A Comprehensive Study and Characterization of Colloidal Emeraldine-Base

Soluble emeraldine-base (PANI-EB) was prepared and its structure was characterized using ¹H, ¹³C and 2D (COSY, HMQC and HMBC) NMR. The solubility of the polymer in two solvents (N-methylpyrrolidone (NMP) and dimethyl sulfoxide (DMSO), the structure of the solution (aggregation) and the behavior of polyaniline were studied by viscometry and by dynamic light scattering (DLS) in dilute solution. Viscometric behavior in NMP and Huggins constant determination confirm supramolecular interactions also evidenced by DLS; at end, the molecular weight of the soluble fraction of PANI-EB is determined.     

Effect of Acute Exposure to Hydrogen Peroxide on the Production of Phytoplankton and Bacterioplankton in a Mesohumic Lake

Abstract— Active oxygen species such as hydrogen peroxide are produced as a result of UV radiation interaction with natural organic matter and can build up to high concentrations in many aquatic environments. Although the resulting oxidizing potential may affect biological materials and processes, the ecological effects have not yet been studied in any detail. We examined the influence of hydrogen peroxide exposure on phytoplankton and bacterioplankton production in Lac Cromwell, a small humic lake in the Laurentian Hills (Quebec, Canada). A range of hydrogen peroxide concentrations were added to natural samples that were incubated in situ; results indicate that even small amounts of added hydrogen peroxide (50 n M inhibited bacterial production in this lake. A 100 n M addition inhibited bacteria by as much as 40%. On the other hand, low concentrations of added hydrogen peroxide usually stimulated photosynthesis. Catalase addition to eliminate hydrogen peroxide from water usually stimulated bacterial production but had no effect on algal carbon fixation. If these results represent true changes in growth rate, they indicate very different sensitivities of phytoplankton and bacteria to oxidative stress.     

The Effect of Diapause on Neutral Lipids in the Pitcher-Plant Mosquito Wyeomyia smithii as Determined by HPTLC-Densitometry

JPC – Journal of Planar Chromatography – Modern TLC - Diapause in insects typically results in metabolic adjustments that may include the levels of feeding and activity, metabolic rate,...     

Computer generation of network cost from one link's equilibrium data

Our computer implemented algorithm generates global network equilibrium information from the local network equilibrium data at one arbitrary link. This data consists of variations in its flow and in its cost resulting from variations in its obstruction level, as well as in network demand. Output and timings from two test networks are given.     

Selective enhancement of scopadulcic acid B production in the cultured tissues of Scoparia dulcis by methyl jasmonate

The effects of methyl jasmonate (MeJA) on isoprenoid production were evaluated in cultured tissues of Scoparia dulcis. It was found that MeJA suppressed the accumulation of chlorophylls, carotenoids, phytol and beta-sitosterol in the tissues. MeJA, however, remarkably enhanced the production of scopadulcic acid B (SDB), with 10 microM being optimal observed concentration for stimulation of SDB production. The maximum concentration of SDB was observed 6 d after MeJA treatment.     

Synthesis and characterization of carboxymethylcelluloses (CMC) from non-wood fibers I.Accessibility of cellulose fibers and CMC synthesis

This paper explores the production of carboxymethylcellulose (CMC) fromseveral bleached cellulose pulps obtained from non-wood species. The chemicalcomposition (-cellulose, hemicellulose and lignin content), the degreeofswelling, viscosity, solubility in concentrated NaOH and crystallinity ofsoda/AQ cellulose pulps from abaca, jute, sisal, linen and Miscanthussinensis were determined. The pulps were carboxymethylated by one andtwo successive reaction steps in aqueous medium under identical conditions. Thedegree of substitution (DS) of CMC was found to be dependent upon the source ofthe cellulose pulp, but generally it was close to 1 with one etherificationtreatment and around 2 after the second. The molar mass of CMC was found to bedependent on the initial intrinsic viscosity of the cellulose pulp. The weightaverage molar mass of our CMCs ranged from 1.5×10⁵ to2.8×10⁵. Increasing the DS up to 2 improved the CMC solubility, butviscosity slightly decreased due to a slight degradation of the polymer.     

Euler equations involving nonlinearities without growth conditions

A functional is considered, whose Euler equation involves a nonlinearity without growth conditions. It is shown that every minimum point of the functional is a solution of the Euler equation in a suitable weak sense.This work was partially supported by a national research grant financed by the Ministero dell'Università e della Ricerca Scientifica e Tecnologica (40%-1992).     

Instability results related to compressible Korteweg system

This paper presents the study of surface tension effects in compressible mixtures in the framework of diffuse interface models. In the first part, we describe results previously obtained on the so-called compressible Korteweg and shallow water models and we present nonlinear stability using energy estimates and a new entropy equality recently discovered. These diffuse interface models also allow to take account of capillarity effects in turbulent mixtures and plasma flows subject to Rayleigh–Taylor instabilities. The aim of the last part is to study the influence of surface tension on this instability phenomena. More precisely we look at the expression of the growth rate under a small perturbation of wave number k. We prove that for an appropriate choice of the capillary number σ in terms on the surface tension coefficient T _s (that means particular pressure laws), we find the same expression as for the two incompressible fluids model with surface tension coefficient on a sharp interface studied for instance by Chandrasekhar (Hydrodynamic and hydromagnetic stability. Dover Publications, Inc. New York, 1981). The first author would like to thank the CEA/DAM (Bruyères le Chatel, France) for its financial support through the contract no. 4600052302/P6H28. He is also partially supported by the IDOPT project in Grenoble and the “ACI jeunes chercheurs 2004” du ministère de la Recherche “études mathématiques de paramétrisations en océanographie”.     

An evaluation of some simple sulfonic acids as nonaqueous titrants

The simple aliphatic and aromatic sulfonic acids show evidence of possibilities as new titrants in a glacial acetic acid medium. Excellent precision is obtained in potentiometric titrations with both ethane- and methane sulfonic acids with a standard deviation of 0.2%. Benzenemonosulfonic and naphthalenesulfonic acids both give an average precision of 0.4%. In visual titrations with with crystal violet indicator, the color changes at the end-point are very sharp. The chief advantage of these acids as titrants lies in the fact that they dissolve readily in glacial acetic acid and can be titrated to give reproducible results with the glass-calomel electrode system. None of the sulfonic acids tested was as strong a titrant as perchloric acid, but, unlike perchloric acid, they did not form precipitates or gels in the titration with potassium acid phthalate.