Size Of Medium Research Articles

Correlation distance measurements of the female breast

Ultrasonic waves propagating through soft tissue experience wavefront distortion. Adaptive wavefront compensation algorithms attempt to correct such distortion. A valuable design parameter is the isoplanatic patch size of the imaging medium. Its lateral extent is the FWHM of the correlation function. The range extent is defined similarly. The significance of the isoplanatic patch is that a new wavefront correction vector must be obtained whenever the ultrasound beam is moved a patch length. This paper reports measurements of wavefront correlation functions as well as statistics of the lateral correlation distance rho d (half the FWHM) within the female breast obtained from a population of 22 women (44 breasts) and measured at 3 and 4 MHz with a large acoustic aperture (9.6 cm). A set of complex wavefronts radiated from single pointlike sources was measured from the opposing side of the breast. The propagation distance was 12 cm. rho d is the distance between two sources at which the correlation between their wavefronts drops to 0.5. The mean value at 3 MHz was found to be less than 1.5 mm for the premenopausal dense breast, 2.5 mm for the premenopausal fatty breast, and 2.0 mm for the postmenopausal breast. The mean value dropped by a factor of 2 at 4 MHz for a group consisting of premenopausal fatty and postmenopausal breasts.

New approaches to concentration on a microliter scale of dilute samples, particularly biopolymers with special reference to analysis of peptides and proteins by capillary electrophoresis I. Theory

New methods are described for the concentration of ionic analytes, particularly ampholytes, such as peptides and proteins. In most of these methods the sample is depleted (partially) of strong electrolytes concomitantly with the concentration. The methods are based on the fact that electrophoretic migration velocities decrease upon decreasing the absolute value of the zeta potential of a solute and the pore size of the electrophoresis medium and upon increasing the cross section of the electrophoresis chamber, the viscosity and the electrical conductivity of the electrophoresis medium. We have also utilized the zone-sharpening properties of displacement electrophoresis in combination with a hydrodynamic counter flow to create a stationary zone where the sample solutes can be collected continuously. In practice, the whole electrophoresis tube is filled with the sample solution to be concentrated. When a voltage is applied the solutes begin to migrate, but finally cease to move as they approach the end of the tube, provided that the above-mentioned parameters in that section of the tube have been given appropriate values. By means of this technique the sample can be concentrated into a zone of a width of 0.2–0.5 mm. Accordingly, a 400–1000 fold concentration is obtained when a 200 mm long tube is filled completely with the sample and still more if also an electrode vessel (or a vessel connected to this electrode vessel) is loaded with sample. The narrow sample zone can be withdrawn from the tube and subjected to further studies or used as a starting zone for an in-tube zone electrophoresis. The tendency for broadening of the very narrow starting zone during the initial phase of this electrophoresis step can be counteracted by a short mobilization step involving displacement electrophoresis, electrophoresis in a steep pH gradient, or on-tube dialysis against a (diluted) buffer. This step can be omitted when the concentration is accomplished by a combination of displacement electrophoresis and a counter flow. In Part II we show how the theory developed in this paper can be utilized practically.

Solidification around Horizontal Cylinder in Porous Medium Saturated with Aqueous Solution.

In order to clarify phenomena such as the solidification of soil containing seawater in the ground freezing technique, a horizontal copper cylinder was set in a porous medium saturated with an aqueous solution, and the porous medium, whose size was sufficiently large compared with the cylinder, was solidified by cooling the cylinder. Such a solidification process with natural convection caused by the temperature and concentration gradients in the liquid and mushy regions was studied analytically and experimentally. From the comparison of the analytical results with the experimental ones, the present analysis was found to be useful to simulate this solidification process. By the analysis, the characteristic of the solidification process, especially, the influence of grain size of the porous medium on the solidification phenomenon, was clarified.

Influence of temperature on particle separation in granular bed filters

The present study deals with the influence of temperature on the separation of fine dust particles in granular bed filters. Collection within the diffusion regime for particles smaller than 0.5 μm becomes more effective with increasing temperature. However, for larger particles subject to the influence of inertial forces, a drop in separation efficiency is to be expected due to increasing drag forces. With the aid of experimentally determined grade efficiencies at temperatures up to 800 °C, the influence of temperature and other important filtration parameters such as the filter medium's grain size or the filter face velocity, are quantitatively derived and discussed. Investigations concerning the long-term filter behavior have shown that the formation of a filter cake significantly improves separation efficiency. This not only depends upon the characteristics of the dust in question, but also is a function of the grain size of the filter medium and the filtration velocity. Under cake filtration conditions, high collection efficiencies may also be attained at temperatures up to 800 °C.

