Diffusive Losses and Scaling Law for Large Tokamaks

Under plasma conditions aimed for in the next generation of tokamak devices, it is necessary to consider a multi-parameter model for diffusive energy losses which would limit the temperatures and confinement times attainable. In this paper, we study a model for plasma diffusion in a reactor size tokamak considering various plasma parameters (like density, temperature, spatial gradients, collisional effects, etc.) and also topological elements of the magnetic configuration (like magnetic shear, magnetic curvature, etc.).     

Effect of aromatic substitution in aniline on the properties of polyaniline

Substitution in aniline has tremendous effect in the synthesis of poly(substituted anilines) as well as in their properties. In this investigation polyaniline (PANI), poly(m-nitro aniline) (PMNA), poly(m-amino phenol) (PMAP) and poly(o-ethyl aniline) (POEA) were synthesized by oxidative polymerization under identical conditions. Different properties were measured and compared with PANI to find out the presence of electron donating -OH group, electron withdrawing -NO₂ group and less effecting ethyl group on the properties of poly(substituted anilines). It was found that presence of any type of substitution in the benzene ring of aniline increases the solubility of the resulted polymer but reduces the yield, degree of polymerization, thermal stability, electrical and thermal conductivity. The colors, bulk density, particle size, percentage of crystallinity vary considerably depending on the nature of substitution.     

Radiation response behaviour of Al codoped germano-silicate SM fiber at high radiation dose

Radiation response behaviour of Ge + Al doped SM fiber fabricated by the solution doping process has been studied at room temperature with respect to 1310 nm transmission wavelength under three different dose rates of 200, 400 and 600 Rad/min to compare with that of standard Er doped as well as Ge doped SM fibers. Their radiation sensitivity has been observed with variation of dose rates, transmission wavelength along with their recovery nature. Radiation response behaviour of Al doped SM fiber is found to be slightly non-linear in nature with very low dose rate dependency. No saturation level was found upto 13 Krad cumulative dose. Thermobleaching as well as photobleaching phenomena have also been studied. Gamma irradiated Al doped preform shows an absorption peak at around 300 nm due to generation of Al (E′) defect center and gets annihilated after thermobleaching process. Gamma irradiated Al doped SM fiber shows prominent photobleaching effect on their optical attenuation with respect to the 850 nm transmission wavelength. From ESR study resonance signals for Al³⁺ related radiation-induced defect centers are not clearly observed in this study. A very weak hyperfine pattern has been observed for gamma irradiated Al doped preform sample. The high radiation sensitivity along with linear response behaviour, low recovery and almost dose rate independence behaviour of the material system of Ge + Al codoped SM core optical fiber under gamma radiation shows their potential for application as fiber optic radiation sensor in comparison to the universal standard erbium doped SM fiber.     

Strong lensing of a regular black hole with an electrodynamics source

In this paper we have investigated the gravitational lensing phenomenon in the strong field regime for a regular, charged, static black holes with non-linear electrodynamics source. We have obtained the angle of deflection and compared it to a Schwarzschild black hole and Reissner Nordström black hole with similar properties. We have also done a graphical study of the relativistic image positions and magnifications. We hope that this method may be useful in the detection of non-luminous bodies like this current black hole.     

Effect of carbon nanotube functionalization in micro-solid-phase extraction (μ-SPE) integrated into the needle of a syringe

In this paper, we report the implementation of polar and nonpolar functionalized multiwalled carbon nanotubes (MWCNTs) as sorbent in μ-SPE integrated into the needle of a syringe. Excellent preconcentration of diverse pharmaceutical analytes was possible without the need for specific pH adjustments using just 300 μg of functionalized nanotubes. Enrichment factors were as high as 6.4, extraction efficiencies were as high as 25.6%, and detection limits as low as 0.08 ng/ml were obtained. The sorption on nanotubes followed Freundlich isotherms, and it was seen that polar analytes adsorbed more strongly on carboxylated MWCNTs, while amphoteric, relatively less polar and basic analytes had greater affinity for MWCNT and those with octadecylamine functionalization.     

Decarboxylative etherification of aromatic carboxylic acids

Decarboxylative Chan-Evans-Lam-type couplings are presented as a new strategy for the regiospecific construction of diaryl and alkyl aryl ethers starting from easily available aromatic carboxylic acids. They allow converting various aromatic carboxylate salts into the corresponding aryl ethers by reaction with alkyl orthosilicates or aryl borates, under aerobic conditions in the presence of silver carbonate as the decarboxylation catalyst and copper acetate as the cross-coupling catalyst.     

Measurement of στ product of solid state laser materials by an alternative method: Application to Nd3+ doped YVO4 crystal for 4 F 3/2→4 I 11/2 transition

In this paper an alternative approach for measurement of στ product for ⁴ F _3/2→⁴ I _11/2 transition of Nd³⁺ doped YVO₄ crystal is reported. In this method a microchip laser is formed by keeping a small piece of the sample in plane-plane resonator and a diode laser (808 nm) is used for pumping. The pump power induced thermal lensing effect is used to make the cavity stable. The cavity mode area is estimated by measuring the thermal lens focal length at the threshold and the average pump area is measured by Gaussian fit to the intensity profiles of the pump beam. The value of στ product of Nd:YVO₄ crystal obtained by this method is within 10% of the reported values. The advantage of this method is that it is a simple method for direct measurement of στ product of laser crystals.