Drexel University

About: Drexel University is a education organization based out in Philadelphia, Pennsylvania, United States. It is known for research contribution in the topics: Population & Poison control. The organization has 26770 authors who have published 51438 publications receiving 1949443 citations. The organization is also known as: Drexel & Drexel Institute.

On Cooperative Relaying Schemes for Wireless Physical Layer Security

Abstract: We consider a cooperative wireless network in the presence of one or more eavesdroppers, and exploit node cooperation for achieving physical (PHY) layer based security. Two different cooperation schemes are considered. In the first scheme, cooperating nodes retransmit a weighted version of the source signal in a decode-and-forward (DF) fashion. In the second scheme, referred to as cooperative jamming (CJ), while the source is transmitting, cooperating nodes transmit weighted noise to confound the eavesdropper. We investigate two objectives: i) maximization of the achievable secrecy rate subject to a total power constraint and ii) minimization of the total power transmit power under a secrecy rate constraint. For the first design objective, we obtain the exact solution for the DF scheme for the case of a single or multiple eavasdroppers, while for the CJ scheme with a single eavesdropper we reduce the multivariate problem to a problem of one variable. For the second design objective, existing work introduces additional constraints in order to reduce the degree of difficulty, thus resulting in suboptimal solutions. Our work raises those constraints, and obtains either an analytical solution for the DF scheme with a single eavesdropper, or reduces the multivariate problem to a problem of one variable for the CJ scheme with a single eavesdropper. Numerical results are presented to illustrate the proposed results and compare them to existing work.

Axon pathology in Parkinson's disease and Lewy body dementia hippocampus contains alpha-, beta-, and gamma-synuclein.

Abstract: Pathogenic α-synuclein (αS) gene mutations occur in rare familial Parkinson’s disease (PD) kindreds, and wild-type αS is a major component of Lewy bodies (LBs) in sporadic PD, dementia with LBs (DLB), and the LB variant of Alzheimer’s disease, but β-synuclein (βS) and γ-synuclein (γS) have not yet been implicated in neurological disorders. Here we show that in PD and DLB, but not normal brains, antibodies to αS and βS reveal novel presynaptic axon terminal pathology in the hippocampal dentate, hilar, and CA2/3 regions, whereas antibodies to γS detect previously unrecognized axonal spheroid-like lesions in the hippocampal dentate molecular layer. The aggregation of other synaptic proteins and synaptic vesicle-like structures in the αS- and βS-labeled hilar dystrophic neurites suggests that synaptic dysfunction may result from these lesions. Our findings broaden the concept of neurodegenerative “synucleinopathies” by implicating βS and γS, in addition to αS, in the onset/progression of PD and DLB.

A thirty-year follow-up of treatment effects.

