The separation of bacteria by electromigration techniques was a subject of several of our previous papers. This contribution presents the results of investigation of the porosity of the monolithic bed and migration of Staphylococcus aureus cells through it. The gigaporous monolith was thermally synthesized using glycidyl methacrylate, triethylene glycol dimethacrylate and trimethylolpropane trimethacrylate as the monomers in the presence of porogen solvent containing 1-decanol, polyethylene glycol and 2-methoxyethanol. The porous properties were evaluated by inverse size-exclusion chromatography (ISEC) using a wide range of polystyrene standards of different molecular weights. The results have shown, that large pores (ca. 300 nm) dominate in the monolithic bed structure, however much larger flow-through pores must also be present as ca. 1 μm sized S. aureus bacteria were able to migrate through the bed. 相似文献
Nonlinear dynamics of a bouncing ball moving in gravitational field and colliding with a moving limiter is considered. Displacement
of the limiter is a quadratic function of time. Several dynamical modes, such as fixed points, 2-cycles, grazing and chaotic
bands are studied analytically and numerically. It is shown that chaotic bands appear due to homoclinic structures created
from unstable 2-cycles in a corner-type bifurcation. 相似文献
Results of the investigation of volatile organic compounds emission during polyethylene extrusion are presented. Two polymers
of different processing properties were tested, namely linear low density polyethylene (ExxonMobil) and high density polyethylene
(Liten FB 29). Blowing film extrusion in experimental technological line using a single screw extruder as the imported element
was done. VOCs were collected on sorbent tubes containing Tenax. Gas chromatography coupled with mass spectrometry (GC/MS)
was applied for the identification of volatile degradation products. PE LLD material emits a significantly larger amount of
hydrocarbons than PE-HD. Its emission contains mainly C18 and C20 hydrocarbons (alkanes, 1-alkenes, and α,ω-alkadienes). In case of the PE-HD polymer, lower degradation was observed and C18 and C23 hydrocarbons were emitted. 相似文献
Synthesis and properties are described of multilayered stationary phases containing quaternary amine functional groups used for the analysis of inorganic anions by ion chromatography. The bonded phases were characterized by elemental analysis, solid state (13)C NMR spectroscopy and chromatographic methods. The surface of polyhydroxyethyl methacrylate (solid support) was coated with polymeric layers formed by condensation polymerization of primary amine with diepoxide. Each layer of the anion exchange stationary phase consisted of methylamine and 1,4-butanedioldiglycidyl ether copolymer. A series of stationary phases with different number of polymerized layers were tested. Separation of inorganic anions, such as F(-), Cl(-), NO(2) (-), Br(-), NO(3) (-), were performed. Aqueous hydroxide, carbonate and bicarbonate solutions were used as mobile phases. 相似文献
A new method is presented for the determination of five selected β-receptor antagonists by HPLC, which emphasizes sample preparation
via retention on a new type of silica gel sorbent used for solid-phase extraction (SPE). Sorbents of this type were obtained
by the chemical modification of silica gels of various porosities by cholesterol ligands. The cholesterol-based packing material
was investigated by spectroscopic methods and elemental analysis. The recoveries obtained with the extraction procedure were
optimum over a relatively broad sample pH range (3.08–7.50). Analytical factors such as the sample loading, the washing step
and elution conditions, the concentration of β-receptor antagonists to be extracted, and the type of sorbent were found to
play significant roles in the sample preparation procedure and would therefore need to be controlled to achieve optimum recoveries
of the analytes. Under optimum conditions, the recoveries of nadolol, acebutolol, esmolol, oxprenolol and propranolol from
spiked buffers, blood and urine were reproducible and dependent on the polarity or hydrophilicity of the compounds. The above
analytes were determined by reverse-phase high-performance liquid chromatography (HPLC) with UV and ESI-ion trap mass spectrometry
(MS) detection. The described method was found to be suitable for the routine measurement of compounds that are both polar
and basic, and can be applied for the analysis of biological samples such as urine and blood in clinical, toxicological or
forensic laboratories. The recovery measurements were performed on spiked human urine and serum, and on real samples of mouse
blood serum. 相似文献
The refreshable mercury film silver based electrode Hg(Ag)FE applied for determination of Cr(VI) traces using catalytic adsorptive striping voltammetry (CAdSV) will be presented. The film electrode is characterized by its very good surface reproducibility (not less than 2%) and long-term stability (1500–2000 measurement cycles). The mechanical refreshing of mercury film is realized in the specially constructed device, in a time shorter than 1–2 s.
In the paper, it will be proved that a mechanically weak hanging mercury drop electrode (HMDE) may be substituted by mercury film Hg(Ag)FE electrode with a surface area adjustable from 1.5 to 12 mm2. For the electrode surface 4 mm2 the detection limit obtained for Cr(VI) was 0.19 nM, while the linearity range measured for a 20 s accumulation time was between 0.5 and 50 nM. The relative standard deviation (R.S.D.) in determination of Cr(VI) varied from 1 to 5%. The influence of the excess of Cr(III) on determination of Cr(VI) was analyzed using samples from the Dobczyce reservoir spiked with known amounts of Cr(VI) and Cr(III). 相似文献
The chemical character, geometry, and architecture of chemically formed surface layers determine interactions between stationary phase, analyte, and mobile phase, and therefore the retention mechanisms (partitioning, adsorption, ion exchange, steric exclusion) of separated analytes. These interactions also depend on the structure and chemical character of the solutes and the composition of the mobile phase. High-molecular-weight fullerenes (C60 and C70) and water-soluble selenium-containing peptides (833 and 2607 Da) were used for the evaluation of laboratory-prepared octadecyl stationary phases with high and low coverage density before and after end-capping. The aim of this work was to study differences in surface coverage density and homogeneity and conformational changes of chemically bonded moieties and the influence of these parameters on the separation of mixtures of selenopeptides and fullerenes with significantly different molecular masses. A topographical model of the chemically modified stationary surface is presented. 相似文献
A first-principles theory of interfacial segregation of dopants and defects in heterostructures is developed and applied to GAN/A1N superlattices. The results indicate that the equilibrium concentrations of a dopant at two sides of an interface may differ by up to a few orders of magnitude, depending on its chemical identity and charge state, and that these cannot be obtained from calculations for bulk constituents alone. In addition, the presence of an internal electric field in polar heterostructures induces electro-migration and accumulation of hydrogen at the appropriate interfaces. 相似文献
It has been shown that the primary, old-fashioned idea of Sakharov's induced gravity and gauge interactions, in the “one-loop dominance” version, works astonishingly well yielding phenomenologically reasonable results. As a byproduct, the issue of the role of the UV cutoff in the context of the induced gravity has been reexamined (an idea of self-cutoff induced gravity). As an additional check, the black hole entropy has been used in the place of the action. Finally, it has been explicitly shown that the induced coupling constants of gauge interactions of the standard model assume qualitatively realistic values. 相似文献