University of Calcutta (informally known as Calcutta University or CU) is a collegiate public state university located in Kolkata, West Bengal, India.&nbsp;Within India it is recognized as a &quot;Five-Star University&quot; and accredited &quot;A&quot; Grade by National Assessment and Accreditation Council.

&nbsp;

The University of Calcutta has secured the Fifth position among the Universities of India in the prestigious &quot;Indian University Ranking 2019&quot; list, released by the NIRF of the Ministry of Human Resource Development, Government of India.

&nbsp;

It was established on 24 January 1857, and was one of the first institutions in Asia to be established as a multidisciplinary and Western-style university. Its alumni and faculty include several heads of state, heads of government, social reformers, prominent artists, only academy award winner and Dirac medal winner in India, many Fellows of the Royal Society and five Nobel laureates as of 2019 which is highest in South Asia.

University Of Calcutta

Fixation of Zn and Cu applied to tropical rice-growing lateritic soils rich in Fe-oxides may be reduced if the soils are kept flooded for a few days before their application. There may be a further reduction if such flooding is combined with incorporation of green manures. To investigate this effect, a laboratory experiment was conducted to study the effect of different periods (0 and 15 days) of preflooding combined with (0 and 0.50% of soil weight) Sesbania rostrata and Azolla microphylla incorporation as green manures on the transformation of applied Zn and Cu in two lateritic rice-growing soils. Recovery of added Zn/Cu in DTPA (diethylene triamine pentaacetate)-extractable form was always found to be higher when they were applied after the soils were maintained in a flooded state for 15 days than when applied immediately after flooding; this effect was more prominent in respect of Cu. Contrary to expectations, green manure incorporation along with preflooding caused a significant decrease in recovery of Zn/Cu; the effect, however, showed a decreasing trend as incubation progressed. The effect was more marked with A. microphylla than with S. rostrata, particularly with Cu. Possible causes of such changes and their implications on the Zn/Cu nutrition of rice are discussed.

World University root node

Applied Optics and Photonics

Biology and Fertility of Soils

Effects of Sesbania rostrata and Azolla microphylla incorporation on transformation of applied zinc and copper in lateritic rice soils with different flooding regimes

Measurement and analysis of birefringence distribution in samples such as silicon wafers, electro-optic crystals and some biological specimens often poses a challenging task. Most of the standard methods for photoelastic analysis are not exactly suited to testing of samples having microscopic dimensions. The present paper proposes an interference microscopic technique where, unlike conventional interference microscopy, both the interference beams are derived from the light transmitted through the sample. As a consequence of this, the surface finish of the sample need not be of the optical order and thickness variations in the sample are not reflected in the results. © 1996 SPIE. All rights reserved.

Proceedings of SPIE - The International Society for Optical Engineering

A birefringence-sensitive interference microscope

It is well known that circular symmetric phase and amplitude coatings on the lens aperture modify the imaging qualities of a lens. The present paper shows that the effects of such phase and amplitude coatings on the imaging properties of a lens can be achieved by using suitably oriented polarization masks on the lens aperture. The fact that the response of such a system can be continuously varied by changing the orientation of the polarizing devices included in the system lends it a versatility unobtainable by the use of conventional phase and amplitude coatings on the lens aperture. © 1994 Optical Society of America.

GENERAL

Journal of the Optical Society of America A: Optics and Image Science, and Vision

Simulation of effects of phase and amplitude coatings on the lens aperture with polarization masks

It is well known that a suitably shaped birefringent material, placed between two polarizers, exhibits a spatial variation in amplitude transmittance. The present article explores the possibility of using such an arrangement as a spatial frequency filter. The advantage of such filters is that the nature of filtering achievable can be changed by rotating any of the two polarizers. The specific case of a biconvex quartz lens as a spatial frequency filter is considered and techniques for real-time edge enhancement and periodic noise removal are discussed. Experimental results are also presented. © 1994 Taylor and Francis Ltd.

Journal of Modern Optics

Optical processing using a birefringence-based spatial filter

An interferometric technique for photoelastic testing of small and transparent samples is proposed. By the introduction of two properly oriented polarisers in the two arms of a Twyman-Green interferometer, it has been shown that the modified interferometer is rendered sensitive to birefringent samples placed in the path of a plane polarised parallel beam of light entering the interferometer. Since the sample is placed in the common arm, unequal phases either inherent in the sample or due to deformation under stress will not be reflected in the output. During the testing procedure, the two arms of the interferometer can be left totally undisturbed. Information on the stress distribution over the sample area can be obtained from the recorded interferometric pattern - since the recorded fringe shifts are proportional to the developed stresses. The principle of the technique is discussed and experimental results are provided. © 1994.

