Complete and incomplete fusion in12C+93Nb and16O+89Y reactions

Excitation functions for the evaporation residues for the reactions¹²C+⁹³Nb and¹⁶O+⁸⁹Y in the projectile energy range of 4 to 6.5 MeV/amu have been measured using off-line gamma spectrometry. The excitation functions for neutron(xn), proton(pxn) and one alpha(xn) emission channels are practically similar for both the reactions. However the products formed by two alpha(2xn) emission show much higher cross sections in the¹²C+⁹³Nb than the¹⁶O+⁸⁹Y system. This has been explained in terms of the incomplete fusion process involving transfer of an alpha particle from the projectile to the target in the former case.Authors thank Shri D.C. Ephraim for making the rolled metal foils and the operation crew of PELLETRON facility for their help in carrying out the irradiations. Authors are grateful to Dr. P.R. Natarajan, Head Radiochemistry Division for his keen interest in this work.     

Application of medium energy plasma focus device in study of radioisotopes

Pulsed neutrons generated in a plasma focus device are used for the thermal neutron activation analysis (TNAA) of selected three elements having widely different half-lives varying from a few seconds to a few days [Dysprosium (Dy), Manganese (Mn) and Gold (Au)]. Neutron pulse having strength of $(1.2\pm 0.3)\times {10}^9$ neutrons/pulse with a pulse width of $46\pm 5\text{ns}$ is produced by “MEPF-12” device operated at a filling gas (deuterium + 0.5% krypton) pressure of 3 mbar. The fast 2.45 MeV D–D neutrons are thermalized before irradiating the sample. The decay gammas from the radioisotopes ^165mDy ($T_{1/2}=1.26\text{min.}$), ⁵⁶Mn ($T_{1/2}=2.58\text{hrs.}$), and ¹⁹⁸Au ($T_{1/2}=2.69\text{days}$) produced via reactions, ¹⁶⁴Dy($n,\gamma$)^165mDy, ⁵⁵Mn($n,\gamma$) ⁵⁶Mn, and ¹⁹⁷Au($n,\gamma$) ¹⁹⁸Au respectively are counted off-line in a lead shielded well type $76\times 76{\text{mm}}^2$ NaI(Tl) detector coupled to a calibrated 2048 channel analyzer. The values of half-lives evaluated from the measured decay gammas, $1.43\pm 0.3\text{min.}$, $2.56\pm 0.5\text{hrs.}$ and $2.84\pm 0.6\text{days}$ respectively for the radioisotopes of Dy, Mn and Au, are seen to be close to the values reported in literature.     

Determination of 90Sr in environmental samples using solid phase extraction chromatography

The p-tert-butyl calix[4]arene thiophenol derivative was successfully synthesized with reflux condition and was characterized by FT-IR and ¹H-NMR. This work mainly adopted the method of controlling variables. The results showed that the optimum pH value, temperature and extraction time were respectively 4.5, 25 °C and 90 min. By calculating the data of the enthalpy change and gibbs free energy, indicating that the process of reaction was an exothermic and spontaneous process, and it demonstrated a close agreement with pseudo-second-order kinetic model. It is also found that the coexisting cations on the extraction of uranium had greater influence.

     

Dispersion data for open suspended microstrip on Alumina and Gallium Arsenide substrates

Accurate dispersion data for open suspended microstrop on RT-duroid and fused quartz substrates was presented in an earlier paper by the authors. The present work repeats the same exercise for two more commonly used substrate materials, namely, Alumina and Gallium Arsenide. The results are new and will be a very useful addition to the millimeter-wave circuit designer's library.     

New modifications in 15 UD pelletron at nuclear science centre

The 15 UD pelletron at NSC has been operational and performed well during the last 11 years. There have been major modifications performed for upgradation of pelletron system over this period. Major upgradations which have been implemented are new resistor network system for voltage gradient, doublet to singlet unit conversion for accelerator units, turbopump based gas stripper system etc. In addition accelerator mass spectroscopy program has also been started. A new multi-cathode source, Wien filter etc. have been procured and will be added soon in the system. An overview of the most significant upgradations undertaken and other activities for the system are being reported in the present paper.     

