Frozen Chirality of Tertiary Aromatic Amides: Access to Enantioenriched Tertiary α-Amino Acid or Amino Alcohol without Chiral Reagent.

PubMed

Mai, Thi Thoa; Viswambharan, Baby; Gori, Didier; Guillot, Régis; Naubron, Jean-Valère; Kouklovsky, Cyrille; Alezra, Valérie

2017-04-27

One of the fundamental and intriguing aspects of life is the homochirality of the essential molecules. In this field, the absolute asymmetric synthesis of α-amino acids is a major challenge. Herein, we report access, by chemical means, to tertiary α-amino acid derivatives in up to 96 % ee without using any chiral reagent. In our strategy, the dynamic axial chirality of tertiary aromatic amides is frozen in a crystal and is responsible for the stereoselectivity of the subsequent steps. Furthermore, we could control the configuration of the final product by manually sorting and selecting the initial crystals. Based on vibrational circular dichroism studies, we could rationalize the observed stereoselectivity. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Quantum melting of a two-dimensional Wigner crystal

NASA Astrophysics Data System (ADS)

Dolgopolov, V. T.

2017-10-01

The paper reviews theoretical predictions about the behavior of two-dimensional low-density electron systems at nearly absolute zero temperatures, including the formation of an electron (Wigner) crystal, crystal melting at a critical electron density, and transitions between crystal modifications in more complex (for example, two-layer) systems. The paper presents experimental results obtained from real two-dimensional systems in which the nonconducting (solid) state of the electronic system with indications of collective localization is actually realized. Experimental methods for detecting a quantum liquid-solid phase interface are discussed.

Dynamic frequency-domain interferometer for absolute distance measurements with high resolution

NASA Astrophysics Data System (ADS)

Weng, Jidong; Liu, Shenggang; Ma, Heli; Tao, Tianjiong; Wang, Xiang; Liu, Cangli; Tan, Hua

2014-11-01

A unique dynamic frequency-domain interferometer for absolute distance measurement has been developed recently. This paper presents the working principle of the new interferometric system, which uses a photonic crystal fiber to transmit the wide-spectrum light beams and a high-speed streak camera or frame camera to record the interference stripes. Preliminary measurements of harmonic vibrations of a speaker, driven by a radio, and the changes in the tip clearance of a rotating gear wheel show that this new type of interferometer has the ability to perform absolute distance measurements both with high time- and distance-resolution.

Second generation crystals for Laue lens applications

NASA Astrophysics Data System (ADS)

Barrière, N.; von Ballmoos, P.; Bastie, P.; Courtois, P.; Abrosimov, N. V.; Andersen, K.; Halloin, H.; Skinner, G.; Smither, R. K.

2006-06-01

A Laue lens gamma-ray telescope represents an exciting concept for a future high-energy mission. The feasibility of such a lens has been demonstrated by the CLAIRE lens prototype; since then various mission concepts featuring a Laue lens are being developed. The latest, which is also the most ambitious, is the European Gamma-Ray Imager (GRI). However, advancing from the CLAIRE prototype to a scientifically exploitable Laue lens requires still substantial research and development. First and foremost, diffracting elements (crystals) that constitute the Laue lens have to be optimized to offer the best efficiency and imaging capabilities for the resulting telescope. The characteristics of selected candidate crystals were measured at the European Synchrotron Radiation Facility on the high-energy beamline ID 15A using a beam tuned at 292 keV. The studied low mosaicity copper crystals have shown absolute reflectivity reaching 30%. These crystals are promising for the realization of a Laue lens, despite the fact that they produce a diffracted beam featuring a Gaussian intensity profile, which contributes to the spread of the focal spot. A composition gradient Si 1-x-Ge x crystal has been investigated as well, which showed a diffraction efficiency reaching 50% (disregarding absorption) - half of the theoretical maximum - that represents an absolute reflectivity around 39 %, the best that we measured at this energy to date. This gradient crystal also showed a square-shaped rocking curve that is almost the best case to minimize the spread of the focal spot. We also show that bending a gradient crystal could still enhance the focusing. Thanks to the better focusing, a factor of 2 in sensitivity improvement may be achieved.

A probabilistic analysis of the crystal oscillator behavior at low drive levels

NASA Astrophysics Data System (ADS)

Shmaliy, Yuriy S.; Brendel, Rémi

2008-03-01

The paper discusses a probabilistic model of a crystal oscillator at low drive levels where the noise intensity is comparable with the oscillation amplitude. The stationary probability density of the oscillations envelope is derived and investigated for the nonlinear resonator loses. A stochastic explanation is given for the well-known phenomenon termed sleeping sickness associated with losing a facility of self-excitation by a crystal oscillator after a long storage without a power supply. It is shown that, with low drive levels leading to an insufficient feedback, a crystal oscillator generates the noise-induced oscillations rather than it absolutely "falls in sleep".

The influence of growth environment on the crystallization of nortriptyline hydrochloride, a tricyclic antidepressant

NASA Astrophysics Data System (ADS)

MacCalman, M. L.; Roberts, K. J.; Hendriksen, B. A.

1993-03-01

The preparation of the nortriptyline hydrochloride, an important pharmaceutical product, by crystallization from both alcohol and aqueous solutions is presented. At low temperatures this material shows a higher solubility in absolute alcohol compared to aqueous solutions in a trend which reverses at higher temperatures. Examination of crystals prepared from alcohol solutions reveal essentially a needle-like crystal habit which is in excellent agreement with morphological predictions based on the bulk crystallographic structure. In contrast crystals prepared from aqueous solution at high temperatures reveal a particulate structure dominated by heavily agglomerated crystallites with plate-like morphology. When this material is crystallized at the lower temperatures, where the solubility curve is steep, X-ray and thermal analysis appear to show that crystallization results in a new polymorphic structure associated with a less agglomerated product.

Calibration and characterization of a highly efficient spectrometer in von Hamos geometry for 7-10 keV x-rays

DOE PAGES

Jarrott, L. C.; Wei, M. S.; McGuffey, C.; ...

2017-04-27

Here, we have built an absolutely calibrated, highly efficient, Bragg crystal spectrometer in von Hamos geometry. This zinc von Hamos spectrometer uses a crystal made from highly oriented pyrolytic graphite that is cylindrically bent along the non-dispersive axis. It is tuned to measure x-ray spectra in the 7–10 keV range and has been designed to be used on a Ten Inch Manipulator for the Omega and OmegaEP target chambers at the Laboratory for Laser Energetics in Rochester, USA. Significant shielding strategies and fluorescence mitigation have been implemented in addition to an imaging plate detector making it well suited for experimentsmore » in high-intensity environments. Here we present the design and absolute calibration as well as mosaicity and integrated reflectivity measurements.« less

A variable temperature EPR study of Mn(2+)-doped NH(4)Cl(0.9)I(0.1) single crystal at 170 GHz: zero-field splitting parameter and its absolute sign.

PubMed

Misra, Sushil K; Andronenko, Serguei I; Chand, Prem; Earle, Keith A; Paschenko, Sergei V; Freed, Jack H

2005-06-01

EPR measurements have been carried out on a single crystal of Mn(2+)-doped NH(4)Cl(0.9)I(0.1) at 170-GHz in the temperature range of 312-4.2K. The spectra have been analyzed (i) to estimate the spin-Hamiltonian parameters; (ii) to study the temperature variation of the zero-field splitting (ZFS) parameter; (iii) to confirm the negative absolute sign of the ZFS parameter unequivocally from the temperature-dependent relative intensities of hyperfine sextets at temperatures below 10K; and (iv) to detect the occurrence of a structural phase transition at 4.35K from the change in the structure of the EPR lines with temperature below 10K.

Conglomerate formative precursor of chiral drug timolol: 3-(4-Morpholino-1,2,5-thiadiazol-3-yloxy)-propane-1,2-diol

NASA Astrophysics Data System (ADS)

Bredikhin, Alexander A.; Zakharychev, Dmitry V.; Fayzullin, Robert R.; Bredikhina, Zemfira A.; Gubaidullin, Aidar T.

2015-05-01

Solid state properties of 3-(4-N-morpholino-1,2,5-thiadiazol-3-yloxy)-propane-1,2-diol 3, the synthetic precursor of popular drug timolol, have been investigated. The original solubility test, the data of X-ray diffraction and DSC methods indicate that the compound is prone to spontaneous resolution. Diol 3 crystallizing from both enantiopure or racemic feed material forms "guaifenesin-like" crystal packing in which the classic H-bonded bilayers, framed in both sides by hydrophobic molecular fragments, act as the basic supramolecular motif. The main chain conformation of the molecules in the crystals of diol 3 differs from that in the guaifenesin crystals, and this fact changes the absolute configuration of spiral columns formed by intermolecular hydrogen bonds in crystals of 3 as compared with guaifenesin crystals.

Solid state structure and absolute configuration of filifolinol acetate.

PubMed

Muñoz, Marcelo A; Urzúa, Alejandro; Echeverría, Javier; Modak, Brenda; Joseph-Nathan, Pedro

2011-06-01

Careful reevaluation of the 1H and 13C NMR spectroscopic data of filifolinol acetate (4) led to the reassignment of the C-10 and C-11 signals, as well as the gem-dimethyl signals. Single crystal X-ray analysis provided an independent structural confirmation of 4, and comparison of the experimental vibrational circular dichroism spectrum with calculations performed using density functional theory provided the absolute configuration of this 3H-spiro-1-benzofuran-2,1'-cyclohexane and related molecules.

Cooperative use of VCD and XRD for the determination of tetrahydrobenzoisoquinolines absolute configuration: a reliable proof of memory of chirality and retention of configuration in enediyne rearrangements.

PubMed

Mondal, Shovan; Naubron, Jean-Valère; Campolo, Damien; Giorgi, Michel; Bertrand, Michéle P; Nechab, Malek

2013-12-01

The absolute configurations (AC) of azaheterocylic compounds resulting from the cascade rearrangement of enediynes involving only light atoms were unambiguously assigned by the joint use of vibrational circular dichroism (VCD) and copper radiation single crystal X-ray diffraction (XRD). These AC determinations proved that the rearrangements of enediynes proceeded with memory of chirality and retention of configuration. © 2013 Wiley Periodicals, Inc.

On determination of sign of the piezo-optic coefficients using torsion method.

PubMed

Vasylkiv, Yurij; Savaryn, Viktoriya; Smaga, Ihor; Skab, Ihor; Vlokh, Rostyslav

2011-06-10

We have shown that a high-accuracy torsion method recently developed by the authors for measuring piezo-optic coefficients allows determining not only the absolute value of the coefficients but also their sign. The techniques and experimental procedures used for determination of the sign are described in detail and proven based on studies of α-BaB2O4 and LiNbO3 crystals. The piezo-optic coefficients are determined for both crystals, and a combination of the corresponding photoelastic coefficients is determined for the case of α-BaB2O4 crystals.

Accessibility of Nitroxide Side Chains: Absolute Heisenberg Exchange Rates from Power Saturation EPR

PubMed Central

Altenbach, Christian; Froncisz, Wojciech; Hemker, Roy; Mchaourab, Hassane; Hubbell, Wayne L.

2005-01-01

In site-directed spin labeling, the relative solvent accessibility of spin-labeled side chains is taken to be proportional to the Heisenberg exchange rate (Wex) of the nitroxide with a paramagnetic reagent in solution. In turn, relative values of Wex are determined by continuous wave power saturation methods and expressed as a proportional and dimensionless parameter Π. In the experiments presented here, NiEDDA is characterized as a paramagnetic reagent for solvent accessibility studies, and it is shown that absolute values of Wex can be determined from Π, and that the proportionality constant relating them is independent of the paramagnetic reagent and mobility of the nitroxide. Based on absolute exchange rates, an accessibility factor is defined (0 < ρ < 1) that serves as a quantitative measure of side-chain solvent accessibility. The accessibility factors for a nitroxide side chain at 14 different sites in T4 lysozyme are shown to correlate with a structure-based accessibility parameter derived from the crystal structure of the protein. These results provide a useful means for relating crystallographic and site-directed spin labeling data, and hence comparing crystal and solution structures. PMID:15994891

TT-Cut Torsional Quartz Crystal Resonators of Free-Free Bar-Type

NASA Astrophysics Data System (ADS)

Kawashima, Hirofumi; Nakazato, Mitsuhiro

1994-05-01

This paper describes a TT-cut torsional quartz crystal resonator of free-free bar type. An object of this paper is to clarify the frequency temperature behavior, series resistance and a quality factor for TT-cut torsional quartz crystal resonators of free-free bar-type. The analysis results are then compared with the measured data. The principal results indicate that the calculated values of frequency temperature behavior for resonators of free-free bar-type agree comparatively well with the measured ones. Similar to the torsional resonators of tuning fork-type, a torsional quartz crystal resonator of free-free bar-type is also found to have an absolute value of the second order temperature coefficient β smaller than half a value of that for a flexural mode quartz crystal resonator.

Telling in-tune from out-of-tune: widespread evidence for implicit absolute intonation.

PubMed

Van Hedger, Stephen C; Heald, Shannon L M; Huang, Alex; Rutstein, Brooke; Nusbaum, Howard C

2017-04-01

Absolute pitch (AP) is the rare ability to name or produce an isolated musical note without the aid of a reference note. One skill thought to be unique to AP possessors is the ability to provide absolute intonation judgments (e.g., classifying an isolated note as "in-tune" or "out-of-tune"). Recent work has suggested that absolute intonation perception among AP possessors is not crystallized in a critical period of development, but is dynamically maintained by the listening environment, in which the vast majority of Western music is tuned to a specific cultural standard. Given that all listeners of Western music are constantly exposed to this specific cultural tuning standard, our experiments address whether absolute intonation perception extends beyond AP possessors. We demonstrate that non-AP listeners are able to accurately judge the intonation of completely isolated notes. Both musicians and nonmusicians showed evidence for absolute intonation recognition when listening to familiar timbres (piano and violin). When testing unfamiliar timbres (triangle and inverted sine waves), only musicians showed weak evidence of absolute intonation recognition (Experiment 2). Overall, these results highlight a previously unknown similarity between AP and non-AP possessors' long-term musical note representations, including evidence of sensitivity to frequency.

Absolute structure and structure-function relationships of 4R,2‧R and 4S,2‧S Pidotimod®

NASA Astrophysics Data System (ADS)

Sarno, Simone; Manzo, Angelo M.; Ferraris, Davide M.; Miggiano, Riccardo; Rizzi, Menico; Palin, Luca; Boccaleri, Enrico; Milanesio, Marco

2017-11-01

Pidotimod® is a dipeptide with widely recognized immunomodulatory properties and with particularly beneficial effects for the treatment of acute respiratory and urinary tract infections. Pidotimod® presents two chiral centres which originate four stereoisomers. (4R,2‧S, 4S,2‧R, 4R,2‧R and 4S,2‧S). To date, only the 4R,2‧S and 4S,2‧R stereoisomers are reported in the literature. We report here the absolute crystal structure of the 4R,2‧R and 4S,2‧S diastereoisomers of Pidotimod®, obtained by crystals grown by slow evaporation of a mixture of water and ethanol. The analysis of the crystal structures revealed the key role of a solvent water molecule in the crystal packing engaged in an extended hydrogen bonds network. This water-assisted H-bond network explained the recalcitrance of 4R,2‧R and 4S,2‧S Pidotimod® to crystallize in pure ethanol, despite their high solubility, and the growth of well-diffracting crystals only in presence of water. Hence, Pidotimod®4R,2‧R and 4S,2‧S stereoisomers markedly differ from the 4R,2‧S and 4S,2‧R ones, which crystallize in absence of water. The molecular and crystal structures of the 4R,2‧R and 4S,2‧S Pidotimod® stereoisomers here presented gave some hints on the differences in bioactivity with respect to the 4R,2‧S stereoisomer. In fact, beyond an expected different dispositions of hydrophilic ligands, 4R,2‧R and 4S,2‧S showed an incremented tendency to intermolecular H-bonds with water.

Crystal structure and absolute configuration of (3aS,4S,5R,7aR)-2,2,7-trimethyl-3a,4,5,7a-tetra-hydro-1,3-benzodioxole-4,5-diol.

PubMed

Macías, Mario A; Suescun, Leopoldo; Pandolfi, Enrique; Schapiro, Valeria; Tibhe, Gaurao D; Mombrú, Álvaro W

2015-09-01

The absolute configuration of the title compound, C10H16O4, determined as 3aS,4S,5R,7aR on the basis of the synthetic pathway, was confirmed by X-ray diffraction. The mol-ecule contains a five- and a six-membered ring that adopt twisted and envelope conformations, respectively. The dihedral angle between the mean planes of the rings is 76.80 (11)° as a result of their cis-fusion. In the crystal, mol-ecules are linked by two pairs of O-H⋯O hydrogen bonds, forming chains along [010]. These chains are further connected by weaker C-H⋯O inter-actions along [100], creating (001) sheets that inter-act only by weak van der Waals forces.

Development and applications of optical interferometric micrometrology in the angstrom and subangstrom range

NASA Technical Reports Server (NTRS)

Lauer, James L.; Abel, Phillip B.

1988-01-01

The recent development of the scanning electron tunneling microscope and the atomic force microscope requires absolute standards for measurements in the angstrom and subangstrom range. Optical interferometry with lasers and multiple mode laser resonances can provide absolute measurements as the laser wavelengths are very accurately known. A key feature of such measurements is the use of piezoelectric crystals as translators of the highest accuracy for very small disturbances. However, the dimensional changes of these crystals resulting from electrical potential changes depend on many variables, among them the method of mounting, so that accurate calibrations are necessary. Starting from advances in optical metrology made by physicists trying to find gravity waves, advances which led to measurements down to 10 to the -5 A, the author designed and built a much simpler system for the angstrom range. The major limiting factors were mechanical vibrations, air currents, thermal changes and laser instabilities.

Large area Czochralski silicon

NASA Technical Reports Server (NTRS)

Rea, S. N.; Gleim, P. S.

1977-01-01

The overall cost effectiveness of the Czochralski process for producing large-area silicon was determined. The feasibility of growing several 12 cm diameter crystals sequentially at 12 cm/h during a furnace run and the subsequent slicing of the ingot using a multiblade slurry saw were investigated. The goal of the wafering process was a slice thickness of 0.25 mm with minimal kerf. A slice + kerf of 0.56 mm was achieved on 12 cm crystal using both 400 grit B4C and SiC abrasive slurries. Crystal growth experiments were performed at 12 cm diameter in a commercially available puller with both 10 and 12 kg melts. Several modifications to the puller hoz zone were required to achieve stable crystal growth over the entire crystal length and to prevent crystallinity loss a few centimeters down the crystal. The maximum practical growth rate for 12 cm crystal in this puller design was 10 cm/h, with 12 to 14 cm/h being the absolute maximum range at which melt freeze occurred.

Optically stimulated luminescence dating of sediments

NASA Astrophysics Data System (ADS)

Troja, S. O.; Amore, C.; Barbagallo, G.; Burrafato, G.; Forzese, R.; Geremia, F.; Gueli, A. M.; Marzo, F.; Pirnaci, D.; Russo, M.; Turrisi, E.

2000-04-01

Optically stimulated luminescence (OSL) dating methodology was applied on the coarse grain fraction (100÷500 μm thick) of quartz crystals (green light stimulated luminescence, GLSL) and feldspar crystals (infrared stimulated luminescence, IRSL) taken from sections at different depths of cores bored in various coastal lagoons (Longarini, Cuba, Bruno) in the south-east coast of Sicily. The results obtained give a sequence of congruent relative ages and maximum absolute ages compatible with the sedimentary structure, thus confirming the excellent potential of the methodology.

Structure elucidation and absolute stereochemistry of isomeric monoterpene chromane esters.

PubMed

Batista, João M; Batista, Andrea N L; Mota, Jonas S; Cass, Quezia B; Kato, Massuo J; Bolzani, Vanderlan S; Freedman, Teresa B; López, Silvia N; Furlan, Maysa; Nafie, Laurence A

2011-04-15

Six novel monoterpene chromane esters were isolated from the aerial parts of Peperomia obtusifolia (Piperaceae) using chiral chromatography. This is the first time that chiral chromane esters of this kind, ones with a tethered chiral terpene, have been isolated in nature. Due to their structural features, it is not currently possible to assess directly their absolute stereochemistry using any of the standard classical approaches, such as X-ray crystallography, NMR, optical rotation, or electronic circular dichroism (ECD). Herein we report the absolute configuration of these molecules, involving four chiral centers, using vibrational circular dichroism (VCD) and density functional theory (DFT) (B3LYP/6-31G*) calculations. This work further reinforces the capability of VCD to determine unambiguously the absolute configuration of structurally complex molecules in solution, without crystallization or derivatization, and demonstrates the sensitivity of VCD to specify the absolute configuration for just one among a number of chiral centers. We also demonstrate the sufficiency of using the so-called inexpensive basis set 6-31G* compared to the triple-ζ basis set TZVP for absolute configuration analysis of larger molecules using VCD. Overall, this work extends our knowledge of secondary metabolites in plants and provides a straightforward way to determine the absolute configuration of complex natural products involving a chiral parent moiety combined with a chiral terpene adduct.

Tachistoscopic exposure and masking of real three-dimensional scenes

PubMed Central

Pothier, Stephen; Philbeck, John; Chichka, David; Gajewski, Daniel A.

2010-01-01

Although there are many well-known forms of visual cues specifying absolute and relative distance, little is known about how visual space perception develops at small temporal scales. How much time does the visual system require to extract the information in the various absolute and relative distance cues? In this article, we describe a system that may be used to address this issue by presenting brief exposures of real, three-dimensional scenes, followed by a masking stimulus. The system is composed of an electronic shutter (a liquid crystal smart window) for exposing the stimulus scene, and a liquid crystal projector coupled with an electromechanical shutter for presenting the masking stimulus. This system can be used in both full- and reduced-cue viewing conditions, under monocular and binocular viewing, and at distances limited only by the testing space. We describe a configuration that may be used for studying the microgenesis of visual space perception in the context of visually directed walking. PMID:19182129

Bridgman growth and scintillation properties of calcium tungstate single crystal

NASA Astrophysics Data System (ADS)

Wang, Zhenhai; Jiang, Linwen; Chen, Yaping; Chen, Peng; Chen, Hongbing; Mao, Rihua

2017-12-01

CaWO4 single crystal with large size was grown by Bridgman method. The results of transmission spectra show that the transmittance of CaWO4 crystal reaches 79-85% in 320-800 nm wavelength range. The refraction index is near 1.80 in visible and infrared region. CaWO4 crystal shows a broad emission band centered at 424 nm under X-ray excitation and centered at 416 nm under ultraviolet (λex = 280 nm) excitation. The decay kinetics of CaWO4 single crystal shows double-exponential decay with fast decay constant τ1 = 5.4 μs and slow decay constant τ2 = 177.1 μs. The energy resolution of CaWO4 crystal was found to be 31.6% in the net peak of 545.9 channel. Meanwhile, the absolute output is at the lever of 19,000 ± 1000 photons/MeV. The results indicate the scintillator of CaWO4 single crystal has great potential in the applications of high-energy physics and nuclear physics due to its high light output and great energy resolution.

Static photoelasticity of gallium phosphide crystals

NASA Astrophysics Data System (ADS)

Mytsyk, B. G.; Andrushchak, A. S.; Kost', Ya. P.

2012-01-01

The piezo-optic effect (POE) in cubic GaP crystals (symmetry class bar 43 m) is studied in detail by interferometry. The relations for determining the absolute piezo-optic coefficients (POCs) π im or their combinations on a sample of X/45° cut at all allowable geometries of the experiment are recorded. The determination of a specific coefficient π im at different experimental geometries on samples of right cuts and a X/45° cut made it possible to find the π im values with a high accuracy and reliability.

A new lunar absolute control point: established by images from the landing camera on Chang'e-3

NASA Astrophysics Data System (ADS)

Wang, Fen-Fei; Liu, Jian-Jun; Li, Chun-Lai; Ren, Xin; Mu, Ling-Li; Yan, Wei; Wang, Wen-Rui; Xiao, Jing-Tao; Tan, Xu; Zhang, Xiao-Xia; Zou, Xiao-Duan; Gao, Xing-Ye

2014-12-01

The establishment of a lunar control network is one of the core tasks in selenodesy, in which defining an absolute control point on the Moon is the most important step. However, up to now, the number of absolute control points has been very sparse. These absolute control points have mainly been lunar laser ranging retroreflectors, whose geographical location can be observed by observations on Earth and also identified in high resolution lunar satellite images. The Chang'e-3 (CE-3) probe successfully landed on the Moon, and its geographical location has been monitored by an observing station on Earth. Since its positional accuracy is expected to reach the meter level, the CE-3 landing site can become a new high precision absolute control point. We use a sequence of images taken from the landing camera, as well as satellite images taken by CE-1 and CE-2, to identify the location of the CE-3 lander. With its geographical location known, the CE-3 landing site can be established as a new absolute control point, which will effectively expand the current area of the lunar absolute control network by 22%, and can greatly facilitate future research in the field of lunar surveying and mapping, as well as selenodesy.

Automatic twin vessel recrystallizer. Effective purification of acetaminophen by successive automatic recrystallization and absolute determination of purity by DSC.

PubMed

Nara, Osamu

2011-01-24

I describe an interchangeable twin vessel (J, N) automatic glass recrystallizer that eliminates the time-consuming recovery and recycling of crystals for repeated recrystallization. The sample goes in the dissolution vessel J containing a magnetic stir-bar K; J is clamped to the upper joint H of recrystallizer body D. Empty crystallization vessel N is clamped to the lower joint M. Pure solvent is delivered to the dissolution vessel and the crystallization vessel via the head of the condenser A. Crystallization vessel is heated (P). The dissolution reservoir is stirred and heated by the solvent vapor (F). Continuous outflow of filtrate E out of J keeps N at a stable boiling temperature. This results in efficient dissolution, evaporation and separation of pure crystals Q. Pure solvent in the dissolution reservoir is recovered by suction. Empty dissolution and crystallization vessels are detached. Stirrer magnet is transferred to the crystallization vessel and the role of the vessels are then reversed. Evacuating mother liquor out of the upper twin vessel, the apparatus unit is ready for the next automatic recrystallization by refilling twin vessels with pure solvent. We show successive automatic recrystallization of acetaminophen from diethyl ether obtaining acetaminophen of higher melting temperatures than USP and JP reference standards by 8× automatic recrystallization, 96% yield at each stage. Also, I demonstrate a novel approach to the determination of absolute purity by combining the successive automatic recrystallization with differential scanning calorimetry (DSC) measurement requiring no reference standards. This involves the measurement of the criterial melting temperature T(0) corresponding to the 100% pure material and quantitative ΔT in DSC based on the van't Hoff law of melting point depression. The purity of six commercial acetaminophen samples and reference standards and an eight times recrystallized product evaluated were 98.8 mol%, 97.9 mol%, 99.1 mol%, 98.3 mol%, 98.4 mol%, 98.5 mol% and 99.3 mol% respectively. Copyright © 2010 Elsevier B.V. All rights reserved.

bcc-iron as a promising new monochromator material for thermal neutrons

NASA Astrophysics Data System (ADS)

Kirscht, Patrick; Sobolev, Oleg; Eckold, Götz

2018-04-01

The development of high-performance neutron monochromators is a long-standing and still actual topic in neutron instrumentation. Due to its high scattering cross section, iron is a particularly interesting material since it offers the possibility to obtain high reflectivities at small wavelength and good resolution. Phase transitions between bcc- and fcc-phases hindered the growth of large and high-quality single crystals in the past and only recently bcc-crystals became commercially available. We have characterized the reflecting properties of as-grown and deformed crystals using γ-rays and thermal neutrons. Absolute reflectivities well above 30% for neutron wavelengths near 1 Å could be obtained that are superior to that of all other existing monochromator materials. Hence, the progress in crystal growth along with the knowledge of directed plastic deformation makes the development of bcc-Fe neutron monochromators feasible. Their application in crystal-monochromator instruments is suitable to increase the useful neutron flux at large energies considerably.

Scintillation properties of a 2-inch diameter KCa0.8Sr0.2I3:Eu2+ single crystal

NASA Astrophysics Data System (ADS)

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

2017-09-01

Inch-sized scintillating crystals are required for practical radiation detectors such as hand-held radio-isotope identification devices. In this work, a transparent and colorless 2-inch diameter KCa0.8Sr0.2I3: 0 . 5 mo% Eu2+ single crystal was grown by the vertical Bridgman method, and the scintillation properties of a ∅ 50 mm × 45 mm long sample were evaluated. The Eu2+ 5d1- 4 f emission under X-ray excitation is centered at 472 nm. Its scintillation decay time under 137 Cs source irradiation is 2 . 37 μs, and the absolute light output is 51,000 ± 3000 photons/MeV. The energy resolution at 662 keV was evaluated for different orientations of the crystals with respect to the PMT, and the effect of 40 K background subtraction on energy resolution was evaluated. The performance of the packaged crystal was also investigated.

Cytotoxic 14-Membered Macrolides from a Mangrove-Derived Endophytic Fungus, Pestalotiopsis microspora.

PubMed

Liu, Shuai; Dai, Haofu; Makhloufi, Gamall; Heering, Christian; Janiak, Christoph; Hartmann, Rudolf; Mándi, Attila; Kurtán, Tibor; Müller, Werner E G; Kassack, Matthias U; Lin, Wenhan; Liu, Zhen; Proksch, Peter

2016-09-23

Seven new 14-membered macrolides, pestalotioprolides C (2), D-H (4-8), and 7-O-methylnigrosporolide (3), together with four known analogues, pestalotioprolide B (1), seiricuprolide (9), nigrosporolide (10), and 4,7-dihydroxy-13-tetradeca-2,5,8-trienolide (11), were isolated from the mangrove-derived endophytic fungus Pestalotiopsis microspora. Their structures were elucidated by analysis of NMR and MS data and by comparison with literature data. Single-crystal X-ray diffraction analysis was used to confirm the absolute configurations of 1, 2, and 10, while Mosher's method and the TDDFT-ECD approach were applied to determine the absolute configurations of 5 and 6. Compounds 3-6 showed significant cytotoxicity against the murine lymphoma cell line L5178Y with IC50 values of 0.7, 5.6, 3.4, and 3.9 μM, respectively, while compound 5 showed potent activity against the human ovarian cancer cell line A2780 with an IC50 value of 1.2 μM. Structure-activity relationships are discussed. Coculture of P. microspora with Streptomyces lividans caused a roughly 10-fold enhanced accumulation of compounds 5 and 6 compared to axenic fungal control.

Determination of Residual Stress Distributions in Polycrystalline Alumina using Fluorescence Microscopy

PubMed Central

Michaels, Chris A.; Cook, Robert F.

2016-01-01

Maps of residual stress distributions arising from anisotropic thermal expansion effects in a polycrystalline alumina are generated using fluorescence microscopy. The shifts of both the R1 and R2 ruby fluorescence lines of Cr in alumina are used to create maps with sub-µm resolution of either the local mean and shear stresses or local crystallographic a- and c-stresses in the material, with approximately ± 1 MPa stress resolution. The use of single crystal control materials and explicit correction for temperature and composition effects on line shifts enabled determination of the absolute values and distributions of values of stresses. Temperature correction is shown to be critical in absolute stress determination. Experimental determinations of average stress parameters in the mapped structure are consistent with assumed equilibrium conditions and with integrated large-area measurements. Average crystallographic stresses of order hundreds of MPa are determined with characteristic distribution widths of tens of MPa. The stress distributions reflect contributions from individual clusters of stress in the structure; the cluster size is somewhat larger than the grain size. An example application of the use of stress maps is shown in the calculation of stress-intensity factors for fracture in the residual stress field. PMID:27563163

Temperature responsive transmitter

NASA Technical Reports Server (NTRS)

Kleinberg, Leonard L. (Inventor)

1987-01-01

A temperature responsive transmitter is provided in which frequency varies linearly with temperature. The transmitter includes two identically biased transistors connected in parallel. A capacitor, which reflects into the common bases to generate negative resistance effectively in parallel with the capacitor, is connected to the common emitters. A crystal is effectively in parallel with the capacitor and the negative resistance. Oscillations occur if the magnitude of the absolute value of the negative resistance is less than the positive resistive impedance of the capacitor and the inductance of the crystal. The crystal has a large linear temperature coefficient and a resonant frequency which is substantially less than the gain-bandwidth product of the transistors to ensure that the crystal primarily determines the frequency of oscillation. A high-Q tank circuit having an inductor and a capacitor is connected to the common collectors to increase the collector current flow which in turn enhances the radiation of the oscillator frequency by the inductor.

Frequency and Thermal Behavior of Acoustic Absorption in ɛ-GaSe Crystals

NASA Astrophysics Data System (ADS)

Dzhafarova, S. Z.

2018-04-01

The paper presents results of measuring acoustic absorption in ɛ-GaSe crystals. The absorption of a longitudinal wave which propagates normal to the crystal layers, quadratically depends on frequency. However, it does not depend on temperature, i.e. it displays an Akhiezer behavior although its absolute value considerably exceeds the expected. The analysis of the frequency and thermal behavior of absorption of piezoelectric waves propagating along the layers, includes the deduction of contribution made by the interaction between waves and charge carriers. This analysis shows the linear dependence between the lattice absorption of these waves and the frequency. The linear frequency and weak temperature dependences of the acoustic absorption characterize the additional ultra-Akhiezer absorption in glasses. In our case, it can be caused by various polytypes forming in GaSe crystals which differ merely in a mutual arrangement of layers.

Crystal structure, electronic structure, optical and scintillation properties of self-activated Cs 4YbI 6 [Crystal structure, optical and scintillation properties of self-activated Cs 4YbI 6

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

Wu, Yuntao; Chakoumakos, Bryan C.; Shi, Hongliang

A self-activated Cs 4YbI 6 single crystal was grown by the vertical Bridgman method. Crystal structure refinements verified the phase purity and the trigonal crystal system with a space group of more » $$\\bar{R}$$3 c. By using differential scanning calorimetry, the melting and crystallization points were determined to be 550 and 510 °C, respectively. Luminescence and scintillation properties were systematically studied. Upon ultraviolet light (360 nm) excitation, the Cs 4YbI 6 crystal exhibits bluish-green emission centered at 450 and 480 nm due to spin-allowed and spin-forbidden transitions of Yb 2+ activators. The lifetimes of the corresponding emission bands at room temperature are tens and hundreds of nanoseconds, respectively. X-ray excited radioluminescence spectrum is dominated by the spin-forbidden transition of Yb 2+ at 480 nm. The absolute light yield is 2700 ± 200 photons/MeV with a principal scintillation decay time of 33 ns. In conclusion, the physical explanation for the low light yield observed is proposed from experimental and theoretical insights.« less

Crystal structure, electronic structure, optical and scintillation properties of self-activated Cs 4YbI 6 [Crystal structure, optical and scintillation properties of self-activated Cs 4YbI 6

DOE PAGES

Wu, Yuntao; Chakoumakos, Bryan C.; Shi, Hongliang; ...

2018-05-14

A self-activated Cs 4YbI 6 single crystal was grown by the vertical Bridgman method. Crystal structure refinements verified the phase purity and the trigonal crystal system with a space group of more » $$\\bar{R}$$3 c. By using differential scanning calorimetry, the melting and crystallization points were determined to be 550 and 510 °C, respectively. Luminescence and scintillation properties were systematically studied. Upon ultraviolet light (360 nm) excitation, the Cs 4YbI 6 crystal exhibits bluish-green emission centered at 450 and 480 nm due to spin-allowed and spin-forbidden transitions of Yb 2+ activators. The lifetimes of the corresponding emission bands at room temperature are tens and hundreds of nanoseconds, respectively. X-ray excited radioluminescence spectrum is dominated by the spin-forbidden transition of Yb 2+ at 480 nm. The absolute light yield is 2700 ± 200 photons/MeV with a principal scintillation decay time of 33 ns. In conclusion, the physical explanation for the low light yield observed is proposed from experimental and theoretical insights.« less

Effects of thermal expansion of the crystal lattice on x-ray crystal spectrometers used for fusion research

NASA Astrophysics Data System (ADS)

Delgado-Aparicio, L.; Bitter, M.; Podpaly, Y.; Rice, J.; Burke, W.; Sanchez del Rio, M.; Beiersdorfer, P.; Bell, R.; Feder, R.; Gao, C.; Hill, K.; Johnson, D.; Lee, S. G.; Marmar, E.; Pablant, N.; Reinke, M. L.; Scott, S.; Wilson, R.

2013-12-01

X-ray imaging crystal spectrometers with high spectral and spatial resolution are currently being used on magnetically confined fusion devices to infer the time history profiles of ion and electron temperatures as well as plasma flow velocities. The absolute measurement of flow velocities is important for optimizing various discharge scenarios and evaluating the radial electric field in tokamak and stellarator plasmas. Recent studies indicate that the crystal temperature must be kept constant to within a fraction of a degree to avoid changes of the interplanar 2d-spacing by thermal expansion that cause changes in the Bragg angle, which could be misinterpreted as Doppler shifts. For the instrumental parameters of the x-ray crystal spectrometer on Alcator C-Mod, where those thermal effects were investigated, a change of the crystal temperature by 1 °C causes a change of the lattice spacing of the order of Δd = 1 × 10-5 Å introducing a fictitious velocity drift of the order of ˜3 km s-1. This effect must be considered for x-ray imaging crystals spectrometers installed on LHD, KSTAR, EAST, J-TEXT, NSTX and, in the future, W7-X and ITER.

Mapping 180° polar domains using electron backscatter diffraction and dynamical scattering simulations

DOE PAGES

Burch, Matthew J.; Fancher, Chris M.; Patala, Srikanth; ...

2016-11-18

A novel technique, which directly and nondestructively maps polar domains using electron backscatter diffraction (EBSD) is described and demonstrated. Through dynamical diffraction simulations and quantitative comparison to experimental EBSD patterns, the absolute orientation of a non-centrosymmetric crystal can be determined. With this information, the polar domains of a material can be mapped. The technique is demonstrated by mapping the non-ferroelastic, or 180°, ferroelectric domains in periodically poled LiNbO 3 single crystals. Furthermore, the authors demonstrate the possibility of mapping polarity using this technique in other polar materials system.

Single crystal substrates for surface acoustic wave devices

NASA Astrophysics Data System (ADS)

Barsch, G. R.; Spear, K. E.

1981-01-01

In order to search for new temperature compensated materials for surface acoustic wave (SAW) devices with low ultrasonic attenuation and high electromechanical coupling, the following experimental and theoretical investigations were carried out: (1) Crystal growth research centered around: designing, constructing, and writing the software for a computer controlled constant-diameter attachment for our Czochralski crystal pullers; a major experimental effort on the growth of lead potassium niobate (PKN); Pb2KNb5O15, and lead bismuth niobate (PBN) PbBi2Nb2O9, and a minor experimental effort on the growth of lithium metasilicate, Li2SiO3; and bismuth molybdate, Bi2MoO6. (2) The dielectric constants and the associated loss tangents of alpha-berlinite were measured at eleven frequencies from 100 to 10,000 Hz between -150 and 200 C. The temperature dependence of the dielectric constants and the relaxation behavior are similar to the results obtained earlier, but the absolute values are 20 to 30 percent smaller than reported previously. (3) The temperature dependence of the two shear modes propagating in (001) has been measured from 10 to 315K for Bi4Ti3O12. A monotonical decrease of the associated shear moduli has been found. (4) Considerable effort was devoted to specimen preparation of lead bismuth niobate which was hampered by the easy cleavage of this material perpendicular to 001 .

Structural changes that occur upon photolysis of the Fe(II)a3 - CO complex in the cytochrome ba3-oxidase of Thermus thermophilus: A combined X-ray crystallographic and infrared spectral study demonstrates CO binding to CuB

PubMed Central

Liu, Bin; Zhang, Yang; Sage, J. Timothy; Soltis, S. Michael; Doukov, Tzanko; Chen, Ying; Stout, C. David; Fee, James A.

2012-01-01

The purpose of the work was to provide a crystallographic demonstration of the venerable idea that CO photolyzed from ferrous heme-a3 moves to the nearby cuprous ion in the cytochrome c oxidases. Crystal structures of CO-bound cytochrome ba3-oxidase from Thermus thermophilus, determined at ~ 2.8 – 3.2 Å resolution, reveal a Fe-C distance of ~2.0 Å, a Cu-O distance of 2.4 Å and a Fe-C-O angle of ~126°. Upon photodissociation at 100 K, X-ray structures indicate loss of Fea3-CO and appearance of CuB-CO having a Cu-C distance of ~1.9 Å and an O-Fe distance of ~2.3 Å. Absolute FTIR spectra recorded from single crystals of reduced ba3–CO that had not been exposed to X-ray radiation, showed several peaks around 1975 cm−1; after photolysis at 100 K, the absolute FTIR spectra also showed a significant peak at 2050 cm−1. Analysis of the “light’ minus ‘dark’ difference spectra showed four very sharp CO stretching bands at 1970 cm−1, 1977 cm−1, 1981 cm−1, and 1985 cm−1, previously assigned to the Fea3-CO complex, and a significantly broader CO stretching band centered at ~2050 cm−1, previously assigned to the CO stretching frequency of CuB bound CO. As expected for light propagating along the tetragonal axis of the P43212 space group, the single crystal spectra exhibit negligible dichroism. Absolute FTIR spectrometry of a CO-laden ba3 crystal, exposed to an amount of X-ray radiation required to obtain structural data sets before FTIR characterization, showed a significant signal due to photogenerated CO2 at 2337 cm−1 and one from traces of CO at 2133 cm−1; while bands associated with CO bound to either Fea3 or to CuB in “light” minus “dark” FTIR difference spectra shifted and broadened in response to X-ray exposure. In spite of considerable radiation damage to the crystals, both X-ray analysis at 2.8 and 3.2 Å and FTIR spectra support the long-held position that photolysis of Fea3-CO in cytochrome c oxidases leads to significant trapping of the CO on the CuB atom; Fea3 and CuB ligation, at the resolutions reported here, are otherwise unaltered. PMID:22226917

Quantitative Kα line spectroscopy for energy transport in ultra-intense laser plasma interaction

NASA Astrophysics Data System (ADS)

Zhang, Z.; Nishimura, H.; Namimoto, T.; Fujioka, S.; Arikawa, Y.; Nakai, M.; Koga, M.; Shiraga, H.; Kojima, S.; Azechi, H.; Ozaki, T.; Chen, H.; Pakr, J.; Williams, G. J.; Nishikino, M.; Kawachi, T.; Sagisaka, A.; Orimo, S.; Ogura, K.; Pirozhkov, A.; Yogo, A.; Kiriyama, H.; Kondo, K.; Okano, Y.

2012-10-01

X-ray line spectra ranging from 17 to 77 keV were quantitatively measured with a Laue spectrometer, composed of a cylindrically curved crystal and a detector. The absolute sensitivity of the spectrometer system was calibrated using pre-characterized laser-produced x-ray sources and radioisotopes, for the detectors and crystal respectively. The integrated reflectivity for the crystal is in good agreement with predictions by an open code for x-ray diffraction. The energy transfer efficiency from incident laser beams to hot electrons, as the energy transfer agency for Au Kα x-ray line emissions, is derived as a consequence of this work. By considering the hot electron temperature, the transfer efficiency from LFEX laser to Au plate target is about 8% to 10%.

Toward polarizable AMOEBA thermodynamics at fixed charge efficiency using a dual force field approach: application to organic crystals.

PubMed

Nessler, Ian J; Litman, Jacob M; Schnieders, Michael J

2016-11-09

First principles prediction of the structure, thermodynamics and solubility of organic molecular crystals, which play a central role in chemical, material, pharmaceutical and engineering sciences, challenges both potential energy functions and sampling methodologies. Here we calculate absolute crystal deposition thermodynamics using a novel dual force field approach whose goal is to maintain the accuracy of advanced multipole force fields (e.g. the polarizable AMOEBA model) while performing more than 95% of the sampling in an inexpensive fixed charge (FC) force field (e.g. OPLS-AA). Absolute crystal sublimation/deposition phase transition free energies were determined using an alchemical path that grows the crystalline state from a vapor reference state based on sampling with the OPLS-AA force field, followed by dual force field thermodynamic corrections to change between FC and AMOEBA resolutions at both end states (we denote the three step path as AMOEBA/FC). Importantly, whereas the phase transition requires on the order of 200 ns of sampling per compound, only 5 ns of sampling was needed for the dual force field thermodynamic corrections to reach a mean statistical uncertainty of 0.05 kcal mol -1 . For five organic compounds, the mean unsigned error between direct use of AMOEBA and the AMOEBA/FC dual force field path was only 0.2 kcal mol -1 and not statistically significant. Compared to experimental deposition thermodynamics, the mean unsigned error for AMOEBA/FC (1.4 kcal mol -1 ) was more than a factor of two smaller than uncorrected OPLS-AA (3.2 kcal mol -1 ). Overall, the dual force field thermodynamic corrections reduced condensed phase sampling in the expensive force field by a factor of 40, and may prove useful for protein stability or binding thermodynamics in the future.

Magnetic resonance imaging determination of left ventricular mass: junior Olympic weightlifters.

PubMed

Fleck, S J; Pattany, P M; Stone, M H; Kraemer, W J; Thrush, J; Wong, K

1993-04-01

The relationship between left ventricular mass (LVM) and peak VO2 in junior elite Olympic-style weightlifters and sedentary subjects was investigated. Ten male weightlifters (mean +/- SE, age = 17.5 +/- 0.4 yr, wt = 72.9 +/- 3.3 kg) and 15 sedentary males (age = 18.8 +/- 0.4 yr, wt = 69.6 +/- 2.0 kg) served as subjects. Peak VO2 was measured using a continuous, incrementally loaded bicycle ergometry protocol. LVM was measured using magnetic resonance imaging techniques. Absolute peak VO2 was not significantly different (P > or = 0.05) between the weightlifters and the control subjects (3.5 +/- 0.1 vs 3.3 +/- 0.11.min-1). Absolute LVM (g) was significantly (P < or = 0.05) correlated to absolute peak VO2 (1.min-1) in the weightlifters (r = 0.723), but not in the control subjects. No other correlations between LVM in absolute or normalized by body weight, body surface area, or fat free mass terms, and absolute peak or normalized by body weight peak VO2 were significant. The weightlifters absolute LVM was significantly greater (P < or = 0.05) than that of the controls (208.1 +/- 10.0 vs 179.7 +/- 8.4 g). LVM normalized by body weight and body surface area but not by fat free mass, was significantly greater (P < or = 0.05) in the weightlifters than the control subjects. These data indicate that LVM in junior elite weightlifters is greater than that of control subjects and absolute LVM is related to absolute peak VO2 in weightlifters but not control subjects.

Concave Urinary Crystallines: Direct Evidence of Calcium Oxalate Crystals Dissolution by Citrate In Vivo

PubMed Central

Shang, Yun-Feng; Xu, Meng; Zhang, Guang-Na; Ouyang, Jian-Ming

2013-01-01

The changes in urinary crystal properties in patients with calcium oxalate (CaOx) calculi after oral administration of potassium citrate (K3cit) were investigated via atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray powder diffractometry (XRD), and zeta potential analyzer. The AFM and SEM results showed that the surface of urinary crystals became concave, the edges and corners of crystals became blunt, the average size of urinary crystallines decreased significantly, and aggregation of urinary crystals was reduced. These changes were attributed to the significant increase in concentration of excreted citrate to 492 ± 118 mg/L after K3cit intake from 289 ± 83 mg/L before K3cit intake. After the amount of urinary citrate was increased, it complexed with Ca2+ ions on urinary crystals, which dissolved these crystals. Thus, the appearance of concave urinary crystals was a direct evidence of CaOx dissolution by citrate in vivo. The XRD results showed that the quantities and species of urinary crystals decreased after K3cit intake. The mechanism of inhibition of formation of CaOx stones by K3cit was possibly due to the complexation of Ca2+ with citrate, increase in urine pH, concentration of urinary inhibitor glycosaminoglycans (GAGs), and the absolute value of zeta potential after K3cit intake. PMID:24363634

Conductive properties of switchable photoluminescence thermosetting systems based on liquid crystals.

PubMed

Tercjak, Agnieszka; Gutierrez, Junkal; Ocando, Connie; Mondragon, Iñaki

2010-03-16

Conductive properties of different thermosetting materials modified with nematic 4'-(hexyl)-4-biphenyl-carbonitrile (HBC) liquid crystal and rutile TiO(2) nanoparticles were successfully studied by means of tunneling atomic force miscroscopy (TUNA). Taking into account the liquid crystal state of the HBC at room temperature, depending on both the HBC content and the presence of TiO(2) nanoparticles, designed materials showed different TUNA currents passed through the sample. The addition of TiO(2) nanoparticles into the systems multiply the detected current if compared to the thermosetting systems without TiO(2) nanoparticles and simultaneously stabilized the current passed through the sample, making the process reversible since the absolute current values were almost the same applying both negative and positive voltage. Moreover, thermosetting systems modified with liquid crystals with and without TiO(2) nanoparticles are photoluminescence switchable materials as a function of temperature gradient during repeatable heating/cooling cycle. Conductive properties of switchable photoluminescence thermosetting systems based on liquid crystals can allow them to find potential application in the field of photoresponsive devices, with a high contrast ratio between transparent and opaque states.

Absolute Stability Analysis of a Phase Plane Controlled Spacecraft

NASA Technical Reports Server (NTRS)

Jang, Jiann-Woei; Plummer, Michael; Bedrossian, Nazareth; Hall, Charles; Jackson, Mark; Spanos, Pol

2010-01-01

Many aerospace attitude control systems utilize phase plane control schemes that include nonlinear elements such as dead zone and ideal relay. To evaluate phase plane control robustness, stability margin prediction methods must be developed. Absolute stability is extended to predict stability margins and to define an abort condition. A constrained optimization approach is also used to design flex filters for roll control. The design goal is to optimize vehicle tracking performance while maintaining adequate stability margins. Absolute stability is shown to provide satisfactory stability constraints for the optimization.

Characterization of iron-doped lithium niobate for holographic storage applications

NASA Technical Reports Server (NTRS)

Shah, R. R.; Kim, D. M.; Rabson, T. A.; Tittel, F. K.

1976-01-01

A comprehensive characterization of chemical and holographic properties of eight systematically chosen Fe:LiNbO3 crystals is performed in order to determine optimum performance of the crystals in holographic storage and display applications. The discussion covers determination of Fe(2+) and Fe(3+) ion concentrations in Fe:LiNbO3 system from optical absorption and EPR measurements; establishment of the relation between the photorefractive sensitivity of Fe(2+) and Fe(3+) concentrations; study of the spectral dependence, the effect of oxygen annealing, and of other impurities on the photorefractive sensitivity; analysis of the diffraction efficiency curves for different crystals and corresponding sensitivities with the dynamic theory of hologram formation; and determination of the bulk photovoltaic fields as a function of Fe(2+) concentrations. In addition to the absolute Fe(2+) concentration, the relative concentrations of Fe(2+) and Fe(3+) ions are also important in determining the photorefractive sensitivity. There exists an optimal set of crystal characteristics for which the photorefractive sensitivity is most favorable.

Band Gap Optimization Design of Photonic Crystals Material

NASA Astrophysics Data System (ADS)

Yu, Y.; Yu, B.; Gao, X.

2017-12-01

The photonic crystal has a fundamental characteristic - photonic band gap, which can prevent light to spread in the crystals. This paper studies the width variation of band gaps of two-dimension square lattice photonic crystals by changing the geometrical shape of the unit cells’ inner medium column. Using the finite element method, we conduct numerical experiments on MATLAB 2012a and COMSOL 3.5. By shortening the radius in vertical axis and rotating the medium column, we design a new unit cell, with a 0.3*3.85e-7 vertical radius and a 15 degree deviation to the horizontal axis. The new cell has a gap 1.51 percent wider than the circle medium structure in TE gap and creates a 0.0124 wide TM gap. Besides, the experiment shows the first TM gap is partially overlapped by the second TE gap in gap pictures. This is helpful to format the absolute photonic band gaps and provides favorable theoretical basis for designing photonic communication material.

Purification, crystallization and preliminary X-ray diffraction analysis of the glyoxalase II from Leishmania infantum

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

Trincão, José; Sousa Silva, Marta; Barata, Lídia

2006-08-01

A glyoxalase II from L. infantum was cloned, purified and crystallized and its structure was solved by X-ray crystallography. In trypanosomatids, trypanothione replaces glutathione in all glutathione-dependent processes. Of the two enzymes involved in the glyoxalase pathway, glyoxalase I and glyoxalase II, the latter shows absolute specificity towards trypanothione thioester, making this enzyme an excellent model to understand the molecular basis of trypanothione binding. Cloned glyoxalase II from Leishmania infantum was overexpressed in Escherichia coli, purified and crystallized. Crystals belong to space group C222{sub 1} (unit-cell parameters a = 65.6, b = 88.3, c = 85.2 Å) and diffract beyondmore » 2.15 Å using synchrotron radiation. The structure was solved by molecular replacement using the human glyoxalase II structure as a search model. These results, together with future detailed kinetic characterization using lactoyltrypanothione, should shed light on the evolutionary selection of trypanothione instead of glutathione by trypano-somatids.« less

Limitations on the Estimation of Parental Magma Temperature Using Olivine-melt Equilibria: Hotspots Not So Hot

NASA Astrophysics Data System (ADS)

Natland, J. H.

2004-12-01

Estimates of temperatures of magmas parental to picritic tholeiites using olivine-melt equilibria and FeO-MgO relationships depend strongly on the assumption that a liquid composition, usually a glass, is related to the most magnesian olivine in the rock, or to an olivine composition in equilibrium with mantle peridotite, along an olivine-controlled liquid line of descent. The liquid Fe2+/Fe3+ also has to be known; where data exist, average values from wet chemical determinations are used. Crystallization histories of tholeiitic picrites from islands, spreading ridges, and large igneous provinces, however, usually reveal them to be hybrid rocks that are assembled by two types of magma mixing: 1) between a) differentiated magmas that are on olivine-plagioclase or olivine-plagioclase-clinopyroxene cotectics and b) crystal sludges with abundant olivine that may have accumulated from liquids crystallizing olivine alone; and 2) between primitive magma strains in which olivine crystallized either alone or with other silicate minerals at elevated pressure on separate liquid lines of descent. Many picrites give evidence that both types of mixing have occurred. If either type has occurred, the assumption of olivine-control linking a glass and an olivine composition can only circumstantially be correct. Oxidation state can also be underestimated and therefore FeO contents overestimated if basalts have degassed S, as at Hawaii. In Case 1, hybrid host glass compositions often have higher FeO at given MgO content than liquids which produced many olivine crystals in the rock. In Case 2, the separate parental melt strains are revealed by diversity of compositions of both melt inclusions and Cr-spinel and are most often interpreted to mean local heterogeneity of the mantle source. The inclusions do not always affirm an olivine-controlled liquid line of descent. Instead, inclusions with <13% Al2O3 are increasingly interpreted from both major oxides and trace elements to be derived from melt strains produced by partial melting of both depleted and enriched pyroxenite or recycled ocean-crust (eclogite) (e.g., refs.1 and 2). Some Icelandic picrites also contain large phenocrysts of plagioclase and clinopyroxene; their abundant olivine evidently resulted from mechanical processes of concentration of olivine such as flowage differentiation. Using compositions of low-Al2O3 melt inclusions and host liquids to estimate spinel compositions (ref. 3) reveals many instances of crystallization at higher oxidation states than occur during MORB crystallization, and successfully predicts presence of spinel with Cr/(Cr+Al) = 60-75 actually found in picrites from Hawaii, Iceland, elsewhere in the North Atlantic Igneous Province, and the komatiites of Gorgona, but not in MORB. Where fresh glass is lacking (e.g., Gorgona), bulk-rock compositions have been used to reconstruct conditions of crystallization of parental liquids; but this is greatly complicated by the type and extent of alteration of the rocks. The consequence of all of these factors is that FeO in presumed olivine-controlled liquids is often overestimated, thus many estimated temperatures of crystallization of primitive magnesian liquids are too high by as much as 50-100o absolute, and derived potential temperatures consequently are too high by more than this. (1) Hansteen, T., 1991. Contrib. Mineral. Petrol. 109, 225. (2) Sobolev, A., Hofmann, A., and Nikogosian, I., 2000. Nature, 404, 986. (3) Poustovetov, A., and Roeder, P., 2001, Canad. Mineral. 39, 309.

Cryogenic Research

DTIC Science & Technology

1952-05-01

needed work lies in the ultra low- temperature range available only through use of the demagnetization cycle. SUPERCONDUCTIVITY BELOW 10 ABSOLUTE In...In Figure 1 is plotted, as a function of temperature, the magnetic field required to change hafnium from the superconducting to the normal state. For...fields of crystal physics, properties of metals, and magnetism and magnetic resonance. This article discusses the work of one group, the Cryogenics

Quantification of water in hydrous ringwoodite

DOE PAGES

Thomas, Sylvia -Monique; Jacobsen, Steven D.; Bina, Craig R.; ...

2015-01-28

Here, ringwoodite, γ-(Mg,Fe) 2SiO 4, in the lower 150 km of Earth’s mantle transition zone (410-660 km depth) can incorporate up to 1.5-2 wt% H 2O as hydroxyl defects. We present a mineral-specific IR calibration for the absolute water content in hydrous ringwoodite by combining results from Raman spectroscopy, secondary ion mass spectrometery (SIMS) and proton-proton (pp)-scattering on a suite of synthetic Mg- and Fe-bearing hydrous ringwoodites. H 2O concentrations in the crystals studied here range from 0.46 to 1.7 wt% H 2O (absolute methods), with the maximum H 2O in the same sample giving 2.5 wt% by SIMS calibration.more » Anchoring our spectroscopic results to absolute H-atom concentrations from pp-scattering measurements, we report frequency-dependent integrated IR-absorption coefficients for water in ringwoodite ranging from 78180 to 158880 L mol -1cm -2, depending upon frequency of the OH absorption. We further report a linear wavenumber IR calibration for H 2O quantification in hydrous ringwoodite across the Mg 2SiO 4-Fe 2SiO 4 solid solution, which will lead to more accurate estimations of the water content in both laboratory-grown and naturally occurring ringwoodites. Re-evaluation of the IR spectrum for a natural hydrous ringwoodite inclusion in diamond from the study of the crystal contains 1.43 ± 0.27 wt% H 2O, thus confirming near-maximum amounts of H 2O for this sample from the transition zone.« less

Measurement of emission cross sections for n = 3 → 2 transitions in Neon-like Fe XVII and Ni XIX ions

NASA Astrophysics Data System (ADS)

Lockard, Tom; Brown, Gregory V.; Hell, Natalie; Scofield, J. H.; Beiersdorfer, Peter; Porter, Frederick Scott; Kilbourne, Caroline; Kelley, Richard L.; Leutenegger, Maurice A.; Betancourt-Martinez, Gabriele

2018-06-01

The absolute excitation cross sections of the strong 1s2 2s2 2p51/2 3d3/2 1P1 → 1s2 2s2 2p6 1S0 and 1s2 2s2 2p53/2 3d5/2 3D1 → 1s2 2s2 2p6 1S0 strong resonance and intercombination lines, commonly known as 3C and 3D, have been measured in neon-like Fe16+ and Ni18+. These measurements were carried out at the Lawrence Livermore National Laboratory's EBIT-I electron beam ion trap facility using the EBIT Calorimeter Spectrometer (ECS) quantum microcalorimeter and a flat crystal spectrometer. The absolute excitation cross sections were determined by normalizing the measured spectrum to the X-ray emission from radiative recombination. The direct excitation lines 3C and 3D and radiative recombination (RR) lines were measured simultaneously using the ECS. By normalizing the measured RR flux to their theoretical cross sections, the emission from lines 3C and 3D was made absolute. Using simultaneous measurements from the higher resolution flat crystal spectrometer, it was possible to check for potential blends from lower charge states. Results of our measurements including comparison to theory, will be presented.This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Red-light-controllable liquid-crystal soft actuators via low-power excited upconversion based on triplet-triplet annihilation.

PubMed

Jiang, Zhen; Xu, Ming; Li, Fuyou; Yu, Yanlei

2013-11-06

A red-light-controllable soft actuator has been achieved, driven by low-power excited triplet-triplet annihilation-based upconversion luminescence (TTA-UCL). First, a red-to-blue TTA-based upconversion system with a high absolute quantum yield of 9.3 ± 0.5% was prepared by utilizing platinum(II) tetraphenyltetrabenzoporphyrin (PtTPBP) as the sensitizer and 9,10-bis(diphenylphosphoryl)anthracene (BDPPA) as the annihilator. In order to be employed as a highly effective phototrigger of photodeformable cross-linked liquid-crystal polymers (CLCPs), the PtTPBP&BDPPA system was incorporated into a rubbery polyurethane film and then assembled with an azotolane-containing CLCP film. The generating assembly film bent toward the light source when irradiated with a 635 nm laser at low power density of 200 mW cm(-2) because the TTA-UCL was effectively utilized by the azotolane moieties in the CLCP film, inducing their trans-cis photoisomerization and an alignment change of the mesogens via an emission-reabsorption process. It is the first example of a soft actuator in which the TTA-UCL is trapped and utilized to create photomechanical effect. Such advantages of using this novel red-light-controllable soft actuator in potential biological applications have also been demonstrated as negligible thermal effect and its excellent penetration ability into tissues. This work not only provides a novel photomanipulated soft actuation material system based on the TTA-UCL technology but also introduces a new technological application of the TTA-based upconversion system in photonic devices.

Generation of narrowband, high-intensity, carrier-envelope phase-stable pulses tunable between 4 and 18  THz.

PubMed

Liu, B; Bromberger, H; Cartella, A; Gebert, T; Först, M; Cavalleri, A

2017-01-01

We report on the generation of high-energy (1.9 μJ) far-infrared pulses tunable between 4 and 18 THz frequency. Emphasis is placed on tunability and on minimizing the bandwidth of these pulses to less than 1 THz, as achieved by difference-frequency mixing of two linearly chirped near-infrared pulses in the organic nonlinear crystal DSTMS. As the two near-infrared pulses are derived from amplification of the same white light continuum, their carrier envelope phase fluctuations are mutually correlated, and hence the difference-frequency THz field exhibits absolute phase stability. This source opens up new possibilities for the control of condensed matter and chemical systems by selective excitation of low-energy modes in a frequency range that has, to date, been difficult to access.

On the calculation of the absolute grand potential of confined smectic-A phases

NASA Astrophysics Data System (ADS)

Huang, Chien-Cheng; Baus, Marc; Ryckaert, Jean-Paul

2015-09-01

We determine the absolute grand potential Λ along a confined smectic-A branch of a calamitic liquid crystal system enclosed in a slit pore of transverse area A and width L, using the rod-rod Gay-Berne potential and a rod-wall potential favouring perpendicular orientation at the walls. For a confined phase with an integer number of smectic layers sandwiched between the opposite walls, we obtain the excess properties (excess grand potential Λexc, solvation force fs and adsorption Γ) with respect to the bulk phase at the same μ (chemical potential) and T (temperature) state point. While usual thermodynamic integration methods are used along the confined smectic branch to estimate the grand potential difference as μ is varied at fixed L, T, the absolute grand potential at one reference state point is obtained via the evaluation of the absolute Helmholtz free energy in the (N, L, A, T) canonical ensemble. It proceeds via a sequence of free energy difference estimations involving successively the cost of localising rods on layers and the switching on of a one-dimensional harmonic field to keep layers integrity coupled to the elimination of inter-layers and wall interactions. The absolute free energy of the resulting set of fully independent layers of interacting rods is finally estimated via the existing procedures. This work opens the way to the computer simulation study of phase transitions implying confined layered phases.

On a program manifold's stability of one contour automatic control systems

NASA Astrophysics Data System (ADS)

Zumatov, S. S.

2017-12-01

Methodology of analysis of stability is expounded to the one contour systems automatic control feedback in the presence of non-linearities. The methodology is based on the use of the simplest mathematical models of the nonlinear controllable systems. Stability of program manifolds of one contour automatic control systems is investigated. The sufficient conditions of program manifold's absolute stability of one contour automatic control systems are obtained. The Hurwitz's angle of absolute stability was determined. The sufficient conditions of program manifold's absolute stability of control systems by the course of plane in the mode of autopilot are obtained by means Lyapunov's second method.

Picrotoxane sesquiterpenoids from the stems of Dendrobium nobile and their absolute configurations and angiogenesis effect.

PubMed

Meng, Chun-Wang; He, Yu-Lin; Peng, Cheng; Ding, Xing-Jie; Guo, Li; Xiong, Liang

2017-09-01

Five picrotoxane sesquiterpenoids belonging to the unusual dendrobine-type (1 and 4) and the picrotoxinin-type (2, 3, and 5) were isolated from the stems of Dendrobium nobile Lindl. Their structures were established by spectroscopic analyses and physical properties. Compound 1 was a new dendrobine analogue. Although the planar structure of 2 and 3 had been reported, their absolute configurations were first determined by single-crystal X-ray diffraction and circular dichroism. Compound 2 exhibited angiogenesis effect against sunitinib-induced damage on intersegmental blood vessels in Tg (flk1: EGFP) and Tg (fli1: nEGFP) transgenic zebrafish at concentrations of 3.13, 6.25, 12.50, and 25.00μM. Copyright © 2017. Published by Elsevier B.V.

Amyloid Polymorphism in the Protein Folding and Aggregation Energy Landscape.

PubMed

Adamcik, Jozef; Mezzenga, Raffaele

2018-02-15

Protein folding involves a large number of steps and conformations in which the folding protein samples different thermodynamic states characterized by local minima. Kinetically trapped on- or off-pathway intermediates are metastable folding intermediates towards the lowest absolute energy minima, which have been postulated to be the natively folded state where intramolecular interactions dominate, and the amyloid state where intermolecular interactions dominate. However, this view largely neglects the rich polymorphism found within amyloid species. We review the protein folding energy landscape in view of recent findings identifying specific transition routes among different amyloid polymorphs. Observed transitions such as twisted ribbon→crystal or helical ribbon→nanotube, and forbidden transitions such helical ribbon↛crystal, are discussed and positioned within the protein folding and aggregation energy landscape. Finally, amyloid crystals are identified as the ground state of the protein folding and aggregation energy landscape. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Advances and new directions in crystallization control.

PubMed

Nagy, Zoltan K; Braatz, Richard D

2012-01-01

The academic literature on and industrial practice of control of solution crystallization processes have seen major advances in the past 15 years that have been enabled by progress in in-situ real-time sensor technologies and driven primarily by needs in the pharmaceutical industry for improved and more consistent quality of drug crystals. These advances include the accurate measurement of solution concentrations and crystal characteristics as well as the first-principles modeling and robust model-based and model-free feedback control of crystal size and polymorphic identity. Research opportunities are described in model-free controller design, new crystallizer designs with enhanced control of crystal size distribution, strategies for the robust control of crystal shape, and interconnected crystallization systems for multicomponent crystallization.

(S)-N-[1-(5-Benzyl-sulfan-yl-1,3,4-oxa-diazol-2-yl)-2-phenyl-eth-yl]-4-methyl-benzene-sulfonamide.

