Home About us Contact
|
Home About us Contact | ||
|
|
||
Short Delay (short + delay)
Selected AbstractsDistributed end-host multicast algorithms for the Knowledge GridCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 15 2007Wanqing Tu Abstract The Knowledge Grid built on top of the peer-to-peer (P2P) network has been studied to implement scalable, available and sematic-based querying. In order to improve the efficiency and scalability of querying, this paper studies the problem of multicasting queries in the Knowledge Grid. An m -dimensional irregular mesh is a popular overlay topology of P2P networks. We present a set of novel distributed algorithms on top of an m -dimensional irregular mesh overlay for the short delay and low network resource consumption end-host multicast services. Our end-host multicast fully utilizes the advantages of an m -dimensional mesh to construct a two-layer architecture. Compared to previous approaches, the novelty and contribution here are: (1) cluster formation that partitions the group members into clusters in the lower layer where cluster consists of a small number of members; (2) cluster core selection that searches a core with the minimum sum of overlay hops to all other cluster members for each cluster; (3) weighted shortest path tree construction that guarantees the minimum number of shortest paths to be occupied by the multicast traffic; (4) distributed multicast routing that directs the multicast messages to be efficiently distributed along the two-layer multicast architecture in parallel, without a global control; the routing scheme enables the packets to be transmitted to the remote end hosts within short delays through some common shortest paths; and (5) multicast path maintenance that restores the normal communication once the membership alteration appears. Simulation results show that our end-host multicast can distributively achieve a shorter delay and lower network resource consumption multicast services as compared with some well-known end-host multicast systems. Copyright © 2006 John Wiley & Sons, Ltd. [source] The role of competition in word learning via referent selectionDEVELOPMENTAL SCIENCE, Issue 5 2010Jessica S. Horst Previous research suggests that competition among the objects present during referent selection influences young children's ability to learn words in fast mapping tasks. The present study systematically explored this issue with 30-month-old children. Children first received referent selection trials with a target object and either two, three or four competitor objects. Then, after a short delay, children were tested on their ability to retain the newly fast-mapped names. Overall, the number of competitors did not affect children's ability to form the initial name,object mappings. However, only children who encountered few competitors during referent selection demonstrated significant levels of retention. Results and implications are discussed in terms of the role of competition in studies of children's fast mapping. The relationship between referent selection and full word learning is also discussed. [source] Rats with lesions of the hippocampus are impaired on the delayed nonmatching-to-sample task,HIPPOCAMPUS, Issue 2 2001Robert E. Clark Abstract Rats with ibotenic acid lesions of the hippocampus (H-IBO) were trained on the trial-unique delayed nonmatching-to-sample task (DNMS) using a short delay of 4 s. The H-IBO group learned the nonmatching rule as quickly as control animals. However, performance was impaired on the DNMS task when the delay between the sample and choice phase was increased to 1 or 2 min. The use of 4-s delay (probe) trials indicated that the H-IBO animals retained the nonmatching-to-sample rule throughout testing. In a second experiment, using the same groups of rats, extended training at the 1-min delay did not ameliorate the deficit produced by H-IBO lesions. The finding of impaired recognition memory in rats after hippocampal lesions is consistent with findings from humans and monkeys. Several methodological issues are considered that have complicated the interpretation of earlier studies of recognition memory in rats following hippocampal lesions. The capacity for recognition memory in humans, monkeys, and rodents is discussed as a straightforward example of hippocampus-dependent (declarative) memory. Hippocampus 2001;11:176,186. © 2001 Wiley-Liss, Inc. [source] Nowcasting quarterly GDP growth in a monthly coincident indicator modelJOURNAL OF FORECASTING, Issue 8 2005Luis C. NunesArticle first published online: 20 DEC 200 Abstract This paper presents an extension of the Stock and Watson coincident indicator model that allows one to include variables available at different frequencies while taking care of missing observations at any time period. The proposed procedure provides estimates of the unobserved common coincident component, of the unobserved monthly series underlying any included quarterly indicator, and of any missing values in the series. An application to a coincident indicator model for the Portuguese economy is presented. We use monthly indicators from business surveys whose results are published with a very short delay. By using the available data for the monthly indicators and for quarterly real GDP, it becomes possible to produce simultaneously a monthly composite index of coincident indicators and an estimate of the latest quarter real GDP growth well ahead of the release of the first official figures. Copyright © 2005 John Wiley & Son, Ltd. [source] Effects of delayed excision of oviducts/ovaries on mouse oocytes and embryosMOLECULAR REPRODUCTION & DEVELOPMENT, Issue 4 2007De-Qiang Miao Abstract To achieve the best and reproducible results of experiments, effects of delayed excision of oviducts/ovaries on mouse ovarian/ovulated oocytes and embryos have been studied. Oviducts/ovaries were excised at different times after death of mice and effects of the postmortem interval on ovarian/ovulated oocytes and embryos were analyzed. When oviduct excision was delayed 10 min, many ovulated oocytes lysed or underwent in vitro spontaneous activation, and this postmortem effect aggravated with the extension of postmortem interval and oocyte aging. Oocytes from different mouse strains responded differently to delayed oviduct removal. Delayed oviduct excision did not