Showing papers by "University of Rochester published in 1991"

Predicting User Intentions: Comparing the Technology Acceptance Model with the Theory of Planned Behavior

Abstract: Information systems IS cannot be effective unless they are used. However, people sometimes do not use systems that could potentially increase their performance. This study compares two models that predict an individual's intention to use an IS: the technology acceptance model TAM and the theory of planned behavior TPB. The comparison was designed to be as fair as possible, not favoring one model over the other. Both TAM and TPB predicted intention to use an IS quite well, with TAM having a slight empirical advantage. TAM is easier to apply, but only supplies very general information on users' opinions about a system. TPB provides more specific information that can better guide development.

Algorithms for scalable synchronization on shared-memory multiprocessors

Abstract: Busy-wait techniques are heavily used for mutual exclusion and barrier synchronization in shared-memory parallel programs. Unfortunately, typical implementations of busy-waiting tend to produce large amounts of memory and interconnect contention, introducing performance bottlenecks that become markedly more pronounced as applications scale. We argue that this problem is not fundamental, and that one can in fact construct busy-wait synchronization algorithms that induce no memory or interconnect contention. The key to these algorithms is for every processor to spin on separate locally-accessible flag variables, and for some other processor to terminate the spin with a single remote write operation at an appropriate time. Flag variables may be locally-accessible as a result of coherent caching, or by virtue of allocation in the local portion of physically distributed shared memory.We present a new scalable algorithm for spin locks that generates 0(1) remote references per lock acquisition, independent of the number of processors attempting to acquire the lock. Our algorithm provides reasonable latency in the absence of contention, requires only a constant amount of space per lock, and requires no hardware support other than a swap-with-memory instruction. We also present a new scalable barrier algorithm that generates 0(1) remote references per processor reaching the barrier, and observe that two previously-known barriers can likewise be cast in a form that spins only on locally-accessible flag variables. None of these barrier algorithms requires hardware support beyond the usual atomicity of memory reads and writes.We compare the performance of our scalable algorithms with other software approaches to busy-wait synchronization on both a Sequent Symmetry and a BBN Butterfly. Our principal conclusion is that contention due to synchronization need not be a problem in large-scale shared-memory multiprocessors. The existence of scalable algorithms greatly weakens the case for costly special-purpose hardware support for synchronization, and provides a case against so-called “dance hall” architectures, in which shared memory locations are equally far from all processors. —From the Authors' Abstract

The long QT syndrome. Prospective longitudinal study of 328 families.

Abstract: BACKGROUNDThe Long QT Syndrome (LQTS) is an infrequently occurring familial disorder in which affected individuals have electrocardiographic QT interval prolongation and a propensity to ventricular tachyarrhythmic syncope and sudden death. We prospectively investigated the clinical characteristics and the long-term course of 3,343 individuals from 328 families in which one or more members were identified as affected with LQTS (QTc greater than 0.44 sec1/2).METHODS AND RESULTSThe first member of a family to be identified with LQTS, the proband, was usually brought to medical attention because of a syncopal episode during childhood or teenage years. Probands (n = 328) were younger at first contact (age 21 +/- 15 years), more likely to be female (69%), and had a higher frequency of preenrollment syncope or cardiac arrest with resuscitation (80%), congenital deafness (7%), a resting heart rate less than 60 beats/min (31%), QTc greater than or equal to 0.50 sec1/2 (52%), and a history of ventricular tachyarrhy...

Measuring Internal Political Efficacy in the 1988 National Election Study.

Abstract: Political efficacy has been studied extensively since the 1950s, hut analysts have never been fully satisfied with its measurement. After considerable testing, four new questions tapping internal political efficacy were added to the 1988 National Election Study. Our investigation shows that inter-item correlations among these questions indicate high internal consistency, that by both exploratory and confirmatory factor analysis the items measure a single concept distinct from external efficacy and political trust, that the measurement model is robust across major subgroups, and that the overall scale is externally valid and provides a good distribution of efficacy scores across the population. Further, the results of an order experiment in the survey suggest that responses are unaffected by mode of presentation. In short, the four new questions constitute the most satisfactory measure of internal political efficacy to date.

