Emotional responding following experimental manipulation of facial electromyographic activity.

Thirty female subjects were instructed to imagine three positive affective scenes and three negative affective scenes. During the initial imagination of each scene, the subject was told simply to imagine the situation. The subject then imagined the situation again and was instructed to enhance the muscle tension in one of two muscle groups (the zygomatic muscles for positive scenes and the corrugator muscle for negative scenes). The subject then imagined the scene a third time and was instructed to suppress the muscle tension in the same muscle group. Feedback was available during practice trials and during the enhancement and suppression trials of the experiment. Continuous monitoring of both zygomatic and corrugator electromyogram (EMG) during the study indicated that subjects were successful in altering muscle tension in accord with the experimental instructions, and videotapes of subjects' faces indicated no overt changes in facial responding during imagination of the scenes. Subjects' ratings of emotional responding during each scene indicated that subjects experienced less enjoyment and more distress during positive affective trials in which they suppressed zygomatic EMG activity. The results are discussed in terms of the facial feedback hypothesis. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Operant autonomic conditioning and rod-and-frame test performance

Forty subjects were administered the portable rod-and-frame test (RFT) before and after operant autonomic conditioning training or control experiences. Ten subjects were assigned to each of four groups: a heart rate conditioning group; a false heart rate feedback group; a galvanic skin-response conditioning group; and a control group. Half of the subjects in the three experimental groups were informed of the response-reinforcement contingencies, and half were not informed. Informed subjects in the conditioning groups exhibited significantly lower portable RFT scores after conditioning. The results suggest that awareness of and control over autonomic functioning may be an important determinant of RFT performance.     

Scalable multimedia communication using IP Multicast andlightweight sessions

This survey describes the roots of IP Multicast, the evolution of the Internet Multicast Backbone, or Mbone, and the technologies that have risen around the Mbone to support large-scale Internet-based multimedia conferencing. The author explains the technical rationale for design decisions that underlay the Mbone tools, describes the evolution of this work from early prototypes into Internet standards, and outlines the open challenges that remain and must be overcome to realize a ubiquitous multicast infrastructure     

Network visualization with Nam, the VINT network animator

Network protocol designers face many difficult tasks, including simultaneously monitoring state in a potentially large number of nodes, understanding and analyzing complex message exchanges, and characterizing dynamic interactions with competing traffic. Traditionally they have used packet traces to accomplish these tasks, but traces have two major drawbacks: they present an incredible amount of detail, which challenges the designer's ability to comprehend the data; and they are static, which hides an important dimension of protocol behavior. As a result, detailed analysis frequently becomes tedious and error-prone. Although network simulators such as the VINT project's ns can easily generate numerous detailed traces, they provide limited help for analyzing and understanding the data. Nam, the network animator that we developed in our work at the VINT project, provides packet-level animation, protocol graphs, traditional time-event plots of protocol actions, and scenario editing capabilities. Nam benefits from a close relationship with ns, which can collect detailed protocol information from a simulation. With some preprocessing. Nam can visualize data taken directly from real network traces     

Relationship of childhood sexual, physical, and combined sexual and physical abuse to adult victimization and posttraumatic stress disorder

OBJECTIVE: Prior research has suggested that women who experience childhood sexual abuse are at increased risk for sexual victimization and Posttraumatic Stress Disorder (PTSD) in adulthood. However, previous studies have paid insufficient attention to the overlap of childhood sexual and physical abuse. In the present study we disentangled the separate and combined effects of childhood sexual and physical abuse by comparing groups of participants who reported contact childhood sexual abuse only (SA), sequelae of childhood physical abuse only (PA), combined childhood sexual and physical abuse (CA), or no child abuse (NA). METHOD: A sample of 475 female college students completed measures of sexual and physical abuse in childhood (before age 15) and adulthood (after age 15), PTSD and trauma symptoms, and demographic variables. Of these participants, 27 were assigned to the SA group, 53 to the PA group, 31 to the CA group, and 211 to the NA group. RESULTS: The highest rate of adult sexual and/or physical victimization was reported by the CA group, followed by the PA group, with lower rates reported by the SA and NA groups. Using adult victimization as a covariate, the analyses revealed that the CA group reported significantly higher rates of PTSD and trauma symptoms compared to the NA group. CONCLUSIONS: The results suggest that prior reports of differences in rates of adult victimization and PTSD between women who experienced childhood sexual abuse and women who did not may be attributable to the inclusion of participants with a history of combined childhood sexual and physical abuse in childhood sexual abuse groups. The importance of separating physical and combined forms of victimization from sexual abuse is discussed.     

