Showing papers by "Cornell University published in 1992"

An Introduction to Kernel and Nearest-Neighbor Nonparametric Regression

Abstract: Nonparametric regression is a set of techniques for estimating a regression curve without making strong assumptions about the shape of the true regression function. These techniques are therefore useful for building and checking parametric models, as well as for data description. Kernel and nearest-neighbor regression estimators are local versions of univariate location estimators, and so they can readily be introduced to beginning students and consulting clients who are familiar with such summaries as the sample mean and median.

Nitric oxide as a secretory product of mammalian cells.

Abstract: Evolution has resorted to nitric oxide (NO), a tiny, reactive radical gas, to mediate both servoregulatory and cytotoxic functions. This article reviews how different forms of nitric oxide synthase help confer specificity and diversity on the effects of this remarkable signaling molecule.

A net carbohydrate and protein system for evaluating cattle diets: II. Carbohydrate and protein availability.

Abstract: The Cornell Net Carbohydrate and Protein System (CNCPS) has a submodel that predicts rates of feedstuff degradation in the rumen, the passage of undegraded feed to the lower gut, and the amount of ME and protein that is available to the animal. In the CNCPS, structural carbohydrate (SC) and nonstructural carbohydrate (NSC) are estimated from sequential NDF analyses of the feed. Data from the literature are used to predict fractional rates of SC and NSC degradation. Crude protein is partitioned into five fractions. Fraction A is NPN, which is trichloroacetic (TCA) acid-soluble N. Unavailable or protein bound to cell wall (Fraction C) is derived from acid detergent insoluble nitrogen (ADIP), and slowly degraded true protein (Fraction B3) is neutral detergent insoluble nitrogen (NDIP) minus Fraction C. Rapidly degraded true protein (Fraction B1) is TCA-precipitable protein from the buffer-soluble protein minus NPN. True protein with an intermediate degradation rate (Fraction B2) is the remaining N. Protein degradation rates are estimated by an in vitro procedure that uses Streptomyces griseus protease, and a curve-peeling technique is used to identify rates for each fraction. The amount of carbohydrate or N that is digested in the rumen is determined by the relative rates of degradation and passage. Ruminal passage rates are a function of DMI, particle size, bulk density, and the type of feed that is consumed (e.g., forage vs cereal grain).

Shape and motion from image streams under orthography: a factorization method

Abstract: Inferring scene geometry and camera motion from a stream of images is possible in principle, but is an ill-conditioned problem when the objects are distant with respect to their size. We have developed a factorization method that can overcome this difficulty by recovering shape and motion under orthography without computing depth as an intermediate step. An image stream can be represented by the 2FxP measurement matrix of the image coordinates of P points tracked through F frames. We show that under orthographic projection this matrix is of rank 3. Based on this observation, the factorization method uses the singular-value decomposition technique to factor the measurement matrix into two matrices which represent object shape and camera rotation respectively. Two of the three translation components are computed in a preprocessing stage. The method can also handle and obtain a full solution from a partially filled-in measurement matrix that may result from occlusions or tracking failures. The method gives accurate results, and does not introduce smoothing in either shape or motion. We demonstrate this with a series of experiments on laboratory and outdoor image streams, with and without occlusions.

Explaining the Gibbs Sampler

Abstract: Computer-intensive algorithms, such as the Gibbs sampler, have become increasingly popular statistical tools, both in applied and theoretical work. The properties of such algorithms, however, may sometimes not be obvious. Here we give a simple explanation of how and why the Gibbs sampler works. We analytically establish its properties in a simple case and provide insight for more complicated cases. There are also a number of examples.

Quantum cryptography without Bell's theorem.

Abstract: Ekert has described a cryptographic scheme in which Einstein-Podolsky-Rosen (EPR) pairs of particles are used to generate identical random numbers in remote places, while Bell's theorem certifies that the particles have not been measured in transit by an eavesdropper. We describe a related but simpler EPR scheme and, without invoking Bell's theorem, prove it secure against more general attacks, including substitution of a fake EPR source. Finally we show our scheme is equivalent to the original 1984 key distribution scheme of Bennett and Brassard, which uses single particles instead of EPR pairs.