Quantum interference effect in laser patterned BSCCO thick film

DC SQUID structure consisting of two microbridges and a circular hole was patterned on BSCCO thick film using laser ablation technique. Quantum interference effects on these patterned films were studied at fixed biasing current by applying changing magnetic field. The SQUID with 100 μm × 70 μm microbridges showed noisy and irregular V-B behaviour whereas the SQUID containing smaller microbridges showed better V-B characteristic. Temperature dependence of the I-V and V-B characteristics of the SQUID is also reported.     

Provably secure dynamic identity-based three-factor password authentication scheme using extended chaotic maps

With the aim of guaranteeing secure communication through public networks, three-factor password authentication (TF-PWA) scheme plays a key role in many internet applications. Since in TF-PWA scheme, the communicating entities can mutually authenticate each other and generate a shared session key, which will be used for secure exchange of messages in succeeding communication among them. As a result, the TF-PWA schemes gain enormous consideration in recent years. More recently, due to light-weight features of the extended chaotic map, it is also extensively applied in designing of public key encryption, key agreement, image encryption, S-box, hash function, digital signature, password authentication, etc. The aim of this paper was to design a dynamic identity-based three-factor password authentication scheme using extended chaotic map (ECM-TF-PWA) in the random oracle model. The proposed scheme is provably secure based on the intractability assumption of chaotic map-based Diffie–Hellman problem. The informal security analysis gives the evidence that our scheme protects all attacks and provides functionality attributes that are needed in a three-factor authentication system. Besides, the performance discussion shows that our scheme performs better than others in respect of computation and communication cost.     

Poly(PEGDMA‐MAA) copolymeric micro and nanoparticles for oral insulin delivery

Poly(ethylene glycol) dimethacrylate (PEGDMA) and methacrylic acid (MAA) based micro and nanoparticles were prepared and evaluated as a carrier for oral delivery of insulin. PEGDMA was synthesized by esterification reaction of the PEG4000 with MAA in the presence of an acid catalyst. Particles of different size were prepared by emulsion polymerization reaction using different concentration of sodium lauryl sulphate (SLS) as an emulsifying agent. Synthesized copolymeric particle were characterized by attenuated total reflectance‐Fourier transform infrared spectroscopy (ATR‐FTIR), scanning electron microscopy, and acid value. The mean particle diameter of the polymeric micro and nanoparticles at various physiologically relevant pH values was measured using dynamic light scattering. Insulin loading efficiency of the particles was found to be directly proportional to the particle size and inversely proportional to the acid value of the particles. In vitro insulin release studies from various insulin loaded particles were performed by simulating the gastrointestinal tract conditions using HPLC. At pH 2.5, the release of insulin from polymeric particles was observed in the range of 5–8% while a significant higher release (20–35%) was observed at pH 7.4 during first 15 min of in vitro release. Largest size copolymeric particles of 8.3 µm also showed the highest efficiency to reduce the blood glucose level in diabetic rabbits. Copyright © 2010 John Wiley & Sons, Ltd.     

Sorption behaviour of nanocrystalline MOR type zeolite for Th(IV) and Eu(III) removal from aqueous waste by batch treatment

The nanocrystalline mordenite (MOR) type zeolite materials with initial chemical composition Na(2)O:Al(2)O(3):10SiO(2):48H(2)O have been synthesized under hydrothermal conditions. MOR1 and MOR2 are spherically shaped nanocrystals, whereas MOR3 and MOR4 have rod-like morphology. This paper reports the sorption characteristics of MOR analogues for Th(IV) and Eu(III) removal from aqueous nuclear waste. Sorption of Th(IV) and Eu(III) on MOR1, MOR2, MOR3 and MOR4 in a single component system with varying initial metal ion concentration, solution pH, contact times, sorbent dose and temperatures has also been investigated. Further, the Langmuir and Freundlich sorption models have been applied to describe equilibrium isotherms at different temperatures. The adsorption capacity increases largely with increasing solution pH and temperature of the system. Specific surface area and pore volume have been investigated by Brunauer-Emmett-Teller (BET) method. The N(2) adsorption isotherm presents a type IV isotherm with narrow hysteresis loop which indicates the presence of mesopores related to inter-particle voids. Thermodynamic results indicate that the sorption follows an endothermic physisorption process. It has been found that these exchangers have good sorption capacity and out of which MOR4 has highest sorption capacity. Thus, nanocrystalline MOR4 is proved to be good sorbent for both Th(IV) and Eu(III).