scholarly journals Strahleninaktivierung von Ribonuclease bei erhöhten Temperaturen und unterschiedlichen Dosisraten

1968 ◽  
Vol 23 (7) ◽  
pp. 949-952 ◽  
Author(s):  
Klaus Kürzinger ◽  
Horst Jung
Keyword(s):  
Dose Rate ◽  
Cross Section ◽  
Room Temperature ◽  
Activation Energies ◽  
The Other ◽  
Radical Reactions ◽  
Kcal Mole ◽  
Apparent Activation Energies ◽  
Mev Protons ◽  
Dose Rate Effect

The radiosensitivity of dry ribonuclease was determined at various temperatures between 120 °K and 440 °K using 2 MeV protons. Within this temperature range the inactivation cross section S (T) of ribonuclease may be described as a function of temperature by the expression S(T) = (1.28 + 16·e-1000/RT+14000·e-6500/7RT)·10-14 cm2 .This result indicates that the observed radiation damage to ribonuclease is produced by three different mechanisms, one being independent of temperature, the other two having apparent activation energies of 1 kcal/mole and 6.5 kcal/mole, respectively. From these relatively small activation energies the conclusion may be drawn that radical reactions contribute to the inactivation of enzymes in the dry state. Experiments with Co gamma radiation showed that the radiosensitivity of ribonuclease at 77 °K depends on dose rate; at room temperature a dose rate effect was not observed.

scholarly journals Der Einfluß der Temperatur auf die Strahlenempfindlichkeit von Ribonuclease

1967 ◽  
Vol 22 (3) ◽  
pp. 313-320 ◽  
Author(s):  
Wolfgang Günther ◽  
Horst Jung
Keyword(s):  
Gamma Radiation ◽  
Cross Section ◽  
Gamma Rays ◽  
Room Temperature ◽  
Bacterial Spores ◽  
Kcal Mole ◽  
Biological Objects ◽  
The Cross ◽  
Apparent Activation Energies ◽  
Mev Protons

The radiosensitivity of dry ribonuclease was determined at various temperatures ranging from 90 °K to 300 °K and using 60Co gamma-radiation, 2 MeV protons, and 2 MeV deuterons. The cross section for the inactivation of RNase S (T) is, in this range, given as a function of temperature byS(T) =S0+S1·e-Ea/RT.For inactivation of ribonuclease with Co gamma-rays we found S0=0 and Ea=1000 cal/mole; S1= =0.125 Mrad-1 when irradiation is carried out in vacuo, and S1=0.265 Mrad-1 in oxygen. With protons and deuterons the following values were determined: S0=1.28·10-14 cm2, S1=19.5·10-14 cm2, Ea=1050 cal/mole for 2 MeV protons; S0=2.45·10-14 cm2, S1=31·10-14 cm2, and Ea = 1050 cal/mole for 2 MeV deuterons. Furthermore, by analysis of some recent data from the literature we found that the cross section for inactivation by ionizing radiation of various enzymes, bacteriophages, and bacterial spores in the range from 4 °K to temperatures higher than room temperature can satisfactorily be described by the more general equationS(T) =S0+S1·e-E₁/RT+S2·e-E₂/RT,with E1=1 kcal/mole and E2=4 kcal/mole being constant for all objects and for all circumambient conditions tested. This correlation between inactivation cross section S (T) and temperature T shows three mechanisms of inactivation to occur in biological objects: one (S0) being independent of temperature, while the two others have apparent activation energies of 1 kcal/mole and 4 kcal/mole, respectively.

