NOPR Collection:

Study of Different Ferrofluid Systems by Electron Paramagnetic Resonance Technique: A Review

2014-02-27T16:43:52Z

Title: Study of Different Ferrofluid Systems by Electron Paramagnetic Resonance Technique: A Review Authors: Gupta, S. K.; Pant, R. P.; Arora, Manju Abstract: Magnetic fluids have been receiving considerable importance due to their wide range of technological applications in the domain of nano - structured material. In such fluids magnetic particles are randomly dispersed in carrier fluid and resembles like a paramagnetic gas. In this paper we reviewed our earlier EPR work on different ferrot1uid systems viz. ionic ferrofluid, ferrofluid - conducting polymer composite, magnetite particles dispersed in PVA polymer matrix composite films. Single domain Fe₃O₄magnetic particles of size 10 to 100 Ǻ are dispersed in carrier fluid like water, diester, paraffin and other liquid hydrocarbons and are similar to colloidal state. In these ferrofluids, EPR spectra showed a single, isotropic broad line spectra at all temperatures. At low temperatures, line width of the signal increases with the decrease in g-value. This may be due to the increase in viscosity of the carrier fluid at low temperatures which locks the spin direction and rotation of magnetic particles and hinders their bulk rotation. In ionic ferrofluid, due to freezing of water with local expansion leads to the randomization of spins and formation of new spin glass or cluster glass states. In all these EPR recorded spectra at different low temperatures, we have not obtained signal pertaining to superparamagnetic state. The reason for this may be non - availability of magnetic particles smaller than critical size and their desired concentration. In conducting polymer - ferrofluid composite, EPR signal was much broader than pure ferrot1uid which was attributed to the decrease in dipole - dipole interaction due to the bonding of magnetic particles with polymer chains and increase in distance between them. While magnetite particles dispersed in PVA polymer matrix thin films, were grown in the absence and presence of magnetic field. In these composites also a broad line EPR signal was obtained for both types. The change in line width and intensity confirms the orientation of magnetic domains in film network. Page(s): 143-145

Establishment of DC High Voltage Standard at National Physical Laboratory

2014-02-25T16:41:58Z

Title: Establishment of DC High Voltage Standard at National Physical Laboratory Authors: Ravat, Kul Bhushan; Mahajan, Surender Kumar Abstract: In the beginning of this millennium National Physical Laboratory, New Delhi has established DC high voltage measurement facility up to 100 kV. It is a unique calibration facility in India. The main theme of this laboratory is to maintain and upgrade DC high voltage standards through continuous research and development. The principle of calibration is based on the comparison method .The ratio of standard divider is 100000/1 0 and uncertainty is 0.01%. The DC High Voltage standard is traceable to primary standard of voltage i.e., Josephson voltage standard with the expanded uncertainty of measurement at k=2.
The standard divider and the UUC divider are put in parallel and supplied with a HV source up to 100 kV. The output voltage at the lower end of the standard divider as well as UUC divider are measured with the help of two separate calibrated multimeters. Standard divider ratio is used to define the HV source voltage. In to days' world transmission by means DC high voltage is considered to be the most appropriate. Some of its important properties have been defined in this paper. Page(s): 139-142

Protection of Wild Animals: Why? & How?

2014-02-26T16:44:09Z

Title: Protection of Wild Animals: Why? & How? Authors: Chowdhuri, D. N.; Ghosh, T. K. Abstract: Each living being, whether plant or animal has its own status with a view to natural balance. Forests and forest animals are an undetachable and essential part of environment. Entire vegetation and the forest animals of the world are associated together with the food chain. They all have such a close natural alliance that the abolition or absence of even a single entity can affect the balance of nature which cannot be recouped by any other at all. To be able to sustain the balance of life and environment the existence of forest animals is very essential. Page(s): 135-138

Antarctica : World's Largest Open Air Scientific Laboratory

2014-02-25T16:45:05Z

Title: Antarctica : World's Largest Open Air Scientific Laboratory Authors: Bera, Samir Kumar Abstract: Antarctica is an excellent and ideal place that renders opportunities to sort out several scientific problems such as in the field of geology, meteorology, environmental sciences, biology and medical sciences. Even in the fields of engineering and communication it comes forward to deal with the problems. Indian scientists have taken important steps in the fields of ice layer of Antarctica/marine ice interaction and marine base; stratospheric ozone and tropospheric chemicals; long term environment monitoring and global climate, ancient environmental records; giant ice; geoscientific map and scientific study of ice; distant earthquake and water studies; studies in bryobotany and polar horticulture; longterm monitoring of Antarctic mammals and birds; physiological and biochemical development of nutritive requirements of man; communication, wind energy, fire retardant engineering etc. Antarctica expedition organized by National Centre for Antarctic and Ocean Research (NCAOR), Goa is joinend by many distinguished scientists/ organizations. India has established a research station called 'Maitry' which is considered to be the best research station in the world today. Antaricta is the continent of future. It is an open air Laboratory in itself. Page(s): 128-134