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131.
Andrea Schenkmayerová Anikó Bertóková Jana Šefčovičová Vladimír Štefuca Marek Bučko Alica Vikartovská Peter Gemeiner Ján Tkáč Jaroslav Katrlík 《Analytica chimica acta》2015
A microbial biosensor for 2-phenylethanol (2-PE) based on the bacteria Gluconobacter oxydans was developed and applied in monitoring of a biotechnological process. The cells of G. oxydans were immobilized within a disposable polyelectrolyte complex gel membrane consisting of sodium alginate, cellulose sulphate and poly(methylene-co-guanidine) attached onto a miniaturized Clark oxygen electrode, forming whole cell amperometric biosensor. Measured changes in oxygen concentration were proportional to changes in 2-PE concentration. The biosensor sensitivity was 864 nA mM−1 (RSD = 6%), a detection limit of 1 μM, and the biosensor response towards 2-PE was linear in the range 0.02–0.70 mM. The biosensor preserved 93% of its initial sensitivity after 7 h of continuous operation and exhibited excellent storage stability with loss of only 6% of initial sensitivity within two months, when stored at 4 °C. The developed system was designed and successfully used for an off-line monitoring of whole course of 2-PE biooxidation process producing phenylacetic acid (PA) as industrially valuable aromatic compound. The biosensor measurement did not require the use of hazardous organic solvent. The biosensor response to 2-PE was not affected by interferences from PA and phenylacetaldehyde at concentrations present in real samples during the biotransformation and the results were in a very good agreement with those obtained via gas chromatography. 相似文献
132.
Sustainable Synthesis of Chiral Tetrahydrofurans through the Selective Dehydration of Pentoses
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Robert W. Foster Dr. Christopher J. Tame Dr. Dejan‐Krešimir Bučar Prof. Helen C. Hailes Dr. Tom D. Sheppard 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(45):15947-15950
L ‐Arabinose is an abundant resource available as a waste product of the sugar beet industry. Through use of a hydrazone‐based strategy, L ‐arabinose was selectively dehydrated to form a chiral tetrahydrofuran on a multi‐gram scale without the need for protecting groups. This approach was extended to other biomass‐derived reducing sugars and the mechanism of the key cyclization investigated. This methodology was applied to the synthesis of a range of functionalized chiral tetrahydrofurans, as well as a formal synthesis of 3R‐3‐hydroxymuscarine. 相似文献
133.
A weighted (unweighted) graph is called equiarboreal if the sum of weights (the number) of spanning trees containing a given edge in is independent of the choice of edge. In this paper, we give some resistance characterizations of equiarboreal weighted and unweighted graphs, and obtain the necessary and sufficient conditions for -subdivision graphs, iterated double graphs, line graphs of regular graphs and duals of planar graphs to be equiarboreal. Applying these results, we obtain new infinite families of equiarboreal graphs, including iterated double graphs of 1-walk-regular graphs, line graphs of triangle-free 2-walk-regular graphs, and duals of equiarboreal planar graphs. 相似文献
134.
Let \(\mathcal {U}=\{U(t,s)\}_{t\ge s\ge 0}\) be a strongly continuous and exponentially bounded evolution family acting on a complex Banach space X and let \(\mathcal {X}\) be a certain Banach function space of X-valued functions. We prove that the growth bound of the family \(\mathcal {U}\) is less than or equal to \(-\frac{1}{c(\mathcal {U}, \mathcal {X})}\) provided that the convolution operator \(f\mapsto \mathcal {U}*f\) acts on \(\mathcal {X}.\) It is well known that under the latter assumption, the convolution operator is bounded and then \(c(\mathcal {U}, \mathcal {X})\) denotes (ad-hoc) its norm in \(\mathcal {L}(\mathcal {X}).\) As a consequence, we prove that if \(\sup \nolimits _{s\ge 0}\int \nolimits _{s}^\infty \Vert U(t,s)\Vert dt=u_1(\mathcal {U})<\infty ,\) then \(\omega _0(\mathcal {U})u_1(\mathcal {U})\le -1.\) Finally, we give an example showing that the accuracy of the estimates may be quite accurate. 相似文献
135.
