2-DIMENSIONAL QUANTUM GAS

Identical impenetrable particles in a 2-dimensional configuration space obey braid statistics, intermediate between bosons and fermions. This statistics, based on braid groups, is introduced as a generalization of the usual statistics founded on the symmetric groups. The main properties of an ideal gas of such particles are presented. They do interpolate the properties of bosons and fermions but include classical particles as a special case. Restriction to 2 dimensions precludes lambda points but originates a peculiar symmetry, responsible in particular for the identity of boson and fermion specific heats.

Winged leaf-cutting ants on nuptial flights used as transport by Attacobius spiders for dispersal

1. Sexuals of a leaf-cutting ant, Atta bisphaerica Forel, left their nest for nuptial flights in October to December.2. When leaving a nest, 53 of the 479 winged sexuals (or alates) observed (11.1%) carried up to three inquiline spiders of Attacobius luederwaldti.3. Spiders exclusively selected winged sexuals, not workers, and preferred females, indicating their expectation of the stronger flight ability of females. Neither these sexuals nor workers that appeared out of the nest on flight days attempted to remove or attack spiders on the body of alates.4. New qucens landing from their nuptial flight did not carry spiders, indicating that the spiders had left the ants in the sky to be dispersed by wind.5. No spiders were found in more than 100 incipient nests, which were estimated to be 2-3 months old. This suggests that the spiders jumped off the alate during mid-flight and dispersed on the wind to inhabit larger nests.

Isolamento e avaliação da atividade biológica dos alcalóides majoritários de Tabernaemontana angulata Mart. ex Müll. Arg., Apocynaceae

"Isolation and evaluation of the biological activity related to the major alkaloids in Tabernaemontana angulata Mart. ex Mull Arg., Apocynaceae." Introducing-new chemotherapeutic agents is a, great demand. in the control of infections diseases.' Brazil is one of the richest countries in biodiversity and the Laboratorio de Extracao at UNIP has been collecting plants from. the Amazon and Atlantic Rain Forests with the aim of screening for new antibacterial and antitumor plant extracts. Previous studies demonstrated that the ethanol fraction obtained from the crude extract of Tabernaemontana angulata stems showed antibacterial activity against Staphylococcus aureus (ATCC 6538 in the microdilution broth assay. Two alkaloids were the major compounds in the active fraction, verified by thin layer chromatography analysis. In the present study, the total alkaloids were obtained from the crude extract and were fractionated by preparative thin layer chromatography for the isolation of the main components. The isolated. compounds were identified by GC/MS and (1)H-NMR as coronaridine,e and voacangine. The alkaloid fractions obtained from the isolation procedure were tested for antibacterial activity, but no activity was detected.

The in vivo electrical parameters of toad skin

1. 1. Open-circuit voltage (PD) and short-circuit current (SCC) across toad skin were studied in in vivo conditions. An improved technique for fastening a lucite chamber on the abdominal region of the animal was developed. 2. 2. Saline bridges (230 mM Nacl in 4% agar solution) were placed subcutaneously to make the connections between the extracellular fluid and the half-cells. 3. 3. A clear relationship was observed between the electrical parameters and sodium transport by the skin, since PD and SCC were related to the sodium concentration of the bathing solution, and abolished by the presence of amiloride-a specific sodium transport inhibitor in epithelia. 4. 4. The initial control values of SCC in vivo were higher than those in vitro, which was attributed to hormonal stimulation. However, these high initial control values of SCC in vivo fell with time, reaching steady levels after a 2 hr period. 5. 5. Vasopressin failed to increase SCC in vivo when the external sodium concentration was 115 mM, being effective only when the sodium concentration was low (5 mM). 6. 6. On the other hand, in isolated preparations vasopressin significantly promoted an increase in both PD and SCC. © 1983.