Showing papers by "Dartmouth College published in 1985"

Sequence and structure of a human glucose transporter

Abstract: The amino acid sequence of the glucose transport protein from human HepG2 hepatoma cells was deduced from analysis of a complementary DNA clone. Structural analysis of the purified human erythrocyte glucose transporter by fast atom bombardment mapping and gas phase Edman degradation confirmed the identity of the clone and demonstrated that the HepG2 and erythrocyte transporters are highly homologous and may be identical. The protein lacks a cleavable amino-terminal signal sequence. Analysis of the primary structure suggests the presence of 12 membrane-spanning domains. Several of these may form amphipathic alpha helices and contain abundant hydroxyl and amide side chains that could participate in glucose binding or line a transmembrane pore through which the sugar moves. The amino terminus, carboxyl terminus, and a highly hydrophilic domain in the center of the protein are all predicted to lie on the cytoplasmic face. Messenger RNA species homologous to HepG2 glucose transporter messenger RNA were detected in K562 leukemic cells, HT29 colon adenocarcinoma cells, and human kidney tissue.

What is computer ethics

Abstract: Computers are special technology and they raise some special ethical issues. This chapter discusses what makes computers different from other technology and how this difference makes a difference in ethical considerations. It describes computer ethics and shows why this emerging field is both intellectually interesting and enormously important. A typical problem in computer ethics arises because there is a policy vacuum about how computer technology should be used. Computers provide us with new capabilities and these in turn give us new choices for action. Computer ethics include consideration of both personal and social policies for the ethical use of computer technology. The mark of a basic problem in computer ethics is one in which computer technology is essentially involved and there is an uncertainty about what to do and even about how to understand the situation. Hence, not all ethical situations involving computers are central to computer ethics.

The Molecular Basis of Cancer

Abstract: Malignant Transformation Growth and Spread of Cancer Molecular Abnormalities in Specific Malignancies, Molecular Basis of Cancer Therapy.

The Effect of Pore Size Distribution on the Rate of Enzymatic Hydrolysis of Cellulosic Substrates

Abstract: Hard and softwoods were pretreated by mild acid hydrolysis and their pore size distribution determined. Regardless of the substrate, the initial rate of hydrolysis using cellulase from Trichoderma reesei is linearly correlated with the pore volume of the substrate accessible to a nominal diameter of 51 A representative of the size of the cellulase. In contrast, crystallinity index has no relationship to the rate of hydrolysis.

Valuation Effects of Corporate Debt Offerings

Abstract: This paper analyzes the effect of corporate debt offerings on stock prices. Straight debt offerings have non-positive price effects, while convertible debt offerings have significantly negative effects. Public utility mortgage (non-convertible) bond offerings have marginally negative effects, and the effect is significantly negative when the proceeds are used to finance the utility’s investment program. Cross-sectional regressions reveal no relation between offer-induced price effects and offering size, rating, post-offer changes in abnormal earnings or debt-related tax shields. The evidence is inconsistent with theories predicting that the price effects of capital structure changes go in the direction of the leverage change.

Consumer Promotions and the Acceleration of Product Purchases

Abstract: One potential consequence of consumer promotions is the acceleration of consumer category purchases. Purchase acceleration can assume two forms: purchasing of a larger quantity or shortening of interpurchase time. This research presents an analytical framework for measuring purchase acceleration, and applies that framework to the analysis of two product classes. The effects of coupons, manufacturer and retailer advertising, and price cuts are examined. Different market segments and loyalty groups are also compared in terms of the degree of purchase acceleration exhibited.

Proactive feedback seeking: The instrumental use of the information environment

Abstract: This paper presents a field test of several hypotheses concerning proactive feedback seeking behaviour (FSB). The hypotheses are derived from the general assertion that feedback is a valuable individual resource. As such, feedback is hypothesized to be subject to active seeking behaviour by individuals. Feedback seeking is proposed as an instrumental response of employees attempting to achieve their goals within an evaluative context. Hypotheses relating such seeking to both personal (length of tenure, job involvement and tolerance for ambiguity) and organizational (contingency uncertainty and role ambiguity) variables are formulated and tested. Role ambiguity, contingency uncertainty, tenure within the organization and job involvement were found to predict FSB. The relationships between both role ambiguity and contingency uncertainty and proactive FSB were found to be moderated by an individual's ability to tolerate ambiguity.

