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排序方式: 共有1793条查询结果,搜索用时 15 毫秒
931.
932.
A hexagon triple is a graph consisting of three triangles of the form (a, x, b), (b, y, c), and (c,z,a), where a, b, c, x, y, z are distinct. The triangle (a, b, c) is called the inside triangle and the triangles (a, x, b), (b,y,c), and (c, z, a) are called outside triangles. A 3k-fold hexagon triple system of order n is a pair (X, H), where H is an edge-disjoint collection of hexagon triples which partitions the edge set of 3kK n with vertex set X. Note that the outside triangles form a 3k-fold triple system. If the 3k-fold hexagon triple system (X, H) has the additional property that the inside triangles form a k-fold triple system, then (X, H) is said to be perfect. A covering of 3kK n with hexagon triples is a triple (X, H, P) such that: 1.3kK n has vertex set X. 2.P is a subset of E(λ K n ) with vertex set X for some λ, and 3.H is an edge disjoint partition of E(3kK n )∪ P with hexagon triples. If P is as small as possible (X, H, P) is called a minimum covering of 3kK n with hexagon triples. If the inside triangles of the hexagon triples in H form a minimum covering of kK n with triangles, the covering is said to be perfect. A complete solution for the problem of constructing perfect 3k-fold hexagon triple system and perfect maximum packing of 3kK n with hexagon triples was given recently by the authors [2]. In this work, we give a complete solution of the problem of constructing perfect minimum covering of 3kK n with hexagon triples. 相似文献
933.
Ján Tkác Igor Vostiar Peter Gemeiner Ernest Sturdík 《Bioelectrochemistry (Amsterdam, Netherlands)》2002,55(1-2):149-151
The prevention of ferrocene leakage from an electrode by physical retention of mediator in a matrix of cellulose acetate membrane is reported. Five types of the cellulose acetate membranes were prepared, containing 1.8%, 5.3%, 8.5%, 20.0% of ferrocene and a membrane containing 1.8% of ferrocene and 0.05 % of Nafion in the matrix. Ferrocene embedded membranes were successfully applied in the construction of a fructose biosensor by immobilization of PQQ-dependent fructose dehydrogenase (FDH). The biosensor comprising a cellulose acetate membrane with 1.8% of ferrocene and 0.05% of Nafion had good stability characteristics, retained almost 40% of the initial response after 8 h of continuous use with an initial sensitivity of 226 nA mM(-1) and response time of 75 s. 相似文献
934.
Hanna Kowalska Jolanta Kowalska Anna Ignaczak Ewelina Masiarz Ewa Domian Sabina Galus Agnieszka Ciurzyska Agnieszka Salamon Agnieszka Zajc Agata Marzec 《Molecules (Basel, Switzerland)》2021,26(13)
The aim of this study was to find the effect of kale and dietary fibre (DF) on the physicochemical properties, nutritional value and sensory quality of multigrain bars. A recipe of multigrain bars was prepared with the addition of fresh kale (20% and 30%) and DF preparations (apple, blackcurrant, chokeberry and hibiscus). The bars were baked at 180 °C for 20 min. These snack bars, based on pumpkin seeds, sunflower seeds, flaxseed and wholegrain oatmeal, are a high-calorie product (302–367 kcal/100 g). However, the composition of the bars encourages consumption. In addition to the ability to quickly satisfy hunger, such bars are rich in many natural ingredients that are considered pro-health (high fibre content (9.1–11.6 g/100 g), protein (11.2–14.3 g/100 g), fat (17.0–21.1 g/100 g, including unsaturated fatty acids), carbohydrates (20.5–24.0 g/100 g), as well as vitamins, minerals and a large number of substances from the antioxidant group. The addition of kale caused a significant increase of water content, but reduction in the value of all texture parameters (TPA profiles) as well as calorific values. The content of polyphenols was strongly and positively correlated with the antioxidant activity (r = 0.92). In the bars with 30% addition of kale (422 mg GA/100 g d.m.), the content of polyphenols was significantly higher than based ones (334 mg GA/100 g d.m.). Bars with the addition of the DF were characterized by a higher antioxidant activity, and the content of carotenoids, chlorophyll A and B and polyphenols. High sensory quality was demonstrated for all (from 4.8 to 7.1 on a 10-point scale). The addition of fibre preparations was also related to technological aspects and allows to create attractive bars without additional chemicals. 相似文献
935.
