Study of semileptonic and nonleptonic decays of the B<Subscript>c</Subscript><Superscript>-</Superscript> meson

We evaluate semileptonic and two-meson nonleptonic decays of the B _c ^- meson in the framework of a nonrelativistic quark model. The former are done in spectator approximation using one-body current operators at the quark level. Our model reproduces the constraints of heavy-quark spin symmetry obtained in the limit of infinite heavy-quark mass. For the two-meson nonleptonic decays we work in factorization approximation. We compare our results to the ones obtained in different relativistic approaches.     

12α-hydroxy-N-demethyl-sauroxine,a lycodane type alkaloid from Phlegmariurus saururus

Abstract

12α-hydroxy-N-demethyl-sauroxine (1), another new Lycopodium alkaloid from the Lycodane group, was isolated from Phlegmariurus saururus (Lam.) B. Øllg. (Lycopodiaceae). Elucidation of the chemical structure and relative stereochemistry were stated by spectroscopic data and chemical correlation. In addition, the inhibitory activity on acetylcholinesterase for 1 was determined as well as for N-methyllycodine (2), a derivative with the same nucleus, previously identified in P. saururus (IC₅₀ = 33.8?±?0.8?μM and 547.5?±?0.5?μM, respectively) and N-demethylsauroxine (3) whose inhibition in the actual conditions was better than the previously informed.     

Explicit solution for a Stefan problem with variable latent heat and constant heat flux boundary conditions

In Voller, Swenson and Paola [V.R. Voller, J.B. Swenson, C. Paola, An analytical solution for a Stefan problem with variable latent heat, Int. J. Heat Mass Transfer 47 (2004) 5387-5390], and Lorenzo-Trueba and Voller [J. Lorenzo-Trueba, V.R. Voller, Analytical and numerical solution of a generalized Stefan problem exhibiting two moving boundaries with application to ocean delta formation, J. Math. Anal. Appl. 366 (2010) 538-549], a model associated with the formation of sedimentary ocean deltas is studied through a one-phase Stefan-like problem with variable latent heat. Motivated by these works, we consider a two-phase Stefan problem with variable latent of fusion and initial temperature, and constant heat flux boundary conditions. We obtain the sufficient condition on the data in order to have an explicit solution of a similarity type of the corresponding free boundary problem for a semi-infinite material. Moreover, the explicit solution given in the first quoted paper can be recovered for a particular case by taking a null heat flux condition at the infinity.     

Energetic characterization of forest biomass by calorimetry and thermal analysis

The rational and sustainable exploitation of natural resources is one the priority objectives of our consumer society as an unavoidable strategy for survival. In previous articles, research group TERBIPROMAT has established the bases for the elaboration of energy maps of forest biomass. With those data, it is possible to classify the species in terms of their energy content and of their possible application as biofuels following European Norm CEN/TS 14961/2005 on solid biofuels. Main forest species used in this study were Populus and Paulownia. These species have a fast growth and produce big amounts of energetic biomass. To complete this study a comparison with autochthonous forest species, Eucalyptus and Pinus, was made. In this study, a thermogravimetric analysis is employed to qualitative study the resistance to thermal degradation of different forest species. These studies complete those made through static bomb calorimetry, elemental analysis, and different mechanical tests trying to get relationships between thermal behaviour and some physical properties.     

Exchange bias in iron oxide nanoclusters

Iron oxide nanoclusters have been prepared by the gas-phase aggregation technique to form thin film structures with very high exchange bias values (up to 3000?Oe at low temperatures). Composition has been analysed by x-ray absorption and M?ssbauer spectroscopies in order to elucidate the actual origin of the observed magnetic behaviour. The formation of a metal-oxide core-shell arrangement to explain the observed exchange bias has to be discarded since results show no metallic iron content and the main presence of α-Fe(2)O(3). The observed weak ferromagnetism and exchange bias are in agreement with the obtained size of α-Fe(2)O(3) nanoparticles: weak ferromagnetism because of the well-known spin canting in this antiferromagnetic structure and exchange bias because of the interaction between different spin sublattice configurations promoted by the modification of iron coordination in α-Fe(2)O(3) nanoparticles. Moreover, the preparation method is proposed for tuning both magnetization and exchange bias values by modification of the preparation conditions of α-Fe(2)O(3) nanoparticles, which open new possibilities in the design of new materials with required properties.     

New Access to Sesquiterpene Hydroquinones: Synthesis of (+)‐ent‐Chromazonarol

A facile access to optically active (+)‐ent‐chromazonarol ent‐1, isolated from the sponge Disidea pallescens, is reported from commercially available (+)‐manool 4.     

Semileptonic bc to cc and bb to bc baryon decays and heavy quark spin symmetry

We study the semileptonic decays of the lowest-lying bc baryons to the lowest-lying cc baryons （Ξ （＊） bc → Ξ （＊） cc and Ω （ ＊） bc → Ω （＊） cc ）,in the limit m b,m c Λ QCD and close to the zero recoil point.The separate heavy quark spin symmetries make it possible to describe all these decays using a single form factor.We also show how these constraints can be used to test the validity of different quark model calculations.bb to bc baryon decays are also discussed.     

Copper (I)-BOX Catalyzed Asymmetric 3-Component Reaction for the Synthesis of Trifluoromethylated Propargylic Ethers and Anilines**

An asymmetric 3-component reaction between EthynylBenziodoXoles (EBXs), 2,2,2-trifluorodiazoethane and nucleophiles catalyzed by a Cu^I-BOX (Bisoxazoline) catalyst is described. This protocol gives access to chiral trifluoromethylated propargyl ethers and anilines, which are valuable building blocks in synthetic and medicinal chemistry. The reaction proceeds with high enantioselectivity and yield with different nucleophiles such as primary, secondary and tertiary alcohols, as well as both electron-rich and electron-poor anilines. Aryl-, alkyl- and silyl-substituted alkynes can be successfully introduced as electrophiles. In case of chiral substrates, high catalyst control was observed, leading to good diastereoselectivity.