New multicomponent catalysts for the selective aerobic oxidative condensation of benzylamine to N-benzylidenebenzylamine

Aerobic oxidative condensation of benzylamine to N-benzylidenebenzylamine was carried out on new gold-based catalysts using as support bimodal UVM-7-like mesoporous silica containing Ni and Ce (or Sn) as oxide nanodomains partially embedded inside the mesoporous UVM-7 silica walls. These nanodomains acted as effective and stable inorganic anchors favoring the nucleation, growth and stability of supported gold particles. Following the atrane method (a “one-pot” strategy able to harmonize the hydrolytic reactivity of different heteroelements through the use of complexes containing triethanolamine-derived ligands (atranes) as precursors) the stability of the oxide nanodomains during oxidation …

Adenocarcinoma de células basales del saco lacrimal bien diferenciado. A propósito de un caso

El adenocarcinoma de celulas basales es un tumor raro y descrito por la Organizacion Mundial de la Salud (OMS) en 1991 como entidad propia. La edad media de presentacion es de 48 anos y no muestra predominio sexual. El curso es insidioso con signos y sintomas inespecificos. Presentamos un caso de adenocarcinoma de saco lacrimal, cuyo diagnostico se realizo por anatomia patologica. Mostramos los hallazgos de tomografia computarizada, resonancia magnetica y anatomia patologica. Se comenta el diagnostico diferencial y el tratamiento.

Glycosidase enzymes stabilization through immobilization onto nanoparticulated bimodal organosilicas

Enhanced manganese content in Mn-MCM-41 mesoporous silicas

The use of triethanolamine containing complexes of Si and Mn as hydrolytic precursors allows the synthesis of doped mesoporous silicas in which the Mn content can be modulated up to reach a minimum value of the Si/Mn molar ratio of 3. This limit value corresponds to a Mn relative content significantly higher than those reported to date for similar materials (Si/Mn = 6). According to XRD, TEM and porosity data, the mesoporous nature typical of the MCM-41 silicas is retained even for the samples having the highest Mn content.

Hyaluronic Acid–Silica Nanohybrid Gels

Excessive water sorption and low mechanical properties are a severe drawback in some biomedical applications of hyaluronic acid (HA). A way to improve these properties is here explored through the novel concept of nanohybrid hydrogels consisting of a HA matrix including different amounts of silica-derived species. This inorganic filler phase controls the mechanical and swelling properties of HA cross-linked matrices. Below a 2 wt % of silica in the systems, nanoparticle aggregates of tens of nanometers and silica oligomers are distributed more or less homogeneously throughout the organic matrix, without percolating. This morphology of the silica phase is accompanied by an increased swelling…

ChemInform Abstract: Crystal Structure and Magnetic Properties of α-Mn(H2PO2)2× H2O.

Abstract The crystal structure of α-Mn(H2PO2)2·H2O has been refined from X-ray powder diffraction data. The cell is monoclinic (space group P21/c, Z − 4) with α = 7.8601(3) A , b = 7.4411(3) A , c = 10.7717(4) A and β = 102.859(2)°. The structure was refined with the Rietveld refinement principles, using as starting model the parameters of the presumably isostructural compound Zn(H2PO2)2·H2O. The structure can be described as being formed by dimeric entities Mn2O2 of edge-sharing manganese octahedra. Each group is linked through Mn-O-P-O-Mn bridges to four other groups, resulting in a three-dimensional network. The thermal variation in the susceptibility shows a sharp peak at T = 6.5 K and …

Polymer solution processing of (Bi, Pb)SrCaCuO

Abstract A simple polymer processing route to the 110 K phase (Bi, Pb) 2 Sr 2 Ca 2 Cu 3 O 10+δ superconductor has been developed. The influence of the polymer to metal starting ratio, as well as the sintering temperature and time on the quality of the resulting superconducting powders has been studied by XRD, a.c. susceptibility and resistivity measurements. Microstructure of ceramic compacts has been studied by SEM, and qualitatively analysed by EDS for compositional homogeneity. The results indicate that the polymer synthesis route described here may offer a good alternative to the conventional solid state preparation methods towards attaining homogeneous 110 K superconductor powder withi…

Structural effects of Co and Cr substitution in LaMnO3 + δ

Series of perovskite oxides with the composition LaMn1 − xMxO3 + δ (M = Cr, Co; 0 ≤ x ≤ 1) have been synthesized by thermal treatment of precursors obtained by freeze-drying of acetic acid solutions. The oxides have been characterized by X-ray diffraction, and the Mn4+ content and, thus, the oxygen excess, δ, has been determined by redox back-titration. LaMnO3.14 and LaCrO3 phases have the rhombohedral-LaAlO3 and the orthorhombic-GdFeO3 structures, respectively. The LaMn1 − xCrxO3 + δ phases have the rhombohedral structure for x ≤ 0.3, and the orthorhombic structure for x ≥ 0.5. LaCoO3 has, as LaMnO3.14, the rhombohedral structure. However, the LaMn1 − xCoxO3 + δ phases have orthorhombic st…

