Skeletal diversity through radical cyclization of tetrahydropyridine scaffolds

Suitably functionalized tetrahydropyridines (methyl pipecolates) have been used as conformationally biased templates for radical cyclizations to access benzoisoquinuclidines and linearly fused indenopiperidines. Variation of skeletal types is determined by location of a radical-initiating element.     

Generalized (anti) Yetter-Drinfeld modules as components of a braided T-category

If H is a Hopf algebra with bijective antipode and α, β ∈ Aut _Hopf (H), we introduce a category , generalizing both Yetter-Drinfeld modules and anti-Yetter-Drinfeld modules. We construct a braided T-category having all the categories as components, which, if H is finite dimensional, coincides with the representations of a certain quasitriangular T-coalgebra DT(H) that we construct. We also prove that if (α, β) admits a so-called pair in involution, then is isomorphic to the category of usual Yetter-Drinfeld modules . Research partially supported by the programme CERES of the Romanian Ministry of Education and Research, contract no. 4-147/2004.     

Asymptotic behaviour of families of real curves

We consider the family of fibres of a polynomial function f on a smooth noncompact algebraic real surface and we characterise the regular fibres of f which are atypical due to their asymptotic behaviour at infinity. We compare to the similar problem in the complex case. Received: 5 May 1998 / Revised version: 20 March 1999     

Total Aseptization of Boar Semen,to Increase the Biosecurity of Reproduction in Swine

The aim of the study was to establish the complete microbiological profile of boar semen (Sus scrofa domesticus) and to choose the most effective antiseptic measures in order to control and optimize AI reproduction in pig farms. One hundred and one semen samples were collected and analyzed from several pig farms. The microbiological profile of ejaculates was determined by evaluating the degree of contamination of fresh semen and after dilution with specific extenders. The bacterial and fungal load of fresh boar semen recorded an average value of 82.41/0.149 × 10³ CFU/mL, while after diluting the ejaculates the contamination value was 0.354/0.140 × 10³ CFU/mL. Twenty-four germs (15 bacterial and 9 fungal species) were isolated, the most common being Candida parapsilosis/sake (92%) and Escherichia coli (81.2%). Modification of the sperm collection protocol (HPBC) reduced contamination in raw sperm by 49.85% in bacteria (significant (p < 0.00001) and by 9.67% in fungi (non-significant (p < 0.111491). The load in bacteria and filamentous fungi can be controllable, but not in levuras fungi. Some fluconazole-added extenders (12.5 mg%), ensure fungal aseptization, and even an increase in sperm progressivity (8.39%) for at least a 12 h shelf life after dilution. Validation of sperm aseptization was done by maintaining sow fecundity unchanged after AI (insignificant p > 0.05).     

Synthesis and Biological Evaluation of New N-Acyl-α-amino Ketones and 1,3-Oxazoles Derivatives

In order to develop novel bioactive substances with potent activities, some new valine-derived compounds incorporating a 4-(phenylsulfonyl)phenyl fragment, namely, acyclic precursors from N-acyl-α-amino acids and N-acyl-α-amino ketones classes, and heterocycles from the large family of 1,3-oxazole-based compounds, were synthesized. The structures of the new compounds were established using elemental analysis and spectral (UV-Vis, FT-IR, MS, NMR) data, and their purity was checked by reversed-phase HPLC. The newly synthesized compounds were evaluated for their antimicrobial and antibiofilm activities, for toxicity on D. magna, and by in silico studies regarding their potential mechanism of action and toxicity. The 2-aza-3-isopropyl-1-[4-(phenylsulfonyl)phenyl]-1,4-butanedione 4b bearing a p-tolyl group in 4-position exhibited the best antibacterial activity against the planktonic growth of both Gram-positive and Gram-negative strains, while the N-acyl-α-amino acid 2 and 1,3-oxazol-5(4H)-one 3 inhibited the Enterococcus faecium biofilms. Despite not all newly synthesized compounds showing significant biological activity, the general scaffold allows several future optimizations for obtaining better novel antimicrobial agents by the introduction of various substituents on the phenyl moiety at position 5 of the 1,3-oxazole nucleus.     

