Discriminative stimulus functions of drugs of abuse play an important role in the acquisition, maintenance and reinstatement of drug-taking behavior. The present study tested whether two different schedules of stressor presentation, i.e., repeated and variable, for 10 days, can modify the discriminative stimulus effects of cocaine in male rats trained to discriminate cocaine (10 mg/kg, i.p.) fr...

Gamma-aminobutyric acid (GABA) is important in plant responses to environmental stresses. We wished to clarify the role of GABA in maintenance of photosynthesis in muskmelon seedlings (Cucumis melo L., cv. Yipintianxia) during saline-alkaline stress. To this end, we assessed the effect of GABA on the structure and function of the photosynthetic apparatus in muskmelon seedlings grown under salin...

The resistance to sliding and the extent of till deformation beneath soft-bedded glaciers depend on the spatially averaged level of effective stress N, which is controlled by the distribution of water pressure at the bed. Major subglacial conduits that facilitate large-scale water transport are expected to be predominantly aligned with the direction of maximum hydraulic gradient, which is norma...

This paper reports on a joint theoretical and experimental study of the Pauli quantum-mechanical stress tensor T ␣␤ ͑x , y͒ for open two-dimensional chaotic billiards. In the case of a finite current flow through the system the interior wave function is expressed as ␺ = u + iv. With the assumption that u and v are Gaussian random fields we derive analytic expressions for the statistical distribut...

Photosynthetic characteristics and induction of crassulacean acid metabolism (CAM) by drought stress were investigated in Sedum album, Sedum stoloniferum and Rosularia elymaitica from Crassulaceae. Titratable acidity, malate content, phosphoenolpyruvate carboxylase (PEPC) activity and gas exchange parameters were determined in plants at the end and beginning of the photoperiod. Results showed t...

Studies with seedlings of tropical rainforest trees ( Calophyllum longifolium Willd.; Tectona grandis L. f.) were designed to test whether high-light stress affects photosynthetic performance and growth. Seedlings were cultivated in pots at a field site in Central Panama (9 degrees N) and separated into two groups: (1) plants exposed to full solar radiation; (2) plants subjected to automatic ne...