Search PubMed⌕ Search

Biomedical subjects

W Richards

Publications and source records attributed to W Richards.

At least 73 records · Page 4Linked to original sources
PubMed1986

Effects of nutritional environment and ram effect on breeding season in range sheep.

Effects of season, nutritional environment, and presence of rams on incidence and rate of ovulation in fine-wool sheep in southern New Mexico were investigated over 14 months (February 1983-March 1984). Number of corpora lutea (CL) were observed each month by laparoscopy in random samples from six ewes in each subgroup. Seasonality of ovulation in fine-wool sheep managed on range was much more marked than in animals managed on alfalfa hay in drylot. Incidence of ovulation approached zero in range-managed ewes during May, June, and July (8%, 0%, 4%) but was higher (P<0.05) in the alfalfa-drylot group (42%, 17%, 75%), respectively. Although the incidence remained lower (P<0.05) in August in range-managed than in drylot ewes (50% and 83%, respectively), both groups were ovulating at a high rate during September through January. Incidence of ovulation dropped dramatically both years in the range-managed group in February compared with that of the alfalfa-drylot group (48% and 36% vs 100% and 83%). Mean ovulation rate per ewe ovulating did not differ (P>0.10) between nutrition groups within the 14 months. Body weight was related to CL number during periods of seasonal transition only. Continuous or intermittent presence of a ram had no real effect on either incidence or rate of ovulation during the transitional months. Nutritional environment can affect seasonality of breeding in fine-wool range sheep. This effect may not be consistently modified by presence of rams.

Journal Article↗
PubMed1986

Encoding contour shape by curvature extrema.

Curvature extrema provide significant information about the shape of an image contour, such as a silhouette, and are the basis for the Hoffman-Richards codon representation for shape. This representation based on curvature easily translates into a binary string that will describe the abstract shape of any smooth image curve. The computation of the basic shape primitives requires dealing with two ever-pervasive problems: contour noise and scale. We show how contour noise can be estimated given knowledge of the shape of the filter used to compute curvature from the edge list of the contour. To handle the scale problem, we use an adaptation of Witkin's scale space. Our algorithm differs from Witkin's by using a notion of parts to set criteria for significant structures.

Algorithms↗
PubMed1985

Correlation between stereo ability and the recovery of structure-from-motion.

Many dynamic graphics displays appear three-dimensional (3D) because of our ability to reconstruct a rotating 3D configuration from its two-dimensional (2D) projection. This ability to infer 3D shape from 2D motion might be considered to be independent of stereopsis because only one eye's view is necessary. On the contrary, however, our data suggest that the mechanisms for both stereopsis and depth-from-motion are not independent but rather must share some components.

Biomechanical Phenomena↗
PubMed1985

Structure from stereo and motion.

Stereopsis and motion parallax are two methods for recovering three-dimensional (3D) shapes. Theoretical analyses of each method show that neither alone can recover rigid 3D shapes correctly unless other information, such as perspective and vertical disparity, is included. The solutions for recovering rigid structure from motion have a reflection ambiguity; the depth scale of the stereoscopic solution will not be known unless the fixation distance is specified in units of interpupil separation. (Hence the configuration will appear distorted.) However, the correct configuration and disposition of a rigid 3D shape can be recovered if stereopsis and motion are integrated, for then a unique solution follows from a set of linear equations. The correct interpretation requires only three points and two stereo views.

Form Perception↗
PubMed1985

Theophylline-associated seizures in children.

Four patients are reported who experienced seizures in association with serum theophylline concentrations which were in the mildly toxic range. In three patients, erythromycin administration was a probable factor contributing to the elevated theophylline levels. One patient suffered severe neurologic damage as a result of the seizure.

Child↗
PubMed1985

Therapy of acute asthma: I. Evaluation of successive bronchodilator treatments.

Ninety-one children with acute asthma were studied to determine the extent of incremental improvement in pulmonary function afforded by successive doses of subcutaneous epinephrine, and by a bronchodilator aerosol in those patients refractory to epinephrine. A significant proportion of patients (69%), as expected, responded to the first injection. Among those who did not respond to the first injection a significant proportion (30%) responded to the second injection. Markedly fewer patients responded to subsequent bronchodilator treatments, including aerosols, if they did not improve significantly after the first two treatments. Patients with higher initial peak flow rates (PEFR) generally required fewer epinephrine injections, and achieved higher maximal PEFR than those with lower initial PEFR. Most asthmatic patients who required hospital admission had lower initial peak flow rates, were less responsive to epinephrine injections, and achieved lower maximal rates than those who could be discharged home.

