technical Reports Server (NTRS)

    Baumgardner, Darrel; Kok, Greg; Anderson, Bruce

    2004-01-01

    Droplet Measurement Technologies (DMT), under funding from NASA, participated in the CRYSTAL/FACE field campaign in July, 2002 with measurements of cirrus cloud hydrometeors in the size range from 0.5 to 1600 microns. The measurements were made with the DMT Cloud, Aerosol and Precipitation Spectrometer (CAPS) that was flown on NASA's WB57F. With the exception of the first research flight when the data system failed two hours into the mission, the measurement system performed almost flawlessly during the thirteen flights. The measurements from the CAPS have been essential for interpretation of cirrus cloud properties and their impact on climate. The CAPS data set has been used extensively by the CRYSTAL/FACE investigators and as of the date of this report, have been included in five published research articles, 10 conference presentations and six other journal articles currently in preparation.

  7. Liquid crystals in tribology.

    PubMed

    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.

  8. Tactical Miniature Crystal Oscillator.

    DTIC Science & Technology

    1981-04-01

    87 6.2 Outgassing experiments o......... 88 6.3 Electropolishing ......... 95 6.4 Leaks in the TMXO package...machinable and sealing properties. After considering the thermal and mech- anical characteristics of many materials, nickel was selected. Table 7 gives...and the nickel type used in this program. TABLE 7. CHARACTERISTICS OF CRYSTAL ENCLOSURES Old copper Alumina* Nickel enclosures enclosures enclosure

  9. Nematic liquid crystal bridges

    NASA Astrophysics Data System (ADS)

    Doss, Susannah; Ellis, Perry; Vallamkondu, Jayalakshmi; Danemiller, Edward; Vernon, Mark; Fernandez-Nieves, Alberto

    We study the effects of confining a nematic liquid crystal between two parallel glass plates with homeotropic boundary conditions for the director at all bounding surfaces. We find that the free surface of the nematic bridge is a surface of constant mean curvature. In addition, by changing the distance between the plates and the contact angle with the glass plates, we transition between loops and hedgehogs that can be either radial or hyperbolic.

  10. The Crystal Set

    NASA Astrophysics Data System (ADS)

    Greenslade, Thomas B.

    2014-04-01

    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 I knew, but actually did not.

  11. Diamond drumhead crystals (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Kolodziej, Tomasz; Vodnala, Preeti; Terentyev, Sergey A.; Blank, Vladimir D.; Shvyd'ko, Yuri V.

    2016-09-01

    Ultra-thin (< 100 um) diamond single crystals are essential for the realization of numerous next generation x-ray optical devices. Fabrication and handling of such ultra-thin crystal components without introducing damage and strain is a challenge. Drumhead crystals, monolithic crystal structures comprised of a thin membrane furnished with a surrounding solid collar would be a solution for the proper handling ensuring mechanically stable and strain-free mount of the membranes with efficient thermal transport. However, diamond being one of the hardest and chemically inert materials poses insurmountable difficulties in the fabrication. Here we report on a successful manufacturing of the diamond drumhead crystals using picosecond laser milling. Subsequent temperature treatment appears to be crucial for the membranes to become defect-free and unstrained, as revealed by x-ray double-crystal topography on an example of drumhead crystals with 1-mm in diameter and 28 um to 47 um-thick membranes in the (100) orientation.

  12. High density protein crystal growth

    NASA Technical Reports Server (NTRS)

    Rouleau, Robyn (Inventor); Delucas, Lawrence (Inventor); Hedden, Douglas Keith (Inventor)

    2004-01-01

    A protein crystal growth assembly including a crystal growth cell and further including a cell body having a top side and a bottom side and a first aperture defined therethrough, the cell body having opposing first and second sides and a second aperture defined therethrough. A cell barrel is disposed within the cell body, the cell barrel defining a cavity alignable with the first aperture of the cell body, the cell barrel being rotatable within the second aperture. A reservoir is coupled to the bottom side of the cell body and a cap having a top side is disposed on the top side of the cell body. The protein crystal growth assembly may be employed in methods including vapor diffusion crystallization, liquid to liquid crystallization, batch crystallization, and temperature induction batch mode crystallization.

  13. Crystallization of human nicotinamide phosphoribosyltransferase

    SciTech Connect

    Takahashi, Ryo; Nakamura, Shota; Yoshida, Takuya; Kobayashi, Yuji; Ohkubo, Tadayasu

    2007-05-01

    Human nicotinamide phosphoribosyltransferase has been crystallized using microseeding methods and X-ray diffraction data have been collected at 2.0 Å resolution. In the NAD biosynthetic pathway, nicotinamide phosphoribosyltransferase (NMPRTase; EC 2.4.2.12) plays an important role in catalyzing the synthesis of nicotinamide mononucleotide from nicotinamide and 5′-phosphoribosyl-1′-pyrophosphate. Because the diffraction pattern of the initally obtained crystals was not suitable for structure analysis, the crystal quality was improved by successive use of the microseeding technique. The resultant crystals diffracted to 2.0 Å resolution. These crystals belonged to space group P21, with unit-cell parameters a = 60.56, b = 106.40, c = 82.78 Å. Here, the crystallization of human NMPRTase is reported in the free form; the crystals should be useful for inhibitor-soaking experiments on the enzyme.

  14. Modern trends in technical crystallization

    NASA Astrophysics Data System (ADS)

    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.

  15. Slotted Photonic Crystal Sensors

    PubMed Central

    Scullion, Mark G.; Krauss, Thomas F.; Di Falco, Andrea

    2013-01-01

    Optical biosensors are increasingly being considered for lab-on-a-chip applications due to their benefits such as small size, biocompatibility, passive behaviour and lack of the need for fluorescent labels. The light guiding mechanisms used by many of them results in poor overlap of the optical field with the target molecules, reducing the maximum sensitivity achievable. This review article presents a new platform for optical biosensors, namely slotted photonic crystals, which provide higher sensitivities due to their ability to confine, spatially and temporally, the optical mode peak within the analyte itself. Loss measurements showed values comparable to standard photonic crystals, confirming their ability to be used in real devices. A novel resonant coupler was designed, simulated, and experimentally tested, and was found to perform better than other solutions within the literature. Combining with cavities, microfluidics and biological functionalization allowed proof-of-principle demonstrations of protein binding to be carried out. Higher sensitivities were observed in smaller structures than possible with most competing devices reported in the literature. This body of work presents slotted photonic crystals as a realistic platform for complete on-chip biosensing; addressing key design, performance and application issues, whilst also opening up exciting new ideas for future study. PMID:23503295

  16. Cholesterol crystal embolism (atheroembolism).

    PubMed

    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.

  17. Quartz crystal fabrication facility

    NASA Astrophysics Data System (ADS)

    Ney, R. J.

    1980-05-01

    The report describes the design and operation of a five chamber, interconnected vacuum system, which is capable of cleaning, plating, and sealing precision quartz crystal units in ceramic flatpack enclosures continuously in a high vacuum environment. The production rate design goal was 200 units per eight hour day. A unique nozzle beam gold deposition source was developed to operate for extended periods of time without reloading. The source puts out a narrow beam of gold typically in the order of 2 1/2 deg included cone angle. Maximum deposition rates are in the order of 400 a/min at 5.5 in. 'throw' distance used. Entrance and exit air lock chambers expedite the material throughput, so that the processing chambers are at high vacuum for extended periods of time. A stainless steel conveyor belt, in conjunction with three vacuum manipulators, transport the resonator components to the various work stations. Individual chambers are normally separated from each other by gate valves. The crystal resonators, mounted in flatpack frames but unplated, are loaded into transport trays in a lid-frame-lid sequency for insertion into the system and exit as completed crystal units. The system utilizes molybdenum coated ball bearings at essentially all friction surfaces. The gold sources and plating mask heads are equipped with elevators and gate valves, so that they can be removed from the system for maintenance without exposing the chambers to atmosphere.

  18. Cholesterol crystal embolism (atheroembolism)

    PubMed Central

    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

  19. Datamining protein structure databanks for crystallization patterns of proteins.

    PubMed

    Valafar, Homayoun; Prestegard, James H; Valafar, Faramarz

    2002-12-01

    A study of 345 protein structures selected among 1,500 structures determined by nuclear magnetic resonance (NMR) methods, revealed useful correlations between crystallization properties and several parameters for the studied proteins. NMR methods of structure determination do not require the growth of protein crystals, and hence allow comparison of properties of proteins that have or have not been the subject of crystallographic approaches. One- and two-dimensional statistical analyses of the data confirmed a hypothesized relation between the size of the molecule and its crystallization potential. Furthermore, two-dimensional Bayesian analysis revealed a significant relationship between relative ratio of different secondary structures and the likelihood of success for crystallization trials. The most immediate result is an apparent correlation of crystallization potential with protein size. Further analysis of the data revealed a relationship between the unstructured fraction of proteins and the success of its crystallization. Utilization of Bayesian analysis on the latter correlation resulted in a prediction performance of about 64%, whereas a two-dimensional Bayesian analysis succeeded with a performance of about 75%.

  20. Lessons from ten years of crystallization experiments at the SGC

    PubMed Central

    Ng, Jia Tsing; Dekker, Carien; Reardon, Paul; von Delft, Frank

    2016-01-01

    Although protein crystallization is generally considered more art than science and remains significantly trial-and-error, large-scale data sets hold the promise of providing general learning. Observations are presented here from retrospective analyses of the strategies actively deployed for the extensive crystallization experiments at the Oxford site of the Structural Genomics Consortium (SGC), where comprehensive annotations by SGC scientists were recorded on a customized database infrastructure. The results point to the importance of using redundancy in crystallizing conditions, specifically by varying the mixing ratios of protein sample and precipitant, as well as incubation temperatures. No meaningful difference in performance could be identified between the four most widely used sparse-matrix screens, judged by the yield of crystals leading to deposited structures; this suggests that in general any comparison of screens will be meaningless without extensive cross-testing. Where protein sample is limiting, exploring more conditions has a higher likelihood of being informative by yielding hits than does redundancy of either mixing ratio or temperature. Finally, on the logistical question of how long experiments should be stored, 98% of all crystals that led to deposited structures appeared within 30 days. Overall, these analyses serve as practical guidelines for the design of initial screening experiments for new crystallization targets. PMID:26894670

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

    PubMed

    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.

  2. Crystal growth and agglomeration of calcium sulfite hemihydrate crystals

    SciTech Connect

    Tai, C.Y.; Chen, P.C.

    1995-04-01

    Flue gas desulfurization (FGD) processes are most commonly utilized to remove sulfur dioxide from stack gases of coal- or oil-fired plants. In the simple slurry technology, SO{sub 2} is absorbed by a slurry of lime/limestone to form calcium sulfite crystals of acicular habit and its strong agglomeration, requiring large clarifiers and filters to dewater the sludge to make an acceptable landfill. Crystal growth and agglomeration of calcium sulfite hemihydrate crystals from solution were studied by reacting Ca(OH){sub 2} with NaHSO{sub 3} in a pH-stat semibatch crystallizer. Single platelet crystals and agglomerates of platelet crystals were produced in the pH range from 5.80 to 6.80. The crystallization mechanism changed from primary nucleation to crystal growth in the progressive precipitation. Using the titration curves, the growth rate was calculated from the titration rate at the final stage of operation. The crystal growth rates of calcium sulfate hemihydrate crystals were found to obey the parabolic rate law in the low supersaturation range. Another point to be noted is that the precipitates of calcium sulfite hemihydrate in agitated suspensions have a tendency to form agglomerates. It was found that the degree of agglomeration is a weak function of relative supersaturation and magma density, while the pH value is a key factor that affects the degree of agglomeration. Addition of EDTA also has an effect on the agglomeration of calcium sulfite hemihydrates.

  3. Discrete breathers in crystals

    NASA Astrophysics Data System (ADS)

    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

  4. Unifying the crystallization behavior of hexagonal and square crystals with the phase-field-crystal model

    NASA Astrophysics Data System (ADS)

    Tao, Yang; Zheng, Chen; Jing, Zhang; Yongxin, Wang; Yanli, Lu

    2016-03-01

    By employing the phase-field-crystal models, the atomic crystallization process of hexagonal and square crystals is investigated with the emphasis on the growth mechanism and morphological change. A unified regime describing the crystallization behavior of both crystals is obtained with the thermodynamic driving force varying. By increasing the driving force, both crystals (in the steady-state) transform from a faceted polygon to an apex-bulged polygon, and then into a symmetric dendrite. For the faceted polygon, the interface advances by a layer-by-layer (LL) mode while for the apex-bulged polygonal and the dendritic crystals, it first adopts the LL mode and then transits into the multi-layer (ML) mode in the later stage. In particular, a shift of the nucleation sites from the face center to the area around the crystal tips is detected in the early growth stage of both crystals and is rationalized in terms of the relation between the crystal size and the driving force distribution. Finally, a parameter characterizing the complex shape change of square crystal is introduced. Project supported by the National Natural Science Foundation of China (Grant Nos. 54175378, 51474176, and 51274167), the Natural Science Foundation of Shaanxi Province, China (Grant No. 2014JM7261), and the Doctoral Foundation Program of Ministry of China (Grant No. 20136102120021).

