Showing papers by "Rutgers University published in 1983"

Beyond the local-density approximation in calculations of ground-state electronic properties

Abstract: Justification, as extensive as is possible, is given for our previously published nonlocal approximation for exchange and correlation. Some new exact limits for atoms and interfaces are obtained, as well as formal quantitative criteria for the validity of the local-density approximation and the gradient corrections to it. The scheme is applied to planar surface calculations, as well as to extensive self-consistent calculations of energies and densities in atoms. The results compare favorably, in every case attempted, to experimental and exact results that are available. A method is devised for separating exchange from correlation in atoms within the Kohn-Sham method, and is tested favorably against exact-exchange calculations. Finally, we apply these results to atoms using exact exchange plus our appropriately separated correlation expression. The results give atomic total energies to accuracies of \ensuremath{\sim}\ifmmode\pm\else\textpm\fi{}0.01 Ry, and typically reduce the local-density-approximation error in density by an order of magnitude.

Solution of the Kondo problem

Abstract: This review covers in great detail the Bethe-ansatz approach to the solution of various versions of the Kondo problem.

The Clinical Significance of Positive Blood Cultures: A Comprehensive Analysis of 500 Episodes of Bacteremia and Fungemia in Adults. I. Laboratory and Epidemiologic Observations

Abstract: Five hundred episodes of septicemia were reviewed, with emphasis on laboratory and epidemiologic findings. The isolation of facultative and anaerobic gram-negative bacilli, fungi, and gram-positive cocci (except viridans streptococci and Staphylococcus epidermidis) almost always indicated true bacteremia, whereas the isolation of aerobic and anaerobic gram-positive bacilli, including Clostridium species, often represented contamination. More than 99% of all episodes were detected when two samples of blood (a total of 30 ml) were cultured. The five most common isolates were Escherichia coli, Staphylococcus aureus, Streptococcus pneumoniae, Klebsiella pneumoniae, and Pseudomonas aeruginosa. The incidence of septicemia was highest among medical patients and lowest among obstetric-gynecologic patients. Two-thirds of all episodes were nosocomial; S. aureus, enterococci, facultative gram-negative bacilli, and fungi were especially common nosocomial pathogens. The microorganisms isolated varied with the hospital service; polymicrobial episodes were especially common among surgical patients and transplant recipients. The most common sources of bacteremia were the respiratory, genitourinary, and gastrointestinal tracts; however, the source was unknown in nearly one-third of episodes. Microorganisms causing septicemia in neutropenic and nonneutropenic patients were not different; however, polymicrobial infections were more frequent in the presence of neutropenia. After antimicrobial susceptibility data became available, therapy was appropriate greater than 90% of the time.

Evidence for the neuropeptide cholecystokinin as an antagonist of opiate analgesia

Abstract: The endogenous neuropeptide cholecystokinin, when administered systemically or perispinally, potently antagonizes opiate analgesia produced by foot shock and morphine. Nonopiate foot-shock analgesia is not reduced by this neuropeptide. The spinal cord appears to be a critical site of cholecystokinin action. These experiments suggest a physiological role for cholecystokinin as a specific opiate antagonist in analgesia-mediating systems. A similar mode of action may explain other behavioral effects of cholecystokinin, such as suppression of food intake.

An Overview of Machine Learning

Abstract: Learning is a many-faceted phenomenon. Learning processes include the acquisition of new declarative knowledge, the development of motor and cognitive skills through instruction or practice, the organization of new knowledge into general, effective representations, and the discovery of new facts and theories through observation and experimentation. Since the inception of the computer era, researchers have been striving to implant such capabilities in computers. Solving this problem has been, and remains, a most challenging and fascinating long-range goal in artificial intelligence (AI). The study and computer modeling of learning processes in their multiple manifestations constitutes the subject matter of machine learning.

Parkinson's disease in 65 pairs of twins and in a set of quadruplets.

Abstract: Among 43 monozygotic (MZ) and 19 dizygotic (DZ) pairs in which an index case had definite Parkinson9s disease (PD), only one MZ pair was definitely concordant for PD. When pairs with questionable clinical features were included, 4 of 48 MZ and 1 of 19 DZ pairs were concordant. The frequency of PD in MZ cotwins of index cases with PD was similar to that expected in an unrelated control group matched for age and sex. Although we were unable to identify a single environmental agent, we conclude that the major factors in the etiology of PD are nongenetic.

The structural complexity of old field vegetation and the recruitment of bird-dispersed plant species.

