Further comparisons between the conventional and the modified Schwarzschild objectives

The performance of the modified Schwarzschild objective configuration in comparison with the ordinary configuration is further investigated, completing the analysis presented in a previous work, which was concerned with the trend of the image-plane resolution against the numerical aperture. Here, we compare the third-order aberration coefficients in both configurations, illustrating the dependence of each coefficient on both the on-axis object position and the numerical aperture. This conveys the tolerances of the two configurations to lateral and mirrors’ axial misalignments. Also, the nonconcentric mirror configuration is considered and the relative performance confronted with that of the modified configuration. PACS 42.15.Eq; 42.82.Cr     

Diversity oriented synthesis of hispanane-like terpene derivatives from (R)-(+)-sclareolide

(R)-(+)-Sclareolide 1 has been used as a starting material to develop a diversity oriented methodology to access hispanane 28 a, and hispanane-like derivatives 27 b-27 e. This methodology is based on the intramolecular Friedel-Crafts acylation of the corresponding 12-desoxylabdanoic-like acids 27, for the construction of the cycloheptane ring which is characteristic of the hispananes. Acids 27 are obtained from alcohols 20, available by addition of the lithium or magnesium reagents to amide 12 (followed by Luche reduction), or to aldehyde 21. This sequence has resulted in the preparation of hispanane framework 27 a. The versatility of this methodology therefore allows a structural diversity oriented synthesis, since it allows the access to a wide variety of hispanane-like derivatives.     

Heterodyne detected transient gratings in supercooled molecular liquids

We present an analysis, based on a phenomenological set of Generalised Navier-Stokes equations, of Heterodyne Detected Transient Gratings on supercooled molecular liquids of anisotropic molecules. This set of equations generalises equations proven in Franosch, Latz and Pick [24] for the same type of liquids. It also takes into account the three different sources generated by the laser pumping process pertinent for these experiments. We give analytical expressions for the response functions that can be measured using the different polarisation of the experimental set-up. Specialising to the case of parallel polarisation (where longitudinal phonons are launched), we show that each response function is a sum of the same seven elementary response functions (ERFs) whose time and temperature evolutions are individually analysed. We also show that the response functions corresponding to two of the sources can be directly connected to the Laplace Transform of a light scattering signal. The ERFs generated by the heat-absorption process, which is the third source, are of a different nature. They do not have the same time and temperature behaviours and they can provide, inter alia, unique information on the rotation-translation coupling function characteristic of these liquids.Received: 5 January 2004, Published online: 29 June 2004PACS: 64.70.Pf Glass transitions - 78.47. + p Time-resolved optical spectroscopies and other ultrafast optical measurements in condensed matter - 61.25.Em Molecular liquidsR. Gupta: Present address: Dept of Physics,1110 W Green St, Urbana, Ill 61801, USA.     

Evaluation of the effect of rennet type on casein proteolysis in an ovine milk cheese by means of capillary electrophoresis

Capillary electrophoresis was used to study the evolution of casein throughout the ripening process of Roncal Denomination of Origin ewe's milk cheese and to assess the type of rennet in its hydrolysis. Two manufactures were prepared, each with four vats; two of them had added lamb artisan rennet, batch A [clotting activity of 97.54 rennet units (RU) ml(-1)] and batch B [clotting activity of 16.26 RU ml(-1)]; one vat included calf industrial rennet, batch I (clotting activity of 45.70 RU ml(-1)); and the fourth vat had added mixed rennet, batch M, a 50:50 mixture of lamb (batch A) and calf (batch I) (clotting activity of 77.53 RU ml(-1)). The content of casein nitrogen in fractions alpha-casein1CE, alpha-casein2CE, beta-casein1CE and beta-casein2CE was quantified in cheese after 1, 15, 30, 60, 120 and 180 days of ripening. Beta-casein fractions undergo lesser degradation during the ripening time than alpha-casein proteins. The degradation of alpha-caseins is very much influenced by the clotting activity of the rennet used, so that the more active the clotting activity the greater the hydrolysis of those caseins. Nevertheless, it is at the level of beta-caseins that we observe the evidence of the influence of the type of rennet, thus noting a less intense proteolytic activity in the batch made with calf rennet, batch I.     

