Fair Sample Research Articles

The local extragalactic velocity field, the local mean mass density, and biased galaxy formation

view Abstract Citations (39) References (16) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Local Extragalactic Velocity Field, the Local Mean Mass Density, and Biased Galaxy Formation Brown, M. E. ; Peebles, P. J. E. Abstract In this paper, a relationship is derived between the local mass density and the perturbation of the local Hubble flow. The local mass density is estimated by the method used in the Virgocentric flow. The infrared Tully-Fisher relation of Aaronson et al. (1982) is used to find limits on the gravitational perturbation to the local Hubble flow and bright galaxy counts (N) are used to estimate the local galaxy concentration. It is concluded that if mass is proportional to N, with no fluctuations, and the local mass per galaxy is a fair sample, then the density parameter is roughly 0.1, consistent with other dynamical estimates and inconsistent with the naive interpretation of biasing which accounts for the low apparent mass density derived from clustering dynamics by the assumption that the mass per galaxy is unusually low in the regions of high density where clustering has been studied. Publication: The Astrophysical Journal Pub Date: June 1987 DOI: 10.1086/165304 Bibcode: 1987ApJ...317..588B Keywords: Galactic Clusters; Galactic Evolution; Local Group (Astronomy); Mass Distribution; Space Density; Velocity Distribution; Astronomical Models; Computational Astrophysics; Red Shift; Astrophysics; COSMOLOGY; GALAXIES: CLUSTERING; GALAXIES: FORMATION; GALAXIES: REDSHIFTS full text sources ADS | data products NED (16) SIMBAD (15)

Dark matter influence on velocity dispersion profiles of clusters of galaxies

We have performed a series ofN-body experiments including the effects of a massive dominant background which follows Schuster's density law in order to simulate clusters of galaxies in which a smoothly distributed dark component is present. The existence of this background is inferred from the weak luminosity segregation observed in clusters which, however, show several characteristics of well-relaxed systems. The comparison of the velocity dispersion profiles of three clusters of galaxies (Coma, Perseus, and Virgo) with those obtained in the numerical experiments allows us to place some constraints on both the distribution and amount of distributed dark material in these clusters. The profiles are rather insensitive to variations in the ratio of the background mass to the mass attached to galaxies (Mb/Mg), but exhibit a strong dependence on their relative concentration. We conclude that highly concentrated background models are not consistent with observations. We find a maximum value for the ratio of the gravitational radius of the galaxies and the background (Rg/Rb) (approximately 0.6) and using previous results (Navarroet al., 1986) we conclude that virial theorem masses underestimate the total mass (Mb+Mg) of the clusters. As a final result, we derive a minimum value for theMb/Mg ratio. All these conclusions could apply in general if Coma, Perseus, and Virgo constitute a fair sample of the rich clusters of galaxies in the Universe.

Structure of superclusters and supercluster formation - V. Spatial correlation and voids

Galaxian spatial correlation function is calculated for various observational samples having different sample volume. It is demonstrated that the correlation length, |$r_0$|⁠, increases with sample volume. For volumes considerably smaller than the size of the Local Supercluster the correlation length is about half the conventional value, |$5h^{-1}$| Mpc, which corresponds to sizes of intermediate samples, containing the whole supercluster. Samples containing several superclusters have correlation lengths twice the conventional one. Similar calculations have been carried out for various theoretical models. Samples representing luminous matter in a neutrino-dominated universe and having different sample volumes have correlation length |$r_0$| which increases with volume until the sample size reaches the average size of voids. Further increase in the sample size does not change the correlation length, indicating that fair samples of the model universe have been reached. These calculations and simple theoretical estimates indicate that the value of the correlation length reflects the filling factor of the sample and the presence of large voids in galaxy distribution. The observed correlation function of galaxies reflects the distribution of luminous matter. After correcting for the difference between the correlation functions of true mass and galaxies, the correlation length for a fair sample of the Universe is estimated to be |$r_0=10h^{-1}$| Mpc.

