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排序方式: 共有922条查询结果,搜索用时 15 毫秒
911.
Joaquín Barrio Jorge Chamón Ana Isabel Pardo Margarita Arroyo 《Journal of Solid State Electrochemistry》2009,13(11):1767-1776
The conservation and restoration of archaeological metals is one of the most complex conservation issues. Therefore, conservators usually employ the most advanced techniques, with the purpose of obtaining positive results for the preservation of the objects. One of the aims of conservation treatments is avoiding the reactivation of corrosion processes. Electrochemical treatments applied on archaeological metals were employed in Spain since the beginning of the twentieth century. During its history, the treatments were praised and reviled, practiced and discontinued. Conservation criteria have also exerted an influence over electrochemical treatments. Nowadays, electrochemical techniques are provided with control devices, such as potentiostatic control and could be considered again as a very valuable option, in combination with traditional and vanguard techniques, to recover the archaeological metallic heritage. 相似文献
912.
Until now there are almost no results on the precise geometric location of minimal enclosing balls of simplices in finite-dimensional real Banach spaces. We give a complete solution of the two-dimensional version of this problem, namely to locate minimal enclosing discs of triangles in arbitrary normed planes. It turns out that this solution is based on the classification of all possible shapes that the intersection of two norm circles can have, and on a new classification of triangles in normed planes via their angles. We also mention that our results are closely related to basic notions like coresets, Jung constants, the monotonicity lemma, and d-segments. 相似文献
913.
Partha Sarkar R.K. Roy A. Mitra A.K. Panda Margarita Churyukanova Sergey Kaloshkin 《Journal of magnetism and magnetic materials》2012
Rapidly quenched microwires with a nominal composition of Fe39Co39Si8B14 (#AO), Fe37Co37Nb4Si8B14 (#AN) and Fe36Co36Nb4Cr2Si8B14 (#ANC) have been investigated. Devitrification of as-quenched microwires showed that crystallization temperatures increased with simultaneous incorporation of Nb and Cr as in #ANC alloy. Addition of these elements also contributed to an increase in activation energy in #AN and #ANC alloys. Nb addition reduced the particle size, which became much finer in the case of the Cr-containing alloy. Although Nb addition did not have much effect on lowering the Curie temperature TC of the amorphous phase, Cr substitution lowered TC to 698 K from high values of 785 K and 787 K observed in the #AO and #ANC alloys, respectively. However, the Cr addition revealed a better Giant magneto-impedance (GMI) response compared to the other alloys. Such improved GMI properties in the Cr-containing alloy are attributed to lower values of the coercivity and magnetostriction in the alloy containing both Nb and Cr. 相似文献
914.
S Rummel M Herrmann M Wahren SM Yunusov MA Ilatovskaya YB Isaev ND Lapkina YN Novikov VB Shur 《Isotopes in environmental and health studies》2012,48(3):391-392
Potassium graphite intercalation compounds are able to activate C-H bonds of hydrocarbons at room temperature. In this paper, the hydrogen-deuterium exchange of CHD(3) in the presence of C(8)K, C(24)K and C(36)K is described. 相似文献
915.