Rapid Migration of Defects in Ion-Implanted Silicon

1997 ◽  
Vol 469 ◽  
Author(s):  
J. Lalita ◽  
P. Pellegrino ◽  
A. Hallén ◽  
B. G. Svensson ◽  
N. Keskitalo ◽  
...  
Keyword(s):  
Activation Energy ◽  
Temperature Dependence ◽  
Dose Rate ◽  
Long Range ◽  
Room Temperature ◽  
Rate Effect ◽  
High Dose ◽  
Range Migration ◽  
Mev Protons ◽  
Dose Rate Effect

ABSTRACTThe temperature dependence of the so-called reverse dose rate effect for generation of vacancy-type defects in silicon has been investigated using samples implanted with 1.3 MeV protons at temperatures between 70 and 300 K. The effect is found to involve a thermally controlled process which exhibits an activation energy of ∼0.065 eV, possibly associated with rapid migration of Si self-interstitials (I). Further, using a concept of dual Si ion-implants long range migration of I:s at room temperature has been studied. Annihilation of vacancy-type defects at a depth of ∼3 μm is obtained by injection of I:s from a shallow implant with sufficiently high dose.

scholarly journals Der Einfluß der Temperatur auf die Strahlenempfindlichkeit von Ti-Bakteriophagen

1966 ◽  
Vol 21 (7) ◽  
pp. 678-690 ◽  
Author(s):  
Klaus-Otto Hermann
Keyword(s):  
Activation Energy ◽  
Total Cross Section ◽  
Cross Section ◽  
The Other ◽  
Base Substitution ◽  
Kcal Mole ◽  
Temperature Dependent ◽  
Direct Radiation ◽  
Dependent Component ◽  
Mev Protons

The radiosensitivity of dry bacteriophage was determined in vacuo at temperatures varying continuously between 100 ° and 300 °K using 2 MeV protons. Moreover, the influence of added cystamine and of base substitution by 5-bromouracil was investigated in the same range of temperatures. The variation of total cross section σ(Τ) with temperature is given by the expression:σ(T) =σ0·(1+5,3. e-EaRT) ±15 per cent.The constant σ0 is 3,3.10-12cm2 for normal Tl phage, 4,9.10-12cm2 for base substituted Tl phage, 1,3.10-12cm2 for Tl phage in presence of cystamine, and 1,6.10-12cm2 for base substituted Tl phage in presence of cystamine; Ea amounts to 1 kcal/mole in all four cases. The correlation between inactivation cross section σ and temperature T shows that two mechanisms of inactivation are present, one (σ0) being independent of temperature, the other having an activation energy of about 1 kcal/mole. The first mechanism is ascribed to direct radiation action, while the temperature dependent component probably originates from small diffusible radicals.

scholarly journals Unbeeinflußbarkeit ihrer Wirkung auf Ribonuclease durch Cystamin und tiefe Temperaturen

1966 ◽  
Vol 21 (12) ◽  
pp. 1165-1170 ◽  
Author(s):  
H. Jung
Keyword(s):  
Cross Section ◽  
Low Temperatures ◽  
Room Temperature ◽  
High Efficiency ◽  
Reduction Factor ◽  
Biological Damage ◽  
Nuclear Collisions ◽  
Different Temperatures ◽  
Fast Protons ◽  
Mev Protons

Slow protons having energies below 1.5 keV dissipate their kinetic energy in matter through elastic nuclear collisions. By this process atoms are displaced out from their original positions in macromolecules. This was recently shown to cause biological damage with high efficiency. Experiments are described to test the possibility of modifying the sensitivity of ribonuclease towards elastic collisions by protective agents and by low temperatures. When cystamine is present during irradiation dry ribonuclease is protected against the action of “ionizing” fast protons (2 MeV), the dose reduction factor being 1.8. But no protection is observed when inactivation is achieved by elastic nuclear collisions (proton energy 1 keV and 1.4 keV). Similar results were obtained when the irradiations were carried out at different temperatures. Using 2 MeV protons the radiosensitivity of ribonuclease was found to be 3 times higher at room temperature than at 125 °K, but when using slow protons of 1.4 keV energy the inactivation cross section turned out to be independent of temperature. This shows that the action of elastic nuclear collisions can be modified neither by cystamine nor by low temperatures.

