Phase formation, thermal stability and magnetic moment of cobalt nitride thin films

Cobalt nitride (Co-N) thin films prepared using a reactive magnetron sputtering process by varying the relative nitrogen gas flow (\pn) are studied in this work. As \pn~increases, Co(N), \tcn, Co$_3$N and CoN phases are formed. An incremental increase in \pn, after emergence of \tcn~phase at \pn=10\p, results in a continuous expansion in the lattice constant ($a$) of \tcn. For \pn=30\p, $a$ maximizes and becomes comparable to its theoretical value. An expansion in $a$ of \tcn, results in an enhancement of magnetic moment, to the extent that it becomes even larger than pure Co. Though such higher (than pure metal) magnetic moment for Fe$_4$N thin films have been theoretically predicted and evidenced experimentally, higher (than pure Co) magnetic moment are evidenced in this work and explained in terms of large-volume high-moment model for tetra metal nitrides.Comment: 4 pages, 4 figure

Ideology in organized Indian politics, 1880-1948

African Studies Seminar series. Paper presented 28 March 1983This paper is an attempt to place in perspective the ideologies which have helped shape South African Indian politics. The history of organized Indian politics from the 1880s to the 1940s is mainly the history of trader politics - an almost unbroken line of accommodation to the demands of the ruling white minority; or, at most, selective reformism. This line has twice been breached though. Between 1907 and 1913, and again in the 1940s, a radical leadership emerged in the Transvaal and Natal which attempted to transform Indian politics. The process of transformation began at the level of ideology. Thus the two periods of radicalism are useful focal points: they demand an examination of not only the new ideologies, but also the old. No attempt is made here to discuss the course of the passive resistance movements which were the end result of Indian radicalism, except insofar as is necessary to explore some of the issues which this paper has sought to address: the articulation of trader and radical ideologies; the potential of radical ideologies to forge cross-class or, indeed crossrace alliances; the extent to which that potential was realized, and the role of the Indian lower middle classes in that realization. The paper begins, however, with a discussion of Indian social stratification at the turn of the century, and in the 1940s. This is meant, first of all, to provide the background to an understanding of the nature of the essentially conservative, entrenched political parties which the radicals attempted to transform. The discussion also illuminates the conditions under which radicalism emerged. Finally it sketches the social and economic conditions of the mass of the Indian people in order to identify their specific interests. The varying extent to which, and the way in which, those interests were represented by Indian politics at different times is in itself a significant commentary on changes in the content of their ideological underpinning

Insect Mediated Species Interactions: Examining Methods to Improve Artificial Buzz Pollination and Testing the Effects of Plant Based Bioactive Compounds on Herbivore Life-history Traits

Pollination and herbivory are two major interactions in insect-plant ecology. Specialized pollination systems such as buzz pollination where pollen grains have to be extracted by bees with special thoracic vibrations and indirect flight muscles, is observed in ~6% of all flowering plants. Breeding and research programs in these species demand artificial pollination, but natural buzz pollinators are unreliable for this purpose. To find an alternative, we tested the pollen extraction efficiency of using inexpensive electric toothbrush over tuning fork (another commonly used device) in two buzz-pollinated species (Tomato and Silverleaf nightshade) at different buzzing frequencies and multiple buzzing time intervals. Our results show that species and extraction time significantly influenced pollen extraction, while there were no significant differences for the different vibration frequencies and more importantly, the use of a toothbrush over tuning fork. We conclude that electric toothbrushes can be used as a viable and inexpensive alternative to tuning forks for pollen extraction. As the second most important insect mediated species interaction, herbivory, is one of the major threats in crop production and food security. Although synthetic chemicals and pesticides are used to manage insect-pests, their use have led to major concerns of resistance development, pest resurgence as well as toxicity to non-target organisms. Plant-based bioactive compounds are good alternatives, but their use is limited by complicated and expensive extraction and purification methods. We tested the effects of polyphenol rich purple corn pericarp extract (extracted inexpensively) on the growth and development of Manduca sexta, a damaging herbivore. We found that pericarp extract negatively affects egg hatching, mass gain, developmental time and these effects cascade through pupal, adult and next generation offspring suggesting its potential suitability as a biopesticide. Taken together, our findings of inexpensive pollen extraction and sustainable pest management methods can have implications in improving agricultural practices

