Positive ion speed at the plasma–sheath boundary of a negative ion-emitting electrode

One-dimensional fluid model for a planar sheath in front of a negative ion-emitting electrode surface immersed in a collision-less, non-magnetized, electronegative plasma is presented. It was found that the positive ion speed at the plasma–sheath boundary (PSB) increases linearly with negative ion emission from the electrode but attains a saturation value as soon as a virtual cathode is formed near the electrode surface. The effect of negative ion emission on the pre-sheath region shows that the potential drop increases across the pre-sheath in accordance with the rise in positive ion speed at the PSB. The sheath width obtained using the present model shows a similar trend as the Child-Langmuir law, but its magnitude is found to be consistently higher compared with a non-emitting electrode. A plausible explanation has been given to explain these effects.     

The role of air in the radiolytic degradation of polycarbonate

Bisphenol A polycarbonate (PC) was irradiated with Co-60 γ-rays at room temperature in presence of air or nitrogen. Changes were followed by IR and NMR spectroscopy as well as GPC, X-ray diffraction, melting temperature, DTA, and isothermal TG. The changes observed include chain scission, chain branching/cross-links, decrease in thermal stability, crystallinity and scission of the product. However, there are some differences in samples irradiated in presence of air as opposed to those irradiated in nitrogen, but many changes are similar. Air accelerates the radiolytic degradation of PC. The radiochemical yield of chain scission, G(s), increased to 0.20 from 0.13; the chain branching/cross-links are less numerous as compared to those after irradiation in nitrogen the thermal stability decreases along with the temperature of that rate of maximum mass loss, crystallinity and the melting temperature. The chemical products in both air and nitrogen irradiations are almost identical. The formation of these products could be explained by multiple pathways-free radical formation and by ring as well as side chain attack. The studies suggest that Fries' rearrangement is not an important pathway during the radiolytic degradation as compared with photodegradation.     

APPLICATION OF GENETIC ALGORITHM IN PARTICLE SIZE ANALYSIS BY MULTISPECTRAL EXTINCTION MEASUREMENTS

Both dependent and independent model algorithms are designed with genetic algorithm (GA) to retrieve aerosol size data from multispectral extinction measurements. Compared with the traditional dependent model algorithm, e.g., simplex, GA can locate the global optimized solution instead of local ones. As an independent model algonthm, when combined with B-splines, GA gives consistent results with Chahine and Phillip-Twomey-NNLS algorithms. Numerical simulations also show that GA has high stability and good resistance to relatively higher error levels. For a population size of 50 in the present paper, the feasible ranges for genetic operators Pc and pm are found to be [0.01, 0.5] and [0.01, 0.15], respectively, and the generation number Gen_Max should be larger than 250.     

Fluorescein dye derivative: Synthesis,characterization, quantum chemical and promising antimicrobial activity studies

The dimethyl sulfite as an alkylating as well as alkoxylating reagent is well known in synthetic organic as well as organometallic chemistry for a long time. Herein, we have utilized dimethyl sulfite as an alkylating reagent and reacted with fluorescein derivative, N-fluorescein-lactam-hydrazine ( B ). This reaction leads to the generation of tetramethylated fluorescein lactam hydrazine ( A ). The newly designed and synthesized molecule ( A ) has been characterized by ¹H, ¹³C NMR and HRMS data. The antimicrobial activity of the synthesized alkylated fluorescein derivative has been tested against E. coli, P. aeruginosa, Salmonella typhimurium and S. aureus microbial agents. Time-kill assay results also confirmed that fluorescein derivative is a potent antimicrobial agent and revealed that the time-kill assay of fluorescein derivative is value-added than the well-known antibiotic. In addition, quantum chemical study was used to analyze its activity trend and correlated with the experimental data. The computed results of DFT revealed that the lipophilicity as well as the LUMO-HOMO band gap (ΔE_LUMO-HOMO = 4.75 eV) of compound A make it more suitable as an antimicrobial agent to match with in vitro antimicrobial experimental results. The MIC and MBC values of compound A were observed to be lower in contrast to fluorescein and ampicillin for all the tested bacterial strains, which were approximately 3- to 4-fold lower than MIC and MBC values of the later. Results obtained from the study clearly indicate that compound A has better antimicrobial and bactericidal activity in comparison to ampicillin and fluorescein. Synthesized compound can be a better substitute of traditionally used antibiotics, Ampicillin.     

