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41.
42.
Petrakis PV Spanos K Feest A Daskalakou E 《International journal of molecular sciences》2011,12(5):2769-2782
Beech forests play an important role in temperate and north Mediterranean ecosystems in Greece since they occupy infertile montane soils. In the last glacial maximum, Fagus sylvatica (beech) was confined to Southern Europe where it was dominant and in the last thousand years has expanded its range to dominate central Europe. We sampled four different beech forest types. We found 298 insect species associated with beech trees and dead beech wood. While F. sylvatica and Quercus (oak) are confamilial, there are great differences in richness of the associated entomofauna. Insect species that inhabit beech forests are less than one fifth of those species living in oak dominated forests despite the fact that beech is the most abundant central and north European tree. There is a distinct paucity of monophagous species on beech trees and most insect species are shared between co-occurring deciduous tree species and beech. This lack of species is attributed to the vegetation history and secondary plant chemistry. Bark and leaf biophenols from beech indicate that differences in plant secondary metabolites may be responsible for the differences in the richness of entomofauna in communities dominated by beech and other deciduous trees. 相似文献
43.
Irene Kanellopoulou Evangelia K. Karaxi Anna Karatza Ioannis A. Kartsonakis Costas A. Charitidis 《Fatigue & Fracture of Engineering Materials & Structures》2019,42(7):1494-1509
This study presents the development of novel submicron super absorbent polymers (SAPs) used as admixtures in cement‐based matrices with significant advantages over conventional products. The produced SAPs were characterized in respect of their morphology and composition, while their water absorption capacity was determined in different electrolyte solutions. The hybrid core‐shell spherical structure of the fabricated materials offered significant compatibility enhancement with cement while the workability of the mixture was maintained. The assessment of the cement‐based composites including SAPs revealed that their flexural strength increased by 78%. Self‐healing/sealing behavior was assessed by monitoring the crack sealing via SEM, elemental analysis of the healing products, and determination of the water absorbance coefficient for different times of treatment. The cement/SAPs composites with a concentration of SAPs 2% by weight of cement exhibited self‐healing/sealing responsive capability when an artificial crack was induced. According to the SEM characterization, the crack demonstrated complete healing for the better part of its length after 28 days of treatment. 相似文献
44.
Nicolas SPYRELLIS Evangelia A. PAVLATOU Styliani SPANOU Alexandros ZOIKIS-KARATHANASIS 《中国有色金属学会会刊》2009,19(4):800-804
Nickel and nickel-phosphorous matrix composite coatings reinforced by TiO2, SiC and WC particles were produced under direct and pulse current conditions from an additive-free Watts' type bath. The influence of the variable electrolysis parameters (type of current, frequency of current pulses and current density) and the reinforcing particles properties (type, size and concentration in the bath) on the surface morphology and the structure of the deposits was examined. It is demonstrated that the embedding of ceramic particles modifies in various ways the nickel electrocrystallisation process. On the other hand, Ni-P amorphous matrix is not affected by the occlusion of the particles. Overall, the imposition of pulse current conditions leads to composite coatings with increased embedded percentage and more homogenous distribution of particles in the matrix than coatings produced under direct current regime. 相似文献
45.
Two experiments examined possible negative transfer in nonexperts from the use of pictorial examples in a laboratory design problem-solving situation. In Experiment 1, 89 participants were instructed to "think aloud" and were assigned to 1 of 3 conditions: (a) control (standard instructions), (b) fixation (inclusion of a problematic example, describing its problematic elements), or (c) defixation (inclusion of a problematic example, with instructions to avoid using problematic elements). Negative transfer due to examples was measured both quantitatively and qualitatively through verbal protocols. Verbal protocols (N = 176) were analyzed for participants' reasons for reference to the examples. In Experiment 2, fixation to examples was evaluated in nonverbalizing participants (N = 60). Results of both experiments suggest that (a) although participants consulted the problem instructions, they tended to follow the examples even when they included inappropriate elements and (b) the fixation effects can be diminished with the use of defixating instructions. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
46.
The long-term (6 months) oxidization of hcp-InN (wurtzite, InN-w) nanostructures (crystalline/amorphous) synthesized on Si [100] substrates is analyzed. The densely packed layers of InN-w nanostructures (5-40 nm) are shown to be oxidized by atmospheric oxygen via the formation of an intermediate amorphous In-Ox-Ny (indium oxynitride) phase to a final bi-phase hcp-InN/bcc-In2O3 nanotexture. High-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy, electron energy loss spectroscopy and selected area electron diffraction are used to identify amorphous In-Ox-Ny oxynitride phase. When the oxidized area exceeds the critical size of 5 nm, the amorphous In-Ox-Ny phase eventually undergoes phase transition via a slow chemical reaction of atomic oxygen with the indium atoms, forming a single bcc In2O3 phase. 相似文献
47.
