Radiation Chemistry of Dithionates

1971 ◽  
Vol 49 (22) ◽  
pp. 3733-3738 ◽  
Author(s):  
G. S. Murthy ◽  
R. L. Eager ◽  
K. J. McCallum
Keyword(s):  
Thermal Annealing ◽  
Gamma Rays ◽  
Room Temperature ◽  
Absorbed Dose ◽  
Radiation Chemistry ◽  
Radical Ions ◽  
Slight Effect ◽  
Sulfate Ions ◽  
Product Yields ◽  
Sulfite Ions

The salts Na2S2O6, Na2S2O6•2H2O, K2S2O6, BaS2O6, and BaS2O6•2H2O were irradiated at room temperature with 60Co gamma rays. When the irradiated salts were dissolved in water sulfite ions, sulfate ions, and acid were found as irradiation products. The dependence of yield upon absorbed dose was studied. The G-values found ranged from unity to 20. Thermal annealing of the irradiated salts had only a slight effect on product yields. For BaS2O6 there is a large increase in product yields after a dose of 28.3 × 1022 eV per mol has been absorbed. A mechanism involving SO3− and S2O6− radical ions is proposed.

RADIATION CHEMISTRY OF ALKALI THIOSULFATES

1965 ◽  
Vol 43 (3) ◽  
pp. 614-623 ◽  
Author(s):  
R. L. Eager ◽  
D. S. Mahadevappa
Keyword(s):  
Low Temperature ◽  
Gamma Rays ◽  
Room Temperature ◽  
Absorbed Dose ◽  
Radiation Chemistry ◽  
Sulfate Ions ◽  
Sodium Salts ◽  
Colloidal Sulfur ◽  
Central Oxygen ◽  
Annealing Experiments

The salts Na2S2O3, Na2S2O3•5H2O, K2S2O3, and [Formula: see text] were irradiated at room temperature with 60Co gamma rays. When the irradiated salts were dissolved in water, sulfite and sulfate ions, H2S gas, colloidal sulfur, and a relatively small quantity of acid were found among the irradiation products. The dependence of yields on the absorbed dose was studied. G-values of approximately unity were found. Using 35S as a label, it was found that the inner sulfur (the central, oxygen-bonded sulfur atom of the complex) appears in the sulfite and sulfate whereas the outer sulfur (the sulfur linked only to the central sulfur and not to oxygen) appears in the H2S and colloidal sulfur. Annealing experiments using irradiated Na2S2O3 and K2S2O3 showed that the yields of sulfite, sulfate, and H2S were decreased by heating. The sodium salts were also irradiated at 77°K. The yields of sulfate and H2S were higher for the low temperature irradiations as compared to room temperature irradiations, whereas the yields of sulfite were lower. A tentative mechanism which partially explains the results is proposed.

Reduction of Interface Traps and Enhancement of Channel Mobility in n-Channel 6H-SiC MOSFETs by Irradiation with Gamma-Rays

2008 ◽  
Vol 600-603 ◽  
pp. 703-706 ◽  
Author(s):  
Shigeomi Hishiki ◽  
Sergey A. Reshanov ◽  
Takeshi Ohshima ◽  
Hisayoshi Itoh ◽  
Gerhard Pensl
Keyword(s):  
Gamma Rays ◽  
Room Temperature ◽  
Inversion Layer ◽  
Absorbed Dose ◽  
Interface Trap Density ◽  
Interface Trap ◽  
Similar Increase ◽  
Channel Mobility ◽  
Hall Effect Measurements ◽  
Effective Channel

N-channel MOSFETs are irradiated with gamma-rays (g-rays) up to 3.16 MGy(SiO2) at room temperature. Above 1 MGy, the effective channel mobility increases with increasing absorbed dose. A similar increase is observed for the Hall mobility in the inversion layer. In addition, the Hall-effect measurements indicate a reduction of the interface trap density.

scholarly journals Creation of pure non-crystalline diamond nanostructures via room temperature ion irradiation and subsequent thermal annealing