Fast synthesis of single-phased 110 K bismuth superconductor by freeze-drying of acetic precursors. Kinetic role of calcium and copper oxides

Abstract Although the usefulness of solution procedures to improve the synthesis of bismuth HTSC has been argued, an adequate control of the procedural variables has allowed us to isolate the 110 K phase as the only superconducting phase after such a short sintering time as 22 h. The precursors used have been freeze-dried powders resulting from acetic solutions containing excess Ca and Cu. TGA-DTA and XRD experiments have been performed to follow the subsequent solid-state reaction processes. The initial formation of a mixed bismuth-lead oxoacetate, as intermediate to (Bi 1− y Pb y ) 2 CuO 4 , and the presence of an excess of Ca 2 CuO 3 in the last reaction step are two of the main factors …

Chromogenic Discrimination of Primary Aliphatic Amines in Water with Functionalized Mesoporous Silica

Soft hydrothermal synthesis of new microporous materials based on phosphate-like species

ABSTRACTFactors controlling hydrothermal synthetic procedures are not well understood. A good knowledge of the solution chemistry of precursor species is the best reference for the design of rational procedures. Examples of the predictive character of simple models in order to rationalize complex syntheses are discussed in detail.

Fast and compact data acquisition for gas-filled detectors with delay line

This article describes the functionality, implementation and performance of a PCI data acquisition board that can be used in conjunction with gas-filled detectors with delay line readout. The board combines a large on-board 256-MByte histogramming memory with a maximum 10-MHz count rate in continuous operation and integrates the time frame generation, histogram building and buffering functionalities in a single PCI board, resulting in a fast, compact and cost-effective data acquisition solution for the Spanish beamline BM16 at ESRF.

Comparative hydroamination of aniline and substituted anilines with styrene on different zeolites, triflate based catalysts and their physical mixtures

Abstract Catalytic performances of different zeolites (Beta and mordenites), scandium triflate based catalysts, mesoporous UVM-7 encapsulated scandium triflate and physical mixtures prepared under ultrasound irradiation were evaluated in the hydroamination of aniline and substituted anilines with styrene. The performances of these catalysts were controlled by the type of acidity and strength. Thus, the conversion was mainly controlled by the strength of the acid sites and their accessibility, while the selectivity appeared to be controlled by the Lewis/Bronsted type of acidity. Lewis acid catalysts directed the reactions mainly to the formation of the Markovnikov adducts while Bronsted acid…

Paraganglioma carotídeo maligno. A propósito de un caso

Resumen Los tumores del cuerpo carotideo son neoplasias poco frecuentes, de lento crecimiento, muy destructivos y vascularizados, que tienen un origen neuroectodermico. Los tumores malignos representan el 5-13% de los casos y presentan un comportamiento agresivo local con infiltracion de los ganglios linfaticos adyacentes o metastasis a distancia. Presentamos el caso de un varon de 60 anos al que en el estudio por dolor y parestesias en miembro superior se le realiza una resonancia magnetica donde se visualiza una gran tumoracion en el espacio carotideo izquierdo, la cual se biopsio obteniendo el diagnostico histologico de paraganglioma. Al realizar el estudio de extension se identifico la …

Epoxidation of dibenzocycloalkenes on Ti–Ge-MCM-41 and Ti-SBA-15 catalysts

Abstract Epoxidation of a series of dibenzocycloalkenes: phenanthrene, 5H-dibenzo[ a , e ]cycloheptene, 5H-dibenzo[ a , c ] cycloheptene, 5,6-dihydrodibenzo[ a , e ]cyclo-octene, and dibenzo[ a , e ]cyclooctene with hydrogen peroxide was investigated on Ti- and Ge-modified Ti-incorporated-type mesoporous catalysts including MCM-41 and SBA-15 structures looking for the effect of the porous texture and Ge-promoting on both activity and selectivity to epoxide and H 2 O 2 efficiency. Ti–Ge-MCM-41 catalysts (Si/Ti = 43; Si/Ge = 85 and Si/Ti = 41; Si/Ge = 62) were prepared by a one-pot surfactant-assisted procedure based on the use of a cationic surfactant (CTAB, cetyltrimethylammonium bromide), …

A study of the thermal decomposition of amorphous bimetallic CDTA complexes

Abstract The study of the thermal behaviour of a family of bimetallic amorphous MM'(CDTA)· n H 2 O complexes has been performed using TG and DTA. The complexes decompose in three steps: dehydration, ligand pyrolysis and inorganic residue evoluation.

