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991.
Krzysztof E. Krakowiak Reed M. Izatt Jerald S. Bradshaw 《Journal of heterocyclic chemistry》2001,38(6):1239-1248
Macrocyclic ligands have been prepared by various one‐step cyclooligomerization processes. This short review covers one‐step cyclization reactions involving the formation of four to twenty or more new covalent bonds. The new macrocycles reviewed include cyclophanes, biscrown ethers, cryptands, macrolides, cage compounds, calixarenes, homocalixarenes, cucubiturils, and supercryptands all prepared by one‐step syntheses. 相似文献
992.
Lynne A. McCullough Bruno Dufour Krzysztof Matyjaszewski 《Journal of polymer science. Part A, Polymer chemistry》2009,47(20):5386-5396
2‐Acrylamido‐2‐methyl‐N‐propanesulfonic acid (AMPSA) was successfully polymerized via atom transfer radical polymerization (ATRP) using a copper chloride/2,2′‐bipyridine (bpy) catalyst complex after in situ neutralization of the acidic proton in AMPSA with tri(n‐butyl)amine (TBA). A 5 mol % excess of TBA was required to completely neutralize the acid and prevent protonation of the bpy ligand, as well as to avoid side reactions caused by large excess of TBA. The use of activators generated by electron transfer (AGET) ATRP with ascorbic acid as reducing agent resulted in both increased conversion of the AMPSA monomer during polymerization (up to 50% with a 0.8 [ascorbic acid]/[Cu(II)] ratio) and much shorter polymerization times (<30 min). Block copolymers and molecular brushes containing AMPSA side chains were prepared using this method, and the solution and surface behavior of these materials were investigated. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5386–5396, 2009 相似文献
993.
The review covers the chemistry of organoboron heterocycles structurally related to benzoxaboroles where one of the carbon atoms in a boracycle or a fused benzene ring is replaced by a heteroelement such as boron, silicon, tin, nitrogen, phosphorus, or iodine. Related ring expanded systems including those based on naphthalene and biphenyl cores are also described. The information on synthetic methodology as well as the basic structural and physicochemical characteristics of these emerging heterocycles is complemented by a presentation of their potential applications in organic synthesis and medicinal chemistry, the latter aspect being mostly focused on the promising antimicrobial activity of selected compounds. 相似文献
994.
In this paper we prove that every collineation of the Segre product of strongly connected partial line spaces is (up to permutation
of indices) the product of collineations of its components (Thm. 1.10). Spaces of pencils are strongly connected, so the claim
holds for Segre products of them (Thm. 1.14). In the second part we study the extendability of collineations of Segre products
of spaces of pencils under some natural embeddings.
Received 4 Mai 1998. 相似文献
995.
We consider super-Brownian motion whose historical paths reflect from each other, unlike those of the usual historical super-Brownian
motion. We prove tightness for the family of distributions corresponding to a sequence of discrete approximations but we leave
the problem of uniqueness of the limit open. We prove a few results about path behavior for processes under any limit distribution.
In particular, we show that for any γ > 0, a “typical” increment of a reflecting historical path over a small time interval
Δt is not greater than (Δt)3/4−γ.
Received: 16 March 2000 / Revised version: 26 February 2001 / Published online: 9 October 2001 相似文献
996.
Piotr Jamróz Krzysztof Gręda Paweł Pohl Wiesław Żyrnicki 《Plasma Chemistry and Plasma Processing》2014,34(1):25-37
Miniaturized atmospheric pressure glow discharges (APGDs) were generated in contact with small sized flowing liquid cathode systems. As anodes a solid pin electrode or a miniature flow Ar microjet were applied. Both discharge systems were operated in the open to air atmosphere. Hydrogen peroxide (H2O2) as well as ammonium (NH4 +), nitrate (NO3 ?), and nitrite (NO2 ?) ions were quantified in solutions treated by studied discharge systems. Additionally, an increase in the acidification of these solutions was noted in each case. Emission spectra of the near cathode zone of both systems were measured in order to elucidate mechanisms that lead to the formation of active species in gas and liquid phases of the discharge. Additionally, the concentration of active species in the liquid phase (H2O2, NH4 +, NO3 ? and NO2 ?) was monitored as a function of the solution uptake rate and the flow rate of Ar. The suitability of investigated discharge systems in the water treatment was tested on artificial wastewaters containing an organic dye (methyl red), hardly removable by classical methods non-ionic surfactants (light Triton x-45 and heavy Triton x-405) and very toxic Cr(VI) ions. Preliminary results presented here indicate that both investigated flow-through APGD systems may successfully be applied for the efficient and fast on-line continuous flow chemical degradation of toxic and hazardous organic and inorganic species in wastewater solutions. 相似文献
997.
John P. Greene Philip J. Voss Krzysztof Starosta 《Journal of Radioanalytical and Nuclear Chemistry》2014,299(2):1121-1124
For targets requiring thick backing foils, the straight-forward and usual method is to deposit the target material directly on the backing by thermal evaporation. In some instances the reverse is more desirable, adding a backing to an already existing target foil, for example. A recent study involving measurement of the lifetime of the first 2+ excited state in 36Ar by the Doppler shift attenuation method required 0.5 mg/cm2 natural carbon targets on thick (18 mg/cm2) gold and lead backings. Problems of delamination had arisen after beam irradiation using thick gold backings for these experiments. Carbon target foils were then prepared by mechanical rolling in direct contact with a thick lead backing using an intermediate layer of indium to assure good adhesion of the layers. Details of the method will be discussed. 相似文献
998.
999.
Radula-Janik Klaudia Kupka Teobald Ejsmont Krzysztof Daszkiewicz Zdzisław Sauer Stephan P. A. 《Structural chemistry》2016,27(1):199-207
Structural Chemistry - The first report on crystal and molecular structure of 3,6-diiodo-9-ethyl-9H-carbazole is presented. Experimental room-temperature X-ray and 13C chemical shift studies were... 相似文献
1000.