Is Our Model for Contention Resolution Wrong?

Randomized binary exponential backoff (BEB) is a popular algorithm for coordinating access to a shared channel. With an operational history exceeding four decades, BEB is currently an important component of several wireless standards. Despite this track record, prior theoretical results indicate that under bursty traffic (1) BEB yields poor makespan and (2) superior algorithms are possible. To date, the degree to which these findings manifest in practice has not been resolved. To address this issue, we examine one of the strongest cases against BEB: $n$ packets that simultaneously begin contending for the wireless channel. Using Network Simulator 3, we compare against more recent algorithms that are inspired by BEB, but whose makespan guarantees are superior. Surprisingly, we discover that these newer algorithms significantly underperform. Through further investigation, we identify as the culprit a flawed but common abstraction regarding the cost of collisions. Our experimental results are complemented by analytical arguments that the number of collisions -- and not solely makespan -- is an important metric to optimize. We believe that these findings have implications for the design of contention-resolution algorithms.Comment: Accepted to the 29th ACM Symposium on Parallelism in Algorithms and Architectures (SPAA 2017

Extended Spectrum β-Lactamases among Gram-Negative Bacterial Isolates from Clinical Specimens in Three Major Hospitals in Northern Jordan

Background and Objectives. Extended spectrum β-lactamase (ESBL) production is increasing all over the world, and organisms other than E. coli and K. pneumoniae are acquiring this character. ESBL production is detectable by automation, E-test, double disk diffusion (DDD), and PCR. This study aimed to determine the prevalence of ESBL production among clinical isolates of gram-negative rods, and to evaluate the effectiveness of augmentation of clavunate with Cefotaxime, Ceftazoxime, Aztreonam, Ceftriaxone, and Cefpodoxime in detecting ESBL production. Methods. 472 clinical gram-negative isolates identified by standard methods were tested for ESBL-production by (DDD) method using six cephalosporins and amoxicillin-clavulinate discs. Results. 108/472 (22.9%) of the isolates were ESBL producers, and were prevalent in tertiary care hospitals. 88.2% of E. cloacae, 71.4% of K. pneumoniae, 28.6% of K. oxytoca, 12.5% of C. freundii, 11.1% of A. calcoacceticus, and 10.8% of E. coli were ESBL producers. The DDD test demonstrated some variations in the efficacy of the different cephalosporins in detecting all the ESBL producers. The inclusion of ceftizoxime discs increased the efficacy of the test. It is concluded that ESBL-producing bacteria were prevalent among our hospitalized patients, and involved genera other than Klebsiella and Escherichia, and the inclusion of ceftizoxime increased the efficacy of ESBL detection by the DDD test

Dinamička distribucija sigurnosnih ključeva i koalicijski protokol IP adresa za mobilne ad hoc mreže

In mobile adhoc networks (MANETs) a tree-based dynamic address auto-configuration protocol (T-DAAP) is one of the best protocols designed for address assignment as far as the network throughput and packet delays are concerned. Moreover, MANET security is an important factor for many applications given that any node can listen to the channel and overhear the packets being transmitted. In this paper, we merge the address assignment with the security key delivery into one protocol, such that a node in the MANET is configured with IP address and security key simultaneously. To the best of our knowledge, no single protocol provides concurrent assignment of IP addresses and security keys for MANET nodes. The proposed method, which is based on T-DAAP, shows significant enhancements in the required control packets needed for assigning network nodes IP addresses and security keys, MAC layer packets, total end-to-end delay, and channel throughput over those obtained when using separate protocols. Additionally, it provides not only efficient security keys to the nodes from the first moment they join the network, but also secure delivery of the address and security key to all participating nodes. It is noteworthy to mention that providing a complete security model for MANET to detect and countermeasure network security threats and attacks is beyond the scope of our proposed protocol.Kod mobilnih ad hoc mreža (MANET) dinamički protokol za autokonfiguraciju adresa baziran na stablu (T-DAAP) je jedan od najboljih protokola dizajniranih za dodjelu adresa iz perspektive propusnosti mreže i i kašnjenja paketa. štoviše, sigurnost MANET-a je važan faktor za mnoge aplikacije s obzirom da bilo koji čvor može osluškivati kanal i slučajno čuti pakete koji se šalju. U ovom radu, dodjela adresa i dostava sigurnosnih ključeva spojeni su u jedan protokol tako da je čvor u MANET-u konfiguriran simultano s IP adresom i sigurnosnim ključem. Prema saznanjima autora, niti jedan postojeći protokol ne pruža istovremeno dodjeljivanje IP adrese i sigurnosnog ključa za MANET čvorove. Predložena metoda, koja se bazira na T-DAAP-u, pokazuje značajna poboljšanja u odnosu na metode koje koriste odvojene porotokole, kod traženih kontrolnih paketa koji su potrebni za dodjeljivanje IP adresa i sigurnosnih ključeva čvorovima mreže, MAC paketa, ukupnog end-to-end kašnjenja i propusnosti kanala. Dodatno pruža ne samo efikasne sigurnosne ključeve čvorovima od trenutka kad se priključe mreži, nego i sigurno dostavljanje adrese i sigurnosnog ključa svim čvorovima koji sudjeluju u mreži. Važno je spomenuti da je pružanje cjelokupnog sigurnosnog modela za MANET koji detektira dodatno i protumjere prijetnjama i napadima na sigurnost mreže izvan dosega predloženog protokola