Human operant heart rate conditioning: The importance of individual differences.

Respiratory, somatic-muscular, and CNS responses have all been suggested as possible mediators of operant heart rate changes. A review of studies concerned with each proposed mediator indicates that such responses can mediate heart rate change, but no studies have demonstrated the necessity for such mediation. Current hypotheses concerning mediating variables appear to oversimplify the complex interactions of autonomic and CNS modalities. A review of research on physiological patterns of response during stress, classical conditioning, and avoidance conditioning indicates that there are considerable individual differences in automatic and CNS responses during those tasks. It is suggested that individual differences in physiological responding also occur during operant heart rate conditioning and that E's should utilize such differences in constructing models of events that might mediate operant heart rate changes. (21/2 p ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A Receiver-Driven Transport Protocol for the Web

In this paper, we present a receiver-oriented, request/response protocol for the Web that is compatible with the dynamics of TCP's congestion control algorithm. The protocol, called WebTP, is designed to be completely receiver-based in terms of transport initiation, flow-control and congestion-control. We propose a dual window-cum-rate based congestion control mechanism that is compatible with parallel TCP flows, and in fact interacts better with a congested network state. In support of our receiver-driven design, we developed a novel retransmission scheme that is robust to delay variations. The resulting flows achieve efficient network utilization and are qualitatively fair in their interaction amongst themselves and even with competing TCP flows. The paper also provides detailed simulation results to support the protocol design.     

A framework for computation-memory algorithmic optimization for signal processing

The heterogeneity of today's computing environment means computation-intensive signal processing algorithms must be optimized for performance in a machine dependent fashion. In this paper, we present a dynamic memory model and associated optimization framework that finds a machine-dependent, near-optimal implementation of an algorithm by exploiting the computation-memory tradeoff. By optimal, we mean an implementation that has the fastest running time given the specification of the machine memory hierarchy. We discuss two instantiations of the framework: fast IP address lookup, and fast nonuniform scalar quantizer and unstructured vector quantizer encoding. Experiments show that both instantiations outperform techniques that ignore this computation-memory tradeoff.     

A reliable multicast framework for light-weight sessions andapplication level framing

This paper describes scalable reliable multicast (SRM), a reliable multicast framework for light-weight sessions and application level framing. The algorithms of this framework are efficient, robust, and scale well to both very large networks and very large sessions. The SRM framework has been prototyped in wb, a distributed whiteboard application, which has been used on a global scale with sessions ranging from a few to a few hundred participants. The paper describes the principles that have guided the SRM design, including the IP multicast group delivery model, an end-to-end, receiver-based model of reliability, and the application level framing protocol model. As with unicast communications, the performance of a reliable multicast delivery algorithm depends on the underlying topology and operational environment. We investigate that dependence via analysis and simulation, and demonstrate an adaptive algorithm that uses the results of previous loss recovery events to adapt the control parameters used for future loss recovery. With the adaptive algorithm, our reliable multicast delivery algorithm provides good performance over a wide range of underlying topologies     

Heart rate and cardiac phase influences on visual perception.

26 undergraduates were tested with a tachistoscopic recognition task while heart rate (HR) and several other autonomic indexes were monitored. In Exp I, HR was employed as an independent variable, and stimulus presentation was contingent upon the presence of individually determined low, middle, and high HRs. Results indicate that low HR facilitated performance especially for stimuli presented at the fastest exposure. In Exp II, stimulus presentation was dependent upon cardiac phase. Findings indicate that stimulus recognition was enhanced during the cardiac P wave, but the effect was apparent only during the fastest exposure. Multiple regression analyses of the individual S's data during both experiments indicated that highly idiosyncratic patterns of physiological responses predicted perceptual performance. Results are consistent with the formulations of B. C. Lacey and J. I. Lacey (1958, 1967, 1974, etc.) and suggest that cerebral perfusion be considered as a relevant determinant of behavior. (39 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)