Restriction Of Size Research Articles

An Experimental Evaluation of the Recovery Potential of Ryegrass Populations from Genetic Stress Resulting from Restriction of Population Size

An Experimental Evaluation of the Recovery Potential of Ryegrass Populations from Genetic Stress Resulting from Restriction of Population Size

Transverse Fracture in Unidirectional Graphite/Polysulfone Composites

The transverse fracture properties of unidirectional graphite/polysulfone composites were used as a measure of the "in situ" fracture toughness of polysulfone, an amorphous thermoplastic matrix. At room temperature, the "in situ" plane-strain energy release rate, GIc, of polysulfone was a factor of four lower than the neat resin GIc. By comparing the temperature dependencies of the composite GIc to the neat resin GIc, we concluded that the release of residual thermal strain energy did not contribute to the observed loss of tough ness. The observed toughness loss is probably related to restriction of matrix yield zone size by the graphite fibers.

Mitochondrial DNA in natural populations: An improved routine for the screening of genetic variation based on sensitive silver staining

AbstractWhen screening natural populations for genetic variation in mitochondrial (mt) DNA it is necessary to screen as many individuals as possible for as large a number of base pairs as possible. This report describes a combination of laboratory techniques – isolation of mtDNA by either density ultracentrifugation or a phenol extraction procedure and DNA fragment visualization by a sensitive silver staining technique. These routines remove the major restriction of tissue sample size and number of individuals that can be screened and allows the investigation of at least 1000 base pairs from 1 g of tissue or 3–400 base pairs from 100 mg of frozen tissue.

SOME STATISTICAL CONCEPTS IN THE ANALYSIS OF VISION AND VISUAL ACUITY

As conventionally recorded, visual acuity data constitute an ordinal scale of measurement. An investigation of four different clinical samples shows that visual acuity is not normally distributed amongst these populations. Furthermore, acuity is often measured on charts which, by the inherent restriction of the stimulus size, have the effect of truncating the upper limit of the scale producing, in statistical terms, an incomplete distribution. The distribution of acuity for each sample is found to be adequately described in terms of the equation: F(x) = Ax alpha (T - x) beta, where F(x) is the cumulative distribution of the statistical population, T is the truncation level (known), x is the Snellen decimal acuity (known) and A, alpha and beta are parameters. Alternative analytical procedures based upon this model, which overcome these limitations, are discussed.

Effect of Half‐Sib and S1 Recurrent Selection for Increased Grain Yield on Allozyme Polymorphisms in Maize1

Allozyme frequencies at nine enzyme loci were monitored over eight cycles of selection for grain yield with the half‐sib (HT) and S1 progeny methods in maize (Zea mays L.) population ‘Krug BSK.’ Allozyme frequencies generally weres table over cycles in the presence of repeated small population size and high ~10% selection intensity. The average amount of genetic polymorphism for the nine enzyme loci was not different from the original population after the eight cycles of HT and S1 recurrent selection. Simple linear regression suggested the possibility of directional selection for changing allozyme frequencies at locus Peroxidase 1 (Prx1) in HT selections and loci Alcohol dehydrogenase 1 (Adh1), Malate dehydrogenase 2 (Mdh2), Acid phosphatase 1 (Acp1), and Prxl in S1 selections. However, more precise chi‐square analyses indicated that directional selection alone could not account for the observed allozyme frequency changes for any of the enzyme loci studied. It is concluded that stabilizing selection or random genetic drift associated with restriction of population size when lines were chosen to advance to the next cycle, or perhaps these two factors combined with undetected (because of small populatlon size) super imposed directional selection, can account for the observed allozyme frequency changes in the BSK populations studied.

Experimental Design for Bayesian Estimations in the Linear Regression Model Taking Costs into Account

It is assumed that a known, correct, linear regression model (model I) is given. Let the problem be based on a Bayesian estimation of the regression parameter so that any available a priori information regarding this parameter can be used. This Bayesian estimation is, squared loss, an optimal strategy for the overall problem, which is divided into an estimation and a design problem. For practical reasons, the effort involved in performing the experiment will be taken into account as costs. In other words, the experimental design must result in the greatest possible accuracy for a given total cost (restriction of the sample size n). The linear cost function k(x) = 1 + c (x ‐ a)/(b ‐ a) is used to construct costoptimal experimental designs for simple linear regression by means of V = H = [a, b] in a way similar to that used for classical optimality criteria. The complicated structures of these designs and the difficulty in determining them by a direct approach have made it appear advisable to describe an iterative procedure for the construction of cost‐optimal designs.

