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81.
Víctor Valcárcel Carmen Cerecedo Francisco Guitián 《Journal of the American Ceramic Society》2003,86(10):1683-1690
α-alumina (α-Al2 O3 , corundum) fibers exhibit high thermal and chemical stability, as well as good mechanical properties, even at high temperatures. Such characteristics make them good candidates for use in composites. Nevertheless, very few methods of producing α-Al2 O3 fibers are available. In the present work, we describe a method that uses aluminum pieces deposited on SiO2 powder, in an argon atmosphere, at temperatures in the range 1300°–1600°C. The α-Al2 O3 fibers are obtained via vapor-liquid-solid deposition. The novel addition of nickel and cobalt (or their oxides) allows the use of temperatures >1500°C, resulting in improved fiber production. We demonstrate that the metals do not contaminate the fibers produced in this way. Finally, we also estimate the tensile strength of the Al2 O3 fibers produced through this method. 相似文献
82.
Rosario?Zamora Gemma?Gómez Francisco?J.?HidalgoEmail author 《Journal of the American Oil Chemists' Society》2002,79(3):267-272
13C NMR spectra of oil fractions obtained chromatographically from 109 vegetable oils were obtained and analyzed to evaluate
the potential use of those fractions in the classification of vegetable oils and to compare the results with the NMR analysis
of complete oils. The oils included the following: virgin olive oils from different cultivars and regions of Europe and north
Africa; “lampante” olive, refined olive, refined olive pomace, hazelnut, rapeseed, high-oleic sunflower, corn, grapeseed,
soybean, and sunflower oils; and mixtures of virgin olive oils from different geographical origins. Oils were divided into
two sets of samples. The training set (98 samples) was employed to select the variables that resulted in significant discrimination
among the different oil classes. By using stepwise discriminant analysis, more than 98% of correct validated assignments were
obtained; these results were confirmed when applied to the test set (11 blind samples). Results suggest that the use of oil
fractions considerably increases the discriminating power of NMR in the analysis of vegetable oils. 相似文献
83.
Azizeh‐Mitra Yousefi Chantal Gauvin Louise Sun Robert W. DiRaddo Julio Fernandes 《Polymer Engineering and Science》2007,47(5):608-618
Regenerating the load‐bearing tissues requires 3D scaffolds that balance the temporary mechanical function with the biological requirements. In functional tissue engineering, designing scaffolds with biomimetic mechanical properties could promote tissue ingrowth since the cells are sensitive to their local mechanical environment. This work aims to design scaffolds that mimic the mechanical response of the biological tissues under physiological loading conditions. Poly(L ‐lactide) (PLLA) scaffolds with varying porosities and pore sizes were made by the 3D‐plotting technique. The scaffolds were tested under unconfined ramp compression to compare their stress profile under load with that of bovine cartilage. A comparison between the material parameters estimated for the scaffolds and for the bovine cartilage based on the biphasic theory enabled the definition of an optimum window for the porosity and pore size of these constructs. Moreover, the finite element prediction for the stress distribution inside the scaffolds, surrounded by the host cartilaginous tissue, demonstrated a negligible perturbation of the stress field at the site of implantation. The finite element modeling tools in combination with the developed methodology for optimal porosity/pore size determination can be used to improve the design of biomimetic scaffolds. POLYM. ENG. SCI., 47:608–618, 2007. © 2007 Society of Plastics Engineers. 相似文献
84.
Robert K. Vander Meer Francisco Alvarez Clifford S. Lofgren 《Journal of chemical ecology》1988,14(3):825-838
TheSolenopsis invicta trail pheromone is synthesized by the Dufour's gland and is released through the sting apparatus. The recruitment subcategory of theS. invicta trail pheromone was shown to be composed of a mixture of the orientation pheromone, (Z,E)--farnesene and an unidentified homosesquiterpene consisting of three rings and one double bond (C-1). C-1 is present in worker Dufour's glands at only 75 pg per worker equivalent. This is the first report that demonstrates that different exocrine products from the same gland control different subcategories of behavior related to mass recruitment. 相似文献
85.
Auguste Fernandes Maria Filipa Ribeiro Cristina Borges Joo Paulo Loureno Joo Rocha Zelimir Gabelica 《Microporous and mesoporous materials》2006,90(1-3):112-128
This study is aimed at exploring the ability of very small sized N-bearing molecules to generate and stabilize microporous aluminophosphates. Two new AlPO4-n materials, called IST-1 and IST-2, have been obtained in aqueous media using, as main template, methylamine (MA), directly added, or generated in situ from methylformamide (MF) degradation. While IST-1 topology proved to be novel, IST-2 appears structurally related to AlPO4-53(A). The obtained materials were characterized by powder XRD, TG/DSC, SEM and solid-state NMR. Tetraalkylammonium (TEA) cations were used as potential co-templates but only MA and water were found incorporated in the pore volumes of both structures, which argues for their true templating role. In IST-1, 13C solid-state NMR studies showed that half of MA species, presumably protonated, is H-bonded to framework oxygens while the other half surprisingly bonds directly to framework Al atoms. 13C NMR showed that only protonated MA occurs in IST-2 channels. TEA+ cations definitely do not play any specific template role. They indirectly favor the crystallization of IST-1 or IST-2 devoid from other crystalline or amorphous side phases, by interacting with part of the Al and P in solution and forming soluble [AlPO4(OH)]–[TEA,HMA] complexes, substantially modifying the compositions of gels precursors to each phase during nucleation and/or growth steps. While both IST-1 and IST-2 crystallize from gels of similar initial compositions, it was demonstrated that the new MA/T ratio (T = Al or P) obtained after in situ complexation was the key parameter that specifically governs the crystallization of each phase. 相似文献
86.
Ciesielczyk Tomasz Cabrera Alberto Oleksiak Ariel Piątek Wojciech Waligóra Grzegorz Almeida Francisco Blanco Vicente 《Journal of Scheduling》2021,24(5):489-505
Journal of Scheduling - Rapid growth of demand for remote computational power, along with high energy costs and infrastructure limits, has led to treating power usage as a primary constraint in... 相似文献
87.
Quintanar-Reséndiz Ana L. Rodríguez-Santos Francisco Pichardo-Méndez Josué L. Delgado-Gutiérrez Guillermo Ramírez Omar Jiménez Vázquez-Medina Rubén 《Multimedia Tools and Applications》2021,80(13):19513-19538
Multimedia Tools and Applications - It is proposed a forensic method for the capture device identification from digital images, which requires two elements: i) a digital image subject to... 相似文献
88.
de Almeida Jhony Luiz Comunello Eros Sobieranski Antonio da Rocha Fernandes Anita Maria Cardoso Gabriel Schade 《Pattern Analysis & Applications》2021,24(3):907-914
Pattern Analysis and Applications - Digital holography is an imaging process able to recreate three-dimensional representations of objects from recording pattern interference among distinct waves.... 相似文献
89.
Procopio Lorenzo M. Delgado Francisco Enríquez Marco Belabas Nadia 《Quantum Information Processing》2021,20(6):1-3
Quantum Information Processing - A Correction to this paper has been published: https://doi.org/10.1007/s11128-019-2234-5 相似文献
90.
Baldassarri Sandra Passerino Liliana Ramis Silvia Riquelme Inma Perales Francisco J. 《Universal Access in the Information Society》2021,20(2):239-254
Universal Access in the Information Society - Technology and videogames have been proven as motivating tools for working attention and complex communication skills, especially in children with... 相似文献