Showing papers by "University of North Carolina at Chapel Hill published in 1977"

An Algorithm for Finding Best Matches in Logarithmic Expected Time

Abstract: An algorithm and data structure are presented for searching a file containing N records, each described by k real valued keys, for the m closest matches or nearest neighbors to a given query record. The computation required to organize the file is proportional to kNlogN. The expected number of records examined in each search is independent of the file size. The expected computation to perform each search is proportional to logN. Empirical evidence suggests that except for very small files, this algorithm is considerably faster than other methods.

Nonmetric individual differences multidimensional scaling: An alternating least squares method with optimal scaling features.

Abstract: A new procedure is discussed which fits either the weighted or simple Euclidian model to data that may (a) be defined at either the nominal, ordinal, interval or ratio levels of measurement; (b) have missing observations; (c) be symmetric or asymmetric; (d) be conditional or unconditional; (e) be replicated or unreplicated; and (f) be continuous or discrete. Various special cases of the procedure include the most commonly used individual differences multidimensional scaling models, the familiar nonmetric multidimensional scaling model, and several other previously undiscussed variants. The procedure optimizes the fit of the model directly to the data (not to scalar products determined from the data) by an alternating least squares procedure which is convergent, very quick, and relatively free from local minimum problems. The procedure is evaluated via both Monte Carlo and empirical data. It is found to be robust in the face of measurement error, capable of recovering the true underlying configuration in the Monte Carlo situation, and capable of obtaining structures equivalent to those obtained by other less general procedures in the empirical situation.

Bias due to misclassification in the estimation of relative risk.

Abstract: Lack of bias in the estimation of relative effect in epidemiologic studies depends on the internal validity of the study. This paper conveys in graphic and tabular form the direction and magnitude of bias due to misclassification of study subjects. A series of computer-generated graphs shows that the departure of the estimate of effect (relative risk or odds ratio) from its true value is a function of sensitivity and specificity (measures of classification validity), disease frequency, and exposure frequency. The discussion of bias emphasizes misclassification of the "outcome" variable; i.e., disease occurrence in a cohort study and exposure rate in a case-control study. Examples are used to illustrate that the magnitude of the bias can be large under circumstances which occur readily in epidemiologic research. When misclassification is equal for the two compared groups, the estimate is biased toward the null value, and in some instances beyond; when differential misclassification occurs (as in selective recall in case-control studies) the bias can be in either direction, and may be great. Formulas are derived to estimate the underlying true value of the relative risk or odds ratio using the investigator's observations together with the estimated sensitivity and specificity of the classification procedure.

A new specific, sensitive and non-carcinogenic reagent for the demonstration of horseradish peroxidase

Abstract: 3,3'-Diaminobenzidine (DAB), introduced by Graham & Karnovsky (J. Histochem. Cytochem. 1966, 14, 291 & J. exp. Med. 1966, 124, 1123) is one of the most widely employed reagents in histochemistry. It has been very useful in demonstrating the sites to which the exogenous ultrastructural tracer horseradish peroxidase (HRP) is transported in vertebrate tissues. Over the past five years, DAB staining of transported HRP in neurons has developed into a powerful neuroanatomical tool for labelling the cells of origin of pathways in the central nervous system (La Vail, 1975, in: The use o f axonal transport for studies o f neuronal connectivity (eds. W. M. Cowan & M. Cuenod), pp. 217-248. Amsterdam: Elsevier.). Reports of the borderline carcinogenicity of DAB in rats (Griswold, Casey, Weisburger & Weisburger, Cancer Res. 1968, 28,924) may be responsible for the decreased availability of good quality DAB. Recent studies (Hanker, Anderson & Bloom, Science 1972, 175, 991; Hanker & Rabin, J. clin. Mierobiol. 1975, 2, 463) suggested that oxidative coupling reactions of aromatic amines in the presence of phenols might provide a suitable substitute for DAB. Some of these reactions yield deeply-coloured synthetic melanin-like compounds which are osmiophilic and sufficiently insoluble to be suitable end-products for histochemistry. In addition, the reaction must be sufficiently rapid to deposit the end-product at the sites of the plant hydroperoxidase alone. Such a reaction was realized when it was found that the peroxidation of p-phenylenediamine (PPD) was greatly accelerated by the presence of pyrocatechol (PC). The co-polymer formed as a result of this oxidative coupling reaction was osmiophilic and was bluer than oxidized DAB. It was insoluble and conformed well to biological ultrastructure. Neither PPD nor PC used individually gave satisfactory results and the best results were obtained when a mixture of 1 part (by weight) PPD to 2 parts PC was employed as the reagent. The administration of HRP and fixation of tissue for studies in mice, other than those involving axonal transport, were carried out according to Graham & Karnovsky (J. Histochem. Cytochem. 1966, 14, 291 &J. exp. Med. 1966, 124, 1123). For the demonstration of retrograde axonal transport in cats, rats, and rhesus monkeys, 30% HRP (Boehringer) in distilled water was injected into the sensorimotor cortex, or the ventrobasal complex of the thalamus (VB injection) or in the cerebellar cortex. The volume of HRP solution injected varied from 0.05 to 2/al. The animals were perfused with a mixture of 0.5% (para)formaldehyde and 2.5% glutaraldehyde in 0. t M phosphate buffer, pH 7.2. Tissue blocks (brain) were excised and immersed in 30% sucrose in 0.1 M phosphate buffer (pH 7.2) immediately after the perfusion. Cryostat or Vibratome* sections of mouse tissues were cut at 10-20/~m. Frozen sections of the rat, cat or monkey brains were cut at 40/2m.

