The problem of pika control in Baluchistand, Pakistan

The collared pika, Ochotona rufescens, has been recorded as a serious pest in apple orchards in the uplands valley of Ziarat in Baluchistan. In the winter, when the natural vegetation is lacking, the pikas debark the apple tree trunks or branches resulting in the killing of the tree and reduced fruit production. In summer, damage to wheat, corn and potatoes is also very severe. It is estimated that pikas cause hundreds of thousands of dollars (US) in annual apple production losses. The apple production in Baluchistan accounts for about 35 percent of the total provincial income through food production. During the six years (1974-1979), the winter of 1973-74 was noted for heavy damage to apple trees and thereafter it declined steadily. The control measures evaluated were of various kinds among which repellent "Ostico" was very effective in protecting the trees. Poison baiting with brodifacoum (0.005%), Vacor (1%) and thallium sulphate (1%) were also effective in reducing the pika population. To alleviate damage caused by pikas, the farmers also practice some traditional protective methods which in some cases are quite effective but very laborious

Sulfur-oxygen processes on Io

Laboratory studies of irradiated sulfur dioxide frost have found that sulfur trioxide should be formed as a consequence of the irradiation process. The spectral reflectance of solid sulfur trioxide was measured in the laboratory and it was found that the compound has strong absorption features at 3.37 and 3.70 microns. These features are not present in the spectral geometric albedo of Io. This is interpreted as an indication that sulfur trioxide may exist in such limited abundance that it is undetectable in disk averaged spectrophotometry. It is suggested that the Near-Infrared Mapping Spectrometer on the Galileo spacecraft should be able to identify condensed sulfur trioxide on Io particularly in regions bordering the sulfur dioxide deposits. The presence of elemental sulfur on Io's surface has been questioned on several grounds, most notably the suggested production process (quenched molten sulfur extrusions) and the effect of radiation (particularly X-rays) on some of the allotropes. Mixtures of sulfur allotropes were produced in the laboratory by quenching molten sulfur and it was found that the spectra indicate the presence of certain red-colored allotropes which are preserved upon quenching. The color of the sulfur glass produced is redder when the temperature of the original melt is higher. This is consistent with the suggestion that Io's spectral geometric albedo can be partly explained by the presence of quenched sulfur glasses

Electromagnetics from a quasistatic perspective

Quasistatics is introduced so that it fits smoothly into the standard textbook presentation of electrodynamics. The usual path from statics to general electrodynamics is rather short and surprisingly simple. A closer look reveals however that it is not without confusing issues as has been illustrated by many contributions to this Journal. Quasistatic theory is conceptually useful by providing an intermediate level in between statics and the full set of Maxwell's equations. Quasistatics is easier than general electrodynamics and in some ways more similar to statics. It is however, in terms of interesting physics and important applications, far richer than statics. Quasistatics is much used in electromagnetic modeling, an activity that today is possible on a PC and which also has great pedagogical potential. The use of electromagnetic simulations in teaching gives additional support for the importance of quasistatics. This activity may also motivate some change of focus in the presentation of basic electrodynamics

A Velocity Filter for Electrons and Ions

If a charged particle, moving along the x-axis with a velocity v, encounters successively two identical alternating electric fields of frequency ν, which are everywhere perpendicular to the x-axis, it will emerge from the last field undisplaced and traveling in the original direction under the following conditions: (1) Each field has two similar halves whose distance between centers is a; (2) The distance between the fields, center to center, is D=sa/n, where s and n are odd integers; (3) The velocity of the particle is v_0=2aν/n. The distribution about the velocity v_0 is computed when particles enter and leave the system through slits of width y_0 on the x-axis. The results show that the emergent beam can be confined to a very narrow velocity range

The Cause of the Hot Spot in Vegetation Canopies and Soils: Shadow-Hiding Versus Coherent Backscatter

Two different mechanisms, shadow-hiding and coherent backscatter, can cause a hot spot, or opposition effect, in the bidirectional reflectance of vegetation and soils. Because the two mechanisms sample different properties, it is important to know which one is primarily responsible in a given medium. This question can be answered by measuring the bidirectional reflectance in circularly polarized light. If the results of the limited experiments reported here can be extrapolated to a wider range of materials, it appears that the primary cause of the hot spot in most vegetation canopies and in moist, clumpy soils is shadow-hiding. However, in vegetation with large numbers of wavelength-sized structures, such as mosses, and in dry, fine-grained soils, the hot spot is dominated by coherent backscatter

Interview with William Ralph Smythe

An interview in two sessions, February 1978, with William Ralph Smythe, professor of physics, emeritus, in the Division of Physics, Mathematics, and Astronomy. He recalls his youth in Colorado and Santa Fe, NM, and his father’s career as a civil engineer. Undergraduate physics at Colorado College; six months’ graduate work at Dartmouth. Enlists as U.S. enters WW I; sent to officers’ training camp, Plattsburgh NY, and thence to France as artillery officer. Recollections of the war. Returns to Dartmouth; moves to University of Chicago to complete PhD. Works with A. A. Michelson. Two-year instructorship at the University of the Philippines. Comes to Caltech as a research fellow, 1923. Isotope separation. His recollections of early physics dept. faculty and teaching his course in electricity and magnetism. Joins C. C. Lauritsen’s Caltech rocket project; works with Navy in Key West on the anti-submarine “Mousetrap” rocket. Invents yaw camera. Caltech in postwar era. His work on heavy-carbon separation