2021 ◽  
Author(s):  
Federico Picollo ◽  
Alfio Battiato ◽  
Federico Bosia ◽  
Fabio Scaffidi Muta ◽  
Paolo Olivero ◽  
...  
Keyword(s):  
Thermal Annealing ◽  
Room Temperature ◽  
Ion Irradiation ◽  
Group Iv ◽  
Chemical Bonds ◽  
Group Iv Elements ◽  
Silicon And Germanium ◽  
Subsequent Thermal Annealing

Carbon exhibits a remarkable range of structural forms, due to the availability of sp3, sp2 and sp1 chemical bonds. Contrarily to other group IV elements such as silicon and germanium,...

scholarly journals Radiation damage effects on protein conformation at room temperature and 100K

2014 ◽  
Vol 70 (a1) ◽  
pp. C344-C344
Author(s):  
Silvia Russi ◽  
Shawn Kann ◽  
Henry van den Bedem ◽  
Ana M. González
Keyword(s):  
Data Collection ◽  
Radiation Damage ◽  
Crystal Structures ◽  
Room Temperature ◽  
Relative Rate ◽  
Absorbed Dose ◽  
Conformational Ensemble ◽  
Data Sets ◽  
Cryogenic Temperatures ◽  
Full Data

Protein crystallography data collection at synchrotrons today is routinely carried out at cryogenic temperatures to mitigate radiation damage to the crystal. Although damage still takes place, at 100 K and below, the immobilization of free radicals increases the lifetime of the crystals by orders of magnitude. Increasingly, experiments are carried out at room temperature. The lack of adequate cryo-protectants, the induced lattice changes or internal disorders during the cooling process, and the convenience of collecting data directly from the crystallization plates, are some of the reasons. Moreover, recent studies have shown that flash-freezing affects the conformational ensemble of crystal structures [1], and can hide important functional mechanisms from observation [2]. While there has been a considerable amount of effort in studying radiation damage at cryo-temperatures, its effects at room temperature are still not well understood. We investigated the effects of data collection temperature on secondary local damage to the side chain and main chain from different proteins. Data were collected from crystals of thaumatin and lysozyme at 100 K and room temperature. To carefully control the total absorbed dose, full data sets at room temperature were assembled from a few diffraction images per crystal. Several data sets were collected at increasing levels of absorbed dose. Our analysis shows that while at cryogenic temperatures, radiation damage increases the conformational variability, _x0004_at room temperature it has the opposite effect_x0005_. We also observed that disulfide bonds appear to break up at a different relative rate at room temperature, perhaps because of a more active repair mechanism. Our analysis suggests that elevated conformational heterogeneity in crystal structures at room temperature is observed despite radiation damage, and not as a result thereof.

Das Kombinationsschwingungsspektrum von Gips im Bereich von 10 000—1200 cm-1

1968 ◽  
Vol 23 (5) ◽  
pp. 708-715 ◽  
Author(s):  
V. Hohler ◽  
H. D. Lutz
Keyword(s):  
Hydrogen Bonds ◽  
Ir Spectrum ◽  
Room Temperature ◽  
Polarized Light ◽  
Water Molecules ◽  
Lattice Vibrations ◽  
Frequency Range ◽  
Sulfate Ions ◽  
Normal Vibrations

The IR-spectrum of gypsum (CaSO4·2 H2O) in the frequency range from 10 000 to 1200 cm-1 has been investigated with polarized light at room temperature. Between 3700 and 1200 cm-1, the measurements confirm the data of HASS and SUTHERLAND and as well as those of SCHAAK derived from IR and reflection measurements. The IR-spectrum shows a great number of bands, most of which can be assigned to combination and fundamental vibrations in terms of normal vibrations of the water molecules and the sulfate ions. The influence of the lattice vibrations is briefly discussed. The existence of hydrogen bonds between the water molecules and the sulfate ions gives rise to combinations of fundamental vibrations of both complexes.