Influence of optimal cavity shapes on the size of polymer molecules in random media

The importance of noncompact (nonspherical) cavities in determining the size of polymer molecules in random media is studied by means of generalized Flory–Lifschitz arguments and computer simulations. The simulations are performed for a freely jointed chain in one and two dimensions using a novel Monte Carlo algorithm that effectively eliminates the effects of the finite size of the random medium. For the one-dimensional case, the simulation result for the exponent ν (=0.31±0.02), characterizing the scaling of the mean-square end-to-end distance of the chain R with the number of monomers, is in excellent agreement with the ν (=0.33) predicted by the previously developed Flory–Lifschitz theory based on the notion of compact cavities. A generalized version of the theory that accounts for noncompact (for d>1) ‘‘tube’’-like cavities with L(αR2 ) being the length of the tube, and D being the diameter in d-1 transverse directions, predicts that ν=1/(2d+4), or 1/6, depending on the nature of the tube for d>1. This result is consistent with simulation results for the Gaussian chain in two dimensions. The theory also predicts that when one end of the chain is anchored and self-avoidance is included ν=2/3, which suggests a certain similarity between this problem and that of the directed walk in a random environment.

Manufacturing Decline and Technology Lags in Nonmetropolitan Illinois

ABSTRACTNumerous studies have focused on national and regional manufacturing decline in the U.S., but far less attention has been placed on decline in substate areas. This oversight is troublesome because manufacturing decline in substate areas, particularly in the Midwest, has been severe and prolonged. This paper, therefore, examines the causes of manufacturing decline at the substate level. Specifically, I evaluate whether the impact of factors influencing decline varies according to the size and location of medium‐ and small‐sized cities in Illinois. Survey data and loglinear modeling methods are used for the empirical analysis. The results indicate that the impact of technology lags in substate areas varies significantly by the size of cities. The effects of technology, the regional shift of manufacturing, and federal trade policies are influenced by the relative location of cities.

Laboratory study of attrition grinding : Davis S B; Dawson, M F J S Afr Inst Min Metall V89, N8, Aug 1989, P231–241

This paper descriptionbes the size reduction of limestone smaller than 1 mm by attrition grinding, using quartz (1 to 3 mm) as the grinding medium in a laboratory rig. The ore and grinding medium were closely sized fractions, and the particle size of the grinding medium was at least three sizes larger than that of the ore. Batch tests showed that the size reduction of the feed followed two first-order rate processes: one for an apparently fast-breaking ore fraction, and a slower one for most of the ore (86 per cent). The production of fines (material smaller than 10 ?m) followed a zero-order rate equation. Continuous runs showed that the process could be modelled as a perfectly mixed system provided that the discharge screen did not selectively retain coarser particles of ore. The ratio of medium to ore (both by mass and by volume) was found to have a significant effect, the most energyefficient grinding occurring at ratios between 1 and 2. The solids content of the slurry also had a significant effect, the greatest efficiency being obtained at 50 to 65 per cent solids (by mass). Within these energy-efficient ranges of medium-to-ore and solids content, the lower values resulted in maximum feed breakage and the higher values in maximum fines production. The most important factor in the breakage of feed was the difference in the particle size of the grinding medium and the ore; the amount of ore broken out of the feed size for a given energy input was found to increase linearly with the difference between the size of the grinding medium and that of the ore up to 2 mm. The production of fines increased similarly, but only up to a difference of about 1,2 mm, when it levelled off at about 5 kg/kW.h. The mechanism proposed for attritioning is mainly the abrasion of 1 ?m planes of limestone along the crystal axes, with some fracturing along existing lines of weakness. The energy consumption of nearly 200 kW, h per ton of product smaller than 10 ?m appears to be higher than that in other types of milling. It is concluded that the value of attrition milling lies in its selectivity; in this work, only the softer limestone and virtually none of the hard quartz grinding medium was comminuted.

Removal of chrome dye from aqueous solutions by mixed adsorbents: Fly ash and coal

The removal of Omega Chrome Red ME (a popular chrome dye) from its aqueous solutions by adsorption on a homogeneous mixture of fly ash and coal in different proportions has been carried out. It has been noted that low adsorbate concentration, small particle size of adsorbent, low temperature and acidic medium favour the removal of the dye. A 100% removal of the said dye was achieved at 10 mg1 −1, 30°C, 2.0 pH and 53 μm particle size, using a 1:1 ratio of fly ash and coal. The kinetics and mass transfer studies were made using the models suggested by Lagergren and McKay et al. respectively. The equilibrium data fit well in the Langmuir model of adsorption, showing the formation of monolayer coverage of dye molecules at the outer surface of the adsorbent. Effect of temperature was explained on the basis of solubility and chemical potential of the adsorbate. An attempt has been made to explain the results thus obtained on the basis of various physiochemical properties of the solid-solution interface involved in the process of removal.

