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61.
62.
River ecosystems have witnessed a long history of human pressure, particularly the disruption of freshwater fish populations. The awareness of this situation has led to many habitat improvement projects, with a variable degree of success. In natural situations, fish populations co‐inhabit throughout the hydrological cycle with different degrees of adequacy, and the sequence of favourable and unfavourable conditions dictates abiotic constraints and biotic interactions that shape the final biological assemblages. We postulate that a part of unsuccessful restoration results is related to insufficient closeness to the natural habitat conditions of the river type that is to be restored, including the naturally adverse periods. We used the river2d model to predict habitat availability as weighted usable area (WUA) at a degraded site that is to be restored, for two native Mediterranean species and their life stages—the Southwestern nase Iberochondrostoma almacai and the Arade chub Squalius aradensis. We then analysed the yearly evolution of the natural WUA at a nearby reference site. Overall, the reference site exhibited the longest periods during which the WUA was continuously lower than the chosen WUA thresholds for each of the four bioperiods. Considerable divergences from natural habitat availability values can be seen for the spawning, rearing and growth bioperiods. Restoration outcomes can result in appreciable deviations—favourable or unfavourable to fish populations—from the WUA occurring under natural conditions over the course of the year. Restoration should therefore take account of local hydraulic and habitat patterns that govern population dynamics and result in the final fish assemblage. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
63.
Guanghua Liu Kexin Chen Heping Zhou Xiaoshan Ning C. Pereira J. M. F. Ferreira 《Journal of Materials Science》2006,41(6):1791-1796
Single-phase Yb α-SiAlON ceramics in-situ toughened by elongated grains were prepared by pressureless sintering, with the crystalline powder prepared by combustion
synthesis used as seed crystals. The effects of seed addition on the densification, phase transformation, microstructure development,
and mechanical properties of the samples were investigated in detail. From the experimental results, it was found that the
added seed crystals could promote the phase transformation and facilitate the growth of elongated grains. By adding seed crystals
the fracture toughness of the sintered α-SiAlON ceramics was considerably improved, with no obvious degradation in the bulk
density and hardness at the same time. 相似文献
64.
A.J.M. Ferreira R.C. Batra C.M.C. Roque L.F. Qian R.M.N. Jorge 《Composite Structures》2006,75(1-4):593-600
We use the global collocation method, the first and the third-order shear deformation plate theories, the Mori–Tanaka technique to homogenize material properties, and approximate the trial solution with multiquadric radial basis functions to analyze free vibrations of functionally graded plates. Frequencies computed by the present method are found to agree well with those from the analytical solution of Vel and Batra, and the numerical solution of Qian et al. based on the meshless local Petrov–Galerkin formulation. 相似文献
65.
B. Y. C. Wu C. A. Schuh P. J. Ferreira 《Metallurgical and Materials Transactions A》2005,36(7):1927-1936
We present an experimental approach to systematically produce nanostructures with various grain sizes and twin densities in
the Ni-Co binary system. Using electrodeposition with various applied current densities and organic additive contents in the
deposition bath, we synthesize nanostructured fcc and hcp solid solutions with a range of compositions. Due to the low stacking
fault energy (SFE) of these alloys, growth twins are readily formed during deposition, and by adjusting the deposition conditions,
a range of twin boundary densities is possible. The resulting nanostructured alloys cannot be described by a single characteristic
length scale, but instead must be characterized in terms of (1) a true grain size pertaining to general high-angle grain boundaries
and (2) an effective grain size that incorporates twin boundaries. Analysis of Hall-Petch strength scaling for these materials
is complicated by their dual length scales, but the hardness trends found in Ni-80Co are found to be roughly in line with
those seen in pure nanocrystalline nickel. 相似文献
66.
Balamurugan A Benhayoune H Kannan S Laquerriere P Michel J Balossier G Ferreira JM 《Microscopy research and technique》2008,71(9):684-688
The present study deals with the short-term physicochemical reactions at the interface between bioactive glass particles [55SiO(2)-20CaO-9P(2)O(5)-12Na(2)O-4MgO. mol%] and biological fluid (Dulbecco Modified Eagle's Medium (DMEM)). The physicochemical reactions within the interface are characterized by scanning transmission electron microscopy (TEM) (STEM) associated with Energy-dispersive X-ray spectroscopy (EDXS). Microanalysis of diffusible ions such as sodium, potassium, or oxygen requires a special care. In the present investigation the cryo-technique was adopted as a suitable tool for the specimen preparation and characterization. Cryosectioning is essential for preserving the native distribution of ions so that meaningful information about the local concentrations can be obtained by elemental microanalysis. The bioglass particles immersed in biological fluid for 24 h revealed five reaction stages: (i) dealkalization of the surface by cationic exchange (Na(+), Ca(2+) with H(+) or H(3)O(+)); (ii) loss of soluble silica in the form of Si(OH)(4) to the solution resulting from the breakdown of Si--O--Si bonds (iii); repolymerization of Si(OH)(4) leading to condensation of SiO(2)); (iv) migration of Ca(2+) and PO(4) (3-) to the surface through the SiO(2)-rich layer to form CaO-P(2)O(5) film; (v) crystallization of the amorphous CaO-P(2)O(5) by incorporating OH-- or CO(3) (2-) anions with the formation of three different surface layers on the bioactive glass periphery. The thickness of each layer is approximately 300 nm and from the inner part to the periphery they consist of Si--OH, which permits the diffusion of Ca(2+) and PO(4) (3-) ions and the formation of the middle Ca--P layer, and finally the outer layer composed of Na--O, which acts as an ion exchange layer between Na(+) ions and H(+) or H(3)O(+) from the solution. 相似文献
67.
