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Biomedical subjects

T J Cox

Publications and source records attributed to T J Cox.

10 recordsLinked to original sources
PubMed2005

Lost and found dark matter in elliptical galaxies.

There is strong evidence that the mass of the Universe is dominated by dark matter, which exerts gravitational attraction but whose exact nature is unknown. In particular, all galaxies are believed to be embedded in massive haloes of dark matter. This view has recently been challenged by the observation of surprisingly low random stellar velocities in the outskirts of ordinary elliptical galaxies, which has been interpreted as indicating a lack of dark matter. Here we show that the low velocities are in fact compatible with galaxy formation in dark-matter haloes. Using numerical simulations of disk-galaxy mergers, we find that the stellar orbits in the outer regions of the resulting ellipticals are very elongated. These stars were torn by tidal forces from their original galaxies during the first close passage and put on outgoing trajectories. The elongated orbits, combined with the steeply falling density profile of the observed tracers, explain the observed low velocities even in the presence of large amounts of dark matter. Projection effects when viewing a triaxial elliptical can lead to even lower observed velocities along certain lines of sight.

Journal Article↗
PubMed2003

Speech transmission index from running speech: a neural network approach.

Speech transmission index (STI) is an important objective parameter concerning speech intelligibility for sound transmission channels. It is normally measured with specific test signals to ensure high accuracy and good repeatability. Measurement with running speech was previously proposed, but accuracy is compromised and hence applications limited. A new approach that uses artificial neural networks to accurately extract the STI from received running speech is developed in this paper. Neural networks are trained on a large set of transmitted speech examples with prior knowledge of the transmission channels' STIs. The networks perform complicated nonlinear function mappings and spectral feature memorization to enable accurate objective parameter extraction from transmitted speech. Validations via simulations demonstrate the feasibility of this new method on a one-net-one-speech extract basis. In this case, accuracy is comparable with normal measurement methods. This provides an alternative to standard measurement techniques, and it is intended that the neural network method can facilitate occupied room acoustic measurements.

Humans↗
PubMed2000

Surface diffusion coefficients for room acoustics: free-field measures.

A surface diffusion coefficient is needed in room acoustics to enable the quality of diffusing surfaces to be evaluated. It may also facilitate more accurate geometric room acoustic models. This paper concentrates on diffusion coefficients derived from free-field polar responses. An extensive set of two- and three-dimensional measurements and predictions was used to test the worth of different diffusion coefficient definitions. The merits and problems associated with these types of coefficients are discussed, and past parameters reviewed. Two new coefficients are described. The new measure based on the autocorrelation function is forwarded as the best free-field coefficient. The strengths and weaknesses of the coefficient are defined.

Acoustics↗
PubMed1993

Interleukin-6 and interleukin-8 production by mononuclear cells of chronic alcoholics during treatment.

Chronic alcohol consumption has been associated with suppression of a number of immune parameters. This study was designed to investigate the relationship between chronic alcohol ingestion and cessation with respect to release of interleukin-6 (IL-6) and interleukin-8 (IL-8) using highly specific and sensitive ELISA assays, as well as a functional assay, natural killer cell cytotoxic activity. ELISAs were developed to determine the amount of IL-6 and IL-8 release by peripheral blood mononuclear cells (PBMCs). Two groups of subjects were recruited: young (18-22 years old), nonalcoholic users (controls) and long-term alcoholics (35-55 years old). Blood samples were collected at time 0 from all subjects and from alcoholics 28 days after treatment had begun and alcohol use had ceased. Then mitogen-stimulated release of cytokines by peripheral blood cells was determined. The abstaining controls, and the alcoholics, after 30 days of abstinence, tended to produce lower amounts of IL-6 and IL-8, although these differences were not statistically significant. Natural killer cell activity was not statistically different between the young groups, yet appeared to increase once alcohol use discontinued. Some of the cells from the controls (abstainers) were incubated with ethanol (EtOH). Its content in sealed wells was measured after the time of incubation of PBMCs. When EtOH was serially diluted in plates, some well-well diffusion was noted, but the maximum concentration of EtOH never fell below 0.3% from an initial concentration of 0.5%, and at no time was the EtOH concentration gradient completely lost, even after 66 hr of incubation.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1979

A twenty-year follow-up of narcotic addicts in Tucson, Arizona.

This preliminary report from an epidemiological study of heroin addiction in Tucson, Arizona, 1956-1976, examines the status of heroin addicts 20 years after they have been identified as narcotics abusers, focusing on the maturation hypothesis which holds that heroin addicts tend to cease use of narcotics spontaneously by age forty. A cohort of 51 subjects was identified from Public Records of Court Appearances for narcotic offenses during a 36-month period (1955-1957), located and, where possible, interviewed. Records from a minimum of two agencies (law enforcement, corrections, treatment, welfare) were used to establish current status of the individual with reference to the use of narcotics and/or other drugs. Demographic, ethnic, socioeconomic makeup of the sample, as well as criminal involvement and treatment episodes, is included. After 20 years, one individual is drug-free or abstinent. Twenty-three are considered still addicted to heroin, 16 of these are in prison; seven are addicted to methadone or alcohol. Thirteen are dead. Six could not be located; however, five could be traced well beyond 1956 through criminal activities. All but one person have passed their fortieth birthdays. For these 51 addicts, the maturation hypothesis does not hold.

Adolescent↗
PubMed1979

Side effects in methadone patients: a survey of self-reported complaints.

Fifty-one patients in a methadone maintenance program completed a questionnaire containing 38 complaints upon admission and after 3 and 9 months in treatment. The questionnaire contained a graded scale of five possible responses from "no problem" to "a very bad problem." Only three complaints at 3 months and five complaints at 9 months showed an increase in the percentage of clients reporting them as a problem compared to before methadone matinenance (BMM). When analyzed by summed mean, only one complaint at 3 months and two at 9 months showed an increase in severity on the graded scale compared to BMM. However, when each patient's responses were analyzed as to whether problems showed no change in severity, were improved, or increased in severity comparing BMM and after 9 months of methadone, 11 of 38 complaints showed a significant number of patients reporting them as more severe.

Adult↗
PubMed1976

The Brighton resuscitation ambulances: a continuing experiment in prehospital care by ambulance staff.

Two ambulances from the existing fleet in Brighton and one in Hove are equipped with portable defibrillator-oscilloscope units. Selected attendants have been trained not only to defibrillate patients but also to perform endotracheal intubation and administer intravenous atropine and lignocaine for carefully defined indications. In the two years up to December 1975 the ambulances responded to 2253 calls which were considered possible emergencies. Retrospective analysis showed that half of these had been for patients with myocardial infarction, coronary insufficiency, or angina. The ambulances took a median time of five minutes to reach a patient. Attempts at resuscitation were made in 207 patients with circulatory arrest, of whom 160 had ventricular fibrillation. Coordinated rhythm was restored at least transiently in 66 patients, and 27 of them survived to leave hospital. Sixteen of the survivors had been in ventricular fibrillation before the arrival of the ambulance. The delay before admission to hospital was reduced: over 50% of patients carried in the ambulances were admitted within two hours of the onset of major symptoms. No extra ambulance staff have been employed for the scheme. The increased load on hospital services has been limited by encouraging a rational admission policy and also by early discharge.

Ambulances↗