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991.
Alves HL Dos Santos LA Bergmann CP 《Journal of materials science. Materials in medicine》2008,19(5):2241-2246
Calcium phosphate cements are biomaterials made from a mixture of calcium phosphate powder in aqueous solutions that forms
a paste that reacts at the body temperature and hardens as a result of precipitation reactions. These cements are commonly
used in dentistry and orthopedic bone filling surgeries, which require extremely invasive procedures. The challenge consists
in formulating an injectable paste by additives incorporation. In this work, three different additives (carboxymethylcellulose,
agar polymer and sodium alginate) were incorporated to tricalcium phosphate, in concentrations of 0.4, 0.8, 1.6, 3.2 and 6.4 wt.%.
Injectability was evaluated through a new method developed for this purpose. Results showed that it was possible to obtain
injectable compositions of α-tricalcium phosphate cement. It was verified that the injectability depends on the rheological
behavior of the pastes and injection time. In this study, pastes with viscosity suitable for good homogenization and injection
were obtained. 相似文献
992.
Rubio JC Garcia-Alonso MC Alonso C Alobera MA Clemente C Munuera L Escudero ML 《Journal of materials science. Materials in medicine》2008,19(1):369-375
Metallic transfer from implants does not stop at surrounding tissues, and metallic elements may be transferred by proteins
to become lodged in organs far from the implant. This work presents an in vivo study of metallic implant corrosion to measure
metallic element accumulation in organs located far from the implant, such as kidneys, livers, lungs and spleens. The studied
metallic implant materials were CoCr alloy, Ti, and the experimental alloy MA956 coated with α-alumina. The implants were
inserted in the hind legs of Wistar rats. Analysis for Co, Cr, Ti and Al metallic traces was performed after a long exposure
time of 12 months by Inductively Coupled Plasma (ICP) with Mass Spectrometry (MS). According to the results, the highest Cr
and Ti concentrations were detected in spleens. Co is mainly found in kidneys, since this element is eliminated via urine.
Cr and Ti traces increased significantly in rat organs after the long implantation time. The organs of rats implanted with
the α-alumina coated experimental MA956 did not present any variation in Al content after 12 months, which means there was
no degradation of the alumina layer surface. 相似文献
993.
Meso-structural study of concrete fracture using interface elements. I: numerical model and tensile behavior 总被引:2,自引:0,他引:2
A recently developed FE-based mesostructural model for the mechanical behavior of heterogeneous quasi-brittle materials is
used systematically to analyze concrete specimens in 2D. The numerical model is based on the use of zero-thickness interface
elements equipped with a normal-shear traction-separation constitutive law representing non-linear fracture, which may be
considered a mixed-mode generalization of Hillerborg’s “Fictitious Crack Model.” Specimens with 4 × 4 and 6 × 6 arrays of
aggregates are discretized into finite elements. Interface elements are inserted along the main lines in the mesh, representing
potential crack lines. The calculations presented in this paper consist of uniaxial tension loading, and the continuum elements
themselves are assumed to behave as linear elastic. In this way, the influence of various aspects of the heterogeneous geometry
and interface parameters on the overall specimen response has been investigated. These aspects are aggregate volume fraction,
type of arrangement and geometry, interface layout, and values of the crack model parameters chosen for both the aggregate-aggregate
and matrix-aggregate interfaces. The results show a good qualitative agreement with experimental observations and illustrate
the capabilities of the model. In the companion second part of the paper, the model is used to represent other loading states
such as uniaxial compression, Brazilian test, or biaxial loading. 相似文献
994.
M?nica Garcez Leila Meneghetti Luiz Carlos Pinto da Silva Filho 《Canadian Metallurgical Quarterly》2008,12(5):522-530
The use of fiber-reinforced polymers (FRPs) to poststrengthen concrete structures started to be investigated in the mid-1970s and today is widely recognized as an attractive technique to be used in civil structures, especially when aggressive environments prevent the use of materials that are susceptible to corrosion, such as steel. Different FRP poststrengthening techniques have been developed and applied in existing structures, aiming to increase their load capacity. Most FRP systems used nowadays consist of carbon fibers embedded in epoxy matrix. Regardless of the advantages and the good results achieved using carbon fiber-reinforced polymers, some new possibilities, such as the use of prestressing and lower cost fiber materials, are being analyzed in an attempt to provide viable alternatives for a more efficient, safe, and rational use of FRP systems. The main purpose of the present work was to make a comparative analysis of the behavior of reinforced concrete beams poststrengthened with carbon, aramid, and glass FRP subjected to static loading tests. Experimental results were evaluated against theoretical ones obtained through an analytical model that considers a trilinear behavior for the load versus displacement curves. The experimental results indicate that all FRP systems applied have appropriate structural performance for use in poststrengthening applications of RC. The choice of the more suitable system would, therefore, be strongly influenced by circumstances regarding cost limitations and level of reinforcement required. 相似文献
995.