A general methodology for the analysis of experiments with repeated measurement of categorical data.

Abstract: This paper is concerned with the analysis of multivariate categorical data which are obtained from repeated measurement experiments. An expository discussion of pertinent hypotheses for such situations is given, and appropriate test statistics are developed through the application of weighted least squares methods. Special consideration is given to computational problems associated with the manipulation of large tables including the treatment of empty cells. Three applications of the methodology are provided.

Family History and The Life Course.

Abstract: *Glen Elder is Professor of Sociology at the University of North Carolina and Fellow at the Boys Town Center for the Study of Youth Development. His work Children of the Great Depression was published in 1974. At present he is doing research on four generations of families (1870-1970), based on data collected at the Institute of Human Development, University of California at Berkeley. Change within families over the life course has been documented by studies since the turn of the century, in particular the sequential change in family relationships, adaptive options, and material welfare that occurs through the addition, aging, and loss of members. Rowntree’s study of York, England (1901) is generally acknowledged as the earliest antecedent of research in the family cycle tradition, most of which has been carried out since 1955.

A guide to the Burr type XII distributions

Abstract: SUMMARY A set of families of distributions which might be useful for fitting data was described by Burr (1942). Special attention was focused on the family, Type XII, with generic distribution function 1- (1 + Xc)-k (X > 0) which yields a wide range of values of skewness, 1fl1, and kurtosis, fi2. The area in the (Ifi1, /2) plane corresponding to the Type XIT distributions is derived and presented in two figures. 1. INTRODIUCTION Suppose that Z is a positive random variable with probability density function

Androgen concentration in motor neurons of cranial nerves and spinal cord

Abstract: After injection of [3H]dihydrotestosterone, a major testosterone metabolite, radioactivity is concentrated in nuclei of certain cells in the midbrain, pons, medulla oblongata, cerebellum, and spinal cord. While there is some overlap between androgen and estrogen target neuron distribution, certain motor neurons appear to be selectively labeled by androgen; in contrast, estrogen localization prevails in sensory neurons. These results may help to explain why male sexual behavior in some rodents is not fully activated with dihydrotestosterone alone but in addition requires estradiol, a testosterone metabolite.

An Efficient Branch and Bound Algorithm for the Capacitated Warehouse Location Problem

Abstract: This paper describes an efficient solution procedure for the warehouse location problem in which limitations on the amount of goods which can be handled are also imposed. The proposed branch-and-bound solution method is made efficient by developing dominance, lower and upper bounding procedures and branch and node selection rules utilizing the special structure of this problem. Computational results are provided for large sized problems.