PubMed

Syed, Tayyaba; Hameed, Shahid; Jones, Peter G

2011-11-01

The title compound, C(24)H(23)N(3)O(3)S(2), crystallizes with two independent mol-ecules in the asymmetric unit. They differ essentially in the orientation of the tolyl rings, between which there is π-π stacking (centroid-centroid distance = 3.01 Å). The absolute configuration was confirmed by the determination of the Flack parameter [x = 0.008 (9)]. In the crystal, mol-ecules are connected by two classical N-H⋯N hydrogen bonds and two weak but very short C-H⋯O(sulfon-yl) inter-actions, forming layers lying parallel to the bc plane.

Theonellapeptolide IIIe, a new cyclic peptolide from the New Zealand deep water sponge, Lamellomorpha strongylata.

PubMed

Li, S; Dumdei, E J; Blunt, J W; Munro, M H; Robinson, W T; Pannell, L K

1998-06-26

The structure, stereochemistry, and conformation of theonellapeptolide IIIe (1), a new 36-membered ring cyclic peptolide from the New Zealand deep-water sponge Lamellomorpha strongylata, is described. The sequence of the cytotoxic peptolide was determined through a combination of NMR and MS-MS techniques and confirmed by X-ray crystal structure analysis, which, with chiral HPLC, established the absolute stereochemistry.

Characterization of PbWO4 crystals for high-energy physics experiments

NASA Astrophysics Data System (ADS)

Kim, M. J.; Park, H.; Kim, H. J.

2016-09-01

High-energy physics (HEP) experiments have employed many new types of scintillators. Specifically, bismuth germanate, thallium-doped cesium iodide, and lead tungstate (PbWO4, PWO) have been used for the L3 experiment; CLEO II, Belle and BES-III; and CMS, respectively. PWO has particularly beneficial properties, such as high density, fast decay time, short radiation length and radiation hardness. In this study, we tested the PWO crystals at low temperatures to determine their applicability in future calorimeters. Various crystals from the Proton Antiproton Annihilations at Darmstadt (PANDA) experiment in Giessen, the Bogoroditsk Techno-Chemical Plant (BTCP) in Russia and by Shanghai Institute of Ceramics, Chinese Academy of Sciences (SICCAS) in China were investigated. We studied the scintillation properties of PWO crystals, such as their X-ray luminescence, relative light yields, absolute light yields, energy resolutions, decay times and longitudinal uniformities of their light yields. In addition, we measured the temperature dependences of the light yields and decay times by using a 137Cs γ-ray source. The emission spectra of the PWO crystals consisted of a broad band from 350 nm to 700 nm, and the peak emission wavelength in each spectrum was 420 nm. The emission spectra of the PWO crystals from SICCAS were slightly shifted to longer wavelengths compared with those of the crystals from the other institutions.

Influence of a change in helical twisting power of photoresponsive chiral dopants on rotational manipulation of micro-objects on the surface of chiral nematic liquid crystalline films.

PubMed

Thomas, Reji; Yoshida, Yohei; Akasaka, Takehito; Tamaoki, Nobuyuki

2012-09-24

Herein we report a group of five planar chiral molecules as photon-mode chiral switches for the reversible control of the self-assembled superstructures of doped chiral nematic liquid crystals. The chiral switches are composed of an asymmetrically substituted aromatic moiety and a photoisomerizing azobenzene unit connected in a cyclic manner through methylene spacers of varying lengths. All the molecules show conformational restriction in the rotation of the asymmetrically substituted aromatic moiety in both the E and Z states of the azobenzene units resulting in planar chirality with separable enantiomers. Our newly synthesized compounds in pure enantiomeric form show high helical twisting power (HTP) in addition to an improved change in HTP between the E and Z states. The molecule with a diphenylnaphthalene unit shows the highest ever known initial helical twisting power among chiral dopants with planar chirality. In addition to the reversible tuning of reflection colors, we employed the enantiomers of these five compounds in combination with four nematic liquid crystalline hosts to study their properties as molecular machines; the change in HTP of the chiral dopant upon photoisomerization induces rotation of the texture of the liquid crystal surfaces. Importantly, this study has revealed a linear dependence of the ratio of the difference between HTPs before and after irradiation against the absolute value of the initial HTP, not the absolute value of the change in helical twisting power between two states, on the angle of rotation of micro-objects on chiral nematic liquid crystalline films. This study has also revealed that a change in irradiation intensity does not affect the maximum angle of rotation, but it does affect the speed of rotational reorganization of the cholesteric helix. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

New crystal spectrograph designs and their application to plasma diagnostics (invited)

NASA Astrophysics Data System (ADS)

Förster, E.; Gäbel, K.; Uschmann, I.

1992-10-01

A special crystal monolith was fabricated for absolute measurements of x-ray wavelength. It consists of two flat quartz plates, accurately cut relative to reflecting net planes, with a fixed distance between them. Absolute wavelengths (i.e., without use of reference lines) of L-shell laser produced spectra of Cu, Ge, As, etc. have been measured in the 7.5-8.5 Å with an accuracy of Δλ/λ=10-5. Our Johann type x-ray spectrometer with a cylindrically bent quartz has been used to reveal line coincidences necessary for photopumping processes. In this scheme source-size influences are smaller, therefore, line profiles have been measured at a spectrometer resolution better than 5000. Because of its focusing in the sagittal plane, a von Hámos type x-ray spectrometer has been used to detect the small x-ray emission of subpicosecond laser-produced plasmas (E=2 mJ, t=100 fs). X-ray spectra of Al both Kα, Kβ lines and Heα-resonance line with its satellites. Finally, a multichannel x-ray microscope has been designed and fabricated. It consists of several two-dimensionally bent crystals where each of them images one x-ray line emitted by a laser-produced plasma. The spatial resolution of x-ray line images is about 5 μm, and the width of the spectral ranges is Δλ/λ=10-4 to 10-2. Thus, the spatial distribution of ions radiating in selected x-ray lines have been found being of interest in the study of population inversions.

Investigation of OPET Performance Using GATE, a Geant4-Based Simulation Software.

PubMed

Rannou, Fernando R; Kohli, Vandana; Prout, David L; Chatziioannou, Arion F

2004-10-01

A combined optical positron emission tomography (OPET) system is capable of both optical and PET imaging in the same setting, and it can provide information/interpretation not possible in single-mode imaging. The scintillator array here serves the dual function of coupling the optical signal from bioluminescence/fluorescence to the photodetector and also of channeling optical scintillations from the gamma rays. We report simulation results of the PET part of OPET using GATE, a Geant4 simulation package. The purpose of this investigation is the definition of the geometric parameters of the OPET tomograph. OPET is composed of six detector blocks arranged in a hexagonal ring-shaped pattern with an inner radius of 15.6 mm. Each detector consists of a two-dimensional array of 8 × 8 scintillator crystals each measuring 2 × 2 × 10 mm(3). Monte Carlo simulations were performed using the GATE software to measure absolute sensitivity, depth of interaction, and spatial resolution for two ring configurations, with and without gantry rotations, two crystal materials, and several crystal lengths. Images were reconstructed with filtered backprojection after angular interleaving and transverse one-dimensional interpolation of the sinogram. We report absolute sensitivities nearly seven times that of the prototype microPET at the center of field of view and 2.0 mm tangential and 2.3 mm radial resolutions with gantry rotations up to an 8.0 mm radial offset. These performance parameters indicate that the imaging spatial resolution and sensitivity of the OPET system will be suitable for high-resolution and high-sensitivity small-animal PET imaging.

Online absolute pose compensation and steering control of industrial robot based on six degrees of freedom laser measurement

NASA Astrophysics Data System (ADS)

Yang, Juqing; Wang, Dayong; Fan, Baixing; Dong, Dengfeng; Zhou, Weihu

2017-03-01

In-situ intelligent manufacturing for large-volume equipment requires industrial robots with absolute high-accuracy positioning and orientation steering control. Conventional robots mainly employ an offline calibration technology to identify and compensate key robotic parameters. However, the dynamic and static parameters of a robot change nonlinearly. It is not possible to acquire a robot's actual parameters and control the absolute pose of the robot with a high accuracy within a large workspace by offline calibration in real-time. This study proposes a real-time online absolute pose steering control method for an industrial robot based on six degrees of freedom laser tracking measurement, which adopts comprehensive compensation and correction of differential movement variables. First, the pose steering control system and robot kinematics error model are constructed, and then the pose error compensation mechanism and algorithm are introduced in detail. By accurately achieving the position and orientation of the robot end-tool, mapping the computed Jacobian matrix of the joint variable and correcting the joint variable, the real-time online absolute pose compensation for an industrial robot is accurately implemented in simulations and experimental tests. The average positioning error is 0.048 mm and orientation accuracy is better than 0.01 deg. The results demonstrate that the proposed method is feasible, and the online absolute accuracy of a robot is sufficiently enhanced.

Quantitative determination of zero-gravity effects on electronic materials processing germanium crystal growth with simultaneous interface demarcation. Experiment MA-060

NASA Technical Reports Server (NTRS)

Gatos, H. C.; Witt, A. F.

1977-01-01

Experiment MA-060 was designed to establish the crystal growth and segregation characteristics of a melt in a directional solidification configuration under near zero-g conditions. The interface demarcation technique was incorporated into the experiment since it constitutes a unique tool for recording the morphology of the growth rate throughout solidification, and for establishing an absolute time reference framework for all stages of the solidification process. An extensive study was performed of the germanium crystals grown during the Apollo-Soyuz Test Project mission. It was found that single crystal growth was achieved and that the interface demarcation functioned successfully. There was no indication that convection driven by thermal or surface tension gradients was present in the melt. The gallium segregation, in the absence of gravity, was found to be fundamentally different in its initial and its subsequent stages from that of the ground-based tests. None of the existing theoretical models for growth and segregation can account for the observed segregation behavior in the absence of gravity.

Nanoparticle guests in lyotropic liquid crystals

NASA Astrophysics Data System (ADS)

Dölle, Sarah; Park, Ji Hyun; Schymura, Stefan; Jo, Hyeran; Scalia, Giusy; Lagerwall, Jan P. F.

In this chapter we discuss the benefits, peculiarities and main challenges related to nanoparticle templating in lyotropic liquid crystals. We first give a brief bird's-eye view of the field, discussing different nanoparticles as well as different lyotropic hosts that have been explored, but then quickly focus on the dispersion of carbon nanotubes in surfactant-based lyotropic nematic phases. We discuss in some detail how the transfer of orientational order from liquid crystal host to nanoparticle guest can be verified and which degree of ordering can be expected, as well as the importance of choosing the right surfactant and its concentration for the stability of the nanoparticle suspension. We introduce a method for dispersing nanoparticles with an absolute minimum of stabilizing surfactant, based on dispersion below the Krafft temperature, and we discuss the peculiar phenomenon of filament formation in lyotropic nematic phases with a sufficient concentration of well-dispersed carbon nanotubes. Finally, we describe how the total surfactant concentration in micellar nematics can be greatly reduced by combining cat- and anionic surfactants, and we discuss how nanotubes can help in inducing the liquid crystal phase close to the isotropic-nematic boundary.

Growth of raspberry-, prism- and flower-like ZnO particles using template-free low-temperature hydrothermal method and their application as humidity sensors

NASA Astrophysics Data System (ADS)

Pál, Edit; Hornok, Viktória; Kun, Robert; Chernyshev, Vladimir; Seemann, Torben; Dékány, Imre; Busse, Matthias

2012-08-01

Zinc oxide particles with different morphologies were prepared by hydrothermal method at 60-90 °C. The structure formation was controlled by the addition rate and temperature of hydrolyzing agent, while the particles size (10 nm-2.5 μm) was influenced by the preparation (hydrothermal) temperature. Scanning electron microscopy studies showed that raspberry-, prism- and flower-like ZnO particles were prepared, whose average size decreased with increasing reaction temperature. X-ray diffraction investigations confirmed that ZnO particles with hexagonal crystal structure formed in all syntheses. The raspberry-, prism- and flower-like ZnO particles showed a weak UV-emission in the range of 390-395 nm and strong visible emission with a maximum at 586, 593 and 598 nm, respectively. Morphology effect on electrical and water vapour sensing properties of ZnO samples was investigated by impedance spectroscopy and quartz crystal microbalance, respectively. The absolute impedance of raspberry-, prism- and flower-like ZnO particles was found to be strong dependent on the morphology. Space-charge-limited conductivity transport mechanism was proved by the oscillatory behaviour of impedance. Humidity sensor tests also revealed morphology and specific surface area dependency on the sensitivity and water vapour adsorption property.

Absolute configuration of podophyllotoxone and its inhibitory activity against human prostate cancer cells.

PubMed

Li, Juan; Feng, Juan; Luo, Cheng; Herman, Ho-Yung Sung; Jiang, Ren-Wang

2015-01-01

Podophyllotoxone (1) was isolated from the roots of Dysosma versipellis. The structure was determined by spectroscopic analysis in combination with single-crystal X-ray analysis. The absolute configuration of compound 1 was assigned based on the Flack parameter. It showed significant inhibitory activities against human prostate cancer cells PC3 and DU145 with IC50 values being 14.7 and 20.6 μmol·L(-1), respectively. It also arrested the cells at G2/M phase. Tubulin polymerization assay showed that it inhibited the tubulin polymerization in a dose-dependent manner, and molecular docking analysis revealed a different binding mode with tubulin as compared with those known tubulin inhibitors. Copyright © 2015 China Pharmaceutical University. Published by Elsevier B.V. All rights reserved.

Experimental and theoretical calculation studies on the structure elucidation and absolute configuration of calyxins from Alpinia katsumadai.

PubMed

Wang, Xiao-Bing; Yang, Chang-Shui; Luo, Jian-Guang; Zhang, Chao; Luo, Jun; Yang, Ming-Hua; Kong, Ling-Yi

2017-06-01

Six novel calyxins, named calyxin T-W, ent-calyxin T and ent-calyxin U were isolated from the seeds of Alpinia katsumadai Hayata. Their relative configurations were elucidated by means of detailed UV, IR, NMR and MS spectroscopic data. Their absolute configurations were assigned by collaborative studies on single crystal X-ray diffraction analysis, Mosher's method, electronic circular dichroism (ECD), optical rotation and theoretical calculations. These compounds are Friedel-Cranft alkylation adducts composed of coexisted diarylheptanoids and flavanone from the seeds of Alpinia katsumadai. The antiproliferative activity of the six compounds against NCI-H460, HeLa, SMMC-7721 and HCT-116 cell lines was also reported, and most of them showed moderate to strong activities. Copyright © 2017. Published by Elsevier B.V.

Isobenzofuranones and Isochromenones from the Deep-Sea Derived Fungus Leptosphaeria sp. SCSIO 41005

PubMed Central

Luo, Xiaowei; Lin, Xiuping; Salendra, Limbadri; Pang, Xiaoyan; Dai, Yu; Yang, Bin; Liu, Juan; Wang, Junfeng; Liu, Yonghong

2017-01-01

Four new isobenzofuranones, leptosphaerins J–M (1–4), including an unusual naturally-occurring centrosymmetric dimer skeleton (1), and two new isochromenones, clearanols I–J (9–10), were obtained from a culture of a deep-sea sediment-derived fungus Leptosphaeria sp. SCSIO 41005, together with four known isobenzofuranones (5–8) and six known isochromenones (11–16). These structures were elucidated by extensive spectroscopic analyses, and absolute configurations were assigned on the basis of electronic circular dichroism and optical rotations data comparison. Additionally, the absolute configurations of the new compounds 1 and 9, together with the known one 7 with stereochemistry undetermined, were further confirmed by single crystal X-ray diffraction experiments. A plausible biosynthetic pathway of these isobenzofuranones and isochromenones was also proposed. PMID:28661451

Phenolic Polyketides from the Co-Cultivation of Marine-Derived Penicillium sp. WC-29-5 and Streptomyces fradiae 007

PubMed Central

Wang, Yi; Wang, Liping; Zhuang, Yibin; Kong, Fandong; Zhang, Cuixian; Zhu, Weiming

2014-01-01

Penicillium sp. WC-29-5 was co-cultured with Streptomyces fradiae 007 to produce five natural products (1–3, 4a and 4b) that were isolated and characterized by spectroscopic analysis. Interestingly, these compounds were found to be different from those produced in discrete fungal and bacterial controls. Among these compounds, the absolute configurations of compounds 4a and 4b were determined for the first time by X-ray single crystal diffraction experiments and electronic circular dichroism (ECD) calculations. An evaluation of the cytotoxic activities of these compounds revealed that 4b was moderately cytotoxic towards HL-60 and H1975 tumor cells with IC50 values of 3.73 and 5.73 µM, respectively, whereas compound 4a was only moderately cytotoxic towards H1975 cells with an IC50 value of 3.97 µM. PMID:24714124

Phenolic polyketides from the co-cultivation of marine-derived Penicillium sp. WC-29-5 and Streptomyces fradiae 007.

PubMed

Wang, Yi; Wang, Liping; Zhuang, Yibin; Kong, Fandong; Zhang, Cuixian; Zhu, Weiming

2014-04-04

Penicillium sp. WC-29-5 was co-cultured with Streptomyces fradiae 007 to produce five natural products (1-3, 4a and 4b) that were isolated and characterized by spectroscopic analysis. Interestingly, these compounds were found to be different from those produced in discrete fungal and bacterial controls. Among these compounds, the absolute configurations of compounds 4a and 4b were determined for the first time by X-ray single crystal diffraction experiments and electronic circular dichroism (ECD) calculations. An evaluation of the cytotoxic activities of these compounds revealed that 4b was moderately cytotoxic towards HL-60 and H1975 tumor cells with IC₅₀ values of 3.73 and 5.73 µM, respectively, whereas compound 4a was only moderately cytotoxic towards H1975 cells with an IC₅₀ value of 3.97 µM.

System Performance of Absolute Quartz-Crystal Barometers with Sub-Microbar Precision

DTIC Science & Technology

2009-09-01

respectively. signals , which falls in the microbarom frequency band. This affirms the detection of ocean generated infrasound (microbaroms) using a single...scales down to seconds is demonstrated. The first observations of ocean- generated , atmospheric infrasound with periods of about 5 s and sub-microbar...demonstrated. The first observations of ocean- generated , atmospheric infrasound with periods of about 5 s and sub-microbar amplitudes, called microbaroms

Coumarin Derivative Directly Coordinated to Lanthanides Acts as an Excellent Antenna for UV-Vis and Near-IR Emission.

PubMed

Guzmán-Méndez, Óscar; González, Federico; Bernès, Sylvain; Flores-Álamo, Marcos; Ordóñez-Hernández, Javier; García-Ortega, Héctor; Guerrero, Joselin; Qian, Wenjie; Aliaga-Alcalde, Nuria; Gasque, Laura

2018-02-05

A chelating coumarin-derived ligand sensitizes all emitting lanthanide ions in the solid state and gives high absolute quantum yields for ethanol solutions of complexes of Sm, Eu, Tb, and Dy, above 20% for the last two. Crystal structures of these four complexes are [Ln(Cum) 3 (H 2 O)(X)]·X where X = MeOH or EtOH.

The Perfect Glass Paradigm: Disordered Hyperuniform Glasses Down to Absolute Zero

NASA Astrophysics Data System (ADS)

Zhang, G.; Stillinger, F. H.; Torquato, S.

2016-11-01

Rapid cooling of liquids below a certain temperature range can result in a transition to glassy states. The traditional understanding of glasses includes their thermodynamic metastability with respect to crystals. However, here we present specific examples of interactions that eliminate the possibilities of crystalline and quasicrystalline phases, while creating mechanically stable amorphous glasses down to absolute zero temperature. We show that this can be accomplished by introducing a new ideal state of matter called a “perfect glass”. A perfect glass represents a soft-interaction analog of the maximally random jammed (MRJ) packings of hard particles. These latter states can be regarded as the epitome of a glass since they are out of equilibrium, maximally disordered, hyperuniform, mechanically rigid with infinite bulk and shear moduli, and can never crystallize due to configuration-space trapping. Our model perfect glass utilizes two-, three-, and four-body soft interactions while simultaneously retaining the salient attributes of the MRJ state. These models constitute a theoretical proof of concept for perfect glasses and broaden our fundamental understanding of glass physics. A novel feature of equilibrium systems of identical particles interacting with the perfect-glass potential at positive temperature is that they have a non-relativistic speed of sound that is infinite.

The Perfect Glass Paradigm: Disordered Hyperuniform Glasses Down to Absolute Zero.

PubMed

Zhang, G; Stillinger, F H; Torquato, S

2016-11-28

Rapid cooling of liquids below a certain temperature range can result in a transition to glassy states. The traditional understanding of glasses includes their thermodynamic metastability with respect to crystals. However, here we present specific examples of interactions that eliminate the possibilities of crystalline and quasicrystalline phases, while creating mechanically stable amorphous glasses down to absolute zero temperature. We show that this can be accomplished by introducing a new ideal state of matter called a "perfect glass". A perfect glass represents a soft-interaction analog of the maximally random jammed (MRJ) packings of hard particles. These latter states can be regarded as the epitome of a glass since they are out of equilibrium, maximally disordered, hyperuniform, mechanically rigid with infinite bulk and shear moduli, and can never crystallize due to configuration-space trapping. Our model perfect glass utilizes two-, three-, and four-body soft interactions while simultaneously retaining the salient attributes of the MRJ state. These models constitute a theoretical proof of concept for perfect glasses and broaden our fundamental understanding of glass physics. A novel feature of equilibrium systems of identical particles interacting with the perfect-glass potential at positive temperature is that they have a non-relativistic speed of sound that is infinite.

The Perfect Glass Paradigm: Disordered Hyperuniform Glasses Down to Absolute Zero

PubMed Central

Zhang, G.; Stillinger, F. H.; Torquato, S.

2016-01-01

Rapid cooling of liquids below a certain temperature range can result in a transition to glassy states. The traditional understanding of glasses includes their thermodynamic metastability with respect to crystals. However, here we present specific examples of interactions that eliminate the possibilities of crystalline and quasicrystalline phases, while creating mechanically stable amorphous glasses down to absolute zero temperature. We show that this can be accomplished by introducing a new ideal state of matter called a “perfect glass”. A perfect glass represents a soft-interaction analog of the maximally random jammed (MRJ) packings of hard particles. These latter states can be regarded as the epitome of a glass since they are out of equilibrium, maximally disordered, hyperuniform, mechanically rigid with infinite bulk and shear moduli, and can never crystallize due to configuration-space trapping. Our model perfect glass utilizes two-, three-, and four-body soft interactions while simultaneously retaining the salient attributes of the MRJ state. These models constitute a theoretical proof of concept for perfect glasses and broaden our fundamental understanding of glass physics. A novel feature of equilibrium systems of identical particles interacting with the perfect-glass potential at positive temperature is that they have a non-relativistic speed of sound that is infinite. PMID:27892452

An automated LS(β)- NaI(Tl)(γ) coincidence system as absolute standard for radioactivity measurements.

PubMed

Joseph, Leena; Das, A P; Ravindra, Anuradha; Kulkarni, D B; Kulkarni, M S

2018-07-01

4πβ-γ coincidence method is a powerful and widely used method to determine the absolute activity concentration of radioactive solutions. A new automated liquid scintillator based coincidence system has been designed, developed, tested and established as absolute standard for radioactivity measurements. The automation is achieved using PLC (programmable logic controller) and SCADA (supervisory control and data acquisition). Radioactive solution of 60 Co was standardized to compare the performance of the automated system with proportional counter based absolute standard maintained in the laboratory. The activity concentrations determined using these two systems were in very good agreement; the new automated system can be used for absolute measurement of activity concentration of radioactive solutions. Copyright © 2018. Published by Elsevier Ltd.

A low phase noise microwave frequency synthesis for a high-performance cesium vapor cell atomic clock

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

François, B.; Boudot, R.; Calosso, C. E.

2014-09-15

We report the development, absolute phase noise, and residual phase noise characterization of a 9.192 GHz microwave frequency synthesis chain devoted to be used as a local oscillator in a high-performance cesium vapor cell atomic clock based on coherent population trapping (CPT). It is based on frequency multiplication of an ultra-low phase noise 100 MHz oven-controlled quartz crystal oscillator using a nonlinear transmission line-based chain. Absolute phase noise performances of the 9.192 GHz output signal are measured to be −42, −100, −117 dB rad{sup 2}/Hz and −129 dB rad{sup 2}/Hz at 1 Hz, 100 Hz, 1 kHz, and 10 kHz offset frequencies, respectively. Comparedmore » to current results obtained in a state-of-the-art CPT-based frequency standard developed at LNE-SYRTE, this represents an improvement of 8 dB and 10 dB at f = 166 Hz and f = 10 kHz, respectively. With such performances, the expected Dick effect contribution to the atomic clock short term frequency stability is reported at a level of 6.2 × 10{sup −14} at 1 s integration time, that is a factor 3 higher than the atomic clock shot noise limit. Main limitations are pointed out.« less

Frequency standard stability for Doppler measurements on-board the shuttle

NASA Technical Reports Server (NTRS)

Harton, P. L.

1974-01-01

The short and long term stability characteristics of crystal and atomic standards are described. Emphasis is placed on crystal oscillators because of the selection which was made for the shuttle baseline and the complexities which are introduced by the shuttle environment. Attention is given, first, to the definitions of stability and the application of these definitions to the shuttle system and its mission. Data from time domain measurements are used to illustrate the definitions. Results of a literature survey to determine environmental effects on frequency reference sources are then presented. Finally, methods of standard frequency dissemination over radio frequency carriers are noted as a possible means of measuring absolute accuracy and long term stability characteristics during on one way Doppler equipment.

Multivariable control of a rapid thermal processor using ultrasonic sensors

NASA Astrophysics Data System (ADS)

Dankoski, Paul C. P.

The semiconductor manufacturing industry faces the need for tighter control of thermal budget and process variations as circuit feature sizes decrease. Strategies to meet this need include supervisory control, run-to-run control, and real-time feedback control. Typically, the level of control chosen depends upon the actuation and sensing available. Rapid Thermal Processing (RTP) is one step of the manufacturing cycle requiring precise temperature control and hence real-time feedback control. At the outset of this research, the primary ingredient lacking from in-situ RTP temperature control was a suitable sensor. This research looks at an alternative to the traditional approach of pyrometry, which is limited by the unknown and possibly time-varying wafer emissivity. The technique is based upon the temperature dependence of the propagation time of an acoustic wave in the wafer. The aim of this thesis is to evaluate the ultrasonic sensors as a potentially viable sensor for control in RTP. To do this, an experimental implementation was developed at the Center for Integrated Systems. Because of the difficulty in applying a known temperature standard in an RTP environment, calibration to absolute temperature is nontrivial. Given reference propagation delays, multivariable model-based feedback control is applied to the system. The modelling and implementation details are described. The control techniques have been applied to a number of research processes including rapid thermal annealing and rapid thermal crystallization of thin silicon films on quartz/glass substrates.

Fluctuation theorems in feedback-controlled open quantum systems: Quantum coherence and absolute irreversibility

NASA Astrophysics Data System (ADS)

Murashita, Yûto; Gong, Zongping; Ashida, Yuto; Ueda, Masahito

2017-10-01

The thermodynamics of quantum coherence has attracted growing attention recently, where the thermodynamic advantage of quantum superposition is characterized in terms of quantum thermodynamics. We investigate the thermodynamic effects of quantum coherent driving in the context of the fluctuation theorem. We adopt a quantum-trajectory approach to investigate open quantum systems under feedback control. In these systems, the measurement backaction in the forward process plays a key role, and therefore the corresponding time-reversed quantum measurement and postselection must be considered in the backward process, in sharp contrast to the classical case. The state reduction associated with quantum measurement, in general, creates a zero-probability region in the space of quantum trajectories of the forward process, which causes singularly strong irreversibility with divergent entropy production (i.e., absolute irreversibility) and hence makes the ordinary fluctuation theorem break down. In the classical case, the error-free measurement ordinarily leads to absolute irreversibility, because the measurement restricts classical paths to the region compatible with the measurement outcome. In contrast, in open quantum systems, absolute irreversibility is suppressed even in the presence of the projective measurement due to those quantum rare events that go through the classically forbidden region with the aid of quantum coherent driving. This suppression of absolute irreversibility exemplifies the thermodynamic advantage of quantum coherent driving. Absolute irreversibility is shown to emerge in the absence of coherent driving after the measurement, especially in systems under time-delayed feedback control. We show that absolute irreversibility is mitigated by increasing the duration of quantum coherent driving or decreasing the delay time of feedback control.

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.

On-line near infrared spectroscopy as a Process Analytical Technology (PAT) tool to control an industrial seeded API crystallization.

PubMed

Schaefer, C; Lecomte, C; Clicq, D; Merschaert, A; Norrant, E; Fotiadu, F

2013-09-01

The final step of an active pharmaceutical ingredient (API) manufacturing synthesis process consists of a crystallization during which the API and residual solvent contents have to be quantified precisely in order to reach a predefined seeding point. A feasibility study was conducted to demonstrate the suitability of on-line NIR spectroscopy to control this step in line with new version of the European Medicines Agency (EMA) guideline [1]. A quantitative method was developed at laboratory scale using statistical design of experiments (DOE) and multivariate data analysis such as principal component analysis (PCA) and partial least squares (PLS) regression. NIR models were built to quantify the API in the range of 9-12% (w/w) and to quantify the residual methanol in the range of 0-3% (w/w). To improve the predictive ability of the models, the development procedure encompassed: outliers elimination, optimum model rank definition, spectral range and spectral pre-treatment selection. Conventional criteria such as, number of PLS factors, R(2), root mean square errors of calibration, cross-validation and prediction (RMSEC, RMSECV, RMSEP) enabled the selection of three model candidates. These models were tested in the industrial pilot plant during three technical campaigns. Results of the most suitable models were evaluated against to the chromatographic reference methods. Maximum relative bias of 2.88% was obtained about API target content. Absolute bias of 0.01 and 0.02% (w/w) respectively were achieved at methanol content levels of 0.10 and 0.13% (w/w). The repeatability was assessed as sufficient for the on-line monitoring of the 2 analytes. The present feasibility study confirmed the possibility to use on-line NIR spectroscopy as a PAT tool to monitor in real-time both the API and the residual methanol contents, in order to control the seeding of an API crystallization at industrial scale. Furthermore, the successful scale-up of the method proved its capability to be implemented in the manufacturing plant with the launch of the new API process. Copyright © 2013 Elsevier B.V. All rights reserved.

Calibration of a High Resolution X-ray Spectrometer for High-Energy-Density Plasmas on NIF

NASA Astrophysics Data System (ADS)

Kraus, B.; Gao, L.; Hill, K. W.; Bitter, M.; Efthimion, P.; Schneider, M. B.; Chen, H.; Ayers, J.; Beiersdorfer, P.; Liedahl, D.; Macphee, A. G.; Thorn, D. B.; Bettencourt, R.; Kauffman, R.; Le, H.; Nelson, D.

2017-10-01

A high-resolution, DIM-based (Diagnostic Instrument Manipulator) x-ray crystal spectrometer has been calibrated for and deployed at the National Ignition Facility (NIF) to diagnose plasma conditions and mix in ignition capsules near stagnation times. Two conical crystals in the Hall geometry focus rays from the Kr He- α, Ly- α, and He- β complexes onto a streak camera for time-resolved spectra, in order to measure electron density and temperature by observing Stark broadening and relative intensities of dielectronic satellites. Signals from these two crystals are correlated with a third crystal that time-integrates the intervening energy range. The spectrometer has been absolutely calibrated using a microfocus x-ray source, an array of CCD and single-photon-counting detectors, and K- and L-absorption edge filters. Measurements of the integrated reflectivity, energy range, and energy resolution for each crystal will be presented. The implications of the calibration on signal levels from NIF implosions and x-ray filter choices will be discussed. This work was performed under the auspices of the U.S. DoE by Princeton Plasma Physics Laboratory under contract DE-AC02-09CH11466 and by Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344.

New asymmetric and symmetric 2-((pyridin-4-yl)methylenamino)-3 aminomaleo nitrile and 2,3-bis((pyridin-4-yl)methylenamino)maleonitrile Schiff bases: Synthesis, experimental characterization along with theoretical studies

NASA Astrophysics Data System (ADS)

Zare, Nahid; Zabardasti, Abedien; Dusek, Michal; Eigner, Vaclav

2018-07-01

Two novel Schiff bases 2-((pyridin-4-yl)methelenamino)-3-aminomaleonitrile (L1) and 2,3-bis((pyridin-yl)methylenamino)maleonitrile (L2) were synthesized by the condensation of 2,3-diaminomaleonitrile and 4-pyridine carboxaldehyde using the reflux in absolute methanol. The light yellow crystalline precipitates of L1 were used for single-crystal X-ray crystallography. Two ligans L1 and L2 were characterized by UV-Vis, FT-IR and 1H/13C NMR spectroscopy. Also the FT-IR, 1H NMR and 13C NMR spectra of the compounds were calculated at the B3LYP/6-31 + G(d) level of theory. The Schiff base L1 with unit cell parameters: a = 19.8380(9), b = 4.7221(2), c = 12.9703(6) Å, V = 1215.02(9) Å3, Z = 4 crystallizes in the orthorhombic crystal system with space group Pna21. The crystal structure was solved by charge flipping using single crystal X-ray diffraction data collected at 120 K. For both ligands, the experimentally obtained NMR and IR spectra were a good agreement with their calculated counterparts.

Phenomenological crystal-field model of the magnetic and thermal properties of the Kondo-like system UCu2Si2

NASA Astrophysics Data System (ADS)

Troć, R.; Gajek, Z.; Pikul, A.; Misiorek, H.; Colineau, E.; Wastin, F.

2013-07-01

The transport properties described previously [Troć , Phys. Rev. BPRBMDO1098-012110.1103/PhysRevB.85.224434 85, 224434 (2012)] as well as the magnetic and thermal properties presented in this paper, observed for single-crystalline UCu2Si2, are discussed by assuming a dual (localized-itinerant) scenario. The electronic states of the localized 5f electrons in UCu2Si2 are constructed using the effective Hamiltonian known for ionic systems, allowing us to treat the Coulomb, spin-orbital, and crystal-field interactions on equal footing. The space of parameters has been restricted in the initial steps with the aid of the angular overlap model approximation. The final crystal-field parameters, obtained from the refined steps of calculations, are relatively large (in absolute values), which we attribute to the hybridization characteristic of the metallic systems on the verge of localization. The proposed crystal-field model reproduces correctly with satisfactory accuracy the magnetic and thermal properties of UCu2Si2 in agreement also with the transport properties reported previously. Considerable crystal-field splitting of the ground multiplet of 2760 K is responsible for a large anisotropy in the magnetic behavior, observed in the whole temperature range explored.

Highly oxygenated ent-pimarane-type diterpenoids from the Chinese liverwort Pedinophyllum interruptum and their allelopathic activities.

PubMed

Liu, Na; Li, Rui-Juan; Wang, Xiao-Ning; Zhu, Rong-Xiu; Wang, Lei; Lin, Zhao-Min; Zhao, Yu; Lou, Hong-Xiang

2013-09-27

Ten highly oxygenated ent-pimarane-type diterpenoids, pedinophyllols A-J (1-10), were isolated from the Chinese liverwort Pedinophyllum interruptum. Their structures were determined by comprehensive analysis of spectroscopic data together with single-crystal X-ray diffraction analysis. The absolute configurations were elucidated by comparison of experimental and theoretically calculated electronic circular dichroism spectra. Allelopathic testing showed that several new diterpenoids inhibited germination of Arabidopsis thaliana seeds.

X-ray diffraction measurement of cosolvent accessible volume in rhombohedral insulin crystals

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

Soares, Alexei S.; Caspar, Donald L. D.

We report x-ray crystallographic measurement of the number of solvent electrons in the unit cell of a protein crystal equilibrated with aqueous solutions of different densities provides information about preferential hydration in the crystalline state. Room temperature and cryo-cooled rhombohedral insulin crystals were equilibrated with 1.2 M trehalose to study the effect of lowered water activity. The native and trehalose soaked crystals were isomorphous and had similar structures. Including all the low resolution data, the amplitudes of the structure factors were put on an absolute scale (in units of electrons per asymmetric unit) by constraining the integrated number of electronsmore » inside the envelope of the calculated protein density map to equal the number deduced from the atomic model. This procedure defines the value of F(0 0 0), the amplitude at the origin of the Fourier transform, which is equal to the total number of electrons in the asymmetric unit (i.e. protein plus solvent). Comparison of the F(0 0 0) values for three isomorphous pairs of room temperature insulin crystals, three with trehalose and three without trehalose, indicates that 75 ± 12 electrons per asymmetric unit were added to the crystal solvent when soaked in 1.2 M trehalose. If all the water in the crystal were available as solvent for the trehalose, 304 electrons would have been added. Thus, the co-solvent accessible volume is one quarter of the total water in the crystal. Finally, determination of the total number of electrons in a protein crystal is an essential first step for mapping the average density distribution of the disordered solvent.« less

X-ray diffraction measurement of cosolvent accessible volume in rhombohedral insulin crystals

DOE PAGES

Soares, Alexei S.; Caspar, Donald L. D.

2017-08-31

We report x-ray crystallographic measurement of the number of solvent electrons in the unit cell of a protein crystal equilibrated with aqueous solutions of different densities provides information about preferential hydration in the crystalline state. Room temperature and cryo-cooled rhombohedral insulin crystals were equilibrated with 1.2 M trehalose to study the effect of lowered water activity. The native and trehalose soaked crystals were isomorphous and had similar structures. Including all the low resolution data, the amplitudes of the structure factors were put on an absolute scale (in units of electrons per asymmetric unit) by constraining the integrated number of electronsmore » inside the envelope of the calculated protein density map to equal the number deduced from the atomic model. This procedure defines the value of F(0 0 0), the amplitude at the origin of the Fourier transform, which is equal to the total number of electrons in the asymmetric unit (i.e. protein plus solvent). Comparison of the F(0 0 0) values for three isomorphous pairs of room temperature insulin crystals, three with trehalose and three without trehalose, indicates that 75 ± 12 electrons per asymmetric unit were added to the crystal solvent when soaked in 1.2 M trehalose. If all the water in the crystal were available as solvent for the trehalose, 304 electrons would have been added. Thus, the co-solvent accessible volume is one quarter of the total water in the crystal. Finally, determination of the total number of electrons in a protein crystal is an essential first step for mapping the average density distribution of the disordered solvent.« less

Piezo-, elasto- and acousto-optic properties of Tl3AsS4 crystals.

PubMed

Mytsyk, Bohdan; Kryvyy, Taras; Demyanyshyn, Natalya; Mys, Oksana; Martynyuk-Lototska, Iryna; Kokhan, Oleksandr; Vlokh, Rostyslav

2018-05-10

Complete matrices of piezo-optic and elasto-optic tensors are experimentally determined for Tl 3 AsS 4 crystals. It is revealed that the piezo-optic coefficients are very high, ∼10 -11   N/m 2 in the order of magnitude. This implies that Tl 3 AsS 4 can be referred to the best piezo-optic materials. The same concerns the elasto-optic coefficients, of which absolute values are in the interval 0.28-0.54. It is also found that, at the anisotropic and isotropic interactions with the slowest transverse and longitudinal acoustic waves, the acousto-optic figure of merit reaches extremely high values (1.99×10 -12   s 3 /kg and 9.45×10 -13   s 3 /kg, respectively). In other words, the Tl 3 AsS 4 crystals can be referred to as one of the best acousto-optic materials for the visible and infrared spectral ranges.

The metabolism of plant sterols is disturbed in postmenopausal women with coronary artery disease.

PubMed

Gylling, Helena; Hallikainen, Maarit; Rajaratnam, Radhakrishnan A; Simonen, Piia; Pihlajamäki, Jussi; Laakso, Markku; Miettinen, Tatu A

2009-03-01

In postmenopausal coronary artery disease (CAD) women, serum plant sterols are elevated. Thus, we investigated further whether serum plant sterols reflect absolute cholesterol metabolism in CAD as in other populations and whether the ABCG5 and ABCG8 genes, associated with plant sterol metabolism, were related to the risk of CAD. In free-living postmenopausal women with (n = 47) and without (n = 62) CAD, serum noncholesterol sterols including plant sterols were analyzed with gas-liquid chromatography, cholesterol absorption with peroral isotopes, absolute cholesterol synthesis with sterol balance technique, and bile acid synthesis with quantitating fecal bile acids. In CAD women, serum plant sterol ratios to cholesterol were 21% to 26% (P < .05) higher than in controls despite similar cholesterol absorption efficiency. Absolute cholesterol and bile acid synthesis were reduced. Only in controls were serum plant sterols related to cholesterol absorption (eg, sitosterol; in controls: r = 0.533, P < .001; in CAD: r = 0.296, P = not significant). However, even in CAD women, serum lathosterol (relative synthesis marker) and lathosterol-cholestanol (relative synthesis-absorption marker) were related to absolute synthesis and absorption percentage (P range from .05 to <.001) similarly to controls. Frequencies of the common polymorphisms of ABCG5 and ABCG8 genes did not differ between coronary and control women. In conclusion, plant sterol metabolism is disturbed in CAD women; so serum plant sterols only tended to reflect absolute cholesterol absorption. Other relative markers of cholesterol metabolism were related to the absolute ones in both groups. ABCG5 and ABCG8 genes were not associated with the risk of CAD.

ent-Kaurane Diterpenoids with Neuroprotective Properties from Corn Silk ( Zea mays).

PubMed

Qi, Xiao-Li; Zhang, Ying-Ying; Zhao, Peng; Zhou, Le; Wang, Xiao-Bo; Huang, Xiao-Xiao; Lin, Bin; Song, Shao-Jiang

2018-05-25

Thirteen new ent-kaurane diterpenoids, stigmaydenes A-M (1-13), together with two known compounds (14, 15), were isolated from the crude extract of corn silk ( Zea mays). The structures of the compounds were confirmed by comprehensive spectroscopic analyses. The absolute configuration of compound 1 was defined by single-crystal X-ray diffraction. The absolute configurations of the compounds were also confirmed by comparison of experimental and calculated specific rotations. The compounds were evaluated for their neuroprotective effects against H 2 O 2 -induced SH-SY5Y cell injury, and compound 8 was active at 100 μM, as determined by flow cytometry (annexin V-FITC/PI staining) and Hoechst 33258 staining. The results suggested that compound 8 could protect neuronal cells from H 2 O 2 -induced injury by inhibiting apoptosis in SH-SY5Y cells.

A density-functional study of the phase diagram of cementite-type (Fe,Mn)3C at absolute zero temperature.

PubMed

Von Appen, Jörg; Eck, Bernhard; Dronskowski, Richard

2010-11-15

The phase diagram of (Fe(1-x) Mn(x))(3)C has been investigated by means of density-functional theory (DFT) calculations at absolute zero temperature. The atomic distributions of the metal atoms are not random-like as previously proposed but we find three different, ordered regions within the phase range. The key role is played by the 8d metal site which forms, as a function of the composition, differing magnetic layers, and these dominate the physical properties. We calculated the magnetic moments, the volumes, the enthalpies of mixing and formation of 13 different compositions and explain the changes of the macroscopic properties with changes in the electronic and magnetic structures by means of bonding analyses using the Crystal Orbital Hamilton Population (COHP) technique. 2010 Wiley Periodicals, Inc.

Confidence-Accuracy Calibration in Absolute and Relative Face Recognition Judgments

ERIC Educational Resources Information Center

Weber, Nathan; Brewer, Neil

2004-01-01

Confidence-accuracy (CA) calibration was examined for absolute and relative face recognition judgments as well as for recognition judgments from groups of stimuli presented simultaneously or sequentially (i.e., simultaneous or sequential mini-lineups). When the effect of difficulty was controlled, absolute and relative judgments produced…

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.

Thyroxine revisited.

PubMed

Katrusiak, Andrzej; Katrusiak, Anna

2004-12-01

The crystal structure of the common therapeutic agent, the pentahydrated sodium salt of L-thyroxine hormone (3-[4-(4-hydroxy-3,5-diiodophenoxy)-3,5-diiodophenyl]-L-alanine), has been determined and discussed in relation to the drug's stability. The stoichiometry and absolute configuration (-)-C(8)S-[C15H10I4NO4]-.Na+.5H2O have been confirmed. The crystals are built of a three-dimensional supramolecular network with two symmetry-independent L-thyroxine anions, in two distinct conformations not previously reported, linked by strong NH-O hydrogen bonds into dimers. Two independent sodium cations are fivefold and sixfold coordinated. The cations and two independent water molecules not involved in coordinating the Na cations form sheets along the crystallographic (001) planes. The presence of differently coordinated cations and non-coordinating water molecules may be responsible for water transport and loss, for decay of the crystals, and subsequent low stability of the drug. Only a conglomerate could be obtained when racemic sodium thyroxine was crystallized from ethanol and methanol solutions by evaporation, which explains the equal penta-hydration of the sodium salts of enantiomorphic and racemic thyroxine, and the fact that there are no apparent differences in their stability. (c) 2004 Wiley-Liss, Inc. and the American Pharmacists Association

A comparative study of the luminescence properties of LYSO:Ce, LSO:Ce, GSO:Ce and BGO single crystal scintillators for use in medical X-ray imaging.

PubMed

Valais, I; Michail, C; David, S; Nomicos, C D; Panayiotakis, G S; Kandarakis, I

2008-06-01

The present study is a comparative investigation of the luminescence properties of (Lu,Y)(2)SiO(5):Ce (LYSO:Ce), Lu(2)SiO(5):Ce (LSO:Ce), Gd(2)SiO(5):Ce (GSO:Ce) and (Bi(4)Ge(3)O(12)) BGO single crystal scintillators under medical X-ray excitation. All scintillating crystals have dimensions of 10 x 10 x 10 mm(3) are non-hygroscopic exhibiting high radiation absorption efficiency in the energy range used in medical imaging applications. The comparative investigation was performed by determining the absolute luminescence efficiency (emitted light flux over incident X-ray exposure) in X-ray energies employed in general X-ray imaging (40-140 kV) and in mammographic X-ray imaging (22-49 kV). Additionally, light emission spectra of crystals at various X-ray energies were measured, in order to determine the spectral compatibility to optical photon detectors incorporated in medical imaging systems and the overall efficiency (effective efficiency) of a scintillator-optical detector combination. The light emission performance of LYSO:Ce and LSO:Ce scintillators studied was found very high for X-ray imaging.

Thermal vacancies and phase separation in bcc mixtures of helium-3 and helium-4

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

Fraass, Benedick Andrew

1980-01-01

Thermal vacancy concentrations in crystals of 3He- 4He mixtures have been determined. A new x-ray diffractometer-position sensitive detector system is used to make measurements of the absolute lattice parameter of the helium crystals with an accuracy of 300 ppM, and measurements of changes in lattice parameters to better than 60 ppM. The phase separation of the concentrated 3He- 4He mixtures has been studied in detail with the x-ray measurements. Vacancy concentrations in crystals with 99%, 51%, 28%, 12%, and 0% 3He have been determined. Phase separation has been studied in mixed crystals with concentrations of 51%, 28%, and 12% 3Hemore » and melting pressures between 3.0 and 6.1 MPa. The phase separation temperatures determined in this work are in general agreement with previous work. The pressure dependence of T c, the phase separation temperature for a 50% mixture, is found to be linear: dT c/dP = -34 mdeg/MPa. The x-ray measurements are used to make several comments on the low temperature phase diagram of the helium mixtures.« less

Charge-carrier mobilities in Cd(0.8)Zn(0.2)Te single crystals used as nuclear radiation detectors

NASA Technical Reports Server (NTRS)

Burshtein, Z.; Jayatirtha, H. N.; Burger, A.; Butler, J. F.; Apotovsky, B.; Doty, F. P.

1993-01-01

Charge-carrier mobilities were measured for the first time in Cd(0.8)Zn(0.2)Te single crystals using time-of-flight measurements of charge carriers produced by short (10 ns) light pulses from a frequency-doubled Nd:YAG laser (532 nm). The electron mobility displayed a T exp -1.1 dependence on the absolute temperature T in the range 200-320 K, with a room-temperature mobility of 1350 sq cm/V s. The hole mobility displayed a T exp -2.0 dependence in the same temperature range, with a room-temperature mobility of 120 sq cm/V s. Cd(0.8)Zn(0.2)Te appears to be a very favorable material for a room-temperature electronic nuclear radiation detector.

Calibration of X-ray spectrometers for opacity experiments at the Orion laser facility (invited).

PubMed

Bentley, C; Allan, P; Brent, K; Bruce, N; Hoarty, D; Meadowcroft, A; Percival, J; Opie, C

2016-11-01

Accurately calibrated and characterised x-ray diagnostics are a key requirement in the fielding of experiments on the Orion laser where absolute measurements of x-ray emission are used to underpin the validity of models of emissivity and opacity. Diffraction crystals are used in spectrometers on Orion to record the dispersed spectral features emitted by the laser produced plasma to obtain a measurement of the plasma conditions. The ability to undertake diffraction crystal calibrations supports the successful outcome of these Orion experiments. This paper details the design and commissioning of a system to undertake these calibrations in the energy range 2.0 keV to approximately 8.5 keV. Improvements to the design are detailed which will extend the commissioned range of energies to below 1 keV.

Pd-catalyzed arylation reactions with phenol diazonium salts: application in the synthesis of diarylheptanoids.

PubMed

Schmidt, Bernd; Hölter, Frank; Kelling, Alexandra; Schilde, Uwe

2011-05-06

The first total synthesis of the natural product (3S,7R)-5,6-dehydro-de-O-methyl centrolobine and various analogues is reported, using a highly regio- and diastereoselective Mizoroki-Heck reaction of phenol diazonium salts and enantiopure dihydropyrans. The assigned relative configuration was confirmed by single-crystal X-ray structure analysis, but a revision of the absolute configuration is proposed based on polarimetric measurement. © 2011 American Chemical Society

A chiral self-assembled monolayer derived from a resolving agent and its performance as a crystallization template for an organic compound from organic solvents.

PubMed

Bejarano-Villafuerte, Ángela; van der Meijden, Maarten W; Lingenfelder, Magalí; Wurst, Klaus; Kellogg, Richard M; Amabilino, David B

2012-12-07

A new chiral nonracemic thiol derived from a popular acidic resolving agent that incorporates a cyclic disubstituted phosphate group (phencyphos) has been prepared in enantiomerically pure form. The stereochemistry and absolute configuration were established by performing a single-crystal X-ray structural analysis of a synthetic intermediate. The thiol compound was used for the preparation of self-assembled monolayers (SAMs) on both monocrystalline and polycrystalline metallic gold, which have very different surface roughness. The monolayers were used to promote the nucleation and growth of crystals from nonaqueous solutions of an organic molecule (the parent phencyphos) of similar structure to the compound present in the monolayer. The template layers influence the nucleation and growth of the phencyphos crystals despite the lack of two-dimensional order in the surfaces. Heterogeneous nucleation of phencyphos takes place upon evaporation of either CHCl(3) or isopropanol solutions of the compound on the SAM surfaces, where the evaporation rate merely influences the size and homogeneity of the crystals. The roughness of the surface also plays an important role; the polycrystalline gold produces more homogeneous samples because of the greater number of nucleation sites. Clear evidence for nucleation and growth on the surfaces is shown by scanning electron microscopy. The variation in crystal form achieved by using different surfaces and solvents suggests that the layers are applicable for the preparation of organic crystals from organic solutions. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The Crystal Structure of Oxaliplatin: A Case of Overlooked Pseudo Symmetry.

PubMed

Johnstone, Timothy C

2014-01-08

The crystal structure of the anticancer drug oxaliplatin, [Pt( R,R- DACH)(oxalate)] (DACH = diaminocyclohexane), was first reported in the non-centrosymmetric space group P2 1 , confirming the sole presence of the R , R enantiomer of the DACH ligand [M. A. Bruck et al. , Inorg. Chim. Acta , 92 (1984) 279-284]. It was later proposed that the crystal structure is better described in the centrosymmetric space group P2 1 /m, signifying the presence of the compound as a racemic mixture [A. S. Abu-Surrah et al. , Polyhedron , 22 (2003) 1529-1534]. Herein is presented a reinvestigation of this crystal structure, which shows that the discrepancy between the two proposed space group assignments arises from overlooked pseudo symmetry. The crystal structures of the synthetic precursor to oxaliplatin, Pt( R , R -DACH)I 2 , and a platinum(IV) derivative, trans -[Pt( R , R -DACH)(oxalate)(OH) 2 ], were also determined, and the absolute configuration of the DACH ligand in each was confirmed to be R , R . A spectroscopic investigation of the optical rotatory dispersion (ORD) of the oxaliplatin crystals was carried out to further confirm the lack of the true crystallographic mirror plane required for a P2 1 /m solution. The ORD was theoretically simulated, in one instance, by applying the Kramers-Kronig transform to the computed circular dichroism spectrum and was found to corroborate the spectroscopic and crystallographic findings. Finally, a brief discussion is given of the importance of discussing the details of nuanced crystal structures and of providing evidence in addition to X-ray structure determination if chemically unexpected results are obtained.

The Crystal Structure of Oxaliplatin: A Case of Overlooked Pseudo Symmetry

PubMed Central

Johnstone, Timothy C.

2013-01-01

The crystal structure of the anticancer drug oxaliplatin, [Pt(R,R-DACH)(oxalate)] (DACH = diaminocyclohexane), was first reported in the non-centrosymmetric space group P21, confirming the sole presence of the R,R enantiomer of the DACH ligand [M. A. Bruck et al., Inorg. Chim. Acta, 92 (1984) 279–284]. It was later proposed that the crystal structure is better described in the centrosymmetric space group P21/m, signifying the presence of the compound as a racemic mixture [A. S. Abu-Surrah et al., Polyhedron, 22 (2003) 1529–1534]. Herein is presented a reinvestigation of this crystal structure, which shows that the discrepancy between the two proposed space group assignments arises from overlooked pseudo symmetry. The crystal structures of the synthetic precursor to oxaliplatin, Pt(R,R-DACH)I2, and a platinum(IV) derivative, trans-[Pt(R,R-DACH)(oxalate)(OH)2], were also determined, and the absolute configuration of the DACH ligand in each was confirmed to be R,R. A spectroscopic investigation of the optical rotatory dispersion (ORD) of the oxaliplatin crystals was carried out to further confirm the lack of the true crystallographic mirror plane required for a P21/m solution. The ORD was theoretically simulated, in one instance, by applying the Kramers-Kronig transform to the computed circular dichroism spectrum and was found to corroborate the spectroscopic and crystallographic findings. Finally, a brief discussion is given of the importance of discussing the details of nuanced crystal structures and of providing evidence in addition to X-ray structure determination if chemically unexpected results are obtained. PMID:24415827

Dynamically controlled crystal growth system

NASA Technical Reports Server (NTRS)

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

2002-01-01

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

Quantitative control of CaCO3 growth on quartz crystal microbalance sensors as a signal amplification method.

PubMed

Wu, Congcong; Sun, Zhaomei; Liu, Li-Shang

2017-07-10

The surface crystallization of CaCO 3 on gold was monitored by a quartz crystal microbalance (QCM). Quantitative control of the grown crystals was realized by adjusting the ratio of two functional groups, -N(CH 3 ) 3 and -COOH, on SAMs. Crystals with uniform size, morphology and polymorphism were obtained. The amount of crystals formed was found to increase with an increase in the -COOH group. The proposed quantitative control of crystallization can be an effective mass amplification strategy for QCM to enhance its assay sensitivity.

Advances in food crystallization.

PubMed

Hartel, Richard W

2013-01-01

Crystals often play an important role in food product quality and shelf life. Controlling crystallization to obtain the desired crystal content, size distribution, shape, and polymorph is key to manufacturing products with desired functionality and shelf life. Technical developments in the field have improved the tools with which we study and characterize crystals in foods. These developments also help our understanding of the physico-chemical phenomena that govern crystallization and improve our ability to control it during processing and storage. In this review, some of the more important recent developments in measuring and controlling crystallization are discussed.

Effect of surfactant concentration on nifedipine crystal habit and its related pharmaceutical properties

NASA Astrophysics Data System (ADS)

Kumar, Dinesh; Thipparaboina, Rajesh; Modi, Sameer R.; Bansal, Arvind K.; Shastri, Nalini R.

2015-07-01

Crystallization in the presence of Polysorbate-80 (T-80), a non-ionic surfactant was explored for crystal habit modification of nifedipine polymorph I (Nif). A concentration dependent reduction in aspect ratio was observed with T-80. Generation of any new solvates/polymorphs was ruled out by Fourier Transform Infrared spectroscopy, differential scanning calorimetry, powder X-ray diffraction, and thermogravimetric analysis, while the absence of T-80 on the surface or bulk of the recrystallized samples was established by liquid chromatography mass spectroscopy. The dissolution rate order of the re-crystallized Nif habits was in the order of; Nif-D (Nif with 0.6%v/v T-80)>Nif-C (Nif with 0.4% v/v T-80)>Nif-B (Nif with 0.2% v/v T-80)>Nif-A (plain Nif). Wetting ability and surface free energy determination from contact angle measurements were used to explain the order of dissolution rate. The consequences of varying concentration of T-80 on Nif crystal habit was supported by means of molecular dynamics (MD) which was executed using COMPASS force field while modified attachment energy was computed to acquire the absolute morphology. The mechanism for alteration in the morphology was suggested based on the computed crystal surface chemistry. Nif-D crystal habit was nearly iso-diametric with majority of facets occupied by polar dominant surfaces {0 1 1} and {0 0 2} which ultimately resulted in higher dissolution rate. In Nif-B and Nif-C the dissolution rate was dependent on the proportion of polar and non-polar facet area. The methodology used in this study could be an influential tool for selection of concentration of habit-modifying additives in other crystallization studies.

The Absolute Stability Analysis in Fuzzy Control Systems with Parametric Uncertainties and Reference Inputs

NASA Astrophysics Data System (ADS)

Wu, Bing-Fei; Ma, Li-Shan; Perng, Jau-Woei

This study analyzes the absolute stability in P and PD type fuzzy logic control systems with both certain and uncertain linear plants. Stability analysis includes the reference input, actuator gain and interval plant parameters. For certain linear plants, the stability (i.e. the stable equilibriums of error) in P and PD types is analyzed with the Popov or linearization methods under various reference inputs and actuator gains. The steady state errors of fuzzy control systems are also addressed in the parameter plane. The parametric robust Popov criterion for parametric absolute stability based on Lur'e systems is also applied to the stability analysis of P type fuzzy control systems with uncertain plants. The PD type fuzzy logic controller in our approach is a single-input fuzzy logic controller and is transformed into the P type for analysis. In our work, the absolute stability analysis of fuzzy control systems is given with respect to a non-zero reference input and an uncertain linear plant with the parametric robust Popov criterion unlike previous works. Moreover, a fuzzy current controlled RC circuit is designed with PSPICE models. Both numerical and PSPICE simulations are provided to verify the analytical results. Furthermore, the oscillation mechanism in fuzzy control systems is specified with various equilibrium points of view in the simulation example. Finally, the comparisons are also given to show the effectiveness of the analysis method.

Precise Stabilization of the Optical Frequency of WGMRs

NASA Technical Reports Server (NTRS)

Savchenkov, Anatoliy; Matsko, Andrey; Matsko, Andrey; Yu, Nan; Maleki, Lute; Iltchenko, Vladimir

2009-01-01

Crystalline whispering gallery mode resonators (CWGMRs) made of crystals with axial symmetry have ordinary and extraordinary families of optical modes. These modes have substantially different thermo-refractive constants. This results in a very sharp dependence of differential detuning of optical frequency on effective temperature. This frequency difference compared with clock gives an error signal for precise compensation of the random fluctuations of optical frequency. Certain crystals, like MgF2, have turnover points where the thermo-refractive effect is completely nullified. An advantage for applications using WGMRs for frequency stabilization is in the possibility of manufacturing resonators out of practically any optically transparent crystal. It is known that there are crystals with negative and zero thermal expansion at some specific temperatures. Doping changes properties of the crystals and it is possible to create an optically transparent crystal with zero thermal expansion at room temperature. With this innovation s stabilization technique, the resultant WGMR will have absolute frequency stability The expansion of the resonator s body can be completely compensated for by nonlinear elements. This results in compensation of linear thermal expansion (see figure). In three-mode, the MgF2 resonator, if tuned at the turnover thermal point, can compensate for all types of random thermal-related frequency drift. Simplified dual-mode method is also available. This creates miniature optical resonators with good short- and long-term stability for passive secondary frequency ethalon and an active resonator for active secondary frequency standard (a narrowband laser with long-term stability).

U-series disequilibria in crystals: ages as tracers

NASA Astrophysics Data System (ADS)

Cooper, K. M.

2005-12-01

U-series disequilibria offer a unique perspective on the fates of crystals within magmatic systems. In addition to delimiting the timescales of magmatic processes, crystal ages can be used as a tracer of different crystal populations even in the case where only subtle differences exist between major- and trace-element chemistries of populations. For example, 226Ra-230Th ages of crystals in Mt St Helens lavas erupted since 2 ka are in some cases several kyr older than eruption ages which, when combined with significant Ra-Th disequilibria in the whole-rocks, suggests protracted crystal storage and entrainment in subsequent batches of magma passing through the reservoir. More broadly, in many cases 230Th-238U and 226Ra-230Th ages measured in the same crystals are discordant. This pattern likely indicates progressive and/or episodic crystal growth where the Th-U ages more closely represent average crystallization ages while Ra-Th ages are weighted toward recent growth, suggesting in turn that some significant fraction of the mass of crystals represent xenocrysts or "antecrysts" recycled from earlier generations of magmas within the same system. Conversely, in cases where ages of different parent-daughter pairs are concordant, mineral separates must be dominated by crystal growth within a relatively narrow time interval relative to the half-life of the shortest-lived daughter isotope. The duration of the crystal record within a given magma can be complicated by crystal recycling and obscured by average ages derived from measurement of bulk mineral separates. One way to extract more information about the proportion and ages of older and younger parts of the crystal population(s) is to analyze different size fractions within the same sample; for example, analyses of different sizes of plagioclase from the ongoing eruption at Mt St Helens are in progress. U-series ages and other crystal-scale geochemical information can also be a powerful combination. For example, preservation of major- or trace-element disequilibrium between zones within crystals limits the duration of crystal residence at high temperature; when combined with absolute age information from U-series disequilibria, these data can provide clues about the thermal conditions of crystal storage and thus whether such storage is likely to have occurred in a mostly-liquid or mostly-crystalline part of the magma system.

Zeolite Crystal Growth (ZCG) Flight on USML-2

NASA Technical Reports Server (NTRS)

Sacco, Albert, Jr.; Bac, Nurcan; Warzywoda, Juliusz; Guray, Ipek; Marceau, Michelle; Sacco, Teran L.; Whalen, Leah M.

1997-01-01

The extensive use of zeolites and their impact on the world's economy has resulted in many efforts to characterize their structure, and improve the knowledge base for nucleation and growth of these crystals. The zeolite crystal growth (ZCG) experiment on USML-2 aimed to enhance the understanding of nucleation and growth of zeolite crystals, while attempting to provide a means of controlling the defect concentration in microgravity. Zeolites A, X, Beta, and Silicalite were grown during the 16 day - USML-2 mission. The solutions where the nucleation event was controlled yielded larger and more uniform crystals of better morphology and purity than their terrestrial/control counterparts. The external surfaces of zeolite A, X, and Silicalite crystals grown in microgravity were smoother (lower surface roughness) than their terrestrial controls. Catalytic studies with zeolite Beta indicate that crystals grown in space exhibit a lower number of Lewis acid sites located in micropores. This suggests fewer structural defects for crystals grown in microgravity. Transmission electron micrographs (TEM) of zeolite Beta crystals also show that crystals grown in microgravity were free of line defects while terrestrial/controls had substantial defects.

Mammographic Density Phenotypes and Risk of Breast Cancer: A Meta-analysis

PubMed Central

Graff, Rebecca E.; Ursin, Giske; dos Santos Silva, Isabel; McCormack, Valerie; Baglietto, Laura; Vachon, Celine; Bakker, Marije F.; Giles, Graham G.; Chia, Kee Seng; Czene, Kamila; Eriksson, Louise; Hall, Per; Hartman, Mikael; Warren, Ruth M. L.; Hislop, Greg; Chiarelli, Anna M.; Hopper, John L.; Krishnan, Kavitha; Li, Jingmei; Li, Qing; Pagano, Ian; Rosner, Bernard A.; Wong, Chia Siong; Scott, Christopher; Stone, Jennifer; Maskarinec, Gertraud; Boyd, Norman F.; van Gils, Carla H.

2014-01-01

Background Fibroglandular breast tissue appears dense on mammogram, whereas fat appears nondense. It is unclear whether absolute or percentage dense area more strongly predicts breast cancer risk and whether absolute nondense area is independently associated with risk. Methods We conducted a meta-analysis of 13 case–control studies providing results from logistic regressions for associations between one standard deviation (SD) increments in mammographic density phenotypes and breast cancer risk. We used random-effects models to calculate pooled odds ratios and 95% confidence intervals (CIs). All tests were two-sided with P less than .05 considered to be statistically significant. Results Among premenopausal women (n = 1776 case patients; n = 2834 control subjects), summary odds ratios were 1.37 (95% CI = 1.29 to 1.47) for absolute dense area, 0.78 (95% CI = 0.71 to 0.86) for absolute nondense area, and 1.52 (95% CI = 1.39 to 1.66) for percentage dense area when pooling estimates adjusted for age, body mass index, and parity. Corresponding odds ratios among postmenopausal women (n = 6643 case patients; n = 11187 control subjects) were 1.38 (95% CI = 1.31 to 1.44), 0.79 (95% CI = 0.73 to 0.85), and 1.53 (95% CI = 1.44 to 1.64). After additional adjustment for absolute dense area, associations between absolute nondense area and breast cancer became attenuated or null in several studies and summary odds ratios became 0.82 (95% CI = 0.71 to 0.94; P heterogeneity = .02) for premenopausal and 0.85 (95% CI = 0.75 to 0.96; P heterogeneity < .01) for postmenopausal women. Conclusions The results suggest that percentage dense area is a stronger breast cancer risk factor than absolute dense area. Absolute nondense area was inversely associated with breast cancer risk, but it is unclear whether the association is independent of absolute dense area. PMID:24816206

Food crystallization and eggs.

USDA-ARS?s Scientific Manuscript database

Egg products can be utilized to control crystallization in a diverse realm of food products. Albumen and egg yolk can aid in the control of sugar crystal formation in candies. Egg yolk can enhance the textural properties and aid in the control of large ice crystal formation in frozen desserts. In...

A simple apparatus for controlling nucleation and size in protein crystal growth

NASA Technical Reports Server (NTRS)

Gernert, Kim M.; Smith, Robert; Carter, Daniel C.

1988-01-01

A simple device is described for controlling vapor equilibrium in macromolecular crystallization as applied to the protein crystal growth technique commonly referred to as the 'hanging drop' method. Crystal growth experiments with hen egg white lysozyme have demonstrated control of the nucleation rate. Nucleation rate and final crystal size have been found to be highly dependent upon the rate at which critical supersaturation is approached. Slower approaches show a marked decrease in the nucleation rate and an increase in crystal size.

Tetrahedral cluster and pseudo molecule: New approaches to Calculate Absolute Surface Energy of Zinc Blende (111)/(-1-1-1) Surface

NASA Astrophysics Data System (ADS)

Zhang, Yiou; Zhang, Jingzhao; Tse, Kinfai; Wong, Lun; Chan, Chunkai; Deng, Bei; Zhu, Junyi

Determining accurate absolute surface energies for polar surfaces of semiconductors has been a great challenge in decades. Here, we propose pseudo-hydrogen passivation to calculate them, using density functional theory approaches. By calculating the energy contribution from pseudo-hydrogen using either a pseudo molecule method or a tetrahedral cluster method, we obtained (111)/(-1-1-1) surfaces energies of Si, GaP, GaAs, and ZnS with high self-consistency. Our findings may greatly enhance the basic understandings of different surfaces and lead to novel strategies in the crystal growth. We would like to thank Su-huai Wei for helpful discussions. Computing resources were provided by the High Performance Cluster Computing Centre, Hong Kong Baptist University. This work was supported by the start-up funding and direct Grant with the Project.