Grilo Carlos M.; Hrabosky Joshua I.; White Marney A.; Allison Kelly C.; Stunkard Albert J.; Masheb Robin M. 《Canadian Metallurgical Quarterly》2008,117(2):414
Debate continues regarding the nosological status of binge eating disorder (BED) as a diagnosis as opposed to simply reflecting a useful marker for psychopathology. Contention also exists regarding the specific criteria for the BED diagnosis, including whether, like anorexia nervosa and bulimia nervosa, it should be characterized by overvaluation of shape/weight. The authors compared features of eating disorders, psychological distress, and weight among overweight BED participants who overvalue their shape/weight (n = 92), BED participants with subclinical levels of overvaluation (n = 73), and participants in an overweight comparison group without BED (n = 45). BED participants categorized with clinical overvaluation reported greater eating-related psychopathology and depression levels than those with subclinical overvaluation. Both BED groups reported greater overall eating pathology and depression levels than the overweight comparison group. Group differences existed despite similar levels of overweight across the 3 groups, as well as when controlling for group differences in depression levels. These findings provide further support for the research diagnostic construct and make a case for the importance of shape/weight overvaluation as a diagnostic specifier. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
996.
Gerardo Espinosa-Velázquez Ana Mayela Ramos-de-la-Peña Julio Montanez Juan Carlos Contreras-Esquivel 《Food science and biotechnology》2018,27(2):411-415
Functional food has been highly demanded lately because of its benefits in counteracting diseases. Fucoidan and agave fructan are ingredients that enhance the growth of beneficial bacteria in the gut (prebiotics). This mixture has great potential to develop innovative products but it has never been explored before. Because of fucoidan is more expensive than agave fructan, the innovative proposed mixture is vulnerable to adulteration. This research was aimed to assess the accuracy of Fourier transform infrared spectroscopy with attenuated total reflectance (ATR–FTIR) coupled with chemometrics to identify and predict concentration of both polysaccharides in powder mixtures (0–100%). Absorption bands at 1240–1255 and 836–840 cm?1 were attributed to fucoidan and a strong peak at ~ 936 cm?1 confirmed the fructan presence. Peak areas were best fitted into linear models (\({\text{R}}_{\text{adj}}^{2}\) ≥ 0.92, RMSE ≤ 3.54%). This achievement may be useful to certificate ingredients contained in fucoidan–fructan mixtures, preventing adulteration. 相似文献
997.
Carlos Richer 《生活用纸》2016,(9):42-43
成人失禁用品和婴儿纸尿裤就像是葡萄酒和红酒,尽管它们起源相同,但实际上却是两种截然不同的东西。婴儿纸尿裤的目标很简单,就是为了满足婴儿父母的需求。一是确保纸尿裤不漏尿,二是让婴儿纸尿裤穿着时保持干爽舒适。成人失禁用品却没有这么简单。 相似文献
998.
Stephane Parola Beatriz Julián‐López Luís D. Carlos Clément Sanchez 《Advanced functional materials》2016,26(36):6506-6544
Research on hybrid inorganic‐organic materials has experienced an explosive growth since the 1980s, with the expansion of soft inorganic chemistry based processes. Indeed, mild synthetic conditions, low processing temperatures provided by “chimie douce” and the versatility of the colloidal state allow for the mixing of the organic and inorganic components at the nanometer scale in virtually any ratio to produce the so called hybrid materials. Today a high degree of control over both composition and nanostructure of these hybrids can be achieved allowing tunable structure‐property relationships. This, in turn, makes it possible to tailor and fine‐tune many properties (mechanical, optical, electronic, thermal, chemical…) in very broad ranges, and to design specific multifunctional systems for applications. In particular, the field of “Hybrid‐Optics” has been very productive not only scientifically but also in terms of applications. Indeed, numerous optical devices based on hybrids are already in, or very close, to the market. This review describes most of the recent advances performed in this field. Emphasis will be given to luminescent, photochromic, NLO and plasmonic properties. As an outlook we show that the controlled coupling between plasmonics and luminescence is opening a land of opportunities in the field of “Hybrid‐Optics”. 相似文献
999.
Metal Organic Framework Crystals in Mixed‐Matrix Membranes: Impact of the Filler Morphology on the Gas Separation Performance 下载免费PDF全文
Anahid Sabetghadam Beatriz Seoane Damla Keskin Nicole Duim Tania Rodenas Salman Shahid Sara Sorribas Clément Le Guillouzer Guillaume Clet Carlos Tellez Marco Daturi Joaquin Coronas Freek Kapteijn Jorge Gascon 《Advanced functional materials》2016,26(18):3154-3163
Mixed‐matrix membranes comprising NH2‐MIL‐53(Al) and Matrimid or 6FDA‐DAM have been investigated. The metal organic framework (MOF) loading has been varied between 5 and 20 wt%, while NH2‐MIL‐53(Al) with three different morphologies, nanoparticles, nanorods, and microneedles has been dispersed in Matrimid. The synthesized membranes have been tested in the separation of CO2 from CH4 in an equimolar mixture. At 3 bar and 298 K for 8 wt% MOF loading, incorporation of NH2‐MIL‐53(Al) nanoparticles leads to the largest improvement compared to nanorods and microneedles. The incorporation of the best performing filler, i.e., NH2‐MIL‐53(Al) nanoparticles, into the highly permeable 6FDA‐DAM has a larger effect, and the CO2 permeability increases up to 85% with slightly lower selectivities for 20 wt% MOF loading. Specifically, these membranes have a permeability of 660 Barrer with a CO2/CH4 separation factor of 28, leading to a performance very close to the Robeson limit of 2008. Furthermore, a new non‐destructive technique based on Raman spectroscopy mapping is introduced to assess the homogeneity of the filler dispersion in the polymer matrix. The MOF contribution can be calculated by modeling the spectra. The determined homogeneity of the MOF filler distribution in the polymer is confirmed by focused ion beam scanning electron microscopy analysis. 相似文献
1000.