Proton-Electron Hyperfine Coupling Constants of the Chlorophyll a Cation Radical by ENDOR Spectroscopy

In this paper we describe the assignment of the major coupling constants in monomer chlorophyll a cation free radical by ENDOR spectroscopy. To facilitate chemical manipulation methylpyrochlorophyllide a has been used as a stand-in, and a suite of six selectively deuterated derivatives have been subjected to ENDOR investigation. Details of the synthesis of these compounds are described. To study the effect of structural features on the spin distribution in the free radicals, six additional chlorophyll derivatives have been studied. Five coupling constants have been assigned, which account for about 80% of the observed electron spin resonance line width in the chlorophyll a monomer cation radical. The spin distribution appears to be highly asymmetric

Substitution of stable isotopes in Chlorella

Replacement of biologically important isotopes in the alga Chlorella by corresponding heavier stable isotopes produces increasingly greater deviations from the normal cell size and changes the quality and distribution of certain cellular components. The usefulness of isotopically altered organisms increases interest in the study of such permuted organisms

A simple method for designing or analyzing an optical communication link

A simple method is described for determining the performance of a free space optical communication link. The method can be used either in the system design (synthesis) mode or in the performance evaluation (analysis) mode. Although restricted to photo counting based detection of pulse position modulated signals, the method is still sufficiently general to accommodate space-based, as well as ground-based, reception

The use of x-ray scattering to study the anomalous elastic properties of fe-ni alloys

X-ray scattering technique for study of elastic properties of nickel-iron allo

Implications of the Visible and X-Ray Counterparts to GRB970228

The gamma-ray burst source GRB970228 has been observed after a delay of 8--12 hours in X-rays and after one day in visible and near infrared light. This marks the first detection of emission at lower frequencies following the gamma-ray observation of a GRB and the first detection of any visible counterpart to a GRB. We consider possible delayed visible and X-ray emission mechanisms, and conclude that the intrinsic gamma-ray activity continued at a much reduced intensity for at least a day. There are hints of such continued activity in other GRB, and future observations can decide if this is true of GRB in general. The observed multi-band spectrum of GRB970228 agrees with the predictions of relativistic shock theory when the flux is integrated over a time longer than that required for a radiating electron to lose its energy.Comment: 5 pp., tex, 1 figur

Application of advanced on-board processing concepts to future satellite communications systems: Bibliography

Abstracts are presented of a literature survey of reports concerning the application of signal processing concepts. Approximately 300 references are included