Cation-pi interactions as a tool to enhance the power of a chiral auxiliary during asymmetric photoreactions within zeolites

Owing to the existence of cation-pi interactions, aryl chiral auxiliaries perform far better than alkyl chiral auxiliaries during asymmetric photoreaction.     

Determination of arsenic in sea water by sorbent extraction with hydride generation atomic absorption spectrometry

A rapid and sensitive sorbent extraction hydride generation-flow injection analysis atomic absorption spectrometric (HG-FIAS-AAS) method is described for the determination of As(III) and As(V) based upon online preconcentration on a microcolumn packed with activated alumina. In the present procedure these arsenicals are complexed with quinolin-8-ol-5-sulphonic acid from neutral solutions in the flow injection system and adsorbed on the column. The preconcentrated species are eluted with 10% HCl, mixed with 0.5% sodium borohydride and carried to the HG-FIAS cell with a carrier gas flow rate of 75 ml min(-1). The retention efficiency is found to be better than 98% with sensitivity enhancement of 12 and 10 for As(III) and As(V), respectively, for a 20 s preconcentration period. The respective detection limits are 0.05 and 2 ng ml(-1) for As(III) and As(V). The throughput of the samples is found to be 60 h(-1), with a loading time of 20 s. The method has been applied to sea water samples.     

Effect of rope mat and random orientation on mechanical and thermal properties of banana ribbon-reinforced polyester composites and its application

The present work deals with the characterization of banana ribbon, a new natural fiber, and the effect of rope mat and random orientation on the mechanical and thermal properties of banana ribbon-reinforced polyester composites. Of all the fabricated composites, the banana ribbon rope mat composites showed improved mechanical and thermal properties compared to randomly oriented composites and other natural fiber composites. The surface morphologies of fractured mechanical testing samples were studied by scanning electron microscope to probe the fiber–matrix interaction. Furthermore, the mat composites are used to fabricate windshield of four wheelers and mudguard of two wheelers.     

Extraction and characterization of new cellulosic fibers from Indian mallow stem: An exploratory investigation

Natural fibers are one of the good alternative sources for replacing synthetic fiber and reinforcing polymer matrices because of their eco-friendly nature. This investigation deals with the extraction and characterization of new natural fiber from Indian mallow plant stem. The physico-chemical, thermal, and mechanical properties of Indian mallow fibers (IMFs) were reported and compared with other natural fibers for the first time. Cellulose (78.22%), wax (0.47%), density (1.33 g/cm³), and tensile strength (979.83 MPa) were recognized in IMFs. Fourier transform-infrared spectroscopy, X-ray diffraction, and thermo-gravimetric analysis confirmed that IMFs are rich in cellulose content and thermally stable with a crystallinity index of 72%.     

Characterization of new natural cellulosic fiber from kusha grass

The present research work aimed to characterize new natural cellulosic kusha fibers extracted from the kusha grass plants. The physical and chemical properties of kusha fibers such as cellulose content (70.58%), lignin (14.35%), wax content (1.52%), ash content (2.46%), moisture content (8.01%), and density (1.1025 g cc^?1) were identified. An X-ray diffraction of kusha fibers confirms the presence of cellulose with a crystalline index of 55.4%. Fourier transform infrared spectroscopy analysis was carried out to establish the certainty of using them as reinforcement fiber. Thermogravimetric analysis ensures thermal stability up to 357°C which is within the polymerization process temperature.     

Catalytic Influence of Bimetallic Bifunctional Ni-Pd/H-β and H-Mordenite Nanoporous Catalysts for Hydroisomerisation of <Emphasis Type="Italic">n</Emphasis>-Octane

Zeolite-β and mordenite were impregnated with 0.1 wt% Pd and varying the amount (0.1–0.5 wt%) of Ni. The prepared nanoporous catalyst were characterized by various physico-chemical techniques such as XRD, nitrogen adsorption–desorption isotherm (BET), NH₃-TPD and TPR, XPS and TEM. Hydroisomerisation of n-octane was carried out in the temperature range from 200 to 450 °C in the presence of flowing H₂ gas under 1 atm. Finally we found that Ni addition up to 0.3 and 0.2 wt% over 0.1 wt% Pd/H-β and H-mordenite enhances the n-octane conversion and isomerisation selectivity. As the Ni amount exceeds the threshold values, the conversion decreases with increase in cracked products, and also, the selectivity of mono and dibranched isomers were improved suggestion operation of PCP intermediate mechanism. The bimetallic catalysts were more selective to the formation of dibranched isomers with higher octane number, when compared with monometallic catalysts. Ni-Pd loaded zeolite-β supports always show higher activity and selectivity than mordenite supports. Moreover, we achieved higher conversion (74.9 %) and isomerisation selectivity (92.5 %) at low Ni loading (0.3 Ni wt% over 0.1 Pd wt%/Hβ) for the first time.     