X-ray microscopy of inertial fusion targets using a laser-produced plasma as an x-ray source

With the advent of an ablation layer coating technology for mechanically nonsupported inertial fusion targets, the conventional optical interferometric technique for the characterization of these targets is no longer feasible since the batch process of this bounce coating technique makes it difficult to account for individual targets. A soft x-ray contact microradiography method, which was developed for this purpose, is limited in resolution by the 0.5-μm grain size of the photographic medium used. Utilization of an x-ray sensitive photoresist extends the resolution to as low as 50 Å. The use of a laser-generated x-ray source for x-ray microscopy appears to require much less energy than published photoresist sensitivity data. A single-shot exposure of 100 J, 0.527-μm wavelength, and 1-ns laser shot suffices for image formation. The resulting x-ray micrographs show a higher spatial resolution than the images obtained by previous radiography techniques. The resolution of 0.2 μm in the present study is due to the finite size of the x-ray source.

Influence of Leaching Parameters on the Biological Removal of Uranium from Coal by a Filamentous Cyanobacterium

Axenic cultures of the filamentous cyanobacterium LPP OL3 were incubated with samples of uraniumbearing coal from a German mining area. The influence of leaching parameters such as coal concentration (pulp density), initial biomass, particle size, temperature, and composition of the growth medium on the leaching of uranium from the ore by the cyanobacterial strain was studied. When low pulp densities were applied, the yield of biologically extracted uranium was optimal (reaching 96% at 1% [wt/vol] coal) and all released uranium was found in the culture liquid. Above 10% (wt/vol) coal in the medium, the amount of cell-bound uranium increased. Initial biomass concentration (protein content of the cultures) and particle size were not critical parameters of leaching by LPP OL3. However, temperature and composition of the growth medium profoundly influenced the leaching of uranium and growth of the cyanobacterium. The yield of leached uranium (at 10% [wt/vol] coal) could not be raised with a tank leaching apparatus. Also, coal ashes were not suitable substrates for the leaching of uranium by LPP OL3. In conclusion, the reactions of the cyanobacterium to variations in leaching parameters were different from reactions of acidic leaching organisms.

Flow rate and bead size as critical parameters for immobilized-yeast reactors

The productivity of immobilized yeast cell reactors varies with a number of parameters, including flow, amount and growth rate of yeast, bead size and type of medium. Variation of these parameters has a pronounced effect on reaction rate. This paper presents typical ranges for these productivities and demonstrates the patterns of changes that take place when bead size, flow and reaction medium are varied. Saccharomyces cerevisiae cells were immobilized in calcium alginate beads for the production of ethanol. The productivity of immobilized yeast in a batch reactor (0.2 g ethanol/g yeast · h) was only two-thirds that of free cells suspended at an equivalent cell density (0.3 g ethanol/g yeast · h). Different flow rates and bead sizes were used to ‘optimize’ the productivity. The productivity of 3.34 mm beads at a flow rate of 8.8 litre h −1 (superficial velocity: 0.12 cm s −1 ) was 95% higher than that at 1.0 l h −1. Maximum productivities of 0.34, 0.27, 0.22 g/g yeast· h were obtained (at a flow rate of 8.8 l h −1 ) for 9.2% yeast-immobilized beads of 3.34, 4.45 and 5.65 mm in diameter, respectively.

Compressibility of zeolite 4A is dependent on the molecular size of the hydrostatic pressure medium

Unit-cell parameters of synthetic zeolite 4A were determined at several pressures to 4.0 GPa in four different hydrostatic pressure media: ethanol, methanol, glycerol, and an organofluorine compound, C8F16O (FC-75). These data, when combined with previously published results on zeolite in water and a water-bearing 4 : 1 methanol : ethanol mixture, reveal that compression of zeolite depends on the relative sizes of the hydrostatic fluid molecules compared with the structural channels in the zeolite framework. Zeolite 4A is most compressible (ΔV/VΔP =β=0.046 GPa−1) in glycerol and FC-75, which have molecular dimensions that are larger than the zeolite channels. Zeolite is least compressible ( β=0.007 GPa−1) in water, which has a maximum molecular dimension that is significantly smaller than the channel diameter. In methanol and ethanol alcohols, which have intermediate molecular diameters, zeolite 4A also has intermediate compressibility. This zeolite in alcohols, furthermore, progressively undergoes a series of transitions to more compressible states as pressure is raised.

