Effective Removal of Methylene Blue from Simulated Wastewater Using ZnO-Chitosan Nanocomposites: Optimization,Kinetics, and Isotherm Studies

Successful synthesis of ZnO-chitosan nanocomposites was conducted for the removal of methylene blue from an aqueous medium. Remarkable performance of the nanocomposites was demonstrated for the effective uptake of the dye, thereby achieving 83.77, 93.78 and 97.93 mg g⁻¹ for the chitosan, 5 wt.% ZnO-Chitosan and 10 wt.% ZnO-Chitosan, respectively. The corresponding adsorption efficiency was 88.77, 93.78 and 97.95 for the chitosan, 5 wt.% ZnO-Chitosan and 10 wt.% ZnO-Chitosan, respectively. Upon regeneration, good reusability of the nanocomposites was manifested for the continuous removal of the dye up to six consecutive cycles. The adsorption process was kinetically described by a pseudo-first order model, while the isotherms were best fitted by the Langmuir model.     

Dystrophin Protein Quantification as a Duchenne Muscular Dystrophy Diagnostic Biomarker in Dried Blood Spots Using Multiple Reaction Monitoring Tandem Mass Spectrometry: A Preliminary Study

Duchenne muscular dystrophy (DMD) is an X-linked recessive disorder characterized by progressive muscle loss, leading to difficulties in movement. Mutations in the DMD gene that code for the protein dystrophin are responsible for the development of DMD disorder, where the synthesis of this protein is completely halted. Therefore, circulating dystrophin protein could be a promising biomarker of DMD disease. Current methods for diagnosing DMD have sensitivity, specificity, and reproducibility limitations. Herein, a quantitative liquid chromatography–tandem spectrometry (LC–MS/MS) technique in multiple reaction monitoring (MRM) mode was designed and validated for accurate dystrophin protein measurement in a dried blood spot (DBS). The method was successfully validated on the basis of international guidelines regarding calibration curves, precision, and accuracy. In addition, patients and healthy controls were used to test the amount of dystrophin protein circulating in DBS samples as a potential biomarker for DMD disorders. DMD patients were found to have considerably lower levels than controls. To the best of our knowledge, this is the first study to report dystrophin levels in DBS through LC–MS/MS as a diagnostic marker for DMD to the proposed MRM method, providing a highly specific and sensitive approach to dystrophin quantification in a DBS that can be applied in DMD screening.     

Estimation of radiation doses associated with natural radioactivity in sand samples of the north western areas of Pakistan using Monte Carlo simulation

Summary Activity concentrations of naturally occurring radionuclides, i.e., ²²⁶Ra, ²³²Th and ⁴⁰K, were measured in sand samples of north western areas of Pakistan using gamma-spectrometry. The measured ranges of activity concentrations for ²²⁶Ra, ²³² Th and ⁴⁰K were 36.9-51.9, 52.5-67.6 and 680-784 Bq ^. kg^-1, respectively. Associated external dose was calculated using Monte Carlo simulation technique. A theoretical model to determine the gamma dose rate at 1 m height from the sand was employed for calculation the mass attenuation coefficient and self absorption in sand slab for the gamma-energies of these radionuclides and their progeny. The weighted average values of the measured gamma dose rates were 3.3, 4.5 and 12.4 nGyh^-1 for ²²⁶Ra, ²³² Th and ⁴⁰K, respectively, with effective dose of 0.022±0.004 mSv ^. y^-1. Monte Carlo simulation shows that the sand slabs having more than 15 cm effective thickness contribute very little to the external gamma dose rate. The values of the external dose rate and annual effective dose were found to be much lower than the world average as well as from other countries of the world.     

Atomic structure and chemical order in binary Ge–Te and As–Te glasses: A Te K-edge X-ray absorption fine structure spectroscopic study

The nearest-neighbor coordination environments of Te atoms in Ge_xTe_100?x glasses with x = 15 and 20 and in As_xTe_100?x glasses with 40 ? x ? 65 have been studied with Te K-edge EXAFS spectroscopy. The average coordination number of Te atoms in all glasses is found to be ～2.0 and no violation of the 8-N rule is observed. The compositional makeup of the first coordination shell of Te atoms indicates that chemical order is largely preserved in both glass-forming binary systems. Sudden changes in the Te coordination environment and violation of chemical order are observed at the stoichiometric As₄₀Te₆₀ glass implying formation of a constrained network. The compositional dependence of the physical properties in both systems can be correlated to short-range chemical order.     