Acta Mathematicae Applicatae Sinica, English Series - Let G be a graph and H a subgraph of G. A backbone-k-coloring of (G, H) is a mapping f: V(G) → {1, 2, ···, k} such that... 相似文献
136.
The optimal concentration of a blue dye solution with 'tracer' properties, enabling a pollutant to be marked was determined by the use of numerical, theoretical and experimental approaches. Experimental investigations were performed on a transparent Hele–Shaw cell and the concentration distribution was analyzed using an optical technique based on dye light absorption properties. The injected optimal concentration was established thanks to a theoretical and experimental study carried out on the output signal dynamics. Using the same experimental conditions, numerical simulations were performed. The very good agreement between the data (experimental and numerical) clarified that: (i) the choice of the blue dye optimal concentration was valid and (ii) the concentration-dependent density should not be neglected in flow and transport equations even if it concerns a so-called 'tracer'. Following this remark, a theoretical aspect was developed in order to determine the analogous conditions between a Hele–Shaw cell and a porous medium for the variable density transport phenomenon. The structure of the concentration-dependent dispersion tensor used in the numerical code was obtained by homogenizing the Stokes flow of a bi-component mixture. The numerical results show that, as long as the tracer density does not exceed a certain value, it is not necessary to take into account a density contrast in terms of the dispersion tensor. The classical form of the Taylor dispersion tensor can be used successfully. 相似文献
137.
Christophe Felder Constantin Oltean Mikhail Panfilov Michel Buès 《Comptes Rendus Mecanique》2004,332(3):223-229
The investigation of non-reactive miscible solute dispersion in a vertical Hele–Shaw cell is considered. An asymptotic method is used to extend Taylor model to the case of the fluid density, the dynamic viscosity and the molecular diffusion coefficient are solute concentration-dependent. It is demonstrated that the averaged variables over the gap are governed by a convection–dispersion equation in which the dispersion tensor is concentration-dependent. To cite this article: C. Felder et al., C. R. Mecanique 332 (2004). 相似文献
138.
Buğra Kabil 《PAMM》2016,16(1):657-658
We prove the local existence of an undercompressive hydrodynamical shock to the isothermal Euler equations with a non-monotone pressure function. This nonlinear problem will be formulated as an abstract hyperbolic initial boundary value problem. The existence of a weak solution to a linearized version of the problem is shown with the use of Riesz theorem. Using the results of the linear system yields by an iteration scheme (local in time) well-posedness of the nonlinear problem. The system of equations is obtained by modeling the motion of sharp liquid-vapor interfaces including configurational forces as well as surface tension. The considered non-viscous Van der Waals fluid is compressible and allows phase transitions. The propagating phase boundary is controlled by a modified version of the Rankine-Hugoniot jump condition obtained by the Young-Laplace law. Entropy dissipation at the interface is precisely described by a kinetic relation. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
139.
Gang Xu Tingting Bu Minghong Wu Jisan Zheng Ning Liu Liang Wang 《Journal of Radioanalytical and Nuclear Chemistry》2011,288(3):759-764
The degradation characteristics of clopyralid irradiated by electron beam (EB) was studied in aqueous solutions. The effects of factors, such as initial clopyralid concentrations, addition of radicals scavenger, initial solution pH and addition of H2O2, were investigated on clopyralid degradation efficiency and mechanism. It was found that the EB-radiolysis was an effective way to degrade clopyralid and its degradation rate decreased with the increasing of substrate concentration. In the investigated initial concentrations range of 100?C400 mg L?1, the radiolytic degradation of clopyralid followed a pseudo-first kinetic order. The results from addition of radicals scavenger indicated that both ?OH and e aq ? played significant roles in the degradation of clopyralid. Furthermore, the alkaline condition and addition of H2O2 (<10 mM) in the solution also slightly enhanced the efficiency of clopyralid degradation. The ion chromatography analysis showed that some organic acids (formic acid, acetic acid and oxalic acid) were formed, while the completely dechlorination of the substrate was achieved and organic nitrogen was recovered in the form of ammonium and nitrate ions during the irradiation process. 相似文献
140.