Wood-Concrete and Wood-Wood Mixed Beams: Rational Basis for Selecting Connections

Many studies have approached the problem of mixed beams with a slip at the connection. An analysis of the problem has been carried out globally and Eurocode-5 solves the problem for the use of simple supported beams or similar structures in a precise way and with a simple formulation. Other methods to solve the structural analysis of this issue include matrix as well as several finite-element procedures. Nevertheless, the design process for selecting the connection is now iterative and the variables of the problem can be presented in a more condensed and useful way. The problems of strength and stiffness in this research have been separated. Variables in a powerful nondimensional way and their exact relationships in simple supported beams are presented here. These variables show the nature of the problem in a clear way, and provide a rational basis for selecting the connection

The flexibility matrix o timber composite beams with a discrete connection system

This work presents a method for the analysis of timber composite beams which considers the slip in the connection system, based on assembling the flexibility matrix of the whole structure. This method is based on one proposed by Tommola and Jutila (2001). This paper extends the method to the case of a gap between two pieces with an arbitrary location at the first connector, which notably broadens its practical application. The addition of the gap makes it possible to model a cracked zone in concrete topping, as well as the case in which forming produces the gap. The consideration of induced stresses due to changes in temperature and moisture content is also described, while the concept of equivalent eccentricity is generalized. This method has important advantages in connection with the current European Standard EN 1995-1-1: 2004, as it is able to deal with any type of load, variable section, discrete and non-regular connection systems, a gap between the two pieces, and variations in temperature and moisture content. Although it could be applied to any structural system, it is specially suited for the case of simple supported and continuous beams. Working examples are presented at the end, showing that the arrangement of the connection notably modifies shear force distribution. A first interpretation of the results is made on the basis of the strut and tie theory. The examples prove that the use of EC-5 is unsafe when, as a rule of thumb, the strut or compression field between the support and the first connector is at an angle with the axis of the beam of less than 60º

Alcohol activation by [Ir(COD)(tris(pyrazol-1-yl)methane)]+ and [Ir(COD) (tris(pyrazol-1-yl)ethanel+ cations: formation of alkoxycarbonyl derivatives [(tpzm)IrH(CO2R′)(CO)]+ and [(tpze)IrH(CO2R′)]+ (R′ = Me, Et, i-Pr)

The reactions of iridium and rhodium complexes derived from tris(pyrazolyl)-methane (tpzm) and tris(pyrazolyl)ethane (tpze) have been examined. One of the most interesting reactions involves the formation of alkoxycarbonyl derivatives of iridium tris(pyrazolyl)alkanes from carbon monoxide and alcohols. In the case of rhodium derivatives, a dimer of formula [(tpzm)]2Rh2(CO)3](CIO42 has been obtained. A careful 1H and 13C NMR study has allowed assignment of all the signals of the compound [(tpzm)IrH(CO2Me)(CO)]BF4.We thank CAICYT for financial support (Project Number 326/84) and one of us (C.L.) is indebted to the “Secretaria General Tecnica de la Consejeria de Education y Juventud de la Comunidad the Madrid” of Spain for a Grant.Peer reviewe

Conformation of 5,6,11,12-tetrahydrodibenzo[a,e]cyclooctene: an experimental and theoretical NMR study

Hybrid ab initio calculations (GIAO/B3LYP/6-31G*) together with new DNMR experiments (1H and 13C) have been used to clarify the problem of the conformation of 5,6,11,12-tetrahydrodibenzo[a,e]cyclooctene. The carbon-13 chemical shifts have been assigned unambiguously to the chair C and twist-boat TB conformations. Lineshape analysis of the 1H NMR spectra has been carried out at several temperatures using an estimated set of Karplus-type vicinal coupling constants.Financial support from the Spanish DGICYT (Project No. PB96-0001-C03) is gratefully acknowledged.Peer reviewe

Aromatic propellenes .8. Semiempirical calculations and DNMR studies of hexakis(pyrazol-1-yl)benzenes

The stability of all possible conformers of hexa(pyrazol-1-yl)benzene [(pz)6bz], hexakis(3,5-dimethylpyrazol-1-yl)benzene [(dmpz)6bz], 1,2,4,5-tetra(pyrazol-1-yl)-3,6-bis(3,5-dimethylpyrazol-1-yl)benzene [(pz)4(dmpz)2bz] and 1,4-di(pyrazol-1-yl)-2,3,5,6-tetrakis(3,5-dimethylpyrazol-1-yl)benzene [(pz)2(dmpz)4bz] has been determined by semiempirical AM1 calculations. In all series the absolute minimum corresponds to the conformation where the nitrogen lone pair of consecutive pyrazole rings is alternatively oriented to opposite sides of the benzene plane. The case of (pz)2(dmpz)4bz has been studied by 1H NMR studies in solution. Three isomers have been identified and all the signals assigned. The slow evolution to other isomers from those found in the solid state has been followed by 1H NMR spectroscopy thus allowing determination of the barrier to rotation of a (dmpz) substituent (ΔG‡ = 21–22 kcal mol–1)We thank the CICYT (Spain) for financial support (project numbers PB93-0125 and PB93-0197-C02).Peer reviewe

Itinerarios educativos del Principado de Asturias 2003

Resumen basado en la publicaciónSe presenta un conjunto de recursos educativos, socioculturales y medioambientales, que debidamente coordinados se ofertan a los Centros Educativos de los niveles no Universitarios del Principado de Asturias. La presente edición recoge la información necesaria para conocer y utilizar las 17 Aulas de la Naturaleza que configuran la red de Aulas del Principado de Asturias. Cada Aula hace una propuesta de rutas e itinerarios, de las tradiciones de la zona, etc, relacionadas con el entorno en el que se encuentra. La finalidad de esta acción es promover la educación ambiental desde una perspectiva de la educación en valores utilizando como recurso la Aulas de la Naturaleza, favoreciendo la relación y convivencia en el espacio educativo asturiano y profundizando en el conocimiento de Asturias.AsturiasUniversidad de Oviedo.Facultad de Ciencias de la Educación; Calle Aniceto Sela s. n.; 33005 Oviedo; +34985103215; 985103214;ES

Identification and Activity of a Series of Azole-based Compounds with Lactate Dehydrogenase-directed Anti-malarial Activity.

Plasmodium falciparum, the causative agent of malaria, relies extensively on glycolysis coupled with homolactic fermentation during its blood-borne stages for energy production. Selective inhibitors of the parasite lactate dehydrogenase (LDH), central to NAD(+) regeneration, therefore potentially provide a route to new antimalarial drugs directed against a novel molecular target. A series of heterocyclic, azole-based compounds are described that preferentially inhibit P. falciparum LDH at sub-micromolar concentrations, typically at concentrations about 100-fold lower than required for human lactate dehydrogenase inhibition. Crystal structures show these competitive inhibitors form a network of interactions with amino acids within the active site of the enzyme, stacking alongside the nicotinamide ring of the NAD(+) cofactor. These compounds display modest activity against parasitized erythrocytes, including parasite strains with known resistance to existing anti-malarials and against Plasmodium berghei in BALB/c mice. Initial toxicity data suggest the azole derivatives have generally low cytotoxicity, and preliminary pharmoco-kinetic data show favorable bioavailability and circulation times. These encouraging results suggest that further enhancement of these structures may yield candidates suitable for consideration as new therapeutics for the treatment of malaria. In combination these studies also provide strong support for the validity of targeting the Plasmodium glycolytic pathway and, in particular, LDH in the search for novel anti-malarials