Reactions of Cp2MCl2 (M=Ti or Zr) with imine-oxime ligands. Formation of metallacycles

The reactions of bis(cyclopentadienyl)titanium(IV)/zirconium(IV) dichloride with a series of imine-oxime ligands (LH2), derived by condensing benzil-alpha-monoxime and 2-phenylenediamine, 4-phenylenediamine, 4-methyl-2-phenylenediamine, 2,6-diamino-pyridine, have been studied in anhydrous tetrahydrofuran in the presence of base and metallocycles of the [Cp2M(L)] (M=Ti or Zr) type have been isolated. Tentative structures have been proposed for the products based on elemental analysis, electrical conductance and spectral (electronic, IR and (1)H-NMR) data. Proton NMR spectra indicate that on the NMR time scale there is rapid rotation of the cyclopentadienyl ring around the metal-ring axis at 25 degrees C. Studies were conducted to assess the growth inhibiting potential of the complexes synthesized and the ligands against various bacterial strains.     

The Raychaudhuri equations: A brief review

We present a brief review on the Raychaudhuri equations. Beginning with a summary of the essential features of the original article by Raychaudhuri and subsequent work of numerous authors, we move on to a discussion of the equations in the context of alternate non-Riemannian spacetimes as well as other theories of gravity, with a special mention on the equations in spacetimes with torsion (Einstein-Cartan-Sciama-Kibble theory). Finally, we give an overview of some recent applications of these equations in general relativity, quantum field theory, string theory and the theory of relativisitic membranes. We conclude with a summary and provide our own perspectives on directions of future research.      

Synthesis,physico-chemical and biological studies on oxovanadium(IV) derivatives of mercaptotriazoles

Summary Complexes of 3-methyl- or 3-ethyl-4-amino-5-thiolato-1,2,4-triazole (LH) and its Schiff base derivatives with oxovanadium(IV), of the types [VOL₂(H₂O)], [VOL₂-(H₂O)] and [VOL(H₂O)₂] (where LH = Schiff bases derived from condensation of LH with benzaldehyde, 2-chlorobenzaldehyde, 4-methoxybenzaldehyde or acetophenone; LH₂ = Schiff bases derived from condensation of LH with salicylaldehyde or o-hydroxyacetophenone) have been prepared and characterized by elemental analyses, electrical conductance, magnetic moments and spectral data. The thermal behaviour of selected complexes was investigated by t.g., d.t.g. and d.s.c. techniques. The antifungal and antiviral activities of the Schiff bases and their corresponding complexes were also investigated.Author to whom all correspondence should be directed.     

Binuclear oxovanadium(IV) complexes of phthalazine hydrazone ligands

Summary The oxovanadium(IV) complexes [(VOSO₄·H₂O)₂L] and [(VO)₂L¹(-SO₄)] (L = hydrazone ligands derived from 1,4-dihydrazinophthalazine and benzaldehyde, 4-chlorobenzaldehyde, 4-methoxybenzaldehyde or acetophenone; L ¹H₂ = hydrazone ligands derived from 1,4-dihydrazinophthalazine and salicylaldehyde, 2-hydroxyacetophenone or 2-hydroxynaphthaldehyde) have been prepared and characterized by elemental analyses, electrical conductance, magnetic moments and spectral data. Reduced magnetic moments are observed for all sulfato-bridged derivatives, indicating antiferromagnetically coupled vanadium(IV) centres. The vanadium(IV) centres appear to have five-coordinated stereochemistries in the systems which involve two metals bound to each ligand. The thermal behaviour of the complexes was investigated by t.g. and d.t.g. techniques. The antifungal and antiviral activities of the hydrazones and their corresponding complexes were also investigated. The screening results have been correlated with the structural features of the tested compounds.     

Microwave assisted synthesis,spectroscopic and antibacterial studies of titanocene chelates of Schiff bases derived from 3-substituted-4-amino-5-hydrazino-1,2,4-triazoles

The reactions of bis(cyclopentadienyl)titanium(IV) chloride with a new series of Schiff bases (LH₂), derived by condensing 3-(phenyl/2-chlorophenyl/4-nitrophenyl)-4-amino-5-hydrazino-1,2,4-triazoles with salicylaldehyde or 2-hydroxyacetophenone, have been studied both by conventional stirring method and also by using microwave technology. The products of type [(η⁵-C₅H₅)₂Ti(L)] have been isolated in both cases. Tentative structural conclusions are drawn for the reaction products based upon physico-chemical and spectroscopic methods. The ligands behave as dibasic, tetradentate chelating agents and a six-coordinated structure have been assigned to these derivatives. Studies were conducted to assess the growth inhibiting potential of the free Schiff bases and their complexes against various bacterial strains.     

Lanthanum(III) and praseodymium(III) complexes of acetylferrocenyl mercaptotriazoles

Schiff base complexes derived from 3-substituted phenyl-4-amino-thiolato-1,2,4-triazoles and acetylferrocene (LH), with lanthanum(III) and praseodymium(III) of the type [M(L)₃] have been prepared and characterised by elemental analysis, electrical conductance, magnetic moments and spectral (electronic, i.r., ¹H-n.m.r. and ¹³C-n.m.r.) data. The thermal behaviour of selected complexes was investigated by t.g. and d.t.g. techniques.     

Experimental investigation on martensitic transformation and fracture morphologies of austenitic stainless steel

Formation and nucleation mechanisms (i.e. γ → ε, γ → α′, γ → deformation twins → ε → α′ and γ → ε → α′) of deformation- induced martensite (DIM) have been studied through analytical transmission electron microscopy (TEM) after tensile deformation of AISI 304LN stainless steel at various strain rates (SR) at room temperature (RT). Quantitative metallography has been employed extensively to assess martensitic transformation (MT) as function of strain and SR. It has been observed that the enhancement of SR during tensile deformation promotes the early formation of DIM, while suppressing its saturation value at fracture. Fracture surface morphologies and dimple geometries (i.e. dimple density, dimple diameter and dimple size distribution) have been quantified through image processing (IP) of tensile fractographs. It is noted that at lower SR, dimple density is high while dimple diameter is smaller, and vice versa. Concomitantly, the strength is noted to be low and ductility is high at lower SR, and vice versa. DIM has been found to be responsible for high dimple density at low SR. At high SR, MT is suppressed and hence low dimple density. The variation in SR dependent MT accounts for the variation in dimple metrics vis-à-vis tensile properties.     

Optimal observable analysis for the decay $$b \rightarrow s$$ plus missing energy

The decay \(b\rightarrow s\nu {\bar{\nu }}\) has received comparatively less attention than the semileptonic decay \(b\rightarrow s\ell ^+\ell ^-\), because neutrinos pass undetected and hence the process offers lesser number of observables. We show how the decay \(b\rightarrow s~+\) invisible(s) can shed light, even with a limited number of observables, on possible new physics beyond the Standard Model and also show, quantitatively, the reach of future B factories like SuperBelle to uncover such new physics. Depending on the operator structure of new physics, different channels may act as the best possible probe. We show, using the optimal observable technique, how almost the entire parameter space allowed till now can successfully be probed at a high-luminosity B factory.     

On the sum of two subnormal kernels

We show, by means of a class of examples, that if $K_1$ and $K_2$ are two positive definite kernels on the unit disc such that the multiplication by the coordinate function on the corresponding reproducing kernel Hilbert space is subnormal, then the multiplication operator on the Hilbert space determined by their sum $K_1+K_2$ need not be subnormal. This settles a recent conjecture of Gregory T. Adams, Nathan S. Feldman and Paul J. McGuire in the negative. We also discuss some cases for which the answer is affirmative.