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排序方式: 共有457条查询结果,搜索用时 78 毫秒
91.
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Auyeung E Cutler JI Macfarlane RJ Jones MR Wu J Liu G Zhang K Osberg KD Mirkin CA 《Nature nanotechnology》2012,7(1):24-28
Crystalline nanoparticle arrays and superlattices with well-defined geometries can be synthesized by using appropriate electrostatic, hydrogen-bonding or biological recognition interactions. Although superlattices with many distinct geometries can be produced using these approaches, the library of achievable lattices could be increased by developing a strategy that allows some of the nanoparticles within a binary lattice to be replaced with 'spacer' entities that are constructed to mimic the behaviour of the nanoparticles they replace, even though they do not contain an inorganic core. The inclusion of these spacer entities within a known binary superlattice would effectively delete one set of nanoparticles without affecting the positions of the other set. Here, we show how hollow DNA nanostructures can be used as 'three-dimensional spacers' within nanoparticle superlattices assembled through programmable DNA interactions. We show that this strategy can be used to form superlattices with five distinct symmetries, including one that has never before been observed in any crystalline material. 相似文献
94.
Darin A. Ray Sarbjit Kaur Raymond A. Cutler Dinesh K. Shetty 《Journal of the American Ceramic Society》2008,91(4):1135-1140
The combined-stage sintering model was used to determine the activation energy, Q , of sintering for selected SiC-based materials. SiC densified with a liquid (1.65 wt% Al) had an activation energy of 842±79 kJ/mol, a value between those for a silicon carbide densified with 1 wt% C and 0.25 wt% B4 C ( Q =643±37 kJ/mol) and one densified with 2.5 wt% AlN ( Q =1022±122 kJ/mol), compositions which have no liquid phase below 1850°C. The SiC with Al additive began densification by 1500°C and the densification curve was offset by approximately 100°C compared with the other two materials below 1850°C. The choice and amount of additives not only affect densification and activation energy, but also influence microstructure and fracture mode, allowing engineering of mechanical properties. 相似文献
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Righi V Di Nunzio M Danesi F Schenetti L Mucci A Boschetti E Biagi P Bonora S Tugnoli V Bordoni A 《Lipids》2011,46(7):627-636
It is well recognized that a high dietary intake of long-chain polyunsaturated fatty acids (LC-PUFA) has profound benefits
on health and prevention of chronic diseases. In particular, in recent years there has been a dramatic surge of interest in
the health effects of n-3 LC-PUFA derived from fish, eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids. Notwithstanding,
the metabolic fate and the effects of these fatty acids once inside the cell has seldom been comprehensively investigated.
Using cultured neonatal rat cardiomyocytes as model system we have investigated for the first time, by means of high-resolution
magic-angle spinning nuclear magnetic resonance (HR-MAS NMR) spectroscopy in combination with gas chromatography (GC), the
modification occurring in the cell lipid environment after EPA and DHA supplementation. The most important difference between
control and n-3 LC-PUFA-supplemented cardiomyocytes highlighted by HR-MAS NMR spectroscopy is the increase of signals from
mobile lipids, identified as triacylglycerols (TAG). The observed increase of mobile TAG is a metabolic response to n-3 LC-PUFA
supplementation, which leads to an increased lipid storage. The sequestration of mobile lipids in lipid bodies provides a
deposit of stored energy that can be accessed in a regulated fashion according to metabolic need. Interestingly, while n-3
LC-PUFA supplementation to neonatal rat cardiomyocytes causes a huge variation in the cell lipid environment, it does not
induce detectable modifications in water-soluble metabolites, suggesting negligible interference with normal metabolic processes. 相似文献
98.