Fouling Analysis and Performance of Tubular Ultrafiltration on Pretreated Olive Mill Waste Water 总被引:1,自引:0,他引:1
This study deals with the performance of a tubular ultrafiltration system on sieved and centrifuged olive mill waste water.
A generalized statistical model was developed describing the impact and the relative importance of major experimental parameters
(membrane pore size, transmembrane pressure, feed flow rate, and feed temperature) on permeate flux. According to this model,
process pressure appeared to have the largest impact on permeate flux, followed by process temperature. As membrane treatment
of such a difficult material largely depends on fouling, a systematic analysis of prevailing fouling mechanisms was also run.
Despite sieving and centrifugation of the original waste, membrane fouling caused a flux decline of 60–65% within 15–20 min.
Internal fouling, pore blocking, and cake layer formation were all responsible for membrane fouling during the first 40 min
of operation. After that period, cake formation appeared to play a predominant role. Based on the proposed generalized model,
the relative importance of process parameters can be evaluated and process performance can be improved by proper interventions.
Independent of membrane size, fouling is a serious problem to be resolved. The qualitative performance of this process, including
chemical oxygen demand distribution, polyphenol profile, and antioxidant capacity, is discussed in a separate paper. 相似文献
48.
The efficiency of grape stem extracts to express antiradical activity was assessed using two different approaches and DPPH as the radical probe. In addition, the mixture effects when the extracts were combined with ascorbic acid (AA) and α-tocopherol (α-Tcp) were also evaluated. The approaches included a simple linear regression analysis between the response (antiradical activity) and concentration, but also a response surface methodology, which permitted the monitoring of the response upon simultaneous variation of both the concentration of the total polyphenols of the extracts and either of the antioxidants (AA and α-Tcp). The deployment of linear regression poses important constraints with regard to concentration ranges, whereas response surface methodology might be a valuable statistical tool for similar assessments and credible modelling of binary mixtures of antioxidants. In all combinations tested it was found that an antagonism was manifested, presumably as a result of AA and α-Tcp regeneration by the extract polyphenols, at the expense of the latter. 相似文献
49.
Zacharaki EI Hogea CS Biros G Davatzikos C 《IEEE transactions on bio-medical engineering》2008,55(3):1233-1236
Simulating the brain tissue deformation caused by tumor growth has been found to aid the deformable registration of brain tumor images. In this paper, we evaluate the impact that different biomechanical simulators have on the accuracy of deformable registration. We use two alternative frameworks for biomechanical simulations of mass effect in 3-D magnetic resonance (MR) brain images. The first one is based on a finite-element model of nonlinear elasticity and unstructured meshes using the commercial software package ABAQUS. The second one employs incremental linear elasticity and regular grids in a fictitious domain method. In practice, biomechanical simulations via the second approach may be at least ten times faster. Landmarks error and visual examination of the coregistered images indicate that the two alternative frameworks for biomechanical simulations lead to comparable results of deformable registration. Thus, the computationally less expensive biomechanical simulator offers a practical alternative for registration purposes. 相似文献
50.
Nikolaos Spyropoulos-Antonakakis Evangelia Sarantopoulou Goran Drazic Zoe Kollia Dimitrios Christofilos Gerasimos Kourouklis Dimitrios Palles Alkiviadis Constantinos Cefalas 《Nanoscale research letters》2013,8(1):432
Amorphous semiconducting materials have unique electrical properties that may be beneficial in nanoelectronics, such as low leakage current, charge memory effects, and hysteresis functionality. However, electrical characteristics between different or neighboring regions in the same amorphous nanostructure may differ greatly. In this work, the bulk and surface local charge carrier transport properties of a-TaNx amorphous thin films deposited in two different substrates are investigated by conductive atomic force microscopy. The nitride films are grown either on Au (100) or Si [100] substrates by pulsed laser deposition at 157 nm in nitrogen environment. For the a-TaNx films deposited on Au, it is found that they display a negligible leakage current until a high bias voltage is reached. On the contrary, a much lower threshold voltage for the leakage current and a lower total resistance is observed for the a-TaNx film deposited on the Si substrate. Furthermore, I-V characteristics of the a-TaNx film deposited on Au show significant hysteresis effects for both polarities of bias voltage, while for the film deposited on Si hysteresis, effects appear only for positive bias voltage, suggesting that with the usage of the appropriate substrate, the a-TaNx nanodomains may have potential use as charge memory devices. 相似文献