Throughput and delay analysis of an opportunistic tree algorithm

Tree algorithms are a well-known class of random access algorithms with a provable maximum stable throughput under the infinite population model (as opposed to ALOHA or the binary exponential backoff algorithm). In this article, we propose a tree algorithm for opportunistic spectrum usage in cognitive radio networks. A channel in such a network is shared among so-called primary and secondary users, where the secondary users are allowed to use the channel only if there is no primary user activity. The tree algorithm designed in this article can be used by the secondary users to share the channel capacity left by the primary users.

We analyze the maximum stable throughput and mean packet delay of the secondary users by developing a tree structured Quasi-Birth Death Markov chain under the assumption that the primary user activity can be modeled by means of a finite state Markov chain and that packets lengths follow a discrete phase-type distribution.

Numerical experiments provide insight on the effect of various system parameters and indicate that the proposed algorithm is able to make good use of the bandwidth left by the primary users.     

Deaf studies meets autistic studies

What might deaf studies and autistic studies have in common? Why, in many cases, is deafness considered to be a norm to be analyzed through linguistic and cultural frameworks, while autism is (still) seen as pathological? Utilizing ethnographic research, participation in two conferences on autism and sign language, and an analysis of deaf peoples’ and autistic peoples’ self-(re)presentation, we attend to sensory solidarities that might exist between deaf and autistic people, communities, and studies. We argue that an analysis of the two fields side-by-side offers important insights into new ways of conceptualizing sociality, identity, and community both in the specific cases of deafness and autism, and more broadly. Additionally, attending to deaf and autistic peoples’ language and communication desires and practices opens up analytic and empirical space for considering interdependent and multimodal communicative approaches.     

Road socialism

Road socialists maintain that government is the best manager for the nation's vehicular transportation arteries. Contrary to their views, the present author maintains that the managerial role can best be fulfilled by private entrepreneurs. Under highway privatization, he claims, traffic fatalities and automobile congestion will be sharply reduced.The author wishes to thank the North American Editor of Transport Policy, and an anonymous referee from the present journal, for helpful suggestions and commentary on an earlier draft of this paper.     

Professionalism and the physician leader

The perception of the well-respected, knowledgeable, empathetic physician of early 20th century medicine is slowly being eroded in American society today. Consider the causes of the breakdown and how to restore the image.     

Couple age discrepancy and risk of intimate partner homicide

Although national level studies in the United States and Canada find that extreme partner age discrepancy is a risk factor for intimate partner homicide in opposite-sex couples, these studies carry two caveats: They are limited to cohabiting marital or common-law couples and they are not detailed enough to explore alternative explanations for the age discrepancy-homicide risk association. Using the Chicago Homicide Dataset, which includes all homicides that occurred in Chicago from 1965 to 1996, we analyze the 2,577 homicides in which the victim was killed by a current or former legal spouse, common-law spouse, or heterosexual boyfriend or girlfriend, and in which the woman was at least 18 years of age. Within each of 14 categories of couple age discrepancy, we estimate the population of intimate heterosexual couples and calculate the population-based risk of homicide. The results replicate national level findings showing that the risk of intimate partner homicide is considerably elevated for couples with a large discrepancy between their ages-where the man is at least 16 years older than the woman or the woman is at least 10 years older than the man. This risk pattern occurs regardless of whether the man or the woman was the homicide offender. We then investigate whether the link between partner age discrepancy and homicide risk is explained by the offender's arrest record. Results show that the higher risk of intimate partner homicide for age discrepant couples is robust, and does not depend on the previous arrest record of the offender. Discussion addresses other possible explanations for the increased risk of partner homicide for age discrepant couples, and the practical implications of these findings.     

Enterprising Education: Doing Away with the Public School System

We critically examine the accepted notion that primary education is a legitimate and necessary function of the state. The notion is based upon three tenets: 1) public education is a necessary condition for democracy, 2) the market will not provide equal access and quality of education to all, and 3) education represents an external economy. Each tenet is addressed and evaluated according to its merits. In doing so, we also contrast the fulfillment of the ends implicit in the tenets under state and market provisions. We conclude that the state provision of primary education cannot be justified by these goals, and that market provision is a preferable alternative. This revised version was published online in July 2006 with corrections to the Cover Date.     

CMHS/CSAT Collaborative Demonstration Program for Homeless Individuals

The Collaborative Demonstration Program for Homeless Individuals is providing an opportunity for several community agencies in the United States to explore innovative intervention and treatment strategies to address the needs of homeless people with co-occurring (mental illness and substance abuse) disorders. This cooperative agreement, funded jointly by the Center for Mental Health Services (CMHS) and the Center for Substance Abuse Treatment (CSAT), is a $3 million project supporting programs in various community agencies to develop, document, and evaluate programs for persons who are homeless with co-occurring disorders to be used as models in other communities. The program models include: Assertive Community Treatment, Psychosocial Rehabilitation, Therapeutic Community, and an integrated treatment model. The first phase of the two-phase project funded 16 programs in the U.S. to develop manuals within their primary treatment modalities for homeless people with co-occurring disorders. For Phase II of the project, six of the 16 model programs were competitively selected to demonstrate program impact through formal program evaluation efforts. The data derived from the various projects will be compiled into a compendium of information for state agencies and community service providers throughout the U.S.     

The Dilemma of Social Work Education: Restructuring the Curriculum

The roles of social work libraries are reexamined in light of recent trends in library information science The implementation of special services is advocated in the following areas: Information Retrieval and Selective Dissemination of Information (SDI) programs, computer-produced subject bibliographies, regional and national union catalogues in book format, cooperative acquisition plans, and improved interlibrary loan services. Local, regional, and national consortia social work libraries are seen as a possible approach, utilizing existing and future data bank networks.