Search results for " solution"
showing 10 items of 3084 documents
Protein diffusion through charged nanopores with different radii at low ionic strength
2014
[EN] The diffusion of two similar molecular weight proteins, bovine serum albumin (BSA) and bovine haemoglobin (BHb), through nanoporous charged membranes with a wide range of pore radii is studied at low ionic strength. The effects of the solution pH and the membrane pore diameter on the pore permeability allow quantifying the electrostatic interaction between the chargedpore and the protein. Because of the large screening Debye length, both surface and bulk diffusion occur simultaneously. By increasing the pore diameter, the permeability tends to the bulk self-diffusion coefficient for each protein. By decreasing the pore diameter, the charges on the pore surface electrostatically hinder …
Analysis of a parabolic cross-diffusion population model without self-diffusion
2006
Abstract The global existence of non-negative weak solutions to a strongly coupled parabolic system arising in population dynamics is shown. The cross-diffusion terms are allowed to be arbitrarily large, whereas the self-diffusion terms are assumed to disappear. The last assumption complicates the analysis since these terms usually provide H 1 estimates of the solutions. The existence proof is based on a positivity-preserving backward Euler–Galerkin approximation, discrete entropy estimates, and L 1 weak compactness arguments. Furthermore, employing the entropy–entropy production method, we show for special stationary solutions that the transient solution converges exponentially fast to its…
Selective and Sensitive Chromogenic Detection of Cyanide and HCN in Solution and in Gas Phase
2013
Two triphenylmethane based chemodosimeters for selective and chromogenic sensing of cyanide anions in aqueous environments and of hydrogen cyanide in gas phase were prepared and studied.
Fiber-Optic Aqueous Dipping Sensor Based on Coaxial-Michelson Modal Interferometers
2009
Fiber-optic modal interferometers with a coaxial-Michelson configuration can be used to monitor aqueous solutions by simple dipping of few centimeters of a fiber tip. The fabrication of these sensors to work around 850 nm enables the use of compact, robust, and low-cost optical spectrum analyzers. The use of this type of portable sensor system to monitor sewage treatment plants is shown.
A sequence of positive solutions for sixth-order ordinary nonlinear differential problems
2021
Infinitely many solutions for a nonlinear sixth-order differential equation are obtained. The variational methods are adopted and an oscillating behaviour on the nonlinear term is required, avoiding any symmetry assumption.
Application of sequential injection analysis to pharmaceutical analysis.
2005
Sequential injection analysis is a well established tool for automation of pharmaceutical analysis. A short historical background of this technique is given as well as a brief discussion on the basic principles and potentials. The current applications of SIA in the pharmaceutical analysis are also described and discussed. The manifolds developed offer good analytical characteristics and are suitable for analysis of drug formulations, process analysis, drug-dissolution, drug-release testing and functional assays for screening potential drugs. The results obtained are in good agreement with those furnished by the application of the reference methods presented in the pharmacopoeias.
Risedronate complexes with Mg2+, Zn2+, Pb2+, and Cu2+: Species thermodynamics and sequestering ability in NaCl(aq) at different ionic strengths and a…
2021
Abstract In this paper, potentiometry and calorimetry were used to determine the thermodynamics of interaction between risedronate and four bivalent metal cations, namely: Mg2+, Zn2+, Pb2+, and Cu2+ in aqueous NaCl solutions at different ionic strengths and at T = 298.15 K. The data analysis allowed us to ascertain that the main species formed were the MLH2, MLH, ML and M2L; however scarcely soluble species precipitated at acidic pH values, between 4 and 7 depending on the metal cation involved, probably due to the formation of the neutral M2L(s) species. Comparison of the stability constants with other similar ligands suggests that metal complexation occurs through the phosphonate with an …
Sequestering ability of polyaminopolycarboxylic ligands towards dioxouranium(VI) cation
2006
Abstract In the present paper, some results of an investigation (at t = 25 °C by potentiometry, ISE-H+ glass electrode) on the sequestering ability of five different polyaminopolycarboxylic ligands [Nitrilotriacetate (NTA), ethylenediamine-N,N,N′,N′-tetraacetate (EDTA), ethylene glycol-bis(2-aminoethylether)-N,N,N′,N′-tetraacetate (EGTA), diethylenetriamine-N,N,N′,N″,N″-pentaacetate (DTPA), triethylenetetraamine-N,N,N′,N″,N′′′,N′′′-hexaacetate (TTHA)] towards dioxouranium(VI) cation in sodium chloride aqueous solutions, at I = 0.7 mol L−1 are reported. Calculations performed on potentiometric data gave evidence of the formation of the following species (log β in parenthesis): UO2(NTA)H0 (12…
Sequestration of (CH3)Hg+ by amino‐polycarboxylic chelating agents
2012
Abstract The speciation of mono-methylmercury(II) cation (MeHg+) in the presence of Nitrilotriacetate (NTA), Ethylenediamine-N,N,N′,N′-tetraacetate (EDTA), diethylenetriamine-N,N,N′,N″,N″-pentaacetate (DTPA) and (S,S)- Ethylenediamine-N,N′-disuccinic acid (S,S-EDDS) was investigated at I = 0.1 mol L− 1 (NaCl) with the aim to assess a trend of sequestering capacity of the amino‐polycarboxylic (APCs) ligand class towards this cation in aqueous solution. The results obtained gave evidence for the formation of a mononuclear [MeHg(APC)] complex species, differently protonated MeHg(HiL) species (i = 1 to 3, depending on the APC considered), a mixed hydroxo species [MeHg(APC)(OH)] and a binuclear …
Development of predictive retention-activity relationship models of tricyclic antidepressants by micellar liquid chromatography.
1999
The distribution of tricyclic antidepressants from plasma to brain, where these drugs exert their main clinical action, and other organs is related to transport events across the cell membranes of the different tissues. It could be expected that all the molecular features that condition the transport processes (mainly hydrophobicity and molar total charge) also control the pharmacokinetic and biochemical behavior. Micellar liquid chromatography (MLC) has been proposed to emulate in vitro the partitioning process in the biomembranes. The use of micellar solutions of Brij35 as mobile phases in reversed-phase liquid chromatography has proven to be valid to predict the biological activities of …