Crystal structure of a new variety of lead dodecaborate Pb{sub 6}(Li{sub 0.65}Na{sub 0.19})[B{sub 12}O{sub 24}]I{sub 0.84} {center_dot} 0.168H{sub 2}O and its comparison with beryl and cordierite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Belokoneva, E. L., E-mail: elbel@geol.msu.ru; Derkach, I. K.; Dimitrova, O. V.

2013-05-15

Crystals of a new representative of ring-radical dodecaborates Pb{sub 6}(Li{sub 0.65}Na{sub 0.19})[B{sub 12}O{sub 24}]I{sub 0.84} {center_dot} 0.168H{sub 2}O, space group R3bar m , are obtained under hydrothermal conditions. The structure is determined with-out preliminary knowledge of the chemical formula. It is close to that of the Pb{sub 6}[B{sub 12}O{sub 24}] {center_dot} H{sub 2}O dodecaborate studied earlier, but unlike the latter structure it contains admixtures of iodide anion, lithium cation, and water molecule, which incompletely populate positions in channels. The formation of the second variety, which brings to light ion-exchange properties of the crystals, is due to mineralizing ions available inmore » the concen-trated solution in the course of crystallization. The new compound is compared with beryl and cordierite, which have close structures with channels capable of capturing various groups. Structures of synthetic Na and Ag dodecaborates with analogous but distorted ring dodecaborate radicals are discussed.« less

Ground-water data for the Beryl-Enterprise area, Escalante Desert, Utah

USGS Publications Warehouse

Mower, R.W.

1981-01-01

This report contains a compilation of selected ground-water data for the Beryl-Enterprise area, Iron and Washington Counties, Utah. The records of the wells include such information as driller 's logs, yield, drawdown, use, and temperature of the well water. There are also records of water levels in selected wells for the period 1973-79, chemical analyses of ground water, records of selected springs, and a tabulation of ground-water withdrawals for 1937-78. (USGS)

Lung function, biological monitoring, and biological effect monitoring of gemstone cutters exposed to beryls

PubMed Central

Wegner, R.; Heinrich-Ramm, R.; Nowak, D.; Olma, K.; Poschadel, B.; Szadkowski, D.

2000-01-01

OBJECTIVES—Gemstone cutters are potentially exposed to various carcinogenic and fibrogenic metals such as chromium, nickel, aluminium, and beryllium, as well as to lead. Increased beryllium concentrations had been reported in the air of workplaces of beryl cutters in Idar-Oberstein, Germany. The aim of the survey was to study the excretion of beryllium in cutters and grinders with occupational exposure to beryls—for example, aquamarines and emeralds—to examine the prevalence of beryllium sensitisation with the beryllium lymphocyte transformation test (BeLT), to examine the prevalence of lung disease induced by beryllium, to describe the internal load of the respective metals relative to work process, and to screen for genotoxic effects in this particular profession.
METHODS—In a cross sectional investigation, 57 out of 100 gemstone cutters working in 12 factories in Idar-Oberstein with occupational exposure to beryls underwent medical examinations, a chest radiograph, lung function testing (spirometry, airway resistance with the interrupter technique), and biological monitoring, including measurements of aluminium, chromium, and nickel in urine as well as lead in blood. Beryllium in urine was measured with a newly developed direct electrothermal atomic absorption spectroscopy technique with a measurement limit of 0.06 µg/l. Also, cytogenetic tests (rates of micronuclei and sister chromatid exchange), and a BeLT were performed. Airborne concentrations of beryllium were measured in three factories. As no adequate local control group was available, the cutters were categorised into those with an exposure to beryls of >4 hours/week (group A) and ⩽4 hours/week (group B).
RESULTS—Clinical, radiological, or spirometric abnormalities indicating pneumoconiosis were detected in none of the gemstone cutters. Metal concentrations in biological material were far below the respective biological limit values, and beryllium in urine was only measurable in

Quantum Tunneling of Water in Beryl. A New State of the Water Molecule

DOE PAGES

Kolesnikov, Alexander I.; Reiter, George F.; Choudhury, Narayani; ...

2016-04-22

When using neutron scattering and ab initio simulations, we document the discovery of a new “quantum tunneling state” of the water molecule confined in 5 Å channels in the mineral beryl, characterized by extended proton and electron delocalization. We observed a number of peaks in the inelastic neutron scattering spectra that were uniquely assigned to water quantum tunneling. Additionally, the water proton momentum distribution was measured with deep inelastic neutron scattering, which directly revealed coherent delocalization of the protons in the ground state.

Quantum Tunneling of Water in Beryl. A New State of the Water Molecule

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kolesnikov, Alexander I.; Reiter, George F.; Choudhury, Narayani

When using neutron scattering and ab initio simulations, we document the discovery of a new “quantum tunneling state” of the water molecule confined in 5 Å channels in the mineral beryl, characterized by extended proton and electron delocalization. We observed a number of peaks in the inelastic neutron scattering spectra that were uniquely assigned to water quantum tunneling. Additionally, the water proton momentum distribution was measured with deep inelastic neutron scattering, which directly revealed coherent delocalization of the protons in the ground state.

Structure analysis on synthetic emerald crystals

NASA Astrophysics Data System (ADS)

Lee, Pei-Lun; Lee, Jiann-Shing; Huang, Eugene; Liao, Ju-Hsiou

2013-05-01

Single crystals of emerald synthesized by means of the flux method were adopted for crystallographic analyses. Emerald crystals with a wide range of Cr3+-doping content up to 3.16 wt% Cr2O3 were examined by X-ray single crystal diffraction refinement method. The crystal structures of the emerald crystals were refined to R 1 (all data) of 0.019-0.024 and w R 2 (all data) of 0.061-0.073. When Cr3+ substitutes for Al3+, the main adjustment takes place in the Al-octahedron and Be-tetrahedron. The effect of substitution of Cr3+ for Al3+ in the beryl structure results in progressively lengthening of the Al-O distance, while the length of the other bonds remains nearly unchanged. The substitution of Cr3+ for Al3+ may have caused the expansion of a axis, while keeping the c axis unchanged in the emerald lattice. As a consequence, the Al-O-Si and Al-O-Be bonding angles are found to decrease, while the angle of Si-O-Be increases as the Al-O distance increases during the Cr replacement.

Hydrology of the Beryl-Enterprise area, Escalante Desert, Utah, with emphasis on ground water; With a section on surface water

USGS Publications Warehouse

Mower, Reed W.; Sandberg, George Woodard

1982-01-01

An investigation of the water resources of the Beryl-Enterprise area, Escalante Desert, Utah (pl. 1), was made during 1976-78 as part of a cooperative program with the Utah Department of Natural Resources, Division of Water Rights. Wells were the most important source of water for all purposes in the Beryl-Enterprise area during 1978, but it has not always been so. For nearly a century after the first settlers arrived in about 1860, streams supplied most of the irrigation water and springs supplied much of the water for domestic and stock use. A few shallow wells were dug by the early settlers for domestic and stock water, but the widespread use of ground water did not start until the 1920's when shallow wells were first dug to supply irrigation water. Ground-water withdrawals from wells, principally for irrigation, have increased nearly every year since the 1920's. The quantity withdrawn from wells surpassed that diverted from surface sources during the mid-1940's and was about eight times that amount during the 1970's. As a result, water levels have declined measurably throughout the area resulting in administrative water-rights problems.The primary purpose of this report is to describe the water resources with emphasis on ground water. The surface-water resources are evaluated only as they pertain to the understanding of the ground-water resources. A secondary purpose is to discuss the extent and effects of the development of ground water in order to provide the hydrologic information needed for the orderly and optimum development of the resource and for the effective administration and adjudication of water rights in the area. The hydrologic data on which this report is based are given in a companion report by Mower (1981).

Digital-computer model of the principal ground-water reservoir in Beryl-Enterprise area, Escalante Desert, Utah

USGS Publications Warehouse

Mower, R.W.; Bartholoma, Scott D.

1981-01-01

The computer model presented in this report was used to simulate the principal ground-water reservoir in the Beryl-Enterprise area, Escalante Desert, Beaver, Iron, and Washington Counties, Utah (Mower, 1981). The details of the formulation of the model, testing of its validity, and the results of predictions are discussed in the cited report. This report was prepared as part of a cooperative program with the Utah Department of Natural Resources, Division of Water Rights, to investigate the water resources of the State. It is an addendum to the principal interpretive report, and it is presented in order to make the model available to anyone desiring to use it for additional predictions. The main program used was the finite-difference model for aquifer simulation in two dimensions documented by Trescott, Pinder, and Larson, (1976). Minor modifications were made to adapt the program to the principal ground-water reservoir in the Beryl-Enterprise area. All the modifications are listed at the top of table 1, and were related to parameter input and output, thus none of the computational subroutines were affected. The parameter arrays (table 1) and map of the area with a grid overlay (pi. 1) are given on following pages. The model simulates an aquifer- under water-table conditions, mostly composed of unconsoliuated basin-fill deposits. The boundaries of the modeled area (pi. 1) generally coincide with the boundaries of the saturated basin fill. However, in the southwest-central part of the model, permeable consolidated rock is included; and that part of the northern boundary between the Black and Wah Wah Mountains is an arbitrary boundary in basin fill between the Beryl-Enterprise area and the Milford area that lies to the northeast. The ignimbrite at Table Butte also was included in the active part of the model. The model includes simulation of discharge by evapotranspiration from phreatophytes. The areal recharge array was used to simulate recharge entering the modeled

Effects of Cr 3+ impurity concentration on the crystallography of synthetic emerald crystals

NASA Astrophysics Data System (ADS)

Lee, Pei-Lun; Huang, Eugene; Lee, Jan-Shing; Yu, Shu-Cheng

2011-06-01

Flux method has been adopted for the synthesis of emerald crystals using PbO-V 2O 5 as a flux in order to study the crystallography of the synthetic crystals. In general, the hue of green color of emerald deepens with the addition of Cr 3+. The molar volume of the synthesized crystals was found to increase with the incorporation of Cr 2O 3 dopant. The substitution of Cr 3+ for Al 3+ in the octahedral sites of beryl results in the expansion of a-axis, while c-axis remains nearly unchanged. The maximum Cr 2O 3-content allowed in the crystal lattice of emerald has been found to be about 3.5 wt%. When the doping Cr 2O 3-content exceeds 3.5 wt%, a significant anomaly in lattice parameters starts to take place, accompanying the precipitation of an unknown phase in the emerald matrix.

Analytical network-averaging of the tube model: Strain-induced crystallization in natural rubber

NASA Astrophysics Data System (ADS)

Khiêm, Vu Ngoc; Itskov, Mikhail

2018-07-01

In this contribution, we extend the analytical network-averaging concept (Khiêm and Itskov, 2016) to phase transition during strain-induced crystallization of natural rubber. To this end, a physically-based constitutive model describing the nonisothermal strain-induced crystallization is proposed. Accordingly, the spatial arrangement of polymer subnetworks is driven by crystallization nucleation and consequently alters the mesoscopic deformation measures. The crystallization growth is elucidated by diffusion of chain segments into crystal nuclei. The crystallization results in a change of temperature and an evolution of heat source. By this means, not only the crystallization kinetics but also the Gough-Joule effect are thoroughly described. The predictive capability of the constitutive model is illustrated by comparison with experimental data for natural rubbers undergoing strain-induced crystallization. All measurable values such as stress, crystallinity and heat source are utilized for the comparison.

Novel photonic crystals: incorporation of nano-CdS into the natural photonic crystals within peacock feathers.

PubMed

Han, Jie; Su, Huilan; Song, Fang; Gu, Jiajun; Di, Zhang; Jiang, Limin

2009-03-03

In this investigation, the natural 2D photonic crystals (PhCs) within peacock feathers are applied to incorporate CdS nanocrystallites. Peacock feathers are activated by ethylenediaminetetraacetic/dimethylformamide suspension to increase the reactive sites on the keratin component, on which CdS nanoparticles (nano-CdS) are in situ formed in succession and serve as the "seeds" to direct further incorporation during the following solvothermal procedure. Thus, homogeneous nano-CdS are loaded both on the feathers' surface layer and inside the 2D PhCs. The obtained nano-CdS/peacock feathers hybrids are novel photonic crystals whose photonic stop bands are markedly different from that of the natural PhCs within original peacock feathers, as observed by the reflection spectra.

Gypsum crystals observed in experimental and natural sea ice

NASA Astrophysics Data System (ADS)

Geilfus, N.-X.; Galley, R. J.; Cooper, M.; Halden, N.; Hare, A.; Wang, F.; Søgaard, D. H.; Rysgaard, S.

2013-12-01

gypsum has been predicted to precipitate in sea ice, it has never been observed. Here we provide the first report on gypsum precipitation in both experimental and natural sea ice. Crystals were identified by X-ray diffraction analysis. Based on their apparent distinguishing characteristics, the gypsum crystals were identified as being authigenic. The FREeZing CHEMistry (FREZCHEM) model results support our observations of both gypsum and ikaite precipitation at typical in situ sea ice temperatures and confirms the "Gitterman pathway" where gypsum is predicted to precipitate. The occurrence of authigenic gypsum in sea ice during its formation represents a new observation of precipitate formation and potential marine deposition in polar seas.

The dynamic nature of crystal growth in pores

DOE PAGES

Godinho, Jose R. A.; Gerke, Kirill M.; Stack, Andrew G.; ...

2016-09-12

We report that the kinetics of crystal growth in porous media controls a variety of natural processes such as ore genesis and crystallization induced fracturing that can trigger earthquakes and weathering, as well as, sequestration of CO 2 and toxic metals into geological formations. Progress on understanding those processes has been limited by experimental difficulties of dynamically studying the reactive surface area and permeability during pore occlusion. Here, we show that these variables cause a time-dependency of barite growth rates in microporous silica. The rate is approximately constant and similar to that observed on free surfaces if fast flow velocitiesmore » predominate and if the time-dependent reactive surface area is accounted for. As the narrower flow paths clog, local flow velocities decrease, which causes the progressive slowing of growth rates. We conclude that mineral growth in a microporous media can be estimated based on free surface studies when a) the growth rate is normalized to the time-dependent surface area of the growing crystals, and b) the local flow velocities are above the limit at which growth is transport-limited. Lastly, accounting for the dynamic relation between microstructure, flow velocity and growth rate is shown to be crucial towards understanding and predicting precipitation in porous rocks.« less

Ion beam radiation effects on natural halite crystals

NASA Astrophysics Data System (ADS)

Arun, T.; Ram, S. S.; Karthikeyan, B.; Ranjith, P.; Ray, D. K.; Rout, B.; Krishna, J. B. M.; Sengupta, Pranesh; Parlapalli, Venkata Satyam

2017-10-01

Halites are one of the interesting material due to its color variations. Natural halites whose color ranges from transparent to dark blue were studied by UV-VIS and Raman spectroscopy. The halite crystals were irradiated with 3 MeV proton micro-beam (∼20 μm beam width with ∼80 PA beam current) for 10 and 90 min to study the radiation damage. After 10 mins of irradiation, small spot developed on the surface of transparent halite crystal whereas after 90 mins of irradiation the spot spread inside the bulk leading to a brown coloration (20 μm initial size to ∼2.0 mm final size). The irradiated portion and the un-irradiated portion of the halites was characterized by Raman spectroscopic technique. The variation in the population density was observed from the UV-Vis spectra. The change in the Raman band intensities was observed for transparent, blue colored and proton beam irradiation halites. Such variation of spectroscopic characteristics due to proton irradiation suggests that the halite can be used for the radiation monitoring.

The natural weathering of staurolite: crystal-surface textures, relative stability, and the rate-determining step

Treesearch

Michael A. Velbel; Charles L. Basso; Michael J. Zieg

1996-01-01

Mineral surface-textures on naturally weathered crystals of staurolite [monoclinic, pseudo-orthorhombic; Fe4Al18Si8O46(OH)2] indicate that staurolite weathering is generally interface-limited. Etch pits on naturally weathered staurolites are disk-shaped,...

Salt or cocrystal of salt? Probing the nature of multicomponent crystal forms with infrared spectroscopy

NASA Astrophysics Data System (ADS)

da Silva, Cameron Capeletti; Guimarães, Freddy Fernandes; Ribeiro, Leandro; Martins, Felipe Terra

2016-10-01

The recognition of the nature of a multicomponent crystal form (solvate, salt, cocrystal or cocrystal of salt) is of great importance for pharmaceutical industry because it is directly related to the performance of a pharmaceutical ingredient, since there is interdependence between the structure, its energy and its physical properties. In this context, here we have identified the nature of multicomponent crystal forms of the anti-HIV drug lamivudine with mandelic acid through infrared spectroscopy. These investigated crystal forms were the known S-mandelic acid cocrystal of lamivudine R-mandelate trihydrate (1), a cocrystal of salt, and lamivudine R-mandelate (2), a salt. This approach also supports the identification and distinction of both ionized and unionized forms of mandelic acid in the infrared spectrum of 1. In this way, infrared spectroscopy can be useful to distinguish a cocrystal of salt from either salt or cocrystal forms. In the course of this study, for the first time we have also characterized and determined the crystal structure of R-mandelic acid cocrystal of sodium R-mandelate (3).

Development of beamline U3A for AXAF synchrotron reflectivity calibrations

NASA Astrophysics Data System (ADS)

Burek, Anthony J.; Cobuzzi, J. C.; Fitch, Jonathan J.; Graessle, Dale E.; Ingram, R. H.; Sweeney, J. B.; Blake, Richard L.; Francoeur, R.; Sullivan, E. S.

1998-11-01

We discuss the development of beamline U3A at NSLS for AXAF telescope witness mirror reflectivity calibrations in the 1- 2 keV energy range. The beamline was originally constructed as a white light beamline and has been upgraded with the addition of a monochromator to meet the needs of the AXAF calibration program. The beamline consists of an upstream horizontally focussing gold coated elliptical mirror, a differential pumping section, a sample/filter chamber, a monochromator and a downstream filter set. The mirror is set at a 2 degree incident angle for a nominal high energy cutoff at 2 keV. The monochromator is a separated element, scanning, double crystal/multilayer design having low to moderate energy resolution. A fixed exit beam is maintained through the 7-70 degree Bragg angle range by longitudinal translation of the second scanning crystal. Tracking is achieved by computer control of the scan motors with lookup table positioning of the crystal rotary tables. All motors are in vacuum and there are no motional feedthroughs. Several different multilayer or crystal pairs are co-mounted on the monochromator crystal holders and can be exchanged in situ. Currently installed are a W/Si multilayer pair, beryl, and Na-(beta) alumina allowing energy coverage from 180 eV to 2000 eV. Measurements with Na-(beta) alumina and beryl show that beam impurity less than 0.1 percent can be achieved in the 1-2 keV energy range. Measured resolving powers are E/(Delta) E equals 60 for W/Si, 500-800 for (beta) alumina and 1500 to 3000 for beryl. Initial results suggest that signal to noise and beam purity are adequate in the 1-2 keV region to achieve the 1 percent calibration accuracy required by AXAF. This allows overlap of Ir MV edge data taken on x-ray beamline X8A and with low energy data taken on ALS beamline 6.3.2.

A view inside the nature of protein crystals

NASA Astrophysics Data System (ADS)

Oswald, R.; Pietzsch, M.; Ulrich, J.

2017-07-01

In this work a fundamental analysis of protein crystal modifications was presented to compare and confirm the components of protein crystal modifications. The result is that a protein crystal contains besides the protein, the precipitant and water. A mass spectrometer coupled to a thermogravimetry device was used to confirm the different waters (free water -the chosen buffer- and bound water) inside the crystals. Here the biggest amount of water is the free water (the buffer) with an amount of approximately 35%. The bound water (in the sense of a hydrate) has only an amount of about 1-1.5%. Furthermore, an x-ray analysis to confirm the influence range of pH value on the stability of one crystal modification for the understanding of effects on dissolution mechanism of protein crystals was investigated. The crystals of the tetragonal modification crystallized at pH 4.7, 4.85, 5.0, 5.15 and 5.3 maintain according to the x-ray measurements the same lattice parameters. The measured data are discussed.

Physicochemical characteristics of aerosol particles generated during the milling of beryllium silicate ores: implications for risk assessment.

PubMed

Stefaniak, Aleksandr B; Chipera, Steve J; Day, Gregory A; Sabey, Phil; Dickerson, Robert M; Sbarra, Deborah C; Duling, Mathew G; Lawrence, Robert B; Stanton, Marcia L; Scripsick, Ronald C

2008-01-01

Inhalation of beryllium dusts generated during milling of ores and cutting of beryl-containing gemstones is associated with development of beryllium sensitization and low prevalence of chronic beryllium disease (CBD). Inhalation of beryllium aerosols generated during primary beryllium production and machining of the metal, alloys, and ceramics are associated with sensitization and high rates of CBD, despite similar airborne beryllium mass concentrations among these industries. Understanding the physicochemical properties of exposure aerosols may help to understand the differential immunopathologic mechanisms of sensitization and CBD and lead to more biologically relevant exposure standards. Properties of aerosols generated during the industrial milling of bertrandite and beryl ores were evaluated. Airborne beryllium mass concentrations among work areas ranged from 0.001 microg/m(3) (beryl ore grinding) to 2.1 microg/m(3) (beryl ore crushing). Respirable mass fractions of airborne beryllium-containing particles were < 20% in low-energy input operation areas (ore crushing, hydroxide product drumming) and > 80% in high-energy input areas (beryl melting, beryl grinding). Particle specific surface area decreased with processing from feedstock ores to drumming final product beryllium hydroxide. Among work areas, beryllium was identified in three crystalline forms: beryl, poorly crystalline beryllium oxide, and beryllium hydroxide. In comparison to aerosols generated by high-CBD risk primary production processes, aerosol particles encountered during milling had similar mass concentrations, generally lower number concentrations and surface area, and contained no identifiable highly crystalline beryllium oxide. One possible explanation for the apparent low prevalence of CBD among workers exposed to beryllium mineral dusts may be that characteristics of the exposure material do not contribute to the development of lung burdens sufficient for progression from sensitization to

Multi-element analysis of emeralds and associated rocks by k(o) neutron activation analysis

PubMed

Acharya; Mondal; Burte; Nair; Reddy; Reddy; Reddy; Manohar

2000-12-01

Multi-element analysis was carried out in natural emeralds, their associated rocks and one sample of beryl obtained from Rajasthan, India. The concentrations of 21 elements were assayed by Instrumental Neutron Activation Analysis using the k0 method (k0 INAA method) and high-resolution gamma ray spectrometry. The data reveal the segregation of some elements from associated (trapped and host) rocks to the mineral beryl forming the gemstones. A reference rock standard of the US Geological Survey (USGS BCR-1) was also analysed as a control of the method.

Spectroscopy and crystal structures of natural stereoisomers of neoclerodane diterpenoids from Teucrium yemense of Saudi medicinal plant

NASA Astrophysics Data System (ADS)

Nur-e-Alam, Mohammad; Kanthasamy, Gopikkaa; Yousaf, Muhammad; Alqahtani, Ali S.; Ghabbour, Hazem A.; Al-Rehaily, Adnan J.

2017-11-01

3-O-deacetylteugracilin (1) and teugracilin B (2), two natural stereoisomers, are isolated from Teucrium yemense (Defl). These two compounds are almost identical to each other, differing only at the C6 stereocenter. We now crystallise these two compounds and for the first time, determine the crystal structure through single crystal X-ray diffraction, and the stereochemistry for all positions using spectroscopic data. These techniques enable us to establish the difference between the two compounds. Careful interpretation of the results indicates that HRMS and 1 and 2D NMR spectroscopy, are in agreement with single crystal X-ray diffraction data.

Naturally occurring reverse tilt domains in a high-pretilt alignment nematic liquid crystal

NASA Astrophysics Data System (ADS)

Wang, Ruiting; Atherton, Timothy J.; Zhu, Minhua; Petschek, Rolfe G.; Rosenblatt, Charles

2007-08-01

A cell whose substrates were coated with the polyamic acid SE1211 (Nissan Chemical Industries) and baked at high temperatures was filled with a nematic liquid crystal in the isotropic phase. On cooling into the nematic phase, naturally occurring and temporally and thermally robust reverse tilt domains separated by thin filamentlike walls were observed. The properties of these structures are reported.

Numerical modeling of crystal growth on a centrifuge for unstable natural convection configurations

NASA Technical Reports Server (NTRS)

Ramachandran, N.; Downey, J. P.; Curreri, P. A.; Jones, J. C.

1993-01-01

The fluid mechanics associated with crystal growth processes on centrifuges is modeled using 2D and 3D models. Two-dimensional calculations show that flow bifurcations exist in such crystal growth configurations where the ampoule is oriented in the same direction as the resultant gravity vector and a temperature gradient is imposed on the melt. A scaling analysis is formulated to predict the flow transition point from the natural convection dominated regime to the Coriolis force dominated regime. Results of 3D calculations are presented for two thermal configurations of the crystal growth cell: top heated and bottom heated with respect to the centrifugal acceleration. In the top heated configuration, a substantial reduction in the convection intensity within the melt can be attained by centrifuge operations, and close to steady diffusion-limited thermal conditions can be achieved over a narrow range of the imposed microgravity level. In the bottom heated configuration the Coriolis force has a stabilizing effect on fluid motion by delaying the onset of unsteady convection.

Crystal Systems.

ERIC Educational Resources Information Center

Schomaker, Verner; Lingafelter, E. C.

1985-01-01

Discusses characteristics of crystal systems, comparing (in table format) crystal systems with lattice types, number of restrictions, nature of the restrictions, and other lattices that can accidently show the same metrical symmetry. (JN)

3D Micro-topography of Transferred Laboratory and Natural Ice Crystal Surfaces Imaged by Cryo and Environmental Scanning Electron Microscopy

NASA Astrophysics Data System (ADS)

Magee, N. B.; Boaggio, K.; Bancroft, L.; Bandamede, M.

2015-12-01

Recent work has highlighted micro-scale roughness on the surfaces of ice crystals grown and imaged in-situ within the chambers of environmental scanning electron microscopes (ESEM). These observations appear to align with theoretical and satellite observations that suggest a prevalence of rough ice in cirrus clouds. However, the atmospheric application of the lab observations are indeterminate because the observations have been based only on crystals grown on substrates and in pure-water vapor environments. In this work, we present details and results from the development of a transfer technique which allows natural and lab-grown ice and snow crystals to be captured, preserved, and transferred into the ESEM for 3D imaging. Ice crystals were gathered from 1) natural snow, 2) a balloon-borne cirrus particle capture device, and 3) lab-grown ice crystals from a diffusion chamber. Ice crystals were captured in a pre-conditioned small-volume (~1 cm3) cryo-containment cell. The cell was then sealed closed and transferred to a specially-designed cryogenic dewer (filled with liquid nitrogen or crushed dry ice) for transport to a new Hitachi Field Emission, Variable Pressure SEM (SU-5000). The cryo-cell was then removed from the dewer and quickly placed onto the pre-conditioned cryo transfer stage attached to the ESEM (Quorum 3010T). Quantitative 3D topographical digital elevation models of ice surfaces are reported from SEM for the first time, including a variety of objective measures of statistical surface roughness. The surfaces of the transported crystals clearly exhibit signatures of mesoscopic roughening that are similar to examples of roughness seen in ESEM-grown crystals. For most transported crystals, the habits and crystal edges are more intricate that those observed for ice grown directly on substrates within the ESEM chamber. Portions of some crystals do appear smooth even at magnification greater than 1000x, a rare observation in our ESEM-grown crystals. The

Optical Properties and Crystallization of Natural Waxes at Several Annealing Temperatures: a Terahertz Time-Domain Spectroscopy Study

NASA Astrophysics Data System (ADS)

Tian, Lu; Xu, Xinlong

2018-03-01

The thermal analysis and optical properties of paraffin wax, beeswax, and liquid paraffin annealed at variable temperatures have been conducted using terahertz time-domain spectroscopy (THz-TDS) coupled with SEM methods. The characteristic optical properties of natural waxes can be used to analyze natural wax adulteration. The lamellar structure of paraffin wax and beeswax grew by a sheet of chain expansion. Furthermore, the crystallization process of paraffin wax can be assigned: rotator-solid transition and liquid-solid ones. According to the temperature-dependent refractive index curves, the refractive index of paraffin wax varies from large to small followed by rotator-liquid transition, untreated one, and liquid-solid one, respectively. The results indicated that THz-TDS has been proved to be of great potential in identification the crystallization of waxes.

Glassy nature and glass-to-crystal transition in the binary metallic glass CuZr

NASA Astrophysics Data System (ADS)

Wei, Zi-Yang; Shang, Cheng; Zhang, Xiao-Jie; Liu, Zhi-Pan

2017-06-01

The prediction for the stability of glassy material is a key challenge in physical science. Here, we report a theoretical framework to predict the glass stability based on stochastic surface walking global optimization and reaction pathway sampling. This is demonstrated by revealing for the first time the global potential energy surface (PES) of two systems, CuZr binary metallic glass and nonglassy pure Cu systems, and establishing the lowest energy pathways linking glassy/amorphous structures with crystalline structures. The CuZr system has a significant number of glassy structures on PES that are ˜0.045 eV /atom above the crystal structure. Two clear trends are identified from global PES in the glass-to-crystal transition of the CuZr system: (i) the local Zr-Cu coordination (nearest neighbor) increases, and (ii) the local Zr bonding environment becomes homogeneous. This allows us to introduce quantitative structural and energetics conditions to distinguish the glassy structures from the crystalline structures. Because of the local Zr-Cu exchange in the glass-to-crystal transition, a high reaction barrier (>0.048 eV /atom ) is present to separate the glassy structures and the crystals in CuZr. By contrast, the Cu system, although it does possess amorphous structures that appear at much higher energy (˜0.075 eV /atom ) with respect to the crystal structure, has very low reaction barriers for the crystallization of amorphous structures, i.e. <0.011 eV /atom . The quantitative data on PES now available from global optimization techniques deepens our understanding on the microscopic nature of glassy material and might eventually facilitate the design of stable glassy materials.

Dimensions and aspect ratios of natural ice crystals

DOE PAGES

Um, J.; McFarquhar, G. M.; Hong, Y. P.; ...

2015-04-15

During the 2006 Tropical Warm Pool International Cloud Experiment (TWP-ICE) in the tropics, the 2008 Indirect and Semi-Direct Aerosol Campaign (ISDAC) in the Arctic, and the 2010 Small PARTicles In CirrUS (SPARTICUS) campaign at mid-latitudes, high-resolution images of ice crystals were recorded by a Cloud Particle Imager at temperatures ( T) between -87 and 0 °C. The projected maximum dimension ( D'), length ( L'), and width ( W') of pristine columns, plates, and component bullets of bullet rosettes were measured using newly developed software, the Ice Crystal Ruler. The number of bullets in each bullet rosette was also measured.more » Column crystals were further distinguished as either horizontally oriented columns or columns with other orientations to eliminate any orientation effect on the measured dimensions. The dimensions and aspect ratios (AR, the dimension of the major axis divided by the dimension of the minor axis) of crystals were determined as functions of temperature, geophysical location, and type of cirrus. Dimensions of crystals generally increased with temperature. Columns and bullets had larger dimensions (i.e., W') of the minor axis (i.e., a axis) for a given dimension (i.e., D' or L') of the major axis (i.e., c axis), and thus smaller AR, as T increased, whereas this trend did not occur for plate crystals. The average number of branches in bullet rosettes was 5.50 ± 1.35 during three campaigns and 6.32 ± 1.34 (5.46 ± 1.34; 4.95 ± 1.01) during TWP-ICE (SPARTICUS; ISDAC). The AR of bullets increased with the number of branches in bullet rosettes. Most dimensions of crystals and ARs of columnar crystals measured during SPARTICUS were larger than those measured during TWP-ICE and ISDAC at −67 < T < -35 °C and at −40 < T < −15 °C, respectively. The relative occurrence of varying pristine habits depended strongly on cirrus type (i.e., anvil or non-anvil clouds), with plates especially occurring more frequently in anvils. Finally, the

Dimensions and aspect ratios of natural ice crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Um, J.; McFarquhar, G. M.; Hong, Y. P.

During the 2006 Tropical Warm Pool International Cloud Experiment (TWP-ICE) in the tropics, the 2008 Indirect and Semi-Direct Aerosol Campaign (ISDAC) in the Arctic, and the 2010 Small PARTicles In CirrUS (SPARTICUS) campaign at mid-latitudes, high-resolution images of ice crystals were recorded by a Cloud Particle Imager at temperatures ( T) between -87 and 0 °C. The projected maximum dimension ( D'), length ( L'), and width ( W') of pristine columns, plates, and component bullets of bullet rosettes were measured using newly developed software, the Ice Crystal Ruler. The number of bullets in each bullet rosette was also measured.more » Column crystals were further distinguished as either horizontally oriented columns or columns with other orientations to eliminate any orientation effect on the measured dimensions. The dimensions and aspect ratios (AR, the dimension of the major axis divided by the dimension of the minor axis) of crystals were determined as functions of temperature, geophysical location, and type of cirrus. Dimensions of crystals generally increased with temperature. Columns and bullets had larger dimensions (i.e., W') of the minor axis (i.e., a axis) for a given dimension (i.e., D' or L') of the major axis (i.e., c axis), and thus smaller AR, as T increased, whereas this trend did not occur for plate crystals. The average number of branches in bullet rosettes was 5.50 ± 1.35 during three campaigns and 6.32 ± 1.34 (5.46 ± 1.34; 4.95 ± 1.01) during TWP-ICE (SPARTICUS; ISDAC). The AR of bullets increased with the number of branches in bullet rosettes. Most dimensions of crystals and ARs of columnar crystals measured during SPARTICUS were larger than those measured during TWP-ICE and ISDAC at −67 < T < -35 °C and at −40 < T < −15 °C, respectively. The relative occurrence of varying pristine habits depended strongly on cirrus type (i.e., anvil or non-anvil clouds), with plates especially occurring more frequently in anvils. Finally, the

Characterization of natural photonic crystals in iridescent wings of damselfly Chalcopteryx rutilans by FIB/SEM, TEM, and TOF-SIMS.

PubMed

Carr, David M; Ellsworth, Ashley A; Fisher, Gregory L; Valeriano, Wescley W; Vasco, Juan P; Guimarães, Paulo S S; de Andrade, Rodrigo R; da Silva, Elizabeth R; Rodrigues, Wagner N

2018-02-05

The iridescent wings of the Chalcopterix rutilans damselfly (Rambur) (Odonata, Polythoridae) are investigated with focused ion beam/scanning electron microscopy, transmission electron microscopy, and time-of-flight secondary ion mass spectrometry. The electron microscopy images reveal a natural photonic crystal as the source of the varying colors. The photonic crystal has a consistent number and thickness (∼195 nm) of the repeat units on the ventral side of the wing, which is consistent with the red color visible from the bottom side of the wing in all regions. The dorsal side of the wing shows strong color variations ranging from red to blue depending on the region. In the electron microscopy images, the dorsal side of the wing exhibits varied number and thicknesses of the repeat units. The repeat unit spacings for the red, yellow/green, and blue regions are approximately 195, 180, and 145 nm, respectively. Three-dimensional analysis of the natural photonic crystals by time-of-flight secondary ion mass spectrometry reveals that changes in the relative levels of Na, K, and eumelanin are responsible for the varying dielectric constant needed to generate the photonic crystal. The photonic crystal also appears to be assembled with a chemical tricomponent layer structure due to the enhancement of the CH 6 N 3 + species at every other interface between the high/low dielectric constant layers.

Sintering polycrystalline olivine and polycrystalline clinopyroxene containing trace amount of graphite from natural crystals

NASA Astrophysics Data System (ADS)

Tsubokawa, Yumiko; Ishikawa, Masahiro

2017-09-01

Graphite-bearing polycrystalline olivine and polycrystalline clinopyroxene with submicron to micron grain size were successfully sintered from a single crystal of naturally occurring olivine (Fo88-92Fa12-8: Mg1.76-1.84Fe0.16-0.24SiO4) and a single crystal of naturally occurring clinopyroxene (Di99Hed1: Ca0.92Na0.07Mn0.01Mg0.93Fe0.01Al0.06Si2O6). The milled powders of both these crystals were sintered under argon gas flow at temperatures ranging from 1130 to 1350 °C for 2 h. As the sintering temperature increased, the average grain size of olivine increased from 0.2 to 1.4 µm and that of clinopyroxene increased from 0.1 to 2.4 µm. The porosity of sintered samples remained at an almost-constant volume of 2-5% for olivine and 3-4% for clinopyroxene. The samples sintered from powders milled with ethanol exhibited trace amount of graphite, identified via Raman spectroscopy analysis. As the sintering temperature increased, the intensity of the graphite Raman peak decreased, compared with both olivine and clinopyroxene peaks. The carbon content of the sintered samples was estimated to be a few hundred ppm. The in-plane size ( L a ) of graphite in the sintered olivine was estimated to be <15 nm. Our experiments demonstrate new possibilities for preparing graphite-bearing silicate-mantle mineral rocks, and this method might be useful in understanding the influence of the physical properties of graphite on grain-size-sensitive rheology or the seismic velocity of the Earth's mantle.[Figure not available: see fulltext.

Heat capacities and thermodynamic functions for beryl, Be3Al2Si6O18, phenakite, Be2SiO4, euclase, BeAlSiO4(OH), bertrandite, Be4Si2O7(OH)2, and chrysoberyl, BeAl2O4.

USGS Publications Warehouse

Hemingway, B.S.; Barton, M.D.; Robie, R.A.; Haselton, H.T.

1986-01-01

The heat capacities of beryl, phenakite, euclase and bertrandite have been measured between approx 5 and 800 K by combined quasi-adiabatic cryogenic calorimetry and differential scanning calorimetry. The heat capacities of chrysoberyl have been measured from 340 to 800 K. The resulting data have been combined with solution and phase-equilibrium experimental data and simultaneously adjusted using the programme PHAS20 to provide an internally consistent set of thermodynamic properties for several important beryllium phases. The experimental heat capacities and tables of derived thermodynamic properties are presented.-J.A.Z.

Modeling the Crystallization of Proteins

NASA Astrophysics Data System (ADS)

Liu, Hongjun; Kumar, Sanat; Garde, Shekhar

2007-03-01

We have used molecular dynamics and monte carlo simulations to understand the pathway to protein crystallization. We find that models which ignore the patchy nature of protein-protein interactions only crystallize inside the metastable gas-lqiuid coexistence region. In this regime they crystallize through the formation of a critical nucleus. In contrast, when patchiness is introduced we find that there is no need to be inside this metastable gas-liquid boundary. Rather, crystallization occurs through an intermediate which is composed of disordered aggregates. These are formed by patchy interactions. Further, there appears to be no need for the formation of a critical nucleus. Thus the pathways for crystallization are strongly controlled by the nature of protein-protein interactions, in good agreement with current experiments.

Emerald mineralization and metasomatism of amphibolite, khaltaro granitic pegmatite - Hydrothermal vein system, Haramosh Mountains, Northern Pakistan

USGS Publications Warehouse

Laurs, B.M.; Dilles, J.H.; Snee, L.W.

1996-01-01

Emerald mineralization is found within 0.1- to 1-m-thick hydrothermal veins and granitic pegmatites cutting amphibolite within the Nanga Parbat - Haramosh massif, in northern Pakistan. The amphibolite forms a sill-like body within garnet-mica schist, and both are part of a regional layered gneiss unit of Proterozoic (?) age. The 40Ar/39Ar data for muscovite from a pegmatite yield a plateau age of 9.13 ?? 0.04 Ma. Muscovite from mica schist and hornblende from amphibolite yield disturbed spectra with interpreted ages of 9 to 10 Ma and more than 225 Ma, respectively, which indicate that peak Tertiary metamorphism reached 325 to 550??C prior to 10 Ma. Pegmatites were emplaced after peak metamorphism during this interval and are older than pegmatites farther south in the massif. At Khaltaro, simply zoned albite-rich miarolitic pegmatites and hydrothermal veins containing various proportions of quartz, albite, tourmaline, muscovite, and beryl are associated with a 1- to 3-m-thick heterogeneous leucogranite sill, that is locally albitized. The pegmatites likely crystallized at 650 to 600??C at pressures of less than 2 kbar. Crystals of emerald form within thin (0.20, 0.54-0.89 wt%), to pale blue beryl (<0.07, 0.10-0.63%), to colorless beryl (<0.07, 0.07-0.28%). The amphibolite is metasomatized in less than 20-cm-wide selvages that are symmetrically zoned around veins or pegmatites. A sporadic inner zone containing F-rich biotite, tourmaline, and fluorite, with local albite, muscovite, quartz, and rare beryl, gives way to an intermediate zone containing biotite and fluorite with local plagioclase and quartz, and to an outer zone of amphibolite containing sparse biotite and local quartz. The inner and intermediate zones experienced gains of K, H, F, B, Li, Rb, Cs, Be, Ta, Nb, As, Y and Sr, and losses of Si, Mg, Ca, Fe, Cr, V and Sc. The outer alteration zone has gained F, Li, Rb, Cs, and As. Oxygen isotope analyses of igneous and hydrothermal minerals indicate that a

Crystal structure and crystal chemistry of melanovanadite, a natural vanadium bronze.

USGS Publications Warehouse

Konnert, J.A.; Evans, H.T.

1987-01-01

The crystal structure of melanovanadite from Minas Ragra, Peru, has been determined in space group P1. The triclinic unit cell (non-standard) has a 6.360(2), b 18.090(9), c 6.276(2) A, alpha 110.18(4)o, beta 101.62(3)o, gamma 82.86(4)o. A subcell with b' = b/2 was found by crystal-structure analysis to contain CaV4O10.5H2O. The subcell has a layer structure in which the vanadate sheet consists of corner-shared tetrahedral VO4 and double square-pyramidal V2O8 groups, similar to that previously found in synthetic CsV2O5. Refinement of the full structure (R = 0.056) showed that the Ca atom, which half-occupies a general position in the subcell, is 90% ordered at one of these sites in the whole unit cell. Bond length-bond strength estimates indicate that the tetrahedra contain V5+, and the square pyramids, V4+.-J.A.Z.

Microstructures and Crystallographic Misorientation in Experimentally Deformed Natural Quartz Single Crystals

NASA Astrophysics Data System (ADS)

Thust, Anja; Heilbronner, Renée.; Stünitz, Holger

2010-05-01

Samples of natural milky quartz were deformed in a Griggs deformation apparatus at different confining pressures (700 MPa, 1000 MPa, 1500 MPa), with constant displacement rates of 1 * 10-6s-1, axial strains of 3 - 19%, and at a temperature of 900° C. The single crystal starting material contains a large number of H2O-rich fluid inclusions. Directly adjacent to the fluid inclusions the crystal is essentially dry (50-150H/106Si, determined by FTIR). The samples were cored from a narrow zone of constant 'milkyness' (i.e. same density of fluid inclusions) in a large single crystal in two different orientations (1) normal to one of the prism planes (⊥{m} orientation) and (2) 45° to and to (O+ orientation).During attaining of the experimental P and T conditions, numerous fluid inclusions decrepitate by cracking. Rapid crack healing produces regions of very small fluid inclusions ('wet' quartz domains). Only these regions are subsequently deformed by dislocation glide, dry quartz domains without cracking and decrepitation of fluid inclusions remain undeformed. Sample strain is not sufficient to cause recrystallization, so that deformation is restricted to dislocation glide. In experiments at lower temperatures (800, 700° C) or at lower strain rate (10-5s-1) there is abundant cracking and semi-brittle deformation, indicating that 900° C, (10-6s-1) represents the lower temperature end of crystal plastic deformation in these single crystals. Peak strengths (at 900° C) range between 150 and 250 MPa for most samples of both orientations. There is a trend of decreasing strength with increasing confining pressure, as described by Kronenberg and Tullis (1984) for quartzites, but the large variation in strength due to inhomogeneous sample strain precludes a definite analysis of the strength/pressure dependence in our single crystals. In the deformed samples, we can distinguish a number of microstructures and inferred different slip systems. In both orientations, deformation

Gemstones

USGS Publications Warehouse

Olson, D.W.

2013-01-01

The estimated value of natural gemstones produced from U.S. deposits during 2012 was $11.1 million, a slight increase from 2011. U.S. gemstone production included agate, amber, beryl, coral, garnet, jade, jasper, opal, pearl, quartz, sapphire, shell, topaz, tourmaline, turquoise and many other gem materials.

Gemstones

USGS Publications Warehouse

Olson, D.W.

2011-01-01

The estimated value of natural gemstones produced from U.S. deposits during 2010 was $8.5 million, a slight increase from 2009. U.S. gemstone production included agate, amber, beryl, coral, garnet, jade, jasper, opal, pearl, quartz, sapphire, shell, topaz, tourmaline, turquoise and many other gem materials.

Sponge-like nanoporous single crystals of gold

PubMed Central

Khristosov, Maria Koifman; Bloch, Leonid; Burghammer, Manfred; Kauffmann, Yaron; Katsman, Alex; Pokroy, Boaz

2015-01-01

Single crystals in nature often demonstrate fascinating intricate porous morphologies rather than classical faceted surfaces. We attempt to grow such crystals, drawing inspiration from biogenic porous single crystals. Here we show that nanoporous single crystals of gold can be grown with no need for any elaborate fabrication steps. These crystals are found to grow following solidification of a eutectic composition melt that forms as a result of the dewetting of nanometric thin films. We also present a kinetic model that shows how this nano-porous single-crystalline structure can be obtained, and which allows the potential size of the porous single crystal to be predicted. Retaining their single-crystalline nature is due to the fact that the full crystallization process is faster than the average period between two subsequent nucleation events. Our findings clearly demonstrate that it is possible to form single-crystalline nano porous metal crystals in a controlled manner. PMID:26554856

Gemstones

USGS Publications Warehouse

Olson, D.W.

2012-01-01

The estimated value of natural gemstones produced from U.S. deposits during 2011 was $10.6 million, a 6-percent increase from 2010. U.S. gemstone production included agate, amber, beryl, coral, garnet, jade, jasper, opal, pearl, quartz, sapphire, shell, topaz, tourmaline, turquoise and many other gem materials.

Spodumene, α-LiAlSi2O6 - A new natural SRS-active crystal with three χ(3)-promoting vibrational modes

NASA Astrophysics Data System (ADS)

Kaminskii, Alexander A.; Bohatý, Ladislav; Libowitzky, Eugen; Rhee, Hanjo; Lux, Oliver; Eichler, Hans J.; Kleinschrodt, Reiner; Yoneda, Hitoki; Shirakawa, Akira; Becker, Petra

2018-04-01

α-LiAlSi2O6, known as mineral spodumene, is introduced as a novel SRS-active crystal with monoclinic symmetry C2/c. Under picosecond laser excitation Raman-induced steady-state χ(3)-nonlinear generation in the visible and near-IR is observed in the crystals. All recorded Stokes and anti-Stokes high-order lasing components are identified and correspond to three SRS-promoting phonon modes with ωSRS1 ≈ 709 cm-1, ωSRS2 ≈ 357 cm-1 and ωSRS3 ≈ 1074 cm-1. On the basis of the results of a spontaneous Raman scattering study they were assigned to vibrations of the tetrahedral [SiO4] groups of the silicate chains and lattice modes of Li-O or Al-O of the crystal structure. A brief review in tabular form of so far known SRS-active natural crystals (minerals) is given as well.

Effect of Fe2O3 on the crystallization behavior of glass-ceramics produced from naturally cooled yellow phosphorus furnace slag

NASA Astrophysics Data System (ADS)

Liu, Hong-pan; Huang, Xiao-feng; Ma, Li-ping; Chen, Dan-li; Shang, Zhi-biao; Jiang, Ming

2017-03-01

CaO-Al2O3-SiO2 (CAS) glass-ceramics were prepared via a melting method using naturally cooled yellow phosphorus furnace slag as the main raw material. The effects of the addition of Fe2O3 on the crystallization behavior and properties of the prepared glass-ceramics were studied by differential thermal analysis, X-ray diffraction, and scanning electron microscopy. The crystallization activation energy was calculated using the modified Johnson-Mehl-Avrami equation. The results show that the intrinsic nucleating agent in the yellow phosphorus furnace slag could effectively promote the crystallization of CAS. The crystallization activation energy first increased and then decreased with increasing amount of added Fe2O3. At 4wt% of added Fe2O3, the crystallization activation energy reached a maximum of 676.374 kJ·mol-1. The type of the main crystalline phase did not change with the amount of added Fe2O3. The primary and secondary crystalline phases were identified as wollastonite (CaSiO3) and hedenbergite (CaFe(Si2O6)), respectively.

A multistep single-crystal-to-single-crystal bromodiacetylene dimerization

NASA Astrophysics Data System (ADS)

Hoheisel, Tobias N.; Schrettl, Stephen; Marty, Roman; Todorova, Tanya K.; Corminboeuf, Clémence; Sienkiewicz, Andrzej; Scopelliti, Rosario; Schweizer, W. Bernd; Frauenrath, Holger

2013-04-01

Packing constraints and precise placement of functional groups are the reason that organic molecules in the crystalline state often display unusual physical or chemical properties not observed in solution. Here we report a single-crystal-to-single-crystal dimerization of a bromodiacetylene that involves unusually large atom displacements as well as the cleavage and formation of several bonds. Density functional theory computations support a mechanism in which the dimerization is initiated by a [2 + 1] photocycloaddition favoured by the nature of carbon-carbon short contacts in the crystal structure. The reaction proceeded up to the theoretical degree of conversion without loss of crystallinity, and it was also performed on a preparative scale with good yield. Moreover, it represents the first synthetic pathway to (E)-1,2-dibromo-1,2-diethynylethenes, which could serve as synthetic intermediates for the preparation of molecular carbon scaffolds. Our findings both extend the scope of single-crystal-to-single-crystal reactions and highlight their potential as a synthetic tool for complex transformations.

Laboratory studies of crystal growth in magma

NASA Astrophysics Data System (ADS)

Hammer, J. E.; Welsch, B. T.; First, E.; Shea, T.

2012-12-01

The proportions, compositions, and interrelationships among crystalline phases and glasses in volcanic rocks cryptically record pre-eruptive intensive conditions, the timing of changes in crystallization environment, and the devolatilization history of eruptive ascent. These parameters are recognized as important monitoring tools at active volcanoes and interpreting geologic events at prehistoric and remote eruptions, thus motivating our attempts to understand the information preserved in crystals through an experimental appoach. We are performing laboratory experiments in mafic, felsic, and intermediate composition magmas to study the mechanisms of crystal growth in thermochemical environments relevant to volcanic environments. We target features common to natural crystals in igneous rocks for our experimental studies of rapid crystal growth phenomena: (1) Surface curvature. Do curved interfaces and spongy cores represent evidence of dissolution (i.e., are they corrosion features), or do they record the transition from dendritic to polyhedral morphology? (2) Trapped melt inclusions. Do trapped liquids represent bulk (i.e., far-field) liquids, boundary layer liquids, or something intermediate, depending on individual species diffusivity? What sequence of crystal growth rates leads to preservation of sealed melt inclusions? (3) Subgrain boundaries. Natural phenocrysts commonly exhibit tabular subgrain regions distinguished by small angle lattice misorientations or "dislocation lamellae" and undulatory extinction. Might these crystal defects be produced as dendrites undergo ripening? (4) Clusters. Contacting clusters of polymineralic crystals are the building blocks of cumulates, and are ubiquitous features of mafic volcanic rocks. Are plagioclase and clinopyroxene aligned crystallographically, suggesting an epitaxial (surface energy) relationship? (5) Log-normal size distribution. What synthetic cooling histories produce "natural" distributions of crystal sizes, and

Natural Cr3+-rich ettringite: occurrence, properties, and crystal structure

NASA Astrophysics Data System (ADS)

Seryotkin, Yurii V.; Sokol, Ella V.; Kokh, Svetlana N.; Murashko, Mikhail N.

2017-08-01

Cr3+-rich ettringite with Cr3+→Al substitution and Cr/(Cr + Al) ratios up to 0.40-0.50 was found in mineral assemblages of the Ma'aleh Adumim area of Mottled Zone (Judean Desert). The Cr3+-rich compositions were the latest in the thaumasite → ettringite-thaumasite solid solution → ettringite → ettringite-bentorite solid solution series. The mineral-forming solution was enriched in Cr3+ and had a pH buffered by afwillite at 11-12. Chromium was inherited from larnite rocks produced by high-temperature combustion metamorphic alteration of bioproductive calcareous sediments. The Cr/(Cr + Al) ratios are within 0.10-0.15 in most of the analysed crystals. This degree of substitution imparts pink colouration to the crystals, but does not affect their habit (a combination of monohedra and a prism). The habit changes to pyramid faces in coarse and later Cr3+-bearing crystals as Cr/(Cr + Al) ratios increase abruptly to 0.40-0.50. Single-crystal XRD analysis of one Cr-free and two Cr3+-rich samples and their structure determination and refinement indicate that the Cr-rich crystals (with Cr/(Cr + Al) to 0.3) preserve the symmetry and metrics of ettringite. The Ca-O bonding network undergoes differentiation with increase of Cr3+ concentration at octahedral M sites. The compression of Ca2 and expansion of Ca1 polyhedra sub-networks correlates with the degree of Cr3+→Al substitution.

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

PubMed Central

Maghsoodi, Maryam

2015-01-01

Crystallization is often used for manufacturing drug substances. Advances of crystallization have achieved control over drug identity and purity, but control over the physical form remains poor. This review discusses the influence of solvents used in crystallization process on crystal habit and agglomeration of crystals with potential implication for dissolution. According to literature it has been known that habit modification of crystals by use of proper solvents may enhance the dissolution properties by changing the size, number and the nature of crystal faces exposed to the dissolution medium. Also, the faster dissolution rate of drug from the agglomerates of crystals compared with the single crystals may be related to porous structure of the agglomerates and consequently their better wettability. It is concluded from this review that in-depth understanding of role of the solvents in crystallization process can be applied to engineering of crystal habit or crystal agglomeration, and predictably dissolution improvement in poorly soluble drugs. PMID:25789214

Vibrational spectra and natural bond orbital analysis of organic crystal L-prolinium picrate

NASA Astrophysics Data System (ADS)

Edwin, Bismi; Amalanathan, M.; Hubert Joe, I.