Abstract: The input of bird-disseminated seeds into four old fields of different structural complexity was examined. Seed input was greatest along the edges of fields. Significantly more seeds were found in a 13 year old field that had structurally complex vegetation, than in a 3-year-old field with a single layer of vegetation. The lower input into the latter field was a function of both low fruit availability and low structural complexity of the field. Similarly, more seeds were found in a 2-year-old field which had artificial structures, simulating saplings, placed in it than in an adjacent control field of the same age. The shape of the structures was not a significant factor in the input of seeds. Timing of seed deposition was correlated with fruit ripening times, relative nutritional value of the fruit and the movements of frugivorous birds. The input of bird-disseminated seeds into fields appears to be directly related to the structural complexity of the vegetation. Woody plants increase the structural complexity of the old fields and serve as recruitment foci for bird-disseminated seeds. Thus, seed deposition by birds influences vegetation pattern, and conversely, the presence of recruitment foci in the vegetation may influence bird dispersal patterns of bird-disseminated seeds.

Investment Patterns and Financial Leverage

Abstract: This study Investigates the influence of the type of investment opportunities facing a firm on its choice of capital structure. It is shown that the more discretionary investment opportunities a firm faces,the lower its financial leverage. Inclusion of other possible determinants of capital structure, such as availability of internal funds, tax effects and risk, while significant, do not affect the importance of discretionary investment. The evidence supports (1) the existence of a moral bazzard problem which inversely relates risky debt and discretionary investment choice, and (2) a desire by most firms to use sources of internal funds prior to entering the capital market.

Vaginal Atrophy in the Postmenopausal Woman: The Importance of Sexual Activity and Hormones

Abstract: The effect of sexual activity on vaginal atrophy was investigated in a group of 52 postmenopausal women (mean age, 57 years). Subjects were divided into two groups: sexually active (intercourse frequency, three or more times monthly) and sexually inactive (intercourse frequency, less than ten times yearly). Two gynecologists examined all subjects and completed an index of vaginal atrophy that assessed six genital dimensions. Blood samples were also analyzed by radioimmunoassay for levels of circulating estrone, estradiol, androstenedione, testosterone, follicle-stimulating hormone, and luteinizing hormone (LH). As predicted, less vaginal atrophy was apparent in the sexually active women as opposed to the sexually inactive women. Further, women with less vaginal atrophy had significantly higher mean levels of androgens (androstenedione and testosterone) and gonadotropins (particularly LH). We discuss herein the implications of this study, particularly the importance of androgens in reducing atrophy and maintaining sexual interest.

Phase transitions in stationary nonequilibrium states of model lattice systems

Abstract: We investigated the stationary nonequilibrium states of a lattice gas of interacting particles subject to an external field $\stackrel{\ensuremath{\rightarrow}}{E}$. The dynamics of the system are given by hoppings of particles to nearby empty sites with rates biased for jumps in the direction of $\stackrel{\ensuremath{\rightarrow}}{E}$. This system is often used to model fast ionic conductors. Using computer simulations of a two-dimensional lattice with nearest-neighbor interactions we studied the dependence of the structure function, current, etc., on temperature and $\stackrel{\ensuremath{\rightarrow}}{E}$. We found evidence for a transition line in the temperature-field plane at which the system develops (anisotropic) long-range order. $\stackrel{\ensuremath{\rightarrow}}{E}$ enhances the transition for attractive interactions and represses it for repulsive ones.

Progressive contextualization: Methods for research in human ecology

Abstract: Theoretically or practically significant research results concerning transitory as well as persistent phenomena can be obtained by human ecologists while avoiding commitment to long-term, expensive projects, rigid frameworks, traditional disciplinary goals, and unwarranted assumptions about the stability and purposiveness of units or systems. The procedures to be followed, as illustrated by research on people-forest interactions in East Kalimantan, involve a focus on significant human activities or people-environment interactions and the explanation of these by their placement within progressively wider or denser contexts. Guides for progressively contextualizing activities or interactions include a rationality principle, comparative knowledge of contexts, and the principle of pursuing the surprising.

Density constraints on the formation of the continental Moho and crust

Abstract: The densities of mantle magmas such as MORB-like tholeiites, picrites, and komatiites at 10 kilobars are greater than densities for diorites, quartz diorites, granodiorites, and granites which dominate the continental crust. Because of these density relations primary magmas from the mantle will tend to underplate the base of the continental crust. Magmas ranging in composition from tholeiites which are more evolved than MORB to andesite can have densities which are less than rocks of the continental crust at 10 kilobars, particularly if they have high water contents. The continental crust can thus be a density filter through which only evolved magmas containing H2O may pass. This explains why primary magmas from the mantle such as the picrites are so rare. Both the over-accretion (i.e., Moho penetration) and the under-accretion (i.e., Moho underplating) of magmas can readily explain complexities in the lithological characteristics of the continental Moho and lower crust. Underplating of the continental crust by dense magmas may perturb the geotherm to values which are characteristic of those in granulite to greenschist facies metamorphic sequences in orogenic belts. An Archean continental crust floating on top of a magma flood or ocean of tholeiite to komatiite could have undergone a major cleansing process; dense blocks of peridotite, greenstone, and high density sediments such as iron formation could have been returned to the mantle, granites sweated to high crustal levels, and a high grade felsic basement residue established.