Competitive Organization of the Soft-Bottom Macrobenthic Communities of Southern California Lagoons

Abstract: The sandy-bottom macrobenthic community of Mugu Lagoon, a relatively pristine southern California (USA) marine lagoon, demonstrated (1) nearly constant community composition over 37 months of observation, (2) relatively little temporal variability in the population densities of the most abundant species over 37 months, and (3) a pattern of depth stratification in which very little vertical overlap existed among the six most abundant species. The only two species whose vertical distributions overlapped broadly showed horizontal spatial segregation, each abundant in different areas within the sand habitat. These community characteristics imply the importance of biological factors in structuring the sand benthos. The relatively large volume required for living space by these macrofauna suggests that competition for space may be the biological factor most important in determining the observed temporal and spatial abundance patterns. The muddy-sand community and the mud community of Mugu Lagoon also revealed similar patterns of stratification: new abundant species replaced species at the same sedimentary level while not greatly affecting species populations at other non-overlapping levels. In the sand community of Tijuana Slough, two of the abundant species of Mugu Lagoon's sand community were nearly absent as an apparent result of human over-exploitation. Probably in response, densities of species living at the sedimentary levels normally occupied by the missing species were much higher than would be predicted if competition for space were unimportant. In field experiments, removal of the deposit feeder Callianassa californiensis resulted in high recruitment of Sanguinolaria nuttallii, whereas control areas showed no S. nuttallii recruitment. Experiments also suggest that negative intraspecific interactions between Cryptomya californica individuals may explain the observed rapid emigration from areas of artificially high density. Perhaps the relatively great environmental predictability of southern California lagoons has permitted competitive interactions to play a singnificant role in determining the temporal and spatial abundance patterns of the soft-bottom macrobenthos.

Surface parasitism by Mycoplasma pneumoniae of respiratory epithelium.

Abstract: Identification of the attachment factor on virulent Mycoplasma pneumoniae organisms which permits surface parasitism of respiratory epithelium was attempted. Brief pretreatment of M. pneumoniae monolayers with protease prevented mycoplasma attachment ot sensitive host cells without reducing viability of the microorganisms. Gel electrophoretic analysis of mycoplasma proteins before and after exposure of intact mycoplasmas to protease revealed the absence of a major protein species (P1) in enzyme-treated preparations while other protein bands with the exception of P2 were virtually unaffected. The absence of P1 correlated with the failure of enzyme-treated mycoplasmas to attach to tracheal explants. P1 regeneration after protease treatment of mycoplasma monolayers was directly associated with reattachment capabilities in M. pneumoniae. Erythromycin inhibited P1 resynthesis, thus preventing resumed attachment activity by mycoplasmas. Lactoperoxidase-catalyzed iodination of intact M. pneumoniae organisms further confirmed that P1 was an external membrane protein and suggested that his surface component was required for the successful membrane-membrane interaction between host and parasite.

Sesquiterpene antitumor agents: inhibitors of cellular metabolism

Abstract: Helenalin and tenulin injected into CF1 male mice bearing Ehrlich ascites tumors inhibit DNA synthesis and DNA polymerase enzymatic activity in the tumor cells. Helenalin inhibited protein synthesis. Both drugs increased the concentration of adenosine 3',5'-monophosphate, and interfered with glycolytic and mitochondrial energy processes. Cholesterol synthesis was also inhibited, resulting in lower serum cholesterol levels in tumor-bearing animals. Data obtained in vitro indicate that the cyclopentenone-bearing sesquiterpene lactone and related compounds do not alkylate puring bases of nucleic acids but rather undergo a Michael-type addition reaction with the sulfhydryl groups of reduced glutathione and l-cysteine. Thus, the inhibition of cellular enzyme activities and metabolism that has been observed with these drugs might be explained by the occurrence of a Michael-type teaction.

The cytogenetics of Neurospora.

Abstract: Publisher Summary This chapter concerns genetically significant aspects of Neurospora cytology, and the relation between genes and chromosomes, with special emphasis on chromosome rearrangements. In addition to reviewing the published literature, numerous results have been presented. Many of these are cytological, appearing under various headings. The chapter is also concerned with the morphology and identification of individual chromosomes. New genetic results concerning chromosome rearrangements and general characteristics of aberrations are given and a brief description of each known rearrangement has been provided. The chapter also deals briefly with other topics such as accessory, the genetic control of recombination, and the cytoplasmic genome. Neurospora possesses several favorable features compared to the more conventional organisms that are used in cytogenetic research, and these, in part, compensate for the small size of its chromosomes. All four products of individual meioses survive. Progeny can be obtained either as random meiotic products, as unordered tetrads, or as ordered tetrads whose linear spore arrangement reflects the events of meiosis. The spores show high viability and germination. The vegetative (somatic) part of the life cycle is haploid. Duplications are more readily identified as partial diploids against a haploid background than as partial triploids against a diploid background. Somatic variants can be obtained in pure culture. Any somatic cell can serve as a germ cell. For Aspergillus, only a few rearrangements have been recognized in other eukaryotic microorganisms, where usually they are more difficult to detect than in Neurospora, with its pigmented spores. Failure to recognize an existing rearrangement can lead to spurious conclusions regarding linkage, recombination, interference, preferential segregation, or the presence of synthetic lethal genes.

