Comparaison de deux indicateurs de la régularité en variation des queues de distributionsComparison between two indicators for the variation regularity of tails of distributions

We compare assumptions used in [4] in order to study the rate of convergence to 0, as u→s₊(F), of , where $\text{F}{}_{\mathrm{u}}$ is the survival function of the excesses over u, s₊(F)=sup{x,F(x)<1} is the upper end point of the distribution function (d.f.) F and $\text{G}{}_{\mathrm{\gamma }}$ is the survival function of the Generalized Pareto Distribution, with assumptions used in [2] in order to study the rate of convergence to 0, as n→+∞, of $\text{d}\text{?}{}_{\mathrm{n}}\text{=}\text{sup}{}_{\mathrm{<mtext>x\in </mtext><mtext>R</mtext>}}\text{|F}{}^{\mathrm{n}}\text{(x)?H}{}_{\mathrm{\gamma }}\text{(}\text{x?α}{}_{\mathrm{n}}\text{σ}{}_{\mathrm{n}}\text{)|}$, where H_γ is the d.f. of an extreme value distribution. In each case, an indicator linked to regular variation assumptions had been introduced. We characterize situations where these two indicators coincide, and others where they are different. To cite this article: R. Worms, C. R. Acad. Sci. Paris, Ser. I 334 (2002) 709–712.     

Über 1-Hydroxyalkan-1,1- diphosphonsäuren

The reaction of acylating agents with H₃PO₃ or carbonic acids with PCl₃ and calculated amounts of water gives raw products converted by steam treatment into high yields of 1-hydroxyalkane-1,1-diphosphonic acids. A cyclic condensation product of two molecules 1-hydroxyethane-1,1-diphosphonic acid was found in the raw product of the reaction of acetylating agents with H₃PO₃. Two structure proposals are discussed.     

Herstellung von 1-Aminoalkan-1,1-diphosphonsäuren

1-Aminoalkane-1,1-diphosphonic acids 1 , 2 or 3 are formed in the reaction of carboxylic acid amide dihalides or carboxylic acid amide hydrohalogenides with phosphorous acid. Phosphorus trihalides plus water may be used in lieu of phosphorous acid in the reaction with carboxylic acid amides. With formamide either aminomethanediphosphonic acid ( 1a ) or 2-oxo-2-hydroxy-5-amino-1,4,2-oxazaphospholidine-3-phosphonic acid ( 5 ) are obtained depending on the reaction conditions.     

Calix[4]azacrowns: self-assembly and effect of chain length and O-alkylation on their metal ion-binding properties

Both the consequences of 1,3-cyclization of calix[4]arenes by diamide formation, and the effect of 2- and 2,4-alkoxycarbonylmethylation of two 1,3-bridged calix[4]azacrowns on their metal ion-binding capacities have been studied by synthesis of the derivatives in their cone conformation and measurement of the stability constants for their complexation in a range of alkaline earth and transition metal cations. In these two cases, the conformation of the ligand in the solid state has been defined in detail by a crystal structure determination. In the first case, a tubular architecture performing methanol channels is displayed, however, in the second case a zigzag architecture generated by a chloroform network connecting calixarene molecules is present. Speciation in solution appears to be limited to the formation of 1:2 and/or 1:1 and/or 2:1 (M-L) complexes, depending on the system, with values of the stability constants determined by absorption spectroscopy in acetonitrile, lying in the ranges log β₁₂ ca. 10, log β₁₁ ca. 2-5, and log β₂₁ ca. 7-9. There is evidence for selectivity toward Cu(II) and for some unexpected anion effects. None of these ligands appear to be an efficient extractant for the metals as their picrate.     

Conductivity study by complex impedance spectroscopy of solid solution AgxK1 − xNb4AsO13 (x = 0.2 and 0.62): effect of the substitution of K+ by Ag+ cations on the ionic conduction properties

Journal of Solid State Electrochemistry - Crystals of Ag0.2K0.8Nb4AsO13 (I) and Ag0.62K0.38Nb4AsO13 (II) were synthesized by a solid-state reaction. Both of them crystallize in the orthorhombic...     

Adaptive and restarting techniques-based algorithms for circular packing problems

In this paper, we study the circular packing problem (CPP) which consists of packing a set of non-identical circles of known radii into the smallest circle with no overlap of any pair of circles. To solve CPP, we propose a three-phase approximate algorithm. During its first phase, the algorithm successively packs the ordered set of circles. It searches for each circle’s “best” position given the positions of the already packed circles where the best position minimizes the radius of the current containing circle. During its second phase, the algorithm tries to reduce the radius of the containing circle by applying (i) an intensified search, based on a reduction search interval, and (ii) a diversified search, based on the application of a number of layout techniques. Finally, during its third phase, the algorithm introduces a restarting procedure that explores the neighborhood of the current solution in search for a better ordering of the circles. The performance of the proposed algorithm is evaluated on several problem instances taken from the literature.     

