Mean Volume Fraction Research Articles

Effect of helium-oxygen mixture on myocardiac mitochondria of the rat

Ultrastructural and stereological analysis of mitochondria of myocardiac cells from rats was performed after 2-hour breathing of helium-oxygen mixture. The following changes were observed in the cells of experimental animals as compared with the control ones: swelling of mitochondria, increase of the mean volume fraction of these structures and decrease of axial ratio of mitochondria.

Pumping effect due to gas evolution in flow-through electrolysers

In electrolysers with recirculation where a gas is evolved, the pumping of electrolyte from a lower to a higher level can be effected by the air-lift effect due to the difference between the densities of the inlet electrolyte and the gaseous dispersion at the outlet. A balance equation for calculation of the rate of flow of the pumped liquid is derived. An equation for the calculation of the mean volume fraction of bubbles in the space between the electrodes is proposed and verified experimentally on a pilot electrolyser. The pumping efficiency of the air-lift effect is determined.

Organisation of collagen fibrils in tendon: changes induced by an anabolic steroid. II. A morphometric and stereologic analysis.

Morphometric and stereologic analysis of the organisation of collagen fibrils in tendon tissue after a treatment with an anabolic steroid hormone allowed the following observations: In a short-term study stereological data revealed a potent accumulation of collagen fibrils in the extra-cellular matrix after the administration of an anabolic steroid. Compared with controls, the anabolic steroid significantly increased the number of dysplastic collagen fibrils dependent on duration of treatment. Inter- and intrafibrillary dysplastic collagen fibrils possess characteristic diameter distributions which differ considerably from those of normal collagen fibrils. The functional significance of the changes in mean diameter, diameter distribution, numerical density and volume fraction of collagen fibrils in tendons following hormone treatment may be relevant to the use of these drugs in clinical practice and in competitive sports.

Quantitative evaluation of hepatic foci of cellular alteration occurring spontaneously in Fischer-344 rats

Stereologic procedures were used to quantitate spontaneously occurring liver foci of altered staining in control Fischer-344 rats at 33, 59, 85, and 111 weeks of age. Foci were identified using hematoxylin and eosin stained sections. In both males and females, foci were first observed at 59 weeks. The number of foci per cubic centimeter of liver, as well as mean focal volume, increased significantly with age. Between 85 and 111 weeks, the number of foci per liver increased 3.5 times in females but was unchanged in males. When three groups of 111-week-old animals were evaluated, females consistently had a greater number of foci per cubic centimeter of liver and mean focal volume than males of the same group. For the three groups evaluated at 111 weeks, the mean number of foci per liver ranged from 431 to 1865 in males and from 727 to 1654 in females. The mean volume fraction (% of the liver) occupied by foci ranged from 0.28 to 1.0% in males and from 1.42 to 4.15% in females. When focal staining characteristics were investigated, the majority of foci were basophilic in both sexes at all time points examined. However, males consistently had a higher percentage of eosinophilic foci than females.

Precipitation in iron–chromium–aluminium alloys

AbstractSmall angle neutron scattering was used to study the precipitation in two iron–chromium–aluminium alloys of similar composition, the main difference being the addition of yttrium to one alloy. The mean diameter, separation, and volume fraction of the precipitates is determined as a function of aging time and temperature. The two alloys behaved differently, the precipitate growing more quickly in the yttrium containing alloy. The upper limit of stability of the chromium rich phase was established as lying between 480 and 485°C in both alloys.

Relationship between human enamel structure and the formation of caries-like lesions in vitro

Caries-like enamel lesions were produced in deciduous and permanent human teeth by exposure to acidified hydroxymethyl-cellulose gel, pH 4.5, for 21 days. Mean lesion depth was significantly greater in deciduous than in permanent enamel, in agreement with previous studies. The greater lesion depth in deciduous enamel was associated with greater mean prism-junction density and mean volume fraction of interprismatic enamel, as measured by planimetry of scanning electron micrographs. The greater susceptibility of deciduous enamel appears to be due to greater porosity. The order of lesion depths in vitro among permanent teeth suggests that in vivo the pattern of caries incidence among the various tooth types is governed mainly, not by intrinsic susceptibility but by other factors, such as morphology and salivary composition and flow rate. Some of the variation in caries incidence between individuals and between contralateral teeth may, however, be due to variations in intrinsic susceptibility.