Emotional reactions to a political leader's expressive displays.

Abstract: Forty college students viewed videotaped excerpts of happiness/reassurance, anger/ threat, and fear/evasion expressive displays by President Reagan. Within each display condition one excerpt was presented in image-only and one in sound-plus-image format. Emotional reactions were assessed by facial electromyography (EMG) from the brow and cheek regions and by skin resistance and heart rate. Following each excerpt, subjects also reported verbally the intensity of eight emotions. Self-reported emotions were influenced strongly by both the expressive displays and prior attitude toward Reagan as well as by media condition. Facial EMG indicated smiling during happiness/reassurance displays and frowning during anger/threat and fear/evasion displays, especially during image-only presentations. Display effects were also found for skin resistance responses when the media conditions were combined and for heart rate changes in the sound-plus-image condition. In contrast to the self-report measures, expressive and autonomic differences did not reveal an interaction between prior attitude and display condition. These results indicate that expressive displays had a direct emotional impact on viewers and that prior attitudes influenced retrospective self-reports of emotion but did not affect autonomic or facial muscle responses during stimulus exposure.

Voronoi diagrams based on convex distance functions

Abstract: We present an “expanding waves” view of Voronoi diagrams that allows such diagrams to be defined for very general metrics and for distance measures that do not qualify as metrics. If a pebble is dropped into a still pond, circular waves move out from the point of impact. If n pebbles are dropped simultaneously, the places where wave fronts meet define the Voronoi diagram on the n points of impact.The Voronoi diagram for any normed metric, including the Lp metrics, can be obtained by changing the shape of the wave front from a circle to the shape of the “circle” in that metric. (For example, the “circle” in the L1 metric is diamond shaped.) For any convex wave shape there is a corresponding convex distance function. If the shape is not symmetric about its center (a triangle, for example) then the resulting distance function is not a metric, although it can still be used to define a Voronoi diagram.Like Voronoi diagrams based on the Euclidean metric, the Voronoi diagrams based on other normed metrics can be used to solve various closest-point problems (all-nearest-neighbors, minimum spanning trees, etc.). Some of these problems also make sense under convex distance functions which are not metrics. In particular, the “largest empty circle” problem becomes the “largest empty convex shape” problem, and “motion planning for a disc” becomes “motion planning for a convex shape”. These problems can both be solved quickly given the Voronoi diagram. We present an asymptotically optimal algorithm for computing Voronoi diagrams based on convex distance functions.

Relations among regular and irregular morphologically related words in the lexicon as revealed by repetition priming.

Abstract: Several experiments examined repetition priming among morphologically related words as a tool to study lexical organization. The first experiment replicated a finding by Stanners, Neiser, Hernon, and Hall (Journal of Verbal Learning and Verbal Behavior, 1979,18, 399-412), that whereas inflected words prime their unaffixed morphological relatives as effectively as do the unaffixed forms themselves, derived words are effective, but weaker, primes. The experiment also suggested, however, that this difference in priming may have an episodic origin relating to the less formal similarity of derived than of inflected words to unaffixed morphological relatives. A second experiment reduced episodic contributions to priming and found equally effective priming of unaffixed words by themselves, by inflected relatives, and by derived relatives. Two additional experiments found strong priming among relatives sharing the spelling and pronunciation of the unaffixed stem morpheme, sharing spelling alone, or sharing neither formal property exactly. Overall, results with auditory and visual presentations were similar. Interpretations that repetition priming reflects either repeated access to a common lexical entry or associative semantic priming are both rejected in favor of a lexical organization in which components of a word (e.g., a stem morpheme) may be shared among distinct words without the words themselves, in any sense, sharing a “lexical entry.”

Group Decision Making Under Threat: The Tycoon Game

Abstract: The relationship between external threat and group decision-making processes was tested with 24 groups involved in a management simulation called Tycoon.1 Results indicate a restriction in informat...

