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F O'Brien

Publications and source records attributed to F O'Brien.

51 records · Page 3Linked to original sources
PubMed1990

A crowding index for finite populations.

The classical definition of population density used in social science disciplines as a measure of density or physical crowding has severe shortcomings since actual spatial orientation is disregarded. A formula is proposed to measure physical crowding or population density which corrects the deficiency of the conventional formulation. As a generalization of the Euclidean distance formula, the proposed index measures relative population density as a function of spatial orientation and size of geometric area. Three mathematical properties of the index stated as conjectures have been supported by Monte Carlo simulations. The formula is evaluated and justified on three key scientific criteria: parsimony, mathematical soundness and empirical verifiability. Crowding is an obvious problem in the small compartmentalized workspaces of U.S. Navy nuclear submarines. The measurement of physical crowding by use of the proposed formula in Concepts of Operations Experiments conducted at the Newport Laboratory of the Naval Underwater Systems Center is reported and discussed.

Adaptation, Psychological↗
PubMed1987

Association between mortality among women and socioeconomic factors in general practices in Edinburgh: an application of small area statistics.

Women aged 45-64 in 78 general practices in the city of Edinburgh were followed up for five to seven years and all cause mortality noted. Standardised mortality ratios were calculated for the individual practices. Postcodes were available for a 20% sample of these women and were used to retrieve relevant measures of social class and deprivation from the 1981 census for the smallest division, the enumeration district. Weighted averages gave socioeconomic variables at the level of the general practice. High positive correlations were found between standardised mortality ratios and the socioeconomic variables, with the highest being for percentage overcrowding. This study established that the relation between deprivation and excess mortality can be shown in general practices in one large city and gave a direct relation for women without reference to their husbands' occupations, thus obviating problems of assigning social class. The data also partially refute the "social drift" hypothesis as an explanation of the association between mortality and social class.

Female↗
PubMed1976

Modification and characterization of the permanent sympathectomy produced by the administration of guanethidine to newborn rats.

The administration of guanethidine to newborn rats has been shown to produce a permanent sympathectomy with potential advantages over immunosympathectomy and 6-hydroxydopamine-induced chemical sympathectomy. In this paper, we report on a revised treatment regimen involving initiation of treatment (50 mg/kg/day) on day 7 after birth and continuing for 3 weeks. Animals treated by this protocol have a low mortality rate (approx. 10% above saline-treated controls) and no permanent growth deficit. Analysis of tyrosine hydroxylase activity in and light microscopic examination of superior cervical ganglia of the guanethidine-treated animals indicate complete destruction of sympathetic neurons by the end of the second week of treatment. During and after treatment there are no decreases in norepinephrine in whole brain of the treated animals. Norepinephrine levels in peripheral tissues are markedly reduced at both 9 and 16 weeks of age. Stimulation of vasomotor outflow produces no increase in blood pressure in guanethidine-treated rats at 9 or 26 weeks of age, indicating a complete and permanent functional denervation of the vasculature. The adrenal glands of the guanethidine-treated animals are not destroyed, but rather respond, apparently by transsynaptic induction, with increases in tyrosine hydroxylase and epinephrine content. Interestingly, despite the continued deprivation of a peripheral sympathetic nervous system in these animals. adrenal tyrosine hydroxylase and epinephrine levels return to control levels by 10 weeks of age. These data indicate that administration of guanethidine to newborn rats produces a very complete and permanent sympathectomy with significant advantages over immunosympathectomy and 6-hydroxydopamine-induced chemical sympathectomy.

Adrenal Glands↗
PubMed1976

Evaluation of the permanent sympathectomy produced by the administration of guanethidine to adult rats.

The administration of guanethidine to adult rats has been shown by morphological criteria to destroy sympathetic neurons. The objective of this study was to evaluate by biochemical and functional criteria the degree and permanence of this sympathectomy. Young adult male rats (260-300 g) were injected with saline (controls) or with guanethidine for 5 weeks. The status of the sympathetic nervous system in the animals was evaluated 1, 3 and 6 to 7 months after cessation of treatment. Seven months after cessation of treatment; the activity of tyrosine hydroxylase in the superior cervical ganglia of treated animals was greatly reduced, as were the norepinephrine levels in peripheral tissues. The concentration of epinephrine and the activity of tyrosine hydroxylase in adrenals were not different from controls at any of the times studied. Norepinephrine concentrations in several areas of the central nervous system were unchanged. Increases in blood pressure in response to stimulation of the sympathetic vasomotor outflow in the pithed rat preparation were markedly and permanently reduced in guanethidine-treated animals. Isolated intestinal nerve-muscle preparations from guanethidine-treated animals usually contracted in response to nerve stimulation, rather than relaxing as in controls. The response to stimulation of the hypogastric nerve in vas deferens preparations was reduced 1 month after cessation of treatment. The responses of the vas deferens from guanethidine-treated and control animals were the same 7 months after treatment despite a 93% reduction in norepinephrine concentration. The data demonstrate that the administration of guanethidine to adult rats produces a marked and permanent destruction of the peripheral sympathetic nervous system.

Adrenal Glands↗
PubMed1968

Sequential contrast effects with human subjects.

Institutionalized retardates were exposed to a multiple variable-interval: extinction schedule of reinforcement in which 5-min periods of variable-interval reinforcement and 5-min periods of extinction were presented in a random order. This schedule was found to generate sequential contrast effects: response rates during variable-interval reinforcement were higher when a variable-interval period followed an extinction period than when it followed another variable-interval period. The rate of responding within a variable-interval period also was affected by the number of extinction periods preceding a variable-interval period. As the number of successive extinction periods that preceded a variable-interval period increased, the rate of responding during that variable-interval period increased. The sequential contrast effects were transient, being most evident during the early sessions and generally disappearing by the tenth session.

Adolescent↗
PubMedDate not supplied

A champion of nursing.

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History, 19th Century↗