2012-10-01

Vibrational spectral analysis and quantum chemical computations based on density functional theory (DFT) have been performed on the organic crystal L-prolinium picrate (LPP). The equilibrium geometry, various bonding features and harmonic vibrational wavenumbers of LPP have been investigated using B3LYP method. The calculated molecular geometry has been compared with the experimental data. The detailed interpretation of the vibrational spectra has been carried out with the aid of VEDA 4 program. The various intramolecular interactions confirming the biological activity of the compound have been exposed by natural bond orbital analysis. The distribution of Mulliken atomic charges and bending of natural hybrid orbitals associated with hydrogen bonding also reflects the presence of intramolecular hydrogen bonding thereby enhancing bioactivity. The analysis of the electron density of HOMO and LUMO gives an idea of the delocalization and low value of energy gap indicates electron transport in the molecule and thereby bioactivity. Vibrational analysis reveals the presence of strong O-H⋯O and N-H⋯O interaction between L-prolinium and picrate ions providing evidence for the charge transfer interaction between the donor and acceptor groups and is responsible for its bioactivity.

Large three-dimensional photonic crystals based on monocrystalline liquid crystal blue phases.

PubMed

Chen, Chun-Wei; Hou, Chien-Tsung; Li, Cheng-Chang; Jau, Hung-Chang; Wang, Chun-Ta; Hong, Ching-Lang; Guo, Duan-Yi; Wang, Cheng-Yu; Chiang, Sheng-Ping; Bunning, Timothy J; Khoo, Iam-Choon; Lin, Tsung-Hsien

2017-09-28

Although there have been intense efforts to fabricate large three-dimensional photonic crystals in order to realize their full potential, the technologies developed so far are still beset with various material processing and cost issues. Conventional top-down fabrications are costly and time-consuming, whereas natural self-assembly and bottom-up fabrications often result in high defect density and limited dimensions. Here we report the fabrication of extraordinarily large monocrystalline photonic crystals by controlling the self-assembly processes which occur in unique phases of liquid crystals that exhibit three-dimensional photonic-crystalline properties called liquid-crystal blue phases. In particular, we have developed a gradient-temperature technique that enables three-dimensional photonic crystals to grow to lateral dimensions of ~1 cm (~30,000 of unit cells) and thickness of ~100 μm (~ 300 unit cells). These giant single crystals exhibit extraordinarily sharp photonic bandgaps with high reflectivity, long-range periodicity in all dimensions and well-defined lattice orientation.Conventional fabrication approaches for large-size three-dimensional photonic crystals are problematic. By properly controlling the self-assembly processes, the authors report the fabrication of monocrystalline blue phase liquid crystals that exhibit three-dimensional photonic-crystalline properties.

Crystal growth and characterization of semi organic nonlinear optical (NLO) piperazinium tetrachlorozincate monohydrate (PTCZ) single crystal

NASA Astrophysics Data System (ADS)

Karuppasamy, P.; Pandian, Muthu Senthil; Ramasamy, P.

2018-04-01

The semi-organic single crystal of piperazinium tetrachlorozincate monohydrate (PTCZ) was successfully grown by slow evaporation solution technique (SEST). The grown crystal was subjected to the single crystal XRD studies for confirming the unit cell parameters. The optical quality of the grown crystal was identified by the UV-Vis NIR spectrum analysis and the optical band gap energy was calculated. The photoconductivity study reveals that the grown crystal has positive photoconductive nature. The mechanical stability of the grown crystal was analyzed using Vickers microhardness analyzer. The third-order nonlinear optical properties such as nonlinear refractive index (n2), absorption co-efficient (β) and susceptibility (χ(3)) were studied by Z-scan technique at 640 nm using solid state laser.

Statistical Nature of Atomic Disorder in Irradiated Crystals

NASA Astrophysics Data System (ADS)

Boulle, A.; Debelle, A.

2016-06-01

Atomic disorder in irradiated materials is investigated by means of x-ray diffraction, using cubic SiC single crystals as a model material. It is shown that, besides the determination of depth-resolved strain and damage profiles, x-ray diffraction can be efficiently used to determine the probability density function (PDF) of the atomic displacements within the crystal. This task is achieved by analyzing the diffraction-order dependence of the damage profiles. We thereby demonstrate that atomic displacements undergo Lévy flights, with a displacement PDF exhibiting heavy tails [with a tail index in the γ =0.73 - 0.37 range, i.e., far from the commonly assumed Gaussian case (γ =2 )]. It is further demonstrated that these heavy tails are crucial to account for the amorphization kinetics in SiC. From the retrieved displacement PDFs we introduce a dimensionless parameter fDXRD to quantify the disordering. fDXRD is found to be consistent with both independent measurements using ion channeling and with molecular dynamics calculations.

SSME single-crystal turbine blade dynamics

NASA Technical Reports Server (NTRS)

Moss, Larry A.

1988-01-01

A study was performrd to determine the dynamic characteristics of the Space Shuttle Main Engine high pressure fuel turbopump (HPFTP) blades made of single crystal (SC) material. The first and second stage drive turbine blades of HPFTP were examined. The nonrotating natural frequencies were determined experimentally and analytically. The experimental results of the SC second stage blade were used to verify the analytical procedures. The study examined the SC first stage blade natural frequencies with respect to crystal orientation at typical operating conditions. The SC blade dynamic response was predicted to be less than the directionally solidified base. Crystal axis orientation optimization indicated that the third mode interference will exist in any SC orientation.

SSME single crystal turbine blade dynamics

NASA Technical Reports Server (NTRS)

Moss, Larry A.; Smith, Todd E.

1987-01-01

A study was performed to determine the dynamic characteristics of the Space Shuttle main engine high pressure fuel turbopump (HPFTP) blades made of single crystal (SC) material. The first and second stage drive turbine blades of HPFTP were examined. The nonrotating natural frequencies were determined experimentally and analytically. The experimental results of the SC second stage blade were used to verify the analytical procedures. The analytical study examined the SC first stage blade natural frequencies with respect to crystal orientation at typical operating conditions. The SC blade dynamic response was predicted to be less than the directionally solidified blade. Crystal axis orientation optimization indicated the third mode interference will exist in any SC orientation.

Protein Crystallization.

PubMed

McPherson, Alexander

2017-01-01

Protein crystallization was discovered by chance nearly 200 years ago and was developed in the late nineteenth century as a powerful purification tool, and 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 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 due to the advent of practical, easy-to-use screening kits, and the application of laboratory robotics.

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

Electron transfer kinetics on natural crystals of MoS2 and graphite.

PubMed

Velický, Matěj; Bissett, Mark A; Toth, Peter S; Patten, Hollie V; Worrall, Stephen D; Rodgers, Andrew N J; Hill, Ernie W; Kinloch, Ian A; Novoselov, Konstantin S; Georgiou, Thanasis; Britnell, Liam; Dryfe, Robert A W

2015-07-21

Here, we evaluate the electrochemical performance of sparsely studied natural crystals of molybdenite and graphite, which have increasingly been used for fabrication of next generation monolayer molybdenum disulphide and graphene energy storage devices. Heterogeneous electron transfer kinetics of several redox mediators, including Fe(CN)6(3-/4-), Ru(NH3)6(3+/2+) and IrCl6(2-/3-) are determined using voltammetry in a micro-droplet cell. The kinetics on both materials are studied as a function of surface defectiveness, surface ageing, applied potential and illumination. We find that the basal planes of both natural MoS2 and graphite show significant electroactivity, but a large decrease in electron transfer kinetics is observed on atmosphere-aged surfaces in comparison to in situ freshly cleaved surfaces of both materials. This is attributed to surface oxidation and adsorption of airborne contaminants at the surface exposed to an ambient environment. In contrast to semimetallic graphite, the electrode kinetics on semiconducting MoS2 are strongly dependent on the surface illumination and applied potential. Furthermore, while visibly present defects/cracks do not significantly affect the response of graphite, the kinetics on MoS2 systematically accelerate with small increase in disorder. These findings have direct implications for use of MoS2 and graphene/graphite as electrode materials in electrochemistry-related applications.

Statistical Nature of Atomic Disorder in Irradiated Crystals.

PubMed

Boulle, A; Debelle, A

2016-06-17

Atomic disorder in irradiated materials is investigated by means of x-ray diffraction, using cubic SiC single crystals as a model material. It is shown that, besides the determination of depth-resolved strain and damage profiles, x-ray diffraction can be efficiently used to determine the probability density function (PDF) of the atomic displacements within the crystal. This task is achieved by analyzing the diffraction-order dependence of the damage profiles. We thereby demonstrate that atomic displacements undergo Lévy flights, with a displacement PDF exhibiting heavy tails [with a tail index in the γ=0.73-0.37 range, i.e., far from the commonly assumed Gaussian case (γ=2)]. It is further demonstrated that these heavy tails are crucial to account for the amorphization kinetics in SiC. From the retrieved displacement PDFs we introduce a dimensionless parameter f_{D}^{XRD} to quantify the disordering. f_{D}^{XRD} is found to be consistent with both independent measurements using ion channeling and with molecular dynamics calculations.

Topographically induced homeotropic alignment of liquid crystals on self-assembled opal crystals.

PubMed

Kumar, Pankaj; Oh, Su Yeon; Baliyan, Vijay K; Kundu, Sudarshan; Lee, Seung Hee; Kang, Shin-Woong

2018-04-02

The surface of multilayered opal crystals resulted in homeotropic alignment of liquid crystal (LC), originated from the surface topography of opal crystals rather than a chemical nature of the nanoparticles. The polar anchoring energy (5.51 × 10 -5 J/m 2 ) of the crystal surface for nematic LC molecules was in a similar range to the conventional polyimide alignment layer (2.11 × 10 -5 J/m 2 ) used for commercial applications. The critical length scale for anchoring transition was approximately Lw = ~1 μm. If a diameter of particle d < 1 μm for opal crystals, LC molecules preferred to anchor vertically to the surface to minimize elastic free energy of bulk LCs. The LC favored a planar anchoring if d > 1 μm. The results provide crucial insights to understand the homeotropic alignment of LCs on solid surfaces and therefore offer opportunities to develop novel materials for a vertical alignment of LCs.

Characterizing the effect of growth conditions and crystal habit on the distribution of imperfections amongst populations of crystals

NASA Astrophysics Data System (ADS)

Price, C. J.

1993-03-01

The distribution of gross imperfections amongst populations of copper sulphate pentahydrate crystals grown under different conditions of purity and temperature are examined. The frequency of imperfection increases with decreasing crystal size. The nature of the imperfections vary with growth temperature and impurities present.

Viewing Ice Crystals Using Polarized Light.

ERIC Educational Resources Information Center

Kinsman, E. M.

1992-01-01

Describes a method for identifying and examining single ice crystals by photographing a thin sheet of ice placed between two inexpensive polarizing filters. Suggests various natural and prepared sources for ice that promote students' insight into crystal structures, and yield colorful optical displays. Includes directions, precautions, and sample…

CRYSTAL GROWTH. Crystallization by particle attachment in synthetic, biogenic, and geologic environments.

PubMed

De Yoreo, James J; Gilbert, Pupa U P A; Sommerdijk, Nico A J M; Penn, R Lee; Whitelam, Stephen; Joester, Derk; Zhang, Hengzhong; Rimer, Jeffrey D; Navrotsky, Alexandra; Banfield, Jillian F; Wallace, Adam F; Michel, F Marc; Meldrum, Fiona C; Cölfen, Helmut; Dove, Patricia M

2015-07-31

Field and laboratory observations show that crystals commonly form by the addition and attachment of particles that range from multi-ion complexes to fully formed nanoparticles. The particles involved in these nonclassical pathways to crystallization are diverse, in contrast to classical models that consider only the addition of monomeric chemical species. We review progress toward understanding crystal growth by particle-attachment processes and show that multiple pathways result from the interplay of free-energy landscapes and reaction dynamics. Much remains unknown about the fundamental aspects, particularly the relationships between solution structure, interfacial forces, and particle motion. Developing a predictive description that connects molecular details to ensemble behavior will require revisiting long-standing interpretations of crystal formation in synthetic systems, biominerals, and patterns of mineralization in natural environments. Copyright © 2015, American Association for the Advancement of Science.

Liquid Crystal Colloids

NASA Astrophysics Data System (ADS)

Smalyukh, Ivan I.

2018-03-01

Colloids are abundant in nature, science, and technology, with examples ranging from milk to quantum dots and the colloidal atom paradigm. Similarly, liquid crystal ordering is important in contexts ranging from biological membranes to laboratory models of cosmic strings and liquid crystal displays in consumer devices. Some of the most exciting recent developments in both of these soft matter fields emerge at their interface, in the fast-growing research arena of liquid crystal colloids. Mesoscale self-assembly in such systems may lead to artificial materials and to structures with emergent physical behavior arising from patterning of molecular order and nano- or microparticles into precisely controlled configurations. Liquid crystal colloids show exceptional promise for new discovery that may impinge on composite material fabrication, low-dimensional topology, photonics, and so on. Starting from physical underpinnings, I review the state of the art in this fast-growing field, with a focus on its scientific and technological potential.

Radiating dipoles in photonic crystals

PubMed

Busch; Vats; John; Sanders

2000-09-01

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

Polariton effects in naphthalene crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Robinette, Susan Louise

1977-10-01

The experimental verification of the two-step nature of energy dissipation of photon energy by a crystal is the subject of this dissertation. The ..cap alpha..(O,O) Davydov component of the lowest energy singlet transition in pure strain-free napthalene single crystals is shown to exhibit an increase in absorption with increasing temperature, due to an increase in polariton damping via polariton-phonon scattering processes. (GHT)

High resolution synchrotron X-radiation diffraction imaging of crystals grown in microgravity and closely related terrestrial crystals

NASA Technical Reports Server (NTRS)

Steiner, Bruce; Dobbyn, Ronald C.; Black, David; Burdette, Harold; Kuriyama, Masao; Fripp, Archibald; Simchik, Richard

1991-01-01

Irregularities in three crystals grown in space and in four terrestrial crystals grown under otherwise comparable conditions have been observed in high resolution diffraction imaging. The images provide important new clues to the nature and origins of irregularities in each crystal. For two of the materials, mercuric iodide and lead tin telluride, more than one phase (an array of non-diffracting inclusions) was observed in terrestrial samples; but the formation of these multiple phases appears to have been suppressed in directly comparable crystals grown in microgravity. The terrestrial seed crystal of triglycine sulfate displayed an unexpected layered structure, which propagated during directly comparable space growth. Terrestrial Bridgman regrowth of gallium arsenide revealed a mesoscopic structure substantially different from that of the original Czochralski material. A directly comparable crystal is to be grown shortly in space.

Butterfly wing color: A photonic crystal demonstration

NASA Astrophysics Data System (ADS)

Proietti Zaccaria, Remo

2016-01-01

We have theoretically modeled the optical behavior of a natural occurring photonic crystal, as defined by the geometrical characteristics of the Teinopalpus Imperialis butterfly. In particular, following a genetic algorithm approach, we demonstrate how its wings follow a triclinic crystal geometry with a tetrahedron unit base. By performing both photonic band analysis and transmission/reflection simulations, we are able to explain the characteristic colors emerging by the butterfly wings, thus confirming their crystal form.

Monitoring and modeling of ultrasonic wave propagation in crystallizing mixtures

NASA Astrophysics Data System (ADS)

Marshall, T.; Challis, R. E.; Tebbutt, J. S.

2002-05-01

The utility of ultrasonic compression wave techniques for monitoring crystallization processes is investigated in a study of the seeded crystallization of copper II sulfate pentahydrate from aqueous solution. Simple models are applied to predict crystal yield, crystal size distribution and the changing nature of the continuous phase. A scattering model is used to predict the ultrasonic attenuation as crystallization proceeds. Experiments confirm that modeled attenuation is in agreement with measured results.

X-ray Microscopic Characterization of Protein Crystals

NASA Technical Reports Server (NTRS)

Hu, Z. W.; Holmes, A.; Thomas, B.R.; Chernov, a. A.; Chu, Y. S.; Lai, B.

2004-01-01

The microscopic mapping of the variation in degree of perfection and in type of defects in entire protein crystals by x-rays may well be a prerequisite for better understanding causes of lattice imperfections, the growth history, and properties of protein crystals. However, x-ray microscopic characterization of bulk protein crystals, in the as-grown state, is frequently more challenging than that of small molecular crystals due to the experimental difficulties arising largely from the unique features possessed by protein crystals. In this presentation, we will illustrate ssme recent activities in employing coherence-based phase contrast x-ray imaging and high-angular-resolution diffraction techniques for mapping microdefects and the degree of perfection of protein crystals, and demonstrate a correlation between crystal perfection, diffraction phenomena., and crystallization conditions. The observed features and phenomena will be discussed in context to gain insight into the nature of defects, nucleation and growth, and the properties of protein crystals.

Crystal growth, structural, thermal and mechanical behavior of l-arginine 4-nitrophenolate 4-nitrophenol dihydrate (LAPP) single crystals.

PubMed

Mahadevan, M; Ramachandran, K; Anandan, P; Arivanandhan, M; Bhagavannarayana, G; Hayakawa, Y

2014-12-10

Single crystals of l-arginine 4-nitrophenolate 4-nitrophenol dihydrate (LAPP) have been grown successfully from the solution of l-arginine and 4-nitrophenol. Slow evaporation of solvent technique was adopted to grow the bulk single crystals. Single crystal X-ray diffraction analysis confirms the grown crystal has monoclinic crystal system with space group of P21. Powder X-ray diffraction analysis shows the good crystalline nature. The crystalline perfection of the grown single crystals was analyzed by HRXRD by employing a multicrystal X-ray diffractometer. The functional groups were identified from proton NMR spectroscopic analysis. Linear and nonlinear optical properties were determined by UV-Vis spectrophotometer and Kurtz powder technique respectively. It is found that the grown crystal has no absorption in the green wavelength region and the SHG efficiency was found to be 2.66 times that of the standard KDP. The Thermal stability of the crystal was found by obtaining TG/DTA curve. The mechanical behavior of the grown crystal has been studied by Vicker's microhardness method. Copyright © 2014 Elsevier B.V. All rights reserved.

Crystal structure of the human natural killer cell inhibitory receptor KIR2DL1-HLA-Cw4 complex.

PubMed

Fan, Q R; Long, E O; Wiley, D C

2001-05-01

Inhibitory natural killer (NK) cell receptors down-regulate the cytotoxicity of NK cells upon recognition of specific class I major histocompatibility complex (MHC) molecules on target cells. We report here the crystal structure of the inhibitory human killer cell immunoglobulin-like receptor 2DL1 (KIR2DL1) bound to its class I MHC ligand, HLA-Cw4. The KIR2DL1-HLA-Cw4 interface exhibits charge and shape complementarity. Specificity is mediated by a pocket in KIR2DL1 that hosts the Lys80 residue of HLA-Cw4. Many residues conserved in HLA-C and in KIR2DL receptors make different interactions in KIR2DL1-HLA-Cw4 and in a previously reported KIR2DL2-HLA-Cw3 complex. A dimeric aggregate of KIR-HLA-C complexes was observed in one KIR2DL1-HLA-Cw4 crystal. Most of the amino acids that differ between human and chimpanzee KIRs with HLA-C specificities form solvent-accessible clusters outside the KIR-HLA interface, which suggests undiscovered interactions by KIRs.

Hingganite-(Y) from a small aplite vein in granodiorite from Oppach, Lusatian Mts., E-Germany

NASA Astrophysics Data System (ADS)

Thomas, Rainer; Davidson, Paul

2017-12-01

Crystals of hingganite-(Y) occur co-trapped in quartz crystals from miarolitic cavities in an aplite vein in the Cadomian granodiorite from Oppach/Lusatian, Germany. We describe the chemical composition and provide a reference Raman spectrum of this mineral, for which little useful spectral data has been published. In addition, we provide some inferences as to the genesis of this mineral in relationship to melt and fluid inclusions in quartz. The paragenetic sequence of minerals conserved only as small crystal inclusions in quartz, demonstrates an unusual occurrence in the Lusatian aplites, characterized by an unusual, extremely water-rich, near-supercritical melt-fluid system with high concentrations in alkali carbonates and sulfates. We propose that a sulfate-rich system was responsible for the fixation of Be and REE as hingganite-(Y), rather than the more common beryl + REE mineral assemblage. This may provide an explanation for the formation of this otherwise rare mineral

Formation of curved micrometer-sized single crystals.

PubMed

Koifman Khristosov, Maria; Kabalah-Amitai, Lee; Burghammer, Manfred; Katsman, Alex; Pokroy, Boaz

2014-05-27

Crystals in nature often demonstrate curved morphologies rather than classical faceted surfaces. Inspired by biogenic curved single crystals, we demonstrate that gold single crystals exhibiting curved surfaces can be grown with no need of any fabrication steps. These single crystals grow from the confined volume of a droplet of a eutectic composition melt that forms via the dewetting of nanometric thin films. We can control their curvature by controlling the environment in which the process is carried out, including several parameters, such as the contact angle and the curvature of the drops, by changing the surface tension of the liquid drop during crystal growth. Here we present an energetic model that explains this phenomenon and predicts why and under what conditions crystals will be forced to grow with the curvature of the microdroplet even though the energetic state of a curved single crystal is very high.

Raman spectroscopic investigations on natural samples from the Integrated Ocean Drilling Program (IODP) Expedition 311: indications for heterogeneous compositions in hydrate crystals.

PubMed

Schicks, J M; Ziemann, M A; Lu, H; Ripmeester, J A

2010-12-01

Natural gas hydrates usually are found in the form of structure I, encasing predominantly methane in the hydrate lattices as guest molecules, sometimes also minor amount of higher hydrocarbons, CO2 or H2S. Raman spectroscopy is an approved tool to determine the composition of the hydrate phase. Thus, in this study Raman spectroscopic analyses have been applied to hydrate samples obtained from Integrated Ocean Drilling Program (IODP) Expedition 311 in two different approaches: studying the samples randomly taken from the hydrate core, and--as a new application--mapping small areas on the surface of clear hydrate crystals. The results obtained imply that the gas composition of hydrate, in terms of relative concentrations of CH4 and H2S, is not homogeneous over a core or even within a crystal. The mapping method yielded results with very high lateral resolution, indicating the coexistence of different phases with the same structure but different compositions within a hydrate crystal. Copyright © 2010 Elsevier B.V. All rights reserved.

Identification of surface domain structure on enamel crystals using polyamidoamine dendrimer

NASA Astrophysics Data System (ADS)

Chen, Haifeng; Clarkson, Brian H.; Orr, Bradford; Majoros, Istvan; Banaszak Holl, Mark M.

2002-03-01

The control of hydroxyapatite crystal nucleation and crystal growth is central to the mineralization and remineralization of enamel and dentin of teeth. However, the precise biomolecular mechanisms involved remain obscure. The intimate association between the crystal's surface and extracellular protein components implies a modulating role for organic crystal interactions probably mediated via specific crystal surface domains. These include lattice defects and specific stereochemical arrays on associated organic molecules. The nature of protein-crystal interaction depends upon the physical forces of attraction / repulsion between specific biomolecular groups and crystal surface domains. The proposed study is to utilize specific polyamidoamine (PAMAM) dendrimers, also known as “artificial proteins”, acting as nanoprobe. These will be used to probe specific surface domain on the surface of the naturally derived crystals of hydroxyapatite and to determine how control of growth and dissolution may be affected at the biomolecular level. The hydroxyapatite crystals are extracted from the maturation stage enamel of rats. Three types of PAMAM dendrimers, respectively with amine-, carboxylic acid and methyl-capped surface, will be applied in the study. The dendrimer binding on the surface of the hydoxyapatite crystals will be characterized using atomic force microscopy (AFM). The different dendrimer binding on the crystals will disclose the specific surface domain structure on the crystals, which is assumed to be important in binding the extracellular protein.

Transrotational Crystals Revealed by TEM in Crystallizing Amorphous Films: New Solid State Order or Novel Extended Imperfection?

NASA Astrophysics Data System (ADS)

Kolosov, Vladimir Yu.

2011-03-01

Uunusual transrotational structure is presented for crystal growth in thin amorphous films. Experimental results have been obtained for the microcrystals of different chemical nature (oxides, chalcogenides, metals and alloys) grown in thin films prepared by various methods. Basically we used transmission electron microscopy (TEM): our original bend contour technique combined with selected area diffraction (HREM, EDX and CBED used in due cases as well as AFM). The unusual phenomenon (also traced inside TEM in situ) resides in strong (up to the whole rotation per micrometer) regular internal bending of crystal lattice planes (transrotation) in a growing crystal. As a result permanent rotation of the lattice orientation (realized round an axis lying in the film plane) is revealed by TEM. Different geometries of transrotational nanostructures are described: cylindrical, ellipsoidal, etc. Such crystal with transrotational atom periodicity resembles ideal single crystal enclosed in a curved space. Transrotational crystals can be considered as endless 2.5 D analogy of nanotubes, nanonions. Transrotation is strongly increasing as the film gets thinner in the range 100-15 nm. Transrotations supplement well known dislocations (in crystals) and disclinations (in liquid crystals). Support of RF Ministry of Education and Science is acknowledged.

Spectroscopic study of gel grown L-Valine Zinc Glycine Thiourea Sulfate (VZGTS) crystal: A novel NLO crystal

NASA Astrophysics Data System (ADS)

Rathod, Kiran T.; Patel, I. B.

2017-05-01

In recent years, organometalic non linear optical (NLO) materials have attained immense appeal form researchers due to its range of technological applications in photonic field and optoelectronic technology. In present research work, novel semi organic NLO L-Valine Zinc Glycine Thiourea Sulfate crystals (VZGTS) with different morphologies were grown by gel method at ambient temperature. Presence and identification of functional groups were confirmed by FITR analysis. Spectroscopic studies were carried out for it. The UV-Vis spectroscopy is recorded for crystal. PL study stats that the crystal has insulating nature. Spectroscopic study shows that this crystal has good transparency in the case of fundamental wavelength of Nd : YAG laser. Second Harmonic Generation (SHG) efficiency was confirmed by Kurtz - Perry powder method. Results are discussed in the paper.

Liquid Crystals for Laser Applications

DTIC Science & Technology

1992-07-01

336. Zei’dovich, B . Ya. and Tabiryan, N. V., Induced light scattering in the mesophase of a nematic liquid crystal (NLC), JETP Lett., 30, 478- 482 ...and devices. ADVANCES IN MATERIALS I Ferroelectric LC’s Ferroelectricity in liquid crystals was first suggested in 1974 by R. B . Meyer2 3 who, by means...most recently, 2 4 the M* phase. These tilted chiral smectic phases are classified according to the nature of the intermolecular I I packing within

Fundamental Studies of Crystal Growth of Microporous Materials

NASA Technical Reports Server (NTRS)

Dutta, P.; George, M.; Ramachandran, N.; Schoeman, B.; Curreri, Peter A. (Technical Monitor)

2002-01-01

Microporous materials are framework structures with well-defined porosity, often of molecular dimensions. Zeolites contain aluminum and silicon atoms in their framework and are the most extensively studied amongst all microporous materials. Framework structures with P, Ga, Fe, Co, Zn, B, Ti and a host of other elements have also been made. Typical synthesis of microporous materials involve mixing the framework elements (or compounds, thereof) in a basic solution, followed by aging in some cases and then heating at elevated temperatures. This process is termed hydrothermal synthesis, and involves complex chemical and physical changes. Because of a limited understanding of this process, most synthesis advancements happen by a trial and error approach. There is considerable interest in understanding the synthesis process at a molecular level with the expectation that eventually new framework structures will be built by design. The basic issues in the microporous materials crystallization process include: (1) Nature of the molecular units responsible for the crystal nuclei formation; (2) Nature of the nuclei and nucleation process; (3) Growth process of the nuclei into crystal; (4) Morphological control and size of the resulting crystal; (5) Surface structure of the resulting crystals; (6) Transformation of frameworks into other frameworks or condensed structures. The NASA-funded research described in this report focuses to varying degrees on all of the above issues and has been described in several publications. Following is the presentation of the highlights of our current research program. The report is divided into five sections: (1) Fundamental aspects of the crystal growth process; (2) Morphological and Surface properties of crystals; (3) Crystal dissolution and transformations; (4) Modeling of Crystal Growth; (5) Relevant Microgravity Experiments.

Gemstones

USGS Publications Warehouse

Olson, D.W.

2006-01-01

During 2005, the estimated value of natural gemstones produced from US deposits was $13.9 million. Production included agates, amber, beryl, coral, garnet, jade, jasper, opal, pearl, quartz, sapphire, shell, topaz, tourmaline, and torquoise among others. For the year, the US gemstone trade with all countries and territories exceeded $26 billion. There are indication that there may be continued growth in the US diamond and jewelry markets in 2006.

Synthesis, crystal growth, optical, thermal, and mechanical properties of a nonlinear optical single crystal: ammonium sulfate hydrogen sulphamate (ASHS)

NASA Astrophysics Data System (ADS)

Sudhakar, K.; Nandhini, S.; Muniyappan, S.; Arumanayagam, T.; Vivek, P.; Murugakoothan, P.

2018-04-01

Ammonium sulfate hydrogen sulphamate (ASHS), an inorganic nonlinear optical crystal, was grown from the aqueous solution by slow evaporation solution growth technique. The single-crystal XRD confirms that the grown single crystal belongs to the orthorhombic system with the space group of Pna21. Powder XRD confirms the crystalline nature and the diffraction planes were indexed. Crystalline perfection of grown crystal was analysed by high-resolution X-ray diffraction rocking curve technique. UV-Vis-NIR studies revealed that ASHS crystal has optical transparency 65% and lower cut-off wavelength at 218 nm. The violet light emission of the crystal was identified by photoluminescence studies. The particle size-dependent second-harmonic generation efficiency for ASHS crystal was evaluated by Kurtz-Perry powder technique using Nd:YAG laser which established the existence of phase matching. Surface laser damage threshold value was evaluated using Nd:YAG laser. Optical homogeneity of the crystal was evaluated using modified channel spectrum method through birefringence study. Thermal analysis reveals that ASHS crystal is stable up to 213 °C. The mechanical behaviour of the ASHS crystal was analysed using Vickers microhardness study.

Growth and characterization of hexamethylenetetramine crystals grown from solution

NASA Astrophysics Data System (ADS)

Babu, B.; Chandrasekaran, J.; Balaprabhakaran, S.

2014-06-01

Organic nonlinear optical single crystals of hexamethylenetetramine (HMT; 10 × 10 × 5 mm3) were prepared by crystallization from methanol solution. The grown crystals were subjected to various characterization techniques such as single crystal XRD, powder XRD, UV-Vis and electrical studies. Single crystal XRD analysis confirmed the crystalline structure of the grown crystals. Their crystalline nature was also confirmed by powder XRD technique. The optical transmittance property was identified from UV-Vis spectrum. Dielectric measurements were performed as a function of frequency at different temperatures. DC conductivity and photoconductivity studies were also carried out for the crystal. The powder second harmonic generation efficiency (SHG) of the crystal was measured using Nd:YAG laser and the efficiency was found to be two times greater than that of potassium dihydrogen phosphate (KDP).

Biogenic twinned crystals exhibiting unique morphological symmetry

NASA Astrophysics Data System (ADS)

Hirsch, Anna; Gur, Dvir; Palmer, Ben; Addadi, Lia; Leiserowitz, Leslie; Kronik, Leeor

Guanine crystals are widely used in nature as components of multilayer reflectors. Organisms control the size, morphology, and arrangement of these crystals, to obtain a variety of optical ''devices''. The reflection systems found in the lens of the scallop eye and in the copepod cuticle are unique in that the multilayered reflectors are tiled together to form a contiguous packed array. In the former, square crystals are tiled to form a reflecting mirror. In the latter, hexagonal crystals are closely packed to produce brilliant colors. Based on electron diffraction, morphology considerations, and density functional theory, these crystals were shown to possess similar monoclinic crystal symmetry, which we have previously identified as different from that of synthetic anhydrous guanine. However, the crystals are different in that multiple twinning about the {012} and the {011} crystallographic planes results in square and hexagonal morphology, respectively. This is a unique example where controlled twinning is used as a strategy to form a morphology with higher symmetry than that of the underlying crystal, allowing for tilling that facilitates optical functionality.

Enzymatically Controlled Vacancies in Nanoparticle Crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barnaby, Stacey N.; Ross, Michael B.; Thaner, Ryan V.

In atomic systems, the mixing of metals results in distinct phase behavior that depends on the identity and bonding characteristics of the atoms. In nanoscale systems, the use of oligonucleotides as programmable “bonds” that link nanoparticle “atoms” into superlattices allows for the decoupling of atom identity and bonding. While much research in atomic systems is dedicated to understanding different phase behavior of mixed metals, it is not well understood on the nanoscale how changes in the nanoscale “bond” affect the phase behavior of nanoparticle crystals. In this work, the identity of the atom is kept the same but the chemicalmore » nature of the bond is altered, which is not possible in atomic systems, through the use of DNA and RNA bonding elements. These building blocks assemble into single crystal nanoparticle superlattices with mixed DNA and RNA bonding elements throughout. The nanoparticle crystals can be dynamically changed through the selective and enzymatic hydrolysis of the RNA bonding elements, resulting in superlattices that retain their crystalline structure and habit, while incorporating up to 35% random vacancies generated from the nanoparticles removed. Therefore, the bonding elements of nanoparticle crystals can be enzymatically and selectively addressed without affecting the nature of the atom.« less

Dynamics of melt crystal interface and thermal stresses in rotational Bridgman crystal growth process

NASA Astrophysics Data System (ADS)

Ma, Ronghui; Zhang, Hui; Larson, David J.; Mandal, Krishna C.

2004-05-01

The growth process of potassium bromide (KBr) single crystals in a vertical Bridgman furnace has been studied numerically using an integrated model that combines formulation of global heat transfer and thermal elastic stresses. The global heat transfer sub-model accounts for conduction, convection and interface movement in the multiphase system. Using the elastic stress sub-model, thermal stresses in the growing crystal caused by the non-uniform temperature distribution is predicted. Special attention is directed to the interaction between the crystal and the ampoule. The global temperature distribution in the furnace, the flow pattern in the melt and the interface shapes are presented. We also investigate the effects of the natural convection and rotational forced convection on the shape of the growth fronts. Furthermore, the state of the thermal stresses in the crystal is studied to understand the plastic deformation mechanisms during the cooling process. The influence of the wall contact on thermal stresses is also addressed.

Expression, crystallization and preliminary crystallographic analysis of the extracellular IgV-like domain of the human natural killer cell inhibitory receptor p75/AIRM1.

PubMed

Dimasi, Nazzareno; Moretta, Lorenzo; Biassoni, Roberto; Mariuzza, Roy A

2003-10-01

p75/AIRM1 (Siglec-7) is a sialic acid-binding Ig-like lectin recently identified as an inhibitory receptor on natural killer cells. The expression, in vitro folding, circular-dichroism spectroscopy, crystallization and preliminary X-ray characterization of the Ig-V like domain of p75/AIRM1 are reported. X-ray data were collected from a single crystal at 100 K, with a maximum useful diffraction pattern extending to 1.45 A resolution on a synchrotron source. The crystal belongs to a primitive monoclinic space group, with unit-cell parameters a = 32.65, b = 49.72, c = 39.79 A, alpha = gamma = 90, beta = 113 degrees. The systematic absences indicate that the space group is P2(1). Assuming one molecule per asymmetric unit, V(M) (the Matthews coefficient) was calculated to be 1.879 A(3) Da(-1) and the solvent content was estimated to be 32.01%.

Unique Conformation in a Natural Interruption Sequence of Type XIX Collagen Revealed by Its High-Resolution Crystal Structure.

PubMed

Xu, Tingting; Zhou, Cong-Zhao; Xiao, Jianxi; Liu, Jinsong

2018-02-20

Naturally occurring interruptions in nonfibrillar collagen play key roles in molecular flexibility, collagen degradation, and ligand binding. The structural feature of the interruption sequences and the molecular basis for their functions have not been well studied. Here, we focused on a G5G type natural interruption sequence G-POALO-G from human type XIX collagen, a homotrimer collagen, as this sequence possesses distinct properties compared with those of a pathological similar Gly mutation sequence in collagen mimic peptides. We determined the crystal structures of the host-guest peptide (GPO) 3 -GPOALO-(GPO) 4 to 1.03 Å resolution in two crystal forms. In these structures, the interruption zone brings localized disruptions to the triple helix and introduces a light 6-8° bend with the same directional preference to the whole molecule, which may correspond structurally to the first physiological kink site in type XIX collagen. Furthermore, at the G5G interruption site, the presence of Ala and Leu residues, both with free N-H groups, allows the formation of more direct and water-mediated interchain hydrogen bonds than in the related Gly → Ala structure. These could partly explain the difference in thermal stability between the different interruptions. In addition, our structures provide a detailed view of the dynamic property of such an interrupted zone with respect to hydrogen bonding topology, torsion angles, and helical parameters. Our results, for the first time, also identified the binding of zinc to the end of the triple helix. These findings will shed light on how the interruption sequence influences the conformation of the collagen molecule and provide a structural basis for further functional studies.

Nonlinear dielectric spectroscopy in a fragile plastic crystal

NASA Astrophysics Data System (ADS)

Michl, M.; Bauer, Th.; Lunkenheimer, P.; Loidl, A.

2016-03-01

In this work we provide a thorough examination of the nonlinear dielectric properties of a succinonitrile-glutaronitrile mixture, representing one of the rare examples of a plastic crystal with fragile glassy dynamics. The detected alteration of the complex dielectric permittivity under high fields can be explained considering the heterogeneous nature of glassy dynamics and a field-induced variation of entropy. While the first mechanism was also found in structural glass formers, the latter effect seems to be more pronounced in plastic crystals. Moreover, the third harmonic component of the dielectric susceptibility is reported, revealing a hump-like spectral shape as predicted, e.g., within a model considering cooperative molecular dynamics. If assuming the validity of this model, one can deduce the temperature dependence of the number of correlated molecules Ncorr from these data. In accord with the fragile nature of the glass transition in this plastic crystal, we obtain a relatively strong temperature dependence of Ncorr, in contrast to the much weaker temperature dependence in plastic-crystalline cyclo-octanol, whose glass transition is of strong nature.

Fluid inclusion constraints on the genesis of the Puladi muscovite deposit in Gongshan County, Yunnan Province

NASA Astrophysics Data System (ADS)

Yin, Qiong; Liu, Wei

2017-12-01

This paper focuses on beryl mines in the Maji region of Yunnan Province, which are characterized by fluid inclusions. Based on petrography theory, mineralogy, and ore-forming geological conditions, beryl can be divided as CO2 and CO2-H2O inclusions. In addition, the characteristics of inclusions in the coordinate of A/B is summarized. The homogenization temperature of fluid inclusions in the coordinate of A ranges from 250 °C to 397 °C, while the salinity of fluid inclusions ranges from 0.18% to 4.27%. By contrast, the homogenization temperature in the coordinate of B ranges from 210 °C to 340 °C, and the salinity is from 0.22% to 5.11%. The pressure of ore-forming fluid in the coordinate of A/B is approximately 83 MPa with densities of 0.8034 g/m3 and 0.8363 g/m3, which are characteristic of mediumtemperature, low-salinity, and medium-density fluids. Based on Raman spectra and different metallogenic depths, the two types of beryl belong to different metallogenic belts. The beryl deposits in Gongshan are of medium-temperature gas-hydrothermal type.

Crystallization of Skeletal Diamonds from Graphite and Natural Coal in Presence of Hydrous Fluids at P=8 GPa and T=1400-1500° C

NASA Astrophysics Data System (ADS)

Dobrzhinetskaya, L. F.; Renfro, A. P.; Green, H. W.

2001-12-01

Most metamorphic microdiamonds from crustal UHP rocks of the Kokchetav massive, Kazakhstan are characterized by skeletal-hopper crystals, cuboid-like crystals with cavities "healed over" by graphite, rose-like crystals, and other imperfect morphologies. According to the classical theory of crystal growth at thermodynamic equilibrium, only shapes with a minimum surface energy are stable. Thus imperfect crystallographic forms of most metamorphic diamonds formally may be interpreted as metastable while the presence of other high pressure phases associated with diamond indicates that the rocks have been subjected to UHP metamorphism within the diamond stability field. The classical theory also says that a skeletal-hopper crystal is one that develops under conditions of rapid growth, a high degree of supersaturation and in the presence of impurities. In contrast to these observations, most experiments on diamond synthesis at high P (5-7.7 GPa) and T (1250 - 1900° C) from graphite (Wang et al., 1999; Hong et al., 1999; Yamaoka et al., 2000) and carbonate material (Pal'anov et al., 1999; Sokol et al.,2000) in presence of fluid phase produced perfect octahedral and cube-octahedral diamond crystals. Advanced analytical research on metamorphic diamonds and their inclusions has demonstrated that they were crystallized from a multicomponent COH-rich supercritical fluid phase, the composition of which suggests intermixture of crustal and mantle components (de Corte et al., 1999; Dobrzhinetskaya et al., 2001, Stockhert et al., 2001). We have recently synthesized imperfect diamond crystals (skeletal-hopper morphologies with effect of etching of the diamond surfaces) from graphite and natural coal + 2% Mg(OH)2 as a source for fluid phase. Conditions of experiments are: P=8-8.5 GPa, T=1400-1500° C, t=14 to 136 hours. Our experimental data are in a good agreement with similar experiments conducted by Kanda et al. (1984) who showed that with increasing water content of the system

Current trends in protein crystallization.

PubMed

Gavira, José A

2016-07-15

Proteins belong to the most complex colloidal system in terms of their physicochemical properties, size and conformational-flexibility. This complexity contributes to their great sensitivity to any external change and dictate the uncertainty of crystallization. The need of 3D models to understand their functionality and interaction mechanisms with other neighbouring (macro)molecules has driven the tremendous effort put into the field of crystallography that has also permeated other fields trying to shed some light into reluctant-to-crystallize proteins. This review is aimed at revising protein crystallization from a regular-laboratory point of view. It is also devoted to highlight the latest developments and achievements to produce, identify and deliver high-quality protein crystals for XFEL, Micro-ED or neutron diffraction. The low likelihood of protein crystallization is rationalized by considering the intrinsic polypeptide nature (folded state, surface charge, etc) followed by a description of the standard crystallization methods (batch, vapour diffusion and counter-diffusion), including high throughput advances. Other methodologies aimed at determining protein features in solution (NMR, SAS, DLS) or to gather structural information from single particles such as Cryo-EM are also discussed. Finally, current approaches showing the convergence of different structural biology techniques and the cross-methodologies adaptation to tackle the most difficult problems, are presented. Current advances in biomacromolecules crystallization, from nano crystals for XFEL and Micro-ED to large crystals for neutron diffraction, are covered with special emphasis in methodologies applicable at laboratory scale. Copyright © 2015 Elsevier Inc. All rights reserved.

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

Introduction to protein crystallization.

PubMed

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.

Retardation of ice crystallization by short peptides

NASA Astrophysics Data System (ADS)

Kim, Jun Soo; Yethiraj, Arun

2009-03-01

The effect of short peptides on the growth of ice crystals is studied using molecular dynamics simulations. The simulations focus on two sequences (Gly-Pro-Ala-Gly and Gly-Gly-Ala-Gly) that are found in collagen hydrolysate, a substance that is known to retard crystal growth. In the absence of peptides, the growth of ice crystal in the solution with the ice/water interface is observed in at a rate comparable to the experimental data. When peptides are present in the liquid phase, the crystal growth is retarded to a significant extent compared to the pure water. It is found that Gly-Pro-Ala-Gly is more effective (crystallization is up to 5 times slower than in its absence) than Gly-Gly-Ala-Gly (up to 3 times slower) implying that the role of the proline residue is important. The mechanism can be understood in the nature of binding of the peptides to the growing crystal.

Growth and surface topography of WSe{sub 2} single crystal

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dixit, Vijay, E-mail: vijdix1@gmail.com; Vyas, Chirag; Pataniya, Pratik

2016-05-06

Tungsten Di-Selenide belongs to the family of TMDCs showing their potential applications in the fields of Optoelectronics and PEC solar cells. Here in the present investigation single crystals of WSe{sub 2} were grown by Direct Vapour Transport Technique in a dual zone furnace having temperature difference of 50 K between the two zones. These single crystals were characterized by EDAX which confirms the stiochiometry of the grown crystals. Surface topography of the crystal was studied by optical micrograph showing the left handed spirals on the surface of WSe{sub 2} crystals. Single crystalline nature of the crystals was confirmed by SAED.

Noble metal free photocatalytic H 2 generation on black TiO 2: On the influence of crystal facets vs. crystal damage

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Ning; Steinrück, Hans-Georg; Osvet, Andres

In this study, we investigate noble metal free photocatalytic water splitting on natural anatase single crystal facets and on wafer slices of the [001] plane before and after these surfaces have been modified by high pressure hydrogenation and hydrogen ion-implantation. Here, we find that on the natural, intact low index planes, photocatalytic H 2 evolution (in the absence of a noble metal co-catalyst) can only be achieved when the hydrogenation treatment is accompanied by the introduction of crystal damage, such as simple scratching and miscut in the crystal, or by implantation damage. X-ray reflectivity, Raman, and optical reflection measurements showmore » that plain hydrogenation leads to a ≈ 1 nm thick black titania surface layer without activity, while a colorless, density modified, and ≈7 nm thick layer with broken crystal symmetry is present on the ion implanted surface. These results demonstrate that (i) the H-treatment of an intact anatase surface needs to be combined with defect formation for catalytic activation and (ii) activation does not necessarily coincide with the presence of black color.« less

Noble metal free photocatalytic H 2 generation on black TiO 2: On the influence of crystal facets vs. crystal damage

DOE PAGES

Liu, Ning; Steinrück, Hans-Georg; Osvet, Andres; ...

2017-02-13

In this study, we investigate noble metal free photocatalytic water splitting on natural anatase single crystal facets and on wafer slices of the [001] plane before and after these surfaces have been modified by high pressure hydrogenation and hydrogen ion-implantation. Here, we find that on the natural, intact low index planes, photocatalytic H 2 evolution (in the absence of a noble metal co-catalyst) can only be achieved when the hydrogenation treatment is accompanied by the introduction of crystal damage, such as simple scratching and miscut in the crystal, or by implantation damage. X-ray reflectivity, Raman, and optical reflection measurements showmore » that plain hydrogenation leads to a ≈ 1 nm thick black titania surface layer without activity, while a colorless, density modified, and ≈7 nm thick layer with broken crystal symmetry is present on the ion implanted surface. These results demonstrate that (i) the H-treatment of an intact anatase surface needs to be combined with defect formation for catalytic activation and (ii) activation does not necessarily coincide with the presence of black color.« less

Fundamental Studies of Crystal Growth of Microporous Materials

NASA Technical Reports Server (NTRS)

Singh, Ramsharan; Doolittle, John, Jr.; Payra, Pramatha; Dutta, Prabir K.; George, Michael A.; Ramachandran, Narayanan; Schoeman, Brian J.

2003-01-01

Microporous materials are framework structures with well-defined porosity, often of molecular dimensions. Zeolites contain aluminum and silicon atoms in their framework and are the most extensively studied amongst all microporous materials. Framework structures with P, Ga, Fe, Co, Zn, B, Ti and a host of other elements have also been made. Typical synthesis of microporous materials involve mixing the framework elements (or compounds, thereof) in a basic solution, followed by aging in some cases and then heating at elevated temperatures. This process is termed hydrothermal synthesis, and involves complex chemical and physical changes. Because of a limited understanding of this process, most synthesis advancements happen by a trial and error approach. There is considerable interest in understanding the synthesis process at a molecular level with the expectation that eventually new framework structures will be built by design. The basic issues in the microporous materials crystallization process include: (a) Nature of the molecular units responsible for the crystal nuclei formation; (b) Nature of the nuclei and nucleation process; (c) Growth process of the nuclei into crystal; (d) Morphological control and size of the resulting crystal; (e) Surface structure of the resulting crystals; and (f) Transformation of frameworks into other frameworks or condensed structures.

The rheology of crystal-rich magmas (Kuno Award Lecture)

NASA Astrophysics Data System (ADS)

Huber, Christian; Aldin Faroughi, Salah; Degruyter, Wim

2016-04-01

The rheology of magmas controls not only eruption dynamics but also the rate of transport of magmas through the crust and to a large extent the rate of magma differentiation and degassing. Magma bodies stalled in the upper crust are known to spend most of their lifespan above the solidus at a high crystal content (Cooper and Kent, 2014; Huber et al., 2009), where the probability of melt extraction (crystal fractionation) is the greatest (Dufek and Bachmann, 2010). In this study, we explore a new theoretical framework to study the viscosity of crystal bearing magmas. Since the seminal work of A. Einstein and W. Sutherland in the early 20th century, it has been shown theoretically and tested experimentally that a simple self-similar behavior exist between the relative viscosity of dilute (low crystal content) suspensions and the particle volume fraction. The self-similar nature of that relationship is quickly lost as we consider crystal fractions beyond a few volume percent. We propose that the relative viscosity of crystal-bearing magmas can be fully described by two state variables, the intrinsic viscosity and the crowding factor (a measure of the packing threshold in the suspension). These two state variables can be measured experimentally under different conditions, which allows us to develop closure relationships in terms of the applied shear stress and the crystal shape and size distributions. We build these closure equations from the extensive literature on the rheology of synthetic suspensions, where the nature of the particle shape and size distributions is better constrained and apply the newly developed model to published experiments on crystal-bearing magmas. We find that we recover a self-similar behavior (unique rheology curve) up to the packing threshold and show that the commonly reported break in slope between the relative viscosity and crystal volume fraction around the expected packing threshold is most likely caused by a sudden change in the state

Capillarity creates single-crystal calcite nanowires from amorphous calcium carbonate.

PubMed

Kim, Yi-Yeoun; Hetherington, Nicola B J; Noel, Elizabeth H; Kröger, Roland; Charnock, John M; Christenson, Hugo K; Meldrum, Fiona C

2011-12-23

Single-crystal calcite nanowires are formed by crystallization of morphologically equivalent amorphous calcium carbonate (ACC) particles within the pores of track etch membranes. The polyaspartic acid stabilized ACC is drawn into the membrane pores by capillary action, and the single-crystal nature of the nanowires is attributed to the limited contact of the intramembrane ACC particle with the bulk solution. The reaction environment then supports transformation to a single-crystal product. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

C-terminal Amidation of an Osteocalcin-derived Peptide Promotes Hydroxyapatite Crystallization*

PubMed Central

Hosseini, Samaneh; Naderi-Manesh, Hossein; Mountassif, Driss; Cerruti, Marta; Vali, Hojatollah; Faghihi, Shahab

2013-01-01

Genesis of natural biocomposite-based materials, such as bone, cartilage, and teeth, involves interactions between organic and inorganic systems. Natural biopolymers, such as peptide motif sequences, can be used as a template to direct the nucleation and crystallization of hydroxyapatite (HA). In this study, a natural motif sequence consisting of 13 amino acids present in the first helix of osteocalcin was selected based on its calcium binding ability and used as substrate for nucleation of HA crystals. The acidic (acidic osteocalcin-derived peptide (OSC)) and amidic (amidic osteocalcin-derived peptide (OSN)) forms of this sequence were synthesized to investigate the effects of different C termini on the process of biomineralization. Electron microscopy analyses show the formation of plate-like HA crystals with random size and shape in the presence of OSN. In contrast, spherical amorphous calcium phosphate is formed in the presence of OSC. Circular dichroism experiments indicate conformational changes of amidic peptide to an open and regular structure as a consequence of interaction with calcium and phosphate. There is no conformational change detectable in OSC. It is concluded that HA crystal formation, which only occurred in OSN, is attributable to C-terminal amidation of a natural peptide derived from osteocalcin. It is also proposed that natural peptides with the ability to promote biomineralization have the potential to be utilized in hard tissue regeneration. PMID:23362258

Cloud-to-Ground Lightning Characteristics of a Major Tropical Cyclone Tornado Outbreak

NASA Technical Reports Server (NTRS)

McCaul, Eugene W., Jr.; Buechler, Dennis; Goodman, Steven J.

1999-01-01

It is well known that most tropical cyclones (TCs) that make landfall along the Gulf coast of the United States spawn at least a few tornadoes. Although most landfalling TCs generate fewer than a dozen such tornadoes, a small proportion produce large swarm outbreaks, with as many as 25 or more tornadoes. Usually, these major outbreaks occur in large, intense hurricane-strength TCs, but on 15-17 August 1994 Tropical Storm Beryl spun off 37 tornadoes along its path from the Florida panhandle through the mid-Atlantic states. Some 32 of these tornadoes occurred on 16 August 1994 from eastern Georgia to southern Virginia, with most of these taking place in South Carolina. Beryl's 37 tornadoes moved it into what was at that time fifth place historically in terms of TC tornado productivity. The Beryl outbreak is especially noteworthy in that at least three of the tornadoes achieved peak intensity of F3 on the Fujita damage intensity scale. Although no fatalities resulted from the Beryl outbreak, at least 50 persons suffered injuries, and property damages totalled more than $50 million . The Beryl outbreak is a good example of a TC whose greatest danger to the public is its post-landfall severe weather. In this respect, and in the character of its swarm outbreak of tornadoes, it resembles another large tornado outbreak spawned by a relatively weak TC, Hurricane Danny of 1985). In the Danny outbreak, numerous shallow mini-supercell storms were found to have occurred, and it was noted that, because of the storms' relatively shallow depth, cloud-to-ground (CG) lightning was negligible. Better observations of future TC tornado outbreaks, especially with modern surveillance tools such as Doppler radars and the National Lightning Detection Network (NLDN), were recommended. Although the Beryl tornado outbreak is not the first set of TC-spawned tornado storms to be observed with the NLDN, it is one of the largest and likely the most intense such outbreak. The purpose of this paper

A thermodynamic framework for the study of crystallization in polymers

NASA Astrophysics Data System (ADS)

Rao, I. J.; Rajagopal, K. R.

