Direct and Enantioselective Vinylogous Michael Addition of α‐Alkylidenepyrazolinones to Nitroolefins Catalyzed by Dual Cinchona Alkaloid Thioureas

While several protocols exist for the asymmetric functionalization of pyrazolinones at the α‐position relying on nucleophilic addition or annulation procedures, use of α‐alkylidene electron‐rich analogues in asymmetric vinylogous coupling to carbon electrophiles is substantially an uncharted domain. We now report, for the first time, that alkylidenepyrazolinones carrying an enolizable carbon at the γ‐position efficiently participate in direct and asymmetric, catalytic vinylogous Michael‐type additions to nitroolefins providing the expected adducts in high yields, with complete γ‐site selectivity and with extraordinary levels of enantio‐, diastereo‐, and geometrical selectivities. Both enantiomeric adducts were equally accessed by employing a quasi‐enantiomeric quinine‐ or quinidine‐based thiourea catalyst pair.

     

Computer simulations reveal complex distribution of haemodynamic forces in a mouse retina model of angiogenesis

There is currently limited understanding of the role played by haemodynamic forces on the processes governing vascular development. One of many obstacles to be overcome is being able to measure those forces, at the required resolution level, on vessels only a few micrometres thick. In this paper, we present an in silico method for the computation of the haemodynamic forces experienced by murine retinal vasculature (a widely used vascular development animal model) beyond what is measurable experimentally. Our results show that it is possible to reconstruct high-resolution three-dimensional geometrical models directly from samples of retinal vasculature and that the lattice-Boltzmann algorithm can be used to obtain accurate estimates of the haemodynamics in these domains. We generate flow models from samples obtained at postnatal days (P) 5 and 6. Our simulations show important differences between the flow patterns recovered in both cases, including observations of regression occurring in areas where wall shear stress (WSS) gradients exist. We propose two possible mechanisms to account for the observed increase in velocity and WSS between P5 and P6: (i) the measured reduction in typical vessel diameter between both time points and (ii) the reduction in network density triggered by the pruning process. The methodology developed herein is applicable to other biomedical domains where microvasculature can be imaged but experimental flow measurements are unavailable or difficult to obtain.     

Computational expressiveness of Genetic Systems

We introduce Genetic Systems, a formalism inspired by genetic regulatory networks and suitable for modeling the interactions between the genes and the proteins, acting as regulatory products.The generation of new objects, representing proteins, is driven by genetic gates: a new object is produced when all the activator objects are available in the system, and no inhibitor object is available. Activators are not consumed by the application of such an evolution rule. Objects disappear because of degradation: each object is equipped with a lifetime, and the object decays when such a lifetime expires.We investigate the computational expressiveness of Genetic Systems: we show that they are Turing equivalent by providing encodings of Random Access Machines in Genetic Systems.     

On the design of a monolithic 4-bounce high resolution X-ray monochromator

A monolithic monochromator (+n, −n, −m, +m) made of a single block of Ge crystal designed for CoK_α1 radiation was developed and tested numerically and experimentally by means of X-ray diffraction. The advantage of monolithic devices is their mechanical stability and the alignment of such optics is much easier than with polylithic optics, but the development of these devices is rather demanding. The presented monochromator belongs to a group of coplanar in-line devices, which means that the input beam is parallel with the output beam. For the estimation of the spectral and angular properties of a diffracted beam of this monochromator (such as bandpass width, output divergence and input acceptance) we used a numerical approach which we call spectral-angular function. It takes into account both the vertical and the horizontal divergence of the input radiation and uses two-beam X-ray dynamical theory of diffraction. Experimentally, the monochromator was tested by means of X-ray diffraction (synchrotron radiation testing) and the results from this characterization are presented. The influence of the vertical divergence on the spectral distribution of the diffracted beam is discussed and compared with previously published analytical results.     

Peroxide macro‐initiators for improving biodegradability of polymers

Modification of dextrin by tert‐butylperoxy methanol or its acylation with cyclic anhydride containing a peroxide group resulted in macro‐initiators with randomly located peroxide fragments in the polysaccharide. When dextran was oxidized with iodic acid, dialdehydedextran was obtained. Its aldehyde groups reacted with tert‐butyl hydroperoxide to give functional peroxide groups. The content of peroxide fragments depended directly on the ratio of reagents. The resulting macro‐initiators may be used for synthesizing graft copolymers with polystyrene on poly(butyl acrylate) containing polysaccharide. © 2001 Society of Chemical Industry     

Obtaining CeO2–ZrO2 mixed oxides by coprecipitation: role of preparation conditions

