Radiation-Induced Conformation Changes of the Pyrimidine Ring in a Single Crystal of Dihydrothymine

1970 ◽  
Vol 25 (8-9) ◽  
pp. 1299-1302 ◽  
Author(s):  
J. N. Herak
Keyword(s):  
Single Crystal ◽  
Room Temperature ◽  
Pyrimidine Ring ◽  
Orientation Dependence ◽  
Ordered Structure ◽  
Radical Species ◽  
Conformation Changes ◽  
Radiation Induced ◽  
Hyperfine Couplings

Abstract Radiation-induced radicals in a single crystal of dihydrothymine were studied with EPR. It was found that the 5-thymyl radical is the dominant radical species at room temperature. The orientation dependence of the hyperfine couplings can only by explained if one assumes that C(5), C(6) and C(7) lie in the plane defined by the rest of the nonhydrogen atoms of the ring. The highly dis-ordered structure of the ring in the undamaged crystal is ordered if a proton bound to C(5) is removed.

scholarly journals Crystallographic Orientation Dependence of Mechanical Responses of FeCrAl Micropillars

Crystals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 943
Author(s):  
Dongyue Xie ◽  
Binqiang Wei ◽  
Wenqian Wu ◽  
Jian Wang
Keyword(s):  
Grain Boundary ◽  
Slip System ◽  
Single Crystal ◽  
Room Temperature ◽  
Orientation Dependence ◽  
Slip Systems ◽  
Flow Strength ◽  
Mechanical Responses ◽  
Fecral Alloy ◽  
Strain Hardening Rate

Iron-chromium-aluminum (FeCrAl) alloys are used in automobile exhaust gas purifying systems and nuclear reactors due to its superior high-temperature oxidation and excellent corrosion resistance. Single-phase FeCrAl alloys with a body centered cubic structure plastically deform through dislocation slips at room temperature. Here, we investigated the orientation dependence of mechanical responses of FeCrAl alloy through testing single-crystal and bi-crystal micropillars in a scanning electron microscopy at room temperature. Single-crystal micropillars were fabricated with specific orientations which favor the activity of single slip system or two slip systems or multiple slip systems. The strain hardening rate and flow strength increase with increasing the number of activated slip system in micropillars. Bi-crystal micropillars with respect to the continuity of slip systems across grain boundary were fabricated to study the effect of grain boundary on slip transmission. The high geometrical compatibility factor corresponds to a high flow strength and strain hardening rate. Experimental results provide insight into understanding mechanical response of FeCrAl alloy and developing the mechanisms-based constitutive laws for FeCrAl polycrystalline aggregates.

ESR of Paramagnetic Species Produced by Gamma Irradiation in Cadmium Oxalate Three Hydrate Single Crystal

1976 ◽  
Vol 31 (1) ◽  
pp. 80-83 ◽  
Author(s):  
F. Köksal ◽  
H. Yiiksel
Keyword(s):  
Gamma Irradiation ◽  
Single Crystal ◽  
Unpaired Electron ◽  
Room Temperature ◽  
Paramagnetic Species ◽  
Temperature Analysis ◽  
Hydrogen Atoms ◽  
Radical Species ◽  
Average Value ◽  
Spin Resonance

Paramagnetic species produced in a single crystal of cadmium oxalate three hydrate (CdC2O4 · 3H2O) by gamma irradiation have been investigated with the method of electron spin resonance. Only one radical species was observed at room temperature. Analysis of the experimental results leads to the conclusion that the species has the form RCHOH in which the unpaired electron is concentrated at the carbon atom and interacts with the two hydrogen atoms. The ESR pattern was observed nearly undiminished for more than three months after the irradiation. The g factor was found to be only very slightly anisotropic with an average value of 2.0124. The hyperfine interaction tensors of the unpaired electron with the two H nuclei have been determined.

Mechanical Properties and Dislocation Structure of Single Crystal Cdte Deformed in Compression at 300°C

1976 ◽  
Vol 34 ◽  
pp. 592-593
Author(s):  
Ernest L. Hall ◽  
J. B. Vander Sande
Keyword(s):  
Mechanical Properties ◽  
Single Crystal ◽  
Dislocation Structure ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Strain Curve ◽  
Optical Devices ◽  
Semiconductor Compound ◽  
Wide Range ◽  
Sample Orientation

The present paper describes research on the mechanical properties and related dislocation structure of CdTe, a II-VI semiconductor compound with a wide range of uses in electrical and optical devices. At room temperature CdTe exhibits little plasticity and at the same time relatively low strength and hardness. The mechanical behavior of CdTe was examined at elevated temperatures with the goal of understanding plastic flow in this material and eventually improving the room temperature properties. Several samples of single crystal CdTe of identical size and crystallographic orientation were deformed in compression at 300°C to various levels of total strain. A resolved shear stress vs. compressive glide strain curve (Figure la) was derived from the results of the tests and the knowledge of the sample orientation.

