Showing papers by "Cornell University published in 1990"
TL;DR: The fluorescence emission increased quadratically with the excitation intensity so that fluorescence and photo-bleaching were confined to the vicinity of the focal plane as expected for cooperative two-photon excitation.
Abstract: Molecular excitation by the simultaneous absorption of two photons provides intrinsic three-dimensional resolution in laser scanning fluorescence microscopy. The excitation of fluorophores having single-photon absorption in the ultraviolet with a stream of strongly focused subpicosecond pulses of red laser light has made possible fluorescence images of living cells and other microscopic objects. The fluorescence emission increased quadratically with the excitation intensity so that fluorescence and photo-bleaching were confined to the vicinity of the focal plane as expected for cooperative two-photon excitation. This technique also provides unprecedented capabilities for three-dimensional, spatially resolved photochemistry, particularly photolytic release of caged effector molecules.
8,905 citations
TL;DR: The state machine approach is a general method for implementing fault-tolerant services in distributed systems and protocols for two different failure models—Byzantine and fail stop are described.
Abstract: The state machine approach is a general method for implementing fault-tolerant services in distributed systems. This paper reviews the approach and describes protocols for two different failure models—Byzantine and fail stop. Systems reconfiguration techniques for removing faulty components and integrating repaired components are also discussed.
2,559 citations
TL;DR: The VFA, also known as short-chain fatty acids, are produced in the gastrointestinal tract by microbial fermentation of carbohydrates and endogenous substrates, such as mucus and may indirectly influence cholesterol synthesis and even help regulate insulin or glucagon secretion.
Abstract: The VFA, also known as short-chain fatty acids, are produced in the gastrointestinal tract by microbial fermentation of carbohydrates and endogenous substrates, such as mucus. This can be of great advantage to the animal, since no digestive enzymes exist for breaking down cellulose or other complex carbohydrates. The VFA are produced in the largest amounts in herbivorous animal species and especially in the forestomach of ruminants. The VFA, however, also are produced in the lower digestive tract of humans and all animal species, and intestinal fermentation resembles that occurring in the rumen. The principal VFA in either the rumen or large intestine are acetate, propionate, and butyrate and are produced in a ratio varying from approximately 75:15:10 to 40:40:20. Absorption of VFA at their site of production is rapid, and large quantities are metabolized by the ruminal or large intestinal epithelium before reaching the portal blood. Most of the butyrate is converted to ketone bodies or CO2 by the epithelial cells, and nearly all of the remainder is removed by the liver. Propionate is similarly removed by the liver but is largely converted to glucose. Although species differences exist, acetate is used principally by peripheral tissues, especially fat and muscle. Considerable energy is obtained from VFA in herbivorous species, and far more research has been conducted on ruminants than on other species. Significant VFA, however, are now known to be produced in omnivorous species, such as pigs and humans. Current estimates are that VFA contribute approximately 70% to the caloric requirements of ruminants, such as sheep and cattle, approximately 10% for humans, and approximately 20-30% for several other omnivorous or herbivorous animals. The amount of fiber in the diet undoubtedly affects the amount of VFA produced, and thus the contribution of VFA to the energy needs of the body could become considerably greater as the dietary fiber increases. Pigs and some species of monkey most closely resemble humans, and current research should be directed toward examining the fermentation processes and VFA metabolism in those species. In addition to the energetic or nutritional contributions of VFA to the body, the VFA may indirectly influence cholesterol synthesis and even help regulate insulin or glucagon secretion. In addition, VFA production and absorption have a very significant effect on epithelial cell growth, blood flow, and the normal secretory and absorptive functions of the large intestine, cecum, and rumen. The absorption of VFA and sodium, for example, seem to be interdependent, and release of bicarbonate usually occurs during VFA absorption.(ABSTRACT TRUNCATED AT 400 WORDS)
2,188 citations
TL;DR: An ac technique for measuring the thermal conductivity of dielectric solids between 30 and 750 K is described in this article, which can be applied to bulk amorphous solids and crystals.
