An INDO study of the hyperfine coupling constants and equilibrium geometries of some tetra-atomic radicals

Equilibrium geometries and isotropic hyperfine coupling constants have been estimated for the series of radicals CH _n F_3-n , CH _n Cl_3-n , CCl _n F_3-n and S₁H _n F_3-n using the INDO method. The theoretical hyperfine splittings agree well with experimental values including the unusually large proton splittings of 34·6 G and 89·9 G recently reported for SiH₂F and SiHF₂.     

Antiviral Activities of Photoactive Perylenequinones

Nine perylenequinones (PQ), including some familiar naturally occurring pigments, were compared for their light-mediated antiviral efficacies. Calphostin C was the most active compound against the two target viruses, herpes simplex virus type 1 and Sindbis virus. Hypo-crellins A and B were also very active. However, three cercosporin-like PQ were substantially less active in spite of their high quantum yields of singlet oxygen, whereas phleichrome, another efficient singlet oxygen producer, showed no detectable antiviral activity. One other PQ, which was a very weak singlet oxygen producer, also showed no antiviral activity. None of the active compounds showed significant antiviral activity in the dark. Thus, for some groups of PQ there was correlation between quantum yield of singlet oxygen C0₂) and antiviral efficacy, but there are evidently other structural features of PQ that influence activity.     

Non-linear response of liquid crystal spatial light modulators

This technical note outlines the results of a series of experiments performed on two spatial light modulators. The two modulators were a Hughes Corporation LCLV and an optically-addressed ferroelectric liquid crystal SLM fabricated by the University of Colorado at Boulder and Displaytech. These experiments were performed to determine the modulated response of the read beam as a function of the write light intensity.     

Synthesis of cross-conjugated polyketones by the crossed-aldol condensation of cyclic ketones with aromatic dialdehydes

Insoluble cross-conjugated polyketones were prepared from terephthalaldehyde and a variety of cycloaliphatic ketones by the crossed-aldol condensation. Elemental analyses and infrared spectra suggest that the polymeric aldol intermediates were not completely dehydrated. Evidence is also presented that suggests conjugate addition of the base to the α,β-unsaturated ketone may occur. Soluble cross-conjugated polyketones were prepared from terephthalaldehyde and 2-indanone, which contains no beta hydrogens, and from cycloaliphatic ketones and 1,2-bis(4-formylphenoxy)ethane, a dialdehyde containing isolated aldehyde groups. It is proposed, therefore, that the lack of solubility in the terephthalaldehyde-based polyketones arises from crosslinking via enolate anions formed at the beta position of the cyclic ketones, which are delocalized through the carbonyl groups of neighboring backbone repeating units. © 1995 John Wiley & Sons, Inc.     

Mathematics of Environmental Processes

Journal of the Operational Research Society -     

Definitive evidence that the ESR spectrum observed during photolysis of Mn2(CO)10 in THF is due to octahedral high-spin (d5) manganese(II)

The reassignment to a manganese(0) quartet state by C.L. Kwan and J.K. Kochi (J. Organometal. Chem., 101 (1975) C9) of the ESR spectrum obtained during photolysis of Mn₂(CO)₁₀ in THF is shown to be in error; computer simulation of the X-band spectrum and observation of the S-band spectrum confirm our previous assignment to sextet manganese(II) and chemical and IR evidence indicate the presence of [Mn(CO)₅]^? as a counter ion.     

Science Teacher Supply in the United States

The purpose of this study was to describe the supply and potential shortages of science teachers in the United States. Ninety-six percent of the State Science Consultants of the 50 State Boards of Education responded to a 1992 survey to assess the supply of science teachers. This survey was modeled after Howe and Gerlovich's 1982 study to provide an assessment of changes in science teacher supply over the last 10 years. Although there were improvements in the supply of science teachers, shortages were reported in all science subjects and were particularly critical in physics, chemistry, and earth science. In addition to providing a needed update on science teacher supply, this study analyzed 45 previous studies of science teacher supply and found convincing evidence to support the hypothesis that there is a persistent but fluctuating long term shortage of science teachers. This shortage is attributed to competition with business and industry. To alleviate critical shortages of science teachers, it is recommended that salaries be raised to be more competitive with industry and a national database be established to facilitate monitoring the supply of science teachers.     

THE ANTI-HIV ACTIVITIES OF PHOTOACTIVE TERTHIOPHENES

Abstract— Various synthetic analogues of the naturally occurring terthiophene, α-terthienyl (αT), were evaluated for anti-human immunodeficiency virus (HIV) activity. The compounds were incubated individually with a known amount of the virus, with or without UVA radiation (long-wavelength ultraviolet) and residual virus was monitored for its ability to produce cytopathic effects in cell culture and the production of virus-specific protein (p24). The basic terthiophene structure was essential for good anti-HIV activity, although various side chains, such as alcohols, bromo, methyl, thiomethyl and trimethylsilyl groups, permitted retention of maximum activity. Under optimum conditions, as little as 12 ng/mL of these compounds ( i.e approximately 3 × 10⁻⁸ M ) could inactivate 10³ infectious virions. None of the compounds however were more active than αT itself. In all cases, UVA radiation was essential. Several side chains decreased the antiviral efficacy, and some side chains abrogated the activity.