cause lysis of zygotes or embryos but compromised their developmental potential. When ovaries were excised at 30 min after death, percentages of atretic follicles increased while blastocyst cell number declined significantly after oocyte maturation in vitro. Preservation of oviducts in vitro, in intact or opened abdomen at different temperatures and histological analysis of oviducts from different treatments suggested that toxic substance(s) were secreted from the dying oviducts which induced oocyte lysis and spontaneous activation and both this effect itself and the sensitivity of oocytes to this effect was temperature dependent. It is concluded that a short delay of oviduct/ovary removal had marked detrimental effects on oocytes and embryos. This must be taken into account in experiments using oocytes or embryos from slaughtered animals. The data may also be important for estimation of the time of death in forensic medicine and for rescue of oocytes from deceased valuable or endangered mammals. Mol. Reprod. Dev. 74: 468,477, 2007. © 2006 Wiley-Liss, Inc. [source] Drawing facilitates children's reports of factual and narrative information: implications for educational contextsAPPLIED COGNITIVE PSYCHOLOGY, Issue 7 2009Julien Gross In the present study, we examined the effect of drawing on children's reports of an educational event. Five- and 6-year-old children visited a local museum and were interviewed either 1,2 days or 7 months later. After each delay, half of the children were asked to tell about what they had learned during their visit to the museum and the other half were given the opportunity to draw while telling. All children were also given a standard comprehension test, covering material that the museum staff considered to be most relevant to the visit. When tested after a short delay, children who drew while talking reported more factual and more narrative information than children who did not draw. When tested after a long delay, drawing only enhanced children's reports of narrative information. After both delays, children's verbal descriptions of the event exceeded their scores on the comprehension test. These data have important practical implications for the educational value of museum visits and suggest a new method of assessing children's learning in educational contexts. Copyright © 2008 John Wiley & Sons, Ltd. [source] Phenomenal characteristics of co-created guided imagery and autobiographical memoriesAPPLIED COGNITIVE PSYCHOLOGY, Issue 7 2003Kinda L. K. Kealy Concern has recently been raised about the potential for guided images to be mistaken for memories of actual events. According to the reality-monitoring framework, such misattributions can occur due to the similarity of sensory and reflective memory characteristics acquired at encoding, or due to source judgement processes at retrieval. A study was conducted to examine the similarity of guided images and perceived memories at imagery encoding, and after a short delay. Participants rated the characteristics of an actual event, a natural imagery event (e.g. a fantasy), and a guided imagery experience, immediately and after a one-week interval. For each condition, participants discussed their memory or guided imagery experience with the researcher as they reviewed or created it. Ratings indicated that guided imagery was similar to perceived memory with respect to sensory characteristics. However, the factors associated with supporting memories (contextual and temporal detail, setting familiarity, and recollection of surrounding events) were less vivid for guided imagery than for perceived events. In all cases, these patterns were stable over time. Copyright © 2003 John Wiley & Sons, Ltd. [source] Visuospatial encoding deficits and compensatory strategies in schizophrenia revealed by eye movement analysis during a working memory taskACTA NEUROPSYCHIATRICA, Issue 2 2009Luca Cocchi Objective: To investigate scanpath abnormalities during the encoding of static stimuli in schizophrenia and their interaction with visuospatial working memory (VSWM) dysfunction. Methods: Outpatients with schizophrenia and control subjects were asked to encode a static pattern for subsequent recognition after a short delay. We measured the number of correct and incorrect choices. We also assessed the number and the distribution of fixations, the scanning time in specific regions of interest (ROIs) and the head movements during the encoding of the stimuli. The distributions of fixations and scanning time in definite ROIs during the discrimination of the correct pattern from the foils were also measured. Results: Patients recognised fewer correct patterns than controls. Correct trials in patients were characterised by a specific exploration of the central part of the stimulus during its presentation, whereas this feature was absent in incorrect trials. However, the scanning time and the numbers of fixations and head movements during encoding were similar in both groups and unrelated to recognition accuracy. In both groups, correct trials were associated with a selective exploration of the correct pattern amongst the six possibilities during recognition. Furthermore, patients gave more attention to incorrect patterns with a leftmost element identical to that of the correct response and also those approximating its global structure. Conclusion: Patients showed a VSWM deficit independent of oculomotor dysfunctions and head movements during encoding. Patients' correct trials were related to specific scanning during encoding and discrimination phases. Analysis of these patterns suggests that patients try to compensate for reduced VSWM ability by using specific encoding strategies. [source] Distributed end-host multicast algorithms for the Knowledge GridCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 15 2007Wanqing Tu Abstract The Knowledge Grid built on top of the peer-to-peer (P2P) network has been studied to implement scalable, available and sematic-based querying. In order to improve the efficiency and scalability of querying, this paper studies the problem of multicasting queries in the Knowledge Grid. An m -dimensional irregular mesh is a popular overlay topology of P2P networks. We present a set of novel distributed algorithms on top of an m -dimensional irregular mesh overlay for the short delay and low network