Abstract: An ac technique for measuring the thermal conductivity of dielectric solids between 30 and 750 K is described This technique, the 3ω method, can be applied to bulk amorphous solids and crystals as well as amorphous films tens of microns thick Errors from black‐body radiation are calculated to be less than 2% even at 1000 K Data for a‐SiO2, Pyrex 7740, and Pyroceram 9606 are compared to results obtained by conventional techniques
1,729 citations
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01 Jan 1990TL;DR: In this paper, a key-finding algorithm based on tonal hierarchical relations was proposed to find the key of a key in a tonal music, and the algorithm was applied to both tonal and non-tonal music.
Abstract: 1. Objectives and Methods 2. Quantifying Tonal Hierarchies and Key Distances 3. Musical Correlates of Perceived Tonal Hierarchies 4. A Key-Finding Algorithm Based on Tonal Hierarchies 5. Perceived Relations Between Musical Tones 6. Perceptual Organization and Pitch Memory 7. Quantifying Harmonic Hierarchies and Key Distances 8. Perceived Harmonic Relations 9. Perceiving Multiple Keys: Modulation and Polytonality 10. Tonal Hierarchies in Atonal and Non-Western Tonal Music 11. Music Cognition: Theoretical and Empirical Generalizations
1,292 citations
TL;DR: A Bell inequality is derived for a state of n spin-1/2 particles which superposes two macroscopically distinct states and quantum mechanics violates this inequality by an amount that grows exponentially with n.
Abstract: A Bell inequality is derived for a state of n spin-1/2 particles which superposes two macroscopically distinct states. Quantum mechanics violates this inequality by an amount that grows exponentially with n.
1,218 citations
TL;DR: K, a hematopoietic growth factor obtained from conditioned medium of BALB/c 3T3 fibroblasts that stimulates the proliferation of mast cells and early erythroid progenitors, specifically binds to the c-kit receptor.
1,201 citations
TL;DR: The possibility that love and work in adulthood are functionally similar to attachment and exploration in infancy and early childhood was investigated in this paper, and two questionnaire studies indicated that relations between adult attachment type and work orientation are similar with attachment/exploration dynamics in early childhood, suggesting that the dynamics may be similar across the life span.
Abstract: The possibility that love and work in adulthood are functionally similar to attachment and exploration in infancy and early childhood was investigated. Key components of attachment theory—developed by Bowlby, A insworth, and others to explain the role of attachment in exploratory behavior —were translated into terms appropriate to adult love and work. The translation centered on the 3 major types of infant attachment and exploration identified by Ainsworth: secure, anxious/ambivalent, and avoidant. Two questionnaire studies indicated that relations between adult attachment type and work orientation are similar to attachment/exploration dynamics in infancy and early childhood, suggesting that the dynamics may be similar across the life span. Implications for research on the link between love and work are discussed, as are measurement problems and other issues related to future tests of an attachment-theoretical approach to the study of adults.
1,170 citations
TL;DR: The availability of efficient nuclear and chloroplast transformation in Chlamydomonas provides specific advantages for the study of chloropleft biogenesis, photosynthesis, and nuclear-chloroplast genome interactions.
Abstract: By using a method in which cell-wall-deficient Chlamydomonas reinhardtii cells were agitated in the presence of DNA, glass beads, and polyethylene glycol, nuclear transformation rates of approximately 10(3) transformants per micrograms of plasmid DNA were achieved. The nitrate reductase gene from wild-type Chlamydomonas was used to complement a mutation in the corresponding gene of a strain containing nit1-305. Transformants were selected by growth with nitrate as sole source of nitrogen. The transforming DNA integrated into the genome at a low-copy number in nit+ transformants. When cells carrying nit1-305 were agitated in the presence of two plasmids, one with the gene for nitrate reductase and the second with an unselected gene, the unselected gene was present in 10-50% of nit+ transformants. This high frequency of cotransformation will allow any cloned gene to be introduced into Chlamydomonas. Moreover, the overall efficiency of transformation should be high enough to permit isolation of genes from genomic libraries by complementation of stable nuclear mutants. The availability of efficient nuclear and chloroplast transformation in Chlamydomonas provides specific advantages for the study of chloroplast biogenesis, photosynthesis, and nuclear-chloroplast genome interactions.
