Low temperature synthesis of fluorescent ZnO nanoparticles

Fluorescent ZnO nanoparticles have been prepared by mixing aqueous solutions of zinc nitrate and ammonium carbonate in the presence of a non-ionic surfactant, Tween-80. Increased concentrations of the surfactant were found to affect both the morphology and purity of the synthesized ZnO nanoparticles. XRD, SEM, FTIR, TGA and Confocal laser scanning microscopy were employed to characterize the as-prepared samples. ZnO nanoparticles ranging in particle size from 11 to 15 nm were formed at the reaction temperature of 70-80 °C. The results of FTIR and TGA analysis indicate the self assembly of Tween molecules on the surface of ZnO nanoparticles. A bright emission in the visible region from the as-prepared ZnO nanoparticles was recorded using confocal laser scanning microscopy. This property of the as-prepared nanoparticles may find potential application in bio-imaging.     

Giant magnetostriction in rapidly quenched Fe–Ga?

Substituting Fe by nonmagnetic Ga causes a dramatic increase of the magnetostriction. The reason for this effect is related to structure and also due to softening of the elastic properties. Of special interest is that in literature “giant” magnetostriction values (up to 2100 ppm) for rapidly quenched Fe–Ga (15–20% Ga) ribbons were reported. In this work, careful investigations using a strain gauge method as well as a capacitance cell were performed. Especially for the case applying an external field perpendicular to the ribbon plane, it is demonstrated that bending effects can occur and they are difficult to avoid without introducing any stress into the sample. This effect leads to large signals in the strain gauge of more than ±3000 ppm, which sign depends on the occurrence of strain or stress. Experiments on a 25-μm-thin Fe foil leads to similar results. Avoiding bending by gluing ribbons or thin foils or splat-cooled thin pure Ni on a thin plastic plate, gave magnetostriction values close to those of polycrystalline bulk materials.     

EPR Study of γ-Irradiated UHMWPE Doped with Vitamin E: Assessment of Thermal Effects on the Organic Radicals During Vitamin E Diffusion

Thermal effects on ultra-high-molecular-weight polyethylene (UHMWPE) residual radicals during the vitamin E diffusion process were studied in detail. Electron paramagnetic resonance (EPR) technique showed a significant reduction in concentrations of radiation-induced primary (alkyl (–CH₂– ^?CH–CH₂–), allyl (–CH₂–^?CH=CH–CH–CH₂–) and polyenyl (–^?CH–[CH=CH–] _m –) with m > 3) radicals for both control and vitamin E-doped samples. The concentrations of radiation-induced primary radicals (RIPRs) were found to decrease proportionally with the heat/diffusion time. While the EPR spectra of the control samples showed only polyethylene (PE) radicals, the spectra of vitamin E-doped samples were found to exhibit vitamin E radicals in addition to PE radicals. Of particular interest, the heat involved during vitamin E diffusion plays a significant role in reducing the radiation-induced primary radicals of UHMWPE. For 120 min of heat/diffusion time, the available quantity of primary radicals in control samples were found to be ~7.5 % of initial radicals. The leftover amounts of these primary radicals for vitamin E-doped samples were approximately ~10.0 %. In addition to this, EPR power saturation techniques were also used to assess the effects of initial heat/diffusion treatment on the oxygen-induced residual radicals (OIRRs): R₁ (–^?CH–[CH=CH–] _m –) with m > 3 and R₂ (^?OCH–[CH=CH–] _m –) with m = 2 or 3. It was found that the concentration of OIRRs also decreases proportionally with initial heat/diffusion time. The remaining amount of OIRRs relative to leftover RIPRs after heat/diffusion was found to be approximately 4.0 % in controls and was still found to be 10.0 % in vitamin E-doped UHMWPE. This may indicate that vitamin E slows down the oxidation processes, which may contribute to the strong oxidation resistance of vitamin E-doped UHMWPE.     

Amperometric detection of nitric oxide using a glassy carbon electrode modified with gold nanoparticles incorporated into a nanohybrid composed of reduced graphene oxide and Nafion

Microchimica Acta - The authors show that the electrocatalytic performance toward the detection of nitric oxide (NO) can be enhanced by making use of gold nanoparticles (AuNP) in a matrix...     

Innovative kinetic and thermodynamic analysis of a purified superactive xylanase from Scopulariopsis sp.

