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81.
82.
Tetramethoxysilane (TMOS) or tetraethoxysilane (TEOS), an organic monomer [methylmethacrylate (MMA) or styrene (St)] and either α‐propylmethacryloxy‐ω‐trimethylsiloxy‐oligo(dimethylsiloxane) (OMS), as a compatibilizing agent, or α,ω‐bis(vinyl) oligo(dimethylsiloxane) (OVS), as compatibilizing and crosslinking agent, were allowed to undergo a sol–gel reaction under acidic condition and in the presence of 2,2′‐azoisobutyronitrile (AIBN) as a free‐radical initiator. The hydrolysis‐condensation and in situ free‐radical polymerization occur independently, to give a hybrid consisting of both inorganic and organic components. The conversion of the monomers to the proper polymers was monitored by IR spectroscopy and TGA. The resistance of the organic polymers to solvent extraction was also studied. The hybrids were pyrolyzed in an oxidative atmosphere. By decomposition, the organic polymer generated pores in the inorganic matrix. A quantitative evaluation of the characteristics for the resulting porous material was made by determination of the specific area, pore volume, and average radius. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2060–2067, 2003 相似文献
83.
Yao J Wang Y Tsai KT Liu Z Yin X Bartal G Stacy AM Wang YL Zhang X 《Philosophical transactions. Series A, Mathematical, physical, and engineering sciences》2011,369(1950):3434-3446
Indefinite optical properties, which are typically characterized by hyperbolic dispersion relations, have not been observed in naturally occurring materials, but can be realized through a metamaterial approach. We present here the design, fabrication and characterization of nanowire metamaterials with indefinite permittivity, in which all-angle negative refraction of light is observed. The bottom-up fabrication technique, which applies electrochemical plating of nanowires in porous alumina template, is developed and demonstrated in achieving uniform hyperbolic optical properties at a large scale. We developed techniques to improve the uniformity and to reduce the defect density in the sample. The non-magnetic design and the off-resonance operation of the nanowire metamaterials significantly reduce the energy loss of electromagnetic waves and make the broad-band negative refraction of light possible. 相似文献
84.
Oscar D'Agostini-JuniorCarmen Lucia Petkowicz Angelica Garcia CoutoSergio Faloni de Andrade Rilton Alves Freitas 《Materials science & engineering. C, Materials for biological applications》2011,31(3):677-682
Chitosan and polyacrylic acid (PAA) both have weak, short-lasting bioadhesive properties; therefore, a hybrid particle composed of a chitosan derivative and PAA could be used as a new bioadhesive agent. Using simultaneous in-situ monitoring with a multidetection system, N-carboxymethyl chitosan was ionically bonded to acrylic acid and then polymerized using potassium persulphate as the initiator (N-CMCA-Dh of 165 nm). The PAA on N-CMCA was crosslinked using N,N-methylene-bisacrylamide (N-CMCAC-Dh of 141 nm). During polymerization, the solution developed a milky white appearance, and polymerization kinetics was determined to be 3.2 × 10−3 ± 4.0 × 10−6 mmol/min. The reaction for PAA alone was 1.7 times faster than that of the hybrid system. The particles showed an increase in thermal stability and reduction of thermal-mass loss compared with the N-CMC alone. The N-CMCAC particles showed the highest bioadhesion onto the stomach. The gastroprotection index of N-CMChAC particles against ethanol/HCl-induced ulcers in mice was 68.2 ± 6.4%. Similar results were observed for omeprazole (74.2 ± 5.3%). The particles obtained in this work have potential for use in drug delivery to the stomach, perhaps to aid in treating ulceration and inflammation, and can be used as a system for the prevention of ethanol-induced ulcers. 相似文献
85.
86.
Lidia Romani Andrea Speltini Carlo Nazareno Dibenedetto Andrea Listorti Francesco Ambrosio Edoardo Mosconi Angelica Simbula Michele Saba Antonella Profumo Paolo Quadrelli Filippo De Angelis Lorenzo Malavasi 《Advanced functional materials》2021,31(46):2104428
The rational design of heterojunctions based on metal halide perovskites (MHPs) is an effective route to create novel photocatalysts to run relevant solar-driven reactions. In this work, an experimental and computational study on the synergic coupling between a lead-free Cs3Bi2Br9 perovskite derivative and g-C3N4 is presented. A relevant boost of the hydrogen photogeneration by more than one order of magnitude is recorded when going from pure g-C3N4 to the Cs3Bi2Br9/g-C3N4 system. Effective catalytic activity is also achieved in the degradation of the organic pollutant with methylene blue as a model molecule. Based upon complementary experimental outputs and advanced computational modeling, a rationale is provided to understand the heterojunction functionality as well as the trend of hydrogen production as a function of perovskite loading. This work adds further solid evidence for the possible application of MHPs in photocatalysis, which is emerging as an extremely appealing and promising field of application of these superior semiconductors. 相似文献
87.
