A dual detector capillary waveguide biosensor for detection and quantification of hybridized target

We describe a novel technique for improving the sensitivity of analytical instruments based on the measurement of fluorescent intensity. Independent measurement of the Rayleigh scattered intensity component by means of a second photodetector leads to normalized data, which are independent of various experimental parameters. Incorporation of this technique into a fully automated capillary waveguide biosensor improved the instrument sensitivity by a factor of three. The technique enables quantification, as well as detection, of the hybridized target molecules.     

On the steady laminar flow in a curved pipe of varying elliptic cross-section

The fully developed steady flow of a fluid through a curved tube with elliptic cross-section is studied, the cross-sectional area varying slowly with longitudinal distance. Using a perturbation scheme in terms of two small parameters (geometric parameter and curvature parameter), complete analytical solutions are obtained to the first order. The effects of constriction combined with constant curvature of the centre line are discussed. The phenomenon of secondary flow, shear stress and the increased impedance (due to the constriction) are calculated. The possibility of the application of the results to various engineering problems and physiological flows is indicated.     

Synthesis, Characterization and X-Ray Structure of Bis(O-propyldithiocarbonato-κ2S,S′)bis(4-cyanopyridine-κN)nickel(II)

Abstract  

The [Ni(S₂COCH₂CH₂CH₃)₂(C₆H₄N₂)₂] adduct of 4-cyanopyridine with [Ni(S₂COCH₂CH₂CH₃)₂] was synthesized and characterized by elemental analysis, magnetic susceptibility measurement, IR, electronic spectral data, Thermogravimetric analysis/DTA techniques and X-ray diffraction analysis. The Ni atom in the title complex is octahedrally coordinated within a trans-N₂S₄ donor set, with the Ni atom located on a centre of inversion. The title complex crystallizes in the monoclinic space group P2 ₁ /c with unit cell parameters a = 11.75(4), b = 11.62(3), c = 9.20(2) ?, β = 104.99(3)°. Crystal structure was solved by direct methods and refined by full matrix least squares procedures to a final R-value of 0.0294 for 1895 observed reflections. The packing of layers of molecules is stabilized by weak C–H···N and C–H···π interactions.     

A Homologous Series containing Ester and Amide Groups as Central Linkages: 4(4'-n-Alkoxybenzoyloxy)-4”-n-Heptyloxy Benzanilides

The first extensive homologous series, comprising thirteen members, with both ester and amide groups as central linkages has been synthesised and the mesomorphic properties have been determined. The homologues are comparatively high melting and exhibit liquid crystal phases. The molecular structure seems to favour smectic properties since smectic phases commence with the ethoxy derivative as a monotropic phase. The ethoxy to hexadecyloxy derivatives are poly-mesomorphic in nature, while the octadecyloxy derivative is purely smectic. The mesomorphic behaviour and mesophase thermal stabilities are compared with those of other structurally related series, and the effect of the amide group on mesomorphism is evaluated.     

Controlling the size and the activity of Fe particles for synthesis of carbon nanotubes