Optics Communications

Photoelastic testing using a birefringence-sensitive interferometer

The optical transfer function (OTF) of an imaging system using polarization devices depends in general on the state of polarization of the input beam. In fact, the `amplitude point spread function' (APSF) of such a system is different for different linearly polarized components of the input beam. This implies that the APSF of a system using polarizing devices behaves as a vector quantity. The nature of the final image is determined by the relative contribution of the two components of the vector APSF. The specific imaging system considered in the present study consists of a circularly symmetric polarization mask with linear polarizers having different orientations for the central circular and annular regions of an ideal lens aperture. If the light originating from an object point is in general elliptically polarized, the OTF of such a system with an analyser at the output is seen to have three additive components, which are, in fact, the Fourier coefficients of the OTF which varies periodically with the orientation of the analyser. It is also observed that the images produced by each additive component of the OTF can be separated—a fact that seems rewarding in view of potential applications. © 1993 Taylor and Francis Ltd.

Vector wave imagery with a lens masked by polarizers

Quinalphos (O,O-diethyl-O-[quinoxalinyl-(2)-thionophosphate]) is a well-known organophosphorus insecticide used extensively in agriculture that adversely interferes with the activity of testicular steroidogenic enzymes in rats. To investigate its effects on spermatogenesis, the other function of testes, quantitative evaluation of different varieties of germ cells at stage VII of the seminiferous epithelium cycle, namely, type A spermatogonia (ASg), preleptotene spermatocytes (pLSc), midpachytene spermatcytes (mPSc), and step 7 spermatids (7Sd), along with the radioimmunoassay of plasma FSH, LH, testosterone, and testicular testosterone, were performed in Wistar rats following treatment with quinalphos (250 μg/kg, ip) for approximately one (13 days) and two cycles (26 days) of the seminiferous epithilium. Massive degeneration of all varieties of germ cells at stage VII, remarkable reduction in the sperm count, and significant reductions in plasma concentrations of FSH and testosterone, along with testicular testosterone, were observed after quinalphos treatment. Significant reduction in the plasma concentration of LH was observed only after treatment for two cycles. Administration of human chorionic gonadotrophin for 26 days in rats injected with quinalphos partially prevented the degeneration of germ cells and increased testosterone production. It is suggested that quinalphos may have a suppressive influence on gonadotrophin release but its direct detrimental action at the level of the testes may also be responsible for the observed changes in spermatogenesis and in testicular testosterone production in rats. © 1992 Academic Press, Inc.

Environmental Research

Quinalphos-induced suppression of spermatogenesis, plasma gonadotrophins, testicular testosterone production, and secretion in adult rats

Journal of Optics

Realisation of Phase And Amplitude Steps On Lens Aperture Using Polarisation Masks

Display of Hilbert Transform Using Polarization Filter

Analytical Derivatives for Optical System Analysis: Use of Gaussian Brackets

Quantitative evaluation of the different varieties of germ cells at stage VII of the seminiferous epithelium cycle, namely type-A spermatogonia (ASg), preleptotene spermatocytes (pLSc), mid-pachytene spermatocytes (mPSc) and step 7 spermatids (7Sd), along with radioimmunoassay of plasma gonadotrophins (FSH and LH), testosterone and testicular testosterone were performed in Wistar rats following treatment with aldrin (polycyclic chlorinated hydrocarbon insecticide) for approximately one (13 days) or two cycles (26 days) of the seminiferous epithelium. Extensive degeneration of all varieties of germ cells at stage VIII, reduction in the sperm count and significant reductions in plasma concentrations of LH and testosterone were observed following aldrin treatment. The reduction in plasma concentrations of FSH was statistically significant only after treatment for two cycles. The inhibitory effect of aldrin on plasma gonadotrophins, testosterone levels, testicular testosterone content and numbers of 7Sd and ASg was maximum after treatment for two cycles. Administration of human chorionic gonadotrophin along with aldrin treatment for two cycles partially prevented the degeneration of germ cells and enhanced testosterone production. The results indicate that aldrin may have a direct inhibitory influence on gonadotrophin release, but the possibility of a direct action of the insecticide at the level of the testes is also discussed.