  5. Evaluation of crystal mush extraction models to explain crystal-poor rhyolites

    NASA Astrophysics Data System (ADS)

    Streck, Martin J.

    2014-09-01

    Mush models have become the new paradigm for explaining crystal-poor rhyolites in a variety of settings. Despite this general acceptance, there are cases where this model is problematic. Rhyolites from two specific areas are used to highlight examples where mush extraction models are inconsistent with erupted compositions. Rhyolites from eastern Oregon are used to address a mush origin of hot and dry (or A-type) rhyolites from bimodal volcanic suites and rocks from the San Luis Caldera Complex of the San Juan Volcanic Field in Colorado are used to address crystal-poor rhyolites of calc-alkaline suites. Crystal-poor A-type rhyolites from Oregon resemble those from the neighboring Snake River Plain-Yellowstone centers. They are Fe-rich and high-field-strength-element enriched in comparison to regional calc-alkaline rhyolites and they vary widely in their degree of fractionation. A compositional assessment between least fractionated A-type rhyolites and a variety of intermediate magmas, including co-genetic intermediate magmas that erupted along with rhyolites during ignimbrite eruptions, indicates that intermediate, calc-alkaline and alkaline crystal mushes are unlikely to be able to generate interstitials melts after > 50% crystallization that match observed rhyolites with high Ba/Rb and Ba/Sr as long as alkali-feldspar, low An plagioclase (~< An40) or biotite are part of the crystallizing magma mush assemblage before extraction. Arguments specifically against granodioritic mush as rhyolitic nursery for Oregon hot & dry, Fe-rich, A-type rhyolites are multifold and strong. The San Luis Caldera Complex consists of crystal-rich intermediate magmas as well as crystal-poor rhyolites that erupted over a narrow time window. This association allows us to directly apply the mush model by comparing silicic interstitial melts of crystal-rich magmas with erupted rhyolites. REE contents of rhyolitic interstitial melt have MREE depleted patterns relative to bulk rock in all cases

  6. Additive manufacturing of micrometric crystallization vessels and single crystals

    PubMed Central

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

    2016-01-01

    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. PMID:27830827

  7. Additive manufacturing of micrometric crystallization vessels and single crystals.

    PubMed

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

    2016-11-10

    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.

  8. Additive manufacturing of micrometric crystallization vessels and single crystals

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Technical Reports Server (NTRS)

    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 < or = fcrystal < or = 0.74. Radial transport models that predict the enrichment of the outer disk (>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 < or = fcrystal < or = 0.35 and with polyhedral-shaped Forsterite 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

  10. New organic second-order nonlinear optical crystals of benzylidene-aniline derivative

    NASA Astrophysics Data System (ADS)

    Tsunekawa, Tetsuya; Gotoh, Tetsuya; Mataki, Hiroshi; Kondo, Toshiyuki; Fukuda, Seiji; Iwamoto, Masao

    1990-12-01

    The benzylidene-aniline derivative with an electron-donating group at 4-position and an electron-accepting group at 4'-position has been suggested by MO calculation, to have a small molecular dipole moment but a large second-order hyperpolarizability in comparison with those of p-nitroaniline analogous molecules, hence, to be a promising molecule on searching for a new organic crystal with large second-order optical nonlinearity. Chemical modification of the molecule suggested led to a discovery of a series of crystals having high activities in second harmonic generation ( SHG ) ; one of which, 4'-nitrobenzylidene-3-acetamino-4-methoxyaniline ( MNBA ) crystal in monodinic Cc with four molecules per unit cell showed larger powder SHG than 2-methyl-4-mtroaniline ( MNA ) crystal in a preliminary powder SHG experiment. A strongly polarized non-centrosymmetric molecular packing has been achieved in this crystal by the presence of intermolecular hydrogen bond between neighboring acetainino groups. Calculation by an oriented gas model with the use of the detailed structural data from X-ray analysis for the MNBA crystal predicted that the crystal may have up to ca. 2.9 times larger macroscopic optical nonlinearity than MNA crystal. This has been experimentally proven by measuring the d for SHG by Maker fringe method. The largest d coefficient was found to be dii , and the value obtained was 454 pm/V which is 1.8 times larger than d11 of MNA crystal and 13 times larger than of lithium mobate ( ) crystal.

  11. All-atom crystal simulations of DNA and RNA duplexes

    PubMed Central

    Liu, Chunmei; Janowski, Pawel A.; Case, David A.

    2014-01-01

    Background Molecular dynamics simulations can complement experimental measures of structure and dynamics of biomolecules. The quality of such simulations can be tested by comparisons to models refined against experimental crystallographic data. Methods We report simulations of a DNA and RNA duplex in their crystalline environment. The calculations mimic the conditions for PDB entries 1D23 [d(CGATCGATCG)2] and 1RNA [(UUAUAUAUAUAUAA)2], and contain 8 unit cells, each with 4 copies of the Watson-Crick duplex; this yields in aggregate 64 µs of duplex sampling for DNA and 16 µs for RNA. Results The duplex structures conform much more closely to the average structure seen in the crystal than do structures extracted from a solution simulation with the same force field. Sequence-dependent variations in helical parameters, and in groove widths, are largely maintained in the crystal structure, but are smoothed out in solution. However, the integrity of the crystal lattice is slowly degraded in both simulations, with the result that the interfaces between chains become heterogeneous. This problem is more severe for the DNA crystal, which has fewer inter-chain hydrogen bond contacts than does the RNA crystal. Conclusions Crystal simulations using current force fields reproduce many features of observed crystal structures, but suffer from a gradual degradation of the integrity of the crystal lattice. General significance The results offer insights into force-field simulations that tests their ability to preserve weak interactions between chains, which will be of importance also in non-crystalline applications that involve binding and recognition. PMID:25255706

  12. Crystal nephropathies: mechanisms of crystal-induced kidney injury.

    PubMed

    Mulay, Shrikant R; Anders, Hans-Joachim

    2017-04-01

    Crystals can trigger a wide range of kidney injuries that can lead to acute kidney injury, chronic kidney disease, renal colic or nephrocalcinosis, depending on the localization and dynamics of crystal deposition. Studies of the biology of crystal handling by the kidney have shown that the formation of different crystals and other microparticles and the associated mechanisms of renal damage share molecular mechanisms, such as stimulation of the NLRP3 inflammasome or direct cytotoxicity through activation of the necroptosis signalling pathway. By contrast, crystal granuloma formation is limited to chronic crystallopathies that lead to chronic kidney disease and renal fibrosis. Here, we discuss current understanding of the pathomechanisms underlying the different types of crystal-induced kidney injury and propose a classification of crystal nephropathies based on the localization of crystal deposits in the renal vasculature (type 1), the nephron (type 2), or the draining urinary tract (type 3). Further exploration of the molecular mechanisms of crystal-induced kidney injury and renal remodelling might aid the development of innovative cures for these diseases.

  13. Dynamically controlled crystallization method and apparatus and crystals obtained thereby

    NASA Technical Reports Server (NTRS)

    Arnowitz, Leonard (Inventor); Steinberg, Emanuel (Inventor)

    2003-01-01

    A method and apparatus for dynamically controlling the crystallization of molecules including a crystallization chamber (14) or chambers for holding molecules in a precipitant solution, one or more precipitant solution reservoirs (16, 18), communication passages (17, 19) respectively coupling the crystallization chamber(s) with each of the precipitant solution reservoirs, and transfer mechanisms (20, 21, 22, 24, 26, 28) configured to respectively transfer precipitant solution between each of the precipitant solution reservoirs and the crystallization chamber(s). The transfer mechanisms are interlocked to maintain a constant volume of precipitant solution in the crystallization chamber(s). Precipitant solutions of different concentrations are transferred into and out of the crystallization chamber(s) to adjust the concentration of precipitant in the crystallization chamber(s) to achieve precise control of the crystallization process. The method and apparatus can be used effectively to grow crystals under reduced gravity conditions such as microgravity conditions of space, and under conditions of reduced or enhanced effective gravity as induced by a powerful magnetic field.

  14. Crystal growth from the vapor phase. Experiment MA-085

    NASA Technical Reports Server (NTRS)

    Wiedemeier, H.

    1977-01-01

    The positive effects of microgravity on crystal quality and the fundamental properties of the vapor transport reaction were established by analyzing the results of three transport experiments on multicomponent systems performed during the Apollo-Soyuz Test Project mission. The systems employed were GeSe0.99Te0.01-GeI4(A), GeS0.98Se0.02-GeCl4(B), and GeS-GeCl4-Ar (C). The crystallographic analysis is based on a direct comparison of space and ground-based (prototype) crystals employing X-ray diffraction, microprobe, microscopic, and chemical etching techniques. The results demonstrate a considerable improvement of the space-grown crystals in terms of chemical and crystalline homogeneity, surface morphology, and bulk perfection relative to ground specimens.

  15. Crystal growth from the vapor phase experiment MA-085

    NASA Technical Reports Server (NTRS)

    Wiedemeir, H.; Sadeek, H.; Klaessig, F. C.; Norek, M.

    1976-01-01

    Three vapor transport experiments on multicomponent systems were performed during the Apollo Soyuz mission to determine the effects of microgravity forces on crystal morphology and mass transport rates. The mixed systems used germanium selenide, tellurium, germanium tetraiodide (transport agent), germanium monosulfide, germanium tetrachloride (transport agent), and argon (inert atmosphere). The materials were enclosed in evacuated sealed ampoules of fused silica and were transported in a temperature gradient of the multipurpose electric furnace onboard the Apollo Soyuz spacecraft. Preliminary evaluation of 2 systems shows improved quality of space grown crystals in terms of growth morphology and bulk perfection. This conclusion is based on a direct comparison of space grown and ground based crystals by means of X-ray diffraction, microscopic, and chemical etching techniques. The observation of greater mass transport rates than predicted for a microgravity environment by existing vapor transport models indicates the existence of nongravity caused transport effects in a reactive solid/gas phase system.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Technical Reports Server (NTRS)

    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.

  18. Crystal structure of inactive form of Rab3B

    SciTech Connect

    Zhang, Wei; Shen, Yang; Jiao, Ronghong; Liu, Yanli; Deng, Lingfu; Qi, Chao

    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.

  19. Lasing from fluorescent protein crystals.

    PubMed

    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.

  20. Photonic crystal microspheres

    NASA Astrophysics Data System (ADS)

    Zhokhov, A. A.; Masalov, V. M.; Sukhinina, N. S.; Matveev, D. V.; Dolganov, P. V.; Dolganov, V. K.; Emelchenko, G. A.

    2015-11-01

    Spherical samples of photonic crystals formed by colloidal SiO2 nanoparticles were synthesized. Synthesis of microspheres from 160 nm, 200 nm and 430 nm diameter colloidal nanoparticles was performed over a wide size range, from 5 μm to 50 μm. The mechanism of formation of void microparticles exceeding 50 μm is discussed. The spectral measurements verified the association of the spectra with the peaks of selective reflection from the cubic lattice planes. The microparticle morphology is characterized by scanning electron microscopy (SEM).

  1. Polymerizable ionic liquid crystals.

    PubMed

    Jazkewitsch, Olga; Ritter, Helmut

    2009-09-17

    Polymerizable vinylimidazolium ionic liquids (ILs) that contain mesogenic coumarin and biphenyl units, respectively, have been synthesized. The N-alkylation of N-vinylimidazole with bromoalkylated mesogenic units 7-(6-bromohexyloxy)coumarin (1) and 4,4'-bis(6-bromohexyloxy)biphenyl (2) was then carried out. The thermal behavior of the obtained ILs 3 and 4 was investigated by differential scanning calorimetry and polarizing optical microscopy. These measurements showed that the attached mesogenic units induce the self-assembly of ILs and, therefore, the occurrence of liquid crystalline phases. Subsequently, the ionic liquid crystals (ILCs) 3 and 4 were polymerized by a free-radical mechanism.

  2. Electrohydrodynamically patterned colloidal crystals

    NASA Technical Reports Server (NTRS)

    Hayward, Ryan C. (Inventor); Poon, Hak F. (Inventor); Xiao, Yi (Inventor); Saville, Dudley A. (Inventor); Aksay, Ilhan A. (Inventor)

    2003-01-01

    A method for assembling patterned crystalline arrays of colloidal particles using ultraviolet illumination of an optically-sensitive semiconducting anode while using the anode to apply an electronic field to the colloidal particles. The ultraviolet illumination increases current density, and consequently, the flow of the colloidal particles. As a result, colloidal particles can be caused to migrate from non-illuminated areas of the anode to illuminated areas of the anode. Selective illumination of the anode can also be used to permanently affix colloidal crystals to illuminated areas of the anode while not affixing them to non-illuminated areas of the anode.

