An investigation on visible luminescence of Ho activated LBTAF glasses

Different concentrations of Ho³⁺-doped lead borate titanate aluminum fluoride (LBTAFHo) glasses with chemical composition of PbO-H₃BO₃-TiO₂-AlF₃-Ho₂O₃ were prepared by the melt quenching method. The spectral properties were investigated using the absorption, emission and decay measurements. The experimental oscillator strengths were calculated from the area under the absorption bands. Applying Judd-Ofelt theory, the intensity parameters (Ω_{λ=2, 4, 6}) were calculated, by the least square fit approach from which the radiative transition rates, luminescence branching ratios and radiative decay times were determined. The photoluminescence spectra revealed the quenching of luminescence intensity beyond 1.0 mol% of Ho³⁺ ion concentration. To investigate the luminescence potentiality of ⁵F₄→⁵I₈ emission level, the effective bandwidth and the stimulated emission cross-section were determined. The quenching in experimental decay time is attributed to the resonance energy transfer among the excited Ho³⁺ ions.     

Cycloaddition profile of pentafulvenes with 3-oxidopyrylium betaine: experimental and theoretical investigations

A detailed investigation on the effect of solvent polarity, temperature, and microwave irradiation on periselectivity in cycloaddition reactions of pentafulvenes with 3-oxidopyrylium betaine is described. The base catalyzed generation of 3-oxidopyrylium betaine in CHCl₃ resulted in the exclusive formation of [6+3] adducts. With increase in solvent polarity and temperature, mixtures of [6+3] and [3+2] adducts were formed, where as under microwave irradiation, [3+2] adducts were formed exclusively. The experimental results have been rationalized on the basis of theoretical calculations.     

Stereochemical preference of Candida parapsilosis ATCC 7330 mediated deracemization: E- versus Z-aryl secondary alcohols

The stereochemical preference of the biocatalyst, Candida parapsilosis ATCC 7330, was investigated with respect to the E/Z configuration in the deracemization and the asymmetric reduction of aryl secondary alcohols and prochiral ketones, respectively. The biocatalyst preferred the E-isomers over Z-isomers as substrates as evidenced from the experimental results of >99% ee and up to 86% isolated yield for E-secondary alcohols. The synthesis of enantiomerically pure E-4-phenylbut-3-ene-1,2-diol (ee >99%, isolated yield 86%) by whole cell mediated deracemization is reported here for the first time. The geometric preference of the enzymes was confirmed by using the cell free extract of this biocatalyst. Mechanistic insights using in silico studies showed that the E-isomers when located in the active site are favourably placed with respect to the catalytic triad (Ser-Tyr-Lys) for hydride transfer from NADPH.     

Aptamer-based fluorometric determination of norovirus using a paper-based microfluidic device

Microchimica Acta - The authors describe a rapid and highly sensitive point-of-care device for rapid determination of noroviruses, a leading cause of acute gastroenteritis. The assay is based on...     

Effects of structural properties of silicon carbide-derived carbons on their electrochemical double-layer capacitance in aqueous and organic electrolytes

High surface area silicon carbide-derived carbons (Si-CDCs) synthesized by chlorination of beta silicon carbide (βSiC) with two different particle sizes (6 μm and 50 nm) show different porosities with graphitic structure. Transmission electron microscopy, Raman spectroscopy and argon (Ar) and carbon dioxide (CO₂) sorption analyses are used to examine the textural properties of the Si-CDCs. The results show that the particle size of the precursor affects the surface area and porosity of carbons. Furthermore, an additional heat treatment of the Si-CDC with 50-nm particle size for 24 h at 1,000 °C results in a collapse of the pore structure and reduces the surface area. The capacitive behaviours are investigated in H₂SO₄ and in tetraethyl ammonium tetrafluoroborate (TEABF₄)/acetonitrile (AN). The electrochemical performance of the Si-CDCs is influenced by the particle size, surface area, pore volume and pore size distribution. The Si-CDCs exhibit capacitances in 1 M H₂SO₄ of up to 179 F g^?1 and very stable charge–discharge performance over 5,000 cycles. This study shows the crucial importance of ultramicropores less than 1 nm combined with nanosized particles for achieving high capacitance in aqueous electrolyte. Moreover, the graphitic degree at the surface of the Si-CDCs enhances considerably the rate capability and stability in both electrolytes.     