In this paper, we present a new thermodynamic framework within the context of continuum mechanics, to predict the behavior of crystallizing polymers. The constitutive models that are developed within this thermodynamic setting are able to describe the main features of the crystallization process. The model is capable of capturing the transition from a fluid like behavior to a solid like behavior in a rational manner without appealing to any adhoc transition criterion. The anisotropy of the crystalline phase is built into the model and the specific anisotropy of the crystalline phase depends on the deformation in the melt. These features are incorporated into a recent framework that associates different natural configurations and material symmetries with distinct microstructural features within the body that arise during the process under consideration. Specific models are generated by choosing particular forms for the internal energy, entropy and the rate of dissipation. Equations governing the evolution of the natural configurations and the rate of crystallization are obtained by maximizing the rate of dissipation, subject to appropriate constraints. The initiation criterion, marking the onset of crystallization, arises naturally in this setting in terms of the thermodynamic functions. The model generated within such a framework is used to simulate bi-axial extension of a polymer film that is undergoing crystallization. The predictions of the theory that has been proposed are consistent with the experimental results (see [28] and [7]).

VO{sub 2} (A): Reinvestigation of crystal structure, phase transition and crystal growth mechanisms

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rao Popuri, Srinivasa; University of Bordeaux, ICMCB, UPR 9048, F-33608 Pessac; National Institute for Research and Development in Electrochemistry and Condensed Matter, Timisoara, Plautius Andronescu Str. No. 1, 300224 Timisoara

2014-05-01

Well crystallized VO{sub 2} (A) microrods were grown via a single step hydrothermal reaction in the presence of V{sub 2}O{sub 5} and oxalic acid. With the advantage of high crystalline samples, we propose P4/ncc as an appropriate space group at room temperature. From morphological studies, we found that the oriented attachment and layer by layer growth mechanisms are responsible for the formation of VO{sub 2} (A) micro rods. The structural and electronic transitions in VO{sub 2} (A) are strongly first order in nature, and a marked difference between the structural transition temperatures and electronic transitions temperature was evidenced. The reversiblemore » intra- (LTP-A to HTP-A) and irreversible inter- (HTP-A to VO{sub 2} (M1)) structural phase transformations were studied by in-situ powder X-ray diffraction. Attempts to increase the size of the VO{sub 2} (A) microrods are presented and the possible formation steps for the flower-like morphologies of VO{sub 2} (M1) are described. - Graphical abstract: Using a single step and template free hydrothermal synthesis, well crystallized VO{sub 2} (A) microrods were prepared and the P4/ncc space group was assigned to the room temperature crystal structure. Reversible and irreversible phase transitions among different VO{sub 2} polymorphs were identified and their progressive nature was highlighted. Attempts to increase the microrods size, involving layer by layer formation mechanisms, are presented. - Highlights: • Highly crystallized VO{sub 2} (A) microrods were grown via a single step hydrothermal process. • The P4/ncc space group was determined for VO{sub 2} (A) at room temperature. • The electronic structure and progressive nature of the structural phase transition were investigated. • A weak coupling between structural and electronic phase transitions was identified. • Different crystallite morphologies were discussed in relation with growth mechanisms.« less

Effect of L-Valine on the growth and characterization of Sodium Acid Phthalate (SAP) single crystals.

PubMed

Nirmala, L Ruby; Thomas Joseph Prakash, J

2013-06-01

Undoped and amino acid doped good quality single crystals of Sodium Acid Phthalate crystals (SAP) were grown by slow evaporation solution growth technique which are semiorganic in nature. The effect of amino acid (L-Valine) dopant on the growth and the properties of SAP single crystal was investigated. The single crystal X-ray diffraction studies and FT-IR studies were carried out to identify the crystal structure and the presence of functional groups in undoped and L-Valine doped SAP crystals. The transparent nature of the grown crystal was observed using UV-Visible spectrum. The thermal decomposition of the doped SAP crystals was investigated by thermo gravimetric analysis (TGA) and differential thermal analysis (DTA). The enhancement in the NLO property of the undoped and L-Valine doped SAP crystals using KDP crystal as a reference was studied using SHG measurements. Vickers micro hardness measurements are used for the study of mechanical strength of the grown crystals. Copyright © 2013 Elsevier B.V. All rights reserved.

An assessment of calcite crystal growth mechanisms based on crystal size distributions

USGS Publications Warehouse

Kile, D.E.; Eberl, D.D.; Hoch, A.R.; Reddy, M.M.

2000-01-01

was established and maintained during the constant-composition experiments. CSDs having shapes intermediate between lognormal and Ostwald also were generated by varying the initial levels of supersaturation (initial Ω = 28.2 to 69.2) in rapidly mixed solutions. Lognormal CSDs were observed for natural calcite crystals that are found in septarian concretions occurring in southeastern Colorado. Based on the model described above, these CSDs indicate initial growth by surface control, followed by supply-controlled growth. Thus, CSDs may be used to deduce crystal growth mechanisms from which geologic conditions early in the growth history of a mineral can be inferred. Conversely, CSD shape can be predicted during industrial crystallization by applying the appropriate conditions for a particular growth mechanism.

Synthesis and Physical Properties of Liquid Crystals: An Interdisciplinary Experiment

ERIC Educational Resources Information Center

Van Hecke, Gerald R.; Karukstis, Kerry K.; Hanhan Li; Hendargo, Hansford C.; Cosand, Andrew J.; Fox, Marja M.

2005-01-01

A study involves multiple chemistry and physics concepts applied to a state of matter that has biological relevance. An experiment involving the synthesis and physical properties of liquid crystals illustrates the interdisciplinary nature of liquid crystal research and the practical devices derived from such research.

Strategies for the crystallization of viruses: using phase diagrams and gels to produce 3D crystals of Grapevine fanleaf virus.

PubMed

Schellenberger, Pascale; Demangeat, Gérard; Lemaire, Olivier; Ritzenthaler, Christophe; Bergdoll, Marc; Oliéric, Vincent; Sauter, Claude; Lorber, Bernard

2011-05-01

The small icosahedral plant RNA nepovirus Grapevine fanleaf virus (GFLV) is specifically transmitted by a nematode and causes major damage to vineyards worldwide. To elucidate the molecular mechanisms underlying the recognition between the surface of its protein capsid and cellular components of its vector, host and viral proteins synthesized upon infection, the wild type GFLV strain F13 and a natural mutant (GFLV-TD) carrying a Gly₂₉₇Asp mutation were purified, characterized and crystallized. Subsequently, the geometry and volume of their crystals was optimized by establishing phase diagrams. GFLV-TD was twice as soluble as the parent virus in the crystallization solution and its crystals diffracted X-rays to a resolution of 2.7 Å. The diffraction limit of GFLV-F13 crystals was extended from 5.5 to 3 Å by growth in agarose gel. Preliminary crystallographic analyses indicate that both types of crystals are suitable for structure determination. Keys for the successful production of GFLV crystals include the rigorous quality control of virus preparations, crystal quality improvement using phase diagrams, and crystal lattice reinforcement by growth in agarose gel. These strategies are applicable to the production of well-diffracting crystals of other viruses and macromolecular assemblies. Copyright © 2011 Elsevier Inc. All rights reserved.

Helium Diffusion in Natural Xenotime

NASA Astrophysics Data System (ADS)

Anderson, A. J.; Hodges, K. V.; Van Soest, M. C.; Hanchar, J. M.

2017-12-01

Xenotime (nominally YPO4) occurs as an accessory mineral in felsic igneous rocks, pegmatites, and gneisses, often incorporating weight percent levels of U, Th, and REEs. Although commonly used for precise U-Pb geochronology, xenotime is seldom used for (U-Th)/He thermochronometry despite the fact that its high radionuclide content allows for the rapid accumulation of radiogenic He that could potentially allow for the precise dating of very young cooling events in active geologic settings. Xenotime's likely high concentrations of radiogenic 4He also make it a promising candidate for laser microprobe (U-Th)/He dating. Unfortunately, limited data are currently available for He diffusion in xenotime, and previous experimental studies of natural and synthetic xenotime have led to discrepant results (1). Published estimates of the (U-Th)/He closure temperature for xenotime based on these experiments range from 60˚C to 300˚C. In this contribution, we report new results for incremental step heating `bulk' 4He diffusion experiments on a fragment of a natural xenotime crystal from the Torghar district of the Khyber Agency in the Federally Administered Tribal Areas of Pakistan. Laser ablation 238U/206Pb dating of this crystal yields a crystallization age of 28.82 ± 0.13 Ma. The results of our He diffusion experiments- which display excellent linearity on an Arrhenius plot assuming a spherical geometry - indicate kinetic parameters of E 133 kJ/mol and ln(D0/a2) 10.9 s-1. Our results imply a preliminary (U-Th)/He closure temperature of 80˚C for xenotime crystals with a diffusion dimension of 220 μm. This closure temperature is much lower than that previously estimated for natural xenotime (1), and it is possible, perhaps likely, that He diffusion in natural xenotime crystals display a strong compositional dependency (1). Nevertheless, our experimental data suggest that near-end member (YPO4) xenotime has an intrinsic helium diffusivity consistent with a closure temperature

Large Three-Dimensional Photonic Crystals Based on Monocrystalline Liquid Crystal Blue Phases (Postprint)

DTIC Science & Technology

2017-09-28

5192 (2011). 39. Shi, Y., Mo, J., Wei, J. & Guo, J. Chiral assembly and plasmonic response of silver nanoparticles in a three-dimensional blue-phase... synthesis of a silicon photonic crystal with a complete three-dimensional bandgap near 1.5 µm. Nature 405, 437–440 (2000). 3. Arsenault, A. et al

Identification of Gravity-Related Effects on Crystal Growth From Melts With an Immiscibility Gap

NASA Technical Reports Server (NTRS)

Kassemi, M.; Sayir, A.; Farmer, S.

1999-01-01

This work involves an experimental-numerical approach to study the effects of natural and Marangoni convections on solidification of single crystals from a silicate melt with a liquid-liquid immiscibility gap. Industrial use of crystals grown from silicate melts is becoming increasingly important in electronic, optical, and high temperature structural applications. Even the simplest silicate systems like Al203-SiO2 have had, and will continue to have, a significant role in the development of traditional and advanced ceramics. A unique feature of crystals grown from the silicate systems is their outstanding linear electro-optic properties. They also exhibit exceptionally high optical rotativity. As a result, these crystals are attractive materials for dielectric, optical, and microwave applications. Experimental work in our laboratory has indicated that directional solidification of a single crystal mullite appears to be preceded by liquid-liquid phase separation in the melt. Disruption of the immiscible state results in crystallization of a two phase structure. There is also evidence that mixing in the melt caused by density-driven convection can significantly affect the stability of the immiscible liquid layers and result in poly-crystalline growth. On earth, the immiscible state has only been observed for small diameter crystals grown in float zone systems where natural convection is almost negligible. Therefore, it is anticipated that growth of large single crystals from silicate melts would benefit from microgravity conditions because of the reduction of the natural convective mixing. The main objective of this research is to determine the effects of transport processes on the phase separation in the melt during growth of a single crystal while addressing the following issues: (1) When do the immiscible layers form and are they real?; (2) What are the main physical characteristics of the immiscible liquids?; and (3) How mixing by natural or Marangoni convection

Lunar Magma Ocean Crystallization: Constraints from Fractional Crystallization Experiments

NASA Technical Reports Server (NTRS)

Rapp, J. F.; Draper, D. S.

2015-01-01

The currently accepted paradigm of lunar formation is that of accretion from the ejecta of a giant impact, followed by crystallization of a global scale magma ocean. This model accounts for the formation of the anorthosite highlands crust, which is globally distributed and old, and the formation of the younger mare basalts which are derived from a source region that has experienced plagioclase extraction. Several attempts at modelling the crystallization of such a lunar magma ocean (LMO) have been made, but our ever-increasing knowledge of the lunar samples and surface have raised as many questions as these models have answered. Geodynamic models of lunar accretion suggest that shortly following accretion the bulk of the lunar mass was hot, likely at least above the solidus]. Models of LMO crystallization that assume a deep magma ocean are therefore geodynamically favorable, but they have been difficult to reconcile with a thick plagioclase-rich crust. A refractory element enriched bulk composition, a shallow magma ocean, or a combination of the two have been suggested as a way to produce enough plagioclase to account for the assumed thickness of the crust. Recently however, geophysical data from the GRAIL mission have indicated that the lunar anorthositic crust is not as thick as was initially estimated, which allows for both a deeper magma ocean and a bulk composition more similar to the terrestrial upper mantle. We report on experimental simulations of the fractional crystallization of a deep (approximately 100km) LMO with a terrestrial upper mantle-like (LPUM) bulk composition. Our experimental results will help to define the composition of the lunar crust and mantle cumulates, and allow us to consider important questions such as source regions of the mare basalts and Mg-suite, the role of mantle overturn after magma ocean crystallization and the nature of KREEP

Selective Metal Cation Capture by Soft Anionic Metal-Organic Frameworks via Drastic Single-Crystal-to-Single-Crystal Transformations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tian, Jian; Saraf, Laxmikant V.; Schwenzer, Birgit

2012-05-25

Flexible anionic metal-organic frameworks transform to neutral heterobimetallic systems via single-crystal-to-single-crystal processes invoked by cation insertion. These transformations are directed by cooperative bond breakage and formation, resulting in expansion or contraction of the 3D framework by up to 33% due to the flexible nature of the organic linker. These MOFs displays highly selective uptake of divalent transition metal cations (Co2+ and Ni2+ for example) over alkali metal cations (Li+ and Na+).

Probabilistic approach to lysozyme crystal nucleation kinetics.

PubMed

Dimitrov, Ivaylo L; Hodzhaoglu, Feyzim V; Koleva, Dobryana P

2015-09-01

Nucleation of lysozyme crystals in quiescent solutions at a regime of progressive nucleation is investigated under an optical microscope at conditions of constant supersaturation. A method based on the stochastic nature of crystal nucleation and using discrete time sampling of small solution volumes for the presence or absence of detectable crystals is developed. It allows probabilities for crystal detection to be experimentally estimated. One hundred single samplings were used for each probability determination for 18 time intervals and six lysozyme concentrations. Fitting of a particular probability function to experimentally obtained data made possible the direct evaluation of stationary rates for lysozyme crystal nucleation, the time for growth of supernuclei to a detectable size and probability distribution of nucleation times. Obtained stationary nucleation rates were then used for the calculation of other nucleation parameters, such as the kinetic nucleation factor, nucleus size, work for nucleus formation and effective specific surface energy of the nucleus. The experimental method itself is simple and adaptable and can be used for crystal nucleation studies of arbitrary soluble substances with known solubility at particular solution conditions.

Multicoaxial cylindrical inclusions in locally resonant phononic crystals

NASA Astrophysics Data System (ADS)

Larabi, H.; Pennec, Y.; Djafari-Rouhani, B.; Vasseur, J. O.

2007-06-01

It is known that the transmission spectrum of the so-called locally resonant phononic crystal can exhibit absolute sharp dips in the sonic frequency range due to the resonance scattering of elastic waves. In this paper, we study theoretically, using a finite difference time domain method, the propagation of acoustic waves through a two-dimensional locally resonant crystal in which the matrix is a fluid (such as water) instead of being a solid as in most of the previous papers. The transmission is shown to be dependent upon the fluid or solid nature of the matrix as well as upon the nature of the coating material in contact with the matrix. The other main purpose of this paper is to consider inclusions constituted by coaxial cylindrical multilayers consisting of several alternate shells of a soft material (such as a soft rubber) and a hard material (such as steel). With respect to the usual case of a hard core coated with a soft rubber, the transmission spectrum can exhibit in the same frequency range several peaks instead of one. If two or more phononic crystals are associated together, we find that the structure displays all the zeros of transmission resulting from each individual crystal. Moreover, we show that it is possible to overlap the dips by an appropriate combination of phononic crystals and create a larger acoustic stop band.

Deducing growth mechanisms for minerals from the shapes of crystal size distributions

USGS Publications Warehouse

Eberl, D.D.; Drits, V.A.; Srodon, J.

1998-01-01

Crystal size distributions (CSDs) of natural and synthetic samples are observed to have several distinct and different shapes. We have simulated these CSDs using three simple equations: the Law of Proportionate Effect (LPE), a mass balance equation, and equations for Ostwald ripening. The following crystal growth mechanisms are simulated using these equations and their modifications: (1) continuous nucleation and growth in an open system, during which crystals nucleate at either a constant, decaying, or accelerating nucleation rate, and then grow according to the LPE; (2) surface-controlled growth in an open system, during which crystals grow with an essentially unlimited supply of nutrients according to the LPE; (3) supply-controlled growth in an open system, during which crystals grow with a specified, limited supply of nutrients according to the LPE; (4) supply- or surface-controlled Ostwald ripening in a closed system, during which the relative rate of crystal dissolution and growth is controlled by differences in specific surface area and by diffusion rate; and (5) supply-controlled random ripening in a closed system, during which the rate of crystal dissolution and growth is random with respect to specific surface area. Each of these mechanisms affects the shapes of CSDs. For example, mechanism (1) above with a constant nucleation rate yields asymptotically-shaped CSDs for which the variance of the natural logarithms of the crystal sizes (??2) increases exponentially with the mean of the natural logarithms of the sizes (??). Mechanism (2) yields lognormally-shaped CSDs, for which ??2 increases linearly with ??, whereas mechanisms (3) and (5) do not change the shapes of CSDs, with ??2 remaining constant with increasing ??. During supply-controlled Ostwald ripening (4), initial lognormally-shaped CSDs become more symmetric, with ??2 decreasing with increasing ??. Thus, crystal growth mechanisms often can be deduced by noting trends in ?? versus ??2 of CSDs for

Thermal-gradient migration of brine inclusions in salt crystals. [Synthetic single crystals of NaCl and KCl

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yagnik, S.K.

1982-09-01

It has been proposed that high-level nuclear waste be disposed in a geologic repository. Natural-salt deposits, which are being considered for this purpose, contain a small volume fraction of water in the form of brine inclusions distributed throughout the salt. Radioactive-decay heating of the nuclear wastes will impose a temperature gradient on the surrounding salt which mobilizes the brine inclusions. Inclusions filled completely with brine migrate up the temperature gradient and eventually accumulate brine near the buried waste forms. The brine may slowly corrode or degrade the waste forms which is undesirable. In this work, thermal gradient migration of bothmore » all-liquid and gas-liquid inclusions was experimentally studied in synthetic single crystals of NaCl and KCl using a hot-stage attachment to an optical microscope which was capable of imposing temperature gradients and axial compressive loads on the crystals. The migration velocities of the inclusions were found to be dependent on temperature, temperature gradient, and inclusion shape and size. The velocities were also dictated by the interfacial mass transfer resistance at brine/solid interface. This interfacial resistance depends on the dislocation density in the crystal, which in turn, depends on the axial compressive loading of the crystal. At low axial loads, the dependence between the velocity and temperature gradient is non-linear.At high axial loads, however, the interfacial resistance is reduced and the migration velocity depends linearly on the temperature gradient. All-liquid inclusions filled with mixed brines were also studied. For gas-liquid inclusions, three different gas phases (helium, air and argon) were compared. Migration studies were also conducted on single crystallites of natural salt as well as in polycrystalline natural salt samples. The behavior of the inclusions at large angle grain boundaries was observed. 35 figures, 3 tables.« less

Roles of bond orientational ordering in glass transition and crystallization.

PubMed

Tanaka, Hajime

2011-07-20

It is widely believed that crystallization in three dimensions is primarily controlled by positional ordering, and not by bond orientational ordering. In other words, bond orientational ordering is usually considered to be merely a consequence of positional ordering and thus has often been ignored. This one-order-parameter (density) description may be reasonable when we consider an equilibrium liquid-solid transition, but may not be enough to describe a metastable state and the kinetics of the transition. Here we propose that bond orientational ordering can play a key role in (i) crystallization, (ii) the ordering to quasi-crystal and (iii) vitrification, which occurs under rather weak frustration against crystallization. In a metastable supercooled state before crystallization, a system generally tends to have bond orientational order at least locally as a result of a constraint of dense packing. For a system interacting with hard-core repulsions, the constraint is intrinsically of geometrical origin and thus the basic physics is the same as nematic ordering of rod-like particles upon densification. Furthermore, positional ordering is easily destroyed even by weak frustration such as polydispersity and anisotropic interactions which favour a symmetry not consistent with that of the equilibrium crystal. Thus we may say that vitrification can be achieved by disturbing and prohibiting long-range positional ordering. Even in such a situation, bond orientational ordering still survives, accompanying its critical-like fluctuations, which are the origin of dynamic heterogeneity for this case. This scenario naturally explains both the absence of positional order and the development of bond orientational order upon cooling in a supercooled state. Although our argument is speculative in nature, we emphasize that this physical picture can coherently explain crystallization, vitrification, quasi-crystallization and their relationship in a natural manner. For a strongly

Crystallization mechanisms of acicular crystals

NASA Astrophysics Data System (ADS)

Puel, François; Verdurand, Elodie; Taulelle, Pascal; Bebon, Christine; Colson, Didier; Klein, Jean-Paul; Veesler, Stéphane

2008-01-01

In this contribution, we present an experimental investigation of the growth of four different organic molecules produced at industrial scale with a view to understand the crystallization mechanism of acicular or needle-like crystals. For all organic crystals studied in this article, layer-by-layer growth of the lateral faces is very slow and clear, as soon as the supersaturation is high enough, there is competition between growth and surface-activated secondary nucleation. This gives rise to pseudo-twinned crystals composed of several needle individuals aligned along a crystallographic axis; this is explained by regular over- and inter-growths as in the case of twinning. And when supersaturation is even higher, nucleation is fast and random. In an industrial continuous crystallization, the rapid growth of needle-like crystals is to be avoided as it leads to fragile crystals or needles, which can be partly broken or totally detached from the parent crystals especially along structural anisotropic axis corresponding to weaker chemical bonds, thus leading to slower growing faces. When an activated mechanism is involved such as a secondary surface nucleation, it is no longer possible to obtain a steady state. Therefore, the crystal number, size and habit vary significantly with time, leading to troubles in the downstream processing operations and to modifications of the final solid-specific properties. These results provide valuable information on the unique crystallization mechanisms of acicular crystals, and show that it is important to know these threshold and critical values when running a crystallizer in order to obtain easy-to-handle crystals.

Nucleation and growth of the Naica giant gypsum crystals.

PubMed

Otálora, Fermín; García-Ruiz, JuanMa

2014-04-07

The Cave of Giant Crystals in the Naica mine (Mexico) is one of the most amazing displays of mineral beauty ever created in nature. In addition to the colossal crystals of gypsum, which in some cases exceed eleven meters in length and one meter in thickness, the scenery fashioned by the crystalline beams that thrust through the darkness of the cave from floor to ceiling with a luster like moonlight is a unique example of harmony based on crystal symmetry. We review the crystallogenesis of this remarkable and challenging phenomenon of mineralization near equilibrium that can be used to teach the basics of nucleation and crystal growth.

Weak crystallization theory of metallic alloys

DOE PAGES

Martin, Ivar; Gopalakrishnan, Sarang; Demler, Eugene A.

2016-06-20

Crystallization is one of the most familiar, but hardest to analyze, phase transitions. The principal reason is that crystallization typically occurs via a strongly first-order phase transition, and thus rigorous treatment would require comparing energies of an infinite number of possible crystalline states with the energy of liquid. A great simplification occurs when crystallization transition happens to be weakly first order. In this case, weak crystallization theory, based on unbiased Ginzburg-Landau expansion, can be applied. Even beyond its strict range of validity, it has been a useful qualitative tool for understanding crystallization. In its standard form, however, weak crystallization theorymore » cannot explain the existence of a majority of observed crystalline and quasicrystalline states. Here we extend the weak crystallization theory to the case of metallic alloys. In this paper, we identify a singular effect of itinerant electrons on the form of weak crystallization free energy. It is geometric in nature, generating strong dependence of free energy on the angles between ordering wave vectors of ionic density. That leads to stabilization of fcc, rhombohedral, and icosahedral quasicrystalline (iQC) phases, which are absent in the generic theory with only local interactions. Finally, as an application, we find the condition for stability of iQC that is consistent with the Hume-Rothery rules known empirically for the majority of stable iQC; namely, the length of the primary Bragg-peak wave vector is approximately equal to the diameter of the Fermi sphere.« less

Magneto-photonic crystal optical sensors with sensitive covers

NASA Astrophysics Data System (ADS)

Dissanayake, Neluka; Levy, Miguel; Chakravarty, A.; Heiden, P. A.; Chen, N.; Fratello, V. J.

2011-08-01

We report on a magneto-photonic crystal on-chip optical sensor for specific analyte detection with polypyrrole and gold nano particles as modified photonic crystal waveguide cover layers. The reaction of the active sensor material with various analytes modifies the electronic structure of the sensor layer causing changes in its refractive index and a strong transduction signal. Magneto-photonic crystal enhanced polarization rotation sensitive to the nature of the cover layer detects the index modification upon analyte adsorption. A high degree of selectivity and sensitivity are observed for aqueous ammonia and methanol with polypyrrole and for thiolated-gold- with gold-nanoparticles covers.

Linking Crystal Populations to Dynamic States: Crystal Dissolution and Growth During an Open-System Event

NASA Astrophysics Data System (ADS)

Bergantz, G. W.; Schleicher, J.; Burgisser, A.

2016-12-01

a second length scale to the mixing. It simultaneously forms a small mixing bowl in the pile of crystals sedimenting at the base. This can produce very complex populations even in a simple open-system event. Bergantz et al., 2015, Open-system dynamics and mixing in magma mushes, Nature Geosci., DOI: 10.1038/NGEO2534

A comparative study on the crystal structure of bicycle analogues to the natural phytotoxin helminthosporins

NASA Astrophysics Data System (ADS)

Barbosa, Luiz Cláudio de Almeida; Teixeira, Robson Ricardo; Nogueira, Leonardo Brandão; Maltha, Celia Regina Alvares; Doriguetto, Antônio Carlos; Martins, Felipe Terra

2016-02-01

Herein we described structural insights of a series of analogues to helminthosporin phytotoxins. The key reaction used to prepare the compounds corresponded to the [3 + 4] cycloaddition between the oxyallyl cation generated from 2,4-dibromopentan-3-one and different furans. Their structures were confirmed upon IR, NMR and X-ray diffraction analyses. While bicycles 7, 8 and 9 crystallize in the centrosymmetric monoclinic space group P21/c, compound 10 was solved in the noncentrosymmetric orthorhombic space group P212121. The solid materials obtained were shown to be racemic crystals (7, 8, 9) or racemic conglomerate (10). In all compounds, there is formation of a bicycle featured by fused tetrahydropyranone and 2,5-dihydrofuran rings. They adopt chair and envelope conformations, respectively. Crystal packing of all compounds is stabilized through C-H•••O contacts. Conformational aspects as well as similarities and differences among the crystal structures of the synthesized analogues are discussed.

Crystal growth and characterization of third order nonlinear optical piperazinium bis(4-hydroxybenzenesulphonate) (P4HBS) single crystal

NASA Astrophysics Data System (ADS)

Pichan, Karuppasamy; Muthu, Senthil Pandian; Perumalsamy, Ramasamy

2017-09-01

The organic single crystal of piperazinium bis(4-hydroxybenzenesulphonate) (P4HBS) was grown by slow evaporation solution technique (SEST) at room temperature. The lattice parameters of the grown crystal were confirmed by single crystal X-ray diffraction analysis. Functional groups of P4HBS crystal were confirmed by FTIR spectrum analysis. The optical quality of the grown crystal was identified by the UV-Vis NIR spectrum analysis. The grown crystal has good optical transmittance in the range of 410-1100 nm. In photoluminescence spectrum, sharp emission peaks are observed, which indicates the ultraviolet (UV) emission. The photoconductivity study reveals that the grown crystal has negative photoconductive nature. The thermal behaviour of the P4HBS crystal was investigated by thermogravimetric and differential thermal analysis (TG-DTA). The mechanical stability of grown crystal was analyzed and the indentation size effect (ISE) was explained by Hays-Kendall's (HK) approach and proportional specimen resistance model (PSRM). Chemical etching study was carried out and the etch pit density (EPD) was calculated. The dielectric constant (ε‧) and dielectric loss (tan δ) as a function of frequency were measured for the grown crystal. The solid state parameters such as valence electron, plasma energy, Penn gap and Fermi energy were evaluated theoretically for the P4HBS using the empirical relation. The estimated values are used to calculate the electronic polarizability. The third-order nonlinear optical properties such as nonlinear refractive index (n2), absorption co-efficient (β) and susceptibility (χ(3)) were studied by Z-scan technique at 632.8 nm using He-Ne laser.

Natural age dispersion arising from the analysis of broken crystals. Part I: Theoretical basis and implications for the apatite (U-Th)/He thermochronometer

NASA Astrophysics Data System (ADS)

Brown, Roderick W.; Beucher, Romain; Roper, Steven; Persano, Cristina; Stuart, Fin; Fitzgerald, Paul

2013-12-01

Over the last decade major progress has been made in developing both the theoretical and practical aspects of apatite (U-Th)/He thermochronometry and it is now standard practice, and generally seen as best practice, to analyse single grain aliquots. These individual prismatic crystals are often broken and are fragments of larger crystals that have broken during mineral separation along the weak basal cleavage in apatite. This is clearly indicated by the common occurrence of only 1 or no clear crystal terminations present on separated apatite grains, and evidence of freshly broken ends when grains are viewed using a scanning electron microscope. This matters because if the 4He distribution within the whole grain is not homogeneous, because of partial loss due to thermal diffusion for example, then the fragments will all yield ages different from each other and from the whole grain age. Here we use a numerical model with a finite cylinder geometry to approximate 4He ingrowth and thermal diffusion within hexagonal prismatic apatite crystals. This is used to quantify the amount and patterns of inherent, natural age dispersion that arises from analysing broken crystals. A series of systematic numerical experiments were conducted to explore and quantify the pattern and behaviour of this source of dispersion using a set of 5 simple thermal histories that represent a range of plausible geological scenarios. In addition some more complex numerical experiments were run to investigate the pattern and behaviour of grain dispersion seen in several real data sets. The results indicate that natural dispersion of a set of single fragment ages (defined as the range divided by the mean) arising from fragmentation alone varies from c. 7% even for rapid (c. 10 °C/Ma), monotonic cooling to over 50% for protracted, complex histories that cause significant diffusional loss of 4He. The magnitude of dispersion arising from fragmentation scales with the grain cylindrical radius, and is of

Investigating the Effect of Impurities on Macromolecule Crystal Growth in Microgravity

NASA Technical Reports Server (NTRS)

Snell, Edward H.; Judge, Russell A.; Crawford, Lisa; Forsythe, Elizabeth L.; Pusey, Marc L.; Sportiello, Michael; Todd, Paul; Bellamy, Henry; Lovelace, Jeff; Cassanto, John M.;

Potassium-cobalt sulphate crystal growth assisted by low frequency vibrations

NASA Astrophysics Data System (ADS)

Sadovsky, A.; Ermochenkov, I.; Dubovenko, E.; Sukhanova, E.; Bebyakin, M.; Dubov, V.; Avetissov, I.

2018-02-01

Single crystals of K2Co(SO4)2·6H2O were grown from solution using the temperature reduction method enhanced by the axial low frequency vibration control technique (AVC-technique). Physical modeling of heat-mass transfer in solution under the AVC action was performed. The growth rate of the AVC grown crystal was found to be twice that of the crystal grown under natural convection conditions. Analysis of spectral characteristics (absorption and Raman spectra) as well as structural properties (dislocation density and microhardness) of the grown crystals showed the significant superiority of the AVC technique for the growth of K2Co(SO4)2·6H2O crystals.

Maximizing Macromolecule Crystal Size for Neutron Diffraction Experiments

NASA Technical Reports Server (NTRS)

Judge, R. A.; Kephart, R.; Leardi, R.; Myles, D. A.; Snell, E. H.; vanderWoerd, M.; Curreri, Peter A. (Technical Monitor)

2002-01-01

A challenge in neutron diffraction experiments is growing large (greater than 1 cu mm) macromolecule crystals. In taking up this challenge we have used statistical experiment design techniques to quickly identify crystallization conditions under which the largest crystals grow. These techniques provide the maximum information for minimal experimental effort, allowing optimal screening of crystallization variables in a simple experimental matrix, using the minimum amount of sample. Analysis of the results quickly tells the investigator what conditions are the most important for the crystallization. These can then be used to maximize the crystallization results in terms of reducing crystal numbers and providing large crystals of suitable habit. We have used these techniques to grow large crystals of Glucose isomerase. Glucose isomerase is an industrial enzyme used extensively in the food industry for the conversion of glucose to fructose. The aim of this study is the elucidation of the enzymatic mechanism at the molecular level. The accurate determination of hydrogen positions, which is critical for this, is a requirement that neutron diffraction is uniquely suited for. Preliminary neutron diffraction experiments with these crystals conducted at the Institute Laue-Langevin (Grenoble, France) reveal diffraction to beyond 2.5 angstrom. Macromolecular crystal growth is a process involving many parameters, and statistical experimental design is naturally suited to this field. These techniques are sample independent and provide an experimental strategy to maximize crystal volume and habit for neutron diffraction studies.

Broadband slow light in one-dimensional logically combined photonic crystals.

PubMed

Alagappan, G; Png, C E

2015-01-28

Here, we demonstrate the broadband slow light effects in a new family of one dimensional photonic crystals, which are obtained by logically combining two photonic crystals of slightly different periods. The logical combination slowly destroys the original translational symmetries of the individual photonic crystals. Consequently, the Bloch modes of the individual photonic crystals with different wavevectors couple with each other, creating a vast number of slow modes. Specifically, we describe a photonic crystal architecture that results from a logical "OR" mixture of two one dimensional photonic crystals with a periods ratio of r = R/(R - 1), where R > 2 is an integer. Such a logically combined architecture, exhibits a broad region of frequencies in which a dense number of slow modes with varnishing group velocities, appear naturally as Bloch modes.

Shear induced orientation of edible fat and chocolate crystals

NASA Astrophysics Data System (ADS)

Mazzanti, Gianfranco; Welch, Sarah E.; Marangoni, Alejandro G.; Sirota, Eric B.; Idziak, Stefan H. J.

2003-03-01

Shear-induced orientation of fat crystallites was observed during crystallization of cocoa butter, milk fat, stripped milk fat and palm oil. This universal effect was observed in systems crystallized under high shear. The minor polar components naturally present in milk fat were found to decrease the shear-induced orientation effect in this system. The competition between Brownian and shear forces, described by the Peclet number, determines the crystallite orientation. The critical radius size, from the Gibbs-Thomson equation, provides a tool to understand the effect of shear at the onset stages of crystallization.

The Crystals Cave in a test tube

NASA Astrophysics Data System (ADS)

Puig, C.; Romero, M. L.

2012-04-01

It's quite easy to understand formation of crystals in Nature by evaporation of the solutions that contain minerals, but many times we have realised that our pupils hardly understand that precipitation is a process mostly caused by changing parameters in a solution, like pH, temperature, etc. and not necessarily depending on evaporation. We propose a hands-on activity using the context of the Cave of the Crystals in Naica's mine, Mexico. The Crystals Cave is a wonderful place where giant crystals of selenite (gypsum) have grown feeding from a supersaturated anhydrite solution1. Miners discovered the cave filled with hot water, and drained it to explore the gallery. The cave is now a giant laboratory where scientists are looking for the keys to understand geological processes. Teaching sequence (for students 15 years old) is as follows: DISCOVERING A MARVELLOUS PLACE: We showed our pupils several images and a short video of the Cave of the Crystals and ask them about the process that may have caused the phenomenon. Whole-class discussion. PRESENTING A CHALLENGE TO OUR STUDENTS: "COULD WE CREATE A CRYSTALS CAVE IN A TEST TUBE?" EXPERIMENTING TO IMITATE NATURE: Students tried to grow crystals simulating the same conditions as those in Naica's mine. We have chosen KNO3, a salt more soluble than gypsum. We added 85 g of salt to 200 ml of water (solubility of KNO3 at 25°C is 36 g per 100 gr of water) and heated it until it is dissolved. Afterwards, we poured the solution into some test tubes and other recipients and let them cool at room temperature. And they got a beautiful crystals cave!! THINKING A LITTLE MORE: we asked pupils some questions to make them think about the process and to predict what would happen in different situations. For example: a) What would happen with crystals if we heated the tubes again? or b) What would happen if we took the remaining solution from the tubes and keep it in the fridge? PROVING A NEW HYPOTHESIS: Pupils collected the remaining

Trace fluorescent labeling for protein crystallization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pusey, Marc, E-mail: marc.pusey@ixpressgenes.com; Barcena, Jorge; Morris, Michelle

2015-06-27

The presence of a covalently bound fluorescent probe at a concentration of <0.5% does not affect the outcome of macromolecule crystallization screening experiments. Additionally, the fluorescence can be used to determine new, not immediately apparent, lead crystallization conditions. Fluorescence can be a powerful tool to aid in the crystallization of proteins. In the trace-labeling approach, the protein is covalently derivatized with a high-quantum-yield visible-wavelength fluorescent probe. The final probe concentration typically labels ≤0.20% of the protein molecules, which has been shown to not affect the crystal nucleation or diffraction quality. The labeled protein is then used in a plate-screening experimentmore » in the usual manner. As the most densely packed state of the protein is the crystalline form, then crystals show as the brightest objects in the well under fluorescent illumination. A study has been carried out on the effects of trace fluorescent labeling on the screening results obtained compared with nonlabeled protein, and it was found that considering the stochastic nature of the crystal nucleation process the presence of the probe did not affect the outcomes obtained. Other effects are realised when using fluorescence. Crystals are clearly seen even when buried in precipitate. This approach also finds ‘hidden’ leads, in the form of bright spots, with ∼30% of the leads found being optimized to crystals in a single-pass optimization trial. The use of visible fluorescence also enables the selection of colors that bypass interfering substances, and the screening materials do not have to be UV-transparent.« less

Molecular Dynamics Characterization of Protein Crystal Contacts in Aqueous Solutions

NASA Astrophysics Data System (ADS)

Pellicane, Giuseppe; Smith, Graham; Sarkisov, Lev

2008-12-01

We employ nonequilibrium molecular dynamics simulation to characterize the effective interactions between lysozyme molecules involved in the formation of two hydrophobic crystal contacts. We show that the effective interactions between crystal contacts do not exceed a few kT, the range of the attractive part of the potential is less than 4 Å, and, within this range, there is a significant depletion of water density between two protein contacts. Our findings highlight the different natures of protein crystallization and protein recognition processes.

Light-induced dynamic structural color by intracellular 3D photonic crystals in brown algae

PubMed Central

2018-01-01

Natural photonic crystals are responsible for strong reflectance at selective wavelengths in different natural systems. We demonstrate that intracellular opal-like photonic crystals formed from lipids within photosynthetic cells produce vivid structural color in the alga Cystoseira tamariscifolia. The reflectance of the opaline vesicles is dynamically responsive to environmental illumination. The structural color is present in low light–adapted samples, whereas higher light levels produce a slow disappearance of the structural color such that it eventually vanishes completely. Once returned to low-light conditions, the color re-emerges. Our results suggest that these complex intracellular natural photonic crystals are responsive to environmental conditions, changing their packing structure reversibly, and have the potential to manipulate light for roles beyond visual signaling. PMID:29651457

Light-induced dynamic structural color by intracellular 3D photonic crystals in brown algae.

PubMed

Lopez-Garcia, Martin; Masters, Nathan; O'Brien, Heath E; Lennon, Joseph; Atkinson, George; Cryan, Martin J; Oulton, Ruth; Whitney, Heather M

2018-04-01

Natural photonic crystals are responsible for strong reflectance at selective wavelengths in different natural systems. We demonstrate that intracellular opal-like photonic crystals formed from lipids within photosynthetic cells produce vivid structural color in the alga Cystoseira tamariscifolia . The reflectance of the opaline vesicles is dynamically responsive to environmental illumination. The structural color is present in low light-adapted samples, whereas higher light levels produce a slow disappearance of the structural color such that it eventually vanishes completely. Once returned to low-light conditions, the color re-emerges. Our results suggest that these complex intracellular natural photonic crystals are responsive to environmental conditions, changing their packing structure reversibly, and have the potential to manipulate light for roles beyond visual signaling.

Using textons to rank crystallization droplets by the likely presence of crystals

PubMed Central

Ng, Jia Tsing; Dekker, Carien; Kroemer, Markus; Osborne, Michael; von Delft, Frank

2014-01-01

The visual inspection of crystallization experiments is an important yet time-consuming and subjective step in X-ray crystallo­graphy. Previously published studies have focused on automatically classifying crystallization droplets into distinct but ultimately arbitrary experiment outcomes; here, a method is described that instead ranks droplets by their likelihood of containing crystals or microcrystals, thereby prioritizing for visual inspection those images that are most likely to contain useful information. The use of textons is introduced to describe crystallization droplets objectively, allowing them to be scored with the posterior probability of a random forest classifier trained against droplets manually annotated for the presence or absence of crystals or microcrystals. Unlike multi-class classification, this two-class system lends itself naturally to unidirectional ranking, which is most useful for assisting sequential viewing because images can be arranged simply by using these scores: this places droplets with probable crystalline behaviour early in the viewing order. Using this approach, the top ten wells included at least one human-annotated crystal or microcrystal for 94% of the plates in a data set of 196 plates imaged with a Minstrel HT system. The algorithm is robustly transferable to at least one other imaging system: when the parameters trained from Minstrel HT images are applied to a data set imaged by the Rock Imager system, human-annotated crystals ranked in the top ten wells for 90% of the plates. Because rearranging images is fundamental to the approach, a custom viewer was written to seamlessly support such ranked viewing, along with another important output of the algorithm, namely the shape of the curve of scores, which is itself a useful overview of the behaviour of the plate; additional features with known usefulness were adopted from existing viewers. Evidence is presented that such ranked viewing of images allows faster but more

Transient rheology of crystallizing andesitic magmas

NASA Astrophysics Data System (ADS)

de Biasi, L. J.; Chevrel, M. O.; Hanson, J. B.; Cimarelli, C.; Lavallée, Y.; Dingwell, D. B.

2012-04-01

The viscosity of magma strongly influences its rheological behaviour, which is a key determinant of magma transport processes and volcanic eruptions. Understanding the factors controlling the viscosity of magma is important to our assessment of hazards posed by active volcanoes. In nature, magmas span a very wide range in viscosity (10-1 to 1014 Pa s), depending on chemical composition (including volatile content), temperature, and importantly, crystal fraction, which further induces a complex strain rate dependence (i.e. non-Newtonian rheology). Here, we present results of transient viscosities of a crystallizing andesitic melt (57 wt.% SiO2) from Tungurahua volcano (Ecuador). We followed the experimental method developed by Vona et al. (2011) for the concentric cylinder apparatus, but optimized its implementation by leaving the spindle in situ before quenching the experimental products, to preserve the complete developed texture of the sample. The viscosity is investigated under super-liquidus (1400 ° C) and sub-liquidus temperatures (1162 and 1167 ° C). For each temperature increment, thermal equilibrium is achieved over a period of days while the spindle constantly stirs the magma. Simultaneous monitoring of the torque is used to calculate the apparent viscosity of the transient suspension. To get a better understanding of the nucleation and crystal growth processes that are involved at sub-liquidus conditions, further time-step experiments were carried out, where the samples were quenched at various equilibration stages. The mineralogical assemblage, as well as the crystal fraction, distribution and preferential alignment were then quantitatively analyzed. At temperatures below the liquidus, the suspension shows a progressive, but irregular increase of the relative shear viscosity. First, the viscosity slightly increases, possibly due to the crystallization of small, equant oxides and the formation of plagioclase nuclei. After some time (1.5-2.5 days

Hard-sphere crystallization gets rarer with increasing dimension

NASA Astrophysics Data System (ADS)

van Meel, J. A.; Charbonneau, B.; Fortini, A.; Charbonneau, P.

2009-12-01

We recently found that crystallization of monodisperse hard spheres from the bulk fluid faces a much higher free-energy barrier in four than in three dimensions at equivalent supersaturation, due to the increased geometrical frustration between the simplex-based fluid order and the crystal [J. A. van Meel, D. Frenkel, and P. Charbonneau, Phys. Rev. E 79, 030201(R) (2009)]. Here, we analyze the microscopic contributions to the fluid-crystal interfacial free energy to understand how the barrier to crystallization changes with dimension. We find the barrier to grow with dimension and we identify the role of polydispersity in preventing crystal formation. The increased fluid stability allows us to study the jamming behavior in four, five, and six dimensions and to compare our observations with two recent theories [C. Song, P. Wang, and H. A. Makse, Nature (London) 453, 629 (2008); G. Parisi and F. Zamponi, Rev. Mod. Phys. (to be published)].

Graphene chiral liquid crystals and macroscopic assembled fibres

PubMed Central

Xu, Zhen; Gao, Chao

2011-01-01

Chirality and liquid crystals are both widely expressed in nature and biology. Helical assembly of mesophasic molecules and colloids may produce intriguing chiral liquid crystals. To date, chiral liquid crystals of 2D colloids have not been explored. As a typical 2D colloid, graphene is now receiving unprecedented attention. However, making macroscopic graphene fibres is hindered by the poor dispersibility of graphene and by the lack of an assembly method. Here we report that soluble, chemically oxidized graphene or graphene oxide sheets can form chiral liquid crystals in a twist-grain-boundary phase-like model with simultaneous lamellar ordering and long-range helical frustrations. Aqueous graphene oxide liquid crystals were continuously spun into metres of macroscopic graphene oxide fibres; subsequent chemical reduction gave the first macroscopic neat graphene fibres with high conductivity and good mechanical performance. The flexible, strong graphene fibres were knitted into designed patterns and into directionally conductive textiles. PMID:22146390

Proline: Mother Nature;s cryoprotectant applied to protein crystallography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pemberton, Travis A.; Still, Brady R.; Christensen, Emily M.

L-Proline is one of Mother Nature's cryoprotectants. Plants and yeast accumulate proline under freeze-induced stress and the use of proline in the cryopreservation of biological samples is well established. Here, it is shown that L-proline is also a useful cryoprotectant for protein crystallography. Proline was used to prepare crystals of lysozyme, xylose isomerase, histidine acid phosphatase and 1-pyrroline-5-carboxylate dehydrogenase for low-temperature data collection. The crystallization solutions in these test cases included the commonly used precipitants ammonium sulfate, sodium chloride and polyethylene glycol and spanned the pH range 4.6-8.5. Thus, proline is compatible with typical protein-crystallization formulations. The proline concentration neededmore » for cryoprotection of these crystals is in the range 2.0-3.0 M. Complete data sets were collected from the proline-protected crystals. Proline performed as well as traditional cryoprotectants based on the diffraction resolution and data-quality statistics. The structures were refined to assess the binding of proline to these proteins. As observed with traditional cryoprotectants such as glycerol and ethylene glycol, the electron-density maps clearly showed the presence of proline molecules bound to the protein. In two cases, histidine acid phosphatase and 1-pyrroline-5-carboxylate dehydrogenase, proline binds in the active site. It is concluded that L-proline is an effective cryoprotectant for protein crystallography.« less

Solubility prediction of naphthalene in carbon dioxide from crystal microstructure

NASA Astrophysics Data System (ADS)

Sang, Jiarong; Jin, Junsu; Mi, Jianguo

2018-03-01

Crystals dissolved in solvents are ubiquitous in both natural and artificial systems. Due to the complicated structures and asymmetric interactions between the crystal and solvent, it is difficult to interpret the dissolution mechanism and predict solubility using traditional theories and models. Here we use the classical density functional theory (DFT) to describe the crystal dissolution behavior. As an example, naphthalene dissolved in carbon dioxide (CO2) is considered within the DFT framework. The unit cell dimensions and microstructure of crystalline naphthalene are determined by minimizing the free-energy of the crystal. According to the microstructure, the solubilities of naphthalene in CO2 are predicted based on the equality of naphthalene's chemical potential in crystal and solution phases, and the interfacial structures and free-energies between different crystal planes and solution are determined to investigate the dissolution mechanism at the molecular level. The theoretical predictions are in general agreement with the available experimental data, implying that the present model is quantitatively reliable in describing crystal dissolution.

X-ray Diffraction Crystal Calibration and Characterization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Michael J. Haugh; Richard Stewart; Nathan Kugland

2009-06-05

National Security Technologies’ X-ray Laboratory is comprised of a multi-anode Manson type source and a Henke type source that incorporates a dual goniometer and XYZ translation stage. The first goniometer is used to isolate a particular spectral band. The Manson operates up to 10 kV and the Henke up to 20 kV. The Henke rotation stages and translation stages are automated. Procedures have been developed to characterize and calibrate various NIF diagnostics and their components. The diagnostics include X-ray cameras, gated imagers, streak cameras, and other X-ray imaging systems. Components that have been analyzed include filters, filter arrays, grazing incidencemore » mirrors, and various crystals, both flat and curved. Recent efforts on the Henke system are aimed at characterizing and calibrating imaging crystals and curved crystals used as the major component of an X-ray spectrometer. The presentation will concentrate on these results. The work has been done at energies ranging from 3 keV to 16 keV. The major goal was to evaluate the performance quality of the crystal for its intended application. For the imaging crystals we measured the laser beam reflection offset from the X-ray beam and the reflectivity curves. For the curved spectrometer crystal, which was a natural crystal, resolving power was critical. It was first necessary to find sources of crystals that had sufficiently narrow reflectivity curves. It was then necessary to determine which crystals retained their resolving power after being thinned and glued to a curved substrate.« less

Nanorelief of the natural cleavage surface of triglycine sulphate crystals with substitutional and interstitial impurities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Belugina, N. V.; Gainutdinov, R. V.; Tolstikhina, A. L., E-mail: alla@ns.crys.ras.ru

2011-11-15

Ferroelectric triglycine sulphate crystals (TGS) with substitutional (LADTGS+ADP, DTGS) and interstitial (Cr) impurities have been studied by atomic-force microscopy, X-ray diffraction, and X-ray fluorescence. The nanorelief parameters of the mirror cleavage TGS(010) surface have been measured with a high accuracy. A correlation between the crystal defect density in the bulk and the cleavage surface nanorelief is revealed at the submicrometer level.

Simulation of the temperature distribution in crystals grown by Czochralski method

NASA Technical Reports Server (NTRS)

Dudokovic, M. P.; Ramachandran, P. A.

1985-01-01

Production of perfect crystals, free of residual strain and dislocations and with prescribed dopant concentration, by the Czochralski method is possible only if the complex, interacting phenomena that affect crystal growth in a Cz-puller are fully understood and quantified. Natural and forced convection in the melt, thermocapillary effect and heat transfer in and around the crystal affect its growth rate, the shape of the crystal-melt interface and the temperature gradients in the crystal. The heat transfer problem in the crystal and between the crystal and all other surfaces present in the crystal pulling apparatus are discussed at length. A simulation and computer algorithm are used, based on the following assumptions: (1) only conduction occurs in the crystal (experimentally determined conductivity as a function of temperature is used), (2) melt temperature and the melt-crystal heat transfer coefficient are available (either as constant values or functions of radial position), (3) pseudo-steady state is achieved with respect to temperature gradients, (4) crystal radius is fixed, and (5) both direct and reflected radiation exchange occurs among all surfaces at various temperatures in the crystal puller enclosure.

The snowmaker: nature identical snow production in the laboratory

NASA Astrophysics Data System (ADS)

Schleef, S.; Jaggi, M.; Loewe, H.; Schneebeli, M.

2013-12-01

Using natural snow for laboratory experiments can be tricky due to shortage of winter periods and snowfall, difficulties of sample casting and transport, and the great variability of natural snow due to the varying conditions of crystal growth in the clouds. This hinders repeatable laboratory experiments with reproducible specimen and microstructural characteristics. To minimize experimental uncertainties we designed an improved machine called snowmaker, which enables us to produce nature-identical snow in a cold laboratory under well defined conditions. The snowmaker is based on well-known principles: warm humid air from a heated water basin is advected into a cold nucleation chamber where the vapor resublimates on stretched Nylon wires. Crystals are automatically harvested by a motor driven brush rack and collected in a box, thereby several kilograms of snow can be produced per day with minimum maintenance. The excess vapor is collected in a moisture trap to avoid frost in the laboratory. The entire construction is designed as a rolling, modular assembly system which can easily carried out of the laboratory for defrosting. In addition to previous attempts we focus on the reproducibility of the samples and the comparison to natural snow down to the microscale. We show that the settings of water temperature and cold laboratory temperature facilitates the production of different crystal shapes like dendrites and needles in a reproducible way. Besides photography, we analyzed the microstructure of snowmaker crystals in aggregated specimen by X-ray microtomography. Depending on the settings we can create reproducible samples with density of 50-170 kg/m3 and specific surface areas of 50-80 mm-1. We briefly touch similarities between artificial and natural snow samples with respect to crystal habit, microstructural parameters and short-time metamorphism.

Steering a crystallization process to reduce crystal polydispersity; case study of insulin crystallization

NASA Astrophysics Data System (ADS)

Nanev, Christo N.; Petrov, Kostadin P.

2017-12-01

The use of the classical nucleation-growth-separation principle (NGSP) was restricted hitherto to nucleation kinetics studies only. A novel application of the NGSP is proposed. To reduce crystal polydispersity internal seeding of equally-sized crystals is suggested, the advantage being avoidance of crystal grinding, sieving and any introduction of impurities. In the present study, size distributions of grown insulin crystals are interpreted retrospectively to select the proper nucleation stage parameters. The conclusion is that when steering a crystallization process aimed at reducing crystal polydispersity, the shortest possible nucleation stage duration has to be chosen because it renders the closest size distribution of the nucleated crystal seeds. Causes of inherent propensity to increasing crystal polydispersity during prolonged growth are also explored. Step sources of increased activity, present in some crystals while absent in others, are pointed as the major polydispersity cause. Insulin crystal morphology is also considered since it determines the dissolution rate of a crystalline medicine.

