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151.
Filtered lakewater samples, mainly collected in the province of Torino (Piedmont, NW Italy) were characterised from a spectrophotometric point of view. Spectral data were then used for the direct determination of nitrate by three-wavelength photometry, which should account for the spectral interference by dissolved organic matter (DOM), and the results compared with nitrate quantification by ion chromatography. The spectrophotometric method proved very suitable for nitrate measurement, with unity slope (micro +/- sigma = 0.99 +/- 0.03) of the correlation plot (spectral vs. ion chromatography data) up to 0.1 mM nitrate, and with r2 = 0.97 for 26 data points. Lakewater spectra were also used for the characterisation of DOM by means of the specific absorption at 285 and 254 nm (absorbance vs. NPOC, the latter to quantify the DOM amount), and the E2/E3 and E3/E4 indexes. The latter two make only use of radiation absorption data (250 vs. 365 and 300 vs. 400 nm). It could be concluded that lakewater DOM is mainly composed of autochthonous material (biologically produced aliphatic compounds and only a minor fraction of aromatic groups), with generally low molecular weight and degree of aromaticity. Some exceptions could be found in high-mountain lakes, but it should also be considered that NPOC measurement cannot be avoided if DOM origin is to be studied. From the absorption spectrum alone it is possible to get indication on the aromaticity degree of radiation-absorbing DOM, but most of the autochthonous DOM would escape spectrophotometric characterisation. 相似文献
152.
Peter Cass Kerry Pratt Terry Mann Bob Laslett Ezio Rizzardo Robert Burford 《Journal of polymer science. Part A, Polymer chemistry》1999,37(16):3277-3284
The catalytic system Co/methylaluminoxane/tert-butyl chloride has been studied and optimized for the polymerization of 1,3-butadiene to high cis-1,4-polybutadiene. The ratio of the individual catalyst components was investigated to achieve maximum conversion, stereoregularity, and molecular weight. It was found that the specific order of addition of catalyst components to the feedstock and aging time therein has critical influence in the polymerization reaction. This can be attributed to the rate of chlorinating the aluminoxane and the stability of the active catalyst sites obtained. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3277–3284, 1999 相似文献
153.
Improving the knowledge and design of end groups in polymers produced by free radical polymerization
W. Ken Busfield Ian D. Jenkins Tomoyuki Nakamura Michael J. Monteiro Ezio Rizzardo Shuji Sayama San H. Thang Phuc Van Le Clovia I. Zayas-Holdsworth 《先进技术聚合物》1998,9(1):94-100
Several techniques have been used to probe polymer end groups. The nitroxide radical trapping technique has been used (i) to show that initiator-derived unsaturated end groups in polymethyl methacrylate can be minimized by using t-hexyl peroxypivalate as the initiator (ii) to predict the end and penultimate groups in acrylonitrile/ethyl vinyl ether copolymer produced by t-butoxyl initiation by analogy with the initiation mechanism (iii) to predict probable end groups in polyacrylonitrile and polystyrene produced by cyanoisopropyl initiation in the presence of adventitious oxygen. NMR techniques have been used to show that the end groups of functionalized oligomers, made from styrene and methacrylonitrile by the addition-fragmentation chain transfer technique with allylic sulphides, conform to the expected structures. © 1998 John Wiley & Sons, Ltd. 相似文献
154.
Hisao Hidaka Yuji Suzuki Kayo Nohara Satoshi Horikoshi Yoshiharu Hisamatsu Ezio Pelizzetti Nick Serpone 《Journal of polymer science. Part A, Polymer chemistry》1996,34(7):1311-1316
The photocatalyzed oxidative decompositions of solid particles of polyvinylchloride (PVC; size about 100 to 200 μm), of the polyvinylidene chloride copolymer (95% PVC/5% PVLC; size ∼ 400–600 μm), and a PVC film have been examined in suspensions of titania and zinc oxide illuminated by UV light and/or by natural sunlight. Dechlorination and evolution of carbon dioxide were monitored, the latter occurring by the intermediacy of acetic and formic acids. The photodegradation of polymer specimens was enhanced in TiO2/water media by such added oxidants as hydrogen peroxide and potassium persulfate. Photocorrosion of these particulates was also examined by scanning electron microscopy. © 1996 John Wiley & Sons, Inc. 相似文献
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Dr. Elena Lucenti Dr. Alessandra Forni Dr. Chiara Botta Dr. Clelia Giannini Dr. Daniele Malpicci Dr. Daniele Marinotto Dr. Andrea Previtali Dr. Stefania Righetto Prof. Elena Cariati 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(10):2452-2456
Considering that heavy halogen atoms can be used to tune the emissive properties of organic luminogens, the understanding of their role in photophysics is fundamental for materials engineering. Here, the extrinsic and intrinsic heavy-atom effects on the photophysics of organic crystals were separately evaluated by comparing cyclic triimidazole ( TT ) with its monoiodo derivative ( TTI ) and its co-crystal with diiodotetrafluorobenzene ( TTCo ). Crystals of TT showed room-temperature ultralong phosphorescence (RTUP) originated from H-aggregation. TTI and TTCo displayed two additional long-lived components, the origin of which is elucidated through single-crystal X-ray and DFT/TDDFT studies. The results highlight the different effects of the I atom on the three phosphorescent emissions. Intrinsic heavy-atom effects play a major role on molecular phosphorescence, which is displayed at room temperature only for TTI . The H-aggregate RTUP and the I⋅⋅⋅N XB-induced (XB=halogen bond) phosphorescence on the other side depend only on packing features. 相似文献
157.
Roberta Macrì Vincenzo Musolino Micaela Gliozzi Cristina Carresi Jessica Maiuolo Saverio Nucera Miriam Scicchitano Francesca Bosco Federica Scarano Stefano Ruga Maria Caterina Zito Lorenza Guarnieri Ezio Bombardelli Vincenzo Mollace 《Molecules (Basel, Switzerland)》2020,25(23)
The employment studies of natural extracts in the prevention and treatment of several diseases highlighted the role of different species of genus Ferula L., belonging to the Apiaceae family, dicotyledonous plants present in many temperate zones of our planet. Ferula communis L. is the main source of sesquiterpene ferutinin, a bioactive compound studied both in vitro and in vivo, because of different effects, such as phytoestrogenic, antioxidant, anti-inflammatory, but also antiproliferative and cytotoxic activity, performed in a dose-dependent and cell-dependent way. The present review will focus on the molecular mechanisms involved in the different activities of Ferutinin, starting from its antioxidant potential at low doses until its ionophoric property and the subsequent mitochondrial dysfunction induced through administration of high doses, which represent the key point of its anticancer action. Furthermore, we will summarize the data acquired from some experimental studies on different cell types and on several diseases. The results obtained showed an important antioxidant and phytoestrogenic regulation with lack of typical side effects related to estrogenic therapy. The preferential cell death induction for tumor cell lines suggests that ferutinin may have anti-neoplastic properties, and may be used as an antiproliferative and cytotoxic agent in an estrogen dependent and independent manner. Nevertheless, more data are needed to clearly understand the effect of ferutinin in animals before using it as a phytoestrogen or anticancer drug. 相似文献
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