A content analysis of the Public Relations Journal

Thesis (M.S.)--Boston Universit

Some effects of subdivision of finite populations on genetic diversity measures

Random genetic drift and mutation in subdivided populations are considered in terms of the infinite-alleles Wright-Fisher model.;Moments of the multidimensional frequency spectrum of order n correspond to probabilities of identity for n genes drawn from specified subpopulations. Recursions are developed for moments of arbitrary order.;Several authors have studied the second moments of frequency spectrums for certain population structures. They point out that these second moments can be used to approximate expectations, under the neutrality hypothesis, of some common measures of genetic identity and distance. In the present work, fourth moments and related probabilities are used to approximate variances of these measures. Specific examples are given for two demes, the island model, and the circular stepping stone model.;It stands to reason that the effects of subdivision should vanish if there are large rates of migration among the demes. An analytic proof of this result has recently been given by Nagylaki (1980). This result is confirmed and the effects of smaller migration rates are studied for certain population structures. Even when the population as a whole is not effectively panmictic, the individual subpopulations are, although their effective sizes may be considerably larger than their actual sizes. Moreover, it seems that the distribution of genes in k of the P subpopulations is similar to that of a population with exactly k subpopulations, where the deme sizes and migration rates are so chosen to give the same second moments of the frequency spectrum as from the original population.;Since the distribution of genes can be approximated in this fashion, variances of the genetic identity or distance between two demes of an arbitrary subdivided population can be approximated using a two deme model with appropriate effective migration, mutation and size parameters. Similarly, when the appropriate effective parameters can be found, covariances of distance can be approximated via a four deme model.;;Reference;Nagylaki, T. 1980. The strong-migration limit in geographically structured populations. J. Math. Biol. 9:101-114

Splitting at the seams: Extensive Stanford Type A aortic dissection

We present a rare case of extensive Stanford Type A aortic dissection extending from the ascending aorta superiorly to the carotids and inferiorly to the infra-renal abdominal aorta. A 34-year-old male with history of hypertension and tobacco use presents with chest pain, dyspnoea, slurred speech and altered mental status. Chest radiograph showed no mediastinal widening. CT head showed multiple sub-cortical infarcts and CT chest showed mild dilation of the thoracic aorta but no dissection. He subsequently reported bilateral lower extremity numbness and weakness and was intubated for hypoxic respiratory failure. A CT scan of the chest showed extensive Type A aortic dissection. He underwent emergent surgical intervention but due to the extensive dissection and blood loss, he ultimately expired

Evaluation of Plant- waxes to Estimate Forage Intake in Grazing Cattle

Although key to the efficiency of a cattle operation, feed intake is challenging to evaluate in a grazing setting. However, even within forage- based systems, plant- wax markers may be used to predict dietary choices and feed intake. Plant- waxes are a complex mixture of lipids found on the surface of plants. When sufficiently unique among plants, the composition of diets can be determined from the pattern of these compounds in the forages ingested. These markers were used to delineate the parts of the corn plant and, separately, 8 western rangeland grasses and legumes. Using plant waxes, the components of the corn plant were clearly distinguished. Th is technique therefore could be useful in a monoculture, such as a corn residue field, to determine the plant parts predominating in the diet. Delineating plants in a complex sward was more difficult, particularly among like species. Th e use of more markers may help to more explicitly distinguish plants within diverse pastures, such as western rangelands

The University of Maryland McNair Scholars Undergraduate Research Journal, Volume 2

The McNair Scholars Undergraduate Research Journal is a collection of abstracts and papers written by McNair scholars at the University of Maryland (http://www.aap.umd.edu/mcnairprogram.html). This issue features papers from the summer 2009 research institute written by participants from the University of Maryland, College Park; Frostburg State University; and Saint Mary's College of Maryland

Empirical Application of Durable Resource Theory in the Investment/ Disinvestment of Farm Machinery

This study empirically applies durable resource theory in the investment/disinvestment of farm machinery on a hypothetical farm in Northcentral Oklahoma. A key aspect of the durable replacement model used is the recognition of all cost and returns attributable to the durable. The effects of forecasted returns, repair costs, salvage values, farm size, tax considerations, and uncertainty on the optimal economic investment/disinvestment decision are examined.Agricultural Economic

Comparison of Gavage, Water Bottle, and a High-Moisture Diet Bolus as Dosing Methods for Quantitative D-xylose Administration to B6D2F1 (Mus musculus) Mice

Gavage, water bottle, and diet incorporation are 3 dosing methods used orally to administer test compounds to rodents. These 3 methods were compared in mice to determine which represented the most quantitative delivery system. For dietary incorporation, a high-moisture bolus form of NIH-31 rodent meal was developed using hydroxypropyl methylcellulose as an autoclave-stable binding agent. A high-moisture bolus were selected to increase the acceptability of the dosed diet and to promote quantitative consumption through reduced wastage. The test compound used was D-xylose, a pentose sugar that may be quantitatively detected, colorimetrically, in urine following oral dosing. Six male and 6 female B6D2FI mice were placed in metabolism cages and dosed with a known quantity of D-xylose by each of the 3 methods. Urine was collected before and after each method of administration and analysed for total D-xylose; the per cent recovery was based upon the amount of D-xylose consumed. Quantitative consumption was apparently greatest for water bottle dosing with an average recovery of 56.0% of the original D-xylose dose. High-moisture bolus incorporation ranked second with 50.0% D-xylose recovery, and gavage was third with 41.0% D-xylose recovery

Principles of Educational Outreach ('Academic Detailing') to Improve Clinical Decision Making

With the efficacy and costs of medications rising rapidly, it is increasingly important to ensure that drugs be prescribed as rationally as possible. Yet, physicians' choices of drugs frequently fall short of the ideal of precise and cost-effective decision making. Evidence indicates that such decisions can be improved in a variety of ways. A number of theories and principles of communication and behavior change can be found that underlie the success of pharmaceutical manufacturers in influencing prescribing practices. Based on this behavioral science and several field trials, it is possible to define the theory and practice of methods to improve physicians' clinical decision making to enhance the quality and cost-effectiveness of care. Some of the most important techniques of such "academic detailing" include (1) conducting interviews to investigate baseline knowledge and motivations for current prescribing patterns, (2) focusing programs on specific categories of physicians as well as on their opinion leaders, (3) defining clear educational and behavioral objectives, (4) establishing credibility through a respected organizational identity, referencing authoritative and unbiased sources of information, and presenting both sides of controversial issues, (5) stimulating active physician participation in educational interactions, (6) using concise graphic educational materials, (7) highlighting and repeating the essential messages, and (8) providing positive reinforcement of improved practices in follow-up visits. Used by the nonprofit sector, the above techniques have been shown to reduce inappropriate prescribing as well as unnecessary health care expenditures