The Role of Media and Islamic Criminal Legislation in Reducing Crime (From the perspective of students of the University of Jordan)

The study aimed to know the role of the media and its various styles, as well as the role of Islamic criminal legislation in reducing crime and identifying the obstacles that limit the effectiveness of the media in the prevention of crime. A random sample of 600 students was selected at different university levels at the University of Jordan, as well as personal background factors (independent variables): sex, place of residence, specialty, so that eleven different positions were identified, asking the respondents to determine their opinion on their respective trends. Keywords: Role, Media, Islamic Criminal Legislation, Crime DOI: 10.7176/JPCR/44-05 Publication date: September 30th 201

Sensitivity and Bias in Decision-Making under Risk: Evaluating the Perception of Reward, Its Probability and Value

BACKGROUND: There are few clinical tools that assess decision-making under risk. Tests that characterize sensitivity and bias in decisions between prospects varying in magnitude and probability of gain may provide insights in conditions with anomalous reward-related behaviour. OBJECTIVE: We designed a simple test of how subjects integrate information about the magnitude and the probability of reward, which can determine discriminative thresholds and choice bias in decisions under risk. DESIGN/METHODS: Twenty subjects were required to choose between two explicitly described prospects, one with higher probability but lower magnitude of reward than the other, with the difference in expected value between the two prospects varying from 3 to 23%. RESULTS: Subjects showed a mean threshold sensitivity of 43% difference in expected value. Regarding choice bias, there was a 'risk premium' of 38%, indicating a tendency to choose higher probability over higher reward. An analysis using prospect theory showed that this risk premium is the predicted outcome of hypothesized non-linearities in the subjective perception of reward value and probability. CONCLUSIONS: This simple test provides a robust measure of discriminative value thresholds and biases in decisions under risk. Prospect theory can also make predictions about decisions when subjective perception of reward or probability is anomalous, as may occur in populations with dopaminergic or striatal dysfunction, such as Parkinson's disease and schizophrenia

Big Losses Lead to Irrational Decision-Making in Gambling Situations: Relationship between Deliberation and Impulsivity

In gambling situations, we found a paradoxical reinforcing effect of high-risk decision-making after repeated big monetary losses. The computerized version of the Iowa Gambling Task (Bechara et al., 2000), which contained six big loss cards in deck B', was conducted on normal healthy college students. The results indicated that the total number of selections from deck A' and deck B' decreased across trials. However, there was no decrease in selections from deck B'. Detailed analysis of the card selections revealed that some people persisted in selecting from the “risky” deck B' as the number of big losses increased. This tendency was prominent in self-rated deliberative people. However, they were implicitly impulsive, as revealed by the matching familiar figure test. These results suggest that the gap between explicit deliberation and implicit impulsivity drew them into pathological gambling

A qualitative study exploring midlife women’s stages of change from domestic violence towards freedom