Instructions for the Collection and Preservation of Botanical Specimens

In gathering plants you will do well to pay attention to all the plants you come across, whether showy or unsightly. Do not neglect the latter on account of their appearance. Collect if possible several specimens ofthe same plant, partly to show different states of the same species, and partly to be able to distribute them among different botanists. Do not be deterred from gathering what appears to be the same species at different places and seasons. It may prove not to be the very same species, but only an allied species; or even if identical it is interesting for the study of geographical botany to have the same species from distant localities. On the whole collect only such plants as you find in flower or fruit; but trees and shrubs ought to form an exception, as also smaller plants, if they afford some particular interest, either by their medicinal or other properties, great preponderance in certain districts, etc. The most important part of the plant is the flower and fruit. Get if possible such specimens as present both states, flower and fruit, or both on different specimens. You will find plants which have fertile and sterile flowers distinct, they occur either on the same plant, as in the oaks, hickories, etc., or in different plants, as in the willows, cottonwoods and others. In both cases it is important to collect specimens which show each of them. Many plants develope the leaves after the flowers, as the oaks, redbuds and many others. In these the flowers must be preserved, and later in the season, the leaves with the fruits; but great care must be taken to get them from the same species. If the specimen you obtain is not too large, gather it entire, with the root or at least with part of it, so as to show the nature of that organ. Try to have the lower as well as upper leaves complete on the specimen, especially if they should differ from each other. In case the specimen is too large for a sheet of paper, say more than 17 inches high, it may still be preserved entire, by bending or rather breaking (without entirely severing the parts) the stem in an acute angle. If necessary, this may be repeated and branches or leaves may also be treated in the same manner. This is better than cutting it in different segments, as these might become separated and much confusion ensue from this cause. Of still larger plants, shrubs, trees, it is possible to take only a part, a branch, etc.; but if there should be different leaves on the plant, it will be necessary to cut off such leaves with a small piece of stem attached, and preserve them with the other specimens. Make the specimen large enough to present a fair sample of the plant, its manner of growth, ramification etc. It will be well to put your specimens in paper as soon as gathered; their parts are then fresh and still and are easily spread out in a neat way; but if they become flaccid they present much difficulty, and the dried specimens will appear unsightly. Large specimens with thick stems or roots (bulbs especially) or even very clumsy flowers (as

The University of Limburg family practice preceptorship programme.

A six-year experience with a required preceptorship programme for fifth-year students in the Netherlands is described. After one week of introduction students spend 11 weeks with a family physician. Students prepare records of their independent contact with a patient, which are discussed with their preceptors and their faculty tutor. Analysis of the records revealed that students see a fair sample of problems presented in primary care. The programme is well accepted by students and preceptors. The importance of good relations between the school and the preceptors is stressed.

PROGNOSIS OF REFRACTIVE CORRECTIONS

The validity and efficacy of the prognosis equation published by Saunders (1984b) is tested against previously reported longitudinal data. In a fair and random sample and over a short interval, nearly 60% of the sample was found to have a prediction error of less than 0.25 DS and, in 92%, the error involved was less than 0.5 DS. Long-term prediction was found to have a less favourable outcome but 50% were correct within an error of 0.5 DS and 90% were found to have a prediction error of less than 1 DS. The largest prediction errors occur in the medium to high myopes whose myopia progresses rapidly.

Dominance, allele frequency and selection in a population ofDrosophila melanogaster