  3. Crystallization in detergent performance

    NASA Astrophysics Data System (ADS)

    Verdoes, D.; Van Landschoot, R. C.; Van Rosmalen, G. M.

    1990-01-01

    The effects of various polymeric additives on the crystallization of CaCO 3 in simple soda-based detergent formulations were investigated. The adherence of CaCO 3 on cotton, a great disadvantage of soda-based detergents, was significantly diminished by copolymers of polystyrene sulfonates. A mechanism in which these additives promote the nucleation of CaCO 3 is proposed. Polyacrylates cause an increasing adherence of CaCO 3 on cotton, because the chains adsorb on cotton and CaCO 3

  4. Crystallization of fluorozirconate glasses

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.; Doremus, Robert H.; Bruce, A. J.; Moynihan, C. T.

    1984-01-01

    The crystallization of a number of glasses of the fluorozirconate family has been studied (using powder X-ray diffraction and DSC) as a function of time and temperature of heating. The main crystalline phases were beta BaZrF6 and beta BaZr2F10. Stable and metastble transformations to the low-temperature alpha phases were also investigated. The size of crystallites in fully devitrified glasses was calculated (from line broadening of the X-ray diffraction peaks) to be about 60 nm.

  5. Crystallization modifiers in lipid systems.

    PubMed

    Ribeiro, Ana Paula Badan; Masuchi, Monise Helen; Miyasaki, Eriksen Koji; Domingues, Maria Aliciane Fontenele; Stroppa, Valter Luís Zuliani; de Oliveira, Glazieli Marangoni; Kieckbusch, Theo Guenter

    2015-07-01

    Crystallization of fats is a determinant physical event affecting the structure and properties of fat-based products. The stability of these processed foods is regulated by changes in the physical state of fats and alterations in their crystallization behavior. Problems like polymorphic transitions, oil migration, fat bloom development, slow crystallization and formation of crystalline aggregates stand out. The change of the crystallization behavior of lipid systems has been a strategic issue for the processing of foods, aiming at taylor made products, reducing costs, improving quality, and increasing the applicability and stability of different industrial fats. In this connection, advances in understanding the complex mechanisms that govern fat crystallization led to the development of strategies in order to modulate the conventional processes of fat structuration, based on the use of crystallization modifiers. Different components have been evaluated, such as specific triacyglycerols, partial glycerides (monoacylglycerols and diacylglycerols), free fatty acids, phospholipids and emulsifiers. The knowledge and expertise on the influence of these specific additives or minor lipids on the crystallization behavior of fat systems represents a focus of current interest for the industrial processing of oils and fats. This article presents a comprehensive review on the use of crystallization modifiers in lipid systems, especially for palm oil, cocoa butter and general purpose fats, highlighting: i) the removal, addition or fractionation of minor lipids in fat bases; ii) the use of nucleating agents to modify the crystallization process; iii) control of crystallization in lipid bases by using emulsifiers. The addition of these components into lipid systems is discussed in relation to the phenomena of nucleation, crystal growth, morphology, thermal behavior and polymorphism, with the intention of providing the reader with a complete panorama of the associated mechanisms

  6. Liquid crystals for photonic applications

    NASA Astrophysics Data System (ADS)

    Miniewicz, A.; Gniewek, A.; Parka, J.

    2003-01-01

    In this paper we describe application of liquid crystals in optical imaging and processing. Electrically and optically addressed liquid crystal spatial light modulators are key elements in real-time holographic devices. Their implementation for beam steering and hologram formation is briefly discussed. The Joint Fourier transform optical correlator for pattern recognition is presented as well as the use of liquid crystals for the adaptive optics purposes is discussed.

  7. Protein crystal growth tray assembly

    NASA Technical Reports Server (NTRS)

    Carter, Daniel C. (Inventor); Miller, Teresa Y. (Inventor)

    1992-01-01

    A protein crystal growth tray assembly includes a tray that has a plurality of individual crystal growth chambers. Each chamber has a movable pedestal which carries a protein crystal growth compartment at an upper end. The several pedestals for each tray assembly are ganged together for concurrent movement so that the solutions in the various pedestal growth compartments can be separated from the solutions in the tray's growth chambers until the experiment is to be activated.

  8. Inorganic Crystal Structure Database (ICSD)

    National Institute of Standards and Technology Data Gateway

    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. Magnetic Field Applications in Semiconductor Crystal Growth and Metallurgy

    NASA Technical Reports Server (NTRS)

    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

  10. Crystal Chemistry of Melanite Garnet

    NASA Technical Reports Server (NTRS)

    Nguyen, Dawn Marie

    1999-01-01

    This original project resulted in a detailed crystal chemical data map of a titanium rich garnet (melanite) suite that originates from the Crowsnest Volcanics of Alberta Canada. Garnet is typically present during the partial melting of the earth's mantle to produce basalt. Prior studies conducted at Youngstown State University have yielded questions as to the crystal structure of the melanite. In the Studies conducted at Youngstown State University, through the use of single crystal x-ray diffraction, the c-axis appears to be distorted creating a tetragonal crystal instead of the typical cubic crystal of garnets. The micro probe was used on the same suite of titanium rich garnets as used in the single crystal x-ray diffraction. The combination of the single crystal x-ray research and the detailed microprobe research will allow us to determine the exact crystal chemical structure of the melanite garnet. The crystal chemical data was gathered through the utilization of the SX100 Electron Probe Micro Analyzer. Determination of the exact chemical nature may prove useful in modeling the ultramafic source rock responsible for the formation of the titanium rich lunar basalts.

  11. Protein crystal growth in space

    NASA Technical Reports Server (NTRS)

    Bugg, C. E.; Clifford, D. W.

    1987-01-01

    The advantages of protein crystallization in space, and the applications of protein crystallography to drug design, protein engineering, and the design of synthetic vaccines are examined. The steps involved in using protein crystallography to determine the three-dimensional structure of a protein are discussed. The growth chamber design and the hand-held apparatus developed for protein crystal growth by vapor diffusion techniques (hanging-drop method) are described; the experimental data from the four Shuttle missions are utilized to develop hardware for protein crystal growth in space and to evaluate the effects of gravity on protein crystal growth.

  12. Quartz-crystal-oscillator hygrometer

    NASA Technical Reports Server (NTRS)

    Kruger, R.

    1977-01-01

    Measuring device, which eliminates complex and expensive optical components by electronically sensing dewpoint of water vapor in gas, employs piezoelectric crystal oscillator, supportive circuitry, temperature regulators, and readout.

  13. Surface Relaxation in Protein Crystals

    NASA Technical Reports Server (NTRS)

    Boutet, S.; Robinson, I. K.; Hu, Z. W.; Thomas, B. R.; Chernov, A. A.

    2002-01-01

    Surface X-ray diffraction measurements were performed on (111) growth faces of crystals of the Cellular iron-storage protein horse spleen ferritin. Crystal Trunkation Rods (CTR) were measured. A fit of the measured profile of the CTR revealed a surface roughness of 48 +/- 4.5 A and a top layer spacing contraction of 3.9 +/- 1.5%. In addition to the peak from the CTR, the rocking curves of the crystals displayed unexpected extra peaks. Multiple-scattering is demonstrated to account for them. Future applications of the method could allow the exploration of hydration effects on the growth of protein crystals.

  14. Crystal face temperature determination means

    DOEpatents

    Nason, D.O.; Burger, A.

    1994-11-22

    An optically transparent furnace having a detection apparatus with a pedestal enclosed in an evacuated ampule for growing a crystal thereon is disclosed. Temperature differential is provided by a source heater, a base heater and a cold finger such that material migrates from a polycrystalline source material to grow the crystal. A quartz halogen lamp projects a collimated beam onto the crystal and a reflected beam is analyzed by a double monochromator and photomultiplier detection spectrometer and the detected peak position in the reflected energy spectrum of the reflected beam is interpreted to determine surface temperature of the crystal. 3 figs.

  15. Better photonic crystal fibres

    NASA Astrophysics Data System (ADS)

    Knight, J. C.

    2008-11-01

    The development of optical fibers with two-dimensional patterns of air holes running down their length has reinvigorated research in the field of fiber optics. It has greatly - and fundamentally - broadened the range of specialty optical fibers, by demonstrating that optical fibers can be more 'special" than previously thought. Applications of such special fibers have not been hard to find. Fibers with air cores have made it possible to deliver energetic femtosecond-scale optical pulses, transform limited, as solitons, using single-mode fiber. Other fibers with anomalous dispersion at visible wavelengths have spawned a new generation of single-mode optical supercontinuum sources, spanning visible and near-infrared wavelengths and based on compact pump sources. A third example is in the field of fiber lasers, where the use of photonic crystal fiber concepts has led to a new hybrid laser technology, in which the very high numerical aperture available using air holes have enabled fibers so short they are more naturally held straight than bent. However, commercial success demands more than just a fiber and an application. The useful properties of the fibers need to be optimized for the specific application. This tutorial will describe some of the basic physics and technology behind these photonic crystal fibers (PCF's), illustrated with some of the impressive demonstrations of the past 18 months.

  16. Sonofragmentation of Ionic Crystals.

    PubMed

    Kim, Hyo Na; Suslick, Kenneth S

    2017-02-24

    Mechanochemistry deals with the interface between the chemical and the mechanical worlds and explores the physical and chemical changes in materials caused by an input of mechanical energy. As such, the chemical and physical effects of ultrasound, i.e., sonochemistry, are forms of mechanochemistry. In this paper, the fragmentation of ionic crystals during ultrasonic irradiation of slurries has been quantitatively investigated: the rate of fragmentation depends strongly on the strength of the materials (as measured by Vickers hardness or by Young's modulus). This is a mechanochemical extension of the Bell-Evans-Polanyi Principle or Hammond's Postulate: activation energies for solid fracture correlate with binding energies of solids. Sonofragmentation is unaffected by slurry loading or liquid vapor pressure, but is suppressed by increasing liquid viscosity. The mechanism of the particle breakage is consistent with a direct interaction between the shockwaves created by the ultrasound (through acoustic cavitation) and the solid particles in the slurry. Fragmentation is proposed to occur from defects in the solids induced by compression-expansion, bending, or torsional distortions of the crystals.

  17. Crystal structure of triclopyr.

    PubMed

    Cho, Seonghwa; Kim, Jineun; Jeon, Youngeun; Kim, Tae Ho

    2014-09-01

    In the title compound {systematic name: 2-[(3,5,6-tri-chloro-pyridin-2-yl)-oxy]acetic acid}, the herbicide triclopyr, C7H4Cl3NO3, the asymmetric unit comprises two independent mol-ecules in which the dihedral angles between the mean plane of the carb-oxy-lic acid group and the pyridyl ring plane are 79.3 (6) and 83.8 (5)°. In the crystal, pairs of inter-molecular O-H⋯O hydrogen bonds form dimers through an R 2 (2)(8) ring motif and are extended into chains along [100] by weak π-π inter-actions [ring centroid separations = 3.799 (4) and 3.810 (4) Å]. In addition, short inter-molecular Cl⋯Cl contacts [3.458 (2) Å] connect the chains, yielding a two-dimensional architecture extending parallel to (020). The crystal studied was found to be non-merohedrally twinned with the minor component being 0.175 (4).

  18. Crystal structure of triclopyr

    PubMed Central

    Cho, Seonghwa; Kim, Jineun; Jeon, Youngeun; Kim, Tae Ho

    2014-01-01

    In the title compound {systematic name: 2-[(3,5,6-tri­chloro­pyridin-2-yl)­oxy]acetic acid}, the herbicide triclopyr, C7H4Cl3NO3, the asymmetric unit comprises two independent mol­ecules in which the dihedral angles between the mean plane of the carb­oxy­lic acid group and the pyridyl ring plane are 79.3 (6) and 83.8 (5)°. In the crystal, pairs of inter­molecular O—H⋯O hydrogen bonds form dimers through an R 2 2(8) ring motif and are extended into chains along [100] by weak π–π inter­actions [ring centroid separations = 3.799 (4) and 3.810 (4) Å]. In addition, short inter­molecular Cl⋯Cl contacts [3.458 (2) Å] connect the chains, yielding a two-dimensional architecture extending parallel to (020). The crystal studied was found to be non-merohedrally twinned with the minor component being 0.175 (4). PMID:25309266

  19. Crystal Compton Camera

    SciTech Connect

    Ziock, Klaus-Peter; Braverman, Joshua B.; Harrison, Mark J.; Hornback, Donald Eric; Fabris, Lorenzo; Newby, Jason

    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. Liquid Crystals in Tribology

    PubMed Central

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

    2009-01-01

    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. PMID:19865534

  1. Frustrated polymer crystal structures

    NASA Astrophysics Data System (ADS)

    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.)

