Rf transparent, energy absorbing structural elements monthly progress report no. 9, feb. 1 - mar. 31, 1964

Radio frequency energy absorbing structural elements and material

Dynamics of Epidemics

This article examines how diseases on random networks spread in time. The disease is described by a probability distribution function for the number of infected and recovered individuals, and the probability distribution is described by a generating function. The time development of the disease is obtained by iterating the generating function. In cases where the disease can expand to an epidemic, the probability distribution function is the sum of two parts; one which is static at long times, and another whose mean grows exponentially. The time development of the mean number of infected individuals is obtained analytically. When epidemics occur, the probability distributions are very broad, and the uncertainty in the number of infected individuals at any given time is typically larger than the mean number of infected individuals.Comment: 4 pages and 3 figure

RF transparent, energy absorbing, structural elements, phase II Final report, 5 Jun. 1963 - 16 Mar. 1964

Energy absorbing, structural elements having high specific energy absorption and low dielectric constant and loss tangent - space vehicle applicatio

The New International Trade Architecture and Food Regulation

In analyzing the likely impact of the global trade regime on food safety, this study proceeds in the following way. Part I examines the Codex Alimentarius Commission's newly elevated status as the WTO designated key reference authority in trade disputes. Part II considers the Beef Hormone dispute between the European Union (EU) and the United States, as the first instance of the WTO invocation of Codex standards as a reference in evaluating national food safety measures. Part III examines Codex's structure and standard-setting process. Part IV compares Codex's and FDA' food safety standards and makes policy recommendations with regard to the FDA's review of Codex standards. Part V investigates the role of culture in food regulation and its impact on harmonization. Finally, Part VI offers concluding remarks about the implications of the new global trade regime for food safety and suggests possible governmental responses

Interpretation of Long-term Trade Projections: China's Role in Forecast Discrepancies and its Impact on Expectations for World Agricultural Trade

Agricultural and Food Policy, International Relations/Trade,

Experimental studies on Goertler vortices

Goertler vortices arise in laminar boundary layers along concave walls due to an imbalance between pressure and centrifugal forces. In advanced laminar-flow control (LFC) supercritical airfoil designs, boundary-layer suction is primarily used to control Tollmien-Schlichting instability and cross-flow vortices in the concave region near the leading edge of the airfoil lower surface. The concave region itself is comprised of a number of linear segments positioned to limit the total growth of Goertler vortices. Such an approach is based on physical reasonings but rigorous theoretical justification or experimental evidence to support such an approach does not exist. An experimental project was initiated at NASA Langley to verify this concept. In the first phase of the project an experiment was conducted on an airfoil whose concave region has a continuous curvature distribution. Some results of this experiment were previously reported and significant features are summarized

Abnormal early cleavage events predict early embryo demise: sperm oxidative stress and early abnormal cleavage.

Human embryos resulting from abnormal early cleavage can result in aneuploidy and failure to develop normally to the blastocyst stage. The nature of paternal influence on early embryo development has not been directly demonstrated although many studies have suggested effects from spermatozoal chromatin packaging, DNA damage, centriolar and mitotic spindle integrity, and plasma membrane integrity. The goal of this study was to determine whether early developmental events were affected by oxidative damage to the fertilizing sperm. Survival analysis was used to compare patterns of blastocyst formation based on P2 duration. Kaplan-Meier survival curves demonstrate that relatively few embryos with short (<1 hr) P2 times reached blastocysts, and the two curves diverged beginning on day 4, with nearly all of the embryos with longer P2 times reaching blastocysts by day 6 (p < .01). We determined that duration of the 2nd to 3rd mitoses were sensitive periods in the presence of spermatozoal oxidative stress. Embryos that displayed either too long or too short cytokineses demonstrated an increased failure to reach blastocyst stage and therefore survive for further development. Although paternal-derived gene expression occurs later in development, this study suggests a specific role in early mitosis that is highly influenced by paternal factors