Experimentally the real and imaginary parts of the Fourier spectrum are separated and used to detect the nature of the object, i.e., whether the object is an odd or even function or a combination of both. A modified Twyman–Green setup is used for this purpose. This type of splitting of the object function into even and odd parts may become useful in different fields of image processing. As an application the same technique is used for accurate measurement of the grating frequency. © 1995 Optical Society of America.

P GANGULY

J C BISWAS

A GHOSH

A K CHAKRABORTY

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.

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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.

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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

Technique for measuring grating frequency.

Applied Optics

Four new NiII complexes, [Ni(L1)](NO3)·1.5H2O (1), [Ni(L1)][Ni(HL2)](NO3)2·H2O (2), [Ni4(L2)2(μ3-OCH3)2(NO3)](NO3)·CH3OH (3), and [Ni6(L2)2(o-van)2(μ3-OH)4](NO3)2·H2O (4), where HL1 = 2-{[2-(2-aminoethylamino)ethylimino]methyl}-6-methoxyphenol and H2L2 = N,N′-bis(3-methoxysalicylidene)diethylenetriamine, have been synthesized by changing the reaction conditions and stoichiometry of the reactants. Single-crystal X-ray diffraction study reveals that complexes 1 and 2 are mononuclear with a square planar geometry around the NiII centre, whereas complexes 3 and 4 possess tetranuclear and hexanuclear structures, respectively, with octahedral NiII centres. The differences in nuclearity, coordination numbers and geometry of the NiII centres in the complexes have been explained considering the flexible coordination modes and denticity of the Schiff base ligands. Variable temperature molar magnetic susceptibility measurements show that the tetranuclear NiII4 complex (3) is ferromagnetically coupled with two exchange couplings, J1 = 0.64 cm-1 and J2 = 8.41 cm-1, whereas the hexanuclear NiII6 complex (4) is antiferromagnetically coupled with four exchange couplings, J1 = -5.60 cm-1, J2 = -9.39 cm-1, J3 = -5.18 cm-1 and J4 = 3.72 cm-1. The sign and magnitude of these exchange couplings in complexes 3 and 4 are correlated with similar types of reported cubane or defective cubane-like NiII complexes. Electrochemical measurements of these complexes reveal that the NiII centres are irreversibly reduced with one reduction potential for 1, 3 and 4, whereas for 2 the NiII centres are irreversibly reduced with two reduction potentials. © 2019 The Royal Society of Chemistry.

Journal	Applied Optics
Publisher	OPTICAL SOC AMER
ISSN	1559-128X