A tagging system for linearly polarized photons

A bremsstrahlung tagging system was installed at the Mainz microtron facility and was successfully used for experiments. At a primary electron energy of 184 MeV photons from 14 to 144 MeV could simultaneously be tagged. The magnetic electron optics for the tagging spectrometer were chosen in such a way, that the linear polarization of an off-axis tagged photon beam was considerably enhanced. The setup is described and results of performance tests are discussed.     

On an analogy to the area–velocity relation of gasdynamics in slender vortices

Inviscid compressible flow in a slender longitudinal vortex with the axis parallel to the main flow direction is discussed. The Euler equations for steady, axially symmetric flow are simplified for the neighbourhood of the axis of the vortex. The resulting relations, expressing the angular velocity in terms of the axial mass flow, when recast and integrated, represent an analogy to the area–velocity and the area-Mach number relation of one-dimensional gasdynamics. By restricting the analysis to the flow in a Rankine vortex with constant stagnation enthalpy, the static pressure on the axis can be related to the free-stream pressure far away from the axis and the maximum value of the azimuthal velocity. The influence of a radial wake-like distribution of the axial velocity component on the axial pressure is discussed. Its dependence on variable external boundary conditions is given. A condition is formulated, which has to be satisfied for the formation of a free stagnation point on the axis.     

A method for the characterization of breakdown/reforming behaviour of faba bean protein dispersions

The present paper is concerned with the Doherty/Hurd method [1] for the investigation of the influence of NaCl, CaCl₂ and pectin on the structural breakdown/reforming behaviour of dispersions containing acetylated faba bean protein isolate (AFBPI).     

Structured singular value analysis of multidimensional systemstability

Structured singular value computations are being developed for analysis of robustness of multivariable control systems. It is shown that the same computational tools can be used to test the stability of multidimensional systems     

Robust parameter adjustment with nonparametricweighted-ball-in-H∞ uncertainty

Using a parameter adjustment law, robust monotonic parameter error reduction is proved for a linear parameter estimation problem in which the signal is corrupted by the presence of nonparametric dynamical uncertainty. The nonparameterized dynamics are characterized by a known frequency-domain magnitude bound. A nonconservative bound on the finite-time energy of the nonparametric-dynamics output is constructed in real time. When the error single energy is small enough to be due to nonparametric dynamics alone, the parameter adjustment is shut off to avoid misadjustment. The approach is an extension of existing adaptive control error-dead-zone ideas to the case of frequency-domain bounded uncertainty     

Universals and cultural differences in the judgments of facial expressions of emotion.

We present here new evidence of cross-cultural agreement in the judgment of facial expression. Subjects in 10 cultures performed a more complex judgment task than has been used in previous cross-cultural studies. Instead of limiting the subjects to selecting only one emotion term for each expression, this task allowed them to indicate that multiple emotions were evident and the intensity of each emotion. Agreement was very high across cultures about which emotion was the most intense. The 10 cultures also agreed about the second most intense emotion signaled by an expression and about the relative intensity among expressions of the same emotion. However, cultural differences were found in judgments of the absolute level of emotional intensity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Iron‐Catalyzed Cross‐Coupling of 1‐Alkynylcyclopropyl Tosylates and Related Substrates

1‐Alkynylcyclopropyl tosylates react with alkylmagnesium halides in the presence of catalytic ferric acetylacetonate [Fe(acac)₃] under net propargylic substitution; allene formation, which is the prevalent reactivity mode of propargylic substrates otherwise, was noticed as a side reaction only when branched alkyl‐ or aryl‐Grignard reagents were used. These transformations represent the first successful iron‐catalyzed cross‐coupling reactions of tert‐alkyl electrophiles.

     

Safety aspects in modelling and operating of batch and semibatch stirred tank chemical reactors

Safety aspects in modelling of batch and semibatch stirred tank reactors as well as a model based safety analysis have been considered. Applicability of two basic types of models – i.e. the perfectly mixed reactor model and the CFD model, both formulated for laboratory scale as well as pilot plant scale reactors – has been discussed. A formulation of the appropriate reactor model, which is adequate to the considered case study has been demonstrated and tested experimentally. Particular attention has been devoted to the formulation of robust CFD models employed to simulate a performance of the stirred tank reactors. It has been found that models for perfectly mixed reactors may have quite wide range of application, while the CFD models should be definitely used in case of fast reactions, high viscosity of the reacting mixture as well as of failure leading to stopping of the impeller. The CFD models are able to predict a dynamic behaviour of reactors at any circumstances, so they can play a significant role in safety analysis carried out for industrial scale reactors, for which experimental safety tests are expensive and dangerous.     

Organocatalyzed Conjugate Addition of Carbonyl Compounds to Nitrodienes/Nitroenynes and Synthetic Applications

The purpose of this study is to point out the synthetic utility of a new class of Michael acceptors (nitrodienes and nitroenynes). The highly enantioselective organocatalytic Michael addition of carbonyl compounds to these functionalized nitroolefins has been carried out in the presence of (S)‐diphenylprolinol silyl ether to achieve some interesting building blocks in high selectivities. The adducts thus obtained can be easily converted by taking advantage of the corresponding unsaturated carbon‐carbon bond. In presence of the double bond, metathesis or electrophilic activation could be carried out whereas in the presence of the triple bond electrophilic activation could be conducted. We thus focused on a gold‐catalyzed cyclization of the bis‐homopropargylic alcohol to afford the corresponding substituted tetrahydrofuran. Then, we also demonstrated that organic and gold catalysts were compatible in a one‐pot process. Indeed, we developed a one‐pot enantioselective organocatalytic Michael addition to a nitroenyne followed by a gold‐catalyzed acetalization/cyclization to achieve tetrahydrofuranyl ethers in high diastereo‐ and enantioselectivities with excellent yields.