Showing papers by "Brown University published in 1989"

The Yale-Brown Obsessive Compulsive Scale: II. Validity

Abstract: • The development design and reliability of the Yale-Brown Obsessive Compulsive Scale have been described elsewhere. We focused on the validity of the Yale-Brown Scale and its sensitivity to change. Convergent and discriminant validity were examined in baseline ratings from three cohorts of patients with obsessive-compulsive disorder (N = 81). The total Yale-Brown Scale score was significantly correlated with two of three independent measures of obsessive-compulsive disorder and weakly correlated with measures of depression and of anxiety in patients with obsessive-compulsive disorder with minimal secondary depressive symptoms. Results from a previously reported placebo-controlled trial of fluvoxamine in 42 patients with obsessive-compulsive disorder showed that the Yale-Brown Scale was sensitive to drug-induced changes and that reductions in Yale-Brown Scale scores specifically reflected improvement in obsessive-compulsive disorder symptoms. Together, these studies indicate that the 10-item Yale-Brown Scale is a reliable and valid instrument for assessing obsessive-compulsive disorder symptom severity and that it is suitable as an outcome measure in drug trials of obsessive-compulsive disorder.

TVB Runge-Kutta local projection discontinuous galerkin finite element method for conservation laws. II: General framework

Abstract: Construction et analyse d'une classe de methodes a elements finis de Galerkin discontinues a variation totale bornee pour la resolution des lois de conservation. Etude de la convergence. Resultats numeriques

Asymptotic symmetry and local behavior of semilinear elliptic equations with critical sobolev growth

Abstract: On etudie les solutions regulieres non negatives de l'equation conformement invariante −Δu=u (n+2)/(n−2) , u>0 dans une boule perforee, B 1 (0)\{0}⊂R n , n≥3, avec une singularite isolee a l'origine

A model for reasoning about persistence and causation

Abstract: In this paper, we describe a model of causal reasoning that accounts for knowledge concerning cause-and-effect relationships and knowledge concerning the tendency for propositions to persist or not as a function of time passing. Our model has a natural encoding in the form of a network representation for probabilistic models. We explore the computational properties of our model by considering recent advances in computing the consequences of models encoded in this network representation.

Experimental calibration of the aluminum-in-hornblende geobarometer with application to Long Valley caldera (California) volcanic rocks

Abstract: A new geobarometer based on the Al content of igneous hornblendes in equilibrium with melt, fluid, biotite, quartz, sanidine, plagioclase, sphene, and magnetite or ilmenite has been calibrated experimentally. The calibration was performed by equilibrating the required phase assemblage over the pressure range 2-8 kbar at 740-780C, and then analyzing euhedral hornblendes in equilibrium with glass (melt). Experiments were performed on natural samples of both volcanic and plutonic rocks. Earlier empirical calibrations of this geobarometer relied on analyzing natural hornblendes from plutons with the required phase assemblage and inferring pressure from nearby metamorphic country rocks. The experimental calibration differs from the empirical calibrations, especially above 5 kbar, and shows that the Al content of hornblendes in equilibrium with the required phase assemblage is greater for a given total pressure than previously thought. The geobarometers uncertainty is dramatically reduced. The derived equation is P ({plus minus}0.5 kbar) = 3 {minus}3.46 ({plus minus}0.24) + 4.23 ({plus minus}0.13) (Al{sup T}). The geobarometer is applied to post-Bishop Tuff volcanic rocks from Long Valley caldera, California, and reveals that most rhyodacites in this complex erupted from depths of about 6 km. These eruptions occurred over 500,000 yr, suggesting that the rhyodacitic magma reservoir beneath Longmore » Valley had reached a steady P (depth)-T state.« less

Saccade preparation inhibits reorienting to recently attended locations.

Abstract: We measured manual reaction time in normal human subjects to confirm that an eccentric visual signal has a biphasic effect on covert attention and eye movements. First, it summons attention and biases a saccade toward the signal; a subsequent inhibition of return then slows responses to signals at that location. A temporal hemifield dominance for inhibition of return was shown; this finding coverges with observations in neurologic patients to suggest that it is mediated by midbrain pathways. Endogenous orienting of attention, from a central arrow cue, did not activate inhibition of return, whereas endogenous saccade preparation did so as effectively as an exogenous signal, even when no saccade was made. Inhibition of return is activated by midbrain oculomotor pathways and may function as a location "tagging" mechanism to optimize efficiency of visual search. The selectivity of visual perception is guided by brain mechanisms that orient attention in the visual field. One manifestation of visual orienting is overt, consisting of movements of the head or eyes, or both, to focus on the attended spatial position. Covert orienting may occur, however, independently of motor activity and serves to align attention to a spatial location to enhance the processing of or response to signals that occur there. Researchers have studied covert orienting in humans by measuring the pattern of facilitation and inhibition in responding to an eccentric visual target, which result from preliminary cues that either correctly prepare the subject to detect the target at the cued location or summon attention elsewhere in the visual field (Posner, 1980). In this kind of experiment, the eyes remain fixed in the center of the display, and inasmuch the required response is always a simple reaction time (RT) manual key press regardless of target location, these facilitations and inhibitions in RT performance serve as a measure of visual attention that is independent of eye position or response selection. This method has also been used in experiments in which eye movements are made to show that when a peripheral signal is the target ofa saccade, attention moves to the signal before the onset of the saccade (Posner & Cohen, 1980) and that under some circumstances, attention can move in one direction while the eyes move in another (Posner, 1980). A major goal of research in visual attention, addressed in this study, is to determine how neural systems responsible for the covert allocation of visual attention are integrated with