  2. Direct observation of interface instability during crystal growth

    NASA Technical Reports Server (NTRS)

    Tiller, W. A.; Feigelson, R. S.; Elwell, D.

    1982-01-01

    The general aim of this investigation was to study interface stability and solute segregation phenomena during crystallization of a model system. Emphasis was to be placed on direct observational studies partly because this offered the possibility at a later stage of performing related experiments under substantially convection-free conditions in the space shuttle. The major achievements described in this report are: (1) the development of a new model system for fundamental studies of crystal growth from the melt and the measurement of a range of material parameters necessary for comparison of experiment with theory. (2) The introduction of a new method of measuring segregation coefficient using absorption of a laser beam by the liquid phase. (3) The comparison of segregation in crystals grown by gradient freezing and by pulling from the melt. (4) The introduction into the theory of solute segregation of an interface field term and comparison with experiment. (5) The introduction of the interface field term into the theories of constitutional supercooling and morphological stability and assessment of its importance.

  3. Glasses crystallize rapidly at free surfaces by growing crystals upward.

    PubMed

    Sun, Ye; Zhu, Lei; Kearns, Kenneth L; Ediger, Mark D; Yu, Lian

    2011-04-12

    The crystallization of glasses and amorphous solids is studied in many fields to understand the stability of amorphous materials, the fabrication of glass ceramics, and the mechanism of biomineralization. Recent studies have found that crystal growth in organic glasses can be orders of magnitude faster at the free surface than in the interior, a phenomenon potentially important for understanding glass crystallization in general. Current explanations differ for surface-enhanced crystal growth, including released tension and enhanced mobility at glass surfaces. We report here a feature of the phenomenon relevant for elucidating its mechanism: Despite their higher densities, surface crystals rise substantially above the glass surface as they grow laterally, without penetrating deep into the bulk. For indomethacin (IMC), an organic glass able to grow surface crystals in two polymorphs (α and γ), the growth front can be hundreds of nanometers above the glass surface. The process of surface crystal growth, meanwhile, is unperturbed by eliminating bulk material deeper than some threshold depth (ca. 300 nm for α IMC and less than 180 nm for γ IMC). As a growth strategy, the upward-lateral growth of surface crystals increases the system's surface energy, but can effectively take advantage of surface mobility and circumvent slow growth in the bulk.

  4. Single-crystal silicon optical fiber by direct laser crystallization

    SciTech Connect

    Ji, Xiaoyu; Lei, Shiming; Yu, Shih -Ying; Cheng, Hiu Yan; Liu, Wenjun; Poilvert, Nicolas; Xiong, Yihuang; Dabo, Ismaila; Mohney, Suzanne E.; Badding, John V.; Gopalan, Venkatraman

    2016-12-05

    Semiconductor core optical fibers with a silica cladding are of great interest in nonlinear photonics and optoelectronics applications. Laser crystallization has been recently demonstrated for crystallizing amorphous silicon fibers into crystalline form. Here we explore the underlying mechanism by which long single-crystal silicon fibers, which are novel platforms for silicon photonics, can be achieved by this process. Using finite element modeling, we construct a laser processing diagram that reveals a parameter space within which single crystals can be grown. Utilizing this diagram, we illustrate the creation of single-crystal silicon core fibers by laser crystallizing amorphous silicon deposited inside silica capillary fibers by high-pressure chemical vapor deposition. The single-crystal fibers, up to 5.1 mm long, have a very welldefined core/cladding interface and a chemically pure silicon core that leads to very low optical losses down to ~0.47-1dB/cm at the standard telecommunication wavelength (1550 nm). Furthermore, tt also exhibits a photosensitivity that is comparable to bulk silicon. Creating such laser processing diagrams can provide a general framework for developing single-crystal fibers in other materials of technological importance.

  5. Single-crystal silicon optical fiber by direct laser crystallization

    DOE PAGES

    Ji, Xiaoyu; Lei, Shiming; Yu, Shih -Ying; ...

    2016-12-05

    Semiconductor core optical fibers with a silica cladding are of great interest in nonlinear photonics and optoelectronics applications. Laser crystallization has been recently demonstrated for crystallizing amorphous silicon fibers into crystalline form. Here we explore the underlying mechanism by which long single-crystal silicon fibers, which are novel platforms for silicon photonics, can be achieved by this process. Using finite element modeling, we construct a laser processing diagram that reveals a parameter space within which single crystals can be grown. Utilizing this diagram, we illustrate the creation of single-crystal silicon core fibers by laser crystallizing amorphous silicon deposited inside silica capillarymore » fibers by high-pressure chemical vapor deposition. The single-crystal fibers, up to 5.1 mm long, have a very welldefined core/cladding interface and a chemically pure silicon core that leads to very low optical losses down to ~0.47-1dB/cm at the standard telecommunication wavelength (1550 nm). Furthermore, tt also exhibits a photosensitivity that is comparable to bulk silicon. Creating such laser processing diagrams can provide a general framework for developing single-crystal fibers in other materials of technological importance.« less

  6. Engineering calcium oxalate crystal formation in Arabidopsis

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Many plants accumulate crystals of calcium oxalate. Just how these crystals form remains unknown. To gain insight into the mechanisms regulating calcium oxalate crystal formation, a crystal engineering approach was initiated utilizing the non-crystal accumulating plant, Arabidopsis. The success of t...

  7. Finite element simulation of sheet metal forming and springback using a crystal plasticity approach

    SciTech Connect

    Bertram, A.; Boehlke, T.; Krawietz, A.; Schulze, V.

    2007-05-17

    In this paper the application of a crystal plasticity model for body-centered cubic crystals in the simulation of a sheet metal forming process is discussed. The material model parameters are identified by a combination of a texture approximation procedure and a conventional parameter identification scheme. In the application of a cup drawing process the model shows an improvement of the strain and earing prediction as well as the qualitative springback results in comparison with a conventional phenomenological model.

  8. Optics of globular photonic crystals

    SciTech Connect

    Gorelik, V S

    2007-05-31

    The results of experimental and theoretical studies of the optical properties of globular photonic crystals - new physical objects having a crystal structure with the lattice period exceeding considerably the atomic size, are presented. As globular photonic crystals, artificial opal matrices consisting of close-packed silica globules of diameter {approx}200 nm were used. The reflection spectra of these objects characterising the parameters of photonic bands existing in these crystals in the visible spectral region are presented. The idealised models of the energy band structure of photonic crystals investigated in the review give analytic dispersion dependences for the group velocity and the effective photon mass in a globular photonic crystal. The characteristics of secondary emission excited in globular photonic crystals by monochromatic and broadband radiation are presented. The results of investigations of single-photon-excited delayed scattering of light observed in globular photonic crystals exposed to cw UV radiation and radiation from a repetitively pulsed copper vapour laser are presented. The possibilities of using globular photonic crystals as active media for lasing in different spectral regions are considered. It is proposed to use globular photonic crystals as sensitive sensors in optoelectronic devices for molecular analysis of organic and inorganic materials by the modern methods of laser spectroscopy. The results of experimental studies of spontaneous and stimulated globular scattering of light are discussed. The conditions for observing resonance and two-photon-excited delayed scattering of light are found. The possibility of accumulation and localisation of the laser radiation energy inside a globular photonic crystal is reported. (review)

  9. Graphene Oxide Restricts Growth and Recrystallization of Ice Crystals.

    PubMed

    Geng, Hongya; Liu, Xing; Shi, Guosheng; Bai, Guoying; Ma, Ji; Chen, Jingbo; Wu, Zhuangyuan; Song, Yanlin; Fang, Haiping; Wang, Jianjun

    2017-01-19

    We show graphene oxide (GO) greatly suppresses the growth and recrystallization of ice crystals, and ice crystals display a hexagonal shape in the GO dispersion. Preferred adsorption of GO on the ice crystal surface in liquid water leads to curved ice crystal surface. Therefore, the growth of ice crystal is suppressed owing to the Gibbs-Thompson effect, that is, the curved surface lowers the freezing temperature. Molecular dynamics simulation analysis reveals that oxidized groups on the basal plane of GO form more hydrogen bonds with ice in comparison with liquid water because of the honeycomb hexagonal scaffold of graphene, giving a molecular-level mechanism for controlling ice formation. Application of GO for cryopreservation shows that addition of only 0.01 wt % of GO to a culture medium greatly increases the motility (from 24.3 % to 71.3 %) of horse sperms. This work reports the control of growth of ice with GO, and opens a new avenue for the application of 2D materials.

  10. Comparison of thermal lensing effects between single-end and double-end diffusion-bonded Nd:YVO4 crystals for 4F 3/2-->4I 11/2 and 4F 3/2-->4I 13/2 transitions.

    PubMed

    Chang, Y T; Huang, Y P; Su, K W; Chen, Y F

    2008-12-08

    The effective focal lengths of thermal lens in diode-end-pumped continuous-wave Nd:YVO(4) lasers for the (4)F(3/2)-->(4)I(11/2) and (4)F(3/2)-->(4)I(13/2) transitions were determined. The experimental results revealed that the thermal lensing effect for the (4)F(3/2)-->(4)I(11/2) transition can be sufficiently improved by employing a single-end diffusion-bonded Nd:YVO(4) crystal replacing a conventional Nd:YVO(4) crystal. However, using a double-end diffusion-bonded Nd:YVO(4) crystal was a great improvement over a single-end diffusion-bonded Nd:YVO(4) crystal for the (4)F(3/2)-->(4)I(13/2) transition with stronger thermal lensing effect.

  11. Towards protein-crystal centering using second-harmonic generation (SHG) microscopy

    PubMed Central

    Kissick, David J.; Dettmar, Christopher M.; Becker, Michael; Mulichak, Anne M.; Cherezov, Vadim; Ginell, Stephan L.; Battaile, Kevin P.; Keefe, Lisa J.; Fischetti, Robert F.; Simpson, Garth J.

    2013-01-01

    The potential of second-harmonic generation (SHG) microscopy for automated crystal centering to guide synchrotron X-­ray diffraction of protein crystals was explored. These studies included (i) comparison of microcrystal positions in cryoloops as determined by SHG imaging and by X-ray diffraction rastering and (ii) X-ray structure determinations of selected proteins to investigate the potential for laser-induced damage from SHG imaging. In studies using β2 adrenergic receptor membrane-protein crystals prepared in lipidic mesophase, the crystal locations identified by SHG images obtained in transmission mode were found to correlate well with the crystal locations identified by raster scanning using an X-­ray minibeam. SHG imaging was found to provide about 2 µm spatial resolution and shorter image-acquisition times. The general insensitivity of SHG images to optical scatter enabled the reliable identification of microcrystals within opaque cryocooled lipidic mesophases that were not identified by conventional bright-field imaging. The potential impact of extended exposure of protein crystals to five times a typical imaging dose from an ultrafast laser source was also assessed. Measurements of myoglobin and thaumatin crystals resulted in no statistically significant differences between structures obtained from diffraction data acquired from exposed and unexposed regions of single crystals. Practical constraints for integrating SHG imaging into an active beamline for routine automated crystal centering are discussed. PMID:23633594

  12. Growing Crystals on the Ceiling.

    ERIC Educational Resources Information Center

    Christman, Robert A.

    1980-01-01

    Described is a method of studying growing crystals in a classroom utilizing a carrousel projector standing vertically. A saturated salt solution is placed on a slide on the lens of the projector and the heat from the projector causes the water to evaporate and salt to crystalize. (Author/DS)

  13. Dynamically controlled crystal growth system

    NASA Technical Reports Server (NTRS)

    Bray, Terry L. (Inventor); Kim, Larry J. (Inventor); Harrington, Michael (Inventor); DeLucas, Lawrence J. (Inventor)

    2002-01-01

    Crystal growth can be initiated and controlled by dynamically controlled vapor diffusion or temperature change. In one aspect, the present invention uses a precisely controlled vapor diffusion approach to monitor and control protein crystal growth. The system utilizes a humidity sensor and various interfaces under computer control to effect virtually any evaporation rate from a number of different growth solutions simultaneously by means of an evaporative gas flow. A static laser light scattering sensor can be used to detect aggregation events and trigger a change in the evaporation rate for a growth solution. A control/follower configuration can be used to actively monitor one chamber and accurately control replicate chambers relative to the control chamber. In a second aspect, the invention exploits the varying solubility of proteins versus temperature to control the growth of protein crystals. This system contains miniature thermoelectric devices under microcomputer control that change temperature as needed to grow crystals of a given protein. Complex temperature ramps are possible using this approach. A static laser light scattering probe also can be used in this system as a non-invasive probe for detection of aggregation events. The automated dynamic control system provides systematic and predictable responses with regard to crystal size. These systems can be used for microgravity crystallization projects, for example in a space shuttle, and for crystallization work under terrestial conditions. The present invention is particularly useful for macromolecular crystallization, e.g. for proteins, polypeptides, nucleic acids, viruses and virus particles.

