Linear focusing by a plane grating with curved grooves

We study the field diffracted by a plane grating with curved (parabolic) grooves. We will demonstrate that when a monochromatic plane wave is incident on a grating with parabolic grooves the diffracted field has a focal line whose position depends on the curvature radius of the parabolas and the incidence angle of the light onto the grating. The effect described has potential applications in grating-based devices for focusing light without requiring any additional optics.     

Quantitative imaging through a spectrograph. 2. Stoichiometry mapping by Raman scattering

The Bayesian deconvolution algorithm described in a preceding paper [Appl. Opt. 43, 5669-5681 (2004)] is applied to measurement of the two-dimensional stoichiometry field in a combustible methane-air mixture by Raman imaging through a spectrograph. Stoichiometry (fuel equivalence ratio) is derived from the number density fields of methane and nitrogen, with a signal-to-noise ratio of approximately 10 in a 600-laser-shot average. Prospects for single-shot Raman imaging are discussed.     

Aerosol lidar intercomparison in the framework of the EARLINET project. 1. Instruments

In the framework of the European Aerosol Research Lidar Network to Establish an Aerosol Climatology (EARLINET), 19 aerosol lidar systems from 11 European countries were compared. Aerosol extinction or backscatter coefficient profiles were measured by at least two systems for each comparison. Aerosol extinction coefficients were derived from Raman lidar measurements in the UV (351 or 355 nm), and aerosol backscatter profiles were calculated from pure elastic backscatter measurements at 351 or 355, 532, or 1064 nm. The results were compared for height ranges with high and low aerosol content. Some systems were additionally compared with sunphotometers and starphotometers. Predefined maximum deviations were used for quality control of the results. Lidar systems with results outside those limits could not meet the quality assurance criterion. The algorithms for deriving aerosol backscatter profiles from elastic lidar measurements were tested separately, and the results are described in Part 2 of this series of papers [Appl. Opt. 43, 977-989 (2004)]. In the end, all systems were quality assured, although some had to be modified to improve their performance. Typical deviations between aerosol backscatter profiles were 10% in the planetary boundary layer and 0.1 x 10(-6) m(-1) sr(-1) in the free troposphere.     

On the graphical analysis of the electronic structure of ferromagnetic clusters of medium size

In a previous work, a theoretical approach, suitable to describe systems having a large number of fermions, was proposed, and results for ferromagnetic surface clusters of medium size (100-1000 atoms) were presented. The aim of the present contribution is to complete this previous work. Several significant theoretical and technical details, omitted previously, are provided here. The obtained spin orbitals are analyzed, by studying their symmetry, energy, and d contribution properties.     

Epoxidationen mit Peressigsäure V: Zur Kenntnis epoxidierter technischer Monoglyceride

Epoxidation with Peracetic Acid V: Epoxidised Technical Monoglycerides For the direct epoxidation of the technical monoglycerides with differently prepared peracetic acid, which is described for the first time, a number of monoglycerides as well as mixtures of linseed oil, esterified with different polybasic alcohols, were used. In all the cases, where a preprepared peracetic acid in acetic acid or especially in acetic acid ester was used, epoxide yields ranging from 84% to nearly 95% were obtained. Linseed oil monoglyceride, when treated by in-situ procedure with DOWEX-50 resin as an acidic catalyst also gave 84% yield of epoxides. The comparison of different epoxidations and the contents of the secondary products at the maximum level of epoxides, showed, that the reaction takes the most favourable course in homogeneous phase. Free glycerin had no effect on the yield of epoxides from glycerin monooleate.     

Les niobates CaUNb2O8 et MThNb2O8 (M = Ca,Sr, Cd). Etude des transformations monoclinique - quadratique

New compounds M^IIThNb₂O₈ with M^II = Ca, Sr, Cd, and CaUNb₂O₈ have been prepared by solid state reaction. These compounds isotypic with the rare-earth niobates LnNbO₄ cristallize in a monoclinic system with space group I2/c. Like the niobates LnNbO₄, they present a displacive and non quenchable transition (monoclinic to tetragonal) which is probably of second order.     

Zur Mikrostruktur von Ölsaaten unter dem Aspekt der extraktiven Trennung

Microstructure of Oilseeds Under the Aspect of Extractive Separation In the direct extraction of oilseeds with high oil content, the extractive transport in the solids is of great significance. The knowledge of the structure of the tissue and its features, which are relevant to the transport, is a prerequisite for the clarification of the rate-determining step in the extraction process. Results of structural studies on soya are presented, which show that in the cotyledone, in addition to the orienting intercellular system, an internal bunch system holds the tissue in a solid matrix. This bunch system is also characteristic for other oilseeds, such as rapeseed.     

Stationary catalytic kinetics via surface concentrations from transient data: Methanol dehydration

A novel approach to the analysis of the transient data from CSTR is illustrated on the catalytic dehydration of methanol. The method allows to determine adsorbed amounts of reaction components under reaction conditions and it is applicable in cases where at least one reaction component is not (or slighty) adsorbed. Because new types of data can be obtained in this way a deeper discrimination between rival kinetic models is possible. The method permits also determination of total concentration of active sites on the catalyst surface. Comparison of transient data analysis with the steady-state results is presented.