Microbial transformation of rubijervine

Preparative-scale fermentation of rubijervine (1), the known 22,26-epiminocholestane Veratrum alkaloid, with Cunninghamella echinulata ATCC 9244 has resulted in the isolation of the new metabolites 7alpha-hydroxyrubijervine (2) and solanid-5-ene-3beta,12alpha-diol-1-one (3). Structure elucidation of these metabolites was based primarily on 1D- and 2D-NMR analyses. The microbe C. echinulata ATCC 9244 was able to metabolize rings A and B of rubijervine but failed to metabolize rings C, D or its N-containing side chain, a finding which is analogous to the results of previous fermentation studies of steroidal alkaloids.     

Synthesis and characterization of new poly(ester-amide)s containing diarylidenecyclohexanone in the main chain. Part: II

A new category of poly(ester-amide)s based on diarylidenecyclohexanone in the main chain were synthesized via interfacial polycondensation of two monomers namely: 2,6-bis(4-hydroxybenzylidene) cyclohexanone I and 2,6-bis(4-hydroxy-3-methoxybenzylidene) cyclohexanone II with diacid chlorides IIIa–c. The model compounds were synthesized by reacting one mole of compounds IVa–c with two monomers I and II. The structure of the model compounds was confirmed by correct elemental and spectral analyses. The various characteristics of the resulting polymers including: solubility, viscosity, thermal analysis, and X-ray diffraction analysis were determined and discussed. The majority of the polymers were insoluble in most common organic solvents. The viscosity measurements in dimethylsulfoxide showed the values 0.58–0.79 dl/g. Thermal analysis showed that they were thermally stable up to 500 °C. X-ray analysis showed that the polymers had some degree of crystallinity in the region 2θ = 5–50°.     

Structural analysis and band gap tailoring of Fe3+-doped Zn–TiO2 nanoparticles

We report on the analysis of morphology and electronic structure of Fe³⁺-doped Zn–TiO₂ nanoparticles. Crystalline nature, phase, and preferred growth direction of the nanoparticles were all determined. Due to size effects and OH⁻–(TiO₄) ⁿ complexes, variation in the energy gap with metallic and semiconducting characters on the same sample was found. The variation in the energy gap decreased, and the bang gap decayed exponentially with Fe doping and independent of the supporting substrates. Simultaneous effect of the OH⁻ ligands on the electronic structure and the formation mechanism of nanorods and nanosheets as manifested by the rutile TiO₆ octahedra units edge- and corner-shared bonding was discussed.     

Some fixed point theorems of the Schauder and the Krasnosel'skii type and application to nonlinear transport equations

In [J. Math. Phys. 37 (1996) 1336-1348] the existence of solutions to the boundary value problem (1.1)-(1.2) was analyzed for isotropic scattering kernels on L_p spaces for p∈(1,∞). Due to the lack of compactness in L₁ spaces, the problem remains open for p=1. The purpose of this work is to extend this analysis to the case p=1 for anisotropic scattering kernels. Our strategy consists in establishing new variants of the Schauder and the Krasnosel'skii fixed point theorems in general Banach spaces involving weakly compact operators. In L₁ context these theorems provide an adequate tool to attack the problem. Our analysis uses the specific properties of weakly compacts sets on L₁ spaces and the weak compactness results for one-dimensional transport equations established in [J. Math. Anal. Appl. 252 (2000) 767-789].     

Use of solid-phase extraction, reverse osmosis and vacuum distillation for recovery of aromatic sulfonic acids from aquatic environment followed by their determination using liquid chromatography-electrospray ionization tandem mass spectrometry

Three different sample preparation techniques (i) solid-phase extraction, (ii) reverse osmosis and (iii) vacuum distillation have been investigated and the recoveries were compared for determination of highly water-soluble benzene and stilbene sulfonic acids in aqueous environment by liquid chromatography with photodiode array (PDA) and electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS). The recoveries were quite high using vacuum distillation (>90%) compared to solid phase extraction and reverse osmosis. The negative ion ESI mass spectra containing the peaks of quasimolecular ion [M-H]- allow the molecular mass determination of unknown compounds whereas the structures were proposed using fragments obtained from MS/MS analysis of [M-H]- ions. At lower fragmentation voltages only the quasimolecular ion [M-H]- was observed and as fragmentation voltages increased, it led to the formation of fragment ions corresponding to [M-H-SO3]-, [M-H-SO2]-, and SO3-. The detection limits were 1-28 microg/L with LC-ESI-MS. The sample collected from wastewater treatment plant was found to contain 21.1, 13.3, 12.1, 41.8 and 9.9 microg/L of cis-4,4(l)-diaminostilbene-2,2(l)-disulfonic acid (cis-DASDA), trans-4,4(l)-diaminostilbene-2,2(l)-disulfonic acid (trans-DASDA), 3-amino acetanilide-4-sulfonic acid (3-AASA), 4-chloroaniline-2-sulfonic acid (4-CASA), 2-chloroaniline-5-sulfonic acid (2-CASA), respectively.