  14. Crystals Out of "Thin Air".

    ERIC Educational Resources Information Center

    Vollmer, John J.

    2000-01-01

    Describes how to grow crystals of para-dichlorobenzene beginning with household mothballs. The crystals form through sublimation (solid to gas) and deposition (gas to solid). Also discusses demonstrations of evaporation and condensation and odor perception, which can support a study of the kinetic theory and phases of matter. (WRM)

  15. Crystallization of steroids in gels

    NASA Astrophysics Data System (ADS)

    Kalkura, S. Narayana; Devanarayanan, S.

    1991-03-01

    The crystal growth and characterization of certain steriods, viz., cholesterol, cholesteryl acetate, β-sitosterol, progesterone and testosterone, in a silica gel medium is discussed. The present study shows that the single test tube diffusion method can be used to grow crystals of steroids in a silica gel medium by the reduction of steroid solubility.

  16. Photoelastic sphenoscopic analysis of crystals

    SciTech Connect

    Montalto, L.; Rinaldi, D.; Scalise, L.; Paone, N.; Davì, F.

    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.

  17. Novel inclusion in laser crystals

    SciTech Connect

    Ma Xiaoshan; Wang Siting; Jin Zhongru; Shen Yafang; Chen Jiaguang

    1986-12-01

    In growing alexandrite crystals, a novel inclusion has been found. The inclusions are quantitatively analyzed by an electronic probe and the mechanism for forming inclusions is suggested. In our Bridgman MgF/sub 2/ crystals, the inclusions in <001> direction have also been observed.

  18. Protein crystal growth in microgravity

    NASA Technical Reports Server (NTRS)

    Carter, Daniel

    1992-01-01

    The overall scientific goals and rationale for growing protein crystals in microgravity are discussed. Data on the growth of human serum albumin crystals which were produced during the First International Microgravity Laboratory (IML-1) are presented. Potential scientific advantages of the utilization of Space Station Freedom are discussed.

  19. Photoelastic sphenoscopic analysis of crystals

    NASA Astrophysics Data System (ADS)

    Montalto, L.; Rinaldi, D.; Scalise, L.; Paone, N.; Davı, F.

    2016-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

  1. Exploring structural phase transitions of ion crystals

    PubMed Central

    Yan, L. L.; Wan, W.; Chen, L.; Zhou, F.; Gong, S. J.; Tong, X.; Feng, M.

    2016-01-01

    Phase transitions have been a research focus in many-body physics over past decades. Cold ions, under strong Coulomb repulsion, provide a repealing paradigm of exploring phase transitions in stable confinement by electromagnetic field. We demonstrate various conformations of up to sixteen laser-cooled 40Ca+ ion crystals in a home-built surface-electrode trap, where besides the usually mentioned structural phase transition from the linear to the zigzag, two additional phase transitions to more complicated two-dimensional configurations are identified. The experimental observation agrees well with the numerical simulation. Heating due to micromotion of the ions is analysed by comparison of the numerical simulation with the experimental observation. Our investigation implies very rich and complicated many-body behaviour in the trapped-ion systems and provides effective mechanism for further exploring quantum phase transitions and quantum information processing with ultracold trapped ions. PMID:26865229

  2. Enhanced photoacoustic detection using photonic crystal substrate

    SciTech Connect

    Zhao, Yunfei; Liu, Kaiyang; McClelland, John; Lu, Meng

    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.

  3. Crystal structure of fluroxypyr

    PubMed Central

    Park, Hyunjin; Choi, Myong Yong; Kwon, Eunjin; Kim, Tae Ho

    2016-01-01

    In the title pyridine herbicide {systematic name: 2-[(4-amino-3,5-di­chloro-6-fluoro­pyridin-2-yl)­oxy]acetic acid}, C7H5Cl2FN2O3, the mean plane of the carb­oxy­lic acid substituent and the pyridyl ring plane subtend a dihedral angle of 77.5 (1)°. In the crystal, pairs of O—H⋯O hydrogen bonds form inversion dimers with R 2 2(8) ring motifs. These are extended into chains along [011] by N—H⋯F hydrogen bonds. In addition, inter­molecular N—H⋯O hydrogen bonds and weak π–π inter­actions [ring centroid separation = 3.4602 (9) Å] connect these chains into a three-dimensional network. PMID:27980844

  4. Frequency mixing crystal

    DOEpatents

    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.

  5. Lamella settler crystallizer

    DOEpatents

    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.

  6. Lamella settler crystallizer

    DOEpatents

    Maimoni, A.

    1990-12-18

    A crystallizer is described 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. 3 figs.

  7. Crystal structure of mandipropamid.

    PubMed

    Park, Hyunjin; Kim, Jineun; Kang, Gihaeng; Kim, Tae Ho

    2015-10-01

    In the title compound, C23H22ClNO4 (systematic name: (RS)-2-(4-chloro-phen-yl)-N-{2-[3-meth-oxy-4-(prop-2-yn-1-yl-oxy)phen-yl]eth-yl}-2-(prop-2-yn-yloxy)acetamide), an amide fungicide, the dihedral angle between the chloro-benzene and benzene rings is 65.36 (6)°. In the crystal, N-H⋯O hydrogen bonds lead to zigzag supra-molecular chains along the c axis (glide symmetry). These are connected into layers by C-H⋯O and C-H⋯π inter-actions; the layers stack along the a axis with no specific inter-molecular inter-actions between them.

  8. Adaptive liquid crystal iris

    NASA Astrophysics Data System (ADS)

    Zhou, Zuowei; Ren, Hongwen; Nah, Changwoon

    2014-09-01

    We report an adaptive iris using a twisted nematic liquid crystal (TNLC) and a hole-patterned electrode. When an external voltage is applied to the TNLC, the directors of the LC near the edge of the hole are unwound first. Increasing the voltage can continuously unwind the LC toward the center. When the TNLC is sandwiched between two polarizers, it exhibits an iris-like character. Either a normal mode or a reverse mode can be obtained depending on the orientations of the transmission axes of the two polarizers. In contrast to liquid irises, the aperture of the LC iris can be closed completely. Moreover, it has the advantages of large variability of the aperture diameter, good stability, and low power consumption. Applications of the device for controlling the laser energy and correcting optical aberration are foreseeable.

  9. Natural photonic crystals

    NASA Astrophysics Data System (ADS)

    Vigneron, Jean Pol; Simonis, Priscilla

    2012-10-01

    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.

  10. Clathrate colloidal crystals

    NASA Astrophysics Data System (ADS)

    Lin, Haixin; Lee, Sangmin; Sun, Lin; Spellings, Matthew; Engel, Michael; Glotzer, Sharon C.; Mirkin, Chad A.

    2017-03-01

    DNA-programmable assembly has been used to deliberately synthesize hundreds of different colloidal crystals spanning dozens of symmetries, but the complexity of the achieved structures has so far been limited to small unit cells. We assembled DNA-modified triangular bipyramids (~250-nanometer long edge, 177-nanometer short edge) into clathrate architectures. Electron microscopy images revealed that at least three different structures form as large single-domain architectures or as multidomain materials. Ordered assemblies, isostructural to clathrates, were identified with the help of molecular simulations and geometric analysis. These structures are the most sophisticated architectures made via programmable assembly, and their formation can be understood based on the shape of the nanoparticle building blocks and mode of DNA functionalization.

  11. Voxelated liquid crystal elastomers

    NASA Astrophysics Data System (ADS)

    Ware, Taylor H.; McConney, Michael E.; Wie, Jeong Jae; Tondiglia, Vincent P.; White, Timothy J.

    2015-02-01

    Dynamic control of shape can bring multifunctionality to devices. Soft materials capable of programmable shape change require localized control of the magnitude and directionality of a mechanical response. We report the preparation of soft, ordered materials referred to as liquid crystal elastomers. The direction of molecular order, known as the director, is written within local volume elements (voxels) as small as 0.0005 cubic millimeters. Locally, the director controls the inherent mechanical response (55% strain) within the material. In monoliths with spatially patterned director, thermal or chemical stimuli transform flat sheets into three-dimensional objects through controlled bending and stretching. The programmable mechanical response of these materials could yield monolithic multifunctional devices or serve as reconfigurable substrates for flexible devices in aerospace, medicine, or consumer goods.

  12. Crystal structure of flumioxazin

    PubMed Central

    Park, Hyunjin; Kim, Jineun; Kwon, Eunjin; Kim, Tae Ho

    2015-01-01

    The title compound {systematic name: 2-[7-fluoro-3,4-di­hydro-3-oxo-4-(prop-2-yn-1-yl)-2H-1,4-benzoxazin-6-yl]-4,5,6,7-tetra­hydro-1H-iso­indole-1,3(2H)-dione}, C19H15FN2O4, is a dicarboximide herbicide. The dihedral angle between the male­imide and benzene ring planes is 66.13 (5)°. In the crystal, C—H⋯O and C—H⋯F hydrogen bonds and weak C—H⋯π inter­actions [3.5601 (19) Å] link adjacent mol­ecules, forming two-dimensional networks extending parallel to the (110) plane. PMID:26594468

  13. Bacterial ice crystal controlling proteins.

    PubMed

    Lorv, Janet S H; Rose, David R; Glick, Bernard R

    2014-01-01

    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.

  14. Bacterial Ice Crystal Controlling Proteins

    PubMed Central

    Lorv, Janet S. H.; Rose, David R.; Glick, Bernard R.

    2014-01-01

    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. PMID:24579057

  15. Development of single crystal membranes

    NASA Technical Reports Server (NTRS)

    Stormont, R. W.; Cocks, F. H.

    1972-01-01

    The design and construction of a high pressure crystal growth chamber was accomplished which would allow the growth of crystals under inert gas pressures of 2 MN/sq m (300 psi). A novel crystal growth technique called EFG was used to grow tubes and rods of the hollandite compounds, BaMgTi7O16, K2MgTi7O16, and tubes of sodium beta-alumina, sodium magnesium-alumina, and potassium beta-alumina. Rods and tubes grown are characterized using metallographic and X-ray diffraction techniques. The hollandite compounds are found to be two or three-phase, composed of coarse grained orientated crystallites. Single crystal c-axis tubes of sodium beta-alumina were grown from melts containing excess sodium oxide. Additional experiments demonstrated that crystals of magnesia doped beta-alumina and potassium beta-alumina also can be achieved by this EFG technique.

  16. Texturing studies on ? bulk crystals

    NASA Astrophysics Data System (ADS)

    Prabhakaran, D.; Subramanian, C.

    1998-08-01

    Textured crystals of 0953-2048/11/8/013/img2 have been grown by the platinum strip heater-floating zone technique. Texturing ratio and phase purity (Bi-2212) of the grown crystals were calculated from the x-ray diffraction data. Chemical compositions of the grown crystals were quantified from the inductively coupled plasma analysis. 0953-2048/11/8/013/img3 was found to be increased by 2 K for a lower level of substitution and a superconductor to semiconductor transition was observed for the higher order Y substitution. Oxygen stoichiometries of the Y substituted crystals were quantified from the iodometry titration method. Micro-twinning along the growth axis was revealed during etching studies for the cleaved crystals.

  17. Modeling liquid crystal polymeric devices

    NASA Astrophysics Data System (ADS)

    Gimenez Pinto, Vianney Karina

    The main focus of this work is the theoretical and numerical study of materials that combine liquid crystal and polymer. Liquid crystal elastomers are polymeric materials that exhibit both the ordered properties of the liquid crystals and the elastic properties of rubbers. Changing the order of the liquid crystal molecules within the polymer network can induce shape change. These materials are very valuable for applications such as actuators, sensors, artificial muscles, haptic displays, etc. In this work we apply finite element elastodynamics simulations to study the temperature induced shape deformation in nematic elastomers with complex director microstructure. In another topic, we propose a novel numerical method to model the director dynamics and microstructural evolution of three dimensional nematic and cholesteric liquid crystals. Numerical studies presented in this work are in agreement with experimental observations and provide insight into the design of application devices.

  18. The crystallization of hydroxyapatite and dicalcium phosphate dihydrate; representation of growth curves

    NASA Astrophysics Data System (ADS)

    Hohl, H.; Koutsoukos, P. G.; Nancollas, G. H.