Mergers and the Market Concentration Doctrine: Evidence from the Capital Market

Abstract: The market concentration doctrine predicts that a horizontal merger is more likely to have collusive, anticompetitive effects the greater the merger-induced change in industry concentration. Since a collusive, anticompetitive merger generates an increase in the industry's quality-adjusted product price (or a decrease in factor prices), it also follows from the doctrine that the merger-induced expected benefits to the product market rivals of the merging firms should be an increasing function of the concentration change. The empirical results of this paper, which are based on the industry wealth effect of a large sample of horizontal mergers, including cases found in violation of antimonopoly laws, fail to support this prediction. This conclusion is robust with respect to assumptions concerning the probability that a proposed merger will be prevented by the law enforcement agencies, and it continues to hold after transforming the industry wealth effect into a hypothetical, constant expected change in the industry's product price. The results imply that the levels of concentration and market shares found in the Department of Justice's merger guidelines are unlikely to identify truly anticompetitive mergers.

Terminal Cretaceous Environmental Events

Abstract: The geologic record of terminal Cretaceous environmental events indicates that iridium and other associated elements were not deposited instantaneously but during a time interval spanning some 10,000 to 100,000 years. The available geologic evidence favors a mantle rather than meteoritic origin for these elements. These results are in accord with the scenario of a series of intense eruptive volcanic events occurring during a relatively short geologic time interval and not with the scenario of a single large asteroid impact event.

Antimerger Policy Under the Hart-Scott-Rodino Act: A Reexamination of the Market Power Hypothesis

Abstract: Enforcement powers granted under the 1978 Hart-Scott-Rodino Antitrust Improvements Act were intended to enhance the antitrust agencies' ability to select truly anticompetitive mergers for prosecution. For example, the HSR Act imposes automatic delays on proposed mergers, so that the agencies have time to consider the mergers' competitive effects before they are completed. Also, it provides the agencies with the legal right to compel industry participants to reveal merger-related information during precomplaint investigations. Earlier studies by Eckbo (1983) and Stillman (1983) show that the HSR Act addressed a genuine problem: they conclude that the challenged horizontal mergers in their samples, which cover the 1963-78 period, were not anticompetitive. In this paper we test the proposition that the HSR Act has in fact produced a significant improvement in the agencies' case selection record. We reject this proposition and conclude instead that he merger cases in our sample that were filed after 1978 were mounted against mergers that apparently would not have harmed competition.

Spatial maps of directed visual attention.

Abstract: Simple reaction times (RTs) to a visual target are facilitated when the target occurs at a location expected by an observer, and are slowed when the target occurs at the mirror-symmetric location contralateral to the expectancy (e.g., Posner, 1978; Posner, Snyder, & Davidson, 1980). The spatial extent of this attention effect was examined by inducing subjects to expect the target at one location and introducing occasional probe flashes at other locations throughout the visual field. The results indicated that RTs to these probes were equivalent to those obtained at the expected location so long as the probe was in the same hemifield as the subject's expectancy. Conversely, RTs to probes in the hemifield opposite the expectancy generated uniformly slower response times. These results were obtained when the expected location varied in eccentricity from 2 degrees to 16 degrees along the horizontal meridian. In addition, when the expected and unexpected locations were within the same hemifield, no expectancy effects were observed. Under these conditions, the frequently used metaphor that directed visual attention operates like a spatially restricted "beam" appears inaccurate. The implications of these findings for current views of directed attention are considered. Language: en

Basic curricular goals in medical ethics.

Abstract: Formal teaching of ethics in the medical school curriculum has increased greatly during the past 15 years. Yet, schools vary in how much attention they give the subject, and even those that do offe...