Role of the configuration interaction in the CNDO/S calculation of optical rotatory strengths

The rotatory strengths calculated directly by the CNDO/S method exhibit a pronounced dependence on the size of configuration interaction (CI). In order to elucidate the role of highly excited configurations in such calculations the perturbation theory is employed. It is shown that the restriction of the CI size to 20–40 may be quite inadequate in some cases. The calculations of rotatory strengths of several optically active molecules containing carbonyl and amide chromophores has shown that the best results can be obtained for half of full CI but sometimes it is possible to restrict the CI size to 100 configurations. The agreement with experiment for all molecules considered is satisfactory.

The Welfare Analysis of Fertility Reduction

The various cost-benefit studies of fertility reduction are discusse d. The main weakness of all types of cost-benefit studies is that they have no welfare content. They measure the costs of raising a child in different societies but do not measure the psychic pleasures that children give to their parents. In this study it is assumed that parents enjoy their children in general and that actual family sizes will not be reduced much without prior motivation toward smaller familie s. Government policies to change reproductive behavior will depend on net external costs of various family sizes the receptiveness of couples to bribes and incentives and the effects of government policy on income distribution between families in the society. There is little evidence to show that more available contraceptive information and subsidized contraceptives will result in a change in reproductive behavior. Incentive payments for restriction of family size are shown to be ineffective. Government-established disability and old-age pension systems may have an effect in motivating couples to have fewer children.

Enhancement of prenatal development in the rat by operative restriction of litter size.

The number of fetuses in the rat has been operatively restricted between 50 and 90% of normal by destruction of the other implantation sites by cauterization on the 8th day of pregnancy. The surviving offspring had significant increases in placental weights, body weights, cerebral weights, cerebral protein and cerebral DNA (cell number). Placental weights followed the extent of restriction.

Enhancement of prenatal development by operative restriction of litter size in the rabbit

The number of fetuses in the rabbit has been operatively restricted to one per experimental animal on the 9th day of pregnancy, by destruction of all but one of the implantation sites. As compared with the sham-operated controls, the experimental offspring had significant increases in placental weights (up to 105%), body weights (up to 50%) and cerebral DNA (cell number) (up to 21%).

研削砥石の動弾性係数

In this paper, the relation between the dynamic elastic modulus measured by ultrasonic pulse method and the grade of the grinding wheel is discussed.The results obtained are as follows: 1. The grade of the grinding wheel can be determined by the dynamic elastic modulus.2. The dynamic elastic modulus obtained experimentally has correlations not only with the percentage of the grain and the bond, but also with the bending strength of the grinding wheel.3. By ultrasonic pulse method, it is not necessary to rectify the type and the shape of the grinding wheel, thus, this method is more convienient than sonic resonance frequency method, and the dynamic elastic modulus of it is easily calculated with the den sity and the ultrasonic velocity of the grinding wheel.4. The dynamic elastic modulus has relation to the bitten-depth measured by bit-method, and there is no restriction of the grain size upon appiying this method to the grade determination.

Purification and Regulatory Properties of the Biosynthetic L-Glycerol 3-Phosphate Dehydrogenase from Escherichia coli

Abstract The l-glycerol-3-phosphate:NAD(P) oxidoreductase (EC 1.1.1.8), referred to as glycerol phosphate dehydrogenase, was purified from extracts of Escherichia coli by a combination of chromatographic procedures. The over-all purification was approximately 1000-fold and the yield was about 10%. The elution profile from the final DEAE-Sephadex column and zone electrophoresis indicated that the enzyme preparation was not homogenous. Kinetic studies showed that the enzyme was both stabilized and inhibited by 0.1 to 1.0 m salts, and that l-glycerol 3-phosphate specifically inhibited dihydroxyacetone phosphate reduction. The curve describing the degree of inhibition as a function of l-glycerol 3-phosphate concentration was sigmoid, with 35 µm glycerol 3-phosphate producing 50% inhibition. Michaelis-Menten type kinetics were found with glycerol 3-phosphate, acting as a substrate, dihydroxyacetone phosphate, and TPNH. The calculated Km values were 210 µm, 170 µm, and 10 µm, respectively. Glycerol 3-phosphate was a competitive inhibitor with respect to dihydroxyacetone phosphate and an uncompetitive inhibitor with respect to TPNH. The addition of TPNH to the enzyme solution quenched the fluorescence of the protein at 340 mµ and enhanced the TPNH fluorescence at 450 mµ. Glycerol 3-phosphate further enhanced the fluorescence of the TPNH-enzyme complex in the 430 to 440 mµ region. The fluorimetric titration of the TPNH-enzyme complex with glycerol 3-phosphate gave a sigmoid curve with the same characteristics as the inhibition curve. The inhibition of the pyridine nucleotide-linked glycerol phosphate dehydrogenase of Escherichia coli, whose most likely function is to provide glycerol 3-phosphate for lipid syntheses, could act in the cell as an effective mechanism for the restriction of the pool size of glycerol phosphate.