Two phase flow in large diameter pipes

When gas and liquid flow together up a vertical tube, several flow patterns are possible. An isolated bubble will rise, relative to the liquid, with its terminal velocity. As the bubble concentration increases, the rise velocity decreases due to interference between the bubbles, as shown by Nicklin. At higher bubble concentrations coalescence can produce larger bubbles with higher rise velocities and, more significantly, convection cells can be formed which enable some of the bubbles to rise extremely fast. On the small scale the situation is complicated, with some bubbles rising rapidly and others, possibly, being carried downward. On the large scale this can be averaged out to give a mean gas velocity, which is the superficial gas velocity divided by the mean volume fraction of gas, which can then be correlated with the superficial gas and liquid velocities.

Study of pumping effect in flow-through electrolysers

In electrolysers with recirculation, where a gas is evolved, the pumping of electrolyte from a lower to a higher level can be effected by natural convection due to the difference between the densities of the inlet electrolyte and the gaseous emulsion at the outlet. An accurate balance equation for calculation of the rate of flow of the pumped liquid is derived. An equation for the calculation of the mean volume fraction of bubbles in the space between the electrodes is proposed and verified experimentally on a pilot electrolyser. Two examples of industrial applications are presented.

A viscometric study of the flocculation of the components in stored homogenized ultra-heat-treated cream

SUMMARYThe apparent relative viscosity (ηr) of stored homogenized ultra-heat-treated ‘coffee’ cream increased with time (t) at a rate which was a function of mean fat globule diameter (d) and fat volume fraction (ø); the rate was also influenced by Na2CO3and Na citrate when present as stabilizing additives. Viscosity increases were attributed to the progressive flocculation of fat globules and to the strengthening of the structure formed by the gradual accretion of casein micelles on to globule surfaces and their points of contact (bridging). The expressionwheretis in days anddin μm, was found to hold over a 12-week storage period for a batch of creams (ø = 0·143) of differentdvalues prepared from the bulk cream containing carbonate and citrate stabilizers; η0is the relative viscosity att= 0 andkis a rate parameter. In the absence of stabilizers the parameterkassumed a smaller value and so appeared to be a function of chemical composition of the cream and of forces of particle interaction; seasonal factors were also suspected of influencingk. The effect of the fat volume fraction on storage behaviour was not fully resolved, but there was some evidence that the proportionality log ηrα1/ø½ was appropriate.

Plasma clearance of intravenous chenodeoxycholic acid in rabbits with varying severity of hepatocellular necrosis.

The plasma clearance of an i.v. bolus of chenodeoxycholic acid (10 micrometer per kg) was determined in rabbits with graded degrees of hepatocellular necrosis produced by i.p. injection of carbon tetrachloride. Plasma chenodeoxycholic acid levels were determined by radioimmunoassay, and the volume fraction of necrosis was quantitated by a computerized (Quantimet 720) system. Impaired plasma clearance was observed only when necrosis was extensive, and the volume fraction of necrosis greater than 34%. In contrast, measurement of fasting plasma chenodeoxycholic acid concentration was more sensitive, and elevated levels were associated with a mean volume fraction of necrosis of 12.5%. This study reinforces the conclusion based on clinical studies that measurement of fasting bile acid concentration is a more sensitive discriminant of hepatic dysfunction than is measurement of the plasma clearance of an i.v. bolus of bile acid.

Some stereological problems for random discs in R3

Random spherical discs in R 3 and their planar intersections are considered, By means of the theory of random point processes the relationship between distributions of random diameters of the discs and random intersection lengths is found. The mean surface fraction S v per unit volume for a non-isotropic model is given similary to the classical stereological formula in the isotropic case. Furthermore, the mean volume fraction V v (d) of the discs dilated by a ball of radius d in terms of planar quantities is found.

