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- Andersson, Per, et al.
(författare)
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Effect of guest molecule size on the thermal conductivity and heat capacity of clathrate hydrates
- 1983
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Ingår i: Journal of Physics C: Solid State Physics. - : Institute of Physics Publishing (IOPP). - 0022-3719. ; 16:8, s. 1423-1432
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Tidskriftsartikel (refereegranskat)abstract
- Using the transient hot-wire method, we have measured both the thermal conductivity, lambda, and the heat capacity per unit volume, rho cp, for structure II clathrate hydrates of 1,3-dioxolane (DO) and cyclobutanone (CB), and compared the results with similar previous measurements for tetrahydrofuran (THF). All three clathrate hydrates showed a glass-like temperature dependence of lambda. The magnitude of lambda was small, about the same as liquid water, and decreased in the sequence DO-THF-CB which corresponds to an increase in the size of the guest molecule. There was some evidence to support the suggestion that the dominant process in the thermal resistivity was associated with excitation of rotational vibrations of the guest molecules. In all cases, the pressure dependence of lambda was unusually small. We found evidence that there was a phase transition on the CB clathrate hydrate (and almost certainly also in the DO clathrate) at 135K and 1 GPa, which are essentially the same conditions under which we previously found an analogous transition for THF. In each case, the resultant presumably metastable phase may be a new type of clathrate hydrate arising from densification of the host structure. For the three clathrates, our results for rho cp did not depend on the nature of the guest species, and at 0.1 GPa, were the same as previously found for ice Ih.
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- Andersson, Per
(författare)
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Thermal conductivity, heat capacity and phase diagram of furan under pressure
- 1980
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Ingår i: High Temperatures-High Pressures. - 0018-1544 .- 1472-3441. ; 12:6, s. 655-662
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Tidskriftsartikel (refereegranskat)abstract
- The thermal conductivity and heat capacity per unit volume of the solid phases of furan (C4H4O) have been measured by the hot-wire method in the ranges 120-300 K and up to 2.8 GPa. The results indicate that phases I and IV are plastic-crystal phases, and that there is considerable structural disorder in phase II. Thermal data suggest the existence of a low-temperature high-pressure phase, probably phase III, which is only slightly more ordered than phase II. The character of the III-IV transition is second-order.
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- Andersson, Per, et al.
(författare)
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Thermal conductivity, heat capacity and phase diagrams of the trichloroethanes under pressure : II. 1,1,2-trichloroethane
- 1981
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Ingår i: Molecular Crystals and Liquid Crystals. - : Taylor & Francis. - 1542-1406 .- 1563-5287 .- 0026-8941. ; 69:1-2, s. 157-166
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Tidskriftsartikel (refereegranskat)abstract
- The thermal conductivity, λ, the heat capacity per unit volume, ρcp, and the phase diagram of 1,1,2-trichloroethane have been investigated in the temperature range 115 to 300 K and at pressures up to 2.5 GPa. The transient hot-wite method was used for the simultaneous measurement of λ and ρcp. Only solid phases I and II were detected, in agreement with the known phase diagram. A phase I-II transition was detected at about 200K and 0.1 GPa, which are conditions under which it had not priviously been observed. It was doubtful whether phase I could be retained metastably to low temperatures at low pressures with the most rapid cooling rate we were able to employ. The thermal resistivity of phase I was proportioned to temperature. The thermal resistivity of phase II contained an additional constant term, which we inferred to be a residual contribution associated with static structural imperfection in this phase.
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- Andersson, Per, et al.
(författare)
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Thermal resistivity, heat capacity and phase diagram of CBr4 under pressure
- 1980
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Ingår i: Molecular Physics. - : Taylor & Francis. - 0026-8976 .- 1362-3028. ; 39:6, s. 1359-1368
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Tidskriftsartikel (refereegranskat)abstract
- We have measured simultaneously the thermal resistivity and the heat capacity per unit volume for phases I, II, III and IV of CBr4. We have used the transient hot-wire method, and have made measurements over the ranges 170 K to 425 K, and up to 2 GPa. Our results, and other evidence, indicate that I and III are plastic crystal phases, and that there is a significant degree of structural disorder in phase II. Three-phonon interactions probably provide the dominant contribution to the thermal resistivity of phase IV. Using structural analogies with the phases of CCl4, we find that the relative values of the thermal resistivities are roughly as predicted by simple theory.
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- Andersson, Per, et al.
(författare)
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Thermal resistivity of ice Ih near the melting point
- 1980
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Ingår i: Journal of Physics C: Solid State Physics. - : Institute of Physics Publishing (IOPP). - 0022-3719 .- 1747-3802. ; 13:4, s. L73-L76
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Tidskriftsartikel (refereegranskat)abstract
- The thermal resistivity r(T) of ice Ih has been re-measured from 120K to as close as practicable to melting. Measurements were made under isobaric conditions at a pressure of 0.07 GPa, and corrected to isochoric conditions. The resultant deviation from the simple theoretical prediction, r/T=constant, has been plausibly accounted for by interaction between optic and acoustic phonons. Thermal resistivity arising from the presence of point defects has been shown to be of negligible importance.
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- Berglin, Ewa, MD, PhD, 1955-, et al.
(författare)
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Potentiation by L-cysteine of the bactericidal effect of hydrogen peroxide in Escherichia coli
- 1982
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Ingår i: Journal of Bacteriology. - : American Society for Microbiology. - 0021-9193 .- 1098-5530. ; 152:1, s. 81-88
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Tidskriftsartikel (refereegranskat)abstract
- Under anaerobic conditions an exponentially growing culture of Escherichia coli K-12 was exposed to hydrogen peroxide in the presence of various compounds. Hydrogen peroxide (0.1 mM) together with 0.1 mM L-cysteine or L-cystine killed the organisms more rapidly than 10 mM hydrogen peroxide alone. The exposure of E. coli to hydrogen peroxide in the presence of L-cysteine inhibited some of the catalase. This inhibition, however, could not fully explain the 100-fold increase in hydrogen peroxide sensitivity of the organism in the presence of L-cysteine. Of other compounds tested only some thiols potentiated the bactericidal effect of hydrogen peroxide. These thiols were effective, however, only at concentrations significantly higher than 0.1 mM. The effect of L-cysteine and L-cystine could be annihilated by the metal ion chelating agent 2,2'-bipyridyl. DNA breakage in E. coli K-12 was demonstrated under conditions where the organisms were killed by hydrogen peroxide.
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