Showing papers by "Brown University published in 1983"

Equation of motion for a small rigid sphere in a nonuniform flow

Abstract: The forces on a small rigid sphere in a nonuniform flow are considered from first prinicples in order to resolve the errors in Tchen’s equation and the subsequent modified versions that have since appeared. Forces from the undisturbed flow and the disturbance flow created by the presence of the sphere are treated separately. Proper account is taken of the effect of spatial variations of the undisturbed flow on both forces. In particular the appropriate Faxen correction for unsteady Stokes flow is derived and included as part of the consistent approximation for the equation of motion.

THE McMASTER FAMILY ASSESSMENT DEVICE

Abstract: This paper describes the McMaster Family Assessment Device (FAD), a newly developed questionnaire designed to evaluate families according to the McMaster Model of Family Functioning. The FAD is made up of seven scales which measure Problem Solving, Communication, Roles, Affective Responsiveness, Affective Involvement, Behavior Control and General Functioning. The paper describes the procedures used to develop the FAD and presents scale means and scale reliabilities from a sample of 503 individuals.

Assessing Self‐maintenance: Activities of Daily Living, Mobility, and Instrumental Activities of Daily Living

Abstract: The aging of the population of the United States and a concern for the well-being of older people have hastened the emergence of measures of functional health. Among these, measures of basic activities of daily living, mobility, and instrumental activities of daily living have been particularly useful and are now widely available. Many are defined in similar terms and are built into available comprehensive instruments. Although studies of reliability and validity continue to be needed, especially of predictive validity, there is documented evidence that these measures of self-maintaining function can be reliably used in clinical evaluations as well as in program evaluations and in planning. Current scientific evidence indicates that evaluation by these measures helps to identify problems that require treatment or care. Such evaluation also produces useful information about prognosis and is important in monitoring the health and illness of elderly people.

Micromechanics of Crystals and Polycrystals

Abstract: Publisher Summary This chapter focuses on micromechanics of crystals and polycrystals. In Section II of the chapter, a brief outline of only some of the important features of the micromechanics of crystalline plasticity is given. The discussion is confined to plastic flow caused by dislocation slip, and face-centered-cubic crystals are used in the examples of dislocation mechanisms. Particular attention is paid to kinematics and to the phenomenology of strain hardening, because these are shown to play dominant roles in macroscopic response. In Section III, constitutive laws for elastic-plastic crystals are developed. The framework draws heavily on Hill's analysis of the mechanics of elasticplastic crystals, but the theory is extended by incorporating the possibility of deviations from the Schmid rule of a critical resolved shear stress for slip. Deviations from the Schmid rule are motivated by micromechanical models for dislocation motion and are shown to lead to deviations from the “normality flow rule” of continuum plasticity. The implications of these “non-Schmid effects” regarding the stability of plastic flow are brought out via some examples of models for kinks bands and shear bands in Section IV. In Section IV some examples of analyses of elastic-plastic deformation in crystals are discussed. The chapter concludes with some suggestions for fruitful research. These involve extensions of the theory to finite-strain rate-dependent polycrystalline models.

A mode control model of counting and timing processes

Abstract: The similarity of animal counting and timing processes was demonstrated in four experiments that used a psychophysical choice procedure. In Experiment 1, rats initially learned a discrimination between a two-cycle auditory signal of 2-sec duration and an eight-cycle auditory signal of 8-sec duration. For the number discrimination test, the number of cycles was varied, and the signal duration was held constant at an intermediate value. For the duration discrimination test, the signal duration was varied, and the number of cycles was held constant at an intermediate value. Rats were equally sensitive to a 4:1 ratio of counts (with duration controlled) and a 4:1 ratio of times (with number controlled). The point of subjective equality for the psychophysical functions that related response classification to signal value was near the geometric mean of the extreme values for both number and duration discriminations. Experiment 2 demonstrated that 1.5 mg/kg of methamphetamine administered intraperitoneally shifted the psychophysical functions for both number and duration leftward by approximately 10%. Experiment 3 demonstrated that the magnitude of cross-modal transfer from auditory signals to cutaneous signals was similar for number and duration. In Experiment 4 the mapping of number onto duration demonstrated that a count was approximately equal to 200 msec. The psychophysical functions for number and duration were fit with a scalar expectancy model with the same parameter values for each attribute. The conclusion was that the same internal mechanism is used for counting and timing. This mechanism can be used in several modes: the "event" mode for counting or the "run" and the "stop" modes for timing.

