Floating ZnO QDs-Modified TiO2/LLDPE Hybrid Polymer Film for the Effective Photodegradation of Tetracycline under Fluorescent Light Irradiation: Synthesis and Characterisation

In this work, mesoporous TiO₂-modified ZnO quantum dots (QDs) were immobilised on a linear low-density polyethylene (LLDPE) polymer using a solution casting method for the photodegradation of tetracycline (TC) antibiotics under fluorescent light irradiation. Various spectroscopic and microscopic techniques were used to investigate the physicochemical properties of the floating hybrid polymer film catalyst (8%-ZT@LLDPE). The highest removal (89.5%) of TC (40 mg/L) was achieved within 90 min at pH 9 due to enhanced water uptake by the LDDPE film and the surface roughness of the hybrid film. The formation of heterojunctions increased the separation of photogenerated electron-hole pairs. The QDs size-dependent quantum confinement effect leads to the displacement of the conduction band potential of ZnO QDs to more negative energy values than TiO₂. The displacement generates more reactive species with higher oxidation ability. The highly stable film photocatalyst can be separated easily and can be repeatedly used up to 8 cycles without significant loss in the photocatalytic ability. The scavenging test indicates that the main species responsible for the photodegradation was O₂^●−. The proposed photodegradation mechanism of TC was demonstrated in further detail based on the intermediates detected by LC-time-of-flight/mass spectrometry (LC/TOF-MS).     

Microbial transformation of danazol

Danazol (17beta-hydroxy-17alpha-pregna-2,4-dien-20-yno-[2,3-d] isoxazole) (1) on fermentation with Fusarium lini, Aspergillus niger, and Cephalosporium aphidicola yielded 17beta-hydroxy-2-(hydroxymethyl)-17-alpha-pregn-4-en-20-yn-3-one (2) and 17beta-hydroxy-2-(hydroxymethyl)-17 alpha-pregna-1,4-dien-20-yn-3-one (3), while the fermentation of 1 with Bacillus cerus yielded compound 2 only.     

Some solutions of the linear and nonlinear Klein-Gordon equations using the optimal homotopy asymptotic method

We investigate the effectiveness of the Optimal Homotopy Asymptotic Method (OHAM) in solving time dependent partial differential equations. To this effect we consider the homogeneous, non-homogeneous, linear and nonlinear Klein-Gordon equations with boundary conditions. The results reveal that the method is explicit, effective, and easy to use.     

L2-approximation of real-valued functions with interpolatory constraints

We construct the polynomial p_m,n^* of degree m which interpolates a given real-valued function f L²[a, b] at pre-assigned n distinct nodes and is the best approximant to f in the L₂-sense over all polynomials of degree m with the same interpolatory character. It is shown that the L₂-error p_m,n^* − f → 0 as m → ∞ if f C[a, b].     

Polarized Raman scattering and low frequency infrared study of hydroxyapatite

A detailed investigation of the polarized Raman spectrum of monoclinic hydroxyapatite (OHAp) and a careful study of the low frequency infrared spectrum of polycrystalline OHAp, is reported. Most of the spectral details of Raman scattering are consistent with the local pseudo-hexagonal C₆ factor group symmetry of OHAp. However, some features, for example the absence of TO-LO splitting for particular E₁ phonon geometries and the splitting of the lowest frequency Raman line, are a reflection of the centrosymmetric monoclinic lattice of OHAp. Between 0 and 50cm^?1, a temperature-dependent background, having E₁ symmetry, and probably associated with OH^? disordering flucuations, was observed in OHAp. Both OHAp and FAp displayed low frequency Raman lines which softened with decreasing temperature. However, no evidence for a phase transition was found in either OHAp or FAp in the 12–295 K temperature range.     

The impact of distribution system characteristics on computational tractability

Mathematical programming models that seek optimal design and operational plans for distribution systems can be computationally intractable. This paper examines the extent to which distribution configuration and demand characteristics affect the ease of obtaining an optimal solution. Problem characteristics, which are reflected in a model by the parameter values, can render the model for one distribution scenario to be computationally intractable and that for another to yield an optimal solution easily. We introduce echelon-flow-based valid inequalities and use them to explicate the extent to which problem characteristics impact computational tractability.     

Solvent extraction of chromium(VI) from base metal ions with diphenyl-2-pyridylmethane as a liquid anion exchanger

The extraction of chromium(VI) from aqueous hydrochloric, nitric and sulfuric acid solutions by diphenyl-2-pyridylmethane(DPPM) dissolved in chloroform has been studied. Chromium(VI) is quantitatively extracted from hydrochloric acid solutions in the range 0.1–1M. With increasing acid concentration, the extraction of chromium diminishes and in concentrated acid solutions practically all the chromium remains in the aqueous phase. The quantitative back-extraction of chromium from the organic phase is possible with HCl or HNO₃ at concentrations higher than 5M through the use of reducing agents. The composition of the extracted chromium(VI) species was studied in solution. The complexes (DPPMH)⁺HCrO ₄ ⁻ and (DPPMH)₂Cr₂O ₇ ⁻ are extracted for tracer and macro amounts of chromium(VI) respectively. The data have been utilized for the separation of chromium(VI) from base metal ions.     

Kinetics studies on flavone glycosides: inhibitors of <Emphasis Type="Italic">α</Emphasis>-chymotrypsin

The mechanism of inhibition of α-chymotrypsin enzyme by two flavone glycosides having an apigenin basic skeleton, namely, apigenin 7-O-β-D(-6′′-p-E-coumaroyl)-glucoside (1) and apigenin 7-O-β-D-glucoside (2), isolated from Clematis orientalis L. (Ranunculaceae), was investigated. Lineweaver-Burk and Dixon plots and their secondary replots have shown that both of the compounds are competitive inhibitors of this enzyme. K_i values for 1 and 2 were found to be 71.75 ± 0.85 and 680.11 ± 0.11 μM, respectively.     

Colorimetric analysis of water and sand samples performed on a mobile phone

Analysis of water and sand samples was done by reflectance measurements using a mobile phone. The phone's screen served as light source and front view camera as detector. Reflected intensities for white, red, green and blue colors were used to do principal component analysis for classification of several compounds and their concentrations in water. Analyses of colored solutions and colorimetric reactions based on widely available chemicals were performed. Classification of iron(III), chromium(VI) and sodium salt of humic acid was observed using reflected intensities from blue and green light for concentrations 2-10 mg/l. Addition of complex forming sodium salt of ethylenediaminetetraacidic acid enabled the discrimination of Cu(II) ions in the 2-10 mg/l concentration range based on reflection of red light. An alternate method using test strips for copper solutions with the phone as reader also demonstrated a detection limit of 2 mg/l. Analysis of As(III) from 25 to 400 μg/l based on reflection of red light was performed utilizing the bleaching reaction of tincture of iodine containing starch. Enhanced sensitivity to low concentrations of arsenic was obtained by including reflected intensities from white light in the analysis. Model colored sand samples representing discoloration caused by the presence of arsenic in groundwater were analyzed as a complementary method for arsenic detection.     

Leufolins A and B, potent butyrylcholinesterase-inhibiting flavonoid glucosides from Leucas urticifolia

New flavonoidal glucosides leufolins A (1) and B (2), have been isolated from the ethyl acetate soluble fraction of the whole plants of Leucas urticifolia. Their structures were elucidated on the basis of extensive analysis of nuclear magnetic resonance (1D and 2D NMR) spectral data. Both of these compounds exhibited significant inhibitory potential against the enzyme butyrylcholinesterase.