Nomenclature and research case definitions for neurologic manifestations of human immunodeficiency virus-type 1 (HIV-1) infection

Abstract: Infection with human immunodeficiency virus-type 1 (HIV-1) has been associated with avariety of neurologic disorders thought to be caused, directly or indirectly, by HIV-1.1-6 Although these disorders have been described clinically, there is no consensus terminology or criteria for diagnosis. To develop consensus nomenclature and case definitions for HIV-1-associated neurologic conditions for research purposes, the American Academy of Neurology AIDS Task Force convened a working group of neurologists, neuropsychologists, psychiatrists, and sociologists that included representatives of the American Neurological Association, the World Federation of Neurology, the International Neuropsychological Society, the National Academy of Neuropsychology, the American Psychological Association, the American Psychiatric Association, the World Health Organization, and the Centers for Disease Control (CDC). These definitions have been developed in conjunction with the International Classification of Diseases-10 (ICD-10, unpublished draft of the World Health Organization) and the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV, unpublished draft of the American Psychiatric Association). Although consistent with the ICD-10, the definitions are not identical. HIV-2 may cause similar disorders, but the neurologic manifestations of HIV-2 are unknown and are not addressed in this article.

Immunity to and Frequency of Reinfection with Respiratory Syncytial Virus

Abstract: To better understand the duration of immunity against respiratory syncytial virus (RSV) and the role of serum antibodies to the surface glycoproteins, F and G, in susceptibility to reinfection, 15 adults with previous natural RSV infection were challenged with RSV of the same strain group (A) at 2, 4, 8, 14, 20, and 26 months after natural infection. By 2 months about one-half and by 8 months two-thirds of the subjects became reinfected. Each challenge resulted in infection in at least one-fourth of the subjects. Within 26 months 73% had two or more and 47% had three or more infections. The duration of immunity tended to increase after two closely spaced infections. Higher neutralizing, F and GA antibody levels before challenge correlated significantly with protection against infection. However, even in subjects with the highest antibody levels, the risk of reinfection was 25%. Specific nasal IgA antibody titers did not correlate significantly with protection. This suggests that humoral neutralizing, F, and G antibodies correlate with resistance to reinfection, but protection is far from complete and is of short duration.

Cloning and characterization of the Pseudomonas aeruginosa lasR gene, a transcriptional activator of elastase expression.

Abstract: We report the discovery of the lasR gene, which positively regulates elastase expression in Pseudomonas aeruginosa PAO1. The lasR gene was cloned by its ability to restore a positive elastase phenotype in strain PA103, a strain which possesses the elastase structural gene (lasB) but fails to synthesize the enzyme. Nucleotide sequence analysis revealed an open reading frame of 716 nucleotides encoding a protein of approximately 27 kDa. A labeled LasR protein of 27 kDa was detected in Escherichia coli by using a T7 RNA polymerase expression system. A chromosomal deletion mutant of the lasR gene was constructed in PAO1 by gene replacement. This mutant (PAO-R1) is devoid of elastolytic activity and elastase antigen. The deduced amino acid sequence of LasR is 27% homologous to the positive activator LuxR of Vibrio fischeri and the suspected activator 28K-UvrC of E. coli. Northern (RNA) analysis of total cellular RNA from PAO1, PAO-R1, and PAO-R1 containing the lasR gene on a multicopy plasmid (pMG1.7) revealed that a functional lasR gene is required for transcription of the elastase structural gene (lasB). Images

Spiral calcium wave propagation and annihilation in Xenopus laevis oocytes

Abstract: Intracellular calcium (Ca2+) is a ubiquitous second messenger. Information is encoded in the magnitude, frequency, and spatial organization of changes in the concentration of cytosolic free Ca2+. Regenerative spiral waves of release of free Ca2+ were observed by confocal microscopy in Xenopus laevis oocytes expressing muscarinic acetylcholine receptor subtypes. This pattern of Ca2+ activity is characteristic of an intracellular milieu that behaves as a regenerative excitable medium. The minimal critical radius for propagation of focal Ca2+ waves (10.4 micrometers) and the effective diffusion constant for the excitation signal (2.3 x 10(-6) square centimeters per second) were estimated from measurements of velocity and curvature of circular wavefronts expanding from foci. By modeling Ca2+ release with cellular automata, the absolute refractory period for Ca2+ stores (4.7 seconds) was determined. Other phenomena expected of an excitable medium, such as wave propagation of undiminished amplitude and annihilation of colliding wavefronts, were observed.