The numbers of sternopleural chaetae of 18 inbred lines derived from the Texas population ofDrosophila melanogasterwere ascertained for flies raised at each of two temperatures, 18 and 25°C. Two characters were then defined:M, the average of the chaeta numbers at the two tempera­tures; andS, half of the difference between the average chaeta numbers at the two temperatures. The inbred lines differed among themselves in both characters, so revealing genetic variation in the Texas population for them both. There was no correlation between the values ofMandSamong the lines. The mean of the inbred lines did not differ significantly from that of the progenies of 22 single-pair matings among flies taken from the population in either character, so suggesting that the 18 inbred lines provided a fair sample of the genes in the population. The differ­ences between the variances among the inbred lines, on the one hand, and the biparental progenies, on the other, suggested that dominance was present for both characters and that dominant alleles were, in general, present at higher frequencies than their recessive fellows. This was confirmed by a half-diallel experiment with 11 of the 18 inbred lines as parents. The half-diallel further showed that dominance was ambidirectional for characterS, but gave no conclusive evidence in this respect forM. The theoretical consequences of ambidirectional dominance combined with higher frequencies of dominant alleles were considered for a simple model involving four loci. This showed, in particular, that when one homozygous line (the recurrent parent) is crossed to a number of other lines (the non-recurrent parents), the amount by which the phenotype of the F1exceeds the mean of its two parents shows a regres­sion of negative slope on the phenotype of the non-recurrent parent. The regression line is expected to cut the axis of zero excess at a point that is, on average, as far away from the phenotype of maximum dominance as is the expression of the character in the recurrent parent, but in the opposite direction. The point mid-way between the recurrent parent and the inter­cept thus provides an estimate of the phenotype of maximum dominance. Estimates of the phenotypes of maximum dominance were obtained in this way for both characters,MandS, by means of data from the half-diallel and from a further experiment carried out for the purpose. For characterM, the phenotype of maximum dominance does not depart significantly from the mean of the inbreds or from that of the Texas population itself; but, forS, though close to the means, it is significantly higher than them. It is concluded that this type of genetical architecture is to be expected with characters under stabilizing selection and that the phenotype of maximum dominance is the optimal phenotype towards which the selection has been acting.

Multistate Demography and its Data: A Comment

Much of sociology and practically all of demography deal with transitions of people from one state at a certain moment to another state a year or more later. It is now clear that all such calculations of transition or movement are formally identical with what may be called the basic migration problem. The arithmetic for handling people moving from the single to the married state is identical with that for them moving from New York to Pennsylvania. The papers in this issue cover a wide range of substantive problems and exemplify several points concerning the methodology of demography. They provide a fair sample of multidimensional theory, of the means of application to data, and of the results of that application. They demonstrate the advantage of incorporating several demographic processes in a single model, even though they leave some questions unanswered.

Color Vision Deficiencies in American Youths

<h3>To the Editor.</h3> —In the course of the third program of the US National Health Survey,¹the opportunity was taken to estimate incidence of color vision deficiency in a specially selected group, designed to be a fair sample of youths between the ages of 12 and 17 years. Taking into account age, sex, race, family income, geographic region, and population size of place of residence, a stratified probability sample in each of five successive stages was taken; details of the method are given in an appendix.¹The object of the study was to determine factors of physical and intellectual growth and development. Color vision testing was performed in the total sample by means of a selection of seven Ishihara plates, as suggested by Sloan and Habel.²Those failing any of the Ishihara plate tests were then screened with the American Optical Company (AOC)³and Hardy-Rand-Rittler (HRR)

Statistical Analysis of Catalogs of Extragalactic Objects. III. The Shane-Wirtanen and Zwicky Catalogs

Statistical investigation of clustering in the galaxy catalogs compiled by Zwicki et al. (1961-1968) and Shane and Wirtanen (1967). The covariance and power spectrum of the angular distributions are estimated. The space region surveyed in the Zwicki catalog is found to represent a 'fair sample of the universe' in that the statistical nature of the clustering in this catalog is found to be mirrored at smaller angular scales in the deeper survey of Shane and Wirtanen.

A kinetic approach to the study of absorption of solutes by isolated perfused small intestine.