On the dynamics of multiple-reggeon exchange cuts

We discuss the circumstances under which multiple-pomeron exchange amplitudes can become iterative and show how the intermediate states involved in these amplitudes can be related to the states produced in diffractive dissociation. In order to obtain a soluble model, we construct a simple integral equation, which in an iterative way leads to a multi-pomeron exchange series, including contributions of cut mechanisms involving spectator particles. From a particular solution of this equation we are able to illustrate how the longitudinal-momentum distributions of the diffractive intermediate states influence the relative strength of the cuts. Further from a qualative analysis, we show why one might expect the helicity-non-flip vacuum amplitudes to have strong cuts, while all other amplitudes have weak cuts. A number of related points are also discussed.     

Substituent effect on the 1H NMR Spectra of trans aryl methyl oxiranes and arylpropenes

The ¹H NMR spectra of 1-aryl-2-methyl oxiranes substituted in the phenyl ring and of the corresponding vinyl derivatives have been analysed. The substituent effect on oxiran protons seems mostly polar in character, as shown by correlations with substituent constants, solvent effects and the fact that perturbation decreases with increasing distance from the substituent. The comparison with the corresponding vinyl derivatives, in which conjugation effects are present, confirms this point. The results also seem to exclude the possibility of substituents causing significant changes on the preferred conformation of the phenyl ring. Ring current contributions on oxirane protons, evaluated by SCF procedure, show that their change with substituents is very small and does not represent a significant part of the change of proton chemical shift with substituents.     

Enhancing the enantioselectivity of an epoxide hydrolase by directed evolution

[reaction: see text] The epoxide hydrolase (EH) from Aspergillus niger, which shows a selectivity factor of only E = 4.6 in the hydrolytic kinetic resolution of glycidyl phenyl ether, has been subjected to directed evolution for the purpose of enhancing enantioselectivity. After only one round of error-prone polymerase chain reaction (epPCR), enantioselectivity was more than doubled (E = 10.8). The improved mutant enzyme contains three amino acid exchanges, two of which are spatially far from the catalytically active center.     

Amplified extended modes in random lasers

We report on a new random laser phenomenon that gives rise to narrow emission modes without requiring optical cavities. Sharp emission peaks are observed experimentally over a broad range of scattering strengths and analyzed in numerical calculations. We find that the introduction of exponential gain in a multiple light scattering process strongly increases the importance of very long light paths. Such long paths are rare and often neglected in passive disordered materials but we show that they can dominate the emission spectrum from an amplifying disordered system.     

Novel Cobalt (II) Phthalocyanine‐Containing Polyimides: Synthesis,Characterization, Thermal and Optical Properties

Summary: A novel class of polymer has been prepared by reaction of a copolyimide containing carboxylic acid groups, and a cobalt phthalocyanine peripherally substituted with a reactive hydroxyl group. The incorporation of the phthalocyanine ring was achieved by esterification of the carboxylic acid groups of the polyimide with the free hydroxyl group of the phthalocyanine. In this work, a limited number of phthalocyanine rings have been introduced in order to avoid extensive modification of the copolyimide properties. The extent of modification (percentage of esterified carboxylic groups) was estimated to be about 18%. The resulting material showed good thermal stability and a high glass transition temperature (above 300 °C). The incorporation of the bulky phthalocyanine ring brought about a light decrease of thermal properties, relative to those of the initial polyimide. The presence of phthalocyanine was confirmed by the absorption band at 670 nm showing in the visible region for the modified polyimide. The novel copolyimide also exhibited a remarkable emission peak at 430 nm, when excited at 350 nm, corresponding to the emission of the cobalt phthalocyanine moiety.

Schematic representation of the PI‐CoPc molecule and the chemical structure of the repeat unit.     

1‐Chloro‐1,1‐di­fluoro‐N‐(4‐methoxy­phenyl)‐3‐(pyrrolidin‐2‐yl­idene)­propan‐2‐imine

In the title compound, C₁₄H₁₅ClF₂N₂O, the Z configuration has been confirmed. The molecular structure shows an intramolecular N—H?N hydrogen bond [H?N 2.04 (6), N?N 2.709 (6) Å and N—H?N 124 (5)°]. This interaction could be responsible for the Z configuration.