Adsorption of tracer cations,and the separation of carrier-free95Nb from95Zr,XU1 from U and45Ca from46Sc on titanium phosphate column

Titanium phosphate as ion exchanger for column operation has been prepared by mixing TiCl₄ and H₃PO₄ in suitable proportion. The ratio of titanium: phosphate was obtained to be 1:2.02. The uptake of Na⁺, K⁺, Rb⁺, Cs⁺, Ag⁺, Ca²⁺, Sr²⁺, Ba²⁺, Pb²⁺, Sc³⁺, Co³⁺, Y³⁺, Tb³⁺, Zr⁴⁺ and Th⁴⁺ cations at very small concentrations has been studied on this exchanger. The data indicated that the different cations are adsorbed in the exchanger by different mechanisms. Radiochemical separations of carrier free⁹⁵Nb from⁹⁵Zr, UX₁ from U and⁴⁵Ca from⁴⁶Sc have been achieved by adopting very simple chemical procedures through a column of titanium phosphate. The -spectrum of the separated⁹⁵Nb, UX₁ and⁴⁶Sc showed that the products are of high radionuclidic purity. The individual separation procedures took less than 20 min and the yields are quantitative.     

Oscillating laminar electrokinetic flow in infinitely extended rectangular microchannels

This paper has addressed analytically the problem of laminar flow in microchannels with rectangular cross-section subjected to a time-dependent sinusoidal pressure gradient and a sinusoidal electric field. The analytical solution has been determined based on the Debye-Hückel approximation of a low surface potential at the channel wall. We have demonstrated that Onsager's principle of reciprocity is valid for this problem. Parametric studies of streaming potential have shown the dependence of the electroviscous effect not only on the Debye length, but also on the oscillation frequency and the microchannel width. Parametric studies of electroosmosis demonstrate that the flow rate decreases due to an increase in frequency. The obtained solutions for both the streaming potential and electroosmotic flows become those for flow between two parallel plates in the limit of a large aspect ratio.     

Ion exchange separation of different oxidation states of sulphur formed by35Cl(n,p)35S reaction in alkali halides

Cesium and potassium were determined in muscle-tissues of squid, dover sole, albacore, and bocaccio by NAA. Potassium was measured instrumentally, while cesium was radio-chemically separated. For the separation of cesium, hydrated antimony pentoxide (HAP) was used to retain²⁴Na, and ammonium molybdophosphate (AMP) was used to absorb quantitatively the radiocesium,^134mCs. The cesium and potassium contents were based on measuring the short-lived radionuclide of cesium, 2.90 h-^134mCs, and 12.4 h-⁴²K. The mean concentrations of cesium found, based on 3–4 replicate measurements for each fish, were: 4.18±0.32 ng/g squid, 11.51±0.30 ng/g dover sole, 43.64±1.03 ng/g albacore, and 56.85±3.61 ng/g bocaccio. The mean concentrations of potassium found were: 1.28±0.10 mg/g squid, 2.78±0.29 mg/g dover sole, 3.69±0.06 mg/g albacore, and 4.18±0.10 mg/g bocaccio.     

Absorption and fluorescence behavior of cytosine irradiated at different pH and in the presence of Cu(II) ions at neutral pH

Dilute aqueous solutions of cytosine were irradiated with⁶⁰Co -rays under N₂O saturated conditions at different pH and in the presence of Cu(II) ions at neutral pH. The base degradation decreased from neutral to acidic and basic conditions. In the presence of metal ions at neutral pH conditions there was a significant increase in the base degradation compared to that in the absence of metal ions under similar conditions. From the difference absorption spectra and fluorescence behavior of the irradiated solutions it was observed that the major radiolytic products of cytosine under different conditions are cytosine glycols, 5-hydroxycytosine, hydroxy-hydrocytosine and cytosine dimers. The yields of dimers is maximum in neutral conditions and it decreased from basic to acidic conditions. However, in the presence of Cu(II) ions formation of cytosine dimers is completely restricted and there is an increase in the yields of cytosine glycol, hydroxy-hydrocytosine and 5-hydroxycytosine. From the post-radiolytic changes in absorption and fluorescence behavior of irradiated solutions, it is revealed that some of the radiolytic products, namely cytosine glycol and hydroxy-hydrocytosine decompose to 5-hydroxycytosine and cytosine, respectively.     