The preparation of CeO₂–ZrO₂ mixed oxides preparation was studied by evaluating the influence of several conditions. Coprecipitation was taken as the standard method and the effects brought about by the cerium salt precursor ((NH₄)₂Ce(NO₃)₆ or Ce(NO₃)₃), the introduction of drying and aging steps as well as pH controlling upon precipitation were analyzed. The samples were characterized by X-ray diffraction, Raman spectroscopy, temperature-programmed reduction, infrared spectroscopy, oxygen storage capacity and surface area. The use of Ce(NO₃)₃ leads to the formation of c-CeO₂ and t-ZrO₂ mixed oxide whereas a solid solution is achieved by using (NH₄)₂Ce(NO₃)₆. It was observed that the cerium precursor is the most significant parameter of preparation procedure since it defines the crystalline phases and consequently the reducibility behavior of the CeO₂–ZrO₂ system.     

Pd and Pt–Ru anode electrocatalysts supported on multi-walled carbon nanotubes and their use in passive and active direct alcohol fuel cells with an anion-exchange membrane (alcohol = methanol, ethanol, glycerol)

Palladium and platinum–ruthenium nanoparticles supported on multi-walled carbon nanotubes (MWCNT) are prepared by the impregnation-reduction procedure. The materials obtained, Pd/MWCNT and Pt–Ru/MWCNT, are characterized by TEM, ICP-AES and XRPD. Electrodes coated with Pd/MWCNT are scrutinized for the oxidation of methanol, ethanol or glycerol in 2 M KOH solution in half cells. The catalyst is very active for the oxidation of all alcohols, with glycerol providing the best performance in terms of specific current density and ethanol showing the lowest onset potential. Membrane-electrode assemblies have been fabricated using Pd/MWCNT anodes, commercial cathodes and anion-exchange membrane and evaluated in both single passive and active direct alcohol fuel cells fed with aqueous solutions of 10 wt.% methanol, 10 wt.% ethanol or 5 wt.% glycerol. Pd/MWCNT exhibits unrivalled activity as anode electrocatalyst for alcohol oxidation. The analysis of the anode exhausts shows that ethanol is selectively oxidized to acetic acid, detected as acetate ion in the alkaline media of the reaction, while methanol yields carbonate and formate. A much wider product distribution, including glycolate, glycerate, tartronate, oxalate, formate and carbonate, is obtained from the oxidation of glycerol. The results obtained with Pt–Ru/MWCNT anodes in acid media are largely inferior to those provided by Pd/MWCNT electrodes in alkaline media.     

Effect of gold addition on Pt and Pd catalysts in liquid phase oxidations

Single phase Au–Pd and Au–Pt on carbon catalysts have been compared in the liquid phase oxidation of glycerol (representative for polyols) and n-octanol (representative for long chain aliphatic alcohol). The observed overall enhancement of catalytic activity appeared to be function of support, substrate and reaction conditions. Effect of substrate structure has been disentangled: synergistic effect between Au and Pt was maximized when polyol-like substrates were oxidized whereas Au–Pd based catalyst showed a more general match.     

Vitamin C and E Supplementation Effects in Professional Soccer Players Under Regular Training

Exercise training is known to induce an increase in free radical production potentially leading to enhanced muscle injury. Vitamins C and E are well known antioxidants that may prevent muscle cell damage. The purpose of this study was to determine the effects of these supplemental antioxidant vitamins on markers of oxidative stress, muscle damage and performance of elite soccer players. Ten male young soccer players were divided into two groups. Supplementation group (n = 5) received vitamins C and E supplementation daily during the pre-competitive season (S group), while the placebo group (PL group, n = 5) received a pill containing maltodextrin. Both groups performed the same training load during the three-month pre-season training period. Erythrocyte antioxidant enzymes glutathione reductase, catalase and plasma carbonyl derivatives did not show any significant variation among the experimental groups. Similarly, fitness level markers did not differ among the experimental groups. However, S group demonstrated lower lipid peroxidation and muscle damage levels (p < 0.05) compared to PL group at the final phase of pre-competitive season. In conclusion, our data demonstrated that vitamin C and E supplementation in soccer players may reduce lipid peroxidation and muscle damage during high intensity efforts, but did not enhance performance.     

Studying Bluetooth Malware Propagation: The BlueBag Project

Current Bluetooth worms pose relatively little danger compared to Internet scanning worms?but things might change soon. The authors' BlueBag project shows targeted attacks through Bluetooth malware using proof-of-concept codes and devices that demonstrate their feasibility.