An experimental study on characterization and properties of eco-friendly nanolubricant containing polyaniline (PANI) nanotubes blended in RBD palm olein oil

Journal of Thermal Analysis and Calorimetry - Polyaniline nanotubes (PANI NTs) blended in refined, bleached and deodorized palm olein (RBDL) nanolubricants were prepared via a two-step method....     

Frequency and temperature dependence of the dielectric parameters of wide temperature range TGBA and TGBC* phases of unsymmetrical liquid crystal dimers

In the present work we have carried out frequency and temperature dependent dielectric studies of an optically active dimeric compound, 4-n-undecyloxy-4′-(cholesteryloxycarbonyl-1-butyloxy)chalcone which shows wide temperature range twist grain boundary (TGB) phases namely TGBA and TGBC*. Dielectric permittivities and DC conductivities have been determined along and normal to the TGB helix axes. Two weak collective modes of dielectric relaxations have been detected for the planar oriented sample where permittivity is measured normal to the long axes of the molecules (but along the TGB helix axis). One mode, which exists in the MHz region, has behavior similar to those of the soft mode due to the amplitude fluctuation. The second one exists in the low frequency region (～100 Hz) and appears due to phase fluctuation as happens in the case of Goldstone mode. Sample confined between electrodes treated for the homeotropic alignment (permittivity measured normal to the helix axis) does not show any mode of relaxation in the frequency range of 1 Hz to 1 MHz. Measured permittivities suggest negative dielectric anisotropy for the system.     

Determination of ultra traces amount of uranium in raffinates of Purex process by laser fluorimetry

A simple and rapid, laser fluorimetric method for the determination of uranium concentration in raffinate stream of Purex process during reprocessing of spent nuclear fuel has been developed. It works on the principle of detection of fluorescence of uranyl complex formed by using fluorescence enhancing reagent like sodium pyrophosphate. The uranium concentration was determined in the range of 0–40 ppb and detection limit of 0.2 ppb. The optimum time discrimination is obtained when the uranyl ion is complexed with sodium pyrophosphate. Need of preconcentration step or separation of uranium from interfering elements is not an essential step.     

Effect of processing parameters on structural and optical properties of CeO2 nanoparticles for the removal of crystal violet dye

Journal of Sol-Gel Science and Technology - The present work reports the synthesis of CeO2 nanoparticles (NPs) via chemical route by optimizing synthesis parameters such as solvent, capping agent,...     

Ionic liquid-induced unprecedented size enhancement of aggregates within aqueous sodium dodecylbenzene sulfonate

Physicochemical properties of aqueous micellar solutions may change in the presence of ionic liquids (ILs). Micelles help to increase the aqueous solubility of ILs. The average size of the micellar aggregates within aqueous sodium dodecylbenzene sulfonate (SDBS) is observed by dynamic light scattering (DLS) and transmission electron microscopy (TEM) to increase in a sudden and drastic fashion as the IL 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF(6)]) is added. Similar addition of [bmim][PF(6)] to aqueous sodium dodecyl sulfate (SDS) results in only a slow gradual increase in average aggregate size. While addition of the IL [bmim][BF(4)] also gives rise to sudden aggregate size enhancement within aqueous SDBS, the IL 1-ethyl-3-methylimidazolium tetrafluoroborate ([emim][BF(4)]), and inorganic salts NaPF(6) and NaBF(4), only gradually increase the assembly size upon their addition. Bulk dynamic viscosity, microviscosity, dipolarity (indicated by the fluorescent reporter pyrene), zeta potential, and electrical conductance measurements were taken to gain insight into this unusual size enhancement. It is proposed that bmim(+) cations of the IL undergo Coulombic attractive interactions with anionic headgroups at the micellar surface at all [bmim][PF(6)] concentrations in aqueous SDS; in aqueous SDBS, beyond a critical IL concentration, bmim(+) becomes involved in cation-π interaction with the phenyl moiety of SDBS within micellar aggregates with the butyl group aligned along the alkyl chain of the surfactant. This relocation of bmim(+) results in an unprecedented size increase in micellar aggregates. Aromaticity of the IL cation alongside the presence of sufficiently aliphatic (butyl or longer) alkyl chains on the IL appear to be essential for this dramatic critical expansion in self-assembly dimensions within aqueous SDBS.