Thermal studies on arsenic,antimony and bismuth alkylxanthate complexes

Six xanthate derivatives of arsenic(III), antimony(III), and bismuth(III) {(ROCS₂)₃M; R=methyl, ethyl, isopropyl, n-butyl, cyclohexyl and benzyl} have been prepared and the thermal behaviour investigated by thermogravimetry. A thermal decomposition mechanism for the complexes is proposed on the basis of the thermogravimetric data and mass spectral measurements.     

Synthesis of new 14- and 16-membered macrocycles and their transition metal complexes

Summary Benzoylacetic acid (1 mol) interacts with ethylenediamine or with propanediamine (2 mol) to yield new N₄ macrocycles 1,5,8,12-tetraazacyclotetradeca-2,4,9,11-tetraphenyl-3, 10-dicarboxylic-4,11-diacetic acid- 1,8-diene (L¹) and 1,5,9,13-tetraazacyclohexadeca-2,4,10,12-tetraphenyl-3, 11-dicarboxylic-4,12-diacetic acid-1,9-diene (L²), respectively. These macrocycles have been successfully complexed with Cr^III, Fe^III, Mn^II, Co^II, Ni^II, Cu^II and Zn^II. The complexes of the divalent metal ions are non-electrolytes, while those of Fe^III and Cr^III are 1:1 electrolytes in DMSO. On the basis of ligand field spectra and magnetic moments an octahedral geometry has been proposed for all the complexes.     

Efficient delivery of Cre-recombinase to neurons in vivo and stable transduction of neurons using adeno-associated and lentiviral vectors

Background

As development proceeds the human embryo attains an ever more complex three dimensional (3D) structure. Analyzing the gene expression patterns that underlie these changes and interpreting their significance depends on identifying the anatomical structures to which they map and following these patterns in developing 3D structures over time. The difficulty of this task greatly increases as more gene expression patterns are added, particularly in organs with complex 3D structures such as the brain. Optical Projection Tomography (OPT) is a new technology which has been developed for rapidly generating digital 3D models of intact specimens. We have assessed the resolution of unstained neuronal structures within a Carnegie Stage (CS)17 OPT model and tested its use as a framework onto which anatomical structures can be defined and gene expression data mapped.

Results

Resolution of the OPT models was assessed by comparison of digital sections with physical sections stained, either with haematoxylin and eosin (H&E) or by immunocytochemistry for GAP43 or PAX6, to identify specific anatomical features. Despite the 3D models being of unstained tissue, peripheral nervous system structures from the trigeminal ganglion (~300 μm by ~150 μm) to the rootlets of cranial nerve XII (~20 μm in diameter) were clearly identifiable, as were structures in the developing neural tube such as the zona limitans intrathalamica (core is ~30 μm thick). Fourteen anatomical domains have been identified and visualised within the CS17 model. Two 3D gene expression domains, known to be defined by Pax6 expression in the mouse, were clearly visible when PAX6 data from 2D sections were mapped to the CS17 model. The feasibility of applying the OPT technology to all stages from CS12 to CS23, which encompasses the major period of organogenesis for the human developing central nervous system, was successfully demonstrated.

Conclusion

In the CS17 model considerable detail is visible within the developing nervous system at a minimum resolution of ~20 μm and 3D anatomical and gene expression domains can be defined and visualised successfully. The OPT models and accompanying technologies for manipulating them provide a powerful approach to visualising and analysing gene expression and morphology during early human brain development.     

Mechanism of phosphine photolysis. Application to Jovian atmospheric photochemistry

