Optimization and Validation of an LC Method for the Determination of Cefdinir in Dosage Form and Human Urine

A simple and reliable liquid chromatographic method has been developed and validated for the determination of cefdinir in human urine and capsule samples. A chromatographic separation was achieved on a C₁₈ column using a mobile phase consisting of potassium dihydrogen phosphate (10 mM, pH 4.5)–acetonitrile (90:10, v/v). Quantitation was achieved with UV detection at 285 nm, based on peak area with linear calibration curve at a concentration range of 0.7–39 µg mL^?1. This method was successfully applied for the establishment of an urinary excretion pattern after oral dose.     

Gas phase hydration and deprotonation of the cyclic C3H3+ cation. Solvation by acetonitrile, and comparison with the benzene radical cation

The binding energies of the first 5 H2O molecules to c-C3H3+ were determined by equilibrium measurements. The measured binding energies of the hydrated clusters of 9-12 kcal/mol are typical of carbon-based CH+...X hydrogen bonds. The ion solvation with the more polar CH3CN molecules results in stronger bonds consistent with the increased ion-dipole interaction. Ab initio calculations show that the lowest energy isomer of the c-C3H3+(H2O)4 cluster consists of a cyclic water tetramer interacting with the c-C3H3+ ion, which suggests the presence of orientational restraint of the water molecules consistent with the observed large entropy loss. The c-C3H3+ ion is deprotonated by 3 or more H2O molecules, driven energetically by the association of the solvent molecules to form strongly hydrogen bonded (H2O)nH+ clusters. The kinetics of the associative proton transfer (APT) reaction C3H3+ + nH2O --> (H2O)nH+ + C3H2* exhibits an unusually steep negative temperature coefficient of k = cT(-63+/-4) (or activation energy of -37 +/- 1 kcal mol(-1)). The behavior of the C3H3+/water system is exactly analogous to the benzene+*/water system, suggesting that the mechanism, kinetics and large negative temperature coefficients may be general to multibody APT reactions. These reactions can become fast at low temperatures, allowing ionized polycyclic aromatics to initiate ice formation in cold astrochemical environments.     

Young Integrals and SPDEs

In this note, we study the non-linear evolution problem $dY_t = -A Y_t dt + B(Y_t) dX_t,$ where $XIn this note, we study the non-linear evolution problem where is a -H?lder continuous function of the time parameter, with values in a distribution space, and the generator of an analytical semigroup. Then, we will give some sharp conditions on in order to solve the above equation in a function space, first in the linear case (for any value of in ), and then when satisfies some Lipschitz type conditions (for ). The solution of the evolution problem will be understood in the mild sense, and the integrals involved in that definition will be of Young type.     

Inégalités de Harnack pour les opérateurs elliptiques d'ordre 2 et 4 et phénomène de concentration

We give some results concerning $\sup \times \inf$ inequalities for some elliptic operators of order 2 and 4. With those inequalities and the concentration phenomena we can describe the asymptotic behavior of those PDE solutions. To cite this article: S.S. Bahoura, C. R. Acad. Sci. Paris, Ser. I 342 (2006).     

Nanocatalysis on tailored shape supports: Au and Pd nanoparticles supported on MgO nanocubes and ZnO nanobelts

Active gold and palladium nanoparticles supported on MgO nanocubes and ZnO nanobelts and transition-metal-containing MgO nanobelts were synthesized by combining evaporation and deposition-precipitation techniques. The high activity and stability of the Au/CeO2 and Pd/CeO2 nanoparticle catalysts deposited on the MgO cubes are remarkable and imply that a variety of efficient catalysts can be designed and tested using this approach. The significant increase in the concentration of corner and edge sites in MgO nanocubes make them well-defined supports to study the detailed mechanism of the catalytic activity enhancement.     

