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51.
Summary: Natural and synthetic polymers with heteroatom, such as oxygen, nitrogen, sulfur or phosphorous, potentially can efficiently remove metal ions from aqueous solutions. The ability of synthetic polymers derived from imino diacetic acid, acrylamido glycolic copolymer, and the natural polymer alginic acid to remove metal ions from dilute solution in conjunction with ultrafiltration membranes was studied. The maximum retention capacity was determined and its polymer-metal ion-complexes were studied as possible antibacterial agents. 相似文献
52.
Bernabé L. Rivas Julio Sánchez S. Amalia Pooley Luis Basaez Eduardo Pereira Christophe Bucher Guy Royal Eric Saint Aman Jean-Claude Moutet 《Macromolecular Symposia》2010,296(1):416-428
Arsenic species can be removed from aqueous solutions using the liquid-phase polymer-based retention, LPR, technique. The LPR technique removes ionic species by functional groups of water-soluble polyelectrolytes (WSP) and then using a ultrafiltration membrane that does not let them pass through the membrane, thus separating them from the solution. The ability of WSP with groups (R)4N+X− to remove arsenate ions using LPR was studied. The interaction and arsenate anion retention capacity depended on: pH, the quaternary ammonium group's counter ion, and the ratio polymer: As(V), using different concentrations of As(V). Water-soluble polychelates were also used for one-step retention of As(III) in solution. The complex of poly(acrylic acid)-Sn, 10 and 20 wt-% of metal gave a high retention of As(III) species at pH 8, although the molar ratio polychelate: As(III) was 400:1. The enrichment method was used to determine the maximum retention capacity (C) for arsenate anions in aqueous solutions at pH 8. In similar conditions, the values of C were 142 mg g−1 for P(ClAETA) and 75 mg g−1 for P(SAETA). The combined treatment of arsenic aqueous solutions by electrocatalytic oxidation (EO) to convert the species of As(III) to As(V) with the LPR technique quantitatively removed arsenic. 相似文献
53.
The minimum number of rows in covering arrays (equivalently, surjective codes) and radius-covering arrays (equivalently, surjective codes with a radius) has been determined precisely only in special cases. In this paper, explicit constructions for numerous best known covering arrays (upper bounds) are found by a combination of combinatorial and computational methods. For radius-covering arrays, explicit constructions from covering codes are developed. Lower bounds are improved upon using connections to orthogonal arrays, partition matrices, and covering codes, and in specific cases by computation. Consequently for some parameter sets the minimum size of a covering array is determined precisely. For some of these, a complete classification of all inequivalent covering arrays is determined, again using computational techniques. Existence tables for up to 10 columns, up to 8 symbols, and all possible strengths are presented to report the best current lower and upper bounds, and classifications of inequivalent arrays. 相似文献
54.
Cristóbal Rivas 《代数通讯》2013,41(7):2596-2612
We study the space of left-orderings on groups with (only) finitely many Conradian orderings. We show that, within this class of groups, having an isolated left-ordering is equivalent to having finitely many left-orderings. 相似文献
55.
D. Serantes D. Baldomir M. Pereiro J.E. Arias C. Mateo-Mateo M.C. Buján-Núñez C. Vázquez-Vázquez J. Rivas 《Journal of Non》2008,354(47-51):5224-5226
We have studied the influence of the applied magnetic field on the blocking temperature (TB) of a fine magnetic particle system. By means of a Monte Carlo technique we have simulated zero field cooling (ZFC) curves under different applied fields, obtaining the respective TB as a function of H. We have focused our study on the limit H → HK (where HK is the anisotropy field), since the results found in the literature usually lack a detailed study of this range. The simulations were done at different sample concentration of the nanoparticles, with the purpose of observing how the magnetic dipolar interaction affects the field dependence of TB. The classical expression predicts TB to disappear for H ? HK, independently of the dipolar interaction strength. Our simulations show that at strong interacting conditions TB exists even for fields H > HK. 相似文献
56.