Two isoenzymes of endo-1,4-beta-xylanase (EC 3.2.1.8) from Scopulariopsis sp. were purified by a combination of ammonium sulfate precipitation, hydrophobic interaction, and anion-exchange and gel filtration chromatography. The native mol wts of the least acidic xylanase (LAX) and the highly acidic xylanase (HAX) were 25 and 144 kDa and the subunit mol wts were 25 and 36 kDa, respectively. The kcat values of LAX and HAX for oat-spelt xylan at 40 degrees C, pH 6.5, were 95,000 and 9900 min-1 and the Km values of LAX and HAX were 30 and 3.3 mg/mL. The thermodynamic activation parameters of xylan hydrolysis showed that the high activity of LAX when compared with HAX was not owing to a reduction in DeltaH# but was entropically driven. High-performance liquid chromatography analysis of the degradation products showed that LAX formed both xylotrioses and xylobioses, but HAX predominantly formed xylotrioses. The half-lives of LAX and HAX at 50 degrees C in 50 mM 2-N-morpholino ethanesulfonic acid (MES), pH 6.5 buffer were 267 and 69 min, respectively. Thermodynamic analysis showed that at lower temperatures, the increased thermostability of LAX (DeltaH#=306 kJ/mol) compared with HAX (DeltaH#=264 kJ/mol) was owing to more noncovalent surface interactions. At higher temperatures, LAX (DeltaS*=-232 J/[mol.K]) was more thermostable than HAX (DeltaS*=490 J/[mol.K]) owing to a more ordered transition-state conformation. An energy-activity diagram was introduced showing that kcat/Km does not successfully explain the true kinetic behavior of both xylanase isoenzymes. The simultaneously thermostable and highly active LAX could be utilized in biotechnological processes involving xylan hydrolysis.     

Synthesis and Crystal Structure of a Cyano-Bridged Bimetallic Nickel(II)–Silver(I) Complex, [Ni(dmen)<Subscript>2</Subscript>{Ag(CN)<Subscript>2</Subscript>}<Subscript>2</Subscript>] · 0.5H<Subscript>2</Subscript>O

A cyano-bridged heteronuclear bimetallic complex [Ni(dmen)₂{Ag(CN)₂}₂] · 0.5H₂O (dmen = N,N′-dimethylethylenediamine) has been prepared and characterized by IR spectroscopy and X-ray Crystallography. The compound crystallizes in the monoclinic space group P2₁/c. The crystal structure of the complex consists of two independent centrosymmetric trinuclear molecules made up of a [Ni(dmen)₂] ⁺² unit linked to two [Ag(CN)₂]⁻ anions in a trans configuration. The trinuclear units are joined by hydrogen bonding to form irregular chains.     

Efficient power computation for r out of m runs rules schemes

In this article we develop a power computation code in the R language which provides an easy to use tool to researchers in designing Shewhart control charts. It enables researchers to use different existing and newly introduced sensitizing rules and runs rules schemes designed for Shewhart-type control charts for location and spread. The code provides researchers to compute the power for different options of r out of m rules/schemes. The code is flexible to apply for any sample size, false alarm rate, type of control limits (one- or two-sided), amount of shift in the process parameters and a variety of popular distributions for commonly used Shewhart-type control charts (i.e. ${\bar{{X}} ,R ,S}$ and S ² charts). These mentioned benefits of the developed functional code are only partially found in features of the existing software packages and these programs may be enhanced by adding the features of the developed code as a function in their libraries dealing with quality control charting.     

Bioactive Heteroleptic Bismuth(V) Complexes: Synthesis,Structural Analysis and Binding Pattern Validation

Heteroleptic triorganobismuth (V) complexes of general formula, R₃Bi(OOCR')₂ ( 1 – 7 ), where R = C₆H₅ ( 1 – 3 ), p‐CH₃C₆H₄ ( 4 – 7 ) and R' = 3,5‐Cl₂C₆H₃ ( 1 , 5 ); 3,4,5‐(OCH₃)₃C₆H₂ ( 2 , 6 ); 3‐CH₃C₆H₄ ( 3 , 7 ); 2‐OH‐3‐OCH₃C₆H₃ ( 4 ) have been synthesized and fully characterized by FT‐IR, ¹H &¹³C NMR spectroscopy, single crystal X‐ray crystallography and elemental analysis. The molecular geometry observed for the compounds is predominantly distorted trigonal bipyramidal, the fact which was subsequently authenticated through X‐ray analyses for ( 1 – 4 ). All the synthesized compounds have been bio‐assayed for antileishmanial (Leishmania tropica KWH23) and Jack beans urease inhibitory activity, and human Lymphocytes were used to measure the general toxicity. Of these, ( 4 ) proved to be highly effective against the target species (Leishmania tropica KWH23), while being non‐toxic towards the mammalian cells at levels below 0.74 μgmL^?1, making it highly promising drug candidate. The high activities for ( 2 , 4 , and 6 ) against Jack beans Urease as compared to the reference standard demonstrate their significance in searching of therapeutic agents in future programs. The significant binding score of ( 2 & 4 ) against H. pylori in molecular docking studies further revealed their importance in future drug discovery processes.