Crystal growth and annealing for minimized residual stress

DOEpatents

Gianoulakis, Steven E.

2002-01-01

A method and apparatus for producing crystals that minimizes birefringence even at large crystal sizes, and is suitable for production of CaF.sub.2 crystals. The method of the present invention comprises annealing a crystal by maintaining a minimal temperature gradient in the crystal while slowly reducing the bulk temperature of the crystal. An apparatus according to the present invention includes a thermal control system added to a crystal growth and annealing apparatus, wherein the thermal control system allows a temperature gradient during crystal growth but minimizes the temperature gradient during crystal annealing.

Absolute configurations of organometallic compounds. III. Structure and absolute configuration of the square-pyramidal complex ((+)/sub 579/-(C/sub 5/H/sub 5/)Mo(CO)/sub 2/(NN*))PF/sub 6/(NN* = Schiff base derived from pyridine-2-carbaldehyde and (S)-(-)-. cap alpha. -phenylethylamine)

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

Bernal, I.; LaPlaca, S.J.; Korp, J.

The structure of (+)/sub 579/-(eta/sup 5/-C/sub 5/H/sub 5/Mo(CO)/sub 2/(NN*))PF/sub 6/ with NN* = the Schiff base derived from pyridine-2-carbaldehyde and (S)-(--)-..cap alpha..-phenylethylamine was determined using standard single-crystal x-ray diffraction methods. The absolute configuration was determined by refinement of the data using the anomalous scattering contributions of Mo and P to a final R(F) = 0.056 for 2634 independent reflections having I greater than 3 sigma (I). The substance crystallizes in the space group P2/sub 1/2/sub 1/2/sub 1/ with unit cell dimensions of a = 12.249 (4), b = 9.236 (3), and c = 20.692 (9) A and Z = 4more » molecules/unit cell. The square-pyramidal coordination of the Mo atom is defined by two carbonyl carbons and two Schiff base nitrogens occupying the four basal plane sites and the five carbons of the eta/sup 5/-C/sub 5/H/sub 5/ ligand in the axial position. The Mo--ligand distances and the bond lengths and angles within the ligands are normal and compare closely with those of recent structure determinations of comparable precision. The Mo atom is 0.95 A above the plane formed by the four basal plane ligands. The conformation of the (S)-..cap alpha..-phenylethyl group with respect to the ligand plane, defined by the pyridine ring, the imine system, and the Mo atom, is discussed. The configuration at the metal atom in the (+)/sub 579/ isomer is specified as (S). The PF/sub 6//sup -/ anion executes large amplitude torsional motion in the lattice, as is commonly the case for this anion when not hydrogen bonded.« less

Humidity control and hydrophilic glue coating applied to mounted protein crystals improves X-ray diffraction experiments

PubMed Central

Baba, Seiki; Hoshino, Takeshi; Ito, Len; Kumasaka, Takashi

2013-01-01

Protein crystals are fragile, and it is sometimes difficult to find conditions suitable for handling and cryocooling the crystals before conducting X-ray diffraction experiments. To overcome this issue, a protein crystal-mounting method has been developed that involves a water-soluble polymer and controlled humid air that can adjust the moisture content of a mounted crystal. By coating crystals with polymer glue and exposing them to controlled humid air, the crystals were stable at room temperature and were cryocooled under optimized humidity. Moreover, the glue-coated crystals reproducibly showed gradual transformations of their lattice constants in response to a change in humidity; thus, using this method, a series of isomorphous crystals can be prepared. This technique is valuable when working on fragile protein crystals, including membrane proteins, and will also be useful for multi-crystal data collection. PMID:23999307

Morphological diversity of nitroguanidine crystals with enhanced mechanical performance and thermodynamic stability

NASA Astrophysics Data System (ADS)

Luo, Zhilong; Cui, Yingdan; Dong, Weibing; Xu, Qipeng; Zou, Gaoxing; Kang, Chao; Hou, Baohong; Chen, Song; Gong, Junbo

2017-12-01

Nitroguanidine (NQ) is a commonly used explosive, which has been widely used for both civilian and military explosive applications. However, the weak flowability and mechanical performance limit its application. In this work, mechanical performance and thermodynamic stability of NQ crystals were improved by controlling crystal morphologies in the crystallization process. Typical NQ crystals with multiple morphologies and single crystal form were obtained in the presence of additives during the cooling crystallization. The morphology controlled NQ crystals showed higher density, unimodal crystal size distribution and enhanced flowability. The additives showed the inhibitory effect on the nucleation of NQ crystals by in-situ FBRM and PVM determination, and the mechanism was analyzed by means of morphological prediction and molecular simulation. Furthermore, the morphology controlled NQ crystals suggested higher thermodynamic stability according to the calculation of entropy, enthalpy, Gibbs free energy and apparent activation energy on the basis of DSC results.

Frequency measurement of the 260-THz (1. 15-. mu. m) He--Ne laser

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

Jennings, D.A.; Petersen, F.R.; Evenson, K.M.

1979-05-01

Absolute infrared frequency measurement has been extended to 260 THz with the measurement of the strong 1.15-..mu..m laser line in /sup 20/Ne. The frequency was synthesized in nonlinear crystals of CdGeAs/sub 2/ and Ag/sub 3/AsS/sub 3/ from stabilized CO/sub 2/ lasers and the 1.5-..mu..m laser line in /sup 20//sub Ne.Themeasuredfrequencyis/..nu..20/sub Ne,1.15mum/ =260.103 284 (30) THz.

(+)- and (-)-Cajanusine, a pair of new enantiomeric stilbene dimers with a new skeleton from the leaves of Cajanus cajan.

PubMed

Li, Xiao-Long; Zhao, Bing-Xin; Huang, Xiao-Jun; Zhang, Dong-Mei; Jiang, Ren-Wang; Li, Ying-Jie; Jian, Yu-Qing; Wang, Ying; Li, Yao-Lan; Ye, Wen-Cai

2014-01-03

A pair of new enantiomeric stilbene dimers, (+)- and (-)-cajanusine [(+)-1 and (-)-1], with a unique coupling pattern were isolated from the leaves of Cajanus cajan . Their structures including absolute configurations were elucidated on the basis of comprehensive spectroscopic and single-crystal X-ray diffraction analyses, as well as CD calculations. The plausible biogenetic pathway of 1 was also proposed. Additionally, (±)-1, (+)-1, and (-)-1 exhibited inhibitory activities on the growth of human hepatocellular carcinoma cells.

Quinolizidine alkaloids from Lupinus lanatus

NASA Astrophysics Data System (ADS)

Neto, Alexandre T.; Oliveira, Carolina Q.; Ilha, Vinicius; Pedroso, Marcelo; Burrow, Robert A.; Dalcol, Ionara I.; Morel, Ademir F.

2011-10-01

In this study, one new quinolizidine alkaloid, lanatine A ( 1), together with three other known alkaloids, 13-α- trans-cinnamoyloxylupanine ( 2), 13-α-hydroxylupanine ( 3), and (-)-multiflorine ( 4) were isolated from the aerial parts of Lupinus lanatus (Fabaceae). The structures of alkaloids 1- 4 were elucidated by spectroscopic data analysis. The stereochemistry of 1 was determined by single crystal X-ray analysis. Bayesian statistical analysis of the Bijvoet differences suggests the absolute stereochemistry of 1. In addition, the antimicrobial potential of alkaloids 1- 4 is also reported.

Volvalerelactones A and B, two new sesquiterpenoid lactones with an unprecedented skeleton from Valeriana officinalis var. latifolia.

PubMed

Wang, Peng-Cheng; Ran, Xin-Hui; Luo, Huai-Rong; Hu, Jiang-Miao; Chen, Rui; Ma, Qing-Yun; Dai, Hao-Fu; Liu, Yu-Qing; Xie, Ming-Jin; Zhou, Jun; Zhao, You-Xing

2011-06-17

Volvalerelactones A and B (1 and 2), two new sesquiterpenoid lactones with an unprecedented 3/7/6 tricyclic ring system, were isolated from the roots of Valeriana officinalis var. latifolia. Their structures and relative configurations were elucidated by spectroscopic data and single-crystal X-ray diffraction crystallography, and the absolute configuration was assigned by computational methods. The possible biosynthetic pathways of 1 and 2 were also proposed. © 2011 American Chemical Society

Anti-Proliferative and Anti-Inflammatory Lanostane Triterpenoids from the Polish Edible Mushroom Macrolepiota procera.

PubMed

Chen, He-Ping; Zhao, Zhen-Zhu; Li, Zheng-Hui; Huang, Ying; Zhang, Shuai-Bing; Tang, Yang; Yao, Jian-Neng; Chen, Lin; Isaka, Masahiko; Feng, Tao; Liu, Ji-Kai

2018-03-28

This study features the isolation and identification of 12 lanostane-type triterpenoids, namely lepiotaprocerins A-L, 1-12, from the fruiting bodies of the Poland-collected edible mushroom Macrolepiota procera. The structures and the absolute configurations of the new compounds were ambiguously established by extensive spectroscopic analyses, ECD calculation, and single-crystal X-ray diffraction analyses. Structurally, lepiotaprocerins A-F, 1-6, are distinguished by the presence of a rare "1-en-1,11-epoxy" moiety which has not been previously described in the lanostane class. Biologically, lepiotaprocerins A-F, 1-6, displayed more significant inhibitions of nitric oxide (NO) production than the positive control L- N G -monomethyl arginine (L-NMMA) (IC 50 47.1 μM), and lepiotaprocerins G-L, 7-12, showed various cytotoxicity potencies against a panel of human cancer cell lines. Compound 9 also displayed antitubercular activity against Mycobacterium tuberculosis H37Ra with a minimal inhibitory concentration (MIC) 50 μg/mL.

Data Acquisition Visualization Development for the MAJORANA DEMONSTRATOR

NASA Astrophysics Data System (ADS)

Wendlandt, Laura; Howe, Mark; Wilkerson, John; Majorana Collaboration

2013-10-01

The MAJORANA Project is building an array of germanium detectors with very low backgrounds in order to search for neutrinoless double-beta decay, a rare process that, if detected, would give us information about neutrinos. This decay would prove that neutrinos are their own anti-particles, would show that lepton number is not conserved, and would help determine absolute neutrino mass. An object-oriented, data acquisition software program known as ORCA (Object-oriented Real-time Control and Acquisition) will be used to collect data from the array. This paper describes the implementation of computer visualizations for detector calibrations, as well as tools for more general computer modeling in ORCA. Specifically, it details software that converts a CAD file to OpenGL, which can be used in ORCA. This paper also contains information about using a barium-133 source to take measurements from various locations around the detector, to better understand how data varies with detector crystal orientation. Work made possible by National Science Foundation Award OCI-1155614.

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

Shi,J.; Sivaraman, J.; Song, J.

Unlike 3C protease, the severe acute respiratory syndrome coronavirus (SARS-CoV) 3C-like protease (3CLpro) is only enzymatically active as a homodimer and its catalysis is under extensive regulation by the unique extra domain. Despite intense studies, two puzzles still remain: (i) how the dimer-monomer switch is controlled and (ii) why dimerization is absolutely required for catalysis. Here we report the monomeric crystal structure of the SARS-CoV 3CLpro mutant R298A at a resolution of 1.75 Angstroms . Detailed analysis reveals that Arg298 serves as a key component for maintaining dimerization, and consequently, its mutation will trigger a cooperative switch from a dimermore » to a monomer. The monomeric enzyme is irreversibly inactivated because its catalytic machinery is frozen in the collapsed state, characteristic of the formation of a short 310-helix from an active-site loop. Remarkably, dimerization appears to be coupled to catalysis in 3CLpro through the use of overlapped residues for two networks, one for dimerization and another for the catalysis.« less

A high sensitivity real-time NVR monitor. [Nonvolatile Residue

NASA Technical Reports Server (NTRS)

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

1992-01-01

The use of a temperature-controlled 200-MHz SAW resonator piezoelectric mass microbalance to monitor the mass of nonvolatile residue (NVR) deposited on its surface in real time is reported. The fundamental frequency of this device is mainly dependent on the configuration of the transducers and not on the thickness of the substrate. Therefore, higher operating frequencies can be achieved without reducing the thickness of the crystal. The real-time instrument was integrated onto a conventional stainless steel NVR plate and operated flawlessly over a 14-d period at Kennedy Space Center and successfully measured less than 1 ng/sq cm d NVR contamination. Contamination episodes detected by the instrument were correlated with scheduled activities on the test stand. Under the assumption of a baseline noise level of +/- 2 Hz, the absolute mass lower limit of detection would be 0.065 ng/sq cm. This would enable the detection of a daily NVR deposition rate of less than 0.1 ng/sq cm d.

Relative and Absolute Error Control in a Finite-Difference Method Solution of Poisson's Equation

ERIC Educational Resources Information Center

Prentice, J. S. C.

2012-01-01

An algorithm for error control (absolute and relative) in the five-point finite-difference method applied to Poisson's equation is described. The algorithm is based on discretization of the domain of the problem by means of three rectilinear grids, each of different resolution. We discuss some hardware limitations associated with the algorithm,…

Lanthanides in molecular magnetism: old tools in a new field.

PubMed

Sorace, Lorenzo; Benelli, Cristiano; Gatteschi, Dante

2011-06-01

In this tutorial review we discuss some basic aspects concerning the magnetic properties of rare-earth ions, which are currently the subject of a renovated interest in the field of molecular magnetism, after the discovery that slow relaxation of the magnetization at liquid nitrogen temperature can occur in mononuclear complexes of these ions. Focusing on Dy(III) derivatives a tutorial discussion is given of the relation of the crystal field parameters, which determine the anisotropy of these systems and consequently their interesting magnetic properties, with the geometry of the coordination sphere around the lanthanide centre and with the pattern of f orbitals. The problem of systems of low point symmetry is also addressed by showing how detailed single crystal investigation, coupled to more sophisticated calculation procedures, is an absolute necessity to obtain meaningful structure-property relationships in these systems.

High mobility emissive organic semiconductor

PubMed Central

Liu, Jie; Zhang, Hantang; Dong, Huanli; Meng, Lingqiang; Jiang, Longfeng; Jiang, Lang; Wang, Ying; Yu, Junsheng; Sun, Yanming; Hu, Wenping; Heeger, Alan J.

2015-01-01

The integration of high charge carrier mobility and high luminescence in an organic semiconductor is challenging. However, there is need of such materials for organic light-emitting transistors and organic electrically pumped lasers. Here we show a novel organic semiconductor, 2,6-diphenylanthracene (DPA), which exhibits not only high emission with single crystal absolute florescence quantum yield of 41.2% but also high charge carrier mobility with single crystal mobility of 34 cm2 V−1 s−1. Organic light-emitting diodes (OLEDs) based on DPA give pure blue emission with brightness up to 6,627 cd m−2 and turn-on voltage of 2.8 V. 2,6-Diphenylanthracene OLED arrays are successfully driven by DPA field-effect transistor arrays, demonstrating that DPA is a high mobility emissive organic semiconductor with potential in organic optoelectronics. PMID:26620323

Refractive index dispersion sensing using an array of photonic crystal resonant reflectors

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

Hermannsson, Pétur G.; Vannahme, Christoph; Smith, Cameron L. C.

2015-08-10

Refractive index sensing plays a key role in various environmental and biological sensing applications. Here, a method is presented for measuring the absolute refractive index dispersion of liquids using an array of photonic crystal resonant reflectors of varying periods. It is shown that by covering the array with a sample liquid and measuring the resonance wavelength associated with transverse electric polarized quasi guided modes as a function of period, the refractive index dispersion of the liquid can be accurately obtained using an analytical expression. This method is compact, can perform measurements at arbitrary number of wavelengths, and requires only amore » minute sample volume. The ability to sense a material's dispersion profile offers an added dimension of information that may be of benefit to optofluidic lab-on-a-chip applications.« less

Revisiting polarimetry near the isotropic point of an optically active, non-enantiomorphous, molecular crystal.

PubMed

Martin, Alexander T; Tan, Melissa; Nichols, Shane M; Timothy, Emily; Kahr, Bart

2018-07-01

Accurate polarimetric measurements of the optical activity of crystals along low symmetry directions are facilitated by isotropic points, frequencies where dispersion curves of eigenrays cross and the linear birefringence disappears. We report here the optical properties and structure of achiral, uniaxial (point group D 2d ) potassium trihydrogen di-(cis-4-cyclohexene-1,2-dicarboxylate) dihydrate, whose isotropic point was previously detected (S. A. Kim, C. Grieswatch, H. Küppers, Zeit. Krist. 1993; 208:219-222) and exploited for a singular measurement of optical activity normal to the optic axis. The crystal structure associated with the aforementioned study was never published. We report it here, confirming the space group assignment I 4¯c2, along with the frequency dependence of the fundamental optical properties and the constitutive tensors by fitting optical dispersion relations to measured Mueller matrix spectra. k-Space maps of circular birefringence and of the Mueller matrix near the isotropic wavelength are measured and simulated. The signs of optical rotation are correlated with the absolute crystallographic directions. © 2018 Wiley Periodicals, Inc.

Spectroscopic determination of crystal-field levels in CeRh2Si2 and CeRu2Si2 and of the 4f0 contributions in CeM2Si2 (M=Cu, Ru, Rh, Pd, and Au)

NASA Astrophysics Data System (ADS)

Willers, T.; Adroja, D. T.; Rainford, B. D.; Hu, Z.; Hollmann, N.; Körner, P. O.; Chin, Y.-Y.; Schmitz, D.; Hsieh, H. H.; Lin, H.-J.; Chen, C. T.; Bauer, E. D.; Sarrao, J. L.; McClellan, K. J.; Byler, D.; Geibel, C.; Steglich, F.; Aoki, H.; Lejay, P.; Tanaka, A.; Tjeng, L. H.; Severing, A.

2012-01-01

We have determined the ground-state wave functions and crystal-field-level schemes of CeRh2Si2 and CeRu2Si2 using linear polarized soft x-ray-absorption spectroscopy (XAS) and inelastic neutron scattering. We find large crystal-field splittings and ground-state wave functions which are made of mainly Jz = |±5/2> with some amount of |∓3/2> in both the compounds. The 4f0 contribution to the ground state of several members of the CeM2Si2 family with M=(Cu, Ru, Rh, Pd, and Au) has been determined with XAS, and the comparison reveals a trend concerning the delocalization of the f electrons. Absolute numbers are extracted from scaling to results from hard x-ray photoelectron spectroscopy on CeRu2Si2 by Yano [Phys. Rev. BPRBMDO1098-012110.1103/PhysRevB.77.035118 77, 035118 (2008)].

Crystal-chemistry insight into the photocatalytic activity of BiOCl x Br1- x nanoplate solid solutions

NASA Astrophysics Data System (ADS)

Xu, Huan-Yan; Han, Xu; Tan, Qu; Wu, Ke-Jia; Qi, Shu-Yan

2017-06-01

In this study, a facile alcoholysis method was developed to synthesize BiOCl x Br1- x nanoplates at room temperature and atmospheric pressure. In this route, strong acid or alkaline environment was absolutely avoided to realize the high exposure of {001} crystal facets. The regular changes in XRD peaks and cell parameters as a function of the Br content strongly declared that the obtained BiOCl x Br1- x products belonged to a group of solid solutions. The 2D nanosheets with in-plane wrinkles were clearly observed in TEM images. Interestingly, as the Br content increased, band gaps of BiOCl x Br1- x solid solutions gradually decreased. The photocatalytic degradation of RhB under simulated sunlight irradiation indicated that BiOCl0.5Br0.5 had the best photocatalytic activity. From the viewpoint of crystal chemistry, the photocatalytic activity of BiOCl x Br1- x solid solutions was closely related with the exposure amount of {001} facets, interlayer spacing of (001) plane and energy-level position of valence band.

Thermometric diagnosis of peripheral nerve injuries. Assessment of the diagnostic accuracy of a new practical technique.

PubMed

Ya'ish, F M M; Cooper, J P; Craigen, M A C

2007-07-01

The diagnosis of nerve injury using thermotropic liquid crystal temperature strips was compared blindly and prospectively against operative findings in 36 patients requiring surgical exploration for unilateral upper limb lacerations with suspected nerve injury. Thermotropic liquid crystal strips were applied to affected and non-affected segments in both hands in all subjects. A pilot study showed that a simple unilateral laceration without nerve injury results in a cutaneous temperature difference between limbs, but not within each limb. Thus, for detection of a nerve injury, comparison was made against the unaffected nerve distribution in the same hand. Receiver operating characteristic curve analysis showed that an absolute temperature difference > or = 1.0 degrees C was diagnostic of a nerve injury (area under the curve = 0.985, sensitivity = 100%, specificity = 93.8%). Thermotropic liquid crystal strip assessment is a new, reliable and objective method for the diagnosis of traumatic peripheral nerve injuries. If implemented in the acute setting, it could improve the reliability of clinical assessment and reduce the number of negative surgical explorations.

Promoted nitrogen dissolution due to the addition of Li or Ca to Ga-Na melt; some effects of additives on the growth of GaN single crystals using the sodium flux method

NASA Astrophysics Data System (ADS)

Morishita, Masanori; Kawamura, Fumio; Kawahara, Minoru; Yoshimura, Masashi; Mori, Yusuke; Sasaki, Takatomo

2005-10-01

The effect of the addition of Li or Ca to Ga-Na melt on the promotion of nitrogen dissolution was examined quantitatively in the growth of GaN single crystals using the sodium flux method. The addition of Li or Ca to Ga-Na melt increased both the solubility of solid GaN and that of gaseous nitrogen against the solution. The increase in the solubility of gaseous nitrogen seems to be caused by additives having a high binding energy with nitrogen. We measured the solubility of GaN and that of gaseous nitrogen against Ga-Na, Ga-Na-Li and Ga-Na-Ca melt in this study. On the basis of these data, we clarified the relationship between the N/Ga ratio in the solution and the coloration of GaN crystals grown in each system, and between changes in the yield of GaN and the absolute value of supersaturation.

Uranium series, volcanic rocks

USGS Publications Warehouse

Vazquez, Jorge A.

2014-01-01

Application of U-series dating to volcanic rocks provides unique and valuable information about the absolute timing of crystallization and differentiation of magmas prior to eruption. The 238U–230Th and 230Th-226Ra methods are the most commonly employed for dating the crystallization of mafic to silicic magmas that erupt at volcanoes. Dates derived from the U–Th and Ra–Th methods reflect crystallization because diffusion of these elements at magmatic temperatures is sluggish (Cherniak 2010) and diffusive re-equilibration is insignificant over the timescales (less than or equal to 10^5 years) typically associated with pre-eruptive storage of nearly all magma compositions (Cooper and Reid 2008). Other dating methods based on elements that diffuse rapidly at magmatic temperatures, such as the 40Ar/39Ar and (U–Th)/He methods, yield dates for the cooling of magma at the time of eruption. Disequilibrium of some short-lived daughters of the uranium series such as 210Po may be fractionated by saturation of a volatile phase and can be employed to date magmatic gas loss that is synchronous with volcanic eruption (e.g., Rubin et al. 1994).

Estimating the Aqueous Solubility of Pharmaceutical Hydrates

PubMed Central

Franklin, Stephen J.; Younis, Usir S.; Myrdal, Paul B.

2016-01-01

Estimation of crystalline solute solubility is well documented throughout the literature. However, the anhydrous crystal form is typically considered with these models, which is not always the most stable crystal form in water. In this study an equation which predicts the aqueous solubility of a hydrate is presented. This research attempts to extend the utility of the ideal solubility equation by incorporating desolvation energetics of the hydrated crystal. Similar to the ideal solubility equation, which accounts for the energetics of melting, this model approximates the energy of dehydration to the entropy of vaporization for water. Aqueous solubilities, dehydration and melting temperatures, and log P values were collected experimentally and from the literature. The data set includes different hydrate types and a range of log P values. Three models are evaluated, the most accurate model approximates the entropy of dehydration (ΔSd) by the entropy of vaporization (ΔSvap) for water, and utilizes onset dehydration and melting temperatures in combination with log P. With this model, the average absolute error for the prediction of solubility of 14 compounds was 0.32 log units. PMID:27238488

Control of interface shape during high melting sesquioxide crystal growth by HEM technique

NASA Astrophysics Data System (ADS)

Hu, Kaiwei; Zheng, Lili; Zhang, Hui

2018-02-01

During crystal growth in heat exchanger method (HEM) system, the shape of the growth interface changes with the proceeding of the growth process, which limits the crystal size and reduces the quality of the crystal. In this paper, a modified HEM system is proposed to control the interface shape for growth of sesquioxide crystals. Numerical simulation is performed to predict heat transfer, melt flow and interface shape during growth of high melting sesquioxide crystals by the heat exchanger method. The results show that a flat or slightly convex interface shape is beneficial to reduce the solute pileup in front of the melt/crystal interface and decrease the radial temperature gradient inside the crystal during growth of sesquioxide crystals. The interface shape can be controlled by adjusting the gap size d and lower resistance heater power during growth. The growth rate and the melt/crystal interface position can be obtained by two measured temperatures.

Comparison of the temperature accuracy between smart phone based and high-end thermal cameras using a temperature gradient phantom

NASA Astrophysics Data System (ADS)

Klaessens, John H.; van der Veen, Albert; Verdaasdonk, Rudolf M.

2017-03-01

Recently, low cost smart phone based thermal cameras are being considered to be used in a clinical setting for monitoring physiological temperature responses such as: body temperature change, local inflammations, perfusion changes or (burn) wound healing. These thermal cameras contain uncooled micro-bolometers with an internal calibration check and have a temperature resolution of 0.1 degree. For clinical applications a fast quality measurement before use is required (absolute temperature check) and quality control (stability, repeatability, absolute temperature, absolute temperature differences) should be performed regularly. Therefore, a calibrated temperature phantom has been developed based on thermistor heating on both ends of a black coated metal strip to create a controllable temperature gradient from room temperature 26 °C up to 100 °C. The absolute temperatures on the strip are determined with software controlled 5 PT-1000 sensors using lookup tables. In this study 3 FLIR-ONE cameras and one high end camera were checked with this temperature phantom. The results show a relative good agreement between both low-cost and high-end camera's and the phantom temperature gradient, with temperature differences of 1 degree up to 6 degrees between the camera's and the phantom. The measurements were repeated as to absolute temperature and temperature stability over the sensor area. Both low-cost and high-end thermal cameras measured relative temperature changes with high accuracy and absolute temperatures with constant deviations. Low-cost smart phone based thermal cameras can be a good alternative to high-end thermal cameras for routine clinical measurements, appropriate to the research question, providing regular calibration checks for quality control.

A Flexible Parameterization for Shortwave Optical Properties of Ice Crystals

NASA Technical Reports Server (NTRS)

VanDiedenhoven, Bastiaan; Ackerman, Andrew S.; Cairns, Brian; Fridlind, Ann M.

2014-01-01

A parameterization is presented that provides extinction cross section sigma (sub e), single-scattering albedo omega, and asymmetry parameter (g) of ice crystals for any combination of volume, projected area, aspect ratio, and crystal distortion at any wavelength in the shortwave. Similar to previous parameterizations, the scheme makes use of geometric optics approximations and the observation that optical properties of complex, aggregated ice crystals can be well approximated by those of single hexagonal crystals with varying size, aspect ratio, and distortion levels. In the standard geometric optics implementation used here, sigma (sub e) is always twice the particle projected area. It is shown that omega is largely determined by the newly defined absorption size parameter and the particle aspect ratio. These dependences are parameterized using a combination of exponential, lognormal, and polynomial functions. The variation of (g) with aspect ratio and crystal distortion is parameterized for one reference wavelength using a combination of several polynomials. The dependences of g on refractive index and omega are investigated and factors are determined to scale the parameterized (g) to provide values appropriate for other wavelengths. The parameterization scheme consists of only 88 coefficients. The scheme is tested for a large variety of hexagonal crystals in several wavelength bands from 0.2 to 4 micron, revealing absolute differences with reference calculations of omega and (g) that are both generally below 0.015. Over a large variety of cloud conditions, the resulting root-mean-squared differences with reference calculations of cloud reflectance, transmittance, and absorptance are 1.4%, 1.1%, and 3.4%, respectively. Some practical applications of the parameterization in atmospheric models are highlighted.

Strain Analysis of Stretched Tourmaline Crystals Using ImageJ, Microsoft Excel and PowerPoint

NASA Astrophysics Data System (ADS)

Bosbyshell, H.

2012-12-01

This poster describes an undergraduate structural geology lab exercise utilizing the Mohr's circle diagram for finite strain, constructed using measurements obtained from stretched tourmaline crystals. A small building housing HVAC equipment at the south end of West Chester University's Recitation Hall (itself made of serpentinite) is constructed of early-Cambrian Chickies Quartzite. Stretched tourmaline crystals, with segments joined by fibrous quartz, are visible on many surfaces (presumably originally bedding). While the original orientation of any stone is unknown, these rocks provide an opportunity for a short field exercise during a two-hour lab period and a great base for conducting strain analysis. It is always fun to ask how many in the class have ever noticed the tourmaline (few have). Students take photos using their cell phones or cameras. Since strain is a ratio the absolute size of the tourmaline crystals is immaterial. Nonetheless, this is a good opportunity to remind students of the importance of including a scale in their photographs. The photos are opened in ImageJ and the line tool is used to determine the original and final lengths of selected crystals. Students calculate strain parameters using Microsoft Excel. Then, we use Adobe Illustrator or the drafting capabilities of Microsoft PowerPoint 2010 to follow Ramsay and Huber's techniques using a Mohr's circle construction to determine the finite strain ellipse. If a stretching direction can be estimated, elongation of two crystals is all that is required to determine the strain ratio. If no stretching direction is apparent, three crystals are required for a more complicated analysis that allows for determination of the stretching direction, as well as the strain ratio.

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

Ramadhar, Timothy R.; Zheng, Shao -Liang; Chen, Yu -Sheng

A detailed set of synthetic and crystallographic guidelines for the crystalline sponge method based upon the analysis of expediently synthesized crystal sponges using third-generation synchrotron radiation are reported. The procedure for the synthesis of the zinc-based metal–organic framework used in initial crystal sponge reports has been modified to yield competent crystals in 3 days instead of 2 weeks. These crystal sponges were tested on some small molecules, with two being unexpectedly difficult cases for analysis with in-house diffractometers in regard to data quality and proper space-group determination. These issues were easily resolved by the use of synchrotron radiation using data-collectionmore » times of less than an hour. One of these guests induced a single-crystal-to-single-crystal transformation to create a larger unit cell with over 500 non-H atoms in the asymmetric unit. This led to a non-trivial refinement scenario that afforded the best Flack x absolute stereochemical determination parameter to date for these systems. The structures did not require the use of PLATON/SQUEEZE or other solvent-masking programs, and are the highest-quality crystalline sponge systems reported to date where the results are strongly supported by the data. A set of guidelines for the entire crystallographic process were developed through these studies. In particular, the refinement guidelines include strategies to refine the host framework, locate guests and determine occupancies, discussion of the proper use of geometric and anisotropic displacement parameter restraints and constraints, and whether to perform solvent squeezing/masking. The single-crystal-to-single-crystal transformation process for the crystal sponges is also discussed. The presented general guidelines will be invaluable for researchers interested in using the crystalline sponge method at in-house diffraction or synchrotron facilities, will facilitate the collection and analysis of reliable high-quality data, and will allow construction of chemically and physically sensible models for guest structural determination.« less

Analysis of rapidly synthesized guest-filled porous complexes with synchrotron radiation: Practical guidelines for the crystalline sponge method

DOE PAGES

Ramadhar, Timothy R.; Zheng, Shao -Liang; Chen, Yu -Sheng; ...

2015-01-01

A detailed set of synthetic and crystallographic guidelines for the crystalline sponge method based upon the analysis of expediently synthesized crystal sponges using third-generation synchrotron radiation are reported. The procedure for the synthesis of the zinc-based metal–organic framework used in initial crystal sponge reports has been modified to yield competent crystals in 3 days instead of 2 weeks. These crystal sponges were tested on some small molecules, with two being unexpectedly difficult cases for analysis with in-house diffractometers in regard to data quality and proper space-group determination. These issues were easily resolved by the use of synchrotron radiation using data-collectionmore » times of less than an hour. One of these guests induced a single-crystal-to-single-crystal transformation to create a larger unit cell with over 500 non-H atoms in the asymmetric unit. This led to a non-trivial refinement scenario that afforded the best Flack x absolute stereochemical determination parameter to date for these systems. The structures did not require the use of PLATON/SQUEEZE or other solvent-masking programs, and are the highest-quality crystalline sponge systems reported to date where the results are strongly supported by the data. A set of guidelines for the entire crystallographic process were developed through these studies. In particular, the refinement guidelines include strategies to refine the host framework, locate guests and determine occupancies, discussion of the proper use of geometric and anisotropic displacement parameter restraints and constraints, and whether to perform solvent squeezing/masking. The single-crystal-to-single-crystal transformation process for the crystal sponges is also discussed. The presented general guidelines will be invaluable for researchers interested in using the crystalline sponge method at in-house diffraction or synchrotron facilities, will facilitate the collection and analysis of reliable high-quality data, and will allow construction of chemically and physically sensible models for guest structural determination.« less

Effect of Eu magnetism on the electronic properties of the candidate Dirac material EuMnBi2

NASA Astrophysics Data System (ADS)

May, Andrew F.; McGuire, Michael A.; Sales, Brian C.

2014-08-01

The crystal structure and physical properties of the layered material EuMnBi2 have been characterized by measurements on single crystals. EuMnBi2 is isostructural with the Dirac material SrMnBi2 based on single-crystal x-ray diffraction, crystallizing in the I4/mmm space group (No. 139). Magnetic susceptibility measurements suggest antiferromagnetic (AFM) ordering of moments on divalent Eu ions near TN=22 K. For low fields, the ordered Eu moments are aligned along the c axis, and a spin flop is observed near 5.4 T at 5 K. The moment is not saturated in an applied field of 13 T at 5 K, which is uncommon for compounds containing Eu2+. The magnetic behavior suggests an anisotropy enhancement via interaction between Eu and the Mn moments that appear to be ordered antiferromagnetically below ≈310 K. A large increase in the magnetoresistance is observed across the spin flop, with absolute magnetoresistance reaching ≈650% at 5 K and 12 T. Hall effect measurements reveal a decrease in the carrier density below TN, which implies a manipulation of the Fermi surface by magnetism on the sites surrounding the Bi square nets that lead to Dirac cones in this family of materials.

Mind and body therapy for fibromyalgia.

PubMed

Theadom, Alice; Cropley, Mark; Smith, Helen E; Feigin, Valery L; McPherson, Kathryn

2015-04-09

Mind-body interventions are based on the holistic principle that mind, body and behaviour are all interconnected. Mind-body interventions incorporate strategies that are thought to improve psychological and physical well-being, aim to allow patients to take an active role in their treatment, and promote people's ability to cope. Mind-body interventions are widely used by people with fibromyalgia to help manage their symptoms and improve well-being. Examples of mind-body therapies include psychological therapies, biofeedback, mindfulness, movement therapies and relaxation strategies. To review the benefits and harms of mind-body therapies in comparison to standard care and attention placebo control groups for adults with fibromyalgia, post-intervention and at three and six month follow-up. Electronic searches of the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (Ovid), EMBASE (Ovid), PsycINFO (Ovid), AMED (EBSCO) and CINAHL (Ovid) were conducted up to 30 October 2013. Searches of reference lists were conducted and authors in the field were contacted to identify additional relevant articles. All relevant randomised controlled trials (RCTs) of mind-body interventions for adults with fibromyalgia were included. Two authors independently selected studies, extracted the data and assessed trials for low, unclear or high risk of bias. Any discrepancy was resolved through discussion and consensus. Continuous outcomes were analysed using mean difference (MD) where the same outcome measure and scoring method was used and standardised mean difference (SMD) where different outcome measures were used. For binary data standard estimation of the risk ratio (RR) and its 95% confidence interval (CI) was used. Seventy-four papers describing 61 trials were identified, with 4234 predominantly female participants. The nature of fibromyalgia varied from mild to severe across the study populations. Twenty-six studies were classified as having a low risk of bias for all domains assessed. The findings of mind-body therapies compared with usual care were prioritised.There is low quality evidence that in comparison to usual care controls psychological therapies have favourable effects on physical functioning (SMD -0.4, 95% CI -0.6 to -0.3, -7.5% absolute change, 2 point shift on a 0 to 100 scale), pain (SMD -0.3, 95% CI -0.5 to -0.2, -3.5% absolute change, 2 point shift on a 0 to 100 scale) and mood (SMD -0.5, 95% CI -0.6 to -0.3, -4.8% absolute change, 3 point shift on a 20 to 80 scale). There is very low quality evidence of more withdrawals in the psychological therapy group in comparison to usual care controls (RR 1.38, 95% CI 1.12 to 1.69, 6% absolute risk difference). There is lack of evidence of a difference between the number of adverse events in the psychological therapy and control groups (RR 0.38, 95% CI 0.06 to 2.50, 4% absolute risk difference).There was very low quality evidence that biofeedback in comparison to usual care controls had an effect on physical functioning (SMD -0.1, 95% CI -0.4 to 0.3, -1.2% absolute change, 1 point shift on a 0 to 100 scale), pain (SMD -2.6, 95% CI -91.3 to 86.1, -2.6% absolute change) and mood (SMD 0.1, 95% CI -0.3 to 0.5, 1.9% absolute change, less than 1 point shift on a 0 to 90 scale) post-intervention. In view of the quality of evidence we cannot be certain that biofeedback has a little or no effect on these outcomes. There was very low quality evidence that biofeedback led to more withdrawals from the study (RR 4.08, 95% CI 1.43 to 11.62, 20% absolute risk difference). No adverse events were reported.There was no advantage observed for mindfulness in comparison to usual care for physical functioning (SMD -0.3, 95% CI -0.6 to 0.1, -4.8% absolute change, 4 point shift on a scale 0 to 100), pain (SMD -0.1, CI -0.4 to 0.3, -1.3% absolute change, less than 1 point shift on a 0 to 10 scale), mood (SMD -0.2, 95% CI -0.5 to 0.0, -3.7% absolute change, 2 point shift on a 20 to 80 scale) or withdrawals (RR 1.07, 95% CI 0.67 to 1.72, 2% absolute risk difference) between the two groups post-intervention. However, the quality of the evidence was very low for pain and moderate for mood and number of withdrawals. No studies reported any adverse events.Very low quality evidence revealed that movement therapies in comparison to usual care controls improved pain (MD -2.3, CI -4.2 to -0.4, -23% absolute change) and mood (MD -9.8, 95% CI -18.5 to -1.2, -16.4% absolute change) post-intervention. There was no advantage for physical functioning (SMD -0.2, 95% CI -0.5 to 0.2, -3.4% absolute change, 2 point shift on a 0 to 100 scale), participant withdrawals (RR 1.95, 95% CI 1.13 to 3.38, 11% absolute difference) or adverse events (RR 4.62, 95% CI 0.23 to 93.92, 4% absolute risk difference) between the two groups, however rare adverse events may include worsening of pain.Low quality evidence revealed that relaxation based therapies in comparison to usual care controls showed an advantage for physical functioning (MD -8.3, 95% CI -10.1 to -6.5, -10.4% absolute change) and pain (SMD -1.0, 95% CI -1.6 to -0.5, -3.5% absolute change, 2 point shift on a 0 to 78 scale) but not for mood (SMD -4.4, CI -14.5 to 5.6, -7.4% absolute change) post-intervention. There was no difference between the groups for number of withdrawals (RR 4.40, 95% CI 0.59 to 33.07, 31% absolute risk difference) and no adverse events were reported. Psychological interventions therapies may be effective in improving physical functioning, pain and low mood for adults with fibromyalgia in comparison to usual care controls but the quality of the evidence is low. Further research on the outcomes of therapies is needed to determine if positive effects identified post-intervention are sustained. The effectiveness of biofeedback, mindfulness, movement therapies and relaxation based therapies remains unclear as the quality of the evidence was very low or low. The small number of trials and inconsistency in the use of outcome measures across the trials restricted the analysis.

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

Baba, Seiki; Hoshino, Takeshi; Ito, Len

A new crystal-mounting method has been developed that involves a combination of controlled humid air and polymer glue for crystal coating. This method is particularly useful when applied to fragile protein crystals that are known to be sensitive to subtle changes in their physicochemical environment. Protein crystals are fragile, and it is sometimes difficult to find conditions suitable for handling and cryocooling the crystals before conducting X-ray diffraction experiments. To overcome this issue, a protein crystal-mounting method has been developed that involves a water-soluble polymer and controlled humid air that can adjust the moisture content of a mounted crystal. Bymore » coating crystals with polymer glue and exposing them to controlled humid air, the crystals were stable at room temperature and were cryocooled under optimized humidity. Moreover, the glue-coated crystals reproducibly showed gradual transformations of their lattice constants in response to a change in humidity; thus, using this method, a series of isomorphous crystals can be prepared. This technique is valuable when working on fragile protein crystals, including membrane proteins, and will also be useful for multi-crystal data collection.« less

Circuit for Communication over DC Power Line Using High Temperature Electronics

NASA Technical Reports Server (NTRS)

Krasowski, Michael J. (Inventor); Prokop, Norman F. (Inventor)

2014-01-01

A high temperature communications circuit includes a power conductor for concurrently conducting electrical energy for powering circuit components and transmitting a modulated data signal, and a demodulator for demodulating the data signal and generating a serial bit stream based on the data signal. The demodulator includes an absolute value amplifier for conditionally inverting or conditionally passing a signal applied to the absolute value amplifier. The absolute value amplifier utilizes no diodes to control the conditional inversion or passing of the signal applied to the absolute value amplifier.

Controlled dehydration improves the diffraction quality of two RNA crystals.

PubMed

Park, HaJeung; Tran, Tuan; Lee, Jun Hyuck; Park, Hyun; Disney, Matthew D

2016-11-03

Post-crystallization dehydration methods, applying either vapor diffusion or humidity control devices, have been widely used to improve the diffraction quality of protein crystals. Despite the fact that RNA crystals tend to diffract poorly, there is a dearth of reports on the application of dehydration methods to improve the diffraction quality of RNA crystals. We use dehydration techniques with a Free Mounting System (FMS, a humidity control device) to recover the poor diffraction quality of RNA crystals. These approaches were applied to RNA constructs that model various RNA-mediated repeat expansion disorders. The method we describe herein could serve as a general tool to improve diffraction quality of RNA crystals to facilitate structure determinations.

An ignored variable: solution preparation temperature in protein crystallization.

PubMed

Chen, Rui-Qing; Lu, Qin-Qin; Cheng, Qing-Di; Ao, Liang-Bo; Zhang, Chen-Yan; Hou, Hai; Liu, Yong-Ming; Li, Da-Wei; Yin, Da-Chuan

2015-01-19

Protein crystallization is affected by many parameters, among which certain parameters have not been well controlled. The temperature at which the protein and precipitant solutions are mixed (i.e., the ambient temperature during mixing) is such a parameter that is typically not well controlled and is often ignored. In this paper, we show that this temperature can influence protein crystallization. The experimental results showed that both higher and lower mixing temperatures can enhance the success of crystallization, which follows a parabolic curve with an increasing ambient temperature. This work illustrates that the crystallization solution preparation temperature is also an important parameter for protein crystallization. Uncontrolled or poorly controlled room temperature may yield poor reproducibility in protein crystallization.

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.

Polycrystalline silicon thin-film transistors with location-controlled crystal grains fabricated by excimer laser crystallization

NASA Astrophysics Data System (ADS)

Tsai, Chun-Chien; Lee, Yao-Jen; Chiang, Ko-Yu; Wang, Jyh-Liang; Lee, I.-Che; Chen, Hsu-Hsin; Wei, Kai-Fang; Chang, Ting-Kuo; Chen, Bo-Ting; Cheng, Huang-Chung

2007-11-01

In this paper, location-controlled silicon crystal grains are fabricated by the excimer laser crystallization method which employs amorphous silicon spacer structure and prepatterned thin films. The amorphous silicon spacer in nanometer-sized width formed using spacer technology is served as seed crystal to artificially control superlateral growth phenomenon during excimer laser irradiation. An array of 1.8-μm-sized disklike silicon grains is formed, and the n-channel thin-film transistors whose channels located inside the artificially-controlled crystal grains exhibit higher performance of field-effect-mobility reaching 308cm2/Vs as compared with the conventional ones. This position-manipulated silicon grains are essential to high-performance and good uniformity devices.

Experiment 3: Zeolite Crystal Growth in Microgravity- The USML-2 Mission

NASA Technical Reports Server (NTRS)

Bac, Nurcan; Warzywoda, Juliusz; Sacco, Albert, Jr.

1998-01-01

The extensive use of zeolites and their impact on the world's economy leads to many efforts to characterize their structure, and to improve the knowledge base for nucleation and growth of these crystals. The Zeolite Crystal Growth (ZCG) experiment on USML-2 aims to enhance the understanding of nucleation and growth of zeolite crystals while attempting to provide a means of controlling the defect concentration in microgravity. Zeolites A, X, Beta, and Silicalite were grown during the 16-day USML-2 mission. The solutions where the nucleation event was controlled yielded larger and more uniform crystals of better morphology and purity than their terrestrial/control counterparts. Space-grown Beta crystals were free of line defects while terrestrial/controls had substantial defects.

Microgravity vibration isolation: An optimal control law for the one-dimensional case

NASA Technical Reports Server (NTRS)

Hampton, Richard D.; Grodsinsky, Carlos M.; Allaire, Paul E.; Lewis, David W.; Knospe, Carl R.

1991-01-01

Certain experiments contemplated for space platforms must be isolated from the accelerations of the platform. An optimal active control is developed for microgravity vibration isolation, using constant state feedback gains (identical to those obtained from the Linear Quadratic Regulator (LQR) approach) along with constant feedforward gains. The quadratic cost function for this control algorithm effectively weights external accelerations of the platform disturbances by a factor proportional to (1/omega) exp 4. Low frequency accelerations are attenuated by greater than two orders of magnitude. The control relies on the absolute position and velocity feedback of the experiment and the absolute position and velocity feedforward of the platform, and generally derives the stability robustness characteristics guaranteed by the LQR approach to optimality. The method as derived is extendable to the case in which only the relative positions and velocities and the absolute accelerations of the experiment and space platform are available.

Microgravity vibration isolation: An optimal control law for the one-dimensional case

NASA Technical Reports Server (NTRS)

Hampton, R. D.; Grodsinsky, C. M.; Allaire, P. E.; Lewis, D. W.; Knospe, C. R.

1991-01-01

Certain experiments contemplated for space platforms must be isolated from the accelerations of the platforms. An optimal active control is developed for microgravity vibration isolation, using constant state feedback gains (identical to those obtained from the Linear Quadratic Regulator (LQR) approach) along with constant feedforward (preview) gains. The quadratic cost function for this control algorithm effectively weights external accelerations of the platform disturbances by a factor proportional to (1/omega)(exp 4). Low frequency accelerations (less than 50 Hz) are attenuated by greater than two orders of magnitude. The control relies on the absolute position and velocity feedback of the experiment and the absolute position and velocity feedforward of the platform, and generally derives the stability robustness characteristics guaranteed by the LQR approach to optimality. The method as derived is extendable to the case in which only the relative positions and velocities and the absolute accelerations of the experiment and space platform are available.

Segregation control in vertical Bridgman crystal growth

NASA Astrophysics Data System (ADS)

Tao, Y.; Kou, S.

1996-11-01

To help the crystal grow at a constant dopant concentration in vertical Bridgman crystal growth, the dopant concentration of the growth melt, i.e. the melt from which the crystal grows, was kept constant. To achieve this, three different methods were used to replenish the growth melt at a controlled rate and suppress dopant diffusion between the growth melt and the replenishing melt. In method one, a replenishing crucible having a long melt passageway was immersed in the growth melt. In method two, a replenishing crucible having an independent feed-rate control mechanism was held above the growth melt. In method three, a submerged diffusion baffle was used to form a long melt passageway between the growth melt and the replenishing melt. NaNO 3 was used as a model material for crystal growth. Single crystals were grown by these three methods with effective segregation control. Method two was applied to InSb and single crystals were also grown with effective segregation control.

Demand Controlled Economizer Cycles: A Direct Digital Control Scheme for Heating, Ventilating, and Air Conditioning Systems,

DTIC Science & Technology

1984-05-01

Control Ignored any error of 1/10th degree or less. This was done by setting the error term E and the integral sum PREINT to zero If then absolute value of...signs of two errors jeq tdiff if equal, jump clr @preint else zero integal sum tdiff mov @diff,rl fetch absolute value of OAT-RAT ci rl,25 is...includes a heating coil and thermostatic control to maintain the air in this path at an elevated temperature, typically around 80 degrees Farenheit (80 F

Crystal growth mechanisms in miarolitic cavities in the Lake George ring complex and vicinity, Colorado

USGS Publications Warehouse

Kile, D.E.; Eberl, D.D.

1999-01-01

The Crystal Peak area of the Pikes Peak batholith, near Lake George in central Colorado, is world-renowned for its crystals of amazonite (the blue-green variety of microcline) and smoky quartz. Such crystals, collected from individual miarolitic pegmatites, have a remakably small variation in crystal size within each pegmatite, and the shapes of plots of their crystal size distributions (CSDs) are invariably lognormal or close to lognormal in all cases. These observations are explained by a crystal growth mechanism that was governed initially by surface-controlled kinetics, during which crystals tended to grow larger in proportion to their size, thereby establishing lognormal CSDs. Surface-controlled growth was followed by longer periods of supply controlled growth, during which growth rate was predominantly size-independent, consequently preserving the lognormal shapes of the CSDs and the small size variation. The change from surface- to supply controlled growth kinetics may have resulted from an increasing demand for nutrients that exceeded diffusion limitations of the system. The proposed model for crystal growth in this locality appears to be common in the geologic record, and can be used with other information, such as isotopic data, to deduce physico-chemical conditions during crystal formation.

Properties of high quality GaP single crystals grown by computer controlled liquid encapsulated Czochralski technique

NASA Astrophysics Data System (ADS)

Kokubun, Y.; Washizuka, S.; Ushizawa, J.; Watanabe, M.; Fukuda, T.

1982-11-01

The properties of GaP single crystals grown by an automatically diameter controlled liquid encapsulated Czochralski technique using a computer have been studied. A dislocation density less than 5×104 cm-2 has been observed for crystal grown in a temperature gradient lower than 70 °C/cm near the solid-liquid interface. Crystals have about 10% higher electron mobility than that of commercially available coracle controlled crystals and have 0.2˜0.5 compensation ratios. Yellow light emitting diodes using computer controlled (100) substrates have shown extremely high external quantum efficiency of 0.3%.

Protein crystal growth in low gravity

NASA Technical Reports Server (NTRS)

Feigelson, Robert S.

1993-01-01

This Final Technical Report for NASA Grant NAG8-774 covers the period from April 27, 1989 through December 31, 1992. It covers five main topics: fluid flow studies, the influence of growth conditions on the morphology of isocitrate lyase crystals, control of nucleation, the growth of lysozyme by the temperature gradient method and graphoepitaxy of protein crystals. The section on fluid flow discusses the limits of detectability in the Schlieren imaging of fluid flows around protein crystals. The isocitrate lyase study compares crystals grown terrestrially under a variety of conditions with those grown in space. The controlling factor governing the morphology of the crystals is the supersaturation. The lack of flow in the interface between the drop and the atmosphere in microgravity causes protein precipitation in the boundary layer and a lowering of the supersaturation in the drop. This lowered supersaturation leads to improved crystal morphology. Preliminary experiments with lysozyme indicated that localized temperature gradients could be used to nucleate crystals in a controlled manner. An apparatus (thermonucleator) was designed to study the controlled nucleation of protein crystals. This apparatus has been used to nucleate crystals of materials with both normal (ice-water, Rochelle salt and lysozyme) and retrograde (horse serum albumin and alpha chymotrypsinogen A) solubility. These studies have lead to the design of an new apparatus that small and more compatible with use in microgravity. Lysozyme crystals were grown by transporting nutrient from a source (lysozyme powder) to the crystal in a temperature gradient. The influence of path length and cross section on the growth rate was demonstrated. This technique can be combined with the thermonucleator to control both nucleation and growth. Graphoepitaxy utilizes a patterned substrate to orient growing crystals. In this study, silicon substrates with 10 micron grooves were used to grow crystals of catalase, lysozyme and canavalin. In all cases, the crystals grew oriented to the substrate. The supersaturation needed for nucleation and growth was lower on the patterned substrates. In some cases, isolated, large crystals were grown.

Fractional order absolute vibration suppression (AVS) controllers

NASA Astrophysics Data System (ADS)

Halevi, Yoram

2017-04-01

Absolute vibration suppression (AVS) is a control method for flexible structures. The first step is an accurate, infinite dimension, transfer function (TF), from actuation to measurement. This leads to the collocated, rate feedback AVS controller that in some cases completely eliminates the vibration. In case of the 1D wave equation, the TF consists of pure time delays and low order rational terms, and the AVS controller is rational. In all other cases, the TF and consequently the controller are fractional order in both the delays and the "rational parts". The paper considers stability, performance and actual implementation in such cases.

Robust control design with real parameter uncertainty using absolute stability theory. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

How, Jonathan P.; Hall, Steven R.

1993-01-01

The purpose of this thesis is to investigate an extension of mu theory for robust control design by considering systems with linear and nonlinear real parameter uncertainties. In the process, explicit connections are made between mixed mu and absolute stability theory. In particular, it is shown that the upper bounds for mixed mu are a generalization of results from absolute stability theory. Both state space and frequency domain criteria are developed for several nonlinearities and stability multipliers using the wealth of literature on absolute stability theory and the concepts of supply rates and storage functions. The state space conditions are expressed in terms of Riccati equations and parameter-dependent Lyapunov functions. For controller synthesis, these stability conditions are used to form an overbound of the H2 performance objective. A geometric interpretation of the equivalent frequency domain criteria in terms of off-axis circles clarifies the important role of the multiplier and shows that both the magnitude and phase of the uncertainty are considered. A numerical algorithm is developed to design robust controllers that minimize the bound on an H2 cost functional and satisfy an analysis test based on the Popov stability multiplier. The controller and multiplier coefficients are optimized simultaneously, which avoids the iteration and curve-fitting procedures required by the D-K procedure of mu synthesis. Several benchmark problems and experiments on the Middeck Active Control Experiment at M.I.T. demonstrate that these controllers achieve good robust performance and guaranteed stability bounds.

An ignored variable: solution preparation temperature in protein crystallization

PubMed Central

Chen, Rui-Qing; Lu, Qin-Qin; Cheng, Qing-Di; Ao, Liang-Bo; Zhang, Chen-Yan; Hou, Hai; Liu, Yong-Ming; Li, Da-Wei; Yin, Da-Chuan

2015-01-01

Protein crystallization is affected by many parameters, among which certain parameters have not been well controlled. The temperature at which the protein and precipitant solutions are mixed (i.e., the ambient temperature during mixing) is such a parameter that is typically not well controlled and is often ignored. In this paper, we show that this temperature can influence protein crystallization. The experimental results showed that both higher and lower mixing temperatures can enhance the success of crystallization, which follows a parabolic curve with an increasing ambient temperature. This work illustrates that the crystallization solution preparation temperature is also an important parameter for protein crystallization. Uncontrolled or poorly controlled room temperature may yield poor reproducibility in protein crystallization. PMID:25597864

Stabilization of a non-aqueous self-double-emulsifying delivery system of rutin by fat crystals and nonionic surfactants: preparation and bioavailability study.

PubMed

Wang, Qiang; Huang, Juan; Hu, Caibiao; Xia, Nan; Li, Tong; Xia, Qiang

2017-07-19

Literature examples of non-aqueous Pickering emulsions stabilized by fat crystals are very rare. Moreover, the applications of rutin are limited due to its low solubility in both water and oils (less than 0.10 mg g -1 and 0.25 mg g -1 , respectively). Thus, herein, we developed an optimum formulation of a non-aqueous self-double-emulsifying delivery system (SDEDS) containing rutin and evaluated its oral bioavailability. The new formulation stabilized by fat crystals (glycerol monostearate, GMS) and nonionic surfactants was prepared via a two-step emulsification process. The presence of a mixture of GMS crystals and nonionic surfactants effectively improves the stability of the emulsions. The non-aqueous SDEDS spontaneously forms oil-in-oil-in-water (O/O/W) double emulsions in the gastrointestinal environment with the inner oil phase mainly containing the active ingredients. It is stable at both 4 °C and 25 °C for 30 days and could enhance the dissolution properties of the active ingredients. Furthermore, the protection of rutin against digestion-mediated precipitation was observed when the formulation contained a high concentration of GMS crystals. The oral absolute bioavailability of rutin obtained from SDEDS (8.62%) is 1.76-fold higher than that of the actives suspension (4.90%). Thus, the non-aqueous SDEDS is an attractive candidate for the encapsulation of water-insoluble and simultaneously oil-insoluble nutrients (such as rutin) and for use in oral delivery applications.

Development of a model for on-line control of crystal growth by the AHP method

NASA Astrophysics Data System (ADS)

Gonik, M. A.; Lomokhova, A. V.; Gonik, M. M.; Kuliev, A. T.; Smirnov, A. D.

2007-05-01

The possibility to apply a simplified 2D model for heat transfer calculations in crystal growth by the axial heat close to phase interface (AHP) method is discussed in this paper. A comparison with global heat transfer calculations with the CGSim software was performed to confirm the accuracy of this model. The simplified model was shown to provide adequate results for the shape of the melt-crystal interface and temperature field in an opaque (Ge) and a transparent crystal (CsI:Tl). The model proposed is used for identification of the growth setup as a control object, for synthesis of a digital controller (PID controller at the present stage) and, finally, in on-line simulations of crystal growth control.

Full-Field Calibration of Color Camera Chromatic Aberration using Absolute Phase Maps.

PubMed

Liu, Xiaohong; Huang, Shujun; Zhang, Zonghua; Gao, Feng; Jiang, Xiangqian

2017-05-06

The refractive index of a lens varies for different wavelengths of light, and thus the same incident light with different wavelengths has different outgoing light. This characteristic of lenses causes images captured by a color camera to display chromatic aberration (CA), which seriously reduces image quality. Based on an analysis of the distribution of CA, a full-field calibration method based on absolute phase maps is proposed in this paper. Red, green, and blue closed sinusoidal fringe patterns are generated, consecutively displayed on an LCD (liquid crystal display), and captured by a color camera from the front viewpoint. The phase information of each color fringe is obtained using a four-step phase-shifting algorithm and optimum fringe number selection method. CA causes the unwrapped phase of the three channels to differ. These pixel deviations can be computed by comparing the unwrapped phase data of the red, blue, and green channels in polar coordinates. CA calibration is accomplished in Cartesian coordinates. The systematic errors introduced by the LCD are analyzed and corrected. Simulated results show the validity of the proposed method and experimental results demonstrate that the proposed full-field calibration method based on absolute phase maps will be useful for practical software-based CA calibration.

Absolute configuration of 2,2',3,3',6-pentachlorinatedbiphenyl (PCB 84) atropisomers.

PubMed

Li, Xueshu; Parkin, Sean R; Lehmler, Hans-Joachim

2017-05-23

Nineteen polychlorinated biphenyl (PCB) congeners, such as 2,2',3,3',6-pentachlorobiphenyl (PCB 84), display axial chirality because they form stable rotational isomers, or atropisomers, that are non-superimposable mirror images of each other. Although chiral PCBs undergo atropselective biotransformation and atropselectively alter biological processes, the absolute structure of only a few PCB atropisomers has been determined experimentally. To help close this knowledge gap, pure PCB 84 atropisomers were obtained by semi-preparative liquid chromatography with two serially connected Nucleodex β-PM columns. The absolute configuration of both atropisomers was determined by X-ray single-crystal diffraction. The PCB 84 atropisomer eluting first and second on the Nucleodex β-PM column correspond to (aR)-(-)-PCB 84 and (aS)-(+)-PCB 84, respectively. Enantioselective gas chromatographic analysis with the β-cyclodextrin-based CP-Chirasil-Dex CB gas chromatography column showed the same elution order as the Nucleodex β-PM column. Based on earlier reports, the atropisomers eluting first and second on the BGB-172 gas chromatography column are (aR)-(-)-PCB 84 and (aS)-(+)-PCB 84, respectively. An inversion of the elution order is observed on the Cyclosil-B gas chromatography and Cellulose-3 liquid chromatography columns. These results advance the interpretation of environmental and human biomonitoring as well as toxicological studies.

German Views of Irregular Warfare

DTIC Science & Technology

2015-06-01

closely observed much of the Napoleonic Wars (1803–1815). His military experiences occurred during the end of the Age of Absolutism10 in Europe when...10 The Age of Absolutism refers to a period when absolute monarchs controlled much of Europe and is commonly considered to...concluded with a chapter related to irregular warfare and the nuclear age and an appendix dedicated to the training notes of the famed English

Tracking the evolution of a giant magmatic system from assembly to supereruption

NASA Astrophysics Data System (ADS)

Wotzlaw, J. F.; Schaltegger, U.; Frick, D. A.; Dungan, M. A.; Gerdes, A.; Günther, D.

2012-12-01

The chemical and physical characteristics of large magma bodies prior to eruption are closely related consequences of the balance between the rate of magma influx and the rate of cooling. The products of caldera-related silicic supereruptions, and less voluminous associated precursor and post-caldera activity preserve information about the thermal and chemical states of the system at the moment of evacuation of the magma chamber. Numerous studies of the Oligocene Fish Canyon Tuff (5000 km3; Colorado, USA) and related eruptive products of the La Garita caldera have addressed the origin and evolution of large-volume crystal-rich magmas. We use the presence of zircon in all eruptive products of the Fish Canyon magmatic system to gain a high-resolution geochronologic control on the thermal evolution of the magmatic system by using the trace element composition of U-Pb dated zircons as a proxy for magma crystallinity. New analytical protocols permit to obtain age, chemical and isotopic information from the exact same volume of single zircons (Schoene et al., 2010, GCA) allowing us to trace magma crystallinity as a function of time. Zircon U-Pb dates record ~400,000 years of crystallization. Variations in trace element composition in U-Pb dated zircons can be attributed to trace element fractionation imposed by co-crystallization of titanite. Due to the relatively high modal abundance of titanite in Fish Canyon magma and the extreme compatibility of the rare earth elements (REE) in this phase, titanite is the major control on many trace element concentrations and ratios (e.g. Yb/Dy) in coexisting zircons via varying degrees of depletion of these elements in the host melt. Modeling of compositional variations as a result of fractional crystallization suggests that the range of zircon compositions can be explained by 50-70% crystallization of a fractionating assemblage containing 0.4-0.8 vol.% titanite. The period of cooling centered around 28.4 Ma and is marked by an apparent crystallinity that is ~30% higher than at the time of eruption, implying that the Fish Canyon magma was perilously close to complete solidification, hence 'plutonic death', prior to late reheating. We estimate the duration of the reheating event from the age difference of the chemically most evolved (highest Yb/Dy) and the youngest dated zircon to be ~170 ka. This duration for reactivation of the near solidus crystal mush is in excellent agreement with estimates derived from numerical modeling of remelting by upward percolation of a hot gas-phase derived from underplated mafic magma ('gas sparging'; Bachmann and Bergantz, 2003, Geology). This investigation, which is the first in which high resolution U-Pb zircon geochronology has been coupled with geochemical modeling of systematic compositional variations in an accessory mineral, ties together many of the threads which have been developed independently during previous studies of the Fish Canyon magmatic system and places related petrogenetic processes into an absolute time frame.

Multiple electrokinetic actuators for feedback control of colloidal crystal size.

PubMed

Juárez, Jaime J; Mathai, Pramod P; Liddle, J Alexander; Bevan, Michael A

2012-10-21

We report a feedback control method to precisely target the number of colloidal particles in quasi-2D ensembles and their subsequent assembly into crystals in a quadrupole electrode. Our approach relies on tracking the number of particles within a quadrupole electrode, which is used in a real-time feedback control algorithm to dynamically actuate competing electrokinetic transport mechanisms. Particles are removed from the quadrupole using DC-field mediated electrophoretic-electroosmotic transport, while high-frequency AC-field mediated dielectrophoretic transport is used to concentrate and assemble colloidal crystals. Our results show successful control of the size of crystals containing 20 to 250 colloidal particles with less than 10% error. Assembled crystals are characterized by their radius of gyration, crystallinity, and number of edge particles, and demonstrate the expected size-dependent properties. Our findings demonstrate successful ensemble feedback control of the assembly of different sized colloidal crystals using multiple actuators, which has broad implications for control over nano- and micro- scale assembly processes involving colloidal components.

TES-Based Light Detectors for the CRESST Direct Dark Matter Search

NASA Astrophysics Data System (ADS)

Rothe, J.; Angloher, G.; Bauer, P.; Bento, A.; Bucci, C.; Canonica, L.; D'Addabbo, A.; Defay, X.; Erb, A.; Feilitzsch, F. v.; Ferreiro Iachellini, N.; Gorla, P.; Gütlein, A.; Hauff, D.; Jochum, J.; Kiefer, M.; Kluck, H.; Kraus, H.; Lanfranchi, J.-C.; Langenkämper, A.; Loebell, J.; Mancuso, M.; Mondragon, E.; Münster, A.; Pagliarone, C.; Petricca, F.; Potzel, W.; Pröbst, F.; Puig, R.; Reindl, F.; Schäffner, K.; Schieck, J.; Schipperges, V.; Schönert, S.; Seidel, W.; Stahlberg, M.; Stodolsky, L.; Strandhagen, C.; Strauss, R.; Tanzke, A.; Trinh Thi, H. H.; Türkoğlu, C.; Ulrich, A.; Usherov, I.; Wawoczny, S.; Willers, M.; Wüstrich, M.

2018-05-01

The CRESST experiment uses cryogenic detectors based on transition-edge sensors to search for dark matter interactions. Each detector module consists of a scintillating CaWO_4 crystal and a silicon-on-sapphire (SOS) light detector which operate in coincidence (phonon-light technique). The 40-mm-diameter SOS disks (2 g mass) used in the data taking campaign of CRESST-II Phase 2 (2014-2016) reached absolute baseline resolutions of σ = 4-7 eV. This is the best performance reported for cryogenic light detectors of this size. Newly developed silicon beaker light detectors (4 cm height, 4 cm diameter, 6 g mass), which cover a large fraction of the target crystal surface, have achieved a baseline resolution of σ = 5.8 eV. First results of further improved light detectors developed for the ongoing low-threshold CRESST-III experiment are presented.

Comparative Study of the Magnetoelectric Effect in HoAl3(BO3)4 and HoGa3(BO3)4 Single Crystals

NASA Astrophysics Data System (ADS)

Freidman, A. L.; Dubrovskii, A. A.; Temerov, V. L.; Gudim, I. A.