Transforming growth factor alpha may be a physiological regulator of liver regeneration by means of an autocrine mechanism.

Abstract: We investigated whether transforming growth factor alpha (TGF-alpha) is involved in hepatocyte growth responses both in vivo and in culture. During liver regeneration after partial hepatectomy in rats, TGF-alpha mRNA increased; it reached a maximum (approximately 9-fold higher than normal) at the peak of DNA synthesis. The message and the peptide were localized in hepatocytes and found in higher amounts in hepatocytes obtained from regenerating liver. TGF-alpha caused a 13-fold elevation of DNA synthesis in hepatocytes in primary culture and was slightly more effective than epidermal growth factor. TGF-beta blocked TGF-alpha stimulation when added either simultaneously with TGF-alpha or a day later. TGF-alpha message increased in hepatocytes stimulated to undergo DNA synthesis by TGF-alpha or epidermal growth factor, and the peptide was detected in the culture medium by RIA. In the regenerating liver, the increase in TGF-alpha mRNA during the first day after partial hepatectomy coincided with an increase in epidermal growth factor/TGF-alpha receptor mRNA and a decrease (already reported) in the number of these receptors. We conclude that TGF-alpha may function as a physiological inducer of hepatocyte DNA synthesis during liver regeneration by means of an autocrine mechanism and that its stimulatory effects in this growth process are balanced by the inhibitory action of TGF-beta 1.

An efficient method of computing static single assignment form

Abstract: In optimizing compilers, data structure choices directly influence the power and efficiency of practical program optimization. A poor choice of data structure can inhibit optimization or slow compilation to the point where advanced optimization features become undesirable. Recently, static single assignment form and the control dependence graph have been proposed to represent data flow and control flow properties of programs. Each of these previously unrelated techniques lends efficiency and power to a useful class of program optimizations. Although both of these structures are attractive, the difficulty of their construction and their potential size have discouraged their use. We present a new algorithm that efficiently computes these data structures for arbitrary control flow graph We also give analytical and experimental evidence that they are usually {\em linear} in the size of the original program. This paper thus presents strong evidence that these structures can be of {\em practical} use in optimization.

Persistence in infinite-dimensional systems

Abstract: The concept of persistence reflects the survival of all components of a model ecosystem. Most of the results to date are restricted to ordinary differential equations or to dynamics on locally compact spaces. The concept is investigated here in the setting of a $C^0 $-semigroup which is asymptotically smooth. Since the equations of population dynamics often involve delays or diffusion this seems the appropriate setting. Conditions are placed on the flow on the boundary which, given the presence of a global attractor provided by the assumption of dissipativeness and asymptotic smoothness, are necessary and sufficient for persistence.

Growth in a restricted solid-on-solid model.

Abstract: Extensive simulations of growth in a stochastic ballistic deposition model on a (d-1)-dimensional substrate with a constraint on neighboring interface heights are described. The interface width obeys scaling even for small systems and grows as ${t}^{\ensuremath{\beta}}$ with \ensuremath{\beta}=1/(d+1). Generalizations to include irrevelant effects such as noise reduction are discussed as are possible reasons for the discrepancies in earlier results.

Flux lattice melting in high- T c superconductors

Abstract: We derive the wave-vector-dependent elastic moduli for a flux line lattice in compounds with underlying tetragonal crystalline symmetry. We find that it is essential to retain wave-vector dependence of the moduli when dealing with compounds where \ensuremath{\kappa} is large, as it is in the high-${T}_{c}$ materials. We use our results to establish a Lindemann criterion for flux lattice melting, which we then compare with experimental data on two materials, and find excellent agreement. The melting curves are suppressed well below the mean-field superconducting-normal transition line and are linear in temperature over a wide range of magnetic fields. The point H=0, T=${T}_{c}$ is approached as 1-T/${T}_{c}$\ensuremath{\sim}${H}^{1/2}$. The degree of suppression of the melting curves among the different compounds is accounted for in the main by differences in mass anisotropy.