Single Crystal Growth of High-Pressure Phases of Ice and Salt Hydrate Far Below the Original Melting Point by Mixing Alcohol: Crystal Structure Determination of Magnesium Chloride Heptahydrate

2020 ◽  
Author(s):  
Keishiro Yamashita ◽  
Kazuki Komatsu ◽  
Hiroyuki Kagi
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
Crystal Growth ◽  
Single Crystal ◽  
Room Temperature ◽  
Growth Technique ◽  
Salt Hydrate ◽  
X Ray

An crystal-growth technique for single crystal x-ray structure analysis of high-pressure forms of hydrogen-bonded crystals is proposed. We used alcohol mixture (methanol: ethanol = 4:1 in volumetric ratio), which is a widely used pressure transmitting medium, inhibiting the nucleation and growth of unwanted crystals. In this paper, two kinds of single crystals which have not been obtained using a conventional experimental technique were obtained using this technique: ice VI at 1.99 GPa and MgCl<sub>2</sub>·7H<sub>2</sub>O at 2.50 GPa at room temperature. Here we first report the crystal structure of MgCl2·7H2O. This technique simultaneously meets the requirement of hydrostaticity for high-pressure experiments and has feasibility for further in-situ measurements.

Kinetics of the Thermal Disappearance of Radicals Formed During the Radiolysis of Aspartic Acid

2009 ◽  
Vol 59 (12) ◽  
Author(s):  
Mihai Contineanu ◽  
iulia Contineanu ◽  
Ana Neacsu ◽  
Stefan Perisanu
Keyword(s):  
Thermal Resistance ◽  
Aspartic Acid ◽  
Room Temperature ◽  
Esr Spectra ◽  
Complex Mechanism ◽  
Radical Species ◽  
Mechanisms Of Formation ◽  
Kinetics Of

The radiolysis of the isomers L-, D- and DL- of the aspartic acid, in solid polycrystalline state, was investigated at room temperature. The analysis of their ESR spectra indicated the formation of at least two radicalic entities. The radical, identified as R3, resulting from the deamination of the acid, exhibits the highest concentration and thermal resistance. Possible mechanisms of formation of three radical species are suggested, based also on literature data. The kinetics of the disappearance of radical R3 indicated a complex mechanism. Three possible variants were suggested for this mechanism.

scholarly journals Old Donors for New Molecular Conductors: Combining TMTSF and BEDT-TTF with Anionic (TaF6)1−x/(PF6)x Alloys

Crystals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 386
Author(s):  
Magali Allain ◽  
Cécile Mézière ◽  
Pascale Auban-Senzier ◽  
Narcis Avarvari
Keyword(s):  
Single Crystal ◽  
Room Temperature ◽  
Density Wave ◽  
Spin Density Wave ◽  
Orthorhombic Phase ◽  
Molecular Conductors ◽  
Bechgaard Salts ◽  
Temperature Conductivity ◽  
Room Temperature Conductivity ◽  
Resistivity Measurements

Tetramethyl-tetraselenafulvalene (TMTSF) and bis(ethylenedithio)-tetrathiafulvalene (BEDT-TTF) are flagship precursors in the field of molecular (super)conductors. The electrocrystallization of these donors in the presence of (n-Bu4N)TaF6 or mixtures of (n-Bu4N)TaF6 and (n-Bu4N)PF6 provided Bechgaard salts formulated as (TMTSF)2(TaF6)0.84(PF6)0.16, (TMTSF)2(TaF6)0.56(PF6)0.44, (TMTSF)2(TaF6)0.44(PF6)0.56 and (TMTSF)2(TaF6)0.12(PF6)0.88, together with the monoclinic and orthorhombic phases δm-(BEDT-TTF)2(TaF6)0.94(PF6)0.06 and δo-(BEDT-TTF)2(TaF6)0.43(PF6)0.57, respectively. The use of BEDT-TTF and a mixture of (n-Bu4N)TaF6/TaF5 afforded the 1:1 phase (BEDT-TTF)2(TaF6)2·CH2Cl2. The precise Ta/P ratio in the alloys has been determined by an accurate single crystal X-ray data analysis and was corroborated with solution 19F NMR measurements. In the previously unknown crystalline phase (BEDT-TTF)2(TaF6)2·CH2Cl2 the donors organize in dimers interacting laterally yet no organic-inorganic segregation is observed. Single crystal resistivity measurements on the TMTSF based materials show typical behavior of the Bechgaard phases with room temperature conductivity σ ≈ 100 S/cm and localization below 12 K indicative of a spin density wave transition. The orthorhombic phase δo-(BEDT-TTF)2(TaF6)0.43(PF6)0.57 is semiconducting with the room temperature conductivity estimated to be σ ≈ 0.16–0.5 S/cm while the compound (BEDT-TTF)2(TaF6)2·CH2Cl2 is also a semiconductor, yet with a much lower room temperature conductivity value of 0.001 to 0.0025 S/cm, in agreement with the +1 oxidation state and strong dimerization of the donors.

Room-Temperature KIc Values for Single-Crystal and Polycrystalline MgAl2O4

1981 ◽  
Vol 64 (2) ◽  
pp. C-22-C-23 ◽  
Author(s):  
R. L. Stewart ◽  
M. Iwasa ◽  
R. C. Bradt
Keyword(s):  
Single Crystal ◽  
Room Temperature
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