Indian-set fires in the forests of the northeastern United States

Abstract: The historical evidence for the Indians' burning the forests of the northeastern United States is reevaluated. Of 35 documents that describe vegetation or Indian life in the 16th or 17th centuries, only half mention any use of fire except for cooking. Only six purportedly first—hand accounts might refer to purposeful, widespread, and frequent use of fire. These six are all consistent with use of fire only locally near camps or villages, or with accidentally escaped fires. It is concluded that the frequent use of fires by the Indians to burn the forests was probably at most a local occurrence. The Indians' presence in the region and their use of fire for many purposes did, however, increase the frequency of fires above the low levels caused by lightning, and thus had some effect on the vegetation; for example, grasses characterized the ground cover at small, local, frequently burned sites.

Viscoelastic Behavior of Human Connective Tissues: Relative Contribution of Viscous and Elastic Components

Abstract: Stress-relaxation tests were performed at successive strain levels on strips of human aorta, skin, psoas tendon, dura mater, and pericardium. The elastic fraction, the equilibrium force divided by the initial force, was calculated at each strain increment. In the aorta, the elastic fraction decreased with strain and was modeled as the transfer of stress from elastic to collagen fibers, while in skin it increased with strain, probably due to the rearrangement of individual collagen fiber orientations, resulting in an aligned collagen network at high strains. The strain-independent elastic fractions for tendon, dura mater, and pericardium were similar, and approximately equal to the values found for aorta and skin at high strains. It was hypothesized that the elastic fraction is related to the type of fiber loaded, and the tissue geometry. This analysis may be useful in studying disease-induced changes in the mechanical properties of connective tissues.

Salt-dependent conformational transitions in the self-complementary deoxydodecanucleotide d(CGCAATTCGCG): evidence for hairpin formation.

Abstract: Differential scanning calorimetry (DSC), temperature-dependent uv-absorption spectroscopy, and temperature-dependent CD were used to monitor and characterize the salt-dependent, thermally induced structural transitions in the deoxydodecanucleotide d(CGCGAATTCGCG). At the high oligomer concentrations required for DSC, the calorimetric scans revealed a single, monophasic transition curve at all salt concentrations. Based on previous nmr melting studies under similar conditions, we conclude that these monophasic transitions correspond to the cooperative duplex-to-single-strand conversion of the dodecamer. By contrast, at the lower oligomer concentrations used for the spectroscopic studies, the shapes of the uv and CD melting curves were found to depend on the concentration of the added salt. At high salt (≥0.1M Na+), a single, monophasic transition curve was observed. At lower salt (⩽0.01M Na+), the CD and uv melting curves exhibit biphasic behavior. Based on the concentration dependence, the enthalpy, and the cooperativity of each transition in the biphasic curve, we conclude that at low salt and low oligomer concentrations, the dodecamer melts in a sequential manner involving initial disruption of a duplex structure and subsequent disruption of a hairpin structure.

HTLV-III/LAV-Like retrovirus particles in the brains of patients with aids encephalopathy

Abstract: It has been postulated that the retrovirus HTLV-III/LAV thought to be the etiologic agent of AIDS also infects the central nervous system and directly causes AIDS encephalopathy. Electron microscopical studies performed on brain sections from three patients with AIDS complicated by progressive encephalopathy revealed structures morphologically consistent with HTLV-III/LAV retrovirus particles. The particles were located principally within multinucleated giant cells but were also present in astrocytes. Many particles were also noted in the extracellular space.

Sales Territory Alignment: A Review and Model

Abstract: The sales territory alignment problem may be viewed as the problem of grouping small geographic sales coverage units into larger geographic clusters called sales territories in a way that the sales territories are acceptable according to managerially relevant alignment criteria. This paper first reviews sales territory alignment models which have appeared in the marketing literature. A framework for sales territory alignment and several properties of a good sales territory alignment are developed in the course of the review. A general sales territory alignment model which accommodates these properties is developed. A solution procedure for the general model is presented. Finally, an actual implementation of the general model is described. The implementation provides a comparison of the general model with a similar model which has been frequently cited in the marketing literature.