Crystallization of hydrogenated amorphous silicon carbon films with laser and thermal annealing

The crystallization of silicon rich hydrogenated amorphous silicon carbon films prepared by Plasma Enhanced Chemical Vapor Deposition technique has been induced by excimer laser annealing as well as thermal annealing. The excimer laser energy density (E_d) and the annealing temperature were varied from 123 to 242 mJ/cm² and from 250 to 1200 °C respectively. The effects of the two crystallization processes on the structural properties and bonding configurations of the films have been studied. The main results are that for the laser annealed samples, cubic SiC crystallites are formed for E_d ≥ 188 mJ/cm², while for the thermal annealed samples, micro-crystallites SiC and polycrystalline hexagonal SiC are observed for the annealing temperature of 800 and 1200 °C respectively. The crystallinity degree has been found to improve with the increase in the laser energy density as well as with the increase in the annealing temperature.     

The effect of PVC on thermal and catalytic degradation of polyethylene, polypropylene and polystyrene by a continuous flow reactor

A continuous flow reactor was operated at atmospheric pressure and feed rate of 0–1.5 kg h⁻¹ for degradation of PE, PP and PS in presence of 1–2 wt% PVC. The degradation temperatures were between 360 and 440 °C depending on the feeding material. The influence of PVC, temperature and silica-alumina catalysts on degradation behavior and on the properties of the products was studied and discussed. Different effects were observed for binary PE/PVC, PP/PVC, PS/PVC and complex PE/PP/PS/PVC mixtures due to specific interactions between PVC and each hydrocarbon polyolefin. Silica-alumina catalysts decreased the Cl concentration in oils but it seems to generate high amounts of Cl-containing organic compounds in gases.     

Conformational changes of strong polycations in the presence of divalent counterions and their influence upon the flocculation efficiency

The interaction between strong polycations, which possess the ammonium quaternary centers attached to an acrylic macromolecular chain derived from poly(N,N-dimethylaminoethyl methacrylate) (polycations Q_x), and divalent counterions was investigated by viscometry and turbidimetry. Conformational changes of polycations were influenced by the polycation charge density, counterion nature (SO₄²⁻ or S₂O₈²⁻) and concentration. The morphology of the polycation layers deposited onto silicon wafers has been studied by tapping mode atomic force microscopy, a strong influence of the polycation and ammonium persulfate concentration on the surface topography being observed. The optimum flocculation concentration of polycation decreased and the flocculation window increased in the presence of S₂O₈²⁻, in the destabilization of kaolin model dispersion. Removal of Congo Red from aqueous solution by the complex system formed between polycations and divalent counterions was also investigated. The behavior of polycations Q_x in separation processes was compared with that of one polycation containing 95 mol% N,N-dimethyl-2-hydroxypropyleneammonium chloride units in the backbone (PCA₅).     

Bergman polynomials on an archipelago: Estimates, zeros and shape reconstruction

Growth estimates of complex orthogonal polynomials with respect to the area measure supported by a disjoint union of planar Jordan domains (called, in short, an archipelago) are obtained by a combination of methods of potential theory and rational approximation theory. The study of the asymptotic behavior of the roots of these polynomials reveals a surprisingly rich geometry, which reflects three characteristics: the relative position of an island in the archipelago, the analytic continuation picture of the Schwarz function of every individual boundary and the singular points of the exterior Green function. By way of explicit example, fine asymptotics are obtained for the lemniscate archipelago |z^m−1|<r^m, 0<r<1, which consists of m islands. The asymptotic analysis of the Christoffel functions associated to the same orthogonal polynomials leads to a very accurate reconstruction algorithm of the shape of the archipelago, knowing only finitely many of its power moments. This work naturally complements a 1969 study by H. Widom of Szegő orthogonal polynomials on an archipelago and the more recent asymptotic analysis of Bergman orthogonal polynomials unveiled by the last two authors and their collaborators.