Irradiation-enhanced coarsening in Ni-12.8 at.% Al

Precipitation of γ′-Ni 3Al in Ni-12.8 at.% Al was investigated during low-dose irradiation with 3.5 MeV 58Ni + ions at 450–700°C. Mean precipitate size, number density and volume fraction were determined by transmission electron microscopy (TEM). At constant displacement rate, mean γ′ size increased with the one-third power of irradiation dose at all temperatures investigated, consistent with a diffusion-controlled (Lifschitz-Slyozov-Wagner) model for precipitate coarsening during aging. The vol.% of precipitate increased rapidly early in the irradiation, then reached and maintained a constant value consistent with coarsening during thermal ageing. Log-log plots of precipitate number density vs dose are linear with slope ~ ′-1.0, as predicted by coarsening theory. The rate constants observed for irradiated samples were always greater than those observed at the same temperatures during thermal ageing. The difference decreased at higher temperature (~ 700°C). The rate constants reached a plateau between 500 and 600°C with k ′- 10 6Å 3/h, close to the value observed during electron irradiation of this alloy. The significance of the similarity between the effects of heavy-ion and electron irradiation for cascade dissolution of precipitates is discussed. Agreement between observed and calculated rate constants is good, particularly in view of the changing sink structure with irradiation temperature.

Proofs of some fundamental formulas of stereology for non-poissoh grain models

Using a formula for the intensity measure of stationary marked point processes some of fundamental formulas of stereology are proved for a grain model with non-Poisson germ, process, for example that for mean volume fraction and mean surface area per unit area.

Measurement of the fat content of meat using ultrasonic waves

The velocity of 2·5 MHz ultrasound in muscle, fatty tissue and muscle/fatty tissue mixtures has been measured over the temperature range −20°C to +40°C. At a set temperature there is a relation between the velocity of ultrasound and the composition of the tissue, and this relation was studied at −9°C, 0°C and +37°C. Measurements at 37°C appeared to have the best predictive value, and at that temperature, a linear relation existed between the reciprocal of the velocity and the volume fraction of fat. This relation is such that a measurement of the time taken for a pulse to travel through meat consisting of multiple, parallel layers of muscle and fatty tissue of arbitrary fatness could be used to estimate the overall mean volume fraction of fat. This property could be useful in assessing at selected sites the composition of the soft tissue of living animals. Muscles are acoustically anisotropic and the slight difference between velocities along, and parallel to, the fibres has been measured. The effect of dehydration has also been investigated.

Perturbation method for incorporating the concentration dependence of the Flory–Huggins parameter into the theory of steric stabilization

Theories for the mixing contribution to steric stabilization assume that the Flory–Huggins interaction parameter (χ) is constant whereas experiments demonstrate that χ is usually concentration dependent. A perturbation method is elaborated that allows this concentration dependence to be incorporated into the theory for steric stabilization. It is shown that the first order perturbation term, if compared with the leading term, is of order text-decoration:overlineν, where text-decoration:overlineν is the mean segment volume fraction in the steric barrier. Consequently, the concentration dependence may contribute significantly to the repulsion, especially for low molecular weight polymers and high compressions. The complete mixing term is evaluated for the simple model of a constant segment density. The predictions of the theory are compared with the experimental disjoining pressures recently reported by Homola and Robertson. The correlation between the critical flocculation point and the theta-point is not significantly affected by the concentration dependence of χ.