Abstract: VioLit summary: OBJECTIVE: This study by McCord was designed to follow up the subjects who had participated in the Cambridge-Somerville Youth study after 1942. Criminal behavior, health, lifestyle, and beliefs/attitudes were primary subjects of inquiry. METHODOLOGY: The original study was a quasi-experimental design which followed 253 problem boys and 253 matched controls who were selected by various public sources and identified as "difficult" or "average." Boys were paired by age, delinquency-prone histories, family background, and home environments and then randomly assigned to the experimental and the control group. Treatment began in 1939 when the subjects were 5-13 (median, 10.5) and continued for an average of 5 years (except those dropped from the program during 1941 because of counselor shortage). Counselors visited the home an average of twice a month and encouraged families to call on the program for assistance. This assistance included family counseling, tutoring, medical and/or psychiatric attention, summer camps, and connection with Boy Scouts, YMCA, or other community programs. The control group only participated insofar as they gave information about themselves. Each group included boys from "difficult" and "average" groups. The study this author conducted was a follow-up, thirty years later, on the men who had participated in the original study. Official records (court records, mental hospital records, statistics from alcohol treatment centers, and vital statistics) and personal contacts were used to obtain information about the long-term effects of the Cambridge-Somerville Youth Study. The follow-up took place in 1975 and 1976. The men were located using telephone calls, city directories, motor-vehicle registration, marriage and death records, and researcher intuition. 480 (95%) of the men were located; 48 (9%) of these had died and 340 (79%) were living in Massachusetts. Questionnaires were mailed to 208 men from the treatment group and 202 men from the control group. The items in the questionnaire covered the topics of family, occupation, drinking, health, and attitudes. Former members of the treatment group were asked how (if at all) the treatment program had been useful to them. Responses to the questionnaire were received from 113 men in the treatment group (54%) and 122 men in the control group (60%). Men who lived outside of Massachusetts were significantly (p= FINDINGS/DISCUSSION: The treatment and control groups were compared on a variety of measures for criminal behavior. With the exception of Crime Prevention Bureau records for unofficial crimes committed by juveniles, court convictions served as the standard by which criminal behavior was assessed. Almost equal numbers of each groups had committed crimes as juveniles on both official and unofficial measures. On dimensions of "difficult" and "average" distinctions, there were also no differences. As adults, equal numbers (168) had been convicted for some crime. From the treatment group, 119 committed minor crimes, and 49 had committed serious crimes against property or person as adults. For the control group, 126 had committed minor crimes, and 42 had committed serious crimes. 29 of the treatment group and 25 from the control group had committed serious crimes after age 25. When comparing adult criminal records controlling for juvenile records, there was no evidence that the treatment program had any effect. There were no differences in number of serious crimes committed, age at which the first crime was committed, age at which first serious crime was committed, or age after which no serious crime was committed. Chi-square revealed that a significantly higher proportion of criminals from the treatment group committed more than one crime. 78% of the treatment group committed at least two crimes versus 67% of the control group who had. Dimensions of health that were evaluated were alcoholism, stress-related diseases, and early death. There were no differences in mental hospitalization/alcohol treatment between the groups. A significantly higher proportion of the treatment group mentioned that they were alcoholic or were judged by the CAGE test be alcoholic when compared to the control group (17% versus 7%). Of those men who had received treatment in mental hospitals for non-alcoholic problems, a significant majority of the men who had been in the treatment group were diagnosed with more serious diagnoses (71%) whereas the control group was diagnosed with less serious diagnoses (67%). A significantly higher proportion of the men from the treatment group reported stress-related diseases than the control group, particularly for heart trouble. In comparisons of family and work, the only significant difference was in the number who were white collar professionals (43% for the control group, 29% for the treatment group) and, in general, the control group had a significantly higher level of prestige in their jobs. Among blue-collar workers, a significantly greater number of the treatment group expressed dissatisfaction (p=.02). There were no significant differences in authoritarianism, political orientation, or identification of the best periods of their lives. The majority of the men (2/3) who had been in the treatment program reported that it had been helpful to them, and some responded that the program had helped keep them out of trouble and made them more law-abiding. In general, the author concluded that the program did not, according to objective measures, improve the lives of the treatment group. AUTHOR'S RECOMMENDATIONS: The author suggested a cautious stance to intervention programs, though it is also suggested that new programs should be developed with attention to the problems of potential damage through the use of pilot projects with mandatory evaluations. EVALUATION: This study serves as an interesting follow-up to one of the best known experiments in delinquency prevention. It is surprising to see the negative effects the author found in the treatment group thirty years after being in the program. This study, however, cannot make a strong empirical claim that the program did not work. First, the initial selection and identification of youth casts doubts on the original methodology. Additionally, the present study relies upon mailed questionnaires. It has been shown that there is a likely self-selection bias which makes findings difficult to generalize to the population which confounds the usual difficulties with mailed questionnaires. Face-to-face interviews or even telephone interviews would add some credibility. Thirdly, the data collection could have been tightened up (for example, using FBI rap sheets as an additional measure of criminal activity). Finally, the data analysis techniques do not provide for an adequate level of control to establish the causal linkages which one would want to see. Additional analyses using regression techniques would have been helpful. This study was published in 1978, and methodology has improved since then. It would be insightful to do another follow-up or a reanalysis of the original data to see if the lack of effect or opposite effects of treatment hold. (CSPV Abstract - Copyright © 1992-2007 by the Center for the Study and Prevention of Violence, Institute of Behavioral Science, Regents of the University of Colorado) KW - Massachusetts KW - Geographic Location KW - Long-Term KW - Criminal Behavior KW - Delinquency KW - Diagnosis KW - Follow-Up Studies KW - Problem Behavior KW - Life Course KW - Prevention KW - Nutrition-Health KW - Ideology KW - Perceptions KW - Lifestyle KW - Juvenile Offender KW - Male Offender KW - Adult Offender

A map of the universe

Abstract: We have produced a new conformal map of the universe illustrating recent discoveries, ranging from Kuiper Belt objects in the solar system to the galaxies and quasars from the Sloan Digital Sky Survey. This map projection, based on the logarithm map of the complex plane, preserves shapes locally and yet is able to display the entire range of astronomical scales from the Earth's neighborhood to the cosmic microwave background. The conformal nature of the projection, preserving shapes locally, may be of particular use for analyzing large-scale structure. Prominent in the map is a Sloan Great Wall of galaxies 1.37 billion light-years long, 80% longer than the Great Wall discovered by Geller and Huchra and therefore the largest observed structure in the universe.