Synthesis,cytotoxicity assessment and antioxidant activity of some new thiazol-2-yl carboxamides

Dependence on the biological activity of 2-aminothiazole, the synthesis and chemical reactions of ethyl 3-oxo-3-(thiazol-2-ylamino)propanoate ( 1 ) with some different reagents were described for cytotoxic and antioxidant evaluation. The new derivatives 2–19 could be synthesized and characterized by correct analytical and spectral data. In addition to the thiazole ring, these compounds contain 2H-1,2,3-triazole ( 3 ), 1H-pyrazole ( 5 , 12 ), 1,3-dithiane ( 7 ), benzothiazole ( 10 ), thiazolidine ( 13 ), thiazolidinone ( 14 , 15 ), 2H-chromene ( 17 ), pyridine ( 19 ) moieties. The preparation of compounds 2–19 was performed through the formation of the isolable 2-(2-phenylhydrazineylidene) 2 , 2-dimethylaminomethylidene 4 , 2-phenylcarbamothioyl 9 , 2-(methylthio)(phenylamino) methylidene 11 and non-isolable potassium bis(thiolate) 6 , potassium thiolate 8 intermediates from precursor 1 . The activity of these derivatives 1–19 against human lung fibroblast (WI38) and human prostate cancer (PC3) were examined in vitro using the MTT assay. The assessment of their antioxidant activities was carried out by following the ABTS method to evaluate their pharmaceutical importance.     

On the Brownian-directed polymer in a Gaussian random environment

In this paper, we introduce a model of Brownian polymer in a continuous random environment. The asymptotic behavior of the partition function associated to this polymer measure is studied, and we are able to separate a weak and strong disorder regime under some reasonable assumptions on the spatial covariance of the environment. Some further developments, concerning some concentration inequalities for the partition function, are given for the weak disorder regime.     

Structural aspects for evolution of beta-lactamases from penicillin-binding proteins

Penicillin-binding proteins (PBPs), biosynthetic enzymes of bacterial cell wall assembly, and beta-lactamases, resistance enzymes to beta-lactam antibiotics, are related to each other from an evolutionary point of view. Massova and Mobashery (Antimicrob. Agents Chemother. 1998, 42, 1-17) have proposed that for beta-lactamases to have become effective at their function as antibiotic resistance enzymes, they would have had to undergo structure alterations such that they would not interact with the peptidoglycan, which is the substrate for PBPs. A cephalosporin analogue, 7beta-[N-Acetyl-L-alanyl-gamma-D-glutamyl-L-lysine]-3-acetoxymethyl-3-cephem-carboxylic acid (compound 6), was conceived and synthesized to test this notion. The X-ray structure of the complex of this cephalosporin bound to the active site of the deacylation-deficient Q120L/Y150E variant of the class C AmpC beta-lactamase from Escherichia coli was solved at 1.71 A resolution. This complex revealed that the surface for interaction with the strand of peptidoglycan that acylates the active site, which is present in PBPs, is absent in the -lactamase active site. Furthermore, insertion of a peptide in the beta-lactamase active site at a location where the second strand of peptidoglycan in some PBPs binds has effectively abolished the possibility for such interaction with the beta-lactamase. A 2.6 ns dynamics simulation was carried out for the complex, which revealed that the peptidoglycan surrogate (i.e., the active-site-bound ligand) undergoes substantial motion and is not stabilized for binding within the active site. These factors taken together disclose the set of structure modifications in the antibiotic resistance enzyme that prevent it from interacting with the peptidoglycan, en route to achieving catalytic proficiency for their intended function.     

Hexafluoroacetone as Protecting and Activating Reagent. A New Approach to N-linked Glycopeptoids

A preparatively simple synthesis of N-linked glycopeptoids starting from iminodiacetic acid and glycosylamines, using hexafluoroacetone as protecting and activating reagent is described.     

A characterization of permutation modules

Let k be a field of positive characteristic p, and let P be a finite p-group. In this paper, I state a combinatorial characterization of finite dimensional permutation kP-modules.