Luso-African trade and settlement in the Gambia and Guinea-Bissau regions, 16th-19th centuries

African Studies Center Working Paper No. 24This paper examines the economic, social, and cultural influences of Luso-Africans living along the Gambia River and in the Guinea-Bissau region from the sixteenth to the nineteenth centuries, in terms of two general themes. The first is the significance of the sustained economic, social, and cultural ties between the Cape Verde Islands and the Guinea-Bissau region which began in the fifteenth century, and which continue to the present day. The second concerns how interrelationships between African societies, incoming Portuguese and Cape Verdean "strangers," and their Luso-African descendants changed over time

Long range holographic contour mapping concept

Plan for generating a two dimensional contour map of a distant object with range contour intervals of a few millimeters to a few inches is accomplished by using a laser light source which has a periodically varying coherence function to form a hologram of the object

A review of rodent control programs in New York State

The history of rodent control programs in New York State is reviewed, beginning with state-funded efforts in August 1967. In 1969, Federal rodent control grant funds were used to establish four Model Cities programs. At its peak in 1970, programs were active in 18 counties, eight cities and villages, and in six Model Cities areas. The program encompasses all the major metropolitan areas of the state, serving some nine million persons. As part of the state program, the Rodent Control Evaluation laboratory was established to investigate chemosterilants as a means of rodent control and to develop knowledge of pest rodent biology. Since then, the investigations program has turned to the problem of rodent resistance to anticoagulant rodenticides both in New York and other states in the eastern United States. Initial rat infestations, which ran 24.4 percent statewide in 1969, have been decreased 84 percent by late 1973. Similarly, in the same time period, unapproved refuse storage deficiencies were decreased 55.6 percent and exposed garbage conditions declined 44.7 percent. Rat bites showed a 40 percent decrease during these same years. By all measures, then, the program has been a success. Most programs have relied heavily upon anticoagulant rodenticides in the chemical control or rodent populations. Zinc phosphide, red squill, and norbormide are also used. Harborage removal and environmental improvement are stressed through active cleanups and educational efforts. During the four-year period 1969-1972, some 177,000 tons of rat harborage were removed from 66,000 premises in the state

Method for separating biological cells

A method for separating biological cells by suspending a mixed cell population in a two-phase polymer system is described. The polymer system consists of droplet phases with different surface potentials for which the cell populations exhibit different affinities. The system is subjected to an electrostatic field of sufficient intensity to cause migration of the droplets with an attendant separation of cells

Cell partition in two phase polymer systems

Aqueous phase-separated polymer solutions can be used as support media for the partition of biological macromolecules, organelles and cells. Cell separations using the technique have proven to be extremely sensitive to cell surface properties but application of the systems are limited to cells or aggregates which do not significantly while the phases are settling. Partition in zero g in principle removes this limitation but an external driving force must be applied to induce the phases to separate since their density difference disappears. We have recently shown that an applied electric field can supply the necessary driving force. We are proposing to utilize the NASA FES to study field-driven phase separation and cell partition on the ground and in zero g to help define the separation/partition process, with the ultimate goal being to develop partition as a zero g cell separation technique

Countercurrent distribution of biological cells

A neutral polymer phase system consisting of 7.5 percent dextran 40/4.5 percent PEG 6, 0.11 M Na phosphate, 5 percent fetal bovine serum (FBS), pH 7.5, was developed which has a high phase droplet electrophoretic mobility and retains cell viability over many hours. In this and related systems, the drop mobility was a linear function of drop size, at least in the range 4-30 micron diameter. Applications of and electric field of 4.5 v/cm to a system containing 10 percent v/v bottom phase cleared the system more than two orders of magnitude faster than in the absence of the field. At higher bottom phase concentrations a secondary phenomenon intervened in the field driven separations which resulted in an increase in turbidity after clearing had commenced. The increase was associated with a dilution of the phase system in the chamber. The effect depended on the presence of the electric field. It may be due to electroosmotic flow of buffer through the Amicon membranes into the sample chamber and flow of phase system out into the rinse stream. Strategies to eliminate this problem are proposed

SPAR project: Counter current distribution of biologicals

Preliminary ground based experiments strongly support the validity of a proposed space experiment in the separation of biological cells by counter current distribution (CCD). It was shown that a low level applied selective field can accelerate the separation of the phases by a very large factor. An electric field therefore should be very effective in space in lieu of gravity for the phase separation step. This appears to solve a central problem in implementing CCD in space and opens the technique to many types of large cell mixtures for which it has not been applicable before due to rapid settling effects. It was determined that electrophoretic migration of the cells, as a possibly disturbing factor, will be of negligible effect. Attenuation of a light beam by scattering generated a signal indicating the course of the phase separation

Tungsten-rhenium alloy thermocouples effective for high-temperature measurement

Tungsten-rhenium alloy thermocouples, specifically, insulated, sheathed W/W plus 26Re and W plus 5 Re/W plus 26 Re thermocouples, are effective for temperature measurement in excess of 2920 degrees C. These thermocouples have a high thermoelectric output and excellent relationship to temperatures up to 2760 degrees C

Multipass holographic interferometer improves image resolution

Multipass holographic interferometer forms a hologram of high diffraction efficiency, and hence provides a bright and high contrast interferogram. It is used to study any effect which changes the index of refraction and to study surface deformations of a flat reflecting surface

Edge-region grouping in figure-ground organization and depth perception.

Edge-region grouping (ERG) is proposed as a unifying and previously unrecognized class of relational information that influences figure-ground organization and perceived depth across an edge. ERG occurs when the edge between two regions is differentially grouped with one region based on classic principles of similarity grouping. The ERG hypothesis predicts that the grouped side will tend to be perceived as the closer, figural region. Six experiments are reported that test the predictions of the ERG hypothesis for 6 similarity-based factors: common fate, blur similarity, color similarity, orientation similarity, proximity, and flicker synchrony. All 6 factors produce the predicted effects, although to different degrees. In a 7th experiment, the strengths of these figural/depth effects were found to correlate highly with the strength of explicit grouping ratings of the same visual displays. The relations of ERG to prior results in the literature are discussed, and possible reasons for ERG-based figural/depth effects are considered. We argue that grouping processes mediate at least some of the effects we report here, although ecological explanations are also likely to be relevant in the majority of cases