Crystal structure of extracellular domain of human lectin-like transcript 1 (LLT1), the ligand for natural killer receptor-P1A.

PubMed

Kita, Shunsuke; Matsubara, Haruki; Kasai, Yoshiyuki; Tamaoki, Takaharu; Okabe, Yuki; Fukuhara, Hideo; Kamishikiryo, Jun; Krayukhina, Elena; Uchiyama, Susumu; Ose, Toyoyuki; Kuroki, Kimiko; Maenaka, Katsumi

2015-06-01

Emerging evidence has revealed the pivotal roles of C-type lectin-like receptors (CTLRs) in the regulation of a wide range of immune responses. Human natural killer cell receptor-P1A (NKRP1A) is one of the CTLRs and recognizes another CTLR, lectin-like transcript 1 (LLT1) on target cells to control NK, NKT and Th17 cells. The structural basis for the NKRP1A-LLT1 interaction was limitedly understood. Here, we report the crystal structure of the ectodomain of LLT1. The plausible receptor-binding face of the C-type lectin-like domain is flat, and forms an extended β-sheet. The residues of this face are relatively conserved with another CTLR, keratinocyte-associated C-type lectin, which binds to the CTLR member, NKp65. A LLT1-NKRP1A complex model, prepared using the crystal structures of LLT1 and the keratinocyte-associated C-type lectin-NKp65 complex, reasonably satisfies the charge consistency and the conformational complementarity to explain a previous mutagenesis study. Furthermore, crystal packing and analytical ultracentrifugation revealed dimer formation, which supports a complex model. Our results provide structural insights for understanding the binding modes and signal transduction mechanisms, which are likely to be conserved in the CTLR family, and for further rational drug design towards regulating the LLT1 function. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Tunable alumina 2D photonic-crystal structures via biomineralization of peacock tail feathers

NASA Astrophysics Data System (ADS)

Jiang, Yonggang; Wang, Rui; Feng, Lin; Li, Jian; An, Zhonglie; Zhang, Deyuan

2018-04-01

Peacock tail feathers with subtle periodic nanostructures exhibit diverse striking brilliancy, which can be applied as natural templates to fabricate artificial photonic crystals (PhCs) via a biomineralization method. Alumina photonic-crystal structures are successfully synthesized via an immersion and two-step calcination process. The lattice constants of the artificial PhCs are greatly reduced compared to their natural matrices. The lattice constants are tunable by modifying the final annealing conditions in the biomineralization process. The reflection spectra of the alumina photonic-crystal structures are measured, which is related to their material and structural parameters. This work suggests a facile fabrication process to construct alumina PhCs with a high-temperature resistance.

Allium To Zircon: Mathematics and Nature.

ERIC Educational Resources Information Center

Harrell, Marvin E.; Fosnaugh, Linda S.

1997-01-01

Discusses how nature can illustrate mathematical structures and concepts in the classroom. For example, the upper surface of a typical leaf structure illustrates the notion of tessellating with polygons. Also lists classroom applications and hands-on activities such as growing crystals to investigate the natural forms of polyhedra and measuring…

Crystal growth, physical properties and computational insights of semi-organic non-linear optical crystal diphenylguanidinium perchlorate grown by conventional solvent evaporation method

NASA Astrophysics Data System (ADS)

Kajamuhideen, M. S.; Sethuraman, K.; Ramamurthi, K.; Ramasamy, P.

2018-02-01

A splendid nonlinear optical single crystals diphenylguanidinium perchlorate (DPGP) was lucratively grown by low cost solvent evaporation method with the dimensions of 8 × 4 × 2 mm3. Structural and morphological studies of grown crystal were confirmed using X-ray diffraction studies. The presence of diverse functional groups was identified using FTIR and RAMAN studies. The molecular structure of a grown crystal was inveterate by NMR studies. The optical transmittance of DPGP crystal was analyzed using UV-vis-NIR studies. Photoluminescence spectrum shows sharp, well defined emission peak at 388 nm. Thermal studies assign that adduct is stable with the melting point of 164 °C. Microhardness studies declare that DPGP crystal belongs to the soft material class and their yield strength and elastic stiffness constant values were evaluated. Photoconductivity studies revealed the negative photoconductive nature of DPGP crystal. Second harmonic generation (SHG) efficiency of the DPGP crystal was 1.4 times that of potassium dihydrogen phosphate. Etching studies were carried out for different etching time. The dielectric studies were performed at different frequency. Laser damage threshold properties of DPGP crystal were examined using Nd:YAG laser system. The HOMO-LUMO energy gap evident the charge transfer interaction of the molecule. The calculated first order hyperpolarizability value is 5 times greater than that of urea. Thus, the grown DPGP single crystals are well suited for NLO device fabrications.

Can computed crystal energy landscapes help understand pharmaceutical solids?

PubMed Central

Price, Sarah L.; Braun, Doris E.; Reutzel-Edens, Susan M.

2017-01-01

Computational crystal structure prediction (CSP) methods can now be applied to the smaller pharmaceutical molecules currently in drug development. We review the recent uses of computed crystal energy landscapes for pharmaceuticals, concentrating on examples where they have been used in collaboration with industrial-style experimental solid form screening. There is a strong complementarity in aiding experiment to find and characterise practically important solid forms and understanding the nature of the solid form landscape. PMID:27067116

Nanometre-scale crystals formed in the presence of natural organic matter .

NASA Astrophysics Data System (ADS)

Frisia, Silvia; Borsato, Andrea; Zhang, Huiming; Meister, Patrick; Della Porta, Giovanna; Marjo, Chris; Cheong, Soshan; Hartland, Adam; Gattolin, Giovanni; Ischia, Gloria; Anderson, Ebony; Rich, Anne

2017-04-01

Nanocrystals have been observed to form micrite in several environments where natural organic matter (NOM) is present in dissolved, colloidal and particulate form, in both modern and ancient continental and marine sediments. In ancient (Triassic) marine deposits, we found perfectly preserved nanocrystal aggregates entombed by NOM, which appears to be associated with clay particulate. These nanocrystal, which have been preserved through million of years, bear similarities with nanocrystal observed in diverse, freshwater, modern settings. In modern and Holocene continental environments, micrite is of interest because of its association with archives of past climate, such as stalagmites. Nanocrystal aggregates forming micrite have been observed in association with microbial structures in tufa, thermal spring pisoids and in cave speleothems. We carried out "instant precipitation" experiments in several caves from New Zealand, Australia and and Italy, cut in both limestones and dolomites, with a focus on finding a relationship between NOM and micrite precipitation. Transmission Electron Microscope (TEM) investigations of the experimental precipitates suggest that nanocrystals nucleated already after 30 minutes on NOM colloids (as confirmed by EDS spectra) possibly originated in the soil zone. Some samples were left to "mature" for 24 hours: aggregates began to show some preferred orientation and a few single crystals on micrometer scale were also observed, which do not seem to be associated with NOM. Our preliminary results suggest that NOM, such as soil-derived humid and fulvic acids, aids nanocrystal aggregate nucleation and growth. The cave experiments seem to indicate that it is not necessary to have microbial mats, or EPS to favor formation of micrite. Our experiments did not capture the occurrence of amorphous precursors, but the amorphous phase may have been gone undetected as NOM is amorphous. Our findings have potential implications for the interpretation of

Mesoscale martensitic transformation in single crystals of topological defects

PubMed Central

Martínez-González, José A.; Ramírez-Hernández, Abelardo; Zhou, Ye; Sadati, Monirosadat; Zhang, Rui; Nealey, Paul F.; de Pablo, Juan J.

2017-01-01

Liquid-crystal blue phases (BPs) are highly ordered at two levels. Molecules exhibit orientational order at nanometer length scales, while chirality leads to ordered arrays of double-twisted cylinders over micrometer scales. Past studies of polycrystalline BPs were challenged by the existence of grain boundaries between randomly oriented crystalline nanodomains. Here, the nucleation of BPs is controlled with precision by relying on chemically nanopatterned surfaces, leading to macroscopic single-crystal BP specimens where the dynamics of mesocrystal formation can be directly observed. Theory and experiments show that transitions between two BPs having a different network structure proceed through local reorganization of the crystalline array, without diffusion of the double-twisted cylinders. In solid crystals, martensitic transformations between crystal structures involve the concerted motion of a few atoms, without diffusion. The transformation between BPs, where crystal features arise in the submicron regime, is found to be martensitic in nature when one considers the collective behavior of the double-twist cylinders. Single-crystal BPs are shown to offer fertile grounds for the study of directed crystal nucleation and the controlled growth of soft matter. PMID:28874557

Excitation Spectra in Crystal Plasticity

NASA Astrophysics Data System (ADS)

Ovaska, Markus; Lehtinen, Arttu; Alava, Mikko J.; Laurson, Lasse; Zapperi, Stefano

2017-12-01

Plastically deforming crystals exhibit scale-free fluctuations that are similar to those observed in driven disordered elastic systems close to depinning, but the nature of the yielding critical point is still debated. Here, we study the marginal stability of ensembles of dislocations and compute their excitation spectrum in two and three dimensions. Our results show the presence of a singularity in the distribution of excitation stresses, i.e., the stress needed to make a localized region unstable, that is remarkably similar to the one measured in amorphous plasticity and spin glasses. These results allow us to understand recent observations of extended criticality in bursty crystal plasticity and explain how they originate from the presence of a pseudogap in the excitation spectrum.

Macromolecular Crystal Growth by Means of Microfluidics

NASA Technical Reports Server (NTRS)

vanderWoerd, Mark; Ferree, Darren; Spearing, Scott; Monaco, Lisa; Molho, Josh; Spaid, Michael; Brasseur, Mike; Curreri, Peter A. (Technical Monitor)

2002-01-01

We have performed a feasibility study in which we show that chip-based, microfluidic (LabChip(TM)) technology is suitable for protein crystal growth. This technology allows for accurate and reliable dispensing and mixing of very small volumes while minimizing bubble formation in the crystallization mixture. The amount of (protein) solution remaining after completion of an experiment is minimal, which makes this technique efficient and attractive for use with proteins, which are difficult or expensive to obtain. The nature of LabChip(TM) technology renders it highly amenable to automation. Protein crystals obtained in our initial feasibility studies were of excellent quality as determined by X-ray diffraction. Subsequent to the feasibility study, we designed and produced the first LabChip(TM) device specifically for protein crystallization in batch mode. It can reliably dispense and mix from a range of solution constituents into two independent growth wells. We are currently testing this design to prove its efficacy for protein crystallization optimization experiments. In the near future we will expand our design to incorporate up to 10 growth wells per LabChip(TM) device. Upon completion, additional crystallization techniques such as vapor diffusion and liquid-liquid diffusion will be accommodated. Macromolecular crystallization using microfluidic technology is envisioned as a fully automated system, which will use the 'tele-science' concept of remote operation and will be developed into a research facility for the International Space Station as well as on the ground.

Study on optical properties of L-valine doped ADP crystal

NASA Astrophysics Data System (ADS)

Shaikh, R. N.; Anis, Mohd.; Shirsat, M. D.; Hussaini, S. S.

2015-02-01

Single crystal of L-valine doped ammonium dihydrogen phosphate has been grown by slow evaporation method at room temperature. The crystalline nature of the grown crystal was confirmed using powder X-ray diffraction technique. The different functional groups of the grown crystal were identified using Fourier transform infrared analysis. The UV-visible studies were employed to examine the high optical transparency and influential optical constants for tailoring materials suitability for optoelectronics applications. The cutoff wavelength of the title crystal was found to be 280 nm with wide optical band gap of 4.7 eV. The dielectric measurements were carried to determine the dielectric constant and dielectric loss at room temperature. The grown crystal has been characterized by thermogravimetric analysis. The second harmonic generation efficiency of the grown crystal was determined by the classical Kurtz powder technique and it is found to be 1.92 times that of potassium dihydrogen phosphate. The grown crystal was identified as third order nonlinear optical material employing Z-scan technique using He-Ne laser operating at 632.8 nm.

An expanded model and application of the combined effect of crystal-size distribution and crystal shape on the relative viscosity of magmas

NASA Astrophysics Data System (ADS)

Klein, Johannes; Mueller, Sebastian P.; Helo, Christoph; Schweitzer, Silja; Gurioli, Lucia; Castro, Jonathan M.

2018-05-01

This study examines the combined effect of crystal-size distributions (CSD) and crystal shape on the rheology of vesicle free magmatic suspensions and provides the first practical application of an empirical model to estimate the relative effect of crystal content and CSD's on the viscosity of magma directly from textural image analysis of natural rock samples in the form of a user-friendly texture-rheology spreadsheet calculator. We extend and apply established relationships between the maximum packing fraction ϕm of a crystal bearing suspension and both its rheological properties and the polydispersity γ of a CSD. By using analogue rotational rheometric experiments with glass fibres and glass flakes in silicone oil acting as magma equivalent, this study also provides new insights in the relationship between ϕm and the aspect ratio rp of suspended particles.

Quantum Behavior of Water Molecules Confined to Nanocavities in Gemstones.

PubMed

Gorshunov, Boris P; Zhukova, Elena S; Torgashev, Victor I; Lebedev, Vladimir V; Shakurov, Gil'man S; Kremer, Reinhard K; Pestrjakov, Efim V; Thomas, Victor G; Fursenko, Dimitry A; Dressel, Martin

2013-06-20

When water is confined to nanocavities, its quantum mechanical behavior can be revealed by terahertz spectroscopy. We place H2O molecules in the nanopores of a beryl crystal lattice and observe a rich and highly anisotropic set of absorption lines in the terahertz spectral range. Two bands can be identified, which originate from translational and librational motions of the water molecule isolated within the cage; they correspond to the analogous broad bands in liquid water and ice. In the present case of well-defined and highly symmetric nanocavities, the observed fine structure can be explained by macroscopic tunneling of the H2O molecules within a six-fold potential caused by the interaction of the molecule with the cavity walls.

Effects of humidity and surfaces on the melt crystallization of ibuprofen.

PubMed

Lee, Dong-Joo; Lee, Suyang; Kim, Il Won

2012-01-01

Melt crystallization of ibuprofen was studied to understand the effects of humidity and surfaces. The molecular self-assembly during the amorphous-to-crystal transformation was examined in terms of the nucleation and growth of the crystals. The crystallization was on Al, Au, and self-assembled monolayers with -CH(3), -OH, and -COOH functional groups. Effects of the humidity were studied at room temperature (18-20 °C) with relative humidity 33%, 75%, and 100%. Effects of the surfaces were observed at -20 °C (relative humidity 36%) to enable close monitoring with slower crystal growth. The nucleation time of ibuprofen was faster at high humidity conditions probably due to the local formation of the unfavorable ibuprofen melt/water interface. The crystal morphologies of ibuprofen were governed by the nature of the surfaces, and they could be associated with the growth kinetics by the Avrami equation. The current study demonstrated the effective control of the melt crystallization of ibuprofen through the melt/atmosphere and melt/surface interfaces.

On the Importance of Small Ice Crystals in Tropical Anvil Cirrus

NASA Technical Reports Server (NTRS)

Jensen, E. J.; Lawson, P.; Baker, B.; Pilson, B.; Mo, Q.; Heymsfield, A. J.; Bansemer, A.; Bui, T. P.; McGill, M.; Hlavka, D.;

Au crystal growth on natural occurring Au-Ag aggregate elucidated by means of precession electron diffraction (PED)

NASA Astrophysics Data System (ADS)

Roqué Rosell, Josep; Portillo Serra, Joaquim; Aiglsperger, Thomas; Plana-Ruiz, Sergi; Trifonov, Trifon; Proenza, Joaquín A.

2018-02-01

In the present work, a lamella from an Au-Ag aggregate found in Ni-laterites has been examined using Transmission Electron Microscope to produce a series of Precision Electron Diffraction (PED) patterns. The analysis of the structural data obtained, coupled with Energy Dispersive X-ray microanalysis, made it possible to determine the orientation of twinned native gold growing on the Au-Ag aggregate. The native Au crystal domains are found to have grown at the outermost part of the aggregate whereas the inner core of the aggregate is an Au-Ag alloy (∼4 wt% Ag). The submicron structural study of the natural occurring Au aggregate points to the mobilization and precipitation of gold in laterites and provides insights on Au aggregates development at supergene conditions. This manuscript demonstrates the great potential of electron crystallographic analysis, and in particular, PED to study submicron structural features of micron sized mineral aggregates by using the example of a gold grain found in a Ni-laterite deposits.

Anti-solvent crystallization of L-threonine in Taylor crystallizers and MSMPR crystallizer: Effect of fluid dynamic motions on crystal size, shape, and recovery

NASA Astrophysics Data System (ADS)

Lee, Sooyun; Lee, Choul-Ho; Kim, Woo-Sik

2017-07-01

The influence of the fluid dynamic motions of a periodic Taylor vortex and random turbulent eddy on the anti-solvent crystallization of L-threonine was investigated. The Taylor vortex flow and random turbulent eddy flow were generated by the inner cylinder rotation in a Couette-Taylor (CT) crystallizer and the impeller agitation in a mixed-suspension mixed product removal (MSMPR) crystallizer, respectively. Furthermore, the circumferentially sinusoidal fluctuation of a Taylor vortex was induced in an elliptical Couette-Taylor (ECT) crystallizer . The periodic Taylor vortex flows in the CT and ECT crystallizers resulted in a smaller crystal size and higher crystal recovery ratio of L-threonine than the random turbulent flow in the MSMPR crystallizer due to induction of a higher supersaturation, resulting in a higher nucleation in the CT and ECT crystallizers than in the MSMPR crystallizer. Thus, the crystal size was reduced and the crystal recovery ratio enhanced when increasing the rotation/agitation speed and feed flow rate in the CT, ECT, and MSMPR crystallizers. When increasing the temperature, the crystal size and crystal recovery ratio were both increased due an enhanced mass transfer for crystal growth. The crystal morphology changes according to the fluid dynamic motion with various crystallization conditions were well correlated in terms of the supersaturation.

Crystallization by Particle Attachment in Synthetic, Biogenic, and Geologic Environments

DOE Office of Scientific and Technical Information (OSTI.GOV)

De Yoreo, James J.; Gilbert, Pupa U.; Sommerdijk, Nico

Field and laboratory observations show that crystals commonly form by the addition and attachment of particles that range from multi-ion complexes to fully formed nanoparticles. These non-classical pathways to crystallization are diverse, in contrast to classical models that consider the addition of monomeric chemical species. We review progress toward understanding crystal growth by particle attachment processes and show that multiple pathways result from the interplay of free energy landscapes and reaction dynamics. Much remains unknown about the fundamental aspects; particularly the relationships between solution structure, interfacial forces, and particle motion. Developing a predictive description that connects molecular details to ensemblemore » behavior will require revisiting long-standing interpretations of crystal formation in synthetic systems and patterns of mineralization in natural environments.« less

Better than Nature: Nicotinamide Biomimetics That Outperform Natural Coenzymes.

PubMed

Knaus, Tanja; Paul, Caroline E; Levy, Colin W; de Vries, Simon; Mutti, Francesco G; Hollmann, Frank; Scrutton, Nigel S

2016-01-27

The search for affordable, green biocatalytic processes is a challenge for chemicals manufacture. Redox biotransformations are potentially attractive, but they rely on unstable and expensive nicotinamide coenzymes that have prevented their widespread exploitation. Stoichiometric use of natural coenzymes is not viable economically, and the instability of these molecules hinders catalytic processes that employ coenzyme recycling. Here, we investigate the efficiency of man-made synthetic biomimetics of the natural coenzymes NAD(P)H in redox biocatalysis. Extensive studies with a range of oxidoreductases belonging to the "ene" reductase family show that these biomimetics are excellent analogues of the natural coenzymes, revealed also in crystal structures of the ene reductase XenA with selected biomimetics. In selected cases, these biomimetics outperform the natural coenzymes. "Better-than-Nature" biomimetics should find widespread application in fine and specialty chemicals production by harnessing the power of high stereo-, regio-, and chemoselective redox biocatalysts and enabling reactions under mild conditions at low cost.

Structural, chemical and physical properties of pure and La3+ doped L-Threonine acetate crystals

NASA Astrophysics Data System (ADS)

Senthamizhan, A.; Sambathkumar, K.; Nithiyanantham, S.; Venkatachalapathy, M.; Rajkamal, N.

2017-12-01

The pure and La3+ doped L- Threonine crystals can be grown by slow evaporation techniques. The crystal structure were examined through X-Ray diffraction (XRD) analysis, confirmed the P212121 system. The quantitative nature of dopant can be analyzed with Inductively Coupled Plasma (ICP) study. The Fourier Transform Infra-Red (FTIR) and Fourier Transform (FT- Raman) investigations yields the possible stretching/bonding with their functional groups and the qualitative/quantitative nature of both crystals is analyzed. The optical behavior of crystals can be studied through Ultra Violet (UV) - Visible spectrometer. The mechanical, thermal and decomposition studies can be carried out through Vickers hardness test, Thermo Gravometric Analysis (TGA) and Differential Thermal Analysis (DTA). The Non Linear Optical (NLO) properties are found more than Potassium Phosphate (KDP) through Kurtz powders technique. The dielectric and optical absorption studies for both pure and L-doped crystals were studied and interpreted all the properties. The La3+ dopant increases the properties are investigated.

Crystallization and diffraction analysis of [beta]-N-acetylhexosaminidase from Aspergillus oryzae

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vanek, Ondrej; Brynd, Jirí; Hofbauerová, Katerina

2012-05-08

Fungal {beta}-N-acetylhexosaminidases are enzymes that are used in the chemoenzymatic synthesis of biologically interesting oligosaccharides. The enzyme from Aspergillus oryzae was produced and purified from its natural source and crystallized using the hanging-drop vapor-diffusion method. Diffraction data from two crystal forms (primitive monoclinic and primitive tetragonal) were collected to resolutions of 3.2 and 2.4 {angstrom}, respectively. Electrophoretic and quantitative N-terminal protein-sequencing analyses confirmed that the crystals are formed by a complete biologically active enzyme consisting of a glycosylated catalytic unit and a noncovalently attached propeptide.

Growth and characterization of unidirectional benzil single crystal for photonic applications

NASA Astrophysics Data System (ADS)

Saranraj, A.; Thirupathy, J.; Dhas, S. Sahaya Jude; Jose, M.; Vinitha, G.; Dhas, S. A. Martin Britto

2018-06-01

Organic nonlinear optical benzil single crystal of fine quality with the dimensions of 168 × 14 mm2 was successfully grown in (100) plane from saturated solution by unidirectional SR method. The structural identity of the grown crystal was confirmed by powder XRD. High-resolution X-ray diffraction analysis indicates the crystalline perfection of the grown benzil crystal. The optical analysis was carried out by UV-visible spectroscopy which shows that the benzil crystal's cut off wavelength is 437 nm. The dielectric constant and dielectric loss of benzil crystal are found to be very much depending upon temperature and frequency. Ferroelectric nature of grown crystal was identified by P- E hysteresis analysis and to find the values of spontaneous polarization and coercive field. The laser damage threshold energy was studied with the help of Nd:YAG laser. The presence of third harmonic generation was identified by z-scan techniques.

Photonic Crystal Sensors Based on Porous Silicon

PubMed Central

Pacholski, Claudia

2013-01-01

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. PMID:23571671

Organic field-effect transistors using single crystals.

PubMed

Hasegawa, Tatsuo; Takeya, Jun

2009-04-01

Organic field-effect transistors using small-molecule organic single crystals are developed to investigate fundamental aspects of organic thin-film transistors that have been widely studied for possible future markets for 'plastic electronics'. In reviewing the physics and chemistry of single-crystal organic field-effect transistors (SC-OFETs), the nature of intrinsic charge dynamics is elucidated for the carriers induced at the single crystal surfaces of molecular semiconductors. Materials for SC-OFETs are first reviewed with descriptions of the fabrication methods and the field-effect characteristics. In particular, a benchmark carrier mobility of 20-40 cm 2 Vs -1 , achieved with thin platelets of rubrene single crystals, demonstrates the significance of the SC-OFETs and clarifies material limitations for organic devices. In the latter part of this review, we discuss the physics of microscopic charge transport by using SC-OFETs at metal/semiconductor contacts and along semiconductor/insulator interfaces. Most importantly, Hall effect and electron spin resonance (ESR) measurements reveal that interface charge transport in molecular semiconductors is properly described in terms of band transport and localization by charge traps.

Large-scale crystallization of proteins for purification and formulation.

PubMed

Hekmat, Dariusch

2015-07-01

Since about 170 years, salts were used to create supersaturated solutions and crystallize proteins. The dehydrating effect of salts as well as their kosmotropic or chaotropic character was revealed. Even the suitability of organic solvents for crystallization was already recognized. Interestingly, what was performed during the early times is still practiced today. A lot of effort was put into understanding the underlying physico-chemical interaction mechanisms leading to protein crystallization. However, it was understood that already the solvation of proteins is a highly complex process not to mention the intricate interrelation of electrostatic and hydrophobic interactions taking place. Although many basic questions are still unanswered, preparative protein crystallization was attempted as illustrated in the presented case studies. Due to the highly variable nature of crystallization, individual design of the crystallization process is needed in every single case. It was shown that preparative crystallization from impure protein solutions as a capture step is possible after applying adequate pre-treatment procedures like precipitation or extraction. Protein crystallization can replace one or more chromatography steps. It was further shown that crystallization can serve as an attractive alternative means for formulation of therapeutic proteins. Crystalline proteins can offer enhanced purity and enable highly concentrated doses of the active ingredient. Easy scalability of the proposed protein crystallization processes was shown using the maximum local energy dissipation as a suitable scale-up criterion. Molecular modeling and target-oriented protein engineering may allow protein crystallization to become part of a platform purification process in the near future.

Trichoderma koningii as a biomineralizing fungous agent of calcium oxalate crystals in typical Argiudolls of the Los Padres Lake natural reserve (Buenos Aires, Argentina).

PubMed

Oyarbide, F; Osterrieth, M L; Cabello, M

2001-01-01

The aim of the present study, performed on typical Argiudolls in a natural reserve with little or no anthropic impact, was to characterize the fungous biomineralizing process of calcium oxalate crystals in organic horizons of the soil. The chosen sites possessed different plant cover, identified as acacia woods and grassy meadows with particular micro environmental conditions that have differing effects in the process of biomineralization. The contribution of the plant material in the soil is a key factor since 1) it generates the particular composition of the organic horizons, 2) it determines the nature of decomposing organisms, and 3) it affects the presence, composition and development of biominerals. According to the results obtained, the acacia woods prove to be a site comparatively more favorable to the fungous biomineralizing process. This makes itself manifest in the greater abundance and development of crystals in the organic horizons of the soil, resulting in whewellite (CaC2O4.H2O) and weddellite (CaC2O4.(2+x) H2O) regarding biomineral species developed, the latter being the major component. The observation of both species of biominerals is noteworthy since it represents the first cited in the country. The isolated fungous organisms were Trichoderma koningii, and Absidia corymbifera. T. koningii was identified as the most active biomineralizing organism thus constituting the first reference to indicate this species as a biomineral producing agent.

At last! The single-crystal X-ray structure of a naturally occurring sample of the ilmenite-type oxide FeCrO3.

PubMed

Pérez-Cruz, María Ana; Elizalde-González, María de la Paz; Escudero, Roberto; Bernès, Sylvain; Silva-González, Rutilo; Reyes-Ortega, Yasmi

2015-10-01

A natural single crystal of the ferrimagnetic oxide FeCrO3, which was found in an opencast mine situated in the San Luis Potosí State in Mexico, has been characterized in order to elucidate some outstanding issues about the actual structure of this material. The single-crystal X-ray analysis unambiguously shows that transition metal cations are segregated in alternating layers normal to the threefold crystallographic axis, affording a structure isomorphous to that of ilmenite (FeTiO3), in the space group R3̅. The possible occurrence of cation antisite and vacancy defects is below the limit of detection available from X-ray data. Structural and magnetic results are in agreement with the coherent slow intergrowth of magnetic phases provided by the two antiferromagnetic corundum-type parent oxides Fe2O3 (hematite) and Cr2O3 (eskolaite). Our results are consistent with the most recent density functional theory (DFT) studies carried out on digital FeCrO3 [Sadat Nabi & Pentcheva (2011). Phys. Rev. B, 83, 214424], and suggest that synthetic samples of FeCrO3 might present a cation distribution different to that of the ilmenite structural type.

Realignment of Nanocrystal Aggregates into Single Crystals as a Result of Inherent Surface Stress

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Zhaoming; Pan, Haihua; Zhu, Genxing

2016-07-19

Assembly of nanoparticles building blocks during single crystal growth is widely observed in both natural and synthetic environments. Although this form of non-classical crystallization is generally described by oriented attachment, random aggregation of building blocks leading to single crystal products is also observed, but the mechanism of crystallographic realignment is unknown. We herein reveal that random attachment during aggregation-based growth initially produces a non-oriented growth front. Subsequent evolution of the orientation is driven by the inherent surface stress applied by the disordered surface layer and results in single crystal formation via grain boundary migration. This mechanism is corroborated by measurementsmore » of orientation rate vs external stress, demonstrating a predictive relationship between the two. These findings advance our understanding of aggregation-based growth of natural minerals by nanocrystals, and suggest an approach to material synthesis that takes advantage of stress induced co-alignment.« less

A proposed mechanism for the formation of spherical vivianite crystal aggregates in sediments

USGS Publications Warehouse

Zelibor, J.L.; Senftle, F.E.; Reinhardt, J.L.

1988-01-01

Vivianite [Fe3(PO4)2??8H2O] is often found in the form of nodules composed of spherical aggregates of crystals. Crystallization of vivianite in agar gels of various concentrations yield crystal aggregates (nodules) that have spherical morphology and a bimodal size distribution. The aggregates were formed under both biotic and abiotic conditions. When special redox cells fitted with electrodes were used, more perfect spherical structures were formed when the electrodes were shorted than when they were on open circuit. In nature, vivianite nodules generally are found in sediments or clays that are gelatinous, often caused by the presence of organic debris. A model consistent with experimental observations and based on the dynamics of gels is proposed to explain a possible origin of nodular vivianite. To maintain iron and phosphate concentrations in sedimentary pore spaces filled with gel-like organic debris, the electric field spanning the aerobic-anerobic zones in the upper sediments may be an important driving force in addition to diffusion. It is suggested that the combination of the gel medium in the pore spaces and the natural electric field in the upper sediments could be contributing causes to explain the spherical aggregates of vivianite crystals found in nature. ?? 1988.

Habit modification of bis-thiourea zinc chloride (ZTC) semi organic crystals by impurities

NASA Astrophysics Data System (ADS)

Ruby Nirmala, L.; Thomas Joseph Prakash, J.

2013-06-01

Single crystals of bis-thiourea zinc chloride (ZTC) doped with metal ion (Li+) possess excellent nonlinear optical properties. These crystals were grown by slow evaporation solution growth technique. The effect of Li+ dopant on the growth and properties of ZTC single crystal were investigated and reported. The grown crystals were crystallized in orthorhombic structure with non-centro symmetric space group Pn21a through the parent compound. The amount of dopant incorporated in the parent crystal was revealed by the inductively coupled plasma (ICP-OES) studies. The FT-IR spectroscopy study was done for finding and confirming the functional groups present in the compound. The UV-Visible spectral study was carried out to find the optical behavior and transparency nature of the grown crystal. TG/DTA measurements and Vickers microhardness measurements were traced to find out the thermal and mechanical stability of the grown crystals respectively. Using Nd:YAG laser, the Second harmonic generation (SHG) for the grown crystals were confirmed.

Ultra-Rapid Crystallization of L-alanine Using Monomode Microwaves, Indium Tin Oxide and Metal-Assisted and Microwave-Accelerated Evaporative Crystallization.

PubMed

Lansiquot, Carisse; Boone-Kukoyi, Zainab; Shortt, Raquel; Thompson, Nishone; Ajifa, Hillary; Kioko, Bridgit; Constance, Edward Ned; Clement, Travis; Ozturk, Birol; Aslan, Kadir

2017-01-01

The use of indium tin oxide (ITO) and focused monomode microwave heating for the ultra-rapid crystallization of L-alanine (a model amino acid) is reported. Commercially available ITO dots (< 5 mm) attached to blank poly(methyl)methacrylate (PMMA, 5 cm in diameter with 21-well silicon isolators: referred to as the iCrystal plates) were found to withstand prolonged microwave heating during crystallization experiments. Crystallization of L-alanine was performed at room temperature (a control experiment), with the use of two microwave sources: a 2.45 GHz conventional microwave (900 W, power level 1, a control experiment) and 8 GHz (20 W) solid state, monomode microwave source with an applicator tip that focuses the microwave field to a 5-mm cavity. Initial appearance of L-alanine crystals and on iCrystal plates with ITO dots took 47 ± 2.9 min, 12 ± 7.6 min and 1.5 ± 0.5 min at room temperature, using a conventional microwave and focused monomode microwave heating, respectively. Complete evaporation of the solvent using the focused microwaves was achieved in 3.2 ± 0.5 min, which is ~52-fold and ~172-fold faster than that observed at room temperature and using conventional microwave heating, respectively. The size and number of L-alanine crystals was dependent on the type of the 21-well iCrystal plates and the microwave heating method: 33 crystals of 585 ± 137 μm in size at room temperature > 37 crystals of 542 ± 100 μm in size with conventional microwave heating > 331 crystals of 311 ± 190 μm in size with focused monomode microwave. FTIR, optical microscopy and powder X-ray diffraction analysis showed that the chemical composition and crystallinity of the L-alanine crystals did not change when exposed to microwave heating and ITO surfaces. In addition, theoretical simulations for the binding of L-alanine molecules to ITO and other metals showed the predicted nature of hydrogen bonds formed between L-alanine and these surfaces.

Ultra-Rapid Crystallization of L-alanine Using Monomode Microwaves, Indium Tin Oxide and Metal-Assisted and Microwave-Accelerated Evaporative Crystallization

PubMed Central

Lansiquot, Carisse; Boone-Kukoyi, Zainab; Shortt, Raquel; Thompson, Nishone; Ajifa, Hillary; Kioko, Bridgit; Constance, Edward Ned; Clement, Travis; Ozturk, Birol; Aslan, Kadir

2018-01-01

The use of indium tin oxide (ITO) and focused monomode microwave heating for the ultra-rapid crystallization of L-alanine (a model amino acid) is reported. Commercially available ITO dots (< 5 mm) attached to blank poly(methyl)methacrylate (PMMA, 5 cm in diameter with 21-well silicon isolators: referred to as the iCrystal plates) were found to withstand prolonged microwave heating during crystallization experiments. Crystallization of L-alanine was performed at room temperature (a control experiment), with the use of two microwave sources: a 2.45 GHz conventional microwave (900 W, power level 1, a control experiment) and 8 GHz (20 W) solid state, monomode microwave source with an applicator tip that focuses the microwave field to a 5-mm cavity. Initial appearance of L-alanine crystals and on iCrystal plates with ITO dots took 47 ± 2.9 min, 12 ± 7.6 min and 1.5 ± 0.5 min at room temperature, using a conventional microwave and focused monomode microwave heating, respectively. Complete evaporation of the solvent using the focused microwaves was achieved in 3.2 ± 0.5 min, which is ~52-fold and ~172-fold faster than that observed at room temperature and using conventional microwave heating, respectively. The size and number of L-alanine crystals was dependent on the type of the 21-well iCrystal plates and the microwave heating method: 33 crystals of 585 ± 137 μm in size at room temperature > 37 crystals of 542 ± 100 μm in size with conventional microwave heating > 331 crystals of 311 ± 190 μm in size with focused monomode microwave. FTIR, optical microscopy and powder X-ray diffraction analysis showed that the chemical composition and crystallinity of the L-alanine crystals did not change when exposed to microwave heating and ITO surfaces. In addition, theoretical simulations for the binding of L-alanine molecules to ITO and other metals showed the predicted nature of hydrogen bonds formed between L-alanine and these surfaces. PMID:29657884

Crystallization and preliminary X-ray crystallographic analysis of the cysteine protease inhibitor clitocypin

DOE Office of Scientific and Technical Information (OSTI.GOV)

Galeša, Katja; Brzin, Jože; Sabotič, Jerica

2006-01-01

Clitocypin is a cysteine protease inhibitor from the mushroom Clitocybe nebularis. The protein has been purified from natural sources and crystallized in a variety of non-isomorphous forms belonging to monoclinic and triclinic space groups. Clitocypin is a cysteine protease inhibitor from the mushroom Clitocybe nebularis. The protein has been purified from natural sources and crystallized in a variety of non-isomorphous forms belonging to monoclinic and triclinic space groups. A diffraction data set to 1.55 Å resolution was obtained from a crystal belonging to space group P2, with unit-cell parameters a = 38.326, b = 33.597, c = 55.568 Å, βmore » = 104°. An inability to achieve isomorphism forced the use of MAD and SAD phasing methods. Phasing is in progress.« less

Constitutive and life modeling of single crystal blade alloys for root attachment analysis

NASA Technical Reports Server (NTRS)

Meyer, T. G.; Mccarthy, G. J.; Favrow, L. H.; Anton, D. L.; Bak, Joe

1988-01-01

Work to develop fatigue life prediction and constitutive models for uncoated attachment regions of single crystal gas turbine blades is described. At temperatures relevant to attachment regions, deformation is dominated by slip on crystallographic planes. However, fatigue crack initiation and early crack growth are not always observed to be crystallographic. The influence of natural occurring microporosity will be investigated by testing both hot isostatically pressed and conventionally cast PWA 1480 single crystal specimens. Several differnt specimen configurations and orientations relative to the natural crystal axes are being tested to investigate the influence of notch acuity and the material's anisotropy. Global and slip system stresses in the notched regions were determined from three dimensional stress analyses and will be used to develop fatigue life prediction models consistent with the observed lives and crack characteristics.

Numerical simulation of flow and mass transfer for large KDP crystal growth via solution-jet method

NASA Astrophysics Data System (ADS)

Yin, Huawei; Li, Mingwei; Hu, Zhitao; Zhou, Chuan; Li, Zhiwei

2018-06-01

A novel technique of growing large crystals of potassium dihydrogen phosphate (KDP) named solution-jet method is proposed. The aim is to increase supersaturation on the pyramidal face, especially for crystal surface regions close to the rotation axis. The fluid flow and surface supersaturation distribution of crystals grown under different conditions were computed using the finite-volume method. Results indicate that the time-averaged supersaturation of the pyramidal face in the proposed method significantly increases and the supersaturation difference from the crystal center to edge clearly decreases compared with the rotating-crystal method. With increased jet velocity, supersaturation on the pyramidal face steadily increases. Rotation rate considerably affects the magnitude and distribution of the prismatic surface supersaturation. With increased crystal size, the mean value of surface supersaturation averaged over the pyramid gradually decreases; conversely, standard deviation increases, which is detrimental to crystal growth. Moreover, the significant roles played by natural and forced convection in the process of mass transport are discussed. Results show that further increased jet velocity to 0.6 m/s renders negligible the effects of natural convection around the pyramid. The simulation for step propagation indicates that solution-jet method can promote a steady step migration and enhance surface morphology stability, which can improve the crystal quality.

A strategic approach to physico-chemical analysis of bis (thiourea) lead chloride - A reliable semi-organic nonlinear optical crystal

NASA Astrophysics Data System (ADS)

Rajagopalan, N. R.; Krishnamoorthy, P.; Jayamoorthy, K.

2017-03-01

Good quality crystals of bis thiourea lead chloride (BTLC) have been grown by slow evaporation method from aqueous solution. Orthorhombic structure and Pna21 space group of the crystals have been identified by single crystal X-ray diffraction. Studies on nucleation kinetics of grown BTLC has been carried out from which meta-stable zone width, induction period, free energy change, critical radius, critical number and growth rate have been calculated. The experimental values of interfacial surface energy for the crystal growth process have been compared with theoretical models. Ultra violet transmittance studies resulted in a high transmittance and wide band gap energy suggested the required optical transparency of the crystal. The second harmonic generation (SHG) and phase matching nature of the crystal have been justified by Kurtz-Perry method. The SHG nature of the crystal has been further attested by the higher values of theoretical hyper polarizability. The dielectric nature of the crystals at different temperatures with varying frequencies has been thoroughly studied. The activation energy values of the electrical process have been calculated from ac conductivity study. Solid state parameters including valence electron plasma energy, Penn gap, Fermi energy and polarisability have been unveiled by theoretical approach and correlated with the crystal's SHG efficiency. The values of hardness number, elastic stiffness constant, Meyer's Index, minimum level of indentation load, load dependent constant, fracture toughness, brittleness index and corrected hardness obtained from Vicker's hardness test clearly showed that the BTLC crystal has good mechanical stability required for NLO device fabrication.

Modeling ultrasonic compression wave absorption during the seeded crystallization of copper (II) sulphate pentahydrate from aqueous solution.

PubMed

Marshall, Thomas; Challis, Richard E; Holmes, Andrew K; Tebbutt, John S

2002-11-01

Ultrasonic compression wave absorption is investigated as a means to monitor the seeded crystallization of copper (II) sulphate pentahydrate from aqueous solution. Simple models are applied to predict crystal yield, crystal size distribution, and the changing nature of the continuous phase. The Allegra-Hawley scattering formulation is used to simulate ultrasonic absorption as crystallization proceeds. Experiments confirm that simulated attenuation is in agreement with measured results.

Visualization of boundary-layer development on turbomachine blades with liquid crystals

NASA Technical Reports Server (NTRS)

Vanzante, Dale E.; Okiishi, Theodore H.

1991-01-01

This report documents a study of the use of liquid crystals to visualize boundary layer development on a turbomachine blade. A turbine blade model in a linear cascade of blades was used for the tests involved. Details of the boundary layer development on the suction surface of the turbine blade model were known from previous research. Temperature sensitive and shear sensitive liquid crystals were tried as visual agents. The temperature sensitive crystals were very effective in their ability to display the location of boundary layer flow separation and reattachment. Visualization of natural transition from laminar to turbulent boundary layer flow with the temperature sensitive crystals was possible but subtle. The visualization of separated flow reattachment with the shear sensitive crystals was easily accomplished when the crystals were allowed to make a transition from the focal-conic to a Grandjean texture. Visualization of flow reattachment based on the selective reflection properties of shear sensitive crystals was achieved only marginally because of the larger surface shear stress and shear stress gradient levels required for more dramatic color differences.

Effects of Humidity and Surfaces on the Melt Crystallization of Ibuprofen

PubMed Central

Lee, Dong-Joo; Lee, Suyang; Kim, Il Won

2012-01-01

Melt crystallization of ibuprofen was studied to understand the effects of humidity and surfaces. The molecular self-assembly during the amorphous-to-crystal transformation was examined in terms of the nucleation and growth of the crystals. The crystallization was on Al, Au, and self-assembled monolayers with –CH3, –OH, and –COOH functional groups. Effects of the humidity were studied at room temperature (18–20 °C) with relative humidity 33%, 75%, and 100%. Effects of the surfaces were observed at −20 °C (relative humidity 36%) to enable close monitoring with slower crystal growth. The nucleation time of ibuprofen was faster at high humidity conditions probably due to the local formation of the unfavorable ibuprofen melt/water interface. The crystal morphologies of ibuprofen were governed by the nature of the surfaces, and they could be associated with the growth kinetics by the Avrami equation. The current study demonstrated the effective control of the melt crystallization of ibuprofen through the melt/atmosphere and melt/surface interfaces. PMID:22949861

Crystal Quality, the Long and the Short of It

NASA Technical Reports Server (NTRS)

Snell, Eddie H.

2004-01-01

The term "crystal quality" is ambiguous and implies different meanings to different crystallographers. For the physical crystallographer who aims to understand long-range aspects of crystal growth mosaicity is one of the leading measures of perfection. For the structural crystallographer and those seeking to understand growth at a short-range, molecular level, the detail in the resulting structure is a key goal. Different quality measures have been developed due to different needs. Each of the measures has advantages and each has limitations. In this talk a sample of these measures will be discussed with particular emphasis applied to their application in the analysis of microgravity grown crystals. The advantages and limitations of each will be discussed. Ultimately, the choice of crystal quality measurement lies in the nature of the question asked. It is scfill to remember that beauty is often in the eye of the beholder.

Single crystalline hollow metal-organic frameworks: a metal-organic polyhedron single crystal as a sacrificial template.

PubMed

Kim, Hyehyun; Oh, Minhak; Kim, Dongwook; Park, Jeongin; Seong, Junmo; Kwak, Sang Kyu; Lah, Myoung Soo

2015-02-28

Single crystalline hollow metal-organic frameworks (MOFs) with cavity dimensions on the order of several micrometers and hundreds of micrometers were prepared using a metal-organic polyhedron single crystal as a sacrificial hard template. The hollow nature of the MOF crystal was confirmed by scanning electron microscopy of the crystal sliced using a focused ion beam.

Inexpensive Electrooptic Experiments on Liquid Crystal Displays.

ERIC Educational Resources Information Center

Ciferno, Thomas M.; And Others

1995-01-01

Describes the construction and use of an electrooptic apparatus that can be incorporated into the classroom to test liquid crystal displays (LCDs) and introduce students to experiments of an applied physics nature with very practical implications. Presents experiments that give students hands-on experience with technologies of current interest to…

Two-dimensional crystals: managing light for optoelectronics.

PubMed

Eda, Goki; Maier, Stefan A

2013-07-23

Semiconducting two-dimensional (2D) crystals such as MoS2 and WSe2 exhibit unusual optical properties that can be exploited for novel optoelectronics ranging from flexible photovoltaic cells to harmonic generation and electro-optical modulation devices. Rapid progress of the field, particularly in the growth area, is beginning to enable ways to implement 2D crystals into devices with tailored functionalities. For practical device performance, a key challenge is to maximize light-matter interactions in the material, which is inherently weak due to its atomically thin nature. Light management around the 2D layers with the use of plasmonic nanostructures can provide a compelling solution.

Weyl points and Fermi arcs in a chiral phononic crystal

NASA Astrophysics Data System (ADS)

Li, Feng; Huang, Xueqin; Lu, Jiuyang; Ma, Jiahong; Liu, Zhengyou

2018-01-01

Topological semimetals are materials whose band structure contains touching points that are topologically nontrivial and can host quasiparticle excitations that behave as Dirac or Weyl fermions. These so-called Weyl points not only exist in electronic systems, but can also be found in artificial periodic structures with classical waves, such as electromagnetic waves in photonic crystals and acoustic waves in phononic crystals. Due to the lack of spin and a difficulty in breaking time-reversal symmetry for sound, however, topological acoustic materials cannot be achieved in the same way as electronic or optical systems. And despite many theoretical predictions, experimentally realizing Weyl points in phononic crystals remains challenging. Here, we experimentally realize Weyl points in a chiral phononic crystal system, and demonstrate surface states associated with the Weyl points that are topological in nature, and can host modes that propagate only in one direction. As with their photonic counterparts, chiral phononic crystals bring topological physics to the macroscopic scale.

Predicting crystal growth via a unified kinetic three-dimensional partition model

NASA Astrophysics Data System (ADS)

Anderson, Michael W.; Gebbie-Rayet, James T.; Hill, Adam R.; Farida, Nani; Attfield, Martin P.; Cubillas, Pablo; Blatov, Vladislav A.; Proserpio, Davide M.; Akporiaye, Duncan; Arstad, Bjørnar; Gale, Julian D.

2017-04-01

Understanding and predicting crystal growth is fundamental to the control of functionality in modern materials. Despite investigations for more than one hundred years, it is only recently that the molecular intricacies of these processes have been revealed by scanning probe microscopy. To organize and understand this large amount of new information, new rules for crystal growth need to be developed and tested. However, because of the complexity and variety of different crystal systems, attempts to understand crystal growth in detail have so far relied on developing models that are usually applicable to only one system. Such models cannot be used to achieve the wide scope of understanding that is required to create a unified model across crystal types and crystal structures. Here we describe a general approach to understanding and, in theory, predicting the growth of a wide range of crystal types, including the incorporation of defect structures, by simultaneous molecular-scale simulation of crystal habit and surface topology using a unified kinetic three-dimensional partition model. This entails dividing the structure into ‘natural tiles’ or Voronoi polyhedra that are metastable and, consequently, temporally persistent. As such, these units are then suitable for re-construction of the crystal via a Monte Carlo algorithm. We demonstrate our approach by predicting the crystal growth of a diverse set of crystal types, including zeolites, metal-organic frameworks, calcite, urea and L-cystine.

Crystal-to-Crystal Transition of Ultrasoft Colloids under Shear

NASA Astrophysics Data System (ADS)

Ruiz-Franco, J.; Marakis, J.; Gnan, N.; Kohlbrecher, J.; Gauthier, M.; Lettinga, M. P.; Vlassopoulos, D.; Zaccarelli, E.

2018-02-01

Ultrasoft colloids typically do not spontaneously crystallize, but rather vitrify, at high concentrations. Combining in situ rheo-small-angle-neutron-scattering experiments and numerical simulations we show that shear facilitates crystallization of colloidal star polymers in the vicinity of their glass transition. With increasing shear rate well beyond rheological yielding, a transition is found from an initial bcc-dominated structure to an fcc-dominated one. This crystal-to-crystal transition is not accompanied by intermediate melting but occurs via a sudden reorganization of the crystal structure. Our results provide a new avenue to tailor colloidal crystallization and the crystal-to-crystal transition at the molecular level by coupling softness and shear.

Crystallization tendency of active pharmaceutical ingredients following rapid solvent evaporation--classification and comparison with crystallization tendency from undercooled melts.

PubMed

Van Eerdenbrugh, Bernard; Baird, Jared A; Taylor, Lynne S

2010-09-01

In this study, the crystallization behavior of a variety of compounds was studied following rapid solvent evaporation using spin coating. Initial screening to determine model compound suitability was performed using a structurally diverse set of 51 compounds in three different solvent systems [dichloromethane (DCM), a 1:1 (w/w) dichloromethane/ethanol mixture (MIX), and ethanol (EtOH)]. Of this starting set of 153 drug-solvent combinations, 93 (40 compounds) were selected for further evaluation based on solubility, chemical solution stability, and processability criteria. These systems were spin coated and their crystallization was monitored using polarized light microscopy (7 days, dry conditions). The crystallization behavior of the samples could be classified as rapid (Class I: 39 cases), intermediate (Class II: 23 cases), or slow (Class III: 31 cases). The solvent system employed influenced the classification outcome for only four of the compounds. The various compounds showed very diverse crystallization behavior. Upon comparison of classification results with those of a previous study, where cooling from the melt was used as a preparation technique, a good similarity was found whereby 68% of the cases were identically classified. Multivariate analysis was performed using a set of relevant physicochemical compound characteristics. It was found that a number of these parameters tended to differ between the different classes. These could be further interpreted in terms of the nature of the crystallization process. Additional multivariate analysis on the separate classes of compounds indicated some potential in predicting the crystallization tendency of a given compound.

Vacuum lamination approach to fabrication of high-performance single-crystal organic field-effect transistors.

PubMed

Yi, H T; Chen, Y; Czelen, K; Podzorov, V

2011-12-22

A novel vacuum lamination approach to fabrication of high-performance single-crystal organic field-effect transistors has been developed. The non-destructive nature of this method allows a direct comparison of field-effect mobilities achieved with various gate dielectrics using the same single-crystal sample. The method also allows gating delicate systems, such as n -type crystals and SAM-coated surfaces, without perturbation. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The crystallization behavior and kinetics of a barium fluorozirconate type glass

NASA Technical Reports Server (NTRS)

Neilson, G. F.; Smith, G. L.; Weinberg, M. C.

1984-01-01

An investigation of the crystallization behavior of a Zr-Ba-La-Al-F glass which is subjected to isothermal heat treatments is presented. The number and nature of the crystalline phases which form and their nucleation sites are determined at three temperatures. Also, the growth rate and volume fraction of crystals which nucleate internally in the glass, when heated at 320 C, are determined as a function of time.

Role of local assembly in the hierarchical crystallization of associating colloidal hard hemispheres

NASA Astrophysics Data System (ADS)

Lei, Qun-li; Hadinoto, Kunn; Ni, Ran

2017-10-01

Hierarchical self-assembly consisting of local associations of simple building blocks for the formation of complex structures widely exists in nature, while the essential role of local assembly remains unknown. In this work, by using computer simulations, we study a simple model system consisting of associating colloidal hemispheres crystallizing into face-centered-cubic crystals comprised of spherical dimers of hemispheres, focusing on the effect of dimer formation on the hierarchical crystallization. We found that besides assisting the crystal nucleation because of increasing the symmetry of building blocks, the association between hemispheres can also induce both reentrant melting and reentrant crystallization depending on the range of interaction. Especially when the interaction is highly sticky, we observe a novel reentrant crystallization of identical crystals, which melt only in a certain temperature range. This offers another axis in fabricating responsive crystalline materials by tuning the fluctuation of local association.

Better than Nature: Nicotinamide Biomimetics That Outperform Natural Coenzymes

PubMed Central

2016-01-01

The search for affordable, green biocatalytic processes is a challenge for chemicals manufacture. Redox biotransformations are potentially attractive, but they rely on unstable and expensive nicotinamide coenzymes that have prevented their widespread exploitation. Stoichiometric use of natural coenzymes is not viable economically, and the instability of these molecules hinders catalytic processes that employ coenzyme recycling. Here, we investigate the efficiency of man-made synthetic biomimetics of the natural coenzymes NAD(P)H in redox biocatalysis. Extensive studies with a range of oxidoreductases belonging to the “ene” reductase family show that these biomimetics are excellent analogues of the natural coenzymes, revealed also in crystal structures of the ene reductase XenA with selected biomimetics. In selected cases, these biomimetics outperform the natural coenzymes. “Better-than-Nature” biomimetics should find widespread application in fine and specialty chemicals production by harnessing the power of high stereo-, regio-, and chemoselective redox biocatalysts and enabling reactions under mild conditions at low cost. PMID:26727612

Crystal growth of triphenylphosphine oxide 4-nitrophenol (TP4N) for nonlinear optical (NLO) applications

NASA Astrophysics Data System (ADS)

Pandian, Muthu Senthil; Karuppasamy, P.; Kamalesh, T.; Ramasamy, P.; Verma, Sunil

2018-04-01

The optically good quality organic single crystals of triphenylphosphine oxide 4-nitrophenol (TP4N) were successfully grown by slow evaporation solution technique (SEST) using methanol as solvent. The lattice parameters of the grown crystal were confirmed by single crystal X-ray diffraction analysis. The optical transmittance, cut-off wavelength and band gap of the TP4N crystal were obtained by UV-Vis NIR spectrum analysis. The photoluminescence studies were carried out to find out the luminesce properties of TP4N single crystal. The photoconductivity studies reveal that the TP4N crystal has negative photoconductive nature. The third order nonlinear susceptibility (χ(3)) of TP4N crystal was evaluated using the Z-scan technique at 640 nm.

