The determination of technetium-99 in seawater and marine algae

Technetium-99 is preconcentrated from acidified seawater containing a trace of bromine by adsorbing it as the pertechnetate ion on the anion exchanger Duolite A101D. After elution with 4 M nitric acid, it is purified from other radionuclides by scavenging with hydrous iron(III) oxide and extracting from 5 M sodium hydroxide medium into methyl ethyl ketone. The organic phase is then evaporated and technetium is electrodeposited from oxalic acid medium onto a bronze disc and counted with a low background β-counter. Overall recovery is > 90% and the precision is ±0.2 pCi l^-1 at a technetium level of 0.6–1.0 pCi l^-1. Concentrations of the radionuclide in the central Irish Sea were found to lie in the range 0.4–2 pCi l^-1. The same analytical scheme can be used for determining the element in nitric acid digests of marine algae.     

New anthraquinones from the stem of Morinda citrifolia Linn

Studies on the chemical constituents of the stem of Morinda citrifolia, Linn. have led to the isolation of two new compounds, morindicinone (=2-hydroxy-1,8-dimethoxy-7-methoxymethylanthraquinone, 1) and morindicininone (=4-hydroxymethyl-1,3-dimethoxyanthraquinone, 2), as well as two known constituents, 2-hydroxyanthraquinone (3) and 2-methoxyanthraquinone (4). Their structures were elucidated by spectral analysis including 2D-NMR techniques.     

A new flavanoid from the flowers of Azadirachta indica

Studies on the chemical constituents of the flowers of Azadirachta indica have led to the isolation of one new flavanone named as azharone (5,7,4'-trihydroxy-3'-(3'-methyl-2',3'-epoxybutyl)flavan-4-one (3)) along with two known constituents azadirone (1), and isoazadironolide (2). Their structures have been elucidated through spectral studies including 2D-NMR (COSY-45, NOESY, J-resolved, HMQC, HMBC) experiments.     

Creeping flow analysis of slightly non-Newtonian fluid in a uniformly porous slit

This paper provides the analysis of the steady, creeping flow of a special class of slightly viscoelastic, incompressible fluid through a slit having porous walls with uniform porosity. The governing two dimensional flow equations along with non-homogeneous boundary conditions are non-dimensionalized. Recursive approach is used to solve the resulting equations. Expressions for stream function, velocity components, volumetric flow rate, pressure distribution, shear and normal stresses in general and on the walls of the slit, fractional absorption and leakage flux are derived. Points of maximum velocity components are also identified. A graphical study is carried out to show the effect of porosity and non-Newtonian parameter on above mentioned resulting expressions. It is observed that axial velocity of the fluid decreases with the increase in porosity and non-Newtonian parameter. The outcome of this theoretical study has significant importance both in industry and biosciences.     

Radiation-induced synthesis of RuO2 nanoparticles by thermal decomposition of Ru-tris-acetylacetonate

Pure-phase RuO₂ nanoparticles were obtained by thermal decomposition of unirradiated and γ-irradiated Ru-tris-acetylacetonate precursors. Several influencing factors including absorbed dose, calcination times and temperatures and addition of surfactants were thoroughly investigated. The newly synthesized RuO₂ nanoparticles were characterized by X-ray diffraction, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. The results showed that the best conditions for the preparation of mono-dispersed RuO₂ nanoparticles were achieved by calcinations of unirradiated Ru-tris-acetylacetonate for 6 h at 600°C. For γ-irradiated Ru-tris-acetylacetonate with 10² Gy total γ-ray doses, the optimal conditions for RuO₂ preparation were calcination for 2 h at 200°C. Thermal stability of RuO₂ nanoparticles was studied using thermogravimetric (TG) and differential thermal analysis (DTA) techniques, and the results were evaluated and discussed.     

A Stabilized,Rationally Mode-Locked 10GHz Erbium Fiber Laser

A rationally mode-locked 10 GHz erbium fiber laser stabilized by a simple technique for extended time operation is described. The laser generates stable ~ 5 ps pulses that can be used in communications experiments. Back-to-back bit error rate (BER) measurements confirmed error-free operation for 6-8 hours, giving an error floor below 10 -14 . A receiver sensitivity of -19.7 dBm was achieved for BER of 10 -9 .     

Sub-ppt level voltammetric sensor for Hg2+ detection based on nafion stabilized l-cysteine-capped Au@Ag core-shell nanoparticles

Journal of Solid State Electrochemistry - Bimetallic nanoparticles (BMNPs) have received considerable attention due to their distinctive properties when compared to the corresponding monometallic...