Vibrational spectra, normal coordinate analysis and thermodynamics of 2, 5-difluorobenzonitrile

The FTIR spectrum of 2, 5-difluorobenzonitrile has been recorded in the region 200–4000 cm⁻¹ (in liquid phase). The laser Raman spectrum in the range of 0–3500 cm⁻¹ (in liquid phase) has also been recorded. The spectra have been analyzed assuming C _s point group symmetry for the molecule. A zero-order normal coordinate analysis has been made for the molecule using force constants derived earlier. On the basis of potential energy distributions and eigen vectors unambiguous vibrational assignments have been made for all the fundamentals of the molecule. Thermodynamic functions have also been computed in the temperature range 200–1000 K by utilizing the observed fundamental frequencies assuming rigid-rotor harmonic oscillator approximation.     

Paal knorr reaction for novel pyrrolo[2,3‐d]pyrimidines

An expeditious and convenient solid supported synthesis of 1,3,7‐triaryl‐6‐phenyl‐2‐thioxo‐1,2,3,7‐tetrahydropyrrolo [2,3‐d]pyrimidin‐4‐one derivatives from readily accessible N,N‐disubstituted thiobarbituric acids under microwaves utilising Paal Knorr reaction is described.     

Recent developments in bio-molecular electronics techniques for food pathogens

Food borne illnesses contribute to the majority of infections caused by pathogenic microorganisms. Detection of these pathogens originating from different sources has led to increased interest of researchers. New bio-molecular techniques for food pathogen detection are being developed to improve the sensor characteristics such as sensitivity, reusability, simplicity and economic viability. Present article deals with the various methods of food pathogen detection with special emphasis on bio-molecular electronics techniques such as biosensors, microarrays, electronic nose, and nano-materials based methods.     

A physicochemical model for analyzing DNA sequences

In search of an ab initio model to characterize DNA sequences as genes and nongenes, we examined some physicochemical properties of each trinucleotide (codon), which could accomplish this task. We constructed three-dimensional vectors for each double-helical trinucleotide sequence considering hydrogen-bonding energy, stacking energy, and a third parameter, which we provisionally identified with DNA-protein interactions. As this three-dimensional vector moves along any genome, the net orientation of the resultant vector should differ significantly for gene and nongene regions to make a distinction feasible, if the underlying model has some merits. An analysis of 331 prokaryotic genomes comprising a total of 294 786 experimentally verified genes (nonoverlapping) and an equal number of nongenes presents a proof of concept of the model without the need for further parametrization. Also, initial analyses on Saccharomyces cerevisiae and Arabidopsis thaliana suggest that the methodology is extendable to eukaryotes. The physicochemical model (ChemGenome1.0) introduced has the potential to be developed into a gene-finding algorithm and, more pressingly, could be employed for an independent assessment of the annotation of DNA sequences.     

Bounds on Lifting Continuous-State Markov Chains to Speed Up Mixing

It is often possible to speed up the mixing of a Markov chain \(\{ X_{t} \}_{t \in \mathbb {N}}\) on a state space \(\Omega \) by lifting, that is, running a more efficient Markov chain \(\{ \widehat{X}_{t} \}_{t \in \mathbb {N}}\) on a larger state space \(\hat{\Omega } \supset \Omega \) that projects to \(\{ X_{t} \}_{t \in \mathbb {N}}\) in a certain sense. Chen et al. (Proceedings of the 31st annual ACM symposium on theory of computing. ACM, 1999) prove that for Markov chains on finite state spaces, the mixing time of any lift of a Markov chain is at least the square root of the mixing time of the original chain, up to a factor that depends on the stationary measure of \(\{X_t\}_{t \in \mathbb {N}}\). Unfortunately, this extra factor makes the bound in Chen et al. (1999) very loose for Markov chains on large state spaces and useless for Markov chains on continuous state spaces. In this paper, we develop an extension of the evolving set method that allows us to refine this extra factor and find bounds for Markov chains on continuous state spaces that are analogous to the bounds in Chen et al. (1999). These bounds also allow us to improve on the bounds in Chen et al. (1999) for some chains on finite state spaces.     

Vanishing pseudo–Schur complements,reverse order laws,absorption laws and inheritance properties

The problem of vanishing of a (generalized) Schur complement of a block matrix (corresponding to the leading principal subblock) implying that the other (generalized) Schur complement (corresponding to the trailing principal subblock) is zero, is revisited. Absorption laws for two important classes of generalized inverses are considered next. Inheritance properties of the generalized Schur complements in relation to the absorption laws are derived. Inheritance by the generalized principal pivot transform is also studied.     

Geometrical parameters,vibrational wavenumbers,and relationships established with six difluorobenzonitriles

The geometry, vibrational wavenumbers, and thermodynamical parameters have been calculated using density functional methods (DFT) for benzonitrile (BN) and the six difluorobenzonitriles (DFBNs) of the series. The results were compared with the available experimental data, and correlations were established for the ? C?N and C? F moieties between the natural atomic charges and the geometrical parameters of the compounds. These relations were found as linear or slightly parabolic in most cases. Investigations were carried out to examine the effect of substituents on structural deformations and other properties. Correlations were also determined with the stretching vibrations. Other general conclusions have also been drawn. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

A Spectrophotometric Determination of Ascorbic Acid

A new, simple and sensitive method for the spectrophotometric indirect determination of ascorbic acid in fruits, beverages, and pharmaceuticals is described. In this method, the ascorbic acid reduces Cu²⁺ to Cu⁺ and reacts with 2,9‐dimethyl‐1,10‐phenanothroline (neucoproine) to form Cu (neucoproine)⁺ complex, and it was extracted with N‐phenylbenzimidoylthiourea (PBITU) in chloroform. The apparent value of molar absorptivity of the complex in terms of ascorbic acid is (3.52) × 10⁴ L mole^?1 cm^?1 at λ_max, 460. The detection limit of ascorbic acid is 40 μg L^?1 and the method obeys Beer's law over the concentration range of 0.1–4.0 μg mL^?1. The proposed method was successfully applied for the determination of ascorbic acid in various samples. The validity of the present method was checked by the flow injection analysis (FIA) method.     

Studies on metallochromic indicators--I. Pyrocatecholphthalein as metallochromic indicator

Pyrocatecholphthalein has been used as a metallochromic indicator for the direct complexometric titrations of a number of metal ions with EDTA, both in acidic and in alkaline medium. Th, Bi(III), Ba, Sr, Ca, Mg, Mn(II), Pb(II), Cu(II), Cd, Ni, Co(II) and Zn have been successfully titrated. In comparison with Pyrocatechol Violet, this dyestuff gives sharper end-points when the titrations are done at high pH.     

Low-angle x-ray estimation of macromolecular parameters of the scattering particles in Agave sisalana

Various macromolecular parameters of Agave sisalana (sisal) fiber were investigated by the low-angle x-ray scattering method. The well known Kratky camera of the latest design was utilized for the experimental measurements. The sample studied was a densely packed colloidal system belonging to a general micelle system, and the theories of Kratky and Kratky and Porod were utilized to estimate the parameters. Pore analysis of the substance yields a value for the specific inner surface of the dispersed phase of 0.406 × 10^?1 m²/cm³; the transversal length is the same as the length of inhomogeneity, 107.31 Å, and the length of coherence is 342.21 Å. The air fraction of the scattering particles was found to be 0.01%.