Light off temperature based approach to determine diesel oxidation catalyst effectiveness level and the corresponding outlet NO and NO2 characteristics

According to the latest EPA emission regulations, the NOx (Nitrogen oxide compounds) emissions from heavy duty compression ignition engines need to see a dramatic reduction. The current technology used for this purpose is the selective catalytic reduction (SCR) system, which achieves NOx reduction of around 90% [9]. This involves urea injection which is influenced by the NO: NO2 ratio at the inlet to the SCR. Thus, the role of the DOC (Diesel Oxidation Catalyst) where most of the oxidation of the NOx compounds takes place, comes to fore. The focus is also on the effectiveness of the catalyst as it thermally ages. Therefore, the aim of this research project is to correlate the aging in the DOC with the light off temperature of the catalyst and subsequent variation in the NO and NO2 concentration at the outlet of the DOC. This shall be achieved through means of a model developed after extensive experimental procedures. Also, further exhaustive experiments to validate the model over multiple aging cycles of the catalyst shall be undertaken. ^ The DOC was subjected to 2 rigorous kinds of experiments aimed at determining the light off temperature shift as the catalyst aged and to determine the NO and NO2 concentrations at the DOC outlet as it aged. Exhaust stream compounds were measured using exhaust analyzers and DOC temperatures were determined using thermocouples installed inside the DOC and at its inlet and outlet. ^ The data thus obtained was then analyzed and 2 separate models were developed, one for the light off experiments, and the other for the NOx experiments. Aging procedures were carried out at an oven according to prescribed techniques and the DOC was subjected to similar experiments again. Analysis was carried out on the data. From the light off experiments and the model analysis, a clear positive shift in light off temperatures was observed from one aging level to another across the range of set points. It was also observed that even after subjecting the DOC to three thermal aging exercises, its conversion efficiency went up to 90%. Also, as the DOC aged, the NO concentration at the DOC outlet showed a downward trend which was observed across the spectrum of engine set points and aging levels. These experiments were repeated for consistency so that the models could be rendered more useful

H-alpha and Free-Free Emission from the WIM

Recent observations have found the ratio of H-alpha to free-free radio continuum to be surprisingly high in the diffuse ionized ISM (the so-called WIM), corresponding to an electron temperature of only ~3000K. Such low temperatures were unexpected in gas that was presumed to be photoionized. We consider a 3-component model for the observed diffuse emission, consisting of a mix of (1) photoionized gas, (2) gas that is recombining and cooling, and (3) cool H I gas. This model can successfully reproduce the observed intensities of free-free continuum, H-alpha, and collisionally-excited lines such as NII 6583. To reproduce the low observed value of free-free to H-alpha, the PAH abundance in the photoionized regions must be lowered by a factor ~3, and ~20% of the diffuse H-alpha must be reflected from dust grains, as suggested by Wood & Reynolds (1999).Comment: 25 pages, 7 figures, 4 tables, single column, details of the calculation and atomic physics added, accepted by Ap

Safe Legged Locomotion using Collision Cone Control Barrier Functions (C3BFs)

Legged robots exhibit significant potential across diverse applications, including but not limited to hazardous environment search and rescue missions and the exploration of unexplored regions both on Earth and in outer space. However, the successful navigation of these robots in dynamic environments heavily hinges on the implementation of efficient collision avoidance techniques. In this research paper, we employ Collision Cone Control Barrier Functions (C3BF) to ensure the secure movement of legged robots within environments featuring a wide array of static and dynamic obstacles. We introduce the Quadratic Program (QP) formulation of C3BF, referred to as C3BF-QP, which serves as a protective filter layer atop a reference controller to ensure the robots' safety during operation. The effectiveness of this approach is illustrated through simulations conducted on PyBullet.Comment: 5 Pages, 5 Figures. arXiv admin note: text overlap with arXiv:2303.1587