An evaluation of criteria to deduce the sense of movement in sheared rocks

Abstract: Some of the most useful criteria for the deduction of the sense of shear are summarized for use in areas where unequivocal field evidence is lacking. Apparently conflicting evidence from rotated pressure-shadow regions around porphyroclasts and porphyroblasts is clarified. The use of quartz-crystallographic fabric asymmetry to deduce the shear sense in the bulk rock should be treated with caution and used only together with detailed microstructural observations.

Analyzing insect movement as a correlated random walk.

Abstract: This paper develops a procedure for quantifying movement sequences in terms of move length and turning angle probability distributions. By assuming that movement is a correlated random walk, we derive a formula that relates expected square displacements to the number of consecutive moves. We show this displacement formula can be used to highlight the consequences of different searching behaviors (i.e. different probability distributions of turning angles or move lengths). Observations of Pieris rapae (cabbage white butterfly) flight and Battus philenor (pipe-vine swallowtail) crawling are analyzed as a correlated random walk. The formula that we derive aptly predicts that net displacements of ovipositing cabbage white butterflies. In other circumstances, however, net displacements are not well-described by our correlated random walk formula; in these examples movement must represent a more complicated process than a simple correlated random walk. We suggest that progress might be made by analyzing these more complicated cases in terms of higher order markov processes.

Intersection homology II

Abstract: In [19, 20] we introduced topological invariants IH~,(X) called intersection homology groups for the study of singular spaces X. These groups depend on the choice of a perversity p: a perversity is a function from {2, 3, ...} to the non-negative integers such that both /~(c) and c 2 / ~ ( c ) are positive and increasing functions of c (2.1). The group IHr is defined for spaces X called pseudomanifolds: a pseudomanifold of dimension n is a space that admits a stratification X ~ X n ~ X n _ z ~ X n _ 3 ~ . . . ~ x 1 ~ X 0

Selective adjustment of the speed of internal clock and memory processes.

Abstract: Four experiments studied the scaling of time by rats. The purpose was to determine if internal clock and memory processes could be selectively adjusted by pharmacological manipulations. All of the experiments used a temporal discrimination procedure in which one response ("short") was reinforced following a 2-sec noise signal and a different response ("long") was reinforced following an 8-sec noise signal; unreinforced signals of intermediate duration were also presented. The proportion of "long" responses increased as a function of signal duration. All drugs were administered intraperitoneally (ip) and their effect on clock or memory processes was inferred from the observed pattern of change in the point of subjective equality of the psychophysical functions under training and testing conditions. Experiment 1 demonstrated that methamphetamine (1.5 mg/kg) can selectively increase clock speed and that haloperidol (.12 mg/kg) can selectively decrease clock speed. Experiment 2 demonstrated that footshock stress (.2 mA) can selectively increase clock speed during continuous administration but leads to a decrease in clock speed below control values when the footshock is abruptly terminated. Experiment 3 demonstrated that vasopressin (.07 pressor units/kg) and oxytocin (.02 pressor units/kg) can selectively decrease the remembered durations of reinforced times, which suggests that memory storage speed increased. Experiment 4 demonstrated that physostigmine (.01 mg/kg) can selectively decrease the remembered durations of reinforced times and that atropine (.05 mg/kg) can selectively increase these remembered durations, which suggests that memory storage speed was differentially affected. The conclusion is that internal clock and memory processes can be dissociated by selectively adjusting their speed of operation and that these changes can be quantitatively modeled by a scalar timing theory.

11B NMR studies and structural modeling of Na2O-B2O3-SiO2 glasses of high soda content

Abstract: NMR techniques are employed to determine the relative fractions of boron atoms in Na2OB2O3SiO2 glasses of high soda content. The data show that if enough Na2O is added, four-coordinated borons are destroyed and borons with one or two non-bridging oxygens are created, but that both the beginning point and the rate of these processes depend strongly on the amount of silica present. These findings are shown to be quantitatively inconsistent with structural models previously suggested in the literature. Utilizing the concept of proportionate atomic sharing of the additional Na2O, a new structural model is proposed for K

Movements of attention across the visual field

Abstract: Vocal reaction times were measured for targets presented at three distances from fixation The targets were preceded by a cue, and the time interval between the cue and the target (stimulus-onset asynchrony; SOA) was varied For each peripheral distance, the reaction time function initially declined as SOA was increased and then reached asymptote The further the target from fixation, the longer the SOA at which the function reached asymptote The asymptotic SOA values were taken as a measure of the time it takes attention to reach a given target Comparisons of these values for the three peripheral distances permitted estimating the velocity of attention movements These measurements suggest that when summoned by a peripheral cue, attention travels through space at a constant velocity of about 1 degree per 8 msec Language: en

