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排序方式: 共有163条查询结果,搜索用时 15 毫秒
81.
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
82.
Legendrian submanifolds in Sasakian space forms play an important role in contact geometry. Defever et al. (Boll Unione Mat Ital B 7(11):365–374, 1997) established the first Chen inequality for C-totally real submanifolds in Sasakian space forms. In this article, we improve this first Chen inequality for Legendrian submanifolds in Sasakian space forms. 相似文献
83.
The extraction of two specimens of Pseudopterogorgia elisabethae, each collected from a different location at the San Andrés Archipelago, afforded two new norditerpenes, caribenols A (1) and B (2). Metabolites 1 and 2 contain unusual carbon skeletons that are previously undescribed and therefore constitute new classes of C19 rearranged terpenes. Their molecular structures were established by a combination of single-crystal X-ray analysis and comprehensive 2D NMR measurements. 相似文献
84.
León IR Neves-Ferreira AG Valente RH Mota EM Lenzi HL Perales J 《Journal of mass spectrometry : JMS》2007,42(6):781-792
Matrix-assisted laser desorption ionization (MALDI), Peptide Mass Fingerprinting (PMF) and MALDI-MS/MS ion search (using MASCOT) have become the preferred methods for high-throughput identification of proteins. Unfortunately, PMF can be ambiguous, mainly when the genome of the organism under investigation is unknown and the quality of spectra generated is poor and does not allow confident identification. The post-source decay (PSD) fragmentation of singly charged tryptic peptide ions generated by MALDI-TOF/TOF typically results in low fragmentation efficiency and/or complex spectra, including backbone fragmentation ions (series b and y), internal fragmentation etc. Interpreting these data either manually and/or using de novo sequencing software can frequently be a challenge. To overcome this limitation when studying the proteome of adult Angiostrongylus costaricensis, a nematode with unknown genome, we have used chemical N-terminal derivatization of the tryptic peptides with 4-sulfophenyl isothiocyanate (SPITC) prior to MALDI-TOF/TOF MS. This methodology has recently been reported to enhance the quality of MALDI-TOF/TOF-PSD data, allowing the obtainment of complete sequence of most of the peptides and thus facilitating de novo peptide sequencing. Our approach, consisting of SPITC derivatization along with manual spectra interpretation and Blast analysis, was able to positively identify 76% of analyzed samples, whereas MASCOT analysis of derivatized samples, MASCOT analysis of nonderivatized samples and PMF of nonderivatized samples yielded only 35, 41 and 12% positive identifications, respectively. Moreover, de novo sequencing of SPITC modified peptides resulted in protein sequences not available in NCBInr database paving the way to the discovery of new protein molecules. 相似文献
85.
Ileana B. Recalde Agustín Campos Iaki Mondragon Clara M. Gmez 《Macromolecular Symposia》2001,174(1):175-186
A dicyanate ester resin was modified by blending with polysulfone (PSF) and cured at different temperatures with or without cobalt catalyst. Size exclusion chromatography was used to determine the cyanate conversion until the gel point. The morphology of the cured samples, characterised by scanning electron microscopy, varied from PSF particle structure to a combined particle structure. 相似文献
86.
Maria Zaharescu Maria Crisan A. Jitianu D. Crisan Aurelia Meghea Ileana Rau 《Journal of Sol-Gel Science and Technology》2000,19(1-3):631-635
Composite SiO2-iron oxide materials were prepared by three experimental procedures. In the first case (1), the iron oxides were precipitated during the sol-gel process. In the second case (2), the SiO2 matrix was initially obtained, and the iron oxides were formed by thermal treatment after impregnation of a soluble Fe2+ salt in the previously processed matrix. In the third method (3), ferrite powders, prepared by wet chemical method, were embedded into a SiO2 based sol-gel matrix. Two type of precursors (tetraethoxysilane (TEOS) or methyltriethoxysilane (MTEOS) were used as SiO2 sources. Various properties versus both type of precursor and on the method of preparation were noticed. Materials with high porosity and nano-sized iron oxide content could be prepared using the mentioned above methods. 相似文献
87.