Proposal for the recognition of minimally differentiated acute myeloid leukaemia (AML-MO)

Abstract: We describe a form of acute myeloid leukaemia (AML), designated AML-MO, with minimal myeloid differentiation, not included previously in the FAB classification. AML-MO cannot be diagnosed on morphological grounds alone as the blast cells are large and agranular, sometimes resembling L2 or, rarely, L1 lymphoblasts, and should be identified by the following features: negative myeloperoxidase (MPO) and Sudan Black B reaction (or positive in less than 3% of blasts), negative B and T lineage markers and expression of myeloid antigens recognized by at least one monoclonal antibody, CD13 or CD33. Other myeloid markers are also often positive and these include CD11b and the enzyme MPO demonstrated by immunocytochemistry and/or electron microscopy analysis. The findings in a group of 10 cases satisfying the criteria for AML-MO are described. AML-MO represents 2-3% of all cases of AML and 1-1.5% of all acute leukaemias. Its clinical and biological significance is not yet apparent but its identification in a larger number of cases may achieve this aim.

Self‐Recording of Everyday Life Events: Origins, Types, and Uses

Abstract: I In this article we review the history of the scientific use of * self-recording and conclude that there are three basic methods: (a) intervalcontingent, in which respondents report on their experiences at regular intervals, (i>) signal-contingent, in which respondents report when signaled, and (c) event-contingent, in which respondents report whenever a defined event occurs. We then discuss the relative merits of these techniques for answering different questions. Finally, we note that self-recording of small events is a departure from the science of psychology as typically practiced, requiring an acceptance of reality as defined by respondents. History is always informative, usually fascinating, and often useful. Accordingly, our first inclination when researching a topic is to look to the past. In this article, we are concerned with the history of the selfrecording of everyday life events. Our use of the term "self-recording of everyday life events" refers to the ongoing recording of any kind of personal experience. One-time measures such as personality and attitude questionnaires and projective tests, meant to measure enduring characteristics, are not included. The use of these self-recording methods has increased significantly since the last half of the 1970s (Larsen, 1990). Although such methods have been largely ignored in the literature, new treatments of research methodology will have to be considered incom

Induced coherence and indistinguishability in optical interference.

Abstract: Second-order interference is observed in the superposition of signal photons from two coherently pumped parametric down-converters, when the paths of the idler photons are aligned. The interference exhibits certain nonclassical features; it disappears when the idlers are misaligned or separated by a beam stop. The interpretation of this effect is discussed in terms of the intrinsic indistinguishability of the photon paths.

Ego-involved persistence: When free-choice behavior is not intrinsically motivated

Abstract: Experiments on factors affecting intrinsic motivation have generally inferred intrinsic motivation from subjects' engagement in a target activity during a “free-choice period” when external contingencies are no longer operative. However, internally controlling regulation is a form of internal motivation that is very different from intrinsic motivation and can underlie free-choice-period activity. This paper presents three experiments concerned with differentiating internally controlling from intrinsically motivated persistence in situations where ego-involved vs. task-involved subjects had received positive vs. nonconfirming (or no) performance feedback. The first experiment showed that ego-involved (relative to task-involved) subjects displayed less free-choice persistence when they received positive feedback, whereas the second experiment showed that ego-involved (relative to task-involved) subjects displayed more free-choice persistence when they received nonconfirming feedback. In both experiments, however, it was shown that ego-involved subjects did not report the expected affective correlates of intrinsic motivation—namely, interest/enjoyment and perceived choice—whereas task-involved subjects did. In the third experiment, as predicted, ego-involved subjects tended to show less free-choice persistence than task-involved subjects when they received positive performance feedback but greater free-choice persistence when they received no performance feedback. The problem of distinguishing intrinsically motivated activity from internally controlled behavior is discussed.

Applications of high efficiency lithium acetate transformation of intact yeast cells using single-stranded nucleic acids as carrier.

