Zur Ausbreitung des Lichtes in Kalomel-Einkristallen

Relations for a calculation of the direction of spreading of the light through a birefractive uniaxial crystal for an arbitrary angle of the crystallographical orientation and for an arbitrary angle of incidence of the light in the plane of the main section were derived. For a single crystal of calomel (Hg₂Cl₂) refracting angles of the ordinary and extraordinary ray were computed for angles of the crystallographical orientation from 1° to 90°, for angles of incidence of the light from +90° to −90° and for wave lengths of the light from 380 nm to 16 μm.     

Linearly polarised photon beams at ELSA and measurement of the beam asymmetry in \pi^{0}_{} photoproduction off the proton

At the electron accelerator ELSA a linearly polarised tagged photon beam is produced by coherent bremsstrahlung off a diamond crystal. Orientation and energy range of the linear polarisation can be deliberately chosen by accurate positioning of the crystal with a goniometer. The degree of polarisation is determined by the form of the scattered electron spectrum. Good agreement between experiment and expectations on the basis of the experimental conditions is obtained. Polarisation degrees of % are typically achieved at half of the primary electron energy. The determination of is confirmed by measuring the beam asymmetry, , in photoproduction and by a comparison of the results to independent measurements using laser backscattering.     

Response of Wood Bars to Non-Destructive Impact

Experimental Techniques - The wood bars with rectangular cross section (25 × 25 mm, 300 mm in length) were impacted by an aluminum cylindrical bar in R and T...     

Transport velocities of different particulate materials in pneumatic conveying

Particle horizontal transport and vertical entrainment of widely different materials (silica sand, alumina, ceramsite, dry sludge, and wood shreds) are explored by experimental measurements. Experiments have been performed with two very narrow fractions of solids (0.315–0.50 mm and 1.4–1.6 mm) on a laboratory setup. Simple empirical correlations are proposed in terms of the Reynolds and Archimedes criteria for the commencement of the horizontal conveying as well as the vertical entrainment of particles in pipelines.     

New Types of Polarizers Made from Crystals of the Calomel Group

The present work deals with the applicability of the mercurous halide crystals to the production of polarizers of light. The wide transmission region of these crystals mainly in the infrared region allows to use them for wavelenghts up to about 20 m̈m for mercurous chloride and 30 m̈m for mecrurous bromide. Especially high double refraction allows a construction of classical polarizer types having very advantageous parameters, i.e. small thickness of the element and large angle of splitting of the ordinary and extraordinary ray. Besides, high double refraction allows an original design of single-piece (monolithic) polarizers which are characterized by relatively simple treatment, high quality and low losses.     

Synthesis and activity of ruthenium alkylidene complexes coordinated with phosphine and N-heterocyclic carbene ligands

This paper reports the synthesis and characterization of a variety of ruthenium complexes coordinated with phosphine and N-heterocyclic carbene (NHC) ligands. These complexes include several alkylidene derivatives of the general formula (NHC)(PR(3))(Cl)(2)Ru=CHR', which are highly active olefin metathesis catalysts. Although these catalysts can be prepared adequately by the reaction of bis(phosphine) ruthenium alkylidene precursors with free NHCs, we have developed an alternative route that employs NHC-alcohol or -chloroform adducts as "protected" forms of the NHC ligands. This route is advantageous because NHC adducts are easier to handle than their free carbene counterparts. We also demonstrate that sterically bulky bis(NHC) complexes can be made by reaction of the pyridine-coordinated precursor (NHC)(py)(2)(Cl)(2)Ru=CHPh with free NHCs or NHC adducts. Two crystal structures are presented, one of the mixed bis(NHC) derivative (H(2)IMes)(IMes)(Cl)(2)Ru=CHPh, and the other of (PCy(3))(Cl)(CO)Ru[eta(2)-(CH(2)-C(6)H(2)Me(2))(N(2)C(3)H(4))(C(6)H(2)Me(3))], the product of ortho methyl C-H bond activation. Other side reactions encountered during the synthesis of new ruthenium alkylidene complexes include the formation of hydrido-carbonyl-chloride derivatives in the presence of primary alcohols and the deprotonation of ruthenium vinylcarbene ligands by KOBu(t). We also evaluate the olefin metathesis activity of NHC-coordinated complexes in representative RCM and ROMP reactions.     

Die Röntgenolumineszenz der Kristalle von NaCl: Fe

Ohne Zusammenfassung

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Nacl: Fe