2018-03-01

The comparative study of the magnetoelectric properties and magnetostriction of HoGa3(BO3)4 and HoAl3(BO3)4 single crystals has been carried out. The investigated compounds exhibit qualitatively similar magnetodielectric and inverse magnetoelectric ME E effects with the close absolute values, which is indicative of the weak effect of a nonmagnetic metal ion. On the contrary, the magnetostriction of the galloborate has been found to be threefold higher than that of the alumoborate. In addition, the difference between the qualitative behaviors of magnetostriction has been established: the magnetic-field dependence of magnetostriction for the alumoborate has the maximum near 70 kOe at T = 4.2 K, while the galloborate magnetostriction has no maximum and does not saturate in a field of 140 kOe.

Optical phonon behavior of columbite MgNb2O6 single crystals

NASA Astrophysics Data System (ADS)

Xu, Dapeng; Liu, Wenqiang; Zhou, Qiang; Cui, Tian; Yuan, Hongming; Wang, Wenquan; Liu, Ying; Shi, Zhan; Li, Liang

2014-08-01

To explore potential applications, MgNb2O6 single crystal grown previously by optical floating zone method was used as a prototype for optical phonon behavior investigation. Polarized Raman spectra obtained in adequate parallel and crossed polarization were presented. All the obtained Raman modes were identified for the MgNb2O6, in good agreement with previous theory analysis. The selection rules of Raman for the columbite group were validated. Additionally, in-site temperature-dependent Raman spectra of MgNb2O6 were also investigated in the range from 83 to 803 K. The strong four Ag phonon modes all exhibits red shift with the temperature increasing. But thermal expansion of spectra is sectional linear with inflection points at about 373 K. And the absolute value of dω/dT at high temperature is higher than the one at lower temperature.

Research on spectrum broadening covering visible light of a fiber femtosecond optical frequency comb for absolute frequency measurement

NASA Astrophysics Data System (ADS)

Xing, Shuai; Wu, Tengfei; Li, Shuyi; Xia, Chuanqing; Han, Jibo; Zhang, Lei; Zhao, Chunbo

2018-03-01

As a bridge connecting microwave frequency and optical frequency, femtosecond laser has important significance in optical frequency measurement. Compared with the traditional Ti-sapphire femtosecond optical frequency comb, with the advantages of compact structure, strong anti-interference ability and low cost, the fiber femtosecond optical frequency comb has a wider application prospect. An experiment of spectrum broadening in a highly nonlinear photonic crystal fiber pumped by an Er-fiber mode-locked femtosecond laser is studied in this paper. Based on optical amplification and frequency doubling, the central wavelength of the output spectrum is 780nm and the average power is 232mW. With the femtosecond pulses coupled into two different photonic crystal fibers, the coverage of visible spectrum is up to 500nm-960nm. The spectral shape and width can be optimized by changing the polarization state for satisfying the requirments of different optical frequencies measurement.

Crystal structure of (1S,2S,2′R,3a′S,5R)-2′-[(5-bromo-1H-indol-3-yl)meth­yl]-2-isopropyl-5,5′-dimethyl­dihydro-2′H-spiro­[cyclo­hexane-1,6′-imidazo[1,5-b]isoxazol]-4′(5′H)-one

PubMed Central

Ghannay, Siwar; Brahmi, Jihed; Nasri, Soumaya; Aouadi, Kaïss; Jeanneau, Erwann; Msaddek, Moncef

2016-01-01

In the title compound, C24H32BrN3O2, the six-membered cyclo­hexane ring adopts a chair conformation and the isoxasolidine ring adopts a twisted conformation. The mol­ecule has five chiral centres and the absolute configuration has been determined in this analysis. The mol­ecular structure is stabilized by weak intra­molecular C—H⋯O and C—H⋯N contacts. In the crystal, mol­ecules are linked by N—H⋯N and C—H⋯O hydrogen bonds, forming undulating sheets parallel to the bc plane. PMID:27536387

Apparatus for mounting crystal

DOEpatents

Longeway, Paul A.

1985-01-01

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

Phase equilibrium and preparation, crystallization and viscous sintering of glass in the alumina-silica-lanthanum phosphate system

NASA Astrophysics Data System (ADS)

He, Feng

The phase equilibrium, viscosity of melt-quenched glasses, and processing of sol-gel glasses of the alumina-silica-lanthanum phosphate system were studied. These investigations were directed towards serving the objective of synthesizing nano-structured ceramic-matrix-composites via controlled crystallization of glass precursors. The thermal stability, phase equilibrium, and liquidus temperatures of the alumina- and mullite-lanthanum phosphate systems are determined. An iridium wire heater was constructed to anneal samples up to 2200°C. Phosphorus evaporation losses were significant at high temperatures, especially over 1800°C. The tentative phase diagrams of the two quasi-binary systems were presented. The viscosity of the melt-quenched mullite-lanthanum phosphate glasses was measured by three different methods, including viscous sintering of glass powder compacts, neck formation between two Frenkel glass beads, and thermal analysis of the glass transition. Improved methodologies were developed for applying the interpretative mathematical models to the results of the sintered powder and thermal analytical experiments. Good agreement was found between all three methods for both absolute values and temperature dependence. A sol-gel process was developed as a low temperature route to producing glasses. A unique, single phase mullite gel capable of low temperature (575°C) mullitization was made from tetraethoxysilane and aluminum isopropoxide at room temperature in three days. Low temperature crystallization was attributed to the avoidance of phase segregation during gel formation and annealing. This was greatly enhanced by a combination of low temperature preheating in the amorphous state, a high heating rate during crystallization and low water content. The Al2O3 content in mullite (61-68 mol%) depended on the highest annealing temperature. Two mullite-lanthanum phosphate gels were made based upon modifying the chemical procedures used for the homogeneous single phase and heterogeneous diphasic mullite gels from same starting chemicals. Amorphous powders were obtained after optimized calcinations. Their different crystallization routes and sintering behavior were investigated and correlated with the different homogeneities of precursor gels. Structurally stable open, porous ceramics (up to 80% porosity) were produced from the single-phase gel derived powder, where gases exsolved during calcination caused foaming coincident with sintering. Translucent, dense glass ceramic was made from the calcined diphasic gel by hot-pressing.

Absolute colorimetric characterization of a DSLR camera

NASA Astrophysics Data System (ADS)

Guarnera, Giuseppe Claudio; Bianco, Simone; Schettini, Raimondo

2014-03-01

A simple but effective technique for absolute colorimetric camera characterization is proposed. It offers a large dynamic range requiring just a single, off-the-shelf target and a commonly available controllable light source for the characterization. The characterization task is broken down in two modules, respectively devoted to absolute luminance estimation and to colorimetric characterization matrix estimation. The characterized camera can be effectively used as a tele-colorimeter, giving an absolute estimation of the XYZ data in cd=m2. The user is only required to vary the f - number of the camera lens or the exposure time t, to better exploit the sensor dynamic range. The estimated absolute tristimulus values closely match the values measured by a professional spectro-radiometer.

Cosmic ray production rates of Be-10 and Al-26 in quartz from glacially polished rocks

NASA Technical Reports Server (NTRS)

Nishiizumi, K.; Kohl, C. P.; Winterer, E. L.; Klein, J.; Middleton, R.

1989-01-01

The concentrations of Be-10 and Al-26 in quartz crystals extracted from glacially polished granitic surfaces from the Sierra Nevada range are studied. These surfaces are identified with the glacial advance during the Tioga period about 11,000 yr ago. The measurements yield the most accurate estimates to date for the absolute production rates of three nuclides in SiO2 due to cosmic ray nucleons and muons for geomagnetic latitudes 43.8-44.6 N and altitudes 2.1-3.6 km.

Three New Indole Diterpenoids from the Sea-Anemone-Derived Fungus Penicillium sp. AS-79.

PubMed

Hu, Xue-Yi; Meng, Ling-Hong; Li, Xin; Yang, Sui-Qun; Li, Xiao-Ming; Wang, Bin-Gui

2017-05-12

Three new indolediterpenoids, namely, 22-hydroxylshearinine F ( 1 ), 6-hydroxylpaspalinine ( 2 ), and 7- O -acetylemindole SB ( 3 ), along with eight related known analogs ( 4 - 11 ), were isolated from the sea-anemone-derived fungus Penicillium sp. AS-79. The structures and relative configurations of these compounds were determined by a detailed interpretation of the spectroscopic data, and their absolute configurations were determined by ECD calculations ( 1 and 2 ) and single-crystal X-ray diffraction ( 3 ). Some of these compounds exhibited prominent activity against aquatic and human pathogenic microbes.

(M)- and (P)-bicelaphanol A, dimeric trinorditerpenes with promising neuroprotective activity from Celastrus orbiculatus.

PubMed

Wang, Luo-Yi; Wu, Jian; Yang, Zhuo; Wang, Xu-Jie; Fu, Yan; Liu, Shuang-Zhu; Wang, Hong-Min; Zhu, Wei-Liang; Zhang, Hai-Yan; Zhao, Wei-Min

2013-04-26

(M)-Bicelaphanol A (1) and (P)-bicelaphanol A (2), two unprecedented dimeric trinorditerpenes existing as atropisomers, together with their monomer celaphanol A (3), were isolated from the root bark of Celastrus orbiculatus. The structures and absolute configurations of 1 and 2 were determined by spectroscopic and single-crystal X-ray diffraction analyses. Compound 1 exhibited a significant in vitro neuroprotective effect against a hydrogen peroxide-induced cell viability decrease in PC12 cells at 1 μM, while compounds 2 and 3 showed such effects at 10 μM.

Third law of thermodynamics in the presence of a heat flux

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

Camacho, J.

1995-01-01

Following a maximum entropy formalism, we study a one-dimensional crystal under a heat flux. We obtain the phonon distribution function and evaluate the nonequilibrium temperature, the specific heat, and the entropy as functions of the internal energy and the heat flux, in both the quantum and the classical limits. Some analogies between the behavior of equilibrium systems at low absolute temperature and nonequilibrium steady states under high values of the heat flux are shown, which point to a possible generalization of the third law in nonequilibrium situations.

Optical characterization of Nd (3+):AgBr.

PubMed

Bunimovich, D; Nagli, L; Katzir, A

1997-10-20

The luminescence of silver bromide crystals, doped with neodymium, was investigated over the visible and near-infrared spectral ranges. The emission, excitation, and absorption spectra were measured over a broad temperature range. The absolute luminescence quantum yield was estimated by comparing the luminescence with that of a neodymium-doped phosphate glass, for which the manufacturer gives a value of 0.4. The Judd-Ofelt analysis was applied to both materials, and transition rates, branching ratios, and quantum efficiencies were calculated for all the observed bands. Good agreement was obtained between theory and experiment.

Rare-Earth Ion-Host Lattice Interactions: 15. Analysis of the Spectra of Nd3+ in Gd3Sc2Ga3O12.

DTIC Science & Technology

1984-05-01

Luminescence of Cr3+ Ions in Gadolinium Gallium and Gadolinium Scandium Gallium Garnet CT’stals, Soy. J. Quant. Electron. 12 (1982), 1124. 6M. Dutoit, J. C...Shcherbakov, Absolute Quantum Efficiency of the Luminescence of Cr3+ Ions in Gadolinium Gallium and Gadolinium Scandium Gallium Garnet Crystals, Soy. J...HDL Project: 324332 19. KEY WORDS (Continue on reverse side it necessary end Identify by block number) Rare earth Mixed garnet Spectra Laser Judd-Ofelt

Absolutely relative or relatively absolute: violations of value invariance in human decision making.

PubMed

Teodorescu, Andrei R; Moran, Rani; Usher, Marius

2016-02-01

Making decisions based on relative rather than absolute information processing is tied to choice optimality via the accumulation of evidence differences and to canonical neural processing via accumulation of evidence ratios. These theoretical frameworks predict invariance of decision latencies to absolute intensities that maintain differences and ratios, respectively. While information about the absolute values of the choice alternatives is not necessary for choosing the best alternative, it may nevertheless hold valuable information about the context of the decision. To test the sensitivity of human decision making to absolute values, we manipulated the intensities of brightness stimuli pairs while preserving either their differences or their ratios. Although asked to choose the brighter alternative relative to the other, participants responded faster to higher absolute values. Thus, our results provide empirical evidence for human sensitivity to task irrelevant absolute values indicating a hard-wired mechanism that precedes executive control. Computational investigations of several modelling architectures reveal two alternative accounts for this phenomenon, which combine absolute and relative processing. One account involves accumulation of differences with activation dependent processing noise and the other emerges from accumulation of absolute values subject to the temporal dynamics of lateral inhibition. The potential adaptive role of such choice mechanisms is discussed.

Positioning and joining of organic single-crystalline wires

PubMed Central

Wu, Yuchen; Feng, Jiangang; Jiang, Xiangyu; Zhang, Zhen; Wang, Xuedong; Su, Bin; Jiang, Lei

2015-01-01

Organic single-crystal, one-dimensional materials can effectively carry charges and/or excitons due to their highly ordered molecule packing, minimized defects and eliminated grain boundaries. Controlling the alignment/position of organic single-crystal one-dimensional architectures would allow on-demand photon/electron transport, which is a prerequisite in waveguides and other optoelectronic applications. Here we report a guided physical vapour transport technique to control the growth, alignment and positioning of organic single-crystal wires with the guidance of pillar-structured substrates. Submicrometre-wide, hundreds of micrometres long, highly aligned, organic single-crystal wire arrays are generated. Furthermore, these organic single-crystal wires can be joined within controlled angles by varying the pillar geometries. Owing to the controllable growth of organic single-crystal one-dimensional architectures, we can present proof-of-principle demonstrations utilizing joined wires to allow optical waveguide through small radii of curvature (internal angles of ~90–120°). Our methodology may open a route to control the growth of organic single-crystal one-dimensional materials with potential applications in optoelectronics. PMID:25814032

The control of ice crystal growth and effect on porous structure of konjac glucomannan-based aerogels.

PubMed

Ni, Xuewen; Ke, Fan; Xiao, Man; Wu, Kao; Kuang, Ying; Corke, Harold; Jiang, Fatang

2016-11-01

Konjac glucomannan (KGM)-based aerogels were prepared using a combination of sol-gel and freeze-drying methods. Preparation conditions were chosen to control ice crystal growth and aerogel structure formation. The ice crystals formed during pre-freezing were observed by low temperature polarizing microscopy, and images of aerogel pores were obtained by scanning electron microscopy. The size of ice crystals were calculated and size distribution maps were drawn, and similarly for aerogel pores. Results showed that ice crystal growth and aerogel pore sizes may be controlled by varying pre-freezing temperatures, KGM concentration and glyceryl monostearate concentration. The impact of pre-freezing temperatures on ice crystal growth was explained as combining ice crystal growth rate with nucleation rate, while the impacts of KGM and glyceryl monostearate concentration on ice crystal growth were interpreted based on their influences on sol network structure. Copyright © 2016 Elsevier B.V. All rights reserved.

Controlling Vapor Pressure In Hanging-Drop Crystallization

NASA Technical Reports Server (NTRS)

Carter, Daniel C.; Smith, Robbie

1988-01-01

Rate of evaporation adjusted to produce larger crystals. Device helps to control vapor pressure of water and other solvents in vicinity of hanging drop of solution containing dissolved enzyme protein. Well of porous frit (sintered glass) holds solution in proximity to drop of solution containing protein or enzyme. Vapor from solution in frit controls evaporation of solvent from drop to control precipitation of protein or enzyme. With device, rate of nucleation limited to decrease number and increase size (and perhaps quality) of crystals - large crystals of higher quality needed for x-ray diffraction studies of macromolecules.

LiCoO2 Concaved Cuboctahedrons from Symmetry-Controlled Topological Reactions

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

Chen, H.; Wu, L.; Zhang, L.

2011-01-19

Morphology control of functional materials is generally performed by controlling the growth rates on selected orientations or faces. Here, we control particle morphology by 'crystal templating': by choosing appropriate precursor crystals and reaction conditions, we demonstrate that a material with rhombohedral symmetry - namely the layered, positive electrode material, LiCoO{sub 2} - can grow to form a quadruple-twinned crystal with overall cubic symmetry. The twinned crystals show an unusual, concaved-cuboctahedron morphology, with uniform particle sizes of 0.5-2 {micro}m. On the basis of a range of synthetic and analytical experiments, including solid-state NMR, X-ray powder diffraction analysis and HRTEM, we proposemore » that these twinned crystals form via selective dissolution and an ion-exchange reaction accompanied by oxidation of a parent crystal of CoO, a material with cubic symmetry. This template crystal serves to nucleate the growth of four LiCoO{sub 2} twin crystals and to convert a highly anisotropic, layered material into a pseudo-3-dimensional, isotropic material.« less

In-situ and real-time growth observation of high-quality protein crystals under quasi-microgravity on earth.

PubMed

Nakamura, Akira; Ohtsuka, Jun; Kashiwagi, Tatsuki; Numoto, Nobutaka; Hirota, Noriyuki; Ode, Takahiro; Okada, Hidehiko; Nagata, Koji; Kiyohara, Motosuke; Suzuki, Ei-Ichiro; Kita, Akiko; Wada, Hitoshi; Tanokura, Masaru

2016-02-26

Precise protein structure determination provides significant information on life science research, although high-quality crystals are not easily obtained. We developed a system for producing high-quality protein crystals with high throughput. Using this system, gravity-controlled crystallization are made possible by a magnetic microgravity environment. In addition, in-situ and real-time observation and time-lapse imaging of crystal growth are feasible for over 200 solution samples independently. In this paper, we also report results of crystallization experiments for two protein samples. Crystals grown in the system exhibited magnetic orientation and showed higher and more homogeneous quality compared with the control crystals. The structural analysis reveals that making use of the magnetic microgravity during the crystallization process helps us to build a well-refined protein structure model, which has no significant structural differences with a control structure. Therefore, the system contributes to improvement in efficiency of structural analysis for "difficult" proteins, such as membrane proteins and supermolecular complexes.

Compound semi-conductors and controlled doping thereof

NASA Technical Reports Server (NTRS)

Larkin, David J. (Inventor); Neudeck, Philip G. (Inventor); Powell, J. Anthony (Inventor); Matus, Lawrence G. (Inventor)

1998-01-01

A method of controlling the amount of impurity incorporation in a crystal grown by a chemical vapor deposition process. Conducted in a growth chamber, the method includes the controlling of the concentration of the crystal growing components in the growth chamber to affect the demand of particular growth sites within the growing crystal thereby controlling impurity incorporation into the growth sites.

Vermistatin derivatives with α-glucosidase inhibitory activity from the mangrove endophytic fungus Penicillium sp. HN29-3B1.

PubMed

Liu, Yayue; Xia, Guoping; Li, Hanxiang; Ma, Lin; Ding, Bo; Lu, Yongjun; He, Lei; Xia, Xuekui; She, Zhigang

2014-07-01

Three new vermistatin derivatives, 6-demethylpenisimplicissin (1), 5'-hydroxypenisimplicissin (2), and 2''-epihydroxydihydrovermistatin (3), along with five known vermistatin analogues, methoxyvermistatin (4), vermistatin (5), 6-demethylvermistatin (6), hydroxyvermistatin (7), and penisimplicissin (8), were isolated from the culture of the mangrove endophytic fungus Penicillium sp. HN29-3B1 from Cerbera manghas. Their structures were elucidated mainly by nuclear magnetic resonance spectroscopy. The absolute configurations of compounds 1 and 2 were deduced on the basis of circular dichroism data. The absolute structures of compounds 3 and 5 were confirmed by a single-crystal X-ray diffraction experiment using Cu Kα radiation. In the bioactivity assay, compounds 1 and 3 exhibited α-glucosidase inhibitory activity with IC50 values of 9.5 ± 1.2 and 8.0 ± 1.5 µM, respectively. The plausible biosynthetic pathways for all compounds are discussed. Georg Thieme Verlag KG Stuttgart · New York.

Chrodrimanins K-N and Related Meroterpenoids from the Fungus Penicillium sp. SCS-KFD09 Isolated from a Marine Worm, Sipunculus nudus.

PubMed

Kong, Fan-Dong; Ma, Qing-Yun; Huang, Sheng-Zhuo; Wang, Pei; Wang, Jun-Feng; Zhou, Li-Man; Yuan, Jing-Zhe; Dai, Hao-Fu; Zhao, You-Xing

2017-04-28

Six new meroterpenoids, chrodrimanins K-N (1-4), including two uncommon chlorinated ones (1 and 2), and verruculides B2 (5) and B3 (6), as well as seven known ones (7-13), were isolated from the fermentation broth of Penicillium sp. SCS-KFD09 isolated from a marine worm, Sipunculus nudus, from Haikou Bay, China. The structures including the absolute configurations of the new compounds were unambiguously elucidated by spectroscopic data, X-ray diffraction analysis, and ECD spectra analysis along with quantum ECD calculations. In addition, the X-ray crystal structures and absolute configurations of two previously reported meroterpenoids, chrodrimanins F (9) and A (11), are described for the first time. Compounds 1, 4, and 7 displayed anti-H1N1 activity with IC 50 values of 74, 58, and 34 μM, respectively, while compound 5 showed weak inhibitory activity against Staphylococcus aureus with an MIC of 32 μg/mL.

Redetermined structure, inter-molecular inter-actions and absolute configuration of royleanone.

PubMed

Fun, Hoong-Kun; Chantrapromma, Suchada; Salae, Abdul Wahab; Razak, Ibrahim Abdul; Karalai, Chatchanok

2011-05-01

The structure of the title diterpenoid, C(20)H(28)O(3), {systematic name: (4bS,8aS)-3-hy-droxy-2-isopropyl-4b,8,8-trimethyl-4b,5,6,7,8,8a,9,10-octa-hydro-phenanthrene-1,4-dione} is confirmed [Eugster et al. (1993 ▶). Private communication (refcode HACGUN). CCDC, Union Road, Cambridge] and its packing is now described. Its absolute structure was established by refinement against data collected with Cu radiation: the two stereogenic centres both have S configurations. One cyclo-hexane ring adopts a chair conformation whereas the other cyclo-hexane ring is in a half-chair conformation and the benzoquinone ring is slightly twisted. An intra-molecular O-H⋯O hydrogen bond generates an S(5) ring motif. In the crystal, mol-ecules are linked into chains along [010] by O-H⋯O hydrogen bonds and weak C-H⋯O inter-actions. The packing also features C⋯O [3.131 (3) Å] short contacts.

Imaging System For Measuring Macromolecule Crystal Growth Rates in Microgravity

NASA Technical Reports Server (NTRS)

Corder, Eric L.; Briscoe, Jeri

2004-01-01

In order to determine how macromolecule crystal quality improvement in microgravity is related to crystal growth characteristics, a team of scientists and engineers at NASA's Marshal Space Flight Center (MSFC) developed flight hardware capable of measuring the crystal growth rates of a population of crystals growing under the same conditions. As crystal growth rate is defined as the change or delta in a defined dimension or length (L) of crystal over time, the hardware was named Delta-L. Delta-L consists of three sub assemblies: a fluid unit including a temperature-controlled growth cell, an imaging unit, and a control unit (consisting of a Data Acquisition and Control Unit (DACU), and a thermal control unit). Delta-L will be used in connection with the Glovebox Integrated Microgravity Isolation Technology (g-LIMIT) inside the Microgravity Science Glovebox (MSG), onboard the International Space Station. This paper will describe the Delta-L imaging system. The Delta-L imaging system was designed to locate, resolve, and capture images of up to 10 individual crystals ranging in size from 10 to 500 microns with a point-to-point accuracy of +/- 2.0 microns within a quartz growth cell observation area of 20 mm x 10 mm x 1 mm. The optical imaging system is comprised of a video microscope camera mounted on computer controlled translation stages. The 3-axis translation stages and control units provide crewmembers the ability to search throughout the growth cell observation area for crystals forming in size of approximately 10 microns. Once the crewmember has selected ten crystals of interest, the growth of these crystals is tracked until the size reaches approximately 500 microns. In order to resolve these crystals an optical system with a magnification of 10X was designed. A black and white NTSC camera was utilized with a 20X microscope objective and a 0.5X custom designed relay lens with an inline light to meet the magnification requirement. The design allows a 500 pm crystal to be viewed in the vertical dimension on a standard NTSC monitor (4:3 aspect ratio). Images of the 10 crystals are collected periodically and stored in sets by the DACU.

Chitosan-Assisted Crystallization and Film Forming of Perovskite Crystals through Biomineralization.

PubMed

Yang, Yang; Sun, Chen; Yip, Hin-Lap; Sun, Runcang; Wang, Xiaohui

2016-03-18

Biomimetic mineralization is a powerful approach for the synthesis of advanced composite materials with hierarchical organization and controlled structure. Herein, chitosan was introduced into a perovskite precursor solution as a biopolymer additive to control the crystallization and to improve the morphology and film-forming properties of a perovskite film by way of biomineralization. The biopolymer additive was able to control the size and morphology of the perovskite crystals and helped to form smooth films. The mechanism of chitosan-mediated nucleation and growth of the perovskite crystals was explored. As a possible application, the chitosan-perovskite composite film was introduced into a planar heterojunction solar cell and increased power conversion efficiency relative to that observed for the pristine perovskite film was achieved. The biomimetic mineralization method proposed in this study provides an alternative way of preparing perovskite crystals with well-controlled morphology and properties and extends the applications of perovskite crystals in photoelectronic fields, including planar-heterojunction solar cells. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Survey of predictors of propensity for protein production and crystallization with application to predict resolution of crystal structures

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

Gao, Jianzhao; Wu, Zhonghua; Hu, Gang

Selection of proper targets for the X-ray crystallography will benefit biological research community immensely. Several computational models were proposed to predict propensity of successful protein production and diffraction quality crystallization from protein sequences. We reviewed a comprehensive collection of 22 such predictors that were developed in the last decade. We found that almost all of these models are easily accessible as webservers and/or standalone software and we demonstrated that some of them are widely used by the research community. We empirically evaluated and compared the predictive performance of seven representative methods. The analysis suggests that these methods produce quite accuratemore » propensities for the diffraction-quality crystallization. We also summarized results of the first study of the relation between these predictive propensities and the resolution of the crystallizable proteins. We found that the propensities predicted by several methods are significantly higher for proteins that have high resolution structures compared to those with the low resolution structures. Moreover, we tested a new meta-predictor, MetaXXC, which averages the propensities generated by the three most accurate predictors of the diffraction-quality crystallization. MetaXXC generates putative values of resolution that have modest levels of correlation with the experimental resolutions and it offers the lowest mean absolute error when compared to the seven considered methods. We conclude that protein sequences can be used to fairly accurately predict whether their corresponding protein structures can be solved using X-ray crystallography. Moreover, we also ascertain that sequences can be used to reasonably well predict the resolution of the resulting protein crystals.« less

Control of Protein Crystal Nucleation and Growth Using Stirring Solution

NASA Astrophysics Data System (ADS)

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

2004-11-01

We have previously developed a protein crystallization technique using a stirring protein solution and revealed that (i) continuous stirring prevents excess spontaneous nucleation and accelerates the growth of protein crystals and (ii) prestirring (solution stirring in advance) promotes the crystal nucleation of hen egg-white lysozyme. In bovine adenosine deaminase (ADA) crystallization, continuous stirring improves the crystal quality but elongates the nucleation time. In this paper, in order to control both the crystal nucleation and growth of ADA using a Micro-Stirring technique, we carried out five different stirring patterns such as (i) no stirring, (ii) continuous stirring, (iii) prestirring, (iv) poststirring (stirring late in the growth period) and (v) restirring (combined pre- and poststirring). The results showed that high-quality well-shaped crystals were obtained under the continuous stirring and restirring conditions and the nucleation time under the prestirring and restirring conditions was shorter than that under the continuous stirring and poststirring conditions. Consequently, high-quality crystals were promptly obtained under the restirring condition. These results suggest that we are able to control both the nucleation and growth of protein crystals with the stirring techniques.

Controlling Second Harmonic Efficiency of Laser Beam Interactions

NASA Technical Reports Server (NTRS)

Barnes, Norman P. (Inventor); Walsh, Brian M. (Inventor); Reichle, Donald J. (Inventor)

2011-01-01

A method is provided for controlling second harmonic efficiency of laser beam interactions. A laser system generates two laser beams (e.g., a laser beam with two polarizations) for incidence on a nonlinear crystal having a preferred direction of propagation. Prior to incidence on the crystal, the beams are optically processed based on the crystal's beam separation characteristics to thereby control a position in the crystal along the preferred direction of propagation at which the beams interact.

Identification and control of a multizone crystal growth furnace

NASA Technical Reports Server (NTRS)

Batur, C.; Sharpless, R. B.; Duval, W. M. B.; Rosenthal, B. N.; Singh, N. B.

1992-01-01

This paper presents an intelligent adaptive control system for the control of a solid-liquid interface of a crystal while it is growing via directional solidification inside a multizone transparent furnace. The task of the process controller is to establish a user-specified axial temperature profile and to maintain a desirable interface shape. Both single-input-single-output and multi-input-multi-output adaptive pole placement algorithms have been used to control the temperature. Also described is an intelligent measurement system to assess the shape of the crystal while it is growing. A color video imaging system observes the crystal in real time and determines the position and the shape of the interface. This information is used to evaluate the crystal growth rate, and to analyze the effects of translational velocity and temperature profiles on the shape of the interface. Creation of this knowledge base is the first step to incorporate image processing into furnace control.

Crystal growth and annealing method and apparatus

DOEpatents

Gianoulakis, Steven E.; Sparrow, Robert

2001-01-01

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

Comparative analysis of anti-polyglutamine Fab crystals grown on Earth and in microgravity.

PubMed

Owens, Gwen E; New, Danielle M; Olvera, Alejandra I; Manzella, Julia Ashlyn; Macon, Brittney L; Dunn, Joshua C; Cooper, David A; Rouleau, Robyn L; Connor, Daniel S; Bjorkman, Pamela J

2016-10-01

Huntington's disease is one of nine neurodegenerative diseases caused by a polyglutamine (polyQ)-repeat expansion. An anti-polyQ antigen-binding fragment, MW1 Fab, was crystallized both on Earth and on the International Space Station, a microgravity environment where convection is limited. Once the crystals returned to Earth, the number, size and morphology of all crystals were recorded, and X-ray data were collected from representative crystals. The results generally agreed with previous microgravity crystallization studies. On average, microgravity-grown crystals were 20% larger than control crystals grown on Earth, and microgravity-grown crystals had a slightly improved mosaicity (decreased by 0.03°) and diffraction resolution (decreased by 0.2 Å) compared with control crystals grown on Earth. However, the highest resolution and lowest mosaicity crystals were formed on Earth, and the highest-quality crystal overall was formed on Earth after return from microgravity.

Comparative analysis of anti-polyglutamine Fab crystals grown on Earth and in microgravity

PubMed Central

Owens, Gwen E.; New, Danielle M.; Olvera, Alejandra I.; Manzella, Julia Ashlyn; Macon, Brittney L.; Dunn, Joshua C.; Cooper, David A.; Rouleau, Robyn L.; Connor, Daniel S.; Bjorkman, Pamela J.

2016-01-01

Huntington’s disease is one of nine neurodegenerative diseases caused by a polyglutamine (polyQ)-repeat expansion. An anti-polyQ antigen-binding fragment, MW1 Fab, was crystallized both on Earth and on the International Space Station, a microgravity environment where convection is limited. Once the crystals returned to Earth, the number, size and morphology of all crystals were recorded, and X-ray data were collected from representative crystals. The results generally agreed with previous microgravity crystallization studies. On average, microgravity-grown crystals were 20% larger than control crystals grown on Earth, and microgravity-grown crystals had a slightly improved mosaicity (decreased by 0.03°) and diffraction resolution (decreased by 0.2 Å) compared with control crystals grown on Earth. However, the highest resolution and lowest mosaicity crystals were formed on Earth, and the highest-quality crystal overall was formed on Earth after return from microgravity. PMID:27710941

Improvements in the order, isotropy and electron density of glypican-1 crystals by controlled dehydration

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

Awad, Wael; Cairo University, Cairo; Svensson Birkedal, Gabriel

The anisotropy of crystals of glypican-1 was significantly reduced by controlled dehydration using the HC1 device, allowing the building of previously disordered parts of the structure. The use of controlled dehydration for improvement of protein crystal diffraction quality is increasing in popularity, although there are still relatively few documented examples of success. A study has been carried out to establish whether controlled dehydration could be used to improve the anisotropy of crystals of the core protein of the human proteoglycan glypican-1. Crystals were subjected to controlled dehydration using the HC1 device. The optimal protocol for dehydration was developed by carefulmore » investigation of the following parameters: dehydration rate, final relative humidity and total incubation time T{sub inc}. Of these, the most important was shown to be T{sub inc}. After dehydration using the optimal protocol the crystals showed significantly reduced anisotropy and improved electron density, allowing the building of previously disordered parts of the structure.« less

Progressive freezing and sweating in a test unit

NASA Astrophysics Data System (ADS)

Ulrich, J.; Özoğuz, Y.

1990-01-01

Crystallization from melts is applied in several fields like waste water treatment, fruit juice or liquid food concentration and purification of organic chemicals. Investigations to improve the understanding, the performance and the control of the process have been carried out. The experimental unit used a vertical tube with a falling film on the outside. With an specially designed measuring technique process controlling parameters have been studied. The results demonstrate the dependency of those parameters upon each other and indicate the way to control the process by controlling the dominant parameter. This is the growth rate of the crystal coat. A further purification of the crystal layer can be achieved by introducing the procedure of sweating, which is a controlled partial melting of the crystal coat. Here again process parameters have been varied and results are presented. The strong effect upon the final purity of the product by an efficient executed sweating which is effectively tuned on the crystallization procedure should save crystallization steps, energy and time.

Control of liquid crystal molecular orientation using ultrasound vibration

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

Taniguchi, Satoki; Wave Electronics Research Center, Doshisha University, 1-3 Tataramiyakodani, Kyotanabe, Kyoto 610-0321; Koyama, Daisuke

2016-03-07

We propose a technique to control the orientation of nematic liquid crystals using ultrasound and investigate the optical characteristics of the oriented samples. An ultrasonic liquid crystal cell with a thickness of 5–25 μm and two ultrasonic lead zirconate titanate transducers was fabricated. By exciting the ultrasonic transducers, the flexural vibration modes were generated on the cell. An acoustic radiation force to the liquid crystal layer was generated, changing the molecular orientation and thus the light transmission. By modulating the ultrasonic driving frequency and voltage, the spatial distribution of the molecular orientation of the liquid crystals could be controlled. The distributionmore » of the transmitted light intensity depends on the thickness of the liquid crystal layer because the acoustic field in the liquid crystal layer is changed by the orientational film.« less

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

An in-plane nano-mechanics approach to achieve reversible resonance control of photonic crystal nanocavities.

PubMed

Chew, Xiongyeu; Zhou, Guangya; Yu, Hongbin; Chau, Fook Siong; Deng, Jie; Loke, Yee Chong; Tang, Xiaosong

2010-10-11

Control of photonic crystal resonances in conjunction with large spectral shifting is critical in achieving reconfigurable photonic crystal devices. We propose a simple approach to achieve nano-mechanical control of photonic crystal resonances within a compact integrated on-chip approach. Three different tip designs utilizing an in-plane nano-mechanical tuning approach are shown to achieve reversible and low-loss resonance control on a one-dimensional photonic crystal nanocavity. The proposed nano-mechanical approach driven by a sub-micron micro-electromechanical system integrated on low loss suspended feeding nanowire waveguide, achieved relatively large resonance spectral shifts of up to 18 nm at a driving voltage of 25 V. Such designs may potentially be used as tunable optical filters or switches.

Growth of Cadmium-Zinc Telluride Crystals by Controlled Seeding Contactless Physical Vapor Transport

NASA Technical Reports Server (NTRS)

Palosz, W.; Grasza, K.; Gillies, D.; Jerman, G.

1996-01-01

Bulk crystals of cadmium-zinc telluride, 23 mm in diameter and up to 45 grams in weight were grown. Controlled seed formation procedure was used to limit the number of grains in the crystal. Most uniform distribution of ZnTe in the crystals was obtained using excess (Cd + Zn) pressure in the ampoule.

Structural studies on a 2,3-diphosphoglycerate independent phosphoglycerate mutase from Bacillus stearothermophilus.

PubMed

Chander, M; Setlow, P; Lamani, E; Jedrzejas, M J

1999-06-15

Phosphoglycerate mutase (PGM), an important enzyme in the glycolytic pathway, catalyzes the transfer of a phosphate group between the 2 and the 3 positions of glyceric acid. The gene coding for the 2, 3-diphosphoglycerate independent monomeric PGM from Bacillus stearothermophilus (57 kDa), whose activity is extremely pH sensitive and has an absolute and specific requirement for Mn2+, has been cloned and the enzyme overexpressed and purified to homogeneity. Circular dichroism studies showed at most only small secondary structure changes in the enzyme upon binding to Mn2+ or its 3-phosphoglycerate substrate, but thermal unfolding analyses revealed that Mn2+ but not 3-phosphoglycerate caused a large increase in the enzyme's stability. Diffraction-quality crystals of the enzyme were obtained at neutral pH in the presence of 3-phosphoglyceric acid with ammonium sulfate as the precipitating agent; these crystals diffract X rays to beyond 2.5-A resolution and belong to the orthorhombic space group C2221 with unit cell dimensions, a = 58.42, b = 206.08, c = 124.87 A, and alpha = beta = gamma = 90.0 degrees. The selenomethionyl version of the B. stearothermophilus protein has also been overexpressed, purified, and crystallized. Employing these crystals, the determination of the three-dimensional structure of this PGM by the multiwavelength anomalous dispersion method is in progress. Copyright 1999 Academic Press.

Sensitivity-enhanced Tm3+/Yb3+ co-doped YAG single crystal optical fiber thermometry based on upconversion emissions

NASA Astrophysics Data System (ADS)

Yu, Lu; Ye, Linhua; Bao, Renjie; Zhang, Xianwei; Wang, Li-Gang

2018-03-01

Optical thermometry based on Y3Al5O12 (YAG) single crystal optical fiber with end Tm3+/Yb3+ co-doped is presented. The YAG crystal fiber with end Tm3+/Yb3+ co-doped was grown by laser heated pedestal growth (LHPG) method. Under a 976 nm laser diode excitation, the upconversion (UC) emissions, originating from 3F2,3 →3H6 and 3H4 →3H6 transitions of Tm3+ ions, were investigated in the temperature range from 333 K to 733 K. Interestingly, the UC emission intensity of 3F2,3 →3H6 transition was significantly enhanced with increase of temperature, as compared with the other Tm3+/Yb3+ co-doped materials. The temperature dependence of fluorescence intensity ratio (FIR) of these two emission bands (3F2,3/3H4 →3H6) suggests that this doped YAG crystal fiber can be used as a highly sensitive optical thermal probe, which demonstrates a high absolute sensitivity with the maximum value of 0.021 K-1 at 733 K. In addition, due to the compact structure, strong mechanical strength and high thermal stability, such thermal probe may be a more promising candidate for temperature sensor with a high spatial resolution.

Crystal structure of diaphorin methanol monosolvate isolated from Diaphorina citri Kuwayama, the insect vector of citrus greening disease.

PubMed

Szebenyi, D Marian; Kriksunov, Irina; Howe, Kevin J; Ramsey, John S; Hall, David G; Heck, Michelle L; Krasnoff, Stuart B

2018-04-01

The title compound C 22 H 39 NO 9 ·CH 3 OH [systematic name: ( S )- N -(( S )-{(2 S ,4 R ,6 R )-6-[( S )-2,3-di-hydroxy-prop-yl]-4-hy-droxy-5,5-di-methyl-tetra-hydro-2 H -pyran-2-yl}(hy-droxy)meth-yl)-2-hy-droxy-2-[(2 R ,5 R ,6 R )-2-meth-oxy-5,6-dimeth-yl-4-methyl-ene-tetra-hydro-2 H -pyran-2-yl]acetamide methanol monosolvate], was isolated from the Asian citrus psyllid, Diaphorina citri Kuwayama, and crystallizes in the space group P 2 1 . ' Candidatus Profftella armatura' a bacterial endosymbiont of D. citri , biosynthesizes diaphorin, which is a hybrid polyketide-nonribosomal peptide comprising two highly substituted tetra-hydro-pyran rings joined by an N -acyl aminal bridge [Nakabachi et al. (2013 ▸). Curr. Biol. 23 , 1478-1484]. The crystal structure of the title compound establishes the complete relative configuration of diaphorin, which agrees at all nine chiral centers with the structure of the methanol monosolvate of the di- p -bromo-benzoate derivative of pederin, a biogenically related compound whose crystal structure was reported previously [Furusaki et al. (1968 ▸). Tetra-hedron Lett. 9 , 6301-6304]. Thus, the absolute configuration of diaphorin is proposed by analogy to that of pederin.

Citrate, not phosphate, can dissolve calcium oxalate monohydrate crystals and detach these crystals from renal tubular cells.

PubMed

Chutipongtanate, Somchai; Chaiyarit, Sakdithep; Thongboonkerd, Visith

2012-08-15

Dissolution therapy of calcium oxalate monohydrate (COM) kidney stone disease has not yet been implemented due to a lack of well characterized COM dissolution agents. The present study therefore aimed to identify potential COM crystal dissolution compounds. COM crystals were treated with deionized water (negative control), 5 mM EDTA (positive control), 5 mM sodium citrate, or 5mM sodium phosphate. COM crystal dissolution activities of these compounds were evaluated by phase-contrast and video-assisted microscopic examinations, semi-quantitative analysis of crystal size, number and total mass, and spectrophotometric oxalate-dissolution assay. In addition, effects of these compounds on detachment of COM crystals, which adhered tightly onto renal tubular cell surface, were also investigated. The results showed that citrate, not phosphate, had a significant dissolution effect on COM crystals as demonstrated by significant reduction of crystal size (approximately 37% decrease), crystal number (approximately 53% decrease) and total crystal mass (approximately 72% decrease) compared to blank and negative controls. Spectrophotometric oxalate-dissolution assay successfully confirmed the COM crystal dissolution property of citrate. Moreover, citrate could detach up to 85% of the adherent COM crystals from renal tubular cell surface. These data indicate that citrate is better than phosphate for dissolution and detachment of COM crystals. Copyright © 2012 Elsevier B.V. All rights reserved.

Estimating the Aqueous Solubility of Pharmaceutical Hydrates.

PubMed

Franklin, Stephen J; Younis, Usir S; Myrdal, Paul B

2016-06-01

Estimation of crystalline solute solubility is well documented throughout the literature. However, the anhydrous crystal form is typically considered with these models, which is not always the most stable crystal form in water. In this study, an equation which predicts the aqueous solubility of a hydrate is presented. This research attempts to extend the utility of the ideal solubility equation by incorporating desolvation energetics of the hydrated crystal. Similar to the ideal solubility equation, which accounts for the energetics of melting, this model approximates the energy of dehydration to the entropy of vaporization for water. Aqueous solubilities, dehydration and melting temperatures, and log P values were collected experimentally and from the literature. The data set includes different hydrate types and a range of log P values. Three models are evaluated, the most accurate model approximates the entropy of dehydration (ΔSd) by the entropy of vaporization (ΔSvap) for water, and utilizes onset dehydration and melting temperatures in combination with log P. With this model, the average absolute error for the prediction of solubility of 14 compounds was 0.32 log units. Copyright © 2016 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

Quantum-mechanical ab initio simulation of the Raman and IR spectra of Mn3Al2Si3O12 spessartine

NASA Astrophysics Data System (ADS)

Valenzano, Loredana; Meyer, Alessio; Demichelis, Raffaella; Civalleri, Bartolomeo; Dovesi, Roberto

2009-07-01

The IR and Raman spectra of spessartine garnet Mn3Al2Si3O12, are simulated with the periodic ab initio CRYSTAL code by adopting an all-electron Gaussian-type basis set and the B3LYP Hamiltonian. The frequencies of the 25 Raman active modes (3 of A 1 g , 8 of E g and 14 of F 2 g symmetry) and of the two sets of 17 F 1 u transverse-optical and longitudinal-optical frequencies are generated, as well as the IR oscillator strength. The agreement between calculated and experimental data is excellent: for the IR and Raman sets, the mean absolute difference overline{|Updelta|} is 4.0 and 6.8 cm-1, respectively. Isotopic substitution permits to highlight the Mn, Al and Si participation to the various zones of the spectrum. Graphical animation, available on the authors’ web-site ( http://www.crystal.unito.it/vibs/garnets/spessartine/ ), provides a very readable description of the movement of atoms and groups in each vibrational mode.

Synthesis, crystal structure and photo physical properties of isomeric fluorinated s-shaped polyaromatic dibenzo[c,l]chrysene derivatives

NASA Astrophysics Data System (ADS)

Moriguchi, Tetsuji; Tabuchi, Daichi; Yakeya, Daisuke; Tsuge, Akihiko; Jalli, Venkataprasad; Yoza, Kenji

2018-01-01

Two s-shaped fluorinated isomeric polyaromatic dibenzo[c,l]chrysene derivatives have been synthesized by a two step process using the Wittig, Heck and iodine promoted cyclization reactions. These cyclized compounds were characterized by 1H NMR and EI-MS. Further, absolute configurations of isomeric 4a and 4b were determined by X-ray diffraction analysis. Compound 4a crystallized under monoclinic system with space group P21/c and compound 4b crystallized under monoclinic system with space group Cc. They have good solubility in common organic solvents such as dichloromethane, chloroform and THF. Photophysical properties of 4a and 4b were evaluated by using UV-Visible and Fluorescence spectrophotometer. Compounds 4a and 4b showed strong absorption maximum wavelength at 317 nm. The emission spectra of 4a and 4b displayed sharp peaks in the visible region from 417 to 441 nm. The shape of the UV-Visible and Fluorescence spectra of 4a and 4b looks almost identical. But compound 4a exhibited better fluorescence intensity than compound 4b. This difference may be due to the difference in the configuration of compounds 4a and 4b.

Thermoelectric Properties of n-type SnSe Single Crystal

NASA Astrophysics Data System (ADS)

Nguyen, Phuong; Duong, Anh Tuan; Rhim, S. H.; Nguyen, Van Quang; Duong, Van Thiet; Shin, Yooleemi; Cho, Sunglae; Kwon, Suyong; Song, Jae Yong; Park, Hyun Min

Although thermoelectric materials are well known for their reliability and have been used for many years, even in the field of space engineering, their performance is quite small due to low energy conversion efficiency. Dimensionless figure of merit, ZT = S2. σ.T.κ-1 (where S, σ, T, κ are Seebeck coefficient, electrical conductivity, absolute temperature and thermal conductivity, respectively) is conveniently used to evaluate the conversion efficiency of a thermoelectric materials. Recently, the highest value of ZT to date has been reported for single crystal SnSe, ZT = 2.6 along the b axis of unit cell at 923 K. This temperature is rather high and the range of temperature for high reported ZT is quite narrow. Here we report an attempt to modify the thermoelectric properties of SnSe by using group V and VII as n-type dopant. A negative value of Seebeck coefficient was observed and the power factor reached a peak of 10 μW.K-2.cm-1 at around 600 K. The maximum n-type ZT was 0.57 at 650 K. We will discuss on dopant dependent thermoelectric properties of n-type SnSe single crystals.

Development of a High Resolution X-ray Spectrometer on the National Ignition Facility

NASA Astrophysics Data System (ADS)

Gao, L.; Kraus, B.; Hill, K. W.; Bitter, M.; Efthimion, P.; Schneider, M. B.; Chen, H.; Ayers, J.; Liedahl, D.; Macphee, A. G.; Le, H. P.; Thorn, D.; Nelson, D.

2017-10-01

A high-resolution x-ray spectrometer has been designed, calibrated, and deployed on the National Ignition Facility (NIF) to measure plasma parameters for a Kr-doped surrogate capsule imploded at NIF conditions. Two conical crystals, each diffracting the He α and He β complexes respectively, focus the spectra onto a steak camera photocathode for time-resolved measurements with a temporal resolution of <20 ps. A third cylindrical crystal focuses the entire He α to He β spectrum onto an image plate for a time-integrated spectrum to correlate the two streaked signals. The instrument was absolutely calibrated by the x-ray group at the Princeton Plasma Physics Laboratory using a micro-focus x-ray source. Detailed calibration procedures, including source and spectrum alignment, energy calibration, crystal performance evaluation, and measurement of the resolving power and the integrated reflectivity will be presented. Initial NIF experimental results will also be discussed. This work was performed under the auspices of the U.S. Department of Energy by Princeton Plasma Physics Laboratory under contract DE-AC02-09CH11466 and by Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344.

Fast surface crystallization of amorphous griseofulvin below T g.

PubMed

Zhu, Lei; Jona, Janan; Nagapudi, Karthik; Wu, Tian

2010-08-01

To study crystal growth rates of amorphous griseofulvin (GSF) below its glass transition temperature (T (g)) and the effect of surface crystallization on the overall crystallization kinetics of amorphous GSF. Amorphous GSF was generated by melt quenching. Surface and bulk crystal growth rates were determined using polarized light microscope. X-ray powder diffraction (XRPD) and Raman microscopy were used to identify the polymorph of the crystals. Crystallization kinetics of amorphous GSF powder stored at 40 degrees C (T (g)-48 degrees C) and room temperature (T (g)-66 degrees C) was monitored using XRPD. Crystal growth at the surface of amorphous GSF is 10- to 100-fold faster than that in the bulk. The surface crystal growth can be suppressed by an ultrathin gold coating. Below T (g), the crystallization of amorphous GSF powder was biphasic with a rapid initial crystallization stage dominated by the surface crystallization and a slow or suspended late stage controlled by the bulk crystallization. GSF exhibits the fastest surface crystallization kinetics among the known amorphous pharmaceutical solids. Well below T (g), surface crystallization dominated the overall crystallization kinetics of amorphous GSF powder. Thus, surface crystallization should be distinguished from bulk crystallization in studying, modeling and controlling the crystallization of amorphous solids.

Non-isothermal Crystallization Kinetics of Mold Fluxes for Casting High-Aluminum Steels

NASA Astrophysics Data System (ADS)

Zhou, Lejun; Li, Huan; Wang, Wanlin; Wu, Zhaoyang; Yu, Jie; Xie, Senlin

2017-12-01

This paper investigates the crystallization behavior of CaO-SiO2- and CaO-Al2O3-based mold fluxes for casting high-aluminum steels using single hot thermocouple technology, developed kinetic models, and scanning electron microscope. The results showed that the crystallization ability of the typical CaO-SiO2-based Flux A (CaO/SiO2 0.62, Al2O3 2 mass pct) is weaker than that of CaO-Al2O3-based Flux B (CaO/SiO2 4.11, Al2O3 31.9 mass pct) because of its higher initial crystallization temperature. The crystallization kinetics of Flux A was "surface nucleation and growth, interface reaction control" in the overall non-isothermal crystallization process, whereas that of Flux B was "constant nucleation rate, 1-dimensional growth, diffusion control, in the primary crystallization stage, and then transformed into constant nucleation rate, 3-dimensional growth, interface reaction control in the secondary crystallization stage." The energy dispersive spectroscopy results for Flux B suggested that the variations in the crystallization kinetics for Flux B are due to different crystals precipitating in the primary (BaCa2Al8O15) and secondary (CaAl2O4) crystallization periods during the non-isothermal crystallization process.

Self-Referenced Method for Estimating Refractive Index and Absolute Absorption of Loose Semiconductor Powders

DOE PAGES

Huang, Huafeng; Colabello, Diane M.; Sklute, Elizabeth C.; ...

2017-04-23

The absolute absorption coefficient, α(E), is a critical design parameter for devices using semiconductors for light harvesting associated with renewable energy production, both for classic technologies such as photovoltaics and for emerging technologies such as direct solar fuel production. While α(E) is well-known for many classic simple semiconductors used in photovoltaic applications, the absolute values of α(E) are typically unknown for the complex semiconductors being explored for solar fuel production due to the absence of single crystals or crystalline epitaxial films that are needed for conventional methods of determining α(E). In this work, a simple self-referenced method for estimating bothmore » the refractive indices, n(E), and absolute absorption coefficients, α(E), for loose powder samples using diffuse reflectance data is demonstrated. In this method, the sample refractive index can be deduced by refining n to maximize the agreement between the relative absorption spectrum calculated from bidirectional reflectance data (calculated through a Hapke transform which depends on n) and integrating sphere diffuse reflectance data (calculated through a Kubleka–Munk transform which does not depend on n). This new method can be quickly used to screen the suitability of emerging semiconductor systems for light-harvesting applications. The effectiveness of this approach is tested using the simple classic semiconductors Ge and Fe 2O 3 as well as the complex semiconductors La 2MoO 5 and La 4Mo 2O 11. The method is shown to work well for powders with a narrow size distribution (exemplified by Fe 2O 3) and to be ineffective for semiconductors with a broad size distribution (exemplified by Ge). As such, it provides a means for rapidly estimating the absolute optical properties of complex solids which are only available as loose powders.« less

Structure and Growth Control of Organic-Inorganic Halide Perovskites for Optoelectronics: From Polycrystalline Films to Single Crystals.

PubMed

Chen, Yani; He, Minhong; Peng, Jiajun; Sun, Yong; Liang, Ziqi

2016-04-01

Recently, organic-inorganic halide perovskites have sparked tremendous research interest because of their ground-breaking photovoltaic performance. The crystallization process and crystal shape of perovskites have striking impacts on their optoelectronic properties. Polycrystalline films and single crystals are two main forms of perovskites. Currently, perovskite thin films have been under intensive investigation while studies of perovskite single crystals are just in their infancy. This review article is concentrated upon the control of perovskite structures and growth, which are intimately correlated for improvements of not only solar cells but also light-emitting diodes, lasers, and photodetectors. We begin with the survey of the film formation process of perovskites including deposition methods and morphological optimization avenues. Strategies such as the use of additives, thermal annealing, solvent annealing, atmospheric control, and solvent engineering have been successfully employed to yield high-quality perovskite films. Next, we turn to summarize the shape evolution of perovskites single crystals from three-dimensional large sized single crystals, two-dimensional nanoplates, one-dimensional nanowires, to zero-dimensional quantum dots. Siginificant functions of perovskites single crystals are highlighted, which benefit fundamental studies of intrinsic photophysics. Then, the growth mechanisms of the previously mentioned perovskite crystals are unveiled. Lastly, perspectives for structure and growth control of perovskites are outlined towards high-performance (opto)electronic devices.

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

NASA Astrophysics Data System (ADS)

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

2017-07-01

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

Liquid crystal polymer substrate MMIC receiver modules for the ECE Imaging system on the DIII-D

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

Zhu, Y.; Ye, Y.; Yu, J-H

A new generation of millimeter-wave heterodyne imaging receiver arrays has been developed and demonstrated on the DIII-D ECEI system. Improved circuit integration, allowing for absolute calibration, improved noise performance, and shielding from out-of-band emission, is made possible by using advanced liquid crystal polymer (LCP) substrates and MMIC (Monolithic Microwave Integrated Circuit) receiver chips. This array exhibits ~ 15 dB additional gain and > 30x reduction in noise temperature compared to the previous generation and provide ECEI capability for absolute 2-D electron temperature profile measurements. Each LCP horn-waveguide module houses a 3x3 mm GaAs MMIC receiver chip, which consists of amore » low noise amplifier (LNA), balanced mixer, local oscillator multiplier chain driven by ~12 GHz input via an RF cable to the enclosure box, and IF amplifier. A proof-of-principle instrument with 5 poloidal channels was installed on DIII-D in 2017. The full proof-of-principle system installation (20 poloidal x 8 radial channels) was commissioned early in 2018. The LCP ECEI system is used for pedestal region measurements, especially focusing on temperature evolution during ELM bursting. The DIII-D ECE Imaging signal has been significantly improved with extremely effective shielding of out-of-band microwave noise which plagued previous ECE Imaging studies on DIII-D. In H-mode ELM bursting, the radial propagation of electron heat flow has been detected on DIII-D. The LCP ECE Imaging is expected to be a valuable diagnostic tool for ELM physics investigations.« less

Structure and absolute configuration of some 5-chloro-2-methoxy-N-phenylbenzamide derivatives

NASA Astrophysics Data System (ADS)

Galal, Alaaeldin M. F.; Shalaby, Elsayed M.; Abouelsayed, Ahmed; Ibrahim, Medhat A.; Al-Ashkar, Emad; Hanna, Atef G.

2018-01-01

The absolute configuration of 5-chloro-2-methoxy-N-phenylbenzamide single crystal [compound (1)] and the effect of introducing -[CH2]n-, n = 1,2 group adjacent to the amide group [compounds (2) and (3)], were studied. Furthermore, the replacement of the methoxy group with a hydroxy group [compound (4)] was defined. Proton and carbon-13 NMR spectrometer were used to record the structural information of the prepared compounds. X-ray single crystal diffractometer were used to elucidate the 3D structural configurations. Intensity data for the studied compounds were collected at room temperature. The X-ray data prove that compound (1) is almost planar, with maximum r.m.s. deviations of 0.210(3) Å corresponds to C13. This planarity starts to disturb by adding -[CH2]n-, n = 1,2 groups between the NH group and the phenyl ring in compounds (2) and (3), respectively. By replacing the OCH3 group by an OH group in compound (4), the plane of the chlorophenyl moiety is nearly perpendicular to that of the phenyl ring. Such new structural configurations were further illustrated by the infrared, and ultraviolet-visible spectroscopy measurements in the frequency range 400-4000 cm-1 and 190-1100 nm, respectively. Spectroscopic analyses were verified with the help of molecular modeling using density functional theory. The estimated total dipole moment for the prepared compounds reflects its ability to interact with its surrounding molecules. The higher dipole moment for a given structures is combined with the higher reactivity for potential use in medicinal applications.

Controlling Chirality of Entropic Crystals

NASA Astrophysics Data System (ADS)

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

2015-10-01

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

Characteristic Time Scales of Characteristic Magmatic Processes and Systems

NASA Astrophysics Data System (ADS)

Marsh, B. D.

2004-05-01

Every specific magmatic process, regardless of spatial scale, has an associated characteristic time scale. Time scales associated with crystals alone are rates of growth, dissolution, settling, aggregation, annealing, and nucleation, among others. At the other extreme are the time scales associated with the dynamics of the entire magmatic system. These can be separated into two groups: those associated with system genetics (e.g., the production and transport of magma, establishment of the magmatic system) and those due to physical characteristics of the established system (e.g., wall rock failure, solidification front propagation and instability, porous flow). The detailed geometry of a specific magmatic system is particularly important to appreciate; although generic systems are useful, care must be taken to make model systems as absolutely realistic as possible. Fuzzy models produce fuzzy science. Knowledge of specific time scales is not necessarily useful or meaningful unless the hierarchical context of the time scales for a realistic magmatic system is appreciated. The age of a specific phenocryst or ensemble of phenocrysts, as determined from isotopic or CSD studies, is not meaningful unless something can be ascertained of the provenance of the crystals. For example, crystal size multiplied by growth rate gives a meaningful crystal age only if it is from a part of the system that has experienced semi-monotonic cooling prior to chilling; crystals entrained from a long-standing cumulate bed that were mechanically sorted in ascending magma may not reveal this history. Ragged old crystals rolling about in the system for untold numbers of flushing times record specious process times, telling more about the noise in the system than the life of typical, first generation crystallization processes. The most helpful process-related time scales are those that are known well and that bound or define the temporal style of the system. Perhaps the most valuable of these times comes from the observed durations and rates of volcanism. There can be little doubt that the temporal styles of volcanism are the same as those of magmatism in general. Volcano repose times, periodicity, eruptive fluxes, acoustic emission structures, lava volumes, longevity, etc. must also be characteristic of pluton-dominated systems. We must therefore give up some classical concepts (e.g., instantaneous injection of crystal-free magma as an initial condition) for any plutonic/chambered system and move towards an integrated concept of magmatism. Among the host of process-related time scales, probably the three most fundamental of any magmatic system are (1) the time scale associated with crystal nucleation (J) and growth (G) (tx}=C{1(G3 J)-{1}/4; Zieg & Marsh, J. Pet. 02') along with the associated scales for mean crystal size (L) and population (N), (2) the time scale associated with conductive cooling controlled by a local length scale (d) (tc}=C{2 d2/K; K is thermal diffusivity), and (3) the time scale associated with intra-crystal diffusion (td}=C{3 L2/D; D is chemical diffusivity). It is the subtle, clever, and insightful application of time scales, dovetailed with realistic system geometry and attention paid to the analogous time scales of volcanism, that promises to reveal the true dynamic integration of magmatic systems.

Self-tuning multivariable pole placement control of a multizone crystal growth furnace

NASA Technical Reports Server (NTRS)

Batur, C.; Sharpless, R. B.; Duval, W. M. B.; Rosenthal, B. N.

1992-01-01

This paper presents the design and implementation of a multivariable self-tuning temperature controller for the control of lead bromide crystal growth. The crystal grows inside a multizone transparent furnace. There are eight interacting heating zones shaping the axial temperature distribution inside the furnace. A multi-input, multi-output furnace model is identified on-line by a recursive least squares estimation algorithm. A multivariable pole placement controller based on this model is derived and implemented. Comparison between single-input, single-output and multi-input, multi-output self-tuning controllers demonstrates that the zone-to-zone interactions can be minimized better by a multi-input, multi-output controller design. This directly affects the quality of crystal grown.

DKDP crystal growth controlled by cooling rate

NASA Astrophysics Data System (ADS)

Xie, Xiaoyi; Qi, Hongji; Shao, Jianda

2017-08-01

The performance of deuterated potassium dihydrogen phosphate (DKDP) crystal directly affects beam quality, energy and conversion efficiency in the Inertial Confinement Fusion（ICF）facility, which is related with the initial saturation temperature of solution and the real-time supersaturation during the crystal growth. However, traditional method to measure the saturation temperature is neither efficient nor accurate enough. Besides, the supersaturation is often controlled by experience, which yields the higher error and leads to the instability during the crystal growth. In this paper, DKDP solution with 78% deuteration concentration is crystallized in different temperatures. We study the relation between solubility and temperature of DKDP and fit a theoretical curve with a parabola model. With the model, the measurement of saturation temperature is simplified and the control precision of the cooling rate is improved during the crystal growth, which is beneficial for optimizing the crystal growth process.

Phase diagram of a symmetric electron–hole bilayer system: a variational Monte Carlo study

NASA Astrophysics Data System (ADS)

Sharma, Rajesh O.; Saini, L. K.; Prasad Bahuguna, Bhagwati

2018-05-01

We study the phase diagram of a symmetric electron–hole bilayer system at absolute zero temperature and in zero magnetic field within the quantum Monte Carlo approach. In particular, we conduct variational Monte Carlo simulations for various phases, i.e. the paramagnetic fluid phase, the ferromagnetic fluid phase, the anti-ferromagnetic Wigner crystal phase, the ferromagnetic Wigner crystal phase and the excitonic phase, to estimate the ground-state energy at different values of in-layer density and inter-layer spacing. Slater–Jastrow style trial wave functions, with single-particle orbitals appropriate for different phases, are used to construct the phase diagram in the (r s , d) plane by finding the relative stability of trial wave functions. At very small layer separations, we find that the fluid phases are stable, with the paramagnetic fluid phase being particularly stable at and the ferromagnetic fluid phase being particularly stable at . As the layer spacing increases, we first find that there is a phase transition from the ferromagnetic fluid phase to the ferromagnetic Wigner crystal phase when d reaches 0.4 a.u. at r s   =  20, and before there is a return to the ferromagnetic fluid phase when d approaches 1 a.u. However, for r s   <  20 and a.u., the excitonic phase is found to be stable. We do not find that the anti-ferromagnetic Wigner crystal is stable over the considered range of r s and d. We also find that as r s increases, the critical layer separations for Wigner crystallization increase.

Antisolvent membrane crystallization of pharmaceutical compounds.

PubMed

Di Profio, Gianluca; Stabile, Carmen; Caridi, Antonella; Curcio, Efrem; Drioli, Enrico

2009-12-01

This article describes a modification of the conventional membrane crystallization technique in which a membrane is used to dose the solvent/antisolvent composition to generate supersaturation and induce crystallization in a drug solution. Two operative configurations are proposed: (a) solvent/antisolvent demixing crystallization, where the solvent is removed in at higher flow rate than the antisolvent so that phase inversion promotes supersaturation and (b) antisolvent addition, in which the antisolvent is dosed into the crystallizing drug solution. In both cases, solvent/antisolvent migration occurs in vapor phase and it is controlled by the porous membrane structure, acting on the operative process parameters. This mechanism is different than that observed when forcing the liquid phases through the pores and the more finely controllable supersaturated environment would generate crystals with the desired characteristics. Two organic molecules of relevant industrial implication, like paracetamol and glycine, were used to test the new systems. Experiments demonstrated that, by using antisolvent membrane crystallization in both configurations, accurate control of solution composition at the crystallization point has been achieved with effects on crystals morphology. 2009 Wiley-Liss, Inc. and the American Pharmacists Association

Improvements in the order, isotropy and electron density of glypican-1 crystals by controlled dehydration.

PubMed

Awad, Wael; Svensson Birkedal, Gabriel; Thunnissen, Marjolein M G M; Mani, Katrin; Logan, Derek T

2013-12-01

The use of controlled dehydration for improvement of protein crystal diffraction quality is increasing in popularity, although there are still relatively few documented examples of success. A study has been carried out to establish whether controlled dehydration could be used to improve the anisotropy of crystals of the core protein of the human proteoglycan glypican-1. Crystals were subjected to controlled dehydration using the HC1 device. The optimal protocol for dehydration was developed by careful investigation of the following parameters: dehydration rate, final relative humidity and total incubation time Tinc. Of these, the most important was shown to be Tinc. After dehydration using the optimal protocol the crystals showed significantly reduced anisotropy and improved electron density, allowing the building of previously disordered parts of the structure.

Crystallization of a salt of a weak organic acid and base: solubility relations, supersaturation control and polymorphic behavior.

PubMed

Jones, H P; Davey, R J; Cox, B G

2005-03-24

Control of crystallization processes for organic salts is of importance to the pharmaceutical industry as many active pharmaceutical materials are marketed as salts. In this study, a method for estimating the solubility product of a salt of a weak acid and weak base from measured pH-solubility data is described for the first time. This allows calculation of the supersaturation of solutions at known pH. Ethylenediammonium 3,5-dinitrobenzoate is a polymorphic organic salt. A detailed study of the effects of pH, supersaturation, and temperature of crystallization on the physical properties of this salt shows that the desired polymorph may be produced by appropriate selection of the pH and supersaturation of crystallization. Crystal morphology is also controlled by these crystallization conditions.

Nanocrystals: The preparation, precise control, and application toward the pharmaceutics and foods industry.

PubMed

Wu, Cao; Chen, Zhou; Hu, Ya; Rao, Zhiyuan; Wu, Wangping; Yang, Zhaogang

2018-05-15

Crystallization is a significant process employed to produce a wide variety of materials in pharmaceutical and food area. The control of crystal dimension, crystallinity, and shape is very important because they will affect the subsequent filtration, drying and grinding performance as well as the physical and chemical properties of the material. This review summarizes the special features of crystallization technology and the preparation methods of nanocrystals, and discusses analytical technology which is used to control crystal quality and performance. The crystallization technology applications in pharmaceutics and foods are also outlined. These illustrated examples further help us to gain a better understanding of the crystallization technology for pharmaceutics and foods. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

Bacterial Ice Crystal Controlling Proteins

PubMed Central

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

2014-01-01

Across the world, many ice active bacteria utilize ice crystal controlling proteins for aid in freezing tolerance at subzero temperatures. Ice crystal controlling proteins include both antifreeze and ice nucleation proteins. Antifreeze proteins minimize freezing damage by inhibiting growth of large ice crystals, while ice nucleation proteins induce formation of embryonic ice crystals. Although both protein classes have differing functions, these proteins use the same ice binding mechanisms. Rather than direct binding, it is probable that these protein classes create an ice surface prior to ice crystal surface adsorption. Function is differentiated by molecular size of the protein. This paper reviews the similar and different aspects of bacterial antifreeze and ice nucleation proteins, the role of these proteins in freezing tolerance, prevalence of these proteins in psychrophiles, and current mechanisms of protein-ice interactions. PMID:24579057

Bacterial ice crystal controlling proteins.

