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Biomedical subjects

A Levinson

Publications and source records attributed to A Levinson.

At least 19 recordsLinked to original sources
PubMed2001

Probing microquasars with TeV neutrinos.

The jets associated with galactic microquasars are believed to be ejected by accreting stellar mass black holes or neutron stars. We show that if the energy content of the jets in the transient sources is dominated by electron-proton plasma, then a several hour outburst of 1-100 TeV neutrinos produced by photomeson interactions should precede the radio flares associated with major ejection events. Several neutrinos may be detected during a single outburst by a 1 km(2) detector, thereby providing a powerful probe of microquasar jet physics.

Journal Article↗
PubMed2000

Particle acceleration and curvature TeV emission by rotating, supermassive black holes

It is shown that particles accelerating near the event horizon of a spinning supermassive black hole that is threaded by externally supported magnetic field lines suffer severe curvature losses that limit the maximum energy they can attain to values well below that imposed by the maximum voltage drop induced by the black hole dynamo. It is further shown that the dominant fraction of the rotational energy extracted from the black hole is radiated in the TeV band. The implications for vacuum breakdown and the observational consequences are discussed.

Journal Article↗
PubMed2000

Hydrodynamic collimation of gamma-ray-burst fireballs

Analytic solutions are presented for the hydrodynamic collimation of a relativistic fireball by a surrounding baryonic wind emanating from a torus. The opening angle is shown to be the ratio of the power output of the inner fireball to that of the exterior baryonic wind. The gamma ray burst 990123 might thus be interpreted as a baryon-poor jet (BPJ) with an energy output of order 10(50) erg or less, collimated by a baryonic wind from a torus with an energy output of order 10(52.5) erg, roughly the geometric mean of the BPJ and its isotropic equivalent.

Journal Article↗
PubMed1998

Medicaid managed care and infant health.

This paper provides estimates of the effects of Medicaid managed care on prenatal care adequacy and infant birthweights, using a census of 1994 Medicaid births in Wisconsin, where some Medicaid recipients were enrolled in fully capitated health maintenance organizations (HMOs) while others remained in traditional fee-for-service (FFS) systems. The results indicate that while Medicaid patients enrolled in managed care programs may be more likely to receive adequate prenatal care, birth outcomes under managed care are not significantly different from those under FFS financing systems. We conclude that cost savings generated by Wisconsin Medicaid managed care are not coming at the expense of maternity patients' or infants' welfare.

Adult↗
PubMed1997

The JIM interview. Art Levinson, PhD.

In the early 1980s several prominent scientists left the hallowed halls of respected universities seeking to exploit the revolution occurring in biology in an environment devoid of the bureaucratic and political confines of academia. The emergence of the biotechnology industry has been marked by both spectacular failures and success stories. Genentech was founded in 1976 by biochemist Herbert Boyer and venture capitalist Robert Swanson and went public in 1980. In 1995 Genentech merged with Roche Holdings Ltd., of Basel Switzerland. Distinguished from other biotech companies by the varied array of products it has brought to market, Genentech has also developed a unique corporate culture embodying many traditional academic values. Just as Genentech went public in 1980, Arthur D. Levinson, PhD, finished a post-doctoral appointment in Michael Bishop's lab at the University of California, San Francisco. Despite the disapproval of colleagues, he joined the fledgling company as a senior scientist. Working his way though the ranks, Levinson became Vice President of Research Technology in 1989 and was named President and CEO in 1995. Interviewed at the sprawling corporate headquarters in South San Francisco, Levinson reflected on the process of high risk science, the benefits of the private sector, and the changing relationship between biotech companies and the academic world.

Biotechnology↗
PubMed1993

Descriptive cataloging for collections of medical art.

Conserving our profession's historical record would be aided by creating a guide for recording bibliographical information associated with medical art. A guide of this nature should conform to currently accepted national standards for bibliographical listings, reflect the cataloging needs of these specialized materials, and contain a sample data collection sheet. Such a guide would provide a starting point for new or undocumented collections to begin organizing and listing their holdings. This article presents a cataloging guide that is specific to the needs of collecting medical art and that conforms, in both language and structure, to established guidelines for descriptive cataloging.

Archives↗
PubMed1992

Reaching special populations with breast and cervical cancer public education.

With passage of the Breast and Cervical Cancer Mortality Prevention Act of 1990, significant activity has emerged in the development, implementation, and evaluation of breast and cervical cancer screening programs targeting underserved populations. This activity has prompted health educators and program planners to identify barriers to breast and cervical cancer screening specific to low-income and minority women, those traditionally underserved by cancer control programs, and to develop strategies that address these barriers. The authors reviewed current knowledge regarding barriers to breast and cervical cancer screening and public education interventions that address them. The results and implications for program planning activities are presented.

Adult↗
PubMed1988

The influence of carbohydrate structure on the clearance of recombinant tissue-type plasminogen activator.