Analysis of the disruption in hypothalamic-pituitary regulation in rats treated neonatally with monosodium L-glutamate (MSG): evidence for the involvement of tuberoinfundibular cholinergic and dopaminergic systems in neuroendocrine regulation.

Abstract: Adult rats which have received monosodium-L-glutamate (MSG) (4 mg/g body weight) on alternate days for the first ten days of life acquire neurotoxic lesions of the retina and arcuate nucleus and manifest an endocrine deficiency syndrome characterized by stunted growth, obesity, hypothyroidism, hypogonadism and pituitary atrophy. In the present study, the biochemical basis for the MSG-induced endocrine dysfunction has been examined and the findings of note are as follows: normal serum levels of TSH and LH despite hypothyroidism and gonadal atrophy, and significantly reduced serum GH levels in both males and females; elevated serum PRL levels in males, but not females; normal or augmented pituitary release of LH and TSH to exogenous LHRH and TRH. Within the central nervous system: a normal diurnal rhythm of pineal N-acetyltransferase activity despite optic atrophy; normal concentrations of LHRH, TRH and somatostatin within the medial basal hypothalamus; normal concentrations of norepinephrine (NE), choline ...

Some Properties of Tests for Specification Error in a Linear Regression Model

Abstract: This article considers the test reset which is intended to detect a nonzero mean of the disturbance in a linear regression model. Analysis of an approximation to the test statistic's distribution and Monte Carlo experiments reveal that the power of the test may decline as the size of the disturbance mean increases. However, the possibility is remote and declines with increasing sample size. Alternative sets of test variables are considered, and their effect on the power of the test is studied in Monte Carlo experiments. The best set seems to be composed of powers of the explanatory variables.

Electron centers in single-crystal Al 2 O 3

Abstract: The two prominent absorption bands centered at 6.1 and 4.8 eV in neutron-bombarded ${\mathrm{Al}}_{2}$${\mathrm{O}}_{3}$ single crystals have been investigated. Optical excitation into the 6.1 eV causes growth of bands at 5.4, 4.8, and 4.1 eV, whereas excitation into these latter bands causes growth of the 6.1-eV band. The oscillator strength of the 4.8-eV band was found to be in the range 0.5-1 as compared to a value nearly twice that for the 6.1-eV band. Excitation with 4.8-eV light produces an emission band at 3.75 eV and the yield and polarization of this emission as a function of the polarization of the exciting light was studied. This polarization behavior together with previous theoretical calculations is consistent with an assignment of the 4.8-eV band to the transition of the ${F}^{+}$ center. The oscillator strength ratio and the reciprocal relationship between the 4.8-eV band and the 6.1-eV band strongly indicate that the latter is associated with the $F$ center.

The heart: a target organ for estradiol

Abstract: Autoradiographic studies of rat heart reveal that tritiated estradiol concentrates in cell nuclei of the myocardium of the atria and auricles, similar to the myometrium of the uterus. This suggests that estrogen has a direct effect on atrial myocytes through which its "protective" action may be mediated. Cardiac glycosides that are known to exert estrogen-like effects on classical estrogen target tissues, such as uterine muscle, endometrium, vagina, and mammary gland, probably act on atrial muscle through a genomic, steroid hormone-like mechanism of action.

