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排序方式: 共有235条查询结果,搜索用时 15 毫秒
61.
In this work, Amberlite XAD-2 resin functionalized with 4,5-dihydroxy-1,3-benzenedisulfonic acid was synthesized, characterized and applied as a new packing material for an on-line system to nickel preconcentration. The method is based on the sorption of Ni(II) ions in a minicolumn containing the synthesized resin, posterior desorption using an acid solution and measurement of the nickel by spectrophotometry (PAR method). The optimization of the system was performed using factorial design and Doehlert matrix considering five variables: eluent concentration, PAR solution pH, sample flow rate, PAR solution concentration and sample pH. Signals were measured as peak height by using an instrument software. Using the experimental conditions defined in the optimization, the method allowed nickel determination with achieved sampling rate of 25 samples per hour, detection limit (3 s) of 2 μg l−1 and precision (assessed as the relative standard deviation) of 8.2-2.6%, for nickel solutions of 10.0-200.0 μg l−1 concentration, respectively. The experimental enrichment factor of the proposed system was 46, for 120 s preconcentration time. The proposed procedure was applied for nickel determination in food samples. Recoveries of spike additions (5 or 10 μg g−1) to food samples were quantitative (94-110%). 相似文献
62.
We consider the Vlasov–Poisson–Fokker–Planck equation in three dimensions as the backward Kolmogorov equation associated to a non‐linear diffusion process. In this way we derive new L∞‐estimates on the spatial density which are uniform in the diffusion parameters. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
63.
Serena Coppola Carmen Avagliano Antonia Sacchi Sonia Laneri Antonio Calignano Luana Voto Anna Luzzetti Roberto Berni Canani 《Molecules (Basel, Switzerland)》2022,27(6)
Human skin is the largest organ and the most external interface between the environment and the body. Vast communities of viruses, bacteria, archaea, fungi, and mites, collectively named the skin microbiome (SM), cover the skin surface and connected structures. Skin-resident microorganisms contribute to the establishment of cutaneous homeostasis and can modulate host inflammatory responses. Imbalances in the SM structure and function (dysbiosis) are associated with several skin conditions. Therefore, novel target for the skincare field could be represented by strategies, which restore or preserve the SM natural/individual balance. Several of the beneficial effects exerted by the SM are aroused by the microbial metabolite butyrate. Since butyrate exerts a pivotal role in preserving skin health, it could be used as a postbiotic strategy for preventing or treating skin diseases. Herein, we describe and share perspectives of the potential clinical applications of therapeutic strategies using the postbiotic butyrate against human skin diseases. 相似文献
64.
The boundary layer equations are investigated by constructing a suitably related stochastic process. 相似文献
65.
Giuseppe Pulvirenti 《Annali di Matematica Pura ed Applicata》1961,56(1):177-191
Sunto Viene studiato il problema diCauchy per una equazione differenziale in forma implicita F(t, x, x) =0 in uno spazio diBanach. Si dimostra, sotto certe ipotesi valendosi di metodi funzionali, un teorema di esistenza e, sotto altre, col metodo delle
approssimazioni successive, un teorema di esistenza ed unicità.
Summary TheCauchy's problem for an implicit differential equation F(t, x, x) =0 in aBanach space is studied. Under some hypothesis, using functional methods, a theorem of existence and, under others, using the method of the successive approximations, a theorem of existence and uniqueness are demonstrated.相似文献
66.
Giuseppe Pulvirenti 《Annali di Matematica Pura ed Applicata》1961,56(1):281-300
Sunto Si stabilisce un teorema di esistenza per equazioni differenziali in uno spazio diBanach sotto ipotesi diCarathéodory. Viene studiata la struttura del pennello delle soluzioni pervenendo a teoremi che estendono quelli, noti nel caso degli
spazi euclidei, diH. Kneser eM. Hukuhara.
L'A. fa parte del 6° gruppo di ricerca del C. N. R.. 相似文献
Summary An existence theorem for differential equations in aBanach space is proved under hypothesis ofCarathéodory type. The set of solutions issued from a given point is studied and results analogous to those valid in case of a euclidean space, byH. Kneser andM. Hukuhara, are obtained.
L'A. fa parte del 6° gruppo di ricerca del C. N. R.. 相似文献
67.
