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151.
Reschiglian P Zattoni A Roda B Cinque L Melucci D Min BR Moon MH 《Journal of chromatography. A》2003,985(1-2):519-529
Interest in low-cost, analytical-scale, highly efficient and sensitive separation methods for cells, among which bacteria, is increasing. Particle separation in hollow-fiber flow field-flow fractionation (HF FlFFF) has been recently improved by the optimization of the HF FIFFF channel design. The intrinsic simplicity and low cost of this HF FlFFF channel allows for its disposable usage. which is particularly appealing for analytical bio-applications. Here, for the first time, we present a feasibility study on high-performance, hyperlayer HF FIFFF of micrometer-sized bacteria (Escherichia coli) and of different types of cells (human red blood cells, wine-making yeast from Saccharomyces cerevisiae). Fractionation performance is shown to be at least comparable to that obtained with conventional, flat-channel hyperlayer FIFFF of cells, at superior size-based selectivity and reduced analysis time. 相似文献
152.
The mobile phase of a fraction eluted from a first LC column is removed by an on-line evaporator in order to reconcentrate the solute material or to exchange the eluent before performing a subsequent LC separation. Evaporation essentially occurs by concurrent evaporation, i.e. the solvent evaporates at a rate equal to the flow rate of the incoming eluent, and is driven by the overflow principle, i.e. vapors leave the tube as a result of the expansion resulting from evaporation. The liquid is introduced into a small tube (e.g., 4 cm × 1.3 mm i.d.) which is packed, e.g., with a coarse silica gel. The outlet of the evaporator is connected to vacuum in order to enable evaporation at reduced temperature and to increase retention of the volatile components. With normal phase eluents, evaporation rates may approach 1 ml/min; n-dodecane was the most volatile n-alkane fully retained by the evaporator. 相似文献
153.
Gluconacetobacter spp. synthesize a pure form of hydrophilic cellulose that has several industrial specialty applications. Literature reports
have concentrated on intensive investigation of static and agitated culture in liquid media containing high nutrient concentrations
optimized for maximal cellulose production rates. The behavior of these bacteria on semisolid and solid surfaces has not been
specifically addressed. The species Gluconacetobacter hansenii was examined for cellulose synthesis and colony morphology on a range of solid supports, including cotton linters, and on
media thickened with agar, methyl cellulose, or gellan. The concentration and chemical structure of the thickening agent were
found to be directly related to the formation of contiguous cellulose pellicules. Viability of the bacteria following freezer
storage was improved when the bacteria were frozen in their cellulose pellicules.
This article was authored by a contractor of the US government under contract no. DEAC05-00OR22725. Accordingly, the US government
retains a nonexclusive, royalty-free license to publish or reproduce the published form of this contribution, or allow others
to do so, for US government purposes. 相似文献
154.
InIII-Phthalocyanines: Synthesis, Properties, and Crystal Structure of Tetra(n-butyl)ammonium-cis-di(nitrito-O,O')phthalocyaninato(2–)indate(III) [In(Cl)Pc2?] reacts with (nBu4N)NO2 in acetone yielding green-blue (nBu4N)cis[In(NO2)2Pc2?], which crystallizes in the monoclinic space group P21/n (No. 14). Both nitrite anions are coordinated as chelating nitrito-O,O'(NO2) ligands to InIII in cis-geometry. Consequently InIII is octa-coordinated within a distorted “quadratic” antiprism and directed towards the Pc2?-ligand. One of the NO2 ligands has equivalent N? O bonds similar to free nitrite, while the other has asymmetric N? O bonds. Both (In,O,N,O) rings are approximately planar with a dihedral angle of 80°. The Pc2? ligand is distorted in an asymmetrically convex manner. Partially overlapping pairs of Pc2? ligands related by an inversion center form double layers, which are separated by layers containing the (nBu4N)+ cations. The cyclic voltammogram shows three electrode processes, which are assigned to the redox pairs: Pc3?/Pc2? (?0.94 V) < InI/InIII (-0.78 V) < Pc2?/Pc? (0.64 V). The UV-VIS-NIR spectra and vibrational spectra are discussed. 相似文献
155.
Summary In this paper, we continue earlier works of one of the authors on vague convergence of the sequence
k,n=
k+1 *...*
n, where
n is a sequence of probability measures on semigroups or groups. Typical results in this paper are: Theorem. Let S be a locally compact noncompact second countable group such that
being the support of a probability measure on S. Suppose there exists an open set V with compact closure such that x
–1
Vx=V for every xS. Then for all compact sets K, sup{
n
(Kx): xS0 as n. Theorem. Let S be an at most countable discrete group. Let
n be a sequence of probability measures on S. Then for all nonnegative integers k, the sequence
k,n converges vaguely to some probability measure if and only if there exists a finite subgroup G such that the series
and for any proper subgroup G of G and any choice of elements gn in S, the series
. A sufficient condition for the vague convergence of the sequence
k,n to a probability measure is that (i) there exists a finite subgroup G such that
and (ii)
n(e)>s>0 for all n, e being the identity.The author was supported by NSF grant MCS77-03639 相似文献
156.
157.
Nicolas P. Cheval Barbara Hoffmann Anna Dikova Fatih Sirindil Philippe Bertus Aurélien Blanc Jean-Marc Weibel Patrick Pale 《Tetrahedron》2018,74(50):7111-7119
Vinyl nosylates, readily obtained from β-dicarbonyl derivatives, could be efficiently engaged in Sonogashira cross-coupling reactions, either cocatalyzed by copper or silver salts. The para-nitrobenzenesulfonate (nosylate) group allows this coupling to be performed under very mild conditions (room temperature). These new leaving group and mild conditions could be applied to the synthesis of acetylenic coumarinyl derivatives and to the total synthesis of an acetylenic monoterpene natural product, named cleviolide. 相似文献
158.
159.
160.
Ulrich A. HarrÉus Barbara C. Wallner Ernst R. Kastenbauer Norbert H. Kleinsasser 《International journal of environmental analytical chemistry》2013,93(6):395-401
Surfactants, which are prevalent at industrial sites and in the environment generally, are potential risk factors in human carcinogenesis. The widespread industrial use of surfactants such as 4-alkylphenol ethoxylates and their prevalence in many cleaning products have provoked studies about surfactant concentrations in water and their toxicity levels. Up to now, these substances have mainly been tested on aquatic organisms. Though tests on human cell lines are rare. The alkaline Comet assay was performed to evaluate the genotoxicity of 4-nonylphenol ethoxylate, a biodegradable product of 4-alkylphenol ethoxylate, in human lymphocytes. Concentrations tested ranged from 0.15 to 150 µg/mL. Test concentrations of 10 to 15 µg/mL caused an increase level of DNA migration in human cells, but without inducing excessive toxicity (viability > 80%). Though induced levels of DNA migration starting at concentrations of 30 µg/mL may have been due to excessive levels of cytotoxicity (viability < 70%). Based on these data, 4-nonylphenol ethoxylate can induce DNA damage in human lymphocytes but at higher concentrations than are normally found in river or drinking water. However, considering the prevalence of surfactants, the measured genotoxicity of these substances is of concern. Further investigations on human target cells are necessary to evaluate the carcinogenic impact of surfactants and reconsider their environmental acceptance. 相似文献