Steffi Franke Steffen Kümmel Ivonne Nijenhuis 《Rapid communications in mass spectrometry : RCM》2018,32(17):1583-1583
57.
Yamile Jalit Marcela C. Rodríguez María D. Rubianes Soledad Bollo Gustavo A. Rivas 《Electroanalysis》2008,20(15):1623-1631
We report the analytical performance of glassy carbon electrodes (GCE) modified with a dispersion of multiwall carbon nanotubes (MWCNT) in polylysine (Plys) (GCE/MWCNT‐Plys). The resulting electrodes show an excellent electrocatalytic activity towards different bioanalytes like ascorbic acid, uric acid and hydrogen peroxide, with important decrease in their oxidation overvoltages. The dispersion of 1.0 mg/mL MWCNT in 1.0 mg/mL polylysine is highly stable, since after 2 weeks the sensitivity for hydrogen peroxide at GCE modified with this dispersion remained in a 90% of the original value. The MWCNT‐Plys layer immobilized on glassy carbon electrodes has been also used as a platform to build supramolecular architectures by self‐assembling of polyelectrolytes based on the polycationic nature of the polylysine used to disperse the nanotubes. The self‐assembling of glucose oxidase has allowed us to obtain a supramolecular multistructure for glucose biosensing. The influence of glucose oxidase concentration and adsorption time as well as the effect of using polylysine or MWCNT‐Plys as polycationic layers for further adsorption of GOx is also evaluated. 相似文献
58.
Rivas AB Gascón JM Lahoz FJ Balana AI Pardey AJ Oro LA Pérez-Torrente JJ 《Inorganic chemistry》2008,47(13):6090-6104
The reaction of gem-dithiol compounds R 2C(SH) 2 (R = Bn (benzyl), (i) Pr; R 2 = -(CH 2) 4-) with dinuclear rhodium or iridium complexes containing basic ligands such as [M(mu-OH)(cod)] 2 and [M(mu-OMe)(cod)] 2, or the mononuclear [M(acac)(cod)] (M = Rh, Ir, cod = 1,5-cyclooctadiene) in the presence of a external base, afforded the dinuclear complexes [M 2(mu-S 2CR 2)(cod) 2] ( 1- 4). The monodeprotonation of 1,1-dimercaptocyclopentane gave the mononuclear complex [Rh(HS 2Cptn)(cod)] ( 5) that is a precursor for the dinuclear compound [Rh 2(mu-S 2Cptn)(cod) 2] ( 6). Carbonylation of the diolefin compounds gave the complexes [Rh 2(mu-S 2CR 2)(CO) 4] ( 7- 9), which reacted with P-donor ligands to stereoselectively produce the trans isomer of the disubstituted complexes [Rh 2(mu-S 2CR 2)(CO) 2(PR' 3) 2] (R' = Ph, Cy (cyclohexyl)) ( 10- 13) and [Rh 2(mu-S 2CBn 2)(CO) 2{P(OR') 3} 2] (R' = Me, Ph) ( 14- 15). The substitution process in [Rh 2(mu-S 2CBn 2)(CO) 4] ( 7) by P(OMe) 3 has been studied by spectroscopic means and the full series of substituted complexes [Rh 2(mu-S 2CBn 2)(CO) 4- n {P(OR) 3} n ] ( n = 1, 4) has been identified in solution. The cis complex [Rh 2(mu-S 2CBn 2)(CO) 2(mu-dppb)] ( 16) was obtained by reaction of 7 with the diphosphine dppb (1,4-bis(diphenylphosphino)butane). The molecular structures of the diolefinic dinuclear complexes [Rh 2(mu-S 2CR 2)(cod) 2] (R = Bn ( 1), (i) Pr ( 2); R 2 = -(CH 2) 4- ( 6)) and that of the cis complex 16 have been studied by X-ray diffraction. 相似文献
59.