scholarly journals To scavenge or not to scavenge, that is STILL the question

2012 ◽  
Vol 20 (1) ◽  
pp. 23-36 ◽  
Author(s):  
Elizabeth G. Allan ◽  
Melissa C. Kander ◽  
Ian Carmichael ◽  
Elspeth F. Garman
Keyword(s):  
Crystal Size ◽  
Chemical Species ◽  
Absorbed Dose ◽  
Dose Dependence ◽  
Radiation Chemistry ◽  
X Ray ◽  
On Line ◽  
Crystallization Conditions ◽  
Effects Of Radiation ◽  
Dose Tolerance

An extensive radiation chemistry literature would suggest that the addition of certain radical scavengers might mitigate the effects of radiation damage during protein crystallography diffraction data collection. However, attempts to demonstrate and quantify such an amelioration and its dose dependence have not yielded consistent results, either at room temperature (RT) or 100 K. Here the information thus far available is summarized and reasons for this lack of quantitative success are identified. Firstly, several different metrics have been used to monitor and quantify the rate of damage, and, as shown here, these can give results which are in conflict regarding scavenger efficacy. In addition, significant variation in results from data collected from crystals treated in nominally the same way has been observed. Secondly, typical crystallization conditions contain substantial concentrations of chemical species which already interact strongly with some of the X-ray-induced radicals that the added scavengers are intended to intercept. These interactions are probed here by the complementary technique of on-line microspectrophotometry carried out on solutions and crystals held both at 100 K and RT, the latter enabled by the use of a beamline-mounted humidifying device. With the help of computational chemistry, attempts are made to assign some of the characteristic spectral features observed experimentally. A further source of uncertainty undoubtedly lies in the challenge of reliably measuring the parameters necessary for the accurate calculation of the absorbed dose (e.g.crystal size and shape, beam profile) and its distribution within the volume of the crystal (an issue addressed in detail in another article in this issue). While microspectrophotometry reveals that the production of various species can be quenched by the addition of scavengers, it is less clear that this observation can be translated into a significant gain in crystal dose tolerance for macromolecular crystallographers.

Thermogravimetric study of the desorption of cyclohexylamine and pyridine from an acid-treated Wyoming bentonite

Clay Minerals ◽  
1991 ◽  
Vol 26 (4) ◽  
pp. 473-486 ◽  
Author(s):  
C. Breen
Keyword(s):  
Catalytic Activity ◽  
Room Temperature ◽  
Product Yield ◽  
Efficient Catalyst ◽  
X Ray ◽  
Product Yields ◽  
Thermogravimetric Study ◽  
Wyoming Bentonite

AbstractFour 15 g samples of an unsedimented Wyoming bentonite were treated with 200 cm3 of 0·025, 0·050, 0·100 and 0·250 mol dm−3 H2SO4 for 1 h at room temperature (samples I–IV, respectively). Three further 15 g samples were treated with 200 cm3 of 50% (v/v) H2SO4 for 1 h at 20°C (sample V), and 1 and 2 h under reflux (samples VI and VII, respectively). X-ray fluorescence and diffraction studies revealed that only samples VI and VII suffered any substantial structural attack. The resulting acidity of the clays, determined by cyclohexylamine desorption, indicated that sample V contained the largest number of protons at 0·59 mmol H+ (g clay)−1. Sample V was also the most efficient catalyst for the dehydration and etherification of hexan-1-ol, giving a combined product yield of 17·0% after 2 h reflux in neat reactant. The parent bentonite and samples I and II showed no discernible catalytic activity despite measured acidities of 0·1, 0·24 and 0·34 mmol H+ (g clay)−1. In contrast samples III and IV gave combined product yields of 4·5 and 11·0%, respectively, which correlated well with the measured acidities of 0·38 and 0·48 mmol H+ (g clay)−1. Samples VI and VII, prepared by reflux in acid, contained 0·3 and 0·1 mmol H+ (g clay)−1, respectively, and gave combined product yields of 13·0 and 6·0%.

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