Pisignano D Di Benedetto F Persano L Gigli G Cingolani R 《Langmuir : the ACS journal of surfaces and colloids》2004,20(12):4802-4804
The growing demand for new solutions to pursue the trend of micro- and nanoelectronics predicted by Moore's law is stimulating the development of new high-resolution, low-cost lithographies. Here we demonstrate that several bottom-up approaches can be used to increase the throughput of soft lithography by exploiting the enhanced hydrophilicity, the low viscosity, and the fragility of the employed materials. In particular, the customized functionalization of the involved surfaces to improve the wettability to polymer fluids and the dramatic decrease of the viscosity of polymer compounds as the temperature is increased, together with the good thermal stability of the functionalized surfaces, allow a faster filling of elastomeric channels, up to almost an order of magnitude with respect to conventional microfluidics. 相似文献
68.
Steady-periodic heat conduction with relaxation time in an infinitely long hollow cylinder is considered. Four boundary value
problems, with boundary conditions of the first and of the second kind, are solved analytically. The solution for a solid
cylinder with a sinusoidally varying surface temperature is obtained as a special case of a solution found for the hollow
cylinder. The effects of the relaxation time on the steady-periodic temperature field are analysed, in details, for a solid
cylinder with a sinusoidally varying surface temperature and for a hollow cylinder with a sinusoidally varying heat flux at
the inner surface and with a constant temperature at the outer surface. The results show that thermal resonances may occur
and suggest that accurate measurements of the relaxation time could be obtained by means of experiments on steady-periodic
heat conduction in cylindrical geometry.
Received on 15 April 1997 相似文献
69.
Luana Parras Meleiro Ana Lucia Ribeiro Latorre Zimbardi Flavio Henrique Moreira Souza Douglas Chodi Masui Tony Marcio Silva João Atilio Jorge Rosa Prazeres Melo Furriel 《Applied biochemistry and biotechnology》2014,173(2):391-408
Humicola insolens produced a new β-glucosidase (BglHi2) under solid-state fermentation. The purified enzyme showed apparent molecular masses of 116 kDa (sodium dodecyl sulfate–polyacrylamide gel electrophoresis) and 404 kDa (gel-filtration), suggesting that it is a homotetramer. Mass spectrometry analysis showed amino acid sequence similarity with a β-glucosidase from Chaetomium thermophilum. Optima of pH and temperature were 5.0 and 65 °C, respectively, and the enzyme was stable for 60 min at 50 °C, maintaining 71 % residual activity after 60 min at 55 °C. BglHi2 hydrolyzed p-nitrophenyl-β-d-glucopyranoside and cellobiose. Cellobiose hydrolysis occurred with high apparent affinity (K M?=?0.24?±?0.01 mmol L?1) and catalytic efficiency (k cat/K M?=?1,304.92?±?53.32 L mmol?1 s?1). The activity was insensitive to Fe+3, Cr+2, Mn+2, Co+2, and Ni2+, and 50–60 % residual activities were retained in the presence of Pb2+, Hg2+, and Cu2+. Mixtures of pure BglHi2 or H. insolens crude extract (CE) with crude extracts from Trichoderma reesei fully hydrolyzed Whatman no. 1 paper. Mixtures of H. insolens CE with T. reesei CE or Celluclast 1.5 L fully hydrolyzed untreated printed office paper, napkin, and magazine papers after 24–48 h, and untreated cardboard was hydrolyzed by a H. insolens CE/T. reesei CE mixture with 100 % glucose yield. Data revealed the good potential of BglHi2 for the hydrolysis of waste papers, promising feedstocks for cellulosic ethanol production. 相似文献
70.
Agissilaos Athanassoulis Thierry Paul Federica Pezzotti Mario Pulvirenti 《Annales Henri Poincare》2011,12(8):1613-1634
In this paper we consider the nonlinear Hartree equation in presence of a given external potential, for an initial coherent
state. Under suitable smoothness assumptions, we approximate the solution in terms of a time dependent coherent state, whose
phase and amplitude can be determined by a classical flow. The error can be estimated in L
2 by C ?{e}{C \sqrt {\varepsilon}} , e{\varepsilon} being the Planck constant. Finally we present a full formal asymptotic expansion. 相似文献