1. A new technique has been developed for making serial measurements of water and solute absorption from the lumen of isolated small intestine.2. The isolated intestine is perfused in a single pass with a segmented flow of slugs of liquid separated by bubbles of oxygen-carbon dioxide mixture. Simultaneous collections are made of effluent from the lumen and of the fluid which is transported across the mucosa. This latter fluid appears to be a fair sample of the tissue fluid.3. Conditions in the lumen can be changed within less than 5 min. The effects of two or more treatments applied to the same segment of intestine can be determined and the time course of a change in luminal conditions.4. The rate of appearance of solutes on the serosal side depends on the rate of water absorption, and changes exponentially towards a steady state. The rate constant is a function of tissue fluid volume.5. In the steady state the concentration of glucose in the tissue fluid is 71 mM when the luminal concentration is 28 mM, and is 45 mM when the luminal concentration is 8.3 mM.6. For solutes such as glucose for which reflux from tissue fluid to lumen is small relative to flux from lumen to tissue fluid, the time of attainment of a steady state in secretion is usually 50-60 min.7. For solutes such as sodium for which the reflux is relatively high, the steady state may be reached in 15-20 min.8. The K(m) for glucose absorption (14-19 mM) is much lower than is found with unsegmented flow perfusion.9. These findings emphasize problems in interpreting results from other types of intestinal preparation.10. The rate of glucose absorption from the lumen falls only gradually when the luminal sodium concentration is reduced abruptly. In contrast the rate of glucose absorption falls suddenly when the luminal glucose concentration is reduced abruptly. This suggests that glucose absorption is not directly dependent on luminal sodium ions.

Russian journals dealing with the Middle East

Some of the more important Soviet research on the Middle East is published, obviously, not as monographs, but as articles. Some of these appear in special collections on a given subject, frequently based on teamwork or on the proceedings of a conference at one or another of the centres of higher learning. Many of these bring together a fair sample of the best in Russian research on the Middle East. Several examples have been mentioned in Middle Eastern Studies, VI (2), May 1970, pp. 212-13, and VI (3), October 1970, pp. 346-49. Many articles of interest for the student of the Middle East are published in Russian-language journals, not confined to Oriental Studies, but specializing in history, politics, economics, ethnography, linguistics or literature. Many of these articles are not easy to spot, unless and until listed in a bibliography. Therefore, the several Russian journals specializing in Oriental studies are of more immediate relevance to the scholar who wants to keep abreast of Soviet research on the Muslim Middle East, both medieval and modem. Four of these are in hand; the first two are periodicals, while the other two are published occasionally, with no obvious pattern of irregularity. Narody Azii i Afriki (The Peoples of Asia and Africa) is the more scholarly of the two periodicals. It is published in Moscow by the Institute of Orientalism and the Institute of Africa, both affiliated to the Soviet Academy of Sciences. It has been appearing since 1960, when it replaced another periodical, Sovetskoye Vostokovedeniye (Soviet Orientalism). This had ceased publication at the end of 1958 and was followed, during 1959 only, by Problemy Vostokovedeniya (Problems of Orientalism). Narody Azii i Afriki, like its two predecessors, appears bimonthly. Each issue comprises between 240 and 260 pages in 80, and costs 1.60 roubles-rather prohibitive for the general public. But then it is hardly meant for the average reader-rather for the Orientalist community in the Soviet Union and abroad. For the benefit of the latter, the editors include English summaries of the major articles, and tables of contents in English and French. Until the end of 1967 there was a table of contents in Chinese too, but this was discontinued, probably because the number of readers in China was not large enough to justify it. The articles are usually divided into the following sections: economics and politics, history, culture and language. These are followed by shorter notes, review articles, book reviews and bibliographical notes. Personalia and scholarly events (i.e. reports of conferences and meetings in the Soviet Union and abroad) are the last sections. Some issues also include letters to the Editor. In this manner, the contents are not only varied, but broad in scope. While they practically always publish the results of research done only in the Soviet Union and the Eastern Bloc-and, almost without exception, all contributors live there-the book reviews and bibliography include a sizeable share of works published elsewhere. The articles, although following a more or less rigid Marxist approach, cover the whole span of oriental studies, topically and geographically; they are generally long, amply footnoted pieces of research by both reputable scholars and promising doctoral candidates. While many articles deal with India, South-east Asia and sub-Saharan Africa, students of the Middle East and the Maghreb will find much of interest. Recent issues, during 1970, included articles on subjects such as: The new economic