Thermal hazards evaluation for sym-TCB nitration reaction using thermal screening unit (TSU)

A set of experiments was conducted in an HEL thermal screening unit with synthetic mixtures of raw materials in various proportions to evaluate the potential thermal hazards at normal and offset process conditions for nitration of symmetrical trichlorobenzene (TCB). The experiments were carried out in the adiabatic condition. The onset temperatures of the exotherms along with maximum temperature and pressure rise data for the desired and undesirable reactions were obtained. In the presence of excess nitric acid and oleum, the reaction shows a severe thermal runaway at the onset temperature of 138°C with a rapid rise in temperature and pressure leading to a potential explosion. This revised version was published online in July 2006 with corrections to the Cover Date.     

Determination of gold by neutron activation analysis in some selected rocks and plants and its bearing on the genesis of auriferous quartz veins in Singhbhum district,Bihar, Eastern India

Present investigation deals with neutron activation analysis of gold in some varieties of geological samples related to auriferous quartz veins. A few plant specimens of the area were also analyzed. The gold contents in the rock samples as determined by the destructive way of analysis vary in the range 10⁻⁵ to 10⁻⁷%. In case of plant samples, however, the non-destructive method of analysis of the plant ashes was followed and the concentration of gold was found to be of the order of 10⁻⁵%. In plants, besides gold, some associated elements, such as La, Ce, Sm, Lu, Zr, Hf, Se, W, As and Sb were also identified.     

Low temperature thermal conductivity and specific heat of elastomers

The specific heat C and thermal conductivity κ of polybutadiene are characteristic of all non-crystalline materials at temperatures below ≈ K, reflecting the presence of localized excitations. The changes in C and κ with variation in crosslinking suggest that the relaxation times of the localized excitations may vary with crosslink density. Extension of an elastomer does not reveal a change in density of localized excitations as monitored by measuring κ, possibly because other phonon scattering mechanisms mask the effect. For T ? 10 K the phonon mean-free-path is independent of the microscopic anisotropy of the elastomer.     

Selective Reduction of Dienones Synthesis of Intermediates for Sesqui-and Diterpenes

The tricyclic enones 15–20, intermediates to several sesqui-and diterpenes, have been synthesised in high yields involving selective hydrogenation of the disubstituted double bonds of the dienones 9-14 respectively in the presence of tris (triphenylphosphine)rhodium(I) chloride catalyst.     

Comprehensive and High-throughput Electrolysis of Water and Urea by 3–5 nm Nickel and Copper Coordination Polymers

Metal-organic coordination polymers (CP) have attracted the scientific attention for electrochemical water oxidation as it has the similar coordination structure like natural photosynthetic coordinated complex. However, the harsh synthesis conditions and bulky nature pose a major challenge in the field of catalysis. Herein, 3–5 nm CP particles synthesized at room temperature using aqueous solutions of Ni²⁺/Cu²⁺ and 2,5-dihydroxyterepthalic acid as precursor were applied for alkaline water and urea electrolysis. The overpotential required is only 300 mV at 10 mA cm⁻² by Nano-Ni CP for water oxidation, with turnover frequency (TOF) of 21.4 s⁻¹ which is around 8 times higher than its bulk-counterpart. Overall water and urea splitting were achieved with Nano-Cu (−) ∥ Nano-Ni (+) couple on Ni foam at 1.69 and 1.52 V to achieve 10 mA cm⁻², respectively. High electrochemical surface area (ECSA), high TOF, and enhanced mass diffusion are found to be the key parameters responsible for the state-of-the-art water and urea splitting performances of nano-CPs as compared to their bulk counterparts.     

Degeneracy in one dimension: Role of singular potentials

That the bound energy eigenstates of one-dimensional quantum systems can be degenerate in the presence of specific singular or supersingular potentials is demonstrated by choosing a family of bistable and other oscillators. Relevance of our study to spectroscopic observations is noted. Quasi-degeneracy is found even in the absence of any singularity in the potential and the importance of tunneling is highlighted in this context to analyze the general nature of such potentials leading to double degeneracy. Additionally, the case of spiked oscillators is discussed with particular reference to the “Klauder phenomenon,” revealing clearly that the mere presence of singularity in the potential is not a sufficient criterion for the occurrence of degeneracy. © 1996 John Wiley & Sons, Inc.