Entropy Generation Through Heat and Fluid Flow

Abstract: The first textbook to bridge the gap between three cornerstones of engineering education: fluid mechanics, thermodynamics and heat transfer. It provides an effective method to teach the thermodynamic (second law) aspects of heat and fluid flow processes, and shows how to use such processes in the design of energy-efficient devices. The text offers a wide range of original research to support the entropy generation minimazation'' philosophy and includes 250 references in the field of thermodynamic optimization and the thermodynamics of heat and fluid flow.

Crack deflection: Implications for the growth of long and short fatigue cracks

Abstract: The influences of crack deflection on the growth rates ofnominally Mode I fatigue cracks are examined. Previous theoretical analyses of stress intensity solutions for kinked elastic cracks are reviewed. Simple elastic deflection models are developed to estimate the growth rates of nonlinear fatigue cracks subjected to various degrees of deflection, by incorporating changes in the effective driving force and in the apparent propagation rates. Experimental data are presented for intermediate-quenched and step-quenched conditions of Fe/2Si/0.1C ferrite-martensite dual phase steel, where variations in crack morphology alone influence considerably the fatigue crack propagation rates and threshold stress intensity range values. Such results are found to be in good quantitative agreement with the deflection model predictions of propagation rates for nonlinear cracks. Experimental information on crack deflection, induced by variable amplitude loading, is also provided for 2020-T651 aluminum alloy. It is demonstrated with the aid of elastic analyses and experiments that crack deflection models offer a physically-appealing rationale for the apparently slower growth rates of long fatigue cracks subjected to constant and variable amplitude loading and for the apparent deceleration and/or arrest of short cracks. The changes in the propagation rates of deflected fatigue cracks are discussed in terms of thelocal mode of crack advance, microstructure, effective driving force, growth mechanisms, mean stress, slip characteristics, and crack closure.

CCS expressions, finite state processes, and three problems of equivalence

Abstract: We examine the computational complexity of testing finite state processes for equivalence, in the Calculus of Communicating Systems (CCS). This equivalence problem in CCS is presented as a refinement of the familiar problem of testing whether two nondeterministic finite state automata (n.f.s.a.) accept the same language. Three notions of equivalence, proposed for CCS, are investigated: (1) observation equivalence, (2) congruence, and (3) failure equivalence. We show that observation equivalence (

The Bottomn-Left Bin-Packing Heuristic: An Efficient Implementation

Abstract: We study implementations of the bottom-left heuristic for two-dimensional bin-packing. To pack N rectangles into an infinite vertical strip of fixed width, the strategy considered here places each rectangle in turn as low as possible in the strip in a left-justified position. For reasons of simplicity and good performance, the bottom-left heuristic has long been a favorite in practical applications; however, the best implementations found so far require a number of steps O(N3). In this paper, we present an implementation of the bottom-left heuristic which requires linear space and quadratic time. The algorithm is fairly practical, and we believe that even for relatively small values of N, it gives the most efficient implementation of the heuristic, to date. It proceeds by first determining all the possible locations where the next rectangle can fit, then selecting the lowest of them. It is optimal among all the algorithms based on this exhaustive strategy, and its generality makes it adaptable to different packing heuristics.

Strength of mineral absorption features in the transmitted component of near‐infrared reflected light: First results from RELAB

Abstract: Bidirectional reflectance measurements are the only type of reflectance data available to the remote observer. For compositional interpretations, data are desired not only for identification of possible mineral components but also for modal abundance. The latter requires detailed information about the strength of absorption features. Using a new laboratory facility, the RELAB, laboratory data in the near infrared are presented that document effects of particle size, mineral mixtures, and viewing geometry for selected materials with well-developed absorption bands. The commonly observed increase in reflectance with decrease in particle size is also observed for absorption bands as well as a related decrease in absorption strength. For small particles in parts of the spectrum of maximum reflectance, however, a minor decrease in reflectance with a decrese in particle size is sometimes observed. Small particles dominate the observed characteristics of particulate surfaces, which contain a range of particle sizes. The mean optical path length (transmission through particles) of reflected radiation measured for a variety of particle sizes has an apparent upper limit of about 2 mm for particles of less than 250 microns. The typical number of particles involved in the optical path is less than 50.