Aura Argseal Ctlin Maxim Mihaela Badea Larisa Ioni Mariana Carmen Chifiriuc Arpad Mihai Rostas Mihaela Bacalum Mina Rileanu Lavinia L. Ru Ileana C. Farcaanu Emilia Elena Iorgulescu Rodica Olar 《Molecules (Basel, Switzerland)》2022,27(3)
In an attempt to increase the biological activity of the 1,2,4-triazolo[1,5-a]pyrimidine scaffold through complexation with essential metal ions, the complexes trans-[Cu(mptp)2Cl2] (1), [Zn(mptp)Cl2(DMSO)] (2) (mptp: 5-methyl-7-phenyl-1,2,4-triazolo[1,5-a]pyrimidine), [Cu2(dmtp)4Cl4]·2H2O (3) and [Zn(dmtp)2Cl2] (4) (dmtp: 5,7-dimethyl-1,2,4-triazolo[1,5-a]pyrimidine), were synthesized and characterized as new antiproliferative and antimicrobial species. Both complexes (1) and (2) crystallize in the P21/n monoclinic space group, with the tetrahedral surroundings generating a square-planar stereochemistry in the Cu(II) complex and a tetrahedral stereochemistry in the Zn(II) species. The mononuclear units are interconnected in a supramolecular network through π–π interactions between the pyrimidine moiety and the phenyl ring in (1) while supramolecular chains resulting from C-H∙∙∙π interactions were observed in (2). All complexes exhibit an antiproliferative effect against B16 tumor cells and improved antibacterial and antifungal activities compared to the free ligands. Complex (3) displays the best antimicrobial activity against all four tested strains, both in the planktonic and biofilm-embedded states, which can be correlated to its stronger DNA-binding and nuclease-activity traits. 相似文献
88.
Ileana Mares Constantin Mares Venera Dobrica Crisan Demetrescu 《Entropy (Basel, Switzerland)》2022,24(10)
The purpose of this study was to obtain synergistic information and details in the time–frequency domain of the relationships between the Palmer drought indices in the upper and middle Danube River basin and the discharge (Q) in the lower basin. Four indices were considered: the Palmer drought severity index (PDSI), Palmer hydrological drought index (PHDI), weighted PDSI (WPLM) and Palmer Z-index (ZIND). These indices were quantified through the first principal component (PC1) analysis of empirical orthogonal function (EOF) decomposition, which was obtained from hydro-meteorological parameters at 15 stations located along the Danube River basin. The influences of these indices on the Danube discharge were tested, both simultaneously and with certain lags, via linear and nonlinear methods applying the elements of information theory. Linear connections were generally obtained for synchronous links in the same season, and nonlinear ones for the predictors considered with certain lags (in advance) compared to the discharge predictand. The redundancy–synergy index was also considered to eliminate redundant predictors. Few cases were obtained in which all four predictors could be considered together to establish a significant information base for the discharge evolution. In the fall season, nonstationarity was tested through wavelet analysis applied for the multivariate case, using partial wavelet coherence (pwc). The results differed, depending on the predictor kept in pwc, and on those excluded. 相似文献
89.
Silvia Ptruic Ersilia Alexa Diana Obitioiu Ileana Cocan Isidora Radulov Adina Berbecea Roxana Nicoleta Lazr Eliza Simiz Nicoleta Maria Vicar Anca Hulea Drago Moraru 《Molecules (Basel, Switzerland)》2022,27(13)
Honey is a natural product with multiple health benefits. The paper presents the chemical characterization and the antioxidant and antimicrobial potential of ten types of honey (knotweed, linden, wild cherry, acacia, honeydew, oilseed rape, sunflower, phacelia, plain polyflora and hill polyflora) from the Banat region, Romania. We studied the water content, dry matter, impurities, acidity and pH of honey. We also determined the content of reducing sugar, minerals and flavonoids and the total phenolic content. All honey samples analysed showed good nutritional characteristics according to the standard codex for honey. From the analysis of the mineral content of the honey samples, we observed a variability in the macro and microminerals, influenced by the botanical origin, ranging between 0.25% (wild cherry honey) and 0.54% (honeydew). The toxic metals’ (Cd and Pb) levels met the standard for almost all samples analysed except for knotweed. The flavonoid content of the samples ranged from 9.29 mg QE/100 g for wild cherry honey to 263.86 mg QE/100 g for linden honey, and for polyphenols between 177.6 mgGAE/100 g for acacia honey and 1159.3 mgGAE/100 g for honeydew. The best antioxidant capacity was registered in the case of linden honey (79.89%) and honeydew (79.20%) and the weakest in acacia (41.88%) and wild cherries (50.4%). All studied honey samples showed antimicrobial activity, depending on the type of honey, concentration and strain analysed. The novelty of this study is given by the complex approach of the study of honey quality, both from the perspective of chemical attributes and the evaluation of the antimicrobial potential on specific strains in correlation with the botanical and geographical origin of the analyzed area. 相似文献
90.