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排序方式: 共有104条查询结果,搜索用时 15 毫秒
1.
Sorichetti P.A. Matteo C.L. Lambri O.A. Manguzzi G.C. Salvatierra L.M. Herrero O. 《Dielectrics and Electrical Insulation, IEEE Transactions on》2007,14(5):1170-1182
This work presents a study of the structural changes in aged EPDM (ethylene-propylene-diene monomer) from outdoor high voltage transmission lines. Samples were taken from failed and non-failed insulators after up to ten years in service on a 33 kV line. Infrared absorption, hydrophobicity index, dynamical mechanical analysis (DMA) and dielectric relaxation (DR) were employed as experimental techniques. The same experimental techniques were also applied to new samples of EPDM that were subjected to high electric fields (up to 14 kV/mm) for several hours. Results from DMA and DR techniques are in good agreement and, together with previous results from neutron irradiation techniques, suggest that the experimental data obtained from outdoor-aged and laboratory tested samples may be explained by a decrease in the degree of crystallinity due to the interaction between electrical and mechanical effects in the dielectric. The proposed model is based on the disentanglement of the crystallites by forces originated in the interaction of the electric field with the polar groups located in the amorphous phase of the polymer matrix. An alternative explanation, based on a relaxation process appearing at the interfaces between the filler (ATH) and the polymer matrix conflicts with several experimental results presented in this work. 相似文献
2.
Dolors Costal Cristina Gómez Anna Queralt Ruth Raventós Ernest Teniente 《Software and Systems Modeling》2008,7(4):469-486
An important aspect in the specification of conceptual schemas is the definition of general constraints that cannot be expressed
by the predefined constructs provided by conceptual modeling languages. This is generally achieved by using general-purpose
languages like OCL. In this paper we propose a new approach that facilitates the definition of such general constraints in
UML. More precisely, we define a profile that extends the set of predefined UML constraints by adding certain types of constraints
that are commonly used in conceptual schemas. We also show how our proposal facilitates reasoning about the constraints and
their automatic code generation, study the application of our ideas to the specification of two real-life applications, and
present a prototype tool implementation.
相似文献
Ernest TenienteEmail: |
3.
Dolors Izquierdo Montserrat Roura Míriam Prez-Trujillo Sandra Soto-Heras María-Teresa Paramio 《International journal of molecular sciences》2022,23(8)
In goats, embryo oocyte competence is affected by follicle size regardless the age of the females. In previous studies we have found differences in blastocyst development between oocytes coming of small (<3 mm) and large follicles (>3 mm) in prepubertal (1–2 months-old) goats. Oocyte competence and Follicular Fluid (FF) composition changes throughout follicle growth. The aim of this study was to analyze Fatty Acids (FAs) composition and metabolomic profiles of FF recovered from small and large follicles of prepubertal goats and follicles of adult goats. FAs were analyzed by chromatography and metabolites by 1H-Nuclear Magnetic Resonance (1H-NMR) Spectrometry. The results showed important differences between adult and prepubertal follicles: (a) the presence of α,β-glucose in adult and no detection in prepubertal; (b) lactate, -N-(CH3)3 groups and inositol were higher in prepubertal (c) the percentage of Linolenic Acid, Total Saturated Fatty Acids and n-3 PUFAs were higher in adults; and (d) the percentage of Linoleic Acid, total MUFAs, PUFAs, n-6 PUFAs and n-6 PUFAs: n-3 PUFAs ratio were higher in prepubertal goats. Not significant differences were found in follicle size of prepubertal goats, despite the differences in oocyte competence for in vitro embryo production. 相似文献
4.
A new method is presented that enables sensitive measurement of free concentrations of radiolabeled ligands. Additionally, protein binding of radiochemicals in complex matrixes can be determined with this new technique that combines negligible depletion solid-phase microextraction (nd-SPME) with liquid scintillation counting (LSC) as detection. [3H]Estradiol was taken as an example compound. Possible matrix effects of protein on fiber uptake kinetics were studied. No matrix effect was found, either by fouling of the fiber, or by changed uptake kinetics. The validity of the method was shown in the determination of the affinity constant (Ka) of estradiol for human serum albumin (HSA). The Ka was estimated at 8.9 x 10(4) M(-1), which corresponds well with literature values. This study shows that nd-SPME is suitable to study the free concentration and protein binding of [3H]estradiol. The method described in this paper combines the advantages of nd-SPME with the advantages of radiolabeled analytes, creating a timesaving, simple, and sensitive analytical tool that will be particularly useful in complex matrixes containing many potential interferences for chromatographic methods. 相似文献
5.