Radiation protection in irradiated dimethylsiloxane polymers

1963 ◽  
Vol 273 (1352) ◽  
pp. 117-132 ◽  
Keyword(s):  
Protective Effect ◽  
Dose Rate ◽  
Reaction Mechanisms ◽  
Radical Reactions ◽  
Gas Evolution ◽  
Dose Rates ◽  
Dose Rate Effects ◽  
Rate Effects ◽  
Colloidal Sulphur ◽  
Dose Rate Effect

Small concentrations of certain additives can greatly modify the effects produced by radiation of macromolecules such as polymers and biological systems. Various mechanisms of protection can be envisaged, and these lead to different kinetics in protection effects. Most published work studies the elimination of the additive, rather than the change in the macromolecule. In previous papers in this series, the dose rate effects expected for radical reactions were observed for anthracene solutions in hexane and cyclohexane. With anthracene in dimethylsiloxane polymers, however, no such dependence was observed. This problem is studied in greater detail in the present paper. The additives studied were anthracene, iodine, sulphur and benzophenone, and their protective effect on the crosslinking of dimethylsiloxane polymer was investigated a t various dose rates. Contrary to generally accepted views on reaction mechanisms no dose-rate effect was observed; anthracene provided no protection against crosslinking, although it was itself destroyed. Iodine and colloidal sulphur provided a considerable measure of protection, but had no effect on gas evolution. Benzophenone also offered protection, but also reduced the gas yield. To explain these very different patterns of behaviour, it is necessary to modify some present views on the nature of the protection offered; this leads to a discussion as to the mechanism of crosslinking.

Electron Microscopy investigations of buried Si3N4 isolation layers

1990 ◽  
Vol 48 (4) ◽  
pp. 642-643
Author(s):  
S.K. Maksimov ◽  
V.N. Kukin
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Cross Section ◽  
Room Temperature ◽  
Ion Beam ◽  
The Other ◽  
Silicon Epitaxial Layer ◽  
P Type ◽  
Structure Investigations ◽  
Plane View

Formation of buried Si3N4 layers obtained by using repeated cycles of implantation and annealing has been investigated. Structure investigations were made with the use of a CM30 Twin electron microscope (whose diaphragm is 0.18 nm-1 ). In HREM studies, axial micrographs in Si reflections of the 000, 111 and 220 types were employed. Two types of samples were used: "plane view" samples and those of a "cross section". Si3N4 precipitates were identified by application of the EELS method on the LN and Lsiedges.N+ - ions were implanted into silicon wafers (of p-type, (001), 10 Ω cm) at a room temperature- The dose pf ions implanted in each cycle was 5.1010 cm-2 . The total dose was 5.1017 cm-2 , The energy of ions - 150 keV, the current density of the ion beam 25 μA/cm-2 . Annealing in the atmosphere of nitrogen was made at 1100° C which lasted 2 hours after the first cycle of implantation; in the other cycles it lasted 0.5 hours at 850° C. After the operation of ion beam synthesis was completed a silicon epitaxial layer 0.8-1 μm thick was grown.

Hydrogenation of methylacetylene. IV. The reaction of methylacetylene with hydrogen catalyzed by palladium, platinum, iridium, rhodium, and ruthenium catalysts

1969 ◽  
Vol 47 (2) ◽  
pp. 215-221 ◽  
Author(s):  
R. S. Mann ◽  
K. C. Khulbe
Keyword(s):  
Activation Energies ◽  
Ruthenium Catalysts ◽  
Kcal Mole ◽  
Wide Range ◽  
Apparent Activation Energies ◽  
Palladium Platinum

The reaction between methylacetylene and hydrogen over pumice supported and unsupported palladium, platinum, iridium, rhodium, and ruthenium catalysts has been investigated between 12 and 160 °C for a wide range of reactant ratios. The order of reaction with respect to hydrogen was one and with respect to methylacetylene was zero to slightly negative. The overall apparent activation energies for supported and unsupported palladium, platinum, iridium, and rhodium were 10.5, 9.5, 12.4, 14.7, 8.6, 6.2, 10.7, and 11.7 kcal/mole respectively.

