2,821 research outputs found
Transfer molding of PMR-15 polyimide resin
Transfer molding is an economically viable method of producing small shapes of PMR-15 polyimide. It is shown that with regard to flexural, compressive, and tribological properties transfer-molded PMR-15 polyimide is essentially equivalent to PMR-15 polyimide produced by the more common method of compression molding. Minor variations in anisotropy are predictable effects of molding design and secondary finishing operations
DETERMINANTS OF FERTILIZER ADOPTION BY AFRICAN FARMERS: POLICY ANALYSIS FRAMEWORK, ILLUSTRATIVE EVIDENCE, AND IMPLICATIONS
Crop Production/Industries,
Improving the Measurement and Analysis of African Agricultural Productivity: Promoting Complementarities between Micro and Macro Data
Productivity Analysis,
Promoting Farm Investment for Sustainable Intensification of African Agriculture
Farm Management, Downloads July 2008-July 2009: 9,
Cash Crop and Foodgrain Productivity in Senegal: Historical View, New Survey Evidence, and Policy Implications
Crop Production/Industries, Productivity Analysis, Downloads July 2008 - June 2009: 10,
Approximate analysis and stability of pressure oscillations in ramjets
This paper summarizes work accomplished during the past five years on analysis of stability related to
recent experimental results on combustion instabilities in dump combustors. The primary purpose is to provide
the information in a form useful to those concerned with design and development of operational systems. Thus
most substantial details are omitted; the material is presented in a qualitative fashion
Analysis of existing mathematics textbooks for use in secondary schools.
Thesis (Ed.M.)--Boston University
Thesis (M.A.)--Boston Universit
Calorimetric Analysis Using DNA Thermal Stability to determine protein concentration
It was recently reported for two globular proteins and a short DNA hairpin in NaCl buffer that values of the transition heat capacities, Cp,DNA and Cp,PRO for equal concentrations (mg/mL) of DNA and proteins, are essentially equivalent (differ by less than 1%). Additional evidence for this equivalence is presented that reveals this phenomenon does not depend on DNA sequence, buffer salt, or Tm. Sequences of two DNA hairpins were designed to confer a near 20°C difference in their Tm’s. For the molecules, in NaCl and CsCl buffer the evaluated Cp,PRO and Cp,DNA were equivalent. Based on the equivalence of transition heat capacities, a calorimetric method was devised to determine protein concentrations in pure and complex solutions. The scheme uses direct comparisons between the thermodynamic stability of a short DNA hairpin standard of known concentration, and thermodynamic stability of protein solutions of unknown concentrations. In all cases, evaluated protein concentrations determined from the DNA standard curve agreed with the UV-Vis concentration for monomeric proteins. For samples of multimeric proteins, streptavidin (tetramer), Herpes Simplex Virus glycoprotein D (trimer/dimer), and a 16 base pair DNA duplex (dimer), evaluated concentrations were greater than determined by UV-Vis by factors of 3.94, 2.65, and 2.15, respectively
Optimal Pacing for Running 400 m and 800 m Track Races
Physicists seeking to understand complex biological systems often find it
rewarding to create simple "toy models" that reproduce system behavior. Here a
toy model is used to understand a puzzling phenomenon from the sport of track
and field. Races are almost always won, and records set, in 400 m and 800 m
running events by people who run the first half of the race faster than the
second half, which is not true of shorter races, nor of longer. There is
general agreement that performance in the 400 m and 800 m is limited somehow by
the amount of anaerobic metabolism that can be tolerated in the working muscles
in the legs. A toy model of anaerobic metabolism is presented, from which an
optimal pacing strategy is analytically calculated via the Euler-Lagrange
equation. This optimal strategy is then modified to account for the fact that
the runner starts the race from rest; this modification is shown to result in
the best possible outcome by use of an elementary variational technique that
supplements what is found in undergraduate textbooks. The toy model reproduces
the pacing strategies of elite 400 m and 800 m runners better than existing
models do. The toy model also gives some insight into training strategies that
improve performance.Comment: 14 pages, 4 figures, submitted to the American Journal of Physic
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