Positive‐tone,aqueous‐developable,polynorbornene dielectric: Lithographic,and dissolution properties
A positive‐tone, aqueous base soluble, polynorbornene (PNB) dielectric formulation has been developed. The photolithographic solubility switching mechanism is based on diazonaphthoquinone (DNQ) inhibition of PNB resin functionalized with pendent fluoroalcohol and carboxylic acid substituents. The optical contrast (at 365 nm) was found to be 2.3. The maximum height‐to‐width aspect ratio of developed line and space features was 3 : 2. The sensitivity, D100, of a formulation containing 20 pphr of DNQ photoactive compound (PAC) was calculated to be 408 mJ cm?2. The effects of the PAC molecule structure on miscibility and dissolution of the photosensitive films in aqueous base developer were studied. The effect of the monomer composition of the PNB polymer on the dissolution rate of the formulated PNB resin was evaluated. A unique dissolution and swelling behavior was observed. The effect is attributed to a copolymer synthesized with two monomers each of which is susceptible to deprotonation in aqueous base. FTIR measurements showed that the pure PNBFA has a small percentage of free hydroxyl groups, which did not change appreciably by the addition of PAC to the mixture. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 相似文献
88.
89.
The use of complex amplitude correlation to compensate for large in-plane motion in digital speckle pattern interferometry is investigated. The result is compared with experiments where digital speckle photography (DSP) is used for compensation. An advantage of using complex amplitude correlation instead of intensity correlation (as in DSP) is that the phase change describing the deformation is retrieved directly from the correlation peak, and there is no need to compensate for the large movement and then use the interferometric algorithms. A discovered drawback of this method is that the correlation values drop quickly if a phase gradient larger than pi is present in the subimages used for cross correlation. This means that, for the complex amplitude correlation to be used, the size of the subimages must be well chosen or a third par?meter in the cross-correlation algorithm that compensates for the phase variation is needed. Correlation values and wrapped phase maps from the two techniques (intensity and complex amplitude correlation) are presented. 相似文献
90.
Subclinical mastitis causes an increase in milk somatic cell count (SCC) and can lead to reduced milk production and early culling. In many countries, non-aureus staphylococci (NAS) is the most common bacterial finding in subclinical mastitis of dairy cows. New methodology makes it possible to identify NAS species, but knowledge about the epidemiology is limited. The objective of this project was to improve advisory services for mastitis control by investigating associations between NAS and SCC, milk production, and persistence of intramammary infections (IMI). Farmers who had sent milk samples to the Swedish National Veterinary Institute (Uppsala, Sweden) were asked to participate if NAS was identified in the samples. Participating farmers were asked to resample all udder quarters of the cow once within 1 mo. Regression models were used to investigate associations between NAS and cow factors, udder quarter California mastitis test and SCC, and persistence of IMI. Associations with cow composite milk yield and SCC were also investigated. In total, 671 cows from 201 herds were enrolled in the study, and 19 NAS species were identified, of which the 4 most common were Staphylococcus epidermidis, Staphylococcus simulans, Staphylococcus chromogenes, and Staphylococcus haemolyticus. Persistent IMI was more common in udder quarters with Staphylococcus hyicus and S. simulans and less common in those with Staphylococcus saprophyticus IMI. β-Lactamase production by the different NAS species varied from 0 to 100%. There was a significant association between NAS species and California mastitis test and SCC of udder quarters, and this varied depending on parity. The cow composite milk SCC at the test milking before the initial sample was taken differed significantly with NAS species, but not at the subsequent test milking. Milk yield—at the test milking before or after the initial sample—did not differ significantly for NAS species. There were no significant associations between milk yield or SCC and persistent NAS IMI. In conclusion, the NAS species affects SCC and persistent IMI differently but not milk yield. 相似文献