Far-infrared-solar imaging from a balloon-borne platform

Far-infrared solar imaging with a balloonborne 60 cm-diameter Cassegrain telescope is described and related to previous solar observations in the millimeter range, the ir, vis and uv spectral regions. Solar images have been taken at 50 m, 80 m and 200 m and represented as brightness temperature maps. The spectral windows observed correspond to the transition zone chromosphere-phocosphere of the solar atmosphere with a characteristic temperature minimum. Temperature enhancements of a few 100 K over the temperature of the quiet sun are reported for active solar regions, e.g. plages and sunspot regions. Far-infrared images provide less spatial resolution but more reliable temperature assignements than corresponding white-light, Ca II K and H pictures.     

SnO2 negative electrode for lithium ion cell: in situ Mössbauer investigation of chemical changes upon discharge

In situ ¹¹⁹Sn Mössbauer study of an SnO₂ electrode was performed during discharge of a lithium ion cell. The first step is lithium intercalation into the SnO₂ host structure. This lithium intercalation results in reinforcement of the SnO₂ lattice instead of direct decomposition of the oxide upon reduction. This first step is followed by the reduction of tin dioxide into unusual tin species (possibly “exotic” forms of Sn(II) or Sn(0)). The last step of the discharge consists in Li-Sn alloy formation. However, non-reduced SnO₂ is present nearly up to the end of the discharge despite a very low discharge regime. It seems highly probable that this fact is related both to slow Li diffusion and disconnection of SnO₂ particles due to Li₂O formation. The working electrode appears to be rather far from equilibrium during continuous discharge, which means that ideal succession of well-defined stages cannot describe the real phenomena involved in the operating battery.     

Trace analysis of germanium

Summary The dp-polarographic and stripping voltammetric behaviour of germanium(IV) in the presence of various supporting electrolytes is discussed. Moreover, a highly sensitive adsorptive stripping voltammetric technique has been developed. The determination is based on the accumulation of germanium(IV)-diol complexes by adsorption at a hanging mercury drop electrode, followed by cathodic stripping voltammetry. Suitable for the complex forming reaction are catechol (1,2-dihydroxybenzol) and pyrogallol (1,2,3-trihydroxybenzol). By using pyrogallol the detection limit is 0.1 ng ml^–1 with a standard deviation of ±13%. A multistage combined procedure with adsorptive stripping voltammetry is described for the determination of germanium traces in ginseng and garlic. The results are compared with those using extraction-spectrophotometry and atomic absorption spectrometry.Dedicated to Prof. Dr. G. Schulze on the occasion of his 60th birthday     

Measurement of the average polarization of12B in the polarized-muon capture by12C: Magnitude of the induced pseudoscalar form factor

The average polarization of the nucleus¹²B (bound state) produced in the polarized-muon capture reaction¹²C(μ ^?,v _μ )¹²B was measured by the muon spin resonance method in a pulsed muon beam. The polarization of¹²B was maintained completely under a magnetic field of 3 kG in a Grafoil target. After the observed result was corrected for the contribution from the excited states of¹²B, P_av (ground state) was deduced to be 0.462±0.053. This result yieldsg _P /g _A =10.1 _?2.6 ^+2.4 , which is almost consistent with the PCAC prediction.     

High‐Pressure Synthesis of Manganese Oxyhydride with Partial Anion Order

The high‐pressure synthesis of a manganese oxyhydride LaSrMnO_3.3H_0.7 is reported. Neutron and X‐ray Rietveld analyses showed that this compound adopts the K₂NiF₄ structure with hydride ions positioned exclusively at the equatorial site. This result makes a striking contrast to topochemical reductions of LaSrMnO₄ that result in only oxygen‐deficient phases down to LaSrMnO_3.5. This suggests that high H₂ pressure plays a key role in stabilizing the oxyhydride phase, offering an opportunity to synthesize other transition‐metal oxyhydrides. Magnetic susceptibility revealed a spin‐glass transition at 24 K that is due to competing ferromagnetic (Mn²⁺–Mn³⁺) and antiferromagnetic (Mn²⁺–Mn², Mn³⁺–Mn³⁺) interactions.     

Quantum dot solar cells. Tuning photoresponse through size and shape control of CdSe-TiO2 architecture

Different-sized CdSe quantum dots have been assembled on TiO2 films composed of particle and nanotube morphologies using a bifunctional linker molecule. Upon band-gap excitation, CdSe quantum dots inject electrons into TiO2 nanoparticles and nanotubes, thus enabling the generation of photocurrent in a photoelectrochemical solar cell. The results presented in this study highlight two major findings: (i) ability to tune the photoelectrochemical response and photoconversion efficiency via size control of CdSe quantum dots and (ii) improvement in the photoconversion efficiency by facilitating the charge transport through TiO2 nanotube architecture. The maximum IPCE (photon-to-charge carrier generation efficiency) obtained with 3 nm diameter CdSe nanoparticles was 35% for particulate TiO2 and 45% for tubular TiO2 morphology. The maximum IPCE observed at the excitonic band increases with decreasing particle size, whereas the shift in the conduction band to more negative potentials increases the driving force and favors fast electron injection. The maximum power-conversion efficiency 相似文献   

Anwendung der Störungstheorie auf den Vertauschungssatz der Liereihen

Ohne ZusammenfassungDiese Arbeit wurde am Mathematischen Institut der Universität Innsbruck im Rahmen der vom European Research Office, Frankfurt, geförderten Forschungen ausgeführt.