Effects of vortex flaps on the low-speed aerodynamic characteristics of an arrow wing

Tests were conducted in the Langley 12-foot low-speed wind-tunnel to determine the longitudinal and lateral-directional aerodynamic effects of plain and tabbed vortex flaps on a flat-plate, highly swept arrow-wing model. Flow-visualization studies were made using a helium-bubble technique. Static forces and moments were measured over an angle-of-attack range from 0 deg to 50deg for sideslip angles of 0 deg and + or - 4 deg

Effects of spanwise nozzle geometry and location on the longitudinal aerodynamic characteristics of a vectored-engine-over-wing configuration at subsonic speeds

A V/STOL tunnel study was performed to determine the effects of spanwise blowing on longitudinal aerodynamic characteristics of a model using a vectored-over-wing powered lift concept. The effects of spanwise nozzle throat area, internal and external nozzle geometry, and vertical and axial location were investigated. These effects were studied at a Mach number of 0.186 over an angle-of-attack range from 14 deg to 40 deg. A high pressure air system was used to provide jet-exhaust simulation. Engine nozzle pressure ratio was varied from 1.0 (jet off) to approximately 3.75

Control of germ-band retraction in Drosophila by the zinc-finger protein HINDSIGHT

Drosophila embryos lacking hindsight gene function have a normal body plan and undergo normal germ-band extension. However, they fail to retract their germ bands. hindsight encodes a large nuclear protein of 1920 amino acids that contains fourteen C2H2-type zinc fingers, and glutamine-rich and proline-rich domains, suggesting that it functions as a transcription factor. Initial embryonic expression of hindsight RNA and protein occurs in the endoderm (midgut) and extraembryonic membrane (amnioserosa) prior to germ-band extension and continues in these tissues beyond the completion of germ-band retraction. Expression also occurs in the developing tracheal system, central and peripheral nervous systems, and the ureter of the Malpighian tubules. Strikingly, hindsight is not expressed in the epidermal ectoderm which is the tissue that undergoes the cell shape changes and movements during germ-band retraction. The embryonic midgut can be eliminated without affecting germ-band retraction. However, elimination of the amnioserosa results in the failure of germ-band retraction, implicating amnioserosal expression of hindsight as crucial for this process. Ubiquitous expression of hindsight in the early embryo rescues germ-band retraction without producing dominant gainof-function defects, suggesting that hindsight’s role in germ-band retraction is permissive rather than instructive. Previous analyses have shown that hindsight is required for maintenance of the differentiated amnioserosa (Frank, L. C. and Rushlow, C. (1996) Development 122, 1343-1352). Two classes of models are consistent with the present data. First, hindsight’s function in germ-band retraction may be limited to maintenance of the amnioserosa which then plays a physical role in the retraction process through contact with cells of the epidermal ectoderm. Second, hindsight might function both to maintain the amnioserosa and to regulate chemical signaling from the amnioserosa to the epidermal ectoderm, thus coordinating the cell shape changes and movements that drive germ-band retraction

Phase diagrams of a p-Wave superconductor inside a mesoscopic disc-shaped sample

We study the finite-size and boundary effects on a time-reversal-symmetry breaking p-wave superconducting state in a mesoscopic disc geometry using Ginzburg-Landau theory. We show that, for a large parameter range, the system exhibits multiple phase transitions. The superconducting transition from the normal state can also be reentrant as a function of external magnetic field.Comment: Revised version published in Physical Review

On government credit programs

Credit rationing is a common feature of most developing economies. In response to it, the governments of these countries often operate extensive credit programs and lend, either directly or indirectly, to the private sector. We analyze the macroeconomic consequences of a typical government credit program in a small open economy. We show that such programs increase long-run production if the economy is in a development trap and that such programs often lead to endogenously arising aggregate volatility. On the other hand, they may eliminate certain indeterminacies created by endogenous credit market frictions.Banks and banking, Central ; Credit ; Productivity

Barriers to international capital flows: when, why, how big, and for whom?

Until recently, the trend in world capital markets has been toward increasing “globalization.” Recent events in Latin America and Asia have forced a rethinking of the desirability of unrestricted world capital flows. In this paper we ask whether simple restrictions on capital mobility can succeed in reducing the volatility of funds flows, whether such restrictions are consistent with the long-term development of the countries that might impose them, whether such restrictions are beneficial for poorer countries while harming wealthier countries, and whether barriers to capital movements should be reduced in magnitude as the development process proceeds. ; We find first that appropriately selected barriers to capital movements can be used by a poorer country to eliminate the short-term volatility of capital flows and other economic volatility as well. Second, we find that these barriers are consistent with increased rather than reduced levels of economic development in both the short and long run. Third, we show that it is empirically plausible that such barriers will be reduced over time as economies develop. Fourth, we show that, in the long run, all countries can benefit from the presence of barriers to capital mobility. And, fifth, we show that barriers to capital mobility can increase the magnitude of net capital flows in a steady state.International economic relations ; International finance ; Capital movements ; Monetary policy