PubMed

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

2014-01-01

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

Use of anomolous thermal imaging effects for multi-mode systems control during crystal growth

NASA Technical Reports Server (NTRS)

Wargo, Michael J.

1989-01-01

Real time image processing techniques, combined with multitasking computational capabilities are used to establish thermal imaging as a multimode sensor for systems control during crystal growth. Whereas certain regions of the high temperature scene are presently unusable for quantitative determination of temperature, the anomalous information thus obtained is found to serve as a potentially low noise source of other important systems control output. Using this approach, the light emission/reflection characteristics of the crystal, meniscus and melt system are used to infer the crystal diameter and a linear regression algorithm is employed to determine the local diameter trend. This data is utilized as input for closed loop control of crystal shape. No performance penalty in thermal imaging speed is paid for this added functionality. Approach to secondary (diameter) sensor design and systems control structure is discussed. Preliminary experimental results are presented.

Controlling in situ crystallization of pharmaceutical particles within the spray dryer.

PubMed

Woo, Meng Wai; Lee, May Ginn; Shakiba, Soroush; Mansouri, Shahnaz

2017-11-01

Simultaneous solidification and in situ crystallization (or partial crystallization) of droplets within the drying chamber are commonly encountered in the spray drying of pharmaceuticals. The crystallinity developed will determine the functionality of the powder and its stability during storage. This review discusses strategies that can be used to control the in situ crystallization process. Areas covered: The premise of the strategies discussed focuses on the manipulation of the droplet drying rate relative to the timescale of crystallization. This can be undertaken by the control of the spray drying operation, by the use of volatile materials and by the inclusion of additives. Several predictive approaches for in situ crystallization control and new spray dryer configuration strategies are further discussed. Expert opinion: Most reports, hitherto, have focused on the crystallinity of the spray dried material or the development of crystallinity during storage. More mechanistic understanding of the in situ crystallization process during spray drying is required to guide product formulation trials. The key challenge will be in adapting the mechanistic approach to the myriad possible formulations in the pharmaceutical industry.

Control of solvent evaporation in hen egg white lysozyme crystallization

NASA Technical Reports Server (NTRS)

Wilson, L. J.; Suddath, F. L.

1992-01-01

An investigation of the role of solvent evaporation in tetragonal lysozyme crystallization was preformed with a device that employs N2(g) to control the evaporation of solvent from a micro-volume crystallization hanging drop. The number of crystals was found to vary with the rate at which the final supersaturation level was achieved. It was found that the more rapid the approach to supersaturation the larger the number of crystals. Accordingly, the crystals reached a smaller terminal size. Elongation of the (110) face parallel to the four-fold axis was observed with the slower evaporation rates.

Electron Scattering and Doping Mechanisms in Solid-Phase-Crystallized In2O3:H Prepared by Atomic Layer Deposition.

PubMed

Macco, Bart; Knoops, Harm C M; Kessels, Wilhelmus M M

2015-08-05

Hydrogen-doped indium oxide (In2O3:H) has recently emerged as an enabling transparent conductive oxide for solar cells, in particular for silicon heterojunction solar cells because its high electron mobility (>100 cm(2)/(V s)) allows for a simultaneously high electrical conductivity and optical transparency. Here, we report on high-quality In2O3:H prepared by a low-temperature atomic layer deposition (ALD) process and present insights into the doping mechanism and the electron scattering processes that limit the carrier mobility in such films. The process consists of ALD of amorphous In2O3:H at 100 °C and subsequent solid-phase crystallization at 150-200 °C to obtain large-grained polycrystalline In2O3:H films. The changes in optoelectronic properties upon crystallization have been monitored both electrically by Hall measurements and optically by analysis of the Drude response. After crystallization, an excellent carrier mobility of 128 ± 4 cm(2)/(V s) can be obtained at a carrier density of 1.8 × 10(20) cm(-3), irrespective of the annealing temperature. Temperature-dependent Hall measurements have revealed that electron scattering is dominated by unavoidable phonon and ionized impurity scattering from singly charged H-donors. Extrinsic defect scattering related to material quality such as grain boundary and neutral impurity scattering was found to be negligible in crystallized films indicating that the carrier mobility is maximized. Furthermore, by comparison of the absolute H-concentration and the carrier density in crystallized films, it is deduced that <4% of the incorporated H is an active dopant in crystallized films. Therefore, it can be concluded that inactive H atoms do not (significantly) contribute to defect scattering, which potentially explains why In2O3:H films are capable of achieving a much higher carrier mobility than conventional In2O3:Sn (ITO).

Polyketides with α-Glucosidase Inhibitory Activity from a Mangrove Endophytic Fungus, Penicillium sp. HN29-3B1.

PubMed

Liu, Yayue; Yang, Qin; Xia, Guoping; Huang, Hongbo; Li, Hanxiang; Ma, Lin; Lu, Yongjun; He, Lei; Xia, Xuekui; She, Zhigang

2015-08-28

Five new compounds, pinazaphilones A and B (1, 2), two phenolic compounds (4, 5), and penicidone D (6), together with the known Sch 1385568 (3), (±)-penifupyrone (7), 3-O-methylfunicone (8), 5-methylbenzene-1,3-diol (9), and 2,4-dihydroxy-6-methylbenzoic acid (10) were obtained from the culture of the endophytic fungus Penicillium sp. HN29-3B1, which was isolated from a fresh branch of the mangrove plant Cerbera manghas collected from the South China Sea. Their structures were determined by analysis of 1D and 2D NMR and mass spectroscopic data. Structures of compounds 4 and 7 were further confirmed by a single-crystal X-ray diffraction experiment using Cu Kα radiation. The absolute configurations of compounds 1-3 were assigned by quantum chemical calculations of the electronic circular dichroic spectra. Compounds 2, 3, 5, and 7 inhibited α-glucosidase with IC50 values of 28.0, 16.6, 2.2, and 14.4 μM, respectively, and are thus more potent than the positive control, acarbose.

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

Calcite crystal growth experiments were undertaken to test a recently proposed model that relates crystal growth mechanisms to the shapes of crystal size distributions (CSDs). According to this approach, CSDs for minerals have three basic shapes: (1) asymptotic, which is related to a crystal growth mechanism having constant-rate nucleation accompanied by surface-controlled growth; (2) lognormal, which results from decaying-rate nucleation accompanied by surface-controlled growth; and (3) a theoretical, universal, steady-state curve attributed to Ostwald ripening. In addition, there is a fourth crystal growth mechanism that does not have a specific CSD shape, but which preserves the relative shapes of previously formed CSDs. This mechanism is attributed to supply-controlled growth. All three shapes were produced experimentally in the calcite growth experiments by modifying nucleation conditions and solution concentrations. The asymptotic CSD formed when additional reactants were added stepwise to the surface of solutions that were supersaturated with respect to calcite (initial Ω = 20, where Ω = 1 represents saturation), thereby leading to the continuous nucleation and growth of calcite crystals. Lognormal CSDs resulted when reactants were added continuously below the solution surface, via a submerged tube, to similarly supersaturated solutions (initial Ω = 22 to 41), thereby leading to a single nucleation event followed by surface-controlled growth. The Ostwald CSD resulted when concentrated reactants were rapidly mixed, leading initially to high levels of supersaturation (Ω >100), and to the formation and subsequent dissolution of very small nuclei, thereby yielding CSDs having small crystal size variances. The three CSD shapes likely were produced early in the crystallization process, in the nanometer crystal size range, and preserved during subsequent growth. Preservation of the relative shapes of the CSDs indicates that a supply-controlled growth mechanism 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.

Control of heat transfer in continuous-feeding Czochralski-silicon crystal growth with a water-cooled jacket

NASA Astrophysics Data System (ADS)

Zhao, Wenhan; Liu, Lijun

2017-01-01

The continuous-feeding Czochralski method is an effective method to reduce the cost of single crystal silicon. By promoting the crystal growth rate, the cost can be reduced further. However, more latent heat will be released at the melt-crystal interface under a high crystal growth rate. In this study, a water-cooled jacket was applied to enhance the heat transfer at the melt-crystal interface. Quasi-steady-state numerical calculation was employed to investigate the impact of the water-cooled jacket on the heat transfer at the melt-crystal interface. Latent heat released during the crystal growth process at the melt-crystal interface and absorbed during feedstock melting at the feeding zone was modeled in the simulations. The results show that, by using the water-cooled jacket, heat transfer in the growing crystal is enhanced significantly. Melt-crystal interface deflection and thermal stress increase simultaneously due to the increase of radial temperature at the melt-crystal interface. With a modified heat shield design, heat transfer at the melt-crystal interface is well controlled. The crystal growth rate can be increased by 20%.

Mapping with MAV: Experimental Study on the Contribution of Absolute and Relative Aerial Position Control

NASA Astrophysics Data System (ADS)

Skaloud, J.; Rehak, M.; Lichti, D.

2014-03-01

This study highlights the benefit of precise aerial position control in the context of mapping using frame-based imagery taken by small UAVs. We execute several flights with a custom Micro Aerial Vehicle (MAV) octocopter over a small calibration field equipped with 90 signalized targets and 25 ground control points. The octocopter carries a consumer grade RGB camera, modified to insure precise GPS time stamping of each exposure, as well as a multi-frequency/constellation GNSS receiver. The GNSS antenna and camera are rigidly mounted together on a one-axis gimbal that allows control of the obliquity of the captured imagery. The presented experiments focus on including absolute and relative aerial control. We confirm practically that both approaches are very effective: the absolute control allows omission of ground control points while the relative requires only a minimum number of control points. Indeed, the latter method represents an attractive alternative in the context of MAVs for two reasons. First, the procedure is somewhat simplified (e.g. the lever-arm between the camera perspective and antenna phase centers does not need to be determined) and, second, its principle allows employing a single-frequency antenna and carrier-phase GNSS receiver. This reduces the cost of the system as well as the payload, which in turn increases the flying time.

Performance of a flight qualified, thermoelectrically temperature controlled QCM sensor with power supply, thermal controller and signal processor

NASA Technical Reports Server (NTRS)

Wallace, D. A.

1980-01-01

A thermoelectrically temperature controlled quartz crystal microbalance (QCM) system was developed for the measurement of ion thrustor generated mercury contamination on spacecraft. Meaningful flux rate measurements dictated an accurately held sensing crystal temperature despite spacecraft surface temperature variations from -35 C to +60 C over the flight temperature range. An electronic control unit was developed with magentic amplifier transformer secondary power supply, thermal control electronics, crystal temperature analog conditioning and a multiplexed 16 bit frequency encoder.

Carrier-envelope phase control of femtosecond mode-locked lasers and direct optical frequency synthesis

PubMed

Jones; Diddams; Ranka; Stentz; Windeler; Hall; Cundiff

2000-04-28

We stabilized the carrier-envelope phase of the pulses emitted by a femtosecond mode-locked laser by using the powerful tools of frequency-domain laser stabilization. We confirmed control of the pulse-to-pulse carrier-envelope phase using temporal cross correlation. This phase stabilization locks the absolute frequencies emitted by the laser, which we used to perform absolute optical frequency measurements that were directly referenced to a stable microwave clock.

Alpha absolute power measurement in panic disorder with agoraphobia patients.

PubMed

de Carvalho, Marcele Regine; Velasques, Bruna Brandão; Freire, Rafael C; Cagy, Maurício; Marques, Juliana Bittencourt; Teixeira, Silmar; Rangé, Bernard P; Piedade, Roberto; Ribeiro, Pedro; Nardi, Antonio Egidio; Akiskal, Hagop Souren

2013-10-01

Panic attacks are thought to be a result from a dysfunctional coordination of cortical and brainstem sensory information leading to heightened amygdala activity with subsequent neuroendocrine, autonomic and behavioral activation. Prefrontal areas may be responsible for inhibitory top-down control processes and alpha synchronization seems to reflect this modulation. The objective of this study was to measure frontal absolute alpha-power with qEEG in 24 subjects with panic disorder and agoraphobia (PDA) compared to 21 healthy controls. qEEG data were acquired while participants watched a computer simulation, consisting of moments classified as "high anxiety"(HAM) and "low anxiety" (LAM). qEEG data were also acquired during two rest conditions, before and after the computer simulation display. We observed a higher absolute alpha-power in controls when compared to the PDA patients while watching the computer simulation. The main finding was an interaction between the moment and group factors on frontal cortex. Our findings suggest that the decreased alpha-power in the frontal cortex for the PDA group may reflect a state of high excitability. Our results suggest a possible deficiency in top-down control processes of anxiety reflected by a low absolute alpha-power in the PDA group while watching the computer simulation and they highlight that prefrontal regions and frontal region nearby the temporal area are recruited during the exposure to anxiogenic stimuli. © 2013 Elsevier B.V. All rights reserved.

An evaluation of adhesive sample holders for advanced crystallographic experiments

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

Mazzorana, Marco; Sanchez-Weatherby, Juan, E-mail: juan.sanchez-weatherby@diamond.ac.uk; Sandy, James

Commercially available adhesives have been evaluated for crystal mounting when undertaking complex macromolecular crystallography experiments. Here, their use as tools for advanced sample mounting and cryoprotection is assessed and their suitability for room-temperature data-collection and humidity-controlled studies is investigated. The hydration state of macromolecular crystals often affects their overall order and, ultimately, the quality of the X-ray diffraction pattern that they produce. Post-crystallization techniques that alter the solvent content of a crystal may induce rearrangement within the three-dimensional array making up the crystal, possibly resulting in more ordered packing. The hydration state of a crystal can be manipulated by exposingmore » it to a stream of air at controlled relative humidity in which the crystal can equilibrate. This approach provides a way of exploring crystal hydration space to assess the diffraction capabilities of existing crystals. A key requirement of these experiments is to expose the crystal directly to the dehydrating environment by having the minimum amount of residual mother liquor around it. This is usually achieved by placing the crystal on a flat porous support (Kapton mesh) and removing excess liquid by wicking. Here, an alternative approach is considered whereby crystals are harvested using adhesives that capture naked crystals directly from their crystallization drop, reducing the process to a one-step procedure. The impact of using adhesives to ease the harvesting of different types of crystals is presented together with their contribution to background scattering and their usefulness in dehydration experiments. It is concluded that adhesive supports represent a valuable tool for mounting macromolecular crystals to be used in humidity-controlled experiments and to improve signal-to-noise ratios in diffraction experiments, and how they can protect crystals from modifications in the sample environment is discussed.« less

Free-energy calculations using classical molecular simulation: application to the determination of the melting point and chemical potential of a flexible RDX model.

PubMed

Sellers, Michael S; Lísal, Martin; Brennan, John K

2016-03-21

We present an extension of various free-energy methodologies to determine the chemical potential of the solid and liquid phases of a fully-flexible molecule using classical simulation. The methods are applied to the Smith-Bharadwaj atomistic potential representation of cyclotrimethylene trinitramine (RDX), a well-studied energetic material, to accurately determine the solid and liquid phase Gibbs free energies, and the melting point (Tm). We outline an efficient technique to find the absolute chemical potential and melting point of a fully-flexible molecule using one set of simulations to compute the solid absolute chemical potential and one set of simulations to compute the solid-liquid free energy difference. With this combination, only a handful of simulations are needed, whereby the absolute quantities of the chemical potentials are obtained, for use in other property calculations, such as the characterization of crystal polymorphs or the determination of the entropy. Using the LAMMPS molecular simulator, the Frenkel and Ladd and pseudo-supercritical path techniques are adapted to generate 3rd order fits of the solid and liquid chemical potentials. Results yield the thermodynamic melting point Tm = 488.75 K at 1.0 atm. We also validate these calculations and compare this melting point to one obtained from a typical superheated simulation technique.

Controlling Chirality of Entropic Crystals.

PubMed

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

2015-10-09

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

Active porous transition towards spatiotemporal control of molecular flow in a crystal membrane

NASA Astrophysics Data System (ADS)

Takasaki, Yuichi; Takamizawa, Satoshi

2015-11-01

Fluidic control is an essential technology widely found in processes such as flood control in land irrigation and cell metabolism in biological tissues. In any fluidic control system, valve function is the key mechanism used to actively regulate flow and miniaturization of fluidic regulation with precise workability will be particularly vital in the development of microfluidic control. The concept of crystal engineering is alternative to processing technology in microstructure construction, as the ultimate microfluidic devices must provide molecular level control. Consequently, microporous crystals can instantly be converted to microfluidic devices if introduced in an active transformability of porous structure and geometry. Here we show that the introduction of a stress-induced martensitic transition mechanism converts a microporous molecular crystal into an active fluidic device with spatiotemporal molecular flow controllability through mechanical reorientation of subnanometre channels.

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

Huang, Huafeng; Colabello, Diane M.; Sklute, Elizabeth C.

The absolute absorption coefficient, α(E), is a critical design parameter for devices using semiconductors for light harvesting associated with renewable energy production, both for classic technologies such as photovoltaics and for emerging technologies such as direct solar fuel production. While α(E) is well-known for many classic simple semiconductors used in photovoltaic applications, the absolute values of α(E) are typically unknown for the complex semiconductors being explored for solar fuel production due to the absence of single crystals or crystalline epitaxial films that are needed for conventional methods of determining α(E). In this work, a simple self-referenced method for estimating bothmore » the refractive indices, n(E), and absolute absorption coefficients, α(E), for loose powder samples using diffuse reflectance data is demonstrated. In this method, the sample refractive index can be deduced by refining n to maximize the agreement between the relative absorption spectrum calculated from bidirectional reflectance data (calculated through a Hapke transform which depends on n) and integrating sphere diffuse reflectance data (calculated through a Kubleka–Munk transform which does not depend on n). This new method can be quickly used to screen the suitability of emerging semiconductor systems for light-harvesting applications. The effectiveness of this approach is tested using the simple classic semiconductors Ge and Fe 2O 3 as well as the complex semiconductors La 2MoO 5 and La 4Mo 2O 11. The method is shown to work well for powders with a narrow size distribution (exemplified by Fe 2O 3) and to be ineffective for semiconductors with a broad size distribution (exemplified by Ge). As such, it provides a means for rapidly estimating the absolute optical properties of complex solids which are only available as loose powders.« less

Controllable fabrication of copper phthalocyanine nanostructure crystals.

PubMed

Liu, Fangmei; Sun, Jia; Xiao, Si; Huang, Wenglong; Tao, Shaohua; Zhang, Yi; Gao, Yongli; Yang, Junliang

2015-06-05

Copper phthalocyanine (CuPc) nanostructure crystals, including nanoflower, nanoribbon, and nanowire, were controllably fabricated by temperature gradient physical vapor deposition (TG-PVD) through controlling the growth parameters. In a controllable growth system with carrier gas N2, nanoflower, nanoribbon, and nanowire crystals were formed in a high-temperature zone, medium-temperature zone, and low-temperature zone, respectively. They were proved to be β-phase, coexist of α-phase and β-phase, and α-phase respectively based on x-ray diffraction results. Furthermore, ultralong CuPc nanowires up to several millimeters could be fabricated by TG-PVD without carrier gas, and they were well-aligned to form large-area CuPc nanowire crystal arrays by the Langmuir-Blodgett method. The nanostructure crystals showed unusual optical absorption spectra from the ultraviolet-visible to near-infrared range, which was explained by the diffraction and scattering caused by the wavelength-sized nanostructures. These CuPc nanostructure crystals show potential applications in organic electronic and optoelectronic devices.

Structure and Growth Control of Organic–Inorganic Halide Perovskites for Optoelectronics: From Polycrystalline Films to Single Crystals

PubMed Central

Chen, Yani; He, Minhong; Peng, Jiajun; Sun, Yong

2016-01-01

Recently, organic–inorganic halide perovskites have sparked tremendous research interest because of their ground‐breaking photovoltaic performance. The crystallization process and crystal shape of perovskites have striking impacts on their optoelectronic properties. Polycrystalline films and single crystals are two main forms of perovskites. Currently, perovskite thin films have been under intensive investigation while studies of perovskite single crystals are just in their infancy. This review article is concentrated upon the control of perovskite structures and growth, which are intimately correlated for improvements of not only solar cells but also light‐emitting diodes, lasers, and photodetectors. We begin with the survey of the film formation process of perovskites including deposition methods and morphological optimization avenues. Strategies such as the use of additives, thermal annealing, solvent annealing, atmospheric control, and solvent engineering have been successfully employed to yield high‐quality perovskite films. Next, we turn to summarize the shape evolution of perovskites single crystals from three‐dimensional large sized single crystals, two‐dimensional nanoplates, one‐dimensional nanowires, to zero‐dimensional quantum dots. Siginificant functions of perovskites single crystals are highlighted, which benefit fundamental studies of intrinsic photophysics. Then, the growth mechanisms of the previously mentioned perovskite crystals are unveiled. Lastly, perspectives for structure and growth control of perovskites are outlined towards high‐performance (opto)electronic devices. PMID:27812463

Polymer-mediated growth of crystals and mesocrystals.

PubMed

Cölfen, Helmut

2013-01-01

Polymers are important additives for the control of mineralization reactions in both biological and bioinspired mineralization. The reason is that they allow for a number of interactions with the growing crystals and even amorphous minerals. These can substantially influence the way the mineral grows on several levels. Already in the prenucleation phase, polymers can control the formation of prenucleation clusters and subsequently the nucleation event. Also, polymers can control whether the further crystallization follows a classical or nonclassical particle-mediated growth path. In this chapter, the main ways in which polymers can be used to control a crystallization reaction will be highlighted. In addition, polymers that are useful for this purpose and the experimental conditions suitable for directing a crystallization reaction into the desired direction through the use of polymers will be described. © 2013 Elsevier Inc. All rights reserved.

Crystallization characteristics of iron-rich glass ceramics prepared from nickel slag and blast furnace slag

NASA Astrophysics Data System (ADS)

Wang, Zhong-Jie; Ni, Wen; Li, Ke-Qing; Huang, Xiao-Yan; Zhu, Li-Ping

2011-08-01

The crystallization process of iron-rich glass-ceramics prepared from the mixture of nickel slag (NS) and blast furnace slag (BFS) with a small amount of quartz sand was investigated. A modified melting method which was more energy-saving than the traditional methods was used to control the crystallization process. The results show that the iron-rich system has much lower melting temperature, glass transition temperature ( T g), and glass crystallization temperature ( T c), which can result in a further energy-saving process. The results also show that the system has a quick but controllable crystallization process with its peak crystallization temperature at 918°C. The crystallization of augite crystals begins from the edge of the sample and invades into the whole sample. The crystallization process can be completed in a few minutes. A distinct boundary between the crystallized part and the non-crystallized part exists during the process. In the non-crystallized part showing a black colour, some sphere-shaped augite crystals already exist in the glass matrix before samples are heated to T c. In the crystallized part showing a khaki colour, a compact structure is formed by augite crystals.

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 a series of related samples.

Large scale crystallization of protein pharmaceuticals in microgravity via temperature change

NASA Technical Reports Server (NTRS)

Long, Marianna M.

1992-01-01

The major objective of this research effort is the temperature driven growth of protein crystals in large batches in the microgravity environment of space. Pharmaceutical houses are developing protein products for patient care, for example, human insulin, human growth hormone, interferons, and tissue plasminogen activator or TPA, the clot buster for heart attack victims. Except for insulin, these are very high value products; they are extremely potent in small quantities and have a great value per gram of material. It is feasible that microgravity crystallization can be a cost recoverable, economically sound final processing step in their manufacture. Large scale protein crystal growth in microgravity has significant advantages from the basic science and the applied science standpoints. Crystal growth can proceed unhindered due to lack of surface effects. Dynamic control is possible and relatively easy. The method has the potential to yield large quantities of pure crystalline product. Crystallization is a time honored procedure for purifying organic materials and microgravity crystallization could be the final step to remove trace impurities from high value protein pharmaceuticals. In addition, microgravity grown crystals could be the final formulation for those medicines that need to be administered in a timed release fashion. Long lasting insulin, insulin lente, is such a product. Also crystalline protein pharmaceuticals are more stable for long-term storage. Temperature, as the initiation step, has certain advantages. Again, dynamic control of the crystallization process is possible and easy. A temperature step is non-invasive and is the most subtle way to control protein solubility and therefore crystallization. Seeding is not necessary. Changes in protein and precipitant concentrations and pH are not necessary. Finally, this method represents a new way to crystallize proteins in space that takes advantage of the unique microgravity environment. The results from two flights showed that the hardware performed perfectly, many crystals were produced, and they were much larger than their ground grown controls. Morphometric analysis was done on over 4,000 crystals to establish crystal size, size distribution, and relative size. Space grown crystals were remarkably larger than their earth grown counterparts and crystal size was a function of PCF volume. That size distribution for the space grown crystals was a function of PCF volume may indicate that ultimate size was a function of temperature gradient. Since the insulin protein concentration was very low, 0.4 mg/ml, the size distribution could also be following the total amount of protein in each of the PCF's. X-ray analysis showed that the bigger space grown insulin crystals diffracted to higher resolution than their ground grown controls. When the data were normalized for size, they still indicated that the space crystals were better than the ground crystals.

Three New Indole Diterpenoids from the Sea-Anemone-Derived Fungus Penicillium sp. AS-79

PubMed Central

Hu, Xue-Yi; Meng, Ling-Hong; Li, Xin; Yang, Sui-Qun; Li, Xiao-Ming; Wang, Bin-Gui

2017-01-01

Three new indolediterpenoids, namely, 22-hydroxylshearinine F (1), 6-hydroxylpaspalinine (2), and 7-O-acetylemindole SB (3), along with eight related known analogs (4–11), were isolated from the sea-anemone-derived fungus Penicillium sp. AS-79. The structures and relative configurations of these compounds were determined by a detailed interpretation of the spectroscopic data, and their absolute configurations were determined by ECD calculations (1 and 2) and single-crystal X-ray diffraction (3). Some of these compounds exhibited prominent activity against aquatic and human pathogenic microbes. PMID:28498358

Molecular structure studies of (1S,2S)-2-benzyl-2,3-dihydro-2-(1H-inden-2-yl)-1H-inden-1-ol

PubMed Central

Zhang, Tao; Paluch, Krzysztof; Scalabrino, Gaia; Frankish, Neil; Healy, Anne-Marie; Sheridan, Helen

2015-01-01

The single enantiomer (1S,2S)-2-benzyl-2,3-dihydro-2-(1H-inden-2-yl)-1H-inden-1-ol (2), has recently been synthesized and isolated from its corresponding diastereoisomer (1). The molecular and crystal structures of this novel compound have been fully analyzed. The relative and absolute configurations have been determined by using a combination of analytical tools including X-ray crystallography, X-ray Powder Diffraction (XRPD) analysis and Nuclear Magnetic Resonance (NMR) spectroscopy. PMID:25750458

Mollolide A, a diterpenoid with a new 1,10:2,3-disecograyanane skeleton from the roots of Rhododendron molle.

PubMed

Li, Yong; Liu, Yun-Bao; Zhang, Jian-Jun; Li, Yu-Huan; Jiang, Jian-Dong; Yu, Shi-Shan; Ma, Shuang-Gang; Qu, Jing; Lv, Hai-Ning

2013-06-21

Mollolide A (1), a diterpenoid featuring a new 1,10:2,3-disecograyanane skeleton, was isolated from the roots of Rhododendron molle. Its structure was elucidated through extensive MS, IR, and NMR spectroscopy analyses. The absolute configuration was determined by single-crystal X-ray diffraction of its p-bromobenzoate derivative (1b). Compound 1 exhibits a significant analgesic effect at a dose of 20 mg/kg and antiviral activity against the Coxsackie B3 virus with an IC50 value of 27.7 μM.

Determination of the calcium elemental abundance for 43 flares from SMM-XRP solar X-ray spectra

NASA Astrophysics Data System (ADS)

Lemen, J. R.; Sylwester, J.; Bentley, R. D.

The helium and lithium-like X-ray transitions of Ca XVIII-XIX have been used to make an absolute measurement of the coronal calcium elemental abundance relative to hydrogen (ACa) in solar flares. Cooling phase spectra of 43 flares obtained in channel 1 of the Bent Crystal Spectrometer on the Solar Maximum Mission have been analyzed. The abundance is determined from the intensity ratio of the Ca XIX resonance line (1S0 - 1P1) and nearby continuum. Attempts to correlate the ACa measurements with other observable features are discussed.

Arctigenin: a lignan from Arctium lappa.

PubMed

Gao, Haiyan; Li, Guanglei; Zhang, Junhe; Zeng, Jie

2008-07-19

The title compound {systematic name: (3R-trans)-4-[(3,4-dimethoxy-phen-yl)meth-yl]-3-[(4-hydr-oxy-3-methoxy-phen-yl)meth-yl]-4,5-dihydrofuran-2(3H)-one}, C(21)H(24)O(6), has a dibenz-yl-butyrolactone skeleton. The two aromatic rings are inclined at a dihedral angle of 68.75 (7)° with respect to each other. The lactone ring adopts an envelope conformation. A series of O-H⋯O and C-H⋯O hydrogen bonds contribute to the stabilization of the crystal packing. The absolute configuration was assigned on the basis of the published literature.

Improvement of Gaofen-3 Absolute Positioning Accuracy Based on Cross-Calibration

PubMed Central

Deng, Mingjun; Li, Jiansong

2017-01-01

The Chinese Gaofen-3 (GF-3) mission was launched in August 2016, equipped with a full polarimetric synthetic aperture radar (SAR) sensor in the C-band, with a resolution of up to 1 m. The absolute positioning accuracy of GF-3 is of great importance, and in-orbit geometric calibration is a key technology for improving absolute positioning accuracy. Conventional geometric calibration is used to accurately calibrate the geometric calibration parameters of the image (internal delay and azimuth shifts) using high-precision ground control data, which are highly dependent on the control data of the calibration field, but it remains costly and labor-intensive to monitor changes in GF-3’s geometric calibration parameters. Based on the positioning consistency constraint of the conjugate points, this study presents a geometric cross-calibration method for the rapid and accurate calibration of GF-3. The proposed method can accurately calibrate geometric calibration parameters without using corner reflectors and high-precision digital elevation models, thus improving absolute positioning accuracy of the GF-3 image. GF-3 images from multiple regions were collected to verify the absolute positioning accuracy after cross-calibration. The results show that this method can achieve a calibration accuracy as high as that achieved by the conventional field calibration method. PMID:29240675

Absolute Humidity and the Seasonality of Influenza (Invited)

NASA Astrophysics Data System (ADS)

Shaman, J. L.; Pitzer, V.; Viboud, C.; Grenfell, B.; Goldstein, E.; Lipsitch, M.

2010-12-01

Much of the observed wintertime increase of mortality in temperate regions is attributed to seasonal influenza. A recent re-analysis of laboratory experiments indicates that absolute humidity strongly modulates the airborne survival and transmission of the influenza virus. Here we show that the onset of increased wintertime influenza-related mortality in the United States is associated with anomalously low absolute humidity levels during the prior weeks. We then use an epidemiological model, in which observed absolute humidity conditions temper influenza transmission rates, to successfully simulate the seasonal cycle of observed influenza-related mortality. The model results indicate that direct modulation of influenza transmissibility by absolute humidity alone is sufficient to produce this observed seasonality. These findings provide epidemiological support for the hypothesis that absolute humidity drives seasonal variations of influenza transmission in temperate regions. In addition, we show that variations of the basic and effective reproductive numbers for influenza, caused by seasonal changes in absolute humidity, are consistent with the general timing of pandemic influenza outbreaks observed for 2009 A/H1N1 in temperate regions. Indeed, absolute humidity conditions correctly identify the region of the United States vulnerable to a third, wintertime wave of pandemic influenza. These findings suggest that the timing of pandemic influenza outbreaks is controlled by a combination of absolute humidity conditions, levels of susceptibility and changes in population mixing and contact rates.

Charge Stabilized Crystalline Colloidal Arrays As Templates For Fabrication of Non-Close-Packed Inverted Photonic Crystals

PubMed Central

Bohn, Justin J.; Ben-Moshe, Matti; Tikhonov, Alexander; Qu, Dan; Lamont, Daniel N.

2010-01-01

We developed a straightforward method to form non close-packed highly ordered fcc direct and inverse opal silica photonic crystals. We utilize an electrostatically self assembled crystalline colloidal array (CCA) template formed by monodisperse, highly charged polystyrene particles. We then polymerize a hydrogel around the CCA (PCCA) and condense the silica to form a highly ordered silica impregnated (siPCCA) photonic crystal. Heating at 450 °C removes the organic polymer leaving a silica inverse opal structure. By altering the colloidal particle concentration we independently control the particle spacing and the wall thickness of the inverse opal photonic crystals. This allows us to control the optical dielectric constant modulation in order to optimize the diffraction; the dielectric constant modulation is controlled independently of the photonic crystal periodicity. These fcc photonic crystals are better ordered than typical close-packed photonic crystals because their self assembly utilizes soft electrostatic repulsive potentials. We show that colloidal particle size and charge polydispersity has modest impact on ordering, in contrast to that for close-packed crystals. PMID:20163800

Ultrahigh-Repetition Pulse Train with Absolute-Phase Control Produced by AN Adiabatic Raman Process

NASA Astrophysics Data System (ADS)

Katsuragawa, M.; Suzuki, T.; Shiraga, K.; Arakawa, M.; Onose, T.; Yokoyama, K.; Hong, F. L.; Misawa, K.

2010-02-01

We describe the generation of an ultrahigh-repetition-rate train of ultrashort pulses on the basis of an adiabatic Raman process. We also describe recent progress in studies toward the ultimate regime: realization of an ultrahigh-repetition-rate train of monocycle pulses with control of the absolute phase. We comment on the milestones expected in the near future in terms of the study of such novel light sources and the new field of optical science stimulated by their development.

Innovative remotely-controlled bending device for thin silicon and germanium crystals

NASA Astrophysics Data System (ADS)

De Salvador, D.; Carturan, S.; Mazzolari, A.; Bagli, E.; Bandiera, L.; Durighello, C.; Germogli, G.; Guidi, V.; Klag, P.; Lauth, W.; Maggioni, G.; Romagnoni, M.; Sytov, A.

2018-04-01

Steering of negatively charged particle beams below 1 GeV has demonstrated to be possible with thin bent silicon and germanium crystals. A newly designed mechanical holder was used for bending crystals, since it allows a remotely-controlled adjustment of crystal bending and compensation of unwanted torsion. Bent crystals were installed and tested at the MAMI Mainz MIcrotron to achieve steering of 0.855-GeV electrons at different bending radii. We report the description and characterization of the innovative bending device developed at INFN Laboratori Nazionali di Legnaro (LNL).

Controllable Growth of Monolayer MoS2 and MoSe2 Crystals Using Three-temperature-zone Furnace

NASA Astrophysics Data System (ADS)

Zheng, Binjie; Chen, Yuanfu

2017-12-01

Monolayer molybdenum disulfide (MoS2) and molybdenum diselenide (MoSe2) have attracted a great attention for their exceptional electronic and optoelectronic properties among the two dimensional family. However, controllable synthesis of monolayer crystals with high quality needs to be improved urgently. Here we demonstrate a chemical vapor deposition (CVD) growth of monolayer MoS2 and MoSe2 crystals using three-temperature-zone furnace. Systematical study of the effects of growth pressure, temperature and time on the thickness, morphology and grain size of crystals shows the good controllability. The photoluminescence (PL) characterizations indicate that the as-grown monolayer MoS2 and MoSe2 crystals possess excellent optical qualities with very small full-width-half-maximum (FWHM) of 96 me V and 57 me V, respectively. It is comparable to that of exfoliated monolayers and reveals their high crystal quality. It is promising that our strategy should be applicable for the growth of other transition metal dichalcogenides (TMDs) monolayer crystals.

Structural Color Patterns by Electrohydrodynamic Jet Printed Photonic Crystals.

PubMed

Ding, Haibo; Zhu, Cun; Tian, Lei; Liu, Cihui; Fu, Guangbin; Shang, Luoran; Gu, Zhongze

2017-04-05

In this work, we demonstrate the fabrication of photonic crystal patterns with controllable morphologies and structural colors utilizing electrohydrodynamic jet (E-jet) printing with colloidal crystal inks. The final shape of photonic crystal units is controlled by the applied voltage signal and wettability of the substrate. Optical properties of the structural color patterns are tuned by the self-assembly of the silica nanoparticle building blocks. Using this direct printing technique, it is feasible to print customized functional patterns composed of photonic crystal dots or photonic crystal lines according to relevant printing mode and predesigned tracks. This is the first report for E-jet printing with colloidal crystal inks. Our results exhibit promising applications in displays, biosensors, and other functional devices.

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

Ramadhar, Timothy R.; Zheng, Shao-Liang; Chen, Yu-Sheng

This report describes complete practical guidelines and insights for the crystalline sponge method, which have been derived through the first use of synchrotron radiation on these systems, and includes a procedure for faster synthesis of the sponges. These guidelines will be applicable to crystal sponge data collected at synchrotrons or in-house facilities, and will allow researchers to obtain reliable high-quality data and construct chemically and physically sensible models for guest structural determination. A detailed set of synthetic and crystallographic guidelines for the crystalline sponge method based upon the analysis of expediently synthesized crystal sponges using third-generation synchrotron radiation are reported.more » The procedure for the synthesis of the zinc-based metal–organic framework used in initial crystal sponge reports has been modified to yield competent crystals in 3 days instead of 2 weeks. These crystal sponges were tested on some small molecules, with two being unexpectedly difficult cases for analysis with in-house diffractometers in regard to data quality and proper space-group determination. These issues were easily resolved by the use of synchrotron radiation using data-collection times of less than an hour. One of these guests induced a single-crystal-to-single-crystal transformation to create a larger unit cell with over 500 non-H atoms in the asymmetric unit. This led to a non-trivial refinement scenario that afforded the best Flack x absolute stereochemical determination parameter to date for these systems. The structures did not require the use of PLATON/SQUEEZE or other solvent-masking programs, and are the highest-quality crystalline sponge systems reported to date where the results are strongly supported by the data. A set of guidelines for the entire crystallographic process were developed through these studies. In particular, the refinement guidelines include strategies to refine the host framework, locate guests and determine occupancies, discussion of the proper use of geometric and anisotropic displacement parameter restraints and constraints, and whether to perform solvent squeezing/masking. The single-crystal-to-single-crystal transformation process for the crystal sponges is also discussed. The presented general guidelines will be invaluable for researchers interested in using the crystalline sponge method at in-house diffraction or synchrotron facilities, will facilitate the collection and analysis of reliable high-quality data, and will allow construction of chemically and physically sensible models for guest structural determination.« less

A flow-free droplet-based device for high throughput polymorphic crystallization.

PubMed

Yang, Shih-Mo; Zhang, Dapeng; Chen, Wang; Chen, Shih-Chi

2015-06-21

Crystallization is one of the most crucial steps in the process of pharmaceutical formulation. In recent years, emulsion-based platforms have been developed and broadly adopted to generate high quality products. However, these conventional approaches such as stirring are still limited in several aspects, e.g., unstable crystallization conditions and broad size distribution; besides, only simple crystal forms can be produced. In this paper, we present a new flow-free droplet-based formation process for producing highly controlled crystallization with two examples: (1) NaCl crystallization reveals the ability to package saturated solution into nanoliter droplets, and (2) glycine crystallization demonstrates the ability to produce polymorphic crystallization forms by controlling the droplet size and temperature. In our process, the saturated solution automatically fills the microwell array powered by degassed bulk PDMS. A critical oil covering step is then introduced to isolate the saturated solution and control the water dissolution rate. Utilizing surface tension, the solution is uniformly packaged in the form of thousands of isolating droplets at the bottom of each microwell of 50-300 μm diameter. After water dissolution, individual crystal structures are automatically formed inside the microwell array. This approach facilitates the study of different glycine growth processes: α-form generated inside the droplets and γ-form generated at the edge of the droplets. With precise temperature control over nanoliter-sized droplets, the growth of ellipsoidal crystalline agglomerates of glycine was achieved for the first time. Optical and SEM images illustrate that the ellipsoidal agglomerates consist of 2-5 μm glycine clusters with inner spiral structures of ~35 μm screw pitch. Lastly, the size distribution of spherical crystalline agglomerates (SAs) produced from microwells of different sizes was measured to have a coefficient variation (CV) of less than 5%, showing crystal sizes can be precisely controlled by microwell sizes with high uniformity. This new method can be used to reliably fabricate monodispersed crystals for pharmaceutical applications.

Field-controllable Spin-Hall Effect of Light in Optical Crystals: A Conoscopic Mueller Matrix Analysis.

PubMed

Samlan, C T; Viswanathan, Nirmal K

2018-01-31

Electric-field applied perpendicular to the direction of propagation of paraxial beam through an optical crystal dynamically modifies the spin-orbit interaction (SOI), leading to the demonstration of controllable spin-Hall effect of light (SHEL). The electro- and piezo-optic effects of the crystal modifies the radially symmetric spatial variation in the fast-axis orientation of the crystal, resulting in a complex pattern with different topologies due to the symmetry-breaking effect of the applied field. This introduces spatially-varying Pancharatnam-Berry type geometric phase on to the paraxial beam of light, leading to the observation of SHEL in addition to the spin-to-vortex conversion. A wave-vector resolved conoscopic Mueller matrix measurement and analysis provides a first glimpse of the SHEL in the biaxial crystal, identified via the appearance of weak circular birefringence. The emergence of field-controllable fast-axis orientation of the crystal and the resulting SHEL provides a new degree of freedom for affecting and controlling the spin and orbital angular momentum of photons to unravel the rich underlying physics of optical crystals and aid in the development of active photonic spin-Hall devices.

High quantum-yield phosphors via quantum splitting and upconversion

NASA Astrophysics Data System (ADS)

Jeong, Joayoung

The Gd3+ ion has been used to induce quantum splitting in luminescent materials by using cross-relaxation energy transfer (CRET). In Nd:LiGdF4, quantum splitting results from a two-step CRET between Gd3+ and Nd3+, first involving a transition 6G→6I on Gd3+ and an excitation within the 4f3 configuration of Nd3+ followed by a second CRET that brings Gd3+ to 6P7/2. The excited Nd3+ ion rapidly relaxes nonradiatively to the emitting 4F3/2. The excited Gd3+ ion then transfers its energy back to Nd3+, which gives rise to the second photon. The result is a quantum yield of 1.05 +/- 0.35 with emission in the NIR following excitation at 175 nm. GdF3:Pr3+, Eu 3+ also exhibits quantum splitting, but only at very low concentration of Pr3+ (0.3%) and Eu3+ (0.2%), resulting in a quantum yield of approximately 20% under 160-nm excitation. Host intrinsic emission via a self-trapped exciton (STE) was also examined as a means to sensitize Gd3+ emission. The material ScPO4:Gd 3+ exhibits a high absolute quantum yield of 0.9 +/- 0.2 under 170-nm excitation, demonstrating a potentially new and efficient pathway for exciting quantum splitting phosphors. Single crystals of the material GdZrF7 were grown, and its structure was established via single-crystal X-ray diffraction methods. Doped samples of GdZrF7:Yb3+, Er3+ exhibit bright up-conversion luminescence with light output that is up to twice that of a commercial material based on the host Gd2O2S. When doped with Eu3+, the fluoride also emits a nearly white color under vacuum ultraviolet excitation with an absolute quantum yield near 0.9. The new compound Gd4.67(SiO4)3S was synthesized and studied. The structure was established via single-crystal X-ray methods, and the luminescence of Tb3+ samples was investigated.

The evolution of self-control

PubMed Central

MacLean, Evan L.; Hare, Brian; Nunn, Charles L.; Addessi, Elsa; Amici, Federica; Anderson, Rindy C.; Aureli, Filippo; Baker, Joseph M.; Bania, Amanda E.; Barnard, Allison M.; Boogert, Neeltje J.; Brannon, Elizabeth M.; Bray, Emily E.; Bray, Joel; Brent, Lauren J. N.; Burkart, Judith M.; Call, Josep; Cantlon, Jessica F.; Cheke, Lucy G.; Clayton, Nicola S.; Delgado, Mikel M.; DiVincenti, Louis J.; Fujita, Kazuo; Herrmann, Esther; Hiramatsu, Chihiro; Jacobs, Lucia F.; Jordan, Kerry E.; Laude, Jennifer R.; Leimgruber, Kristin L.; Messer, Emily J. E.; de A. Moura, Antonio C.; Ostojić, Ljerka; Picard, Alejandra; Platt, Michael L.; Plotnik, Joshua M.; Range, Friederike; Reader, Simon M.; Reddy, Rachna B.; Sandel, Aaron A.; Santos, Laurie R.; Schumann, Katrin; Seed, Amanda M.; Sewall, Kendra B.; Shaw, Rachael C.; Slocombe, Katie E.; Su, Yanjie; Takimoto, Ayaka; Tan, Jingzhi; Tao, Ruoting; van Schaik, Carel P.; Virányi, Zsófia; Visalberghi, Elisabetta; Wade, Jordan C.; Watanabe, Arii; Widness, Jane; Young, Julie K.; Zentall, Thomas R.; Zhao, Yini

2014-01-01

Cognition presents evolutionary research with one of its greatest challenges. Cognitive evolution has been explained at the proximate level by shifts in absolute and relative brain volume and at the ultimate level by differences in social and dietary complexity. However, no study has integrated the experimental and phylogenetic approach at the scale required to rigorously test these explanations. Instead, previous research has largely relied on various measures of brain size as proxies for cognitive abilities. We experimentally evaluated these major evolutionary explanations by quantitatively comparing the cognitive performance of 567 individuals representing 36 species on two problem-solving tasks measuring self-control. Phylogenetic analysis revealed that absolute brain volume best predicted performance across species and accounted for considerably more variance than brain volume controlling for body mass. This result corroborates recent advances in evolutionary neurobiology and illustrates the cognitive consequences of cortical reorganization through increases in brain volume. Within primates, dietary breadth but not social group size was a strong predictor of species differences in self-control. Our results implicate robust evolutionary relationships between dietary breadth, absolute brain volume, and self-control. These findings provide a significant first step toward quantifying the primate cognitive phenome and explaining the process of cognitive evolution. PMID:24753565

Shape-Evolution Control of hybrid perovskite CH3NH3PbI3 crystals via solvothermal synthesis

NASA Astrophysics Data System (ADS)

Zhang, Baohua; Guo, Fuqiang; Yang, Lianhong; Jia, Xiuling; Liu, Bin; Xie, Zili; Chen, Dunjun; Lu, Hai; Zhang, Rong; Zheng, Youdou

2017-02-01

We systematically synthesized CH3NH3PbI3 crystals using solvothermal process, and the reaction conditions such as concentration of the precursor, temperature, time, and lead source have been comprehensively investigated to obtain shape-controlled CH3NH3PbI3 crystals. The results showed that the CH3NH3PbI3 crystals exhibit tetragonal phase and the crystals change from nanoparticles to hopper-faced cuboids. Photoluminescence spectra of the crystals obtained with different lead sources show a blue shift due to the presence of defects in the crystals, and the peak intensity is very sensitive to the lead sources. Moreover, impurities (undesirable byproducts and excess components like HI or CH3NH2) presented during crystal growth can result in hopper growth.

Crystal structures of two novel dye-decolorizing peroxidases reveal a beta-barrel fold with a conserved heme-binding motif.

PubMed

Zubieta, Chloe; Krishna, S Sri; Kapoor, Mili; Kozbial, Piotr; McMullan, Daniel; Axelrod, Herbert L; Miller, Mitchell D; Abdubek, Polat; Ambing, Eileen; Astakhova, Tamara; Carlton, Dennis; Chiu, Hsiu-Ju; Clayton, Thomas; Deller, Marc C; Duan, Lian; Elsliger, Marc-André; Feuerhelm, Julie; Grzechnik, Slawomir K; Hale, Joanna; Hampton, Eric; Han, Gye Won; Jaroszewski, Lukasz; Jin, Kevin K; Klock, Heath E; Knuth, Mark W; Kumar, Abhinav; Marciano, David; Morse, Andrew T; Nigoghossian, Edward; Okach, Linda; Oommachen, Silvya; Reyes, Ron; Rife, Christopher L; Schimmel, Paul; van den Bedem, Henry; Weekes, Dana; White, Aprilfawn; Xu, Qingping; Hodgson, Keith O; Wooley, John; Deacon, Ashley M; Godzik, Adam; Lesley, Scott A; Wilson, Ian A

2007-11-01

BtDyP from Bacteroides thetaiotaomicron (strain VPI-5482) and TyrA from Shewanella oneidensis are dye-decolorizing peroxidases (DyPs), members of a new family of heme-dependent peroxidases recently identified in fungi and bacteria. Here, we report the crystal structures of BtDyP and TyrA at 1.6 and 2.7 A, respectively. BtDyP assembles into a hexamer, while TyrA assembles into a dimer; the dimerization interface is conserved between the two proteins. Each monomer exhibits a two-domain, alpha+beta ferredoxin-like fold. A site for heme binding was identified computationally, and modeling of a heme into the proposed active site allowed for identification of residues likely to be functionally important. Structural and sequence comparisons with other DyPs demonstrate a conservation of putative heme-binding residues, including an absolutely conserved histidine. Isothermal titration calorimetry experiments confirm heme binding, but with a stoichiometry of 0.3:1 (heme:protein). (c) 2007 Wiley-Liss, Inc.

Piezo-optic tensor of crystals from quantum-mechanical calculations.

PubMed

Erba, A; Ruggiero, M T; Korter, T M; Dovesi, R

2015-10-14

An automated computational strategy is devised for the ab initio determination of the full fourth-rank piezo-optic tensor of crystals belonging to any space group of symmetry. Elastic stiffness and compliance constants are obtained as numerical first derivatives of analytical energy gradients with respect to the strain and photo-elastic constants as numerical derivatives of analytical dielectric tensor components, which are in turn computed through a Coupled-Perturbed-Hartree-Fock/Kohn-Sham approach, with respect to the strain. Both point and translation symmetries are exploited at all steps of the calculation, within the framework of periodic boundary conditions. The scheme is applied to the determination of the full set of ten symmetry-independent piezo-optic constants of calcium tungstate CaWO4, which have recently been experimentally reconstructed. Present calculations unambiguously determine the absolute sign (positive) of the π61 constant, confirm the reliability of 6 out of 10 experimentally determined constants and provide new, more accurate values for the remaining 4 constants.

Piezo-optic tensor of crystals from quantum-mechanical calculations

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

Erba, A., E-mail: alessandro.erba@unito.it; Dovesi, R.; Ruggiero, M. T.

2015-10-14

An automated computational strategy is devised for the ab initio determination of the full fourth-rank piezo-optic tensor of crystals belonging to any space group of symmetry. Elastic stiffness and compliance constants are obtained as numerical first derivatives of analytical energy gradients with respect to the strain and photo-elastic constants as numerical derivatives of analytical dielectric tensor components, which are in turn computed through a Coupled-Perturbed-Hartree-Fock/Kohn-Sham approach, with respect to the strain. Both point and translation symmetries are exploited at all steps of the calculation, within the framework of periodic boundary conditions. The scheme is applied to the determination of themore » full set of ten symmetry-independent piezo-optic constants of calcium tungstate CaWO{sub 4}, which have recently been experimentally reconstructed. Present calculations unambiguously determine the absolute sign (positive) of the π{sub 61} constant, confirm the reliability of 6 out of 10 experimentally determined constants and provide new, more accurate values for the remaining 4 constants.« less

Minerals of the earth's deep interior

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

Schiferl, D.; Zhao, Y.; Shankland, T.J.

1998-11-01

This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). The project addresses the major geophysical issue of the nature of the seismic velocity and density discontinuity at 670 km depth (the boundary between upper and lower mantle with temperature about 1,900 K and pressure about 23 GPa). A phase change at this depth would represent a relatively small barrier to mantle convection through the discontinuity, but compositional change would inhibit thermal convection throughout the mantle. To address this problem the authors measured equation of state parameters in mantlemore » minerals as functions of high P-T using single crystal x-ray diffraction with a unique, new diamond-anvil cell (DAC) at simultaneous high temperature and pressure. Single-crystal diffraction improves absolute accuracy in lattice constants over those from powder diffraction by a factor of 5 to 10. The authors have measured equations of state of orthoenstatite MgSiO{sub 3} and hexagonal boron nitride hBN.« less

Design of activated serine-containing catalytic triads with atomic level accuracy

PubMed Central

Rajagopalan, Sridharan; Wang, Chu; Yu, Kai; Kuzin, Alexandre P.; Richter, Florian; Lew, Scott; Miklos, Aleksandr E.; Matthews, Megan L.; Seetharaman, Jayaraman; Su, Min; Hunt, John. F.; Cravatt, Benjamin F.; Baker, David

2014-01-01

A challenge in the computational design of enzymes is that multiple properties must be simultaneously optimized -- substrate-binding, transition state stabilization, and product release -- and this has limited the absolute activity of successful designs. Here, we focus on a single critical property of many enzymes: the nucleophilicity of an active site residue that initiates catalysis. We design proteins with idealized serine-containing catalytic triads, and assess their nucleophilicity directly in native biological systems using activity-based organophosphate probes. Crystal structures of the most successful designs show unprecedented agreement with computational models, including extensive hydrogen bonding networks between the catalytic triad (or quartet) residues, and mutagenesis experiments demonstrate that these networks are critical for serine activation and organophosphate-reactivity. Following optimization by yeast-display, the designs react with organophosphate probes at rates comparable to natural serine hydrolases. Co-crystal structures with diisopropyl fluorophosphate bound to the serine nucleophile suggest the designs could provide the basis for a new class of organophosphate captures agents. PMID:24705591

Effect of Low-Concentration Polymers on Crystal Growth in Molecular Glasses: A Controlling Role for Polymer Segmental Mobility Relative to Host Dynamics.

PubMed

Huang, Chengbin; Powell, C Travis; Sun, Ye; Cai, Ting; Yu, Lian

2017-03-02

Low-concentration polymers can strongly influence crystal growth in small-molecule glasses, a phenomenon important for improving physical stability against crystallization. We measured the velocity of crystal growth in two molecular glasses, nifedipine (NIF) and o-terphenyl (OTP), each doped with four or five different polymers. For each polymer, the concentration was fixed at 1 wt % and a wide range of molecular weights was tested. We find that a polymer additive can strongly alter the rate of crystal growth, from a 10-fold reduction to a 10-fold increase. For a given polymer, increasing molecular weight slows down crystal growth and the effect saturates around DP = 100, where DP is the degree of polymerization. For all the systems studied, the polymer effect on crystal growth rate forms a master curve in the variable (T g,polymer - T g,host )/T cryst , where T g is the glass transition temperature and T cryst is the crystallization temperature. These results support the view that a polymer's effect on crystal growth is controlled by its segmental mobility relative to the host-molecule dynamics. In the proposed model, crystal growth rejects impurities and creates local polymer-rich regions, which must be traversed by host molecules to sustain crystal growth at rates determined by polymer segmental mobility. Our results do not support the view that host-polymer hydrogen bonding plays a controlling role in crystal growth inhibition.

Two Beam Energy Exchange in Hybrid Liquid Crystal Cells with Photorefractive Field Controlled Boundary Conditions (Postprint)

DTIC Science & Technology

2016-09-12

AFRL-RX-WP-JA-2017-0209 TWO BEAM ENERGY EXCHANGE IN HYBRID LIQUID CRYSTAL CELLS WITH PHOTOREFRACTIVE FIELD CONTROLLED BOUNDARY...estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the... CRYSTAL CELLS WITH PHOTOREFRACTIVE FIELD CONTROLLED BOUNDARY CONDITIONS (POSTPRINT) 5a. CONTRACT NUMBER FA8650-16-D-5402-0001 5b. GRANT

High-Temperature Controlled Redox Crystallization Studies

NASA Technical Reports Server (NTRS)

Williams, R. J.

1985-01-01

The crystallization of silicates containing redox sensitive ions (e.g., Fe, Ti, Ce) must be performed under controlled and known redox conditions in order to obtain the maximum scientific benefit from experimental study. Furthermore, many compositions crystallize dense phases which settle during ground-based experiments. This settling influences the texture and chemical evolution of the crystallizing system. The purpose of this investigation is to develop a test system in which controlled redox experiments can be performed in the microgravity environment. The system will use solid ceramic oxygen electrolyte cells for control, measurements, and production of the required redox conditions. A preliminary design for a prototype is developed, the electrolyte and furnace tested, and a tentative protocol for experiment developed. The control parameter is to be established and a laboratory prototype built.

A low temperature furnace for solution crystal growth on the International Space Station

NASA Astrophysics Data System (ADS)

Baç, Nurcan; Harpster, Joseph; Maston, Robert A.; Sacco, Albert

2000-01-01

The Zeolite Crystal Growth Furnace Unit (ZCG-FU) is the first module in an integrated payload designed for low temperature crystal growth in solutions on the International Space Station (ISS). This payload is scheduled to fly on the ISS flight 7A.1 in an EXPRESS rack. Its name originated from early shuttle flight experiments limited to the growth of zeolite crystals but has since grown to include other materials of significant commercial interest using the solution method of crystal growth. Zeolites, ferroelectrics, piezeoelectrics and silver halides are some of the materials considered. The ZCG-FU experiment consists of a furnace unit and its electronic control system, and mechanically complex, crystal growth autoclaves suitable for use with a particular furnace and solution. The ZCG facility is being designed to grow into four independent furnaces controlled by IZECS (Improved Zeolite Electronic Control System). IZECS provides monitoring of critical parameters, data logging, safety monitoring, air-to-ground control and operator interfacing. It is suitable for controlling the four furnaces either individually or all at one time. It also contains the power management solid-state drivers and switches for the ZCG-FU furnace. The furnace contains 19 tubes operating at three different temperature zones. .

IMPROVEMENT OF SMVGEAR II ON VECTOR AND SCALAR MACHINES THROUGH ABSOLUTE ERROR TOLERANCE CONTROL (R823186)

EPA Science Inventory

The computer speed of SMVGEAR II was improved markedly on scalar and vector machines with relatively little loss in accuracy. The improvement was due to a method of frequently recalculating the absolute error tolerance instead of keeping it constant for a given set of chemistry. ...

Nucleation and growth of crystals under cirrus and polar stratospheric cloud conditions

NASA Technical Reports Server (NTRS)

Hallett, John; Queen, Brian; Teets, Edward; Fahey, James

1995-01-01

Laboratory studies examine phase changes of hygroscopic substances which occur as aerosol in stratosphere and troposphere (sodium chloride, ammonium sulfate, ammonium bisulfate, nitric acid, sulfuric acid), under controlled conditions, in samples volume 1 to 10(exp -4) ml. Crystallization of salts from supersaturated solutions is examined by slowly evaporating a solution drop on a substrate, under controlled relative humidity, until self nucleation occurs; controlled nucleation of ice in a mm capillary U-tube gives a measured ice crystallization velocity at known supercooling. Two states of crystallization occur for regions where hydrates exist. It is inferred that all of the materials readily exist as supersaturated/supercooled solutions; the degree of metastability appears to be slightly enhanced by inclusion of aircraft produced soot. The crystallization velocity is taken as a measure of viscosity. Results suggest an approach to a glass transition at high molality, supersaturation and/or supercooling within the range of atmospheric interest. It is hypothesized that surface reactions occur more readily on solidified particles - either crystalline or glass, whereas volume reactions are more important on droplets with sufficiently low viscosity and volume diffusivity. Implications are examined for optical properties of such particles in the atmosphere. In a separate experiment, crystal growth was examined in a modified thermal vapor diffusion chamber over the range of cirrus temperature (-30 to -70 C) and under controlled supersaturation and air pressure. The crystals grew at a velocity of 1-2 microns/s, thickness 60-70 micron, in the form of thin column crystals. Design criteria are given for a system to investigate particle growth down to -100 C, (PSC temperatures) where nitric acid particles can be grown under similar control and in the form of hydrate crystals.

Dispersion corrected hartree-fock and density functional theory for organic crystal structure prediction.

PubMed

Brandenburg, Jan Gerit; Grimme, Stefan

2014-01-01

We present and evaluate dispersion corrected Hartree-Fock (HF) and Density Functional Theory (DFT) based quantum chemical methods for organic crystal structure prediction. The necessity of correcting for missing long-range electron correlation, also known as van der Waals (vdW) interaction, is pointed out and some methodological issues such as inclusion of three-body dispersion terms are discussed. One of the most efficient and widely used methods is the semi-classical dispersion correction D3. Its applicability for the calculation of sublimation energies is investigated for the benchmark set X23 consisting of 23 small organic crystals. For PBE-D3 the mean absolute deviation (MAD) is below the estimated experimental uncertainty of 1.3 kcal/mol. For two larger π-systems, the equilibrium crystal geometry is investigated and very good agreement with experimental data is found. Since these calculations are carried out with huge plane-wave basis sets they are rather time consuming and routinely applicable only to systems with less than about 200 atoms in the unit cell. Aiming at crystal structure prediction, which involves screening of many structures, a pre-sorting with faster methods is mandatory. Small, atom-centered basis sets can speed up the computation significantly but they suffer greatly from basis set errors. We present the recently developed geometrical counterpoise correction gCP. It is a fast semi-empirical method which corrects for most of the inter- and intramolecular basis set superposition error. For HF calculations with nearly minimal basis sets, we additionally correct for short-range basis incompleteness. We combine all three terms in the HF-3c denoted scheme which performs very well for the X23 sublimation energies with an MAD of only 1.5 kcal/mol, which is close to the huge basis set DFT-D3 result.

238U-230Th dating of chevkinite in high-silica rhyolites from La Primavera and Yellowstone calderas

USGS Publications Warehouse

Vazquez, Jorge A.; Velasco, Noel O.; Schmitt, Axel K.; Bleick, Heather A.; Stelten, Mark E.

2014-01-01

Application of 238U-230Th disequilibrium dating of accessory minerals with contrasting stabilities and compositions can provide a unique perspective on magmatic evolution by placing the thermochemical evolution of magma within the framework of absolute time. Chevkinite, a Th-rich accessory mineral that occurs in peralkaline and metaluminous rhyolites, may be particularly useful as a chronometer of crystallization and differentiation because its composition may reflect the chemical changes of its host melt. Ion microprobe 128U-230Th dating of single chevkinite microphenocrysts from pre- and post-caldera La Primavera, Mexico, rhyolites yields model crystallization ages that are within 10's of k.y. of their corresponding K-Ar ages of ca. 125 ka to 85 ka, while chevkinite microphenocrysts from a post-caldera Yellowstone, USA, rhyolite yield a range of ages from ca. 110 ka to 250 ka, which is indistinguishable from the age distribution of coexisting zircon. Internal chevkinite-zircon isochrons from La Primavera yield Pleistocene ages with ~5% precision due to the nearly two order difference in Th/U between both minerals. Coupling chevkinite 238U-230Th ages and compositional analyses reveals a secular trend of Th/U and rare earth elements recorded in Yellowstone rhyolite, likely reflecting progressive compositional evolution of host magma. The relatively short timescale between chevkinite-zircon crystallization and eruption suggests that crystal-poor rhyolites at La Primavera were erupted shortly after differentiation and/or reheating. These results indicate that 238U-230Th dating of chevkinite via ion microprobe analysis may be used to date crystallization and chemical evolution of silicic magmas.

Phase diagram of a symmetric electron-hole bilayer system: a variational Monte Carlo study.

PubMed

Sharma, Rajesh O; Saini, L K; Bahuguna, Bhagwati Prasad

2018-05-10

We study the phase diagram of a symmetric electron-hole bilayer system at absolute zero temperature and in zero magnetic field within the quantum Monte Carlo approach. In particular, we conduct variational Monte Carlo simulations for various phases, i.e. the paramagnetic fluid phase, the ferromagnetic fluid phase, the anti-ferromagnetic Wigner crystal phase, the ferromagnetic Wigner crystal phase and the excitonic phase, to estimate the ground-state energy at different values of in-layer density and inter-layer spacing. Slater-Jastrow style trial wave functions, with single-particle orbitals appropriate for different phases, are used to construct the phase diagram in the (r s , d) plane by finding the relative stability of trial wave functions. At very small layer separations, we find that the fluid phases are stable, with the paramagnetic fluid phase being particularly stable at [Formula: see text] and the ferromagnetic fluid phase being particularly stable at [Formula: see text]. As the layer spacing increases, we first find that there is a phase transition from the ferromagnetic fluid phase to the ferromagnetic Wigner crystal phase when d reaches 0.4 a.u. at r s   =  20, and before there is a return to the ferromagnetic fluid phase when d approaches 1 a.u. However, for r s   <  20 and [Formula: see text] a.u., the excitonic phase is found to be stable. We do not find that the anti-ferromagnetic Wigner crystal is stable over the considered range of r s and d. We also find that as r s increases, the critical layer separations for Wigner crystallization increase.

The field theory of specific heat

NASA Astrophysics Data System (ADS)

Gusev, Yu. V.

2016-01-01

Finite temperature quantum field theory in the heat kernel method is used to study the heat capacity of condensed matter. The lattice heat is treated à la P. Debye as energy of the elastic (sound) waves. The dimensionless functional of free energy is re-derived with a cut-off parameter and used to obtain the specific heat of crystal lattices. The new dimensionless thermodynamical variable is formed as Planck's inverse temperature divided by the lattice constant. The dimensionless constant, universal for the class of crystal lattices, which determines the low temperature region of molar specific heat, is introduced and tested with the data for diamond lattice crystals. The low temperature asymptotics of specific heat is found to be the fourth power in temperature instead of the cubic power law of the Debye theory. Experimental data for the carbon group elements (silicon, germanium) and other materials decisively confirm the quartic law. The true low temperature regime of specific heat is defined by the surface heat, therefore, it depends on the geometrical characteristics of the body, while the absolute zero temperature limit is geometrically forbidden. The limit on the growth of specific heat at temperatures close to critical points, known as the Dulong-Petit law, appears from the lattice constant cut-off. Its value depends on the lattice type and it is the same for materials with the same crystal lattice. The Dulong-Petit values of compounds are equal to those of elements with the same crystal lattice type, if one mole of solid state matter were taken as the Avogadro number of the composing atoms. Thus, the Neumann-Kopp law is valid only in some special cases.

Vibration analysis of a new polymer quartz piezoelectric crystal sensor for detecting characteristic materials of volatility liquid

NASA Astrophysics Data System (ADS)

Gu, Yu; Li, Qiang; Xu, Bao-Jun; Zhao, Zhe

2014-01-01

We present a new polymer quartz piezoelectric crystal sensor that takes a quartz piezoelectric crystal as the basal material and a nanometer nonmetallic polymer thin film as the surface coating based on the principle of quartz crystal microbalance (QCM). The new sensor can be used to detect the characteristic materials of a volatile liquid. A mechanical model of the new sensor was built, whose structure was a thin circle plate composing of polytef/quartz piezoelectric/polytef. The mechanical model had a diameter of 8 mm and a thickness of 170 μm. The vibration state of the model was simulated by software ANSYS after the physical parameters and the boundary condition of the new sensor were set. According to the results of experiments, we set up a frequency range from 9.995850 MHz to 9.997225 MHz, 17 kinds of frequencies and modes of vibration were obtained within this range. We found a special frequency fsp of 9.996358 MHz. When the resonant frequency of the new sensor's mechanical model reached the special frequency, a special phenomenon occurred. In this case, the amplitude of the center point O on the mechanical model reached the maximum value. At the same time, the minimum absolute difference between the simulated frequency based on the ANSYS software and the experimental measured stable frequency was reached. The research showed that the design of the new polymer quartz piezoelectric crystal sensor perfectly conforms to the principle of QCM. A special frequency value fsp was found and subsequently became one of the most important parameters in the new sensor design.