An Oxidant- and Solvent-Stable Protease Produced by <Emphasis Type="Italic">Bacillus cereus</Emphasis> SV1: Application in the Deproteinization of Shrimp Wastes and as a Laundry Detergent Additive

The current increase in amount of shrimp wastes produced by the shrimp industry has led to the need in finding new methods for shrimp wastes disposal. In this study, an extracellular organic solvent- and oxidant-stable metalloprotease was produced by Bacillus cereus SV1. Maximum protease activity (5,900 U/mL) was obtained when the strain was grown in medium containing 40 g/L shrimp wastes powder as a sole carbon source. The optimum pH, optimum temperature, pH stability, and thermal stability of the crude enzyme preparation were pH 8.0, 60 °C, pH 6–9.5, and <55 °C, respectively. The crude protease was extremely stable toward several organic solvents. No loss of activity was observed even after 60 days of incubation at 30 °C in the presence of 50% (v/v) dimethyl sulfoxide and ethyl ether; the enzyme retained more than 70% of its original activity in the presence of ethanol and N,N-dimethylformamide. The protease showed high stability toward anionic (SDS) and non-ionic (Tween 80, Tween 20, and Triton X-100) surfactants. Interestingly, the activity of the enzyme was significantly enhanced by oxidizing agents. In addition, the enzyme showed excellent compatibility with some commercial liquid detergents. The protease of B. cereus SV1, produced under the optimal culture conditions, was tested for shrimp waste deproteinization in the preparation of chitin. The protein removal with a ratio E/S of 20 was about 88%. The novelties of the SV1 protease include its high stability to organic solvents and surfactants. These unique properties make it an ideal choice for application in detergent formulations and enzymatic peptide synthesis. In addition, the enzyme may find potential applications in the deproteinization of shrimp wastes to produce chitin.     

Fibrinolytic Serine Protease Isolation from <Emphasis Type="Italic">Bacillus amyloliquefaciens</Emphasis> An6 Grown on <Emphasis Type="Italic">Mirabilis jalapa</Emphasis> Tuber Powders

In this study, Mirabilis jalapa tuber powder (MJTP) was used as a new complex organic substrate for the growth and production of fibrinolytic enzymes by a newly isolated Bacillus amyloliquefaciens An6. Maximum protease activity (1,057 U/ml) with casein as a substrate was obtained when the strain was grown in medium containing (grams per liter) MJTP 30, yeast extract 6, CaCl₂ 1, K₂HPO₄ 0.1, and K₂HPO₄ 0.1. The strain was also found to grow and produce extracellular proteases in a medium containing only MJTP, indicating that it can obtain its carbon, nitrogen, and salts requirements directly from MJTP. The B. amyloliquefaciens An6 fibrinase (BAF1) was partially purified, and fibrinolytic activity was assayed in a test tube with an artificial fibrin clot. The molecular weight of the partially purified BAF1 fibrinolytic protease was estimated to be 30 kDa by sodium dodecyl sulfate polyacrylamide gel electrophoresis and gel filtration. The optimum temperature and pH for the caseinolytic activity were 60 °C and 9.0, respectively. The enzyme was highly stable from pH 6.0 to 11.0 and retained 62% of its initial activity after 1 h incubation at 50 °C. However, the enzyme was inactivated at higher temperatures. The activity of the enzyme was totally lost in the presence of phenylmethylsulfonyl fluoride, suggesting that BAF1 is a serine protease.     

Cadmium bioavailability and speciation using the permeation liquid membrane

The permeation liquid membrane (PLM) technique was used to evaluate cadmium speciation in media resembling natural freshwaters. A planar sheet PLM system was characterized by measuring Cd fluxes in the absence and presence of complexing agents such as citrate, malonate, nitrilotriacetate and the Suwannee River standard humic acid. Comparison with theoretical speciation calculations and the results of a Cd²⁺ selective electrode, showed that free Cd was correctly measured using the planar sheet PLM within the studied concentration range, i.e. 10⁻⁸ to 10⁻⁴ M. The effect of pH and potentially co-transported ions on Cd transport through the PLM was also studied. An example of the ability of the hollow-fiber PLM (HFPLM) to measure free Cd in the nM range is also presented. In order to evaluate the usefulness of the technique as a predictor of bioavailability, Cd PLM measurements (fluxes) were compared to Cd biouptake (internalization flux) for a freshwater alga, Chlorella kesslerii, in the absence and presence of SRHA. The use of PLM measurements is shown to be an attractive tool to better understand Cd biouptake.