Structural and spectral study of 7-bromo-1,3-dihydro-5-(2-pyridyl)-2H-1,4-benzodiazepin-2-one (bromazepam) platinum(II) dichloride bisdimethylsulfoxide

The synthesis and crystal and molecular structure of the title compound are reported. It belongs to the monoclinic space groupC2/c, witha=17.889(2),b=13.511(1),c=19.912(2) Å,=99.841(4)°, andZ=8. The structure was refined to a finalR of 2.77% (R _w =2.88%) for 3617 observed reflections. Vibrational spectra are recorded and discussed.     

Restricted rotation in amides—VI : Configurations and conformations of unsymmetrical tertiary benzamides

Configurational assignments in a series of N-alkyl-N-benzylbenzamides using a variety of NMR techniques lead to consistent assignments in amides with two isomers but are inconclusive for amides with single isomers. Single crystal X-ray structure determination shows the configuration of o-bromo-N-benzyl-N-t-butyl-benzamide to have the t-Bu group syn to the carbonyl oxygen. Surprisingly, the major isomer of o-chloro-N-benzyl-N-i-propylbenzamide, appears to have the opposite configuration, i.e., the i-Pr group is anti to the carbonyl oxygen. The structural details of o-bromo-N-benzyl-N-t-butylbenzamide reveal slight deviation from planarity for the amide group and chirality of the benzoyl group.     

Structural consequences of metal complexation of cyclo[Pro-Phe-Phe-Ala-Xaa]2 decapeptides

The conformational features of both free and Ca2+-complexed cyclo[Pro-Phe-Phe-Ala-Xaa]2 (with Xaa= Glu(OtBu), Lys(CIZ), Leu, and Ala) in solution have been determined by NMR spectroscopy and extensive distance-geometry calculations. The decapeptides are conformationally homogeneous in solution and show common structural features in their free and complexed forms. The structures of the free form contain only trans peptide bonds and are topologically similar to the structure of gramicidin-S, folded up in two antiparallel extended structures, stabilized by interstrand hydrogen bonds, and closed at both ends by two beta-turns. In contrast, the Ca2+-complexed peptides present two cis peptide bonds and are generally similar to those observed for the metal-complexed forms of antamanide and related analogues, folded into a saddle shape with two beta-turns. The Glu(OtBu)-, Leu-, and Lys(ClZ)-containing peptides examined here maintain the biological activity of the cyclolinopeptide A in their ability to competitively inhibit cholate uptake. The natural antamanide and cyclolinopeptide A are both able to inhibit the uptake of bile salts into hepatocytes. They share the same postulated active sequence Pro-Phe-Phe. Based on our structural results, we conclude that the ability to adopt a global conformation, characterized by a clear amphipathic separation of hydrophobic and hydrophilic surfaces, is an important feature for the functioning of this class of peptides.     

Solid-state structure and conformation of (Z)-2-(phenylbenzylidene)-3-quinuclidinone,an intermediate in the synthesis of quinuclidine derivatives

(Z)-2-(2-phenylbenzylidene)-3-quinuclidinone, C₂₀H₁₉NO,M _r =300.47D crystallizes in the monoclinicP2₁/c space group witha = 6.9809(2) Å,b=19.0523(2) Å,c = 11.7733(1) Å,=100.92(2)°,V=1537.5(3) ų,Z=4,D _c = 1.298 g/cm³,D _x =1.29 g/cm³ (flotation). Diffractometric data, using CuK radiation,=1.54178 Å, were collected on plate-like crystals. The structure, solved by direct methods was refined to a final R value of 0.037 for the 2645 observed reflections withF _o >3.0(F _o ). The molecule shows a trans conformation around the double bond. The quinuclidine and the diphenyl moieties present deformations in their geometric and conformational parameters due to the need of releasing intramolecular strains and/or nonbonded interactions.     