Modification of the carbohydrate structures of recombinant tissue-type plasminogen activator (rt-PA) can increase or decrease its rate of clearance in rabbits. When rt-PA was treated with sodium periodate to oxidize carbohydrate residues, the rate of clearance was decreased from 9.6 +/- 1.9 ml min-1 kg-1 to 3.5 +/- 0.6 ml min-1 kg-1 (mean +/- SD, n = 5). A similar change in the clearance of rt-PA was introduced by the use of endo-beta-N-acetyl-glucosaminidase H (Endo-H), which selectively removes high mannose asparagine-linked oligosaccharides; the clearance of Endo-H-treated rt-PA was 5.0 +/- 0.5 ml min-1 kg-1. A mutant of rt-PA was produced with an amino acid substitution at position 117 (Asn replaced with Gln) to remove a potential glycosylation site that normally contains a high mannose structure. The clearance of this material was also decreased, similar to the periodate and Endo-H-treated rt-PA. Conversely, when rt-PA was produced in the CHO 15B cell line, which can produce only high mannose oligosaccharide structures on glycoproteins, the clearance was increased by a factor of 1.8. These results demonstrate that the removal of rt-PA from the blood depends significantly upon the nature of its oligosaccharide structures.

Animals↗
PubMed1987

School of optometry at Tel Aviv University.

The following article describes the program for the study of optometry to begin at Israel's Tel Aviv University in the 1987/1988 academic year. Details of the proposed structure, facilities and curriculum are presented. In addition, background is provided as to the current vision care system in Israel, and how the absence of a school of optometry has influenced its condition.

Delivery of Health Care↗
PubMed1985

Measurement of stress as it affects the work of the general practitioner.

This paper describes a preliminary study which collected information on the work of 18 general practitioners during a total of 52 days, and also recorded their feelings of pressure and stress from hour to hour throughout each day. The instruments used to record information on day-to-day activities and to measure self-perceived pressure, stress and arousal are described. The reliability and validity of the methods used are discussed, and some suggestions made for future development. A few preliminary findings are presented.

Appointments and Schedules↗
PubMed1984

Minimal size plasmids containing an M13 origin for production of single-strand transducing particles.

We have studied the requirements for efficient production of single-strand transducing particles from minimal size plasmids containing the phage M13 origin of replication. The most favorable origin fragment for production of transducing particles was found to extend from nucleotides 5372 to 5943 of the phage sequence, which includes a segment of the phage gene IV coding region and eliminates part of the gene II promoter. Minimizing vector size for M13 origin plasmids appears to be beneficial since transducing particle titer decreases with increasing plasmid size. A mutant helper phage was isolated and shown to improve the production of transducing particles from small plasmids, but to outcompete plasmids bearing large inserts. Several plasmid vectors which produce high yields of single-strand transducing particles and good ratios of transducing particles to helper phage have been constructed.

Coliphages↗
PubMed1981

Report on the status of vision care in Israel.

Recognition of optometry in Israel has not been achieved due to various factors: the lack of recognition by the Ministry of Health in proposing a law of optometry to the Knesset (Parliament); the opposition of organized ophthalmology; the internal conflict between the various associations of opticians and optometrists within the country which lead to a lack of unification for propagation of a law of optometry; the absence of an academic institution of learning in optometry. The establishment of the Optometric Centre by the American Friends of Israel Optometry has instituted low vision clinics and post-graduate courses which have helped to advance optometry. Optometry must become organized in order to apply pressure on the Ministry of Health in order to recognize optometry as an independent profession. There is a need for the establishment of operating courses to equalize the standard of eye-care in the profession, and for the founding of an academic school of optometry to maintain a constant supply of qualified optometrists.

Humans↗
PubMed1980

Recruitment of a clinical field trial population: reasons for nonparticipation.

Open-ended telephone interviews were conducted with 294 families who refused participation in a school-based program of professionally applied topical fluoride. While the program was conducted in a flouride-deficient community, the level of topical fluoride contact in the homes of the nonparticipants was high. The traditional antifluoridationist reasons for nonparticipation were not expressed with frequency. Instead, the most frequent reason for returning a negative consent form was that the child was already receiving topical flouride applications from the family dentist. The second most frequent reason was that the child did not wish to participate. Many of the reasons given for nonparticipation were not cogent, suggesting that if the parents had been more informed about the nature of the project and about fluoride in general their responses might have been positive.

Attitude↗
PubMed1980

Supervised weekly rinsing with a 0.2% neutral NaF solution: results from a demonstration program after three school years.

A school-based fluoride rinsing program was instituted in 1975 in the Three Village Central School District, Long Island, NY. The children rinsed once a week with a 0.2% neutral NaF solution under supervision of the homeroom teachers. After three years, the participants had rinsed an average of 77 times. Children in grades 3 through 7 who had participated during all three years of rinsing had a reduction in caries prevalence of 30.9% for DMFS and 28.5% for DMFT. The greatest reduction occurred on proximal surfaces (48.7%), followed by buccolingual surfaces (30.0%) and occlusal surfaces (28.2%). The benefits of fluoride rinsing increased with the duration of the program.

Child↗