A Novel Synthesis of 5-Aryltropoxe Derivatives

The reaction of substituted arylboronic acids with 5-bromo-2-methoxytropone catalyzed by palladium(0) complex furnished 5-arylated tropone derivatives in good yield.     

Nonspecific Effect of Double-Stranded (ds) RNA on Prophenoloxidase (proPO) Expression in Penaeus monodo n

RNA interference-mediated silencing is an effective way of controlling white spot syndrome virus (WSSV). However, the effect of RNAi on the innate immune mechanism is not well understood. Prophenoloxidase (proPO) is an important component of the shrimp innate immunity. In the present study, nonspecific effect of two double-stranded (ds)RNA-expressing constructs, one targeting vp28 gene of WSSV (pCMV-VP28-LH) and another targeting green fluorescent protein (GFP) (pCMV-GFP-LH) on proPO2 gene expression, is investigated. mRNA expression levels of proPO2 in hemocytes of DNA construct-injected shrimp were estimated using real-time PCR with elongation factor 1-α as internal control. Empty vector (pcDNA)-injected shrimp were used as experimental control. In pCMV-VP28-LH-injected shrimp, proPO2 showed significant upregulation until 48 h post-injection (p.i.). Similarly, pCMV-GFP-LH-injected animals showed high levels of expression until 72 h p.i. WSSV-challenged animals, compared to pcDNA-injected control group, showed no significant change in expression of the gene until 24 h. However, an increased expression was noticed at 48 h p.i. Our results suggest that neither the plasmids nor the long hairpin RNA expressed by the constructs has any nonspecific silencing effect on the proPO2 expression. On the contrary, the consistent upregulation of proPO2 observed in shrimp injected with dsRNA at early time-points indicates the possibility of nonspecific protection against WSSV infection.     

Silicon‐containing trifunctional and tetrafunctional cyanate esters: Synthesis,cure kinetics,and network properties

The synthesis and physical properties of new silicon‐containing polyfunctional cyanate ester monomers methyl[tris(4‐cyanatophenyl)]silane and tetrakis(4‐cyanatophenyl)silane, as well as polycyanurate networks formed from these monomers are reported. The higher crosslinking functionality compared to di(cyanate ester) monomers enables much higher ultimate glass transition temperatures to be obtained as a result of thermal cyclotrimerization. The ability to reach complete conversion is greatly enhanced by cocure of the new monomers with di(cyanate ester) monomers such as 1,1‐bis(4‐cyanatophenyl)ethane. The presence of silicon in these polycyanurate networks imparts improved resistance to rapid oxidation at elevated temperatures, resulting in char yields as high as 70% under nitrogen and 56% in air in the best‐performing networks. The water uptake in the silicon‐containing networks examined is 4–6 wt % after 96 h of immersion at 85 °C, considerably higher than both carbon‐containing and/or di(cyanate ester) analogs. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 767–779     

Spectral and electrochemical investigation of 1,8-diaminonaphthalene upon encapsulation of p-sulfonatocalix[4]arene

The ligand salt, Me₆[14]diene·2HClO₄ (L·2HClO₄) was prepared by condensation of acetone and ethylene diamine in the presence of perchloric acid. On reduction of this diene ligand salt, L·2HClO₄ with sodium borohydride, the two isomeric ligands, ‘tet-a’ and ‘tet-b’ were produced. The ligands, on reaction with ZnX₂ (X=Cl, ClO₄, NO₃ or CH₃COO) and ZnSO₄ produced the corresponding complexes. These complexes have been characterized on the basis of elemental analyses; IR, UV–Vis and ¹H-NMR spectroscopies; magnetic and conductance data. Based on these data, all of the complexes of the diene ligand L, as well as the perchlorate complexes of all of the ligands attained a square-pyramidal arrangement, whereas the complexes of ‘tet-a’ and ‘tet-b’, with X=NO₃, Cl or CH₃COO and with ZnSO₄ salt, were octahedral. Moreover, all complexes were monometallic except the nitrato complex, [(ZnL)₂(µ-NO₃)](ClO₄)₃ which is bimetallic. The structure of [(ZnL)₂(µ-NO₃)](ClO₄)₃ has been confirmed by X-ray crystallography. In this complex the zinc centres lie within a N₄O donor set, with the four nitrogen donors from L and one of the oxygen atom stemming from the bridging NO₃. The complexes show different electrolytic behavior in different solvents. The antibacterial activities of the ligands and complexes towards different phytopathogenic bacteria have been investigated.