Elemental and cooperative diffusion in a liquid, supercooled liquid and glass resolved

NASA Astrophysics Data System (ADS)

Cassar, Daniel R.; Lancelotti, Ricardo F.; Nuernberg, Rafael; Nascimento, Marcio L. F.; Rodrigues, Alisson M.; Diz, Luiza T.; Zanotto, Edgar D.

2017-07-01

The diffusion mechanisms controlling viscous flow, structural relaxation, liquid-liquid phase separation, crystal nucleation, and crystal growth in multicomponent glass-forming liquids are of great interest and relevance in physics, chemistry, materials, and glass science. However, the diffusing entities that control each of these important dynamic processes are still unknown. The main objective of this work is to shed some light on this mystery, advancing the knowledge on this phenomenon. For that matter, we measured the crystal growth rates, the viscosity, and lead diffusivities in PbSiO3 liquid and glass in a wide temperature range. We compared our measured values with published data covering 16 orders of magnitude. We suggest that above a certain temperature range Td (1.2Tg-1.3Tg), crystal growth and viscous flow are controlled by the diffusion of silicon and lead. Below this temperature, crystal growth and viscous flow are more sluggish than the diffusion of silicon and lead. Therefore, Td marks the temperature where decoupling between the (measured) cationic diffusivity and the effective diffusivities calculated from viscosity and crystal growth rates occurs. We reasonably propose that the nature or size of the diffusional entities controlling viscous flow and crystal growth below Td is quite different; the slowest is the one controlling viscous flow, but both processes require cooperative movements of some larger structural units rather than jumps of only one or a few isolated atoms.

Fast optical switch having reduced light loss

NASA Technical Reports Server (NTRS)

Nelson, Bruce N. (Inventor); Cooper, Ronald F. (Inventor)

1992-01-01

An electrically controlled optical switch uses an electro-optic crystal of the type having at least one set of fast and slow optical axes. The crystal exhibits electric field induced birefringence such that a plane of polarization oriented along a first direction of a light beam passing through the crystal may be switched to a plane of polarization oriented along a second direction. A beam splitting polarizer means is disposed at one end of the crystal and directs a light beam passing through the crystal whose plane of polarization is oriented along the first direction differently from a light beam having a plane of polarization oriented along the second direction. The electro-optic crystal may be chosen from the crystal classes 43m, 42m, and 23. In a preferred embodiment, the electro-optic crystal is a bismuth germanium oxide crystal or a bismuth silicon oxide crystal. In another embodiment of the invention, polarization control optics are provided which transmit substantially all of the incident light to the electro-optic crystal, substantially reducing the insertion loss of the switch.

Influence of crystal phases on electro-optic properties of epitaxially grown lanthanum-modified lead zirconate titanate films

NASA Astrophysics Data System (ADS)

Masuda, Shin; Seki, Atsushi; Masuda, Yoichiro

2010-02-01

We describe here how we have improved the crystal qualities and controlled the crystal phase of the lanthanum-modified lead zirconate titanate (PLZT) film without changing the composition ratio using an oxygen-pressure crystallization process. A PLZT film deposited on a SrTiO3 substrate with the largest electro-optic (EO) coefficient of 498 pm/V has been achieved by controlling the crystal phase of the film. Additionally, a fatigue-free lead zirconate titanate (PZT) capacitor with platinum electrodes has been realized by reducing the oxygen vacancies in the films.

Structure-Kinetics Correlations in Isostructural Crystals of α-(ortho-Tolyl)-acetophenones: Pinning Down Electronic Effects Using Laser-Flash Photolysis in the Solid State.

PubMed

Ayitou, Anoklase J-L; Flynn, Kristen; Jockusch, Steffen; Khan, Saeed I; Garcia-Garibay, Miguel A

2016-03-02

Aqueous suspensions of nanocrystals in the 200-500 nm size range of isostructural α-(ortho-tolyl)-acetophenone (1a) and α-(ortho-tolyl)-para-methylacetophenone (1b) displayed good absorption characteristics for flash photolysis experiments in a flow system, with transient spectra and decay kinetics with a quality that is similar to that recorded in solution. In contrast to solution measurements, reactions in the solid state were characterized by a rate limiting hydrogen transfer reaction from the triplet excited state and a very short-lived biradical intermediate, which does not accumulate. Notably, the rate for δ-hydrogen atom transfer of 1a (2.7 × 10(7) s(-1)) in the crystalline phase is 18-fold larger than that of 1b (1.5 × 10(6) s(-1)). With nearly identical molecular and crystal structures, this decrease in the rate of δ-hydrogen abstraction can be assigned unambiguously to an electronic effect by the para-methyl group in 1b, which increases the contribution of the (3)π,π* configuration relative to the reactive (3)n,π* configuration in the lowest triplet excited state. These results highlight the potential of relating single crystal X-ray structural data with absolute kinetics from laser flash photolysis.

Precise real-time polarization measurement of terahertz electromagnetic waves by a spinning electro-optic sensor.

PubMed

Yasumatsu, Naoya; Watanabe, Shinichi

2012-02-01

We propose and develop a method to quickly and precisely determine the polarization direction of coherent terahertz electromagnetic waves generated by femtosecond laser pulses. The measurement system consists of a conventional terahertz time-domain spectroscopy system with the electro-optic (EO) sampling method, but we add a new functionality in the EO crystal which is continuously rotating with the angular frequency ω. We find a simple yet useful formulation of the EO signal as a function of the crystal orientation, which enables a lock-in-like detection of both the electric-field amplitude and the absolute polarization direction of the terahertz waves with respect to the probe laser pulse polarization direction at the same time. The single measurement finishes around two periods of the crystal rotations (∼21 ms), and we experimentally prove that the accuracy of the polarization measurement does not suffer from the long-term amplitude fluctuation of the terahertz pulses. Distribution of the measured polarization directions by repeating the measurements is excellently fitted by a gaussian distribution function with a standard deviation of σ = 0.56°. The developed technique is useful for the fast direct determination of the polarization state of the terahertz electromagnetic waves for polarization imaging applications as well as the precise terahertz Faraday or Kerr rotation spectroscopy.

Seismic wave propagation in anisotropic ice - Part 2: Effects of crystal anisotropy in geophysical data

NASA Astrophysics Data System (ADS)

Diez, A.; Eisen, O.; Hofstede, C.; Lambrecht, A.; Mayer, C.; Miller, H.; Steinhage, D.; Binder, T.; Weikusat, I.

2015-02-01

We investigate the propagation of seismic waves in anisotropic ice. Two effects are important: (i) sudden changes in crystal orientation fabric (COF) lead to englacial reflections; (ii) the anisotropic fabric induces an angle dependency on the seismic velocities and, thus, recorded travel times. Velocities calculated from the polycrystal elasticity tensor derived for the anisotropic fabric from measured COF eigenvalues of the EDML ice core, Antarctica, show good agreement with the velocity trend determined from vertical seismic profiling. The agreement of the absolute velocity values, however, depends on the choice of the monocrystal elasticity tensor used for the calculation of the polycrystal properties. We make use of abrupt changes in COF as a common reflection mechanism for seismic and radar data below the firn-ice transition to determine COF-induced reflections in either data set by joint comparison with ice-core data. Our results highlight the possibility to complement regional radar surveys with local, surface-based seismic experiments to separate isochrones in radar data from other mechanisms. This is important for the reconnaissance of future ice-core drill sites, where accurate isochrone (i.e. non-COF) layer integrity allows for synchronization with other cores, as well as studies of ice dynamics considering non-homogeneous ice viscosity from preferred crystal orientations.

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.

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.

Manipulating crystallization with molecular additives.

PubMed

Shtukenberg, Alexander G; Lee, Stephanie S; Kahr, Bart; Ward, Michael D

2014-01-01

Given the importance of organic crystals in a wide range of industrial applications, the chemistry, biology, materials science, and chemical engineering communities have focused considerable attention on developing methods to control crystal structure, size, shape, and orientation. Tailored additives have been used to control crystallization to great effect, presumably by selectively binding to particular crystallographic surfaces and sites. However, substantial knowledge gaps still exist in the fundamental mechanisms that govern the formation and growth of organic crystals in both the absence and presence of additives. In this review, we highlight research discoveries that reveal the role of additives, either introduced by design or present adventitiously, on various stages of formation and growth of organic crystals, including nucleation, dislocation spiral growth mechanisms, growth inhibition, and nonclassical crystal morphologies. The insights from these investigations and others of their kind are likely to guide the development of innovative methods to manipulate crystallization for a wide range of materials and applications.

Rapid and reversible photoinduced switching of a rotaxane crystal

NASA Astrophysics Data System (ADS)

Chen, Kai-Jen; Tsai, Ya-Ching; Suzaki, Yuji; Osakada, Kohtaro; Miura, Atsushi; Horie, Masaki

2016-11-01

Crystalline phase transitions caused by external stimuli have been used to detect physical changes in the solid-state properties. This study presents the mechanical switching of crystals of ferrocene-containing rotaxane controlled by focused laser light. The expansion and contraction of the crystals can be driven by turning on and off laser light at 445 nm. The irradiation-induced expansion of the crystal involves elongation along the a, b and c axes at 30 °C, whereas heating of the crystal at 105 °C causes the shortening of c axis. The expansions reversibly occur and have the advantage of a rapid relaxation (reverse) process. Single-crystal X-ray crystallography reveals the detailed structural changes of the molecules, corresponding to a change in the size of the crystals on laser irradiation. This molecular crystal behaviour induced by laser irradiation, is demonstrated for the remote control of objects, namely, microparticle transport and microswitching in an electric circuit.

Temperature controller for crystal resonators

NASA Technical Reports Server (NTRS)

Turlington, T. R.

1980-01-01

Controller operates on less than 5W prime power and heats crystal from -10 C to 75 C in less than 45s. Unit is faster and more accurate (to within 0.7 C) than other inexpensive controllers and faster and less expensive than very precise controllers in vacuum flasks.

Improved Radiative Control of Ribbon Growth

NASA Technical Reports Server (NTRS)

Mchugh, J. P.; Seidensticker, R. G.; Skutch, M. E.

1984-01-01

Shield modifications enhance growth rate while reducing silicon oxide formation. Control of dendritic-web crystal growth requires precise control of web temperature profile. Achieved by using series of thermal radiation shields to control thermal-radiation field in region where melt solidifying onto crystal ribbon being pulled from melt.

Preparation and Analysis of RNA Crystals

NASA Technical Reports Server (NTRS)

Todd, Paul

2000-01-01

The crystallization of RiboNucleic Acids (RNA) was studied from the standpoint of mechanisms of crystal growth in three tasks: (1) preparation of high-quality crystals of oligonuclotides for X-ray diffraction, (2) finding pathways to the growth of high-quality crystals for X-ray diffraction and (3) investigation of mechanisms of action of inertial acceleration on crystal growth. In these tasks: (1) RNA crystals were prepared and studied by X-ray diffraction; (2) a pathway to high-quality crystals was discovered and characterized; a combination of kinetic and equilibrium factors could be optimized as described below; and (3) an interplay between purity and gravity was found in a combination of space and ground experiments with nucleic acids and proteins. Most significantly, the rate of concentration of precipitant and RNA can be controlled by membrane-based methods of water removal or by diffusion of multivalent cations across an interface stabilized by a membrane. Oligonucleotide solutions are electrokinetically stabilized colloids, and crystals can form by the controlled addition of multivalent cations.

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.

Habit control of deuterated potassium dihydrogen phosphate crystal for laser applications

NASA Astrophysics Data System (ADS)

Guzman, L. A.; Suzuki, M.; Fujimoto, Y.; Fujioka, K.

2016-03-01

In this study we investigate the habit of partially deuterated potassium dihydrogen phosphate (DKDP) crystals in the presence of Al3+ ions. We have grown single DKDP crystals in (50wt% and 80wt%) partially deuterated solutions and in solutions doped with Al3+ ions (2 ppm) by the point-seed rapid growth technique at controlled supercooling (ΔT=10°C). The growth length of each crystal face was measured and the aspect ratio was calculated. We found that crystals grown in partially deuterated solutions are similar in aspect ratio, while, crystals grown in deuterated solutions doped with Al3+ ions showed a relative change in aspect ratio, the crystal increased in size in the pyramidal direction (vertical axis direction). Crystal characteristics were also analyzed by X-ray diffraction, FTIR and Raman spectroscopy. We have speculated that the relative habit modification is due to a probably adsorption and inclusions of Al3+ ions in the prismatic section of the crystal.

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.

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

NASA Astrophysics Data System (ADS)

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

2015-12-01

Crystal-like structures at nano and micron scales have promise for purification and confined reactions, and as starting points for fabricating highly ordered crystals for protein engineering and drug discovery applications. However, developing controlled crystallization techniques from batch processes remain challenging. We show that neutrally charged nanoscale spherical micelles from biocompatible nonionic surfactant solutions can evolve into nano- and micro-sized branched networks and crystal-like structures. This occurs under simple combinations of temperature and flow conditions. Our findings not only suggest new opportunities for developing controlled universal crystallization and encapsulation procedures that are sensitive to ionic environments and high temperatures, but also open up new pathways for accelerating drug discovery processes, which are of tremendous interest to pharmaceutical and biotechnological industries.

Linearly polarized pumped passively Q-switched Nd:YVO4 microchip laser for Ince-Gaussian laser modes with controllable orientations

NASA Astrophysics Data System (ADS)

He, Hong-Sen; Zhang, Ming-Ming; Dong, Jun; Ueda, Ken-Ichi

2016-12-01

A tilted, linearly polarized laser diode end-pumped Cr4+:YAG passively Q-switched a-cut Nd:YVO4 microchip laser for generating numerous Ince-Gaussian (IG) laser modes with controllable orientations has been demonstrated by selecting the crystalline orientation of an a-cut Nd:YVO4 crystal. The same IG laser mode with different orientations has been achieved with the same absorbed pump power in a passively Q-switched Nd:YVO4 microchip laser under linearly polarized pumping when the incident pump power and the crystalline orientation of an a-cut Nd:YVO4 crystal are both properly selected. The significant improvement of pulsed laser performance of controllable IG modes has been achieved by selecting the crystalline orientation of an a-cut Nd:YVO4 crystal. The maximum pulse energy is obtained along the a-axis of an a-cut Nd:YVO4 crystal and the highest peak power is achieved along the c-axis of an a-cut Nd:YVO4 crystal, respectively, which has potential applications on quantum computation and optical manipulation. The generation of controllable IG laser modes in microchip lasers under linearly polarized pumping provides a convenient and universal way to control IG laser mode numbers with anisotropic crystal as a gain medium.

Modeling of axial vibrational control technique for CdTe VGF crystal growth under controlled cadmium partial pressure

NASA Astrophysics Data System (ADS)

Avetissov, I.; Kostikov, V.; Meshkov, V.; Sukhanova, E.; Grishechkin, M.; Belov, S.; Sadovskiy, A.

2014-01-01

A VGF growth setup assisted by axial vibrations of baffle submerged into CdTe melt with controlled Cd partial pressure was designed. An influence of baffle shape on flow velocity map, temperature distribution in CdTe melt and interface shape of growing crystal was analyzed by numerical simulation and physical modeling. To produce the desirable shape of crystal melt interface we slant under different angles vertical generatrix in a cylindrical disk and made chasing on faceplates of a disk. It was ascertained that a disk with conical generatrix formed more intensive convective flows from a faceplate with larger diameter. It was shown that at CdTe VGF crystal growth rate about 10 mm/h application of AVC technique made it possible to produce convex interface for 2 in. crystal diameter.

Large-area sheet task advanced dendritic web growth development

NASA Technical Reports Server (NTRS)

Duncan, C. S.; Seidensticker, R. G.; Mchugh, J. P.; Hopkins, R. H.; Meier, D. L.; Schruben, J.

1982-01-01

Thermal models were developed that accurately predict the thermally generated stresses in the web crystal which, if too high, cause the crystal to degenerate. The application of the modeling results to the design of low-stress experimental growth configurations will allow the growth of wider web crystals at higher growth velocities. A new experimental web growth machine was constructed. This facility includes all the features necessary for carrying out growth experiments under steady thermal conditions. Programmed growth initiation was developed to give reproducible crystal starts. Width control permits the growth of long ribbons at constant width. Melt level is controlled to 0.1 mm or better. Thus, the capability exists to grow long web crystals of constant width and thickness with little operator intervention, and web growth experiments can now be performed with growth variables controlled to a degree not previously possible.

Using Magnetic Fields to Control Convection during Protein Crystallization: Analysis and Validation Studies

NASA Technical Reports Server (NTRS)

Ramachandran, N.; Leslie, F. W.

2004-01-01

The effect of convection during the crystallization of proteins is not very well understood. In a gravitational field, convection is caused by crystal sedimentation and by solutal buoyancy induced flow and these can lead to crystal imperfections. While crystallization in microgravity can approach diffusion limited growth conditions (no convection), terrestrially strong magnetic fields can be used to control fluid flow and sedimentation effects. In this work, we develop the analysis for magnetic flow control and test the predictions using analog experiments. Specifically, experiments on solutal convection in a paramagnetic fluid were conducted in a strong magnetic field gradient using a dilute solution of Manganese Chloride. The observed flows indicate that the magnetic field can completely counter the settling effects of gravity locally and are consistent with the theoretical predictions presented. This phenomenon suggests that magnetic fields may be useful in mimicking the microgravity environment of space for some crystal growth ana biological applications where fluid convection is undesirable.

The Distinct Role of Comparative Risk Perceptions in a Breast Cancer Prevention Program

PubMed Central

Dillard, Amanda J.; Ubel, Peter A.; Smith, Dylan M.; Zikmund-Fisher, Brian J.; Nair, Vijay; Derry, Holly A.; Zhang, Aijun; Pitsch, Rosemarie K.; Alford, Sharon Hensley; McClure, Jennifer B.; Fagerlin, Angela

2013-01-01

Background Comparative risk perceptions may rival other types of information in terms of effects on health behavior decisions. Purpose We examined associations between comparative risk perceptions, affect, and behavior while controlling for absolute risk perceptions and actual risk. Methods Women at an increased risk of breast cancer participated in a program to learn about tamoxifen which can reduce the risk of breast cancer. Women reported comparative risk perceptions of breast cancer and completed measures of anxiety, knowledge, and tamoxifen-related behavior intentions. Three months later, women reported their behavior. Results Comparative risk perceptions were positively correlated with anxiety, knowledge, intentions, and behavior three months later. After controlling for participants’ actual risk of breast cancer and absolute risk perceptions, comparative risk perceptions predicted anxiety and knowledge, but not intentions or behavior. Conclusions Comparative risk perceptions can affect patient outcomes like anxiety and knowledge independently of absolute risk perceptions and actual risk information. PMID:21698518

Pestalpolyols A-D, Cytotoxic Polyketides from Pestalotiopsis sp. cr013.

PubMed

Li, Jing; Xie, Jin; Yang, Yin-He; Li, Xiao-Lian; Zeng, Ying; Zhao, Pei-Ji

2015-09-01

Four novel polyketides, named pestalpolyols A (1), B (2), C (3), and D (4), were isolated from solid fermentation products of Pestalotiopsis sp. cr013. Their structures were elucidated by extensive spectroscopic methods, including 1D and 2D nuclear magnetic resonance and high-resolution electrospray ionization mass spectrometry experiments, and the absolute configuration was confirmed by single-crystal X-ray diffraction analysis using the anomalous scattering of Cu Kα radiation. The inhibitory activities of compounds 1, 2, and 4 against five human tumor lines were tested in vitro, and showed IC50 values 2.3-31.2 µM. Georg Thieme Verlag KG Stuttgart · New York.

Caryophyllene sesquiterpenoids from the endophytic fungus, Pestalotiopsis sp.

PubMed

Liu, Yi; Yang, Ming-Hua; Wang, Xiao-Bing; Li, Tian-Xiao; Kong, Ling-Yi

2016-03-01

Eight new caryophyllene sesquiterpenoids named pestaloporinates A-G (1-7) and 14-acetylhumulane (8) have been isolated from the solid cultures of an endophytic fungus Pestalotiopsis sp., which was obtained from the fresh stem bark of Melia azedarach Linn. Their structures as well as absolute configurations were determined by spectroscopic data, ECD experimentation, and single-crystal X-ray diffraction. Among all the isolates, compound 2 displayed potent inhibitory activity with IC50 value of 19.0 μM during the evaluation of nitric oxide (NO) inhibition in lipopolysaccharide (LPS)-induced RAW 264.7 macrophage cells. Copyright © 2015 Elsevier B.V. All rights reserved.

Dysidinoid A, an unusual meroterpenoid with anti-MRSA activity from the South China Sea sponge Dysidea sp.

PubMed

Jiao, Wei-Hua; Li, Jing; Liu, Qian; Xu, Ting-Ting; Shi, Guo-Hua; Yu, Hao-Bing; Yang, Fan; Han, Bing-Nan; Li, Min; Lin, Hou-Wen

2014-11-05

An unusual meroterpenoid, dysidinoid A (1), was isolated from the South China Sea sponge Dysidea sp. Its structure was elucidated by extensive spectroscopic methods including HRESIMS and 2D NMR, and its absolute configuration was determined by single-crystal X-ray diffraction analysis. Dysidinoid A (1) is the first meroterpenoid from Nature bearing a 9,4-friedodrime skeleton and a 2,5-dionepyrrole unit. Dysidinoid A (1) showed potent antibacterial activity against two strains of pathogenic bacteria methicillin-resistant Staphylococcus aureus (MRSA) with MIC90 values of 8.0 μg/mL against both.

Synthesis of a new (1R)-(-)-myrtenal-derived dioxadithiadodecacycle and its use as an efficient chiral auxiliary.

PubMed

Vargas-Díaz, M Elena; Joseph-Nathan, Pedro; Tamariz, Joaquín; Zepeda, L Gerardo

2007-01-04

[reaction: see text] The new macrocycle 9 (>70% yield from hydroxythiol 10) was treated with several nucleophilic reagents (RMgX, RLi, and LiAlH4) affording carbinols 12a-j (80-96% yield, >99:1 dr). Oxidative hydrolysis of 12a,c,e, followed by LiAlH4 reduction of the resulting mixture, gave 16a,c,e in >95% ee,16c being a key precursor for the preparation of fungicide 17. The absolute configuration of 9 and 12j (Nu = H) was established by single-crystal X-ray diffraction analyses and chemical correlation.

Rauvomines A and B, Two Monoterpenoid Indole Alkaloids from Rauvolfia vomitoria.

PubMed

Zeng, Jun; Zhang, Dong-Bo; Zhou, Pan-Pan; Zhang, Qi-Li; Zhao, Lei; Chen, Jian-Jun; Gao, Kun

2017-08-04

Two unusual normonoterpenoid indole alkaloids rauvomine A (1) and rauvomine B (2), together with two known compounds peraksine (3) and alstoyunine A (4), were isolated from the aerial parts of Rauvolfia vomitoria. The structures with absolute configurations of 1 and 2 were elucidated by spectroscopic analysis, single-crystal X-ray diffraction, and electronic circular dichroism (ECD) calculations. Compound 2 is a novel C 18 normonoterpenoid indole alkaloid with a substituted cyclopropane ring that forms an unusual 6/5/6/6/3/5 hexcyclic rearranged ring system. The plausible biogenetic pathways of 1 and 2 were proposed. Compound 2 exhibited significant anti-inflammatory activity.

Efficient approach to the free energy of crystals via Monte Carlo simulations

NASA Astrophysics Data System (ADS)

Navascués, G.; Velasco, E.

2015-08-01

We present a general approach to compute the absolute free energy of a system of particles with constrained center of mass based on the Monte Carlo thermodynamic coupling integral method. The version of the Frenkel-Ladd approach [J. Chem. Phys. 81, 3188 (1984)], 10.1063/1.448024, which uses a harmonic coupling potential, is recovered. Also, we propose a different choice, based on one-particle square-well coupling potentials, which is much simpler, more accurate, and free from some of the difficulties of the Frenkel-Ladd method. We apply our approach to hard spheres and compare with the standard harmonic method.

Neutrinoless double-beta decay search with CUORE and CUORE-0 experiments

DOE PAGES

Moggi, N.; Artusa, D. R.; F. T. Avignone; ...

2015-03-24

The Cryogenic Underground Observatory for Rare Events (CUORE) is an upcoming experiment designed to search for the neutrinoless double-beta decays. Observation of the process would unambiguously establish that neutrinos are Majorana particles and provide information on their absolute mass scale hierarchy. CUORE is now under construction and will consist of an array of 988 TeO 2 crystal bolometers operated at 10 mK, but the first tower (CUORE-0) is already taking data. The experimental techniques used will be presented as well as the preliminary CUORE-0 results. The current status of the full-mass experiment and its expected sensitivity will then be discussed.

Cyclodepsipeptides and other O-containing heterocyclic metabolites from Beauveria felina EN-135, a marine-derived entomopathogenic fungus.

PubMed

Du, Feng-Yu; Li, Xiao-Ming; Zhang, Peng; Li, Chun-Shun; Wang, Bin-Gui

2014-05-13

Bioassay-guided fractionation of a culture extract of Beauveria felina EN-135, an entomopathogenic fungus isolated from a marine bryozoan, led to the isolation of a new cyclodepsipeptide, iso-isariin D (1); two new O-containing heterocyclic compounds that we have named felinones A and B (2 and 3); and four known cyclodepsipeptides (4-7). The structures were elucidated via spectroscopic analysis, and the absolute configurations of 1 and 2 were determined using single-crystal X-ray diffraction and CD, respectively. All isolated compounds were evaluated for antimicrobial activity and brine-shrimp (Artemia salina) lethality.

Nonthmicin, a Polyether Polyketide Bearing a Halogen-Modified Tetronate with Neuroprotective and Antiinvasive Activity from Actinomadura sp.

PubMed

Igarashi, Yasuhiro; Matsuoka, Noriaki; In, Yasuko; Kataura, Tetsushi; Tashiro, Etsu; Saiki, Ikuo; Sudoh, Yuri; Duangmal, Kannika; Thamchaipenet, Arinthip

2017-03-17

Nonthmicin (1), a new polyether polyketide bearing a chlorinated tetronic acid, was isolated from the culture extract of a soil-derived Actinomadura strain. The structure of 1 was elucidated by interpretation of NMR and MS spectroscopic data, and the absolute configuration of 1 was proposed on the basis of the crystal structure of its dechloro congener ecteinamycin (2) also isolated from the same strain. Tetronic acids modified by halogenation have never been reported from natural products. Compounds 1 and 2 were found to have neuroprotective activity and antimetastatic properties at submicromolar concentrations in addition to antibacterial activity.

New lanostane-type triterpenoids from the fruiting body of Ganoderma hainanense.

PubMed

Li, Wei; Lou, Lan-Lan; Zhu, Jian-Yong; Zhang, Jun-Sheng; Liang, An-An; Bao, Jing-Mei; Tang, Gui-Hua; Yin, Sheng

2016-12-01

Five new lanostane-type triterpenoids, ganoderenses A-E (1-5), two new lanostane nor-triterpenoids, ganoderenses F and G (6 and 7), along with 13 known analogues (8-20) were isolated from the fruiting body of Ganoderma hainanense. Their structures were determined by combined chemical and spectral methods, and the absolute configurations of compounds 1 and 13 were confirmed by single crystal X-ray diffraction. All compounds were evaluated for inhibitory activity against thioredoxin reductase (TrxR), a potential target for cancer chemotherapy with redox balance and antioxidant functions, but were inactive. Copyright © 2016 Elsevier B.V. All rights reserved.

Moessbauer spectroscopy of Mg(0.9)Fe(0.1)SiO3 perovskite

NASA Technical Reports Server (NTRS)

Jeanloz, Raymond; O'Neill, Bridget; Pasternak, Moshe P.; Taylor, R. D.; Bohlen, Steven R.

1992-01-01

Ambient pressure Moessbauer spectra of Mg(0.9)Fe-57(0.1)SiO3 perovskite synthesized at pressure-temperature conditions of about 50 GPa and 1700 K show that the iron is entirely high-spin Fe(2+) and appears to be primarily located in the octahedral site within the crystal structure. We observe broad Moessbauer lines, suggesting a distribution of electric-field gradients caused by disorder associated with the Fe ions. Also, the perovskite exhibits magnetic ordering at temperatures lower than 5 K, implying that there is a magnetic contribution to the absolute ('third-law') entropy of this phase.

In-plane pitch control of cholesteric liquid crystals by formation of artificial domains via patterned photopolymerization.

PubMed

Yoshida, Hiroyuki; Miura, Yusuke; Tokuoka, Kazuki; Suzuki, Satoshi; Fujii, Akihiko; Ozaki, Masanori

2008-11-10

A controlled helix pitch modulation in the in-plane direction of a planarly aligned cholesteric liquid crystal cell is demonstrated by using photopolymerizable cholesteric liquid crystals. By fabricating artificial domains with a closed volume via two-photon excitation laser-lithography, the degree of pitch modulation could be controlled by adjusting the surface area to volume ratio of the domain. A pitch modulation of over 60 nm was realized by designing the shape of the artificial domain.

Optical control of graphene plasmon using liquid crystal layer 29K New One

DTIC Science & Technology

2017-03-01

AFRL-AFOSR-UK-TR-2017-0014 Optical control of graphene plasmon using liquid crystal layer 29K New One Viktor Yuriyovych Reshetnyak SCIENCE AND... plasmon using liquid crystal layer 29K New One 5a.  CONTRACT NUMBER 5b.  GRANT NUMBER STCU-P652 5c.  PROGRAM ELEMENT NUMBER 61102F 6. AUTHOR(S) Viktor...the basic research and establishes possible optical ways to control the surface plasmon polariton in graphene layer. A system comprises the graphene

Crystallization of proteins by dynamic control of supersaturation. Ph.D. Thesis Semiannual Status Report, 21 Mar. - 20 Sep. 1990

NASA Technical Reports Server (NTRS)

Wilson, Lori June

1990-01-01

The growth of protein crystals is known to be the limiting factor in the determination of the three-dimensional structures of most proteins. It is expected that the kinetics of supersaturation, which is directly related to solvent evaporation, will affect protein crystal growth and nucleation and accordingly determine the quality, number, size, and morphology of the crystals. With a technique that controls the evaporation of solvent from a protein solution with N2(g) it is possible to determine the effect of different evaporation profiles on hen egg white lysozyme crystals. Hen egg white lysozyme was chosen as the model protein because it crystallizes easily and has solubility data available for most salt, pH, and temperature ranges. Commercially available lysozyme was further purified by a number of methods. Crystals grown with the purified lysozyme and with the unpurified lysozyme in citrate buffer were different shapes but were found to be of the same symmetry space group by precession photos. Differences were seen in the lysozyme crystals grown using different evaporation rates. At three of the four initial conditions for lysozyme crystal growth, longer evaporation times yielded better crystals. The evaporation times required to see a change in the appearance of the crystals was much longer than expected. The number of rates studied so far represent only a small fraction of the ones now available with the gas evaporation device. The technique also provides for control of both solution pH and temperature which are related to the solubilities of proteins.

An evaluation of adhesive sample holders for advanced crystallographic experiments

PubMed Central

Mazzorana, Marco; Sanchez-Weatherby, Juan; Sandy, James; Lobley, Carina M. C.; Sorensen, Thomas

2014-01-01

The hydration state of macromolecular crystals often affects their overall order and, ultimately, the quality of the X-ray diffraction pattern that they produce. Post-crystallization techniques that alter the solvent content of a crystal may induce rearrangement within the three-dimensional array making up the crystal, possibly resulting in more ordered packing. The hydration state of a crystal can be manipulated by exposing it to a stream of air at controlled relative humidity in which the crystal can equilibrate. This approach provides a way of exploring crystal hydration space to assess the diffraction capabilities of existing crystals. A key requirement of these experiments is to expose the crystal directly to the dehydrating environment by having the minimum amount of residual mother liquor around it. This is usually achieved by placing the crystal on a flat porous support (Kapton mesh) and removing excess liquid by wicking. Here, an alternative approach is considered whereby crystals are harvested using adhesives that capture naked crystals directly from their crystallization drop, reducing the process to a one-step procedure. The impact of using adhesives to ease the harvesting of different types of crystals is presented together with their contribution to background scattering and their usefulness in dehydration experiments. It is concluded that adhesive supports represent a valuable tool for mounting macromolecular crystals to be used in humidity-controlled experiments and to improve signal-to-noise ratios in diffraction experiments, and how they can protect crystals from modifications in the sample environment is discussed. PMID:25195752

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.

Interface and facet control during Czochralski growth of (111) InSb crystals for cost reduction and yield improvement of IR focal plane array substrates

NASA Astrophysics Data System (ADS)

Gray, Nathan W.; Perez-Rubio, Victor; Bolke, Joseph G.; Alexander, W. B.

2014-10-01

Focal plane arrays (FPAs) made on InSb wafers are the key cost-driving component in IR imaging systems. The electronic and crystallographic properties of the wafer directly determine the imaging device performance. The "facet effect" describes the non-uniform electronic properties of crystals resulting from anisotropic dopant segregation during bulk growth. When the segregation coefficient of dopant impurities changes notably across the melt/solid interface of a growing crystal the result is non-uniform electronic properties across wafers made from these crystals. The effect is more pronounced in InSb crystals grown on the (111) axis compared with other orientations and crystal systems. FPA devices made on these wafers suffer costly yield hits due to inconsistent device response and performance. Historically, InSb crystal growers have grown approximately 9-19 degree off-axis from the (111) to avoid the facet effect and produced wafers with improved uniformity of electronic properties. It has been shown by researchers in the 1960s that control of the facet effect can produce uniform small diameter crystals. In this paper, we share results employing a process that controls the facet effect when growing large diameter crystals from which 4, 5, and 6" wafers can be manufactured. The process change resulted in an increase in wafers yielded per crystal by several times, all with high crystal quality and uniform electronic properties. Since the crystals are grown on the (111) axis, manufacturing (111) oriented wafers is straightforward with standard semiconductor equipment and processes common to the high-volume silicon wafer industry. These benefits result in significant manufacturing cost savings and increased value to our customers.

Pseudo Landau levels and quantum oscillations in strained Weyl semimetals

NASA Astrophysics Data System (ADS)

Alisultanov, Z. Z.

2018-05-01

The crystal lattice deformation in Weyl materials where the two chiralities are separated in momentum space leads to the appearance of gauge pseudo-fields. We investigated the pseudo-magnetic field induced quantum oscillations in strained Weyl semimetal (WSM). In contrast to all previous works on this problem, we use here a more general tilted Hamiltonian. Such Hamiltonian, seems to be is more suitable for a strained WSMs. We have shown that a pseudo-magnetic field induced magnetization of strained WSM is nonzero due to the fact that electric field (gradient of the deformation potential) is induced simultaneously with the pseudo-magnetic field. This related with fact that the pseudo Landau levels (LLs) in strained WSM are differ in vicinities of different WPs due to the presence of tilt in spectrum. Such violation of the equivalence between Weyl points (WPs) leads to modulation of quantum oscillations. We also showed that magnetization magnitude can be changed by application of an external electric field. In particular, it can be reduced to zero. The possibility of controlling of the magnetization by an electric field is interesting both from a fundamental point of view (a new type of magneto-electric effect) and application point of view (additional possibility to control diamagnetism of deformed WSMs). Finally, a coexistence of type-I and type-II Weyl fermions is possible in the system under investigation. Such phase is absolutely new for physics of topological systems.

The modeling, simulation, and control of transport phenomena in a thermally destabilizing Bridgman crystal growth system

NASA Astrophysics Data System (ADS)

Sonda, Paul Julio

This thesis presents a comprehensive examination of the modeling, simulation, and control of axisymmetric flows occurring in a vertical Bridgman crystal growth system with the melt underlying the crystal. The significant complexity and duration of the manufacturing process make experimental optimization a prohibitive task. Numerical simulation has emerged as a powerful tool in understanding the processing issues still prevalent in industry. A first-principles model is developed to better understand the transport phenomena within a representative vertical Bridgman system. The set of conservation equations for momentum, energy, and species concentration are discretized using the Galerkin finite element method and simulated using accurate time-marching schemes. Simulation results detail the occurrence of fascinating nonlinear dynamics, in the form of stable, time-varying behavior for sufficiently large melt regimes and multiple steady flow states. This discovery of time-periodic flows for high intensity flows is qualitatively consistent with experimental observations. Transient simulations demonstrate that process operating conditions have a marked effect on the hydrodynamic behavior within the melt, which consequently affects the dopant concentration profile within the crystal. The existence of nonlinear dynamical behavior within this system motivates the need for feedback control algorithms which can provide superior crystal quality. This work studies the feasibility of using crucible rotation to control flows in the vertical Bridgman system. Simulations show that crucible rotation acts to suppress the axisymmetric flows. However, for the case when the melt lies below the crystal, crucible rotation also acts to accelerate the onset of time-periodic behavior. This result is attributed to coupling between the centrifugal force and the intense, buoyancy-driven flows. Proportional, proportional-integral, and input-output linearizing controllers are applied to vertical Bridgman systems in stabilizing (crystal below the melt) and destabilizing (melt below the crystal) configurations. The spatially-averaged, axisymmetric kinetic energy is the controlled output. The flows are controlled via rotation of the crucible containing the molten material. Simulation results show that feedback controllers using crucible rotation effectively attenuate flow oscillations in a stabilizing configuration with time-varying disturbance. Crucible rotation is not an optimal choice for suppressing inherent flow oscillations in the destabilizing configuration.

Inertial Measures of Motion for Clinical Biomechanics: Comparative Assessment of Accuracy under Controlled Conditions - Effect of Velocity

PubMed Central

Lebel, Karina; Boissy, Patrick; Hamel, Mathieu; Duval, Christian

2013-01-01

Background Inertial measurement of motion with Attitude and Heading Reference Systems (AHRS) is emerging as an alternative to 3D motion capture systems in biomechanics. The objectives of this study are: 1) to describe the absolute and relative accuracy of multiple units of commercially available AHRS under various types of motion; and 2) to evaluate the effect of motion velocity on the accuracy of these measurements. Methods The criterion validity of accuracy was established under controlled conditions using an instrumented Gimbal table. AHRS modules were carefully attached to the center plate of the Gimbal table and put through experimental static and dynamic conditions. Static and absolute accuracy was assessed by comparing the AHRS orientation measurement to those obtained using an optical gold standard. Relative accuracy was assessed by measuring the variation in relative orientation between modules during trials. Findings Evaluated AHRS systems demonstrated good absolute static accuracy (mean error < 0.5o) and clinically acceptable absolute accuracy under condition of slow motions (mean error between 0.5o and 3.1o). In slow motions, relative accuracy varied from 2o to 7o depending on the type of AHRS and the type of rotation. Absolute and relative accuracy were significantly affected (p<0.05) by velocity during sustained motions. The extent of that effect varied across AHRS. Interpretation Absolute and relative accuracy of AHRS are affected by environmental magnetic perturbations and conditions of motions. Relative accuracy of AHRS is mostly affected by the ability of all modules to locate the same global reference coordinate system at all time. Conclusions Existing AHRS systems can be considered for use in clinical biomechanics under constrained conditions of use. While their individual capacity to track absolute motion is relatively consistent, the use of multiple AHRS modules to compute relative motion between rigid bodies needs to be optimized according to the conditions of operation. PMID:24260324

Speed and Accuracy of Absolute Pitch Judgments: Some Latter-Day Results.

ERIC Educational Resources Information Center

Carroll, John B.

Nine subjects, 5 of whom claimed absolute pitch (AP) ability were instructed to rapidly strike notes on the piano to match randomized tape-recorded piano notes. Stimulus set sizes were 64, 16, or 4 consecutive semitones, or 7 diatonic notes of a designated octave. A control task involved motor movements to notes announced in advance. Accuracy,…

Test-retest reliability of the Middlesex Assessment of Mental State (MEAMS): a preliminary investigation in people with probable dementia.

PubMed

Powell, T; Brooker, D J; Papadopolous, A

1993-05-01

Relative and absolute test-retest reliability of the MEAMS was examined in 12 subjects with probable dementia and 12 matched controls. Relative reliability was good. Measures of absolute reliability showed scores changing by up to 3 points over an interval of a week. A version effect was found to be in evidence.

Relative versus Absolute Stimulus Control in the Temporal Bisection Task

ERIC Educational Resources Information Center

de Carvalho, Marilia Pinhiero; Machado, Armando

2012-01-01

When subjects learn to associate two sample durations with two comparison keys, do they learn to associate the keys with the short and long samples (relational hypothesis), or with the specific sample durations (absolute hypothesis)? We exposed 16 pigeons to an ABA design in which phases A and B corresponded to tasks using samples of 1 s and 4 s,…

40 CFR Appendix to Subpart Eee of... - Quality Assurance Procedures for Continuous Emissions Monitors Used for Hazardous Waste Combustors

Code of Federal Regulations, 2014 CFR

2014-07-01

... and CEMS control capabilities. 2.2Relative Accuracy (RA). The absolute mean difference between the... readings at the zero pollutant level after a stated period of operation during which no unscheduled... Evaluation for CO, O2, and HC CEMS Carbon Monoxide (CO), Oxygen (O2), and Hydrocarbon (HC) CEMS. An Absolute...

40 CFR Appendix to Subpart Eee of... - Quality Assurance Procedures for Continuous Emissions Monitors Used for Hazardous Waste Combustors

Code of Federal Regulations, 2013 CFR

2013-07-01

... and CEMS control capabilities. 2.2Relative Accuracy (RA). The absolute mean difference between the... readings at the zero pollutant level after a stated period of operation during which no unscheduled... Evaluation for CO, O2, and HC CEMS Carbon Monoxide (CO), Oxygen (O2), and Hydrocarbon (HC) CEMS. An Absolute...

Novel protein crystal growth technology: Proof of concept

NASA Technical Reports Server (NTRS)

Nyce, Thomas A.; Rosenberger, Franz

1989-01-01

A technology for crystal growth, which overcomes certain shortcomings of other techniques, is developed and its applicability to proteins is examined. There were several unknowns to be determined: the design of the apparatus for suspension of crystals of varying (growing) diameter, control of the temperature and supersaturation, the methods for seeding and/or controlling nucleation, the effect on protein solutions of the temperature oscillations arising from the circulation, and the effect of the fluid shear on the suspended crystals. Extensive effort was put forth to grow lysozyme crystals. Under conditions favorable to the growth of tetragonal lysozyme, spontaneous nucleation could be produced but the number of nuclei could not be controlled. Seed transfer techniques were developed and implemented. When conditions for the orthorhombic form were tried, a single crystal 1.5 x 0.5 x 0.2 mm was grown (after in situ nucleation) and successfully extracted. A mathematical model was developed to predict the flow velocity as a function of the geometry and the operating temperatures. The model can also be used to scaleup the apparatus for growing larger crystals of other materials such as water soluble non-linear optical materials. This crystal suspension technology also shows promise for high quality solution growth of optical materials such as TGS and KDP.

Absolute gravimetry as an operational tool for geodynamics research

NASA Astrophysics Data System (ADS)

Torge, W.

Relative gravimetric techniques have been used for nearly 30 years for measuring non-tidal gravity variations with time, and thus have contributed to geodynamics research by monitoring vertical crustal movements and internal mass shifts. With today's accuracy of about ± 0.05µms-2 (or 5µGal), significant results have been obtained in numerous control nets of local extension, especially in connection with seismic and volcanic events. Nevertheless, the main drawbacks of relative gravimetry, which are deficiencies in absolute datum and calibration, set a limit for its application, especially with respect to large-scale networks and long-term investigations. These problems can now be successfully attacked by absolute gravimetry, with transportable gravimeters available since about 20 years. While the absolute technique during the first two centuries of gravimetry's history was based on the pendulum method, the free-fall method can now be employed taking advantage of laser-interferometry, electronic timing, vacuum and shock absorbing techniques, and on-line computer-control. The accuracy inherent in advanced instruments is about ± 0.05 µms-2. In field work, generally an accuracy of ±0.1 µms-2 may be expected, strongly depending on local environmental conditions.

In-situ measurement of sulfur isotopic ratios in zoned apatite crystals via SIMS: a new tool for interpreting dynamic sulfur behavior in magmas

NASA Astrophysics Data System (ADS)

Economos, R. C.; Boehnke, P.; Burgisser, A.

2017-12-01

Sulfur is an important element in igneous systems due to its impact on magma redox, its role in the formation of economically valuable ore deposits, and the influence of catastrophic volcanogenic sulfur degassing on global climate. The mobility and geochemical behavior of sulfur in magmas is complex due to its multi-valent (from S2- to S6+) and multi-phase (solid, immiscible liquid, gaseous, dissolved ions) nature. Sulfur behavior is closely linked with the evolution of oxygen fugacity (fO2) in magmas; the record of fO2 evolution is often difficult to extract from rock records, particularly for intrusive systems that undergo cyclical magmatic processes and crystallize to the solidus. We apply a novel method of measuring S isotopic ratios via secondary ion mass spectrometry (SIMS) in zoned apatite crystals that we interpret as a record of open-system magmatic processes. We analyzed the S concentration and isotopic variations preserved in multiple apatite crystals from single hand specimens from the Cadiz Valley Batholith, CA via electron microprobe and ion microprobe at UCLA. A single, isotopically homogeneous crystal of Durango apatite was characterized for absolute isotopic ratio for this study (UCLA-D1). Isotopic variations in single apatite crystals ranged from 0 to 3.8‰ δ34S and total variation within a single hand sample was 6.1‰ δ34S. High S concentration cores yielded high isotopic ratios while low S concentration rims yielded low isotopic ratios. We favor an explanation of a combination of magma mixing and open-system, ascent-driven degassing under moderately reduced conditions: fO2 at or below NNO +1, although the synchronous crystallization of apatite and anhydrite is also a viable scenario. These findings have implications for the coupled S and fO2 evolution of granitic plutons and suggest that in-situ apatite S isotopic measurements could be a powerful new tool for evaluating redox and S systematics in magmatic systems.

Ultrasound liquid crystal lens

NASA Astrophysics Data System (ADS)

Shimizu, Yuki; Koyama, Daisuke; Fukui, Marina; Emoto, Akira; Nakamura, Kentaro; Matsukawa, Mami

2018-04-01

A variable-focus lens using a combination of liquid crystals and ultrasound is discussed. The lens uses a technique based on ultrasound vibration to control the molecular orientation of the liquid crystal. The lens structure is simple, with no mechanical moving parts and no transparent electrodes, which is helpful for device downsizing; the structure consists of a liquid crystal layer sandwiched between two glass substrates with a piezoelectric ring. The tens-of-kHz ultrasonic resonance flexural vibration used to excite the lens generates an acoustic radiation force on the liquid crystal layer to induce changes in the molecular orientation of the liquid crystal. The orientations of the liquid crystal molecules and the optical characteristics of the lens were investigated under ultrasound excitation. Clear optical images were observed through the lens, and the focal point could be controlled using the input voltage to the piezoelectric ring to give the lens its variable-focus action.

Magnetic Control of MOF Crystal Orientation and Alignment.

PubMed

Cheng, Fei; Marshall, Ellis S; Young, Adam J; Robinson, Peter J; Bouillard, Jean-Sebastien G; Adawi, Ali M; Vermeulen, Nicolaas A; Farha, Omar K; Reithofer, Michael R; Chin, Jia Min

2017-11-07

Most metal-organic frameworks (MOFs) possess anisotropic properties, the full exploitation of which necessitates a general strategy for the controllable orientation of such MOF crystals. Current methods largely rely upon layer-by-layer MOF epitaxy or tuning of MOF crystal growth on appropriate substrates, yielding MOFs with fixed crystal orientations. Here, the dynamic magnetic alignment of different MOF crystals (NH 2 -MIL-53(Al) and NU-1000) is shown. The MOFs were magnetized by electrostatic adsorption of iron oxide nanoparticles, dispersed in curable polymer resins (Formlabs 1+ clear resin/ Sylgard 184), magnetically oriented, and fixed by resin curing. The importance of crystal orientation on MOF functionality was demonstrated whereby magnetically aligned NU-1000/Sylgard 184 composite was excited with linearly polarized 405 nm light, affording an anisotropic fluorescence response dependent on the polarization angle of the excitation beam relative to NU-1000 crystal orientation. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

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.

Hot zone design for controlled growth to mitigate cracking in laser crystal growth

NASA Astrophysics Data System (ADS)

Zhang, Hui; Zheng, Lili; Fang, Haisheng

2011-03-01

Cracking is a major problem during large diameter crystal growth. The objective of this work is to design an effective hot zone for a controlled growth of Yb:S-FAP [Yb3+:Sr5(PO4)3F] laser crystal by the Czochralski technology and effective cooling that can reduce stress. Theoretical and numerical analyses are performed to study the causes of cracking, mitigate the major cracking, as well as reduce cooling time. In the current system, three locations in the crystal are prone to crack, such as the top shoulder of the crystal, the middle portion above the crucible edge, and the bottom tail portion. Based on numerical simulations, we propose a new hot zone design and cooling procedure to grow and cool large diameter crystal without cracking.

Quality inspection of anisotropic scintillating lead tungstate (PbWO 4) crystals through measurement of interferometric fringe pattern parameters

NASA Astrophysics Data System (ADS)

Cocozzella, N.; Lebeau, M.; Majni, G.; Paone, N.; Rinaldi, D.

2001-08-01

Scintillating crystals are widely used as detectors in radiographic systems, computerized axial tomography devices and in calorimeters employed in high-energy physics. This paper results from a project motivated by the development of the CMS calorimeter at CERN, which will make use of a large number of scintillating crystals. In order to prevent crystals from breaking because of internal residual stress, a quality control system based on optic inspection of interference fringe patterns was developed. The principle of measurement procedures was theoretically modelled, and then a dedicated polariscope was designed and built, in order to observe the crystals under induced stresses or to evaluate the residual internal stresses. The results are innovative and open a new perspective for scintillating crystals quality control: the photoelastic constant normal to the optic axis of the lead tungstate crystals (PbWO 4) was measured, and the inspection procedure developed is applicable to mass production, not only to optimize the crystal processing, but also to establish a quality inspection procedure.

Controlled In Meso Phase Crystallization – A Method for the Structural Investigation of Membrane Proteins

PubMed Central

Kubicek, Jan; Schlesinger, Ramona; Baeken, Christian; Büldt, Georg; Schäfer, Frank; Labahn, Jörg

2012-01-01

We investigated in meso crystallization of membrane proteins to develop a fast screening technology which combines features of the well established classical vapor diffusion experiment with the batch meso phase crystallization, but without premixing of protein and monoolein. It inherits the advantages of both methods, namely (i) the stabilization of membrane proteins in the meso phase, (ii) the control of hydration level and additive concentration by vapor diffusion. The new technology (iii) significantly simplifies in meso crystallization experiments and allows the use of standard liquid handling robots suitable for 96 well formats. CIMP crystallization furthermore allows (iv) direct monitoring of phase transformation and crystallization events. Bacteriorhodopsin (BR) crystals of high quality and diffraction up to 1.3 Å resolution have been obtained in this approach. CIMP and the developed consumables and protocols have been successfully applied to obtain crystals of sensory rhodopsin II (SRII) from Halobacterium salinarum for the first time. PMID:22536388

Adaptive temperature profile control of a multizone crystal growth furnace

NASA Technical Reports Server (NTRS)

Batur, C.; Sharpless, R. B.; Duval, W. M. B.; Rosenthal, B. N.

1991-01-01

An intelligent measurement system is described which is used to assess the shape of a crystal while it is growing inside a multizone transparent furnace. A color video imaging system observes the crystal in real time, and determines the position and the shape of the interface. This information is used to evaluate the crystal growth rate, and to analyze the effects of translational velocity and temperature profiles on the shape of the interface. Creation of this knowledge base is the first step to incorporate image processing into furnace control.

Enhanced control of a flexure-jointed micromanipulation system using a vision-based servoing approach

NASA Astrophysics Data System (ADS)

Chuthai, T.; Cole, M. O. T.; Wongratanaphisan, T.; Puangmali, P.

2018-01-01

This paper describes a high-precision motion control implementation for a flexure-jointed micromanipulator. A desktop experimental motion platform has been created based on a 3RUU parallel kinematic mechanism, driven by rotary voice coil actuators. The three arms supporting the platform have rigid links with compact flexure joints as integrated parts and are made by single-process 3D printing. The mechanism overall size is approximately 250x250x100 mm. The workspace is relatively large for a flexure-jointed mechanism, being approximately 20x20x6 mm. A servo-control implementation based on pseudo-rigid-body models (PRBM) of kinematic behavior combined with nonlinear-PID control has been developed. This is shown to achieve fast response with good noise-rejection and platform stability. However, large errors in absolute positioning occur due to deficiencies in the PRBM kinematics, which cannot accurately capture flexure compliance behavior. To overcome this problem, visual servoing is employed, where a digital microscopy system is used to directly measure the platform position by image processing. By adopting nonlinear PID feedback of measured angles for the actuated joints as inner control loops, combined with auxiliary feedback of vision-based measurements, the absolute positioning error can be eliminated. With controller gain tuning, fast dynamic response and low residual vibration of the end platform can be achieved with absolute positioning accuracy within ±1 micron.

Temperature and melt solid interface control during crystal growth

NASA Technical Reports Server (NTRS)

Batur, Celal

1990-01-01

Findings on the adaptive control of a transparent Bridgman crystal growth furnace are summarized. The task of the process controller is to establish a user specified axial temperature profile by controlling the temperatures in eight heating zones. The furnace controller is built around a computer. Adaptive PID (Proportional Integral Derivative) and Pole Placement control algorithms are applied. The need for adaptive controller stems from the fact that the zone dynamics changes with respect to time. The controller was tested extensively on the Lead Bromide crystal growth. Several different temperature profiles and ampoule's translational rates are tried. The feasibility of solid liquid interface quantification by image processing was determined. The interface is observed by a color video camera and the image data file is processed to determine if the interface is flat, convex or concave.

Anatase TiO2 single crystals with dominant {0 0 1} facets: Synthesis, shape-control mechanism and photocatalytic activity

NASA Astrophysics Data System (ADS)

Tong, Huifen; Zhou, Yingying; Chang, Gang; Li, Pai; Zhu, Ruizhi; He, Yunbin

2018-06-01

Anatase TiO2 micro-crystals with 51% surface exposing highly active {0 0 1} facets are prepared by hydrothermal synthesis using TiF4 as Ti resource and HF as morphology control agent. In addition, anatase TiO2 single crystals exposing large {0 0 1} crystal facets are facilely synthesized with "green" NaF plus HCl replacing HF for the morphology control. A series of comparative experiments are carried out for separately studying the effects of F- and H+ concentrations on the growth of TiO2 crystals, which have not been understood very much in depth so far. The results indicate that both F- and H+ synergistically affect the synthesis of truncated anatase octahedrons, where F- is preferentially adsorbed on the {0 0 1} facets resulting in lateral growth of these facets and H+ adjusts the growth rate of anatase TiO2 along different orientations by tuning the hydrolysis rate. Based on this information, anatase TiO2 single crystals with small size (1.3 μm) and large exposure of {0 0 1} facets (45%) are successfully prepared under optimal conditions ([H+]/[F-] = 20:1). Photocatalytic activities of the as-prepared products toward methylene blue photo-degradation are further tested. It is revealed that both crystal size and percentage of {0 0 1} facets are decisive for the photocatalytic performance, and the crystals with a small size (1.3 μm) and large exposure of {0 0 1} facets (45%) are catalytically most active. This work has clarified the main factors that control the growth process and morphology of anatase TiO2 single crystals for achieving superior photocatalytic properties.

Controlling Chirality of Entropic Crystals

NASA Astrophysics Data System (ADS)

Damasceno, Pablo; Karas, Andrew; Schultz, Benjamin; Engel, Michael; Glotzer, Sharon

Colloidal crystal structures with complexity and diversity rivaling atomic and molecular crystals have been predicted and obtained for hard particles by entropy maximization. However, thus far homochiral colloidal crystals, which are candidates for photonic metamaterials, are absent. Using Monte Carlo simulations we show that chiral polyhedra exhibiting weak directional entropic forces self-assemble either an achiral crystal or a chiral crystal with limited control over the crystal handedness. Building blocks with stronger faceting exhibit higher selectivity and assemble a chiral crystal with handedness uniquely determined by the particle chirality. Tuning the strength of directional entropic forces by means of particle rounding or the use of depletants allows for reconfiguration between achiral and homochiral crystals. We rationalize our findings by quantifying the chirality strength of each particle, both from particle geometry and potential of mean force and torque diagrams. Work supported by the National Science Foundation, Division of Materials Research Award No. DMR 1120923, U.S. Army Research Office under Grant Award No. W911NF-10-1-0518, and also by the DOD/ASD (R&E) under Award No. N00244-09-1-0062.

Supersaturation Control using Analytical Crystal Size Distribution Estimator for Temperature Dependent in Nucleation and Crystal Growth Phenomena

NASA Astrophysics Data System (ADS)

Zahari, Zakirah Mohd; Zubaidah Adnan, Siti; Kanthasamy, Ramesh; Saleh, Suriyati; Samad, Noor Asma Fazli Abdul

2018-03-01

The specification of the crystal product is usually given in terms of crystal size distribution (CSD). To this end, optimal cooling strategy is necessary to achieve the CSD. The direct design control involving analytical CSD estimator is one of the approaches that can be used to generate the set-point. However, the effects of temperature on the crystal growth rate are neglected in the estimator. Thus, the temperature dependence on the crystal growth rate needs to be considered in order to provide an accurate set-point. The objective of this work is to extend the analytical CSD estimator where Arrhenius expression is employed to cover the effects of temperature on the growth rate. The application of this work is demonstrated through a potassium sulphate crystallisation process. Based on specified target CSD, the extended estimator is capable of generating the required set-point where a proposed controller successfully maintained the operation at the set-point to achieve the target CSD. Comparison with other cooling strategies shows a reduction up to 18.2% of the total number of undesirable crystals generated from secondary nucleation using linear cooling strategy is achieved.

Effect of high pressure microfluidization on the crystallization behavior of palm stearin - palm olein blends.

PubMed

Han, Lijuan; Li, Lin; Li, Bing; Zhao, Lei; Liu, Guoqin; Liu, Xinqi; Wang, Xuede

2014-04-24

Moderate and high microfluidization pressures (60 and 120 MPa) and different treatment times (once and twice) were used to investigate the effect of high-pressure microfluidization (HPM) treatment on the crystallization behavior and physical properties of binary mixtures of palm stearin (PS) and palm olein (PO). The polarized light microscopy (PLM), texture analyzer, X-ray diffraction (XRD) and differential scanning calorimetry (DSC) techniques were applied to analyze the changes in crystal network structure, hardness, polymorphism and thermal property of the control and treated blends. PLM results showed that HPM caused significant reductions in maximum crystal diameter in all treated blends, and thus led to changes in the crystal network structure, and finally caused higher hardness in than the control blends. The XRD study demonstrated that HPM altered crystalline polymorphism. The HPM-treated blends showed a predominance of the more stable β' form, which is of more interest for food applications, while the control blend had more α- and β-form. This result was further confirmed by DSC observations. These changes in crystallization behavior indicated that HPM treatment was more likely to modify the crystallization processes and nucleation mechanisms.

Thermoelectric Properties of Sr-Filled Ge-Based Type I Single-Crystal Clathrate Grown by Sn-Flux Method

NASA Astrophysics Data System (ADS)

Deng, Shuping; Liu, Hongxia; Li, Decong; Wang, Jinsong; Cheng, Feng; Shen, Lanxian; Deng, Shukang

2017-05-01

Single-crystal samples of Sr-filled Ge-based type I clathrate have been prepared by the Sn-flux method, and their thermoelectric properties investigated. The obtained samples exhibited n-type conduction with carrier concentration varying from 2.8 × 1019/cm3 to 6.8 × 1019/cm3 as the carrier mobility changed from 23.9 cm2/V-s to 15.1 cm2/V-s at room temperature. Structural analysis indicated that all samples were type I clathrate in space group pm\\bar{it{3}}n . The total content of group IV (Ge + Sn) atoms in the crystalline structure increased with increasing x value (where x defines the atomic ratio of starting elements, Sr:Ga:Ge:Sn = 8:16: x:20), reaching a maximum value of 31.76 at.% for the sample with x = 30; consequently, the lattice parameters increased. The melting points for all samples were approximately 1012 K, being considerably lower than that of single-crystal Sr8Ga16Ge30 prepared by other methods. The electrical conductivity increased while the absolute value of α increased gradually with increasing temperature; the maximum value of α reached 193 μV/K at 750 K for the sample with x = 24. The sample with x = 30 exhibited lower lattice thermal conductivity of 0.80 W/m-K. As a result, among all the Sn-flux samples, single-crystal Sr7.92Ga15.04Sn0.35Ge30.69 had the largest ZT value of 1.0 at about 750 K.

Thermal conductivity and thermoelectric power of melt processed (Nd/Y)BCO intergrowth crystals

NASA Astrophysics Data System (ADS)

Shams, G. A.; Cochrane, J. W.; Russell, G. J.

2000-07-01

In a previous paper [C. Cipagauta Mino, J.W. Cochrane, E.H. Volckmann, G.J. Russell, J. Electron. Mater. 26 (1997) 915.], we described a cryogenic thermoelectric cooler with a superconducting passive branch. The efficiency of this device depends on selecting an optimal cross-sectional area for the superconducting element based on its thermal conductivity in a magnetic field. (Nd/Y)BCO intergrowth crystals make an ideal superconducting element due to their relativity low thermal conductivity, high critical current, and large size. In this paper, we describe the thermal conductivity and thermoelectric power over the temperature range 20-300 K in applied magnetic fields up to 5000 G, for a specimen cut from a large high quality melt processed (Nd/Y)BCO intergrowth crystal that has almost optimum oxygen content, estimated to be 6.92±0.02. The shape of the κab and κc curves, without applied field, are similar to those reported for Y123 single crystals, but the absolute values are significantly smaller. This result is discussed in terms of the presence of dispersed particles of the (Nd/Y)211 phase and increased phonon and carrier scattering. However, in the normal state, the anisotropic ratio κabn/ κcn is almost identical in shape and magnitude to that of the electrical conductivity ratio σabn/ σcn. The application of magnetic fields either parallel or perpendicular to the heat flow direction always decreases κab and κc for temperatures below Tc and 120 K, respectively. Superconducting fluctuation phenomena was observed about Tc for both the thermoelectric power and κab data.

A DNA Crystal Designed to Contain Two Molecules per Asymmetric Unit

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

T Wang; R Sha; J Birktoft

2011-12-31

We describe the self-assembly of a DNA crystal that contains two tensegrity triangle molecules per asymmetric unit. We have used X-ray crystallography to determine its crystal structure. In addition, we have demonstrated control over the colors of the crystals by attaching either Cy3 dye (pink) or Cy5 dye (blue-green) to the components of the crystal, yielding crystals of corresponding colors. Attaching the pair of dyes to the pair of molecules yields a purple crystal.

Molecular Recognition of Methyl α-d-Mannopyranoside by Antifreeze (Glyco)Proteins

PubMed Central

2015-01-01

Antifreeze proteins and glycoproteins [AF(G)Ps] have been well-known for more than three decades for their ability to inhibit the growth and recrystallization of ice through binding to specific ice crystal faces, and they show remarkable structural compatibility with specific ice crystal faces. Here, we show that the crystal growth faces of methyl α-d-mannopyranoside (MDM), a representative pyranose sugar, also show noteworthy structural compatibility with the known periodicities of AF(G)Ps. We selected fish AFGPs (AFGP8, AFGP1–5), and a beetle AFP (DAFP1) with increasing antifreeze activity as potential additives for controlling MDM crystal growth. Similar to their effects on ice growth, the AF(G)Ps can inhibit MDM crystal growth and recrystallization, and more significantly, the effectiveness for the AF(G)Ps are well correlated with their antifreeze activity. MDM crystals grown in the presence of AF(G)Ps are smaller and have better defined shapes and are of higher quality as indicated by single crystal X-ray diffraction and polarized microscopy than control crystals, but no new polymorphs of MDM were identified by single crystal X-ray diffraction, solid-state NMR, and attenuated total reflectance infrared spectroscopy. The observed changes in the average sizes of the MDM crystals can be related to the changes in the number of the MDM nuclei in the presence of the AF(G)Ps. The critical free energy change differences of the MDM nucleation in the absence and presence of the additives were calculated. These values are close to those of the ice nucleation in the presence of AF(G)Ps suggesting similar interactions are involved in the molecular recognition of MDM by the AF(G)Ps. To our knowledge this is the first report where AF(G)Ps have been used to control crystal growth of carbohydrates and on AFGPs controlling non-ice-like crystals. Our finding suggests MDM might be a possible alternative to ice for studying the detailed mechanism of AF(G)P–crystal interactions. The relationships between AF(G)Ps and carbohydrate binding proteins are also discussed. The structural compatibility between AF(G)Ps and growing crystal faces demonstrated herein adds to the repertoire of molecular recognition by AF(G)Ps, which may have potential applications in the sugar, food, pharmaceutical, and materials industries. PMID:24918258

Liquid crystal dynamic flow control by bidirectional alignment surface

NASA Astrophysics Data System (ADS)

Li, Y. W.; Lee, C. Y.; Kwok, H. S.

2009-02-01

We investigate the behavior of liquid crystal dynamic flow in a cell with a bidirectional alignment (BDA) surface. Numerical simulations show that with a BDA surface having a pitch comparable to the cell gap d, the liquid crystal dynamic flow direction can be controlled by the driving voltage. Such an effect can be applied to bistable twisted nematic displays without the need for anchoring breaking.

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.

Drug crystallization - implications for topical and transdermal delivery.

PubMed

Hadgraft, Jonathan; Lane, Majella E

2016-06-01

Crystallization of actives in skin following topical application was suggested by studies in the 1950s and 1960s but is poorly understood. In contrast, the problem of crystallization of actives on skin and in transdermal formulations has been known for many years. With respect to crystallization in skin, this review describes early reports of a skin 'reservoir' and possible reasons underlying its genesis. Techniques to study crystallization on and in skin and in transdermal patches are outlined. The role of the vehicle in skin delivery is emphasised. Studies which have investigated permeation from crystalline particles are described. Approaches to limit crystallization of actives are discussed. Using supersaturation and antinuclean polymers, control of crystal size is possible; controlled release from crystals is also employed in transdermal patches. Drug crystallization has significant implications for topical and transdermal delivery. Approaches have been developed to counteract the issue for transdermal patches but crystallization in and on the skin for other formulations remains unresolved. Greater knowledge of residence time of excipients and their interaction with skin at the molecular level is critical in order to address the problem. This will lay the foundations for better design of topical/transdermal formulations.