Long-Term Prognosis of Mitral-Valve Prolapse

Abstract: We examined the natural history of mitral-valve prolapse in 53 patients who had had a midsystolic click or late systolic murmur (or both) documented phonocardiographically a mean of 13.7 years earlier. Thirty-eight patients were alive without serious complications, and seven had died of unrelated causes. In two patients prolapse was implicated in the cause of death. Other complications were ventricular fibrillation in one patient and bacterial endocarditis in three. Progressive mitral regurgitation developed in five patients, requiring valve replacement in two. These complications occurred in a total of eight patients (15 per cent), and were significantly (P = 0.15) associated with a late systolic murmur rather than an isolated midsystolic click. Thus it appears that the diagnosis of mitral-valve prolapse should not be regarded as ominous; however, patients in whom this diagnosis is associated with a late systolic murmur should be followed carefully.

Some determinants of the reinforcing and punishing effects of timeout

Abstract: Some determinants of the reinforcing and punishing properties of timeout were investigated in two experiments. Experiment I began as an attempt to reduce the frequency of tantrums in a 6-yr-old autistic girl by using timeout. Unexpectedly, the result was a substantial increase in the frequency of tantrums. Using a reversal design, subsequent manipulations showed that the opportunity to engage in self-stimulatory behavior during the timeout period was largely responsible for the increase in tantrums. Experiment II was initiated following the failure of timeout to reduce the spitting and self-injurious behavior of a 16-yr-old retarded boy. Using a multiple-baseline design, the nature of the timein environment was shown to be an important determinant of the effects of timeout. When the timein environment was "enriched", timeout was effective as a punisher. A conception of timeout in terms of the relative reinforcing properties of timein and timeout and their clinical implications are discussed.

Mass-length ratio of fibrin fibers from gel permeation and light scattering.

Abstract: Mass–length ratios of fibers in fibrin gels were obtained from measurements of the angular dependence of the intensity of light scattered by dilute gels and from the permeability of more concentrated gels. The permeability was determined by measuring the forced flow of buffer through a short column of gel held in a glass tube. The results obtained with the two methods are consistent. At high pH and high ionic strength the mass–length ratio is found to be that calculated for a protofibril, i.e., a double strand of fibrin molecules laid end to end at a separation of 450 A. This same value is found under conditions where the polymerized fibrin is not gelled (pH 10.25) and where it is just gelled (pH 10.0). At pH 7.4, ionic strength 0.35, the fibers are found to have a higher mass–length ratio, the average fiber consisting of some three protofibrils associated laterally. At pH 7.4 and low ionic strength (0.10 M) the fibers are up to a hundred times more massive.

Collagen Cross-Linking Alterations in Joint Contractures: Changes in the Reducible Cross-Links in Periarticular Connective Tissue Collagen After Nine Weeks of Immobilization

Abstract: A significant increase in the NaBH4 reducible intermolecular cross-links in the 9 week immobilized rabbit periarticular connective tissue was found. Dihydroxylysinonorleucine, hydroxylysinonorleucine, and histidinohydroxymerodesmosine were the major cross-links which increased during the period of immobilization. No change in the hydroxlysine/lysine ratio between the immobilized and control periarticular connective tissue collagen was detected during the 9 weeks of enforced immobilization of the rabbit knee. Since the collagen mass in the immobilized periarticular connective tissue does not change, or at most is reduced 10%, we suggest that there is an increase in collagen cross-links expressed both in per unit weight of collagen and on the basis of collagen mass per knee due to the lack of physical stress and motion.

Influence of life events and family routines on childhood respiratory tract illness

Abstract: Respiratory illnesses account for nearly two thirds of the total illness in a community,1 account for as much as 40% of the problems seen in a pediatric practice,2,3 and are responsible for over one third of school absences.4 Despite major advances in the microbiology of respiratory disease, why and how a child becomes ill remain poorly understood. In over half of respiratory illnesses, complete cultures fail to yield an etiologic agent.5 Conversely, 30% of a school-age population can harbor group A streptococci without developing symptoms,6 three quarters of preschool children infected with Mycoplasma pneumoniae remain asymptomatic,7 and as many as 42% of upper respiratory tract cultures from well children yield pneumococci.8 Furthermore, there is no satisfactory explanation for the observation that certain children are predisposed to more frequent or more severe respiratory illnesses.9 The limited ability of microbiologic data to account for clinical experience has increased interest in studying the influence of social factors upon childhood disease. The family is undoubtedly the most important social context in which illness occurs, and many studies have documented the link between pediatric disease and family dynamics.10-18 Meyer and Haggerty reported a strong relationship between patterns of streptococcal illness and the degree of chronic family stress.19 Another group of observers found an accumulation of major family life events in the year preceding general pediatric hospitalizations.20 Others have demonstrated the prevalence of psychosocial problems in the families of children with repeated accidents and ingestions of poisons.21,22 There has, however, been little study of the general relationship between social environment and respiratory illness in children.