Figueiras E Campos R Semedo S Oliveira R Requicha Ferreira LF Humeau-Heurtier A 《The Review of scientific instruments》2012,83(3):034302
Laser Doppler flowmetry (LDF) is now commonly used in clinical research to monitor microvascular blood flow. However, the dependence of the LDF signal on the microvascular architecture is still unknown. That is why we propose a new laser Doppler flowmeter for depth dependent monitoring of skin microvascular perfusion. This new laser Doppler flowmeter combines for the first time, in a device, several wavelengths and different spaced detection optical fibres. The calibration of the new apparatus is herein presented together with in vivo validation. Two in vivo validation tests are performed. In the first test, signals collected in the ventral side of the forearm are analyzed; in the second test, signals collected in the ventral side of the forearm are compared with signals collected in the hand palm. There are good indicators that show that different wavelengths and fibre distances probe different skin perfusion layers. However, multiple scattering may affect the results, namely the ones obtained with the larger fibre distance. To clearly understand the wavelength effect in LDF measurements, other tests have to be performed. 相似文献
68.
Amel Djoudi Rodolfo Molina-Pea Natalia Ferreira Ilaria Ottonelli Giovanni Tosi Emmanuel Garcion Frank Boury 《International journal of molecular sciences》2022,23(20)
Hyaluronic acid (HA) is a Glycosaminoglycan made of disaccharide units containing N-acetyl-D-glucosamine and glucuronic acid. Its molecular mass can reach 10 MDa and its physiological properties depend on its polymeric property, polyelectrolyte feature and viscous nature. HA is a ubiquitous compound found in almost all biological tissues and fluids. So far, HA grades are produced by biotechnology processes, while in the human organism it is a major component of the extracellular matrix (ECM) in brain tissue, synovial fluid, vitreous humor, cartilage and skin. Indeed, HA is capable of forming hydrogels, polymer crosslinked networks that are very hygroscopic. Based on these considerations, we propose an overview of HA-based scaffolds developed for brain cancer treatment, central and peripheral nervous systems, discuss their relevance and identify the most successful developed systems. 相似文献
69.
Ana Sofia Ferreira Ana Margarida Silva Diana Pinto Manuela M. Moreira Ricardo Ferraz Jaroslava varc-Gaji Paulo C. Costa Cristina Delerue-Matos Francisca Rodrigues 《International journal of molecular sciences》2022,23(23)
Oral mucositis (OM), a common side effect of oncological treatment, is an oral mucosal disorder characterized by painful ulcerations and increased risk of infection. The use of natural antioxidants to suppress the redox imbalance responsible for the OM condition has emerged as an interesting approach to prevent/treat OM. This study aims to explore the chestnut (Castana sativa) shells as potential active ingredient against OM. Therefore, chestnut shells were extracted at different temperatures (110–180 °C) by Subcritical Water Extraction (SWE), aiming to recover antioxidants. The extracts were also evaluated against microorganisms present in the oral cavity as well as on human oral cell lines (TR146 and HSC3). The highest phenolic content was obtained with the extraction temperature of 110 °C, exhibiting the best antioxidant/antiradical activities and scavenging efficiencies against HOCl (IC50 = 4.47 μg/mL) and ROO• (0.73 μmol TE/mg DW). High concentrations of phenolic acids (e.g., gallic and protocatechuic acids) and flavanoids (catechin, epicatechin and rutin) characterized the phenolic profile. The antimicrobial activity against several oral microorganisms present in the oral cavity during OM, such as Streptococcus, Staphylococcus, Enterococcus, and Escherichia, was demonstrated. Finally, the effects on HSC3 and TR146 cell lines revealed that the extract prepared at 110 °C had the lowest IC50 (1325.03 and 468.15 µg/mL, respectively). This study highlights the potential effects of chestnut shells on OM. 相似文献
70.
Ana Patrícia Simes Francisco Q. Gonalves Daniel Rial Samira G. Ferreira Joo Pedro Lopes Paula M. Canas Rodrigo A. Cunha 《International journal of molecular sciences》2022,23(21)
Adenosine A2A receptors (A2AR) control fear memory and the underlying processes of synaptic plasticity in the amygdala. In other brain regions, A2AR activation is ensured by ATP-derived extracellular adenosine formed by ecto-5′-nucleotidase or CD73. We now tested whether CD73 is also responsible to provide for the activation of A2AR in controlling fear memory and amygdala long-term potentiation (LTP). The bilateral intracerebroventricular injection of the CD73 inhibitor αβ-methylene ADP (AOPCP, 1 nmol/ventricle/day) phenocopied the effect of the A2AR blockade by decreasing the expression of fear memory, an effect disappearing in CD73-knockout (KO) mice and in forebrain neuronal A2AR-KO mice. In the presence of PPADS (20 μM) to eliminate any modification of ATP/ADP-mediated P2 receptor effects, both AOPCP (100 μM) and the A2AR antagonist, (50 nM), decreased LTP magnitude in synapses of projection from the external capsula into the lateral amygdala, an effect eliminated in slices from both forebrain neuronal A2AR-KO mice and CD73-KO mice. These data indicate a key role of CD73 in the process of A2AR-mediated control of fear memory and underlying synaptic plasticity processes in the amygdala, paving the way to envisage CD73 as a new therapeutic target to interfere with abnormal fear-like emotional processing. SCH58261相似文献