resource consumption end-host multicast services. Our end-host multicast fully utilizes the advantages of an m -dimensional mesh to construct a two-layer architecture. Compared to previous approaches, the novelty and contribution here are: (1) cluster formation that partitions the group members into clusters in the lower layer where cluster consists of a small number of members; (2) cluster core selection that searches a core with the minimum sum of overlay hops to all other cluster members for each cluster; (3) weighted shortest path tree construction that guarantees the minimum number of shortest paths to be occupied by the multicast traffic; (4) distributed multicast routing that directs the multicast messages to be efficiently distributed along the two-layer multicast architecture in parallel, without a global control; the routing scheme enables the packets to be transmitted to the remote end hosts within short delays through some common shortest paths; and (5) multicast path maintenance that restores the normal communication once the membership alteration appears. Simulation results show that our end-host multicast can distributively achieve a shorter delay and lower network resource consumption multicast services as compared with some well-known end-host multicast systems. Copyright © 2006 John Wiley & Sons, Ltd. [source] Selective hippocampal damage in rhesus monkeys impairs spatial memory in an open-field test,HIPPOCAMPUS, Issue 7 2004Robert R. Hampton Abstract The hippocampus is critical for remembering locations in a wide variety of species, including humans. However, recent findings from monkeys following selective hippocampal lesions have been equivocal. To approximate more closely the situations in which rodents and birds are tested, we used a spatial memory task in which rhesus monkeys (Macaca mulatta) moved about freely in a large room, on a tether. We used MRI-guided stereotaxic surgery to produce selective hippocampal lesions in five monkeys, and retained five unoperated control monkeys. In the study phase of each trial of the matching-to-location task, monkeys found food in one site in an array of identical foraging sites. During the test, which occurred after a delay, monkeys could return to the site where the food had been found during study to obtain more food. In Experiment 1, normal monkeys showed a small significant tendency to return directly to a site where they had previously found food that day. Operated monkeys showed no such matching tendency. In Experiment 2, further training produced reliable matching-to-location performance in both groups at short delays, but monkeys with selective hippocampal lesions rapidly forgot the location of the food. In Experiment 3, we tested whether monkeys used a "cognitive map" to encode the location of the hidden food, by requiring them to relocate the food from a starting location different from that used during study. As a group, monkeys were more accurate than expected by chance, indicating that they did encode the rewarded location with respect to allocentric landmarks; however, both groups of monkeys were significantly worse at relocating the food when required to approach from a different location. In Experiment 4, probe trials using symmetrical test arrays found no evidence for egocentric coding of the rewarded location. © 2004 Wiley-Liss, Inc. [source] Studying the relation between temporal reward discounting tasks used in populations with ADHD: A factor analysisINTERNATIONAL JOURNAL OF METHODS IN PSYCHIATRIC RESEARCH, Issue 3 2010Anouk Scheres Abstract Background: This study aimed at investigating the relationship between tasks that have been used in attention deficit hyperactivity disorder (ADHD) to measure choices between smaller immediate and larger delayed rewards: real and hypothetical temporal discounting tasks, and single-choice paradigms. Methods: Participants were 55 undergraduate psychology students. Tasks included a real and hypothetical version of a temporal discounting (TD) task with choices between a large reward (10 cents) after delays up to 60 seconds, and smaller immediate rewards (2,8 cents); two versions of a hypothetical temporal discounting task with choices between a large reward ($100) after delays up to 120 months, and smaller immediate rewards ($1,$95); a Choice Delay Task with choices between one point now and two points after 30 seconds (one point is worth five cents). Results: Correlation analyses showed that the real and the hypothetical TD tasks with 10 cents were very strongly associated. However, the hypothetical TD tasks with $100 did not correlate with either the real or the hypothetical TD task with 10 cents. Principal component analysis extracted two components: one for small amounts and short delays, and a second one for large rewards and long delays. Conclusions: Temporal reward discounting is not a uniform construct. Functional brain imaging research could shed more light on unique brain activation patterns associated with different forms of temporal reward discounting. Copyright © 2010 John Wiley & Sons, Ltd. [source] Do early interviews affect children's long-term event recall?APPLIED COGNITIVE PSYCHOLOGY, Issue 7 2004Margaret-Ellen Pipe The present study examined the effects of the timing of an initial interview on children's recall of an event over delays of 1 and 2 years. Fifty-five children who had originally participated in a novel event when they were between 5- and 6-years old and had been interviewed about it following either short (1 week or less) or long (1 or 6 month) delays were re-interviewed 1 and 2 years after the original experience. An additional 20 children not interviewed prior to the 1-year interview were included as a no-prior-interview control group. Long delays to the initial interview led to better open-ended recall at the 1-year delay than short delays to initial interview or no prior interview. However, initial interviews that followed short delays had a greater impact on children's responses to specific questions. The results suggest that prior interview history is an important consideration when examining the effects of long delays on children's event reports, and that the effects of the timing of an initial interview depend on the nature of the information recalled. Copyright © 2004 John Wiley & Sons, Ltd. [source] | ||||||||||||||||