Crystal chemistry and temperature behavior of the natural hydrous borate colemanite, a mineral commodity of boron

NASA Astrophysics Data System (ADS)

Lotti, Paolo; Gatta, G. Diego; Demitri, Nicola; Guastella, Giorgio; Rizzato, Silvia; Ortenzi, Marco Aldo; Magrini, Fabrizio; Comboni, Davide; Guastoni, Alessandro; Fernandez-Diaz, Maria Teresa

2018-05-01

Colemanite, CaB3O4(OH)3ṡH2O, is the most common hydrous Ca-borate, as well as a major mineral commodity of boron. In this study, we report a thorough chemical analysis and the low-temperature behavior of a natural sample of colemanite by means of a multi-methodological approach. From the chemical point of view, the investigated sample resulted to be relatively pure, its composition being very close to the ideal one, with only a minor substitution of Sr2+ for Ca2+. At about 270.5 K, a displacive phase transition from the centrosymmetric P21/ a to the acentric P21 space group occurs. On the basis of in situ single-crystal synchrotron X-ray (down to 104 K) and neutron diffraction (at 20 K) data, the hydrogen-bonding configuration of both the polymorphs and the structural modifications at the atomic scale at varying temperatures are described. The asymmetric distribution of ionic charges along the [010] axis, allowed by the loss of the inversion center, is likely responsible for the reported ferroelectric behavior of colemanite below the phase transition temperature.

Organic field-effect transistors using single crystals

PubMed Central

Hasegawa, Tatsuo; Takeya, Jun

2009-01-01

Organic field-effect transistors using small-molecule organic single crystals are developed to investigate fundamental aspects of organic thin-film transistors that have been widely studied for possible future markets for ‘plastic electronics’. In reviewing the physics and chemistry of single-crystal organic field-effect transistors (SC-OFETs), the nature of intrinsic charge dynamics is elucidated for the carriers induced at the single crystal surfaces of molecular semiconductors. Materials for SC-OFETs are first reviewed with descriptions of the fabrication methods and the field-effect characteristics. In particular, a benchmark carrier mobility of 20–40 cm2 Vs−1, achieved with thin platelets of rubrene single crystals, demonstrates the significance of the SC-OFETs and clarifies material limitations for organic devices. In the latter part of this review, we discuss the physics of microscopic charge transport by using SC-OFETs at metal/semiconductor contacts and along semiconductor/insulator interfaces. Most importantly, Hall effect and electron spin resonance (ESR) measurements reveal that interface charge transport in molecular semiconductors is properly described in terms of band transport and localization by charge traps. PMID:27877287

Invariant patterns in crystal lattices: Implications for protein folding algorithms

DOE Office of Scientific and Technical Information (OSTI.GOV)

HART,WILLIAM E.; ISTRAIL,SORIN

2000-06-01

Crystal lattices are infinite periodic graphs that occur naturally in a variety of geometries and which are of fundamental importance in polymer science. Discrete models of protein folding use crystal lattices to define the space of protein conformations. Because various crystal lattices provide discretizations of the same physical phenomenon, it is reasonable to expect that there will exist invariants across lattices related to fundamental properties of the protein folding process. This paper considers whether performance-guaranteed approximability is such an invariant for HP lattice models. The authors define a master approximation algorithm that has provable performance guarantees provided that a specificmore » sublattice exists within a given lattice. They describe a broad class of crystal lattices that are approximable, which further suggests that approximability is a general property of HP lattice models.« less

Magnetic Control of Convection during Protein Crystallization

NASA Technical Reports Server (NTRS)

Ramachandran, N.; Leslie, F. W.

2004-01-01

An important component in biotechnology, particularly in the area of protein engineering and rational drug design is the knowledge of the precise three-dimensional molecular structure of proteins. The quality of structural information obtained from X-ray diffraction methods is directly dependent on the degree of perfection of the protein crystals. As a consequence, the growth of high quality macromolecular Crystals for diffraction analyses has been the central focus for bio-chemists, biologists, and bioengineers. Macromolecular crystals are obtained from solutions that contain the crystallizing species in equilibrium with higher aggregates, ions, precipitants, other possible phases of the protein, foreign particles, the walls of container, and a likely host of other impurities. By changing transport modes in general, i.e., reduction of convection and Sedimentation as is achieved in "microgravity", we have been able to dramatically affect the movement and distribution of macromolecules in the fluid, and thus their transport, f o d o n of crystal nuclei, and adsorption to the crystal surface. While a limited number of high quality crystals from space flights have been obtained, as the recent National Research Council (NRC) review of the NASA microgravity crystallization program pointed out, the scientific approach and research in crystallization of proteins has been mainly empirical yielding inconclusive results. We postulate that we can reduce convection in ground-based experiments and we can understand the different aspects of convection control through the use of strong magnetic fields and field gradients. We postulate that limited convection in a magnetic field will provide the environment for the growth of high quality crystals. The approach exploits the variation of fluid magnetic susceptibility with counteracts on for this purpose and the convective damping is realized by appropriately positioning the crystal growth cell so that the magnetic susceptibility

Habit modification of bis-thiourea zinc chloride (ZTC) semi organic crystals by impurities.

PubMed

Ruby Nirmala, L; Thomas Joseph Prakash, J

2013-06-01

Single crystals of bis-thiourea zinc chloride (ZTC) doped with metal ion (Li(+)) possess excellent nonlinear optical properties. These crystals were grown by slow evaporation solution growth technique. The effect of Li(+) dopant on the growth and properties of ZTC single crystal were investigated and reported. The grown crystals were crystallized in orthorhombic structure with non-centro symmetric space group Pn21a through the parent compound. The amount of dopant incorporated in the parent crystal was revealed by the inductively coupled plasma (ICP-OES) studies. The FT-IR spectroscopy study was done for finding and confirming the functional groups present in the compound. The UV-Visible spectral study was carried out to find the optical behavior and transparency nature of the grown crystal. TG/DTA measurements and Vickers microhardness measurements were traced to find out the thermal and mechanical stability of the grown crystals respectively. Using Nd:YAG laser, the Second harmonic generation (SHG) for the grown crystals were confirmed. Copyright © 2013 Elsevier B.V. All rights reserved.

A generalized crystal-cutting method for modeling arbitrarily oriented crystals in 3D periodic simulation cells with applications to crystal-crystal interfaces

NASA Astrophysics Data System (ADS)

Kroonblawd, Matthew P.; Mathew, Nithin; Jiang, Shan; Sewell, Thomas D.

2016-10-01

A Generalized Crystal-Cutting Method (GCCM) is developed that automates construction of three-dimensionally periodic simulation cells containing arbitrarily oriented single crystals and thin films, two-dimensionally (2D) infinite crystal-crystal homophase and heterophase interfaces, and nanostructures with intrinsic N-fold interfaces. The GCCM is based on a simple mathematical formalism that facilitates easy definition of constraints on cut crystal geometries. The method preserves the translational symmetry of all Bravais lattices and thus can be applied to any crystal described by such a lattice including complicated, low-symmetry molecular crystals. Implementations are presented with carefully articulated combinations of loop searches and constraints that drastically reduce computational complexity compared to simple loop searches. Orthorhombic representations of monoclinic and triclinic crystals found using the GCCM overcome some limitations in standard distributions of popular molecular dynamics software packages. Stability of grain boundaries in β-HMX was investigated using molecular dynamics and molecular statics simulations with 2D infinite crystal-crystal homophase interfaces created using the GCCM. The order of stabilities for the four grain boundaries studied is predicted to correlate with the relative prominence of particular crystal faces in lab-grown β-HMX crystals. We demonstrate how nanostructures can be constructed through simple constraints applied in the GCCM framework. Example GCCM constructions are shown that are relevant to some current problems in materials science, including shock sensitivity of explosives, layered electronic devices, and pharmaceuticals.

Electrochemical growth of linear conducting crystals in microgravity

NASA Technical Reports Server (NTRS)

Cronise, Raymond J., IV

1988-01-01

Much attention has been given to the synthesis of linear conducting materials. These inorganic, organic, and polymeric materials have some very interesting electrical and optical properties, including low temperature superconductivity. Because of the anisotropic nature of these compounds, impurities and defects strongly influences the unique physical properties of such crystals. Investigations have demonstrated that electrochemical growth has provided the most reproducible and purest crystals. Space, specifically microgravity, eliminates phenomena such as buoyancy driven convection, and could permit formation of crystals many times purer than the ones grown to date. Several different linear conductors were flown on Get Away Special G-007 on board the Space Shuttle Columbia, STS 61-C, the first of a series of Project Explorer payloads. These compounds were grown by electrochemical methods, and the growth was monitored by photographs taken throughout the mission. Due to some thermal problems, no crystals of appreciable size were grown. The experimental results will be incorporated into improvements for the next 2 missions of Project Explorer. The results and conclusions of the first mission are discussed.

Intangible pointlike tracers for liquid-crystal-based microsensors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brasselet, Etienne; Juodkazis, Saulius

2010-12-15

We propose an optical detection technique for liquid-crystal-based sensors that is based on polarization-resolved tracking of optical singularities and does not rely on standard observation of light-intensity changes caused by modifications of the liquid crystal orientational ordering. It uses a natural two-dimensional network of polarization singularities embedded in the transverse cross section of a probe beam that passes through a liquid crystal sample, in our case, a nematic droplet held in laser tweezers. The identification and spatial evolution of such a topological fingerprint is retrieved from subwavelength polarization-resolved imaging, and the mechanical constraint exerted on the molecular ordering by themore » trapping beam itself is chosen as the control parameter. By restricting our analysis to one type of point singularity, C points, which correspond to location in space where the polarization azimuth is undefined, we show that polarization singularities appear as intangible pointlike tracers for liquid-crystal-based three-dimensional microsensors. The method has a superresolution potential and can be used to visualize changes at the nanoscale.« less

Uncovering the inertia of dislocation motion and negative mechanical response in crystals.

PubMed

Tang, Yizhe

2018-01-09

Dislocations are linear defects in crystals and their motion controls crystals' mechanical behavior. The dissipative nature of dislocation propagation is generally accepted although the specific mechanisms are still not fully understood. The inertia, which is undoubtedly the nature of motion for particles with mass, seems much less convincing for configuration propagation. We utilize atomistic simulations in conditions that minimize dissipative effects to enable uncovering of the hidden nature of dislocation motion, in three typical model metals Mg, Cu and Ta. We find that, with less/no dissipation, dislocation motion is under-damped and explicitly inertial at both low and high velocities. The inertia of dislocation motion is intrinsic, and more fundamental than the dissipative nature. The inertia originates from the kinetic energy imparted from strain energy and stored in the moving core. Peculiar negative mechanical response associated with the inertia is also discovered. These findings shed light on the fundamental nature of dislocation motion, reveal the underlying physics, and provide a new physical explanation for phenomena relevant to high-velocity dislocations.

Modeling elasticity in crystal growth.

PubMed

Elder, K R; Katakowski, Mark; Haataja, Mikko; Grant, Martin

2002-06-17

A new model of crystal growth is presented that describes the phenomena on atomic length and diffusive time scales. The former incorporates elastic and plastic deformation in a natural manner, and the latter enables access to time scales much larger than conventional atomic methods. The model is shown to be consistent with the predictions of Read and Shockley for grain boundary energy, and Matthews and Blakeslee for misfit dislocations in epitaxial growth.

Crystal Growth of ZnSe and Related Ternary Compound Semiconductors by Vapor Transport

NASA Technical Reports Server (NTRS)

Su, Ching-Hua; Brebrick, Robert F.; Volz, Martin P.; Burger, Arnold; Dudley, Michael; Matyi, Richard J.; Ramachandran, Narayanan; Sha, Yi-Gao; Volz, Martin P.; Shih, Hung-Dah

2001-01-01

Crystal growth by vapor transport has several distinct advantages over melt growth techniques. Among various potential benefits from material processing in reduced gravity the followings two are considered to be related to crystal growth by vapor transport: (1) elimination of the crystal weight and its influence on the defect formation and (2) reduction of natural buoyancy-driven convective flows arising from thermally and/ or solutally induced density gradient in fluids. The previous results on vapor crystal growth of semiconductors showed the improvements in surface morphology, crystalline quality, electrical properties and dopant distribution of the crystals grown in reduced gravity as compared to the crystals grown on Earth. But the mechanisms, which are responsible for the improvements and cause the gravitational effects on the complicated and coupled processes of vapor mass transport and growth kinetics, are not well understood.

Geology of the Quartz Creek Pegmatite District, Gunnison County Colorado

USGS Publications Warehouse

Staatz, Mortimer H.; Trites, A.F.

1952-01-01

Inferred reserves of the district are estimated for beryl, scrap mica, both hand-cobbing and milling feldspar, lepidolite, columbite-tantalite, topaz, monazite, and microlite. No sheet mica was found. Reserves are small and transportation costs are high so substantial production of low-priced feldspar and scrap mica will depend on the adoption of economica milling techniques for recovering the large quantities of feldspar available.  Beryl is irregularly distributed and its recovery as a byproduct will depend on the establishment of a stable market for feldspar and scrap mica.  Lepidolite reserves are small low grade.

Photonic Crystals-Inhibited Spontaneous Emission: Optical Antennas-Enhanced Spontaneous Emission

NASA Astrophysics Data System (ADS)

Yablonovitch, Eli

Photonic crystals are also part of everyday technological life in opto-electronic telecommunication devices that provide us with internet, cloud storage, and email. But photonic crystals have also been identified in nature, in the coloration of peacocks, parrots, chameleons, butterflies and many other species.In spite of its broad applicability, the original motivation of photonic crystals was to create a ``bandgap'' in which the spontaneous emission of light would be inhibited. Conversely, the opposite is now possible. The ``optical antenna'' can accelerate spontaneous emission. Over 100 years after the radio antenna, we finally have tiny ``optical antennas'' which can act on molecules and quantum dots. Employing optical antennas, spontaneous light emission can become faster than stimulated emission.

Natural convection in melt crystal growth - The influence of flow pattern on solute segregation

NASA Technical Reports Server (NTRS)

Brown, R. A.; Yamaguchi, Y.; Chang, C. J.

1982-01-01

The results of two lines of research aimed at calculating the structure of the flows driven by buoyancy in small-scale crystal growth systems and at understanding the coupling between these flows, the shape of the solidification interface, and dopant segregation in the crystal are reviewed. First, finite-element methods are combined with computer-aided methods for detecting multiple steady solutions to analyze the structure of the buoyancy-driven axisymmetric flows in a vertical cylinder heated from below. This system exhibits onset of convection, multiple steady flows, and loss of the primary stable flow beyond a critical value of the Rayleigh number. Second, results are presented for calculations of convection, melt/solid interface shape, and dopant segregation within a vertical ampoule with thermal boundary conditions that represent a prototype of the vertical Bridgman growth system.

The Biological Macromolecule Crystallization Database and NASA Protein Crystal Growth Archive

PubMed Central

Gilliland, Gary L.; Tung, Michael; Ladner, Jane

1996-01-01

The NIST/NASA/CARB Biological Macromolecule Crystallization Database (BMCD), NIST Standard Reference Database 21, contains crystal data and crystallization conditions for biological macromolecules. The database entries include data abstracted from published crystallographic reports. Each entry consists of information describing the biological macromolecule crystallized and crystal data and the crystallization conditions for each crystal form. The BMCD serves as the NASA Protein Crystal Growth Archive in that it contains protocols and results of crystallization experiments undertaken in microgravity (space). These database entries report the results, whether successful or not, from NASA-sponsored protein crystal growth experiments in microgravity and from microgravity crystallization studies sponsored by other international organizations. The BMCD was designed as a tool to assist x-ray crystallographers in the development of protocols to crystallize biological macromolecules, those that have previously been crystallized, and those that have not been crystallized. PMID:11542472

The electric field gradient in natural iron-doped chrysoberyl Al2BeO4 and sinhalite MgAlBO4 single crystals

NASA Astrophysics Data System (ADS)

Lottermoser, Werner; Redhammer, Günther J.; Weber, Sven-Ulf; Litterst, Fred Jochen; Tippelt, Gerold; Dlugosz, Stephen; Bank, Hermann; Amthauer, Georg; Grodzicki, Michael

2011-12-01

This work reports on the evaluation of the electric field gradient (EFG) in natural chrysoberyl Al2BeO4 and sinhalite MgAlBO4 using two different procedures: (1) experimental, with single crystal Mössbauer spectroscopy (SCMBS) on the three principal sections of each sample and (2) a "fully quantitative" method with cluster molecular orbital calculations based on the density functional theory. Whereas the experimental and theoretical results for the EFG tensor are in quantitative agreement, the calculated isomer shifts and optical d-d-transitions exhibit systematic deviations from the measured values. These deviations indicate that the substitution of Al and Mg with iron should be accompanied by considerable local expansion of the coordination octahedra.

A new mineral species rossovskyite, (Fe3+,Ta)(Nb,Ti)O4: crystal chemistry and physical properties

NASA Astrophysics Data System (ADS)

Konovalenko, Sergey I.; Ananyev, Sergey A.; Chukanov, Nikita V.; Rastsvetaeva, Ramiza K.; Aksenov, Sergey M.; Baeva, Anna A.; Gainov, Ramil R.; Vagizov, Farit G.; Lopatin, Oleg N.; Nebera, Tatiana S.

2015-11-01

A new mineral rossovskyite named after L.N. Rossovsky was discovered in granite pegmatites of the Bulgut occurrence, Altai Mts., Western Mongolia. Associated minerals are microcline, muscovite, quartz, albite, garnet of the almandine-spessartine series, beryl, apatite, triplite, zircon, pyrite, yttrobetafite-(Y) and schorl. Rossovskyite forms flattened anhedral grains up to 6 × 6 × 2 cm. The color of the mineral is black, and the streak is black as well. The luster is semi-metallic, dull. Mohs hardness is 6. No cleavage or parting is observed. Rossovskyite is brittle, with uneven fracture. The density measured by the hydrostatic weighing method is 6.06 g/cm2, and the density calculated from the empirical formula is 6.302 g/cm3. Rossovskyite is biaxial, and the color in reflection is gray to dark gray. The IR spectrum contains strong band at 567 cm-1 (with shoulders at 500 and 600 cm-1) corresponding to cation-oxygen stretching vibrations and weak bands at 1093 and 1185 cm-1 assigned as overtones. The reflection spectrum in visible range is obtained. According to the Mössbauer spectrum, the ratio Fe2+:Fe3+ is 35.6:64.4. The chemical composition is as follows (electron microprobe, Fe apportioned between FeO and Fe2O3 based on Mössbauer data, wt%): MnO 1.68, FeO 5.92, Fe2O3 14.66, TiO2 7.69, Nb2O5 26.59, Ta2O5 37.51, WO3 5.61, total 99.66. The empirical formula calculated on four O atoms is: {{Mn}}_{0.06}^{2 + } {{Fe}}_{0.21}^{2 + } {{Fe}}_{0.47}^{3 + } Ti0.25Nb0.51Ta0.43W0.06O4. The crystal structure was determined using single-crystal X-ray diffraction data. The new mineral is monoclinic, space group P2/ c, a = 4.668(1), b = 5.659(1), c = 5.061(1) Å, β = 90.21(1)º; V = 133.70(4) Å3, Z = 2. Topologically, the structure of rossovskyite is analogous to that of wolframite-group minerals. The crystal-chemical formula of rossovskyite is [(Fe3+, Fe2+, Mn)0.57Ta0.32Nb0.11][Nb0.40Ti0.25Fe0.18Ta0.11W0.06]O4. The strongest lines of the powder X-ray diffraction pattern

Synthesis, growth and characterization of L-Phenylalaninium methanesulfonate nonlinear optical single crystal

NASA Astrophysics Data System (ADS)

Mangaiyarkarasi, K.; Ravichandran, A. T.; Anitha, K.; Manivel, A.

2018-03-01

The titled compound, L-Phenylalaninium methanesulfonate (LPA-MS) was synthesized and grown into single crystals by slow solvent evaporation solution growth technique in aqueous solution containing equimolar concentrations of L-phenylalanine and methanesulfonic acid at room temperature. The grown crystals were subjected to single crystal X-ray diffraction studies. It crystallizes in the monoclinic crystal structure with P21 space group and the unit cell parameters are a = 5.312 (10) Å, b = 8.883 (2) Å and c = 25.830 (7) Å. The functional groups of the LPA-MS crystal were confirmed with FT-IR and FT-Raman analysis. The carbon-hydrogen skeleton was confirmed with 1H NMR and 13C NMR analysis. TG-DTG and DSC studies were carried out to determine the thermal stability of the crystals. The optical transparency ranges were studied through UV-vis-spectroscopy and the crystal was found to be transparent in the visible region. The second Harmonic generation (SHG) efficiency of the grown LPA-MS crystal was measured by the Kurtz-Perry powder technique. The dipolar nature of the L-phenylalaninium methanesulfonate and the presence of the intermolecular hydrogen bonding between the molecules are the vital factors responsible for the existence of SHG activity in the crystal.

Morphological Features of Diamond Crystals Dissolved in Fe0.7S0.3 Melt at 4 GPa and 1400°C

NASA Astrophysics Data System (ADS)

Sonin, V. M.; Zhimulev, E. I.; Pomazanskiy, B. S.; Zemnuhov, A. L.; Chepurov, A. A.; Afanasiev, V. P.; Chepurov, A. I.

2018-01-01

An experimental study of the dissolution of natural and synthetic diamonds in a sulfur-bearing iron melt (Fe0.7S0.3) with high P-T parameters (4 GPa, 1400°C) was performed. The results demonstrated that under these conditions, octahedral crystals with flat faces and rounded tetrahexahedral diamond crystals are transformed into rounded octahedroids, which have morphological characteristics similar to those of natural diamonds from kimberlite. It was suggested that, taking into account the complex history of individual natural diamond crystals, including the dissolution stages, sulfur-bearing metal melts up to sulfide melts were not only diamond-forming media during the early evolution of the Earth, but also natural solvents of diamond in the mantle environment before the formation of kimberlitic melts.

The role of superheating in the formation of Glass Mountain obsidians (Long Valley, CA) inferred through crystallization of sanidine

NASA Astrophysics Data System (ADS)

Waters, Laura E.; Andrews, Benjamin J.

2016-10-01

The Glass Mountain obsidians (Long Valley, CA) are crystal poor (<8 vol%) and highly evolved (high SiO2, low Sr), and therefore, their formation required extremely efficient separation of melts from a crystal-rich source. A petrologic and experimental investigation of the mineral phases in Glass Mountain lavas identifies conditions under which phenocrysts grew and the driving mechanism for crystallization, which places constraints on the possible processes that generated the obsidians. The obsidian in this study (GM-11) is saturated in nine phases (sanidine + quartz + plagioclase + titanomagnetite + ilmenite + zircon + apatite + allanite + biotite), and results of high-resolution SEM compositional mapping and electron microprobe analysis reveal that individual sanidine crystals are normally zoned and span a range of compositions (Or40-78). Sanidines have a "granophyric" texture, characterized by intergrowths of quartz and sanidine. Mineral phases in the natural sample are compared to H2O-saturated phase equilibrium experiments conducted in cold-seal pressure vessels, over a range of conditions (700-850 °C; 75-225 MPa), and all are found to be plausible phenocrysts. Comparison of sanidine compositions from the natural sample with those grown in phase equilibrium experiments demonstrates that sanidine in the natural sample occurs in a reduced abundance. Further comparison with phase equilibrium experiments suggests that sanidine compositions track progressive loss of dissolved melt water (±cooling), suggesting that crystallization in the natural obsidian was driven predominantly by degassing resulting from decompression. It is paradoxical that an effusively (slowly) erupted lava should contain multiple phenocryst phases, including sanidine crystals that span a range of compositions with granophyric textures, and yet remain so crystal poor. To resolve this paradox, it is necessary that the solidification mechanism (degassing or cooling) that produced the sanidine

Adsorption mechanisms of the nonequilibrium incorporation of admixtures in a growing crystal

NASA Astrophysics Data System (ADS)

Franke, V. D.; Punin, Yu. O.; Smetannikova, O. G.; Kenunen, D. S.

2007-12-01

The nonequilibrium partition of components between a crystal and solution is mainly controlled by impurity adsorption on the surface of the growing crystal. The specificity of adsorption on the faces of various simple forms leads to the sectorial zoning of crystals. This effect was studied experimentally for several crystallizing systems with different impurities, including isomorphous, 2d-isomorphous, and nonisomorphous, readily adsorbed impurities. In all systems, the sectorial selectivity of impurity incorporation into host crystals has been detected with partition coefficients many times higher than in the case of equilibrium partition. Specific capture of impurities by certain faces is accompanied by inhibition of their growth and modification of habit. The decrease in nonequilibrium partition coefficients with degree of oversaturation provides entrapment of impurities in the growing crystals. Thereby, the adsorption mechanism works in much the same mode for impurities of quite different nature. The behavior of partition coefficient differs drastically from impurity capturing by diffusion mechanism.

Photonic time crystals.

PubMed

Zeng, Lunwu; Xu, Jin; Wang, Chengen; Zhang, Jianhua; Zhao, Yuting; Zeng, Jing; Song, Runxia

2017-12-07

When space (time) translation symmetry is spontaneously broken, the space crystal (time crystal) forms; when permittivity and permeability periodically vary with space (time), the photonic crystal (photonic time crystal) forms. We proposed the concept of photonic time crystal and rewritten the Maxwell's equations. Utilizing Finite Difference Time Domain (FDTD) method, we simulated electromagnetic wave propagation in photonic time crystal and photonic space-time crystal, the simulation results show that more intensive scatter fields can obtained in photonic time crystal and photonic space-time crystal.

Thin film modeling of crystal dissolution and growth in confinement.

PubMed

Gagliardi, Luca; Pierre-Louis, Olivier

2018-01-01

We present a continuum model describing dissolution and growth of a crystal contact confined against a substrate. Diffusion and hydrodynamics in the liquid film separating the crystal and the substrate are modeled within the lubrication approximation. The model also accounts for the disjoining pressure and surface tension. Within this framework, we obtain evolution equations which govern the nonequilibrium dynamics of the crystal interface. Based on this model, we explore the problem of dissolution under an external load, known as pressure solution. We find that in steady state, diverging (power-law) crystal-surface repulsions lead to flat contacts with a monotonic increase of the dissolution rate as a function of the load. Forces induced by viscous dissipation then surpass those due to disjoining pressure at large enough loads. In contrast, finite repulsions (exponential) lead to sharp pointy contacts with a dissolution rate independent of the load and the liquid viscosity. Ultimately, in steady state, the crystal never touches the substrate when pressed against it. This result is independent from the nature of the crystal-surface interaction due to the combined effects of viscosity and surface tension.

Thin film modeling of crystal dissolution and growth in confinement

NASA Astrophysics Data System (ADS)

Gagliardi, Luca; Pierre-Louis, Olivier

2018-01-01

We present a continuum model describing dissolution and growth of a crystal contact confined against a substrate. Diffusion and hydrodynamics in the liquid film separating the crystal and the substrate are modeled within the lubrication approximation. The model also accounts for the disjoining pressure and surface tension. Within this framework, we obtain evolution equations which govern the nonequilibrium dynamics of the crystal interface. Based on this model, we explore the problem of dissolution under an external load, known as pressure solution. We find that in steady state, diverging (power-law) crystal-surface repulsions lead to flat contacts with a monotonic increase of the dissolution rate as a function of the load. Forces induced by viscous dissipation then surpass those due to disjoining pressure at large enough loads. In contrast, finite repulsions (exponential) lead to sharp pointy contacts with a dissolution rate independent of the load and the liquid viscosity. Ultimately, in steady state, the crystal never touches the substrate when pressed against it. This result is independent from the nature of the crystal-surface interaction due to the combined effects of viscosity and surface tension.

High-resolution transmission electron microscopy of hexagonal and rhombohedral molybdenum disulfide crystals.

PubMed

Isshiki, T; Nishio, K; Saijo, H; Shiojiri, M; Yabuuchi, Y; Takahashi, N

1993-07-01

Natural (molybdenite) and synthesized molybdenum disulfide crystals have been studied by high-resolution transmission electron microscopy. The image simulation demonstrates that the [0001] and [0110] HRTEM images of hexagonal and rhombohedral MoS2 crystals hardly disclose their stacking sequences, and that the [2110] images can distinguish the Mo and S columns along the incident electron beam and enable one to determine not only the crystal structure but also the fault structure. Observed [0001] images of cleaved molybdenite and synthesized MoS2 crystals, however, reveal the strain field around partial dislocations limiting an extended dislocation. A cross-sectional image of a single molecular (S-Mo-S) layer cleaved from molybdenite has been observed. Synthesized MoS2 flakes which were prepared by grinding have been found to be rhombohedral crystals containing many stacking faults caused by glides between S/S layers.

Dielectric studies on struvite urinary crystals, a gateway to the new treatment modality for urolithiasis

NASA Astrophysics Data System (ADS)

Rajan, Reshma; Raj, N. Arunai Nambi; Madeswaran, S.; Babu, D. Rajan

2015-09-01

Struvite or magnesium ammonium phosphate hexahydrate (MAPH) are biological crystals, found in the kidney, which are formed due to the infection caused by urea splitting bacteria in the urinary tract. The struvite crystals observe different morphologies and were developed using single diffusion gel growth technique. The crystalline nature and its composition were studied from different characterization techniques like X-ray Diffraction (XRD) and FTIR. The dielectric behavior of the developed crystal was studied by varying temperature and at different frequencies. The parameters like dielectric constant, dielectric loss, ac conductivity, ac resistivity, impedance and admittance of the struvite crystals were calculated. The studies proved that the dielectric loss or dissipation heat is high in lower frequencies at normal body temperature, which develops a plasma state in the stones and in turn leads to the disintegration of urinary stones. The dielectric nature of the stones leads to the dielectric therapy, which will be a gateway for future treatment modality for urolithiasis.

Noncovalent Polymerization of Mesogens Crystallizes Lysozyme: Correlation between Nonamphiphilic Lyotropic Liquid Crystal Phase and Protein Crystal Formation

PubMed Central

Simon, Karen A.; Shetye, Gauri S.; Englich, Ulrich; Wu, Lei; Luk, Yan-Yeung

2011-01-01

Crystallization of proteins is important for fundamental studies and biopharmaceutical development but remains largely an empirical science. Here, we report the use of organic salts that can form a class of unusual non-amphiphilic lyotropic liquid crystals to crystallize the protein lysozyme. Certain non-amphiphilic organic molecules with fused aromatic rings and two charges can assemble into stable thread-like noncovalent polymers that may further form liquid crystal phases in water, traditionally termed chromonic liquid crystals. Using five of these mesogenic molecules as additives to induce protein crystallization, we discover that molecules that can form liquid crystal phases in water are highly effective at inducing the crystal formation of lysozyme, even at concentrations significantly lower than that required for forming liquid crystal phases. This result reveals an example of inducing protein crystallization by the molecular assembly of the additives, and is consistent with a new mechanism by which the strong hydration of an assembly process provides a gradual means to compete for the water molecules to enable solvated proteins to form crystals. PMID:21786812

An affine microsphere approach to modeling strain-induced crystallization in rubbery polymers

NASA Astrophysics Data System (ADS)

Nateghi, A.; Dal, H.; Keip, M.-A.; Miehe, C.

2018-01-01

Upon stretching a natural rubber sample, polymer chains orient themselves in the direction of the applied load and form crystalline regions. When the sample is retracted, the original amorphous state of the network is restored. Due to crystallization, properties of rubber change considerably. The reinforcing effect of the crystallites stiffens the rubber and increases the crack growth resistance. It is of great importance to understand the mechanism leading to strain-induced crystallization. However, limited theoretical work has been done on the investigation of the associated kinetics. A key characteristic observed in the stress-strain diagram of crystallizing rubber is the hysteresis, which is entirely attributed to strain-induced crystallization. In this work, we propose a micromechanically motivated material model for strain-induced crystallization in rubbers. Our point of departure is constructing a micromechanical model for a single crystallizing polymer chain. Subsequently, a thermodynamically consistent evolution law describing the kinetics of crystallization on the chain level is proposed. This chain model is then incorporated into the affine microsphere model. Finally, the model is numerically implemented and its performance is compared to experimental data.

Large-area photonic crystals

NASA Astrophysics Data System (ADS)

Ruhl, Tilmann; Spahn, Peter; Hellmann, Gotz P.; Winkler, Holger

2004-09-01

Materials with a periodically modulated refractive index, with periods on the scale of light wavelengths, are currently attracting much attention because of their unique optical properties which are caused by Bragg scattering of the visible light. In nature, 3d structures of this kind are found in the form of opals in which monodisperse silica spheres with submicron diameters form a face-centered-cubic (fcc) lattice. Artificial opals, with the same colloidal-crystalline fcc structure, have meanwhile been prepared by crystallizing spherical colloidal particles via sedimentation or drying of dispersions. In this report, colloidal crystalline films are introduced that were produced by a novel technique based on shear flow in the melts of specially designed submicroscopic silica-polymer core-shell hybrid spheres: when the melt of these spheres flows between the plates of a press, the spheres crystallize along the plates, layer by layer, and the silica cores assume the hexagonal order corresponding to the (111) plane of the fcc lattice. This process is fast and yields large-area films, thin or thick. To enhance the refractive index contrast in these films, the colloidal crystalline structure was inverted by etching out the silica cores with hydrofluoric acid. This type of an inverse opal, in which the fcc lattice is formed by mesopores, is referred to as a polymer-air photonic crystal.

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.

Optical Properties of Natural Minerals in the Far-Infrared

NASA Astrophysics Data System (ADS)

Long, Larry Lavern

The reflectivity of natural mineral powders were measured in the far infrared. The complex indices of refraction were then determined by Kramers-Kronig analysis or dispersive analysis. The samples were constructed by pressing the powdered sample into a 13 mm diameter pellet. A few of the samples that were measured were kaolin, illite, and montmorillonite, clay samples that could not be obtained in large single crystals. For calcite and gypsum crystals a comparison between the single crystal measurements and powder measurements was done to determine the effect of sample preparation on the measured spectra.

Viral capsomere structure, surface processes and growth kinetics in the crystallization of macromolecular crystals visualized by in situ atomic force microscopy

NASA Astrophysics Data System (ADS)

Malkin, A. J.; Kuznetsov, Yu. G.; McPherson, A.

2001-11-01

In situ atomic force microscopy (AFM) was used to investigate surface evolution during the growth of single crystals of turnip yellow mosaic virus (TYMV), cucumber mosaic virus (CMV) and glucose isomerase. Growth of these crystals proceeded by two-dimensional (2D) nucleation. For glucose isomerase, from supersaturation dependencies of tangential step rates and critical step length, the kinetic coefficients of the steps and the surface free energy of the step edge were calculated for different crystallographic directions. The molecular structure of the step edges, the adsorption of individual virus particles and their aggregates, and the initial stages of formation of 2D nuclei on the surfaces of TYMV and CMV crystals were recorded. The surfaces of individual TYMV virions within crystals were visualized, and hexameric and pentameric capsomers of the T=3 capsids were clearly resolved. This, so far as we are aware, is the first direct visualization of the capsomere structure of a virus by AFM. In the course of recording the in situ development of the TYMV crystals, a profound restructuring of the surface arrangement was observed. This transformation was highly cooperative in nature, but the transitions were unambiguous and readily explicable in terms of an organized loss of classes of virus particles from specific lattice positions.

Crystal deodorant dermatitis: irritant dermatitis to alum-containing deodorant.

PubMed

Gallego, H; Lewis, E J; Crutchfield, C E

1999-07-01

Two patients developed an irritant dermatitis of the axillae shortly after using an over-the-counter "natural deodorant crystal" product containing alum. We discuss this previously unreported, untoward reaction to alum, an ancient agent with newfound popularity as an alternative health product.

35 GHz Measurements of CO2 Crystals for Simulating Observations of the Martian Polar Caps

NASA Technical Reports Server (NTRS)

Foster, J. L.; Chang, A. T. C.; Hall, D. K.; Tait, A. B.; Barton, J. S.

1998-01-01

In order to learn more about the Martian polar caps, it is important to compare and contrast the behavior of both frozen H2O and CO2 in different parts of the electromagnetic spectrum. Relatively little attention has been given, thus far, to observing the thermal microwave part of the spectrum. In this experiment, passive microwave radiation emanating from within a 33 cm snowpack was measured with a 35 GHz hand-held radiometer, and in addition to the natural snow measurements, the radiometer was used to measure the microwave emission and scattering from layers of manufactured CO2 (dry ice). A 1 m x 2 m plate of aluminum sheet metal was positioned beneath the natural snow so that microwave emissions from the underlying soil layers would be minimized. Compared to the natural snow crystals, results for the dry ice layers exhibit lower' microwave brightness temperatures for similar thicknesses, regardless of the incidence angle of the radiometer. For example, at 50 degree H (horizontal polarization) and with a covering of 21 cm of snow and 18 cm of dry ice, the brightness temperatures were 150 K and 76 K, respectively. When the snow depth was 33 cm, the brightness temperature was 144 K, and when the total thickness of the dry ice was 27 cm, the brightness temperature was 86 K. The lower brightness temperatures are due to a combination of the lower physical temperature and the larger crystal sizes of the commercial CO2 Crystals compared to the snow crystals. As the crystal size approaches the size of the microwave wavelength, it scatters microwave radiation more effectively, thus lowering the brightness temperature. The dry ice crystals in this experiment were about an order of magnitude larger than the snow crystals and three orders of magnitude larger than the CO2 Crystals produced in the cold stage of a scanning electron microscope. Spreading soil, approximately 2 mm in thickness, on the dry ice appeared to have no effect on the brightness temperatures.

Optical and dielectric studies of KH2PO4 crystal influenced by organic ligand of citric acid and L-valine: A single crystal growth and comparative study

NASA Astrophysics Data System (ADS)

Anis, Mohd; Hakeem, D. A.; Muley, G. G.

In the present study pure, citric acid (CA) and L-valine (LV) doped potassium dihydrogen phosphate (KDP) crystals have been grown with the aim to investigate the nonlinear optical applications facilitated by UV-visible, third order nonlinear optical (TONLO) and dielectric properties. The structural parameters of grown crystals have been confirmed by single crystal X-ray diffraction analysis. The enhancement in optical transparency of KDP crystal due to addition of CA and LV has been examined within 200-900 nm by means of UV-visible spectral analysis. In addition, the transmittance data have been used to evaluate the effect of dopants on reflectance, refractive index and extinction coefficient of grown crystals in the visible region. The Z-scan analysis has been performed at 632.8 nm to identify the nature of photoinduced nonlinear refraction and nonlinear absorption in doped KDP crystals. The influence of π-bonded ligand of dopant CA and LV on TONLO susceptibility (χ3), refractive index (n2) and absorption coefficient (β) of KDP crystals has been evaluated to discuss laser assisted device applications. The decrease in dielectric constant and dielectric loss of KDP crystal due to addition of CA and LV has been explored using the temperature dependent dielectric studies.

Optical Investigation of Nanoconfined Crystal Growth

NASA Astrophysics Data System (ADS)

Kohler, F.; Dysthe, D. K.

2015-12-01

Crystals growing in a confined space exert forces on their surroundings. This crystallization force causes deformation of solids and is therefore particularly relevant for the comprehension of geological processes such as replacement and weathering [1]. In addition, these forces are relevant for the understanding of damages in porous building materials caused by crystallization, which is of great economical importance and fundamental for methods that can help to preserve our cultural heritage [2,3]. However, the exact behavior of the growth and the dissolution process in close contact to an interface are still not known in detail. The crystallization, the dissolution and the transport of material is mediated by a nanoconfined water film. We observe brittle NaClO3 crystals growing against a glass surface by optical methods such as reflective interference contrast microscopy (RICM) [4]. In order to carefully control the supersaturation of the fluid close to the crystal interface, a temperature regulated microfluidic system is used (fig. A). The interference based precision of RICM enables to resolve distance variations down to the sub nanometer range without any unwanted disturbances by the measuring method. The combination of RICM with a sensitive camera allows us to observe phenomena such as periodic, wavelike growth of atomic layers. These waves are particularly obvious when observing the difference between two consecutive images (fig. B). In contradiction to some theoretical results, which predict a smooth interface, some recent experiments have shown that the nanoconfined growth surfaces are rough. In combination with theoretical studies and Kinetic Monte Carlo simulations we aim at providing more realistic descriptions of surface energies and energy barriers which are able to explain the discrepancies between experiments and current theory. References:[1] Maliva, Diagenetic replacement controlled by force of crystallization, Geology, August (1988), v. 16 [2] G

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.

Oleoresin crystallization in eastern white pine: relationships with chemical components of cortical oleoresin and resistance to the white-pine weevil

Treesearch

Ronald C. Wilkinson

1979-01-01

Natural and weevil-larva-induced crystallization of oleoresin from 45 eastern white pine trees with known resin acid and monoterpene composition, and from 59 pairs of nonweeviled and heavily weeviled trees from the same seed sources, was examined in mid- and late spring. Very little difference was found between larva-induced and natural crystallization. Strobic acid-...

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. Copyright © 2016 Elsevier Inc. All rights reserved.

Computational crystallization

PubMed Central

Altan, Irem; Charbonneau, Patrick; Snell, Edward H.

2016-01-01

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. PMID:26792536

Crystal Growth Technology

NASA Astrophysics Data System (ADS)

Scheel, Hans J.; Fukuda, Tsuguo

2004-06-01

This volume deals with the technologies of crystal fabrication, of crystal machining, and of epilayer production and is the first book on industrial and scientific aspects of crystal and layer production. The major industrial crystals are treated: Si, GaAs, GaP, InP, CdTe, sapphire, oxide and halide scintillator crystals, crystals for optical, piezoelectric and microwave applications and more. Contains 29 contributions from leading crystal technologists covering the following topics:

General aspects of crystal growth technology Silicon Compound semiconductors Oxides and halides Crystal machining Epitaxy and layer deposition Scientific and technological problems of production and machining of industrial crystals are discussed by top experts, most of them from the major growth industries and crystal growth centers. In addition, it will be useful for the users of crystals, for teachers and graduate students in materials sciences, in electronic and other functional materials, chemical and metallurgical engineering, micro-and optoelectronics including nanotechnology, mechanical engineering and precision-machining, microtechnology, and in solid-state sciences.

• Crystal engineering: co-crystals of cinnamic acid derivatives with a pyridyl derivative co-crystallizer.

  PubMed

  Lorenzo, Daniel A; Forrest, Sebastian J K; Sparkes, Hazel A

  2016-02-01

  A number of hydrogen-bonded co-crystals, consisting of a cinnamic acid derivative and a pyridyl co-crystallizer, have been synthesized and their properties investigated by X-ray diffraction. Samples were prepared by recrystallization or solvent drop grinding of trans-cinnamic acid (1), 4-methylcinnamic acid (2), 4-methoxy cinnamic acid (3) or 3,4-methoxy cinnamic acid (4), with 4,4-dipyridyl (A), iso-nicotinamide (B) or nicotinamide (C). The X-ray single-crystal structures of seven novel co-crystals, obtained through recrystallization, are examined and the hydrogen-bonding interactions discussed. Consistent hydrogen-bonding motifs were observed for samples prepared when using 4,4-dipyridyl (A) or iso-nicotinamide (B) as the co-crystallizing agent. Powder X-ray diffraction analysis of the samples prepared by solvent drop grinding suggests the formation of ten co-crystals.

• Extended-Range Ultrarefractive 1D Photonic Crystal Prisms

  NASA Technical Reports Server (NTRS)

  Ting, David Z.

  2007-01-01

  A proposal has been made to exploit the special wavelength-dispersive characteristics of devices of the type described in One-Dimensional Photonic Crystal Superprisms (NPO-30232) NASA Tech Briefs, Vol. 29, No. 4 (April 2005), page 10a. A photonic crystal is an optical component that has a periodic structure comprising two dielectric materials with high dielectric contrast (e.g., a semiconductor and air), with geometrical feature sizes comparable to or smaller than light wavelengths of interest. Experimental superprisms have been realized as photonic crystals having three-dimensional (3D) structures comprising regions of amorphous Si alternating with regions of SiO2, fabricated in a complex process that included sputtering. A photonic crystal of the type to be exploited according to the present proposal is said to be one-dimensional (1D) because its contrasting dielectric materials would be stacked in parallel planar layers; in other words, there would be spatial periodicity in one dimension only. The processes of designing and fabricating 1D photonic crystal superprisms would be simpler and, hence, would cost less than do those for 3D photonic crystal superprisms. As in 3D structures, 1D photonic crystals may be used in applications such as wavelength-division multiplexing. In the extended-range configuration, it is also suitable for spectrometry applications. As an engineered structure or artificially engineered material, a photonic crystal can exhibit optical properties not commonly found in natural substances. Prior research had revealed several classes of photonic crystal structures for which the propagation of electromagnetic radiation is forbidden in certain frequency ranges, denoted photonic bandgaps. It had also been found that in narrow frequency bands just outside the photonic bandgaps, the angular wavelength dispersion of electromagnetic waves propagating in photonic crystal superprisms is much stronger than is the angular wavelength dispersion obtained

• Living liquid crystals

  DOE Office of Scientific and Technical Information (OSTI.GOV)

  Zhou, S.; Sokolov, A.; Lavrentovich, O. D.

  2014-01-13

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

Growth and characterization of diammonium copper disulphate hexahydrate single crystal

DOE Office of Scientific and Technical Information (OSTI.GOV)

Siva Sankari, R.; Perumal, Rajesh Narayana, E-mail: r.shankarisai@gmail.com

2014-03-01

Graphical abstract: Diammonium copper disulphate hexahydrate (DACS) is one of the most promising inorganic dielectric crystals with exceptional mechanical properties. Good quality crystals of DACS were grown by using solution method in a period of 30 days. The grown crystals were subjected to single crystal X-ray diffraction analysis in order to establish their crystalline nature. Thermo gravimetric, differential thermal analysis, FTIR, and UV–vis–NIR analysis were performed for the crystal. Several solid state physical parameters have been determined for the grown crystals. The dielectric constant and the dielectric loss and AC conductivity of the grown crystal were studied as a functionmore » of frequency and temperature has been calculated and plotted. - Highlights: • Diammonium copper disulphate is grown for the first time and CCDC number obtained. • Thermal analysis is done to see the stability range of the crystals. • Band gap and UV cut off wavelength of the crystal are determined to be 2.4 eV and 472.86 nm, respectively. • Dielectric constant, dielectric loss and AC conductivity are plotted as a function of applied field. - Abstract: Diammonium copper disulphate hexahydrate is one of the most promising inorganic crystals with exceptional dielectric properties. A good quality crystal was harvested in a 30-day period using solution growth method. The grown crystal was subjected to various characterization techniques like single crystal X-ray diffraction analysis, thermo gravimetric, differential thermal analysis, FTIR, and UV–vis–NIR analysis. Unit cell dimensions of the grown crystal have been identified from XRD studies. Functional groups of the title compounds have been identified from FTIR studies. Thermal stability of the samples was checked by TG/DTA studies. Band gap of the crystal was calculated. The dielectric constant and dielectric loss were studied as a function of frequency of the applied field. AC conductivity was plotted as a

The Influence of Mechanical Stress on the Growth of Crystals

DTIC Science & Technology

2001-01-01

crystal surface. In Fig. 7 we present interferograms taken at various points during the straining of a paracetamol crystal28. In Fig. 7 we show the overall...dependence of growth rate on stress. The curvature observed fits well with the nature of the material. Paracetamol shows a well-defined plastic...0 6.6 -0.3 S13.5 4-0.7 21 *1 Fig. 6. Interferograms of the growth of a (001) surface of paracetamol as a function of applied tensile strain. 2.0

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.

Liquid crystal interfaces: Experiments, simulations and biosensors

NASA Astrophysics Data System (ADS)

Popov, Piotr

Interfacial phenomena are ubiquitous and extremely important in various aspects of biological and industrial processes. For example, many liquid crystal applications start by alignment with a surface. The underlying mechanisms of the molecular organization of liquid crystals at an interface are still under intensive study and continue to be important to the display industry in order to develop better and/or new display technology. My dissertation research has been devoted to studying how complex liquid crystals can be guided to organize at an interface, and to using my findings to develop practical applications. Specifically, I have been working on developing biosensors using liquid-crystal/surfactant/lipid/protein interactions as well as the alignment of low-symmetry liquid crystals for potential new display and optomechanical applications. The biotechnology industry needs better ways of sensing biomaterials and identifying various nanoscale events at biological interfaces and in aqueous solutions. Sensors in which the recognition material is a liquid crystal naturally connects the existing knowledge and experience of the display and biotechnology industries together with surface and soft matter sciences. This dissertation thus mainly focuses on the delicate phenomena that happen at liquid interfaces. In the introduction, I start by defining the interface and discuss its structure and the relevant interfacial forces. I then introduce the general characteristics of biosensors and, in particular, describe the design of biosensors that employ liquid crystal/aqueous solution interfaces. I further describe the basic properties of liquid crystal materials that are relevant for liquid crystal-based biosensing applications. In CHAPTER 2, I describe the simulation methods and experimental techniques used in this dissertation. In CHAPTER 3 and CHAPTER 4, I present my computer simulation work. CHAPTER 3 presents insight of how liquid crystal molecules are aligned by

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.

Modified Bridgman-Stockbarger growth and characterization of LiInSe{sub 2} single crystal

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vijayakumar, P., E-mail: ramasamyp@ssn.edu.in; Magesh, M., E-mail: ramasamyp@ssn.edu.in; Arunkumar, A., E-mail: ramasamyp@ssn.edu.in

2014-04-24

The LiInSe{sub 2} polycrystalline materials were successfully synthesized from melt and temperature oscillation method. 8 mm diameter and 32 mm length single crystal was grown from Bridgman-Stockbarger method with steady ampoule rotation. Crystalline phase was confirmed by powder XRD pattern. Thermo gravimetric and differential thermal analysis confirms that the melting point of the grown crystal is 897°C. Rutherford backscattering analysis (RBS) gives the crystal composition as Li{sub 0.8}In{sub 1.16}Se{sub 2.04}. The crystalline perfection of the grown crystal was analyzed by High resolution X-ray diffraction measurements (HRXRD). The electrical properties of the grown crystal were analyzed by Hall effect measurements andmore » it confirms the n-type semiconducting nature.« less

Growth and characterization of Cadmium Thiosemicarbazide Bromide crystals for antibacterial and nonlinear optical applications

NASA Astrophysics Data System (ADS)

Thomas Joseph Prakash, J.; Martin Sam Gnanaraj, J.

2015-01-01

Semiorganic nonlinear optical crystals of Cadmium Thiosemicarbazide Bromide was grown by slow evaporation solution growth technique. The unit cell parameters were estimated by subjecting the crystals to single crystal X-ray diffraction. The grown crystals were subjected to Powder X-ray diffraction for analyzing the crystalline nature of the sample. FTIR studies reveal the functional groups and the optical characters were analyzed by UV-Vis spectral studies. Mechanical stability of the sample was assessed by Vicker's micro hardness test. The presence of surface dislocations was identified by chemical etching technique. Antibacterial study was carried out against ACDP declared harmful pathogens. SHG efficiency of CTSB crystal was tested using Nd: YAG laser and it was found to be ∼1.8 times that of potassium dihydrogen phosphate.

Crystal regularity with high-resolution synchrotron X-radiation diffraction imaging

NASA Technical Reports Server (NTRS)

Steiner, Bruce; Dobbyn, Ronald C.

1991-01-01

New, high-resolution sources of X-radiation such as monochromatic synchrotron radiation beams with subarcsec divergence allow observation of regularities in a range of crystals with sufficient clarity for comprehensive analyses, whose results can deepen understanding of the nature of various crystal irregularities, their sources, and their effects on device performance. An account is presented of the results thus achievable with irregularities encountered in lattice orientation and strain, grain and subgrain boundaries, dislocations, domain boundaries, additional phases, and surface scratches. Significant achievements to date encompass the observation of critical anomalies in lead tin telluride, the reconciliation of disparate observations of GaAs, the determination of the performance effects of irregularities in mercuric iodide, and the characterization of the origins of crystal growth in bismuth silicon oxide.

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

NMR spectroscopy of experimentally shocked single crystal quartz: A reexamination of the NMR shock barometer

NASA Technical Reports Server (NTRS)

Fiske, P. S.; Gratz, A. J.; Nellis, W. J.

1993-01-01

Cygan and others report a broadening of the Si-29 nuclear magnetic resonance (NMR) peak for synthetic quartz powders with increasing shock pressure which they propose as a shock wave barometer for natural systems. These results are expanded by studying single crystal quartz shocked to 12 and 33 GPa using the 6.5 m two-stage light-gas gun at Lawrence Livermore National Laboratories. Our NMR results differ substantially from those of Cygan and others and suggest that the proposed shock wave barometer may require refinement. The difference in results between this study and that of Cygan and others is most likely caused by different starting materials (single crystal vs. powder) and different shock loading histories. NMR results from single crystal studies may be more applicable to natural systems.

Crystallization of bi-functional ligand protein complexes.

