Polarization-independent tunable optical filters using bilayer polarization gratings.

We demonstrate a polarization-independent tunable optical filter based on switchable polarization gratings (PGs) formed using reactive and nonreactive liquid crystals (LCs). PGs are anisotropic diffraction gratings that exhibit unique properties, including a zero-order transmittance that is independent of incident polarization and that can vary from approximately 0% to approximately 100%, depending on wavelength and applied voltage. A stack of several PGs of varying thicknesses combined with an elemental angle filter yields polarization-independent bandpass tuning with minimal loss.

[Fibrinolysis during pregnancy. The pre- and postpartal changes].

Our previous research as well as data in literature (Yuasas, Ishizawa M.--1992) emphasised increased plasma fibrinolytic activity (PFA) in women during labor. Starting from these data we have tried to observe plasma fibrinolytic activity studied through euglobulin lysis time (ELT) in women during pregnancy and after delivery.

Blood coagulation and fibrinolysis after confinement hypokinesia.

Our previous studies dealt with the dynamics of the fluid-coagulant equilibrium in rats after confinement hypokinesia (CHK) for 1, 2 and 3 weeks obtained by placing them in small cages permitting only slight movements for spontaneous feeding. We found an acceleration of blood coagulation and fibrinolysis, with a maximal response after 1-2 weeks. In this work attention focussed on the initial more dynamic interval of 1, 3 and 7 days of exposure to CHK.

Blood coagulation and fibrinolysis in rats after hypokinesia and hyperthermia.

Coagulation and fibrinolysis were studied in rats exposed to hypokinesia (HK) obtained by including rats (for 1, 2 and 3 weeks) in small cages designed to limit their movements, permitting only spontaneous feeding (a method widely used for mimicking space flight conditions). The number of thrombocytes, the Quick time, the Howell time and the euglobulinlysis time (ELT) decreased after 1 and 2 weeks of HK; however, after 3 weeks, the parameters of coagulation approached normal control levels, while ELT was still significantly under the control values. An increased blood level of corticosterone in animals subjected to HK suggested that changes observed in the blood coagulation could be linked with it.

Blood coagulation and fibrinolysis in hyperthermic rats.

Exposure of rats to an environment of +40 degrees C that increases central (rectal) temperature to about 40 degrees C, importantly decrease the number of thrombocytes, the blood coagulation (the Quick time and Howel time) and euglobulin lysis time (ELT). In order to search for the mechanism responsible for coagulability and fibrinolysis we studied the relations of these changes with the sympatheticoadrenergic system and with the adrenal hormonal secretion. Some parameters were thus explored after adrenalectomy and under the influence of a beta-blocking agent, Eraldin.

The influence of magnetic fields on some humoral parameters and on resistance to hyperthermia in rats.

The influence of magnetic fields of moderate intensities (50 and 120 Oe) was studied in rats after single or repeated exposures with or without a rise in environmental temperature. The following parameters were investigated: the number of erythrocytes and leucocytes, the percentage of different varieties of leucocytes, serum Na+ and K+, plasma corticosterone, ascorbic acid in adrenals, blood catecholamines, plasma fibrinolytic activity, plasma antidiuretic hormone. The resistance to hyperthermia was tested after single exposures to magnetic fields and the survival time was measured.

Circulatory adaptive reactions under hypergravity in normal and cold environments.

Rats subjected to various levels of +Gz acceleration exhibited an increased blood concentration of noradrenalin and adrenalin, indicative of a sympatho-adrenergic reaction. Under the same conditions, from plasma determinations, and by histochemical examination of the supra-optic nucleus, an increased antidiuretic response was noted. This response was reduced in cold environment.

Hypergravitation and sympatho-adrenergic reactivity.

The sympatho-adrenergic reaction of the organism subjected to hypergravitation was investigated in rats exposed to +6 Gz. The electro- and cardiotachograms recorded telemetrically were correlated with the adrenal catecholamine content. The determinations were made in controls and in rats treated with hexamethonium and atropine administered separately or together.

The role of the sympathoadrenergic reaction in adaptation of the organism to the action of + 6 Gz acceleration.

In experiments on rats the symphathoadrenergic reactivity after a + 6 Gz acceleration was investigated. Hypergravitation produced as a rule a short initial bradycardia, followed by tachycardia. Hexamethonium (C6), a peripheric ganglion-blocking agent, produced bradycardia, diminution or vanishing of the initial bradycardic episode, and a decreased tachycardic reaction.