Video microscopy of fast axonal transport in extruded axoplasm: A new model for study of molecular mechanisms

Abstract: The development of AVEC-DIC microscopy and the application of this method to the study of fast axonal transport in isolated axoplasm extruded from the giant axon of the squid Loligo pealei provides a new paradigm for analyzing the intracellular transport of membranous organelles. The size of the axon, the number of transported particles, and the absence of permeability barriers like the plasma membrane in this preparation permit many experiments that are difficult or impossible to perform using other model systems. The use and features of this preparation are described in detail and a number of properties are evaluated for the first time. The process of extrusion is characterized. Particle movement is evaluated both in the interior of extruded axoplasm and along individual fibrils that extend from the periphery of perfused axoplasm. The role of divalent cations, particularly Ca2+, and the effects of elevated Ca2+ on axoplasmic organization and transport are analyzed. A series of pharmacological agents and polypeptides that alter cytoskeletal organization are used to examine the role of microfilaments and microtubules in fast transport. Finally, the effects of depleting ATP and of adding ATP analogues are discussed. The extruded axoplasm preparation is shown to be an invaluable model system for biochemical and pharmacological analyses of the molecular mechanisms of intracellular transport.

Suicide attempts associated with akathisia.

Abstract: The authors report two cases of impulsive suicide attempts associated with akathisia. In both cases, suicidal ideation appeared suddenly, concurrent with neuroleptic-induced akathisia, and disappeared when the akathisia was treated.

Exposure to a cat produces opioid analgesia in rats.

Abstract: Two experiments were conducted to test the prediction that rats should react with reduced sensitivity/reactivity to nociceptive stimulation in the presence of a cat. In Experiment 1, naloxone or saline was administered, and rats were exposed to no stimulus, a novel stimulus, or a cat. In Experiment 2, rats were exposed to either no stimulus or a cat, and naltrexone was administered. In both experiments, rats tested in the presence of the cat showed a significant reduction in sensitivity/reactivity to a skin-irritating formalin injection. Naltrexone reversed this analgesia.

Neogene mammalian faunal change in southern Asia: Correlations with climatic, tectonic, and eustatic events

Abstract: The fluvial Neogene Siwalik formations of northern Pakistan span long time intervals with only minor hiatuses and, being highly fossiliferous, are uniquely suited for studies of change in mammalian faunas. Magnetostratigraphic correlations of a critical stratigraphic section give dates for 45 middle and late Miocene biostratigraphic events. These mark either first appearances or extinctions in the mammal fauna and show that in the Siwaliks there were major fauna turnovers at between 20 and 16 Ma and at 9.5 and 7.4 Ma. Two minor faunal events are dated at 13.2 and about 12 Ma. Many species making their first appearance were immigrants from Europe or Africa and indicate when connections to those regions existed. Immigration and extinction were the dominant modes of faunal change; in situ evolution was much less important. The Siwalik biostratigraphic record correlates closely to climatic, oceanographic, and tectonic events, which probably controlled immigration into southern Asia. Abiotic events were therefore important factors affecting evolution of the mammal communities.

Pathologic features of the CHARGE association: Support for involvement of the neural crest

Abstract: Defects associated with choanal atresia include coloboma, cardiac anomalies (usually involving the conotruncal region), physical or mental retardation, genital hypoplasia, and abnormalities of the ear. This constellation of defects is known as the "CHARGE" association and may be accompanied by other anomalies. Many of these defects seem to result from abnormalities in the development, migration, or interaction of cells of the cephalic neural crest. The range of variation in neural crest development is substantial, as indicated by the rather large number of malformation complexes and syndromes that are related phenotypically to the CHARGE association. The increasingly unwieldy nature of this collection of malformations demonstrates the need for an expanded classification of the "neurocrestopathies."

Recursive methods for computing the Abel transform and its inverse

Abstract: The Abel transform and its inverse appear in a wide variety of problems in which it is necessary to reconstruct axisymetric functions from line-integral projections. We present a new family of algorithms, principally for Abel inversion, that are recursive and hence computationally efficient. The methods are based on a linear, space-variant, state-variable model of the Abel transform. The model is the basis for deterministic algorithms, applicable when data are noise free, and least-squares-estimation (Kalman filter) algorithms, which accommodate the noisy data case. Both one-pass (filtering) and two-pass (smoothing) estimators are considered. In computer simulations, the new algorithms compare favorably with previous methods for Abel inversion.

