Hyperboloid,instanton, oscillator

We suggest the exactly solvable model of the oscillator on a four-dimensional hyperboloid which interacts with a SU(2)$\mathit{SU}(2)$ instanton. We calculate its wavefunctions and spectrum.     

Public perception of nanotechnology

While several studies on the public opinion of nanotechnology have pointed to a rather enthusiastic U.S. public, the public uptake of nanotechnology in Europe is more contained. The results of the Swiss publifocus on nanotechnology reveal a pragmatic attitude of citizens toward the emerging technologies, thus confirming what has been identified as a “balanced approach” in the NanoJury UK.

Deflection of a 100-MeV positron beam by repeated reflections in thin crystals

The phenomenon of the deflection of a charged particle beam due to channeling in a bent crystal is thoroughly investigated and successfully applied for the extraction of the beam in high-energy accelerators, at the energies of about 10 GeV and higher. However, a big practical interest lies in the task of bending and extracting charged particles with energies below 1 GeV, for example, for the production of ultrastable beams of low emittance for medical and biological applications. That is why a novel crystal technique, namely thin straight crystal targets, is investigated in this article, using crystals as elements for extraction and collimation of the circulating beam in a ring accelerator. The advantages of reflection in straight crystals in comparison with bent crystal channeling consist in the small length of straight crystals along the beam that reduces the amount of nuclear interactions and improves the background. Experimental results were obtained for the bending of a 100 MeV positron beam with using five sequential straight crystals.     

Designing Cascades of Electron Transfer Processes in Multicomponent Graphene Conjugates

A novel family of nanocarbon-based materials was designed, synthesized, and probed within the context of charge-transfer cascades. We integrated electron-donating ferrocenes with light-harvesting/electron-donating (metallo)porphyrins and electron-accepting graphene nanoplates (GNP) into multicomponent conjugates. To control the rate of charge flow between the individual building blocks, we bridged them via oligo-p-phenyleneethynylenes of variable lengths by β-linkages and the Prato–Maggini reaction. With steady-state absorption, fluorescence, Raman, and XPS measurements we realized the basic physico-chemical characterization of the photo- and redox-active components and the multicomponent conjugates. Going beyond this, we performed transient absorption measurements and corroborated by single wavelength and target analyses that the selective (metallo)porphyrin photoexcitation triggers a cascade of charge transfer events, that is, charge separation, charge shift, and charge recombination, to enable the directed charge flow. The net result is a few nanosecond-lived charge-separated state featuring a GNP-delocalized electron and a one-electron oxidized ferrocenium.     

Planetary Fourier spectrometer: An interferometer for atmospheric studies on board Mars 94 mission

Summary PFS is a two-channel Fourier spectrometer operating in the infra-red wavelengths between 1.25 and 45 μm. The instrument will be used mainly in the study of the Martian atmosphere. The principal goals are the measurements of the atmospheric temperature and pressure, atmospheric constituents, aerosol and clouds, ground pressure for surface topography, optical and thermophysics properties of the Martian soil. PFS will fly on the Mars 94 spacecraft which should be launched in 1994 and reach the planet in 1995. It is essentially constituted by two different interferometers located in the same box which is divided into two parts. A dichroic placed on the PFS entrance is used to separate the spectral range into two parts, a division needed by the different optical materials which have to be used in each spectral range. The optical layout of the experiment is very compact. Each channel uses two cubic mirrors mounted on an L-structure pivoted on a motor. The motor moves the mechanics and permits the optical-path difference between the arms to be varied. Each interformeter operates in a different spectral range, respectively, between (1.25÷4.8) μm (8000÷2083cm⁻¹) and (6÷45)μm (1666÷220)cm⁻¹). The spectral resolution is 2 cm⁻¹. The entrance aperture area is 30 cm² per channel and the field of view is 2 and 4 degrees. Every measurement lasts about 4 s. The time and, therefore, the relative optical-path difference for the measurement of every point of the interferogram is given by the zero crossings of the interferogram of a reference monochromatic channel at 1.2 μm which uses a laser diode as source. The two interferograms are double-sided and will have 16384 and 4096 points, respectively, corresponding to spectra of 6250 and 1823 useful points. Paper presented at the 6th Cosmic Physics National Conference, Palermo, 3–7 November 1992.     

Nachweis, Bestimmung und Trennung des Zirkoniums von anderen Elementen

Ohne Zusammenfassung     

The influence of a t-Butyl group on the conformational equilibrium and the Hydrogen Bromide catalyzed isomerization of 2-Bromocyclohexanones

The trans and cis diastereoisomers of 2-bromo-6-t-butylcyclohexanone (7 and 8) and of 2-bromo-3-t-butylcyclohexanone (10 and 9) have been prepared and subjected to hydrogen bromide catalyzed isomerization. Whereas bromoketones 7 and 8 underwent only epimerization, isomers 9 and 10 were completely converted into an equilibrium mixture of cis- and trans-2-bromo-5-t-butylcyclohexanone (12 and 13). The spectral parameters (IR, UV, NMR), as well as the equilibrium distribution of the couple 7-8, were consistent with chair conformations for compounds 7, 8 and 9, but indicated for isomer 10 a flexible form in which both the bromine-t-butyl steric interaction and the electrostatic repulsion between Br and CO group are relieved.     

Kobalt

Ohne Zusammenfassung