Response of Mythimna unipuncta Males to Components of the Sesamia nonagrioides Pheromone 总被引:1,自引:0,他引:1
Matilde Eizaguirre Carmen López Albert Sans Dolors Bosch Ramon Albajes 《Journal of chemical ecology》2009,35(7):779-784
Several sympatric lepidopteran species feed on maize plants, and the different components of their species-specific female
sex pheromones may play a role in attracting conspecifics and/or deter heterospecific males. In this study, we analyzed the
content of Mythimna unipuncta pheromone glands and tested the response of males to components of their own pheromone blend and that of Sesamia nonagrioides in the wind tunnel. Whole pheromone glands, and lures where (Z)-9-hexadecenyl acetate, Z)-11-hexadecen-1-ol or (Z)-9-hexadecenyl
acetate + (Z)-11-hexadecen-1-ol were added to the major component, (Z)-11-hexadecenyl acetate, elicited significantly higher
responses by M. unipuncta males than lures with main component alone, although the levels varied with concentration. In the field a rather different
outcome was observed, as the addition of other compounds found in the female pheromone gland did not improve trap catch over
lures with only (Z)-11-hexadecenyl acetate. The addition of (Z)-11-hexadecenal, a compound of the S. nonagrioides pheromone, to (Z)-11-hexadecenyl acetate significantly reduced attraction of M. unipuncta males both in the wind tunnel and in the field, as well as the number of sympatric clover cutworm, Discestra trifolii, under field conditions. The addition of (Z)-9-hexadecenyl acetate, a minor component of the M. unipuncta pheromone blend, reduced the number of S. nonagrioides captured in field traps that were baited with the S. nonagrioides lure. The significance of such inhibition in the reproductive isolation of sympatric species that attack maize is discussed. 相似文献
6.
Carpintero Helio; Lafuente Enrique; Quintana José; Ruiz Gabriel; Sáiz Dolors; Sáiz Milagros; Sánchez Natividad 《Canadian Metallurgical Quarterly》2010,13(3):277
History of Psychology has been an extremely active field for many years in Spain. Both the great expansion of psychological studies and the inclusion of history as a compulsory subject in the psychology curriculum are crucial factors helping to understand the current state of affairs. The aim of this paper is to provide a survey of the work done in this area over the last decade, covering research, teaching, and institutional developments. The study includes consideration of aspects such as main research lines, major theoretical and methodological trends, teaching materials, relevant archives and exhibits, and significant websites. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
7.
S. Garroni C. Bonatto Minella D. Pottmaier C. Pistidda C. Milanese A. Marini S. Enzo G. Mulas M. Dornheim M. Baricco O. Gutfleisch S. Suriñach M. Dolors Baró 《International Journal of Hydrogen Energy》2013
The present investigation focuses on a new synthesis route of NaBH4 starting from the 2NaH + MgB2 system subjected to mechanochemical activation under reactive hydrogen atmosphere. The milling process was carried out under two different hydrogen pressures (1 and 120 bar) with two different rotation speeds (300 and 550 rpm). The reaction products were characterized by ex-situ solid state magic angle spinning (MAS) nuclear magnetic resonance (NMR), ex-situ X-ray powder diffraction (XRPD) and Infrared Spectroscopy (IR). From the results of these analyses, it can be concluded that milling in all the considered conditions led to the formation of NaBH4 (cubic-Fm-3m). In particular, a reaction yield of 5 and 14 wt% is obtained after 20 h of milling at 120 bar of H2 for the tests performed at 300 rpm and 550 rpm, respectively. The presence of MgH2 is also detected among the final products on the as milled powders. The influence of the milling conditions and the evaluation of the parameters related the mechanochemical process are here discussed. 相似文献
8.
Growth of a range of 14 common food spoilage fungal species was evaluated along time as a function of both colony diameter and ergosterol content on malt extract agar. Growth was assessed under different environmental conditions following a central composite design. The suitability of using either linear, Gompertz's or Baranyi's models for primary modelling of the results was tested. Regarding colony diameters, using either linear or asymptotic Baranyi's function gave better estimations of growth rate and lag phase when no asymptotic trend was observed. When a decrease in growth rate was observed with time, standard Baranyi's model was chosen, although the search for new mechanistic models specific for moulds would probably improve the estimations. The use of Gompertz equation led, in general, to overestimated parameters. Ergosterol showed good performance as a fungal growth indicator for the whole range of species. Finally, significant correlation coefficients were found between ergosterol and colony diameters, suggesting that both parameters may be useful for primary modelling and thus for subsequent secondary modelling. 相似文献
9.
Antiferromagnets: Unravelling the Elusive Antiferromagnetic Order in Wurtzite and Zinc Blende CoO Polymorph Nanoparticles (Small 15/2018)
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10.
Alberto Quintana Ainhoa Altube Eva García-Lecina Santiago Suriñach Maria Dolors Baró Jordi Sort Eva Pellicer Miguel Guerrero 《Journal of Materials Science》2017,52(24):13779-13789
ZrO2-decorated ZnO (ZrO2|ZnO) nanoparticles (NPs) have been synthesized by a facile co-precipitation method in the presence of cetyltrimethylammonium bromide (CTAB) surfactant. The ZrO2 amount in the NPs has been varied from 1.0, 2.0, 4.9, to 9.3% by weight. The resulting NPs are heterostructured and consist of a crystalline ZnO core (wurtzite phase) surrounded by an amorphous ZrO2 layer. X-ray diffraction analyses support this observation. The NPs show a narrow size distribution and are slightly elongated. Compared to pure ZnO NPs, the hybrid ZrO2|ZnO ones show enhanced photocatalytic activity toward the degradation of Rhodamine B under UV–Vis light. Such enhancement has been partly attributed to the increased amount of oxygen vacancies when ZrO2 is incorporated into the NPs, as shown by X-ray photoelectron spectroscopy analyses. 相似文献