Feedback Obstruction: The Influence of the Information Environment on Employee Turnover Intentions

Abstract: A model of the relationship between feedback obstruction and employee turnover intent is proposed and tested. Eighty-nine pharmaceutical sales representatives completed questionnaires measuring the value of feedback, feedback obstruction across five sources of information, anxiety, (dis)satisfaction, and turnover intent. Results demonstrate that the obstruction of several feedback sources is significantly correlated with anxiety, (dis)satisfaction, and turnover intentions. A regression analysis reveals that self- and supervisory feedback obstruction bear the strongest relationships to turnover intent. Interestingly, the self-feedback obstruction relationship is not in the predicted direction.

Early vascularization of the embryonic cerebral cortex: Golgi and electron microscopic studies

Abstract: Two developmental aspects in the establishment of the vasculature of the embryonic cerebral cortex have been analyzed: the vascular perforation of the external basal lamina and marginal glia by leptomeningeal capillaries and their early intracortical angiogenesis. Electron microscopic and rapid Golgi preparations have been used in this study. Four phases have been identified in the vascular perforation of the cortex. First, the leptomeningeal capillary approaches and establishes direct contact with the external basal lamina and marginal glia of the cerebral cortex. Second, the leading endothelium of the glia-touching capillary undergoes considerable membrane activity forming many filopodia and pseudopodia. Some filopodia of this activated endothelium perforate the vascular and cortical basal laminae and penetrate into the neural tissue. This filopodial perforation is accompanied by swelling and disintegration of the subadjacent marginal glial endfeet. Third, the original perforation enlarges progressively and allows an entire endothelial cell (or cells) to penetrate into the neural tissue. Fourth, proliferation and progressive canalization of penetrated endothelial cells result in the formation of a new cortical capillary in situ. Its proximal wall becomes surrounded by perivascular glial processes which appear to replace the degenerated ones. Thus a vasculoglial barrier is formed around the growing capillary, isolating it from the neural tissue, while the filopodia at its leading edge are still growing among the neural elements without recognizable basal lamina. The formation of a shallow pial-funnel at the capillary entrance can also be recognized at this time. This funnel contains the fine processes of leptomeningeal cells, a few collagen fibers, and the basal laminae of the penetrating vessel and of the perivascular glia. It represents an early stage in the formation of the Virchow-Robin space. The intracortical embryonic vasculature is characterized by both capillary angiogenesis and regression and by the formation of anastomotic plexuses. While capillary angiogenesis and reabsorption are found everywhere and appear as random phenomena, the location of the anastomotic plexuses is specific and always associated with actively growing cortical regions.

Health experiences of operating room personnel.

Abstract: In an attempt to evaluate health experiences of operating room personnel using previously published reports, the authors calculated summary relative risks (RRs) for each outcome under investigation by combining data from six studies For each summary RR, they also calculated 95% confidence limits; when the range of the confidence interval excludes 10, the increased risk is statistically significant at the 005 level The most consistent evidence was for spontaneous abortion among pregnant physicians and nurses who work in operating rooms, where the RR was 13 (95% confidence limits from 12 to 14) For liver disease there were statistically significant increased RRs among both men (16, 13-19) and women (15, 12-19), but these were based on smaller numbers of studies Although the results of pooled analyses are suggestive, most studies of this issue have relied on voluntary responses and self-reported outcomes, so that response and/or recall bias could explain these findings In addition, these investigations generally have examined working in operating rooms rather than actual exposure to anesthetic gases Finally, there have been considerable improvements in operating room scavenging systems during the last decade Thus, prospective cohort studies are needed to determine whether there is a relationship between current levels of occupational exposure to anesthetic gases and adverse outcomes, particularly spontaneous abortion and liver disease

Presenting conditions of 1539 population‐based lung cancer patients by cell type and stage in new hampshire and vermont

Abstract: The authors identified all newly diagnosed lung cancer cases in New Hampshire and Vermont for the period 1973 through 1976 and abstracted clinical data on presenting symptoms and findings from their hospital records. Microscopy slides were also reviewed, when possible, to confirm cell type. The most frequent presenting symptoms were weight loss (46%) and cough (45%). Other common symptoms were dyspnea (37%), weakness (34%), chest pain (27%), and hemoptysis (27%). The presence of symptoms and findings was in general related to disease stage but bore little relationship to cell type. These results differ from those of previously reported case series that were based on surgical, radiation therapy, or Veterans Hospital groups, but the current data agree closely with those from another population-based series in Finland.