Gold OABackground Domestic Violence (DV) remains a significant global health problem for women in contemporary society. Existing literature on midlife women’s experiences of domestic violence is limited and focuses on health implications. Leaving a violent relationship is a dynamic process that often requires multiple attempts and separations prior to final termination. The aim of this study was to explore the process of leaving a violent relationship for midlife women. Methods This qualitative study involved fifteen women aged between 40–55 who had accessed residential and non-residential community support services for domestic violence within the UK. Community-based support agencies provided these women with access to letters of invitation and participant information sheet explaining the study. The women notified agency staff who contacted the research team to arrange a mutually convenient time to meet within a safe place for both the women and researchers. It was stressed to all potential participants that no identifiable information would be shared with the agency staff. Women were considered survivors of DV if they defined themselves as such. Data were gathered through semi structured interviews, transcribed verbatim and thematically analysed. Results Midlife women appear to differ from younger women by transitioning quickly though the stages of change, moving rapidly through the breaking free onto the maintenance stage. This rapid transition is the resultant effect of living with long-term violence causing a shift in the women’s perception towards the violent partner, with an associated reclamation of power from within the violent relationship. A realisation that rapid departure from the violence may be critical in terms of personal safety, and the realisation that there was something ‘wrong’ within the relationship, a ‘day of dawning’ that had not been apparent previously appears to positively affect the trajectory of leaving. Conclusions Midlife women appeared to navigate through the stages of change in a rapid linear process, forging ahead and exiting the relationship with certainty and without considering options. Whilst these findings appear to differ from younger women’s process of leaving, further research is needed to explore and understand the optimum time for intervention and support to maximise midlife women’s opportunities to escape an abusive partner, before being reflected appropriately in policy and practice.This study received funding from The Research and Knowledge Transfer Office, The University of Chester, and from the Western Australian Health Promotion Foundation – ‘Healthway

Frank M. Shurman Collection 1908-1992 Bulk dates: 1970s-1990s

This collection documents the life and significant experiences of Frank M. Sherman. Prominent themes in this collection are his work for the United States military during World War II, his and his family's experiences in Nazi Germany, and his membership in the Deutscher Vortrupp. The collection consists of a large amount of correspondence as well as clippings, audiocassettes, publication, scrapbooks, official papers, notes, and a few photographs of friends or family members.Frank (Fritz) Shurman was born in Hildesheim in 1915 to Willy Schuermann and his wife Alma Mueller. His father owned a men's clothing store in Hildesheim. In 1938, the Gestapo confiscated the account books of the firm and the firm had to be liquidated. Frank and his father were arrested during Kristallnacht and taken to the Buchenwald concentration camp. After his release he managed to flee to a refugee camp in England. With the help of Augusta Hamilton, a Christian American Frank Shurman had met in Berlin in 1938, he and his famil were able to immigrate to the US in 1940. In 1943 he met his future wife Margery Moses; they got married in 1945. He served in the US army and interviewed German prisoners of war. Later, he became a successful businessman in the textile and clothing industry.Margery and Frank Shurman returned to Hildesheim several times. In 1976, Frank Shurman received the Bundesverdienstkreuz.Frank Shurman was friends with Gerhard Loeffler, a Protestant from Dresden. Gerhard Loeffler visited his friend several time while Frank Shurman was imprisoned in Buchenwald after Kristallnacht. They continued to keep in touch and corresponded for 68 years (1934-1992).Frank Shurman's memoir, All Our Hopes are You: a True Story about a Great Woman and her Compassion for Strangers in Need [ME 598] is available in the Memoir Collection of the LBI.digitize

All our hopes are you : A true story about a great woman and her compassion for strangers in need ….

In memory Augusta Dotty Rahr Hamilton, April 12 1893 – April 30 1966.Encounter with Augusta D.R. Hamilton during her visit to Germany; Mrs. Hamilton's assistance in Shurman's immigration to the USA; November pogrom of 1938 in Hildesheim; imprisonment in Buchenwald concentration camp; immigration to USA in 1940; contains exchange of letters between author and Augusta Hamilton.Also included are copies of awards to the author.Schürmann, Frit