A Polymer for Application as a Matrix Phase in a Concept of In Situ Curable Bioresorbable Bioactive Load-Bearing Continuous Fiber Reinforced Composite Fracture Fixation Plates

The use of bioresorbable fracture fixation plates made of aliphatic polyesters have good potential due to good biocompatibility, reduced risk of stress-shielding, and eliminated need for plate removal. However, polyesters are ductile, and their handling properties are limited. We suggested an alternative, PLAMA (PolyLActide functionalized with diMethAcrylate), for the use as the matrix phase for the novel concept of the in situ curable bioresorbable load-bearing composite plate to reduce the limitations of conventional polyesters. The purpose was to obtain a preliminary understanding of the chemical and physical properties and the biological safety of PLAMA from the prospective of the novel concept. Modifications with different molecular masses (PLAMA-500 and PLAMA-1000) were synthesized. The efficiency of curing was assessed by the degree of convergence (DC). The mechanical properties were obtained by tensile test and thermomechanical analysis. The bioresorbability was investigated by immersion in simulated body fluid. The biocompatibility was studied in cell morphology and viability tests. PLAMA-500 showed better DC and mechanical properties, and slower bioresorbability than PLAMA-1000. Both did not prevent proliferation and normal morphological development of cells. We concluded that PLAMA-500 has potential for the use as the matrix material for bioresorbable load-bearing composite fracture fixation plates.     

Fluorescence modulation of eosin Y in a PMMA film by diarylethene switching

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Zero Point Energy of a Massless Scalar Field in the Cosmic String Space-Time

We consider the ground state energy of a massive scalar field in the space-time of a thick cosmic string in the 2+1 dimensional case for arbitrary angle deficit by using the zeta-function approach. Final numerical calculations were made in the massless case, only. We show that the zero point energy is negative, and for small angle deficit it is proportional to the fourth degree of the deficit.     

[1,2,5]Oxadiazolo[3,4-d]pyridazine 1,5,6-trioxides: efficient synthesis via the reaction of 3,4-bis(hydroxyimino)methyl)-1,2,5-oxadiazole 2-oxides with a mixture of concentrated nitric and trifluoroacetic acids and structural characterization

An efficient synthesis of [1,2,5]oxadiazolo[3,4-d]pyridazine 1,5,6-trioxides (1) from 3,4-bis(hydroxyimino)methyl)-1,2,5-oxadiazole 2-oxides using a mixture of concentrated nitric and trifluoroacetic acids has been developed. The scope of the unconventional reaction was established. The 4,7-dinitro[1,2,5]oxadiazolo[3,4-d]pyridazine 1,5,6-trioxide 1f represents a new high energy compound, unfortunately with low thermal stability. The parent [1,2,5]oxadiazolo[3,4-d]pyridazine 1,5,6-trioxide 1c was studied by single-crystal X-ray diffraction analysis which revealed a planar molecule with an unusually long intracyclic NN bond of 1.668(5)?Å and unexpected exo-cyclic bond angles at the nitroxyl nitrogen atoms. In the crystal, the molecules of 1c are bound to each other by strong π-π stacking and CH?O hydrogen bonding interactions into a three-dimensional framework that results in a high crystal density of 1.833?gcm^?3.     

Thermal annealing-induced modification of the structure and electrical conductivity of metallic nanotubes embedded in PET track-etched membranes

This work is dedicated to developing a simple methodology that allows for the application of a thermal annealing process, which can improve the conductivity of metallic nanostructures, embedded in porous track-etched membranes based on polyethylene terephthalate (PET TeMs), but at the same time, does not compromise the mechanical properties. Zinc, copper, and cobalt nanotubes (NTs) prepared by electrochemical deposition in PET TeMs were annealed at 200 °C for different time periods. The effects of annealing treatment on the structural and electrical properties were investigated by scanning electron microscopy, X-ray diffraction, and room-temperature resistance measurements. Choosing the appropriate annealing time for Zn or Cu-NTs allows controlling the formation of an oxide phase in these nanostructures. The presence of the oxide phase in an amount of no more than 10–15 wt% led to a decrease in the resistivity and an increase in the conductivity. Thermal annealing of Co-based NTs changed intensities of the metastable fcc β-Co and stable hcp α-Co phases. The metastable β-Co phase caused additional defects due to a change in the crystallite size after 90 min of thermal annealing.     

Dinuclear copper(ii) complex with novel N,N’,N”,O-tetradentate Schiff base ligand containing trifluoromethylpyrazole and hydrazone moieties

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Reaction of (2-methoxyprop-2-yl)diphenylphosphine oxide with alkyl bromides

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Synthesis and crystal structure of the novel Pb5Sb2MnO11 compound

The new Pb₅Sb₂MnO₁₁ compound was synthesized using a solid-state reaction in an evacuated sealed silica tube at 650°C. The crystal structure was determined ab initio using a combination of X-ray powder diffraction, electron diffraction and high-resolution electron microscopy (a=9.0660(8)Å, b=11.489(1)Å, c=10.9426(9)Å, S.G. Cmcm, R_I=0.045, R_P=0.059). The Pb₅Sb₂MnO₁₁ crystal structure represents a new structure type and it can be considered as quasi-one-dimensional, built up of chains running along the c-axis and consisting of alternating Mn⁺²O₇ capped trigonal prisms and Sb₂O₁₀ pairs of edge sharing Sb⁺⁵O₆ octahedra. The chains are joined together by Pb atoms located between the chains. The Pb⁺² cations have virtually identical coordination environments with a clear influence of the lone electron pair occupying one vertex of the PbO₅E octahedra. Electronic structure calculations and electron localization function distribution analysis were performed to define the nature of the structural peculiarities. Pb₅Sb₂MnO₁₁ exhibits paramagnetic behavior down to T=5 K with Weiss constant being nearly equal to zero that implies lack of cooperative magnetic interactions.