Plinio Alejandro Trinidad-Caldern Laura Margarita Lpez-Castillo Salvador Gallegos-Martínez Grissel Trujillo-de Santiago Silverio García-Lara Mario Moiss lvarez 《Molecules (Basel, Switzerland)》2022,27(9)
The development of novel cancer therapeutic strategies has garnered increasing interest in cancer research. Among the therapeutic choices, chemosensitizers have shown exciting prospects. Peptides are an attractive alternative among the molecules that may be used as chemosensitizers. We rationally designed a new-to-nature peptide, nurP28, derived from the 22-kDa α-zein protein sequence (entry Q00919_MAIZE). The resultant sequence of the nurP28 peptide after the addition of arginine residues was LALLALLRLRRRATTAFIIP, and we added acetyl and amide groups at the N- and C-terminus, respectively, for capping. We evaluated the cytotoxicity of the nurP28 peptide alone and in combination with docetaxel in fibroblast monolayers and breast cancer monolayers and spheroids. Our results indicated that nurP28 is not cytotoxic to human fibroblasts or cancer cells. Nevertheless, when combined with 1 µM docetaxel, 3 ng/mL nurP28 induced equivalent (in MCF7 monolayers) and higher (in MCF7 spheroids) cytotoxic effects than 10-fold higher doses of docetaxel alone. These findings suggest that nurP28 may act as a chemosensitizer in breast cancer treatment. This study describes the enhancing “anti-cancer” effects of nurP28 in breast cancer 2D and 3D cultures treated with docetaxel. Further studies should explore the mechanisms underlying these effects and assess the clinical potential of our findings using animal models. 相似文献
916.
Luis Bustos Carlos Echiburú-Chau Alejandro Castro-Alvarez Ben Bradshaw Mario J. Simirgiotis Marco Mellado Claudio Parra Mauricio Cuellar 《Molecules (Basel, Switzerland)》2022,27(14)
This study aimed to determine the in vitro cytotoxicity and understand possible cytotoxic mechanisms via an in silico study of eleven chalcones synthesized from two acetophenones. Five were synthesized from a prenylacetophenone isolated from a plant that grows in the Andean region of the Atacama Desert. The cytotoxic activity of all the synthesized chalcones was tested against breast cancer cell lines using an MTT cell proliferation assay. The results suggest that the prenyl group in the A-ring of the methoxy and hydroxyl substituents of the B-ring appear to be crucial for the cytotoxicity of these compounds. The chalcones 12 and 13 showed significant inhibitory effects against growth in MCF-7 cells (IC50 4.19 ± 1.04 µM and IC50 3.30 ± 0.92 µM), ZR-75-1 cells (IC50 9.40 ± 1.74 µM and IC50 8.75 ± 2.01µM), and MDA-MB-231 cells (IC50 6.12 ± 0.84 µM and IC50 18.10 ± 1.65 µM). Moreover, these chalcones showed differential activity between MCF-10F (IC50 95.76 ± 1.52 µM and IC50 95.11 ± 1.97 µM, respectively) and the tumor lines. The in vitro results agree with molecular coupling results, whose affinity energies and binding mode agree with the most active compounds. Thus, compounds 12 and 13 can be considered for further studies and are candidates for developing new antitumor agents. In conclusion, these observations give rise to a new hypothesis for designing chalcones with potential cytotoxicity with high potential for the pharmaceutical industry. 相似文献
917.
María del Carmen Fernández-Ramírez Kevin Kan-Shing Ng Margarita Menéndez Douglas V. Laurents Rubén Hervás Mariano Carrión-Vázquez 《Angewandte Chemie (International ed. in English)》2023,62(19):e202209252
Understanding early amyloidogenesis is key to rationally develop therapeutic strategies. Tau protein forms well-characterized pathological deposits but its aggregation mechanism is still poorly understood. Using single-molecule force spectroscopy based on a mechanical protection strategy, we studied the conformational landscape of the monomeric tau repeat domain (tau-RD244-368). We found two sets of conformational states, whose frequency is influenced by mutations and the chemical context. While pathological mutations Δ280K and P301L and a pro-amyloidogenic milieu favored expanded conformations and destabilized local structures, an anti-amyloidogenic environment promoted a compact ensemble, including a conformer whose topology might mask two amyloidogenic segments. Our results reveal that to initiate aggregation, monomeric tau-RD244-368 decreases its polymorphism adopting expanded conformations. This could account for the distinct structures found in vitro and across tauopathies. 相似文献
918.