A first-principle model of 300 mm Czochralski single-crystal Si production process for predicting crystal radius and crystal growth rate

NASA Astrophysics Data System (ADS)

Zheng, Zhongchao; Seto, Tatsuru; Kim, Sanghong; Kano, Manabu; Fujiwara, Toshiyuki; Mizuta, Masahiko; Hasebe, Shinji

2018-06-01

The Czochralski (CZ) process is the dominant method for manufacturing large cylindrical single-crystal ingots for the electronics industry. Although many models and control methods for the CZ process have been proposed, they were only tested with small equipment and only a few industrial application were reported. In this research, we constructed a first-principle model for controlling industrial CZ processes that produce 300 mm single-crystal silicon ingots. The developed model, which consists of energy, mass balance, hydrodynamic, and geometrical equations, calculates the crystal radius and the crystal growth rate as output variables by using the heater input, the crystal pulling rate, and the crucible rise rate as input variables. To improve accuracy, we modeled the CZ process by considering factors such as changes in the positions of the crucible and the melt level. The model was validated with the operation data from an industrial 300 mm CZ process. We compared the calculated and actual values of the crystal radius and the crystal growth rate, and the results demonstrated that the developed model simulated the industrial process with high accuracy.

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.

Preparation and characterization of superfine ammonium perchlorate (AP) crystals through ceramic membrane anti-solvent crystallization

NASA Astrophysics Data System (ADS)

Ma, Zhenye; Li, Cheng; Wu, Rujun; Chen, Rizhi; Gu, Zhenggui

2009-10-01

In this paper, a novel ceramic membrane anti-solvent crystallization (CMASC) method was proposed for the safe and rapid preparation ammonium perchlorate (AP) crystals, in which the acetone and ethyl acetate were chosen as solvent and anti-solvent, respectively. Comparing with the conventional liquid anti-solvent crystallization (LASC), CMASC which successfully introduces ceramic membrane with regular pore structure to the LASC as feeding medium, is favorable to control the rate of feeding rate and, therefore, to obtain size and morphology controllable AP. Several kinds of micro-sized AP particles with different morphology were obtained including polyhedral-like, quadrate-like to rod-like. The effect of processing parameters on the crystal size and shape of AP crystals such as volume ratio of anti-solvent to solvent, feeding pressure and crystallization temperature were investigated. It is found that higher volume ratio of anti-solvent to solvent, higher feeding pressure and higher temperature result in smaller particle size. Scaning electron microscopy (SEM) and X-ray diffraction (XRD) were used to characterize the resulting AP crystals. The nucleation and growth kinetic of the resulting AP crystals were also discussed.

Magnon Splitting Induced by Charge Transfer in the Three-Orbital Hubbard Model

NASA Astrophysics Data System (ADS)

Wang, Yao; Huang, Edwin W.; Moritz, Brian; Devereaux, Thomas P.

2018-06-01

Understanding spin excitations and their connection to unconventional superconductivity have remained central issues since the discovery of cuprates. Direct measurement of the dynamical spin structure factor in the parent compounds can provide key information on important interactions relevant in the doped regime, and variations in the magnon dispersion have been linked closely to differences in crystal structure between families of cuprate compounds. Here, we elucidate the relationship between spin excitations and various controlling factors thought to be significant in high-Tc materials by systematically evaluating the dynamical spin structure factor for the three-orbital Hubbard model, revealing differences in the spin dispersion along the Brillouin zone axis and the diagonal. Generally, we find that the absolute energy scale and momentum dependence of the excitations primarily are sensitive to the effective charge-transfer energy, while changes in the on-site Coulomb interactions have little effect on the details of the dispersion. In particular, our result highlights the splitting between spin excitations along the axial and diagonal directions in the Brillouin zone. This splitting decreases with increasing charge-transfer energy and correlates with changes in the apical oxygen position, and general structural variations, for different cuprate families.

The epidemiology of haemochromatosis: a population-based study.

PubMed

Crooks, C J; West, J; Solaymani-Dodaran, M; Card, T R

2009-01-01

The discovery of the HFE genotype has revolutionized the diagnosis of haemochromatosis, changing the associated mortality and morbidity. To investigate the clinical significance of a diagnosis of haemochromatosis. In a cohort study, we identified 501 people with haemochromatosis and 4950 age- and gender-matched controls from the UK General Practice Research Database between 1987 and 2002. The incidence of a diagnosis of haemochromatosis increased approximately 2-fold over the study period and was associated with a 2.2-fold increase in mortality [hazard ratio, 95% confidence interval (95% CI), 1.6-3.0]. There was no increase in extra hepatic malignancy, but an absolute risk excess of liver cancer of 0.89% per year. Diabetes, impotence, osteoarthritis and crystal arthritis were associated with haemochromatosis with odds ratios of 5.4 (95% CI, 4.1-7.0), 2.7(95% CI, 1.8-4.0), 1.9(95% CI, 1.5-2.4) and 2.1(95% CI, 1.4-3.1) respectively. Increasing numbers of people are being diagnosed with haemochromatosis, and the mortality associated with this disease remains high. However, people are living with considerably lower levels of morbidity than previously reported. This encouragingly suggests earlier diagnoses are being made, prior to the development of complications.

Micromachined edge illuminated optically transparent automotive light guide panels

NASA Astrophysics Data System (ADS)

Ronny, Rahima Afrose; Knopf, George K.; Bordatchev, Evgueni; Tauhiduzzaman, Mohammed; Nikumb, Suwas

2012-03-01

Edge-lit backlighting has been used extensively for a variety of small and medium-sized liquid crystal displays (LCDs). The shape, density and spatial distribution pattern of the micro-optical elements imprinted on the surface of the flat light-guide panel (LGP) are often "optimized" to improve the overall brightness and luminance uniformity. A similar concept can be used to develop interior convenience lighting panels and exterior tail lamps for automotive applications. However, costly diffusive sheeting and brightness enhancement films are not be considered for these applications because absolute luminance uniformity and the minimization of Moiré fringe effects are not significant factors in assessing quality of automotive lighting. A new design concept that involves micromilling cylindrical micro-optical elements on optically transparent plastic substrates is described in this paper. The variable parameter that controls illumination over the active regions of the panel is the depth of the individual cylindrical micro-optical elements. LightTools™ is the optical simulation tool used to explore how changing the micro-optical element depth can alter the local and global luminance. Numerical simulation and microfabrication experiments are performed on several (100mmx100mmx6mm) polymethylmethacrylate (PMMA) test samples in order to verify the illumination behavior.

On the relationship between wave based control, absolute vibration suppression and input shaping

NASA Astrophysics Data System (ADS)

Peled, I.; O'Connor, W. J.; Halevi, Y.

2013-08-01

The modeling and control of continuous flexible structures is one of the most challenging problems in control theory. This topic gains more interest with the development of slender space structures, light weight aeronautical components or even traditional gears and drive shafts with flexible properties. Several control schemes are based on the traveling wave approach, rather than the more common modal methods. In this work we investigate the relationships between two of these methods. The Absolute Vibration Suppression (AVS) controller, which was developed for infinite dimension systems, is compared to Wave Based Control (WBC) which was designed primarily for lumped systems. The WBC was first adjusted to continuous systems and then the two controllers, whose algorithms seem different, are compared. The investigation shows that for the flexible shaft these two control laws are actually the same. Furthermore, when converted into an equivalent open loop controller they appear as an extension to continuous systems of the Input Shaping (IS) methodology.

Delta L: An Apparatus for Measuring Macromolecule Crystal Growth Rates in Microgravity

NASA Technical Reports Server (NTRS)

Judge, Russell A.; Whitaker, Ann F. (Technical Monitor)

2001-01-01

Strongly diffracting high quality macromolecule crystals of suitable volume are keenly sought for X-ray diffraction analysis so that high-resolution molecular structure data can be obtained. Such data is of tremendous value to medical research, agriculture and commercial biotechnology. In previous studies by many investigators microgravity has been reported in some instances to improve biological macromolecule X-ray crystal quality while little or no improvement was observed in other cases. A better understanding of processes effecting crystal quality improvement in microgravity will therefore be of great benefit in optimizing crystallization success in microgravity. In ground based research with the protein lysozyme we have previously shown that a population of crystals grown under the same solution conditions, exhibit a variation in X-ray diffraction properties (Judge et al., 1999). We have also observed that under the same solution conditions, individual crystals will grow at slightly different growth rates. This phenomenon is called growth rate dispersion. For small molecule materials growth rate dispersion has been directly related to crystal quality (Cunningham et al., 1991; Ristic et al., 1991). We therefore postulate that microgravity may act to improve crystal quality by reducing growth rate dispersion. If this is the case then as different, Materials exhibit different degrees of growth rate dispersion on the ground then growth rate dispersion could be used to screen which materials may benefit the most from microgravity crystallization. In order to assess this theory the Delta L hardware is being developed so that macromolecule crystal growth rates can be measured in microgravity. Crystal growth rate is defined as the change or delta in crystal size (defined as a characteristic length, L) over time; hence the name of the hardware. Delta L will consist of an optics, a fluids, and a data acquisition sub-assemblies. The optics assembly will consist of a video microscope camera mounted on three axis computer controlled translation stages. The fluids assembly consists of macromolecule and precipitant reservoirs, a temperature controlled growth cell and waste container, The data acquisition is achieved by using a frame-gabber, with images being stored on a hard drive. In operation, macromolecule and precipitant solution will be injected into the temperature controlled growth cell. As macromolecule crystals grow, the video microscope camera controlled by the translation stages, will be used to locate and record images of individual crystals, returning to the same crystals at specific time intervals. The images will be stored on the hard drive and used to calculate the crystal growth rate. To prevent vibrations interfering in the crystal growth rate measurements (Snell et al., 1997) Delta L will be used in connection with the Glovebox Integrated Microgravity Isolation Technology (g-LIMIT) inside the Microgravity Science Glovebox (MSG), onboard the International Space Station (ISS).

Functional ankle control of rock climbers

PubMed Central

Schweizer, A; Bircher, H; Kaelin, X; Ochsner, P

2005-01-01

Objective: To evaluate whether rock climbing type exercise would be of value in rehabilitating ankle injuries to improve ankle stability and coordination. Results: The rock climbers showed significantly better results in the stabilometry and greater absolute and relative maximum strength of flexion in the ankle. The soccer players showed greater absolute but not relative strength in extension. Conclusion: Rock climbing, because of its slow and controlled near static movements, may be of value in the treatment of functional ankle instability. However, it has still to be confirmed whether it is superior to the usual rehabilitation exercises such as use of the wobble board. PMID:15976164

Gout and subsequent erectile dysfunction: a population-based cohort study from England.

PubMed

Abdul Sultan, Alyshah; Mallen, Christian; Hayward, Richard; Muller, Sara; Whittle, Rebecca; Hotston, Matthew; Roddy, Edward

2017-06-06

An association has been suggested between gout and erectile dysfunction (ED), however studies quantifying the risk of ED amongst gout patients are lacking. We aimed to precisely determine the population-level absolute and relative rate of ED reporting among men with gout over a decade in England. We utilised the UK-based Clinical Practice Research Datalink to identify 9653 men with incident gout age- and practice-matched to 38,218 controls. Absolute and relative rates of incident ED were calculated using Cox regression models. Absolute rates within specific time periods before and after gout diagnosis were compared to control using a Poisson regression model. Overall, the absolute rate of ED post-gout diagnosis was 193 (95% confidence interval (CI): 184-202) per 10,000 person-years. This corresponded to a 31% (hazard ratio (HR): 1.31 95%CI: 1.24-1.40) increased relative risk and 0.6% excess absolute risk compared to those without gout. We did not observe statistically significant differences in the risk of ED among those prescribed ULT within 1 and 3 years after gout diagnosis. Compared to those unexposed, the risk of ED was also high in the year before gout diagnosis (relative rate = 1.63 95%CI 1.27-2.08). Similar findings were also observed for severe ED warranting pharmacological intervention. We have shown a statistically significant increased risk of ED among men with gout. Our findings will have important implications in planning a multidisciplinary approach to managing patients with gout.

Lattice Boltzmann Simulation of Kinetic Isotope Effect During Snow Crystal Formation

NASA Astrophysics Data System (ADS)

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

2007-12-01

The isotopic composition of precipitation, especially that of snow, plays a special role in the global hydrological cycle and in reconstruction of past climates using polar ice cores. The fractionation of the major water isotope species (HHO, HDO, HHO-18) during ice crystal formation is critical to understanding the global distribution of isotopes in precipitation. Ice crystal growth in clouds is traditionally treated with a spherically-symmetric steady state diffusion model, with semi-empirical modifications added to account for ventilation and for complex crystal morphology. Although it is known that crystal growth rate, which depends largely on the degree of vapor over- saturation, determines crystal morphology, there are no quantitative models that relate morphology to the vapor saturation factor. Since kinetic (vapor phase diffusion-controlled) isotopic fractionation also depends on growth rate, there should be direct relationships between vapor saturation, crystal morphology, and crystal isotopic composition. We use a 2D lattice Boltzmann model to simulate diffusion-controlled ice crystal growth from vapor- oversaturated air. In the model, crystals grow solely according to the diffusive fluxes just above the crystal surfaces, and hence crystal morphology arises from the initial and boundary conditions in the model and does not need to be specified a priori. Crystal growth patterns can be varied between random growth and deterministic growth (along the maximum concentration gradient for example). The input parameters needed are the isotope- dependent vapor deposition rate constant (k) and the water vapor diffusivity in air (D). The values of both k and D can be computed from kinetic theory, and there are also experimentally determined values of D. The deduced values of k are uncertain to the extent that the condensation coefficient for ice is uncertain. The ratio D/k is a length (order 1 micron) that determines the minimum scale of dendritic growth features and allows us to scale the numerical calculations to atmospheric conditions. Our calculations confirm that the crystal/vapor isotopic fractionation approaches the equilibrium value, and the crystals are compact (circular in 2D) as the saturation factor approaches unity (S= 1.0). However, few natural crystals form under such conditions. At higher oversaturation (e.g. S = 1.2), dendritic crystals of millimeter size develop on timescales appropriate to cloud processes, and kinetic effects control isotopic fractionation. Fractionation factors for dendritic crystals are similar to those predicted by the spherical diffusion model, but the model also gives estimates of crystal heterogeneity. Dendritic crystals are constrained to be relatively large, with dimension much greater than about 20D/k. The most difficult aspect of the modeling is to account for the large density difference between air and ice, which requires us to use a fictitious higher density for the vapor-oversaturated air and scale the crystal growth time accordingly. An approach using a larger scale simulation and the domain decomposition method can provide a vapor flux for a nested smaller scale calculation. The results clarify the controls on crystal growth, and the relationships between saturation state, growth rate, crystal morphology and isotopic fractionation.

Dynamic global model of oxide Czochralski process with weighing control

NASA Astrophysics Data System (ADS)

Mamedov, V. M.; Vasiliev, M. G.; Yuferev, V. S.

2011-03-01

A dynamic model of oxide Czochralski growth with weighing control has been developed for the first time. A time-dependent approach is used for the calculation of temperature fields in different parts of a crystallization set-up and convection patterns in a melt, while internal radiation in crystal is considered in a quasi-steady approximation. A special algorithm is developed for the calculation of displacement of a triple point and simulation of a crystal surface formation. To calculate variations in the heat generation, a model of weighing control with a commonly used PID regulator is applied. As an example, simulation of the growth process of gallium-gadolinium garnet (GGG) crystals starting from the stage of seeding is performed.

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.

Accuracy analysis of the space shuttle solid rocket motor profile measuring device

NASA Technical Reports Server (NTRS)

Estler, W. Tyler

1989-01-01

The Profile Measuring Device (PMD) was developed at the George C. Marshall Space Flight Center following the loss of the Space Shuttle Challenger. It is a rotating gauge used to measure the absolute diameters of mating features of redesigned Solid Rocket Motor field joints. Diameter tolerance of these features are typically + or - 0.005 inches and it is required that the PMD absolute measurement uncertainty be within this tolerance. In this analysis, the absolute accuracy of these measurements were found to be + or - 0.00375 inches, worst case, with a potential accuracy of + or - 0.0021 inches achievable by improved temperature control.

Photonic crystals at visible, x-ray, and terahertz frequencies

NASA Astrophysics Data System (ADS)

Prasad, Tushar

Photonic crystals are artificial structures with a periodically varying refractive index. This property allows photonic crystals to control the propagation of photons, making them desirable components for novel photonic devices. Photonic crystals are also termed as "semiconductors of light", since they control the flow of electromagnetic radiation similar to the way electrons are excited in a semiconductor crystal. The scale of periodicity in the refractive index determines the frequency (or wavelength) of the electromagnetic waves that can be manipulated. This thesis presents a detailed analysis of photonic crystals at visible, x-ray, and terahertz frequencies. Self-assembly and spin-coating methods are used to fabricate colloidal photonic crystals at visible frequencies. Their dispersion characteristics are examined through theoretical as well as experimental studies. Based on their peculiar dispersion property called the superprism effect, a sensor that can detect small quantities of chemical substances is designed. A photonic crystal that can manipulate x-rays is fabricated by using crystals of a non-toxic plant virus as templates. Calculations show that these metallized three-dimensional crystals can find utility in x-ray optical systems. Terahertz photonic crystal slabs are fabricated by standard lithographic and etching techniques. In-plane superprism effect and out-of-plane guided resonances are studied by terahertz time-domain spectroscopy, and verified by numerical simulations.

Macrodefect-free, large, and thick GaN bulk crystals for high-quality 2–6 in. GaN substrates by hydride vapor phase epitaxy with hardness control

NASA Astrophysics Data System (ADS)

Fujikura, Hajime; Konno, Taichiro; Suzuki, Takayuki; Kitamura, Toshio; Fujimoto, Tetsuji; Yoshida, Takehiro

2018-06-01

On the basis of a novel crystal hardness control, we successfully realized macrodefect-free, large (2–6 in.) and thick +c-oriented GaN bulk crystals by hydride vapor phase epitaxy. Without the hardness control, the introduction of macrodefects including inversion domains and/or basal-plane dislocations seemed to be indispensable to avoid crystal fracture in GaN growth with millimeter thickness. However, the presence of these macrodefects tended to limit the applicability of the GaN substrate to practical devices. The present technology markedly increased the GaN crystal hardness from below 20 to 22 GPa, thus increasing the available growth thickness from below 1 mm to over 6 mm even without macrodefect introduction. The 2 and 4 in. GaN wafers fabricated from these crystals had extremely low dislocation densities in the low- to mid-105 cm‑2 range and low off-angle variations (2 in.: <0.1° 4 in.: ∼0.2°). The realization of such high-quality 6 in. wafers is also expected.

The significance of intergranular diffusion to the mechanisms and kinetics of porphyroblast crystallization

NASA Astrophysics Data System (ADS)

Carlson, William D.

1989-09-01

The spatial disposition, compositional zoning profiles, and size distributions of garnet crystals in 11 specimens of pelitic schist from the Picuris Range of New Mexico (USA) demonstrate that the kinetics of intergranular diffusion controlled the nucleation and growth mechanisms of porphyroblasts in these rocks. An ordered disposition of garnet centers and a significant correlation between crystal radius and near-neighbor distances manifest suppressed nucleation of new crystals in diffusionally depleted zones surrounding pre-existing crystals. Compositional zoning profiles require diffusionally controlled growth, the rate of which increases exponentially as temperature increases with time; an acceleration factor for growth rate can be estimated from a comparison of compositional profiles for crystals of different sizes in each specimen. Crystal size distributions are interpreted as the result of nucleation rates that accelerate exponentially with increasing temperature early in the crystallization process, but decline in the later stages because of suppression effects in the vicinity of earlier-formed nuclei. Simulations of porphyroblast crystallization, based upon thermally accelerated diffusionally influenced nucleation kinetics and diffusionally controlled growth kinetics, quantitatively replicate textural relations in the rocks. The simulations employ only two variable parameters, which are evaluated by fitting of crystal size distributions. Both have physical significance. The first is an acceleration factor for nucleation, with a magnitude reflecting the prograde increase during the nucleation interval of the chemical affinity for the reaction in undepleted regions of the rock. The second is a measure of the relative sizes of the porphyroblast and the diffusionally depleted zone surrounding it. Crystal size distributions for the Picuris Range garnets correspond very closely to those in the literature from a variety of other localities for garnet and other minerals. The same kinetic model accounts quantitatively for crystal size distributions of porphyroblastic garnet, phlogopite, sphene, and pyroxene in rocks from both regional and contact metamorphic occurrences. These commonalities indicate that intergranular diffusion may be the dominant kinetic factor in the crystallization of porphyroblasts in a wide variety of metamorphic environments.

Rhombohedral cubic semiconductor materials on trigonal substrate with single crystal properties and devices based on such materials

NASA Technical Reports Server (NTRS)

Park, Yeonjoon (Inventor); Choi, Sang Hyouk (Inventor); King, Glen C. (Inventor); Elliott, James R. (Inventor)

2012-01-01

Growth conditions are developed, based on a temperature-dependent alignment model, to enable formation of cubic group IV, group II-V and group II-VI crystals in the [111] orientation on the basal (0001) plane of trigonal crystal substrates, controlled such that the volume percentage of primary twin crystal is reduced from about 40% to about 0.3%, compared to the majority single crystal. The control of stacking faults in this and other embodiments can yield single crystalline semiconductors based on these materials that are substantially without defects, or improved thermoelectric materials with twinned crystals for phonon scattering while maintaining electrical integrity. These methods can selectively yield a cubic-on-trigonal epitaxial semiconductor material in which the cubic layer is substantially either directly aligned, or 60 degrees-rotated from, the underlying trigonal material.

Epidermal hydrogen peroxide is not increased in lesional and non-lesional skin of vitiligo.

PubMed

Zailaie, Mohammad Z

2017-01-01

It is widely believed that the loss of the epidermal melanocytes in vitiligo is basically due to excessive oxidative stress. Previous research work described abnormal elevation of the absolute concentration of the epidermal hydrogen peroxide (H 2 O 2 ) in lesional and non-lesional skin of vitiligo. Based on this finding, our primary research objective was to use this feature as a screening marker in individuals at a great risk of developing vitiligo. Ninety-six patients of non-segmental vitiligo (NSV) of varying durations, skin phototypes, and treatment modalities (psoralen UVA-, narrow band UVB-treated) were recruited for this study. Raman spectroscopic measurements, using an external probehead, of the lesional and non-lesional skin were obtained, and the resulting spectra were analyzed using the Opus software package of the MultiRam spectrometer and the intensity of the peak at 875 cm -1 that represents the absolute concentration of H 2 O 2 was calculated. Contrary to previous reports, in patients of skin phototype IV, the absolute concentrations of H 2 O 2 in non-lesional and lesional NSV of all groups were non-significantly decreased compared to normal control. In patients of NSV of skin phototype V, the decrease in the absolute concentrations of H 2 O 2 was not significant in the untreated group, and a slight non-significant increase in the NBUVB-treated group was noted. However, in the PUVA-treated group, the non-lesional skin demonstrated significant increase in the absolute concentration of H 2 O 2 , whereas the lesional skin showed only a slight non-significant increase compared to normal control. In NSV patients of skin phototype VI who were previously treated with PUVA, the non-lesional skin showed a slight non-significant increase in the absolute concentration of H 2 O 2 ; however, the lesional skin showed a marked significant decrease compared to normal control and the non-lesional skin. Thereof, one can conclude that the epidermal H 2 O 2 is not increased in NSV as previously thought and may not be responsible for the oxidative stress that leads to the melanocytes destruction, the hallmark of vitiligo pathogenesis.

Electromagnetic induction heating for single crystal graphene growth: morphology control by rapid heating and quenching

NASA Astrophysics Data System (ADS)

Wu, Chaoxing; Li, Fushan; Chen, Wei; Veeramalai, Chandrasekar Perumal; Ooi, Poh Choon; Guo, Tailiang

2015-03-01

The direct observation of single crystal graphene growth and its shape evolution is of fundamental importance to the understanding of graphene growth physicochemical mechanisms and the achievement of wafer-scale single crystalline graphene. Here we demonstrate the controlled formation of single crystal graphene with varying shapes, and directly observe the shape evolution of single crystal graphene by developing a localized-heating and rapid-quenching chemical vapor deposition (CVD) system based on electromagnetic induction heating. Importantly, rational control of circular, hexagonal, and dendritic single crystalline graphene domains can be readily obtained for the first time by changing the growth condition. Systematic studies suggest that the graphene nucleation only occurs during the initial stage, while the domain density is independent of the growth temperatures due to the surface-limiting effect. In addition, the direct observation of graphene domain shape evolution is employed for the identification of competing growth mechanisms including diffusion-limited, attachment-limited, and detachment-limited processes. Our study not only provides a novel method for morphology-controlled graphene synthesis, but also offers fundamental insights into the kinetics of single crystal graphene growth.

Peripheral Blood Lymphocyte Subset Counts in Pre-menopausal Women with Iron-Deficiency Anaemia

PubMed Central

Reza Keramati, Mohammad; Sadeghian, Mohammad Hadi; Ayatollahi, Hossein; Mahmoudi, Mahmoud; Khajedaluea, Mohammad; Tavasolian, Houman; Borzouei, Anahita

2011-01-01

Background: Iron-deficiency anaemia (IDA) is a major worldwide public health problem. Children and women of reproductive age are especially vulnerable to IDA, and it has been reported that these patients are more prone to infection. This study was done to evaluate alteration of lymphocyte subgroups in IDA. Methods: In this prospective study, we investigated lymphocyte subsets in pre-menopausal women with iron-deficiency anaemia; 50 normal subjects and 50 IDA (hypochromic microcytic) cases were enrolled. Experimental and control anticoagulated blood samples were evaluated using flow cytometry to determine the absolute and relative numbers of various lymphocyte subgroups. Finally, the results of the patient and control groups were compared. Results: Mean (SD) absolute counts of lymphocytes, CD3+ cells, CD3+/CD4+ subsets (T helper) and CD3+/CD8+ subsets (T cytotoxic) in the patient group were 2.08 (0.65) x 109/L, 1.53 (0.53) x 109/L, 0.87 (0.28) x 109/L, and 0.51 (0.24) x 109/L, respectively. The results showed significant differences between case and control groups in mean absolute counts of lymphocytes (P = 0.014), T lymphocytes (P = 0.009), helper T cells (P = 0.004), and cytotoxic T cells (P = 0.043). Conclusion: This study showed that absolute counts of peripheral blood T lymphocytes as a marker of cell-mediated immunity may be decreased in pre-menopausal women with iron-deficiency anaemia, and that these patients may be more prone to infection. PMID:22135572

Distinct abnormalities in the innate immune system of children with Down syndrome.

PubMed

Bloemers, Beatrijs L P; van Bleek, Grada M; Kimpen, Jan L L; Bont, Louis

2010-05-01

To analyze the frequency and phenotype of cells of the innate immune system in the peripheral blood of children with Down syndrome (DS). Flow cytometric analysis of expression of cell surface markers was performed in children with DS (n = 41) and healthy age-matched controls (n = 41). Compared with controls, children with DS had significantly lower absolute total leukocyte counts, lymphocytes, monocytes, and granulocytes, but 1.5-times higher absolute numbers of CD14(dim)CD16(+) monocytes (147 x 10(6)/L vs 93 x 10(6)/L; P = .02). This difference is fully explained by a higher percentage of CD14(dim)CD16(+) monocytes within the monocyte compartment (28.7% vs 13.4%; P <.001). The absolute numbers of myeloid dendritic cells were lower in DS (13.8 x 10(6)/L vs 22.7 x 10(6)/L; P <.001). The numbers of plasmacytoid dendritic cells and natural killer cells were normal. Absolute numbers of invariant natural killer T cells were very low overall, but significantly lower in children with DS than in controls (1.2 x 10(6)/L vs 3.7 x 10(6)/L; P = .01). Children with DS exhibited distinct abnormalities in cells of the innate immune system. Most strikingly, they had a high number of proinflammatory CD14(dim)CD16(+) monocytes. This elevated level of CD14(dim)CD16(+) monocytes may play an important role in the onset and maintenance of chronic inflammatory disease in DS.

New experimental methodology, setup and LabView program for accurate absolute thermoelectric power and electrical resistivity measurements between 25 and 1600 K: application to pure copper, platinum, tungsten, and nickel at very high temperatures.

PubMed

Abadlia, L; Gasser, F; Khalouk, K; Mayoufi, M; Gasser, J G

2014-09-01

In this paper we describe an experimental setup designed to measure simultaneously and very accurately the resistivity and the absolute thermoelectric power, also called absolute thermopower or absolute Seebeck coefficient, of solid and liquid conductors/semiconductors over a wide range of temperatures (room temperature to 1600 K in present work). A careful analysis of the existing experimental data allowed us to extend the absolute thermoelectric power scale of platinum to the range 0-1800 K with two new polynomial expressions. The experimental device is controlled by a LabView program. A detailed description of the accurate dynamic measurement methodology is given in this paper. We measure the absolute thermoelectric power and the electrical resistivity and deduce with a good accuracy the thermal conductivity using the relations between the three electronic transport coefficients, going beyond the classical Wiedemann-Franz law. We use this experimental setup and methodology to give new very accurate results for pure copper, platinum, and nickel especially at very high temperatures. But resistivity and absolute thermopower measurement can be more than an objective in itself. Resistivity characterizes the bulk of a material while absolute thermoelectric power characterizes the material at the point where the electrical contact is established with a couple of metallic elements (forming a thermocouple). In a forthcoming paper we will show that the measurement of resistivity and absolute thermoelectric power characterizes advantageously the (change of) phase, probably as well as DSC (if not better), since the change of phases can be easily followed during several hours/days at constant temperature.

New experimental methodology, setup and LabView program for accurate absolute thermoelectric power and electrical resistivity measurements between 25 and 1600 K: Application to pure copper, platinum, tungsten, and nickel at very high temperatures

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

Abadlia, L.; Mayoufi, M.; Gasser, F.

2014-09-15

In this paper we describe an experimental setup designed to measure simultaneously and very accurately the resistivity and the absolute thermoelectric power, also called absolute thermopower or absolute Seebeck coefficient, of solid and liquid conductors/semiconductors over a wide range of temperatures (room temperature to 1600 K in present work). A careful analysis of the existing experimental data allowed us to extend the absolute thermoelectric power scale of platinum to the range 0-1800 K with two new polynomial expressions. The experimental device is controlled by a LabView program. A detailed description of the accurate dynamic measurement methodology is given in thismore » paper. We measure the absolute thermoelectric power and the electrical resistivity and deduce with a good accuracy the thermal conductivity using the relations between the three electronic transport coefficients, going beyond the classical Wiedemann-Franz law. We use this experimental setup and methodology to give new very accurate results for pure copper, platinum, and nickel especially at very high temperatures. But resistivity and absolute thermopower measurement can be more than an objective in itself. Resistivity characterizes the bulk of a material while absolute thermoelectric power characterizes the material at the point where the electrical contact is established with a couple of metallic elements (forming a thermocouple). In a forthcoming paper we will show that the measurement of resistivity and absolute thermoelectric power characterizes advantageously the (change of) phase, probably as well as DSC (if not better), since the change of phases can be easily followed during several hours/days at constant temperature.« less

Digital phase-locked-loop speed sensor for accuracy improvement in analog speed controls. [feedback control and integrated circuits

NASA Technical Reports Server (NTRS)

Birchenough, A. G.

1975-01-01

A digital speed control that can be combined with a proportional analog controller is described. The stability and transient response of the analog controller were retained and combined with the long-term accuracy of a crystal-controlled integral controller. A relatively simple circuit was developed by using phase-locked-loop techniques and total error storage. The integral digital controller will maintain speed control accuracy equal to that of the crystal reference oscillator.

Visible Quantum Nanophotonics.

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

Subramania, Ganapathi Subramanian; Wang, George T.; Fischer, Arthur J.

2017-09-01

The goal of this LDRD is to develop a quantum nanophotonics capability that will allow practical control over electron (hole) and photon confinement in more than one dimension. We plan to use quantum dots (QDs) to control electrons, and photonic crystals to control photons. InGaN QDs will be fabricated using quantum size control processes, and methods will be developed to add epitaxial layers for hole injection and surface passivation. We will also explore photonic crystal nanofabrication techniques using both additive and subtractive fabrication processes, which can tailor photonic crystal properties. These two efforts will be combined by incorporating the QDsmore » into photonic crystal surface emitting lasers (PCSELs). Modeling will be performed using finite-different time-domain and gain analysis to optimize QD-PCSEL designs that balance laser performance with the ability to nano-fabricate structures. Finally, we will develop design rules for QD-PCSEL architectures, to understand their performance possibilities and limits.« less

Characteristics of a liquid-crystal-filled composite lattice terahertz bandgap fiber

NASA Astrophysics Data System (ADS)

Bai, Jinjun; Ge, Meilan; Wang, Shasha; Yang, Yanan; Li, Yong; Chang, Shengjiang

2018-07-01

A new type of terahertz fiber is presented based on composite lattice photonic crystal bandgap. The cladding is filled selectively with the nematic liquid crystal 5CB which is sensitive to the electric field. The terahertz wave can be modulated by using the electric field to control the orientation of liquid crystal molecules. The plane wave expansion method and the finite element method are employed to theoretically analyze bandgap characteristics, polarization characteristics, energy fraction and material absorption loss. The results show that this fiber structure can be used as tunable terahertz polarization controller.

Flexoelectricity as a bulk property

NASA Astrophysics Data System (ADS)

Resta, Raffaele

2010-03-01

Piezoelectric composites can be created using nonpiezoelectric materials, by exploiting flexoelectricity. This is by definition the linear response of polarization to strain gradient, and is symmetry-allowed even in elemental crystals. However, the basic issue whether flexoelectricity is a bulk or a surface material property is open. We mention that the analogous issue about piezoelectricity is nontrivial either.^1 In this first attempt towards a full theory of flexoelectricity we prove that, for a simple class of strain and strain gradients, flexoelectricity is indeed a bulk effect. The key ingredients of the present theory are the long-range perturbations linearly induced by a unit displacement of a single nucleus in an otherwise perfect crystal: to leading order these are dipolar, quadrupolar, and octupolar. The corresponding tensors have rank 2, 3, and 4, respectively. Whereas dipoles and quadrupoles provide the piezoelectric response,^1 we show that dipoles and octupoles provide the flexoelectric response in nonpiezoelectric crystals. We conjecture that the full dipole and octupole tensors provide the flexoelectric response to the most general form of strain gradient. Our problem has a close relationship to the one of the ``absolute'' deformation potentials, which is based on a similar kind of dipolar and octupolar tensors.^2 ^1 R. M. Martin, Phys. Rev. B 5, 1607 (1972). ^2 R. Resta, L. Colombo and S. Baroni, Phys. Rev. B 41, 12538 (1990).

Site-controlled crystalline InN growth from the V-pits of a GaN substrate

NASA Astrophysics Data System (ADS)

Kuo, Chien-Ting; Hsu, Lung-Hsing; Lai, Yung-Yu; Cheng, Shan-Yun; Kuo, Hao-Chung; Lin, Chien-Chung; Cheng, Yuh-Jen

2017-05-01

A site-controlled crystalline InN growth from the V-pits of a GaN substrate was investigated. The V- pits were fabricated by epitaxial lateral growth of GaN over SiO2 disks patterned on a sapphire substrate. InN crystals were found to preferably grow on the inclined {10-11} crystal planes of the V-pits. A V-pit size of 1 μm or less can provide precise site-controlled InN nucleation at the V-pit bottom, while no InN was grown on the rest of the exposed GaN surfaces. The site-controlled nucleation is attributed to the low surface energy point created by the converging six {10-11} crystal facets at the V-pit bottom. When In source supply is below a certain value, this V-pit bottom is the only location able to aggregate enough active sources to start nucleation, thereby providing site-controlled crystal growth.

Large magnetic penetration depth and thermal fluctuations in a superconducting Ca10(Pt3As8)[(Fe1 xPtx)2As2]5 (x = 0.097) single crystal

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

Kim J.; Nazaretski E.; Ronning, F.

2012-05-18

We have measured the temperature dependence of the absolute value of the magnetic penetration depth {lambda}(T) in a Ca{sub 10}(Pt{sub 3}As{sub 8})[(Fe{sub 1-x}Pt{sub x}){sub 2}As{sub 2}]{sub 5} (x = 0.097) single crystal using a low-temperature magnetic force microscope (MFM). We obtain {lambda}{sub ab}(0) {approx} 1000 nm via extrapolating the data to T = 0. This large {lambda} and pronounced anisotropy in this system are responsible for large thermal fluctuations and the presence of a liquid vortex phase in this low-temperature superconductor with a critical temperature of 11 K, consistent with the interpretation of the electrical transport data. The superconducting parametersmore » obtained from {lambda} and coherence length {zeta} place this compound in the extreme type II regime. Meissner responses (via MFM) at different locations across the sample are similar to each other, indicating good homogeneity of the superconducting state on a submicron scale.« less

Three-dimensional photonic crystals as intermediate filter for thin-film tandem solar cells

NASA Astrophysics Data System (ADS)

Bielawny, Andreas; Miclea, Paul T.; Wehrspohn, Ralf B.; Lee, Seung-Mo; Knez, Mato; Rockstuhl, Carsten; Lisca, Marian; Lederer, Falk L.; Carius, Reinhard

2008-04-01

The concept of a 3D photonic crystal structure as diffractive and spectrally selective intermediate filter within 'micromorphous' (a-Si/μc-Si) tandem solar cells has been investigated numerically and experimentally. Our device aims for the enhancement of the optical pathway of incident light within the amorphous silicon top cell in its spectral region of low absorption. From our previous simulations, we expect a significant improvement of the tandem cell efficiency of about absolutely 1.3%. This increases the efficiency for a typical a-Si / μc-Si tandem cell from 11.1% to 12.4%, as a result of the optical current-matching of the two junctions. We suggest as wavelength-selective optical element a 3D-structured optical thin-film, prepared by self-organized artificial opal templates and replicated with atomic layer deposition. The resulting samples are highly periodic thin-film inverted opals made of conducting and transparent zinc-oxide. We describe the fabrication processes and compare experimental data on the optical properties in reflection and transmission with our simulations and photonic band structure calculations.

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

De La Pierre, Marco, E-mail: cedric.carteret@univ-lorraine.fr, E-mail: marco.delapierre@unito.it; Maschio, Lorenzo; Orlando, Roberto

Powder and single crystal Raman spectra of the two most common phases of calcium carbonate are calculated with ab initio techniques (using a “hybrid” functional and a Gaussian-type basis set) and measured both at 80 K and room temperature. Frequencies of the Raman modes are in very good agreement between calculations and experiments: the mean absolute deviation at 80 K is 4 and 8 cm{sup −1} for calcite and aragonite, respectively. As regards intensities, the agreement is in general good, although the computed values overestimate the measured ones in many cases. The combined analysis permits to identify almost all themore » fundamental experimental Raman peaks of the two compounds, with the exception of either modes with zero computed intensity or modes overlapping with more intense peaks. Additional peaks have been identified in both calcite and aragonite, which have been assigned to {sup 18}O satellite modes or overtones. The agreement between the computed and measured spectra is quite satisfactory; in particular, simulation permits to clearly distinguish between calcite and aragonite in the case of powder spectra, and among different polarization directions of each compound in the case of single crystal spectra.« less

Apparatus for growing crystals

NASA Technical Reports Server (NTRS)

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

1986-01-01

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

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

A Rationale for System-Dependent Advantages and Disadvantages of Solution Crystal Growth at Low Gravity

NASA Technical Reports Server (NTRS)

Rosenberger, Franz; Vekilov, Peter G.; Lin, Hong; Alexander, J. Iwan D.

1997-01-01

Protein crystallization experiments at reduced gravity have yielded crystals that, depending on the specific material, are either superior or inferior in their structural perfection compared to counterparts grown at normal gravity. A reduction of the crystals' quality due to their growth at low gravity cannot be understood from existing models. Our experimental investigations of the ground-based crystallization of the protein lysozyme have revealed pronounced unsteady growth layer dynamics and associated defect formation under steady external conditions. Through scaling analysis and numerical simulations we show that the observed fluctuations originate from the coupling of bulk transport with non-linear interface kinetics under mixed kinetics-transport control of the growth rate. The amplitude of the fluctuations is smallest when either transport or interfacial kinetics dominate the control of the crystallization process. Thus, depending on the specific system, crystal quality may be improved by either enhancing or suppressing the transport in the solution. These considerations provide, for the first time, a material-dependent rationale for the advantages, as well as the disadvantages, of reduced gravity for (protein) crystallization.

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

Li, Xiao; Martínez-González, José A.; Hernández-Ortiz, Juan P.

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 doubletwisted cylinders over micrometer scales. Past studies of polycrystalline BPs were challenged by grain boundaries between randomly oriented crystalline nanodomains. Here, the nucleation of BPs is controlled with considerable precision by relying on chemically nano-patterned surfaces, leading to macroscopic single-crystal BP specimens where the dynamics of meso-crystal formation can be directly observed. Theory and experiments show that transitions between two BPs having a different network structure proceed through local re-organization of the crystalline array,more » 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 sub-micron regime, is found to be martensitic in nature, with the diffusion-less feature associated to 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.« less

Revealing the preferred interlayer orientations and stackings of two-dimensional bilayer gallium selenide crystals.

PubMed

Li, Xufan; Basile, Leonardo; Yoon, Mina; Ma, Cheng; Puretzky, Alexander A; Lee, Jaekwang; Idrobo, Juan C; Chi, Miaofang; Rouleau, Christopher M; Geohegan, David B; Xiao, Kai

2015-02-23

Characterizing and controlling the interlayer orientations and stacking orders of two-dimensional (2D) bilayer crystals and van der Waals (vdW) heterostructures is crucial to optimize their electrical and optoelectronic properties. The four polymorphs of layered gallium selenide (GaSe) crystals that result from different layer stackings provide an ideal platform to study the stacking configurations in 2D bilayer crystals. Through a controllable vapor-phase deposition method, bilayer GaSe crystals were selectively grown and their two preferred 0° or 60° interlayer rotations were investigated. The commensurate stacking configurations (AA' and AB stacking) in as-grown bilayer GaSe crystals are clearly observed at the atomic scale, and the Ga-terminated edge structure was identified using scanning transmission electron microscopy. Theoretical analysis reveals that the energies of the interlayer coupling are responsible for the preferred orientations among the bilayer GaSe crystals. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Valley photonic crystals for control of spin and topology

NASA Astrophysics Data System (ADS)

Dong, Jian-Wen; Chen, Xiao-Dong; Zhu, Hanyu; Wang, Yuan; Zhang, Xiang

2017-03-01

Photonic crystals offer unprecedented opportunity for light manipulation and applications in optical communication and sensing. Exploration of topology in photonic crystals and metamaterials with non-zero gauge field has inspired a number of intriguing optical phenomena such as one-way transport and Weyl points. Recently, a new degree of freedom, valley, has been demonstrated in two-dimensional materials. Here, we propose a concept of valley photonic crystals with electromagnetic duality symmetry but broken inversion symmetry. We observe photonic valley Hall effect originating from valley-dependent spin-split bulk bands, even in topologically trivial photonic crystals. Valley-spin locking behaviour results in selective net spin flow inside bulk valley photonic crystals. We also show the independent control of valley and topology in a single system that has been long pursued in electronic systems, resulting in topologically-protected flat edge states. Valley photonic crystals not only offer a route towards the observation of non-trivial states, but also open the way for device applications in integrated photonics and information processing using spin-dependent transportation.

Valley photonic crystals for control of spin and topology.

PubMed

Dong, Jian-Wen; Chen, Xiao-Dong; Zhu, Hanyu; Wang, Yuan; Zhang, Xiang

2017-03-01

Photonic crystals offer unprecedented opportunity for light manipulation and applications in optical communication and sensing. Exploration of topology in photonic crystals and metamaterials with non-zero gauge field has inspired a number of intriguing optical phenomena such as one-way transport and Weyl points. Recently, a new degree of freedom, valley, has been demonstrated in two-dimensional materials. Here, we propose a concept of valley photonic crystals with electromagnetic duality symmetry but broken inversion symmetry. We observe photonic valley Hall effect originating from valley-dependent spin-split bulk bands, even in topologically trivial photonic crystals. Valley-spin locking behaviour results in selective net spin flow inside bulk valley photonic crystals. We also show the independent control of valley and topology in a single system that has been long pursued in electronic systems, resulting in topologically-protected flat edge states. Valley photonic crystals not only offer a route towards the observation of non-trivial states, but also open the way for device applications in integrated photonics and information processing using spin-dependent transportation.

Protein Crystal Movements and Fluid Flows During Microgravity Growth

NASA Technical Reports Server (NTRS)

Boggon, Titus J.; Chayen, Naomi E.; Snell, Edward H.; Dong, Jun; Lautenschlager, Peter; Potthast, Lothar; Siddons, D. Peter; Stojanoff, Vivian; Gordon, Elspeth; Thompson, Andrew W.;

Crystallization of toxic glycol solvates of rifampin from glycerin and propylene glycol contaminated with ethylene glycol or diethylene glycol.

PubMed

de Villiers, Melgardt M; Caira, Mino R; Li, Jinjing; Strydom, Schalk J; Bourne, Susan A; Liebenberg, Wilna

2011-06-06

This study was initiated when it was suspected that syringe blockage experienced upon administration of a compounded rifampin suspension was caused by the recrystallization of toxic glycol solvates of the drug. Single crystal X-ray structure analysis, powder X-ray diffraction, thermal analysis and gas chromatography were used to identify the ethylene glycol in the solvate crystals recovered from the suspension. Controlled crystallization and solubility studies were used to determine the ease with which toxic glycol solvates crystallized from glycerin and propylene glycol contaminated with either ethylene or diethylene glycol. The single crystal structures of two distinct ethylene glycol solvates of rifampin were solved while thermal analysis, GC analysis and solubility studies confirmed that diethylene glycol solvates of the drug also crystallized. Controlled crystallization studies showed that crystallization of the rifampin solvates from glycerin and propylene glycol depended on the level of contamination and changes in the solubility of the drug in the contaminated solvents. Although the exact source of the ethylene glycol found in the compounded rifampin suspension is not known, the results of this study show how important it is to ensure that the drug and excipients comply with pharmacopeial or FDA standards.

A highly attenuating and frequency tailorable annular hole phononic crystal for surface acoustic waves.

PubMed

Ash, B J; Worsfold, S R; Vukusic, P; Nash, G R

2017-08-02

Surface acoustic wave (SAW) devices are widely used for signal processing, sensing and increasingly for lab-on-a-chip applications. Phononic crystals can control the propagation of SAW, analogous to photonic crystals, enabling components such as waveguides and cavities. Here we present an approach for the realisation of robust, tailorable SAW phononic crystals, based on annular holes patterned in a SAW substrate. Using simulations and experiments, we show that this geometry supports local resonances which create highly attenuating phononic bandgaps at frequencies with negligible coupling of SAWs into other modes, even for relatively shallow features. The enormous bandgap attenuation is up to an order-of-magnitude larger than that achieved with a pillar phononic crystal of the same size, enabling effective phononic crystals to be made up of smaller numbers of elements. This work transforms the ability to exploit phononic crystals for developing novel SAW device concepts, mirroring contemporary progress in photonic crystals.The control and manipulation of propagating sound waves on a surface has applications in on-chip signal processing and sensing. Here, Ash et al. deviate from standard designs and fabricate frequency tailorable phononic crystals with an order-of-magnitude increase in attenuation.

Correlations of Apparent Cellulose Crystallinity Determined by XRD, NMR, IR, Raman, and SFG Methods

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

Johnson, David K; Lee, Christopher; Dazen, Kevin

2015-07-04

Although the cellulose crystallinity index (CI) is used widely, its limitations have not been adequately described. In this study, the CI values of a set of reference samples were determined from X-ray diffraction (XRD), nuclear magnetic resonance (NMR), and infrared (IR), Raman, and vibrational sum frequency generation (SFG) spectroscopies. The intensities of certain crystalline peaks in IR, Raman, and SFG spectra positively correlated with the amount of crystalline cellulose in the sample, but the correlation with XRD was nonlinear as a result of fundamental differences in detection sensitivity to crystalline cellulose and improper baseline corrections for amorphous contributions. It ismore » demonstrated that the intensity and shape of the XRD signal is affected by both the amount of crystalline cellulose and crystal size, which makes XRD analysis complicated. It is clear that the methods investigated show the same qualitative trends for samples, but the absolute CI values differ depending on the determination method. This clearly indicates that the CI, as estimated by different methods, is not an absolute value and that for a given set of samples the CI values can be compared only as a qualitative measure.« less

Correlations of Apparent Cellulose Crystallinity Determined by XRD, NMR, IR, Raman, and SFG Methods

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

Lee, Christopher M; Dazen, Kevin; Kafle, Kabindra

2015-01-01

Although the cellulose crystallinity index (CI) is used widely, its limitations have not been adequately described. In this study, the CI values of a set of reference samples were determined from X-ray diffraction (XRD), nuclear magnetic resonance (NMR), and infrared (IR), Raman, and vibrational sum frequency generation (SFG) spectroscopies. The intensities of certain crystalline peaks in IR, Raman, and SFG spectra positively correlated with the amount of crystalline cellulose in the sample, but the correlation with XRD was nonlinear as a result of fundamental differences in detection sensitivity to crystalline cellulose and improper baseline corrections for amorphous contributions. It ismore » demonstrated that the intensity and shape of the XRD signal is affected by both the amount of crystalline cellulose and crystal size, which makes XRD analysis complicated. It is clear that the methods investigated show the same qualitative trends for samples, but the absolute CI values differ depending on the determination method. This clearly indicates that the CI, as estimated by different methods, is not an absolute value and that for a given set of samples the CI values can be compared only as a qualitative measure.« less

Alignment and absolute wavelength calibration of imaging Bragg spectrometers.

PubMed

Bertschinger, G; Marchuk, O; Barnsley, R

2016-11-01

In the present and the next generation of fusion devices, imaging Bragg spectrometers are key diagnostics to measure plasma parameters in the hot core, especially ion temperature and plasma rotation. The latter quantities are routinely obtained using the Doppler-width and -shift of the emitted spectral lines, respectively. Line shift measurements require absolute accuracies Δλ/λ of about 10 ppm, where λ-is the observed wavelength. For ITER and the present fusion devices, spectral lines of He-and H-like argon, iron, and krypton as well as Ne-like tungsten are foreseen for the measurements. For these lines, Kα lines can be found, some in higher order, which fit into the narrow energy window of the spectrometers. For arbitrary wavelength settings, Kα lines are also used to measure the miscut of the spherical crystals; afterwards the spectrometers can be set according to the geometrical imaging properties using coordinate measurement machines. For the spectrometers measuring Lyα lines of H-like ions, fluorescence targets can provide in situ localized calibration lines on the spectra. The fluorescence targets are used best in transmission and are excited by the thermal x-ray radiation of the plasma. An analytic theory of fluorescence is worked out.

Solar Flare Abundances of Potassium, Argon, and Sulphur

NASA Technical Reports Server (NTRS)

Oegerle, William (Technical Monitor); Phillips, K. J. H.; Sylwester, J.; Sylwester, B.; Landi, E.

2003-01-01

The absolute coronal abundances of potassium has been determined for the first time from X-ray solar flare line and continuous spectra together with absolute and relative abundances of Ar and S. Potassium is of importance in the continuing debate concerning the nature of the coronal/photospheric element abundance ratios which are widely considered to depend on first ionization potential since it has the lowest FIP of any common element in the Sun. The measurements were obtained with the RESIK crystal spectrometer on the Coronas-F spacecraft. A differential emission measure DEM = const. x exp (-(beta)T(sub e) was found to be the most consistent with the data out of three models considered. We find that the coronal ratio [K/H] = 3.7 x 10(exp - 7), a factor 3 times photospheric, in agreement with other observations using line-to-line ratios. Our measured value for the coronal ratio [Ar/H] = 1.5 x 10(exp -6) is significantly less than photospheric, indicating that there is a slight depletion of this high-FIP element in the corona. For S (an intermediate-FIP element) we obtained [S/H] = 2.2 x 10(exp - 5), approximately the same as in previous work.

Optimal design of the absolute positioning sensor for a high-speed maglev train and research on its fault diagnosis.

PubMed

Zhang, Dapeng; Long, Zhiqiang; Xue, Song; Zhang, Junge

2012-01-01

This paper studies an absolute positioning sensor for a high-speed maglev train and its fault diagnosis method. The absolute positioning sensor is an important sensor for the high-speed maglev train to accomplish its synchronous traction. It is used to calibrate the error of the relative positioning sensor which is used to provide the magnetic phase signal. On the basis of the analysis for the principle of the absolute positioning sensor, the paper describes the design of the sending and receiving coils and realizes the hardware and the software for the sensor. In order to enhance the reliability of the sensor, a support vector machine is used to recognize the fault characters, and the signal flow method is used to locate the faulty parts. The diagnosis information not only can be sent to an upper center control computer to evaluate the reliability of the sensors, but also can realize on-line diagnosis for debugging and the quick detection when the maglev train is off-line. The absolute positioning sensor we study has been used in the actual project.

Protein Crystallization by Combining Laser Irradiation and Solution-Stirring Techniques

NASA Astrophysics Data System (ADS)

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

2005-03-01

Bovine adenosine deaminase in the absence of an inhibitor (free-ADA) does not form crystals when using conventional crystallization methods. Using a solution-stirring technique, we recently succeeded in generating a small number of free-ADA crystals. In this paper, we demonstrate the combination of laser-irradiated growth and stirring (COLAS). This technique was found to be useful for controlling crystal nucleation and growth, which led to the production of a much larger number of high-quality free-ADA crystals.

Mesoscopic monodisperse ferromagnetic colloids enable magnetically controlled photonic crystals.

PubMed

Xu, Xiangling; Majetich, Sara A; Asher, Sanford A

2002-11-20

We report here the first synthesis of mesoscopic, monodisperse particles which contain nanoscopic inclusions of ferromagnetic cobalt ferrites. These monodisperse ferromagnetic composite particles readily self-assemble into magnetically responsive photonic crystals that efficiently Bragg diffract incident light. Magnetic fields can be used to control the photonic crystal orientation and, thus, the diffracted wavelength. We demonstrate the use of these ferromagnetic particles to fabricate magneto-optical diffracting fluids and magnetically switchable diffracting mirrors.

Organic Single-Crystal Semiconductor Films on a Millimeter Domain Scale.

PubMed

Kwon, Sooncheol; Kim, Jehan; Kim, Geunjin; Yu, Kilho; Jo, Yong-Ryun; Kim, Bong-Joong; Kim, Junghwan; Kang, Hongkyu; Park, Byoungwook; Lee, Kwanghee

2015-11-18

Nucleation and growth processes can be effectively controlled in organic semiconductor films through a new concept of template-mediated molecular crystal seeds during the phase transition; the effective control of these processes ensures millimeter-scale crystal domains, as well as the performance of the resulting organic films with intrinsic hole mobility of 18 cm(2) V(-1) s(-1). © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Controlled Growth of Rubrene Nanowires by Eutectic Melt Crystallization

NASA Astrophysics Data System (ADS)

Chung, Jeyon; Hyon, Jinho; Park, Kyung-Sun; Cho, Boram; Baek, Jangmi; Kim, Jueun; Lee, Sang Uck; Sung, Myung Mo; Kang, Youngjong

2016-03-01

Organic semiconductors including rubrene, Alq3, copper phthalocyanine and pentacene are crystallized by the eutectic melt crystallization. Those organic semiconductors form good eutectic systems with the various volatile crystallizable additives such as benzoic acid, salicylic acid, naphthalene and 1,3,5-trichlorobenzene. Due to the formation of the eutectic system, organic semiconductors having originally high melting point (Tm > 300 °C) are melted and crystallized at low temperature (Te = 40.8-133 °C). The volatile crystallizable additives are easily removed by sublimation. For a model system using rubrene, single crystalline rubrene nanowires are prepared by the eutectic melt crystallization and the eutectic-melt-assisted nanoimpinting (EMAN) technique. It is demonstrated that crystal structure and the growth direction of rubrene can be controlled by using different volatile crystallizable additives. The field effect mobility of rubrene nanowires prepared using several different crystallizable additives are measured and compared.

Effect of supersaturation on L-glutamic acid polymorphs under droplet-based microchannels

NASA Astrophysics Data System (ADS)

Jiang, Nan; Wang, Zhanzhong; Dang, Leping; Wei, Hongyuan

2016-07-01

Supersaturation is an important controlling factor for crystallization process and polymorphism. Droplet-based microchannels and conventional crystallization were used to investigate polymorphs of L-gluatamic acid in this work. The results illustrate that it is easy to realize the accurate and rapid control of the crystallization temperature in the droplets, which is especially beneficial to heat and mass transfer during crystallization. It is also noted that higher degree of supersaturation favors the nucleation of α crystal form, while lower degree of supersaturation favors the nucleation of β crystal form under droplet-based microchannels for L-gluatamic acid. In addition, there is a different nucleation behavior to be found under droplet-based microchannels both for the β form and α form of L-glutamic acid. This new finding can provide important insight into the development and design of investigation meanings for drug polymorph.

Optical trapping assembling of clusters and nanoparticles in solution by CW and femtosecond lasers

NASA Astrophysics Data System (ADS)

Masuhara, Hiroshi; Sugiyama, Teruki; Yuyama, Ken-ichi; Usman, Anwar

2015-02-01

Laser trapping of molecular systems in solution is classified into three cases: JUST TRAPPING, EXTENDED TRAPPING, and NUCLEATION and GROWTH. The nucleation in amino acid solutions depends on where the 1064-nm CW trapping laser is focused, and crystallization and liquid-liquid phase separation are induced by laser trapping at the solution/air surface and the solution/glass interface, respectively. Laser trapping crystallization is achieved even in unsaturated solution, on which unique controls of crystallization are made possible. Crystal size is arbitrarily controlled by tuning laser power for a plate-like anhydrous crystal of l-phenylalanine. The α- or γ-crystal polymorph of glycine is selectively prepared by changing laser power and polarization. Further efficient trapping of nanoparticles and their following ejection induced by femtosecond laser pulses are introduced as unique trapping phenomena and finally future perspective is presented.

National Electrical Manufacturers Association NU-4 performance evaluation of the PET component of the NanoPET/CT preclinical PET/CT scanner.

PubMed

Szanda, Istvan; Mackewn, Jane; Patay, Gergely; Major, Peter; Sunassee, Kavitha; Mullen, Gregory E; Nemeth, Gabor; Haemisch, York; Blower, Philip J; Marsden, Paul K

2011-11-01

The NanoPET/CT represents the latest generation of commercial preclinical PET/CT systems. This article presents a performance evaluation of the PET component of the system according to the National Electrical Manufacturers Association (NEMA) NU-4 2008 standard. The NanoPET/CT consists of 12 lutetium yttrium orthosilicate:cerium modular detectors forming 1 ring, with 9.5-cm axial coverage and a 16-cm animal port. Each detector crystal is 1.12 × 1.12 × 13 mm, and 1 module contains 81 × 39 of these crystals. An optical light guide transmits the scintillation light to the flat-panel multianode position-sensitive photomultiplier tubes. Analog-to-digital converter cards and a field-programmable gate array-based data-collecting card provide the readout. Spatial resolution, sensitivity, counting rate capabilities, and image quality were evaluated in accordance with the NEMA NU-4 standard. Energy and temporal resolution measurements and a mouse imaging study were performed in addition to the standard. Energy resolution was 19% at 511 keV. The spatial resolution, measured as full width at half maximum on single-slice rebinning/filtered backprojection-reconstructed images, approached 1 mm on the axis and remained below 2.5 mm in the central 5-cm transaxial region both in the axial center and at one-quarter field of view. The maximum absolute sensitivity for a point source at the center of the field of view was 7.7%. The maximum noise equivalent counting rates were 430 kcps at 36 MBq and 130 kcps at 27 MBq for the mouse- and rat-sized phantoms, respectively. The uniformity and recovery coefficients were measured with the image-quality phantom, giving good-quality images. In a mouse study with an (18)F-labeled thyroid-specific tracer, the 2 lobes of the thyroid were clearly distinguishable, despite the small size of this organ. The flexible readout system allowed experiments to be performed in an efficient manner, and the system remained stable throughout. The large number of detector crystals, arranged with a fine pitch, results in excellent spatial resolution, which is the best reported for currently available commercial systems. The absolute sensitivity is high over the field of view. Combined with the excellent image quality, these features make the NanoPET/CT a powerful tool for preclinical research.

Thaumatin crystallization aboard the International Space Station using liquid-liquid diffusion in the Enhanced Gaseous Nitrogen Dewar (EGN).

PubMed

Barnes, Cindy L; Snell, Edward H; Kundrot, Craig E

2002-05-01

This paper reports results from the first biological crystal-growth experiment on the International Space Station (ISS). Crystals of thaumatin were grown using liquid-liquid diffusion in Tygon tubing transported in the Enhanced Gaseous Nitrogen Dewar (EGN). Different volume ratios and concentrations of protein and precipitant were used to test different adaptations of the vapor-diffusion crystallization recipe to the liquid-liquid diffusion method. The EGN warmed up from 77 to 273 K in about 4 d, about the same time it took to warm from 273 to 293 K. The temperature within the EGN was 293-297 K for the majority of the experiment. Air gaps that blocked liquid-liquid diffusion formed in the tubes. Nonetheless, crystals were grown. Synchrotron diffraction data collected from the best space-grown crystal extended to 1.28 A, comparable to previous studies of space-grown thaumatin crystals. The resolution of the best ground-control crystal was only 1.47 A. It is not clear if the difference in diffraction limit arises from factors other than crystal size. Improvements in temperature control and the elimination of air gaps are needed, but the results show that the EGN on the ISS can be used to produce space-grown crystals that diffract to high resolution.

Thaumatin Crystallization Aboard the International Space Station Using Liquid-Liquid Diffusion in the Enhanced Gaseous Nitrogen Dewar (EGN)

NASA Technical Reports Server (NTRS)

Kundrot, Craig; Barnes, Cindy L.; Snell, Edward H.; Stinson, Thomas N. (Technical Monitor)

2002-01-01

This paper reports results from the first biological crystal growth experiment on the International Space Station (ISS). Crystals of thaumatin were grown using liquid-liquid diffusion in Tygon tubing transported in the Enhanced Gaseous Nitrogen Dewar (EGN). Different Volume ratios and concentrations of protein and precipitant were used to test different adaptations of the vapor diffusion crystallization recipe to the liquid-liquid diffusion method. The EGN warmed up from -196 C to 0 C in about four days, about the same time it took to warm from 0 C to 20 C. The temperature within the EGN was 20 - 24 C for the majority of the experiment. Air gaps that blocked liquid-liquid diffusion formed in the tubes. Nonetheless, crystals were grown. Synchrotron diffraction data collected from the best space grown crystal extended to 1.28 Angstroms, comparable to previous studies of space-grown thaumatin crystals. The resolution of the best ground control crystal was only 1.47 Angstroms. It is not clear if the difference in diffraction limit is due to factors other than crystal size. Improvements in temperature control and the elimination of air gaps are needed, but the results show that EGN on the ISS can be used to produce space grown crystals that diffract to high resolution.

Intrinsic Josephson junctions in mesas and ultrathin BSCCO single crystals: Ultimate control of shape and dimensions

NASA Astrophysics Data System (ADS)

Yurgens, A.; You, L. X.; Torstensson, M.; Winkler, D.

2007-09-01

We describe experiments which are only possible through an ultimate control of sample shape and dimensions down to nanometer scale whereby transport measurements can be done in various restricted geometries. We use photolithography patterning together with a flip-chip technique to isolate very thin (d ∼ 100 nm) pieces of Bi2Sr2CaCu2O8+δ (BSCCO) single crystals. Ar-ion milling allows us to further thin these crystals down to a few nanometers in a controlled way. With decreasing thickness below two to three unit cells, the superconducting transition temperature gradually decreases to zero and the in-plane resistivity increases to large values indicating the existence of a superconductor-insulator transition in these ultrathin single crystals. In a refined technique, a precise control of the etching depth from both sides of the crystal makes it possible to form stacks of intrinsic Josephson junctions (IJJs) inside the ultrathin single crystals. The stacks can be tailor-made to any microscopic height (0-9 nm < d), i.e. enclosing a specific number of IJJs (0-6). In certain geometries, by feeding current into the topmost Cu2O4-layer of a mesa on the surface of a BSCCO single crystal, we measured the critical value of this current by detecting a sharp upturn or break in the current-voltage characteristics. From this, we estimate the sheet critical current density of a single Cu2O4 plane to be ∼0.3-0.7 A/cm at 4.5 K, corresponding to a bulk current density of ∼2-5 MA/cm2. These values are among the largest ever reported for BSCCO single crystals, thin-films and tapes.

Patients with Rheumatoid Arthritis and Chronic Pain Display Enhanced Alpha Power Density at Rest.

PubMed

Meneses, Francisco M; Queirós, Fernanda C; Montoya, Pedro; Miranda, José G V; Dubois-Mendes, Selena M; Sá, Katia N; Luz-Santos, Cleber; Baptista, Abrahão F

2016-01-01

Patients with chronic pain due to neuropathy or musculoskeletal injury frequently exhibit reduced alpha and increased theta power densities. However, little is known about electrical brain activity and chronic pain in patients with rheumatoid arthritis (RA). For this purpose, we evaluated power densities of spontaneous electroencephalogram (EEG) band frequencies (delta, theta, alpha, and beta) in females with persistent pain due to RA. This was a cross-sectional study of 21 participants with RA and 21 healthy controls (mean age = 47.20; SD = 10.40). EEG was recorded at rest over 5 min with participant's eyes closed. Twenty electrodes were placed over five brain regions (frontal, central, parietal, temporal, and occipital). Significant differences were observed in depression and anxiety with higher scores in RA participants than healthy controls (p = 0.002). Participants with RA exhibited increased average absolute alpha power density in all brain regions when compared to controls [F (1.39) = 6.39, p = 0.016], as well as increased average relative alpha power density [F (1.39) = 5.82, p = 0.021] in all regions, except the frontal region, controlling for depression/anxiety. Absolute theta power density also increased in the frontal, central, and parietal regions for participants with RA when compared to controls [F (1, 39) = 4.51, p = 0.040], controlling for depression/anxiety. Differences were not exhibited on beta and delta absolute and relative power densities. The diffuse increased alpha may suggest a possible neurogenic mechanism for chronic pain in individuals with RA.

Controlling the volatility of the written optical state in electrochromic DNA liquid crystals

NASA Astrophysics Data System (ADS)

Liu, Kai; Varghese, Justin; Gerasimov, Jennifer Y.; Polyakov, Alexey O.; Shuai, Min; Su, Juanjuan; Chen, Dong; Zajaczkowski, Wojciech; Marcozzi, Alessio; Pisula, Wojciech; Noheda, Beatriz; Palstra, Thomas T. M.; Clark, Noel A.; Herrmann, Andreas

2016-05-01

Liquid crystals are widely used in displays for portable electronic information display. To broaden their scope for other applications like smart windows and tags, new material properties such as polarizer-free operation and tunable memory of a written state become important. Here, we describe an anhydrous nanoDNA-surfactant thermotropic liquid crystal system, which exhibits distinctive electrically controlled optical absorption, and temperature-dependent memory. In the liquid crystal isotropic phase, electric field-induced colouration and bleaching have a switching time of seconds. Upon transition to the smectic liquid crystal phase, optical memory of the written state is observed for many hours without applied voltage. The reorientation of the DNA-surfactant lamellar layers plays an important role in preventing colour decay. Thereby, the volatility of optoelectronic state can be controlled simply by changing the phase of the material. This research may pave the way for developing a new generation of DNA-based, phase-modulated, photoelectronic devices.

