Search Results - (Author, Cooperation:R. E. Martin)

2018-05-05

American Association for the Advancement of Science (AAAS)

2375-2548

Natural Sciences in General

2016-04-02

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

Chemistry, Pharmaceutical/*methods ; Pharmaceutical Preparations/*chemical synthesis

1365-3040

Blackwell Publishing Journal Backfiles 1879-2005

Biology

The effects of different photooxidative stresses on the function of photosystem I were measured in vivo in Chlamydomonas reinhardtii. Pholooxidative stresses included strong light, light combined with chilling to 0 °C, and light combined with several concentrations of methyl viologen. Photosystem I function was measured in vivo using the absorbance change at 820 nm associated with P700 oxidation. Photosystem II function was measured in vivo using chlorophyll fluorescence. Strong light or light combined with chilling caused inhibition of photosystem II function earlier than inhibition of photosystem I function. When photosystem I was inhibited, however, it did not recover. Light combined with 5 mmol m−3 methyl viologen caused inhibition of photosystem I function earlier than inhibition of photosystem II. If the methyl viologen concentration was reduced to 1 mmol m−3, the damage to PSI was accelerated by addition of 90 mmol m−3 chloramphenicol. This effect of chloroamphenicol suggests a role for chloroplast-encoded proteins in protecting photosystem I against photooxidative damage caused by methyl viologen.

Electronic Resource

1432-1939

Springer Online Journal Archives 1860-2000

Biology

Summary Interactions between fire, fungi, bark beetles and lodgepole pines growing on the pumice plateau of central Oregon are described. Mountain pine beetle (Dendroctonus ponderosae) outbreaks occur mainly in forests that are 80–150 years old with a mean diameter of about 25 cm and weakened by a fungus, Phaeolus schweinitzii. The outbreak subsides after most of the large diameter trees are killed. The dead trees fuel subsequent fires which return nutrients to the soil, and a new age class begins. The surviving fire scarred trees are prone to infection by the slow fungal disease and about 100 years later these trees are then susceptible to bark beetle attack.

Electronic Resource

0730-6679

Chemistry ; Polymer and Materials Science

Wiley InterScience Backfile Collection 1832-2000

Chemistry and Pharmacology

Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

The long-term behavior of a glass mat-reinforced polypropylene has been characterized by accelerated flexural creep tests on samples of the laminate. Considerable data were collected for stress levels ranging from 200 to 7500 psi at six temperatures from room temperature to 140 °C. The material was found to behave in accordance with the linear theory of viscoelasticity except at the longer times where the creep rate increases dramatically and the specimen ruptures. The stress and temperature dependence of this “terminal creep” zone was treated by means of a slightly modified version of Schapery's thermodynamic theory of nonlinear viscoelasticity, which involves the superposition of double logarithmic plots of creep compliance versus time. The stress and temperature dependence of both the free energy function and the entropy production emerge from this treatment. A comparison of nonisothermal creep data with a prediction from the isothermal master curve is marginally acceptable. A statistical synthesis of the data discloses that the incidence of terminal creep is log-normally distributed. Moreover, the standard deviation associated with the distribution is independent of temperature. It is therefore possible to assess the probability of failure for any constant stress at any constant temperature.

17 Ill.

Electronic Resource