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排序方式: 共有883条查询结果,搜索用时 203 毫秒
871.
Albano VG Bandini M Barbarella G Melucci M Monari M Piccinelli F Tommasi S Umani-Ronchi A 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(3):667-675
The synthesis, characterization, and structure-guided application of a new class of highly versatile chiral C(2)-symmetric diamine-oligothiophene ligands in Pd-catalyzed asymmetric transformations are presented. Experimental investigations of the intimate role of pendant pi-conjugate oligothiophenes in determining the catalytic activity of the corresponding chiral Pd complexes are described. Their unusual behavior opens up new routes toward the logical design of finely tuned organometallic catalysts by remote structural functionalizations. 相似文献
872.
A new module of membrane-assisted solvent extraction (MASE) with miniaturized membrane bags was applied to the determination of seven volatile organic compounds (VOCs): chloroform, 1,1,1-trichloroethane, trichloroethylene, 1,1,2-trichloroethane, tetrachloroethene, 1,1,1,2-tetrachloroethane, 1,1,2,2-tetrachloroethane with boiling points between 61 and 147 degrees C in aqueous samples. Different from the known procedure the new, shortened membrane bags were filled with 100 microl of an organic solvent. The membrane bags were placed in a 20 ml headspace vial and filled with 15 ml of the aqueous sample. The vial was transferred into an autosampler where it was stirred for a definite time at elevated temperature. After the extraction, 1 microl of the organic extract was transferred into the spilt/splitless injector of a GC system equipped with an electron-capture detector. This work included optimization of the membrane device, the determination of the optimized extraction conditions such as stirring rate, extraction time and the impact of salt addition. The validation of the method involved repeatability, recovery and detection limit studies, followed of its application towards real water samples. The repeatability, expressed as the relative standard deviation of the peak areas of six extractions was below 10%. The detection limits (LODs) were between 5 ng/l (tetrachloroethene) and 50 ng/l (chloroform). Calibration was performed in a range from 5 ng/l to 150 microg/l, since the concentration in the aqueous samples was expected quite various in this concentration range. Five river water samples of Bitterfeld, Saxony-Anhalt, Germany were analyzed with miniaturized-MASE and the results were compared with those obtained with Headspace-Analysis. The method can be fully automated and moreover, it allows the simultaneous determination of volatile and semi volatile compounds. 相似文献
873.
Allenyl carbinols undergo regioselective hydrostannation in the presence of MoBl3, a catalyst originally developed for the hydrostannation of alkynes, giving rise to allyl stannanes. These allyl stannanes can easily be converted into useful synthetic building blocks such as allyl iodides or vinyl epoxides. 相似文献
874.
In this paper, we are interested in real-valued backward stochastic differential equations with jumps together with their applications to non-linear expectations. The notion of non-linear expectations has been studied only when the underlying filtration is given by a Brownian motion and in this work the filtration will be generated by both a Brownian motion and a Poisson random measure. We study at first backward stochastic differential equations driven by a Brownian motion and a Poisson random measure and then introduce the notions of f-expectations and of non-linear expectations in this set-up. 相似文献
875.
Manuela Zubitur Agurtzane Mugica Javier Areizaga Milagros Cortázar 《Colloid and polymer science》2010,288(7):809-818
Nanocomposites of poly(p-dioxanone) (PPDO) with unmodified and organically modified layered double hydroxide (LDH) have been
prepared by melt extrusion method. Dodecyl sulfate was used as organic modifier. The morphology of nanocomposites was analyzed
by X-ray diffraction and transmission electron microscopy and their thermal properties by differential scanning calorimetry
and thermogravimetric analysis. It has been found that the organic modifier decisively influences the nanocomposite morphology,
resulting in a higher level of exfoliation. In addition, the glass transition temperature of nanocomposites was slightly higher
than in case of unfilled PPDO. Moreover, the crystallization was delayed by LDH incorporation. The above behavior was ascribed
to interactions between carbonyl groups of polymer matrix and hydroxyl groups of LDH, as supported by Fourier transformed
infrared analysis. Interestingly, two different crystallization processes have been observed in the nanocomposite of PPDO
and organically modified LDH. Unmodified and organo-modified LDH, practically did not alter the final melting point of PPDO.
However, the thermal decomposition behavior was clearly influenced by the morphology exhibited by nanocomposites. 相似文献
876.
We prove that every subvariety of BL-algebras which is not finitely generated is not σ-canonical. We also prove π-canonicity for an infinite family of subvarieties of BL-algebras that are not finitely generated. To do so we study the behavior
of canonical extensions of ordered sums of posets. 相似文献
877.