Deoxyribonucleic acid of neonatal rat cerebrum increased by operative restriction of litter size

Unilateral ligation of one uterine horn of mature rats was performed to increase nutrient supply to the other horn. One week postoperative, the animals were mated. They gave birth to offspring half the normal number, which were at that time heavier, having higher cerebral weight, higher total cerebral protein and higher total amount of cerebral DNA (an index of number of cells) than the sham-operated controls. All increases were statistically significant. No such differences were observed when comparing newborn rats from litters naturally small in number with those from large litters. We suggest that the animals operated on had a potential for nourishing twice the number of fetuses that they actually produced so that each of the latter received more nutrient, with a concomitant increase in the cerebral DNA (brain cell number). Part of this increase may have been due to an increase in the number of neurons; such a neuron increment would persist throughout the life of the animal.

Survivorship of Sons Under Conditions of Improving Mortality

The strong desire of fathers to be assured that at least one son will outlive them, coupled with the traditional belief in a high probability of sons predeceasing their father, is often a deterrent to restriction of family size. A calculation of the probabilities of survivorship of sons on the basis of the United Nations Model Life Tables, however, shows that the probabilities of a father being outlived by even one son are remarkably high, particularly after that son has survived the first two years of life. When cohort tables are used, reflecting expected mortality improvements, the probabilities are even higher. In general, it is found that the probability that a two-year-old son will outlive his father is 80% or better, subject to the current mortality level and the age of the father.Finally, this paper examines (1) probabilities of a father being outlived by at least one of two or three sons, (2) probabilities of a mother or of both parents being outlived by a son, and (3) the probability that at least one of two sons will outlive a father when allowance is made for the fact that mortality probabilities of the sons are not independent of one another.

Graphite Grains and Graphite-Core-Ice-Mantle Grains

Among the First Requirements for a Grain Model is that it should explain the observed interstellar extinction law or laws as they are now understood; a desirable feature of such a model is that as few ad hoc assumptions be made as possible.A criticism of the classical ice grain theory is that a very narrow range of grain sizes (or a size distribution with a size parameter specified to within a few percent) must be postulated in order to obtain a fit with the mean extinction law. (See refs. 1 and 2.) While it is true that regional variations in the extinction law have recently been detected (refs. 3 and 4), the best available evidence indicates that the extinction law is quite uniform when averaged over individual large regions which are widely distributed in the galaxy. (See ref. 5 and paper by Nandy in the present compilation.) The restriction of particle size to a radius within a few percent of an arbitrarily specified value (r ≈ 3 X 10-5 cm) demanded on the basis of pure ice absorption is therefore considered quite unsatis-factory, particularly in view of the fact that no characteristic size parameter emerges from the Oort-van de Hulst theory for the formation and destruction of grains. (See ref. 6.)

Influence of nutritional level during pre-natal and early post-natal life on adult fleece and body characters

The effect of high and lox- levels of feed intake during pregnancy in ewes, and from birth to 4 months of age in their lambs, on adult body weight and wool production has been studied. As compared with the corresponding high intake groups, lambs from the low intake ewes were 34% smaller at birth and 9% smaller at maturity. They also had c. 15% fewer wool follicles per sheep, and produced c. 8.5% less wool as adults. Low levels of feed intake between birth and 4 months resulted in a slower growth rate and a reduction (c. 10%) in mature body weight. The maturation of the follicle population was delayed by a low feed intake in this period but no permanent reduction in numbers was observed. The post-natal low intake group produced c. 12% less wool as adults, owing to a smaller (c. 10.5%) fibre weight. The major effect on wool growth potential of low levels of nutrient supply during pre-natal life was a restriction of body size and total number of follicles, while restriction of nutrient intake during early post-natal life reduced the capacity of the individual follicles to produce fibre.

