Study of Carbon Nanocapsules (Onions) and Spherulitic Graphite by Stm and Other Techniques†

A scanning tunneling microscopy study of carbon nanocapsules (onions) is reported for the first time. Spherulitic graphite is shown to be purely crystalline graphite based on X-ray diffraction and electron microscopy studies.     

Collaboration in Indian physics: A case study of the macro and micro parametrization of sub-disciplines (1800–1950)

The decade beginning 1920 is an important watershed in the history of physics in modern India. This is evident from the bibliometric data available on the publications in physics between 1800 and 1950. The paper studies the evolution of collaboration in four subdisciplines of physics during this period. In order to do so, two sets of measures of research collaboration have been employed. The collaboration index and collaboration coefficient have been calculated for the sub-disciplines. As far as the micro-parametrization of the discipline is concerned, collaboration measures developed by Egghe are obtained for the research careers of four leading Indian physicists, who were responsible for the institutionalization of physics research in India. In the present case the role of individuals responsible for the institutionalization of physics research is seen to be germane to the explosion of the number of publications in the 1920s. At the conjucture of the history of science and scientometrics, it is evident how the former can endow the latter with a modality of explanation; further, it is evident how scientometrics can inform the efforts of historians of science.     

Comparison of sex pheromone composition and pheromone-mediated male behavior of laboratory-reared and wildHeliothis zea (Lepidoptera: Noctuidae)

Analysis of ovipositor extracts of lab-reared (> 120 generations) and wildHeliothis zea indicated small but significant differences in the percent composition of the four aldehyde components of the sex pheromone. (Z)-11-hexadecen-1-ol (Z11–16OH) was present in both populations and amounted to only 2.8% of the total pheromone. There was no significant difference in four of the six behavioral categories between lab-reared and wild males exposed to the four-component sex pheromone in the flight tunnel. Ninety and 84% males flew to the pheromone source, respectively. However, with the addition ofZ11–16OH to the pheromone blend, none of the wild males flew upwind to the stimulus source, whereas 36% of the lab-reared males completed the flight. It is suggested that prolonged inbreeding in closed quarters rendered these males less discriminating to qualitative differences in a pheromone blend.     

Characterization and thermal behaviour of gel-grown gadolinium tartrate crystals

Gadolinium tartrate crystals in the form of spheru!itoe were synthesized by using a controlled diffusion system in sillica gel. Characterization of the material was performed by utilizing the techniques of chemical analysis, X-ray and electron diffraction, infrared and mass spectroscopy, and by As thermal behaviour. The material turns out to be a dihvdrate and the chemical composition vvoethus established as Gd₂(C₄H₄O₆)₃ · 2H₂O. The data obtained from the thermal analysis show the tendency of the material to decompose, and this is further confirmed by mass spectroscopy The decomposition process is completed in four steps until gadolinium oxide is obtained at 840* C. The energetics of the reactions at each stage of decomposition have been examined and mechanisms for the decomposition reactions are proposed.     

Frequency dependence of rain attenuation measurements at microwave frequencies

The values of attenuation versus frequency for 10 mm/h, 25 mm/h, and 40 mm/h rain rates for frequencies of 11, 18, and 22.2 GHz are presented. On the basis of these observations the attenuation at frequencies below 10 GHz and above 22.2 GHz have been obtained. The values obtained at various frequencies show an agreement with those calculated on the basis of Oguchi's work. Comparison of the above values in dB/km (assuming a path length of 2.5 km) have been made and they show an agreement with International Radio Consultative Committee (CCIR) values. Also cumulative distributions of attenuation at various frequencies have been given taking 11 GHz results as the reference point.     

Characterization and thermal behaviour of gel grown mixed rare-earth (Didymium) tartrate crystals

Sherulites, crystal aggregates and platelets of Di₂ (C₄H₄O₆)₃ · 5H₂O mixed crystals were grown in gel using the single tube diffusion method. The material was characterized by using different techniques such as chemical analysis, EDAX, X-ray and electron diffraction, infrared and mass spectroscopy. The thermal behaviour of the material was studied using differential thermal analysis, DTG, thermogravimetric analysis and differential scanning calorimetry. The material is thermally unstable and starts decomposing at 50‡ C. Thermal analysis results indicate the application of the contracting cylindrical kinetic model for the solid state reactions involved in the decomposition process. The values of kinetic parameters, e.g. order of reaction, activation energy and frequency factor are worked out. The implications are discussed.     