1,099 citations
TL;DR: Use of a functional model system for AAV DNA integration into AAVS1 has allowed us to conclude that the recombination event is directed by cellular DNA sequences.
Abstract: Adeno-associated virus (AAV) has attracted considerable interest as a potential vector for gene delivery. Wild-type virus is notable for the lack of association with any human disease and the ability to stably integrate its genome in a site-specific manner in a locus on human chromosome 19 (AAVS1). Use of a functional model system for AAV DNA integration into AAVS1 has allowed us to conclude that the recombination event is directed by cellular DNA sequences. Recombinant junctions isolated from our integration assay were analyzed and showed characteristics similar to those found in latently infected cell lines. The minimal DNA signals within AAVS1 required for targeted integration were identified and shown to contain functional motifs of the viral origin of replication. A replication mediated model of AAV DNA integration is proposed.
1,067 citations
TL;DR: Findings suggest that a general representation of object unity and boundaries is interposed between representations of surfaces and representations of objects of familiar kinds, related to processes of physical reasoning.
TL;DR: Most behavioral anomalies can be explained by assuming that agents have stable, well-defined preferences and make rational choices consistent with those preferences in markets that (eventually) clear as mentioned in this paper.
Abstract: most (all?) behavior can be explained by assuming that agents have stable, well-defined preferences and make rational choices consistent with those preferences in markets that (eventually) clear. An empirical result qualifies as an anomaly if it is difficult to "rationalize," or if implausible assumptions are necessary to explain it within the paradigm. This column will present a series of such anomalies. Readers are invited to suggest topics for future columns by sending a note with some reference to (or better yet copies of) the relevant research. Comments on anomalies printed here are also welcome. The address
TL;DR: The authors describes the genesis and development of concept mapping as a useful tool for science education and offers an overview of the contents of this special issue and comments on the current state of knowledge representation.
Abstract: This article describes the genesis and development of concept mapping as a useful tool for science education. It also offers an overview of the contents of this special issue and comments on the current state of knowledge representation. Suggestions for further research are made throughout the article.
TL;DR: It is argued that the microsocial dynamics occasioned by new technologies reverberate up levels of analysis in an orderly manner and are held to mediate a technology's structural effects.
Abstract: This paper outlines a role-based approach for conceptualizing and investigating the contention in some previous research that technologies change organizational and occupational structures by transforming patterns of action and interaction. Building on Nadel's theory of social structure, the paper argues that the microsocial dynamics occasioned by new technologies reverberate up levels of analysis in an orderly manner. Specifically, a technology's material attributes are said to have an immediate impact on the nonrelational elements of one or more work roles. These changes, in turn, influence the role's relational elements, which eventually affect the structure of an organization's social networks. Consequently, roles and social networks are held to mediate a technology's structural effects. The theory is illustrated by ethnographic and sociometric data drawn from a comparative field study of the use of traditional and computerized imaging devices in two radiology departments.
TL;DR: It is proved that no polynomial algorithm can achieve a worst-case ratio less than 3/2 unlessP = NP, and a complexity classification for all special cases with a fixed number of processing times is obtained.
Abstract: We consider the following scheduling problem. There arem parallel machines andn independent jobs. Each job is to be assigned to one of the machines. The processing of jobj on machinei requires timep
ij
. The objective is to find a schedule that minimizes the makespan. Our main result is a polynomial algorithm which constructs a schedule that is guaranteed to be no longer than twice the optimum. We also present a polynomial approximation scheme for the case that the number of machines is fixed. Both approximation results are corollaries of a theorem about the relationship of a class of integer programming problems and their linear programming relaxations. In particular, we give a polynomial method to round the fractional extreme points of the linear program to integral points that nearly satisfy the constraints. In contrast to our main result, we prove that no polynomial algorithm can achieve a worst-case ratio less than 3/2 unlessP = NP. We finally obtain a complexity classification for all special cases with a fixed number of processing times.