PubMed

Antoni, Claudia; Vera, Laura; Devel, Laurent; Catalani, Maria Pia; Czarny, Bertrand; Cassar-Lajeunesse, Evelyn; Nuti, Elisa; Rossello, Armando; Dive, Vincent; Stura, Enrico Adriano

2013-06-01

Homodimerization is important in signal transduction and can play a crucial role in many other biological systems. To obtaining structural information for the design of molecules able to control the signalization pathways, the proteins involved will have to be crystallized in complex with ligands that induce dimerization. Bi-functional drugs have been generated by linking two ligands together chemically and the relative crystallizability of complexes with mono-functional and bi-functional ligands has been evaluated. There are problems associated with crystallization with such ligands, but overall, the advantages appear to be greater than the drawbacks. The study involves two matrix metalloproteinases, MMP-12 and MMP-9. Using flexible and rigid linkers we show that it is possible to control the crystal packing and that by changing the ligand-enzyme stoichiometric ratio, one can toggle between having one bi-functional ligand binding to two enzymes and having the same ligand bound to each enzyme. The nature of linker and its point of attachment on the ligand can be varied to aid crystallization, and such variations can also provide valuable structural information about the interactions made by the linker with the protein. We report here the crystallization and structure determination of seven ligand-dimerized complexes. These results suggest that the use of bi-functional drugs can be extended beyond the realm of protein dimerization to include all drug design projects. Copyright © 2013 Elsevier Inc. All rights reserved.

On the Coupling Mechanism of Equiaxed Crystal Generation with the Liquid Flow Driven by Natural Convection During Solidification

NASA Astrophysics Data System (ADS)

Stefan-Kharicha, Mihaela; Kharicha, Abdellah; Wu, Menghuai; Ludwig, Andreas

2018-02-01

The influence of the melt flow on the solidification structure is bilateral. The flow plays an important role in the solidification pattern, via the heat transfer, grain distribution, and segregations. On the other hand, the crystal structure, columnar or equiaxed, impacts the flow, via the thermosolutal convection, the drag force applied by the crystals on the melt flow, etc. As the aim of this research was to further explore the solidification-flow interaction, experiments were conducted in a cast cell (95 * 95 * 30 mm3), in which an ammonium chloride-water solution (between 27 and 31 wt pct NH4Cl) was observed as it solidified. The kinetic energy (KE) of the flow and the average flow velocity were calculated throughout the process. Measurements of the volume extension of the mush in the cell and the velocity of the solid front were also taken during the solidification experiment. During the mainly columnar experiments (8 cm liquid height) the flow KE continuously decreased over time. However, during the later series of experiments at higher liquid height (9.5 cm), the flow KE evolution presented a strong peak shortly after the start of solidification. This increase in the total flow KE correlated with the presence of falling equiaxed crystals. Generally, a clear correlation between the strength of the flow and the occurrence of equiaxed crystals was evident. The analysis of the results strongly suggests a fragmentation origin of equiaxed crystals appearing in the melt. The transition from purely columnar growth to a strongly equiaxed rain (CET) was found to be triggered by (a) the magnitude of the coupling between the flow intensity driven by the equiaxed crystals, and (b) the release and transport of the fragments by the same flow recirculating within the mushy zone.

Follow up on the crystal growth experiments of the LDEF

NASA Technical Reports Server (NTRS)

Nielsen, K. F.; Lind, M. D.

1993-01-01

The results of the 4 solution growth experiments on the LDEF have been published elsewhere. Both the crystals of CaCO3, which were large and well shaped, and the much smaller TTF-TCNQ crystals showed unusual morphological behavior. The follow up on these experiments was begun in 1981, when ESA initiated a 'Concept Definition Study' on a large, 150 kg, Solution Growth Facility (SGF) to be included in the payload of EURECA-1, the European Retrievable Carrier. This carrier was a continuation of the European Spacelab and at that time planned for launch in 1987. The long delay of the LDEF retrieval and of subsequent missions brought about reflections both on the concept of crystal growth in space and on the choice of crystallization materials that had been made for the LDEF. Already before the LDEF retrieval, research on TTF-TCNQ had been stopped, and a planned growth experiment with TTF-TCNQ on the SGF/EURECA had been cancelled. The target of the SGF investigation is now more fundamental in nature. None of the crystals to be grown here are, like TTF-TCNQ, in particular demand by science or industry, and the crystals only serve the purpose of model crystals. The real purpose of the investigation is to study the growth behavior. One of the experiments, the Soret Coefficient Measurement experiment is not growing crystals at all, but has it as its sole purpose to obtain accurate information on thermal diffusion, a process of importance in crystal growth from solution.

Thermodynamics and mechanics of stretch-induced crystallization in rubbers

NASA Astrophysics Data System (ADS)

Guo, Qiang; Zaïri, Fahmi; Guo, Xinglin

2018-05-01

The aim of the present paper is to provide a quantitative prediction of the stretch-induced crystallization in natural rubber, the exclusive reason for its history-dependent thermomechanical features. A constitutive model based on a micromechanism inspired molecular chain approach is formulated within the context of the thermodynamic framework. The molecular configuration of the partially crystallized single chain is analyzed and calculated by means of some statistical mechanical methods. The random thermal oscillation of the crystal orientation, considered as a continuous random variable, is treated by means of a representative angle. The physical expression of the chain free energy is derived according to a two-step strategy by separating crystallization and stretching. This strategy ensures that the stretch-induced part of the thermodynamic crystallization force is null at the initial instant and allows, without any additional constraint, the formulation of a simple linear relationship for the crystallinity evolution law. The model contains very few physically interpretable material constants to simulate the complex mechanism: two chain-scale constants, one crystallinity kinetics constant, three thermodynamic constants related to the newly formed crystallites, and a function controlling the crystal orientation with respect to the chain. The model is used to discuss some important aspects of the micromechanism and the macroresponse under the equilibrium state and the nonequilibrium state involved during stretching and recovery, and continuous relaxation.

Water weakening in experimentally deformed milky quartz single crystals

NASA Astrophysics Data System (ADS)

Stunitz, H.; Thust, A.; Kilian, R.; Heilbronner, R.; Behrens, H.; Tarantola, A.; Fitz Gerald, J. D.

2015-12-01

Natural single crystals of quartz have been experimentally deformed in two orientations: (1) normal to one prism-plane, (2) In O+ orientation at temperatures of 900 and 1000°C, pressures of 1.0 and 1.5 GPa, and strain rates of ~1 x 10-6s-1. The starting material is milky quartz, consisting of dry quartz (H2O contents of <150 H/106Si) with fluid inclusions (FI). During pressurization many FI´s decrepitate. Cracks heal and small neonate FI´s form, increasing the number of FI´s drastically. During subsequent deformation, the size of FI´s is further reduced (down to ~10 nm). Sample deformation occurs by dominant dislocation glide on selected slip systems, accompanied by some dynamic recovery. Strongly deformed regions show FTIR spectra with a pointed broad absorption band in the ~3400 cm-1 region as a superposition of molecular H2O bands and three discrete absorption bands (at 3367, 3400, and 3434 cm-1). In addition, there is a discrete absorption band at 3585 cm-1, which only occurs in deformed regions. The 3585 cm-1 band is reduced or even disappears after annealing. This band is polarized and represents structurally bound H, its H-content is estimated to be 1-3% of the total H2O-content and appears to be associated with dislocations. The H2O weakening effect in our FI-bearing natural quartz crystals is assigned to the processes of dislocation generation and multiplication at small FI´s. The deformation processes in these crystals represent a recycling of H2O between FI´s, dislocation generation at very small fluid inclusions, incorporation of structurally bound H into dislocation cores, and release of H2O from dislocations back into FI´s during recovery. Cracking and crack healing play an important role in the recycling process and imply a close interrelationship between brittle and crystal plastic deformation. The H2O weakening by this process is of a disequilibrium nature and thus depends on the amount of H2O available.

The Question of Impurities in Macromolecule Crystal Quality Improvement in Microgravity

NASA Technical Reports Server (NTRS)

Judge, Russell A.; Snell, Edward H.; Pusey, Marc L.; Sportiello, Michael G.; Todd, Paul; Bellamy, Henry; Borgstahl, Gloria E.; Pokros, Matthew; Cassanto, John M.

2000-01-01

While macromolecule impurities may affect crystal size and morphology the over-riding question is how do macromolecule impurities effect crystal X-ray quality and diffraction resolution. In the case of chicken egg white lysozyme previous researchers have reported that crystals grown in the presence of ovalbumin, ovotransferrin, and turkey egg white lysozyme show no difference in diffraction resolution compared to those grown in pure solutions. One impurity however, a naturally occurring lysozyme dimer, does negatively impact the X-ray crystal properties. For this impurity it has been reported that crystal quality improvement in microgravity may be due to improved impurity partitioning during crystallization. In this study we have examined the incorporation of the dimer into lysozyme crystals, both on the ground and in microgravity experiments, and have performed detailed X-ray analysis of the crystals using a new technique for finely probing the mosaicity of the crystal at the Stanford Synchrotron Radiation Laboratory. Dimer partitioning was not significantly different in microgravity compared to the ground based experiments, although it is significantly better than that previously reported in microgravity. Mosaicity analysis of pure crystals, 1422 indexed reflections (microgravity) and 752 indexed reflections (ground), gave average results of 0.0066 and 0.0092 degrees (FWHM) respectively. The microgravity crystals also provided an increased signal to noise. Dimer incorporation increased the average mosaicity in microgravity but not on the ground. However, dimer incorporation did greatly reduce the resolution limit in both ground and microgravity grown crystals. The data is being treated anisotropically to explore these effects. These results indicate that impurity effects in microgravity are complex and that the conditions or techniques employed may greatly affect the role of impurities.

Review of aragonite and calcite crystal morphogenesis in thermal spring systems

NASA Astrophysics Data System (ADS)

Jones, Brian

2017-06-01

Aragonite and calcite crystals are the fundamental building blocks of calcareous thermal spring deposits. The diverse array of crystal morphologies found in these deposits, which includes monocrystals, mesocrystals, skeletal crystals, dendrites, and spherulites, are commonly precipitated under far-from-equilibrium conditions. Such crystals form through both abiotic and biotic processes. Many crystals develop through non-classical crystal growth models that involve the arrangement of nanocrystals in a precisely controlled crystallographic register. Calcite crystal morphogenesis has commonly been linked to a ;driving force;, which is a conceptual measure of the distance of the growth conditions from equilibrium conditions. Essentially, this scheme indicates that increasing levels of supersaturation and various other parameters that produce a progressive change from monocrystals and mesocrystals to skeletal crystals to crystallographic and non-crystallographic dendrites, to dumbbells, to spherulites. Despite the vast amount of information available from laboratory experiments and natural spring systems, the precise factors that control the driving force are open to debate. The fact that calcite crystal morphogenesis is still poorly understood is largely a reflection of the complexity of the factors that influence aragonite and calcite precipitation. Available information indicates that variations in calcite crystal morphogenesis can be attributed to physical and chemical parameters of the parent water, the presence of impurities, the addition of organic or inorganic additives to the water, the rate of crystal growth, and/or the presence of microbes and their associated biofilms. The problems in trying to relate crystal morphogenesis to specific environmental parameters arise because it is generally impossible to disentangle the controlling factor(s) from the vast array of potential parameters that may act alone or in unison with each other.

The perfection and defect structure of organic hourglass inclusion K 2SO 4 crystals

NASA Astrophysics Data System (ADS)

Vetter, William M.; Totsuka, Hirono; Dudley, Michael; Kahr, Bart

2002-06-01

Hourglass inclusion crystals of K 2SO 4 were grown from aqueous solutions containing the dye acid fuchsin, and studied by synchrotron white-beam X-ray topography and reciprocal space mapping. Both self-nucleated and larger, seeded dye-included crystals were prepared, as well as comparable undoped crystals. While the dye modified the crystals' habit strongly, X-ray topographs showed it had no influence on their dislocation configurations, which were typical for solution-grown crystals. No kinematical contrast arising from the presence of the dye was observed that indicated dye-induced strain in the crystal lattice. Growth sector boundaries were visible in the dyed crystals but not in undoped crystals, implying there was a slightly higher lattice mismatch across growth sector boundaries in the dye-included crystals. Reciprocal space maps of small areas on an hourglass inclusion crystal within either a dye-included growth sector or an undoped growth sector showed single peaks with the same perfect crystal rocking curve width and no dilatation or tilt of the host lattice resulting from the dye's presence. These results showed hourglass inclusion crystals can be grown in which the presence of the dye disturbs the crystalline structure of the host salt minimally, and that hourglass inclusions have the nature of a solid solution.

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.

Properties of pure single crystals of actinide compounds

NASA Astrophysics Data System (ADS)

Vogt, O.

1989-07-01

Actinide research started with substances of poor quality and a multitude of "unexplainable" results mostly found on powder samples of doubtful quality exerted some pressure on the crystal growers. As an example we may mention the measurements on UP. Type I antiferromagnetism was found below 123 K by neutron diffraction experiments on powdered samples. At 23 K another transition becomes apparent in susceptibility measurements. The change of the magnetic moments associated with this transition remained unexplained. It was only after the discovery of multi k structures in other actinide compounds that the need was seen to perform even inelastic neutron diffraction experiments on single crystals so that finally the true nature of the transition in UP could be revealed. NpAs is another illustrative example for the fact that sometimes it takes decades to get a clear understanding for things even so simple as macroscopic magnetic properties. The main reason for the need of single crystals is certainly the anisotropy of the magnetic moment encountered in all actinide compounds. Self-heating effects may prevent research on big crystals or might call for isotopic purity of certain samples.

Computer simulation of rapid crystal growth under microgravity

NASA Astrophysics Data System (ADS)

Hisada, Yasuhiro; Saito, Osami; Mitachi, Koshi; Nishinaga, Tatau

We are planning to grow a Ge single crystal under microgravity by the TR-IA rocket in 1992. The furnace temperature should be controlled so as to finish the crystal growth in a quite short time interval (about 6 min). This study deals with the computer simulation of rapid crystal growth in space to find the proper conditions for the experiment. The crystal growth process is influenced by various physical phenomena such as heat conduction, natural and Marangoni convections, phase change, and radiation from the furnace. In this study, a 2D simulation with axial symmetry is carried out, taking into account the radiation field with a specific temperature distribution of the furnace wall. The simulation program consists of four modules. The first module is applied for the calculation of the parabolic partial differential equation by using the control volume method. The second one evaluates implicitly the phase change by the enthalpy method. The third one is for computing the heat flux from surface by radiation. The last one is for calculating with the Monte Carlo method the view factors which are necessary to obtain the heat flux.

Cloud-to-Ground Lightning Characteristics of a Major Tropical Cyclone Tornado Outbreak

NASA Technical Reports Server (NTRS)

McCaul, Eugene W., Jr.; Buechler, Dennis; Goodman, Steven J.

1999-01-01

A comprehensive analysis has been conducted of the cloud-to-ground lightning activity occurring within a landfalling tropical cyclone that produced an outbreak of strong and damaging tornadoes. Radar data indicate that 12 convective cells were responsible for 29 tornadoes, several of which received an F3 intensity rating, in the southeastern United States on 16 August 1994 within the remnants of Tropical Storm Beryl. Of these 12 tornadic storms, the most active cell produced 315 flashes over a 5.5 hour period, while the other storms were less active. Three tornadic storms failed to produce any CG lightning at all. In general, the tornadic storms were more active electrically than other non-tornadic cells within Beryl's remnants, although the flash rates were rather modest by comparison with significant midlatitude severe storm events. Very few positive polarity flashes were found in the Beryl outbreak. During some of the stronger tornadoes, CG flash rates in the parent storms showed sharp transient decreases. Doppler radar data suggest the stronger tornadic storms were small supercells, and the lightning data indicate these storms exhibited lightning characteristics similar to those found in heavy-precipitation supercell storms.

Crystallization of lithium borate glasses

NASA Technical Reports Server (NTRS)

Goktas, A. A.; Neilson, G. F.; Weinberg, M. C.

1992-01-01

The glass-forming ability and crystallization behavior of lithium borate compositions, in the diborate-to-metaborate-range, were studied. In particular, the nature and sequence of formation of crystalline phases and the tendency toward devitrification were investigated as functions of temperature, thermal history and batch composition. It was found that the sequence of crystalline phase formation was sensitive to all of the three latter factors, and it was observed that under certain conditions metastable defect structures of the metaborate can appear.

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.

Crystal growth and characterization of semi-organic 2-amino-5-nitropyridinium bromide (2A5NPBr) single crystals for third-order nonlinear optical (NLO) applications

NASA Astrophysics Data System (ADS)

Vediyappan, Sivasubramani; Arumugam, Raja; Pichan, Karuppasamy; Kasthuri, Ramachandran; Muthu, Senthil Pandian; Perumal, Ramasamy

2017-12-01

Semi-organic nonlinear optical (NLO) 2-amino-5-nitropyridinium bromide (2A5NPBr) single crystals have been grown by slow evaporation solution technique (SEST) with the growth period of 60 days. The single-crystal XRD analysis confirms the unit cell parameters of the grown crystal. The crystallinity of grown 2A5NPBr was analyzed by powder X-ray diffraction (PXRD) measurement. The presence of functional groups of 2A5NPBr crystal was confirmed by Fourier transform infrared (FTIR) spectrum analysis. The optical transmittance of the grown crystal was analyzed by UV-Vis-NIR analysis. It shows good transparency in the visible and NIR region and it is favorable for nonlinear optical (NLO) device applications. The chemical etching study was carried out and it reveals that the grown crystal has less dislocation density. The photoconductivity study reveals that the grown crystal possesses positive photoconductive nature. The thermal stability of the crystal has been investigated by thermogravimetric (TG) and differential thermal analysis (DTA). The dielectric constant and dielectric loss as a function of frequency were measured. The electronic polarizability (α) of 2A5NPBr molecule has been calculated theoretically by different ways such as Penn analysis, Clausius-Mossotti relation, Lorentz-Lorenz equation, optical bandgap, and coupled dipole method (CDM). The obtained values of electronic polarizability (α) are in good agreement with each other. Laser damage threshold (LDT) of 2A5NPBr crystal has been measured using Nd:YAG laser with the wavelength of 1064 nm. Third-order nonlinear optical property of the grown crystal was studied by Z-scan technique using He-Ne laser of wavelength 632.8 nm.

Fabrication and characterization of non-Brownian particle-based crystals.

PubMed

Lash, Melissa H; Fedorchak, Morgan V; Little, Steven R; McCarthy, Joseph J

2015-01-27

Particle-based crystals have been explored in the literature for applications in molecular electronics, photonics, sensors, and drug delivery. However, much of the research on these crystals has been focused on particles of nano- and submicrometer dimensions (so-called colloidal crystals) with limited attention directed toward building blocks with dimensions ranging from tens to hundreds of micrometers. This can be attributed, in part, to the fact that the underlying thermal effects in these larger systems typically cannot naturally overcome kinetic barriers at the meso- and macroscales so that many of the methods used for nanoscale particle assembly cannot be directly applied to larger components, as they become kinetically arrested in nonequilibrium states. In this work, ultrasonic agitation is being explored as a means of allowing large, non-Brownian microparticles (18-750 μm) to overcome the kinetic barriers to packing in the creation of close-packed, highly ordered, crystalline structures. In addition, we study how the energy input affects bulk particle behavior and describe several new ways to characterize particle-based crystals made from microparticles.

A discrete mechanics approach to dislocation dynamics in BCC crystals

NASA Astrophysics Data System (ADS)

Ramasubramaniam, A.; Ariza, M. P.; Ortiz, M.

2007-03-01

A discrete mechanics approach to modeling the dynamics of dislocations in BCC single crystals is presented. Ideas are borrowed from discrete differential calculus and algebraic topology and suitably adapted to crystal lattices. In particular, the extension of a crystal lattice to a CW complex allows for convenient manipulation of forms and fields defined over the crystal. Dislocations are treated within the theory as energy-minimizing structures that lead to locally lattice-invariant but globally incompatible eigendeformations. The discrete nature of the theory eliminates the need for regularization of the core singularity and inherently allows for dislocation reactions and complicated topological transitions. The quantization of slip to integer multiples of the Burgers' vector leads to a large integer optimization problem. A novel approach to solving this NP-hard problem based on considerations of metastability is proposed. A numerical example that applies the method to study the emanation of dislocation loops from a point source of dilatation in a large BCC crystal is presented. The structure and energetics of BCC screw dislocation cores, as obtained via the present formulation, are also considered and shown to be in good agreement with available atomistic studies. The method thus provides a realistic avenue for mesoscale simulations of dislocation based crystal plasticity with fully atomistic resolution.

Enhanced optical, thermal and piezoelectric behavior in dye doped potassium acid phthalate (KAP) single crystal

NASA Astrophysics Data System (ADS)

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

2017-06-01

Dye inclusion crystals have attracted researchers in the context of crystal growth for applications in solid state lasers. Pure and 0.1 mol% amaranth doped KAP single crystals, were grown from aqueous solutions by slow evaporation technique at room temperature. The grown crystals are up to the dimension of 12×10×3 mm3. Attempt is made to improve the growth rate, optical, piezoelectric and photoconductive properties of pure KAP single crystal with addition of amaranth dye as a dopant. Various characterization studies were made for both pure and dye doped KAP. Thermal stability of the crystals is tested from thermogravimetric and differential thermal analysis (TG/DTA). There is only one endothermic peak indicating decomposition point. Higher optical transparency for dye doped KAP crystal was identified from the UV-vis spectrum. Etching studies showed an improvement in the optical quality of the KAP crystal after doping with amaranth dye. The positive photoconductive nature is observed from both pure and amaranth doped KAP.

Capsize of polarization in dilute photonic crystals.

PubMed

Gevorkian, Zhyrair; Hakhoumian, Arsen; Gasparian, Vladimir; Cuevas, Emilio

2017-11-29

We investigate, experimentally and theoretically, polarization rotation effects in dilute photonic crystals with transverse permittivity inhomogeneity perpendicular to the traveling direction of waves. A capsize, namely a drastic change of polarization to the perpendicular direction is observed in a one-dimensional photonic crystal in the frequency range 10 ÷ 140 GHz. To gain more insights into the rotational mechanism, we have developed a theoretical model of dilute photonic crystal, based on Maxwell's equations with a spatially dependent two dimensional inhomogeneous dielectric permittivity. We show that the polarization's rotation can be explained by an optical splitting parameter appearing naturally in Maxwell's equations for magnetic or electric fields components. This parameter is an optical analogous of Rashba like spin-orbit interaction parameter present in quantum waves, introduces a correction to the band structure of the two-dimensional Bloch states, creates the dynamical phase shift between the waves propagating in the orthogonal directions and finally leads to capsizing of the initial polarization. Excellent agreement between theory and experiment is found.

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

Tunable two-dimensional photonic crystals using liquid crystal infiltration

NASA Astrophysics Data System (ADS)

Leonard, S. W.; Mondia, J. P.; van Driel, H. M.; Toader, O.; John, S.; Busch, K.; Birner, A.; Gösele, U.; Lehmann, V.

2000-01-01

The photonic band gap of a two-dimensional photonic crystal is continuously tuned using the temperature dependent refractive index of a liquid crystal. Liquid crystal E7 was infiltrated into the air pores of a macroporous silicon photonic crystal with a triangular lattice pitch of 1.58 μm and a band gap wavelength range of 3.3-5.7 μm. After infiltration, the band gap for the H polarized field shifted dramatically to 4.4-6.0 μm while that of the E-polarized field collapsed. As the sample was heated to the nematic-isotropic phase transition temperature of the liquid crystal (59 °C), the short-wavelength band edge of the H gap shifted by as much as 70 nm while the long-wavelength edge was constant within experimental error. Band structure calculations incorporating the temperature dependence of the liquid crystal birefringence can account for our results and also point to an escaped-radial alignment of the liquid crystal in the nematic phase.

Carbon agent chemical vapor transport growth of Ga2O3 crystal

NASA Astrophysics Data System (ADS)

Jie, Su; Tong, Liu; Jingming, Liu; Jun, Yang; Guiying, Shen; Yongbiao, Bai; Zhiyuan, Dong; Youwen, Zhao

2016-10-01

Beta-type gallium oxide (β-Ga2O3) is a new attractive material for optoelectronic devices. Different methods had been tried to grow high quality β-Ga2O3 crystals. In this work, crystal growth of Ga2O3 has been carried out by chemical vapor transport (CVT) method in a closed quartz tube using C as transport agent and sapphire wafer as seed. The CVT mass flux has been analyzed by theoretical calculations based on equilibrium thermodynamics and 1D diffusional mass transport. The crystal growth experimental results are in agreement with the theoretical predictions. Influence factors of Ga2O3 crystal growth, such as temperature distribution, amount of C as transport agent used, have also been discussed. Structural (XRD) and optical (Raman spectroscopy, photoluminescence spectrum) properties of the CVT-Ga2O3 crystal are presented. Project supported by the National Natural Science Foundation of China (Nos. 61474104, 61504131).

Crystal growth and DFT insight on sodium para-nitrophenolate para-nitrophenol dihydrate single crystal for NLO applications

NASA Astrophysics Data System (ADS)

Selvakumar, S.; Boobalan, Maria Susai; Anthuvan Babu, S.; Ramalingam, S.; Leo Rajesh, A.

2016-12-01

Single crystals of sodium para-nitrophenolate para-nitrophenol dihydrate (SPPD) were grown by slow evaporation technique and its structure has been studied by FT-IR, FT-Raman and single crystal X-ray diffraction techniques. The optical and electrical properties were characterized by UV-Vis spectrum, and dielectric studies respectively. SPPD was thermally stable up to 128 °C as determined by TG-DTA curves. Using the Kurtz-Perry powder method, the second-harmonic generation efficiency was found to be five times to that of KDP. Third-order nonlinear response was studied using Z-scan technique with a He-Ne laser (632.8 nm) and NLO parameters such as intensity dependent refractive index, nonlinear absorption coefficient and third-order susceptibility were also estimated. The molecular geometry from X-ray experiment in the ground state has been compared using density functional theory (DFT) with appropriate basis set. The first-order hyperpolarizability also calculated using DFT approaches. Stability of the molecule arising from hyperconjugative interactions leading to its nonlinear optical activity and charge delocalization were analyzed using natural bond orbital technique. HOMO-LUMO energy gap value suggests the possibility of charge transfer within the molecule. Based on optimized ground state geometries, Natural bond orbital (NBO) analysis was performed to study donor-acceptor interactions.

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)

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

A Study of Biomolecules as Growth Modifiers of Calcium Oxalate Crystals

NASA Astrophysics Data System (ADS)

Kwak, Junha John

Crystallization processes are ubiquitous in nature, science, and technology. Controlling crystal growth is pivotal in many industries as material properties and functions can be tailored by tuning crystal habits (e.g. size, shape, phase). In biomineralization, organisms exert excellent control over bottom-up synthesis and assembly of inorganic-organic structures (e.g. bones, teeth, exoskeletons). This is made possible by growth modifiers that range from small molecules to macromolecules, such as proteins. Molecular recognition of the mineral phase allows proteins to function as nucleation templates, matrices, and growth inhibitors or promoters. We are interested in taking a biomimetic approach to control crystallization via biomolecular growth modifiers. We investigated calcium oxalate monohydrate (COM), found in plants and kidney stones, as a model system of crystallization. We studied the effects of four common proteins on COM crystallization: bovine serum albumin (BSA), transferrin, lactoferrin, and lysozyme. Through kinetic studies of COM crystallization, we classified BSA and lysozyme as COM growth inhibitor and promoter respectively. Their inhibition and promotion effects were also evident in the macroscopic crystal habit. Through adsorption and microscopy experiments, we showed that BSA exhibits binding specificity for the apical surfaces of macroscopic COM crystals. Lysozyme, on the other, functions via a non-binding mechanism at the surface to accelerate the growth of the apical surfaces. We also synthesized and studied peptides derived from the protein primary sequences to identify putative domains responsible for these inhibition and promotion effects. Collectively, our study of physiologically relevant biomolecules suggests potential roles of COM modifiers in pathological crystallization and helps to develop guidelines for rational design of biomolecular growth modifiers for applications in crystal engineering.

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. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fluid mechanics in crystal growth - The 1982 Freeman scholar lecture

NASA Technical Reports Server (NTRS)

Ostrach, S.

1983-01-01

An attempt is made to unify the current state of knowledge in crystal growth techniques and fluid mechanics. After identifying important fluid dynamic problems for such representative crystal growth processes as closed tube vapor transport, open reactor vapor deposition, and the Czochralski and floating zone melt growth techniques, research results obtained to date are presented. It is noted that the major effort to date has been directed to the description of the nature and extent of bulk transport under realistic conditions, where bulk flow determines the heat and solute transport which strongly influence the temperature and concentration fields in the vicinity of the growth interface. Proper treatment of near field, or interface, problems cannot be given until the far field, or global flow, involved in a given crystal growth technique has been adequately described.

Absolute configuration and crystal packing for three chiral drugs prone to spontaneous resolution: Guaifenesin, methocarbamol and mephenesin

NASA Astrophysics Data System (ADS)

Bredikhin, Alexander A.; Gubaidullin, Aidar T.; Bredikhina, Zemfira A.; Krivolapov, Dmitry B.; Pashagin, Alexander V.; Litvinov, Igor A.

2009-02-01

Popular chiral drugs, guaifenesin, methocarbamol, and mephenesin were investigated by single-crystal X-ray analysis both for enantiopure and racemic samples. The absolute configurations for all substances were established through Flack parameter method. The conglomerate-forming nature for the compounds was confirmed by equivalence of crystal characteristics of enantiopure and racemic samples. The molecular structures and crystal packing details were evaluated and compared with one another for all three investigated substances.

Experimental Investigation of Orthoenstatite Single Crystal Rheology

NASA Astrophysics Data System (ADS)

fraysse, G.; Girard, J.; Holyoke, C. W.; Raterron, P.

2013-12-01

The plasticity of enstatite, upper mantle second most abundant mineral, is still poorly constrained, mostly because of its high-temperature (T) transformation into proto- and clino-enstatite at low pressure (P). Mackwell (1991, GRL, 18, 2027) reports a pioneer study of protoenstatite (Pbcn) single-crystal rheology, but the results do not directly apply to the orthorhombic (Pbca) mantle phase. Ohuchi et al. (2011, Contri. Mineral. Petrol , 161, 961) carried out deformation experiments at P=1.3 GPa on oriented orthoenstatite crystals, investigating the activity of [001](100) and [001](010) dislocation slip systems; they report the first rheological laws for orthoenstatite crystals. However, strain and stress were indirectly constrained in their experiments, which questioned whether steady state conditions of deformation were achieved. Also, data reported for [001](100) slip system were obtained after specimens had transformed by twinning into clinoenstatite. We report here new data from deformation experiments carried out at high T and P ranging from 3.5 to 6.2 GPa on natural Fe-bearing enstatite single crystals, using the Deformation-DIA apparatus (D-DIA) that equipped the X17B2 beamline of the NSLS (NY, USA). The applied stress and specimen strain rates were measured in situ by X-ray diffraction and imaging techniques (e.g., Raterron & Merkel, 2009, J. Sync. Rad., 16, 748; Raterron et al., 2013, Rev. Sci. Instr., 84, 043906). Three specimen orientations were tested: i) with the compression direction along [101]c crystallographic direction, which forms a 45° angle with both [100] and [001] axes, to investigate [001](100) slip-system activity; ii) along [011]c direction to investigate [001](010) system activity; iii) and along enstatite [125] axis, to activate both slip systems together. Crystals were deformed two by two, to compare slip system activities, or against enstatite aggregates or orientated olivine crystals of known rheology for comparison. Run products

Carboxylic acids in crystallization of macromolecules: learning from successful crystallization experiments.

PubMed

Offermann, Lesa R; He, John Z; Mank, Nicholas J; Booth, William T; Chruszcz, Maksymilian

2014-03-01

The production of macromolecular crystals suitable for structural analysis is one of the most important and limiting steps in the structure determination process. Often, preliminary crystallization trials are performed using hundreds of empirically selected conditions. Carboxylic acids and/or their salts are one of the most popular components of these empirically derived crystallization conditions. Our findings indicate that almost 40 % of entries deposited to the Protein Data Bank (PDB) reporting crystallization conditions contain at least one carboxylic acid. In order to analyze the role of carboxylic acids in macromolecular crystallization, a large-scale analysis of the successful crystallization experiments reported to the PDB was performed. The PDB is currently the largest source of crystallization data, however it is not easily searchable. These complications are due to a combination of a free text format, which is used to capture information on the crystallization experiments, and the inconsistent naming of chemicals used in crystallization experiments. Despite these difficulties, our approach allows for the extraction of over 47,000 crystallization conditions from the PDB. Initially, the selected conditions were investigated to determine which carboxylic acids or their salts are most often present in crystallization solutions. From this group, selected sets of crystallization conditions were analyzed in detail, assessing parameters such as concentration, pH, and precipitant used. Our findings will lead to the design of new crystallization screens focused around carboxylic acids.

A novel structure of gel grown strontium cyanurate crystal and its structural, optical, electrical characterization

NASA Astrophysics Data System (ADS)

Divya, R.; Nair, Lekshmi P.; Bijini, B. R.; Nair, C. M. K.; Gopakumar, N.; Babu, K. Rajendra

2017-12-01

Strontium cyanurate crystals with novel structure and unique optical property like mechanoluminescence have been grown by conventional gel method. Transparent crystals were obtained. The single crystal X-ray diffraction analysis reveals the exquisite structure of the grown crystal. The crystal is centrosymmetric and has a three dimensional polymeric structure. The powder X ray diffraction analysis confirms its crystalline nature. The functional groups present in the crystal were identified by Fourier transform infrared spectroscopy. Elemental analysis confirmed the composition of the complex. A study of thermal properties was done by thermo gravimetric analysis and differential thermal analysis. The optical properties like band gap, refractive index and extinction coefficient were evaluated from the UV visible spectral analysis. The etching study was done to reveal the dislocations in the crystal which in turn explains mechanoluminescence emission. The mechanoluminescence property exhibited by the crystal makes it suitable for stress sensing applications. Besides being a centrosymmetric crystal, it also exhibits NLO behavior. Dielectric properties were studied and theoretical calculations of Fermi energy, valence electron plasma energy, penn gap and polarisability have been done.

Optical control of light propagation in photonic crystal based on electromagnetically induced transparency

NASA Astrophysics Data System (ADS)

Dan, Wang; Jin-Ze, Wu; Jun-Xiang, Zhang

2016-06-01

A kind of photonic crystal structure with modulation of the refractive index is investigated both experimentally and theoretically for exploiting electromagnetically induced transparency (EIT). The combination of EIT with periodically modulated refractive index medium gives rise to high efficiency reflection as well as forbidden transmission in a three-level atomic system coupled by standing wave. We show an accurate theoretical simulation via transfer-matrix theory, automatically accounting for multilayer reflections, thus fully demonstrate the existence of photonic crystal structure in atomic vapor. Project supported by the National Natural Science Foundation of China (Grant No. 11574188) and the Project for Excellent Research Team of the National Natural Science Foundation of China (Grant No. 61121064).

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.

The Morse code effect: A crystal-crystal transformation observed in gel-grown lead (II) oxalate crystals

NASA Astrophysics Data System (ADS)

Lisgarten, J. N.; Marks, J. A.

2018-05-01

This paper reports on an unusual crystal-crystal transformation phenomenon, which we have called the Morse Code Effect, based on the change in appearance of lead(II) oxalate crystals grown in agarose gels.

Crystal Growth Rate Dispersion: A Predictor of Crystal Quality in Microgravity?

NASA Technical Reports Server (NTRS)

Kephart, Richard D.; Judge, Russell A.; Snell, Edward H.; vanderWoerd, Mark J.

2003-01-01

In theory macromolecular crystals grow through a process involving at least two transport phenomena of solute to the crystal surface: diffusion and convection. In absence of standard gravitational forces, the ratio of these two phenomena can change and explain why crystal growth in microgravity is different from that on Earth. Experimental evidence clearly shows, however, that crystal growth of various systems is not equally sensitive to reduction in gravitational forces, leading to quality improvement in microgravity for some crystals but not for others. We hypothesize that the differences in final crystal quality are related to crystal growth rate dispersion. If growth rate dispersion exists on Earth, decreases in microgravity, and coincides with crystal quality improvements then this dispersion is a predictor for crystal quality improvement. In order to test this hypothesis, we will measure growth rate dispersion both in microgravity and on Earth and will correlate the data with previously established data on crystal quality differences for the two environments. We present here the first crystal growth rate measurement data for three proteins (lysozyme, xylose isomerase and human recombinant insulin), collected on Earth, using hardware identical to the hardware to be used in microgravity and show how these data correlate with crystal quality improvements established in microgravity.

Simulation of fluid flows during growth of organic crystals in microgravity

NASA Technical Reports Server (NTRS)

Roberts, Gary D.; Sutter, James K.; Balasubramaniam, R.; Fowlis, William K.; Radcliffe, M. D.; Drake, M. C.

1987-01-01

Several counter diffusion type crystal growth experiments were conducted in space. Improvements in crystal size and quality are attributed to reduced natural convection in the microgravity environment. One series of experiments called DMOS (Diffusive Mixing of Organic Solutions) was designed and conducted by researchers at the 3M Corporation and flown by NASA on the space shuttle. Since only limited information about the mixing process is available from the space experiments, a series of ground based experiments was conducted to further investigate the fluid dynamics within the DMOS crystal growth cell. Solutions with density differences in the range of 10 to the -7 to 10 to the -4 power g/cc were used to simulate microgravity conditions. The small density differences were obtained by mixing D2O and H2O. Methylene blue dye was used to enhance flow visualization. The extent of mixing was measured photometrically using the 662 nm absorbance peak of the dye. Results indicate that extensive mixing by natural convection can occur even under microgravity conditions. This is qualitatively consistent with results of a simple scaling analysis. Quantitave results are in close agreement with ongoing computational modeling analysis.

Crystal structure and properties of tetragonal EuAg{sub 4}In{sub 8} grown by metal flux technique

DOE Office of Scientific and Technical Information (OSTI.GOV)

Subbarao, Udumula; Sarkar, Sumanta; Peter, Sebastian C., E-mail: sebastiancp@jncasr.ac.in

The compound EuAg{sub 4}In{sub 8} has been obtained as single crystals in high yield from reactions run in liquid indium. X-ray diffraction on single crystals suggests that EuAg{sub 4}In{sub 8} crystallizes in the CeMn{sub 4}Al{sub 8} structure type, tetragonal space group I4/mmm with lattice constants a=b=9.7937(2) Å and c=5.7492(2) Å. Crystal structure of EuAg{sub 4}In{sub 8} is composed of pseudo Frank–Kasper cages occupied by one europium atom in each ring, which are shared through the corner along the ab plane resulting in a three dimensional network. The magnetic susceptibility of EuAg{sub 4}In{sub 8} was measured in the temperature range 2–300more » K, which obeyed Curie–Weiss law above 50 K. Magnetic moment value calculated from the fitting indicates the presence of divalent europium, which was confirmed by X-ray absorption near edge spectroscopy. Electrical resistivity measurements suggest that EuAg{sub 4}In{sub 8} is metallic in nature with a probable Fermi liquid behavior at low temperature. - Graphical abstract: The tetragonal EuAg{sub 4}In{sub 8} has been grown as single crystals from reactions run in liquid indium. Magnetic and XANES measurements suggest divalent nature of Eu and resistivity measurements suggest metallic nature. - Highlights: • EuAg{sub 4}In{sub 8} phase having tetragonal phase is grown by metal flux technique. • Magnetic and XANES measurements exhibit divalent nature of Eu in EuAg{sub 4}In{sub 8}. • Resistivity measurement suggests metallic nature and probable Fermi liquid behavior.« less

Crystalline perfection, optical and piezoelectric properties of a novel semi-organic single crystal: Zinc guanidinium sulphate

NASA Astrophysics Data System (ADS)

Nandhini, S.; Murugakoothan, P.

2018-04-01

Zinc Guanidinium Sulfate (ZGuS), a semi-organic single crystal, was synthesized using slow evaporation solution growth technique. It is a non-centrosymmetric crystal with space group I4 ¯2d . The crystalline nature of the crystal and the strain were determined using powder X-ray diffraction analysis. The crystalline perfection of the grown crystal was revealed using HR-XRD analysis. The UV-vis-NIR transmittance spectrum depicts 60% transparency with lower-cut off wavelength of 210 nm. The emission spectrum of the crystal was determined using photoluminescence study. Piezoelectricity was confirmed by determining the piezoelectric charge coefficient (d33). These findings shows that the title compound can be employed for photonic and transducer applications.

Dynamic crystallization of silicate melts

NASA Technical Reports Server (NTRS)

Russell, W. J.

1984-01-01

Two types of furnaces with differing temperature range capabilities were used to provide variations in melt temperatures and cooling rates in a study of the effects of heterogeneous nucleation on crystallization. Materials of chondrule composition were used to further understanding of how the disequilibrium features displayed by minerals in rocks are formed. Results show that the textures of natural chondrules were duplicated. It is concluded that the melt history is dominant over cooling rate and composition in controlling texture. The importance of nuclei, which are most readily derived from preexisting crystalline material, support an origin for natural chondrules based on remelting of crystalline material. This would be compatible with a simple, uniform chondrule forming process having only slight variations in thermal histories resulting in the wide range of textures.

Segregation Phenomena on the Crystal Surface of Chemical Compounds

NASA Astrophysics Data System (ADS)

Tomashpol'skii, Yu. Ya.

2018-06-01

The current state of the theoretical and experimental studies of changes in the chemical structure and composition caused by segregation phenomena on the surface of chemical compounds was reviewed. The review considers the experimental data obtained exclusively on single crystals, which were studied by modern instrumental methods, including in situ Auger electron spectrometry, X-ray spectral microanalysis, high-resolution scanning and transmission electron microscopy, secondary electron emission, and atomic force microscopy. The models that suggest the crystal-chemical diffusion and liquid-phase mechanisms of segregation were described. The parameters of the theory include the type of chemical bond, elastic constants, and crystal-chemical characteristics of substances. The models make it possible to predict the nature of changes in the surface composition: segregation tendency, segregant type, and degree of nonstoichiometry. A new direction in surface segregation was considered, which is promising for nanoelectronics and emission electronics.

Fano resonance in anodic aluminum oxide based photonic crystals.

PubMed

Shang, Guo Liang; Fei, Guang Tao; Zhang, Yao; Yan, Peng; Xu, Shao Hui; Ouyang, Hao Miao; Zhang, Li De

2014-01-08

Anodic aluminum oxide based photonic crystals with periodic porous structure have been prepared using voltage compensation method. The as-prepared sample showed an ultra-narrow photonic bandgap. Asymmetric line-shape profiles of the photonic bandgaps have been observed, which is attributed to Fano resonance between the photonic bandgap state of photonic crystal and continuum scattering state of porous structure. And the exhibited Fano resonance shows more clearly when the sample is saturated ethanol gas than air-filled. Further theoretical analysis by transfer matrix method verified these results. These findings provide a better understanding on the nature of photonic bandgaps of photonic crystals made up of porous materials, in which the porous structures not only exist as layers of effective-refractive-index material providing Bragg scattering, but also provide a continuum light scattering state to interact with Bragg scattering state to show an asymmetric line-shape profile.

Crystal-field effects in fluoride crystals for optical refrigeration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hehlen, Markus P

2010-01-01

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

Crystal Nucleation in Liquids: Open Questions and Future Challenges in Molecular Dynamics Simulations.

PubMed

Sosso, Gabriele C; Chen, Ji; Cox, Stephen J; Fitzner, Martin; Pedevilla, Philipp; Zen, Andrea; Michaelides, Angelos

2016-06-22

The nucleation of crystals in liquids is one of nature's most ubiquitous phenomena, playing an important role in areas such as climate change and the production of drugs. As the early stages of nucleation involve exceedingly small time and length scales, atomistic computer simulations can provide unique insights into the microscopic aspects of crystallization. In this review, we take stock of the numerous molecular dynamics simulations that, in the past few decades, have unraveled crucial aspects of crystal nucleation in liquids. We put into context the theoretical framework of classical nucleation theory and the state-of-the-art computational methods by reviewing simulations of such processes as ice nucleation and the crystallization of molecules in solutions. We shall see that molecular dynamics simulations have provided key insights into diverse nucleation scenarios, ranging from colloidal particles to natural gas hydrates, and that, as a result, the general applicability of classical nucleation theory has been repeatedly called into question. We have attempted to identify the most pressing open questions in the field. We believe that, by improving (i) existing interatomic potentials and (ii) currently available enhanced sampling methods, the community can move toward accurate investigations of realistic systems of practical interest, thus bringing simulations a step closer to experiments.

Crystallization of ikaite and its pseudomorphic transformation into calcite: Raman spectroscopy evidence

NASA Astrophysics Data System (ADS)

Sánchez-Pastor, N.; Oehlerich, Markus; Astilleros, José Manuel; Kaliwoda, Melanie; Mayr, Christoph C.; Fernández-Díaz, Lurdes; Schmahl, Wolfgang W.

2016-02-01

Ikaite (CaCO3·6H2O) is a metastable phase that crystallizes in nature from alkaline waters with high phosphate concentrations at temperatures close to 0 °C. This mineral transforms into anhydrous calcium carbonate polymorphs when temperatures rise or when exposed to atmospheric conditions. During the transformation in some cases the shape of the original ikaite crystal is preserved as a pseudomorph. Pseudomorphs after ikaite are considered as a valuable paleoclimatic indicator. In this work we conducted ikaite crystal growth experiments at near-freezing temperatures using the single diffusion silica gel technique, prepared with a natural aqueous solution from the polymictic lake Laguna Potrok Aike (51°57‧S, 70°23‧W) in Patagonia, Argentina. The ikaite crystals were recovered from the gels and the transformation reactions were monitored by in situ Raman spectroscopy at two different temperatures. The first spectra collected showed the characteristic features of ikaite. In successive spectra new bands at 1072, 1081 and 1086 cm-1 and changes in the intensity of bands corresponding to the OH modes were observed. These changes in the Raman spectra were interpreted as corresponding to intermediate stages of the transformation of ikaite into calcite and/or vaterite. After a few hours, the characteristics of the Raman spectrum were consistent with those of calcite. While ikaite directly transforms into calcite at 10 °C in contact with air, at 20 °C this transformation involves the formation of intermediate, metastable vaterite. During the whole process the external shape of ikaite crystals was preserved. Therefore, this transformation showed the typical characteristics of a pseudomorphic mineral replacement, involving the generation of a large amount of porosity to account for the large difference in molar volumes between ikaite and calcite. A mechanism involving the coupled dissolution of ikaite and crystallization of calcite/vaterite is proposed for this

Rare gases in cyclosilicates and cogenetic minerals

NASA Technical Reports Server (NTRS)

Saito, K.; Alexander, E. C., Jr.; Dragon, J. C.; Zashu, S.

1984-01-01

The cyclosilicate minerals, beryl, tourmaline, and cordierite, typically contain large amounts of He-4 and Ar-40 which are not in situ radiogenic products. In the study of excess rare gases in cyclosilicates, one of the most enigmatic observations is the age effect, a qualitative tendency for geologically older samples to contain more excess He-4 and Ar-40 than younger samples. The present investigation is concerned with measurements regarding the abundance and isotopic composition of all five rare gases in a number of cyclosilicates as well as in their cogenetic minerals. The significance of the obtained data is discussed. The data indicate that cyclosilicates sample the rare gases present in the environment in which they crystallize. This 'sampling' involves major elemental fractionations which are variable but mineral specific. Cyclosilicates can, therefore, be used to probe the isotopic ratios and elemental compositions.

Dynamic Crystallization Experiments on LEW97008: Experimental Reproduction of Chondroid Textures

NASA Technical Reports Server (NTRS)

Nettles, J. W.; Le, L.; Lofgren, G. E.; McSween, H. Y, Jr.

2003-01-01

Dynamic crystallization experiments were conducted using LEW97008 (L3.4) as starting material. Experiments were melted at temperatures well below its liquidus (1250-1450 C) in order to document the textural and compositional changes that occur in UOC material with modest amounts of partial melting and subsequent crystallization. The textures of the experimental products compare very well to natural chondroids (partially melted nebular particles that would become chondrules if more completely melted). Thus it is possible to use the textures in these experiments as a guide to unraveling the melting and cooling histories of natural chondroids. The Antarctic meteorite LEW97008 was chosen as the starting material for our experiments. As an L3.4 it is slightly more metamorphosed than would ordinarily be preferred, but this meteorite is unusually fresh for an Antarctic meteorite, which made it attractive.

Development of natural fiber reinforced polylactide-based biocomposites

NASA Astrophysics Data System (ADS)

Arias Herrera, Andrea Marcela

Polylactide or PLA is a biodegradable polymer that can be produced from renewable resources. This aliphatic polyester exhibits good mechanical properties similar to those of polyethylene terephthalate (PET). Since 2003, bio-based high molecular weight PLA is produced on an industrial scale and commercialized under amorphous and semicrystalline grades for various applications. Enhancement of PLA crystallization kinetics is crucial for the competitiveness of this biopolymer as a commodity material able to replace petroleum-based plastics. On the other hand, the combination of natural fibers with polymer matrices made from renewable resources, to produce fully biobased and biodegradable polymer composite materials, has been a strong trend in research activities during the last decade. Nevertheless, the differences related to the chemical structure, clearly observed in the marked hydrophilic/hydrophobic character of the fibers and the thermoplastic matrix, respectively, represent a major drawback for promoting strong fiber/matrix interactions. The aim of the present study was to investigate the intrinsic fiber/matrix interactions of PLAbased natural fiber composites prepared by melt-compounding. Short flax fibers presenting a nominal length of ˜1 mm were selected as reinforcement and biocomposites containing low to moderate fiber loading were processed by melt-mixing. Fiber bundle breakage during processing led to important reductions in length and diameter. The mean aspect ratio was decreased by about 50%. Quiescent crystallization kinetics of PLA and biocomposite systems was examined under isothermal and non-isothermal conditions. The nucleating nature of the flax fibers was demonstrated and PLA crystallization was effectively accelerated as the natural reinforcement content increased. Such improvement was controlled by the temperature at which crystallization took place, the liquid-to-solid transition being thermodynamically promoted by the degree of supercooling

Crystallization and X-ray diffraction analysis of a putative bacterial class I labdane-related diterpene synthase.

PubMed

Serrano-Posada, Hugo; Centeno-Leija, Sara; Rojas-Trejo, Sonia; Stojanoff, Vivian; Rodríguez-Sanoja, Romina; Rudiño-Piñera, Enrique; Sánchez, Sergio

2015-09-01

Labdane-related diterpenoids are natural products with potential pharmaceutical applications that are rarely found in bacteria. Here, a putative class I labdane-related diterpene synthase (LrdC) identified by genome mining in a streptomycete was successfully crystallized using the microbatch method. Crystals of the LrdC enzyme were obtained in a holo form with its natural cofactor Mg(2+) (LrdC-Mg(2+)) and in complex with inorganic pyrophosphate (PPi) (LrdC-Mg(2+)-PPi). Crystals of native LrdC-Mg(2+) diffracted to 2.50 Å resolution and belonged to the trigonal space group P3221, with unit-cell parameters a = b = 107.1, c = 89.2 Å. Crystals of the LrdC-Mg(2+)-PPi complex grown in the same conditions as the native enzyme with PEG 8000 diffracted to 2.36 Å resolution and also belonged to the trigonal space group P3221. Crystals of the LrdC-Mg(2+)-PPi complex grown in a second crystallization condition with PEG 3350 diffracted to 2.57 Å resolution and belonged to the monoclinic space group P21, with unit-cell parameters a = 49.9, b = 104.1, c = 66.5 Å, β = 111.4°. The structure was determined by the single-wavelength anomalous dispersion (SAD) technique using the osmium signal from a potassium hexachloroosmate (IV) derivative.

The effect of oxygen fugacity on the rheological evolution of crystallizing basaltic melts

NASA Astrophysics Data System (ADS)

Kolzenburg, S.; Di Genova, D.; Giordano, D.; Hess, K. U.; Dingwell, D. B.

2018-04-01

Storage and transport of silicate melts in the Earth's crust and their emplacement on the planet's surface occur almost exclusively at sub-liquidus temperatures. At these conditions, the melts undergo crystallization under a wide range of cooling-rates, deformation-rates, and oxygen fugacities (fO2). Oxygen fugacity is known to influence the thermodynamics and kinetics of crystallization in magmas and lavas. Yet, its influence on sub-liquidus rheology remains largely uncharted. We present the first rheological characterization of crystallizing lavas along natural cooling paths and deformation-rates and at varying fO2. Specifically, we report on apparent viscosity measurements for two crystallizing magmatic suspensions 1) at log ⁡ fO2 of -9.15 (quartz-fayalite-magnetite buffer, QFM, -2.1) and 2) in air. These fugacities span a range of reduced to oxidized conditions pertinent to magma migration and lava emplacement. We find that: 1) crystallization at constant cooling-rates results in a quasi-exponential increase in the apparent viscosity of the magmatic suspensions until they achieve their rheological cut off temperature (Tcutoff), where the melt effectively solidifies 2) the rheological departure and Tcutoff increase with increasing fO2 and 3) increasing fO2 results in decreased crystallization-rates. Based on the experimental results and by comparison with previous rheological isothermal studies we propose a generalisation of the effect of fO2 on the dynamic rheological evolution of natural magmatic and volcanic suspensions. We further discuss the implications for magmatic transport in plumbing and storage systems (e.g. conduits, dikes and magma chambers) and during lava flow emplacement.

