Synthesis and applications of graphene oxide aerogels in bone tissue regeneration: a review

Development of biocompatible porous supports is a promising strategy in the field of tissue engineering for the repair and regeneration of bone tissues with severe damage. Graphene oxide aerogels (GOAs) are excellent candidates for the manufacture of these systems due to their porosity, ability to imitate bone structure, and mechanical resistance, and according to their surface chemical reactivity, they can facilitate osseointegration, osteogenesis, osteoinduction and osteoconduction. In this review, synthesis of GOAs from the most primary source is described, and recent studies on the use of these functionalized carbonaceous foams as scaffolding for bone tissue regeneration are presented.     

Reaction of 4-acylaminomethylpyridine N-oxides with phenylbutazone in the presence of acetic anhydride

Reaction of 4-acylaminomethylpyridine N-oxides with phenylbutazone in the presence of acetic anhydride is described. In the pharmacological screening one compound shows an interesting anticonvulsant activity.     

Report on Turbulence and Mixing in Geophysical Flows II

We describe the presentations at the international meeting/workshop on Mixing in Geophysical Flows that took place at Vilanova i la Geltru, near Barcelona during the 20, 21 and 22nd of March 1997. There were more than 100 participants from 20 countries with 66 oral and poster presentations covering experimental and theoretical aspects of rotating and stratified fluids as well as field observations. The main topics discussed at the workshop were stratified flows, rotating stratified flows, gravity waves, instabilities and mixing, convection, experiments and numerical simulations of Geophysical flows and turbulent mixing. The papers are summarised in this report giving a state-of-the-art overview of present research in geophysical turbulent mixing.     

Cobalt(II) complexes of 5,7-dimethyl[1,2,4]-triazolo-[1,5-a]-pyrimidine. Spectroscopic characterization,XRD study and antimicrobial activity

Summary Several cobalt(II) complexes of 5,7-dimethyl-[1,2,4]-tria-zolo-[1,5-a]-pyrimidine (DMTP) have been prepared and characterized by thermal and spectroscopic techniques. The crystal structure of [Co(DMTP)₂(H₂O)₄]Br₂·2H₂O has been determined by XRD; the metal ion is octahedrally coordinated by two DMTP ligands through the usual N(3) site and four water molecules. Metal binding to N(3) for DMTP is consistent with the electronic properties calculated with the MOPAC programme. All the complexes were screened for their activity against several types of bacteria, showing a broad-spectrum antimicrobial activity.     

Nutritional composition,antioxidant activity and isolation of scopoletin from Senecio nutans: support of ancestral and new uses

Continuing with our study characterising Senecio nutans Sch. Bip., we have isolated and identified a simple coumarin, scopoletin, that could be relevant for the biological properties of the species related with the ancestral medical uses. This is the first report of scopoletin from S. nutans. In addition, the extract was analysed for its antioxidant activity using the ABTS and FRAP method as well as providing the first nutritional analyses of this plant from northern Chile highlands.     

Structure Functions in Complex Flows

The turbulence in the ocean and atmosphere is most of the time non-homogeneous in nature. These spatial changes could affect the structure of the turbulence. In this work a classification is proposed to determine the intermittency and mixing ability. The variation of the structure functions and the scaling exponent in decaying non-homogeneous turbulence produced by a grid and by a jet is measured with a sonic velocimeter SONTEK3-D. We use Extended Self Similarity (ESS) to obtain better estimates of the scaling exponents of the structure functions of order up to the 6th. We study the variation of the absolute scaling exponents _p and relative scaling exponents ¯_p as a function of distance from the source of turbulence. In most cases, the absolute scaling exponent ₃ is shown to vary as function of the separation distance l. On the other hand the relative scaling exponents ¯_p depend on the location of the flow and in most cases the deviations from the Kolmogorov 1941 scaling are related to the intermittency.     

