UPS of multilayer nitrogen‐bearing compounds on the Si(100) surface

Ultraviolet photoemission spectra (UPS) are presented for condensed layers of three ethylated amines; mono‐, di‐, and triethylamine (TEA) on the Si(100) surface at 100 K. The photoemission peaks associated with the nitrogen lone pair electrons are identified in the amines and compared with the corresponding spectra for condensed ammonia. Shifts in the lone pair binding energy for the ethyl‐substituted amines are shown to be consistent with conventional chemical paradigms. Also, for comparison purposes spectra for two nonethylated amines, trimethylamine (TMA), and its silicon analog, trisilylamine (TSA), are presented and discussed. Copyright © 2008 John Wiley & Sons, Ltd.     

Interaction studies of diacyl glycerol arginine-based surfactants with DPPC and DMPC monolayers, relation with antimicrobial activity

Antimicrobial agents have a major practical importance in food, pharmaceutical and cosmetic applications for preventing contamination. Our group has developed a novel class of cationic diacyl glycerol arginine-based surfactants denoted 1414RAc and 1212RAc. To assess the antimicrobial properties of these new surfactants we have studied how they interact with 1,2-dipalmitoyl-sn-glycero-3-phosphocoline (DPPC) and 1,2-dimiristoyl-sn-glycero-3-phosphocoline (DMPC) as model membranes, as well with living organisms endowed or not with external barriers, such as gram negative bacteria, the human protozoa Leishmania and mammalian cell line.

The structure and phase characteristics of mixed monolayers have been assessed through the analysis of static elasticity. The extent of component miscibility of surfactant and phospholipid in mixed monolayers has been studied using the additivity rule and the excess free energy of a mixture as a function of the phospholipid molar fraction for different surface pressure values. In all the mixtures studied, the mixed monolayer is thermodynamically favoured except for the 1212RAc/DMPC case that exhibits positive values of excess free energy.

The interaction with living cells has cytotoxic effects only in eukaryotic cells, by unspecific membrane permeabilization.     

Synthesis,Characterization, Thermal Decomposition,and Kinetic Studies of Binuclear Sulfur‐Coordinated Tungsten(V) Complexes with Piperidine‐1‐carbodithioate

We describe the synthesis, characterization by IR and electronic spectra, magnetic susceptibility measurements, analytical data, kinetic study by differential‐scanning calorimetry, and thermogravimetric analysis of the thermal decomposition under N₂ of the adducts 2 – 7 with pyridine or substituted pyridines of bis(piperidine‐1‐carbodithioato‐κS,κS′)di‐μ‐thioxodithioxoditungsten(V) ( 1 ), to which the general formula [W₂B₂(pipCS₂)₂S₂(μ‐S)₂] is assigned (pipCS₂=piperidine‐1‐carbodithioato and B=pyridine (py), 3‐methylpyridine (3‐Mepy), 4‐methylpyridine (4‐Mepy), 3,5‐dimethylpyridine (3,5‐Me₂py), pyridin‐3‐amine (3‐pyNH₂), and pyridin‐4‐amine (4‐pyNH₂)). For the endothermic process of loss of the coordinated base B, we calculated activation energies with a method reported previously by us; the mechanism and pre‐exponential Arrhenius factor of this reaction were also determined. A relationship between the pyridines' basicity, IR and electronic spectral data, and activation energies was established.     

High yield selective acylation of polyamines: proton as protecting group

An advance in the selective acylation of polyamines having identical or similar amine functions is reported. While nucleophilicity differences between the various amine functions are slight, the corresponding conjugate acids exhibit pKa values over a significant range. We have used proton as polyamine protecting group: the monoamine resulting from single deprotonation of a polyammonium compound has allowed for high yields of selective acylation.     

Drug Pharmacokinetics Determined by Real‐Time Analysis of Mouse Breath

Noninvasive, real‐time pharmacokinetic (PK) monitoring of ketamine, propofol, and valproic acid, and their metabolites was achieved in mice, using secondary electrospray ionization and high‐resolution mass spectrometry. The PK profile of a drug influences its efficacy and toxicity because it determines exposure time and levels. The antidepressant and anaesthetic ketamine (Ket) and four Ket metabolites were studied in detail and their PK was simultaneously determined following application of different sub‐anaesthetic doses of Ket. Bioavailability after oral administration vs. intraperitoneal injection was also investigated. In contrast to conventional studies that require many animals to be sacrificed even for low‐resolution PK curves, this novel approach yields real‐time PK curves with a hitherto unmatched time resolution (10 s), and none of the animals has to be sacrificed. This thus represents a major step forward not only in animal welfare, but also major cost and time savings.     