Acute Disease↗
PubMed1984

Abnormal T-cell subsets and mitogen responses in hemophiliacs exposed to factor concentrate.

The acquired immune deficiency syndrome (AIDS) has been reported in hemophiliacs . We examined lymphocyte numbers and functions in 28 patients with hemophilia and 16 healthy adults. Healthy hemophiliacs who had received fewer than 150 commercial factor concentrate (CFC) infusions had normal T-cell numbers, T-cell subsets, and mitogen responses. Healthy hemophiliacs who had received more than 250 CFC infusions had a decreased number of Leu 3+ "helper" T cells, a decreased Leu 3-Leu 2 ratio, and decreased pokeweed mitogen responses. Hemophiliacs who had received greater than 250 CFC infusions and who had persistent lymphadenopathy had decreased Leu 3+ cells, increased Leu 2+ "suppressor" T cells, a decreased Leu 3-Leu 2 ratio, and decreased phytohemagglutinin responses. Abnormal results of T-cell studies were found in 67% of healthy hemophiliacs who had a high degree of CFC exposure and 100% of clinically abnormal hemophiliacs. These findings suggest that hemophiliacs are at risk for the development of the immunologic changes that characterize AIDS and that this risk is related to CFC exposure.

Acquired Immunodeficiency Syndrome↗
PubMed1983

An observation about myelination.

An analysis of the direction of myelination of fibers in the optic tract of a kitten shows that the direction of wrapping of neighboring fibers is not random. Adjacent fibers in contact with the same glial process tend to be wrapped in the same direction. A model for myelination is proposed to account for this observation.

Animals↗
PubMed1983

Intakes of copper, zinc, cadmium, tin, iron, nickel and arsenic in a population exposed to lead from water.

Adult diets obtained from a population in Ayr, Scotland, U.K., known to be exposed to lead from water were analysed for arsenic, cadmium, copper, iron, nickel, tin and zinc to assess the intake of these elements. With few exceptions, the concentration of each element varied little from diet to diet, and therefore the range of intakes varied only in proportion to the weights of the diets. With the exception of nickel, the difference between the observed average dietary intakes of the metals studied and those expected on the basis of a nationwide Total Diet Study is largely accounted for on the basis of the differences between the weights of the duplicate diet and the weight for the Total Diet Study.

Adult↗
PubMed1983

Administration of metered-dose inhalers: comparison of open- and closed-mouth techniques in childhood asthmatics.

It has been suggested that the effectiveness of bronchodilators administered from metered-dose inhalers (MDI) may be improved by altering the inhalation technique with which they are taken. The efficacy of the traditional closed-mouth technique of MDI use was compared with one in which the mouth remained open throughout inhalation. Eighteen asthmatics, aged seven to 16 years whose peak expiratory flow rates (PEFR) were less than 70% predicted, were studied. PEFR was measured before and 5, 10 and 15 minutes after a single inhalation of isoetharine using the open-mouth and closed-mouth techniques on separate days. There was no significant difference in PEFR improvement at any time when the two techniques were compared. Routine re-training of pediatric patients already using the traditional closed-mouth method successfully is not warranted on the basis of these findings.

Adolescent↗
PubMed1983

Distance running improves fitness in asthmatic children without pulmonary complications or changes in exercise-induced bronchospasm.

The effect of a distance running program was studied in 15 children with severe chronic asthma. Following a 6-week control period, the subjects ran four days a week for 6 weeks. The distance was increased gradually to 3.2 km. Clinical status and need for treatment did not change. Episodes of exercise-induced bronchospasm were readily reversed. Fitness improved as measured by the distance run in 12 minutes (P less than .005). Resting pulmonary function did not change. Exercise-induced bronchospasm following a bicycle ergometer stress test under comparable conditions did not change. Ventilatory muscle strength, measured as the maximal inspiratory pressure, and endurance, measured as the sustainable inspiratory pressure, were at a high level initially and did not change. It is concluded that distance running is safe and can increase the fitness of asthmatic children who are receiving adequate therapy.

Adolescent↗