Tannya R. Ibarra-Rivera Manuel Alejandro Rentería-Gómez Eduardo Nieto-Sepúlveda Rocío Gámez-Montaño Verónica M. Rivas Galindo Eugenio Hernandez-Fernandez 《合成通讯》2016,46(6):509-515
Novel tetrahydroindeno[1,2-b]pyrrolidines were conveniently prepared in moderate to good yields via a sequential Ugi multicomponent reaction or Staudinger/aza-Wittig/Ugi combination, followed by the palladium-catalyzed aerobic oxidative cyclization of the resulting Ugi adducts. 相似文献
60.
Ferrocenyl,Alkyl, and Aryl‐Pyrido[2,3‐d]Pyrimidines as Vasorelaxant of Smooth Muscle of Rat Aorta via cAMP Conservation Through Phosphodiesterase Inhibition 下载免费PDF全文
Ivonne Arellano Fernando Rodríguez‐Ramos Martín González‐Andrade Andrés Navarrete Manju Sharma Noé Rosas Pankaj Sharma 《Journal of heterocyclic chemistry》2016,53(4):1147-1154
New pyrido[2,3‐d]pyrimidines 11 , 12 , 13 , and 21 have been synthesized. The vasorelaxant effect on smooth muscle isolated from rat aorta, via PDEs inhibition, of these compounds along with other pyrido[2,3‐d]pyrimidines 14 , 15 , 16 , 17 , 18 , 19 , 20 reported earlier by our group, has also been determined. These pyrido[2,3‐d]pyrimidines 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 were synthesized by the reaction of ferrocenyl‐ethynyl ketones ( 1 , 2 , 3 , 4 ) or α‐alkynyl ketones ( 5 , 6 , 7 , 8 , 9 , 10 ) with 6‐amino‐1,3‐dimethyluracil using [Ni(CN)4]?4 as an active catalytic species, formed in situ in a Ni(CN)2/NaOH/H2O/CO/KCN aqueous system. Evaluation of the vasorelaxant effect of compounds 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 demonstrated that all compounds relax the tissue in a concentration‐dependent manner. The structural changes do not alter the effectiveness; however, there are differences related to potency expressed as EC50. Compounds 12 (7‐ferrocenyl‐1,3‐dimethyl‐5‐(m‐tolyl)‐pyrido[2,3‐d]pyrimidine) and 13 (7‐ferrocenyl‐1,3‐dipropyl‐5‐(4‐metoxyphenyl)‐pyrido[2,3‐d]pyrimidine) were the most potent compounds, even more than rolipram, reference drug; the EC50 was 0.41 ± 0.02 μM and 0.81 ± 0.11 μM for 12 and 13 , correspondingly. The EC50 of compounds 15 (7‐ferrocenyl‐1,3‐dimethyl‐5‐phenyl‐pyrido[2,3‐d]pyrimidine), 14 (7‐ferrocenyl‐5‐(3,5‐dimethoxyphenyl)‐1,3‐dimethylpyrido[2,3‐d]pyrimidine), and 19 (5‐n‐butyl‐7‐ethyl‐1,3‐dimethylpyrido[2,3‐d]pyrimidine) was similar to EC50 of rolipram. Compounds 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 significantly induce concentration‐dependent vasorelaxation in endothelium‐intact aortic rings. In addition, the relaxation responses to each compound in either endothelium‐intact or endothelium denuded aortic rings were comparable, suggesting that removal of the functional endothelium has no significant influence on its intrinsic vasorelaxant activity. In vitro capability of conserving cyclic‐AMP or cyclic‐GMP (adenosine and guanosine 3′, 5′‐cyclic monophosphate) via PDE inhibition for compounds 12 , 13 , 14 , 15 and 19 was evaluated. Compounds 15 and 19 show the highest percent inhibition effect (94.83% and 83.98%, respectively) for the decomposition of c‐AMP. Docking studies showed that the compound 15 was selective for the inhibition of PDE‐4. 相似文献