Quinton L Gilles N Smargiasso N Kiehne A De Pauw E 《Journal of the American Society for Mass Spectrometry》2011,22(11):1891-1897
This study describes the structural characterization of a totally new family of peptides from the venom of the snake green
mamba (Dendroaspis angusticeps). Interestingly, these peptides differ in several points from other already known mamba toxins. First of all, they exhibit
very small molecular masses, ranging from 1.3 to 2.4 kDa. The molecular mass of classical mamba toxins is in the range of
7 to 25 kDa. Second, the new peptides do not contain disulfide bonds, a post-translational modification commonly encountered
in animal toxins. The third difference is the very high proportion of proline residues in the sequence accounting for about
one-third of the sequence. Finally, these new peptides reveal a carbohydrate moiety, indicating a glycosylation in the sequence.
The last two features have made the structural characterization of the new peptides by mass spectrometry a real analytical
challenge. Peptides were characterized by a combined use of MALDI- TOF/TOF and nanoESI-IT-ETD experiments to determine not
only the peptide sequence but also the composition and the position of the carbohydrate moiety. Anyway, such small glycosylated
and proline-rich toxins are totally different from any other known snake peptide and form, as a consequence, a new family
of peptides. 相似文献
936.
Le Pleux L Pellegrin Y Blart E Odobel F Harriman A 《The journal of physical chemistry. A》2011,115(20):5069-5080
A series of multiporphyrin clusters has been synthesized and characterized in which there exists a logical gradient for either energy or electron transfer between the porphyrins. A central free-base porphyrin (FbP), for example, is equipped with peripheral zinc(II) porphyrins (ZnP) which act as ancillary light harvesters and transfer excitation energy to the FbP under visible light illumination. Additional energy-transfer steps occur at the triplet level, and the series is expanded by including magnesium(II) porphyrins and/or tin(IV) porphyrins as chromophores. Light-induced electron transfer is made possible by incorporating a gold(III) porphyrin (AuP(+)) into the array. Although interesting by themselves, these clusters serve as control compounds by which to understand the photophysical processes occurring within a three-stage dendrimer comprising an AuP(+) core, a second layer formed from four FbP units, and an outer layer containing 12 ZnP residues. Here, illumination into a peripheral ZnP leads to highly efficient electronic energy transfer to FbP, followed by charge transfer to the central AuP(+). Charge recombination within the resultant charge-shift state is intercepted by secondary hole transfer to the ZnP, which occurs with a quantum yield of around 20%. The final charge-shift state survives for some microseconds in fluid solution at room temperature. 相似文献
937.
Ion Sava Ştefan Chişcă Maria Brumă Gabriela Lisa 《Journal of Thermal Analysis and Calorimetry》2011,104(3):1135-1143
The processing of polyimide films from polyamidic acid solutions involves the simultaeous loss of solvent and chemical conversion,
and may imply structural reorganization such as orientation or crystallization. The effect of thermal treatment on the thermal,
mechanical and dielectric properties of polymer films based on benzophenonetetracarboxylic dianhydride and 4,4’-diamino-3,3’-dimethyl
diphenylmethane have been investigated. The thermal treatment of polyamidic acid at different temperatures led to compounds
with different degree of imidization; it turned out that the imidization process took place with high speed until 240 °C and
then remained constant. The dynamic mechanical analysis (DMA), contact angles, and dielectric measurements revealed that the
storage modulus and contact angles increased with increasing of curing temperature while the dielectric constant decreased. 相似文献
938.
939.
940.
Noreen R Pineau R Chien CC Cestelli-Guidi M Hwu Y Marcelli A Moenner M Petibois C 《Analytical and bioanalytical chemistry》2011,401(3):795-801
Fourier-transform infrared (FTIR) imaging has been used to investigate brain tumor angiogenesis using a mice solid tumor model
and bare-gold (∅ 25 nm) or BaSO4 (∅ 500 nm) nanoparticles (NP) injected into blood vasculature. FTIR images of 20-μm-thick tissue sections were used for chemical
histology of healthy and tumor areas. Distribution of BaSO4-NP (using the 1,218–1,159 cm−1 spectral interval) revealed clearly all details of blood vasculature with morphological abnormalities of tumor capillaries,
while Au-NP (using the 1,046–1,002 cm−1 spectral interval) revealed also diffusion properties of leaky blood vessels. Diffusion of Au-NP out of vascular space reached
64 ± 29 μm, showing the fenestration of “leaky” tumor blood vessels, which should allow small NP (<100 nm, as for Au-NP) to
diffuse almost freely, while large NP should not (as for BaSO4-NP in this study). Therefore, we propose to develop FTIR imaging as a convenient tool for functional molecular histology
imaging of brain tumor vasculature, both for identifying blood capillaries and for determining the extravascular diffusion
space offered by vessel fenestration. 相似文献