Testing for Hardy-Weinberg equilibrium in small samples

Abstract: An investigation is made of the validity of several statistics to test whether a small sample comes from a population having the binomial proportions p2AA, 2pqAa, q2aa, where q = I p. In particular the significance levels (P-values) indicated by these tests are compared to those of a well-known exact test (Haldane 1954). It is found that, for sample sizes of 20 or greater and significance level 0.15 or less for the exact test, a useful approximation to the significance level is obtained when the X2-statistic, with Yates' correction, is averaged with a similar statistic that used conditional expectations, and the result referred to the x2-distribution. For other situations, or for greater accuracy, a recursive relation is given that reduces the amount of computation necessary to determine the exact significance level.

Validation of Discriminant Analysis in Marketing Research

Abstract: The validation problems inherent in small-sample discriminant analysis are examined. Two recently developed alternatives to the more traditional methods are explained and illustrated in the context...

Replication of EBV in epithelial cells during infectious mononucleosis

Abstract: INFECTIOUS mononucleosis is caused by primary infection with the Epstein–Barr virus (EBV)1,2. This virus is generally held to be trophic for B lymphocytes3–6, but only latently infected cells expressing a nuclear antigen (EBNA)7 have been found among circulating lymphocytes during infectious mononucleosis8. In spite of this, EBV is present in the orophoryngeal secretions of most patients with infectious mononucleosis, and virus continues to be shed in many normal persons for extended periods9,10. The source of this virus, a cell type which freely permits replication of EBV, has never been identified. An intriguing link has recently been advanced between EBV and the malignant epithelial cells of undifferentiated carcinoma of the nasopharynx. Patients with this malignancy maintain high titres of antibodies to the virus11. The tumour itself, which consists of malignant epithelial cells with many infiltrating lymphocytes, contains the EBV genome12. The EBV genetic material is in the malignant epithelial cells13,14, however, and not in the infiltrating lymphocytes which are predominantly T cells. Although superinfection of nasopharyngeal carcinoma cells with EBV leads to the expression of specific early viral antigens15, these cells, like B lymphocytes, are only latently infected in vivo. The primary cell type infected by EBV probably occupies a pivotal position in the pathogenesis of both infectious mononucleosis and nasopharyngeal carcinoma. We report here evidence directly from human material that EBV replicates in epithelial cells of the oropharynx.

ESCA Study of Polymer Surfaces Treated by Plasma

Abstract: Surfaces of polymers [polyethylene, polystyrene, poly(ethylene terephthalate), poly(oxymethylene), cellulose acetate, polyacrylonitrile, nylon 6, and polytetrafluoroethylene] treated with argon (inert) and nitrogen (reactive) plasma were examined by ESCA (electron spectroscopy for chemical analysis). Argon plasma treatment generally introduces oxygen functionalities into the polymer surface. Nitrogen treatment generally incorporates nitrogen and oxygen functionalities into the treated surface. The extent of oxygen incorporation is typically less than that produced by argon plasma. When nitrogen and oxygen functional groups are already in a polymer structure, the extent of additional incorporation of these two elements as a result of plasma treatment is very much less than with other polymers. Polymers which contain only one of the elements tend to incorporate the other element to much the same degree as polymers without either element initially present.

Factors affecting genetic transformation of Neisseria gonorrhoeae.

Abstract: Piliated gonococci were competent in genetic transformation in all stages of growth in minimal and enriched media, but nonpiliated cells were almost totally incompetent. Uptake of deoxyribonucleic acid into a deoxyribonuclease-insensitive state was observed only in competent piliated cells. Competence was not affected by washing of competent cells or treatment of competent cells with proteolytic enzymes. Expression of competence required presence of any of several different monovalent or divalent cations, as well as a utilizable source of energy. Efforts to produce genotypically or phenotypically competent derivatives of nonpiliated cells were unsuccessful. These experiments are consistent with the idea that pili may play a role in the irreversible uptake of transforming deoxyribonucleic acid by the gonococcus, but fail to provide evidence for other types of competence factors.