    1982-04-01

    The kinetics of growth of dicalcium phosphate dihydrate seed crystals has been investigated by a method in which the activities of the lattice ions were maintained constant during the reaction. The constant composition procedure has also been used to study the crystallization of hydroxyapatite at very low supersaturation. Changes in specific area during the resulting appreciable extents of growth have been used to predict the developing morphologies of the crystals. For dicalcium phosphate dihydrate and hydroxyapatite, the predominant crystal growth takes place in two dimensions and one dimension, respectively. In both cases the growth rates are pH dependent. Dimensionless representation of the crystallization rates and driving forces enable comparisons to be made between data for electrolytes of different charge types.

  19. Use of YB(66) as monochromator crystals for soft-energy EXAFS.

    PubMed

    Smith, A D; Cowie, B C; Sankar, G; Thomas, J M

    1998-05-01

    YB(66)(400) crystals present a new advance in monochromator crystals suitable for use at energies below 2 keV. In this paper a comparison of their performance with that provided by the more usual beryl and quartz crystals, which cover the same energy range, is presented. In general, the YB(66) crystals are much superior; however, they do exhibit a pair of large 'crystal glitch'-type features in the 1380-1440 eV region. These fall in the Mg K-EXAFS region and so can present a serious problem in studies of this edge for a wide range of materials. An important class of materials so afflicted are magnesium-substituted aluminophosphate molecular sieves (zeolites), which are used in many applications, in particular as solid acid catalysts for conversion of methanol to hydrocarbon.

  20. Polymeric photonic crystals

    NASA Astrophysics Data System (ADS)

    Fink, Yoel

    Two novel and practical methods for controlling the propagation of light are presented: First, a design criterion that permits truly omnidirectional reflectivity for all polarizations of incident light over a wide selectable range of frequencies is derived and used in fabricating an alldielectric omnidirectional reflector consisting of multilayer films. Because the omnidirectionality criterion is general, it can be used to design omnidirectional reflectors in many frequency ranges of interest. Potential uses depend on the geometry of the system. For example, coating of an enclosure will result in an optical cavity. A hollow tube will produce a low-loss, broadband waveguide, planar film could be used as an efficient radiative heat barrier or collector in thermoelectric devices. A comprehensive framework for creating one-, two- and three-dimensional photonic crystals out of self- assembling block copolymers has been formulated. In order to form useful band gaps in the visible regime, periodic dielectric structures made of typical block copolymers need to be modified to obtain appropriate characteristic distances and dielectric constants. Moreover, the absorption and defect concentration must also be controlled. This affords the opportunity to tap into the large structural repertoire, the flexibility and intrinsic tunability that these self-assembled block copolymer systems offer. A block copolymer was used to achieve a self assembled photonic band gap in the visible regime. By swelling the diblock copolymer with lower molecular weight constituents control over the location of the stop band across the visible regime is achieved. One and three- dimensional crystals have been formed by changing the volume fraction of the swelling media. Methods for incorporating defects of prescribed dimensions into the self-assembled structures have been explored leading to the construction of a self assembled microcavity light- emitting device. (Copies available exclusively from MIT

  1. An evaluation of liquid-crystal thermometry as a screening device for intraoperative hyperthermia.

    PubMed

    Lees, D E; Schuette, W; Bull, J M; Whang-Peng, J; Atkinson, E R; Macnamara, T E

    1978-01-01

    Disposable liquid-crystal temperature-trend indicators were evaluated under clinical conditions that simulated the development of intraoperative hyperthermia during anesthesia. Comparison was made to forehead thermistors for rapidity, accuracy, and linearity of response as well as correlation with esophageal and rectal thermistor recordings. The liquid-crystal monitors were comparable to the forehead thermistors in both rapidity and linearity or response, but not in accuracy. A linear correlation existed with the esophageal thermistor temperatures. Correlation with the rectal temperatures was not as exact. It is concluded that liquid-crystal thermometers may adequately serve as screening devices for intraoperative hyperthermia.

  2. X-Ray Diffraction From Shocked Crystals: Experiments and Predications of Molecular Dynamics Simulations

    SciTech Connect

    Rosolankova, K; Kalantar, D H; Belak, J F; Bringa, E M; Caturla, M J; Hawreliak, J; Holian, B L; Kadau, K; Lomdahl, P S; Germann, T C; Ravelo, R; Sheppard, J; Wark, J S

    2003-09-24

    When a crystal is subjected to shock compression beyond its Hugoniot Elastic Limit (HEL), the deformation it undergoes is composed of elastic and plastic strain components. In situ time-dependent X-ray diffraction, which allows direct measurement of lattice spacings, can be used to investigate such phenomena. This paper presents recent experimental results of X-ray diffraction from shocked fcc crystals. Comparison is made between experimental data and simulated X-ray diffraction using a post-processor to Molecular Dynamics (MD) simulations of shocked fcc crystals.

  3. Neutron study of crystal-field transitions in ErPO{sub 4}

    SciTech Connect

    Loong, C.-K.; Soderholm, L.; Hammonds, J.P.; Abraham, M.M.; Boatner, L.A.; Edelstein, N.M.

    1992-12-01

    The crystal-field splitting of the Er{sup 3+} ground multiplet, {sup 4}I{sub 15/2}, in ErPO{sub 4} is investigated by inelastic neutron scattering. Four excitations from the {Gamma}{sub 7} ground state to the excited states and several transitions between the excited states have been identified. The observed transition energies and intensities are used to refine the parameters of the crystal-field potential. The calculated magnetic susceptibility, {chi}(T), agrees well with experimental values from single-crystal measurements. A comparison of the neutron data with optical absorption and both nonresonance and resonance Raman scattering measurements has been made.

  4. Neutron study of crystal-field transitions in ErPO[sub 4

    SciTech Connect

    Loong, C.-K.; Soderholm, L.; Hammonds, J.P. ); Abraham, M.M.; Boatner, L.A. ); Edelstein, N.M. )

    1992-01-01

    The crystal-field splitting of the Er[sup 3+] ground multiplet, [sup 4]I[sub 15/2], in ErPO[sub 4] is investigated by inelastic neutron scattering. Four excitations from the [Gamma][sub 7] ground state to the excited states and several transitions between the excited states have been identified. The observed transition energies and intensities are used to refine the parameters of the crystal-field potential. The calculated magnetic susceptibility, [chi](T), agrees well with experimental values from single-crystal measurements. A comparison of the neutron data with optical absorption and both nonresonance and resonance Raman scattering measurements has been made.

  5. Light-scattering properties of plate and column ice crystals generated in a laboratory cold chamber.

    PubMed

    Barkey, Brian; Bailey, Matt; Liou, Kuo-Nan; Hallett, John

    2002-09-20

    Angular scattering properties of ice crystal particles generated in a laboratory cloud chamber are measured with a lightweight polar nephelometer with a diode laser beam. This cloud chamber produces distinct plate and hollow column ice crystal types for light-scattering experiments and provides a controlled test bed for comparison with results computed from theory. Ice clouds composed predominantly of plates and hollow columns generated noticeable 22 degrees and 46 degrees halo patterns, which are predicted from geometric ray-tracing calculations. With the measured ice crystal shape and size distribution, the angular scattering patterns computed from geometrical optics with a significant contribution by rough surfaces closely match those observed from the nephelometer.

  6. Raman study of uniaxial deformation of single-crystal mats of ultrahigh molecular weight linear polyethylene

    NASA Astrophysics Data System (ADS)

    Zavgorodnev, Yu V.; Chvalun, S. N.; Nikolaeva, G. Yu; Sagitova, E. A.; Pashinin, P. P.; Gordeyev, S. A.; Prokhorov, K. A.

    2015-03-01

    We present for the first time a Raman spectroscopic study of the deformation process of solution-crystallized single-crystal mats of ultrahigh molecular weight linear polyethylene (UHMW PE). We study the deformed regions of the films, drawn only until the formation of the neck, and the films of much higher draw ratios, just before rupture starts. For comparison, we have also carried out Raman investigations of films produced by compression of UHMW PE powder. We have found that the uniaxial molecular orientation in the neck region of the single-crystal mat films develops more slowly as compared to the films, prepared by compression of the UHMW PE powder.

  7. Growing single crystals in silica gel

    NASA Technical Reports Server (NTRS)

    Rubin, B.

    1970-01-01

    Two types of chemical reactions for crystal growing are discussed. The first is a metathetical reaction to produce calcium tartrate tetrahydrate crystals, the second is a decomplexation reaction to produce cuprous chloride crystals.

  8. Crystallization of Biological Macromolecules in Microgravity

    NASA Technical Reports Server (NTRS)

    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.

  9. Crystal structures of sialyltransferase from Photobacterium damselae

    DOE PAGES

    Huynh, Nhung; Li, Yanhong; Yu, Hai; ...

    2014-11-15

    Sialyltransferase structures fall into either GT-A or GT-B glycosyltransferase fold. Some sialyltransferases from the Photobacterium genus have been shown to contain an additional N-terminal immunoglobulin (Ig)-like domain. Photobacterium damselae α2–6-sialyltransferase has been used efficiently in enzymatic and chemoenzymatic synthesis of α2–6-linked sialosides. In this paper, we report three crystal structures of this enzyme. Two structures with and without a donor substrate analog CMP-3F(a)Neu5Ac contain an immunoglobulin (Ig)-like domain and adopt the GT-B sialyltransferase fold. The binary structure reveals a non-productive pre-Michaelis complex, which are caused by crystal lattice contacts that prevent the large conformational changes. The third structure lacks themore » Ig-domain. Finally, comparison of the three structures reveals small inherent flexibility between the two Rossmann-like domains of the GT-B fold.« less

  10. Determining the Molecular Growth Mechanisms of Tetragonal Lysozyme Crystals

    NASA Technical Reports Server (NTRS)

    Li, Huayu; Nadarajah, Arunan; Konnert, John H.; Pusey, Marc L.

    1998-01-01

    . The theoretical images were constructed by convolution of the crystal surface shape obtained from crystallographic data with the AFM tip shape. The comparison confirmed the prediction that the molecular packing arrangement of these faces corresponded to that for complete 43 helices. The second AFM technique that was developed was used to follow the growth process by measuring the dimensions of individual growth units on the (110) face. Linescans across a growth step, performed near the saturation limit of the crystals, allowed the growth unit dimensions to be measured. These measurements showed that growth on the (110) face proceeded by the formation of new 43 helices from the addition of at least tetramer units in the [110] direction. In the [001] direction growth proceeded by the addition of various aggregate units corresponding to the 4(sub 3) helices.

  11. The crystal's view of upper-crustal magma reservoirs

    NASA Astrophysics Data System (ADS)

    Cooper, K. M.; Kent, A. J.; Huber, C.; Stelten, M. E.; Rubin, A. E.; Schrecengost, K.

    2015-12-01

    Upper-crustal magma reservoirs are important sites of magma mixing, crustal refining, and magma storage. Crystals residing in these reservoirs have been shown to represent valuable archives of the chemical and physical evolution of reservoirs, and the time scales of this evolution. This presentation addresses the question of "What do crystals "see" and record about processes within the upper crust? And how is that view similar or different between plutonic and volcanic records?" Three general observations emerge from study of the ages of crystals, combined with crystal-scale geochemical data: 1) Patterns of isotopic and trace-element data over time in zircon crystals from a given magmatic system (e.g., Yellowstone, WY, and Taupo Volcanic Zone, New Zealand) can show systematic changes in the degree of heterogeneity, consistent with extraction of melts from a long-lived (up to 100s of kyr), heterogeneous crystal mush and in some cases continued crystallization and homogenization of the magma during a short period (< a few kyr) preceding eruption. 2) Thermal histories of magma storage derived from crystal records also show that the vast majority of time recorded by major phases was spent in storage as a crystal mush, perhaps at near-solidus conditions. 3) Comparison of ages of accessory phases in both plutonic blocks and host magmas that brought them to the surface do not show a consistent relationship between the two. In some cases, zircons from plutonic blocks have age spectra much older than zircon in the host magma. In other cases, host and plutonic block zircons have similar age spectra and chemical characteristics, suggesting a closer genetic connection between the two. These observations suggest that crystals in plutonic bodies, if examined at similar spatial and temporal scales to those in volcanic rocks, would show records that are highly heterogeneous in chemistry and age on the scale of a pluton or a lobe of a pluton, but that local regions of limited

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

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

    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 ≤ fcrystal ≤ 0.74. Radial transport models that predict the enrichment of the outer disk (>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 μm, 16, 19, 23.5, 27, and 33 μm), 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 μm-radii porous aggregates with 0.13 ≤ fcrystal ≤ 0.35 and with polyhedral-shaped Forsterite 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 11µm and 23 µm 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

  13. THE CRYSTAL STRUCTURE OF DIPHENYLTELLURIUM DIBROMIDE,

    DTIC Science & Technology

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

  14. Growth and spectroscopic investigation of a new crystal for NLO applications: C₁₀H₂ ₀KN₅O₉.

    PubMed

    Hanumantharao, Redrothu; Kalainathan, S

    2012-12-01

    Nonlinear optical crystals of Bis (l-glutamine) potassium nitrate (BGPN) were grown by slow evaporation technique at ambient temperature. Solubility and metastable zone width of BGPN in aqueous solution were determined. The grown crystal was characterized by single crystal XRD, Powder XRD, FT-IR (1)H NMR, EDAX, mass and optical spectroscopic techniques. Single crystal XRD revealed that compound crystallizes in orthorhombic system with non-centrosymmetric space group P2(1)2(1)2(1). The sharp peaks from powder XRD spectrum show the high crystallinity of the grown crystal. FT-IR confirms the presence of functional groups and molecular structure was confirmed by (1)H NMR spectrum of the grown crystal. Molecular mass of BGPN sample has been verified by high resolution mass spectroscopic analysis. The presence of potassium in the compound and composition of grown crystals was confirmed on the basis of energy dispersive analysis of X-ray (EDAX). Thermal stability of the grown crystal was studied by TGA-DTA analysis. An optical UV-Vis-NIR spectrum for BGPN sample was recorded in the range of 190-1100 nm. Fluorescence studies shows material BGPN emits blue fluorescence. Second harmonic generation (SHG) studies have been performed by famous Kurtz powder technique with reference to standard potassium dihydrogen phosphate single crystals (KDP). It is found from this technique that SHG efficiency of BGPN is in comparison to that of standard KDP crystals.