The anisotropic structure of the upper mantle in the Pacific

Abstract: SUMMARY Anisotropic inversions of surface wave data show that the variations in vertical shear velocity, pv, and anisotropy of the oceanic upper mantle in the Pacific are much smoother and more systematic functions of the age of the seafloor than has been reported in previous studies. The data used in this analysis are the pure-path results of previous studies on the lateral distribution of fundamental-mode Love and Rayleigh wave phase velocities (Nishimura & Forsyth 1985, 1988). The pure-path models include parameters which describe the variations with age, azimuthal anisotropy and residual depth anomalies. The calculated velocity models of the upper mantle are constrained to vary smoothly with depth and to represent the minimum deviation from an isotropic starting model. Inversions were performed using the method of Tarantola & Valette (1982). The two best resolved parameters of the computed transversely isotropic model are the shear wave velocity terms, fiv and 5. The results indicate that pv above 200 km progressively increases as a function of the age of the seafloor with the pattern qualitatively mimicking isotherms of theoretical thermal cooling models. If one selects the depth to the maximum negative gradient in shear velocity as being the best available indicator of lithospheric thickness, then the thickness increases from about 15-35 km beneath 0-4 Myr old seafloor to 70-110km in the oldest seafloor. The magnitude of the shear wave anisotropy term, 5, rapidly increases in the first 20 Myr until some apparent constant value is reached in the older regions. A more realistic upper mantle structure is calculated using a priori information on the correlation between changes in shear and compressional wave velocities and the expected nature of the anisotropy. The general results are the same as the previous inversion without a priori constraints. Finally, the effect of attenuation is included, the primary result being an overall increase in 6". The maximum change occurs at around 150 km depth, which reduces the velocity contrast between the lithosphere and asthenosphere. It is therefore more difficult to make a distinction between the plate and low-velocity zone when the effect of attenuation is included. An estimate of the azimuthal anisotropic structure is obtained by inverting for the Rayleigh wave cos 2v coefficients using derivatives calculated by the method of Montagner & Nataf (1986). The reference frame used to constrain the azimuthal effect is that of fossil seafloor spreading direction. The results indicate that in regions of the Pacific less than 80 Myr in age, there is significant anisotropy down to 200 km depth. In regions older than 80 Myr, azimuthal anisotropy is confined to the upper SO km. The transverse and azimuthal anisotropy structures can be explained by an oceanic upper mantle containing olivine with different orientations.

On uniqueness and existence of viscosity solutions of fully nonlinear second‐order elliptic PDE's

Abstract: We prove several comparison and existence theorems for viscosity solutions of fully nonlinear degenerate elliptic equations. One of them extends some recent uniqueness results by Jensen. Some establish the uniqueness of solutions for second-order Isaacs' equations and hence include the uniqueness results for Bellman equations by P.-L. Lions. Our comparison results apply even for discontinuous solutions and so Perron's method readily yields the existence of continuous solutions.

Synchronized excitation and inhibition driven by intrinsically bursting neurons in neocortex

Abstract: 1. The cellular mechanisms of synchronous synaptic activity were studied in isolated slices of rat SmI neocortex in which gamma-aminobutyric acid (GABA)-mediated inhibition was slightly suppressed. Intracellular measurements were made from single neurons, and extracellular recordings monitored the timing and intensity of population events. 2. Neurons in cortical layers II-VI were classified by the attributes of their single action potentials and repetitive firing patterns during injection of intracellular current pulses. Regular-spiking (RS) cells occurred in all layers and had relatively long-duration spikes and strong frequency adaptation. Intrinsically bursting (IB) cells occurred only in layers IV and V and generated bursts of greater than or equal to 3 spikes; some IB cells of lower-layer V produced repetitive bursts during long depolarizing pulses. Fast-spiking (FS) cells had brief spikes and little or no adaptation and fired at high frequencies. 3. When GABAA-mediated inhibition was slightly reduced with low doses of bicuculline methiodide (BMI, 0.8-1.0 microM), synchronous events were evoked by stimulating layer VI with single shocks. Synchronous events were characterized by prominent, often all-or-none extracellular field potentials that propagated horizontally for variable distances up to several millimeters. Large field potentials were invariably correlated with excitatory and inhibitory postsynaptic potentials (EPSPs and IPSPs) in single neurons. Both PSPs and field potentials often had long (up to 250 ms) and variable latencies, and sometimes two or more events were generated by single stimuli. In all cases the PSPs and field potentials were synchronous. Both field potentials and single cells sometimes generated short epochs (3-7 peaks) of rhythmic events at 20-50 Hz. 4. The physiological class of single neurons was correlated with the relative dominance of excitation and inhibition during each synchronous event. In phase with each synchronous event, most RS cells were very strongly inhibited with only small amounts of concurrent excitation. By contrast, IB cells were strongly and consistently excited, with relatively little inhibition. FS cells were also phasically excited. 5. Anatomic studies have identified RS and IB cells as pyramidal cells and FS cells as GABAergic nonpyramidal cells. This implies that, during the synchronous events of the present study, the majority of pyramidal cells were dominated by IPSPs. Synchronous excitation of FS cells, the presumed inhibitory interneurons, is consistent with this. Only a subset of the pyramidal neurons, almost all of them IB cells of the middle layers, displayed strong, synchronous excitation and clusters of action potentials.(ABSTRACT TRUNCATED AT 400 WORDS)