Bimodal Microcellular Morphology Evaluation in ABS-Foamed Composites Developed Using Step-Wise Depressurization Foaming Process

In this article, the fabrication of bimodal type of cellular structures and multimodal type of cellular structures of acrylonitrile–butadiene–styrene foams has been reported using solid-state batch foaming process by distinct, stepwise depressurization technique. Each depressurization step induces a distinct nucleation phenomenon, which leads to the development of multimodal cellular microstructures. The significance of crucial process parameters, which includes saturation pressure, holding pressure, holding time and holding steps, was studied in the development of bimodal and multimodal cellular structures. Further, the influence of the depressurization rate on the volume ratio of small cells to large cells vice versa was also studied. The morphological attributes, which includes cell size, cell density, and cell morphologies, were investigated in detail. This study puts forward a basic mechanism to develop and simultaneously control bimodal and multimodal cellular microstructures by altering the crucial process parameters. POLYM. ENG. SCI., 60:113–131, 2020. © 2019 Society of Plastics Engineers     

High- performance liquid chromatography method applied to investigate mechanism,kinetics, isotherm,and thermodynamics of bile acid adsorption onto bile acid sequestrants

The purpose of the study was to develop and validate a high-performance liquid chromatography (HPLC) method which can be further applied to understand the mechanism, kinetics, isotherm, and thermodynamics of bile acid adsorption onto bile acid sequestrants. To investigate these properties a HPLC method was developed using peerless C-8 (150 x 4.6?mm, 5?µm) column with a detection wavelength of 200?nm and run time of about 12.5?min. Bile salts glycocholic (GC), glycochenodeoxycholic (GCDC), and taurodeoxycholic acid (TDC), were used and colesevelam hydrochloride was employed as the bile acid sequestrant. The calibration range was found linear from 10 to 6500?mgL^?1 for GC and GCDC and 4to 2400?mg L^?1 for TDC. The precision was less than 8.8% and accuracy was found well within the range of 85 to 115%. On treating the data with various established models, it was known that, the adsorption kinetics followed the pseudo second order equation indicating chemisorption mechanism. Equilibrium isotherms revealed that the linear form of Langmuir model was the best fit. The separation factor (R_L) calculated revealed that the reaction is favorable and reversible. The positive value of heat of sorption (B) calculated from Temkin model indicated towards the exothermic nature of adsorption. The adsorption energy (E) calculated from Dubinin-Kaganer-Radushkevich model was found to be greater than 8 KJmol^?1 conforming chemisorption mechanism. The Gibbs free energy calculated established the affinity of bile salts as TDC?>?GCDC?>?GC.     

Sub-nanometer characterization of activated carbon by inelastic neutron scattering

Inelastic neutron scattering spectra are calculated for hydrogen molecules adsorbed on activated carbon. The slit-shaped pore model is used to calculate the adsorption potentials of a hydrogen molecule in pores of variable width. The motion of the hydrogen molecules is quantized perpendicular to the plane of the pore and both rotational and vibrational transition energies are found. The perturbation of adjacent hydrogen molecules on the transition energies is discussed. Form factors and Debye–Waller factors are calculated for momentum transfer parallel and perpendicular to the pore; this anisotropy is particularly pronounced in pores where there is nearly enough room for two adsorbed layers. A spectrum composed of a uniform distribution of pore sizes agrees only qualitatively with experimental results for activated carbon. Reasons for this disparity are discussed, including the possibility that transitions in the translational motion parallel to the adsorption plane contribute significantly to the spectra. In addition, the positioning of the center of gravity of the first rotational transition is discussed, with several factors contributing to shift it from the 14.7 meV of the gas phase. Our results suggest that inelastic neutron scattering can be valuable as a complementary sub-nanometer pore characterization technique.