COSTS, YIELDS, AND NET RETURNS, COMMERCIAL NO-TILL COTTON PRODUCTION, MISSISSIPPI, 1999

An analysis of a 1999 sample of ten no-till producers indicates that over a reasonable range of cotton lint prices, no-till cotton production may result in larger net returns per acre than conventional tillage. However, the authors caution that additional analysis based on a larger sample of commercial no-till growers on better cotton soils is needed.no-till, spindle harvest, cost of production, yield, Production Economics,

THE IMPACT OF CURRENT COTTON PRICE AND PRODUCTION COSTS ON SKIP-ROW COTTON

According to conventional wisdom, low prices favor skip-row planting patterns while high prices favor solid planted cotton. Production costs have been trending upward for many years. Current high production costs have redefined the point at which a low price becomes a high price relative to skip-row versus solid planting pattern decisions. Growers considering a shift from solid to skip-row cotton must be able to produce high yields, more than 90% of the solid yield on a land acre basis.cotton, no-till yields, returns, Production Economics,

COSTS, YIELDS, AND NET RETURNS, COMMERCIAL ULTRA-NARROW ROW COTTON PRODUCTION, MISSISSIPPI, 1999

An analysis of a 1999 sample of 13 no-till producers indicates that over a reasonable range of cotton lint prices, ultra narrow cotton production may result in larger net returns per acre than conventional production practices. The largest percentage cost reduction is in fixed expenses. In general, total direct expenses per acre are also reduced, although UNRC usually results in higher seed and chemical expenses. UNRC has a lower total cost per pound compared to conventional cotton.UNRC, No-Till, cost of production, yield, stripper, harvest, Production Economics,

ALTERNATIVE COTTON PRODUCTION SYSTEMS

Mississippi cotton farmers are adjusting to the current problem of low cotton price and high cotton production cost by modifying the way(s) they have traditionally grown cotton. This paper compares seven alternative production systems to the costs and returns associated with the conventional or traditional system labeled "solid cotton, 8-row equipment." Systems that combine wider equipment (less labor and machinery time per acre) with reduced tillage technology appear to offer opportunities to increase returns. Specific adjustments on individual farms will probably be dominated by the distribution of soil types.conservation tillage, ultra-narrow, no-till, skip-row, costs, returns, Production Economics,

A polarographic study of respiration in a blue-green alga

The study of many aspects of physiology is accomplished by the study of respiration under varied conditions. For this purpose, a simple, rapid, and relatively accurate respirometer would be useful. This project was undertaken to investigate the possibility of adapting previously described polarographic techniques to the measurement of respiration

Three-dimensional calculation of shuttle charging in polar orbit

The charged particles environment in polar orbit can be of sufficient intensity to cause spacecraft charging. In order to gain a quantitative understanding of such effects, the Air Force is developing POLAR, a computer code which simulates in three dimensions the electrical interaction of large space vehicles with the polar ionospheric plasma. It models the physical processes of wake generation, ambient ion collection, precipitating auroral electron fluxes, and surface interactions, including secondary electron generation and backscattering, which lead to vehicle charging. These processes may be followed dynamically on a subsecond timescale so that the rapid passage through intense auroral arcs can be simulated. POLAR models the ambient plasma as isotropic Maxwellian electrons and ions (0+, H+), and allows for simultaneous precipitation of power-law, energetic Maxwellian, and accelerated Gaussian distributions of electrons. Magnetic field effects will be modeled in POLAR but are currently ignored

Influence of Decompression Rate on Hemodynamic Compensation to Continuous Lower Body Negative Pressure

We applied lower body negative pressure (LBNP) continuously, at three decompression rates, in an attempt to simulate uncontrolled hemorrhage as might be experienced by victims of traumatic injury. The purpose of our study was to determine whether hemodynamic compensations to simulated hemorrhage depend more on the magnitude, or the rate of change in pressure applied. Forty five (45) young, healthy subjects participated. We recorded the electrocardiogram, beat-to-beat arterial pressure (finger photoplethysmography), and measured cardiac output (inert gas rebreathing to calculate stroke volume) during continuous LBNP applied at three different decompression rates (n = 15 subjects for each rate; slow = 3 mm Hg∙min-1; medium = 6 mm Hg∙min-1; and fast = 12 mm Hg∙min-1) to an ending pressure of -60 mmHg. Slopes relating changes of dependent variable responses to the magnitude of decompression were calculated with linear regression, and group results were compared with ANOVA. LBNP increased (pooled across groups from 0 to -60 mmHg) heart rates (+28%; p ≤ .05 ), and decreased mean arterial pressures (-10%; p ≤ .05) and stroke volumes (-66%; p ≤ .05). The magnitude of changes induced by LBNP were not different between groups (p ≥ .4). Slopes (pooled across groups) relating heart rate (.3 bpm/mmHg ), mean arterial pressure (-.16 mmHg/mmHg), and stroke volume (-1.3 ml/mmHg) to the level of LBNP applied were not dependent on decompression rate (all ANOVA comparisons, p ≥ .3). We conclude that hemodynamic changes during continuous LBNP are associated directly with the magnitude of pressure applied, irrespective of the rate of decompression. Our results suggest that hemodynamic compensations to simulated uncontrolled hemorrhage are robust, and are not compromised by increasing the speed of decompression to simulate a greater rate of blood loss