Comments on Ferguson's "Forty years of useless research?" (Vol. 24, no. 2, April 1983).

The authors comment on Kinglsey Ferguson's "Forty Years of Useless Research?" (see record 2007-03833-001). Ferguson has raised an important issue for all readers to consider. He has taken a courageous stand and is attempting to stimulate us, as he does his undergraduate students, to explore nondefensively where we stand as a science and what we need to do to improve the quality of our work. It it is only through the respectful marriage of the art and science of psychology that our field will prosper. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An evaluation of upwind and central difference approximations by a study of recirculating flow

The method of “upwind differencing” to approximate the convection terms in numerical studies of fluid motion was introduced to overcome stability restrictions believed to be imposed by the use of central differencing. Here, both methods are applied to a two dimensional model of the recirculating flow in a cavity with a sliding top. It is shown that the false diffusion associated with first order upwind difference approximations can cause the numerical solution to severely misrepresent the physical transport processes. The instability exhibited by solutions based upon second order approximations is elucidated by examining the conservation laws implied by the governing equations. Finally, by calculating three dimensional solutions, it is shown that the assumption of two dimensionality is of questionable validity at high values of the Reynolds number.     

Effect of titanium,copper and iron on silicon solar cells

The effect of Ti, Cu and Fe on silicon solar cells has been investigated. Ti severely degrades cell performance above a concentration of 10¹¹ cm^?3. The presence of 2 × 10¹⁴ cm^?3 Ti results in a 63% loss in cell performance and more than an order of magnitude reduction in carrier lifetime. Ti gives rise to two deep levels in Si at Ev + 0.30 eV and Ec ? 0.27 eV. Copper, at concentrations below 10¹⁶ cm^?3, has negligible effect on cell performance and carrier lifetime. Above 10¹⁶ cm^?3 copper occasionally produces a 10–15% loss in cell performance with a noticeable increase in junction excess current. No recombination centers were found due to Cu, instead considerable precipitation in the starting material was observed. Fe begins to hurt the cell performance above a concentration of 2 × 10¹⁴ cm^?3. Iron at 1.7 × 10¹⁵ cm^?3 results in 46% loss in cell efficiency and about an order of magnitude reduction in lifetime. Fe induces a deep level in silicon at Ev + 0.4 eV. The active center density, for both Ti and Fe, is only a very small fraction of the total impurity content in the starting silicon wafer.     

Genital sex pheromones of ixodid ticks: 1. Evidence of occurrence in anterior reproductive tract of American dog tick,Dermacentor variabilis (Say) (Acari: Ixodidae)

The occurrence of a genital sex pheromone in the anterior reproductive tract of partially fed femaleDermacentor variabilis was demonstrated by extraction and bioassay. A new type of bioassay, the neutered female assay, was developed to test the potency of extracts or chemically defined fractions to stimulate males to copulate. Electrophysiological tests confirmed the ability of males to detect the pheromone with sensilla on their cheliceral digits. Males of bothD. variabilis andD. andersoni exhibited neuronal excitation when stimulated with extracts of theD. variabilis reproductive tissues. The pheromone, which is soluble in methanol, was fractionated and found to contain at least two fractions that stimulated copulation by sexually excited males. Evidently, the pheromone is a mixture of two or more compounds. Histologic, ultrastructural, and histochemical studies suggest the vestibular vagina as the site of genital sex pheromone occurrence, presumably from secretions of the surrounding lobular accessory gland. The identity of the compounds that comprise the pheromone remains unknown.Supported by grants AI10986 and AI10987 from the National Institute of Allergy and Infectious Diseases, National Institute of Health, U.S. Public Health Service, Bethesda, Maryland 20205.     

Sensitivities of ocular tissues to acute pressure-induced ischemia

Intraocular pressure was artificially elevated for eight hours in eight owl monkeys. The first permanent effect (produced at a perfusion pressure of plus 15 mm Hg) was partial necrosis of iris stroma and ciliary processes, associated with microscopic lesions in the photoreceptors and retina pigment epithelium around the disc and in the retinal periphery. At a slightly higher pressure, visual nerve fibers in the retina and optic nerve and their ganglion cells were affected. Simultaneously, the outer retinal layers showed damage to the pigment epithelium, photoreceptors, and other nuclear layers. At even higher pressures, nearly all the other intraocular tissues were affected except for Müller cells, astroglia in the optic nerve head, epithelium of the pars plana, and the pigment cells of the choroid. The possibility is raised of a nonischemic pressure-induced mechanism for destruction of disc astrocytes in human chronic glaucoma.     

Reduction operations for constraint satisfaction

The problem of labeling a set of units in such a way as to satisfy an order-N compatibility relation is discussed and shown to be NP-complete. Some general procedures for reducing size of the compatibility relation are defined, properties of these procedures are derived, and their incorporation into a backtracking process is discussed. Their computational cost and storage requirements are also considered.