Lower limit to the thermal conductivity of disordered crystals

Abstract: Measurements of the thermal conductivity above 30 K of mixed crystals with controlled disorder, (KBr${)}_{1\mathrm{\ensuremath{-}}\mathit{x}}$(KCN${)}_{\mathit{x}}$, (NaCl${)}_{1\mathrm{\ensuremath{-}}\mathit{x}}$, (NaCn${)}_{\mathit{x}}$ ${\mathrm{Zr}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Y}}_{\mathit{x}}$${\mathrm{O}}_{2\mathrm{\ensuremath{-}}\mathit{x}/2}$, and ${\mathrm{Ba}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{La}}_{\mathit{x}}$${\mathrm{F}}_{2+\mathit{x}}$, support the idea of a lower limit to the thermal conductivity of disordered solids. In each case, as x is increased, the data approach the calculated minimum conductivity based on a model originally due to Einstein. These measurements support the claim that the lattice vibrations of these disordered crystals are essentially the same as those of an amorphous solid.

Cloning and characterization of inducible nitric oxide synthase from mouse macrophages.

Abstract: Nitric oxide (NO) conveys a variety of messages between cells, including signals for vasorelaxation, neurotransmission, and cytotoxicity. In some endothelial cells and neurons, a constitutive NO synthase is activated transiently by agonists that elevate intracellular calcium concentrations and promote the binding of calmodulin. In contrast, in macrophages, NO synthase activity appears slowly after exposure of the cells to cytokines and bacterial products, is sustained, and functions independently of calcium and calmodulin. A monospecific antibody was used to clone complementary DNA that encoded two isoforms of NO synthase from immunologically activated mouse macrophages. Liquid chromatography-mass spectrometry was used to confirm most of the amino acid sequence. Macrophage NO synthase differs extensively from cerebellar NO synthase. The macrophage enzyme is immunologically induced at the transcriptional level and closely resembles the enzyme in cytokine-treated tumor cells and inflammatory neutrophils.

Fractals and Chaos in Geology and Geophysics

Abstract: This book introduces the fundamental concepts of fractal geometry and chaotic dynamics These concepts are then related to a variety of geological and geophysical problems, illustrating just what chaos theory and fractals really tell us and how they can be applied to the earth sciences Petroleum and mineral reserves, earthquakes, mantle convection and magnetic field generation are among the earth's properties that come under scrutiny This is the first book that covers these topics at an accessible level; the concepts are introduced at the lowest possible level of mathematics and are consistently understandable, so that the reader requires only a background in basic physics and mathematics Problems are also included for the reader to solve

High density molecular linkage maps of the tomato and potato genomes.

Abstract: High density molecular linkage maps, comprised of more than 1000 markers with an average spacing between markers of approximately 1.2 cM (ca. 900 kb), have been constructed for the tomato and potato genomes. As the two maps are based on a common set of probes, it was possible to determine, with a high degree of precision, the breakpoints corresponding to 5 chromosomal inversions that differentiate the tomato and potato genomes. All of the inversions appear to have resulted from single breakpoints at or near the centromeres of the affected chromosomes, the result being the inversion of entire chromosome arms. While the crossing over rate among chromosomes appears to be uniformly distributed with respect to chromosome size, there is tremendous heterogeneity of crossing over within chromosomes. Regions of the map corresponding to centromeres and centromeric heterochromatin, and in some instances telomeres, experience up to 10-fold less recombination than other areas of the genome. Overall, 28% of the mapped loci reside in areas of putatively suppressed recombination. This includes loci corresponding to both random, single copy genomic clones and transcribed genes (detected with cDNA probes). The extreme heterogeneity of crossing over within chromosomes has both practical and evolutionary implications. Currently tomato and potato are among the most thoroughly mapped eukaryotic species and the availability of high density molecular linkage maps should facilitate chromosome walking, quantitative trait mapping, marker-assisted breeding and evolutionary studies in these two important and well studied crop species.

A net carbohydrate and protein system for evaluating cattle diets: I. Ruminal fermentation.