On the quantum Teichmüller invariants of fibred cusped 3-manifolds

This paper defines the pressure metric on the Moduli space of Margulis spacetimes without cusps and shows that it is positive definite on the constant entropy sections. It also demonstrates an identity regarding the variation of the cross-ratios.     

A fast 3D dual boundary element method based on hierarchical matrices

In this paper a fast solver for three-dimensional BEM and DBEM is developed. The technique is based on the use of hierarchical matrices for the representation of the collocation matrix and uses a preconditioned GMRES for the solution of the algebraic system of equations. The preconditioner is built exploiting the hierarchical arithmetic and taking full advantage of the hierarchical format. Special algorithms are developed to deal with crack problems within the context of DBEM. The structure of DBEM matrices has been efficiently exploited and it has been demonstrated that, since the cracks form only small parts of the whole structure, the use of hierarchical matrices can be particularly advantageous. Test examples presented show that, with the proposed technique, substantial increase in number of elements over the crack surfaces leads only to moderate increases in memory storage and solution time.     

A New Perspective in Adhesion Science and Technology: Testing Dynamic Failure of Adhesive Junctions for Space Applications

Under micro-gravity conditions, typical of the space environment, adhesion forces may play a relevant role in the manipulation of objects, especially when they must be released into free-fall under controlled residual velocity conditions. When only contact forces may be applied to the body that must be released to free-fall, no solution different from inertia is available to detach it from the manipulating device. If the manipulator is retracted from the body quickly enough, any adhesive bond existing between them is brought to failure, being loaded by the inertia force. The body acquires a residual momentum equal to the impulse developed by the adhesion force upon its failure. An experimental technique has been developed to characterize the impulse that adhesive junctions between two metallic rough surfaces develop upon dynamic failure, as part of the qualification of a system (the Caging Mechanism) designed for this specific function in the frame of the LISA Pathfinder space mission by the European Space Agency (ESA). This paper reports on the recent results obtained through the experimental campaigns performed in the LISA Pathfinder ground testing activities of the Caging Mechanism.     

Structural and photoluminescence properties of ZrO2:Eu @ SiO2 nanophosphors as a function of annealing temperature

The synthesis, morphology and luminescence properties of two systems comprising luminescent Eu³⁺-doped zirconium oxide nanocrystals embedded in an amorphous silica matrix are reported. The two systems, prepared with the same overall wt% composition of silica (75%) and Eu_xZr_(1−x)O_(2−x/2) solid solution (25%), have been annealed in the range 135–1000 °C and subsequently functionalized with (3-aminopropyl)triethoxysilane. Detailed X-ray diffraction analyses and transmission electron micrographs, combined with infrared spectroscopy and luminescence spectroscopy data, have been used to demonstrate the influence of annealing temperature on the: (i) nanostructure, (ii) luminescence properties and (iii) availability of superficial –OH groups for efficient surface functionalization. The optimum calcination temperature was found to be 700 °C for each series in terms of luminescence lifetime efficiency and post-functionalization efficiency with (3-aminopropyl)triethoxysilane.     

Evolution Problems with Nonlinear Nonlocal Boundary Conditions

We provide a new approach to obtain solutions of evolution equations with nonlinear and nonlocal in time boundary conditions. Both, compact and noncompact semigroups are considered. As an example we show a “principle of huge growth”: every control of a reaction-diffusion system necessarily leads to a profile preserving nonlinear huge growth for an appropriate initial value condition. As another example we apply the approach with noncompact semigroups also to a class of age-population models, based on a hyperbolic conservation law.     

Supercharacters,symmetric functions in noncommuting variables,and related Hopf algebras

We identify two seemingly disparate structures: supercharacters, a useful way of doing Fourier analysis on the group of unipotent uppertriangular matrices with coefficients in a finite field, and the ring of symmetric functions in noncommuting variables. Each is a Hopf algebra and the two are isomorphic as such. This allows developments in each to be transferred. The identification suggests a rich class of examples for the emerging field of combinatorial Hopf algebras.