Magnetic domain behaviour of MgFe2O4-CoFe2O4 system

Ferrites with the composition Mg_1−x CO _x Fe₂O₄(0<x≤0·33) were synthesized by solid state reaction between MgO,α-Fe₂O₃ and CoFe₂O₄ at 1300°C. The compounds were analyzed from the results of x-ray diffraction, magnetic hysteresis and initial susceptibility (χ) studies. All the compounds of the series were found to be monophasic with no appreciable change in their lattice parameter. The saturation magnetization and coercive field (H _c ) values increased with increasing cobalt ferrite content. Similarly, the shapes of theχ-T curves and temperature variations ofH _c values indicated that the magnetic behaviour changes from multi-domain to single domain with increasing cobalt content. The results are similar to those observed for the (MgFe₂O₄)_1−x (Co₃O₄) system.     

Global perspectives for secondary reference materials for analysis of food and related biological samples

Primary, secondary and tertiary reference materials (RM) play an important role in quality controls of analytical measurements. Logistics of preparation and proper use of primary and secondary RMs are presented. Tertiary (i.e. in-house) control materials are useful as substitutes in the absence of recognized primary or secondary RMs. The lack of interdisciplinary interaction during development of RMs (e.g. in specific areas such as foods), has an important impact on limiting the usefulness of certain types of RMs. The abundance of RMs in some countries and regions appears to have little effect on the existing paucity in RMs in other regions, and the underlying causes are outlined. The ability of a laboratory to produce good quality in-house RMs traceable to recognized primary or secondary RMs is a direct measure of its quest for reliable analytical data. Therefore many laboratories should be encouraged to engage in secondary and tertiary RM activities designed to answer specific measurement problems. In this context, assistance (e.g. practical training opportunities) in identifying simple methods of analyses for their efficacy in determining specific analytes is a source of help that can be extended to countries experiencing limitations in laboratory instrumentation.     

Azo-hydrazo Tautomerism and Inclusion Complexation of 1-phenylazo-2-naphthols with Various Solvents and β-cyclodextrin

Spectral characteristics of sudan I (SDI), sudan II (SDII) and mordant violet-5 (MV5) have been studied in various solvents and β-cyclodextrin (β-CD). The inclusion complex of the above molecules with β-CD was analyzed by UV-visible, fluorometry, and DFT methods. The solvent study shows that azo-hydrazo tautomer is present in these molecules. The increase in the fluorescence intensity and a large bathochromic shift in the S₁ state indicate these molecules forms 1:1 inclusion complex with β-CD.     

Unweighted linear congruences with distinct coordinates and the Varshamov–Tenengolts codes

In this paper, we first give explicit formulas for the number of solutions of unweighted linear congruences with distinct coordinates. Our main tools are properties of Ramanujan sums and of the discrete Fourier transform of arithmetic functions. Then, as an application, we derive an explicit formula for the number of codewords in the Varshamov–Tenengolts code \(VT_b(n)\) with Hamming weight k, that is, with exactly k 1’s. The Varshamov–Tenengolts codes are an important class of codes that are capable of correcting asymmetric errors on a Z-channel. As another application, we derive Ginzburg’s formula for the number of codewords in \(VT_b(n)\), that is, \(|VT_b(n)|\). We even go further and discuss connections to several other combinatorial problems, some of which have appeared in seemingly unrelated contexts. This provides a general framework and gives new insight into all these problems which might lead to further work.     

Tissue self-affinity and polarized light scattering in the born approximation: a new model for precancer detection

Light scattered from biological tissues can exhibit an inverse power law spectral component. We develop a model based on the Born approximation and von Karman (self-affine) spatial correlation of submicron tissue refractive index to account for this. The model is applied to light scattering spectra obtained from excised esophagi of normal and carcinogen-treated rats. Power law exponents used to fit dysplastic tissue site spectra are significantly smaller than those from normal sites, indicating that changes in tissue self-affinity can serve as a potential biomarker for precancer.     

The canonical Lagrangian approach to three-space general relativity

We study the action for the three-space formalism of general relativity, better known as the Barbour–Foster–Ó Murchadha action, which is a square-root Baierlein–Sharp–Wheeler action. In particular, we explore the (pre)symplectic structure by pulling it back via a Legendre map to the tangent bundle of the configuration space of this action. With it we attain the canonical Lagrangian vector field which generates the gauge transformations (3-diffeomorphisms) and the true physical evolution of the system. This vector field encapsulates all the dynamics of the system. We also discuss briefly the observables and perennials for this theory. We then present a symplectic reduction of the constrained phase space.     

Designing polymer metamaterial for protective armor: a coarse-grained formulation

Meccanica - Designing protective armors is important for varied civil and defense applications. Ceramic-polymer composite armors are particularly interesting for their high strength and light...     

Tertiary-butoxycarbonyl (Boc) – A strategic group for N-protection/deprotection in the synthesis of various natural/unnatural N-unprotected aminoacid cyanomethyl esters

A number of cyanomethyl esters of natural/unnatural aminoacids with un-protected amino functionality were synthesized because of their synthetic and medicinal importance. Critical N-Boc deprotection methods in the presence of labile (hydrolytic sensitivity) cyanomethyl functionality were screened thoroughly and it was found that readily available 4M HCl in 1,4-dioxane solution (2–4 equiv); acetonitrile, 0?°C, 2–4?h was a suitable condition. This condition was generalized and successfully applied to a variety of alkyl, alkynyl, aryl, heteroaryl, benzyl, azido, spiro amino acid cyanomethylesters irrespective of the nature of the amine (primary or secondary) and the distance between the amine and ester group to achieve final deprotected amino esters with high yield, and purity compared to other commonly known N-protecting groups (Cbz, Fmoc, Ac, Bn, Bz etc.). It was also demonstrated that N-Boc protected aminoacid cyanomethylesters are stable enough to carry out further functionalization compared to N-unprotected counterparts.