Abstract: The Cornell Net Carbohydrate and Protein System (CNCPS) has a kinetic submodel that predicts ruminal fermentation. The ruminal microbial population is divided into bacteria that ferment structural carbohydrate (SC) and those that ferment nonstructural carbohydrate (NSC). Protozoa are accommodated by a decrease in the theoretical maximum growth yield (.50 vs .40 g of cells per gram of carbohydrate fermented), and the yields are adjusted for maintenance requirements (.05 vs .150 g of cell dry weight per gram of carbohydrate fermented per hour for SC and NSC bacteria, respectively). Bacterial yield is decreased when forage NDF is < 20% (2.5% for every 1% decrease in NDF). The SC bacteria utilize only ammonia as a N source, but the NSC bacteria can utilize either ammonia or peptides. The yield of NSC bacteria is enhanced by as much as 18.7% when proteins or peptides are available. The NSC bacteria produce less ammonia when the carbohydrate fermentation (growth) rate is rapid, but 34% of the ammonia production is insensitive to the rate of carbohydrate fermentation. Ammonia production rates are moderated by the rate of peptide and amino acid uptake (.07 g of peptide per gram of cells per hour), and peptides and amino acids can pass out of the rumen if the rate of proteolysis is faster than the rate of peptide utilization. The protein-sparing effect of ionophores is accommodated by decreasing the rate of peptide uptake by 34%. Validation with published data of microbial flow from the rumen gave a regression with a slope of .94 and an r2 of .88.

The cultures of work organizations

Abstract: 1. How and Why Organizations are Cultures. 2. The Substance of Organizational Cultures. 3. Cultural Forms. 4. Organizational Passages and Cultural Continuity. 5. Occupational Subcultures. 6. Other Subcultures in Organizations. 7. Leadership and Organizational Cultures. 8. Cultural Interchange Between Organizations and Environments. 9. Managing and Maintaining Organizational Cultures. 10. Changing and Creating Organizational Cultures.

Computational Frameworks for the Fast Fourier Transform

Abstract: 1. The Radix-2 Frameworks. Matrix Notation and Algorithms The FFT Idea The Cooley-Tukey Factorization Weight and Butterfly Computations Bit Reversal and Transposition The Cooley-Tukey Framework The Stockham Autosort Frameworks The Pease Framework Decimation in Frequency and Inverse FFTs 2. General Radix Frameworks. The General Radix Ideas Index Reversal and Transposition Mixed-Radix Factorizations Radix-4 and Radix-8 Frameworks The Split-Radix Frameworks 3. High Performance Frameworks. The Multiple DFT Problem Matrix Transposition The Large Single-Vector FFT Problem Multi-Dimensional FFT Problem Distributed Memory FFTs Shared Memory FFTs 4. Selected Topics. Prime Factor FFTs Convolution FFTs of Real Data Cosine and Sine Transforms Fast Poisson Solvers Bibliography Index.

Origins of knowledge.

Abstract: Experiments with young infants provide evidence for early-developing capacities to represent physical objects and to reason about object motion Early physical reasoning accords with 2 constraints at the center of mature physical conceptions: continuity and solidity It fails to accord with 2 constraints that may be peripheral to mature conceptions: gravity and inertia These experiments suggest that cognition develops concurrently with perception and action and that development leads to the enrichment of conceptions around an unchanging core The experiments challenge claims that cognition develops on a foundation of perceptual or motor experience, that initial conceptions are inappropriate to the world, and that initial conceptions are abandoned or radically changed with the growth of knowledge

Endogenous production, exogenous delivery and impact-shock synthesis of organic molecules: an inventory for the origins of life

Abstract: The contribution of organic-rich comets, carbonaceous asteroids, and interplanetary dust particles and of impact shock-synthesized organics in the atmosphere to the origin of life on earth is studied and quantitatively compared with the principal non-heavy-bombardment sources of prebiotic organics. The results suggest that heavy bombardment before 3.5 Gyr ago either produced or delivered quantities of organics comparable to those produced by other energy sources.