A New Approach to Chemosensors for Anions Using MCM-41 Grafted with Amino Groups

Precursor-based synthetic pathways to nanometer NdNiO3−x particles

Abstract The oxygen deficient neodymium nickel perovskite, NdNiO3−x, has been obtained by different low temperature-low oxygen pressure synthetic procedures. Besides a solid-matrix based route, both ordered and disordered chemical-precursors have been used as starting products. X-ray powder diffraction shows that the structure of this defective perovskite is orthorhombic. The study of the grain morphology of the products as resulting from the different synthetic procedures indicates that the main parameter determining the average particle size, which is in the nanometer range, is the maximum temperature achieved in the synthesis. Resistivity and DSC measurements show the existence of a meta…

Magneto-Structural Correlations in μ-Halo Bridged Copper(II) Chains

To design synthetic pathways to systems of desired properties is a growing challenge for inorganic chemist. Our current interest in this area is focused on copper(II) chemistry. Besides to advance in the understanding of the factors determining the conformation around copper(II) in the solid state, we intend to gain insight into the chemical and structural effects that govern exchange coupling interactions in condensed species. In this context, we have approached the synthesis and characterization of a wide set of pentacoordinated Cu(LIII)XY complexes (LIII=tridentate ligand, X=coordinating anion, Y=coordinating or non-coordinating anion) showing a great structural diversity (including mono…

Malignant carotid paraganglioma: A case report

Tumors of the carotid body are uncommon neoplasms that originate in the neuroectoderm. These tumors are slow growing but well vascularized and very destructive. Between 5% and 13% of carotid body tumors are malignant, behaving aggressively at the local level, invading the adjacent lymph nodes, and resulting in remote metastases. We present the case of a 60-year-old man who was examined for pain and paresthesias in his arm. Magnetic resonance imaging showed a large tumor in the left carotid space. Histologic study of a biopsy specimen from the tumor revealed that it was a paraganglioma. Further studies to determine the extent of disease detected metastases in bone and lung, confirming the tu…

The Influence of Morphological Aspects in the Reaction Pathway and Superconductive Properties of Bi2223-Ca2CuO3 Ceramic Composites

ABSTRACTA variation of the solid-state matrix technique has been developed as a procedure for the preparation of 2223 bismuth superconducting phases [(Bi,Pb)2Sr2Ca1-nCunO4+2n, n=3]. The adequate processing of samples of nominal compositions 2223+x 0021, obtained both by this procedure and by the polymer matrix method, has allowed the modification of the microstructure of the calcium copper excess, with no noticeable change in that of the 2223 grains. The study of the phase evolution in the processing of the samples has shown that the formation rate of the 2223 phase is faster when the particle size of the calcium cuprate is smaller. A dependence of the intergranular superconducting properti…

Polymer-matrix route to (Bi, Pb)2Sr2Ca2Cu3O10+δ: The role of Ca2CuO3☆

Abstract The use of polyethylenimine as active matrix agent has provided a fast synthesis method for (Bi, Pb)2Sr2Ca2Cu3O10+δ, starting from aqueous acetic solutions combined with careful control of the procedural variables. The 110 K phase is obtained as the only superconducting phase after sintering in air during 42 h at 860°C. This technique yields homogeneously sized, large (ca. 20 μm) platelets of the superconducting material. The presence of an excess of calcium and copper over the stoichiometric requirements accelerates the formation of the superconducting phase. This excess, which appears in the resulting material as Ca2CuO3, influences the superconducting properties, other than Tc, …

Synthesis and Characterization of SiC/MC/C Ceramics (M = Ti, Zr, Hf) Starting from Totally Non-oxidic Precursors

The reaction of poly(dimethylsilane) (PDMS) and poly(dimethylcarbosilane) (PCS) with bis(cyclopentadienyl)M dichloride Cp2MCl2 (M ) Ti, Zr, Hf) complexes has been used as a new route to obtain ceramic materials based on SiC-containing M. The reaction is completed at a relatively low temperature, 900 °C, yielding the corresponding amorphous SiC/MC ceramics which have been characterized by means of 29 Si MAS NMR. These amorphous materials have been treated at higher temperatures, 1350 °C, under a purified argon atmosphere, yielding partially crystallized products which have been studied by X-ray powder diffraction and 29 Si MAS NMR. The effect of the composition of the mixture of precursors is