Biomedical subjects

David A Benson

Publications and source records attributed to David A Benson.

5 recordsLinked to original sources

PubMed2006

Random walk approximation of fractional-order multiscaling anomalous diffusion.

Random walks are developed to approximate the solutions of multiscaling, fractional-order, anomalous diffusion equations. The essential elements of the diffusion are described by the matrix-order scaling indexes and the mixing measure, which describes the diffusion coefficient in every direction. Two forms of the governing equation (also called the multiscaling fractional diffusion equation), based on fractional flux and fractional divergence, are considered, where the diffusion coefficient and the drift vary in space. The particle-tracking algorithm is also extended to approximate anomalous diffusion with a streamline-dependent mixing measure, using a streamline-projection technique. In this and other general cases, the random walk method is the only known way to solve the nonhomogeneous equations. Five numerical examples demonstrate the flexibility, simplicity, and efficiency of the random walk method.

Journal Article↗

PubMed2005

Embolization of an acute renal arteriovenous fistula following a stab wound: case report and review of the literature.

Surgery has traditionally been the definitive form of invasive management for renal vascular injuries. There is a growing trend in the use of endovascular techniques as an alternative to surgery in the trauma setting. We present the case of a 24-year-old woman with an acute renal arteriovenous fistula caused by a stab wound in the left flank, which was successfully managed with selective arterial embolization. This represents only the second reported case of such an approach in the acute setting.

Abdominal Injuries↗

PubMed2002

Governing equations and solutions of anomalous random walk limits.

Continuous time random walks model anomalous diffusion. Coupling allows the magnitude of particle jumps to depend on the waiting time between jumps. Governing equations for the long-time scaling limits of these models are found to have fractional powers of coupled space and time differential operators. Explicit solutions and scaling properties are presented for these equations, which can be used to model flow in porous media and other physical systems.

Journal Article↗

PubMed2002

Stochastic solution of space-time fractional diffusion equations.

Classical and anomalous diffusion equations employ integer derivatives, fractional derivatives, and other pseudodifferential operators in space. In this paper we show that replacing the integer time derivative by a fractional derivative subordinates the original stochastic solution to an inverse stable subordinator process whose probability distributions are Mittag-Leffler type. This leads to explicit solutions for space-time fractional diffusion equations with multiscaling space-fractional derivatives, and additional insight into the meaning of these equations.

Journal Article↗

PubMed2002

Practice trends in the management of prostate disease by family practice physicians and general internists: an internet-based survey.

OBJECTIVES: To assess, using an Internet-based survey, the practice patterns of primary care physicians in the management of prostate disease and to assess the differences between family physicians and general internists. Prostate cancer and benign prostatic hyperplasia are common in the elderly population. The optimal management of these diseases is debated. METHODS: An 18-item survey was designed and administered on an Internet website. Members of the Society of General Internal Medicine and members of the Illinois, North Carolina, and New York chapters of the Academy of Family Physicians were surveyed. RESULTS: A total of 354 responses were obtained from 381 primary care physicians who viewed the survey web page. For patients 50 years old and older, 75% of physicians (87% of family physicians and 69% of general internists; P <0.001) recommended annual prostate cancer screening with digital rectal examination and 49% (67% of family physicians and 40% of general internists; P <0.001) recommended annual prostate cancer screening with prostate-specific antigen measurement. For patients diagnosed with prostate cancer, 76% of the primary care physicians estimated that less than one half of their patients are seen by a radiation oncologist. For the treatment and/or prevention of prostate cancer, 62% of physicians surveyed (76% of family physicians and 55% of general internists; P <0.001) believe there is a potential role for alternative herbal and nutritional therapies. CONCLUSIONS: Compared with general internists, family physicians are more likely to screen for prostate cancer and are more likely to believe there is a role for alternative therapies for prostate cancer.

Aged↗