Nadia Alejandra Rodríguez-Uribe Rodrigo Contreras-Martínez Dr. Everardo Jaime-Adán Dr. María Luisa García-Betancourt Prof. Margarita I. Bernal-Uruchurtu Prof. Carolina Godoy-Alcántar 《Chemphyschem》2023,24(12):e202300071
In a one-step reaction, we prepared a dibenzylamine perylene diimide derivative (PDI). Its double hook structure allows for self-association with a constant of Kd ∼108 M−1 determined by fluorescence. We confirmed its ability to bind PAHs using UV/Vis, fluorescence, and 1H NMR titrations in CHCl3. The complex formation signature in UV/vis is a new band at 567 nm. The calculated binding constants (Ka∼104 M−1) follow the trend pyrene>perylene>phenanthrene>naphthalene>anthracene. Theoretical modeling of these systems using DFT ωB97X-D/6-311G(d,p) proved helpful in rationalizing the complex formation and the observed association trend. The distinctive signal in UV/vis is due to a charge transfer in the complex from orbitals in the guest to the host. SAPT(DFT) confirmed that the driving forces in the complex formation are exchange and dispersion (π–π interactions). Still, the recognition ability depends on the electrostatic component of the interaction, a minor fraction. 相似文献
919.
Dimitra Kourti Anastasia Kanioura Theodore Manouras Maria Vamvakaki Panagiotis Argitis Margarita Chatzichristidi Sotirios Kakabakos Panagiota Petrou 《Macromolecular bioscience》2023,23(1):2200301
Surfaces for guided cell adhesion and growth are indispensable in several diagnostic and therapeutic applications. Towards this direction, four diblock copolymers comprising polyethylene glycol (PEG) and poly(2-tetrahydropyranyl methacrylate) (PTHPMA) are synthesized employing PEG macroinitiators of different chain lengths. The copolymer with a 5000 Da PEG block and a PEG-PTHPMA comonomers weight ratio of 43–57 provides a film with the highest stability in the culture medium and the strongest cell repellent properties. This copolymer is used to develop a positive photolithographic material and create stripe patterns onto silicon substrates. The highest selectivity regarding smooth muscle cell adhesion and growth and the highest fidelity of adhered cells for up to 3 days in culture is achieved for stripe patterns with widths between 25 and 27.5 µm. Smooth muscle cells cultured on such patterned substrates exhibit a decrease in their proliferation rate and nucleus area and an increase in their major axis length, compared to the cells cultured onto non-patterned substrates. These alterations are indicative of the adoption of a contractile rather than a synthetic phenotype of the smooth muscle cells grown onto the patterned substrates and demonstrate the potential of the novel photolithographic material and patterning method for guided cell adhesion and growth. 相似文献
920.
Reinier Lemos Dr. Kamil Makowski Dr. Luis Almagro Dr. Blanca Tolón Dr. Hortensia Rodríguez Dr. M. Ángeles Herranz Dr. Dolores Molero Prof. Dr. Nazario Martín Prof. Dr. Margarita Suárez 《European journal of organic chemistry》2023,26(7):e202201301
Cyclopropanation reactions between C60 and different malonates decorated with monosaccharides and steroids using the Bingel-Hirsch methodology have allowed the obtention of a new family of hybrid compounds in good yields. A complete set of instrumental techniques has allowed us to fully characterize the hybrid derivatives and to determine the chemical structure of monocycloadducts. Besides, the proposed structures were investigated by cyclic voltammetry, which evidenced the exclusive reductive pattern of fullerene Bingel-type monoadducts. Theoretical calculations at the DFT-D3(BJ)/PBE 6-311G(d,p) level of the synthesized conjugates predict the most stable conformation and determine the factors that control the hybrid molecules′ geometry. Some parameters such as polarity, lipophilicity, polar surface area, hydrophilicity index, and solvent-accessible surface area were also estimated, predicting its potential permeability and capability as cell membrane penetrators. Additionally, a molecular docking simulation has been carried out using the main protease of SARS-CoV-2 (Mpro) as the receptor, thus paving the way to study the potential application of these hybrids in biomedicine. 相似文献