Performance of a new nebulizer system for simultaneous determination of Sb,Sn (hydride generation), V,and Zn by ICP–OES

A new nebulizer system is described that extends the analytical capability of the inductively coupled plasma technique to include the simultaneous determination of two elements Sb and Sn (hydride-forming), with two conventional elements, V and Zn. The main advantage of this system is its simultaneous determination of elements that form volatile hydrides and elements that do not, without any instrumental changes. Optimization of reaction and instrumental conditions was performed to characterize the new system. The performance of the new nebulizer system was evaluated by studying the effect of some transition metals (Ni, Cu, Co, and Fe, 1–1000 mg L^–1) on the Sb, Sn, V, and Zn emission signals (1 mg L^–1). Interferences from transition metal ions were found to be insignificant for determination of the four elements in presence of L-cysteine. Long-term and short-term stability was also evaluated. The precision, expressed as RSD for 15 replicate measurements was 0.7% for Sb, 1.7% for Sn, 2.5% for V, and 2.3% for Zn at 200 g L^–1 of each analyte. The detection limits obtained were 0.52, 1.3, 3.2, and 4.7 g L^–1 for Sb, Sn, V, and Zn, respectively. Spike and recovery experiments were performed on the NIST 1643c trace metals in water standard reference material and results were in agreement with the certified values.     

Asymmetric synthesis of unusual fused tricyclic beta-lactam structures via aza-cycloadditions/ring closing metathesis

Conveniently substituted bis-beta-lactams, pyrrolidinyl-beta-lactams, and piperidinyl-beta-lactams undergo ring-closing methatesis using Grubbs' carbene, Cl(2)(Cy(3)P)(2)Ru=CHPh, to give medium-sized rings fused to bis-2-azetidinone, pyrrolidinyl-2-azetidinone, or piperidinyl-2-azetidinone systems. The diolefinic cyclization precursors can be obtained from optically pure 4-oxoazetidine-2-carbaldehydes bearing an extra alkene tether at position 1 or 3 of the beta-lactam ring via [2 + 2] cycloaddition of imino 2-azetidinones, N-metalated azometine ylide [3 + 2] cycloaddition, and subsequent N-acylation of the pyrrolidinyl nitrogen atom, or through aza-Diels-Alder cycloaddition of 2-azetidinone-tethered imines. Under standard reaction conditions, the combination of cycloaddition reactions of 2-azetidinone-tethered imines with ring-closing methatesis offers an asymmetric entry to a variety of unusual fused tricyclic 2-azetidinones bearing two bridgehead nitrogen atoms.     

High-precision atomic computations from finite element techniques: Second-order correlation energies for Be,Ca, Sr,Cd, Ba,Yb, and Hg

We have applied the FEM-MP2 method (an implementation of the p-version finite element technique within the framework of second-order Møller–Plesset perturbation theory, [J. Chem. Phys., 98 , 5642 (1993), and references therein]) to calculate second-order correlation energies for the atoms Be, Ca, Sr, Ba, Yb, Cd, and Hg and thus to complete our studies on closed-shell elements. The FEM-MP2 method permits the use of virtual orbitals of very high angular momentum (l_max = 12) in combination with radial basis sets which are very close to completeness, in such a way that we are able to obtain results that could be the most accurate published so far and, in some cases, the only values available in the literature. We hope they may be useful as a reference for basis set saturation tests and for new methods to calculate correlation energies. © 1994 by John Wiley & Sons, Inc.     

Synthesis of 1,2,3,4-tetrahydroquinazoline derivatives as potential alpha-adrenergic blocking agents

The synthesis of N,N′-bis[6-(1,2,3,4-tetrahydro-3-quinazolidyl)hexyl]cystamine (I) and 3-(6-aminohexyl)-1,2,3,4-tetrahydroquinazoline (II) are described. Compound I is obtained by condensation of o-nitrobenzoyl chloride with 3-(6-aminohexyl)-1,3-thiazolidine (III) followed by dimerization, reduction and formation of tetrahydroquinazoline ring. A similar method was used for preparation of compound II. These compounds and some synthesis intermediates are potential alpha-adrenergic blockers.