Large Diameter Channels Research Articles

Optimization of the heat transfer aspect of the thermoelectric power generation system.

A combined type thermoelectric power generation system is proposed to improve the conversion efficiency of thermal energy. In that system, thermoelectric elements are directly attached to the outer wall of the channel of a working fluid without a heat transfer block in order to reduce the thermal resistance; but on the contrary, high performance heat transfer pipes can not be used. Therefore, the effective heat transfer rate of a working fluid is increased by using a larger diameter channel to increase the contact area of the fluid to the channel. The performance of the combined type power generator is experimentally and theoretically investigated and compared with that of the conventional separated type generator. The optimum condition for power generation is also discussed. It is clarified that the maximum efficiency of the combined type generator becomes higher and its optimum Re number becomes larger compared with those of the conventional type. It is also made clear that the effect of the turbulence promoter on the maximum power output is negligible in the case of a generator having a large channel diameter.

小児の気管支異物摘出用内視鏡の一工夫 新たに開発したベンチレーション気管支ファイバースコープとその使用経験

Fiberoptic bronchoscopy with conventional instruments is not feasible in infants and small children because of poor ventilation. Another limiting factor in foreign body removal presently is the small diameter of the instrument channel which precludes passage of standard grasping forceps.To improve this situation, we devised a new flexible ventilating broncho-fiberscope.The specifications for the new broncho-fiberscope are as follows: A light-guided system with forward viewing angle of 70°, with the outer diameter of its tip and flexible part 5.9mm and 6.1mm respectively. It has a working length of 600mm. Angulation angles are 110° upwards and 60° downwards. It has a large channel (diameter, 3mm), compared with the size of the scope.For ventilation, we made a special adaptor, which has two connecting taps with a tube from the anesthesia machine for respiratory gases and a suction tube for aspirating secretions. By pushing the rubber cap of the adaptor, ventilation can be instantaneously switched to suction.For removal of foreign bodies, we made a small sized fenestrated forceps which is especially suitable for grasping peanut.

COMPARISON OF NERNST-PLANCK AND REACTION-RATE MODELS FOR MULTIPLY OCCUPIED CHANNELS

The Nernst-Planck continuum equation for a channel that can be occupied by at most two ions is solved for two different physical cases. The first case is for the assumption that the water and ion cannot get around each other anywhere in the channel, so that if there are two ions in the channel the distance between them is fixed by the number of water molecules between them. The second case is for the assumption that there are regions at he ends of the channel where the ions and water can get around each other. For these two cases, the validity of the simple two-site reaction-rate approximation when there is a continuously varying central energy barrier was evaluated by comparing it with the exact Nernst-Planck solution. For the first continuum case, the kinetics for the continuum and reaction-rate models are nearly identical. For the second case, the agreement depends on the strength of the ion-ion interaction energy. For a low interaction energy (large channel diameter) a high ion concentrations, there is a large difference in the flux as a function of voltage for the two models-with the continuum flux becoming more than four times larger at 250 mV. Simple analytical expressions are derived for the two-ion continuum channel for the case where the ends are in equilibrium with the bulk solution and for the case where ion mobility becomes zero when there are two ions in the channel. The implications of these results for biological channels are discussed.

Raman and infrared spectroscopic study of gramicidin A conformations

Raman scattering and infrared spectroscopic techniques were used to study the vibrational spectrum and conformation of the membrane channel protein gramicidin A in the solid state, in organic solutions and, using Raman scattering only, in a phospholipid environment. The investigation also includes measurements on head- and tail-group-modifled gramicidin A and a potassium thiocyanate-gramicidin A complex. Tentative identification of the molecular vibrations is proposed on the basis of the data on model compounds. The existence of four distinct conformations of the gramicidin A chain is established: conformation I present in the solid state, and CH 3OH and CD 3OD solutions; conformation II present in films cast from CHCl 3 solution; conformation III present in (CH 3) 2SO and (CD 3) 2SO solutions at concentrations below 0.5 m gramicidin A; and conformation IV present in the potassium thiocyanate-gramicidin A complex. The data obtainable on a gramicidin A-phospholipid suspension indicate a gramicidin A conformation in this environment corresponding either to the conformation I or II. The details of the spectra in the amide I region are shown to be consistent with a β-parallel hydrogen-bonded π LD helix for conformational I, in terms of the polypeptide vibrational calculations of Nevskaya and co-workers. Conformation II is found to be consistent with an antiparallel double-stranded π LD helix, while conformations III and IV probably have π-helical structures with larger channel diameters. The data on head- and tail-modified gramicidin A molecules indicate that their conformations are only slightly different from that of gramicidin A in conformation I.

Superchanneling of accelerated ions through crystals with large channels

350-keV protons were transmitted through beryl crystals of thicknesses up to 58 μm. The dependence of the output/input flux ratio upon the angle of incidence indicates the existence of a superchanneling effect caused by the large channel diameter. The channel effect is strongly dependent on purity and perfection of the crystals.

Direkte Bestimmung der Geschwindigkeitskonstanten des Durchtritts vom kleinen zum großen Hohlraumsystem im Molekularsieb Typ 13 X für Sr-und Ba-Ionen / Direct Determination of the Rate Constants for the Sr- and Ba-exchange Between the Small and Large Channels in LMS 13 X

Abstract Direct Determination of the Rate Constants for the Sr-and Ba-exchange Between the Small and Large Channels in LMS 13X The rate constants for the intracristalline Sr-and Ba-exchange between the small and large diameter channels of LMS 13X were measured. For this matter the method of interrupting the ion exchange was modified. It is assumed, that a first order reaction takes place. Using the rate constants and the diffusion coefficients, which were measured by Hoinkis and Levi, the total exchange of Sr 2+ and Ba 2+ could be calculated.

Determination of the base pressure during axisymmetric supersonic jet outflow into a channel

The outflow of an axisymmetric jet into a cylindrical channel of arbitrarily large cross-sectional area is considered. A method is proposed for analysis of the base pressure in the separation zone bounded by the inviscid jet boundary, the channel wall, and the step. New experimental results about the base pressure during jet outflow into a large-diameter channel are presented.