Liquid Crystals in Chromatography

NASA Astrophysics Data System (ADS)

Witkiewicz, Zygfryd

The following sections are included: * INTRODUCTION * LIQUID CRYSTALS SUITABLE FOR GAS CHROMATOGRAPHY * Monomeric Liquid Crystal Stationary Phases * Polymeric Liquid Crystal Stationary Phases * Polymeric Liquid Crystal Stationary Phases * Conventional Analytical Columns * Capillary Columns * FACTORS AFFECTING THE CHROMATOGRAPHIC SEPARATIONS ON LIQUID CRYSTAL STATIONARY PHASES * Kind of Mesophase of the Liquid Crystal * Molecular Structure of the Liquid Crystals and of the Chromatographed Substances * Substrate on which the Liquid Crystal is Deposited * ANALYTICAL APPLICATIONS OF LIQUID CRYSTAL STATIONARY PHASES IN GAS CHROMATOGRAPHY * Separation of Isomers of Benzene and Naphthalene Derivatives * Separation of Alkane and Alkene Isomers * Separation of Mixtures of Benzene and Aliphatic Hydrocarbon Derivatives Containing Heteroatoms * Separation of Polynuclear Hydrocarbons * INVESTIGATION OF THE PROPERTIES OF LIQUID CRYSTALS BY GAS CHROMATOGRAPHY * APPLICATION OF LIQUID CRYSTALS IN LIQUID CHROMATOGRAPHY * Column Chromatography * Thin-Layer Chromatography * APPLICATION OF LIQUID CRYSTAL STATIONARY PHASES IN SUPERCRITICAL FLUID CHROMATOGRAPHY * FINAL REMARKS * References

Structure of a new crystal form of human Hsp70 ATPase domain.

PubMed

Osipiuk, J; Walsh, M A; Freeman, B C; Morimoto, R I; Joachimiak, A

1999-05-01

Hsp70 proteins are highly conserved proteins induced by heat shock and other stress conditions. An ATP-binding domain of human Hsp70 protein has been crystallized in two major morphological forms at pH 7.0 in the presence of PEG 8000 and CaCl2. Both crystal forms belong to the orthorhombic space group P212121, but show no resemblance in unit-cell parameters. Analysis of the crystal structures for both forms shows a 1-2 A shift of one of the subdomains of the protein. This conformational change could reflect a 'natural' flexibility of the protein which might be relevant to ATP binding and may facilitate the interaction of other proteins with Hsp70 protein.

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.

Thermal Decomposition Study on CuInSe2 Single Crystals

NASA Astrophysics Data System (ADS)

Chauhan, Sanjaysinh M.; Chaki, Sunil H.; Deshpande, M. P.; Malek, Tasmira J.; Tailor, J. P.

2018-01-01

The thermal analysis of the chemical vapor transport (CVT)-grown CuInSe2 single crystals was carried out by recording the thermogravimetric, differential thermogravimetric and differential thermal analysis curves. All the three thermo-curves were recorded simultaneously by thermal analyzer in the temperature range of ambient to 1080 K in inert nitrogen atmosphere. The thermo-curves were recorded for four heating rates of 5 K \\cdot min^{-1}, 10 K \\cdot min^{-1}, 15 K \\cdot min^{-1} and 20 K \\cdot min^{-1}. The TG curve analysis showed negligible mass loss in the temperature range of ambient to 600 K, stating the sample material to be thermally stable in this temperature range. Above 601 K to the temperature of 1080 K, the sample showed continuous mass loss. The DTG curves showed two peaks in the temperature range of 601 K to 1080 K. The corresponding DTA showed initial minor exothermic nature followed by endothermic nature up to nearly 750 K and above it showed exothermic nature. The initial exothermic nature is due to absorbed water converting to water vapor, whereas the endothermic nature states the absorption of heat by the sample up to nearly 950 K. Above nearly 950 K the exothermic nature is due to the decomposition of sample material. The absorption of heat in the endothermic region is substantiated by corresponding weight loss in TG. The thermal kinetic parameters of the CVT-grown CuInSe2 single crystals were determined employing the non-mechanistic Kissinger relation. The determined kinetic parameters support the observations of the thermo-curves.

Laboratory multiple-crystal X-ray topography and reciprocal-space mapping of protein crystals: influence of impurities on crystal perfection

NASA Technical Reports Server (NTRS)

Hu, Z. W.; Thomas, B. R.; Chernov, A. A.

2001-01-01

Double-axis multiple-crystal X-ray topography, rocking-curve measurements and triple-axis reciprocal-space mapping have been combined to characterize protein crystals using a laboratory source. Crystals of lysozyme and lysozyme crystals doped with acetylated lysozyme impurities were examined. It was shown that the incorporation of acetylated lysozyme into crystals of lysozyme induces mosaic domains that are responsible for the broadening and/or splitting of rocking curves and diffraction-space maps along the direction normal to the reciprocal-lattice vector, while the overall elastic lattice strain of the impurity-doped crystals does not appear to be appreciable in high angular resolution reciprocal-space maps. Multiple-crystal monochromatic X-ray topography, which is highly sensitive to lattice distortions, was used to reveal the spatial distribution of mosaic domains in crystals which correlates with the diffraction features in reciprocal space. Discussions of the influence of acetylated lysozyme on crystal perfection are given in terms of our observations.

Laboratory multiple-crystal X-ray topography and reciprocal-space mapping of protein crystals: influence of impurities on crystal perfection.

PubMed

Hu, Z W; Thomas, B R; Chernov, A A

2001-06-01

Double-axis multiple-crystal X-ray topography, rocking-curve measurements and triple-axis reciprocal-space mapping have been combined to characterize protein crystals using a laboratory source. Crystals of lysozyme and lysozyme crystals doped with acetylated lysozyme impurities were examined. It was shown that the incorporation of acetylated lysozyme into crystals of lysozyme induces mosaic domains that are responsible for the broadening and/or splitting of rocking curves and diffraction-space maps along the direction normal to the reciprocal-lattice vector, while the overall elastic lattice strain of the impurity-doped crystals does not appear to be appreciable in high angular resolution reciprocal-space maps. Multiple-crystal monochromatic X-ray topography, which is highly sensitive to lattice distortions, was used to reveal the spatial distribution of mosaic domains in crystals which correlates with the diffraction features in reciprocal space. Discussions of the influence of acetylated lysozyme on crystal perfection are given in terms of our observations.

Ultrafast carrier dynamics in organic molecular crystals and conjugated polymers

NASA Astrophysics Data System (ADS)

Hegmann, Frank

2005-03-01

Organic semiconductors are being extensively studied by many research groups around the world for applications in electronic and photonic devices. For example, much work has focused on the development of organic thin film transistors based on thermally evaporated pentacene films, where the polycrystalline morphology typically results in a thermally-activated carrier mobility. On the other hand, more intrinsic bandlike transport, where the carrier mobility increases as the temperature decreases, has been observed in many organic single crystals. However, the nature of charge transport in organic molecular crystals is still not understood. Also, despite many advances in organic photonics, the nature of photocarrier generation in organic semiconductors is not completely understood and remains controversial even today. The generation of mobile charge carriers in photoexcited organic materials occurs over femtosecond to picosecond time scales, and so ultrafast pump-probe experiments are essential in order to improve our understanding of fundamental processes in these materials. Recently, time-resolved terahertz pulse spectroscopy has been used to directly probe transient photoconductivity in pentacene and functionalized pentacene thin films and single crystals [1,2], revealing photogeneration of mobile charge carriers over sub-picosecond time scales as well as bandlike carrier transport in both single crystal and thin film samples [1]. This talk will provide an overview of ultrafast carrier dynamics in organic semiconductors, and will emphasize how time-resolved terahertz pulse spectroscopy can be used to help understand the nature of photoexcitations and carrier transport in organic materials. (This work was supported by NSERC, CFI, CIPI, the Killam Trust, and ONR. Collaborators for this work are listed in Ref. 1.) [1] O. Ostroverkhova, D. G. Cooke, S. Shcherbyna, R. F. Egerton, F. A. Hegmann, R. R. Tykwinski, and J. E. Anthony, Phys. Rev. B., in press. [2] V. K

Effects of impurities on crystal growth in fructose crystallization

NASA Astrophysics Data System (ADS)

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

1989-10-01

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

Phyllotactic transformations as plastic deformations of tubular crystals with defects

NASA Astrophysics Data System (ADS)

Beller, Daniel; Nelson, David

Tubular crystals are 2D lattices in cylindrical topologies, which could be realized as assemblies of colloidal particles, and occur naturally in biological microtubules and in single-walled carbon nanotubes. Their geometry can be understood in the language of phyllotaxis borrowed from botany. We study the mechanics of plastic deformations in tubular crystals in response to tensile stress, as mediated by the formation and separation of dislocation pairs in a triangular lattice. Dislocation motion allows the growth of one phyllotactic arrangement at the expense of another, offering a low-energy, stepwise mode of plastic deformation in response to external stresses. Through theory and simulation, we examine how the tube's radius and helicity affects, and is in turn altered by, dislocation glide. The crystal's bending modulus is found to produce simple but important corrections to the tube's deformation mechanics.

High-throughput crystallization screening.

PubMed

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

2014-01-01

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

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.

Process development and characterization of centrosymmetric semiorganic nonlinear optical crystal: 4-dimethylaminopyridine potassium chloride

NASA Astrophysics Data System (ADS)

Johnson, J.; Srineevasan, R.; Sivavishnu, D.

2018-06-01

Centrosymmetric semiorganic crystal 4-dimethylaminopyridine potassium chloride (4-DMAPKC) has been grown successfully by using slow evaporation solution growth technique. Powder x-ray diffraction shows the 4-DMAPKC crystal has good crystalline nature. Single crystal XRD shows that the grown 4-DMAPKC is cubic crystal system with cell parameters a = 3.09 Å, b = 3.09 Å, c = 3.09 Å. Investigation has been carried out to assign the Vibrational frequencies of the grown crystal by FTIR spectral studies. UVsbnd Visible NIR optical absorption spectral studies in the range of 200-1100 nm shows low absorption in UVsbnd Visible region with lower cutoff wave length at 261 nm and optical band gap energy was found as Eg = 5.52 eV. Optically transmittance spectral shows 4-DMAPKC crystal is very good transparency in UV-Visible NIR region. Thermogravimetry and differential thermal (TG-DTA) analysis were carried out. Dielectric studies of as grown crystal sample exhibit low dielectric constant and loss at higher frequencies and attests the nonlinear optical activity. Micro hardness studies of as grown crystal were discussed. Second harmonic generation (SHG) efficiency of the 4-DMAPKC is 0.69 times as that of KDP.

Synthesis and structural characterization of bulk Sb2Te3 single crystal

NASA Astrophysics Data System (ADS)

Sultana, Rabia; Gahtori, Bhasker; Meena, R. S.; Awana, V. P. S.

2018-05-01

We report the growth and characterization of bulk Sb2Te3 single crystal synthesized by the self flux method via solid state reaction route from high temperature melt (850˚C) and slow cooling (2˚C/hour) of constituent elements. The single crystal X-ray diffraction pattern showed the 00l alignment and the high crystalline nature of the resultant sample. The rietveld fitted room temperature powder XRD revealed the phase purity and rhombohedral structure of the synthesized crystal. The formation and analysis of unit cell structure further verified the rhombohedral structure composed of three quintuple layers stacked one over the other. The SEM image showed the layered directional growth of the synthesized crystal carried out using the ZEISS-EVOMA-10 scanning electron microscope The electrical resistivity measurement was carried out using the conventional four-probe method on a quantum design Physical Property Measurement System (PPMS). The temperature dependent electrical resistivity plot for studied Sb2Te3 single crystal depicts metallic behaviour in the absence of any applied magnetic field. The synthesis as well as the structural characterization of as grown Sb2Te3 single crystal is reported and discussed in the present letter.

Liquid crystal nanocomposites produced by mixtures of hydrogen bonded achiral liquid crystals and functionalized carbon nanotubes

NASA Astrophysics Data System (ADS)

Katranchev, B.; Petrov, M.; Keskinova, E.; Naradikian, H.; Rafailov, P. M.; Dettlaff-Weglikowska, U.; Spassov, T.

2014-12-01

The liquid crystalline (LC) nature of alkyloxybenzoic acids is preserved after adding of any mesogenic or non-mesogenic compound through hydrogen bonding. However, this noncovalent interaction provokes a sizable effect on the physical properties as, e. g. melting point and mesomorphic states. In the present work we investigate nanocomposites, prepared by mixture of the eighth homologue of p-n-alkyloxybenzoic acids (8OBA) with single-walled carbon nanotubes (SWCNT) with the purpose to modify the optical properties of the liquid crystal. We exercise optical control on the LC system by inserting SWCNT specially functionalized by carboxylic groups. Since the liquid crystalline state combines order and mobility at the molecular (nanoscale) level, molecular modification can lead to different macroscopical nanocomposite symmetry. The thermal properties of the functionalized nanocomposite are confirmed by DSC analyses. The mechanism of the interaction between surface-treated nanoparticles (functionalized nanotubes) and the liquid crystal 8OBA bent- dimer molecules is briefly discussed.

Interaction between Convection and Heat Transfer in Crystal Growth

NASA Technical Reports Server (NTRS)

1998-01-01

Crystals are integral components in some of our most sophisticated and rapidly developing industries. Single crystals are solids with the most uniform structures that can be obtained on an atomic scale. Because of their structural uniformity, crystals can transmit acoustic and electromagnetic waves and charged particles with essentially no scattering or interferences. This transparency, which can be selectively modified by controlled additions of impurities known as dopants, is the foundation of modern electronic industry. It has brought about widespread application of crystals in transistors, lasers, microwave devices, infrared detectors, magnetic memory devices, and many other magnets and electro-optic components. The performance of a crystal depends strongly on its compositional homogeneity. For instance, in modern microcircuitry, compositional variations of a few percent (down to a submicron length scale) can seriously jeopardize predicted yields. Since crystals are grown by carefully controlled phase transformations, the compositional adjustment in the solid is often made during growth from the nutrient. Hence, a detailed understanding of mass transfer in the nutrient is essential. Moreover, since mass transfer is often the slowest process during growth, it is usually the rate limiting mechanism. Crystal growth processes are usually classified according to the nature of the parent phase. Nevertheless, whether the growth occurs by solidification from a melt (melt growth), nucleation from a solution (solution growth), condensation from a vapor (physical vapor transport) or chemical reaction of gases (chemical vapor deposition), the parent phase is a fluid. As is with most non-equilibrium processes involving fluids, liquid or vapor, fluid motion plays an important role, affecting both the concentration and temperature gradients at the soli-liquid interface.

Discrete structures in continuum descriptions of defective crystals

PubMed Central

2016-01-01

I discuss various mathematical constructions that combine together to provide a natural setting for discrete and continuum geometric models of defective crystals. In particular, I provide a quite general list of ‘plastic strain variables’, which quantifies inelastic behaviour, and exhibit rigorous connections between discrete and continuous mathematical structures associated with crystalline materials that have a correspondingly general constitutive specification. PMID:27002070

Microgravity protein crystallization

PubMed Central

McPherson, Alexander; DeLucas, Lawrence James

2015-01-01

Over the past 20 years a variety of technological advances in X-ray crystallography have shortened the time required to determine the structures of large macromolecules (i.e., proteins and nucleic acids) from several years to several weeks or days. However, one of the remaining challenges is the ability to produce diffraction-quality crystals suitable for a detailed structural analysis. Although the development of automated crystallization systems combined with protein engineering (site-directed mutagenesis to enhance protein solubility and crystallization) have improved crystallization success rates, there remain hundreds of proteins that either cannot be crystallized or yield crystals of insufficient quality to support X-ray structure determination. In an attempt to address this bottleneck, an international group of scientists has explored use of a microgravity environment to crystallize macromolecules. This paper summarizes the history of this international initiative along with a description of some of the flight hardware systems and crystallization results. PMID:28725714

Characterisation of a natural quartz crystal as a reference material for microanalytical determination of Ti, Al, Li, Fe, Mn, Ga and Ge

USGS Publications Warehouse

Audetat, Andreas; Garbe-Schonberg, Dieter; Kronz, Andreas; Pettke, Thomas; Rusk, Brian G.; Donovan, John J.; Lowers, Heather

2015-01-01

A natural smoky quartz crystal from Shandong province, China, was characterised by laser ablation ICP-MS, electron probe microanalysis (EPMA) and solution ICP-MS to determine the concentration of twenty-four trace and ultra trace elements. Our main focus was on Ti quantification because of the increased use of this element for titanium-in-quartz (TitaniQ) thermobarometry. Pieces of a uniform growth zone of 9 mm thickness within the quartz crystal were analysed in four different LA-ICP-MS laboratories, three EPMA laboratories and one solution-ICP-MS laboratory. The results reveal reproducible concentrations of Ti (57 ± 4 μg g-1), Al (154 ± 15 μg g-1), Li (30 ± 2 μg g-1), Fe (2.2 ± 0.3 μg g-1), Mn (0.34 ± 0.04 μg g-1), Ge (1.7 ± 0.2 μg g-1) and Ga (0.020 ± 0.002 μg g-1) and detectable, but less reproducible, concentrations of Be, B, Na, Cu, Zr, Sn and Pb. Concentrations of K, Ca, Sr, Mo, Ag, Sb, Ba and Au were below the limits of detection of all three techniques. The uncertainties on the average concentration determinations by multiple techniques and laboratories for Ti, Al, Li, Fe, Mn, Ga and Ge are low; hence, this quartz can serve as a reference material or a secondary reference material for microanalytical applications involving the quantification of trace elements in quartz.

Ordered macro-microporous metal-organic framework single crystals

NASA Astrophysics Data System (ADS)

Shen, Kui; Zhang, Lei; Chen, Xiaodong; Liu, Lingmei; Zhang, Daliang; Han, Yu; Chen, Junying; Long, Jilan; Luque, Rafael; Li, Yingwei; Chen, Banglin

2018-01-01

We constructed highly oriented and ordered macropores within metal-organic framework (MOF) single crystals, opening up the area of three-dimensional–ordered macro-microporous materials (that is, materials containing both macro- and micropores) in single-crystalline form. Our methodology relies on the strong shaping effects of a polystyrene nanosphere monolith template and a double-solvent–induced heterogeneous nucleation approach. This process synergistically enabled the in situ growth of MOFs within ordered voids, rendering a single crystal with oriented and ordered macro-microporous structure. The improved mass diffusion properties of such hierarchical frameworks, together with their robust single-crystalline nature, endow them with superior catalytic activity and recyclability for bulky-molecule reactions, as compared with conventional, polycrystalline hollow, and disordered macroporous ZIF-8.

Sparsity-based image monitoring of crystal size distribution during crystallization

NASA Astrophysics Data System (ADS)

Liu, Tao; Huo, Yan; Ma, Cai Y.; Wang, Xue Z.

2017-07-01

To facilitate monitoring crystal size distribution (CSD) during a crystallization process by using an in-situ imaging system, a sparsity-based image analysis method is proposed for real-time implementation. To cope with image degradation arising from in-situ measurement subject to particle motion, solution turbulence, and uneven illumination background in the crystallizer, sparse representation of a real-time captured crystal image is developed based on using an in-situ image dictionary established in advance, such that the noise components in the captured image can be efficiently removed. Subsequently, the edges of a crystal shape in a captured image are determined in terms of the salience information defined from the denoised crystal images. These edges are used to derive a blur kernel for reconstruction of a denoised image. A non-blind deconvolution algorithm is given for the real-time reconstruction. Consequently, image segmentation can be easily performed for evaluation of CSD. The crystal image dictionary and blur kernels are timely updated in terms of the imaging conditions to improve the restoration efficiency. An experimental study on the cooling crystallization of α-type L-glutamic acid (LGA) is shown to demonstrate the effectiveness and merit of the proposed method.

Crystal growth and magnetic properties of equiatomic CeAl

NASA Astrophysics Data System (ADS)

Das, Pranab Kumar; Thamizhavel, A.

2015-03-01

Single crystal of CeAl has been grown by flux method using Ce-Al self-flux. Several needle like single crystals were obtained and the length of the needle corresponds to the [001] crystallographic direction. Powder x-ray diffraction revealed that CeAl crystallizes in orthorhombic CrB-type structure with space group Cmcm (no. 63). The magnetic properties have been investigated by means of magnetic susceptibility, isothermal magnetization, electrical transport, and heat capacity measurements. CeAl is found to order antiferromagnetically with a Neel temperature TN = 10 K. The magnetization data below the ordering temperature reveals two metamagentic transitions for fields less than 20 kOe. From the inverse magnetic susceptibility an effective moment of 2.66 μB/Ce has been estimated, which indicates that Ce is in its trivalent state. Electrical resistivity data clearly shows a sharp drop at 10 K due to the reduction of spin disorder scattering of conduction electrons thus confirming the magnetic ordering. The estimated residual resistivity ratio (RRR) is 33, thus indicating a good quality of the single crystal. The bulk nature of the magnetic ordering is also confirmed by heat capacity data. From the Schottky anomaly of the heat capacity we have estimated the crystal field level splitting energies of the (2J + 1) degenerate ground state as 25 K and 175 K respectively for the fist and second excited states.

Thermally induced gelling of oil-in-water emulsions comprising partially crystallized droplets: the impact of interfacial crystals.

PubMed

Thivilliers, Florence; Laurichesse, Eric; Saadaoui, Hassan; Leal-Calderon, Fernando; Schmitt, Véronique

2008-12-02

We produced triglyceride-in-water emulsions comprising partially crystallized droplets, stabilized by a mixture of protein and low molecular weight surfactant. The emulsions were emulsified in the melted state of the oil phase and stored at low temperature (4 degrees C) right after fabrication to induce oil crystallization. The systems were then warmed to room temperature for a short period of time and cooled again to 4 degrees C. Owing to this treatment referred to as temperature cycling or "tempering", the initially fluid emulsions turned into hard gels. We followed the bulk rheological properties of the materials during and after tempering. The storage modulus, G', exhibited a dramatic increase when tempering was applied. We showed that the systems evolved following two distinct regimes that depend on the average droplet size and on the surfactant-to-protein molar ratio. Gelling may involve partial coalescence of the droplets, i.e., film rupturing with no further shape relaxation because of the solid nature of the droplets. Alternatively, gelling may occur without film rupturing, and is reminiscent of a jamming transition induced by surface roughness. We discussed the origin of these two mechanisms in terms of the properties (size and protuberance) of the interfacial oil crystals.

Constraining Cometary Crystal Shapes from IR Spectral Features

NASA Technical Reports Server (NTRS)

Wooden, Diane H.; Lindsay, Sean; Harker, David E.; Kelley, Michael S. P.; Woodward, Charles E.; Murphy, James Richard

2013-01-01

A major challenge in deriving the silicate mineralogy of comets is ascertaining how the anisotropic nature of forsterite crystals affects the spectral features' wavelength, relative intensity, and asymmetry. Forsterite features are identified in cometary comae near 10, 11.05-11.2, 16, 19, 23.5, 27.5 and 33 microns [1-10], so accurate models for forsterite's absorption efficiency (Qabs) are a primary requirement to compute IR spectral energy distributions (SEDs, lambdaF lambda vs. lambda) and constrain the silicate mineralogy of comets. Forsterite is an anisotropic crystal, with three crystallographic axes with distinct indices of refraction for the a-, b-, and c-axis. The shape of a forsterite crystal significantly affects its spectral features [13-16]. We need models that account for crystal shape. The IR absorption efficiencies of forsterite are computed using the discrete dipole approximation (DDA) code DDSCAT [11,12]. Starting from a fiducial crystal shape of a cube, we systematically elongate/reduce one of the crystallographic axes. Also, we elongate/reduce one axis while the lengths of the other two axes are slightly asymmetric (0.8:1.2). The most significant grain shape characteristic that affects the crystalline spectral features is the relative lengths of the crystallographic axes. The second significant grain shape characteristic is breaking the symmetry of all three axes [17]. Synthetic spectral energy distributions using seven crystal shape classes [17] are fit to the observed SED of comet C/1995 O1 (Hale-Bopp). The Hale-Bopp crystalline residual better matches equant, b-platelets, c-platelets, and b-columns spectral shape classes, while a-platelets, a-columns and c-columns worsen the spectral fits. Forsterite condensation and partial evaporation experiments demonstrate that environmental temperature and grain shape are connected [18-20]. Thus, grain shape is a potential probe for protoplanetary disk temperatures where the cometary crystalline

Chromatographic study of formation conditions of rhombododecahedral diamond crystals

NASA Astrophysics Data System (ADS)

Zhimulev, E. I.; Sonin, V. M.; Chepurov, A. I.; Tomilenko, A. A.

2009-06-01

The results of chromatographic study of the formation of rhombododecahedral diamonds synthesized in the Fe-Ni-(Ti)-C system at 5.5-6.0 GPa and 1350-1450°C are presented, including crystals with rounded surfaces of the rhombododecahedron with parallel striation, which are morphological analogues of natural diamonds abundant at various kimberlite, lamproite, and placer deposits. Chromatography was performed at 150°C with mechanical breakup of diamonds. The stable release of methane when diamonds of habit {110} are crushed is established. It is concluded that the appearance of the habit rhombododecahedron may be related not only to the effect of temperature and pressure on crystal growth but also to reductive conditions of crystallization. At the same time, the appearance of significant amounts of hydrocarbons in the system probably results in stopping of the growth of faces {110} and {100} and, instead, formation of specific surfaces that are composed of microscopic accessories faced by planes {111}.

Structure of Profiled Crystals Based on Solid Solutions of Bi2Te3 and Their X-Ray Diagnostics

NASA Astrophysics Data System (ADS)

Voronin, A. I.; Bublik, V. T.; Tabachkova, N. Yu.; Belov, Yu. M.

2011-05-01

In this work, we used x-ray structural diagnostic data to reveal the formation of structural regularities in profiled polycrystalline ingots based on Bi and Sb chalcogenide solid solutions. In Bi2Te3 lattice crystals, the solid phase grows such that the cleavage surfaces are perpendicular to the crystallization front. The crystallization singularity determines the nature of the growth texture. Because texture is an important factor determining the anisotropy of properties, which in turn determines the suitability of an ingot for production of modules and the possibility of figure of merit improvement, its diagnostics is an important issue for technology testing. Examples of texture analysis using the method of straight pole figure (SPF) construction for profiled crystals are provided. The structure of the surface layers in the profiled ingots was studied after electroerosion cutting. In addition, the method of estimation of the disturbed layer depth based on the nature of texture changes was used.

GIXAFS study of Fe3+ sorption and precipitation on natural quartz surfaces

USGS Publications Warehouse

Waychunas, G.; Davis, J.; Reitmeyer, R.

1999-01-01

Grazing-incidence EXAFS has been used to characterize the structure of Fe3+ sorbed onto natural single crystal quartz surfaces. Fe3+ sorption at ca. 5% monolayer coverage on a natural crystal allowed to equilibrate in air resulted in formation of hematite nuclei with strong texturing on r-and m-planes. EXAFS calculations suggests that both O and Fe backscattering is necessary to yield acceptable structural models, that about 50% of the sorbed iron resides in nuclei, and that the approximate dimensions of the nuclei can be estimated via Feff 7.0 calculations of various nuclei sizes and shapes.

Discovery of a diamond-based photonic crystal structure in beetle scales.

PubMed

Galusha, Jeremy W; Richey, Lauren R; Gardner, John S; Cha, Jennifer N; Bartl, Michael H

2008-05-01

We investigated the photonic crystal structure inside iridescent scales of the weevil Lamprocyphus augustus. By combining a high-resolution structure analysis technique based on sequential focused ion beam milling and scanning electron microscopy imaging with theoretical modeling and photonic band-structure calculations, we discovered a natural three-dimensional photonic structure with a diamond-based crystal lattice operating at visible wavelengths. Moreover, we found that within individual scales, the diamond-based structure is assembled in the form of differently oriented single-crystalline micrometer-sized pixels with only selected lattice planes facing the scales' top surface. A comparison of results obtained from optical microreflectance measurements with photonic band-structure calculations reveals that it is this sophisticated microassembly of the diamond-based crystal lattice that lends Lamprocyphus augustus its macroscopically near angle-independent green coloration.

Incorporation of Uranium into Hematite during Crystallization from Ferrihydrite

PubMed Central

2014-01-01

Ferrihydrite was exposed to U(VI)-containing cement leachate (pH 10.5) and aged to induce crystallization of hematite. A combination of chemical extractions, TEM, and XAS techniques provided the first evidence that adsorbed U(VI) (≈3000 ppm) was incorporated into hematite during ferrihydrite aggregation and the early stages of crystallization, with continued uptake occurring during hematite ripening. Analysis of EXAFS and XANES data indicated that the U(VI) was incorporated into a distorted, octahedrally coordinated site replacing Fe(III). Fitting of the EXAFS showed the uranyl bonds lengthened from 1.81 to 1.87 Å, in contrast to previous studies that have suggested that the uranyl bond is lost altogether upon incorporation into hematite. The results of this study both provide a new mechanistic understanding of uranium incorporation into hematite and define the nature of the bonding environment of uranium within the mineral structure. Immobilization of U(VI) by incorporation into hematite has clear and important implications for limiting uranium migration in natural and engineered environments. PMID:24580024

Ultra-thin ZnSe: Anisotropic and flexible crystal structure

NASA Astrophysics Data System (ADS)

Bacaksiz, C.; Senger, R. T.; Sahin, H.

2017-07-01

By performing density functional theory-based calculations, we investigate the structural, electronic, and mechanical properties of the thinnest ever ZnSe crystal [11]. The vibrational spectrum analysis reveals that the monolayer ZnSe is dynamically stable and has flexible nature with its soft phonon modes. In addition, a direct electronic band gap is found at the gamma point for the monolayer structure of ZnSe. We also elucidate that the monolayer ZnSe has angle dependent in-plane elastic parameters. In particular, the in-plane stiffness values are found to be 2.07 and 6.89 N/m for the arm-chair and zig-zag directions, respectively. The angle dependency is also valid for the Poisson ratio of the monolayer ZnSe. More significantly, the in-plane stiffness of the monolayer ZnSe is the one-tenth of Young modulus of bulk zb-ZnSe which indicates that the monolayer ZnSe is a quite flexible single layer crystal. With its flexible nature and in-plane anisotropic mechanical properties, the monolayer ZnSe is a good candidate for nanoscale mechanical applications.

World's Largest Gold Crystal Studied at Los Alamos

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vogel, Sven; Nakotte, Heinz

2014-04-03

When geologist John Rakovan needed better tools to investigate whether a dazzling 217.78-gram piece of gold was in fact the world's largest single-crystal specimen - a distinguishing factor that would not only drastically increase its market value but also provide a unique research opportunity - he traveled to Los Alamos National Laboratory's Lujan Neutron Scattering Center to peer deep inside the mineral using neutron diffractometry. Neutrons, different from other probes such as X-rays and electrons, are able to penetrate many centimeters deep into most materials. Revealing the inner structure of a crystal without destroying the sample - imperative, as thismore » one is worth an estimated $1.5 million - would allow Rakovan and Lujan Center collaborators Sven Vogel and Heinz Nakotte to prove that this exquisite nugget, which seemed almost too perfect and too big to be real, was a single crystal and hence a creation of nature. Its owner, who lives in the United States, provided the samples to Rakovan to assess the crystallinity of four specimens, all of which had been found decades ago in Venezuela.« less

World's Largest Gold Crystal Studied at Los Alamos

ScienceCinema

Vogel, Sven; Nakotte, Heinz

2018-02-07

When geologist John Rakovan needed better tools to investigate whether a dazzling 217.78-gram piece of gold was in fact the world's largest single-crystal specimen - a distinguishing factor that would not only drastically increase its market value but also provide a unique research opportunity - he traveled to Los Alamos National Laboratory's Lujan Neutron Scattering Center to peer deep inside the mineral using neutron diffractometry. Neutrons, different from other probes such as X-rays and electrons, are able to penetrate many centimeters deep into most materials. Revealing the inner structure of a crystal without destroying the sample - imperative, as this one is worth an estimated $1.5 million - would allow Rakovan and Lujan Center collaborators Sven Vogel and Heinz Nakotte to prove that this exquisite nugget, which seemed almost too perfect and too big to be real, was a single crystal and hence a creation of nature. Its owner, who lives in the United States, provided the samples to Rakovan to assess the crystallinity of four specimens, all of which had been found decades ago in Venezuela.

Direct Photolithography on Molecular Crystals for High Performance Organic Optoelectronic Devices.

PubMed

Yao, Yifan; Zhang, Lei; Leydecker, Tim; Samorì, Paolo

2018-05-23

Organic crystals are generated via the bottom-up self-assembly of molecular building blocks which are held together through weak noncovalent interactions. Although they revealed extraordinary charge transport characteristics, their labile nature represents a major drawback toward their integration in optoelectronic devices when the use of sophisticated patterning techniques is required. Here we have devised a radically new method to enable the use of photolithography directly on molecular crystals, with a spatial resolution below 300 nm, thereby allowing the precise wiring up of multiple crystals on demand. Two archetypal organic crystals, i.e., p-type 2,7-diphenyl[1]benzothieno[3,2- b][1]benzothiophene (Dph-BTBT) nanoflakes and n-type N, N'-dioctyl-3,4,9,10-perylenedicarboximide (PTCDI-C8) nanowires, have been exploited as active materials to realize high-performance top-contact organic field-effect transistors (OFETs), inverter and p-n heterojunction photovoltaic devices supported on plastic substrate. The compatibility of our direct photolithography technique with organic molecular crystals is key for exploiting the full potential of organic electronics for sophisticated large-area devices and logic circuitries, thus paving the way toward novel applications in plastic (opto)electronics.

Magnesium-aspartate-based crystallization switch inspired from shell molt of crustacean

PubMed Central

Tao, Jinhui; Zhou, Dongming; Zhang, Zhisen; Xu, Xurong; Tang, Ruikang

2009-01-01

Many animals such as crustacean periodically undergo cyclic molt of the exoskeleton. During this process, amorphous calcium mineral phases are biologically stabilized by magnesium and are reserved for the subsequent rapid formation of new shell tissue. However, it is a mystery how living organisms can regulate the transition of the precursor phases precisely. We reveal that the shell mineralization from the magnesium stabilized precursors is associated with the presence of Asp-rich proteins. It is suggested that a cooperative effect of magnesium and Asp-rich compound can result into a crystallization switch in biomineralization. Our in vitro experiments confirm that magnesium increases the lifetime of amorphous calcium carbonate and calcium phosphate in solution so that the crystallization can be temporarily switched off. Although Asp monomer alone inhibits the crystallization of pure amorphous calcium minerals, it actually reduces the stability of the magnesium-stabilized precursors to switch on the transformation from the amorphous to crystallized phases. These modification effects on crystallization kinetics can be understood by an Asp-enhanced magnesium desolvation model. The interesting magnesium-Asp-based switch is a biologically inspired lesson from nature, which can be developed into an advanced strategy to control material fabrications. PMID:20007788

Magnesium-aspartate-based crystallization switch inspired from shell molt of crustacean.

PubMed

Tao, Jinhui; Zhou, Dongming; Zhang, Zhisen; Xu, Xurong; Tang, Ruikang

2009-12-29

Many animals such as crustacean periodically undergo cyclic molt of the exoskeleton. During this process, amorphous calcium mineral phases are biologically stabilized by magnesium and are reserved for the subsequent rapid formation of new shell tissue. However, it is a mystery how living organisms can regulate the transition of the precursor phases precisely. We reveal that the shell mineralization from the magnesium stabilized precursors is associated with the presence of Asp-rich proteins. It is suggested that a cooperative effect of magnesium and Asp-rich compound can result into a crystallization switch in biomineralization. Our in vitro experiments confirm that magnesium increases the lifetime of amorphous calcium carbonate and calcium phosphate in solution so that the crystallization can be temporarily switched off. Although Asp monomer alone inhibits the crystallization of pure amorphous calcium minerals, it actually reduces the stability of the magnesium-stabilized precursors to switch on the transformation from the amorphous to crystallized phases. These modification effects on crystallization kinetics can be understood by an Asp-enhanced magnesium desolvation model. The interesting magnesium-Asp-based switch is a biologically inspired lesson from nature, which can be developed into an advanced strategy to control material fabrications.

Crystallization and X-ray diffraction of crystals formed in water-plasticized amorphous lactose.

PubMed

Jouppila, K; Kansikas, J; Roos, Y H

1998-01-01

Effects of storage time and relative humidity on crystallization and crystal forms produced from amorphous lactose were investigated. Crystallization was observed from time-dependent loss of sorbed water and increasing intensities of peaks in X-ray diffraction patterns. The rate of crystallization increased with increasing storage relative humidity. Lactose crystallized mainly as alpha-lactose monohydrate and anhydrous crystals with alpha- and beta-lactose in a molar ratio of 5:3. The results suggested that the crystal form was defined by the early nucleation process. The crystallization data are important in modeling of crystallization phenomena and prediction of stability of lactose-containing food and pharmaceutical materials.

Model of coordination melting of crystals and anisotropy of physical and chemical properties of the surface

NASA Astrophysics Data System (ADS)

Bokarev, Valery P.; Krasnikov, Gennady Ya

2018-02-01

Based on the evaluation of the properties of crystals, such as surface energy and its anisotropy, the surface melting temperature, the anisotropy of the work function of the electron, and the anisotropy of adsorption, were shown the advantages of the model of coordination melting (MCM) in calculating the surface properties of crystals. The model of coordination melting makes it possible to calculate with an acceptable accuracy the specific surface energy of the crystals, the anisotropy of the surface energy, the habit of the natural crystals, the temperature of surface melting of the crystal, the anisotropy of the electron work function and the anisotropy of the adhesive properties of single-crystal surfaces. The advantage of our model is the simplicity of evaluating the surface properties of the crystal based on the data given in the reference literature. In this case, there is no need for a complex mathematical tool, which is used in calculations using quantum chemistry or modeling by molecular dynamics.

Structural investigation of cooperite (PtS) crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rozhdestvina, V. I., E-mail: veronika@ascnet.ru; Udovenko, A. A.; Rubanov, S. V.

2016-03-15

The single-crystal structure of cooperite, a natural platinum sulfide PtS, is studied by X-ray diffraction supported by high-resolution scanning transmission electron microscopy and X-ray spectrum microanalysis. It is found that, in addition to the main reflections corresponding to the known tetragonal cell (a = 3.47 and c = 6.11 Å; space group P4{sub 2}/mmc), many weak reflections with intensities I ≤ 60σ(I) are clearly observed. These reflections fit the tetragonal cell (space group I4/mmm) with doubled parameters. In structures with small (P4{sub 2}/mmc) and large (I4/mmm) cells, the S atoms occupy statistically two special positions. It is shown that themore » chemical composition of the cooperite crystals deviates from the stoichiometric composition: sulfur-deficient specimens predominate.« less

Bacillus thuringiensis and Its Pesticidal Crystal Proteins

PubMed Central

Schnepf, E.; Crickmore, N.; Van Rie, J.; Lereclus, D.; Baum, J.; Feitelson, J.; Zeigler, D. R.; Dean, D. H.

1998-01-01

During the past decade the pesticidal bacterium Bacillus thuringiensis has been the subject of intensive research. These efforts have yielded considerable data about the complex relationships between the structure, mechanism of action, and genetics of the organism’s pesticidal crystal proteins, and a coherent picture of these relationships is beginning to emerge. Other studies have focused on the ecological role of the B. thuringiensis crystal proteins, their performance in agricultural and other natural settings, and the evolution of resistance mechanisms in target pests. Armed with this knowledge base and with the tools of modern biotechnology, researchers are now reporting promising results in engineering more-useful toxins and formulations, in creating transgenic plants that express pesticidal activity, and in constructing integrated management strategies to insure that these products are utilized with maximum efficiency and benefit. PMID:9729609

Manipulation of photons at the surface of three-dimensional photonic crystals.

PubMed

Ishizaki, Kenji; Noda, Susumu

2009-07-16

In three-dimensional (3D) photonic crystals, refractive-index variations with a periodicity comparable to the wavelength of the light passing through the crystal give rise to so-called photonic bandgaps, which are analogous to electronic bandgaps for electrons moving in the periodic electrostatic potential of a material's crystal structure. Such 3D photonic bandgap crystals are envisioned to become fundamental building blocks for the control and manipulation of photons in optical circuits. So far, such schemes have been pursued by embedding artificial defects and light emitters inside the crystals, making use of 3D bandgap directional effects. Here we show experimentally that photons can be controlled and manipulated even at the 'surface' of 3D photonic crystals, where 3D periodicity is terminated, establishing a new and versatile route for photon manipulation. By making use of an evanescent-mode coupling technique, we demonstrate that 3D photonic crystals possess two-dimensional surface states, and we map their band structure. We show that photons can be confined and propagate through these two-dimensional surface states, and we realize their localization at arbitrary surface points by designing artificial surface-defect structures through the formation of a surface-mode gap. Surprisingly, the quality factors of the surface-defect mode are the largest reported for 3D photonic crystal nanocavities (Q up to approximately 9,000). In addition to providing a new approach for photon manipulation by photonic crystals, our findings are relevant for the generation and control of plasmon-polaritons in metals and the related surface photon physics. The absorption-free nature of the 3D photonic crystal surface may enable new sensing applications and provide routes for the realization of efficient light-matter interactions.

Single Crystal Membranes

NASA Technical Reports Server (NTRS)

Stormont, R. W.; Morrison, A.

1974-01-01

Single crystal a- and c-axis tubes and ribbons of sodium beta-alumina and sodium magnesium beta-alumina were grown from sodium oxide rich melts. Additional experiments grew ribbon crystals containing sodium magnesium beta, beta double prime, beta triple prime, and beta quadruple prime. A high pressure crystal growth chamber, sodium oxide rich melts, and iridium for all surfaces in contact with the melt were combined with the edge-defined, film-fed growth technique to grow the single crystal beta-alumina tubes and ribbons. The crystals were characterized using metallographic and X-ray diffraction techniques, and wet chemical analysis was used to determine the sodium, magnesium, and aluminum content of the grown crystals.

Scanning electron microscope view of iron crystal growing on pyroxene crystal

NASA Technical Reports Server (NTRS)

1972-01-01

A scanning electron microscope photograph of a four-micron size iron crystal growing on a pyroxene crystal (calcium-magnesium-iron silicate) from the Apollo 15 Hadley-Apennino lunar landing site. The well developed crystal faces indicate that the crystal was formed from a hot vapor as the rock was cooling.

Nanoparticles in liquid crystals, and liquid crystals in nanoparticles

NASA Astrophysics Data System (ADS)

de Pablo, Juan

2015-03-01

Liquid crystals are remarkably sensitive to interfacial interactions. Small perturbations at a liquid crystal interface, for example, can be propagated over relatively long length scales, thereby providing the basis for a wide range of applications that rely on amplification of molecular events into macroscopic observables. Our recent research efforts have focused on the reverse phenomenon; that is, we have sought to manipulate the interfacial assembly of nanoparticles or the organization of surface active molecules by controlling the structure of a liquid crystal. This presentation will consist of a review of the basic principles that are responsible for liquid crystal-mediated interactions, followed by demonstrations of those principles in the context of two types of systems. In the first, a liquid crystal is used to direct the assembly of nanoparticles; through a combination of molecular and continuum models, it is found that minute changes in interfacial energy and particle size lead to liquid-crystal induced attractions that can span multiple orders of magnitude. Theoretical predictions are confirmed by experimental observations, which also suggest that LC-mediated assembly provides an effective means for fabrication of plasmonic devices. In the second type of system, the structure of a liquid crystal is controlled by confinement in submicron droplets. The morphology of the liquid crystal in a drop depends on a delicate balance between bulk and interfacial contributions to the free energy; that balance can be easily perturbed by adsorption of analytes or nanoparticles at the interface, thereby providing the basis for development of hierarchical assembly of responsive, anisotropic materials. Theoretical predictions also indicate that the three-dimensional order of a liquid crystal can be projected onto a two-dimensional interface, and give rise to novel nanostructures that are not found in simple isotropic fluids.

Mesoscale crystallization of calcium phosphate nanostructures in protein (casein) micelles

NASA Astrophysics Data System (ADS)

Thachepan, Surachai; Li, Mei; Mann, Stephen

2010-11-01

Aqueous micelles of the multi-protein calcium phosphate complex, casein, were treated at 60 °C and pH 7 over several months. Although partial dissociation of the micelles into 12 nm sized amorphous calcium phosphate (ACP)/protein nanoparticles occurred within a period of 14 days, crystallization of the ACP nanoclusters into bundles of hydroxyapatite (HAP) nanofilaments was not observed until after 12 weeks. The HAP nanofilaments were formed specifically within the partially disrupted protein micelles suggesting a micelle-mediated pathway of mesoscale crystallization. Similar experiments using ACP-containing synthetic micelles prepared from β-casein protein alone indicated that co-aligned bundles of HAP nanofilaments were produced within the protein micelle interior after 24 hours at temperatures as low as 35 °C. The presence of Mg2+ ions in the casein micelles, as well as a possible synergistic effect associated with the multi-protein nature of the native aggregates, could account for the marked inhibition in mesoscale crystallization observed in the casein micelles compared with the single-component β-casein constructs.Aqueous micelles of the multi-protein calcium phosphate complex, casein, were treated at 60 °C and pH 7 over several months. Although partial dissociation of the micelles into 12 nm sized amorphous calcium phosphate (ACP)/protein nanoparticles occurred within a period of 14 days, crystallization of the ACP nanoclusters into bundles of hydroxyapatite (HAP) nanofilaments was not observed until after 12 weeks. The HAP nanofilaments were formed specifically within the partially disrupted protein micelles suggesting a micelle-mediated pathway of mesoscale crystallization. Similar experiments using ACP-containing synthetic micelles prepared from β-casein protein alone indicated that co-aligned bundles of HAP nanofilaments were produced within the protein micelle interior after 24 hours at temperatures as low as 35 °C. The presence of Mg2+ ions in

Observing the formation of ice and organic crystals in active sites

PubMed Central

Campbell, James M.; Meldrum, Fiona C.; Christenson, Hugo K.

2017-01-01

Heterogeneous nucleation is vital to a wide range of areas as diverse as ice nucleation on atmospheric aerosols and the fabrication of high-performance thin films. There is excellent evidence that surface topography is a key factor in directing crystallization in real systems; however, the mechanisms by which nanoscale pits and pores promote nucleation remain unclear. Here, we use natural cleavage defects on Muscovite mica to investigate the activity of topographical features in the nucleation from vapor of ice and various organic crystals. Direct observation of crystallization within surface pockets using optical microscopy and also interferometry demonstrates that these sharply acute features provide extremely effective nucleation sites and allows us to determine the mechanism by which this occurs. A confined phase is first seen to form along the apex of the wedge and then grows out of the pocket opening to generate a bulk crystal after a threshold saturation has been achieved. Ice nucleation proceeds in a comparable manner, although our resolution is insufficient to directly observe a condensate before the growth of a bulk crystal. These results provide insight into the mechanism of crystal deposition from vapor on real surfaces, where this will ultimately enable us to use topography to control crystal deposition on surfaces. They are also particularly relevant to our understanding of processes such as cirrus cloud formation, where such topographical features are likely candidates for the “active sites” that make clay particles effective nucleants for ice in the atmosphere. PMID:27994140

A Test of Macromolecular Crystallization in Microgravity: Large, Well-Ordered Insulin Crystals

NASA Technical Reports Server (NTRS)

Borgstahl, Gloria E. O.; Vahedi-Faridi, Ardeschir; Lovelace, Jeff; Bellamy, Henry D.; Snell, Edward H.; Whitaker, Ann F. (Technical Monitor)

2001-01-01

Crystals of insulin grown in microgravity on space shuttle mission STS-95 were extremely well-ordered and unusually large (many > 2 mm). The physical characteristics of six microgravity and six earth-grown crystals were examined by X-ray analysis employing superfine f slicing and unfocused synchrotron radiation. This experimental setup allowed hundreds of reflections to be precisely examined for each crystal in a short period of time. The microgravity crystals were on average 34 times larger, had 7 times lower mosaicity, had 54 times higher reflection peak heights and diffracted to significantly higher resolution than their earth grown counterparts. A single mosaic domain model could account for reflections in microgravity crystals whereas reflections from earth crystals required a model with multiple mosaic domains. This statistically significant and unbiased characterization indicates that the microgravity environment was useful for the improvement of crystal growth and resultant diffraction quality in insulin crystals and may be similarly useful for macromolecular crystals in general.

Protein crystal growth in microgravity: Temperature induced large scale crystallization of insulin

NASA Technical Reports Server (NTRS)

Long, Marianna M.; Delucas, Larry J.; Smith, C.; Carson, M.; Moore, K.; Harrington, Michael D.; Pillion, D. J.; Bishop, S. P.; Rosenblum, W. M.; Naumann, R. J.

1994-01-01

One of the major stumbling blocks that prevents rapid structure determination using x-ray crystallography is macro-molecular crystal growth. There are many examples where crystallization takes longer than structure determination. In some cases, it is impossible to grow useful crystals on earth. Recent experiments conducted in conjuction with NASA on various Space Shuttle missions have demonstrated that protein crystals often grow larger and display better internal molecular order than their earth-grown counterparts. This paper reports results from three Shuttle flights using the Protein Crystallization Facility (PCF). The PCF hardware produced large, high-quality insulin crystals by using a temperature change as the sole means to affect protein solubility and thus, crystallization. The facility consists of cylinders/containers with volumes of 500, 200, 100, and 50 ml. Data from the three Shuttle flights demonstrated that larger, higher resolution crystals (as evidenced by x-ray diffraction data) were obtained from the microgravity experiments when compared to earth-grown crystals.

Molecular modifiers reveal a mechanism of pathological crystal growth inhibition

NASA Astrophysics Data System (ADS)

Chung, Jihae; Granja, Ignacio; Taylor, Michael G.; Mpourmpakis, Giannis; Asplin, John R.; Rimer, Jeffrey D.

2016-08-01

Crystalline materials are crucial to the function of living organisms, in the shells of molluscs, the matrix of bone, the teeth of sea urchins, and the exoskeletons of coccoliths. However, pathological biomineralization can be an undesirable crystallization process associated with human diseases. The crystal growth of biogenic, natural and synthetic materials may be regulated by the action of modifiers, most commonly inhibitors, which range from small ions and molecules to large macromolecules. Inhibitors adsorb on crystal surfaces and impede the addition of solute, thereby reducing the rate of growth. Complex inhibitor-crystal interactions in biomineralization are often not well elucidated. Here we show that two molecular inhibitors of calcium oxalate monohydrate crystallization—citrate and hydroxycitrate—exhibit a mechanism that differs from classical theory in that inhibitor adsorption on crystal surfaces induces dissolution of the crystal under specific conditions rather than a reduced rate of crystal growth. This phenomenon occurs even in supersaturated solutions where inhibitor concentration is three orders of magnitude less than that of the solute. The results of bulk crystallization, in situ atomic force microscopy, and density functional theory studies are qualitatively consistent with a hypothesis that inhibitor-crystal interactions impart localized strain to the crystal lattice and that oxalate and calcium ions are released into solution to alleviate this strain. Calcium oxalate monohydrate is the principal component of human kidney stones and citrate is an often-used therapy, but hydroxycitrate is not. For hydroxycitrate to function as a kidney stone treatment, it must be excreted in urine. We report that hydroxycitrate ingested by non-stone-forming humans at an often-recommended dose leads to substantial urinary excretion. In vitro assays using human urine reveal that the molecular modifier hydroxycitrate is as effective an inhibitor of nucleation

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.

Liquid encapsulated crystal growth

NASA Technical Reports Server (NTRS)

Morrison, Andrew D. (Inventor)

1989-01-01

Low-defect crystals are grown in a closed ampoule under a layer of encapsulant. After crystal growth, the crystal is separated from the melt and moved into the layer of encapsulant and cooled to a first temperature at which crystal growth stops. The crystal is then moved into the inert gas ambient in the ampoule and further cooled. The crystal can be separated from the melt by decanting the melt into an adjacent reservoir or by rotating the ampoule to rotate the crystal into the encapsulant layer.

Liquid encapsulated crystal growth

NASA Technical Reports Server (NTRS)

Morrison, Andrew D. (Inventor)

1987-01-01

Low-defect crystals are grown in a closed ampoule under a layer of encapsulant. After crystal growth, the crystal is separated from the melt and moved into the layer of encapsulant and cooled to a first temperature at which crystal growth stops. The crystal is then moved into the inert gas ambient in the ampoule and further cooled. The crystal can be separated from the melt by decanting the melt into and adjacent reservoir or by rotating the ampoule to rotate the crystal into the encapsulant layer.

Discrete structures in continuum descriptions of defective crystals.

PubMed

Parry, G P

2016-04-28

I discuss various mathematical constructions that combine together to provide a natural setting for discrete and continuum geometric models of defective crystals. In particular, I provide a quite general list of 'plastic strain variables', which quantifies inelastic behaviour, and exhibit rigorous connections between discrete and continuous mathematical structures associated with crystalline materials that have a correspondingly general constitutive specification. © 2016 The Author(s).

Emission from Crystals Irradiated with a Beam of Runaway Electrons

NASA Astrophysics Data System (ADS)

Buranchenko, A. G.; Tarasenko, V. F.; Beloplotov, D. V.; Baksht, E. Kh.

2018-01-01

An investigation of the spectral and amplitude-temporal characteristics of emission from different crystals, promising in terms of their application as detectors of runaway electrons, is performed. This emission is excited by subnanosecond electron beams generated in a gas diode. It is found out that at the electron energies of tens-hundreds of kiloelectronvolts, the main contribution into the emission from CsI, ZnS, type IIa artificial and natural diamonds, sapphire, CaF2, ZrO2, Ga2O3, CaCO3, CdS, and ZnSe crystals comes from the cathodoluminescence; the radiation pulse duration depends on the crystal used and sufficiently exceeds the Cherenkov radiation pulse duration. It is demonstrated that the latter radiation exhibits low intensity and can be detected in the short-wave region of the spectrum in the cases where a monochromator and a high-sensitivity photomultiplier tube (PMT) are used.

Influence of non steady gravity on natural convection during micro-gravity solidification of semiconductors. I - Time scale analysis. II - Implications for crystal growth experiments

NASA Technical Reports Server (NTRS)

Griffin, P. R.; Motakef, S.