Asymptotic stability of reaction-diffusion systems in chemical reactor and combustion theory

Some coupled reaction-diffusion systems arising from chemical diffusion processes and combustion theory are analyzed. This analysis includes the existence and uniqueness of positive time-dependent solutions, upper and lower bounds of the solution, asymptotic behavior and invariant sets, and the stability of steady-state solutions, including an estimate of the stability region. Explicit conditions for the asymptotic behavior and the stability of a steady-state solution are given. These conditions establish some interrelationship among the physical parameters of the diffusion medium, the reaction mechanism, the initial function and the type of boundary condition. Under the same set of physical parameters and reaction function, a comparison between the Neumann type and Dirichlet or third type boundary condition exhibits quite different asymptotic behavior of the solution. For the general nonhomogeneous system, multiple steady-state solutions may exist and only local stability results are obtained. However, for certain models it is possible to obtain global stability of a steady-state solution by either increasing the diffusion coefficients or decreasing the size of the diffusion medium. This fact is demonstrated by a one-dimensional tubular reactor model commonly discussed in the literature.

Formation and Molecular Dynamics of Cycloamylose Inclusion Complexes with Phenylalanine

Abstract The molecular dynamics of the inclusion complexes of cycloamyloses with phenylalanine in aqueous solution at different pD have been studied by means of carbon-13 NMR spectroscopy. As host cycloamyloses we have chosen cyclohexaamylose, cycloheptaamylose, and cyclooctaamylose. The influences of the cavity size of cycloamyloses and of medium pD values on the molecular dynamics of inclusion complexes were studied by using the NT1η values, where T1 is the carbon-13 spin-lattice relaxation time, N the number of directly bonded proton to a given carbon, and η is the viscosity of solution. Upon complexation, the NT1η values of phenyl carbons of guest phenylalanine show larger decreases than those of other carbons, indicating that the guest forms the inclusion complexes with the host by the insertion of its phenyl ring into the host cavity even in the case of cyclooctaamylose. It was found that the strength of the dynamic coupling between host and guest depends on the cavity size and pD values of medium. The strongest coupling was observed for the cycloheptaamylose–phenylalanine system at pD 11.3, where the phenyl ring is deeply and tightly included into the cavity. The inclusion of phenyl ring is shallow and loose in the case of cyclohexaamylose and deep and loose in the case of cyclooctaamylose.

Computer Simulation for UV-preionized Discharge KrF Laser

A computer simulation code for UV-periodized discharge Kr F lasers is developed, including time dependent circuit equations and kinetic rate equations for various atomic and molecular species, electrons and photons. The energy distribution of electrons are calculated with a Boltzmann code. The laser characteristics computed by this code are compared with those of a home-made Kr F laser, and the energy loss mechanism is investigated for the variation of the input voltage, the total gas pressure, and the size of the active medium. The results are qualitatively in good agreement with those of experiment except the absolute output energy. This disagreement is maybe caused by the non-uniform distribution of the discharge. The most important loss effective to the over-all efficiency is the circuit loss by impedance mis-matching. The scalability of these self-sustained discharge excimer lasers is briefly discussed with this simulation code.

Oxygen consumption in six species of chitons in relation to their position on the shore

Abstract Aerial and aquatic oxygen consumption rates have been measured in six species of intertidal chi tons with respect to zonation, size and oxygen concentration of the external medium. Those species occurring highest on the shore were found to have a lower rate of aquatic oxygen consumption than those ~i'eeies occurring lowest on the shore, with mid-shore species showing intermediate rates. Aerial oxygen consumption rates were similar in most species and were not strictly correlated with their position on the shore. High shore chitons had higher or equal rates in air than in water, while low shore species had higher aquatic than aerial rates. It was also found that the six species could be grouped with respect to their oxyregulatory capabilities when exposed to declining oxygen tensions and these groups could be correlated with the species intertidal zonation: high shore species show a high degree of oxygen independence, mid-shore species a moderate degree and low shore animals little or no regulator...

7. Relationship Between Meteorites, Asteroids and Comets

There seem to be no objection any more to regard the asteroid belt as the past and present source of initial and intermediate parent-bodies of meteorites. Initial parent bodies were of the size of the present-day largest asteroids; the irregular size of medium sized asteroids suggests intermediate parent bodies fragmented by collisions. Finally, most of the terminal parent bodies can be identified with Earth-crossing or grazing objects. In contrast, icy planetesimals of the outer zone of the primeval nebula underwent almost no thermal evolution, but only a complicated orbital evolution leading to the comets observed now. This does not exclude the possibility that some extinct comets end up on asteroid-type orbits, although their nuclei might still contain ices covered by an insulating crust that can preserve them for a very long time. These could be the parent bodies of bolides, as opposed to meteorites.