Digital dermatitis is an infectious disease that causes lameness in dairy cattle, a primary welfare concern of the dairy industry. One of the common treatments for this painful hoof disease is through the application of an antibiotic bandage that must be removed following treatment. The objectives of this randomized clinical trial were to determine if topical application of tetracycline hydrochloride in a paste would be as therapeutically effective for the treatment of digital dermatitis as a powdered form of tetracycline hydrochloride held in place by a bandage, and to quantify pain associated with digital dermatitis lesions. Two hundred and fourteen Holstein cow hooves with digital dermatitis lesions were randomly assigned to 1 of 3 treatments: a tetracycline hydrochloride paste, tetracycline hydrochloride powder held in place with a bandage for 2 d, or a negative (untreated) control. Lesions were examined at 2 time periods: 3 to 7 d posttreatment and 8 to 12 d posttreatment to determine healing rates. Nociceptive thresholds were measured using a pressure algometer to quantify the pain at the lesion site. The tetracycline hydrochloride paste was as effective as the powdered bandage treatment in terms of healing rates, with 47.4 and 57.1% hooves healed at 8 to 12 d posttreatment, respectively. Both treatments were more effective than the control, in which no lesions healed 8 to 12 d following initial examination. Mean (±SE) nociceptive thresholds for active, healing, and healed lesions differed, with limb-withdrawal response occurring at 7.45 (±0.67) kg, 12.84 (±1.85) kg, and censored to 25 kg (maximum value of algometer) of force applied, respectively. However, active lesions were not consistently associated with pain, as maximum force was tolerated when applied to 19% of active lesions, perhaps due to variability in stoicism between individual cattle or due to changes in pain during the progression of infection. In conclusion, tetracycline hydrochloride paste was as effective as tetracycline hydrochloride bandage, eliminating the need for bandage removal following treatment application. Digital lesions can be painful during both active and healing stages, suggesting the need for treatment and husbandry interventions for pain mitigation. 相似文献
99.
Giada Arena Giuseppe Barreca Luca Carcone Elena Cini Giovanni Marras Hans G. Nedden Marcello Rasparini Stephen Roseblade Adele Russo Maurizio Taddei Antonio Zanotti‐Gerosa 《Advanced Synthesis \u0026amp; Catalysis》2013,355(8):1449-1454
The novel rhodium complex [Rh(S)‐Phanephos(cod)]‐catalyzed hydrogenation of disubstituted (E)‐enol acetate carboxylic acids is reported. The catalytic cycle works under 30 bar of hydrogen under conventional heating giving different 3‐acetoxy‐2,3‐disubstituted carboxylic acids with ee ≥90%. Hydrogenation occurred also under microwave dielectric heating without eroding the enantioselectivity but improving the overall efficiency of the process. With microwaves, hydrogen pressure and reaction time required for complete hydrogenation dropped to 5 bar and 30 min, respectively. The best performance of this catalyst under microwave irradiation was TON 100, TOF 196 h−1 with ee 99% on a 6‐g scale. 相似文献
100.
Adele Papetti Maria Daglia Pietro Grisoli Cesare Dacarro Cesarina Gregotti Gabriella Gazzani 《Food chemistry》2006
The antiradical activity of water soluble components in six vegetables belonging to the Cichorium genus, i.e., three cultivars of red intybus species var. silvestre (Treviso, Chioggia, Verona red chicories), a white intybus species var. foliosum (Belgian chicory), and two vegetables of the endivia species var. latifolium (escarole chicory) and var. crispum (“crispa” chicory), were studied using two biological systems consisting of: (1) microsome membrane rat hepatocyties in which oxidative damage was induced by CCl4; (2) gram-positive bacterium, Staphylococcus aureus cultures, subjected to damage with cumene hydroperoxyde. The obtained results show that in both systems the red vegetables possess the strongest antioxidant properties and contain different antioxidant compounds whether at a low or high molecular weight, but only those of high molecular-weight (MW > 3500 Da) are able to act as antioxidants in all the used systems. The lower MW fraction (MW < 3500 Da) showed itself to be pro-oxidant in the microsome system. The effects of thermal treatments such as boiling, freezing and freeze-drying were also investigated. 相似文献