Microstress,strain, band gap tuning and photocatalytic properties of thermally annealed and Cu-doped ZnO nanoparticles

ZnO nanoparticles and Cu-doped ZnO nanoparticles were prepared by co-precipitation method. Also, a part of the pure ZnO nanoparticles were annealed at 750 °C for 3, 6, and 9 h. X-ray diffraction studies were carried out and the lattice parameters, unit cell volume, interplanar spacing, and Young’s modulus were calculated for all the samples, and also the crystallite size was found using the Scherrer method. X-ray peak broadening analysis was used to estimate the crystallite sizes and the strain using the Williamson–Hall (W–H) method and the size–strain plot (SSP) method. Stress and the energy density were calculated using the W–H method assuming different models such as uniform deformation model, uniform strain deformation model, uniform deformation energy density model, and the SSP method. Optical absorption properties of the samples were understood from their UV–visible spectra. Photocatalytic activities of ZnO and 5 % Cu-doped ZnO were observed by the degradation of methylene blue dye in aqueous medium under the irradiation of 20-W compact fluorescent lamp for an hour.     

Determination of inorganic oxyanions of As and Se by HPLC-ICPMS

A liquid chromatographic separation of inorganic oxyanions of As (As(V) and As(III)) and Se (Se(VI) and Se(IV)) using mixed ion-pairing reagents followed by ICPMS detection is described. The separation was accomplished in less than 4 min on Capcell C18 RP column using mixed ion-pairing modifier containing 5 mM of butane sulfonic acid (BSA), 2 mM malonic acid, 0.30 mM hexane sulfonic acid (HSA) and 0.5% methanol of pH 2.5. All four species were resolved with retention times of 2.4, 2.6, 3.0, and 3.1 min for Se(VI), As(V), As(III), and Se(IV), respectively. The detection limits were less than 0.08 and 0.77 μg l⁻¹ for arsenic and selenium species, respectively. The relative standard deviation of the proposed method for arsenic (at 2.5 μg l⁻¹) and selenium (at 10 μg l⁻¹) was less than 3.7 and 4.8%, respectively. The technique was used to determine inorganic oxyanions of As and Se in water samples (tap, well, and river) and extracts of coal fly ash and sediment. Low power microwave digestion was employed for extraction from fly ash and sediment samples.     

A Bioresistant Nitroxide Spin Label for In‐Cell EPR Spectroscopy: In Vitro and In Oocytes Protein Structural Dynamics Studies

Approaching protein structural dynamics and protein–protein interactions in the cellular environment is a fundamental challenge. Owing to its absolute sensitivity and to its selectivity to paramagnetic species, site‐directed spin labeling (SDSL) combined with electron paramagnetic resonance (EPR) has the potential to evolve into an efficient method to follow conformational changes in proteins directly inside cells. Until now, the use of nitroxide‐based spin labels for in‐cell studies has represented a major hurdle because of their short persistence in the cellular context. The design and synthesis of the first maleimido‐proxyl‐based spin label (M‐TETPO) resistant towards reduction and being efficient to probe protein dynamics by continuous wave and pulsed EPR is presented. In particular, the extended lifetime of M‐TETPO enabled the study of structural features of a chaperone in the absence and presence of its binding partner at endogenous concentration directly inside cells.     

Synthesis and spectral characterization of lanthanide complexes with sulfamethoxazole and their antibacterial activity

A series of nonelectrolytic lanthanide(III) complexes, [ML₂Cl₃]·2H₂O, where M is lanthanum(III), praseodymium(III), neodymium(III), samarium(III), gadolinium(III), terbium(III), dysprosium(III), and yttrium(III), containing sulfamethoxazole ligand (L) are prepared. The structure and bonding of the ligand are studied by elemental analysis, magnetic susceptibility measurements, IR, ¹HNMR, TG/DTA, X-ray diffraction studies, and electronic spectra of the complexes. The stereochemistry around the metal ions is a monocapped trigonal prism in which four of the coordination sites are occupied by two each from two chelating ligands, sulfonyl oxygen, and nitrogen of the amide group and the remaining three positions are occupied by three chlorines. The ligand and the new complexes were tested in vitro to evaluate their activity against the bacteria Escherichia coli and Staphylococcus aureus. The text was submitted by the authors in English.