Abstract: The highly efficient yeast lithium acetate transformation protocol of Schiestl and Gietz (1989) was tested for its applicability to some of the most important need of current yeast molecular biology. The method allows efficient cloning of genes by direct transformation of gene libraries into yeast. When a random gene pool ligation reaction was transformed into yeast, the LEU2, HIS3, URA3, TRP1 and ARG4 genes were found among the primary transformations at a frequency of approximately 0·1%. The RAD4 gene, which is toxic to Escherichia coli, was also identified among the primary transformants of a ligation library at a frequency of 0·18%. Non-selective transformation using this transformation proctocol was shown to increase the frequency of gene disruption three-fold. Co-transformation showed that 30–40% of the transformation-competent cells take up more than one DNA molecule which can be used to enrich for integration and delection events 30- to 60-fold. Co-transformation was used in the construction of simultaneous double gene disruptions as well as disrupting both copies of one gene in a diploid which occurred at 2–5% the frequency of the single event.

Laser ionization of noble gases by Coulomb-barrier suppression

Abstract: Laser ionization of noble gases was studied with a 1.053-μm, 1-psec Nd:glass laser. A systematic scan of intensities from mid-1013 W/cm2 to mid-1016 W/cm2 was performed, resulting in the production of charge states as high as Xe12+. Ionization occurs exclusively in the tunneling regime. We compare experimental ion production rates with those predicted by several different theories. Agreement between experimental ion-production curves and theoretical predictions is good for two theoretical models: (1) an elaboration of the Keldysh tunneling model, developed by Ammosov et al. [ Sov. Phys. JETP64, 1191 ( 1986)] and (2) a much more primitive model, based on Coulomb-barrier suppression, in which tunneling and other quantum-mechanical effects are ignored completely. The success of the more primitive model suggests that a new term, barrier-suppression ionization, rather than tunneling or multiphoton ionization, may be the most appropriate at this wavelength and in this range of intensities.

Oxygen consumption and diffusion effects in photodynamic therapy.

Abstract: Effects of oxygen consumption in photodynamic therapy (PDT) are considered theoretically and experimentally. A mathematical model of the Type II mechanism of photooxidation is used to compute estimates of the rate of therapy-dependent in vivo oxygen depletion resulting from reactions of singlet oxygen (1O2) with intracellular substrate. Calculations indicate that PDT carried out at incident light intensities of 50 mW/cm2 may consume 3O2 at rates as high as 6-9 microM s-1. An approximate model of oxygen diffusion shows that these consumption rates are large enough to decrease the radius of oxygenated cells around an isolated capillary. Thus, during photoirradiation, cells sufficiently remote from the capillary wall may reside at oxygen tensions that are low enough to preclude or minimize 1O2-mediated damage. This effect is more pronounced at higher power densities and accounts for an enhanced therapeutic response in tumors treated with 360 J/cm2 delivered at 50 mW/cm2 compared to the same light dose delivered at 200 mW/cm2. The analysis further suggests that the oxygen depletion could be partially overcome by fractionating the light delivery. In a transplanted mammary tumor model, a regimen of 30-s exposures followed by 30-s dark periods produced significantly longer delays in tumor growth when compared to the continuous delivery of the same total fluence.

Contributions from the study of high risk populations to understanding the development of emotion regulation

Abstract: In this chapter we shall examine the processes of emotion regulation and dysregulation. We define emotion regulation as the intra- and extraorganismic factors by which emotional arousal is redirected, controlled, modulated, and modified to enable an individual to function adaptively in emotionally arousing situations. Emotion regulation helps maintain internal arousal within a manageable, performance-optimizing range. Whereas the emotions mediate a person's adaptive functioning by providing crucial information to the self and others about internal states, emotion regulatory systems are essential to the individual in order to maintain a tolerable but flexible range of affective expressions necessary for adaptive functioning across the life span. Feedback components of the emotion system also serve a critical role in the development of self-evaluation and selfregulation (Cicchetti & Schneider-Rosen, 1986; Izard, 1977). The guiding theoretical orientation of our study of emotion regulation is based on principles derived from the organizational perspective on development (Cicchetti, 1990; Cicchetti & Aber, 1986; Cicchetti & Sroufe, 1978; Sroufe & Waters, 1976). According to this perspective, development is conceived as a series of qualitative reorganizations among and within behavioral and biological systems. Through the processes of differentiation and hierarchical integration, individuals move from a relatively diffuse, undifferentiated condition to a state of increasingly differential and hierarchically organized behavioral complexity (Werner, 1957). During this process, intrinsic or organismic factors and extrinsic, environmental factors dynamically interact to determine a person's developmental outcome on a number of unfolding stage-salient issues (Cicchetti, 1990).