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排序方式: 共有199条查询结果,搜索用时 15 毫秒
121.
122.
Miguel Melndez-Zamudio Ileana Bravo-Flores Eulalia Ramírez-Oliva Antonio Guerra-Contreras Gilberto lvarez-Guzmn Ramn Zrraga-Nuez Antonio Villegas Merced Martínez-Rosales Jorge Cervantes 《Molecules (Basel, Switzerland)》2021,26(4)
Stone consolidants have been widely used to protect historical monuments. Consolidants and hydrophobic formulations based on the use of tetraethoxysilane (TEOS) and alkylalkoxysilanes as precursors have been widely applied, despite their lack of solubility in water and requirement to be applied in organic media. In the search for a “greener” alternative based on silicon that has potential use in this field, the use of tetrakis(2-hydroxyethyl)silane (THEOS) and tris(2-hydroxyethyl)methyl silane (MeTHEOS) as precursors, due their high water solubility and stability, is proposed in this paper. It is already known that THEOS and MeTHEOS possess remarkable compatibility with different natural polysaccharides. The investigated approach uses the water-soluble silanes THEOS–chitosan and MeTHEOS–chitosan as a basis for obtaining hybrid consolidants and hydrophobic formulations for the conservation of siliceous and calcareous stones. In the case of calcareous systems, their incompatibility with alkoxysilanes is known and is expected to be solved by the developed hybrid consolidant. Their application in the conservation of building stones from historical and archeological sites from Guanajuato, México was studied. The evaluation of the consolidant and hydrophobic formulation treatment was mainly conducted by determining the mechanical properties and contact angle measurements with satisfactory results in terms of the performance and compatibility with the studied stones. 相似文献
123.
Michele M. Schantz Bruce A. Benner Jr. N. Alan Heckert Lane C. Sander Katherine E. Sharpless Stacy S. Vander Pol Y. Vasquez M. Villegas Stephen A. Wise K. Udeni Alwis Benjamin C. Blount Antonia M. Calafat Zheng Li Manori J. Silva Xiaoyun Ye Éric Gaudreau Donald G. Patterson Jr Andreas Sjödin 《Analytical and bioanalytical chemistry》2015,407(11):2945-2954
124.
A hybrid system, consisting of an array of Fe nanodots covered by a superconducting Al thin film, exhibits very unusual magnetotransport, including a giant hysteretic magnetoresistance with different reversible or irreversible regimes related to the magnetic state of the array. These effects originate from the magnetic fields produced by magnetic nanodots in the "magnetic vortex state." This is a unique model system in which properties of a magnetic array are transferred into the superconductor. 相似文献
125.
In this paper we establish the boundedness of the extremal solution u∗ in dimension N=4 of the semilinear elliptic equation −Δu=λf(u), in a general smooth bounded domain Ω⊂RN, with Dirichlet data u|∂Ω=0, where f is a C1 positive, nondecreasing and convex function in [0,∞) such that f(s)/s→∞ as s→∞. 相似文献
126.
Bouit PA Villegas C Delgado JL Viruela PM Pou-Amérigo R Ortí E Martín N 《Organic letters》2011,13(4):604-607
New push-pull dyes featuring π-extended tetrathiafulvalene (exTTF) as the donor group and tricyanofuran (TCF) as the acceptor group were synthesized and characterized. Their broad absorption covers the entire visible spectral range and enters the near-infrared region. Electrochemistry and theoretical calculations provided an understanding of these singular electronic properties. The new dyes are appealing candidates as light harvesters in photovoltaic devices. 相似文献
127.
Antonio Cañada Salvador Villegas 《Nonlinear Analysis: Theory, Methods & Applications》2011,74(5):1913-1925
This paper is devoted to the study of Lyapunov type inequalities for periodic conservative systems. The main results are derived from a previous analysis which relates the best Lyapunov constants to some especial (constrained or unconstrained) minimization problems. We provide some new results on the existence and uniqueness of solutions of nonlinear resonant and periodic systems. Finally, we present some new conditions which guarantee the stable boundedness of linear periodic conservative systems. 相似文献
128.
Modification and intercalation of layered zirconium phosphates: a solid‐state NMR monitoring 下载免费PDF全文
Vladimir I. Bakhmutov Yuwei Kan Javeed Ahmad Sheikh Julissa González‐Villegas Jorge L. Colón Abraham Clearfield 《Magnetic resonance in chemistry : MRC》2017,55(7):648-654
Several layered zirconium phosphates treated with Zr(IV) ions, modified by monomethoxy‐polyethyleneglycol‐monophosphate and intercalated with doxorubicin hydrochloride have been studied by solid‐state MAS NMR techniques. The organic components of the phosphates have been characterized by the 13C{1H} CP MAS NMR spectra compared with those of initial compounds. The multinuclear NMR monitoring has provided to establish structure and covalent attachment of organic/inorganic moieties to the surface and interlayer spaces of the phosphates. The MAS NMR experiments including kinetics of proton‐phosphorus cross polarization have resulted in an unusual structure of zirconium phosphate 6 combining decoration of the phosphate surface by polymer units and their partial intercalation into the interlayer space. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
129.
Andrés L. Medaglia Juan G. Villegas Diana M. Rodríguez-Coca 《Journal of Heuristics》2009,15(2):153-176
Colombian environmental authorities are exploring new alternatives for improving the disposal of hospital waste generated
in the Department of Boyacá (Colombia). To design this hospital waste management network we propose a biobjective obnoxious
facility location problem (BOOFLP) that deals with the existing tradeoff between a low-cost operating network and the negative
effect on the population living near the waste management facilities. To solve the BOOFLP we propose a hybrid approach that
combines a multiobjective evolutionary algorithm (NSGA II) with a mixed-integer program. The algorithms are compared against
the Noninferior Set Estimation (NISE) method and tested on data from Boyacá’s hospital waste management network and publicly
available instances. 相似文献
130.
Nikky Kortbeek Aleida Braaksma Ferry HF Smeenk Piet JM Bakker Richard J Boucherie 《The Journal of the Operational Research Society》2015,66(7):1061-1076
The design and operations of inpatient care facilities are typically largely historically shaped. A better match with the changing environment is often possible, and even inevitable due to the pressure on hospital budgets. Effectively organizing inpatient care requires simultaneous consideration of several interrelated planning issues. Also, coordination with upstream departments like the operating theatre and the emergency department is much-needed. We present a generic analytical approach to predict bed census on nursing wards by hour, as a function of the Master Surgical Schedule and arrival patterns of emergency patients. Along these predictions, insight is gained on the impact of strategic (ie, case mix, care unit size, care unit partitioning), tactical (ie, allocation of operating room time, misplacement rules), and operational decisions (ie, time of admission/discharge). The method is used in the Academic Medical Center Amsterdam as a decision-support tool in a complete redesign of the inpatient care operations. 相似文献