Recovery of Retrograde Condensed Liquids By Revaporization During Dry Gas Injection

Abstract Laboratory experiments were conducted to determine the rates of revaporization of the immobile liquid that was deposited in 'Various porous media as a result of retrograde condensation during pressure depletion of methane n-butane mixtures. The influence of particle size, initial liquid saturation, dry was injection rate and immobile water saturation on the revaporizution process was studied by measuring effluent concentration profiles as a function of volume of methane injected. The revaporization rate was estimated by matching the solution of a Mathematical model, in which mass transfer is expressed by a first-order rate expression, to the experimental effluent concentration data. In general, the rate of mass transfer was found to increase with decreasing particle size of the porous medium, increased condensed liquid saturation and increased immobile water saturation. The increase in each case is attributed to increasing the interfacial area between the gas and the condensed liquid. The magnitude of the measured 1nass transfer rates indicates that thermodllna1nic equilibrium between flowing gas and liquid could be assumed. Introduction WHEN FACED with the problem of planning production operations for gas condensate reservoirs, engineers frequently wish to compare the fluid recoveries and cash flows for various exploitation schemea(1). The simplest scheme consists of continuous pressure depletion or "blow down" to abandonment pressure. This method is attractive because:it requires low initial capital investments,it provides high initial cash flows andit requires the least engineering design. The deficiencies of this process are:loss of valuable condensate liquids resulting from a continual decrease in volatility as the average molecular weight of the reservoir fluid increases during the depletion (2,3,4);large variations in loading of the gas plant during the life of the project(3); andhigh liquid accumulation in the vicinity of the production wells with resulting lowered deliverabilities(3). Another exploitation scheme which is commonly used is gas cycling 'With full pressure maintenance. In this method, gas cycling is initiated at the start of production. The average molecular weight of the reservoir fluid decreases as it is diluted with dry injection gas. After breakthrough of dry gas at the production wells, pressure depletion by blow down is allowed to occur. The advantages of this method are:displacement of dense upper-dew-point fluids by dry gas results in high recoveries for swept portions of the reservoir;the accumulation of liquids in the vicinity of the producing wells is inhibited both during the gas injection and the pressure decline phases of operation;in the case of injection into a gas cap in which there is an immobile residual oil saturation, much of the oil may be recovered by vaporization(5,6). The disadvantages(3) of this method of operation are:high initial and operating costs for gas handling facilities;low cash flows resulting from deferred gas sales (7), and make-up gas purchases. Several variations of these two basic processes have been discussed in the literature(3, 5, 8, 1, 9, 7).

The regulation of haemolymph calcium concentration of the crab Carcinus maenas (L.).

After acclimation, Carcinus can maintain calcium balance in dilute (35-100%) but not in low calcium sea water. 71% of total haemolymph calcium (9-54 +/- 0-42 mM) was in ionic form as compared with 90-9%(9-9mM) in sea water. On acclimation to dilute sea water the calcium activity of the haemolymph was greater than that of the medium, the difference being maintained by active calcium uptake. Carcinus is highly permeable to Ca2+, influx from sea water being 0-513 +/- 0-07 mumoles g-1 h-1 and the time constant for calcium influx 4-3 +/- 0-48 h. Calcium space represented ca. 25% wet body weight independent of body size or salinity of acclimation medium.

Chapter 14 The Plasma Membrane of KB Cells; Isolation and Properties

Publisher Summary This chapter describes the isolation of the plasma membrane of KB cells by two different methods, namely, the latex bead ingestion and the ZnCl 2 methods. In principle, the latex bead method can be employed with any cell type provided the proper conditions for bead ingestion are optimized (size and multiplicity of beads, incubation medium, time and temperature of incubation, and absence of fusion between phagosomes and lysosomes). The method has been used for the isolation of phagosomes from Acanthamoeba, L cells, and polymorphonuclear leukocytes, and macrophages. Optimal conditions are developed for the ingestion of latex beads by mouse neuroblastoma cells (clone Neuro-2A) in monolayer (differentiated state) and suspension cultures (undifferentiated form). It is observed that only lymph node macrophages ingest latex beads (1.01 μm in diameter) after intradermal-subcutaneous injection of a 10% aqueous suspension of beads. Thus the isolation of plasma membranes by the latex bead procedure described can be accomplished with cells grown in culture as well as with certain cells from tissues after in vivo injection of the beads.