Debunking myths about self-quitting: Evidence from 10 prospective studies of persons who attempt to quit smoking by themselves.

Abstract: This article examines data from 10 longterm prospective studies (N greater than 5,000) in relation to key issues about the self-quitting of smoking, especially those discussed by Schachter. When a single attempt to quit was evaluated, self-quitters' success rates were no better than those reported for formal treatment programs. Light smokers (20 or less cigarettes per day) were 2.2 times more likely to quit than heavy smokers. The cyclical nature of quitting was also examined. There was a moderate rate (mdn = 2.7%) of long-term quitting initiated after the early months (expected quitting window) of these studies, but also a high rate (mdn = 24%) of relapsing for persons abstinent for six months. The number of previous unsuccessful quit attempts was unrelated to success in quitting. Finally, there were few occasional smokers (slips) among successful long-term quitters. We argue that quitting smoking is a dynamic process, not a discrete event.

Readings in object-oriented database systems

Abstract: This paper summarizes the interface, implementation, and use of a server process tha t is used as a backend by an object-oriented database system. This server is responsible for managing objects on secondary storage, managing transactions, and implementing a simple form of trigger. We sketch the interface of this system and point out some of the more interesting implementat ion issues tha t were encountered in building

Solving time-dependent planning problems

Abstract: We are interested in constructing solutions to time-dependent planning problems: problems in which time spent planning affects the utility of the system''s performance. In a previous paper, we define a fraomework for constructing solutions to time-dependent planning problems called expectation-driven iterative refinement. In this paper, we analyze and solve a moderately complex time-dependent planning problem involving path planning for a mobile robot, as a way of exploring a methodology for applying expectation-driven iterative refinement.

Treating Alcohol Dependence: A Coping Skills Training Guide

Abstract: Now in a revised and expanded second edition, this book presents a straightforward, multi-session coping skills training program that has been proven effective in helping alcohol-dependent individuals. The volume provides everything needed to implement the program, including a clear theoretical and empirical rationale, step-by-step session guidelines, helpful clinical pointers, and over 40 reproducible client handouts, assessment instruments, and therapist forms. Sessions focus on developing key interpersonal and intrapersonal skills to help participants learn positive strategies for coping with the everyday demands of life and resisting the urge to drink. Updated throughout to reflect current ideas and research findings on addictive behavior change, the protocols in the second edition have been reorganized and streamlined for greater applicability in today's managed care settings. Two entirely new chapters provide guidelines for conducting cue exposure treatment and addressing dual diagnosis issues, with particular attention to tobacco dependence.

Change in boron coordination in alkali borate glasses, and mixed alkali effects, as elucidated by NMR

Abstract: NMR with substantial enhancement in signal-to-noise ratio (primarily from gisnal averaging and fast passage techniques) and thermal analysis are utilized to reinvestigate binary alkali borate glasses. The experimental results for the Li, Na, K, Rb and Cs borate glasses at various alkali contents show a strong dependence of the fraction, N4, of 4-coordinated borons on the particular alkali ion. NMR and thermal analysis experimental results for half-and-half mixed LiNa, LiK, LiRb and LiCs borate glasses at different total alkali content are also presented in this paper. It was found that the measured N4 for the mixed alkali glass is less than the value expected from a simple superposition of the values of the constituent alkalis, and in some cases is even less than either of the N4 values for the relevant single alkali glasses. 11B and 133Cs nuclear magnetic resonance results and Tg measurements are used to strengthen the evidence supporting the pairing model suggested by several workers for the mixed alkali effect.

Context and orientation in hypermedia networks

Abstract: The core of hypermedia's power lies in the complex networks of links that can be created within and between documents. However, these networks frequently overwhelm the user and become a source of confusion. Within Intermedia, we have developed the Web View-a tool for viewing and navigating such networks with a minimum of user confusion and disorientation. The key factors in the Web View's success are a display that combines a record of the user's path through the network with a map of the currently available links; a scope line that summarizes the number of documents and links in the network; and a set of commands that permit the user to open documents directly from the Web View.