TL;DR: The compatibility of the phylogenetic species concept with various biological needs for species and its use at the exclusion of alternative species concepts are discussed.
TL;DR: Deletion analysis of the Act1 5' intron suggests that the intron-mediated stimulation of GUS expression is associated, in part, with an in vivo requirement for efficient intron splicing.
Abstract: We have characterized the 5' region of the rice actin 1 gene (Act1) and show that it is an efficient promoter for regulating the constitutive expression of a foreign gene in transgenic rice. By constructing plasmids with 5' regions from the rice Act1 gene fused to the coding sequence of a gene encoding bacterial beta-glucuronidase, we demonstrate that a region 1.3 kilobases upstream of the Act1 translation initiation codon contains all of the 5'-regulatory elements necessary for high-level beta-glucuronidase (GUS) expression in transient assays of transformed rice protoplasts. The rice Act1 primary transcript has a noncoding exon separated by a 5' intron from the first coding exon. Fusions that lack this Act1 intron showed no detectable GUS activity in transient assays of transformed rice protoplasts. Deletion analysis of the Act1 5' intron suggests that the intron-mediated stimulation of GUS expression is associated, in part, with an in vivo requirement for efficient intron splicing.
TL;DR: In this article, an array of graphical and numerical techniques facilitate qualitative and quantitative kinematic analysis of fault-slip data, including moment tensor summation, contouring and Bingham statistics of the shortening and extension axes for kinematically scale-invariant faults.
01 Apr 1990
TL;DR: This work applies the general approach to data structures, bin packing, graph coloring, and graph coloring to bipartite matching and shows that a simple randomized on-line algorithm achieves the best possible performance.
Abstract: There has been a great deal of interest recently in the relative power of on-line and off-line algorithms. An on-line algorithm receives a sequence of requests and must respond to each request as soon as it is receiveD. An off-line algorithm may wait until all requests have been received before determining its responses. One approach to evaluating an on-line algorithm is to compare its performance with that of the best possible off-line algorithm for the same problem. Thus, given a measure of "profit", the performance of an on-line algorithm can be measured by the worst-case ratio of its profit to that of the optimal off-line algorithm. This general approach has been applied in a number of contexts, including data structures [SITa], bin packing [CoGaJo], graph coloring [GyLe] and the k-server problem [MaMcSI]. Here we apply it to bipartite matching and show that a simple randomized on-line algorithm achieves the best possible performance.
Veterans Health Administration1, University of Miami2, University of Florida3, Brown University4, University of California, Los Angeles5, Mount Sinai St. Luke's and Mount Sinai Roosevelt6, Harvard University7, University of Pennsylvania8, University of Louisville9, Cornell University10, University of Arizona11, Columbia University12, Abbott Laboratories13, Merck & Co.14
TL;DR: Hepatitis B e antigen and hepatitis B viral DNA disappeared from serum significantly more often in the patients given prednisone plus interferon or 5 million units of interferons alone than in the untreated controls.
Abstract: Background and Methods. Chronic hepatitis B is a common and often progressive liver disorder for which there is no accepted therapy. To assess the efficacy of treatment with interferon, we randomly assigned patients with chronic hepatitis B to one of the following regimens: prednisone for 6 weeks followed by 5 million units of recombinant interferon alfa-2b daily for 16 weeks; placebo followed by 5 million units of interferon daily for 16 weeks; placebo followed by 1 million units of interferon daily for 16 weeks; or observation with no treatment. Results. Hepatitis B e antigen and hepatitis B viral DNA disappeared from serum significantly more often in the patients given prednisone plus interferon (16 of 44 patients, or 36 percent) or 5 million units of interferon alone (15 of 41; 37 percent) than in the untreated controls (3 of 43; 7 percent; P<0.001); the difference between those given 1 million units of interferon (7 of 41; 17 percent) and the controls was not significant. The strongest indep...
