Catalytic,Enantioselective Vinylogous Mukaiyama Aldol Reaction of Furan‐Based Dienoxy Silanes: A Chemodivergent Approach to γ‐Valerolactone Flavan‐3‐ol Metabolites and δ‐Lactone Analogues

The asymmetric synthesis of a set of hydroxyphenyl γ‐valerolactones was achieved starting from 2‐silyloxyfuran and alkoxy‐substituted benzaldehydes as common precursors. Key synthesis steps included an enantioselective vinylogous Mukaiyama aldol reaction and a Barton–McCombie deoxygenation. Five enantioenriched γ‐valerolactone targets were obtained in 5–6 steps, 18–63% overall yields and 82–98 % ee, paving the way for the straightforward entry to this class of biologically effective and poorly available flavan‐3‐ol metabolites. In parallel, an unprecedented one‐pot reductive ring expansion process was fortuitously discovered, yielding racemic δ‐lactone analogues from phenolic butanolide precursors.

     

Use of Geophysical Techniques for the Localization of the Restricting Zones of Permeability in the Bottom of Basin： Forecasting the Zones of Clogging

Measurements of dielectric parameters followed by permeability tests are performed on soil samples of infiltration basin. The dielectric parameters are obtained by TDR （time domain reflectrometry） measurements from which it is found that the measurement of the permittivity, the electrical conductivity and the relaxation time of compacted soil allows the mapping of the values of the coefficient of permeability at the surface of an infiltration basin. With the distribution of the coefficient of permeability, the areas of water stagnation can be detected before the basin filling. The study proves that the TDR measurements for the detection of these zones can be used for the management of infiltration basins for sustainable working and their remediation can be undertaken before the rainy seasons.     

Porous NiTi shape memory alloys produced by SHS: microstructure and biocompatibility in comparison with Ti2Ni and TiNi3

Shape memory alloys based on NiTi have found their main applications in manufacturing of new biomedical devices mainly in surgery tools, stents and orthopedics. Porous NiTi can exhibit an engineering elastic modulus comparable to that of cortical bone (12–17 GPa). This condition, combined with proper pore size, allows good osteointegration. Open cells porous NiTi was produced by self propagating high temperature synthesis (SHS), starting from Ni and Ti mixed powders. The main NiTi phase is formed during SHS together with other Ni–Ti compounds. The biocompatibility of such material was investigated by single culture experiment and ionic release on small specimen. In particular, NiTi and porous NiTi were evaluated together with elemental Ti and Ni reference metals and the two intermetallic TiNi₃, Ti₂Ni phases. This approach permitted to clearly identify the influence of secondary phases in porous NiTi materials and relation with Ni-ion release. The results indicated, apart the well-known high toxicity of Ni, also toxicity of TiNi₃, whilst phases with higher Ti content showed high biocompatibility. A slightly reduced biocompatibility of porous NiTi was ascribed to combined effect of TiNi₃ presence and topography that requires higher effort for the cells to adapt to the surface.     

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