Phosphorylation of Guar Gum/Magnetite/Chitosan Nanocomposites for Uranium (VI) Sorption and Antibacterial Applications

The development of new materials is needed to address the environmental challenges of wastewater treatment. The phosphorylation of guar gum combined with its association to chitosan allows preparing an efficient sorbent for the removal of U(VI) from slightly acidic solutions. The incorporation of magnetite nanoparticles enhances solid/liquid. Functional groups are characterized by FTIR spectroscopy while textural properties are qualified by N₂ adsorption. The optimum pH is close to 4 (deprotonation of amine and phosphonate groups). Uptake kinetics are fast (60 min of contact), fitted by a pseudo-first order rate equation. Maximum sorption capacities are close to 1.28 and 1.16 mmol U g⁻¹ (non-magnetic and magnetic, respectively), while the sorption isotherms are fitted by Langmuir equation. Uranyl desorption (using 0.2 M HCl solutions) is achieved within 20–30 min; the sorbents can be recycled for at least five cycles (5–6% loss in sorption performance, complete desorption). In multi-component solutions, the sorbents show marked preference for U(VI) and Nd(III) over alkali-earth metals and Si(IV). The zone of exclusion method shows that magnetic sorbent has antibacterial effects against both Gram+ and Gram- bacteria, contrary to non-magnetic material (only Gram+ bacteria). The magnetic composite is highly promising as antimicrobial support and for recovery of valuable metals.     

Reflected BSDE's with discontinuous barrier and application

We deal with reflected backward stochastic differential equations with right continuous and left limited barrier. We show the existence and uniqueness of the solution and we give a comparison theorem. As an application, we study the link between such an equations with stochastic mixed control problems.     

Conversion of 2(3H)‐furanones bearing indole nuclei into novel amide,pyrrolone, and imidazole derivatives

2(3H)‐Furanones 1a–d having exocyclic double bond and N‐acetylisatin nucleus were converted into the corresponding novel amides, pyrrolones, and imidazoles via nitrogen nucleophiles. All purposed structures were confirmed by NMR, mass spectra GC/MS, and chemical evidence. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:434–442, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10175     

γ-Irradiation effects on the thermal decomposition behaviour and IR absorption spectra of piperacillin

The thermal decomposition behaviour of unirradiated and pre-γ-irradiated piperacillin (pipril) as a semi-synthetic penicillin antibiotic has been studied in the temperature range of (273–1072?K). The decomposition was found to proceed through three major steps both for unirradiated and γ-irradiated samples. Neither appearance nor disappearance of new bands in the IR spectrum of piperacillin was recorded as a result of γ-irradiation but only a decrease in the intensity of most bands was observed. A degradation mechanism was suggested to explain the bond rupture and the decrease in the intensities of IR bands of γ-irradiated piperacillin.     

Synthesis of Some Antimicrobial Purine Nucleoside Derivatives

Some N(6)-substituted adenosine derivatives and adenosine attached to different amino-acid residues and peptides at position 8 have been synthesized using improved methods. The biological activities of the prepared compounds towards gram-positive and gram-negative bacteria are described.     

Synthesis and reactions of 2-mercaptomethyl-1,3,4-oxadiazolin-5-one

Summary The title compound (4) was synthesized from thioglycolic acid hydrazide and ethyl chloroformate. The reactions of4 with aromatic amines, amino derivatives, hydrazine hydrate, hydroxylamine, and formamide were studied. Addition of compound4 to ,-unsaturated compounds,i.e. chalcones, maleic anhydride, quinones, and acrylonitrile, was investigated.

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Synthese und Reaktionen von 2-Mercaptomethyl-1,3,4-oxadiazolin-5-on

Zusammenfassung Die Titelverbindung (4) wurde aus Thioglycolsäurehydrazid und Chlorameisensäureethylester hergestellt. Die Reaktionen von4 mit aromatischen Aminen, Aminoderivaten, Hydrazinhydrat, Hydroxylamin und Formamid sowie die Addition von4 an ,-ungesättigte Verbindungen (Chalkone, Maleinsäureanhydrid, Chinone, Acetonitril) wurden untersucht.

     

Structural and crystal growth kinetics studies for SnO2 nanoparticles prepared via hydrothermal route

Tin oxide nanoparticles with crystallite size (1.9–3 nm) were synthesized via hydrothermal route. The role of autoclave temperature (T_A) on the structural parameters and surface morphology of the as-synthesized SnO₂ nanoparticles (NPs) was followed using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The thermal behavior of the as-synthesized SnO₂ NPs was carried out using thermogravimetric and differential thermal analysis (TGA/DTA) techniques under non-isothermal conditions. The effect of T_A on the activation energy of crystal growth (E_c) and the Avrami exponent (n) of SnO₂ NPs were determined by different methods. The reaction mechanism controlling the growth process was discussed in terms of the results obtained using different iso-conversional methods to determine the local E_c(α) and n(α).