  15. Spatial filtering with photonic crystals

    SciTech Connect

    Maigyte, Lina; Staliunas, Kestutis

    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.

  16. Pressure sensor using liquid crystals

    NASA Technical Reports Server (NTRS)

    Parmar, Devendra S. (Inventor); Holmes, Harlan K. (Inventor)

    1994-01-01

    A pressure sensor includes a liquid crystal positioned between transparent, electrically conductive films (18 and 20), that are biased by a voltage (V) which induces an electric field (E) that causes the liquid crystal to assume a first state of orientation. Application of pressure (P) to a flexible, transparent film (24) causes the conductive film (20) to move closer to or farther from the conductive film (18), thereby causing a change in the electric field (E'(P)) which causes the liquid crystal to assume a second state of orientation. Polarized light (P.sub.1) is directed into the liquid crystal and transmitted or reflected to an analyzer (A or 30). Changes in the state of orientation of the liquid crystal induced by applied pressure (P) result in a different light intensity being detected at the analyzer (A or 30) as a function of the applied pressure (P). In particular embodiments, the liquid crystal is present as droplets (10) in a polymer matrix (12) or in cells (14) in a polymeric or dielectric grid (16) material in the form of a layer (13) between the electrically conductive films (18 and 20). The liquid crystal fills the open wells in the polymer matrix (12) or grid (16) only partially.

  17. Crystallization of copper metaphosphate glass

    NASA Technical Reports Server (NTRS)

    Bae, Byeong-Soo; Weinberg, Michael C.

    1993-01-01

    The effect of the valence state of copper in copper metaphosphate glass on the crystallization behavior and glass transition temperature has been investigated. The crystallization of copper metaphosphate is initiated from the surface and its main crystalline phase is copper metaphosphate (Cu(PO)3),independent of the (Cu sup 2+)/(Cu(total)). However, the crystal morphology, the relative crystallization rates, and their temperature dependences are affected by the (Cu sup 2+)/(Cu (total)) ratio in the glass. On the other hand, the totally oxidized glass crystallizes from all over the surface. The relative crystallization rate of the reduced glass to the totally oxidized glass is large at low temperature, but small at high temperature. The glass transition temperature of the glass increases as the (Cu sup 2+)/(Cu(total)) ratio is raised. It is also found that the atmosphere used during heat treatment does not influence the crystallization of the reduced glass, except for the formation of a very thin CuO surface layer when heated in air.

  18. Photonic crystal enhanced cytokine immunoassay.

    PubMed

    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.

  19. Crystal ball single event display

    SciTech Connect

    Grosnick, D.; Gibson, A.; Allgower, C.; Alyea, J. |

    1997-10-15

    The Single Event Display (SED) is a routine that is designed to provide information graphically about a triggered event within the Crystal Ball. The SED is written entirely in FORTRAN and uses the CERN-based HICZ graphing package. The primary display shows the amount of energy deposited in each of the NaI crystals on a Mercator-like projection of the crystals. Ten different shades and colors correspond to varying amounts of energy deposited within a crystal. Information about energy clusters is displayed on the crystal map by outlining in red the thirteen (or twelve) crystals contained within a cluster and assigning each cluster a number. Additional information about energy clusters is provided in a series of boxes containing useful data about the energy distribution among the crystals within the cluster. Other information shown on the event display include the event trigger type and data about {pi}{sup o}`s and {eta}`s formed from pairs of clusters as found by the analyzer. A description of the major features is given, along with some information on how to install the SED into the analyzer.

  20. Dichroic Liquid Crystal Displays

    NASA Astrophysics Data System (ADS)

    Bahadur, Birendra

    The following sections are included: * INTRODUCTION * DICHROIC DYES * Chemical Structure * Chemical and Photochemical Stability * THEORETICAL MODELLING * DEFECTS CAUSED BY PROLONGED LIGHT IRRADIATION * CHEMICAL STRUCTURE AND PHOTOSTABILITY * OTHER PARAMETERS AFFECTING PHOTOSTABILITY * CELL PREPARATION * DICHROIC PARAMETERS AND THEIR MEASUREMENTS * Order Parameter and Dichroic Ratio Of Dyes * Absorbance, Order Parameter and Dichroic Ratio Measurements * IMPACT OF DYE STRUCTURE AND LIQUID CRYSTAL HOST ON PHYSICAL PROPERTIES OF A DICHROIC MIXTURE * Order Parameter and Dichroic Ratio * EFFECT OF LENGTH OF DICHROIC DYES ON THE ORDER PARAMETER * EFFECT OF THE BREADTH OF DYE ON THE ORDER PARAMETER * EFFECT OF THE HOST ON THE ORDER PARAMETER * TEMPERATURE VARIATION OF THE ORDER PARAMETER OF DYES IN A LIQUID CRYSTAL HOST * IMPACT OF DYE CONCENTRATION ON THE ORDER PARAMETER * Temperature Range * Viscosity * Dielectric Constant and Anisotropy * Refractive Indices and Birefringence * solubility43,153-156 * Absorption Wavelength and Auxochromic Groups * Molecular Engineering of Dichroic Dyes * OPTICAL, ELECTRO-OPTICAL AND LIFE PARAMETERS * Colour And CIE Colour space120,160-166 * CIE 1931 COLOUR SPACE * CIE 1976 CHROMATICITY DIAGRAM * CIE UNIFORM COLOUR SPACES & COLOUR DIFFERENCE FORMULAE120,160-166 * Electro-Optical Parameters120 * LUMINANCE * CONTRAST AND CONTRAST RATIO * SWITCHING SPEED * Life Parameters and Failure Modes * DICHROIC MIXTURE FORMULATION * Monochrome Mixture * Black Mixture * ACHROMATIC BLACK MIXTURE FOR HEILMEIER DISPLAYS * Effect of Illuminant on Display Colour * Colour of the Field-On State * Effect of Dye Linewidth * Optimum Centroid Wavelengths * Effect of Dye Concentration * Mixture Formulation Using More Than Three Dyes * ACHROMATIC MIXTURE FOR WHITE-TAYLOR TYPE DISPLAYS * HEILMEIER DISPLAYS * Theoretical Modelling * Threshold Characteristic * Effects of Dye Concentration on Electro-optical Parameters * Effect of Cholesteric Doping * Effect of Alignment

  1. Spherical colloidal photonic crystals.

    PubMed

    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

  2. Crystal cataracts: Human genetic cataract caused by protein crystallization

    NASA Astrophysics Data System (ADS)

    Pande, Ajay; Pande, Jayanti; Asherie, Neer; Lomakin, Aleksey; Ogun, Olutayo; King, Jonathan; Benedek, George B.

    2001-05-01

    Several human genetic cataracts have been linked recently to point mutations in the D crystallin gene. Here we provide a molecular basis for lens opacity in two genetic cataracts and suggest that the opacity occurs because of the spontaneous crystallization of the mutant proteins. Such crystallization of endogenous proteins leading to pathology is an unusual event. Measurements of the solubility curves of crystals of the Arg-58 to His and Arg-36 to Ser mutants of D crystallin show that the mutations dramatically lower the solubility of the protein. Furthermore, the crystal nucleation rate of the mutants is enhanced considerably relative to that of the wild-type protein. It should be noted that, although there is a marked difference in phase behavior, there is no significant difference in protein conformation among the three proteins.

  3. Aperiodic crystals and superspace concepts.

    PubMed

    Janssen, T; Janner, A

    2014-08-01

    For several decades the lattice periodicity of crystals, as shown by Laue, was considered to be their essential property. In the early sixties of the last century compounds were found which for many reasons should be called crystals, but were not lattice periodic. This opened the field of aperiodic crystals. An overview of this development is given. Many materials of this kind were found, sometimes with very interesting properties. In the beginning the development was slow, but the number of structures of this type increased enormously. In the meantime hundreds of scientists have contributed to this field using a multi-disciplinary approach.

  4. Configurable silicon photonic crystal waveguides

    NASA Astrophysics Data System (ADS)

    Prorok, Stefan; Petrov, Alexander; Eich, Manfred; Luo, Jingdong; Jen, Alex K.-Y.

    2013-12-01

    In this Letter, we demonstrate that the mode cut off of a photonic crystal waveguide can be trimmed with high accuracy by electron beam bleaching of a chromophore doped polymer cladding. Using this method, configurable waveguides are realized, which allow for spatially resolved changes of the photonic crystal's effective lattice constant as small as 7.6 pm. We show three different examples how to take advantage of configurable photonic crystal waveguides: Shifting of the complete transmission spectrum, definition of cavities with high quality factor, and tuning of existing cavities.

  5. Automated protein crystal growth facility

    NASA Technical Reports Server (NTRS)

    Donald, Stacey

    1994-01-01

    A customer for the protein crystal growth facility fills the specially designed chamber with the correct solutions, fills the syringes with their quenching solutions, and submits the data needed for the proper growth of their crystal. To make sure that the chambers and syringes are filled correctly, a NASA representative may assist the customer. The data needed is the approximate growth time, the growth temperature, and the desired crystal size, but this data can be changed anytime from the ground, if needed. The chambers are gathered and placed into numbered slots in special drawers. Then, data is entered into a computer for each of the chambers. Technicians map out when each chamber's growth should be activated so that all of the chambers have enough time to grow. All of this data is up-linked to the space station when the previous growth session is over. Anti-vibrational containers need to be constructed for the high forces encountered during the lift off and the landing of the space shuttle, and though our team has not designed these containers, we do not feel that there is any reason why a suitable one could not be made. When the shuttle reaches the space station, an astronaut removes a drawer of quenched chambers from the growth facility and inserts a drawer of new chambers. All twelve of the drawers can be replaced in this fashion. The optical disks can also be removed this way. The old drawers are stored for the trip back to earth. Once inside the growth facility, a chamber is removed by the robot and placed in one of 144 active sites at a time previously picked by a technician. Growth begins when the chamber is inserted into an active site. Then, the sensing system starts to determine the size of the protein crystal. All during the crystal's growth, the customer can view the crystal and read all of the crystal's data, such as growth rate and crystal size. When the sensing system determines that the crystal has reached the predetermined size, the robot is

  6. Multicolor photonic crystal laser array

    SciTech Connect

    Wright, Jeremy B; Brener, Igal; Subramania, Ganapathi S; Wang, George T; Li, Qiming

    2015-04-28

    A multicolor photonic crystal laser array comprises pixels of monolithically grown gain sections each with a different emission center wavelength. As an example, two-dimensional surface-emitting photonic crystal lasers comprising broad gain-bandwidth III-nitride multiple quantum well axial heterostructures were fabricated using a novel top-down nanowire fabrication method. Single-mode lasing was obtained in the blue-violet spectral region with 60 nm of tuning (or 16% of the nominal center wavelength) that was determined purely by the photonic crystal geometry. This approach can be extended to cover the entire visible spectrum.

  7. Configurable silicon photonic crystal waveguides

    SciTech Connect

    Prorok, Stefan; Petrov, Alexander; Eich, Manfred; Luo, Jingdong; Jen, Alex K.-Y.

    2013-12-23

    In this Letter, we demonstrate that the mode cut off of a photonic crystal waveguide can be trimmed with high accuracy by electron beam bleaching of a chromophore doped polymer cladding. Using this method, configurable waveguides are realized, which allow for spatially resolved changes of the photonic crystal's effective lattice constant as small as 7.6 pm. We show three different examples how to take advantage of configurable photonic crystal waveguides: Shifting of the complete transmission spectrum, definition of cavities with high quality factor, and tuning of existing cavities.