Manuela Zonfrillo Federica Andreola Ewa K. Krasnowska Gianluca Sferrazza Pasquale Pierimarchi Annalucia Serafino 《Molecules (Basel, Switzerland)》2022,27(11)
Eucalyptus essential oil and its major constituent eucalyptol are extensively employed in the cosmetic, food, and pharmaceutical industries and their clinical use has recently expanded worldwide as an adjuvant in the treatment of infective and inflammatory diseases. We previously demonstrated that essential oil from Eucalyptus globulus (Labill.) (EO) stimulates in vitro the phagocytic activity of human monocyte-derived macrophages and counteracts the myelotoxicity induced by the chemotherapeutic 5-fluorouracil in immunocompetent rats. Here we characterize some mechanistic aspects underlying the immunostimulatory ability exerted by EO on macrophages. The internalization of fluorescent beads, fluorescent zymosan BioParticles, or apoptotic cancer cells was evaluated by confocal microscopy. Pro-inflammatory cytokine and chemokine release was determined by flow cytometry using the BD cytometric bead array. Receptor involvement in EO-stimulated phagocytosis was assessed using complement- or IgG-opsonized zymosan particles. The localization and expression of podosome components was analyzed by confocal microscopy and western blot. The main results demonstrated that: EO-induced activation of a macrophage is ascribable to its major component eucalyptol, as recently demonstrated for other cells of innate immunity; EO implements pathogen internalization and clearance by stimulating the complement receptor-mediated phagocytosis; EO stimulates podosome formation and increases the expression of podosome components. These results confirm that EO extract is a potent activator of innate cell-mediated immunity and thereby increase the scientific evidence supporting an additional property of this plant extract besides the known antiseptic and anti-inflammatory properties. 相似文献
878.
苹果品质检测的可见-近红外激光漫反射光谱图像法的方法研究 总被引:3,自引:0,他引:3
利用可见-近红外激光漫反射光谱图像法及化学计量学方法检测了苹果的可溶性固形物含量和硬度。为了消除苹果形状对品质检测的影响,分析了5个不同波长的激光(680,780,880,940和980 nm)照射在富士苹果果面形成的光斑图像,并通过一系列图像处理方法得出了的苹果形状修正算法。分别利用修正前后的光谱图像参数建立苹果可溶性固形物含量和硬度的偏最小二乘回归(PLSR)模型,模型预测值和真实值之间的相关系数从0.78和0.80分别提高到0.87和0.89。为了消除果面镜面反射对苹果内部品质检测的影响,文章提出了象素强度频率检测法,并比较了利用果面光斑图像中光强均值和不同强度对应的象素强度频率建立的苹果硬度和可溶性固形物含量的PLSR模型效果,得出象素强度频率的模型效果更好。苹果可溶性固形物含量和硬度PLSR模型中预测均方根误差(RMSEP)分别从1.28°Brix和8.23 N.cm-2降低到0.84°Brix和6.17 N.cm-2。 相似文献
879.
David Welch Norman J. Kleiman Peter C. Arden Christine L. Kuryla Manuela Buonanno Brian Ponnaiya Xuefeng Wu David J. Brenner 《Photochemistry and photobiology》2023,99(1):168-175
Far-UVC radiation, typically defined as 200–235 nm, has similar or greater anti-microbial efficacy compared with conventional 254-nm germicidal radiation. In addition, biophysical considerations of the interaction of far-UVC with tissue, as well as multiple short-term safety studies in animal models and humans, suggest that far-UVC exposure may be safe for skin and eye tissue. Nevertheless, the potential for skin cancer after chronic long-term exposure to far-UVC has not been studied. Here, we assessed far-UVC induced carcinogenic skin changes and other pathological dermal abnormalities in 96 SKH-1 hairless mice of both sexes that were exposed to average daily dorsal skin doses of 400, 130 or 55 mJ cm−2 of 222 nm far-UVC radiation for 66 weeks, 5 days per week, 8 h per day, as well as similarly-treated unexposed controls. No evidence for increased skin cancer, abnormal skin growths or incidental skin pathology findings was observed in the far-UVC-exposed mice. In addition, there were no significant changes in morbidity or mortality. The findings from this study support the long-term safety of long-term chronic exposure to far-UVC radiation, and therefore its potential suitability as a practical anti-microbial approach to reduce airborne viral and bacterial loads in occupied indoor settings. 相似文献
880.
Sebastiano Mantovani Angela Pintus Dr. Alessandro Kovtun Dr. Giulio Bertuzzi Dr. Manuela Melucci Prof. Marco Bandini 《European journal of organic chemistry》2023,26(37):e202300641
A new metal-free synthetic approach to functionalized indenes is documented. The use of commercially available graphene oxide (GO) allowed the direct access to indenyl cores (yield up to 80 %) via intramolecular Friedel-Crafts-type allylic alkylations with readily available Morita-Baylis-Hillman alcohols. Combined experimental and spectroscopic investigations contributed to shed light on the reaction mechanism dealing with a nanostructured carbon material-based C−C bond forming reaction. 相似文献