The Importance of Being Repetitious

N many activities-advertising, political campaigns, psychological conditioning, programmed learning, the Chinese water torture-repetition commands considerable respect. In expository writing, however, if the undergraduate and graduate students I have had in the past twenty years are a fair sample, it commands about the same respect as a streetwalker, and for somewhat the same reason: the conviction that the writer has no other resources. Since this con-

5 Structure of the Site Defined by the Cultural Features and Correlation with the Surface Distribution of Cultural Items

It has previously been argued (Binford 1964) that because of the differences in the formal properties of cultural items (as distinguished from cultural features) that there are different problems associated with obtaining an adequate and representative sample of both items and features. Excavation and recovery techniques which might be adequate to the recovery of a fair sample of cultural items might not be sufficient for supplying similar information regarding a population of cultural features.The investigation of Hatchery West was conducted with an eye to this problem, and the methods employed were aimed toward insuring an adequate and representative sample of both cultural items and cultural features. These sampling procedures allowed us to investigate the relationship between these two classes of archaeological data and to assess the degree to which the formal-spatial structure of a population of items is correlated with the formal-spatial structure of a population of features.

Helium abundance in the solar wind

Observations of hydrogen and helium ions in the solar wind have been carried out by the Goddard Space Flight Center - University of Maryland plasma instrument on Explorer 34. These ions are completely separated by means of electrostatic and magnetic fields. The average value of the ratio of number densities is 0.051 ± .02, derived from over 3000 h of measurement. Variations about this value from about 0.01 up to greater than 0.15 occur, and there are more high values than can be explained by random variation. A tentative association with some geomagnetic storms is suggested. The above value of abundance, assuming that plasma emitted in the ecliptic plane is a fair sample of the output of the sun, combined with other recent work by other methods indicate that the solar abundance may be about half the previously quoted estimates of approximately 0.1.

MATING SELECTION IN THE CALIFORNIA OAK MOTH (LEPIDOPTERA, DIOPTIDAE).

The quantitative estimation of the components of natural selection, readily feasible in the laboratory, meets with obvious obstacles in studies of natural populations. Mating fitness under natural conditions has been a component which has been especially difficult to approach, owing to the requirements that the populations be large and that mating activity be readily observable and unlikely to be interfered with by the activities of the investigator. Among insect populations, such conditions occasionally arise. In the San Francisco Bay Area, the California Oak Moth, Phryganidia californica, sometimes reaches extremely high population levels, the larvae often defoliating the oaks on which they feed. Large numbers of adult individuals, including many mating pairs, can be collected in very small areas during times of maximum outbreak (such as June, 1965, when the present study was done). Mating (i.e., actual copulation, as opposed to a looser pair-bond relationship) lasts for substantial periods, at least as long as several hours in some cases. By comparing the characteristics of mating individuals with characteristics of those not found mating, estimates can be made of the mating fitnesses of various phenotypes. We must assume only that those insects mating at the time of collection represent a fair sample of the individuals which are fit for mating, i.e., that the likelihood that an individual with a given phenotype will be found mating is a direct function of the capacity for mating associated with that phenotype, and so presumably its likelihood of contributing to subsequent generations. An additional convenient feature of populations of this species makes it possible to gain a measure of insight into the behavioral mechanism by which the selection operates. As is usual among Lepidoptera, males begin to emerge a few days earlier than females, and so a good number of matings involve teneral (i.e., newlyemerged and relatively inactive) females. If teneral females are less able to reject an unsuitable male (and are therefore less able to influence the relative success of male phenotypes), a larger proportion of males ought to be able to mate when most of the females present are teneral. In this study, the following two hypotheses will be examined: (1) That in nature, different phenotypes have measurably different success in mating. (2) That the response of females to the approach of males of differing phenotypes contributes to this difference in fitnesses in the males.