TL;DR: In this article, it was shown that there is no control strategy that stabilizes the system in the traditional sense of making all closed-loop trajectories asymptotic to zero.
Abstract: The problem of stabilizing an unstable, time-invariant, discrete-time, linear system by means of state feedback when the measurements of the state are quantized is addressed. It is found that there is no control strategy that stabilizes the system in the traditional sense of making all closed-loop trajectories asymptotic to zero. If the system is not excessively unstable, feedback strategies that bring closed-loop trajectories arbitrarily close to zero for a long time can be implemented. It is also found that when the ordinary linear feedback of quantized state measurements is applied, the resulting closed-loop system behaves chaotically. The asymptotic pseudorandom closed-loop system dynamics differ substantially from what would be predicted by a conventional signal-with-noise analysis of the quantization's effects. Probabilistic reformulations of the stability problem in terms of the invariant measure are considered. >
TL;DR: The collective effects of n-3 PUFAs may account for the reduction in coronary arterial disease in populations consuming foods containing n-1 polyunsaturated fatty acids.
TL;DR: The authors examined the extent to which organizations facing similar conditions make different managerial compensation decisions regarding base pay, bonus pay, and eligibility for long-term incentives, and explored the consequences of those decisions for organizational performance.
Abstract: This study had two general focuses. First, after reviewing the literature on compensation strategy, we examined the extent to which organizations facing similar conditions make different managerial compensation decisions regarding base pay, bonus pay, and eligibility for long-term incentives. Second, working from expectancy and agency theory perspectives, we explored the consequences of those decisions for organizational performance. Using longitudinal data on about 14,000 top-and middle-level managers and 200 organizations, we found significant differences between organizations. Our results suggest that organizations tend to make different decisions about pay contingency, or variability, rather than about base pay. Findings indicate that contingent pay was associated with financial performance but base pay was not.
TL;DR: The ratio of withinversus between-accession diversity was much lower for SC species, indicating that most of the diversity within these species exists between populations, rather than within populations, and the amount of genetic variation in the SI species far exceeded that found in SC species.
Abstract: Forty single-copy, nuclear probes of known chromosomal position were used to examine restriction fragment length polymorphism in the tomato genus Lycopersion. The probes were from three libraries: one cDNA, and two genomic libraries ⦓ne genomic made with EcoRI and the other with PstI. Total DNA from 156 plants representing eight species was cut with five different restriction enzymes and scored in 198 probe-enzyme combinations. Genetic distances between accessions (populations) and species were calculated from the resultant restriction patterns and proportion of shared bands. Accessions belonging to the same species largely clustered together, confirming their current classification. However, one mountain accession, classified as L. peruvianum var. humifusum (LA2150), was sufficiently distinct from the other accessions of L. peruvianum that it may qualify as a separate species L. esculentum and L. pimpinellifolium were the least clearly differentiated, possibly reflecting introgressive hybridization, known to have been promoted by man in recent history. Dendrograms constructed from cDNA versus genomic clones were nearly identical in their general grouping of species. The dendrograms revealed two major dichotomies in the genus: one corresponding to mating behavior [self-compatible (SC) versus self-incompatible (SI) species] and the other corresponding to fruit color (red versus green-fruited species). The ratio of withinversus between-accession diversity was much lower for SC species, indicating that most of the diversity within these species exists between populations, rather than within populations. Overall, the amount of genetic variation in the SI species far exceeded that found in SC species. This result is exemplified by the fact that more genetic variation could be found within a single accession of one of the SI species (e.g., L. peruvianum) than among all accessions tested of any one of the SC species (e.g., L. esculentum or L. pimpinellifolium). Results from this study are discussed in relationship to germ plasm collection/utilization and with regard to the use of RFLPs in tomato breeding and genetics.
TL;DR: In this article, the authors describe two metacognitive tools, concept mapping and Vee diagramming, and report on research utilizing these tools from grades one through university instruction, and discuss the psychological and epistemological foundations underlying these tools.