  8. Crystal growth and annealing method and apparatus

    DOEpatents

    Gianoulakis, Steven E.; Sparrow, Robert

    2001-01-01

    A method and apparatus for producing crystals that minimizes birefringence even at large crystal sizes, and is suitable for production of CaF.sub.2 crystals. The method of the present invention comprises annealing a crystal by maintaining a minimal temperature gradient in the crystal while slowly reducing the bulk temperature of the crystal. An apparatus according to the present invention includes a thermal control system added to a crystal growth and annealing apparatus, wherein the thermal control system allows a temperature gradient during crystal growth but minimizes the temperature gradient during crystal annealing. An embodiment of the present invention comprises a secondary heater incorporated into a conventional crystal growth and annealing apparatus. The secondary heater supplies heat to minimize the temperature gradients in the crystal during the annealing process. The secondary heater can mount near the bottom of the crucible to effectively maintain appropriate temperature gradients.

  9. Dielectric, magnetic, and lattice dynamics properties of Y-type hexaferrite Ba{sub 0.5}Sr{sub 1.5}Zn{sub 2}Fe{sub 12}O{sub 22}: Comparison of ceramics and single crystals

    SciTech Connect

    Kamba, S.; Goian, V.; Savinov, M.; Buixaderas, E.; Nuzhnyy, D.; Marysko, M.; Kempa, M.; Bovtun, V.; Hlinka, J.; Knizek, K.; Vanek, P.; Novak, P.; Bursik, J.; Hiraoka, Y.; Kimura, T.; Kouril, K.; Stepankova, H.

    2010-05-15

    We prepared multiferroic Y-type hexaferrite Ba{sub 0.5}Sr{sub 1.5}Zn{sub 2}Fe{sub 12}O{sub 22} ceramics and compared their magnetic and dielectric properties with single crystal. Magnetic susceptibility and microwave resonance measurement revealed magnetic phase transition at T{sub C}=312 K, similar as in single crystal. Ferroelectric (FE) phase can be induced by external magnetic field in all investigated samples and the phase diagram in ceramics qualitatively resembles that of the single crystal. The range of magnetic fields, where the FE phase is induced, broadens after annealing of single crystal. Ceramics quenched after sintering exhibit several orders of magnitude lower conductivity than the single crystal. Heavily damped magnetic resonance was discovered in terahertz spectra at 10 K and its frequency softens below 5 GHz near T{sub C}. Number and symmetry of observed infrared (IR) and Raman active phonons correspond to paraelectric phase with D{sub 3d}{sup 5} hexagonal structure. No evidence for a structural phase transition was found in the IR and Raman spectra on cooling (in zero magnetic field) or in the room-temperature IR spectra with external static magnetic field up to 0.3 T.

  10. Magnetic dipole interactions in crystals

    DOE PAGES

    Johnston, David

    2016-01-13

    The influence of magnetic dipole interactions (MDIs) on the magnetic properties of local-moment Heisenberg spin systems is investigated. A general formulation is presented for calculating the eigenvalues λ and eigenvectors μ ˆ of the MDI tensor of the magnetic dipoles in a line (one dimension, 1D), within a circle (2D) or a sphere (3D) of radius r surrounding a given moment μ → i for given magnetic propagation vectors k for collinear and coplanar noncollinear magnetic structures on both Bravais and non-Bravais spin lattices. Results are calculated for collinear ordering on 1D chains, 2D square and simple-hexagonal (triangular) Bravais lattices,more » 2D honeycomb and kagomé non-Bravais lattices, and 3D cubic Bravais lattices. The λ and μ ˆ values are compared with previously reported results. Calculations for collinear ordering on 3D simple tetragonal, body-centered tetragonal, and stacked triangular and honeycomb lattices are presented for c/a ratios from 0.5 to 3 in both graphical and tabular form to facilitate comparison of experimentally determined easy axes of ordering on these Bravais lattices with the predictions for MDIs. Comparisons with the easy axes measured for several illustrative collinear antiferromagnets (AFMs) are given. The calculations are extended to the cycloidal noncollinear 120 ° AFM ordering on the triangular lattice where λ is found to be the same as for collinear AFM ordering with the same k. The angular orientation of the ordered moments in the noncollinear coplanar AFM structure of GdB 4 with a distorted stacked 3D Shastry-Sutherland spin-lattice geometry is calculated and found to be in disagreement with experimental observations, indicating the presence of another source of anisotropy. Similar calculations for the undistorted 2D and stacked 3D Shastry-Sutherland lattices are reported. The thermodynamics of dipolar magnets are calculated using the Weiss molecular field theory for quantum spins, including the magnetic

  11. Magnetic dipole interactions in crystals

    NASA Astrophysics Data System (ADS)

    Johnston, David C.

    2016-01-01

    The influence of magnetic dipole interactions (MDIs) on the magnetic properties of local-moment Heisenberg spin systems is investigated. A general formulation is presented for calculating the eigenvalues λ and eigenvectors μ ̂ of the MDI tensor of the magnetic dipoles in a line (one dimension, 1D), within a circle (2D) or a sphere (3D) of radius r surrounding a given moment μ⃗i for given magnetic propagation vectors k for collinear and coplanar noncollinear magnetic structures on both Bravais and non-Bravais spin lattices. Results are calculated for collinear ordering on 1D chains, 2D square and simple-hexagonal (triangular) Bravais lattices, 2D honeycomb and kagomé non-Bravais lattices, and 3D cubic Bravais lattices. The λ and μ ̂ values are compared with previously reported results. Calculations for collinear ordering on 3D simple tetragonal, body-centered tetragonal, and stacked triangular and honeycomb lattices are presented for c /a ratios from 0.5 to 3 in both graphical and tabular form to facilitate comparison of experimentally determined easy axes of ordering on these Bravais lattices with the predictions for MDIs. Comparisons with the easy axes measured for several illustrative collinear antiferromagnets (AFMs) are given. The calculations are extended to the cycloidal noncollinear 120∘ AFM ordering on the triangular lattice where λ is found to be the same as for collinear AFM ordering with the same k. The angular orientation of the ordered moments in the noncollinear coplanar AFM structure of GdB4 with a distorted stacked 3D Shastry-Sutherland spin-lattice geometry is calculated and found to be in disagreement with experimental observations, indicating the presence of another source of anisotropy. Similar calculations for the undistorted 2D and stacked 3D Shastry-Sutherland lattices are reported. The thermodynamics of dipolar magnets are calculated using the Weiss molecular field theory for quantum spins, including the magnetic transition

  12. Magnetic dipole interactions in crystals

    SciTech Connect

    Johnston, David

    2016-01-13

    The influence of magnetic dipole interactions (MDIs) on the magnetic properties of local-moment Heisenberg spin systems is investigated. A general formulation is presented for calculating the eigenvalues λ and eigenvectors μ ˆ of the MDI tensor of the magnetic dipoles in a line (one dimension, 1D), within a circle (2D) or a sphere (3D) of radius r surrounding a given moment μ i for given magnetic propagation vectors k for collinear and coplanar noncollinear magnetic structures on both Bravais and non-Bravais spin lattices. Results are calculated for collinear ordering on 1D chains, 2D square and simple-hexagonal (triangular) Bravais lattices, 2D honeycomb and kagomé non-Bravais lattices, and 3D cubic Bravais lattices. The λ and μ ˆ values are compared with previously reported results. Calculations for collinear ordering on 3D simple tetragonal, body-centered tetragonal, and stacked triangular and honeycomb lattices are presented for c/a ratios from 0.5 to 3 in both graphical and tabular form to facilitate comparison of experimentally determined easy axes of ordering on these Bravais lattices with the predictions for MDIs. Comparisons with the easy axes measured for several illustrative collinear antiferromagnets (AFMs) are given. The calculations are extended to the cycloidal noncollinear 120 ° AFM ordering on the triangular lattice where λ is found to be the same as for collinear AFM ordering with the same k. The angular orientation of the ordered moments in the noncollinear coplanar AFM structure of GdB 4 with a distorted stacked 3D Shastry-Sutherland spin-lattice geometry is calculated and found to be in disagreement with experimental observations, indicating the presence of another source of anisotropy. Similar calculations for the undistorted 2D and stacked 3D Shastry-Sutherland lattices are reported. The thermodynamics of dipolar magnets are calculated using the Weiss molecular field theory for quantum spins

  13. Electrochemical Quartz Crystal Nanobalance

    NASA Astrophysics Data System (ADS)

    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.

  14. Single Crystal Surfaces

    NASA Astrophysics Data System (ADS)

    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.

  15. Structures beyond crystals

    NASA Astrophysics Data System (ADS)

    Hargittai, István

    2010-07-01

    Dan Shechtman made a seminal observation of the appearance on "non-crystallographic" symmetry in an alloy at the US National Bureau of Standards on April 8, 1982. This day has become known as the date of the discovery of quasicrystals. It was not easy to gain recognition for this discovery and the first printed report about it appeared two and a half years after the observation, which then was followed by an avalanche of publications. This was as if theoreticians and other experimentalists had only been waiting for a pioneer to come out with this revolutionary experiment. The discovery of quasicrystals just as the discovery of the structure of biological macromolecules was part of the development in which the framework of classical crystallography was crumbling and generalized crystallography—the science of structures—has emerged that had long been advanced by J. Desmond Bernal and his pupils. The discovery of quasicrystals offers some lessons about the nature of scientific discovery. This contribution presents selected aspects of the recognition of the importance of structures beyond crystals and is by far not a complete history of the areas involved.

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

    NASA Technical Reports Server (NTRS)

    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.

  17. Crystals and Crystals: On the Mythology of Magmatic Processes

    NASA Astrophysics Data System (ADS)

    Marsh, B.

    2008-12-01

    The intimate records of the deep functioning of magmatic systems reside in the temporal and spatial records of magma flux, composition and crystal load. The records for a single system are piecemeal: Plutons show good spatial records, but poor temporal records. Volcanoes give through lava sequences good temporal records, but no spatial context. Because of this dichotomy, two, almost mutually exclusive, branches of magmatology have developed, whereas in Nature there is only a single process. The processes envisioned in these schools necessary to deliver the end rock record are distinct. It is our tools and historic perspectives that have steered the science, not the subject itself. Due to this approach an almost mythical conception of how magmas function has become commonplace. The circumvention of this dilemma rests in carefully evaluating the records on hand in the light of a broad understanding of the fundamental mechanics of how magma lives and dies. It is these basic principles that promise to unify plutonic and volcanic evidence to reveal the full nature of magmatism on all scales. The two most basic features of all magmatic processes are the universal presence of solidification fronts and the presence or absence of a crystal cargo. Almost without exception (e.g., shallow pressure quenching) all first generation crystals grow in marginal solidification fronts (SFs) bordering all magmas. The package of isotherms bounded by the liquidus and solidus define SFs, which propagate in response to the rate of cooling. All physical and chemical processes occurring within SFs compete with the advancement or retreat of solidification. SFs are governed by crystallinity regimes: Suspension Zone (<25 % xtals), Capture Front (~25 %), Mush Zone (25-55%), Rigidity Front (~55%; Critical Crystallinity), and Rigid Crust Zone (>55% xtals). Magmas are laced with nuclei that multiply and grow when overtaken. Crystal growth rates are bounded; tiny crystals reside at the front of SFs

  18. Oscillatory growth for twisting crystals.

    PubMed

    Ibaraki, Shunsuke; Ise, Ryuta; Ishimori, Koichiro; Oaki, Yuya; Sazaki, Gen; Yokoyama, Etsuro; Tsukamoto, Katsuo; Imai, Hiroaki

    2015-05-18

    We demonstrate the oscillatory phenomenon for the twisting growth of a triclinic crystal through in situ observation of the concentration field around the growing tip of a needle by high-resolution phase-shift interferometry.

  19. Surface energies of elemental crystals.

    PubMed

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

    2016-09-13

    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.

  20. Polaron stability in oligoacene crystals.

    PubMed

    Pereira Junior, Marcelo Lopes; Ribeiro Junior, Luiz Antonio

    2017-03-01

    The polaron stability in organic molecular crystals is theoretically investigated in the scope of a two-dimensional Holstein-Peierls model that includes lattice relaxation. Particularly, the investigation is focused on designing a model Hamiltonian that can address properly the polaron properties in different model oligoacene crystals. The findings showed that a suitable choice for a set of parameters can play the role of distinguishing the model crystals and, consequently, different properties related to the polaron stability in these systems are observed. Importantly, the usefulness of this model is stressed by investigating the electronic localization of the polaron, which provides a deeper understanding into the properties associated with the polaron stability in oligoacene crystals.