Protein, enzyme, and isoenzyme distribution in human serum fractions obtained by ultracentrifugation

We have described the protein, enzyme, and isoenzyme characteristics of three gross fractions of both normal and abnormal human sera, as obtained by application of high centrifugal force. In the absence of solution gradient, such fractions represent pure and undiluted elements of the serum; they are reproducible and sufficiently voluminous for extensive analytical study. Specific features of these fractions may be of interest in planning additional or peripheral investigations of serum. Fraction I appears to be a fair sample of native serum water; Fraction II appears to segregate the pre-β-globulin lipoprotein component observed in some sera; Fraction III is a concentrated solution of LDH, CPK, and SGOT enzymes, and γ-globulin-rich protein, which is hpoprotein-free. More than 95% of the LDH, CPK, and SGOT is located in Fractions II and III. Quantitative activity and qualitative nature of these enzymes appears to survive the stress of the ultracentrifuge technique relatively well.

Soil Animals as Vectors of Organochlorine Insecticides for Ground-Feeding Birds

The uptake of small sublethal doses of organochlorine pesticides by birds appears now to be quite a common phenomenon, but the pathways have been, for the most part, little examined. This paper discusses some of the ecological factors affecting the uptake and passage of organochlorine compounds in terrestrial ecosystems with particular reference to soil animals and ground-feeding birds such as the Robin (Erithacus rubecula), Skylark (Alauda arvensis), Lapwing (Vanellus vanellus), Starling (Sturnus vulgaris), thrushes (Turdus spp.) and corvids (Corvus spp.) for which animals form a large fraction of the diet. Blackbird (Turdus merula) and the Kestrel (Falco tinnunculus), both of which take large numbers of invertebrates, though the Blackbird is an omnivore with a partiality for fruit and the Kestrel a raptor feeding largely on small mammals. The ppm intervals chosen follow approximately a log scale which is rounded to the nearest convenient figures. The two species cannot be compared in detail since liver alone was used for analysis of the Kestrels and mixed viscera, which consisted of liver, heart and spleen (and possibly gut in some instances), in the Blackbirds. Both species came from a large number of counties but as the birds were generally found dead and the cause of death unknown neither set can be assumed to be a fair sample of the population. However, several features can be deduced. First, that both species had picked up residues of all the common organochlor- ine pesticides used in this country and secondly, apparently in contrast to the American situation, dieldrin and heptachlor epoxide residues are commonly present. DDT itself features very insignificantly but the preponderance of DDE indicates a large original DDT source. The relatively high amounts of heptachlor epoxide and low amounts of BHC contrast with the annual depositions of these compounds (see Strickland 1965) and reflect probably the biased nature of the samples as well as the known properties of relative persistence of these compounds in biological tissues.

The Ethical Functions of the Novel

Previous articleNext article No AccessDiscussionThe Ethical Functions of the NovelWilliam ToddWilliam Todd Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by Ethics Volume 75, Number 3Apr., 1965 Article DOIhttps://doi.org/10.1086/291544 Views: 6Total views on this site Copyright 1965 University of Chicago PressPDF download Crossref reports no articles citing this article.

How Do the Genetic Loads Affect the Fitness of Their Carriers in Drosophila Populations?

Most individuals in natural populations of Drosophila carry one or more chromosomes which are lethal, semilethal, subvital, or otherwise injurious in double dose (in homozygous condition). Attempts to find out what effects such chromosomes have in heterozygous carriers have given, as a review of the literature shows, apparently conflicting results. The conflicts are mostly resolved if one realizes that the genetic variants which persist in natural populations are not a fair sample of those arising by mutation. Natural selection tends to eliminate the variants that reduce the fitness of heterozygous carriers, and to conserve the quasi-neutral and useful ones. It is suggested that the genetic diversity in populations can be divided in the categories of adaptive norm, genetic load and the genetic elite. The adaptive norm lies within two standard deviations on either side of the mean fitness of individuals observed in a population under panmixia or whatever other breeding system the population has followed in its evolution. The genetic load and the genetic elite lie respectively below and above two standard deviations from the mean fitness.