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Biomedical subjects

J Morgan

Publications and source records attributed to J Morgan.

At least 235 records · Page 13Linked to original sources
PubMed1987

Young's modulus of sections of living branches and tree trunks.

Young's modulus along the grain (elasticity, E) was measured on 10 sections of branches and three tree trunks, with bark, of Picea sitchensis (Bong.) Carr., Pinus contorta Dougl. ex Loud., Larix decidua Mill. and Betula pendula Roth. syn. verrucosa Ehrh. The sections were simply supported and corrections were made for taper and deflection due to shear. The E values for trunks were at the lower end of the range reported for green timber (2.4-7.5 GPa), and those for branches were still lower (0.7-4.6 GPa). Values of E for branches decreased with decrease in specific gravity, which corresponded with an increase in percentage water content. When E values were calculated using underbark diameters they fell more closely within the range reported for green timber.

Journal Article↗
PubMed1987

Structural analysis of tree trunks and branches: tapered cantilever beams subject to large deflections under complex loading.

The dimensions, deflections and support costs of tree trunks and branches can be deduced using the structural theory for cantilever beams. However, elementary theory applies only as long as deflections are small, and complex analytical solutions are required to account for complex taper and patterns of loading. This paper describes a method that copes with large deflections, any patterns of taper, and any patterns of distributed loading, point loading or externally applied bending moments. A beam is considered to be composed of a series of short segments, such that each has only a small deflection, and each can have specified dimensions, Young's modulus and loading. The transport matrix method of structural analysis is used to determine the end conditions of each segment and of the whole beam. The method is verified by comparing predicted deflections with deflections (a) calculated using an analytical solution by Bisshopp and Drucker (1945), (b) calculated and measured for sapling tree trunks by Leiser and Kemper (1968), and (c) measured on tapered and untapered plastic rods.

Journal Article↗
PubMed1987

The rehabilitation of disabled Native Americans.

The Native American population remains a special ethnic group in the United States that is overrepresented at the lower end of the socioeconomic scale, with a suspected greater than average rate of disabling conditions. Utilization of rehabilitation services by adult Native Americans was studied. Three years of Rehabilitation Services Administration (RSA) data were analyzed to compare the rehabilitation success rate of Native Americans with that of all other population groups. Native Americans were significantly less likely to be rehabilitated than clients from the general population. Factors contributing to the poor rehabilitation of Native Americans were analyzed. Three factors identified as significant were the socioeconomic characteristics of the clients, the type of disabilities presented by the clients, and the inability of the counselors to locate clients and complete the rehabilitation plan. Recommendations for improving the rehabilitation of Native Americans are discussed.

Adult↗
PubMed1987

Characteristics of 'best' and 'worst' clinical teachers as perceived by university nursing faculty and students.

This study identified and compared characteristics of 'best' and 'worst' clinical teachers as perceived by university nursing faculty and students. The Nursing Clinical Teacher Effectiveness Inventory (NCTEI) was distributed to 201 volunteer subjects. This survey instrument, developed by the authors, contains 48 clinical teacher characteristics grouped into five categories. Each participant was asked to rate, using the NCTEI, the 'best' and them the 'worst' clinical teacher from past observations. Results showed both groups perceived that being a good role model was the highest rated characteristic for 'best' teachers and the 'lowest' rated characteristic for 'worst' teachers. Faculty and students' perceptions were fairly similar as to highest rated characteristics of 'best' clinical teachers. Less agreement was noted about the characteristics of 'worst' clinical teachers. When categories of clinical teacher characteristics were compared, there were significant differences between the ratings of faculty and students for 'best' clinical teachers, but none for 'worst' clinical teachers.

Adult↗
PubMed1986

A critical period for macromolecular synthesis in long-term heterosynaptic facilitation in Aplysia.