Chemical composition and insecticidal activity of essential oils of two aromatic plants from Ivory Coast against Bemisia tabaci G. (Hemiptera: Aleyrodidae)

Essential oils of aromatic plants with insecticidal properties are nowadays considered as alternative insecticides to protect cultures from attack by insect pest. The aims of the present work were to evaluate the toxicity of the essential oils vapors of two aromatic plants (Lippia multiflora Mold. and Aframomum latifolium K. Schum) against Bemisia tabaci and to characterize their chemical composition. The highest fumigant toxicity against B. tabaci adults was observed with the L. multiflora oil: by exposure to 0.4 microL/L air, the lethal time inducing 90% mortality (LT90) was below 2 hours for this essential oil whereas it reached 15 h in the case of the A. latifolium oil. Both oils were analyzed by GC-FID and GC-MS on two capillary columns. The oil of L. multiflora contained a majority of oxygenated terpenoids mainly represented by the two acyclic components linalool (46.6%) and (E)-nerolidol (16.5%); the oil of A. latifolium was dominated by hydrocarbonated terpenoids among them beta-pinene (51.6%) and beta-caryophyllene (12.3%) were the two major components.     

Formation of thermally rearranged (TR) polybenzoxazoles: Effect of synthesis routes and polymer form

This study demonstrates that thermal treatment of ortho-hydroxy containing polyimides (HPIs) in the solid state certainly leads to the formation of polybenzoxazoles (PBOs). Thermal conversion protocol, including temperature and dwell time, and the form of the sample (film or powder) determine the rearrangement reaction rate of HPI into PBO. Thermal rearrangement kinetics seems to be faster for film samples rather than for powder ones. Also, mild thermal treatment conditions (i.e., low temperatures and short times) seem to result in negligible or low degrees of conversion to PBO. Moreover, synthetic routes of HPI do not alter in any way the thermal conversion pathway. These findings validate the widely reported imide-to-benzoxazole thermal rearrangement mechanism, and contradict the alternative rearrangement pathway, proposed recently, of HPI into poly(biphenylene bisimide) polymers.     

Reactivity Study of Elementary Steps in the Polymerization Mechanism of Acrylfuranic Compounds by Frontier Molecular Orbital Theory

A reactivity study of the most important elementary steps (propagation, intermolecular degradative transfer, and re‐initiation) in free‐radical polymerization of acrylfuranic systems, furfuryl acrylate (FA), and furfuryl methacrylate (FM), using the frontier molecular orbital theory is described. A qualitative explanation of reactivity trends of these steps for both systems is given based on absolute values of the SOMO/HOMO gap. The small difference between values of k_p for FA and FM compared to that found for MA and MMA ( ) is justified semi‐quantitatively by applying a formulation for the change of energy in the transition state using second‐order perturbation theory.

     

DEA production games

In this paper, linear production games are extended so that instead of assuming a linear production technology with fixed technological coefficients, the more general, non-parametric, DEA production technology is considered. Different organizations are assumed to possess their own technology and the cooperative game arises from the possibility of pooling their available inputs, collectively processing them and sharing the revenues. Two possibilities are considered: using a joint production technology that results from merging their respective technologies or each cooperating organization keeping its own technology. This gives rise to two different DEA production games, both of which are totally balanced and have a non-empty core. A simple way of computing a stable solution, using the optimal dual solution for the grand coalition, is presented. The full cooperation scenario clearly produces more benefits for the organizations involved although the implied technology sharing is not always possible. Examples of applications of the proposed approach are given.     

GRASP algorithms for the robust railway network design problem

This paper analyzes the solvability of a railway network design problem and its robust version. These problems are modeled as integer linear programming problems with binary variables, and their solutions provide topological railway networks maximizing the trip coverage in the presence of a competing mode, both assuming that the network works fine and that links can fail, respectively. Since these problems are computationally intractable for realistic sizes, GRASP heuristics are proposed for finding good feasible solutions. The results obtained in a computational experience indicate that our GRASP algorithms are suitable for railway network design problems.