PH3 is photolyzed to H2 and P2H4 and the P2H4 in turn is converted to red phosphorus. The initial quantum yield of H2 formation was redetermined and found to be 0.93 +/- 0.07. Red phosphorus was identified by its chemical properties and the absence of P-H stretching bands in its infrared spectrum. The reaction pathway was not changed by lowering the PH3 partial pressure from 90 to 11 torr or by performing the photolysis in a 70-fold excess of H2. The initial quantum yields at 11 torr of PH3 are phi P2H4 = 0.04 +/- 0.02 and phi H2 = 0.74 +/- 0.08. The initial rate of P2H4 formation was not affected by lowering the PH3 temperature to 227 or 157 K. The yield was greater at 157 K because the P2H4 condensed and was protected from further destruction. The initial quantum yields for the formation of P2H4 and H2 in PH3-NH3 mixtures were comparable to those observed for PH3 alone. Photolysis of mixtures in which NH3 was absorbing 90% of the light resulted in the rapid formation of P2H4. No N2 was formed when PH3-NH3 mixtures were photolyzed, suggesting that the destruction of NH3 is quenched by PH3. The application of these findings to Jovian atmospheric chemistry is discussed.     

Positive integer solutions of the diophantine equation x 2 − L n xy + (−1) n y 2 = ±5 r

In this paper, we consider the equation x ²?L _n x y+(?1) ⁿ y ² = ±5 ^r and determine the values of n for which the equation has positive integer solutions x and y. Moreover, we give all positive integer solutions of the equation x ²?L _n x y+(?1) ⁿ y ² = ±5 ^r when the equation has positive integer solutions.     

The effect of a substitutional Fe impurity on the magnetic properties of the antiferromagnetic FeRh alloy

We present a simple model for the band structure of the Fe_0.50Rh_0.50 anti-ferromagnetic alloy, and we study the effect of a substitutional Fe impurity on the magnetic properties of this alloy.     

A TEM and XRD study of the SbNbSe3 misfit layer structures

Two new misfit layer structures have been synthesized within the Sb-Nb-Se system. Powder X-ray diffraction and electron microscopy techniques (electron diffraction, HREM, XEDS) have been used to determine the nature of their structure. According to TEM and XEDS data (for more than 15 crystals studied) both phases are monolayer type, i.e. (SbSe)1+delta (NbSe2). Electron microscopy reveals a composite modulated structure that consists of the periodical intergrowth of a pseudotetragonal SbSe layer, denominated as Q, and a pseudohexagonal layer NbSe2, denominated as H. Both layers fit along b, stack along c and do not fit along a (misfit) giving rise to an incommensurate modulation along this direction. The two phases differ in the symmetry of the Q layers being in one case orthorhombic (for delta = 0.17) and monoclinic in the other (for delta = 0.19). After the characterization of the sample by electron microscopy the unit cells of the basic layers could be refined for both phases by powder X-ray diffraction: aQ = 5.824(2) A, bQ = 5.962(5) A, cQ = 23.927(6) A, alpha = 90 degrees, beta = 90 degrees and gamma = 90 degrees and aH = 3.415(5) A, bH = 5.962(6) A,, cH = 11.962(1) A, alpha = 90 degrees, beta = 90 degrees and gamma = 90 degrees for the orthorhombic phase; aQ = 5.844(2) A, bQ = 5.981(1) A, cQ = 23.919(5) A, alpha = 90 degrees, beta = 90 degrees and gamma = 96.00(3)degrees and aH = 3.439(1) A, bH = 5.994(2) A, cH = 11.956(3) A, alpha = 90 degrees, beta = 90 degrees and gamma = 90 degrees for the monoclinic phase. The phase with the monoclinic Q-sublattice often appears as twinned crystals. The more abundant crystals are disordered intergrowths of both monolayer phases.     

Spectral domain analysis of eigenmodes in a shielded multilayer coplanar waveguide for microwave and millimeter-wave integrated circuits

Coplanar waveguide has found increasing use in microwave and millimeter-wave integrated circuits, and a knowledge of its eigenmodes is very useful for circuit design. In this paper, we determine the dispersion properties of the eigenmodes in a shielded multilayer coplanar waveguide using the spectral domain approach. Numerical results of the propagation constants for different combinations of dielectric materials are presented to illustrate the behaviors of the eigenmodes.     

On polynomial EkP matrices

In this paper the relation betweenEP--matrices andE ^k P--matrices over an arbitrary filedF is studied. Further, conditions for the product ofE ^k P--matrices to be anE ^k P--matrix and for the reverse order law to hold for the polynomial Moore-Penrose inverse of the product ofE ^k P--matrices are determined