Levels of naturally occurring DNA polymorphism correlate with recombination rates in D. melanogaster

Abstract: Two genomic regions with unusually low recombination rates in Drosophila melanogaster have normal levels of divergence but greatly reduced nucleotide diversity, apparently resulting from the fixation of advantageous mutations and the associated hitch-hiking effect. Here we show that for 20 gene regions from across the genome, the amount of nucleotide diversity in natural populations of D. melanogaster is positively correlated with the regional rate of recombination. This cannot be explained by variation in mutation rates and/or functional constraint, because we observe no correlation between recombination rates and DNA sequence divergence between D. melanogaster and its sibling species, D. simulans. We suggest that the correlation may result from genetic hitch-hiking associated with the fixation of advantageous mutants. Hitch-hiking thus seems to occur over a large fraction of the Drosophila genome and may constitute a major constraint on levels of genetic variation in nature.

Effects of Work Values on Job Choice Decisions

Abstract: Work values have been receiving increased research attention. Ravlin, Meglino, and their associates have recently conceptualized and provided measurement of work values. Although the effects of work values on job satisfaction, commitment, and individual decision making have been studied, work values have not been explicitly linked to job choice decisions. Using a sample of professional degree students and a policy-capturing design, we examined the influence of organizational work values on job choice in the context of job attributes that have been shown to affect this decision process. Organizational work values significantly affected job choice decisions. Individuals were more likely to choose jobs whose value content was similar to their own value orientation. Values are intrinsic, enduring perspectives of what is fundamentally right or wrong (Rokeach, 1973). Work values represent these perspectives as applied to work settings. England (1967) suggested that individual value orientations affect how people behave on their jobs by demonstrating that managers with strong value orientations tended to act in accordance with what they thought was "right," whereas managers with more pragmatic orientations tended to behave in ways that they thought were "successful." Among individual work values, the work ethic (the belief that work is desirable and rewarding in its own right; Weber, 1958) has received considerable research attention (e.g., Wollack, Goodale, Wijting, & Smith, 1971), and some have suggested that a deteriorating work ethic has negatively affected both the way people feel about their jobs and their commitment to their organizations (Spence, 1985). However, in addition to the work ethic, other individual value orientations have been applied to work settings. For example, Cornelius, Ullman, Meglino, Czajka, and McNeely (1985) used a critical incident technique to elicit the work values of almost 1,000 employees in a variety of organizations. Subsequent work by Ravlin and Meglino (1987) revealed that achievement, concern for others, honesty, and fairness were the most salient work values to individuals. Achievement is descriptive of concern for the advancement of one's career and might be operationalized by willingness to work hard, seeking opportunities to learn new skills, taking on additional responsibilities, or sacrificing personal gratification for work-related objectives. Concern for others is descriptive of a caring, compassionate demeanor and might be operationalized by helping others perform difficult jobs, encouraging

Water uptake by plants: perspectives from stable isotope composition

Abstract: Stable isotope studies of hydrogen and oxygen stable isotope ratios of water within plants are providing new information on water sources, competitive interactions and water use patterns under natural conditions. Variation in the utilization of summer rain by aridland species and limited use of stream water by mature riparian trees are two examples of how stable isotope studies have modified our understanding of plant water relations. Analyses of xylem sap and tree rings have the potential of providing both short-term and long-term information on plant water use patterns.

Prefrontal cortical efferents in the rat synapse on unlabeled neuronal targets of catecholamine terminals in the nucleus accumbens septi and on dopamine neurons in the ventral tegmental area.