Size Distribution of Rock Types in Stream Gravel and Glacial Till

ABSTRACT Studies of alluvial gravel demonstrate that the percentage of a given rock type in the gravel varies with the size distribution of the particles in the sample. The variations are large and account for differences of 25 percent or more between lithologies of unsized samples of the same formation. Accordingly, most pebble counts of alluvial gravel should utilize restricted grade sizes determined by sieving or other methods of accurate size measurement. Studies of the coarse fraction of Kansan till from northwestern Missouri and northeastern Kansas indicate that the lithology of till also varies with the mean diameter of the particles in the sample. The variations are, however, less than one-fifth as great as the variations found in alluvial gravel. This contrast in size-lithology variation may represent a fundamental difference between till and alluvial gravel. Some restriction of grade size is desirable for pebble counts of till. Sorting by visual estimation of size is probably accurate enough for most routine descriptions of till.

A small-volume, high dose technique for the x-ray treatment of some brain tumours.

A method of applying accurately directed multiple small fields to the skull is described. The object prompting this work has been to develop a small volume—high dose treatment technique for patients with cerebral tumours to see if there are any advantages in such an individualised small field treatment technique over the more usual large field methods irradiating one or more quadrants of the brain. The use of numerous mechanical devices is described which render the method rather elaborate, but once these have been put into use it is found that they make for simplicity both mapping treatment fields and setting up for treatment. The extra trouble seems fully justified by providing restriction of field size, accuracy of aim, fixed treatment conditions, and adequate data for accurate estimation of the dose distribution.

Low voltage x-ray therapy with a beryllium window tube. I. Introduction and advantages.

X-ray therapy with a beryllium window tube enables high dose rates and control of depth penetration to be obtained without undue restriction of field size. It provides a means of administering low voltage near distance X-ray therapy and superficial therapy with advantages, e.g., in treating haemangioma in a few seconds, and in the eye and gonadal regions, where penetration is undesirable. The mode of prescription of penetration is the half value depth (H.V.D.) in tissue for convenience. The integral dose is 1/10 of 85 kV superficial X-ray therapy. Over 200 cases have been treated without radionecrosis.

EXPERIMENTAL STUDIES ON GENETICS OF FREE‐LIVING POPULATIONS OF DROSOPHILA

Summary1. The gene mutations and the chromosomal changes obtained in Drosophila under laboratory conditions have their counterparts also in free‐living populations. The fact that individuals of Drosophila found in nature are as a rule homogeneous and only rarely show striking variations is due to the majority of the mutants concealed in them being recessive to the normal or “wild‐type” condition.2. The concealed mutants can be detected either by inbreeding the offspring of wild individuals, or by more complex but more accurate genetic techniques that result in obtaining specimens homozygous for a given “wild” chromosome. As expected, the data obtained with the aid of either method are essentially similar.3. In D. melanogaster the autosomes contain not only mutants producing visible external effects but also many recessive lethals. The kind and the frequency of the mutants found is variable from population to population and from year to year.4. In free‐living populations of D. pseudoobscuru the third chromosome, and probably other autosomes as well, are infested with lethals, semi‐lethals, deleterious viability modifiers, modifiers of the development rate, visible mutants, and other genetic changes. Again, both the quality and the quantity of these changes vary from population to population.5. Knowing the frequency of allelic lethals within a population, one can compute the rate at which they must be eliminated by natural selection. This rate can be compared to that of the origin of new lethals by mutation. Theoretically, the two rates must be alike in populations at equilibrium. Actually, the supposed elimination rate is smaller than the corresponding mutation rate. This may be due either to some of the lethals not being fully recessive, or else to the population size being subject to sharp seasonal fluctuations.6. Inversions of chromosome segments are extremely common in free‐living populations of all species of Drosophila so far studied in this respect. Certain kinds of multiple inversions make it possible to establish the phylogenetic relationships of the chromosome structures involved.7. In D. pseudoobscura, D. azteca and probably in many other species each of the different structural types of the chromosomes occurs in a definite geographical region, thus giving rise to chromosomal races.8. Aside from the above “macrogeographic” variability, there exist also differences, usually of a quantitative nature, between populations inhabiting neighbouring or even contiguous localities. Moreover, the genetic composition of a population does not remain constant from year to year. This “micro‐geographic” variability is probably due to a restriction of the effective size of the breeding population in most species of Drosophila.9. A species of Zhosophila does not represent a single panmictic population, but rather a mass of local colonies that are able to pursue, within limits, different evolutionary courses. The fate of a colony is, of course, controlled by natural selection, yet selection is not the sole determiner of the population dynamics. As predicted on theoretical grounds by Wright (1931, 1932), shifts in the genetic composition of a population may be due to the limitation of its genetically effective size.