Abstract: This paper describes two metacognitive tools, concept mapping and Vee diagramming, and reports on research utilizing these tools from grades one through university instruction. The psychological and epistemological foundations underlying these tools is presented briefly. The issues of the dominantly rote-mode nature of much school learning and the resistance of studients (and teachers) to move to meaningful learning strategies fostered by concept mapping and Vee diagramming are discussed. The data available to date from a variety of qualitative and quantitative research studies strongly support the value of these metacognitive tools both for cognitive and affective gains.
TL;DR: This paper discusses an approach for developing completely parallel multilevel preconditioners and describes the simplest application of the technique to a model elliptic problem.
Abstract: In this paper, we shall report on some techniques for the development of preconditioners for the discrete systems which arise in the approximation of solutions to elliptic boundary value problems. Here we shall only state the resulting theorems. It has been demonstrated that preconditioned iteration techniques often lead to the most computationally effective algorithms for the solution of the large algebraic systems corresponding to boundary value problems in two and three dimensional Euclidean space. The use of preconditioned iteration will become even more important on computers with parallel architecture. This paper discusses an approach for developing completely parallel multilevel preconditioners. In order to illustrate the resulting algorithms, we shall describe the simplest application of the technique to a model elliptic problem.
TL;DR: In this paper, two examples are given that substantially simplify the no-hidden-variables theorem of Kochen and Specker, greatly reducing the number of observables considered and requiring no intricate geometric argument.
Abstract: Two examples are given that substantially simplify the no-hidden-variables theorem of Kochen and Specker, greatly reducing the number of observables considered and requiring no intricate geometric argument. While one of the examples also obeys a more powerful version of Bell's theorem, the other does not. The examples provide a new perspective on both of these fundamental theorems and on the relation between them.
TL;DR: Students attending 56 schools in New York State were involved in a 3-year study testing the effectiveness of a cognitive-behavioral approach to substance abuse prevention, and significant prevention effects were found for cigarette smoking, marijuana use, and immoderate alcohol use.
Abstract: Students (N = 4,466) attending 56 schools in New York State were involved in a 3-year study testing the effectiveness of a cognitive-behavioral approach to substance abuse prevention In a randomized block design, schools were assigned to receive (a) the prevention program with formal provider training and implementation feedback, (b) the prevention program with videotaped provider training and no feedback, or (c) no treatment After pretest equivalence and comparability of conditions with respect to attrition were established, students who received at least 60% of the prevention program (N = 3,684) were included in analyses of program effectiveness Significant prevention effects were found for cigarette smoking, marijuana use, and immoderate alcohol use Prevention effects were also found for normative expectations and knowledge concerning substance use, interpersonal skills, and communication skills
TL;DR: The neuroprotective activity of MK-801 against transient global ischemia appears to be largely a consequence of postischemic hypothermia rather than a direct action on NMDA receptor-channels.
Abstract: Several laboratories have reported a significant reduction of ischemia- induced injury to hippocampal neurons in rodents treated with competitive and noncompetitive N-methyl-D-aspartate (NMDA) receptor- channel antagonists. This study examined the effects of the noncompetitive antagonist (+)-5-methyl-10,11-dihydro-5H- dibenzo[a,d]cyclohepten-5,10-imine maleate (MK-801) in Mongolian gerbils subjected to 5 min of bilateral carotid artery occlusion. In adult female gerbils, single doses of MK-801 injected 1 hr prior to ischemia significantly (p less than 0.01) reduced damage to CA1 hippocampal neurons. However, the drug rendered the postischemic animals comatose and hypothermic for several hours compared with the saline-treated animals. In subsequent experiments, animals pretreated with MK-801 and maintained normothermic during and after forebrain ischemia demonstrated no amelioration of hippocampal damage. Gerbils not treated with MK-801, but kept hypothermic in the postischemic period to approximately the same degree (34.5 degrees C) and duration (8 hr) as was induced by MK-801 therapy showed significant (p less than 0.01) protection of CA1 neurons against ischemia. The neuroprotective activity of MK-801 against transient global ischemia appears to be largely a consequence of postischemic hypothermia rather than a direct action on NMDA receptor-channels.