No abstract

Cambial electrical resistance (CER) and periodic growth rate (PGR) of canopy balsam fir (Abiesbalsamea L.) trees were determined on 26 sites in Maine, New Hampshire, and Vermont, U.S.A., varying in level of spruce budworm defoliation. Determinations of water and potassium concentrations were made of the bark, wood, and vascular cambial zone (VCZ). Low CER was associated with high PGR and vice versa. A decline in PGR on all 26 sites was detected during early 1970's to late 1970's. It was not associated with, but may have been exacerbated by, spruce budworm defoliation. The most probable mechanism relating CER to PGR in balsam fir was variation in the thickness of VCZ and its correlation with potassium content. Thicker VCZ of faster growing trees released more potassium into the solution contacting electrodes than thinner VCZ of slower growing trees.

A freight car in the United States spends approximately two-thirds of its time stationary; a significant portion of this time in hump classification yards is spent in queues waiting to be inspected and classified into outbound trains. This paper describes the development of a model for these queues and the application of the Monte Carlo method to the analysis of these queues for a particular classification yard. An elementary form of feedback is included in the model. Using the model of yard operation, certain methods of improving yard operation are determined. Operations Research, ISSN 0030-364X, was published as Journal of the Operations Research Society of America from 1952 to 1955 under ISSN 0096-3984.

Students in a fourth year epidemiology course were surveyed after participating in a formal Science Research Day in which they presented original research, in poster form, to be judged by scientists from the community. Of 276 participating students, 80 (29%) responded to the study survey. As a result, 19% of respondents were more likely to pursue a career in science, and 27.5% were more likely to pursue a career in epidemiology. Only one respondent reported being less likely to pursue a science career, while seven were less likely to pursue epidemiology. A majority of respondents felt that the poster experience was on par with, or superior to, a comparable research paper, in terms of both educational appeal and enjoyment. Mandatory, formal poster presentations are an innovative format for teaching advanced health sciences, and may more accurately reflect the realities of a science career than do more traditional educational formats.

Electrical resistances of combined bark and wood of 50 red maple (Acerrubrum L.) trees were strongly correlated with phloem width with an inverse correlation coefficient of −0.92. Diameter at 1.4 m aboveground was determined to be transitively correlated with electrical resistance through its strong correlation with phloem width. Little detectable relationship existed between electrical resistance and potassium concentration in phloem tissues. An electrical model is presented to illustrate the path of electrical current between electrodes in the tissues measured.