VAS Demonstration Sounding Workshop: The Proceedings of a satellite sounding workshop

Retrieval techniques that yield satellite derived temperature and moisture profiles are considered, with emphasis on TIROS-N and VISSR atmospheric sounder measurements. Topics covered include operational sounding, colocation concepts, correcting cloud errors, and the First GARP Global Experiment

Mediation of Long Range Charge Transfer by Kondo Bound States

We present a theory of non-equilibrium long range charge transfer between donor and acceptor centers in a model polymer mediated by magnetic exciton (Kondo) bound states. Our model produces electron tunneling lengths easily exceeding 10$\AA$, as observed recently in DNA and organic charge transfer systems. This long ranged tunneling is effective for weak to intermediate donor-bridge coupling, and is enhanced both by weak to intermediate strength Coulomb hole-electron attraction (through the orthogonality catastrophe) and by coupling to local vibrational modes.Comment: Revised content (broadened scope, vibrations added), submitted to Phys Rev Lett, added autho

Measurement of the 187Re({\alpha},n)190Ir reaction cross section at sub-Coulomb energies using the Cologne Clover Counting Setup

Uncertainties in adopted models of particle+nucleus optical-model potentials directly influence the accuracy in the theoretical predictions of reaction rates as they are needed for reaction-network calculations in, for instance, {\gamma}-process nucleosynthesis. The improvement of the {\alpha}+nucleus optical-model potential is hampered by the lack of experimental data at astrophysically relevant energies especially for heavier nuclei. Measuring the Re187({\alpha},n)Ir190 reaction cross section at sub-Coulomb energies extends the scarce experimental data available in this mass region and helps understanding the energy dependence of the imaginary part of the {\alpha}+nucleus optical-model potential at low energies. Applying the activation method, after the irradiation of natural rhenium targets with {\alpha}-particle energies of 12.4 to 14.1 MeV, the reaction yield and thus the reaction cross section were determined via {\gamma}-ray spectroscopy by using the Cologne Clover Counting Setup and the method of {\gamma}{\gamma} coincidences. Cross-section values at five energies close to the astrophysically relevant energy region were measured. Statistical model calculations revealed discrepancies between the experimental values and predictions based on widely used {\alpha}+nucleus optical-model potentials. However, an excellent reproduction of the measured cross-section values could be achieved from calculations based on the so-called Sauerwein-Rauscher {\alpha}+nucleus optical-model potential. The results obtained indicate that the energy dependence of the imaginary part of the {\alpha}+nucleus optical-model potential can be described by an exponential decrease. Successful reproductions of measured cross sections at low energies for {\alpha}-induced reactions in the mass range 141{\leq}A{\leq}187 confirm the global character of the Sauerwein-Rauscher potential

Optical conductivity of wet DNA

Motivated by recent experiments we have studied the optical conductivity of DNA in its natural environment containing water molecules and counter ions. Our density functional theory calculations (using SIESTA) for four base pair B-DNA with order 250 surrounding water molecules suggest a thermally activated doping of the DNA by water states which generically leads to an electronic contribution to low-frequency absorption. The main contributions to the doping result from water near DNA ends, breaks, or nicks and are thus potentially associated with temporal or structural defects in the DNA.Comment: 4 pages, 4 figures included, final version, accepted for publication in Phys. Rev. Let

Solid state 29Si NMR investigation of inorganic-organic polymers with defined silicic acid units

By thermal analysis and 29Si NMR spectroscopy the thermal behaviour and structural changes of two different types of inorganic-organic polymers with defined double four-ring silicic acid units (Si8O20) were characterized. Polymer 1, prepared from the organic silicic acid precursors [(CH3)2HSi]8Si8O20 (Q8M8H) and [CH2=CH(CH3)2Si]8Si8O20 (Q8M8V), preserves the double four-ring structure up to 350°C Higher temperatures lead to structural reorganizations of the SiO4 tetrahedra forming at 900°C a structure similiar to amorphous silica. Polymer 2, synthesized by condensation reaction of the new organic silicic acid precursor [CH3O)3Si(CH2)3OC(O)CH(CH3)CH2Si(CH3)2]8Si8O20, shows with 37% uncondensed SiOH groups a remarkable high content of silanol groups caused by sterical hindrances