1989-01-01

Consideration is given to the influence of temporal variations in the magnitude of gravity on natural convection during unidirectional solidification of semiconductors. It is shown that the response time to step changes in g at low Rayleigh numbers is controlled by the momentum diffusive time scale. At higher Rayleigh numbers, the response time to increases in g is reduced because of inertial effects. The degree of perturbation of flow fields by transients in the gravitational acceleration on the Space Shuttle and the Space Station is determined. The analysis is used to derive the requirements for crystal growth experiments conducted on low duration low-g vehicles. Also, the effectiveness of sounding rockets and KC-135 aircraft for microgravity experiments is examined.

The Use of Atomic-Force Microscopy for Studying the Crystallization Process of Amorphous Alloys

NASA Astrophysics Data System (ADS)

Elmanov, G. N.; Ivanitskaya, E. A.; Dzhumaev, P. S.; Skrytniy, V. I.

The crystallization process of amorphous alloys is accompanied by the volume changes as a result of structural phase transitions. This leads to changes in the surface topography, which was studied by atomic force microscopy (AFM). The changes of the surface topography, structure and phase composition during multistage crystallization process of the metallic glasses with composition Ni71,5Cr6,8Fe2,7B11,9Si7,1 and Ni63,4Cr7,4Fe4,3Mn0,8B15,6Si8,5 (AWS BNi2) has been investigated. The obtained results on changing of the surface topography in crystallization process are in good agreement with the data of X-ray diffraction analysis (XRD). The nature of redistribution of some alloy components in the crystallization process has been suggested.

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

High resolution reversible color images on photonic crystal substrates.

PubMed

Kang, Pilgyu; Ogunbo, Samuel O; Erickson, David

2011-08-16

When light is incident on a crystalline structure with appropriate periodicity, some colors will be preferentially reflected (Joannopoulos, J. D.; Meade, R. D.; Winn, J. N. Photonic crystals: molding the flow of light; Princeton University Press: Princeton, NJ, 1995; p ix, 137 pp). These photonic crystals and the structural color they generate represent an interesting method for creating reflective displays and drawing devices, since they can achieve a continuous color response and do not require back lighting (Joannopoulos, J. D.; Villeneuve, P. R.; Fan, S. H. Photonic crystals: Putting a new twist on light. Nature 1997, 386, 143-149; Graham-Rowe, D. Tunable structural colour. Nat. Photonics 2009, 3, 551-553.; Arsenault, A. C.; Puzzo, D. P.; Manners, I.; Ozin, G. A. Photonic-crystal full-colour displays. Nat. Photonics 2007, 1, 468-472; Walish, J. J.; Kang, Y.; Mickiewicz, R. A.; Thomas, E. L. Bioinspired Electrochemically Tunable Block Copolymer Full Color Pixels. Adv. Mater.2009, 21, 3078). Here we demonstrate a technique for creating erasable, high-resolution, color images using otherwise transparent inks on self-assembled photonic crystal substrates (Fudouzi, H.; Xia, Y. N. Colloidal crystals with tunable colors and their use as photonic papers. Langmuir 2003, 19, 9653-9660). Using inkjet printing, we show the ability to infuse fine droplets of silicone oils into the crystal, locally swelling it and changing the reflected color (Sirringhaus, H.; Kawase, T.; Friend, R. H.; Shimoda, T.; Inbasekaran, M.; Wu, W.; Woo, E. P. High-resolution inkjet printing of all-polymer transistor circuits. Science 2000, 290, 2123-2126). Multicolor images with resolutions as high as 200 μm are obtained from oils of different molecular weights with the lighter oils being able to penetrate deeper, yielding larger red shifts. Erasing of images is done simply by adding a low vapor pressure oil which dissolves the image, returning the substrate to its original state.

Overview: Experimental studies of crystal nucleation: Metals and colloids.

PubMed

Herlach, Dieter M; Palberg, Thomas; Klassen, Ina; Klein, Stefan; Kobold, Raphael

2016-12-07

Crystallization is one of the most important phase transformations of first order. In the case of metals and alloys, the liquid phase is the parent phase of materials production. The conditions of the crystallization process control the as-solidified material in its chemical and physical properties. Nucleation initiates the crystallization of a liquid. It selects the crystallographic phase, stable or meta-stable. Its detailed knowledge is therefore mandatory for the design of materials. We present techniques of containerless processing for nucleation studies of metals and alloys. Experimental results demonstrate the power of these methods not only for crystal nucleation of stable solids but in particular also for investigations of crystal nucleation of metastable solids at extreme undercooling. This concerns the physical nature of heterogeneous versus homogeneous nucleation and nucleation of phases nucleated under non-equilibrium conditions. The results are analyzed within classical nucleation theory that defines the activation energy of homogeneous nucleation in terms of the interfacial energy and the difference of Gibbs free energies of solid and liquid. The interfacial energy acts as barrier for the nucleation process. Its experimental determination is difficult in the case of metals. In the second part of this work we therefore explore the potential of colloidal suspensions as model systems for the crystallization process. The nucleation process of colloids is observed in situ by optical observation and ultra-small angle X-ray diffraction using high intensity synchrotron radiation. It allows an unambiguous discrimination of homogeneous and heterogeneous nucleation as well as the determination of the interfacial free energy of the solid-liquid interface. Our results are used to construct Turnbull plots of colloids, which are discussed in relation to Turnbull plots of metals and support the hypothesis that colloids are useful model systems to investigate crystal

Synthesis, growth and characterization of 3-nitroacetanilide—A new organic nonlinear optical crystal by Bridgman technique

NASA Astrophysics Data System (ADS)

Lenin, M.; Ramasamy, P.

2008-10-01

Single crystals of 3-nitroacetanilide, an organic nonlinear optical material has been grown by the Bridgman-Stockbarger method. The single crystal X-ray diffraction (XRD) data revealed the noncentrosymmetric crystal structure, which is an essential criterion for second harmonic generation. The crystalline nature of the grown crystals was confirmed using powder XRD techniques. The functional group of the compound is identified by FTIR spectrum. The thermal stability and its tendency to grow as single crystal in solution and in melt have been identified for the new title compound. The UV-vis spectrum of mNAA shows the lower optical cut off at 400 nm and was transparent in the visible region. The second harmonic generation efficiency was found using Kurtz powder technique. The dielectric constant and dielectric loss of the crystal were measured as a function of frequency and temperature, and the results are discussed.

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.

Design considerations for a Space Shuttle Main Engine turbine blade made of single crystal material

NASA Technical Reports Server (NTRS)

Abdul-Aziz, A.; August, R.; Nagpal, V.

1993-01-01

Nonlinear finite-element structural analyses were performed on the first stage high-pressure fuel turbopump blade of the Space Shuttle Main Engine. The analyses examined the structural response and the dynamic characteristics at typical operating conditions. Single crystal material PWA-1480 was considered for the analyses. Structural response and the blade natural frequencies with respect to the crystal orientation were investigated. The analyses were conducted based on typical test stand engine cycle. Influence of combined thermal, aerodynamic, and centrifugal loadings was considered. Results obtained showed that the single crystal secondary orientation effects on the maximum principal stresses are not highly significant.

Synthesis and Exfoliation of Discotic Zirconium Phosphates to Obtain Colloidal Liquid Crystals

PubMed Central

Yu, Yi-Hsien; Wang, Xuezhen; Shinde, Abhijeet; Cheng, Zhengdong

2016-01-01

Due to their abundance in natural clay and potential applications in advanced materials, discotic nanoparticles are of interest to scientists and engineers. Growth of such anisotropic nanocrystals through a simple chemical method is a challenging task. In this study, we fabricate discotic nanodisks of zirconium phosphate [Zr(HPO4)2·H2O] as a model material using hydrothermal, reflux and microwave-assisted methods. Growth of crystals is controlled by duration time, temperature, and concentration of reacting species. The novelty of the adopted methods is that discotic crystals of size ranging from hundred nanometers to few micrometers can be obtained while keeping the polydispersity well within control. The layered discotic crystals are converted to monolayers by exfoliation with tetra-(n)-butyl ammonium hydroxide [(C4H9)4NOH, TBAOH]. Exfoliated disks show isotropic and nematic liquid crystal phases. Size and polydispersity of disk suspensions is highly important in deciding their phase behavior. PMID:27284765

A multi-step strategy to obtain crystals of the dengue virus RNA-dependent RNA polymerase that diffract to high resolution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yap, Thai Leong; School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551; Chen, Yen Liang

Crystals of the RNA-dependent RNA polymerase catalytic domain from the dengue virus NS5 protein have been obtained using a strategy that included expression screening of naturally occurring serotype variants of the protein, the addition of divalent metal ions and crystal dehydration. These crystals diffract to 1.85 Å resolution and are thus suitable for a structure-based drug-design program. Dengue virus, a member of the Flaviviridae genus, causes dengue fever, an important emerging disease with several million infections occurring annually for which no effective therapy exists. The viral RNA-dependent RNA polymerase NS5 plays an important role in virus replication and represents anmore » interesting target for the development of specific antiviral compounds. Crystals that diffract to 1.85 Å resolution that are suitable for three-dimensional structure determination and thus for a structure-based drug-design program have been obtained using a strategy that included expression screening of naturally occurring serotype variants of the protein, the addition of divalent metal ions and crystal dehydration.« less

Characterization of calcium carbonate crystals in pigeon yolk sacs with different incubation times.

PubMed

Song, Juan; Cheng, Haixia; Shen, Xinyu; Hu, Jingxiao; Tong, Hua

2014-05-01

Calcium carbonate crystals are known to form in the yolk sacs of fertile pigeon eggs at late stages of incubation. The composition and structure of these crystals were investigated, the crystallization environment was inspected, and the physical chemistry constants of the yolk fluid were determined through the incubation period. Polarized light microscopy was used to observe the generation and distribution of calcium carbonate crystals in the yolk sac. In addition, X-ray diffraction was employed to analyze the composition and crystal phase of the yolk sac. A decalcification and deproteination method was established to analyze the ultrastructure and composition of the crystals, as well as the internal relationship between inorganic and organic phases of the crystals. Additionally, scanning electron microscopy, transmission electron microscopy, X-ray energy dispersive spectroscopy, and Fourier transform infrared spectroscopy were used to evaluate the characteristics of the crystals. Our results demonstrated that the calcium carbonate crystals were mainly composed of vaterite and calcite, with vaterite being the major component. Vaterite, a type of biomaterial generated by an organic template control, presented as a concentric hierarchical spherical structure. The organic nature of the biomaterial prevented vaterite from transforming into calcite, which is more thermodynamically stable than vaterite. Additionally, the configuration, size, and aggregation of vaterite were also mediated by the organic template. This bio-vaterite was found during the incubation period and is valuable in calcium transport during embryonic development. Copyright © 2014 Elsevier Ltd. All rights reserved.

Structural, mechanical, electrical and optical properties of a new lithium boro phthalate NLO crystal synthesized by a slow evaporation method

NASA Astrophysics Data System (ADS)

Mohanraj, K.; Balasubramanian, D.; Jhansi, N.

2017-11-01

A new non-linear optical (NLO) single crystal of lithium boro phthalate (LiBP) was grown by slow solvent evaporation technique. The powder sample was subjected to powder X-ray diffraction (PXRD) to find its crystalline nature and the crystal structure of the grown crystal was determined using single crystal X-ray (SXRD) diffraction analysis. The Fourier Transform Infrared (FTIR) spectrum was recorded for grown crystal to identify the various functional groups present in the compound. The mechanical property of the LiBP single crystal was studied using Vickers microhardness tester. The dielectric constant and dielectric loss measurements were carried out for the grown crystal at various temperatures. The grown crystal was subjected to UV-Visible Spectral Studies to analyze the linear optical behavior of the grown crystal. The Kurtz-Perry Powder technique was employed to measure the Second Harmonic Generation efficiency of the grown crystal.

Crystal conversion between metal-organic frameworks with different crystal topologies for efficient crystal design on two-dimensional substrates

NASA Astrophysics Data System (ADS)

Tsuruoka, Takaaki; Inoue, Kohei; Miyanaga, Ayumi; Tobiishi, Kaho; Ohhashi, Takashi; Hata, Manami; Takashima, Yohei; Akamatsu, Kensuke

2018-04-01

Crystal conversion of metal-organic frameworks (MOFs) between different crystal topologies on a polymer substrate has been successfully achieved by localized dissolution of MOF crystals followed by a rapid self-assembly of framework components. Upon addition of the desired organic linkers to the reaction system containing MOF crystals on the substrate, reversible crystal conversion between the [Cu2(btc)3]n and [Cu2(ndc)2(dabco)]n frameworks (btc = 1,3,5-benzene tricarboxylate, ndc = 1,4-naphthalene dicarboxylate, dabco = 1,4-diazabicyclo[2.2.2]octane) could be routinely achieved in high yields. Most surprisingly, in the case of conversion from the [Cu2(ndc)2(dabco)]n to [Cu2(btc)3]n frameworks, the [Cu2(btc)3]n crystals with unique shapes (cuboctahedron and truncated cube) could be prepared using butanol as a reaction medium.

Highly robust crystalsome via directed polymer crystallization at curved liquid/liquid interface

PubMed Central

Wang, Wenda; Qi, Hao; Zhou, Tian; Mei, Shan; Han, Lin; Higuchi, Takeshi; Jinnai, Hiroshi; Li, Christopher Y.

2016-01-01

Lipids and amphiphilic block copolymers spontaneously self-assemble in water to form a plethora of micelles and vesicles. They are typically fluidic in nature and often mechanically weak for applications such as drug delivery and gene therapeutics. Mechanical properties of polymeric materials could be improved by forming crystalline structures. However, most of the self-assembled micelles and vesicles have curved surfaces and precisely tuning crystallization within a nanoscale curved space is challenging, as the curved geometry is incommensurate with crystals having three-dimensional translational symmetry. Herein, we report using a miniemulsion crystallization method to grow nanosized, polymer single-crystal-like capsules. We coin the name crystalsome to describe this unique structure, because they are formed by polymer lamellar crystals and their structure mimics liposomes and polymersomes. Using poly(L-lactic acid) (PLLA) as the model polymer, we show that curved water/p-xylene interface formed by the miniemulsion process can guide the growth of PLLA single crystals. Crystalsomes with the size ranging from ∼148 nm to over 1 μm have been formed. Atomic force microscopy measurement demonstrate a two to three orders of magnitude increase in bending modulus compared with conventional polymersomes. We envisage that this novel structure could shed light on investigating spherical crystallography and drug delivery. PMID:26837260

Optical, structural, thermal and dielectric spectroscopy characterizations of seeded melt grown 2-hydroxy biphenyl single crystal.

PubMed

Sadhasivam, S; Rajesh, Narayana Perumal

2014-09-15

Organic single crystal of 2-hydroxy biphenyl (2-HB) was grown by top seeded melt growth method. Scanning electron microscopy studies has been carried out on the surface of the grown crystals to investigate the nature of growth and defects. The crystalline perfection and lattice parameters of 2-HB has been determined by single crystal XRD analysis and it belongs to orthorhombic crystal system with space group Fdd2. The functional groups and molecular associations were confirmed by FT-IR. The optical characteristics such as cut-off and transmittance were carried out using UV-Vis-NIR spectra. Absence of absorption in the region between 320 and 1100 nm makes the grown crystal desirable to optical applications. Thermal stability of grown crystals was characterized by thermogravimetric (TGA), differential thermal analysis (DTA) and differential scanning calorimetric (DSC) analyses. Broadband dielectric studies reveals that dielectric constant of grown crystal is low. The resistivity of grown crystal was studied by impedance analysis. The second harmonic generation intensity of 3.8 mJ was studied. The grown crystal belongs to soft material studied by hardness test. Copyright © 2014 Elsevier B.V. All rights reserved.

Gemstones

USGS Publications Warehouse

Olson, D.W.

2007-01-01

Part of the 2006 industrial minerals review. During 2006, total U.S. gemstone trade with all countries and territories exceeded $28.3 billion. Estimates indicate that U.S. gemstone markets accounted for over 35 percent of world gemstone demand in 2006. Natural gemstone production from U.S. deposits during 2006 was worth an estimated $13.3 million, a slight decrease from 2005, and included agates, amber, beryl, coral, garnet, jade, jasper, opal, pearl, quartz, sapphire, shell, topaz, tourmaline, turquoise, and many other gem materials. Laboratory-created gemstone production in the U.S. was worth an estimated $47.4 million, a 7 percent drop compared to 2005 production.

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.

The "Sticky Patch" Model of Crystallization and Modification of Proteins for Enhanced Crystallizability.

PubMed

Derewenda, Zygmunt S; Godzik, Adam

2017-01-01

Crystallization of macromolecules has long been perceived as a stochastic process, which cannot be predicted or controlled. This is consistent with another popular notion that the interactions of molecules within the crystal, i.e., crystal contacts, are essentially random and devoid of specific physicochemical features. In contrast, functionally relevant surfaces, such as oligomerization interfaces and specific protein-protein interaction sites, are under evolutionary pressures so their amino acid composition, structure, and topology are distinct. However, current theoretical and experimental studies are significantly changing our understanding of the nature of crystallization. The increasingly popular "sticky patch" model, derived from soft matter physics, describes crystallization as a process driven by interactions between select, specific surface patches, with properties thermodynamically favorable for cohesive interactions. Independent support for this model comes from various sources including structural studies and bioinformatics. Proteins that are recalcitrant to crystallization can be modified for enhanced crystallizability through chemical or mutational modification of their surface to effectively engineer "sticky patches" which would drive crystallization. Here, we discuss the current state of knowledge of the relationship between the microscopic properties of the target macromolecule and its crystallizability, focusing on the "sticky patch" model. We discuss state-of-the-art in silico methods that evaluate the propensity of a given target protein to form crystals based on these relationships, with the objective to design variants with modified molecular surface properties and enhanced crystallization propensity. We illustrate this discussion with specific cases where these approaches allowed to generate crystals suitable for structural analysis.

Degassing-induced crystallization of basaltic magma and effects on lava rheology

USGS Publications Warehouse

Lipman, P.W.; Banks, N.G.; Rhodes, J.M.

1985-01-01

During the north-east rift eruption of Mauna Loa volcano, Hawaii, on 25 March-14 April 1984 (Fig. 1), microphenocryst contents of erupted lava increased from 0.5 to 30% without concurrent change in either bulk magma composition or eruption temperature (1,140 ?? 3 ??C). The crystallization of the microphenocrysts is interpreted here as being due to undercooling of the magma 20-30 ??C below its liquidas; the undercooling probably resulted from separation and release of volatiles as the magma migrated 12 km from the primary summit reservoir to the eruption site on the north-east rift zone. Such crystallization of magma during an eruption has not been documented previously. The undercooling and crystallization increased the effective viscosity of the magma, leading to decreased eruption rates and stagnation of the lava flow. ?? 1985 Nature Publishing Group.

Cloning, expression, purification, crystallization and preliminary X-ray studies of argininosuccinate lyase (Rv1659) from Mycobacterium tuberculosis

PubMed Central

Paul, A.; Mishra, A.; Surolia, A.; Vijayan, M.

2013-01-01

The last enzyme in the arginine-biosynthesis pathway, argininosuccinate lyase, from Mycobacterium tuberculosis has been cloned, expressed, purified and crystallized, and preliminary X-ray studies have been carried out on the crystals. The His-tagged tetrameric enzyme with a subunit molecular weight of 50.9 kDa crystallized with two tetramers in the asymmetric unit of the orthorhombic unit cell, space group P212121. Molecular-replacement calculations and self-rotation calculations confirmed the space group and the tetrameric nature of the molecule. PMID:24316845

Very unusual "needle- and pencil-like" uric acid crystals in the urine unmasked by infrared spectroscopy investigation.

PubMed

Baroni, S; Garigali, G; Primiano, A; Gervasoni, J; Fogazzi, G B

2018-04-01

In this paper we describe a case with very unusual "needle- and pencil-like" crystals, partly similar to those reported by other investigators, who considered them as due to uric acid. Quite importantly, infrared spectroscopy investigation which, to our knowledge, we have been the first to perform on this type of crystals, confirmed their nature as uric acid structures. This case demonstrates that the planet of urinary crystals still has several unknown facets and still deserves exploration. Copyright © 2018 Elsevier B.V. All rights reserved.

Device and method for screening crystallization conditions in solution crystal growth

NASA Technical Reports Server (NTRS)

Carter, Daniel C. (Inventor)

1995-01-01

A device and method for detecting optimum protein crystallization conditions and for growing protein crystals in either 1g or microgravity environments comprising a housing, defining at least one pair of chambers for containing crystallization solutions is presented. The housing further defines an orifice therein for providing fluid communication between the chambers. The orifice is adapted to receive a tube which contains a gelling substance for limiting the rate of diffusive mixing of the crystallization solutions. The solutions are diffusively mixed over a period of time defined by the quantity of gelling substance sufficient to achieve equilibration and to substantially reduce density driven convection disturbances therein. The device further includes endcaps to seal the first and second chambers. One of the endcaps includes a dialysis chamber which contains protein solution in which protein crystals are grown. Once the endcaps are in place, the protein solution is exposed to the crystallization solutions wherein the solubility of the protein solution is reduced at a rate responsive to the rate of diffusive mixing of the crystallization solutions. This allows for a controlled approach to supersaturation and allows for screening of crystal growth conditions at preselected intervals.

Device and Method for Screening Crystallization Conditions in Solution Crystal Growth

NASA Technical Reports Server (NTRS)

Carter, Daniel C. (Inventor)

1997-01-01

A device and method for detecting optimum protein crystallization conditions and for growing protein crystals in either 1 g or microgravity environments comprising a housing defining at least one pair of chambers for containing crystallization solutions. The housing further defines an orifice therein for providing fluid communication between the chambers. The orifice is adapted to receive a tube which contains a gelling substance for limiting the rate of diffusive mixing of the crystallization solutions. The solutions are diffusively mixed over a period of time defined by the quantity of gelling substance sufficient to achieve equilibration and to substantially reduce density driven convection disturbances therein. The device further includes endcaps to seal the first and second chambers. One of the endcaps includes a dialysis chamber which contains protein solution in which protein crystals are grown. Once the endcaps are in place. the protein solution is exposed to the crystallization solutions wherein the solubility of the protein solution is reduced at a rate responsive to the rate of diffusive mixing of the crystallization solutions. This allows for a controlled approach to supersaturation and allows for screening of crystal growth conditions at preselected intervals.

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

Acoustic interference suppression of quartz crystal microbalance sensor arrays utilizing phononic crystals

NASA Astrophysics Data System (ADS)

Chen, Yung-Yu; Huang, Li-Chung; Wang, Wei-Shan; Lin, Yu-Ching; Wu, Tsung-Tsong; Sun, Jia-Hong; Esashi, Masayoshi

2013-04-01

Acoustic interference suppression of quartz crystal microbalance (QCM) sensor arrays utilizing phononic crystals is investigated in this paper. A square-lattice phononic crystal structure is designed to have a complete band gap covering the QCM's resonance frequency. The monolithic sensor array consisting of two QCMs separated by phononic crystals is fabricated by micromachining processes. As a result, 12 rows of phononic crystals with band gap boost insertion loss between the two QCMs by 20 dB and also reduce spurious modes. Accordingly, the phononic crystal is verified to be capable of suppressing the acoustic interference between adjacent QCMs in a sensor array.

Origin of Aphyric Phonolitic Magmas: Natural Evidences and Experimental Constraints

NASA Astrophysics Data System (ADS)

Masotta, M.; Freda, C.; Gaeta, M.

2010-12-01

Large explosive phonolitic eruptions are commonly characterised by aphyric juvenile eruptive products. Taking into account the low density contrast among phonolitic composition and settling phases (i.e., feldspar and leucite), the almost complete lack of crystals in these differentiated compositions rises the question of which process could produce such an efficient crystal-melt separation. Seeking for an answer, we have investigated crystallization in presence of a thermal gradient as a possible mechanism for crystal-melt separation, considering both chemical and physical effects acting on a variably crystallized system. Using a natural tephri-phonolitic composition as starting material (M.te Aguzzo scoria cone, Sabatini Volcanic District, Central Italy), we have reproduced thermal gradient-driven crystallization in order to simulate the crystallization process in a thermally zoned magma chamber. Crystallization degree (paragenesis made of clinopyroxene±feldspars±leucite) as well as melt composition varies along the thermal gradient. In particular, melt composition ranges from the tephri-phonolitic starting composition at the bottom of the charge (hottest and aphyric zone) to phonolitic at the top (cooler and heterogeneously-crystallised zone). Backscattered images of experimental products clearly evidence: i) the aphyric tephri-phonolitic melt region at the bottom of the charge; ii) a drop-shaped crystal clustering in the middle zone; and iii) large aphyric belt and pockets (up to 100 µm wide) of phonolitic melt, with large deformed-shaped sanidine occurring at their margin, at the charge top region. The latter two features, resulting from solid-melt displacements, suggest that the segregation of phonolitic melt can be related to crystal sinking and compaction. On the other hand, the compositional variability of the melt along the thermal gradient is directly related to the crystallization degree, indicating that chemical diffusion and thermal migration have

Truncated hexa-octahedral magnetite crystals in ALH84001: Presumptive biosignatures

PubMed Central

Thomas-Keprta, Kathie L.; Clemett, Simon J.; Bazylinski, Dennis A.; Kirschvink, Joseph L.; McKay, David S.; Wentworth, Susan J.; Vali, Hojatollah; Gibson, Everett K.; McKay, Mary Fae; Romanek, Christopher S.

2001-01-01

McKay et al. [(1996) Science 273, 924–930] suggested that carbonate globules in the meteorite ALH84001 contained the fossil remains of Martian microbes. We have characterized a subpopulation of magnetite (Fe3O4) crystals present in abundance within the Fe-rich rims of these carbonate globules. We find these Martian magnetites to be both chemically and physically identical to terrestrial, biogenically precipitated, intracellular magnetites produced by magnetotactic bacteria strain MV-1. Specifically, both magnetite populations are single-domain and chemically pure, and exhibit a unique crystal habit we describe as truncated hexa-octahedral. There are no known reports of inorganic processes to explain the observation of truncated hexa-octahedral magnetites in a terrestrial sample. In bacteria strain MV-1 their presence is therefore likely a product of Natural Selection. Unless there is an unknown and unexplained inorganic process on Mars that is conspicuously absent on the Earth and forms truncated hexa-octahedral magnetites, we suggest that these magnetite crystals in the Martian meteorite ALH84001 were likely produced by a biogenic process. As such, these crystals are interpreted as Martian magnetofossils and constitute evidence of the oldest life yet found. PMID:11226210

Truncated hexa-octahedral magnetite crystals in ALH84001: presumptive biosignatures

NASA Technical Reports Server (NTRS)

Thomas-Keprta, K. L.; Clemett, S. J.; Bazylinski, D. A.; Kirschvink, J. L.; McKay, D. S.; Wentworth, S. J.; Vali, H.; Gibson, E. K. Jr; McKay, M. F.; Romanek, C. S.

2001-01-01

McKay et al. [(1996) Science 273, 924-930] suggested that carbonate globules in the meteorite ALH84001 contained the fossil remains of Martian microbes. We have characterized a subpopulation of magnetite (Fe(3)O(4)) crystals present in abundance within the Fe-rich rims of these carbonate globules. We find these Martian magnetites to be both chemically and physically identical to terrestrial, biogenically precipitated, intracellular magnetites produced by magnetotactic bacteria strain MV-1. Specifically, both magnetite populations are single-domain and chemically pure, and exhibit a unique crystal habit we describe as truncated hexa-octahedral. There are no known reports of inorganic processes to explain the observation of truncated hexa-octahedral magnetites in a terrestrial sample. In bacteria strain MV-1 their presence is therefore likely a product of Natural Selection. Unless there is an unknown and unexplained inorganic process on Mars that is conspicuously absent on the Earth and forms truncated hexa-octahedral magnetites, we suggest that these magnetite crystals in the Martian meteorite ALH84001 were likely produced by a biogenic process. As such, these crystals are interpreted as Martian magnetofossils and constitute evidence of the oldest life yet found.

Growth and characterization of new semiorganic nonlinear optical and piezoelectric lithium sulfate monohydrate oxalate single crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yadav, Harsh; Sinha, Nidhi; Kumar, Binay, E-mail: b3kumar69@yahoo.co.in

2015-04-15

Highlights: • A new semiorganic single crystal of LSO grown by slow evaporation technique. • Morphological studies of the LSO crystal deduced by BFDH law. • In the UV–vis spectrum wide transparent region and large band gap were found. • SHG is equal to KDP crystal and d{sub 33} was found to be equal to 6pC/N. • Grown crystal belongs to softer category. - Abstract: New semiorganic crystal of lithium sulfate monohydrate oxalate (LSO) for nonlinear application was synthesized by controlled slow evaporation method. The growth rate of various planes of the grown crystal was estimated by morphological study. Singlemore » crystal XRD analysis confirmed that the crystal belongs to triclinic lattice with space group P1. High transparency (∼95%) with large band gap (4.57 eV) was analyzed by UV–vis studies. FTIR and Raman spectroscopy were used to identify various functional groups present in the LSO crystal. SHG efficiency was found to be equal to the KDP crystal. Thermal stability (up to 117.54 °C) and melting point (242 °C) of the crystal were studied by TG-DTA. In dielectric measurements, the value of dielectric constant decreases with increase in frequency. Hardness studies confirmed soft nature of crystals. The piezoelectric coefficient was found to be 6pC/N along [0 0 1].« less

Theoretical Calculations of Refractive Properties for Hg3Te2Cl2 Crystals

NASA Astrophysics Data System (ADS)

Bokotey, O. V.

2016-05-01

This paper reviews the optical properties, such as refractive index, optical dielectric constant, and reflection coefficient of the Hg3Te2Cl2 crystals. The applications of the Hg3X2Y2 crystals as electronic, optical, and optoelectronic devices are very much determined by the nature and magnitude of these fundamental material properties. The origin of chemical bonding in the crystals is very important for definition of the physical and chemical properties. The main structural feature of the Hg3X2Y2 crystals is the presence of covalent pyramids [XHg3] and linear X-Hg-X groups. Optical properties are calculated according to the model proposed by Harrison. The refractive index in the spectral region far from the absorption edge is determined within the generalized single-oscillator model. The calculated results are found to be in good agreement with experimental data.

Pectin as an Extraordinary Natural Kinetic Hydrate Inhibitor

PubMed Central

Xu, Shurui; Fan, Shuanshi; Fang, Songtian; Lang, Xuemei; Wang, Yanhong; Chen, Jun

2016-01-01

Pectin as a novel natural kinetic hydrate inhibitor, expected to be eco-friendly and sufficiently biodegradable, was studied in this paper. The novel crystal growth inhibition (CGI) and standard induction time methods were used to evaluate its effect as hydrate inhibitor. It could successfully inhibit methane hydrate formation at subcooling temperature up to 12.5 °C and dramatically slowed the hydrate crystal growth. The dosage of pectin decreased by 66% and effective time extended 10 times than typical kinetic inhibitor. Besides, its maximum growth rate was no more than 2.0%/h, which was far less than 5.5%/h of growth rate for PVCap at the same dosage. The most prominent feature was that it totally inhibited methane hydrate crystal rapid growth when hydrate crystalline occurred. Moreover, in terms of typical natural inhibitors, the inhibition activity of pectin increased 10.0-fold in induction time and 2.5-fold in subcooling temperature. The extraordinary inhibition activity is closely related to its hydrogen bonding interaction with water molecules and the hydrophilic structure. Finally, the biodegradability and economical efficiency of pectin were also taken into consideration. The results showed the biodegradability improved 75.0% and the cost reduced by more than 73.3% compared to typical commercial kinetic inhibitors. PMID:26996773

JAXA protein crystallization in space: ongoing improvements for growing high-quality crystals

PubMed Central

Takahashi, Sachiko; Ohta, Kazunori; Furubayashi, Naoki; Yan, Bin; Koga, Misako; Wada, Yoshio; Yamada, Mitsugu; Inaka, Koji; Tanaka, Hiroaki; Miyoshi, Hiroshi; Kobayashi, Tomoyuki; Kamigaichi, Shigeki

2013-01-01

The Japan Aerospace Exploration Agency (JAXA) started a high-quality protein crystal growth project, now called JAXA PCG, on the International Space Station (ISS) in 2002. Using the counter-diffusion technique, 14 sessions of experiments have been performed as of 2012 with 580 proteins crystallized in total. Over the course of these experiments, a user-friendly interface framework for high accessibility has been constructed and crystallization techniques improved; devices to maximize the use of the microgravity environment have been designed, resulting in some high-resolution crystal growth. If crystallization conditions were carefully fixed in ground-based experiments, high-quality protein crystals grew in microgravity in many experiments on the ISS, especially when a highly homogeneous protein sample and a viscous crystallization solution were employed. In this article, the current status of JAXA PCG is discussed, and a rational approach to high-quality protein crystal growth in microgravity based on numerical analyses is explained. PMID:24121350

Carbonate crystals precipitated by freshwater bacteria and their use as a limestone consolidant.

PubMed

Zamarreño, Dania V; Inkpen, Robert; May, Eric

2009-09-01

Bacterial carbonate precipitation is known to be a natural phenomenon associated with a wide range of bacterial species. Recently, the ability of bacteria to produce carbonates has been studied for its value in the conservation of limestone monuments and concrete. This paper describes investigations of carbonate crystals precipitated by freshwater bacteria by means of histological (Loeffler's methylene blue and alcian blue-periodic acid-Schiff stain) and fluorescence (CTC [5-cyano-2,3-ditolyl tetrazolium chloride]) stains, determination of cell viability inside carbonate crystals, and pore size reduction in limestone by image analysis. Carbonate crystals were found to be composed of bacteria embedded in a matrix of neutral and acid polysaccharides. Cell viability inside the carbonate crystals decreased with time. On stone, bacteria were found to form carbonate crystals, with only a few bacteria remaining as isolated cells or as cell aggregates. Pore size was reduced by about 50%, but no blockage was detected. Taken together, the results of this research provide some reassurance to conservators that biocalcification by bacteria could be a safe consolidation tool in a restoration strategy for building stone conservation.

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.

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.

Crystallization of Calcium Carbonate in a Large Scale Field Study

NASA Astrophysics Data System (ADS)

Ueckert, Martina; Wismeth, Carina; Baumann, Thomas

2017-04-01

The long term efficiency of geothermal facilities and aquifer thermal energy storage in the carbonaceous Malm aquifer in the Bavarian Molasse Basin is seriously affected by precipitations of carbonates. This is mainly caused by pressure and temperature changes leading to oversaturation during production. Crystallization starts with polymorphic nuclei of calcium carbonate and is often described as diffusion-reaction controlled. Here, calcite crystallization is favoured by high concentration gradients while aragonite crystallization is occurring at high reaction rates. The factors affecting the crystallization processes have been described for simplified, well controlled laboratory experiments, the knowledge about the behaviour in more complex natural systems is still limited. The crystallization process of the polymorphic forms of calcium carbonate were investigated during a heat storage test at our test site in the eastern part of the Bavarian Molasse Basin. Complementary laboratory experiments in an autoclave were run. Both, field and laboratory experiments were conducted with carbonaceous tap water. Within the laboratory experiments additionally ultra pure water was used. To avoid precipitations of the tap water, a calculated amount of {CO_2} was added prior to heating the water from 45 - 110°C (laboratory) resp. 65 - 110°C (field). A total water volume of 0.5 L (laboratory) resp. 1 L (field) was immediately sampled and filtrated through 10 - 0.1

Purification, crystal growth and characterization of CdSe single crystals

NASA Astrophysics Data System (ADS)

Burger, A.; Henderson, D. O.; Morgan, S. H.; Silberman, E.

1991-02-01

CdSe single crystals have been grown from the stoichiometric melt and from Se rich solutions. Here we report the first mid and far infrared spectra of CdSe crystals free of any known impurity bands. Previous studies of the lattice vibrational properties of CdSe crystals have shown the presence of two bands at 538 and 270 cm -1. Modifications in the purification and crystal growth conditions lead us to assign these two bands to a sulfur impurity. Low temperature photoluminescence spectra are also presented and discussed.

Nacre biomineralisation: A review on the mechanisms of crystal nucleation.

PubMed

Nudelman, Fabio

2015-10-01

The wide diversity of biogenic minerals that is found in nature, each with its own morphology, mechanical properties and composition, is remarkable. In order to produce minerals that are optimally adapted for their function, biomineralisation usually occurs under strict cellular control. This control is exerted by specialised proteins and polysaccharides that assemble into a 3-dimensional organic matrix framework, forming a microenvironment where mineral deposition takes place. Molluscs are unique in that they use a striking variety of structural motifs to build their shells, each made of crystals with different morphologies and different calcium carbonate polymorphs. Much of want is known about mollusc shell formation comes from studies on the nacreous layer, or mother-of-pearl. In this review, we discuss two existing models on the nucleation of aragonite crystals during nacre formation: heteroepitaxial nucleation and mineral bridges. The heteroepitaxial nucleation model is based on the identification of chemical functional groups and aragonite-nucleating proteins at the centre of crystal imprints. It proposes that during nacre formation, each aragonite tablet nucleates independently on a nucleation site that is formed by acidic proteins and/or glycoproteins adsorbed on the chitin scaffold. The mineral bridges model is based on the identification of physical connections between the crystals in a stack, which results in a large number of crystals across several layers sharing the same crystallographic orientation. These observations suggest that there is one nucleation event per stack of tablets. Once the first crystal nucleates and reaches the top interlamellar matrix, it continues growing through pores, giving rise to the next layer of nacre, subsequently propagating into a stack. We compare both models and propose that they work in concert to control crystal nucleation in nacre. De novo crystal nucleation has to occur at least once per stack of aligned crystals

Numerical study on characteristic of two-dimensional metal/dielectric photonic crystals

NASA Astrophysics Data System (ADS)

Zong, Yi-Xin; Xia, Jian-Bai; Wu, Hai-Bin

2017-04-01

An improved plan-wave expansion method is adopted to theoretically study the photonic band diagrams of two-dimensional (2D) metal/dielectric photonic crystals. Based on the photonic band structures, the dependence of flat bands and photonic bandgaps on two parameters (dielectric constant and filling factor) are investigated for two types of 2D metal/dielectric (M/D) photonic crystals, hole and cylinder photonic crystals. The simulation results show that band structures are affected greatly by these two parameters. Flat bands and bandgaps can be easily obtained by tuning these parameters and the bandgap width may reach to the maximum at certain parameters. It is worth noting that the hole-type photonic crystals show more bandgaps than the corresponding cylinder ones, and the frequency ranges of bandgaps also depend strongly on these parameters. Besides, the photonic crystals containing metallic medium can obtain more modulation of photonic bands, band gaps, and large effective refractive index, etc. than the dielectric/dielectric ones. According to the numerical results, the needs of optical devices for flat bands and bandgaps can be met by selecting the suitable geometry and material parameters. Project supported by the National Basic Research Program of China (Grant No. 2011CB922200) and the National Natural Science Foundation of China (Grant No. 605210010).

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

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

Studies on 2-amino-5-nitropyridinium nitrate (2A5NPN): A semi-organic third order nonlinear optical single crystal

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sivasubramani, V.; Pandian, Muthu Senthil, E-mail: senthilpandianm@ssn.edu.in; Ramasamy, P.

2016-05-23

2-amino-5-nitropyridinium nitrate (2A5NPN) is a semi-organic nonlinear optical crystal and optically good quality 2A5NPN single crystals were successfully grown by slow evaporation solution growth technique (SEST) at ambient temperature. The crystallographic structure of the grown crystal was determined by single crystal X-Ray diffraction analysis and it belongs to Monoclinic crystal system with centro symmetric crystalline nature. The crystallinity of the grown crystal was confirmed by powder X-ray diffraction analysis. The other physical properties of grown crystals are also characterized using TG-DTA, UV-Visible NIR, chemical etching, photoconductivity and Z-scan measurements. The Z-scan method reveals that the 2A5NPN crystal possesses multi photonmore » absorption behaviour and the significantly higher third order susceptibility and it is a promising potential NLO material.« less

Hydrogen bonding intermolecular effect on electro-optical response of doped 6PCH nematic liquid crystal with some azo dyes

NASA Astrophysics Data System (ADS)

Kiani, S.; Zakerhamidi, M. S.; Tajalli, H.

2016-05-01

Previous studies on the electro-optical responses of dye-doped liquid crystal have shown that dopant material have a considerable effect on their electro-optical responses. Despite the studies carried out on electro-optical properties of dye-doped liquid crystal, no attention has been paid to study of the interaction and structural effects in this procedure. In this paper, linear dyes and with similar structure were selected as dopants. The only difference in used dyes is the functional groups in their tails. So, doping of these dyes into liquid crystals determines the influence of interaction type on electro-optical behaviours of the doped systems. Therefore, in this work, two aminoazobenzene (;A-dye;: hydrogen bond donor) and dimethyl-aminoazobenzene (;B-dye;) dyes with different compositional percentages in liquid crystal host were used. Electro-optical Kerr behaviour, the pre-transition temperature and third order nonlinear susceptibility were investigated. The obtained results effectively revealed that type of interactions between the dye and liquid crystal is determinative of behavioral difference of doped system, compared to pure liquid crystal. Also, pre-transitional behaviour and thereupon Kerr electro-optical responses were affected by formed interactions into doped systems. In other words, it will be shown that addition of any dopants in liquid crystal, regardless of the nature of interactions, cannot cause appropriate electro-optical responses. In fact, type of dye, nature of interactions between dopant and liquid crystalline host as well as concentration of dye are the key factors in selecting the appropriate liquid crystal and dopant dye.

Ground water in the Escalante Valley, Beaver, Iron, and Washington Counties, Utah

USGS Publications Warehouse

Fix, Philip F.; Nelson, W.B.; Lofgren, B.E.; Butler, R.G.

1950-01-01

Escalante Valley in southwestern Utah is one of the largest and most important ground-water areas of the State, with 1,300 square miles of arid land and an additional 1,500 square miles in its tributary drainage basin. Ground water is obtained from gravel and sand beds in the unconsolidated valley fill. In 1950 more irrigation wells were pumped than in any other basin of Utah, and their total pumpage exceeded 80,000 acre-feet. Farming is done chiefly in the Beryl-Enterprise district at the south (upper) end of the valley, where it depends almost entirely upon ground water, and in the Milford and Minersville districts in the northeast-central part of the valley. This progress report concerns chiefly the Beryl-Enterprise and Milford districts.

Statistical Analysis of Crystallization Database Links Protein Physico-Chemical Features with Crystallization Mechanisms

PubMed Central

Fusco, Diana; Barnum, Timothy J.; Bruno, Andrew E.; Luft, Joseph R.; Snell, Edward H.; Mukherjee, Sayan; Charbonneau, Patrick

2014-01-01

X-ray crystallography is the predominant method for obtaining atomic-scale information about biological macromolecules. Despite the success of the technique, obtaining well diffracting crystals still critically limits going from protein to structure. In practice, the crystallization process proceeds through knowledge-informed empiricism. Better physico-chemical understanding remains elusive because of the large number of variables involved, hence little guidance is available to systematically identify solution conditions that promote crystallization. To help determine relationships between macromolecular properties and their crystallization propensity, we have trained statistical models on samples for 182 proteins supplied by the Northeast Structural Genomics consortium. Gaussian processes, which capture trends beyond the reach of linear statistical models, distinguish between two main physico-chemical mechanisms driving crystallization. One is characterized by low levels of side chain entropy and has been extensively reported in the literature. The other identifies specific electrostatic interactions not previously described in the crystallization context. Because evidence for two distinct mechanisms can be gleaned both from crystal contacts and from solution conditions leading to successful crystallization, the model offers future avenues for optimizing crystallization screens based on partial structural information. The availability of crystallization data coupled with structural outcomes analyzed through state-of-the-art statistical models may thus guide macromolecular crystallization toward a more rational basis. PMID:24988076

Statistical analysis of crystallization database links protein physico-chemical features with crystallization mechanisms.

PubMed

Fusco, Diana; Barnum, Timothy J; Bruno, Andrew E; Luft, Joseph R; Snell, Edward H; Mukherjee, Sayan; Charbonneau, Patrick

2014-01-01

X-ray crystallography is the predominant method for obtaining atomic-scale information about biological macromolecules. Despite the success of the technique, obtaining well diffracting crystals still critically limits going from protein to structure. In practice, the crystallization process proceeds through knowledge-informed empiricism. Better physico-chemical understanding remains elusive because of the large number of variables involved, hence little guidance is available to systematically identify solution conditions that promote crystallization. To help determine relationships between macromolecular properties and their crystallization propensity, we have trained statistical models on samples for 182 proteins supplied by the Northeast Structural Genomics consortium. Gaussian processes, which capture trends beyond the reach of linear statistical models, distinguish between two main physico-chemical mechanisms driving crystallization. One is characterized by low levels of side chain entropy and has been extensively reported in the literature. The other identifies specific electrostatic interactions not previously described in the crystallization context. Because evidence for two distinct mechanisms can be gleaned both from crystal contacts and from solution conditions leading to successful crystallization, the model offers future avenues for optimizing crystallization screens based on partial structural information. The availability of crystallization data coupled with structural outcomes analyzed through state-of-the-art statistical models may thus guide macromolecular crystallization toward a more rational basis.

On the origin of size-dependent and size-independent crystal growth: Influence of advection and diffusion

USGS Publications Warehouse

Kile, D.E.; Eberl, D.D.

2003-01-01

Crystal growth experiments were conducted using potassium alum and calcite crystals in aqueous solution under both non-stirred and stirred conditions to elucidate the mechanism for size-dependent (proportionate) and size-independent (constant) crystal growth. Growth by these two laws can be distinguished from each other because the relative size difference among crystals is maintained during proportionate growth, leading to a constant crystal size variance (??2) for a crystal size distribution (CSD) as the mean size increases. The absolute size difference among crystals is maintained during constant growth, resulting in a decrease in size variance. Results of these experiments show that for centimeter-sized alum crystals, proportionate growth occurs in stirred systems, whereas constant growth occurs in non-stirred systems. Accordingly, the mechanism for proportionate growth is hypothesized to be related to the supply of reactants to the crystal surface by advection, whereas constant growth is related to supply by diffusion. Paradoxically, micrometer-sized calcite crystals showed proportionate growth both in stirred and in non-stirred systems. Such growth presumably results from the effects of convection and Brownian motion, which promote an advective environment and hence proportionate growth for minute crystals in non-stirred systems, thereby indicating the importance of solution velocity relative to crystal size. Calcite crystals grown in gels, where fluid motion was minimized, showed evidence for constant, diffusion-controlled growth. Additional investigations of CSDs of naturally occurring crystals indicate that proportionate growth is by far the most common growth law, thereby suggesting that advection, rather than diffusion, is the dominant process for supplying reactants to crystal surfaces.

Cubic and Hexagonal Liquid Crystals as Drug Delivery Systems

PubMed Central

Chen, Yulin; Ma, Ping; Gui, Shuangying

2014-01-01

Lipids have been widely used as main constituents in various drug delivery systems, such as liposomes, solid lipid nanoparticles, nanostructured lipid carriers, and lipid-based lyotropic liquid crystals. Among them, lipid-based lyotropic liquid crystals have highly ordered, thermodynamically stable internal nanostructure, thereby offering the potential as a sustained drug release matrix. The intricate nanostructures of the cubic phase and hexagonal phase have been shown to provide diffusion controlled release of active pharmaceutical ingredients with a wide range of molecular weights and polarities. In addition, the biodegradable and biocompatible nature of lipids demonstrates the minimum toxicity and thus they are used for various routes of administration. Therefore, the research on lipid-based lyotropic liquid crystalline phases has attracted a lot of attention in recent years. This review will provide an overview of the lipids used to prepare cubic phase and hexagonal phase at physiological temperature, as well as the influencing factors on the phase transition of liquid crystals. In particular, the most current research progresses on cubic and hexagonal phases as drug delivery systems will be discussed. PMID:24995330

Dynamics of the Wigner crystal of composite particles

NASA Astrophysics Data System (ADS)

Shi, Junren; Ji, Wencheng

2018-03-01

Conventional wisdom has long held that a composite particle behaves just like an ordinary Newtonian particle. In this paper, we derive the effective dynamics of a type-I Wigner crystal of composite particles directly from its microscopic wave function. It indicates that the composite particles are subjected to a Berry curvature in the momentum space as well as an emergent dissipationless viscosity. While the dissipationless viscosity is the Chern-Simons field counterpart for the Wigner crystal, the Berry curvature is a feature not presented in the conventional composite fermion theory. Hence, contrary to general belief, composite particles follow the more general Sundaram-Niu dynamics instead of the ordinary Newtonian one. We show that the presence of the Berry curvature is an inevitable feature for a dynamics conforming to the dipole picture of composite particles and Kohn's theorem. Based on the dynamics, we determine the dispersions of magnetophonon excitations numerically. We find an emergent magnetoroton mode which signifies the composite-particle nature of the Wigner crystal. It occurs at frequencies much lower than the magnetic cyclotron frequency and has a vanishing oscillator strength in the long-wavelength limit.

Plastic deformation of tubular crystals by dislocation glide.

PubMed

Beller, Daniel A; Nelson, David R

2016-09-01

Tubular crystals, two-dimensional lattices wrapped into cylindrical topologies, arise in many contexts, including botany and biofilaments, and in physical systems such as carbon nanotubes. The geometrical principles of botanical phyllotaxis, describing the spiral packings on cylinders commonly found in nature, have found application in all these systems. Several recent studies have examined defects in tubular crystals associated with crystalline packings that must accommodate a fixed tube radius. Here we study the mechanics of tubular crystals with variable tube radius, with dislocations interposed between regions of different phyllotactic packings. Unbinding and separation of dislocation pairs with equal and opposite Burgers vectors allow the growth of one phyllotactic domain at the expense of another. In particular, glide separation of dislocations offers a low-energy mode for plastic deformations of solid tubes in response to external stresses, reconfiguring the lattice step by step. Through theory and simulation, we examine how the tube's radius and helicity affects, and is in turn altered by, the mechanics of dislocation glide. We also discuss how a sufficiently strong bending rigidity can alter or arrest the deformations of tubes with small radii.

Plastic deformation of tubular crystals by dislocation glide

NASA Astrophysics Data System (ADS)

Beller, Daniel A.; Nelson, David R.

2016-09-01

Tubular crystals, two-dimensional lattices wrapped into cylindrical topologies, arise in many contexts, including botany and biofilaments, and in physical systems such as carbon nanotubes. The geometrical principles of botanical phyllotaxis, describing the spiral packings on cylinders commonly found in nature, have found application in all these systems. Several recent studies have examined defects in tubular crystals associated with crystalline packings that must accommodate a fixed tube radius. Here we study the mechanics of tubular crystals with variable tube radius, with dislocations interposed between regions of different phyllotactic packings. Unbinding and separation of dislocation pairs with equal and opposite Burgers vectors allow the growth of one phyllotactic domain at the expense of another. In particular, glide separation of dislocations offers a low-energy mode for plastic deformations of solid tubes in response to external stresses, reconfiguring the lattice step by step. Through theory and simulation, we examine how the tube's radius and helicity affects, and is in turn altered by, the mechanics of dislocation glide. We also discuss how a sufficiently strong bending rigidity can alter or arrest the deformations of tubes with small radii.

Crystal Structures of the β2-Adrenergic Receptor

NASA Astrophysics Data System (ADS)

Weis, William I.; Rosenbaum, Daniel M.; Rasmussen, Søren G. F.; Choi, Hee-Jung; Thian, Foon Sun; Kobilka, Tong Sun; Yao, Xiao-Jie; Day, Peter W.; Parnot, Charles; Fung, Juan J.; Ratnala, Venkata R. P.; Kobilka, Brian K.; Cherezov, Vadim; Hanson, Michael A.; Kuhn, Peter; Stevens, Raymond C.; Edwards, Patricia C.; Schertler, Gebhard F. X.; Burghammer, Manfred; Sanishvili, Ruslan; Fischetti, Robert F.; Masood, Asna; Rohrer, Daniel K.

G protein coupled receptors (GPCRs) constitute the largest family of membrane proteins in the human genome, and are responsible for the majority of signal transduction events involving hormones and neuro-transmitters across the cell membrane. GPCRs that bind to diffusible ligands have low natural abundance, are relatively unstable in detergents, and display basal G protein activation even in the absence of ligands. To overcome these problems two approaches were taken to obtain crystal structures of the β2-adrenergic receptor (β2AR), a well-characterized GPCR that binds cate-cholamine hormones. The receptor was bound to the partial inverse agonist carazolol and co-crystallized with a Fab made to a three-dimensional epitope formed by the third intracellular loop (ICL3), or by replacement of ICL3 with T4 lysozyme. Small crystals were obtained in lipid bicelles (β2AR-Fab) or lipidic cubic phase (β2AR-T4 lysozyme), and diffraction data were obtained using microfocus technology. The structures provide insights into the basal activity of the receptor, the structural features that enable binding of diffusible ligands, and the coupling between ligand binding and G-protein activation.

Dynamically tunable graphene/dielectric photonic crystal transmission lines

NASA Astrophysics Data System (ADS)

Williamson, Ian; Mousavi, S. Hossein; Wang, Zheng

2015-03-01

It is well known that graphene supports plasmonic modes with high field confinement and lower losses when compared to conventional metals. Additionally, graphene features a highly tunable conductivity through which the plasmon dispersion can be modulated. Over the years these qualities have inspired a wide range of applications for graphene in the THz and infrared regimes. In this presentation we theoretically demonstrate a graphene parallel plate waveguide (PPWG) that sandwiches a 2D photonic crystal slab. The marriage of these two geometries offers a large two dimensional band gap that can be dynamically tuned over a very broad bandwidth. Our device operates in the low-THz band where the graphene PPWG supports a quasi-TEM mode with a relatively flat attenuation. Unlike conventional photonic crystal slabs, the quasi-TEM nature of the graphene PPWG mode allows the slab thickness to be less than 1/10 of the photonic crystal lattice constant. These features offer up a wealth of opportunities, including tunable metamaterials with a possible platform for large band gaps in 3D structures through tiling and stacking. Additionally, the geometry provides a platform for tunable defect cavities without needing three dimensional periodicity.

Building zeolites from pre-crystallized units: nanoscale architecture.

PubMed