Reticular synthesis of porous molecular 1D nanotubes and 3D networks.

PubMed

Slater, A G; Little, M A; Pulido, A; Chong, S Y; Holden, D; Chen, L; Morgan, C; Wu, X; Cheng, G; Clowes, R; Briggs, M E; Hasell, T; Jelfs, K E; Day, G M; Cooper, A I

2017-01-01

Synthetic control over pore size and pore connectivity is the crowning achievement for porous metal-organic frameworks (MOFs). The same level of control has not been achieved for molecular crystals, which are not defined by strong, directional intermolecular coordination bonds. Hence, molecular crystallization is inherently less controllable than framework crystallization, and there are fewer examples of 'reticular synthesis', in which multiple building blocks can be assembled according to a common assembly motif. Here we apply a chiral recognition strategy to a new family of tubular covalent cages to create both 1D porous nanotubes and 3D diamondoid pillared porous networks. The diamondoid networks are analogous to MOFs prepared from tetrahedral metal nodes and linear ditopic organic linkers. The crystal structures can be rationalized by computational lattice-energy searches, which provide an in silico screening method to evaluate candidate molecular building blocks. These results are a blueprint for applying the 'node and strut' principles of reticular synthesis to molecular crystals.

Reticular synthesis of porous molecular 1D nanotubes and 3D networks

NASA Astrophysics Data System (ADS)

Slater, A. G.; Little, M. A.; Pulido, A.; Chong, S. Y.; Holden, D.; Chen, L.; Morgan, C.; Wu, X.; Cheng, G.; Clowes, R.; Briggs, M. E.; Hasell, T.; Jelfs, K. E.; Day, G. M.; Cooper, A. I.

2017-01-01

Synthetic control over pore size and pore connectivity is the crowning achievement for porous metal-organic frameworks (MOFs). The same level of control has not been achieved for molecular crystals, which are not defined by strong, directional intermolecular coordination bonds. Hence, molecular crystallization is inherently less controllable than framework crystallization, and there are fewer examples of 'reticular synthesis', in which multiple building blocks can be assembled according to a common assembly motif. Here we apply a chiral recognition strategy to a new family of tubular covalent cages to create both 1D porous nanotubes and 3D diamondoid pillared porous networks. The diamondoid networks are analogous to MOFs prepared from tetrahedral metal nodes and linear ditopic organic linkers. The crystal structures can be rationalized by computational lattice-energy searches, which provide an in silico screening method to evaluate candidate molecular building blocks. These results are a blueprint for applying the 'node and strut' principles of reticular synthesis to molecular crystals.

Controlled crystallization of the lipophilic drug fenofibrate during freeze-drying: elucidation of the mechanism by in-line Raman spectroscopy.

PubMed

de Waard, Hans; De Beer, Thomas; Hinrichs, Wouter L J; Vervaet, Chris; Remon, Jean-Paul; Frijlink, Henderik W

2010-12-01

We developed a novel process, "controlled crystallization during freeze-drying" to produce drug nanocrystals of poorly water-soluble drugs. This process involves freeze-drying at a relatively high temperature of a drug and a matrix material from a mixture of tertiary butyl alcohol and water, resulting in drug nanocrystals incorporated in a matrix. The aim of this study was to elucidate the mechanisms that determine the size of the drug crystals. Fenofibrate was used as a model lipophilic drug. To monitor the crystallization during freeze-drying, a Raman probe was placed just above the sample in the freeze-dryer. These in-line Raman spectroscopy measurements clearly revealed when the different components crystallized during freeze-drying. The solvents crystallized only during the freezing step, while the solutes only crystallized after the temperature was increased, but before drying started. Although the solutes crystallized only after the freezing step, both the freezing rate and the shelf temperature were critical parameters that determined the final crystal size. At a higher freezing rate, smaller interstitial spaces containing the freeze-concentrated fraction were formed, resulting in smaller drug crystals (based on dissolution data). On the other hand, when the solutes crystallized at a lower shelf temperature, the degree of supersaturation is higher, resulting in a higher nucleation rate and consequently more and therefore smaller crystals. In conclusion, for the model drug fenofibrate, a high freezing rate and a relatively low crystallization temperature resulted in the smallest crystals and therefore the highest dissolution rate.

A quantified dosing ALD reactor with in-situ diagnostics for surface chemistry studies

NASA Astrophysics Data System (ADS)

Larrabee, Thomas J.

A specialized atomic layer deposition (ALD) reactor has been constructed to serve as an instrument to simultaneously study the surface chemistry of the ALD process, and perform ALD as is conventionally done in continuum flow of inert gas. This reactor is uniquely useful to gain insight into the ALD process because of the combination of its precise, controllable, and quantified dosing/microdosing capability; its in-situ quadrupole mass spectrometer for gas composition analysis; its pair of highly-sensitive in-situ quartz crystal microbalances (QCMs); and its complete spectrum of pressures and operating conditions --- from viscous to molecular flow regimes. Control of the dose is achieved independently of the conditions by allowing a reactant gas to fill a fixed volume and measured pressure, which is held at a controlled temperature, and subsequently dosed into the system by computer controlled pneumatic valves. Absolute reactant exposure to the substrate and QCMs is unambiguously calculated from the molecular impingement flux, and its relationship to dose size is established, allowing means for easily intentionally reproducing specific exposures. Methods for understanding atomic layer growth and adsorption phenomena, including the precursor sticking probability, dynamics of molecular impingement, size of dose, and other operating variables are for the first time quantitatively related to surface reaction rates by mass balance. Extensive characterization of the QCM as a measurement tool for adsorption under realistic ALD conditions has been examined, emphasizing the state-of-the-art and importance of QCM system features required. Finally, the importance of dose-quantification and microdosing has been contextualized in view of the ALD literature, underscoring the significance of more precise condition specification in establishing a better basis for reactor and reactant comparison.

Organic crystal-binding peptides: morphology control and one-pot formation of protein-displaying organic crystals

NASA Astrophysics Data System (ADS)

Niide, Teppei; Ozawa, Kyohei; Nakazawa, Hikaru; Oliveira, Daniel; Kasai, Hitoshi; Onodera, Mari; Asano, Ryutaro; Kumagai, Izumi; Umetsu, Mitsuo

2015-11-01

Crystalline assemblies of fluorescent molecules have different functional properties than the constituent monomers, as well as unique optical characteristics that depend on the structure, size, and morphological homogeneity of the crystal particles. In this study, we selected peptides with affinity for the surface of perylene crystal particles by exposing a peptide-displaying phage library in aqueous solution to perylene crystals, eluting the surface-bound phages by means of acidic desorption or liquid-liquid extraction, and amplifying the obtained phages in Escherichia coli. One of the perylene-binding peptides, PeryBPb1: VQHNTKYSVVIR, selected by this biopanning procedure induced perylene molecules to form homogenous planar crystal nanoparticles by means of a poor solvent method, and fusion of the peptide to a fluorescent protein enabled one-pot formation of protein-immobilized crystalline nanoparticles. The nanoparticles were well-dispersed in aqueous solution, and Förster resonance energy transfer from the perylene crystals to the fluorescent protein was observed. Our results show that the crystal-binding peptide could be used for simultaneous control of perylene crystal morphology and dispersion and protein immobilization on the crystals.Crystalline assemblies of fluorescent molecules have different functional properties than the constituent monomers, as well as unique optical characteristics that depend on the structure, size, and morphological homogeneity of the crystal particles. In this study, we selected peptides with affinity for the surface of perylene crystal particles by exposing a peptide-displaying phage library in aqueous solution to perylene crystals, eluting the surface-bound phages by means of acidic desorption or liquid-liquid extraction, and amplifying the obtained phages in Escherichia coli. One of the perylene-binding peptides, PeryBPb1: VQHNTKYSVVIR, selected by this biopanning procedure induced perylene molecules to form homogenous planar crystal nanoparticles by means of a poor solvent method, and fusion of the peptide to a fluorescent protein enabled one-pot formation of protein-immobilized crystalline nanoparticles. The nanoparticles were well-dispersed in aqueous solution, and Förster resonance energy transfer from the perylene crystals to the fluorescent protein was observed. Our results show that the crystal-binding peptide could be used for simultaneous control of perylene crystal morphology and dispersion and protein immobilization on the crystals. Electronic supplementary information (ESI) available: Schematic representation of PeryBPb1-fused DsRed-Monomer, fluorescence spectra of perylene crystals and DsRed-Monomer, and emission spectra of DsRed-Monomer at various excitation wavelengths. See DOI: 10.1039/c5nr06471f

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

Reduced content of chloroatranol and atranol in oak moss absolute significantly reduces the elicitation potential of this fragrance material.

PubMed

Andersen, Flemming; Andersen, Kirsten H; Bernois, Armand; Brault, Christophe; Bruze, Magnus; Eudes, Hervé; Gadras, Catherine; Signoret, Anne-Cécile J; Mose, Kristian F; Müller, Boris P; Toulemonde, Bernard; Andersen, Klaus Ejner

2015-02-01

Oak moss absolute, an extract from the lichen Evernia prunastri, is a valued perfume ingredient but contains extreme allergens. To compare the elicitation properties of two preparations of oak moss absolute: 'classic oak moss', the historically used preparation, and 'new oak moss', with reduced contents of the major allergens atranol and chloroatranol. The two preparations were compared in randomized double-blinded repeated open application tests and serial dilution patch tests in 30 oak moss-sensitive volunteers and 30 non-allergic control subjects. In both test models, new oak moss elicited significantly less allergic contact dermatitis in oak moss-sensitive subjects than classic oak moss. The control subjects did not react to either of the preparations. New oak moss is still a fragrance allergen, but elicits less allergic contact dermatitis in previously oak moss-sensitized individuals, suggesting that new oak moss is less allergenic to non-sensitized individuals. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

(±)-Evodiakine, A Pair of Rearranged Rutaecarpine-Type Alkaloids From Evodia rutaecarpa.

PubMed

Li, Yan-Hong; Zhang, Yu; Peng, Li-Yan; Li, Xiao-Nian; Zhao, Qin-Shi; Li, Rong-Tao; Wu, Xing-De

2016-12-01

(±)-Evodiakine (1a and 1b), a pair of rearranged rutaecarpine-type alkaloids with an unprecedented 6/5/5/7/6 ring system, were isolated from the nearly ripe fruits of Evodia rutaecarpa. Separation of the enantiomers have been achieved by chiral HPLC column. The structures of (±)-evodiakine were unambiguously elucidated by 1D and 2D NMR spectra, mass spectrometry, and single-crystal X-ray diffraction. Their absolute configurations were determined by comparison of experimental and calculated electronic circular dichroism spectra. A hypothetical biogenetic pathway for (±)-evodiakine was also proposed. Compounds 1a, 1b, and the racemate (1) were tested for their cytotoxic and anti-inflammatory activities.

Low noise cryogenic dielectric resonator oscillator

NASA Technical Reports Server (NTRS)

Dick, G. John (Inventor)

1988-01-01

A microwave oscillator is provided which can operate at a temperature of many degrees above absolute zero while providing very low phase noise that has heretofore generally required temperatures within a few degrees K. The oscillator includes a ring-shaped resonant element of ruby (sapphire plus chromium) or iron sapphire crystal, lying adjacent to a resonator element of sapphire, so that the regenerator element lies directly in the magnetic field of the resonator element. The resonator element is substantially devoid of contact with electrically conductive material. Microwave energy of a pump frequency (e.g., 31 GHz) is outputted from the regenerator element, while signal energy (e.g., 10 GHz) is outputted from the resonator element.

Denhaminols A-H, dihydro-β-agarofurans from the endemic Australian rainforest plant Denhamia celastroides.

PubMed

Levrier, Claire; Sadowski, Martin C; Nelson, Colleen C; Healy, Peter C; Davis, Rohan A

2015-01-23

Eight new dihydro-β-agarofurans, denhaminols A-H (1-8), were isolated from the leaves of the Australian rainforest tree Denhamia celastroides. The chemical structures of 1-8 were elucidated following analysis of 1D/2D NMR and MS data. The absolute configuration of denhaminol A (1) was determined by single-crystal X-ray crystallography. All compounds were evaluated for cytotoxic activity against the human prostate cancer cell line LNCaP, using live-cell imaging and metabolic assays. Denhaminols A (1) and G (7) were also tested for their effects on the lipid content of LNCaP cells. This is the first report of secondary metabolites from D. celastroides.

Highly oxygenated stigmastane-type steroids from the aerial parts of Vernonia anthelmintica Willd.

PubMed

Hua, Lei; Qi, Wei-Yan; Hussain, Syed Hamid; Gao, Kun; Arfan, Mohammad

2012-06-01

Nine new highly oxygenated stigmastane-type steroids, vernoanthelcin A-I (1-9), and two new stigmastane-type steroidal glycosides, vernoantheloside A and B (10 and 11) were isolated from the aerial parts of Vernonia anthelmintica Willd. The structures of compounds 1-11 were determined on the basis of IR, MS, 1D-NMR, and 2D-NMR, and their absolute configurations were deduced using single-crystal X-ray diffraction and the CD exciton chirality method. Compounds 1, 5, 7, 9 and 10 were tested for their effects on estrogen biosynthesis in human ovarian granulosa-like cells (KGN cells). Crown Copyright © 2012. Published by Elsevier Inc. All rights reserved.

Device For Controlling Crystallization Of Protein

NASA Technical Reports Server (NTRS)

Noever, David A.

1993-01-01

Variable sandwich spacer enables optimization of evaporative driving force that governs crystallization of protein from solution. Mechanically more rigid than hanging-drop and sitting-drop devices. Large oscillations and dislodgment of drop of solution in response to vibrations suppressed by glass plates. Other advantages include: suitable for automated delivery, stable handling, and programmable evaporation of protein solution; controlled configuration enables simple and accurate determination of volume of solution without disrupting crystallization; pH and concentration of precipitant controlled dynamically because pH and concentration coupled to rate of evaporation, controllable via adjustment of gap between plates; and enables variation of ratio between surface area and volume of protein solution. Alternative version, plates oriented vertically instead of horizontally.

Neonatal nucleated red blood cells in infants of overweight and obese mothers.

PubMed

Sheffer-Mimouni, Galit; Mimouni, Francis B; Dollberg, Shaul; Mandel, Dror; Deutsch, Varda; Littner, Yoav

2007-06-01

The perinatal outcome of the infant of obese mother is adversely affected and in theory, may involve fetal hypoxia. We hypothesized that an index of fetal hypoxia, the neonatal nucleated red blood cell (NRBC) count, is elevated in infants of overweight and obese mothers. Absolute NRBC counts taken during the first 12 hours of life in 41 infants of overweight and obese mothers were compared to 28 controls. Maternal body mass index and infant birthweight were significantly higher in the overweight and obese group (P < 0.01). Hematocrit, corrected white blood cell and lymphocyte counts did not differ between groups. The absolute NRBC count was higher (P = 0.01), and the platelet count lower (P = 0.05) in infants of overweight and obese mothers than in controls. In stepwise regression analysis, the absolute NRBC count in infants of overweight and obese mothers remained significantly higher even after taking into account birthweight or gestational age and Apgar scores (P < 0.02). Infants of overweight and obese mothers have increased nucleated red blood cells at birth compared with controls. We speculate that even apparently healthy fetuses of overweight and obese mothers are exposed to a subtle hypoxemic environment.

Neonatal nucleated red blood cells in G6PD deficiency.

PubMed

Yeruchimovich, Mark; Shapira, Boris; Mimouni, Francis B; Dollberg, Shaul

2002-05-01

The objective of this study is to study the absolute number of nucleated red blood cells (RBC) at birth, an index of active fetal erythropoiesis, in infants with G6PD deficiency and in controls. We tested the hypothesis that hematocrit and hemoglobin would be lower, and absolute nucleated RBC counts higher, in the G6PD deficient and that these changes would be more prominent in infants exposed passively to fava bean through maternal diet. Thirty-two term infants with G6PD deficiency were compared with 30 term controls. Complete blood counts with manual differential counts were obtained within 12 hours of life. Absolute nucleated RBC and corrected leukocyte counts were computed from the Coulter results and the differential count. G6PD deficient patients did not differ from controls in terms of gestational age, birth weight, or Apgar scores or in any of the hematologic parameters studied, whether or not the mother reported fava beans consumption in the days prior to delivery. Although intrauterine hemolysis is possible in G6PD deficient fetuses exposed passively to fava beans, our study supports that such events must be very rare.

Absolute x-ray energy calibration and monitoring using a diffraction-based method

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

Hong, Xinguo, E-mail: xhong@bnl.gov; Weidner, Donald J.; Duffy, Thomas S.

2016-07-27

In this paper, we report some recent developments of the diffraction-based absolute X-ray energy calibration method. In this calibration method, high spatial resolution of the measured detector offset is essential. To this end, a remotely controlled long-translation motorized stage was employed instead of the less convenient gauge blocks. It is found that the precision of absolute X-ray energy calibration (ΔE/E) is readily achieved down to the level of 10{sup −4} for high-energy monochromatic X-rays (e.g. 80 keV). Examples of applications to pair distribution function (PDF) measurements and energy monitoring for high-energy X-rays are presented.

Three-dimensional analysis of dislocation multiplication during thermal process of grown silicon with different orientations

NASA Astrophysics Data System (ADS)

Gao, B.; Nakano, S.; Harada, H.; Miyamura, Y.; Kakimoto, K.

2017-09-01

We used an advanced 3D model to study the effect of crystal orientation on the dislocation multiplication in single-crystal silicon under accurate control of the cooling history of temperature. The incorporation of the anisotropy effect of the crystal lattice into the model has been explained in detail, and an algorithm for accurate control of the temperature in the furnace has also been presented. This solver can dynamically track the history of dislocation generation for different orientations during thermal processing of single-crystal silicon. Four orientations, [001], [110], [111], and [112], have been examined, and the comparison of dislocation distributions has been provided.

Crystal Growth Control

NASA Technical Reports Server (NTRS)

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

1997-01-01

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

Crystallographic features of poly(vinylidene fluoride) film upon an attractive substrate of KBr.

PubMed

Huang, Rui; Wang, Gang; Guo, Shuo; Wang, Ke; Fu, Qiang

2017-10-18

Among all the polymorphs of poly(vinylidene fluoride) (PVDF), the polar γ-form possesses the highest melting point and electrical breakdown strength as well as the strongest solvent and irradiation resistance, which are beneficial for the durability of PVDF products. Since the γ-form is neither kinetically favorable nor the most thermodynamically stable, it is still difficult to attain the exclusive γ-polymorph, particularly in the case of neat PVDF. In this study, the melt isothermal crystallization of PVDF films was carried out between two KBr wafers. Owing to the characteristics of KBr wafer, including no IR absorbance and high optical transmittance, the crystallographic features originating from the KBr substrate can be conveniently elucidated through the in situ inspected techniques of FTIR and PLM. The KBr wafers significantly accelerated the crystallization kinetics of α-crystals, and then readily triggered the solid-state α- to γ-transformation of the pre-formed α-spherulites, resulting in a 10 μm-thick, neat PVDF film with an absolute crystallinity of 35% and a relative γ fraction as high as 94%. When the film thickness was increased to 40 μm, the crystallization rate of the α-form was still rapid, but the solid-state transformation was not appreciable. These interesting crystallographic phenomena are attributed to the existence of ion-dipole interaction between the -CF 2 or -CH 2 of PVDF chains and the surface of KBr wafer. Unlike most traditional substrate-dominated crystallizations that prevail in a surface epitaxy manner, in which the target films are of ultra-thin thickness (of the order of 10 nm), the ion-dipole interaction promotes the effective thickness to a ten micron level, which enables its production and application at scalable level. Moreover, the triggering of α- to γ-transformation via external fields could be an alternative for achieving the γ-dominant PVDF products, particularly when the introduction of external additives is prohibited.

Progressive Transformation between Two Magnetic Ground States for One Crystal Structure of a Chiral Molecular Magnet.

PubMed

Li, Li; Nishihara, Sadafumi; Inoue, Katsuya; Kurmoo, Mohamedally

2016-03-21

We report the exceptional observation of two different magnetic ground states (MGS), spin glass (SG, T(B) = 7 K) and ferrimagnet (FI, T(C) = 18 K), for one crystal structure of [{Mn(II)(D/L-NH2ala)}3{Mn(III)(CN)6}]·3H2O obtained from [Mn(CN)6](3-) and D/L-aminoalanine, in contrast to one MGS for [{Mn(II)(L-NH2ala)}3{Cr(III)(CN)6}]·3H2O. They consist of three Mn(NH2ala) helical chains bridged by M(III)(CN)6 to give the framework with disordered water molecules in channels and between the M(III)(CN)6. Both MGS are characterized by a negative Weiss constant, bifurcation in ZFC-FC magnetizations, blocking of the moments, both components of the ac susceptibilities, and hysteresis. They differ in the critical temperatures, absolute magnetization for 5 Oe FC (lack of spontaneous magnetization for the SG), and the shapes of the hysteresis and coercive fields. While isotropic pressure increases both T(crit) and the magnetizations linearly and reversibly in each case, dehydration progressively transforms the FI into the SG as followed by concerted in situ magnetic measurements and single-crystal diffraction. The relative strengths of the two moderate Mn(III)-CN-Mn(II) antiferromagnetic (J1 and J2), the weak Mn(II)-OCO-Mn(II) (J3), and Dzyaloshinkii-Moriya antisymmetric (DM) interactions generate the two sets of characters. Examination of the bond lengths and angles for several crystals and their corresponding magnetic properties reveals a correlation between the distortion of Mn(III)(CN)6 and the MGS. SG is favored by higher magnetic anisotropy by less distorted Mn(III)(CN)6 in good accordance with the Mn-Cr system. This conclusion is also born out of the magnetization measurements on orientated single crystals with fields parallel and perpendicular to the unique c axis of the hexagonal space group.

Laser damage resistant nematic liquid crystal cell

NASA Astrophysics Data System (ADS)

Raszewski, Z.; Piecek, W.; Jaroszewicz, L.; Soms, L.; Marczak, J.; Nowinowski-Kruszelnicki, E.; Perkowski, P.; Kedzierski, J.; Miszczyk, E.; Olifierczuk, M.; Morawiak, P.; Mazur, R.

2013-08-01

There exists a problem in diagnostics of a dense plasma (so-called Thomson diagnostics). For this purpose, the plasma is illuminated by series of high energy laser pulses. Such pulses are generated by several independent lasers operating sequentially, and these pulses are to be directed along an exactly the same optical path. In this case, the energy of each separate pulse is as large as 3 J, so it is impossible to generate a burst of such pulses by a single laser. In this situation, several independent lasers have to be used. To form optical path with λ = 1.064 μm and absolute value of the energy of laser pulse through of 3 J, a special refractive index matched twisted Nematic Liquid Crystal Cell (NLCC) of type LCNP2 with switching on time τON smaller than 5 μs might be applied. High laser damage resistance of NLCC and short τON can be fulfilled by preparation of liquid crystal cells with Liquid Crystal Mixture (LCM), well tuned to twisted nematic electro-optical effect, and well tuned all optical interfaces (Air - Antireflection - Quartz Plate - Electrode - Blocking Film - Aligning Layer - LCM - Aligning Layer - Blocking Film - Electrode - Quartz Plate - Antireflection - Air). In such LCNP2 cell, the transmission is higher than 97% at λ = 1.064 μm, as it is presented by Gooch and Tarry [J. Phys. D: Appl. Phys. 8, 1575 (1975)]. The safe laser density energy is about 0.6 J/cm2 for a train of laser pulses (λ = 1.064 μm, pulse duration 10 ns FWHM, pulse repetition rate 100 pps, train duration 10 s), so the area of liquid crystal cell tolerating 3 J through it shall be as large as 5 cm2. Due to the presence of two blocking film layers between electrodes, LCNP2 can be driven by high voltages. Switching on time smaller than τON = 5 μs was obtained under 200 V switching voltage.

Apparatus for growing HgI.sub.2 crystals

DOEpatents

Schieber, Michael M.; Beinglass, Israel; Dishon, Giora

1978-01-01

A method and horizontal furnace for vapor phase growth of HgI.sub.2 crystals which utilizes controlled axial and radial airflow to maintain the desired temperature gradients. The ampoule containing the source material is rotated while axial and radial air tubes are moved in opposite directions during crystal growth to maintain a desired distance and associated temperature gradient with respect to the growing crystal, whereby the crystal interface can advance in all directions, i.e., radial and axial according to the crystallographic structure of the crystal. Crystals grown by this method are particularly applicable for use as room-temperature nuclear radiation detectors.

A microcrystal selection technique in protein crystallization

NASA Astrophysics Data System (ADS)

Han, Qing; Lin, Sheng-Xiang

1996-10-01

The goal of protein crystallization is to obtain high quality single crystals for X-ray diffraction analysis. A new and easy technique was employed to control the number and quality of crystals by eliminating poor microcrystals after the spontaneous nucleation. The process was carried out with two samples: human 17β-hydroxysteroid dehydrogenase (17β-HSD) and hen egg white lysozyme. The present study suggests a useful method for the successful crystal growth of biomacromolecules.

Initiating Growth Of Crystals Away From Container Walls

NASA Technical Reports Server (NTRS)

Kroes, Roger L.; Reiss, Donald A.; Lehoczky, Sandor L.

1991-01-01

Nucleation controlled to obtain better crystals. In technique proposed specifically for growing large protein crystals in microgravity (where no thermal convection), small region of high supersaturation created by injection of hot concentrated solution or by use of cold probe. Crystals nucleate preferably in this small region. Also conceivable technique applied on Earth to crystallizations in melts and solutions sufficiently viscous to suppress convection to extent necessary to prevent cooling-induced nucleation in undesired sites.

Mineral resource of the month: cultured quartz crystal

USGS Publications Warehouse

,

2008-01-01

The article presents information on cultured quartz crystals, a mineral used in mobile phones, computers, clocks and other devices controlled by digital circuits. Cultured quartz, which is synthetically produced in large pressurized vessels known as autoclaves, is useful in electronic circuits for precise filtration, frequency control and timing for consumer and military use. Several ingredients are used in producing cultured quartz, including seed crystals, lascas, a solution of sodium hydroxide or sodium carbonate, lithium salts and deionized water.

The Bombardment History of 4 Vesta as Told by Sample Geochronology

NASA Technical Reports Server (NTRS)

Cohen, B. A.

2014-01-01

The Dawn mission showed asteroid 4 Vesta to be an extensively cratered body, ancient in age, with craters in a variety of morphologies and preservation states [1-3]. Tying Vesta's relative crater ages to an absolute impact history can be accomplished through investigations of the HED (howardite, eucrite, diogenite) meteorites. Eucrites are crustal basalts and gabbros, diogenites are mostly orthopyroxenites representing lower crust or upper mantle materials, and howardites are mixed breccias containing both lithologies. Eucrite 53Mn-53Cr systematics show that the HED parent body globally differentiated by 4.56 Ga and fully crystallized soon afterwards [4]. Much later, many eucrites were brecciated and heated by large impacts into the parent body surface. Disturbance ages in eucrites show that multiple large impacts occurred within 1 Gyr after crystallization, showing a history that largely resembles that of the Moon [5-7]. Dawn images also showed that Vesta is covered with a well-developed regolith that is spectrally similar to howardite meteorites [8]. Howardites are polymict regolith breccias made up mostly of clasts of eucrites and diogenites, but which also contain clasts formed by melting of the regolith by relatively large, energetic impact events. Impact-melt clast ages from howardites extend our knowledge of the impact history of Vesta, expanding on eucrite disturbance ages and helping give absolute age context to the observed crater-counts produced using Dawn data. The distribution of 40Ar-39Ar ages of impact-melt clasts in howardites shows that they formed within the time period 3.3-3.8 Ga [9]. These, and other impact-melted HED materials, have distinct age and compositional characteristics that suggest they formed in discrete impact events. In order to create these crystalline impact-melt products on the surface of Vesta, the impacts during this time period must have had velocities much higher than 5 km/s, the main belt average [10]. This is inconsistent with formation by a normal distribution of impact velocities and points instead to a unique period where high-velocity collisions were more frequent than currently observed. Until now, impact-reset ages in the HED meteorites have been be interpreted under the umbrella of the canonical lunar cataclysm where an increase in the absolute number of bombarding objects is responsible for creating larger absolute amounts of impact-affected and impact-melted rocks, statistically increasing their chances of being found on Earth and dated. However, the distribution of age among the howardite impact-melt clasts may not necessarily result from an increased number of impacts, but rather result from impacts of higher velocity. The changeover from a typical main belt velocity profile to this regime of increased velocity population at Vesta occurs contemporaneously with a similar transition at the Moon, indicating that howardite impact-melt clast ages reinforce the notion of a dynamically unusual episode of bombardment in the inner solar system beginning at around 4.0 Ga.

Shaping plasmon beams via the controlled illumination of finite-size plasmonic crystals

PubMed Central

Bouillard, J.-S.; Segovia, P.; Dickson, W.; Wurtz, G. A.; Zayats, A. V.

2014-01-01

Plasmonic crystals provide many passive and active optical functionalities, including enhanced sensing, optical nonlinearities, light extraction from LEDs and coupling to and from subwavelength waveguides. Here we study, both experimentally and numerically, the coherent control of SPP beam excitation in finite size plasmonic crystals under focussed illumination. The correct combination of the illuminating spot size, its position relative to the plasmonic crystal, wavelength and polarisation enables the efficient shaping and directionality of SPP beam launching. We show that under strongly focussed illumination, the illuminated part of the crystal acts as an antenna, launching surface plasmon waves which are subsequently filtered by the surrounding periodic lattice. Changing the illumination conditions provides rich opportunities to engineer the SPP emission pattern. This offers an alternative technique to actively modulate and control plasmonic signals, either via micro- and nano-electromechanical switches or with electro- and all-optical beam steering which have direct implications for the development of new integrated nanophotonic devices, such as plasmonic couplers and switches and on-chip signal demultiplexing. This approach can be generalised to all kinds of surface waves, either for the coupling and discrimination of light in planar dielectric waveguides or the generation and control of non-diffractive SPP beams. PMID:25429786

Meniscus Imaging for Crystal-Growth Control

NASA Technical Reports Server (NTRS)

Sachs, E. M.

1983-01-01

Silicon crystal growth monitored by new video system reduces operator stress and improves conditions for observation and control of growing process. System optics produce greater magnification vertically than horizontally, so entire meniscus and melt is viewed with high resolution in both width and height dimensions.

Adsorption calorimetry during metal vapor deposition on single crystal surfaces: Increased flux, reduced optical radiation, and real-time flux and reflectivity measurements

NASA Astrophysics Data System (ADS)

Sellers, Jason R. V.; James, Trevor E.; Hemmingson, Stephanie L.; Farmer, Jason A.; Campbell, Charles T.

2013-12-01

Thin films of metals and other materials are often grown by physical vapor deposition. To understand such processes, it is desirable to measure the adsorption energy of the deposited species as the film grows, especially when grown on single crystal substrates where the structure of the adsorbed species, evolving interface, and thin film are more homogeneous and well-defined in structure. Our group previously described in this journal an adsorption calorimeter capable of such measurements on single-crystal surfaces under the clean conditions of ultrahigh vacuum [J. T. Stuckless, N. A. Frei, and C. T. Campbell, Rev. Sci. Instrum. 69, 2427 (1998)]. Here we describe several improvements to that original design that allow for heat measurements with ˜18-fold smaller standard deviation, greater absolute accuracy in energy calibration, and, most importantly, measurements of the adsorption of lower vapor-pressure materials which would have previously been impossible. These improvements are accomplished by: (1) using an electron beam evaporator instead of a Knudsen cell to generate the metal vapor at the source of the pulsed atomic beam, (2) changing the atomic beam design to decrease the relative amount of optical radiation that accompanies evaporation, (3) adding an off-axis quartz crystal microbalance for real-time measurement of the flux of the atomic beam during calorimetry experiments, and (4) adding capabilities for in situ relative diffuse optical reflectivity determinations (necessary for heat signal calibration). These improvements are not limited to adsorption calorimetry during metal deposition, but also could be applied to better study film growth of other elements and even molecular adsorbates.

Adsorption calorimetry during metal vapor deposition on single crystal surfaces: increased flux, reduced optical radiation, and real-time flux and reflectivity measurements.

PubMed

Sellers, Jason R V; James, Trevor E; Hemmingson, Stephanie L; Farmer, Jason A; Campbell, Charles T

2013-12-01

Thin films of metals and other materials are often grown by physical vapor deposition. To understand such processes, it is desirable to measure the adsorption energy of the deposited species as the film grows, especially when grown on single crystal substrates where the structure of the adsorbed species, evolving interface, and thin film are more homogeneous and well-defined in structure. Our group previously described in this journal an adsorption calorimeter capable of such measurements on single-crystal surfaces under the clean conditions of ultrahigh vacuum [J. T. Stuckless, N. A. Frei, and C. T. Campbell, Rev. Sci. Instrum. 69, 2427 (1998)]. Here we describe several improvements to that original design that allow for heat measurements with ~18-fold smaller standard deviation, greater absolute accuracy in energy calibration, and, most importantly, measurements of the adsorption of lower vapor-pressure materials which would have previously been impossible. These improvements are accomplished by: (1) using an electron beam evaporator instead of a Knudsen cell to generate the metal vapor at the source of the pulsed atomic beam, (2) changing the atomic beam design to decrease the relative amount of optical radiation that accompanies evaporation, (3) adding an off-axis quartz crystal microbalance for real-time measurement of the flux of the atomic beam during calorimetry experiments, and (4) adding capabilities for in situ relative diffuse optical reflectivity determinations (necessary for heat signal calibration). These improvements are not limited to adsorption calorimetry during metal deposition, but also could be applied to better study film growth of other elements and even molecular adsorbates.

Determination of the Avogadro constant by the XRCD method using a 28Si-enriched sphere

NASA Astrophysics Data System (ADS)

Kuramoto, Naoki; Mizushima, Shigeki; Zhang, Lulu; Fujita, Kazuaki; Azuma, Yasushi; Kurokawa, Akira; Okubo, Sho; Inaba, Hajime; Fujii, Kenichi

2017-10-01

To determine the Avogadro constant N A by the x-ray crystal density method, the density of a 28Si-enriched crystal was determined by absolute measurements of the mass and volume of a 1 kg sphere manufactured from the crystal. The mass and volume were determined by an optical interferometer and a vacuum mass comparator, respectively. The sphere surface was characterized by x-ray photoelectron spectroscopy and spectroscopic ellipsometry to derive the mass and volume of the Si core of the sphere excluding the surface layers. From the mass and volume, the density of the Si core was determined with a relative standard uncertainty of 2.3  ×  10-8. By combining the Si core density with the lattice constant and the molar mass of the sphere reported by the International Avogadro Coordination (IAC) project in 2015, a new value of 6.022 140 84(15)  ×  1023 mol-1 was obtained for N A with a relative standard uncertainty of 2.4  ×  10-8. To make the N A value determined in this work usable for a future adjustment of the fundamental constants by the CODATA Task Group on Fundamental Constants, the correlation of the new N A value with the N A values determined in our previous works was examined. The correlation coefficients with the values of N A determined by IAC in 2011 and 2015 were estimated to be 0.07 and 0.28, respectively. The correlation of the new N A value with the N A value determined by IAC in 2017 using a different 28Si-enriched crystal was also examined, and the correlation coefficient was estimated to be 0.21.

Patterned solid state growth of barium titanate crystals

NASA Astrophysics Data System (ADS)

Ugorek, Michael Stephen

An understanding of microstructure evolution in ceramic materials, including single crystal development and abnormal/enhanced grain growth should enable more controlled final ceramic element structures. In this study, two different approaches were used to control single crystal development in a patterned array. These two methods are: (1) patterned solid state growth in BaTiO 3 ceramics, and (2) metal-mediated single crystal growth in BaTiO 3. With the patterned solid state growth technique, optical photolithography was used to pattern dopants as well as [001] and [110] BaTiO3 single crystal template arrays with a 1000 microm line pattern array with 1000 microm spacings. These patterns were subsequently used to control the matrix grain growth evolution and single crystal development in BaTiO3. It was shown that the growth kinetics can be controlled by a small initial grain size, atmosphere conditions, and the introduction of a dopant at selective areas/interfaces. By using a PO2 of 1x10-5 atm during high temperature heat treatment, the matrix coarsening has been limited (to roughly 2 times the initial grain size), while retaining single crystal boundary motion up to 0.5 mm during growth for dwell times up to 9 h at 1300°C. The longitudinal and lateral growth rates were optimized at 10--15 microm/h at 1300°C in a PO2 of 1x10 -5 atm for single crystal growth with limited matrix coarsening. Using these conditions, a patterned microstructure in BaTiO3 was obtained. With the metal-mediated single crystal growth technique, a novel approach for fabricating 2-2 single crystal/polymer composites with a kerf < 5 microns was demonstrated. Surface templated grain growth was used to propagate a single crystal interface into a polycrystalline BaTiO3 or Ba(Zr0.05 Ti0.95)O3 matrix with lamellar nickel layers. The grain growth evolution and texture development were studied using both [001] and [110] BaTiO3 single crystals templates. By using a PO 2 of 1x10-11 atm during high temperature heat treatment, matrix coarsening was limited while enabling single crystal boundary motion up to 0.35 mm during growth between 1250°C and 1300°C with growth rates ˜ 3--4 microm/h for both single crystal orientations. By removing the inner electrodes, 2-2 single crystal (or ceramic) composites were prepared. The piezoelectric and dielectric properties of the composites of the two compositions were measured. The d33 and d31 of the composites were similar to the polycrystalline ceramic of the same composition.

Femtosecond Pulse Characterization as Applied to One-Dimensional Photonic Band Edge Structures

NASA Technical Reports Server (NTRS)

Fork, Richard L.; Gamble, Lisa J.; Diffey, William M.

1999-01-01

The ability to control the group velocity and phase of an optical pulse is important to many current active areas of research. Electronically addressable one-dimensional photonic crystals are an attractive candidate to achieve this control. This report details work done toward the characterization of photonic crystals and improvement of the characterization technique. As part of the work, the spectral dependence of the group delay imparted by a GaAs/AlAs photonic crystal was characterized. Also, a first generation an electrically addressable photonic crystal was tested for the ability to electronically control the group delay. The measurement technique, using 100 femtosecond continuum pulses was improved to yield high spectral resolution (1.7 nanometers) and concurrently with high temporal resolution (tens of femtoseconds). Conclusions and recommendations based upon the work done are also presented.

Transparent multi-zone crystal growth furnace and method for controlling the same

NASA Technical Reports Server (NTRS)

Batur, Celal (Inventor); Bennett, Robert J. (Inventor); Duval, Walter (Inventor)

2000-01-01

A crystal growth system, comprising: a furnace; a plurality of heating elements coupled to said furnace, each said plurality of heating elements defining a heat zone, each said heating element set to a desired temperature value; a plurality of thermocouples associated with respective heat zones to detect a temperature value; a translation system for passing an ampoule containing crystal growth material through said furnace into said heat zones and providing a positional location of said ampoule and; a multi-variable self-tuning temperature controller connected to said plurality of heating elements, said plurality of thermocouples and said translation system, said controller monitoring each said zone temperature value and upon considering the thermal interaction of heating zones and the moving thermal inertia of the ampoule, adjusting voltage input to said heat zones to obtain optimal crystal growth within said ampoule.

Transparent multi-zone crystal growth furnace and method for controlling the same

NASA Technical Reports Server (NTRS)

Batur, Celal (Inventor); Duval, Walter (Inventor); Bennett, Robert J. (Inventor)

2001-01-01

A crystal growth system, comprising: a furnace; a plurality of heating elements coupled to said furnace, each said plurality of heating elements defining a heat zone, each said heating element set to a desired temperature value; a plurality of thermocouples associated with respective heat zones to detect a temperature value; a translation system for passing an ampoule containing crystal growth material through said furnace into said heat zones and providing a positional location of said ampoule and; a multi-variable self-tuning temperature controller connected to said plurality of heating elements, said plurality of thermocouples and said translation system, said controller monitoring each said zone temperature value and upon considering the thermal interaction of heating zones and the moving thermal inertia of the ampoule, adjusting voltage input to said heat zones to obtain optimal crystal growth within said ampoule.

A chemical bath deposition route to facet-controlled Ag{sub 3}PO{sub 4} thin films with improved visible light photocatalytic activity

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

Gunjakar, Jayavant L.; Jo, Yun Kyung; Kim, In Young

A facile, economic, and reproducible chemical bath deposition (CBD) method is developed for the fabrication of facet-controlled Ag{sub 3}PO{sub 4} thin films with enhanced visible light photocatalytic activity. The fine-control of bath temperature, precursor, complexing agent, substrate, and solution pH is fairly crucial in preparing the facet-selective thin film of Ag{sub 3}PO{sub 4} nanocrystal. The change of precursor from silver nitrate to silver acetate makes possible the tailoring of the crystal shape of Ag{sub 3}PO{sub 4} from cube to rhombic dodecahedron and also the bandgap tuning of the deposited films. The control of [Ag{sup +}]/[phosphate] ratio enables to maximize themore » loading amount of Ag{sub 3}PO{sub 4} crystals per the unit area of the deposited film. All the fabricated Ag{sub 3}PO{sub 4} thin films show high photocatalytic activity for visible light-induced degradation of organic molecules, which can be optimized by tailoring the crystal shape of the deposited crystals. This CBD method is also useful in preparing the facet-controlled hybrid film of Ag{sub 3}PO{sub 4}–ZnO photocatalyst. The present study clearly demonstrates the usefulness of the present CBD method for fabricating facet-controlled thin films of metal oxosalt and its nanohybrid. - Highlights: • The crystal facet of Ag{sub 3}PO{sub 4} films can be tuned by chemical bath deposition. • The crystal shape of Ag{sub 3}PO{sub 4} is tailorable from cube to rhombic dodecahedron. • Facet-tuned Ag{sub 3}PO{sub 4} film shows enhanced visible light photocatalyst activity.« less

Liquid phase electroepitaxial bulk growth of binary and ternary alloy semiconductors under external magnetic field

NASA Astrophysics Data System (ADS)

Sheibani, Hamdi

2002-01-01

Liquid Phase Electroepitaxy (LPEE) and is a relatively new, promising technique for producing high quality, thick compound semiconductors and their alloys. The main objectives are to reduce the adverse effect of natural convection and to determine the optimum growth conditions for reproducible desired crystals for the optoelectronic and electronic device industry. Among the available techniques for suppressing the adverse effect of natural convection, the application of an external magnetic field seems the most feasible one. The research work in this dissertation consists of two parts. The first part is focused on the design and development of a state of the art LPEE facility with a novel crucible design, that can produce bulk crystals of quality higher than those achieved by the existing LPEE system. A growth procedure was developed to take advantage of this novel crucible design. The research of the growth of InGaAs single crystals presented in this thesis will be a basis for the future LPEE growth of other important material and is an ideal vehicle for the development of a ternary crystal growth process. The second part of the research program is the experimental study of the LPEE growth process of high quality bulk single crystals of binary/ternary semiconductors under applied magnetic field. The compositional uniformity of grown crystals was measured by Electron Probe Micro-analysis (EPMA) and X-ray microanalysis. The state-of-the-art LPEE system developed at University of Victoria, because of its novel design features, has achieved a growth rate of about 4.5 mm/day (with the application of an external fixed magnetic field of 4.5 KGauss and 3 A/cm2 electric current density), and a growth rate of about 11 mm/day (with 4.5 KGauss magnetic field and 7 A/cm2 electric current density). This achievement is simply a breakthrough in LPEE, making this growth technique absolutely a bulk growth technique and putting it in competition with other bulk growth techniques. The growth rates achieved can even be higher for higher electric current and magnetic field intensities. (Abstract shortened by UMI.)

Comparison of lateral abdominal muscle thickness between weightlifters and matched controls.

PubMed

Sitilertpisan, Patraporn; Pirunsan, Ubon; Puangmali, Aatit; Ratanapinunchai, Jonjin; Kiatwattanacharoen, Suchart; Neamin, Hudsaleark; Laskin, James J

2011-11-01

To compare lateral abdominal muscle thickness between weightlifters and matched controls. A case control study design. University laboratory. 16 female Thai national weightlifters and 16 matched controls participated in this study. Ultrasound imaging with a 12-MHz linear array was used to measure the resting thickness of transversus abdominis (TrA), internal oblique (IO) and total thickness (Total) of lateral abdominal muscle (LAM) on the right side of abdominal wall. The absolute muscle thickness and the relative contribution of each muscle to the total thickness were determined. Weightlifters had significantly thicker absolute TrA and IO muscles than matched controls (p < 0.01). Further, the relative thickness of the IO was significantly greater in weightlifters than matched controls (p < 0.05). The findings of this study suggest that routine Olympic style weight training among female weightlifters appears to result in preferential hypertrophy or adaptation of the IO muscle. Copyright © 2011 Elsevier Ltd. All rights reserved.

Commonalities in EEG Spectral Power Abnormalities Between Women With ADHD and Women With Bipolar Disorder During Rest and Cognitive Performance.

PubMed

Rommel, Anna-Sophie; Kitsune, Glenn L; Michelini, Giorgia; Hosang, Georgina M; Asherson, Philip; McLoughlin, Gráinne; Brandeis, Daniel; Kuntsi, Jonna

2016-11-01

While attention-deficit/hyperactivity disorder (ADHD) and bipolar disorder (BD) denote distinct psychiatric conditions, diagnostic delineation is impeded by considerable symptomatic overlap. Direct comparisons across ADHD and BD on neurophysiological measures are limited. They could inform us on impairments that are specific to or shared between the disorders and, therefore, potential biomarkers that may aid in the identification of the diagnostic boundaries. Our aim was to test whether quantitative EEG (QEEG) identifies differences or similarities between women with ADHD and women with BD during resting-state and task conditions. QEEG activity was directly compared between 20 ADHD, 20 BD and 20 control women during an eyes-open resting-state condition (EO) and a cued continuous performance task (CPT-OX). Both ADHD (t 38  = 2.50, p = 0.017) and BD (t 38  = 2.54, p = 0.018) participants showed higher absolute theta power during EO than controls. No significant differences emerged between the two clinical groups. While control participants showed a task-related increase in absolute theta power from EO to CPT-OX (t 19  = -3.77, p = 0.001), no such change in absolute theta power was observed in the ADHD (t 19  = -0.605, p = 0.553) or BD (t 19  = 1.82, p = 0.084) groups. Our results provide evidence for commonalities in brain dysfunction between ADHD and BD. Absolute theta power may play a role as a marker of neurobiological processes in both disorders.

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, and is induced by nucleation sites. We suggest that further growth is controlled both by mineral bridges and nucleation sites. Finally, we discuss the role of amorphous calcium carbonate precursor in nacre formation. Copyright © 2015 Elsevier Ltd. All rights reserved.

Nanopattern-guided growth of single-crystal silicon on amorphous substrates and high-performance sub-100 nm thin-film transistors for three-dimensional integrated circuits

NASA Astrophysics Data System (ADS)

Gu, Jian

This thesis explores how nanopatterns can be used to control the growth of single-crystal silicon on amorphous substrates at low temperature, with potential applications on flat panel liquid-crystal display and 3-dimensional (3D) integrated circuits. I first present excimer laser annealing of amorphous silicon (a-Si) nanostructures on thermally oxidized silicon wafer for controlled formation of single-crystal silicon islands. Preferential nucleation at pattern center is observed due to substrate enhanced edge heating. Single-grain silicon is obtained in a 50 nm x 100 nm rectangular pattern by super lateral growth (SLG). Narrow lines (such as 20-nm-wide) can serve as artificial heterogeneous nucleation sites during crystallization of large patterns, which could lead to the formation of single-crystal silicon islands in a controlled fashion. In addition to eximer laser annealing, NanoPAtterning and nickel-induced lateral C&barbelow;rystallization (NanoPAC) of a-Si lines is presented. Single-crystal silicon is achieved by NanoPAC. The line width of a-Si affects the grain structure of crystallized silicon lines significantly. Statistics show that single-crystal silicon is formed for all lines with width between 50 nm to 200 nm. Using in situ transmission electron microscopy (TEM), nickel-induced lateral crystallization (Ni-ILC) of a-Si inside a pattern is revealed; lithography-constrained single seeding (LISS) is proposed to explain the single-crystal formation. Intragrain line and two-dimensional defects are also studied. To test the electrical properties of NanoPAC silicon films, sub-100 nm thin-film transistors (TFTs) are fabricated using Patten-controlled crystallization of Ṯhin a-Si channel layer and H&barbelow;igh temperature (850°C) annealing, coined PaTH process. PaTH TFTs show excellent device performance over traditional solid phase crystallized (SPC) TFTs in terms of threshold voltage, threshold voltage roll-off, leakage current, subthreshold swing, on/off current ratio, device-to-device uniformity etc. Two-dimensional device simulations show that PaTH TFTs are comparable to silicon-on-insulator (SOI) devices, making it a promising candidate for the fabrication of future high performance, low-power 3D integrated circuits. Finally, an ultrafast nanolithography technique, laser-assisted direct imprint (LADI) is introduced. LADI shows the ability of patterning nanostructures directly in silicon in nanoseconds with sub-10 nm resolution. The process has potential applications in multiple disciplines, and could be extended to other materials and processes.

Comparison of normalized maximum aerobic capacity and body composition of sumo wrestlers to athletes in combat and other sports.

PubMed

Beekley, Matthew D; Abe, Takashi; Kondo, Masakatsu; Midorikawa, Taishi; Yamauchi, Taro

2006-01-01

Sumo wrestling is unique in combat sport, and in all of sport. We examined the maximum aerobic capacity and body composition of sumo wrestlers and compared them to untrained controls. We also compared "aerobic muscle quality", meaning VO2max normalized to predicted skeletal muscle mass (SMM) (VO2max /SMM), between sumo wrestlers and controls and among previously published data for male athletes from combat, aerobic, and power sports. Sumo wrestlers, compared to untrained controls, had greater (p < 0.05) body mass (mean ± SD; 117.0 ± 4.9 vs. 56.1 ± 9.8 kg), percent fat (24.0 ± 1.4 vs. 13.3 ± 4.5), fat-free mass (88.9 ± 4.2 vs. 48.4 ± 6.8 kg), predicted SMM (48.2 ± 2.9 vs. 20.6 ± 4.7 kg) and absolute VO2max (3.6 ± 1.3 vs. 2.5 ± 0.7 L·min(-1)). Mean VO2max /SMM (ml·kg SMM(-1)·min(-1)) was significantly different (p < 0.05) among aerobic athletes (164.8 ± 18.3), combat athletes (which was not different from untrained controls; 131.4 ± 9.3 and 128.6 ± 13.6, respectively), power athletes (96.5 ± 5.3), and sumo wrestlers (71.4 ± 5.3). There was a strong negative correlation (r = - 0.75) between percent body fat and VO2max /SMM (p < 0.05). We conclude that sumo wrestlers have some of the largest percent body fat and fat-free mass and the lowest "aerobic muscle quality "(VO2max /SMM), both in combat sport and compared to aerobic and power sport athletes. Additionally, it appears from analysis of the relationship between SMM and absolute VO2max for all sports that there is a "ceiling "at which increases in SMM do not result in additional increases in absolute VO2max. Key PointsSumo wrestlers have a high absolute VO2max compared to untrained controls.However, sumo wrestlers have a low VO2max /kg of skeletal muscle mass compared to other combat sports, other strength/power sports, and untrained controls.The reason for this is unknown, but is probably related to alterations in sumo skeletal muscle compared to other sports.Based on the present and previous data, there appears to be a "ceiling "at which increases in skeletal muscle mass do not result in additional increases in absolute VO2max.

Single crystalline growth of a soluble organic semiconductor in a parallel aligned liquid crystal solvent using rubbing-treated polyimide films

NASA Astrophysics Data System (ADS)

Matsuzaki, Tomoya; Shibata, Yosei; Takeda, Risa; Ishinabe, Takahiro; Fujikake, Hideo

2017-01-01

For directional control of organic single crystals, we propose a crystal growth method using liquid crystal as the solvent. In this study, we examined the formation of 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) single crystals using a parallel aligned liquid crystal (LC) cell and rubbing-treated polyimide films in order to clarify the effects of LC alignment on anisotropic C8-BTBT crystal growth. Based on the results, we found that the crystal growth direction of C8-BTBT single crystals was related to the direction of the aligned LC molecules because of rubbing treatment. Moreover, by optical evaluation, we found that the C8-BTBT single crystals have a aligned molecular structure.

Protein crystal growth in low gravity

NASA Technical Reports Server (NTRS)

Feigelson, Robert S.

1991-01-01

The objective of this research is to study the effect of low gravity on the growth of protein crystals and those parameters which will affect growth and crystal quality. The application of graphoepitaxy (artificial epitaxy) to proteins is detailed. The development of a method for the control of nucleation is discussed. The factor affecting the morphology of isocitrate lyase crystals is presented.

Study of the possibility of growing germanium single crystals under low temperature gradients

NASA Astrophysics Data System (ADS)

Moskovskih, V. A.; Kasimkin, P. V.; Shlegel, V. N.; Vasiliev, Y. V.; Gridchin, V. A.; Podkopaev, O. I.; Zhdankov, V. N.

2014-03-01

The possibility of growing germanium single crystals under low temperature gradients in order to produce a dislocation-free material has been studied. Germanium crystals with a dislocation density of about 100-200 cm-2 have been grown in a system with a weight control of crystal growth at maximum axial gradients of about 1.5 K/cm.

The Stanford Automated Mounter: Enabling High-Throughput Protein Crystal Screening at SSRL

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

Smith, C.A.; Cohen, A.E.

2009-05-26

The macromolecular crystallography experiment lends itself perfectly to high-throughput technologies. The initial steps including the expression, purification, and crystallization of protein crystals, along with some of the later steps involving data processing and structure determination have all been automated to the point where some of the last remaining bottlenecks in the process have been crystal mounting, crystal screening, and data collection. At the Stanford Synchrotron Radiation Laboratory, a National User Facility that provides extremely brilliant X-ray photon beams for use in materials science, environmental science, and structural biology research, the incorporation of advanced robotics has enabled crystals to be screenedmore » in a true high-throughput fashion, thus dramatically accelerating the final steps. Up to 288 frozen crystals can be mounted by the beamline robot (the Stanford Auto-Mounting System) and screened for diffraction quality in a matter of hours without intervention. The best quality crystals can then be remounted for the collection of complete X-ray diffraction data sets. Furthermore, the entire screening and data collection experiment can be controlled from the experimenter's home laboratory by means of advanced software tools that enable network-based control of the highly automated beamlines.« less

Crystallization, flow and thermal histories of lunar and terrestrial compositions

NASA Technical Reports Server (NTRS)

Uhlmann, D. R.

1979-01-01

Contents: a kinetic treatment of glass formation; effects of nucleating heterogeneities on glass formation; glass formation under continuous cooling conditions; crystallization statistics; kinetics of crystal nucleation; diffusion controlled crystal growth; crystallization of lunar compositions; crystallization between solidus and liquidus; crystallization on reheating a glass; temperature distributions during crystallization; crystallization of anorthite and anorthite-albite compositions; effect of oxidation state on viscosity; diffusive creep and viscous flow; high temperature flow behavior of glass-forming liquids, a free volume interpretation; viscous flow behavior of lunar compositions; thermal history of orange soil material; breccias formation by viscous sintering; viscous sintering; thermal histories of breccias; solute partitioning and thermal history of lunar rocks; heat flow in impact melts; and thermal histories of olivines.

Effects of resistance or aerobic exercise training on total and regional body composition in sedentary overweight middle-aged adults.

PubMed

Donges, Cheyne E; Duffield, Rob

2012-06-01

The purpose of this study was to examine the effects of 10 weeks of aerobic endurance training (AET), resistance exercise training (RET), or a control (CON) condition on absolute and relative fat mass (FM) or fat-free mass (FFM) in the total body (TB) and regions of interest (ROIs) of sedentary overweight middle-aged males and females. Following prescreening, 102 subjects underwent anthropometric measurements, dual-energy X-ray absorptiometry, and strength and aerobic exercise testing. Randomized subjects (male RET, n = 16; female RET, n = 19; male AET, n = 16; and female AET, n = 25) completed supervised and periodized exercise programs (AET, 30-50 min cycling at 70%-75% maximal heart rate; RET, 2-4 sets × 8-10 repetitions of 5-7 exercises at 70%-75% 1 repetition maximum) or a nonexercising control condition (male CON, n = 13 and female CON, n = 13). Changes in absolute and relative TB-FM and TB-FFM and ROI-FM and ROI-FFM were determined. At baseline, and although matched for age and body mass index, males had greater strength, aerobic fitness, body mass, absolute and relative TB-FFM and ROI-FFM, but reduced absolute and relative TB-FM and ROI-FM, compared with females (p < 0.05). After training, both female exercise groups showed equivalent or greater relative improvements in strength and aerobic fitness than did the male exercise groups (p < 0.05); however, the male exercise groups increased TB-FFM and reduced TB-FM more than did the female exercise groups (p < 0.05). Male AET altered absolute FM more than male RET altered absolute FFM, thus resulting in a greater enhancement of relative FFM. Despite equivalent or greater responses to RET or AET by female subjects, the corresponding respective increases in FFM or reductions in FM were lower than those in males, indicating that a biased dose-response relationship exists between sexes following 10 weeks of exercise training.

Pin-Hole Free Perovskite Film for Solar Cells Application Prepared by Controlled Two-Step Spin-Coating Method

NASA Astrophysics Data System (ADS)

Bahtiar, A.; Rahmanita, S.; Inayatie, Y. D.

2017-05-01

Morphology of perovskite film is a key important for achieving high performance perovskite solar cells. Perovskite films are commonly prepared by two-step spin-coating method. However, pin-holes are frequently formed in perovskite films due to incomplete conversion of lead-iodide (PbI2) into perovskite CH3NH3PbI3. Pin-holes in perovskite film cause large hysteresis in current-voltage curve of solar cells due to large series resistance between perovskite layer-hole transport material. Moreover, crystal structure and grain size of perovskite crystal are also other important parameters for achieving high performance solar cells, which are significantly affected by preparation of perovskite film. We studied the effect of preparation of perovskite film using controlled spin-coating parameters on crystal structure and morphological properties of perovskite film. We used two-step spin-coating method for preparation of perovskite film with varied spinning speed, spinning time and temperature of spin-coating process to control growth of perovskite crystal aimed to produce high quality perovskite crystal with pin-hole free and large grain size. All experiment was performed in air with high humidity (larger than 80%). The best crystal structure, pin-hole free with large grain crystal size of perovskite film was obtained from film prepared at room temperature with spinning speed 1000 rpm for 20 seconds and annealed at 100°C for 300 seconds.

Effect of alkali ions (Na+, K+, Cs+) on reaction mechanism of CZTS nano-particles synthesis

NASA Astrophysics Data System (ADS)

Kumar, Suresh; Altosaar, Mare; Grossberg, Maarja; Mikli, Valdek

2018-04-01

The control of morphology, elemental composition and phase composition of Cu2ZnSnS4 (CZTS) nano-crystals depends on the control of complex formation and surface stabilization of nano-particles in solution-based synthesis in oleylamine. At temperatures ≥280 °C, the control of nano-crystal's morphology and homogenous growth is difficult because of fast poly-nuclear growth occurring at higher temperatures. In the present work the effect of oleylamine complex formation with different alkali ions (Na+, K+ and Cs+) on nano-crystals growth at synthesis temperature of 280 °C was studied. It was found that nano-powders synthesized in the presence of Na+ and K+ ions showed the formation of crystals of different sizes - small nano-particles (18 nm-30 nm), large aggregated crystals (few nm to 1 μm) and large single crystals (1 μm - 4 μm). The presence of Cs+ ions in the nano-powder synthesis in oleylamine-metal precursor-CsOH solution promoted growth of nano-crystals of homogenous size. It is proposed that the formed oleylamine-Cs complexes a) enhance the formation and stabilization of oleylamine-metal (Cu, Zn and Sn) complexes before the injection of sulphur precursor into the oleylamine-metal precursor solution and b) after addition of sulphur stabilize the fast nucleated nano-particles and promote diffusion limited growth.

Design considerations for a backlight with switchable viewing angles

NASA Astrophysics Data System (ADS)

Fujieda, Ichiro; Takagi, Yoshihiko; Rahadian, Fanny

2006-08-01

Small-sized liquid crystal displays are widely used for mobile applications such as cell phones. Electronic control of a viewing angle range is desired in order to maintain privacy for viewing in public as well as to provide wide viewing angles for solitary viewing. Conventionally, a polymer-dispersed liquid crystal (PDLC) panel is inserted between a backlight and a liquid crystal panel. The PDLC layer either transmits or scatters the light from the backlight, thus providing an electronic control of viewing angles. However, such a display system is obviously thick and expensive. Here, we propose to place an electronically-controlled, light-deflecting device between an LED and a light-guide of a backlight. For example, a liquid crystal lens is investigated for other applications and its focal length is controlled electronically. A liquid crystal phase grating either transmits or diffracts an incoming light depending on whether or not a periodic phase distribution is formed inside its liquid crystal layer. A bias applied to such a device will control the angular distribution of the light propagating inside a light-guide. Output couplers built in the light-guide extract the propagating light to outside. They can be V-shaped grooves, pyramids, or any other structures that can refract, reflect or diffract light. When any of such interactions occur, the output couplers translate the changes in the propagation angles into the angular distribution of the output light. Hence the viewing-angle characteristic can be switched. The designs of the output couplers and the LC devices are important for such a backlight system.

Calcium carbonate crystals promote calcium oxalate crystallization by heterogeneous or epitaxial nucleation: possible involvement in the control of urinary lithogenesis.

PubMed

Geider, S; Dussol, B; Nitsche, S; Veesler, S; Berthézène, P; Dupuy, P; Astier, J P; Boistelle, R; Berland, Y; Dagorn, J C; Verdier, J M

1996-07-01

A large proportion of urinary stones have calcium oxalate (CaOx) as the major mineral phase. In these stones, CaOx is generally associated with minor amounts of other calcium salts. Several reports showing the presence of calcium carbonate (CaCO3) and calcium phosphate in renal stones suggested that crystals of those salts might be present in the early steps of stone formation. Such crystals might therefore promote CaOx crystallization from supersaturated urine by providing an appropriate substrate for heterogeneous nucleation. That possibility was investigated by seeding a metastable solution of 45Ca oxalate with vaterite or calcite crystallites. Accretion of CaOx was monitored by 45Ca incorporation. We showed that (1) seeds of vaterite (the hexagonal polymorph of CaCO3) and calcite (the rhomboedric form) could initiate calcium oxalate crystal growth; (2) in the presence of lithostathine, an inhibitor of CaCO3 crystal growth, such accretion was not observed. In addition, scanning electron microscopy demonstrated that growth occurred by epitaxy onto calcite seeds whereas no special orientation was observed onto vaterite. It was concluded that calcium carbonate crystals promote crystallization of calcium oxalate and that inhibitors controlling calcium carbonate crystal formation in Henle's loop might play an important role in the prevention of calcium oxalate stone formation.

Risk communication methods in hip fracture prevention: a randomised trial in primary care.

PubMed

Hudson, Ben; Toop, Les; Mangin, Dee; Pearson, John

2011-08-01

Treatment acceptance by patients is influenced by the way treatment effects are presented. Presentation of benefits using relative risk increases treatment acceptance compared to the use of absolute risk. It is not known whether this effect is modified by prior presentation of a patient's individualised risk estimate or how presentation of treatment harms by relative or absolute risk affects acceptance. To compare acceptance of a hypothetical treatment to prevent hip fracture after presentation of the treatment's benefit in relative or absolute terms in the context of a personal fracture risk estimate, and to reassess acceptance following subsequent presentation of harm in relative or absolute terms. Randomised controlled trial of patients recruited from 10 GPs' lists in Christchurch, New Zealand. Women aged ≥ 50 years were invited to participate. Participants were given a personal 10-year hip fracture risk estimate and randomised to receive information on a hypothetical treatment's benefit and harm in relative or absolute terms. Of the 1140 women invited to participate 393 (34%) took part. Treatment acceptance was greater following presentation of benefit using absolute terms than relative terms after adjustment forage, education, previous osteoporosis diagnosis, and self-reported risk (OR 1.73, 95% confidence interval [CI] = 1.10 to 2.73, P = 0.018). Presentation of the treatment's harmful effect in relative terms led to a greater proportion of participants declining treatment than did presentation in absolute terms (OR 4.89, 95% CI = 2.3 to 11.0, P<0.001). Presentation of treatment benefit and harm using absolute risk estimates led to greater treatment acceptance than presentation of the same information in relative terms.

Programmable and electrically controllable light scattering from surface-polymer stabilized liquid crystals.

PubMed

Bédard-Arcand, Jean-Philippe; Galstian, Tigran

2012-08-01

We report the creation and study of a polarization independent light scattering material system based on surface-polymer stabilized liquid crystals. Originally isotropic cell substrates with thin nonpolymerized reactive mesogen layers are used for the alignment of pure nonreactive nematic liquid crystals. The partial interdiffusion of the two materials followed by the application of orienting external electric and magnetic fields and the photo polymerization of the reactive mesogen allow us the control of electro-optic scattering properties of obtained cells.

Control of the formation of vortex Bessel beams in uniaxial crystals by varying the beam divergence

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

Paranin, V D; Karpeev, S V; Khonina, S N

The transformation of zero-order Bessel beams into a second-order vortex Bessel beam in CaCO3 and LiNbO3 crystals is experimentally studied, and a possibility of controlling the beam transformation by changing the wavefront curvature of the illumi-nating beam is shown. A quasi-periodic nature of the Bessel beam transformation in a crystal while illuminating the diffraction axi-con by a convergent beam is observed (laser beams)

Definition study for temperature control in advanced protein crystal growth

NASA Technical Reports Server (NTRS)

Nyce, Thomas A.; Rosenberger, Franz; Sowers, Jennifer W.; Monaco, Lisa A.

1990-01-01

Some of the technical requirements for an expedient application of temperature control to advanced protein crystal growth activities are defined. Lysozome was used to study the effects of temperature ramping and temperature gradients for nucleation/dissolution and consecutive growth of sizable crystals and, to determine a prototype temperature program. The solubility study was conducted using equine serum albumin (ESA) which is an extremely stable, clinically important protein due to its capability to bind and transport many different small ions and molecules.

Time-Lapse, in Situ Imaging of Ice Crystal Growth Using Confocal Microscopy

PubMed Central

2016-01-01

Ice crystals nucleate and grow when a water solution is cooled below its freezing point. The growth velocities and morphologies of the ice crystals depend on many parameters, such as the temperature of ice growth, the melting temperature, and the interactions of solutes with the growing crystals. Three types of morphologies may appear: dendritic, cellular (or fingerlike), or the faceted equilibrium form. Understanding and controlling which type of morphology is formed is essential in several domains, from biology to geophysics and materials science. Obtaining, in situ, three dimensional observations without introducing artifacts due to the experimental technique is nevertheless challenging. Here we show how we can use laser scanning confocal microscopy to follow in real-time the growth of smoothed and faceted ice crystals in zirconium acetate solutions. Both qualitative and quantitative observations can be made. In particular, we can precisely measure the lateral growth velocity of the crystals, a measure otherwise difficult to obtain. Such observations should help us understand the influence of the parameters that control the growth of ice crystals in various systems. PMID:27917410