Abstract: Physiological and pharmacological studies indicate that descending projections from the prefrontal cortex modulate dopaminergic transmission in the nucleus accumbens septi and ventral tegmental area We investigated the ultrastructural bases for these interactions in rat by examining the synaptic associations between prefrontal cortical terminals labeled with anterograde markers (lesion-induced degeneration or transport of Phaseolus vulgaris leucoagglutinin; PHA-L) and neuronal processes containing immunoreactivity for the catecholamine synthesizing enzyme, tryosine hydroxylase Prefrontal cortical terminals in the nucleus accumbens and ventral tegmental area contained clear, round vesicles and formed primarily asymmetric synapses on spines or small dendrites In the ventral tegmental area, these terminals also formed asymmetric synapses on large dendrites and a few symmetric axodendritic synapses In the nucleus accumbens septi, degenerating prefrontal cortical terminals synapsed on spiny dendrites which received convergent input from terminals containing peroxidase immunoreactivity for tyrosine hydroxylase, or from unlabeled terminals In single sections, some tyrosine hydroxylase-labeled terminals formed thin and punctate symmetric synapses with dendritic shafts, or the heads and necks of spines Close appositions, but not axo-axonic synapses, were frequently observed between degenerating prefrontal cortical afferents and tyrosine hydroxylase-labeled or unlabeled terminals In the ventral tegmental area, prefrontal cortical terminals labeled with immunoperoxidase for PHA-L were in synaptic contact with dendrites containing immunogold reaction product for tyrosine hydroxylase, or with unlabeled dendrites These results suggest that: (1) catecholaminergic (mainly dopaminergic) and prefrontal cortical terminals in the nucleus accumbens septi dually synapse on common spiny neurons; and (2) dopaminergic neurons in the ventral tegmental area receive monosynaptic input from prefrontal cortical afferents This study provides the first ultrastructural basis for multiple sites of cellular interaction between prefrontal cortical efferents and mesolimbic dopaminergic neurons

Tumor necrosis factor soluble receptors circulate during experimental and clinical inflammation and can protect against excessive tumor necrosis factor alpha in vitro and in vivo.

Abstract: Tumor necrosis factor alpha (TNF alpha), a primary mediator of systemic responses to sepsis and infection, can be injurious to the organism when present in excessive quantities. Here we report that two types of naturally occurring soluble TNF receptors (sTNFR-I and sTNFR-II) circulate in human experimental endotoxemia and in critically ill patients and demonstrate that they neutralize TNF alpha-induced cytotoxicity and immunoreactivity in vitro. Utilizing immunoassays that discriminate between total sTNFR-I and sTNFR-I not bound to TNF alpha, we show that sTNFR-I-TNF alpha complexes may circulate even in the absence of detectable free TNF alpha. To investigate the therapeutic possibilities of sTNFR-I, recombinant protein was administered to nonhuman primates with lethal bacteremia and found to attenuate hemodynamic collapse and cytokine induction. We conclude that soluble receptors for TNF alpha are inducible in inflammation and circulate at levels sufficient to block the in vitro cytotoxicity associated with TNF alpha levels observed in nonlethal infection. Administration of sTNFR-I can prevent the adverse pathologic sequelae caused by the exaggerated TNF alpha production observed in lethal sepsis.

Microdomains of High Calcium Concentration in a Presynaptic Terminal

Abstract: Increases in intracellular calcium concentration are required for the release of neurotransmitter from presynaptic terminals in all neurons. However, the mechanism by which calcium exerts its effect is not known. A low-sensitivity calcium-dependent photoprotein (n-aequorin-J) was injected into the presynaptic terminal of the giant squid synapse to selectively detect high calcium concentration microdomains. During transmitter release, light emission occurred at specific points or quantum emission domains that remained in the same place during protracted stimulation. Intracellular calcium concentration microdomains on the order of 200 to 300 micromolar occur against the cytoplasmic surface of the plasmalemma during transmitter secretion, supporting the view that the synaptic vesicular fusion responsible for transmitter release is triggered by the activation of a low-affinity calcium-binding site at the active zone.

Harpin, elicitor of the hypersensitive response produced by the plant pathogen Erwinia amylovora

Abstract: A proteinaceous elicitor of the plant defense reaction known as the hypersensitive response was isolated from Erwinia amylovora, the bacterium that causes fire blight of pear, apple, and other rosaceous plants. The elicitor, named harpin, is an acidic, heat-stable, cell-envelope-associated protein with an apparent molecular weight of 44 kilodaltons. Harpin caused tobacco leaf lamina to collapse and caused an increase in the pH of bathing solutions of suspension-cultured tobacco cells. The gene encoding harpin (hrpN) was located in the 40-kilobase hrp gene cluster of E. amylovora, sequenced, and mutated with Tn5tac1. The hrpN mutants were not pathogenic to pear, did not elicit the hypersensitive response, and did not produce harpin.