Both long-term and short-term sensitization of the gill and siphon withdrawal reflex in Aplysia involve facilitation of the monosynaptic connections between the sensory and motor neurons. To analyze the relationship between these two forms of synaptic facilitation at the cellular and molecular level, this monosynaptic sensorimotor component of the gill-withdrawal reflex of Aplysia can be reconstituted in dissociated cell culture. Whereas one brief application of 1 microM serotonin produced short-term facilitation in the sensorimotor connection that lasted minutes, five applications over 1.5 hours resulted in long-term facilitation that lasted more than 24 hours. Inhibitors of protein synthesis or RNA synthesis selectively blocked long-term facilitation, but not short-term facilitation, indicating that long-term facilitation requires the expression of gene products not essential for short-term facilitation. Moreover, the inhibitors only blocked long-term facilitation when given during the serotonin applications; the inhibitors did not block the facilitation when given either before or after serotonin application. These results parallel those for behavioral performance in vertebrates and indicate that the critical time window characteristic of the requirement for macromolecular synthesis in long-term heterosynaptic facilitation is not a property of complex circuitry, but an intrinsic characteristic of specific nerve cells and synaptic connections involved in the long-term storage of information.

Amanitins↗
PubMed1986

Quality control aspects of pulmonary function testing in the Multiple Risk Factor Intervention Trial.

Pulmonary function testing was used in MRFIT to monitor the presence of airways disease and to assess changes in pulmonary function over time. The pulmonary function indices that were measured were FEV1, FVC, and MMEF, (FEF25-75). Quality control of technician training, equipment maintenance, data collection, and data measurement were essential to ensure that results, over time and from various clinics, could be compared. Based on the MRFIT experience, it is strongly recommended that centralized training in testing techniques and spirometer maintenance take place before a clinical trial begins, and periodically throughout a trial. Such training, combined with quality control follow-up, should prevent the loss of data due to inadequate spirometer maintenance and invalid testing procedures.

Allied Health Personnel↗
PubMed1986

Treatment of colorectal hepatic metastases by intrahepatic chemotherapy alone or as an adjuvant to complete or partial removal of metastatic disease.

Because of the wide variation in reported benefits from the use of intrahepatic chemotherapy for colorectal hepatic metastases, the authors performed their own phase II studies comparing the use of intrahepatic chemotherapy alone and intrahepatic chemotherapy as an adjuvant to complete or partial removal of metastatic colorectal cancer to the liver. Techniques for partial removal included unilateral and bilateral wedge resection, peripheral presinusoidal embolization of the liver, and portal vein branch ligation. Patients were staged using the per cent hepatic replacement method of Pettavel and Taylor, and patients with bilateral metastases were included in the study. Twenty-seven patients, mean age 60.3 years, were examined. There were 19 males, mean age 60.4 years, and eight females, mean age 60 years. The patients were divided into four groups. Group A had an implantable pump only; Group B had an implantable pump and resection; Group C had an implantable pump and arterial embolization and portal vein branch ligation; and Group D had an implantable pump, partial resection, arterial embolization, and portal vein branch ligation. Kaplan-Meyer survival curves were calculated for all of these groups. A separate analysis was carried out for each of the stages, and a comparison was made. The study indicated that the overall median survival time was 18 months and that the more radical the treatment in addition to chemotherapy, the better the results. Such results were not totally dependent on the staging of the tumor volume but were dependent on the degree of extirpation of the tumor. In Group C, consisting primarily of Stage IIa, IIIa, and IV patients (i.e., unresectable patients), a doubling of expected median survival to 12 months could be achieved, compared to those in Group A, which achieved a median survival of only 6 months.

Adult↗
PubMed1986

The molecular features of verapamil that promote myocardial enzyme leakage.

The effects of verapamil (Vp) and four Vp derivatives on myocardial enzyme leakage were compared. Norverapamil (N-demethylated; D591) and acyano-Vp (the nitrile-substituted H-derivative; Sz65) produced leakage comparable to and greater than that of verapamil, respectively. In contrast, the derivative with hydroxyl substitution of all four methoxy groups (D573) and the quaternary amine salt derivative (D575) were inert. These data indicate that both lipid solubility and an ionizable amine were critical to the membrane disruptive effect of verpamil.

Animals↗