Progesterone in the Ventromedial Hypothalamus Facilitates Estrous Behavior in Ovariectomized, Estrogen-Primed Rats

Abstract: The putative neural target sites of progesterone (P) action for the facilitation of estrous behavior in female rats were reexamined using the hormone implant technique. Subjects were ovariectomized, estrogen-primed Long-Evans females. All were outfitted with bilateral double barreled cannulae assemblies consisting of 23-gauge guide cannulae and 28-gauge inserts. Subjects in Exp 1 received sc injections of individually determined threshold priming doses of estradiol benzoate. Estrogenic priming for subjects in Exp 2 was provided by sc placed Silastic capsules (5 mm) filled with 17 beta-estradiol-cholesterol (1:20). Each subject was tested for estrous behavior with a male after P-filled cannulae and after blank inserts were lowered into the brain. Behavioral tests were conducted 1 and 4.5 h postcannulae placement. Thirty-five of 40 females with P in the ventromedial hypothalamus exhibited high levels of lordosis behavior during the 4.5-h test. Moreover, 29 of the 35 exhibited solicitation behavior as well. Estrous behavior was not exhibited by these animals during the 1-h test. Implants in other regions of the brain (i.e. mesencephalic reticular formation, preoptic area, central grey, caudate putamen, and hippocampus; n = 80) did not consistently facilitate estrous responsiveness. In Exp 3, levels of estrous responsiveness were similar before and after adrenalectomy (n = 10); thus, facilitation of estrous behavior by P-filled implants in the ventromedial hypothalamus was not dependent upon activation of the hypothalamic-pituitary-adrenal axis.

Population genetics of the American oyster Crassostrea virginica along the Atlantic coast and the Gulf of Mexico

Abstract: An examination by protein-gel electrophoresis of 19 different geographical populations of the American oyster Crassostrea virginica (Gmelin) was conducted along the Atlantic coast and the Gulf of Mexico. Estimates were made of levels of genetic variation and similarity among the populations based on 32 structural loci. The percentage of loci polymorphic ranged from 46.9 to 65.6% along the Atlantic coast while the estimate ranged from 54.8% to 68.8% on the Gulf of Mexico. The percentage of loci heterozygous ranged from 18.6 to 23.6% along the Atlantic coast and from 20.0 to 25.4% in the Gulf of Mexico. The genetic similarities between all contiguous populations from Cape Cod, Massachusetts to Corpus Christi, Texas were estimated as 99%, while the same estimate between Corpus Christi and Brownsville, Texas was computed as 93%, indicating a major transition in genetic structure for the Brownsville population of the Laguna Madre. The study revealed that the migration of planktonic oyster larvae is predominantly in a westerly direction along the Gulf of Mexico and that gene flow appears to be disrupted in the region of the Laguna Madre. Evidence has been presented for single gene selection at the Lap-2 and Pgi loci in the form of macrogeographical clines in allele frequencies with changing environmental conditions.

Analysis of ultrasonic vocalizations emitted by intruders during aggressive encounters among rats (Rattus norvegicus).

Abstract: This investigation was concerned with the identification of the ultrasonic vocalizations produced by intruders during aggressive interactions and the role of these signals in agonistic behavior of rats. In the first experiment, experienced resident males were paired with both devocalized and intact vocalizing naive intruder males. Devocalization of the intruder males resulted in a drastic decrease in 50-kHz vocalizations and the elimination of all 22-kHz vocalizations. This almost total absence of ultrasonic vocalizations was not accompanied by any change in resident aggressive behavior or intruder defensive and submissive behavior. In a second experiment, naive intruders were tested with either deafened or intact resident males. Similarly, preventing residents from hearing intruder ultrasounds had no detectable effect on any aggressive behavior. These experiments are not consistent with the correlative evidence that intruder-produced 22-kHz vocalizations inhibit the aggressive behavior of the resident. The results also show that most of the ultrasonic vocalizations emitted during aggressive encounters are probably produced by the intruder.

Sequences of Social Events: Concepts and Methods for the Analysis of Order in Social Processes

Abstract: (1983). Sequences of Social Events: Concepts and Methods for the Analysis of Order in Social Processes. Historical Methods: A Journal of Quantitative and Interdisciplinary History: Vol. 16, No. 4, pp. 129-147.

On a sharp transition from area law to perimeter law in a system of random surfaces

Abstract: We introduce and study a phase transition which is associated with the spontaneous formation of infinite surface sheets in a Bernoulli system of random plaquettes. The transition is manifested by a change in the asymptotic behavior of the probability of the formation of a surface, spanning a prescribed loop. As such, this transition offers a generalization of the bond percolation phenomenon. At low plaquette densities, the probability for large loops is shown to decay exponentially with the loops' area, whereas for high densities the decay is by a perimeter law. Furthermore, we show that the two phases of the three dimensional plaquette system are in a precise correspondence with the two phases of the dual system of random bonds. Thus, if a natural conjecture about the phase structure of the bond percolation model is true, then there is a sharp transition in the asymptotic behavior of the surface events. Our analysis incorporates block variables, in terms of which a non-critical system is transformed into one which is close to a trivial, high or low density, fixed point. Stochastic geometric effects like those discussed here play an important role in lattice gauge theories.