Action Of Chemical Factors Research Articles

До питання про сполучену дію хімічних чинників та холодового стресу (аналітичний огляд літератури)

До питання про сполучену дію хімічних чинників та холодового стресу (аналітичний огляд літератури)

Application of a new method for the study of surface topography in processes of surface etching and corrosion of industrial glasses, electron emission microscopy

The paper describes a new technique, an electron emission microscopic method for structural and topographic surface studies. This has been applied in practice to a series of composite silica glasses, industrially produced on a technical scale, of the type SiO 2 (≌ 72%) + Na 2O (≌ 15%) + CaO (≌ 8%) + MgO (≌4%) + R 2O 3 (≌ 1%), to quartz glass SiO 2 (≌ 100%), and to other amorphous substances of the same kind subjected in the laboratory to stepwise chemical etching (for corrosion analysis), as well as to surfaces subjected to mechanical processing by grinding and polishing and to subsequent chemical processing by etching, followed by polishing. The structural and topographic state of the glass plate surfaces was analysed, and the kinetics of the processes occuring on the surface and in near-surface layers were studied during the action of chemical factors on corrosion and the formation and variation of the surfaces under laboratory processing and in industrial production. Grain distributions, macro- and microinhomogeneities on the surface and in near-surface layers, and characteristics parameters of surface structure and topology were determined.

Muscular reflex stimuli to the cardiovascular system during isometric contractions of muscle groups of different mass.

1. The cardiovascular responses to voluntary isometric contractions performed by human subjects are determined by the proportion of maximal tension achieved by the muscles contracting, and not by the mass of the contracting muscles, nor by the absolute tension achieved (Lind & McNicol, 1967; confirmed here). When two or more muscle groups contract simultaneously at different relative tensions, the increments in heart rate and blood pressure are the same as when the muscle group at the higher relative tension contracts alone at that tension (Lind & McNicol, 1967). It is known that there are both central and reflex stimuli to the cardiovascular system in exercise, and the present study examines whether the muscular reflex stimuli are related to the proportion of maximal tension achieved or to the mass of contracting muscle. 2. Isometric hind-limb contractions were induced in anaesthetized dogs and cats by stimulation of spinal ventral roots. Pressor responses to contraction of both hind limbs were greater than responses to contractions of either hind limb alone. No differences were observed between heart rate responses to single or combined hind-limb contractions. 3. When human subjects perform isometric contractions, a pressor response can be maintained beyond the conclusion of the exercise by occluding muscle blood flow. This response is generally attributed to a reflex set up in the muscle by the action of chemical factors on afferent nerves. When comparable pressor responses were evoked by comparable proportional efforts with either the whole hand or the little finger, it was found here that the pressor responses remaining during the period of post-exercise occlusion were greater when the greater mass of muscle had been exercised. 4. It is concluded that the muscular reflex drive in isometric exercise is related to the bulk of contracting muscle.