Thermal behavior study of biodiesel standard reference materials

Quality control of fuel-related properties of biodiesel, such as thermal stability, is needed to obtain consistent engine performance by fuel users, since biodiesel is susceptible to auto-oxidation when exposed to air, light, and temperature during storage. In this work two pure standard reference materials of biodiesels produced from soy oil and animal feedstocks were studied. Differential scanning calorimetry and thermogravimetry measurements were performed and the analysis of the results revealed small temperature variations in the thermal events among the two standards, these differences are due mainly to their chemical composition, been highly influenced by the amounts of unsaturated esters.     

Experimental and theoretical analysis of bias ionization by?α-particles in a nitrogen laser

Nitrogen laser performance with TE configuration and wedge electrodes is analyzed with background ionization in the laser discharge channel by α particles at a low exposition rate. With the bias ionization, the laser power presents two peaks as a function of gas pressure, with one at the normal low pressure, without bias ionization, and the other at high pressure generated by bias ionization. A simple theoretical model has been developed in a trial to understand this behavior. This model was first tested in later results for a TE configuration nitrogen laser, with flat electrodes, without and with bias ionization. It has been observed that due to the competition between electrode shielding by positively charged α particles and bulk ionization by impact, the laser energy is suppressed with pressure below 50 Torr and enhanced above it.     

Systems biology reveals biology of systems

In the last decades, genomic and postgenomic technologies obtained a great amount of information on molecular bases of cell physiology and organization. In spite of this, the knowledge of cells and living organisms in their entirety, is far from being achieved. In order to deal with biological complexity, Systems Biology uses a new approach to overcome this inadequacy. Despite different definitions, Systems Biology's view of biological phenomena highlights that a holistic perspective is needed to integrate and understand the huge amount of empirical data which have been collected. This is one of the aspects that makes Systems Biology so interesting, from a theoretical and epistemological point of view, and that renders it a useful tool to help students approach living beings' dynamics within a comprehensive framework of their biological features as well. © 2010 Wiley Periodicals, Inc. Complexity, 2010     

Loss aversion with multiple investment goals

This paper presents a time-continuous portfolio selection model with loss averse investors, who possess multiple investment goals at different time horizons. The model assumes partial narrow framing. Investors follow a two-step approach. First, they optimally allocate wealth among investment goals. Second, they determine an optimal investment strategy for each investment goal separately. We show that when loss aversion is according to the experimental findings, investors mainly invest their wealth to reach long-term goals and adopt investment strategies with high leverage to reach short-term goals. The overall strategy also display high leverage. The same patterns is observed when loss aversion is extreme and goals are very ambitious. By contrast, when loss aversion is extreme but goals are not too ambitious, investors mainly invest to reach short-term goals and adopt safe investment strategies for this purpose.     

Dynamics of wetting and Kramers’ theory

We investigate the potential link between Kramer’s treatment of rate processes and the molecular-kinetic theory of wetting. The results of recent large-scale simulations of dynamic wetting are used to illustrate and validate our analysis. We find that both theories predict that, for a given driving force, the velocity of the contact line is inversely proportional to the viscosity. They also predict that the velocity will depend with a negative exponent on the strength of solid-liquid interactions, which for simple systems can be represented to good approximation by the reversible work of adhesion Wa ⁰.     

Phase transitions of [M(H2O)6](MnO4)2 polycrystalline compounds,where M=Mg2+,Ni2+,Zn2+,Cd2+, studied by DSC

Phase transitions of [M(H₂O)₆](MnO₄)₂, where M=Mg, Ni, Zn and Cd, have been studied at 100–400 K by differential scanning calorimetry (DSC). One solid–solid phase transition for the compounds with M=Mg and Ni and two solid–solid phase transitions for these with M=Zn and Cd have been discovered. Additionally, three phase transitions, connected with three-stage melting process of these compounds, were also found. Thermodynamic parameters of the all detected phase transitions were calculated.     

The Intramolecular Diels-Alder Furan Approach in Synthesis : 11-oxatricyclo|6.2.1.01,6|undec-9-en-5-one

Although the synthetic potential of the intramolecular variant of the Diels-Alder reaction has now been fully recognized³, little attention has so far been paid to this type of addition using the furan nucleus as the diene partner4–8. The presence of an oxygenated cyclohexene system in several complex natural products (e.g. gibberellic acid, morphine), the diverse possibilities of the substituted 7-oxabicyclo |2.2.1|-2-heptene system for further transformation⁹, the expected enhanced reactivity and stereoselectivity of the intramolecular cycloaddition and the availability of a wide variety of commercial furan derivatives make the sequence a → b → c particularly attractive in total synthesis.     

Toward reactant encapsulation for substrate-selectivity

A synthetic tris-(bis-(aminomethyl)pyridine) receptor was prepared in excellent yields via reversible imine condensation strategy. Catalytic activity in Henry reactions of the corresponding copper(II) complex was studied. Capitalizing on previous works by Anslyn with related receptors, the dramatic increase in basicity induced by this type of complex on diketo-derivatives was used to perform a nucleophilic addition of a deprotonated substrate onto an electrophile within the cavity. Hence, a Lewis acid stabilized nitronate was reacted with various aldehydes. A notable preference for small reactants easily accommodated in the cavity over encumbered ones was observed, thus representing an example of substrate-selectivity.