The properties of carbon nanotubes (CNTs) are controlled by their structure and morphology. Therefore, their selective synthesis, using catalytic chemical vapor deposition, requires precise control of a number of parameters including the size and activity of the catalyst nanoparticles. Previously, an environmental scanning transmission electron microscope (ESTEM) has been used to demonstrate that electron beam-induced decomposition (EBID) of Fe containing precursor molecules can be used to selectively deposit Fe catalyst nanoparticles that are active for CNT growth. We have extended these in situ ESTEM observations to further our understanding of the EBID parameters, such as deposition time, and substrate temperature, that control the size and placement of Fe catalyst particles for two precursors, namely diiron nonacarbonyl (Fe(2)(CO)(9)) and ferrocene (Fe(C(5)H(5))(2)). We found that the diameter of deposited particles increased with increasing deposition time. Electron energy-loss spectra, collected during deposition, show the incorporation of C in the Fe particles. The C content decreased as the substrate temperature was increased and was negligible at 100°C for Fe(2)(CO)(9). However, C and Fe were co-deposited at all temperatures (up to 450°C) when Fe(C(5)H(5))(2) was used as an iron source. After deposition, the substrate was heated to the CNT growth temperature in flowing hydrogen to remove the co-deposited C, which was an important step to activate the deposited Fe catalyst for the growth using acetylene. Our measurements revealed that the Fe nanoparticles fabricated from Fe(2)(CO)(9) had higher activity for CNT growth compared to the ones fabricated using Fe(C(5)H(5))(2). We also found that the co-deposited carbon could not be removed by heating in hydrogen in the case of Fe(C(5)H(5))(2). The particles deposited from Fe(C(5)H(5))(2) at 300°C to 450°C formed a core-shell structure with Fe surrounded by graphitic carbon. We speculate that the reduced activity for Fe(C(5)H(5))(2) is due to the C content in the deposit.     

Facile synthesis of (Z)- and (E)-3-allylidene-β-lactams via thermal β-elimination of trans-3-allyl-3-sulfinyl-β-lactams

A competent synthetic route for the synthesis of novel (Z)- and (E)-3-allylidene-β-lactams is described. The strategy involves oxidation of trans-3-allyl-3-phenylthio-β-lactams 1 using sodium metaperiodate (NaIO₄) to diastereomeric trans-3-allyl-3-phenylsulfinyl-β-lactams 2 and 3, which further undergo thermal β-elimination in refluxing carbon tetrachloride to furnish (Z)- and (E)-3-allylidene-β-lactams 5 and 6 in good to excellent yields. The molecular structure of 3b has been established with the help of single crystal X-ray analysis.     

Thermoanalytical and spectroscopic studies on different crystal forms of nevirapine

This study is aimed at exploring the utility of thermoanalytical methods in the characterization of various polymorphs and solvates of nevirapine. The different forms obtained by recrystallization of nevirapine from various solvents showed morphological differences in SEM. The presence of polymorphic forms is suggested by single sharp melting endotherm different from original sample in DSC and no mass loss in TG, while appearance of desolvation peak in TG indicated the formation of solvates. The higher desolvation temperatures of all the solvates than their respective boiling point indicate tighter binding of solvent. The changes in the crystal lattice were demonstrated by X-ray powder diffraction studies. The enthalpy of fusion rule indicated the existence of monotropy in polymorphic pairs I/O and II/O, while I/II is enantiotropically related. The enthalpy of solution, an indirect measure of the lattice energy of a solid, was well correlated with the crystallinity of all the solid forms obtained. The magnitude of ΔH _sol was found to be ?14.26  kJ mol^?1 for Form V and ?8.29  kJ mol^?1 for Form O, exhibiting maximum ease of molecular release from the lattice in Form V. The transition temperature was found to be higher than the melting of both the forms except for polymorphic pair I/II providing complementary evidence for the existence of monotropy as well as enantiotropy in these polymorphic pairs.     

Structural and phonon dynamical properties of perovskite manganites: (Tb, Dy, Ho)MnO3

A shell model has been used to study the structure, phonon dynamics and phase coexistence of perovskite manganites RMnO₃ (R=Tb, Dy, Ho). The calculated crystal structure, Raman and IR frequencies and specific heats are found to be in good agreement with the available experimental data. The phonon density of states, elastic constants, elastic stiffness, shear constants and phonon dispersion curves have been computed for these manganites. A zone center imaginary A_u mode is revealed in these phonon dispersion curves, which indicates the occurrence of the metastability of the perovskite phase. The Gibbs free energy values calculated as a function of temperature and pressure for RMnO₃ in the orthorhombic phase, when compared with those of the hexagonal phase, reveal the possibility of coexistence of these two phases in the present multiferroic manganites under ambient conditions.