Left ventricular hemodynamics and contractile pattern after aortocoronary bypass surgery: Factors affecting reversibility of abnormal left ventricular function

Left ventricular hemodynamics and contractile patterns were evaluated in 104 patients before and after aortocoronary bypass surgery. Patients were selected on the basis of referral for surgery because of angina pectoris and the demonstration, postoperatively, of all grafts being patent. Group I consisted of 47 patients with single grafts (LAD 33 and RCA 14). Mean left ventricular end-diastolic pressure, volume, and ejection fraction revealed no change after surgery. Twenty-four patients had asynergy prior to surgery; of these 24, 16 patients had a normal contractile pattern after surgery. Group II consisted of 47 patients with double vein grafts. Postoperatively, there was a significant decrease in left ventricular end-diastolic pressure (p < 0.005) and increase in ejection fraction (p < 0.001). Asynergy in 29 patients preoperatively revealed synergy after surgery in 15 patients. Group III consisted of ten patients with triple vein grafts. Ejection fraction increased postoperatively (p < 0.01). All but two of the eight patients with asynergy preoperatively showed synergy after surgery. In the entire group of patients, 43 with synergy preoperatively, with but one exception, had synergy after surgery. Asynergesis in 41 instances preoperatively revealed postoperatively that 38 patients (93 per cent) had normal wall movement. In 29 instances of preoperative akinesia of one wall, only 8 patients (28 per cent) showed a return to normal wall movement. Unstable angina pectoris alone did not influence reversibility of abnormal contractile patterns. Unstable angina pectoris with absence of abnormal Q-waves in the ECG was noted in 23 patients with asynergy; all but one of these patients had a normal contractile pattern after surgery. Patients with infarction pattern on the ECG, when accompanied by asynergy, were unlikely to have a normal contractile pattern after surgery (4 out of 23 patients). Reversibility of left ventricular function after surgery is common, not related to number of grafts, but is related to type of wall abnormality noted prior to surgery as well as the ECG and clinical state of the patient.

Anti-arrhythmic efficacy of aprindine in acute myocardial infarction

Anti-arrhythmic efficacy of aprindine in acute myocardial infarction

Morphometric study of normal and phytohemagglutinin-stimulated lymphocytes

The morphological changes of human lymphocytes living in vitro under the influence of phytohemagglutinin (PHA) were estimated quantitatively by stereological methods. Mean volume and volume fractions for average human lymphocyte and average blastoid cell from 72-hour culture with PHA were determined. It was found that the lymphocyte volume increases on an average 3.7 times mainly because of cytoplasmic volume increment by 4.3 times. The greatest enlargement concerned endoplasmic reticulum, the nucleolus, lysosomes and mitochondria. In addition a way of correction of the error in experimentally obtained volume fractions, resulting from the exclusive use of sections involving the nucleus is presented.

The surface area of sheep cardiac Purkinje fibres.

1. Measurements combining the techniques of point counting and line integration were performed on light and electron micrographs of Purkinje fibres from the sheep's heart. The measurements were aimed at determining membrane areas of importance for the cellular electrophysiology of this tissue.2. The mean volume fractions of the cells occupied by various constituents were: myofibrils, 0.234; mitochondria, 0.103; and nuclei, 0.009. The mean volume fraction of the fibres occupied by the interspaces between the tightly packed cells was 0.0023.3. The mean fractions of intercellular surface area occupied by junctional specializations were: nexus, 0.17; desmosome, 0.023; and fascia adherens, 0.014.4. The mean surface to volume ratio of the Purkinje cells and fibres was 0.46 mu(-1) which is 11.5 times the value of the surface to volume ratio of a long right circular cylinder 100 mu in diameter.5. There are two reasons for the increment in the surface to volume ratio of the fibre (when compared to that of a long right circular cylinder 100 mu in diameter): the multicellular composition of the fibres and the extensive folding of the surface of the cells.6. After correction for the intercellular nexal area the surface to volume ratio of a long cylindrical fibre 100 mu in diameter was 0.39 mu(-1), or about 10 times the value for a long right circular cylinder 100 mu in diameter. The surface to volume ratio of the tissue interspaces in the same fibre was 170 mu(-1).7. It was concluded that the total sarcolemmal area in this tissue is great enough so that the specific membrane capacitance could be about 1 muF/cm(2) and the specific membrane resistance 20,000 Omega cm(2).