The differential effects of haloperidol and methamphetamine on time estimation in the rat.

Abstract: Forty rats were trained to make a left lever response if a signal (white noise) was 2.5s and to make a right lever response if the signal was 6.3s. When seven intermediate signal durations, to which responses were not reinforced, were randomly interspersed the probability of a right-lever (‘long’) response increased as a function of signal duration. Methamphetamine shifted this psychometric function leftward and decreased its slope: haloperidol also decreased the slope but shifted the function rightward. A combination of haloperidol and methamphetamine led to a function similar to the saline control function. The leftward shift probably reflects an increase in the speed of an internal clock, and the rightward shift probably reflects a decrease in its speed. Since methamphetamine releases several catecholamines, including dopamine, and haloperidol blocks dopamine receptors, it is plausible that the horizontal location of the psychometric function (the speed of the clock) is related to the effective level of dopamine.

An iterative scheme for variational inequalities

Abstract: In this paper we introduce and study a general iterative scheme for the numerical solution of finite dimensional variational inequalities. This iterative scheme not only contains, as special cases the projection, linear approximation and relaxation methods but also induces new algorithms. Then, we show that under appropriate assumptions the proposed iterative scheme converges by establishing contraction estimates involving a sequence of norms in En induced by symmetric positive definite matrices Gm. Thus, in contrast to the above mentioned methods, this technique allows the possibility of adjusting the norm at each step of the algorithm. This flexibility will generally yield convergence under weaker assumptions.

Models in radiotherapy: volume effects.

Abstract: A model for the dependence of normal tissue radiation dose response functions on volume variations and dose inhomogeneities is derived using probability theory. Power law volume correction factors and the complication probability factor are shown to be special cases arising from approximations applied to this model. Both require the assumption of small probabilities of complication. Power law volume corrections are shown to require a homogeneous dose distribution. The general model is tissue specific and can be used to calculate probabilities of complication for individual organs or isoprobability doses for radiation injury. The model is applicable to both homogeneous and inhomogeneous dose distributions and has been used in computer determination of optimal treatment parameters. Experimental data are presented which are consistent with the general model alone and which demonstrate the limits of applicability of previous models.

Expression of a cellular oncogene during liver regeneration.

Abstract: The number of transcripts of the cellular oncogene ras, which is homologous to the transforming gene of Harvey sarcoma virus, increases during liver regeneration in rats. The increase in these transcripts in liver polysomal polyadenylated RNA occurs at the time of activation of DNA synthesis during the regenerative process induced by partial hepatectomy or carbon tetrachloride injury. The number of ras transcripts returns to basal levels within 72 hours. These observations show that transcription of a cellular oncogene increases in a regulated way in a nonneoplastic growth process.

The Incidence and Significance of Birthmarks in a Cohort of 4,641 Newborns

Abstract: An unselected cohort of 4,641 newborns was ascertained prospectively for the purpose of detecting any cutaneous lesion. These were catalogued into pigmented lesions, vascular lesions, and miscellaneous lesions. Several important findings were elucidated: congenital nevocellular nevi are speckled at their borders; no white newborn in the study had more than one cafe au lait mark; a hypopigmented tuft of hair was seen in one infant with tuberous sclerosis but is found more commonly in normal individuals; a previously undescribed lesion called zosteriform melanocytic nevus was seen as a normal pigmentary variant in blacks; and hypopigmented macules seen at birth are seen primarily in normal infants. It is hoped that these findings will allow the pediatrician and dermatologist to offer more meaningful prognostic information to their patients.

Divisors on general curves and cuspidal rational curves

Abstract: In t roduc t ion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 371 0. Pre l iminar ies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 377 1. A Pl i icker formula . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 378 2. D imens iona l t ransversa l i ty . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 380 3. D i m e n s i o n of families of r a t iona l curves with fixed degree and ass igned cusps in a project ive space . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 383 4. L inear series on curves with universa l s ingular i t ies . . . . . . . . . . . . . . . . . . 386 5. L inear series and project ive embedd ings of general curves . . . . . . . . . . . . . . . 391 6. Embedd ings of general cuspidal curves . . . . . . . . . . . . . . . . . . . . . . . 400 7. Degenera t ion of Schuber t in tersect ions; some special cases . . . . . . . . . . . . . . . 403 8. Degene ra t ion of Schuber t in tersect ions; ma in results . . . . . . . . . . . . . . . . . 407 9. G](C) is reduced for general cuspidal r a t iona l C . . . . . . . . . . . . . . . . . . . 414