scholarly journals Catalytic Hydrogenation of Methylacetylene

1967 ◽  
Vol 45 (10) ◽  
pp. 1023-1030 ◽  
Author(s):  
R. S. Mann ◽  
S. C. Naik
Keyword(s):  
Compensation Effect ◽  
Nickel Catalysts ◽  
Hydrogenation Reaction ◽  
Activation Energies ◽  
Reaction Vessel ◽  
Kcal Mole ◽  
Pressure Time ◽  
Wide Range ◽  
Exponential Factors ◽  
Apparent Activation Energies

The reaction between methylacetylene and hydrogen over supported and unsupported nickel catalysts has been investigated in a static constant volume system for a wide range of temperature and reactant ratios. The pressure–time curves consist of two linear portions of different slopes. The reaction over nickel is largely simple hydrogenation, the early stages being principally a selective production of propylene with small yields of reduced polymers of methylacetylene. The orders of the hydrogenation reaction are first and zero with respect to hydrogen and methylacetylene respectively. The overall apparent activation energies for nickel–pumice and nickel–kieselguhr are 16.8 and 14.0 kcal/mole and for unsupported nickel catalysts vary between 17.2 and 20.0 kcal/mole. A satisfactory "compensation effect" exists between the activation energies and logarithmic values of the pre-exponential factors. The unsupported catalysts were not poisoned when methylacetylene was added first to the reaction vessel.

The hydrogenation of allene. II. The reaction of allene with hydrogen catalyzed by nickel, cobalt, and iron

1968 ◽  
Vol 46 (20) ◽  
pp. 3249-3254 ◽  
Author(s):  
R. S. Mann ◽  
D. E. Tiu
Keyword(s):  
Activation Energies ◽  
Constant Volume ◽  
Cobalt Catalysts ◽  
Kcal Mole ◽  
Nickel Iron ◽  
Early Stages ◽  
Nickel Cobalt ◽  
Wide Range ◽  
Apparent Activation Energies ◽  
Selective Formation

The reaction between allene and hydrogen over unsupported nickel, iron, and cobalt catalysts has been studied in a static constant volume system for a wide range of temperature and reactant ratios. The reaction over metals is largely simple hydrogenation, the early stages being principally a selective formation of propylene with small yields of reduced polymers of allene. The orders of the hydrogenation were 1 and 0 with respect to hydrogen and allene respectively, and were temperature independent. The overall apparent activation energies for nickel, iron, and cobalt were 6.5, 7.6, and 6.9 kcal/mole respectively. Selectivity was highest with nickel, and least with cobalt.

scholarly journals Sustainable Valorization of Animal Manure and Recycled Polyester: Co-pyrolysis Synergy

2019 ◽  
Vol 11 (8) ◽  
pp. 2280 ◽  
Author(s):  
Zuhal Akyürek
Keyword(s):  
Room Temperature ◽  
Animal Manure ◽  
Activation Energies ◽  
Cattle Manure ◽  
Synergistic Interactions ◽  
Kinetics Of Decomposition ◽  
Single Region ◽  
Fwo Method ◽  
Apparent Activation Energies ◽  
Kinetics Of

In this study sustainable valorization of cattle manure, recycled polyester, and their blend (1:1 wt.%) were examined by the thermogravimetric analysis (TGA) method. Pyrolysis tests were performed at 10, 30, and 50 °C/min heating rate from room temperature to 1000 °C under a nitrogen environment with a flow of 100 cm3/min. Kinetics of decomposition were analyzed by using Flynn–Wall–Ozawa (FWO) method. Based on activation energies and conversion points, a single region was established for recycled polyester while three regions of pyrolysis were obtained for cattle manure and their blend. Comparison between experimental and theoretical profiles indicated synergistic interactions during co-pyrolysis in the high temperature region. The apparent activation energies calculated by FWO method for cattle manure, recycled polyester. and their blend were 194.62, 254.22 and 227.21 kJ/mol, respectively. Kinetics and thermodynamic parameters, including E, ΔH, ΔG, and ΔS, have shown that cattle manure and recycled polyester blend is a remarkable feedstock for bioenergy.

Sign in / Sign up

Export Citation Format

Share Document